摘要:

SummaryGlucose oxidation by developing rat intestine changed dramatically during the period of suckling and weaning. After weaning, glucose oxidation to CO2by intestinal slices increased over 3-fold. This was associated with an increase in lactate production from glucose and an increase in the rate of pyruvate decarboxylation.Active pyruvate dehydrogenase in intestine of developing rats also increases in activity at the time of weaning, suggesting that the suppression of glucose oxidation during the suckling period is controlled by pyruvate dehydrogenase. Glucose oxidation to CO2and pyruvate decarboxylation to CO2by intestinal slices of postweaned animals was inhibited by exogenous 3-hydroxybutyrate. But exogenous 3-hydroxybutyrate did not inhibit glucose and pyruvate oxidation in intestine of suckling animals which have higher levels of endogenous 3-hydroxybutyrate than intestine of postweaned rats. Palmitate, in contrast, inhibited glucose and pyruvate oxidation by both pre- and postweaned intestine.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryWe administered sodium meclofenamate, a prostaglandin synthetase inhibitor, to 15 piglets (ages 5-70 d) to test the hypothesis that endogenous prostaglandin pulmonary vasodilators influence total pulmonary resistance under both normoxic and hypoxic conditions. No significant differences in hemodynamic measurements were found between the control group and drug-treated animals more than 12-d-old. When six experimental animals less than 12 d of age were compared with six age-matched controls, meclofenamate produced a small but significant increase in mean pulmonary artery pressure (110 ± 9versus97 ± 10%,P< 0.05) and total pulmonary resistance (135 ± 23versus102 ± 12%,P< 0.03). The magnitude of the change in total pulmonary resistance produced by 2 mg/kg of meclofenamate during normoxia correlated inversely with postnatal age (r= 0.83,P< 0.01). Individual changes in pulmonary hemodynamics produced by acute hypoxia after meclofenamate treatment were the same as pretreatment values and were similar in both young and older animals.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryNeonatal, adult, and fetal rat lungs of 18, 20, and 22 d gestation from four to six litters were examined for cytochrome oxidase, glucose-6-phosphate dehydrogenase, catalase, glutathione peroxidase, copper-zinc and manganese superoxide dismutase activities. All results were corrected for the contribution of enzymes in blood that contaminate homogenates. Because lung protein/ DNA ratios and body water change significantly with gestational age, enzyme activities were expressed as U/mg DNA. All activities were low in d 18 lung and increased with advancing gestational age. Only catalase and copper-zinc superoxide dismutase increased activity in response to air breathing, suggesting that maturation of the antioxidant enzyme system is virtually complete before delivery. Activities of glucose-6-phosphate dehydrogenase, catalase, glutathione peroxidase, and manganese superoxide dismutase were higher in neonatal than in adult lung.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryThe normal effect of feeding an antigen, such as ovalbumin (hens' egg albumin), to adult animals is the induction of a state of specific nonreactivity of the lymphoid tissues when the same antigen is presented again (oral tolerance). We have carried out feeding experiments in neonatal mice to investigate subsequent immune responses after physiologic antigen exposure and to examine the role of the neonatal intestine.We demonstrate for the first time that feeding a weight related dose of ovalbumin within the first week of life results in priming for both humoral and cell-mediated immune responses, despite the profound tolerance found in adult animals when treated in the same way. When the time scale of antigen exposure was extended into the prenatal period, the enhancement of the immune response was even more pronounced. These effects are long lasting and effects on cell-mediated immune responses are still demonstrable 14 wk after the initial priming feed. We postulate that after an antigen feed in the neonatal period, immunologic and digestive immaturity lead to a net gain in T help which prevents the induction of systemic hyporesponsiveness (oral tolerance).

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryA disorder of calcium (Ca2+) metabolism may be central to the pathogenesis of cystic fibrosis (CF). Average cellular Ca2+levels in fibroblasts derived from patients with CF (ages, 14-25 yr;n=25) were 36-77% higher than in matched controls depending on age of cell culture (9.0-10.6versus5.1-7.8 nmol/mg cellular protein). Cellular Ca2+was significantly elevated in CF, but was not a reliable criterion for identifying CF cells because of the high variability of results. Studies of Ca2+fluxes in cell organelles showed that mitochondria isolated from CF fibroblasts accumulate 2-3 times more Ca2+than controls [79.5 ± 8.2versus33.7 ± 4.7 nmols · mg mitochondrial protein-1· min-1(±SD)] Ca2+accumulation in mitochondria reliably distinguished between CF and control or heterozygote cells (P<0.0005,n=11).In vitroexperiments showed that Ca2+influx and efflux are increased in isolated CF mitochondria, resulting in net Ca2+accumulation. Ca2+uptake in mitochondria is energy-dependent; some inhibitors of mitochondrial energy metabolism (atractyloside, oligomycin) influenced Ca2+uptake significantly more in CF than in control mitochondria. Furthermore, the average activities of NADH oxidase, NADH- and succinate-cytochrome c reductase were 77, 58, and 48% higher in CF mitochondria, respectively. This indicates that many functions associated with energy metabolism and the mitochondrial membrane (electron transport, ATP transport, and ATP hydrolysis) are not operating properly in CF, thus possibly causing the derangement of Ca2+metabolism found in CF mitochondria and cells.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryBacterial sepsis is a relatively common problem in the neonatal period, particularly among prematurely delivered infants. The newborn rat has been widely used as a model for sepsis neonatorum, and in that model incomplete development of the neutrophil system has been postulated to be an important factor predisposing neonates to death from bacterial infection. In this study, that hypothesis was further tested by assessing neutrophil development in rats of various pre- and postnatal ages. Using standard soft agar colony techniques for detecting granulocyte-macrophage progenitor cells [CFU(c)], the number of CFU(c)/g of body weight was seen to increase from 0.5 + 0.1 X 103at 19-20 days gestation to 10.5 ± 0.2 x 103at 4 weeks. The anatomic location of CFU(c) changed from totally hepatic at 16 days gestation to almost totally myeloid at 4 weeks. Lastly, the proportion of mature, stored neutrophils/CFU(c) decreased from 2440 ± 40 at 19-20 days gestation to 430 ± 75 at 4 weeks.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryNewborn humans may develop myocardial dysfunction in conjunction with severe birth asphyxia. Subendocardial or papillary muscle ischemia appears to be the basis for the myocardial dysfunction, yet patent coronary arteries have been demonstrated in the nonsurvivors. The asphyxiated newborns also have experienced hypoxemia, which has been suggested as the cause of myocardial ischemia. This study was designed to determine the relationship between reduced aortic blood oxygen content and blood flow as well as oxygen delivery within different regions of the heart. Three days after surgery, we measured blood flow and oxygen delivery to the free walls and papillary muscles of the right and left ventricles, the ventricular septum, and the atria in 10 lambs, during 20-min periods in 8-10% and 5-6% environmental oxygen concentrations. In each region of myocardium, blood flow increased linearly as the aortic blood oxygen content decreased. The slopes of the regression lines were similar for each region of ventricular myocardium. Atrial myocardial blood flow also increased as a linear function of the reductions in aortic blood oxygen content, but at a slower rate than in the ventricular regions. Hypoxemia was associated with increased oxygen delivery in each region of myocardium, but the two variables were not related in a linear or quadratic fashion. The results demonstrate that isolated hypoxemia is associated with increased blood flow and oxygen delivery in the free walls and papillary muscles of the right and left ventricles, the ventricular septum, and the atria.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryFactors modulating the fetal aldosterone response to hypoxemia were studied in three groups of chronically catheterized fetal lambs between 131 and 143 days of gestation (term, 145 days). One group (control group) received an infusion of 5% dextrose in water; the second group (captopril-treated group) was given captopril, an inhibitor of angiotensin-converting enzyme; the third group (captopril plus dexamethasone-treated group) received dexamethasone in addition to captopril. In all groups of fetuses, hypoxemia was associated with a significant increase in plasma K+concentration (+0.7 ± 0.1 meq/liter). In control fetuses, changes in plasma aldosterone concentration during hypoxemia correlated closely with changes in plasma K+concentrationr=0.79;P<0.001) and with changes in plasma angiotensin II concentration (r=0.77;P<0.001). In the captopril-treated fetuses, the rise in plasma aldosterone concentration during hypoxemia correlated closely with plasma K+(r=0.79;P<0.001) but not with plasma angiotensin II values (r=0.17). No significant correlation was found between percent changes in maternal aldosterone and percent changes in fetal aldosterone during hypoxemia and following recovery (r=0.36;P>0.1) in captopril-treated fetuses. Administration of dexamethasone to fetuses receiving captopril completely inhibited the rise in plasma aldosterone associated with hypoxemia. Taken together, the present results suggest that the rise in plasma aldosterone during hypoxemia is not related to the level of activity of the renin-angiotensin system but depends probably on the increased secretion of adrenocorticotrophin by the fetus. It is also suggested that maternal placental transfer of aldosterone is not an important factor controlling the rise in fetal plasma aldosterone concentration during hypoxemia.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryTaurinuria is characteristic of the immature rat. The capacity of the kidney to accumulate the β-amino acid taurine and D-glucose was examined using isolated brush border membrane vesicles (BBMV) prepared from 28-day-old rats. Taurine accumulation was inversely proportional to osmolarity, indicating uptake rather than binding, and taurine accumulation was Na+- dependent. BBMV from 28-day rats did not accumulate D-glucose to the same degree as in adult BBMV, and the initial rate of uptake was slower. Taurine uptake had a similar Kmand Vmaxin BBMV from immature rats. Despite similarities in the kinetics taurine uptake, higher urinary taurine concentrations are found in younger rats, suggesting that other factors, such as an efflux block, account for the taurinuria of young animals.A diet low in methionine and taurine (LTD) given for 7 days resulted in a lower excretion and fractional excretion of taurine than in animals fed a normal sulfur amino acid diet (NTD). A high taurine diet (HTD) causes excessive taurinuria. These patterns of excretion are reflected at the brush border membrane surface with greater uptake after the LTD and reduced uptake after the HTD. A kinetic analysis of adult and 28-day-old animal BBMV reveals that the Vmaxof accumulation is altered by diet, whereas the Kmremains unchanged. The Vmaxis higher in BBMV from LTD animals and lower in BBMV from HTD animals. The kinetics of uptake are similar in adult and 28-day-old rat vesicles on a given diet. Thus, in addition to ontogenic changes in taurine excretion, there is an adaptive response to dietary alteration present at the brush border surface.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryResting cardiac output is high relative to body weight during the neonatal period and there is a limited reserve for further increasing cardiac output. We assessed the effect on the circulation of reducing peripheral vascular resistance by infusing high doses of sodium nitroprusside in 1- and 3-week-old lambs. In a dose of 5 μg · kg-1· min­-­­1over 1 h, nitroprusside caused a decrease in aortic and left atrial pressure, an increase in heart rate, and no significant changes in cardiac output or oxygen consumption. Infusing 10 μg kg­-1· min-1for 2 h resulted in an initial marked decrease in aortic pressure, cardiac output, and also heart rate. Within 50 min aortic pressure gradually increased, but was still well below control levels, while cardiac output returned to control level and heart rate slowly increased. Distribution of cardiac output and organ blood flows was measured by the radionuclide microsphere method. Blood flows to the kidneys and to the skin fell markedly, but flows to other organs did not change significantly.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID