摘要:

In cystinuria, renal clearance of cystine frequently exceeds creatinine clearance, suggesting net cystine secretion; and absorption of the (di) basic amino acid is impaired at the luminal membrane of the jejunal and probably also renal tubular epithelium. We studied cystine transport in vitro in jejunal biopsy specimens of eight subjects with homozygous cystinuria and in 12 controls. Cellular/medium cystine distribution ratio was reduced in cystinuria (1.36 ± 0.36 versus 5.36 ± 0.61, p<0.001). Cystine influx across the luminal membrane was normal (221 ± 48 versus 261 ± 79 pmol.h-1cm-2). Measurement of transepithelial cystine fluxes showed net absorption in controls but secretion in cystinuria. Apparent permeability coefficients were close to normal in cystinuria except that the efflux permeability at the luminal membrane was significantly increased (0.839 ± 0.22 versus 0.186 ± 0.12 h-1cm-2), and, accordingly, at the luminal membrane, the influx over efflux permeability ratio was small (1.01 ± 0.50 versus 4.95 ± 0.80, p<0.001). The defect in cystine transport in cystinuria is apparently not caused by decreased influx but increased efflux of cystine (or cysteine) from the cell to the lumen across the luminal membrane. (PediatrRes 21: 477-481,1987)

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

We tested the hypothesis that isovolemic anemia blunts the thermogenic response to environmental cold stress in 3 to 4-day-old newborn piglets. Eight animals were studied in both thermoneutral (31.6-32.8° C) and cold (19.6-20.2° C) environments, before and after an isovolemic, partial volume exchange transfusion which reduced the hematocrit from 26 to 15 %. In the non anemic phase of study, deep rectal temperatures declined but had plateaued by 30 minutes after onset of cold stress and remained within normal limits for newborn piglets. In the anemic phase of study, deep rectal temperature declined continuously throughout cold stress with true body core hypothermia (<38° C) observed at all measurement points beyond 15 min of cold stress. Baseline oxygen consumption did not differ between the two study phases (17.6 ± 1. 8 versus 16.7 ± 2.1 ml/kg−1min−1, mean ± SEM). However, during environmental cold stress, oxygen consumption increased by 64% over baseline in the nonanemic phase of study (p<0.05) whereas 21% increase over baseline was observed in the anemic phase (p NS). We conclude that isovolemic anemia limited oxygen consumption and heat production during environmental cold stress, resulting in body core hypothermia. (Pediatr Res21: 482-486,1987

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Tin (IV)-protoporphyrin-IXα (tin-heme) may have use in treating neonatal jaundice. To evaluate its effect on bilirubin metabolism, we measured bile-bilirubin excretion in adult, male Sprague-Dawley rats (350-500 g). After a 4-h baseline period, tin-heme (100 umol/kg) or buffer was injected subcutaneously, and bile was collected for 19 h. Bile flow, bile salt excretion, and bile-bilirubin excretion (averaging 600 ± 60 ng/100 g/min for all animals) remained stable in the control period. Tin-heme treatment did not alter bile flow or bile salt excretion, but within 2 h bilirubin output was significantly reduced. The nadir of output was 5 h after injection when it was 380 ± 40 g/ 100 g/min (p<0.001). Cumulative excretion over 19 h was reduced 30.8% (p<0.01). To determine if tin-heme interfered with hepatic uptake or excretion of bilirubin, additional animals were administered intravenous bilirubin at 30 mg/kg/h for 3 h after tin-heme injection. Neither peak bile-bilirubin (37.4 ± 4.68, control; 38.19 ± 3.81 /μg/ 100 g/min, treated) nor cumulative excretion (87.8 ± 4.7, control; 88.9 ± 4.2%, treated) were altered. Biliary excretion of tin-heme was measured under various experimental conditions. When administered alone, maximal excretion was 4 h after injection (4.41 ± 1.58 μg/100 g/min); by 15 h, it fell to 0.024 ± 0.011 μg/100 g/min; 20-h cumulative tin-heme excretion in bile was 21.8 ± 3.1% of the administered dose. Intravenous coadministration of albumin or albumin and bilirubin reduced the peak output but did not alter cumulative excretion of tin-heme. These data indicate that tin-heme reduces endogenous bilirubin formation but does not impair hepatic uptake and excretion. Bile is a major excretory route for tin-heme. (Pediatr Res 21: 487- 491,1987)

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Mitochondrial function was studied in isolated hepatocytes from newborn rats to determine the substrate requirements and oxygen dependence of perinatal respiratory activity. The results show that neonatal O2consumption is markedly dependent on succinate availability; the respiration rate was extremely low in the absence of exogenous substrates, but was stimulated 15-fold by succinate, with half-maximal stimulation of O2consumption at 0.5 mM succinate. Significant inhibition of respiration by low concentrations of antimycin A suggests that the succinate-induced increase in cellular O2consumption was primarily due to mitochondrial activity. In contrast, other potential metabolic fuels at comparable concentrations (2.5 to 10 mM) gave less than 2-fold stimulation. Half-maximal oxidation (P50value) of the mitochondrial cytochromes occurred at very low O2concentrations and was sensitive to factors that alter cellular O2consumption. The P50for cytochrome c oxidation (0.52 µM with 1.5 mM succinate) was, respectively, increased or decreased by additions of succinate or antimycin A. These distinctly lower P50values for mitochondrial function in neonatal cells compared to adult cells could be a major factor in the ability of fetal and neonatal cells to tolerate relatively low O2concentrations.

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Studies were designed to develop an animal model for the syndrome of hypochloremic, hypokalemic metabolic alkalosis (HMA), and failure to thrive in infants due to intake of chloride-deficient formula. Littermate canine puppies, 2 wk old, were fed soy formula containing normal chloride, 20 mEq/liter (NC,η= 5), or low chloride, 1 mEq/liter (LC,η=5) for 4 wk, first by gavage and ad libitum thereafter. After 1 wk of LC formula, HMA developed in LC puppies although both NC and LC puppies had similar fluid and caloric intake and gain in weight and forelimb length. Two wk of LC formula also resulted in a higher serum creatinine and calcium but lower phosphate level in LC than NC puppies. After 4 wk of LC, weight and forelimb length were much less in LC than NC puppies. Plasma renin activity decreased with age in NC but remained elevated in LC. In a separate group of puppies (n=6) with HMA, chloride supplementation of LC formula as NaCI to NC levels corrected HMA despite continued citrate intake. We conclude that the canine puppy is an appropriate model to study HMA due to decreased chloride intake. Low chloride intake independent of citrate caused the HMA. (Pediatr Res 21: 497-501, 1986)

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

A mentally retarded girl with epileptic seizures is described. Urinary organic acid screening revealed a massive excretion of glyceric acid, a normally barely detectable metabolite. Hyperglycinemia was not observed. Capillary gas chromatography of the O-acetylated (-)- menthyl ester of urinary glyceric acid showed the substance to have the D-configuration. The urinary D-glycerate excretion remained unaltered after an oral load with 200 mg/kg L-serine, but oral loading with fructose (1 g/kg) or dihydroxyacetone (1 g/kg) caused a sharp increase of the Dglycerate excretion. Treatment with a diet moderately restricted in fructose led to some clinical improvement as judged by subjective criteria. The metabolic lesion is thought to be located at some step of the fructose catabolic pathway, possibly at the level of hepatic triokinase deficiency. (Pediatr Res 21: 502-506,1987)

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Very low birth weight infants demonstrate significant reductions in red blood cell membrane docosahexaenoic acid (DHA, 22:6n-3) following delivery unless fed human milk. The purpose of the present study was to determine if a dietary source of DHA (MaxEPA, R. P. Scherer Corporation, Troy, MI) could prevent the decline in red blood cell phospholipid DHA in very low birth weight infants whose enteral feeding consisted of a preterm formula without DHA. Longitudinal data were obtained on membrane phospholipid DHA in both un supplemented and MaxEPA-supplemented infants by a combination of thin layer and gas chromatography. These infants (n=39) ranged in age from 10 to 53 days at enrollment (0 time). At enrollment, phospholipid DHA and arachidonic acid (20:4n-6) were inversely correlated with age in days. During the study, mean red blood cell phospholipid DHA declined without supplementary DHA as determined by biweekly measurement, but infants supplemented with MaxEPA maintained the same weight percent of phospholipid (phosphatidylethanolanine, phosphatidylcholine, and phospharidylserine) DHA as at enrollment. The pattern of red blood cell phospholipid fatty acids in supplemented infants was similar to that reported for preterm infants fed human milk. (Pediatr Res 21: 507-510,1987)

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

We investigated the effect of intraventricular blood on cerebral blood flow in the newborn puppy by infusing autologous blood into the lateral ventricle to produce and maintain an intraventricular pressure of approximately 15 mm Hg (mild insult), 30 mm Hg (moderate insult), or 50 mm Hg (severe insult) for 20 min. As the intraventricular pressure increased, flow decreased progressively to all areas of the brain directly proportional to the cerebral perfusion pressure. On return of the intraventricular pressure to baseline level, cerebral blood flow normalized despite the continued presence of a large amount of blood within the lateral ventricles. We suggest that blood within the ventricular system can result in a significant acute reduction of cerebral blood flow which appears to be mediated through the effect on cerebral perfusion pressure.

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID