Reticular inhibition of evoked potentials of the ventro-basal thalamus and somatosensory cortex of the rat brain

In rats immobilized with d-tubocurarine conditioning electrical stimulation (100/s, 300 ms) of the central grey matter, reticular formation of the midbrain and medulla depressed focal potentials in thalamic ventro-basal complex and somatosensory cortex evoked by electrical stimulation of the forelimb or medial meniscus. The average threshold current for conditioning stimulation of these structures was 70, 100 and 120 muA. A comparison of intensity and duration of evoked potentials depression (for two-fold threshold stimulation of the brain stem) is failed to detect any difference between the stimulated structures: immediately after conditioning stimulation the amplitude of the cortical evoked potentials and post-synaptic components of the evoked potentials in the ventro-basal complex were 50-60% less than control amplitude (p less than 0.01) the depression persisting for 0.5-1 s. The presynaptic component of the thalamic evoked potentials was depressed only after three five-fold threshold conditioning stimulation. The brain stem stimulation did not cause any facilitatory effect on focal potentials evoked by maximal and submaximal stimulation of the forelimb or medial lemniscus.     

Making magnesite roof refractories with additions of fused spinel

Conclusions The Nikitov Dolomite Combine has produced an industrial batch of magnesite — spinel roof products containing fused spinel in the batch. The experimental refractories have very high quality factors.Testing of these products in the roof of a large open-hearth furnace with intensive oxygen blow in the bath showed that their resistance is 19% higher than the resistance of roofs made from periclase — spinel brick in identical furnaces at the Krivoi Rog Metallurgical Factory (with a simultaneous increase in output of 3.1%)Translated from Ogneupory, No. 4, pp. 1–6, April, 1971.     

Biosynthesis of mitochondrial DNA. Is 8 S DNA an artifact?

Sucrose density gradient fractionation of isolated rat liver mitochondrial DNA ordinarily yields two peaks, one at 39 S, the other at 27 S. However, when these mitochondria are first incubated with a labeled DNA precursor, a labeled peak at about 8 S is also observed. Is this low molecular weight 8 S DNA merely an artifact of contamination or breakdown, or is it a functioning part of the mitochondrial genome? That it is not a nuclear contaminant is shown by: (a) the absence of nuclei or nuclear fragments in active mitochondrial preparations; (b) the insensitivity of 8 S DNA synthesis to treatment of mitochondria with DNase and RNase; (c) the ability of inner membrane preparations to synthesize this DNA; (d) the ability of atractyloside to inhibit incorporation of [3H]dATP into 8 S and 39 S or 27 S DNA equally; (e) the labeling of 8 S DNA (as well as 39 S and 27 S DNA) but not of nuclear DNA after the administration in vivo of [3H]thymidine. The evidence that 8 S DNA is not an artifact resulting from DNA breakdown during mitochondrial incubation or DNA isolation is as follows: (a) 8 S DNA can be isolated from unincubated mitochondrial; (b) 8 S DNA becomes labeled when labeled DNA precursors are administered in vivo; (c) 8 S DNA biosynthesis continues in the complete absence of labeled 39 S or 27 S DNA (whose synthesis is repressed by ethidium bromide), making it unlikely that 8 S DNA is formed from the breakdown of 39 S or 27 S DNA; (d) substitution of milder methods of DNA extraction does not decrease 8 S DNA labeling; moreover, the usual conditions of extraction, when applied to purified 39 S and 27 S DNA, do not generate 8 S DNA, nor does an additional mitochondrial washing cycle; (e) the specific radioactivity of 8 S DNA is higher than that of 39 S or 27 S DNA, making it improbable that the latter forms are precursors of 8 S DNA. Since 8 S DNA is double-stranded, it is not identical to the 7 S fragment of D loop DNA. The hypothesis that the artifactual nicking of those DNA molecules which contain opposing D loops leads to the release of double-stranded fragments was tested. The DNA which was released was predominantly (and probably completely) single-stranded. We conclude that 8 S DNA is probably not an artifact and studies are in progress on its function.     

Determination of static balance in a spiral spring manipulator

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 7, pp. 23–24, July, 1993.     

Computed tomographic angiography of the thoracic vessels: the method, initial experience and outlook for its use

The paper presents the data available in the literature on computed tomographic angiography and the first experience with it to study thoracic vessels. It details the principles of spiral computed tomography and CT angiography. Practical aspects of their implementation, as well as basic concepts are outlined. It is concluded that CT angiography is promising in studying thoracic vessels in various abnormalities.     

Age changes in cells in Streptococcus diacetilactis cultures

The activity of metabolism changed in the cultures of Streptococcus diacetilactis, strain Bogdan, with aging. The number of viable cells decreased as well as the ability to evolve oxygen, to produce C-4 compounds, and to react to pH changes by liberating acids upon alkalifying or neutral products upon acidifying. After the culture had been grown during 72 hours, 2,3-butyleneglycol was found in the cultural broth, and the number of viable cells was low. As was revealed by electron microscopy, the cells were intact during 48 hours; they started to disintegrate by 72 hours. After 120 hours all cells were disintegrated. First, the cells produced no more mesosomes, became less electron dense; then the cell wall was decomposed and the contents of the cell poured through disruptions in the cytoplasmic membrane.