Activation of ras oncogenes preceding the onset of neoplasia   总被引：24，自引：0，他引：24  

R Kumar  S Sukumar  M Barbacid 《Science (New York, N.Y.)》1990,248(4959):1101-1104

The identification of ras oncogenes in human and animal cancers including precancerous lesions indicates that these genes participate in the early stages of neoplastic development. Yet, these observations do not define the timing of ras oncogene activation in the multistep process of carcinogenesis. To ascertain the timing of ras oncogene activation, an animal model system was devised that involves the induction of mammary carcinomas in rats exposed at birth to the carcinogen nitrosomethylurea. High-resolution restriction fragment length polymorphism analysis of polymerase chain reaction-amplified ras sequences revealed the presence of both H-ras and K-ras oncogenes in normal mammary glands 2 weeks after carcinogen treatment and at least 2 months before the onset of neoplasia. These ras oncogenes can remain latent within the mammary gland until exposure to estrogens, demonstrating that activation of ras oncogenes can precede the onset of neoplasia and suggesting that normal physiological proliferative processes such as estrogen-induced mammary gland development may lead to neoplasia if the targeted cells harbor latent ras oncogenes.  相似文献   

Spatial patterns in the distribution of tropical tree species   总被引：1，自引：0，他引：1  

Condit R  Ashton PS  Baker P  Bunyavejchewin S  Gunatilleke S  Gunatilleke N  Hubbell SP  Foster RB  Itoh A  LaFrankie JV  Lee HS  Losos E  Manokaran N  Sukumar R  Yamakura T 《Science (New York, N.Y.)》2000,288(5470):1414-1418

Fully mapped tree census plots of large area, 25 to 52 hectares, have now been completed at six different sites in tropical forests, including dry deciduous to wet evergreen forest on two continents. One of the main goals of these plots has been to evaluate spatial patterns in tropical tree populations. Here the degree of aggregation in the distribution of 1768 tree species is examined based on the average density of conspecific trees in circular neighborhoods around each tree. When all individuals larger than 1 centimeter in stem diameter were included, nearly every species was more aggregated than a random distribution. Considering only larger trees (>/= 10 centimeters in diameter), the pattern persisted, with most species being more aggregated than random. Rare species were more aggregated than common species. All six forests were very similar in all the particulars of these results.  相似文献   

Arsenic poisoning in west bengal     

Saha DP 《Science (New York, N.Y.)》1996,274(5291):1287b-1288b

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Mutational analysis of the tyrosine kinome in colorectal cancers     

Bardelli A  Parsons DW  Silliman N  Ptak J  Szabo S  Saha S  Markowitz S  Willson JK  Parmigiani G  Kinzler KW  Vogelstein B  Velculescu VE 《Science (New York, N.Y.)》2003,300(5621):949

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Environment. Environmental monitoring network for India     

Sundareshwar PV  Murtugudde R  Srinivasan G  Singh S  Ramesh KJ  Ramesh R  Verma SB  Agarwal D  Baldocchi D  Baru CK  Baruah KK  Chowdhury GR  Dadhwal VK  Dutt CB  Fuentes J  Gupta PK  Hargrove WW  Howard M  Jha CS  Lal S  Michener WK  Mitra AP  Morris JT  Myneni RR  Naja M  Nemani R  Purvaja R  Raha S  Vanan SK  Sharma M  Subramaniam A  Sukumar R  Twilley RR  Zimmerman PR 《Science (New York, N.Y.)》2007,316(5822):204-205

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Access to stem cells and data: persons, property rights, and scientific progress     

Mathews DJ  Graff GD  Saha K  Winickoff DE 《Science (New York, N.Y.)》2011,331(6018):725-727

Many fields have struggled to develop strategies, policies, or structures to optimally manage data, materials, and intellectual property rights (IPRs). There is growing recognition that the field of stem cell science, in part because of its complex IPRs landscape and the importance of cell line collections, may require collective action to facilitate basic and translational research. Access to pluripotent stem cell lines and the information associated with them is critical to the progress of stem cell science, but simple notions of access are substantially complicated by shifting boundaries between what is considered information versus material, person versus artifact, and private property versus the public domain.  相似文献   

Chemical characterization of Klason lignin preparations from plant-based foods     

Bunzel M  Schüssler A  Tchetseubu Saha G 《Journal of agricultural and food chemistry》2011,59(23):12506-12513

To analyze the accuracy of the Klason lignin method as applied for the determination of lignin contents in plant based-food products, Klason lignin preparations from curly kale, pears, whole wheat grains, and corn bran were chemically characterized. Characterization included routine ash and protein determinations and the extraction of fat/waxes as well as cutin/suberin depolymerization and extraction of the liberated monomers. Fat/wax and cutin/suberin amounts in the Klason lignin preparations were determined gravimetrically, and their compositions were analyzed by using GC-MS. Typical fat, wax, and cutin (and suberin) constituents such as saturated and unsaturated fatty acids, hydroxy and/or epoxy fatty acids, and phenolic acids were identified in all samples, whereas the detection of long-chain hydrocarbons, alcohols, and ketones, sterols, stanols, and dioic acids was dependent on the sample analyzed. Estimation of the contribution of non-lignin compounds to the Klason lignin contents reduced the noncorrected Klason lignin contents of the insoluble fibers from 28.7% (kale), 22.8% (pear), 14.8% (wheat), and 9.9% (corn) to maximum lignin contents of 6.5% (kale), 16.4% (pear), 4.9% (wheat), and 2.3% (corn). These data demonstrate that certain commonly used statements such as "cereal brans are highly lignified" need to be revised.  相似文献   

Effects of heating and freezing on the viability of sarcocysts of Sarcocystis levinei from cardiac tissues of buffaloes     

P S Srivastava  A K Saha  S R Sinha 《Veterinary parasitology》1986,19(3-4):329-332

Dogs fed buffalo heart muscle containing sarcocysts of Sarcosystis levinei and heated at 65-75 degrees C did not shed sporocysts, whereas other dogs fed infected heart muscle heated between 40 and 60 degrees C shed sporocysts. Dogs fed infected heart muscle stored at -4 degrees C for 48 h did not shed sporocysts, but those fed similar infected tissues stored at -2 degrees C for 24 h shed sporocysts. The results indicate that sarcocysts of S. levinei are rendered noninfective by heating to 65 degrees C or by freezing at -4 degrees C.  相似文献   

Autoecological Studies on Mottra (Clinogyne dichotomy Salisb)     

A. K. Singha Roy  B. C. Saha  D. K. Saha 《Journal of Agronomy and Crop Science》1993,170(4):281-283

Clinogyne dichotoma , Salisb, belonging to the family Marantaceae, is a perennial crop with remarkable morphological characteristic. Present study on the anatomical features revealed their adaptability in waterlogged low-lying marshy lands unsuitable for the cultivation of any other crop.  相似文献   

Auxin synergists in the rooting of mango cuttings     

M.K. Sadhu  Sanghamitra Bose  Lily Saha 《Scientia Horticulturae》1978,9(4):381-387

Preplanting application of phenolic compounds, p-hydroxybenzoic acid p-coumaric acid and ferulic acid, in most cases promoted auxin-induced rooting on cuttings of mango, a difficult-to-root fruit plant. The ethylene-releasing chemical CEPA (ethrel, ethephon) also stimulated rooting in the presence of auxins. Synergism was more pronounced in the presence of IBA than with IAA. To a certain extent, root-promoting effects of auxins and non-auxin chemicals were related to the utilization of carbohydrate fractions from the region of root formation. Utilization of reserve polysaccharides assumed greater importance only during the root-development phase.  相似文献