摘要:

To determine the influence of maternal smoking on autonomic nervous system in healthy infants, 36 infants were recorded polygraphically for one night. Their mothers were defined, according to their smoking frequency during pregnancy, as “nonsmokers” (no cigarettes smoked during pregnancy) or “smokers” (10 or more cigarettes per day). The infants had a median postnatal age of 10.5 wk (range 6 to 16 wk); 18 were born to nonsmokers, and 18 to smokers. During the whole night, spectral analyses of heart rate (HR) were evaluated as a function of sleep stages. Two major peaks were recognizable: a low-frequency component (LF) related to sympathetic and parasympathetic activities and a high-frequency component (HF) reflecting parasympathetic tonus. The ratio of LF/HF powers was calculated as an index of sympathovagal interaction. In REM sleep, “smokers” infants were characterized by significantly lower HF powers and normalized HF powers, and higher LF/HF ratios than “nonsmokers.” The finding did not reach statistical significance in NREM sleep. In conclusion, maternal smoking induced changes in autonomic control and maturation in infants. These effects of cigarette smoke exposure can be added to those already reported and offer additional evidence for counseling mothers to stop smoking.

ISSN:0031-3998    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Previous studies have shown that plasma lipoproteins are a common target of free radical-induced oxidative stress in hypoxic newborn infants. In contrast to lipids, the reaction of proteins with various oxidants during hypoxia has not been extensively studied. We tested the hypothesis that tissue hypoxia results in increased production of protein oxidation in cord blood of preterm newborns. Heparinized blood samples of 39 hypoxic and 16 control preterm newborns were obtained from the umbilical vein, after cord clamping immediately after delivery. Plasma levels of total hydroperoxide (TH), advanced oxidation protein products (AOPP), hypoxanthine (Hx), xanthine (Xa), and uric acid (UA) were measured. Higher Hx, Xa, UA, TH, and AOPP levels were found in hypoxic newborn infants than in controls. Statistically significant correlations were observed between: TH and Hx (r= 0.54,p= 0.003,n= 28), AOPP and Hx (r= 0.64,p= 0.0001,n= 27), and TH and AOPP plasma levels (r= 0.50,p= 0.02,n= 21). In summary, TH, AOPP, Hx, Xa, and UA production is increased in fetal blood during hypoxia. The more severe the hypoxia, the higher the lipid and protein damage by free radicals.

ISSN:0031-3998    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Bronchopulmonary dysplasia (BPD) is recognized as an important cause of morbidity and mortality in preterm infants. Because the role of congenital infections in BPD has been debated, the purpose of this study was to test the hypothesis that detection of infectious agents in tracheal aspirate samples was associated with the development of BPD. Tracheal aspirate samples were obtained within the 1st week of life and screened by polymerase chain reaction for adenovirus, cytomegalovirus, parvovirus, enteroviruses,Ureaplasma urealyticum, Mycoplasma hominis, Mycoplasma pneumoniae, andChlamydiaspecies. BPD was defined as persistent oxygen dependence at 28 d of age and 36 wk postconceptional age (PCA). Infants that expired before these time points were excluded from statistical analysis. Out of 89 infants studied, at 28 d of life, 13 had expired, 45 had BPD, and 31 had no BPD (controls). At 36 wk PCA, 15 infants expired, 39 still had BPD, and 35 did not. A significant increase in the frequency of adenovirus genome was identified in BPD patients compared with controls, both at 28 d of life (12/45 = 27%versus1/31 = 3%:p≤ 0.01) and at 36 wk PCA (10/39 = 29%versus2/35 = 6%:p= 0.01). Other microorganisms were rarely detected and not associated with the development of BPD. This is the first study reporting the frequency of detection of adenovirus DNA in tracheal aspirate samples obtained during the 1st week of life from infants with BPD and suggests that prenatal acquisition may be important in the development of BPD.

ISSN:0031-3998    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

To determine if alterations in arterial pressure influenced fetal heart rate variability (HRV), experiments were carried out in chronically catheterized fetal sheep aged 128–138 d. Arterial pressure was raised or lowered by intravenous infusion of phenylephrine or sodium nitroprusside, and the effects on heart rate (HR) and HRV were measured (HRV, as the coefficient of variation (CV) in mean pulse interval or by power spectral analysis). Experiments were carried out before and during &bgr;-adrenoceptor blockade with propranolol or before and during cardiac vagal blockade with atropine. There were positive relationships between mean arterial pressure and HRV (slope = 0.074 ± 0.001,r= 0.81 ± 0.06,p< 0.001, measured as the CV of pulse interval) and between mean arterial pressure and power spectral density (slope = 4 ± 0.5,r= 0.89 ± 0.02,p< 0.001) in the frequency range 0.04–0.08 Hz. &bgr;-adrenoceptor blockade had no effect on these relationships, but they were abolished by cardiac vagal blockade. The sigmoid relationship between fetal HR and mean arterial pressure,i.e.the cardiac baroreflex, was affected, however, by blockade of cardiac sympathetics and abolished by blockade of cardiac vagal activity. Thus, fetal HRV was affected by alterations in arterial pressure, and these effects depended on the integrity of the cardiac vagus, not on alterations in cardiac sympathetic activity. Therefore, although baroreflex control of fetal HR depends on the integrity of both sympathetic and parasympathetic efferent pathways, baroreceptor-induced changes in HRV depend only on the cardiac vagus.

ISSN:0031-3998    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

In an acute lung injury model, we previously observed reversal of pulmonary dysfunction with natural surfactant administered by lavage (dose = 18 mg/kg phospholipid). The present study questioned whether a lower dose of phospholipid would be effective if a recombinant preparation rather than natural surfactant were used. Acute lung injury was induced by repeated saline lung lavage in ventilated, sedated, and paralyzed piglets. Three concentrations of recombinant surfactant were studied (low phospholipid, 1 mg/mL; medium phospholipid, 4 mg/mL; high phospholipid, 13.5 mg/mL). Control piglets received no surfactant. Thirty-five milliliters per kilogram of surfactant was administered by gravity, followed by passive drainage of excess fluid. All treatment groups retained similar volumes (4.7 ± 0.3 mL/kg), corresponding to phospholipid doses of 4 ± 0.4, 22 ± 3, and 67 ± 4 mg/kg in low, medium, and high-dose groups, respectively. Treatment groups showed significant improvement in PaO2compared with controls. Other parameters different from controls were found in only the medium and high-dose groups. All surfactant-treated groups showed improvement over time in PaO2, PaCO2, lung resistance,mean airway pressure, functional residual capacity, and dynamic compliance.These data support the statement that whereas there is a dose response to exogenous surfactant, the effective dose of recombinant surfactant in acute lung injury may be as low as 4 mg/kg phospholipid when administered by lavage.

ISSN:0031-3998    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Previous studies have shown the immunoregulatory functions IL-4 in type 1 diabetes mellitus. Therefore, the genes involved in the IL-4 regulatory pathway are candidates for diabetes susceptibility genes. Here we have evaluatedIL4and the alpha subunit of the IL-4 receptor (IL4R&agr;) genes using the affected sibpair (ASP) and transmission/disequilibrium test (TDT). We analyzed 309 diabetic families from the United States and 87 families from various European countries. There was no evidence that either of these two genes are linked or associated with type 1 diabetes. Means by which IL-4 directed signals could indirectly alter diabetes susceptibility are proposed.

ISSN:0031-3998    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

In neonatal rats, expression of serine protease inhibitors 2.1 and 2.3 mRNA peaks on d 2 of life and declines shortly thereafter, coinciding with levels of circulating GH. To evaluate the role of GH in this increase and to test the hypothesis that GH is active in perinatal life, we studied GH action in a model of GH deficiency. Maternal/neonatal hypothyroidism with consequent GH deficiency was induced by methimazole administration to pregnant dams. The resultant hypothyroid neonates were treated at d 2 or 7 of age with GH or saline for 1 h before exsanguination. In d-7 neonates, but not at d 2, GH administration resulted in significant serine protease inhibitors 2.1 and 2.3 mRNA induction. This treatment did not result in increased production of either GH receptor or IGF-I mRNA at either age. There was a slight GH-independent increase in GH receptor and IGF-I mRNA expression by d 7. Electromobility shift assays using hepatic nuclear extracts from these neonates and the GH response element from the serine protease inhibitor 2.1 promoter showed signal transducer and activator of transcription 5 (Stat5) binding in response to GH in extracts from d-7 rats only. Immunoblots of these extracts showed twice as much Stat5 in the nuclei of d-7 treated neonates compared with d-2 treated neonates. We conclude that there is apparent insensitivity to GH treatment in d-2 neonates that remits by d 7 and that this remission correlates with increased abundance of GH receptor and Stat5.

ISSN:0031-3998    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

In periodic breathing, there are repeated cycles of bursts of breaths separated by pauses several seconds long. We consider the mechanics of periodic breathing in human infants using calibrated traces of tidal volume and esophageal pressure recorded during the first few days after delivery. Each cycle of periodic breathing was analyzed in terms of the inspiratory time and beginning and end inspiratory volumes for each breath, the number of breaths in the cycle, and the total observed inspiratory work. A simple model was used to characterize the mechanics of the lung during inspiration, and the recordings were used to calculate the parameters of this model. These varied from breath to breath. A theoretical formula is derived for the sum of external work performed during inspiration for each burst. It is shown mathematically that there exists a local minimum in the calculated work as the values of the individual tidal volumes in this formula are allowed to vary, with the constraint that the sum of the ventilation during the cycle is as measured. The measured values of inspiratory timing, the starting volume and pressure, and the mechanical parameters for each inspiration are also used. We show that during each cycle of periodic breathing, the total of the observed external work is highly correlated with this theoretical minimum work. In addition, during the cycle, there is a pattern of overshoot and subsequent undershoot in the work with respect to the theoretical optimum, which suggests a control process operating during the cycle to minimize the work.

ISSN:0031-3998    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Prematurity has been associated with low glutathione (GSH) concentrations in bronchoalveolar lavage fluid as well as in leukocytes from tracheal aspirates and peripheral blood. To elucidate whether this is caused by deficient GSH synthesis, the expression and activity of &ggr;-glutamylcysteine synthetase (glutamate-cysteine ligase, GCS, EC 6.3.2.2), the rate-limiting enzyme for GSH synthesis, were measured from fetal, neonatal, and adult human liver, lung, and kidney samples. The highest activity was measured in the liver, in which mRNA expression of the catalytic GCS heavy and the regulatory light subunits, as well as activity, were, on average, similar in the various stages of development. Although GCS light subunit mRNA concentrations in the lung were higher in neonates than in fetuses and adults, enzyme activities were similar. In the adult kidney, mean enzyme activity was somewhat higher than in fetal or neonatal kidney, but this may be accounted for by the variation in the small number of samples. In conclusion, GCS is expressed and active already in the second trimester and thus low GSH concentrations found in preterm neonates appear not to be explained by deficient GSH synthesis. Other factors, such as limited availability of the GSH precursor cysteine or increased GSH consumption, may account for the lower concentrations of GSH found in preterm infants.

ISSN:0031-3998    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

L-Alloisoleucine (2S, 3R), a diastereomer of L-isoleucine (2S, 3S), is a normal constituent of human plasma. Considerable amounts accumulate in maple syrup urine disease, in which the branched-chain 2-oxo acid dehydrogenase step is impaired. The mechanism of L-alloisoleucine formation, however, is unclear. We addressed this issue by performing oral L-[1-13C]isoleucine loading (38 &mgr;mol/kg body wt, 50% 1-13C) in overnight-fasted healthy subjects (n= 4) and measuring the 3-h kinetics of13C-label incorporation into L-isoleucine plasma metabolites. Compared with L-isoleucine, the time course of13C-enrichment in the related 2-oxo acid,S-3-methyl-2-oxopentanoate, was only slightly delayed. Peak values, amounting to 18 ± 4 and 17 ± 3 mol percent excess, respectively, were reached within 35 and 45 min, respectively. The kinetics of13C-enrichment inS- andR-3-methyl-2-oxopentanoate enantiomorphs were similar and linearly correlated (p≪ 0.001). In L-alloisoleucine, however,13C-label accumulated only gradually and in minor amounts. Our results indicate thatR-3-methyl-2-oxopentanoate is an immediate and inevitable byproduct of L-isoleucine transamination and further suggest that alloisoleucine is primarily formed via retransamination of 3-methyl-2-oxopenanoatein vivo.

ISSN:0031-3998    

出版商:OVID    

年代:2000

数据来源: OVID