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31.
Relative carriage rates of nuclear dehydrogenating clostridia in two populations of different colorectal cancer risk
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Carriage of nuclear dehydrogenating clostridia has been associated with colon cancer and implicated in its aetiology. This study has compared the carriage of these organisms in a British population at high risk for the development of colon cancer with a low risk Nigerian population. Clostridia were found in all of the stools from both populations. Nuclear dehydrogenating clostridia were only found in the stools of the British subjects (32%). These results support the suggestion that the carriage rate of nuclear dehydrogenating clostridia in a population is related to the risk of colon cancer. 相似文献
32.
33.
Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability 总被引:1,自引:15,他引:1
La Spada AR; Peterson KR; Meadows SA; McClain ME; Jeng G; Chmelar RS; Haugen HA; Chen K; Singer MJ; Moore D; Trask BJ; Fischbeck KH; Clegg CH; McKnight GS 《Human molecular genetics》1998,7(6):959-967
X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG
repeat expansion in the first exon of the androgen receptor (AR) gene.
Disease-associated alleles (37-66 CAGs) change in length when transmitted
from parents to offspring, with a significantly greater tendency to shift
size when inherited paternally. As transgenic mice carrying human AR cDNAs
with 45 and 66 CAG repeats do not display repeat instability, we attempted
to model trinucleotide repeat instability by generating transgenic mice
with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions
in their genomic context. Studies of independent lines of AR YAC transgenic
mice with CAG 45 alleles reveal intergenerational instability at an overall
rate of approximately 10%. We also find that the 45 CAG repeat tracts are
significantly more unstable with maternal transmission and as the
transmitting mother ages. Of all the CAG/CTG repeat transgenic mice
produced to date the AR YAC CAG 45 mice are unstable with the smallest
trinucleotide repeat mutations, suggesting that the length threshold for
repeat instability in the mouse may be lowered by including the appropriate
flanking human DNA sequences. By sequence-tagged site content analysis and
long range mapping we determined that one unstable transgenic line has
integrated an approximately 70 kb segment of the AR locus due to
fragmentation of the AR YAC. Identification of the cis - acting elements
that permit CAG tract instability and the trans -acting factors that
modulate repeat instability in the AR YAC CAG 45 mice may provide insights
into the molecular basis of trinucleotide repeat instability in humans.
相似文献
34.
Activities of ammonia-metabolizing enzymes from Candida maltosa were measured. The synthesis of glutamate and glutamine involves three primary enzymes: glutamate dehydrogenase (GDH), glutamine synthetase (GS), and glutamate synthase (GOGAT). This yeast has two distinct GDH, the first responsible for glutamate catabolism, and the second solely biosynthetic. The GS is derepressed during growth on low ammonia or on a variety of alternative nitrogen sources, whereas the catabolic GDH (NAD) is repressed under this conditions. Ammonia limitation did not significantly affect GOGAT as well as biosynthetic GDH (NADP) levels. The relatively low Km-value for ammonia suggest that the GS is catalytically active during cell growth on low concentrations of ammonia. It seems that under N-limitation ammonia assimilation is achieved via GS/GOGAT and under N-excess via GDH/GS. 相似文献
35.
Variability of skin temperature in the waking monkey 总被引:3,自引:0,他引:3
36.
A. Dornelas de Andrade J. Birnbaum A. Lanteaume J. L. Izard P. Corget M. F. Artillan M. Toumi D. Vervloet D. Charpin 《Allergy》1995,50(2):142-146
Because the mite-allergen content in homes is highly variable even in the same geographic area, we tried to determine which variables influence mite infestation. We evaluated mite-allergen content in bedding relative to housing conditions and living habits. This cross-sectional study included 108 homes. Housing conditions were assessed by an architect and living habits by a researcher specialized in social and family economics. Group I allergen level was measured on the mattress dust with monoclonal antibodies, and relative humidity (RH) was monitored in the bedroom during a 2-week period. Homes with low RH did have low mite-allergen content. In contrast, homes with intermediate RH levels had very variable mite-allergen content. Using analysis of variance and a logistic regression analysis, we were unable to identify any variable predictive of mite-allergen content. Thus, factors other than relative humidity seem to influence mite infestation. Moreover, the absence of association between mite infestation and ventilation rate might be accounted for by the gentle climate in our area with notable outdoor RH. 相似文献
37.
38.
Reciprocal translocations in breast tumor cell lines: cloning of a t(3;20) that targets the FHIT gene 总被引:1,自引:0,他引:1
39.
Permeation of human ovarian tissue with cryoprotective agents in preparation for cryopreservation 总被引:18,自引:10,他引:18
Newton H; Fisher J; Arnold JR; Pegg DE; Faddy MJ; Gosden RG 《Human reproduction (Oxford, England)》1998,13(2):376-380
The recent improvements in the treatment of cancer by chemo- and
radiotherapy have led to a significant increase in the survival rates of
patients with malignant disease, but at the expense of distressing side
effects. One major problem, especially for younger patients, is that
aggressive therapy destroys a significant proportion of the follicular
population, which can result in either temporary or permanent infertility.
Freeze-banking pieces of ovarian cortex prior to treatment is one strategy
for preserving fecundity. When the patient is in remission, fertility
could, theoretically, be restored by autografting the thawed tissue at the
orthotopic site or by growing isolated follicles to maturity in vitro.
Recent studies have found good follicular survival in frozen-thawed human
ovarian tissue but to optimize the process an effective cryopreservation
method needs to be developed. An essential part of such a technique is to
permeate the tissue with a cryoprotectant to minimize ice formation and the
extent of this equilibration is an important determinant of post-thaw
cellular survival. In the current study, we have investigated the diffusion
of four cryoprotective agents into human tissue at both 4 degrees C and 37
degrees C. We have also studied the effect of adding different
concentrations of the non penetrating cryoprotective agent, sucrose, to the
freezing media using the release of lactate dehydrogenase as a measure of
its protective effect. At 4 degrees C propylene glycol and glycerol
penetrated the tissue significantly slower than either ethylene glycol or
dimethyl sulphoxide. At the higher temperature of 37 degrees C all four
cryoprotectants penetrated at a faster rate, however concern about enhanced
toxicity prevents the use of these conditions in practice. Thus, the
results suggest that the best method of preparing tissue for freezing is
exposure for 30 min to 1.5 M solutions of ethylene glycol or dimethyl
sulphoxide at 4 degrees C; this achieved a mean tissue concentration that
was almost 80% that of the bathing solution. We also report that the
addition of low concentrations of sucrose to the freezing medium does not
have a significant protective effect against freezing injury.
相似文献
40.
Vyshkina T Shugart YY Birnbaum G Leist TP Kalman B 《European journal of human genetics : EJHG》2005,13(2):240-247
Linkage studies in multiple sclerosis (MS) identified several susceptibility loci. One of these regions includes chromosome 17q11 where a meta-analysis of data from three genome scans suggested linkage. This region encodes a cluster of genes for beta-chemokines or CC chemokine ligands (CCLs), which may be involved in the development of MS lesions. Here we aimed to test if CCL alleles and haplotypes are associated with MS. Using methods of linkage and association, we observed deviations from the expected 50% transmission of haplotypes from unaffected parents to their affected children at CCL2, CCL11-CCL8-CCL13 and CCL3 within the investigated 1.85 MB chromosomal segment. Analyses of the linkage disequilibrium map support that variants with possible relevance to MS can be located within these subregions. Identification of MS associated CCL variants may have direct clinical significance, as it can lead to the design of small competitive antagonists of these molecules with beneficial effects in the treatment of patients with early and active disease. 相似文献