Determination of the Cellular Mechanisms Regulating Thermo-Induced Stem Growth in Thlaspi arvense L

Field pennycress (Thlaspi arvense L.) is a species with a cold requirement for the initiation of reproductive development (thermoinduction). Work in this laboratory has been focused on elucidating the biochemical and molecular mechanisms underlying the bolting or rapid stem elongation response that is an intricate part of reproductive development in this species. In the present paper the cellular basis for thermo-induced stem growth was determined. Evidence is presented indicating that bolting results from the production of new cells that elongate to their original length before thermoinduction. This increase in cell division occurs in the pith and cortex approximately 0.5 to 5.0 millimeters below the stem apex. For at least the early stages of thermo-induced stem growth, enhanced cell elongation does not appear to be a factor because average lengths of pith cells from stems of thermo-induced plants were similar or less than noninduced controls. In addition, both the amount of increase in the production of new pith cells and stem growth were positively correlated with the length of the cold treatment. Two other lines of evidence are presented corroborating previous assertions (JD Metzger [1985] Plant Physiol 78: 8-13) that gibberellins mediate thermo-induced stem growth in field pennycress. First, treatment of noninduced plants with gibberellin A₃ completely mimicked the effects of a 4-week cold treatment on mitotic activity in the pith and cortex. Second, very little increase in the production of new cells was observed in the pith and cortex of thermo-induced plants of a gibberellin-deficient dwarf mutant of field pennycress. It is also shown that the influence of photoperiod on stem growth is mediated by an effect on the final length that cells ultimately attain.     

Familial and individual variation in chromosome fragility

An extremely high frequency of fra 6q26 (25%) was detected during a routine cytogenetic investigation of a 9-year-old girl. This prompted us to perform an extensive study of fragile site expression in her cells and those of her parents and sister. The very high frequency of fragility at 6q26 which had been discovered initially in the proband was not detected in the first repeat culture under the same experimental conditions. However, in the second repeat culture fragility at 6q26 was clearly present again. In the 4 members of this family fragile site expression was found to vary significantly between repeat samples from the same person. Also, a specific order of individual fragile site expression appeared to be present. This order was the same for the different culture conditions used.     

Tripeptidic BACE1 inhibitors devised by in-silico conformational structure-based design

Previously reported pentapeptidic BACE1 inhibitors, designed using a substrate-based approach, were used as lead compounds for the further design of non-peptidic BACE1 inhibitors. Although these peptidic and non-peptidic inhibitors, with a hydroxymethylcarbonyl isostere as a substrate transition-state mimic, exhibited potent BACE1 inhibitory activities, their molecular-sizes appeared a little too big (molecular weight of >600daltons) for developing practical anti-Alzheimer's disease drugs. To develop lower weight BACE1 inhibitors, a series of tripeptidic BACE1 inhibitors were devised using a design approach based on the conformation of a virtual inhibitor bound to the BACE1 active site, also called 'in-silico conformational structure-based design'. Although these tripeptidic BACE1 inhibitors contained some natural amino acid residues, they are expected to be useful as lead compounds for developing the next generation BACE1 inhibitors, due to their low molecular size and unique structural features compared with previously reported inhibitors.     

La fertilité chez le blessé médullaire. Effet du niveau de la lésion médullaire

The majority of spinal cord injured males cannot procreate naturally due to anejaculation as well as abnormal sperm characteristics. Treatment of this impaired fertility must be associated with treatment of neurogenic urinary tract disorders, bowel dysfunction and spasticity. The level of the spinal lesion and the spinal cord injury syndrome influence the possibility of inducing reflex ejaculation by penile vibratory stimulation and sperm quality.     

Production and immune response of recombinant Hsp60 and Hsp70 from the salmon pathogen Piscirickettsia salmonis

We have isolated and sequenced the genes encoding the heat shock proteins 60 (Hsp60) and 70 (Hsp70) of the salmon pathogen Piscirickettsia salmonis. The sequence analysis revealed the expected two open reading frames that encode proteins with calculated molecular weights of 60,060 and 70,400. The proteins exhibit a 70-80% homology with other known prokaryotic Hsp60 and Hsp70 sequences. The coding regions have been expressed in E. coli as thioredoxin fusion proteins. Both recombinant proteins were shown to elicit a humoral response when injected intraperitoneally in Atlantic salmon and also conferred protection to fish challenged with P. salmonis. The present data will facilitate further studies on the involvement of heat shock proteins in protective immunity of fish to infection by P. salmonis and their potential use in recombinants vaccines against this intracellular pathogen.