Energy‐related metabolites during and after induced myocardial infarction with special emphasis on the reperfusion injury after extracorporeal circulation

In the clinical setting great efforts have been made with contradictory results to operate upon acutely myocardial ischaemic patients. The reasons for the absence of clear‐cut results are not well understood nor are they scientifically explored. To resolve this problem further, we attempted to design an experimental in vivo model to mimic acute myocardial ischaemia followed by extracorporeal circulation (ECC) and reperfusion. One of the main targets of our protocol was monitoring of myocardial energy metabolism by microdialysis (MCD) during the periods of coronary occlusion (60 min), hypothermic (30 °C) ECC and cardioplegia (45 min), followed by reperfusion with (30 min) and without (60 min) ECC. In eight anaesthetized, open‐chest pigs, myocardial lactate, pyruvate, adenosine, taurine, inosine, hypoxanthine and guanosine were sampled with MCD in both ischaemic and non‐ischaemic areas. Myocardial area at risk and infarct size were quantified with the modified topographical evaluation methods. The principal finding with this experimental setup was a biphasic release pattern of lactate, adenosine, taurine, inosine, hypoxanthine and guanosine from ischaemic myocardium. Lactate levels were equally high in reperfused ischaemic and non‐ischaemic myocardial tissue. Pyruvate demonstrated consistently higher values in non‐ischaemic myocardium throughout the experiment. A pattern was discernible, lactate being a marker of compromised cell energy metabolism, and taurine being a marker of disturbed cell integrity. Of special interest was the increased level of pyruvate in microdialysates of non‐ischaemic myocardium as compared with its ischaemic counterpart. In conclusion, we found disturbances in energy metabolism and cell integrity not only in ischaemic but also in non‐ischaemic tissue during reperfusion implying that non‐ischaemic myocardium demonstrated an unexpected accumulation of lactate and pyruvate. These new findings could at least partly be explicatory to the increased risk of heart surgery in connection with acute myocardial infarction.     

Energy-related metabolites during and after induced myocardial infarction with special emphasis on the reperfusion injury after extracorporeal circulation

In the clinical setting great efforts have been made with contradictory results to operate upon acutely myocardial ischaemic patients. The reasons for the absence of clear-cut results are not well understood nor are they scientifically explored. To resolve this problem further, we attempted to design an experimental in vivo model to mimic acute myocardial ischaemia followed by extracorporeal circulation (ECC) and reperfusion. One of the main targets of our protocol was monitoring of myocardial energy metabolism by microdialysis (MCD) during the periods of coronary occlusion (60 min), hypothermic (30 degrees C) ECC and cardioplegia (45 min), followed by reperfusion with (30 min) and without (60 min) ECC. In eight anaesthetized, open-chest pigs, myocardial lactate, pyruvate, adenosine, taurine, inosine, hypoxanthine and guanosine were sampled with MCD in both ischaemic and non-ischaemic areas. Myocardial area at risk and infarct size were quantified with the modified topographical evaluation methods. The principal finding with this experimental setup was a biphasic release pattern of lactate, adenosine, taurine, inosine, hypoxanthine and guanosine from ischaemic myocardium. Lactate levels were equally high in reperfused ischaemic and non-ischaemic myocardial tissue. Pyruvate demonstrated consistently higher values in non-ischaemic myocardium throughout the experiment. A pattern was discernible, lactate being a marker of compromised cell energy metabolism, and taurine being a marker of disturbed cell integrity. Of special interest was the increased level of pyruvate in microdialysates of non-ischaemic myocardium as compared with its ischaemic counterpart. In conclusion, we found disturbances in energy metabolism and cell integrity not only in ischaemic but also in non-ischaemic tissue during reperfusion implying that non-ischaemic myocardium demonstrated an unexpected accumulation of lactate and pyruvate. These new findings could at least partly be explicatory to the increased risk of heart surgery in connection with acute myocardial infarction.     

Altered expression of high-molecular-weight calmodulin-binding protein in human ischaemic myocardium

A high-molecular-weight calmodulin-binding protein (HMWCaMBP) was previously identified and purified from the cytosolic fraction of bovine heart. Based on the sequence homology, amino acid analysis, antibody reactivity, and calpain inhibition, HMWCaMBP has been identified as a homologue of the calpain inhibitor calpastatin. In the present study the expression of HMWCaMBP was investigated in normal and ischaemic human myocardium. Western blot analysis of normal human cardiac muscle extract with the polyclonal antibody raised against bovine HMWCaMBP indicated a prominent immunoreactive band with a molecular mass of 140 kD. HMWCaMBP was localized in the cytoplasm and myofilaments of cardiac myocytes. Furthermore, Western blot analysis of normal and ischaemic cardiac tissues indicated a decrease in the expression of HMWCaMBP in ischaemic tissues. These studies were further substantiated by immunohistochemical studies, indicating strong to moderate HMWCaMBP immunoreactivity in normal cardiac muscle and poor to negative immunoreactivity in ischaemic muscle. The results obtained from the rat ischaemic model suggested that the expression of cardiac HMWCaMBP was significantly decreased during ischaemia/reperfusion. In addition, micro-calpain and m-calpain expression was higher in ischaemic cardiac tissue samples than in normal controls. The calpain inhibitory activity of ischaemic cardiac tissues was significantly lower than normal cardiac tissue samples. In some cases of cardiac ischaemia, HMWCaMBP highlighted the contraction band necrosis seen at the margins of a myocardial infarct. In vitro, HMWCaMBP was proteolysed by micro-calpain and m-calpain. These results indicate that HMWCaMBP could be susceptible to proteolysis by calpains during ischaemia or reperfusion and may play a contributory role in myocardial injury.     

IgM colocalises with complement and C reactive protein in infarcted human myocardium

AIMS: Reperfusion of ischaemic myocardium after acute myocardial infarction (AMI) can induce ischaemia/reperfusion (I/R) injury, as a result of local activation of the complement system. C reactive protein (CRP) is involved in this activation. This study analysed the potential role of IgM in complement activation in the infarcted human myocardium. METHODS: Immunochemical analysis was carried out on heart specimens from 59 patients who died from AMI. Serial slides of frozen tissue from the infarction site were stained for IgM, complement factors C3d and C5b-9 (membrane attack complex), and CRP. RESULTS: IgM deposits were found on the plasma membrane, cross striations, and in the cytoplasm of jeopardised cardiomyocytes in infarcts of one to five days duration. IgM depositions were remarkably similar to those of CRP and both complement factors. The relative staining intensities of IgM and CRP varied greatly among patients. CONCLUSIONS: Similar to CRP, IgM targets complement locally to jeopardised cardiomyocytes in the human heart after AMI. Localisation patterns and relative staining intensities suggest that IgM and CRP recognise similar epitopes in the ischaemic heart, but that the relative contribution of each protein to complement activation in the ischaemic myocardium differs among patients.     

定向诱导骨髓间充质干细胞向心肌细胞分化

目的:采用骨髓间充质干细胞体外转化为心肌样细胞,为心衰的干细胞移植治疗提供基础。方法:分离培养大鼠骨髓间充质干细胞,5-氮杂胞苷诱导24h后正常培养,通过形态学、PAS反应、磷钨酸苏木素染色(PTAH)、免疫细胞化学染色作鉴定。结果:诱导细胞以梭形、柱状为主,部分细胞有分支,单个核、卵圆形、居中,似心肌细胞,PAS及PTAH染色均为阳性。诱导后培养2周的细胞表达Sarcomeric Actin和Connexin-43较弱,以后表达逐渐增强,而且1、3、5代细胞均稳定表达。结论:骨髓MSCs可在体外被诱导分化为心肌样细胞,有望成为心衰干细胞移植治疗的理想细胞材料。     

Impaired sarcolemmal membrane permeability in reperfused ischemic myocardium

Summary Sarcolemmal membrane permeability to intravenously injected horseradish peroxidase HRP (MW=40,000) was examined in 8 Wistar rats which had temporary ischaemia produced by left coronary artery ligation. HRP reaction product was identified following 6 min of circulation time by light and electron microscopy. Controls included 4 uninjected animals with coronary ligation, 2 uninjected animals without myocardial ischaemia and 2 injected non operated rats.In normal myocardium, the tracer permeated endothelial plasmalemmal vesicles, intercellular spaces and intracellular vesicles of the T-tubule system, but never permeated the cytoplasm of myocardium cells.As early as 15 min after coronary artery ligation followed by 6 min of reperfusion with circulation of the tracer, HRP product could be seen in the cytoplasm of muscle cells randomly distributed in the subendocardial area. The quantity of permeated cells increased when the ischaemic myocardium is reperfused during 10 min before injecting the tracer.These data indicate that sarcolemmal membrane alteration is an early event in myocardial ischaemic injury and precede the irreversible cellular degenerative changes.This work was supported by research grant from INSERM (ATP 78-95)     

Pre‐conditioning activates adenosine utilization in a cost‐effective way during myocardial ischaemia

During pre‐conditioning the interstitial concentration of adenosine, in contrast to lactate, presents a die‐away curve‐pattern for every successive episode of ischaemia. This die‐away pattern might not necessarily be attributed to diminished adenosine production. The present study was undertaken to investigate whether pre‐conditioning alters the metabolic turnover of adenosine as observed by the lactate production during ischaemia. Interstitial levels of metabolites in pre‐conditioned (n=21) and non‐preconditioned (n=21) porcine hearts were monitored with microdialysis probes inserted in both ischaemic and non‐ischaemic tissue in an open chest heart model. Three subgroups perturbated with either plain microdialysis buffer (control), buffer containing adenosine (375 μM ), or buffer containing deoxyadenosine (375 μM ) were studied. All animals were subjected to 90 min of equilibrium microdialysis before 40 min of regional myocardial ischaemia and 120 min of reperfusion. Pre‐conditioning consisted of four repetitive episodes of 10 min of ischaemia and 20 min of reperfusion. Significantly higher levels of inosine and lactate were found in the ischaemic tissue of the pre‐conditioned subgroup receiving adenosine (P < 0.05) compared with the other two subgroups receiving deoxyadenosine and plain buffer, respectively. This difference was only valid for pre‐conditioned ischaemic myocardium, and hence equal amounts of inosine and lactate were produced in the non‐preconditioned ischaemic myocardium regardless of the presence of adenosine or deoxyadenosine. In the non‐ischaemic myocardium baseline levels of metabolites were measured in all subgroups. Pre‐conditioning favoured degradation of exogenous adenosine to inosine successively ending up in enhanced lactate production. This was probably because of the involvement of the hexose monophosphate pathway in the pre‐conditioned ischaemic myocardium. This route may therefore be supplementary in energy metabolism as a metabolic flow can be started by adenosine ending up in lactate without initial adenosine 5′‐triphosphate (ATP) investment. Utilization of adenosine in this way may also explain the successive die‐away pattern of adenosine seen in consecutive pre‐conditioning cycles.     

Pre-conditioning activates adenosine utilization in a cost-effective way during myocardial ischaemia.

During pre-conditioning the interstitial concentration of adenosine, in contrast to lactate, presents a die-away curve-pattern for every successive episode of ischaemia. This die-away pattern might not necessarily be attributed to diminished adenosine production. The present study was undertaken to investigate whether pre-conditioning alters the metabolic turnover of adenosine as observed by the lactate production during ischaemia. Interstitial levels of metabolites in pre-conditioned (n=21) and non-preconditioned (n=21) porcine hearts were monitored with microdialysis probes inserted in both ischaemic and non-ischaemic tissue in an open chest heart model. Three subgroups perturbated with either plain microdialysis buffer (control), buffer containing adenosine (375 microM), or buffer containing deoxyadenosine (375 microM) were studied. All animals were subjected to 90 min of equilibrium microdialysis before 40 min of regional myocardial ischaemia and 120 min of reperfusion. Pre-conditioning consisted of four repetitive episodes of 10 min of ischaemia and 20 min of reperfusion. Significantly higher levels of inosine and lactate were found in the ischaemic tissue of the pre-conditioned subgroup receiving adenosine (P < 0.05) compared with the other two subgroups receiving deoxyadenosine and plain buffer, respectively. This difference was only valid for pre-conditioned ischaemic myocardium, and hence equal amounts of inosine and lactate were produced in the non-preconditioned ischaemic myocardium regardless of the presence of adenosine or deoxyadenosine. In the non-ischaemic myocardium baseline levels of metabolites were measured in all subgroups. Pre-conditioning favoured degradation of exogenous adenosine to inosine successively ending up in enhanced lactate production. This was probably because of the involvement of the hexose monophosphate pathway in the pre-conditioned ischaemic myocardium. This route may therefore be supplementary in energy metabolism as a metabolic flow can be started by adenosine ending up in lactate without initial adenosine 5'-triphosphate (ATP) investment. Utilization of adenosine in this way may also explain the successive die-away pattern of adenosine seen in consecutive pre-conditioning cycles.     

Myocardial potassium balance associated with regional ischaemia in the pig: effects of beta-adrenoceptor blockade, duration of ischaemia and preceding ischaemic periods.

The effects of beta-adrenoceptor blockade, duration of ischaemia and preceding ischaemic periods on ischaemia-induced changes in myocardial K+ balance were studied in 12 open-chest pigs. Coronary venous blood was directed through a shunt from the coronary sinus to the right atrium. Continuous recordings of arterial, shunt blood [K+] and shunt flow enabled us to compute myocardial K+ balance during and after consecutive 2-, 2-, 5-, 10- and 2-min periods of regional ischaemia separated by 30 min of reperfusion. beta-adrenoceptor blockade (propranolol 1 mg kg-1 i.v.) given between the first and second ischaemic period did not alter the effects of 2 min ischaemia on myocardial K+ balance. Total K+ losses induced by 2, 5 and 10 min of ischaemia were 67.1 (40.6-93.3), 106.7 (69.4-176.8) and 192.2 (117.7-332.6) mumol 100 g-1, respectively. Thus, the plateau observed in extracellular [K+] between 2 and 10 min of regional ischaemia could, at least partly, be explained by continuous drainage of K+ from ischaemic myocardium into the surrounding normally perfused tissue. The total K+ loss induced by the second and last 2-min ischaemic period were 67.1 (40.6-93.3) and 35.6 (23.1-53.6) mumol 100 g-1 (P less than 0.001), respectively. This reduction shows that ion homeostasis during ischaemia was greatly changed in myocardium which had been 'preconditioned' and 'stunned' by 5 plus 10 min of ischaemia. Total amount, maximal rate and duration of post-ischaemic K+ reuptake increased with the duration of the preceding ischaemia. Moreover, K+ re-uptake after 2 min of ischaemia and the number of sarcolemmal Na/K pumps ([3H]ouabain binding), were normal in stunned myocardium. From these observations we conclude that progressive stimulation of the Na/K-pump occurred when ischaemia was prolonged from 2 to 10 min, and that Na/K-pump function was preserved in stunned myocardium.     

Long-term structural and functional consequences of cardiac ischaemia-reperfusion injury in vivo in mice

The short-term (<24 h) consequences of oxidative stress induced by ischaemia-reperfusion (IR) have been studied extensively in the mouse heart. However, much less is known about the long-term effects inflicted by a brief ischaemic period on the murine heart. We therefore examined the structural and functional consequences of a 30 min ischaemic period after 2 and 8 weeks of reperfusion and compared these to the effects induced by permanent occlusion of the left anterior descending coronary artery (LAD). The latter procedure resulted in transmural myocardial infarcts of about 52% of the left ventricle. In contrast, the single 30 min ischaemic period led to infarct sizes of about 13% of the left ventricle (range, 4-23%) at 2 and 8 weeks after reperfusion. Maximal cardiac contractility responses (+dP/dt) to dobutamine infusion and volume loading were depressed at 2, but not at 8 weeks after IR. The restoration of cardiac contractility at 8 weeks after IR was associated with a significant 20% enlargement of the end-diastolic volume and 16% increase of the left ventricular wall thickness. These changes in cardiac geometry were less pronounced at 2 weeks after IR. Histological examination revealed that the IR injury was associated with prominent calcification. At 2 and at 8 weeks after IR, 25 +/- 5 and 38 +/- 5% of the injured area was calcified as observed in 69 and 73% of the animals, respectively. After permanent occlusion of the LAD, calcification was not observed and healing of the affected area was characterized by thinning and dilatation of the infarcted myocardium. These data indicate that, in mice, a single 30 min period of ischaemia reduced ventricular contractility up to at least 2 weeks after reperfusion. However, 8 weeks after IR, cardiac function was restored by eccentric hypertrophy associated with calcification of the injured ventricular wall.     

Eosinophilic globules in Kaposi's sarcoma. A histochemical, immunohistochemical, and ultrastructural study

Of the 12 cases, 2 (17%) showed eosinophilic globules in the typical cutaneous type of Kaposi's sarcoma. The globules were stained with periodic acid-Schiff (PAS), periodic acid-Schiff reagent after diastase digestion, and phosphotungstic acid hematoxylin (PTAH), but were not stained with Mayer's mucicarmine, and alcian blue. As the results, these globules might be glycoprotein. The shape of the globules was very similar to glycoprotein globules of yolk sac tumor (endodermal sinus tumor) in the tissue of the ovary and testis. In the yolk sac tumor, similar globules are stained with alpha-fetoprotein, beta-subunit of human chorionic gonadotropin, and alpha-1-antitrypsin using immunohistochemical techniques. Immunoperoxidase investigations were done with antibodies to alpha-fetoprotein, beta-subunit of human chorionic gonadotropin, alpha-1-antitrypsin, and carcinoembryonic antigen in the eosinophilic globules of Kaposi's sarcoma, but these antigens were detected in the globules. The morphogenesis of the glycoprotein globules is not clear yet. A better understanding of the source of globules in Kaposi's sarcoma awaits further research.     

Histochemical and immunohistochemical morphology of carcinoid heart disease

Histochemical and immunohistochemical investigations were performed on tissue obtained from the right heart side in three patients subjected to valve, replacement operations because of severe carcinoid heart disease. Extensive fibrotic changes were present on the endocardium of the right atrium, the papillary muscles of the tricuspid valve and the leaflets of the tricuspid and pulmonic valves of all patients. The main constituent of the lesions was a stroma with abundant acid mucopolysaccharides and collagen but devoid of stainable elastic components. The lesions were in some areas sharply delineated from the normal endocardium, but often also extended into the endocardium and myocardium. Small to medium sized vessels were demonstrated histochemically in the lesions and confirmed by positive immunoreaction against endothelial and smooth muscle cells. The moderate number of mesenchymal cells within the lesions had immunoreactivity consistent with muscle cells which seemed to have a very low proliferating activity. The histochemical and immunohistochemical techniques used confirmed some earlier observations in carcinoid heart disease but also rendered new information contradicting previous findings. The infiltrative nature of the carcinoid plaque gives a new dimension to the carcinoid heart disease. The etiology still remains obscure and well known growth factors for connective tissue such as platelet derived growth factor (PDGF) do not seem to be directly involved in the process.     

Enhanced effect of gap junction uncouplers on macroscopic electrical properties of reperfused myocardium

Transient inhibition of gap junction (GJ)-mediated communication with heptanol during myocardial reperfusion limits infarct size. However, inhibition of cell coupling in normal myocardium may be arrhythmogenic. The purpose of this study was to test the hypothesis that the consequences of GJ inhibition may be magnified in reperfused myocardium compared with normal tissue, thus allowing the inhibition of GJs in reperfused tissue while only minimally modifying overall macroscopic cell coupling in normal myocardium. Concentration–response curves were defined for the effects of heptanol, 18α-glycyrrhetinic acid, halothane, and palmitoleic acid on conduction velocity, tissue electrical impedance, developed tension and lactate dehydrogenase (LDH) release in normoxically perfused rat hearts ( n = 17). Concentrations lacking significant effects on tissue impedance were added during the initial 15 min of reperfusion in hearts submitted to 60 min ( n = 43) or 30 min ( n = 35) of ischaemia. These concentrations markedly increased myocardial electrical impedance (resistivity and phase angle) in myocardium reperfused after either 30 or 60 min of ischaemia, and reduced reperfusion-induced LDH release after 1 h of ischaemia by 83.6, 57.9, 51.7 and 52.5% for heptanol, 18α-glycyrrhetinic acid, halothane and palmitoleic acid, respectively. LDH release was minimal in hearts submitted to 30 min of ischaemia, independently of group allocation. In conclusion, the present results strongly support the hypothesis that intercellular communication in postischaemic myocardium may be effectively reduced by concentrations of GJ inhibitors affecting only minimally overall electrical impedance in normal myocardium. Reduction of cell coupling during initial reperfusion was consistently associated with attenuated lethal reperfusion injury.     

形态学检验方法在心肌组织样本中的应用

目的探讨形态学检验方法在心肌疾病中的应用,评价其优缺点。方法运用磷钨酸苏木素(PTAH)染色法、Masson 3色染色法、弹力纤维组织(ET)+Van Gieson(VG)染色法、刚果红染色法、过碘酸雪夫氏(PAS)染色法、革兰氏染色法、以及免疫组织化学法及透射电子显微镜对心肌组织进行检测。结果 HE染色对心肌组织的区分度不好;Masson 3色染色法对心肌细胞和胶原纤维有明确的区分作用;ET+VG染色法可以很好地区分弹力纤维、胶原纤维、肌纤维和淀粉样物质;刚果红染色主要用于淀粉样物质的检测;PAS反应可辅助诊断糖原累积症;免疫组织化学(IHC)技术在疾病模型的研究及对疾病的观察中具有重要辅助作用;电子显微镜对超微结构的观察是病因学诊断的重要手段。结论运用组织水平、亚细胞水平以及分子水平的形态检验方法,对心肌组织样本进行观察与评估,可以得到较好的效果。     

Acute myocardial ischaemia induces specific alterations of ventricular mitochondrial function in experimental pigs

AIMS: As cardiac metabolic flexibility is crucial, this study examined whether acute ischaemia can induce specific qualitative alterations of the mitochondrial metabolic pathways as well as energy transfer systems. METHODS: Left descending coronary artery ligation was performed after sternotomy in eight pigs and the heart was excised after 45 min of ischaemia. Maximal O2 uptake (V(max), micromol O2 min(-1) g(-1) dry weight) of saponin-skinned myofibres were measured from ischaemic and non-ischaemic area of ventricular myocardium. RESULTS: V(max) decreased by approximately 20% in ischaemic myocardium with both glutamate-malate (18.1 +/- 1.3 vs. 22.1 +/- 1.7 in control, P < 0.05) and pyruvate substrates (19.3 +/- 1.0 vs. 23.3 +/- 2.0 in control, P < 0.05) whereas no difference was observed with palmitoyl carnitine (15.6 +/- 1.8 vs. 16.6 +/- 0.9 in control). The K(m) of mitochondrial respiration for ADP decreased in ischaemic heart by 24% (679 +/- 79 vs. 899 +/- 84 microm of ADP in control, P < 0.05). Moreover, the mitochondrial creatine kinase efficacy (K(m) without creatine/K(m) with creatine), representative of the coupling of oxidative phosphorylation process with the mitochondrial creatine kinase, was reduced in ischaemic heart (11.6 +/- 2.5 in ischaemic vs. 18.0 +/- 2.2 in control, P < 0.05). CONCLUSIONS: These findings argue for specific mitochondrial impairments at the level of pyruvate oxidation and creatine kinase channelling system after an acute period of in vivo ischaemia, whereas the lipid mitochondrial oxidation pathway seems to be preserved. Such a loss of metabolic flexibility following acute ischaemia could become an early feature of metabolic dysregulation of the heart.     

EOSINOPHILIC GLOBULES IN KAPOSI'S SARCOMA

Of the 12 cases, 2 (17%) showed eosinophilic globules in the typical cutaneous type of Kaposi's sarcoma. The globules were stained with periodic acid-Schiff (PAS), periodic acid-Schiff reagent after diastase digestion, and phosphotungstic acid hematoxylin (PTAH), but were not stained with Mayer's mucicarmine, and alcian blue. As the results, these globules might be glycoprotein. The shape of the globules was very similar to glycoprotein globules of yolk sac tumor (endodermal sinus tumor) in the tissue of the ovary and testis. In the yolk sac tumor, similar globules are stained with alpha-fetoprotein, beta-subunit of human chorionic gonadotropin, and alpha-1-antitrypsin using immunohistochemical techniques. Immunoperoxidase investigations were done with antibodies to alpha-fetoprotein, beta-subunit of human chorionic gonadotropin, alpha-1-antitrypsin, and carcinoembryonic antigen in the eosinophilic globules of Kaposi's sarcoma, but these antigens were detected in the globules. The morphogenesis of the glycoprotein globules is not clear yet. A better understanding of the source of globules in Kaposi's sarcoma awaits further research. ACTA PATHOL. JPN. 36: 1327–1333, 1986.     

Human coronary microvessels in diabetes and ischaemia. Morphometric study of autopsy material.

The objective of this study was to test the hypothesis that excessive severity of ischaemic heart disease in diabetics is due, in part, to capillary inadequacy. Sections from autopsied hearts of diabetic patients with and without myocardial infarction as well as from those of patients with infarcts and no diabetes were used for morphometric studies of intramural microvessels in areas without infarction. Normoglycaemic patients with normal hearts were also examined. Two to five transverse sections from each of 44 hearts (stained with methenamine silver) were examined for capillary numerical density, capillary to myofibre ratios, and myofibre diameters. Averages for each case and totals for each group were calculated and compared. Normoglycaemic patients with infarcts had increased morphometric values. Diabetics with infarcts had significantly lower capillary densities than the other groups. In conclusion, it is suggested that in diabetes there is an inadequate ischaemia-induced, reactive angiogenesis. This may contribute towards increased myocardial vulnerability in further ischaemic injury and perhaps to diabetic cardiomyopathy.     

Immunopathology of experimental Chagas'' disease: binding of T cells to Trypanosoma cruzi-infected heart tissue.

The immunopathology of Chagas' disease was studied in the experimental model of chronic infection in C57BL/10JT or mice. Sublethal infection with Trypanosoma cruzi, Y strain, induced specific antibodies and a delayed hypersensitivity response to parasite antigens. Mice developed chronic chagasic myocarditis but not skeletal muscle myositis. Binding of T cells to infected heart tissue was investigated during short-term cocultivation of lymphocytes with heart cryostat sections. T cells from infected mice and from normal controls bound equally to myocardium and liver sections from both infected and normal mice. A search in depth was attempted with cells heavily tagged with 99mTc. Labeled T cells from chagasic mice bound to both normal and infected myocardium slices. 99mTc-labeled T cells from controls gave the same binding values. Glass-adherent spleen cells behaved identically to T cells. Prior treatment of the tissue with serum from chronically infected mice did not increase the number of binding cells. Peritoneal macrophages tagged with 99mTc-sulfur colloid also bound to infected myocardium slices. The binding of macrophages was not changed by pretreatment of infected tissue with anti-T, cruzi antibodies. In short, this work did not detect any population of T cells or macrophages which could bind specifically to infected heart tissue to initiate an autoreactive process.     

Response of the border zone to myocardial infarction in rats.

The response of the surviving myocardium 30 days after coronary artery occlusion was measured morphometrically in the regions bordering and remote from infarcts of different sizes. Mean cell volume per nucleus increased with infarct size in both zones, but the rate of change was greater in the border than in the remote portion of the unaffected myocardium. Capillary numerical density within the uninjured tissue progressively decreased with infarct size leading to an increased diffusion distance for oxygen. Although the magnitude of changes in capillary density was similar in the two regions of the ventricle, the analysis of the individual values in each heart showed that in infarcts comprising more than 11% of the ventricular wall capillary concentration and the path length for oxygen supply to the myocytes were affected more in the border zone than in the myocardium remote from the scar. In conclusion, the border zone participates in the hypertrophic recovery process after infarction, but the inadequate growth of the capillary microvasculature suggests that this region is more susceptible to additional ischemic episodes.     

Ultrastructural correlates of ischaemic contracture during global subtotal ischaemia in the rat heart.

The development of left ventricular ischaemic contracture and its correlation with ultrastructural and sarcolemmal permeability defects were studied in isolated rat hearts during global subtotal ischaemia. With acetate as substrate the hearts exhibited a rise in diastolic tension after 8-10 min at which time small foci of contracted myocytes were scattered throughout the myocardium. In hearts with 5% of the maximum diastolic tension (termed 5% contracture), the foci were situated predominantly in the subendocardium and papillary muscle. Contracted myocytes in these foci were capable of excluding ionic lanthanum thus demonstrating retention of normal sarcolemmal permeability properties. With 30% contracture ultrastructural damage had spread to the subepicardium and with further contracture there was an associated increase in the number and size of foci in all regions. In these foci, swelling of the tubular sarcolemmal system and occasionally of the sarcoplasmic reticulum appeared to precede myofibrillar contraction. At 50% contracture lanthanum influx into contracted cells became more frequent. Hearts developed full contracture by 15-18 min at which time most myocytes were contracted and retained lanthanum intracellularly. The heterogeneity of the response at a cellular level may offer a possible explanation for the lack of correlation between contracture and tissue ATP. A possible sequence of structural injury leading to impaired calcium homeostasis is also suggested.