Chemo-enzymatic synthesis of 3-deoxy-beta-D-ribofuranosyl purines and study of their biological properties

9-(3-Deoxy-beta-D-erythro-pentofuranosyl)-2,6-diaminopurine (2) was synthesized by an enzymatic transglycosylation of 2,6-diaminopurine using 3'-deoxycytidine (1) as a donor of the sugar moiety. Nucleoside 2 was transformed to 3'-deoxy guanosine (3), 9-(3-deoxy-beta-D-erythro-pentofuranosyl)-2-amino-6-oxopurine (3'-deoxyisoguanosine; 4), and 9-(3-deoxy-beta-D-erythro-pentofuranosyl)-2-fluoroadenine (5). Compounds 2-5 were evaluated for their anti-HIV activity.     

Electrical capacitance of lipid bilayer membranes of hydrogenated egg lecithin at the temperature phase transition

Electrical capacitance of the planar bilayer lipid membrane (BLM) formed from hydrogenated egg lecithin (HEL) has been studied during many passages through the phase transition temperature. In contrast to the BLM from individual synthetic phospholipids, membranes from HEL did not demonstrate any capacitance change at the phase transition temperature maximum, as measured by differential scanning calorimeter at 52 degrees C. Instead, two temperatures have been discerned by capacitance records: thickening at 42-43 degrees C and thinning at 57-59 degrees C. The first temperature region is close to the transition temperature of dipalmitoyllecithin, whereas the second is close to that of distearoyllecithin, two main components of the HEL. It was suggested that capacitance measurements were able to reveal a phase separation in the BLM from HEL which was not detected by differential scanning calorimetry. The phase transition of the BLM from the liquid crystal state to the gel state is followed by thickening of the bilayer structure, partly due to a gauche- trans transition of lipid molecules but mainly due to redistribution of the solvent n-decane.     

Glycolate oxidase isoforms are distributed between the bundle sheath and mesophyll tissues of maize leaves

Glycolate oxidase (EC 1.1.3.15) activity was detected both in the bundle sheath (79%) and mesophyll (21%) tissues of maize leaves. Three peaks of glycolate oxidase activity were separated from maize leaves by the linear KCl gradient elution from the DEAE-Toyopearl column. The first peak corresponded to the glycolate oxidase isoenzyme located in the bundle sheath cells, the second peak had a dual location and the third peak was related to the mesophyll fraction. The mesophyll isoenzyme showed higher affinity for glycolate (Km 23 micromol x L(-1)) and a higher pH optimum (7.5-7.6) as compared to the bundle sheath isoenzyme (Km 65 micromol x L(-1), pH optimum 7.3). The bundle sheath isoenzyme was strongly activated by isocitrate and by succinate while the mesophyll isoenzyme was activated by isocitrate only slightly and was inhibited by succinate. It is concluded that although the glycolate oxidase activity is mainly attributed to the bundle sheath, conversion of glycolate to glyoxylate occurs also in the mesophyll tissue of C4 plant leaves.     

Morphological and biochemical modifications induced by a static magnetic field on Fusarium culmorum

The effects of the exposure to a static magnetic field (sMF) of 0.3 +/- 0.03 T on the Fusarium culmorum were investigated in vitro. sMF inhibition of mycelia growth was accompanied by morphological and biochemical changes. Fungal conidia germination and cell viability were also reduced. We provide evidence of the influence of sMF on Ca(2+)-dependent signal transduction pathways involved in conidia germination. Perturbation of these pathways by adding different compounds (i.e. CaCl(2), phorbol 12-myristate 13-acetate, neomycin, EGTA, LiCl) to the medium, suggested that exposed conidia are unable to mobilise calcium from intracellular stores and that the hindered mechanism may be IP(3)-dependent.     

Characterisation of SMN hybrid genes in Spanish SMA patients: de novo, homozygous and compound heterozygous cases

Autosomal recessive spinal muscular atrophy (SMA) is classified, by age of onset and maximal motor milestones achieved, into type I (severe form), type II (intermediate form) and type III (mild/moderate form). SMA is caused by mutations in the survival motor neuron telomeric gene (SMN1) and a centromeric functional copy of this gene (SMN2) exists, both genes being located at 5q13. Homozygous deletion of exons 7 and 8 of SMN1 has been detected in approx 85% of Spanish SMA patients regardless of their phenotype. Nineteen cases with the sole deletion of exon 7 but not exon 8 (2 cases of type I, 13 cases of type II, four cases of type III) were further analysed for the presence of SMN2-SMN1 hybrid genes. We detected four different hybrid structures. Most of the patients were carriers of a hybrid structure: centromeric intron 6- centromeric exon 7- telomeric exon 8 (CCT), with or without neuronal apoptosis-inhibitor protein (NAIP). In two patients, a different hybrid structure, viz. telomeric intron 6- centromeric exon 7- telomeric exon 8 (TCT), was detected with or without NAIP. A phenotype-genotype correlation comparing the different structures of the hybrid alleles was delineated. Type I cases in our series are attributable to intrachromosomal deletion with a smaller number of SMN2 copies. Most cases with hybrid genes are type II occurring by a combination of a classical deletion in one chromosome and a hybrid gene in the other. Type III cases are closely associated with homozygozity or compound heterozygozity for hybrid genes resulting from two conversion events and have more copies of hybrid genes and SMN2 than type I or II cases.     

Notentera ivanovi Joffe et al., 1997: a contribution to the question of phylogenetic relationships between ‘turbellarians’ and the parasitic Plathelminthes (Neodermata)

Notentera ivanovi is a parasitic platyhelminth found in the gut of a polychaete, Nephthys ciliata. N. ivanovi has no mouth, pharynx, or intestine; the dorsal epidermis of adult animals forms a thick pad which is very similar to gut epithelia even at the light microscopic level. Structure of ciliary rootlets and dermal glands with peculiar striated secretion bodies point to close relationships with the Fecampiidae, though other important characters imply placing the genus Notentera in a separate family. In mature sperm of N. ivanovi, the axonemes are fully incorporated; they are directed from proximal to distal, as in the Neodermata. We argue that new family, Notenteridae, should be included in the taxon Fecampiida. We also suggest that all Plathelminthes with neodermatan type of spermiogenesis (Fecampiidae, Urastomidae, and Neodermata) form a monophyletic branch within the Plathelminthes Neoophora. This revised version was published online in July 2006 with corrections to the Cover Date.