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Biomedical subjects

R M Levin

Publications and source records attributed to R M Levin.

14 recordsLinked to original sources
PubMed1979

A practical approach for the evaluation of women with abnormal polytomography or elevated prolactin levels.

Based upon the experience gained in the evaluation of 60 patients with abnormal polytomography and/or elevated prolactin levels, the following observations can be made: Patients with amenorrhea, amenorrhea and galactorrhea, galactorrhea alone, or anovulatory cycles and infertility may or may not have pituitary tumors. Clinical symptoms do not always correlate with the prolactin level, and patients with normal prolactins may have pituitary tumors. The incidence of empty sella is significant (15.8% in this series). Visual field examination is not a useful screening procedure, but evaluation of thyroid function is important to detect the occasional patient with hypothyroidism (3.5% in this series). The insulin tolerance test is not helpful in detecting the presence of pituitary tumors or in guiding management decisions, and the CT scan contributes little and should be omitted from the evaluation process. A straightforward, economical, and efficient approach to this clinical problem is presented.

Adenoma↗
PubMed1979

Quantitative analysis of alpha and beta adrenergic receptor densities in the lower urinary tract of the dog and the rabbit.

Using specific radioligand receptor binding assays, we have, for the first time, quantitated both alpha- and beta-adrenergic receptors in the musculature of the lower ureter, bladder body, posterior bladder base, and proximal urethra of the dog, and in the bladder base and body of the rabbit. For the beta receptor assay 3H-dihydroalprenolol was used as the ligand, and, for the alpha receptor assay, 3H-dihydroergocryptine was used. In the dog, there was a significantly greater density of beta receptors in the bladder body than in either the ureter or the posterior bladder base. The urethra had an intermediate density. The bladder base and the proximal urethra had a significantly greater density of alpha receptors than either the ureter or the bladder dome. The dissociation constant of beta receptors for DHA was approximately 9 nM for all tissues studied, and that of alpha receptors for DHE approximately 7 nM. A similar distribution of alpha-and beta adrenergic receptors was seen in the rabbit bladder.

Alprenolol↗
PubMed1979

Plasma estradiol window and urinary estriol glucuronide determinations for monitoring menotropin induction of ovulation.

The plasma estradiol response is maximal 8--10 hours following mentropin injection. To obtain closer control, a menotropin protocol using 5 PM--8 PM injections and 8 AM blood sampling with a plasma estradiol window of 1000--2000 pg/ml was evaluated with simultaneous calibration of a urinary estriol glucuronide radioimmunoassay. One hundred twenty-eight paired urine and plasma samples were assayed in 48 cycles. In 26 cycles with paired samples on the day of human chorionic gonadotropin (hCG) injection, there were no cases of severe hyperstimulation, 2 cases of moderate hyperstimulation, and 11 pregnancies (42% of cycles given hCG). A window of between 40 and 100 micrograms/day of urinary estriol glucuronide corresponded to the 1000--2000 pg/ml plasma estradiol window by regression analysis. The pregnancy and hyperstimulation rates were compared with those observed in protocols previously published. Radioimmunoassay of urinary estriol glucuronide is faster and simpler than radioimmunoassay of plasma estradiol.

Abortion, Spontaneous↗
PubMed1978

Specificity of the binding of trifluoperazine to the calcium-dependent activator of phosphodiesterase and to a series of other calcium-binding proteins.

Trifluoperazine inhibits the activation of phosphodiesterase by binding to the calcium-dependent activator. To determine further the specificity by which trifluoperazine binds to activator, we compared the binding of trifluoperazine to activator prepared from several species and tissues and to a number of other calcium-binding proteins devoid of activator activity. Trifluoperazine binds to activator prepared from human, bovine, rat and rabbit brain and from chick embryo fibroblasts. In each case, the binding of trifluoperazine to activator was qualitatively similar and related quantitatively to the ability of the preparation to activate phosphodiesterase. Of the other calcium-binding proteins examined, namely, troponin-C, S-100 protein, phospholipase A, phospholipase B and myosin light chain, only troponin-C displayed any significant calcium-specific binding of trifluoperazine. The binding to troponin-C, however, appeared to be different from the binding to activator; whereas the binding of trifluoperazine to actovator showed no cooperativity, the binding to troponin-C showed positive cooperatively. These results and earlier data showing that trifluoperazine fails to bind to a variety of other proteins, indicate that the binding of trifluoperazine to the calcium-dependent activator of phosphodiesterase is selective and suggest that this binding may explain some of the biochemical and pharmacological actions of this antipsychotic agent.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1977

A direct radioimmunoassay for estriol-16-glucuronide in urine for monitoring pregnancy and induction of ovulation.

Antibodies to estriol-16alpha-[beta-D-glucuronide] were raised in sheep with the use of keyhold limpet hemocyanin and bovine serum albumin conjugates of estriol-16alpha-[beta-D-glucuronide]. A simple, rapid method is presented for direct radioimmunoassay of estriol-16alpha-[beta-D-glucuronide] in urine with dextran-coated charcoal used for separation of free from bound and deionized water used for dilutions. The method is thrifty in its use of reagents. The assay has been evaluated in the pregnancy range, and the sensitivity has been extended into the range necessary for monitoring induction of ovulation with Pergonal.

Animals↗
PubMed1977

The effect of angiotensin II and indomethacin on uterine artery blood flow in pregnant monkeys.

In experiments performed in anesthetized monkeys in the third trimester of pregnancy, mean maternal arterial blood pressure was continuously monitored, the uterine artery blood flow was measured with an electromagnetic flow probe, and prostaglandin levels were assayed in the uterine venous effluent. After inhibition of prostaglandin systhesis with indomethacin, the mean arterial blood pressure in response to angiotensin II was greater than the response prior to indomethacin treatment, and an increase in uterine artery blood flow was prevented. These findings are consistent with the suggestion that prostaglandins mediate the uterine artery blood flow response to angiotensin II, as well as modifying the maternal systemic blood pressure response.

Angiotensin II↗