Synthesis of Iodoaminoimidazole Arabinoside (IAIA): A Potential Reductive Metabolite of the Spect Imaging Agent,Iodoazomycin Arabinoside (IAZA)

Abstract

The stereospecific synthesis of 1-(5-deoxy-5-iodo-α-D-arabino-furanosyl)-2-aminoimidazole (iodoaminoimidazole arabinoside: IAIA, 2) is described. The reaction of the protected sugar bromide (8) and trifluoroacetamidoimidazole (10B) gave the coupled product (11B), which gave the free nucleoside (4) on deblocking. It was identical with AIA obtained by reduction of AZA (azomycin arabinoside), whose anomeric configuration was found to be a by the X-ray crystallography.     

Synthesis,In Vitro Biological Stability,and Anti-HIV Activity of 5-Halo (or Methoxy)-6-Alkoxy (Azido or Hydroxy)-5,6-Dihydro-2′,3′-Didehydro-3′-Deoxythymidine Diastereomers as Potential Prodrugs of 2′,3′-Didehydro-3′-deoxythymidine (D4T)

Abstract

A new class of 5-halo (or methoxy)-6-alkoxy (azido or hydroxy)-5,6-dihydro-2′,3′-didehydro-3′-deoxythymidines (4–17) were investigated as potential anti-AIDS drugs. These 5,6-dihydro derivatives, which are also potential prodmgs of 2′,3′-didehydro-3′-deoxythymidine (D4T) were designed to have properties which would enhance their duration of action, lipophilicity and cephalic delivery to the central nervous system. The 5,6-dihydro derivatives of D4T (4–15), which differ in configuration at the C-5 and C-6 positions, were synthesized by the regiospecific addition of XR (X = Br, Cl, I; R = OMe, OEt, N₃, OH) to the 5,6-olefinic bond of D4T. These 5,6-disubstituted-5,6-dihydro analogs of D4T are more lipophilic (P = 0.70 – 4.0 range) than D4T (P = 0.12) and are stable to E. coli thymidine phosphorylase. Regeneration of the 5,6-olefinic bond to give D4T, upon incubation of the 5-bromo- and 5-iodo-6-methoxy-5,6-dihydro derivatives (6, 7, 10, 11) with glutathione or a mouse liver soluble enzyme fraction, was extensive (50–95%). The most potent anti-HIV-1 agents, 5-iodo-6-methoxy (10, 11), 5-bromo-6-azido (14, 15) and 5-methoxy-6-hydroxy (16, 17) derivatives of D4T, exhibited anti-HIV activities comparable to D4T.

     

Specificity of Lipoxygenase Pathways Supports Species Delineation in the Marine Diatom Genus Pseudo-nitzschia

Oxylipins are low-molecular weight secondary metabolites derived from the incorporation of oxygen into the carbon chains of polyunsaturated fatty acids (PUFAs). Oxylipins are produced in many prokaryotic and eukaryotic lineages where they are involved in a broad spectrum of actions spanning from stress and defense responses, regulation of growth and development, signaling, and innate immunity. We explored the diversity in oxylipin patterns in the marine planktonic diatom Pseudo-nitzschia. This genus includes several species only distinguishable with the aid of molecular markers. Oxylipin profiles of cultured strains were obtained by reverse phase column on a liquid chromatograph equipped with UV photodiode detector and q-ToF mass spectrometer. Lipoxygenase compounds were mapped on phylogenies of the genus Pseudo-nitzschia inferred from the nuclear encoded hyper-variable region of the LSU rDNA and the plastid encoded rbcL. Results showed that the genus Pseudo-nitzschia exhibits a rich and varied lipoxygenase metabolism of eicosapentaenoic acid (EPA), with a high level of specificity for oxylipin markers that generally corroborated the genotypic delineation, even among genetically closely related cryptic species. These results suggest that oxylipin profiles constitute additional identification tools for Pseudo-nitzschia species providing a functional support to species delineation obtained with molecular markers and morphological traits. The exploration of the diversity, patterns and plasticity of oxylipin production across diatom species and genera will also provide insights on the ecological functions of these secondary metabolites and on the selective pressures driving their diversification.     

Oculomotor Deficits after Chemotherapy in Childhood

Advances in the diagnosis and treatment of pediatric malignancies have substantially increased the number of childhood cancer survivors. However, reports suggest that some of the chemotherapy agents used for treatment can cross the blood brain barrier which may lead to a host of neurological symptoms including oculomotor dysfunction. Whether chemotherapy at young age causes oculomotor dysfunction later in life is unknown. Oculomotor performance was assessed with traditional and novel methods in 23 adults (mean age 25.3 years, treatment age 10.2 years) treated with chemotherapy for a solid malignant tumor not affecting the central nervous system. Their results were compared to those from 25 healthy, age-matched controls (mean age 25.1 years). Correlation analysis was performed between the subjective symptoms reported by the chemotherapy treated subjects (CTS) and oculomotor performance. In CTS, the temporal control of the smooth pursuit velocity (velocity accuracy) was markedly poorer (p<0.001) and the saccades had disproportionally shorter amplitude than normal for the associated saccade peak velocity (main sequence) (p = 0.004), whereas smooth pursuit and saccade onset times were shorter (p = 0.004) in CTS compared with controls. The CTS treated before 12 years of age manifested more severe oculomotor deficits. CTS frequently reported subjective symptoms of visual disturbances (70%), unsteadiness, light-headedness and that things around them were spinning or moving (87%). Several subjective symptoms were significantly related to deficits in oculomotor performance. To conclude, chemotherapy in childhood or adolescence can result in severe oculomotor dysfunctions in adulthood. The revealed oculomotor dysfunctions were significantly related to the subjects’ self-perception of visual disturbances, dizziness, light-headedness and sensing unsteadiness. Assessments of oculomotor function may, thus, offer an objective method to track and rate the level of neurological complications following chemotherapy.     

Zic1 mRNA is transiently upregulated in subcutaneous fat of acutely cold-exposed mice

In the mammalian adipose organ cold exposure not only activates typical brown adipose tissue, but also induces browning, that is the formation of thermogenic multilocular adipocytes in white, or predominantly white, adipose depots such as subcutaneous fat. Unlike typical brown adipocytes, newly formed thermogenic adipocytes have been reported not to express the gene zinc finger of the cerebellum 1 (Zic1). Here, a time course approach enabled us to document a significant increase in Zic1 messenger RNA in inguinal subcutaneous fat from acutely (24 hr) cold-exposed mice, which was paralleled by an increase in multilocular and paucilocular uncoupling protein 1-positive adipocytes and in parenchymal noradrenergic innervation. This transient, depot-specific molecular signature was associated not to Zic1 promoter demethylation, but to chromatin remodeling through an H3K9me3 histone modification. These findings challenge the notion that Zic1 is exclusively expressed by typical brown adipocytes and suggest its involvement in brown adipocyte precursor differentiation and/or white-to-brown adipocyte transdifferentiation.     

Evolution of a recombinant (gucoamylase-producing) strain of Fusarium venenatum A3/5 in chemostat culture

Fusarium venenatum JeRS 325 is a transformant of strain A3/5 which produces Aspergillus niger glucoamylase (GAM) under the control of a Fusarium oxysporum trypsin-like protease promoter. The evolution of JeRS 325 was studied in glucose-limited chemostat cultures grown on NaNO3 or (NH4)2SO4 as the nitrogen source. Thirteen mutants which were more highly branched and four mutants which were more sparsely branched than the parental strain were isolated from the NaNO3 chemostat. The highly branched mutants detected in this chemostat did not displace the sparsely branched population. The mutants isolated from the NaNO3 chemostat complemented representative strains previously isolated from glucose-limited chemostat cultures of F. venenatum A3/5 grown on (NH4)2SO4, but showed little complementation between themselves. By contrast, a highly branched mutant isolated from the (NH4)2SO4 chemostat culture displaced the sparsely branched mycelial population. None of the mutants isolated from the NaNO3 or (NH4)2SO4 chemostats produced as much GAM as JeRS 325. Southern blot analysis showed that all except one mutant had lost copies of both the glucoamylase and the acetamidase (the selectable marker) genes. However, specific GAM production was not necessarily correlated with the extent of glaA gene loss observed. Further, 10 of the mutants had lost the ability to grow on acetamide as the sole nitrogen source, although they retained copies of the amdS gene. In competition studies, mutants which could not utilize acetamide displaced mutants which could. The presence of foreign DNA in JeRS 325 resulted in a reduced specific growth rate (compared to A3/5), but the presence of the foreign DNA did not prevent the evolution of the strain or the isolation of mutants which had improved growth rates.     

The effect of pH on glucoamylase production, glycosylation and chemostat evolution of Aspergillus niger

The effect of ambient pH on production and glycosylation of glucoamylase (GAM) and on the generation of a morphological mutant produced by Aspergillus niger strain B1 (a transformant containing an additional 20 copies of the homologous GAM glaA gene) was studied. We have shown that a change in the pH from 4 to 5.4 during continuous cultivation of the A. niger B1 strain instigates or accelerates the spontaneous generation of a morphological mutant (LB). This mutant strain produced approx. 50% less extracellular protein and GAM during both chemostat and batch cultivation compared to another strain with parental-type morphology (PS). The intracellular levels of GAM were also lower in the LB strain. In addition, cultivation of the original parent B1 strain in a batch-pulse bioreactor at pH 5.5 resulted in a 9-fold drop in GAM production and a 5-fold drop in extracellular protein compared to that obtained at pH 4. Glycosylation analysis of the glucoamylases purified from shake-flask cultivation showed that both principal forms of GAM secreted by the LB strain possessed enhanced galactosylation (2-fold), compared to those of the PS. Four diagnostic methods (immunostaining, mild methanolysis, mild acid hydrolysis and beta-galactofuranosidase digestion) provided evidence that the majority of this galactose was of the furanoic conformation. The GAMs produced during batch-pulse cultivation at pH 5.5 similarly showed an approx. 2-fold increase in galactofuranosylation compared to pH 4. Interestingly, in both cases the increased galactofuranosylation appears primarily restricted to the O-linked glycan component. Ambient pH therefore regulates both GAM production and influences its glycosylation.