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991.
Effect of chronic ethanol and food deprivation on intestinal villus morphology and brush border membrane content of lipid and marker enzymes 总被引:3,自引:0,他引:3
M Keelan K Walker A B Thomson 《Canadian journal of physiology and pharmacology》1985,63(10):1312-1320
Brush border membranes (BBM) were isolated from the jejunum and ileum of control, ad libitum (CAL); control, food-restricted (CFR); control, weight gain (CWG); and ethanol-fed (EF) rabbits. Jejunal alkaline phosphatase activity was similar among control groups, but higher in CAL than EF animals. Sucrase activity was higher in EF and CWG animals than in CAL and CFR. The alkaline phosphatase/sucrase ratio was lower in EF than control animals. Ileal enzyme marker activity was similar among EF and control animals. Sucrase (S) activity was lower in the ileum than in the jejunum. Jejunal free fatty acid and phospholipid/cholesterol (PL/C) were lower in EF than control animals, whereas ileal lipid content was generally similar among all animal groups. Total phospholipid content was similar between sites, but the cholesterol and free fatty acid content were lower in the ileum than the jejunum. The phospholipid/cholesterol ratio was increased only in the ileum of EF animals. The amount of lecithin was decreased in the jejunal BBM of EF animals resulting in a decreased choline/amine phospholipid ratio as compared with control animals. The ileal phospholipid composition was similar among all groups. A large increase in villus height is observed in the jejunum of EF animals. Villus surface area and mucosal surface area are altered with ethanol feeding and food deprivation. Thus, (i) there is a gradient of S and cholesterol between the BBM of jejunum and ileum; (ii) changes in food intake are associated with changes in the morphology as well as the enzyme marker and lipid content of BBM.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
992.
Incubation of protein kinase C (PKC) alpha with phorbol 12,13-dibutyrate and phospholipid vesicles promoted a time-dependent irreversible insertion of the enzyme into the vesicles and the generation of a calcium-independent kinase activity. Calcium neither caused insertion nor influenced the insertion induced by the phorbol ester. The effect was strongly dependent on the phosphatidylserine concentration in the vesicle and could also be supported by other anionic phospholipids. An analysis of the structure-activity relations of PKC activators for the calcium-independent kinase activity revealed marked relative differences in potencies for binding and for insertion. Compounds such as phorbol 13-myristate 12-acetate and mezerein were very efficient at inducing insertion. In contrast, 12-deoxyphorbol esters and diacylglycerol were relatively inefficient at inducing insertion, requiring higher concentrations than expected from their binding affinities. The insertion of PKC alpha depended substantially on the length of the aliphatic esters in the 12- and 13-positions of the phorbol derivatives, and once again, potencies for insertion and binding were not directly proportional. Our findings suggest two different sites for ligand interaction on the molecule of PKC alpha with different structure-activity requirements. We speculate that the differential ability of compounds to promote insertion could contribute to the documented marked differences in the biological behavior of PKC activators. 相似文献
993.
P W Blick M W Flowers A K Marsden D H Wilson A T Ghoneim 《BMJ (Clinical research ed.)》1980,281(6233):111-112
A four-way, double-blind, prospective trial of treatment of abscesses by incision, curettage, and primary closure with and without antibiotic cover (clindamycin injection before operation or capsules after operation, or both) was conducted. There was no appreciable difference in mean healing time between the patients given both the antibiotic injection and the antibiotic capsules and those given the injection and placebo capsules, whereas healing times in those given the placebo injection and antibiotic capsules or placebo only were appreciably longer. Four of the patients who were not given the antibiotic injection developed bacteraemia; one patient who was given the antibiotic injection also developed a bacteraemia, but this was caused by clindamycin-resistant bacteria. These results show that a single injection of an effective antibiotic before operation is sufficient to protect the patient against bacteraemia and permit optimum healing. 相似文献
994.
995.
K. V. Minin 《Paleontological Journal》2012,46(8):927-935
A study of the morphological variability of seven species of sea urchins of the genus Echinus from the Northeast Atlantic and Arctic with different depth preferences showed that in the group of species E. tenuispinus, E. esculentus, E. melo, E. acutus, E. elegans, E. affinis, and E. alexandri, arranged based on increasing depth of occurrence, the maximum test diameter decreases, the diameter of the apical system increases, the ratio of the number of interambulacral plates to the number of ambulacral plates increases, buccal and periproctal spines tend to disappear, and the number of ambulacral plates lacking a primary tubercle sharply decreases. At the same time, the test height decreases, while the number of secondary tubercles on coronal plates and number of lateral teeth on the valves of the globiferous pedicellariae increases. The change in the first six characters reflects the process of retention of juvenile features in deep-water Echinus. Similar trends in test height, apical system diameter and the ratio of the number of interambulacral plates to the number of ambulacral plates are recorded while comparing shallow-water and deep-sea populations of the eurybathic species E. acutus. This suggests that this species may currently be in the process of speciation. 相似文献
996.
Steven I. Higgins Robert B. O’Hara Olga Bykova Michael D. Cramer Isabelle Chuine Eva‐Maria Gerstner Thomas Hickler Xavier Morin Michael R. Kearney Guy F. Midgley Simon Scheiter 《Journal of Biogeography》2012,39(12):2132-2145
Aim To develop a physiologically based model of the plant niche for use in species distribution modelling. Location Europe. Methods We link the Thornley transport resistance (TTR) model with functions which describe how the TTR’s model parameters are influenced by abiotic environmental factors. The TTR model considers how carbon and nutrient uptake, and the allocation of these assimilates, influence growth. We use indirect statistical methods to estimate the model parameters from a high resolution data set on tree distribution for 22 European tree species. Results We infer, from distribution data and abiotic forcing data, the physiological niche dimensions of 22 European tree species. We found that the model fits were reasonable (AUC: 0.79–0.964). The projected distributions were characterized by a false positive rate of 0.19 and a false negative rate 0.12. The fitted models are used to generate projections of the environmental factors that limit the range boundaries of the study species. Main conclusions We show that physiological models can be used to derive physiological niche dimensions from species distribution data. Future work should focus on including prior information on physiological rates into the parameter estimation process. Application of the TTR model to species distribution modelling suggests new avenues for establishing explicit links between distribution and physiology, and for generating hypotheses about how ecophysiological processes influence the distribution of plants. 相似文献
997.
998.
999.
N. Pekkala K. E. Knott J. S. Kotiaho K. Nissinen M. Puurtinen 《Journal of evolutionary biology》2012,25(11):2181-2193
Interpopulation hybridization can increase the viability of small populations suffering from inbreeding and genetic drift, but it can also result in outbreeding depression. The outcome of hybridization can depend on various factors, including the level of genetic divergence between the populations, and the number of source populations. Furthermore, the effects of hybridization can change between generations following the hybridization. We studied the effects of population divergence (low vs. high level of divergence) and the number of source populations (two vs. four source populations) on the viability of hybrid populations using experimental Drosophila littoralis populations. Population viability was measured for seven generations after hybridization as proportion of populations facing extinction and as per capita offspring production. Hybrid populations established at the low level of population divergence were more viable than the inbred source populations and had higher offspring production than the large control population. The positive effects of hybridization lasted for the seven generations. In contrast, at the high level of divergence, the viability of the hybrid populations was not significantly different from the inbred source populations, and offspring production in the hybrid populations was lower than in the large control population. The number of source populations did not have a significant effect at either low or high level of population divergence. The study shows that the benefits of interpopulation hybridization may decrease with increasing divergence of the populations, even when the populations share identical environmental conditions. We discuss the possible genetic mechanisms explaining the results and address the implications for conservation of populations. 相似文献
1000.
Pro-opiomelanocortin (POMC) was expressed in CV-1 (green monkey kidney) cells using a vaccinia virus transient expression system [(1986) Proc. Natl. Acad. Sci. USA 83, 8122]. The system involved infection of cells with a recombinant vaccinia virus carrying the T7 RNA polymerase gene and transfection with a plasmid containing the mouse POMC sequence flanked by the T7 RNA polymerase promoter at its 5'-end and the T7 RNA polymerase terminator at its 3'-end. Assay of the medium from transfected cells showed that 1-2 micrograms of immunoreactive ACTH was produced/10(6) cells. Analysis of the same medium by SDS-PAGE/Western blots revealed a band of 30-36 kDa, which was immunostained with both ACTH and beta-endorphin antisera. Labeling the transfected cells with [3H]Arg, followed by immunoprecipitation and SDS-PAGE showed the synthesis of a major peak of POMC, 33 kDa. Purified [3H]POMC expressed by CV-1 cells was cleaved in vitro by bovine intermediate lobe secretory vesicle pro-opiomelanocortin-converting enzyme to ACTH intermediates (19-25 kDa), beta-lipotropin and beta-endorphin. Thus, this work has demonstrated a technique for expressing microgram quantities of prohormones in mammalian cells, suitable for use as substrates for prohormone-converting enzymes in vitro. 相似文献