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排序方式: 共有266条查询结果,搜索用时 31 毫秒
11.
AbstractThe ingestion of 226Ra, inhalation, and ingestion of 222Rn in water is considered the primary health risk for lungs and stomach. This study presents the concentrations of 226Ra and 222Rn in well and tap water collected from Sik, Malaysia, using HPGe and RAD7 detectors. Maximum average concentrations of 226Ra and 222Rn were found 47.6?±?3.6 mBq/l and 9.3?±?1.4?Bq/l in well water, respectively, and minimum were found 17.1?±?3.6 mBq/l and 1.6?±?1.0?Bq/l in tap water, respectively. A positive correlation (R=.88) was found between 226Ra and 222Rn determined by HPGe and RAD7 detectors, respectively. Infants in the age group of 0–1 y appeared to be at risk with respect to the annual effective doses from 226Ra and 222Rn as compared to the other age groups. However, annual effective doses for all three age groups from intake of 226Ra and 222Rn in well and tap drinking water were found below the World Health Organization (WHO) recommended level of .1 mSv/y. 相似文献
12.
Biology Bulletin - This study investigated the protective effects of quercetin (QUE) in doxorubicin (DOX)-induced testicular toxicity in rats. In the present study, testicular histomorphometry, the... 相似文献
13.
Erlendsson LS Acheson RM Hederstedt L Le Brun NE 《The Journal of biological chemistry》2003,278(20):17852-17858
Covalent attachment of heme to apocytochromes c in bacteria occurs on the outside of the cytoplasmic membrane and requires two reduced cysteinyls at the heme binding site. A constructed ResA-deficient Bacillus subtilis strain was found to lack c-type cytochromes. Cytochrome c synthesis was restored in the mutant by: (i) in trans expression of resA; (ii) deficiency in BdbD, a thiol-disulfide oxidoreductase that catalyzes formation of an intramolecular disulfide bond in apocytochrome c after transfer of the polypeptide across the cytoplasmic membrane; or (iii) by addition of the reductant dithiothreitol to the growth medium. In vivo studies of ResA showed that it is membrane-associated with its thioredoxin-like domain on the outside of the cytoplasmic membrane. Analysis of a soluble form of the protein revealed two redox reactive cysteine residues with a midpoint potential of about -340 mV at pH 7. We conclude that ResA, probably together with another thiol-disulfide oxidoreductase, CcdA, is required for the reduction of the cysteinyls in the heme binding site of apocytochrome c. 相似文献
14.
The intriguing diversity of highly abundant satellite repeats found even among closely related species can result from processes
leading to dramatic changes in copy number of a particular sequence in the genome and not from rapid accumulation of mutations.
To test this hypothesis, we investigated the distribution of the PRAT satellite DNA family, a highly abundant major satellite
in the coleopteran species Palorus ratzeburgii, in eight species belonging to the related genera (Tribolium, Tenebrio, Latheticus), the subfamily (Pimeliinae), and the family (Chrysomelidae). Dot blot analysis and PCR assay followed by Southern hybridization
revealed that the PRAT satellite, in the form of low-copy number repeats, was present in all tested species. The PRAT satellite
detected in the species Pimelia elevata has been sequenced, and compared with previously cloned PRAT monomers from Palorus ratzeburgii and Palorus subdepressus. Although the two Palorus species diverged at least 7 Myr ago, and the subfamily Pimeliinae separated from the genus Palorus 50–60 Myr ago, all PRAT clones exhibit high mutual homology, with average variability relative to the common consensus sequence
of 1.3%. The presence of ancestral mutations found in PRAT clones from all three species as well as the absence of species
diagnostic mutations illustrate extremely slow sequence evolution. This unexpectedly high conservation of PRAT satellite DNA
sequence might be induced by a small bias of turnover mechanisms favoring the ancestral sequence in the process of molecular
drive. 相似文献
15.
In this study, two different semen cryopreservation protocols were compared to freeze goat semen. The ejaculates (n = 12) were collected by using electro-ejaculator from six mature bucks (two ejaculates per each buck). Each ejaculate was divided into two groups as Protocol 1 (P1) and Protocol 2 (P2). In P1, semen was diluted directly in an extender containing 15% egg yolk, 300 mM Tris, 28 mM glucose, 95 mM citric acid 5% glycerol to a concentration of 200 × 106 sperm/mL. In P2, after the removal of seminal plasma by centrifugation, the semen sample was diluted with the first portion of milk extender consist of 100 mg/mL skimmed milk powder and 27.75 mM glucose (without glycerol) to a concentration of 400 × 106 sperm/mL. The second portion of the milk extender containing 14% glycerol was added to semen gradually in order to achieve sperm concentration 200 × 106 sperm/mL and 7% glycerol level in the final volume. Extended semen was loaded in 0.25 mL straws, held for 2 h at 4 °C, frozen in nitrogen vapor and stored in liquid nitrogen. Post-thaw motility and live sperm rate (mean ± SEM) were significantly lower (P < 0.05) in P1 as compared to P2 (47.50 ± 1.23% vs. 55.63 ± 1.72%; 80.04 ± 1.29% vs. 84.04 ± 1.08%, respectively). However, live intact, total intact, abnormal, reacted acrosome and DNA damaged sperm rates were similar (P > 0.05) in both protocols. It was concluded that both protocols used in this study provided reasonable post-thaw parameters; however, P2 yielded better motility and live sperm rate compared to P1. 相似文献
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17.
Katarína Ďurčeková Jana Huttová Igor Mistrík Marta Ollé Ladislav Tamás 《Plant and Soil》2007,290(1-2):61-68
The effect of Cd on H2O2 production, peroxidase (POD) activity and root hair formation were analyzed in barley root. Cd causes a strong H2O2 burst in the root region 0–6 mm behind the root tip. POD activity was activated in root tip and raised toward the root base
in Cd treated roots. In situ analyses showed that both elevated H2O2 production and POD activity are localized in the early metaxylem vascular bundles. Cd induces root hair formation in the
region 2 to 4 mm behind the root tip that was not detected in control roots. These results suggest that Cd-induced root growth
inhibition is at least partially the consequence of Cd-stimulated premature root development involving xylogenesis and root
hair formation, which is correlated with shortening of root elongation zone and therefore with root growth reduction. 相似文献
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19.
Bo?ena?Szewczyk-TaranekEmail author Bo?ena?Paw?owska 《Plant Cell, Tissue and Organ Culture》2015,120(3):1203-1207
A method for secondary somatic embryogenesis was developed on embryos derived from embryogenic callus formed on Hepatica nobilis seedlings. Somatic embryogenesis (SE) was induced on seedlings (on the hypocotyl and epicotyl parts) grown on the Murashige and Skoog (1962) medium (MS) supplemented with 1 µM naphthaleneacetic acid (NAA), and/or 0.1 µM 6-benzyladenine (BA) and on medium without plant growth regulators (PGR). The best response of embryogenic callus formation was observed on the medium containing 1 µM NAA alone or with 0.1 µM BA. Individual somatic embryos, formed on embryogenic callus on the medium without PGR (MS0), at heart, torpedo and cotyledonary stage, were transferred to the media where secondary somatic embryo formation and development into plantlets occurred. Although the most efficient repetitive cycles of secondary SE were recorded for all stages of somatic embryos (heart, torpedo, cotyledonary) on the MS0 medium (77.8–87.4 %), secondary somatic embryos were also obtained on all media supplemented with cytokinins. The best rate of somatic embryos germination was achieved on MS media with 0.2 µM NAA and 2 µM BA, and 0.1 µM NAA and 1 µM BA (48.8–52.0 %) when more mature embryos (cotyledonary stage) were used. Plantlets grown from somatic embryos were successfully acclimatized to greenhouse conditions. 相似文献
20.