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21.
Hydroxyurea was used to study the proliferation rate of haemopoietic stem cells (CFUJ in normal mice, after irradiation or transplantation into irradiated recipients. It was demonstrated that the proliferation rate of endogenous CFUS (endo-CFU,) and exogenous CFUS (exo-CFUs) are identical. After irradiation (650 R) the surviving endo-CFUs begin to proliferate immediately. By contrast exo-CFU, transplanted into the irradiated recipient mouse (850 R), begin to proliferate only after about 30 hr. However, injection of isoproterenol (which stimulates adenyl cyclase) or dibutyryl cyclic adenosine 3′,5′-monophosphate shortly after marrow cell graft, triggers the transplanted CFUS into cell cycle as shown by an almost immediately increased sensitivity to hydroxyurea. Isoproterenol is capable of inducing DNA synthesis also in stem cells of normal mice but it takes about 20 hr before CFU, become to be increasingly sensitive to hydroxyurea. 相似文献
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Ján Lí?KA Július BRTKO Michal DUBOVICKY Dana MACEJOVá Viktória KISSOVá ?tefan POLáK Eduard UJHáZY 《Experimental Animals》2016,65(1):1-9
The mammary gland is a dynamic organ that undergoes structural and functional changes
associated with growth, reproduction, and post-menopausal regression. The postnatal
transformations of the epithelium and stromal cells of the mammary gland may contribute to
its susceptibility to carcinogenesis. The increased cancer incidence in mammary glands of
humans and similarly of rodents in association with their development is believed to be
partly explained by proliferative activity together with lesser degree of differentiation,
but it is not completely understood how the virgin gland retains its higher susceptibility
to carcinogenesis. During its developmental cycle, the mammary gland displays many of the
properties associated with breast cancer. An early first full-term pregnancy may have a
protective effect. Rodent models are useful for investigating potential breast
carcinogens. The purpose of this review is to help recognizing histological appearance of
the epithelium and the stroma of the normal mammary gland in rats, and throughout its
development in relation to tumorigenic potential. 相似文献
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ELIŠKA ZÁVESKÁ TOMÁŠ FÉR OTAKAR ŠÍDA JANA LEONG‐ŠKORNIČKOVÁ MAMYIL SABU KAROL MARHOLD 《Botanical journal of the Linnean Society. Linnean Society of London》2011,165(4):388-401
The relationships between genome size and the systematic and evolutionary patterns in vascular plants are equivocal, although a close relationship between genome size and evolutionary patterns has been previously reported. However, several studies have also revealed the dynamic nature of genome size evolution and its considerable ‘ups’ and ‘downs’. Thus, in this study, the phylogenetic relationships among three previously revealed genome size groups and among species of the highly polyploid genus Curcuma were evaluated using AFLP. Our results suggest two main lineages within Indian Curcuma reflecting evolution of genome size. The first one includes hexaploids and higher polyploids of the previously recognized genome size group I, and the second one includes mainly hexaploids of genome size groups II and III. Within genome size group I, relationships among species seem to be influenced by reticulate evolution and higher polyploids are likely to be of allopolyploid origin. Reproductive systems in Indian Curcuma vary considerably among ploidy levels and these differences considerably affect morphological and genetic variation. In general, clonally reproducing species are expected to exhibit low genotypic diversity, but, at the same time, species of allopolyploid origin are expected to maintain higher levels of heterozygosity compared with their progenitors. We investigated intra‐populational genetic variability in Curcuma spp. to evaluate whether mode of reproduction or ploidy represent the main factor influencing the degree of genetic diversity. We found that hexaploid species exhibited significantly higher genetic diversity than higher polyploids (9x, 15x). Our results suggest that this genetic diversity pattern is largely influenced by the mode of reproduction, as higher polyploids reproduce exclusively vegetatively, whereas hexaploids reproduce mainly sexually. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 165 , 388–401. 相似文献
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The acute toxicity of the aqueous and ethanol extracts of Parkia biglobosa pods against Clarias gariepinus was investigated under laboratory conditions. Agitated behaviours and respiratory distress were also observed during the exposure period. The adverse effects on biochemical parameters were assessed using semi-static bioassays for 28 days. The ethanol extract of P. biglobosa pods was found to be more acutely toxic with a 96 h LC50 value of 13.96 mg l?1 than the aqueous extracts, with a 96 h LC50 value of 19.95 mg l?1 against C. gariepinus. Both extracts induced agitated behaviours and respiratory distress in exposed organisms. The activities of superoxide dismutase (SOD), catalase (CAT) and the concentration of malondialdehyde (MDA) were significantly lower (p < 0.05) in groups of organisms exposed to extracts of P. biglobosa when compared with the control group after 14 days. The activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) were also significantly (p < 0.05) lower compared with activities of the enzymes in the control group after 28 days. The current study has shown that the introduction of P. biglobosa pods into aquatic ecosystems is acutely toxic to fish and would possibly be to other non-target aquatic organisms especially invertebrates. 相似文献
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Newman SH Hill NJ Spragens KA Janies D Voronkin IO Prosser DJ Yan B Lei F Batbayar N Natsagdorj T Bishop CM Butler PJ Wikelski M Balachandran S Mundkur T Douglas DC Takekawa JY 《PloS one》2012,7(2):e30636
A unique pattern of highly pathogenic avian influenza (HPAI) H5N1 outbreaks has emerged along the Central Asia Flyway, where infection of wild birds has been reported with steady frequency since 2005. We assessed the potential for two hosts of HPAI H5N1, the bar-headed goose (Anser indicus) and ruddy shelduck (Tadorna tadorna), to act as agents for virus dispersal along this 'thoroughfare'. We used an eco-virological approach to compare the migration of 141 birds marked with GPS satellite transmitters during 2005-2010 with: 1) the spatio-temporal patterns of poultry and wild bird outbreaks of HPAI H5N1, and 2) the trajectory of the virus in the outbreak region based on phylogeographic mapping. We found that biweekly utilization distributions (UDs) for 19.2% of bar-headed geese and 46.2% of ruddy shelduck were significantly associated with outbreaks. Ruddy shelduck showed highest correlation with poultry outbreaks owing to their wintering distribution in South Asia, where there is considerable opportunity for HPAI H5N1 spillover from poultry. Both species showed correlation with wild bird outbreaks during the spring migration, suggesting they may be involved in the northward movement of the virus. However, phylogeographic mapping of HPAI H5N1 clades 2.2 and 2.3 did not support dissemination of the virus in a northern direction along the migration corridor. In particular, two subclades (2.2.1 and 2.3.2) moved in a strictly southern direction in contrast to our spatio-temporal analysis of bird migration. Our attempt to reconcile the disciplines of wild bird ecology and HPAI H5N1 virology highlights prospects offered by both approaches as well as their limitations. 相似文献
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