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Biomedical subjects

G J Valenzuela

Publications and source records attributed to G J Valenzuela.

48 records · Page 3Linked to original sources
PubMed1987

Estrogen, progesterone, prolactin, prostaglandin E2, prostaglandin F2 alpha, 13,14-dihydro-15-keto-prostaglandin F2 alpha, and 6-keto-prostaglandin F1 alpha gradients across the uterus in women in labor and not in labor.

Before or during labor in humans, changes in peripheral levels of estrogen and progesterone are not evident. Local alterations of estrogen, progesterone, and prolactin concentrations may be present and be accompanied by prostaglandin changes. The purpose of this study was to investigate the differences in concentrations of these hormones across the uterus and to evaluate their interrelationships in patients at term gestation with and without labor. Blood samples were obtained from a radial artery and a uterine vein in 22 women without and in 10 with labor. The difference between levels in the two blood vessels was designated as the gradient. Neither levels nor gradients were different between the two groups for estrone, estradiol, estriol, progesterone, or prolactin. The plasma levels of prostaglandin F2 alpha, 13,14-dihydro-15-keto-prostaglandin F2 alpha, and prostaglandin E2 were significantly increased in labor. Prostacyclin levels, as indicated by the 6-keto-prostaglandin F1 alpha metabolite, were not altered. The gradients for prostaglandin F2 alpha and E2 were significantly increased in labor. The results of the study also suggested that, in gestation at term, serum prolactin is produced mainly by the pituitary and that estrone may originate from peripheral conversion of estradiol. We conclude that in humans prostaglandin gradients of the E and F groups are increased in labor. These increases are not associated with changes in sex steroids or prolactin. Prostacyclin metabolite gradients also appear not to be altered in labor, suggesting that some prostaglandins are selectively increased in early labor either by enhanced production or decreased metabolism or both.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Angiotensin II infusion increases thoracic duct lymph flow in chronically catheterized sheep.

Both pregnancy and estrogen administration are associated with a decrease in the systemic vasculature pressor response to angiotensin II infusion; however, the lymphatic vessel system response is not clear. In the present study we infused angiotensin II to nine nonpregnant splenectomized ewes with 0.1, 10, or 1,000 ng X kg-1 X min-1 for a 5-min period at each dose. At the lowest dose the mean arterial pressure increased from 10 to 20% over base line. At the highest dose, the left thoracic duct flow rate peaked at 361% 10 min after the infusion was started, whereas arterial pressure peaked at 183% of the control value. Peak lymph flow occurred 4-6 min after the maximal increase in mean systemic arterial pressure. Neither hematocrit nor venous pressure were altered at any of the doses administered. This suggests that the interstitial fluid space pressure remained unchanged and that the increase in lymph flow was not secondary to fluid transfer from the intravascular system. We postulate, therefore, that the effect of angiotensin II in the increase of lymph flow rate is by direct action on the lymphatic vessels themselves.

Angiotensin II↗
PubMed1987

Lymphatic and vascular responses to fluid infusion in castrated and noncastrated sheep.

Estrogen administration produces blood volume expansion and interstitial fluid retention. We decided to study the effect of estrogen withdrawal on blood volume and determine whether oophorectomy has an effect on lymph flow or protein concentration. The rate of left thoracic duct lymph flow averaged 0.041 +/- 0.005 (SE) and 0.071 +/- 0.008 ml X min-1 X kg-1 in castrated (n = 9) and noncastrated (n = 9) female sheep, respectively (P = 0.006). After three serial intravenous infusions of Ringer lactate solution (2% body wt/infusion) the thoracic duct lymph flow in the castrated animals increased 358, 457, and 498% over the base-line rate, compared with increase of 200, 235, and 353% in the nonpregnant ewes. However, with the lower control values in the castrated animals, the lymph flow rate reached the same absolute values as those seen in the noncastrated ewes. Lymph protein concentration and the lymph-to-plasma protein concentration ratio, as well as arterial and venous pressures, were unaltered by oophorectomy. Base-line whole blood volumes were 58.2 +/- 1.9 (n = 9) and 64.8 +/- 2.6 ml/kg (n = 9) in the castrated and noncastrated ewes, respectively (P less than 0.05). Systemic vascular compliance averaged 4.5 +/- 0.7 and 7.1 +/- 1.7 ml X kg-1 X mmHg-1 in the castrated and noncastrated ewes, respectively (P less than 0.05), whereas interstitial fluid compliance values were 12 and 32 ml X kg-1 X mmHg-1, respectively. The capillary filtration coefficients were not different in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Magnesium and pregnancy.

Human pregnancy is characterized by several cardiovascular changes, among them a 50% increase in cardiac output, a decrease in the systemic vascular resistance, a 40% blood volume expansion, a decrease in mean arterial blood pressure and a 10-15 beats/min increase in heart rate. It is possible that alterations in magnesium metabolism may be responsible for some of the physiological changes seen during pregnancy and in many diseases related to cardiovascular abnormalities. Magnesium (Mg2+) has been used extensively in obstetrics for the treatment of alterations of uterine contractility (premature labor) or increased neuronal and vascular smooth muscle activity (pre-eclampsia). This review focuses on some of the alterations seen in Mg2+ metabolism during pregnancy. In addition, some of the problems regarding Mg2+ metabolism and parenteral administration of Mg2+ in the treatment of pre-eclampsia and eclampsia are discussed. The use of Mg2+ during labor and as prophylaxis to prevent rupture of membranes and premature labor are also reviewed and discussed.

Eclampsia↗
PubMed1987

Time-dependent changes in bone, placental, intestinal, and hepatic alkaline phosphatase activities in serum during human pregnancy.

To measure changes in bone alkaline phosphatase (EC 3.1.3.1) activity in serum as a function of duration of pregnancy, we adapted our existing alkaline phosphatase (ALP) isoenzyme assay (which has been used to measure bone, hepatic, and intestinal ALP activities in serum, in the absence of placental ALP) to allow quantification of individual ALP isoenzyme activities in the presence of placental ALP. The resulting CV for repeat measurements of bone ALP activity in artificial isoenzyme mixtures ranged from 23% for samples in which the bone isoenzyme represented 7% of total ALP activity to 11% for samples in which bone ALP accounted for 48% of total ALP activity. Values for repeat determinations of bone ALP activity in human serum samples (i.e., including samples obtained from pregnant women and from nonpregnant controls) varied by an average of 18%. We find, in initial applications of this method, that (a) the amount of bone ALP activity in serum is increased during pregnancy (P less than .001), and remains increased at six weeks postpartum, in non-lactating women (P less than .001), and (b) bone ALP activity at term was not significantly different in pregnant women with pre-eclampsia, diabetes, premature rupture of membranes, or premature labor, compared with normal pregnancies at term. Our data support the hypothesis that maternal bone formation may be increased during pregnancy.

Alkaline Phosphatase↗
PubMed1986

Estrogen effects on plasma volume, arterial blood pressure, interstitial space, plasma proteins, and blood viscosity in sheep.

In adult castrated ewes the infusion of 17 beta-estradiol for 3 weeks was associated with a 12% increase in body weight, a 20% increase in whole blood volume (mainly due to a 27% increase of plasma volume), a 13% decrease in mean arterial blood pressure, and a 40% increase in heart rate. The change in plasma volume correlated with the change in estradiol concentration (r = 0.72). Most of the fluid was retained in the interstitial space, as represented by a 6 kg weight gain, 10% of which was in the intravascular compartment. Whole blood and plasma viscosity increased 16% and 21%, respectively, thus reversing some of the blood volume effects toward a hyperdynamic cardiovascular state. We conclude that many of the cardiovascular and hematologic changes with estrogen administration are similar to the changes observed during pregnancy, with the proposed requirement of decrease in mean arterial blood pressure as a condition for blood volume expansion.

Animals↗
PubMed1986

Uteroplacental unit as a source of elevated circulating prorenin levels in normal pregnancy.

Circulating levels of inactive renin, that is, prorenin, are increased in normal pregnant women. To determine whether the uteroplacental unit secretes prorenin into the maternal circulation, we measured enzymatically active and inactive renin in plasma simultaneously obtained from the radial artery and uterine vein of 12 normotensive, nonlaboring patients undergoing elective cesarean section at term. We also measured these forms of renin in the umbilical arterial and venous blood of these patients. Our data reveal that the levels of inactive renin in both arterial and uterine venous blood of normal pregnant women are significantly higher than in peripheral venous blood of nonpregnant, normotensive control subjects; normotensive term patients have a ratio of plasma inactive to active renin of 9:1 in contrast to the 1:1 ratio in normotensive nonpregnant subjects; there is a significant uterine arteriovenous difference of prorenin (66.2 +/- 24.4 ng/ml/hr, p less than 0.05) but not of active renin (1.8 +/- 1.5 ng/ml/hr, not significant). These results suggest that the uteroplacental unit contributes to the elevated prorenin levels at term pregnancy.

Cesarean Section↗
PubMed1985

Is there a need for digital examination in patients with spontaneous rupture of the membranes?

A prospective comparison between digital and visual speculum examination was made in 133 pregnant patients. The coefficient correlation between the two examinations of effacement and dilation of the cervix was 0.74. The present results suggest that cervical evaluation by means of speculum examination in the assessment of pregnant patients with spontaneous rupture of membranes are adequate.

Cervix Uteri↗
PubMed1985

The relation of maternal blood volume to plasma renin activity in the pregnant rabbit.

Blood volume, estradiol 17 beta and estrone concentrations, and plasma renin activity were determined weekly in 26 chronically catheterized nonanesthetized rabbits during pregnancy and after delivery. We determined blood volume by 99technetium, and plasma volume by the microhaematocrit method. The values for whole blood volume were 52.7 (+/- 2.3) and 63 (+/- 2.2) ml X kg-1 for nonpregnant and pregnant animals, respectively. During the course of gestation plasma renin activity increased about 300%, but estradiol 17 beta and estrone concentrations did not change significantly. The increase in whole blood and plasma volumes during pregnancy correlated highly with the increase in plasma renin activity, r = 0.53 and 0.59, respectively.

Animals↗
PubMed1983

Values clarification as a technique for family planning education.

A Spanish language family planning education program utilizing the dynamics of values clarification has been designed and implemented in the state of Oaxaca, Mexico. The design of the program features three basic personality identification activities to help individuals identify other dimensions of adult life expression than child rearing. In addition, a series of simple and precise scenarios specifically related to family planning are presented. Each scenario is accompanied by a set of valuing questions that direct the learner to respond to the scenario. The activity booklet is entitled, "Clarification De Valores En La Planificacion Familar." The booklet requires the learner to make responses to the learning materials. Responses are then used as a basis for inferring that people are comprehending and above all personalizing knowledge about themselves and their culture and family planning. The program is cross cultural and can be used in Spanish speaking communities in the U.S. Its English language form can be used with English speaking target populations. Statistical analysis of seven critical categories of the program indicated that the shifts in attitudes from pre-to post-values, whether positive or negative (desirable or undesirable), were not significant at the .05 level of confidence. It should, however, be noted that small shifts in the rate of natural increase, or rate of natural decrease for population growth can have a dramatic effect on population growth when multiplied by time.

Contraception↗