Occurrence and treatment of the mange mite Notoedres muris in marsh rats from South America

The mange mite Notoedres muris is reported from a new host, the marsh rat (Holochilus brasiliensis) from Argentina. The infection involved alopecia and encrustations on the ears and face, and was treated successfully by a subcutaneous injection of ivermectin. The new record suggests that Notoedres muris has become self-maintaining within this marsh rat population.     

Isolation, purification, and partial characterization of platelet membrane glycoproteins IIb and IIIa

Platelet membrane glycoproteins IIb and IIIa were isolated and purified from human platelet membranes using lentil lectin affinity chromatography and electrophoretic elution from sodium dodecyl sulfate-polyacrylamide gels. Two-dimensional immunoelectrophoresis of a mixture of the purified proteins against monospecific antisera showed antigenic uniqueness of the separate polypeptides. Computerized analysis of autoradiographs of two-dimensional tryptic 125I peptide maps revealed that the two glycoproteins had completely different structures. Monospecific anti-glycoproteins IIb and IIIa Fab'2 fragments, either singly or in combination, induced platelet agglutination but did not inhibit or alter the platelet aggregation response to physiologic stimuli. The results demonstrate that human platelet membrane glycoproteins IIb and IIIa are separate molecular entities. In the native state, the membrane macromolecular IIb.IIIa complex may play an important role in mediating platelet-platelet interactions.     

Cotyledon detachment inhibits development but does not affect precocious flowering of ‘Duncan’ grapefruit

The role of cotyledons in seedling development and precocious flowering was studied in Duncan grapefruit (Citrus paradisi Macf), a cultivar that displays a high frequency of precocious flowering. Cotyledons were detached from the embryo and the embryos were germinated in vitro to form plantlets. Cotyledon detachment dramatically affected the development of Duncan seedlings. The decotyledonized plants were stunted, with small narrow leaves and thin and underdeveloped roots. Decotyledonization did not change significantly the number of leaves developed. Despite the dramatic effects of the cotyledons on seedling development, decotyledonized Duncan seedlings retained their ability to flower precociously. We conclude that although normal growth and development of Duncan grapefruit seedlings is cotyledon-dependent, the ability to flower precociously does not depend on the presence of cotyledons during in vitro germination.Abbreviations MS Murashige & Skoog's medium     

Contrasting evolutionary histories of two introns of the duchenne muscular dystrophy gene, Dmd, in humans

The Duchenne muscular dystrophy (Dmd) locus lies in a region of the X chromosome that experiences a high rate of recombination and is thus expected to be relatively unaffected by the effects of selection on nearby genes. To provide a picture of nucleotide variability at a high-recombination locus in humans, we sequenced 5. 4 kb from two introns of Dmd in a worldwide sample of 41 alleles from Africa, Asia, Europe, and the Americas. These same regions were also sequenced in one common chimpanzee and one orangutan. Dramatically different patterns of genetic variation were observed at these two introns, which are separated by >500 kb of DNA. Nucleotide diversity at intron 44 pi = 0.141% was more than four times higher than nucleotide diversity at intron 7 pi = 0.034% despite similar levels of divergence for these two regions. Intron 7 exhibited significant linkage disequilibrium extending over 10 kb and also showed a significant excess of rare polymorphisms. In contrast, intron 44 exhibited little linkage disequilibrium and no skew in the frequency distribution of segregating sites. Intron 7 was much more variable in Africa than in other continents, while intron 44 displayed similar levels of variability in different geographic regions. Comparison of intraspecific polymorphism to interspecific divergence using the HKA test revealed a significant reduction in variability at intron 7 relative to intron 44, and this effect was most pronounced in the non-African samples. These results are best explained by positive directional selection acting at or near intron 7 and demonstrate that even genes in regions of high recombination may be influenced by selection at linked sites.     

Antimicrobial activity ofo-carboranylalanine

Summary Functionalized polyhedral carboranes, including amino acid analogs, have unique physicochemical properties and are used as experimental anticancer agents. However, our current knowledge on their effect in nonmammalian biological systems is limited. We investigated the activity spectrumin vitro ofo-carboranylalanine (o-Cba), considered to be a highly lipophilic analog of phenylalanine, against representative plant pathogenic bacteria and fungi of various taxonomic position. The antibacterial effect ofo-Cba against some species was comparable to that of the widely used agricultural antibiotic, streptomycin. The sensitivity of individual bacterial species too-Cba within the same genus varied to a greater extent than the average sensitivity of various genera. In general, this carborane-containing amino acid was more toxic to Gram positive bacteria (Bacillus, Corynebacterium, Curtobacterium, Micrococcus, Rhodococcus, and Staphylococcus) than to Gram negative ones (Agrobacterium, Erwinia, Escherichia, Pseudomonas, Rhizobium, and Xanthomonas). Compared to the commercial fungicide, prochloraz,o-Cba was weakly toxic against various fungi (Zygo- and Ascomycota). It was also inferior to the commercial fungicide metalaxyl in inhibiting the vegetative growth of oomyceteous plant pathogens (Pythium irregulare, Phytophthora cryptogea and Plasmopara halstedii). Against the asexual spores of P. halstedii,o-Cba, however, was over a thousandfold more active than tridemorph, a selective zoospore inhibitor fungicide. For all taxonomic groups, the observed antimicrobial effect ofo-Cba could be diminished with histidine, but not with phenylalanine. In studies on healthy and mildew-infected sunflower and tobacco plantso-Cba showed neither fungicidal nor phytotoxic effects at 500ppm. This is the first report on the biological activity spectrum of a carborane-containing amino acid.     

Structure-activity relationships for in vitro diuretic activity of CAP2b in the housefly

A series of truncated and Ala-replacement analogs of the peptide Manse-CAP2b (pELYAFPRV-NH(2)) were assayed for diuretic activity on Malpighian tubules of the housefly Musca domestica (M. domestica). The C-terminal hexapeptide proved to be the active core, the minimum sequence required to retain significant diuretic activity. However, full activity required the C-terminal heptapeptide, which was equipotent with the most active of the native housefly CAP2b peptides. Replacement of Arg(7) and Val(8) with Ala led to inactivity and a large 70-fold drop in potency, respectively, indicating that these were critical residues. The Leu(2) was semicritical, where a six-fold loss in potency was observed. Conversely, the replacement of all other residues with Ala led to much smaller effects on potency and these positions were considered to be noncritical. This structure-activity relationship data can aid in the design of mimetic agonist/antagonist analogs of this diuretic peptide family with enhanced biostability and bioavailability, as tools for arthropod endocrinologists and as potential pest management agents capable of disrupting the water balance in pest flies.     

Nucleotide variation in wild and inbred mice

The house mouse is a well-established model organism, particularly for studying the genetics of complex traits. However, most studies of mice use classical inbred strains, whose genomes derive from multiple species. Relatively little is known about the distribution of genetic variation among these species or how variation among strains relates to variation in the wild. We sequenced intronic regions of five X-linked loci in large samples of wild Mus domesticus and M. musculus, and we found low levels of nucleotide diversity in both species. We compared these data to published data from short portions of six X-linked and 18 autosomal loci in wild mice. We estimate that M. domesticus and M. musculus diverged <500,000 years ago. Consistent with this recent divergence, some gene genealogies were reciprocally monophyletic between these species, while others were paraphyletic or polyphyletic. In general, the X chromosome was more differentiated than the autosomes. We resequenced classical inbred strains for all 29 loci and found that inbred strains contain only a small amount of the genetic variation seen in wild mice. Notably, the X chromosome contains proportionately less variation among inbred strains than do the autosomes. Moreover, variation among inbred strains derives from differences between species as well as from differences within species, and these proportions differ in different genomic regions. Wild mice thus provide a reservoir of additional genetic variation that may be useful for mapping studies. Together these results suggest that wild mice will be a valuable complement to laboratory strains for studying the genetics of complex traits.     

Silencing of chaperonin 21, that was differentially expressed in inflorescence of seedless and seeded grapes,promoted seed abortion in tobacco and tomato fruits

Vitis vinifera L. cv. ‘Thompson Seedless’ presents a type of stenospermocarpy in grape where fertilization occurs but seeds abort and fail to develop. To unravel the molecular basis for stenospermocarpy in grapes, subtractive hybridization was carried out in order to isolate differentially regulated genes that participate in the seedlessness machinery. Two ‘Thompson’ lines, a seeded and a seedless, were screened during different flower developmental stages. One of the genes, that was differentially expressed between the seeded and seedless lines, was the chloroplast chaperonin 21 (ch-Cpn21). ch-Cpn21 is a 21-kDa co-chaperonin polypeptide formed by two GroES-like domains fused together in tandem. Silencing of ch-Cpn21 in Nicotiana benthamiana plants resulted in leaf stunting, chlorosis, as well as ovary necrogenesis leading to seed abortion. Moreover, organ-specific silencing of ch-Cpn21 only in Lycopersicum esculentum fruits resulted in the development of seedless tomatoes. These results suggest that ch-Cpn21 may play a role in seed abortion in stenospermocarpic grapes.