Expression of antisense chalcone synthase RNA in transgenic hybrid walnut microcuttings. Effect on flavonoid content and rooting ability

Walnut somatic embryos (Juglans nigra × Juglans regia) were transformed with a vector containing a neomycin phosphotransferase II, a -glucuronidase and an antisense chalcone synthase (chs) gene. This antisense construct included a 400 bp cDNA fragment of a walnut chs gene under the control of the duplicated CaMV-35S promoter. Molecular, biochemical and biological characterizations were performed both on transformed embryos propagated by secondary somatic embryogenesis and on microshoots developed by in vitro culture of embryonic epicotyls from somatic embryos. Thirteen transformed lines with the vector containing the antisense chs gene, one line with only the gus and nptII genes and one untransformed line were maintained in tissue culture. Six of the antisense lines were shown to be flavonoid-deficient. They exhibited a strongly reduced expression of chs genes, very low chalcone synthase activity and no detectable amounts of quercitrin, myricitrin, flavane-3-ols and proanthocyanidins in stems. Rooting tests showed that decreased flavonoid content in stems of antisense chs transformed lines was associated with enhanced adventitious root formation. Free auxin and conjugated auxin contents were determined during the latter phase of the micropropagation, and no variations were detected between control and antisense chs transformed lines. The in vitro plants developed a large basal callus and apical necrosis upon auxinic induction and the transformed lines highly deficient in flavonoids were more sensitive to exogenous application of indolebutyric acid (IBA).     

Multiple cleavage sites of cholecystokinin heptapeptide by "enkephalinase"

Degradation of Boc CCK7 (Boc Tyr1 (SO3H)-Met2-Gly3-Trp4-Met5-Asp6-Phe7-NH2), a fully active analog of CCK8, by purified rabbit kidney neutral metalloendopeptidase (enkephalinase) was studied as a basis for the rational design of potent peptidases-resistant analogs of cholecystokinin. Characterization of the metabolites was performed by HPLC using several elution procedures. Three cleavage sites were evidenced: one major at the Asp6-Phe7 bond and two minor at Gly3-Trp4 and Trp4-Met5 bonds. All cleavages were fully inhibited by thiorphan, a potent inhibitor of enkephalinase. The relative importance of the different cleavages was established using several cholecystokinin analogs. At 25 degrees C the half-disappearance time was 18 min for Boc CCK7, Boc[diNle2,5]CCK7 and 70 min for Boc[diNle2,5 D.Asp6]CCK7. Although, half-life of Boc CCK7 and Boc[diNle2,5]CCK7 were identical, the replacement of Met by Nle, a more hydrophobic aminoacid, greatly favoured the cleavage at the Trp4-Nle5 bond which became the major breakdown. This feature was exemplified by the substitution of L.Asp by D.Asp, preventing the Trp4-Nle5 cleavage, which gave rise to the most enkephalinase-resistant analog in this series.     

Mapping of a Gene for Long QT Syndrome to Chromosome 4q25-27

Long QT syndrome (LQTS) is a heterogeneous inherited disorder causing syncope and sudden death from ventricular arrhythmias. A first locus for this disorder was mapped to chromosome 11p15.5. However, locus heterogeneity has been demonstrated in several families, and two other loci have recently been located on chromosomes 7q35-36 and 3p21-24. We used linkage analysis to map the locus in a 65-member family in which LQTS was associated with more marked sinus bradycardia than usual, leading to sinus node dysfunction. Linkage to chromosome 11p15.5, 7q35-36, or 3p21-24 was excluded. Positive linkage was obtained for markers located on chromosome 4q25-27. A maximal LOD score of 7.05 was found for marker D4S402. The identification of a fourth locus for LQTS confirms its genetic heterogeneity. Locus 4q25-27 is associated with a peculiar phenotype within the LQTS entity.     

The Ca2+-releasing messenger NAADP, a new player in the nervous system.

Many physiological processes are controlled by a great diversity of Ca2+ signals. Within cell, Ca2+ signals depend upon Ca2+ entry and/or Ca2+ release from internal Ca2+ stores. The control of Ca2+-store mobilization is ensured by a family of messengers comprising inositol 1,4,5 trisphosphate, cyclic ADP-ribose and nicotinic acid adenine dinucleotide phosphate (NAADP). From recent works, new concepts have emerged where activation of the cells by outside stimuli, acting at the plasma membrane, results in the synthesis of multiple Ca2+-releasing messengers which may interact and shape complex Ca2+ signals in the cytosol as well as in the nucleus. This contribution will cover the most recent advances on NAADP signalling with some emphasis on neurons.     

Apoptotic death concurrent with CD3 stimulation in primary human CD8+ T lymphocytes: a role for endogenous granzyme B

We exposed primary CD8(+) T cells to soluble CD3 mAb plus IL-2 and limited numbers of monocytes (3%). These cells were activated but concurrently subjected to ongoing apoptosis ( approximately 25% were apoptotic from day 2 of culture). However, their costimulated CD4(+) counterparts were much less prone to apoptosis. The apoptotic signaling pathway bypassed Fas and TNFRs, and required the activity of cathepsin C, a protease which performs the proteolytic maturation of granzyme (Gr) A and GrB proenzymes within the cytolytic granules. Silencing the GrB gene by RNA interference in activated CD8(+) T cells prevented the activation of procaspase-3 and Bid, and indicated that GrB was the upstream death mediator. A GrB-specific mAb immunoprecipitated a approximately 70-kDa molecular complex from cytolytic extracts of activated CD8(+) (but not resting) T cells, that was specifically recognized by a nucleocytoplasmic protease inhibitor 9 (PI-9) specific mAb. This complex was also detected after reciprocal immunoprecipitation of PI-9. It coexisted in the cytosol with the 32-kDa form of GrB. As neither were detected in the cytosol of CD4(+) bystander T cells (which poorly synthesized GrB), and as silencing the perforin (Pf) gene had no effect in our system, endogenous GrB was likely implicated. Immunoprecipitation experiments failed to reveal Pf in the cytosol of CD8(+) T cells, and only a tiny efflux of granular GrA was detected by ELISA. We propose that some GrB is released from cytolytic granules to the cytosol of CD8(+) T lymphocytes upon CD3/TCR stimulation and escapes PI-9, thereby mediating apoptotic cell death.