ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryWe studied transmission of a constant mean airway pressure through the lungs to the pleural space in nine mechanically-ventilated neonates with low-compliance lung disease. Infants were studied for 3.1 ± 1.6 hr during a period of clinical improvement, but at a time when lung compliance was still markedly reduced. Two of our infants were studied during recovery from fluid overload, while seven infants with hyaline membrane disease were studied at a stage of disease during which maximal diuresis has been found to occur. During the study period, mean esophageal pressuredecreasedin all infants from 5.6 ± 1.3 to 4.2 ± 1.8 cm H2O (P< 0.001) while total compliance increased slightly.SpeculationEdema of the pulmonary interstitium may contribute to airway-closure and gas-trapping. We propose that a loss of fluid from the interstitium during early recovery from low-compliance lung disease may lead to less gas-trapping and a fall in mean esophageal (pleural) pressure.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryAmmonia excretion was studied in rat ileal segments during perfusion of the animal through the saphenous vein. In the first 10 min during and after intravenous infusion of l-glutamine (116 mg/ kg to double arterial glutamine concentration) average net change in lumenal ammonia was 13 ± 8 (S.E.) nmole NH3/min/g ileum; average net change in ileal venous ammonia was 28 ± 9 nmole NH3/min/g ileum; and average net change in total ammonia (lumen + ileal vein) was 41 ± 13 compared to −5 ± 10 nmole/min/g ileum for animals infused with salineP< 0.025. These data suggest that ileal metabolism of arterial glutamine liberates ammonia to both ileal venous blood and intestinal lumen. When a cation-exchange resin which binds ammonia was infused intralumenally, average net change in lumenal ammonia in the first 10 min during and after intravenous infusion of 116 mg/kg l-glutamine was 415 ± 156 nmole NH3/min/g ileum (p< 0.01 compared to value during perfusion of Earle's solution alone). During the first 10 min during and after glutamine infusion net change in ileal venous plasma ammonia was −8 ± 14 when resin was being perfused through the lumen compared to +28 ± 9 nmole/min/g ileum during perfusion of Earle's solution alone without resinP< 0.05. Thus resin in the small intestine can trap very large amounts of ammonia.SpeculationAmmonia-binding cation-exchange resins may be useful therapeutically in lowering portal venous ammonia and increasing intestinal ammonia excretion in patients with hyperammonemia.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryTo investigate a possible disorder of adenine nucleotide turnover in Duchenne muscular dystrophy, we evaluated 15 patients with mild Duchenne muscular dystrophy, eight patients with severe muscular dystrophy, seven patients with other neuromuscular disorders, and eight patients with hypogammaglobulinemia but no muscle disease. The serum urate concentration was similar in all four groups. Base line urinary purine excretion was elevated in all patients with neuromuscular disease with values of 1.72 ± 0.15, 2.37 ± 0.22, 2.49 ± 0.35, and 2.60 ± 0.48 µmoles/100 ml glomerular filtration for control subjects, mild Duchenne muscular dystrophy, severe disease, and other neuromuscular diseases, respectively.Adenine nucleotide pool turnover was measured by labeling with [8-14C]adenine and then 5 days later administering intravenous fructose. Five-day cumulative mean radioactivity excretion was elevated in mild and severe Duchenne muscular dystrophy with excretion values of 11.4 ± 0.7 and 11.5 ± 1.1% of administered radioactivity, respectively, as compared to 9.0 ± 0.9% of administered radioactivity for control subjects. After intravenous fructose infusion, patients with Duchenne muscular dystrophy had a less than normal rise in serum urate concentration, a normal increase of urinary purine excretion, and a greater than normal elevation of urinary radioactivity excretion and urinary purine specific activity. Patients with other neuromuscular diseases had virtually no rise in plasma urate concentration, less than normal increase in urinary total purine excretion, and a greater than normal increase of urinary radioactivity excretion and urinary specific activity.These observations suggest that there is an increased rate of adenine nucleotide turnover in Duchenne muscular dystrophy. In patients with other neuromuscular disease an increased rate of adenine nucleotide turnover resembled the abnormality expected from a diminshed adenine nucleotide pool.SpeculationThe accelerated turnover of adenine nucleotides in Duchenne muscular dystrophy may result from the proposed membrane defect. Treatment directed toward increasing the synthesis of ATP may be beneficial in Duchenne muscular dystrophy.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryThe present studies were designed to assess the individual effects of delivery and umbilical cord cutting on the stimulation of the sympatho-adrenal system during parturition. Pregnant ewes with time-dated singleton pregnancies were used in an acutely exteriorized fetal lamb model with an intact umbilical circulation. We observed a minimal, transient elevation in plasma catecholamines (CAT) coincident with the operative procedures and delivery. Subsequent cord clamping was observed to evoke a rapid and marked increase of both norepinephrine and epinephrine (E), maximal at 5 min and persisting over the 4-hr study period. Animals could be grouped on the basis of the observed CAT responses, severity of postpartum acidosis, the extent of free fatty acid (FFA) mobilization and degree of postpartum hypothermia. A blunted FFA response and slower correction of hypothermia were observed in the more acidotic animals despite higher CAT concentrations. One group of four animals had high peak CAT concentrations, 32,000 pg/ml norepinephrine and 35,000 pg/ml E, a deep nadir in pH of 6.88 ± 0.09, a 2-hr delay in maximal FFA mobilization and slower correction of hypothermia. The other group of four animals had peak norepinephrine of 2800 pg/ml and E of 1100 pg/ml, a nadir in pH of 7.09 ± 0.08, maximal plasma FFA concentration by 1 hr after cord cutting and a higher nadir in body temperature 35.7 versus 32.5°C. The results demonstrate that umbilical cord cutting itself is a potent stimulus for fetal CAT release and FFA mobilization. Acidosis is capable of markedly augmenting E release in the mature fetus and obtunding chemical thermogenesis.SpeculationThe marked catecholamine surge evoked by umbilical cord cutting at the time of birth appears to be a major factor triggering the metabolic events facilitating adaptation to extrauterine life. The mechanism for the catecholamine release is uncertain. However, cardiovascular and chemoreceptor mediated activation of autonomic nervous system activity probably are involved. The separate contributions of increased postganglionic neurosympathetic activity and adrenal-medullary catecholamine release to neonatal adaptation should be explored further.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryPhenobartital (PB) (40 mg/kg/day) was administered to pregnant rats at 12 to 20, 14 to 20, and 17 to 20 days of gestation and female offspring were tested for the onset of puberty, estrous cycle pattern, and fertility. Another group of rats received PB (20 mg/kg/day) during the neonatal period (1 to 8 days). PB administration during both the pre- and postnatal periods resulted in a significant delay in the onset of puberty (control: 34.6 ± 1.2 days, PB: 37.5 ±1.2 days), disorders of estrous cycle (control: normal cycles 91%, PB: normal cycles 40%), and infertility (control: 100% fertile PB: 50% fertile). Associated with these effects, we observed high levels of estrogen in plasma (control: 58.5 ± 12.2 pg/ml, PB: 155.2 ± 25.1 pg/ml) and increased estrogen receptors in the uterus (control: 0.136 ± 0.026 pmole/mg protein, PB: 0.242 ± 0.031 pmole/mg protein. This study shows that PB administration only during the period of neuroendocrine differentiation (17 to 20 days of pregnancy and 1 to 8 postnatal days) is capable of producing all of the adverse effects of PB, indicating that its action is upon neuroendocrine development.SpeculationSince phenobarbital (PB) administration during 17 to 20 days of pregnancy is capable of producing reproductive disorders in the offspring, the results suggest that PB interferes with neuroendocrine differentiation. The mechanism of action of PB, however, has not been delineated. Neuroendocrine differentiation is mediated by gonadotropin, present during the neonatal period. PB may act at this site by interfering with gonadotrophin release or action. Support for this hypothesis is derived from the observation that PB can inhibit gonadotrophin secretion in the adult rat.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryThe free (nonprotein) cystine content of human cystinotic fibroblasts was found to vary with the pH of their culture medium. Intracellular cystine content was highest at alkaline medium pH's and lowest at acidic medium pH's. When maintained in medium of pH 6.3, cystinotic fibroblasts lost 50% of their free-cystuie content in 6 hr and over 95% in 30 hr. Cystine was the only amino acid to show significant variation with changes in the pH of the culture medium.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryTwelve critically ill neonates mechanically ventilated for respiratory failure (mean weight 1.33 kg, mean gestation 31 wk) were studied to quantitate the effects of radiant power from a radiant warming device, body weight, and body surface area on insensible water loss. Radiant power density (Mw/cm2) was measured using a wattmeter and thermopile transducer. Insensible water loss was measured using a Potter Baby Scale. Weight correlated inversely with insensible water loss, (r = −0.86,P< 0.001). Radiant power density correlated inversely to weight, (r = −0.71,P< 0.001). There was a significant increase in insensible water loss as radiant power density increased, (r = 0.54,P< 0.05). Net radiant power received (W/kg) by infants over their exposed surface area, correlated directly to insensible water loss, (r = 0.67,P< 0.01) irrespective of body weight. Critically ill neonates ventilated for respiratory failure and nursed under radiant warmers incurred greater insensible water losses than previously reported for well infants. The magnitude of this increased insensible water loss is inversely related to body size and is determined directly by the radiant power density required to maintain body temperature.SpeculationQuantitative measurement of radiant power density delivered to critically ill newborn infants nursed under servocontrolled radiant warmers facilitates estimation of insensible water loss. Used in conjunction with body mass and surface geometry, quantitative radiant power assessment is clinically applicable to monitoring insensible water loss. Calculation of parenteral fluid requirements might be enhanced using this technique.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryExperiments to determine the effect of the oxygen-hemoglobin dissociation curve on oxygen delivery during neonatal anemia, were carried out on 15 sedated and ventilated lambs less than 48 hr of age. Eight of the animals were exchange transfused with adult blood. The P50of the exchange transfused group was 32.1 mm Hg (low O2affinity) compared to 19.4 mm Hg for the controls (high O2affinity). The animals were made anemic by isovolumic exchange transfusions with plasma. At different levels of hemoglobin defined as mild (8 mg/100 ml), moderate (6 mg/100 ml), and severe (4 mg/100 ml) anemia, tissue oxygenation, hemodynamic status, and blood gases were compared. Mixed venous PO2was significantly lower in the high affinity group throughout the study. Cardiac output was significantly greater in the low affinity group during severe anemia. Oxygen consumption remained stable in the low affinity group, but decreased significantly in the high affinity group when the anemia was severe. The data indicate that during severe anemia, blood with a high P50is more capable of adequately oxygenating tissues than that with a low P50.SpeculationEarly preterm newborn infants may not adequately oxygenate their tissues during anemia because of their high oxygen affinity red cells.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryContinuous nocturnal intragastric feeding, combined with frequent daytime feedings, has been reported to improve both linear growth and the metabolic abnormalities in patients with glucose-6-phosphatase deficiency (Type I Glycogen Storage Disease). However, elevated blood levels of lactate have persisted. The present studies explore the relationship between blood lactate concentrations in six patients with glucose-6-phosphatase deficiency and variations in the rate and composition of the intragastric feeding. Blood lactate and plasma glucose concentrations were determined at rates of dextrose administration ranging from 3–34 mg/kg/min. Dextrose infusion at 100–200% of estimated normal glucose production rates gave the best control of blood lactate concentrations. Lower rates of dextrose infusion resulted in significantly higher blood lactate levels; higher rates produced hyperglycemia, but no significant further reduction of blood lactate. At identical rates of glucose administration, a dextrose-containing infant formula and a high carbohydrate enteric feeding solution gave no significant improvement hi control of blood lactate levels compared to dextrose alone. Plasma glucose levels fell more rapidly when intragastric feeding was stopped than after a mixed meal and hypoglycemia appeared to develop before counter-regulatory responses could be mobilized. These observations may account for the increased susceptibility to symptomatic hypoglycemia reported in patients treated with intragastric feeding.SpeculationThese results indicate that intragastric glucose infusion at a rate equal to or slightly greater than normal hepatic glucose production gives maximal control of the metabolic abnormalities in patients with glucose-6-phosphatase deficiency. Complete normalization of hyperlactatemia and hypertriglyceridemia in these patients may require the development of additional forms of therapy.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID