Physiological Research 

About: Physiological Research is an academic journal. The journal publishes majorly in the area(s): Blood pressure & Oxidative stress. Over the lifetime, 3393 publications have been published receiving 61643 citations.

The mechanism of alloxan and streptozotocin action in B cells of the rat pancreas.

Abstract: Alloxan and streptozotocin are widely used to induce experimental diabetes in animals. The mechanism of their action in B cells of the pancreas has been intensively investigated and now is quite well understood. The cytotoxic action of both these diabetogenic agents is mediated by reactive oxygen species, however, the source of their generation is different in the case of alloxan and streptozotocin. Alloxan and the product of its reduction, dialuric acid, establish a redox cycle with the formation of superoxide radicals. These radicals undergo dismutation to hydrogen peroxide. Thereafter highly reactive hydroxyl radicals are formed by the Fenton reaction. The action of reactive oxygen species with a simultaneous massive increase in cytosolic calcium concentration causes rapid destruction of B cells. Streptozotocin enters the B cell via a glucose transporter (GLUT2) and causes alkylation of DNA. DNA damage induces activation of poly ADP-ribosylation, a process that is more important for the diabetogenicity of streptozotocin than DNA damage itself. Poly ADP-ribosylation leads to depletion of cellular NAD+ and ATP. Enhanced ATP dephosphorylation after streptozotocin treatment supplies a substrate for xanthine oxidase resulting in the formation of superoxide radicals. Consequently, hydrogen peroxide and hydroxyl radicals are also generated. Furthermore, streptozotocin liberates toxic amounts of nitric oxide that inhibits aconitase activity and participates in DNA damage. As a result of the streptozotocin action, B cells undergo the destruction by necrosis.

Some current insights into oxidative stress.

Abstract: Oxidative stress is a phenomenon associated with pathogenetic mechanisms of several diseases including atherosclerosis, neurodegenerative diseases, such as Alzheimer's and Parkinson's disease, cancer, diabetes mellitus, inflammatory diseases, as well as psychological diseases or aging processes. Oxidative stress is defined as an imbalance between production of free radicals and reactive metabolites, so-called oxidants, and their elimination by protective mechanisms, referred to as antioxidative systems. This imbalance leads to damage of important biomolecules and organs with potential impact on the whole organism. Oxidative and antioxidative processes are associated with electron transfer influencing the redox state of cells and the organism. The changed redox state stimulates or inhibits activities of various signal proteins, resulting in a changed ability of signal pathways to influence the fate of cells. At present, the opinion that oxidative stress is not always harmful, has been accepted. Depending on the type of oxidants, intensity and time of redox imbalance as well as on the type of cells, oxidative stress can play a role in the regulation of other important processes through modulation of signal pathways, influencing synthesis of antioxidant enzymes, repair processes, inflammation, apoptosis and cell proliferation, and thus processes of malignity. Imprudent administration of antioxidants may therefore have a negative impact on the organism.

Calprotectin - a pleiotropic molecule in acute and chronic inflammation.

Abstract: Calprotectin (MRP8/14, S100A8/S100A9, 27E10 antigen) is a heterodimer of two calcium-binding proteins present in the cytoplasm of neutrophils and expressed on the membrane of monocytes. Upon neutrophil activation or endothelial adhesion of monocytes, calprotectin is released and may be detected in serum or body fluids as potentially useful clinical inflammatory marker. The soluble form of calprotectin provides both bacteriostatic and cytokine-like effects in the local environment. When calprotectin metabolism is affected on a systemic level, the zinc-binding properties of protein may induce severe dysregulation of zinc homeostasis with severe clinical symptoms. The distribution of membrane form of calprotectin is restricted to monocytes and immature macrophages and the presence of calprotectin-positive infiltrating cells reflects the influx of mononuclear phagocytes to the site of inflammation. Calprotectin expression and release seems to be of particular importance in immune and immunopathological reactions.

Advanced glycation end-products and advanced oxidation protein products in patients with diabetes mellitus.

Abstract: Accelerated glycoxidation takes part in the development of diabetic complications. We determined advanced glycation end-products (AGEs) and advanced oxidation protein products (AOPP) in the sera of 52 patients with diabetes mellitus (DM) - 18 with DM Type 1 and 34 with DM Type 2 and examined their relationship to the compensation of the disease. AGEs were estimated spectrofluorimetrically (350 nm/440 nm) whereas AOPP were determined spectro-photometrically (340 nm). AGEs were elevated only in DM Type 2 (DM2 5.11+/-1.15 x 10(3) AU/g vs controls 4.08+/-0.71 x 10(3) AU/g, p<0.001, vs DM1 4.14+/-0.86 x 10(3) AU/g, p<0.005, DM1 vs controls were not significant). AOPP were elevated significantly in both types of DM with higher levels in DM Type 2 (DM2 157.50+/-75.15 micromol/l vs healthy subjects 79.80+/-23.72 micromol/l, p<0.001, vs DM1 97.50+/-30.91 micromol/l, p<0.005, DM1 vs controls p<0.05). There was a tight correlation between AGEs and AOPP in both types of DM (DM1 r=0.75, DM2 r=0.47 (p<0.05)) and both AGEs and AOPP correlated with triglycerides. In DM Type 1 only, AGEs correlated with HbA1c r=0.47 (p<0.05) and with blood glucose. Slight but not significant differences in AGEs and AOPP levels were observed in patients with or without diabetic complications. Oxidative stress is increased in both types of DM, more in Type 2 where it contributes to the formation of glycoxidation products.

Advanced glycation end-products and the progress of diabetic vascular complications

Abstract: Epidemiological studies have confirmed that hyperglycemia is the most important factor in the onset and progress of vascular complications, both in Type 1 and 2 diabetes mellitus. The formation of advanced glycation end-products (AGEs) correlates with glycemic control. The AGE hypothesis proposes that accelerated chemical modification of proteins by glucose during hyperglycemia contributes to the pathogenesis of diabetic complications including nephropathy, retinopathy, neuropathy and atherosclerosis. Recent studies have shown that increased formation of serum AGEs exists in diabetic children and adolescents with or without vascular complications. Furthermore, the presence of diabetic complications in children correlates with elevated serum AGEs. The level of serum AGEs could be considered as a marker of later developments of vascular complications in children with Type 1 and 2 diabetes mellitus. The careful metabolic monitoring of young diabetics together with monitoring of serum AGEs can provide useful information about impending AGE-related diabetic complications. It is becoming clear that anti-AGE strategies may play an important role in the treatment of young and older diabetic patients. Several potential drug candidates such as AGE inhibitors have been reported recently.