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Pasadena, CA, United States

Disinhibition was induced in the hippocampal CA1/CA3 region of normal adult rats by unilateral perfusion of the GABAAR antagonist, 4-[6-imino-3-(4-methoxyphenyl)pyridazin-1-yl] butanoic acid hydrobromide (gabazine), or a GABABR antagonist, p-(3-aminopropyl)-p-diethoxymethyl-phosphinic acid (CGP 35348), through a microdialysis probe. Effects of disinhibition on EEG recordings and the concentrations of extracellular glutamate (GLUECF), the major excitatory neurotransmitter, and of extracellular glutamine (GLNECF), its precursor, were examined bilaterally in freely behaving rats. Unilateral perfusion of 10μM gabazine in artificial CSF of normal electrolyte composition for 34min induced epileptiform discharges which represent synchronized glutamatergic population bursts, not only in the gabazine-perfused ipsilateral hippocampus, but also in the aCSF-perfused contralateral hippocampus. The concentration of GLUECF remained unchanged, but the concentration of its precursor, GLNECF, decreased to 73±4% (n=5) of the baseline during frequent epileptiform discharges, not only in the ipsilateral, but also in the contralateral hippocampus, where the change can be attributed to recurrent epileptiform discharges per se, with recovery to 95% of baseline when epileptiform discharges diminished.The blockade of GABABR, by CGP 35348 perfusion in the ipsilateral hippocampus for 30min, induced bilateral Na+ spikes in extracellular recording. These can reasonably be attributed to somatic and dendritic action potentials and are indicative of synchronized excitatory activity. This disinhibition induced, in both hippocampi, (a) transient 1.6-2.4-fold elevation of GLUECF which correlated with the number of Na+ spike cluster events and (b) concomitant reduction of GLNECF to ~70%.Intracellular GLN concentration was measured in the hippocampal CA1/CA3 region sampled by microdialysis in separate groups of rats by snap-freezing the brain after 25min of gabazine perfusion or 20min of CGP perfusion when extracellular GLN (GLNECF) was 60-70% of the pre-perfusion level. These intracellular GLN concentrations in the disinhibited hippocampi showed no statistically significant difference from the untreated control. This result strongly suggests that the observed decrease of GLNECF is not due to reduced glutamine synthesis or decrease in the rate of efflux of GLN to ECF. This strengthens the likelihood that reduced GLNECF reflects increased GLN uptake into neurons to sustain enhanced GLU flux during excitatory population bursts in disinhibited hippocampus. The results are consistent with the emerging concept that neuronal uptake of GLNECF plays a major role in sustaining epileptiform activities in the kainate-induced model of temporal-lobe epilepsy. © 2015 Elsevier B.V.. Source

Xia N.,Central South University | Liu L.,California State University, Los Angeles | Harrington M.G.,Huntington Medical Research Institutes | Wang J.,Central South University | Zhou F.,California State University, Los Angeles
Analytical Chemistry

A major constituent in the deposit of the brain in a patient with Alzheimer's disease (AD) is the aggregates/fibrils of amyloid-β (Aβ) peptides containing 39-43 amino acids. The total Aβ levels and the concentration ratio between the most abundant Aβ(1-40) peptide and the more aggregation-prone Aβ(1-42) in body fluids (e.g., cerebrospinal fluid or CSF) have been suggested as possible criteria for early diagnosis of AD. By immobilizing capture antibodies specific to the two peptides in separate fluidic channels, surface plasmon resonance (SPR) has been used to quantify Aβ(1-40) and Aβ(1-42) present in CSF samples collected from AD patients and healthy donors. With signal amplification by streptavidin conjugated to an antibody that is selective to the common N-terminus of the Aβ peptides, concentrations as low as 20 pM can be readily measured. The range of Aβ peptide concentrations measurable by this method spans 4 orders of magnitude. The ability of regenerating the sensor surface for repeated measurements not only improves the reproducibility but also enhances the sample throughput. Our data reveal that the ratio of Aβ(1-40) concentration versus Aβ(1-42) concentration in CSF samples from AD patients is almost twice as high as that from healthy persons. In contrast to the commonly used enzyme-linked immunosorbent assay (ELISA), SPR obviates the need of a more expensive and less stable enzyme conjugate and the use of carcinogenic substrate for the signal detection and allows the binding events to be monitored in real time. © 2010 American Chemical Society. Source

Csete M.,Huntington Medical Research Institutes | Doyle J.,California Institute of Technology
Interface Focus

Blood glucose levels are controlled by well-known physiological feedback loops: high glucose levels promote insulin release from the pancreas, which in turn stimulates cellular glucose uptake. Low blood glucose levels promote pancreatic glucagon release, stimulating glycogen breakdown to glucose in the liver. In healthy people, this control system is remarkably good at maintaining blood glucose in a tight range despite many perturbations to the system imposed by diet and fasting, exercise, medications and other stressors. Type 1 diabetes mellitus (T1DM) results from loss of the insulin-producing cells of the pancreas, the beta cells. These cells serve as both sensor (of glucose levels) and actuator (insulin/glucagon release) in a control physiological feedback loop. Although the idea of rebuilding this feedback loop seems intuitively easy, considerable control mathematics involving multiple types of control schema were necessary to develop an artificial pancreas that still does not function as well as evolved control mechanisms. Here, we highlight some tools from control engineering used to mimic normal glucose control in an artificial pancreas, and the constraints, trade-offs and clinical consequences inherent in various types of control schemes. T1DM can be viewed as a loss of normal physiologic controls, as can many other disease states. For this reason, we introduce basic concepts of control engineering applicable to understanding pathophysiology of disease and development of physiologically based control strategies for treatment. © 2014 The Authors. Source

Despite efforts focused on outreach to minority populations, the literature reveals that the problem of disparities in minority involvement in clinical research persists. Thus, the objective of this article was to present an overview of the barriers to engage minorities in human subject research and the identification of promising strategies for their recruitment and retention. I identified a need for an innovative approach, which would focus recruitment efforts primarily on clinicians and researchers who contribute their own barriers to the process of recruitment and retention. In this way, the most common outreach efforts, which specifically focus on targeted minority groups, would be replaced. The inclusion of minorities in clinical research is an important bioethical issue, particularly when considering drug pharmacokinetics and pharmacodynamics, which may vary widely among different racial and ethnic populations. In conclusion, patient barriers to participation in clinical research are well-documented and remain of great importance; however, clinician and researcher barriers, equally as important, continue to be overlooked. Focusing on clinicians and researchers is needed to help increase their awareness about the barriers to minority participation that they may present. Continued research and efforts are needed to understand how best to identify, address, and overcome these barriers. Source

Migraineurs are more often afflicted by comorbid conditions than those without primary headache disorders, though the linking pathophysiological mechanism(s) is not known. We previously reported that phosphatidylcholine-specific phospholipase C (PC-PLC) activity in cerebrospinal fluid (CSF) increased during migraine compared to the same individual's well state. Here, we examined whether PC-PLC activity from a larger group of well-state migraineurs is related to the number of their migraine comorbidities. In a case-control study, migraineurs were diagnosed using International Headache Society criteria, and controls had no primary headache disorder or family history of migraine. Medication use, migraine frequency, and physician-diagnosed comorbidities were recorded for all participants. Lumbar CSF was collected between the hours of 1 and 5 pm, examined immediately for cells and total protein, and stored at -80°C. PC-PLC activity in thawed CSF was measured using a fluorometric enzyme assay. Multivariable logistic regression was used to evaluate age, gender, medication use, migraine frequency, personality scores, and comorbidities as potential predictors of PC-PLC activity in CSF. A total of 18 migraineurs-without-aura and 17 controls participated. In a multivariable analysis, only the number of comorbidities was related to PC-PLC activity in CSF, and only in migraineurs [parameter estimate (standard error) = 1.77, p = 0.009]. PC-PLC activity in CSF increases with increasing number of comorbidities in migraine-without-aura. These data support involvement of a common lipid signaling pathway in migraine and in the comorbid conditions. Source

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