Function of the superior colliculi of the corpora quadrigemina during creation of a local focus of increased excitability in the mesencephalic reticular formation and sensomotor cortex

In chronic experiments on waking rabbits, the foci of heightened excitability in the sensorimotor cortex and mesencephalic reticular formation affected in a similar way the background neuronal activity in the superior colliculi and that evoked by light stimuli. The effect was manifested in elimination of inhibitory pauses in the neuronal response to light stimulus and in a general increase of discharge frequency. Similarity of the cortical and reticular influences is due to their possible mediation by the same collicular interneurones participating in inhibitory pauses formation in the process of backward inhibition. Increased neuronal activity in the superior colliculi under the action of local foci in the sensorimotor cortex and mesencephalic reticular formation correlated with appearance of forelimb motor reaction to isolated light stimulus testifying to a formation of a functional connection between the visual and motor analyzers. Possible role of the superior colliculi in this process and their participation in the formation of a visually controlled reaction is discussed.     

Differences between cellular mechanisms of ATP-and noradrenaline-induced inhibition of visceral smooth muscles under conditions of selective and combined activation of M<Subscript>2</Subscript> or M<Subscript>3</Subscript> cholinoreceptors

Our studies of the role of phospholipase C in inhibitory synaptic action upon visceral smooth muscles demonstrated that, under conditions of carbachol (CCh)-induced pre-activation of cholinoreceptors, ATP-or noradrenaline (NA)-evoked relaxation of these muscles is mediated by the phospholipase C-independent pathway, while the phospholipase C-dependent pathway does not manifest itself as a mechanism that determines the inhibitory effect of the above transmitters. Under conditions of pre-activation of muscarinic cholinoreceptors, ATP-and NA-induced relaxation is continued due to activation of inositol trisphosphate (InsP₃)-sensitive receptors despite the fact that the pathway of inhibition is phospholipase C-independent. This is confirmed by complete depression of the inhibitory effects of ATP and NA against the background of CCh-induced contraction after pre-incubation of the studied preparations together with 100 μM 2-APB, a blocker of InsP₃ receptors. Selective blockings of either M₂ or M₃ cholinoreceptors are accompanied by a complete loss of the ability of the above blocker of InsP₃ receptors (2-APB) to suppress ATP-and NA-induced contraction of smooth muscles in the state of CCh-induced contraction. It can be hypothesized that, under conditions of selective pre-activation of M₂ or M₃ cholinoreceptors, the mechanisms of intracellular signalling mediating the inhibition events are modified. The InsP₃-dependent pathway that determines both adrenergic and purinergic inhibition of smooth muscles is switched off, and the inhibitory action of neurotransmitters is realized under such conditions through the InsP₃-independent pathway. Therefore, in our study we first found differences between cellular mechanisms underlying ATP-and NA-induced inhibition of smooth muscles under conditions of selective activation of either M₂ or M₃ cholinoreceptors and the mechanisms underlying the relaxing action of inhibitory neurotransmitters under conditions of combined synergistic activation of cholinoreceptors of both the above-mentioned subtypes. Neirofiziologiya/Neurophysiology, Vol. 39, No. 1, pp. 22–31, January–February, 2007.     

Biosynthesis of Pectinase by Fungi of the Genera Bjerkanderaand Coriolusduring Solid-Phase Fermentation

Production of an extracellular pectinase by wood-rot fungi of the genus Bjerkanderaand Corioluswas studied. The active producersB. adusta40 and C. versicolor24 were selected. The dynamics of production of pectinase and effects of temperature, initial pH, humidity of the medium, and addition of nitrogen sources on the biosynthesis of pectinase were studied.     

Methods of using the antibody neutralization test in intestinal coli-infections]

Specificity and sensitivity of the antibody neutralization test intended for detection of the O-antigen of enteropathogenic escherichia were checked under experimental conditions. Only 3 strains of the Klebsiella genus proved to neutralize the antibodies to the enteropathogenic escherichia of the serological group O20:K84. In the rest of the cases a positive result was obtained only in homologous combinations. In comparative study of the microbial cultures of the infected feces on hard nutrient media by means of bacteriological and serological methods the latter was found to be more sensitive, capable of detecting the homologous O-antigen with the bacterial concentration of not less than 5-10(5) microbial cells per 1 ml.     

Oscillatory evoked potentials in the rabbit visual system during experimental retinal pathology induced by administration of monoiodoacetic acid

ERG and EP of the visual cortex (VC) and superior colliculus (SC) were investigated under experimental dystrophy of the retina induced by intravenous injection of monoiodoacetic acid in different doses. The relative resistance of the VC to the derangement of retinal function was established. It was manifested by less marked suppression of its EP as compared with ERG. Taking into consideration the selective projection to the SC of the rod system that was damaged to a greater degree under pathology in question, it is suggested that functional suppression of the SC might facilitate the conduction of visual information through the main retino-geniculo-cortical canal. This might be one of the factors of VC resistance to the impairment of retinal function. This assumption was confirmed in experiments with SC electrocoagulation in which one could observe the facilitation of EP formation of the contralateral VC.     

Biosynthesis of pectinase by fungi Bjerkandera and Coriolus by solid phase fermentation]

Production of an extracellular pectinase by wood-rot fungi of the genus Bjerkandera and Coriolus was studied. The active producers B. adusta 40 and C. versicolor 24 were selected. The dynamics of production of pectinase and effects of temperature, initial pH, humidity of the medium and addition of nitrogen sources on the biosynthesis of pectinase were studied.     

Formation of slow background activity in different parts of the visual analyzer following section of half the tectum mesencephali

Significant changes in the formation of electrical activity rhythms have been revealed in the lateral geniculate body, superior colliculus and visual cortex during section of one half of midbrain operculum in cats anesthetized with nembutal. It was determined that all changes in slow activity generation in the lateral geniculate body, superior colliculus are reflected in changes in the formation of electrical activity of the visual cortex. It is suggested that lateral geniculate body and superior colliculus may be involved in the generation of some electrical activity rhythms of the visual cortex.     

Lipid peroxidation in external and internal mitochondrial membranes during anoxia

Accumulation of lipid peroxidation (LPO) products was investigated in external and internal membranes of mitochondria with anoxia. The increase in LPO intensity in mitochondria membranes during hypoxia was shown to be more expressed in external membranes, with an active involvement of phospholipase A2 in the process revealed. Greater LPO intensity and lability of lysosomal membranes caused by contacts with mitochondria with anoxia have been established.     

Frequency of chromosome variants in human populations]

Chromosome variants were analyzed in the course of the population chromosome investigation of 6000 newborns and clinical cytogenetic studies of 403 married couples with recurrent spontaneous abortions, stillbirths or offsprings having congenital malformations or Down's syndrome. The following variants were determined: 1) Igh+, 9gh+, 16gh+ - the enlargement of the secondary constrictions of the size, more than 1/4 of the long arm of the chromosome; 2) Dp+ or Gp+ - the enlargement of the short arms of acrocentrics, their size being more than the short arm of the chromosome 18; 3) Ds+ or Gs - large satellites of the acrocentrics which are equal or more than the thickness of the chromatids of the long arms; 4) Es+ - satellites on the short arms of the chromosomes 17 or 18; 5) Dss of Gss - double satellites; 6) Yq+ - the enlargement of the long arm of Y chromosome, the size of which being more than G chromosome; 7) Yq- - deletion of the long arm of Y chromosome, the size of the long arm being less than chromosomes 21--22. The total frequency of variants in newborns was 12.8/1000 births. The incidence of different types of variants per 1000 births was as follows: Igh+ - 0.33; 9gh+ - 0.17; 16gh+ - 0.50; Ds+ - 2.33; Dp+ - 1.50; Dp- - 0.17; Gs+ - 0.83; Gp+ - 2.17; Yq+ - 6.91/1000 males; Yg- - 0.99/1000 males; double variants - 0.33; other variants - 0.33. 4.0% of married couples with recurrent spontaneous abortions had major chromosome aberrations, 14.6% - extreme variants of chromosomes. Among 113 couples with the history of congenital malformations in their offsprings major chromosome abnormalities were found in 4.4%, chromosome variants - 13.3%. The frequency of chromosome variants among 139 patients with Down's syndrome was 7.2%. In one case Robertsonian translocation t(DqGa) was determined. The most frequent types of variant chromosomes were Ds+, Dp+, Es+, Yq+.