摘要:

Total lipids, lipoprotein-lipids, and apolipo-proteins were studied in plasma of 20 patients, aged 13.9 ± 3.4 y (mean ± SD, range 7.4 to 19 y), who were treatedwith continuous peritoneal dialysis for a period of 2.1 ± 1.2 (range 0.5 to 4.9) y. Measurements included total plasma cholesterol and triglycerides, triglycerides in the very low density fraction, and cholesterol in the very low density, low density, and high density fractions, as well as apo A-I and apo B. The results were compared with values in 17 healthy control subjects, aged 13.0 ± 5.1 (range 5.1 to 19) y. The patients had significantly elevated levels of total plasma triglycerides, triglycerides in the very low density fraction, total plasma cholesterol, cholesterol in the very low density fraction, and cholesterol in the low density fraction, whereas levels of cholesterol in the high density fraction were normal. Plasma apo B levels were elevated, but apo A-I levels were not different from controls. In addition, the nutritional status of the patients was assessed and apo A-I and apo B concentrations were measured in the dialysate of 10 patients. The losses of apo A-I and apo B in dialysate averaged 13.4 ± 7.4 and 2.1 ± 3.1 mg/kg/d, respectively. Lipoprotein profiles were not correlated with nutritional status. We conclude that pediatric patients treated with continuous peritoneal dialysis have atherogenic lipoprotein profiles, cholesterol ratios, and apolipoprotein ratios, but normal cholesterol in the high density fraction and apo A-I levels despite considerable apo A-I losses in the dialysate.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

We studied the hemodynamic consequences during the first 24 h of life in premature baboons (140 d) with hyaline membrane disease that were treated with high-frequency oscillatory ventilation (HFOV) or conventional intermittent mandatory ventilation (IMV). Cardiac output and organ blood flow were measured at three time-points using the radiolabeled microsphere technique. Seven of seven HFOV and six of eight IMV animals survived the 24-h period. By design, initial mean airway pressure (&OV0440;aw) was higher in the HFOV group (p< 0.01). HFOV &OV0440;awwas progressively reduced during the study period because of improving oxygenation as measured by the arterial to alveolar oxygen ratio. In contrast, it was necessary to increase &OV0440;awin the IMV animals to maintain the arterial to alveolar oxygen ratio. By 23 h, the IMV group required higher &OV0440;awthan the HFOV group (p< 0.05) and had a lower arterial to alveolar oxygen ratio (p< 0.05). We found no significant differences in left ventricular output, effective systemic flow, organ blood flow, or central venous pressure between the two groups at 3, 8, or 23 h. The HFOV strategy used in our study resulted in significant improvement in oxygenation during the initial 24 h of treatment without adverse effect on left ventricular output, cerebral blood flow, or central venous pressure. We conclude that when appropriate changes in &OV0440;aware made during HFOV in response to improvement in arterial oxgenation and changes in lung inflation as assessed by chest radiographs HFOV can be achieved without depressing cardiovascular dynamics more than during conventional therapy with IMV.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Isoproterenol, dobutamine, dopamine, and nitroprusside are four vasoactive drugs used to decrease pulmonary arterial pressure and increase cardiac output in newborns, infants, and children with sepsis. Thromboxane A2likely produces some of the hemodynamic changes in sepsis, and U46619, a thromboxane A2mimetic, produces similar changes in lambs. We studied the hemodynamic effects of these four vasoactive drugs in 10 spontaneously breathing newborn lambs during an infusion of U46619. After baseline hemodynamic measurements, U46619 (1–2 μg/kg/min) was infused to increase pulmonary arterial pressure and to decrease cardiac output. Then, either isoproterenol (0.05–1.0 μg/kg/min), dobutamine (5–20 μg/kg/ min), dopamine (3–30 μg/kg/min), or nitroprusside (0.5–10.0 μg/kg/min) was infused. Every 10 min, measurements were repeated and the dose increased. U46619 significantly increased pulmonary arterial pressure by 182% and decreased cardiac output by 25% (p< 0.05). Isoproterenol decreased pulmonary arterial pressure by 30% (p< 0.05) and increased cardiac output by 25% (p< 0.05) at low doses, and increased cardiac output by 115% at the maximum dose (p< 0.05). Dobutamine decreased pulmonary arterial pressure by 11% (p< 0.05) and increased cardiac output by 28% (p< 0.05) at low doses, and increased cardiac output by 71% at the maximum dose (p< 0.05). Dopamine did not decrease pulmonary arterial pressure or increase cardiac output. Nitroprusside decreased pulmonary arterial pressure by 11% at the maximum dose (p< 0.05). Isoproterenol and dobutamine may be more useful than dopamine and nitroprusside in the management of pulmonary hypertension and decreased cardiac output during sepsis.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

We have examined the effect of dexamethasone on the metabolism of pulmonary surfactant in normal and hyperoxia-treated rats. The relative abundance of the surfactant-specific apoprotein A (SP-A) mRNA in lung tissues and the contents of disaturated phosphatidylcholine (DSPC) and SP-A were measured in bronchoalveolar lavage fluids and in lung tissues in 4-wk-old rats exposed to room air or >90% oxygen for 7 d with or without simultaneous treatment with dexamethasone (0.5 mg/kg body wt for 7 d). The relative abundance of the SP-A mRNA was marginally increased by hyperoxia (1.3-fold over controls). Dexamethasone increased the relative abundance of the SP-A mRNA to a level comparable to that with hyperoxia treatment (1.5-fold over controls). In lavage fluids, the contents of DSPC and SP-A were increased by 4− and 6-fold over controls by hyperoxia, respectively, but they were increased only by 2-fold by dexamethasone. In lung tissues, the contents of DSPC and SP-A were increased by 3− and 2-fold over controls by hyperoxia, respectively. These values in lung tissues in the air-exposed rats were not significantly increased by dexamethasone. In hyperoxia-treated rats, dexamethasone did not significantly affect the relative abundance of the SP-A mRNA level and the contents of DSPC and SP-A in lavage fluids and lung tissues. These results indicate that mechanisms other than increased synthesis of SP-A are involved in hyperoxia-induced SP-A accumulation and that dexamethasone does not affect the abnormal accumulation of pulmonary surfactant induced by hyperoxia.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

In lung-lavaged surfactant-deficient rabbits (n = 6) requiring artificial ventilation, porcine surfactant was instilled endotracheally. This resulted in improvement of lung function so that the animals could be weaned off artificial ventilation. The animals were killed 41/2 h after surfactant administration and the porcine surfactant protein was localized in the lung with a MAb. We found surfactant protein in all lobes of the lung but the distribution was not homogeneous. Surfactant protein C was found in less than 15% of the alveolar spaces and in less than 1% of the bronchi.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Results from a number of studies suggest a role for endogenous opioids in the regulation of lung development and function. Although it is not known which opioid peptides are involved in these processes, accumulated evidence suggests a prominent role for β-endorphin (BE). Our study examines the effect of BE on lung ornithine decarboxylase (ODC) activity in preweanling rats. ODC catalyzes the rate-limiting step in the synthesis of the poly-amines spermidine and spermine, key regulators of cell growth, multiplication, and differentiation. Central (but not peripheral) administration of BE reduced lung ODC activity by as much as 80% in the 6-d-old rat. Significant decreases in ODC activity were seen at doses of BE as low as 0.5 μg/g brain wt. In contrast to the reductions in ODC activity, plasma levels of corticosterone in animals administered BE were approximately five times higher than those seen in control animals. BE's actions on ODC activity and plasma corticosterone levels were prevented by naloxone or naltrexone, indicating that both responses are mediated by opioid receptors. Studies of ODC kinetics showed a profound reduction in Vmax(70% below control values), but no change in Km. The effect was observed only during the first 2 wk of postnatal age, a period of time in lung maturation that is characterized by active alveolarization. Because changes in ODC levels during early postnatal life are associated with perturbations in tissue growth and/or function, the data suggest that CNS BE may influence lung maturation through an indirect action that may involve glucocorticoids.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Intraperitoneal injections of 6.25, 12.5, 25, 50, and 100 μmol/kg cocaine into pregnant Sprague-Dawley rats once a day from d 0 to 19 of gestation caused a dose-dependent increase in fetal soft tissue malformations, primarily of the genitourinary tract. At 100 μmol/kg, all implants were lost and three of the five animals died after six to seven injections. At 50 and 100 μmol/kg but not at lower doses, cocaine caused a small but significant decrease in body weight and food intake. Cocaine did not affect mean fetal and placental weights, although it increased the number of runts and edematous fetuses, and did not cause skeletal malformations. After intraperitoneal injection of 50 μmol/kg, the plasma t1/2of cocaine was 21 ± 5 min and peak plasma concentration (1682 ± 260 pmol/mL, measured by HPLC) was achieved in 5–10 min; a lower peak plasma concentration (486 ± 103 pmol/mL) was achieved in 20–60 min after s.c. injection. Concentrations of dopamine, epinephrine, and norepinephrine in brains of fetuses or newborn pups (<12 h old) of cocaine (50 /umol/kg)-treated rats were not significantly elevated. Cocaine injections did not affect gestational duration nor the growth pattern and the locomotor activity of offspring. However, three pups born to one cocaine-treated animal died 20 d after birth. Cocaine inhibited the growth of 10.5-d-old embryos in culture in a concentration-dependent manner and was more toxic than procaine. Approximately 80% of cocaine was metabolized during a 48-h period in embryo culture medium. It is concluded that cocaine possesses teratogenic potential that may be partly independent of maternal toxicity.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The purpose of these experiments was to determine whether flurothyl-induced status epilepticus causes progressive decline of brain high-energy phosphates and progressive increase in brain lactate in neonatal dogs who are paralyzed and oxygenated.In vivo31P nuclear magnetic resonance spectroscopic measurements showed that the fall in brain pH occurred early in the course of seizure. The decline in phosphocreatine was more gradual, i.e. 50% reduction, during the 1st h of seizure. There was no reduction in ATP during the 3 h of status epilepticus. In vivo1H nuclear magnetic resonance measurement of brain lactate disclosed a steep rise that stabilized by 60 min. Brain and blood lactate were closely related during the initial phase of seizure, suggesting rapid efflux of lactate from brain or systemic production of lactate. Blood lactate exceeded brain lactate after 1 h of status epilepticus. The new steady state for cerebral phosphocreatine and lactate during status epilepticus was achieved much more slowly during neonatal status epilepticus than has been reported during status epilepticus in the adult experimental animal. The lack of change in ATP during 3 h of seizure indicates that brain energy state is not radically altered during prolonged seizure if oxygenation is maintained.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

In an attempt to understand the dynamic change of the gonadotropin-releasing hormone-pituitary axis during the transitional stage from prepuberty to puberty, we investigated gonadotropin secretory patterns using a highly sensitive assay system and frequent blood sampling technique in children with Turner syndrome aged 5–17 y. Blood samples were collected every 20 min for 24 h in 16 cases, or every 30 min for 9 h (daytime 5 h, nighttime 4 h) in nine cases. Serum LH and FSH were measured by time-resolved fluoroimmunoassay. A 24-h profile of LH and FSH was analyzed by a computerized pulse detection program (PC-PULSAR). As early as 5 to 6 y of age, mean daytime LH concentration was significantly higher than nighttime concentration and pulsatile LH secretion existed throughout the day and night. At about 9 to 11 y of age, corresponding to the early stage of puberty, a dramatic increase in LH concentration and amplitude was observed, and both concentration and pulse amplitude were much higher during the night than during the day. However, these day-night differences became less clear at ages corresponding to late pubertal stages. Pulse frequency of LH secretion remained almost constant throughout the day and night at all ages investigated. As for FSH concentration, a trend similar to that of LH was observed, although day-night differences and age-related changes were less remarkable. Furthermore, pulsatile FSH secretion was detected in only a small number of the cases. These findings suggest that in Turner syndrome the hypothalamic gonadotropin-releasing hormone oscillator is functioning actively with constant frequency before the onset of puberty. Although we know that the day-night rhythm of gonadotropin secretion exists long before the onset of puberty, what controls the day-night rhythm of gonadotropin in the younger girls and the factors responsible for the dramatic increase of gonadotropin around the age of early puberty remain to be determined.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

We evaluated circulating levels of biologically active and immunoreactive intact parathyroid hormone [iPTH-(1–84)] in 47 newborns at birth and eight hypocalcemic preterm infants during the first 10 d of life. Use of two sensitive detection systems, the cytochemical bioassay and an immunoradiometric assay specific for intact parathyroid hormone, enabled us to compare plasma concentrations of PTH-like bioactivity (bioPTH) and iPTH-(1–84). Mean umbilical venous plasma bioPTH was elevated in nondiabetic term and preterm newborns [22.5 ± 3.1 (±SEM) and 15.8 ± 2.5 ng-equiv/L, respectively] compared with normal adult subjects (9.8 ± 2.6 ng-equiv/L;p< 0.01). Umbilical bioPTH was suppressed in five term infants of diabetic mothers (2.6 ± 0.4 ng-equiv/L). In contrast, iPTH-(1–84) was low in term and preterm non-diabetic infants' and term infants of diabetic mothers' umbilical samples (5.4 ± 1.5, 4.3 ± 1.5, and 2.4 ±1.0 ng/ L, respectively). Umbilical venous bioPTH was highly correlated with the magnitude of the transplacental calcium gradient (r= 0.90;p< 0.05). In eight preterm infants studied longitudinally, by 24–36 h of life, declining plasma total and ionized calcium (1.71 ± 0.04 and 0.78 ± 0.03 mmol/L, respectively) were accompanied by a significant rise in both bioPTH (41.2 ± 6.3 ng-equiv/L) and iPTH-(1–84) (56.3 ± 11.6 ng/L). These data indicate that the 3rd trimester fetoplacental circulation contains levels of bioPTH several-fold higher than those of immunoreactive intact hormone. We also conclude that even hypocalcemic preterm newborn infants can significantly elevate circulating levels of PTH.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID