Study of correlations in DNA sequences

We present a method for unified statistical analysis of short and long range correlations between various nucleotides in genomic DNA strands. The approach is based on the mutual study of Fourier structure factor spectra and pair correlation functions. The analysis of cross correlations in the different ranges of structural spectra permits identification of the main sources of correlations, namely, the coherent point mutations, coincident periodicities or large scale density variations. The technique for assessment of structural coupling between various genes in the genome is also described.     

Is the nitric oxide system involved in genetic hypertension in Dahl rats?

To address this issue, a series of genetic tests were carried out. Linkage studies showed that the inducible nitric oxide synthase (Nos2) locus cosegregated with blood pressure in three F2 populations originated from crosses of Dahl salt-sensitive (S) rats with rats of various normotensive strains. However, the brain nitric oxidase synthase (Nos1) and endothelial nitric oxide synthase (Nos3) loci did not cosegregate with blood pressure in five F2 populations. Thus, only Nos2, but not Nos1 and Nos3, was considered as a candidate gene for being a quantitative trait locus (QTL) for blood pressure in the S rat. To further test this hypothesis, congenic strains were constructed by substituting regions on Chromosome 10 of the S rat with the homologous regions of the Milan normotensive (MNS) rat. Results showed that the chromosome region including Nos2 did not contain a blood pressure QTL. In consequence, Nos2 per se is not supported as a candidate QTL capable of causing a blood pressure difference between the S and MNS rats. Nevertheless, the nitric oxide system appears to be involved secondarily in the regulation of blood pressure in the S rat, as evidenced by physiological data.     

Nonrandomness in protein sequences: evidence for a physically driven stage of evolution?

The sequences, or primary structures, of existing biopolymers--in particular, proteins--are believed to be a product of evolution. Are the sequences random? If not, what is the character of this nonrandomness? To explore the statistics of protein sequences, we use the idea of mapping the sequence onto the trajectory of a random walk, originally proposed by Peng et al. [Peng, C.-K., Buldyrev, S. V., Goldberger, A. L., Havlin, S., Sciortino, F., Simons, M. & Stanley, H. E. (1992) Nature (London) 356, 168-170] in their analysis of DNA sequences. Using three different mappings, corresponding to three basic physical interactions between amino acids, we found pronounced deviations from pure randomness, and these deviations seem directed toward minimization of the energy of the three-dimensional structure. We consider this result as evidence for a physically driven stage of evolution.     

Activation of KATP channels by Na/K pump in isolated cardiac myocytes and giant membrane patches

Strophanthidin inhibits KATP channels in 2,4-dinitrophenol-poisoned heart cells (). The current study shows that the Na/K pump interacts with KATP current (IK-ATP) via submembrane ATP depletion in isolated giant membrane patches and in nonpoisoned guinea pig cardiac cells in whole-cell configuration. IK-ATP was inhibited by ATP, glibenclamide, or intracellular Cs+. Na/K pump inactivation by substitution of cytoplasmic Na+ for Li+ or N-methylglucamine decreased both IK-ATP by 1/3 (1 mM ATP, zero calcium), and IC50 of ATP for IK-ATP (0.3 +/- 0.1 mM) by 2/5. The Na+/Li+ replacement had no effect on IK-ATP at low pump activity ([ATP] 相似文献   

Formation of High-Intensity Thermal- and Epithermal-Neutron Fields Using Small-Size Polyethylene Moderators

The results of studies of high-intensity thermal- and epithermal-neutron fields formed in fast nuclear reactors using small-size polyethylene moderators are presented. The characteristics of high-intensity neutron fields are compared to those of fields in large-size graphite moderators.     

Assessing the cariogenic potential of some infant formulas, milk and sugar solutions

A method has been developed for the estimation of the distribution coefficient (D), which considers the microspecies of a compound. D is calculated from the microscopic dissociation constants (microconstants), the partition coefficients of the microspecies, and the counterion concentration. A general equation for the calculation of D at a given pH is presented. The microconstants are calculated from the structure using Hammett and Taft equations. The partition coefficients of the ionic microspecies are predicted by empirical equations using the dissociation constants and the partition coefficient of the uncharged species, which are estimated from the structure by a Linear Free Energy Relationship method. The algorithm is implemented in a program module called PrologD.