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71.
Summary We used specific binding of phlorizin to the intact intestinal mucosa in order to measure glucose transport site density in intestines of mice fed a high-carbohydrate or no-carbohydrate diet. Nonspecific binding varied with intestinal position but showed only modest dependence on diet. Specific binding to glucose transporters was 1.9 times greater in jejunum of high-carbohydrate mice than of no-carbohydrate mice; this ratio was the same as the ratio for Vmax values of actived-glucose uptake between the two diet groups. The gradient in specific binding of phlorizin along the intestine paralleled the gradient in Vmax of glucose transport. These results directly demonstrate that the increase in intestinal glucose transport caused by a high-carbohydrate diet is due to induction of glucose transporter. They also indicate that the normal positional graident in glucose transport along the intestine arises from a gradient in transporters, induced by the normal gradient in luminal glucose concentration. 相似文献
72.
73.
Chemical limnology of two artificial lakes used for both stormwater management and recreation 总被引:1,自引:1,他引:0
The aims of this study were to document the mainly chemical behaviour of two linked artificial lakes used for both stormwater management and recreation in the new town of Craigavon. Further, the understanding of their behaviour should help in their management and the design of other similar lakes.The lake mean total phosphorus (73 µg P l–1), nitrate (0.50 mg N l–1) and chlorophyll a (25 µg l–1) concentrations, Secchi depth (1.2 m) and the estimated total phosphorus loading (1.98 g m–2 a–1) all classify the main lake as eutrophic. An important source of the phosphorus load on the lakes is the urban area of Craigavon (52% of the total load). The interrelationships between total phosphorus, chlorophyll a and Secchi depth in the main lake are similar to those in natural ones. In addition, the lake follows the total phosphorus load — trophic state relationships (lake total phosphorus and chlorophyll a concentrations and Secchi depth) found to apply elsewhere. These two points indicate that the artificial lakes in Craigavon behave similarly to natural ones. 相似文献
74.
Summary The tumor promotor 12-O-tetradecanoylphorbol-13-acetate (TPA) was examined for its ability to induce endogenous retrovirus from a high-passage clone
of Kirsten sarcoma virus-transformed Balb/c (K-Balb) mouse cells. TPA activated virus in a concentration-dependent manner
(0.0016 to 4.0 μM). Exposure to 1mM actinomycin D inhibited virus induction, suggesting that cellular RNA synthesis is required de novo by this inducer. A broad-spectrum
neutralizing antibody to murine type C virus, gp70, was shown to neutralize the infectivity of the induced virus. The activated
virus had the host range of the xenotropic Balb virus:2, and after removal of the inducer, the activated state decayed rapidly.
TPA stimulated DNA, RNA, and protein synthesis in K-Balb cells, indicating that the mechanism of inducation may be different
from that of previously identified virus inducers. The effects observed using the well-defined K-Balb system offer an opportunity
to study the modulation of retrovirus gene expression by TPA.
This work was conducted while the authors were with the Biological Carcinogenesis Program, Frederick Cancer Research Facility,
Frederick, MD 21701, and was supported under Contract NO1-CO-75380 with the National Cancer Institute, National Institutes
of Health, Bethesda, MD 20205. 相似文献
75.
用电镜观察了经受诱导作用之后胚胎细胞的冷冻蚀刻复型膜。和未经诱导作用的对照组比较,早期和中期神经胚的神经上皮细胞以及经过豚鼠骨髓粗提液(BME)——一种有效的异源中胚层诱导物——处理过的早期原肠胚外胚层,它们的间隙连接都处于活跃的动态状态。用图像分析仪测得的间隙连接连接子的排列密度,指出经受过诱导作用的三组分别和未经受诱导作用的对照组比较,计算求出P值,神经上皮两组和对照组的差别为非常显著,BME处理过的细胞和对照组的差别为显著。结合对照组与诱导后胚胎细胞间隙连接连接子的变化讨论了它们在信息传递上可能起的作用。 相似文献
76.
The effect of lake restoration measures on the physical,chemical and phytoplankton variables of Lake Bled 总被引:2,自引:2,他引:0
Monthly changes of physical, chemical and biological variables due a combination of artificial inflow of clean water, removal of hypolimnetic water, and diversion of sewage were studied in Lake Bled from December 1980 to December 1982.During the winter period 1981/82 the species composition of the phytoplankton changed. New species replaced those observed in previous years. We conclude that the combined effect of these three lake restoration measures was responsible for the sudden disappearance ofOscillatoria rubescens D.C. A marked decrease in some nutrients and an increase in temperature and oxygen concentration also occurred. 相似文献
77.
Herbert Axelrod Gregory DeLozier Sandra Greene Alexander McPherson 《Journal of Protein Chemistry》1985,4(4):235-243
A chemical modification of the gene 5 DNA binding protein (G5BP) from bacteriophage fd was investigated using X-ray diffraction and difference Fourier analysis. The crystalline protein was reacted with pentaammineruthenium (III) trichloride, Ru(NH3)5Cl3, a reagent believed specific for histidine residues and useful in NMR and chemical modification studies of proteins. The major ruthenium site was found by difference Fourier analysis to be 4 Å from histidine 64, the only histidine residue in the molecule. A second bipartite site, believed to be a ruthenium-anion pair, appeared to be salt-bridged to glutamic acid 40 and arginine 16. Indications were present in the difference Fourier results to suggest that the loop containing tyrosine 41 had undergone a slight conformational rearrangement to accommodate this interaction. 相似文献
78.
George T. Javor 《FEMS microbiology letters》1985,27(2):243-245
Abstract Streptococcus lactis strain IL594 contains 9 plasmids, designated pIL1 to pIL9. On the basis of protoplast-induced curing experiments we showed that derivatives containing pIL7 (31 kb) were resistant to UV-irradiation while derivatives lacking pIL7 were sensitive. The pIL7-determined UV-protection was confirmed by cotransfer of the plasmid and of the character into a plasmid-free derivative of S. lactis IL594. Moreover, prophage induction required higher UV-fluence in this derivative carrying pIL7 than in the plasmid-free strain. This is the first report of a plasmid-mediated UV-protection in group N streptococci. 相似文献
79.
This work describes a neutral and alkaline elution method for measuring DNA single-strand breaks (SSBs), DNA double-strand breaks (DSBs), and DNA-DNA crosslinks in rat testicular germ cells after treatments in vivo or in vitro with both chemical mutagens and gamma-irradiation. The methods depend upon the isolation of testicular germ cells by collagenase and trypsin digestion, followed by filtration and centrifugation.
137Cs irradiation induced both DNA SSBs and DSBs in germ cells held on ice in vitro. Irradiation of the whole animal indicated that both types of DNA breaks are induced in vivo and can be repaired. A number of germ cell mutagens induced either DNA SSBs, DSBs, or cross-links after in vivo and in vitro dosing. These chemicals included methyl methane sulfonate, ethyl methane sulfonate, ethyl nitrosurea, dibromochlorpropane, ethylene dibromide, triethylene melamine, and mitomycin C. These results suggest that the blood-testes barrier is relatively ineffective for these mutagens, which may explain in part their in vivo mutagenic potency.This assay should be a useful screen for detecting chemical attack upon male germ-cell DNA and thus, it should help in the assessment of the mutagenic risk of chemicals. In addition, this approach can be used to study the processes of SSB, DSB, and crosslink repair in DNA of male germ cells, either from all stages or specific stages of development.Abbreviations DBCP
dibromochlorpropane
- DSB(s)
DNA double-strand break(s)
- EDB
ethylene dibromide
- EMS
ethyl methane sulfonate
- ENU
ethyl nitrosurea
- MC
mitomycin C
- MMS
methyl methane sulfonate
- SDS
sodium dodecyl sulfate
- SSB (s)
DNA single-strand break(s)
- TEM
triethylene melamine
- UDS
unscheduled DNA synthesis 相似文献
80.