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Biomedical subjects

G Wong

Publications and source records attributed to G Wong.

195 records · Page 11Linked to original sources
PubMed1976

Maleylacetone cis-trans-isomerase: affinity chromatography on glutathione-bound sepharose. Two-substrate-binding sequence from inhibition patterns.

Maleylacetone cis-trans-isomerase isolated from Vibrio 01 binds glutathione strongly; Km = 1.4 X 10(-4) M. Oxidized glutathione and S-methylglutathione are competitive inhibitors, KI = 9.4 X 10(-4) and 1.2 X 10(-3) M, respectively. Based on these interactions, three different glutathione-bound agarose affinity adsorbents were synthesized and tested. Affinity chromatography of the isomerase with one of these affords 70- to 100-fold purifications. In separate syntheses, portions of the affinity arm were prepared and examined as to their inhibitory properties in the enzyme-catalyzed reaction. The fragment, containing glutathione bound through its sulfur to the carbon chain, is a powerful competitive inhibitor for glutathione (KI = 6 X 10(-5) M). The results described suggest that the isomerase binds glutathione through the backbone of the tripeptide and that the thiol group is required for activity. The initial velocity patterns of the enzyme-catalyzed reaction resulting from simultaneous variation of glutathione and maleylacetone concentrations were examined in the absence and presence of inhibitors resembling glutathione. The observed kinetic patterns suggest an ordered sequence of binding maleylacetone first followed by glutathione.

Binding Sites↗
PubMedDate not supplied

[3H]MK-801 binding in various brain regions of rat lines selected for differential alcohol sensitivity.

N-Methyl-D-aspartate (NMDA) receptors are sensitive to ethanol at concentrations relevant to intoxication. To ascertain possible involvement of NMDA receptors in differential ethanol sensitivity between alcohol-sensitive ANT (alcohol-nontolerant) and alcohol-insensitive AT (alcohol-tolerant) rat lines, characterization of a noncompetitive NMDA antagonist [3H]MK-801 binding to brain membranes was carried out. Saturation analyses of [3H]MK-801 binding to cerebrocortical, hippocampal, and cerebellar synaptosomal membranes revealed no statistically significant differences in either the affinity constant (Kd) or binding site density (Bmax) between the rat lines. Autoradiographic analysis of [3H]MK-801 binding to ANT and AT brain sections revealed a regionally heterogenous distribution of binding, without any detectable differences between the AT and ANT sections whether these were prepared from the brains of acutely ethanol-treated or nontreated animals. Glutamate, glycine, or the two in combination greatly increased [3H]MK-801 binding to brain membranes. In extensively washed crude cerebrocortical membranes, the maximal effect (Emax), but not potency (EC50) of glycine to increase [3H]MK-801 was slightly greater (p < 0.01) in the ANT than AT rats. The effects of glutamate or glutamate in the presence of saturating concentration of glycine (30 microM) were not significantly different between the two lines. Association parameters (t1/2 and Beq values) of [3H]MK-801 to its cortical binding sites were also similar. These results do not indicate any clear qualitative difference in [3H]MK-801 binding to NMDA receptors or in its modulation by glutamate and glycine between the ANT and AT rat lines.

Animals↗
PubMedDate not supplied

Accuracy of clinical impressions and Mini-Mental State Exam scores for assessing capacity to consent to major medical treatment. Comparison with criterion-standard psychiatric assessments.

The authors evaluated the accuracy of clinical impressions and Mini-Mental State Exam scores for assessing patient capacity to consent to major medical treatment, relative to expert psychiatric assessment. Consecutive medical inpatients (N = 63) facing a decision about major medical treatment received a clinical impression of capacity from their treating physician and the Standardized Mini-Mental State Exam (SMMSE); 48 received independent psychiatric assessment of capacity. Analyses revealed that both clinical impressions and SMMSE scores were generally inaccurate in determining capacity, although all 23 participants with a clinical impression of "definitely capable" were found capable by the psychiatrist. Given the importance of assessing capacity to consent to major medical treatment, better approaches to the clinical assessment of capacity are required. Several strategies are discussed.

Adult↗
PubMedDate not supplied

Transient reversion of ras oncogene-induced cell transformation by antibodies specific for amino acid 12 of ras protein.

The proteins encoded by the ras oncogene are thought to trigger expression of the transformed phenotype in some types of cancer cells. In human cells, the ras protein family consists of several members including normal (proto-oncogene) and mutant (oncogene) forms. In general, the proto-oncogene forms are thought to be involved in the normal growth control of cells, while the mutant forms (which apparently result from somatic mutation of the normal ras genes) appear to be responsible, in part, for the loss of normal growth control. On microinjection into living normal cells, the purified ras oncogene protein (p21) induces a characteristic loss of growth control in cells within several hours. The mutant forms of the different ras proteins typically contain a single amino-acid change, usually at position 12 or less frequently at position 61. Here we report that microinjection of antibodies specific for amino acid 12 of the oncogenic v-Ki-ras protein into cells transformed by this protein causes a transient reversion of the cells to a normal phenotype. The fact that this antibody inhibits binding of GTP to the v-Ki-ras protein supports the notion that GTP binding is essential to the transforming function of this oncogene product.

Amino Acid Sequence↗
PubMedDate not supplied

The acupuncture treatment of low back pain: a randomized controlled study.

The acupuncture treatment situation was beneficial to the majority of people with low back pain. This was shown by the use of short-term controls and long-term controls, although the latter were not intended in the study design. After acupuncture, there was a 51% pain reduction in the average pain score in the Immediate Treatment Group. The short-term controls, the Delayed Treatment Group, had no reduction whatsoever in their pain scores at the comparable followup period. Later, the Delayed Treatment Group bere also treated by acupuncturists, and reported 62% less pain. When these two treatment groups were compared at 40 weeks with long-term controls (Inadequate Treatment Group), the Inadequate Treatment Group still had the same pain scores, on the average, as when they enrolled in the study. Both treatment groups, on the average, had 30% lower pain scores. Furthermore, 58% of the treatment groups felt that they were definitely improved at 40 weeks, while only 11% of the Inadequate Treatment Group felt definitely improved at 40 weeks.

Acupuncture Therapy↗
PubMedDate not supplied

Expression of neurotrophins BDNF and NT-3, and their receptors in rat brain after administration of antipsychotic and psychotrophic agents.

We have investigated the potential role of neurotrophic factors in antipsychotic drug action by examining the effects of antipsychotic and psychotropic treatments on the mRNA expression of brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and their receptors, trkB and trkC, respectively, in rat brain. Neither acute nor chronic clozapine treatment significantly affected the expression of these mRNAs in any brain area investigated, except for a decrease in trkB expression in the granule cells of the olfactory bulb. We then examined the effects of the psychotropic agent MK-801. MK-801 (5 mg/kg; 4 h) significantly increased BDNF mRNA in the entorhinal cortex, but did not influence NT-3, trkB, or trkC expression in any brain area except for the olfactory bulb. The induction of BDNF mRNA by MK-801 was attenuated by pre-treatment (1 h prior to MK-801 administration) with the antipsychotics, clozapine (25 mg/kg) and haloperidol (2 mg/kg), but not with the antidepressant desipramine (15 mg/kg). Finally, we confirmed that the effects of MK-801 on BDNF mRNA were reflected in the respective changes in BDNF protein levels: MK-801 significantly increased anti-BDNF reactivity in the entorhinal cortex (126 +/- 7% of control) while concomitantly decreasing in the hippocampus (71 +/- 2% of control). These data do not support the hypothesis that neurotrophins play an important role in antipsychotic drug action, but rather suggest that induction of BDNF in the entorhinal cortex may play a significant role in the psychotropic action of MK-801.

Animals↗
PubMedDate not supplied

[Feeding habits of raccoon (Procyon lotor) (Carnivora: Procyonidae) in a coastal, tropical wet forest of Costa Rica].

Raccoon (Procyon lotor) food habits were studied at Manuel Antonio National Park, a tropical rain forest in the Pacific coast of Costa Rica from May to December 1987, from September to December 1989 and from January to April 1990. A 134 feces sample size was used to assess the most important items in raccoon diet: two crab species (Gecarcinus quadratus and Cardisoma crassum) with a relative frequency of 0.94 in the rainy season of 1987, 0.76 in the rainy season of 1989 and 0.65 in the dry season of 1990. Fruits were the second category in importance, with relative frequencies of 0.09 for 1987, 0.32 for 1989 and 0.44 for 1990.

Animals↗