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Biomedical subjects

D A Silverman

Publications and source records attributed to D A Silverman.

16 recordsLinked to original sources
PubMed1996

Red blood cell spacing in rat coronary capillaries during the cardiac cycle.

Theoretical studies have demonstrated a pronounced effect of red blood cell (RBC) spacing on tissue oxygen supply. Our objective was to collect data regarding RBC spacing and related linear capillary hematocrit (Hct) in rat coronary capillaries, from two distinct locations within the capillary bed (proximal and distal portions), in the subendo- and midmyocardium, during systole and diastole. Hearts were rapidly frozen in situ, and tissue sections were stained in order to distinguish capillaries in proximal and distal portions of the capillary bed, as well as the RBCs within them. Morphometric data were compared according to capillary type, cardiac region, and cardiac phase. Distal portions of the capillary bed had a significantly greater capillary Hct (p < 0.001) and significantly lower RBC spacing values (P < 0.01), compared to proximal portions, irrespective of cardiac phase or region. There was a greater frequency of RBC spacing values equal to O microns in systole compared to diastole (P < 0.001) and a greater frequency of RBC spacing values greater than 40 microns in proximal portions of the capillary bed compared to distal portions (P < 0.001). These results suggest that intracapillary resistance to O2 transport is reduced, and O2 carrying capacity of the blood increased, in distal portions of the capillary bed, where PO2 in the blood is lower.

Animals↗
PubMed1995

Ontogeny of thermoregulation in the Djungarian hamster (Phodopus campbelli).

At birth, altricial Djungarian hamster pups require exogenous heat to grow and gain little benefit from huddling with their littermates. By day 6 huddled pups begin effective thermogenesis although isolated pups do not show spontaneous increases in temperature until day 9. On day 12, isolated pups can resist cooling for short periods of time and huddles do not cool within a 15 min test. By day 15, isolated pups can thermoregulate, although at a lower core body temperature than is typical of adults, and both huddling contact with littermates and direct contact with the dam are reduced. At weaning, pups are effectively thermally independent. This ontogeny is correlated with behavioral, morphological and physiological changes during pup development including brown adipose tissue (BAT) thermogenesis, pelage development and body size. The onset of thermogenesis, and then thermoregulation, causes temporary reductions in pup growth rate on days 6 and 7 and again on days 12 and 13. Body weight, rather than pup age, appears critical for independent thermoregulation. These results are discussed relative to the extent of maternal hyperthermia and the physiological demands of the concurrent gestation characteristic of reproduction in Djungarian hamsters.

Adipose Tissue, Brown↗
PubMed1995

Lymphopenic effect of carbamazepine in a patient with chronic lymphocytic leukemia.

OBJECTIVE: To report a dramatic and reproducible suppressive effect of carbamazepine on circulating lymphocytes in an elderly woman with chronic lymphocytic leukemia. CASE SUMMARY: An elderly woman taking phenytoin for a stroke-associated seizure disorder had lymphocyte count of 28,800 x 10(6) cells/L. Speculating an unusual lymphadenopathic effect of the phenytoin therapy, carbamazepine therapy was substituted. After 15 weeks of carbamazepine treatment, the lymphocyte count declined to 3200 x 10(6) cells/L. Because of severe diarrhea, carbamazepine therapy was stopped and phenytoin therapy was reinstituted. At the end of 4 months of phenytoin treatment, the lymphocyte count had increased to 23,200 x 10(6) cells/L. Phenytoin therapy was discontinued and carbamazepine therapy was begun. The lymphocyte count decreased to 10,700 x 10(6) cells/L. Severe diarrhea recurred and phenytoin treatment was reinstituted. Over 12 days the lymphocyte count increased to 28,900 x 10(6) cells/L. Phenytoin therapy was stopped and valproic acid therapy was started. The lymphocyte count continued to increase during valproic acid therapy, reaching a peak of 114,300 x 10(6) cells/L. DISCUSSION: In this patient with chronic lymphocytic leukemia, carbamazepine therapy had a significant and reproducible lymphopenic effect that was readily reversible upon discontinuation of the drug. Unfortunately, this effect was associated with severe diarrhea, preventing further attempts at exploiting this potentially beneficial action. CONCLUSIONS: Carbamazepine had a reproducible suppressive effect on lymphocyte counts in an elderly patient with chronic lymphocytic leukemia. This unique observation raises the possibility that carbamazepine therapy may have a useful effect in patients with chronic lymphocytic leukemia.

Aged↗
PubMed1989

Constant infusion fluorometry to predict flap survival.

Prediction of surgical flap survival in a dog model was evaluated by using the technique of fluorometry. The model provides a graded variation of flap ischemia with tissue necrosis occurring at the distal end. The indicator sodium fluorescein was administered via the saphenous vein at a constant infusion rate for 20 minutes. Quantitative fluorescence measurements were obtained with surface illumination of the flap at 132 sites for 15 flaps in the five animals. Wash-in slopes and wash-out clearances, both measures of tissue perfusion, were compared with the survival of flap regions observed at seven days. The sensitivity and specificity of fluorometric wash-in and wash-out measurements were compared in their ability to predict flap survival. The study showed sensitivities of 100% and 95% and specificities of 97% and 86%, respectively for the two methods. The wash-in procedure with constant infusion may be preferable to the wash-out technique since it requires less time to complete. In addition, it avoids bolus injections thus reducing the risk of anaphylactoid reactions.

Animals↗
PubMed1976

Enzymatic method for determination of CO2 in serum.

We describe an enzymatic method, requiring only 10 mul of serum, for determining CO2 as bicarbonate or dissolved gas. Phosphoenolpyruvate carboxylase catalyzes the reaction of HCO3- with phosphoenolypyruvate to give oxalacetate. The resulting NADH, in the presence of malate dehydrogenase, is oxidized to NAD+, and the decrease in absorbance at 340 nm is directly proportional to the amount of CO2 present in the sample. Reaction is complete in 3 to 6 min under assay conditions, and is linearly related to CO2 concentrations between 8 and 65 mmol/liter. Analytical recovery is 95-110% (average, 101%). Two laboratories compared values obtained by continuous-flow analysis. The resulting correlation coefficients were 0.966 and 0.987, values for the t-test were t(paired) equals 0.473 and t(paired) equals 0.334, and average day-to-day precisions (three concentrations) were 3.9% and 4.2%.

Autoanalysis↗
PubMed1975

Spontaneous and methylcholanthrene-enhanced thyroiditis in BUF rats. I. The incidence and severity of the disease, and the genetics of susceptibility.

Virgin female Buffalo strain (BUF) rats that were treated with methylcholanthrene (MC) had a higher incidence of lymphocytic thyroiditis than untreated BUF rats. The degree of infiltration was also greater in MC-treated rats. The incidence of thyroiditis in retired breeder female BUF rats approached that found in MC-treated rats. The susceptibility to the effect of MC was not expressed in most F-1 hybrids of BUF and Lewis (LEW), a strain of rat that does not develop thyroiditis after treatment with MC.

Animals↗
PubMed1974

Neonatal thymectomy increases the incidence of spontaneous and methylcholanthrene-enhanced thyroiditis in rats.

At 16 weeks of age, 13 percent of untreated Buffalo strain rats showed evidence of autoimmune thyroiditis. Feeding methylcholanthrene increased the incidence to 42 percent. Neonatal thymectomy significantly raised the incidence of disease so that almost all (87 percent) untreated and all methylcholanthrene-treated animals developed severe disease. It is proposed that the thymus exerts a regulatory effect on autosensitization.

Age Factors↗