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Biomedical subjects

J Bao

Publications and source records attributed to J Bao.

At least 109 records · Page 6Linked to original sources
PubMed1994

Traumatic brain injury reduces hippocampal high-affinity [3H]choline uptake but not extracellular choline levels in rats.

Hippocampal cholinergic hypofunction may contribute to memory deficits following experimental traumatic brain injury. These studies examined two important factors in acetylcholine synthesis: choline availability and neuronal uptake. No reductions in basal extracellular choline levels, using microdialysis, were observed 2 weeks after cortical impact injury. However, studies of high affinity [3H]choline uptake in the hippocampus, measured in a synaptosomal preparation, found a reduction in the maximum velocity of choline uptake (Vmax), while no differences in affinity constants (Km) were found. The results suggest that post-traumatic cholinergic deficits are not attributable to decreased availability of choline, but may be associated with either a decreased ability of cholinergic neurons to take up choline and/or a loss of cholinergic neurons.

Acetylcholine↗
PubMed1994

An integral membrane protein form of brain L-glutamate decarboxylase: purification, characterization and its relationship to insulin-dependent diabetes mellitus.

A new and novel form of L-glutamate decarboxylase (GAD; EC 4.1.1.15) was purified from whole porcine brain to apparent homogeneity by a combination of column chromatographies on DE-52, ultragel AcA 34, hydroxylapatite and Sephadex G-200, and native gel electrophoresis. The purified GAD was established as an integral membrane protein based on hydrophobic interaction chromatography and membrane extraction studies. This membrane GAD (MGAD) has a native molecular weight of 120 +/- 5 kDa and is a homodimer of 60 +/- 2 kDa. Immunoprecipitation and immunoblotting tests using the sera from insulin-dependent diabetes mellitus (IDDM) patients revealed the presence of antibodies against this newly identified MGAD in IDDM. The role of MGAD in the pathogenesis of IDDM and related autoimmune disorders is also discussed.

Diabetes Mellitus, Type 1↗
PubMed1994

Purification and characterization of a novel form of brain L-glutamate decarboxylase. A Ca(2+)-dependent peripheral membrane protein.

L-Glutamic acid decarboxylase (GAD) catalyzes the one-step biosynthesis of gamma-aminobutyric acid (GABA), which is widely accepted as the major inhibitory neurotransmitter in the mammalian brain. In this paper, we report the identification and purification of a new and novel form of peripheral membrane GAD (MGAD) referred to as MGADIII, using a combination of chromatography on DE52, AcA 34, hydroxylapatite and Sephadex G-200, and native gel electrophoresis. The purified MGADIII migrated as a single protein band on a native 5-25% gradient polyacrylamide gel electrophoresis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an apparent molecular mass of 118 +/- 6 and 60 +/- 4 kDa, respectively, suggesting that it is a homodimer of 60 kDa. MGADIII was established as a Ca(2+)-dependent peripheral membrane protein based on Triton X-114 phase partitioning assay, liposome binding experiment, and membrane extraction studies. Several lines of evidence are presented to show that the association of MGADIII with membranes occurs during depolarization of nerve terminal and that this is a reversible process. Based on these results and previous findings that GAD associates with synaptic vesicles and is regulated by phosphorylation, a model for regulation of GAD in the nerve terminal is proposed.

Animals↗
PubMed1994

A membrane form of brain L-glutamate decarboxylase: identification, isolation, and its relation to insulin-dependent mellitus.

A membrane form of L-glutamate decarboxylase (GAD) was identified and purified to apparent homogeneity from hog brain. The purified GAD was established as an integral membrane protein by phase-partitioning assay, charge-shift electrophoresis, and chromatography on a hydrophobic interaction column. This membrane GAD has a native molecular mass of 96 +/- 5 kDa and is a homodimer of 48 +/- 3-kDa subunits. Immunoprecipitation and immunoblotting tests revealed the presence of antibodies against this membrane GAD in sera from patients with insulin-dependent diabetes mellitus. Since this form of GAD appears to be an integral membrane protein and is presumed to have extracellular domains exposed, it seems reasonable to suggest that membrane GAD is more likely than soluble GAD to be involved in the pathogenesis of insulin-dependent diabetes and related autoimmune disorders such as stiff-man syndrome.

Animals↗
PubMed1993

Electrophoretically mediated microanalysis of leucine aminopeptidase in complex matrices using time-resolved laser-induced fluorescence detection.

Leucine aminopeptidase, a clinically significant enzyme, was assayed in complex biological samples using a new technique termed electrophoretically mediated microanalysis. The assay was performed in capillary electrophoresis columns using time-resolved laser-induced fluorescence detection. Human serum, human urine, and Escherichia coli supernatant samples were assayed using this method. Results for serum and urine were within the ranges of expected values found in the literature. A low concentration of 6 x 10(-13) M enzyme in buffer was detected using this method. A detection limit (3 sigma) of 400 enzyme molecules in buffer was determined.

Buffers↗
PubMed1993

Enhancement of c-fos expression in neurons of the rat spinal cord after partial denervation: evidence for functional plasticity.

c-fos immunocytochemistry was used to test a functional correlate of neuroplasticity involving nociceptive primary afferent fibers in the partially denervated adult rat spinal cord. Unilateral dorsal root ganglionectomies were made at L1-L4 (chronic side). After 3 weeks, contralateral L1-L4 ganglionectomies (acute side) were made 1 week prior to sacrifice. Two hours prior to perfusion, the animals were anesthetized and their hindlimbs were immersed in a 52 degrees C water bath for 20 s. The spinal cords were then processed for c-fos immunocytochemistry and the numbers of c-fos-immunoreactive cells determined. Following bilateral noxious thermal stimulation of the hindlimbs, the numbers of c-fos-immunoreactive cells in laminae I-II from L3 to L5 were increased by nearly twofold on the chronically deafferented side of the spinal cord (P < 0.05). This finding suggests augmented functional plasticity of nociceptive primary afferent fibers on the chronically denervated side of spinal cord. These observations are discussed with relation to recent demonstrations of enhanced calcitonin gene-related peptide immunoreactivity and possible primary afferent fiber sprouting in similar denervation models.

Afferent Pathways↗
PubMed1992

Ultramicro enzyme assays in a capillary electrophoretic system.

This paper describes an ultramicro method for achieving enzyme assays. Enzyme saturating concentrations of substrate, coenzyme when appropriate, and running buffer were mixed and used to fill a deactivated fused-silica capillary in a capillary zone electrophoresis apparatus. The enzyme glucose-6-phosphate dehydrogenase was injected by either electrophoresis or siphoning and mixed with the reagents in the capillary by electrophoretic mixing. Enzyme activity was assayed by electrophoresing the product, reduced nicotinamide adenine dinucleotide phosphate, to the detector where it was detected at 340 nm. Under constant potential, the transport velocity of enzyme and the product was generally different. This caused product to be separated from the enzyme after it was formed. Because product formation was much faster than the rate of enzyme-product separation, product accumulated. The amount of accumulated product was inversely related to operating potential. In the extreme case, the operating potential was zero. Zero potential assays were generally carried out by electrophoresing the enzyme partially through the capillary and then switching to zero potential. This capillary was left at zero potential for several minutes to allow additional product to accumulate. After this additional amplification step, potential was again applied and the product transported to the detector. Product formed under constant potential appears as a broad peak with a flat plateau. When the voltage is switched to zero at intermediate migration distance, a peak will be observed on top of this plateau. Either the eight of the plateau or the area of the peak may be used to determine enzyme concentration. The lower limit of detection was 4.6.10(-17) mol of glucose-6-phosphate dehydrogenase.

Electrophoresis↗