The surface to volume ratio of mitochondria, a suitable parameter for evaluating mitochondrial swelling. Correlations during the course of myocardial global ischaemia

Calafiore cardioplegia offers better myocardial protection in adult and senescent rat hearts than Del Nido cardioplegia

OBJECTIVES

We compared the cardioprotective capacity of Del Nido cardioplegia and warm Calafiore blood cardioplegia in an experimental setting during 90 min of ischaemia.

METHODS

20 adult and 20 senescent rat hearts were isolated and mounted on a blood-perfused, pressure-controlled Langendorff apparatus. After a stabilization period, cardiac arrest (90 min) was induced by the administration of either Calafiore (Cala) or Del Nido solution (DNS). While Cala was given warm and intermittently, DNS was given as a cold single shot. During 90 min of reperfusion, cardiac function and metabolism were evaluated and biomarker levels were measured. After the end of the experiment, hearts were prepared for electronmicroscopic investigation.

RESULTS

Hearts exposed to Cala recovered faster during reperfusion compared with hearts administered DNS (Cala vs DNS at 30 min reperfusion: left ventricular developed pressure 72, SD: 22% of baseline (BL) versus 40, SD: 32% of BL, p < .001, and positive derived left ventricular pressure over time was better in both adult and senescent Cala groups (96, SD: 31% of BL) than in the DNS groups (39, SD: 27% of BL, p < .001). Ischaemic contractures were seen in the DNS groups starting after 30 min of ischaemia, whereas no rise in diastolic pressure was observed for the Cala groups. Accordingly, lactate production was higher after DNS (1.23 mg/dl (SD 0.87) than after Cala (0.33 mg/dl (SD 0.68), p = .015) at the beginning of reperfusion. Troponin I levels at the end of reperfusion were higher after DNS treatment in adult hearts (DNS: 287.9 SD: 147.7 ng/mL vs Cala 91.2: SD: 94.7 ng/mL, p = .02) and in senescent hearts (DNS: 376.5 (SD: 162.8) ng/ml versus Cala 104.7 (SD: 150.2) ng/ml, p = .025). Electron microscopy showed that the cellular oedema index was higher in adult DNS hearts (1.2 ± 0.2) than in adult Cala hearts (0.8 ± 0.1, p = .012), whereas the VS ratio was similar (0.18 ± 0.01 vs 0.17 ± 0.03).

CONCLUSION

Calafiore cardioplegia offers better myocardial protection from ischaemia/reperfusion-related damage in isolated perfused adult and senescent rat hearts than Del Nido cardioplegia.

Myocardial Recovery, Metabolism, and Structure after Cardiac Arrest with Cardioplexol

OBJECTIVES

 Clinical studies indicate encouraging cardioprotective potential for Cardioplexol. Its cardioprotective capacities during 45 minutes of ischemia compared with pure no-flow ischemia or during 90 minutes of ischemia compared with Calafiore cardioplegia were investigated experimentally.

METHODS

 Forty-four rat hearts were isolated and inserted into a blood-perfused pressure-controlled Langendorff apparatus. In a first step, cardiac arrest was induced by Cardioplexol or pure no-flow ischemia lasting 45 minutes. In a second step, cardiac arrest was induced by Cardioplexol or Calafiore cardioplegia lasting 90 minutes. For both experimental steps, cardiac function, metabolic parameters, and troponin I levels were evaluated during 90 minutes of reperfusion. At the end of reperfusion, hearts were fixed, and ultrastructural integrity was examined by electron microscopy.

RESULTS

 Step 1: after 90 minutes of reperfusion, hearts exposed to Cardioplexol had significantly higher left ventricular developed pressure (CP-45': 74%BL vs. no-flow-45': 45%BL; p = 0.046) and significantly better maximal left ventricular relaxation (CP-45': 84%BL vs. no-flow-45': 51%BL; p = 0.012). Oxygen consumption, lactate production, and troponin levels were similar in both groups. Step 2: left ventricular developed pressure was lower (22 vs. 48% of BL; p = 0.001) and coronary flow was lower (24 vs. 53% of BL; p = 0.002) when Cardioplexol was used compared with Calafiore cardioplegia. Troponin I levels were significantly higher under Cardioplexol (358.9 vs. 106.1 ng/mL; p = 0.016).

CONCLUSION

 Cardioplexol significantly improves functional recovery after 45 minutes of ischemia compared with pure ischemia. However, Cardioplexol protects the myocardium from ischemia/reperfusion-related damage after 90 minutes of ischemia worse than Calafiore cardioplegia.

Cardioprotection with esmolol-based cardioplegia for non-infarcted and infarcted rat hearts

OBJECTIVES

Esmolol-based cardioplegic arrest offers better cardioprotection than crystalloid cardioplegia but has been compared experimentally with blood cardioplegia only once. We investigated the influence of esmolol crystalloid cardioplegia (ECCP), esmolol blood cardioplegia (EBCP) and Calafiore blood cardioplegia (Cala) on cardiac function, metabolism and infarct size in non-infarcted and infarcted isolated rat hearts.

METHODS

Two studies were performed: (i) the hearts were subjected to a 90-min cardioplegic arrest with ECCP, EBCP or Cala and (ii) a regional myocardial infarction was created 30 min before a 90-min cardioplegic arrest. Left ventricular peak developed pressure (LVpdP), velocity of contractility (dLVP/dtmax), velocity of relaxation over time (dLVP/dtmin), heart rate and coronary flow were recorded. In addition, the metabolic parameters were analysed. The infarct size was determined by planimetry, and the myocardial damage was determined by electron microscopy.

RESULTS

In non-infarcted hearts, cardiac function was better preserved with ECCP than with EBCP or Cala relative to baseline values (LVpdP: 100 ± 28% vs 86 ± 11% vs 57 ± 7%; P = 0.002). Infarcted hearts showed similar haemodynamic recovery for ECCP, EBCP and Cala (LVpdP: 85 ± 46% vs 89 ± 55% vs 56 ± 26%; P = 0.30). The lactate production with EBCP was lower than with ECCP (0.6 ± 0.7 vs 1.4 ± 0.5 μmol/min; P = 0.017). The myocardial infarct size and (ECCP vs EBCP vs Cala: 16 ± 7% vs 15 ± 9% vs 24 ± 13%; P = 0.21) the ultrastructural preservation was similar in all groups.

CONCLUSIONS

In non-infarcted rat hearts, esmolol-based cardioplegia, particularly ECCP, offers better myocardial protection than Calafiore. After an acute myocardial infarction, cardioprotection with esmolol-based cardioplegia is similar to that with Calafiore.

Voluntary activity reverses spermidine-induced myocardial fibrosis and lipid accumulation in the obese male mouse

Obesity due to high calorie intake induces cardiac hypertrophy and dysfunction, thus contributing to cardiovascular morbidity and mortality. Recent studies in aging suggest that oral supplementation with the natural polyamine spermidine has a cardioprotective effect. Here, the hypothesis was tested that spermidine or voluntary activity alone or in combination protect the heart from adverse effects induced by obesity. Therefore, C57Bl/6 mice (n = 8–10 per group) were subjected to control or high fat diet (HFD) and were left untreated, or either received spermidine via drinking water or were voluntarily active or both. After 30 weeks, the mice were killed and the left ventricle of the hearts was processed for light and electron microscopy. Design-based stereology was used to estimate parameters of hypertrophy, fibrosis, and lipid accumulation. HFD induced cardiac hypertrophy as demonstrated by higher volumes of the left ventricle, cardiomyocytes, interstitium, myofibrils and cardiomyocyte mitochondria. These changes were not influenced by spermidine or voluntary activity. HFD also induced myocardial fibrosis and accumulation of lipid droplets within cardiomyocytes. These HFD effects were enhanced in spermidine treated animals but not in voluntarily active mice. This was even the case in voluntarily active mice that received spermidine. In conclusion, the data confirm the induction of left ventricular hypertrophy by high-fat diet and suggest that—under high fat diet—spermidine enhances cardiomyocyte lipid accumulation and interstitial fibrosis which is counteracted by voluntary activity.

Ultrastructural Changes of the Right Ventricular Myocytes in Pulmonary Arterial Hypertension

Background Pulmonary arterial hypertension ( PAH ) is a serious disease without cure. Elevated pulmonary vascular resistance puts strain on the right ventricle ( RV ) and patients die of RV failure. Subjecting Sprague-Dawley rats to SU 5416 injection and hypoxia promotes severe PAH with pulmonary vascular lesions similar to human disease and has been well utilized to investigate pulmonary vascular pathology. However, despite exhibiting severe RV fibrosis, these rats do not die. Recently, subjecting Fischer ( CDF ) rats to the same treatment to promote PAH was found to result in mortality. Thus, the present study performed detailed morphological characterizations of Fischer rats with PAH . Methods and Results Rats were subjected to SU 5416 injection and hypoxia for 3 weeks, followed by maintenance in normoxia. More than 90% of animals died within 6 weeks of the SU 5416 injection. Necropsy revealed the accumulation of fluid in the chest cavity, right ventricular hypertrophy and dilatation, hepatomegaly, and other indications of congestive heart failure. Time course studies demonstrated the progressive thickening of pulmonary arteries with the formation of concentric lamellae and plexiform lesions as well as RV fibrosis in PAH rats. Transmission electron microscopy demonstrated the destruction of the myofilaments, T-tubules, and sarcoplasmic reticulum. RV mitochondrial damage and fission were found in Fischer rats, but not in Sprague-Dawley rats, with PAH . Conclusions These results suggest that the destruction of RV mitochondria plays a role in the mechanism of PAH -induced death. The SU 5416/hypoxia model in Fischer rats should be useful for further investigating the mechanism of RV failure and finding effective therapeutic agents to increase the survival of PAH patients.

Cardiac protective effects of remote ischaemic preconditioning in children undergoing tetralogy of fallot repair surgery: a randomized controlled trial

Aims

Remote ischaemic preconditioning (RIPC) by inducing brief ischaemia in distant tissues protects the heart against myocardial ischaemia-reperfusion injury (IRI) in children undergoing open-heart surgery, although its effectiveness in adults with comorbidities is controversial. The effectiveness and mechanism of RIPC with respect to myocardial IRI in children with tetralogy of Fallot (ToF), a severe cyanotic congenital cardiac disease, undergoing open heart surgery are unclear. We hypothesized that RIPC can confer cardioprotection in children undergoing ToF repair surgery.

Methods and results

Overall, 112 ToF children undergoing radical open cardiac surgery using cardiopulmonary bypass (CPB) were randomized to either a RIPC group (n = 55) or a control group (n = 57). The RIPC protocol consisted of three cycles of 5-min lower limb occlusion and 5-min reperfusion using a cuff-inflator. Serum inflammatory cytokines and cardiac injury markers were measured before surgery and after CPB. Right ventricle outflow tract (RVOT) tissues were collected during the surgery to assess hypoxia-inducible factor (Hif)-1α and other signalling proteins. Cardiac mitochondrial injury was assessed by electron microscopy. The primary results showed that the length of stay in the intensive care unit (ICU) was longer in the control group than in the RIPC group (52.30 ± 13.43 h vs. 47.55 ± 10.34 h, respectively, P = 0.039). Patients in the control group needed longer post-operative ventilation time compared to the RIPC group (35.02 ± 6.56 h vs. 31.96 ± 6.60 h, respectively, P = 0.016). The levels of post-operative serum troponin-T at 12 and 18 h, CK-MB at 24 h, as well as the serum h-FABP levels at 6 h, after CPB were significantly lower, which was coincident with significantly higher protein expression of cardiac Hif-1α, p-Akt, p-STAT3, p-STAT5, and p-eNOS and less vacuolization of mitochondria in the RIPC group compared to the control group.

Conclusion

In ToF children undergoing open heart surgery, RIPC attenuates myocardial IRI and improves the short-term prognosis.

Molecular Understanding of the Cardiomodulation in Myocardial Infarction and the Mechanism of Vitamin E Protections

:

Myocardial infarction is a major cause of deaths globally. Modulation of several molecular mechanisms occurs during the initial stages of myocardial ischemia prior to permanent cardiac tissue damage, which involves both pathogenic as well as survival pathways in the cardiomyocyte. Currently, there is increasing evidence regarding the cardioprotective role of vitamin E in alleviating the disease. This fat-soluble vitamin does not only act as a powerful antioxidant; but it also has the ability to regulate several intracellular signalling pathways including HIF-1, PPAR-γ, Nrf-2, and NF-κB that influence the expression of a number of genes and their protein products. Essentially, it inhibits the molecular progression of tissue damage and preserves myocardial tissue viability. This review aims to summarize the molecular understanding of the cardiomodulation in myocardial infarction as well as the mechanism of vitamin E protection.

Differences in ischemic damage between young and old hearts--Effects of blood cardioplegia

OBJECTIVE

Senescent patients exhibit an elevated perioperative risk for cardiac dysfunction, hemodynamic depression and subsequent cardiac death compared to young patients. Despite the fact that a growing proportion of cardiac surgery patients are octogenarians, cardioplegic regimes remain comparable across patients of all ages. We compared the hemodynamic performance, metabolic parameters and ultrastructural changes in adult and senescent rat hearts after application of Buckberg's blood cardioplegia (BCP) to evaluate differences between the age groups regarding postischemic myocardial function and cellular ultrastructure.

METHODS

Hearts of adult (young adult group, 3-4 months) and senescent (old group, 24 months) male Wistar rats were excised and inserted into a blood perfused isolated heart apparatus (Langendorff perfusion). After a stabilization period of 30 min, in 16 adult and 16 senescent hearts, Buckberg BCP was administered antegradely and repeated every 20 min. Six young adult and 3 senescent hearts served as ischemia control. After an aortic clamping time of 90 min an antegrade hot shot was administered. During reperfusion ex vivo cardiac functional parameters were recorded, including coronary blood flow, left ventricular developed pressure (LVDP) and velocity of myocardial contraction or relaxation (+/-dp/dt). Oxygen consumption and lactate production of the hearts were calculated. After perfusion fixation, the hearts of five rats in each BCP group and 3 rats in each ischemia group were investigated for cellular edema and mitochondrial damage by morphometry using transmission electron microscopy.

RESULTS

While recovery of cardiac function after 90 min of unprotected ischemia was significantly impaired in senescent hearts, functional recovery after ischemia protected by BCP was similar in adult and senescent hearts. Mitochondrial ultrastructure was severely damaged in both age groups after 90 min ischemia, but well preserved in both BCP groups. The qualitative analysis was confirmed by the morphometric cellular edema index and the volume-to-surface ratio of the mitochondria. Myocardial oxygen consumption was highest and lactate production was lowest in senescent hearts.

CONCLUSION

Senescent rat hearts were more susceptible to unprotected ischemia/reperfusion injury than young adult hearts. When protected by BCP, we found no difference in hemodynamic performance between adult and senescent hearts indicating preserved myocardial protection even in senescent individuals.

Intraintestinal drainage as a damage control surgery adjunct in a hypothermic traumatic shock swine model with multiple bowel perforations

BACKGROUND

Temporary bowel ligation (TL) has been proposed to prevent contamination as a damage control procedure in multiple bowel perforations. However, bacteria translocation and intestinal ischemia may develop in a prolonged duration. We here hypothesized that intraintestinal drainage combined with temporary ligation (D-TL) would decrease intestinal injury and improve survivals in a gunshot multiple bowel perforation swine model in the setting of a damage control surgery.

MATERIALS AND METHODS

The abdomen was shot one time with an experimental modified gun whereas pigs were hemorrhaged to a mean arterial pressure of 40 mm Hg and maintained in shock for 40 min. Cold lactated Ringer solution was gradually infused to induce hypothermia. Animals were randomized to primary anastomosis, TL and intraintestinal D-TL groups (n = 8). Animals were resuscitated for 12 h with the shed blood and lactated Ringer solution. Delayed anastomosis was performed in TL and D-TL animals after resuscitation. Surviving animals were humanely killed 24 h after operation. Systemic hemodynamic parameters were recorded and blood samples were obtained for biochemical assays. Intra-abdominal pressure, portal vein and peripheral vein bacterial cultures, small intestine hematoxylin-eosin staining, and transmission electron microscopy examination were performed at 0, 2, 6, 12, and 24 h after the surgery.

RESULTS

All animals suffered extreme physiologic conditions as follows: hypothermia, severe acidosis, hypotension, and depressed cardiac output. Compared with the primary anastomosis and TL group, D-TL animals required less resuscitation fluid, suffered a lower intra-abdominal hypertension and bacterial translocation, normalized lactate levels faster, had lower serum creatine kinase, aspartate aminotransferase levels and tissue TNF-α level, and nuclear factor-kB activations and thus had greater early survival.

CONCLUSIONS

Compared with primary intestinal anastomosis and TL, rapid bowel ligation combined with intraintestinal drainage as a damage control adjunct improved survivals in a multiple bowel perforation swine model in the setting of damage control surgery.

The mitochondrial-targeted compound SS-31 re-energizes ischemic mitochondria by interacting with cardiolipin

Ischemia causes AKI as a result of ATP depletion, and rapid recovery of ATP on reperfusion is important to minimize tissue damage. ATP recovery is often delayed, however, because ischemia destroys the mitochondrial cristae membranes required for mitochondrial ATP synthesis. The mitochondria-targeted compound SS-31 accelerates ATP recovery after ischemia and reduces AKI, but its mechanism of action remains unclear. Here, we used a polarity-sensitive fluorescent analog of SS-31 to demonstrate that SS-31 binds with high affinity to cardiolipin, an anionic phospholipid expressed on the inner mitochondrial membrane that is required for cristae formation. In addition, the SS-31/cardiolipin complex inhibited cytochrome c peroxidase activity, which catalyzes cardiolipin peroxidation and results in mitochondrial damage during ischemia, by protecting its heme iron. Pretreatment of rats with SS-31 protected cristae membranes during renal ischemia and prevented mitochondrial swelling. Prompt recovery of ATP on reperfusion led to rapid repair of ATP-dependent processes, such as restoration of the actin cytoskeleton and cell polarity. Rapid recovery of ATP also inhibited apoptosis, protected tubular barrier function, and mitigated renal dysfunction. In conclusion, SS-31, which is currently in clinical trials for ischemia-reperfusion injury, protects mitochondrial cristae by interacting with cardiolipin on the inner mitochondrial membrane.

Intraspecific variation in the thermal plasticity of mitochondria in killifish

Populations of the Atlantic killifish (Fundulus heteroclitus) inhabit salt marshes and estuaries along the eastern coast of North America from Newfoundland to northern Florida, and are thus exposed to a large range of temperatures. Previous studies have shown higher whole-organism metabolic rates in the northern subspecies (F. h. macrolepidotus) compared with the southern subspecies (F. h. heteroclitus) of these fish. Here, we examine phenotypic plasticity in the response to cold temperatures between the two subspecies by acclimating fish to 5, 15 and 25°C and comparing several mitochondrial and muscle properties. The relative area of oxidative muscle versus glycolytic muscle fibers was greater in the northern subspecies at the 5 and 15°C acclimation temperatures. However, there were no differences in capillary density between the two subspecies or at different temperatures. Mitochondrial volume and surface densities increased in response to cold temperature acclimation in red and white muscle, but only in the northern killifish. Citrate synthase activities also increased in the northern killifish at 5 and 15°C. The ratio of calculated [free ADP] to [ATP] increased in the 5°C acclimated southern killifish but not in the northern killifish at 5°C when compared with the 15°C acclimation group, suggesting that there are differences in adenylate signaling for mitochondrial respiration between subspecies at low temperature. Taken together, our data indicate that the northern subspecies have a greater ability to increase mitochondrial capacity at colder temperatures compared with the southern subspecies, providing one of the few examples of intraspecific variation in phenotypic plasticity in mitochondrial amount in response to cold temperatures.

Comparisons of three surgical procedures on intestine ischemia reperfusion injury in a superior mesenteric artery injury model

BACKGROUND

Temporary ligation, primary anastomosis, and temporary shunt have been reported to deal with superior mesenteric artery (SMA) injuries. We aimed to investigate which brought minimal ischemia reperfusion injury in a hypothermic traumatic shock swine model.

METHODS

SMA was completely clamped while pigs were hemorrhaged to a mean arterial pressure (MAP) of 40 mm Hg. Animals were then randomized into temporary ligation (A, n=8), primary anastomosis (B, n=8), temporary shunt (C, n=8), and control groups (n=4). Animals in group A remained SMA interrupted for additional 1h while the other groups underwent the corresponding procedures immediately. Intestine injury was assessed by histologic examination and measurement of lipid peroxidations at the end of ischemia and experiment.

RESULTS

Overall mortality rate was 50%, 25%, and 0% in groups A, B, and C, respectively (P<0.05). The total intestine ischemia time was predominantly shorter in group C in the other groups. Remarkable elevations of malonaldehyde (MDA) in small intestine were noted after reperfusion in group A. Animals in other groups, however, did not exacerbate during the 6-h reperfusion (resuscitation period). Group C showed the lowest MDA level at the end of experiment. Myeloperoxidase (MPO) levels showed no significant elevations during the ischemia or early reperfusion period; nevertheless, it reached approximately 3- to 6-fold in groups A and B (compared with baseline, P<0.01), and remained unchanged in group C at the end of experiment.

CONCLUSION

Our study suggests that temporary shunt insertion might be preferred as it shortens ischemia time, alleviates intestinal ischemia/reperfusion injury, and thus decreases early mortality in this animal model.

Exposure of the gill epithelial cells of larval lampreys to an ion-deficient environment: a stereological study

Three kinds of epithelial cells comprise the surfaces of the gill filaments and lamellae of larval lampreys (ammocoetes): ammocoete mitochondria-rich cells (AMRCs), intercalated mitochondria-rich cells (IMRCs) and pavement cells. Selected characteristics of these cell types in ammocoetes of Geotria australis held in distilled water and in 10% sea water were compared using an ultrastructural stereological approach to determine which of those cell type(s) respond to exposure to an ion-deficient environment in a manner that indicates that they are involved in ion uptake. Particular focus was placed on the enigmatic AMRC, which comprises ca 60% of the cells and contains numerous mitochondria. The mean percentage contributions of both AMRCs and pavement cells to the total number of the three cell types in the two experimental groups were not significantly different, whereas that of IMRCs was >7% in distilled water and <1% in 10% sea water (P < 0.001). Furthermore, the mean apical surface areas of neither AMRCs nor pavement cells differed significantly between the two experimental groups, whereas that of IMRCs was nearly 3-fold greater in distilled water than in 10% sea water. The volume densities and size of mitochondria in AMRCs did not differ between the two exposure regimes. The above comparisons provide no indications that the uptake of Na(+) and Cl(-) in the gill epithelium of ammocoetes involves either the AMRC or pavement cell but, when considered in conjunction with data on ion-transporting cells in other vertebrates, they are consistent with the conclusion that the IMRC plays a crucial role in this process.

A review of state-of-the-art stereology for better quantitative 3D morphology in cardiac research

The aim of stereological methods in biomedical research is to obtain quantitative information about three-dimensional (3D) features of tissues, cells, or organelles from two-dimensional physical or optical sections. With immunogold labeling, stereology can even be used for the quantitative analysis of the distribution of molecules within tissues and cells. Nowadays, a large number of design-based stereological methods offer an efficient quantitative approach to intriguing questions in cardiac research, such as "Is there a significant loss of cardiomyocytes during progression from ventricular hypertrophy to heart failure?" or "Does a specific treatment reduce the degree of fibrosis in the heart?" Nevertheless, the use of stereological methods in cardiac research is rare. The present review article demonstrates how some of the potential pitfalls in quantitative microscopy may be avoided. To this end, we outline the concepts of design-based stereology and illustrate their practical applications to a wide range of biological questions in cardiac research. We hope that the present article will stimulate researchers in cardiac research to incorporate design-based stereology into their study designs, thus promoting an unbiased quantitative 3D microscopy.

Myocardial ischemia tolerance in the newborn rat involving opioid receptors and mitochondrial K+ channels

Neonatal rat hearts are more tolerant to ischemia compared to adult rat hearts. We hypothesized that opioid receptors and mitochondrial potassium channels are involved in the elevated ischemia tolerance of neonatal rats. Newborn rats were treated by an intraperitoneal injection with sodium chloride (placebo, Pla; n = 7), naloxone (Nal; n = 8), or K+ (ATP) channel blocker 5-hydroxydecanoate (HD; n = 8), or were left untreated (sham; n = 8). Thirty minutes after injection, the rats were sacrificed and hearts were arrested cardioplegically and fixed with aldehyde fixative 90 min after global ischemia at room temperature. For control, newborn rat hearts were fixed immediately after sacrifice. Ventricular tissue blocks were prepared for electron microscopy. Mitochondrial (volume-weighted mean volume of mitochondria) and cardiomyocyte volume (cellular edema index, CEI) were estimated to quantify the ischemic injury. Compared to control myocardium, CEI was increased by 244% +/- 39% in sham, 173% +/- 28% in Nal, 142% +/- 25% in HD, and 101% +/- 24% in Pla (P < 0.05 between groups). Volume-weighted mean volume of mitochondria was increased by 514% +/- 235% in sham, 341% +/- 110% in Nal, 458% +/- 149% in HD, and 175% +/- 70% in Pla. Differences between Pla and other groups were significant (P < 0.01 for all). No significant difference was observed between the other groups. Thus, ischemic injury was smallest with placebo, indicating a mechanism similar to preconditioning induced by the intraperitoneal injection. This response was attenuated by blockade of opioid receptors and mitochondrial potassium channels, suggesting their involvement in the elevated ischemia tolerance of newborn rat hearts.

Electron microscopy and microcalorimetry of the postnatal rat heart (Rattus norvegicus)

The interplay of ultrastructure and tissue metabolism was examined in neonatal, infant and adult rat hearts by electron microscopy and microcalorimetry. Morphometry was used to determine parameters of oxygen diffusion capacity (distance between capillaries and mitochondria, capillary surface density) and oxidative metabolic capacity (mitochondrial volume fraction). Thin slices and large samples of living tissue were examined calorimetrically to quantify aerobic metabolism and ischemia tolerance, respectively. After birth, rat hearts grow in parallel to body mass and show characteristics of cellular hypertrophy. Capillary surface density increases from neonatal to infant rats, and decreases to an intermediate value in adult rats. The distance between capillaries and mitochondria shows no significant changes throughout postnatal development. Mitochondrial volume fraction increases continuously until adulthood. The specific aerobic tissue metabolic rate is higher in the neonatal than in the infant and adult rat. However, the ischemic decline in metabolic rate is much slower in the neonatal rat, reflecting an elevated hypoxia tolerance. In conclusion, the neonatal rat heart exhibits a high metabolic rate despite a low mitochondrial volume fraction. The subsequent structural rearrangements can be interpreted as long-term adaptations to the increased postnatal workload and may contribute to the progressive loss of hypoxia tolerance.

Guided tissue regeneration: porcine matrix does not transmit PERV

OBJECTIVE

For cardiovascular tissue engineering, acellularized scaffolds of porcine matrices have been successfully used. However, the possibility of porcine endogenous retrovirus (PERV) transmission remains debatable. In this study, we investigated whether acellularized porcine vascular scaffolds cause cross-species transmission of PERV in a xenogenic model.

METHODS

Porcine pulmonary arteries were acellularized and implanted into sheep in orthotopic position (n=6). Cardiopulmonary bypass support was used for all operations. Blood samples were collected regularly up to 6 months after the operation, and cellular components were tested for PERV infection by PCR and RT-PCR. Grafts were explanted 6 and 12 months after implantation. Tissue samples were characterized by histology and electron microscopy and tested for PERV sequences.

RESULTS

All animals survived the procedure and follow up until explantation of the grafts. PERV DNA was detectable in acellularized scaffolds of porcine matrices. Acellular porcine pulmonary arteries scaffolds were repopulated in vivo by autologous cells of the host, leading to a vessel consisting of all cellular components of the vessel wall. No PERV sequences were detectable neither in all tested peripheral blood samples nor in tissue samples of in vivo recellularized grafts up to 6 months after implantation. Electron microscopy revealed no signs of graft infection by retrovirus.

CONCLUSIONS

Guided tissue regeneration of acellularized vascular porcine matrix scaffolds leads to structured vessels up to one year without risk of PERV transmisson.

Signal transducer and activator of transcription 3 is required for myocardial capillary growth, control of interstitial matrix deposition, and heart protection from ischemic injury

The transcription factor signal transducer and activator of transcription 3 (STAT3) participates in a wide variety of physiological processes and directs seemingly contradictory responses such as proliferation and apoptosis. To elucidate its role in the heart, we generated mice harboring a cardiomyocyte-restricted knockout of STAT3 using Cre/loxP-mediated recombination. STAT3-deficient mice developed reduced myocardial capillary density and increased interstitial fibrosis within the first 4 postnatal months, followed by dilated cardiomyopathy with impaired cardiac function and premature death. Conditioned medium from STAT3-deficient cardiomyocytes inhibited endothelial cell proliferation and increased fibroblast proliferation, suggesting the presence of paracrine factors attenuating angiogenesis and promoting fibrosis in vitro. STAT3-deficient mice showed enhanced susceptibility to myocardial ischemia/reperfusion injury and infarction with increased cardiac apoptosis, increased infarct sizes, and reduced cardiac function and survival. Our study establishes a novel role for STAT3 in controlling paracrine circuits in the heart essential for postnatal capillary vasculature maintenance, interstitial matrix deposition balance, and protection from ischemic injury and heart failure.

Extent of damage in ischemic, nonreperfused, and reperfused myocardium of anesthetized rats

To investigate the localization of the earliest damage in ischemic and ischemic-reperfused myocardium, anesthetized rats were subjected to coronary occlusion for 15, 30, 45, or 90 min. One-half of the animals in each group had no reperfusion, whereas the other half was reperfused for 14 min. With the use of histological methods, preferentially in the periphery of the area at risk, localized zones were detected that lacked the hypoxia-specific increase in NADH fluorescence. The extent of these areas displaying injured tissue was found to be significantly smaller in the ischemic-nonreperfused hearts than in the ischemic-reperfused organs (15-min ischemia: 0.22 +/- 0.12% vs. 43.0 +/- 5.0%; 30-min ischemia: 5.7 +/- 2.7% vs. 64.6 +/- 2.9%; 45-min ischemia: 5.6 +/- 1.2% vs. 66.0 +/- 7.5%; 90-min ischemia: 39.3 +/- 5.5% vs. 86.7 +/- 1.8% of the area at risk). The results point to a localized initiation of the damage close to the surrounding oxygen-supplied tissue during ischemia and an expansion of this injury by intercellular actions into yet-intact areas upon reperfusion.

The influence of hypoxia on the myocardium of experimentally diabetic rats with and without protection by Ginkgo biloba extract. III: Ultrastructural investigations on mitochondria

Completing our preceding ultrastructural studies on diabetes and additional acute hypoxia of rat myocardium and the protective effect of Ginkgo extract (EGb) we investigated specific ultrastructural-morphometric parameters of corresponding mitochondria. Aim of the study was to answer the question whether mitochondria of diabetic myocardium are more sensitive to hypoxia than in normal condition, and whether antioxidative protection by EGb is effective. Further we compared the ultrastructural reactions of mitochondria of different intracellular locations. Voluminal parameters of mitochondria indicated a moderate swelling after diabetes and a further slight swelling after additional hypoxia, which was slightly reduced after EGb pretreatment. Decrease of volume density of mitochondrial cristae was less expressed after diabetes and much stronger after additional hypoxia; slight protection by EGb was only visible after diabetes. Degenerative intramitochondrial areas increased significantly after diabetes and after hypoxia; EGb was protective only after additional hypoxia. The relative number of ATPase particles (F1-coupling factors) at the inner mitochondrial membranes was slightly but significantly reduced after diabetes and stronger reduced after additional hypoxia; only in the latter condition Ginkgo extract was slightly protective. The product of volume density of mitochondria x volume density of cristae x relative number of ATPase particles at the inner mitochondrial membrane (as structural equivalent of the myocardial capacity for ATP production) indicated better than single parameters the increasing mitochondrial damage after diabetes of 4 months duration and subsequent acute hypoxia of 20 min duration. After hypoxia this capacity amounted only to 46% of the normal and was improved by EGb to 53%.

The protective effect of lipoxygenase inhibitor FLM 5011 on mitochondria ultrastructure of ischemic and reperfused cardiomyocytes

Lipoxygenase inhibitor FLM 5011 was used in experimental ischemia and reperfusion with dogs to investigate its ultrastructure-preserving effects on the mitochondria of myocardium. Ischemic and non-ischemic areas of the heart were ultrastructural-morphometric analysed, which revealed that FLM 5011 was able to diminish ischemic damage especially of mitochondria. The protective effects on mitochondria consisted mainly in reduction of defective intramitochondrial areas and in excellent protection of the structural integrity of cristae and matrix. The injury of mitochondria by ischemia/reperfusion in unprotected condition was partly more pronounced in the non-ischemic than in the ischemic area of the hearts probably caused by compensatory overload of the residual myocardium.

The protective effect of iloprost, a PGL2 analogue, on ultratructure of ischemic and reperfused myocardial myocytes

Iloprost was used in experiments with dogs to investigate its ultrastructure-preserving effects on the myocardium during ischemia and reperfusion, focussed especially on the mitochondria. Ischemia was performed by ligation of the left anterior descending coronary artery (LAD) for 90 min followed by reperfusion of 180 min. Samples were taken from the ischemic and non-ischemic area before ligation of LAD, immediately after ischemia and reperfusion. Iloprost was applicated into the left femoral vein after the end of LAD ligation. Ultrastructural-morphometric analysis revealed that iloprost was able to diminish damages of the mitochondria after ischemia and reperfusion as well. Mitochondrial oedema and intramitochondrial structure degenerations (destruction of cristae and matrix) were minimized in contrast to results of unprotected animals, which had to undergo the same procedure as indicated by volume, volume densities of mitochondria, and of the intramitochondrial compartments, confirmed by independent secondary morphometric parameters. There were no remarkable differences between the corresponding parameters of mitochondria in the ischemic and non-ischemic area.

Biology and pathology of the mitochondrion

The mitochondrion is a highly efficient organelle that is essential for the function of cells. It is currently accepted that mitochondria originated from primitive nonphotosynthetic bacteria that were engulfed by early eucharyotic cells. Most of the normal and pathologic interactions between mitochondria and the cells that contain them can be viewed as symbiotic processes. The main features of mitochondrial structure and function and some of the pathological disorders that involve this organelle are reviewed.

Zinc-bis-histidinate preserves cardiac function in a porcine model of cardioplegic arrest

BACKGROUND

We examined the ability of zinc-bis-histidinate to preserve postarrest myocardial function when added to a standard crystalloid cardioplegic solution.

METHODS

Domestic pigs (35 to 50 kg) on left-sided cardiopulmonary bypass were subjected to 90 minutes of regional ischemia followed by 60 minutes of hypothermic cardioplegic arrest induced by antegrade infusion of 20 mL/kg cold St. Thomas' #2 cardioplegic solution with or without 100 mumol/L of zinc-bis-histidinate and maintained by infusion of 10 mL/kg of the same every 20 minutes. During reperfusion function was assessed at 1 and 3 hours over increasing preloads using the right-sided bypass method.

RESULTS

At roller pump flows up to 2,000 mL/min, stroke work index-end-diastolic pressure curves were significantly (p < 0.05) higher and shifted to the left in treated hearts. In a series of pigs, echocardiography was used to determine end-diastolic and end-systolic volumes. At roller pump flows up to 3,500 mL/min, end-systolic pressure-end-systolic volume curves were significantly higher and shifted to the left in treated hearts. Left ventricular ejection fraction, fractional shortening, stroke volume, and cardiac output were significantly (p < 0.05) higher in treated hearts. Electron microscopy revealed that mitochondria in tissue not at risk appeared more swollen in control hearts.

CONCLUSIONS

The results of this study support the conclusion that zinc-bis-histidinate is effective as a myocardial preservative when added to a crystalloid cardioplegic solution.

Clinical assessment of prolonged myocardial preservation for patients with a severely dilated heart

BACKGROUND

The purpose of this study was to compare the myocardial protective effect of histidine-tryptophan-potassium and glucose-insulin-potassium cardioplegic solutions in patients with a dilated heart (left ventricular diastolic diameter > 55 mm, left ventricular systolic diameter > 45 mm) associated with prolonged cross-clamp time (longer than 200 minutes).

METHODS

We selected 20 patients with dilated hearts due to severe aortic regurgitation. Glucose-insulin-potassium cardioplegia was used in 11 patients and histidine-tryptophan-potassium cardioplegia was used in 9 patients.

RESULTS

After operation, the cardiac index was significantly increased in the histidine-tryptophan-potassium group (p < 0.05). Postoperative percent fractional shortening was 13.4% +/- 3.1% in the glucose-insulin-potassium group and 23.6% +/- 2.6% in the histidine-tryptophan-potassium group (p < 0.05). Creatine kinase levels were significantly lower in the histidine-tryptophan-potassium group than that in the glucose-insulin-potassium group (p < 0.05). The incidence of ventricular arrhythmia (higher than Lown's grade 2) was lower in the histidine-tryptophan-potassium group.

CONCLUSIONS

These data support the superiority of the histidine-tryptophan-potassium method over the glucose-insulin-potassium method for protection of the dilated heart during prolonged ischemia in open heart operations.

Cellular edema and alterations in metabolite content in the ischemic and reperfused canine heart following different forms of cardiac arrest

This study investigates firstly how far cellular edema correlates with parameters of the anaerobic energy turnover independent of the method used for cardiac arrest, and secondly to what extent cellular edema developing during reversible global ischemia is reduced after reperfusion. Canine hearts were arrested 1. by aortic cross clamping (ACC), 2. by coronary perfusion with St. Thomas solution, or 3. HTK (histidine tryptophan ketoglutarate) solution (Custodiol). Samples for biochemical and structural analysis were taken at different times during ischemia and after reperfusion with Tyrode solution. Cellular edema determined morphometrically and given as volume ratio of sarcoplasm and mitochondria to myofibrils (Vvsp + V vmi/Vvmf) varies significantly in the differently arrested hearts. Reperfusion after a decrease in ATP to 4 mumol/gww (revival time) leads to a nearly complete structural recovery. The relationship between cellular edema and defined over-all metabolite tissue concentrations and extracellular pHe values shows: 1. during the decrease of creatine phosphate to 3 mumol/gww, cellular edema does not change; it is, however, significantly higher after ACC and St. Thomas than after HTK perfusion; 2. at each lactate concentration, cellular edema differs significantly depending on the form of cardiac arrest; 3. during the decrease of ATP and pHe cellular edema increases and is comparable at concentrations < 4 mumol/gww and at pHe values < 6.5 independent of the form of cardiac arrest; 4. beyond 10 mumol/gww of inorganic phosphate (Pi), increasing values for cellular edema correspond to defined Pi values in the differently arrested hearts. Thus, the ratio VVSp+ VVMi/VVMf is a powerful parameter for the determination of cellular edema during ischemia, as well as for correlations with metabolic parameters.

Effects of ischaemia and preservation on the ultrastructure of the bronchiolar epithelium. A quantitative electron microscopic study of human and canine lungs

In ten cases of clinical human single-lung transplantation, the nontransplanted Euro-Collins-preserved contralateral lungs were examined using electron microscopy to determine the effects of ischaemia on the bronchiolar epithelium. Existing structural damage at the time of transplantation was characterized using this approach, and nine nonpreserved canine single lungs were also investigated to identify the impact of ischaemia. The study revealed a significant correlation between the duration of ischaemia and the mitochondrial surface-to-volume ratio, which can serve as a morphometric criterion for mitochondrial damage, in canine lungs. However, this correlation was not found in the human donor lungs. Further examination of human donor lungs showed slight to moderate damage to the endoplasmic reticulum and nuclear chromatin. In addition, various degrees of damage to mitochondrial structure, ranging from inconspicuous to severe, were found. The mitochondrial surface-to-volume ratio can be considered to be a suitable criterion for the quantification of ischaemic damage of the bronchiolar epithelium under experimental conditions. Ultrastructural analysis of human donor lungs revealed intact bronchiolar epithelial cell structures at the time of transplantation, reflecting adequate organ preservation with Euro-Collins solution.

High energy phosphates and direct calorimetry as predictive parameters for metabolic recovery of the rat liver following ischemia

BACKGROUND AND METHODS

Alteration of the hepatocellular function following ischemic damage may play a crucial role in the limited recovery after reperfusion. In spite of numerous efforts, finding a simple technique for predicting recovery of the liver after ischemic damage is still an unresolved problem. During ischemic storage of isolated rat livers at 25 degrees C tissue concentrations of high energy phosphates and lactate were determined photometrically and interstitial pH was measured by glass electrodes. In comparison, the metabolic rate was measured continuously by direct calorimetry. In a second series of experiments these results were compared with functional recovery after ischemia and reperfusion. Following ischemic storage at 25 degrees C for 60, 120 or 240 min, the isolated livers were reperfused for 30 min in a non-recirculating system with a constant flow rate. During reperfusion functional recovery, as assessed by oxygen consumption and bile flow, was determined. At the end of reperfusion tissue samples were taken for biochemical analysis of adenine nucleotides. Furthermore, morphologic integrity was determined by electron microscopy.

RESULTS

Whereas the ATP concentration drops within 60 min of ischemia to 6.9% of the control value without further significant change, the continuously measured metabolic rate as assessed by direct calorimetry decreases in an exponential manner. Accordingly, a better correlation of hepatocellular secretory function and calorimetrically measured heat output (r2 = 0.85; P < 0.001) was observed than with high energy phosphates (r2 = 0.56; P < 0.001).

CONCLUSIONS

These data suggest that if the metabolism of the ischemic rat liver falls below a critical level, recovery is incomplete or impossible. Therefore, assessment of the global metabolic rate by direct calorimetry seems not only to be a very good predictor of recovery after ischemic damage but also a good tool in the laboratory for studies concerning the sequelae of ischemic metabolism and for improvement of tissue protection.

Cellular distribution patterns of lanthanum and morphometry of rat hearts exposed to different degrees of ischemic stress

BACKGROUND

The element lanthanum (La) can be used as a tracer for verification of membrane permeability. The aim of this study was to establish whether 1) distribution of La in the myocardium of rat hearts depends on the degree of ischemic stress and 2) morphometrically determined cell and mitochondrial swelling correlates with the La distribution.

MATERIALS AND METHODS

Isolated beating rat hearts were arrested by coronary perfusion with the cardioplegic solution Custodiol (controls) or by aortic cross clamping followed by exposure to different degrees of ischemic stress. The solutions for perfusion-and postfixation as well as for rinsing contained 1.1% La(NO3)3. Cellular and mitochondrial swelling were determined morphometrically and myocytes exhibiting intracellular La were quantified and stated as percentage of test fields.

RESULTS

Immediately after cardiac arrest La was present as precipitates only in a few myocytes adjacent to the outer mitochondrial membrane as seen by cTEM and ESI. In such cells La was also detected by EELS in mitochondrial matrix and myofibrils. Advanced ischemic stress led to an increase of the percentage of myocytes containing detectable intracellular La. After 45 min ischemia at 30 degrees C, myocytes and mitochondria showed a remarkable edema and different intracellular distribution patterns of La. After 90 min of ischemia at 20 degrees C interruptions of sarcolemma could only be detected in a few of the swollen myocytes. Roundish La granules were seen in the myofibrils. The percentage of myocytes containing intracellular La and the extent of cellular and mitochondrial swelling showed a significant correlation.

CONCLUSIONS

Patterns of intracellular La distribution depend on the degree of ischemic stress and correspond to the degree of cellular as well as mitochondrial edema. These results point at a direct relation between alterations of membrane permeability and development of edema.

Morphometric characterisation of the fine structure of human type II pneumocytes

BACKGROUND

Pulmonary type II pneumocytes have been examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and morphometry in numerous mammals. Until now, the fine structure of the human type II pneumocyte has not been studied by means of morphometry.

METHODS

Eleven human donor lungs, which could not be made available for a suitable recipient, were preserved with Euro Collins solution (ECS) according to clinical organ preservation techniques. The lungs were fixed via the airways. Systematic random samples were analyzed by SEM, TEM, and classical stereological methods.

RESULTS

Type II pneumocytes showed normal fine structural characteristics. Morphometry revealed that although inter-individual variation due to some oedematous swelling was present, the cells were in a normal size range as indicated by an estimated mean volume of 763 +/- 64 microns 3. The volume densities were: nucleus 21.9 +/- 2.2%, mitochondria 5.8 +/- 0.9%, lamellar bodies 9.8 +/- 3.6%, and remaining cytoplasmic components 62.4 +/- 2.9% of the cell volume. Since the inter-individual variations in the volume densities referred to the cell may, to variable degrees, reflect the variation in the reference space, the volume densities referred to the constant test point system and the respective volume-to-surface ratios were used for inter-individual comparisons. These parameters indicate that lamellar bodies were independent of cellular swelling, while mitochondria < nucleus < remaining cytoplasmic components increased in size with increasing cell size.

CONCLUSIONS

Two to 7.5 hours of cold ischemia following ECS preservation do not deteriorate the fine structure of type II pneumocytes of human donor lungs. For reliable assessment of fine structural variations, morphometric parameters are required that are independent of variations in cell size.

Morphometric evaluation of volume shifts between intra- and extra-cellular space before and during global ischemia

BACKGROUND

It is well known that all forms of cardiac arrest lead to global ischemia combined with alterations in cellular and interstitial volume. The aim of this study was to investigate the nature of these alterations with respect to different methods of cardiac arrest and establish the extent of their mutual influence at the onset as well as during the course of global ischemia.

METHODS

Three tested clinical methods were employed to induce cardiac arrest by a) aortic cross clamping, b) coronary perfusion with the cardioplegic solution St. Thomas, and c) coronary perfusion with the cardioplegic solution histidine-tryptophane-ketoglutarate (HTK). The arrested hearts were subjected to global ischemia at 25 degrees C. The size of the myocytes, as well as the interstitial space of myocytes, was determined morphometrically. The contraction state of myocytes was evaluated according to a score.

RESULTS

We found that the degree of contraction, as well as nature of alterations in the cellular and interstitial volumes, depended both on the form of cardiac arrest and on the duration of ischemia. The following relationships were established. High contraction at the onset of ischemia leads to expulsion of fluid from the interstitium between bundles of myocytes into the tissue clefts increasing their size. The decrease in contraction during ischemia leads to narrower tissue clefts. Cellular swelling at the onset of and during ischemia is caused by volume shifts between intracellular and interstitial space. An increase in cellular volume during global ischemia and/or additional contraction reduce the interstitium within bundles of myocytes. Sufficient relaxation and/or interstitial edema enlarge the interstitium.

CONCLUSIONS

Cellular and interstitial alterations seen at the onset and during the course of ischemia are dependent upon the method of cardiac arrest. Furthermore, a considerable mutual influence is exerted by the alterations in cellular and interstitial spaces.

The contraction state of myofibrils during global ischemia and after reperfusion following different forms of cardiac arrest. Correlation with metabolic parameters in the canine heart

This study was undertaken in order to obtain information on the mode of reaction of the contractile apparatus after different forms of cardiac arrest, global ischemia and reperfusion, as well as on possible correlations between the contraction state of myofibrils and biochemical parameters. During the survival time, before the level of 3 mumol/gww creatine phosphate (CP) is reached, the contraction state shows only minor changes. During the revival time in which ATP tissue concentrations decay to 4 mumol/gww, the contribution of ATP, lactate, anorganic phosphate (Pa) and acidosis to the degree of relaxation depends on the method of cardiac arrest. At defined biochemical values, the degree of relaxation is comparable after aortic cross clamping (ACC) and St. Thomas perfusion, but significantly different compared to HTK perfusion. Thus, during the revival time, the relaxation of sarcomeres depends predominantly on the composition of the solutions used for cardiac arrest. The re-entry of contraction below 3 mumol/gww ATP is correlated with the ATP concentration, independent of the form of cardiac arrest. Reperfusion after HTK or St. Thomas cardioplegia and reversible ischemia leads to the focal formation of contraction bands, which do not occur during ischemia. This contraction state is significantly more pronounced after reperfusion of St. Thomas arrested hearts. Thus, the contraction state of myofibrils is influenced not only by alterations in metabolite concentrations, but also by the composition of cardioplegic solutions and by the characteristic conditions (sufficient energy, oxygen and Calcium) during reperfusion.

Dynamics of mitochondria in living cells: shape changes, dislocations, fusion, and fission of mitochondria

Mitochondria are semi-autonomous organelles which are endowed with the ability to change their shape (e.g., by elongation, shortening, branching, buckling, swelling) and their location inside a living cell. In addition they may fuse or divide. These dynamics are discussed. Dislocation of mitochondria may result from their interaction with elements of the cytoskeleton, with microtubules in particular, and from processes intrinsic to the mitochondria themselves. Morphological criteria and differences in the fate of some mitochondria argue for the presence of more than one mitochondrial population in some animal cells. Whether these reflect genetic differences remains obscure. Emphasis is laid on the methods for visualizing mitochondria in cells and following their behaviour. Fluorescence methods provide unique possibilities because of their high resolving power and because some of the mitochondria-specific fluorochromes can be used to reveal the membrane potential. Fusion and fission often occur in short time intervals within the same group of mitochondria. At sites of fusion of two mitochondria material of the inner membrane, the matrix compartment seems to accumulate. The original arrangement of the fusion partners is maintained for some minutes. Fission is a dynamic event which, like fusion, in most cases observed in vertebrate cell cultures is not a straight forward process but rather requires several "trials" until the division finally occurs. Regarding fusion and fission hitherto unpublished phase contrast micrographs, and electron micrographs have been included.

Preservation of cardiac myocytes subjected to different preconditions: a comparative morphometric study of beating, fibrillating, and cardioplegically arrested canine hearts

This study compares the ultrastructure of beating canine hearts with that of hearts subjected to different clinically common forms of cardiac arrest. The contraction state per test field was ascertained according to a specially developed classification. The volume density of myofibrils and the surface to volume ratio of mitochondria were used as parameters for cellular and mitochondrial swelling. Contraction bands were not found in any of the differently pretreated hearts. Following immersion fixation, contractions as well as over- and hypercontractions in beating, fibrillating, and St. Thomas-arrested hearts are significantly more pronounced than in HTK-arrested hearts. Cellular and mitochondrial volumes were similar in beating and fibrillating hearts. St. Thomas-perfusion significantly decreased cellular and mitochondrial volume compared to beating hearts, but these values were in the same range as in fibrillating hearts. Only HTK-solution actually led to a strong reduction of these compartments. Compared to immersion, perfusion fixation after coronary perfusion with cardioplegic solutions led to comparable cellular volumes, but significantly elevated the percentage of relaxed sarcomeres and significantly reduced mitochondrial swelling. The best structural preservation of myocytes was found after HTK-perfusion and perfusion fixation. Such ultrastructural quantitative and morphometrical parameters are powerful tools since results confirm that the degree of myocardial preservation depends on the method of cardiac arrest. This forms the basis for the choice of preconditions for subsequent ischemia. Furthermore, significant alterations of myocardial ultrastructure depend on a combination of the functional state of the heart, the method of cardioplegia, and the technique of fixation.

Improved preservation of phospholipid-rich multilamellar bodies in conventionally embedded mammalian lung tissue--an electron spectroscopic study

Different conventional methods of tissue processing were studied to determine the extent to which phospholipid-rich multilamellar bodies of pulmonary alveolar epithelial type II cells of the pig were preserved. Prolonged treatment with half-saturated aqueous uranyl acetate yielded excellent results on the stabilization of the multilamellar substructure, irrespective of whether glutaraldehyde-paraformaldehyde or glutaraldehyde-tannic acid was used as a primary fixative. The lamellar periodicities were observed to be 5.5-6.1 nm. Differences in the phosphorus distribution among several types of lipid bodies of alveolar epithelial type II cells were studied by means of electron spectroscopic imaging and electron energy-loss spectroscopy. Multilamellar bodies gave phosphorus signals which were significantly higher than those obtained from granular regions of composite bodies, whereas homogeneous bodies gave phosphorus signals which were even lower than those obtained from mitochondria, endoplasmic reticulum membranes or ribosomes.

The ultrastructural effects of global ischaemia on Purkinje fibres compared with working myocardium: a qualitative and morphometric investigation on the canine heart

During open heart surgery, reperfusion-induced arrhythmias arising after short periods of ischaemia may originate from subendocardial Purkinje fibres. We investigated the ultrastructure of these fibres during 30 min of global ischaemia at 25 degrees C. The effects both with myocardial protection (HTK cardioplegia) and without it (pure ischaemia) were compared qualitatively and morphometrically. After 30 min pure ischaemia overcontraction of sarcomeres, hypercontraction and contraction bands, together with considerable changes in organelles, predominate over cellular oedema. In Purkinje fibres, both cellular and mitochondrial swelling were significantly increased within this 30-min time period from the onset of pure ischaemia. In contrast, following HTK cardioplegia and 30 min ischaemia, cellular and mitochondrial swelling remain moderate and over-contractions are almost entirely lacking. This means that despite remarkable differences between pure ischaemia and HTK cardioplegia in the degree of protection attained it is clear that, compared with the working myocardium, subendocardial Purkinje fibres do not display a higher resistance to early global ischaemia. Further investigations of this sensitivity of Purkinje fibres to global ischaemia and certain drugs may bring about new insights into myocardial protection and pharmacotherapy of arrhythmias.

Propranolol preserves ultrastructure in adult cardiocytes exposed to anoxia/reoxygenation: a morphometric analysis

The protective effect of d,l-propranolol was studied using freshly isolated canine ventricular cardiocytes (1.5 x 10(6)/mL) exposed to 30 min anoxia (95% N2/5% CO2) and 0, 3, 20, and 45 min of reoxygenation (95% O2/5% CO2). In addition to preventing lipid peroxide formation, propranolol maintained cellular viability, and minimized ultrastructural alterations. In the absence of propranolol, the outer mitochondria become swollen and rounded up within the first few minutes of reoxygenation. The perinuclear mitochondrial area increased only slightly. We observed that the cellular injury process proceeded differentially from the exterior to the interior, with a mitochondrial area increase and outer membrane rupture. Sarcolemmal damage was also observed with prevalent blebbing and membrane loss. The Z-lines became wider and more diffuse with reoxygenation. Injury to the nuclear double membrane was observed. Incubation with propranolol showed significant protection during postanoxia reoxygenation. In contrast, the more water soluble beta-blocker atenolol only exhibited slight protection. In addition, d-propranolol (the non beta-blocking isomer) and the antioxidant enzymes, SOD and catalase, showed significant protection. These data support previous findings concerning the antioxidant properties of propranolol which appear to be independent of beta-receptor blockade.

Occurrence and prevention of contraction bands in Purkinje fibres, transitional cells and working myocardium during global ischaemia

Contraction bands usually occur in the intramural working myocardium following post-ischaemic reperfusion. In the subendocardium, however, they are found during ischaemia. Thus, we ascertained the contraction states of Purkinje fibres, transitional cells, subendocardial and intramural parts of the working myocardium during 30 min global ischaemia at 25 degrees C. The effects with and without myocardial protection were compared. At the onset of pure ischaemia contraction bands are completely lacking in all cell types. During pure ischaemia contraction bands are found in all subendocardial cell types but not in the intramural working myocardium. A peak of pathological contraction states is found in the intramural working myocardium at the onset (0 min), in the subendocardial working myocardium at 10 min, in the transitional cells and Purkinje fibres at 30 min of pure ischaemia. Histidine-, tryptophan-, ketoglutarate-enriched (HTK) cardioplegia prevents contraction bands completely at the onset of ischaemia and prevents both contraction bands and pathological contraction states during ischaemia almost completely. Striking differences in the physiological contraction states are seen only in the working myocardium: HTK cardioplegia brings about dominance of relaxation during ischaemia. These findings may be due mainly to the effects of global ischaemia on the one hand and to catecholamines, calcium and oxygen on the other.

Ultrastructural effects induced by global ischaemia on the AV node compared with the working myocardium. A qualitative and morphometric investigation on the canine heart

The cardiac conduction system is considered to be particularly resistant to ischaemia. Nevertheless, following open heart surgery with short periods of ischaemia disturbances in AV conduction or ventricular arrhythmia have been reported. We compared the ultrastructure of AV node and working myocardium following 30 min global ischaemia at 25 degrees C, during pure ischaemia and with HTK cardioplegia qualitatively and morphometrically. After 30 min of pure ischaemia, interstitial and intracellular oedema together with considerable changes in organelles in AV nodes predominate over mainly cellular oedema in working myocardium. Sometimes irregular overcontractions of sarcomeres occur in the AV node, though very seldom in working myocardium. In pure ischaemia, mitochondrial swelling is comparable in both types of tissue. Following HTK cardioplegia and 30 min ischaemia, cellular oedema and mitochondrial swelling are significantly reduced in AV nodal cells and working myocardium, but remain more extensive in the AV nodes. Irregularities in the contractile state of sarcomeres are not observed. The extent of the ultrastructural alterations corresponds to the degree of metabolic change in the working myocardium. Thus, despite considerable differences during pure ischaemia and HTK cardioplegia, ultrastructurally the AV nodal cells do not display a greater resistance to ischaemia than working myocardium.