摘要:

Content of the 26–38-kD surfactant apoprotein (SP-A) was determined in lung homogenates from fetal (17–21 d gestation), postnatal (1–28 d of life), and adult male and female rats by a double sandwich ELISA. Expression of mRNA for SP-A as well as the hydrophobic apoproteins, SP-B and SP-C, were also determined in lung homogenates from fetal and adult rats of both sexes by Northern blot analysis. SP-A was undetectable in fetal lungs on d 17 (day of birth=d 22) and barely detectable on d 18. On d 19 there was a 3- to 4-fold increase in SP-A content above d 18 levels. Between d 19 and 21 SP-A content significantly increased another 6- to 9-fold. SP-A content on the day of birth was not significantly different from that seen on gestational d 21. SP-A content decreased 35–40% between the day of birth and postnatal d 7. After the second postnatal week SP-A content gradually increased, reaching adult levels after d 28. No sex differences in SP-A content were observed during fetal or postnatal lung maturation. SP-A mRNA was first detected in fetal lungs on d 18 and increased in relative abundance until d 21, but remained below adult levels. Developmental changes in fetal lung SP-A content closely paralleled changes in fetal expression of SP-A mRNA. SP-B mRNA was also first detected on d 18, then increased in relative abundance to adult levels by d 20. SP-C mRNA was clearly detectable on d 17, then increased in relative abundance to adult levels by d 20–21. Unlike surfactant phospholipids, there are no apparent sex differences in the expression of any of the surfactant apoproteins during late gestation. The differences observed during fetal lung maturation in the time of onset and changes in relative abundance among the three apoprotein mRNA imply that their genes may be differentially regulated in the developing rat lung.

ISSN:0031-3998    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Thromboxane A2(TxA2) is an arachidonic acid metabolite which causes severe pulmonary vasoconstriction (PV) and may mediate the PV produced by platelet-activating factor (PAF-acether) and leukotriene D4(LTD4). To determine the role of TxA2receptors on PAF-acether, LTD4, and hypoxia-induced PV, we administered PAF-acether 0.1 nmol/kg, the TxA2analog U-46619 0.2µg/kg/min, LTD43.0µg/kg, or acute hypoxia (Fio2=0.12 for 3 min) before and during the infusion of the selective TxA2receptor blocker SQ 29 548 50µg/kg/min or vehicle into 27 open-chest, anesthetized newborn piglets, measuring pulmonary and systemic arterial pressures, cardiac index, and right and left ventricular pressures and dimensions. Mean pulmonary arterial pressure rose and cardiac index fell in response to PAF-acether (14 ± 1 to 32 ± 2 mm Hg and 91 ± 5 to 15 ± 5 mL/kg/min, bothp<0.01), U-46619 (11 ± 1 to 28 ± 2 mm Hg and 93 ± 10 to 36 ± 9 mL/kg/min, bothp<0.01), and LTD4(13 ± 3 to 22 ± 2 mm Hg and 85 ± 12 to 29 ± 9 mL/kg/min, bothp<0.05). Acute hypoxia increased PAP (12 ± 1 to 26 ± 2 mm Hg,p<0.01) but did not alter cardiac index. Infusion of SQ 29 548 prevented PAF-acether and U-46619-induced increases in pulmonary arterial pressure (13 ± 1 to 14 ± 1 mm Hg and 12 ± 1 to 12 ± 1 mm Hg) and decreases in cardiac index (70 ± 4 to 70 ± 3 mL/kg/min and 94 ± 14 to 92 ± 12 mL/kg/min) but failed to alter the response to LTD4or hypoxia. Vehicle had no effect. We conclude that TxA2receptors are not involved in LTD4or hypoxia-induced PV but play an important role in the PV produced by PAF-acether and U-46619.

ISSN:0031-3998    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

When cardiac output is critically lowered, whole body O2consumption decreases and an O2deficit accumulates. With restoration of cardiac output, an excess O2consumption is expected in order to “repay” some or all of the O2deficit. We tested the hypothesis that young lambs, with higher resting O2consumption, cardiac output and growth rates than older lambs, would repay less of their O2deficit because they have a higher proportion of nonessential metabolism. We reduced cardiac output acutely by inflating a Foley catheter in the right atrium of spontaneously breathing, sedated lambs at ages 2 (n=5) and 8 (n=5) wk. Each lamb was studied with low cardiac output periods of 30 and 60 min on different days. Aortic and pulmonary artery blood pressures, gases, and O2saturations, venous Hb, and arterial lactate concentrations were measured every 10 min during baseline, low output, and 60 min of recovery. Oxygen consumption was monitored continuously. Oxygen deficit and excess O2of recovery were calculated from the time integral of the difference between O2consumption at baseline and during the respective study period. The average percent decreases in cardiac output (66.4 and 64.6%) and O2consumption (38.1 and 35.1%) were similar in the 2- and 8-wk groups, respectively. There was no consistent relation between O2deficit and O2repayment in either age group. However, on average the 2-wk group repaid a significantly lower percentage (3 ± 16%, mean ± SEM) than 8-wk-olds (76 ± 29%). Moreover, lactate increased linearly with time and O2deficit in both age groups, but lactate accumulated at a significantly lower rate in the 2-wk as compared to the 8-wk group for comparable deficits. We speculate that, during periods of very low cardiac output, 2-wk-old lambs not only decrease O2consumption, but also decrease metabolic demands, possibly by suppressing nonessential metabolism. This results in fewer energy stores that need to be replenished during recovery. This is a potential mechanism for the greater tolerance of young animals to hypoxic stresses.

ISSN:0031-3998    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The heart rate and respirations of twenty healthy full-term infants between 30 and 60 h postnatal age were studied during quiet sleep with the objective of defining spectral indices which represent normal neonatal heart rate variability (HRV) characteristics. Total HRV power and the distribution of power across different frequency bands varied considerably among infants. Cluster analysis on the measured variables indicated that the population divided into two groups that represented significantly different patterns of HRV behavior. In one group (11 subjects), infants had lower breathing rates and HRV power in a band about the respiration frequency [respiratory sinus arrhythmia (RSA) band] was more than 20% of the total power (TP). Additionally, the ratio of low frequency band power to RSA band power was <4. The other group of neonates (nine subjects) had relatively higher breathing rates, RSA power <20% of total power, and low frequency to RSA power ratio >4. Regression analysis of low frequencyversusTP and RSAversusTP graphs gave strong support to the hypothesis that there were indeed two distinct patterns of HRV behavior. Separation of apparently normal neonates into two groups may be attributed partially to differences in respiratory rates and breathing patterns. However, it is possible that differences in the balance between sympathetic and parasympathetic nervous system control, perhaps related to autonomic maturation, also contribute to group separation. The indices developed from HRV spectral analysis in this investigation may be of value in the study of cardiorespiratory control in neonates.

ISSN:0031-3998    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The effect of aminophylline on diaphragmatic blood flow was investigated in two groups of newborn piglets. Six animals were studied during spontaneous breathing and seven additional animals were paralyzed and ventilated to assess the effect of aminophylline on blood flow to the nonworking diaphragm. Arterial blood gases and pH, cardiac output, and diaphragmatic blood flow were measured before and 20 min after infusion of 20 mg/kg aminophylline. Blood theophylline concentrations averaged 117 Alt+0181mol/L (21 Alt+0181g/mL) in both groups of animals. Heart rate increased significantly in all animals. Cardiac output increased significantly only in spontaneously breathing animals. Aminophylline had no effect on blood flow to the costal or crural portions of the diaphragm in either the paralyzed or spontaneously breathing animals.

ISSN:0031-3998    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The purpose of the study was to investigate the effect of low doses of dopamine in children. Fourteen cases were studied after open heart surgery. Cardiac output and renal parameters were determined under baseline conditions and under continuous infusion of dopamine 2.5 and 5 Alt+0181g/kg/min. During the control period cardiac index was 2.62 ± 0.19 L/min/m2, renal plasma flow was decreased at 269 ± 41 mL/min/1.73 m2, GFR was 86.6 ± 9.2 mL/min/ 1.73 m2, and filtration fraction was elevated at 37.1 ± 1.9%. Plasma concentration of aldosterone correlated with the filtration fraction. At 5 Alt+0181g/kg/min dopamine increased significantly cardiac output, renal plasma flow, and to a lesser extent GFR, thus decreasing the filtration fraction. At 2.5 Alt+0181g/kg/min dopamine, increased renal plasma flow only in patients older than 5 y and had no effect on the other parameters. The increase of cardiac output in response to dopamine was abolished by propanolol pretreatment. By contrast, the hemodynamic renal response to dopamine was not altered by ß-blockade. These results indicate that 5 Alt+0181g/kg/min of dopamine could prevent renal failure after open heart surgery in children by increasing renal blood flow and attenuating renal compensatory mechanisms.

ISSN:0031-3998    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Although the mechanisms underlying the inhibitory effects of chronic renal insufficiency on growth are poorly understood, large doses of growth hormone (GH) have been used to improve growth. The present study examines the effects of rat GH and a reduced (8%) protein diet on 75% nephrectomized weanling rats by measuring changes in growth parameters, food utilization, serum albumin concentration, and muscle water content. Significantly greater improvement in growth was found in the GH-treated uremic rats compared with the uremic controls. The mean percent change in wt, length (nose to tail tip), and cranial biparietal diameter was significantly increased in the GH-treated uremic rats, compared with the uremic controls, but foot length and femur length showed only moderate improvement. Food utilization efficiency and serum albumin concentration were significantly higher in GH-treated uremic rats compared with uremic controls, achieving levels that were not different from sham-operated rats. Muscle water content was not significantly different between GH-treated uremic rats, uremic controls, and sham-operated rats. Thus, rat GH treatment administered at an early age in mild renal insufficiency significantly improved overall growth, food efficiency, and serum albumin concentrations, despite a low protein diet, suggesting that further evaluation of this form of therapy for growth failure of uremia is warranted.

ISSN:0031-3998    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The 2-deoxy-[14C]-glucose (2-DG) method of Sokoloff was used to assess regional cerebral glucose utilization (CGU) in the immature rat. The 7-d postnatal rats received 2.5 Alt+0181Ci 2-DG subcutaneously, after which blood was collected for measurement of plasma glucose and 2-DG activity at intervals up to 90 min. The brains of the 90-min rat pups either were frozen for analysis of glucose concentration and chromatographic separation of 2-DG and 2-DG-6-phosphate or for [14C]-autoradiography. A lumped constant of 0.55 was calculated from plasma and brain glucose levels of 6.4 and 1.62 mmol/L.kg, respectively. Of the [14C] activity in brain, 75.6% was in the 2-DG-6-phosphate fraction; this percent was substituted for Kl*, K2*, and K3* in the Sokoloff equation. Cerebral hemispheric CGU (n=6) averaged 11.4 ± 1.5 Alt+0181mol/100 g/min, 1/10 the value of adult rat brain. Rates in 16 brain structures (n=10) ranged from 7.8 (frontal white matter) to 16.9 (cerebellum) Alt+0181mol/100 g/min. During hypoxiaischemia (unilateral common carotid artery ligation combined with exposure to 8% oxygen), the lumped constant increased to 1.04, and 99% of 2-DG was converted to 2-DG-6-phosphate. Increases in CGU occurred in all eight structures of the cerebral hemisphere ipsilateral to the carotid artery occlusion (n=9), ranging from 287% (frontal white matter) to 445% (striatum) of control values (p<0.05). Relatively comparable elevations in CGU (234- 435% of control) occurred in the contralateral cerebral hemisphere, which were not significantly different from those of the ipsilateral hemisphere. The relatively proportionate increases in regional CGU of the two cerebral hemispheres, only one of which sustains tissue injury, suggest interhemispheric differences in the extent to which glucose is metabolized via anaerobic glycolysis to maintain cellular energy production. The investigation demonstrates the feasibility of measuring regional CGU in the small laboratory animal, which is applicable to a variety of physiologic and pathologic situations.

ISSN:0031-3998    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Previous work in a neonatal lamb model has demonstrated abnormalities in cerebral blood flow (CBF) and oxygen consumption (CMRO2) after asphyxia. Immediately after resuscitation, there was a marked increase in CBF and a significant decrease in CMRO2compared to control. During the late period after asphyxia (30 min to 4 h), both CBF and CMRO2were significantly depressed. The same postasphyxia model (n=16) was used to examine the hypothesis that generation of oxygen free radicals during cerebral reperfusion may be involved in the genesis of late postasphyxia hypoperfusion and depressed CMRO2. Before asphyxia, the animals were pretreated with either inactivated (n=8) or active (n=8) polyethylene glycol superoxide dismutase, 5000 U/kg, and polyethylene glycol catalase, 100 000 U/kg. CBF (radioactive microspheres) and arterial and venous (superior sagittal sinus) blood gases and O2contents were measured during control, and at 5 min, 1 h, 2 h, and 4 h postasphyxia (PA). In the active enzyme group, 5 min postasphyxia CBF was significantly increased compared to control: 211.5 ± 28.0versus78.6 ± 11.4 ml 100 g-1min-1, ±SEM,p<0.005. At 1 h (82.9 ± 17.6), 2 h (62.3 ± 5.5), and 4 h (78.9 ± 12.2) PA, CBF did not differ significantly from control. More importantly, CMRO2did not differ from control at any time PA. In the inactive enzyme group, both CBF and CMRO2were depressed at 1, 2, and 4 h PA. These findings are consistent with a conclusion that damage by oxygen free radicals during postasphyxia cerebral reperfusion is important to the genesis of late PA blood flow and O2metabolism abnormalities. To the extent that depressions in CBF and CMRO2result in ongoing brain injury, agents that ameliorate these abnormalities may improve neurologic outcome.

ISSN:0031-3998    

出版商:OVID    

年代:1989

数据来源: OVID