Type I cadherins are required for differentiation and coordinated rotation in Xenopus laevis somitogenesis

In Xenopus laevis somitogenesis, somitic blocks undergo coordinated movements resulting in their detachment from the rest of the mesodermal ridge, followed by a 90 degrees rotation of the entire metamere. Here we investigated the function of type I cadherins in somitogenesis. Type I cadherins are Ca(2+)-dependent cell-cell adhesion molecules concentrated in the adherens junctions and highly expressed in the somitic tissue. We analyzed their role in somitogenesis by overexpressing either the intracellular (deltaE) and the extracellular (C-trunc) dominant-negative forms of cadherin. The resulting phenotype was a downward bend of the anterior-posterior axis in tadpole stage embryos. 12/101 antigen and X-Myo-D expression were altered. Microscopy revealed disorganization of the myotomes. Conversely, segmentation was conserved at the microscopic and molecular levels.     

Fatty acids in the species of several zygomycete taxa

The composition of fatty acids synthesized de novo by thirty strains of zygomycetes from various taxa was studied. The qualitative fatty acid compositions of the fungal lipids were found to be virtually identical, but there were significant differences in the contents of individual acids. Highly active producers of essential C18 fatty acids, with their content exceeding 30-40% of total fatty acids, were discovered among the fungi of the families Mucoraceae, Pilobolaceae, and Radiomycetaceae. Linoleic acid was found to predominate in the fungi of the genera Radiomyces, Mycotypha, and Circinella, and linolenic acid (identified as its gamma-isomer by gas-liquid chromatography), in the fungi of the genera Absidia, Circinella, Pilaira, and Hesseltinella. The total yield (mg/l) of bioactive acids (C18:3, C18:2, C18:1) varied from 761.4 in Pilaira anomala to 3477.9 in Syncephalastrum racemosum; the total yield of essential acids, from 520.7 in Pilaira anomala to 1154.5 in Hesseltinella vesiculosa; of linoleic acid, from 279.7 in Pilaira anomala to 836.3 in Mycotypha indica; and of linolenic acid, from 120.8 in Mycotypha indica to 708.0 in Hesseltinella vesiculosa. The data on the efficient synthesis of these acids make the actively producing strains promising for biotechnological synthesis of commercially valuable lipids. Linderina pennispora VKM F-1219, a zygomycete of the family Kickxellaceae, which was earlier singled out into the order Kickxellales [12], was shown to differ from zygomycetes of the order Mucorales in having a high content of cis-9-hexadecenoic (palmitoleic) acid, reaching 37.0% of the fatty acid total.     

Lipids of initial and mutant cultures of Penicillium chrysogenum, producers of penicillin

Comparative investigation of lipogenesis in 2 initial and 4 mutant strains of Penicillium chrysogenum showed that there were no noticeable differences in the composition of the lipid fatty acids in these strains. Certain shifts in the ratio of definite lipid fatty acids in the mutant strain deficient by synthesis of lysine and isoleucine (increased contents of oleic acid) were revealed. A marked influence of the physiological conditions on lipogenesis in the mutant with multiple deficiency by amino acids, vitamins and nucleotides was observed.     

A Similar Pattern of Interaction for Different Antibodies with a Major Antigenic Site of Foot-and-Mouth Disease Virus: Implications for Intratypic Antigenic Variation

The three-dimensional structures of the Fab fragment of a neutralizing antibody raised against a foot-and-mouth disease virus (FMDV) of serotype C₁, alone and complexed to an antigenic peptide representing the major antigenic site A (G-H loop of VP1), have been determined. As previously seen in a complex of the same antigen with another antibody which recognizes a different epitope within antigenic site A, the receptor recognition motif Arg-Gly-Asp and some residues from an adjacent helix participate directly in the interaction with the complementarity-determining regions of the antibody. Remarkably, the structures of the two antibodies become more similar upon binding the peptide, and both undergo considerable induced fit to accommodate the peptide with a similar array of interactions. Furthermore, the pattern of reactivities of five additional antibodies with versions of the antigenic peptide bearing amino acid replacements suggests a similar pattern of interaction of antibodies raised against widely different antigens of serotype C. The results reinforce the occurrence of a defined antigenic structure at this mobile, exposed antigenic site and imply that intratypic antigenic variation of FMDV of serotype C is due to subtle structural differences that affect antibody recognition while preserving a functional structure for the receptor binding site.     

Beyond immune escape: a variant surface glycoprotein causes suramin resistance in Trypanosoma brucei

Suramin is one of the first drugs developed in a medicinal chemistry program (Bayer, 1916), and it is still the treatment of choice for the hemolymphatic stage of African sleeping sickness caused by Trypanosoma brucei rhodesiense. Cellular uptake of suramin occurs by endocytosis, and reverse genetic studies with T. b. brucei have linked downregulation of the endocytic pathway to suramin resistance. Here we show that forward selection for suramin resistance in T. brucei spp. cultures is fast, highly reproducible and linked to antigenic variation. Bloodstream‐form trypanosomes are covered by a dense coat of variant surface glycoprotein (VSG), which protects them from their mammalian hosts' immune defenses. Each T. brucei genome contains over 2000 different VSG genes, but only one is expressed at a time. An expression switch to one particular VSG, termed VSG^Sur, correlated with suramin resistance. Reintroduction of the originally expressed VSG gene in resistant T. brucei restored suramin susceptibility. This is the first report of a link between antigenic variation and drug resistance in African trypanosomes.     

A metabolic engineering strategy for producing free fatty acids by the Yarrowia lipolytica yeast based on impairment of glycerol metabolism

In recent years, bio‐based production of free fatty acids from renewable resources has attracted attention for their potential as precursors for the production of biofuels and biochemicals. In this study, the oleaginous yeast Yarrowia lipolytica was engineered to produce free fatty acids by eliminating glycerol metabolism. Free fatty acid production was monitored under lipogenic conditions with glycerol as a limiting factor. Firstly, the strain W29 (Δgpd1), which is deficient in glycerol synthesis, was obtained. However, W29 (Δgpd1) showed decreased biomass accumulation and glucose consumption in lipogenic medium containing a limiting supply of glycerol. Analysis of substrate utilization from a mixture of glucose and glycerol by the parental strain W29 revealed that glycerol was metabolized first and glucose utilization was suppressed. Thus, the Δgpd1Δgut2 double mutant, which is deficient also in glycerol catabolism, was constructed. In this genetic background, growth was repressed by glycerol. Oleate toxicity was observed in the Δgpd1Δgut2Δpex10 triple mutant strain which is deficient additionally in peroxisome biogenesis. Consequently, two consecutive rounds of selection of spontaneous mutants were performed. A mutant released from growth repression by glycerol was able to produce 136.8 mg L^?1 of free fatty acids in a test tube, whereas the wild type accumulated only 30.2 mg L^?1. Next, an isolated oleate‐resistant strain produced 382.8 mg L^?1 of free fatty acids. Finely, acyl‐CoA carboxylase gene (ACC1) over‐expression resulted to production of 1436.7 mg L^?1 of free fatty acids. The addition of dodecane promoted free fatty acid secretion and enhanced the level of free fatty acids up to 2033.8 mg L^?1 during test tube cultivation.

     

Determination of anti-AGE antibodies in human serum

The aim of this study was to develop an immunoenzyme method for the determination of anti-AGE antibodies in human serum. Human aortic elastin glycatedin vitro (AGE-elastin) was used as an antigen, expressing AGE-epitopes, common to all glycated proteins.Polyclonal serum from guinea-pig against AGE-Hemocyanin was obtained according to Nakayamaet al. [(1989)Biochem Biophys Res Commun 162: 740–45] and its specificity was tested via direct and competitive ELISA. Sera of 20 type 1 diabetic patients and 20 healthy subjects were tested using the method described. Seventeen patients had elevated levels of competing factors that may be anti-AGE antibodies, compared with the healthy group. The method could be used for investigation of different clinical groups of type 1 diabetic patients. Such a study would help in understanding the pathogenic role of autoantibodies against advanced glycation end products of proteins for the development of long-term diabetic complications.