摘要:

The cerebral and systemic hemodynamic effects of negative pressure ventilation by external high frequency oscillation, utilizing a thoracoabdominal chamber, were investigated in six healthy adult monkeys. Cardiac output and cerebral blood flow were compared on external high frequency oscillation and conventional, positive pressure, mechanical ventilation in each animal. Cardiac output was measured by thermodilution and cerebral blood flow was measured by the intraarterial Xenon133clearance technique. Oxygen delivery and consumption and systemic and pulmonary vascular resistances were calculated. There was no significant difference between the two ventilatory modes for any of these variables. Cardiac index on conventional mechanical ventilation was 2.87 ± 0.39 1. min-1m-2(mean ± SD) and on external high frequency oscillation was 2.96 ± 0.87 1. min-1. m-2Cerebral blood flow was 43.9 ± 9.1 ml-100 g-1. min-1on conventional and 39.0 ± 9.0 ml. 100 g-1min-1on external high frequency ventilation. External high frequency oscillation is not associated with any adverse cardiovascular or cerebrovascular effects and could be introduced for short-term human trials.

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Intravital microscopy, a new in vivo technique, documented age-dependent changes in choledochoduodenal junction motility in male guinea pigs. In the guinea pig, the choledochoduodenal junction served as a pump that actively emptied its luminal contents into the duodenum. In the neonates (≥ wk old), this choledochoduodenal junction pump was not fully developed. Unlike the older guinea pigs, some neonates had an incompetent sphincter ductus choledochi (SDC) allowing retrograde flow of bile during ampullary contractions. While fasting, neonates had decreased frequency of SDC (1.2 ± 0.4 contractions/min) and ampullary (0.1 ± 0.1 contractions/ min) contractions as compared to juveniles (4-6 wk old) (SDC=6.4 ± 1.0; ampulla=1.2 ± 0.2 contractions/min) and adults (>1 yr old) (SDC=6.7 ± 1.6; 0.8 ± 0.2 contractions/min). Following a meal (Ensure), unlike older guinea pigs, the neonate did not have a significant increased duration and decreased frequency of SDC contractions. Altered neonatal SDC motility correlated with an incompletely developed SDC including decreased muscle mass and mucosal thickness. By 4 wk of age, choledochoduodenal junction motility was similar to that of the adult. These developmental alterations in junctional motility and structure may affect the flow of bile into the duodenum contributing to physiologic cholestasis and decreased intraduodenal bile acids seen in neonates.

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Leukotriene (LT) C4or D4may mediate pulmonary hypertension induced by hypoxia. LT have also been isolated from patients with persistent pulmonary hypertension of the newborn syndrome and the adult respiratory distress syndrome. To compare the effects of LTC4and D4on the pulmonary and systemic circulations, we performed dose-response studies on spontaneously breathing newborn lambs. To determine whether the hemodynamic effects of LT are mediated through a-adrenergic stimulation, some lambs were pretreated with the α-adrenergic antagonist phentolamine mesylate before LT injection. These results were compared to the effects of pretreatment with the LT receptor antagonist FPL57231. To determine whether the LT-induced decrease in cardiac output was mediated by the decrease in heart rate, other lambs had their heart rate maintained by left atrial pacing. We found that LTC4and D4increased systemic arterial pressure and decreased cardiac output and heart rate. However, LTD4, but not LTC4, increased pulmonary arterial pressure. The hemodynamic effects of LTC4and LTD4were completely blocked by FPL57231 but not by phentolamine mesylate. Maintenance of heart rate by left atrial pacing did not alter the LT-induced decrease in cardiac output. We conclude that LTC4and D4have similar effects on the systemic circulation. However, LTD4produces more pulmonary vasoconstriction. Because FPL57231 did block the pulmonary vasoconstriction caused by LT, LT antagonists may be useful in treating patients with pulmonary hypertension.

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Ten anesthetized, paralyzed adult cats were ventilated by high frequency chest wall compression (HFCWC) at 3, 5, 7, and 9 Hz by means of a single chamber cuff enclosing the thorax from the axillae to the xyphisternum. The effects of HFCWC in terms of gas exchange, end-expiratory lung volume, and respiratory system compliance were compared to conventional intermittent positive pressure ventilation (IPPV) (30 breaths/mn). HFCWC and IPPV were compared at three levels of matched end-expiratory airway pressure [continuous positive airway pressure (CPAP)/positive end-expiratory pressure/( PEEP) of 0, 2, and 5 cm H2O]. In the absence of CPAP, HFCWC resulted in a marked decrease (up to 50%) in end-expiratory lung volume with significantly lower PaO2, lower compliance, and higher alveolar-arterial oxygen gradient than during IPPV. No differences in PaO2and a-ADO2were observed when HFCWC was combined to CPAP ≥2 cm H2O. At frequencies below 9 Hz, PaCO2became significantly lower during HFCWC + CPAP than during IPPV. During HFCWC + 2 cm H2O CPAP, lung volume was lower than during IPPV + 2 cm H2O and similar to the volumes observed during IPPV + 0 positive end-expiratory pressure. Additional studies in six cats at HFCWC + 3 cm H2O confirmed that CPAP>2 cm H2O more than adequately compensated the decrease in lung volume associated with HFCWC alone. Peak cuff pressures between 14 and 17 cm H2O generated oscillary tidal volumes between 4.5 and 2.1 ml/kg. The size of the oscillatory volume was significantly affected by increasing frequencies (decrease in tidal volume) and increasing levels of positive airway pressure (increase in tidal volume). We conclude that in cats with normal lungs, HFCWC can provide for normal gas exchange, provided that it is combined with low level CPAP in order to prevent the occurrence of airway closure associated with HFCWC alone.

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The effects of treatment with 0.2 mg/kg of indomethacin on the cerebral blood flow and cerebral oxygen consumption of hypotensive, unanesthetized, newborn pigs were investigated. Hypotension was induced by hemorrhage (30 ml/kg) which reduced mean arterial pressure from 60 to 34 mm Hg. The decline in cerebral vascular resistance that occurred with hemorrhage allowed blood flow to all brain regions and cerebral oxygen consumption to continue unchanged. Treatment with 0.2 mg of indomethacin decreased plasma 6-keto-prostaglandin F1αmarkedly and caused a modest increase in cerebral vascular resistance from 0.75 ± 0.07 to 0.85 ± 0.02 mm Hg.100g·min/ml at 40 min posttreatment. As a result, blood flow throughout the brain fell about 20%. Similarly, cerebral oxygen consumption declined from 2.88 ± 0.13 to 2.03 ± 0.21 O2/100 g·min following treatment of hypotensive piglets with 0.2 mg/kg of indomethacin. However, all piglets were conscious 40 min after treatment. We conclude that, although 0.2 mg/kg of indomethacin affects cerebral hemodynamics of hypotensive piglets, the effects are very modest in comparison to large increases in cerebral vascular resistance, decreases in cerebral blood flow and oxygen consumption, and coma that follow treatment of hypotensive piglets with 5 mg/kg of indomethacin.

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Children with nephropathic cystinosis store 50 to 100 times normal amounts of free cystine in many cells and display negligible lysosomal cystine transport in their leucocytes and cultured fibroblasts. A patient with intermediate (adolescent) cystinosis exhibited a similar deficiency of egress out of fibroblast lysosome-rich granular fractions. Another individual with benign (adult) cystinosis accumulated only 2.85 nmol 1/2 cystine/mg leucocyte protein, or 20-50% of the amount stored in nephropathic cystinosis leucocytes. His leucocyte granular fractions also displayed substantial residual cystine-carrying capacity, as determined by measurement of lysosomal cystine countertransport. We conclude that the variant forms of cystinosis represent a continuum of lysosomal cystine storage, with the varied clinical presentation depending on the amount of residual cystine-carrying capacity, genetic predispositions, and differential tissue susceptibilities.

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Using analytical techniques, which included capillary column gas-liquid chromatography and mass spectrometry, detailed bile acid profiles were obtained for 24 fetal bile samples collected after legal abortions were performed between the 14th and 20th wk of gestation. Qualitatively, the bile acid profiles of all fetal bile samples were similar. The predominant bile acids identified were chenodeoxycholic and cholic acid. The presence of small but variable amounts of deoxycholic acid and traces of lithocholic acid suggested placental transfer of these bile acids from the maternal circulation. 3β-Hydroxy-5-cholenoic acid was detected at higher levels than lithocholic acid. A conspicuous feature of the profiles was the presence of bile acids with hydroxyl groups at positions C-l and C- 6, and one other nuclear position of unknown origin, indicating fetal hepatic synthesis via pathways different from those normally seen in the adult. Quantitatively total biliary bile acid concentrations were extremely low (<0.05 mM) before wk 17 of gestation, but thereafter concentrations markedly increased reflecting a possible surge in bile acid synthesis; however, the ratio of cholic:chenodeoxycholic acids remained relatively constant over this period (mean ± SD=0.85 ± 0.36) and different from that reported for the healthy newborn (ca. 2.5) and adult (ca. 1.6). These data indicate an immaturity in hepatic 12α-hydroxylation of bile acids during early development and may explain why other pathways, in particular 1βand 6α-hydroxylation, are activated at this stage of life.

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Fractional tubular reabsorption (FTR) of free and acyl carnitine was measured in 15 patients with various selective tubular transport defects and in 19 patients with more generalized tubular dysfunction (Fanconi syndrome). FTR of free carnitine was normal in all patients with a selective tubulopathy, FTR of acyl carnitine was normal in most, and plasma carnitine levels were normal without exception. In these patients, there was no evidence for the existence of a defective renal transport mechanism shared by carnitine. In the patients with Fanconi syndrome, mean FTR of free and acyl carnitine was low; their plasma carnitine levels were lowered and correlated with the FTR. In individual patients, FTR of free and acyl carnitine also correlated with the severity of the disease. In the group of Fanconi syndrome patients, FTR of free and acyl carnitine correlated linearly with that of valine. We concluded that the lowering of plasma carnitine in the patients with Fanconi syndrome was caused by excessive loss of carnitine in urine. Its pathophysiological significance remained to be established.

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Previous studies with neutrophils from newborn infants compared to neutrophils from healthy adults have documented increased respiratory burst activity including enhanced superoxide anion (O2-) production, nitroblue tetrazoleum dye reduction, and hexose monophosphate shunt activity. To investigate the biochemical basis for these observations, we examined oxidative metabolism in membrane-rich fractions of neutrophils. Neutrophils from cord blood of vaginally delivered term infants or healthy adults were disrupted by nitrogen cavitation and subcellular fractions collected on discontinuous sucrose density gradients. Subcellular fractions of newborn neutrophils separated in a fashion identical with samples from healthy adults. Activity of alkaline phosphatase, a plasma membrane marker, was increased 4- to 5-fold in disrupted cells free from nuclei (postnuclear supernatant) as well as plasma membrane fractions from newborn samples compared to those from healthy adults. Content of lactoferrin, a specific granule marker, was decreased in postnuclear supernatants but equivalent in specific granule fractions of newborn cells compared to those from adults. No differences were noted in myeloperoxidase content of postnuclear supernatants or any other subcellular fraction. Plasma membrane fractions from phorbol myristate acetate-stimulated cord blood neutrophils made significantly more O2-than samples from adults (newborn 32.9 ± 8.1 nmol O2-min/mg protein mean ± SEM, n=3versusadult 10.8 ± 4.2,n=3;P<0.05). Plasma membrane-rich fractions were also collected by the technique of differential centrifugation and kinetic parameters of the NADPH-dependent oxidase enzyme(s) were measured for vaginally delivered newborn and adult samples. The Kmappfor NADPH for newborn fractions was significantly increased compared with adult samples (newborn 66 ± 10 nM,n=6versusadult 30 ± 6,n=6;P<0.025) but not to the extent that would be associated with abnormal cell function. In contrast, Vmax of newborn membrane-rich fractions was 1.7 times that of adult samples (newborn 30.6 ± 27 nmol O2-/ min/mg protein,n=6versusadult 18.0 ± 4.0,n=6;P<0.025). Plasma membrane-rich fractions from term infants delivered by cesarean section without labor had a Kmappof 67 ± 20 nM,n=5 which was different from adult samples (P<0.05) and a Vmaxfor O2-production of 14.8 ± 4.5 which was less than that measured from samples from vaginally delivered infants (P< 0.01). The Kmappreimply a qualitative difference in the fetal oxidase enzyme system. In addition, the increased O2-production and Vmaxdemonstrated in samples from vaginally delivered infants as compared to infants delivered by cesarean section or healthy adults suggests an effect of parturition on the fetal neutrophil which is similar to the effect of certain compounds such as lipopolysaccharide. The increased catalytic activity of the NADPH oxidase enzyme system in neutrophils from newborns may reflect “priming” during parturition.

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

We report two children who presented with hypoglycemia and metabolic acidosis in whom acetoacetyl- CoA thiolase (EC 2.3.1.9) measured in fibroblast homogenates was deficient. Deficiency of this enzyme is normally associated with urinary excretion of 2-methylacetoacetate and in one child the urinary excretion of 2-methylacetoacetate, 2-methyl-3-hydroxybutyrate, and tiglylglycine was raised. By contrast, in the other child, the urinary excretion of these metabolites was very low even during ketoacidosis and following an isoleucine load. We suggest that this could be due to deficiency of the extrahepatic isoenzyme, a defect that may be responsible for some of the cases of “ketotic hypoglycemia.”

ISSN:0031-3998    

出版商:OVID    

年代:1987

数据来源: OVID