Synthetic approaches to 6-substituted 9-(3-azido-3,4-dideoxy-β-d,l-erythro-pentopyranosyl)purines

Methyl 3-azido-2-O-benzoyl-3,4-dideoxy-β-dl-erythro-pentopyranoside (6) was synthesized through two routes in five steps from methyl 2,3-anhydro-4-deoxy-β-dl-erythro-pentopyranoside (1). The first route proceeded via selective azide displacement of the 3-tosyloxy group of methyl 4-deoxy-2,3-di-O-tosyl-α-dl-threo-pentopyranoside, followed by detosylation and benzoylation. The second route consisted, with a better overall yield, in the azide displacement of the mesyloxy group of methyl O-benzoyl-4-deoxy-3-O-methylsulfonyl-α-dl-threo-pentopyranoside (10), obtained by benzylate opening of 1, followed by benzoylation, debenzylation, and mesylation. Compound 6 was transformed into its glycosyl chloride, further treated by 6-chloropurine to give the nucleoside 9-(3-azido-2-O-benzoyl-3,4-dideoxy-β-dl-erythro-pentopyranosyl)-6-chloropurine (13). When treated with propanolic ammonia, 13 yielded 9-(3-azido-3,4-dideoxy-β-dl-erythro-pentopyranosyl)adenine.     

FLAVONOID EVOLUTION IN DENDROSERIS (COMPOSITAE,LACTUCEAE) FROM THE JUAN FERNANDEZ ISLANDS,CHILE

Leaf flavonoid chemistry was examined from the three subgenera and 11 species of the endemic genus Dendroseris (Compositae, Lactuceae) of the Juan Fernandez Islands, Chile. Eight of the species are restricted to the older island (Masatierra, ca. 4 million years old), which is also closer to the mainland. Three species, one from each subgenus, are restricted to Masafuera, which is younger geologically (1–2 million years old) and 145 km further west of Masatierra. A total of 16 compounds was identified, with the 7-0-glucosides of the flavones apigenin and luteolin accounting for 12 of the constituents. Two glucosides of the flavonol quercetin were detected. Despite considerable interpopulation variation within species, six of the taxa have distinctive flavonoid profiles. Although there are few absolute differences among the subgenera, they can be distinguished chemically. Subgenus Rea contains the greatest number of compounds, and a previous cladistic analysis based on morphological features suggested this subgenus as most primitive. Subgenus Phoenicoseris is considered highly derived morphologically, and it has a reduced flavonoid chemistry. Very little reduction in flavonoid diversity was seen in the morphologically specialized subg. Dendroseris as compared to subg. Rea. A trend in reduction of numbers of compounds was seen for two of the three species on the younger island of Masafuera when compared to their presumed ancestors on Masatierra. Flavonoids of selected species of Hieracium and Hypochaeris, presumptive mainland progenitors of Dendroseris, reveal a close chemical affinity with the former genus.     

Presence of haemocyte-like cells in coccinellid reflex blood

Abstract.  Contrary to current assumptions, the reflex blood of two-spot ladybirds, Adalia bipunctata , and seven-spot ladybirds, Coccinella septempunctata , contains haemocyte-like cells. Furthermore, DNA can be extracted and amplified from coccinellid reflex blood, confirming the presence of haemocyte-like cells and demonstrating a nondestructive method of DNA extraction.     

Inhibition of growth of Leishmania mexicana mexicana by Leishmania mexicana amazonensis during "in vitro" co-cultivation

Inhibition of one Leishmania subspecies by exometabolites of another subspecies, a phenomenon not previously reported, is suggested by our recent observations in cell cloning experiments with Leishmania mexicana mexicana and Leishmania mexicana amazonensis. Clones were identified using the technique of schizodeme analysis. The phenomenon observed is clearly relevant to studies of parasite isolation, leishmanial metabolism, cross-immunity and chemotherapy.     

Evidence for carrier-mediated,energy-dependent uptake of urea in some bacteria

Evidence for the existence of an energy-dependent urea permease was found for Alcaligenes eutrophus H16 and Klebsiella pneumoniae M5a1 by studying uptake of ¹⁴C-urea. Since intracellular urea was metabolized immediately, uptake did not result in formation of an urea pool. Evidence is based on observations that the in vivo urea uptake and in vitro urease activity differ significantly with respect to kinetic parameters, temperature optimum, pH optimum, response towards inhibitors and regulation. The K _m for urea uptake was 15–20 times lower (38 M and 13 M urea for A. eutrophus and K. pneumoniae, respectively) than the K _m of urease for urea (650 M and 280 M urea), the activity optimum for A. eutrophus was at pH 6.0 and 35°C for the uptake and pH 9.0 and 65°C for urease. Uptake but not urease activity in both organisms strongly decreased upon addition of inhibitors of energy metabolism, while in K. pneumoniae, potent inhibitors of urease (thiourea and hydroxyurea) did not affect the uptake process. Significant differences in the uptake rates were observed during growth with different nitrogen sources (ammonia, nitrate, urea) or in the absence of a nitrogen source; this suggested that a carrier is involved which is subject to nitrogen control. Some evidence for the presence of an energy-dependent uptake of urea was also obtained in Pseudomonas aeruginosa DSM 50071 and Providencia rettgeri DSM 1131, but not in Proteus vulgaris DSM 30118 and Bacillus pasteurii DSM 33.Non-standard abbreviations CCCP Carbonylcyanide-m-chlorphenylhydrazone - DCCD dicyclohexylcarbodiimide - DNP 2,4-dinitrophenole     

Polyamines in liver and their influence on chromatin condensation after 17-β estradiol treatment of Atlantic salmon

Atlantic salmon (Salmo salar) were treated with 17- estradiol to induce vitellogenin synthesis in liver. This led to an increase in liver wet weight and total DNA. After incubation with micrococcal nuclease (EC 3.1.31.1) less soluble chromatin was obtained from nuclei of the estradiol treated than the control fish, but active gene regions were solubilized by the nuclease. Thus, in the estradiol treated fish soluble mononucleosomes contained hybridizable vitellogenin gene sequences. As a result of estradiol treatment the content in total liver of putrescine rose 3-fold, that of spermidine 2-fold, while spermine was unchanged. In muscle no significant changes were observed. The regulatory functions of polyamines during gene expression were investigated by binding (¹⁴C)spermine to isolated liver nuclei depleted of endogenous polyamines. The number of binding sites was higher in nuclei of estradiol treated than control fish. (^14C)spermine associated preferentially with micrococcal nuclease insensitive chromatin. Thus, the high content of putrescine and spermidine in liver supported the view of polyamine accumulation in proliferating tissues. The preferential binding to condensed chromatin indicated a stabilizing effect of polyamines on the organization of inactive chromatin structures.Abbreviations MNase micrococcal nuclease - PMSF phenylmethylsulfonylfluoride     

Genetic and molecular analysis of spontaneous respiratory deficient (res-) mutants of Escherichia coli K-12

Respiratory deficient (res-) mutants of E. coli are slow growing microcolonial, anaerobic, catalase and benzidine negative strains whose broad phenotypic alteration may result from pleiotropic mutations in genes of the hemin biosynthetic pathway. They are easily recovered from platings of sensitive cells on concentrations of gentamicin higher than the minimal inhibitory concentration. These mutants show a dramatic change in their biochemical diagnostic profile resulting primarily from deficiencies in the active transport mechanisms of the cell. Using well-marked F- and Hfr strains, 157 mutants were analyzed from 3 different parent strains; all but 2 resulted from mutations in 3 loci of the hemin biosynthetic pathway. Of these a marked skew to hemB- mutations was seen, with more than 80% mapping there. The possibility that this hot spot resulted from transpositional activity was tested by Southern hybridization of EcoRI digests of the chromosomal DNA, using as a probe, a 2.8-kb fragment containing the hemB gene. The WT and other hemB+ control strains contained a 14.6-kb fragment. Of 18 hemB strains tested, 14 showed deletion and insertion mutations which fell into four classes based on the variation in the size of the fragment or on the absence of hybridization. The latter resulted from complete deletion of the hemB gene. An increase in fragment size from 1.5-kb to 3.4-kb was observed in some of the strains.