[Properties of activated chromatin from rat liver shortly after partial hepatectomy]. / Svoistva aktivirovannogo khromatina iz pecheni krys v rannie sroki posle chastichnoi gepatéktomii.

The properties of rat liver chromatin 1, 2 and 6 hours after partial hepatectomy have been studied by means of cytochemical and biochemical methods. An increase in the accessibility of DNA to low molecular weight ligands, RNA--polymerase and RNAse I and also of the distances between nucleosomes and their heterogeneity in length on electron -- microscopic photographs has been found. Analysis of the isotherms of adsorption has revealed an increase in the number of binding sites for ethidium bromide on DNA and accordingly a decrease in the extent of the filling of the template with protein in activated chromatin. Two hours after partial hepatectomy rat liver chromatin does not differ in all parameters studied from control chromatin. Limited digestion of chromatin with DNAse I almost fully eliminates the difference between the fractions of activated and control chromatin in the number of binding sites for the ligands to the fractions resistent in these conditions to nuclease. A suggestion that the changes in the properties of chromatin upon activation are due to the change in the character of chromatin proteins interaction with DNA are discussed.

[Use of ethidium for the cytochemical study of chromatin]. / Ispol'zovanie étidiiia dlia tsitokhimicheskogo izucheniia khromatina.

A cytochemical method of chromatin study by means of nuclear staining with ethidium (bromide) is described. Dependence of stain binding by chromatin on ethidium concentration, ionic composition and buffer pH value has been analyzed. It is suggested that cells be stained in 2.10(-5) M solution of ethidium in 0.1 M tris-HCl buffer at pH 8.0 during 30 min. The fluorescence of nuclei stained with ethidium under conditions described is shown to reflect changes in physico-chemical properties of chromatin taking place in the course of its chemical modification and physiological activation in regenerating liver. The use of ethidium for chromatin cytochemistry allows to study chromatin properties in wide ranges of pH. Some other advantages of the method suggested over the commonly used method of acridine orange staining are discussed.

[Effect of low-intensity periodic-impulse laser UV radiation on the nucleic acid synthesis rate in proliferating and resting cells]. / Vliianie nizkointensivhnogo impul'sno-peridicheskogo lazernogo UF-izlucheniia na skorost' sinteza nukleinovykh kislot v proliferiruiushchikh i pokoiashchikhsia kletkakh.

A study was made of the effect of the low intensity (10(-6)--10(3)/cm3) high repetition rate (pulse duration 18 nseconds, repetition rate 10 KHz) UV radiation (2nd harmonic of Cu vapour laser, lambda = 271.2 nm) on proliferating and resting cells (HeLa and fibroblast-like cells of Chinese hamster 431). The treatment within the dose range from 0.05 to 5 J/m3 stimulates DNA synthesis in the resting cells rather than in the proliferating ones. It was shown autoradiographically that, within the same dose range, the number of synthesizing cells increased in 2.5 hour.

Increased susceptibility of activated rat liver chromatin to DNAse I.

Rat liver chromatin activated by partial hepatectomy is more susceptible to the action of DNAse I than control chromatin isolated from intact liver. The study on the transfer of chromatin material to the acid-soluble fraction reveals a higher rate of activated chromatin degradation. Activated chromatin shows also an increased capacity for ethidium bromide (EB) binding as estimated from the isotherms of adsorption. The difference in EB binding between activated and control chromatin is abolished after DNAse I treatment. Conditions of mild digestion with DNAse I have been found under which the number of binding sites for EB per nucleotide decreases to almost the same level in activated and non-activated chromatin. The results suggest a preferential degradation of those DNA sequences in activated chromatin that are responsible for the increase in the ligand binding.

Effects of He-Ne laser irradiation on chromatin properties and synthesis of nucleic acids in human peripheral blood lymphocytes.

Irradiation of human peripheral blood lymphocytes with an He-Ne laser (at 632.8 nm) at doses between 28 and 112 J m-2 caused changes in the chromatin during the first 6 h after exposure that were similar to those found after stimulation of the lymphocytes by phytohaemagglutinin (PHA), i.e. it increased chromatin accessibility to the low-molecular-mass ligand acridine orange (AO) and increased incorporation of the labelled RNA precursor [14C]uridine into the cells. The curves of AO-chromatin binding and RNA synthesis after either He-Ne irradiation with an He-Ne laser (56 J m-2) or PHA treatment were multipeak in nature. For the first 6 h after stimulation the curves for the two treatments were similar. After 7 h, the rate of RNA synthesis in laser-irradiated lymphocytes dropped to the control level, whereas in the PHA-stimulated cells [14C]uridine incorporation increased substantially. Unlike the case with PHA, treatment with an He-Ne laser did not induce resumption of DNA synthesis in lymphocytes. Lymphocytes irradiated by laser in the presence of interleukin-2 (IL-2) retained the level of labelled-thymidine incorporation characteristic of intact cells cultivated in the presence of IL-2. On the other hand, irradiation by an He-Ne laser produced a potentiating action on the response of peripheral blood lymphocytes to PHA, with thymidine incorporation being stimulated. This effect may explain the mechanism of wound healing by an He-Ne laser radiation: chromatin activation in the cells of wounds and ulcers makes these cells more responsive to the natural stimulators present in tissues.

[Changes in the structure of lymphocyte chromatin after irradiation with He-Ne-laser]. / Izmenenie struktury khromatina limfotsitov posle oblucheniia He-Ne-lazerom.

The cytofluorometric method was used to study changes occurring in the chromatin structure of lymphocytes during the first few hours following irradiation of lymphocytes with He-Ne-laser (lambda = 632.8 nm) of 28-112 J/m2. The changes were similar to those caused by PHA that is: the increase in acridine-orange binding to DNA during the first 45-90 min, its fall to the control level in 3-4 h and the subsequent increase.

Comparative properties of rat liver chromatin in situ and in vitro at early stages after partial hepatectomy.

The binding of acridine orange and ethidium bromide to rat liver chromatin increases by 30% one hour after partial hepatectomy, returns to the control level by the second hour and increases again by the sixth hour. The changes described were found in investigations carried out on whole cells, on isolated nuclei, and on chromatin preparation in vitro. Increased ligand binding disappears after the treatment of the one-hour chromatin with a 0.3 M NaCl solution, but such a treatment does not change the binding of ligands to chromatin obtained six hours after hepatectomy. The one-hour chromatin is characterized by elongation of distances between individual nucleosomes whereas the two-hour chromatin is the same as in control.

[Effect of He-Ne laser radiation on the chemiluminescence of mouse spleen cells]. / Vliianie izlucheniia He-Ne lazera na khemiliuminestsentsiiu kletok selezenki myshi.

A study was made of He-Ne laser radiation (lambda = 632.8 nm) on spontaneous chemiluminescence of mouse splenic cells and that stimulated by addition of Candida albicans. Irradiation with low-intensity red light was shown to stimulate cell chemiluminescence and to intensify that stimulated by C. albicans within the dose range from 100 to 300 J/m2 with a maximum at about 200 J/m2.