Effect of chitosan on tobacco mosaic virus(TMV) accumulation,hydrolase activity,and morphological abnormalities of the viral particles in leaves of N. tabacum L. cv. Samsun

The effect of chitosan on the development of infection caused by Tobacco mosaic virus(TMV) in leaves of Nicotiana tabacum L. cv. Samsun has been studied. It was shown that the infectivity and viral coat protein content in leaves inoculated with a mixture of TMV(2 μg/mL) and chitosan(1 mg/mL) were lower in the early period of infection(3 days after inoculation), by 63% and 66% respectively, than in leaves inoculated with TMV only. Treatment of leaves with chitosan 24 h before inoculation with TMV also caused the antiviral effects, but these were less apparent than when the virus and polysaccharide were applied simultaneously. The inhibitory effects of the agent decreased as the infection progressed. Inoculation of leaves with TMV together with chitosan considerably enhanced the activity of hydrolases(proteases, RNases) in the leaves, in comparison with leaves inoculated with TMV alone. Electron microscope assays of phosphotungstic acid(PTA)-stained suspensions from infected tobacco leaves showed that, in addition to the normal TMV particles(18 nm in diameter, 300 nm long), these suspensions contained abnormal(swollen, "thin" and "short") virions. The highest number of abnormal virions was found in suspensions from leaves inoculated with a mixture of TMV and chitosan. Immuno-electron microscopy showed that "thin" virus particles, in contrast to the particles of normal diameter, lost the ability to bind to specific antiserum. It seems that the chitosan-induced activation of hydrolases stimulates the intracellular degradation of TMV particles and hence hydrolase activation may be considered to be one of the polysaccharide-mediated cellular defense mechanisms that limit virus accumulation in cells.     

Recent history of Lake Ladoga

Combined paleolimnological investigations of a 1.8 m sediment core from the deepest north-western part of Lake Ladoga show stratigraphic changes in granulometric and chemical composition, organic matter content, diatom species composition and chlorophyll a concentration. The sediment accumulation rate was calculated and 5 stages of lake history over the last 4 000 years were described. Changes in lake environment were mainly caused by changes in climate and lake water balance. Human impact on the lake was also traced.     

The role of the lateral and medial hypothalamus in reproducing a motor reaction as the signal during the acquisition of classical conditioned reflexes]

In experiments on three dogs there was shown that testing electrostimulation of the lateral hypothalamus reproduced the motor reaction which is a signal stimulus at elaboration of classic alimentary conditioned reflexes (CRs) and did not reproduce it at elaboration of classic defensive CR. Testing electrostimulation of medial parts of the hypothalamus reproduced, as LH electrostimulation the "signal" motor reaction, but in less percentage of cases, during elaboration of classic alimentary CRs and did not reproduce it at elaboration of classic defensive CRs. The reproduction of the signal motor reaction at LH electrostimulation is connected with activation of backward conditioned connection from motivation structures of the hypothalamus to representation of the signal stimulus in the motor cortex.     

CD spectra of isoionic DNA solutions

The ion-exchange transition of Na-DNA----H-DNA in concentrated salt-free solutions is accompanied by strong variations in CD spectra. The rotational force of the negative band magnitude of delta epsilon 249 decreases when going to H-DNA by about 4 times, and the value of delta epsilon 279, by 1.2 times. These changes are irreversible to a considerable extent, which is evident because the spectra of Na-DNA obtained by neutralizing isoionic H-DNA solutions with NaOH or by the ion-exchange method significantly differ from those of Na-DNA taken by dissolving solid Na-DNA in deionized water. It has been shown that additions of NaCl to an isoionic solution of DNA leads to variations of spectra, typical for deprotonation processes as well as for an increase in DNA hydration.     

Colorimetric estimation of diamine oxidase activity.

A simple colorimetric method for estimation of DAO activity with 4-nitrobenzylamine as a substrate (9,10) was developed. Sensitivity of this method, based on conversion of the aldehyde formed in course of the enzymatic reaction into its 4-nitrophenylhydrazone with subsequent measuring of optical density at 590 nm in strongly alkaline medium, exceeded about 25-fold that of the conventional colorimetric procedure for estimation of DAO activity (14).Sensitivity of the spectrophotometric method for estimation of DAO activity with 4-dimethylaminomethylbenzylamine as a substrate (4) was increased about fivefold by conversion of the aldehyde formed in course of the enzymatic reaction into its 4-nitrophenylhydrazone with subsequent measuring of optical density at 530 nm in strongly alkaline medium.     

Functional changes in human leukemic cell line HL-60. A model for myeloid differentiation

Polar solvents induce terminal differentiation in the human promyelocytic leukemia cell line HL-60. The present studies describe the functional changes that accompany the morphologic progression from promyelocytes to bands and poly-morphonuclear leukocytes (PMN) over 9 d of culture in 1.3 percent dimethylsulfoxide (DMSO). As the HL-60 cells mature, the rate of O(2-) production increase 18-fold, with a progressive shortening of the lag time required for activation. Hexosemonophosphate shunt activity rises concomitantly. Ingestin of paraffin oil droplets opsonized with complement or Ig increases 10-fold over 9 d in DMSO. Latex ingestion per cell by each morphologic type does not change significantly, but total latex ingestion by groups of cells increases with the rise in the proportion of mature cells with greater ingestion capacities. Degranulation, as measured by release of β-glucuronidase, lysozyme, and peroxidase, reaches maximum after 3-6 d in DMSO, then declines. HL-60 cells contain no detectable lactoferrin, suggesting that their secondary granules are absent or defective. However, they kill staphylococci by day 6 in DMSO. Morphologically immature cells (days 1-3 in DMSO) are capable of O(2-) generation, hexosemonophosphate shunt activity, ingestion, degranulation, and bacterial killing. Maximal performance of each function by cells incubated in DMSO for longer periods of time is 50-100 percent that of normal PMN. DMSO- induced differentiation of HL-60 cells is a promising model for myeloid development.     

Carbon monoxide inhibits superoxide dismutase and stimulates reactive oxygen species production by Desulfovibrio desulfuricans 1388

The hypothesis that oxidative stress characterized by enhanced superoxide generation underlies the toxicity of some factors to living organisms has been investigated. It is shown that CO (5-6% in gas phase) changed some growth parameters (mu, t(d)) of the sulfate-reducing bacterium Desulfovibrio desulfuricans 1388. Enhanced O(2)(-) generation registered by EPR spectroscopy and adrenochrome method was observed when cells were incubated under CO. The SOD activity in cells from the exponential growth phase growing under CO was decreased 1.5-fold compared with the control cells growing under Ar. SOD activities in cells from the stationary growth phase growing with or without CO were comparable. The results support the concept that CO toxicity for sulfate-reducing bacteria is an oxidative stress that arises in cells oxidizing CO to CO(2).     

Significance of initial emotional state for neuroimmunomodulation under conditions of activation or blockade of 5-HT1A receptors

Selective agonist of 5-HT1A receptors--8-OH-DPAT (1 mg/kg) induced a suppression of the immune reaction in aggressive male CBA mice immunized with SRBC (5 x 10(8)). In submissive mice with 10-day defeat experience in confrontation tests, the activation of 5-HT1A receptors with 8-OH-DPAT did not alter the immune response, whereas the application of selective antagonist of 5-HT1A receptors WAY-100635 increased the immune reaction only in submissive mice. It is concluded that activation or blockade of 5-HT1A receptors produced different effects on the immune function of CBA mice depending on the initial emotional state which is known to be provided in aggressive and submissive animals by different activities of the brain neurotransmitter systems including the 5-HTergic system.     

A study of the effect of irradiation hardness on the properties of the fluoropolymeric matrix modified by polyanionic biologically active substances

The properties of a synthetic substrate responsible for the behavior of substrate-dependent cells in the culture were studied. The effect of the composition of a system water-soluble biopolymer (sodium alginate or methyl cellulose)-synthetic latex SKF-26 and the effect of various types of radiations on its biophysical properties were studied. The results obtained indicate that the addition of water-soluble biopolymeric additives to synthetic polymeric films improves the adhesion of cells to the substrate, the adhesion being closely related to the concentration of additives. It was found that the modification methods that determine changes in the charge of the substrate affect the capacity of different cell types for adhesion and proliferation. It was also found that the hardness of irradiation does not affect the vapor permeability and the extent of film swelling.     

Attention and the detectability of weak taste stimuli

Subjects detected weak solutions of sucrose or citric acid under conditions in which attention was directed toward one of the tastants or the other. Detection thresholds were measured using an adaptive, forced-choice procedure, with a three-down one-up rule, which computer simulations suggest should be more reliable than the popular two-down one-up rule. The thresholds were modestly but systematically lower for attended tastants than for unattended ones. Similar results have been reported in other sense modalities, including vision (greater sensitivity to stimuli presented to attended versus unattended spatial locations) and hearing (greater sensitivity to stimuli presented at attended versus unattended sound frequencies). Taken together, the findings are consistent with a general hypothesis regarding attention in sensory systems: gains or losses in detectability occur when a central attentional mechanism (or, conceivably, a preattentive mechanism) selectively and preferentially monitors signals arising from particular subsets of peripheral neural inputs.