摘要:

Changes in high-density lipoprotein (HDL) subclass distribution were evaluated in a group of premature infants during the early postnatal period to ascertain whether enteral feeding brought about a rapid shift from neonatal to adult-like distributions. All infants were fed a combination of breast milk and formula. Cord blood of premature infants had a predominance of large, less dense (HDL2b)ggeand a paucity of intermediate-sized (HDL3a)ggeparticles. Lack of a peak in the (HDL3a)ggeis a characteristic feature for cord blood, whereas a prominent (HDL3a)ggepeak is characteristic of adult plasma. After the start of enteral feeding, blood was obtained at two time-points: 6–14 days (sample A) and 17–32 days (sample B) postdelivery. With the onset of feeding, triglyceride increased significantly from an average of 34 mg/dl in cord blood to 120 mg/dl in sample B, and cholesterol increased from 86 to 112 mg/dl in the same period. Increases in plasma lipid concentrations were paralleled by a redistribution of subclasses such that three components of almost equal intensity were evident in sample B; these consisted of (HDL2b)gge, (HDL2a2)gge, and (HDL3b)gge. A paucity of (HDL3a)ggeparticles persisted even after onset of enteral feeding; thus, increases in plasma triglyceride and cholesterol per se are not sufficient to induce the adult-like distribution. It is suggested that development of the normal adult HDL subclass pattern is complex and is probably related to the development and interaction of several factors, including plasma enzymes involved in lipid hydrolysis and esterification, lipid exchange proteins, and hormonal status.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

A model of impaired oxygen delivery, using an acute surgical preparation in the fetal dog, is described. Fetal heart rate, transcutaneous pO2and pCO2, and tissue pH were simultaneously recorded during hypoxic episodes produced by a series of successive occlusions of the maternal abdominal aorta. Corresponding values were also determined in the arterial blood of the fetus. The following pathophysiologic sequence of events was observed: 1) a latency period with no changes; 2) a drop in pO2which stabilized later at a lower pressure; 3) late fetal heart rate deceleration, the pattern of which was not related to the progressively deteriorating fetal condition; 4) a progressive increase in pCO2; 5) a progressive decrease in pH. Abnormal tissue values consistently preceded and were more adversely affected than corresponding blood values. This experimental model demonstrates first that late decelerations of the fetal heart rate are an early sign of fetal hypoxia and second that a fall in fetal blood pH, beyond that level normally seen during labor, occurs relatively late in this pathophysiologic sequence. Between these two, there are intermediary stages that could be continuously monitored in order to identify worsening fetal condition. Continuous tissue pH and transcutaneous pO2and pCO2recording may potentially be of significant clinical value.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Thromboxane-associated pulmonary hypertension occurs in animals during intravenous infusion of group B streptococcus (GBS), a gram-positive neonatal pathogen. We postulated that other gram-positive neonatal pathogens, such as Streptococcus fecalis (ENT) and Staphylococcus epidermidis (S. epi) would also induce increased thromboxane synthesis and pulmonary hypertension when infused into piglets. We observed similar hemodynamic and gas exchange abnormalities during stepwise increases in the dose of GBS, Ent, and S. epi (n = 3, 4, and 4 piglets receiving each bacteria, respectively). Pulmonary vascular resistance increased significantly in the absence of acidosis or reduced arterial or mixed venous pO2at a dose of 2.5 ± 108cfu/kg/h for Ent and S. epi. In 14 additional piglets, pulmonary vascular resistance increased markedly after 60 min of intravenous infusion of 4 ± 1 ± 108cfu/kg/h for each organism (p < 0.05, GBS: 11.7 ± 1.8 to 75.6 ± 18.4 mm Hg/liter/min, Ent: 12.7 ± 1.7 to 64.9 ± 10.6 mm Hg/liter/min, S. epi: 10.5 ± 0.8 to 56.9 ± 6.0 mm Hg/liter/min), and blood thromboxane B2 levels increased (p < 0.05, GBS: 30 ± 10 to 1830 ± 330 pg/nl, Ent: 20 ± 7 to 1110 ± 300 pg/ml, S. epi: 31 ± 9 to 1260 ± 350 pg/ml). This dose of each bacteria caused a similar degree of mild arterial hypoxemia (57–66 mm Hg). The thromboxane synthetase inhibitor, dazmegrel, completely reversed pulmonary hypertension, reduced TxB2 levels to near baseline values, and partially reversed arterial hypoxemia despite ongoing bacterial infusion. We conclude that thromboxane-associated pulmonary hypertension occurs in piglets during infusion of different gram-positive neonatal pathogens.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Epidermal growth factor (EGF) liver receptor ontogeny and somatic growth were studied in mice from day 7 to day 70 postnatally to assess long-term effects of short-term postnatal thyroxine treatment. The mice were given 0.4μg thyroxine/g body weight/day for the 1st wk of life. EGF receptor binding in liver tissue was studied on days 7, 15, 20, 30, and 70 postnatally. Treated animals had accelerated eyelid opening and tooth eruption, and permanent growth retardation was obvious from the second week of life. Hepatic EGF receptor-binding capacity increased markedly in control mice with increasing age in contrast to a very slow increase in treated mice, making the difference statistically significant (P < 0.01) from day 30. The affinity of EGF receptor binding initially was similar in the two groups of animals (1.09 ± 109M−1and 1.02 ± 109M−1) and increased by day 30 in controls (2.57 ± 109M−1an increase that was not observed in treated animals either at day 30 or 70. These results suggest a sensitive period of imprinting during the first 7 days postnatally, a period when thyroxine can exert a permanent effect on later growth and later hepatic EGF receptor number.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

For use in screening for disorders of pyruvate metabolism, a sensitive assay method was developed for measuring the rate of decarboxylation of [1-14C]pyruvate during in vitro culture of skin fibroblasts with dichloroacetate (DCA). The rate of decarboxylation of [1-14C]pyruvate by skin fibroblasts from control subjects increased from 59.6 ± 13.2 to 97.3 ± 12.0 nmol/h/mg protein during in vitro culture in medium supplemented with 10 mM DCA for 3 days. In contrast, the rate hardly increased in cells from four of 20 patients with congenital lactic acidosis of unknown cause during in vitro culture with DCA. On day 3 of culture, the values for the four patients did not overlap those of control cells and so these four patients could be clearly distinguished from control subjects. Measurements of the original activity and the activity of the pyruvate dehydrogenase (PDH) complex after activation with a broad specificity protein phosphatase and DCA suggested that in three of the patients the aberration was a disorder in the mechanism for activation of PDH, including deficiency of PDH phosphatase or a mutation of PDH itself, whereas that in the fourth patient it might be a disorder of the mitochondrial transport system for pyruvate. Thus, measurement of the rate of decarboxylation of [1-14C] pyruvate by skin fibroblasts cultured in medium supplemented with 10 mM DCA for 3 days is a useful method for screening for disorders of pyruvate metabolism in cultured skin fibroblasts.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Hyperventilation has been shown to cause increased whole body oxygen consumption (VO2) and lactic acid production in human and animal mature subjects, but limited data are available in neonates. We investigated the effect of hypocarbic and normocarbic hyperventilation during normoxia and hypoxia (fractional inspired oxygen concentration = 0.14) upon the VO2in anesthetized and paralyzed piglets. Systemic arterial, pulmonary arterial, and left and right atrial pressures as well as cardiac output and body temperature were continuously recorded. Hypocarbic hyperventilation (PaCO2= 19 ± 1 mm Hg; pH = 7.58 ± 0.02) was associated with a significant decrease in systemic and pulmonary arterial pressures and cardiac output. These measurements returned to values similar to the initial normoventilation ones when PaCO2was increased by adding CO2to the inspired gas, whereas hyperventilation was continued. Neither hyperventilation alone nor in combination with hypoxia induced any significant change in VO2. We conclude that in the newborn pig, unlike what has been reported in mature subjects, cellular metabolic function is unaffected by hyperventilation as evidenced by the unchanged VO2.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Available evidence from in vitro studies suggests that the neurotoxic effects of bilirubin may be exacerbated by, or even require, additional factors such as hypoxia or asphyxia. The aim herein was to use31P nuclear magnetic resonance spectroscopy to study the effects of bilirubin on brain energy metabolism in vitro under conditions of normoxia and hypoxia.31P nuclear magnetic resonance spectra were acquired from guinea pig cerebral hemisphere slices during superfusion with solutions containing bilirubin and albumin in 5:1 molar ratio. The effects of bilirubin at concentrations between 400 nmol/liter and 120 μmol/liter were studied under normoxic conditions. Bilirubin caused no apparent disruption in brain energy metabolism during normoxia. The combined effects of bilirubin (40 μmol/liter) and hypoxia were studied. Hypoxia alone led to a steady state reduction in the phosphocreatine to inorganic phosphate peak-height ratio to 0.30 (0.27–0.32) [mean (range) n = 3]. Bilirubin (40 μmol/liter) in the presence of hypoxia caused a further reduction in the phosphocreatine to inorganic phosphate ratio to 0.18 (0.17–0.20) [mean (range) n = 3, p < 0.01, analysis of variance] which was rapidly reversed on returning to normoxia. These results demonstrate that bilirubin at the concentration studied requires hypoxia, in addition, to cause a measurable disturbance of brain energy metabolism. The nature of this interaction is unknown, but it may reflect the effect of intracellular acidosis on bilirubin solubility or the oxygen dependence of brain mitochondrial bilirubin oxidase.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Erythrocyte transketolase activity and thiamin pyrophosphate effect were examined in the offspring of streptozotocin-diabetic rats. Thiamin reserve was found to be significantly reduced in litters of untreated diabetic rats as compared to control and to insulin-treated diabetic rats. Supplementation of the untreated diabetic dams throughout pregnancy with oral thiamin was associated with a significantly improved thiamin status of the litters. We conclude that, due to enhanced fetal glucose turnover during diabetic gestation, a fetal thiamin deficiency state may evolve; this condition can be remedied with maternal thiamin supplementation.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Random urine samples were obtained from 31 patients with neuroblastoma (newborn to 8 yr of age) and from 100 children without this tumor (newborn to 10 yr). The urine samples were studied for the presence of sulfate and glucuronide conjugates of homovanillic (HVA), dihydroxyphenylacetic, vanilmandelic, and vanillactic acids. The urinary concentrations of these acids were determined by capillary gas-chromatography before and after enzymatic treatment with glucuronidase and sulfatase. Concentrations of the “free” fraction and “total” urinary content of these acids were determined using the results from untreated and treated urines respectively. Age-related reference values were established for children without neuroblastoma. Fractions of the total content of urinary HVA (18–39%) and dihydroxyphenylacetic acid (36–66%) were excreted as glucuronides and/or sulfates by the control group, with the highest conjugated fractions found in the urine of young infants (0–3 months). Vanilmandelic was excreted mainly as “free” acid (unconjugated), whereas vanillactic acid was undetectable in almost all control samples. Patients with neuroblastoma also excreted a fraction of these acids as glucuronide and/or sulfate conjugates, (25% of urinary HVA, 39% of dihydroxyphenylacetic acid and 45% of vanillactic acid) whereas vanilmandelic acid was excreted only as “free” in controls. Determination of “total” rather than “free” urinary HVA was diagnostic in one neuroblastoma patient with borderline “free” HVA levels, whereas determination of “free” or “total” dihydroxyphenylacetic acid and vanillactic acid did not improve the diagnostic sensitivity in the cases examined. We conclude that it may be clinically useful to determine “total” urinary HVA in patients with borderline “free” HVA levels who are suspected of having neuroblastoma.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Although smooth muscle is abundant in the pulmonary vessels of young animals at birth, it is not clear if these vessels respond more vigorously to hypoxia than the less muscular vessels of older neonates. To determine the effect of age on the pulmonary vascular response to hypoxia during the neonatal period in a single species, we measured the steady-state stimulus-response relationship between inspired oxygen tension (200, 50, 30 and 0 mm Hg) and pulmonary artery pressure-flow curves in isolated blood perfused lungs from 2− to 4− and 12− to 14-day-old lambs. Hypoxic vasoconstriction was attenuated in the younger newborns at an inspired oxygen tension of 50 mm Hg, but not at the other oxygen tensions. To determine if this age-related difference was due to differences in modulation of hypoxic vasoconstriction by cyclooxygenase products, we assayed the metabolite of prostacyclin, 6-keto-prostaglandin F1αin the perfusate and determined the effects of indomethacin (40 μg/ml) on the hypoxic stimulus-response relationship. There was no age-related difference in perfusate concentration of 6-keto-prostaglandin F1αat any oxygen tension. However, indomethacin reversed the age-dependent attenuation of hypoxic vasoconstriction at inspired oxygen tension = 50 mm Hg such that in indomethacin-treated lungs pulmonary vasomotor tone was higher in 2− to 4-day-old lungs than in 12− to 14-day-old lungs. This marked enhancement of hypoxic reactivity by indomethacin in the younger lambs suggests that in isolated neonatal lamb lungs cyclooxygenase products exerted a vasodilatory modulation of hypoxic vasoconstriction that decreased with age.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID