摘要:

This investigation was designed to study specific glucocorticoid binding to cytoplasmic fraction and nuclei of thymus cells during rat development and to find out whether these data can be correlated to changes of RNA synthesizing activity of nuclei and cytoplasm. The dexamethasone binding capacity of cytoplasm rose rapidly in rats weighing up to 125 g and decreased significantly in animals weighing more than 160 g. Hormone binding to nuclei revealed similar but less pronounced changes. RNA synthesizing activity of nuclei measured by [3H]uridine incorporationin vitrodecreased from 57 ± 4.6 dpm/μg DNA in young to 23 ± 2.2 dpm/μg DNA in adult rats. RNA synthesizing activity of the cytoplasmic fraction fell 21.6% and that of purified polymerase IIIBfell 27.8% during development. Inhibition of RNA synthesis by dexamethasone appliedin vivoandin vitroshowed age-dependent differences. The RNA synthesizing capacity of nuclei was inhibited up to 39% in animals weighing 130 g and only 9% in aging rats. Similar changes were observed by incubation of intact thymocytes with and without hormone. The observed inhibitory effect of dexamethasone on RNA synthesis is well correlated to changes of cytoplasmic hormone receptor capacities during development.SpeculationIf the observations on developmental changes of hormone binding capacities and on age-dependent responses of thymus cells to glucocorticoid action can be applied in general, it is not the hormone itself, but the receptor concentration which seems to be the limiting factor for the cellular response to the hormone action. Therefore, efforts should be made to find ways to induce synthesis of these receptor proteins.

ISSN:0031-3998    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

Not principally different from the results obtained in more mature subjects, monosynaptic reflex excitability of spinal motoneurones in preterm infants decreases during active sleep. However, in preterm infants the electric reflex response is not abolished, and is not even continuously depressed during the entire active sleep period. Spinal motoneurone inhibition is demonstrable only during certain periods of active sleep, and it is during this state of decreased spinal motoneurone excitability when apneic spells predominantly occur.SpeculationThe concept of apneic spells being promoted by rapid eye movement (REM) sleep brain mechanisms, as outlined by Gabrielel al.(10) and supported by data of this study, can so far mainly explain respiratory pauses in otherwise healthy preterm infants. However, in neonatal sepsis, meningitis, hypoxia, hypoglycemia, etc., the same central nervous system inhibitory processes should increase the risk of apneic spells, provided that active sleep states still exist. Furthermore, Bryan and Bryan (2) have demonstrated a considerable thoracic wall instability during active sleep, which is probably also due to inhibition of spinal motoneurones innervating intercostal muscles. Thus, when respiratory brain stem centers are partly damaged, tonic spinal motoneurone inhibition during active sleep can additionally increase the infant's difficulty in maintaining sufficient respiration.

ISSN:0031-3998    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

Phosphatidylglycerol (PG) was absent from lung effluent in 41 infants with respiratory distress syndrome of the newborn (RDS), whereas effluent from healthy control subjects of similar gestational age contained this phospholipid (4.9 ± 2.4% of lipid-phosphorus (P),n= 32). Control infants of 28 weeks of gestation or less with various respiratory disturbances other than RDS also had low PG (0.2 ± 0.2% of lipid-P,n= 5). In RDS surfactant complex often could be isolated from the airways using differential and density gradient centrifugation. The material thus obtained had prominent phosphatidylinositol (PI) (13.6 ± 2.8% of lipid-P,n= 6), but no PG. Of those 18 infants who had such surfactant even in the early stages of RDS, 13 were 35 weeks of gestation or more, 3 were offspring of diabetic mothers, and 2 had severe perinatal asphyxia. In healthy control subjects PG sometimes appeared first within an hour of birth, but in RDS PG did not appear until recovery from RDS.In RDS type II (transient tachypnea of the newborn) PG in lung effluent also was abnormally low (1.3 ± 0.6% of lipid-P, n = 5) and PI was correspondingly prominent (9.7 ± 3.6% of lipid-P,n= 5), indicating immaturity of surfactant similar to RDS.Surfactant with PG and PI has superior surface-active properties compared to that containing PI, but no PG. Surfactant without PG does not seem to stabilize the alveoli of the newborn as well as does surfactant with PG. The failure of PG appearance following birth therefore may precipitate RDS, especially beyond 35 weeks of gestation.SpeculationPre- and postnatal monitoring of the acidic phospholipids, PG and PI, in lung effluent is useful in diagnosis and follow-up of RDS as well as in evaluation of various therapies.

ISSN:0031-3998    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

The production of14CO2from glutamate and alanine studied in the newborn rat after injection of labeled precursors was intense and revealed an important catabolism from 130 nmol/hr in a 0-hr neonate to 2000 nmol/hr in 3-week-oId rat. The degradative metabolism of leucine was low at birth (10 nmol/hr), but increased up to 500 nmol/hr in 3-week-old rat. Phenylalanine was practically not metabolized into CO2, but its incorporation into protein was higher than leucine, alanine, and glutamate incorporation. Glucose is the major fuel utilized by newborn rat for its energy supply (300–560 nmol/hr). However, the relative part of amino acids in energy production is important in the early neonate (0 and 1 hr after birth).SpeculationIn the early newborn rat, the important oxidative metabolism of amino acids (before phosphoenolpyruvate carboxykinase (PEPCK) biosynthesis and gluconeogenesis activation) indicates that they may be directly utilized for energy requirements. This amino acid oxidation could be considered as a transient energetic pathway in species showing a delayed development of PEPCK activity (e.g., the human neonate).

ISSN:0031-3998    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

The fatty acid chains of lecithin, phosphatidyl ethanolamine (PE), and phosphatidyl dimethylethanolamine (PDME) in human neonatal alveolar washes were analyzed. Both α- and β-palmitic acid increased with gestational age on all phospholipids analyzed. No evidence for high concentrations of myristic acid was found on any phospholipid.Babies who were stillborn or who had died of hyaline membrane disease (HMD) had lower proportions of β-lecithin palmitic acid when compared with babies who breathed normally before death. In the HMD group these levels were significantly lower.SpeculationThe fatty acid chains of the phospholipids in lung surfactant probably influence the degree of surface activity of the phospho-

ISSN:0031-3998    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

Thirty pregnant mice were undernourished by providing low protein diets (PM) or providing approximately one-third their normal diets (PCM) for 9 days from the 8th to the 16th day of gestation. Another 15 pregnant mice, which were fed a normal diet, served as the control. On the 16th day of gestation, all animals were injected with a single dose of [3H]thymidine and were killed one by one at 1− or 2-hr intervals.Mean litter size was statistically insignificant between the control group and two malnourished groups. There was, however, a significant difference in mean body weight between the control group and two malnourished groups (P< 0.005). The cerebral cortex at this stage of development consisted of three different layers,i.e., the cortical plate, the migratory zone, and the matrix layer. The width of the cortical plate of the malnourished embryos was significantly smaller (P< 0.001). There was, however, no significant difference in width of the migratory zone between the control and the malnourished groups. The width of the matrix layer in PM was significantly smaller (P< 0.001), but that of PCM showed no significant difference from the control (P> 0.1).Coronal section of the brains of the embryos were processed for autoradiography. Labeled cells were found almost exclusively at the matrix layer surrounding the lateral ventricels. Labeling index counted in the matrix layer after 1 or 2 hr of [3H]thymidine injection indicated that more than 30% of the cells in this layer were always synthesizing DNA in each group of embryos. The generation times of the matrix cell, precursor of the neurons, in the matrix layer were approximately 18.5 hr in the control and 21.5 hr and 21.8 hr in the malnourished embryos, thus indicating about 3 hr of prolongation in the latter. DNA synthetic time was about 6.5 hr in the control and 7.0 hr and 7.0 hr in the two malnourished groups. The postduplication time was about 2.5 hr in the control and 3.0 hr and 3.5 hr in the malnourished. The preduplication time was about 8.8 hr in the control and 10.6 hr and 10.3 hr in the malnourished.SpeculationMost neurons in the mouse cerebrum are produced at the matrix layer, where active cellular proliferation takes place from the 10th to the 16th days of gestation. Malnutrition during this period caused about 14% prolongation of the generation time of the matrix cell, the precursor of neurons, thus causing a decrease in neuron production. Malnutrition during the first and second trimester may cause similar results in the human embryo.

ISSN:0031-3998    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

A defect in chemotaxis of peripheral blood polymorphonuclear leukocytes (PMN's) was demonstrated in both parents and three of four children in a single family afflicted with varying degrees of respiratory allergy, unusual onset of severe eczema in the first month of life, and recurrent bacterial skin infections. Of great interest was the identification of HLA-B12 at the B locus in all affected members but not in the unaffected child. The two children known since infancy to be most severely affected with eczema and recurrent infections are HLA identical and homozygous for HLA-B12. The child without eczema and infections had an intermediate cellular chemotactic defect most apparent on kinetic studies.SpeculationRecently, several familial defects of neutrophil chemotaxis have been reported in association with syndromes of recurrent bacterial infections, reaginic hypersensitivity, and/or clinical atopy. Our studies extend these observations by describing the possible genetic relationships between atopy (e.g., eczema) chemotactic defects, and the HLA system. Future studies in this field should examine the association between chemotactic defects and the HLA system, and the requirements of both atopy and chemotactic defects to produce recurrent infections.

ISSN:0031-3998    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

Percutaneous absorption of testosterone was determined in newborn rhesus monkeys, an animal model which is relevant to man. Mean percentage of absorptions of 4 and 40 μg/cm2in the newborn were, respectively, 22.5 ± 2.2 (SD) and 6.8 ± 2.1. Statistical comparisons (Student'st-test) of these results with those obtained with adults show no significant difference (P> 0.05) in skin penetration of testosterone in newborn and adult rhesus monkeys. In the newborn, the efficiency of absorption (percentage) decreased when the topical dose was increased 10-fold. However, the total compound absorbed per cm2 area of skin actually increased from 0.9 to 2.7 μg.With one other newborn rhesus, a topical dose of 40 μg/cm2was applied to the ventral forearm and the area was occluded for 24 hr. Percutaneous absorption was 14.7%, a value twice that from nonoccluded absorption.Systemic absorption from a topical dose becomes critical in the newborn because the ratio of surface area (cm2) to body weight (kilograms) in the newborn is 3 times that in the adult. Given equal application area of skin per newborn and adult, the systemic absorption in the newborn becomes 3 times that of the adult when based on kilograms body weight. With a different ratio of skin surface to body weight, the therapeutic ratio probably is lower in the newborn than in the adult when the compound is applied topically.SpeculationA high percentage of a steroid compound can be absorbed through the skin of a newborn as well as an adult. The systemic availability of a drug to the newborn following topical application can be 3 times that of the adult, per unit of body weight.

ISSN:0031-3998    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

The mean ± SEM of the cord, 48-hr, and 7-day values for scrum calcium, magnesium, human calcitonin (HCT), parathyroid hormone (PTH), and 25-hydroxy-vitamin D (25-OHD) for premature and term infants can be seen in Table 1. Mean cord calcium concentrations were similar for term and premature infants. Serum calcium concentrations fell in both term and premature infants at 48 hr, but decreased more in the premature infants (from 10.23 ± 0.30 to 8.74 ± 0.19 mg/dl) than in the term infants (from 10.5 ± 0.26 to 9.6 ± 0.23 mg/dl). Serum calcium values increased from 48 hr to 7 days in both groups, and there was no significant difference between term and premature infants' serum calcium concentrations (10.6 ± 0.28 and 10.12 ± 0.3 mg/dl, respectively) at that time. There was no significant difference between term and premature cord scrum magnesium concentrations. Serum magnesium concentrations increased similarly by 48 hr in both groups and remained at these concentrations at 7 days of life. Serum HCT concentrations were elevated above normal adult levels (71.9 ± 6.6 pg/ml,

ISSN:0031-3998    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

Blood was collected from the umbilical cords of infants with a 1-min Apgar score of 9 or 10. Total cord serum lipoproteins were isolated by ultracentrifugation, at a density of 1.220 g/ml. The isolated serum lipoproteins were then separated by gel filtration chromatography on 6% agarose. The overall recovery of the separated lipoprotein cholesterol was 90% or greater. In cord serum, four lipoprotein peaks were found, whereas three peaks were present in adult lipoproteins. The major lipoproteins of cord serum correspond to low density lipoprotein (LDL) and high density lipoprotein (HDL). Very low density lipoproteins (VLDL) were heterogeneous in cord serum. After gel filtration chromatography, the distribution of cord serum cholesterol is about 5% in peak 1, 10% in peak 2, 40% in peak 3 (LDL), and 45% in peak 4 (HDL). An additional difference between the lipoproteins isolated from cord serum and those from adult serum was the slower electrophoretic mobility of cord serum VLDL in agarose gel.SpeculationThe fetus, during the later stages of pregnancy, accumulates fat at an accelerating rate. Triglycerides, synthesized by the liver, are secreted as VLDL and transported to adipose tissue for degradation, probably by lipoprotein lipase.The heterogeneity of cord blood VLDL and the presence of a significant amount of an intermediate lipoprotein fraction (designated peak 2) may be related to a partial metabolic block in the conversion of VLDL lipoproteins to smaller lipoproteins such as LDL.

ISSN:0031-3998    

出版商:OVID    

年代:1977

数据来源: OVID