摘要:

ExtractA simple technique, precipitation with acetone, was described to separate the surface-active lecithin fraction from the nonsurface-active fraction. Surface activity in lung phospholipids was found in the acetone-precipitated fractions of lecithin, sphingomyelin, phosphatidyl dimethylethanolamine and phosphatidyl inositol. Normal surface activity of saline extract of pooled fetal rabbit lung was observed from 28 days of gestation. It was possible to isolate surface-active lecithin from lung parenchyma long before the 29th day of gestation when surface-active lecithin first is found in the alveolar wash. During the nonbreathing fetal state, even at term, only 11% of lecithin from alveolar wash is surface-active increasing after one hour's breathing to approximately 50% of the total lecithin. The rabbits delivered prematurely after 28 full days of gestation clinically had respiratory distress and their percentage of surface-active lecithin in alveolar wash increased at a slow rate compared to full-term animals. Good temporal correlation was seen between intracellular storage of surface-active lecithin during the fetal state and the findings with electron microscopy of increasing numbers of osmiophilic inclusion bodies as gestation progresses.SpeculationSurface activity is shared by several phospholipids in lung but is related principally to lecithin. During fetal development there is production of intracellular surface-active lecithin with storage possibly in osmiophilic lamellar inclusion bodies until near term when some (11%) begins to appear in alveolar wash. After breathing, a great release of surface-active lecithin into alveolar wash occurs, with 50% of alveolar lecithin being surface active throughout the life of the animal. Prematurely delivered rabbits take much longer to increase their surface-active alveolar lecithin.

ISSN:0031-3998    

出版商:OVID    

年代:1967

数据来源: OVID

摘要:

ExtractIn the lung of the rabbit fetus there was a rise in concentration of total lipids before term, the phospholipids constituting the major fraction. The concentrations of phosphatidylethanolamine and lecithin rose concurrently until day 28 when phosphatidylethanolamine concentration dropped, but lecithin continued to rise to term. From day 28 to term in the nonbreathing fetus there was an increase of 300% in acetone-precipitated surface-active lecithin found almost entirely in the residual parenchyma after wash with little increase in this fraction in alveolar wash. After breathing for 1 hour there were increases in total alveolar lecithin 3–5 fold over nonbreathing fetal lung while increases in acetone-precipitated alveolar wash lecithin from nonbreathing to breathing lung were 20–30 fold. Enzymatic reactions were studiedin vitroaccording to the pathways for thede novosynthesis of lecithin and phosphatidylethanolamine as follows:1. CDP-(1,2-14C) choline+D-α, β-diglyceride→cithin2. Phosphatidylethanolamine+3(14CH3)-S-adenosyl-L-methionine→cithin3. CDP-(1,2-14C) ethanolamine+D-α, β-diglyceride→phosphatidylethanolamine4. Phosphatidylethanolamine+(14C)-L-serine→phosphatidylserine-CO2→phosphatidylethanolamineCDP-choline incorporation declined steadily during gestation, although at term still showed rapid incorporation. The methylation reaction (2) showed peak incorporation on day 28 of gestation, at beginning viability. CDP-ethanolamine incorporation was the most activein vitropathway studied peaking on days 25–26. Serine incorporation showed little activity, following a pattern of incorporation similar to that of CDP-ethanolamine. Activity of all pathways was found in microsomes. Methylation was also found in mitochondrial fraction of the term fetus and adult and in the cell-free soluble fraction from adult alveolar lavage. Reaction rates were similar from CDP-choline incorporation in both fetal and adult lung homogenate, but fetal lung incorporated methyl groups faster than adult lung. Intermediate compounds of methylation reaction were not found in alveolar wash of fetal lung, but were isolated from adult alveolar wash. Methylation in lung was pH sensitive, peak incorporation was seen at pH 7.8. Addition of ethanol or boiling one minute did not stop methylation. After breathing, those rabbit fetuses delivered by cesarean section after 28 full days of gestation synthesized 100% of surface-active alveolar lecithin by one hour of breathing, 90% of incorporation was with3H-choline, 10% with (14CH3)-methionine. Much less incorporation into alveolar wash lecithin was seen with the breathing term fetus, but much more surface-active alveolar wash lecithin was isolated than from the fetus of 28 full days of gestation.

ISSN:0031-3998    

出版商:OVID    

年代:1967

数据来源: OVID

摘要:

ExtractRates of urinary excretion of total hydroxyproline by 38 normal fullsize male infants were determined on 176 occasions. Each urine collection period was 72 hours. When the period of urine collection was begun between the fourth and eighth day of life, mean rate of excretion was 30.6 mg/day (standard deviation 6.9 mg/day). Maximal rates of urinary excretion were observed between 21 and 60 days of age (mean: 48.1 mg/day; standard deviation 9.7 mg/day). Between 121 and 582 days of age, mean rate of excretion had decreased slightly to 43 mg/day.Eleven infants were each studied on at least five occasions between 20 and 120 days of age. Mean rate of urinary excretion of hydroxyproline by each infant was shown to be significantly correlated with rate of gain in length but not with rate of change in weight or surface area.SpeculationDuring normal infancy it seems probable that a major proportion of the hydroxyproline excreted in the urine is derived from collagen of bone. Rate of excretion probably parallels rate of bone growth. Thus, any disorder that depresses the normal rate of linear growth is likely to result in sharp diminution of urinary excretion of hydroxyproline. Such a biochemical index of growth may be clinically useful.

ISSN:0031-3998    

出版商:OVID    

年代:1967

数据来源: OVID

摘要:

ExtractAn intravenous injection of 100 units of thyrocalcitonin was given after an 18-hour fast to seven normal children and seven children with hypothyroidism. The effect on levels of calcium in blood was measured 1, 2, 4, 6 and 24 hours after injection. Among the normal children, the average decrease in levels of calcium in mg/1 was 1 h, 7.70 ± 3.08; 2 h, 5.40 ± 2.82; 4 h, 2.30 ± 2.85; 6 h, 1.30 ± 2.24; 24 h, 1.40 ± 2.35. In the hypothyroid children (5 with athyreosis and 2 with thyroid dysgenesis) the decrease was 1 h, 9.40 ± 2.52; 2 h, 10.50 ± 2.17; 4 h, 9.40 ± 2.29; 6 h, 8.10 ± 2.54; 24 h, 2.00 ± 3.22. In comparison with the normal children, the hypocalcemia in the hypothyroid children was greater and more prolonged.SpeculationThe hypocalcemic effect of the thyrocalcitonin is more important for the child than for the adult. This fact is no doubt related to the mechanism of the hypocalcemic action of the thyrocalcitonin, which is the inhibition of the osseous catabolism. The release of thyrocalcitonin causes an imbalance in calcium metabolism, which results in a hypocalcemia more marked in the normal child than in the adult, and in the hypothyroid than in the normal child.

ISSN:0031-3998    

出版商:OVID    

年代:1967

数据来源: OVID

摘要:

ExtractThis study was devised to ascertain (1) the extent and direction of changes in intracellular hydrogen ion activity in unmodified salicylate intoxication, and (2) whether an intracellular metabolic acidosis was unmasked or decompensated when the Pco2was maintained at normal levels. Sixteen mongrel dogs were studied in 3 groups: 1. Controls; 2. Salicylate intoxicated dogs (given 300 mg/kg of sodium salicylate intravenously; and 3. Mechanically hyperventilated dogs given no salicylate. Skeletal muscle intracellular hydrogen ion activity was determined at intervals in each group using14C-labelled 2,4-dimethyl oxazolidinedione, tritiated water and36Cl ion. In the controls the intracellular hydrogen ion activity did not deviate significantly from the average value of 130.9 nEq/1*over periods ranging from 4–12 hours. In group 2, intracellular hydrogen ion activity fell from a presalicylate value of 129.7 nEq/1 to 102.1 at 2 hours, 87.0 at 3 hours, and 81.5 at 4 hours. When 2–4% CO2was given and the Pco2was stabilized at 30–40 mm Hg, the intracellular hydrogen ion activity returned to normal. In the group 3 dogs it fell from 136.8 nEq/1 to 87.7 over 4 hours and also returned to normal when CO2was given. Results from 3 representative dogs are shown in figure 2. The authors conclude that (1) intracellular hydrogen ion activity falls significantly in salicylate intoxication due to salicylate-induced hyperventilation, and (2) no major metabolic acidosis could be demonstrated within the cells when the Pco2was held at normal levels.SpeculationThe use of THAM or large doses of sodium bicarbonate to alkalinize urine may not be entirely benign though the usefulness of these drugs as salicyluric agents is not questioned. Inhalation of CO2may warrant further research as a possible therapeutic agent for cases of salicylate intoxication in which a metabolic acidosis has not become apparent from extracellular fluid data.*nEq = 10-9equivalents.

ISSN:0031-3998    

出版商:OVID    

年代:1967

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1967

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1967

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1967

数据来源: OVID