Comparison of folylpolyglutamate hydrolases of mouse liver,kidney, muscle and brain

Summary The folylpolyglutamate hydrolase activities of mouse liver, kidney, muscle and brain were examined by incorporation of methylenetetrahydrofolate polyglutamate reaction products into a stable ternary complex with tritiated fluorodeoxyuridylate and L. casei thymidylate synthetase. Complexes were separated electrophoretically on the basis of charge associated with the polyglutamyl moieties to determine distribution of chain lengths throughout the time course of the reaction. Tissue folylpolyglutamate hydrolase activities were allowed to utilize endogenous folylpolyglutamate as substrates by incubating crude tissue extracts at pH 7.4 and pH 4.5. Kidney and muscle contained relatively reactive hydrolases which were capable of generating intermediates of essentially all chain lengths from folylpentaglutamate, the predominant endogenous species. The relatively low activity in brain also gave rise to all possible intermediates. Liver contained a high concentration of methylenetetrahydrofolate but little hydrolase activity. The activity present in liver gave rise to essentially no intermediates but yielded only the monoglutamate form of the cofactor. When purified lysosomal preparations from liver and kidney were allowed to react with synthetic folylpolyglutamates, the same specificity with regard to reaction products was observed as with endogenous substrates.     

Synthesis of peptides from amino acids and ATP with lysine-rich proteinoid

Summary Lysine-rich proteinoids in aqueous solution catalyze the formation of peptides from free amino acids and ATP. This catalytic activity is not found in acidic proteinoids, even though the latter contain some basic amino acid. The pH optimum for the synthesis is about 11, but is appreciable below 8 and above 13. Temperature data indicate an optimum at 20°C or above, with little increase in rate to 60°C. Pyrophosphate can be used instead of ATP, with lesser yields resulting. The ATP-aided syntheses of peptides in aqueous solution occur with several types of proteinous amino acid.Proofs should be sent to S.W. Fox, Institute for Molecular and Cellular Evolution, University of Miami, 521 Anastasia Avenue, Coral Gables, FL 33134     

Chemotactic macrophage subpopulations defined by macrophage chemotactic factors from delayed hypersensitivity reaction sites

The chemotactic specificity of ia-positive and -negative macrophages was studied by using three macrophage chemotactic factors (MCF), -a, -b, and -c, isolated from delayed hypersensitivity reaction (DHR) skin sites in guinea pigs. Listeria-elicited macrophages migrated toward MCF-a, -b, and -c. The chemotactic responses suggested responsive subpopulations to MCF. The electronic programmable individual cell sorter (EPICS) was used to separate macrophages with anti-la monoclonal antibodies. Ia-positive subpopulations responded to MCF-c, although they did not migrate toward MCF-a and -b. In contrast, Ia-negative subpopulations migrated toward MCF-a and -b, but not toward MCF-c. Furthermore, MCF-c attracted Ia-positive macrophages, whereas MCF-a and -b were Ia-negative in vitro; MCF did not induce Ia-negative macrophages to express surface Ia-antigens in vitro. MCF-c was able to produce massive Ia-positive macrophage accumulations when injected i.p., whereas MCF-a accumulated Ia-negative macrophages. The data suggest that MCF-a and -b, which mediate initial macrophage reactions, attract Ia-negative macrophages, and that MCF-c, which mediates predominant macrophage reactions, attract Ia-positive macrophages in the DHR.     

Screening costramid libraries for chromosomal genes: an alternative interspecific hybridization method

Abstract Broad host-range RK2-based cosmid vectors ('costramids') are increasingly used in molecular genetic studies of Gram-negative soil bacteria such as Rhizobium spp. we describe a simple modification of existing methods, whereby a genomic library constructed in a stringently replicated vector can be screened for genes which are undetectable by colony hybridization due to background cross-hybridization. This method allows the use of 'heterologous' probes (interspecies hybridization) to isolate several presumptive genes of interest from a gene bank of Rhizobium sp. NGR234 made in the costramid pRK7813. These are a gene with homology to the citrate synthase gene ( gltA ) or Escherichia coli , the gene encoding δ-aminol evulinic acid synthase ( hemA ), and a gene or genes regulating dicarboxylate transport.     

The effects of date of planting on field establishment of serotinous cape Proteaceae

Season of fire have marked effects on the germination and establishment of serotinous shrubs of the family Proteaceae in fynbos vegetation. To investigate reasons for this, we simulated the effects of different fire seasons by planting seeds into cleared fynbos and then followed their progress. Four species of Proteaceae were planted monthly at four sites over two and a half years. Exclosures were used to exclude rodent seed predators. Germination was confined largely to the three winter months (June–Aug.). Seeds planted from January–June had higher germination than those planted in the second half of the year. Higher levels of regeneration noted after fires in the first half of the year, were previously hypothesised to be results of predation. However, we obtained similar results despite the exclusion of seed predators. Monthly minimum temperature was strongly correlated with germination percentage but monthly rainfall was not. Loss of seed viability may be important, in determining post-fire seedling densities. Differential seedling mortality of earlier and late germinants appears to be unimportant in determining establishment levels. Our results nevertheless support the current practice of restricting management fires in fynbos to the summer-autumn period.     

Separating the climatic signal from tree-ring width and maximum latewood density records

We propose a technique for separating the climatic signal which is contained in two tree-ring parameters widely used in dendroclimatology. The method is based on the removal of the relationship between tree-ring width (TRW) and maximum latewood density (MXD) observed for narrow tree rings from high latitudes. The new technique is tested on data from three larch stands located along the northern timberline in Eurasia. Correlations were calculated between the temperatures of pentads (five consecutive days), TRW chronologies and MXD chronologies calculated according to the standard and proposed methods. The analysis confirms the great importance of summer temperature for tree radial growth and tree-ring formation. TRW is positively correlated with the temperature of four to eight pentads (depending on the region) at the beginning of the growth season, but MXD as obtained by the standard technique is correlated with temperature over a much longer period. For maximum density series from which the relationship between MXD and TRW has been removed (MXD′), there is a clear correlation with temperatures in the second part of the growing season. These results are consistent with the known dynamics of tree-ring growth in high latitudes and mechanisms of tree-ring formation.     

Biopolymer of alginate nature with a predominance of L-guluronic acid

Highly viscous polysaccharide (250–350 kDa) of an alginate nature with a predominance of α-L-guluronic acid (M/G = 0.22) was obtained from Azotobacter vinelandi. The yield of polysaccharide was 20.5 ± 0.5 g/l when cultured in a medium containing molasses at a viscosity of the cultural liquid of over 30000 cSt. The biopolymer is stable at pH 4.0–9.0 in a wide temperature range and well soluble in highly mineralized water; it retains a high viscosity level and can be used in the petroleum industry for enhanced oil recovery.