摘要:

It has been suggested that the liver is not the main source of angiotensinogen during fetal life in rats, but that the kidney is an important site of fetal angiotensinogen synthesis. In an effort to determine if this phenomenon is specific to the rat or applicable to other species, we compared the ontogenic changes in hepatic and renal angiotensinogen mRNA expression in fetal (60, 90, 118, and 138 d of gestation, term being 145 d), newborn (7 d postnatal), and adult sheep. Total RNA was extracted, subjected to Northern blotting and hybridized using a full-length rat radiolabeled antisense RNA. Angiotensinogen mRNA sequences were detected in all fetal liver samples and appeared to increase 3-fold from 60 to 138 d gestation and then to decrease after birth. In contrast, angiotensiogen mRNA could not be detected in renal cortical tissue of 118 or 138 d fetuses, or newborn or adult sheep. We conclude that, unlike in the rat, liver angiotensinogen gene expression is detectable during the 2nd trimester of gestation in sheep and is developmentally regulated. Furthermore, in contrast to the fetal rat, angiotensinogen mRNA sequences were undetectable in fetal sheep kidney.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The effect of maternal ethanol ingestion on fetal tissue vitamin A was investigated. Pregnant rats were pair-fed control diets or diets containing 36% of energy as ethanol. After 17 or 21 d gestation, fetuses were removed and fetal and maternal tissues were analyzed by HPLC for retinol and retinyl palmitate. Ethanol consumption resulted in fewer fetuses per pregnancy, increased number of resorptions, and increased numbers of gross fetal abnormalities. In maternal tissues, ethanol consumption resulted in greater lung and kidney vitamin A concentrations. In the fetuses of ethanol-consuming pregnancies, free retinol in liver was higher at d 17. However, fetal liver palmitate levels and total retinyl palmitate in liver, lung, and kidney were lower in ethanol-fed rats at d 21 of gestation. Fetal lung retinyl palmitate concentrations were greater at both d 17 and d 21, and kidney levels were also greater at d 21. In conclusion, the ingestion of ethanol by pregnant rats is associated with a reduction in fetal liver vitamin A levels and an elevation in the levels of lung and kidney vitamin A, indicating possible altered vitamin A metabolism as a result of ethanol consumption.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

We studied β-adrenergic receptors and responses in human fetal lung (15–25 wk gestation) maintained in explant culture with and without added dexamethasone. To determine β-adrenergic receptor concentration, we performed radioligand binding assays with [125I]-iodocyanopindolol. We also examined the ability of isoproterenol to stimulate cAMP generation as a measure of response to β-adrenergic receptor occupancy. In control cultures, β-receptor concentration increased significantly from d 0 to 3 of culture and thereafter remained stable. The kd(∼24 pM) of [125I]-iodocyanopindolol did not change with time in culture. The ability of isoproterenol to stimulate cAMP generation over basal levels increased in controls throughout the 5 d in explant culture. Addition of dexamethasone (10 nM) to the culture medium partially blocked the increase in β-receptor concentration and decreased both cAMP content and generation (basal and stimulated) in a dose-dependent manner (median effective concentration ±1 nM). In these same explants, dexamethasone increased the activity of fatty acid synthetase, an enzyme important in surfactant synthesis, more than 2-fold. Our results indicate that β-adrenergic receptors and isoproterenol stimulation of cAMP generation increase spontaneously in human fetal lung grown in explant culture. Dexamethasone, which accelerates other aspects of human lung development in vitro, decreases β-adrenergic receptor concentration and inhibits β-adrenergic responses.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Minute ventilation, arterial blood gases, arterial pH, cardiac output, and transdiaphragmatic force generation, both during spontaneous ventilation and in response to phrenic nerve stimulation during airway occlusion at end expiration, were measured in nine anesthetized, tracheostomized piglets before and 30 min after parenteral infusion of 20 mg/kg aminophylline. Serum theophylline levels averaged 109 ± 21 μmol/L (19.7 ± 3.7 μg/mL) at 30 min postinfusion. No significant changes were noted in pH, blood gases, blood pressure, or ventilatory measures after aminophylline. Aminophylline infusion also had no effect on transdiaphragmatic force generation at any frequency of phrenic nerve stimulation studied. It is concluded that aminophylline has no effect on diaphragmatic contractility in the quietly breathing, nonfatigued piglet.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Determination of circulating red cell volume (RCV) in anemic preterm infants is, in theory, a better indicator of transfusion needs than Hb concentration. Our study reports the results of RCV measurement using biotin labeling of red cells on 40 occasions in preterm infants of 25–34 wk gestation. In 20 infants, who had estimations made within 24 h of birth, the RCV varied between 17.7 and 66 mL/kg. Twenty measurements were made at a later age at the time of a blood transfusion. RCV values were between 13.1 and 41.5 mL/kg before transfusion. In 13 infants, RCV was determined simultaneously using two methods, biotin and dilution of autologous HbF with donor HbA at transfusion. There was no significant difference between the results of RCV estimations using these two methods. Our study demonstrates that biotin labeling is an effective method for determining RCV in preterm infants.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

After experimentally inducing growth retardation by unilateral uterine artery ligation in midpreg-nancy, placental blood flow (PBF) (microsphere technique) and placental transfer of14C-aminoisobutyric acid (AIB) and3H-methylglucose (MG) were studied at d 44, 50, or 63 of gestation in 19 chronically catheterized awake guinea pigs. At d 44, fetal wt (FW) and placental wt were reduced by 16 and 18%, respectively, in the ligated horn and FW/ PBF was increased by 122%. Placental efficiency to transfer MG and AIB (fetal dpm/g placenta) was maintained in the ligated horn, feto-placental extraction (feto-placental dpm/PBF) was increased, and placental transfer of the substrate analogs (fetal dpm/g fetus) was unchanged. At d 50 and 63, placental wt and FW were reduced in proportion (∼40%) in the growth-retarded group and FW/PBF was increased by 80 and 51%, respectively. Placental transfer of AIB was reduced by 33% at d 50 and by 18% at d 63. In addition, placental efficiency to transfer AIB was reduced by 36% at d 50 and by 22% at d 63 in the growth-retarded group. Fetal uptake of MG per g fetus was slightly reduced (–6%) at d 50 of gestation, but unaffected at d 63. Extraction of MG from the maternal PBF was increased, whereas the wt-specific transfer capacity of the placenta was unaltered. Our results demonstrate that experimental growth retardation in the guinea pig is associated with a substantial reduction of FW-specific placental transfer of AIB, indicating that the growth-retarded fetus has an impaired supply of amino acids during intrauterine life. This reduction is suggested to be due to alterations at the placental barrier level and will contribute to the development of intrauterine growth retardation independently of the PBF decrease per se. Placental transfer of MG per g fetus was only moderately reduced at d 50 of gestation, but otherwise maintained. Consequently, compromised placental glucose transfer is not likely to be the main cause of fetal hypoglycemia in guinea pig intrauterine growth retardation.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

To assess sleep-associated changes in gonadotropin-releasing hormone secretion during sexual maturation, we studied nighttime and daytime patterns of LH and FSH secretion in two groups with qualitatively similar sex steroid levels: girls with central precocious puberty and young adult women in the early follicular phase of an ovulatory menstrual cycle. In the girls with central precocious puberty, all indices of LH secretion were significantly higher at night than during the day (mean LH levels, 12 ± 2 versus 5 ± 1 IU/L, p < 0.01; LH pulse amplitude 16 ± 2 versus 7 ± 1 IU/L, p < 0.01; and LH pulse frequency 0.70 ± 0.05 versus 0.35 ± 0.08 pulse/patient-h, p < 0.01). Girls with a history of menses, who were presumably the most mature, lacked this diurnal variability. Mean nocturnal FSH levels were only slightly higher than daytime levels (7.6 ± 0.5 versus 7.2 ± 0.5 IU/L, p < 0.05) resulting in alternating periods of LH (nighttime) and FSH (daytime) predominance in this pubertal population. In contrast, the adult women had lower mean gonadotropin levels and LH pulse frequencies at night than during the day (mean LH 7 ± 1 versus 10 + 1 IU/L, p < 0.05; mean FSH 9 ± 1 versus 10 ± 1 IU/L, p < 0.05; LH pulse frequency 0.40 ± 0.08 versus 0.70 ± 0.10 pulse/patient-h, p < 0.05) and often (six of eight) demonstrated striking suspension of gonadotropin-releasing hormone secretion during sleep. The smaller changes in FSH again resulted in periods of relative LH (daytime) and FSH (nighttime) predominance. When between-group comparisons were made, the girls with central precocious puberty differed significantly from the women in the early follicular phase with respect to each index of gonadotropin secretion except for daytime LH pulse amplitude. Thus, neuroendocrine maturation in the human female appears to be characterized by changes in both the pattern of gonadotropin-releasing hormone secretion and the daily alternating periods of relative LH and FSH predominance in response to sleep.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID