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Biomedical subjects

D Rioux

Publications and source records attributed to D Rioux.

17 recordsLinked to original sources
PubMed2006

White pine weevil (Pissodes strobi) biological performance is unaffected by the jasmonic acid or wound-induced defense response in Norway spruce (Picea abies).

In eastern Canada, the white pine weevil (Pissodes strobi Peck) is a pest of several native pine and spruce species and of the introduced species, Norway spruce (Picea abies Karst). We evaluated the feeding activities, oviposition and rate of adult emergence of white pine weevil on field-grown Norway spruce subjected to jasmonic acid or wounding pretreatments. We also monitored the host-plant reaction to white pine weevil attack, jasmonic acid and wounding treatments by quantifying several mono- and sesquiterpenes in bark and characterizing some molecular aspects of the terpenoid response. Two cDNA sequences were identified that had a high percentage of identity with genes encoding monoterpene or sesquiterpene synthases. Both putative terpene synthase genes showed distinctive profiles in Norway spruce bark and needles following all treatments. Although the Norway spruce trees showed different physiological responses to mechanical wounding and white pine weevil attack, transcript activity of the gene encoding terpenoid synthase and consequent accumulation of terpenoid resin did not significantly affect the weevils' feeding activities, oviposition or rate of adult emergence.

Animals↗
PubMed2004

Cytochemical labeling for fungal and host components in plant tissues inoculated with fungal wilt pathogens.

Antibodies to detect pectin in present investigations attached to distinct fibrils in vessel lumina. In carnation infected with an isolate of Fusarium oxysporum f.sp., labeling of pathogen cells also occurred; in a resistant cultivar (cv.), it was coincident with proximate pectin fibrils and linked to altered fungal walls, which was the opposite in the susceptible cv., indicating that hindrance of pathogen ability to degrade pectin may be related to resistance. Labeling of the fungus in culture was nil, except in media containing pectin, showing that pectin is not native to the pathogen. Labeling of fungal walls for cellulose in elm (inoculated with Ophiostoma novo-ulmi) and carnation also occurred, linked to adsorbed host wall components. The chitin probe often attached to dispersed matter, in vessel lumina, traceable to irregularly labeled fungal cells and host wall degradation products. With an anti-horseradish peroxidase probe, host and fungal walls were equally labeled, and with a glucosidase, differences of labeling between these walls were observed, depending on pH of the test solution. Fungal extracellular matter and filamentous structures, present in fungal walls, predominantly in another elm isolate (Phaeotheca dimorphospora), did not label with any of the probes used. However, in cultures of this fungus, extracellular material labeled, even at a distance from the colony margin, with an anti-fimbriae probe.

Cell Wall↗
PubMed2003

Somatic stability of microsatellite loci in Eastern white pine, Pinus strobus L.

Variation at nuclear- and chloroplast-encoded microsatellite loci was studied among and within clonally propagated individuals of Eastern white pine. Total DNA was extracted and assayed from gamete-bearing tissue (megagametophytes) located on six different branch positions on each of 12 individual genets. No within-individual variation was observed among 12 loci studied. Estimates of numbers of mitotic cell divisions required to produce the tissue used as the source of genomic DNA were obtained by combining tree growth and anatomical data. This allowed for the calculation of upper bound estimates of numbers of mutations per locus per somatic cell division. The estimated somatic mutation rate was found to be substantially lower than those published for genomic microsatellite mutation rates in other plant species.

Genetic Variation↗
PubMed1993

Long-term use of intramuscular insulin therapy in a type I diabetic patient with subcutaneous insulin resistance.

We studied a 26-year-old Type 1 diabetic patient who experienced recurrent episodes of ketoacidosis and who was unresponsive to subcutaneous insulin, but normally responsive to intravenous insulin as demonstrated by insulin challenge test. Attempts at intravenous and intraperitoneal insulin administration were complicated by recurrent septicaemia. We therefore investigated the hypoglycaemic effect of intramuscular insulin administration in this patient. After intramuscular injection of NPH and Ultralente human insulin (0.1 U kg-1), the lowest plasma glucose levels occurred 1 and 7 h later, respectively; the hypoglycaemic effect lasted approximately 2 and 12 h, respectively. We based insulin therapy on intramuscular NPH as a fast-acting insulin and Ultralente as an intermediate-acting insulin using four injections a day. During the next 24 months, the patient was hospitalized for 4 weeks versus 56 weeks in the 20 months preceding intramuscular insulin administration, and was able to resume full-time work. HbAlC decreased from 11.7% to 8.7% (normal range: 4.2-5.9%). Thus, long-term intramuscular insulin therapy is a feasible alternative to intravenous or intraperitoneal insulin in patients with well-demonstrated resistance to subcutaneous insulin.

Adult↗
PubMed1993

A Cytochemical Study of Extracellular Sheaths Associated with Rigidoporus lignosus during Wood Decay.

An ultrastructural and cytochemical investigation of the development of Rigidoporus lignosus, a white-rot fungus inoculated into wood blocks, was carried out to gain better insight into the structure and role of the extracellular sheaths produced by this fungus during wood degradation. Fungal sheaths had a dense or loose fibrillar appearance and were differentiated from the fungal cell wall early after wood inoculation. Close association between extracellular fibrils and wood cell walls was observed at both early and advanced stages of wood alteration. Fungal sheaths were often seen deep in host cell walls, sometimes enclosing residual wood fragments. Specific gold probes were used to investigate the chemical nature of R. lignosus sheaths. While labeling of chitin, pectin, beta-1,4- and beta-1,3-glucans, beta-glucosides, galactosamine, mannose, sialic acid, RNA, fucose, and fimbrial proteins over fungal sheaths did not succeed, galactose residues and laccase (a fungal phenoloxidase) were found to be present. The positive reaction of sheaths with the PATAg test indicates that polysaccharides such as beta-1,6-glucans are important components. Our data suggest that extracellular sheaths produced by R. lignosus during host cell colonization play an important role in wood degradation. Transportation of lignin-degrading enzymes by extracellular fibrils indicates that alteration of plant polymers may occur within fungal sheaths. It is also proposed that R. lignosus sheaths may be involved in recognition mechanisms in fungal cell-wood surface interactions.

Journal Article↗