Determination of the structural integrity of DNA from pathogenic enterobacteria

Among the enterobacterial strains under study, more organisms in the stationary phase of growth have been found to have nicks in their DNA than those in the exponential phase. Bacteria less sensitive to ultraviolet irradiation have the least number of nicks in each phase of growth. The number of nicks in different strains belonging to the serovar is sufficiently stable. Virulent and avirulent forms show no difference in this characteristic.     

Decrease in the lower limit of the rat brain vital activity by the physiological method]

The brain temperature, at which the cessation of the lung respiration occurs in the cooled animals, can be named the lower temperature limit of the brain functional competence, since at this temperature the spontaneous respiration is not restored on its own, and without special artificial undertakings the animals perish. In this study upon the total cooling of the rat bodies their lung respiration stopped completely as the temperature of the medulla oblongata in the region of the respiratory center decreased to 18.18 +/- 0.17 degrees C. This occurred simultaneously with an abrupt decrease in the heart rate and in the arterial blood pressure (AP) to 42 +/- 1 mm Hg. Upon an isolated cooling of the rat head the heart rate and AP were maintained at a comparatively high level. Under such conditions the lung respiration did not stop even as the temperature of the medulla oblongata decreased to 17.23 +/- 0.25 degrees C. It retained rhythmicallity, a particular rate, and a comparatively high amplitude. It is suggested that an intensive blood supply of the cooled brain decreases the lower temperature limit of its vital activity.     

Fractionation of chromatin of liver cell nuclei after mild micrococcal nuclease digestion

Mild micrococcal nuclease treatment of rat and mouse nuclei and fractionation were based on the method of Tata and Baker. Three chromatin fractions, S, P1, P2, were separated, and for each of these fractions the sensitivity to the DNase 1 action was determined. The relative content in these fractions of non-transcribed DNA sequences was established by hydridization with a mouse satellite DNA, and the relative content of transcribed DNA sequences--by hydridization with DNA synthesised on the total poly (A) mRNA. None of the fractions displayed the properties characteristic of active chromatin.     

Effects of taurine and dipeptide Tyr-Tyr on ventricular defibrillation]

Results of the study of taurine and dipeptide Tyr-Tyr effect on the threshold values of functional lesions of the myocardium and heart defibrillation are reported. The experiments were carried out on 27 narcotized mongrel dogs weighing 12-30 kg. Defibrillation was performed using Lifepak-7 defibrillator (USA). Lesion threshold (LT), defibrillation threshold (DT) and electrotherapeutic index (ETI) as a LT:DT ratio were determined. In 14 experiments (control group) these parameters were evaluated during 3 h. In group 1 (6 experiments) taurine (100 mg/kg) was infused intravenously by the end of the 1st hour, in group 2--Tyr-Tyr (25 mg/kg). It was shown that infusion of taurine did not have a noticeable effect of the LT, DT and ETI values. Infusion of Tyr-Tyr resulted in an increase in LT and DT. The possibility to use dipeptide Tyr-Tyr in the complex of measures aimed at ceasing ventricular fibrillation is discussed.     

The Grundproblem in the Theory of Art

Ivanov's article presents background information and a methodological approach to Sergei Eisenstein's two-volume work on the method of art. Eisenstein himself considered film to be an art in which the basic problem of art is clearly visible. He argued that successfully combining regressive and progressive elements in art can solve the problem of form and content. The article demonstrates the personal cooperation that took place between Eisenstein, Marr, Luria, and Vygotsky at the beginning of 1930's.     

Spinoreticular neurons that receive group III input are inhibited by MLR stimulation.

In decerebrate paralyzed cats, we examined the responses of 18 spinoreticular neurons to electrical stimulation of the mesencephalic locomotor region. The activity of each of the spinoreticular neurons was recorded extracellularly from laminae IV through VI of the L(7) and S(1) spinal cord. In addition, each of the 18 spinoreticular neurons received group III afferent input from the tibial nerve. Spinoreticular projections were established for each of 18 neurons by antidromic invasion of the ventro lateral medulla at the P11 though P14 levels. The onset latencies and current thresholds for antidromic invasion from the ventro lateral medulla averaged 15.0 +/- 3.8 ms and 117 +/- 11 microA, respectively. Electrical stimulation of the mesencephalic locomotor region attenuated the spontaneous activity or the responses of each of the spinoreticular neurons to tibial nerve stimulation at currents that recruited group III afferents. Our data support the notion that thin-fiber muscle afferent input to the ventrolateral medulla is gated by a central command to exercise.     

Pattern of tonic activity in different groups of rabbit superior cervical ganglion neurons

Tonic activity in rabbit superior cervical ganglion neurons was investigated using intracellular recording techniques as well as changes produced when the animal breathed a gaseous mix with a raised CO₂ level. The test neurons were divided into three groups depending on the pattern of their tonic activity and reflex change. Action potentials were produced by the activity of dominant and accessory preganglionic inputs in the firing pattern of all neuronal groups, implying the existence of other types of inputs into the neurons innervating different organs. Having analyzed changes in action potential rate and EPSP in the tonic activity of neurons from different groups, it was presumed that preganglionic fibers with a similar activity pattern converge on the majority of neurons in each group.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 5, pp. 665–672, September–October, 1987.