摘要:

ExtractBy using a standard electroencephalograph and a signal averager, the visual evoked response (VER) to paired and single light flashes was recorded from the midline occipital scalp regions in 24 low birth weight infants, 13 of whom were studied during periods of respiratory difficulty. Eleven of the latter died in the neonatal period. In seven infants, at the onset and during marked hypoxemia caused by prolonged apnea or airway obstruction, the following VER abnormalities occurred alone or in combination: marked decrease in amplitude of summed responses, absent summed response to first stimulus of the paired flash, and absent summed responses to both stimuli of the paired flash. In six infants, complete loss of VER's and a marked decrease in electroencephalogram (EEG) amplitude were associated with severe hypoxemia. In four of the six, VER's returned to normal following resuscitation, indicating that severe bioelectric abnormalities may be reversible as the blood gases return toward normal and before permanent brain damage occurs. Following repeated or severe and prolonged hypoxemia in these same six infants, isoelectric EEG's and absent evoked responses recorded terminally persisted for 30 min–8 hr prior to cessation of heart activity; during the terminal period, resuscitative efforts resulted in improved blood gas measurements in four of the six but without return of the VER. Abnormalities in VER's were not found in other infants with respiratory distress in whom recordings were obtained prior to the onset of severe hypoxemia. or prolonged apneic episodes. Of 10 infants who had neuropathologic examination, intracranial hemorrhage was found in 9 and intracerebral hemorrhage was found in 6. Five of the latter infants had abnormal neonatal VER's. The exact range of blood gas values associated with abnormal VER's could not be determined in our study, although normal responses were noted at Po2values as low as 34, 37, and 38 mm Hg in three infants. Normal VER's obtained in the infants without respiratory disorders were not always associated with normal neurologic examination in later infancy.SpeculationThe management of low birth weight infants with respiratory disorders is limited by the lack of methods which reliably and quantitatively evaluate neonatal cerebral function. Evoked responses to light flashes recorded from scalp EEG in premature infants and summed by signal averagers permit objective measurement of brain electrical activity. In low birth weight infants with respiratory difficulties, abnormal

ISSN:0031-3998    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

ExtractChanges in thein vitrometabolism of subcutaneous adipose tissue have been compared in normal human newborns from 2 hr to 2 weeks of age. A group of healthy adult volunteers was also included. Samples were obtained by using a needle biopsy technique. More of the isotope from14C-(U)-D-glucose was incorporated into triglycerides (P< 0.05) and also oxidized by suspensions of adipose cells from infants 2–3 hr of age than in older infants (P< 0.01). The ratio of radioactivity in carbon dioxide to radioactivity in triglyceride was also significantly greater in 2− to 3-hr-old infants than in older neonates (P< 0.05). Thin layer chromatography of the total lipid extract showed the greatest amount of radioactivity in the triglycerides, a small amount in 1,3-diglycerides and 1,2-diglycerides, and a trace in fatty acids and monogiycerides. These findings were compared with the developmental changes in two key enzymes: phosphofructokinase (PFK), which represents the glycolytic pathway, and β-hydroxyacyl-coenzyme A (CoA) dehydrogenase (HAD), which is involved in the β oxidation of fatty acids. The activity ratio of these enzymes decreased with age. In a preparation of isolated mitochondria, HAD activity increased with age (P< 0.001). These changes in substrate utilization and enzyme activity are consistent with an active metabolism of glucose in the subcutaneous adipose tissue in the first hours of life and relatively greater catabolism of fatty acids in older newborns.SpeculationSubcutaneous adipose tissue of human newborns is in many respects more active metabolically than the same tissue in adults. For example, lipolysis and reesterification seem

ISSN:0031-3998    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

ExtractVariations in the composition of muscle tissue have been studied by neutron activation analysis of microbiopsies in 66 children dehydrated as a result of diarrhea.In the great majority of cases (53 children) no significant potassium depletion was found in muscle.In 23 cases of hypertonic dehydration, muscle tissue showed an important loss of water in 20 cases and a significant increase of sodium content in 20 cases and of chloride content in 15 cases. Hypertonicity of tissular water was observed.In hypotonic dehydration (21 cases), muscle tissue remained normally hydrated and in one-third of all cases, a low sodium and chloride content was found. Hypo-tonicity of tissular water was observed.Analysis of skin tissue, performed in 21 of these children, showed essential differences; in the majority of cases, including those with hypotonic dehydration, there was an important reduction of the water content of skin without any detectable changes in the amount of electrolytes.The differences in behavior of muscle and skin tissues in acute dehydration were confirmed by the study of seven children with hypotonic dehydration at the time of admission and after complete recovery. In those cases, the increase of cutaneous hydration during treatment was not accompanied by any significant variations in the amount of muscle water.The absence of any significant correlation between variations of plasma chloride concentration and the concentration of chloride in skin water confirms the experimental data showing that, in contrast to other tissues,i.e., muscle, the movement of water between plasma and skin is not accompanied by parallel movement of chloride ions.SpeculationThe data presented in this study suggest that skin may be considered as a mobile depot for water which acts as an emergency regulator for the maintenance of water content of tissues that are richer in cells, such as muscle. Hypotonic dehydration represents a good illustration of this statement.Since only 14 of the 66 dehydrated children studied presented a significantly decreased value of muscle potassium, it seems likely that there exists no systematic cellular depletion of potassium in acute dehydration consecutive to diarrhea of short duration.

ISSN:0031-3998    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

ExtractDevelopment of the constrictor response of the ductus arteriosus to O2and selected vasoactive drugs (acetylcholine and bradykinin) was studied in 20 fetal lambs weighing 680–4800 g (90− to 150-day gestation). The isolated ductus arteriosus was perfusedin vitrowith Tyrode's solution at constant flow, temperature (38°), pH (7.3–7.4), and Pco2(30–40 mm Hg), and the mean pressure difference across the ductus was measured. Ductal resistance was calculated at different levels of PO2(10–700 mm Hg), raised stepwise to produce dose-response curves. Three young fetuses failed to respond initially to O2and in the other 17 the initial response occurred at progressively lower PO2levels with advancing gestation. The maximal degree of constriction developed showed a progressive increase with advancing gestational age.At any given PO2, both acetylcholine and bradykinin produced a further increase in resistance when added to the perfusion solution, but this further increase was independent of age. The level of PO2at which an initial response occurred was decreased after exposure to acetylcholine but not bradykinin.SpeculationThe ductus arteriosus of the fetal lamb constricts when exposed to oxygen. The initial level of PO2at which this constriction occurs decreases, and the maximal degree of constriction increases, with advancing gestational age. The poor response to oxygen of the ductus arteriosus in the immature fetus may be the mechanism responsible for the high incidence of patent ductus arteriosus in premature infants. Constriction following-oxygen may be augmented by the exposure to acetylcholine or bradykinin.

ISSN:0031-3998    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

ExtractNormative data for total body potassium on 462 children (232 boys and 230 girls) are presented. The regression of total body potassium on weight can be described as a straight line for males (grams K = 4.32 + 2.12 × weight) and two significantly different lines for females (grams K = −1.50 + 2.32 × weight for weight ≤ 30 kg, and grams K = 34.90 + 1.11 × weight for weight > 30 kg), with less potassium per kilogram for females weighing more than 30 kg. No sex-related difference is found between 12 and 30 kg. When the regression of total body potassium on height is examined, it is found that a logarithmic transformation of potassium values results in a similar pattern, with no sex-related differences between 100 and 135 cm and less potassium per centimeter in females over this height. For males, log K in grams = 1.761 + 0.0182 × cm of height; and for females, log Kin grams = 1.595 + 0.01942 × cm for height ≤ 135 cm, and log K in grams = 2.574 + 0.01215 × cm for height > 135 cm. The logarithmic transformation of Kversusheight is proposed as a standard because it reflects changes in slope associated with known physiologic and endocrinologic changes occurring with puberty and may be more sensitive than weight in predicting abnormal values in individual patients.SpeculationSince the regression of total body potassium on height appears to be a straight line common to both sexes 100–130 cm tall, with a diverging line indicating progressively less potassium per centimeter for females over 135 cm in height, these data were compared with available data for infants. The total body K values of infants between 50 and 80 cm in length appear to fall on a line with a steeper slope than values of children 100 to 135 cm tall. This observation suggests that, during the 1st year of life, increasing total body potassium per centimeter of length reflects maturation of body composition. Further extension of such observations to low birth weight infants might be expected to give information on their body composition.

ISSN:0031-3998    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

ExtractIn vitrostudies were undertaken to measure the effects of varying concentrations of albumin and flux on the photodecomposition of bilirubin.By using an experimental model, the effect of albumin on photodegradation of bilirubin was determined. Synthetic crystalline bilirubin solutions (20 mg/100 ml, pH 7.4) were exposed to the same flux levels for periods of 4.5 hr. The only variable in this series was the concentration of albumin, ranging from 0.5 to 5 g/100 ml. As the the concentration of albumin increased, the reaction rate decreased (Fig. 5).The efficiency of phototherapy was studied by varying flux levels while maintaining other variables constant. Figure 6 shows a nonlinear relation between reaction rate and flux, in which higher flux levels resulted in less decomposition per amount of flux (i.e., efficiency). More than twice the flux level was required to attain a twofold increase in decomposition rate. The effect of light flux was such that continuous use of the lowest practical level is to be recommended.Data are given on the comparison of therelativeeffectiveness of cool white, high intensity blue, and two experimental lamps. The four lamps were tested at conditions of constant distance and constant flux. The high intensity blue lamp was twice as effective as the cool white. The two experimental lamps showed a 17% increase over the blue lamp (Figs. 2 and 3).The effect of time on the spectral output of the fluorescent lamps in an experimental model was determined by using a spectral radiometer. The energy dropoff within the 420− to 480-nm region at 200 hr was approximately 20% for blue lamps and averaged 7.5% for the experimental lamps.SpeculationAs with any new drug used on the neonate, the effects of phototherapy must be categorized, and the procedure must be standardized. Further investigations are needed to determine exactin vivodecomposition products, optimal timing of exposure, differences in skin attenuation, toxicity reactions, site of action, and photobiologic and photochemical alterations and interreactions.

ISSN:0031-3998    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

ExtractThe excretion of15N in the urine following the oral administration of compounds labeled with15N was evaluated in an infant with congenital hyperammonemia while the infant was receiving a low protein diet. When she received either15N-glycine or15NH4Cl, the ratio of [15N-NH3] to [15N-urea] in urine was strikingly elevated with respect to [15N-NH3]/[15N-urea] found in studies of other infants receiving high protein diets. However, reduction of the protein in the diet of the control infants resulted in elevation of the ratio of [15N-NH3] to [15N-urea] in urine after the administration of15N-glycine or15NH4Cl. No mode of metabolism specific for congenital hyperammonemia was demonstrated in the studies of orally administered15NH4Cl. In the metabolism of15N-glycine, the hyperammonemic infant receiving a low protein diet was different from other infants on both high and low protein diets.In the hyperammonemic infant,15N-urea was much more readily formed from15N-citrulline than from15NH4Cl. On the other hand, the addition of unlabeled citrulline to the diet of this infant did not enhance the synthesis of15N-urea from ingested15NH4Cl when compared with the addition of unlabeled ornithine-HCl to the diet.SpeculationThe data presented lead to the conjecture that inborn errors of ammonia detoxification which result in clinical disease in surviving patients are “partial” defects, and that “complete” defects in ammonia detoxification are so rapidly lethal as to be seldom recognized clinically.

ISSN:0031-3998    

出版商:OVID    

年代:1972

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1972

数据来源: OVID