Gender- and age-related differences in the regulatory influence of thyroid hormone on the contractility and myosin composition of single rat soleus muscle fibres

 The effects of 4 weeks of thyroid hormone (3,5,3′-triiodothyronine, T₃) treatment on the myosin isoform composition and maximum velocity of unloaded shortening (V ₀) of single soleus muscle fibres of young (3–6 months) and old (20–24 months) female (149 fibres) and male (200 fibres) rats were studied. Gender-related differences in the up-regulation of fast myosin heavy chain (MyHC) and myosin light chain (MyLC) isoforms were observed. In the female hyperthyroid rats, pure type I fibres and fibres co-expressing type I and type IIA MyHC (type I/IIA fibres) predominated. Some fibres expressed an α cardiac-like MyHC isoform either purely (α cardiac-like fibre type) or in co-expression with IIA MyHC (α cardiac-like/IIA fibre type). In the male hyperthyroid rats, on the other hand, all fibres were either type I/IIA or type I/IIAX. The relative quantities of fast MyLC isoforms in type I/IIA and type I/IIAX fibres was higher in female than in male hyperthyroid rats. V ₀ was similar in male and female control rats, and decreased with age in both genders (P<0.001). After T₃ treatment, the average V ₀ increased (P<0.001) in females with a concomitant up-regulation of fast MyHC and fast MyLC isoforms irrespective of age. The average V ₀ of the pooled fibres was higher (P<0.001) in female than in male hyperthyroid rats at both ages. In conclusion, gender- and age-related differences were observed in the regulatory influence of 4 weeks’ T₃ treatment on myosin isoform composition and V ₀ in soleus fibres. These differences are presumably related to an interaction of thyroid and sex hormones in the regulation of myosin gene expression. Received: 10 March 1998 / Received after revision 3 June 1998 / Accepted: 14 August 1998     

Comparison of carbon fibre and aluminium materials in the construction of ultralight wheelchairs

Abstract

Carbon fibre-reinforced polymers have been used in the sporting goods industry for decades, and wheelchairs have incorporated the material since the late 1980s. There is no independently collected data available on carbon fibre-reinforced polymer wheelchairs’ performance on the ANSI/RESNA testing standards, however. This study evaluated three full carbon fibre wheelchair specimens to determine their performance versus similar wheelchairs. Testing determined that while the frames survived more testing cycles than any other wheelchair, the casters and rear tires failed similarly to other devices. Overall, due to the purchase cost, the cost benefit of the tested wheelchair model was similar to aluminium wheelchairs.

• Implications for rehabilitation

• Carbon fibre wheelchair construction is a viable alternative to aluminium, titanium, or steel construction, and decreasing costs will continue to improve the benefits of carbon fibre over these models

• Carbon fibre wheelchair found to be more durable than aluminium models, but are also much more expensive. The additional cost may be justified for some users that need the increased durability, however

• Increased durability will reduce the number of repairs and warranty claims, potentially reducing the burden on a wheelchair user, and also improving their ability to travel and participate in their community

• The low weight of carbon fibre wheelchairs may increase the mobility of some users by allowing them to transfer more easily into and out of vehicles and manoeuvre throughout the environment

     

Calf muscle adaptation in intermittent claudication. Side-differences in muscle metabolic characteristics in patients with unilateral arterial disease

Summary. The adaptation of enzyme activities, notably in the oxidative metabolism, and of prerequisites for tissue transport of oxygen in the claudication leg was evaluated by comparing muscle biopsies from the gastrocnemius muscle of the claudication and the symptom-free leg of seven patients with unilateral claudication. The claudication leg had higher activities of a marker enzyme for mitochondrial oxidative capacity, citrate synthase (CS), as well as of the MB and the mitochondrial isoenzyme of creatine kinase (CK), which are considered to be involved in the transfer of high energy phosphate from the mitochondria to the resynthesis of ATP in the cytoplasm. The difference between claudication and healthy leg in activities of these CK isoenzymes were well correlated with the corresponding side difference in CS activity. No significant differences between claudication and healthy leg were found in distribution of muscle fibre types or fibre dimension, capillary density or myoglobin content, nor was there any side difference in phosphofructokinase or lactate dehydrogenase. Side differences tended to be greater in those patients with the most advanced obstructive arterial disease as estimated from non-invasive pressure measurements. It is concluded that in reasonably physically-active patients, the mode of ischaemia to which the claudication leg is subjected leads to a metabolic adaptation characterized by increased activities of enzymes involved in the oxidative metabolism, but no significant adaptation of either the conditions for local oxygen transport, as estimated by myoglobin content, and capillary density, or capacity for anaerobic metabolism.     

The challenge of increasing wholegrain intake in the UK

While fibre and wholegrains are often discussed simultaneously, they are distinct with the former classified as a nutrient and the latter as a food group that provides fibre, along with other important nutrients. Wholegrains are an integral part of a healthy, balanced diet and have been linked to several health benefits, including reduced risk of cardiovascular disease, type 2 diabetes and colorectal cancer. Yet consumption in the UK is low, and barriers to increasing wholegrain intake exist among the UK population. These include confusion around how much to consume, which foods contain wholegrains and how they are beneficial to health, acceptance of the organoleptic properties (e.g. taste, texture) of wholegrain foods, lack of knowledge about how to cook wholegrains and negative perceptions about starchy carbohydrates. The absence of a standardised wholegrains definition and a quantified wholegrain intake recommendation in the UK remains a challenge for consumers and industry, and may limit the impact of public health messages. The Healthgrain Forum has recently proposed definitions for ‘wholegrains’ and ‘wholegrain foods’ that are readily useable by the food industry and regulatory bodies. To help increase wholegrain intake in the UK, co‐operation and collaboration is required by stakeholders to educate consumers about wholegrains and inform initiatives. Food retailers have an important role to play in making wholegrains more accessible, convenient and palatable through actions such as product development and wholegrain labelling.     

High blood pressure and muscle morphology/metabolism – causal relationship or only associated factors?

As muscle tissue constitutes a main target organ for glucose metabolism and is responsible for the development of insulin resistance, it seems plausible to elucidate the relationship between blood pressure and muscle morphology and metabolism. The association between blood pressure and capillarization/morphology of the vastus lateralis muscle and metabolic variables was evaluated in 24 perimenopausal obese women [body mass index (BMI) 34·9 ± 1·1; waist–hip ratio (WHR) 0·90 ± 0·02]. The muscle enzyme activity of lipoprotein lipase (LPL), citrate synthase and glycogen synthase was determined. There was a significant negative correlation between the percentage of type I fibres and relative fibre area of type I on the one hand and systolic and diastolic blood pressure on the other. There was a negative correlation between the capillary density (i.e. number of capillaries/muscle fibre) and a positive correlation between the diffusion distance (fibre area supplied by one capillary) and diastolic blood pressure. The activities of LPL and citrate synthase were positively correlated with the percentage of type I and negatively correlated with the percentage of type II muscle fibres. The activity of LPL was also negatively correlated with plasma glucose and the insulin/C-peptide ratio. The insulin/C-peptide ratio was positively correlated with the percentage of type II muscle fibres. In stepwise multiple regression analyses, 20–30% of the variation in systolic and diastolic blood pressure could be explained by the variables of muscle fibre distribution. Excluding muscle morphological variables from the regression model, the insulin/C-peptide ratio accounted for 13% of the variation in systolic and diastolic blood pressure. The results of the study show the close association between muscle morphology and blood pressure. It remains to be elucidated whether this association indicates a causal relationship.     

Cortical and fibre tract interrelations in conduction aphasia

Background: The syndrome of conduction aphasia is an umbrella term to label clinically heterogeneous language disorders that all include a deficit of repetition due to impaired immediate memory or, in some patients, impaired speech production. The present article reviews the currently available literature on conduction aphasia. It covers aspects of the history of conduction aphasia as a fascicular disconnection syndrome and the objections to this view and discusses the proposed subtypes of this syndrome and the underlying cortical and white matter lesions.

Aims: The primary objectives of this article are to critically review the influence of historical concepts on recent approaches to optimise existing theoretical synergies. In addition, the article seeks to advance our understanding of the first steps of verbal auditory processing in individuals with normal and impaired language skills.

Main Contribution: We present first indications for an involvement of the left hemisphere in both short- and long-term integration of auditory information derived by examining patients with (conduction) aphasia.

Conclusions: Conduction aphasia may result from left hemisphere cortical lesions or from a disconnection of critical bundles of axons (fibre tract). The exact course of the fibre tract connections and the cortical regions involved in conduction aphasia remains controversial.     

Neurotoxicity in Russell’s viper (Daboia russelii) envenoming in Sri Lanka: a clinical and neurophysiological study

Context: Russell’s viper is more medically important than any other Asian snake, due to number of envenoming’s and fatalities. Russell’s viper populations in South India and Sri Lanka (Daboia russelii) cause unique neuromuscular paralysis not seen in other Russell’s vipers. Objective: To investigate the time course and severity of neuromuscular dysfunction in definite Russell’s viper bites, including antivenom response. Methodology: We prospectively enrolled all patients (>16 years) presenting with Russell’s viper bites over 14 months. Cases were confirmed by snake identification and/or enzyme immunoassay. All patients had serial neurological examinations and in some, single fibre electromyography (sfEMG) of the orbicularis oculi was performed. Results: 245 definite Russell’s viper bite patients (median age: 41 years; 171 males) presented a median 2.5?h (interquartile range: 1.75–4.0?h) post-bite. All but one had local envenoming and 199 (78%) had systemic envenoming: coagulopathy in 166 (68%), neurotoxicity in 130 (53%), and oliguria in 19 (8%). Neurotoxicity was characterised by ptosis (100%), blurred vision (93%), and ophthalmoplegia (90%) with weak extraocular movements, strabismus, and diplopia. Neurotoxicity developed within 8?h post-bite in all patients. No bulbar, respiratory or limb muscle weakness occurred. Neurotoxicity was associated with bites by larger snakes (p?<?0.0001) and higher peak serum venom concentrations (p?=?0.0025). Antivenom immediately decreased unbound venom in blood. Of 52 patients without neurotoxicity when they received antivenom, 31 developed neurotoxicity. sfEMG in 27 patients with neurotoxicity and 23 without had slightly elevated median jitter on day 1 compared to 29 normal subjects but normalised thereafter. Neurological features resolved in 80% of patients by day 3 with ptosis and weak eye movements resolving last. No clinical or neurophysiological abnormality was detected at 6 weeks or 6 months. Conclusion: Sri Lankan Russell’s viper envenoming causes mild neuromuscular dysfunction with no long-term effects. Indian polyvalent antivenom effectively binds free venom in blood but does not reverse neurotoxicity.     

Effectiveness of using a behavioural intervention to improve dietary fibre intakes in children with constipation

Background: Functional constipation is common in childhood; diets in affluent industrialised countries may be a significant contributory factor as a result of inadequate fibre content. Only a few intervention studies have been reported where childhood constipation has been treated by increasing dietary fibre. The present study aimed to demonstrate that dietary fibre intakes of children with constipation can be increased using a specifically‐designed behaviour modification technique with a self‐monitoring and reward system. Methods: Forty‐three children, aged 2–14 years, with functional constipation (defined as less than three bowel movements per week with hard stools and difficulty or delay in defecation) were randomised to one of two treatment groups: Control (n = 20), receiving general advice on increasing dietary fibre intake, or Intervention (n = 23), using the intervention tool. Fibre intake, laxative use and stool frequency were assessed at baseline, and at 3, 6 and 12 months, using parent‐filled diaries. Results: A behavioural intervention method significantly increases the fibre intakes of children with constipation at 3 months compared to standard dietary treatment (P = 0.005), remaining so after adjusting for baseline fibre intake (P = 0.007). Follow‐up at 6 and 12 months showed no further increase. No significant benefit in terms of a reduction in laxative use or increased stool frequency associated with additional fibre intake was demonstrated. Conclusions: The findings confirm the difficulties encountered in beginning and maintaining high‐fibre diets in children.     

Alpha-actinin-3 deficiency does not significantly alter oxidative enzyme activity in fast human muscle fibres

Aim: In Western European populations, about 18% of all individuals have a complete deficiency of the alpha‐actinin‐3 protein owing to homozygosity for a stop codon mutation (R577X) in the ACTN3 gene. Actn3^?/? knock‐out mice show increased activity of multiple enzymes in the aerobic metabolic pathway in fast muscle fibres. Whether this observation is also present in human XX genotype carriers compared to RR carriers has not been studied in a fibre‐type‐specific approach in humans. The purpose of this study was therefore to compare fibre‐type‐specific oxidative enzyme activity in humans with a different ACTN3 R577X genotype. Methods: Vastus lateralis muscle biopsy samples of 17 XX and 16 RR subjects were used to measure markers of oxidative capacity [cytochrome c oxidase (CYTOX) and succinate dehydrogenase (SDH)] in a fibre‐type‐specific assay using enzyme histochemistry. Results: Cytochrome c oxidase staining showed no significant genotype group differences in type I or type II muscle fibres. Also, we found no significant differences in SDH staining of fast fibres comparing XX and RR carriers. Conclusion: In conclusion, the increase in oxidative enzyme activity of fast muscle fibres, as reported in an Actn3^?/? knock‐out mouse, was not observed in our human samples. Known differences in metabolic characteristics of muscle fibres in rodents compared to humans may in part explain this discrepancy in findings.     

Fibermalt is well tolerated in healthy men and women at intakes up to 60 g/d: a randomized,double-blind,crossover trial

In this randomized, double-blind crossover trial, the digestive tolerance of a novel dietary fibre (fibermalt, an indigestible maltose alternan oligosaccharide) was assessed in healthy men and women. Twenty-nine subjects consumed 0 (control), 45 or 60 g of fibre in two doses per day for 2-week treatment periods, each separated by a 2-week washout. Results indicated no differences between treatments in composite gastrointestinal (GI) symptom scores (sum of six GI symptom ratings), individual GI symptoms (nausea, bloating, GI rumbling, gas/flatulence, abdominal pain, diarrhoea), bowel characteristics (frequency, faecal consistency, faecal hardness, straining, discomfort and incomplete evacuation) or average daily faecal output. The symptom scores were consistently low for each treatment period with means averaging below 1 out of a possible range of 0–12 for the composite score. The results of this study suggest that fibermalt is well tolerated at intakes up to 60 g of fibre per day.