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D M Magyar

Publications and source records attributed to D M Magyar.

27 records · Page 2Linked to original sources
PubMed1980

Time-trend analysis of plasma cortisol concentrations in the fetal sheep in relation to parturition.

Using a cortisol RIA carefully validated for specificity in fetal ovine plasma, we studied plasma cortisol time-trend changes in eight chronically catheterized sheep fetuses in the last 22 days of gestation before the spontaneous onset of labor. Best fit exponential type curves were drawn for each individual fetus to define the time before the onset of labor at which fetal plasma cortisol was rising at different rates. Fetal plasma cortisol increased at a rate of 0.5 ng ml-1 day-1 as early as 17.1 days before labor in one fetus, whereas the mean value for all eight fetuses occurred 11.8 +/- 1.0 (SEM) days before labor. The rate of increase doubled to 1.0 ng cortisol ml-1 day-1 as early as 14.4 days before labor in one fetus, whereas the mean value for all eight fetuses occurred 9.3 +/- 0.9 days before labor. These findings suggest that the regulatory mechanisms responsible for the prelabor increase in fetal cortisol production are activated earlier in gestation than we previously thought.

Animals↗
PubMed1980

Responsiveness and maximum secretory capacity of isolated fetal lamb adrenocortical cells throughout the last third of gestation.

Although considerable evidence implicates increased fetal adrenal function as a major factor in the initiation of parturition in the sheep, the mechanism responsible for this increased activity has not yet been determined. We have investigated the development of the function of fetal lamb adrenal cortical cells dispersed in vitro. There was no change in the sensitivity of the cells to synthetic ACTH (ACTH1-24), as demonstrated by the concentraton of ACTH1-24 producing a 50% maximum response in corticoid secretion. This finding does not support the suggestion that there is a qualitative change in fetal adrenal receptor function as term approaches. No stimulation of corticoid was observed after the administration of alpha MSH or PRL in vitro at any gestational age or of alpha MSH in vivo in four fetuses at 125--130 days gestation. Both the maximum output and the 50% maximum response in corticoid secretion of adrenal cells from term fetuses were similar to those of adrenal cells from adult ewes. A significant increase in the maximum output of corticoids per cell in response to ACTH1-24 occurs as early as 107 days gestation and continues steadily to term.

Adrenal Cortex↗
PubMed1979

Adrenocorticotropin and glucocorticoid concentrations in fetal and maternal plasma of rabbit does continuously infused with cortisol from day 21 to day 24 of gestation.

Previous studies have suggested that suppression of fetal rabbit adrenocorticotropin (ACTH) secretion results in impaired development of ACTH-specific adenylate cyclase activity. In order to test this hypothesis we measured fetal and maternal plasma ACTH, cortisol, and corticosterone concentrations in control does and does infused with 0.3 mg of cortisol/hour at 21 to 24 days of gestation. This cortisol infusion regimen significantly depressed maternal and fetal plasma ACTH and corticosterone concentrations but did not change fetal serum cortisol concentrations. These findings further support the hypothesis that fetal ACTH plays a role in the normal development of the adenylate cyclase catalytic portion of the ACTH receptor complex and adrenal differentiation during this critical period of fetal life.

Adenylyl Cyclase Inhibitors↗
PubMed1979

Comparison of two rapid cortisol radioimmunoassays for use in the fetal sheep.

Cortisol radioimmunoassays (RIA's) utilizing highly specific antisera combined with a simple ethanol protein precipitation procedure (ETOH-PPT) are widely utilized to measure cortisol in human plasma. This same type of RIA has been assumed specific for measurement of cortisol in the plasma of several different species of experimental animals. In order to test this assumption as applied to fetal ovine plasma, we compared an ETOH-PPT cortisol RIA with another rapid cortisol assay which utilizes a dichloromethane extraction (DM-E) step. The DM-E assay in turn was compared with a chromatographic assay previously shown to be highly specific for measurement of fetal plasma cortisol in this species. Fetal ovine plasma cortisol concentrations determined by the DM-E method were nearly identical to the concentrations obtained by the specific chromatographic RIA procedure. On the other hand, the ETOH-PPT RIA grossly overestimated cortisol concentrations when compared with the DM-E RIA. While the rapid DM-E RIA appears to be suitable for use in fetal ovine plasma, the widely used ETOH-PPT RIA yields spuriously high and unpredictable values and must be considered unreliable. These comparisons demonstrate the need for careful reassessment of steroid assays prior to their application in experimental animals even though they have been previously documented as specific in human plasma.

Animals↗
PubMed1979

Validation of a specific radioimmunoassay to measure plasma cortisol in the fetal sheep.

A procedure utilizing co-chromatography and complementary antiserum comparisons was employed to assess the specificity of a cortisol radioimmunoassay for use in the chronically catheterized fetal sheep preparation. Complementary antiserum comparisons is a technique by which two different cortisol antisera, prepared from conjugates attached at opposite ends of the cortisol molecule, were used to determine cortisol concentrations in the same ovine fetal plasma specimens. Results were not significantly different between the two groups, each measured by a different antiserum. This procedure may be used to assess assay specificity in any species in which steroid radioimmunoassays are being adapted.

Animals↗
PubMed1978

Pituitary tumors and pregnancy.

This paper contains a review of the natural history of pituitary tumors in nonpregnant and pregnant patients. Data were drawn from previously published reports and from responses to a questionnaire and were analyzed by life-table techniques. Follow-up of 62 nonpregnant patients with untreated pituitary tumors with and without visual field changes revealed a median time to treatment of 15 1/2 years and similar, relatively constant hazard functions. In 91 pregnancies occurring in 73 women with previously untreated pituitary tumors, ovulation had occurred spontaneously in 9 per cent, headache occurred in 23 per cent, and visual disturbances in 25 per cent with 61 per cent remaining asymptomatic. In those patients who developed symptoms, median time to headache was 10 weeks and to visual disturbance, 14 weeks. The hazard functions were relatively constant and similar. The relative risk of developing symptoms is independent of whether or not the first or second pregnancy occurred in the presence of the pituitary tumor. Of the pregnant patients with previously untreated pituitary tumors, 30 per cent required surgery or radiation therapy. Median time to treatment was 19 weeks. None of the 69 pregnant women without pituitary therapy had permanent sequelae. Only four patients who underwent surgery or received radiation treatment developed permanent symptoms and none was serious. In 78 pregnancies occurring in 73 women with previously treated pituitary tumors, headache occurred in 4 per cent and visual disturbances in 5 per cent. Only one patient required therapy. Treatment during pregnancy results in significantly increased prematurity rates but unchanged abortion and perinatal mortality rates. Small pituitary tumors do not constitute a contraindication to either induction of ovulation or pregnancy.

Abortion, Spontaneous↗
PubMedDate not supplied

The reproductive performance of women before and after metroplasty.

Nineteen women with congenital uterine anomalies underwent metroplasty. Prior to surgical correction of the uterine malformation, 44 of their 45 (98%) pregnancies had ended with a spontaneous abortion, and no woman had a living child. Following metroplasty, only 4 of 18 (22%) pregnancies aborted, and 12 of the 14 (86%) women attempting pregnancy had a living child. There were no unusual intraoperative or postoperative complications. Metroplasty procedures can be performed safely, and are associated with excellent reproductive outcomes.

Abortion, Spontaneous↗