63 research outputs found
An analysis of the temperature dependence of force, during steady shortening at different velocities, in (mammalian) fast muscle fibres
We examined, over a wide range of temperatures (10–35°C), the isometric tension and tension during ramp shortening at different velocities (0.2–4 L0/s) in tetanized intact fibre bundles from a rat fast (flexor hallucis brevis) muscle; fibre length (L0) was 2.2 mm and sarcomere length ~2.5 μm. During a ramp shortening, the tension change showed an initial inflection of small amplitude (P1), followed by a larger exponential decline towards an approximate steady level; the tension continued to decline slowly afterwards and the approximate steady tension at a given velocity was estimated as the tension (P2) at the point of intersection between two linear slopes, as previously described (Roots et al. 2007). At a given temperature, the tension P2 declined to a lower level and at a faster rate (from an exponential curve fit) as the shortening velocity was increased; the temperature sensitivity of the rate of tension decline during ramp shortening at different velocities was low (Q10 0.9–1.5). The isometric tension and the P2 tension at a given shortening velocity increased with warming so that the relation between tension and (reciprocal) temperature was sigmoidal in both. In isometric muscle, the temperature T0.5 for half-maximal tension was ~10°C, activation enthalpy change (∆H) was ~100 kJ mol−1 and entropy change (∆S) ~350 J mol−1 K−1. In shortening, these were increased with increase of velocity so that at a shortening velocity (~4 L0/s) producing maximal power at 35°C, T0.5 was ~28°C, ∆H was ~200 kJ mol−1 and ∆S ~ 700 J mol−1 K−1; the same trends were seen in the tension data from isotonic release experiments on intact muscle and in ramp shortening experiments on maximally Ca-activated skinned fibres. In general, our findings show that the sigmoidal relation between force and temperature can be extended from isometric to shortening muscle; the implications of the findings are discussed in relation to the crossbridge cycle. The data indicate that the endothermic, entropy driven process that underlies crossbridge force generation in isometric muscle (Zhao and Kawai 1994; Davis, 1998) is even more pronounced in shortening muscle, i.e. when doing external work
Use of anticoagulants and antiplatelet agents in stable outpatients with coronary artery disease and atrial fibrillation. International CLARIFY registry
A 'snip' in time: what is the best age to circumcise?
<p>Abstract</p> <p>Background</p> <p>Circumcision is a common procedure, but regional and societal attitudes differ on whether there is a need for a male to be circumcised and, if so, at what age. This is an important issue for many parents, but also pediatricians, other doctors, policy makers, public health authorities, medical bodies, and males themselves.</p> <p>Discussion</p> <p>We show here that infancy is an optimal time for clinical circumcision because an infant's low mobility facilitates the use of local anesthesia, sutures are not required, healing is quick, cosmetic outcome is usually excellent, costs are minimal, and complications are uncommon. The benefits of infant circumcision include prevention of urinary tract infections (a cause of renal scarring), reduction in risk of inflammatory foreskin conditions such as balanoposthitis, foreskin injuries, phimosis and paraphimosis. When the boy later becomes sexually active he has substantial protection against risk of HIV and other viral sexually transmitted infections such as genital herpes and oncogenic human papillomavirus, as well as penile cancer. The risk of cervical cancer in his female partner(s) is also reduced. Circumcision in adolescence or adulthood may evoke a fear of pain, penile damage or reduced sexual pleasure, even though unfounded. Time off work or school will be needed, cost is much greater, as are risks of complications, healing is slower, and stitches or tissue glue must be used.</p> <p>Summary</p> <p>Infant circumcision is safe, simple, convenient and cost-effective. The available evidence strongly supports infancy as the optimal time for circumcision.</p
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Let's talk about sex: giving children knowledge is giving them power; the power to make better decicions about sex
Children and young people lack accurate and comprehensive knowledge of HIV and how to avoid its sexual transmission. The silence around sexuality in general and children's sexuality in particular generates misconceptions, myths and misinformation which contribute to children and adolescents' risky sexual practices. ARVIN BHANA, VELEPHI RIBA and MOHAMMED VAWDA report on a study to examine attitudes, practices and knowledge of sexuality, as well as gender, sexual and reproductive health (SRH) and HIV among children aged 5 to 17 years old in South Africa and Zambia.
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A baseline study on families in Mpumalanga
Commissioned by the Mpumalanga Department of Social Development, JulyAlthough forces of modernisation such as industrialisation and urbanization have brought about major changes to the social structure, the family remains a key social unit in South Africa (Amoateng & Richter, 2003). Studies (e.g. South African Institute of Race Relations (2011), Amoateng et al. 2004) have established that there are different types of families in the country and these include, among others, extended families, nuclear families, single-parents with children and re-constituted families that include step-parents and step-children. Other unconventional family forms such as child-free couples and the increasing tendency to live in non-biological family households are also emerging in society (Amoateng, Richter, Makiwane & Rama, 2004). Despite the array of family patterns and the well-established literature pointing to the important role of families in socio-economic development, the extent of their prevalence has not been recorded in South Africa. Currently, the South African family is impacted upon by a number of social factors which include traditionalism, modernity, and post-modernism. In addition, urban-rural migration and more recently, the AIDS pandemic have impacted greatly on the South African family. It is against this background that the Department of Social Development invited the services of the Human Science Research Council to analyse the situation of Mpumalanga families
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Enhancing the research capacity of local government planners, community health workers, and community development practitioners engaged in "War on Poverty Survey" in KwaZulu-Natal: a training report
Commissioned by the United Nations Population Fund (UNFPA) South Africa and the Development & Population Studies, University of KwaZulu-Natal, DecemberThe United Nations Population Fund (UNFPA) South Africa contracted the Human Sciences Research Council (HSRC) to provide a service of developing and implementing a training process for the staff of the KwaZulu-Natal Department of Social Development (DSD-KZN) involved in implementing the KwaZulu-Natal provincial government's Operation Sukuma Sakhe (OSS) initiative. The purpose of the OSS initiative is to provide comprehensive, integrated and transversal services to communities through effective and efficient partnerships. At the heart of the OSS is to rebuild the fabric of society by promoting human values, crime, diseases, deprivation and social ills, and most importantly, fighting poverty, ensuring moral regeneration, by working together through effective partnerships
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Conclusion: contesting children's positioning in South African families
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Punching below their weight: young South Africans' recent voting patterns
Tracking young people's election participation is one way of shedding light on the degree to which youth are choosing to engage with society and the national values embedded in the political system. Duncan Scott, Mohammed Vawda, Sharlene Swartz and Arvin Bhana present findings from work done for the most recent South African Status of Youth Report aimed at identifying key developmental issues facing young people between 14 and 35 years old.
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