Jana R. Cooke, MD

• Clinical Instructor, Division of Pulmonary and
• Critical Care Medicine, University of California
• San Diego School of Medicine, San Diego, CA
• Staff Physician, Veterans Administration San Diego
• Healthcare System, La Jolla, USA

The vagus nerve: a tonic inhibitory influence associated with inflammatory bowel disease in a murine model arrhythmia natural supplements buy plendil 2.5 mg low cost. Impaired parasympathetic function increases susceptibility to inflammatory bowel disease in a mouse model of depression heart attack 23 years old 2.5 mg plendil purchase overnight delivery. Local secretion of corticotropin-releasing hormone by enterochromaffin cells in human colon hypertension 4 mg 10 mg plendil purchase visa. Stress neuropeptides evoke epithelial responses via mast cell activation in the rat colon pulse pressure endocarditis proven 10 mg plendil. Corticotropin-releasing hormone receptor 2-deficient mice have reduced intestinal inflammatory responses blood pressure normal lying down order plendil 2.5 mg without a prescription. Early weaning stress impairs development of mucosal barrier function in the porcine intestine. Characteristics of the intestinal epithelial barrier during dietary manipulation and glucocorticoid stress. Adaptation of stress-induced mucosal pathophysiology in rat colon involves opioid pathways. Stress and exacerbation in ulcerative colitis: a prospective study of patients enrolled in remission. Chronic peripheral administration of corticotropin-releasing factor causes colonic barrier dysfunction similar to psychological stress. Chronological assessment of mast cell-mediated gut dysfunction and mucosal inflammation in a rat model of chronic psychosocial stress. Interferon-gamma expression by intraepithelial lymphocytes results in a loss of epithelial barrier function in a mouse model of total parenteral nutrition. Phenotypic changes in colonocytes following acute stress or activation of mast cells in mice: implications for delayed epithelial barrier dysfunction. Interleukin-18 is a crucial determinant of vulnerability of the mouse rectum to psychosocial stress. Human fecal flora: variation in bacterial composition within individuals and a possible effect of emotional stress. Maternal separation disrupts the integrity of the intestinal microflora in infant rhesus monkeys. Catecholamines modulate Escherichia coli O157:H7 adherence to murine cecal mucosa. Enterocyte cytoskeleton changes are crucial for enhanced translocation of nonpathogenic Escherichia coli across metabolically stressed gut epithelia. Enhanced translocation of bacteria across metabolically stressed epithelia is reduced by butyrate. Lactobacillus farciminis treatment suppresses stress induced visceral hypersensitivity: a possible action through interaction with epithelial cell cytoskeleton contraction. Probiotic treatment of rat pups normalises corticosterone release and ameliorates colonic dysfunction induced by maternal separation. Synergy between Lactobacillus paracasei and its bacterial products to counteract stress-induced gut permeability and sensitivity increase in rats. Neonatal maternal deprivation triggers long term alterations in colonic epithelial barrier and mucosal immunity in rats. Long-term alterations of colonic nerve-mast cell interactions induced by neonatal maternal deprivation in rats. Neonatal maternal separation causes colonic dysfunction in rat pups including impaired host resistance. The protective effect of the vagus nerve in a murine model of chronic relapsing colitis. Gastrointestinal dysfunction induced by early weaning is attenuated by delayed weaning and mast cell blockade in pigs. Mediators of stress effects in inflammatory bowel disease: not the usual suspects. Alterations in enteric nerve ans smooth-muscle function in inflammatory bowel diseases. Local production of corticotropin releasing hormone is increased in experimental intestinal inflammation in rats. Corticotropin-releasing hormone antagonists possess antiinflammatory effects in the mouse ileum. Mast cells are an important cellular source of tumour necrosis factor alpha in human intestinal tissue. Characterisation of immune mediator release during the immediate response to segmental mucosal challenge in the jejunum of patients with food allergy. Chronic psychological stress in rats induces intestinal sensitization to luminal antigens. Effects of chronic stress on the immune response to oral human serum albumin-conjugated starch microparticles in rats. Psychometric scores and persistence of irritable bowel after infectious diarrhoea. Intestinal membrane permeability and hypersensitivity in the irritable bowel syndrome. Impaired intestinal barrier integrity in the colon of patients with irritable bowel syndrome: involvement of soluble mediators. Impact of corticotropin-releasing hormone on gastrointestinal motility and adrenocorticotropic hormone in normal controls and patients with irritable bowel syndrome. A, a 44-yr-old attorney, had experienced up to six episodes of cramping lower abdominal pain associated with watery diarrhea per month over a period of 15 years. These symptoms were worsened by stress associated with anticipation of a courtroom trial or the stress of presentation of the defense of a client during the actual trial. Barbara, a 22-year-old second year medical student, walked to the front of the lecture auditorium with a question for the professor at the end of the final lecture in a series on gastrointestinal physiology. The question: Can you explain to me why I routinely experienced lower abdominal distress and diarrhea as I prepared for and anticipated the examinations in the medicine course modules throughout the year A male guinea pig was held in a supine position by placing a tie around each ankle and gently extending and tying each of the four extremities to metal hooks at the corners of a rectangular flat platform. A second male guinea pig of the same weight and age and from the same holding rack in the vivarium was caged at room temperature and allowed to feed and drink H2O ad libitum during the 2 hour period. The three examples illustrate an expanding body of converging clinical and experimental evidence that implicates stress as a factor in disordered gastrointestinal function in both humans and animals. The sympathetic nervous hypothesis had credibility because the Physiology of the Gastrointestinal Tract, Two Volume Set. Descending spinal activation of the sympathetic nervous system cannot explain the stress-associated symptoms of cramping lower abdominal pain, fecal urgency, and watery diarrhea in humans or the similar effects of stress in animals. The evidence against sympathetic activation directs attention to involvement of other enteric neurophysiological mechanisms that come into play in stress and will be dealt with in this chapter. The concept starts with the evidence that enteric mast cells receive brain-derived input in the stressed individual. The same mast cells intercept and become sensitized to microorganisms and other sensitizing antigens that find their way across the intestinal mucosal barrier. The secretory response then links to powerful propulsive motility, which propels the secretions together with the offending agent quickly in the anal direction. The symptom of acute explosive watery diarrhea becomes selfexplanatory in this scenario. Mast cells express high-affinity receptors for IgE antibodies or other immunoglobulins on their surfaces. Symptoms of cramping abdominal pain and acute urgency and diarrhea result from operation of the neural program. Close spatial association of inflammatory/immune cells with the mast cell reflects release of chemoattractant factors from the mast cell in the inflamed mucosa/ submucosa. This work shows that a second exposure to antigens isolated from the infectious agent. Copious neurogenic secretion and elevated intestinal blood flow followed by orthograde power propulsion (see Chapter 21) of the luminal contents are the behavioral components of the program. Mast cell function in immunoneural communication in the gut is an immune counterpart of sensory detection and information coding in sensory neurophysiology. Mast cells, on the other hand, acquire specific detection capabilities through the flexibility of recognition functions inherent in synthesis by the immune system of new specific antibodies that become attached to Fc receptors. Output signals from mast cells, which are triggered by cross-linking of antigens with the attached antibodies, are chemical in nature and analogous to chemical output signals. Both mast cells and sensory neurons ultimately code information on the sensed parameter by releasing a chemical message that is decoded by information processing circuits in the nervous system. The brain-to-enteric mast cell connection can be demonstrated experimentally as a release of mast cell proteases in a Pavlovian-like conditioned response. Assays for the release of mast cell proteases into the systemic circulation or into the intestinal lumen are useful tools for measurement and timing of degranulation of enteric mast cells. The speed of the stress response most likely reflects neurotransmission over a neural pathway to the enteric mast cells and makes it unlikely that the responses resulted from any form of endocrine signaling from the brain. A neural highway for central nervous signaling to enteric mast cells is suggested by close histological proximity between vagal and spinal sensory afferent nerves and enteric mast cells. The evidence for a brain­mast cell connection takes on significance for understanding stress-associated symptoms of gut origin, because the symptoms associated with release of mast cell mediators are the same irrespective of whether mast cells are activated by antigen-antibody cross-linking in allergies and infections or by input down the brain­gut axis during stress. In the large intestine, restraint stress alters motility, induces a diarrheal state, and exacerbates nociceptive pain responses to distension in association with increased release of histamine from enteric mast cells. A group of patients with confirmed allergy to egg albumin and a group of normal subjects were asked to immerse one hand into ice-cold H2O for 1 minute at 15 second intervals in 2 successive 15 minute trials. Cold-pain stress evoked release of mast cell tryptase in both food-allergic patients (O) and normal subjects (·). Downward deflections on the trace are electrotonic potentials evoked by repetitive injection of hyperpolarizing current pulses through the electrode. Increased amplitude of the electrotonic potentials during the depolarizing response reflects increase in input resistance due to closure of potassium channels. Application of a second puff 2 minutes later, apparent on the bottom trace, evoked a much weaker response indicative of tachyphylaxis. Divisions of projections in this manner would be expected if the oral projections were from excitatory musculomotor neurons and those going in the aboral direction were inhibitory musculomotor neurons. It is a biomarker for excitatory musculomotor neurons and two subsets of secretomotor neurons. Small diameter uniaxonal neurons that express calretinin make up about one-fourth of the neurons in the myenteric plexus of guinea pig small intestine. Somatostatin immunoreactivity marks a group of descending interneurons in the guinea pig myenteric plexus, and serotonin is expressed by a different population of descending interneurons. Like the implications for coexpression with excitatory and inhibitory neurotransmitters in musculomotor neurons to circular muscle, coincident release at neuroepithelial and neurovascular junctions might function to modulate the responses of the secretory glands and blood vessels individually in response to input from a single population of secretomotor/vasodilator neurons. Instead, their axons leave the ganglia and continue on through several ganglia without forming contacts with other ganglion cells. Feed-forward synaptic excitation is a mechanism for rapid initiation of synchronous discharge in multiple neural elements of the circuit. Output from the feed-forward circuit drives populations of secretomotor neurons, which in turn drive the behavior of the secretory epithelium and vasculature. Positive feed-forward synaptic networks synchronize simultaneous firing of large numbers of motor neurons to ensure coordination of secretion around and along an extended length of bowel. Three of these subclasses are motor neurons that stimulate mucosal secretion when they fire. This is a form of synaptic connectivity in which the neurons of the circuit make recurrent excitatory synaptic connections with each other. Rapid buildup of firing in the individually interconnected neurons in the circuit ensures simultaneous activation of the whole network around the circumference and along the length of a segment of bowel. Neurons in the circuit have excitatory synaptic connections with adjacent motor neurons. In this arrangement, output of the circuit functions to simultaneously activate large pools of motor neurons around the circumference and up and down an intestinal segment. When submucosal secretomotor neurons are activated in this manner, the effect is to distribute secretion of electrolytes, H2O, and mucin uniformly around the circumference and along a length of bowel. That this might be the case is suggested by reports that pretreatment with the muscarinic receptor antagonist, atropine, suppresses stress-induced stimulation of mucosal secretion and increased permeability of the mucosal barrier in animals12,101,102,143 and humans. The outcome of which results in stimulation of neurogenic secretion, compromise of the mucosal barrier, and enhanced propulsive motility. Evidence that colitis is initiated by environmental stress and sustained by fecal factors in the cotton-top tamarin (Saguinus oedipus). Gastroduodenal motility during the delayed gastric emptying induced by cold stress. Stress-related alterations of gut motor function: role of brain corticotropin-releasing factor receptors. Psychological and physical stress induce differential effects on human colonic motility. Physiological reactivity to stressors in irritable bowel syndrome patients, inflammatory bowel disease patients and non-patient controls. The role of the hypothalamic-pituitary-adrenal axis in neuroendocrine responses to stress. The synaptic interface between the sympathetic and enteric divisions of the autonomic nervous system. Mechanism of synaptic inhibition by noradrenaline acting at alpha 2-adrenoceptors. Epidemiologic study of the irritable bowel syndrome in Beijing: stratified randomized study by cluster sampling. Alterations of brain activity associated with resolution of emotional distress and pain in a case of severe irritable bowel syndrome.

Monitoring of free calcium in the neuronal endoplasmic reticulum: An overview of modern approaches arrhythmia foods to eat buy plendil visa. Plasma-membrane Ca2 pumps: Structural diversity as the basis for functional versatility arteria yahoo discount plendil online. New calcium indicators and buffers with high selectivity against magnesium and protons: Design heart attack 64 lyrics cheap plendil 5 mg buy online, synthesis prehypertension quizlet order plendil line, and properties of prototype structures blood pressure medication edema buy plendil 2.5 mg on line. Apamin-sensitive, smallconductance, calcium-activated potassium channels mediate cholinergic inhibition of chick auditory hair cells. Turning of nerve growth cones induced by localized increases in intracellular calcium ions. Mitogen-regulated Ca2 current of T lymphocytes is activated by depletion of intracellular Ca2 stores. Proceedings of the National Academy of Sciences of the United States of America, 90(13), 6295­6299. From primitive single-cell organisms to complex multicellular organisms, this central regulatory role of protein phosphorylation has been conserved. In fact, in higher eukaryotes, including humans, this role was even further expanded to integrate additional, novel functions that arose at the organ and whole organism level, including intricate extracellular signaling systems. Consistently, protein phosphorylation is the major molecular mechanism through which protein function is regulated in response to extracellular stimuli. Virtually all types of extracellular signals, including cytokines, hormones, neurotransmitters and neurotrophic factors, as well as physical stimuli such as heat and visible light, produce most of their diverse physiological effects by regulating the phosphorylation state of specific phosphoproteins in their target cells. Over one-third of all eukaryotic proteins are phosphorylated and virtually every class of protein is regulated by phosphorylation. Protein phosphorylation usually induces © 2012, American Society for Neurochemistry. Protein phosphorylation is regulated by antagonistic actions of protein kinases and protein phosphatases. An unphosphorylated protein is converted into a phosphoprotein by a protein kinase and the reversal of this reaction is catalyzed by a protein phosphatase. This process is reversible, enabling cells to respond dynamically to a multitude of signals in the environment. Both extraand intracellular stimuli generally elicit complex patterns of protein phosphorylation to produce their physiological effects. The improper functioning of the machinery regulating protein phosphorylation is often highly disruptive to cellular processes. Consequently, many human diseases, including neuronal disorders, have been linked to dysregulation of protein phosphorylation. The organization of the nervous system exhibits an outstanding level of complexity. Neuronal functions underlying synaptic plasticity and memory processes rely on highly specialized molecular complexes, which form intracellular signaling networks. The precise organization and proper functioning of this intracellular network requires an extensive degree of high-fidelity regulation, which is largely achieved via protein phosphorylation. In this chapter, we present the molecular machinery that directs protein phosphorylation. We provide an overview of the crucial role of protein phosphorylation in the regulation of cellular and neuronal functions. Finally, we discuss the consequences of improper functioning of the phosphorylation machinery and its implication in neural disorders. Phosphorylation levels of substrate proteins are regulated by antagonistic actions of protein kinases and protein phosphatases Protein phosphorylation is a post-translational modification of proteins, whereby a phosphate group is covalently attached to either a serine (Ser), threonine (Thr) or tyrosine (Tyr) residue. To enable this catalytic reaction, all kinases require the presence of a divalent metal ion, such as Mg2 or Mn2. Protein phosphatases catalyze the cleavage of this phosphoester bond through hydrolysis. This activity-dependent reversible switch, from the unphosphorylated to the phosphorylated form, is the most widely used molecular mechanism, by which physiological signals are transmitted to regulate cellular functions. The addition of phosphate groups to proteins can induce conformational changes that alter biochemical and cellular functions, such as modulation of enzyme activity, cellular location or molecular association. Under basal conditions, the phosphorylation level of a substrate is determined by an equilibrium in kinase and phosphatase activity. Upon stimulation via extra- and intracellular signals the phosphorylation level can be shifted by increasing or decreasing the activity of either a protein kinase or a protein phosphatase. It may be noted that the transfer of a phosphate group by kinases represents an energy-consuming step. To limit energy expenditure, protein kinases are mostly inactive at a basal cellular state and require activation prior to substrate phosphorylation. Therefore, under basal conditions most substrates exhibit commonly a low phosphorylation level. Two major mechanisms can be distinguished depending whether the extracellular signals directly or indirectly activate kinases and/or phosphatases. Extracellular signals, in the form of first messengers, produce specific physiological responses in target cells via the induction of intracellular signaling cascades. Two fundamental pathways can be distinguished, namely, a direct and an indirect pathway. In the direct pathway, the first messenger elicits the intracellular signaling cascade directly through the interaction with its specific transmembranal receptor, which in most cases is a protein tyr kinase. Some of these enzymes are integral parts of the plasma membrane receptors, such as receptor tyrosine kinases. Others are individual proteins, which can bind to receptors and are regulated indirectly by both second-messenger pathways and receptor protein tyrosine kinases. In the indirect pathway, the first messengers trigger, upon binding to transmembranal receptors, the release or production of second messengers. Each of these second messengers activates specific sets of kinases, termed second messenger­dependent protein kinases, which propagate the intracellular signal. Common protein targets for such second messenger­dependent protein kinases are third-messenger phosphoproteins, second messenger­independent protein Ser/Thr kinases and protein Tyr kinases. Note that in physiological systems there exists virtually every type of molecular cross-talk between the different signaling cascades. Not illustrated in this figure are the actions of protein phosphatases that can antagonize the effect of protein kinases. Indeed, some protein phosphatases can also be regulated directly by second messengers, for example, calcineurin, which is activated by Ca2. Ligand binding induces conformational changes within the receptor, which in turn activates the intrinsic protein kinase or phosphatase properties. Subsequently, this activation triggers a cascade of phosphorylation state changes of substrate proteins, including kinases and phosphatases, which transmit the signal to evoke specific physiological responses. The direct mechanism is employed by most types of neurotrophic factors as well as many cytokines (Ch. Nomenclature and reactions of phosphoinositides are discussed further in Chapter 23. The second messengers subsequently activate protein kinases and/or protein phosphatases, typically from the Ser/ Thr class. These so-called second messenger­dependent kinases and phosphatases in turn regulate the phosphorylation or dephosphorylation of specific substrate proteins, including kinases and phosphatases, triggering a signaling cascade of one or more steps to elicit specific physiological responses. This indirect mechanism is utilized by first messengers that act through G-protein­coupled receptors, including receptors for many neurotransmitters, hormones, cytokines and sensory stimuli such as visible light and odorants (Ch. The human kinome, a term used for the total entity of protein kinases within the human genome, is composed of 518 protein kinase genes and accounts for about 2% of all human genes (Manning et al. According to their substrate specificity protein kinases are grouped into two classes: (1) the protein Ser/Thr kinases, which phosphorylate substrate proteins on Ser and/or Thr residues, and (2) the protein Tyr kinases, which phosphorylate substrate proteins on Tyr residues (Ch. The human kinome comprises 428 protein Ser/Thr kinases and 90 protein Tyr kinases (Manning et al. A small number of protein kinases are referred to as dual-specificity kinases, because they can phosphorylate substrate proteins on Ser and Thr residues as well as Tyr residues. Over 85% of protein phosphorylation occurs on Ser residues, around 12% on Thr residues, and less than 2% on Tyr residues (Shi, 2009). Protein kinases differ in their cellular and subcellular distribution, substrate specificity and regulation Despite their large number, each of the protein kinases has a specific physiological role. This functional specificity amongst kinases is achieved because each of the kinases features unique transcriptional regulation as well as characteristic structural properties. First, protein kinases exhibit distinct spatio-temporal expression patterns and expression levels due to alternative transcriptional and translational regulation. Most of the protein kinases are expressed in brain, albeit with differences amongst cell-types (Hunter, 1995). Second, protein kinases have distinct substrate specificities, enzymatic regulation and subcellular localization due to molecular and structural differences. The catalytic domain is conserved and shares high levels of homology amongst protein kinases. The structural properties of the substrate-binding pocket determine the sequence specificity and hence the consensus motif for substrates of each kinase (Table 25-1). Sequence variability within the kinase domain accounts for most of the diversity in substrate specificity of kinases. Some of the kinases act specifically on only one or a handful of proteins, while others are multifunctional and have a broad range of substrates. In addition to the kinase core, most of the protein kinases feature additional functional domains, which regulate kinase activity, molecular interactions and intracellular localization. Tight control over kinase activity is imperative for proper functioning of the cell, which is reflected in the multitude of regulatory mechanisms amongst kinases. Many kinases contain inhibitory domains that either directly interact with or sterically hinder access to the catalytic site. A special variation of an inhibitory domain is a so-called pseudosubstrate motif, which by mimicking a substrate can bind to the catalytic domain and can thereby block it. Many kinases are subject to allosteric regulation, whereby the kinase is controlled via the binding of an effector molecule at an interaction motif other than the catalytic kinase domain. Allosteric activation of kinases is commonly triggered by binding of small molecules and cofactors, such as second messengers, as well as by protein­protein interactions. Alternatively, activation of kinases can be regulated by phosphorylation and/or dephosphorylation at regulatory motifs. The control of kinase activity via regulatory phosphorylation is of particular importance and widespread application. This dendrogram or phylogenetic tree delineates the different protein kinase families encoded in the human genome. The proximity between the different kinases reflects the relative degree of homology and relationship between the individual protein kinase sequences. In addition to their conserved catalytic kinase domain, protein Ser/ Thr kinases contain multiple functional domains that regulate kinase activity, molecular association and subcellular localization. In fact, regulatory phosphorylation is commonly utilized to filter, specify, diversify and amplify intracellular signaling. Finally, kinase activity can be regulated through control of their location in the cell relative to their substrates. Most kinases contain functional domains, which promote molecular interaction with proteins, lipids and other small molecules. Many of these interaction domains serve to localize the kinases to confined subcellular compartments. The functionality of the different interaction domains is commonly controlled via regulatory phosphorylation. They affect many neuronal functions via phosphorylation of a broad range of neuronal substrates. In the next section of this chapter we will introduce important examples of each major class of protein Ser/Thr kinases (listed in Table 25-1). In mammals, there are three isoforms of the C subunit, designated C, C and C, which exhibit similar substrate specificity. Also indicated are the consensus motifs for substrates of some of the kinases and their corresponding regulatory cofactors. Most of the protein kinases presented here are expressed in many cell types, including neurons. These kinases have been included here because of their particular significance in neuronal functions. Many other protein kinases have been omitted that may also play a vital role in many cellular functions including neuronal processes. Upon activation, the enzyme associates with membranes including the plasmalemma or Golgi membranes, or the nuclear envelope, the locations of many of its physiological substrates. Therefore, the spatial regulation via specific scaffold proteins can confer distinct substrate selectivity to individual isoforms. Such molecular mechanisms are believed to play an important role in synaptic plasticity and memory (see Ch. The regulatory domain contains (1) the autoinhibitory site, which, in the resting state, binds to and inhibits the catalytic domain, (2) the Ca2/calmodulin-binding site and (3) several regulatory phosphorylation sites. The inhibition by the autoinhibitory motif is relieved when Ca2/calmodulin binds to the regulatory domain. Second messenger­independent protein Ser/Thr kinases Although the second messenger­dependent protein kinases were identified first as playing an important role in neuronal function, we now know that many second messenger­ independent protein Ser/Thr kinases regulate numerous fundamental neuronal functions. Their activity is commonly controlled by regulatory phosphorylation and/or association with regulatory cofactors. They are proline-directed protein kinases and hence phosphorylate substrates predominantly at Ser-Pro and Thr-Pro motifs. The signal transduction steps involving protein phosphorylation are indicated with (p).

However pulse pressure aortic regurgitation 2.5 mg plendil with visa, neither this selectivity nor the molecular basis for binding of kinesin and other motors to membranes are well understood arteria sa plendil 5 mg generic. In addition heart attack in 30s plendil 10 mg cheap, biochemical fractionation studies showed differential association of kinesin-1s with specific organelles (Deboer et al blood pressure chart youth order plendil 5 mg mastercard. Current evidence suggests that the different combination of subunits may produce functionally diverse forms of conventional kinesin and allow transport of different types of organelles in mature neurons (Deboer et al blood pressure medication rebound effect plendil 5 mg buy low cost. In most cases, the initial identification of proposed polypeptides was accomplished by approaches aimed to detect isolated, high-affinity protein­protein interactions, including two-hybrid system assays and immunoaffinity purification procedures. These issues raise concerns about the physiological significance of many candidate receptor proteins identified to date. Additional work is needed to establish the precise functional role of each conventional kinesin subunit in this process. Multiple members of the kinesin superfamily are expressed in the nervous system Kinesin has been purified and cloned from many species, including Drosophila, squid, sea urchin, chicken, rat, and human. Both heavy and light chain subunits of conventional kinesin are highly conserved throughout. However, once the sequence of the kinesin motor domain was available, related proteins with homology only in the motor domain began to be identified. A careful analysis of kinesin superfamily sequences from many species led to the definition of a standardized kinesin nomenclature for 15 defined families of kinesins (Lawrence et al. Kinesin-2 family members have been implicated in assembly and maintenance of cilia and flagella and mutations in these motors can lead to sensory defects and polycystic kidney disease (Scholey, 2003). Kinesin-2 motors are heterotrimers with two related heavy chain subunits and a larger accessory subunit. Kinesin-3 family members were proposed as a synaptic vesicle motor because kinesin-3 mutants in the nematode C. The extent to which these kinesins reflect unique transport mechanisms rather than functional redundancy within the kinesin family is not known. For example, members of the kinesin-13 family have been implicated in both mitotic spindle function and in axonal membrane transport. Although kinesins were the last family of motor proteins to be discovered, the kinesin family has proven to be remarkably diverse. Fifteen distinct subfamilies in the kinesin family have been identified, all with homology in their motor domain (Lawrence et al. Within a subfamily, however, the more extensive sequence similarities are presumed to reflect related functions. At present, many questions remain about the function of these various motors in the nervous system. Cytoplasmic dyneins have multiple roles in the neuron the original identification of conventional kinesin as a plus end­directed microtubule motor suggested that it is involved in anterograde transport, but the identity of the retrograde motor remained an open question. Since flagellar dynein was known to be a minus end­directed motor, interest in cytoplasmic dyneins was renewed. Identification of the cytoplasmic form of dynein in nervous tissue came as an indirect result of the discovery of kinesin. This discovery led to purification and characterization of brain cytoplasmic dynein (Paschal et al. Like flagellar dyneins, the cytoplasmic dynein holoenzyme is a high­molecular weight protein complex comprising two heavy chains, two dynein intermediate chains, four light intermediate chains and various light chains that form a complex of more than 1,200 kDa (Brill & Pfister, 2000). As with the kinesins, dynein heavy chains are a multigene family with multiple flagellar and cytoplasmic dynein genes (Asai & Wilkes, 2004). There may be 10­15 dynein heavy chain genes in an organism, but the large size of the dynein heavy chain primary sequence slowed genetic analyses. At present, dynein genes are grouped as members of either flagellar or cytoplasmic dynein subfamilies. The three intermediate (74 kDa), four light intermediate (55 kDa) and a variable number of light chains present in dyneins may also have flagellar and cytoplasmic forms. The two or more cytoplasmic dynein heavy chain genes could be involved in different cellular functions, but much dynein functional diversity may be due to its many associated polypeptides (Susalka & Pfister, 2000). The intermediate and light chains of cytoplasmic dynein are thought to be important both for regulation and for interactions with specific cellular structures (Brill & Pfister, 2000). In addition, a second protein complex known as dynactin copurifies with cytoplasmic dynein under some conditions (Schroer, 2004). The dynactin complex is similar in size to dynein and contains multiple subunits that include p150Glued, dynamitin, an actin-related protein, and two actin capping polypeptides, among others. The p150Glued polypeptide interacts with both dynein intermediate chains and the actin related subunits. Dynamitin may play a role in the binding of cytoplasmic dynein to different types of cargo. Finally, the actin related protein (Arp1) forms a short filament that may include actin as well as actin-capping proteins. This short filament may interact with both p150Glued and components of the membrane cytoskeleton like spectrin. Dynactin may mediate cytoplasmic dynein binding to selected cargoes, including the Golgi complex and the membrane cytoskeleton. The wide range of functions associated with cytoplasmic dynein is matched by its complexity and its ability to interact with accessory factors (Susalka & Pfister, 2000). Additional proposed functions include a role in mitosis and in anchoring and localizing the Golgi complex. A number of studies have implicated cytoplasmic dynein as playing a role in retrograde axonal transport (Brady, 1991; Hirokawa, 1998). In the nervous system, the most frequent role proposed for dynein is a motor for retrograde axonal transport, but its properties are also consistent with a motor for slow axonal transport (Ahmad et al. The ability of dynactin to interact with both cytoplasmic dynein and the membrane cytoskeleton suggests a model in which dynactin links dynein to the membrane cytoskeleton, providing an anchor for dynein-mediated movement of axonal microtubules (Ahmad et al. Some anchoring role for the membrane-associated cytoskeleton in the mechanisms of slow axonal transport is likely, since neurons require interaction with a solid substrate for neurite growth. As observed for conventional kinesin, phosphorylation-based regulatory mechanisms for cytoplasmic dynein have been documented in neurons (Morfini et al. Different classes of myosin are important for neuronal function Myosins are remarkably diverse in structure and function. To date, 15 subfamilies of myosin have been defined by sequence homologies (Kalhammer & Bahler, 2000). The brain is an abundant source of non-muscle myosins and one of the earliest studied. Despite their abundance and variety, the roles of myosins in neural tissues have only recently begun to be defined (Bridgman, 2009; Brown & Bridgman, 2004). Myosin I is a singleheaded myosin with a short tail that uses calmodulin as a light chain (Kalhammer & Bahler, 2000). In many cell types it has been implicated in both endocytosis and exocytosis, so it may play an important role in delivery and recycling of receptors. Myosin I is enriched in microvilli and may also be involved in some aspects of growth cone motility, along with myosins from other subfamilies. The myosin I family has also been implicated in mechanotransduction by the stereocilia of hair cells in the inner ear and vestibular apparatus. A myosin I isoform, myosin I, has been localized to the tips of stereocilia, where it appears to mediate sensory adaptation by opening and closing the stretch-activated calcium channel (see Chapter 53). Two other myosin types have been implicated in hearing and vestibular function (Libby & Steel, 2000). Another myosin type that plays a role in nervous tissue is myosin V (Kalhammer & Bahler, 2000). Of the myosins identified in brain, myosin I and V are the strongest candidates to act as organelle motors, and myosin V has been reported in association with vesicles purified from squid axoplasm. Mice carrying the mutant dilute allele show defects in the movement of pigment granules, and this results in dilution of their coat color. These mice also exhibit complex neurological defects that may be due to altered endoplasmic reticulum localization in dendrites. Finally, there is evidence that myosin V plays a role in growth cone motility, where it is enriched in filopodia. Matching motors to physiological functions may be difficult the three classes of motors are similar in their biochemical and pharmacological sensitivities in many respects (Brady, 1991). The development of new pharmacological and immunochemical probes specific for different motors will facilitate future studies. Although many motor proteins are found in nervous tissue, there are few instances in which we fully understand their cellular functions. The proliferation of different motor molecules and the existence of numerous isoforms raise the I. There may be cases in which motors serve a redundant role to ensure that the physiological activity is maintained in the event of a loss or deregulation of a given motor protein. Finally, the existence of so many different types of motor molecules suggests that novel physiological activities requiring molecular motors may be as yet unrecognized. Inhibition of fast axonal transport results in loss of synaptic function and "dying-back" degeneration of axons. The earliest suggestions that inhibition of fast axonal transport could result in neurodegeneration came from studies on exposure to neurotoxins that inhibit transport. For example, the neurotoxicant acrylamide has been found to inhibit kinesin function directly. Similarly, neuropathies are a common side effect of the cancer therapeutic agent vincristine, which depolymerizes axonal microtubules. More recently, genetic evidence for a role of axonal transport in neurodegeneration has been obtained. Similarly, mutations in dynein have been implicated in "dying back" degeneration as well. For example, certain mutations in dynein heavy chain lead to sensory neuropathies in mammals (Dupuis et al. Curiously, mutations in the dynactin subunit p150Glued can produce symptoms of motor neuron disease (Laird et al. In many cases, mutant motor proteins are expressed in many neuronal and non-neuronal cells. Moreover, different mutations in the same molecular motor protein subunit can cause different pathologies. A molecular basis for the increased vulnerability of selected neuronal populations to mutations in specific motor subunits is currently unknown, but may result from unique functional specializations of these neuronal cell types. Regardless, a strong body of genetic evidence supports the notion that deficits in fast axonal transport suffice to cause "dying-back" degeneration of neurons (Morfini et al. Accordingly, alterations in fast axonal transport have been documented in all these diseases (Morfini et al. These diseases are not associated with mutations in molecular motors, so other mechanisms are thought to underlie the abnormalities in fast axonal transport observed in each disease. A physiological change common to all of these diseases is alterations in the activity of specific protein kinases (Wagey & Krieger, 1998). Interestingly, many of the kinases altered in neurodegeneration have been implicated in regulation of motor protein function, providing a potential pathogenic mechanism (Morfini et al. Such diseases represent a novel class of neurological disease that can be collectively characterized as "dysferopathies" from the Greek word for transport or carry (Morfini et al. Given the unique dependence of neurons on axonal transport for development and maintenance of neuronal function, these processes provide an explanation for the selectivity of these pathologies for neurons. These early pathological events precede neuronal cell death, but correlate well with the onset of early symptoms of disease (Morfini et al. This pattern of cell degeneration suggests that early pathological events in the synaptic and/or axonal compartments may be central to the pathogenesis of disease. Patients exhibit adult-onset progressive muscle weakness and spastic paralysis of the lower limbs and often require a walker or wheelchair. This expression pattern suggests that a partial reduction in fast axonal transport is sufficient to cause neurodegeneration. This suggests that a partial reduction in axonal transport may not produce clinical symptoms in affected neurons for years or even decades. Third, although kinesin-1a is expressed throughout the brain, only upper motor neurons degenerate. This selective degeneration suggests that reductions in specific components of axonal transport can produce degeneration of specific neuronal populations while leaving other neuronal populations relatively unaffected. More recent data have given further insight into the role of axonal transport in neurodegeneration. Recent data show an inhibitory effect of pathogenic spastin mutations on both anterograde and retrograde fast axonal transport (Solowska et al. Deficits in axonal transport have been implicated in other forms of dying back neuropathy (Morfini et al. More work is needed to more clearly elucidate the role of axonal transport in the pathogenesis of these and other dying-back neuropathies, but the common features shared among these various neurodegenerative diseases may provide an avenue for therapeutic intervention based on an understanding of the prominent role played by deficits of axonal transport in neurodegeneration. Quantitative and functional analyses of spastin in the nervous system: implications for hereditary spastic paraplegia. Acknowledgments the authors would like to thank Janet Cyr and Richard Hammerschlag for their efforts on related chapters in earlier editions. Cytoplasmic dynein and dynactin are required for the transport of microtubules into the axon. Inhibition of kinesin synthesis and rapid anterograde axonal transport in vivo by antisense oligonucleotide. Video microscopy of fast axonal transport in isolated axoplasm: A new model for study of molecular mechanisms.

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Despite the lifelong propensity to express intense seizures in response to low-intensity stimulation hypertension jnc8 generic 10 mg plendil with visa, spontaneous seizures or a truly epileptic condition do not occur until approximately 100 stimulation-evoked seizures have occurred blood pressure medication for sleep discount generic plendil canada. A variety of models exist in which epilepsy arises weeks after an episode of status epilepticus pulse pressure of 30 cheap 10 mg plendil with amex, a state of continuous seizures lasting hours blood pressure 10060 buy plendil 5 mg with mastercard. Indeed hypertension 14070 generic 10 mg plendil overnight delivery, the discovery that complicated febrile seizures are followed by and thus are almost certainly one cause of hippocampal sclerosis in young children establishes yet another commonality between these models and the human condition (VanLandingham et al. The uniqueness of the innervation of their targets by the granule cells underscores their function as gatekeepers. Using deoxyglucose autoradiography studies, the dentate granule cells did indeed appear to function as a barrier for invasion of hippocampus by seizure activity in vivo (Collins et al. Functional evidence for the presence of recurrent excitatory synapses has emerged from synaptic physiological studies of slices in the pilocarpine model. Nonetheless, the extent to which this reorganized network of dentate granule cells contributes to the hyperexcitability of the epileptic brain is uncertain at present. While alterations in dentate granule synaptic physiology and anatomy provide a snapshot to begin to understand how a normal brain changes to an "epileptic" brain, the dentate granule cells represent only one small piece of the complex puzzle of how a normal brain becomes epileptic. A myriad of changes have been reported to occur in neurons elsewhere in the hippocampus and other regions of the brain. Therefore, when one begins to assess the hyperexcitability of the epileptic brain, it is imperative to view these alterations on a global platform, and not just localized to a single population of neurons, in order to appreciate the vast complexities that are involved. Epileptogenesis is the process by which a normal brain becomes epileptic the very complexity of understanding mechanisms underlying the hyperexcitability of the epileptic brain has contributed to enhanced emphasis in attempts to prevent development of epilepsy, that is, epileptogenesis. Interestingly, many forms of partial epilepsy are characterized by a seizurefree interval lasting months to years between the occurrence of the causative insult and the emergence of epilepsy; termed the "latent period," this provides a valuable window of opportunity during which pharmacologic intervention might be implemented in high-risk individuals so that development of epilepsy could be prevented. This is manifested as continued presence of seizures in spite of anticonvulsant therapy (Cascino, 2009; Berg et al. Also, consistent with this hypothesis, a progressive increase in spontaneous seizure frequency has been observed in a number of animal models following a diversity of epileptogenic insults (Noè et al. Axonal and dendritic sprouting lead to abnormal recurrent excitatory synaptic circuits among the dentate granule cells in epileptic brain Repeated seizures have been demonstrated to result in a structural reorganization of hippocampal circuitry, a reorganization that increases substantially in the presence of cell death as occurs often in temporal lobe epilepsy. The best-described structural reorganization is that in which axons of the excitatory granule cells sprout and reinnervate themselves and/ or their neighbors through recurrent collaterals, forming a feed-forward excitatory loop coined "mossy fiber sprouting" (Nadler, 2003). More recently, sprouting of basilar dendrites of the granule cells has also been identified and these provide additional targets for the sprouted axons (Ribak et al. Studies of the kindling model established the critical role of pathological activity in the pathogenesis of partial epilepsy. This led to the question as to what molecular consequences of pathologic activity might mediate the transformation of a normal brain to an epileptic brain. The hypothesis that early complicated febrile seizures cause epilepsy has led to intense research into the mechanisms by which "seizures beget seizures. Epileptogenesis research, utilizing a number of animal models, seeks to understand these mechanisms and to identify such targets. Using a number of cellular and molecular approaches to study these animal models, researchers have identified molecules that play important roles in this process and that may therefore be attractive therapeutic targets for preventing epileptogenesis following seizures. Rapamycininduced reductions in the subsequent emergence of spontaneous recurrent seizures have been observed in some but not all of these studies (Buckmaster & Lew, 2011; Zeng et al. Indeed, seizure-induced TrkB activation has been observed in the mossy fiber pathway (Danzer et al. It is thought that TrkB activation is pro-epileptogenic, because mice lacking TrkB in forebrain neurons are unable to undergo epileptogenesis in the kindling model of epileptogenesis (He et al. Consequently, selective inhibitors of TrkB may be effective anti-epileptogenic agents. This research will be greatly assisted by the availability of small molecule libraries that can be screened for favorable interactions with targets identified in animal studies of epileptogenesis. It is hoped that these lines of research will lead to clinical trials for methods of therapeutic intervention after status epilepticus, but before the development of spontaneous recurrent seizures. Rapamycin suppresses mossy fiber sprouting but not seizure frequency in a mouse model of temporal lobe epilepsy. The mammalian target of rapamycin signaling pathway mediates epileptogenesis in a model of temporal lobe epilepsy. By contrast, epileptogenesis in the kindling model is prevented altogether in mice in which both alleles of the TrkB gene are eliminated (He et al. These findings focus the search for mechanisms of epileptogenesis on structural and functional consequences of TrkB activation. By contrast, epileptogenesis develops as in wild-type animals in genetically modified mice in which TrkB activation of Shc signaling is eliminated (He et al. Some antiseizure drugs work mechanistically by prolonging the inactivation of the Na channel, thereby reducing the ability of neurons to fire at high frequencies. Antiseizure drugs known to promote inactivation of this channel include carbamazepine, phenytoin, topiramate, lamotrigine, valproate, and zonisamide. Note that the inactivated channel appears to remain open but is blocked by the inactivation gate (I) at the pore. Stated differently, depolarization-triggered opening of the Na channels in the axonal membrane of a neuron is required for an action potential; after opening, the channels spontaneously close, a process termed inactivation (see Ch. This inactivation is thought to mediate the refractory period-the brief period following an action potential during which it is not possible to evoke another action potential. Upon recovery from inactivation, the Na channels are poised to participate in generation of another action potential. Because firing at a slow rate permits sufficient time for Na channels to recover from inactivation, inactivation has little or no effect on lowfrequency firing. However, reducing the rate of recovery of Na channels from inactivation would limit the ability of a neuron to fire at high frequencies, an effect that most probably underlies the effects of carbamazepine, lacosamide, lamotrigine, phenytoin, rufinamide, topiramate, valproic acid, and zonisamide against partial seizures. The experimental control and accessibility available in these models combined with use of clinically relevant concentrations led to clarification of the mechanisms of various antiseizure medications. Although difficult to prove that a given antiseizure drug effect observed in vitro is the mechanism by which a drug acts in vivo to inhibit a seizure, there is a strong likelihood that the putative mechanisms identified in the laboratory underlie actions in vivo in humans. This pattern of neuronal firing is the hallmark of a seizure and is rare during physiological activity. Therefore, the selective inhibition of this high-frequency firing pattern would be expected to reduce seizures, hopefully with minimal unwanted effects. Carbamazepine, lamotrigine, phenytoin, and valproic acid modulate high-frequency firing at concentrations known to be effective in the limitation of seizures in humans (Macdonald & Greenfield, 1997). This mechanism probably underlies the effectiveness of these compounds against partial and tonic­clonic seizures in humans. Other antiseizure drugs regulate a subset of voltage-gated calcium currents In contrast to partial seizures, which arise from localized regions of the cerebral cortex, the "absence" or "petit mal" form of generalized-onset seizures arises from the reciprocal firing of the thalamus and cerebral cortex (Huguenard, 1999). Although a detailed consideration of the mechanisms is beyond the scope of this chapter, many of the structural and functional properties of thalamus and cortex that underlie the generalized spike-and-wave discharges of petit mal or absence seizures have been clarified in the past decade (Huguenard, 1999). These bilaterally synchronous spike-and-wave discharges, recorded locally from electrodes in both the thalamus and the neocortex, represent oscillations between thalamus and cortex. Certain antiseizure drugs reduce the flow of calcium through T-type Ca2 channels (ethosuximide, valproate), thereby reducing the pacemaker current that underlies spike-wave discharges of generalized absence epilepsy. However, only a small fraction (less than 5%) of the epilepsies are inherited in a Mendelian pattern in which the cause can be traced to a single mutant gene. Tables 40-3 and 40-4 list the genes responsible for idiopathic and symptomatic epilepsies in humans, respectively. As noted above in descriptions of epilepsy syndromes, the idiopathic epilepsies affect individuals who are otherwise normal and in whom no structural cause has been identified. Perhaps the most remarkable feature of the genetic causes of the idiopathic epilepsies is that the vast majority of these genes encode an ion channel gated by voltage or a neurotransmitter. This is of particular interest because several other episodic disorders involving other organs also are caused by mutations of genes encoding ion channels. For example, episodic disorders of the heart (cardiac arrhythmias), skeletal muscle (periodic paralyses, see Ch. In none of these episodic disorders is it understood what triggers an event or what terminates the event. Identification of the genes permits engineering mutant mice that, it is hoped, will exhibit epilepsy. Substantial progress is being made in characterizing mutant mouse models with mutations engineered to mimic those found in humans with epilepsy. These mice, along with other strains, will provide tools vital to determining how the genotype leads to the phenotype. Apart from determining steps, if any, between expression of a mutant ion channel and emergence of epileptic seizures, in some instances the mutant channels suggest some intriguing molecular targets for development of antiseizure drugs acting by novel mechanisms. These channels provide a novel molecular target for development of antiseizure drugs. These results highlight the benefits that may be gained from studying animal models that closely mirror the human condition. Table 40-4 lists a number of symptomatic epilepsies of humans for which mutant genes have been identified. As suggested by the terminology, these epilepsies are symptomatic of some overt underlying disease, some of which begin at various times in the first decade of life or later and are progressive whereas others exhibit catastrophic neurological abnormalities at birth and do not progress further. In contrast to the striking homogeneity with respect to genes encoding ion channels in the idiopathic epilepsies, the genes causing the symptomatic epilepsies are striking in their diversity. Some spontaneous and some engineered mutations of mice result in epilepsy In parallel to identification of the genes causing human epilepsies, many genes causing epilepsy in mice have been identified (Table 40-5). In most instances, the genes were overexpressed or eliminated and the epileptic phenotype was an unexpected consequence. However, the occurrence of an epileptic phenotype in mice carrying null mutations of synapsin 1 was unexpected until this mutation was shown to preferentially compromise the efficacy of inhibitory synaptic transmission (Terada et al. Finally, linkage analysis followed by sequencing led to identification of genes in spontaneously arising mutations that had been found to cause epilepsy in mice. In most of these, the nature of the epilepsy was a generalized spike and wave, mimicking the generalized onset epilepsies like absence. In contrast to absence epilepsy in humans, many of these mutant mouse strains exhibit cerebellar ataxia and often degeneration. Like the idiopathic epilepsies of humans, many of these genes encode ion channels. Interestingly, none of the mutant genes in these mouse strains have been identified as causing a form of absence epilepsy in humans. Interneuron diversity series: Circuit complexity and axon wiring economy of cortical interneurons. Functional anatomy of limbic seizures: Focal discharges from medial entorhinal cortex in rat. Commission on Classification and Terminology of the International League Against Epilepsy, (1981). Commission on Classification and Terminology of the International League Against Epilepsy, (1989). Proposal for revised clinical and electroencephalographic classification of epileptic seizures. Disruption of TrkB-mediated phospholipase C gamma signaling inhibits limbic epileptogenesis. Neuronal circuitry of thalamocortical epilepsy and mechanisms of antiabsence drug action. Continuous electroencephalographic monitoring with radio-telemetry in a rat model of perinatal hypoxia­ischemia reveals progressive post-stroke epilepsy. Kindling increases N-methyl-D-aspartate potency at single N-methyl-D-aspartate channels in dentate gyrus granule cells. Repeated brief seizures induce progressive hippocampal neuron loss and memory deficits. Suppression of pilocarpineinduced status epilepticus and the late development of epilepsy in rats. Supragranular mossy fiber sprouting is not necessary for spontaneous seizures in the intrahippocampal kainate model of epilepsy in the rat. Neuropeptide Y gene therapy decreases chronic spontaneous seizures in a rat model of temporal lobe epilepsy (131). Channelopathies: Ion channel disorders of muscle as a paradigm for paroxysmal disorders of the nervous system. Dendritic growth cones and recurrent basal dendrites are typical features of newly generated dentate granule cells in the adult hippocampus. Spontaneous seizures and loss of axo-axonic and axo-somatic inhibition induced by repeated brief seizures in kindled rats. Development of spontaneous recurrent seizures after kainate-induced status epilepticus. Arrested maturation of excitatory synapses in autosomal dominant lateral temporal lobe epilepsy. Another feature observed in most common neurodegenerative diseases-as well as in other common conditions such as certain forms of cancer-is the prominent dichotomy of familial (rare, often following Mendelian inheritance) vs. The latter are also frequently described as "sporadic" or "idiopathic" forms, although this terminology has proved oversimplistic since a large proportion of apparently "sporadic" cases are actually also significantly influenced by genetic factors. Despite the previous successes and recent advances in molecular and analytic techniques, the identification of genuine risk factors for the diseases outlined in this chapter-genetic and non-genetic-is aggravated by several circumstances. First, while diagnostic criteria have been proposed for all syndromes, these are usually based on clinical and/or neuropathological observations, which are never 100% specific and may even be assessed differently from one research center to the next. Depending on the observed or suspected mode of inheritance, the search for disease-related sequence variants typically involves mutation screenings (Mendelian forms) or association analyses (non-Mendelian or sporadic forms).

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References

• Warren JW: The catheter and urinary tract infection, Med Clin North Am 75:481n493, 1991.
• Isaacson MK, Juckem LK, Compton T. Virus entry and innate immune activation. Curr Top Microbiol Immunol. 2008;325: 85-100.
• Calam R, Gregg L, Simpson B, et al. Childhood asthma, behavior problems, and family functioning. J Allergy Clin Immunol 2003; 112: 499-504.
• Diaz JH. Perioperative management of neonatal Ectopia cordis: report of three cases. Anest Analg. 1992; 75:833-7.
• Griffin T, Tooher R, Nowakowski K, et al: How little is enough? The evidence for post-vasectomy testing, J Urol 174:29n36, 2005.