Sperm nuclei analysis of a Robertsonian t(14q21q) carrier,by FISH,using three plasmids and two YAC probes

The meiotic segregation of chromosomes 14 and 21 was analysed in 1116 spermatozoa from an oligoasthenospermic carrier of a Robsertsonian translocation t(14q21q), and in 16 392 spermatozoa from a control donor, using two-colour fluorescence in situ hybridisation (FISH). Two YAC probes (cloned in yeast artificial chromosomes) specific for regions on the long arms of these chromosomes were co-hybridised. Of the spermatozoa, 12% were unbalanced, resulting from adjacent segregations. Chromosomes X, Y and 1 were also simultaneously detected in 1335 spermatozoa from the same carrier. Whereas gonosomal disomy rates were not significantly different from those of the control donors, disomy 1 were slightly but significantly increased to 0.7%. The diploidy rate was also slightly increased to approximately 1% in the translocation carrier.     

Buchnera aphidicola (Aphid-Endosymbiont) glyceraldehyde-3-phosphate dehydrogenase: Molecular cloning and sequence analysis

Buchnera aphidicola is an endosymbiont of the aphid Schizaphis graminum. A 3.9-kb B. aphidicola DNA fragment was sequenced and found to contain two open reading frames (ORFs). The deduced amino acid sequence of one of the ORFs had an 85% identity to Escherichia coli glyceraldehyde-3-phosphate dehydrogenase (Gap). Both of these proteins have a higher similarity to eukaryotic than to prokaryotic Gaps. The second ORF could not be readily identified. The sequence of the putative product indicated that it was a member of the family of ATP-binding, membrane-associated proteins. The highest amino acid identity (36%) was with E. coli FtsE, a protein involved in cell division.     

Bird species turnover and stochastic extinction in woodland fragments

Year-to-year turnover in bird species composition was recorded across, the whole size range (0 02-30 ha) of 146 woods studied The mean number of resident breeding species both lost and gained per wood between consecutive breeding seasons was 2 (range 0-8) No relationship was found between this absolute turnover rate and woodland area, or any other of 24 predictor variables (describing woodland structure, isolation, connectedness and surrounding land use) Extriction and colonisation rates (in terms of numbers of species lost and gained) were also unrelated to woodland area In all sizes of woods, the species most likely to show local extinctions and colonisations were those with small populations within those woods, but the identity of the species concerned changed as woodland area increased In the smallest woods, the majority of turnover involved common species, such as wren and dunnock, which occurred in only small numbers in these small woods As woodland area increased, these species attained sufficient numbers to usually avoid stochastic extinction The majority of turnover was then due to more specialist (and less numerous) woodland species, such as great-spotted woodpecker and marsh tit, which were usually lacking in small woods In Britain, much existing broadleaved woodland falls within the size range studied Thus the numbers of many bird species are liable to be small enough for yearly turnover in woodland bird communities to be appreciable, and for the long-term persistence of individual species in particular woods to depend on dispersal     

Population structure and mycelial phenotypic variability of the ectomycorrhizal basidiomycete Laccaria bicolor (Maire) Orton

Mating type allele distribution and phenotypic variability were investigated in field populations of Laccaria bicolor. Sporophores associated with Norway spruce (Picea abies), colonized by natural sources of inoculum and growing in a seed orchard, were sampled to obtain dikaryotic strains and assay their phenotypic variability for traits important to the symbiosis. Basid-iospores were also collected for mating type analysis of different mycelia. Four sporophore mating types were identified containing seven A and five B factors. Out-breeding efficiency was estimated at 73.8% and the population was slightly inbred. Crosses with previously characterized L. bicolor strains from two nearby populations identified in total six sporophore mating types and ten A and nine B factors, for an estimated outbreeding efficiency (85.7%) similar to previous studies of more spatially disparate Laccaria spp. populations. Dikaryotic strains were tested for mycelial growth rate, as a measure of their competitive ability, on agar media containing a soluble (NaH₂PO₄), or an insoluble (CaHPO₄) phosphate source. Their ability to solubilize the latter was also tested to assess their relative capacity to access insoluble, inorganic phosphate. In most cases, significant variation was detected among strains from the same site for all variables. On three sites (VC4, VC5 and VC7), each determined previously to possess a uniform mycelial genotype, phenotypic variability was likely due to epigenetic variation among different strains of the same genotype. Possible evidence for dikaryon-monokaryon crosses was observed in vivo on one sample site (VC2) where adjacent mycelia shared two mating factors. The phenotypic variability of different mycelial genotypes reflected their genetic variability observed as mating type allele diversity and underlined the importance of basidiospore dispersal in introducing new genotypes into the population. The reproductive strategies of L. bicolor are discussed and compared to those of other basidiomycete species.     

A new Dol-P-Man:protein O-D-mannosyltransferase activity from Saccharomyces cerevisiae

The deletion of the protein mannosyltransferase 1 gene (PMT1)of Saccharomyces cerevisiae results in viable cells. O-Mannosylationof proteins is reduced to about half of the value in comparisonto wild-type cells. In order to distinguish between the thePMT1 gene product (= Pmt1p) and residual transferase activity,an in vitro assay to measure Dol-P-Man:protein mannosyltransferaseactivity in cells deleted for PMT1 has been developed. The transferaseactivity of these cells exhibits a pH optimum of 6.5 as comparedto pH 7.5 for Pmt1p. The K_$$$ value of the residual enzyme activityfor the hexapeptide YNPTSV is 7 times higher than that of Pmt1pand shows a clear preference for the seryl/residue. Differencesin substrate affinities as well as in seryl/threonyl preferencebetween the two enzymes, however, depend on the specific sequenceof the peptides used in the enzyme assay. The new enzyme activityshows a significantly lower thermal stability as compared toPmt1p. glycoprotein O-glycosylation mannosyltranferase Saccharomyces cerevisiae     

Synthesis and fungicidal activity of 2,2′-bipyridine derivatives

A series of substituted 2,2′-bipyridine derivatives was prepared using the Kröhnke reaction and alkylation of 4,4′-dimethyl-2,2′-bipyridine. These compounds were screened for fungicidal activity against 9 plant diseases. 5-Phenyl-2,2′-bipyridine exhibited strong preventative and curative fungicidal activity against wheat powdery mildew (Erisyphe graminis) and wheat leaf rust (Puccinia recondita).     

The murine 3β-hydroxysteroid dehydrogenase multigene family: Structure, function and tissue-specific expression

The classical form of the enzyme 5-ene-3β-hydroxysteroid dehydrogenase/isomerase (3βHSD), expressed in adrenal glands and gonads, catalyzes the conversion of 5-ene-3β-hydroxysteroids to 4-ene-3-ketosteroids, an essential step in the biosynthesis of all active steroid hormones. To date, four distinct mouse 3βHSD cDNAs have been isolated and characterized. These cDNAs are expressed in a tissue-specific manner and encode proteins of two functional classes. Mouse 3βHSD I and III function as 3β-hydroxysteroid dehydrogenases and 5-en→4-en isomerases using NAD⁺ as a cofactor. The enzymatic function of 3βHSD II has not been completely characterized. Mouse 3βHSD IV functions only as a 3-ketosteroid reductase using NADPH as a cofactor. The predicted amino acid sequences of the four isoforms exhibit a high degree of identity. Forms II and III are 85 and 83% homologous to form I. Form IV is most distant from the other three with 77 and 73% sequence identity to I and III, respectively. 3βHSD I is expressed in the gonads and adrenal glands of the adult mouse. 3βHSD II and III are expressed in the kidney and liver with the expression of form II greater in kidney and form III greater in liver. Form IV is expressed exclusively in the kidney. Although the amino acid composition of forms I, III and IV predicts proteins of the same molecular weight, the proteins have different mobilities on SDS-polyacrylamide gel electrophoresis. This characteristic allows for differential identification of the expressed proteins. The four structural genes encoding the different isoforms are closely linked within a segment of mouse chromosome 3 that is conserved on human chromosome 1.