The prevention of dehydration injury in celery seeds by polyethylene glycol, abscisic acid, dark and high temperature

Celery seeds ( Apium graveolens L.) given a germination induction period (3 days imbibition at 17°C in the light) could be prevented from germinating by up to 14 days subsequent exposure to high temperature (32°C), polyethylene glycol (PEG), abscisic acid (ABA) or dark (22°C). When the seeds were returned to 17°C in the light, germination occurred and, except for the high temperature treatment, was more rapid compared to seeds given a germination induction period only.
Celery seeds incubated for 3 days at 17°C in the light and then air-dried at 20°C germinated slowly when re-sown at 17°C in the light, and achieved only 19% germination after 21 days. Exposing the seeds to high temperature, PEG, ABA or dark for up to 14 days before drying maintained seed viability and subsequent germination was faster. The longer treatment periods gave increased benefit, and PEG was the most effective treatment. It is suggested that the effectiveness of the treatments in inducing dehydration tolerance relates to their ability to inhibit germination possibly via their prevention of cell expansion.     

Targeting Homologous Recombination in Notch-Driven C. elegans Stem Cell and Human Tumors

Mammalian NOTCH1-4 receptors are all associated with human malignancy, although exact roles remain enigmatic. Here we employ glp-1(ar202), a temperature-sensitive gain-of-function C. elegans NOTCH mutant, to delineate NOTCH-driven tumor responses to radiotherapy. At ≤20°C, glp-1(ar202) is wild-type, whereas at 25°C it forms a germline stem cell⁄progenitor cell tumor reminiscent of human cancer. We identify a NOTCH tumor phenotype in which all tumor cells traffic rapidly to G2⁄M post-irradiation, attempt to repair DNA strand breaks exclusively via homology-driven repair, and when this fails die by mitotic death. Homology-driven repair inactivation is dramatically radiosensitizing. We show that these concepts translate directly to human cancer models.     

Winnipeg pediatrician prepares to assume CMA presidency

The CMA''s incoming president is Dr. Jack Armstrong, a Winnipeg pediatrician with a particular interest in aboriginal issues. Armstrong, who graduated from the University of Manitoba in 1966, considers himself a team player. “You have to be a part of a team. My job is to try to be as good a spokesperson as possible, along with the other team members, for the physicians of the country.”     

A three dimensional serial reconstruction of neuronal distributions in the hypostome of a Hydra

The numbers, types, and distributions of neurons in a hypostome of Hydra littoralis were determined from electron micrographs of serial (0.25 μm thick) sections. In 1,080 serial sections examined we found 75 sensory cells and 949 centrally located ganglion cells. More than 96% of the 1,024 neurons identified had a single cilium. Sensory cells were most numerous near the apex of the hypostome. Proceeding away from the apex, they steadily decreased in numbers; at 120 μm they were no longer observed. Ganglion cells were bimodally distributed; some were associated with sensory cells at the apex, but most were found at the sites of tentacle origin. We observed, throughout the hypostome, a total of 64 neuronal clusters (three or more contiguous neurons), with an average of five and a maximum of 11 neurons in a cluster. Clusters were distributed similarly to ganglion cells: an initial concentration of clusters near the apex; the majority at the hypostometentacle junctions. Each neuron identified was traced through succeeding sections in which it was observed. We used a three coordinate system to create a three-dimensional reconstruction of the neuronal locations in the hypostome. Although the functional significance of the neuronal distributions we observed is unknown, we suggest that neurons at the apex of the hypostome transduce sensory information involved in feeding behavior. The neuronal concentrations at sites of tentacle origin may be responsible for initiating Contraction Burst Pulses associated with rhythmic behavioral patterns of Hydra or coordinating tentacle movements involved in prey capture, ingestion or locomotion.     

Inhibition of dehydration-induced fusion between liposomal membranes by carbohydrates as measured by fluorescence energy transfer

The relative abilities of a number of naturally occurring carbohydrates to inhibit dehydration-induced fusion between palmitoyloleoylphosphatidylcholine:phosphatidylserine (85:15) large unilamellar vesicles have been studied. Fusion events were quantified using a fluorescence resonance energy transfer technique. Trehalose was most effective at inhibiting fusion (0.4 g/trehalose/g lipid showed 30% probe intermixing), followed by maltose (60% intermixing), fructose (60%), sucrose (70%), glucose (80%), cellobiose, glycerol, raffinose, and myo-inositol (90%). The relative abilities of these carbohydrates to inhibit fusion correlate directly with their abilities to interact with phospholipids, maintain bilayer fluidity, and preserve biological membranes. The results are discussed in relation to the crystalline structure of the carbohydrates and their possible influence on level of interaction with phosphate head groups.