摘要:

SummaryEnergy balance studies were done during 10–29 days on 15 immature infants of mean birth weight 1581 g. Mean gross energy intake was 757 kJ/kg (181 kcal) and 79 % of this was retained, so that metabolizable energy was 602 kJ/kg (143 kcal). Mean resting metabolic rate was 244 kJ/kg (58.1 kcal), and it increased with advancing maturity. Minimum resting metabolism averaged 199 kJ/kg (47.5 kcal). Energy expended in activity increased with maturity, but amounted to less than 17 % of the total energy turnover. Postprandial metabolism caused the mean &OV0312;O2to rise by 17 % in the hour after a feed, and during 24 hr resulted in consumption of energy equivalent to about 10 % of the resting metabolism. Stored energy amounted to 230 kJ/kg (55 kcal) and was linearly related to weight gain (r= 0.92). Energy cost of weight gain was 24 kJ/g (5.7 kcal) and energy stored in new tissue was 16.8 kJ/g (4.0 kcal). Maintenance energy requirement at zero growth rate was about 270 kJ/kg (64 kcal).SpeculationData on energy balance in immature infants are scanty. There is need for information on energy retention, maintenance energy requirements, postprandial energy expenditure, and energy cost of growth. We have attempted to provide such information, but our data show wide variation between infants. However, in spite of this variation, a clear relationship is present between energy retention and weight gain, the main limiting factor in weight gain probably being energy absorption from the gut. We need more data to show whether efficiency of energy utilization alters with different levels of intake and at different ages.

ISSN:0031-3998    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

SummaryThe hGH response to an ornithin or an insulin test was measured in 105 children from 11–18 yr old with delay of growth more than 2 SD. Besides 74 subjects with normal values and 7 with complete lack of response, 24 subjects exhibited a partial rise of GH. Most of the latter had decreasing growth rate and no sign of puberty. Out of 15 assessed for GH function after onset of puberty, 14 showed a normal response accompanying a markedly increased growth velocity. Four other subjects with partial response who were receiving sexual hormones for 48 hr before the second test showed a normal response also. An exogenous hGH treatment administered in two of these patients resulted in a marked and sustained growth increase far before entering puberty.SpeculationThe findings that plasma GH responses to stimulation tests is reduced in some children with decreasing growth rate before puberty and return to normal after onset of sexual development, would suggest a transient and functional defect in growth hormone secretion and the physiologic role of sexual hormones on GH release mechanism at that period of life.

ISSN:0031-3998    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

SummarySix patients with glucose-6-phosphatase deficiency were treated for 12 hr at night with gastric drip feeding (GDF), containing soy milk plus glucose, dextrimaltose, and starch. An alarm system (thermistor), connected to the gastric tube, was devised in case of displacement of the tube by the child. The effects of GDF were as follows. Base deficit and lacticaciduria decreased, but did not normalize. Serum cholesterol levels tended to normalize, but serum triglycerides remained elevated. The hepatic and extrahepatic components of plasma lipoprotein lipase were measured separately 5 and 40 min after iv heparin injection. Hepatic triglyceride lipase activities which were subnormal to normal increased to the lower normal range. Extrahepatic lipoprotein lipase activities, though increasing after GDF, remained abnormally low.Catch-up growth occurred in all four growth-retarded children. The pronounced liver enlargement of the five patients, not previously treated with GDF, decreased markedly.SpeculationNocturnal GDF in glucose-6-phosphatase deficient children, suppresses the tendency for hypoglycemia and acidosis which are causes for stress, catabolism, and anorexia. By suppressing these factors, GDF promotes anabolism and caloric intake, thus accounting for the catch-up growth seen in the patients with growth retardation.

ISSN:0031-3998    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

SummaryStudies were conducted to assess the effect of fetal thyroidectomy early in the third trimester on lung growth and surfactant maturation in the sheep. At 95–99 days of gestation, a fetal thyroidectomy was performed. The preparation was killed 36–45 days postthyroidectomy. The mean weights of the cerebrum, cerebellum, and combined heart and lungs were significantly smaller and the pituitary gland significantly greater in the thyroidectomized fetus. The mean tracheal fluid lecithin to sphingomyelin (L/S) ratio was significantly lower in the athyrotic fetus; however, there was no significant difference in the mean cortisol concentration or mean whole lung homogenate phosphatidic acid phosphohydrolase (PAPase) specific activity between the two groups. There was a significant direct correlation between the serum cortisol concentration and tracheal fluid L/S ratio and between the whole lung homogenate PAPase specific activity and serum cortisol level in the euthyroid group, which were not present in the thyroidectomized group. The mean lung DNA concentration was significantly increased and mean lung protein/DNA ratio significantly decreased in the thyroidectomized fetus. On histologic examination, the lung from the athyrotic fetus was hypercellular with thickened alveolar septae. The type II pneumocyte in the hypothyroid lung was less mature with fewer lamellar bodies or its precursors. These results suggest that in the ovine fetus, thyroid hormone deficiency during the last trimester of intrauterine development impairs lung growth and surfactant maturation.SpeculationThe present results suggest that thyroid hormones are necessary for normal lung growth and surfactant maturation. In the human preterm infant, idiopathic respiratory distress syndrome is a major cause of morbidity and mortality. Stimulation of the hypothalamic-pituitary-thyroid axis in the fetus at high risk for developing idiopathic respiratory distress syndrome before delivery may accelerate surfactant maturation and decrease the sequelae from this syndrome.

ISSN:0031-3998    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

SummaryAmino acid transfer across human placenta has been studied in anin vitroperfusion system. Transfer rates from maternal to fetal circuit of 12 amino acids were about the same when there was a downhill gradient permitting diffusion and active transport. This was termed “maximal transfer rate.” Cystine, aspartic acid, and glutamic acid were transferred at approximately half the rate of the others under these conditions. Measurement of exchange rates with radioactive tracers and with equimolar concentration of amino acids on both sides of the membrane provided a close estimate of maximal transfer rate. Fetal nutrition requires active transfer against a gradient. The rate of active transfer is a fraction of the exchange rate.The ability to establish a transplacental gradient by perfused placenta was investigated with the maternal circuit open and fetal circuit closed (recirculated). The fetal to maternal concentration ratio for D-leucine and antipyrine was 1.0, for L-leucine, 1.5, indicating a stereospecific transport mechanism for leucine. Gradients of 1.56 ± 0.11 and 1.62 ± 0.10 were demonstrated for L-alanine and L-Iysine, respectively. The establishment of transplacental gradients is a placental function, requiring no assistance from maternal or fetal factors.The ratios of the exchange rates for the L- and D-isomers were determined as a measure of the active, stereospecific transport system. The L:D ratio from the maternal to fetal circulation for leucine was 1.64 ± 0.19, for alanine 1.78 ± 0.49. In the reverse direction, the ratio for leucine was 1.03. The placental membrane exhibits a polarity in active transport directed towards the fetus. The transplacental gradient for leucine is the result of a dynamic equilibrium between active transport towards the fetus and diffusion back towards the maternal circulation.The availability of intracellular amino acids to serve as a reserve for fetal needs was studied by perfusing the placenta with buffer containing no amino acids. After 2 hr of perfusion, 53–84% of each of nine amino acids was still retained within the placenta. It is suggested that the high tissue concentrations of amino acids are related to the metabolic needs of the placenta rather than to its transport functions.SpeculationThe present studies have demonstrated differences between placental uptake and placental transfer of amino acids. It is still uncertain whether the two processes are serving two discrete functions (placental nutrition and fetal nutrition) or whether transplacental transfer involves mechanisms in addition to placental uptake (e.g., placental release).

ISSN:0031-3998    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

SummaryCarbohydrate metabolism in the developing rabbit was investigated for deficiencies that may be responsible for the failure of many preterm (281/2–291/2 day) animals to survive the first hours of life. The preterm animal shows an inability to reverse glycogenolysis or initiate gluconeogenesis from lactate or alanine in the first hours of life. This impairment, coupled with 50% less liver glycogen stores than the term animal, places the preterm animal at jeopardy for energy substrate early on in life. Unexpected was the early, rapid conversion of glycerol to glucose by the preterm animal. This ability seemed to be the primary difference in carbohydrate metabolism between the surviving and nonsurviving preterm rabbit.Speculation Impaired glyconeogenesis from lactate and alanine in the preterm animal coupled with active gluconeogenesis from glycerol suggests that substrates from lipolysis may be very important for early adaptation. Preterm animals endowed with limited fat stores, thus, minimal available glycerol, would be incapable of survival.

ISSN:0031-3998    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

SummaryTo evaluate the role of gonadotropins in the control of Müllerian Inhibiting Substance (MIS) secretion, pregnant rats were injected with rabbit antiserum against luteinizing hormone releasing hormone (LHRH), and their pups replaced with follicle stimulating hormone (FSH) and human chorionic gonadotropin (hCG). The LHRH antiserum (LHRH-AS) was given at 13 and 20 days of gestation. Control dams were injected with an equal volume of normal rabbit serum. The male pups from mothers treated with LHRH antiserum were given 5 daily s.c. injections of the FSH, hCG, or vehicle. The male pups from mothers treated with normal rabbit serum were given vehicle s.c. Testicular fragments of 6 day old pups born to mothers treated with LHRH antiserum during pregnancy showed an increase relative to controls in MIS activity in a graded organ culture bioassay system (grade 3.4 ± 0.3 vs. 2.3 ± 0.2) (P< 0.01). FSH given to pups from mothers treated with LHRH antiserum reduced testicular MIS secretion compared to vehicle treated pups from the same mothers (grade 2.3 ± 0.2 vs. 3.4 ± 0.3) (P< 0.01). Thus, postnatal injections of FSH after immunologic blockade of gonadotropinsin uteroreduced MIS activity of the testes to the same level found in testes of 6 day control pups (grade 2.3 ± 0.2 vs. 2.3 ± 0.2). In contrast, MIS activity remained high despite postnatal hCG injection in pups born to mothers given LHRH-AS (grade 3.4 ± 0.4 vs. 3.4 ± 0.3). These studies suggest that secretion of MIS is dependent on normal hypothalamic secretion of LHRH and may be inhibited by FSH.SpeculationFSH inhibits MIS secretion.

ISSN:0031-3998    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

SummaryMeasurements of respiration were compared in normal, full term and premature infants before and after application of 5 cm H2O continuous negative pressure (CNEG) around the body below the neck. Mean minute ventilation in the full term infants decreased when CNEG was applied, secondary to a decrease in respiratory rate, with tidal volume relatively unchanged. The premature infants showed no consistent ventilatory response to CNEG. There were variable changes in occlusion pressure at increased lung volume. Observation with rib cage and abdomen anterior-posterior (A-P) magnetometers showed that the increase in end-expiratory lung volume was accounted for largely by expansion of the rib cage so that the configuration of the diaphragm and its mechanical advantage were maintained. These results suggest that the diaphragm is the major determinant of mask occlusion pressure in infants.SpeculationThe effects of increased lung volume on the configuration of the chest wall may relate to the success of continuous distending pressure in the treatment of respiratory disorders in infants, including apnea of prematurity.

ISSN:0031-3998    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

SummaryThe plasma sodium, osmolality, and arginine vasopressin (AVP) responses to phlebotomy, hypertonic saline, water loading and fluid restriction were studied in 2–49 day old lambs. Phlebotomy of 10 and 20% of the lamb's estimated blood volume produced 37-and 44-fold increments in plasma AVP, without a concomitant change in plasma sodium or osmolality. The infusion of 10 mEq/kg sodium chloride produced a 12% rise in plasma sodium concentration accompanied by a 7-fold rise in plasma AVP. Water loading with 100 ml/kg hypotonic fluid produced a significant fall in plasma sodium concentration (10.7%) and a decrease in plasma AVP. Eighteen hr of water deprivation evoked a 7-fold increase in AVP.These results indicate that the newborn lamb is capable of responding appropriately to known stimuli for AVP secretion. The stimulus response ratio (SRR):SRR=Log [AVP]1- Log [AVP]2/δ osmolalityof newborn lambs was nearly identical after hypertonic saline and water loading and was also quite similar to that of the adult ewe after a saline challenge. The SRR of water deprived lambs was greater than that after the other stimuli, presumably reflecting combined volume and osmolar stimuli. We conclude that the neurohypophysis and the volume receptor systems of the newborn lamb are capable of appropriate, mature AVP responsiveness during the first days of extrauterine life.SpeculationThe present studies indicate that AVP secretion in the newborn sheep is responsive to both volume and osmolar stimuli. Quantitative responses are equivalent to those of mature ewes. If the newborn human is both osmo- and volume sensitive, as seems likely, AVP secretion may be important in fluid and electrolyte homeostasis in the newborn period. Thus, lack of AVP secretion does not explain the limited ability to concentrate urine demonstrated by the newborn infant.

ISSN:0031-3998    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

SummaryEnd-expiratory lung volume increased 17.5 ± 5.4 ml (mean ± SD) in full term infants and 7.7 ± 2.1 ml in premature infants when 5–7 cm H2O continuous negative pressure (CNEG) was applied around the thorax. In the full term infants, respiratory rate decreased from 52–43 min-1(P< 0.001), mean inspiratory duration (ti) was unchanged, and mean duration of expiration (te) increased from 0.62 ± 0.14 (SE)-0.84 ± 0.22 sec (P< 0.001) after application of CNEG. Teof occluded efforts on CNEG was also prolonged (P< 0.005), although less than teof spontaneous breaths on CNEG (P< 0.005). Teincreased in four of eight premature infants when CNEG was applied. We conclude that phasic vagal feedback regulates Tiand teis controlled by tonic vagal activity.SpeculationPremature infants may have an optimum functional residual capacity (FRC) which can be achieved with continuous distending pressure, resulting in regularization of respiration.

ISSN:0031-3998    

出版商:OVID    

年代:1979

数据来源: OVID