Complexes of aluminium(III) with glucose-6-phosphate in aqueous solutions

The interaction of aluminium(III) with glucose-6-phosphate (GP: LH2) in aqueous solutions has been studied from pH 1 to pH 8, by pH-potentiometry and multinuclear (31P, 27Al, 13C) NMR spectroscopy. Various mononuclear species (MLH2, MLH, ML, ML2H, ML2 and MLH(-3)) and dinuclear complexes M2L2H-n (n=1-4) are formed in the system. NMR clearly indicates that GP is already bound to Al(III) at pH 1. The potentiometric speciation results are confirmed and completed by spectroscopic experiments. Many peaks are observed in the 31P NMR spectra suggesting the formation of isomeric species. An attempt to assign the signals to the corresponding complexes is made, allowing a discussion about their structure. Interestingly enough no metal ion-induced deprotonation and coordination of the alcoholic-OH functions have been observed.     

Cloning the AFURS1 gene which is up-regulated in senescent human parenchymal kidney cells

To study the changes in gene expression in senescent cells we applied the suppression subtractive hybridization of two cDNA pools isolated from human parenchymal kidney cells in the phase of exponential growth and cellular senescence in vitro. In addition to several genes known to be associated with cellular senescence, we identified a new gene, which is overexpressed in senescent kidney parenchymal cells. The full-length cDNA consists of 5226 nucleotides with an open reading frame (ORF) encoding 701 amino acids (Accession number: AJ306929). The gene product has a predicted molecular mass of 77.31 kDa. The ORF of the new gene shows significant homology to P-type ATPase family gene products and therefore was called AFURS1 (ATPase family homolog up-regulated in senescence cells). The consensus sequence phosphorylation site (DKTGTLT) is highly conserved. According to the GenBank database AFURS1 is mapped to the sequence segment NT_005535.3 at chromosomal region 3q26.32 and has 18 exons. The AFURS1 gene might have a role in cellular aging and tumor suppression as well.     

FT-IR study of some seco- and apocarotenoids

FT-IR spectroscopy was applied to investigate 15 different carotenoids. The following compounds were examined: beta-carotenone (1); semi-beta-carotenon-epoxide (2); beta-apo-8'-carotenal (3); ethyl-beta-apo-8'-carotenoate (4); beta-citraurin (5); 5,6-Epoxy-beta-caroten-8'-al (6); beta-citraurin-epoxide (7); apo-10'-violaxanthal (8); persicaxanthin (9); capsylaldehyde (10); capsanthylal (11); retinol (12); retinal (13); retinoic acid (14); and bixin (15). Some characteristic functional groups (Cz.dbnd;C, Cz.dbnd;O, CHO, OH, etc.) were identified. We focused on the influence of conjugation of the keto-, aldehyde- and ester groups on the absorption of the Cz.dbnd;C bonds. This method is useful in the fast analysis of the biologically important carotenoids especially if there are small samples available.     

The role of NPY in the mediation of orexin-induced hypothermia

The mediation of orexin-A-induced hypothermia was investigated. Different doses of orexin-A (140-560 pmol) were administered intracerebroventricularly (i.c.v.) to adult male rats, and the colon temperature was used as an index of the thermoregulatory action. Orexin-A decreased both the basal colon temperature and the lipopolysaccharide-induced fever and exhibited a bell-shaped dose-response curve. I.c.v. pretreatment with neuropeptide Y (NPY) antiserum 24 h before orexin administration significantly decreased the hypothermic effect of orexin-A. These data strengthen the hypothesis that this appetite-regulating peptide might also play a role in thermoregulation, and its hypothermic effect seems to be mediated at least partially by NPY.     

Interaction of Al(III) with the peptides AspAsp and AspAspAsp

The interactions of Al(III) with the dipeptide AspAsp and the tripeptide AspAspAsp in aqueous solutions were studied by pH-potentiometry and multinuclear 1H- and 13C- nuclear magnetic resonance (NMR) spectroscopy. Their numerous negatively charged COO(-) functions allow these ligands to bind Al(III) even in weakly acidic solutions. Various mononuclear 1:1 complexes are formed in different protonation states. 13C-NMR spectroscopy unambiguously proved participation of the COO(-) functions in a monodentate or chelating mode in Al(III) binding, however, the terminal-NH(2) group seems to be excluded from the coordination. Depending on the metal ion to ligand ratio precipitation occurs at pH approximately 5 to 6. This indicates that the COO(-) groups at the low level of preorganization in such small peptides are not sufficient to keep the Al(III) ion in solution and to prevent the precipitation of Al(OH)(3) at physiological pH. To achieve this, a more specific arrangement of the side-chain donors seems necessary.     

Characterisation of an uridine-specific binding site in rat cerebrocortical homogenates

Parameters of [3H]uridine binding to synaptic membranes isolated from rat brain cortex (K(D)=71+/-4 nM, B(max)=1.37+/-0.13 pmol/mg protein) were obtained. Pyrimidine and purine analogues displayed different rank order of potency in displacement of specifically bound [3H]uridine (uridine>5-F-uridine>5-Br-uridine approximately adenosine>5-ethyl-uridine approximately suramin>theophylline) and in the inhibition of [14C]uridine uptake (adenosine>uridine>5-Br-uridine approximately 5-F-uridine approximately 5-ethyl-uridine) into purified cerebrocortical synaptosomes. Furthermore, the effective ligand concentration for the inhibition of [14C]uridine uptake was about two order of magnitude higher than that for the displacement of specifically bound [3H]uridine. Adenosine evoked the transmembrane Na(+) ion influx, whereas uridine the transmembrane Ca(2+) ion influx much more effectively. Also, uridine was shown to increase free intracellular Ca(2+) ion levels in hippocampal slices by measuring Calcium-Green fluorescence. Uridine analogues were found to be ineffective in displacing radioligands that were bound to various glutamate and adenosine-recognition and modulatory-binding sites, however, increased [35S]GTPgammaS binding to membranes isolated from the rat cerebral cortex. These findings provide evidence for a rather specific, G-protein-coupled site of excitatory action for uridine in the brain.     

Expression of cholinesterases in human kidney and its variation in renal cell carcinoma types

Despite the aberrant expression of cholinesterases in tumours, the question of their possible contribution to tumorigenesis remains unsolved. The identification in kidney of a cholinergic system has paved the way to functional studies, but details on renal cholinesterases are still lacking. To fill the gap and to determine whether cholinesterases are abnormally expressed in renal tumours, paired pieces of normal kidney and renal cell carcinomas (RCCs) were compared for cholinesterase activity and mRNA levels. In studies with papillary RCC (pRCC), conventional RCC, chromophobe RCC, and renal oncocytoma, acetylcholinesterase activity increased in pRCC (3.92 ± 3.01 mU·mg(-1), P = 0.031) and conventional RCC (2.64 ± 1.49 mU·mg(-1), P = 0.047) with respect to their controls (1.52 ± 0.92 and 1.57 ± 0.44 mU·mg(-1)). Butyrylcholinesterase activity increased in pRCC (5.12 ± 2.61 versus 2.73 ± 1.15 mU·mg(-1), P = 0.031). Glycosylphosphatidylinositol-linked acetylcholinesterase dimers and hydrophilic butyrylcholinesterase tetramers predominated in control and cancerous kidney. Acetylcholinesterase mRNAs with exons E1c and E1e, 3'-alternative T, H and R acetylcholinesterase mRNAs and butyrylcholinesterase mRNA were identified in kidney. The levels of acetylcholinesterase and butyrylcholinesterase mRNAs were nearly 1000-fold lower in human kidney than in colon. Whereas kidney and renal tumours showed comparable levels of acetylcholinesterase mRNA, the content of butyrylcholinesterase mRNA was increased 10-fold in pRCC. The presence of acetylcholinesterase and butyrylcholinesterase mRNAs in kidney supports their synthesis in the organ itself, and the prevalence of glycosylphosphatidylinositol-anchored acetylcholinesterase explains the splicing to acetylcholinesterase-H mRNA. The consequences of butyrylcholinesterase upregulation for pRCC growth are discussed.     

Endothelial cell markers reflecting endothelial cell dysfunction in patients with mixed connective tissue disease

Introduction  

The aim of the present study was to investigate the association between cardiovascular risk factors and endothelial dysfunction in patients with mixed connective tissue disease (MCTD) and to determine which biomarkers are associated with atherosclerotic complications, such as cardiovascular disease.     

Effect of chromium on photosystem 2 in the unicellular green alga, <Emphasis Type="Italic">Chlorella pyrenoidosa</Emphasis>

We investigated the effect of chromium (20–40 g m⁻³, 8–72 h) on the photosystem 2 (PS2) activities of Chlorella pyrenoidosa cells. By using chlorophyll fluorescence transients, thermoluminescence, oxygen polarography, and Western blot analysis for D1 protein we found that inhibition of PS2 can be accounted for by the enhanced photodestruction of the reaction centres in the cells cultivated in the presence of Cr(VI) at 25 °C in “white light” (18 W m⁻²). Hence photodestruction of D1 is caused by an enhanced oxidative stress and lipid peroxidation, as indicated by the appearance of a high-temperature thermoluminescence band.