摘要:

SummarySurfactant‐deficient premature newborn rabbits obtained by hysterotomy on day 27 of gestation were tracheostomized at birth, kept in a multichambered pressure‐constant body plethysmograph, and subjected to intermittent positive pressure ventilation using a standardized insufflation pressure (30 cm H2O). A sequence of various frequencies (20, 40, and 60/min) and inspiration:expiration (I:E) ratios (1:4, 1:2, 1:1, 2:1, and 4:1) were applied, and the effect of these various respirator settings on tidal volume (VT) and flow was evaluated by means of a Fleisch tube connected to the body plethysmograph. Irrespective of respirator frequency, increasing I: E ratio from the basic setting of 1:1 resulted in increased VT; decreasing I:E ratio had the opposite effect. There was a nearly linear relation between variations in I:E ratio and VT, but the slope of the regression line was steeper at frequencies 40 and 60/min than at 20/min. At a frequency of 20/min, values (X ± S.D.) for lung‐thorax compliance at I:E ratios of 1:4 and 4:1 were 0.50 ± 0.26 and 0.99 ± 0.42 ml/cm H2O·kg, respectively. Corresponding figures for frequency of 60/min were 0.21 ± 0.10 and 0.73 ± 0.36 ml/cm H2O·kg. At the two higher frequencies and low I:E ratios (≤1:1), the duration of the inspiration phase was not sufficient to provide the maximal degree of lung expansion attainable with this insufflation pressure under static conditions. At frequency of 60/min and I:E ratio of 4:1, the expiration was short enough to prevent zero flow before onset of inspiration.SpeculationThe wet lungs of premature neonates with surfactant deficiency are not ventilated effectively with a conventional inspiration:expiration ratio of 1:1, or less. However, by increasing inspiration: expiration ratio to as much as 4:1, the viscosity of the fluid in the airways can be overcome, and the lungs can then be ventilated with a lower insufflation pressure. This alternative setting of the respirator should reduce the risk of long‐term complications, such as bronchopulmonary dysplasia, in surfactant‐deficient babies treated with artificial ventilation in the neonatal period.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryThe activities of plasma and fibroblast cytidine 5'‐monophos‐phate‐sialic acid:glycoprotein sialyltransferases of patients with cystic fibrosis have been found to be within the range of activities of age‐ and sex‐matched normal controls when asialofetuin served as the sialic acid acceptor. The use of desialylated preparations of purified human plasma &agr;2‐macroglobulin, as an acceptor, demonstrated 35 to 52% reduction in the incorporation of sialic acid into the &agr;2‐macroglobulin from patients with cystic fibrosis as compared to that of &agr;2‐macroglobulin from normal controls. The reduced sialylation was dependent upon the source of the &agr;2‐macroglobulin acceptor but independent of the source (cystic fibrosis or normal) of the sialyltransferase enzyme. Using radiolabeled precursors, the rates of the synthesis ofN‐acetylneuraminic acid fromN‐acetyl‐D‐mannosamine, the release of sialic acid from glycoproteins and the conversion of free sialic acid into CMP‐sialic acid have been determined in cultured skin fibroblasts from patients with cystic fibrosis and found to be not significantly different from those of normal controls.SpeculationThe reduced sialylation of desialylated preparations of purified &agr;2‐macroglobulin from patients with cystic fibrosis as compared to that of asialo‐&agr;2‐macroglobulin from age‐ and sex‐matched normal controls indicates a possible alteration in the carbohydrate moiety of glycoproteins in cystic fibrosis. The metabolism of sialic acid appears, however, to be normal in this disease and could not account for the observed differences. Additional glycoproteins and glycosyltransferases should be examined to find out if a general defect in glycosylation is involved in cystic fibrosis.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryWe measured blood flow to the myocardium of the left ventricular free wall, and blood glucose, lactate, pyruvate, and oxygen concentrations simultaneously in the aorta and coronary sinus 13 times in seven previously instrumented newborn sheep, 4 to 25 days after birth. We calculated arteriovenous difference and consumption of oxygen, glucose, lactate, and pyruvate by the newborn myocardium. Results were compared with recently obtained measurements in the myocardium of fetal and adult sheep (6).Myocardial consumption of oxygen in the newborn (577 ± 38 &mgr;M·min−1·100 g LV−1) was higher than in either the fetuses or the adults. This was associated with a greater myocardial blood flow (201 ± 21 mm·min−1·100 g LV−1) in the newborns. However, the increased myocardial oxygen consumption in the newborns was commensurate with their increased cardiac work as compared with both the fetuses and adults.Although there is an abrupt postnatal increase in arterial glucose concentration, there was no significant difference in either the myocardial consumption of glucose or the contribution of glucose to the total myocardial energy supply among fetal, newborn or adult sheep. Postnatal decreases in myocardial consumption of lactate and pyruvate are not compensated for by an increase in glucose consumption. In newborn sheep, carbohydrates including glucose, lactate, and pyruvate supply the substrate for no more than approximately one‐fourth of the total myocardial energy demands (carbohydrate/oxygen quotient was 0.26).SpeculationAlthough glucose and lactate supply most of the substrate for myocardial energy supply in the lamb fetus, postnatally there is an abrupt decrease in lactate utilization that is not compensated for by an increase in glucose utilization. The identity of the primary myocardial energy substrate(s) in newborn and adult sheep remains to be determined.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryUtilizing available data and several assumptions, the body content of water, minerals, protein, carbohydrate, and fat has been estimated for a 9‐year‐old reference boy. This reference boy is leaner than the reference man (13.4versus15.3% of body weight) and his fat‐free body mass exhibits greater concentration of water (75.5versus73.7%) and lesser concentrations of potassium (66.8versus68.1 mEq/kg) and total minerals (4.7versus6.9%). If agespecific values are used for composition of fat‐free body mass (rather than the conventionally used constants based on adult body composition), it will be possible to avoid underestimation of fat content calculated from data on total body water and overestimation of fat content calculated from40K counting data or from body density determined by underwater weighing.SpeculationBy utilizing age‐specific constants for calculating body fat content from indirect measurement of body composition (i.e., total body water,40K counting, and body density) it will be possible to determine the extent of changes in fat content of the body of normal individuals and of those with specific illnesses or disorders, including obesity.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryIf endogenous prolactin secretion is important in normal development of fetal lung surfactant, the inhibition of its secretion should be associated with delayed maturation of fetal lung.We therefore studied the effect of bromoergocriptine administration to pregnant rabbits upon lecithin content of fetal lung washes.The does were treated since the 27th day of gestation with either Mesilate of 2‐Bromo‐&agr;‐ergocriptine (C32H40BrN5O5, CH3SO3H) (Bromocriptine) (Parlodel, Sandoz) (1 mg/kg/day) or solvent twice daily until delivery.The newborns were killed immediately by intraperitoneal administration of sodium penthobarbital and tracheostomized; then lung washes were performed.The extracted lipids were plated and run on heat‐activated thin layers of silica gel H. Lecithin was eluted, and phosphorus determination was performed.The level of lecithin phosphorus in the lung washes of the fetuses whose mothers received Bromocriptine was &OV0398; = 2.24 ± 0.39 &mgr;g/g dry lung weight, whereas that of fetuses of control does was &OV0398; = 6.93 ± 2.64 &mgr;g/g dry lung weight (P< 0.001).The mean body weight of the fetuses from treated mothers was 38.22 ± 6.39 g whereas that of fetuses from control rabbits was 47.63 ± 6.94 g (P< 0.001).The mother's body weight gain from days 26 to 30 in Bromo‐criptine‐treated rabbits was 156.11 ± 99.4 g, whereas that of controls was 374.38 ± 166.21 g (P< 0.01).SpeculationProlactin could be involved in the normal biochemical development of the lung and also be necessary for a normal weight gain of mother and fetuses during the last stage of gestation.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryTo determine whether solute transfer during peritoneal dialysis is age related and to identify those factors which might explain age‐related differences in dialysis kinetics, the peritoneal dialysance of [14C]urea (DU), [3H]inulin (DI), and the permeability index (DR= DI/DU) were examined in six puppies and five adult dogs. Exchange volume of lactated Ringer's (40 ml/kg) and exchange times (30 min) were identical in all studies. Theoretical calculations for urea dialysance for animals of differing body size were made. Assuming the existence of a similar functional peritoneal surface area per kg and the use of similar exchange volumes per kg and dwell times, theoretical values for the urea dialysance per kg for different sized animals were identical. The experimental studies demonstrated that DIper kg and DUper kg were higher in the puppies (0.146 ± 0.023 and 0.765 ± 0.054 ml/min/kg; &OV0398; ± S.E.) than in the adult (0.052 ± 0.01 and 0.462 ± 0.05 ml/min/kg) (P< 0.01). Also, DRwas higher in the puppies (0.187 ± 0.026), than in the adults (0.11 ± 0.015) (P< 0.05). The greater values for DIand DUper kg and DRin the young are best explained by the young having an increased peritoneal membrane permeability as well as an increase in functional peritoneal surface area relative to body weight. This increase in solute movement is independent of the dialysis mechanics used in an exchange and reflects agerelated differences in the intrinsic characteristics of the peritoneal membrane.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryPregnant dogs were starved for 72 hr before a term delivery. Maternal (1.68 ± 0.39versus0.74 ± 0.20 mM) and fetal (0.39 ± 0.03versus0.22 ± 0.07) circulating free fatty acids and maternal (2.99 ± 0.79versus1.04 ± 0.84) and fetal (2.53 ± 0.35versus1.01 ± 0.32) ketones were elevated whereas blood glucose values remained unchanged at the time of delivery. After birth, pups born to starved mothers had significantly lower blood glucose values during 3, 6, 9, and 24 hours of neonatal fasting. Intracerebral glucose concentrations paralleled those in the blood as they were depressed at 3, 6, and 9 hours of age. Cerebral glycogen content was lower in pups born to starved mothers at 6 (2.72 ± 0.43versus4.32 ± 0.56 &mgr;moles/g) and 24 (2.31 ± 0.17versus3.48 ± 0.39 &mgr;moles/g) hr, whereas UDP‐glucose concentrations were significantly elevated in these pups during fetal, 3, 9, and 24 hr of age. Phosphoenolpyruvate was higher after maternal starvation in the fetus and at 6 and 9 hr, whereas cerebral pyruvate concentrations were elevated at 3, 6, and 9 hr of age. The elevation of pyruvate with no alteration of lactate concentration resulted in an elevated cytoplasmic NAD/NADH ratio at 3 hr of age (1381 ± 194versus792 ± 198).Cerebral &agr;‐ketoglutarate and calculated oxaloacetate concentrations were elevated throughout the day after maternal starvation whereas malate concentrations were depressed at 3 and 9 hr of age. Cerebral energy charge was unaffected, whereas the calculated energy reserve was lower at 3, 6, and 24 hours. Cerebral amino acids demonstrated elevated aspartate concentrations at 3 and 6 hr. Cerebral glutamine concentrations were lower during fetal stage (7.86 ± 0.52versus10.01 ± 0.41 &mgr;moles/g) and 3, 6, and 9 hr of life.SpeculationThese data suggest that cerebral glycogen synthesis was diminished and that the oxidation of cerebral amino acids, in particular glutamine, may contribute to maintain cerebral energy production during the relative fasting neonatal hypoglycemia which develops in pups after maternal starvations.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryWe investigated the relative contribution of the two pathways of phosphatidylcholine (PC) synthesis in lungs from chick embryos of 12 to 20 days of incubation as well as from hatched chicks and adult chickens. Lung “blocks” were incubated for 60 minin vitroin the presence of [3H]methionine and [14C]choline. PC was separated by thin‐layer chromatography, and the amount of labeled product was determined by liquid scintillation counting. PC synthesis (expressed as pmoles PC per mg protein per 60 min) by the choline pathway declined from the 12‐day value of 40 to a minimum of 8 at day 16 and then rose gradually to a peak of 74 on day 1 posthatching. PC synthesis via the phosphatidylethanolamine pathway also declined from day 12 (54) to day 16 (13) but peaked on day 19 (65) and again on day 1 posthatching (54). Synthetic activities of the two pathways differed significantly (P≤ 0.05) only on days 14, 18, and 19 of incubation. Unlike the mammalian lung, neither pathway seems to predominate throughout incubation or after hatching. The increase in PC synthesis towards the end of incubation correlates with the time of appearance of lamellar bodies in the lung epithelial cells and of surfactant in the airways.SpeculationBecause normal morphologic and biochemical development of the chick lung resembles that occurring in the mammalian lung in many respects, conclusions drawn from the study of avian lungs may well be germane to an appreciation of mammalian lung differentiation in general. Information concerning regulation of the biosynthetic pathways for phosphatidylcholine in the avian embryo may provide some clues for improved clinical treatment of certain pulmonary disorders, including respiratory distress syndrome of the newborn.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryWe have performed the fetal CO2response test on eight mature lambsin uteroand have found that theophylline is a respiratory stimulant over a wide range of PaO2and pHa. Theophylline produces significant increase in slope of P100, Pmax, and VEq response curves and significant increase in P100, Pmax, f, and VEq responses at PaCO2, 65 torr. It also produces significant lowering of the naturally high fetal absolute threshold to CO2,i.e., PaCO2at which breathing starts during the CO2test. “Offset” threshold,i.e., PaCO2when breathing stops after the test, is the same with and without theophylline and equal to absolute threshold with theophylline. Our studies indicate that: (1) theophylline lowers fetal threshold and increases sensitivity to CO2; (2) increased sensitivity is expressed mainly by heightened Pmax(i.e., the equivalent of tidal volume) with some contribution of f particularly at high PaCO2; (3) decreased CO2threshold is best assessed by determination of absolute threshold rather than the conventional x‐axis intercept method; (4) the low offset threshold is consistent with our understanding that arousal is a requisite for generation and maintenance of fetal breathing; (5) theophylline is as effective a respiratory stimulant during fetal acidemia and hypoxemia as it is under normal conditions; and (6) a number of serious reservations must be held regarding use of theophylline during low pHa, low PaO2states.SpeculationTheophylline, which is shown to be an effective respiratory stimulant in the ovine fetus, activates central respiratory units by a process of recruitment analogous to that of other inputs,e.g., somatosensory and chemoreceptor afferents. Changes in the state of respiratory center arousal, including its return to natural quiescence with apnea when inputs are withdrawn, can be assessed by the fetal CO2test and bear on the phenomena of onset of breathing at birth, neonatal apnea, and sudden infant death.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SummaryCardiovascular changes resulting from continuous distending alveolar pressure during endotracheal intubation (CPAP) and continuous negative pressure (CNP) were studied in two groups of healthy newborn lambs at 6 and 11 mm Hg and ‐6 and ‐11 mm Hg, respectively. Heart rate, left ventricular pressure, and arterial blood gases were unchanged in each group. Cardiac output decreased 16 and 15% at 6 and 11 mm Hg CPAP (P< 0.05), respectively, whereas a fall of 9% occurred at both ‐6 and ‐11 mm Hg CNP (P> 0.05). Central venous pressure (mm Hg) rose from a control value of 7.0 ± 1.4 (mean ± S.E.) to 11 ± 3.1 and 12 ± 2.7 at 6 and 11 mm Hg CPAP (P< 0.025), respectively, and decreased from a control of 7.7 ± 0.7 to 5.8 ± 0.5 at ‐6 mm Hg CNP and 4.8 ± 1.3 at ‐11 mm Hg CNP (P< 0.05). Jugular venous pressure also rose progressively with increasing CPAP (P< 0.05), but was unchanged during CNP. Regional blood flow to the liver fell at both 6 and 11 mm Hg CPAP, whereas renal and gastrointestinal blood flows showed a tendency to decrease at 11 mm Hg CPAP. The removal of CPAP resulted in a prompt return of venous pressure, cardiac output, and regional blood flows to control values. Reductions in blood flows to the gastrointestinal tract at ‐6 mm Hg CNP and spleen at ‐11 mm Hg CNP were observed; blood flows returned toward control values when CNP was removed.SpeculationThe application of continuous distending airway pressure may have potentially deleterious effects on the cardiovascular system of infants with normal or improving lung compliance. The increase in venous pressures that occurs may contribute to the development of intracranial hemorrhage in the neonate.

ISSN:0031-3998    

出版商:OVID    

年代:1981

数据来源: OVID