Browsing by Author "RIQUELME, R"

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    ONTOGENY OF THE CIRCADIAN VARIATION OF PLASMA PROLACTIN IN SHEEP
    (1989) VERGARA, M; PARRAGUEZ, VH; RIQUELME, R; FIGUEROA, JP; LLANOS, AJ; SERONFERRE, M
    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. Newborn lambs, aged 7.9 .+-. 2.3 days old (n = 11), kept under nycthemeral conditions showed a variation of plasma prolactin with a period of 24 h that fits the equation: plasma prolactin (ng ml-1) = 75.3 + 12.9 cos 15 (t-12.0), P = 0.036. This rhythm disappeared in newborns of 23.4 .+-. 3.8 days of age (n = 7). Newborn lambs, aged 22.0 .+-. 2.7 days (n = 5), raised under constant light, showed a 24 h variation of plasma prolactin in the individual data. These newborns showed a tendency to higher prolactin values and a wider dispersion of plasma prolactin concentration than the two other groups. To normalize the variance the group mean was calculated after log transformation. When log values were synchronized considering the acrophase of the theoretical function as 24 h a rhythm that fits the equation: log plasma prolactin (ng ml-1) = 1.8 + 0.29 cos 15 (t-0.5), P = 0.031, was observed. This indicates that the rhythm of prolactin in the newborn sheep free-runs under constant light. The presence of a rhythm in plasma prolactin with a period of 24 h in fetuses and in the newborn, and the existence of this free running rhythm in newborns kept under constant light, suggest that the prolactin rhythm observed is a circadian rhythm endogenously generated. In addition, the disappearance of the rhythm in older newborns raised under short nycthemeral conditions, and its maintenance in newborns of similar age kept under constant light, suggests that the newborn sheep is sensitive to photoperiod.
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    ONTOGENY OF THE CIRCADIAN-RHYTHM OF CORTISOL IN SHEEP
    (1989) PARRAGUEZ, VH; VERGARA, M; RIQUELME, R; RAIMANN, R; LLANOS, AJ; SERONFERRE, M
    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 llight 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.
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    SPERM BINDING TO THE HUMAN ZONA-PELLUCIDA AFTER MIGRATION THROUGH HUMAN CERVICAL-MUCUS
    (1995) VIGIL, P; RIQUELME, R; MORALES, P
    During lactational amenorrhea a special type of cervical mucus, similar to that found during the luteal phase, is produced. This mucus, however, is able to support sperm migration. In the study described, the ability of spermatozoa to bind to the human zona pellucida (hZP) after migration through periovulatory and post-partum mucus was studied. Mucus was obtained from exclusively breastfeeding women in amenorrhea at 30, 60, 120 and 180 days post-partum. Periovulatory mucus samples from normally cycling women were used as a control. Flat capillary tubes were filled with BWW culture medium at the top and cervical mucus at the bottom. The tubes were immersed in a semen reservoir and the spermatozoa allowed to migrate through the mucus for 3 h into the culture media. Then the spermatozoa were coincubated with 3-4 hZP for 30 min and the number of bound spermatozoa per zona was counted. Periovulatory cervical mucus had an average Insler score of 14 +/- 0.5 as compared to 4.6 +/- 0.4 for post-partum mucus. Spermatozoa recovered from periovulatory mucus were always able to bind to the hZP. Spermatozoa recovered from post-partum mucus, however, were able to bind to the hZP in only 68 +/- 7% of the cases. Moreover, spermatozoa recovered from post-partum mucus bound to the ZP in lower numbers than did spermatozoa recovered from periovulatory mucus (p<0.03). These results suggest a greater ability of sperm-hZP binding after migration through periovulatory mucus and they also indicate that sperm binding to the ZP is possible even after sperm migration through a low quality mucus.