[Monomelic amyotrophy]. / Monomelicheskaya amiotrofiya.

Monomelic amyotrophy, also known as Hirayama disease, is a rare neurological disorder characterized by focal and latent onset of upper limb weakness and atrophy in the absence of sensory deficits, bulbar or pyramidal signs. It usually occurs in young patients. The disease usually begins unnoticeably and progresses slowly, and can manifest itself as unilateral or asymmetrical weakness, as well as atrophy of the distal upper limb. Sensory disturbances, reflex changes and signs of lesions of lower motor neurons are rare. This article describes a case of a patient with complaints of weakness not only in the upper but also in the lower extremities.

Morphofunctional Changes in the Spinal Cord of Rats after Contusion Injury with Local Delivery of Methylprednisolone in Combination with a Copolymer.

We studied the neuroprotective effect of local application of methylprednisolone in combination with a block copolymer after contusion spinal cord injury in rats. Histological analysis of the spinal cord showed that delivery of a complex of methylprednisolone with a block copolymer reduced the volume of white and gray matter lesions. An increase in the amplitude of the evoked response of the gastrocnemius muscle was observed during epidural stimulation of the spinal cord 6 h after the injury. The maximum amplitude of the muscle response was greater in the group with local delivery of the methylprednisolone complex with the polymer 72 h after the injury. The obtained results demonstrate the neuroprotective effect of the local administration of the complex and allow to make positive prognosis for the recovery of the sensorimotor functions in rats.

Motor function disturbances: contralateral effects.

Electromyography methods were employed to examine the mechanisms underlying changes in the functional state of the contralateral neuromotor apparatus of rat gastrocnemius muscle during unilateral limitation of the hind leg motor function. Elimination of one hind leg from the total pattern of motor activity affected the state of contralateral neuromotor apparatus via changing the properties of motoneurons in the corresponding spinal motor center resulting mostly from activation of the bilaterally acting spinal mechanism.

Spinal neurons bursting in phase with fictive scratching are not related to spontaneous cord dorsum potentials.

Spontaneous cord dorsum potentials (spontaneous CDPs) are produced by the activation of dorsal horn neurons distributed along the L4 to S1 spinal cord segments, in Rexed's laminae III-VI, in the same region in which there are interneurons rhythmically bursting during fictive scratching in cats. An interesting observation is that spontaneous CDPs are not rhythmically superimposed on the sinusoidal CDPs generated during fictive scratching episodes, thus suggesting that the interneurons producing both types of CDPs belong to different spinal circuits. In order to provide experimental data to support this hypothesis, we recorded unitary activity of neurons in the L6 spinal cord segment. We found that the neurons firing rhythmically during the sinusoidal CDPs associated with the extensor, flexor or intermediate phases of scratching were not synchronized with the spontaneous CDPs. Moreover, we found that the neurons firing during the spontaneous CDPs were not synchronized with the sinusoidal CDPs. These results suggest that the neurons involved in the occurrence of spontaneous CDPs are not part of the spinal cord central pattern generators (CPGs). This study will be relevant for understanding the relationships between the spinal cord neuronal populations firing spontaneously and the CPGs, in the intact and injured spinal cord.

[Effect of vibrostimulation of foot and supporting afferentation on functional state of shin muscles in rats during hindlimb unloading].

The goal of this work was to study the influence of daily 3-hr vibrostimulation of the supporting zones of the foot and 3-hr of usual locomotion on the functional state of the soleus, gastrocnemius, and tibial anterior muscles in rats after 7 and 14 days of hindlimb unloading. After 7 days of unloading the soleus weight decreased, while the weight of gastrocnemius and tibial anterior remained unchanged. After 14 days of hindlimb unloading a weight reduction was observed in all studied muscles. Vibrostimulation of the foot and supporting afferentation prevented the loss of weight in gastrocnemius and tibial anterior during the first week of unloading and reduced the negative effect of hindlimb unloading in 14 days. Our results demonstrate that the amplitude of the M-response after 7 days of hindlimb unloading was decreased predominantly in soleus as compared to gastrocnemius and tibial anterior. By the 14 day we observed restoration of the amplitude of the M-response in gastrocnemius and tibial anterior, and the increased amplitude of the M-response in soleus. Different techniques for foot stimulation in rats during hindlimb unloading demonstrated the positive effect in regard to M-response restoration--the amplitude of the M-response was increased in all studied muscles. Thus, our results demonstrate that foot vibrostimulation or supporting afferentation can completely prevent atrophy caused by hindlimb unloading in gastrocnemius and tibial anterior and decrease atrophy in soleus in rats.

[Effect of local hypothermia on H- and M-responses after spinal cord contusion in dogs].

In this study we investigated a motor-neuronal functional state based on H- and M-responses from m. quadratus plantae in dogs before and after experimental spinal cord contusion with and without following local intraoperative hypothermia. H- and M-responses from m. quadratus plantae were recorded during stimulation of the tibial nerve and results were compared between the groups. Our results demonstrate that local hypothermia applied after spinal cord contusion reduces amplitude of both M- and H-responses and also H(max)/M(max) ratio that may indicate depression of motorneurons excitability. After spinal cord contusion without following hypothermia the excitability of the spinal motorneurons during post-traumatic period, in opposite, was significantly increased. These results support a conclusion that intraoperative hypothermia after spinal cord contusion can delay development of functional excitability of the motoneurons and protect from further changes in H- and M-responses.

[The state of the contralateral motor center of the rat gastrocnemius muscle after unilateral damage of sciatic nerve].

Effects of unilateral damage of the rat sciatic nerve on the spinal motor centre of contralateral gastrocnemius muscle were investigated. The state of contralateral gastrocnemius muscle centre was assessed using the method of paired monosynaptic testings and posttetanic potentiation of reflex response on days 1, 5 and 10 after nerve damage. The obtained data indicate changes in reflex activity of contralateral motor centre in these conditions. The activation of contralateral reflex systems after nerve damage seems to provide regenerative reorganisation of the motor control in the conditions of traumatic influence.

[Effect of vibrostimulation on support zones of rat's feet, and support loading on titin N2A-isoform and T2-fragment in m. soleus under the conditions of simulated microgravity].

Effects of daily 3-hr vibrostimulation of foot support zone and 3 hrs. of usual locomotion on titin N2A-isoform and proteolytic T2-fragment were studied in m. soleus of rats during 7-d suspension. Besides, effects of single one-hour support loading following 7-d weight-deprivation on titin N2A- and T2-forms were also evaluated in the muscle. Relative N2A content in m. soleus of the suspended group was noted to reduce approximately 25% as compared with the group of control. In the meantime, relative T2 content grew 2-3 times. Along with other changes in the muscle apparatus, N2A reduction contributes to the decline of m. soleus contractility in suspended rats, and development of the "hypogravity muscular syndrome" The daily 3-hr vibrostimulation of the foot support zones substantially (almost twice) decreased N2A disintegration with parallel reduction in approximately 1.5 times relative T2 content comparing with the Suspension group. Three hours of locomotion a day during suspension did not appear to decrease the relative N2A content in m. soleus. However, in this group of animals the relative T2 content in m. soleus was twice as high as in the control. Single-time presentation of support load for one hour soon after 7-d suspension resulted in more significant (approximately 30%) reduction in relative N2A content and twofold fall of relative T2 content as compared with m. soleus of the rats in group Suspension. These data attest to the leading role of support stimulation in maintaining the structural and functional properties of the musculoskeletal system, specifically the titin N2A-isoform content in m. soleus of rat deprived of gravitational loading. Besides, it was also shown that tracking changes in titin makes possible to follow the course of hypogravitational muscle syndrome and to evaluate effectiveness of preventive methods.

The state of the contralateral neuromotor apparatus of the rat in conditions of unilateral tenotomy.

The effects of unilateral transection of the Achilles tendon (tenotomy) on the electromyographic characteristics of the gastrocnemius muscle on the contralateral side were studied in rats. Motor responses, reflex responses, and motor unit spike activity in the contralateral gastrocnemius muscle were studied in baseline conditions and on afferent stimulation before and 10 days after tenotomy. Changes in the nature of motor unit spike activity and responses to afferent stimulation were observed. The results obtained here demonstrate increases in the excitability of individual motoneurons in the contralateral motor center of the gastrocnemius muscle after exclusion of the symmetrical gastrocnemius muscle from the overall pattern of movement activity.

[Contralateral neuro-motor apparatus under unilateral restriction of motor activity in rat].

Electromyographic recordings of contralateral m. gastrocnemius of the rat after unilateral section of Achilles' tendon (tenotomy) were studied. Motor reflex, Hoffman reflex and firing of motor units of contralateral m. gastrocnemius were recorded in control and in 10 days after tendotomy. Motor units changed their firing in the background and in reaction to sciatic nerve stimulation. The results of study showed that unilateral section of Achilles' tendon increased the excitability of single motoneurons of contralateral spinal senters.