Strongyloides ratti infection in the large intestine of wild rats, Rattus norvegicus

The large intestine of a rat has been neglected almost completely as a site of Strongyloides sp. infection. We reported that adult Strongyloides ratti remained in the large intestine for more than 80 days, producing more number of infective larvae than small intestine adults, and therefore hypothesized that parasitism in this site could be a survival strategy. In wild rats, however, no study has focused on large intestine infections of Strongyloides. The present study revealed that 32.4% of 68 wild rats, Rattus norvegicus, had the infection of S. ratti in the large intestine, with an average of 4.7 worms. These worms harbored normal eggs in the uterus. In a laboratory experiment with S. ratti and Wister rats, daily output of infective larvae by 4.7 females in the large intestine was estimated to be 4,638.4, suggesting that a few parasites could play a role in the parasite transmission. Five species of nematode found in the wild rats showed seasonality in infection intensity, with highest intensities in March-May. The number of S. ratti in the large intestine was also highest in these months.     

A hepatitis C virus (HCV) internal ribosome entry site (IRES) domain III-IV-targeted aptamer inhibits translation by binding to an apical loop of domain IIId

The hepatitis C virus (HCV) has a positive single-stranded RNA genome, and translation starts within the internal ribosome entry site (IRES) in a cap-independent manner. The IRES is well conserved among HCV subtypes and has a unique structure consisting of four domains. We used an in vitro selection procedure to isolate RNA aptamers capable of binding to the IRES domains III–IV. The aptamers that were obtained shared the consensus sequence ACCCA, which is complementary to the apical loop of domain IIId that is known to be a critical region of IRES-dependent translation. This convergence suggests that domain IIId is preferentially selected in an RNA–RNA interaction. Mutation analysis showed that the aptamer binding was sequence and structure dependent. One of the aptamers inhibited translation both in vitro and in vivo. Our results indicate that domain IIId is a suitable target site for HCV blockage and that rationally designed RNA aptamers have great potential as anti-HCV drugs.     

Studies on photosynthetic oxygen-evolving complex by means of Fourier transform infrared spectroscopy: calcium and chloride cofactors

Structural roles of functional Ca²⁺ and Cl⁻ ions in photosynthetic oxygen-evolving complexes (OEC) were studied using low- (640–350 cm⁻¹) and mid- (1800–1200 cm⁻¹) frequency S₂/S₁ Fourier transform infrared (FTIR) difference spectroscopy. Studies using highly active Photosystem (PS) II core particles from spinach enabled the detection of subtle spectral changes. Ca²⁺-depleted and Ca²⁺-reconstituted particles produced very similar mid- and low-frequency spectra. The mid-frequency spectrum was not affected by reconstitution with ⁴⁴Ca isotope. In contrast, Sr²⁺-substituted particles showed unique spectral changes in the low-frequency Mn–O–Mn mode at 606 cm⁻¹ as well as in the mid-frequency carboxylate stretching modes. The mid-frequency spectrum of Cl⁻-depleted OEC exhibited marked changes in the carboxylate stretching modes and the suppression of protein modes compared with that of Cl⁻-reconstituted OEC. However, Cl⁻-depletion did not exert significant effects on the low-frequency spectrum.     

Ubiquitination of alpha-synuclein

Filamentous alpha-synuclein depositions are the defining hallmarks of a subset of neurodegenerative diseases including Parkinson's disease (PD), dementia with Lewy bodies, and multiple system atrophy. We previously reported that alpha-synuclein in those brains are extensively phosphorylated at Ser129 [Fujiwara et al. (2002) Nat. Cell Biol. 4, 160-164] and also partially ubiquitinated [Hasegawa et al. (2002) J. Biol. Chem. 277, 49071-49076]. Here, we investigate ubiquitination of alpha-synuclein in vitro and in vivo and report the ubiquitination sites and the effects of familial PD-linked mutations, phosphorylation, and fibril formation on ubiquitination. Protein-sequence analysis revealed that Lys21, Lys23, Lys32, and Lys34 within the repeats in the amino-terminal half are liable to ubiquitination in vitro. A site-directed mutagensis study confirmed that these are the major ubiquitination sites. A53T and A30P mutations had no significant effect on ubiquitination. Similarly, phosphorylation of alpha-synuclein at Ser129 did not affect ubiquitination. Notably, we show that assembled, filamentous alpha-synuclein is less ubiquitinated than the soluble form and that the major ubiquitination sites are localized to Lys6, Lys10, and Lys12 at the amino-terminal region of filamentous alpha-synuclein. Furthermore, we successfully detected ubiquitination of alpha-synuclein in 293T cells by cotransfection with alpha-synuclein and ubiquitin. The in vivo ubiquitination sites were found to be identical to those in filamentous alpha-synuclein. PD-linked mutations and phosphorylation at Ser129 had no effects on ubiquitination of alpha-synuclein in vivo. These data may have implications for the mechanisms of the formation of alpha-synuclein deposits in alpha-synucleinopathy brains.     

Advantage of dichromats over trichromats in discrimination of color-camouflaged stimuli in nonhuman primates

Due to a middle- to long-wavelength-sensitive (M/LWS) cone opsin polymorphism, there is considerable phenotypic variation in the color vision of New World monkeys. Many females have trichromatic vision, whereas some females and all males have dichromatic vision. The selective pressures that maintain this polymorphism are unclear. In the present study we compared the performance of dichromats and trichromats in a discrimination task. We examined tri- and dichromatic individuals of two species: brown capuchin monkeys (Cebus apella) and long-tailed macaques (Macaca fascicularis). We also examined one protanomalous chimpanzee (Pan troglodytes). The subjects' task was to discriminate a circular pattern from other patterns in which textural elements differed in orientation and thickness from the background. After they were trained with stimuli of a single color, the subjects were presented with color-camouflaged stimuli with a green/red mosaic overlaid onto the pattern. The dichromatic monkeys and the protanomalous chimpanzee selected the correct stimulus under camouflaged conditions at rates significantly above chance levels, while the trichromats did not. These findings demonstrate that dichromatic nonhuman primates possess a superior visual ability to discriminate color-camouflaged stimuli, and that such an ability may confer selective advantages with respect to the detection of cryptic foods and/or predators.     

Demonstration of a genotype-phenotype correlation in the polymorphic color vision of a non-callitrichine New World monkey, capuchin (Cebus apella)

Color-vision polymorphism in New World monkeys occurs because of an allelic polymorphism of the single-copy red-green middle-to-long-wavelength-sensitive (M/LWS) opsin gene on the X chromosome. Because color-vision types can readily be estimated from allelic types of the M/LWS opsin gene, this polymorphic system offers researchers an excellent opportunity to study the association between vision and behavior. As a prerequisite for such studies, genetically determined color-vision types must be concordant with phenotypes determined directly by behavioral criteria (e.g., by a color discrimination test). However, such correlations between genotypes and phenotypes have been studied only for callitrichine species. Using genetic, electrophysiological, and behavioral approaches, we evaluated the color vision of brown capuchin monkeys (Cebus apella), a representative non-callitrichine model animal for physiology and behavior. Two allelic M/LWS opsins-P545 and P530-were identified in the studied captive population. Females had one or both of the alleles, and males had either one. The retinal sensitivity in P530 dichromats was short-wave shifted relative to that in P545 dichromats, whereas that in P530/P545 trichromats was between the two groups. In a discrimination task using Ishihara pseudo-isochromatic plates, P530/P545 trichromats were successful in discriminating stimuli that P530 and P545 dichromats were unable to discriminate. In a food-search task, P530/P545 trichromats were able to locate red targets among green distracters as quickly as among white distracters, whereas both types of dichromats took longer. These results demonstrate the mutual consistency between genotypes and phenotypes of color vision, and provide a solid genetic basis on which the ecology and evolution of color vision can be investigated.     

Expression of capsule-associated genes of Cryptococcus neoformans

Cryptococcus neoformans produces an extracellular polysaccharide capsule that is related to its virulence. The production of capsular components was reported to be accelerated when cultured on media with lower amount of glucose. In this study, relationship between capsule synthesis and expression of capsule-associated genes (CAP genes) was investigated by quantitative real-time PCR analysis. Normally encapsulated strains and a stable acapsular strain were cultured in 1% polypepton medium with 0.1% or 15% glucose. The results of assessment of the capsule size showed that the capsule of yeast cells cultured in the medium with low amount of glucose was thicker than that with high amount of glucose. The CAP gene expressions of normally encapsulated strains were higher in the medium with 0.1% glucose than in the medium with 15% glucose. Furthermore, CAP10, CAP59 and CAP60 genes were expressed very low in a stable acapsular strain, and CAP64 gene was not expressed. Results of assessment of capsule size and CAP gene expressions by quantitative real-time PCR analysis indicated that CAP gene expressions might be related to the production of capsule, and that glucose concentration in culture media might be related to the expression of CAP genes.