Chronic left ventricular dysfunctional but viable myocardium of patients with chronic hibernation is characterized by structural changes, which consist of depletion of contractile elements, accumulation of glycogen, nuclear chromatin dispersion, depletion of sarcoplasmic reticulum and mitochondrial shape changes. These alterations are not reminiscent of degeneration but are interpreted as de-differentiation of the cardiomyocytes. The above mentioned changes are accompanied by a marked increase in the interstitial space. The present study describes qualitative and quantitative changes in the cellular and non-cellular compartments of the interstitial space. In chronic hibernating myocardial segments the increased extracellular matrix is filled with large amounts of type I collagen, type III collagen and fibronectin. An increase in the number of vimentin-positive cells (endothelial cells and fibroblasts) compared with normal myocardium is seen throughout the extracellular matrix. The increase in interstitial tissue is considered as one of the main determinants responsible for the lack of immediate recovery of contractile function after restoration of the blood flow to the affected myocardial segments of patients with chronic left ventricular dysfunction.

Actins↗

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Effects of lidoflazine and mioflazine against potassium and veratrine induced shape changes in isolated rat cardiac myocytes.

The protective effects of lidoflazine and mioflazine against shape changes in isolated rat cardiac myocytes induced by depolarizing concentrations of potassium and veratrine have been examined. Myocardial cells, isolated from adult rat hearts and plated in Petri-dishes, yielded a population of nearly 100% rod-shaped calcium-tolerant myocytes. Addition of veratrine or potassium resulted in a calcium-dependent cell shortening and finally rounding up of nearly all cells. Ultrastructurally, the shape changes were accompanied by a complete loss of calcium associated with the sarcolemmal and T-tubular bilayer. Calcium deposits accumulated in the mitochondria, indicating intracellular calcium overload. Pretreatment of the myocytes with lidoflazine or mioflazine (10(-7)-10(-5) M) dose-dependently increased the number of remaining rod-shaped cells after potassium or veratrine addition. Such rod-shaped cells retained a normal pattern of calcium distribution along the sarcolemma and T-tubuli with no evidence of mitochondrial calcium overload. The protective effects of lidoflazine and mioflazine are explained in terms of preserving sarcolemmal integrity, whereby excessive calcium influx and subsequent cytosolic calcium overload could be prevented.

Animals↗

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Ultrastructural damage and Ca2(+)-shifts in the canine myocardium subjected to regional incomplete ischemia.

The role of Ca2+ in the pathogenesis leading to ischemic myocardial cell death is still controversial. To gain insight into this phenomenon a cytochemical procedure, the phosphate pyroantimonate method, was used to localize different subcellular Ca2(+)-pools at the ultrastructural level. After 45 min of left anterior descending coronary artery (LAD) occlusion, the coronary arteries were perfused with triphenyltetrazoliumchloride staining (TTC) to identify viable ischemic and infarcted tissue. In non-ischemic tissue, Ca2(+)-deposits were confined to the sarcolemma, sarcolemma-derived vesicles, transverse tubules, and intercalated disks. In infarcted tissue (TTC-negative), the sarcolemma lost its Ca2(+)-binding capacity and mitochondria were either overloaded with Ca2(+)-precipitate or they contained amorphous densities. In viable ischemic areas (determined with the TTC-technique) the sarcolemma was virtually devoid of Ca2(+)-deposits. Mitochondria in this area frequently showed clumping of the cristae, associated with an accumulation of Ca2(+)-precipitate in between the clustered cristae. The results of this study indicate that Ca2(+)-shifts occur in ischemic myocardial cells before the occurrence of other ultrastructural signs of irreversible injury which, therefore, narrows the possibility that Ca2(+)-overload is only a consequence of ischemic cell death.

Animals↗

PubMedDate not supplied

Normothermic ischemic cardiac arrest in the isolated working rabbit heart: effects of dl-nebivolol and atenolol.

The effect of pretreatment with selective beta 1-adrenoceptor blockers (dl-nebivolol or atenolol) on myocardial mechanical activity, mitochondrial function, morphology, and calcium cytochemistry was studied during normothermic ischemic arrest and reperfusion of isolated working rabbit hearts. The hearts subjected to 25 min of ischemia followed by 30 min of post-ischemic reperfusion showed typical signs of severe myocardial ischemic damage. The ultrastructural changes showed a good relation with the changes in mechanical activity and mitochondrial function. To determine whether these changes could be prevented or reduced by beta 1-adrenoceptor blockade, dl-nebivolol or atenolol (0.62 mg/liter) was added to the perfusate 30 min before the induction of ischemia. The results showed that dl-nebivolol exerted a protective effect on recovery of mechanical activity, on mitochondrial function during reperfusion as well as on the ultrastructure as examined at the end of the reperfusion period. On the other hand, atenolol failed to protect the myocardium against ischemia-reperfusion damage in the isolated working rabbit heart.

Adrenergic beta-Antagonists↗

PubMedDate not supplied

Effect of flunarizine on the human red cell shape changes and calcium deposition induced by A 23187.

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Anti-Bacterial Agents↗

PubMedDate not supplied

Structural changes of atrial myocardium during chronic atrial fibrillation.

Of all known arrhythmia's, atrial fibrillation (AF) is the most often met in the clinical setting and it is associated with an increase in mortality risk. Several risk factors for AF have been described and several mechanisms of induction and maintenance have been proposed. Studies in patients with AF have shown that structural changes occur in the atria, but the relationship between the structural remodelling and the chronicity of the arrhythmia are not well understood. The changes mainly concern adaptive (dedifferentiation of cardiomyocytes) and maladaptive (degeneration of cells with replacement fibrosis) features. In order to characterise the time course of the structural remodelling the need for animal models which adequately mimic chronic atrial fibrillation in humans is felt essential. In this review, the structural changes that are observed during prolonged sustained AF in patients and animal models, are described. Furthermore, the time course and potential mechanisms of structural remodelling are discussed and methods for elucidation of the underlying molecular mechanisms are presented.

Actins↗

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Mechanism of action of antifungal drugs, with special reference to the imidazole derivatives.

Currently used antifungal drugs are distinct in terms of spectrum of activity, potency, therapeutic index, development of resistance, and mode of use. An important factor in the usefulnesss of a compound is the mechanism by which it attacks the structure and function of the fungal cell. The target organelles have been established for most antifungal drugs. Polyenes bind irreversibly to cell membranes. Alteration of the permeability of these structures precedes metabolic disruption and cell death. Griseofulvin deteriorates spindle and cytoplasmic microtubules, influencing cell division and outgrowth of hyphal tips. Flucytosine is deaminated to 5-fluorouracil, which is then phosphorylated and incorporated into RNA; protein synthesis is consequently impaired. A mechanism of action via inhibition of DNA synthesis is an alternative explanation. The imidazole derivatives inhibit the biosynthesis of ergosterol, the main sterol in membranes of fungi. These agents also affect the synthesis of triglycerides and phospholipids. Changes in oxidative and peroxidative enzyme activities, leading to an intracellular buildup of toxic concentrations of hydrogen peroxide, may contribute to the observed deterioration of subcellular organelles and to cell necrosis. The imidazole derivatives inhibit the transformation of blastospores of Candida albicans into the invasive mycelial form. This inhibition probably facilitates the task of host defense cells and may be the principal factor leading to clearance of infection.

Animals↗

PubMedDate not supplied

Ketoconazole in experimental candidosis.

A relatively large number of animal models of candidosis exist in which the efficacy of antifungal substances can be evaluated. These include models of candidosis of the skin, gastrointestinal tract, genital system, and internal organs in a variety of animal species. The efficacy of ketoconazole administered orally and topically was evaluated; when given orally in relatively low doses, ketoconazole was found to be efficacious in all of the experimental models used. Scanning and transmission electron micrographs of infected tissue demonstrated the rapidity with which Candida albicans was eradicated from the host after administration of ketoconazole.

Animals↗

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Degenerative changes in fungi after itraconazole treatment.

Changes in morphogenetic behavior and structural degeneration after exposure to itraconazole are illustrated in Candida albicans, Cryptococcus neoformans, Pityrosporum ovale, Paracoccidioides brasiliensis, Trichophyton rubrum, and Aspergillus fumigatus. With the exception of P. ovale, primary alterations are seen at the cell periphery and the cytoplasmic vacuoles in which lipid-like vesicles assemble. These changes are usually accompanied by a marked increase in cell volume, impaired cell division, or abortive hyphal outgrowth. The concentration of itraconazole necessary to induce irreversible structural degeneration (necrosis) depends greatly on the species used, the time of incubation, and the morphogenetic form in which the fungus is grown and varies from 10(-10) M (P. brasiliensis) to greater than 10(-6) M (C. albicans). Itraconazole achieves these effects either at a concentration comparable to that required for ketoconazole (C. albicans and C. neoformans); at concentrations 10- to 100-fold lower (P. ovale, T. rubrum, P. brasiliensis), or at concentrations 100-fold lower (A. fumigatus).

Antifungal Agents↗

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Oral itraconazole versus topical bifonazole treatment in experimental dermatophytosis.

Guinea pigs, infected with either Trichophyton mentagrophytes or Microsporum canis, were treated orally or topically with azole antifungals daily for two weeks. Fungi located in the stratum corneum were affected similarly by both treatment schedules, showing typical cell wall changes after azole exposure and necrosis of internal organelles. Fungi located in the hair sheaths were affected only by the oral treatment, which not only prevented invasion of the inner hair structures and inflammatory responses but also led to a complete clearance of the infection within 7 days. Topically applied azole treatment was not able to injure fungi in the hair sheaths and did not suppress invasion into the hair shafts. These observations are in favour of oral antifungal medication with azoles for the treatment of dermatophyte infections involving hairy skin.

Administration, Oral↗

PubMedDate not supplied

Flunarizine reduces cerebral infarct size after photochemically induced thrombosis in spontaneously hypertensive rats.

The cerebroprotective effect of flunarizine was studied in a minimally invasive model of photochemically induced cerebral infarction in spontaneously hypertensive rats. Intravenous administration of the photosensitizing dye rose bengal and intense focal illumination of the brain produced a deep cortical infarction that resulted from singlet oxygen-induced peroxidative injury to the endothelial membrane, subsequent platelet adhesion, and eventual thrombus formation. The infarct size was calculated from area measurements on consecutive histologic sections prepared from the brain cortex 4 hours after the onset of the insult. Oral treatment with 40 mg/kg flunarizine 3 hours before photoexcitation resulted in a significant reduction of the median infarct size from 11.75 mm3 in the untreated group to 6.40 mm3 in the treated group (n = 13, p less than 0.001). At this dose, flunarizine had no effect on systemic blood pressure. In a separate experiment the area of thrombotic obstruction was quantified 30 minutes after the onset of light exposure. Flunarizine did not significantly reduce early thrombus formation (2.28 mm3 in the untreated and 1.78 mm3 in the treated group) (n = 12, p = 0.2). The infarcted area at 4 hours was considerably larger than the initial thrombotic area. Protection with flunarizine against development of cortical infarction has been unequivocally shown. Although some effect may already be present at the early stage of lesion formation, the major protective action admittedly occurred in the later postinsult period when the lesion was expanding.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗