X-ray structure of Glu 53 human lysozyme.

The three-dimensional structure of a modified human lysozyme (HL), Glu 53 HL, in which Asp 53 was replaced by Glu, has been determined at 1.77 A resolution by X-ray analysis. The backbone structure of Glu 53 HL is essentially the same as the structure of wild-type HL. The root mean square difference for the superposition of equivalent C alpha atoms is 0.141 A. Except for the Glu 53 residue, the structure of the active site region is largely conserved between Glu 53 HL and wild-type HL. However, the hydrogen bond network differs because of the small shift or rotation of side chain groups. The carboxyl group of Glu 53 points to the carboxyl group of Glu 35 with a distance of 4.7 A between the nearest carboxyl oxygen atoms. A water molecule links these carboxyl groups by a hydrogen bond bridge. The active site structure explains well the fact that the binding ability for substrates does not significantly differ between Glu 53 HL and wild-type HL. On the other hand, the positional and orientational change of the carboxyl group of the residue 53 caused by the mutation is considered to be responsible for the low catalytic activity (ca. 1%) of Glu 53 HL. The requirement of precise positioning for the carboxyl group suggests the possibility that the Glu 53 residue contributes more than a simple electrostatic stabilization of the intermediate in the catalysis reaction.     

W-heterochromatin of chicken; its unusual DNA components,late replication,and chromatin structure

About 65% of DNA in the chicken W chromosome has been shown to consist ofXhoI andEcoRI family repetitive sequences. These sequences showed remarkable delay in the electrophoretic mobility at low temperature on a polyacrylamide gel. Three dimensional structures of the 0.7-kbXhoI and the 1.2-kbEcoRI family repeating units were estimated to be irregular solenoids using a computer program based on wedge angles of all the 16 dinucleotide steps. Fluorescencein situ hybridization demonstrated that these two family sequences were localized in a major heterochromatic body in an interphase nucleus. Incorporation of bromodeoxyuridine into the W chromosome in the synchronous culture of MSB-1 cells occurred about 1 h later than the peak of S phase. The chromatin structure formed alongXhoI andEcoRI family sequences was suggested to be different from the total chromatin or chromatin containing the β-actin gene sequence in that the linker DNA lengths of the former were significantly longer. Fractionation of theHaeIII-digested MSB-1 nuclei yielded a chromatin fraction in whichXhoI family sequences were partially enriched. Several DNA-binding proteins showing higher affinity for theXhoI family sequence were present in this fraction.     

Effect of the sugar moiety on complex formation of cycloamyloses with p-nitrophenyl glycosides

Circular diochroism (CD) spectra of four p-nitrophenyl glycosides and their cycloamylose complexes were investigated at various concentrations of cycloamylose and at temperatures ranging from 20 to 60°C. The CD spectra of p-nitrophenyl glycosides changed remarkably in the presence of cycloamyloses, and significant differences in spectral shape and intensity were observed between the cyclohexaamylose complex and the cycloheptaamylose complex. The difference CD spectra between the free guest and its complex indicates that the nitrophenyl group is included in the cycloamylose cavity but its disposition is different between the complexes with cyclohexaamylose and cycloheptaamylose. Values of enthalpy and entropy of the cyclohexaamylose complex are considerably larger than those of the corresponding cycloheptaamylose complex, although the free energy differs only slightly. It is suggested that the nitrophenyl group is more loosely bound to the cycloheptaamylose cavity than to the cyclohexaamylose cavity, and has much more flexibility in its disposition.     

River to river: First evidence of eel movement between distant rivers via the sea

Environmental Biology of Fishes - Eel movement patterns have been frequently studied to learn about their movements within the fresh- and brackish waters of the same river before their spawning...     

Species and Population Level Molecular Profiling Reveals Cryptic Recombination and Emergent Asymmetry in the Dimorphic Mating Locus of C. reinhardtii

Heteromorphic sex-determining regions or mating-type loci can contain large regions of non-recombining sequence where selection operates under different constraints than in freely recombining autosomal regions. Detailed studies of these non-recombining regions can provide insights into how genes are gained and lost, and how genetic isolation is maintained between mating haplotypes or sex chromosomes. The Chlamydomonas reinhardtii mating-type locus (MT) is a complex polygenic region characterized by sequence rearrangements and suppressed recombination between its two haplotypes, MT+ and MT−. We used new sequence information to redefine the genetic contents of MT and found repeated translocations from autosomes as well as sexually controlled expression patterns for several newly identified genes. We examined sequence diversity of MT genes from wild isolates of C. reinhardtii to investigate the impacts of recombination suppression. Our population data revealed two previously unreported types of genetic exchange in Chlamydomonas MT—gene conversion in the rearranged domains, and crossover exchanges in flanking domains—both of which contribute to maintenance of genetic homogeneity between haplotypes. To investigate the cause of blocked recombination in MT we assessed recombination rates in crosses where the parents were homozygous at MT. While normal recombination was restored in MT+×MT+ crosses, it was still suppressed in MT−×MT− crosses. These data revealed an underlying asymmetry in the two MT haplotypes and suggest that sequence rearrangements are insufficient to fully account for recombination suppression. Together our findings reveal new evolutionary dynamics for mating loci and have implications for the evolution of heteromorphic sex chromosomes and other non-recombining genomic regions.     

Chicken- and duck-associated Bacteroides–Prevotella genetic markers for detecting fecal contamination in environmental water

Bacteroides–Prevotella group is one of the most promising targets for detecting fecal contamination in water environments, principally due to its host-specific distributions and high concentrations in feces of warm-blooded animals. We developed real-time PCR assays for quantifying chicken/duck-, chicken-, and duck-associated Bacteroides–Prevotella 16S rRNA genetic markers (Chicken/Duck-Bac, Chicken-Bac, and Duck-Bac). A reference collection of DNA extracts from 143 individual fecal samples and wastewater treatment plant influent was tested by the newly established markers. The quantification limits of Chicken/Duck-Bac, Chicken-Bac, and Duck-Bac markers in environmental water were 54, 57, and 12 copies/reaction, respectively. It was possible to detect possible fecal contaminations from wild ducks in environmental water with the constructed genetic marker assays, even though the density of total coliforms in the identical water samples was below the detection limit. Chicken/Duck-Bac marker was amplified from feces of wild duck and chicken with the positive ratio of 96 and 61 %, respectively, and no cross-reaction was observed for the other animal feces. Chicken-Bac marker was detected from 70 % of chicken feces, while detected from 39 % of cow feces, 8.3 % of pig feces, and 12 % of swan feces. Duck-Bac marker was detected from 85 % of wild duck feces and cross-reacted with 31 % of cow feces. These levels of detection specificity are common in avian-associated genetic markers previously proposed, which implies that there is a practical limitation in the independent application of avian-associated Bacteroides–Prevotella 16S rRNA genetic markers and a combination with other fecal contamination markers is preferable for detecting fecal contamination in water environments.     

Intranasal administration of Lactobacillus rhamnosus GG protects mice from H1N1 influenza virus infection by regulating respiratory immune responses

Aims: To investigate whether intranasal Lactobacillus administration protects host animals from influenza virus (IFV) infection by enhancing respiratory immune responses in a mouse model. Methods and Results: After 3 days of intranasal exposure to Lactobacillus rhamnosus GG (LGG), BALB/c mice were infected with IFV A/PR/8/34 (H1N1). Mice treated with LGG showed a lower frequency of accumulated symptoms and a higher survival rate than control mice (P < 0·05). The YAC‐1 cell‐killing activity of lung cells isolated from mice treated with LGG was significantly greater than those isolated from control mice (P < 0·01). Intranasal administration of LGG significantly increased mRNA expression of interleukin (IL)‐1β, tumour necrosis factor (TNF) and monocyte chemotactic protein (MCP)‐1 (P < 0·01). Conclusions: These results suggest that intranasal administration of LGG protects the host animal from IFV infection by enhancing respiratory cell‐mediated immune responses following up‐regulation of lung natural killer (NK) cell activation. Significance and Impact of Study: We have demonstrated that probiotics might protect host animals from viral infection by stimulating immune responses in the respiratory tract.