Complex investigation of the thermal and electrophysical properties of refractory oxides in the liquid and solid phases

Results of an experimental investigation of the enthalpy and specific electrical conductivity of aluminum and scandium oxides in the 1570–3100°K range and also of the heats of fusion of these oxides are presented.This issue of the journal contains papers presented to the Organizing Committee of the Sixth All-Union Conference on Thermophysical Properties of Substances. Information about the conference was published in Inzh.-Fiz. Zh.,36, No. 5 (1979).Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 38, No. 4, pp. 581–586, April, 1980.     

Evidence for plasmid-associated crystal toxin production in Bacillus thuringiensis subsp. israelensis

Three crystalliferous (Cry+) strains of Bacillus thuringiensis subsp. israelensis (serotype 14) that produce parasporal protein crystals toxic to dipteran larvae and several acrystalliferous (Cry-) mutants, either induced or spontaneously derived from a single Cry+ parent, were examined for the presence of covalently closed circular (CCC) DNA in attempts to correlate toxin production with the presence of a specific plasmid. The plasmid profiles of both Cry+ and Cry- variants were analyzed by both a cleared lysate- and a modified Eckhardt lysate-electrophoresis technique. All of the Cry- mutants derived from the Cry+ parental strain had lost a 4.0- to 4.4-megadalton (Mdal) plasmid. Bioassay data confirmed loss of toxin production by the Cry- variants. All three Cry+ strains, including the parent of the Cry- strains, contained CCC plasmids DNAs of the following approximate molecular weights: 4.0 to 4.4, 5.2 to 6.0, and 11.4 to 13.0 Mdal. One Cry+ strain contained an additional CCC plasmid of 6.7 to 7.2 Mdal. The plasmid patterns for several Cry- derivatives differed in other respects from the pattern for their parent strain. The various Cry+ and Cry- strains could be distinguished either by phenotypical differences in antibiotic sensitivity, crystal production, and toxicity, or by differences in their plasmid profiles.     

Muscle fiber composition and blood ammonia levels after intense exercise in humans

The relationship between fiber type composition and the increase in blood ammonia was examined following a maximal O2 consumption (VO2max) test. Muscle biopsies were taken from the middle portion of the vastus lateralis for determination of fiber type percentages. Two subject groups were selected on the basis of a high (HST) or low (LST) percentage of slow-twitch fibers and compared for blood ammonia and lactate levels after exercise at work loads of approximately 85 and 110% of VO2max. An inverse relationship was found between the percentage of slow-twitch fibers and the increase in blood ammonia. Blood ammonia increased after exercise at both 85 and 110% of VO2max. However, the increase was twofold greater for the LST group following the 110% work effort. The increases in blood ammonia and lactate were positively correlated for both groups following exercise. The results suggest that the proportion of slow-twitch fibers plays an important role in determining the magnitude of the increase in blood ammonia after intense exercise.     

庆大霉素/α半水硫酸钙载药体系的体外释药研究

对硫酸庆大霉素/α半水硫酸钙载药体系进行了模拟条件下体外释药研究，并对其晶体结构进行了分析。X-射线衍射分析结果表明，载药体系中一定含量的硫酸庆大霉素不会影响α半水硫酸钙的水化；模拟条件下体外释药研究表明，各种药物含量的载药体系均表现出了良好的缓释性能，持续释放时间超过了360h；随着试样中载药量的增加，其药物释放速率加快；另外，构制了均一分散和核壳结构两种载药体系，研究结果表明，均一分散型在前期释放速度要大于核壳结构型，而后期核壳结构型则比均一分散型要高。     

The effect of hypertonic ointments on corneal alkali burns

Alkali-burned rabbit corneas were treated with 40% glucose or 5% sodium chloride ophthalmic ointments 3 times daily for 6 weeks and examined clinically and histologically. Treatment with hypertonic ointment as compared to untreated controls demonstrated decreased corneal neovascularization and ulceration. The possible nutritional advantage of hypertonic glucose did not prove beneficial compared to hypertonic sodium chloride.     

Cholinergic responsiveness of neurons in the ventroposterior thalamus of the anesthetized rat

Acetylcholine has been implicated as an important neurotransmitter in the mechanisms of thalamic activation. Cholinergic mechanisms are thought to directly underlie the high level of excitability observed in thalamic relay neurons during waking and rapid eye movement sleep. We sought to determine if the cholinergic responsiveness of neurons in the ventroposterior nuclei of the thalamus in rat is consistent with this view. Neurons in the chloral hydrate-anesthetized rat were studied with extracellular recording and microiontophoretic application of cholinergic agents. In most cases (63% of 63 cells), the ejection of the agonist, carbachol, had no observable effect on spontaneous activity. Facilitation (25%), inhibition (8%) and inhibition followed by facilitation (3%) were also observed. Carbachol ejections that by themselves were ineffective in altering spontaneous activity proved capable, in 93% of 28 cells, of antagonizing the uniformly facilitatory responses produced by glutamate ejection. The putative M1-selective, cholinergic agonist, McN-A-343, was also ineffective alone in altering spontaneous activity in the majority of cases (74% of 27 cells) and produced only inhibitory responses in the remaining seven neurons studied. Interacting applications of McN-A-343 and glutamate resulted, in all cases, in antagonism of glutamate facilitation (N = 12). The various responses to applied cholinergic agonists were all capable of being antagonized by muscarinic receptor-blocking agents. Both the high proportion of inhibitory responses and the antagonism of glutamate facilitatory responses suggest that ventroposterior neurons in the rat differ from other thalamocortical relay neurons in the rat and cat with regard to cholinergic responsiveness. Additionally, the lack of predominantly facilitatory responding renders it unlikely that cholinergic mechanisms directly underlie increases in excitability of ventroposterior neurons observed during waking and rapid eye movement sleep.