In the present study the effects of the novel cardiotonic agent EMD-57033 on contraction and energetic demand of isolated, electrically stimulated cardiomyocytes were investigated and compared with the effects of enhancement of extracellular calcium and of the beta-mimetic isoproterenol. In a specially designed setup [H. Rose, K.H. Strotmann, S. Pöpping, Y. Fischer, D. Kulsch, and H. Kammermeier. Am. J. Physiol. 261 (Heart Circ. Physiol. 30): H1329-H1334, 1991] parameters of contractile behavior and metabolic demand (O2 consumption) of isolated cardiac myocytes were measured. For a given enhancement of contractile performance (cell shortening) the increase in energetic demand (VO2) after application of EMD-57033 were markedly lower than on treatment with elevated extracellular Ca2+ concentration or with isoproterenol. This economization of positive inotropic effects was proposed to be due to two factors. First, stimulation-related ion cycling was only slightly enhanced with marked increase in contraction amplitude after application of EMD-57033. Second, calcium sensitization reflected in a leftward shift of the calcium concentration needed for half-maximum force development could be interpreted to be mediated by modulation of the cross-bridge dynamics of the myofilaments, where reduction of the switch-off rate of the cross bridges and prolongation of their force-generating states were presumed to be involved. Lowered pH (7.0) decreased economy of contraction. EMD-57033 restored contraction amplitude and economy of contraction at lowered pH.
Purpose of the study: The aim of the study is to analyze the way the disinfectants embedded in the plaster affect the setting linear dimensional stability, flexural and compressive strength of dental stone models. Material and Methods: Samples were made of type IV dental stone in which different disinfectants had been incorporated (sodium hypochlorite 1%, chlorhexidine 2%) in two concentrations (50%, 100%), thus obtaining four test groups. Mentioned parameters are measured using a micro comparison device and an universal testing machine, analyzing statistically the results in comparison with the control group, prepared by standard indications. Results: Disinfectants cause a decrease of the setting expansion value (ΔL) compared to the standard group in all type of mixing percentage. Variations of compressive and flexural strength are statistically significant, particularly when adding 100% of hypochlorite 1%. Conclusions: Within the limits of this study, replacing the distilled water with disinfectants, alter the value of setting expansion and cause the model dental stone to be brittle in compression and bending.
In this paper are highlighted the stresses that appear in the peri-implantation area through the forces induced by the masticatory process. The analysis consists of computer modeling of the dental implant and simulation of the load with a distributed force. It is considered a variable direction loading related to the axial insertion of the dental implant, thus simulating an important masticatory process. This type of load reveals stresses developed in the periimplantary bone area, the risk areas where the stresses can cause the appearance of hard tissue damage near the implant and its failure. Increases in stresses up to 159% in the ruminant type of chewing compared with the cutter type are highlighted. An aggravating factor that can lead to implant failure is bruxism that tangentially stresses the implant leading to the concentration of forces at the abutment-implant junction. Conclusions regarding the decrease of stresses at bone-implant junction with up to 23% by a corresponding increase of the implant diameter by 25% are also issued.
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