Consumer-driven nutrient release to the water by a small omnivorous fish enhanced ramet production but reduced the growth rate of the submerged macrophyte Vallisneria denseserrulata (Makino) Makino

Small fish are highly associated with submerged macrophytes but may potentially hamper their growth due to nutrient excretion that stimulate growth of phytoplankton and periphyton growth. We conducted a mesocosm experiment to elucidate the effects of the small omnivore Chinese bitterling Acheilognathus macropterus on the growth of phytoplankton, periphyton and the submerged macrophyte Vallisneria denseserrulata. The treatments were fishless as well as low (LF) and high (HF) fish density. We found that the concentrations of nutrients and the phytoplankton biomass increased substantially in both fish treatments, leading to a significantly higher light attenuation compared with the control. Moreover, bitterling substantially enhanced the biomass of periphyton on plant leaves. Consequently, the relative growth rate (RGR) of V. denseserrulata was significantly suppressed in HF, while RGR in the LF treatment did not differ significantly from the controls. However, the bitterling also stimulated the ramet production of V. denseserrulata, significantly. Our results indicate that Chinese bitterling reduce the RGR of V. denseserrulata under high fish density condition. Therefore, the density of Chinese bitterling should be kept low in order to reduce the negative effects of the fish on the RGR of submerged macrophytes (e.g. V. denseserrulata), when restoring lakes by plant transplantation.

     

Syntheses et Activites Biologiques de Nouvelles (E)-Alcenyl-5 Desoxy-2′ Uridines

Abstract

(E) 5-Alkenyl 2′-deoxyuridines were synthesized with moderate to high yields by the palladium catalyzed coupling of alkenyl-zirconium reagents with 0–3′, 5′-his (trimethylsilyl) deoxyuridine in T H F. Some of these 5-alkenyl-dUrd analogues, i.e. the 1-decenyl (5g) and 2- (1-hydroxycyclopentyl) ethenyl (5f) derivatives, inhibited murine L1210 cell growth at a concentration of about 4 μg/ml, whereas the 5-chloro-1-pentenyl (5c), 5-cyano-1-pentenyl (5d), 5-hexyn-1-enyl (5e) and 2-(1-hydroxycyclopentyl) ethenyl (5f) were inhibitory towards herpes simplex and vaccinia virus within the concentration range of 2–60 μg/ml. However, none of the newly synthesized 5-alkenyl-dUrd analogues proved selective in its antiviral action.     

Anti-Hiv-1 Activity of 2′,3′-Dideoxinucleoside Analogues : Structure-Activity Relationship

Abstract

Among the purine and pyrimidine 2′,3′-dideoxynucleosides, 2′,3′-didehydro-2′,3′-dideoxynucleosides, 3′-azido-2′,3′-dideoxynucleosides and 3′-fluoro-2′,3′-dideoxynucleosides, several congeners have been identified which achieve a potent and selective inhibition of HIV-1 replication in vitro.     

Synthesis and DNA Binding Properties of a New Benzo[f]Imidazo[1,5b]-Isoquinoline-Butan-1,2-Diol Derivative

A benzo[f]imidazo[1,5b]-isoquinoline derivative 4 with a 1,2-butandiol linker was prepared by reaction of a trimethylsilylated 5-naphthylidenehydantoin 3 with a 2,3-dideoxy-D-glycero-pentafuranoside 2 in 22% yield. After deprotection, the resulting compound 5 was converted to a DMT protected phosphoramidite building block 7 for standard DNA synthesis. DNA/DNA, DNA/RNA duplexes with 5 inserted as bulges were destabilized, except when the new amidite was used for the synthesis of a zipping duplex.     

Synthesis and Evaluation of Acyclic Nucleotide Analogs

Abstract

Acyclic nucleotide analogs derived from antiviral 9-(2-phosphonylmethoxyethyl)adenine by modification at the side chain or by alternation of the heterocyclic base were synthesized and investigated for their antiviral activity.