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Biomedical subjects

R Resnik

Publications and source records attributed to R Resnik.

At least 37 records · Page 2Linked to original sources
PubMed1985

Uterine blood flow and catecholamine response to repetitive nicotine exposure in the pregnant ewe.

In order to simulate human smoking, experiments were designed to determine what dose of nicotine in the pregnant sheep would produce those plasma nicotine concentrations observed in human smokers and to measure uterine blood flow and plasma catecholamines in response to repetitive exposure (every 30 minutes) to that nicotine dose. Utilizing seven chronically catheterized pregnant sheep equipped with electromagnetic flow probes around both uterine arteries, we observed that a nicotine dose of 0.2 mg/min for 5 minutes results in mean plasma nicotine concentrations of 23.1 +/- 1.1 ng/ml SEM (n = 17) immediately following infusion. This dose of nicotine was then infused every 30 minutes for 4 hours, and aliquots of blood were drawn immediately before and after nicotine infusion for determination of plasma catecholamines. No significant alterations in plasma epinephrine and norepinephrine were observed throughout the experiments (n = 8), and no significant changes in uterine blood flow occurred at any time during the experiment (n = 30). We conclude that there is a species difference between sheep and man with respect to the nicotinic threshold for catecholamine release.

Animals↗
PubMed1985

Barrier contraception in the teenager: a comparison of four methods in adolescent girls.

The use-effectiveness and continuation rates of 4 methods of contraception were studied during a 2 year follow-up period in a group of 405 teenage girls. Results were compared in 2 groups of adolescents, 1 of highly motivated, high socioeconomic status girls (A) and 1 of poorly motivated, low socioeconomic status adolescent clinic patients (B). The method of contraception was selected by the girls, who were instructed in their proper use. Results showed good rates of continuation among girls of the 1st group as compared to those of the 2nd group. Pregnancy rates after 24 months of use, as calculated by Pearl's formula, was 3.6 and 5.4 respectively with the use of a condom, and 5.8 and 10.8 when the diaphragm was used. When using vaginal foam alone, the rates were 4.2 and 12.3 and with the rhythm method, 8.5 and 13.1. The foam-alone method was unpopular in both groups. No serious side effects or complications were recorded. The study demostrated a reasonable acceptability and use-effectiveness for barrier contraceptives. It is suggested that these harmless and complication-free methods, especially the condom and diaphragm, may be reasonable alternatives for the more modern methods in teens of all socioeconomic strata; an effort must be made to educate and instruct the poorly motivated and encourage them to present themselves for regular follow-up.

Adolescent↗
PubMed1984

Expanded care in obstetrics for the 1980s: preconception and early postconception counseling.

This paper is an essay in which the suggestion is made to expand obstetric care during this decade to include preconception as well as early postconception counseling. The development of perinatal and neonatal medicine is traced and medical problems that might be improved by medical counseling before pregnancy occurs are tabulated. Diabetes is suggested as a prototype of a medical disorder for which preconception counseling would be helpful. The expansion of obstetric services into an area of preventive medicine might well begin in already established regional medical centers but should quickly expand to the offices of private obstetricians. In this broader interpretation of obstetric care, prevention of maternal and fetal or neonatal problems could decrease the cost of high-risk medical care.

Counseling↗
PubMed1983

The effects of maternally administered magnesium sulfate on the neonate.

The effects of parenterally administered magnesium sulfate on maternal and neonatal calcium and magnesium metabolism in nonasphyxiated, term pregnancies complicated by pregnancy-induced hypertension were studied prospectively. In addition, the neurobehavioral effects of neonatal hypermagnesemia were investigated by means of a neonatal assessment scale that specifically measures reflex activity and both passive and active muscle tone. Maternal magnesium sulfate infusion was associated with maternal and neonatal hypermagnesemia when compared with that of control subjects (1.8 +/- 0.10 to 3.6 +/- 0.5 mg/dl, p less than 0.001, and 1.75 +/- 0.2 to 3.6 +/- 0.5 mg/dl, p less than 0.005, respectively). Maternal serum calcium levels fell with magnesium therapy (9.3 +/- 0.18 to 7.9 +/- 0.1 mg/dl, p less than 0.001), while neonatal calcium levels were unaffected (10.8 +/- 0.44 to 10.5 +/- 0.38 mg/dl, p less than 0.05). Neurological status examinations in the neonate were similar in both the control and treatment groups. In addition, neurological performance of the neonate did not correlate with cord magnesium levels or to the total dose of magnesium administered.

Adult↗
PubMed1983

Maternal cardiovascular response to caffeine infusion in the pregnant ewe.

The effect of maternal caffeine infusion on uterine blood flow and fetal oxygenation was studied in chronically catheterized pregnant sheep equipped with electromagnetic flow probes. The systemic administration of caffeine in doses of 8 and 24 mg/kg of body weight resulted in peak maternal serum levels of 16.7 +/- 0.9 and 38.5 +/- 2.1 micrograms/ml and fetal serum levels of 10.9 +/- 0.7 and 34.9 +/- 4.5 micrograms/ml, respectively. While no significant effects were noted at the 8 mg/kg dose, administration of 24 mg/kg was associated with a 5% reduction in uterine blood flow (p less than 0.05) and a 7% increase in mean arterial pressure (p less than 0.05). No significant alteration in maternal or fetal oxygenation occurred at either dose. These findings suggest that any adverse effects on fetal development attributed to caffeine are not likely exerted by influencing uterine blood flow.

Animals↗
PubMed1983

Maternal and fetal cardiovascular effects of nicotine infusion in pregnant sheep.

The effects of nicotine on uterine and umbilical hemodynamics were studied in seven pregnant ewes equipped with electromagnetic flow probes around the main uterine and common umbilical arteries, and with polyvinyl catheters inserted into the fetal aorta and maternal femoral vessels. Maternal systemic infusions of 1.0 to 1.5 mg/min significantly decreased uterine blood flow by 42% (p less than 0.001) and 32% (p less than 0.05), respectively. However, nicotine infusion rates of 0.5 mg/min, resulting in mean peak maternal nicotine concentrations of 130 +/- 5.0 ng/ml (SE), a value substantially higher than that reported in smoking humans, did not significantly alter uterine or umbilical vascular hemodynamics. Furthermore, at this lower nicotine dose, no alterations were observed in maternal or fetal plasma norepinephrine and epinephrine. The findings suggest either a species difference between sheep and humans in the threshold of catecholamine release to nicotine exposure or the need for repetitive nicotine infusions throughout the day to stimulate the human smoking experience.

Animals↗
PubMed1983

Endocrine modulation of uterine blood flow in pregnancy.

Uterine blood flow increases 15- to 20-fold during pregnancy. The fact that pregnancy is also characterized by dramatic increases in the production rate and plasma concentrations of estrogenic and progestational sex steroids has prompted investigators to explore a cause and effect relationship between these endocrine and physiologic changes. This article reviews the evidence that pregnancy-related increases in uterine blood flow are, at least in part, sex-steroid induced.

Animals↗
PubMed1982

Postpartum pleural effusion: a common radiologic finding.

We did a retrospective study of 112 patients and prospective study of 30 patients and 30 controls to ascertain the incidence of postpartum pleural effusion. An effusion was shown on chest radiographs in 51 patients (46%) in the retrospective study, and 20 patients (67%) in the prospective study. The incidence of pleural effusion in obstetric patients in the prospective study was significantly greater than that of controls (chi-squared test, 20.4, p less than 0.001). There was no difference between patients with effusion and those without in age, race, parity, antepartum complications, method of delivery, fetal outcome, or postpartum complications. We conclude that pleural effusion occurs frequently in the first 24 hours after delivery and that, in the absence of symptoms or signs of cardiopulmonary disorder, no intervention is necessary.

Female↗
PubMed1981

The endocrine regulation of uterine blood flow in the nonpregnant uterus: a review.

Evidence is presented to demonstrate the role of steroid hormones in the regulation of blood flow through the nonpregnant uterine vasculature. Estrogens appear to increase blood flow, as documented by the observed increases in flow during proestrus and estrus, as well as the response to exogenous hormone stimulation in laboratory animals. The mechanism for the stimulation of blood flow is apparently indirect, and mediated by another vasoactive agent(s) which remains unknown at this time. Conversely, progesterone decreases estrogen-induced uterine blood flow, probably by depleting the amount of available cytoplasmic estrogen receptor.

Endocrine Glands↗
PubMed1981

Corticosteroid suppression of estrogen-induced uterine blood flow in nonpregnant sheep.

Estrogenic stimulation of uterine hyperemia and water imbibition are well-described endocrine events. Uterine blood flow responses to estrogen appear to have a similar mechanism of action. Although corticosteroids inhibit the uterine hyperemic and water imbibition effects, their influence on estrogen-induced uterine blood flow has not been clarified. Accordingly, the effects of hydrocortisone on estrogen-induced uterine blood flow were studied in seven nonpregnant castrate ewes equipped with electromagnetic flow probes around the main uterine arteries and with polyvinyl catheters inserted into postbifurcational branches of the uterine arteries. Inferior vena cava infusions of hydrocortisone, 0.50 to 9.25 mg/kg of body weight, administered 1 hour before estrogenic stimulation suppressed uterine blood flow increases by 10% to 35%. Direct uterine intra-arterial infusions of hydrocortisone also inhibited estrogen-induced uterine blood flow at calculated concentrations as low as 5.65 microM in uterine arterial blood. These findings support the conclusion that estrogen-induced uterine blood flow and water imbibition are correlative events and further serve to elucidate the mechanisms by which steroid hormones interact to modify uterine blood flow.

Animals↗
PubMed1980

Uterine vascular response to prostacyclin in nonpregnant sheep.

Two effects of prostacyclin (PGI2) on uterine blood flow were investigated in nonpregnant, castrated ewes with chronically implanted polyvinyl catheters and electromagnetic flow probes. Intra-arterial infusion of PGI2 resulted immediately in increased uterine blood flow, which returned rapidly to baseline after termination of the infusion. A dose-response curve was constructed and demonstrated that a uterine arterial PGI2 concentration of 1.2 times 10(-6)M (0.5 microgram/ml) produced flows 50% of those achieved by a reference dose of 1 microgram of 17 beta-estradiol. Increases in uterine blood flow were not associated with changes in mean systemic arterial pressure. These findings demonstrate that PGI2 has a vasodilatory effect on the uterine circulation and suggest that this substance has a role in the regulation of uterine blood flow.

Animals↗
PubMed1980

Age-related glucose metabolism alterations in nondiabetic and potentially diabetic women.

The incidence of pathological glucose tolerance was investigated in women of three age groups: 20--39, 40--59 and over 60 yr, by means of oral glucose tolerance tests and the Danowski Index. The incidence was found to be significantly higher in older women: thus an age-related deterioration of glucose metabolism was confirmed. The women in each are group were further divided into "healthy" nondiabetic and "potentially diabetic" women. The parameter of "potential diabetes" was found to be associated to a greater extent with age-related glucose tolerance deterioration than advancing age alone. The existing theories for the etiology of carbohydrate metabolism alteration in older women are reviewed. it is suggested that in view of the age-related deterioration of glucose metabolism, a new normal range of glucose tolerance should be established in an ageing population.

Adult↗
PubMed1980

Management of shoulder girdle dystocia.

Avoidance of shoulder dystocia is the best form of management. The potential for such a situation should be considered in the presence of a large fetus when the second stage of labor is prolonged and the fetal head fails to descend to the pelvic outlet. Awareness of a past history of delivery of a large infant is also helpful. Liberal use of cesarean section in such cases will prevent serious neurologic sequelae. If shoulder dystocia occurs, the obstetrician should have a well-conceived approach directed toward disimpaction of the anterior shoulder. The most effective maneuver includes suprapubic pressure and delivery of the posterior arm.

Dystocia↗