摘要:

Effects of hyperthermia on the cardiovascular function of the mammalian embryo have not been well defined. The effect of hyperthermia on the blood flow and umbilical artery blood pressure was studied in rat embryos at gestational d 12 by using a method developed in our laboratory. When the temperature was changed from 37 to 42°C, the heart rate increased by 15% (n= 33). Mean umbilical artery blood pressure, measured by a servo-null micropressure system, decreased from 0.64 ± 0.05 to 0.53 ± 0.04 mm Hg (n= 11), whereas blood flow velocity at the conotruncus, a measure of cardiac output, obtained by a 20-MHz pulsed Doppler ultrasound flowmeter, increased by 36 ± 11% (n= 11). Mean umbilical artery blood flow increased by 66 ± 13% (n= 11) and its vascular resistance, calculated by ratio analysis, decreased from 3.7 (median) to 1.8 units. These changes returned to baseline values when the temperature was returned to 37°C. The change in blood pressure was different from that seen in the chick embryo, indicating that there is species difference in the hemodynamic effect. (Pediatr Res30: 505–508, 1991)

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Microcinephotography was used to study early heart development in chick embryos with ablations of the neural crest known to result in persistent truncus arteriosus with associated aortic arch anomalies. The premigratory neural crest destined for the 3rd and 4th pharyngeal arches and the aorticopulmonary septum were ablated. When the embryos reached the looped cardiac tube stage (stage 18), 15 experimental and 15 control embryos were filmed at 100 frames/s under controlled environmental conditions. End-diastolic and end-systolic dimensions were determined for the conotruncus and presumptive right ventricle that together compose the bulbus cordis. The results showed that the shortening fractions and ejection fractions were significantly depressed in the experimental embryos. The experimental embryos exhibited dilation and decreased emptying of the ventricle. There was no difference in heart rate or stroke volume between the control and experimental embryos. Thus, the calculated cardiac output was the same in the control and experimental groups. It appeared that the experimental embryos compensated for decreased contractility by ventricular dilation. These functional compensations in very early cardiac development may play an etiologic role in the subsequent development of structural heart defects. (Pediatr Res30:509–512, 1991)

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The initiation of thermogenesis at birth is an important adaptation for survival. We examined the sequential effects of cooling, increased oxygenation, and repeated episodes of umbilical cord occlusion on nonshivering thermogenesis in six fetal sheep at 139 to 145 d of gestation. The fetal sheep were cooled by circulating cold water through a coil placed around the trunk for 4 h. The fetal core temperature fell 2.47 ± 0.24°C in the first 60 min of cooling with minimal changes in plasma FFA and glycerol levels. After fetal arterial O2tension was increased above 6.65 kPa by ventilation, fetal temperature and thermogenic indices rose significantly in 60 min. After occlusion of the umbilical cord by a reversible occluder cuff, plasma FFA levels rapidly increased to 635 ± 69 μEq/L (p< 0.005) by 30 min, fetal temperature increased a further 0.96 ± 0.20°C (p< 0.001) and fetal O2consumption peaked at 25.3 ± 4.9 mL·min-1·kg-1. Release of cord occlusion caused a rapid fall in FFA to 149 ± 23 μEq/L (p< 0.005) and a fall in fetal core temperature of 0.90 ± 0.13°C (p< 0.001) in 30 min. After irreversibly snaring the umbilical cord, the plasma FFA rose to 611 ± 83 μEq/L (p< 0.005) and the fetal temperature rose 0.78 ± 0.09°C (p< 0.02). The effects on thermogenesis of interrupting and reestablishing placental flow are rapid and reversible and suggest the presence of placental inhibitors of brown adipose tissue thermogenesis. (Pediatr Res30: 513–517, 1991)

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Forty-three twin lamb fetuses of 121 ± 1 d gestation were catheterized and received i.v. saline (n= 8), 0.75 mgjkg/h cortisol for 60 h (n= 15), 5 μg/kg thyrotropin-releasing hormone (TRH) every 12 h for five doses (n= 9), or cortisol and TRH (n= 11) before delivery at 128 ± 1 d. After delivery, the lambs were randomized for natural sheep surfactant treatment or sham treatment, ventilated for 75 min, and killed. Superoxide dismutase, catalase, and glutathione peroxidase activities were measured in fetal lung tissue. Superoxide dismutase and catalase activities were increased in both the corticosteroid (p< 0.001) and the corticosteroid with TRH (p< 0.01) groups. Glutathione peroxidase activity was higher after prenatal corticosteroid treatment, but statistical significance was not reached (p= 0.06). Although prenatal exposure to corticosteroids increased superoxide dismutase, catalase, and glutathione peroxidase activities, TRH alone or TRH added to corticosteroids provided no additional benefit. Lambs treated with surfactant had higher lung catalase activities than lambs that did not receive surfactant, probably secondary to the presence of catalase activity in the surfactant preparation. Increased pulmonary antioxidant enzyme activity may be an additional feature of the overall beneficial effect of corticosteroids on fetal lung development. (Pediatr Res30: 518–521, 1991)

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Whereas glucocorticoid administration to pregnant rats produces parallel acceleration of lung surfactant and antioxidant enzyme system maturation in late gestation, prenatal thyroid hormone treatment results in acceleration of surfactant maturation, with a paradoxical decrease in antioxidant enzyme (AOE) development. In these studies, we tested whether prenatal thyroid releasing hormone (TRH) treatment would act like prenatal thyroid hormone on pulmonary surfactant and AOE system maturation and whether combined prenatal treatment with TRH plus dexamethasone (DEX) would alter these effects. Secondly, we tested whether prenatal TRH and prenatal TRH plus DEX would inhibit the ability of newborn rats to respond to hyperoxia with protective increases in AOE activities. Results of the developmental studies revealed significantly increased fetal lung disaturated phosphatidylcholine content with significantly decreased pulmonary AOE activities as a result of prenatal TRH treatment that was not reversed with the addition of DEX. Combined TRH plus DEX treatment resulted in statistically significant decreases in body weight, lung weight, and lung weight to body weight ratios at both 21 and 22 d of gestation; growth effects were not seen with TRH alone. In tenns of hyperoxic AOE response, despite being born with lower baseline AOE levels, the newborn animals prenatally treated with TRH or TRH plus DEX were able to induce a normal pulmonary AOE response to high O2exposure. Although requiring further investigation, this reassuring finding suggests that clinical prenatal therapy with TRH or the combination of TRH plus DEX is not contraindicated for those infants delivered prematurely who go on to require intensive hyperoxic therapy. (Pediatr Res30: 522–527, 1991)

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The administration of growth hormone (GH) in conjunction with calcitriol in uremia may increase urinary calcium and decrease renal phosphate excretion, which could have an adverse effect on the kidney in chronic renal insufficiency. The effect of 40 d of ovine GH, calcitriol, and the combination of GH and calcitriol on mineral excretion was studied in rapidly growing uremic rats. Uremia was produced by 75% nephrectomy, and the animals were fed a diet containing 8% protein with equal quantities of calcium (0.6%) and phosphate (0.6%). The uremic rats treated with ovine GH were significantly longer and heavier than the uremic control rats and the uremic rats treated with calcitriol alone. However, the combination of calcitriol and GH abolished the beneficial effect of GH on growth and increased urinary calcium excretion 4-fold over uremic controls whether expressed as calcium excretion per 100 g body weight, urine calcium to creatinine ratio, or as fractional calcium excretion. Calcitriol therapy alone also significantly increased calcium excretion, but not to the extent that the combination therapy did. This increased urinary calcium excretion in the GH plus calcitriol group was not associated with an increase in calcium and sodium intake, plasma ionized calcium, or urinary sodium excretion. The calcium content of the femurs from all uremic rat groups was significantly lower than that of the sham control rats; however, there was also no further decrease in bone calcium content in the GH plus calcitriol group compared with uremic controls. This indicated that bone was not the source of this excess urinary calcium. Our data indicate that the combination of GH and calcitriol significantly increases urinary calcium excretion in growing uremic rats. These results suggest the need to monitor such untoward side effects in children with chronic renal failure who receive this combination of therapies. (Pediatr Res30: 528–533, 1991)

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

We tested the hypothesis that overfeeding with a high caloric (concentrated) formula increases growth without influencing adipocyte volume in preweaning infant baboons. Female infant baboons from three sires and 25 dams were fed either 67.5 kcal (normal formula) or 94.5 kcal (concentrated formula)/100 g Similac formula. Immediately before weaning (19 wk), adipocyte volume was measured in biopsied adipose tissue from omentum, flank, and popliteal depots. From birth until weaning, infants fed the concentrated formula consumed 20% more total calories, averaged 15% more calories/kg/wk, and gained 14% more weight than normally fed infants. Adipocyte volume differed significantly among different sites (omentum > popliteal > flank) and among different sire groups. Increased caloric intake alone did not increase adipocyte volume. There was a small but significant sire by infant formula interaction on adipocyte volume. When fed the concentrated formula, progeny from one sire had larger adipocytes than normally fed infants, whereas progeny from the other two sires had smaller adipocytes or adipocytes that were comparable to infants fed normal formula. Variability in adipocyte volume at 19 wk of age was best accounted for by maternal weight and sire group (omentumR2= 0.334,p= 0.026; flankR2= 0.532,p= 0.01; poplitealR2= 0.482,p= 0.01) and not by caloric intake. These results suggest that the level of triglyceride deposition into adipocytes attained during preweaning growth is determined to a greater extent by genetic and other factors rather than caloric intake. (Pediatr Res30: 534–540, 1991)

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Lipase activities were measured at pH 4 and pH 8 in the placentas of rats made diabetic by streptozotocin treatment and also in the placentas of women classified as having1) impaired glucose tolerance or type 2 diabetes,2) type 1 diabetes with no associated vascular complication, and3) type 1 diabetes with associated vascular disease. In both sets of experiments, the placentas were compared with normal control groups. The placental lipase activity measured at pH 8 was not significantly different in either streptozotocin-treated rats or impaired glucose tolerance/diabetic women as compared with controls, whereas the lipase activity measured at pH 4 increased significantly as compared with controls in both species. Furthermore, in the women there was a significant correlation between placental lipase activity at pH 4 and birth weight in impaired glucose tolerance/type 2 diabetes. It is suggested that the increased placental lipase activity may contribute to the increased fetal weight in human diabetic pregnancy, by contributing to the increased fat transfer across the placenta from mother to fetus. (Pediatr Res30:541–543, 1991)

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

To investigate early detection of young families with inherited dyslipidemia, we assessed changes in circulating apolipoprotein (apo) B and A-I levels and the apo B/A-I ratio during the 1st year of life and their relations to parental values. After measuring initial dried blood spot capillary blood levels in 919 babies when aged 4.25 ± 0.98 d (mean ± SD), we recalled at a mean age of 8.5 ± 2.3 mo, those with levels in one or more of the following categories: the top 5% of apo B values (group 1), the top 5% of apo B/A-I ratios (group 2), the bottom 5% of apo A-I values (group 3), and a group of 18 infants (group 4) who were not in any of the above three categories. We thus obtained serum lipid measurements in 51 infants and their parents. Two of the 13 group 1 infants had persistent hyperapo B at 8.5 mo; there was an inverse relationship between apo B and apo A-I levels in this group (p< 0.001). Two of 11 babies in group 2 had lipid profiles consistent with familial hypercholesterolemia. However, none of the infants in group 3 had evidence at 8.5 mo of abnormal apo A-I or HDL levels, nor did their parents. For groups 1, 2, and 3, there was at 8.5 mo a regression of apo B and A-I toward mean levels for the "normal" 18 babies of group 4. In contrast, the high apo B/A-I ratios in group 2 remained high (p< 0.01) and showed evidence of tracking. Correlations between birth weight and apo B (positive) and apo A-I (negative) that were found previously at 1 wk were still evident at 8.5 mo. Thus, individual apo B/A-I ratio measurements during the 1st week of life are predictive of levels at 8.5 mo, and this finding may facilitate familial hypercholesterolemia detection. Persistence of significant correlations between birth weight and apolipoprotein levels suggests an ongoing relationship between birth weight and subsequent lipid metabolism. (Pediatr Res30: 544–549, 1991)

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID