摘要:

SummaryTriamcinolone (20 μg per fetus) administeredin uteroto term rat fetuses (day 21 of gestation) increases the activities of renal G-6-Pase and PEPCK. The absence (or marked decrease) of circulating corticosteroids in fetuses from adrenalectomized, metopirone-treated mothers has, however, no clear effect on the enzyme activities. Therefore, it is doubtful that corticosteroids play a role in the development of G-6-Pase and PEPCK activities during the fetal period of life.In 21-day-old fetuses entirely decapitated on day 18, both enzyme activities are lower than in intact fetuses of the same litter (G-6-Pase, −48%; PEPCK, −36%). In partially decapitated fetuses, the activity of G-6-Pase remains at the control level, whereas the PEPCK activity is clearly reduced (-39%). These results strongly suggest that on the last days of gestation the hormone group of parathormone, calcitonine, or thyroxine controls the G-6-Pase activity, whereas the hypothalamo-hypophysis system is implied in the development of PEPCK activity.Parathormone (1 unit per fetus) administered to decapitated fetuses completely restores the G-6-Pase activity. Neither rat growth hormone, synacthene, nor arginine vasopressin has significant effects on the activity of PEPCK in the kidneys of decapitated fetuses.The administration of 0.5 μmole of dibutyryl-cAMP or cyclic adenosine 3′5′-monophosphate (cAMP) to decapitated fetuses completely restores the activity of renal PEPCK, suggesting that the development of PEPCK is controlled by cAMP-dependent hormone. The same dose of dibutyryl-cAMP has no effect on the activity of G-6-Pase; cAMP produces a slight but significant increase of this enzyme activity.SpeculationThe development of renal gluconeogenesis during the fetal period is probably controlled by several hormonal factors which do not include corticosteroids.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryResponse characteristics of a transcutaneous PO2electrode to step changes in PaO2were determined.In vitrolag time and 95% response time of a transcutaneous PO2monitor were compared toin vivoresponse. Release of arterial occlusion was used to produce rapid local Pao2changes in human infants and adults.In vitrolag time and 95% response time varied according to whether an increment or decrement in PO2was produced.In vivo95% response time of this electrode was two to six times slower than previous estimates, and it varied significantly with the magnitude of the step change, subject age, anatomic location, and local hemodynamic factors. Also, we found thatin vivolag time is two to three times faster than previously reported.SpeculationUnder steady-state conditions, transcutaneous PO2correlates well with PaO2, but when rapid change is encountered as during oxygen administration or apnea, transcutaneous PO2will significantly underestimate PaO2change. On the other hand, the relatively short lag time suggests that the transcutaneous PO2electrode may be useful in following rapid PaO2changes qualitatively.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryIndomethacin, because of its prostaglandin inhibition, may cause constriction of the ductus arteriosus and affect the pulmonary circulation. To study this possibility, we gave indomethacin daily by gavage to two groups of pregnant rats from the 17th day of pregnancy through delivery (group 1, 2 mg/kg/day; group 2, 4 mg/kg/day). Group 3, untreated control pregnant rats, received saline. The pups were killed 30 min after birth and heart-lung preparations were perfused with glutaraldehyde. Appropriate blocks were processed for quantitative morphometry of the pulmonary arteries and arterioles. For analysis, the vessels were grouped by external diameter,i.e., <30, 30 to 50, and 50 to 100 μm. Groups 1 and 2 showed an increased medial smooth muscle mass in both 30 to 50 and 50 to 100-μm vessels as indicated by medial thickness and medial areas (P< 0.05). Muscularized arterioles, <30 μm, were present in groups 1 and 2, but not in controls. The relative mass of lung parenchymal components were determined by point counting. Indomethacin-treated animals had an increased saccular wall mass, decreased airspace mass, and a decreased capillary to saccular wall ratio (P< 0.05). These results show that the fetal pulmonary circulation's response to indomethacin comprises the appearance of medial hypertrophy and newly muscularized arterioles. When these changes occur in lungs with immature, thick saccular walls, there is a decreased surface for oxygen exchange and an increased pulmonary vascular resistance resulting in a persistent fetal circulation.SpeculationIndomethacin, during pregnancy, may cause constriction of the ductus arteriosus and induce a persistent fetal circulation in the newborn. Inasmuch as salicylates also may be causative agents of persistent fetal circulation, their use by pregnant women should be carefully examined.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryPlacental blood flow in the maternal side and transfer of [14C]-α-amino isobutyric acid (AIB) and [3H]methylglucose (MG) were measured in 22 pregnant guinea pigs at various gestational ages. The fetuses were divided in three groups according to their body weights: small, average, and large. Body weight was 85.25% of average values in the small fetuses and 114.12% in the large fetuses. Placental weight was 121.73% of average in the large fetuses and 84.42% in the small fetuses. Placental blood flow was 134.48% of average in large fetuses and 73.18% in small fetuses. AIB and MG transfers were significantly lower in the small fetuses (80.33% and 86.06%, respectively, of average values). In contrast, in large fetuses, AIB transfer was 123.43%, and MG transfer was 113.96% of average. Significant correlations were found between fetal and placental weight and placental blood flow and transfer of AIB and MG in the various groups. Placental transfer of AIB and placental blood flow were significantly correlated in the small (r= 0.59) and average weight fetuses (r= 0.37). In addition, the slope of the regression curve for AIB was significantly steeper in the small fetuses when compared with the slope of average and large fetuses. Placental blood flow and transfer of MG were significantly correlated only in the large fetuses (r= 0.48). In the small fetuses, the rate of AIB transfer was proportionally more reduced than that of MG transfer as the rate of placental blood flow decreased.The results demonstrate that spontaneous fetal growth retardation in the guinea pig is associated with a smaller placenta, a reduced placental blood flow, and a reduced transfer of AIB and MG. Inasmuch as in the small fetuses AIB transfer was proportionally more reduced than MG transfer, it is suggested that in addition to the reduced blood flow limited availability of certain essential ammo acids may be a cause of fetal growth retardation.SpeculationA reduced placental transfer of certain essential amino acids may further aggravate the fetal growth retardation associated with low placental blood flow.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryFourteen children between 2.5 and 16 years of age were studied to provide a quantitative estimate of the changes in gonadotropin-releasing hormone (GnRH) pulse amplitude in hypophysial portal plasma during puberty. Responses to physiologic doses of synthetic GnRH were measured [induced luteinizing hormone (ΔLH) and induced follicle-stimulating hormone (ΔFSH)] and compared with spontaneous fluctuations in gonadotropins [spontaneous luteinizing hormone (ΔaLH) and spontaneous follicle-stimulating hormone (ΔaFSH)]. One to four low-dose (0.0125 or 0.025 μg/kg IV) pulses of GnRH were given every 2 hr between 0800 and 1600 or 2200 and 0400 hr. Maximal peripheral plasma concentrations of GnRH one mm after pulses averaged 107 ± 25 pg/ml (S.E.) (0.0125 μg/kg dose) and 218 ± 33 pg/ml (0.025 μg/kg dose). In early pubertal children, the maximal ΔLH was similar to or less than the maximal nocturnal ΔaLH (maximum, ΔLH 7.0 ± 0.2versusmaximum ΔaLH 7.0 ± 1.3 mIU/ml in boys, 7.0 ± 1.2versus16.0 ± 3.0 mIU/ml in girls). Luteinizing hormone (LH) responses were low or undetectable in children whose bone ages were less than 10 years. When discernible, LH pulse frequency was similar during daytime and nighttime sampling periods in early pubertal boys. However, two hourly injections of GnRH given during the day did not simulate the initial nocturnal rise in LH. Overall mean ΔFSH and ΔaFSH were similar in three prepubertal female patients (3.0 ± 0.2versus2.8 ± 0.2 mIU/ml). ΔFSH was greater than ΔaFSH in two patients with gonadal dysgenesis (bone ages, 2.5 and 5 years) and in one prepubertal girl. The gonadotropin responses seen in early pubertal children suggest that the amplitude of nocturnal GnRH pulses is equal to or greater than that previously reported in normal men.SpeculationDirect measurement of hypophysial portal plasma concentrations of GnRH in human beings is unpractical. Nevertheless, detailed comparison of spontaneous fluctuations in plasma follicle-stimulating and luteinizing hormones with gonadotropin responses induced by a known concentration of exogenous gonadotropin-releasing hormone (GnRH) should provide reasonable estimates of GnRH pulse amplitude. The current studies suggest that: (1) in early pubertal children, the amplitude of nocturnal GnRH pulses equals or exceeds that of normal men; (2) the initial nocturnal rise in plasma LH characteristically noted in early pubertal boys is the result of a transient increase in the frequency of GnRH secretion; and (3) if GnRH is secreted episodically before puberty, GnRH pulse amplitude is low.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummarySeven chronically catheterized fetal lambs between 100 and 130 days gestation (term, 140 to 145 days) and five newborn lambs were infused withd-aldosterone monoacetate, 100 μg/kg bolus, and 100 μg/kg over 60 min. Fetal lamb plasma aldosterone levels increased from a mean and S.E. baseline of 4.5 ± 0.3 μg/dl to >100 μg/dl. Maternal plasma aldosterone concentrations increased from 10.2 ± 0.8 to 26.2 ± 2.4 μg/dl after 15 min (P< 0.05) of the infusion. Amniotic fluid levels increased from 13.3 ± 0.8 to 23.8 ± 2.3 μg/dl (P< 0.05) after 15 min of the infusion. There was no change in plasma renin activity levels in the fetus or pregnant ewe. Urine sodium excretion decreased from 0.87 ± 0.09 to 0.34 total mEq (P< 0.05), and urine potassium increased from 0.25 ± 0.06 to 0.38 ± 0.07 total mEq (P< 0.05) between 60 and 90 min after the start of the infusion in the fetal lamb. There was no change in creatinine clearance or urinary sodium and potassium excretion in the newborn lamb. These data show that aldosterone crosses the placenta during the last trimester in the fetal lamb and can control sodium and potassium transport in the distal renal tubule. Lack of distal tubular responsiveness to aldosterone in the newborn is not due to maturational factors.SpeculationAldosterone can cross the placenta during the last trimester in the sheep, but the fetal adrenal cannot be stimulated. Sodium balance in the fetus is dependent on sodium balance in the mother.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID