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61.
W B Matthews 《BMJ (Clinical research ed.)》1990,300(6722):412-413
62.
63.
Characterization of an antigenically related family of cell-type specific proteins implicated in slug migration in Dictyostelium discoideum 总被引:1,自引:0,他引:1
Stephen Alexander Elizabeth Smith Loralie Davis rew Gooley Suzanne B. Por Lois Browne Keith L. Williams 《Differentiation; research in biological diversity》1988,38(2):82-90
The monoclonal antibody MUD50 recognizes a group of developmentally regulated proteins, which are almost exclusively expressed by prespore cells in developing aggregates of Dictyostelium discoideum. Some of these antigens are integrally associated with the cell membrane, as assessed by physical and detergent-fractionation procedures. The MUD50-reactive proteins are glycosylated and some are phosphorylated. Post-translational modification is the common antigenic feature that is recognized by the MUD50 antibody in these cell-type-specific proteins. A glycosylation-defective mutant, DL118, (modB) does not express the MUD50 epitope, but does express the MUD52 epitope, which is found on a different group of glycoproteins. Therefore, we conclude that MUD50 recognizes a particular carbohydrate epitope on a restricted group of proteins. These proteins are structurally diverse, but are apparently involved in the maintenance of structure and movement of the multicellular D. discoideum slug. 相似文献
64.
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
65.
A catalogue of Clostridium thermocellum endoglucanase, β-glucosidase and xylanase genes cloned in Escherichia coli 总被引:3,自引:0,他引:3
Geoffrey P. Hazlewood Marek P.M. Romaniec Keith Davidson Olivier Grépinet Pierre Béguin Jacqueline Millet Odette Raynaud Jean-Paul Aubert 《FEMS microbiology letters》1988,51(2-3):231-236
Abstract Two independent collections of clones containing Clostridium thermocellum genes involved in cellulose have been previously obtained at IAPGR, Cambridge, and at the Pasteur Institute, Paris. The two collections were compared for cross-hybridization, restriction maps and enzyme phenotypes. Truly distinct genes were one β-glucosidase gene, two xylanase genes, and fifteen endogluconase genes. Two of the cloned fragments contained extraneous DNA which was absent from their respective counterparts isolated in the other collection. The dicrepancies resulted from in vivo rearrangements which had occurred in either of the C. thermocellum NCIB 10682 stocks used to generate the two gene banks. 相似文献
66.
Comparison of zona cutting and zona drilling as techniques for assisted fertilization in the mouse 总被引:2,自引:0,他引:2
H T Depypere K J McLaughlin R F Seamark G M Warnes C D Matthews 《Journal of reproduction and fertility》1988,84(1):205-211
Zona cutting and zona drilling of the mouse oocyte significantly increased the fertilization rate (3.8-90%) at low sperm concentrations (less than 200,000/ml) compared with zona-intact controls (0-45%). More oocytes were fertilized after zona drilling. Zona cutting was associated with a low loss of oocytes (less than 1%), no increase in polyspermy and normal development in vitro and in vivo after fertilization. There was a 4% oocyte loss rate after zona drilling, mostly due to extrusion of the oocyte from the zona during the procedure. Hatching of blastocysts occurred about 12 h earlier for zona-drilled than for zona-cut and zona-intact control oocytes. Zona drilling was associated with a higher, but not statistically significant, rate of polyspermy at all sperm concentrations tested. The proportion of zygotes developing to the blastocyst stage was not different between the techniques (zona cut, 77%; zona drilled, 66%; control, 71%). Similarly, no difference was found in the percentage of embryos implanting after blastocyst transfer to the uterine horns of pseudopregnant female mice (zona cut, 67%; zona drilled, 68%; control, 77%). Transmission electron microscopy demonstrated the induced defects in the zona with no damage to the oocyte or oolemma. Parthenogenetic activation was not seen after either of the micromanipulative techniques. Both techniques have promise for application to the human. 相似文献
67.
The relationship among egg size,density and food level on larval development in the wood frog (Rana sylvatica) 总被引:1,自引:0,他引:1
Summary Although inter- and intraspecific variation in egg size among amphibians has been well documented, the relationship between egg size and fitness remains unclear. Recent attempts to correlate egg size intraspecifically with larval developmental patterns have been equivocal. In this study the development of larvae derived from large eggs and small eggs, from a single population in Maryland were compared under a range of food levels and larval population densities. Both food level and density had significant effects on the length of the larval period and size at metamorphosis. However, the response among larvae derived from different egg sizes was not additive. At low densities and high food levels, larvae from small eggs had longer larval periods and a larger size at metamorphosis than larvae derived from large eggs. In contrast, at high densities larvae from small eggs had longer developmental periods but were smaller at metamorphosis than larvae from large eggs. In addition, larvae from small eggs were more sensitive to density irrespective of food level. These results suggest that optimal egg size is correlated with environmental factors, which may explain the maintenance of both geographic and within population variation in egg size commonly observed in amphibians. 相似文献
68.
Differential effects of largemouth and smallmouth bass on habitat use by stoneroller minnows in stream pools 总被引:2,自引:0,他引:2
Previous investigations of within-reach distribution patterns of the stoneroller minnow, Campostoma anomalum Rafinesque, suggest that this species behavioural response to piscivorous bass differs among streams with different bass species. This study compares the responses of Camposloma to two common piscivorous fishes, largemouth bass, Micropterus salmoides Lacepede, and smallmouth bass, M. dolomieui Lacepede. Field experiments in Brier Creek, Oklahoma, U.S.A. showed that Campostoma responded to the presence of adult largemouth bass by shifting to shallow water habitats (commonly < 20 cm), but responded weakly or not at all to adult smallmouth bass. The magnitude of the response of Campostoma was positively related to activity level of the predators. Differences in behaviour between these two predator species may contribute to the differences in spatial distribution patterns of Micropterus and Campostoma observed in earlier investigations, but differences in stream channel morphology and temperature regimes among streams may also be important. 相似文献
69.
Summary Water and sodium turnovers of 6–7 week old gentoo penguin chicks and breeding adults were measured using isotopically labelled water and sodium. Influx rates for chicks averaged 188 ml·kg-1·day-1 and 13.9 mmol·kg-1·day-1 for water and sodium, respectively. Chicks consumed an estimated 228 g·kg-1·day-1 fresh food or 886 kJ kg-1 day. These values correspond to 761 g·day-1 or 2945 kJ·day-1 for a gentoo chick mid-way through the growth period. Flux rates for adults attending chicks ranged from 199 to 428 ml·kg-1·day-1 for water and from 15 to 36 mmol·kg-1·ay-1 for sodium. 相似文献
70.