摘要:

The particulate fractions of culture supernatants from peripheral blood mononuclear cells from 39 patients with Kawasaki disease (KD) were examined for the presence of particle-associated reverse transcriptase activity. The peak polymerase activity was significantly higher in cultures from KD patients compared to controls (mean=6.4 versus 3.6 pmol of dTMP incorporated,p=0.001). PBMC cultured between the 3rd and 9th wk after onset of fever were most likely to be associated with reverse transcriptase activity. Peak polymerase activity was positively associated with older age (r=0.41,p=0.01) and greater magnitude of the serum IgA response at 7-14 d after onset of fever (r=0.45,p=0.01) and IgM response at 6-9 wk after onset of fever (r=0.46,p=0.01). The appearance of enzyme activity was not associated with a decrease in viability of the cultured cells. A purified enzyme preparation showed radiolabel incorporation only with an RNA template with DNA primer. These data suggest that circulating mononuclear cells from KD patients may harbor a polymerase-associated agent and that these cells can be most readily detected in the early convalescent phase of KD from older patients who mount a marked humoral immune response.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Oscillatory patterns in ventilation have been seen in term and premature infants and are indicative of the stability of the respiratory blood gas feedback control system. Apneas are related to these patterns and apnea duration is correlated with pattern characteristics. In our study breathing patterns were analyzed in recordings from 10 term infants who subsequently died of sudden infant death syndrome (SIDS) and 10 control infants matched for birth wt, gestational age, and postnatal age. Subjects were drawn from a prospectively studied population of 9856 infants. Breath-by-breath minute ventilation was estimated in each of these 24-h recordings and oscillatory patterns were detected using a comb of digital bandpass filters. Confidence limits on the filter output and a bad data flag for rejection of data during gross body movements or crying insured that only significant patterns in ventilation were evaluated. Pattern prevalence and amplitude were compared in three frequency regimes: 6- to 87-s cycle times, 6- to 28-s cycle times, and 28- to 87-s cycle times. There was no significant difference between the SIDS and the control infants in any of these pattern comparisons (paired t and Wilcoxon paired rank sum tests,p<0.05). In light of the normal breathing patterns found in the SIDS infants, it is unlikely that susceptibility to SIDS is distinguished, at the time of these recordings, by instability of the respiratory blood gas feedback control system.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The relationship between periodic breathing and idiopathic apnea of prematurity was investigated. We recorded respiratory impedance, heart rate, pulse oximetry and end-tidal CO2from 68 untreated infants of less than or equal to 34 wk gestation with a diagnosis of idiopathic apnea of prematurity. Mean birth wt was 1476 g (SD 420) and mean gestational age was 29.9 wk (SD 2.6). Apneas of more than 15 s duration that were associated with hypoxemia or bradycardia were identified by semiautomated analysis of computerized records. A total of 1116 significant apneic spells were identified, only one of which occurred during an epoch of periodic breathing, five others occurred within 2 min of the end of an epoch of periodic breathing. Less than 0.6% of significant apneic spells occur within 2 min of periodic breathing. In all of the 12 infants that were monitored starting in the first 12 h or life, significant apneic spells were identified before 36 h of age and no precipitating factors were identified. Periodic breathing did not occur during the first 48 h of life, a finding that supports the concept that the peripheral chemoreceptor is inactive in the first 48 h of life. Periodic breathing in the premature infant is not a precursor to significant apnea.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Pulmonary hypoplasia has been associated with absent or hypoplastic pulmonary artery in four cases in humans. Despite these reports, the effects of decreased pulmonary arterial flow on fetal lung growth have not been adequately studied. This study defines the effects of left pulmonary artery (LPA) ligation on fetal lung growth in sheep by comparing morphometrically determined pulmonary volumes from LPA-ligated, sham-operated, and unoperated control fetuses. LPA ligation (n= 5) or sham operation (n=4) was performed at 105- to 114-d gestation. At 140-d gestation these fetuses were delivered and the lungs were intratracheally fixed for light microscopy. At 112 d (n=4) and at 140 d (n=4), unoperated control fetuses were similarly delivered. Absolute pulmonary volumes were then measured using standard stereologic methods. Normal growth of the left lung from 112 to 140 d resulted in significant increases in wet and dry wt, displacement volume, and volumes of future airspace and capillary contents. LPA ligation caused significant decreases in left lung wet and dry wt, displacement volume, and in absolute volumes of fine nonparenchyma, future airspace, parenchymal tissue, and capillary contents compared to sham-operated and 140-d controls. Parenchymal tissue volume was also less than in 112-d controls. In addition, lung wt, displacement volume, and future airspace volume were significantly decreased in sham-operated fetuses compared to 140-d controls. The effects of LPA ligation on bronchial collateral circulation and factors known to affect lung growth (i.e. lung fluid volume) remain to be determined. Clearly, during the canalicular and alveolar stage of fetal lung development, pulmonary arterial flow is necessary for normal lung growth.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Endothelium-derived relaxing factor (EDRF), believed to be nitric oxide or a compound that releases nitric oxide, is a potent vasodilator produced by some arteries in response to acetylcholine (ACh) and bradykinin (BK). ACh and BK are potent dilators of perinatal pulmonary and systemic arteries. The objectives of this study were to determine if EDRF is present in newborn vessels and if EDRF mediates the vasodilator actions of ACh and BK. Arterial rings from newborn guinea pigs, 1 to 3 d old, were obtained from a branch of the main pulmonary artery and the descending aorta for isometric force bioassays. At their optimal resting tension, the rings were preconstricted with phenylephrine 10-5M in Krebs- Henseleit solution before adding incremental doses of ACh or BK. If the endothelium was intact, ACh (10s M) relaxed pulmonary arteries and aortas (64 ± 7%, 72 ± 9% relaxation, respectively, mean ± SE). ACh-induced relaxation (ACh 10-5M) in the pulmonary artery and aorta, respectively, was significantly (p<0.05) attenuated by 1) endothelial removal (11 ± 9%, 28 ± 10%) by rubbing the ring lumen; 2) methylene blue, 10-6M, (6 ± 8%, 7 ± 3%) that inhibits EDRF-associated cGMP production in smooth muscle; and 3) methemoglobin, 10-5M, (13 ± 9%, 17 ± 7%) that binds EDRF. The results for BK were similar to ACh for the pulmonary artery but BK did not relax the aorta. Indomethacin diminished relaxation of the pulmonary artery and aorta to the submaximal dose (10-5M) of ACh but indomethacin did not effect the relaxation to ACh 10-4M or BK. We conclude that EDRF is produced in the guinea pig pulmonary artery and descending aorta at birth and that EDRF is a mediator of the vasodilator actions of ACh and BK. Vasodilation by ACh may also involve activation of the cyclooxygenase pathway.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Methylprednisolone (30 mg/kg), which inhibits a number of mediators of hypoxic pulmonary vasoconstriction derived from arachidonic acid, has been found to alleviate hypoxic pulmonary vasoconstriction in adult humans and in the isolated rat lung preparation. We studied the effect of 30 mg/kg of methylprednisolone on the pulmonary vascular response to hypoxia in six late-gestation newborn lambs. During hypoxia, pulmonary vascular resistance nearly doubled compared with the baseline hyperoxic state. This was true both before and after administration of methylprednisolone. We conclude that methylprednisolone, when administered at the dosage used in previous studies of adult humans and animals, does not affect the response of the pulmonary vascular bed to hypoxia in newborn lambs.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

In the adult, atrial natriuretic peptide (ANP) regulates renal and cardiovascular function when blood volume is expanded, when atrial pressure is increased, and when arterial oxygen content is decreased. In late gestation fetal sheep, plasma ANP concentrations are higher than in pregnant adults; however, ANP function in the fetus is unclear. To assess the possible role of ANP in mediating changes in pulmonary blood flow, we studied six chronically cannulated fetal sheep at 132-134 d gestation (term 145 d). We infused ANP in doses of 4.0 ± 0.48, 16.0 ± 1.9, and 64.0 ± 7.7 ng/ kg/ min, and vehicle into all fetuses. ANP increased hematocrit, which suggests that blood volume decreased. Pulmonary blood flow, measured by the radionuclide-labeled microsphere technique, increased in response to the 4.0, 16.0, and 64.0 ng/ kg/ min dose ANP infusions from a control value of 126.5 ± 32.2 to 141.8 ± 26.9 to 170.4 ± 37.2 to 300.8 ± 84.8* mL/ min/ 100 g (*p<0.05), respectively, and calculated pulmonary vascular resistance decreased from a control value of 0.45 ± 0.08 to 0.42 ± 0.08 to 0.43 ± 0.09 to 0.21 ± 0.04* (*p<0.05) mm Hg/ mL/ min/ kg, respectively. Pulmonary blood flow decreased to 54.5 ± 6.0 mL/ min/ 100 g and calculated pulmonary vascular resistance increased to 0.81 ± 0.09 mm Hg/ mL/ min/ kg during the recovery period. Mean pulmonary and carotid arterial blood pressures, venous blood pressure, and heart rate did not change significantly. Thus, ANP may play a role in maintaining right ventricular output in the fetus by increasing pulmonary blood flow through its ability to decrease pulmonary vascular resistance.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The effect of the bipyridine compound, amrinone, on tension generation in neonatal and adult myocardium was studied over the concentration range 30-500 Mg/ mL. Increasing concentrations of amrinone caused a monotonic increase in twitch tension and the rate of tension development in adult papillary muscles. In contrast, lower concentrations of amrinone (30 and 100 ng/ mL) caused a decrease in twitch tension and dP/ dt in newborn papillary muscles, whereas 500 µg/ mL amrinone caused a significant increase in both parameters in the younger age group. Lactic acid, used to dissolve amrinone, was shown to have no effect on tension development. Half relaxation time was decreased in adult preparations at all concentrations of amrinone. In comparison, the decrease in half relaxation time produced by amrinone in the newborn was significant only at a concentration of 500 jug/ mL. Action potential duration in the newborn was significantly shortened by 30 /ug/ mL amrinone. In voltage clamp experiments, 30 Mg/ mL amrinone was shown to have no effect on tension accompanying two second voltage clamp steps to the plateau potential in newborn myocardium. Developed tension at 400 ms into the clamp step, final tension, and the ratio of early peak tension to final tension were all unchanged by the low concentration of amrinone. In contrast, 500 µg/ mL amrinone in the newborn increased tension at 400 ms and final tension but had no effect on the ratio of early peak tension to final tension. These results suggest that the negative inotropic effect of lower concentrations of amrinone on neonatal myocardium is the result of changes in action potential configuration and not a true alteration in basic mechanisms of intracellular Ca2+regulation. Further, the positive inotropic effect of higher concentrations of amrinone appears to result from enhancement of transmembrane Ca2+influx as well as augmentation of Ca2+sequestration and rerelease by the sarcoplasmic reticulum.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The purpose of this study is to describe the developmental course of arterial baroreflex control of heart rate in swine. Tests of baroreflex function were performed with eight conscious piglets serially over their first 2 mo of life. Systemic blood pressure was raised with phenylephrine (pressor test) and lowered with nitroprusside (depressor test), and stimulus-response curves relating heart rate to mean blood pressure were constructed. Baroreflex sensitivity was determined as the slope of the linear portion of the curve. Baroreflex sensitivity decreased with increasing age. Baroreflex sensitivity was not different between pressor and depressor tests except when the piglets were >52 d old and sensitivity was greater with the depressor test. The heart rates at threshold and saturation, and therefore the heart rate response range, shifted to lower heart rates with increasing age. This shift was more than can be accounted for by the simultaneously decreasing resting heart rate.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID