摘要:

We studied the activity of the diaphragm and of the genioglossus at the onset and at the end of obstructive sleep apnea in children. Seven children (mean age 46 months, range 15–87) with obstructive sleep apneas mainly due to enlarged tonsils were tested during natural sleep. We recorded sleep stages (neurophysiological criteria), nasal and buccal air flow (thermistors), thoracoabdominal motion (magnetometers), genioglossus and diaphragm electromyographic activity (EMG) (surface electrodes), and transcutaneous partial pressure of oxygen (Radiometer 44° C). A total of 153 obstructive apneas for the whole group of patients was studied. Compared to the preceding unoccluded breaths, genioglossus and diaphragm EMG data showed that 1) at the onset of obstructive apnea there was no significant decrease in genioglossus and/or diaphragm EMG, contrasting with published data for obese adults, and 2) at the end of obstructive apnea, significant preferential increase in genioglossus EMG, not related to the decrease in transcutaneous partial pressure of oxygen, was found as in obese adults. This study showed that different mechanisms may control the onset of obstructive apnea in children as compared to adults, whereas children and obese adults share the same preferential increase in genioglossus EMG at the end of obstructive apnea.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

The placenta supplies many nutrients to the fetus, including amino acids by active transport. Although the exact regulatory mechanism is unknown, a few studies have suggested a role for calcium in amino acid transport. Therefore, we examined the relationship between calcium and amino acid uptake by term human placental slices. Calcium depletion of slices significantly reduced uptake of α-aminoisobutyric (AIB), which is actively transported primarily by a sodium-dependent, carrier-mediated mechanism. Impairment of AIB uptake induced by calcium depletion was reversed by repletion with calcium but not with other divalent cations. In contrast, uptake of phenylalanine, which is transported primarily by a sodium-independent mechanism, was not affected by calcium depletion. Uptake of leucine and valine, which accumulate by both sodium-dependent and independent mechanisms, was partially affected by calcium depletion. Verapamil (10 μM), an inhibitor of transmembrane calcium flux, significantly reduced AIB uptake. Trifluoperazine, a calmodulin antagonist, also inhibited AIB uptake. Analysis of AIB uptake kinetic constants for control and calcium-depleted slices showed no change in the diffusion constant, a 37% reduction in Vmax, and a 2-fold increase in Km. The results indicate that calcium may be an important factor in the cellular regulation of active transport of amino acids.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

We evaluated the formation of specific and functional antibody in preterm infants born weighing less than 1500 g (mean 1088 g) and less than 32 wk gestational age (mean 28.8 wk). Plasma IgG antibody against tetanus and diphtheria toxoids were measured by an enzyme-linked immunosorbent assay. Opsonic activity of heat-inactivated plasma was measured using radiolabeled bacteria, adult polymorphonuclear leukocytes and exogenous human complement. In the presence of complement, the strain of coagulase negative staphylococcus used was opsonized by IgG antibody, and the strain ofEscherichia coliby IgM. Geometric mean plasma levels of tetanus and diphtheria IgG antibody fell from birth to 4 months chronological age, but rose significantly by 9 months (approximately 2 months after the third dose of diphtheria, tetanus, pertussis vaccine). However, at 9 months they remained lower than the respective geometric mean levels in 9-month-old term infants (tetanus:p< 0.001; diphtheria:p= 0.02). The preterm infants' mean plasma IgG staphylococcal opsonic activity fell from birth to 2.5 months, but by 9 months was comparable to that of term infants of the same age. Mean IgM opsonic activity forE. coliwas very low at birth in both preterm and term infants. It rose with chronological age, correlating with the rise in total IgM (r= 0.48,p< 0.001) and by 9 months the mean preterm and term infants' levels of IgM opsonic activity forE. coliwere comparable. In the newborn period, the preterm infants' levels of plasma IgG tetanus and diphtheria antibody, but not IgG staphylococcal opsonic activity, correlated with their mothers' levels (tetanus:r= 0.84,p< 0.001; diphtheria:r= 0.86,p< 0.001; staphylococcal:r= 0.17,p= 0.38). Placentally transferred maternal tetanus, diphtheria, and opsonic staphylococcal IgG antibody did not inhibit the infants' subsequent antibody responses to the respective antigens. We conclude that the ability of preterm infants to form specific and functional antibody may place them at lower risk for infection than might be expected from their very low plasma levels of total IgG and IgM antibodies. In addition, the good correlation between newborn and maternal plasma levels of IgG antibody to tetanus and diphtheria toxoids, but not IgG-dependent staphylococcal opsonic activity, suggests preferential transport of some IgG antibodies across the placenta or, alternatively, that the function of some IgG antibodies may be impaired by placental transport.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Chloroform:methanol extracts of bovine pulmonary surfactant contain small hydrophobic proteins, designated surfactant-associated apoproteins 6,000 (SAP-6), but do not contain the major surfactant-associated 35,000-dalton glycoprotein, designated SAP-35. Examination of lipid extract surfactant on sodium dodecylsulfatepolyacrylamide gel electrophoresis revealed hydrophobic proteins with apparent molecular masses of 15,000, 7,000, and 3,500 daltons prior to reduction. After reduction, the 15,000-dalton species largely disappeared and was replaced by a 5,000-dalton species. In addition, the 7000-and 3500-dalton species exhibited a slightly enhanced mobility. Amino acid analysis demonstrated that SAP-6 possesses a more highly hydrophobic profile than SAP-35. Combining the protein-containing fractions from silicic acid chromatography of lipid extract with synthetic dipalmitoylphosphatidylcholine produced a reconstituted surfactant preparation which was just as active as lipid extract surfactant on a pulsating bubble surfactometer. The reconstituted surfactant contained SAP-6 but not SAP-35. Pressure-volume studies revealed that, at the optimal dose, reconstituted surfactant containing half the SAP-6 concentration of lipid extract exhibited similar effectiveness to lipid extract surfactant in promoting lung expansion with prematurely delivered rabbit fetuses of 27 days gestation. Reconstituted surfactant with an identical SAP-6 protein concentration as lipid extract possessed the same biological properties as the preparation with 1% SAP-6 protein. These studies support the view that an artificial surfactant composed of synthetic or semisynthetic lipids plus human SAP-6 produced via biotechnology could be useful for prevention and/or treatment of the neonatal respiratory distress syndrome.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

The functional activity of naturally acquired IgG and IgM with specificity for the capsular polysaccharide of type III, group B Streptococcus (III-GBS) was compared. Sera collected during convalescence from 14 infants who had developed specific antibodies following III-GBS infection were employed for separation of IgG from IgM by ion-exchange chromatography. Bactericidal killing of III-GBS was similar for IgG- and IgM-rich samples (37 and 42%, respectively) in reactions containing a mean of 1.0 or 1.9 μg/ml of III-GBS specific IgG or IgM antibody. Purified IgA lacked opsonophagocytic activity for III-GBS. These results indicate that III-GBS-specific IgG and IgM antibodies in infant sera promote opsonophagocytosis at low concentrations, and that their functional capacity is comparable.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

We studied the effect of 8-wk dietary taurine depletion on the vulnerability to hypernatremic dehydration in postweanling kittens. While experimental taurine depletion was not associated with increased susceptibility to acute hypernatremia (1.5 M NaCl/NaHCO3, 35 ml/kg body weight, single injection), there was an increase in mortality (five of sevenversusone of seven,p= 0.05) and seizure activity (three of sevenversusnone of seven,p= 0.08) in taurine-depleted compared to taurine-replete kittens rendered chronically hypernatremic over 96 h. Furthermore, there was a significant decrease in brain cell water (517.4 ± 21.7versus671.6 ± 32.3 ml/100 g fat-free dry weight,p< 0.05), derived almost exclusively from the intracellular compartment (352.5 ± 12.3versus483.8 ± 34.6 ml/100 g fat-free dry weight,p< 0.05) that correlated with the reduction in the cerebral taurine content in the taurine-depletedversuscontrol kittens during chronic hypernatremic dehydration. These results suggest that taurine is an important cerebral osmoprotective molecule. This aminoacid constitutes nearly 50% of the adaptable intracellular osmolal pool whose concentration varies in the course of osmoregulating in response to perturbations in the extracellular fluid tonicity.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Transamination and oxidative decarboxylation of branched-chain L-amino acid derived 2-oxo acids in cultured human skin fibroblasts from normal subjects and from a patient with maple syrup urine disease (variant form) were comparatively studied in incubations with 1-14C-labeled substrates (1 mmol/liter). With normal cells,14CO2release ranged from about 11 to 3 nmol/90 min/mg of cell protein in the order 3-methyl-2-oxo[14C]butanoate > (S)-3-methyl-2-oxo[14C]pentanoate > 4-methyl-2-oxo[14C]pentanoate > (R)-3-methyl-2-oxo[14C]pentanoate. Formation of the corresponding branched-chain amino[14C] acids was substantially higher than14CO2production (around 10-fold) and similar with L-valine, L-isoleucine, and L-leucine. L-Allo-isoleucine production [from (R)-3-methyl-2-oxopentanoate] was significantly lower. With maple syrup urine disease fibroblasts, comparable transamination rates were observed. Related to the findings with normal cells,14CO2release from each substrate was differently reduced and apparent residual branched-chain 2-oxo acid dehydrogenase complex activity with 3-methyl-2-oxobutanoate, 4-methyl-2-oxopentanoate, (S)-, and (R)-3-methyl-2-oxopentanoate amounted to 12, 13, 22, and 50%, respectively.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

During the last half of pregnancy, the fetal guinea pig grows exponentially at 7.1%/day. In order to define the metabolic requirements of the gravid uterus during this period of rapid growth, catheters were placed in the femoral artery and uterine vein of guinea pigs at gestational ages ranging from 40 days to term (68 days). The animals were studied in the unstressed state after full recovery from surgery and anesthesia. Arterial and venous concentrations of oxygen, glucose, lactate, acetoacetate,β-hydroxybutyrate, and acetate were measured, and metabolic quotients and coefficients of extraction were calculated. The glucose/oxygen quotient did not change significantly in the last half of pregnancy averaging 1.26, while the lactate/oxygen quotient remained unchanged at −0.42, and the (glucose + lactate)/oxygen quotient remained unchanged at 0.82. Coefficients of extraction of glucose and oxygen increased linearly with gestational age. The increase in supply of substrates for the rapid growth of the conceptus toward the end of gestation is accounted for by increasing extraction of substrate and by greatly increasing blood flow with increasing gestation. While glucose remains the major metabolic fuel of the guinea pig conceptus and acetate is consistently taken up by the uterus, these substrates alone cannot account for the metabolic fate of the oxygen taken up and fall far short of the predicted nutritional requirements of the fetus for both oxidative metabolism and growth.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

We assessed thein vivoandin vitroeffects of antibiotics and tin-protoporphyrin (TP) on intestinal heme oxygenase (HO) activity using a gas chromatographic assay. This method measures the carbon monoxide produced from heme in the presence of NADPH. Afterin vivoadministration of kanamycin (10 mg/kg body weight), ampicillin (200 mg/kg body weight) or neomycin (60 mg/kg body weight) with or without TP (65 μmol/kg body weight) to suckling rats, no significant difference in HO activity along the small intestine was observed.In vitroexposure of adult rat intestinal preparations to the antibiotics showed no significant decrease in HO activity between control and experimental tissue preparations. A concentration-dependent stimulatory effect of neomycin was observed. Subcutaneous administration of TP (25 μmol/kg body weight) to adult male Wistar rats revealed no significant inhibition of the intestine. However,in vitroaddition of TP (12.5 μM) to the control tissue preparations of adult Wistar rats revealed highly significant inhibition in liver and spleen when compared to the unexposed control tissues. In contrast, when TP was added to control intestinal preparations no inhibition was observed. These findings suggest that suckling rat intestinal heme oxygenase is not inhibited byin vivotreatment with high concentrations of kanamycin, ampicillin, or neomycin. Furthermore, these antibiotics are notin vitroinhibitors of adult rat intestinal HO. Finally, adult rat intestinal HO is not inhibited eitherin vivoorin vitroby a concentration of TP that significantly inhibits liver and spleen activity.

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID