Establishing interspecific mosaic genome lines between Drosophila ananassae and Drosophila pallidosa by means of parthenogenesis

Strong sexual isolation exists between the closely related species Drosophila ananassae and D. pallidosa, but there is no obvious post-mating isolation; both sexes of the hybrids and their descendants appear to be completely viable and fertile. Strains exhibiting parthenogenesis have been derived from wild populations of both species. We intercrossed such strains and established iso-female lines after the second generation of parthenogenesis. These lines are clones, carrying homozygous chromosomes that are interspecific recombinants. We established 266 such isogenic lines and determined their genetic constitution by using chromosomal and molecular markers. Strong pseudo-linkage was seen between loci on the left arm of chromosome 2 and on the right arm of chromosome 3; the frequency of inheriting the two chromosome regions from the same species was significantly larger than expected. One possible cause of pseudo-linkage is female meiotic bias, so that chromosomes of the same species origin tend to be distributed to the same gamete. But this possibility is ruled out; backcross analysis indicated that the two chromosome regions segregated independently in female hybrids. The remaining possibility is elimination of low-fitness flies carrying the two chromosome regions from different species. Thus, genetic incompatibility was detected in the species pair for which no hybrid breakdown had previously been indicated. The 'interspecific mosaic genome' lines reported here will be useful for future research to identify genes involved in speciation and phenotypic evolution.     

Phylogeny of Allium L. subg. Melanocrommyum (Webb et Berth.) Rouy based on DNA sequence analysis of the internal transcribed spacer region of nrDNA

 Sequence analysis of the ITS region of nuclear ribosomal DNA from subgeneric representatives of Allium L. produced phylogenetic trees which concurred with previous conclusions based on classical taxonomy. Phylogenetic analysis revealed a closer relationship between Nectaroscordum siculum and Allium cernuum (representing Amerallium) than between A. cernuum and the rest of the Allium species employed in this study. The phylogeny of subg. Melanocrommyum based on ITS sequences largely agreed with inferences made by previous researchers based on morphology or a restriction analysis of chloroplast DNA. However, the phylogenetic positions of Allium protensum and Allium macleanii based on ITS sequences did not correspond to their morphological similarity with Allium schubertii and Allium giganteum, respectively. Received: 15 February 1998 / Accepted: 12 March 1998     

C-Nucleoside Analogues of Nicotinamide Mononucleotide (NMN)

Abstract

5-(β-D-Ribofuranosyl)nicotinamide (lie) and 6-(β-D-ribo-furanosyDpicolinamide (IId) and their corresponding o-isomers (III) were synthesized from ribonolactone. The C-nucleoside lie was further converted to its 5′-monophosphate Up which is isosteric to NMN Ip).     

Bitter Taste of H-Pro-Phe-Pro-Gly-Pro-Ile-Pro-OH Corresponding to the Partial Sequence (Positions 61 ~ 67) of Bovine β-Casein,and Related Peptides

The bitter components of cheese are hydrophobic peptides which are produced during the process of enzymatic digestion, and some of the isolated bitter peptides are derived from the middle portion of β-casein. However, quantitative examination of the bitter taste is seldom performed. We synthesized two hydrophobic peptides, H-Pro⁶¹-Phe-Pro-Gly-Pro-Ile-Pro⁶⁷-OH and H-Tyr⁶⁰-Pro-Phe-Pro-Gly-Pro-Ile⁶⁶-OH, which correspond to common portions among the isolated bitter peptides, in order to determine how bitter they were. From the results of sensory analysis, it was found that the synthetic peptides exhibited a bitter taste with threshold values 0.25 and 0.16mm, respectively. We also synthesized their fragments and analogs, and discussed the structure-bitterness relationship.     

The Lin28/let-7 axis regulates glucose metabolism

The let-7 tumor suppressor microRNAs are known for their regulation of oncogenes, while the RNA-binding proteins Lin28a/b promote malignancy by inhibiting let-7 biogenesis. We have uncovered unexpected roles for the Lin28/let-7 pathway in regulating metabolism. When overexpressed in mice, both Lin28a and LIN28B promote an insulin-sensitized state that resists high-fat-diet induced diabetes. Conversely, muscle-specific loss of Lin28a or overexpression of let-7 results in insulin resistance and impaired glucose tolerance. These phenomena occur, in part, through the let-7-mediated repression of multiple components of the insulin-PI3K-mTOR pathway, including IGF1R, INSR, and IRS2. In addition, the mTOR inhibitor, rapamycin, abrogates Lin28a-mediated insulin sensitivity and enhanced glucose uptake. Moreover, let-7 targets are enriched for genes containing SNPs associated with type 2 diabetes and control of fasting glucose in human genome-wide association studies. These data establish the Lin28/let-7 pathway as a central regulator of mammalian glucose metabolism.     

Recruitment of the amphidromous goby <Emphasis Type="Italic">Sicyopterus japonicus</Emphasis> to the estuary of the Ota River,Wakayama, Japan

Ecological aspects of recruitment in the amphidromous goby, Sicyopterus japonicus, were studied from larval collections made with a set net in the estuary of the Ota River, Wakayama, Japan. The abundance patterns of the 12,766 larvae collected from 18 April to 26 August 2006 showed several peaks during the recruitment season. Their body sizes at recruitment ranged from 23.5 to 30.0 mm standard length (mean ± SD, 26.3 ± 1.1 mm), 0.11 to 0.49 g body weight (0.22 ± 0.05 g), and 8 to 20 condition factor (11 ± 2). The standard length of the goby larvae tended to decrease with the season, while their body weight slightly increased and resulted in an increase in condition factor. The recruitment of larvae occurred mainly during the daytime. Otolith growth increment analysis of 30 larvae collected by a square lift net on 30 April 2005 revealed that the oceanic larval duration after downstream migration ranged from 173 to 253 days (208 ± 22) after hatching. A limited time of recruitment in early summer and a considerably long duration of oceanic life (about a half year) appeared to be unique characteristics of this Sicyopterus species that lives in a temperate region in comparison to other tropical species of the genus Sicyopterus that all have year-round recruitment.     

Strain difference in pituitary-adrenal axis between Wistar-Imamichi and Long Evans adult male rats.

In the present study, we used closed colony-Wistar-Imamichi (WI), inbred WI and Long Evans (LE) adult male rats to examine the secretion of ACTH and corticosterone in response to restraint stress. Blood (0.3 ml) was withdrawn through a jugular cannula at 0, 15, 30, 60 and 120 min after the onset of restraint stress. Plasma concentrations of ACTH and corticosterone increased after stress in all groups, but the responses of ACTH and corticosterone secretion were higher in LE rats than in WI rats. Present data suggest that the LE rat might be a good model as a high-response strain and the closed colony or the inbred WI rat might be a good model as a low-response strain in restraint stress experiments.     

Serological Characterization of Trichosporon cutaneum and Related Species

Recent molecular biological, chemical, physiological and morphological studies indicate that Trichosporon cutaneum and related species should be reclassified. In this study, antigenic characteristics of the species were determined. The results of adsorption experiments revealed that there were at least three serological types: I, II and III. Specific factor sera I, II and III were prepared on the basis of adsorption experiments and isolates were serotyped by cell slide agglutination (CSA). Since the CSA test was difficult to read in some strains, the results of the CSA test were compared with the findings from an enzyme-linked immunosorbent assay (ELISA). For the ELISA, crude polysaccharide antigens prepared from the culture supernatant were used as the antigen. The types determined by ELISA correlated well with those determined by the CSA test. These data suggest that T. cutaneum and related species have at least three serological types, and that the typing can be done by either CSA or ELISA.