Dynamics of functional interconnections between cerebral motor cortex neurons of cats under stimulation

In acute experiments on cats the activity of the motor cortex neurons was recorded. The dynamics of interneuronal connections at passive bending and electrostimulation of the limb contralateral to the place of recording was studied by methods of cross-correlation analysis of impulse trains. At passive bending a considerable decrease of the number of common inputs between neighbouring neurons (within 50-100 microns) and an increase in their number between remote (from 100 till 400 microns) cortical neurons. During electro-stimulation a certain increase in the number of direct inhibitory interactions between the neighbouring neurons was observed.     

Bioavailability of Soil-Bound TCDD: Dermal Bioavailability in the Rat

Bioavailability of Soil-Bound TCDD: Dermal Bioavailability inthe Rat. SHU, H., TEITELBAUM, T., WEBB, A. S., MARPLE, L., BRUNCK,B. DEI ROSSI, D., MURRAY, J., AND PAUSTENBACH, D. (1988). Fundam.Appl. Toxicol. 10, 335-343. 2,3,7,8-Tetrachlorodibenzo-p-dioxin(TCDD), an unwanted by-product formed during the manufactureof hexachlorophene and phenoxyherbicides, has been found asan environmental contaminant in many U.S. and Western Europeansites. This study examines in the rat the degree of dermal absorptionof TCDD bound to soil. Such information would assist regulatoryagencies in evaluating the degree of exposure of humans whocome in contact with TCDD-contaminated soil. Several parameterswhich may influence dermal absorption were studied, includingTCDD dose, duration of contact, presence of crankcase oil asa co-contaminant, and environmentally contaminated vs laboratory-preparedsoil. The dermal penetration of TCDD following 4 hr of contactwith skin was approximately 60% of that following 24 hr of contact(P 0.05). Following 24 hr of contact with the skin, the degreeof dermal uptake of TCDD contaminated soil was approximately1% of the administered dose. Under the conditions of the presentstudy, the degree of uptake does not appear to be influencedto any significant extent by the concentration of TCDD on soil,the presence of crankcase oil as co-contaminants, or by environmentallyvs laboratory-contaminated soil. Although a number of parametersexamined in this study did not significantly influence the degreeof dermal absorption of TCDD in the rat following 24 hr of contactwith the contaminated soil, the unqualified use of the 1% valueto estimate human exposure would overestimate human exposure,since there is general agreement among researchers that ratskin tends to be more permeable than human skin to highly lipid-solublecompounds such as TCDD.     

Comparative Analysis of the Frequency of Neuron Spike Activity in the Sensorimotor Cortex of the Right and Left Hemispheres in Conditions of Immobilization Catatonia in Rabbits

Multineuron activity was recorded from the sensorimotor cortex of the right and left hemispheres during immobilization catatonia in rabbits. The first session of immobilization of the animals was followed by changes in spike frequency in 47% of neurons in the sensorimotor cortex of the right hemisphere. Of these, 30% showed decreases in spike frequency and 17% showed increases. Spike frequency in the sensorimotor cortex of the left hemisphere changed in only 18% of cells, of which 13% showed decreases in spike frequency and 5% showed increases. The spike frequency of neighboring (recorded with the same electrode) neurons could change reciprocally. Differences in neuron activity in the two hemispheres were virtually absent after the second session of immobilization (several days after the first) – spike activity changed in 21% of neurons in the right hemisphere and 24% in the left hemisphere. The ratios of the numbers of neurons with increases and decreases in spike activity in hypnosis also became identical in the cortex of the right and left hemispheres. A hypothesis is proposed for the involvement of cortical neurons in the organization of hypnosis-like states.     

A method of analyzing of the “Dose-effect” dependence in multifactor medico-biological experiments

A conceptual-logical and mathematical approximation model has been created for the organism's response to external factors. The mathematical model of the “dose-effect” dependence for the combined effect of several factors is constructed using the basic equation of the Volterra mathematical theory of the struggle for existence. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 117, N ^o 3, pp. 328–331, March, 1994 Presented by L. A. Tiunov, Member of the Russian Academy of Medical Sciences     

Intergenerational instability of the CAG repeat of the gene for Machado- Joseph disease (MJD1) is affected by the genotype of the normal chromosome: implications for the molecular mechanisms of the instability of the CAG repeat

Machado-Joseph disease (MJD) is an autosomal dominant neurodegenerative disorder caused by unstable expansion of a CAG repeat in the MJD1 gene at 14q32.1. To identify elements affecting the intergenerational instability of the CAG repeat, we investigated whether the CGG/GGG polymorphism at the 3' end of the CAG repeat affects intergenerational instability of the CAG repeat. The [expanded (CAG)n-CGG]/[normal (CAG)n- GGG] haplotypes were found to result in significantly greater instability of the CAG repeat compared to the [expanded (CAG)n- CGG]/[normal (CAG)n-CGG] or [expanded (CAG)nGGG]/[normal (CAG)n-GGG] haplotypes. Multiple stepwise logistic regression analysis revealed that the relative risk for a large intergenerational change in the number of CAG repeat units (< -2 or > 2) is 7.7-fold (95% CI: 2.5-23.9) higher in the case of paternal transmission than in that of maternal transmission and 7.4-fold (95% CI: 2.4-23.3) higher in the case of transmission from a parent with the [expanded (CAG)n-CGG]/[normal (CAG)n-GGG] haplotypes than in that of transmission from a parent with the [expanded (CAG)n-CGG]/[normal (CAG)n-CGG] or [expanded (CAG)n- GGG]/[normal (CAG)n-GGG] haplotypes. The combination of paternal transmission and the [expanded (CAG)n-CGG]/[normal (CAG)n-GGG] haplotypes resulted in a 75.2-fold (95% CI: 9.0-625.0) increase in the relative risk compared with that of maternal transmission and the [expanded (CAG)n-CGG]/[normal (CAG)n-CGG] or [expanded (CAG)n- GGG]/[normal (CAG)n-GGG] haplotypes. The results suggest that an inter- allelic interaction is involved in the intergenerational instability of the expanded CAG repeat.      

Chromosomal aberrations and micronucleus frequency in nurses occupationally exposed to cytotoxic drugs

In this study, we evaluated the effect of low level occupationalexposure of nurses in a medical oncology unit in Cairo, Egypt,to anticancer drugs. Twenty nurses who constantly handled thesedrugs and 20 controls, matched according to age and sex, wereexamined. Metaphase chromosomes were studied. Percentages ofmetaphases with chromosomal aberrations were significantly higher(P < 0.001) in the exposed group (6.1 ± 2.7) versusthe controls (2.6 ± 1.6). The detected chromosomal aberrationswere in the form of chromatid gaps, chromatid breaks and acentricfragments. Micronucleated peripheral blood lymphocytes werealso analyzed in cytochalasin B treated binucleated lymphocytes.There was significant increase in cells with micronuclei (P< 0.001) in nurses (10.05 ± 4.71) in comparison tothe matched control (5.42 ± 2.22) (P < 0.001). Nursesexposed to the cytotoxic drugs for     

The mouse Mid1 gene: implications for the pathogenesis of Opitz syndrome and the evolution of the mammalian pseudoautosomal region

We have recently reported isolation of the gene responsible for X- linked Opitz G/BBB syndrome, a defect of midline development. MID1 is located on the distal short arm of the human X chromosome (Xp22. 3) and encodes a novel member of the B box family of zinc finger proteins. We have now cloned the murine homolog of MID1 and performed preliminary expression studies during development. Mid1 expression in undifferentiated cells in the central nervous, gastrointestinal and urogenital systems suggests that abnormal cell proliferation may underlie the defect in midline development characteristic of Opitz syndrome. We have also found that Mid1 is located within the mouse pseudoautosomal region (PAR) in Mus musculus , while it seems to be X- specific in Mus spretus. Therefore, Mid1 is likely to be a recent acquisition of the M. musculus PAR. Genetic and FISH analyses also demonstrated a high frequency of unequal crossovers in the murine PAR, creating spontaneous deletion/duplication events involving Mid1. These data provide evidence for the first time that genetic instability of the PAR may affect functionally important genes. In addition, we show that MID1 is the first example of a gene subject to X-inactivation in man while escaping it in mouse. These data contribute to a better understanding of the molecular content and evolution of the rodent PAR.