Modified Nucleosides. II.1 Economical Synthesis of 2′,3′-Dideoxycytidine

Abstract

An economical two pot synthesis of 2′,3′-dideoxycytidine (2) from N⁴-acetyl-cytidine (4) has been developed. The key feature of this sequence is the in situ reductive elimination of a mixture of 1-(3-bromo-3-deoxy-2,5-di-O-acetyl-β-D-xylofuranosyl)-N⁴-acetylcytosine (5) and 1-(2-bromo-3-deoxy-3,5-di-O-acetyl-β-D-arabinofuranosyl)-N⁴-acetylcytosine (6) and subsequent hydrogenation of the resultant olefin over palladised charcoal.     

γ-Aminobutyric Acid Receptor Ionophore Complexes: Differential Effects of Deltamethrin, Dichlorodiphenyltrichloroethane, and Some Novel Insecticides in a Rat Brain Membrane Preparation

The binding of [35S]t-butylbicyclophosphorothionate ([35S]TBPS), a gamma-aminobutyric acid (GABA)-activated chloride ionophore ligand; [3H]diazepam, a benzodiazepine agonist; and [3H]muscimol, a GABA receptor probe, were used to assess the effects at 100 microM of deltamethrin, dichlorodiphenyltrichloroethane (DDT), and three experimental insecticides--a DDT-pyrethroid hybrid, GH414 (cycloprothrin), and two DDT-analogues, GH266 and GH149 (EDO), on GABA receptor ionophore complexes in a rat brain membrane preparation. GH266 and GH149 were found to inhibit a greater percentage of [35S]TBPS binding than the same concentration of deltamethrin or DDT, although GH414 had little effect. GH266 and GH149 enhanced [3H]diazepam binding by nearly 200%, in contrast to the inhibitory effects of deltamethrin, DDT, and GH414. GH266 and GH149 also caused a dramatic enhancement of [3H]muscimol binding, 367 and 236% of control, respectively, whereas DDT and deltamethrin caused only a moderate enhancement. The effects of the insecticides on binding affinity and density were examined for each of the ligands. The results show a differential interaction of the insecticides on the various ligand binding sites.     

A Bayesian functional data model for surveys collected under informative sampling with application to mortality estimation using NHANES

Functional data are often extremely high-dimensional and exhibit strong dependence structures but can often prove valuable for both prediction and inference. The literature on functional data analysis is well developed; however, there has been very little work involving functional data in complex survey settings. Motivated by physical activity monitor data from the National Health and Nutrition Examination Survey (NHANES), we develop a Bayesian model for functional covariates that can properly account for the survey design. Our approach is intended for non-Gaussian data and can be applied in multivariate settings. In addition, we make use of a variety of Bayesian modeling techniques to ensure that the model is fit in a computationally efficient manner. We illustrate the value of our approach through two simulation studies as well as an example of mortality estimation using NHANES data.     

The glucan-chitin complex in Saccharomyces cerevisiae

Scar rings (SR) from scarless cells at the early stages of budding and mature bud scars from Saccharomyces cerevisiae isolated by both chemical and enzymic treatment of cell walls were observed by selected-area electron diffraction (SAED), X-ray diffraction and electron microscopy with simultaneous physico-chemical characterization (including molar mass, intrinsic viscosity and crystallite size) of -chitin and glucan. The SR, composed of glucan with strong 0.608; 0.397 and 0.293 nm X-ray reflections, was formed at the start of budding. The SAED patterns of -chitin both in the adjacent circular zone and in the parts of newly formed primary septum (PS), observed when the development of the PS started, did not differ from those of -chitin in the single mature bud scar. The bud scar consisted of -chitin, glucan and mannan and their content, as well as the crystallite size of chitin, depended on the mode of preparation.Non-Standard Abbreviations ACZ Adjacent circular zone - BS Birth scar - CFW Calcofluor white M2R new: Disodium salt of 4,4-bis-(4-anilino-bis-diethyl-amino-S-triazine-2-yl-amino)-2,2-stilbene-disulfonic acid - EDI Electron dense istmus - PS Primary septum - SAED Selected area electron diffraction - SEM Scanning electron microscopy - SR Scar ring - TEM Transmission electron microscopy - XRD X-ray diffraction     

Tumor necrosis factor and its induction by bacterial endotoxins

Using suitable immunomodulators (Corynebacterium parvum vaccine, Zymosan or muramyl dipeptide), lipopolysaccharides (LPS) from various members of the family Enterobacteriaceae (Escherichia, Salmonella, Serratia, Shigella) were tested on rabbits in relation to the production of tumor necrosis factor (TNF). TNF was determined by means of the serum titration of L-929 cell cultures in the presence of Actinomycin D, this with resulting titres of 3.2 x 10(3) to 5.1 x 10(4) IU TNF/ml. Analogous titres were noted after the action of denatured LPS (ie LPS subjected to alkaline hydrolysis or H2O2).     

Cytokine interplay among the diseased retina,inflammatory cells and mesenchymal stem cells - a clue to stem cell-based therapy

Retinal degenerative disorders, such as diabetic retinopathy, retinitis pigmentosa, age-related macular degeneration or glaucoma, represent the most common causes of loss of vision and blindness. In spite of intensive research, treatment options to prevent, stop or cure these diseases are limited. Newer therapeutic approaches are offered by stem cell-based therapy. To date, various types of stem cells have been evaluated in a range of models. Among them, mesenchymal stem/stromal cells (MSCs) derived from bone marrow or adipose tissue and used as autologous cells have been proposed to have the potential to attenuate the negative manifestations of retinal diseases. MSCs delivered to the vicinity of the diseased retina can exert local anti-inflammatory and repair-promoting/regenerative effects on retinal cells. However, MSCs also produce numerous factors that could have negative impacts on retinal regeneration. The secretory activity of MSCs is strongly influenced by the cytokine environment. Therefore, the interactions among the molecules produced by the diseased retina, cytokines secreted by inflammatory cells and factors produced by MSCs will decide the development and propagation of retinal diseases. Here we discuss the interactions among cytokines and other factors in the environment of the diseased retina treated by MSCs, and we present results supporting immunoregulatory and trophic roles of molecules secreted in the vicinity of the retina during MSC-based therapy.     

Cadmium biosorption by Saccharomyces cerevisiae

Cadmium uptake by nonliving and resting cells of Saccharomyces cerevisiae obtained from aerobic or anaerobic cultures from pure cadmium-bearing solutions was examined. The highest cadmium uptake exceeding 70 mg Cd/g was observed with aerobic baker's yeast biomass from the exponential growth phase. Nearly linear sorption isotherms featured by higher sorbing resting cells together with metal deposits localized exclusively in vacuoles indicate the possibility of a different metal-sequestering mechanism when compared to dry nonliving yeasts which did not usually accumulate more than 20 mg Cd/g. The uptake of cadmium was relatively fast, 75% of the sorption completed in less than 5 min. (c) 1993 Wiley & Sons, Inc.     

Repellency of insecticides to resistant strains of housefly

The contact repellency of 6 insecticides on one susceptible and 6 resistant strains of the housefly Musca domestica L. were compared. No effect of synergist on repellency was observed and the temperature effect was minor. Both Kdr and Pen resistance factors were significant in repellency resistance to the tested compounds.

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Zusammenfassung Die Berührungs-Abstossung von DDT, Pyrethrum, Bioresmethrin, Permethrin, 1,1-bis-(4-äthoxyphenyl)-2-nitropropan und 3-phenoxybenzyl 1-(4-äthoxyphenyl)-2,2-dichlorocyclopropancarboxylat gegenüber einem empfindlichen Stamm sowie sechs resistenten Stämmen der Stubenfliege Musca domestica L. wurde verglichen. Zu den resistenten Stämmen gehörten solche, die DDT-Dehydrochlorinase, Ses, Kdr sowie Resistenzfaktorkombinationen besassen. Die Wirkung der Synergisten Sesamex und Warf-Antiresistent auf die Berührungs-Abstossung und der Einfluss der Temperatur wurden untersucht.

     

Biosorption of lead and nickel by biomass of marine algae

Screening tests of different marine algae biomas types revealed a high passive biosorptive uptake of lead up to 270 mg Pb/g of biomass in some brown marine algae. Members of the order Fucales perfomed particularly well in this descending sequence: Fucus > Ascophyllum > Sargassum. Although decreasing the swelling of wetted biomass particles, their reinforcement by crosslinking may significantly affect the biosorption performance. Lead uptakes up to 370 mg Pb/g were observed in crosslinked Fucus vesiculosus and Ascophyllum nodosum. At low equilibrium residual concentrations of lead in solution, however, ion exchange resin Amberlite IR-120 had a higher lead uptake than the biosorbent materials. An order-of-magnitude lower uptake of nickel was observed in all of the sorbent materials examined. (c) 1994 John Wiley & Sons, Inc.