Median frequency of the myoelectric signal

Summary A study was performed to investigate the changes that occur in the median frequency of the myoelectric signal during local ischemia or reduction of intramuscular temperature produced by surface cooling. Data was obtained from experiments which involved the first dorsal interosseous muscle of 10 female and 16 male subjects. These subjects were asked to perform isometric constant-force abduction contractions of the index finger at 20% and 80% of maximal voluntary contraction level. The initial median frequency (IMF) of the myoelectric signal during the first 0.5 s of contraction was calculated. Results showed a significant reduction of the IMF in contractions performed under ischemic conditions; upon release, the IMF recovered quickly. At 80% maximal voluntary level of contraction, a greater decrease of the IMF was recorded. Similar results were demonstrated during reduction of intramuscular temperature with gradual recovery of the IMF after cooling. These results demonstrate that the median frequency of the myoelectric signal displays behavior similar to that reported for conduction velocity and this is consistent with the notion that accumulation of metabolic byproducts in muscle tissue causes a decrease in the conduction velocity of the muscle fibers.Dr. R. Merletti was on a leave of absence from the Institute of Electrical Engineering, Politecnico di Torino, Italy     

Optically active vinyl polymers containing fluorescent groups, 2. Synthesis of optically active vinyl carbazole derivatives

Synthesis and characterization of (S)-3-sec-butyl-9-vinylcarbazole ( 7 ), (S)-9-(2-methylbutyl)-2-vinylcarbazole ( 14 ), and (S)-9-(2-methylbutyl)-3-vinylcarbazole ( 18 ) are described in detail.     

Primary osteoblasts response to shock wave therapy using different parameters

Over the past decade extracorporeal shock-wave therapy (ESWT) has been increasingly applied to orthopaedic and musculoskeletal pathologies, the aim of this study was to assess how the energy density of the shock waves and the number of impulses affect viability, differentiation and synthetic activity of osteoblasts. Primary sheep osteoblasts cultures were treated with ESWT with an electro-hydraulic shock wave generator by selecting three different energy levels (14-21-28 kV corresponding at 0.15-0.31-0.40 mJ/mm2) and two different total numbers of impulses (500, 1000) for each level. At the end of treatment, cell counts and viability were recorded. Cells were then cultivated for 48 hours starting from a concentration of 1 x 10(4) cells/ml. The biological activity and viability were evaluated at 24 and 48 hours after treatment. No cytodestructive effects were observed in Group A, while a cytodestructive effect of ESWT was seen in cultures receiving the highest energy treatments. The different shock wave treatment induced differences in MTT assays after 24 and 48 hours, in particular the highest level showed a detrimental effect on cell respiration at both experimental times as compared to the Control Group and the protein metabolism was generally depressed by ESWT with impulses at the highest energy level. After 24 hours such effect further increased with the growing number of impulses. The lowest energy level appeared to significantly improve the metabolic parameter in primary cell cultures as compared to controls when 500 impulses were selected. The current study has demonstrated that one of the most important aspects to be considered is not the total number of impulses used but the energy level of the shock waves, thus confirming that ESWT has a dose-dependent effect on cells.     

Walking modality affects respiratory muscle action and contribution to respiratory effort

We hypothesized that walking at increased speed or increasing gradient might have different effects on chest wall kinematics and respiratory muscle power components, and contribute differently to respiratory effort sensation. We measured the volumes of chest wall compartments by optoelectronic plethysmography, esophageal, gastric and transdiaphragmatic (P _di) pressures, and the sensation of the respiratory effort by a Borg scale in five normal subjects walking both at ascending gradient with constant speed (AG) and at ascending speed with constant gradient (AS). Chest wall kinematics, evaluated by displacement of chest wall compartments, did not show any significant difference between AS and AG. Muscle power, calculated as the product of mean flow and mean pressure, increased similarly, but its partitioning into pressure and velocity of shortening differed in the two modes. A greater increase in the pressure developed by the abdominal muscles (P _abm) (4.06-fold), and in the velocity of shortening of both rib cage inspiratory muscles (v _rcm,i) (2.01-fold) and the diaphragm (v _di) (1.90-fold) was associated with a lower increase in the pressure developed by the rib cage inspiratory muscles (P _rcm,i) (1.24-fold) and P _di (0.99-fold) with AG. Instead, with AS, a lower increase in P _abm (2.12-fold), v _rcm,i (1.66-fold) and v _di (1.54-fold) was associated with a greater increase in P _rcm,i (1.56-fold) and P _di (1.97-fold). A combination of P _abm and v _di during AG (Wald ²=23.19, P<0.0000), with the addition of P _rcm,i during AS (Wald ²=29.46, P<0.0000), was the best predictor of Borg score. In conclusion, the general strategy adopted by respiratory centers during different walking modes does not differ in terms of ventilation, chest wall kinematics, and respiratory muscle power production, whereas it does in terms of partitioning of power into pressure and velocity of shortening, and respiratory muscle contribution to respiratory effort sensation. Combinations of different patterns of flow and pressure generation made the respiratory effort sensation similar during AS and AG modes.     

Neutrophils CD11b and fibroblasts PGE(2) are elevated in Alzheimer's disease

To evaluate whether inflammation-like mechanisms present in the brain of Alzheimer's disease (AD) patients are reflected in the periphery, the expression of CD11b in peripheral blood neutrophils and the expression and activity of inflammatory markers in cultured skin fibroblasts were examined. We found significantly higher levels of CD11b in neutrophils from sporadic AD patients than in controls and this elevation was positively correlated with disease severity and progression rate of mental decline. Cultured skin fibroblasts from familial (FAD) and sporadic AD patients and from controls were immunopositive for both isoforms of cyclooxygenase with no differences between groups. In unstimulated culture, the production of prostaglandin-E2 in the medium was significantly higher in fibroblasts from sporadic AD and FAD patients than in controls, and this elevation was reverted by the addition of 25 microM of ibuprofen. Our findings provide further evidence of the presence of inflammatory and immuno-related markers in the periphery of AD patients and support those studies indicating the beneficial effects of anti-inflammatory therapy in AD.     

The CARD15 2936insC mutation and TLR4 896 A>G polymorphism in African Americans and risk of preterm premature rupture of membranes (PPROM)

Infection is believed to be a leading cause of preterm premature rupture of membranes (PPROM). The bacterial cell wall component, lipopolysaccharide (LPS), is thought to initiate tissue responses leading to PPROM in the setting of Gram negative infection. LPS is recognized by the innate immune system, including the proteins encoded by the CARD15 and TLR4 genes. A recently described mutation (2936insC) in CARD15 and a polymorphism in TLR4 896 A>G impair responses to LPS. The objective of this study was to determine if African Americans, who have a higher incidence of PPROM than Caucasians, have different frequencies of the mutant CARD15 allele and the TLR4 hyporesponsive variant, and if risk of PPROM is influenced by fetal carriage of these alleles. The allele frequencies for the CARD15 mutation and the TLR4 896G variant in African Americans were similar to those reported for Caucasians. There was no association between the TLR4 alleles examined and PPROM. However, the CARD15 mutation was only detected in controls and not in PPROM cases. We conclude that the CARD15 mutation and hyporesponsive TLR4 allele do not contribute to ethnic variation in the incidence of PPROM.     

Anaphylaxis: a 7-year follow-up survey of 46 children.

BACKGROUND: Little is known about the frequency of and the features associated with recurrent anaphylaxis in pediatric populations. During 1994 to 1996, we enrolled 76 children affected by anaphylaxis in a prospective study to analyze their clinical and allergic features. OBJECTIVE: To undertake a follow-up study of these children to ascertain how many experienced a recurrence of anaphylaxis. METHODS: After a mean interval of 7 years, a pediatric allergist conducted a telephone interview of patients who had been enrolled in our 1994-1996 study. RESULTS: A telephone interview was successfully completed in 46 (61%) of the 76 patients who had been enrolled in our 1994-1996 study. Of these 46 patients, 14 (30%) had experienced a recurrence of anaphylaxis. Children with atopic dermatitis either during 1994 to 1996 (64% vs 34%; P = .04) or at the time of the current study (43% vs 16%; P = .03) and those with urticaria-angioedema at the time of the current study (93% vs 31%; P = .0002) were found to be at a significantly higher risk for recurrent anaphylaxis. Furthermore, those children who were sensitive to at least 1 food allergen during 1994 to 1996 were more likely to have experienced a recurrence of anaphylaxis (93% vs 56%; P < .04). CONCLUSIONS: This study suggests that patients may have a greater risk of recurrence of anaphylaxis if they have atopic dermatitis, urticaria-angioedema, or at least 1 positive result of skin prick tests to food allergens.     

Enhanced inhibitory avoidance learning prevents the memory-impairing effects of post-training hippocampal inactivation

Rats were trained on an inhibitory avoidance task to study the effects of post-training administration of tetrodotoxin (TTX, which temporarily inactivates neural activity) on memory consolidation. During training, independent groups of rats received either a mild foot shock (0.8 mA) or a stronger (1.0 mA) foot shock. TTX was administered bilaterally into the dorsal hippocampus immediately after training, and memory of the task was measured 48 h later. We corroborated the typical amnesic effect of intrahippocampal infusions of TTX in those rats trained with the mild-intensity foot shock. More importantly, with the stronger foot shock, the same treatment was ineffective in producing amnesia. These results suggest that, after an enhanced learning experience, other brain regions are also activated, which may compensate for the amnesic effect of TTX infusions into the hippocampus.Due to an error in the citation line, this revised PDF (published in December 2003) deviates from the printed version, and is the correct and authoritative version of the paper.