Study of Current Sheets in Three-Dimensional Magnetic Fields with an X-Line by Holographic Interferometry

Results are presented from experimental studies of the spatial electron density distribution in current sheets formed in three-dimensional magnetic configurations with X-lines. The electron density is measured by using two-exposure holographic interferometry. It is shown that plasma sheets can form in a magnetic configuration with an X-line in the presence of a sufficiently strong longitudinal magnetic-field component B_∥ when the electric current is excited along the X-line. As the longitudinal magnetic-field component increases, the electron density decreases and the plasma sheet thickness increases; i.e., the plasma is compressed into a sheet less efficiently.     

Genetic Control of Chromosome Synapsis at Meiosis in Rye Secale cereale L.: The sy19 Gene Controlling Heterologous Synapsis

Analysis of manifestation and inheritance of a new mutation inducing irregular synapsis in rye showed that abnormal phenotype is determined by a recessive allele of the sy19 gene. In the homozygotes for this mutation, even at the light microscopic level, abnormal formation of bivalents is already observed at pachytene–diakinesis. At metaphase I, the univalent frequency varies from 0 to 14; in a few cells, multivalent associations of chromosomes, which are not clearly oriented in the spindle, are detected. Electron microscopy of synaptonemal complexes revealed both homologous and heterologous synapsis in homozygotes for sy19, namely partial loss of the ability to stringent homology search. Analysis of joint inheritance of sy19 and asynaptic sy1 mutations showed that they are nonallelic, inherited independently, and interact by recessive epistasis. The phenotype of doublesy1sy19 mutants indicates that thesy19 gene conditioning heterologous synapsis operates at meiosis later than the synaptic gene sy1. The epistatic group of mutations, sy9 > sy1 > sy19 and sy3, was determined.     

Morphological characteristics of changes in the skeletal muscle tissue of the extremities after experimental post-ischemic recirculation

The canine ischemic muscle tissue was subjected to a comprehensive morphological study after the recovery of the blood flow in the limbs for 2 hours. The effectiveness of of the recovery of the blood flow after the 3-hour ischemia was supported in acute experimental occlusion of the artery. The blood flow recovery after 6 hours of ischemia was associated with appreciable structural and metabolic abnormalities in the skeletal muscle fibers. These abnormalities were more demonstrable during recirculation after 9 and 12 hours of ischemia. No morphological criteria that might indicate whether the ischemic damage to the skeletal muscle is reversible or irreversible were defined. A comprehensive morphological study with an assay of structural and metabolic alterations is required instead.     

Etiology of acute bronchitis in adults

A total of 126 adult patients with acute bronchitis were subjected to microbiological, virological and immunological examination. Influenza and other acute respiratory viral infections were detected in 104 (82.5%) cases of acute bronchitis. The results of microbiological examination and the study of local and systemic immunity showed that in 94.4 +/- 2.6% of the patients the development of acute bronchitis was linked with the appearance of acute pneumococcal infection irrespective of the presence, or absence, of virologically and serologically confirmed acute viral or mycoplasmal infections.     

Dynamics of functional reciprocal connections between cerebral motor cortex neurons under stimulation in cats

Activity was recorded from neurons belonging to the representation of the forelimb in the motor cortex (sulcus cruciatus, L 7–9 mm) using multiple multi-channel/barrel electrodes during acute experiments on cats. Cross-correlation analysis of impulse trains was adopted to investigate dynamics of interneuronal connections during passive flexion and electrical stimulation of the limb contralateral to the recording site. It was found that neither passive bending nor electrical stimulation of the limb leads to a significant increase in the total number of direct relationships between cortical neurons. At the same time, passive flexion does produce a considerable decrease in the number of instances of both inputs operating in neighboring neurons (50–100 µm apart) and an increase in cells located further (between 100 and 400 µm) apart. Some increase in the number of direct inhibitory interactions between neighboring neurons was observed during electrical stimulation.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Nentskii Institute of Experimental Biology, Warsaw, Poland. Center of Experimental and Clinical Medicine, Warsaw, Poland. Translated from Neirofiziologiya, Vol. 23, No. 1, pp. 73–80, January–February, 1991.     

The action of ultrasound on the contraction strength and action potential of the papillary muscle of the rat heart

In experiments on isolated rat papillary muscles the effects of therapeutic doses of ultrasound (US) (intensity, less than 2 W/cm2) with frequency of 0.88 MHz on contraction force and action potential (AP) were studied. 12 muscles (from 14) responded to 3-min exposition of the US with a rise both in contraction force and in resting tension. Sensitivity to US and a value of inotropic effect changed significantly between the preparation, and the threshold intensities of US varied from 0.3 to 2 W/cm2. In 3 experiments the inotropic effect of US was more than 100%, but in others it was about 50%. Two preparations were not sensitive to the US. The positive inotropic effect of US was accompanied by membrane depolarization (up to 20 mV) and by prolongation of AP duration measured at 10% of its amplitude (APD10). The correlation between the increase in contraction force and APD10 was demonstrated. Some preparations responded to US with high depolarization (up to 50 mV) and were inexcitable. The US induced an increase in temperature less than 1 degree C, therefore all the effects of US could not be explained as a result of temperature rise.     

Taxonomic Interpretation of Allopatric Mammalian Forms on the Example of Two Karyoforms of <Emphasis Type="Italic">Microtus (Terricola) subterraneus</Emphasis> (Rodentia,Arvicolinae) from Eastern Europe

New European pine vole records from the Novgorod, Kaluga, Voronezh, and Belgorod oblasts were studied by sequencing of the mtDNA cytb gene (1143 bp) and by karyotyping (routine staining and G-banding techniques). The results enabled us to summarize chromosome variability of this species throughout Eastern Europe. In the sample studied, two geographically replacing chromosomal forms have been identified: northern, 2n = 54 (Novgorod and Kaluga oblasts), and southern, 2n = 52 (Voronezh and, presumably, Belgorod oblasts). Our data make the boundaries of these two karyoforms in Eastern Europe more precise and testify to intraspecific level of their taxonomic differentiation.