The major pterin in Tetrahymena pyriformis is 6-(D-threo-1,2,3-trihydroxypropyl)-pterin (D-monapterin) and not 6-(L-threo-1,2-dihydroxypropyl)-pterin (ciliapterin).

The major pterin in Tetrahymena pyriformis, strain W, earlier suggested to be L-threo-biopterin and named ciliapterin [1] is now identified as D-threo-neopterin (D-monapterin). This is the first example of a natural D-monapterin. This compound was characterized by its chromatographic behavior, its fluorescence properties and by its oxidation product with alkaline permanganate. The final identification was obtained by comparison with an authentic material using an exchange ligand chromatography method with D-phenylalanine as chiral modifier and Cu (II) as metal ion. D-monapterin is also present as the major pterin in Tetrahymena pyriformis strains GL and ST, and in Tetrahymena thermophila.     

Prion replication-once again blaming the dendritic cell.

The lymphoid system is known to be involved in the propagation and spread of scrapie. However, the identity of the cell type responsible for scrapie replication remains controversial. A new study provides evidence that the follicular dendritic cells in the spleen are the targets of this infectious form of prion (pages 1308-1312).     

Biotinylated oligonucleotide probes for the detection and the characterization of TEM-type extended broad spectrum β-lactamases in enterobacteriaceae

Point mutations in the nucleotide sequence of the structural genes for the TEM-type penicillinases can broaded their substrate spectrum towards all beta-lactams except cephamycins and imipenem. The presence of such variants on self-transferable plasmids accounts for the dissemination of this new type of resistance to numerous species of Enterobacteriaceae in various countries. We have synthetized biotinylated oligonucleotide probes for the detection and the discrimination of parental and mutated nucleotide sequences of TEM enzymes. Seven clinical isolates belonging to four species and harbouring TEM-1, TEM-3 or TEM-6 were studied. The results obtained indicate that detection of TEM-derived broad spectrum beta-lactamases in clinical isolates of Entero-bacteriaceae is possible with biotinylated oligonucleotide probes.     

Alkaloids of callus tissues and redifferentiated plantlets in the papaveraceae

The callus tissues from 11 representative species of the Papaveraceae and the redifferentiated plantlets from four species were successfully derived and maintained. The alkaloids in the callus tissues and redifferentiated plantlets were examined in comparison with those of the original plants. All the callus tissues are similar in their alkaloid chemistry and contain benzophenanthridine, protopine and aporphine type alkaloids. By contrast, the plantlets have a more specific alkaloid pattern, being similar in content to the original plants.     

Anomeric specificity of glucose effect on cAMP, fructose 1,6-bisphosphatase, and trehalase in yeast

The addition of beta-D-glucose (final concentration, 50 mM) to a cell suspension of Saccharomyces cerevisiae in stationary phase caused a rapid 4-fold increase in the concentration of cAMP, while a 2-fold increase of cAMP was observed by the addition of alpha-D-glucose. beta -D-Glucose was also more effective than alpha-D-glucose in the inactivation of fructose 1,6-bisphosphatase and the activation of trehalase. These results, taken together with the previous report that alpha-D-glucose is transported more rapidly than beta-D-glucose in Saccharomyces cerevisiae, do not support the view currently proposed by some investigators that cotransport of D-glucose with protons causes the depolarization of the cell membrane, resulting in the activation of adenylate cyclase. The present data, however, provides supporting evidence for the view that cAMP-dependent protein kinase is implicated in the inactivation of fructose 1,6-bisphosphatase and the activation of trehalase.     

Oxidative impairment in scrapie-infected mice is associated with brain metals perturbations and altered antioxidant activities

Prion diseases are characterized by the conversion of the normal cellular prion protein (PrP(C)) into a pathogenic isoform (PrP(Sc)). PrP(C) binds copper, has superoxide dismutase (SOD)-like activity in vitro, and its expression aids in the cellular response to oxidative stress. However, the interplay between PrPs (PrP(C), PrP(Sc) and possibly other abnormal species), copper, anti-oxidation activity and pathogenesis of prion diseases remain unclear. In this study, we reported dramatic depression of SOD-like activity by the affinity-purified PrPs from scrapie-infected brains, and together with significant reduction of Cu/Zn-SOD activity, correlates with significant perturbations in the divalent metals contents. We also detected elevated levels of nitric oxide and superoxide in the infected brains, which could be escalating the oxidative modification of cellular proteins, reducing gluathione peroxidase activity and increasing the levels of lipid peroxidation markers. Taken together, our results suggest that brain metal imbalances, especially copper, in scrapie infection is likely to affect the anti-oxidation functions of PrP and SODs, which, together with other cellular dysfunctions, predispose the brains to oxidative impairment and eventual degeneration. To our knowledge, this is the first study documenting a physiological connection between brain metals imbalances, the anti-oxidation function of PrP, and aberrations in the cellular responses to oxidative stress, in scrapie infection.     

Protein stability and plasticity of the hydrophobic cavity in wheat ns-LTP

Plant ns-LTPs display an original structure with four helices and a flexible C-terminus, maintained together by four disulphide bridges and delineating an elongated central hydrophobic cavity. In order to relate these structural features to the protein stability and plasticity, combined molecular mechanics and simulated annealing calculations were undertaken on a wheat ns-LTP "mutant" with Cys-Ala replacement and with the application of core inter-residue restraints up to 2 A, reducing the cross-section size of the hydrophobic cavity. Analysis of the energy-minimized structures shows that removal of the disulphide bridges results in structures with a lower total energy and a smaller cavity volume. A 1-ns MD simulation at 300K in water, underlines that, despite the absence of a well-packed hydrophobic core, the native structure is extremely stable at room temperature and the cavity is not hydrated. This confirms that the disulphide bridges are essential for the existence of the cavity, whereas its plasticity depends both on the hydrophobic chain lining the cavity and on the C-terminal flexibility. A high temperature (500K) MD simulation confirms the stability of the secondary structure elements and the flexibility of the loops and of the C-terminal segment. Two important structural transitions during this simulation are discussed and possible routes for the insertion and release of hydrophobic ligands are suggested.