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排序方式: 共有909条查询结果,搜索用时 234 毫秒
901.
BS Baker JB Boyd AT Carpenter MM Green TD Nguyen P Ripoll PD Smith 《Canadian Metallurgical Quarterly》1976,73(11):4140-4144
Recombination-defective meiotic mutants and mutagen-sensitive mutants of D. melanogaster have been examined for their effects on meiotic chromosome behavior, sensitivity to killing by mutagens, somatic chromosome integrity, and DNA repair processes. Several loci have been identified that specify functions that are necessary for both meiotic recombination and DNA repair processes, whereas mutants at combination and DNA repair processes, whereas mutants at other loci appear to be defective in only one pathway of DNA processing. 相似文献
902.
The effects of vasectomy on the development and maintenance of spermatogenesis was studied using immature and mature dog testes. Bilateral vasectomy in immature dogs delayed the development of advanced spermatocytes, spermatids, and spermatozoa for about 3 months postsurgery. Spermatogenesis appeared to be recovered to control levels by 4 months postvasectomy. Spermatogenesis in mature dogs was also altered after bilateral vasectomy. Decreased numbers of advanced spermatocytes as well as maturation arrest was observed by 3 weeks postvasectomy. Seminiferous tubule cell layers quickly decreased to one to three layers as the lumina became occluded with sloughed cells by 3 to 6 weeks postvasectomy. Recovery in terms of the numbers of spermatocytes, spermatids, and spermatozoa was evident by 13 weeks postvasectomy, although occasional dog testes did not recover and appeared to be more sensitive to vasectomy-induced damage. It thus appears that vasectomy temporarily inhibits both the development and maintenance of spermatogenesis in immature as well as mature dog testes. Spermatogenesis does recover but may be maintained at somewhat lower levels after vasectomy. Changes are rapid in onset and take several weeks to be reversed. Some dog testes appear to be more sensitive to the damage and it may be irreversible in these testes. 相似文献
903.
A cytogenetic survey was carried out on 200 patients with mental retardation and multiple congenital anomalies, and on 200 normal adult controls. Patients with a known syndrome were excluded from the survey. Chromosome analyses were carried out on 'blind-coded' slides using the ASG banding technique as the routine stain. After the initial analyses (at least 15 cells per person) the slides were decoded, destained and reused for C and Q band polymorphism studies. Five major chromosome abnormalities were detected in the patient group during the survey. They included three patients with de novo, apparently balanced, reciprocal translocations, karyotypes 46,XY,rcp(3;16)(q21;p12); 46,XX,rcp(5;8)(p15;q22); and 46,XX,rcp(5;12)(p11;q24); one with karyotype 47,XX,+mar and one with karyotype 46,XX,der(13),t(13;?)(q34;?). One additional patient whose karyotype in lymphocytes was 46,XX,inv(9)(p11;q13) was found to have a mosaic karyotype 46,XX,inv(9)(p11;q13)/46,XX,inv(9) (p11;q13), der(12),t(12;?)p13;?) in cultured skin fibroblasts. None of the 200 controls had a major chromosome abnormality. From the combined results of this and previous surveys it is now apparent that about 6.2% of the unclassifiable mentally retarded patients with three or more congenital anomalies and about 0.7% of the controls reveal major chromosome abnormalities. 相似文献
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908.
RC Hickson WW Heusner WD Huss DE Jackson DA Anderson DA Jones AT Psaledas 《Canadian Metallurgical Quarterly》1976,8(3):191-195
The practice of sequential incubation in radio-immunoassay of TSH improves the sensitivity and precision without affecting the specificity compared with the method using simultaneous incubation of the constituents of the radio-immunological reaction. The determination of basic levels of TSH is more sensitive and more precise. 相似文献
909.