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Zenon J. Sienkiewicz Richard G.E. Haylock Richard D. Saunders 《Bioelectromagnetics》1996,17(3):180-186
A series of four experiments was performed to determine whether acute exposure to a range of 50 Hz magnetic fields had any effect on a learning task in adult male CD1 mice. A radial-arm maze placed within the bore of an electromagnet was used to assess spatial discrimination learning for food reward. Subjects were reduced to 85% of their free-feeding weight and were placed in the maze for up to 15 minutes each day for 10 days. Performance of the task was measured by using maximum likelihood techniques to calculate the probability that an animal would not reenter any given arm of the maze. Experimental subjects were exposed to a vertical, 50 Hz sinusoidal magnetic field at 5 μT, 50 μT, 0.5 mT, or 5.0 mT (rms). Control subjects were exposed only to a background time-varying field of less than 50 nT and the ambient static field of about 40 μT. The variation in the applied magnetic field was less than 5% except at the ends of the arms, where it approached 10%. It was found that all eight groups of subjects (n = 10 in all cases) showed similar increases in performance with testing, and the acquisition curve for each group of experimental subjects was not significantly different from that of their control group (P > 0.05 in all cases). It was concluded that exposure had no effect on learning at any flux density. This result is contrary to the findings of a number of preliminary studies, although other studies have reported that magnetic fields do not affect spatial learning in adult male rodents. It is possible that differences between experimental conditions might explain some of this apparent discrepancy. © 1996 Wiley-Liss, Inc. 相似文献
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Moseeva MB Azizova TV Muirhed CR Grigor'eva ES Vlasenko EV Sumina MV O'Hagan JA Zang W Haylock RG Hunter N 《Radiatsionnaia biologiia, radioecologiia / Rossi?skaia akademiia nauk》2012,52(2):149-157
Incidence of cerebrovascular diseases (CVD) has been studied in a cohort of 12210 workers first employed at one of the main plants (reactors, radiochemical or plutonium) of the Mayak nuclear facility during 1948-1958 and followed up to the end of 2000. Information on external gamma doses is available for virtually all (99.9%) of these workers; the mean (+/- one standard deviation) total gamma dose was 0.91 +/- 0.95 Gy (99% percentile 3.9 Gy) for men and 0.65 +/- 0.75 Gy (99% percentile 2.99 Gy) for women. Plutonium body burden was measured only for 30.0% of workers. Amongst those monitored, the mean (+/- standard deviation) cumulative liver dose from plutonium alpha exposure was 0.40 +/- 1.15 Gy (99% percentile 5.88 Gy) for men and 0.81 +/- 4.60 Gy (99% percentile 15.95 Gy) for women 4418 cases (first diagnosis) of CVD were identified in the studied cohort. A statistically significant increasing trend in CVD incidence with total external gamma dose was revealed after adjustment for non-radiation factors and internal exposure from incorporated plutonium-239. Excess relative risk per Gy was 0.464 (95% confidence interval 0.360-0.567). Incidence of CVD was statistically significantly higher for the workers chronically exposed to external gamma rays at a dose above 1.0 Gy A statistically significant increasing trend in CVD incidence with internal liver dose from plutonium alpha exposure was observed after adjustment for non-radiation factors and external exposure. ERR per Gy was 0.155 (95% confidence interval 0.075-0.235). CVD incidence was statistically significantly higher among workers with a plutonium liver dose above 0.1 Gy, although the trend estimates differed between workers at different plants. The incidence risk estimates for external radiation are generally compatible with estimates from the study of Chernobyl clean-up workers, although the incidence data point to higher risk estimates compared to those from the Japanese A-bomb survivors. 相似文献
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Zenon J. Sienkiewicz Richard G. E. Haylock Richard D. Saunders 《Bioelectromagnetics》1998,19(2):79-84
A series of four experiments was performed to determine the effect of exposure to a 50 Hz magnetic field on memory-related behaviour of adult, male C57BL/6J mice. Experimental subjects were exposed to a vertical, sinusoidal magnetic field at 0.75 mT (rms), for 45 min immediately before daily testing sessions on a spatial learning task in an eight-arm radial maze. Control subjects were only exposed to a background time-varying field of less than 50 nT and the ambient static field of about 40 μT. In each experiment, exposure significantly reduced the rate of acquisition of the task but did not affect overall accuracy. This finding is consistent with the results of another study that found that prior exposure to 60 Hz magnetic fields affected spatial learning in rats. Bioelectromagnetics 19:79–84, 1998. © 1998 Wiley-Liss, Inc. 相似文献
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Maria B. Moseeva Tamara V. Azizova Evgenia S. Grigoryeva Richard Haylock 《Radiation and environmental biophysics》2014,53(2):469-477
The new Mayak Worker Dosimetry System 2008 (MWDS-2008) was published in 2013 and supersedes the Doses-2005 dosimetry system for Mayak Production Association (PA) workers. It provides revised external and internal dose estimates based on the updated occupational history data. Using MWDS-2008, a cohort of 18,856 workers first employed at one of the main Mayak PA plants during 1948–1972 and followed up to 2005 was identified. Incidence and mortality risks from ischemic heart disease (IHD) (International Classification of Diseases (ICD)-9 codes 410–414) and from cerebrovascular diseases (CVD) (ICD-9 codes 430–438) were examined in this cohort and compared with previously published risk estimates in the same cohort based on the Doses-2005 dosimetry system. Significant associations were observed between doses from external gamma-rays and IHD and CVD incidence and also between internal doses from alpha-radiation and IHD mortality and CVD incidence. The estimates of excess relative risk (ERR)/Gy were consistent with those estimates from the previous studies based on Doses-2005 system apart from the relationship between CVD incidence and internal liver dose where the ERR/Gy based on MWDS-2008 was just over three times higher than the corresponding estimate based on Doses-2005 system. Adjustment for smoking status did not show any effect on the estimates of risk from internal alpha-particle exposure. 相似文献
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Background
Molluscs are the most diverse marine phylum and this high diversity has resulted in considerable taxonomic problems. Because the number of species in Canadian oceans remains uncertain, there is a need to incorporate molecular methods into species identifications. A 648 base pair segment of the cytochrome c oxidase subunit I gene has proven useful for the identification and discovery of species in many animal lineages. While the utility of DNA barcoding in molluscs has been demonstrated in other studies, this is the first effort to construct a DNA barcode registry for marine molluscs across such a large geographic area.Methodology/Principal Findings
This study examines patterns of DNA barcode variation in 227 species of Canadian marine molluscs. Intraspecific sequence divergences ranged from 0–26.4% and a barcode gap existed for most taxa. Eleven cases of relatively deep (>2%) intraspecific divergence were detected, suggesting the possible presence of overlooked species. Structural variation was detected in COI with indels found in 37 species, mostly bivalves. Some indels were present in divergent lineages, primarily in the region of the first external loop, suggesting certain areas are hotspots for change. Lastly, mean GC content varied substantially among orders (24.5%–46.5%), and showed a significant positive correlation with nearest neighbour distances.Conclusions/Significance
DNA barcoding is an effective tool for the identification of Canadian marine molluscs and for revealing possible cases of overlooked species. Some species with deep intraspecific divergence showed a biogeographic partition between lineages on the Atlantic, Arctic and Pacific coasts, suggesting the role of Pleistocene glaciations in the subdivision of their populations. Indels were prevalent in the barcode region of the COI gene in bivalves and gastropods. This study highlights the efficacy of DNA barcoding for providing insights into sequence variation across a broad taxonomic group on a large geographic scale. 相似文献8.
Katie J Torley Juliano C da Silveira Peter Smith Russell V Anthony DN Rao Veeramachaneni Quinton A Winger Gerrit J Bouma 《Reproductive biology and endocrinology : RB&E》2011,9(1):2
Background
Gonadal differentiation in the mammalian fetus involves a complex dose-dependent genetic network. Initiation and progression of fetal ovarian and testicular pathways are accompanied by dynamic expression patterns of thousands of genes. We postulate these expression patterns are regulated by small non-coding RNAs called microRNAs (miRNAs). The aim of this study was to identify the expression of miRNAs in mammalian fetal gonads using sheep as a model. 相似文献9.
Molecular evolution of mitochondrial 12S RNA and cytochrome b sequences in the pantherine lineage of Felidae 总被引:4,自引:2,他引:2
DNA sequence comparisons of two mitochondrial DNA genes were used to infer
phylogenetic relationships among 17 Felidae species, notably 15 in the
previously described pantherine lineage. The polymerase chain reaction
(PCR) was used to generate sequences of 358 base pairs of the mitochondrial
12S RNA gene and 289 base pairs of the cytochrome b protein coding gene.
DNA sequences were compared within and between 17 felid and five nonfelid
carnivore species. Evolutionary trees were constructed using phenetic,
cladistic, and maximum likelihood algorithms. The combined results
suggested several phylogenetic relationships including (1) the recognition
of a recently evolved monophyletic genus Panthera consisting of Panthera
leo, P. pardus, P. onca, P. uncia, P. tigris, and Neofelis nebulosa; (2)
the recent common ancestry of Acinonyx jubatus, the African cheetah, and
Puma concolor, the American puma; and (3) two golden cat species, Profelis
temmincki and Profelis aurata, are not sister species, and the latter is
strongly associated with Caracal caracal. These data add to the growing
database of vertebrate mtDNA sequences and, given the relatively recent
divergence among the felids represented here (1-10 Myr), allow 12S and
cytochrome b sequence evolution to be addressed over a time scale different
from those addressed in most work on vertebrate mtDNA.
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The virulence and viability of various serovars of Leptospira interrogans were successfully preserved by storage in liquid nitrogen. Dimethyl sulphoxide at a final concentration of 2.5% (v/v) was added as cryoprotectant to a culture of leptospires grown in Ellinghausen-McCullough-Johnson-Harris medium. Ampoules were cooled at a controlled rate of 1 degree-3 degrees C/min to -70 degrees C, then transferred to the liquid phase of a liquid nitrogen storage unit. Glycerol was discounted as a cryoprotectant as it was found to be approximately 10 times more toxic than dimethyl sulphoxide to four of five serovars used in this study. The viability of nine strains has so far been observed over a period of 8-22 months storage in liquid nitrogen and full viability of all strains has been preserved over this period. Virulence of strains of serovars pomona and hardjo was well preserved, as demonstrated by challenge tests in guinea pigs and domestic pigs. 相似文献