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1.
C. L. Peel 《BMJ (Clinical research ed.)》1897,1(1880):105-106
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Summary
Drosophila imaginal disc cell lines show a characteristic pattern of aggregation in culture, which appears to be due to cell-cell rather than cell-substrate interactions. We have examined the distribution of PS integrins in wing and leg cell lines, and find that these integrin homologues are expressed preferentially in aggregates. Cell sheets, small cell clumps and chains of cells express antigen at points of cell-cell contact only. 相似文献
5.
Tracer studies on the biosynthesis of amino acids from lactate by Peptostreptococcus elsdenii 总被引:3,自引:3,他引:0
Peptostreptococcus elsdenii, a strict anaerobe from the rumen, was grown on a medium containing yeast extract and [1-(14)C]- or [2-(14)C]-lactate. Radioisotope from lactate was found in all cell fractions, but mainly in the protein. The label in the protein fraction was largely confined to a few amino acids: alanine, serine, aspartic acid, glutamic acid and diaminopimelic acid. The alanine, serine, aspartic acid and glutamic acid were separated, purified and degraded to establish the distribution of (14)C from lactate within the amino acid molecules. The labelling patterns in alanine and serine suggested their formation from lactate without cleavage of the carbon chain. The pattern in aspartic acid suggested formation by condensation of a C(3) unit derived directly from lactate with a C(1) unit, probably carbon dioxide. The distribution in glutamic acid was consistent with two possible pathways of formation: (a) by the reactions of the tricarboxylic acid cycle leading from oxaloacetate to 2-oxoglutarate, followed by transamination; (b) by a pathway involving the reaction sequence 2 acetyl-CoA-->crotonyl-CoA-->glutaconate-->glutamate. 相似文献
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Anonymous nuclear DNA markers in the American oyster and their implications for the heterozygote deficiency phenomenon in marine bivalves 总被引:4,自引:0,他引:4
A puzzling population-genetic phenomenon widely reported in allozyme
surveys of marine bivalves is the occurrence of heterozygote deficits
relative to Hardy-Weinberg expectations. Possible explanations for this
pattern are categorized with respect to whether the effects should be
confined to protein-level assays or are genomically pervasive and expected
to be registered in both protein- and DNA-level assays. Anonymous nuclear
DNA markers from the American oyster were employed to reexamine the
phenomenon. In assays based on the polymerase chain reaction (PCR), two
DNA-level processes were encountered that can lead to artifactual genotypic
scorings: (a) differential amplification of alleles at a target locus and
(b) amplification from multiple paralogous loci. We describe symptoms of
these complications and prescribe methods that should generally help to
ameliorate them. When artifactual scorings at two anonymous DNA loci in the
American oyster were corrected, Hardy-Weinberg deviations registered in
preliminary population assays decreased to nonsignificant values.
Implications of these findings for the heterozygote-deficit phenomenon in
marine bivalves, and for the general development and use of PCR-based
assays, are discussed.
相似文献
8.
Distribution of the catabolic transposon Tn5271 in a groundwater bioremediation system. 总被引:4,自引:2,他引:2 下载免费PDF全文
The distribution of Tn5271-related DNA sequences in samples of groundwater and a groundwater bioremediation system at the Hyde Park (Niagara Falls, N.Y.) chemical landfill site was investigated. PCR amplification of target sequences within the cha genes of Tn5271 revealed similar sequences in the groundwater community and in samples from the sequencing batch reactors treating that groundwater. Cell dilution combined with PCR amplification indicated that cha sequences were carried in about 1 of 10 culturable bacteria from the treatment system. Characterization of isolates involved in chlorobenzoate and toluene biodegradation in the treatment system indicated that two phenotypic clusters, Alcaligenes faecalis type 2 and CDC group IVC-2, contained all of the Tn5271 probe-positive isolates from the community. These two groups differed phenotypically from recipient groups isolated following horizontal transfer of pBRC60 (Tn5271) in pristine freshwater microcosms. A genetic rearrangement in Tn5271 attributable to the intramolecular transposition of the flanking element IS1071R was detected in an isolate from the treatment system. Comparison of the structure of the intramolecular transposition derivative from groundwater isolate OCC13(pBRC13) with a laboratory-derived intramolecular transposition derivative of pBRC60 revealed similarities. The rearrangement was shown to increase the stability of the plasmid under starvation conditions. 相似文献
9.
Linden Ellie Rittenhouse Chadwick D. Peel Michael J. S. Ortega Isaac M. Smit Izak P. J. 《Ecosystems》2023,26(4):768-783
Ecosystems - In the early 1990’s, reserves adjacent to Kruger National Park (KNP) removed their fences to create a continuous landscape within the Kruger to Canyons Biosphere Reserve.... 相似文献
10.
One of the oldest known helcionelloid molluscs, Anabarella Vostokova, is redescribed on the basis of type material from the lower Cambrian of north Siberia. Published records of the type species, Anabarella plana Vostokova, show a very wide range in morphology, but studies of variation through ontogeny and in taphonomy confirm assignment to a single variable species. Other described species are reviewed. 相似文献