Effect of ions on the dielectric relaxation of DNA

The dielectric relaxation of DNA solutions has been investigated with and without extraneous ions covering a wide frequency range. The effect of monovalent ions such as Na, K, and Li as well as divalent ions such as Mg, Ca, and Hg have been included in the study. These ions are found to have a profound effect on the dielectric increment and the relaxation time without affecting the molecular dimension drastically. This dielectric effect is interpreted as indicating the importance of counterion fluctuation on the low frequency dielectric constant of DNA in solution. The effect of an organic ion, tetra-methylammoniun bromide, has also been studied. This ion has no noticeable effect. A simple theory is derived on the basis of a microscopic model to account for the effect of external ions on the dielectric behavior of solutions of DNA.     

A morphological evaluation of the action of collagenase from the king crab Paralithodes camtschatica on the experimental wound process]

The paper presents the results of experimental morphological evaluation of the effect of a new proteolytic enzyme collagenase of crab Paralithodes camtschatica on wound healing in infected and aseptic rabbit wounds. The enzyme was applied on wounds using gauze and gelevin. The findings show that this protease is highly effective for debridement of infected wounds, the effect increasing at gelevin addition. To reach maximal therapeutical effect and diminish the inhibition effect of collagenase on granulation tissue, it is recommended to reduce the dose of protease during debridement process. Clinical application of crab collagenase must be individual as well as duration of wound enzymotherapy.     

Studies on the thermal insulation effect of the Korean women's folk clothes

The purpose of this study is to examine the basic data useful for more comfortable folk clothes of Korean women, with respect to their thermal insulation effect. The result of this study is summarized as follows, by comparing the calculated thermal insulation effect of Korean women's folk clothes with that of the western style clothes. 1. The thermal insulation effect of the Korean women's folk clothes showed that summer clothes accounted for 0.67-0.93 Clo, while spring and autumn clothes showed 1.09-1.20 Clo. 2. Air layer had more effect on the thermal insulation of the Korean women's folk clothes than one of their material properties. 3. The thermal insulation of the Korean women's folk clothes features higher effect in the lower part of the body as compared with one the western style clothes, which act as an important factor in the thermal insulation.     

The reflection of the simulated movement of a sound source in the evoked potentials of the inferior colliculus in the cat

EP series from the cat's inferior colliculus were recorded following binaural stimulation with click series imitating sound source movement due to variation of the interaural time delay (and thus evoking in man the sensation of the moving fused auditory image, FI). The "movement effect" was evaluated as the change in the EP amplitude during the series. The movement effect itself as well as its predominance under conditions of the ipsilateral FI movement as compared to those of the contralateral movement, proved to be connected with greater effectiveness of the contralateral stimulation relative the ipsilateral one.     

The Development of the Mental Representations of the Magnitude of Fractions

We investigated the development of the mental representation of the magnitude of fractions during the initial stages of fraction learning in grade 5, 6 and 7 children as well as in adults. We examined the activation of global fraction magnitude in a numerical comparison task and a matching task. There were global distance effects in the comparison task, but not in the matching task. This suggests that the activation of the global magnitude representation of fractions is not automatic in all tasks involving magnitude judgments. The slope of the global distance effect increased during early fraction learning and declined by adulthood, demonstrating that the development of the fraction global distance effect differs from that of the integer distance effect.     

NO-dependent pathway of the modifying of the cellular sensitivity to gamma- and neutron irradiation

The modifying effect of L-NAME, the NO-synthase inhibitor and D-NAME, the inactive enantiomer was investigated in human carcinoma cells (HeLa) and Chinese hamster fibroblasts (V-79) exposed to different doses of gamma-rays and 0.85 MeV neutrons. We estimated the level of the chromosome aberrations manifested as the bridges and fragments in anaphases. Radioprotective effect of L-NAME showed the inverse dependence on the exposure dose and at low doses (1 Gy) it was higher in the V-79 cells, than in the HeLa cells. However, at high doses (3, 4, 6 Gy) the efficiency of L-NAME for these cellular lines was almost equal (DFR = 2). The modifying effect of L-NAME was almost equal for gamma-irradiation and neutrons, although the exposure of V-79 cells to neutrons induced more the asymmetric chromosome aberrations (RBE = 4). The D-NAME had no effect on the level of the radiation-induced chromosome aberrations, although D-NAME treatment of cells increased the chromatin condensation, as well as L-NAME. The counteractive condensation does not play the major role in the radioprotective effect of L-NAME. We suggest that the radioprotective effect of L-NAME resulted from the action on the generation reactive radicals due to the inhibition of the inducible NO-synthase.     

The effect of the sterol oxygen function on the interaction with phospholipids

The effect of cholesteryl ethers (namely cholesteryl methyl ether, cholesteryl ethyl ether, cholesteryl n-propyl ether, cholesteryl isopropyl ether, cholesteryl butyl ether, cholesteryl methoxymethyl ether, cholesteryl (2'-hydroxy)-3-ethyl ether) and cholesteryl ester (namely cholesteryl acetate) is tested on the interaction with phosphatidylcholines in liquid-crystalline and crystalline state. The interfacial properties of sterols are tested at the air-water interface. The cholesteryl ethers show a reduced interfacial stability with increasing hydrophobicity of the ether-linked moiety. The interaction between the sterol derivatives and phospholipids in mixed monolayers is indicated by measuring the deviation from the simple addivity rule (condensing effect). An interaction is found only for cholesteryl (2'-hydroxy)-3-ethyl ether, cholesteryl methyl ether and cholesteryl ethyl ether. These sterols also reduce the glucose permeability of liposomal membranes in this order. In this respect cholesteryl (2'-hydroxy)-3-ethyl ether is as effective as cholesterol. Cholesteryl methyl ether and cholesteryl ethyl ether show 62 and 33 percent of the effect observed with cholesterol. The effect of the sterol derivatives on the gel-to-liquid-crystalline phase transition of dipalmitoylphosphatidylcholine is measured by differential scanning calorimetry. Cholesteryl methyl ether, cholesteryl ethyl ether, and cholesteryl (2'-hydroxy)-3-ethyl ether reduce the energy content of the phase transition nearly as effective as cholesterol, cholesteryl n-propyl ether has only a small effect. Although cholesteryl acetate, and cholesteryl methoxymethyl ether have no condensing or permeability-reducing effect, they have a considerable effect on the gel-to-liquid-crystalline phase transition. Cholesteryl isopropyl ether and cholesteryl butyl ether have no effect. It is concluded that a free 3 beta-hydroxy group is not a prerequisite to observe a sterol-like effect in membranes. However, the interfacial stability and the orientation of the sterol and oxygen moiety at the sterol 3-position are important.     

Effect of methionine-enkephalin on the spontaneous electrical and mechanical activity of the smooth muscle of the rat portal vein

In the longitudinal smooth muscle of the isolated rat portal vein, methionine-enkephalin (Met-enkephalin) increased the spontaneous contraction with a concentration as low as 10(-8)M. When the membrane activity was recorded using a microelectrode, Met-enkephalin enhanced the spike burst activity but without any effect on the resting membrane potential. Naloxone, phentolamine, atropine and reserpine pre-treatment did not inhibit the excitatory effect of Met-enkephalin on the spontaneous contraction. These results suggest that the excitatory effect of Met-enkephalin on the mechanisms involved in the automaticity may be a direct action on smooth muscle or relate to presynaptic action on a non-adrenergic non-cholinergic system.     

The impact of the bystander effect on the low-dose hypersensitivity phenomenon

The aim of this study was to investigate the possible relationship between the bystander effect and the low-dose hypersensitivity/increased radio-resistance phenomenon in BJ fibroblast cells taking as response criteria different end points of radiation damage such as cell survival, chromosomal damage (as detected by using micronucleus assay) and double strand breaks (DSBs) of the DNA. Although γ-H2AX foci were observed in confluent bystander BJ cells, our data suggest that X-irradiation does not lead to a significant rate of DSBs in bystander cells. Thus, neither bystander effect induced unstable chromosomal aberrations nor bystander effect induced DSBs are sufficiently pronounced to explain the apparent relationship between bystander effect and low-dose hypersensitivity. The experiments described here suggest that the hyper-radiosensitivity phenomenon might be related to bystander factor induced cell inactivation in the low-dose region (lower than 1 Gy).     

Effects of internal motions on the development of the two-dimensional transferred nuclear Overhauser effect

Summary In this paper we address the influence of internal motions on the development of the transferred nuclear Overhauser effect in a ligand undergoing chemical exchange between a free and a bound state. We examine the effects of varying the effective correlation time as well as the motional order parameter for methyl group and phenyl ring rotations in the free and bound ligand conformations. The effect of decreasing the motional order for a proton pair on a methyl group or phenyl ring is to decrease the effective correlation time of the internuclear vector, and thus to decrease the cross-relaxation rate between the proton pair. This functions to dampen the effects of spin diffusion, especially in the bound ligand- where cross-relaxation rates are much faster than in the free ligand. The effect of changing the effective correlation time for methyl group motions has little effect on the build-up behaviour of the transferred nuclear Overhauser effect for small values of fraction bound, but a larger effect on how fast it decays. This effect is greater for internal motions in the free peptide than it is for internal motions in the bound peptide.Dedicated to the memory of Professor V.F. Bystrov     

Propagule interactions and the evolution of virulence

The evolution of parasite virulence is thought to involve a trade‐off between parasite reproductive rate and the effect of increasing the number of propagules on host survivorship. Such a trade‐off should lead to selection for an intermediate level of within‐host reproduction (λ). Here I consider the effects of parasite propagule number on selection affecting λ when (i) the effect of each propagule is independent of propagule number, and (ii) when the effect of each propagule changes as a function of propagule number. Virulence evolves in these models as a correlated response to selection on λ. If each propagule has the same effect (s) as all previous propagules, the survivorship of infected hosts is reduced by more than 60% at equilibrium, independent of the value of s. If, instead, each propagule has a more negative effect on host survivorship than previous propagules, host survivorship at equilibrium is expected to increase as the effect becomes more pronounced. These results are directly parallel to results derived for population mean fitness at mutation‐selection balance; and they suggest that high virulence should be associated with parasites for which the effect of adding propagules either remains constant or diminishes with propagule number.     

Effect of freezing-thawing on the adenylate cyclase activity of the rat liver

Various regimes of freezing and thawing as well as adrenaline and fluoride ions are studied for their effect on the adenylate cyclase activity in liver tissue preparations. The reduction of basal and fluoride-stimulating adenylate cyclase activity and a decrease in the adrenaline-stimulating activity of the enzyme after freezing and thawing are shown. Freezing and thawing are studied for molecular mechanisms of their damaging effect on adenylate cyclase.     

Role of prostaglandins in the mechanism of the effect of cholecystokinin on the gallbladder

Secretion of prostaglandins (Pg) E and F2 alpha in bile in basic condition (without stimulation) and under stimulation with cholecystokinin (CCK) ("Boots", England, 1 unit/kg) in patients with fatty liver with normal (15) and hypokinetic (20) function of gallbladder by radioimmunoassay method was investigated. The mediator role of Pg F2 alpha in the realization of effect of CCK on the contractile function of gallbladder was found. It was concluded, that the disturbance of mediator effect of Pg F2 alpha in the hormone regulation of bile excretion may play an important role in the pathogenesis of biliary dyskinesia. This disturbance of mediator effect of Pg was connected with the reducing of concentration and debit Pg F2 alpha in bile, as well as with the slowing of maximal Pg excretion under stimulation with CCK.     

Dependence of the degree of synergism in the simultaneous action of UV light and hyperthermia on yeast cells on the intensity of the UV light

In experiments with wild-type diploid yeast cells of Saccharomyces cerevisiae it was shown that the definite temperature interval revealed the synergistic effect under simultaneous action of UV radiation and hyperthermia. The correlation between the degree of synergistic interaction and UV light intensity and irradiation temperature was estimated: the temperature interval synergistically enhancing the UV light effect was shifted towards higher temperatures as the UV light intensity was increasing, the optimal temperature to achieve the most synergistic effect existing for every intensity examined.     

Role of macrophytes in the variability of zooplankton community structure in the littoral zone of shallow lakes

Distribution, diurnal variability, aggregation of zooplankton in the littoral zone of lakes and effect of various macrophyte species on the structure of its community are considered. It is shown that the horizontal migrations of zooplankton, both direct and reverse ones, are caused mainly by the pressure of fish. The effect of predacious zooplankton is less important and is directed mainly at small-sized species. The intensity of horizontal migrations of zooplankton decreases with depth, while the effect of shore avoidance is observed for the large-sized zooplankton species and is caused not only by the pressure of fish but also by other factors, most likely abiotic. The problem of interaction between macrophytes and zooplankton cannot be reduced to the role of macrophytes as a refuge. Allelopathic properties of macrophytes, competitive relations between separate zooplankton species in macrophyte thickets, as well as the effect of predacious invertebrates associated with macrophytes on zooplankton remain unclear. The role of macrophytes as a factor causing changes in hydrodynamic processes in the littoral regions of lakes is also unknown.     

The effect of the osmolyte trimethylamine N-oxide on the stability of the prion protein at low pH

A study of the effect of trimethylamine N-oxide on the stability of two recombinant forms of the prion protein PrP, an ovine full-length and a human truncated form, is here reported. Both thermal denaturation and denaturation at room temperature were analyzed at pH values above and below the pKa of trimethylamine N-oxide, which is close to 4.7. Surprisingly, results showed that not only is trimethylamine N-oxide able to decrease PrP thermal stability at low pH but it also acts as a strong denaturant at room temperature. Likely, this destabilization is due to the capability of the cationic form of trimethylamine N-oxide to interact with the protein backbone as well as to weaken electrostatic interactions which are important for PrP fold. These results constitute the first experimental measurement of the effect of trimethylamine N-oxide on PrP stability and provide an unambiguous proof of the destabilizing effect of this osmolyte on PrP at low pH.     

Role of phosphate in the regulation of the Pasteur effect in Saccharomyces cerevisiae

The occurrence of the Pasteur effect in Saccharomyces cerevisiae in several conditions has been examined. In these conditions measurements of a series of metabolites potentially involved in the regulation of the effect were performed. These included, among others, adenine nucleotides, citrate, fructose 2,6-bisphosphate and phosphate. Only phosphate changed in a consistent way, increasing in anaerobiosis when the Pasteur effect occurred. It is concluded that, with the available data, only phosphate may be considered as a regulator of the Pasteur effect in this microorganism.     

Structure of heterotrophic plankton in the littoral zone of the plain reservoir under effect of hydrophilic birds

The eutrophic effect of products of vital activity of colonies of hydrophilic birds on the community of heterotrophic plankton in shallow parts of the plain reservoir is shown. The strongest effect of birds is observed in a protected part of the reservoir. Specific changes in some characteristics of zooplankton as distinct from the response to the anthropogenic effect are found.     

The effect of plastic restructuring of the local chemoexcitable zone in the somatic membrane of the PPa4 neuron of Helix lucorum on the excitability of neighboring chemo- and electrically excited zones

Rhythmic application of acetylcholine or serotonin to the local zone of somatic membrane was used to study the effect of extinction of RPa4 neuron depolarization in Helix lucorum on the excitability of adjacent chemo- and electroexcitable zone. It has been found that the extinction of response to iontophoretic application of acetylcholine to one somatic zone decreases the sensitivity of serotonin and cholinoreceptors in adjacent zones, as well as the excitability of electroexcitable membrane. The effect on the excitability of adjacent zones does not depend on the type of receptors activated rhythmically, as the extinction of RPa4 response to the repeated application of serotonin also reduces the sensitivity of adjacent cholinoreceptor zones. A cause of this effect may lie in modification of chemoreceptors and ionic channels, by intracellular regulatory systems that become activated by repeated stimulation.     

Studies on the effect of 2-hydroxy-5-nitrobenzyl bromide on the mechanism of insulin.

The effects of HNB were tested on the binding of insulin to fat cells and fat cell membranes as well as the responsiveness of fat cells to insulin. Although metabolism was found to be inhibited, the reagent was found to stimulate the binding of insulin. The stimulatory effect on insulin binding as well as inhibitory effect on metabolism was reversed by free tryptophan consumption of the reagent. The results are discussed relative to these findings.