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991.
Bloom Syndrome and Maternal Uniparental Disomy for Chromosome 15 总被引:4,自引:1,他引:3
Trevor Woodage Madhuri Prasad Joanne W. Dixon Roslyn E. Selby Dennis R. Romain Letizia M. Columbano-Green David Graham Peter K. Rogan James R. Seip Arabella Smith Ronald J. Trent 《American journal of human genetics》1994,55(1):74-80
Bloom syndrome (BS) is an autosomal recessive disorder characterized by increases in the frequency of sister-chromatid exchange and in the incidence of malignancy. Chromosome-transfer studies have shown the BS locus to map to chromosome 15q. This report describes a subject with features of both BS and Prader-Willi syndrome (PWS). Molecular analysis showed maternal uniparental disomy for chromosome 15. Meiotic recombination between the two disomic chromosomes 15 has resulted in heterodisomy for proximal 15q and isodisomy for distal 15q. In this individual BS is probably due to homozygosity for a gene that is telomeric to D15S95 (15q25), rather than to genetic imprinting, the mechanism responsible for the development of PWS. This report represents the first application of disomy analysis to the regional localization of a disease gene. This strategy promises to be useful in the genetic mapping of other uncommon autosomal recessive conditions. 相似文献
992.
993.
Genetic Structure and Symbiotic Characteristics of a Bradyrhizobium Population Recovered from a Pasture Soil 总被引:2,自引:2,他引:0 下载免费PDF全文
We examined the genetic structure and symbiotic characteristics of Bradyrhizobium isolates recovered from four legume species (Lupinus albus [white lupine], Lupinus angustifolius [blue lupine], Ornithopus compressus [yellow serradella], and Macroptilium atropurpureum [sirato]) grown in an Oregon soil. We established that multilocus enzyme electrophoresis (MLEE) can provide insights into the genetic relatedness among Bradyrhizobium strains by showing a positive correlation (r2 = ≥0.90) between the relatedness of Bradyrhizobium japonicum strains determined by MLEE at 13 enzyme loci and that determined by other workers using either DNA-DNA hybridization or DNA sequence divergence estimates. MLEE identified 17 electrophoretic types (ETs) among 95 Bradyrhizobium isolates recovered from the four hosts. Although the overall genetic diversity among the ETs (H = 0.69) is one of the largest measured to date in a local population of any soilborne bacterial species, there was no evidence of multilocus structure (linkage disequilibrium) within the population. The majority of the isolates (73%) were represented by two closely related ETs (2 and 3) which dominated the root nodules of white lupine, serradella, and siratro. In contrast, ET1 dominated nodules of blue lupine. Although representative isolates from all of the 17 ETs nodulated siratro, white lupine, blue lupine, and big trefoil (Lotus pedunculatus), they were either completely ineffective or poorly effective at fixing nitrogen on these hosts. Despite the widespread use of serradella as a surrogate host for lupine-nodulating bradyrhizobia, 7 of the 17 ETs did not nodulate this host, and the remaining 10 ETs were ineffective at fixing nitrogen. 相似文献
994.
Subunit c of the F1F0-ATPase from Propionigenium modestum was extracted from the particulate cell fraction with chloroform/methanol. The protein was further purified by carboxymethyl cellulose chromatography and anion exchange HPLC in the organic solvent. SDS-PAGE of the purified protein indicated a single stained protein band migrating as expected for the c-subunit. Incubation of isolated subunit c in chlorform/methanol or aqueous buffer containing dodecyl-β-
-maltoside with [14C]dicyclohexylcarbodiimide (DCCD) resulted in the incorporation of radioactivity into the protein. The rate of this reaction depended on the external pH; it was significantly faster in the more acidic than in the alkaline pH range. In the presence of Na+ subunit c was partially protected from labeling with [14C]DCCD at pH 6.1 and at pH 7.5, whereas no protection was evident at pH 5.5. At pH 7.5, the rate of subunit c labeling by [14C]DCCD in the presence of 20 mM NaCl was about 50% lower than in the absence of Na+ ions. The isolated c-subunit therefore apparently retains in part the Na+ binding site which, when occupied, diminishes the reactivity of the protein towards DCCD. 相似文献
995.
Paul D. Hempstead Aaron J. Hudson Peter J. Artymiuk Simon C. Andrews Mark J. Banfield John R. Guest Pauline M. Harrison 《FEBS letters》1994,350(2-3):258-262
X-Ray analysis of the ferritin of Escherichia coli (Ec-FTN) and of Ec-FTN crystals soaked in (NH4)2Fe(SO4)2 has revealed the presence of three iron-binding sites per subunit. Two of these form a di-iron site in the centre of the subunit as has been proposed for the ‘ferroxidase centres’ of human ferritin H chains. This di-iron site, lying within the 4-alpha-helix bundle, resemble those of ribonucleotide reductase, methane monoxygenase and haemerythrin. The third iron is bound by ligands unique to Ec-FTN on the inner surface of the protein shell. It is speculated that this state may represent the nucleation centre of a novel type of Fe(III) cluster, recently observed in Ec-FTN. 相似文献
996.
Consumption of benthic invertebrates by waterbirds in the Oosterschelde estuary,SW Netherlands 总被引:7,自引:7,他引:0
The number of waders in the Oosterschelde, S.W. Netherlands, declined after a reduction in intertidal area due to the construction of a storm surge barrier and secondary dams, suggesting that the carrying capacity had been reached (Schekkerman et al., 1993). In this paper we present data on consumption and predation pressure by birds to explore whether the reduction in their numbers is due to prey depletion or to other factors.The total annual consumption of benthic invertebrates by birds in the Oosterschelde amounted to 1573 × 103 g ADW y–1 in the period before the coastal engineering works (pre-barrier) and 1500 × 103 kg ADW y–1 in the post-barrier period. More than half of the total amount of biomass is eaten by the Oystercatcher, and only seven (pre-barrier) or even six (post-barrier) bird species together take 90% of the total.Although the consumption by individual species may vary considerably among years, the total consumption was remarkably stable, with a CV of only 3–4% of the mean, especially compared to the variability of the prey populations. In the pre-barrier period, consumption was lowest in mid summer, increased sharply from August onwards until a peak was reached in January. A sharp decrease took place in March. In the post-barrier period, consumption peaked in October.The total consumption per unit area per year does not differ much between different sectors of the Oosterschelde, apart from a distinctly lower value in the eastern part. Of the total amount of food taken by birds, only 0.1–0.4% is taken in the subtidal compartment. In several study plots on an individual tidal flat, there was a clear relation between consumption and benthic biomass.The predation pressure was 13 and 23% of the standing stock, in the post- and pre-barrier period respectively. When cockles, mussels and their main predator, the Oystercatcher, are excluded from the calculations, the predation pressure of the other species was 30 and 37% of the biomass, respectively.Predation pressure of Oystercatchers in individual study plots varied from less than 10% to more than 70% of the standing stock. On cockle beds the predation pressure was positively related to the average length of the cockles present.Based on these results and a comparison with the literature we conclude that, at least for several species that feed intertidally, carrying capacity could be limited by the stocks of food. This does not mean that birds face food shortage each season. As the variability of the benthos populations is much higher than that of the bird densities it is likely that at some times food is not limiting, at other times it is. On the other hand, consumption is very low in the subtidal compartment and species feeding here could potentially increase substantially in numbers in the Oosterschelde. 相似文献
997.
One of the most extreme freshwater habitats in Peninsular Malaysia is the peat swamp forest, with dark-coloured and highly acidic waters. Surprisingly, little is known about blackwater fishes in Peninsular Malaysia. Until 1968, only 26 fish species were known from blackwaters throughout Peninsular Malaysia, of which only one can be regarded as stenotopic. A recent intensive survey of part of the North Selangor peat swamp forest yielded 47 species, of which 14 are probably stenotopic taxa. These include four undescribed species and several new records for western Peninsular Malaysia. These discoveries are significant in that they include the family Chaudhuriidae which until 1985, was not reported from Sundaic Southeast Asia, and the rare genus Encheloclarias which had not been encountered for over 50 years. The rapid rate of destruction of the peat swamp forest owing to development, forestry and agricultural activities must be halted or slowed significantly to enable the proper zoological surveys and studies to be conducted. Conservation plans and environmental impact assessments based on inadequate sampling and knowledge of species present is acutely dangerous. There are no longer substantial undisturbed blackwater peat swamp forests left in most of Peninsular Malaysia. Conservation of the remaining blackwater biotopes is critically important if extinction of many species, here regarded as economically valuable renewable resources, is to be prevented. 相似文献
998.
The profundal zone of Lake Esrom, Denmark has a dense population of Chironomus anthracinus, which survives 2–4 months of oxygen depletion each summer during stratification. The metabolism of 3rd and 4th instar larvae was examined in regard to variation in biomass and temperature. Respiration at air saturation was described by a curvilinear multiple regression relating oxygen consumption to individual AFDW and temperature. At 10 °C and varying oxygen regimes the O2 consumption and CO2 production of 4th instar larvae were almost unaltered from saturation to about 3 mg O2 l–1, but decreased steeply below this level. The respiratory quotient increased from 0.82 at saturation to about 3.4 at oxygen concentrations near 0.5 mg O2 l–1. This implied a shift from aerobic to partially anaerobic metabolism. At 0.5 mg O2 l–1 the total energy production equalled 20% of the rate at saturation of which more than one third was accounted for by anaerobic degradation of glycogen. This corresponded to a daily loss of 12 µg mg AFDW–1 or approximately 5% of the body reserves. At unchanged metabolic rate the glycogen store would last three weeks, but long term oxygen deficiency causes a further suppression of the energy metabolism in C. anthracinus. 相似文献
999.
Seven species of snakeheads (Channidae) are known from Peninsular Malaysia and Singapore, viz. Channa bankanensis, C. gachua, C. lucius, C. marulioides, C. melasoma, C. micropeltes and C. striata. Up-to-date distribution maps of each species are presented, including new records. Their systematics is reviewed and partially revised. The taxonomic status of C. marulioides and C. melanoptera is clarified. Specimens from Peninsular Malaysia identified as C. melanoptera sensu Weber & de Beaufort, 1922, proved to be the adult form of C. marulioides s.str. The real C. melanoptera appears to be restricted to Borneo and possibly Sumatra. The life history of a blackwater species C. bankanensis is also documented, with regards to the morphological and colour-pattern changes associated with growth. An updated key to the seven species based on morphometric measurements and meristic counts is presented. 相似文献
1000.
Pradip Bhatnagar William Huffman Andrew King Louis Pelus William Potts et al. 《Journal of Ornithology》1994,135(1):61-71