An alternate carbon source for enhancing production of polysaccharides by Silene vulgaris callus

Pectin termed silenan and acidic arabinogalactan were isolated as cell-wall polysaccharides of Silene vulgaris callus in the presence of various carbon sources as components of the media. The maximum yields, productivity per litre of medium and production per day of acidic arabinogalactan, were achieved using glucose or galactose as the carbon source. Sucrose was found to increase the production of the polysaccharides. Yields, productivity and rate of production of arabinogalactan per day were decreased in the presence of arabinose. Yields of silenan, productivity and rate of production per day were closely related irrespective of the sugar used as the carbon source in the media (sucrose, glucose or galactose) and yields of silenan from the callus growing on arabinose were comparable. A concentration of sucrose in the 20-50 g/L range enhanced the biosynthesis of silenan and at 50 g/L the silenan contained the linear backbone and the ramified regions of the macromolecule.     

N-(2-Carboxyethyl)chitosans: regioselective synthesis,characterisation and protolytic equilibria

N-(2-Carboxyethyl)chitosans were obtained by reaction of low molecular weight chitosan with a low degree of acetylation and 3-halopropionic acids under mild alkaline media (pH 8-9, NaHCO3) at 60 degrees C. The chemical structure of the derivatives obtained was determined by 1H and 13C NMR spectroscopies. It was found that alkylation of chitosan by 3-halopropionic acids proceeds exclusively at the amino groups. The products obtained are described in terms of their degrees of carboxyethylation and ratio of mono-, di-substitution and free amine content. The protonation constants of amino and carboxylate groups of a series of N-(2-carboxyethyl)chitosans were determined by pH-titration at ionic strength 0.1 M KNO3 and 25 degrees C.     

Na2CO3 influence on DNA double helix stability: strong anion destabilizing effect

Addition of Na(2)CO(3) to almost salt-free DNA solution (5.10(-5)M EDTA, pH=5.7, T(m)=26.5 degrees C) elevates both pH and the DNA melting temperature (T(m)) if Na(2)CO(3) concentration is less than 0.004 M. For 0.004 M Na(2)CO(3), T(m)=58 degrees C is maximal and pH=10.56. Further increase in concentration gives rise to a monotonous decrease in T(m) to 37 degrees C for 1M Na(2)CO(3) (pH=10.57). Increase in pH is also not monotonous. The highest pH=10.87 is reached at 0.04 M Na(2)CO(3) (T(m)=48.3 degrees C). To reveal the cause of this DNA destabilization, which happens in a narrow pH interval (10.56/10.87) and a wide Na(2)CO(3) concentration interval (0.004/1M), a procedure has been developed for determining the separate influences on T(m) of Na(+), pH, and anions formed by Na(2)CO(3) (HCO(3)(-) and CO(3)(2-)). Comparison of influence of anions formed by Na(2)CO(3) on DNA stability with Cl(-) (anion inert to DNA stability), ClO(4)(-) (strong DNA destabilizing "chaotropic" anion) and OH(-) has been carried out. It has been shown that only Na(+) and pH influence T(m) in Na(2)CO(3) solution at concentrations lower than 0.001 M. However, the T(m) decrease with concentration for [Na(2)CO(3)]>/=0.004 M is only partly caused by high pH=10.7. Na(2)CO(3) anions also exert a strong destabilizing influence at these concentrations. For 0.1M Na(2)CO(3) (pH=10.84, [Na(+)]=0.2M, T(m)=42.7 degrees C), the anion destabilizing effect is higher 20 degrees C. For NaClO(4) (ClO(4)(-) is a strong "chaotropic" anion), an equal anion effect occurs at much higher concentrations approximately 3M. This means that Na(2)CO(3) gives rise to a much stronger anion effect than other salts. The effect is pH dependent. It decreases fivefold at neutral pH after addition of HCl to 0.1M Na(2)CO(3) as well as after addition of NaOH for pH greater than 11.2.     

Morphometric analysis of the degree of aggregation of follicular cells in the diagnosis of malignant thyroid tumors

OBJECTIVE: To develop a system of decision criteria based on a set of features of the degree of thyrocyte aggregation with assessment of their weighting coefficient in the diagnosis of malignant and benign thyroid pathology. STUDY DESIGN: Autopsy, operative and aspiration biopsy material were the object of the study. Light microscopic morphometry was performed with semiautomated computer analysis of images. RESULTS: Of all the sets of features of the degree of thyrocyte aggregation, 10 were chosen that provided the least overlap between the groups of malignant and benign pathology. Boundary values of these features to discriminate between malignant and benign pathology were assembled into a set of diagnostic decision criteria for thyroid carcinoma diagnosis. Based on results from trials, an equation for the calculation of a weighting coefficient for each feature was derived. A diagnostic index was determined by the sum of values of weighting coefficients of the features within the range of values listed in the set of diagnostic decision criteria. CONCLUSION: A set of diagnostic decision criteria was developed for thyroid carcinoma diagnosis that is based on morphometric features reflecting the regularities of changes in the structure of thyrocyte aggregates with malignant and benign pathology. Weighting coefficients of features were assessed, making it possible to perform a probabilistic carcinoma diagnosis.     

Construction of stochastic context trees for genetic texts

A method has been developed for constructing a tree source model for genetic text generation. Model visualisation in the form of suffix (context) trees provides a new way of context analysis of symbol sequences. Estimation of the stochastic complexity of the data in the frame of the model serves as a criterion for the model's ascertainment. The model and complexity values are used for analysis of genetic texts. The software realisation of this algorithm enables to reveal statistical properties of genetic sequences based on an information measure. The program developed is available via Internet at http://wwwmgs.bionet.nsc.ru/mgs/programs/complexity/.     

GeneNet database: description and modeling of gene networks

Almost all cellular processes in an organism are controlled by gene networks. Here we report on the analysis of gene networks functioning using two associated methods - data accumulation in GeneNet system and generalized chemical kinetic method for mathematical simulation of gene network functional dynamics. The technology of the usage of these methods is shown on the example of the gene network of macrophage activation.     

Characteristic thermodependence of the RadA recombinase from the hyperthermophilic archaeon Desulfurococcus amylolyticus

The Desulfurococcus amylolyticus RadA protein (RadA(Da)) promotes recombination at temperatures approaching the DNA melting point. Here, analyzing ATPase of the RadA(Da) presynaptic complex, we described other distinguishing characteristics of RadA(Da). These include sensitivity to NaCl, preference for lengthy single-stranded DNA as a cofactor, protein activity at temperatures of over 100 degrees C, and bimodal ATPase activity. These characteristics suggest that RadA(Da) is a founding member of a new class of archaeal recombinases.     

Different combinations of gap repressors for common stripes in Anopheles and Drosophila embryos

Drosophila segmentation is governed by a well-defined gene regulation network. The evolution of this network was investigated by examining the expression profiles of a complete set of segmentation genes in the early embryos of the mosquito, Anopheles gambiae. There are numerous differences in the expression profiles as compared with Drosophila. The germline determinant Oskar is expressed in both the anterior and posterior poles of Anopheles embryos but is strictly localized within the posterior plasm of Drosophila. The gap genes hunchback and giant display inverted patterns of expression in posterior regions of Anopheles embryos, while tailless exhibits an expanded pattern as compared with Drosophila. These observations suggest that the segmentation network has undergone considerable evolutionary change in the dipterans and that similar patterns of pair-rule gene expression can be obtained with different combinations of gap repressors. We discuss the evolution of separate stripe enhancers in the eve loci of different dipterans.