Roberto Salles Meirelles

Vasodilating Effect of Estrogen on the Human Umbilical Artery

The effects of estradiol, estrone and estriol on the tonus of the isolated vascular segments of human umbilical artery were studied by a perfusion technique. Estradiol (10 µg/ml), estrone (10 µg/ml) or estriol (2 and 10 µg/ml) produce relaxation of the vascular bed which was reflected in a significant reduction in basal pressure of segments perfused at constant rate. A dose-dependent relationship was demonstrated for estriol. The time dependence and extent of relaxation were similar for all three natural estrogens.The effects of estradiol, estrone and estriol on the tonus of the isolated vascular segments of human umbilical artery were studied by a perfusion technique. Estradiol (10 microgram/ml), estrone (10 microgram/ml) or estriol (2 and 10 microgram/ml) produce relaxation of the vascular bed which was reflected in a significant reduction in basal pressure of segments perfused at constant rate. A dose-dependent relationship was demonstrated for estriol. The time dependence and extent of relation were similar for all three natural estrogens.

Angiotensin-converting enzyme: Serum levels during normal pregnancy

ACE activity of the serum of 52 normal pregnant women was measured in vitro under conditions of substrate saturation with Hip-His-Leu as substrate. The product His-Leu was measured by fluorimetry after reaction with o-phthaldehyde. ACE activity (nmol/min/ml serum) was 30.6 +/- 7.8, 28.8 +/- 7.4, and 30.9 +/- 8.2 for the first, second, and third trimester of pregnancy, respectively. No statistically significant differences (p greater than 0.05) in ACE activity were detected among the three trimesters of normal pregnancy with either serum volume or serum protein as reference value. These values are within the range reported by Friedland and Silverstein13 for 51 male and seven female healthy blood bank donors. We conclude that the evolution of normal pregnancy does not significantly modify the levels of ACE in peripheral blood serum.

Constriction of Human Umbilical Artery Induced by Local Anesthetics

In order to study the direct effects of local anesthetics on the umbilical artery, an in vitro perfusion technique, utilizing 3-cm segments of human umbilical artery obtained within 15 min of delivery, has been developed. Basal perfusion pressure (tonus) and the frequency of phasic contractions were determined in 37 arterial segments perfused for 240-min periods with Tyrodes solution containing lidocaine in concentrations of 2.0, 8.0 or 16 microgram/ml of bupivacaine in concentrations of 0.25 or 9.8 microgram/ml. A control group consisting of 11 arterial segments was perfused only with Tyrodes solution. The lowest concentration of each anesthetic approximated that reportedly present in the umbilical arteries following administration of epidural anesthesia during labor. Both lidocaine and bupivacaine induced dose-related increases of up to 100% in tonus above the control levels of approximately 60 mm Hg, statistically significant (p less than 0.05) except for 2 microgram/ml lidocaine. At the same molar concentration, bupivacaine was more effective than lidocaine (p less than 0.05). Both anesthetics also increased the frequency of phasic contractions. These data suggest that these agents may exert their effects on the fetus, at least in part, through a direct constricting action on the umbilical artery.

Estriol Reduces the Reactivity of the Human Umbilical Artery to Mechanical Stimuli

The effect of estriol on the reactivity of the human umbilical artery to mechanical stimulation was studied using an in vitro perfusion method. The mechanical stimuli were produced by force applied to the outer surface of the vessel through a system consisting of a lever with equal length arms which was activated by small weights of known mass placed on one of the arms. The contractions of the preparations were proportional to the weights applied. When a 0.5-gram stimulus was applied, the mean contractile response of seven preparations was 46.7 +/- 2.72 mm Hg (mean +/- SEM). The addition of 10 micrograms/ml estriol to the nutrient fluid (Tyrode) caused a (mean 6.8 +/- 1.32 mm Hg) reduction of the response to the mechanical stimuli. We suggest that estrogens, and estriol in particular, play an important role in the modulation of the reactivity of the human umbilical artery during pregnancy in the presence of the mechanical stimulation caused by intrauterine fetal movements.

Diabetes e gravidez: aspectos clínicos e perinatais

Durante a gestacao, as pacientes que nao se ajustam as alteracoes metabolicas proprias da gravidez e aquelas com alteracoes previas no metabolismo dos carboidratos apresentam um aumento significativo da morbimortalidade perinatal. Visando contribuir para o aperfeicoamento da conduta pre-natal na gestante diabetica, os autores estudaram retrospectivamente 60 casos de gravidez associada ao diabetes, atendidos no Departamento de Ginecologia e Obstetricia da Faculdade de Medicina de Ribeirao Preto, Universidade de Sao Paulo. A amostra estudada foi dividida em dois grupos: com controle pre-natal segundo o protocolo para a gestante diabetica e encaminhadas ao Servico para resolucao da gravidez. No grupo com pre-natal adequado nao ocorreram obitos fetais ou neonatais e as complicacoes neonatais observadas estiveram associadas principalmente com a prematuridade. No grupo encaminhado para resolucao e sem seguimento pre-natal adequado foram diagnosticados 3 casos de malformacao fetal multipla, 1 caso de hipoglicemia neonatal grave, 3 casos de prematuridade, 1 caso de retardo de crescimento intra-uterino, 1 caso de macrossomia fetal e ainda um caso de obito neonatal. A comparacao entre os grupos estudados demonstra claramente os beneficios do controle pre-natal adequado para a gestante diabetica e expoe tambem a necessidade de uma maior integracao entre a rede periferica regional e os centros de atencao terciaria, permitindo o diagnostico e o encaminhamento precoce de todos os casos de gestacao complicada pelo diabetes.

Effects of maternal and fetal plasma from toxemic patients on the vasomotility of the human umbilical artery

Maternal and fetal plasmas from patients with specific hypertensive disease of pregnancy (SHDP) are shown to have a greater vasoconstrictive effect on perfused human unbilical artery than plasma from normal parturients. The vasomotility of isolated segments of artery was determined by measuring perfusion pressure at constant flow rate. The differences were demonstrable with plasmas and artery segments from the same parturients and also when plasma from patients with SHDP and arteries from normal parturients were used. These results, which show that plasmas from SHDP patients have a larger vasoconstrictive effect on human umbilical artery than normal plasma, support and extend the suggestion that there may be humoral mechanism which participates in the physiopathology of SHDP. This humoral factor can be detected with human umbilical artery from both normal and SHDP parturients.

Action of Alpha-Methyldopa on Human Umbilical Circulation in vitro

To determine the possible effects of alpha-methyldopa on the motility of human umbilical artery, a total of 53 arterial segments were perfused with different concentrations of the drug as follows: 38 segments with 125, 250 and 500 ng/ml of the drug, 9 segments with 500 ng/ml alpha-methyldopa in combination with 10(-7) M yohimbine, and 6 segments with 10(-7) M yohimbine alone. alpha-Methyldopa had a vasoconstrictor effect at all doses employed, with a clear dose-effect correlation (p less than 0.01). The vasoconstrictor effect of 500 ng/ml alpha-methyldopa was fully inhibited in the presence of 10(-7) M yohimbine. These results suggest that alpha 2-adrenergic receptors are present in the umbilical circulation and that alpha-methyldopa may play a role in the control of this circulation.

Estriol Antagonism of the Action of Bradykinin and Adrenalin on Human Umbilical Artery

The effect of estriol on the response of human umbilical artery to bradykinin (0.2 microgram/ml) and adrenalin (0.8 microgram/ml) was studied by an in vitro perfusion method. Estriol (10 microgram/ml) added to the nutrient medium decreased the response of the preparation to the two vasoactive agents. The results suggest the participation of estriol as a modulator of the vascular response at the level of the umbilical circulation, where it may act to protect the maternal-fetal circulatory system from physical or chemical stimuli.