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991.
M. Hixon Elise Millie L. A. Judis Stephanie Sherman Katherine Allran Lisa Taft Terry Hassold 《Human genetics》1998,103(6):654-657
Paternal nondisjunction accounts for approximately 5% of cases of trisomy 21. To test the hypothesis that, in some such cases,
the fathers might be predisposed to meiotic nondisjunction, we utilized fluorescence in situ hybridization (FISH) to screen
for aneuploidy in sperm. We analyzed sperm samples from ten males with a trisomy 21 offspring of paternal origin. Among these
individuals, the overall frequency of disomy 21 was 0.15%, comparable to estimates of disomy 21 in the general male population.
Furthermore, none of the ten fathers of trisomy 21 individuals had significantly elevated levels of disomic sperm. Thus, our
results provide no evidence that the occurrence of a trisomy 21 conceptus of paternal origin imparts an increased risk of
trisomy in subsequent pregnancies.
Received: 9 September 1998 / Accepted: 30 September 1998 相似文献
992.
The contribution of the allelicMtz
3 andMtz
4 genes to the formation of individual rabbit serum α2-macroglobulin (α2M) molecules was examined by precipitation of α2M from rabbits of known genotype with antiallotype antisera. The α2M was isolated fromz
3z3 andz
4z4 homozygous andz
3z4 heterozygous rabbits, iodinated with I125 and precipitated by sequential reactions with antiallotype antiserum and goat anti-rabbit IgG. Purified unlabeled α2M or α2M in serum was used to inhibit competitively the reaction of antiallotype antiserum and labeled α2M. Nearly all α2M molecules have z3 or z4 antigenic determinants; approximately 50% of α2M molecules in heterozygotes have both. Altogether, the z3, z3,4, and z4 molecules in heterozygotes have approximately 60%
of the number of z3 and 40% of the number of z4 determinants as compared to the respective homozygotes. Unlike all other known
allelic blood protein systems of rabbits, allelic exclusion does not occur in α2M molecules of heterozygotes; rather, hybrid molecules are formed.
Presented in part at the Fifty-fourth and Fifty-fifth Annual Meetings of the Federation of American Societies for Experimental
Biology, Atlantic City, New Jersey, April 12–17, 1970, and Chicago, Illinois, April 12–17, 1971. This investigation was supported
in part by U.S. Public Health Service Grants AI-09241 and AI-07043. B.H.B. performed this investigation in partial fulfillment
of the requirements for the Doctor of Philosophy Degree in the Graduate College; he is supported by a postdoctoral fellowship
from the Schweppe Foundation. K.L.K. is the recipient of U.S. Public Health Service Research Career Development Award AI-28687. 相似文献
993.
Glycerylphosphorylcholine phosphodiesterase in rat liver. Subcellular distribution and localization in plasma membranes 总被引:7,自引:7,他引:0
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Katherine A. Lloyd-Davies Robert H. Michell Roger Coleman 《The Biochemical journal》1972,127(2):357-368
1. A simple new assay for glycerylphosphorylcholine phosphodiesterase is described, in which radioactive glycerylphosphorylcholine is used as substrate and the reaction products are separated by adsorption on an anion-exchange resin. 2. Rat liver subcellular fractions contained both particulate (58%) and soluble (42%) glycerylphosphorylcholine phosphodiesterase. Both activities released free choline from glycerylphosphorylcholine. 3. The particulate glycerylphosphorylcholine phosphodiesterase was recovered mainly in the nuclear and microsomal fractions and showed a distribution similar to those of 5'-nucleotidase and alkaline phosphodiesterase I, both of which are constituents of the liver plasma membrane. 4. During purification of plasma membranes glycerylphosphorylcholine phosphodiesterase, 5'-nucleotidase and alkaline phosphodiesterase I showed largely similar behaviour, indicating that glycerylphosphorylcholine phosphodiesterase is also localized in liver plasma membranes. Slight differences in the distributions of these three enzymes in density-gradient separations are discussed in relation to the possibility that they are unevenly distributed on different areas of the cell surface. 5. The differences between glycerylphosphorylcholine phosphodiesterase and alkaline phosphodiesterase I indicate that these two activities are not functions of a single enzyme. 6. The glycerylphosphorylcholine phosphodiesterase of liver plasma membranes has a pH optimum of 8.5 and a K(m) for glycerylphosphorylcholine of 0.95mm. It is inhibited by EDTA and fully reactivated by a variety of bivalent cations (and Fe(3+)). 相似文献
994.
995.
996.
Vernon I. Cheadle Ernest M. Gifford Jr. Katherine Esau 《Biotechnic & histochemistry》1953,28(2):49-53
A technic is described for producing critically stained preparations of phloem tissue. The preparations promise to be relatively stable. Sections of fixed unembedded or of embedded (paraffin or celloidin) phloem, cambium, and xylem are (1) stained in Foster's tannic acid-ferric chloride combination; (2) treated with 1% NaHCOg in 25% or 50% ethyl alcohol for 30 minutes; (3) stained in a saturated solution of lacmoid (made alkaline by adding a few ml. of 1% NaHCO3 in 25% alcohol) for 12 to 18 hours; (4) dehydrated and cleared in a series composed of 1% solution of NaHCOs in 50% ethyl alcohol, 80%, 95%, and absolute alcohol, equal proportions of absolute alcohol, clove oil, and xylene, and finally pure xylene; and (5) mounted in a neutral resin. Callose and lignified secondary walls are blue or blue-green in color, cellulose walls and stainable protoplasmic contents are generally light brown. The technic has been successful with sections from 5 to 40μ in thickness, and the staining has been satisfactory for both color and black and white photomicrography. 相似文献
997.
998.
F.-Nora Vögtle Björn Brändl Austin Larson Manuela Pendziwiat Marisa W. Friederich Susan M. White Alice Basinger Cansu Kücükköse Hiltrud Muhle Johanna A. Jähn Oliver Keminer Katherine L. Helbig Carolyn F. Delto Lisa Myketin Dirk Mossmann Nils Burger Noriko Miyake Audrey Burnett Ingo Helbig 《American journal of human genetics》2018,102(4):557-573
999.
Comparative population genomics of latitudinal variation in Drosophila simulans and Drosophila melanogaster
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Heather E. Machado Alan O. Bergland Katherine R. O’Brien Emily L. Behrman Paul S. Schmidt Dmitri A. Petrov 《Molecular ecology》2016,25(3):723-740
Examples of clinal variation in phenotypes and genotypes across latitudinal transects have served as important models for understanding how spatially varying selection and demographic forces shape variation within species. Here, we examine the selective and demographic contributions to latitudinal variation through the largest comparative genomic study to date of Drosophila simulans and Drosophila melanogaster, with genomic sequence data from 382 individual fruit flies, collected across a spatial transect of 19 degrees latitude and at multiple time points over 2 years. Consistent with phenotypic studies, we find less clinal variation in D. simulans than D. melanogaster, particularly for the autosomes. Moreover, we find that clinally varying loci in D. simulans are less stable over multiple years than comparable clines in D. melanogaster. D. simulans shows a significantly weaker pattern of isolation by distance than D. melanogaster and we find evidence for a stronger contribution of migration to D. simulans population genetic structure. While population bottlenecks and migration can plausibly explain the differences in stability of clinal variation between the two species, we also observe a significant enrichment of shared clinal genes, suggesting that the selective forces associated with climate are acting on the same genes and phenotypes in D. simulans and D. melanogaster. 相似文献
1000.