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1.
S A Tanumihardjo H C Furr J W Erdman J A Olson 《European journal of clinical nutrition》1990,44(3):219-224
After an appropriate dose of 3,4-didehydroretinol (vitamin A2, DR) is given orally in corn oil to retinol (R)-depleted rats, the ratio of plasma DR/R values at 3.5 h is inversely related to the liver concentration of vitamin A (Tanumihardjo & Olson, 1988). In the present study, a similar procedure, termed the modified relative dose response (MRDR) assay, was employed with rats containing a much broader range of liver reserves; ie, less than 2 to 107 nmol of vitamin A per g wet weight of liver (less than 1 to 30 micrograms/g). The DR/R ratio for 15 of 16 rats with liver reserves less than 17 nmol/g (less than 5 micrograms/g) was greater than 0.15, whereas the ratio was less than 0.15 for 7 of 8 rats with liver reserves greater than 17 nmol/g. This distribution provides sensitivity, specificity and positive predictive values of 94, 88 and 94 per cent, respectively. The DR/R ratios reached a maximal plateau in two other groups of rats between 3.5 and 8 h. At all times up to 24 h, mean DR/R ratios for vitamin A-depleted rats (45 +/- 6 nmoles of vitamin A/g liver) were approximately twice those for vitamin A-sufficient rats (230 +/- 40 nmoles of vitamin A/g liver). In three well-nourished adults, presumably with liver reserves of greater than 300 nmol/g wet weight liver (greater than 80 micrograms retinol equivalents/g), and in two young (1- and 3-years old) well-nourished children, maximal DR/R ratios were less than 0.023. In these cases, peak DR/R ratios were observed, with one possible exception, between 8 and 12 h.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
2.
Factors influencing women to undergo screening mammography 总被引:2,自引:0,他引:2
3.
Braffman BH; Coleman BG; Ramchandani P; Arger PH; Nodine CF; Dinsmore BJ; Louie A; Betsch SE 《Radiology》1994,190(3):797
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Rupture of the distal biceps tendon: evaluation with MR imaging 总被引:2,自引:0,他引:2
6.
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
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It is well recognized that the ability to cryopreserve unfertilizedhuman oocytes would make a significant contribution to infertilitytreatment. However, despite considerable interest, very fewsuccessful pregnancies have arisen from cryopreserved oocytesafter thawing, insemination and transfer of the subsequent embryo.The reasons for this lack of progress may well result from adearth of information on how the various biophysical changesduring a cryopreservation regimen affect human oocyte function.Recently, fundamental studies on the effects of cooling, membranepermeability, cryoprotectant addition and ice formation havebeen performed on human oocytes by a number of groups, and theseform the basis of the current review. It is likely that successfulhuman oocyte cryopreservation will only follow once these factorsare fully understood, but the existing base of knowledge shouldprovide a platform for further improvements in the techniquescurrently employed. 相似文献
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