Skeletal myotube integration with planar microelectrode arrays in vitro for spatially selective recording and stimulation: a comparison of neuronal and myotube extracellular action potentials

Microelectrode array (MEA) technology holds tremendous potential in the fields of biodetection, lab-on-a-chip applications, and tissue engineering by facilitating noninvasive electrical interaction with cells in vitro. To date, significant efforts at integrating the cellular component with this detection technology have worked exclusively with neurons or cardiac myocytes. We investigate the feasibility of using MEAs to record from skeletal myotubes derived from primary myoblasts as a way of introducing a third electrogenic cell type and expanding the potential end applications for MEA-based biosensors. We find that the extracellular action potentials (EAPs) produced by spontaneously contractile myotubes have similar amplitudes to neuronal EAPs. It is possible to classify myotube EAPs by biological signal source using a shape-based spike sorting process similar to that used to analyze neural spike trains. Successful spike-sorting is indicated by a low within-unit variability of myotube EAPs. Additionally, myotube activity can cause simultaneous activation of multiple electrodes, in a similar fashion to the activation of electrodes by networks of neurons. The existence of multiple electrode activation patterns indicates the presence of several large, independent myotubes. The ability to identify these patterns suggests that MEAs may provide an electrophysiological basis for examining the process by which myotube independence is maintained despite rapid myoblast fusion during differentiation. Finally, it is possible to use the underlying electrodes to selectively stimulate individual myotubes without stimulating others nearby. Potential uses of skeletal myotubes grown on MEA substrates include lab-on-a-chip applications, tissue engineering, co-cultures with motor neurons, and neural interfaces.     

Can asthma control be improved by understanding the patient's perspective?

Background

Clinical trials show that asthma can be controlled in the majority of patients, but poorly controlled asthma still imposes a considerable burden. The level of asthma control achieved reflects the behaviour of both healthcare professionals and patients. A key challenge for healthcare professionals is to help patients to engage in self-management behaviours with optimal adherence to appropriate treatment. These issues are particularly relevant in primary care, where most asthma is managed. An international panel of experts invited by the International Primary Care Respiratory Group considered the evidence and discussed the implications for primary care practice.

Discussion

Causes of poor control Clinical factors such as exposure to triggers and concomitant rhinitis are important but so are patient behavioural factors. Behaviours such as smoking and nonadherence may reduce the efficacy of treatment and patients' perceptions influence these behaviours. Perceptual barriers to adherence include doubting the need for treatment when symptoms are absent and concerns about potential adverse effects. Under-treatment may also be related to patients' underestimation of the significance of symptoms, and lack of awareness of achievable control. Implications Three key implications for healthcare professionals emerged from the debate. First, the need for simple tools to assess asthma control. Two approaches considered were the monitoring of biometric markers of control and questionnaires to record patient-reported outcomes. Second, to understand the reasons for poor control for individual patients, identifying both clinical (e.g. rhinitis) and behavioural factors (e.g. smoking and nonadherence to treatment). Third was the need to incorporate, within asthma review, an assessment of patient perspectives including their goals and aspirations and to elicit their beliefs and concerns about asthma and its treatment. This can be used as a basis for agreement between the healthcare professional and patient on a predefined target regarding asthma control and a treatment plan to achieve this.

Summary

Optimum review of asthma is essential to improve control. A key priority is the development of simple and effective tools for identifying poor control for individual patients coupled with a tailored approach to treatment to enable patients to set and achieve realistic goals for asthma control.     

Reproduction and development of the South American freshwater stingrays,Potamotrygon circularis and P. motoro

Synopsis Observations of reproductive features and body measurements were made on wild-caught, freshwater stingrays, Potamotrygon circularis and P. motoro, from the Amazon drainage of western Brazil and southern Colombia. Further observations were made in Detroit's Belle Isle Aquarium on a captive pair of P. motoro and their descendants, which constitute the first known captive breeding colony of potamotrygonids. The gross structure and function of female and male reproductive systems are described. There is no obvious difference between those of the two species. They are aplacentally viviparous, the young being nourished in advanced stages by uterine milk secreted by trophonemata. Size at onset and completion of sexual maturation, breeding season and behavior, gestation period, litter size and sex ratios are discussed. Up to 21 proportional measurements were made on several fetal and postnatal stages of both species. Several proportional changes occur in very early fetal life, but most body proportions undergo only minor changes from advanced fetal through adult stages. A growth curve is proposed for P. motoro based on observations of the captive colony.     

Partial structure of a polysaccharide from leaves of Welwitschia mirabilis

Gum-tears from the leaves of Welwitschia mirabilis contain a polysaccharide composed of arabinose, galactose and glucuronic acid as main constituents with xylose, fucose and rhamnose in smaller quantities. Periodate oxidation and permethylation studies indicated that the gum could consist of a framework of glucuronic acid residues linked 1 → 4 and galactose residues linked 1 → 6 and of short chains of arabinose, xylose, fucose and rhamnose linked 1 → 3 to both residues. All rhamnose and fucose and part of arabinose were found as non-reducing terminal units.     

Coupling of enzymes to modified styrene-maleic anhydride copolymers]

A copolymer of styrene and maleic anhydride is modified with low molecular weight polyoles in a very convenient manner, so that it can be applied as a carried for the fixation of biologically active compounds without further pretreatment. The modified products show storage stability over a long time without loss of coupling capacity. Examples for the fixation of trypsin, alkaline phosphatase and a bacterial glutamate dehydrogenase are given, and some properties of the resulting enzyme products are described.