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Biomedical subjects

C E Ganote

Publications and source records attributed to C E Ganote.

At least 19 recordsLinked to original sources
PubMed1992

Effects of the protein phosphatase inhibitors okadaic acid and calyculin A on metabolically inhibited and ischaemic isolated myocytes.

Isolated adult rat myocytes were subjected to 180 min of metabolic inhibition or incubated in ischaemic pellets, in the presence and absence of 10 microM okadaic acid (OA) or calyculin A (CL-A). Contracture and viability was determined by light microscopic analysis of trypan blue-stained preparations and ATP levels by HPLC. Osmotic fragility was assessed by brief hypotonic swelling of cells in 170 or 85 mOsm media prior to determination of viability. Neither drug significantly affected the relatively rapid rates of contracture of myocytes during metabolic inhibition, and both afforded significant protection from development of trypan blue permeability and osmotic fragility. Both OA and CL-A significantly accelerated the rates of contracture and ATP depletion of myocytes during ischaemic incubations. Despite an enhanced rate of ATP depletion, which would be expected to accelerate development of injury, neither drug accelerated development of loss of viability or development of osmotic fragility as measured by 170 mOsm swelling. Mathematical compensation for different rates of ATP depletion confirmed that a protective effect of the drugs, during ischaemic incubation, was masked by their enhancement of the rate of injury, following swelling at 170 mOsm. When the effects of CL-A on ischaemic cells were examined at 85 mOsm, a more stringent test for osmotic fragility, protection was found without compensation for differing rates of ATP depletion. A dose/response curve for CL-A showed some effect at 100 nM and a nearly full effect during metabolic inhibition at 1 microM concentrations. It is concluded that protein phosphatase inhibitors reduce the rates of development of osmotic fragility of metabolically inhibited cells and reduces the rate of injury relative to the rate of ATP depletion of ischaemic cardiomyocytes. Phosphorylation mechanisms may be important to development of irreversible myocardial cell injury.

Adenosine Triphosphate↗
PubMed1992

Flow cytometric analysis of isolated adult cardiomyocytes: vinculin and tubulin fluorescence during metabolic inhibition and ischemia.

Immunofluorescence and quantitative flow cytometry was used to determine if alterations in cytoskeletal proteins (vinculin and tubulin) occur during metabolic inhibition and ischemic incubation of isolated adult rat cardiomyocytes. Effects of cell shape changes on fluorescence, were controlled for by the contractile inhibitor, butanedione monoxime (BDM) and gated analysis. Flow cytometry differentiated rod- and round-shaped myocytes on the basis of forward and side scattering. Severe contracture of metabolically inhibited (iodoacetic acid and amytal) myocytes caused an artefactual increase in fluorescence intensity and a redistribution of tubulin into microblebs on the cell surface, which tended to mask specific losses of fluorescence. Fluorescence microscopy showed that round cells stained intensely for vinculin, but not for tubulin and that vinculin redistributed into coarse patches between 60 and 90 min, times which corresponded to small rebounds of fluorescence. With gated analysis, to exclude severely contracted round and squared cells, and with BDM inhibition of contracture, both metabolically inhibited and ischemic pelleted myocytes showed an early decrease in specific immunofluorescence staining for tubulin and vinculin, which preceded loss of cell viability, as determined by trypan blue staining. In both ischemic and metabolically inhibited cells, decreases of vinculin fluorescence preceded or coincided with increasing osmotic fragility. It is concluded that early cytoskeletal alterations of vinculin in ischemic and anoxic injury correlate with the development of osmotic fragility and irreversible myocyte injury.

Animals↗
PubMed1991

Effects of 2,3-butanedione monoxime (BDM) on contracture and injury of isolated rat myocytes following metabolic inhibition and ischemia.

The relationship between myocardial cell contracture and injury during total metabolic inhibition (amylobarbital and iodoacetic acid) and ischemia was examined, using 5-50 mM butanedione monoxime (BDM) as an inhibitor of contracture. BDM had no apparent effect on control myocytes during 180 min incubations, but inhibited contracture following anoxia or ischemia in a dose-dependent fashion, as directly quantitated by length/width ratios. Cellular ATP levels decreased at a similar rate in the absence or presence of BDM, following metabolic inhibition. BDM-mediated inhibition of contracture was associated with accelerated cell injury, as defined by: the uptake of an extracellular marker (trypan blue) by the cardiomyocytes, by direct analysis of myoglobin released into the supernatant and by ultrastructural demonstration of defects in sarcolemmal membrane integrity. Calcium was not required for BDM's enhancement of injury, in that cells incubated in calcium free-EGTA buffer showed a similar BDM-mediated acceleration of injury. In the presence or absence of calcium, enhancement of injury was more marked in cells osmotically stressed with a brief incubation in hypotonic buffer, than in cells resuspended in isotonic media. It is concluded that BDM enhances development of osmotic fragility of inhibited or ischemic cardiomyocytes and that contracture is not a necessary contributing factor to myocardial cell death.

Adenosine Triphosphate↗
PubMed1991

Effects of the phospholipase inhibitor mepacrine on injury in ischemic and metabolically inhibited adult isolated myocytes.

The phospholipase inhibitor mepacrine has been shown to delay cell death of metabolically inhibited cultured cardiomyocytes. The present study was initiated to determine if mepacrine also delays cell death and development of osmotic fragility of both metabolically inhibited and ischemic adult rat cardiomyocytes. Isolated myocyte suspensions were incubated with 3 mmol/l (millimolar) iodoacetic acid and 6 mmol/l amytal (inhibited) or were pelleted into a slurry and layered with oil (ischemic) in the presence and absence of 10 or 50 mumol/l (micromolar) mepacrine. Rates of contracture, cell viability as determined by trypan blue permeability, cell viability after osmotic swelling in 170 mOsm media (osmotic fragility), and cell morphology were monitored. Mepacrine had no effects on rates of contracture, but was found to significantly delay cell death during isotonic incubations of both metabolically inhibited and ischemic cells. In contrast, mepacrine had no effect on the development of osmotic fragility. Incubation of metabolically inhibited myocytes in calcium-free media did not delay contracture or cell injury, but did attenuate the protective effects of mepacrine. This study confirms previous reports that mepacrine protects cells from injury, extends the observations of protection to ischemic isolated adult myocytes, but shows that development of osmotic fragility is not inhibited by mepacrine.

Animals↗
PubMed1990

An in vitro model of myocardial ischemia utilizing isolated adult rat myocytes.

Isolated adult rat myocytes were used to develop an in vitro model of myocardial ischemia. Freshly isolated myocytes were spun into a cell pellet to limit extracellular volume. Excess supernatant was removed and the pellet was covered with mineral oil and incubated in a temperature controlled water bath. After various periods of incubation, cells were analyzed for adenine nucleotide levels, lactate accumulation, rate of cell death, and cell morphology. Adenine nucleotide profiles after 60 min incubation at 37 degrees C showed marked depletion of adenosine triphosphate (ATP) and large increases in adenosine monophosphate (AMP), adenosine, inosine, and lactate and no significant difference in levels of inosine monophosphate. These results are consistent with ischemic conditions. Reduction of the incubation temperature to 34 and 30 degrees C slowed the rate of cell squaring and the onset of cell death. Resuspension of ischemic cells after 30, 45, 60 and 90 min incubation in hypotonic buffer (170 mosmol) to induce acute cell swelling caused an increase in the number of non-viable cells at each time point. Control cells and ischemic cells incubated less than 30 min did not show increases in non-viable cells when subjected to hypotonic swelling. Morphological analysis revealed that isolated myocytes respond to ischemia in a heterogeneous fashion and exhibit changes at both light and electron microscopic levels similar to those seen in other ischemic models. These results indicate that pelleted isolated adult rat myocytes may be a useful in vitro model to study myocardial ischemic cells injury.

Adenine Nucleotides↗
PubMed1990

Effects of calcium depletion and loading on injury during metabolic inhibition of isolated adult rat myocytes.

The hypothesis that calcium influxes from the extracellular space play an important role in the pathogenesis of irreversible anoxic injury was tested using isolated adult rat myocytes. Myocytes treated with 6 mM amytal and 3 mM iodoacetate and subsequently incubated in either calcium-containing (1.12 mM) or calcium-free media (with or without 1 mM EGTA) developed rigor contracture (cell squaring) and cell death (trypan blue permeability) at the same rate. The rates of cell death in both calcium-containing and calcium-free media were increased by incubation in hypotonic media even though the rates of contracture development remained unaltered. Cells developed osmotic fragility prior to membrane permeability increases. The calcium ionophore, A23187 (10 microM), induced rapid rounding of rod-shaped cells subjected only to mitochondrial inhibition in calcium containing media, confirming its ability to cause an increase in cellular permeability to calcium. However, A23187 did not alter the rates of cell death of totally metabolically inhibited myocytes in either calcium-containing or calcium-free media with EGTA. The results indicate that influxes of calcium are not necessary for the development of irreversible injury in metabolically inhibited, isolated myocytes.

Animals↗
PubMed1988

Irreversible injury of isolated adult rat myocytes. Osmotic fragility during metabolic inhibition.

Isolated myocytes can be established as a valid model for studying changes in cytoskeletal proteins during the development of irreversible injury only if isolated cells develop lesions similar to those that occur during irreversible injury to intact hearts, specifically osmotic fragility and subsarcolemmal blebs. In the first experiment, isolated cells were irreversibly injured by metabolic inhibition with 5 mM Iodoacetic acid (IAA) and 6 mM amobarbital (Amy). Osmotic fragility of control and injured cells was determined by comparing the rates of development of trypan blue permeability during 60 minutes of isotonic or hypotonic (50% reduction in osmolality) incubations. Cell morphology was monitored by light and electron microscopy. Control cells remained elongated and excluded trypan blue. Metabolically inhibited cells rapidly contracted to a nearly square shape. The inhibited squared cells initially excluded trypan blue, but during 60 minutes of incubation became permeable to trypan blue. Cells in hypotonic buffer developed blue staining at a more rapid rate than cells in isotonic buffer, indicating increased osmotic fragility. In a second experiment, control and inhibited cells were first incubated for 25 minutes in isotonic buffer and then in either isotonic or hypotonic buffer. In this experiment, inhibited cells also developed more extensive and rapid permeability increases when transferred to the hypotonic buffer than cells maintained in the isotonic buffer. In both experiments, increased permeability of cells to trypan blue was accompanied by formation of subsarcolemmal blebs along the lateral cell border and at the intercalated disks. The results show that metabolically inhibited, isolated myocytes do exhibit morphologic lesions and increased osmotic fragility properties similar to those reported during anoxic or ischemic injury to intact hearts. Therefore, isolated myocytes may be a useful model with which to study cytoskeletal-sarcolemmal membrane changes during development of irreversible injury.

Animals↗
PubMed1987

Increased myocyte fragility following anoxic injury.

The ability of cells in anoxic-perfused hearts to withstand two types of physical stresses (stretching and swelling), in the absence of reoxygenation was determined. Isolated rat hearts were perfused for 20, 40, or 60 mins with anoxic buffer after which hearts were either reoxygenated for 20 mins or exposed for 15 s to a physical stress caused by inflation of a intraventricular balloon to an appropriate volume (0.35 ml), while maintaining anoxic perfusion for an additional 20 mins. At 20, 40, or 60 mins of anoxic perfusion, reoxygenation induced CK releases of (n = 5) 14.13 +/- 13.15, 62.42 +/- 2.87, and 83.22 +/- 6.41 IUCK/g wet wt, respectively. After 0.35 ml balloon inflation, in the absence of reoxygenation, corresponding CK releases were respectively 8.10 +/- 1.63, 39.13 +/- 8.27, and 59.64 +/- 2.57 IUCK/g wet wt. Increasing the volume of balloon inflation from 0.2 to 0.6 ml at a constant (60 mins) duration of anoxic perfusion resulted in a corresponding increase in CK release. Control hearts released no CK even following 0.6 ml balloon inflation. In the second experimental protocol, hearts were perfused for 30, 45, 60, or 75 mins with isotonic (300 mOsm) anoxic buffer followed by 15 mins with hypotonic (150, 200, or 250 mOsm) anoxic buffer. At each time interval there was a graded increase in cell injury as the duration of anoxia was increased. Control hearts perfused for 75 mins with oxygenated buffer released no CK when perfused with 150 mOsm buffer. Electron microscopy revealed that injured cells contained lesions in sarcomere attachment sites (balloon) and/or in sarcomere-sarcolemmal membrane connections (osmotic). These results suggest that hearts develop latent injury during prolonged anoxic perfusion which can be exposed by application of a physical stress. The extent of injury increases with both the duration of anoxic perfusion and with the degree of stress. It is hypothesized that following prolonged anoxic perfusion, myocardial cells become fragile and respond abnormally to a variety of stresses including the ventricular distensions hypotonic cell swelling, or the effects of reoxygenation.

Aerobiosis↗
PubMed1987

Effects of the free radical scavenger DMTU and mannitol on the oxygen paradox in perfused rat hearts.

The oxygen paradox refers to the abrupt release of cytoplasmic enzymes and severe cellular disruption that occurs following reoxygenation of anoxic perfused hearts. In this study, the ability of a series of oxygen-derived free radical inhibitors and scavenging agents to protect isolated perfused rat hearts from the oxygen-induced enzyme release following 30 or 60 mins of anoxic perfusion (oxygen paradox) and cumene hydroperoxide-induced injury was evaluated. Malondialdehyde (MDA) release, an indicator of lipid peroxidation, and creatine kinase (CK) release, an indicator of cellular injury, were monitored. We evaluated five agents previously reported to scavenge or inhibit the formation of oxygen free radicals. The putative hydroxyl radical scavengers dimethylthiourea (DMTU) and mannitol; catalase, an agent protective against peroxide injury; allopurinol, an inhibitor of xanthine oxidase; and albumin, a non-specific protein control, were evaluated. Coronary flow rates and myocardial temperature were continuously monitored to ensure uniform perfusion conditions. The MDA assay was carefully monitored by constructing standard curves on each experimental day. Addition of 20 microM cumene hydroperoxide to oxygenated perfused hearts caused peroxidative cell injury as evidenced by significant MDA and CK release in the coronary effluent. DMTU and catalase provided near complete protection from cumene hydroperoxide-induced cell injury but did not reduce CK release from hearts subjected to either the mild (30-min) or the severe (60-min) oxygen paradox (reoxygenation-induced injury). Allopurinol caused a significant reduction in MDA release but not CK release from oxygen paradox-injured hearts. Allopurinol and albumin had no significant effect on MDA release from cumene-hydroperoxide-injured hearts. Catalase (300 U/ml) caused a mild but not statistically significant reduction in MDA release from cumene hydroperoxide injury but did not provide protection from the oxygen paradox at either injury level. Mannitol (120 mM), in contrast to DMTU, was ineffective in reducing cumene-induced injury but showed a significant protective effect against oxygen paradox-induced damage. It is concluded that the ability of mannitol to reduce reoxygenation-induced CK release in the oxygen paradox may be due to its osmotic activity and consequent ability to prevent cellular swelling rather than its activity as an oxygen-free radical scavenger.

Animals↗
PubMed1987

Cytoskeletal lesions in anoxic myocardial injury. A conventional and high-voltage electron-microscopic and immunofluorescence study.

The role of cell swelling in mediating myocardial injury was studied in control (normoxic) and anoxic Langendorf perfused rat hearts. Control and 45-, 75-, or 90-minute anoxic hearts were exposed to hypotonic (200 mOsm/l) perfusion media to induce osmotic swelling. Anoxic hearts, but not control hearts, released myoglobin when subjected to osmotic swelling. Control hearts, exposed to hypotonic swelling, retained an intact cytoskeletal system of intermediate filaments, microfilaments and microtubules, intact sarcoplasmic reticulum, and intact sarcolemmal membranes. In contrast, swollen anoxic hearts showed a variety of ultrastructural lesions, including formation of large subsarcolemmal blebs associated with lysis of lateral Z-, M-, and A-band intermediate filament attachments, vesiculation of sarcoplasmic reticulum, and rupture of sarcolemmal membranes. Inter-mediate filament attachments with nuclear membranes were also broken, and microtubules disappeared from the perinuclear space. Sarcomere changes included distortion of Z bands, loss of lateral Z band-sarcolemmal attachments, and separations of myofibrils from internal faces in intercalated disks. Immunofluorescence studies of control hearts showed normal staining patterns for the cytoskeletal-associated proteins vinculin, alpha-actinin, and desmin. After 90 minutes of anoxia, hearts exhibited diminished staining of vinculin and alpha-actinin and relatively little change in desmin staining. The results demonstrate that a critical period of anoxia causes lesions in the cytoskeletal apparatus of myocardial cells which correlate with the increased osmotic fragility of irreversibly injured anoxic myocardial cells.

Aerobiosis↗
PubMed1986

Release of unassembled rat cardiac myosin light chain 1 following the calcium paradox.

To determine the intracellular source and release kinetics of myosin light chain 1 immediately following irreversible myocytic injury, we perfused rat hearts in a Langendorff apparatus under control conditions (20 minutes), or during global cellular injury produced by oxygenated, calcium-free perfusion (5 minutes), followed by reperfusion with buffer containing 2.5 mM calcium (15 minutes). Light chain 1 concentration (double antibody radioimmunoassay) and creatine kinase activity were measured in both the coronary effluent and the 140,000 g supernatant extract of perfused ventricular tissue (after homogenization and ultracentrifugation). Calcium reperfusion caused the rapid release of both light chain 1 and creatine kinase activity (peak light chain 1 = 1.09 +/- 0.19 micrograms/g; peak creatine kinase = 74.9 +/- 10.7 IU/ g at 1 minute, mean +/- SD, n = 3); 28.5 +/- 13.5% of total light chain 1 and 86.5 +/- 0.6% of total creatine kinase activity were depleted from the tissue extract during the 15-minute reperfusion. No light chain 1 or creatine kinase was detected in the effluents of control-perfused hearts. Dodecyl sulfate polyacrylamide gel electrophoresis and immunodetection with specific antibody to myosin heavy chain and light chain 1 showed that the effluent light chain 1 was of similar molecular weight (mol wt = 27,000) to the subunit bound to myofibrils. In addition, light chain 1 was released in the absence of myosin heavy chain. Thus, a small soluble pool of unassembled myosin light chain 1 subunits exists in the cytoplasm of cardiac myocytes that is released from irreversibly injured cells. This pool demonstrates initial washout kinetics similar to creatine kinase.

Animals↗
PubMed1986

Modification of caffeine-induced injury in Ca2+-free perfused rat hearts. Relationship to the calcium paradox.

The pathogenesis of the calcium paradox has not been established. In calcium-free perfused hearts, caffeine, which releases calcium from the sarcoplasmic reticulum, causes severe myocardial injury, with creatine kinase (CK) release and contraction band necrosis similar in many respects to the calcium paradox. It has been postulated that contracture, initiated by a small rise in intracellular calcium, may cause sarcolemmal injury in both the calcium paradox and caffeine-induced myocardial injury. The present study was initiated to determine whether interventions which modulate caffeine-induced contracture will also correspondingly alter cellular injury. The effects of caffeine dose, procaine, extended calcium-free perfusion, elevated potassium, temperature, and increasing intracellular sodium on caffeine-induced contracture were examined in Langendorff-perfused adult rat hearts. Caffeine-induced contracture at 22 C increased over a dose range of 5-40 mM caffeine. Procaine, which inhibits caffeine-induced calcium release at doses between 5 and 20 mM, progressively reduced contracture caused by addition of 20 mM caffeine at 22 C. Hearts perfused with calcium-free solution containing 16 mM K+ showed a reduction in caffeine-induced contracture. Extended calcium-free perfusion (20 minutes) at temperatures from 18 to 37 C resulted in a progressive reduction of caffeine-induced contracture. Each of these interventions was also found to inhibit caffeine-induced injury at 37 C. Low temperature was found to have complex effects. Hypothermia enhanced caffeine contractures but also protected hearts from cell separations and CK release. Increasing intracellular sodium was found to enhance caffeine-induced contracture at 37 C. There was a direct correlation between measured intracellular sodium levels and the magnitude and duration of caffeine-induced contracture. These results demonstrate a direct correlation between the magnitude of contracture and myocardial injury in calcium-free hearts. It is proposed that contracture is the primary mediator of sarcolemmal membrane injury in hearts with intercalated disks weakened by prior calcium-free perfusion.

Animals↗
PubMed1986

Energy dependence of contraction band formation in perfused hearts and isolated adult myocytes.

Aggregation of sarcomeres into contraction bands is a prominent feature of the oxygen paradox, the calcium paradox, and caffeine injury to calcium-free perfused hearts. For investigation of the mechanism of contraction banding, it was necessary to devise a method of evaluating the degree of sarcomere contraction and to define objectively a contraction band. Hearts with mechanical detachment of cells caused by hypocalcemic perfusion and isolated myocytes both allow unrestrained contracture of cells and permit direct optical measurements to quantitate the degree of cell contracture. With the use of the calcium paradox as a model of contraction band necrosis, it was found that cells with lengths of less than 37.3 mu could be considered as containing contraction bands. It was found that the mitochondrial inhibitors cyanide and amytal, as well as the uncoupler 2,4-dinitrophenol, allowed cell contracture but inhibited hypercontracture of sarcomeres into contraction bands during both the calcium paradox and caffeine injury to perfused hearts. However, when 2mM adenosine triphosphate (ATP) was included in the perfusion media, contraction band formation occurred despite the continued presence of cyanide or amytal. In isolated myocyte preparations the addition of the glycolytic inhibitor iodoacetate (IAA, 5 mM) and the mitochondrial inhibitor amytal (3 mM) caused relaxed rod-shaped cells (length/width ratio greater than 3:1) to contract into a stable population of square-shaped forms (length/width ratio less than 3:1), indicating an abrupt and severe decline in cellular ATP levels. Removal of amytal from the incubation medium in the presence of IAA produced a significant conversion of square-shaped cells into round-shaped cells containing contraction bands. Either IAA alone or amytal alone resulted in a mixed population of square and round cells. The results indicate that ATP is required for the formation of contraction bands in intact hearts and for the rounding of isolated myocytes. Formation of contraction bands appears to be an energy-dependent process requiring ATP.

2,4-Dinitrophenol↗
PubMed1985

Unilateral renal vein occlusion in rats.

To study the relationship of renal vein thrombosis to membranous glomerulonephritis with the nephrotic syndrome, we attempted to simulate the former by occluding to 0.5 mm one renal vein in rats. Although increased proteinuria did occur during the first 3 days after such occlusion, there was little difference from control animals in the amount of proteinuria thereafter, up to 46 days, and no evidence of membranous glomerulonephritis by light, immunofluorescent, or electron microscopy.

Animals↗
PubMed1985

Caffeine-induced myocardial injury in calcium-free perfused rat hearts.

Hearts depleted of extracellular calcium become susceptible to injury caused by repletion of extracellular calcium (calcium paradox). It has been suggested that calcium-free perfusion causes weakening of intercalated disks and that the physical stress of contracture may cause sarcolemmal membrane rupture and creatine kinase (CK) release. To further investigate this hypothesis, the effects of caffeine on contracture, cellular morphology, and CK release were studied in control and calcium-free perfused isolated rat hearts. Control hearts perfused with 2.5 mM calcium retained normal ultrastructure for long periods of perfusion. Calcium-free hearts perfused for 12 minutes developed separations of fascia adherens portions of intercalated disks but retained intact nexus junctions. Hearts subjected to 5-minute calcium-free perfusion, followed by calcium repletion, developed a massive CK release and extensive contraction band necrosis (calcium paradox). Ten millimolar caffeine, which causes rapid calcium release from sarcoplasmic reticulum (SR), produced contracture, but not CK release, from control hearts perfused with medium containing 2.5 mM calcium. In calcium-free perfused hearts, caffeine caused sudden CK release accompanied by contracture, development of contraction bands, wide separations of cells at intercalated disks, and sarcolemmal membrane injury. Caffeine-induced injury occurred despite 3 mM amobarbital inhibition of mitochondrial respiration. Hearts perfused with caffeine in the presence of calcium relaxed when made calcium-free and did not release CK. Addition of caffeine following calcium-free perfusion at 22 C, which protects the heart from the calcium paradox, produced a rapid, transient contracture. These results are compatible with the hypothesis that myocardial cell injury in calcium-free hearts is not dependent on repletion of extracellular calcium or mitochondrial function, but can result from contracture following caffeine-induced release of intracellular calcium from the SR.

Amobarbital↗