Biomedical subjects

P E Glaser

Publications and source records attributed to P E Glaser.

5 recordsLinked to original sources

PubMed1999

No difference between platelet serotonin--5-HT(2A) receptors from children with and without ADHD.

To further investigate the possible function of the serotonergic system in the pathophysiology of attention deficit hyperactivity disorder (ADHD), platelet serotonin 5-HT2A receptors were characterized for 19 ADHD children and 17 age-matched control subjects. Subjects were evaluated using the Diagnostic Interview for Children and Adolescents (DICA-R-C)-DSM IV and the Children's Depression Inventory. An aggressive subgroup was also determined by the presence of two or more positive aggressive symptoms on either subjects' or parents' reports. Platelets were isolated from venous blood and 5-HT2A receptor number, and affinity was determined using 125I-LSD binding. There was no difference in platelet 5-HT2A receptor binding characteristics between the two groups. The results from this pilot study suggest a limited function of 5-HT2A receptors in the pathophysiology of ADHD and extend the findings of other previous negative studies of the peripheral serotonergic system in ADHD.

Adolescent↗

PubMed1995

Rapid plasmenylethanolamine-selective fusion of membrane bilayers catalyzed by an isoform of glyceraldehyde-3-phosphate dehydrogenase: discrimination between glycolytic and fusogenic roles of individual isoforms.

Recently we demonstrated that the unique stereoelectronic relationships inherent in the structure of plasmenylethanolamine facilitate membrane fusion, and we postulated the existence of a membrane fusion protein which could exploit the propensity of plasmenylethanolamine molecular species to adapt an inverted hexagonal phase [Glaser & Gross (1994) Biochemistry 33, 5805-5812]. We now report a cryptic membrane fusion activity in rabbit brain cytosol, which requires separation from an endogenous inhibitor to express its activity, and demonstrate that vesicle fusion catalyzed by this protein is highly selective for membrane vesicles containing plasmenylethanolamine. The cytosolic protein catalyzing membrane fusion activity was purified to apparent homogeneity by sequential column chromatographies, revealing a single 38-kDa protein band after sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver staining. Automated Edman degradation demonstrated that the purified protein is an isoform of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which was confirmed by Western blot analysis utilizing polyclonal antibodies and by solution-state inactivation of membrane fusion activity by a monoclonal antibody directed against GAPDH. Both GTP-affinity and Mono Q chromatographies resolved GAPDH isoforms that catalyzed dehydrogenase activity from the GAPDH isoform that catalyzed membrane fusion activity. The purified fusion protein was calcium-independent, resistant to treatment with N-ethylmaleimide, and possessed an obligatory requirement for plasmenylethanolamine and cholesterol. High-resolution stopped-flow kinetic analysis of plasmenylethanolamine-facilitated membrane fusion demonstrated that one tetramer of the GAPDH isoform catalyzed one fusion event between two vesicles containing plasmenylethanolamine every millisecond (on average). Collectively, these results constitute the first description of a protein which can catalyze the fusion of vesicles at a rate which satisfies the mathematical constraints imposed by the observed rates of fusion of synaptic vesicles with the presynaptic membrane in vivo.

Amino Acid Sequence↗

PubMed1994

Plasmenylethanolamine facilitates rapid membrane fusion: a stopped-flow kinetic investigation correlating the propensity of a major plasma membrane constituent to adopt an HII phase with its ability to promote membrane fusion.

A critical step in membrane fusion involves the formation of a lipid intermediate which shares a conformational similarity with an inverted hexagonal phase (HII). Since plasmenylethanolamines possess a marked propensity for hexagonal phase formation and represent a major lipid constituent of several membrane systems which undergo rapid membrane fusion (e.g., plasma membranes and synaptic vesicle membranes), we compared the relative fusogenicity of lipid vesicles containing plasmenylethanolamine to that of vesicles containing their diacyl phospholipid counterpart (i.e., phosphatidylethanolamine). Vesicles comprised of equimolar mixtures of phosphatidylcholine and phosphatidylethanolamine fused slowly with phosphatidylserine vesicles in the presence of 10 mM CaCl2, as assessed either by lipid mixing (dequenching of octadecyl rhodamine fluorescence, 7.4 Fmax% s-1) or internal contents mixing (fluorescence enhancement from the resultant Tb/dipicolinic acid charge transfer complex, 8.7Fmax% s-1). In stark contrast, vesicles comprised of equimolar mixtures of phosphatidylcholine and plasmenylethanolamine fused three times more rapidly, as assessed by both lipid mixing (22.1 Fmax% s-1) and internal contents mixing (21.4Fmax% s-1) assays. The importance of an HII-like intermediate in membrane fusion was further substantiated by demonstration that plasmenylethanolamines containing arachidonic acid at the sn-2 position (which demonstrate a greater propensity for HII phase formation) exhibited the most rapid rate of membrane fusion (five times greater than phosphatidylethanolamine containing oleic acid at the sn-2 position). Furthermore, vesicles containing plasmenylethanolamines in physiologic ratios with other phospholipids (i.e., PC/PE/PS, 45:45:10, mol/mol) underwent fusion six times more rapidly (4.4Fmax% min-1) than corresponding vesicles in which plasmenylethanolamine was replaced with phosphatidylethanolamine (0.7Fmax% min-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Activation of protein kinase C by naturally occurring ether-linked diglycerides.

Recent studies have demonstrated that ether-linked diglycerides are endogenous constituents of biologic tissues and accumulate during agonist stimulation (Daniel, L. W., Waite, M., and Wykle, R. L. (1986) J. Biol. Chem. 261, 9128-9132) and myocardial ischemia (Ford, D. A., and Gross, R. W. (1989) Circ. Res. 64, 173-177). Although protein kinase C previously had been thought to specifically require 1,2-diacyl-sn-glycerol (DAG) molecular species for activation, the present study demonstrates that purified rat brain protein kinase C is activated by naturally occurring ether-linked diglycerides (e.g. 1-O-hexadec-1'-enyl-2-octa-dec-9'-enoyl-sn-glycerol and 1-O-hexadecyl-2-octa-dec-9'-enoyl-sn-glycerol) with a similar dose response curve to that for DAG molecular species. Although in vitro assays demonstrated that DAG could partially activate protein kinase C in the absence of free calcium, activation by ether-linked diglycerides required free calcium concentrations found only in stimulated cells (greater than 1 microM [Ca2+]free). To substantiate these findings the alpha and beta isoforms of protein kinase C from rat brain cortical grey matter were resolved by hydroxylapatite chromatography. Although the beta isoform of protein kinase C was substantially activated by DAG in the absence of free calcium, activation by ether-linked diglycerides had an absolute requirement for physiologic increments in free calcium ion found in stimulated cells. Since ether lipids are localized in specific subcellular membrane compartments, accumulate during several pathophysiologic perturbations and are effective activators of protein kinase C with separate and distinct calcium requirements in comparison to DAG, these results suggest that ether-linked diglycerides are important and potentially specific biologic activators of one or more isoforms of protein kinase C.

Animals↗

PubMed1989

The Initial Blood Storage Experiment--the spaceflight hardware program.

The Initial Blood Storage Experiment (IBSE) was conceived to investigate the effects of microgravity on the formed elements of human blood. The experiment flew on the January 1986, 61-C mission of the Space Shuttle Columbia. The experiment hardware was designed to provide a closely controlled temperature and air flow environment for all blood samples. During the mission, two IBSE modules were on board the orbiter and an identical set of hardware and blood samples were maintained on Earth as a control. This paper describes the development and performance of the IBSE hardware which was converted from a conceptual design to an on-orbit, man-rated, mid-deck locker experiment in 17 months.

Blood Platelets↗