The infectivity of two Blastocystis hominis strains, RN94-9 and NIH:1295:1, was examined in 3-week-old SPF Wistar rats. The NIH:1295:1 strain, originally isolated from a guinea pig, was only able to infect rats via intracecal inoculation of the cultured organisms, while the RN94-9 strain, originally isolated from a laboratory rat, was able to infect rats by oral inoculation of the cultures due to the presence of a cystic form in the in vitro culture. Since many cysts were discharged in the feces of the infected rats, the infectivity of the concentrated cysts was compared between the two strains. Successful oral infection was observed in rats inoculated with 1 x 10(2)-1 x 10(6) cysts of the RN94-9 and NIH:1295:1 strains. The infectivity of the ten cysts varied in the three experiments of ten rats, being 20-100% and 30-100% in the RN94-9 and NIH:1295:1 strains, respectively. When an uninfected normal rat was housed with five experimentally inoculated rats, the normal rat became infected, demonstrating the fecal-oral transmission of the cyst form of this parasite. These results show that the Wistar rat is an ideal host for the propagation of strains RN94-9 and NIH:1295:1 of B. hominis, and demonstrate that the cyst form is the only transmissible form of this parasite.
We revealed the chloride ion pumping mechanism in halorhodopsin from Natronobacterium pharaonis ( pHR) by exploring sequential structural changes in the retinal chromophore during its photocycle using time-resolved resonance Raman (RR) spectroscopy on the nanosecond to millisecond time scales. A series of RR spectra of the retinal chromophore in the unphotolyzed state and of the three intermediates of pHR were obtained. Using singular value decomposition analysis of the C═C and C-C stretch bands in the time-resolved RR spectra, we identified the spectra of the K, L, and N intermediates. We focused on structural markers of the RR bands to explore the structure of the retinal chromophore. In the unphotolyzed state, the retinal chromophore is in the planar all- trans, 15- anti geometry. The bound ion affects the polyene chain but does not interact with the protonated Schiff base. In the observed intermediates, the chromophore is in the 13- cis configuration. The chromophore in the K intermediate is distorted due to the photoisomerization of retinal. The hydrogen bond is weak in the unphotolyzed state and in the K intermediate, resulting in exchange of the hydrogen-bond acceptor to a water molecule in the K-to-L transition, relaxation of the polyene chain distortion, and generation of an alternative distortion near the Schiff base. The bound halide ion interacts with the protonated Schiff base through the water molecule bound to the protonated Schiff base. In the L-to-N transition, the hydrogen acceptor of the protonated Schiff base switches from the water molecule to another species, although the strong hydrogen bond of the protonated Schiff base remains. This paper reports the first observation of sequential changes in the RR spectra in the pHR photocycle, provides information on the structural evolution of the retinal chromophore, and proposes a model for chloride ion translocation in pHR.
Two scombropid fishes, Scombrops boops and Scombrops gilberti, are closely related and commercially important species in Japan. These species are often confused in commercial markets because of their morphological similarity. In this study, scombropid specimens collected from various Japanese coastal waters were subjected to polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis and phylogenetic analysis of the 16S rRNA gene in mitochondrial DNA. These analyses showed that all the scombropid specimens collected from localities in the Sea of Japan were identified as S. boops, whereas those from the Pacific Ocean included two species, S. boops and S. gilberti. Almost all juvenile (<200 mm standard body length, S(L)) S. gilberti originated from the Pacific coastal waters of the northern Japan, whereas adults (>400 mm S(L)) were found only in deep water off the Izu Peninsula to the Izu Islands. This suggests that S. gilberti might migrate extensively during its life cycle. In addition, differences in the number of specimens and the distribution between the two species suggest that S. gilberti is less abundant than S. boops in Japanese waters.
The expression of asparagine synthetase (AS; EC 6.3.5.4) in response to externally supplied nitrogen was investigated with respect to enzyme activity and protein levels as detected immunologically in rice (Oryza sativa) seedlings. The asparagine content was very low in leaves and roots of nitrogen-starved rice plants but increased significantly after the supply of 1 mM NH4+ to the nutrient solution. While neither AS activity nor AS protein could be detected in leaves and roots prior to the supply of nitrogen, levels became detectable in roots but not in leaves within 12 h of the supply of 1 mM NH4+ or 10 mM glutamine. Other nitrogen compounds, such as nitrate, glutamate, aspartate and asparagine had no effect. Methionine sulfoximine completely inhibited the NH4+-induced accumulation of AS protein but did not affect the glutamine-induced accumulation of the enzyme. The results suggested that glutamine or glutamine-derived metabolites regulate AS expression in rice roots.
A cDNA enceding gl-tamine-dependent asparagine synthetase was isolated from dark-adapted Glycine max cell culture. The deduced amino acid seq"ence showed 76-89% fidentity with other plant sequences. The gene for asparagine synthetase is expressed predominantly in shoets as compared to roots of etiolated plants and the leyel of expression decreases following light treatment, suggesting that the gelle expression is dewn-regulated by light.
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