摘要:

SummaryIn order to test the hypothesis that a defect in cardiorespiratory regulation contributes to death of infants from sudden infant death syndrome (SIDS), we analyzed the power spectra of heart rate and respiratory activity during 256‐sec epochs of quiet sleep. Data were obtained from pneumogram recordings performed for 12 h at night on eight infants who subsequently died from SIDS and 22 age‐matched control infants. We computed the heart rate and respiratory power spectra from a single epoch on each infant using an algorithm developed for an 8085 microprocessor system dedicated to this investigation. There was no statistically significant difference between SIDS and controls based on mean respiratory and heart rates. Spectral analysis revealed enhancement of low frequency power in the 0.02 to 0.1 Hz band in the heart rate power spectrum in the SIDS group compared to control (p< 0.002) and dispersion in respiratory frequency as determined by the respiratory band width (p< 0.00001). These data suggest that a predisposition to SIDS manifests itself in an abnormal pattern of fluctuations in heart rate and respiratory activity.AbbreviationsSIDS, sudden infant death syndromeECG, electrocardiogramEEG, electroencephalogramGER, gastroesophageal refluxHR, heart rate

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryThyroxine (T4), triiodothyronine (T3), and thyrotropin (TSH) concentrations were measured on cord sera of 21 preterm infants with idiopathic respiratory distress syndrome (IRDS) and were compared to the values obtained from 15 healthy preterm infants. When log T3, log T4, and log TSH were considered as the dependent variables in the multivariate test Hotelling‐Lawley‐Trace, there was an overall difference between the two groups:F= 3.94,p= 0.03. When log T3and log T4were considered separately in an analysis of covariance, there was a significant difference between the two groups for log T3affter adjusting for birth weight and gestational age (F= 7.98,p= 0.008). However, for log T4and TSH, there was no difference between the IRDS and control infants. These findings exclude the possibility of antenatal thyroid dysfunction in babies with IRDS. An explanation for reduced cord blood T3concentration in infants with IRDS is lacking at present. Extrathyroidal factors that predispose to IRDS may also affect peripheral T3generation. Alternatively, one might postulate that there is relative immaturity of both peripheral T3generating pathway and lung development in infants who develop IRDS.AbbreviationsTSH, thyrotropinT3, triiodothyronineT4, thyroxineIRDS, idiopathic respiratory distress syndrome

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryWe have developed a method for measuring oxygen consumption (&OV0312;O2) in preterm infants in their normal incubator environment over prolonged periods. The results of measurements made over 24 h in 18 infants are presented. In normally grown infants, the mean &OV0312;O2was 9.66 ± 1.25 liters/kg•24 h (SD) (6.71 ± 0.87 ml/kg•min), and in small for gestation infants it was 10.09 ± 1.21 liters/kg•24 h (7.00 ± 0.84 ml/kg•min). During the 24‐h measurements, the highest mean &OV0312;O2during 3 consecutive h was 7.75 ± 0.89 ml/kg•min and the lowest was 5.95 ± 0.92 ml/kg•min. The difference between the highest and the lowest values was significant (p< 0.001). There is room for considerable error if short term measurements are assumed to represent values over a whole day. “Short” measurements should be made over at least 6 h.Abbreviations&OV0312;O2, oxygen consumption rateMR, metabolic rateME, metabolizable energy intakeRQ, respiratory quotient

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummarySaline or triiodothyronine (T3) (50‐1000 &mgr;g) was injected into the amniotic sac of 17 pregnant ewes under general anesthesia at 130 days gestation. Forty‐eight h later, the lambs were delivered by hysterotomy. Cord plasma T3and cortisol and amniotic fluid T3were assayed, and the maturity of the fetal lung was assessed in terms of its pressure‐volume response and its surfactant (lamellar body phospholipid) content. With the highest dose of T3, cord plasma T3and cortisol were raised, and lung maturity was enhanced compared with saline‐treated controls; the pressure‐volume curve showed increased hysteresis on inflation and deflation, and the lung retained air on return to zero pressure. There was also an apparent, but not statistically significant, increase in the lamellar body phospholipid content of the lung. Irrespective of treatment, lungs which were more mature, in terms of their pressure‐volume characteristics, tended to contain a higher proportion of lamellar body phospholipid relative to total phospholipid.AbbreviationsT4, thyroxineT3, triiodothyronine

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryThe effects of dichloroacetate (DCA) on the activity of the pyruvate dehydrogenase (PDH) complex and associated changes in the lactate and glucose levels in rat brain were investigatedin vivo.The average activities of the active form of the PDH complex in the brain, liver and muscle of starved rats were respectively 0.40 ± 0.04, 0.07 ± 0.04, and 0.17 ± 0.11 &mgr;mol/min/g tissue, and amounted to 21, 11, and 16% of the total activity of the complex. Intraperitoneal injection of DCA (125 mg/kg) increased the percentage of the active form of the PDH complex in the brain, liver, and muscle to 107, 40, and 84%, respectively. DCA significantly lowered the lactate and glucose concentrations of the brain and blood. A lower dose of DCA (12.5 mg/kg) also caused significant increase in activity of the PDH complex in the brain, but did not significantly change the lactate or glucose concentration of the brain. These results suggest that DCA crosses the blood‐brain barrier reasonably well.AbbreviationsPDH, pyruvate dehydrogenaseDCA, dichloroacetate

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryThe purpose of the present study was to determine if pulmonary prostacyclin synthesis was stimulated by spontaneous onset of breathing by unanesthetized fetuses at birth. Cannulae were implanted and flow cuffs placed in fetal lambs and goats (0.93 term). Fetuses were delivered by cesarean section at 0.95 term and began breathing spontaneously. Prostacyclin in blood was determined by radioimmunoassay of its hydrolysis product, 6‐ketoprostaglandin F1&agr;using methods that produced the same values in duplicate samples as did gas chromatography with electron capture detection. Fetal pulmonary prostacyclin production (left lung) [(left pulmonary venous concentration — pulmonary arterial concentration) × left pulmonary blood flow] was undetectable [−1.7 ± 1.0 (SEM) ng PGI2·kg−1·min−1] and fetal pulmonary vascular resistance (left lung) high (5.1 ± 0.9 mm Hg · kg·min · ml−1). Pulmonary prostacyclin production increased to 30.1 ± 12.3 ngPGI2· kg−1· min−1and pulmonary vascular resistance declined to 0.5 ± 0.1 mm Hg · kg · min · ml−115 min after‐birth. Pulmonary vascular resistance remained low even though pulmonary prostacyclin production fell 2‐5 h after birth. These results, coupled with earlier studies using indomethacin to inhibit prostaglandin synthesis, support the hypothesis that pulmonary prostacyclin synthesis participates in the decline of pulmonary vascular resistance that accompanies the onset of ventilation at birth, but may be less important in maintenance of low pulmonary vascular resistance once reduced pulmonary vascular tone has been established.AbbreviationsPG, prostaglandinTX, thromboxaneGC‐ECD, gas chromatography‐electron capture detectionRIA, radioimmunoassay

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryComparison between 21 2‐day‐old infant monkeys and 17 21‐day‐old infants during non‐rapid eye movement sleep demonstrated that minute ventilation (&OV0312;1) increased from 141 ± 30 to 257 ± 65 ml/min secondary to elevations in tidal volume (VT) and mean inspiratory flow (VT/Ti) with little change in respiratory timing. These volumetric parameters of ventilation as well as functional residual capacity remained significantly augmented when standardized for gain in body weight. Dynamic lung compliance increased from 0.69 ± 0.19 to 0.89 ± 0.39 ml/cm H2O with age while inspiratory pulmonary resistance did not change. Effective elastance fell significantly with maturation (5.27 ± 1.51 cm H2O/ml on day 2versus4.15 ± 1.35 cm H2O/ml on day 21) while effective impedance was elevated postnatally. The postnatal ventilatory gain (80% increase in&OV0312;1) was attributable to increases both in dynamic lung compliance (30%) and inspiratory effort (50%) as determined by esophageal pressure changes. Isometric occlusion pressures (P0.1,P0.2…Pmax) also significantly increased during this time span, suggesting that the increased ventilation resulted from an elevated respiratory drive.AbbreviationsVT,tidal volumeNREM, non‐rapid eye movement sleep&OV0312;1,minute ventilationTi,inspiratory timeTe,expiratory timeTtot,total cycle durationP,airway pressureFRC, functional residual capacityE'rs, effective elastanceI'rs, effective impedance

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryThe effects of postnatal development on the systolic and diastolic responses to pharmacologic blockade of the slow inward calcium current were investigated in blood‐perfused hearts isolated from immature (14‐21‐day‐old) and adult rabbits. Isovolumic left ventricular developed pressure, resting pressure, and maximal rate of pressure development (+dP/dt) at cumulative doses of either verapamil, nifedipine, or diltiazem were determined by means of an intracavitary balloon. Myocardial contractile function in the immature heart was more sensitive to pharmacologic blockade of the slow inward calcium current than is the adult heart. Doses of verapamil, or nifedipine, that comparably reduced pretreatment developed pressure and +dP/dtwere approximately 10‐fold less in immature as compared to the adult heart. The dose of diltiazem which reduced developed pressure anddP/dtby 50% was 3‐fold less in immature as compared to the adult heart. Verapamil and nifedipine decreased resting pressure in the adult but not in the immature heart. Conversely, diltiazem decreased resting pressure in the immature while not affecting resting pressure in adult hearts. Thus, postnatal cardiac development affects both the systolic and diastolic responses to calcium channel blockade. In addition, diltiazem appears to be qualitatively and quantitatively different from verapamil and nifedipine with respect to the age‐related cardiac effects of calcium channel blockade.AbbreviationsSR, sarcoplasmic reticulumSL, sarcolemmaLV, left ventricular

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummarySomatostatin is a known inhibitor of hormone secretion and of nutrient transport. Because somatostatin‐like immunoreactivity has been detected in amniotic fluid and the placenta has both hormone secretory and nutrient transport functions, we investigated the possible existence of somatostatin receptors on placenta cell membranes. Binding of125I‐Tyr1‐and125I‐Tyr11‐somatostatin (5‐21%) to solubilized placenta cell membranes was observed. Binding was time‐, temperature‐, and pH‐dependent and occurred maximally with incubation at concentrations of 25 &mgr;g of membrane protein. Displacement of binding of125I‐Tyr1and Tyr11somatostatin by cold cyclic and linear somatostatin and somatostatin analogs Ala‐5, Ala‐8, and Ala‐11 was observed. Scatchard analysis of data revealed high capacity of (Ro0.44 mol/&mgr;g × 10−12) but low affinity (Kd1.8 M × 10−7) binding sites similar to that reported in other tissues. Binding was not reversible under our experimental conditions. The significance of this low affinity binding of somatostatin to placenta cell membranes remains to be determined.AbbreviationSRIF, somatostatin

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryHigh concentrations of immunoreactive trypsin (IRT) in the blood, and low concentrations of trypsin activity in fecal specimens have been found in newborn infants with cystic fibrosis (CF). The amniotic fluid concentrations of IRT and of IRT in complex with &agr;1‐antitrypsin (&agr;1AT) were studied in 39 samples taken in about the 17th gestational week, and in 7 samples taken because the mothers had previously given birth to children with CF. The midtrimester samples contained trypsin in complex with &agr;1AT in a concentration of 30‐200 &mgr;g/liter, and small amounts of trypsinogen, 0‐50 &mgr;g/liter. Three of four amniotic fluid samples from CF fetuses had very low concentrations of trypsin in complex with &agr;1AT (<10 &mgr;g/liter), and only small amounts of trypsinogen (<10 &mgr;g/liter). Further prospective studies are needed to ascertain whether the determination of IRT in amniotic fluid may be of use in prenatal diagnosis of CF.Abbreviations&agr;1AT, &agr;1‐antitrypsinCF, cystic fibrosisg.w., gestational weekIRT, immunoreactive trypsinRIA, radioimmunoassay

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID