[Physiological effects, mechanisms of action and application of lactulose].

The discovery of lactulose as a bifidogenic factor became the background for the appearance of the prebiotics concept. Currently, lactulose is the most studied in terms of medical use oligosaccharide with a high prebiotic index. The exact mechanisms of action of lactulose remain largely unknown despite a number of new researches based on modern methods of molecular biology, genetics, and bioinformatics. The aim of this review to summarize and analyze the actual information about biological activity, probable mechanisms of action, and possible uses of lactulose in human nutrition. Results. The structure of lactulose, methods for its determination and preparation are briefly described. Promising methods for producing lactulose include enzymatic synthesis from lactose using ß-galactosidase or epimerase. Information on the physiological effects of lactulose and the mechanisms of its action on the human organism is presented. The works confirming the ability of lactulose to stimulate the growth of bifidobacteria and to influence the metabolism of the intestinal microbiota are summarized. The results of studies of the ability of lactulose to have antitoxic and anticarcinogenic effects are presented. The mechanisms of the positive effect of the prebiotic on the absorption of minerals, increased absorption of Ca and Mg in the human organism are described. The effect of lactulose on immunity and the possibility of its use to reduce the glucose blood level in patients with type 2 diabetes mellitus are shown. The main directions of the use of lactulose in food production are systematized. The data confirming the possibility of using lactulose as a growth factor for probiotics, as well as a protective agent to increase the survival of some starter cultures, are presented. Brief information on the doses and forms of lactulose apply in medicine is presented. The dependence of the effects of lactulose on the dose, health condition and age of patients has been established. Conclusion. Perspective directions of lactulose using in combination with probiotics, other prebiotics, and as an encapsulating ingredient for vitamins and other functional nutrition ingredients are determined. In this regard, the study of lactulose interaction with the components of complex products is relevant.

Involving schoolchildren in radon surveys by means of the "RadonTest" online system.

A 'citizen science' approach was evaluated as an approach to organize an extensive radon survey to be representative of the population of either single regions or a whole country. The "RadonTest" online system allowed schoolchildren to undertake and record short-term radon tests in their homes. Measurements were carried out in Israel using charcoal in miniature flacons and simple detectors with high sensitivity. Among other things, the "RadonTest" online system implements an alternative principle of building a radon map, allowing the display of radon tests more clearly than the traditional approach, while ensuring the confidentiality of test participants. Examples of public radon maps are presented, and the first test results are discussed. A scientifically based approach for the effective identification of buildings with a high radon concentration, based on the principle of radon regulation, is proposed.

[HYBRID OSTEOCHONDRAL TRANSPLANTATION - A NEW METHOD FOR SURGICAL TREATMENT OF OSTEOCHONDRITIS DISSECANS OF THE KNEE JOINT].

Knee osteochondritis desiccans, or Koenig's disease, is commonly found in active young people engaged in manual labor, sports etc., i.e. socially active population. Today, we have a good number of surgical methods to treatment of this disorder; however, there is still much controversy about their application, and no single approach is considered to be the optimal one. Plus, high-quality biomaterials required for the intervention are sometimes unavailable. The analysis of the results of treatment of patients (spanning several years) proved urgency of the problem and highlighted the necessity to solve a number of related issues. This paper presents the optimal method for surgical correction of Koenig's disease - "hybrid osteochondral transplantation". Indications for surgical intervention are justified, the technique of the operation is described, recommendations are given based on the practical experience of the authors. An analysis of the use of this technique in 27 patients showed its high efficiency, which allows the authors to recommend it for widespread use in clinical practice.

The information content of a character under a Markov model of evolution.

The rate of evolutionary change associated with a character determines its utility for the reconstruction of phylogenetic history. For a given age of lineage splits, we examine the information content of a character to assess the magnitude and range of an optimal rate of substitution. On the one hand an optimal transition rate must provide sufficiently many character changes to distinguish subclades, whereas on the other hand changes must be sufficiently rare that reversals on a single branch (and hence homoplasy) are uncommon. In this study, we evolve binary characters over three tree topologies with fixed branch lengths, while varying transition rate as a parameter. We use the character state distribution obtained to measure the "information content" of a character given a transition rate. This is done with respect to several criteria-the probability of obtaining the correct tree using parsimony, the probability of infering the correct ancestral state, and Shannon-Weaver and Fisher information measures on the configuration of probability distributions. All of the information measures suggest the intuitive result of the existence of optimal rates for phylogeny reconstruction. This nonzero optimum is less pronounced if one conditions on there having been a change, in which case the parsimony-based results of minimum change being the most informative tends to hold.

Asymmetry of configuration space induced by unequal crossover: implications for a mathematical theory of evolutionary innovation.

Evolution can be regarded as the exploration of genetic or morphological state space by populations. In traditional models of population and quantitative genetics, the state space can be formally represented as a configuration space with clearly defined concepts of neighborhood and distance, defined by the action of variational operators such as mutation and/or recombination. In this paper, we describe a process where no genetic configuration space closure (and hence, no non-arbitrary notion of distance and neighborhood) exists. The process is gene duplication by means of unequal crossover, which we regard as an example of an "innovation" process that changes the state space of the system rather than exploring a closed state space. We assert that such processes are qualitatively distinct from representations of the adaptation process, which occur on regular configuration spaces.

The stability of symmetric solutions to polygenic models.

Analysis of multilocus evolution is usually intractable for more than n approximately 10 genes, because the frequencies of very large numbers of genotypes must be followed. An exact analysis of up to n approximately 100 loci is feasible for a symmetrical model, in which a set of unlinked loci segregate for two alleles (labeled "0" and "1") with interchangeable effects on fitness. All haploid genotypes with the same number of 1 alleles can then remain equally frequent. However, such a symmetrical solution may be unstable: for example, under stabilizing selection, populations tend to fix any one genotype which approaches the optimum. Here, we show how the 2(n)x2(n) stability matrix can be decomposed into a set of matrices, each no larger than nxn. This allows the stability of symmetrical solutions to be determined. We apply the method to stabilizing and disruptive selection in a single deme and to selection against heterozygotes in a linear cline.

The effect of epistasis on the structure of hybrid zones.

Within hybrid zones that are maintained by a balance between selection and dispersal, linkage disequilibrium is generated by the mixing of divergent populations. This linkage disequilibrium causes selection on each locus to act on all other loci, thereby steepening clines, and generating a barrier to gene flow. Diffusion models predict simple relations between the strength of linkage disequilibrium and the dispersal rate, sigma, and between the barrier to gene flow, B, and the reduction in mean fitness, W. The aim of this paper is to test the accuracy of these predictions by comparison with an exact deterministic model of unlinked loci (r = 0.5). Disruptive selection acts on the proportion of alleles from the parental populations (p,q): W = exp[-S(4pq)beta], such that the least fit genotype has fitness e-s. Where beta << 1, fitness is reduced for a wide range of intermediate genotypes; where beta >> 1, fitness is only reduced for those genotypes close to p = 0.5. Even with strong epistasis, linkage disequilibria are close to sigma 2p'ip'j/rij, where p'i, p'j are the gradients in allele frequency at loci i, j. The barrier to gene flow, which is reflected in the steepening of neutral clines, is given by [formula: see text] where r, the harmonic mean recombination rate between the neural and selected loci, is here 0.5. This is a close approximation for weak selection, but underestimates B for strong selection. The barrier is stronger for small beta, because hybrid fitness is then reduced over a wider range of p. The widths of the selected clines are harder to predict: though simple approximations are accurate for beta = 1, they become inaccurate for extreme beta because, then, fitness changes sharply with p. Estimates of gene number, made from neutral clines on the assumption that selection acts against heterozygotes, are accurate for weak selection when beta = 1; however, for strong selection, gene number is overestimated. For beta > 1, gene number is systematically overestimated and, conversely, when beta < 1, it is underestimated.

On the origin of species by means of assortative mating.

Assortative mating may split a population even in the absence of natural selection. Here, we study when this happens if mating depends on one or two quantitative traits. Not surprisingly, the modes of assortative mating that can cause sympatric speciation without selection are rather strict. However, some of them may occur in nature. Slow elimination of intermediate individuals caused by the gradual tightening of assortative mating, which evolves owing to relatively weak disruptive selection, provides the alternative scenario for sympatric speciation, in addition to fast elimination of intermediate individuals as a result of the direct action of strong disruptive selection under an invariant mode of assortative mating. Even when assortative mating alone cannot split an initially coherent population, it may be able to prevent the merging of species after their secondary contact.