Measurement of smooth muscle function in the isolated tissue bath-applications to pharmacology research.

Isolated tissue bath assays are a classical pharmacological tool for evaluating concentration-response relationships in a myriad of contractile tissues. While this technique has been implemented for over 100 years, the versatility, simplicity and reproducibility of this assay helps it to remain an indispensable tool for pharmacologists and physiologists alike. Tissue bath systems are available in a wide array of shapes and sizes, allowing a scientist to evaluate samples as small as murine mesenteric arteries and as large as porcine ileum - if not larger. Central to the isolated tissue bath assay is the ability to measure concentration-dependent changes to isometric contraction, and how the efficacy and potency of contractile agonists can be manipulated by increasing concentrations of antagonists or inhibitors. Even though the general principles remain relatively similar, recent technological advances allow even more versatility to the tissue bath assay by incorporating computer-based data recording and analysis software. This video will demonstrate the function of the isolated tissue bath to measure the isometric contraction of an isolated smooth muscle (in this case rat thoracic aorta rings), and share the types of knowledge that can be created with this technique. Included are detailed descriptions of aortic tissue dissection and preparation, placement of aortic rings in the tissue bath and proper tissue equilibration prior to experimentation, tests of tissue viability, experimental design and implementation, and data quantitation. Aorta will be connected to isometric force transducers, the data from which will be captured using a commercially available analog-to-digital converter and bridge amplifier specifically designed for use in these experiments. The accompanying software to this system will be used to visualize the experiment and analyze captured data.

Defining the diversity of phenotypic respecification using multiple cell lines and reprogramming regimens.

To better understand the basis of variation in cellular reprogramming, we performed experiments with two primary objectives: first, to determine the degree of difference, if any, in reprogramming efficiency among cells lines of a similar type after accounting for technical variables, and second, to compare the efficiency of conversion of multiple similar cell lines to two separate reprogramming regimens-induced neurons and induced skeletal muscle. Using two reprogramming regimens, it could be determined whether converted cells are likely derived from a distinct subpopulation that is generally susceptible to reprogramming or are derived from cells with an independent capacity for respecification to a given phenotype. Our results indicated that when technical components of the reprogramming regimen were accounted for, reprogramming efficiency was reproducible within a given primary fibroblast line but varied dramatically between lines. The disparity in reprogramming efficiency between lines was of sufficient magnitude to account for some discrepancies in published results. We also found that the efficiency of conversion to one phenotype was not predictive of reprogramming to the alternate phenotype, suggesting that the capacity for reprogramming does not arise from a specific subpopulation with a generally "weak grip" on cellular identity. Our findings suggest that parallel testing of multiple cell lines from several sources may be needed to accurately assess the efficiency of direct reprogramming procedures, and that testing a larger number of fibroblast lines--even lines with similar origins--is likely the most direct means of improving reprogramming efficiency.

Functional voltage-gated Ca2+ channels in muscle fibers of the platyhelminth Dugesia tigrina.

The presence and function of voltage-gated Ca(2+) channels were examined in individual muscle fibers freshly dispersed from the triclad turbellarian Dugesia tigrina. Individual muscle fibers contracted in response to elevated extracellular K(+) in a concentration-dependent fashion. These depolarization-induced contractions were blocked by extracellular Co(2+) (2.5 mM), suggesting that they were dependent on depolarization-induced Ca(2+) influx across the sarcolemma. A voltage-gated inward current was apparent in whole cell recordings when the outward K(+) current was abolished by replacement of intracellular K(+) by Cs(+). This inward current was amplified with increasing concentration (