Impaired Cell Metabolism Research Articles

Effect of cold hypoxic storage and reoxygenation at 37 degrees C of cultured precision-cut rat liver slices on paracetamol metabolism.

The influence of cold storage and reoxygenation at 37 degrees C of precision-cut rat liver slices on paracetamol metabolism was studied. A depressed metabolism was observed after cold preservation, but during reoxygenation at 37 degrees C slices were capable of synthesizing proteins and maintaining both glutathione and ATP levels. Recovery was faster in slices under aerobic cold conditions than in those under cold hypoxia. Glycogen levels were dramatically decreased under both conditions and subsequent reoxygenation at 37 degrees C still increased the glycogenolysis. Xenobiotic metabolism after reoxygenation of cold-preserved slices shows that glucuronide and sulfate conjugates of paracetamol represent about 50% of those of fresh slices at zero time. The amounts of phase II apoproteins were virtually unchanged, thus suggesting that loss of enzyme activities are most probably due to lack of cofactors. Reoxygenation at 37 degrees C did not impair cell metabolism, and a potential role for nitric oxide and other cytokines released form Kupffer cells appears unlikely since nitrite was not formed after bacterial endotoxin stimulation. The maintenance of energetic stores during cold preservation appears, therefore, to be a critical issue for the survival and metabolic activity of cells.

Erythropoietin and oxidative stress in haemodialysis: beneficial effects of vitamin E supplementation.

Oxidative stress can produce profound alterations to cellular membrane lipids, impairing cell metabolism and viability. This phenomenon, previously observed in haemodialysis patients, has been proposed as a significant factor in regard to haemodialysis-related shortened red blood cells (RBC) survival. In the present study, several parameters associated with oxidative stress were evaluated in a group of haemodialysis patients either receiving erythropoietin therapy (n = 12, mean erythropoietin dose 88 +/- 24 U/kg/week) or not receiving such therapy (n = 30), and in 38 controls. Malonyldialdehyde (MDA, nmol/ml), an end-product of lipid peroxidation, and RBC antioxidant systems were measured, including RBC alpha-tocopherol (RBC vitamin E, mg/l), RBC glutathione (GSH, nmol/mgHb), and RBC superoxide dismutase activity (SOD, U/mgHb). Plasma vitamin E concentrations were also evaluated. Finally, oral vitamin E supplementation (500 mg daily), an exogenous antioxidant, was administered for 6 months to seven patients from the dialysis group receiving erythropoietin while oxidative parameters were repeatedly evaluated and erythropoietin requirements monitored, in order to appreciate the therapeutic relevance of an antioxidant supplementation. An elevation of serum MDA was observed in all haemodialysis patients and a significant decrease in RBC vitamin E, despite normal serum vitamin E levels. Furthermore, the reduction in RBC vitamin E was more important in patients treated with erythropoietin. Vitamin E supplementation resulted in a significant increase in RBC vitamin E (from 0.3 +/- 0.1 to 1.2 +/- 0.2 mg/l of pellet) and a reduction in erythropoietin dose (from 93 +/- 24 to 74 +/- 26 U/kg/week) while maintaining stable haemoglobin concentrations. These results suggest that the oxidative stress could be one of the resistance factors to erythropoietin response in haemodialysis and that vitamin E supplementation could have a sparing effect on erythropoietin dosage requirement.

Dynamic extracellular matrix remodeling in the heart failure: cardiac hypertrophy, dilatation and fibrosis

Abstract Over 40% of patients awaiting heart transplant surgery suffer from dilated cardiomyopathy, a life-threatening condition of impaired muscle cell metabolism, which forces the walls of the heart to balloon out under pressure. Myocardial infarction, which leads to remodeling, thinning of the ventricle wall, dilatation and heart failure, is one of the leading causes of death. Remodeling of the myocardium following infarction is a poorly understood biological process. Remodeling, by its very nature, implies an alteration in the extracellular matrix (ECM) and in the spatial orientation of cells and intracellular components. Understanding of molecular and cellular mechanisms of remodeling are an extremely worthwhile topic for exploration. Extracellular matrix, in connection with its receptor integrins and cytoskeletal cellular matrix in a 3-D orientation, is responsible for cardiac cell alignment and myocardial structural integrity. Substances that break down the extracellular matrix, specialized proteinases as well as inhibitors of proteinases, appear to be normally balanced in maintaining the integrity of the myocardium. Myocardial infarction leads to an imbalance in proteinase antiproteinase activities allowing alterations in the stability and integrity of the extracellular matrix, leading to tissue remodeling. The latent matrix proteinases are activated following infarct-injury. The degradation of ECM induces contractile and proliferative phenotypes in cardiac fibroblast cells and transforms to myofibroblast cells. The extracellular matrix-derived peptides induce maladaptive response in myofibroblasts and activate MMPs, causing ventricular dilatation and myocardial dysfunction. This review presents new and significant information regarding the role of activated matrix proteinases and their endogenous inhibitors in ischemic heart disease. This will have a significant impact on both our understanding of the tissue remodeling and on basic cell physiology of extracellular matrix turnover, as well as potential avenues for pharmacological approaches for the treatment of ischemic heart disease and heart failure.

Inhibition of the cellular metabolism of Caco-2 cells by prolamin peptides from cereals toxic for coeliacs

Peptic-tryptic (PT) digests of prolamins derived from several cereals were tested on differentiated Caco-2 cells to study the effect on cellular metabolism, particularly on DNA, RNA, protein and glycoprotein synthesis. Cell viability was evaluated after treatment with the same cereals. Whereas PT digests from bovine serum albumin and both durum wheat types (diploid and tetraploid) did not exert any effect, bread wheat, oats, barley and rye exerted an inhibitory effect close to 80% for DNA and RNA synthesis and close to 60% for (glyco)protein synthesis. Cell viability evaluated by MTT tests did not show any differences between treated and untreated cells. These observations, and previous results, suggest that, whereas prolamin-derived peptides from bread wheat, barley, rye and oats did not cause an immediate cytotoxic effect, they, were however, responsible for cell damage impairing cell metabolism.

Metabolic inhibitors affect the conductance of low voltage-activated calcium channels in brain capillary endothelial cells.

The brain capillary endothelium plays an essential role in the preservation of the blood-brain barrier and in the control of blood microcirculation. Since hypoxia (Po2: 20 Torr) increases K+ conductance in brain capillary endothelial cells (BCECs) (Delpiano, 1994), the question arises whether chemical agents that impair cell metabolism may produce similar changes in Ca2+ conductance. To better understand the signal transduction mechanism that operates on BCECs during hypoxia and which may be of physiological relevance for the control of brain blood flow microcirculation, these cells were investigated in voltage-clamp experiments using the perforated nystatin patch-clamp technique (Horn & Marty, 1988).KeywordsCarotid BodyGlomus CellBrain Capillary Endothelial CellRabbit Portal VeinBrain Capillary EndotheliumThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Effect of Different Buffers on the Biocompatibility of Capd Solutions

Commercially available solutions for continuous ambulatory peritoneal dialysis (CAPD) affect the viability and function of the cells in the peritoneal cavity. The low biocompatibility of the solutions may be caused by a low pH, hyperosmolality, high glucose content, and lack of potassium, glutamine, and other components essential for normal cellular functions. The nature of the buffer employed is also important for the cytotoxicity of the solutions. Lactate, the most frequently used buffer, has been shown to inhibit cellular functions important for the peritoneal defense system including phagocytosis, bacterial killing, and secretion of cytokines. It is generally believed that the cytotoxicity of lactate is caused by lowering of intracellular pH and impairment of metabolism due to changed redox potentials. However, the cytotoxicity of lactate is highly dependent upon the pH of the solutions, indicating that passive or active diffusion across the cell membrane is determining the effects of lactate. Bicarbonate has been heavily advocated as an alternative buffer because it is the most important naturally occurring buffer in plasma and it enables a pH of approximately 7.4 in the solutions. However, due to sedimentation of calcium carbonate (CaCO3) and production of toxic glucose metabolites it is difficult to prepare and store bicarbonate-based solutions. Moreover, investigations have revealed that even bicarbonate-based solutions are not optimal regarding biocompatibility, presumably due to a paradoxical intracellular acidification caused by influx of carbon dioxide (CO2). More recently, the effect of other buffers such as pyruvate and histidine have been examined. Especially pyruvate is a promising new buffer candidate.

The promise of enzymes in therapy of hyperlipidemia

Treatment of hyperlipidemias must be commenced in that intestinal segment where alimentary lipoprotein aggregate generation is initiated postprandially and the aggregates are still in nascent form. This is to prevent the formation of potentially pathological units that do not equilibrate with the blood colloid. The colloid chemical state of the alimentary lipoprotein entities in the systemic circulation is decisive for maintenance of thair stability and for their disposal from the blood. The causes of impaired, “unripe,” lipoprotein aggregate formation include: (a) the action of human pancreatic lipase is even normally a restricted and vulnerable process, (b) inadequate ratio of protein to fat to stabilize the aggregates, (c) defective proteolysis in the small intestine, and (d) the dual behavior of the surface tension-lowering agent, the lecithin antagonist cholesterol. On the one hand, cholesterol represents physicochemically the weakest link in the lipoprotein interfaces. On the other hand, an excess of cholesterol in lipoprotein interfaces decreases the stability of the surface film. This leads to changes in the decay of the entities and the cell surface-active lipid constituents of the “unripe” plasma lipoprotein colloid complexes can easily be adsorbed to the endothelial cell surface plasma membrane: the excess aggregate-cholesterol molecules simply join, or dissolve in, the cell membrane-cholesterol which thus acts as its own receptor or solvent: cholesterol dimers occur. This causes rigidity of the endothelial cell surface membrane and leads to impaired cell metabolism. The intima recognizes the impairment as a foreign body and initiates a physiological defense reaction including phagocytosis. The event may be still more dangerous if the adrenergic receptors of the autonomous nervous system involved in lipolysis with subsequent plasma efflux are simultaneously stimulated. The therapeutic measure indicated is production of balanced alimentary lipoprotein aggregates. This can be achieved by oral administration of (a) protease, and (b) non-specific micellar lipase. The lipase functions without restriction and can perform all the activities that human pancreatic lipase cannot. The enzymes utilized are of mold origin and generally available.

Studies of biochemical markers in cerebrospinal fluid in patients with meningoencephalitis

Several biochemical markers in the cerebrospinal fluid (CSF) of 120 patients with serous meningoencephalitis (SM) of viral origin were compared with those of 74 patients with viral or bacterial infections accompanied by neck stiffness but no CSF abnormality (i.e., meningism). CSF adenylate kinase was higher (P less than 0.025) in SM and correlated with lactate concentration (r = 0.37; P less than 0.01). CSF hypoxanthine was lower (P less than 0.001) in SM, whereas CSF xanthine was similar in the two conditions. The xanthine/hypoxathine ratio correlated with the CSF leukocyte count (r = 0.32; P less than 0.01), and especially with the mononuclear cell count (r = 0.45; P less than 0.001). CSF adenylate kinase correlated with fever in SM (r = 0.28; P less than 0.01). CSF urate and protein displayed a mutual correlation in both conditions (r = 0.26 and P less than 0.05 for SM; r = 0.55 and P less than 0.001 for meningism). These results support the hypothesis of impaired brain cell metabolism, probably of ischemic nature, in viral meningoencephalitis, causing leakage of adenylate kinase into the CSF, where hypoxanthine may be reutilized by mononuclear leukocytes.

Transferrin endocytosis in reticulocytes: an electron microscope study using colloidal gold.

The endocytosis of transferrin by rabbit reticulocytes was investigated by electron microscopy using transferrin labelled with colloidal gold. This complex was shown to bind and donate its iron to the cells in a manner comparable to native iron-transferrin. After incubation at 37 degrees C approximately 70% of the transferrin-gold particles were located within endocytotic vesicles. Treatment of the cells with pronase, EDTA, metabolic inhibitors and heating to 46 degrees C inhibited the endocytosis. The uptake of colloidal gold complexes of albumin and concanavalin A were compared with that of transferrin. Little endocytosis of these proteins was observed. It is concluded that colloidal gold is a suitable label for the investigation of transferrin endocytosis and that the endocytosis is specific for transferrin and sensitive to the action of reagents which damage membrane receptors, alter membrane function or impair cell metabolism.

The pathophysiology of shock.

This is a very brief, superficial and biased discussion of the pathophysiologic changes in shock. It was designed to provide some insight into the very complex changes that occur, with particular attention to a few examples of the impaired cell metabolism, including changes in ATP, cAMP, and calcium. Although inadequate tissue perfusion through nutrietn capillaries is the main etiologic factor in most types of shock, it is not the primary problem in many patients, particularly those with early or hyperdynamic sepsis. The importantance of oxygen consumption and the possible benefits of higher hemoglobin levels are discussed to some extent because of their possible clinical application.

Shock in the emergency department

Shock continues to be associated with a high mortality rate primarily because of delays in diagnosis and therapy. To diagnose shock early, and thereby increase the chances of reversal before there is extensive deterioration of vital organs, one should look for any decrease in pulse pressure, urine output, urine sodium concentration, alertness or any increase in urine osmolarity, tachypnea or tachycardia. Systolic hypotension, oliguria, metabolic acidosis and a cold clammy skin are late signs of shock. The pathophysiology of early hypovolemic shock includes hyperventilation, vasoconstriction, cardiac stimulation, fluid shifts into the vascular system and platelet aggregation. Late shock is characterized by lysosomal breakdown, subsequent release of kinins (especially bradykinin), impaired cell metabolism and organ function, fluid shifts out of the vascular system because of capillary endothelial damage and intravascular coagulation. The primary cause of shock should not be neglected in favor of treating signs, symptoms, and laboratory data. The resuscitation from the shock process itself involves correction of pathophysiologic changes, based on objective trends and responses rather than isolated measurements. A suggested outline of therapies in order of their use includes: 1) correction of the primary problem; 2) ventilation and oxygen; 3) fluid-loading: 4) inotropic agents; 5) correction of acid-based and electrolyte abnormalities; 6) steroids ("physiologic" or "pharmacologic" doses); 7) vasopressors (especially in elderly, severely hypotensive patients); 8) vasodilators (if excess vasoconstriction); 9) diuretics (if oliguric in spite of the above), and 10) heparin (if DIC). The most common errors are 1) late diagnosis; 2) inadequate control of the primary problems; 3) inadequate fluid loading; 4) delayed ventilator assistance, and 5) excessive reliance on and use if vasopressors and diuretics.