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1.
Studies on the ecology of microbial parasites and their hosts are predicated on understanding the assemblage of and relationship among the species present. Changes in organismal morphology and physiology can have profound effects on host–parasite interactions and associated microbial community structure. The marine rickettsial organism, “Candidatus Xenohaliotis californiensis” (WS-RLO), that causes withering syndrome of abalones has had a consistent morphology based on light and electron microscopy. However, a morphological variant of the WS-RLO has recently been observed infecting red abalone from California. We used light and electron microscopy, in situ hybridization and16S rDNA sequence analysis to compare the WS-RLO and the morphologically distinct RLO variant (RLOv). The WS-RLO forms oblong inclusions within the abalone posterior esophagus (PE) and digestive gland (DG) tissues that contain small rod-shaped bacteria; individual bacteria within the light purple inclusions upon hematoxylin and eosin staining cannot be discerned by light microscopy. Like the WS-RLO, the RLOv forms oblong inclusions in the PE and DG but contain large, pleomorphic bacteria that stain dark navy blue with hematoxylin and eosin. Transmission electron microscopy (TEM) examination revealed that the large pleomorphic bacteria within RLOv inclusions were infected with a spherical to icosahedral-shaped putative phage hyperparasite. TEM also revealed the presence of rod-shaped bacteria along the periphery of the RLOv inclusions that were morphologically indistinguishable from the WS-RLO. Binding of the WS-RLO-specific in situ hybridization probe to the RLOv inclusions demonstrated sequence similarity between these RLOs. In addition, sequence analysis revealed 98.9–99.4 % similarity between 16S rDNA sequences of the WS-RLO and RLOv. Collectively, these data suggest that both of these RLOs infecting California abalone are “Candidatus Xenohaliotis californiensis,” and that the novel variant is infected by a putative phage hyperparasite that induced morphological variation of its RLO host. 相似文献
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Carolyn Beebe Smith 《Neurochemical research》1991,16(9):1037-1046
Special issue dedicated to Dr. Louis Sokoloff. 相似文献
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F. F. Snyder A. E. Chudley P. M. MacLeod R. J. Carter E. Fung J. K. Lowe 《Human genetics》1984,67(1):18-22
Summary A family is described in which four affected males, spanning two generations, have hyperuricemia and gout accompanied by hematuria but are without severe neurologic involvement. The affected males were found to have markedly reduced levels of erythrocytic hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity; these were 5–12% with hypoxanthine and 0.5–3% with guanine as compared to controls. Erythrocytic adenine phosphoribosyltransferase (APRT) was approximately three-fold elevated in the affected individuals.The residual HGPRT activity in affected males enabled characterization of some of the properties of this mutation. The apparent Michaelis constants (km) for both hypoxanthine and guanine were essentially unchanged, whereas the km for PP-ribose-P was approximately 10–20-fold elevated for all four affected males. The enzyme was more sensitive to product inhibition by IMP and GMP than controls, and exhibited greater thermal lability at 65°C than found with control lysates. 相似文献
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Ken Walder Carolyn R. Dascaliuc Paul A. Lewandowski Andrew J. Sanigorski Paul Zimmet Greg R. Collier 《Obesity (Silver Spring, Md.)》1997,5(3):193-200
Food intake was restricted to 75% of ad libitum levels in 37 male Psammomys obesus (Israeli Sand Rats) from the ages of 4 (weaning) to 10 weeks. Energy restriction reduced the mean body weight at 10 weeks by 29% compared with 44 ad libitum fed controls. Hyperglycemia was prevented completely in the food-restricted group, and mean blood glucose concentrations were significantly reduced (3.8 ± 0.2 vs. 5.5 ± 0.4 μmol/L; p<0.05) compared with control animals. Plasma insulin concentrations were also decreased significantly compared with ad libitum fed controls (105 ± 13 vs. 241 ± 29 mU/L;p<0.05). Although energy restriction prevented hyperglycemia from developing in 10-week-old P. obesus, 19% of the food restricted animals still developed hyperinsu-linemia. We concluded that hyperphagia between the ages of 4 to 10 weeks may be essential for the development of noninsulin-dependent diabetes mellitus in P. obesus, but that hyperinsulinemia may still occur in the absence of hyperphagia and hyperglycemia, suggesting a significant genetic influence on the development of hyperinsulinemia in this animal model. 相似文献
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Thermal sensitivity of scope for activity in Pagothenia borchgrevinki, a cryopelagic Antarctic nototheniid fish 总被引:1,自引:1,他引:0
The thermal sensitivity of scope for activity was studied in the Antarctic nototheniid fish Pagothenia borchgrevinki. The scope for activity of P. borchgrevinki at 0°C was 189 mg O2 kg−1 h−1 (factorial scope 6.8) which is similar to that of temperate and tropical species at their environmental temperatures, providing no evidence for metabolic cold adaptation of maximum activity. The scope for activity increased to a maximum value of 266 mg O2 kg−1 h−1 (factorial scope 8.3) at 3°C and then decreased from 3 to 6°C. The thermal sensitivity of critical swimming speed was also investigated and followed a similar pattern to aerobic scope for activity, suggesting oxygen limitation of aerobic performance. Oxygen consumption rates and ventilation frequencies were monitored for 24 h after the swimming challenge and the recovery of both parameters to resting levels was rapid and independent of temperature. 相似文献
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Lyn D. Olson Carolyn A. Renshaw Shlomo Rottem Jila H. Boal 《FEMS microbiology letters》1993,108(1):47-51
Abstract Electrofusion of protoplasts of two mutant strains of Hansenula polymorpha resulted in high fusion and hybrid yields when the calcium ions present in the conventional fusion medium replaced by zinc ions. The optimal fusion conditions were an alignment field of 0.4 kV cm−1 strength and 2 MHz frequency for 30 s, followed by two consecutive pulses of 12 kV cm−1 strength and 15 μs duration. With 0.05–0.1 mM zinc ions in the fusion medium an average clone number of 104 –105 clones per 108 input cells was reached. The presence of about 0.6 mM magnesium ions in the zinc fusion medium was essential. 相似文献
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