Parasitism ofLygus lineolaris eggs onCoronilla varia,solanum tuberosum,and three host weeds in southeastern Québec

Parasitism ofLygus lineolaris (Palisot de Beauvois) eggs by three species ofMymaridae, Anaphes iole Girault,Erythmelus miridiphagus Dozier andPolynema pratensiphagum Walley and one species ofScelionidae, Telenomus sp., was investigated at Ste-Anne-de-Bellevue, Québec. The maximum level of field parasitism ofL. lineolaris eggs by individual species was 15.4, 53.8, 70.0 and 16,7%, respectively. Parasitoids were retrieved from eggs ofL. lineolaris inserted in stems and branches ofAmaranthus retroflexus L.,Chenopodium album L.,Coronilla varia L.,Rumex obtusifolius L. andSolanum tuberosum L. Amaranthus retroflexus andS. tuberosum sustained a large population ofL. lineolaris and egg parasitism was high enough to consider it as a potential control factor.      

Genetic analysis of a region of the Rhizobium meliloti pSym plasmid specifying catabolism of trigonelline, a secondary metabolite present in legumes.

Genes controlling the catabolism of trigonelline, a secondary metabolite that is often present in legumes, are located on the pSym megaplasmid of Rhizobium meliloti. To investigate the role of bacterial trigonelline catabolism in the Rhizobium-legume symbiosis, we identified and characterized the R. meliloti RCR2011 genetic loci (trc) controlling trigonelline catabolism. Tn5-B20 mutagenesis showed that the trc region is a continuous DNA segment of 9 kb located 4 kb downstream of the nifAB and fdxN genes. Trc mutants fell into two classes according to their phenotype and location: (i) mutants carrying Tn5-B20 insertions in the right-hand part of the trc region were incapable of growing on trigonelline as the sole carbon and/or nitrogen source, and (ii) insertions in the left-hand part of the trc region resulted in delayed growth on trigonelline as the sole carbon and/or nitrogen source. No significant defect in nodule formation or nitrogen fixation was detected for mutants of either class. Screening of a set of R. meliloti strains from various geographical origins showed that all of these strains are able to catabolize trigonelline and show sequence homology between their megaplasmids and a trc probe.     

Hereditary pyropoikilocytosis and elliptocytosis in a Caucasian family

Summary Hereditary pyropoikilocytosis (HPP) is a severe hemolytic anemia characterized by a material instability of the red cell membrane leading to cell fragmentation. This fragility may be correlated with functional and structural defects of spectrin. Most HPP patients have been black. We now report three HPP patients from a Caucasian family, the proposita and her two maternal uncles. The proposita's mother and daughter presented mild type I hereditary elliptocytosis (HE), while the proposita's father was clinically and hematologically normal. Our studies revealed a defective ability of spectrin to self-associate, resulting in an excess of spectrin dimer in 4°C extracts in the three HPP patients and to a similar extent in HE relatives. Limited tryptic digestion of spectrin showed a molecular variant in the I domain as expressed by a decreased amount of 80 000-dalton peptide with a concomitant increase in the 74 000-dalton peptide. Investigations in the proposita's father revealed no abnormalities of the erythrocyte membrane. The co-transmission of HPP and HE phenotypes in the same lineage might suggest variability in the clinical expression of the same molecular defect and lead us to discuss the hypothesis of a double heterozygosity in HPP patients.     

Assessment of the state of activity of individual bacterial cells by hybridization with a ribosomal RNA targeted fluorescently labelled oligonucleotidic probe

Abstract A fluorescently labelled oligonucleotide probe complementary to an evolutionarily conserved domain of the small subunit ribosomal RNA sequence has been used with an image analysis equipment to quantify cellular rRNA contents during the successive phase of a bacterial culture ( Escherichia coli ). The amount of hybridization increased steadily upon inoculation of stationary phase bacteria into a new medium, while cell divisions were delayed. This hybridization signal was abruptly reduced by 50% at the onset of the exponential growth phase during which it then remained stable. A further slow decrease took place during stationary phase. The amount of rRNA per cell is thus maximal immediately before the beginning of active cell division. The implications of these results are discussed in terms of bacterial ecology.     

Interactions of the human red cell membrane tyrosine kinase with heparin

Heparin interacts with protein kinases in various ways; the different patterns of behavior of heparin towards protein kinases contributes to the characterization of these enzymes. We studied the interactions between heparin and a new type of tyrosine kinase extracted from the normal human red cell membrane. We found that heparin inhibited kinase activity by competition with ATP. Furthermore the interaction of heparin with the red cell membrane tyrosine kinase allowed us to use heparin-agarose chromatography as a step towards tyrosine kinase purification.     

Inhibitors of type 1 17β-hydroxysteroid dehydrogenase with reduced estrogenic activity: Modifications of the positions 3 and 6 of estradiol

Breast cancer is the second most frequent cancer affecting women. Among all endocrine therapies for the treatment of breast cancer, inhibition of estrogen biosynthesis is becoming an interesting complementary approach to the use of antiestrogens. The enzyme type 1 17β-hydroxysteroid dehydrogenase (17β-HSD) plays a critical role in the biosynthesis of estradiol catalyzing preferentially the reduction of estrone into estradiol, the most active estrogen. Consequently, this enzyme is an interesting biological target for designing drugs for the treatment of estrogen-sensitive diseases such as breast cancer. Our group has reported the synthesis and the biological evaluation of N-methyl, N-butyl 6β-(thiaheptamamide)estradiol as a potent reversible inhibitor of type 1 17β-HSD. Unfortunately, this inhibitor has shown an estrogen effect, thus reducing its possible therapeutic interest. Herein three strategies to modify the biological profile (estrogenicity and inhibitory potency) of the initial lead compound were reported. In a first approach, the thioether bond was replaced with a more stable ether bond. Secondly, the hydroxyl group at position 3, which is responsible for a tight binding with the estrogen receptor, was removed. Finally, the amide group of the side-chain was changed to a methyl group. Moreover, the relationship between the inhibitory potency and the configuration of the side-chain at position 6 was investigated. The present study confirmed that the 6β-configuration of the side chain led to a much better inhibition than the 6α-configuration. The replacement of the 3-OH by a hydrogen atom as well as that of the amide group by a methyl was clearly unfavorable for the inhibition of type 1 17β-HSD. Changing the thioether for an ether bond decreased by 10-fold the estrogenic profile of the lead compound while the inhibitory potency on type 1 17β-HSD was only decreased by 5-fold. This study contributes to the knowledge required for the development of compounds with the desired profile, that is, a potent inhibitor of type 1 l7β-HSD without estrogen-like effects.