Biogeography and ecological setting of Indian Ocean hydrothermal vents.

Within the endemic invertebrate faunas of hydrothermal vents, five biogeographic provinces are recognized. Invertebrates at two Indian Ocean vent fields (Kairei and Edmond) belong to a sixth province, despite ecological settings and invertebrate-bacterial symbioses similar to those of both western Pacific and Atlantic vents. Most organisms found at these Indian Ocean vent fields have evolutionary affinities with western Pacific vent faunas, but a shrimp that ecologically dominates Indian Ocean vents closely resembles its Mid-Atlantic counterpart. These findings contribute to a global assessment of the biogeography of chemosynthetic faunas and indicate that the Indian Ocean vent community follows asymmetric assembly rules biased toward Pacific evolutionary alliances.

Serum dehydroepiandrosterone sulfate in premature infants and infants with intrauterine growth retardation.

Serum dehydroepiandrosterone sulfate (DHAS) was measured by radioimmunoassay in blood samples obtained in 128 ill newborn infants. Serial sampling was carried out in 40 infants. There were wide ranges found in the values in all gestational age groups, and there were not significant differences in the first day of life between DHAS levels in less than 30 week gestation prematures, 6819 +/- 4631 (SD) ng/ml, and near term or term infants, 4307 +/- 1498 ng/ml. Mean DHAS concentrations did not decline over the first three weeks of life in prematures less than 36 weeks gestation. In six infants, age 35-73 days, and 29-34 weeks gestation at birth, the DHAS concentration was 1068 +/- 138 ng/ml. High concentrations were frequent in prematures less than 33 weeks gestation and could be correlated to epiodes of severe clinical stress. There were no significant differences in serum DHAS levels, on the first day of life, between infants with no hyaline membrane disease, nonfatal hyaline membrane disease and fatal hyaline membrane disease. Intrauterine growth retarded (IUGR) infants, who were greater than 35 weeks gestation, had significantly lower (P less than .032) DHAS levels in the first day of life than normally grown infants. The results show that there is a persistence during the postnatal period of the prominent delta5-3beta-hydroxysteroid production by the adrenal cortex characteristic of the fetus. Low concentrations of serum DHAS in IUGR infants suggest that the fetal zone of the neonatal adrenal cortex is a major source of circulating DHAS in the newborn period.

Umbilical serum DHAS and total oestriol in relation to gestational age and mode of delivery.

The concentrations of mixed umbilical cord serum dehydroepiandrosterone sulphate (DHAS) and total oestriol, were determined by radioimmunoassay in 301 infants. Of 280 infants born between 36 and 42 weeks of gestation, 260 were born by vaginal delivery and 20 were delivered by Caesarean (C-section). We found that there was a significant elevation of serum total oestriol (P < 0.005) after 35 weeks with no concomitant gestational change of DHAS. Within the vaginal delivery group steroid values were similar among infants born following spontaneous, oxytocin augmented, and oxytocin induced labour. Within the C-section delivery group, steroid values were similar in infants who experienced spontaneous labour and those who did not. However, DHAS level was significant higher (P < 0.005) in the vaginal delivery group than in the C-section group. We postulate that the higher DHAS levels in the vaginal delivery group are the result of stress during the late first stage of labour or later.