Synthesis and antitumor activity of camptothecin derivatives bearing five-membered heterocycle containing 10-substituents

A series of new camptothecin derivatives bearing five-membered ring heterocycle containing substituents in the 10-position were synthesized and evaluated for in vitro cytotoxic activity. Camptothecin derivatives bearing a pyrrole or a thiophene ring were significantly more potent than camptothecin, however those bearing furan were less potent than camptothecin.     

Development of a pollen-mediated transformation method forNicotiana glutinosa

The development is described of a new procedure to genetically transform plant species using the male gametophyte as a natural transformation vector. Our system avoids the need for complicated regeneration procedures thus making it broadly applicable. Naked plasmid DNA encoding kanamycin resistance and GUS activity was introduced by particle gun bombardment into mature pollen grains ofNicotiana glutinosa. Bombarded pollen was used for pollinations and the resulting seeds were selected for kanamycin resistance. Two different kanamycin-resistant plants, designated VIP A and VIP B, were obtained in two independent experiments. In VIP A, TR2-driven GUS activity was observed in vascular bundles, trichomes and in a small number of pollen grains. DNA gel blot analysis indicated that the introduced DNA was integrated independently into the genome of VIP A and VIP B. It was shown that male and female gametophyte development and seed set were highly aberrant in both VIP A and VIP B and that the offspring of self- and cross-pollinations did not contain the transgenes. This might be caused by a recombination event during the integration of the naked DNA resulting in a deletion of part of the target chromosome. After meiosis such a deletion is lethal for the gametes. Our observation that the transgenes were detected in DNA isolated from sporophytic tissues but not in DNA from VIP A and VIP B pollen grains is in line with this explanation. Future experiments designed to increase the frequency of transformation and to transfer the transgenes to the offspring are discussed.     

Comparative aspects of hydroxamic acid production by thiamine-dependent enzymes

The reactions of 4-chloronitrosobenzene with pyruvate decarboxylase and transketolase were investigated by use of a new high-pressure liquid chromatography method to determine any differences between these two enzymes with respect to hydroxamic acid production. In addition to the previously established difference in the type of hydroxamic acid produced by the two enzymes, several new and interesting differences in their reaction with nitrosoaromatics were discovered. Most notable was the finding that pyruvate decarboxylase gave 4-chlorophenylhydroxylamine as the major product from 4-chloronitrosobenzene, while transketolase did not produce any detectable hydroxylamine. A redox mechanism was proposed to account for arylhydroxylamine production by pyruvate decarboxylase. This redox mechanism can also explain hydroxamic acid production by pyruvate decarboxylase; however, a previously proposed nucleophilic reaction mechanism occurring simultaneously could not be totally disproven. Either of the two mechanisms is equally likely for transktolase action in view of the present evidence. Another major difference between these enzymes is that the rate of 4-chloronitrosobenzene conversion was found to be much faster for pyruvate decarboxylase than for transketolase when each enzyme was subjected to its own optimal reaction conditions. Transketolase displayed typical enzyme saturation kinetics with 4-chloronitrosobenzene with a K_m of 0.31 mM and V_max of 0.033 μmol ml^?1 min^?1 unit^?1 relative to 5 mMd-fructose 6-phosphate as sugar substrate. On the other hand, the reaction with pyruvate decarboxylase was first order in 4-chloronitrosobenzene with a combined rate constant of 2.0 min^?1 unit^?1 ml.     

Simultaneous concentration of Salmonella and enterovirus from surface water by using micro-fiber glass filters.

A method using micro-fiber glass filters (8-micrometers porosity) at pH 3.5 was successfully used for simultaneous concentration of Salmonella and enterovirus from Meurthe River samples, collected 8 km south of Nancy, France. A concentration of 10-liter samples was indispensable and permitted recovery of several enterovirus and Salmonella serotypes in concentrations of 1.3 most probable number of cytopathogenic units per liter and 18 bacteria per liter, respectively.     

Synthesis and characterization by 1H and 13C nuclear magnetic resonance spectroscopy of 17 alpha-hexanoic derivatives of 5 alpha-dihydrotestosterone and testosterone.

The synthesis and characterization of 17 alpha-(6'-hexanoic acid) derivatives of 5 alpha-dihydrotestosterone and testosterone, useful as ligands for affinity chromatography purification or as precursors for affinity-labeling of androgen-binding proteins, is described. Alkynylation of 3-ethylenedioxy-, 3 beta-hydroxy-, and 3 beta,5-dihydroxy-5 alpha-androstan-17-one precursors with the potassium derivative of 5-hexyn-1-ol led to the corresponding 17 alpha-(6'-hydroxyhex-1'-ynyl) derivatives, which were hydrogenated over 10% Pt-C catalyst to give 17 alpha-(6'-hydroxyhexyl) derivatives. Chromic acid oxidation of the primary hydroxy group of the 3-ethylenedioxy-17-hexyl intermediate into carboxylic acid followed by acid cleavage of the 3-ketal group gave 17 alpha-(5'-carboxypentyl)-5 alpha-dihydrotestosterone, which was also obtained directly by chromic acid oxidation of the 3 beta-hydroxy intermediate. Chromic acid oxidation of the primary hydroxy group of the 3 beta,5 alpha-dihydroxy precursor resulted in a 5 alpha-hydroxy-3-oxo intermediate, which was dehydrated to give 17 alpha-(5'-carboxypentyl)testosterone. The 17 alpha configuration of these derivatives and of synthetic precursors was established by comparing their molecular rotations and their 1H and 13C nuclear magnetic resonance (NMR) spectra including solvent effects, with data reported for 17 alpha- or 17 beta-substituted steroid analogs as well as with 1H and 13C NMR reference data recorded in this work for 17 alpha-ethynyltestosterone, 17 alpha-ethynyl-19-nortestosterone, 17 alpha-ethyl-19-nortestosterone, 17 alpha-methyltestosterone, and 17 alpha-methyl-5 alpha-dihydrotestosterone.     

Biomass and photosynthesis of size-fractionated phytoplankton in Canadian Shield lakes

Both in situ primary production and biomass (chlorophyll ) of fractionated phytoplankton (<64,µ, <25 µm and < 10 µm) were studied in 10 Canadian Shield lakes to elucidate the spatial and temporal variability of the contribution of size fractions to the biomass and primary production of the phytoplankton community. Mean summer biomass and production of each size fraction varied significantly between lakes. Within lakes, temporal variation was low for biomass but great for production. However, temporal variation can be considered of minor importance during the sampling period, as compared to the spatial variation between lakes. Algae from the < 10 µm size fraction were the most important in biomass (41–65 %) and production (23–69%). The temporal trends for both phytoplankton variables thus generally followed closely that of the < 10 µm size fraction. Among the physical, chemical and morphometric variables of the studied lakes, water transparency (Secchi disk), total phosphorus, lake volume, lake area, and mean depth gave the best correlations with phytoplankton variables.Contribution number 354 from the Groupe de recherches en Ecologie des Eaux douces, Limnological Research Group, Université de Montréal.     

Molecular cloning and characterization of double-stranded cDNA coding for bovine chymosin

A full-length cDNA copy of the mRNA encoding calf chymosin (also known as rennin), a proteolytic enzyme with commercial importance in the manufacture of cheese, has been cloned in an f1 bacteriophage vector. The nucleotide sequence of the cDNA was determined, and translation of that sequence into amino acids predicts that the zymogen prochymosin is actually synthesized in vivo as preprochymosin with a 16 amino acid signal peptide. In vitro translation of total poly(A)-enriched RNA from the calf fourth stomach (abomasum) and immunoprecipitation with antichymosin antiserum revealed that a form of chymosin (probably preprochymosin judging from the M_r-value) is the major in vitro translation product of RNA from that tissue. Gel-transfer hybridization of restriction endonuclease-cleaved bovine chromosomal DNA with labeled cDNA probes indicated that the two known forms of chymosin, A and B, must be products of two different alleles of a single chymosin gene.