A RECESSIVE BLACK VARIETY OF ROOF RAT     

Feldman HW 《Science (New York, N.Y.)》1923,58(1496):163

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Retinoic acid signaling restricts the cardiac progenitor pool   总被引：1，自引：0，他引：1  

Keegan BR  Feldman JL  Begemann G  Ingham PW  Yelon D 《Science (New York, N.Y.)》2005,307(5707):247-249

Organogenesis begins with specification of a progenitor cell population, the size of which provides a foundation for the organ's final dimensions. Here, we present a new mechanism for regulating the number of progenitor cells by limiting their density within a competent region. We demonstrate that retinoic acid signaling restricts cardiac specification in the zebrafish embryo. Reduction of retinoic acid signaling causes formation of an excess of cardiomyocytes, via fate transformations that increase cardiac progenitor density within a multipotential zone. Thus, retinoic acid signaling creates a balance between cardiac and noncardiac identities, thereby refining the dimensions of the cardiac progenitor pool.  相似文献   

Genetic structure of human populations   总被引：1，自引：0，他引：1  

Rosenberg NA  Pritchard JK  Weber JL  Cann HM  Kidd KK  Zhivotovsky LA  Feldman MW 《Science (New York, N.Y.)》2002,298(5602):2381-2385

We studied human population structure using genotypes at 377 autosomal microsatellite loci in 1056 individuals from 52 populations. Within-population differences among individuals account for 93 to 95% of genetic variation; differences among major groups constitute only 3 to 5%. Nevertheless, without using prior information about the origins of individuals, we identified six main genetic clusters, five of which correspond to major geographic regions, and subclusters that often correspond to individual populations. General agreement of genetic and predefined populations suggests that self-reported ancestry can facilitate assessments of epidemiological risks but does not obviate the need to use genetic information in genetic association studies.  相似文献   

Bacterial rhodopsin: evidence for a new type of phototrophy in the sea     

Béjà O  Aravind L  Koonin EV  Suzuki MT  Hadd A  Nguyen LP  Jovanovich SB  Gates CM  Feldman RA  Spudich JL  Spudich EN  DeLong EF 《Science (New York, N.Y.)》2000,289(5486):1902-1906

Extremely halophilic archaea contain retinal-binding integral membrane proteins called bacteriorhodopsins that function as light-driven proton pumps. So far, bacteriorhodopsins capable of generating a chemiosmotic membrane potential in response to light have been demonstrated only in halophilic archaea. We describe here a type of rhodopsin derived from bacteria that was discovered through genomic analyses of naturally occuring marine bacterioplankton. The bacterial rhodopsin was encoded in the genome of an uncultivated gamma-proteobacterium and shared highest amino acid sequence similarity with archaeal rhodopsins. The protein was functionally expressed in Escherichia coli and bound retinal to form an active, light-driven proton pump. The new rhodopsin exhibited a photochemical reaction cycle with intermediates and kinetics characteristic of archaeal proton-pumping rhodopsins. Our results demonstrate that archaeal-like rhodopsins are broadly distributed among different taxa, including members of the domain Bacteria. Our data also indicate that a previously unsuspected mode of bacterially mediated light-driven energy generation may commonly occur in oceanic surface waters worldwide.  相似文献   

Observations at venus encounter by the plasma science experiment on mariner 10     

Bridge HS  Lazarus AJ  Scudder JD  Ogilvie KW  Hartle RE  Asbridge JR  Bame SJ  Feldman WC  Siscoe GL 《Science (New York, N.Y.)》1974,183(4131):1293-1296

Preliminary results from the rearward-looking electrostatic analyzer of the plasma science experiment during the Mariner 10 encounter with Venus are described. They show that the solar-wind interaction with the planet probably involves a bow shock rather than an extended exosphere, but that this is not a thin boundary at the point where it was crossed by Mariner 10. An observed reduction in the flux of electrons with energies greater than 100 electron volts is interpreted as evidence for somne direct interaction with the exosphere. Unusual intermittent features observed downstream of the planet indicate the presence of a comet-like tail hundreds of scale lengths in length.  相似文献   

Cytology in veterinary practice. A review of clinical cytology--body fluids, lymph nodes and skin neoplasms     

A Kristensen  B F Feldman 《Nordisk veterinaermedicin》1986,38(6):321-332

A review over the most applicable areas of veterinary clinical cytology is given. The areas described are body fluids, lymph nodes and selected skin neoplasms. The review includes tables that survey general and specific cytologic criteria and is supplemented by photomicrographs. A classification of effusions according to cytologic criteria is discussed and there is a short discussion of 62 cases which also included histopathology.  相似文献   

Hypoadrenocorticism.     

E C Feldman  J B Tyrrell 《The Veterinary clinics of North America》1977,7(3):555-581

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Digestion of bentiromide and absorption of xylose in healthy cats and absorption of xylose in cats with infiltrative intestinal disease     

E C Hawkins  S M Meric  R J Washabau  E C Feldman  J M Turrel 《American journal of veterinary research》1986,47(3):567-569

The digestion of bentiromide and the absorption of D-xylose was measured in 17 clinically healthy cats. The plasma xylose concentrations of the healthy cats were compared with values from 9 cats with diffuse infiltrative intestinal disease. The cats were administered 16.7 mg of bentiromide/kg and 0.5 g of xylose/kg via a stomach tube. Plasma samples were obtained before administration and 30, 60, 90, and 120 minutes after administration. The maximum mean plasma p-aminobenzoic acid concentration occurred at 60 minutes, with a value of 386 +/- 134 micrograms/dl (mean +/- SD). The maximum mean plasma xylose concentration also occurred at 60 minutes, with a value of 26.0 +/- 9.2 mg/dl. Plasma concentrations of p-aminobenzoic acid and xylose were lower in healthy cats than those reported for healthy dogs. There was no significant difference between xylose concentrations in healthy cats and cats with infiltrative intestinal disease.  相似文献   

Scanning electron microscopic studies of megakaryocytes and platelet formation in the dog and rat     

P Handagama  N C Jain  C S Kono  B F Feldman 《American journal of veterinary research》1986,47(11):2454-2460

Megakaryocyte morphology and platelet formation in canine and murine bone marrows were studied by scanning electron microscopy. In situ-fixed bone marrow preparations and cell suspensions of bone marrow provided complementary information for the 2 species (dogs and rats). Cylindrical processes (proplatelets) of variable length and thickness, originating from the megakaryocyte surface, were in the larger marrow sinusoids and the central vein. Regional constrictions along the length of proplatelets, particularly near their apical region, and the presence of fragments of such processes supported the concept of platelet formation through segmentation of proplatelets. Megakaryocytes presented varied morphology. Surface features resembling platelets were observed on megakaryocytes, indicating that platelets may have been released through surface budding. In conclusion, megakaryocytes formed long proplatelet processes that actively migrated to venous sinusoids to release platelets by fragmentation. Scanning electron microscopy analysis revealed a complex and variable megakaryocyte surface topography. The platelet-like structures on megakaryocyte surfaces may represent platelet release by a budding mechanism. The similarity between murine platelet release and canine platelet release demonstrates that data from rodent models may be applicable to nonrodents.  相似文献   

Radiographic features of canine hyperadrenocorticism caused by autonomously functioning adrenocortical tumors: 23 cases (1978-1986)   总被引：1，自引：0，他引：1  

D G Penninck  E C Feldman  T G Nyland 《Journal of the American Veterinary Medical Association》1988,192(11):1604-1608

Radiographic features of 23 dogs with functioning adrenocortical tumors are described. In 56% of the dogs, radiographic detection of adrenomegaly, with or without calcification, was an aid in the diagnosis of adrenocortical neoplasia. Adrenal gland calcification did not distinguish adrenocortical adenoma from carcinoma.  相似文献