摘要:

SummaryThe factors associated with increased renal excretion of vasopressin (VP) were examined in the hypoxic fetus and newborn. Studies were conducted on six chronically instrumented fetal (117-136 days gestation) and seven newborn lambs (2-6-dayold). Hypoxia was produced by administration of 10% oxygen to the ewe or neonate for 30 min. This procedure caused a 50% reduction in PaO2, no significant change in pHa in either fetus or neonate and a slight fall in PaCO2. Hypoxia caused an increase in VP concentrations in plasma from 1.3 ± 0.53 to 46.4 ± 4.71 pg/ml in the fetus and from 5.9 ± 2.80 to 50.2 ± 26.68 pg/ml in the neonate. After hypoxia there was a fall in urine output from 0.27 ± 0.045 to 0.17 ± 0.046 ml/(min·kg) in the fetus and from 0.15 ± 0.033 to 0.09 ± 0.022 ml/(min·kg) in the newborn. The corresponding values for urine osmolality were the following: 168 ± 30.8 to 325 ± 30.6 mOsm/kg in the fetus and 388 ± 65.4 to 523 ±51.8 mOsm/kg in the newborn. VP concentration in urine increased from 13 ± 9.4 to a maximum of 176 ± 32.4 pg/ml after 30 min of recovery in the fetus and 39 ± 4.6 to 278 ± 132.5 pg/ml after 1 h of recovery in the newborn. These levels remained high for at least 1 h after the end of hypoxia. There was a good linear correlation between plasma VP levels and the corresponding urine levels and excretion rates in both the fetus and newborn. No correlation was found between VP urinary excretion and either osmolar excretion or GFR. These results, therefore, indicate that urinary VP levels and excretion rates can be used as a reflection of levels in plasma after hypoxia.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryThis study explores the effects of several divalent metal ions on thein vitroproduction of cyclic AMP, cyclic GMP, and testosterone by rat testicular tissue and on the amount of binding of [125I]human chorionic gonadotropin (hCG) in the testis. Zn2+at concentrations of 10-6to10-4M enhanced the hCG-stimulated production of cyclic AMP and testosterone, but only in the presence of Ca2+. [125I]hCG binding to rat testicular tissue was not affected by Zn2+. Cu2+, Ni2+, Co2+, and Mn2+ did not increase cyclic AMP or testosterone production in concentrations of 10-7to 10-3M and even inhibited them at a high concentration (10-2M). Cyclic GMP production was not affected by these divalent ions. These results suggest that Zn2+may play an important role in rat testicular steroidogenesis.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryYoung animals absorb and retain more calcium (Ca) than their older counterparts. The mechanism(s) for this age-related difference and the kinetics of intestinal calcium transport during maturation are not known. We determined, therefore, the unidirectional uptake and the transmural flux of [45Ca] in everted duodenal and jejunal sacs of suckling, weanling, adolescent, and adult rats using [3H] dextran as a marker of adherent mucosal volume. These measurements were carried out over a wide range of Ca concentrations (0.5-30 mM). Results indicate an evolving pattern of intestinal calcium transport with different kinetic characteristics emerging as the animals matured. The active component of transport became more pronounced with increasing age. In adult rats Km and Jmax of [45Ca] duodenal and jejunal uptake were several-fold greater than corresponding values for suckling rats. Transport at higher calcium concentrations (10- 30 mM) was non-saturable, and the' permeability coefficient decreased with age. The transition to a more saturable process occurred around the time of weaning. These findings suggest that intestinal calcium transport is characterized by a maturation pattern that starts with a predominantly passive system during infancy and changes to a saturable active mechanism during maturation.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryTo determine if some specific “preparation for birth” occurs in the developing lung to help assure its successful adaptation to a comparatively O2-rich world at birth, we measured the activities of the antioxidant enzymes in the developing lungs of rabbit fetuses from 10 d before parturition to several days after birth. Superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GP) activities showed similar maturational patterns with significant increases in activity, compared with earlier gestational levels, during the last 3-5 d before birth. During the final days in utero, SOD and CAT activities increased by ~110% and lung GP activity by ~200%. There were no parallel changes in lung O2consumption demonstrable over this same prenatal period.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryWe compared the concentration-response relationship of intralobar pulmonary arteries tol-norepinephrine with that of femoral arteries from newborn lambs. In addition, the effect of inhibition of the neuronal and extra-neuronal uptake mechanisms on these concentration-response relationships was examined. Concentration-response curves on 10 intralobar pulmonary arteries were performed with and without inhibition of the uptake mechanisms. Uptake inhibition shifts the curve to the left; thus, the -log EC50with uptake inhibition (6.63 ± 0.15) is greater than that without uptake inhibition (6.13 ± 0.14). Similar curves on 10 femoral arteries demonstrated that the -log EC50with and without uptake inhibition (6.20 ± 0.13 and 6.00 ± 0.04, respectively) are not statistically different.Because, in the presence of intact uptake mechanisms the concentration ofl-norepinephrine in the a-receptor microenvironment is less than that placed in the organ bath, the appropriate comparison of pulmonary and femoral arterial response tol- norepinephrine stimulation requires uptake inhibition in both vessels. The concentration-response curve with uptake inhibition for the intralobar pulmonary artery is significantly to the left of that for the femoral; the -log EC50for the pulmonary vessel (6.63 ± 0.15) is greater than that of the femoral vessel (6.20 ± 0.13). The intralobar pulmonary artery in vitro is more sensitive tol-norepinephrine stimulation than is the femoral.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryDigestion of dietary fat starts in the stomach, where lingual lipase hydrolyzes triglycerides to free fatty acids and partial glycerides at pH 3.0-6.0. Lingual lipase is secreted continuously from lingual serous glands and accumulates in the stomach between meals, when gastric pH is <3.0. We have, therefore, examined the resistance of lingual lipase to low pH and its possible protection by dietary components present in the stomach contents. Partially purified rat lingual lipase (7-15 µg enzyme protein) was preincubated at 37°C for 10-60 min at pH 1.0-6.0 before incubation for assay of lipolytic activity, hydrolysis of tri- [3H]olein at pH 5.4. The data show that partially purified rat lingual lipase preparations are stable at 37°C in the pH range of 2.5-6.0. Enzyme activity, however, is rapidly and irreversibly lost during preincubation at pH 1.0-2.4 for 10-30 min. Protein (gelatin 1% or albumin 1% or 2.5%) cannot prevent the inactivation of lingual lipase at low pH. The large molecular species (molecular weight >500,000) of lingual lipase (thought to be an aggregate of enzyme with lipids) is slightly more resistant to inactivation than the 46,000 dalton preparation, suggesting that lipids might protect the enzyme from inactivation. Indeed, about 60% of the initial lipase activity is preserved during incubation at pH 2.0 in the presence of 50 mM lecithin or 10 mM triolein. The data indicate that triglycerides which are hydrolyzed by this enzyme as well as phospholipids that are not hydrolyzed can prevent the inactivation of the enzyme. Lingual lipase is resistant to peptic digestion, even at high pepsin concentrations. Because of the special importance of lingual lipase in neonatal fat digestion, we compared the stability of the lipase in gastric aspirates of newborn infants to that of rat lingual lipase. The lipase in human gastric aspirates is more resistant to inactivation than the rat enzyme. There are however individual variations in enzyme stability: from preservation of 100% of original activity to the loss of 80% of activity during incubation for 30 min at pH 1.6. The data suggest that substances within the newborn infant's stomach stabilize the enzyme at low pH. We suggest that the extensive intragastric hydrolysis of dietary fat (in formula or breast milk) is related to the stability of the lipase in the stomach of newborn infants.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryLongitudinal studies on total and resting metabolic rate and total heat loss were made in 14 LBW infants, age 1-58 d. Metabolic rate was calculated from indirect calorimetry, heat loss was measured by direct calorimetry. Total metabolic rate and total heat loss were lowest during the first week of life, 178.9 ± 18.0 and 171.8 ± 15.5 kJ·kg-1·24 h-1, respectively. During the age period of 8-58 d both total metabolic rate and heat loss showed a very slight increase with age: mean total metabolic rate was 278.8 ± 2.6 and mean total heat loss 257.0 ± 3.4 kJ·kg-1·24 h-1. Resting metabolic rate was 171.0 ± 25.2 kJ· kg-124 h-1during the first week of life and 248.0 ± 2.5 during d 8-58.The energy cost of components of new tissue was calculated from the energy balance equation. Ecomponentsduring the second week of life was 25.5 ± 4.9 kJ/g weight gain and 11.9 ± 0.4 kJ/ g weight gain over subsequent weeks. The net energy cost of tissue synthesis, calculated from the difference between indirect and direct calorimetry was 3.2 ±1.1 kJ/g weight gain during the second week and 1.1 ± 0.1 kJ/g weight gain in the following weeks. A neonate who receives a caloric intake of 535 kJ · kg-1· 24 h-1and is growing at a rate of 17 g ·kg-1· 24 h-1will use 42% of the caloric intake for maintenance and thermoregulation, 6% for activity, 38% for the components of new tissue, 4% for tissue synthesis and 10% for loss in faeces and urine.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryNewborn blood from three siblings with prolidase deficiency contained no detectable prolidase activity. Umbilical cord blood contained no prolidase activity in one sibling and only 6.8% of control activity in another sibling. In prolidase deficiency the enzyme defect is expressed at birth, well before the appearance of skin ulcers, and is demonstrable in filter paper specimens of blood obtained for routine screening.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryAt 10 d of age miniature pigs were randomized to receive either of two total parenteral nutrition fuel mixes; oral feedings were discontinued. Both groups received 170 kcal·kg-1·d-1and 11 g·kg-1·d-1of synthetic amino acids. Nonprotein energy was supplied as glucose in group A, whereas in group B, it was divided equally between glucose and fat. Blood samples were drawn on the second and eighth postoperative days for hematologic, biochemical, and hormonal measurements. On the ninth postoperative day, total body water was determined and the animals were killed for carcass analysis. The animals tolerated the intravenous nutrition without ill effects as indicated by both clinical and biochemical parameters. Group A had significantly elevated levels of insulin and a higher insulin/glucagon ratio than group B. Cortisol levels did not differ significantly between groups. Total body fat, nitrogen, ash, K, Na, Cl, Ca, and P were similar between groups. TBW was significantly greater in group A compared with group B. Extracellular space calculated from body Cl and plasma Cl was similar between groups.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryShort-term (0-30min) pulmonary and systemic vascular responses of oophorectomized ewes infused intravenously with a trichloroacetic acid (TCA) extract of a type III (strain 878) group B streptococcus (GBS) were studied. TCA-878 extract induced significant pulmonary hypertension, reduction in femoral artery pressure and reduced femoral artery PO2. These responses were similar to those observed after the infusion of sublethal doses ofE. coliendotoxin and could be prevented by priming the animal with ibuprofen or indomethacin. Ewes rechallenged 48 h after their initial dose of TCA-878 extract experienced pulmonary arterial pressure significantly higher than those induced by the first infusion. Similar augmented responses were not seen after rechallenge with endotoxin. Larger doses of TCA-878 extract resulted in increasingly higher pulmonary arterial pressure. We conclude that the venous infusion of TCA extracts of GBS-878 induces significant pulmonary hypertension in sheep and that this response may be mediated by prostaglandins. The vasoactive substance extracted from these streptococci could play a role in promoting the vascular instability experienced by the human neonate with early onset GBS disease

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID