Jacqueline M. Cook, MD

• Department of Medicine
• Yale University School of Medicine
• Yale-New Haven Hospital
• New Haven, CT

Divergent outcomes in cognitive-behavioral therapy and pharmacotherapy for adult depression disease that causes erectile dysfunction purchase cheap tadalis sx online. Selective serotonin reuptake inhibitors and tricyclic antidepressants in the acute treatment of chronic depression and dysthymia: a systematic review and meta-analysis erectile dysfunction over 80 tadalis sx 20 mg purchase on line. Prevalence and incidence studies of mood disorders: a systematic review of the literature erectile dysfunction kits generic tadalis sx 20 mg buy. A prospective follow-up of patients with bipolar and primary unipolar affective disorder impotence with blood pressure medication best order tadalis sx. A family history study of prevalences erectile dysfunction drugs nz buy tadalis sx 20 mg with amex, sex differences, and possible genetic factors. Effects of lowdose and very low-dose ketamine among patients with major depression: a systematic review and meta-analysis. These symptoms are widely considered to be hallmarks of mental disorder and thus are of great interest to psychiatrists. Psychotic symptoms may be seen in a wide variety of illnesses, including mood disorders, neurocognitive disorders, alcohol and drug use disorders, and a group of conditions that may be called the "schizophrenic disorders. In general, but not always, the schizophrenic disorders have a worse long-term prognosis compared with psychotic mood disorders, which tend to be more remitting (97). Many investigators believe that schizophrenic disorders comprise a number of different conditions (11, 133, 164). Psychiatrists have historically grouped the schizophrenias into paranoid, catatonic, hebephrenic, and simple types, depending on whether the predominant symptoms are delusions, bizarre motor behavior, disturbances in affect and associations, or social withdrawal and inadequacy (15, 80). In practice, however, these diagnostic subtypes of schizophrenia have not been demonstrated to represent stable entities over time, and patients may fall into different subcategories at different points of the course of their illness (112). The schizophrenic disorders have classically been divided into two main categories: one with a relatively poor prognosis, the other with a relatively good prognosis (97, 140). Research has clarified that schizophrenic conditions have considerable variability in outcome (56, 110, 116, 133). Patients with more favorable prognosis are those whose previous general adjustment has been good, and their illness presents episodically with intervening periods of remission (56, 116, 135). Many patients show striking mood symptoms during the acute psychotic illness (79, 98, 113). Prominent mood disturbances during episodes of psychosis predict a more favorable course and outcome (97). A cardinal feature of schizophrenia is the occurrence of delusions and hallucinations in a clear sensorium. Other noteworthy features are a blunted, shallow, or strikingly inappropriate affect; odd, sometimes bizarre, motor behavior; and disordered thinking in which goal directedness and normal associations between ideas are markedly distorted (loosening of associations and tangential thinking). Cognitive functioning is often impaired, and many patients experience extensive loss of motivation, drive, and social functioning, referred to as "negative" symptoms. Careful follow-up of hospitalized patients led Kraepelin to separate "manic depressive psychosis" from "dementia praecox. His "narrow" view of schizophrenia has been followed by most European psychiatrists, particularly those in the Scandinavian countries and Great Britain. A broader approach to schizophrenia (and the name itself) was offered by Eugene Bleuler (1857­1939), a Swiss psychiatrist, who realized that he might be dealing with a group of disorders (15). By this he meant inconsistency, inappropriateness, and disorganization of affect, thought, and action, in the absence of obvious brain disease. Despite his less-strict approach to diagnosis and the variable course that his patients experienced, Bleuler believed that patients with schizophrenia never recovered completely, never returned to their premorbid state (restituo ad integrum). In this psychoanalytic view of schizophrenia, all signs of weak ego (including a wide range of personality handicaps and abnormalities) or of "primary process" (such as hallucinations, delusions, poor reality-testing, tangential thinking, and ambivalence) are manifestations of the illness. It is not surprising, therefore, that the diagnosis was used in a wide range of clinical situations. In the late 1930s, a number of European and American investigators began again to approach the problem of studying the schizophrenias for predicting course, response to treatment, and long-term outcomes. They recognized that proper evaluation of treatment requires knowledge of the natural history of the disorder in patients and their families, especially the factors associated with different clinical courses and outcomes. As a result, clinical and research approaches to the schizophrenic disorders have been based on extensive longitudinal follow-up studies, supplemented by family studies (122). Most psychiatrists around the world came to accept the narrower approach to schizophrenia, referred to as "neo-Kraepelinian" (33). This consensus is largely based on empirical and systematic studies indicating that the narrower approach produces more consistent findings with regard to course, response to treatment, long-term outcome, and familial illness patterns. Historically, epidemiological studies have typically neither distinguished between good- and poor-prognosis forms of schizophrenia nor considered the possibility that some of the good-prognosis cases may represent other disorders. Available evidence suggests that the good-prognosis cases may be relatively common (125). The combined prevalence of both good- and poor-prognosis disorders is probably between 1% and 2%. A number of studies have indicated that they are more prevalent among people from lower socioeconomic backgrounds (84). For some investigators, this has suggested that poverty, limited education, and associated handicaps predispose to schizophrenic illness. If a disorder interferes with education and work performance, so that individuals are not able to complete advanced schooling or hold positions of responsibility, their socioeconomic status-characteristically defined by income, educational achievement, and job prestige-cannot be high. Classic studies of schizophrenia in the United States and Europe have shown that the distribution of socioeconomic class among the fathers of children with the illness is not different from that in the general population, indicating that the lower socioeconomic status of patients with schizophrenic illness is at least partially the result of downward drift (84). Immigrants to European countries-especially ethnic minority groups and those from underdeveloped countries-have been found to have substantially higher rates of schizophrenia than in native-born groups (18, 154, 162). The intersection of low social status and schizophrenia in these immigrants cannot be entirely explained by selective downward social drift. Environmental stressors such as unemployment, social adversity, racial discrimination, and cultural hardships appear to have contributed to their risk for developing psychotic illness (131, 162). In hundreds of studies, dating as far back as 1929, researchers have consistently identified an excess of births during the late winter and early spring months among individuals who develop schizophrenia in the Northern Hemisphere (12, 22, 110). This line of research is supported by a study documenting a seven-fold increase in risk for schizophrenia among children with maternal serological evidence of first-trimester exposure to influenza (107). Other research has demonstrated convincing evidence of increased rates of schizophrenia among individuals with prenatal exposure to maternal starvation during famines (22, 118, 137, 144). Males also seem to have poorer premorbid adjustment, more severe clinical manifestations, and a more chronic course (1, 86). Patients with schizophrenia may be socially withdrawn, produce little spontaneous speech, and lack ability to initiate and sustain goal-directed activities. These patients may exhibit neurocognitive difficulties, especially in memory, attention, and executive functions. Common delusions in schizophrenia are those of persecution and control in which patients believe others are spying on them, spreading false rumors about them, planning to harm them, trying to control their thoughts or actions, or reading their minds. For instance, a young woman complained bitterly that her brother was sending special mysterious messages to her by means of television in order to make her do things that would call attention to her and lead to trouble with the police. A young man was convinced that he was being followed and observed on the streets and in various buildings, but he concluded that this was being directed by his psychiatrist as a way to monitor his progress. These may be feelings that bizarre bodily changes are taking place, sometimes as a result of the deliberate but obscure actions of others, for example: "My insides are rotting because they are poisoning my food. The voices may criticize, ridicule, or threaten; often they urge the patient to do something she or he believes is wrong. Visual hallucinations may not be as prevalent in schizophrenia as in bipolar disorder, but neither are they unusual (10). These hallucinations may vary from frightening, vague forms to images of dead or absent relatives to scenes of violence or hell. Although the so-called typical flat schizophrenic affect is highly characteristic when it is severe, its diagnostic value is limited because it frequently is subtle, leading to disagreement about its presence. They can talk about frightening or shocking thoughts without seeming to experience their usual emotional impact ("inappropriate" affect). It is often difficult to feel compassion and sympathy for the patient or to believe that he or she can empathize with others. Recurrent posturing, grimacing, prolonged immobility, and "waxy flexibility" are dramatic examples of catatonic behavior. The impaired goal-directedness of schizophrenic thought and speech may take various forms, all likely to occur in the same patient. Delusions, hallucinations, bizarre and disorganized behavior, and formal thought disorder in schizophrenia have been collectively termed "positive" symptoms; blunted affect, social withdrawal, amotivation, apathy, anhedonia, and social and occupational deficits are considered "negative" symptoms (19, 40). The negative symptoms have consistently been shown to be associated with a poorer prognosis (40, 86). Positive- and negative-symptom groupings have not offered enduring utility for subtyping forms of schizophrenia. Recognition of the positive­negative symptom distinction has, however, stimulated clinicians to pay more attention to the full spectrum of clinical features of schizophrenia (40) and spurred the development of novel medications to target negative symptoms that were largely unresponsive to the earlier antipsychotic medications (121, 138). In the nineteenth century, however, the cognitive deficits were viewed merely as secondary to positive and negative symptoms that were considered the core psychopathology of schizophrenia. In the last two decades, the cognitive deficits have come to be appreciated as primary and central features of the illness and recognized as responsible for the socio-occupational decline seen in many of these patients (76). Schizophrenia research has identified impairments in higher neurocognitive abilities that map to prefrontal cortex circuitry abnormalities and frontotemporal structural brain changes (67, 76, 110). Specific deficits have been demonstrated in memory encoding and retrieval, sustained and selective attention and vigilance, perceptual and cognitive processing, response speed, visuospatial skills, and verbal fluency (16, 17, 76, 133). These cognitive abnormalities result in difficulties with neurobehavioral regulation and executive functions involving planning and pursuing the goal-directed activities that are essential to real-world functioning (76, 110). Patients with schizophrenic disorders may display prominent alterations of mood, usually depression but sometimes euphoria, during the course of illness (79, 98, 113). Other affective symptoms-such as insomnia, anorexia, weight loss, alterations in interest and energy, impairment of mental concentration, guilt, and suicidal preoccupation-may also be present. In fact, many patients with schizophrenia experience episodes of depression that symptomatically resemble those seen in major depressive disorder (110, 112). Because the first-degree relatives of such patients do not appear to have an increased prevalence of mood disorders, their depression may be regarded as symptomatic of schizophrenia rather than the manifestation of a second illness. The likelihood that the schizophrenias represent a collection of syndromes representing the end state of different biological pathways only complicates the scientific search for the source of the illness (110, 164). Although neuropathology, neurochemistry, neuroimaging, and neurocognitive studies have demonstrated consistent brain abnormalities in schizophrenia, there are as yet no reliable biomarkers for schizophrenia and no diagnostic laboratory tests for the disorder (27, 54, 91, 110, 147). Brain pathology in schizophrenia has been investigated through studies of postmortem brains and in brain imaging research. Postmortem brains of patients with schizophrenia have revealed subtle macroscopic and microscopic differences from nonschizophrenic brains, including reduced neuronal numbers and neuronal size (69). Consistently identified brain abnormalities in schizophrenia are low brain weight and decreased cortical volume. The most remarkable reductions of brain tissue are found in limbic and associated areas, including the temporal lobe, superior temporal gyrus, hippocampus, parahippocampal gyrus, anterior cingulate cortex, and amygdala (9, 53, 110). These abnormalities are more pronounced in gray matter than in white matter (110). A corresponding increased volume found in the lateral and third ventricles-on the order of 26%-has been one of the most consistent brain findings in schizophrenia (27, 61, 104, 127, 155). A recognized methodological limitation of neuropathological and brain imaging studies is that first-episode and medication-naïve patients have generally not been included. Thus, some brain findings from these studies may represent artifacts of antipsychotic medication, illness chronicity, medical comorbidity, or even smoking (27, 127). However, many of the brain abnormalities in schizophrenia have been demonstrated in young, first-episode, or never-medicated patients with the illness without association with age, illness chronicity, duration of antipsychotic treatment, length of previous hospitalization, or the use of electroconvulsive therapy. This suggests that these brain abnormalities are primary features of the illness rather than artifacts of associated characteristics of the individuals studied, and that they may be present early in the course of the illness (41, 64). A long-standing assumption, dating back to Kraepelin (80) a century ago, is that schizophrenia is a neurodegenerative condition, based on observations of the progressive, deteriorating course of many of these patients (89, 153). More recently, however, the dominant view of schizophrenia is that it represents a neurodevelopmental condition (89). Strongly supporting this assumption is the finding that gliosis is not a consistent brain finding in schizophrenia (11), a finding that is more consistent with the neurodevelopmental hypothesis. Considerable evidence has accumulated to implicate abnormalities in three main neurotransmitter systems-the dopaminergic, serotonergic, and glutamatergic systems-in schizophrenia (21, 27, 31). Historically, the main neurochemical theory has been the "dopamine hypothesis," which arose in the 1960s from animal experiments demonstrating that antipsychotic medications blocked dopamine receptors (87). The dopamine hypothesis postulates presynaptic dysfunction of the dopamine D2 receptors, resulting in excessive synthesis and release of dopamine in the limbic striatum (62, 72). This dopamine excess is considered the source of psychotic symptoms such as hallucinations and delusions (62, 110) and a main target of antipsychotic medications directed toward reduction of these symptoms (72). In the 1990s, the dopamine hypothesis was revised to suggest that the positive symptoms of schizophrenia result from hyperactive mesolimbic dopamine projections functioning to hyperstimulate striatal dopamine receptors of the D2 subclass, and that the negative symptoms and cognitive impairments of schizophrenia result from hypoactive mesolimbic dopamine projections that hypostimulate prefrontal cortex dopamine receptors of the D1 subclass (21, 87). Serotonin is central to neurobiological processes of emotional and mood regulation, and it is thought to be involved in negative symptoms as well as in depressive states that are observed in patients with schizophrenia (132). The evidence for a primary role of the serotonin system in schizophrenia is not as strong as the evidence implicating the dopamine system, and is largely derived from indirect drug challenge studies (132). Glutamate disturbances are thought to be especially associated with cognitive dysfunction in schizophrenia (110, 141). Increasing evidence suggests dopamine as the final common pathway of various predisposing environmental and genetic contributors to the development of schizophrenia. Evidence of the contribution of these neurotransmitter systems to psychosis has stimulated research to develop and test pharmacological agents acting on various neurotransmitter receptors in efforts to improve pharmacotherapy for schizophrenia (94, 143).

Evidence of an excessive gender gap in the risk of psychotic disorder among North African immigrants in Europe: a systematic review and metaanalysis erectile dysfunction causes n treatment tadalis sx 20 mg order free shipping. Neuroimmunological aberrations and cerebral asymmetry abnormalities in schizophrenia: select perspectives on pathogenesis impotence jelqing cheap 20 mg tadalis sx overnight delivery. Increased developmental deviance and premorbid dysfunction in early onset schizophrenia impotence over 60 buy discount tadalis sx 20 mg. Elaboration on the association between immigration and schizophrenia: a population-based national study disaggregating annual trends erectile dysfunction best treatment discount tadalis sx 20 mg visa, country of origin and sex over 15 years erectile dysfunction holistic treatment cheap tadalis sx 20 mg on line. Risk factors for violence in psychosis: systematic review and meta-regression analysis of 110 studies. Comorbid obsessive-compulsive symptoms in schizophrenia: insight into pathomechanisms facilitates treatment. Panic disorder is a chronic illness characterized by recurrent, acute panic attacks. Panic attacks are discrete episodes of anxiety or fearfulness with definite onset, rapid increase, and spontaneous termination. The attacks are accompanied by symptoms associated with the autonomic nervous system: palpitations, tachycardia, rapid or shallow breathing, dizziness, and tremor. Between attacks, patients may be relatively asymptomatic though some experience fatigue, headache, and symptoms of anxiety attacks that persist. A panic attack is a symptom rather than a disorder, and panic attacks can be part of the course of any psychiatric illness. When panic attacks occur together, independent of other significant psychiatric symptoms, the diagnosis of panic disorder is made. Panic is distinguished from ordinary fear by the lack of an appropriate stimulus precipitating the emotions. Sometimes, however, patients experience panic attacks in response to a fear-provoking situation, such as facing an angry employer or giving a public speech. In these cases the clinician must decide whether the anxiety is grossly out of proportion to the fearprovoking stimulus, as well as make a diagnosis based on the complete history. A phobia is an intense, recurrent, unreasonable fear of a specific object, activity, or situation that results in a compelling desire to avoid the dreaded object, activity, or situation. Agoraphobia is characterized by multiple phobias involving a fear of being in places where help might not be available in the event of an anxiety attack. In the nineteenth century, "anxiety reactions" referring to fainting- which was fashionable among women of that era-were called "vapors. In Victorian times the prototype of a refined young woman was "a swooner, pale and trembling, who responded to unpleasant or unusual social situations by taking to the floor in a graceful and delicious maneuver, in no way resembling the crash of the epileptic" (p. A Jane Austen heroine found one social situation "too pathetic for the feelings of Sophie and myself. John Brown, cured fainting by "cutting the stay laces, which ran before the knife and cracked like a bow string" (p. Neurasthenia broadly included patients with hysteria, obsessional illness, and anxiety disorders, as well as hypochondria and swooning (15). Panic disorder was later subdivided into two types, with and without agoraphobia (2), but ultimately panic disorder and agoraphobia were separated into two distinct disorders (3). The term "phobia" originates from the name of a Greek god, Phobos, whose likeness was painted on masks and shields for the purpose of frightening the enemy (58). The word phobia first appeared in medical terminology in Rome 2,000 years ago, when hydrophobia was used to describe a symptom of rabies. During the nineteenth century, phobia appeared increasingly in descriptions of morbid fears, beginning with syphilophobia, defined in a medical dictionary published in 1848 as "a morbid dread of syphilis giving rise to fancied symptoms of the disease" (p. Later authorities compiled long lists of phobias, naming each in Greek or Latin terms after the object or situation feared. Thus, as Nemiah pointed out, "the patient who was spared the pangs of taphaphobia (fear of being buried alive) or ailurophobia (fear of cats) might yet fall prey to belonophobia (fear of needles), siderodromophobia (fear of railways), or triskaidekaphobia (fear of thirteen at table), and pantaphobia was the diagnostic fate of that unfortunate soul who feared them all" (p. The term "phobia" was not applied in a psychiatric sense until the nineteenth century. In 1871, Westphal described three men who feared public places and labeled the condition "agoraphobia," agora derived from the Greek word for "place of assembly or marketplace" (98). Westphal recommended companionship, alcohol, or the use of a cane to treat the condition. Numerous theories were advanced to explain phobias, including poor upbringing (52). Phobias and panic attacks have long been known to occur in a variety of psychiatric conditions. Controversy has continued since the late nineteenth century over the relationship of phobias and panic to other psychiatric disorders, such as obsessional and mood disorders, substance abuse, and personality disorders (5, 36, 42, 58, 85, 105). As many as 2%­4% of the adult population may have panic disorder at some time in their lifetimes (6, 25, 43, 44, 79), and women have at least twice the prevalence of men (6, 25, 41, 62). Panic disorder appears to be more common in whites than in African Americans and Hispanics (26). The previous linkage of panic disorder and agoraphobia in the diagnostic criteria was not without basis, because one-third to onehalf of general-population panic disorder cases are associated with agoraphobia, and this proportion is greater, 80% or more, in clinical samples (6, 13, 26, 42). Panic disorder has inconsistently been found to be associated with low educational level and socioeconomic status (25, 26). The disorder has been found to be associated with self-reported childhood abuse history, but the association was modest, much of it explained by other childhood and family factors (18, 33). Many people with panic disorder experience a mild form and, like those with phobic disorders, do not seek medical care for their symptoms (6, 19). Patients with panic disorder who see psychiatrists may represent a small group with a high prevalence of comorbid mood disorder (6). Two population studies using structured diagnostic interviews have provided lifetime prevalence rates of phobic disorders. Despite the higher overall prevalence of phobic disorders in these studies, the findings challenged prevailing notions of the ubiquitous nature of specific phobias, such as fear of snakes and heights, especially in childhood and among women. The reported prevalence of phobic disorders varies according to the sample surveyed, the interview employed, and the choice of diagnostic criteria (6, 31, 62). Because inconsistency in methods between studies is a common problem in psychiatric epidemiology, findings often must be considered only tentative. Use of different diagnostic criteria and instruments of measure across epidemiological studies has undoubtedly contributed to disparities in prevalence rates reported for phobic disorders. In clinical samples, discrepancy in prevalence data for phobias may also be attributed to two other reasons. First, some physicians may include what others consider normal fears in their statistics. Second, many people are embarrassed about their phobias and tend to be secretive about them. It is not unusual in psychiatric practice to see patients for years before they describe, almost in passing, a phobia that has bothered them for a long time. This finding contradicts previous clinical observations and studies characterizing phobias as chronic conditions. Because few individuals with phobias ever receive treatment for them, most of the difference between lifetime and 12-month rates cannot be attributed to medications or psychotherapy. People with phobic disorders are less likely to be employed and their socioeconomic status is lower compared to other people. The attacks usually begin suddenly, sometimes in a public place or at a social gathering, or even at home. Some patients, especially those with agoraphobia, describe a disturbing sense of their body changing or becoming distorted (depersonalization) (91). Patients examined during such an attack manifest signs of distress: tachycardia, sweating, tachypnea, tremor, hyperactive deep tendon reflexes, and dilated pupils. These are accompanied by sustained worry about further attacks or maladaptive behavioral changes to avoid attacks. Some experience them on a daily basis; others have them only once or twice a year. A 51-year-old electrical engineer was brought to an emergency room by ambulance, complaining of severe left anterior chest pain. His breathing was labored and he complained of numbness and tingling in his lips and fingers. However, the electrocardiogram was normal, and blood enzymes were within normal limits. The history revealed that the patient had first experienced severe chest pain at the age of 21 while watching a movie. He had experienced many subsequent episodes of chest pain accompanied by dyspnea and anxiety and had been taken to an emergency room on at least 10 previous occasions. Although the examinations were always normal, he had undergone a variety of cardiovascular procedures, including cardiac catheterization. He had never been seen by a psychiatrist and at no time had been told that he very likely suffered from a common psychiatric disorder characterized by panic attacks. Symptoms may become associated with specific situations that patients will try to avoid. Or patients may avoid social situations in which an attack would be both frightening and embarrassing. Phobias can be distinguished from "normal" fears by their intensity, duration, irrationality, and the disablement resulting from avoidance of the feared situation. The fear is irrational and excessive but not always disabling because the object or situation can sometimes be easily avoided. Impairment may be considerable if the phobic object is common and cannot be avoided, such as a fear of elevators for someone who must use elevators at work. People with specific phobias typically are no more (or less) anxious than anyone else until exposed to the phobic object or situation. Then they become overwhelmingly uncomfortable and fearful, sometimes having panic attack symptoms (palpitations, sweating, dizziness, difficulty breathing). Called "anticipatory anxiety," this leads to avoidance of situations in which the stimulus might be present. Some common specific phobias are fear of animals, heights, closed spaces, wind, storms, lightning, loud noises, driving a car, flying in airplanes, riding in subways, hypodermic needles, and blood. There is even the case of the tennis player who wore gloves because he was afraid of fuzz, and tennis balls are fuzzy. Animal phobias are perhaps the most common specific phobias, or at least the most commonly studied. The phobia usually involves only one kind of animal but may lead to frequent distress with mild social disablement if the animals are domestic, such as dogs or cats (32). The person may be close enough to the ground so that a fall would not cause injury. Some people with phobias will not walk down a flight of stairs if they see the open stairwell. Some will not look out a window from the second floor or above, particularly if the window goes from floor to ceiling. Social phobia is another form of isolated phobia that generally leads to only mild forms of impairment. The individual with social phobia fears embarrassment, humiliation, or rejection if the fearful behavior is noticed by others. Her husband made excuses for her but felt his career was being damaged by their lack of social life. At first her explanation for refusing to join in dinner parties was that it was a waste of time or too much trouble. Later she confessed, tearfully and with much embarrassment, that she was afraid of being unable to eat if strangers were watching. Questioned by her concerned husband, she said she was afraid that once food was in her mouth she would be unable to swallow it and then find herself in the embarrassing situation of not knowing where to dispose of the food. She could eat in front of her husband with no difficulty until she told him about the phobia and then became concerned that he was watching her eat and expecting her to gag or vomit. Unlike specific and social phobias, agoraphobia has a complex clinical picture involving the combination of a wide range of phobic fears, including the following: 1. These fears belong to the category of claustrophobia, but most people with claustrophobia have only a single phobia and do not actually have agoraphobia. Paradoxically, people with agoraphobia may also be fearful of open spaces, such as empty parking lots. Being home alone: Some people with agoraphobia require constant companionship, to the despair of friends, neighbors, and family. Being away from home or another "safe" place where help cannot be readily obtained if needed: the agoraphobia sufferer is sometimes comforted just knowing there is a police officer or a doctor somewhere nearby. When confronted with these types of situations, people with these phobias worry that they will be trapped in a terrible situation. No one would be available to help in the event that they would become incapacitated. Klein and associates observed that most agoraphobia patients describe a history of panic attacks preceding the onset of phobias, and anticipatory anxiety about another panic attack leads to phobic avoidance of places where panic attacks might occur (47). Thus, a bridge phobia may not involve a fear of bridges per se, but may develop from a fear of experiencing panic on a bridge. Phobias about buses, trains, or airplanes may arise from concern that a panic attack might occur in a vehicle from which escape is impossible or embarrassing. Although the cause of panic disorder remains unknown, discovery of physiological abnormalities associated with panic disorder and advances in understanding of the neural circuitry of anxiety states have led to the elaboration of plausible theoretical models of anxiety disorders.

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Placement in foster care enhances quality of attachment among young institutionalized children erectile dysfunction treatment uk generic tadalis sx 20 mg overnight delivery. The brain-derived neurotrophic factor Val66Met polymorphism modulates the effects of parental rearing on personality in healthy subjects erectile dysfunction pills herbal purchase on line tadalis sx. Paternal deprivation affects social behaviors and neurochemical systems in the offspring of socially monogamous prairie voles erectile dysfunction injection drugs purchase generic tadalis sx from india. Control of parental investment changes plastically over time with residual reproductive value zolpidem impotence tadalis sx 20 mg buy on line. Thinking and doing: the effects of dopamine and oxytocin genes and executive function on mothering behaviours erectile dysfunction kit tadalis sx 20 mg purchase without a prescription. Wasp gene expression supports an evolutionary link between maternal behavior and eusociality. Brain transcriptomic analysis in paper wasps identifies genes associated with behaviour across social lineages. Timing of intervention affects brain electrical activity in children exposed to severe psychosocial neglect. Local environment but not genetic differentiation influences biparental care in ten plover populations. Time-contingent change in infanticide and parental behavior induced by ejaculation in male mice. Individual variation in parental care reaction norms: integration of personality and plasticity. Instead, a number of systems are highlighted that have been studied in greater depth, including, for example, what has been learned about the population level effects, both positive and negative, of the intracellular bacterium Wolbachia on the reproductive biology of its insect hosts. I will also highlight several outstanding examples of how endosymbionts, viruses, and various mobile genetic elements can alter host behaviour, often by targeting the nervous system (Moore 2002; Poulin 2011; Lefevre et al. The interactions and behaviour between microbes themselves will also not be covered. This definition is not clear-cut since many mobile genetic elements with bacterial, viral, plasmid, or sometimes even eukaryotic origin become incorporated into the host genome and can make up a large part of it, especially in invertebrates (Drezen et al. For example, in bdelloid rotifers 8­9% of the genome derives from horizontal gene transfer from other organisms (Boschetti et al. While these selfish genetic elements can be suppressed, inactivated, and/or sometimes domesticated to take on a beneficial role for the host organism, they persist because of their selfish vertical transmission. They can also sometimes be found in specialized structures of the gut, although the majority of gut bacteria are free living (Dillon and Dillon 2004). Endosymbionts housed in specific organs or organelles are frequently vertically transmitted from mother to offspring, and hence share part of their evolutionary history with their hosts. This association can lead to cospeciation between hosts and their mutualistic endosymbionts (Moran et al. Some organisms become entirely reliant on their endosymbionts for successful reproduction. Females of the parasitic wasp Asobara tabida are unable to develop ovaries in the absence of their obligate endosymbiotic Wolbachia bacteria (Dedeine et al. While to date there has been little systematic examination of this possibility, a recent comparative study of >100 host­symbiont associations showed that host dependence is strongly associated with vertical transmission (Fisher et al. For example, some populations of the butterfly Hypolimnas bolina harbour male-killing endosymbionts (Wolbachia) that cause population-level female-biased sex ratios. In high-prevalence populations, males are rare ­ 1 male per 100 females ­ but the frequency varies between populations (Dyson and Hurst 2004). Variation in male killer prevalence in turn affects female mating behaviour, with females evolving to be less choosy, and male ejaculate size is negatively correlated with the frequency of male killers (Charlat et al. In high-frequency populations, females run the risk of not obtaining sufficient sperm to fertilize all their eggs due to a shortage of males. This sperm shortage is exacerbated by males in these populations suffering ejaculate depletion due to high mating rate, further promoting increased female mating to obtain more sperm (Charlat et al. In African Acraea encedon butterflies, in populations harbouring male-killing endosymbionts, there is even evidence of sex role reversal with females adopting lekking behaviour to advertise their presence to the rare males and thereby increase their mating success (Jiggins et al. In contrast, in populations without male killers, lekking is only performed by males, illustrating the impact of sex ratio distorters in indirectly shaping female mating behaviour. Similarly, sex ratio distorters in flies promote female mating strategies that affect male ejaculate evolution. Some populations of Drosophila pseudoobscura flies harbour a selfish gene (an X-linked meiotic driving chromosome) that kills Y-linked sperm (because they do not pass on the selfish gene) resulting in population-level, female-biased sex ratios (Price et al. Male flies that carry the sperm killer suffer reduced paternity in sperm competition due to low sperm number (Price et al. This in turn favours multiple mating by females as a strategy that effectively biases paternity against sex ratio distorting males. Experiments have shown that females in populations that are at risk of sex ratio distorting males rapidly evolve increased remating frequency to promote sperm competition, demonstrating the potency of sex ratio distorters to alter female mating behaviour (Price et al. As a consequence of increased female remating, male ejaculates evolve in response to the higher risk of sperm competition in these populations (Price et al. This male-female coevolution occurs even when the sex ratio distorter is present at low frequency (5%; Price et al. They achieve this through a variety of sophisticated manipulations by targeting neurological pathways, including neural peptides and neurotransmitters. This is also the case for gut bacteria, and there is growing evidence that gut microbiota can communicate directly with the host nervous system (Cryan and Dinan 2012). Their impacts on behaviour are well documented in vertebrates where specific bacterial neurotransmitters can affect anxiety levels (Forsythe and Kunze 2013), and influence behaviours ranging from cognitive performance to sleep (Cryan and Clark 2016). In insects and arthropods, the brain includes the antennal lobes, that receive input from the olfactory sensory neurons, and mushroom bodies, that play a central role in sensory learning and memory, and microbes have been identified that specifically target these brain regions (Temple and Richard 2015; Strunov et al. In vertebrates, viruses such as rabies, herpes, and measles enter neurons through cell surface receptors, and once inside the neuron, use synapses to spread from cell to cell (Mothes et al. Similarly, the endosymbiont Wolbachia has been recorded in the central nervous system of flies, butterflies, mosquitoes, springtails, and terrestrial isopod hosts (Strunov et al. Gut microbiota can also directly affect the development and function of the nervous system by influencing neurogenesis, neurotransmitter signalling and neurodevelopment and thereby also influence the behaviour of animals (Diaz Heijtz et al. There is even evidence that the host can make use of their endosymbionts to reduce the risk of additional infection. Fungus-growing ants employ a specific behaviour whereby they use antibiotics produced by actinomycetous bacteria housed in specialized structures (infrabuccal pockets) to kill spores of a virulent parasite (Escovopsis) attacking their fungal gardens (Little et al. Many insects, nematodes, and arachnids harbour maternally transmitted endosymbionts, with more than >50% of all insects infected with Wolbachia (Hilgenboecker et al. However, since endosymbionts can only be passed on via females to eggs, the interest of females and the endosymbiont are likely to align over time. Interestingly, this spread in frequency has been accompanied by a shift from parasitic to mutualistic associations with the host. From initially causing a 20­15% loss in fecundity to females, Wolbachia has become associated with a 10% fecundity advantage after only 20 years of host­microbe coevolution (Weeks et al. A variety of mutualistic endosymbiotic microbes aid their hosts by providing nutrients or defence against pathogens. Bumblebees and honeybees harbour distinct bacterial communities in their guts that are not shared with related solitary bee species. These microbiota protect bee hosts against a natural trypanosomatid gut parasite, and hence provide an additional benefit of group living to these social insects (Koch and Schmid-Hempel 2011). It has been suggested that one overlooked benefit of group living and sociality is that this serves to facilitate the transmission of beneficial microbes (Lombardo 2008). Microbes that manipulate their hosts to act altruistically in certain situations may be favoured by selection and may therefore also play a role in the evolution of co-operation. Co-operation could favour the microbes as they can be transferred horizontally between hosts during social interactions. Altruistic behaviour could also be favoured by bacteria that are vertically transmitted between mother and offspring, as helping behaviour will increase host survival and reproduction and hence transmission of the microbes (Lewin-Epstein et al. The flip side of social interactions is that they can of course potentially lead to increased risk of disease transmission, and both processes (transmission of pathogenic and protective microbes) are likely to have shaped social behaviour of hosts. Micro-organisms were the first life forms on our planet and therefore have a long history of associating with later emerging multicellular life forms. So it comes as no surprise that microbes have shaped host evolution, and may directly influence the nervous system of their hosts to alter their behaviour (Archie and Tung 2015; Eisthen and Theis 2015). Odour-based signals are 162 8 the Effect of Non-Self Genes on the Behaviour of Hosts also key components in most animal communication. Since these are traits known to shape mate preferences, odour also plays a large role in mate choice. Wolbachia infections are associated with changes in responses to olfactory cues (Peng and Wang 2009; Rohrscheib et al. In Drosophila simulans flies, the wRi strain of Wolbachia increases the responsiveness of flies to food cues, whereas the Wolbachia strains wMel and wMelPop in D. There is a growing realization that microbes can also regulate behaviours between individuals in a social context, and that microbe-based chemical communication commonly occurs between species, as discussed below. Furthermore, these interactions are not restricted to communication between animals. Plants also release volatiles when being consumed by herbivorous insects that in turn can attract parasitoid wasps that attack the herbivores and thereby provide some protection to the plant (Moraes et al. The bacterial pathogen Candidatus modifies the odours released by its citrus tree plant host to attract its vector, the psyllid Diaphorina citri, and thereby facilitate its own proliferation (Martini et al. In humans, the bacterial composition of armpit odours functions as a reliable individual recognition cue as it shows stability over time and conveys distinctive odour profiles (Penn et al. For instance, humans are able to match the scent of monozygotic twins even if they do not live together (Roberts et al. Similar findings have also been shown in a range of mammals where gut microbiota shape the odour cues used in kin recognition (Archie and Tung 2015). There is therefore scope for a complex interaction between diet, the gut microbiota, and resulting individual odours (also see below). In birds, feather-degrading bacteria can affect plumage coloration and therefore influence mate choice. This has been shown in house finches where females prefer redder males that have fewer feather-degrading bacteria than dull males (Shawkey et al. Currently, the precise mechanisms underlying these different results are unclear, but it is possible the former is a case of parasite-mediated sexual selection, with birds of higher quality having lower bacterial loads. In the latter case, brighter males may spend less time preening their feathers and socially dominant males may pay a health cost for dominance, and/or higher bacterial loads are in fact beneficial, but bright birds are better at acquiring these bacteria than their dull male counterparts (Archie and Theis 2011). Internal gut microbiota can also affect odours of animals that directly regulate their sexual behaviours (Sharon et al. Evidence that endosymbionts such as Wolbachia are present in the central nervous system of certain insects and terrestrial isopod hosts suggests that they could act to affect mate preferences (Strunov et al. Intriguingly, in mate choice assays, female mate preferences are dependent on their own Wolbachia variant, with females preferring to mate with males that carry the same compatible Wolbachia strain as themselves. This mate preference disappears after partial depletion of Wolbachia (Miller et al. It is therefore possible that the restriction of Wolbachia to brain areas involved in processing cues relating to sexual behaviour may have evolved to reduce any fitness costs of unrestricted Wolbachia presence in the brain (Strunov et al. The difference in localization of Wolbachia in brain tissue between fly species has been proposed to be the outcome of the age of the association and therefore the potential for coevolution between the host and the endosymbiont. The Wolbachia strain wPau is considered an obligate mutualist that has had a long association with its host and clearing of Wolbachia in D. In other Drosophila species, findings are mixed for the role of Wolbachia-mediated mate preferences. Removal of species-specific Wolbachia infection removes assortative mating preferences. Mating preferences in combination between untreated and treated heterogametic pairs. Grey bars indicate untreated controls; black bars indicate assays with antibiotic-treated flies. However, it is also possible that the different findings could be due to the presence of other agents such as viruses that may also influence mate preferences (Ritschof et al. In the terrestrial isopod Armadillidium vulgare, feminizing Wolbachia influences mate attraction by altering the cuticular compounds and therefore female odours. Males prefer Wolbachia-free females that have different odour profiles, and this preference will result in increased fitness through the production of both sons and daughters (Richard 2017). Sex-specific effects seem likely for maternally inherited endosymbionts that cannot be passed on through males. In mice populations that carry an autosomal segregation distorter (the t-complex), heterozygous females discriminate against heterozygous males using odour cues (Lenington 1991). Females that preferentially mate with males with large eye-stalks enjoy the production of both sons and daughters, and sons in turn enjoy a higher mating success as they will also have large eye-stalks and a mating advantage (Wilkinson et al. Females are just as likely to mate with males whether they carry the sex ratio distorter or not (Price et al. In general, the modest evidence of mate preferences based on selfish genetic elements (Price and Wedell 2008; Wedell 2013) may be due to a lack of linkage between the selfish gene and the female preference gene due to recombination (Nicholls and Butlin 1998). When a virus is transmitted sexually, the host may exhibit increased sexual activity, which can increase virus transmission (Knell and Webberley 2004). Female Helicoverpa zea moths infected with a parasitic virus (Hz-2V) have increased pheromone production and calling frequencies. Virus-infected females are therefore more attractive to males than uninfected females, resulting in increased mating activity and higher reproductive success. This seems to be due to virus-infected females producing six- to sevenfold more pheromone than uninfected females (Burand et al.

Your somatic cell nuclei contain 46 chromosomes each erectile dysfunction 45 year old male buy tadalis sx in united states online, in 23 homologous pairs erectile dysfunction endovascular treatment tadalis sx 20 mg order mastercard, so your diploid number is 46 impotence in young men discount 20 mg tadalis sx mastercard. The diploid number varies among species (each species having its characteristic number of pairs) erectile dysfunction when pills don't work tadalis sx 20 mg order line, so the characteristic diploid number for animal species in general is described as 2n erectile dysfunction treatment south africa discount tadalis sx 20 mg. Some plant cell nuclei, such as those of pea plants, also have two sets of chromosomes and are diploid. They may be triploid (3n), tetraploid (4n), hexaploid (6n), octoploid (8n), or some other multiple of n. The value n represents the haploid number of chromosomes, and it is one-half the diploid number. Gametes, produced from germ-line cells, are the germinal, or reproductive, cells: sperm and egg in animals or pollen and egg in plants. Meiotic cell division reduces the number of chromosomes in the nucleus of each daughter cell by one-half to the haploid number. Each of the 23 human chromosome pairs has one representative in each sperm or egg. The union of the sperm and egg nuclei at fertilization produces the fertilized egg with 46 chromosomes in its nucleus. Thus human reproduction, like that of other sexually reproducing organisms ensures that exactly one-half of the genetic information in an offspring comes from each parent. We also explore patterns of sex determination in eukaryotes and look at processes that equalize the expression of genes carried on sex chromosomes, the chromosomes that determine sex. In addition, we study the special patterns of inheritance of genes on the X chromosome, and we see how the discovery of genes on the X chromosome supported the chromosome theory of heredity, the theory that chromosomes are the cell structures that carry genes. It is a genetically controlled process that follows a precise script to enable organisms to grow and develop normally and to maintain the structures and functions of their organs, tissues, and other bodily components. If too little cell division takes place or cell division occurs too slowly, an organism may fail to develop at all, or it may have morphologic abnormalities. On the other hand, too much cell division can lead to growth of structures beyond their normal boundaries, likewise producing morphologic abnormality and possible death. Since well-regulated cell division is such an integral part of life, it will not surprise you to learn that 3. Furthermore, in powerful testament to the single origin of life, plants and animals share a number of cell cycle genes with the Bacteria and Archaea domains of life. During interphase the cell expresses genetic information, it replicates its chromosomes, and it prepares for entry into M phase. M phase is divided into multiple substages that correspond to the progress of the cell during its division. When viewed under a light microscope, somatic cells in interphase may appear rather placid, but their outward appearance gives little indication of the complex activity taking place inside. Cells of different types vary in how many genes they express, in how they function in the body, and in how they interact with other cells. Consequently, the duration of G 1 varies among different types of cells in the body. Some types of cells are rapidly dividing and spend only a short time, perhaps as little as a few hours, in G 1. Several kinds of cells in your body, including certain cells in your eyes and bones, reach a mature state of differentiation, enter G 0, and rarely if ever divide again. Most G 0 cells maintain their specialized functions until they enter programmed cell death (apoptosis) and die. The completion of S phase brings about the transition to the G2, or Gap 2, phase of the cell cycle, during which cells prepare for division. Interphase ends when cells enter M phase, from which two identical daughter cells emerge. The successive generations of cells produced through mitosis as one cell cycle follows the next are known as cell lines or cell lineages. Mitosis ensures that the genetic information in cells is faithfully passed to successive generations of cell lineages. Although duplicated, the chromosomes are diffuse and not visible within the nucleus. Microtubules begin to extend from the centrosomes in radial patterns that form asters. Chromosome condensation begins in and progresses throughout prophase, making the coalescing chromosomes increasingly visible under the light microscope. In the cytoplasm, the paired centrosomes begin to migrate toward opposite poles of the cell, extending their microtubules to form the early mitotic spindle. By the end of prophase, the two sister chromatids that make up each chromosome can be seen. Having reached opposite poles of the cell, the centrosomes extend microtubules that attach to kinetochores of chromosome centromeres. Microtubules extending from opposite poles exert pulling forces in both directions. Cohesin binds sister chromatids to resist premature separation due to pulling forces. The chromosomes are shown in blue, and the centrosomes, asters, and spindle fibers are shown in green. These five substages accomplish two important functions of cell division-(1) the equal partitioning of the chromosomal material into the nuclei of the two daughter cells, a process called karyokinesis, and (2) the partitioning of the cytoplasmic contents of the parental cell into the daughter cells, a process known as cytokinesis. During interphase chromosomes are diffuse and cannot be clearly seen by light microscopy. Chromosome condensation, a process that progressively condenses chromosomes into more compact structures, begins in early prophase. Chromosomes become visible in midprophase, and the process continues until chromosomes reach their maximum level of condensation in metaphase. Nuclear envelope breakdown also occurs in prophase, and chromosome centromeres become visible as do the sister chromatids of each chromosome. The daughter chromosomes, tethered to depolymerizing kinetochore microtubules, move toward opposite poles and congregate near centrosomes. Polymerization of nonkinetochore microtubules accompanies the movement of daughter chromosomes, giving the cell an oblong shape at the end of anaphase. Nuclear envelope re-forming Nonkinetochore microtubule polymerization continues to elongate the cell in telophase, pushing the poles apart. The nuclear envelope begins to reassemble and will shortly surround the chromosomes. Cytokinesis divides the cytoplasm to create two new cells by formation of new cell walls, in plant cells, or a contractile ring and cleavage furrow, in animal cells. Complete chromosome condensation is reached in metaphase, and the fully condensed chromosomes align so that the sister chromatids of each chromosome lie on either side of the metaphase plate. The sister chromatids of each chromosome are attached to kinetochore microtubules emanating from centrosomes at opposite poles of the cell. Kinetochore, nonkinetochore, and astral microtubules are fully extended from the centrosomes, and a complete mitotic spindle is in place. The meaning and usage of the terms chromosome, chromatid, and sister chromatid sometimes cause confusion, and this is a good time to provide functional definitions. In animal cells, although not in most plants, fungi, or algae, two organelles called centrosomes appear that migrate during M phase to form the two opposite poles of the dividing cell. Spindle fiber microtubules are polymers of tubulin protein subunits that elongate by the addition of tubulin subunits and shorten by the removal of tubulin subunits. Microtubules are polar; they have a "minus" (-) end anchored at the centrosome and a "plus" (+) end that grows away from the centrosome. Three kinds of spindle fibers emanate from centrosomes in a 360° pattern identified as the aster: 1. Kinetochore microtubules embed in the protein complex called the kinetochore (described shortly) that assembles at the centromere of each chromatid. Kinetochore microtubules are responsible for chromosome movement during cell division. Nonkinetochore microtubules extend toward each other from the two polar centrosomes and overlap to help elongate and stabilize the cell during division. Astral microtubules grow toward the membrane of the cell, where they attach and contribute to cell stability. The kinetochore is a protein complex that assembles on each chromatid at the centromere. It is composed of an outer plate and an inner plate and is attached to the plus end of a kinetochore microtubule extending from a centrosome. Metaphase chromosomes have condensed more than 10,000-fold in comparison with their form at the beginning of prophase. This makes them easily visible under the microscope and allows them to be easily moved within the cell. Astral microtubules and nonkinetochore microtubules control and stabilize cell shape during division. The tension created by the pull of kinetochore microtubules is balanced by a companion process known as sister chromatid cohesion. Cohesin is a four-subunit protein; its central component is a polypeptide produced by the gene Scc1 for "sister chromatid cohesion. As microtubules move chromosomes toward the midline of the cell, cohesin helps keep the sister chromatids together, to ensure proper chromosome positioning and to prevent their premature separation. Anaphase is the part of M phase during which sister chromatids separate and begin moving to opposite poles in the cell. Anaphase includes two distinct events tied to microtubule action: anaphase A, characterized by the separation of sister chromatids, and anaphase B, characterized by the elongation of the cell into an oblong shape. First, the enzyme separase initiates cleavage of polypeptides in cohesin, thus breaking down the connection between (a) Prophase Microtubule sister chromatids. Second, kinetochore microtubules begin to depolymerize at their (+) ends to initiate chromosome movement toward the centrioles. The separation of sister chromatids in anaphase A is called chromosome disjunction. As anaphase progresses, sister chromatids complete their disjunction and eventually congregate around the centrosomes at the cell poles. The next part of anaphase, anaphase B, is characterized by the polymerization of polar microtubules that extends their length and causes the cell to take on an oblong shape. The oblong shape facilitates cytokinesis at the end of telophase, which leads to the formation of two daughter cells. Completion of Cell Division In telophase, nuclear membranes begin to reassemble around the chromosomes gathered at each pole, eventually enclosing the chromosomes in nuclear envelopes. Chromosome decondensation begins and ultimately returns chromosomes to their diffuse interphase state. As telophase comes to an end, two identical nuclei are observed within a single elongated cell that is about to be divided into two daughter cells by the process of cytokinesis. At anaphase (c), separase protein digests cohesin and allows sister chromatids to separate. In both plant and animal cells, cytokinesis divides the cytoplasmic fluid and organelles. Mitosis separates the members of each pair of sister chromatids into identical nuclei, thus forming two genetically identical daughter cells. The figure follows major events of the cell cycle, showing the generation of sister chromatids in S phase, chromosome alignment on the metaphase plate in metaphase, and the production of two identical (GgRr) daughter cells at the end of telophase. Metaphase Chromosomes align randomly along the metaphase plate with the aid of the mitotic spindle. Cell Cycle Checkpoints Cell biologists find that no matter what the duration of the cell cycle, most cells follow the same basic program; this suggests that common, genetically controlled signals drive the cell cycle. Knowledge of the genes and proteins controlling the cell cycle comes largely from the study of cell lineages possessing mutations that affect their progression through the cell cycle. These studies have produced important insights into genetic control of the cell cycle, and in recent decades, biologists have discovered the identities and functions of many genes responsible for cell cycle control. In more than three centuries of observation, biologists have identified a dizzying array of reproductive methods, mechanisms, and behaviors in animals, plants, and microbes. Even so, reproduction can be divided into two broad categories: (1) asexual reproduction, in which organisms reproduce without mating, giving rise to progeny that are genetically identical to their parent; and (2) sexual reproduction, in which cells called reproductive cells or gametes are produced by cell division and unite during fertilization. Cell division follows shortly after the completion of chromosome replication; each cell produces two genetically identical daughter cells. Single-celled eukaryotes, such as yeast, have multiple chromosomes and may be either haploid or diploid, and these organisms can reproduce either sexually or asexually. Although yeast spend most of their life cycle in a haploid state and actively reproduce as haploids, it is also common for two haploid yeast cells to fuse and form a diploid cell that produces haploid spores by meiosis. In contrast to single-celled eukaryotes, multicellular eukaryotes reproduce predominantly by sexual means. Mating requires the production of haploid gametes from both male structures and female structures. In monoecious plant species, including the Pisum sativum that Mendel worked with, male and female reproductive tissues are present in each plant, and self-fertilization is the common mode of reproduction, although fertilization involving pollen from one plant fertilizing the flower of another also occurs. In sexually reproducing animals, specialized germ-line cells undergo meiosis to produce haploid gametes, or reproductive cells. Female gametes are produced by the ovary in female animals or by the ovule in plants. In the anthers of flowering plants, pollen containing two sperm cells is produced. These descriptions are broadly true for most plants and animals, but there are many exceptions, including the observation of asexual reproduction in several species of fish, rotifers (small aquatic organisms), and salamanders. In addition, male ants, bees, and wasps have haploid somatic cells, and their processes of gamete production are distinctive. Meiosis Features Two Cell Divisions Interphase of the germ-line cell cycle contains stages G 1, S, and G 2 that are indistinguishable from those in somatic cells.

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