By W. Onatas. Knoxville College. 2018.
The two service users linked the study to the wider SUCCESS group by reporting back on the study and seeking feedback from the SUCCESS group to inform their contributions generic confido 60caps visa. We recruited two service users to the TSC through Involving People (URL: www discount confido 60caps with visa. We followed best practice by ensuring all users received honoraria, expenses, training and support, a named contact, information and networking opportunities. Ethics We obtained full ethics approval for the main protocol and all subsequent amendments from the Multicentre Research Ethics Committee for Wales (reference number 10/MRE09/25). We received research and development permissions to conduct the trial across Wales, and Information Governance Review Panel permission to use the SAIL databank. We complied with the CONSORT guidelines82 for reporting randomised trials and completed the CONSORT checklist when presenting findings from the trial. We also completed the CONSORT extension checklists for cluster trials, patient-reported outcomes, abstracts and harms. Changes to the published protocol The follow-up qualitative interviews/questionnaires were carried out at the end of the intervention phases (between October 2014 and January 2015). They were originally planned for 9 months after implementation of the intervention within each network. We originally intended to compare time to first emergency admission but revised this plan without carrying out this analysis – on consideration, we concluded that emergency admissions per patient per year at risk would be the most appropriate analysis for this highly skewed data. We did not include mortality as an outcome in our original protocol. We think it is important to document this as part of the study and have included it within Chapter 4. Some practices were unable to facilitate PRISM receipt and training in their allocated month, and hence their receipt dates occurred later in the intervention phase in Figure 4. Clinical effectiveness results Data analysed and baseline characteristics We have history of NHS contacts over the study period [from 1 February 2013 (study day 1) until 30 September 2014] on 230,114 participants, 15 of whom spent the whole study period in hospital. We were therefore able to include outcomes from routine NHS records in control and/or intervention phases on 230,099 participants. Table 15 summarises various characteristics of these participants, both overall and by PRISM risk group. Durations in the control and intervention phases As Figure 4 illustrates, the study design includes a relatively short initial period in which all participants are in the control phase, and a longer final period in which all participants still registered at a study practice are in the intervention phase; between these periods, participants transfer from one phase to another as the PRISM tool is made available at their practices. This design means that the mean length of time spent by a participant in the intervention phase is longer than in the control phase. Outcomes from anonymised routine linked NHS data Tables 17–22 present the results of primary and secondary outcomes derived from anonymised routine linked NHS data sets. We provide raw and adjusted comparisons between groups, ICC in variables between participants at the same study practice, and details of statistically significant factors and covariates. The adjusted comparison reflects the nature of the variable under consideration: we present an OR for logistic regression models for binary variables; an incident or event rate ratio Λ from negative binomial models for count variables, and an additive group effect (Δ, in the same units as the dependent variable) for linear models for continuous variables. This issue may be freely reproduced for the purposes of private research and study and extracts (or indeed, the full report) may be included in professional journals 35 provided that suitable acknowledgement is made and the reproduction is not associated with any form of advertising. Applications for commercial reproduction should be addressed to: NIHR Journals Library, National Institute for Health Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK. CLINICAL EFFECTIVENESS TABLE 15 Baseline demographic and clinical characteristics for participants Variable Proportion % Gender Group All Female 115,251/230,098 50. TABLE 16 Durations of the control and intervention phases for participants Variable Mean SD n Days in the control phase Group All 226. This issue may be freely reproduced for the purposes of private research and study and extracts (or indeed, the full report) may be included in professional journals 39 provided that suitable acknowledgement is made and the reproduction is not associated with any form of advertising. Applications for commercial reproduction should be addressed to: NIHR Journals Library, National Institute for Health Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK. T im a r y o utc o m e: em er gen c y ho sp ita la dm issio n a n a lysis b y tea tm en ta llo c a ted da te P ha se ( un co ected f ha se dur a ti O utco e up ter ven ti t l djusted co a r is sti a te Proporti on ofparti ci pants lla OR p to 1 to 0 w i th one ormore b emerg ency h ospi tal R i sk g roup 1 to 9 OR p to 1 admi ssi on: proporti on ( % R i sk g roup 2 c to 3 OR p to 1 R i sk g roup 3 d to 2 OR p to 2 R i sk g roup 4 e OR p to 2 N umberofemerg ency llf [ ] [ ] p to 1 to 0 h ospi taladmi ssi ons per g parti ci pant mean ( S D [ ] R i sk g roup 1 [ ] [ ] p to 1 R i sk g roup 2 h [ ] [ ] p to 1 R i sk g roup 3 [ ] [ ] p to 1 j R i sk g roup 4 [ ] [ ] p to 1 N umbers ofemerg ency ll [ ] [ ] p to 0 to 0 h ospi taladmi ssi ons per l parti ci pantperyearatri sk R i sk g roup 1 [ ] [ ] p to 0 mean ( S D [ ] m R i sk g roup 2 [ ] [ ] p to 0 R i sk g roup 3 n [ ] [ ] p to 0 R i sk g roup 4 o [ ] [ ] p to 1 P ha se ( un co ected f ha se dur a ti O utco e up ter ven ti t l djusted co a r is sti a te p L og - transformed numbers ll [ ] [ ] p to 0 to 0 ofemerg ency h ospi tal q admi ssi ons perparti ci pant R i sk g roup 1 [ ] [ ] p to 0 peryearatri sk mean ( S D R i sk g roup 2 r [ ] [ ] p to 0 L [ ] R i sk g roup 3 s [ ] [ ] p to 0 L R i sk g roup 4 t [ ] [ ] p to 0 L S D standard dev i ati on. S i g ni fi cantcov ari ates and factors ( p unless oth erw i se stated) are: a g e atstudy day 1 W score; PR I S M score; days atri sk seasonali ty; and trend. Table 18 and so on follow broadly the same format for selected secondary outcomes; Table 21, on inpatient visits, considers only the days per year each participant is hospitalised in each phase. Table 17 shows, following adjustment for length of time in each phase and all other significant covariates, an increase in the proportion of participants who experienced an emergency admission to hospital in the intervention phase compared with the control phase. The number of emergency admissions per participant was also higher in the intervention phase. These data are highly skewed, with most participants (> 90%) not experiencing any admissions, but a few experiencing multiple admissions. Analysis using log-transformed data is therefore appropriate, and shows an increase of 1% in emergency admissions per participant per year at risk in the intervention phase.
A double-blind placebo-con- traumatic stress disorder proven confido 60 caps. Int Clin Psychopharmacol 1998;13(5): trolled trial of paroxetine in the management of social phobia 233–234 order confido 60 caps with mastercard. Risperidone as an adjunct therapy for 89(4):402–406. Paroxetine in social anxiety disorder: a random- 606. Paroxetine in social phobia/ in veterans with posttraumatic stress disorder: a report of 4 cases. Use of the selective serotonin reuptake chopharmacol 1997;12(4):231–237. Divalproex in posttrau- phobia with clonazepam and placebo. J Clin Psychopharmacol matic stress disorder: an open-label clinical trial. What might the psychobiology of posttraumatic stress disorder. GREENBERG No society can afford to guarantee universal health insur- arching goal of GBD is to help health policy planners priori ance coverage for treatment of all illnesses for all of its citi- tize disorder-specific resource allocation decisions. The number of illnesses is simply too large and the cuses on economic costs of illness using a metric known costs of treatment too great for such a guarantee even in as the disability-adjusted life year (DALY) (6), a weighted the most economically advantaged societies. Resource allo- composite that combines expected years of lost life with cation rules are consequently needed (1). The most widely expected years of decreased functioning due to a particular accepted of these rules emphasizes cost-effectiveness. Ac- disease (or constellation of comorbid diseases). Although the GBD rated in which the costs of treatment are usually defined (i. To create suggest that the GBD underestimated the costs of anxiety transformations across these different metrics to allow for and stress disorders and that the true costs of anxiety disor comparisons of costs and benefits on a single metric, a num- ders are actually quite comparable to the costs of mood ber of strategies have been developed, such as assessments disorders (7,8). In addition, a anxiety and stress disorders in the GBD are worthy of note. First, the epidemiologic studies used in GBD absence and disability from work. The costs of these role underestimated the prevalences of anxiety disorders. Sec impairments can be more easily assessed than the costs of ond, the estimated effects of specific diseases on functioning other adverse effects of illness and represent the cost-benefit were based on the judgments of experts rather than on ob trade-off to purchasers of employer-sponsored health insur- jective evaluations of actual impairments in representative ance plans (4). These judgments under- The most ambitious effort to date to evaluate the costs estimated the impairments due to anxiety disorders. Third, of illness in terms of role impairments and disabilities is comorbidities were ignored in making GBD cost estimates. By focusing on eight factors that lead to the high societal costs of these disorders, we present evidence on the three sources of GBD underesti mation listed above. Kessler: Department of Health Care Policy, Harvard Medical School, Boston, Massachusetts. Second, the prevalences of 982 Neuropsychopharmacology: The Fifth Generation of Progress these disorders are increasing in recent cohorts in many spondents, as part of the WHO World Mental Health 2000 countries. Third, these disorders have much earlier ages of (WMH2000) Initiative (15). The DIS and CIDI surveys show that anxiety and stress Fourth, anxiety and stress disorders are usually very chronic. Clear illustration can be found in a recent report range of adverse effects on secondary outcomes, such as teen based on the results of six CIDI surveys carried out in Latin childbearing, marital stability, and educational attainment America, North America, and Europe (16). These surveys that have substantial economic implications. Sixth, these found that the lifetime prevalences of DSM third edition disorders are often associated with substantial impairments revised (III-R) anxiety disorders were as high as 25%, in role functioning. Seventh, anxiety and stress disorders whereas prevalences in the year before the survey were as are highly comorbid and usually temporally primary. These prevalences were higher than those of of the disorders that are temporally secondary to anxiety any other class of mental disorders in the vast majority of and stress disorders, such as ulcers and substance abuse, have the surveys.
H epatic extraction of exogenous substrate infusions (see Fig purchase confido 60caps fast delivery. In the liver safe confido 60 caps, protein am ino acids from the circulation— hepatic gluconeogenesis, A, and synthesis and secretion of acute phase proteins are also stim ulated. Circles— livers from acutely urem ic rats; squares— livers from sham The dom inant m ediator of protein catabolism in ARF is this accel- operated rats. Nutrition and M etabolism in Acute Renal Failure 18. In m uscle, the m axim al rate of insulin-stim ulated CATABOLISM IN ACUTE RENAL FAILURE protein synthesis is depressed by ARF and protein degradation is increased even in the presence of insulin. Acidosis was identified as an im portant factor in m uscle protein breakdown. M etabolic acidosis activates the catabolism of protein Impairment of metabolic functions by uremia toxins and oxidation of am ino acids independently of azotem ia, and Endocrine factors nitrogen balance can be im proved by correcting the m etabolic Insulin resistance acidosis. These findings were not uniform ly confirm ed for Increased secretion of catabolic hormones (catecholamines, ARF in anim al experim ents. The Hyperparathyroidism secretion of catabolic horm ones (catecholam ines, glucagon, Suppression of release or resistance to growth factors glucocorticoids), hyperparathyroidism which is also present in ARF Acidosis (see Fig. M oreover, the release of inflam m ato- Inadequate supply of nutritional substrates ry m ediators such as tum or necrosis factor and interleukins have Loss of nutritional substrates (renal replacement therapy) been shown to m ediate hypercatabolism in acute disease [1, 2]. The type and frequency of renal replacem ent therapy can also affect protein balance. Aggravation of protein catabolism , certainly, is m ediated in part by the loss of nutritional substrates, but som e FIGURE 18-8 findings suggest that, in addition, both activation of protein Protein catabolism in acute renal failure (ARF): contributing factors. In experim ental anim als, starvation potentiates and, finally, the type and intensity of renal replacement therapy. FIGURE 18-9 Am ino acid pools and am ino acid utilization in acute renal failure extraction of am ino acids observed in anim al experim ents, (ARF). As a consequence of these m etabolic alterations, im bal- overall am ino acid clearance and clearance of m ost glucoplastic ances in am ino acid pools in plasm a and in the intracellular com - am ino acids is enhanced. In contrast, clearances of PH E, proline partm ent occur in ARF. A typical plasm a am ino acid pattern is (PRO ), and, rem arkably, VAL are decreased [16, 17]. Plasm a concentrations of cysteine (CYS), taurine (TAU), alanine; ARG— arginine; ASN — asparagine; ASP— aspartate; m ethionine (M ET), and phenylalanine (PH E) are elevated, where- CIT— citrulline; GLN — glutam ine; GLU— glutam ate; GLY— as plasm a levels of valine (VAL) and leucine (LEU) are decreased. As expected from the stim ulation of hepatic (From Drum l et al. Thus, loss of renal function can contribute to the altered am ino acid pools in ARF and to the fact that several am ino acids, such as arginine or tyrosine, which conventionally are term ed nonessential, m ight becom e conditionally indispensable in ARF (see Fig. In addition, the kidney is an im portant organ of protein degrada- tion. M ultiple peptides are filtered and catabolized at the tubular brush border, with the constituent am ino acids being reabsorbed and recycled into the m etabolic pool. In renal failure, catabolism of peptides such as peptide horm ones is retarded. This is also true for acute urem ia: insulin requirem ents decrease in diabetic patients who develop of ARF. W ith the increased use of dipeptides in artificial nutrition as a source of am ino acids (such as tyrosine and glutam ine) which are not soluble or stable in aqueous solutions, this m etabolic function of the kidney m ay also gain im portance for utilization of these novel nutritional substrates. In the case of glycyl-tyrosine, m etabol- ic clearance progressively decreases with falling creatinine clearance FIGURE 18-10 (open circles, 7 healthy subjects and a patient with unilateral M etabolic functions of the kidney and protein and am ino acid nephrectom y*) but extrarenal clearance in the absence of renal m etabolism in acute renal failure (ARF). Protein and am ino acid function (black circles) is sufficient for rapid utilization of the m etabolism in ARF are also affected by im pairm ent of the m eta- dipeptide and release of tyrosine. Infusion of arginine-free am ino acid solutions can cause life-threatening com - plications such as hyperam m onem ia, com a, and acidosis. H ealthy subjects readily form tyrosine from phenylalanine in the liver: During infusion of am ino acid solutions containing phenylalanine, plasm a tyrosine concentration rises (circles). In contrast, in patients with ARF (triangles) and chronic renal failure (CRF, squares) phenylalanine infusion does not increase plasm a tyrosine, indicating inadequate interconversion. Recently, it was suggested that glutam ine, an am ino acid that traditionally was designated non-essential exerts im portant m eta- bolic functions in regulating nitrogen m etabolism , supporting im m une functions, and preserving the gastrointestinal barrier. Thus, it can becom e conditionally indispensable in catabolic ill- ness. Because free glutam ine is not stable in aqueous solu- tions, dipeptides containing glutam ine are used as a glutam ine source in parenteral nutrition. The utilization of dipeptides in FIGURE 18-11 part depends on intact renal function, and renal failure can im pair Am ino acids in nutrition of acute renal failure (ARF): Conditionally hydrolysis (see Fig. N o system atic studies have been essential am ino acids.
A further limitation of the models used to predict annual hospitalisation risk buy cheap confido 60caps line, is the fact that these require extrapolation beyond the period of follow-up in the data sets used to develop them (i generic 60caps confido fast delivery. We therefore had to assume that estimated probabilities of hospitalisation at 6 years on dialysis are generalisable across future years on dialysis. Further adjustments to baseline risks To allow for modelled scenarios in which effects are mediated through associations between hydration status and outcomes, the model was structured to enable mortality and hospitalisation rates to be adjusted upwards for proportions of the dialysis cohorts estimated to be severely overhydrated (ROH of > 15%). Modelled reductions in severe overhydration were then used to drive effects in scenarios using this version of the model. The expected prevalence of severe overhydration (ROH of > 15%) was based on studies taking BCM measures at clinic visits (not necessarily first thing in the morning) for the PD cohort, and pre dialysis for the HD cohort. The threshold of ROH of > 15% was selected because, as noted in Non-randomised evidence, it has been associated with increased rates of mortality and hospitalisation in observational 30 50 82 88, , , studies. Time-averaged volume overload may give a more accurate estimate of the average exposure to fluid overload, but this measure has not been linked with mortality in observational studies. Limited data were identified regarding the prevalence of ROH of > 15% in UK dialysis cohorts. One observational study of 529 PD patients from a single UK centre82 reported that ≈ 31% of patients had ROH of > 10%. A multicentre European study, which included 734 patients from centres in Belgium, France, Romania, the UK (167 patients from two centres) and Switzerland, reported that 25. However, a further multicentre European study matched PD patients from France, Romania and the UK with HD patients from the corresponding countries. Based on these available data, the baseline prevalence of ROH of > 15% was set at 25% for both the HD and the PD cohorts. The mortality rate for the severely overhydrated proportion of the HD cohort was increased using an adjusted HR of 1. It is plausible that any mortality/morbidity benefits associated with bioimpedance testing are also partly attributable to the avoidance of underhydration. However, no studies were identified linking underhydration, as measured using bioimpedance spectroscopy, to mortality and adverse events. Therefore, an underhydration state was not included in the model. As mentioned in Framework (method of synthesis), this could potentially underestimate the benefits if bioimpedance-guided fluid management can simultaneously reduce the proportion of patients that are seriously over- and underhydrated. Conversely, if the use of bioimpedance testing to guide fluid management decreases the proportion of patients who are overhydrated at the expense of increasing the proportion who are underhydrated, this model could potentially overestimate the benefits. This issue may be freely reproduced for the purposes of private research and study and extracts (or indeed, the full report) may be included in professional journals 39 provided that suitable acknowledgement is made and the reproduction is not associated with any form of advertising. Applications for commercial reproduction should be addressed to: NIHR Journals Library, National Institute for Health Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK. ASSESSMENT OF COST-EFFECTIVENESS Incorporation of relative treatment effects Alternative approaches to modelling effects of bioimpedance-guided fluid management on the baseline event rates were considered. Given the limitations in the existing evidence base for the clinical effectiveness of bioimpedance testing, combined with further limitations in the evidence base to inform certain baseline events, the modelled cost-effectiveness scenarios are subject to a significant degree of uncertainty. With the availability of some trial evidence for the technology, the application of direct evidence for effects on final health outcomes was considered the preferred approach for modelling benefits. However, given the limitations in the trial evidence base, this was only possible for all-cause mortality. Of the three available 61 76 77, , BCM trials that included all-cause hospitalisation rates, these showed inconsistent and insignificant effects on this outcome. Therefore, we did not incorporate an effect on the overall hospitalisation rate in scenarios applying direct estimates of effects. Alternative approaches were explored in further scenario analyses to model plausible effects on CV event-related and non-CV event-related hospitalisation rates. As a number of the trials reported effects on surrogate end points, including LVMI and PWV, we conducted a focused literature search to identify appropriate published sources of evidence to link changes in these surrogates to final health outcomes in the relevant patient population. A hierarchical approach was adopted to identify suitable sources of evidence, with priority given in descending order to the following types of evidence: 1. One systematic review, conducted in 2016, considered the value of LVMI as a treatment target in the area of ESRD, and concluded that there was no clear and consistent association between intervention-induced LVM change and all-cause or CV event-related mortality. The search of available evidence did not identify any existing data showing a clear link between intervention-induced changes in PWV and final health outcomes in ESRD, but a large European observational study was identified. It highlighted the importance of simultaneously considering abdominal aortic calcification (AAC) when assessing the prognostic value of PWV. Based on a multivariate Cox regression, both variables were found to be significant predictors of mortality and non-fatal CV events, but the effect of PWV was ameliorated at higher levels of aortic calcification (incorporated as tertiles), as a result of a significant negative interaction. The relevant HRs from the published Cox regression are provided in Table 9. Based on these estimates, and assuming that the UK dialysis cohort is similarly distributed across aortic calcification tertiles, we estimated an average effect on all-cause mortality and non-fatal CV events of a unit change in PWV, accounting for the interaction. We then explored the impact of scaling this effect to the magnitude of the pooled mean reduction in PWV (1.
In AD 46 purchase 60caps confido mastercard, Scribonius Largus described the application of electric torpedo fish to the head as a treatment for headache cheap confido 60 caps mastercard. In 1470, a Jesuit missionary in Ethiopia applied electric catfish to people (anatomical site unknown) as a means of expelling devils. In th the 18 century electric eels were applied to the head (condition treated unknown). However, there is no clear history of the application of electricity to the head for the treatment of mental disorders before 1938. Convulsions had been induced by other means for medical purposes at different times over the centuries. Paracelsus (1490-1541) administered camphor by mouth to induce convulsions in the treatment of mental disorders. In 1785 an account appeared in the London Medical Journal of camphor induced convulsions for the treatment of psychosis. Then came a series of active treatments which encouraged optimism and set the scene for the development of ECT. From around 1917 Julius Wagner-Jauregg (Professor of Psychiatry, Vienna) began treating the otherwise progressive and fatal general paresis of the insane (terminal syphilis) by infecting sufferers with malaria. Other psychiatrist had used insulin to stimulate appetite, however, Sakel sought to induce coma. In the process, some patients experienced seizures, and this may have been responsible for observed improvement. In1934, Ladislaus von Meduna (1896-1964; Budapest) injected camphor into a person with schizophrenia with the intention of inducing convulsion; this was the first modern convulsive therapy. Von Meduna had developed the theory of “biological antagonism”, between epilepsy and schizophrenia. First, when a person with severe mental disorder had a seizure (for whatever reason) their mental state improved. Second, was an epidemiological mistake, the “observation” that people with schizophrenia did not suffer epilepsy. But the induction of convulsions with camphor, and subsequent commercial agents was unpredictable and unsatisfactory. ECT has the advantages of immediacy and predictability. The first patient, SE, was a 39 year old engineer from Milan who was found wandering the streets of Rome in a psychotic state. He received 11 treatments, obtained a good response and wrote to the doctors the following year thanking them for their treatment. Ugo Cerletti (1877-1963), supervised the first ECT treatment (1938). It is now used more widely in major depression than in schizophrenia. Improvements in technique ECT has been in continuous use over the last 80 years. However, there have been technical improvements: • The introduction of anaesthesia to ECT practice made the process less distressing for patients. It is especially indicated where drugs have failed or there is risk of suicide. Active ECT has been shown superior to placebo ECT in many trials (e. ECT has also been found to be superior to the available antidepressant drugs in more than a dozen trials. A typical design is for patients were divided into two groups: one receiving active ECT and placebo medication, and the other receiving placebo ECT and active medication (Gangadhar et al, 1982). In this way ECT can be compared with and antidepressant medication, and both groups of patients received an active form of treatment. Mania Mania is a state of mood elevation or irritability and physical over-activity. Treatment may be a necessary to ensure food and fluid intake and prevent exhaustion and physical injury. This is a difficult population to study for various reasons. Universal clinical experience is that ECT is an effective treatment and can be lifesaving. ECT has been shown superior to lithium carbonate in acute mania (Small et al, 1988). ECT is currently used in schizophrenia when there are marked catatonic features (Raveendranathan et al, 2012; Pompili et al, 2013) with limited food and fluid intake and when other psychotic symptoms are unresponsive to medication. Postpartum disorders A range of psychiatric disorders may develop following childbirth. The majority can be managed with support and the judicious use of medication. Acute, severe disorders may develop, however, and mother may represent a danger to herself and/or the baby.
The concept of a metabolically inac- such as [2-13C] acetate and higher sensitivity MRS measure- tive neurotransmitter pool was brought into question in ments should allow the contributions of these cell types to 1995 60 caps confido fast delivery, when purchase confido 60 caps with visa, using 13C nuclear magnetic resonance (NMR), be more accurately determined. Within the error of the we measured a high rate of glutamine labeling from [1-13C] MRS measurements, and the contribution of glutamate glucose in the occipital/parietal lobe of human subjects (12). At the time of the initial 13C NMRstudy, the available for other cell types such as dopaminergic and sero- rate of the glutamate/glutamine cycle could not be calcu- toninergic nerve terminals. An objection that has been raised lated due to the lack of a model for distinguishing isotopic to these findings is the possibility that small highly metaboli- labeling from this cycle from other sources of glutamine cally active pools may be missed by the MRS method. Net ammonia removal requires the de novo glutamine ments of total glucose consumption indicate that the contri- synthesis via the anaplerotic pathway in the glia. In addition, bution of these small pools is not large. MRS measurements several other pathways, including the glial TCA cycle, have of glucose metabolism during cortical activation will be re- been proposed as providing significant precursors for gluta- 25: Glutamate and GABA Neurotransmitter Cycles 321 mine synthesis (61,62). To calculate the rate of the gluta- constant, loss of glutamine by efflux (Vefflux) must be com- mate/glutamine cycle, Sibson et al. The important and surprising the TCA cycle oxaloacetate is converted to -ketoglutarate, result of these studies is that the glutamate/glutamine cycle which may be converted to glutamate either by ammonia is a major metabolic flux, far exceeding de novo glutamine fixation via glia glutamate dehydrogenase or alternatively synthesis. The rate of the glutamate/glutamine cycle in the through transamination with other amino acids (37). Glial awake resting human cerebral cortex is between 60% and glutamate is then converted to glutamine by glutamine syn- 80% of total glucose oxidation. One or two ammonia molecules are fixed per gluta- mine molecule synthesized through anaplerosis, depending on the relative fluxes of NH fixation versus transamina- 4 Development of a Two-Compartment tion. Applying nitrogen mass balance constraints leads to Metabolic Model of Glutamine the relationship VNH4 (1 to 2)Vefflux at steady state. The Metabolism to Separately Determine the additional requirement of carbon mass balance leads to the Rate of the Glutamate/Glutamine Cycle following relationship: and Anaplerotic Glutamine Synthesis 1 Vana Vefflux VCO2 ( ⁄2 to 1)VNH4 The rate of the glutamate/glutamine cycle is calculated from 13 Total glutamine synthesis is then related to synthesis for the time course C labeling of glutamine relative to the ammonia detoxification (Vana) and the glutamate/glutamine labeling of its precursor neuronal glutamate. If neuronal cycle (Vcycle) by the following expression: glutamate were the only precursor of glutamine, the calcula- tion would be straightforward. Unfortunately, the calcula- Vgln Vcycle Vana tion is complicated by label from [1-13C] glucose entering Note that V may be higher than V if anaplerosis is CO2 ana both the neuronal and glial TCA cycles via pyruvate dehy- needed to replace TCA cycle intermediates lost by oxidative drogenase. Glutamate in both cell types will be labeled in processes or pyruvate recycling (63,64). The flow of label from C4-glutamate gln into C4-glutamine is proportional to the total rate of gluta- in combination with a measurement of any of the rates mine synthesis. However, unless the relative flow of 13C linked by mass balance considerations to anaplerotic gluta- label into the glial glutamate pool from the glial pyruvate mine synthesis. A limitation of isotopic measurements of dehydrogenase and neuronal glutamate are distinguished, flux is that isotopic exchange cannot be distinguished from the fraction of glutamine synthesis due to the glutamate/ net flux. The linkage between the labeling of glutamine glutamine cycle cannot be calculated. To determine the rate through glial pyruvate dehydrogenase and the brain an- of the glutamate/glutamine cycle from a [1-13C] glucose aplerosis flux allows the validation of isotopic measurements of glutamine 13C and 15N labeling against traditional AV precursor, we developed a metabolic model to constrain the rate of glutamine labeling from glial pyruvate dehydro- difference measurements. The glutamate/glutamine cycle measurement using a [1-13C] glucose precursor also includes contributions from Glutamine production via glutamine synthetase requires two substrates, glutamate and ammonia. As shown in the the GABA/glutamine cycle (34,57,65). A mathemati- and the Effects of Disease and Pharmacologic Treatment cal model was developed to interpret isotopic data in order on Human GABA Metabolism, below). The glutamate/glu- to separate these pathways (25,27,29,36). The model ex- tamine and GABA/glutamine pathway may be distin- tends previous formulations by imposing mass balance con- 13 13 guished using [2- C] glucose and [2- C] acetate as precur- straints on the brain glutamate and glutamine pools that sors as described below and in the section In Vivo MRS relate the rate of de novo glutamine synthesis to the net Studies of GABA Metabolism. Glutamine efflux is the primary source of nitrogen removal from the 13 C NMR Studiesof the Glutamate/ brain (49,62). Nitrogen must be removed from the brain Glutamine Cycle in Rat Cerebral Cortex in order to maintain low concentrations of ammonia, which when elevated will interfere with brain function (62). Be- To determine the rate of glutamine synthesis, rats were stud- cause at steady state the concentration of glutamine remains ied under -chloralose anesthesia in a 7-T modified Bruker 322 Neuropsychopharmacology: The Fifth Generation of Progress Biospec spectrometer. A small 13C surface coil was used for tamine under hyperammonemic conditions are also consis- transmission and reception. The spectroscopic volume was tent with the predictions of the model. The agreement be- localized primarily to the motor and somatosensory cortices.
Because indirect controls require the forebrain to be connected to the caudal brainstem in order to control eating buy cheap confido 60caps on line, the reciprocal connec- tions between forebrain and hindbrain are necessary for the modulation of the direct controls by the indirect controls purchase confido 60caps fast delivery. This theory asserts that indirect controls have no direct ac- tion on the cpg during a meal in the absence of direct con- FIGURE 115. Flow diagram of the direct controls of meal size trols activated by ingested food. Specifying the peptidergic stimulated by ingested food acting on preabsorptive receptors of and aminergic connections that mediate an indirect con- the gastrointestinal tract. The efferent output of the central networks for the con- the neural control of eating converge. Because some The identification of the importance of the positive and of the direct controls are stimulated by ingested food in every meal, indirect controls of meal size exert their effects by modulat- negative feedbacks from the periphery in the direct controls ing direct controls. Feeding: tates the investigation of human eating disorders in three control of eating. The peripheral, preabsorptive sites of action are accessi- ble to controlled stimulation in the conscious human before, during, and after test meals. An increase or a decrease in meal size can be explained persion over large areas provides for the effect of stimulus by changes in feedback potency (Table 115. Identifying which combination of changes in feedback The second point is that all of the afferent fibers from the underlies the change in meal size focuses the search for mouth, stomach, and small intestine project to the caudal neurobiological mechanism because the feedbacks have brainstem. The direct preabsorptive stimulation by the stimuli of ingested food and its digestive products that provide feed- back control during a meal is a criterion for distinguishing these feedback controls from all other controls. CHANGES IN POTENCY OF AFFERENT back controls are direct controls of meal size (Fig. This is not an arbitrary classification because it is based Afferent Feedback on a biological criterion of site of action. The classification Change of Meal Size Positive Negative Increase Increase Decrease Increase Increase No change a Increase Increase Smaller increase TABLE 115. INDIRECT CONTROLS OF MEAL SIZE Increase No change Decrease Decrease Decrease Increase Categories Examples Decrease Decrease No change Rhythmic Diurnal, estrogen Decrease Decrease Smaller decrease Metabolic Changes in leptin, insulin, and fatty acids Decrease No change Increase Thermal Environmental and fever a Some changes of afferent feedbacks responsible for increased or Conditioned Preferences, aversions, and satiations decreased meal size. Identification of the mechanisms of a specific Cognitive Social and, in humans, cultural and esthetic change(s) in potency of feedbacks is an experimental problem. The controls of eating: a shift from aThe list of categories is neither mutually exclusive nor exhaustive; nutritional homeostasis to behavioral neuroscience. Nutrition this is particularly true for conditioned, cognitive, and ecological. Chapter 115: The Behavioral Neuroscience of Eating 1669 TABLE 115. MOLECULAR MECHANISMS OF DIRECT CONTROLS OF MEAL SIZE Direct controls Peripheral Central Orosensory Gustatory and olfactory transducers Dopaminea Opioidsa Gastric CCKa at CCK vagal mechanoreceptors, Amino acids from gastric vagal A other mechanoreceptors, and afferent terminals in NTS bombesin-like peptides Serotonina Small intestinal CCKaat CCK receptors on vagal Amino acids from duodenal and A mechanoreceptors and hepatic vagal afferent terminals chemoreceptors; glucagon,a in NTS amylin, enterostatin, apolipoprotein Serotonina IV, and insulin released by nutrient or digestive stimuli through contact with mucosal receptors or by the release of incretins NTS, nucleus tractus solitarius. The physiologic sta- tus of the other molecules is uncertain. The controls of eating: brain meanings of food stimuli. New York: Elsevier, 2000:173–186, with permission of the publisher. The combination of decreased central serotonergic pro- An example of the use of this theory of the control of cessing with decreased peripheral negative feedback could meal size is the recent work concerning the pathophysiology be particularly disruptive of satiation because the satiating of the abnormally large meals that characterize patients with potency of CCK in rats is synergistic with gastric distension bulimia nervosa. Since the 1970s there has been evidence and is reduced by decreased central serotonergic function, that these patients do not feel as full as normal after the particularly at 5-HT2C receptors (6). This has been confirmed more precisely in In addition to decreased negative feedback, bulimia pa- recent work that showed that bulimics require more food tients also have an abnormal cognitive indirect control. This suggests a defect in the They eat much larger meals when they are instructed to satiating process (21), specifically a defect in the potency of binge compared to when they are instructed not to binge negative feedback. The decreased negative feed- back could involve peripheral mechanisms or central modu- Numerous regions of the brain can be implicated in eating lation. Two peripheral abnormalities have been found: an by a variety of techniques in animals and humans. This enlarged stomach capacity (23) and a decreased release of reflects the fundamental biological importance of eating to CCK (24). The decreased release of CCK was ameliorated individual life and reproduction, and the functional require- when binge eating stopped in one experiment (25), but ments of a foraging omnivore. From this viewpoint, it is further experiments are required to evaluate this phenom- not surprising that learning and memory are important pro- enon. Three important types of There may also be a defect in the central processing of learning have been identified using Pavlovian procedures the decreased peripheral negative feedback information and theory: conditioned preference, conditioned aversion owing to abnormal function of the central serotonin system. If central serotonin function is decreased in bulimia pa- Conditioned preferences are formed by flavor–flavor as- tients, they should be more vulnerable than controls to a sociations or flavor–postingestive associations (28). Once further decrease in serotonin function produced by seroto- formed, the preferences increase the size of meals. This prediction has been confirmed: Acute the postingestive unconditioned stimulus is omitted, the tryptophan depletion that probably decreased central sero- conditioned preference persists for months, but its effect on 1670 Neuropsychopharmacology: The Fifth Generation of Progress intake extinguishes rapidly.