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14C-Sterigmatocystin isolated from cultures of supplemented with (1-14C)acetate was shown to be efficiently converted to aflatoxin B1 by the resting mycelium of . The experimental results may indicate a biosynthetic pathway leading from 5-hydroxysterigmatocystin to sterigmatocystin and then to aflatoxin B1. 相似文献
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Hsieh JJ 《Biometrical journal. Biometrische Zeitschrift》1989,31(3):339-357
"This paper aims to identify net and partial-crude probabilities in the competing-risk life table context, by using probabilistic approaches. Five types of lifelength random variables are defined to formulate these nonidentifiable probabilities. General expressions for net and partial-crude probabilities are first derived under independent risks assumptions. Two sets of explicit formulas for estimating the net and partial-crude probabilities are then derived in terms of the identifiable overall and crude probabilities by making the additional assumption of piecewise uniform distribution of the lifelength random variables. A study of the degree to which nonidentifiability can affect the net and partial-crude probabilities in a variety of situations is developed. An example from cross-sectional studies is employed to illustrate the methodology developed." 相似文献
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Isotype switching of an immunoglobulin heavy chain transgene occurs by DNA recombination between different chromosomes 总被引:17,自引:0,他引:17
R M Gerstein W N Frankel C L Hsieh J M Durdik S Rath J M Coffin A Nisonoff E Selsing 《Cell》1990,63(3):537-548
Transgenic mice carrying an immunoglobulin mu heavy chain transgene exhibit isotype switching of the transgene. We have now characterized the mechanism of transgene switching in these mice. The site of mu transgene insertion in one transgenic line has been localized to chromosome 5 using a series of polymorphic endogenous retroviruses as genetic markers in backcross mice. The endogenous immunoglobulin heavy chain locus resides on mouse chromosome 12, which shows that transgene isotype switching can occur between two different chromosomes even though normal antibody gene switching has generally been thought to occur within one chromosome. We find that transgene isotype switching involves interchromosomal DNA recombination, and our data suggest that the same enzymatic mechanisms mediate both normal isotype switch recombination and interchromosomal transgene switching. Our findings also support the notion that the isotype switching mechanism can induce chromosomal translocations such as observed for the c-myc gene in some B cell tumors. 相似文献
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Localization of the photoreceptor gene ROM1 to human chromosome 11 and mouse chromosome 19: sublocalization to human 11q13 between PGA and PYGM. 总被引:5,自引:0,他引:5 下载免费PDF全文
R A Bascom J García-Heras C L Hsieh D S Gerhard C Jones U Francke H F Willard D H Ledbetter R R McInnes 《American journal of human genetics》1992,51(5):1028-1035
Rom-1 is a retinal integral membrane protein that, together with the product of the human retinal degeneration slow gene (RDS), defines a photoreceptor-specific protein family. The gene for rom-1 (HGM symbol: ROM1) has been assigned to human chromosome 11 and mouse chromosome 19 by Southern blot analysis of somatic cell hybrid DNAs. ROM1 was regionally sublocalized to human 11p13-11q13 by using three mouse-human somatic cell hybrids; in situ hybridization refined the sublocalization to human 11q13. Analysis of somatic cell hybrids suggested that the most likely localization of ROM1 is in the approximately 2-cM interval between human PGA (human pepsinogen A) and PYGM (muscle glycogen phosphorylase). ROM1 appears to be a new member of a conserved syntenic group whose members include such genes as CD5, CD20, and OSBP (oxysterol-binding protein), on human chromosome 11 and mouse chromosome 19. Localization of the ROM1 gene will permit the examination of its linkage to hereditary retinopathies in man and mouse. 相似文献
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In this paper we analyze a model for the HIV-infection transmission in a male homosexual population. In the model we consider two types of infected individuals. Those that are infected but do not know their serological status and/or are not under any sort of clinical /therapeutical treatment, and those who are. The two groups of infectives differ in their incubation time, contact rate with susceptible individuals, and probability of disease transmission. The aim of this article is to study the roles played by detection and changes in sexual behavior in the incidence and prevalence of HIV. The analytical results show that there exists a unique endemic equilibrium which is globally asymptotically stable under a range of parameter values whenever a detection /treatment rate and an indirect measure of the level of infection risk are sufficiently large. However, any level of detection/ treatment rate coupled with a decrease of the transmission probability lowers the incidence rate and prevalence level in the population. In general, only significant reductions in the transmission probability (achieved through, for example, the adoption of safe sexual practices) can contain effectively the spread of the disease. 相似文献
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Association of the catalytic subunit of aspartate transcarbamoylase with a zinc-containing polypeptide fragment of the regulatory chain leads to increases in thermal stability. 总被引:1,自引:1,他引:0 下载免费PDF全文
C. B. Peterson B. B. Zhou D. Hsieh A. N. Creager H. K. Schachman 《Protein science : a publication of the Protein Society》1994,3(6):960-966
The regulatory enzyme aspartate transcarbamoylase (ATCase), comprising 2 catalytic (C) trimers and 3 regulatory (R) dimers, owes its stability to the manifold interchain interactions among the 12 polypeptide chains. With the availability of a recombinant 70-amino acid zinc-containing polypeptide fragment of the regulatory chain of ATCase, it has become possible to analyze directly the interaction between catalytic and regulatory chains in a complex of simpler structure independent of other interactions such as those between the 2 C trimers, which also contribute to the stability of the holoenzyme. Also, the effect of the interaction between the polypeptide, termed the zinc domain, and the C trimer on the thermal stability and other properties can be measured directly. Differential scanning microcalorimetry experiments demonstrated that the binding of the zinc domain to the C trimer leads to a complex of markedly increased thermal stability. This was shown with a series of mutant forms of the C trimer, which themselves varied greatly in their temperature of denaturation due to single amino acid replacements. With some C trimers, for which tm varied over a range of 30 degrees C due to diverse amino acid substitutions, the elevation of tm resulting from the interaction with the zinc domain was as large as 18 degrees C. The values of tm for a variety of complexes of mutant C trimers and the wild-type zinc domain were similar to those observed when the holoenzymes containing the mutant C trimers were subjected to heat denaturation.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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本文应用反义RNA探针原位杂交法,研究雄激素对大鼠腹侧前列腺(VP)上皮细胞角蛋白(CK)8 mRNA表达的影响。发现1.在任何VP组织切片中,CK 8探针专一、大量定位于VP腺上皮细胞中,CK 8 mRNA是前列腺上皮细胞特异而灵敏的标志。2.去睾大鼠VP CK 8 mRNA染色增强,提示CK 8mRNA有过度表达,注射雄激素又可抑制其过度表达。3.与已知受雄激素抑制性基因不同,即使大鼠VP完全萎缩之后达2个月之久,其存留腺上皮细胞CK 8 mRNA表达仍持续增高。4.前列腺发育早期,迅速增殖的幼稚腺上皮细胞高度表达CK 8 mRNA,以后随着体内雄激素水平升高,VP上皮CK 8 mRNA表达下降,分布转移。以上结果进一步支持前列腺CK 8基因是新的一类受雄激素抑制性基因的推测,同时表明前列腺CK 8基因的表达与前列腺干细胞的增殖分化有密切联系,CK 8 mRNA高度表达是前列腺干细胞一个重要特征。 相似文献