摘要:

ExtractLitter-mate homozygous and heterozygous weanling rats of the Gunn strain were thirsted and fasted for 24 hours. The response of the animals to thirsting was compared by analysis of solute content of serum and composition of fluid in the renal medullae. The results are given in tables I and II. When the mean values for weight loss and serum solute concentrations were compared, it was found that the jaundiced rats were able to conserve body water as well as the non-jaundiced rats and to generate equally high concentrations of total solute in the tissue water of the renal medulla. Only two of the twelve jaundiced animals showed evidence of failure to develop the expected hypertonicity of the medullary tissue water. This failure was qualitatively similar to that found in adult jaundiced rats. Despite the presence of higher concentrations of bilirubin in serum, the medullary bilirubin content of the jaundiced weanling rat was only 5 % of the concentration found in adult animals. The sodium and urea concentrations in the renal medullary fluid were correlated (pSpeculationIn vitro studies of bilirubin have previously suggested that toxicity is exerted by its surface activity on mitochondrial membranes. The examination of renal function in the intact jaundiced animal has revealed the possibility that tubular transport systems for urea and sodium are impaired in the presence of high concentrations of bilirubin in the renal medulla. These transport systems involve the maintenance of concentration gradients of sodium and urea across tubular epithelium. Bilirubin, through its surface activity, could impair the selective permeability of the membranes involved in urea and sodium transport within the renal medulla.

ISSN:0031-3998    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

ExtractThe neuro-behavioral organization of three groups of infants who differed in their condition at birth as determined by their Apgar score was examined during the first week of life. At the time of testing, all infants, regardless of birth status, were in good condition according to clinical evaluation. Testing consisted of the presentation of 30 lateralized somesthetic stimuli to the perioral region of each infant (15 to each side). The response measure used was the lateral direction of the first head turn. As a group, normal infants (Apgar scores of 9–10) were found to be more responsive to stimulation of the right than of the left, and to make more ipsilateral responses to stimulation of the right than of the left. Infants whose condition at birth was poor (Apgar scores 1–6) did not show these patterns of response but were equally likely to be preponderantly responsive to stimulation at either side. The degree of lateral differentiation was atypically small even for those infants of poor birth status who exhibited the typical direction of differentiation, i. e., who made more ipsilateral responses to stimulation of the right than of the left. Furthermore, the proportion of infants of poor birth status who made any contralateral responses was higher than the proportion of normal infants who made such responses. Results from a group of infants whose condition at birth was questionable (Apgar scores 7–8) fell between those from the extreme groups with respect to all of the analyses.SpeculationPoor condition at birth has persistent effects on behavioral organization even in babies who, in clinical judgment, have recovered normal functioning. To the extent that early behavioral organization may be relevant to the subsequent development of lateral differentiation, these effects could be related to the association between a variety of disabilities and disturbances in lateral differentiation which has been found in older children and adults.

ISSN:0031-3998    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

ExtractA male infant with hyperglycinemia presented with neonatal seizures and lethargy, but had neither ketosis nor hematologic abnormalities. Treatment with a low protein diet and glycine-binding agents was instituted at the age of 2 1/2 months. Although greater alertness and reduced irritability were noted immediately, the treatment failed to prevent severe developmental retardation and persistent seizures.SpeculationThe structural and metabolic basis for the severe neurological damage seen in this rare hereditary metabolic defect is unclear. It seems imperative, however, that prompt diagnosis and therapy be instituted if one expects to offer a better prognosis. Attempts to maintain normoglycmemia by using a low-protein diet and glycine-binding agents may be useful if serum glycine levels are monitored carefully.

ISSN:0031-3998    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

ExtractHyperglycinemia is a disorder of amino acid metabolism characterized by the presence of increased concentrations of glycine in the blood, urine, and cerebrospinal fluid. It is now recognized that there are two forms of hyperglycinemia each representing distinct diseases. These studies were designed to assess the metabolism of glycine in the nonketotic form of hyperglycinemia. Isotope content was assessed in respiratory CO2and in glycine, serine and the β carbon of serine of plasma after the separate intravenous injections of glycine-I-14C and glycine-2-14C.The specific activities of14CO2isolated from expired air after the injection of glycine-1-14C (fig. 2) declined in control subjects from peak values at 10 to 15 minutes in nearly linear fashion over a 2-hour period. In contrast, curves obtained in the patients were rather flat, rising slowly after injection to highest values at about 60 minutes. At 15 minutes, values for the control individuals exceeded those of the patients by a factor of 5− to 10-fold. These data indicate a defect in the formation of14CO2from the first carbon of glycine. When the control subjects were infused with nonisotopic glycine to produce pools comparable to those found in the patient, the specific activities of the serine isolated from plasma after the injection of glycine-1-14C (table II) were virtually the same in both groups. The rate of conversion of glycine-2-14C to serine (fig. 3) in the patients was, however, considerably slower than it was in the control subjects for at least the first 30 minutes, and the curves were flat throughout. Degradation of the serine isolated from plasma and precipitation of the β carbon as formaldemethone indicated that the incorporation of the α carbon of glycine into the β carbon of serine was much higher in the controls than in the patients (fig. 4). The curves for the patients approximated the abscissa indicating virtually no conversion.These data indicate that in nonketotic hyperglycinemia there is a defect in the oxidation of carbon 1 of glycine to CO2and in the conversion of carbon 2 of glycine to carbon 3 of serine. This is consistent with a defect in an enzyme catalyzing the transformation of glycine to CO2, NH3and hydroxymethyltetrahydrofolate.SpeculationThe data obtained indicate that patients with nonketotic hyperglycinemia are unablein vivoto convert the first carbon of glycine directly to CO2and the second carbon of glycine to the third carbon of serine. This is consistent with a genetic defect in an enzyme which catalyzes decarboxylation and formation of hydroxymethyltetrahydrofolate from glycine. It should be possible to document such a defect at a cellular and subcellular level.

ISSN:0031-3998    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

ExtractIncreased activity of the carotid chemoreceptors from hypoxia and hypercarbia, induced by occlusion of the umbilical cord, has importance in initiating effective respiration of the term lamb. The state of hypoxia and hypercarbia continuing after birth should also evoke strong stimulation from the carotid glomi. The present experiments measure the effects on ventilation resulting from interruption of carotid chemoreceptor stimulation to the respiratory center by division of each carotid sinus nerve of the lamb during the newborn period.Ewes were given spinal anesthesia and each lamb was partly removed from the uterus to permit an operative approach through the neck. The carotid sinus nerves were exposed and tagged with loose threads to facilitate division of the nerve at a later stage. The lamb was then delivered, its umbilical cord clamped, and its inspiratory volume measured by pneumotachometric techniques.Each of the seven lambs studied was permitted to establish respiration before its first carotid sinus nerve was divided. The time intervals between birth and division of the first nerves varied from 5.5 to 38.5 minutes after birth. The second nerves were divided several minutes later when respiration had recovered from the effects of division of the first nerve. A significant fall in ventilation was observed within 50 seconds after division of each carotid sinus nerve. Improved ventilation began to occur in some animals 150 seconds later, and occurred in all animals within several minutes after division of each nerve. Levels of PO2pH and PCO2in carotid artery blood before nerve division revealed hypoxia, hypercarbia and acidosis; this aberrant state became worse during the period of diminished ventilation. The minimal changes in heart rate and blood pressure resulting from interruption of baroreceptor fibers were insufficient to influence respiration.SpeculationWhen viewed in conjunction with experiments performed in lambs immediately at birth and with those performed in older newborn lambs, these experiments reveal a continuum of physiologic activity of the carotid chemoreceptors which is important in the establishment and regulation of breathing. The consistent recovery of ventilation after the initial depression produced by division of the second carotid sinus nerve indicates that under these conditions, chemical regulatory mechanisms other than those of the carotid glomi are important in the lamb. The only peripheral chemoreceptors known to be active in the newborn are those in the carotid bodies. Accordingly, some central chemosensor mechanisms must be invoked to explain the recovery of respiration.

ISSN:0031-3998    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

ExtractThis is the first description of the fine structure of the kidney in nephrogenic diabetes insipidus. Striking changes were found throughout the entire kidney. In both proximal and distal tubules, mitochondria contained concentric ringed structures, and many mitochondria had myelin figures associated with their outer membranes as seen in figures 6–13. In figure 9, the intramitochondrial body is seen to be deforming the outer mitochondrial membrane, and in figure 7, it is shown to be continuous with this membrane. Cristae were virtually absent in the areas where the concentric ringed structures are found. There was a disruption of the mitochundrial architecture with formation of the ringed bodies which may be the precursors of the myelin figures. In addition to the tubular changes, the glomerular ultrastructure had a predominately fetal configuration which would seem to be unusual in a seven-month-old infant.SpeculationThe alteration in mitochondrial membranes should be correlated with enzymatic studies in this and other tubular disorders. It might then be ascertained whether these mitochondrial changes can be related to the decrease in content of 3′-5′ cyclic AMP.

ISSN:0031-3998    

出版商:OVID    

年代:1968

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1968

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1968

数据来源: OVID