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171.
Summary Seven mutant strains defective for utilization of glycerol, glyceraldehyde or dihydroxyacetone were isolated. One strain was deficient for NAD-linked glycerol-3-phosphate dehydrogenase, two for glycerol kinase, and four had no detected enzymatic deficiency, although one of the latter strains was deficient in glycerol uptake. Glycerol uptake was increased by incubation in glycerol, glycerol-3-phosphate, erythritol, and propanediol, and was protein-mediated below 0.14 mM glycerol, but at higher concentrations free diffusion predominated. Glycerol uptake was decreased by cycloheximide and was more sensitive to sodium azide than to iodoacetate. 相似文献
172.
Jane E. Langridge-Smith Joseph H. Sellin Michael Field 《The Journal of membrane biology》1983,72(1-2):131-139
Summary In intact ileal mucosa, uptake of SO4 across the brush border membrane requires the presence of Na and is saturable, withK1/2=1.3mm at 140mm Na (P.L. Smith, S.A. Orellana & M. Field, 1981.J. Membrane Biol.
63:199–206). The present study examines the substrate specificities and transport stoichiometry of the Na-dependent SO4 uptake process. The effects of variations in medium anion and cation composition on lumen-to-epithelium influx of SO4 (J
me
SO4
) were determined under short-circuit conditions.J
me
SO4
is inhibited by thiosulfate, but not by phosphate, methylsulfate, vanadate or taurocholate. Cl is weakly inhibitory. Uptake of SO4 is poorly supported by Li, and is unaffected by K, indicating a specific dependence on Na. At low SO4 concentration (0.22mm),J
me
SO4
is a hyperbolic function of medium Na concentration; the corresponding Hill plot is linear with a slope of 1.0, suggesting a transport stoichiometry of 1 Na: 1 SO4. At high SO4 concentration (6.7mm), the Na-dependent SO4 velocity curve is sigmoidal and yields a Hill plot which is again linear but has a slope of 1.56, suggesting transport of more than 1 Na per SO4. SO4 uptake in presence of Na exhibits a dependence on medium pH. At 0.22mm SO4 and 140mm Na,J
me
SO4
was doubled by lowering pH from 7.4 to 6.8. However, at 6.7mm SO4 and 140mm Na, changing pH had no effect onJ
me
SO4
over the range 6.8 to 8.5. The pH dependence ofJ
me
SO4
at 6.7mm SO4 was restored when medium Na was lowered to 3mm, suggesting that pH sensitivity is a function of the concentration of preformed NaSO
4
–
ion pair. The results suggest that SO4 influx across the ileal brush border occurs by electroneutral Na+/NaSO
4
–
or Na+/H+/SO
4
2–
cotransport, the former being favored by high concentrations of Na and SO4. 相似文献
173.
Health care attitudes reflect the basic world view and values of a culture, such as how we relate to nature, other people, time, being, society versus community, children versus elders and independence versus dependence. Illness behavior determines who is vulnerable to illness and who agrees to become a patient—since only about one third of the ill will see a physician. Cultural values determine how one will behave as a patient and what it means to be ill and especially to be a hospital patient. They affect decisions about a patient''s treatment and who makes the decisions. Cultural differences create problems in communication, rapport, physical examination and treatment compliance and follow through. The special meaning of medicines and diet requires particular attention. The perception of physical pain and psychologic distress varies from culture to culture and affects the attitudes and effectiveness of care-givers as much as of patients. Religious beliefs and attitudes about death, which have many cultural variations, are especially relevant to hospital-based treatment. Linguistic and cultural interpreters can be essential; they are more available than realized, though there are pitfalls in their use. Finally, one must recognize that individual characteristics may outweigh the ethnic and that a good caring relationship can compensate for many cultural missteps. 相似文献
174.
Copper deficiency was produced in developing rodents to study a possible interaction between copper and the selenoenzyme, glutathione peroxidase (GSH-Px). Dietary copper deficiency was investigated in Sprague-Dawley rats and in three mouse strains (C57BL, C3H/HeJ, C58); genetic copper deficiency was studied in two of the mouse strains, C57BL and C3H/HeJ, using brindled mice. In certain cases it appeared that copper deficiency was associated with depressed liver GSH-Px activity; values from copper-deficient livers were 40–70% of control values. However, the decrease in liver GSH-Px in both rats and mice was only observed when body weight was also depressed and did not necessarily correlate with copper deficiency signs, such as lower serum ceruloplasmin or liver cytochrome oxidase activities. In weanling rats, serum GSH-Px activity was normal despite a 60% reduction in liver activity. Mouse liver GSH-Px activity rose fourfold during the first 3 weeks of life to 75% of the adult level. Rat liver GSH-Px also increased during the suckling period. When perinatal copper deficiency, nutritional or genetic, was severe enough to retard growth, liver GSH-Px activity was depressed. Unlike rats, adult murine liver GSH-Px was equivalent in males and females. 相似文献
175.
The purpose of this study was to investigate the coexistence of gamma-aminobutyric acid (GABA) and leu-enkephalin in single neurons from the corpus striatum. Monolayer cell cultures, started from newborn rat corpus striatum, were grown in serum-free medium and examined using GABA autoradiography and leu-enkephalin immunocytochemistry in a double-label protocol. Examples of cells were found which were positive for one or the other neurotransmitter or for neither transmitter, but not for both. Furthermore, cells which appear similar by morphological criteria alone differed in transmitter specificity. We conclude that the two transmitters tested are not localized within single cells and that morphology alone is inadequate to identify functional cell classes in this area. 相似文献
176.
Lymphocytes obtained from CLL patients exhibited a delayed and reduced response to PHA when cultured in diffusion chambers. DNA synthesis (8–10 hr) and general time (15–19 hr) of the late-developing CLL blasts were consistent with normal values ( T s : 8–10 hr; T c : 14–17 hr). However, the G2 period of CLL blasts seemed more variable, and their mitotic index during the response at 5–6 days was 30–50% of the values determined for normal blasts during their peak response at 2–3 days. 相似文献
177.
Lambs of known genotype with respect to the locus determining cation composition of red cells were obtained by selective matings. Numbers of K+ pump sites per cell were determined on HK and LK lambs 10–20 days postnatal by simultaneously determining [3H]ouabain binding and inhibition of active K+ transport. Red cells from HK lambs were indistinguishable from adult HK cells with regard to the K+ pump flux and number of pump sites. Cells from genetically LK lambs had pump fluxes and numbers of pump sites intermediate between those from adult HK and LK sheep. The results suggest that the change in cation composition and in the K+ pump during the first 60 days in genetically LK lambs can be correlated with a reduced number of K+ pump sites. 相似文献
178.
179.
180.
THE EFFECTS OF IRON DEFICIENCY ON THE HEPATOCYTE: A BIOCHEMICAL AND ULTRASTRUCTURAL STUDY 总被引:4,自引:1,他引:3
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Effects of iron deficiency on the hepatocyte were studied quantitatively in the rat by combining ultrastructural and biochemical techniques. After 3–8 wk of an iron-deficient diet, the percentage of cytoplasm occupied by mitochondria increased progressively compared with complete diet values. The increment resulted primarily from an enlargement of individual mitochondria rather than from an increased mitochondrial number. Many mitochondria were completely divided by a double membrane, often at a point of constriction. After 2 days of iron administration, mitochondria were of heterogeneous size, shape, and electron opacity. After 5 days, essentially all mitochondria had become normal in configuration. The rate of reversal of the morphological abnormality was more rapid than would be anticipated if it coincided with known rates of renewal of mitochondrial DNA or protein. The concentrations of mitochondrial cytochromes were more rapidly depressed as a result of iron deprivation than those of microsomal cytochromes. Cytochromes c and a were decreased after 3 and 8 wk of exposure to the deficient regimen. Cytochrome P 450 was not decreased after a 3 wk exposure to the deficient diet and responded normally to phenobarbital treatment with a fourfold increase in total hepatic content; its concentration was depressed only after 8 wk of exposure to the deficient diet. There was no reduction in cytochrome b5 concentration. 相似文献