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Biomedical subjects

A White

Publications and source records attributed to A White.

At least 469 records · Page 26Linked to original sources
PubMed1976

Effect of concanavalin A on expression of cell surface sialyltransferase activity of mouse thymocytes.

Incubation of mouse thymocytes with mitogenic concentrations of concanavalin A causes a 2-fold increase in cell-surface-associated (but not total cell) sialyltransferase activity (ectosialyltransferase, CMP-N-acetylneuraminate:D-galactosyl-glycoprotein N-acetylneuraminyltransferase, EC 2.4.99.1) as judged by incorporation of [14C]sialic acid into endogenous cell acceptors and into added desialylated fetuin acceptor. The concanavalin-A-induced enhancement of enzymic activity is essentially complete within 1 hr after addition of mitogen and remains at elevated levels for 12 hr, declining rapidly thereafter. Intact cells labeled previously with [14C]sialic acid and then incubated briefly with hydrolytic enzymes, including neuraminidase and insoluble trypsin, released 43-66% of total cell-associated radioactivity without appreciably changing cell viability. Alterations in sialyltransferase activity due to concanavalin A treatment could not be explained by a mitogen-mediated (a) uptake of radioactive precursors, (b) cell death, (c) increased product catabolism, or (d) activation of sialyltransferase by mitogen binding to the enzyme. Furthermore, the process does not require active protein synthesis. The results are consistent with a rapid concanavalin-A-induced exposure of potential enzymic activity that was previously inaccessible to substrate.

Animals↗
PubMed1975

The topography of lactose synthesis.

1. At short incubation times, and under suitable osmotic conditions, the lactose synthesized by Golgi-derived vesicles of rat mammary gland is 85-90% particulate. Evidence is presented for its occlusion within the lumen of the vesicles. 2. Ovalbumin is used as a bulky active-site inhibitor to show that the active site of lactose synthase lies on the inner face of the Golgi membrane. 3. Phlorrhizin and phloretin inhibit lactose synthesis by such vesicles, indicating the presence of a glucose-transport system. 4. The relationship of this topography to the synthesis of N-acetylneuraminyl-lactose and to the secretion of milk sugars is discussed.

Animals↗
PubMed1975

Species, strain, sex and individual differences in enflurane metabolism.

Species, sex and individual differences in serum inorganic fluoride concentrations were demonstrated in mice, guineapigs and rats exposed to either 0.07% or 0.2% enflurane for 35 days, suggesting differences in enflurane biotransformation. Exposure of Fischer 344 rats and Sprague-Dawley rats to 0.2% enflurane for 8 days resulted in enzyme induction as demonstrated by increasing serum inorganic fluoride and cytochrome P-450 concentrations. However, there was no difference in cytochrome P-450 concentrations between the strains despite differences in inorganic fluoride concentration. These results emphasize the multiplicity of factors and the lack of predictability in patterns of enflurane metabolism among species, strains and individuals.

Animals↗
PubMed1975

Anatomical factors in difficult direct laryngoscopy.

The anatomical factors in difficult direct laryngoscopy have been assessed. Thirteen patients in whom direct laryngoscopy proved difficult and thirteen control patients, all with teeth, had lateral, postero-anterior and submento-vertical radiographs taken. Several measurements were made and compared. The most important factor determining the ease of examination was the posterior depth of the mandible. An increase in this measurement was thought to hinder displacement of the soft tissues by the laryngoscope blade. Other factors of importance were: an increase in the anterior depth of the mandible; a reduction in the distance between the occiput and the spinous process of C1, and to a lesser extent the C1-C2 interspinous gap; and reduced mobility of the mandible associated with temporo-mandibular joint arthritis or trismus.

Adult↗
PubMed1975

Comparative toxicities of halothane, isoflurane, and diethyl ether at subanesthetic concentrations in laboratory animals.

Effects of 35-day exposures to subanesthetic concentrations of halothane, isoflurane, and diethyl ether were measured in mice, rats, and guinea pigs which were in a phase of rapid body growth. Halothane produced a greater decrement in weight gain and a greater incidence of hepatic degenerative changes than isoflurane or diethyl ether despite its administration at lower anesthetic concentrations. Isoflurane results were intermediate between those of halothane and diethyl ether. No consistent injury to any organ other than the liver was found.

Anesthesia, Inhalation↗
PubMed1975

The importance of sodium balance on the effect of angiotensin II on aldosterone production.

The action of angiotensin II on the adrenal cortex can be modified by body sodium balance. The secretion rate of aldosterone was compared with the late biosynthetic pathway in dogs kept under different sodium states. The conversion of corticosterone (B) to aldosterone was significantly increased by the infusion of angiotensin II into sodium depleted dogs. ACTH infusion failed to increase the late aldosterone pathway in sodium depleted animals, even though the secretion rate increased by 10 times. These results confirm previously indirect evidence that angiotensin II has a direct stimulatory effect on the late step of aldosterone biosynthesis. This stimulation does not appear to be the result of enzyme-substrate activation by aldosterone precursors. The results favour the hypothesis that sodium balance can modulate the action of angiotensin II not only on the first steps, but that there is also a regulatory effect on the conversion of corticosterone to aldosterone.

Adrenal Glands↗
PubMed1975

Selective immunosuppressive activity of steroids in mice inoculated with the Moloney Sarcoma virus (38503).

A steroid, 6-chloro-17-hydroxypregna-1,4,6-triene-3,20-doine (CHP) that exhibits selective activity in several models of cellular immunity including an apparent inhibitory action on the elicitation of delayed hypersensitivity, was examined in a new, simple experimental model for assessing aspects of host-cell-mediated immunological competence. This model is based upon the capacity of the adult mouse to prevent the progressive growth of tumors induced by the Moloney sarcoma virus. Two steroids reported to have immunosuppressive activity in other assay systems, namely, cortisol and progesterone, were also studied. Control mice and those injected with CHP maintained their capacity to reject the tumor. In contrast, significant numbers of mice receiving a single large injection of cortisol or progesterone succumbed to progressive tumor growth under the experimental conditions used. The data indicate that CHP, while influencing selected parameters of cellular immunity, e.g., the elicitation of delayed hypersensitivity, does not decrease the capacity of the host to mount a defense against the progressive growth of the Moloney virus-induced sarcoma. The results indicate that CHP may be useful in modulating specific aspects of cellular immunity without altering others. In addition, the experimental model described provides a simple method of assessing the possible immunosuppressive effects of naturally occurring and synthetic agents on viral-induced tumor growth.

Animals↗