[Discussion of the immunomorphological role of interactions between mast cells and Helicobacter pylori in the gastric mucosa].

Helicobacter pylori induced gastritis accounts for 70% of cases in the structure of this pathology. Features of the long-term inflammatory reaction of the mucous membrane are directly related to the mechanisms of bacterial pathogenicity, and features of immunogenesis within narrow limits of the specific tissue microenvironment of organ structures. Mast cells appear to be one of the key players (promoters) in the regulation of the inflammatory mediator cascade and the formation of cytokine-induced expression. Possessing a wide arsenal of biologically active substances, mast cells are able to participate in the formation of the immune response and resistance of the gastric mucosa, modulating both pro- and anti-inflammatory effects. The antigen-presenting features of mast cells are of interest in terms of interaction with H. pylori and induction of mucosa bacterial colonization. The aim of study was to assess the mast cell tryptase profile of the gastric mucosa in the immunopathogenesis of H. pylori-associated inflammation. Material and methods. The study included 19 biopsies of the gastric mucosa with unknown status of H. pylori infection. Microslides were stained with hematoxylin and eosin, and Giemsa's dye for plain microscopy. H. pylori infection of the gastric mucosa was detected using the immunohistochemical method. Using double immunofluorescent labeling, localization of tryptase-positive mast cells and H. pylori strains was detected. Results. In patients infected with H. pylori (n=12), there was a significant increase in the number of tryptase-positive mast cells (177.99±30.55 vs 88.58±11.49; p<0.05) with activation of secretory pathways and release of protease into the extracellular matrix of the gastric mucosa. The quantitative parameters of mast cells in the group of patients with an undetected pathogen and signs of a chronic inflammation of the gastric mucosa were statistically significantly lower than in the group of infected patients. Co-localization of tryptase-positive mast cells and H. pylori strains (with the formation of areas of large free-lying granule accumulation around the glands with pronounced degree of H. pylori contamination) was detected in gastrobiopsy specimens, the fact evidencing their close involvement in the development of inflammatory reactions of the gastric mucosa. Conclusion. The study demonstrated the features of mast cells and H. pylori interaction revealing previously unknown aspects of gastritis pathophysiology. The data obtained contribute a valuable insight to choose a treatment strategy for H. pylori-associated gastritis.

[Lower urinary tract symptoms in young adult men: analysis of prevalence, profile and relationship with metabolic syndrome risk factors].

AIM: To evaluate LUTS prevalence and characteristics of lower urinary tract symptoms in young men and to investigate the relationship between LUTS and metabolic syndrome risk factors. MATERIALS AND METHODS: One hundred and one male student (age between 19 and 29, mean 21,2+/-1,5 years) of St Petersburg universities (63 (62,4%) students of First State Pavlov Medical University and 38 (37,6%) students of National Research University Higher School of Economics) were anonymously questioned. Students were asked about their height, weight, metabolic syndrome risk factors and interviewed by I-PSS and QoL questionnaire. The obtained data was analyzed in order to find significant relationship. RESULTS: Lower urinary tract symptoms (I-PSS>0) were found in 84 (84%) men, mild and moderate LUTS - in 77 (77%) and 7 (7%) men, respectively. 39 (39%) men had both storage and voiding symptoms, storage only and voiding only symptoms were found in 31 (31%) and 14 (14%) students respectively. I-PSS score was higher in men with hypertension, diabetes, chronic stress and unmotivated fatigue (p=0,032, p=0,027, p=0,015 and p=0,003, respectively). In regression model (R2=0,268) I-PSS score was associated with diabetes (p<0,001), chronic stress (p=0,002) and hypertension (p=0,020). CONCLUSION: LUTS prevalence in young men is high. The relationship between LUTS and metabolic syndrome risk factors in young adult men can be considered as a reason for clinical investigation.

[Extracellular matrix collagen fiber structures of the gastrointestinal connective tissues in mice after a 30 day orbital flight].

The organs of the digestive system experience high sensitivity to the orbital flight factors and may limit the implementation of the professional activities of crews on International space station. The connective tissue as a system-forming matrix of the integrative and buffering metabolic environment has a particular importance in the space biomedicine because it provides the inner organ functionality in the conditions of changing level of the gravitational incentive. Aim - to study the adaptive mechanisms of the fibrous component of the extracellular matrix of the connective tissue of stomach and intestines on the effect of prolonged microgravity. MATERIAL AND METHODS: Using histochemical methods the condition of collagen fibers of a specific tissue microenvironment of the membranes of stomach and intestines of C57BL/6N mice (58 males with an initial body weight of 27.1±0.7 g) after a 30-day space flight and the following 7-day land readaptation was studied as well as in the animals representing corresponding control groups. RESULTS AND DISCUSSION: Laboratory animal presence on the biosatellite «BION-M¼ No. 1 has led to the fibrous reduction of extracellular matrix of connective tissue in the studied organs of digestive system structure except for the proper lamina of the gastric mucous membrane. Fibrillogenesis increase in the gastrointestinal tract in comparison with the indicators of space flight animal group has been found after 7 days of the biosatellite landing. The collagen fibers were not characterized by the significance change from the vivarium control group during the experiment with the land modelling of orbital flight conditions. CONCLUSION: The obtained results represent the evidence of fibrous structure gravity sensitivity of extracellular matrix of the connective tissue and show the relevance in the sphere of preventive measure improvement of the digestive system organs in the profession of astronauts in the orbital flight conditions.

[The analysis of acoustic activity unsynchronized with the stimulus with the use of TEOAE]. / Analiz akusticheskoi aktivnosti, ne sinkhronizirovannoi so stimulom, pri registratsii zaderzhannoi vyzvannoi otoakusticheskoi emissii.

The presence of ambient noise or the troubled child's behavior during the registration of transiently induced optoacoustic emission (TEOAE) can lead to false positive results at the first stage of hearing screening. The aim of this study is to evaluate the effectiveness of the noise reduction method based on weighted averaging of the data in the frequency and time slot, to check TEOAE, and to improve the effectiveness of universal hearing screening. Particular attention is paid to the analysis of the origin of noise recorded during the UAE. PATIENTS AND METHODS: We have developed a method of noise reduction, based on weighted averaging of the data in the frequency and time cells. In this study, 20 people were examined (9 adults and 11 children). TEOAE was performed using the probe of the ILO 288 instrument manufactured by Otodinamics Ltd. that was connected to the E-MU 0204 sound card. The probe microphone was connected through the preamplifier to one input channel of the sound card, and the second channel was used to receive a signal from the ECG and the respiration recorder. Thereafter, the data thus obtained were processed by several methods, including the method of averaging in the frequency and time slot designed to average a set of implementations that contain a noisy signal. The comparison of the results of the use of noise suppression method based on weighted averaging of the data in the frequency and time cells showed that it increases the accuracy of TEOAE. MAIN RESULTS: Our work suggests that the use of the noise suppression method based on weighted averaging of the data in the frequency and time cells, increases the accuracy of TEOAE. Similar results were obtained by the weighted averaging method.

[Identification of people at the latent stage of Parkinson's disease (the PARKINLAR study): first results and an optimization of the algorithm].

AIM: To work out an optimal algorithm to identify people at the latent stage of neurodegenerative process of «parkinsonian¼ type in the Russian population. MATERIAL AND METHODS: Authors launched a two-step study aimed at identifying people at the latent stage of Parkinson's disease (PD) in the Russian population - the PARKINLAR (PARKINsonism, LAtent stage, Russia). As the first step, we formed a group of «primary risk¼ by the identification in neurologically healthy people of at least one of the following confirmed PD risk factors: a) the substantia nigra hyperechogenicity (ultrasound screening was performed in 193 people); b) mutations in «parkinsonian¼ genes (genetic screening was performed in 29 relatives of PD patients from families with LRRK2, PARK2 and GBA mutations). Thereby, 37 people comprised the «primary risk¼ group, of whom 23 agreed to continue further examination (44±10.2 years). A matched group of people without the aforementioned primary biomarkers of PD served as control. As the second step, we undertook in the prescreened groups a complex of investigations assessing the presence of secondary («minor¼) biomarkers of PD: Sniffin' Sticks olfactory testing; color visual evoked potentials; analysis of goal-directed eye-head-hand movements with the use of a special neuro-cybernetic system; assessment of motor and non-motor symptoms with the use of UPDRS and NMSS scales. RESULTS: When comparing the «primary risk¼ group with controls, maximal differences in the occurrence of symptoms were seen for goal-directed eye movements (43.5% vs. 20.0%) and color vision (39.1% vs. 26.7%). Among these individuals, we found two people with 4 secondary biomarkers and one with 3, and no such observations in controls. People with the combination of a primary biomarker with several secondary biomarkers of PD comprised a group of «high risk¼ in our study. CONCLUSION: Optimization of this algorithm of population screening of people predisposed to the development of PD may be done by expanding the spectrum of biomarkers and assessing their validity in a long-term prospective observational study.

[MICROBIAL COMMUNITIES ON KIDNEY STONES].

The clinical material obtained surgically in patients with kidney stone disease (KSD) was tested for content of the stone microflora using PCR and standard microbiological methods. It was demonstrated that about 50% of stones in patients with KSD were infected with various infection agents as observed using standard microbiological and molecular genetic methods. The percentage of detection of the Mycoplasma hominis using cultural method is lower than the percentage detected using PCR, which is due to difficult isolation and cultivation, as well as DNA fragments of mycoplasma observed after antibiotic therapy. Studies based on modern microscopy methods showed that microorganisms on the surface of the kidney stone formed multispecies biofilms.

THE PREVALENCE OF CHRONIC VIRAL HEPATITIS IN CHILDREN AND ADOLESCENTS IN YAKUTIA.

UNLABELLED: Chronic hepatitis in children represents a serious health and social problem. Under the conditions of the high prevalence of viral hepatitis in Yakutia epidemiological process has a number of peculiarities. In children chronic hepatitis often occurs with minor clinical manifestations, which complicate diagnosis. The study of the epidemiological, clinical and laboratory data is an important task.The aim of the study was to investigate the epidemiological characteristics of chronic hepatitis in children and adolescents living in hyper-endemic region. MATERIALS AND METHODS: The study included 1568 patients'data, registered in the dispensary with a diagnosis of chronic hepatitis in the period from 2000 to 2012. Epidemiological history data of 304 patients with chronic hepatitis were analyzed. The data from official statistics were used for epidemiological analysis. Processing of clinical and laboratory studies was performed using the statistical package IBM SPSS STATISTICS 19. RESULT: CH epidemiological features were identified, including the prevalence of HBV-infection in etiological structure, the high incidence of the disease among the indigenous population, a high risk of intra-familial infection with hepatitis B virus , high frequency of perinatal infection with hepatitis C virus. It was proposed to maximize screening tests for markers of viral hepatitis and to improve quality control of vaccination. CONCLUSIONS: The epidemic process of viral hepatitis in children and adolescents in Yakutia is characterized by domination of HBV-infection in the structure of chronic hepatitis. The predominance of the indigenous nationalities among patients with chronic hepatitis B and the leading role of family contact in the routes structure of infection transmission indicates the importance of ethnic and social factors in contraction of the disease.

Subterahertz chaos generation by coupling a superlattice to a linear resonator.

We investigate the effects of a linear resonator on the high-frequency dynamics of electrons in devices exhibiting negative differential conductance. We show that the resonator strongly affects both the dc and ac transport characteristics of the device, inducing quasiperiodic and high-frequency chaotic current oscillations. The theoretical findings are confirmed by experimental measurements of a GaAs/AlAs miniband semiconductor superlattice coupled to a linear microstrip resonator. Our results are applicable to other active solid state devices and provide a generic approach for developing modern chaos-based high-frequency technologies including broadband chaotic wireless communication and superfast random-number generation.

Controlling high-frequency collective electron dynamics via single-particle complexity.

We demonstrate, through experiment and theory, enhanced high-frequency current oscillations due to magnetically-induced conduction resonances in superlattices. Strong increase in the ac power originates from complex single-electron dynamics, characterized by abrupt resonant transitions between unbound and localized trajectories, which trigger and shape propagating charge domains. Our data demonstrate that external fields can tune the collective behavior of quantum particles by imprinting configurable patterns in the single-particle classical phase space.

Prevalence and determinants of left ventricular hypertrophy and remodelling patterns in hypertensive patients: the St. Petersburg study.

OBJECTIVE: The primary aim of the present study was to determine the prevalence of left ventricular hypertrophy (LVH) in hypertensive patients with the use of different threshold values and also to assess the distribution of left ventricular (LV) geometry patterns verified by two different methods of relative wall thickness (RWT) calculation. The secondary aim was to evaluate the impact of different demographic determinants into prevalence of LVH and remodelling patterns. PATIENTS AND METHODS: A cross-sectional study in a population-based sample of 734 essential hypertensives from the primary care clinic was undertaken. Echocardiography was performed and analysed by trained observers. The LV posterior wall thickness (PWd), interventricular septum (IVSd) and LV mass index (LVMI) were measured. The following criteria for LVH definition were used: LVMI >125 g/m2 and 134/110 g/m2, and >131/110 and 116/104 g/m2 in males/females, respectively. The RWT was calculated as a 2PWd/LVDD or PWd + IVSd/LVDD, where LVDD is the LV internal dimension at the end of diastole. The values exceeding 0.45 were considered evidence for concentric remodelling. RESULTS: Prevalence of LVH ranged from 52.2 to 72.2% by the use of different threshold for LVH definition. It was shown that the LVH estimation without sex-specific criteria underestimates the prevalence of LVH in women and overestimates it in men. The prevalence of concentric LVH and concentric remodelling was higher when the IVSd was included in the RWT calculation. Only one-quarter of patients were free from morphological alterations and eccentric LVH was as frequently observed as concentric LVH. Sex, obesity stage and type as well as hypertension level and duration contributed to LVH level and remodelling pattern. CONCLUSIONS: The use of different threshold values can significantly influence the assessment of prevalence of LVH in hypertension. The "mild" criteria, to our opinion, can overestimate the prevalence of structural LV remodelling, while implementation of sex-specific criteria for the definition of LVH increases the sensitivity of the method. In any way, eccentric LVH is as common for hypertension as a concentric LVH, the proportion of the latter increasing with age and more frequently observed in males. Concomitant obesity, in particular abdominal, significantly increases LVH prevalence.

Two- and three-dimensional oscillons in nonlinear faraday resonance.

We study 2D and 3D localized oscillating patterns in a simple model system exhibiting nonlinear Faraday resonance. The corresponding amplitude equation is shown to have exact soliton solutions which are found to be always unstable in 3D. On the contrary, the 2D solitons are shown to be stable in a certain parameter range; hence the damping and parametric driving are capable of suppressing the nonlinear blowup and dispersive decay of solitons in two dimensions. The negative feedback loop occurs via the enslaving of the soliton's phase, coupled to the driver, to its amplitude and width.

Relationship between EMG and muscle force after spinal cord injury.

OBJECTIVE: The purpose of this study was to compare the electromyography (EMG) score during contraction of a given muscle to the independently measured manual muscle test (MMT) score for that same muscle (or muscle group), to determine whether EMG measures could serve as a reasonable approximation of muscle contraction force in persons with acute spinal cord injury (SCI). METHODS: We examined the strength of relationship between surface-recorded EMG and estimated muscle strength using the MMT in a population of 45 subjects with acute (<1 week) traumatic SCI. Eight different muscle groups were compared in each individual; measures were repeated on these subjects approximately 2 months later. A 6-point numeric index was used for assignment of EMG scores, all of which were done in a blinded fashion by 1 investigator from tape-recorded evaluations. RESULTS: Nearly all of the individual muscle comparisons led to positive and significant (P < .01) correlations between EMG and MMT scores, at both the acute and subacute time points following injury. CONCLUSIONS: These findings support the use of EMG scoring as an indicator of recovery of volitional strength following SCI in a given subject. However, caution must be used when attempting to extrapolate EMG scores to absolute forces or when comparing EMG scores among different subjects.

Antismoking activity in Novosibirsk.

The prevalence of smoking is very high and growing in Siberia. Three population surveys carried out by the Institute of Internal medicine within the framework of the MONICA project (WHO) during 1988-1995 revealed that 59% of the men and 11% of the women aged 25-64 are smokers (2). The number of smokers among children is also growing: 21% of girls and 40% of boys aged 14-17 are smokers (1). Tobacco product advertising is widespread in the city. Cheap cigarettes of bad quality are easily available for the population. The economic situation in the region makes it difficult for people to pay for specialised treatment. That is why new methods of smoking prevention should be found. The main components of our work are: involving local decision-makers in the activity, educating the population, work with mass media, epidemiological studies, international Quit & Win campaigns.

Distribution and latency of muscle responses to transcranial magnetic stimulation of motor cortex after spinal cord injury in humans.

Noninvasive transcranial magnetic stimulation (TMS) of the motor cortex was used to evoke electromyographic (EMG) responses in persons with spinal cord injury (n = 97) and able-bodied subjects (n = 20, for comparative data). Our goal was to evaluate, for different levels and severity of spinal cord injury, potential differences in the distribution and latency of motor responses in a large sample of muscles affected by the injury. The spinal cord injury (SCI) population was divided into subgroups based upon injury location (cervical, thoracic, and thoracolumbar) and clinical status (motor-complete versus motor-incomplete). Cortical stimuli were delivered while subjects attempted to contract individual muscles, in order to both maximize the probability of a response to TMS and minimize the response latency. Subjects with motor-incomplete injuries to the cervical or thoracic spinal cord were more likely to demonstrate volitional and TMS-evoked contractions in muscles controlling their foot and ankle (i.e., distal lower limb muscles) compared to muscles of the thigh (i.e., proximal lower limb muscles). When TMS did evoke responses in muscles innervated at levels caudal to the spinal cord lesion, response latencies of muscles in the lower limbs were delayed equally for persons with injury to the cervical or thoracic spinal cord, suggesting normal central motor conduction velocity in motor axons caudal to the lesion. In fact, motor response distribution and latencies were essentially indistinguishable for injuries to the cervical or thoracic (at or rostral to T10) levels of the spine. In contrast, motor-incomplete SCI subjects with injuries at the thoracolumbar level showed a higher probability of preserved volitional movements and TMS-evoked contractions in proximal muscles of the lower limb, and absent responses in distal muscles. When responses to TMS were seen in this group, the latencies were not significantly longer than those of able-bodied (AB) subjects, strongly suggestive of "root sparing" as a basis for motor function in subjects with injury at or caudal to the T11 vertebral body. Both the distribution and latency of TMS-evoked responses are consistent with highly focal lesions to the spinal cord in the subjects examined. The pattern of preserved responsiveness predominating in the distal leg muscles is consistent with a greater role of corticospinal tract innervation of these muscles compared to more proximal muscles of the thigh and hip.

Latency of changes in spinal motoneuron excitability evoked by transcranial magnetic brain stimulation in spinal cord injured individuals.

OBJECTIVES: To examine the basis for delay in the excitatory effects of transcranial magnetic stimulation (TMS) of motor cortex on motoneuron pools of muscles left partially-paralyzed by traumatic spinal cord injury (SCI). METHODS: The effect of subthreshold transcranial magnetic stimulation (TMS) on just-suprathreshold H-reflex amplitude was examined in subjects (n = 10) with incomplete cervical SCI, and in able-bodied (AB) subjects (n = 20) for comparison. EMG activity was recorded from the soleus and the abductor hallucis muscles, and H-reflex was elicited by stimulation of the tibial nerve behind the knee. Comparison of the peak-to-peak amplitude of the TMS-conditioned H-reflex to that of the H-reflex alone (i.e. unconditioned H-reflex) was made for different conditioning-test intervals with multivariate analysis of variance and (when called for) t testing. RESULTS: The absolute latencies of motor responses to suprathreshold TMS delivered during a weak voluntary contraction of the soleus and abductor hallucis were significantly prolonged in the SCI group relative to AB subjects. For the TMS-conditioned H-reflex, the time-course effect of TMS on the H-reflex amplitude in different AB subjects included an early effect (typically facilitation, but occasionally inhibition) seen between -5 and 0 ms, followed by a later period (i.e. >5 ms) of H-reflex facilitation. In contrast, the earliest indication of a TMS effect on H-reflex excitability in SCI subjects was between 5 and 10 ms after TMS. This difference between SCI and AB subjects of approximately 10 ms was similar to the prolongation of TMS-evoked response latencies in the soleus and the abductor hallucis muscles of the SCI subjects. CONCLUSIONS: The results suggest that motor conduction slowing after traumatic SCI most likely occurs across the population of the descending tract axons mediating the TMS-evoked motor responses.

"Threshold-level" multipulse transcranial electrical stimulation of motor cortex for intraoperative monitoring of spinal motor tracts: description of method and comparison to somatosensory evoked potential monitoring.

UNLABELLED: Numerous methods have been pursued to evaluate function in central motor pathways during surgery in the anesthetized patient. At this time, no standard has emerged, possibly because each of the methods described to date requires some degree of compromise and/or lacks sensitivity. OBJECT: The goal of this study was to develop and evaluate a protocol for intraoperative monitoring of spinal motor conduction that: 1) is safe; 2) is sensitive and specific to motor pathways; 3) provides immediate feedback; 4) is compatible with anesthesia requirements; 5) allows monitoring of spontaneous and/or nerve root stimulus-evoked electromyography; 6) requires little or no involvement of the surgical team; and 7) requires limited equipment beyond that routinely used for somatosensory evoked potential (SSEP) monitoring. Using a multipulse electrical stimulator designed for transcranial applications, the authors have developed a protocol that they term "threshold-level" multipulse transcranial electrical stimulation (TES). METHODS: Patients considered at high risk for postoperative deficit were studied. After anesthesia had been induced and the patient positioned, but prior to incision, "baseline" measures of SSEPs were obtained as well as the minimum (that is, threshold-level) TES voltage needed to evoke a motor response from each of the muscles being monitored. A brief, high-frequency pulse train (three pulses; 2-msec interpulse interval) was used for TES in all cases. Data (latency and amplitude for SSEP; threshold voltage for TES) were collected at different times throughout the surgical procedure. Postoperative neurological status, as judged by evaluation of sensory and motor status, was compared with intraoperative SSEP and TES findings for determination of the sensitivity and specificity of each electrophysiological monitoring technique. Of the 34 patients enrolled, 32 demonstrated TES-evoked responses in muscles innervated at levels caudal to the lesion when examined after anesthesia induction and positioning but prior to incision (that is, baseline). In contrast, baseline SSEPs could be resolved in only 25 of the 34 patients. During surgery, significant changes in SSEP waveforms were noted in 12 of these 25 patients, and 10 patients demonstrated changes in TES thresholds. Fifteen patients experienced varying degrees and durations of postoperative neurological deficit. Intraoperative changes in TES thresholds accurately predicted each instance of postoperative motor weakness without error, but failed to predict four instances of postoperative sensory deficit. Intraoperative SSEP monitoring was not 100% accurate in predicting postoperative sensory status and failed to predict five instances of postoperative motor deficit. As a result of intraoperative TES findings, the surgical plan was altered or otherwise influenced in six patients (roughly 15% of the sample population), possibly limiting the extent of postoperative motor deficit experienced by these patients. CONCLUSIONS: This novel method for intraoperative monitoring of spinal motor conduction appears to meet all of the goals outlined above. Although the risk of postoperative motor deficit is relatively low for the majority of spine surgeries (for example, a simple disc), high-risk procedures, such as tumor resection, correction of vascular abnormalities, and correction of major deformities, should benefit from the virtually immediate and accurate knowledge of spinal motor conduction provided by this new monitoring approach.

Central cord syndrome of cervical spinal cord injury: widespread changes in muscle recruitment studied by voluntary contractions and transcranial magnetic stimulation.

Muscle recruitment after central cord syndrome (CCS), a cervical spinal cord injury leading to a weaker motor function in the upper limbs versus the lower limbs, was examined in 14 individuals by means of voluntary muscle contractions and transcranial magnetic stimulation (TMS). Previously obtained data from able-bodied (AB) and non-CCS spinal cord injured subjects were used for comparison. Surface EMG was recorded from as many as six pairs of affected muscles. Individual muscle EMG activity was scored from 0 to 5. Cortical stimulation was applied while subjects maintained a weak contraction in each muscle. When CCS subjects attempted to produce a maximal voluntary contraction of an isolated muscle, this frequently resulted in cocontraction of nonsynergists in the same limb or/and in other limbs. Although the EMG scores in both upper and lower extremity muscles improved within postinjury time, in general, the lower extremity muscles, particularly the distal ones, demonstrated better recovery than the upper extremity muscles. CCS and AB subjects showed a similar high probability of "well-defined" responses to TMS (amplitude >150 microV) in all studied muscles. In contrast, latencies to TMS-evoked motor responses were prolonged by significant amounts after CCS. The delays in muscle responses were not significantly different from those observed in subjects with more severe cervical injury. Despite improvement in EMG scores, repeated measurements of TMS-evoked muscle response latencies in the same CCS subjects did not reveal significant shortening in central conduction latency. This argues against remyelination as an important contributor to the recovery process.

After-potentials and control of repetitive firing in human motoneurones.

Characteristics of motoneurone after-potentials in man were derived from the recovery curve of motoneurone excitability after a single discharge evoked by threshold stimulation of Ia afferents or by gentle voluntary muscle contraction. The motoneurone excitability was estimated by the firing index of a single motor unit whose potentials were recorded by needle electrodes. The soleus (a slow muscle) and the flexor carpi ulnaris (a fast muscle) were investigated. The duration of motoneurone after-hyperpolarization of the soleus evaluated by this method ranged between 145 and 255 msec; for the flexor carpi ulnaris it was 55-150 msec. In some motoneurones of the fast muscle, an early short-lasting recovery of excitability (within 5-20 msec after a discharge) was revealed. It was accounted for by delayed depolarization of the motoneurone. The relationship between after-potentials and the characteristics of repetitive firing of motoneurones activated by weak voluntary muscle contraction was analysed. It was observed that the motoneurones with early excitability recovery were capable of firing double discharges with a 5-15 msec interspike interval. It was found also that the minimal firing rate of motoneurones (up to 3.1-5.2 imp/sec in the soleus and 3.8-9.0 imp/sec in the flexor carpi ulnaris) was not correlated with the after-hyperpolarization duration. This differs from the results obtained for cat's motoneurones under intracellular stimulation. The findings suggest that after-hyperpolarization is not the only leading mechanism controlling the low firing rate of motoneurones under conditions of their natural activity in man.

Repetitive doublets of human motoneurones: analysis of interspike intervals and recruitment pattern.

In order to study the probable mechanisms of repetitive doublets in human motoneurones, the firing patterns of single motor units (MUs) of the trapezius were analysed during a weak voluntary muscle contraction. The mean frequencies of MUs were 9.4-21.7 imp/sec (the mean interspike interval ranged from 46.0 to 106.7 msec). Repetitive doublets (up to 28 in succession) were recorded in 21 out of 120 MUs, mostly at the onset of a slow recruitment. These were followed by single discharges. Intradoublet intervals ranged between 2.5 and 20.0 msec. A significant difference between single spike firing and doublet firing was revealed by plotting interspike interval histograms, showing that two distinct mechanisms were involved. The analysis of interspike interval successions belonging to several MUs firing simultaneously showed that one of the MUs could start with doublets while the others went on firing single spikes with the regular mean frequency and interspike interval scatter. The results lead us to suggest that the intrinsic properties of motoneurones can be regarded as the main factor in the origin of repetitive doublets. It seems that a descending synaptic drive also contributes to the control of double firing since in a number of cases no doublets were produced at the beginning of MU activity. The findings are discussed with regard to the problems of regulating repetitive firing of human motoneurones by after-potentials. Steady delayed depolarization is assumed to be a possible mechanism of repetitive doublets.