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1.
BHK cells either untreated or infected with Semliki Forest virus have been fractionated on sucrose density gradients. Virus infection caused an increase in density of a membrane fraction enriched in sphingomyelin (SM), cholesterol, SM synthase and sialyltransferase activity. This increase in density was related to incorporation of viral proteins into this fraction, which is likely to contain trans-Golgi network (TGN) membranes. In contrast, glucosylceramide synthase and galactosyltransferase activities (markers for cis/medial and trans-Golgi respectively) underwent no density shift and alkaline phosphodiesterase, a plasma membrane marker, was only slightly density-shifted in infected cells. When cells were incubated with NBD-ceramide to enable them to synthesise NBD-SM and then washed with albumin to remove surface label, fluorescence in untreated cells was concentrated in a single juxtanuclear spot but in infected cells this region of bright fluorescence was larger and extended around the nucleus. After fractionation of these cells, NBD-SM (but only a small proportion of the NBD-ceramide) was found to be shifted into the higher density fraction in infected cells. This work provides further evidence that SM synthase is not mainly localised in the early Golgi cisternae as previously thought, but is associated more with a cholesterol-rich compartment which could be the TGN. 相似文献
2.
3.
Allan M. Littell 《Applied microbiology》1977,33(2):485-487
A differential plating medium developed for isolation of Salmonella arizonae produces a uniform reaction for both lactose-negative and -positive S. arizonae and differentiates S. arizonae from other salmonellae. 相似文献
4.
The ras oncogene and tumour metastasis: observations on murine cells transfected with activated human c-Ha-ras 总被引:1,自引:0,他引:1
Jeannie S. Wallace Allan J. Hayle Allan J. Syms Margaret Cairney Ben Tutty rew Gazzard Mark F. Evans Kenneth A. Fleming David Tarin 《Differentiation; research in biological diversity》1989,41(3):208-215
Transfection of cells with cloned genes or total genomic DNA offers a means for studying aspects of neoplastic behaviour. We have used this method to examine whether incorporation of the cloned 6.6-kilobase (kb) fragment of DNA containing the mutant c-Ha-ras human oncogene can confer metastatic capability on murine NIH 3T3 cells. Cells co-transfected with the mutated ras gene and the neomycin resistance marker pSV2neo were selected by culture in neomycin. On subcutaneous inoculation into MF 1 nude mice, these cells proved to be tumourigenic with short latent periods (approximately 14 days)--nude mice were used to circumvent immunological rejection of the mouse cells expressing the product of the human oncogene. Transfectants were capable of lung colonisation after intravenous injection, but there was no evidence of spontaneous metastasis at autopsy, or on histological examination of the lungs and other organs, 90 days after inoculation. Incorporation of the transfected oncogene was confirmed by Southern blotting and its expression by dot-blot hybridisation and immunoprecipitation. The results in this experimental system indicate that transfection of a mutated human ras oncogene into non-neoplastic 3T3 cells can confer part of the metastatic phenotype, namely lung colonisation, but is not by itself sufficient to induce spontaneous metastatic behaviour. 相似文献
5.
Reclustering of scattered Golgi elements occurs along microtubules 总被引:43,自引:0,他引:43
W C Ho V J Allan G van Meer E G Berger T E Kreis 《European journal of cell biology》1989,48(2):250-263
Depolymerization of the interphase microtubules by nocodazole results in the scattering and apparent fragmentation of the Golgi apparatus in Vero fibroblast cells. Upon removal of the drug, the interphase microtubules repolymerize, and the scattered Golgi elements move back to the region around the microtubule-organizing center (MTOC) within 40 to 60 min. Using a fluorescent lipid analogue (C6-NBD-ceramide) as a vital stain for the scattered Golgi elements, their relocation was visualized by video-enhanced fluorescence microscopy in Vero cells maintained at 20 degrees C. The NBD-labeled structures were identified as Golgi elements by their colocalization with galactosyltransferase in the fixed cells. During reclustering, NBD-labeled Golgi elements were observed to move by discontinuous saltations towards the MTOC with velocities of 0.1 to 0.4 micron/s. Paths along which Golgi elements moved were super-imposable on microtubules visualized by indirect immunofluorescence. Neither the collapse of intermediate filaments caused by microinjection of antibodies to vimentin nor the disruption of microfilaments by cytochalasin D had an effect on the reclustering of Golgi elements or the positioning of the Golgi apparatus. These data show that scattered Golgi elements move along microtubules back to the region around the MTOC, while neither intact intermediate filaments nor microfilaments are involved. 相似文献
6.
Testosterone, and winning and losing in human competition 总被引:9,自引:4,他引:5
Alan Booth Greg Shelley Allan Mazur Gerry Tharp Roger Kittok 《Hormones and behavior》1989,23(4):556-571
Testosterone and cortisol were measured in six university tennis players across six matches during their varsity season. Testosterone rose just before most matches, and players with the highest prematch testosterone had the most positive improvement in mood before their matches. After matches, mean testosterone rose for winners relative to losers, especially for winners with very positive moods after their victories and who evaluated their own performance highly. Winners with rising testosterone had higher testosterone before their next match, in contrast to losers with falling testosterone, who had lower testosterone before their next match. Cortisol was not related to winning or losing, but it was related to seed (top players having low cortisol), and cortisol generally declined as the season progressed. These results are consistent with a biosocial theory of status. 相似文献
7.
In situ high-temperature, high-pressure Raman experiments on 3 mM (pH 5) aqueous solutions of hen egg-white (HEW) lysozyme show a decrease in the relative height of the 505 cm–1 band associated with S-S stretching vibrations at 72°C (1 bar). The peak height changes are accompanied by significant band broadening, and the integrated band intensity does not change within experimental error. The effect of increased pressure at 72°C was to hinder broadening of the 505 cm–1 band. HEW lysozyme (2.4 mM,pH 5) was also heated at 76°C, 80°C, and 95°C for different periods of time, and aliquots were quenched to room temperature for Raman and enzymatic activity measurements. After 9 hr at 76°C, the protein exhibits enzyme activity less than 50% of the initial value, and approximately 50% reduction in activity is achieved after 3 hr at 80°C or 1 hr at 95°C. The Raman results suggest that different irreversibly denatured conformations are attained during prolonged exposures at these different temperatures. It is apparent from these studies that the S-S stretch intensity is decreased irreversibly. 相似文献
8.
Marijo G. Kent Robert N. Shoffner Allan Hunter Keith O. Elliston Wesley Schroder Elizabeth Tolley Stephen S. Wachtel 《Human genetics》1988,79(4):321-328
Summary An inherited genetic disorder causes XY embryos of the horse to develop as mares. On the basis of our study of 38 such mares, we have identified four grades or classes of XY sex reversal according to this scheme: class I, nearly normal female, of which some are fertile; class II, female with gonadal dysgenesis, normal mullerian development; calss III, intersex mare with gonadal dysgenesis, abnormal mullerian development, enlarged clitoris; class IV, virilized intersex characterized by high levels of testosterone. In general, class I and calss II mares were typed H-Y antigen-negative whereas class III and class IV mares were typed H-Y antigen-positive. 相似文献
9.
We describe practical, effective, office-based methods for physicians to use to assist patients to stop smoking that do not require special training or support personnel. Brief counseling achieves smoking cessation in a small percent of well patients but is more effective in patients with smoking-related illnesses or abnormal laboratory test results. Routine prescribing of nicotine gum without participation by the patient in a smoking-cessation program does not increase smoking cessation, and we do not recommend it. The prevention of smoking relapse can probably be enhanced by scheduling follow-up office visits after the patient has quit. Failure to quit on initial attempts should not discourage physicians and patients, since most successful abstainers usually must make several attempts to quit. We outline for physicians two approaches, one brief and one more intensive, to help patients stop smoking. 相似文献
10.
The effects of light intensity and nutrient availability on the biomass allocation of Calamagrostis canadensis were studied under both greenhouse and field conditions In the greenhouse, seedlings from forest and wetland populations were grown in sand-peat mixtures, under three light intensities and three fertilizer levels Total above and below ground growth increased with light intensity and nutrient availability, nutrient availability, however, only altered plant growth when light intensity was above moderate levels Numbers of rhizomes were greatest under low and moderate nutrient regimes but high light was also needed for maximum numbers of rhizomes In the field, tillers and rhizomes were examined under open, 40% and 85% canopy cover Tiller and rhizome weight and diameter of rhizomes decreased with canopy closure However, proportional allocation of biomass to rhizomes was greatest and percentage total non-structural carbohydrates of rhizomes was lowest under a 40% canopy 相似文献