Arg-Gly-Asp (RGD) sequence conjugated in a synthetic copolymer bearing a sugar moiety for improved culture of parenchymal cells (hepatocytes)

A copolymer, including a Gly-Arg-Gly-Asp-Ser (GRGDS) sequence and sugar moieties, was synthesized for the culturing of parenchymal cells (hepatocytes). Hepatocyte cells attached to poly[N-p-vinylbenzyl-d-maltonamide-co-6-(p-vinylbenzamido)-hexanoic acid-GRGDS] [poly(VMA-co-VBRGD)]-coated dishes grew approximately 60% better than on other polymer-coated surface for 12 h. Also, about 80% greater albumin secretion (0.38 pg ml^–1) and about 70% greater urea synthesis (0.495 pg ml^–1) from hepatocytes were produced in this matrix as compared with unstimulated cells. The behaviour of hepatocytes on poly(VMA-co-VBGRGDS)-coated dishes was not distinct from those attached to a collagen. The conjugation of the adhesion molecules of the RGD peptide in the poly(VMA-co-VBGRGDS) copolymer therefore specifically interacts with integrin families on the hepatocyte cell membrane.     

The transient and constitutive inflammatory signaling in tumorigenesis

Comment on: Rokavec M, et al. Mol Cell 2012; 45:777-89.     

Plant action: Multiple levels of regulation

This lecture is devoted to the relative contribution of various levels of regulation of the actin cytoskeleton functioning in the cell. Regulation at the levels of gene expression, mRNA and protein synthesis and stability, processes of actin polymerization/depolymerization and actin structures reorganization is briefly considered. Novel information about the pathways of signal transduction to the actin cytoskeleton with the involvement of Arp2/3 complex and RIC proteins is highlighted.     

NP7 protects from cell death induced by oxidative stress in neuronal and glial midbrain cultures from parkin null mice

Parkin mutations produce Parkinson’s disease (PD) in humans and nigrostriatal dopamine lesions related to increased free radicals in mice. We examined the effects of NP7, a synthetic, marine derived, free radical scavenger which enters the brain, on H₂O₂ toxicity in cultured neurons and glia from wild-type (WT) and parkin null mice (PK-KO).NP7, 5-10 μM, prevented the H₂O₂ induced apoptosis and necrosis of midbrain neuronal and glial cultures from WT and PK-KO mice. NP7 suppressed microglial activation and the H₂O₂ induced drop-out of dopamine neurons_. Furthermore, NP7 prevented the increased phosphorylation of ERK and AKT induced by H₂O₂. NP7 may be a promising neuroprotector against oxidative stress in PD.     

Relationship between the concentration of sugars in the roots and VA mycorrhizal infection

Summary The VA-infected wheat varieties showed an increase of total (Lozano var.) and reducing (Lozano and Pane vars.) sugars in their root extracts. However, no clear relationship between sugar concentration in the root and VA mycorrhizal infection level could be established.In addition, the VA mycorrhizal hosts sorghum, alfalfa, sunflower and maize, and non-host radish and cabbage plants were tested for sugar content in their root extracts after fifteen days of growth. Sugars present in the root extracts of these plants did not seem to be a decisive factor in plant susceptibility to VA infection.     

Digitalis receptor sugar binding site characteristics: A model based upon studies of Na+, K+-ATPase preparations with differing digitalis sensitivities

The structure-activity relationships of the genin moieties of digitalis glycosides are commonly elucidated by determining the inhibitory potency of a variety of genins toward the plasma membrane Na⁺, K⁺-ATPase; qualitatively these relationships appear to be fairly independent of the specific Na⁺, K⁺-ATPase preparation utilized for the analysis. To determine whether this is the case with regard to the sugar moieties of glycosides, the inhibitory effects of 12 monoglycosides of digitoxigenin toward four Na⁺, K⁺-ATPase preparations of different origin were measured. It was found that while recognition of the major structural determinants of sugar activity appeared to be independent of enzyme source, recognition of the minor structural determinants of activity showed some source dependence. It was also observed that the intrinsic sensitivity to sugar potentiation may be source dependent and unrelated to intrinsic sensitivity to inhibition by digitoxigenin. These observations are compatible with a model of the Na⁺, K⁺-ATPase sugar binding site(s) in which intrinsic sensitivity to sugar attachment as well as recognition characteristics (for sugar structural features) both determine the extent to which a sugar moiety may contribute to the activity of monoglycosides. Further, in these studies one of the Na⁺, K⁺-ATPase preparations employed was obtained from rat brain, a tissue known to contain a mixture of ouabain sensitive and insensitive isoforms. We have observed that the rigorous purification techniques employed appear to have selectively removed from or denatured the less ouabain sensitive al isoform found in this enzyme preparation.     

Water transport parameters and regulatory processes inEremosphaera viridis

Summary The water relations parameters and the osmoregulatory response ofEremosphaera viridis were investigated both by using the pressure probe technique and by analyzing the intracellular pool of osmotically active agents. In the presence of various concentrations of different salts a biphasic osmoregulatory response was recorded, consisting of a rapid decrease in turgor pressure due to water loss followed by an increase in turgor pressure to the original turgor pressure value (depending on the salt). The values of turgor pressure, volumetric elastic modulus and hydraulic conductivity depended on the composition of the media. Nonelectrolytes did not cause a turgor recovery after the initial water efflux. The second phase of turgor regulation in the presence of salts was characterised by the intracellular accumulation of ions and sugars and required at least 24 hr. Analysis of the cell sap showed that the increase in the internal osmotic pressure was mainly achieved by accumulation of sucrose. Additionally, accumulation of glucose was observed in illuminated cells in the presence of Rb and K. Electron micrographs suggested that the sucrose was produced by degradation of starch granules. Turgor pressure recovery after salt stress seemed to be dependent on temperature and is well correlated with the according photosynthetic activity. The data suggest that a temperature-dependent enzyme which is activated by potassium or rubidium is involved in the regulatory response.