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Biomedical subjects

M Shi

Publications and source records attributed to M Shi.

118 records · Page 7Linked to original sources
PubMed1989

Further characterization of phasic calcium influx in rat cerebrocortical synaptosomes: inferences regarding calcium channel type(s) in nerve endings.

Under conditions minimizing the contribution of Na+/Ca2+ exchange to calcium entry in synaptosomes, the K+ depolarization-dependent calcium influx (JCa) is a single exponential function of time. JCa activates and slowly inactivates at membrane potentials positive to -50 mV, a result indicating the involvement of moderate voltage-activating, slowly inactivating calcium channels. Calcium channels in synaptosomes are characterized by stronger sensitivity to blockage by Cd2+ than Co2+, insensitivity to dihydropyridine calcium antagonists or the agonist Bay K 8644, and weak, partial sensitivity to the peptide toxin omega-conotoxin GVIA. These characteristics suggest that voltage-sensitive calcium channels in rat cerebrocortical synaptosomes are dissimilar from the somatic T, N, or L channel types. JCa is not affected by treatment of synaptosomes with the adenylate cyclase activator forskolin, the membrane permeant dibutyryl-cyclic AMP, or the kinase C activator phorbol 12-myristate 13-acetate diester, results suggesting that calcium channels in synaptosomes are not directly modulated by protein kinase A- or C-mediated phosphorylation.

Animals↗
PubMed1989

The effect of washing on the surface charge of Mycobacterium bovis BCG vaccine, Tice substrain.

The zeta potential of three lots of Tice substrain BCG organisms was measured over a pH range of 2.0 to 11.0 at low electrolyte concentration. For two lots, the cells were cationic at pH 4.2-4.4 and anionic above this isoelectric point. Washing the cells twice with water lowered the isoelectric point to 2.7. The cationic/anionic profile was retained in all three lots, although the third lot had an isoelectric point of 3.0 initially. Cells of the Glaxo substrain, on the other hand, were anionic over the entire pH range and are evidently unaffected by the washing process. It appears that cells of the Glaxo strain have only electronegative phosphate groups at their surface whereas the Tice substrain may possess a loosely adhering cell-surface protein.

BCG Vaccine↗
PubMed1989

Comparison of Karl Fischer titrimetric and gravimetric methods for determination of moisture content in BCG vaccine.

A model 447 Coulomatic K-F titrimeter was used to determine the water content of seventeen lots of freeze-dried Tice-substrain BCG vaccine. The results were compared with corresponding moisture contents determined by a standard gravimetric method at the time of manufacture. The advantages of the titrimetric method include simplicity, rapidity, convenience, sensitivity, reproducibility and specificity, whereas the gravimetric method is tedious and time-consuming. Although moisture content determined by the K-F titrimeter tended to be higher than that determined by the gravimetric method, the results correlated significantly (r = 0.882, P less than 10(-5]. Alteration of national and international regulations to permit use of the K-F titrimeter is recommended.

BCG Vaccine↗
PubMed1988

Organ weight standards for human fetuses.

Five hundred fifty-eight fresh human embryos and fetuses were obtained from the universities of Washington and Michigan following spontaneous loss, elective termination, or neonatal death within 2 days of delivery. The body weights ranged from 1.5 to 1500 g. Each of these autopsied specimens was morphologically normal. Specimens from diabetic or hypertensive mothers were not included. Correlations between fetal body weight and weights of adrenal, brain, kidney, liver, lung, spleen, and thymus were established. For analysis, regression curves were calculated as quadratic equations of best fit by the weighted least squares. The relation of the weights of brain, heart, and liver to body weight appeared linear. The ratios of thymus, spleen, and kidney to body weight were nonlinear and gradually increased. The ratios of lung and adrenal weights to body weight were also nonlinear and gradually decreased. Ninety-five percent prediction intervals were generated for each of the eight organs using a computerized statistical package. The results compare closely with smaller studies in the literature.

Body Weight↗
PubMedDate not supplied

Acute adaptation of mice to hypoxic hypoxia.

Tolerance to hypoxia in vivo and in vitro was significantly increased by acute and repetitive exposure of mice to autoprogressive hypoxia. The average tolerance times of the successive 2nd, 3rd, 4th and 5th runs of exposure were, respectively, 2, 4, 6 and 8 times as long as that of the first exposure. The survival times under hypobaric chamber and cyanide toxification in the 4th exposure were, respectively, 10 (and even as much as 86) and 4 times those in control mice without exposure to hypoxia. Mandibular respiration and spinal reflex in vitro in hypoxia-resistant animals lasted 5-6 times as long as in control animals not previously exposed to hypoxia. Animals that received brain homogenate from hypoxia-resistant mice remained alive in a hypobaric chamber 2 times as long as those that received homogenate from controls and those that received saline. These results indicate that a kind of quickly developing adaptation with increased tolerance is achieved by acute and repetitive exposure of mice to progressive autohypoxia and some plastic or adaptive changes occur in the brain of hypoxia-resistant animals, including the production of some kind of water-soluble antihypoxic factors.

Adaptation, Physiological↗