Paramolybdate anion-exchange resin, an improved catalyst for the C-1-C-2 rearrangement and 2-epimerization of aldoses

Aqueous solutions of molybdate at 90 degrees bring about the inversion of the C-1-C-2 fragment of aldoses having four or more carbon atoms, generating thermodynamically equilibrated mixtures of the starting aldose and its 2-epimer. In some cases, notably with the aldopentoses, substantial proportions of the 3-epimers are produced, as well as 2-epimers that have not undergone inversion of the C-1-C-2 fragment. These side-reactions can be controlled by using the paramolybdate form of an anion-exchange resin (AG MP-1) together with the formate form of the same resin. The latter acts to scavenge unbound molybdate and paramolybdate anions that appear to be responsible for the side reactions.     

Expression of polyoma virus middle-T antigen in Saccharomyces cerevisiae

The polyoma middle-T gene, lacking its intron, was inserted into a yeast expression plasmid containing the phosphoglycerate kinase promoter. Such plasmids transformed yeast at low frequency and these transformants expressed middle-T antigen at a level of approximately 0.1% cell protein. Furthermore, expression of this protein was frequently lost during growth in liquid culture and this loss of middle-T was accompanied by a twofold increase in the rate of growth. The spontaneous production of a truncated middle-T antigen, lacking the C terminus, was also observed; the expression of this protein did not inhibit the growth rate of the cells. Recovery and analysis of the expression plasmids encoding the truncated molecule showed that a single C X G base pair had been deleted from a run of nine consecutive C X G base pairs (Pyr nucleotide 1239--1247) within the middle-T coding region. This frame-shift mutation results in premature termination of the protein and loss of the strongly hydrophobic region of the molecule believed to be responsible for the membrane association of middle-T antigen.     

Relative Virulence of Meloidogyne incognita Host Races on Soybean

Sensitivity and host efficiency of susceptible (''Lee 68'', ''Coker 156'') and resistant (''Bragg'', ''Centennial'', ''Forrest'', ''Lee 74'') soybean (Glycine max (L.) Merr.) cultivars for races of Meloidogyne incognita (Mi) were determined in greenhouse experiments. Eight Mi populations collected from the southeastern United States were utilized. All Mi races reproduced readily on Lee 68 and Lee 74 and moderately on Forrest and Bragg. Coker 156 exhibited resistance to races 1 and 2, and some race 3 populations, but was very susceptible to certain race 3 and 4 populations. Reproduction of all races was lowest on Centennial. Forrest and Centennial shoot growth was not significantly suppressed by any race. There were no distinct differences in virulence between races except for a race 3 population which reproduced readily on all cultivars, stunting their growth. Considerable variation in reproduction existed within races 1 and 3.     

island biogeography of Day Geckos (Phelsuma) in the Indian Ocean

Summary Step-wise multiple regression was employed to probe the determinants of species diversity of day geckos (Phelsuma) in the Indian Ocean. Independent variables were area, elevation, and two measures of isolation. Distance from Madagascar and island height (an indicator of habitat diversity) were the two most important predictors of species richness. Similar studies on other taxa rarely find isolation to be a major factor. The relatively poor dispersal abilities of reptiles may explain why isolation, rather than attributes of the islands, are more important in this case. The regressions also indicate that habitat diversity (assumed to correlate with maximum island elevation) is more important than area per se in determining species diversity. These results agree with predictions of the equilibrium theory of island biogeography, but historical processes have also greatly influenced species richness.     

Spatial variation in larval concentrations as a cause of spatial variation in settlement for the barnacle,Balanus glandula

Summary Settlement rates of the high intertidal barnacle, Balanus glandula, were monitored at three sites in the rocky intertidal zone in Central California simultaneously with measurements of larval concentrations in the adjacent water column. In both 1983 and 1984, settlement rates onto vacant substrate differed among the sites by nearly two orders of magnitude. For all sampling dates, this spatial variation in settlement mirrored the spatial distribution of Balanus glandula cyprid concentration in the water column. A perfect rank correlation was found between cyprid concentrations near a site and subsequent settlement. A noteworthy observation was that the sites switched rank in their settlement rates from 1983 to 1984. This change in settlement rankings matched a switch in rankings for cyprid concentrations.Settlement itself appears to be an important cause of the spatial pattern of cyprid concentrations. Comparing the rates of settlement to estimates of the number of cyprids available at a site suggests that settlement causes a large drain on the cyprid population as a water mass passes over successive sites. No consistent spatial patterns were found in the distribution of other major plankton groups (calanoid copepods) that are similar in size to Balanus cyprids but do not settle.The large differences in settlement rates among these sites were previously shown to be a leading cause of large differences in the structure of benthic barnacle populations. The close correspondence shown here between these large differences in settlement and differences in larval concentrations suggests that nearshore oceanic processes affecting larval arrival contribute to the control of benthic community structure.     

Electron microscopic studies of condensed mitotic chromosomes in the fission yeast Schizosaccharomyces pombe

By blocking cells in mitosis with the anti-fungal drug thiabendazole, it has been possible to carry out ultrastructural studies on the condensed chromosomes of the fission yeast, Schizosaccharomyces pombe. It is estimated that the DNA in these chromosomes is compacted approximately 1000-fold, and that the nucleoprotein density is similar to that of higher eukaryotic metaphase chromosomes. A basic structural component of the condensed chromosomes appears to be a 50-60 nm fibre, which is often visible in a loop configuration on the periphery of the chromatids. This is reminiscent of the 50-60 nm fibre loops which are frequently seen in preparations of metaphase chromosomes, and suggests that mechanisms of nucleoprotein folding may be similar in both lower and higher eukaryotes.     

Enhanced enzymatic hydrolysis of lignocellulosic biomass pretreated by low-pressure steam autohydrolysis

Summary The use of low-pressure steam autohydrolysis in the pretreatment of corn stover and hybrid poplar has been assessed. In terms of yield of prehydrolyzed solids, minimal by-product formation and extent of subsequent enzymatic saccharification, the results of low-pressure steam pretreatment were found to be as good as or better than those reported for more severe pretreatment processes. Almost complete saccharification of the cellulose in the prehydrolyzed biomass solids was obtained within 24h with a commercial cellulase preparation — Celluclast. The presence of grinding elements (glass beads) during the enzymatic hydrolysis was found to increase the extent of saccharification by 40% to 50% over controls without any grinding elements.     

Carbon content of the neritic scyphomedusa Chrysaora fuscescens

An analysis of the role of scyphomedusae in a planktonic ecosystemrequires that biomass or numerical abundance estimates be convertibleinto standard units for comparison with other components ofthe planktonic community. One species under investigation isthe brown sea nettle, Chrysaora fuscescens, which is very abundantin coastal waters of the west coast of North America (Shenker,1984). For this species, the carbon content of whole immatureanimals and the body components of sexually mature medusae weredetermined. Immature medusae contained a mean carbon content0.202% of the wet weight. The bell, oral arms and gonadal tissueof mature medusae had mean carbon levels 0.156, 0.554 and 0.576%of the wet weight, respectively. When the relative proportionsof these body tissues were calculated, the mean carbon contentof whole mature medusae was determined to be 0.280% of the wetweight.     

Structural analysis of heparin by methylation and g.l.c.-m.s.: preliminary results

Heparin is a complex mixture of polysaccharides differing in biological activity and structure, and attempts to relate this activity to structure have suffered, owing to a lack of sufficiently sensitive and specific analytical methods. Application of methylation analysis to determination of the structure of heparin is described. Carboxyl-reduced heparin was converted into its pyridinium salt, this was dissolved in Me2SO, and free OH and NH groups were methylated with dimethylsulfinyl anion. Sulfate groups were removed by solvolysis, and after dialysis, the polymer was acetylated and depolymerized by acetolysis. The resulting monosaccharides were converted into alditol acetates, which were separated by capillary, gas-liquid chromatography, and identified by both electron impact and chemical ionization mass spectrometry. Seventeen different monosaccharides were identified in the hydrolyzate. All of the expected internal hexosaminyl and glycosyluronic residues were identified. Although several sugars were identified as nonreducing termini, only a hexosamine 6-sulfate was identified as a reducing-terminus sugar. The results indicate that methylation analysis of heparins and other complex, sulfated glycosaminoglycans is feasible.     

Distorted segregation and linkage of alcohol dehydrogenase genes in Camellia japonica L. (Theacease)

Alcohol dehydrogenase isozymes in Camellia japonica are encoded by two genes, Adh-1 and Adh-2. Both loci are expressed in seeds, and their products randomly associate into intragenic and intergenic dimers. Electrophoresis of leaf extracts reveals only the products of Adh-2. Formal genetic analysis indicated that the two Adh loci are tightly linked (combined estimate of r=0.004). Most segregations fit expected Mendelian ratios, but in some families distorted segregation was observed at Adh-1, Adh-2, or both loci. The deficient progeny class varied across families, and in two apparent backcrosses three rather than two phenotypic classes were recovered. The mechanism underlying these distortions is not known, but evidence is presented that suggests that the phenomenon is genic or segmental in nature. Plausible hypotheses include linkage of the Adh structural genes with a gametophytic self-incompatibility locus, translocation heterozygosity involving the segment bearing Adh-1 and Adh-2, or a combination of these two mechanisms.