Enzyme-histochemical and morphological characteristics of fast- and slow-twitch skeletal muscle after brain infarction in the rat

An Exercise Mimetic Approach to Reduce Poststroke Deconditioning and Enhance Stroke Recovery

Evidence supports early rehabilitation after stroke to limit disability. However, stroke survivors are typically sedentary and experience significant cardiovascular and muscular deconditioning. Despite growing consensus that preclinical and clinical stroke recovery research should be aligned, there have been few attempts to incorporate cardiovascular and skeletal muscle deconditioning into animal models of stroke. Here, we demonstrate in rats that a hindlimb sensorimotor cortex stroke results in both cardiovascular and skeletal muscle deconditioning and impairments in gait akin to those observed in humans. To reduce poststroke behavioral, cardiovascular, and skeletal muscle perturbations, we then used a combinatorial intervention consisting of aerobic and resistance exercise in conjunction with administration of resveratrol (RESV), a drug with exercise mimetic properties. A combination of aerobic and resistance exercise mitigated decreases in cardiovascular fitness and attenuated skeletal muscle abnormalities. RESV, beginning 24 hours poststroke, reduced acute hindlimb impairments, improved recovery in hindlimb function, increased vascular density in the perilesional cortex, and attenuated skeletal muscle fiber changes. Early RESV treatment and aerobic and resistance exercise independently provided poststroke benefits, at a time when individuals are rapidly becoming deconditioned as a result of inactivity. Although no additive effects were observed in these experiments, this approach represents a promising strategy to reduce poststroke behavioral impairments and minimize deconditioning. As such, this treatment regime has potential for enabling patients to engage in more intensive rehabilitation at an earlier time following stroke when mechanisms of neuroplasticity are most prevalent.

Stroke Induces Prolonged Changes in Lipid Metabolism, the Liver and Body Composition in Mice

During recovery, stroke patients are at risk of developing long-term complications that impact quality of life, including changes in body weight and composition, depression and anxiety, as well as an increased risk of subsequent vascular events. The aetiologies and time-course of these post-stroke complications have not been extensively studied and are poorly understood. Therefore, we assessed long-term changes in body composition, metabolic markers and behaviour after middle cerebral artery occlusion in mice. These outcomes were also studied in the context of obesity, a common stroke co-morbidity proposed to protect against post-stroke weight loss in patients. We found that stroke induced long-term changes in body composition, characterised by a sustained loss of fat mass with a recovery of lean weight loss. These global changes in response to stroke were accompanied by an altered lipid profile (increased plasma free fatty acids and triglycerides) and increased adipokine release at 60 days. After stroke, the liver also showed histological changes indicative of liver damage and a decrease in plasma alanine aminotransferase (ALT) was observed. Stroke induced depression and anxiety-like behaviours in mice, illustrated by deficits in exploration, nest building and burrowing behaviours. When initial infarct volumes were matched between mice with and without comorbid obesity, these outcomes were not drastically altered. Overall, we found that stroke induced long-term changes in depressive/anxiety-like behaviours, and changes in plasma lipids, adipokines and the liver that may impact negatively on future vascular health.

Characterization of fiber types in different muscles of the hindlimb in female weanling and adult Wistar rats

We analyzed lesser diameter and distribution of fiber types in different skeletal muscles from female Wistar rats using a histoenzymology Myofibrillar Adenosine Tri-phosphatase (mATPase) method. Fragments from muscles were frozen and processed by mATPase in different pH. Adult and weanling rat soleus muscles presented a predominance of type I fibers and larger fiber diameters. In the plantar muscle in adult rats, the type IIB fibers demonstrated greater lesser diameter while in the weanling animals, types I and IIB fibers were larger. The plantar muscle of animals of both ages was composed predominantly of the type IID fibers. The type IID fibers were observed in similar amounts in the lateral gastrocnemius and the medial gastrocnemius muscles. Type IIB fibers showed predominance and presented higher size in comparison with other types in the EDL muscle. The present study shows that data on fiber type distribution and fiber lesser diameter obtained in adult animals cannot always be applied to weanling animals of the same species. Using the mATPase, despite the difficult handling, is an important tool to determine the different characteristics of the specific fibers in the skeletal muscle tissue.

Is the ipsilateral cortex surrounding the lesion or the non-injured contralateral cortex important for motor recovery in rats with photochemically induced cortical lesions?

PRIMARY OBJECTIVE

To determine whether the ipsilateral cortex surrounding the lesion or the non-injured contralateral cortex is important for motor recovery after brain damage in the photochemically initiated thrombosis (PIT) model.

RESEARCH DESIGN

We induced PIT in the sensorimotor cortex in rats and examined the recovery of motor function using the beam-walking test.

METHODS AND PROCEDURES

In 24 rats, the right sensorimotor cortex was lesioned after 2 days of training for the beam-walking test (group 1). After 10 days, PIT was induced in the left sensorimotor cortex. Eight additional rats (group 2) received 2 days training in beam walking, then underwent the beam-walking test to evaluate function. After 10 days of testing, the left sensorimotor cortex was lesioned and recovery was monitored by the beam-walking test for 8 days.

MAIN OUTCOMES AND RESULTS

In group 1 animals, left hindlimb function caused by a right sensorimotor cortex lesion recovered within 10 days after the operation. Right hindlimb function caused by the left-side lesion recovered within 6 days. In group 2, right hindlimb function caused by induction of the left-side lesion after a total of 12 days of beam-walking training and testing recovered within 6 days as with the double PIT model. The training effect may be relevant to reorganization and neuromodulation. Motor recovery patterns did not indicate whether motor recovery was dependent on the ipsilateral cortex surrounding the lesion or the cortex of the contralateral side.

CONCLUSION

The results emphasize the need for selection of appropriate programs tailored to the area of cortical damage in order to enhance motor functional recovery in this model.

Histochemical characterization of skeletal muscles in rats with photochemically-induced stroke

PRIMARY OBJECTIVE

The aim of this study was to assess skeletal muscle showing a complete functional recovery after induction of pan-necrotic lesions in the right sensorimotor cortex in rats.

RESEARCH DESIGN AND METHODS

A focal lesion of the right sensorimotor cortex was induced photochemically. Rats were divided into three groups; the sham-operated group (CON), Stroke (RB) and Stroke plus severed right sciatic nerve (RBD).

MAIN OUTCOMES AND RESULTS

All RB rats showed complete functional recovery in the beam-walking test within 10 days. The score of CON rats was 7 for 21 days. The wet weight of the soleus muscle (SOL) only in the RB and RBD was significantly greater than in the CON. The cross-sectional area of type I fibres was increased in SOL.

CONCLUSIONS

It was concluded that the functional recovery was mainly due to increased wet weight and cross-sectional area of type I SOL fibres, which probably reflected the functional reorganization and neuromodulation in the non-damaged contralateral sensorimotor cortex and ipsilateral sensorimotor cortex lateral to the lesion identified in a previous study.

Increased H(max):M(max) ratio in community walkers poststroke without increase in ankle plantarflexion during walking

OBJECTIVE

To investigate whether changes in H-reflex response at midswing and midstance are related to excessive plantarflexion during walking in community walkers poststroke compared with control subjects without stroke.

DESIGN

Survey of functional walking handicap in a random sample of an annual stroke cohort followed by H-reflex and M(max) testing of a smaller sample.

SETTING

Community and laboratory testing.

PARTICIPANTS

Forty individuals with stroke (IWS group) completed the functional walking handicap survey, 10 of whom agreed (with 10 age-matched controls) to enroll in a study of of the H(max):M(max) ratio in soleus during walking.

INTERVENTION

Electromyography during treadmill walking.

MAIN OUTCOME MEASURES

Functional Walking Handicap Scale, soleus H(max):M(max) ratio, and the ankle joint's angle of displacement.

RESULTS

Nine of the 10 stroke patients were community walkers. All had significantly (p <.05) more variable ankle movement during walking than the controls. The H(max):M(max) ratio was significantly (p <.01) increased in the IWS group because of a decrease in M(max) response without significant (p >.05) increase in H(max) response.

CONCLUSIONS

Individuals with community-level walking ability after stroke have significantly (p <.05) less repeatability of ankle joint movement than controls at both midswing and midstance. Simultaneous soleus H(max) and M(max) testing showed a significant (p <.01) reduction in the H(max) and H(max):M(max) ratio at midswing in controls only. This inhibition at midswing was lost by the IWS group without significant increase in H(max), suggesting that central synaptic excitability was within the normal range, and possibly accounting for the absence of excessive ankle plantarflexion during walking in the IWS group with community level walking ability.