Membrane depolarization and NADPH oxidase activation in aortic endothelium during ischemia reflect altered mechanotransduction

Vascular endothelial growth factor (VEGF) is considered to be important in promotion of capillary growth in skeletal muscles exposed to increased activity. We studied its interactions with nitric oxide (NO) by examining the expression of endothelial NO synthase (NOS), VEGF, and VEGF receptor-2 (VEGFR-2) proteins in relation to capillary growth in rat extensor digitorum longus muscles electrically stimulated for 2, 4, or 7 days with and without NOS inhibition by N(omega)-nitro-L-arginine (L-NNA, 3 mg/day). Stimulation increased all proteins from 2 days onward, concomitantly with capillary proliferation (labeling for proliferating cell nuclear antigen). Capillary-to-fiber ratio was elevated by 25% after 7 days. Concurrent oral administration of L-NNA did not affect the increase in endothelial NOS but depressed its activity, as shown by increased blood pressure and decreased arteriolar diameters in 2-day-stimulated muscles. NOS inhibition eliminated the increased expression of VEGFR-2 and VEGF proteins in muscles stimulated for 2 and 4 days but not for 7 days. However, it depressed capillary proliferation and the increase in C/F at all time points. We conclude that, in stimulated muscles, NO, generated by activation of neuronal NOS by muscle activity or endothelial NOS by increased blood flow and capillary shear stress, may increase capillary proliferation in the early stages of stimulation through upregulation of VEGFR-2 and VEGF. With longer stimulation, capillary growth appears to require NO, and high levels of VEGF and VEGFR-2 may be contributing to maintenance of the increased capillary bed.     

Effect of inland water salinity on growth performance and nutritional physiology in growing milkfish, Chanos chanos (Forsskal): field and laboratory studies

To investigate the effect of inland groundwater salinity on growth performance, feed conversion efficiency, nutrient retention and intestinal enzyme activity in milkfish, two experiments were conducted. In the first experiment (Expt I), a 100‐day monoculture of Chanos chanos [mean body weight (BW): 2.2 g] at different salinities (0, 10, 15, 20 and 25‰) was carried out in ponds fertilized with cowdung (about 10 000 kg ha^?1 year^?1) and poultry droppings (about 3000 kg ha^?1 year^?1). The fish were fed a compounded supplementary diet (containing 40% protein) at 5% BW day^?1. Studies have revealed that growth increased with each increase in the salinity level; the highest values in weight gain and energy assimilated were observed in ponds maintained at 25‰ salinity [weight: 322.2 g and specific growth rate (SGR): 8.3]. Highest values of condition factor (0.7) and exponential value (n) of the length–weight relationship (LWR; n = 3.25) were also observed in ponds maintained at 25‰ salinity. Dissolved oxygen (DO), biological oxygen demand (BOD), pH and nutrient release remained at the optimal level during the culture period. High values of chlorophyll a, net primary productivity (NPP), phytoplankton and zooplankton population coincided with the highest values of alkalinity and turbidity in ponds maintained at 25‰ salinity. Multivariate analysis revealed a significant positive correlation of chlorides (r = 0.91), conductivity (r = 0.89) and hardness (r = 0.96) with fish growth. Productivity indicating parameters viz. NPP (r = 0.45), nitrate (r = 0.94) and o‐PO₄ (r = 0.52) also showed a significant positive correlation with fish weight gain. In the second experiment (Expt II), milkfish (mean BW: 3.7 g) fry were exposed to different levels of salinity (0.0, 10, 15, 20, 25 and 30‰), and maintained for 90 days in the laboratory. Significantly (P < 0.05) high growth (percentage increase in BW: 183.1 and SGR: 1.2), feed conversion efficiency (64.5%) and intestinal enzyme activity (protease 5.1, amylase 4.1 and cellulolytic 3.2) were observed in the group maintained at 25 ppt salinity in comparison with other groups similarly maintained at low or high salinity levels. Carcass composition, muscle and liver glycogen levels were also significantly (P < 0.05) affected by salinity changes. The significance of these findings is discussed in this paper.     

Attenuation of doxorubicin-induced cardiotoxicity and genotoxicity by an indole-based natural compound 3,3′-diindolylmethane (DIM) through activation of Nrf2/ARE signaling pathways and inhibiting apoptosis

The most crucial complication related to doxorubicin (DOX) therapy is nonspecific cytotoxic effect on healthy normal cells. The clinical use of this broad-spectrum chemotherapeutic agent is restricted due to development of severe form of cardiotoxicity, myelosuppression, and genotoxicity which interfere with therapeutic schedule, compromise treatment outcome and may lead to secondary malignancy. 3,3′-diindolylmethane (DIM) is a naturally occurring plant alkaloid formed by the hydrolysis of indolylmethyl glucosinolate (glucobrassicin). Therefore, the present study was undertaken to investigate the protective role of DIM against DOX-induced toxicity in mice. DOX was administered (5?mg/kg b.w., i.p.) and DIM was administered (25?mg/kg b.w., p.o.) in concomitant and 15 days pretreatment schedule. Results showed that DIM significantly attenuated DOX-induced oxidative stress in the cardiac tissues by reducing the levels of free radicals and lipid peroxidation, and by enhancing the level of glutathione (reduced) and the activity of antioxidant enzymes. The chemoprotective potential of DIM was confirmed by histopathological evaluation of heart and bone marrow niche. Moreover, DIM considerably mitigated DOX-induced clastogenicity, DNA damage, apoptosis, and myeloid hyperplasia in bone marrow niche. In addition, oral administration of DIM significantly (p?相似文献   

Impact of hyperglycemia on the expression of GLUT1 during oral carcinogenesis in rats

Molecular Biology Reports - On the background of the epidemiological link between diabetes and oral cancer, the present study aimed to analyze the potential involvement of selected glucose...     

Lung Ischemia: A Model for Endothelial Mechanotransduction

Endothelial cells in vivo are constantly exposed to shear associated with blood flow and altered shear stress elicits cellular responses (mechanotransduction). This review describes the role of shear sensors and signal transducers in these events. The major focus is the response to removal of shear as occurs when blood flow is compromised (i.e., ischemia). Pulmonary ischemia studied with the isolated murine lung or flow adapted pulmonary microvascular endothelial cells in vitro results in endothelial generation of reactive oxygen species (ROS) and NO. The response requires caveolae and is initiated by endothelial cell depolarization via K_ATP channel closure followed by activation of NADPH oxidase (NOX2) and NO synthase (eNOS), signaling through MAP kinases, and endothelial cell proliferation. These physiological mediators can promote vasodilation and angiogenesis as compensation for decreased tissue perfusion.     

Synthesis, crystal structures, DNA binding and cleavage activity of l-glutamine copper(II) complexes of heterocyclic bases

Ternary l-glutamine (l-gln) copper(II) complexes [Cu(l-gln)(B)(H₂O)](X) (B = 2,2′-bipyridine (bpy), , 1; B = 1,10-phenanthroline (phen), , 2) and [Cu(l-gln)(dpq)(ClO₄)] (3) (dpq, dipyridoquinoxaline) are prepared and characterized by physicochemical methods. The DNA binding and cleavage activity of the complexes have been studied. Complexes 1-3 are structurally characterized by X-ray crystallography. The complexes show distorted square pyramidal (4+1) CuN₃O₂ coordination geometry in which the N,O-donor amino acid and the N,N-donor heterocyclic base bind at the basal plane with a H₂O or perchlorate as the axial ligand. The crystal structures of the complexes exhibit chemically significant hydrogen bonding interactions besides showing coordination polymer formation. The complexes display a d-d electronic band in the range of 610-630 nm in aqueous-dimethylformamide (DMF) solution (9:1 v/v). The quasireversible cyclic voltammetric response observed near −0.1 V versus SCE in DMF-TBAP is assignable to the Cu(II)/Cu(I) couple. The binding affinity of the complexes to calf thymus (CT) DNA follows the order: 3 (dpq) > 2 (phen) ? 1 (bpy). Complexes 2 and 3 show DNA cleavage activity in dark in the presence of 3-mercaptopropionic acid (MPA) as a reducing agent via a mechanistic pathway forming hydroxyl radical as the reactive species. The dpq complex 3 shows efficient photo-induced DNA cleavage activity on irradiation with a monochromatic UV light of 365 nm in absence of any external reagent. The cleavage efficiency of the DNA minor groove binding complexes follows the order: 3 > 2 ? 1. The dpq complex exhibits photocleavage of DNA on irradiation with visible light of 647.1 nm. Mechanistic data on the photo-induced DNA cleavage reactions reveal the involvement of singlet oxygen (¹O₂) as the reactive species in a type-II pathway.     

GroEL Can Unfold Late Intermediates Populated on the Folding Pathways of Monellin

The modulation of the folding mechanism of the small protein single-chain monellin (MNEI) by the Escherichia coli chaperone GroEL has been studied. In the absence of the chaperone, the folding of monellin occurs via three parallel routes. When folding is initiated in the presence of a saturating concentration of GroEL, only 50-60% of monellin molecules fold completely. The remaining 40-50% of the monellin molecules remain bound to the GroEL and are released only upon addition of ATP. It is shown that the basic folding mechanism of monellin is not altered by the presence of GroEL, but that it occurs via only one of the three available routes when folding is initiated in the presence of saturating concentrations of GroEL. Two pathways become nonoperational because GroEL binds very tightly to early intermediates that populate these pathways in a manner that makes the GroEL-bound intermediates incompetent to fold. This accounts for the monellin molecules that remain GroEL-bound at the end of the folding reaction. The third pathway remains operational because the GroEL-bound early intermediate on this pathway is folding-competent, suggesting that this early intermediate binds to GroEL in a manner that is different from that of the binding of the early intermediates on the other two pathways. It appears, therefore, that the same protein can bind GroEL in more than one way. The modulation of the folding energy landscape of monellin by GroEL occurs because GroEL binds folding intermediates on parallel folding pathways, in different ways, and with different affinities. Moreover, when GroEL is added to refolding monellin at different times after commencement of refolding, the unfolding of two late kinetic intermediates on two of the three folding pathways can be observed. It appears that the unfolding of late folding intermediates is enabled by a thermodynamic coupling mechanism, wherein GroEL binds more tightly to an early intermediate than to a late intermediate on a folding pathway, with preferential binding energy being larger than the stability of the late intermediate. Hence, it is shown that GroEL can inadvertently and passively cause, through its ability to bind different folding intermediates differentially, the unfolding of late productive intermediates on folding pathways, and that its unfolding action is not restricted solely to misfolded or kinetically trapped intermediates.     

Search for glucose/galactose-binding proteins in newly discovered protein sequences using molecular modeling techniques and structural analysis

Sugar moieties serve as specificity markers in a wide variety of biochemical functions, and periplasmic glucose/galactose-binding proteins (GGBPs) serve as the primary receptors for transport and chemotaxis. Recently, complete genome sequencing projects have revealed many open reading frames for such receptors. On the basis of the homology search with the known x-ray structures (PDB ID: 3GBP/1GCA) of a periplasmic receptor protein from Salmonella typhimurium, we selected four putative proteins with amino acid identities between 30 and 48% for the prediction of three-dimensional (3D) structures of the proteins as well as their complexes with glucose and galactose. We could successfully identify the key residues involved in coordination with calcium ion spanning over two loop structures. We calculated the ligand-binding affinities and hydrogen bonding patterns of the modeled structures and compared with those of the x-ray structures. The calculation of free energies of binding of the modeled structures to glucose and galactose in the presence of water suggested that two of four putative proteins can form complexes with dissociation constants in the micromolar range (1-10 microM). Electrostatic potentials on the surfaces near the sugar and calcium-binding sites of the modeled structures were predominately negative as found in case of the x-ray structure. Taken together, our results suggest that the products of two newly discovered genes would serve as receptors for the transport of glucose and galactose.