Plasma chemistry of the sealed-off slab CO laser active medium pumped by radio-frequency discharge with liquid-nitrogen-cooled electrodes

The long-term time behavior of the output power of a sealed-off cryogenic slab CO laser pumped by a repetitively pulsed RF discharge and operating on the overtone (λ = 2.6–3.5 μm) vibrational?rotational transitions of the CO molecule was studied experimentally. It is shown that adding of an anomalously large amount of oxygen (up to 50% with respect to the CO concentration) to the initial gas mixture CO : He = 1 : 10 leads to a manyfold (by several tens of times) increase in the duration of the laser operating cycle (until lasing failure due to the degradation of the active medium). In this case, the laser life-time without replacement of the active medium reaches 10⁵–10⁶ pulses. Using various diagnostics (including luminescence spectroscopy and IR and UV absorption spectroscopy), regularities in the time-behavior of the concentrations of the main component of the active medium (CO molecules) and the products of plasmachemical reactions (O₃, CO₂) generated in the discharge gap during the laser operating cycle are revealed. Time correlation between the characteristics of the active medium and the laser output power are analyzed. A phenomenological approach to describing the entirety of plasmachemical, purely chemical, gas-dynamic, and diffusion processes determining the behavior of the laser output characteristics throughout the laser operating cycle is offered.     

A Serological Survey of Ruminant Livestock in Kazakhstan During Post-Soviet Transitions in Farming and Disease Control

The results of a serological survey of livestock in Kazakhstan, carried out in 1997–1998, are reported. Serum samples from 958 animals (cattle, sheep and goats) were tested for antibodies to foot and mouth disease (FMD), bluetongue (BT), epizootic haemorrhagic disease (EHD), rinderpest (RP) and peste des petits ruminants (PPR) viruses, and to Brucella spp. We also investigated the vaccination status of livestock and related this to changes in veterinary provision since independence in 1991. For the 2 diseases under official surveillance (FMD and brucellosis) our results were similar to official data, although we found significantly higher brucellosis levels in 2 districts and widespread ignorance about FMD vaccination status. The seroprevalence for BT virus was 23%, and seropositive animals were widespread suggesting endemicity, despite the disease not having being previously reported. We found a few seropositives for EHDV and PPRV, which may suggest that these diseases are also present in Kazakhstan. An hierarchical model showed that seroprevalence to FMD and BT viruses were clustered at the farm/village level, rather than at a larger spatial scale. This was unexpected for FMD, which is subject to vaccination policies which vary at the raion (county) level.     

Study of protein adsorption on indigo particles confirms the existence of enzyme--indigo interaction sites in cellulase molecules

Adsorption of several crude and purified cellulases (from Trichoderma reesei, Penicillium verruculosum and Chrysosporium lucknowense) on indigo particles and Avicel cellulose was studied. Much higher amounts of protein were bound to indigo than to cellulose under similar conditions. For different purified enzymes, the quantity of bound protein per mg of adsorbent (indigo or cellulose) varied in the range of 57-111 and 0-62 microg x mg(-1), respectively. However, in general, the enzyme adsorption on indigo was less specific than the adsorption on cellulose. Three endoglucanases, having the highest indigo-binding ability, demonstrated the best washing performance in the process of enzymatic denim treatment. These data confirmed our previous findings that certain cellulases, which have indigo-binding sites (clusters of closely located aromatic and other non-polar residues) on the surface of their molecules, may remove indigo from the denim fabric better than cellulases with lower content of hydrophobic residues exposed to solvent.     

Quantification of volume of tissue damage in stroke using T2- weighed MRI images

We have developed a quantitative technique for scoring of the severity of ischemic damage of the brain using quantitative data of the T2-weighted MRI images of brain in stroke. The principle of the method is the assumption that T2 signal increases proportionally to the severity of ischemic damage of cerebral tissue up to the level equal to intraventricular liquor signal in the case of postinfarction cystic degeneration. Depicting the mean T2-signal from the intraventricular liquor region as Iliq, the signal from ischemic brain area as Iinsult, and from the intact brain as Inorm, obviously, the volume quota of damaged tissue in the total volume of the stroke region is represented by the ratio (Iinsult - Inorm)/(Iliq - Inorm). The total volume of damaged tissue (VDT, cub.cm) in the stroke region is then the following sum taken over all slices i, where the stroke damage can be: VDT = sigma i d.Si.[(Iinsult - Inorm)/(Iliq - Inorm)]i, where d is the slice thickness, Si--area of the ischemic region in the slice i. The quota of damaged tissue in the physical volume of the stroke region is henceforth the following ratio: Q = [sigma i d.Si.[(Iinsult - Inorm)/(Iliq - Inorm)]i]/[sigma i d.Si]. The technique was applied in retrospective analysis of routine MRI studies in 15 patients referred because of acute ischemic stroke. The studies were performed using low-field MRI tomograph Magnetom-Open (Siemens Medical) with field strength 0.22 T. In patients studied during the first day after occurrence of ischemic insult with the minimal degree of acute neurologic deficit, who later have demonstrated clinically full recovery, the VDT was below 20 cm3, and Q was below 10%. In cases with VDT > 25 cm3 and Q > 20% the full regress was not observed in any patient. Henceforth, the quantification of cerebral damage in stroke using quantitative indices based on measurement of T2-parameters over ischemic and intact zones of the brain are of independent prognostic clinical value and improve clinical usefulness of the MRI in ischemic brain stroke.     

Functional interactions of the influenza virus glycoproteins

Hemagglutinin (HA) and neuraminidase (NA) are functionally related coat glycoproteins of the influenza virus (Flu). HA interacts with terminal sialyl residues of oligosaccharides and ensures the binding of the virus particle to the cell surface. NA is a receptor-destroying enzyme that removes sialyl residues from oligosaccharides contained in cell and virus components and thereby prevents aggregation of virus particles. Analysis of reasortants combining low-functional NA of human Flu with HA of avian Flu showed that sialyl residues are not completely removed in some cases. With high HA affinity for sialyl substrates, such virus particles aggregate, aggregates accumulate on the cell surface, and virus yield decreases. Serial passaging of low-yield aggregating reassortants may lead to selection of high-yield variants, which do not aggregate. A loss of aggregation is due to a decrease in HA affinity for high-molecular-weight sialyl substrates. On evidence of sequencing of the HA gene in original reassortants and their nonaggregating variants, HA affinity is reduced and aggregation lost owing to a mechanism common for different HA antigenic subtypes (H2, H3, H4, and H13). This is an increase in the negative charge as a result of an amino acid substitution in the vicinity of the receptor-binding pocket of HA. Taken together, these findings suggest a way of postreassortment adaptation which improves the functional match of HA and NA. The experimental system employed provides a model of natural processes associated with generation of Flu variants having a pandemic potential.     

Isolation and Properties of Major Components of Penicillium canescens Extracellular Enzyme Complex

The composition of the enzyme complex secreted by Penicillium canescens was investigated. A scheme for purification of the main components of the complex by chromatofocusing on a Mono P column was developed. It was found that along with beta-galactosidase, the major components of the complex were endo-beta-1,4-xylanase (31 kD, pI 8.2-9.3), alpha-L-arabinofuranosidase (60 kD, pI 7.6), arabinoxylan-arabinofuranohydrolase (70 kD, pI 3.8-4.0), and endo-beta-1,3/1,4-glucanase (40 kD, pI 4.4). The substrate specificity, pH and temperature activity optima, adsorbability, thermal stability, and ability for synergic interaction of the isolated enzymes were studied.     

Electrochemical assay of endo-depolymerase activity of cellulases

A method for determination of endo-1,4-beta-D-glucanase activity of cellulase samples based on the indirect measurement of decrease in viscosity of a carboxymethylcellulose solution in an electrochemical cell in the presence of an electron carrier was developed. A rotating disk electrode is used as the working electrode. When two reactions (enzymatic and electrochemical) proceeded in the cell simultaneously, the limiting diffusion current at a constant applied potential increases as the viscosity of the solution decreases. Conditions where the initial rate of change of diffusion current (dI/dt) is proportional to the enzyme concentration were found. A good correlation between the new method and a previously known viscometric method for determination of endoglucanase activity was observed.     

Patterns of cerebral blood flow reactivity in adenosine stress-test in patients with carotid stenosis evaluated with MRI and emission tomography with 99m Tc-HMPAO

In this study we evaluated the adenosine stress-test combined with 99mTc-HMPAO SPECT as a possible tool for evaluation of brain perfusion reserve in patients with various degrees of cortical neurologic damage due to internal carotid artery stenosis. The investigation comprised 37 patients with atherosclerotic carotid disease, in everybody of whom the stenosis was detected by echo-Doppler study of carotids and later in 28 verified also using invasive intraarterial digital subtractive angiography. In everybody the 99mTc-HMPAO SPECT study was performed twice: at rest and during stress-test with intravenous injection of adenosine with the patient in the supine position. It was gathered three groups of patients with different kinds of cerebral blood flow reactivity in adenosine stress-test. Henceforth, we conclude that, first, the 99mTc-HMPAO SPECT adenosin stress challenge of cerebral blood flow is a reliable functional test for every group of patients with extensive atherosclerosis and can be used for detection of patients with exhausted or decreased cerebral perfusion reserve in whom the risk of future cerebral vascular ischaemic events is elevated.