CD36 signaling inhibits the translation of heat shock protein 70 induced by oxidized low density lipoprotein through activation of peroxisome proliferators-activated receptor gamma

Oxidized LDL (OxLDL), a causal factor in atherosclerosis, induces the expression of heat shock proteins (Hsp) in a variety of cells. In this study, we investigated the role of CD36, an OxLDL receptor, and peroxisome proliferator-activated receptor gamma (PPAR gamma) in OxLDL-induced Hsp70 expression. Overexpression of dominant-negative forms of CD36 or knockdown of CD36 by siRNA transfection increased OxLDL-induced Hsp70 protein expression in human monocytic U937 cells, suggesting that CD36 signaling inhibits Hsp70 expression. Similar results were obtained by the inhibition of PPAR gamma activity or knockdown of PPAR gamma expression. In contrast, overexpression of CD36, which is induced by treatment of MCF-7 cells with troglitazone, decreased Hsp70 protein expression induced by OxLDL. Interestingly, activation of PPAR gamma through a synthetic ligand, ciglitazone or troglitazone, decreased the expression levels of Hsp70 protein in OxLDL-treated U937 cells. However, major changes in Hsp70 mRNA levels were not observed. Cycloheximide studies demonstrate that troglitazone attenuates Hsp70 translation but not Hsp70 protein stability. PPAR gamma siRNA transfection reversed the inhibitory effects of troglitazone on Hsp70 translation. These results suggest that CD36 signaling may inhibit stress- induced gene expression by suppressing translation via activation of PPAR gamma in monocytes. These findings reveal a new molecular basis for the anti-inflammatory effects of PPAR gamma.

Quantitative Analysis of Aortic Atherosclerosis in Korean Female: A Necropsy Study

To assess the regional difference and influence of the biological variables on atherosclerosis in female, we analyzed 7 segments of aorta (2 ascending, 3 thoracic, and 2 abdominal) from 90 superficially healthy Korean women (39+/-14 yr of age) who died from external causes. Tissue specimens were macroscopically examined and histopathologically divided into 7 grades for scoring (ATHERO, from 0=intact, to 6=thrombi formation). Lumen diameter (LD), wall thickness (WT), intima thickness (INT), and media thickness (MED) were obtained by computed morphometry. Atherosclerosis was common in the distal infrarenal (C2), proximal thoracic (B1), and proximal ascending (A1) segments. Total 95.6% of all subjects had atherosclerosis of variable degree in one or more segments, but an aneurysmal change was not found. The number of atherosclerotic segments and atherosclerosis score in the 7 segments increased with aging. However, the body size did not affect the aortic size and ATHERO. With aging, LD and INT of the A1, B1 and C2 increased (p<.00001); WT of the B1 and C2 increased (p<.01); and MED of C2 decreased (p<.01). LD and WT of the B1 and C2 (p<.05), INT of the A1, B1 and C2 (p<.00001) increased, and MED of C2 decreased (p<.01) with ATHERO. These data suggest that age is simple but a reliable parameter for estimating the progression of atherosclerosis.

Infarct Size-limiting Effect of Calcium Preconditioning in Rabbit Hearts

Recent studies demonstrated that brief period of Ca2+ depletion and repletion (Ca2+ preconditioning, CPC) has strong protective effects against ischemia in a rat heart. CPC and classic preconditioning (IPC) were compared in relation with infarct size and protein kinase C (PKC) isozymes. Isolated Langendorff-perfused rabbit hearts were subjected to 45-min ischemia (Isc) followed by 120-min reperfusion (R) with or without IPC, induced by 5-min Isc and 10-min R. In the CPC hearts, 5-min Ca2+ depletion and 10-min repletion (CPC) were given before 45-min Isc, with or without concurrent PKC inhibition (calphostin C, 200 nmol/L). IPC enhanced recovery of LV function, while CPC did not. Infarct size was significantly reduced by both CPC and IPC (p < 0.05 vs. ischemic control). Membrane PKC was significantly increased from 2.53 +/- 0.07 (baseline, nmol/g tissue) to 3.11+/-0.07, 3.34 +/- 0.11, 3.15 +/- 0.09, and 3.06 +/- 0.08 by IPC, IPC and 45-min Isc, CPC and 45-min Isc, respectively (p < 0.01). Immunoblots of membrane PKC were increased by IPC, IPC and 45-min Isc, and CPC. These effects were abolished by PKC inhibition. Thus, activation of PKC may have trigger role in the mechanism of cardioprotective effect by CPC.

Effect of Preconditioning by Low-Flow Perfusion on Cardioprotection

BACKGROUND AND OBJECTIVES: Recent reports suggest that brief periods of low-flow ischemia (lf Isc) and reperfusion (R) before prolonged Isc mimic ischemic preconditioning (IPC) in murine hearts, probably by a preservation of high energy phosphates. MATERIALS AND METHODS: In order to test this hypothesis, Langendorff-perfused isolated rabbit hearts were subjected to 45 min lf Isc (5% of baseline perfusion flow) with lf IPC or not, followed by 120 min R. lf IPC was induced by a single episode of 5 min lf Isc and 10 min R. These were compared with IPC hearts by 5 min no-flow Isc and 10 min R. RESULTS: lf IPC as well as IPC enhanced post-ischemic functional recovery although IPC did not reduce infarct size (Isc control, 37.5+/-3.1, IPC, 16.2+/-1.5, lf Isc, 43.0+/-0.7, and lf IPC, 40.4+/-1.0% of the left ventricle). Myocardial ATP hydrolysis and lactate production during the preischemic, ischemic, and reperfusion periods were not differ between the experimental groups. CONCLUSION: These results suggest that a brief period of lf Isc could not precondition the rabbit heart and the energy metabolism hypothesis may not be a universal mechanism for the cardioprotective effect of IPC.

The Delayed Phase of Protection in Heat-Induced Preconditioning: Role of the Heat Shock Protein associated with cytoskeleton

BACKGROUND AND OBJECTIVES: We investigated the ability of a brief heat shock on day one to provide delayed protection against lethal heat stress on day two in a rat-derived H9c2 cardiomyoblast cell line with reference to the role of heat shock protein 25/27, 70i and the p38MAPK signalling pathway. MATERIALS, METHODS AND RESULTS: Heat preconditioning(Heat P; 20min at 42+/-0.1degrees C) and adenosine(ADO) administered on day 1 protected against cell death under lethal heat challenge (75min at 42+/-0.1degrees C) on day 2 as measured by MTT test: ( % cell viability: Heat P: 79.9+/-3.23%, ADO: 71.9+/-4.10% vs. control: 52.7+/-1.65% respectively ). This protection was abolished by treatment with SB203580 or cytochalasine D prior to the protective stimulus on day 1( SB203580: 64.1+/-4.37%, cytochalasine D: 73.1+/-4.33% vs. Heat P ). Western blotting analysis indicated a significant accumulation of hsp70i in Heat P and SB203580-treated Heat P cells compared to control and adenosine-, SB203580-treated cells. Phosphorylation of hsp25 was significantly increased in Heat P cells compared to control cells. We also observed fragmentation of F-actin and formation of F-actin aggregates in cells exposed to lethal heat challenge. In contrast, the delayed cytoprotection preserved the F-actin bundles under lethal heat challenge. Hsp27-overexpressed, stable clones were more resistant to lethal heat shock when compared to control cells transfected with the vector alone. CONCLUSION: These data suggest an important role for p38MAPK/hsp25/27 pathway as a potential distal effector of heat-induced delayed protection.

Cardioprotective Effect of Ischemic Preconditioning: Relationship between Intracellular Glycogen and Protein Kinase C

BACKGROUND: Recent studies suggest that the cardioprotective effect of ischemic preconditioning (IPC) is related to intracellular glycogen content in rat hearts, however, controversies still remain. METHODS: To test this hypothesis, isolated Langendorff-perfused rabbit hearts were subjected to 45 min global ischemia followed by 120 min reperfusion with IPC (n=0) or without IPC (ischemic control, n=). IPC was induced by one cycle of 5 min global ischemia and 10 min reperfusion. In the glucose (G)-free preconditioned group (n=0), G depletion-repletion was induced by perfusion with G-free Tyrode solution for 5 min and then G-containing Tyrode solution for 10 min followed by 45 min ischemia and 120 min reperfusion. For glycogen depletion or loading, hearts were treated with sodium acetate (NA, 5 mM, n=) or insulin (Ins, 1 unit/L, n=) for 15 min before 45 min ischemia. Left ventricular function and coronary flow (CF) were continuously recorded during experiments. Myocardial cytosolic and membrane protein kinase C (PKC) activities were measured by 32P-gamma-ATP incorporation into PKC-specific pepetide; glycogen content in the cardiac myocytes was determined by spectrophotometry with amyloglucosidase; expression of PKC isozymes was determined by Western blot with monoclonal antibodies. Infarct size was determined by staining with tetrazolium salt and planimetry. Data were analyzed by ANOVA and Tukey's post-hoc test. RESULTS: IPC or G-free preconditioning enhanced LV functional recovery; NA did not influence on functional recovery but Ins depressed it. Infarct size was significantly reduced by IPC, G-free preconditioning, and NA treatment (35.3+/-2.1% in the ischemic control, 18.7+/-1.2% in the IPC, 22.1+/-1.2% in the G-free preconditioned, 16.3+/-1.2% in the NA-treated group, and 32.8+/-1.6% in the Ins-treated group, p<0.05). Membrane PKC activities significantly increased by IPC, IPC and 45 min ischemia, G-free preconditioning, and G-free preconditioning and 45 min ischemia; especially, expression of membrane PKC-epsilon increased by IPC and G-free preconditioning. Glycogen content decreased by 45 min ischemia, IPC, G-free preconditioning, and by NA treatment, but increased by Ins treatment. CONCLUSION: These results suggest that in rabbit heart, intracellular glycogen may not significantly be related with the cardioprotective effect of IPC; G-free preconditioning could not improve post-ischemic contractile dysfunction but it has an infarct size-limiting effect; this cardioprotective effect may be related in part to activation of PKC, especially epsilon isozyme.

Role of adenosine in the cardioprotective effect of ischemic preconditioning in the isolated rabbit hearts / 대한해부학회지

This study was designed to provide a evidence that adenosine-mediated activation of protein kinase C and K(ATP) channel was a important step on the cardioprotection mechanism of ischemic preconditioning (IP). Isolated Langendorff-perfused New Zealand White rabbit hearts were subjected to 45 min of global ischemia (I) and 120 min reperfusion (R) with or without IP. IP was induced by a single dose of 5 min I and 10 min R. Part of the IP hearts was treated with non-specific adenosine receptor blocker 8-sulfophenyltheophylline (SPT; 100 micromol) and K(ATP) channel blocker glibenclamide (10 micromol) 5min before IP, respectively. To determine the effect of IP, we measured the left ventricular function, infarct size, adenosine concentration in the coronary flow and total protein kinase C activity. PKC activity was determined by (32)P-gamma-ATP incorporation into PKC specific peptide. IP enhanced improvement of functional recovery and caused a decrease in the infarct size from 19.9+/-0.05% in the ischemic-control group to 5.5+/-1.39% in the IP group (p<0.05). In the SPT- and glibenclamid-treated hearts, however, these anti-ischemic effect was disappeared. Adenosine release from the cardiac tissue was abruptly increased to 10~20 folds baseline just after IP. Cytosolic PKC activity decreased significantly in the IP hearts, while in the membrane fraction, activity was increased (45 min I, p<0.05; 120 min R, p<0.01). In the SPT-treated hearts, IP did not make those activity changes of PKC. These data suggest that adenosine induced the anti-ischemic effect via PKC activation. And it also show that K(ATP) channel may work on the protection as a final effector.

Ischemic Preconditioning and Its Relation to Glycogen Depletion / 대한흉부외과학회지

BACKGROUND: Recent studies have suggested that the cardioprotective effect of ischemic preconditioning (IP) is closely related to glycogen depletion and attenuation of intracellular acidosis. In the present study, the authors tested this hypothesis by perfusion isolated rabbit hearts with glucose(G) is closely related to glycogen depletion and attenuation of intracellular acidosis. In the present study, the authors tested this hypothesis by perfusion isolated rabbit hearts with glucose(G)-free perfusate. MATERIAL AND METHOD: Hearts isolated from New Zealand white rabbits (1.5~2.0 kg body weight) were perfused with Tyrode solution by Langendorff technique. After stabilization of baseline hemodynamics, the hearts were subjected to 45 min global ischemia followed by 120 min reperfusion with IP(IP group, n=13) or without IP(ischemic control group, n=10). IP was induced by single episode of 5 min global ischemia and 10 min reperfusion. In the G-free preconditioned group(n=12), G depletion was induced by perfusionwith G-free Tyrode solution for 5 min and then perfused with G-containing Tyrode solution for 10 min; and 45 min ischemia and 120 min reperfusion. Left ventricular functionincluding developed pressure(LVDP), dP/dt, heart rate, left ventricular end-distolic pressure (LVEDP) and coronary flow (CF) were measured. Myocardial cytosolic and membrane PKC activities were measured by 32P-gamma-ATP incorporation into PKC-specific peptide and PKC isozymes were analyzed by Western blot with monoclonal antibodies. Infarct size was determined by staining with TTC (tetrazolium salt) and planimetry. Data were analyzed by one-way analysis of variance (ANOVA) and Turkey's post-hoc test. RESULT: In comparison with the ischemic control group, IP significantly enhanced functional recovery of the left ventricle; in contrast, functional significantly enhanced functional recovery of the left ventricle; in contrast, functional recovery were not significantly different between the G-free preconditioned and the ischemic control groups. However, the infarct size was significantly reduced by IP or G-free preconditioning (39+/-2.7% in the ischemic control, 19+/-1.2% in the IP, and 15+/-3.9% in the G-free preconditioned, p<0.05). Membrane PKC activities were increased significantly after IP (119%), IP and 45 min ischemia(145%), G-free [recpmdotopmomg (150%), and G-free preconditioning and 45 min ischemia(127%); expression of membrane PKC isozymes, alpha and beta, tended to be increased after IP or G-free preconditioning. CONCLUSION: These results suggest that in isolated Langendorff-perfused rabbit heart model, G-free preconditioning (induced by single episode of 5 min G depletion and 10 min repletion) colud not improve post-ischemic contractile dysfunction(after 45-minute global ischemia); however, it has an infarct size-limiting effect.

Relationship between normal heart size and body indices in Korean

We provided a curve-fit equation to predict the normal heart weight (g) in Koreans by examining 422 autopsies (215 males and 207 females, from newborn to age 77 yr) who were relatively in good general condition. Heart weight was well correlated with body surface area (m2), body weight (kg), and body height (cm) but poorly with age in both sex. Heart weight progressively increased from birth to the earlier 3rd and 4th decades in male and female, respectively, and then gradually decreased; mean heart weight of all age group was greater in male than in female and significantly different from birth to 4th decade. In both sex, heart weight exponentially increased in accordance with the increase of body height, body weight, and body surface (in male, heart weight=0.00312 x body height(2.239), r2=0.750, p<0.0001; in female, heart weight=0.00443 x body height(2170), r2=0.781, p<0.0001; in male, heart weight=9.22 x body weight(0.853), r2=0.770, p<0.0001; in female, heart weight=9.00 x body weight0.855, r2=0.820, p<0.0001; in male, heart weight=155.18 x body surface area1.290, r=0.808, p<0.0001; in female, heart weight=124.13 x body surface area1.242, r=0.834, p<0.0001). These results indicate that heart weight is better correlated with body surface area than with body weight; however, body weight should be a better determinant of a predicted heart weight, since body surface area is entirely dependent on body height and body weight.

Cardioprotective Effect of the Ischemic Preconditioning: Its Relation to Activation of Protein Kinase C

BACKGROUND: We tested recent evidences that IP triggers selective activation of protein kinase C (PKC) isozymes using isolated Langendorff-perfused rabbit heart with PKC activator, phorbol ester (PMA, 0.01 nM) or inhibitor (calphostin C, 200 nM). METHODS: After stabilization of baseline hemodynamics, the hearts were subjected to 45 min global ischemia (I) followed by 120 min reperfusion (R) with IP (IP group, n=18) or without IP (ischemic control group, n=16). IP was induced by single episode of 5 min I and 10 min R. In the PMA-treated group (n=19) and calphostin C-treated preconditioned group (n=15), PMA and calphostin C was given for 5 and 15 min before 45 min I, respectively. Myocardial cytosolic and membrane PKC activities were measured by 32P- -ATP incorporation into PKC-specific pepetide: PKC isozymes were analyzed by Western blot with monoclonal antibodies. RESULTS: IP significantly increased the recovery of the LV function including LVDP and coronary flow (p <0.05):however, enhancement of the functional recovery disappeared by calphostin C or PMA treatment. Cytosolic PKC activity decreased to 82-76% in the IP and PMA-treated group (p <0.05): membrane PKC activity increased to 218-272% (p <0.01). However, both fraction of PKC activity was not changed in the calphostin C-treated preconditioned group. In addition, Western blot revealed that PKC- alpha and epsilon, especially epsilon, were selectively translocated during subsequent sustained ischemia after IP or PMA administration. IP and PMA also reduced infarct size (frim 38 to 10-20%, p <0.05). However, calphostin C blocked infarct reduction effect of IP. CONCLUSION: These results indicate that in isolated rabbit heart model, cardioprotective effect of IP may be related, at least in part, to trigger selective translocation of PKC, especially epsilon isotype.

The Cardioprotective Effect of Ischemic Preconditioning : Role of Adenosine and Protein Kinase C

BACKGROUND: Brief episodes of coronary blood flow interruption, ischemic preconditioning (IP), following a prolonged ischemia induces myocardial tolerance to ischemia and improves myocardial function during reperfusion by undefined mechanism. Recently, it has been suggested that the signal transduction pathway of the cardiomyocyte itself may involve in this protection. The aims of the present study were : (1) to examine the effect of adenosine in early phase of IP, (2) to define the relationship between the adenosine and protein kinase C(PKC) METHOD AND RESULTS: Heart isolated from New Zealand White rabbit (1.2 - 1.5kg body weight, n=78) were perfused with Tyrode solution by non-recirculating Langendorff technique. After stabilization of baseline hemodynamics, the hearts were subjected to receiving 45min global ischemia (I) and 120min reperfusion (R) with or without IP. IP was induced by a single dose of 5min I and 10min R. A part of the IP hearts, calphostin C (200nmol/L), a PKC inhibitor, was administered 5min before IP and sustained during IP regimen. Left ventricular function and coronary flow were monitored. Infarct size was determined by staining with 1% triphenyltetrazolium chloride solution and computerized planimetry. Adenosine concentration in the coronary flow was determined by HPLC. Myocardial cytosolic and membrane PKC activities were measured by (32)P-r-ATP incorporation into PKC specific peptide. Expression of PKC-e and PKC-o was determined by SDS-PAGE and Western blot. IP enhanced improvement of functional recovery (p<0.05, in the left ventricular developed and end-diastolic pressure ; p<0.01, in the coronary flow) during 120min R after 45min I. Preconditioned hearts showed reduction in the infarct size compared with the non-preconditioned hearts (p<0.05) ; however, IP-induced protection was lost by calphostin C. Adenosine release from the cardiomyocytes abruptly increased to 10-20 folds baseline just after IP manipulation and decreased rapidly on reperfusion. Cytosolic PKC activity significantly decreased in the preconidtioned hearts which received 45min I(p<0.05) and 45min I and 120min R(p<0.01), while the membrane fraction increased in the former(p<0.05) and the latter(p<0.01) groups. There was no significant difference in the PKC-o activity among all experimental groups in cytosolic and membrane fraction, however, the membrane PKC-e isoenzyme activity was increased in the preconditioned hearts which received 45min I. CONCLUSION: These results indicate that (1) a single dose of brief ischemia has an infarctlimiting effect and can improve post-ischemic contractile dysfunction after 45min subsequent sustained I ; and (2) increase of adenosine release in the earlier period of IP regimen and translocation of PKC from the cytosol to myocyte membrane may be important processes signal transduction for protection. These results suggest that cardioprotective mechanism responsible for IP in isolated rabbit heart may be initiated by adenosine and PKC.

Ischemic Preconditioning in Isolated Rabbit Heart : Effect on Left Ventricular Function, Infarct Size, and Protein Kinase C*

BACKGROUND: It has been demonstrated that ischemic preconditioning(IP, repetitive brief period of ischemia and reperfusion) enhances recovery of post-ischemic contractile dysfunction and reduces incidences of reperfusion-arrhythmia and infarct size after a prolonged ischemia. A lot of mechanisms have been proposed, however, controversies still remain. Recent studies suggested that IP could activate protein kinase C(PKC). Therefore, we measured left ventricular function, myocardial creatinin and PKC activities, and infarct size to assess whether IPs cardioprotective effect is related to PKC activation using isolated rabbit hearts. METHODS AND RESULTS: Hearts isolated from New Zealand White rabbits(1.5-2.0kg body weight) were perfused with Tyrode solution by Langendorff technique. After stabilization of baseline hemodynamics, the hearts were subjected to 60-min ischemia followed by 120-min reperfusion with IP(IP group, n=15) or without IP(control group, n=14), IP was induced by 4 cycles of 5-min global ischemia and 5-min reperfusion. Left ventricular function including developed pressure(LVEDP), dp/dt, heart rate(HR), and coronary flow(CF) was measured to determine the recovery of LVEDP, RPP(rate-pressure product, HRXLVEDP) and CF to baseline measurement. Frequency of arrhythmia was counted on reperfusion. Myocardial CK-MB, myocardial cytosolic and membrance PKC were measured and the infarct size was determined by staining with tetrazolium salt and planimetry. Data were analyzed by one-way ANOVA, Tukey's post-hoc test and t-test. There was no significant differences in the recovery of LVEDP, dp/dt, RPP, and CF and frequency of arrhythmia during reperfusion between the control and the IP groups. In comparison with the control groups, however, CK-MB was significantly lowered in the IP group(P < 0.05). Cytosolic PKC was significantly decreased but membrance PKC was increased(p < 0.05). These findings indicate that PKC was translocated and activated by IP. Furthermore infarct size was smaller and limited to the antero-lateral or posterior wall and papillary muscle in the IP group(p < 0.05). CONCLUSION: These results indicate that IP dose not improve post-ischemic contractile dysfunction after a prolonged ischemia of 60 minutes but has an infarct-limiting effect. This cardioprotective effect of IP may be related to PKC activation.

Effects of Ischemic Preconditioning on the Left Ventricular Function, Myosin Isozyme, Myofibrillar ATPase Activity and Ultrastructure of the Rabbit Heart

BACKGROUND: Single or multiple episodes of brief period of ischemia and reperfusion(ischemic preconditioning, IP) have been shown to limit infarct size after a subsequent longer period of ischemia. A considerable number of possible mechanisms has been proposed, however, controversies still remain. Accordingly, we evaluated the effect of four cycles of 5 minutes ischemia and 5 minutes reperfusion(IP) followed by subsequent 30 minutes ischemia(ISCH) and 60 minutes reperfusion using isolated Langendorff-Perfused rabbit hearts. Methods and RESULTS: After a 50-minute recovery phase, parameters of the left ventricular function(LVF) including left ventricular developed pressure(LVDP), contractility and the heart rate were recorded, and ultrastructure was examined. Myosin ATPase activity was determined by measurement of inorganic phosphorus and isozymes of the myosin heavy chain were examined by polyacrylamide gel electrophoresis containing pyrophosphate buffer. The ISCH hearts showed severe to irreversible change of the cardiac myocytes homogenously in contrast to the IP hearts in which changes were not homogenous and irreversible injury was only focal. However, parameters of the LVF were not significantly different between the IP and the ISHC hearts during reperfusion. Myosin ATPase activities were also not significantly different(0.67+/-0.123 micromol/mg protein/h in the IP hearts, 0.56+/-0.172 micromol/mg protein/h in the ISCH hearts, and 0.76+/-0.239 micromol/mg protein/h in the control hearts). Band patterns of the myofibrillar proteins, separated by sodium ddodecyl sulfate-polyacrylamide gel electrophoresis, revealed no differences between the IP, ISCH and the control hearts. Myosin heavy chains in the IP and the ISCH hearts were separated into 3 isozymes, V1,V2and V3in pyrophosphate gel electrophoresis in contrast that the control hearts revealed two isozymes, V1and V2. However, there were no differences in the protein composition and electrophoretic motility between the IP and the ISCH hearts. CONCLUSION: These results indicate that IP could not attenuate the changes in LVF, myosin ATPase activity and myosin isozymes on reperfusion, however, it could attenuate the ultrastructural changes of the cardiac myocytes.

Relation between ischemic preconditioning and the duration of sustained ischemia

It has been reported that repetitive brief periods of ischemia and reperfusion (ischemic preconditioning, IP) cause a significant reduction in the extent of myocardial necrosis or in the incidence of reperfusion arrhythmias in rat heart. However, recent reports have stated that IP effect is diminished or lost in the canine or bovine heart if ischemia (mostly regional) is sustained for 40 min or longer. The main objective of this study is to assess whether IP provides myocardial protection in prolonged sustained ischemia under the condition of global ischemia in isolated rabbit heart. The hearts were subjected to 10-60 min sustained ischemia (SI) followed by 60 min reperfusion with (IP heart) or without IP (ISCH heart). IP was induced by 4 cycles of 5 min global ischemia and 5 min reperfusion. Left ventricular function (LVF), extent of infarction (EI) and ultrastructural changes were examined. As a whole, the LVF began to recover on reperfusion but there was no significant difference in the functional parameters. However, extracellular Ca2+ concentration was lower in the ISCH hearts (p <0.05) and the EI was significantly different between the hearts which had received 60 min SI (67% in the ISCH versus 32% in the IP heart, p <0.01). Ultrastructural changes were homogeneous in the ISCH hearts and became irreversible in accordance with increase of the duration of ischemia, while these changes were heterogeneous and restricted in the IP heart. These results suggest that IP does not attenuate the postischemic dysfunction in prolonged ischemia but it can provide an infarct size-limiting effect and delay ultrastructural changes. This cardioprotective effect may be related to calcium homeostasis.

Ultrastructural changes in the cardiac myocyte and the extracellular space in different duration of ischemia / 대한해부학회지

No abstract available.

Effect of Preconditioning on Postischemic Reperfused Rabbit Heart

BACKGROUND: It has been reported that one or more intermittent reperfusion(s) during ischemia may be beneficial to the myocardium by washing out catabolites that have accumlated during ischemia. We evaluated the effect of four cycles of ichemia (2 minutes) and reperfusion (3 miutes), i.e., preconditioning on sustained ischemia (20 minutes) and reperfusion (60 minutes) using isolated Langendorff-perfused rabbit hearts. METHODS: After a fifty-minutes recovery phase, LVP , dLVP/dt and ECG were simultaneously recorded and ultrastructure of the stunned(or risk) area of the left ventricle was examined with conventional methods. RESULTS: In the preconditioned hearts, functional parameters such as LVPP(peak pressure), LVPP recovery rate and LVEDP(end-diastolic pressure) reached to 99.6+/-4.38mmHg, 98.0+/-4.67% and 14.0+/-2.90mmHg (109.3+/-2.91mmHg, 109.4+/-1.29mmHg and 10.7+/-2.67mmHg for the controls), respectively, after 30 minutes from the onset of reperfusion and maintained as in the controls(p>0.01). In contrast, in the ischemia-reperfusion hearts, LVPP and LVPP recovery rate were significantly reduced(81.6+/-6.83mmHg and 85.7+/-5.30%;p<0.05) and LVEDP elevated(21.2+/-3.00mmHg) but dP/dtmax, heart rate and ECG patterns were not significantly different between the preconditioned and the ischemia-refusion hearts during reperfusion. Furthermore, irreversible myocardial injury was homogeneous(both subendo- and subepicardial) in the ischmia-reperfusion hearts but only focal(subendocardial) in preconditioned hearts. CONCLUSION: These results suggest that preconditioning induced by very short periods of ischemia and reperfusion may enhance recovery of the left ventricular function and delay ultrastructhral changes to a certain extent during reperfusion.

Studies on the Development of Lung and Distribution of Elastic and Reticular Fibers during Fetal Period Proper / 체질인류학회지

To investigate the human lung development and the distribution of elastic and reticular fibers during the fetal period proper, lung tissues taken from the periphery of the right lower lobes of Korean fetuses (n=49) of both sex were studied. The fetuses were the prodocts of spontaneous or therapeutic abortions and were found to have no associated lesions or anomalies at autopsy. The fetal age were estimated from crown-rump length or foot length. Paraffin sections, cut at 5-7 µm, were stained with routine hematoxylin and eosin for general structure, acid orcein and a1dehyde fuchsin for elastic fiber, and with Gomori's silver technique for reticular fiber, respectively. The lung development during fetal period proper, could be subdivided into three continuous periods according to the relation between airspaces, surrounding mesenchymal tissue, their structural changes and distribution, i.e., an early stage of the formation of conductive airways (pseudoglandular period, before 16th week of gestation), a middle stage of the development of lung parenchyma and new blood vessels (canalicular period, between 16th and 28th week of gestation), and a late stage of transition of respiratory portion to vascular organ (terminal sac stage, after 28th week of gestation). In places, secondary septa of sac or saccule formed by capillaries, capillary connective tissue, elastic and reticular fuel could be identified by the 33rd week of gestation. Elastic fibers could be noted in pleura, subepithelial areas of bronchioles and the wall of blood vessels in the late stage of pseudoglandular period. By the 28th week of gestation, elastic fibers were seen in the wall of small blood vessels or capillaries in the septal wall among the airspaces. And these fibers were observed in the tip of the secondary septa by the 33rd week of gestation but were not still completely developed in the walls of primary or secondary septa. Reticular fibers were already developed and widely distributed in fetal lung by the 10th week of gestation. These fibers were concentrated particular around the subepithelial area of bronchicoles, the airspaces and the blood vessel wall in the canalicular period. By the late stage of terminal sac period, reticular fibers formed a network along the small blood vessels in the septum of airspaces. These results indicate that primitive alveoli might be formed by the late stage of fetal period proper. The fibrous framework could partially formed by collagenous and reticular fibers during the pseudoglandular period, by addition of elastic fiber to the preformed network, and incompletely still finally by the three kinds of connective tissue fiber.

Morphometric Study on the Development of the Human Fetal Heart after Mid-term / 체질인류학회지

A total of 23 human fetal hearts from 18 to 40 weeks of gestation were provided for histologic and morphometric studies. The fetuses were the products of spontaneous or artificial abortions and were found to have no congential anomalies or associated lesions at autopsy. Maxima thickness of the left anterior, left lateral, left posterior, right anterior, right lateral, right posterior ventricular wall, and of the interventricular septal wall were measured and the left / right wall thickness ratio was calculated. The cross-sectional area of each ventricle parallel to the base of the heart at about 3-5mm below from the origin of the aorta was measured under drawing attachment-equipped light microscope with the application of point counting or cut-and-weigh method. Data were analyzed by the Anderson-ell ABSTAT dBASE ll statistical package program. The ventricular wall consisted of endocardium, myocardium and epicardium. The myocardium showed epithelial character by stratification of barrel-shaped myocardial cells, but the epithelial character progressively changed to as in adult myocardial tissue from the myocardial area close to the epicardium with increasing fetal age. However, any significant histologic difference between the left and the right ventricular wall at the same fetal age was not found. The growth pattern of both ventricular wall, the interventricular septal wall, and of the cross sectional area were linear (p0.1).