Ultrastructural view of astrocyte arborization, astrocyte-astrocyte and astrocyte-synapse contacts, intracellular vesicle-like structures, and mitochondrial network.

The complexity of astrocyte morphology and syncytial coupling through gap junctions are crucial for astrocyte function in the brain. However, the ultrastructural details of astrocyte arborization and interactions between neighboring astrocytes remain unknown. While a prevailing view is that synapses selectively contact peripheral astrocyte processes, the precise spatial-location selectivity of synapses abutting astrocytes is unresolved. Additionally, knowing the location and quantity of vesicles and mitochondria are prerequisites to answer two emerging questions - whether astrocytes have a signaling role within the brain and whether astrocytes are highly metabolically active. Here, we provided structural context for these questions by tracing and 3D reconstructing three neighboring astrocytes using serial block-face scanning electron microscopy. Our reconstructions reveal a spongiform astrocytic morphology resulting from the abundance of reflexive and leaflet processes. At the interfaces, varying sizes of astrocyte-astrocyte contacts were identified. Inside an astrocyte domain, synapses contact the entire astrocyte, and synapse-astrocyte contacts increase from soma to terminal leaflets. In contrast to densely packed vesicles at synaptic boutons, vesicle-like structures were scant within astrocytes. Lastly, astrocytes contain dense mitochondrial networks with a mitochondrial volume ratio similar to that of neurites. Together, these ultrastructural details should expand our understanding of functional astrocyte-astrocyte and astrocyte-neuron interactions.

A comparative study: tongue muscle performance in weightlifters and runners.

Exercise mode (i.e., resistance training, endurance training) is known to yield mode-specific effects on strength and endurance of muscles that are directly targeted during the exercise. Such mode-specific effects can also be observed in indirectly involved (i.e., nontargeted) muscles. Mode-specific muscle performance changes of nontargeted muscles, however, have only been investigated within the skeletal system. Therefore, as a first step, this study aimed to determine if bulbar muscle performance (tongue strength [TS], tongue endurance [TE]) differs between weightlifters and runners and if group differences are tongue region-specific. The Iowa Oral Performance Instrument (IOPI) was used to measure TS and TE of the anterior and posterior tongue regions in 21 weightlifters and 23 runners. In weightlifters anterior TS was significantly greater than posterior TS (P = 0.008), whereas in runners anterior and posterior TS were comparable. Furthermore, weightlifters produced significantly greater anterior TS than runners (P = 0.001). Finally, TE was overall significantly greater in runners than in weightlifters (P = 0.001). Findings suggest that exercise mode may differentially impact performance patterns of nontargeted bulbar muscles. More research is warranted to better understand the mechanisms underlying tongue muscle performance differences between weightlifters and runners.

Validation of measures from the smartphone sway balance application: a pilot study.

PURPOSE/BACKGROUND: A number of different balance assessment techniques are currently available and widely used. These include both subjective and objective assessments. The ability to provide quantitative measures of balance and posture is the benefit of objective tools, however these instruments are not generally utilized outside of research laboratory settings due to cost, complexity of operation, size, duration of assessment, and general practicality. The purpose of this pilot study was to assess the value and validity of using software developed to access the iPod and iPhone accelerometers output and translate that to the measurement of human balance. METHODS: Thirty healthy college-aged individuals (13 male, 17 female; age = 26.1 ± 8.5 years) volunteered. Participants performed a static Athlete's Single Leg Test protocol for 10 sec, on a Biodex Balance System SD while concurrently utilizing a mobile device with balance software. Anterior/posterior stability was recorded using both devices, described as the displacement in degrees from level, and was termed the "balance score." RESULTS: There were no significant differences between the two reported balance scores (p = 0.818. Mean balance score on the balance platform was 1.41 ± 0.90, as compared to 1.38 ± 0.72 using the mobile device. CONCLUSIONS: There is a need for a valid, convenient, and cost-effective tool to objectively measure balance. Results of this study are promising, as balance score derived from the Smartphone accelerometers were consistent with balance scores obtained from a previously validated balance system. However, further investigation is necessary as this version of the mobile software only assessed balance in the anterior/posterior direction. Additionally, further testing is necessary on a healthy populations and as well as those with impairment of the motor control system. LEVEL OF EVIDENCE: Level 2b (Observational study of validity)(1.)

Exercise capacity in an individual with LVAD explantation without heart transplantation.

PURPOSE: Left ventricular assist devices (LVADs) have become a viable treatment alternative to heart transplantation, in some instances providing for a level of improvement of native heart function to allow for device explantation. The aim of this case study was to describe changes in physical work capacity following 9 months of LVAD support. CLINICAL CASE: The patient described here was diagnosed with idiopathic dilated cardiomyopathy and demonstrated worsening heart failure over a 5-year period with a maximum left ventricular end-diastolic diameter of 8.99 cm and an ejection fraction of 15% to 25%. Upon implantation of an LVAD, central hemodynamic function improved and the device was removed after 9 months of support. Left ventricular diastolic and systolic diameter decreased by 39.8% and more than 30%, respectively. The left atrium decreased by 21.7% and ejection fraction was maintained by the LVAD and stabilized at 20%. Four months postexplantation, a cycle ergometry graded cardiopulmonary exercise test was performed. Exercise began at 0 W and increased 25 W per 3-minute stage. RESULTS: The patient showed improvement in peak aerobic capacity when compared to pre-LVAD cardiopulmonary stress tests. Peak oxygen uptake increased from pre-LVAD measures of 11.8 mL x kg(-1) x min(-1) to 17.0 mL x kg(-1) x min(-1). Time to maximal exertion increased from 5 minutes 27 seconds to 15 minutes. CONCLUSION: Results of this case study indicate that significant improvements in native heart function leading to an increased ability to perform work is possible following a period of mechanical unloading through LVAD support.

Exercise limitations in a competitive cyclist twelve months post heart transplantation.

It has been well documented that for heart transplant recipients (HTrecipient) post transplantation exercise capacity does not exceed 60% of healthy age-matched controls. Few studies have been undertaken to determine the cause of exercise limitations following heart transplantation (HT) for an elite athlete. Participant was a 39 year old elite male cyclist who suffered an acute myocardial infarction after a cycling race and received a heart transplant (HT) four months later. Six weeks prior to his AMI fitness testing was completed and a predicted VO2max of 58 mL·kg(-1)·min(-1) and HRmax of 171 bpm was achieved. The participant underwent maximal exercise testing 6 and 12 months post transplant to determine exercise limitations. His results 6 and 12 months post transplant were a VO2max of 33.8 and 44.2 mL·kg(-1)·min(-1) respectively, and a HR max that was 97% and 96% of HRmax measured. The participant showed an increase in both HRmax and VO2max 12 months post HT compared to previous testing. Results suggest that the limiting factors to exercise following HT are likely due to peripheral function, which became diminished as a result accumulated from 4 months of congestive heart failure, the strain of HT, and immunosuppressive therapy leading up to the exercise testing. Lifestyle before HT and a more aggressive approach to HT recovery should be considered necessary in the improvement of peripheral functioning following HT. Key pointsPhysical work capacity following heart transplantation is not limited by cardiac denervation.Heart transplant rehabilitation should focus efforts on endothelial and muscular limitations.

Case report on PWC of a competitive cyclist before and after heart transplant.

INTRODUCTION: It has been well documented that for heart transplant recipients (HTR), posttransplantation physical work capacity (PWC) normally does not exceed 60% of the value for healthy age-matched controls. Few, if any, studies have undertaken posttransplantation PWC measurements of well-conditioned individuals (i.e., PWC>300 W). CASE SUMMARY: A 37-yr-old professionally trained male cyclist suffered an acute myocardial infarction (AMI) immediately after a road race and received a heart transplant (HT) 4 months after the AMI. The participant resumed training 1 month after surgery and underwent a maximal exercise test 6 months after surgery. Peak PWC (33.8 mL.kg(-1).min(-1), 250 W) was 92% of the age-predicted maximum, and peak heart rate (165 bpm) was 96% of his known maximum. These results were similar to the participants in a study who had been training regularly for 36+/-24 months before testing, and PWC evaluations occurred 43+/-12 months after HT. CONCLUSION: Results suggest that 1) lifestyle before HT may positively affect posttransplantation PWC, 2) exercise capacity was not limited by chronotropic incompetence, and 3) a more aggressive approach to HT recovery could be applied to HTR with similar activity histories.