Isotope Bioassay for “Thrombopoietin”

An assay system has been developed in mice for the humoral agent “thrombopoietin.” This is based on utilization in newly-formed platelets of the radio-amino-acid ⁷⁵Se selenomethionine 24 hours after intravenous injection. The possibility that the results could be due to the effects of species antibody, to foreign protein, or to an effect primarily on selenomethionine metabolism, has been explored, but the findings are consistent with the presence of a physiological humoral factor. Thrombopoietin has been shown to be present in the plasma of patients suffering from severe thrombocytopenia of varied aetiology.     

Implication of connexins 40 and 43 in functional coupling between mouse cardiac fibroblasts in primary culture

Cardiac fibroblasts contribute to the structure and function of the myocardium. However their involvement in electrophysiological processes remains unclear; particularly in pathological situations when they proliferate and develop fibrosis. We have identified the connexins involved in gap junction channels between fibroblasts from adult mouse heart and characterized their functional coupling. RT-PCR and Western blotting results show that mRNA and proteins of connexin40 and connexin43 are expressed in cultured cardiac fibroblasts, while Cx45 is not detected. Analysis of gap junctional communications established by these connexins with the gap-FRAP technique demonstrates that fibroblasts are functionally coupled. The time constant of permeability, k, calculated from the fluorescence recovery curves between cell pairs is 0.066 ± 0.005 min^− 1 (n = 65). Diffusion analysis of Lucifer Yellow through gap junction channels with the scrape-loading method demonstrates that when they are completely confluent, a majority of fibroblasts are coupled forming an interconnecting network over a distance of several hundred micrometers. These data show that cardiac fibroblasts express connexin40 and connexin43 which are able to establish functional communications through homo and/or heterotypic junctions to form an extensive coupled cell network. It should then be interesting to study the conditions to improve efficiency of this coupling in pathological conditions.