Melanin pigmentation: an in vivo model for studies of melanosome kinetics within keratinocytes   总被引：3，自引：0，他引：3  

K Wolff  K Konrad 《Science (New York, N.Y.)》1971,174(13):1034-1035

The phagocytosis of latex beads by epidermal cells is proposed as a model for stludies on melanosome kinetics within the epidermis. Large latex beads (0.8 micrometer) are ingested singly, whereas, small beads (0.1 micrometer) are taken up in groups, results showing that the uptake mechanism depends on the size of thze indlividual particles. This size-dependency may explain the different distribution patterns of melanosomes and thus the differences of skin color in the Caucasoid and Negroid races.  相似文献   

Ocean science. Whither Antarctic sea ice?     

Wolff EW;British Antarctic Survey  High Cross  Madingley Road  Cambridge CB ET  UK. ewwo@bas.ac.uk 《Science (New York, N.Y.)》2003,302(5648):1164

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Review journal, science books & films, approaches milestone     

Wolff K 《Science (New York, N.Y.)》1984,225(4661):496

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On the sources of summertime haze in the eastern United States     

Wolff GT  Kelly NA  Ferman MA 《Science (New York, N.Y.)》1981,211(4483):703-705

The summertime haze transported from the Gulf Coast northward in maritime tropical air masses is partially formed from emissions in the midwestern and northeastern United States. Several cases are documented in which sulfate particulates, formed from emissions in the Midwest and Northeast, traveled to the Gulf of Mexico and, in some cases, returned to their source regions.  相似文献   

Saccharin-induced sister chromatid exchanges in Chinese hamster and human cells     

S Wolff  B Rodin 《Science (New York, N.Y.)》1978,200(4341):543-545

Since the induction of sister chromatid exchanges in cultured cells has been shown to be the most sensitive mammalian system to detect the effects of mutagenic carcinogens, Chinese hamster ovary cells and human lymphocytes were exposed to the sodium saccharin found to induce bladder cancer in rats. Both that saccharin and a highly purified extract of it increased the yield of sister chromatid exchanges in both types of cells. The results, which were repeatable and statistically highly significant, indicated that the weak carcinogen, saccharin, is also mutagenic in the sense that it induces cytogenetic changes.  相似文献   

Gas chromatographs: health effects     

Wolff MS  Langer AM  Shirey SB 《Science (New York, N.Y.)》1976,191(4225):339-340

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Photography of the Earth's Cloud Satellites from an Aircraft     

Wolff C  Dunkelman L  Haughney LC 《Science (New York, N.Y.)》1967,157(3787):427-429

Under astronomically favorable circumstances, photographs do not reveal excess light near the triangular libration points of the earth-moon system. We find that the visible surface brightness of anomalous dust populations, if these populations do exist, is less than 10(-9) candela per square centimeter.  相似文献   

Initial results from the Mini-TES experiment in Gusev Crater from the Spirit Rover     

Christensen PR  Ruff SW  Fergason RL  Knudson AT  Anwar S  Arvidson RE  Bandfield JL  Blaney DL  Budney C  Calvin WM  Glotch TD  Golombek MP  Gorelick N  Graff TG  Hamilton VE  Hayes A  Johnson JR  McSween HY  Mehall GL  Mehall LK  Moersch JE  Morris RV  Rogers AD  Smith MD  Squyres SW  Wolff MJ  Wyatt MB 《Science (New York, N.Y.)》2004,305(5685):837-842

The Miniature Thermal Emission Spectrometer (Mini-TES) on Spirit has studied the mineralogy and thermophysical properties at Gusev crater. Undisturbed soil spectra show evidence for minor carbonates and bound water. Rocks are olivinerich basalts with varying degrees of dust and other coatings. Dark-toned soils observed on disturbed surfaces may be derived from rocks and have derived mineralogy (+/-5 to 10%) of 45% pyroxene (20% Ca-rich pyroxene and 25% pigeonite), 40% sodic to intermediate plagioclase, and 15% olivine (forsterite 45% +/-5 to 10). Two spectrally distinct coatings are observed on rocks, a possible indicator of the interaction of water, rock, and airfall dust. Diurnal temperature data indicate particle sizes from 40 to 80 microm in hollows to approximately 0.5 to 3 mm in soils.  相似文献   

Effect of bacitracin on tetracycline resistance in Escherichia coli and Salmonella     

Jun Lin  Teddi Wolff  Alan Erickson  David Francis   《Veterinary microbiology》2009,138(3-4):353-360

Tetracyclines and bacitracin are used extensively as a growth promotant and a therapeutic, respectively in livestock. In this study, we test whether there is an interaction between bacitracin and tetracycline that can select for an increase in microbial tetracycline sensitivity, using Escherichia coli and Salmonella as a model. We found via in vitro studies that bacitracin at sublethal concentrations preferentially selects for outgrowth of tetracycline-sensitive bacteria from among a population of tetracycline-resistant and tetracycline-sensitive E. coli and Salmonella strains. Most of the bacterial strains employed in our study were shown by PCR to possess the tetracycline resistance gene tet(A) or tet(C), either of whose activity is associated with tetracycline efflux. Bacitracin could be substituted for the lipophylic chelator, fusaric acid, used as a positive selective agent for tetracycline sensitivity. Together, these observations suggest that bacitracin-mediated selection for tetracycline sensitivity alters the function of tetracycline efflux proteins. Using bacitracin and tetracycline simultaneously may improve the effectiveness of the antibiotics, while decreasing the risk of selecting for a population of tetracycline-resistant microorganisms.  相似文献   

Linking fish ecomorphotypes to food categories and local-scale habitat uses along a Brazilian coastal stream     

Luciano Lazzarini Wolff  Edson Fontes de Oliveira  Javier Lobón-Cerviá 《Ecology of Freshwater Fish》2023,32(1):195-208

Fish ecomorphological analyses often deal with several traits simultaneously, making it challenging to interpret general patterns, and have not addressed the longitudinal component of streams in morphology-habitat relationships. We identified ecomorphotypes of fishes and correlated their morphological variation with food, structural/hydrological variables, and abundances to detect their links with diet and local-scale habitat categories. Eighteen morphometric traits were obtained from specimens collected by electrofishing in a coastal Atlantic stream in Brazil. To test for morphology-habitat associations, headwaters, middle, and mouth reaches were divided into shorter sampling sites, with the middle reach being classified into riffle, run, and pool mesohabitats. Multivariate analyses highlighted the morphological variations and associated the form categories of 18 fish species with food and habitat categories. It resulted in four combined trophic and habitat ecomorphotypes: (1) benthic AB/lithophilic, composed of smaller to longer loricariids, detritivores, of fast-water, and pebbly habitats; (2) benthic C/lithophilic of very fast-waters, algal and detritus scrapers, with longer intestines than the other benthic species, wider suctorial mouths, inhabitants of headwaters, and riffles habitats; (3) nektobenthic/lithophilic with streamlined bodies, invertebrate feeders, and dwellers of faster-water, cobbly habitats; and (4) nektonic/limnophilic composed mainly by characins, which had strong correlations with terrestrial insect consumption, and lentic/pool, sandy habitats. The morphology–environment correlations linked these ecomorphotypes to the broad habitat gradient arrayed in longitudinal and local scales. These results permit inferring the larger form patterns expected for local fish assemblages and emphasise the fish trait categorisation as a possible surrogate to reveal broader ecomorphological associations.  相似文献