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21.
22.
Roelof-Jan Oostra Stephan Kemp Pieter A. Bolhuis Elisabeth M. Sleeker-Wagemakers 《Human genetics》1996,97(4):500-505
Leber’s hereditary optic neuropathy (LHON) is a maternally inherited disorder of the optic nerves. It has been proposed that
the specific mutations in the mitochondrial DNA (mtDNA) that are associated with LHON require and X-chromosomally encoded
permissive factor in order to become expressed. This would explain both the preponderance of male patients and the fact that
most carriers of specific mtDNA mutations remain unaffected. Although linkage studies have been negative so far, the existence
of such a factor has not been ruled out. We investigated the genealogical data of 24 large LHON pedigrees and concluded that
the presumed X-linked factor would be recessively inherited and that at least 57% of the affected females would be heterozygous.
Therefore, these females must be the victim of nonrandom X-chromosomal inactivation (skewed lyonization). However, analysis
of X-chromosomal methylation patterns in 16 LHON-affected females revealed substantial skewing in only 15%–20% of cases, which
is not significantly different from the patterns in 49 controls. Moreover, we found the frequency of LHON in daughters of
affected heterozygous females to be twice to three times as high as in daughters of unaffected heterozygous females, which
cannot be explained by an X-chromosomally inherited factor. We conclude that the results of our investigations do not support
the hypothesis that LHON is a digenic disease with an X-linked factor being the main cause of loss of vision in the presence
of relevant mtDNA mutations.
Received: 1 June 1995 / Revised: 20 September 1995 相似文献
23.
Kazutoyo Osoegawa Rie Susukida Saishi Okano Jun Kudoh Shinsei Minoshima Nobuyoshi Shimizu Pieter J. de Jong Juergen Groet Jane Ives Hans Lehrach Dean Nizetic Eiichi Soeda 《Genomics》1996,32(3):375
The major phenotypic features of Down syndrome have been correlated with partial trisomies of chromosome 21, allowing us to define the candidate gene region to a 4-Mb segment on the 21q22.2 band. We present here a high-resolution physical map with megabase-sized cosmid/PAC contigs. This ordered clone library has provided unique material for the integration of a variety of mappable objects, including exons, cDNAs, restriction sites, etc. Furthermore, our results have exemplified a strategy for the completion of the chromosome 21 map to sequencing. 相似文献
24.
Anthocyanin pigments responsible for purple and pink flower colours in the tribe Podalyrieae have been identified. The considerable variation in flower colour is not reflected in the chemical variation and the flower pigments are surprisingly conservative. Virgilia flowers always have the acetic acid esters of cyanidin-3-glucoside and peonidin-3-glucoside as major compounds, together with trace amounts of the coumaroyl ester of cyanidin-3-glucoside. Podalyria flowers invariably have the rather more stable coumaroyl ester of cyanidin. The data support a close affinity between the two genera but also show that flower colour is only partially homologous. 相似文献
25.
Suzanne A. Adjoa Claude Bouchard Pieter Coetzer Tim D. Noakes France T. Dionne 《Human genetics》1994,93(3):347-348
A DNA polymorphism of the nuclear-encoded subunit Va of the human cytochrome c oxidase (COX), a mitochondrial respiratory enzyme, is reported. No polymorphism was detected in genes for the subunits IV and Vb of the same enzyme. 相似文献
26.
Organic Thiols as Organolithotrophic Substrates for Growth of Phototrophic Bacteria 总被引:1,自引:1,他引:0 下载免费PDF全文
Rhodopseudomonas sp. strain BB1, isolated from a coastal marine sediment, immediately metabolized mercaptomalate when grown on mercaptomalate. Sulfide was detected as an intermediate. Extracts of cells grown on mercaptomalate converted mercaptomalate or 3-mercaptopropionate to equimolar amounts of sulfide and either fumarate or acrylate, respectively. Rhodopseudomonas sp. strain BB1 gave higher growth yields on mercaptomalate than on sulfide or malate, consistent with metabolism of the carbon chain of the thiol and the liberated sulfide; i.e., the organic thiol was an organolithotrophic substrate. In contrast, Thiocapsa roseopersicina, isolated previously from a marine microbial mat, had similar growth yields on sulfide, mercaptomalate, or 3-mercaptopropionate, with fumarate or acrylate accumulation from the thiols. T. roseopersicina did not grow photoorganotrophically on fumarate or acrylate, and the thiols were only a source of sulfide for photolithoautotrophic growth. 相似文献
27.
Pieter W. H. Heinstra 《Genetica》1993,92(1):1-22
Evolutionary genetics embodies a broad research area that ranges from the DNA level to studies of genetic aspects in populations. In all cases the purpose is to determine the impact of genetic variation on evolutionary change. The broad range of evolutionary genetics requires the involvement of a diverse group of researchers: molecular biologists, (population) geneticists, biochemists, physiologists, ecologists, ethologists and theorists, each of which has its own insights and interests. For example, biochemists are often not concerned with the physiological function of a protein (with respect to pH, substrates, temperature, etc.), while ecologists, in turn, are often not interested in the biochemical-physiological aspects underlying the traits they study. This review deals with several evolutionary aspects of the Drosophila alcohol dehydrogenase gene-enzyme system, and includes my own personal viewpoints. I have tried to condense and integrate the current knowledge in this field as it has developed since the comprehensive review by van Delden (1982). Details on specific issues may be gained from Sofer and Martin (1987), Sullivan, Atkinson and Starmer (1990); Chambers (1988, 1991); Geer, Miller and Heinstra (1991); and Winberg and McKinley-McKee (1992).Dedicated to Professor Billy W. Geer, because of his contributions to knowledge of the biochemical genetics of Drosophila. 相似文献
28.
Rosalie J. Harris Callum Bryant Melinda A. Coleman Andrea Leigh Verónica F. Briceño Pieter A. Arnold Adrienne B. Nicotra 《Journal of phycology》2023,59(1):179-192
Foundation seaweed species are experiencing widespread declines and localized extinctions due to increased instability of sea surface temperature. Characterizing temperature thresholds are useful for predicting patterns of change and identifying species most vulnerable to extremes. Existing methods for characterizing seaweed thermal tolerance produce diverse metrics and are often time-consuming, making comparisons between species and techniques difficult, hindering insight into global patterns of change. Using three kelp species, we adapted a high-throughput method – previously used in terrestrial plant thermal biology – for use on kelps. This method employs temperature-dependent fluorescence (T–F0) curves under heating or cooling regimes to determine the critical temperature (Tcrit) of photosystem II (PSII), i.e., the breakpoint between slow and fast rise fluorescence response to changing temperature, enabling rapid assays of photosynthetic thermal tolerance using a standardized metric. This method enables characterization of Tcrit for up to 48 samples per two-hour assay, demonstrating the capacity of T–F0 curves for high-throughput assays of thermal tolerance. Temperature-dependent fluorescence curves and their derived metric, Tcrit, may offer a timely and powerful new method for the field of phycology, enabling characterization and comparison of photosynthetic thermal tolerance of seaweeds across many populations, species, and biomes. 相似文献
29.
Pollen records of Holocene sediment cores from the Costa Rican Cordillera de Talamanca (La Chonta bog, 2310 m and La Trinidad bog, 2700 m) show the postglacial development of the montane oak forest zone from ca. 9500 to 1500 yr BP. During the early Holocene (ca. 9500–700 yr BP), alder vegetation covered the La Chonta and La Trinidad bogs and their adjacent hills. The upper forest line is inferred to be at 2800–3000 m elevation. A Podocarpus-Quercus forest characterised the middle Holocene (ca. 7000–4500 yr BP). The upper forest line is located at >3000 m reaching the present-day altitudinal distribution. A Quercus forest characterised the late Holocene (ca. 4500–1500 yr BP). Compared to modern conditions, the early Holocene has similar average temperatures, but the moisture level was probably higher. Pollen evidence for the late Holocene indicates drier environmental conditions than today. In order to improve the paleoecological interpretation, we described the local vegetation and used moss samples as pollen traps at both montane bogs along strong soil moisture gradients.The Netherlands Centre for Geo-ecological Research, ICG 相似文献
30.
Pieter H. B. De Visser Willem G. Keltjens Günther R. Findenegg 《Trees - Structure and Function》1996,10(5):301-307
In a pot trial growth and transpiration of 3-year-old Douglas-fir seedlings on an acid, sandy soil was examined at a deficient
(30 kg N ha –
1 year –
1) and an excessive level (120 kg N ha –
1 year –
1) of NH4 application. Dissolved ammonium sulphate was applied to the pots weekly for two growing seasons. In half of the pots a complete
set of other nutrients was applied in optimal proportions to the applied nitrogen. Water supply was optimal and transpiration
was recorded. At the end of the second treatment season irrigation was stopped for 2 weeks during dry and sunny weather. Both
high application of NH4 and additional nutrients increased shoot growth and transpiration demand in the first treatment year. The root system was
smaller at higher N level and this reduced water uptake accordingly. In the second year the combination of high NH4
+ and additional nutrients affected root functioning predominantly due to salinity effects and this seriously decreased water
uptake capacity and shoot water potentials, finally resulting in tree death. Without addition of other nutrients the high
NH4
+ application resulted in a high degree of soil acidification, which damaged the roots, that showed a decrease in water uptake
capacity. At the low NH4 supply level soil acidification was lower, and root functioning was not affected, and the trees recovered quickly from the
imposed drought. Higher needle K and P status depressed transpiration rates at the low NH4 application rate.
Received: 9 January 1995 / Accepted: 18 September 1995 相似文献