Chydorus arcticus n.sp., a new cladoceran crustacean (Chydoridae: Chydorinae) from the North Atlantic arctic and Subarctic areas

Chydorus arcticus n.sp. (Cladocera: Chydoridae: Chydorinae) is described, figured, and differentiated from the closely relatedC. sphaericus (O.F. Müller, 1785). The known distribution of the species is given, and some aspects of speciation of arctic crustaceans are pointed out.     

Concentration gradients of free sterols,steryl esters and lipid phosphorus in the trunkwood of Scot's pine (Pinus sylvestris L.)

The amounts of free sterols, steryl esters and lipid phosphorus were determined in the sapwood and heartwood of mature, and in the outer and inner sapwood of young Pinus sylvestris trees. In the mature trees (up to 70 years old) the heartwood contains significantly higher amounts of free sterols than the sapwood. No radial gradient can be demonstrated in the amounts of steryl esters. Lipids extracted from the sapwood contain higher amounts of phosphorus than those from the heartwood. Stems of young Pinus sylvestris trees (up to 13 years old) show in the inner sapwood higher amounts of both free sterols and steryl esters than the peripheral younger wood zone. The inner sapwood of the young stems shows slightly higher amounts of lipid phosphorus than the outer sapwood. The results indicate that Pinus sylvestris accumulates both free sterols and steryl esters in the stems at a very early stage of the life cycle. Sterol accumulation in the innermost parts of the stems seems not to depend on heartwood formation.     

Carbon and nitrogen metabolism in ectomycorrhizal fungi and ectomycorrhizas

The literature concerning the metabolism of carbon and nitrogen compounds in ectomycorrhizal associations of trees is reviewed. The absorption and translocation of mineral ions by the mycelia require an energy source and a reductant which are both supplied by respiratory catabolism of carbohydrates produced by the host plant. Photosynthates are also required to generate the carbon skeletons for amino acid and carbohydrate syntheses during the growth of the mycelia. Competition for photosynthates occurs between the fungal cells and the various vegetative sinks in the host tree. The nature of carbon compounds involved in these processes, their routes of metabolism, the mechanisms of control and the partitioning of metabolites between the various sites of utilization are only poorly understood. Both ascomycetous and basidiomycetous ectomycorrhizal fungi synthesize and some, if not all, accumulate mannitol, trehalose and triglycerides. The fungal strains employ the Embden--Meyerhof pathway of glucose catabolism and the key enzymes of the pentose phosphate pathway (6-phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase, transaldolase and transketolase). Anaplerotic CO2 fixation, via pyruvate carboxylase and/or phosphoenolpyruvate carboxykinase, provides high pools of amino acids. This process could be important in the recapture and assimilation of respired CO2 in the rhizosphere. The ectomycorrhizas are thought to contain the Embden--Meyerhof pathway, the pentose phosphate pathway and the tricarboxylic acid cycle, which provide the carbon skeletons for the assimilation of ammonia into amino acids. The main route of assimilation of ammonia appears to be through the glutamine synthetase-glutamate synthase cycle in the ectomycorrhizas. Glutamate dehydrogenase plays a minor role in this process. Glutamate dehydrogenase and glutamine synthetase are present in free-living ectomycorrhizal fungi and they participate in the assimilation of ammonia and the synthesis of amino acids through the glutamate dehydrogenase/glutamine synthetase sequence. In both in vitro cultures of fungi and ectomycorrhizas, the assimilated nitrogen accumulates in glutamine. Glutamine, but also ammonia, are thought to be exported from the fungal tissues to the host cells. Studies on the metabolism of ectomycorrhizas and ectomycorrhizal fungi have focused on the metabolic pathways and compounds which accumulate in the symbiotic tissues. Studies on regulation of the overall process, and the control of enzyme activity in particular, are still fragmentary.(ABSTRACT TRUNCATED AT 400 WORDS)     

Connective tissue influences on the expression of epithelial cell-surface antigens

Summary Adult mice were found to show regional variation in the epithelial expression of some molecules of the blood-group antigen series. To investigate connective tissue influences on such differences, heterotypic recombinants of epithelia and connective tissues from various regions were prepared and examined using monoclonal antibodies directed against bloodgroup antigens H and Le^y. The results indicate that epithelia may maintain a preexisting regionally specific pattern following recombination but that, in some recombinant matches, the connective tissue is capable of signalling redirection of the pattern of expression towards that typical of the epithelium with which it is normally associated.This work was supported by NIH-NIDR RO1-DEO-5190     

Cloning and characterization of the gene coding for cytoplasmic seryl-tRNA synthetase from Saccharomyces cerevisiae.

We have screened a Saccharomyces cerevisiae expression library with antibodies against seryl-tRNA synthetase (SerRS) from baker's yeast. In this way we obtained clones which contain serS, the structural gene for seryl-tRNA synthetase. Genomic Southern blots show that the serS gene resides on a 5.0 kb SalI fragment. Nucleotide sequence analysis of the genes revealed a single open reading frame from which we deduced the amino acid sequence of the enzyme consistent with that of two peptides isolated from SerRS. The enzyme is comprised of 462 amino acids consistent with earlier determinations of its molecular weight. The codon usage of serS is typical of abundant yeast proteins. Nuclease S1 analysis of serS mRNA defined the RNA initiation site 20-40 bases downstream from an AT rich sequence containing the TATA box and 21-39 nucleotides upstream of the translation initiation codon. Yeast strains transformed with the cloned gene overproduce seryl-tRNA synthetase in vivo.     

Osmoregulation in Escherichia coli by accumulation of organic osmolytes: betaines,glutamic acid,and trehalose

Like other cyanobacteria, Chlorogloeopsis fritschii contained as major lipid classes monogalactosyldiacyl-glycerols, digalactosyldiacylglycerols, sulfoquinovosyldiacylglycerols and diacylglycerophosphoglycerols. In addition to these lipid classes this cyanobacterium also contained small amounts of diacylglycerophosphocholines and sterols, predominantly lanosterol, thus showing similarity to photosynthetic eukaryotes. Dark incubated cells contained larger proportions of the latter two lipid classes than light grown cells. Like other prokaryotes, C. fritschii lacked linolenic acid (18:3) in its lipids. Lipids from the thylakoids were richer in palmitoleic acid (16:1) than those of whole cells. There was no effect of light on the patterns of constituent fatty acids of lipids from C. fritschii, in contrast to photosynthetic eukaryotes.Abbreviations MGDG Monogalactosyldiacylglycerols - PA Phosphatidic acids - PE Diacylglycerophosphoethanolamines - PG Diacylglycerophosphoethanolamines - DGDG Digalactosyldiacylglycerols - SQDG Sulfoquinovosyldiacylglycerols - PC Diacylglycerophosphocholines     

Tranexamic acid as an aid to reducing blood transfusion requirements in gastric and duodenal bleeding.

A prospective randomised double blind study examined the effect of the antifibrinolytic drug tranexamic acid compared with placebo in 154 patients bleeding from verified benign lesions in the stomach or duodenum or both. Three out of 72 patients receiving tranexamic acid underwent emergency surgery compared with 15 out of 82 given placebo (p = 0.010). Nineteen patients receiving placebo rebled during their admission as compared with 10 in the active treatment group (p = 0.097). Blood transfusion requirements were significantly reduced by tranexamic acid (p = 0.018). Side effects occurred in six patients, of which an uncomplicated deep venous thrombosis was the most severe. Tranexamic acid reduces the blood transfusion requirement and need for emergency surgery in patients bleeding from a benign gastric or duodenal lesion.     

Biosynthesis of the Cyanogenic Glucoside Dhurrin in Seedlings of Sorghum bicolor (L.) Moench and Partial Purification of the Enzyme System Involved

The cyanogenic glucoside dhurrin is rapidly synthesized in etiolated seedlings of Sorghum bicolor (L.) Moench. The dhurrin content of the seedlings increases sigmoidally with the germination time. Shoots of 10 centimeters height contain 850 nanomoles of dhurrin per shoot corresponding to 6% of the dry weight. The biosynthetic activity sharply rises upon germination and reaches a maximum level of 10 nanomoles dhurrin/(hour × shoot) after 48 hours when the shoots are 3 centimeters high. This maximum level is followed by a sharp decline in activity when germination time exceeds 65 hours. Dhurrin and the dhurrin-synthesizing enzyme system are primarily located in the upper part of the etiolated shoot where both are evenly distributed between the coleoptile, the primary leaves and the upper 0.5 centimeter of the first internode including the shoot apex. Dhurrin constitutes 30% of the dry weight of the upper 1.2 centimeter of 10 centimeter high shoots. The seed and root contain neither dhurrin nor the dhurrin-synthesizing enzyme system. The codistribution of dhurrin and the enzyme system throughout the seedling indicates that production and storage sites are located within the same cell. Purification of the dhurrin-synthesizing enzyme by gel filtration or by sucrose gradient centrifugations results in a tenfold increase in specific activity. Further purification is accompained by a decline in specific activity due to loss of essential components as demonstrated by reconstitution experiments.