By W. Pedar. Liberty University. 2018.
Such currents are thought to stimulate only a few neurons generic tenormin 50 mg otc high blood pressure medication and zyrtec, but the exact number of stimulated cells and APs is unknown in these studies generic tenormin 100mg online heart attack 1 hour. Small Numbers of APs in Single Cells of the Primary Motor Cortex Can Evoke Movements If few APs mediate information processing in the primary motor cortex, one may assume that small numbers of APs can affect movement generation. Consistent with this idea, it is known that intracortical microstimulation can evoke movements at current levels of 1–2 µA. Whisker movements offer special advantages because they can be easily quantiﬁed and they escape anesthesia-induced paralysis (Figure 1. Whisker movements evoked by intracellular stimu- lation were usually of small amplitudes (on the average about 0. Movements evoked by intracellular stimulation were complex because they consisted of long sequences of movements (a duration of many seconds, Figures 1. B, coronal section through M1 with topographic position, and the morphology of the stimulated pyramid in L6. The cell was recorded close to a site where extracellular stimulation evoked backward movement of C and B whisker rows. C, membrane potential recordings and injection pattern of depolarizing current steps during intracellular stimulation (10 action potentials (APs) at 100 Hz). Thus, it seems that small numbers of APs in single M1 cells could specify motor programs for whisker movements. However, it is of considerable size if one takes into account that movements are very small under anesthesia. The ongoing whisker movements in the case shown above were only about 1˚ or less in amplitude (see the single trial data in Figure 1. Thus, 10 APs in one of a million cells can evoke movements with amplitude within the range of the ongoing movements. Taken together, the evidence suggests that APs in M1 are highly effective in evoking movements and that only a very small fraction of M1 cells is active during movement generation in the vibrissae motor cortex. The number of cells that are effective in evoking movements, however, is much larger (20%). SILENT NEURONS AND CORTICAL PLASTICITY The second part of this chapter is concerned with the functional signiﬁcance of silent cortical neurons. If >90% of neurons are silent, the presence of so many silent neurons is a central problem of cortical physiology. The major goal of this section will be to frame questions that could guide research on the signiﬁcance of silent cortical cells. Silent Cortical Cells as a Corollary of Metabolic Demands Theory holds that it is implausible that many cortical cells can be active at any given time due to energetic costs of ﬁring APs. Contribution of Silent Cells to Learning and Cortical Plasticity What if the animal was posed with learning a novel situation where it could adapt, learn, and perform? An attractive hypothesis for silent cortical cells places them in © 2005 by Taylor & Francis Group. They are conspicuously quiet targets for transformation during plasticity into substrates for nascent neural activity. A con- version of a silent to a spiking neuron is thought to occur as a consequence of a plastic change/learning process and may enhance the ability of the cortical network to adapt to changing demands. A hypothesis like this was expressed (among others) by Dykes and colleagues2 and by Moore and Nelson 199823 which suggested that the large subthreshold RFs of cortical cells serve this purpose. Tenuous support for an idea like this is that silent cortical cells seem to be anatomically integrated into the normal network of cortical neurons and evidence implicates networks in learning and memory. Studies on expression of immediate early genes show that large num- bers of cortical neurons change gene expression during cortical plasticity; these data thus point to activity in (putatively the erstwhile) silent cells. Silent Cells May Signal by Non AP-Dependent Signaling Not all neural communication among cortical neurons depends on AP generation. Thus, pre- and postsynaptic neurons exchange complex molecular signals and com- municate electrically via miniature PSPs in the absence of APs. These forms of neural communication deserve special attention and may be important for maintain- ing synaptic strengths in cortical and particularly silent cortical cells. Silent Cells May Function by Sparse AP Activity Although most cortical cells in sensorimotor cortices ﬁre APs only rarely, even such sparse AP activity, if it is close temporal relation with other sparsely ﬁring neurons (ie. DATA ON AN INVOLVEMENT OF SILENT CELLS IN PLASTICITY ARE LARGELY ABSENT Critical experiments on the signiﬁcance of silent cortical neurons have not been done yet.
Heart failure in the normal mend prenatal interruption of the blood vessel connec- twin is common buy cheap tenormin 100mg line blood pressure medication gluten free. The normal twin of an acardiac twin tions (thus sacrificing the acardiac twin) before heart pregnancy has about a 10% risk for malformations buy generic tenormin 50mg on line blood pressure chart for excel. Improvement of thera- be accomplished by cauterizing or burning the blood ves- pies will undoubtedly lead to a better outlook for preg- sel connections. GALE ENCYCLOPEDIA OF GENETIC DISORDERS 9 Resources The same cannot be said for drugs derived from vita- min A. Accutane, like other retinoids, displays some of PERIODICALS the same biologic properties as vitamin A, such as its role Arias, Fernando, et al. Four to five months of Accutane treatment usually leads to clearing of the acne for one Mohanty, C. Milder cases of acne that produce scarring or other related skin disorders ORGANIZATIONS may also be treated with this medication. Hawkins, MS Common side effects of Accutane are chapped lips, dry skin with itching, mild nosebleeds, joint and muscle pain, and temporary thinning of hair. Depression, includ- ing thoughts of suicide, has been reported more recently as another, much more serious, potential side effect. Severe acne on its own is associated with lower self- IAccutane embryopathy esteem. As of 2001, no studies have been published to try to determine if Accutane use somehow makes it more Definition likely for a person to be depressed or to attempt suicide. Accutane is commonly used to treat severe acne that The United States Food and Drug Administration has not responded to other forms of treatment. Accutane-related birth defects typi- provision that the drug label would describe its risk of cally include physical abnormalities of the face, ears, causing birth defects. Description The first report of an infant with Accutane-related Accutane is one of several man-made drugs derived birth defects was published in 1983. The generic name for Accutane is tional cases were subsequently reported to the FDA and isotretinoin. Vitamin A is an essential defects involving the head, ears, face, and heart was nutrient for normal growth and development. Edward Lammer reviewed a total in foods such as green leafy and yellow vegetables, of 154 pregnancies exposed to Accutane. Each of the oranges, pineapple, cantaloupe, liver, egg yolks, and but- pregnancies had included use of the drug during the first ter. It is also available in multivitamins and separately as three months of pregnancy. Vitamin A is important in a number first trimester, is a critical and sensitive time during of biological processes. Chemical growth and differentiation of the epithelium, the cells that insults during this part of pregnancy often result in form the outer layer of skin as well as some of the layers abnormal formation of internal organs with or without beneath. Of these, twelve (20%) ended does not seem to be associated with an increased risk for in a spontaneous pregnancy loss, or miscarriage. These preg- abnormalities observed among the stillborn and living nancies have been voluntarily reported either directly to infants were similar, most frequently involving the head, the manufacturer or to the Slone Survey. Thus, use of tors have referred some, a majority of participating Accutane during the first several months of pregnancy women obtained the appropriate phone numbers from was shown to be associated with an increased risk of the insert included with their medication. Elective termi- pregnancy loss (miscarriage or stillbirth) as well as with nations of pregnancy were performed in 1,214 pregnan- a significant risk of birth defects in living children. Spontaneous pregnancy losses were reported in 213 pattern of abnormalities has since become known as pregnancies and 383 infants were delivered. The term retinoic acid embry- 162, or 42%, were born with malformations consistent opathy is also occasionally used to describe the same with AE. Any woman to whom Accutane is prescribed is psoriasis and can cause birth defects even if stopped invited to contact and participate in the project. September 2000, the survey had identified a total of 1,019 pregnancies out of more than 300,000 women Genetic profile enrolled. Some women were already pregnant when they Accutane embryopathy (AE) is not an inherited or had started Accutane but others conceived while taking hereditary type of abnormality. The pregnancy data allows for examination of exposure of a developing embryo to the drug, Accutane, the risk factors that lead to becoming pregnant as well as during the first trimester of pregnancy. Among the 1,019 pregnancies known, powerful teratogen, or agent that causes physi- that occurred, 681 were electively terminated, 177 cal or mental abnormalities in an embryo.
EON also uses Protégé as the medical knowledge acquisition tool to help medical practitioners provide medical decision criteria 100 mg tenormin mastercard hypertension jokes. This code is platform independent and can be shared between decision support systems that are EON compliant cheap 100mg tenormin mastercard hypertension 55 years. EON is widely used in European countries and one of the major decision support system that uses EON is PRODIGY. The decision support system ATHENA, which provides hypertension related advices, also uses the EON guideline model as its decision support architecture. GEM (Guideline Elements Model) GEM, an XML- (Extensible Markup Language) based guideline document model was introduced in 2000 by Yale center of medical informatics. This initiative is intended to facilitate the translation of medical guideline documents to a standard computer inter- pretable format. The key difference between the other techniques and GEM is that it uses the industry standard XML for knowledge transfer purposes. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. Medical Decision Support Systems and Knowledge Sharing Standards 213 made up of 100 discrete tags and 9 major branches. These branches are identity, developer, intended audience, target population, method of development, testing, review plan, and knowledge components (Shiffman, Karras, Agrawal, Chen, Marenco, & Nath, 2000). While the goal of all of these knowledge transfer techniques is the same, they differ in their implementation strategies. The strength of this model is that it encodes both the recommendations and adequate information about the guideline recommendations, including its reason and quality of evidence (Shiffman et al. Knowledge extraction in GEM is a simple document markup rather than a programming task. GEM uses a knowledge acquisition tool called GEM Cutter to interactively gather he knowledge data and store it in a XML format. GLARE (Guide Line Acquisition Representation and Execution) GLARE is a medical domain independent guideline model system for acquiring, repre- senting, and executing clinical guidelines. GLARE was introduced in 1997 by the Dipartimento di Informatica, Universita del Piemonto Orientale, Alexandria, Italy. The GLARE Knowledge representation language is designed to satisfy both the complexity and expressive rules. It consists of plans and atomic actions that can be queries, decisions, work actions, and conclusions (Open Clinical-Glare, 2004). GLARE knowledge acquisition system is an easy to use graphical user interface with syntactic and semantic verifications to check the formulated guidelines. Artificial intelligence temporal reasoning techniques are applied to weed out inconsistencies. The GLARE system goes one step ahead and also incorporates a decision support system for knowledge execution purposes. GLARE system has been tested for applicability in medical domains like bladder cancer, reflux esophagitis, and heart failure at the Laboratorio di Informatica Clinica, Torino, Italy. Future Trends While medical decision support systems have been around for the past four decades, its usage among clinicians is still questionable. Several variables play a role in a success of a medical decision support system and it is important to address these to move ahead from where we stand now. Issues like physician reluctance, intimidating systems, proprietary interests, local practice, technological factors, and outdated knowledgebase are all limiting factors for the growth and acceptance of computer-based decision support Copyright © 2005, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. In addition to these limitations, the decision making functions are no longer limited to the physicians. The patients, healthcare administrators, insurance carriers, healthcare professionals, policy makers, risk analysts, and the government at large are all stakeholders in this medical decision making process. It will be extremely limiting to tie down these requirements to local proprietary computer systems. While the field of medicine pioneered the knowledge sharing techniques among decision support systems, the introduction of several sharing standards segmented market as a net result defeated the purpose of such standard.