Twelve tips for developing and implementing curriculum in dedicated 'collaborative classrooms'.

Many health professional schools may be investing time and resources on dedicated educational spaces intended to promote collaborative learning. Alone, innovative physical space or technologies are not sufficient to ensure success in this. Lesson plans informed by collaborative praxis, individual motivation, faculty development, learner feedback, and team interactions also play a necessary and substantial role. We have used faculty observations, quantitative and qualitative student evaluation data, and the existing educational literature to provide twelve tips on leveraging curricular content, activity setup, physical space, learner behavior, and faculty facilitation to make the most of collaborative learning spaces.

Increased CaVbeta1A expression with aging contributes to skeletal muscle weakness.

Ca2+ release from the sarcoplasmic reticulum (SR) into the cytosol is a crucial part of excitation-contraction (E-C) coupling. Excitation-contraction uncoupling, a deficit in Ca2+ release from the SR, is thought to be responsible for at least some of the loss in specific force observed in aging skeletal muscle. Excitation-contraction uncoupling may be caused by alterations in expression of the voltage-dependent calcium channel alpha1s (CaV1.1) and beta1a (CaVbeta1a) subunits, both of which are necessary for E-C coupling to occur. While previous studies have found CaV1.1 expression declines in old rodents, CaVbeta1a expression has not been previously examined in aging models. Western blot analysis shows a substantial increase of CaVbeta1a expression over the full lifespan of Friend Virus B (FVB) mice. To examine the specific effects of CaVbeta1a overexpression, a CaVbeta1a-YFP plasmid was electroporated in vivo into young animals. The resulting increase in expression of CaVbeta1a corresponded to decline of CaV1.1 over the same time period. YFP fluorescence, used as a measure of CaVbeta1a-YFP expression in individual fibers, also showed an inverse relationship with charge movement, measured using the whole-cell patch-clamp technique. Specific force was significantly reduced in young CaVbeta1a-YFP electroporated muscle fibers compared with sham-electroporated, age-matched controls. siRNA interference of CaVbeta1a in young muscles reduced charge movement, while charge movement in old was restored to young control levels. These studies imply CaVbeta1a serves as both a positive and negative regulator CaV1.1 expression, and that endogenous overexpression of CaVbeta1a during old age may play a role in the loss of specific force.

Loss of skeletal muscle strength by ablation of the sarcoplasmic reticulum protein JP45.

Skeletal muscle constitutes approximately 40% of the human body mass, and alterations in muscle mass and strength may result in physical disability. Therefore, the elucidation of the factors responsible for muscle force development is of paramount importance. Excitation-contraction coupling (ECC) is a process during which the skeletal muscle surface membrane is depolarized, causing a transient release of calcium from the sarcoplasmic reticulum that activates the contractile proteins. The ECC machinery is complex, and the functional role of many of its protein components remains elusive. This study demonstrates that deletion of the gene encoding the sarcoplasmic reticulum protein JP45 results in decreased muscle strength in young mice. Specifically, this loss of muscle strength in JP45 knockout mice is caused by decreased functional expression of the voltage-dependent Ca(2+) channel Ca(v)1.1, which is the molecule that couples membrane depolarization and calcium release from the sarcoplasmic reticulum. These results point to JP45 as one of the molecules involved in the development or maintenance of skeletal muscle strength.

Motor neuron targeting of IGF-1 attenuates age-related external Ca2+-dependent skeletal muscle contraction in senescent mice.

A population of fast muscle fibers from aging mice is dependent on external Ca(2+) to maintain tetanic force during repeated contractions. We hypothesized that age-related denervation in muscle fibers plays a role in initiating this contractile deficit, and that prevention of denervation by IGF-1 overexpression would prevent external Ca(2+)-dependent contraction in aging mice. IGF-1 overexpression in skeletal muscle prevents age-related denervation, and prevented external Ca(2+)-dependent contraction in this work. To determine if the effects of IGF-1 overexpression are on muscle or nerve, aging mice were injected with a tetanus toxin fragment-C (TTC) fusion protein that targets IGF-1 to spinal cord motor neurons. This treatment prevented external Ca(2+)-dependent contraction. We also show evidence that injections of the IGF-1-TTC fusion protein prevent age-related alterations to the nerve terminals at the neuromuscular junctions. We conclude that the slow age-related denervation of fast muscle fibers underlies dependence on external Ca(2+) to maintain tetanic force in a population of muscle fibers from senescent mice.

Motor neurone targeting of IGF-1 prevents specific force decline in ageing mouse muscle.

IGF-1 is a potent growth factor for both motor neurones and skeletal muscle. Muscle IGF-1 is known to provide target-derived trophic effects on motor neurones. Therefore, IGF-1 overexpression in muscle is effective in delaying or preventing deleterious effects of ageing in both tissues. Since age-related decline in muscle function stems partly from motor neurone loss, a tetanus toxin fragment-C (TTC) fusion protein was created to target IGF-1 to motor neurones. IGF-1-TTC retains IGF-1 activity as indicated by [(3)H]thymidine incorporation into L6 myoblasts. Spinal cord motor neurones effectively bound and internalized the IGF-1-TTC in vitro. Similarly, IGF-1-TTC injected into skeletal muscles was taken up and retrogradely transported to the spinal cord in vivo, a process prevented by denervation of injected muscles. Three monthly IGF-1-TTC injections into muscles of ageing mice did not increase muscle weight or muscle fibre size, but significantly increased single fibre specific force over aged controls injected with saline, IGF-1, or TTC. None of the injections changed muscle fibre type composition, but neuromuscular junction post-terminals were larger and more complex in muscle fibres injected with IGF-1-TTC, compared to the other groups, suggesting preservation of muscle fibre innervation. This work demonstrates that induced overexpression of IGF-1 in spinal cord motor neurones of ageing mice prevents muscle fibre specific force decline, a hallmark of ageing skeletal muscle.

Life-long calorie restriction in Fischer 344 rats attenuates age-related loss in skeletal muscle-specific force and reduces extracellular space.

The decline in muscle function is associated with an age-related decrease in muscle mass and an age-related decline in strength. However, decreased strength is not solely due to decreased muscle mass. The age-related decline in muscle-specific force (force/muscle cross-sectional area), a measure of intrinsic muscle function, also contributes to age-related strength decline, and the mechanisms by which this occurs are only partially known. Moreover, changes in the extracellular space could have a profound effect on skeletal muscle function. Life-long calorie restriction in rodents has shown to be a powerful anti-aging intervention. In this study, we examine whether calorie restriction is able to attenuate the loss of muscle function and elevations in extracellular space associated with aging. We hypothesize that calorie restriction attenuates the age-associated decline in specific force and increases in extracellular space. Measurements of in vitro contractile properties of the extensor digitorum longus (type II) and soleus (type I) muscles from 12-mo and 26- to 28-mo-old ad libitum-fed, as well as 27- to 28-mo-old life-long calorie-restricted male Fischer 344 rats, were performed. We found that calorie restriction attenuated the age-associated decline in muscle mass-to-body mass ratio (mg/g) and strength-to-body mass ratio (N/kg) in the extensor digitorum longus muscle (P < 0.05) but not in the soleus muscle (P > 0.05). Importantly, muscle-specific force (N/cm2) in the extensor digitorum longus, but not in the soleus muscle, of the old calorie-restricted rats was equal to that of the young 12-mo-old animals. Moreover, the age-associated increase in extracellular space was reduced in the fast-twitch extensor digitorum longus muscle (P < 0.05) but not in the soleus muscle with calorie restriction. We also found a significant correlation between the extracellular space and the muscle-specific force in the extensor digitorum longus (r = -0.58; P < 0.05) but not in the soleus muscle (r = -0.38; P > 0.05). Hence, this study shows a loss of muscle function with age and suggests that long-term calorie restriction is an effective intervention against the loss of muscle function with age.