Home About us Contact
|
Home About us Contact | ||
|
|
||
Force Reduction (force + reduction)
Selected AbstractsSurface Action Potential and Contractile Properties of the Human Triceps Surae Muscle: Effect of ,Dry' Water ImmersionEXPERIMENTAL PHYSIOLOGY, Issue 1 2002Yuri A. Koryak The effects of 7 days of ,dry' water immersion were investigated in six subjects. Changes in the contraction properties were studied in the triceps surae muscle. After immersion, the maximal voluntary contraction (MVC) was reduced by 18.9% (P < 0.01), and the electrically evoked (150 impulses s,1) maximal tension during tetanic contraction (Po) was reduced by 8.2% (P > 0.05). The difference between Po and MVC expressed as a percentage of Po and referred to as force deficiency was also calculated. The force deficiency increased by 44.1% (P < 0.001) after immersion. The decrease in Po was associated with increased maximal rates of tension development (7.2%) and relaxation. The twitch time-to-peak was not significantly changed, and half-relaxation and total contraction time were decreased by 5.3% and 2.8%, respectively, but the twitch tension (Pt) was not significantly changed and the Pt/Po ratio was decreased by 8.7%. The 60 s intermittent contractions (50 impulses s,1) decreased tetanic force to 57% (P < 0.05) of initial values, but force reduction was not significantly different in the two fatigue-inducing tests: fatigue index (the mean loss of force of the last five contractions, expressed as a percentage of the mean value of the first five contractions) was 36.2 ± 5.4% vs. 38.6 ± 2.8%, respectively (P > 0.05). While identical force reduction was present in the two fatigue-inducing tests, it would appear that concomitant electrical failure was considerably different. Comparison of the electrical and mechanical alterations recorded during voluntary contractions, and in contractions evoked by electrical stimulation of the motor nerve, suggests that immersion not only modifies the peripheral processes associated with contraction, but also changes central and/or neural command of the contraction. At peripheral sites, it is proposed that the intracellular processes of contraction play a role in the contractile impairment recorded during immersion. [source] Mouse diaphragm assay for detection of antibodies against botulinum toxin type BMOVEMENT DISORDERS, Issue 12 2005Dirk Dressler MD Abstract With the advent of a commercial preparation of botulinum toxin type B (BT-B) for treatment of cervical dystonia detection of antibodies against BT-B (BT-B-AB) becomes necessary. For this purpose, we carried out a mouse diaphragm assay (MDA) by continuous measurement of the twitch force of a mouse hemidiaphragm preparation elicited by electric stimulation of its phrenic nerve. After exposing the preparation to BT-B 3 ng/ml the time to half-maximal twitch force reduction (paralysis time [PT]) was 69 ± 4 min (n = 25). Addition of sera from patients with antibodies against BT-A produced a PT of 68 ± 5 min (n = 24), whereas addition of sera from controls with antibodies against tetanus toxoid produced a PT of 67 ± 6 min (n = 30). When defined amounts of BT-B-AB were added to the MDA, PT was prolonged. This prolongation was correlated closely to the amount of BT-B-AB added, thus producing a calibration curve. The threshold for BT-B-AB detection was 0.4 mU/ml. When sera from 7 patients (4 women, 3 men; age 50.6 ± 14.2 years) with cervical dystonia (Toronto Western Spasmodic Torticollis Rating Scale score, 18.9 ± 2.9) and complete secondary failure of BT-B therapy (NeuroBloc; Elan Pharmaceuticals, Shannon, Ireland; 12,229 ± 2,601 MU/injection series, 1.86 ± 0.69 injection series before complete secondary therapy failure; 100.4 ± 15.8 days between injection series with normal therapeutic effect) were tested, BT-B-AB titers of more than 10 mU/ml were found in all of them. The MDA can be used to measure neutralizing BT-B-AB titers quantitatively and with adequate sensitivity and specificity. Further studies are necessary to understand the role of intermediate BT-B-AB titers in partial BT-B therapy failure. © 2005 Movement Disorder Society [source] Behenamidopropyl Dimethylamine: unique behaviour in solution and in hair care formulationsINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 4 2010M. Minguet Synopsis The rise of ecological awareness among consumers and industry has impacted the cationic surfactants market. The most used cationic surfactants present some drawbacks in this sense. Therefore, new molecules are being studied and developed which fulfil eco-toxicological requirements without losing performance. One of these surfactants is Behenamidopropyl Dimethylamine (BAPDMA). This biodegradable amidoamine, which converts into a cationic surfactant at acidic pH, shows outstanding water solubility, despite its very long alkyl chain. Its behaviour in solution has been exhaustively studied. The conditioning performance of this product is superior to that of commonly used cationic surfactants, providing a superior sensorial profile and improved combing force reductions on hair. Moreover, other applications for this product in the non-ionic form have been studied, such as conditioning agent in 2 in 1 shampoos, where it also shows colour protection effects, and as gelling agent in hair colouration creams. This multifunctional and high performance profile, together with an improved biodegradation and aquatic toxicity compared with currently used cationic surfactants, make this product a very interesting eco-friendly alternative for the hair care market. Résumé L'essor de la conscience écologique parmi les consommateurs et l'industrie a eu un fort impact dans le marché des tensioactifs cationiques. Les plus employés d'entre eux ont quelques désavantages de ce point de vue. À ce sujet, on est en train d'étudier et développer des nouvelles molécules qui accomplissent les conditions éco-toxicologiques, sans perdre leur efficacité adoucissante. Un de ces tensioactifs c'est la Behenamidopropyl Dimethylamine (BAPDMA). Cette amidoamine, qui est totalement biodégradable et non toxique pour l'environnement, évolue dans un tensioactif cationique à des pHs acides. Dans l'eau le produit montre une solubilité inespérément élevée, malgré qu'il a une chaîne alchilyque très longue. On a étudiéà fond son comportement en dissolution. L'efficacité de conditionnement du produit se montre supérieure à celle des tensioactifs cationiques employés habituellement, en donnant un profil sensoriel supérieur et en améliorant la souplesse de coiffure. En plus, pour ce produit, d'autres applications ont étéétudiées dans la forme non ionique, par exemple, son emploi comme agent conditionneur dans des shampooings 2 en 1, où il montre aussi un effet protecteur de la couleur et comme agent de texture dans des crèmes de coloration capillaire. Ce profil multifonctionnel et de haute efficacité, ainsi que un bon profil éco-toxicologique, en comparaison avec les tensioactifs cationiques employés actuellement, fait que la behenamidopropyl dimethylamine soit une très bonne alternative pour le marché du soin capillaire. [source] Gait dynamics of Cebus apella during quadrupedalism on different substratesAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2010Kristian J. Carlson Abstract Primates are distinguished from many mammals by emphasizing arboreal lifestyles. Primate arboreal adaptations include specializations for enhancing balance and manipulative skills. Compliant gait and diagonal sequence (DS) footfalls are hypothesized mechanisms for improving balance during arboreal quadrupedalism (AQ), while simultaneously permitting vertical peak force reductions sustained by limbs, particularly forelimbs (FLs). Capuchin monkeys (Cebus apella) are arboreally-adapted quadrupeds that use both lateral sequence (LS) and DS footfalls. As tool-users, capuchins experience selective pressures for FL manipulative capabilities, which seemingly conflict with encountering substantial locomotor stresses. We evaluate kinetic and 3-D kinematic data from 172 limb contacts of two adult males on terrestrial and arboreal substrates to address questions about C. apella gait compliancy, kinematics of LS and DS footfalls during quadrupedalism on different substrates, and whether capuchins reduce FL vertical peak forces relative to hind limb (HL) forces more than other primates that use tools or those that do not. Lower vertical peak forces during AQ are consistent with compliant gait, but mixed kinematic results obscure how the reduction occurs. Forearm adduction angle is one consistent kinematic difference between terrestrial and arboreal quadrupedalism, which may implicate frontal plane movements in gait compliancy. Major differences between DS and LS gaits were not observed in kinetic or kinematic comparisons. Capuchins exhibit low FL/HL vertical peak force ratios like several anthropoids, including tool-users (e.g., chimpanzees), and species not considered tool-users in free-ranging conditions (e.g., spider monkeys). Additional selective pressures besides simply tool use appear responsible for the relative reduction in primate forelimb forces. Am J Phys Anthropol, 2010. © 2010 Wiley-Liss, Inc. [source] | |||||||||||||