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J Schaper

Publications and source records attributed to J Schaper.

At least 91 records · Page 5Linked to original sources
PubMed1996

Myocyte degeneration and cell death in hibernating human myocardium.

OBJECTIVES: The aim of this study was to analyze the morphologic characteristics of myocyte degeneration leading to replacement fibrosis in hibernating myocardium by use of electron microscopy and immunohistochemical techniques. BACKGROUND: Data on the ultrastructure and the cytoskeleton of cardiomyocytes in myocardial hibernation are scarce. Incomplete or delayed functional recovery might be due to variable degree of cardiomyocyte degeneration in hibernating myocardium. METHODS: In 24 patients, regional wall motion abnormalities were analyzed by use of the centerline method before and 6 +/- 1 months after coronary artery bypass surgery. Preoperative technetium-99m sestamibi uptake was measured by single-photon emission computed tomography for assessing regional perfusion. Fluorine-18 fluorodeoxyglucose uptake was measured by positron emission tomography to assess glucose metabolism. Transmural biopsy specimens were taken during coronary artery bypass surgery from the center of the hypocontractile area of the anterior wall. RESULTS: The myocytes showed varying signs of mild-to-severe degenerative changes and an increased degree of fibrosis. Immunohistochemical analysis demonstrated disruption of the cytoskeletal proteins titin and alpha-actinin. Electron microscopy of the cell organelles and immunohistochemical analysis of the cytoskeleton showed a similarity in the degree of degenerative alterations. Group 1 (n = 11) represented patients with only minor structural alterations, whereas group 2 (n = 13) showed severe morphologic degenerative changes. Wall motion abnormalities showed postoperative improvements, and nuclear imaging revealed a perfusion-metabolism mismatch without significant differences between the groups. CONCLUSIONS: Long-term hypoperfusion causes different degrees of morphologic alterations leading to degeneration. Preoperative analysis of regional contractility and perfusion-metabolism imaging does not distinguish the severity of morphologic alterations nor the functional outcome after revascularization. The insufficient act of self-preservation in hibernating myocardium may lead to a progressive structural degeneration with an incomplete and delayed recovery of function after restoration of blood flow.

Adult↗
PubMed1996

Pathogenesis of dilated cardiomyopathy and heart failure: insights from cell morphology and biology.

The cause of dilated cardiomyopathy is not yet clear but the recent discovery of a chromosomal aberration as well as the presence of autoantibodies indicate a multicausal origin. Knowledge of pathogenetic mechanisms continues to evolve and includes decreased sarcoplasmic reticulum Ca2+ uptake, reduced beta-receptor density and decreased contractility, the presence of enlarged myocytes showing numerous degenerative alterations, and fibrosis. Defects in titin, a large sarcomeric protein, may be responsible for disturbances of sarcomerogenesis in dilated cardiomyopathy. New animal models are promising but significant progress will also be made using cell culture systems like adult cardiac myocytes.

Animals↗
PubMed1995

Structural organization and chromosomal localization of the mouse collagenase type I gene.

A clone containing genomic sequences of part of the murine collagenase type 1 (MMP-1) gene was isolated. It contains exons 1-6 encoding all the domains required for collagenase function and 9 kb of 5'-flanking sequences. The gene organization and exon/intron borders are highly similar to the already described human and rabbit MMP-1 genes. However, neither the intron sequences, nor the promoter region up to position -660 exhibit significant sequence homologies with rabbit and human MMP-1, except for an AP-1-binding site and two PEA-3 consensus sequences. Binding studies in vitro revealed that the AP-1-binding site is recognized by Fos/Jun heterodimers with very high affinity. By in situ hybridization the mouse MMP-1 gene was located to the A1-A2 region of chromosome 9 in proximity to the curly whiskers (cw) locus. Based on the lack of sequence homologies of the promoter and intron regions, and since the chromosomal localization of the mouse and human MMP-1 genes may not be syntenic, these data strongly support previous suggestions that the MMP-1 genes from mouse, compared with rabbit and human, have evolved from different ancestral genes. The presence of the AP-1- and PEA-3- binding sites in all mammalian MMP-1 genes isolated so far, may, however, suggest evolutionary selection for common regulatory mechanisms of MMP-1 transcription.

3T3 Cells↗
PubMed1995

Pathological changes of myocardial cytoskeleton in cardiomyopathic hamster.

Immunocytochemical investigation was performed on the cytoskeletal proteins in cardiac tissue of the cardiomyopathic hamster. Male cardiomyopathic UM-X7.1 hamsters at 180 days of age (n = 8) and age- and sex-matched normal BIO-RB hamsters (n = 8) were used in this study. Immunofluorescence microscopy using monoclonal antibodies against desmin, alpha-actinin, titin, and vincullin was employed. The heart weight to body weight ratio was significantly increased in the heart of cardiomyopathic hamster compared with that of normal hamster. In cardiomyopathic hamster, the left ventricular cavity was markedly dilated. Light microscopically, hypertrophy and atrophy of myocytes and myocardial fibrosis were prominently observed in cardiomyopathic myocardium. Immunocytochemically, desmin, alpha-actinin and titin showed the cross striations along the myofibers in normal myocardium. In contrast, in cardiomyopathic myocardium, desmin was irregularly distributed in myocytes and the amount of desmin was increased. Loss of cross striations of alpha-actinin and titin were frequently observed. Immunofluorescence against vinculin was not significantly altered. We conclude that the alterations of cytoskeletal proteins in myocardial cells may relate to decreased myocardial function in cardiomyopathic hamster failing heart.

Actinin↗
PubMed1995

Ischemia affects cardiac proteins in healthy animals less severely than in human patients.

BACKGROUND: Recently, our group showed that in human hearts proteins are extremely sensitive to ischemic injury. The purpose of this investigation was to evaluate the effects of ischemia on contractile and cytoskeletal proteins in rabbit and pig hearts and to compare these findings with those obtained in humans. METHODS: Rabbit hearts were arrested by perfusion with Euro-Collins solution at different temperatures. Hearts perfused with buffer served as controls. Tissue samples were incubated for varying time intervals and processed for immunohistochemistry and electron microscopy. Porcine hearts were treated in the same manner. Changes in the localization of myosin, desmin, and tropomyosin antibodies were evaluated and the degree of ischemic injury was determined by electron microscopy. RESULTS: Healthy animal hearts tolerate ischemia better than human hearts. Cardiac proteins are more sensitive to ischemia than the ultrastructural cellular organelles. Temperatures as low as 0 degree C produce more cell damage than 4 degrees C and should therefore be avoided. The Euro-Collins solution protects the myocardium better than buffer. CONCLUSIONS: We conclude that healthy animal hearts are more resistant to ischemia than diseased human hearts and that results from experimental studies should be interpreted with caution with regard to the human situation.

Animals↗
PubMed1995

Ischemia induces early changes to cytoskeletal and contractile proteins in diseased human myocardium.

Ischemia is known to produce damage to subcellular organelles, such as nuclei and mitochondria, in myocardial tissue. We tested the hypothesis that during myocardial ischemia various cytoskeletal and contractile proteins also undergo changes. We induced total global ischemia by incubation in buffer of tissue samples from six human left ventricles that were obtained from heart transplant recipients. Samples were removed from the incubation medium at different time intervals and investigated by immunohistochemistry using monoclonal antibodies against myosin, actin, tropomyosin, troponin T, myomesin, desmin, tubulin, and vinculin. The degree of ischemic injury was determined by electron microscopy. Ischemic cardiomyopathic human tissue showed disturbances of the localization pattern of myosin, actin, tropomyosin, and troponin T as early as 10 minutes after the onset of ischemia; this disruption was complete at 20 minutes. Tubulin also started changing at 10 minutes, but complete disruption was only evident after 120 minutes. Desmin and myomesin showed an intermediate response; changes began at 30 to 40 minutes, and disruption was complete at 90 to 120 minutes. Vinculin was most resistant to ischemia. Ultrastructurally, the tissue showed moderate reversible ischemic injury during the entire period of 180 minutes. Measuring the exposure time in seconds allowed quantitation of the intensity of the fluorescence. We reached the following conclusions: (1) Ischemia causes damage to the contractile proteins sooner than to the cytoskeleton and subcellular organelles. (2) Diseased human hearts are extremely susceptible to the effects of ischemia. These findings are important for the situation of induced cardiac arrest in heart operations and for preservation of donor hearts for transplantation.

Actins↗
PubMed1995

Extracellular matrix deposition in hypertensive hearts antifibrotic effects of ramipril.

Hypertension induced in rats by suprarenal banding has a blood pressure elevating effect that is accompanied by the occurrence of cardiac hypertrophy and fibrosis. This phenomenon is already present at 2 weeks after banding and persists up to 1.5 years. The increase in cardiac weight is mostly due to the development of fibrosis, since myocytes are only slightly increased in size. The fibrotic tissue consists mainly of fibronectin and collagen and contains numerous cellular elements. The occurrence of fibrosis can be completely inhibited by the administration of the specific ACE inhibiting drug, ramipril, which indicated that angiotensin II may directly stimulate fibroblasts to produce fibronectin and collagen. The antifibrotic effect of ramipril was also present in a low dosage that did not lower blood pressure, confirming the hypothesis that angiotensin II has a direct effect on connective tissue cells and their ability to produce extracellular matrix proteins. The direct effect of the renin-angiotensin system on the activity of interstitial cells was further proven by molecular biology techniques showing an upregulation of transcription for collagen I and III which is prevented by ACE inhibition.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1995

Insulin-like growth factor I is involved in inflammation linked angiogenic processes after microembolisation in porcine heart.

OBJECTIVE: Angiogenesis in the porcine heart can be induced by myocardial ischaemia following vascular occlusions. This process is characterised by increased numbers of monocytes/macrophages, known to be potent producers of various mitogens such as insulin-like growth factors (IGF) and interleukins (IL). The aim of the study was to examine gene expression of these factors by means of northern blot hybridisation, slot blot analysis, and in situ hybridisation in a porcine model of coronary angiogenesis. METHODS: Experimental ischaemia and subsequent focal necroses were induced by selective injection of 25 microns microspheres into the left circumflex artery. The hearts were excised after 3-168 h of microembolisation, and tissue was collected from a non-ischaemic control area and the circumflex region of the same heart for further analysis. RESULTS: IGF-I was constitutively transcribed in normal porcine myocardium mainly by myocytes. Following microembolisation, IGF-I mRNA expression was significantly increased in the experimental region (1.8-fold) after 72 h and to a lesser extent after 168 h. In the ischaemic region, characterised by capillary sprouting, numerous mononuclear cells contained IGF-I mRNA. In contrast, IGF-II mRNA levels, constitutively produced by porcine myocytes, were not altered by microembolisation. IL-1 alpha, IL-1 beta, and IL-4 mRNA expression was undetectable in our animal model, whereas IL-6 was constitutively transcribed in normal and ischaemic heart and remained insensitive to microembolisation and focal necrosis. CONCLUSION: After microembolisation, increased IGF-I mRNA expression occurred by infiltrating monocytes in areas of microsphere induced focal necrosis, where capillary sprouting can be detected, suggesting that IGF-I is involved in inflammation linked angiogenic processes.

Animals↗
PubMed1995

Insulin-like growth factor II is an experimental stress inducible gene in a porcine model of brief coronary occlusions.

OBJECTIVE: Previous observations have shown that myocardium activates many adaptive processes after brief ischaemia. The aim of this study was to determine whether insulin-like growth factors (IGF) as well as their receptors and binding proteins (IGFBP), which control the activity of the IGF, may play an important role during these processes. METHODS: Ischaemia was induced in anaesthetised open chest pigs by two 10 min occlusions of the left anterior descending coronary artery, separated by 30 min of reperfusion, and followed by reperfusion up to 210 min. Tissue from the ischaemic area and from a non-ischaemic control region of the same heart was examined by means of northern blot, slot blot, and in situ hybridisation. RESULTS: IGF-I, IGF-II, the type I receptor, the insulin receptor, and IGFBP-2-6 are constitutively expressed in porcine myocardium. In situ hybridisation showed that IGF-I and IGF-II are mainly transcribed by myocytes. Ischaemia/reperfusion led to an early and significant increase in IGF-II mRNA compared to non-sham controls but not in comparison with sham operated animals, which already showed a (not significantly) enhanced IGF-II expression. In each case the IGF-II mRNA levels are equal in the control and the experimental region of the same heart. Whereas IGF-II expression was already increased by experimental stress, IGFBP-5 mRNA was enhanced only by ischaemia/reperfusion. The expression of IGF-I, the receptors, and IGFBP-2, 3, 4, and 6 remained unchanged during the experimental protocol. IGFBP-1 was neither expressed nor induced in our model. CONCLUSIONS: IGF-II acts like a stress-response gene activated by the experimental conditions (surgery, anaesthesia) and remains induced during following episodes of ischaemia/reperfusion. A possible interaction of IGFBP-5 with other components of the IGF system may contribute to the preconditioning response.

Animals↗
PubMed1995

Collagen VI in the extracellular matrix of normal and failing human myocardium.

Our own previous studies of the composition of the extracellular matrix of human failing hearts showed that collagen VI seems to play a major role in the origin of cardiac fibrosis. Therefore, collagen VI was investigated in more detail in tissue samples taken from clinically normal left ventricle and from myocardium failing because of dilated cardiomyopathy. Tissue sections prepared with collagen VI antibodies were examined by fluorescence microscopy using conventional or confocal laser scanning microscopy. In normal myocardium, collagen VI was located in both, endomysium and perimysium, in blood vessels it surrounded closely individual myocytes. Failing myocardium showed enlargement of the extracellular space and collagen VI was abundant. The localisation was perivascular as well as interstitial in fine or thick bundles enclosing the myocytes completely. In hearts with far progressed failure areas of replacement fibrosis containing increased amounts of collagen VI were evident. Double-staining for vimentin and collagen VI revealed a close interaction with fibroblasts. Although the function of collagen VI is not yet entirely clear it seems obvious that collagen VI plays an important role in the development of fibrosis in the failing heart.

Actins↗
PubMed1995

[Clinical and morphologic findings in the "hibernating myocardium"].

From the clinical point of view, the diagnosis of "hibernating myocardium" is of predominant importance in patients with LV-dysfunction, because a prediction of a possible functional recovery allows to determine risk and outcome of an intervention. Alone or in combination, thalliumscintigraphy with reinjection and dobutamine echocardiography are suitable to detect "hibernating myocardium". In addition, morphological investigations of biopsies taken from hibernating regions permit the evaluation of structural changes. The spectrum of alterations is wide and at a certain degree of severity they are irreversible. The relation between clinical and morphological results provides further insight into the degree of injury and of functional recovery after adequate revascularization.

Biopsy↗
PubMed1995

[Interactions between cardiomyocytes and extracellular matrix in the failing human heart].

Numerous morphological changes can be observed in human myocardium failing because of dilated cardiomyopathy. These can be observed by electron microscopy and by immunofluorescence microscopy using monoclonal antibodies. These changes include: 1) the occurrence of hypertrophied and atrophied myocytes as well as cells of normal size, 2) degenerative changes in myocytes; these consist of nuclei of varying size and shape, lack of contractile material, disorganization of the cytoskeleton, and sequestration of cellular particles into the extracellular space and 3) an enlarged extracellular space, that is, fibrosis, which contains increased amounts of the different matrix proteins such as fibronectin and laminin, the various collagens, and chondroitin sulfate, in addition to cellular debris and numerous macrophages and fibroblasts. On the basis of these findings it is hypothetized that there exists an interaction between myocytes and the extracellular matrix. The cells of the latter may be stimulated to higher rates of proteins synthesis by the presence of cellular debris. This process, in turn, may be harmful for the structural integrity of myocytes which consequently sequester more cellular particles. In this manner, a vicious circle may be started that leads to further structural and functional deterioration of the myocardium, finally resulting in failure.

Cardiomyopathy, Dilated↗
PubMed1994

Phenotypic alterations in fos-transgenic mice correlate with changes in Fos/Jun-dependent collagenase type I expression. Regulation of mouse metalloproteinases by carcinogens, tumor promoters, cAMP, and Fos oncoprotein.

Using specific cDNAs isolated from mouse fibroblasts we determined tissue-specific expression of different matrix metalloproteinase genes: both stromelysin-1 and collagenase IV are highly expressed in heart and lung, whereas collagenase I is expressed most abundantly in skeletal muscle, kidney, and bone. High basal level expression of stromelysin-2 is found in heart and kidney. Like in man and rat, the expressions of collagenase I, stromelysin-1, and stromelysin-2 are regulated by the tumor promoter 12-O-tetradecanoyl-phorbol 13-acetate and by UV irradiation, but not by cAMP. In contrast, the expression of the 72-kDa collagenase IV is not affected by either stimuli. We and others have shown previously that under cell culture conditions, the regulation of human collagenase I is regulated by the transcription factor Fos/Jun (AP-1). Here we show that in c-fos transgenic mice transcription of collagenase I is induced in thymus, spleen, and, most dominantly, in bone upon overexpression of Fos. Neither collagenase IV nor stromelysin-1 or stromelysin-2 expression is affected by c-Fos. The sites of induced collagenase I expression correlate with the sites of Fos-induced long-term cellular alterations in transgenic mice including bone remodeling and T cell development. In fact, in the developing bone tumors strongly enhanced levels of collagenase I transcripts were detectable. These results identify collagenase I as a Fos-regulated gene in vivo and suggest a possible role for Fos/Jun heterodimers in establishing the pathological phenotype of c-fos transgenic mice.

3T3 Cells↗
PubMed1994

Effects of canine donor heart preservation temperature on posttransplant left ventricular function and myocardial metabolism.

The generally accepted method of preserving donor heart integrity during transfer is to arrest it with cold cardioplegic solution, then store it in a plastic bag immersed in an iced electrolyte solution. Temperatures between 0 degree C and 4 degrees C are maintained by this method until the heart is transplanted. Although profound hyperthermia best inhibits metabolic processes, it may damage the myocardium. Higher myocardial temperatures may be more advantageous and may result in better preservation. The efficacy of this hypothesis has been investigated in a canine model. The hearts of 40 dogs were isolated, arrested with cold cardioplegia, removed from the animal, and stored at different temperature ranges from 0-3 degree C to 12-15 degrees C for 4 hr. After this time period, the hearts were transplanted into a recipient animal in the cervical heterotopic position. The degree and speed of myocardial functional recovery were monitored by measuring end-systolic elastance generated from pressure-diameter loops using sonomicrometry techniques. Myocardial metabolism was studied simultaneously by monitoring coronary flow, O2, glucose, lactate, pyruvate, and free fatty acid uptakes. The results were compared with those from a control group of hearts transplanted immediately after their removal. Our results indicate that donor heart function was significantly depressed 30 min after heterotopic transplantation, but returned to "control" levels after 2 hr when stored between 0 degrees C and 6 degrees C. Myocardial function remained significantly depressed throughout the 2-hr recovery period in hearts stored at higher (6-15 degrees C) temperatures. Hearts stored at all temperatures continued to extract glucose, lactate, and free fatty acids, but produced significantly higher levels of pyruvate at higher storage temperatures, which may be related to the favored use of free fatty acids. In conclusion, donor hearts stored at colder temperatures for 4 hr regain complete left ventricular function faster than hearts stored at higher temperatures. Our experiments support the presently applied methods of donor heart preservation for 4 hr.

Animals↗
PubMed1994

Decreased expression of calmodulin mRNA in human end-stage heart failure.

Calmodulin (CaM) is the primary Ca2+ regulatory protein in cardiac cells, thus alterations in calmodulin would greatly influence the contractile response and may play a role in the abnormal calcium handling observed in human heart failure. We used Northern blot analysis to determine changes in calmodulin mRNA expression in left ventricular tissues isolated from 20 failing and four control human hearts. Only hearts with failure due to idiopathic dilated cardiomyopathy (DCM) or ischaemic heart disease (IHD) were studied. A human calmodulin cDNA probe 95% homologous to Type 3 CaM was used, which hybridized to a single 2.3 kb mRNA. CaM mRNA levels were expressed as a function of total RNA, as determined by hybridization to an 18S cDNA probe, and as a function of myocyte specific mRNA, as determined by hybridization to a myosin heavy chain (MHC) cDNA probe. In both DCM and IHD, CaM mRNA expression relative to total RNA (CaM/18S), was significantly decreased (45% and 61%, respectively) compared to control hearts. CaM mRNA expression in DCM tissues was also significantly decreased (45%) relative to myocyte specific mRNA (CaM/MHC), when compared to control hearts. In IHD, CaM mRNA was not significantly decreased in relation to myocyte specific mRNA, which suggests a greater loss of myocytes or contractile proteins in IHD as compared with DCM. The decreased expressed of CaM mRNA observed in failing hearts could affect many Ca(2+)-dependent processes, and contribute to the inability of these hearts to handle Ca2+ in a viable manner.

Adult↗
PubMed1994

Altered expression of titin and contractile proteins in failing human myocardium.

Our own previous ultrastructural studies in human hearts with dilated cardiomyopathy and heart failure showed sarcomeric and cytoskeletal disarrangement. On the basis of these findings we tested the hypothesis that in cardiomyopathic failing hearts not only the sarcomere structure but also the organization and the amount of numerous contractile proteins are disturbed. Titin was included in this study because it is the elastic "third" filament of the sarcomere and also plays an important role as template for myosin and actin filaments in sarcomerogenesis. Human cardiac tissue obtained at the time of transplantation surgery was investigated using immunohistochemistry with monoclonal antibodies against titin, myosin, actin, tropomyosin, and troponin T. Additionally, isolated myocytes from rat or pig heart were used for the standardization of the localization pattern. In normal tissue, myosin and the thin filament complex showed a regular cross striation that was wider in myosin staining than for actin, troponin T, and tropomyosin corresponding with the different width of the A and I bands in the sarcomere. Titin localization in normal human and animal myocardium showed a regular cross striation pattern. In diseased cardiac tissue titin fluorescence intensity was reduced and frequently disorganization or almost complete loss of titin from many myocytes were present. Severe abnormalities of contractile proteins consisting of disarrangement or lack of filaments were also observed. Double staining procedures showed that in the same myocyte defects of the contractile apparatus were accompanied by a simultaneous reduction of titin indicating that the "third" sarcomeric filament system is involved in heart failure. Abnormalities of titin expression may be especially important because titin significantly influences sarcomeric elastic behaviour and is necessary as template for the organization of newly synthesized myosin and actin filaments. The loss of titin may contribute to the altered compliance in failing hearts. It is concluded that disorganization and loss of titin, myosin, and the thin filament complex are severe in the failing human heart because of dilated cardiomyopathy and that these changes may represent several of the most important components of the structural correlate of reduced cardiac function.

Adult↗