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Summary In a series of 450 products of conception received for cytogenetic analysis, tissue culture was attempted on 309, and karyotypes were established using banding techniques in 154 singleton specimens. Abnormalities of karyotype were identified in 19%; of these abnormalities, 48% were autosomal trisomies. Gestational age was decreased in the abnormal specimens, and their developmental age was retarded by comparison with their gestational age. Factors contributing to the relatively low incidence of abnormality are examined. The major factor appears to be the clinical interest of collaborating staff, leading to selection, either intentional or unintentional, of particular phenotypes and hence a non-random series. A negative relationship is suggested between frequency of monsomy X and autosomal trisomy, both being associated with maternal age. 相似文献
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New developments in magnetic labelling techniques for cells and microspheres have extended the useful range of magnetic separation, particularly high gradient magnetic separation, into biotechnical areas. The basic magnetic principles involved are reviewed and representative samples of labelling techniques and results drawn from the past three years are presented. Illustrative examples of large scale operation in other industries are also presented, demonstrating the potential of the biotechnological applications. 相似文献
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The presence of free D-aspartic acid in rodents and man 总被引:4,自引:0,他引:4
D S Dunlop A Neidle D McHale D M Dunlop A Lajtha 《Biochemical and biophysical research communications》1986,141(1):27-32
Free D-aspartic acid is present in appreciable quantities in the brain and other tissues of rodents and in human blood. In the newborn rat, the highest concentration of D-aspartic acid was found in cerebral hemispheres, where, at 164 nmol/g (8.4% of the total aspartic acid), the level of D-aspartic acid exceeds that of many essential L-amino acids. The highest ratio of D- to total aspartic acid (38%) occurred in neonatal blood cells. In the adult rat, the highest concentration was present in the pituitary gland (127 nmol/g, 3.8%). Within the central nervous system marked regional differences are present and characteristic changes with development take place. In general, the levels of D-aspartic acid fall rapidly with increasing age. In cerebral hemispheres adult values (13 nmol/g, 0.43%) are approached within one week. D-aspartic acid concentrations may also be higher in young humans since fetal blood, taken from placental cord, contains 2.6 nmol/g (4.9%) of D-aspartic acid, a value five times that of adult human blood. These distributional patterns and developmental changes may be the result of differences in the ability of various tissues to dispose of an extraneous metabolite, or, reflect alterations in a specific functional requirement for D-aspartic acid. 相似文献
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The biosynthesis of asparaginase II in Saccharomyces cerevisiae is subject to nitrogen catabolite repression. In the present study we examined the physiological effects of glutamate auxotrophy on cellular metabolism and on the nitrogen catabolite repression of asparaginase II. Glutamate auxotrophic cells, incubated without a glutamate supplement, had a diminished internal pool of alpha-ketoglutarate and a concomitant inability to equilibrate ammonium ion with alpha-amino nitrogen. In the glutamate auxotroph, asparaginase II biosynthesis exhibited a decreased sensitivity to nitrogen catabolite repression by ammonium ion but normal sensitivity to nitrogen catabolite repression by all amino acids tested. 相似文献
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Sophie C. Payne Carole A. Bartlett Donna L. Savigni Alan R. Harvey Sarah A. Dunlop Melinda Fitzgerald 《PloS one》2013,8(6)
Partial injury to the central nervous system (CNS) is exacerbated by additional loss of neurons and glia via toxic events known as secondary degeneration. Using partial transection of the rat optic nerve (ON) as a model, we have previously shown that myelin decompaction persists during secondary degeneration. Failure to repair myelin abnormalities during secondary degeneration may be attributed to insufficient OPC proliferation and/or differentiation to compensate for loss of oligodendrocyte lineage cells (oligodendroglia). Following partial ON transection, we found that sub-populations of oligodendroglia and other olig2+ glia were differentially influenced by injury. A high proportion of NG2+/olig2–, NG2+/olig2+ and CC1−/olig2+ cells proliferated (Ki67+) at 3 days, prior to the onset of death (TUNEL+) at 7 days, suggesting injury-related cues triggered proliferation rather than early loss of oligodendroglia. Despite this, a high proportion (20%) of the NG2+/olig2+ OPCs were TUNEL+ at 3 months, and numbers remained chronically lower, indicating that proliferation of these cells was insufficient to maintain population numbers. There was significant death of NG2+/olig2– and NG2−/olig2+ cells at 7 days, however population densities remained stable, suggesting proliferation was sufficient to sustain cell numbers. Relatively few TUNEL+/CC1+ cells were detected at 7 days, and no change in density indicated that mature CC1+ oligodendrocytes were resistant to secondary degeneration in vivo. Mature CC1+/olig2– oligodendrocyte density increased at 3 days, reflecting early oligogenesis, while the appearance of shortened myelin internodes at 3 months suggested remyelination. Taken together, chronic OPC decreases may contribute to the persistent myelin abnormalities and functional loss seen in ON during secondary degeneration. 相似文献
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Changiz Geula Sara R. Dunlop Ivan Ayala Allegra S. Kawles Margaret E. Flanagan Tamar Gefen Marek-Marsel Mesulam 《Journal of neurochemistry》2021,158(6):1394-1411