摘要:

SummaryLungs were obtained from rabbit fetuses (on each day from d 24 to d 30 of gestation), neonates and adults, and were fractionated for enzyme assays. The developmental profile of cytidyltransferase shows a decrease in specific activity from d 25 to d 29 (P<0.05) then a sharp rise from d 30 to adult values in d 0 neonates (P<0.05). Cholinephosphotransferase specific activity changes little from d 25 to birth, apart from a non-significant peak on d 29. There is a sharp rise from neonatal d 0 to adult values on d 1 (P<0.01). The specific activity of microsomal phospholipase A2declines from d 25 to reach adult values in the neonate (P=0.05). In contrast, the specific activity of lysosomal phospholipase A2rises from d 24-28 then falls in the neonate (P<0.05). Adult values are higher than those in the fetus and neonate. Three other lysosomal enzyme specific activities rise to d 28 then decline: phospholipase A1,β -gaIactosidase, and β - glucuronidase. The results demonstrate that the level of microsomal phospholipase A2does not control the extent of remodelling of phosphatidylcholine for surfactant production. Lysosomal phospholipase A2only increases in parallel with the other lysosomal enzymes, indicating an increase in the number of lysosomes in the lung.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryTen to 30% of dietary fat is hydrolyzed in the stomach by lingual lipase, an enzyme secreted from lingual serous glands. We investigated the substrate specificity of this enzyme as well as the potential of lingual lipase to act in the upper small intestine i.e., in the presence of bile salts and lecithin. The data presented show that partially purified preparations of rat lingual lipase and the lipase in gastric aspirates of newborn infants have identical substrate specificity: medium-chain triglycerides were hydrolyzed at rates 5-8-fold higher than long-chain triglycerides; the rat and human enzymes do not hydrolyze the ester bond of lecithin or cholesteryl-ester. In contrast to pancreatic lipase, the hydrolysis of triglycerides by lingual lipase is not inhibited by lecithin. But, similar to pancreatic lipase the activity of lingual lipase is inhibited by bile salts, the extent of inhibition varying with its nature and concentration. This inactivation is not prevented by colipase but is partially averted by lipids and protein, suggesting that lingual lipase can remain active in the duodenum. The pH optimum of the enzyme (2.2-6.5 in the rat and 3.5-6.0 in human gastric aspirates) is compatible with continued activity in the upper small intestine, especially during the neonatal period, when the luminal pH is under 6.5. The marked variation in lipase activity levels in gastric aspirates of newborn infants is probably due to individual variations in enzyme amounts. The characteristics of the lipase are however identical in infants with low, intermediate or high activity levels. Our results indicate that hydrolysis of dietary fat by lingual lipase may not be limited to the stomach but may continue in the upper small intestine.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryWe studied the effect of changes in the arterial tensions of oxygen and carbon dioxide on blood flow to the retinal (RBF) and choroidal (ChBF) capillary beds in 20 lambs. One to three days after placement of catheters in the left ventricle, abdominal aorta, and brachiocephalic artery, different gas mixtures were delivered to a bag enclosing the lamb's head. One group of lambs was studied at normal and low oxygen tensions while normocarbic, and another group was studied at normal and high carbon dioxide tensions while normoxic. RBF and ChBF were measured using the radioactive microsphere technique. RBF increased as PaO2and, thus, arterial oxygen content ([O2]a) fell; in contrast, ChBF was not related to [O2]a. Oxygen delivery to the capillary bed of the retinal artery (i.e., RBF × [O2]a) was independent of arterial oxygen content because the change in [O2]awas balanced by a reciprocal change in RBF. Oxygen delivery to the choroidal capillary bed, however, rose with [O2]abecause there was no reciprocal decrease in ChBF. Both RBF and ChBF increase as arterial carbon dioxide tension rose. Although an increase in arterial carbon dioxide tension produced an increase in RBF with no change in [O2]a, oxygen delivery to the retinal capillaries rose. Similarly, oxygen delivery to the capillaries of the choroid rose with carbon dioxide tension. Oxygenation of retinal tissue, which depends on oxygen diffusion from both the retinal and choroidal capillary beds, may change with variations in arterial oxygen content (increase in oxygen delivered to the choroidal capillary bed) or arterial carbon dioxide tension (increase in oxygen delivered to both the retinal and choroidal capillary beds).

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryBetween 1:120 and 1:180 of human newborn T cells proliferate in limiting dilution cultures with allogeneic lymphocytes or with la-bearing monocytic stimulator cells. The proliferating responder cells were derived from both the OKT 4+and OKT 8+subsets as determined by immunofluorescence and by thymidine uptake. Five to seven days after an exchange blood transfusion there was a slight increase in the percentage of OKT 8+T lymphocytes in the recipient's blood. Newborn blood also contains a population of non-T cells which proliferate in the absence of allogeneic stimulator cells. In limiting dilution cultures, the frequency of these spontaneously dividing cells was 1:3125 of mononuclear cells. Our results suggest that the newborn T lymphocyte proliferative response to alloantigen is mature by the time of birth and they provide no phenotypic explantion for the previous report of mixed lymphocyte culture-induced suppression by newborn T cells. The predominance of newborn metaphases in 2-way mixed lymphocyte cultures with adult cells (on which the previous report of suppression was based) is not seen if the non-T (stimulator) cells are irradiated. These results suggest that the data previously interpreted as evidence for suppression arose through proliferation of newborn non-T cells.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryThe purpose of this study was to investigate the compensatory change in circulation and oxygenation of the newborn Iamb gastrointestinal (GI) tract in response to anemic and hypoxic hypoxemia. Radiolabeled microspheres were used to measure blood flow. We subjected the newborn lamb to a 30-35% reduction in hematocrit 4 d before study and to a 10% oxygen environment for 30 min during the study to induce chronic anemic and acute hypoxic hypoxemia, respectively. The circulatory and oxygenation responses were measured 1 h after a standard milk feeding in all cases. During the experimental periods, no change in total GI blood flow was observed. Because of a failure to augment blood flow during hypoxemia, O2delivery to the GI tract decreased significantly. Despite this, GI O2consumption was not compromised because tissue O2extraction by the GI tract rose significantly. The response of the newborn lamb GI tract to hypoxemia after feeding is augmentation of O2extraction. The newborn's GI tract did not regulate local GI blood flow.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryTo determine which warming system more closely approximates a neutral thermal environment, the oxygen consumptions of 16 premature babies <1500 g were measured in a convectively heated incubator and a radiantly heated incubator. Both systems were controlled to maintain a skin temperature of 36°C. The oxygen consumptions of the infants were not significantly different in the two incubators; thus, there was no detectable advantage to the use of convective or radiant energy in approximating a neutral thermal environment in an incubator for the small premature infant. That proportion of total heat loss from the babies due to radiant losses in the convective incubator was directly calculated from incubator temperature using equations described in the paper, and found to be 68 ± 3% SE.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryThe plasma concentrations of 25-hydroxyvitamin D (25- OHD), 1,25-dihydroxyvitamin D (1,25-(OH)2D), and 24,25-dihydroxyvitamin D (24,25-(OH)2D) were determined pre- and postexchange, and in donors' blood in 10 blood exchange transfusions with citrated blood for neonatal hyperbilirubinemia. The postexchange concentrations of 25-OHD and 24,25- (OH)2D were intermediate between the levels before exchange and in donors' blood. Before therapy, the 1,25-(OH)2D concentrations were higher in the infants' than in donors' blood, and the pre-exchange levels were re-established during the procedure. The results suggest that postexchange concentrations of 25- OHD and 24,25-(OH)2D could be explained on the basis of redistribution of the metabolites between plasma and extravascular pools, whereas de novo synthesis was the most likely cause for the restoration of 1,25-(OH)2D levels.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryAntibodies in cystic fibrosis (CF) sera to Pseudomonas aeruginosa mucoid exopolysaccharide and to sodium alginate (a polysaccharide from seaweed chemically similar to mucoid exopolysaccharide) were measured in sera of CF patients to determine if the exopolysaccharide is immunogenic. An enzyme-linked immunosorbent assay was used to test sera from 26 CF patients (18 colonized with pseudomonas and eight non-colonized) and 26 healthy controls. CF patients colonized with pseudomonas had more antibody to mucoid exopolysaccharide (P=0.0008) and to sodium alginate (P=0.0008) than did non-colonized CF patients. Virtually none was found in healthy controls. Duration of colonization was correlated with the level of antibody to sodium alginate (P=0.003) but not with antibody to mucoid exopolysaccharide. Mucoid exopolysaccharide is immunogenic in patients with CF.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryIn spontaneously breathing newborn lambs, alveolar hypoxia increases lung microvascular pressure, which causes lung lymph flow to increase and the concentration of protein in lymph to decrease. To see if this response derives from hypoxia itself rather than from the change in breathing pattern that occurs during hypoxia, we measured lung vascular pressures, pleural pressure, cardiac output, and lung lymph flow in 12 anesthetized lambs that were ventilated at a fixed rate and tidal volume, first with air, then with 10-14% O2in nitrogen. Alveolar hypoxia did not affect pleural pressure, but pulmonary arterial pressure increased from 19 to 32 torr, lung lymph flow increased from 2.20 to 3.83 ml/h and lymph protein concentration decreased from 3.4 to 2.8 g/dl. To be certain that the increased lymph flow associated with hypoxia is not simply the result of an acute release of fluid from the lungs and to assess the effects of carbon dioxide on lymph flow during hypoxia, we next studied six unanesthetized lambs kept hypoxic for a total of 12 h. After a 2-4-h period in air the lambs breathed 9-11% O2in nitrogen for 2-4 h, then 8- 11% O2and 3-5% CO2in nitrogen for 8-10 h. In these lambs we injected intravenously radioactive albumin and measured its uptake in lymph to see if sustained hypoxia alters microvascular permeability to protein in the lungs. In these experiments pulmonary arterial pressure increased from 17 to 37 torr, lung lymph flow increased from 1.74 to 3.28 ml/h, and lymph protein concentration decreased from 3.8 to 3.1 g/dl during hypoxia. Addition of CO2to the inspired gas did not affect steady state lung lymph flow. Lymph flow remained elevated throughout the 12 h of alveolar hypoxia, and postmortem lung water determinations were not different from those of controls (4.65 ± 0.28 versus 4.72 ± 0.14 g/g dry bloodless lung). The time required for radioactive albumin to equilibrate in lymph at one-half the specific activity of plasma was no different before and during hypoxia (130 ± 7 versus 125 ± 11 min). We conclude that in the newborn lamb, alveolar hypoxia increases transvascular fluid filtration by increasing microvascular hydraulic pressure without altering microvascular permeability to protein. This response is independent of changes in pleural pressure or inspired carbon dioxide.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

SummaryThe possible acute deleterious effects of maternal glucocorticoid administration on the fetal nervous system and the pathologic significance of sudanophilic lipids in glial cells were studied in the premature pigtail monkey (macaca mulatta). At 72, 48, and 24 h before delivery at 135 ± 1 d gestation, dams were treated with either 4 mg dexamethasone or saline. After delivery, respiratory function of each fetus was determined and supported. The animals were sacrificed at 3 h of age.Brain weights were similar in the two groups. Dark, shrunken, pyknotic neurons were present in the hippocampus of three treated and two control animals. Lipid-containing glial cells were present in all animals. Neither appeared to be related to steroid treatment or to the degree of respiratory distress.We conclude that short-term glucocorticoid therapy in doses analogous to those used in humans for the prevention of hyaline membrane disease does not result in acute neuronal damage. Sudanophilic lipid accumulation in glial cells is not always abnormal and must be distinguished from glial fatty metamorphosis.

ISSN:0031-3998    

出版商:OVID    

年代:1984

数据来源: OVID