The mechanism of inhibition of the cyclin-dependent kinase-2 as revealed by the molecular dynamics study on the complex CDK2 with the peptide substrate HHASPRK

Molecular dynamics (MD) simulations were used to explain structural details of cyclin-dependent kinase-2 (CDK2) inhibition by phosphorylation at T14 and/or Y15 located in the glycine-rich loop (G-loop). Ten-nanosecond-long simulations of fully active CDK2 in a complex with a short peptide (HHASPRK) substrate and of CDK2 inhibited by phosphorylation of T14 and/or Y15 were produced. The inhibitory phosphorylations at T14 and/or Y15 show namely an ATP misalignment and a G-loop shift (~5 A) causing the opening of the substrate binding box. The biological functions of the G-loop and GxGxxG motif evolutionary conservation in protein kinases are discussed. The position of the ATP gamma-phosphate relative to the phosphorylation site (S/T) of the peptide substrate in the active CDK2 is described and compared with inhibited forms of CDK2. The MD results clearly provide an explanation previously not known as to why a basic residue (R/K) is preferred at the P(2) position in phosphorylated S/T peptide substrates.     

Cholesterol is the major component of native lipoproteins activating the p38 mitogen-activated protein kinases

Elevated low-density lipoprotein (LDL) levels induce activation of the p38 mitogen-activated protein kinase (MAPK), a stress-activated protein kinase potentially participating in the development of atherosclerosis. The nature of the lipoprotein components inducing p38 MAPK activation has remained unclear however. We show here that both LDLs and high-density lipoproteins (HDLs) have the ability to stimulate the p38 MAPKs with potencies that correlate with their cholesterol content. Cholesterol solubilized in methyl-beta-cyclodextrin was sufficient to activate the p38 MAPK pathway. Liposomes made of phosphatidylcholine (PC) or sphingomyelin, the two main phospholipids found in lipoproteins, were unable to stimulate the p38 MAPKs. In contrast, PC liposomes loaded with cholesterol potently activated this pathway. Reducing the cholesterol content of LDL particles lowered their ability to activate the p38 MAPKs. Cell lines representative of the three main cell types found in blood vessels (endothelial cells, smooth muscle cells and fibroblasts) all activated their p38 MAPK pathway in response to LDLs or cholesterol-loaded PC liposomes. These results indicate that elevated cholesterol content in lipoproteins, as seen in hypercholesterolemia, favors the activation of the stress-activated p38 MAPK pathway in cells from the vessel wall, an event that might contribute to the development of atherosclerosis.     

Genetic screening for glucocorticoid-remediable aldosteronism (GRA): experience of three clinical centres in Poland

Glucocorticoid-remediable aldosteronism (GRA), also known as familial hyperaldosteronism type I (FH-I, OMIM 103900), is a monogenic form of inherited hypertension caused by the presence of a chimaeric gene originating from an unequal cross-over between the CYP11B1 (11beta-hydroxylase) and CYP11B2 (aldosterone synthase) genes. The hybrid gene has the CYP11B1 sequence at the 5' end, including the promoter, and the CYP11B2 sequence at the 3' end. The aim of our study was to evaluate the prevalence of GRA in a Polish population of 129 patients with primary hyperaldosteronism (PHA) and 132 patients with essential hypertension (EH), through the use of a PCR-based test revealing the chimaeric gene. None of our PHA or EH patients was positive for the CYP11B1/CYP11B2 chimaeric gene. These data suggest that GRA is unlikely to be a common cause of hypertension in Polish subjects. However, the real prevalence of GRA in Poland, both in the high-risk group of individuals with primary hyperaldosteronism and in the general population, remains to be established.     

Biomechanical properties of oesophagus wall under loading

In this investigation, firstly, the biomechanical properties of different parts of oesophagus were determined. Oesophagus stress and strain are the greatest in the cervical part for all age groups. The human oesophagus deforms unevenly, depending on the direction of load in relation to the organ's axis, it exhibits anisotropical behaviour. With the age the values of mechanical parameters of the oesophagus wall reduce, in particular beginning from 45 years of age, but the modulus of elasticity increases. Biomechanical properties of the oesophagus depend on the architecture of its structure. By loading the organ in the circumferential direction, microfibrilae rupture and deformation of the muscular fibres occurs. With increase of load, collagenous fibres straighten and microruptures in collagenous fibrilae occur. With stretching of oesophagus longitudinally, collagenous fibres partially preserve their wavy and helical configuration. Therefore, higher resistance of the oesophageal wall occurs in the longitudinal direction.     

Microbiota,Phagocytic Activity,Biochemical Parameters and Parasite Control in Horses with Application of Autochthonous,Bacteriocin-Producing,Probiotic Strain Enterococcus faecium EF 412

Probiotics and Antimicrobial Proteins - The beneficial influence of bacteriocin-producing, probiotic, mostly non-autochthonous bacteria has already been reported in various animals. However, their...     

Changes of sodium and ATP affinities of the cardiac (Na,K)-ATase during and after nitric oxide deficient hypertension

In the cardiovascular system, NO is involved in the regulation of a variety of functions. Inhibition of NO synthesis induces sustained hypertension. In several models of hypertension, elevation of intracellular sodium level was documented in cardiac tissue. To assess the molecular basis of disturbances in transmembraneous transport of Na⁺, we studied the response of cardiac (Na,K)-ATPase to NO-deficient hypertension induced in rats by NO-synthase inhibition with 40 mg/kg/day N^G-nitro-L-arginine methyl ester (L-NAME) for 4 four weeks. After 4-week administration of L-NAME, the systolic blood pressure (SBP) increased by 36%. Two weeks after terminating the treatment, the SBP recovered to control value. When activating the (Na,K)-ATPase with its substrate ATP, no changes in K_m and V_max values were observed in NO-deficient rats. During activation with Na⁺, the V_max remained unchanged, however the K_Na increased by 50%, indicating a profound decrease in the affinity of the Na⁺-binding site in NO-deficient rats. After recovery from hypertension, the activity of (Na,K)-ATPase increased, due to higher affinity of the ATP-binding site, as revealed from the lowered K_m value for ATP. The K_Na value for Na⁺ returned to control value. Inhibition of NO-synthase induced a reversible hypertension accompanied by depressed Na⁺-extrusion from cardiac cells as a consequence of deteriorated Na⁺-binding properties of the (Na,K)-ATPase. After recovery of blood pressure to control values, the extrusion of Na⁺ from cardiac cells was normalized, as revealed by restoration of the (Na,K)-ATPase activity. (Mol Cell Biochem 000: 000-000, 1999)     

Enterocin M in Interaction in Broiler Rabbits with Autochthonous,Biofilm-Forming Enterococcus hirae Kr8 Strain

Probiotics and Antimicrobial Proteins - Young rabbits are susceptible to gastrointestinal diseases caused by bacteria. Enterococcus hirae can be associated with diseases. But enterocins produced by...     

Mitochondria as a target of cardioprotection in models of preconditioning

Over the recent years the view on mitochondria in the heart as a cellular powerhouse providing ATP supply needed to sustain contractile function, basal metabolic processes, and ionic homeostasis has changed radically. At present it is known that dysfunctions of these organelles are essential in the development of a large number of diseases, including cardiovascular diseases. Moreover, mitochondria are considered to be a very promising target of endogenous strategies that are essential in the protection of the myocardium from acute ischemia/reperfusion injury. These strategies including ischemic preconditioning, remote ischemic preconditioning as well as the acute phase of streptozotocin-induced diabetes mellitus, provide a similar effect of protection. Alterations observed in the functional and structural properties of heart mitochondria caused by short-term pathological impulses are associated with endogenous cardioprotective processes. It seems that the extent of mitochondrial membrane fluidization could be an active response mechanism to injury with a subtle effect on membrane-associated processes which further affect the environment of the whole organelle, thus inducing metabolic changes in the heart. In this review article, we provide an overview of endogenous protective mechanisms induced by hypoxic, pseudohypoxic and ischemic conditions with special consideration of the role of heart mitochondria in these processes.     

Effects of deoxynivalenol and zearalenone on oxidative stress and blood phagocytic activity in broilers

Effects of dietary contamination with various levels of deoxynivalenol (DON) and zearalenone (ZEA) were investigated on Ross 308 hybrid broilers of both sexes. After hatching, all chickens were fed an identical control diet for two weeks. Then chickens of Group 1 received a diet contaminated with DON and ZEA, both being 3.4 mg kg(-1), while Group 2 received DON and ZEA at 8.2 and 8.3 mg kg(-1), respectively. The diet of the control group contained background levels of mycotoxins. Samples of blood and tissues were collected after two weeks. Intake of both contaminated diets resulted in a significantly decreased activity of glutathione peroxidase (GPx) and increased level of malondialdehyde (MDA) in liver tissue, while in kidneys the concentration of MDA was significantly increased only in Group 1. On the other hand, activities of blood GPx and plasma gamma-glutamyltransferase (GGT) were elevated in Group 2 only. Activities of thioredoxin reductase in liver and GPx in duodenal mucosa tissues, superoxide dismutase (SOD) in erythrocytes as well as levels of MDA in duodenal mucosa and alpha-tocopherol in plasma were not affected by dietary mycotoxins. Blood phagocytic activity was significantly depressed in Group 1 and 2. These results demonstrate that diets contaminated with DON and ZEA at medium levels are already able to induce oxidative stress and compromise the blood phagocytic activity in fattening chickens.