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Biomedical subjects

M Vergara

Publications and source records attributed to M Vergara.

At least 55 records · Page 3Linked to original sources
PubMed1992

Differing responses of plasma bioactive and immunoreactive follicle-stimulating hormone and luteinizing hormone to gonadotropin-releasing hormone antagonist and agonist treatments in postmenopausal women.

Plasma bioactive (B) and immunoreactive (I) FSH and LH were measured every 10 min for 8 h in the same postmenopausal women in a three-phase study: 1) during normal pulsatile gonadotropin secretion (basal study; n = 8), 2) 8 h after a single injection of a GnRH antagonist (5 mg Nal-Glu, sc; n = 5), and 3) 21 days after a GnRH agonist injection (D-Trp6, 3.75 mg depot preparation, im; n = 7). I-FSH and I-LH were measured by monoclonal antibody immunoradiometric assays. B-FSH and B-LH were measured in selected samples with the immature rat granulosa cell and mouse interstitial cell assays, respectively. Significant pulsatility of B- and I-FSH and LH was demonstrated in the basal samples, but only the B/I ratio of LH was slightly elevated within the secretion peaks. After GnRH antagonist treatment, I-FSH decreased from a mean pretreatment level of 55.7 +/- 7.8 IU/L by 26% (P less than 0.001), and B-FSH from 313.8 +/- 61.9 IU/L by 44% (P less than 0.01). The B/I ratio decreased from 6.4 +/- 1.7 to 4.5 +/- 1.0 (P less than 0.05). After agonist treatment, the I- and B-FSH levels decreased by 92% and 83% (P less than 0.0001), respectively, but the B/I ratio increased to 17.3 +/- 4.7 (P less than 0.05). The concentrations of I- and B-LH decreased by 75% and 80%, respectively (P less than 0.001), after antagonist treatment. After agonist treatment, I-LH decreased by 92%, and B-LH by 93% (P less than 0.0001). No changes in the B/I ratios of LH were found after either treatment. In conclusion, no changes were found in the quality of circulating LH during the treatments, whereas the antagonist treatment decreased and the agonist treatment increased the B/I ratio of FSH. These findings provide further evidence that the qualitative responses of FSH and LH to treatment with the same GnRH analog are different, and that the suppressive mechanisms of GnRH antagonist and agonist action on gonadotropin secretion are different.

Adult↗
PubMed1992

The retino-hypothalamic tract is involved in prolactin regulation in fetal sheep.

To investigate the role of the retino-hypothalamic tract on fetal prolactin regulation, we examined the effect of ocular enucleation on fetal plasma prolactin. Eleven fetuses of Suffolk ewes were chronically catheterized during fall, and six of them were subjected to bilateral ocular enucleation. All ewes were kept at 12h:12h light:dark cycle (lights on at 0800 and off at 2000). The experiments were performed 5-9 days after surgery (GA control fetuses 125 +/- 1.5, optical enucleation 121.3 +/- 1.5 days). Blood samples were taken from fetuses hourly around the clock, and plasma prolactin and cortisol were measured by radioimmunoassay (RIA). Luteinizing hormone (LH) and Growth hormone (GH) were measured in pooled plasma samples from control and enucleated fetuses by RIA. Average plasma prolactin was 5-fold lower in enucleated than in control fetuses (9.6 +/- 0.5 and 54.2 +/- 3.3 ng/ml, SEM; P < 0.005). Both control and enucleated fetuses presented circadian rhythm of prolactin with acrophase between 1400 and 1830 h. An enucleated fetus was tested for response of prolactin to TRH. Prolactin increased as described in the literature. There was no change in plasma concentration of cortisol, LH or GH after ocular enucleation. Our data indicate that the optical pathway participates in prolactin regulation in the fetal sheep.

Animals↗
PubMed1992

[Hospital crisis and the hospital of the XXI century].

The present hospital situation and a projection for the XXIth century, the national and international information, is analyzed. Outstanding characteristics include better health indicators and an explosive growth of costs due to technological advance and health insurance. Inadequate use of resources is noted. The state expense in public health was greatly decreased during the Chilean military government who privileged private investment. At present, the public sector counts 184 hospitals, 373 outpatient clinics and 1053 rural health posts and takes care of the health needs of 80% of the population. There has been no increase in expenses in the public sector compared to a 150% increase in the number of beds in the private sector. Decentralization, a redefinition of the health care model, an investment program and better administration are needed to improve the situation long-term. The health system and levels of health care as well as a model for hospitals in the coming century are described.

Chile↗
PubMed1991

Detection of two atypical rotaviruses in the province of Misiones, Argentina.

Out of 317 human gastroenteritis cases studied between August 1988-August 1989, two atypical antigenically distinct rotaviruses (pararotaviruses) were detected in faecal samples among 19 rotaviruses shedding children from Misiones province, North-Eastern Argentina. A 1 3/4 year old girl a 3 years old boy, both with vomiting and normal temperature, shed these atypical rotaviruses. Their morphology by electron microscopy was identical to other rotaviruses; they contained 11 double-stranded RNA segments detected by polyacrylamide gel electrophoresis and failed to react with the antibody directed against the rotavirus group specific antigen (Rotazyme II ELISA). The electrophoretic migration of these RNAs (electropherotype) in polyacrylamide gels did not coincide with the typical pattern of distinct size classes observed in most human rotaviruses reported, instead, they appeared to be related to patterns of rotaviruses group C.

Argentina↗
PubMed1991

Effect of a melatonin implant on the circadian variation of plasma prolactin and rectal temperature in newborn sheep.

Plasma prolactin and rectal temperature show a circadian rhythm in newborn sheep raised under continuous light. Melatonin lowers the concentration of plasma prolactin but it is not known if it affects its circadian rhythm. To detect whether melatonin acts on the circadian system we studied the effect of a subcutaneous melatonin implant in the circadian rhythms of prolactin and rectal temperature in newborn lambs raised under continuous light. We placed catheters in the pedal artery and vein in 9 newborn lambs (2-5 days of age). A subcutaneous melatonin implant was placed in 4 of the lambs at 9-12 days of age. Blood samples and rectal temperature measurements were obtained hourly for a period of 24 h, 11-15 days after the implant, at 20-27 days of age. To avoid interferences of heparin in our melatonin assay, serum melatonin concentration was measured before and during the implant in three additional newborns. Prolactin and melatonin were measured by RIA. Melatonin concentrations were 52.8 +/- 45.9 pg/ml (day) and 315.5 +/- 77.0 pg/ml (night) before treatment (SEM, P less than 0.001), and increased to 594.1 +/- 54.5 pg/ml after placing the implant (there was no difference in melatonin concentration between day and night during the time that the implant was in place). Melatonin had no effect on rectal temperature or its rhythm, but decreased basal plasma prolactin concentration (control: 97.5 +/- 11.3 ng/ml; treated: 25.1 +/- 2.4 ng/ml, P less than 0.001) and abolished the prolactin circadian rhythm, (Cosinor analysis): control: log prolactin (ng/ml) = 1.8 + 0.26 cos 15 (t - 11.16), p = 0.05; treated: log prolactin (ng/ml) = 1.2 + 0.14 cos 15 (t - 9.43), P = 0.36.

Animals↗
PubMed1990

[Deficiency of prostacyclin stimulating factor in type I diabetes mellitus. Correlation with the duration of the disease].

The prostacyclin stimulating plasma factor (PSPF) was studied in 40 children affected by insulin dependent diabetes (type I), using smooth muscle cells of rat aorta as substrate. The patients were divided into three groups according to the duration of the disease; recently diagnosed patients (n = 10), patients with less than 5 years of evolution (23 cases), and patients with more than 5 years duration (n = 7). The most significant data were that all the patients with more than 5 years duration had decreased PSPF with values below I SD (p less than 0.001). No statistically significant differences were found among the group with less than 5 years duration, recently diagnosed patients and the normal control group. Neither could a correlation be found between the value of PSPF and the dose of insulin required by each patient, or the rate of hyperglycemia, triglycerides, cholesterol and Hb A1C.

Adolescent↗
PubMed1990

Deficient activity of prostacyclin stimulating plasma factor (PSPF) in newborns.

The activity of PSPF was studied in 38 normal newborns. The production of 6-keto-PGF1 (PGI2 stable metabolite) after stimulation with cord blood plasma, 0.72 +/- 0.50 pmol/10(5) cells, was lesser than after stimulation with plasma from 2-3 years old children, 3.00 +/- 0.89 pmol/10(5) cells (p less than 0.01), or from adults, 7.74 +/- 5.00 pmol/10(5) cells (p less than 0.001). No differences were shown during neonatal period. The presence of a circulating inhibitor factor in newborns was dismissed by mixed cultures. The behaviour of neonatal plasma after consecutive stimulations with AA was similar to adult plasma response. We proved that newborns show a deficient capacity to stimulate PGI2, which is not due to circulating inhibitor factor, and we think that this deficiency is due to a weaker action of stimuli, rather than to an immaturity.

Adult↗
PubMed1989

Ontogeny of the circadian rhythm of cortisol in sheep.

In this work we investigated the ontogeny of the rhythm of plasma cortisol in sheep. Plasma cortisol was measured by radioimmunoassay in blood samples obtained every 1 or 2 h, for periods of 24 or 48 h, in 13 fetal sheep (124-140 days of gestation; 130.6 +/- 1.5, mean +/- SE) and in 23 newborn (5-39 days of age). To this end, indwelling polyvinyl catheters were implanted into the femoral artery and vein in all animals. The presence of rhythm was determined by Cosinor Analysis. Newborns were separated into four groups. Group 1, newborns younger than 15 days of age (7.9 +/- 0.7 days), and Group 2, newborns older than 15 days of age (25.4 +/- 2.3), were raised under nyctohemeral conditions (12L:12D). Group 3, newborns younger than 15 days of age (11.4 +/- 0.9 days), and Group 4, newborns older than 15 days of age (22.0 +/- 1.2 days), were raised under constant light conditions. A 24-h rhythm of plasma cortisol (F) was observed in newborns over 15 days of age under both nyctohemeral: F (ng/ml) = 16.1 + 7.6 cos [15 (t-12.9)], (p = 0.01, n = 8) and constant light conditions: F (ng/ml) = 17.1 + 3.9 cos [15 (t-7.9)], (p = 0.02, n = 5). No rhythm was observed in fetal sheep or in newborn sheep younger than 15 days of age under nyctohemeral or constant light conditions.

Animals↗
PubMed1989

Fetal prolactin levels respond to a maternal melatonin implant.

Seasonal PRL changes in adult sheep are controlled by photoperiod. The ability to detect photoperiod is mediated by the pineal gland through melatonin secretion. A rhythm in plasma melatonin has been described in fetal sheep. In this work we investigated whether the fetus responds to changes in circulating levels of melatonin. Fetal plasma PRL was measured every 2 h for 24 h, 7 days after the mother had received a sc Silastic implant containing approximately 1 g melatonin. Control fetuses received an empty implant. Melatonin is slowly released from implants, and it is known to cross the sheep placenta. Fetal plasma melatonin increased 10-fold after the implant. Plasma PRL in fetuses treated with melatonin was a third of that of control fetuses. Fetal plasma PRL concentrations were 56.6 +/- 5.7 ng/ml (mean +/- SE) in control and 18.1 +/- 2.7 ng/ml 7 days after the melatonin implant. We conclude from these data that the ability to respond to melatonin is present in sheep during fetal life.

Animals↗
PubMed1989

The circadian variation of prolactin in fetal sheep is affected by the seasons.

Plasma PRL concentration shows a circadian variation in fetal and adult sheep. In the adult sheep the presence of this variation depends on the season. In this paper we investigated whether season affects the presence of the circadian variation of PRL in the fetal sheep. To that effect we measured plasma PRL concentration every 2 h for 24 h during summer, fall, and winter in three groups of fetal sheep whose gestational ages ranged from 125-133 days. Mean (+/- SEM) fetal plasma PRL concentrations were 352.8 +/- 65.0 ng/ml during summer (n = 6), 98.7 +/- 12.9 during fall (n = 8), and 10.5 +/- 2.6 during winter (n = 4). A 24-h variation of plasma PRL was detected during summer [PRL (ng/ml) = 352.8 + 85.2 cos 15 (t - 18.5); P = 0.007] and fall [PRL (ng/ml) = 98.7 + 26.6 cos 15 (t - 23.6); P = 0.041] but not during winter. The mesor and amplitude of the variation are higher in summer than in fall, and the acrophases differ by 5 h, taking place at dusk in summer and close to midnight in fall. These findings show that in fetal sheep, PRL responds to seasons in utero. The signal triggering this response is most likely photoperiod.

Animals↗
PubMed1989

Ontogeny of the circadian variation of plasma prolactin in sheep.

The ontogeny of circadian rhythms is unknown. The newborn sheep has a circadian rhythm of temperature; to study the ontogeny of other rhythms, we examined the 24-h variation of plasma prolactin concentration in fetal and newborn sheep. To this effect, we measured plasma prolactin concentration in chronically catheterized fetuses (n = 7) and in newborn lambs raised under short day nycthemeral (12 light:12 dark, n = 13) or constant light conditions (n = 5). Indwelling catheters were implanted into the jugular vein and carotid artery of late gestation fetuses (0.9 gestation) and newborns (5-29 days old). Experiments were performed 4 or more days after surgery. Lambs were kept in a canvas sling and were fed cow's milk either by mouth or through a nasogastric catheter at established time intervals. Haematocrit, pH, and blood gases were measured before and after the experiments in all cases and remained within normal values. Lights were on and room temperature was maintained constant during the whole experiment. Samples were obtained every 1-2 h for 24 h in fetuses and newborn lambs under nycthemeral conditions and every hour for 48 h in newborn lambs kept under constant light. Plasma prolactin was measured by radioimmunoassay. The presence of a 24 h rhythm was determined by Cosinor analysis. Fetuses, aged 129 +/- 6 days (SD) n = 7, showed a variation in plasma prolactin concentration with a period of 24 h that fits the equation: plasma prolactin (ng ml-1) = 97.0 + 15.4 cos 15 (t-23.0), P = 0.035.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Tissue damage markers in experimental Chagas' disease.

Malondialdehydemia (MDA), measurements of heart and liver tissue damage (TDU), plasma activity of heart alpha-hydroxybutyrate dehydrogenase (LDH1) and liver lactate dehydrogenase (LDH5) were determined in non-infected mice and in mice infected with 10(5) T. cruzi, Y strain, bloodstream trypomastigotes. All the parameters measured were increased (P less than 0.01) in infected mice 8 days after intraperitoneal inoculation. The results indicate that plasma MDA levels can serve as a useful indicator of the systemic tissue injury found in Chagas' disease.

Animals↗
PubMed1987

Circadian variation of rectal temperature in newborn sheep.

In adult animals, body temperature shows a 24 h rhythm that is endogenously generated. We examined the existence of 24 h rhythms of temperature in 10 newborn sheep. Four newborns, aged 5 to 28 days were kept with their mothers under nycthemeral conditions, and the remaining 6 lambs, aged 21 to 43 days, were kept with their mothers in constant light from day 3 after birth. Experiments were performed with both groups of lambs in the laboratory. Additional experiments were performed with the 6 lambs kept under constant light while they were in the pen with their mothers to rule out artifacts due to manipulation or artificial feeding. During the experiments done in the laboratory, the lambs were kept blindfolded in a canvas sling and were fed baby formula approximately every four hours (lambs kept under nycthemeral conditions) or every hour (constant light lambs). Lights were on in the room during the whole experiment. Temperature in the room was maintained at 18 +/- 0.1 degrees C (mean +/- SEM). In the experiments done in the pen, animals remained with the mother and room temperature was not controlled. In all experiments, rectal temperature was hourly measured for 24 h with a thermocouple inserted in the lamb's rectum and connected to a Philipp Schenk digital recorder. Lambs kept under nycthemeral conditions show a variation of mean rectal temperature (t degree) with a period of 24 h, that fits a cosine function (P less than 0.001): Rectal t degree (degree C) = 40.6 + 0.4 cos [15 (t-16.22)]. The mesor is 40.6, the amplitude 0.4, and the acrophase expressed in h is 16.22 (n = 4). Lambs kept under constant light show a variation of rectal temperature with a period of 24 h, independently of whether the measurements were done in the laboratory or in the pens. The acrophases varied widely in these animals, when the acrophase were synchronized so theta = 2400, mean rectal temperature showed a variation with a period of 24 h that fits the equation (P less than 0.001): Rectal t degree (degree C) = 39.5 + 0.18 cos [15 (t-0.23)]. The presence of a 24 h rhythm of rectal t degree in lambs kept under nycthemeral conditions, and its persistence in lambs kept under constant light suggests that the rhythm of rectal temperature observed in the newborn lamb is a true circadian rhythm.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Urinary excretion of activatable kallikrein in one-kidney pole-ligated hypertensive rats.

Kallikrein activatable by trypsin was found in the urine of normal rats, corresponding to about 33% of the total kallikrein excretion. This fraction was inhibited by aprotinin and kallikrein antiserum. There was no spontaneous activation at 20 degrees C for 24 h or at 37 degrees C for 15 h which indicates that the amount detectable in the urine may represent the levels of activatable kallikrein in the renal tubule. Sephacryl S-200 chromatography of the urine disclosed the presence of two forms of kallikrein, active and activatable, with apparent molecular weights of 30 000 and 34 500 respectively. These findings allow us to assume that the activatable fraction would correspond to prokallikrein, as described by others. In hypertensive one-kidney pole-ligated rats, the total urinary kallikrein did not differ from that excreted by solely uninephrectomized rats, though the active kallikrein showed a significant drop (P less than 0.001). These results suggest that in hypertensive rats there is an alteration in the activation mechanisms of kallikrein.

Animals↗