Increased oxysterol contents in diabetic rat hearts: their involvement in diabetic cardiomyopathy

BACKGROUND

Abnormal lipid metabolism associated with diabetes mellitus has been proposed to be involved in the pathogenesis of diabetic cardiomyopathy. Oxysterols, oxidation derivatives of cholesterol, are known to be highly cytotoxic.

OBJECTIVE

To monitor changes in myocardial oxysterols and to assess the effect of probucol, a lipid lowering agent, on myocardial lipids and oxysterols in diabetic rats.

METHODS AND RESULTS

Streptozotocin-induced diabetic rats were divided into two groups; one group was put on a standard diet, and the other a diet containing 1% (weight/weight) probucol for eight weeks. Two oxysterols, 7 beta-hydroxycholesterol and 7-ketocholesterol, were identified in myocardium by capillary gas chromatography. Both 7 beta-hydroxycholesterol and 7-ketocholesterol were significantly increased in diabetic rats (49.9 +/- 9.4 ng/mg dry weight versus 5.8 +/- 1.2 in controls, P < 0.05; and 5.3 +/- 1.2 ng/mg dry weight versus 1.7 +/- 0.1 in controls, P < 0.01, respectively). Probucol reduced not only plasma lipids but also myocardial lipids except for cholesterol and sphingomyelin fractions. However, probucol did not improve insulin deficiency, glucose metabolism or myocardial oxysterol contents.

CONCLUSIONS

This study demonstrated an increase in oxysterols in the myocardium of diabetic rats, suggesting that oxysterols may play a role in the development of diabetic cardiomyopathy. Probucol did not decrease the myocardial oxysterol content at the dose used in this study, suggesting that the increase in oxysterols may not be attributed to high circulating concentrations of lipids, but rather to disturbed myocardial metabolism due to insulin deficiency.

Improved insulin sensitivity by bezafibrate in rats: relationship to fatty acid composition of skeletal-muscle triglycerides

We investigated the effect of the lipid-lowering agent, bezafibrate, on insulin sensitivity in a dietary model of insulin resistance. Male Sprague-Dawley rats were divided into four groups: control group, administered a standard diet; high-fructose group, given a 40% fructose diet; high-fructose plus lard group, given a 40% fructose diet with 7% lard; and bezafibrate group, given a 40% fructose plus 7% lard diet with 10 mg x kg-1 x day-1 of oral bezafibrate. Insulin action was assessed after 2 weeks with a steady-state plasma glucose (SSPG) level. The fatty acid (FA) composition of skeletal-muscle triglycerides was also determined. A higher SSPG level (20.9 +/- 0.9 vs. 16.5 +/- 1.1 mmol/l in the control group, P < 0.05) as well as a higher systolic blood pressure (120 +/- 2 vs. 101 +/- 2 mmHg, P < 0.01) was observed in the high-fructose plus lard group, but not in the high-fructose group. These changes were prevented by bezafibrate administration. The FA composition of skeletal-muscle triglycerides demonstrated a higher percentage of saturated and monounsaturated FAs (P < 0.01) and a lower percentage of polyunsaturated FAs (P <0.01) in the high-fructose plus lard group versus the control group. These changes were consistent with differences in the dietary intake of FAs. Bezafibrate virtually normalized the FA composition in the high-fructose plus lard group. The ratio of C20:4 to C20:3, an index of delta5 desaturase activity, was significantly higher in the bezafibrate group versus the high-fructose plus lard group (8.60 +/- 0.76 vs. 2.04 +/- 0.27, P < 0.01). In conclusion, the dietary FA composition was closely related to insulin resistance in rats fed 40% fructose. Bezafibrate increased delta5 desaturase activity. Such action may contribute to the improvement of insulin sensitivity.

Role of K+ channels in EDHF-dependent relaxation induced by acetylcholine in canine coronary artery

To identify the K+ channels responsible for endothelium-derived hyperpolarizing factor (EDHF)-dependent relaxation, we studied the effects of various K+ channel blockers on acetylcholine-induced relaxation, which persists even in the presence of both an inhibitor of nitric oxide synthase and that of cyclooxygenase, in canine coronary artery rings. A nonselective K+ channel blocker, tetrabutylammonium (TBA), a large and intermediate conductance Ca2+-activated K+ channel blocker, charybdotoxin (CTX), and a voltage-dependent K+ channel blocker, 4-aminopyridine (4-AP), significantly inhibited this residual relaxation. A combined treatment with CTX and 4-AP almost completely blocked the relaxation. Neither a large (iberiotoxin) nor a small (apamin) conductance Ca2+-activated K+ channel blocker blocked the relaxation. We also investigated effects of K+ channel blockers on basal tone to determine whether or not EDHF is involved in regulating basal tone. TBA and CTX substantially raised basal tone to a greater degree in endothelium-intact preparations than in endothelium-denuded preparations. These results indicate that EDHF may exert its relaxing action through intermediate conductance Ca2+-activated and voltage-dependent K+ channels in canine coronary arteries. In addition, EDHF may play a role in maintaining basal vascular tone.

XTEM sample preparation technique for n-type compound semiconductors using photochemical etching

A sample preparation technique based on photochemical etching (PCE) is described for cross-sectional transmission electron microscopy (XTEM) of n-type compound semiconductors. XTEM samples of an InGaAsP/InP single-layer structure, prepared by using a moderately focused laser beam and Br2-methanol solution, gave high quality, damage-free XTEM images. The PCE technique is applicable to other n-type compound semiconductors.

Time courses of cell electroporation as revealed by submicrosecond imaging of transmembrane potential

Changes in the membrane conductance of sea urchin eggs, during the course of electroporation, were investigated over the time range of 0.5 microsecond to 1 ms by imaging the transmembrane potential at a submicrosecond resolution with the voltage-sensitive fluorescent dye RH292. When a rectangular electric pulse of moderate intensity was applied across an egg, a position-dependent potential developed synchronously with the pulse, as theory predicts for a cell with an insulating membrane. From the rise and fall times, the membrane capacitance of unfertilized eggs was estimated to be 0.95 microF/cm2 and the intracellular conductance 220 omega.cm. Under an electric pulse of much higher intensity, the rise of the induced potential stopped at a certain level and then slowly decreased on the microsecond time scale. This saturation and subsequent reversal of the potential development was ascribed to the introduction of finite membrane conductance, or permeabilization of the membrane, by the action of the intense pulse (electroporation). Detailed analysis indicated the following: already at 0.5 microsecond in the rectangular electric pulse, the two sides of the egg facing the positive and negative electrodes were porated and gave a high membrane conductance in the order of 1 S/cm2; the conductance on the positive side appeared higher. Thereafter, the conductance increased steadily, reaching the order of 10 S/cm2 by 1 ms. This increase was faster on the negative-electrode side; by 1 ms the conductance on the negative side was more than twice that on the positive side. The recovery of the porated membrane after the pulse treatment was assessed from the membrane conductance estimated in a second electric pulse of a small amplitude. At least two recovery processes were distinguished, one with a time constant of 7 microseconds and the other 0.5 ms, at the end of which the membrane conductance was already < 0.1 S/cm2.

[Management of infected transvenous permanent pacemakers]

Between November, 1980, and January 1991, a total of 115 transvenous pacemakers were implanted in 102 patients at our hospital. Infection at the site of implantation developed in three cases or 2.6%. The median time of the onset of infection postoperatively was eleven and a half months, the range being two and a half to twenty-four months. Coagulase positive Staphylococcus aureus was cultured from the infected site of one patient and coagulase negative Staphylococcus epidermidis and saprophyticus in two patients. Staphylococcus aureus septicemia developed in one patient. Conservative medical treatment consisting of the application of two or more antibiotics was unsuccessful in all three cases. In two patients, removal of the infected pacemaker generator and implantation of a completely new pacemaker system at a new, clean site were conducted. In one of these two patients, the septic pacemaker electrode was withdrawn 3 months after removal of the infected pacemaker generator. In the other patient, limited thoracotomy with incision of the left brachiocephalic vein was performed for removal of the electrode three weeks after removal of the infected pacemaker generator.

Membrane conductance of an electroporated cell analyzed by submicrosecond imaging of transmembrane potential

Transmembrane potential was induced in a sea urchin egg by applying a microsecond electric pulse across the cell. The potential was imaged at a submicrosecond time resolution by staining the cell membrane with the voltage-sensitive fluorescent dye RH292. Under moderate electric fields, the spatial distribution of the induced potential as well as its time dependence were in accord with the theoretical prediction in which the cell membrane was regarded as an insulator. At higher field intensities, however, the potential apparently did not fully develop and tended to saturate above a certain level. The saturation is ascribed to the introduction of a large electrical conductance, in the form of aqueous openings, in the membrane by the action of the induced potential (electroporation). Comparison of the experimental and theoretical potential profiles indicates that the two regions of the membrane that opposed the electrodes acquired a high membrane conductance of the order of 1 S/cm2 within 2 microseconds from the onset of the external field. The conductance was similar in the two regions, although permeability in the two regions of the membrane long after the pulse treatment appeared quite different.

Distribution-analyzing latex immunoassay (DALIA): methods for determination of antigen and for elimination of non-specific reaction induced by rheumatoid factor

A highly sensitive distribution-analyzing latex immunoassay method (DALIA), which is based on analysis of the volume distribution of latex particles including both the agglutinates and the residual non-agglutinating particles, has been established. Numbers of latex particles, which are sensitized with specific antibodies, are counted by using an electric particle counter with a personal computer and simultaneously the extent of agglutination was quantified by analyzing the volume distribution of the reacted latex particles. It was found that ultramicrospheres coated with normal goat immunoglobulin G can completely eliminate non-specific reactions induced by human serum containing rheumatoid factor (RF) in this DALIA method. The degree of absorption of RF activity by these ultramicrospheres was associated with the diameters of the ultramicrospheres. Moreover, by use of the combination of ultramicrospheres and latex particles coated with monoclonal antibodies against alpha-fetoprotein (AFP) or with polyclonal antibody specific to C-reactive protein, specific DALIA systems were able to be developed. Both DALIA systems exhibited the high sensitivity (1 to 7 ng/ml). The correlation coefficient (gamma) of the results of DALIA with those of enzyme-linked immunoadsorbent assay in measuring AFP was 0.994.

A high-voltage scanning transmission electron microscope at Nagoya University

A high-voltage scanning transmission electron microscope (STEM) H-1250ST of the maximum accelerating voltage of 1.25 MV was constructed at Nagoya University in 1983. The microscope, equipped with a field-emission gun, is designed with high-level STEM performance as well as conventional transmission microscopy mode operation. The aim of developing the microscope, basic design schemes, principal instrumentation, and techniques developed are described.

Studies on Nature of So-Called Antiplasmin Measured By Chromogenic Substrate S-2251 and Its Automatic Determination With ABA 100

Using chromogenic substrate S-2251, authors studied on the nature of so-called antiplasmin and on the application of Coatest to automatic determination. As to several protease inhibitors, correlation performed vs single radial immunodiffusion yielded a regression of Y=19.5X-18.6 and r=0.91 for α2PI ;r=-0.15, 0.13, 0.46 0.28 for α2M, α2AT, AT-III and CIINA respectively. Purified protease inhibitors except α2PI did not exhibit immediate inhibition to human plasmin. The automation of chromogenic substrate method was studied with ABA Bichromatic Analyser Model 100 and auxiliary dispenser. 25 microliter of diluted plasma and 250 microliter of plasmin of known activity were added simultaneously to 100 microliter of substrate S-2251. Reaction rate was assayed with the use of two wavelengths, 450/415. Excellent correlation with manual protocol was observed, r=0.985 and Y=0.88X=8.7. Determination of within-day precision of automatic assay for three sample concentrations (Antiplasmin 25%, 100%, 150%) gave C.V. of 1.5%, 1.71% and 4.46% respectively. Thus, authors arrived at the conclusion that 1) α2PI is mainly determined as protesae inhibitor with the use of S-2251, 2) ABA 100 was successfully employed for automatic determination of antiplasmin with the use of simultaneous addition of plasma and plasmin to substrate solution.

Studies on Nature of So-Called Antiplasmin Measured by Chromogenic Substrate S-2251 and its Automatic Determination with ABA 100

Using chromogenic substrate S-2251, authors studied on the nature of so-called antiplasmin and on the application of Coatest to automatic determination. As to several protease inhibitors, correlation performed vs single radial immunodiffusion yielded a regression of Y=19.5X-18.6 and r=0.91 for α2 PI;r=-0.15, 0,13, 0.46 0.28 for α2M, α1AT, AT-III and CIINA respectively. Purified protease inhibitors except α2PI did not exhibit immediate inhibition to human plasmin. The automation of chromogenic substrate method was studied with ABA Bichromatic Analyser Model 100 and auxiliary dispenser. 25 microliter of diluted plasma and 250 microliter of plasmin of known activity were added simultaneously to 100 microliter of substrate S-2251. Reaction rate was assayed with the use of two wavelengths, 450/415. Excellent correlation with manual protocol was observed, r=0.985 and Y=0,88X=8.7. Determination of within-day precision of automatic assay for three sample concentrations (Antiplasmin 252, 100%, 150%) gave C.V. of 1.5%, 1.71% and 4.46% respectively. Thus, authors arrived at the conclusion that 1) OfiPI is mainly determined as protesae inhibitor with the use of S-2251, 2) ABA 100 was successfully employed for automatic determination of antiplasmin witli the use of simultaneous addition of plasma and plasmin to substrate solution.