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Conductance measurements for generation of an instantaneous left ventricular (LV) volume signal in the mouse are limited, because the volume signal is a combination of blood and LV muscle, and only the blood signal is desired. We have developed a conductance system that operates at two simultaneous frequencies to identify and remove the myocardial contribution to the instantaneous volume signal. This system is based on the observation that myocardial resistivity varies with frequency, whereas blood resistivity does not. For calculation of LV blood volume with the dual-frequency conductance system in mice, in vivo murine myocardial resistivity was measured and combined with an analytic approach. The goals of the present study were to identify and minimize the sources of error in the measurement of myocardial resistivity to enhance the accuracy of the dual-frequency conductance system. We extended these findings to a gene-altered mouse model to determine the impact of measured myocardial resistivity on the calculation of LV pressure-volume relations. We examined the impact of temperature, timing of the measurement during the cardiac cycle, breeding strain, anisotropy, and intrameasurement and interanimal variability on the measurement of intact murine myocardial resistivity. Applying this knowledge to diabetic and nondiabetic 11- and 20- to 24-wk-old mice, we demonstrated differences in myocardial resistivity at low frequencies, enhancement of LV systolic function at 11 wk and LV dilation at 20-24 wk, and histological and electron-microscopic studies demonstrating greater glycogen deposition in the diabetic mice. This study demonstrated the accurate technique of measuring myocardial resistivity and its impact on the determination of LV pressure-volume relations in gene-altered mice. gene-altered mouse; diabetes; left ventricular volume; dual-frequency conductance method; myocardial resistivity

Research was conducted to study left ventricular performance in mice using echocardiography at different times after inoculation with coxsackievirus B3. The animals were anesthetized with ketamine while tissues were processed and embedded in paraffin. Results showed no signs of inflammation in the control mice. They also indicated that myocardial dysfunction parallels myocardial expression of proinflammatory cytokines and iNOS in coxsackievirus myocarditis.

A study was conducted to determine whether the rate of left ventricle (LV)relaxation, or LV pressure decay, is consistent from beat to beat when other factors that could affect it are controlled. A monoexponential time constant T, a half-time T 1/2 and an average rate Ravg were used to evaluate LV pressure decay in nine chronically instrumented dogs. The results indicate an substantial inherent variability in LV pressure decay regardless of the parameter used to assess it. Nevertheless, it was found out that Ravg could be a reliable measure of LV pressure decay.

Abstract: Stimulated production of reactive oxygen species (ROS) by plasma membrane-associated nicotinamide adenine dinucleotide phosphate oxidases (Nox) in non-phagocytic cells regulates a number of biological processes including growth, vessel tone, and oxygen sensing. The purpose of this study was to investigate H2O2-stimulated ROS production in primary adult cardiac fibroblasts (CF). Results demonstrate that CF express an H2O2-inducible oxidant generating system that is inhibitable by diphenylene iodonium (DPI) and sensitive to antioxidants. In addition to H2O2, generation of ROS was stimulated potently by 1-oleoyl-2-acetyl-sn-glycerol (OAG) and arachidonic acid (AA) in a protein kinase C-independent manner. Pretreatment with arachidonyl trifluoromethyl ketone was nearly as effective as DPI at reducing H2O2- and OAG-stimulated oxidant generation indicating a central role for phospholipase A2 (PLA2) in this signaling pathway. Co-stimulation with H2O2 and OAG did not increase ROS generation as compared to OAG alone suggesting both agonists signal through a shared, rate-limited enzymatic pathway involving PLA2. Co-stimulation with H2O2 and AA had additive effects indicating these two agonists stimulate oxidant production through a parallel activation pathway. Reverse transcriptase-coupled polymerase chain reaction and Western blotting demonstrate primary cardiac fibroblasts express transcripts and protein for Nox4, p22, p47, and p67 phox. Transfections with Nox4 small inhibitory ribonucleic acid oligonucleotides or p22 phox antisense oligonucleotides significantly downregulated stimulated Nox activity. Inhibitors of nitric oxide synthases were without effect. We conclude adult CF express Nox4/p22 phox-containing oxidant generating complex activated by H2O2, OAG, and AA through a pathway that requires activation of PLA2. [Copyright &y& Elsevier]

Objective: The extent to which apoptosis contributes to myocyte cell loss during acute carditic viral infection is unknown. To assess whether apoptosis occurs in acute viral myocarditis, and how it is modulated, we studied mice inoculated with coxsackievirus B3 (CVB3). Methods: Five CD1 and C3H.HeJ (C3H) mice/group were sacrificed as saline vehicle-injected controls, and at 1, 2, and 3 weeks post-inoculation (p.i.) with 5×106 pfu CVB3. Histopathological status and terminal transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assays quantified inflammation, necrosis and apoptosis in myocardium. Apoptosis-related protein immunoreactivity defined presence and location of Bax, Fas, Fas Ligand (FasL), Bcl-2, interleukin-1β converting enzyme (ICE), inducible nitric oxide synthase (iNOS) and the proto-oncogene p53. Results: Both strains exhibited significant histopathology at all time points. Saline-injected control animals showed no signs of inflammation and no significant difference in apoptosis-related protein immunoreactivity was observed between strains. Myocardial TUNEL-positive cells were exceedingly rare though apoptosis was present in thymic medulla and spleen follicles. Pro-apoptotic proteins Bax, Fas, and FasL were present in all groups though no clear correlation with histopathology was apparent. By contrast, the anti-apoptotic protein Bcl-2 showed mild immunoreactivity in controls, which increased following infection and correlated well with histopathological scores in both strains. Myocardial iNOS immunoreactivity displayed a similar though weaker staining pattern to Bcl-2 over the 3 week study period in both strains. Neither ICE nor p53 immunoreactivity could be demonstrated in myocardium. Conclusion: Thus, despite marked inflammatory activity, myocyte apoptosis is rare in acute CVB3 myocarditis in CD1 and C3H.HeJ mice. [ABSTRACT FROM PUBLISHER]