A kinetic model of telomere shortening in infants and adults

We have previously demonstrated that telomeres shorten more rapidly in peripheral mononuclear cells (PBMC) of infants than in adults (Zeichner et al., Blood 93 (1999) 2824). Here we describe a mathematical model that allows quantification of telomere dynamics both in infants and in adults. In this model the dependence of the telomere dynamics on age is accounted by assuming proportionality between the body growth, as approximated by the Gompertz equation, and the increase in the number of PBMCs. The model also assumes the existence of two subpopulations of PBMC with significantly different rates of division. This assumption is based on the results from a previous analysis of in vitro data for telomere dynamics in presence of telomerase inhibitors and our recent data obtained by measurements of BrdU incorporation in T lymphocytes in humans (Kovacs et al., J. Exp. Med. 194 (2001) 1731). The average telomere length of PBMC was calculated as the average length of these two subpopulations. The model fitted our experimental data well and allowed to derive a characteristic time of conversion of the rapidly proliferating cells to slowly proliferating cells on the order of 20 days. The half-life of the slowly proliferating cells was estimated to be about 6 months, which is in good agreement with data obtained by independent methodologies. Comparison of the one-population and two-subpopulations models demonstrated that one population model cannot explain the observed parameters of the terminal restriction fragment (TRF) dynamics while two-subpopulations model does. These results suggest that the rapid telomere shortening in infants is largely determined by the faster PBMC turnover compared to adults. This may have major implications for elucidation of the HIV pathogenesis in infants. One can speculate that the more rapid course of the HIV disease in infants is due to the existence of rapidly dividing cells, which are susceptible to HIV infection. In addition, these results could have implications for understanding of mechanisms of aging.     

Determination of maximum permissible concentrations of industrial toxicants using the integral biochemical index

Effects of patented mixtures of substances, used as drilling fluids in petroleum industry, on the activity of enzymes (cathepsin D, EC 3.4.23.5; catalase, EC 1.11.1.6; and DNase, EC 3.1.4.6) and the content of analytes (malondialdehyde, fatty acids, free and collagen-associated hydroxyproline, bile acids, and total protein) in liver, gills, muscles, gonads, and bile have been studied under aquarium conditions in mature river flounder and one-year-old salmon for the purpose of determining maximum permissible concentrations. Measuring 25-30 independent biochemical parameters per organ is sufficient for establishing a direct relationship between the concentration of an industrial toxicant and the integral biochemical index, a new characteristic defined as the ratio of the number of biochemical parameters significantly deviating from control values to the total number of the parameters measured.     

Mechanism of spontaneous DNA-DNA interaction of homologous linear duplexes

Previously, we demonstrated the interaction of homologous linear duplexes with formation of four-way DNA structures on the model of five PCR products. We propose that homologous duplex interaction is initiated by the nucleation of several dissociated base pairs of the complementary ends of two fragments with Holliday junction formation, in which cross point migration occurs via spooling of DNA strands from one duplex to the other one, finally resulting in complete resolution into new or previously existing duplexes. To confirm that DNA-DNA interaction involves formation of four-way DNA structures with strand exchange at the cross point, we have demonstrated the strand exchange process between identical duplexes using homologous fragments, harboring either biotin label or (32)P-label. Incubation of the mixture resulted in the addition of (32)P-label to biotin-labeled fragments, and the intensity of (32)P-labeling of biotinylated fragments was dependent upon the incubation duration. DNA-DNA interaction is not based on surface-dependent denaturing, as Triton X-100 does not decrease the formation of complexes between DNA duplexes. The equilibrium concentration of Holliday junctions depends on the sequences of the fragment ends and the incubation temperature. The free energy of Holliday junction formation by the fragments with GC and AT ends differed by 0.6 kcal/mol. Electron microscopic analysis demonstrated that the majority of Holliday junctions harbor the cross point within a 300 base pair region of the fragment ends. This insight into the mechanism of homologous duplex interaction extends our understanding of different DNA rearrangements. Understanding of DNA-DNA interaction is of practical use for better interpretation and optimization of PCR-based analyses.     

Characteristics of the pKMR plasmids found in Shigella flexneri

The clinical isolate of Sh. flexneri 1b, resistant to 5 antibiotics and sulfonamides, has been studied by the method of conjugation and found to have a group of transfer-suppressed pKMR-plasmids: pKMR 204-1 (Ap Sm Tc Cm Km Su), pKMR 204-2 (Sm Km Su), pKMR 204-5 (Km Su) and pKMR 204-7 (Sm Tc Cm Km Su), whose molecular weight was 99, 71.2, 73.8 and 59.5 Md respectively. The treatment of the plasmids with restriction endonuclease BamHI has revealed that plasmids pKMR 204-2 and pKMR 204-5 are definitely related to plasmid KMR 204-1, being its deletion mutants. At the same time plasmids pKMR 204-1 and pKMR 204-7 differ in their sensitivity to endonuclease BamHI and stably coexist within the same cell, thus seeming to belong to different compatibility groups.     

Rabies prognosis in western Siberia and the regulatory factors of the epizootic process

In this article the regulatory factors of the epizootic process are considered and the spatial-temporal prognostication of rabies infection in the region is proposed on the basis of data on rabies morbidity among animals, the purchase of skins of carnivorous animals for 20-25 years, virological experiments on wild animals, calculation of the number of carnivores and small mammals, as meteorological observations. The study has shown that a variety of animal species serving as hosts for the virus and its population differences contribute to the stable existence of the infection. Rabies morbidity has been found to be positively linked with its preceding level, the number of wild animals, the height and hardness of the snow cover and negatively with the number of small mammals.     

Discovery of an essential nucleotidylating activity associated with a newly delineated conserved domain in the RNA polymerase-containing protein of all nidoviruses

RNA viruses encode an RNA-dependent RNA polymerase (RdRp) that catalyzes the synthesis of their RNA(s). In the case of positive-stranded RNA viruses belonging to the order Nidovirales, the RdRp resides in a replicase subunit that is unusually large. Bioinformatics analysis of this non-structural protein has now revealed a nidoviral signature domain (genetic marker) that is N-terminally adjacent to the RdRp and has no apparent homologs elsewhere. Based on its conservation profile, this domain is proposed to have nucleotidylation activity. We used recombinant non-structural protein 9 of the arterivirus equine arteritis virus (EAV) and different biochemical assays, including irreversible labeling with a GTP analog followed by a proteomics analysis, to demonstrate the manganese-dependent covalent binding of guanosine and uridine phosphates to a lysine/histidine residue. Most likely this was the invariant lysine of the newly identified domain, named nidovirus RdRp-associated nucleotidyltransferase (NiRAN), whose substitution with alanine severely diminished the described binding. Furthermore, this mutation crippled EAV and prevented the replication of severe acute respiratory syndrome coronavirus (SARS-CoV) in cell culture, indicating that NiRAN is essential for nidoviruses. Potential functions supported by NiRAN may include nucleic acid ligation, mRNA capping and protein-primed RNA synthesis, possibilities that remain to be explored in future studies.     

Obtainment and Characterization of Alhagi persarum Boiss. et Buhse Callus Cell Cultures that Produce Isoflavonoids

Applied Biochemistry and Microbiology - The physiological characteristics of callus cell cultures of Alhagi persarum Boiss et Buhse, a representative of the legume family widely used in folk...     

Formation of Starting Plasma Flow in an Open Trap Using Arc Plasma Gun

Plasma Physics Reports - The system is described for the formation of the low-temperature starting plasma flow in the GOL-NB trap. The starting plasma is a target for capturing heating neutral...     

Differential rotation of plasma in the GOL-3 multiple-mirror trap during injection of a relativistic electron beam

Results of spectral and magnetic diagnostics of plasma differential rotation in the GOL-3 multiplemirror trap are presented. It is shown that the maximum frequency of plasma rotation about the longitudinal axis reaches 0.5 MHz during the injection of a relativistic electron beam into the plasma. The data of two diagnostics agree if there is a region with a higher rotation frequency near the boundary of the electron beam. Plasma differential rotation can be an additional factor stabilizing interchange modes in the GOL-3 facility.     

New noninvasive methodology for real-time monitoring of lipid flip

A new methodology for the detection of lipid flip was developed. This methodology relies on the quenching of the fluorescence of the cascade-blue-labeled lipid through complex formation with a membrane-impermeable cyclen-tetranaphthalenethiourea synthetic receptor for this dye. The high affinity of the receptor to cascade-blue label allows the use of micromolar concentrations of this receptor during the experiment. At these low concentrations, the receptor does not interfere with the membrane integrity and, therefore, renders this new methodology less invasive to the model and cell membranes than commonly utilized 7-nitro-1,2,3-benzoxadiazol-4-yl (NBD)-dithionite methodology. Unlike with the NBD-dithionite assay, where the fluorescence quenching of the NBD group is achieved through its chemical modification, this new assay relies on the noncovalent interactions between cascade-blue label and the receptor. Therefore, the quenching can be reverted by either competitive displacement of the lipid-attached label with a water-soluble substrate or by enzymatic degradation of the receptor leading to the label release and fluorescence dequenching. We demonstrate that this new methodology is suitable for the study of lipid flip in both model spherical bilayer membranes and in-vitro experiments.