Effects of a new cardiomyoplasty technique on cardiac function

OBJECTIVE: The current cardiomyoplasty technique was modified to maintain the resting tension of the latissimus dorsi muscle and to prevent lateral movement of the heart during muscle stimulation. The aim of this study is to compare the short term hemodynamic effects of the new cardiomyoplasty wrap (W1) with those of the clinically applied cardiomyoplasty wrap (W2). Preliminary indications of the long-term hemodynamic effects of W1 are presented. METHODS: In three acute experiments in sheep mean central venous pressure (MCVP), mean arterial pressure (MAP), mean cardiac output (MCOP), mean left ventricular systolic pressure (MLVSP), and mean left ventricular diastolic pressure (MLVDP) were measured for 30s before and five minutes after applying each procedure with and without stimulation of the muscle graft. The same parameters were also recorded 5min after removing each muscle wrap. Hemodynamic changes associated with unstimulated muscle wraps were compared to the baseline data. Hemodynamic effects of muscle stimulation were determined by comparing the assisted to the preceding unassisted cardiac cycle. The long-term effects of W1 on the hemodynamics of another three sheep were studied at 6-12months after the operation. The viability of the muscles used in the chronic experiments were evaluated by morphometric analysis. RESULTS: Unstimulated W2 significantly increased mean central venous pressure and reduced mean cardiac output. It also increased mean left ventricular diastolic pressure and reduced peak negative dP/dt. Unstimulated W1 had no deleterious effect on mean central venous pressure, mean left ventricular diastolic pressure or peak -dP/dt, but it also reduced mean cardiac output and increased mean left atrial pressure (MLAP). Synchronised muscle stimulation, in both techniques, augmented the mean arterial pressure, mean cardiac output and mean left ventricular systolic pressure. In W2, however, myostimulation was also associated with a significant increase of the mean left ventricular diastolic pressure. In two long-term experiments significant hemodynamic assistance was observed at 6months and at 1yr after W1. In those sheep 68% of the cross-sectional area of the muscle was well preserved. CONCLUSIONS: Unstimulated cardiomyoplasty wraps acutely impair left ventricular function in sheep. The new technique, however, may offer significant long-term hemodynamic assistance and adequate preservation of the structural and functional integrity of the muscle flap for up to 1yr.     

Annexin V for flow cytometric detection of phosphatidylserine expression on B cells undergoing apoptosis

Apoptosis, or programmed cell death, is a general mechanism for removal of unwanted cells from the immune system. It is characterized by chromatin condensation, a reduction in cell volume, and endonuclease cleavage of DNA into oligonucleosomal length fragments. Apoptosis is also accompanied by a loss of membrane phospholipid asymmetry, resulting in the exposure of phosphatidylserine at the surface of the cell. Expression of phosphatidylserine at the cell surface plays an important role in the recognition and removal of apoptotic cells by macrophages. Here we describe a new method for the detection of apoptotic cells by flow cytometry, using the binding of fluorescein isothiocyanate-labeled annexin V to phosphatidylserine. When Burkitt lymphoma cell lines and freshly isolated germinal center B cells are cultured under apoptosis inducing conditions, all cells showing chromatin condensation strongly stain with annexin V, whereas normal cells are annexin V negative. Moreover, DNA fragmentation is only found in the annexin V-positive cells. The nonvital dye ethidium bromide was found to stain a subpopulation of the annexin V-positive apoptotic cells, increasing with time. Our results indicate that the phase in apoptosis that is characterized by chromatin condensation coincides with phosphatidylserine exposure. Importantly, it precedes membrane damage that might lead to release from the cells of enzymes that are harmful to the surrounding tissues. Annexin V may prove important in further unravelling the regulation of apoptosis.     

Insulin and insulin-like growth factor I in brain tumors: binding and in vitro effects

We have measured insulin and insulin-like growth factor I (IGF-I) binding in human gliomas, meningiomas, and normal brain and studied the effect of insulin on the morphology, proliferation, and differentiation of central nervous system tumor and normal fetal cells in culture. Specific 125I-insulin and 125I-IGF-I binding was demonstrated by competition-inhibition binding assays. Insulin binding was measured in plasma membrane preparations from 9 freshly isolated human meningiomas, 4 glioblastomas multiforme (GBMs), a low-grade glioma, a normal adult brain, and a fetal brain. IGF-I binding was measured in similar preparations from 5 meningiomas, 4 GBMs, a low-grade glioma, and a normal adult brain. Incubations were carried out at 4 degrees C for 18 to 20 hours. Meningiomas showed higher specific insulin binding per 0.25 mg of protein than GBMs (19% versus 3%, P less than 0.005), and this difference was not related to small differences observed in insulin degradation. By contrast, IGF-I binding was significantly higher in gliomas than in meningiomas (27% versus 12%, P less than 0.05). Also, IGF-I binding was significantly higher than insulin binding in GBMs (27% versus 3%, P less than 0.03); binding of both IGF and insulin was high in meningiomas. In normal adult brain IGF-I and insulin binding was 7 to 10%. The ability of insulin to support and enhance the growth of central nervous system tumor cells in culture was investigated. Cell cultures were derived from a freshly isolated glioblastoma, a low-grade glioma, and 3 meningiomas.(ABSTRACT TRUNCATED AT 250 WORDS)     

Endothelial lipase promotes the catabolism of ApoB-containing lipoproteins

Endothelial lipase (EL) has been found to be a key enzyme in high-density lipoprotein (HDL) metabolism in mice, leading to the concept that inhibition of EL could be a novel strategy for raising HDL cholesterol levels. However, mice are "HDL animals" and the effect of EL on atherogenic apoB-containing lipoproteins has not been elucidated. We previously found that EL is capable of hydrolyzing very low-density lipoprotein (VLDL) and LDL lipids ex vivo. To investigate the role of EL in the metabolism of apoB-containing lipoproteins in vivo, we expressed human EL in three mouse models of elevated apoB-containing lipoproteins: apoE-deficient, LDL receptor-deficient, and human apoB transgenic mice. Unexpectedly, hepatic expression of EL resulted in markedly decreased levels of VLDL/LDL cholesterol, phospholipid, and apoB accompanied by significantly increased LDL apolipoprotein and phospholipid catabolism. To determine whether lipolytic activity is required for this effect, we also expressed a catalytically inactive form of human EL (ELS149A); unexpectedly, expression of ELS149A did not lower and in fact increased plasma lipids. Coexpression and coimmunoprecipitation studies suggested that catalytically inactive ELS149A inhibits endogenous mouse EL, accounting for the increased lipid levels. We conclude that (1) in addition to its known effects on HDL metabolism, EL influences the metabolism of apoB-containing particles; (2) catalytic activity of EL is required for its effects on apoB-containing lipoproteins; and (3) overexpressed catalytically inactive EL inhibits endogenous mouse EL, resulting in increased levels of plasma lipids. In light of these results, inhibition of EL has the potential to raise levels of atherogenic lipoproteins in addition to HDL-C levels.     

Natural bioburden levels detected on rigid lumened medical devices before and after cleaning

Controversy exists concerning the degree of microbial contamination associated with the us of rigid lumened medical devices, the efficacy of standard cleaning techniques used to remove pathogenic microorganisms from lumen channels, and whether patients are placed at risk of cross infection because of microbial contamination. In this study the level and types of microorganisms found on rigid lumened medical devices before and after cleaning in a hospital environment were investigated. The bioburden level after clinical use was found to be relatively low, ranging from 10¹ to 10⁴ colony forming units (CFU) per device. After the instruments were cleaned, none of the devices studied contained bioburden levels greater than 10⁴ CFU and 83% had bioburden levels less than or equal to 10² CFU. The bioburden present before cleaning was comprised of organisms derived from the handling of the device, from the hospital environment, and from the patient. The bioburden present after cleaning was comprised of organisms typically derived from the handling of the device and from the hospital environment. The level of bioburden per device was also related to the anatomic site where the device was used, with lower numbers of organisms found on devices exposed to sterile body sites and the respiratory tract.     

Glycopeptides from Surface Membranes of Neuroblastoma Cells

Sequential removal of surface glycopeptides was achieved by subjection of mouse neuroblastoma cells to a two-step trypsin treatment under different conditions. The glycopetides released by each trypsinization step were digested by Pronase and examined on columns of Sephadex G-50. Different chromatographic patterns were found for the two digests. Thus, several groups of glycopeptides can be distinguished by the trypsinization procedure. One group is readily removed and appears to be at a more accessible location on the cell surface. Among the four neuroblastoma clones examined, the glycopeptide patterns from axon-forming cells differed from those of axon-minus cells.