We report the genome sequence of Theileria parva, an apicomplexan pathogen causing economic losses to smallholder farmers in Africa. The parasite chromosomes exhibit limited conservation of gene synteny with Plasmodium falciparum, and its plastid-like genome represents the first example where all apicoplast genes are encoded on one DNA strand. We tentatively identify proteins that facilitate parasite segregation during host cell cytokinesis and contribute to persistent infection of transformed host cells. Several biosynthetic pathways are incomplete or absent, suggesting substantial metabolic dependence on the host cell. One protein family that may generate parasite antigenic diversity is not telomere-associated. 相似文献
The ice-rich south polar layered deposits of Mars were probed with the Mars Advanced Radar for Subsurface and Ionospheric Sounding on the Mars Express orbiter. The radar signals penetrate deep into the deposits (more than 3.7 kilometers). For most of the area, a reflection is detected at a time delay that is consistent with an interface between the deposits and the substrate. The reflected power from this interface indicates minimal attenuation of the signal, suggesting a composition of nearly pure water ice. Maps were generated of the topography of the basal interface and the thickness of the layered deposits. A set of buried depressions is seen within 300 kilometers of the pole. The thickness map shows an asymmetric distribution of the deposits and regions of anomalous thickness. The total volume is estimated to be 1.6 x 10(6) cubic kilometers, which is equivalent to a global water layer approximately 11 meters thick. 相似文献
Responses of wheat grown on a heavy clay soil in the Goulburn-Murray Irrigation Region of south-eastern Australia to a factorial combination of three irrigation treatments and nitrogen and gypsum application were investigated.Irrigation treatments included a rainfed control (treatment RF) and irrigation on either a weekly (treatment Iw) or fortnightly (treatmnt IF) basis beginning in spring and maintained until physiological maturity. Nitrogen was applied at 0 and 150 kg N ha−1 (treatments N0 and N150, respectively) and gypsum at 0 and 5 t ha−1. Nitrogen and gypsum treatments were applied at sowing.
Yield increased from a mean of 4 t ha−1 treatment RF to 6.6 t ha−1 in treatments IF and IW, largely because of promotive effects of irrigation on kernel weight (increase from 31 mg to 42 mg kernel−1 and kernel spikelet−1 (1.4 as compared with 1.7). Seasonal conditions and the relative fertility of the site were sufficient to maximise spike number and spikelet spike−1. Nitrogen increased kernel spikelet−1 but effects on yield were not significant because of a decrease in kernel weight. Effects of gypsum on yield were not significant.
Water-use efficiency of both rainfed and irrigated treatments was ca. 1.25 g grain kg−1 H2O. However, transpirational water-use efficiency, calculated after allowing 110 mm water for soil evaporation, fell from 2 g kg−1 in treatment RF to 1.7 and 1.5 g kg−1 in treatments IF and IW, respectively. The decrease was ascribed, in part, to lodging and soil evaporative losses may have been in excess of 110 mm with more frequent irrigation. Effects of N on water use could not be distinguished, again because of the initial fertility of the site, which supported rapid growth and resulted in complete canopy closure.
Nitrogen and irrigation treatments had independent effects on the concentration of N in the grain (%NG) which increased by a mean of 0.6% with N treatment despite a decrease in N harvest index (HIN) from 0.77 to .70. Irrigation decreased %NG by approximately 0.5%. Approximately 90 kg pN ha−1 was found in the grain of treatments RFN0, IWN0, IwN0 and RFN150 and differences in %NG in these treatments attributed to a ‘dilution’ effect mediated by the increase in yield effected by irrigation. The grain accounted for approximately 115 kg N ha−1 in treatments IFN150 and IWN150, countering the inverse relationship between %Ng and yield despite the increase in HIN index caused by N application. 相似文献
Plasmid DNA of 68 strains of Salmonella that belonged to 18 serovars and exhibited 48 different plasmid profiles was examined for hybridization with a 32P-labelled DNA probe which consisted of a 3750 base pairs (bp) HindIII-HindIII fragment derived from the virulence region of the 60 megadalton (Mdal) plasmid of Salmonella typhimurium. The 32 Mdal plasmid of S. cholerae-suis, the 50 Mdal plasmid of S. dublin, the 36 Mdal plasmid of S. enteritidis, the 60 Mdal plasmid of S. gallinarum, the 60 Mdal plasmid of S. pullorum, and the 60 Mdal plasmid of S. typhimurium, plasmids that have been associated with virulence, all hybridized with the probe. Digestion of plasmid DNA of these strains with PvuII and hybridization with the probe revealed that the plasmids of strains of all six serovars contained fragments of approximately 2520 and 1520 bp that hybridized with the probe. Similarly, hybridization with BglI digests of DNA of the virulence-associated plasmids of strains of these six serovars showed that all six plasmids contained a fragment of approximately 3690 bp that hybridized with the probe. No other plasmids of these strains nor any plasmids of 12 other Salmonella serovars hybridized with the probe. Chromosomal DNA did not hybridize with the probe. The 60 Mdal plasmids of S. gallinarum and S. pullorum showed similar digestion patterns with restriction endonucleases BglI, BglII and PvuII. 相似文献
The plasmid content of 104 strains of Salmonella muenster collected from bovine and human sources in Ontario from 1982 to 1984 was determined. The strains were classified into 17 different groups on the basis of the sizes of the plasmids they contained. Further division was made on the basis of the fragments obtained following digestion of the plasmids with restriction endonucleases BglI and BglII. Representative strains from each plasmid profile group were compared for resistance to serum and for virulence in mice. No differences in serum resistance or in LD50 by the oral or intraperitoneal route in mice could be associated with the presence of plasmids. Although the strains of S. muenster were recovered from clinical cases in cattle and humans, they were of low virulence for mice: the LD50 values were approximately 10,000-fold greater than that of Salmonella typhimurium. 相似文献
Among 300 isolates of bovine Escherichia coli, 56 which had been found enterotoxigenic in calf gut loops were characterized on the basis of O and K antigens, colonial morphology and resistance to seven antimicrobial drugs. The 56 isolates enterotoxigenic in the calf were compared with the nonenterotoxigenic ones. Of the 56 enterotoxigenic E. coli the majority possessed the A type of K antigen and had OK groups, O9:K(PS274) or O101:K(RVC118). Fourteen of these isolates had the K99 antigen. None of 27 isolates found enterotoxigenic in the piglet but not in the calf possessed the K99 antigen or belonged to OK groups O9:K(PS274) or O101:K(RVC118). Comparison of the patterns of resistance to seven antimicrobial drugs showed that all enterotoxigenic and nonenterotoxigenic isolates were susceptible to nitrofurantoin and sulphachlorphyridiazine and that there was no significant difference in the patterns between the two groups. The majority of enterotoxigenic isolates were mucoid, whereas most of the nonenterotoxigenic isolates were nonmucoid. 相似文献
The lesions caused by excess oral pyridoxine hydrochloride (150 mg/kg body weight/day) and clioquinol (200 mg/kg body weight/day), given individually and in combination to adult Beagle dogs, were evaluated. The experimental period was 100 to 112 days, except that four dogs in each of the clioquinol and combined-treatment groups were killed early because of severe debilitation or neurologic disease, and one dog given both compounds died on the third day of compound administration. Degenerative neurologic lesions had distribution specific for the compound given. Pyridoxine-treated dogs had lesions limited to tracts and nerves with neuronal bodies of their nerve fibers in the spinal and trigeminal ganglia. Clioquinol-treated dogs had neurologic lesions limited to the central nervous system. The most lesions were in the rostral dorsal funiculus and distal aspects of the optic nerve fibers, but minimal to mild degenerative changes also occurred in distal aspects of the corticospinal and spinocerebellar tracts. Dogs given both pyridoxine hydrochloride and clioquinol had a combination of the lesions in dogs given pyridoxine or clioquinol individually. Several dogs given clioquinol or pyridoxine plus clioquinol had extraneural lesions, including myocardial degeneration and thyroidal alterations. 相似文献
Six experimental stocks were evaluated in two trials at seven locations to determine if genetically diverse meat‐type stocks would be useful in identifying specific causes of genotype‐environment interactions.
Stock differences in body weights (at 1, 5 and 8 weeks) were significant and responsible for 55 to 80% of the total phenotypic variation. Location effects were also significant, while trial effects were significant only at 1 and 5 weeks of age. Stock‐location interactions were significant (P < 0.01) for body weight at 1 and 5 weeks of age in both sexes while male 8‐week body weight and shank length differences were also significant (P< 0.05). The importance of stock‐location interactions for juvenile body weight decreased with age, being reponsible for 3% of the total phenotypic variation at 1 week and less than 1 % at 8 weeks of age.
These data support previous reports indicating stock‐location interactions are of minor importance for juvenile body weights in broiler stocks and responsible for less than 2% of the total phenotypic variation in 8‐week body weight. Utilisation of genetically diverse stocks did not materially increase the importance of or aid in identifying these interactions. 相似文献
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