Sarcomere length changes during end-held (isometric) contractions in intact mammalian (rat) fast and slow muscle fibres

The sarcomere length change, within a 2 mm region, during end-held isometric contractions in intact rat fast and slow muscle fibre bundles was investigated at 20°C and an initial sarcomere length of 2.68 m using He–Ne laser diffraction. In some experiments, the fibre segment displacement was monitored with markers (pieces of human hair) placed at regular intervals on the surface of the muscle fibre bundles. The sarcomere length changes, monitored near the proximal end of the bundle (transducer end), during tetanic contractions were similar to those previously reported in frog muscle fibres. Thus, throughout the tension plateau, sarcomere length remained constant (and shortened) but showed evidence of non-uniform sarcomere behaviour (further shortening) during the rapid tension relaxation phase. Such non-uniform behaviour was not seen during twitch contractions. During a twitch contraction, sarcomeres at the proximal end shortened rapidly at first and continued to shorten – or remained shortened – until the tension had relaxed to between 20–23% of its peak value before lengthening back to the original length. The maximum twitch sarcomere shortening (mean ± SEM) was 5.9 ± 0.2% (n = 16) in fast and 5.4 ± 0.3% (n = 14) in slow fibre bundles at 20°C; sarcomere shortening near body temperature (35°C) was greater, 8.8 ± 0.2% (n = 7) in fast and 8.1 ± 0.2% (n = 5) in slow fibre bundles. Increasing the initial sarcomere length of a preparation decreased the extent of sarcomere shortening and reducing the amount of sarcomere shortening, by sarcomere length clamping, markedly increased the peak twitch tension without significantly altering the twitch time course. When examined at different positions along muscle fibres, a sarcomere shortening was observed along much of the fibre length in most preparations. However, in about a third of the preparations some sarcomere lengthening was recorded in the distal end, but its amplitude was too small to accommodate the fibre shortening elsewhere. Complementary data were obtained using the surface marker technique. The displacement was largest and in opposite – but fibre shortening – direction in the markers placed 0.5–1.0 mm away from the two tendon attachments; the markers placed at or near the centre of the fibre bundle showed the least amount of displacement. The findings suggest that the compliant region, where lengthening occurs, is at fibre ends, i.e. near myotendinous junction.     

Introducing criteria based audit into Ugandan maternity units*

Problem: Maternal mortality in Uganda has remained unchanged at 500/100 000 over the past 10 years despite concerted efforts to improve the standard of maternity care. It is especially difficult to improve standards in rural areas, where there is little money for improvements. Furthermore, staff may be isolated, poorly paid, disempowered, lacking in morale, and have few skills to bring about change.

Design: Training programme to introduce criteria based audit into rural Uganda.

Setting: Makerere University Medical School, Mulago Hospital (large government teaching hospital in Kampala), and Mpigi District (rural area with 10 small health centres around a district hospital).

Strategies for change: Didactic teaching about criteria based audit followed by practical work in own units, with ongoing support and follow up workshops.

Effects of change: Improvements were seen in many standards of care. Staff showed universal enthusiasm for the training; many staff produced simple, cost-free improvements in their standard of care.

Lessons learnt: Teaching of criteria based audit to those providing health care in developing countries can produce low cost improvements in the standards of care. Because the method is simple and can be used to provide improvements even without new funding, it has the potential to produce sustainable and cost effective changes in the standard of health care. Follow up is needed to prevent a waning of enthusiasm with time.

     

Do cross-bridges contribute to the tension during stretch of passive muscle? a response

Journal of Muscle Research and Cell Motility -     

An Outcome Assessment of an ABC-Based HIV Peer Education Intervention Among Kenyan University Students

This study reports an outcome assessment on an HIV peer education intervention at the main campus of Kenyatta University in Nairobi, Kenya. A quasiexperimental separate sample pretest–posttest design was used. Campuswide baseline and endline surveys were conducted with 632 and 746 students, respectively, soliciting information on HIV-related knowledge, attitudes, and behavior. After 2 years of on-campus intervention, no changes in behavior were evident with respect to either abstinence or number of sexual partners. Small but statistically significant changes were found in condom attitudes and behavior, and a large increase in HIV testing was evident. It is recommended that future research more specifically compare abstinence versus multiple option peer education programs, giving special attention to the role of peer educators as models.     

Carbohydrate restriction and dietary cholesterol modulate the expression of HMG-CoA reductase and the LDL receptor in mononuclear cells from adult men

The liver is responsible for controlling cholesterol homeostasis in the body. HMG-CoA reductase and the LDL receptor (LDL-r) are involved in this regulation and are also ubiquitously expressed in all major tissues. We have previously shown in guinea pigs that there is a correlation in gene expression of HMG-CoA reductase and the LDL-r between liver and mononuclear cells. The present study evaluated human mononuclear cells as a surrogate for hepatic expression of these genes. The purpose was to evaluate the effect of dietary carbohydrate restriction with low and high cholesterol content on HMG-CoA reductase and LDL-r mRNA expression in mononuclear cells. All subjects were counseled to consume a carbohydrate restricted diet with 10–15% energy from carbohydrate, 30–35% energy from protein and 55–60% energy from fat. Subjects were randomly assigned to either EGG (640 mg/d additional dietary cholesterol) or SUB groups [equivalent amount of egg substitute (0 dietary cholesterol contributions) per day] for 12 weeks. At the end of the intervention, there were no changes in plasma total or LDL cholesterol (LDL-C) compared to baseline (P > 0.10) or differences in plasma total or LDL-C between groups. The mRNA abundance for HMG-CoA reductase and LDL-r were measured in mononuclear cells using real time PCR. The EGG group showed a significant decrease in HMG-CoA reductase mRNA (1.98 ± 1.26 to 1.32 ± 0.92 arbitrary units P < 0.05) while an increase was observed for the SUB group (1.13 ± 0.52 to 1.69 ± 1.61 arbitrary units P < 0.05). Additionally, the LDL-r mRNA abundance was decreased in the EGG group (1.72 ± 0.69 to 1.24 ± 0.55 arbitrary units P < 0.05) and significantly increased in the SUB group (1.00 ± 0.60 to 1.67 ± 1.94 arbitrary units P < 0.05). The findings indicate that dietary cholesterol during a weight loss intervention alters the expression of genes regulating cholesterol homeostasis.     

Activation of Akt is increased in the dysplasia-carcinoma sequence in Barrett's oesophagus and contributes to increased proliferation and inhibition of apoptosis: a histopathological and functional study

Background  

The incidence of oesophageal adenocarcinoma is increasing rapidly in the developed world. The serine-threonine protein kinase and proto-oncogene Akt has been reported to regulate proliferation and apoptosis in several tissues but there are no data on the involvement of Akt in oesophageal carcinogenesis. Therefore we have examined the activation of Akt in Barrett's oesophagus and oesophageal adenocarcinoma and the functional effects of Akt activation in vitro.     

Promotion of handwashing as a measure of quality of care and prevention of hospital-acquired infections in Eritrea: the Keren study

A complex interplay of cognitive, socio-economic and technical factors may determine hand-washing practice among hospital-based health workers, particularly doctors, regardless of the location of the country or hospital they work in.

Objective