Neuro-mechanics of muscle coordination during recumbent pedaling in post-acute stroke patients.

Motor impairment after stroke has been hypothesized to be related, among others, to impairments in the modular control of movement. In this study we analyzed muscle coordination and pedal forces during a recumbent pedaling exercise from a sample of post-acute stroke patients (n=5) and a population of age-matched healthy individuals (n=4). Healthy subjects and the less impaired patients showed a shared modular organization of pedaling based on 4 similar muscle synergies. The most impaired patient, characterized by a Motricity Index of 52/100, showed a reduced complexity (only 2 muscle synergies for the affected side). Differences between healthy subjects and post-stroke patients in the execution of the task were identified in terms of unbalance in mechanical work production, which well corresponded to the level of impairment. This pedaling unbalance could be traced back to different activation strategies of the 4 identified modules. Investigation on a more representative sample will provide a full characterization of the neuro-mechanics of pedaling after stroke, helping our understandings of the disruption of motor coordination at central level after stroke and of the most effective solutions for functional recovery.

Preterm infants with severe extrauterine growth retardation (EUGR) are at high risk of growth impairment during childhood.

UNLABELLED: Extrauterine growth retardation (EUGR) seriously affects premature newborns and is related to the impairment of growth during childhood. There are very limited data available concerning the growth outcome of EUGR children. Our aim was to assess the growth outcome in a cohort of children born before 34 weeks of gestation with severe EUGR. This was a retrospective multicenter study, performed in outpatient endocrinology clinic. A total of 103 premature children with weight and/or length below -2 standard deviation score (SDS) of "intrauterine" growth expectation at the time of discharge from hospital (within 42 weeks of postmenstrual age) were included in the study. The study participants underwent a thorough anthropometric assessment at a mean age of 3.9 years ± 1.7 SD. Of the EUGR children, 12.6 % showed a height below -2 SDS and 7.7 % even below -2.5 SDS. Growth impairment was more common in males than in females (17 vs. 8 %). The prevalence of subnormal weight (below -2 SDS) was 13.6 %, being higher in males than in females (17 vs. 10 %). BMI values below -2 SDS were found in 18.4 % of our study population (22.7 % in males and 12 % in females). The 19.6 % of EUGR children did not catch up in head circumference during early childhood. Length at term was the major predictor of height in childhood (P < 0.001). CONCLUSION: A significant proportion of children born prematurely with severe EUGR show growth retardation in childhood thus suggesting the need for a close clinical follow-up to determine their growth potential and implement effective intervention strategies.

Immune responses to tetanus vaccination in Italian healthy subjects and children with recurrent infections.

The ability of vaccine antigen to generate protection is a challenge that cannot be restricted to the antibody response; however, the contribution of T cell-mediated mechanisms has not been extensively analyzed. Age and administration to specific categories of patients, i.e. children with recurrent infections (RI), are some of the factors that might affect the vaccine immune response. We investigated the humoral and cellular response to tetanus toxoid (TT) vaccine in 104 healthy children (HC), 11 newborns and 22 healthy adults to characterize the status of immunity according to age and compared it to 118 RI children. Humoral and cellular responses varied in both groups according to age and doses of TT administered. The prevalence of antibody and cellular response was similar in both cohorts (HC 88 percent and 82 percent versus RI 86 percent and 85 percent), however, TT antibody values were significantly higher in 12-18 months old RI children compared to HC (median: 5 IU/ml vs 1.10 IU/ml) (p = 0.02). The lack of an efficient immune response was observed in 12-15 percent of children from both cohorts. Our data showed that specific antibodies were responsible for early protection, whereas cell-mediated mechanisms may contribute to the generation of long-term immunity after an appropriate vaccine recall. The occurrence of higher TT antibody values in 12-18 months old RI children deserves additional research to determine whether they are caused by different infectious agents and/or by other environmental factors. Clarification of this issue is important for categorizing patients into an optimal vaccine policy.

Muscle synergies are consistent when pedaling under different biomechanical demands.

In this study we investigate the muscle coordination underlying the execution of a pedaling exercise across different biomechanical demands, by using the muscle synergies paradigm. 9 non professional subjects performed a cycling exercise using their preferred pedaling strategy (Preferred Strategy, PS) and then, through the use of a feedback based on the presentation of a real-time index of mechanical efficiency determined by means of instrumented pedals, they were helped to optimize their pedaling technique (Effective Strategy, ES). EMG activity was recorded from 8 muscles of the dominant leg. Nonnegative Matrix Factorization was applied for the extraction of muscle synergies. 4 modules were sufficient to reconstruct the repertoire of muscle activations for all the subjects during PS condition, and these modules were found consistent across all the subjects (correlation > 83%). 5 muscle synergies were necessary for the characterization in ES condition; 4 out of these modules were shared with PS condition, and the resulting additional module appeared subject-specific. These preliminary results support the existence of a modular motor control in humans.

Neuromuscular adaptations during submaximal prolonged cycling.

This study aims at evaluating the neuromuscular adaptations occurring during submaximal prolonged cycling tasks. In particular, we want to assess changes in surface electromyographic (sEMG) signal recorded during a pedaling task, performed by six subjects on a cycle-simulator at a constant power output, until voluntary exhaustion. Task failure was defined as the instant the subject was no longer able to maintain the required task. Electromyographic activity was recorded from eight muscles of the dominant leg and burst characteristics of sEMG signals were analyzed in order to assess the changes in muscle activity level produced by the occurrence of neuromuscular fatigue. In particular, three features were extracted from the sEMG signal for each burst: amplitude, location of the maxima and mean profile of the burst envelope. We have reported an increase in the amplitude parameter for all subjects only for Vastii while bi-articular muscles presented a high variability among subjects. Also the location of the maximal values of the mean envelope of the bursts was found to change when considering bi-articular or mono-articular muscles. The envelope profile was found not to be subject to alterations when comparing the end of the task with the beginning. We speculated that neuromuscular fatigue induces changes essentially in the mono-articular muscles which produce power. This phenomenon is highly correlated with the adopted pedaling strategy which, being not constrained, induces subjects to express the maximal power in the downstroke phase, related to knee extension and involving mainly mono-articular muscles.

A SNR-independent formulation of a double threshold algorithm for the estimation of muscle activation intervals.

The aim of this work is to propose an improvement to the double threshold algorithm for muscular activation intervals estimation developed by Bonato and his co-workers. The proposed method has been designed in order to be adaptive also when the Signal to Noise ratio (SNR) of the sEMG signal changes during the trial, by re-evaluating the parameters of the algorithm according to the estimated local SNR and the desired detection and false alarm probabilities. This novel implementation is also suitable for working in pseudo real-time since it can give information on burst estimation shortly after the end of the current muscular activity. The proposed method was tested on simulated signals taking into account changes in the SNR during the trial, and results were compared with those obtained with the classical implementation of the algorithm.

Detection of tremor bursts from the sEMG signal: an optimization procedure for different detection methods.

Two different detection techniques for EMG burst detection are here used to reveal tremor in both a set of synthetic data and in a small sample of experimental trials. An optimization procedure that employs the minimization of a cost function to provide the parameter set characterizing the two techniques is here presented and its performance assessed. The results obtained with the optimization procedure are satisfactory and suitable for practical use: the values for both bias and standard deviation in the estimation of both onset and offset time instants are lower than 10 ms, and the sensitivity and positive predictive value in the detection of tremor bursts are > 96% for SNR levels higher than 6 dB.

[Hypoxic-ischemic encephalopathy in newborns]. / Encefalopatia ipossico-ischemica nel neonato.

Cerebral hypoxia-ischaemia occurring in the fetus and newborn is a major cause of acute mortality and chronic neurologic disability in survivors. Statistics suggest an incidence of systemic asphyxia in 1-2/1000 full-term infants and an incidence that approaches 60% in very low birth-weight newborns. Although the neuropathological features are not exclusively characteristic of full-term or preterm babies, it is well known that the gray matter is predominantly involved in the term baby while the white matter is damaged in the preterm newborn. In the premature infant encephalopathy is often accompanied by peri-intraventricular haemorrhage. The different distribution of neuropathologic lesions arising from perinatal hypoxia-ischaemia depend on several factors such as intrinsic cellular and regional vulnerability, vascular factors, nature and duration of the insult, age and maturity of the infant.

Epidemiology of hepatitis B virus in non-institutionalized children and adolescents affected by handicap.

The aim of the study is to evaluate the prevalence of hepatitis B virus (HBV) markers in a population of non-institutionalized handicapped 1-19-year-old patients. Thirty-six out of 70 patients lived in southern Italy and 19 were affected by Down's syndrome. Only three (4.2%) were positive for anti-HBc (one of these also for anti-HBs) and none for HBsAg. Low prevalence seems to indicate that no particular anti-HBV vaccination strategy is to be considered on this subset of population and on their contacts. Serum prevalence of HBV among nurses and other members of personnel was 11.3%.

Probing the sulfhydryl groups of nuclear matrix proteins with 6-iodoacetamidofluorescein.

Rat liver nuclear matrices were reacted with the fluorescent dye 6-iodoacetamidofluorescein and the matrix proteins were then separated by one and two-dimensional polyacrylamide gel electrophoresis. Upon transillumination with U.V. light it was possible to see that several proteins had reacted with the dy, thus indicating the presence of free -SH groups. This labelling technique allowed the detection of a large number of proteins, being several folds more sensitive than conventional Coomassie Blue staining, as demonstrated by two-dimensional electrophoretical separation. If nuclear matrices were treated with reducing agents before being reacted with 6-iodoacetamidofluorescein, the fluorescence increased with about the same intensity in all the protein bands. It is proposed that 6-iodoacetamidofluorescein can be used as a specific and very sensitive probe to study the -SH groups of nuclear matrix proteins.

Evidence for a reduction of the replicative activity of matrix-bound DNA polymerase alpha following treatment with phospholipase C.

Since phospholipids have been suggested to play some role in the molecular organisation of the nuclear matrix, the effect of their removal by means of phospholipase C has been investigated in regenerating rat liver nuclear matrix. The matrix-bound DNA polymerase alpha shows an almost complete loss of activity following the digestion with phospholipase C. Since the polymerase activity is restored by adding exogenous DNA, we suggest that the effect is due to the removal of matrix residual DNA, which is in some way linked to the nuclear matrix by means of hydrophobic interactions.