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Biomedical subjects

J B Peterson

Publications and source records attributed to J B Peterson.

16 recordsLinked to original sources
PubMed1992

Dependence of oxygen-tolerant nitrogenase activity on divalent cations in Azotobacter vinelandii.

Nitrogenase activity of washed Azotobacter vinelandii cells was enhanced by the addition of Ca2+ and Mg2+, and the enhancement increased with the O2 concentration. In assays provided with a level of O2 that was initially supraoptimal and inhibitory to nitrogenase activity, the addition of Ca2+ or Mg2+ affected both the maximum respiration rate (Vmax) of the cells and the apparent affinity [KS(O2)] of cell respiration for O2. Changes in these parameters correlated with changes in nitrogenase activity. Aeration-dependent increases in Vmax and KS(O2) were inhibited by rifampin and chloramphenicol and were also observed in ammonium-grown cultures.

Acetylene↗
PubMed1992

Cognitive dysfunction and the inherited predisposition to alcoholism.

A battery of neuropsychological tests was administered to 22 nonalcoholic sons of male alcoholics (SOMAs) from families with extensive histories of male alcoholism and to 22 nonalcoholic controls with no history of familial alcoholism. In each group 11 subjects were tested while sober and 11 were tested while alcohol-intoxicated. Analyses of the results of this battery suggested (1) that SOMAs may be characterized by comparative decrements in those cognitive functions associated with the organization of novel information, dependent in theory upon the prefrontal cortex; and (2) that alcohol detrimentally affects delayed memory, associated with the temporal cortex, equally across groups. Of these SOMAs 20 had previously participated in one of two studies that demonstrated their cardiovascular hyper-reactivity to threat/stress and their increased sensitivity to the reactivity-dampening effects of alcohol intoxication. Correlational analyses of the results of the present and previous studies demonstrated the existence of a highly significant relationship between cognitive impairment, cardiovascular hyper-reactivity and susceptibility to the reactivity-dampening effects of alcohol.

Adult↗
PubMed1992

Factor structure and correlates of the Tridimensional Personality Questionnaire.

Cloninger has proposed a model linking personality characteristics to patterns of responses to various stimuli, including alcohol. The model also uses personality characteristics to divide alcoholics into two types. In order to assess the relevant aspects of personality, the Tridimensional Personality Questionnaire (TPQ) was developed. This study examined the factor structure and correlates of the questionnaire to shed light on its validity. A confirmatory factor analysis of the TPQ failed to replicate the three proposed factors of novelty seeking, harm avoidance and reward dependence. Alternative models also failed to fit the data. The three factors were correlated with other personality measures theoretically linked to drinking (MacAndrew, Socialization and Sensation-Seeking scales), quantity and frequency measures of alcohol use and a measure of alcohol abuse (the Michigan Alcoholism Screening Test). The pattern of correlations provides evidence for the convergent validity of the TPQ. Nevertheless, the failure to replicate the factor structure suggests that the scale requires further revision before the model can be adequately tested.

Adolescent↗
PubMed1991

The Tridimensional Personality Questionnaire and the inherited risk for alcoholism.

The Tridimensional Personality Questionnaire (TPQ) (Cloninger, 1987c) was administered to four groups of young men. The first group was composed of nonalcoholic sons of male alcoholics with extensive multigenerational family histories of male alcohol abuse. The second was made up of nonalcoholic men with alcoholic fathers. The third group was composed of nonalcoholic men with no family history of alcoholism, taken from the general population. The fourth group contained male undergraduates with no family history of alcoholism. There were no significant differences between the mean scores obtained by members of all four groups on the three major subscales of the TPQ.

Alcoholism↗
PubMed1991

A biobehavioural model for the inherited predisposition to alcoholism.

Sons of male alcoholics are at increased risk for the development of alcoholism, and are characterized as well by other traits, that may serve as markers for the alcoholic predisposition. These other traits include mild cognitive abnormalities, cardiac hyper-reactivity to signalled electric shock, susceptibility to alcohol-intoxication elimination of that hyper-reactivity, and increased baseline heart-rate while drinking.

Alcohol Drinking↗
PubMed1990

Information processing, neuropsychological function, and the inherited predisposition to alcoholism.

Sons of male alcoholics are at particularly heightened risk for the development of alcoholism. This heightened risk frequently appears in association with increased incidence of conduct disorder or hyperactivity, with deficits in abstract thinking and poor school performance, with abnormalities in cued psychophysiological response, and with increased sensitivity to the putatively stress-response-dampening effects of alcohol intoxication. This risk and its associated features are discussed within the context of a neuropsychological theory, predicted on the notions (1) that deficits in cognitive functions theoretically dependent upon the intact functioning of the prefrontal cortex could underlie manifestation of the idiosyncracies commonly attributed to sons of male alcoholics, and (2) that acute alcohol intoxication could relieve the subjective discomfort associated with the consequences of such deficits.

Alcoholism↗
PubMed1990

Acute alcohol intoxication and cognitive functioning.

Acute alcohol intoxication produces changes in the cognitive functioning of normal individuals. These changes appear similar prima facie to those exhibited by individuals who sustain prefrontal lobe damage during adulthood. In order to test the validity of this observation, and to control for the confounding effects of expectancy, 72 male subjects were administered a battery of neuropsychological tests, within the context of a balanced-placebo design. Each subject received one of three widely different doses of alcohol. Analysis of the results of the cognitive test battery demonstrated that a high dose of alcohol detrimentally affects a number of functions associated with the prefrontal and temporal lobes, including planning, verbal fluency, memory and complex motor control. Expectancy does not appear to play a significant role in determining this effect. The implications of this pattern of impairment are analyzed and discussed.

Adolescent↗
PubMed1989

Fluorescence monitoring of flavins during preparation of respiratory membranes.

Azotobacter vinelandii large and small membrane particles were examined by fluorescence spectroscopy through purification to qualitatively monitor contamination by non-respiratory flavin. Flavin was analyzed by observing the effects of reduction by dithionite or NAD(P)H and subsequent oxidation. Flavin of the large particles did not change significantly with purification on a sucrose gradient. The small particle or R3 fraction contained relatively large amounts of non-respiratory flavin. Small particles eluted from a Sepharose CL-6B column with a fluorescence peak but still contained contaminating flavin. After centrifugation on a sucrose gradient, the flavin of these particles was essentially the same as the large particles. This method is an improvement over just observation of fluorescence intensity for monitoring flavoprotein purity of membrane particle preparations.

Azotobacter↗
PubMed1987

Chromogranin A-like proteins in the secretory granules of a protozoan, Paramecium tetraurelia.

The ciliate protozoan Paramecium tetraurelia produces secretory granules (trichocysts) which release needle-like structures composed of small, acidic proteins. Using antibodies against isolated chromogranin A (CGA) and against trichocyst proteins, we found cross-reactive proteins in chromaffin granules and trichocysts. Four independently derived sera against isolated CGA stained bands of the Mr 15,000-25,000 family of trichocyst proteins on immunoblots. A positive response was also obtained with antiserum against chemically synthesized peptides (PL26 and GE25) corresponding to defined regions of the CGA amino acid sequence. In extracts of whole Paramecium, larger proteins (Mr 53,000 and 49,000) also reacted with antibodies against CGA and the related synthetic peptides. These larger proteins may represent unprocessed precursors to the smaller proteins of mature trichocysts. Antiserum to trichocysts recognized CGA in chromaffin granule lysates. Further evidence of a Paramecium protein related to CGA was provided by hybridization of Paramecium mRNA with cloned cDNA for bovine CGA. Our results suggest striking conservation in evolution of CGA-like proteins that may play some role, as yet unknown, in secretion.

Animals↗
PubMed1987

Dissociation and reassociation of trichocyst proteins: biochemical and ultrastructural studies.

Trichocysts, the crystalline exocytotic organelles in Paramecium tetraurelia, are composed of small, acidic proteins existing primarily as disulphide-linked dimers. We have disaggregated trichocyst proteins with heat, simultaneously observing the changes in morphology and protein composition. The tip matrix was most heat-labile; its subunits progressively broke away from the distal end. During this process, breakdown of the cylindrical shaft began. Shafts first became flattened and torn lengthwise, yielding smaller, interconnected pieces still having the crystalline arrangement of their 5 nm thick fibres. Ultimately this pattern became disordered, and discrete fibrils of the same thickness disengaged from the meshwork. In freeze-etched preparations these fibrils were composed of thinner filaments in side-by-side association. Disaggregation of the tip sheath began from the distal end before shaft dissociation was complete. Trichocysts broke down to thin fibrils, but probably not to monomeric subunits. At least three proteins were preferentially released in the initial phase of dissociation. Disulphide-reducing agent present during heating increased the rate of dissociation without altering the sequence of morphological changes or the order of release of individual proteins. The rate and extent of heat-induced dissociation were strongly dependent on pH and cation concentration. The stabilizing effects of low pH and of cations were additive. A cooled suspension of fully dissociated trichocysts reassociated into sedimentable aggregates with discernible filamentous order, but without the crystalline structure of intact trichocysts. Reassociation was dependent upon time, temperature and protein concentration. All but one of the trichocyst proteins re-entered the sedimentable aggregate during reassociation. Reassociation was faster and more complete at pH 6 than at pH 8 and was stimulated by Ca2+, Mg2+ and La3+. Trichocyst proteins dissociated in the presence of dithiothreitol did not reassociate, even after removal of the reducing agent. Trichocysts from mutants defective to varying degrees in trichocyst formation were subjected to similar experimental protocols. Heat-dissociated trichocysts of the mutants scc6 and ptA1 reassociated at rates similar to those of wild-type; ftA3 showed slower reassociation, and tam38 showed little or no reassociation. Reassociation of wild-type trichocyst proteins was blocked by the addition of an equal amount of tam38 trichocyst proteins.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Antibodies to the ciliary membrane of Paramecium tetraurelia alter membrane excitability.

Immobilization of Paramecium followed the binding of antibodies to the major proteins of the ciliary membrane (the immobilization antigens, i-antigens, approximately 250,000 mol wt). Immunoelectron microscopy showed this binding to be serotype-specific and to occur over the entire cell surface. Antibody binding also reduced the current through the Ca-channel of the excitable ciliary membrane as monitored using a voltage-clamp. The residual Ca-current appeared normal in its voltage sensitivity and kinetics. As a secondary consequence of antibody binding, the Ca-induced K-current was also reduced. The resting membrane characteristics and other activatable currents, however, were not significantly altered by the antibody treatment. Since monovalent fragments of the antibodies also reduced the current but did not immobilize the cell, the electrophysiological effects were not the secondary consequences of immobilization. Antibodies against the second most abundant family of proteins (42,000-45,000 mol wt) had similar electrophysiological effects as revealed by experiments in which the Paramecia and the serum were heterologous with respect to the i-antigen but homologous with respect to the 42,000-45,000-mol-wt proteins. Protease treatment, shown to remove the surface antigen, also caused a reduction of the Ca-inward current. The loss of the inward Ca-current does not seem to be due to a drop in the driving force for Ca++ entry since increasing the external Ca++ or reducing the internal Ca++ (through EGTA injection) did not restore the current. Here we discuss the possibilities that (a) the major proteins define the functional environment of the Ca-channel and that (b) the Ca-channel is more susceptible to certain general changes in the membrane.

Animals↗
PubMed1979

Phosphoenolpyruvate carboxylase from soybean nodule cytosol. Evidence for isoenzymes and kinetics of the most active component.

Phosphoenolpyruvate carboxylase (orthophosphate:oxaloacetate carboxylase (phosphorylating), EC 4.1.1.31) from plant cells of soybean nodules was studied to assess its role in providing carbon skeletons for aspartate and asparagine synthesis. The enzyme was purified 119-fold by (NH4)2SO4 fractionation and DEAE-cellulose, BioGel A-1.5m, and hydroxyapatite chromatography. Five activity bands were resolved with discontinuous polyacrylamide gel electrophoresis. A small quantity of enzyme from the most active band was separated from the others by preparative electrophoresis. The apparent Michaelis constants of this enzyme for phosphoenolpyruvate and HCO3- were 9.4.10(-2) and 4.1.10(-1) mM, respectively. A series of metabolite tested at 1 mM had no significant effect on enzyme activity. These experiments indicate that the major factors directly controlling phosphoenolpyruvate carboxylase activity in vivo are phosphoenolpypyruvate and HCO3- concentrations.

Adenosine Monophosphate↗
PubMed1976

Electron-microscopic study of the spindle and chromosome movement in the yeast Saccharomyces cerevisiae.

Mitosis in yeast Saccharomyces cerevisiae was investigated in thick (0-25-I mum) serial sections with a high voltage electron microscope and in preparations of spheroplasts spread on a water surface. Spindle microtubules originate from a plaque-like structure called the spindle pole bosis the SPB duplicates and a set of long and short microtubules develops on each SPB. The spindle arises as the SPBs separate on the nuclear membrane adense and are not individually visible. Genetic studies, however, have indicated that there are 17 linkage groups. The number of microtubules was determined in diploid and haploid spindles on serial stereo micrographs. In diploid mitosis about 40 microtubules issue from a SPB. Most are non-continuous and often they are visibly associated with a chromatin fibre. The spindle in haploid cells is similar except that the number of microtubules is about half that in diploid cells and the SPB is smaller. The pole-to-pole microtubules vary in number from spindle to spindle, but in each case enough microtubules are present to account for each linkage group being associated with a single non-continuous microtubule. We conclude that mitosis in yeast is comparable in its general aspect to that observed in typical eukaryotes.

Chromatin↗
PubMedDate not supplied

Small GTP-binding proteins associated with secretory vesicles of Paramecium.

GTP-binding proteins act as molecular switches in a variety of membrane-associated processes, including secretion. One group of GTP-binding proteins, 20-30 kDa, is related to the product of the ras proto-oncogene. In Saccharomyces cerevisiae, ras-like GTP-binding proteins regulate vesicular traffic in secretion. The ciliate protist Paramecium tetraurelia contains secretory vesicles (trichocysts) whose protein contents are released by regulated exocytosis. Using [alpha-32P]GTP and an on-blot assay for GTP-binding, we detected at least seven GTP-binding proteins of low molecular mass (22-31 kDa) in extracts of Paramecium tetraurelia. Subcellular fractions contained characteristic subsets of these seven; cilia were enriched for the smallest (22 kDa). The pattern of GTP-binding proteins was altered in two mutants defective in the formation or discharge of trichocysts. Trichocysts isolated with their surrounding membranes intact contained two minor GTP-binding proteins (23.5 and 29 kDa) and one major GTP-binding protein (23 kDa) that were absent from demembranated trichocysts. This differential localization of GTP-binding proteins suggests functional specialization of specific GTP-binding proteins in ciliary motility and exocytosis.

Animals↗