Dependence of efferent activity parameters on limb position during fictitious scratching in decerebrate cats

The influence of tonic afferent inflow as conditioned by ipsilateral hindlimb position on the efferent activity parameters of the spinal generator governing scratching motion was investigated in immobilized decerebrate cats. A significant correlation was observed between motor activity parameters and ensuing bouts of scratching in the absence of afferent flow (after deafferentation of the limbs). This correlation was less pronounced when afferentation remained intact and declined when the limb was shifted from the "aimed" to either the "overaimed" or "deflecting backwards" placing of the limb. The statistically significant correlations found between the parameters of different stages of motor activity and their dependence on hindlimb positions during actual scratching could be responsible for the stability of intended placing of the limbs during the performance of oscillatory movements. Hindlimb deafferentation would appear closest to "aimed" position judging by the parameters of efferent activity and the nature of correlations between them.A. A. Bogomolets Institute of Physiology. Academy of Sciences of the Ukrainian SSR. Kiev. Translated from Neirofiziologiya, Vol. 15, No. 5, pp. 636–645, September–October, 1986.     

Depolarization of primary afferents during fictitious scratching in thalamic cats

The dorsal cord and dorsal root potentials were recorded in immobilized thalamic cats during fictitious scratching evoked by mechanical stimulation of the ear. Depolarization of primary afferents was shown to be simulated by the central scratching generator. Antidromic spike discharges appeared at the peak of the primary afferent depolarization waves in certain afferent fibers. Similar discharges arise in the resting state in response to stimulation of limb mechanoreceptors. It is suggested that during real scratching primary afferent depolarization and antidromic spikes evoked by it may effectively modulate the level of the afferent flow to spinal neurons.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 2, pp. 173–176, March–April, 1978.     

Reorganization of segmental responses to peripheral stimulation during fictitious scratching in cats

Segmental reflex responses of the lumbosacral region of the spinal cord to stimulation of peripheral afferents were studied in immobilized decerebrate cats before and after application of D-tubocurarine or bicuculline to the superior cervical segments, potentiating the scratch reflex, and also during fictitious scratching evoked by mechanical stimulation of the ear. Application of these substances led to inhibition of the N₁-component of the dorsal cord potential, the dorsal root potential, and polysynaptic responses in efferent nerves. The appearance of fictitious scratching was accompanied by additional tonic inhibition of these responses, against the background of which modulation of the amplitudes of the responses was observed depending on the phase of fictitious scratching. Modulation of amplitudes of monosynaptic reflexes also developed during fictitious scratching. Against the background of these results the mechanisms and physiological role of reorganization of segmental responses during activation of the spinal scratching generator are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 2, pp. 196–203, March–April, 1981.     

Background activity of neurons of the dorsal spinocerebellar tract

We investigated background activity (BA) of neurons of the dorsal spinocerebellar tract (DSCT) during experimental limitation of the number of afferent inputs to these neurons. Complete unilateral deafferentation of the lumbar and sacral segments leads to total inhibition of the BA of most of the neurons of the DSCT, or to reduction of its frequency (not more than 4 impulses/sec) if it survives. With partial deafferentation of DSCT neurons, their BA can be divided into two types that differ with respect to interspike interval distribution (for type I >100 msec and >15 msec for type II <100 msec and <15 msec). It is hypothesized that the type of BA is mainly determined by the functional state of afferent inputs, viz., the presence or absence of activation of the neuron from afferents of group Ia. The presence of such activation leads to formation of BA of the second type. Analysis of the renewal density function and serial correlation coefficients reinforces the conclusion that BA of DSCT neurons is caused by their periodical activation from extension receptors, which receive considerably fewer regular synaptic influences from secondary afferent inputs and from interneurons. Following generation of an action potential in neurons of the DSCT there apparently develops an after subnormality, the accumulation of which at interspike intervals of less than 50 msec can lead to the appearance of negative serial correlation coefficients of the first order. When BA frequency is lower, serial correlation coefficients of the first order are positive.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 2, No. 1, pp. 26–34, January–February, 1970.     

Change in the hybridization characteristics of rapidly-labelled ribonucleic acids during tumor "progression"]

The hybridization properties of in vivo rapidly labeled with 14C-orotate both nuclear and mitochondrial ribonucleic acids from the MD hepatoma were investigated. During tumour progression the repression of nuclear genome found at its early stages (5th to 6th passages) is replaced by the increase of hybridizability of nuclear DNA with a population of 14C-RNA's as well as by the appearance of new classes of pulse labeled RNA's. In other words, at late stages of tumour progression (60th passage) there occur a de-repression of nuclear genome. The hybridizability of mitochondrial RNA with nuclear DNA remains almost the same at different tumour progression stages. The results obtained are discussed in the light of literature data available.     

Correlation between the kinematics of hindlimb movement and efferent activity in the decerebrate cat during scratching

The statistical relationship was investigated between temporal and amplitude parameters of scratching motion performed by the hindlimb and those of muscular activity during naturally-occurring scratching in the course of experiments on decerebrate cats. The factors mainly determining movement parameters, such as amplitude or the speed and duration of a specific phase were found to be the intensity of EMG activity displayed by scratching and aiming muscles and the duration of aiming muscle activity. Findings from experiments involving limb deafferentation showed that the statistical relationship between the parameters of motion and muscular electrical activity reflect certain patterns of scratch generator operation. Certain relationships linking parameters of electrical activity changed due to the effects of afferent signals.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 4, pp. 525–533, July–August.     

Significance of extracellular concentration of sodium ions in the protective effect during the "calcium paradox"]

Increasing of extracellular sodium concentration up to 200 mM diminishes heart damage under "calcium paradox". Phosphocreatine (10(-4) M) potentiates the effect of high sodium perfusion media; in this case myoglobin release from the myocardium is minimal (5-9% of control). An the same time, ATP and phosphocreatine concentrations and oxidation to phosphorylation coupling in mitochondria remain at a sufficiently high level. Elevation of osmotic pressure by the effect of 120 mM sucrose enhances heart damage under "calcium paradox" both in the presence and absence of phosphocreatine. The protective effects of superhigh (200 mM) sodium concentrations and phosphocreatine are completely reversed by strophanthin or decreasing K+ concentration down to 0.5 mM.     

Diffusion tensor tractography for the dorsal spinocerebellar tract in the human brain

Using diffusion tensor tractography, we attempted to investigate and identify the anatomy of the dorsal spinocerebellar tract (SCT) in the human brain. We recruited 26 healthy volunteers. The dorsal SCT was determined by selection of fibers passing through three regions of interest. We found that all dorsal SCTs terminated in the ipsilateral cerebellum; in contrast, in 25 (48%) of 52 hemispheres, the dorsal SCT crossed into the contralateral hemisphere via the vermis of the anterior lobe.     

Ornithine decarboxylase activity during neonatal development of the rat ventral prostate

The relationship between ornithine decarboxylase activity and growth has been examined in ventral prostates from rats aged 2–60 weeks. The incorporation of [¹²⁵I]iododeoxyuridine in vitro was used to assess DNA-synthetic activity. During 2–7 weeks post-partum ornithine decarboxylase activity/prostate and the protein content and wet weight increased exponentially. In contrast, the incorporation of [¹²⁵I]iododeoxyuridine/prostate fell during the first 4 weeks. This decline was reversed at about the time when the systemic concentrations of gonadal androgens start to rise. After 10 weeks post-partum the incorporation of [¹²⁵I]iododeoxyuridine/prostate and ornithine decarboxylase activity/prostate levelled off, whereas the DNA and protein content of the prostate contonued to increae at a slow rate.     

Site-specific mutagenesis in a homogeneous polyglutamine tract: application to spinocerebellar ataxin-3

In recent years, nine neurodegenerative diseases have been found to be caused by the expansion of a CAG-triplet repeat in the coding region of the respective genes, resulting in lengthening of an otherwise harmless polyglutamine tract in the gene products. To facilitate structural studies of these disease mechanisms, a general protocol is described that allows site-specific mutations to be introduced into the polyglutamine tract. Based on 'cassette mutagenesis', this protocol involves engineering unique restriction sites into the flanking regions of the CAG repeat and subsequently replacing the wild-type CAG repeat with a double-stranded synthetic DNA fragment containing the desired mutations. This method was applied to the spinocerebellar ataxin-3 protein, such that the wild-type amino acid sequence -Q(3)KQ(22)- was replaced by a -Q(9)CQ(9)- sequence. In this case, the incorporated cysteine residue can be exploited for various chemical modifications, lending the host glutamine repeat to many structural and biophysical techniques for the resolution of a specific residue. The method reported here bypasses many problems that can arise from PCR-based mutagenesis methods.     

Determination of levomycetin in the aerosol preparation, "Levovinysol"]

A spectrophotometric method for determination of levomycetin in "Levovinysol", an antiburn aerosol preparation was developed. The determination was performed after levomycetin extraction with a hydrochloric acid solution from the composition. The results of the determination were statistically treated.     

Schistosoma mansoni: proteinase activity of "hemoglobinase" from the digestive tract of adult worms

A method of collecting samples from the Schistosoma mansoni digestive tract was used to study proteinase activity. Activity against hemoglobin and a low molecular weight synthetic substrate, carbobenzoxy-arginyl-arginyl-7-amino-4-trifluoromethylcoumarin, was demonstrated in the soluble fraction of material regurgitated by S. mansoni adults and was dependent on the addition of a thiol compound, cysteine, to the assays. Using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration chromatography (AcA54), two proteins with estimated mol wt of 32,500 and 28,500 were found in the regurgitant and were associated with proteinase activity against both hemoglobin and the synthetic substrate. Homogenates of intact worms showed greater specific activity (synthetic substrate) in the females. Further, in bisected worms proteinase activity paralleled protein content, suggesting that, once secreted into the lumen, proteinase activity was distributed throughout the worm digestive tract.     

Experimental model of tooth mobility in the human "in vivo"]

The aim of the present study was to investigate experimentally the mechanical properties of tooth deflection under external loading. These properties have a significant impact on tooth movement during orthodontic treatment. The stresses and strains caused by tooth movement influence bone remodelling, which is the basis of orthodontic treatment. The movement of a tooth as a direct reaction to the forces acting on it is termed "initial" movement. It is nonlinear and has a clearly time-dependent component. While the initial tooth movement represents the totality of the reaction mechanisms of all the tissues of the tooth unit, it is determined primarily by the mechanical properties of the periodontal ligament (PDL). The PDL is the softest tissue of the tooth unit and is therefore subject to the largest deformations when forces act on the crown of the tooth. The objective of orthodontic treatment is to achieve as precise and rapid tooth movement as possible, without provoking such undesired effects as bone and root resorption. To enable the implementation of an optimal orthodontic force system that meets these requirements, a thorough knowledge of the biomechanics of tooth movement is a must.