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Y Ouellette

Publications and source records attributed to Y Ouellette.

6 recordsLinked to original sources
PubMed2001

Lipopolysaccharide reduces intercellular coupling in vitro and arteriolar conducted response in vivo.

Our recent in vitro study (Lidington et al. J Cell Physiol 185: 117-125, 2000) suggested that lipopolysaccharide (LPS) reduces communication along blood vessels. The present investigation extended this study to determine whether any effect of LPS and/or inflammatory cytokines [tumor necrosis factor-alpha, interleukin (IL)-1beta, and IL-6] on endothelial cell coupling in vitro could also be demonstrated for an arteriolar conducted response in vivo. Using an electrophysiological approach in monolayers of microvascular endothelial cells, we found that LPS (10 microg/ml) but not these cytokines reduced intercellular conductance (c(i)) (an index of cell communication) and that LPS together with these cytokines did not further reduce c(i). Also, c(i) was restored after LPS washout, and the LPS-induced reduction was prevented by protein tyrosine kinase (PTK) inhibitors (1.5 microM Tyr A9 and 10 nM PP-2). In our in vivo experiments in arterioles of the mouse cremaster muscle, local electrical stimulation evoked vasoconstriction that conducted along arterioles. LPS in the muscle superfusate did not alter local vasoconstriction but reduced the conducted response. Washout of LPS restored the conducted response, whereas PTK inhibitors prevented the effect of LPS. On the basis of a newly developed mathematical model, the LPS-induced reduction in conducted response was predicted to reduce the arteriolar ability to increase resistance to blood flow. We conclude that LPS can reduce communication in in vitro and in vivo systems comparably in a reversible and tyrosine kinase-dependent manner. Based on literature and present results, we suggest that LPS may compromise microvascular hemodynamics at both the arteriolar responsiveness and the conduction levels.

Animals↗
PubMed2000

Endotoxin increases intercellular resistance in microvascular endothelial cells by a tyrosine kinase pathway.

Gap junction communication between microvascular endothelial cells has been proposed to contribute to the coordination of microvascular function. Septic shock may attenuate microvascular cell-to-cell communication. We hypothesized that lipopolysaccharide (LPS) attenuates communication between microvascular endothelial cells derived from rat hindlimb skeletal muscle. Endothelial cells grown in monolayers expressed mRNA for connexin 37, 40, and 43. The expression of connexin 43 protein was confirmed, but connexin 40 protein was not detected by immunocytochemistry or immunoblot analysis. Intercellular resistance between cells of the monolayer, calculated using a Bessel function model, was increased from 3.3 to 5.3 MOmega by LPS. The effect was seen after 1 h of exposure and required a minimum concentration of 10 ng/ml. Intercellular resistance returned to normal 1 h following removal of LPS. Neither the response to LPS, nor its reversal, was blocked by the protein synthesis inhibitor cycloheximide (10 microg/ml). Pretreatment of monolayers with the tyrosine kinase inhibitors PP-2 (10 nM), lavendustin-C (1 microM), and geldanamycin (200 nM) prevented this LPS response; geldanamycin was also able to reverse the response. Inhibitors of MAP kinases, PD 98059 (5 microM) and SB 202190 (5 microM), and PKC (500 nM bisindolylmaleimide I) were unable to block the LPS response. We propose that LPS attenuates cell-to-cell communication through a signaling pathway that is tyrosine kinase dependent.

Animals↗
PubMed2000

A new in vitro model for agonist-induced communication between microvascular endothelial cells.

Microvascular endothelial cells (MECs) grown in Matrigel form capillary-like structures. We hypothesized that these "capillaries" better mimic communication properties of microvessels than conventional cell monolayers. MECs were isolated from the rat hindlimb skeletal muscle. Functional communication was tested by visualizing the spread of microinjected 6-carboxyfluorescein (CF) dye and by measuring a conducted change of membrane potential after micropipette application of 500 mM KCl or 10 mM adenosine triphosphate (ATP) on the capillary and monolayer. MECs grown under both conditions were dye-coupled, as demonstrated by the spread of CF injected into a single cell. The membrane potential of cells grown in capillaries (-59 +/- 5 mV) was significantly greater than that of cells grown in monolayers (-24 +/- 2 mV). KCl and ATP caused local depolarization (18 +/- 3 mV) and hyperpolarization (21 +/- 3 mV) in capillaries that yielded conducted 13 +/- 3 mV depolarization and 15 +/- 5 mV hyperpolarization at a 300-microm distal site, respectively. In monolayers, local and distal responses to agonists were 3- to 6-fold and 9- to 10-fold less, respectively, than the corresponding responses in capillaries. Cells grown under both conditions expressed connexin 43, as demonstrated by immunohistochemistry and Western blotting. We conclude that cells grown in capillaries yield substantially larger local and communicated responses than cells in monolayers and thus offer a more sensitive model for mechanistic studies of MEC communication.

Adenosine Triphosphate↗
PubMed1997

Evidence for K+ channels involvement in capillary sensing and for bidirectionality in capillary communication.

Although the capillary sensing and communication phenomenon has been characterized, its mechanism is not clear. It has been hypothesized that capillary sensing involves a membrane potential change in the capillary endothelium and/or pericyte and that communication represents an electrotonic spread of this change along the capillary. The goal of the present study was to address this hypothesis by examining the presence of K+ channels on the capillary and by determining bidirectionality of communication. Using intravital microscopy, we locally applied K+ (100 mM), acetylcholine (ACh; 3 mM), and norepinephrine (NE; 0.3 mM) on capillaries, 400-500 microns downstream from the arteriole, at the surface of the sartorius muscle in anesthetized frogs. Responses were measured in terms of red blood cell velocity (VRBC) changes in the stimulated capillary (control prestimulation VRBC ranged from 110 to 770 microns/sec). K+ and ACh caused significant 19 and 38% increases in VRBC, while NE caused a -46% decrease, respectively. The K+ response was blocked by local pretreatment with K+ channel blocker BaCl2 (1 microM) and by pretreatment with tetraethyl ammonium chloride (TEA; 5 mM). Responses to ACh and NE were attenuated by pretreatment with 1 microM BaCl2 (to 1%) and with 50 mM TEA (to -25%), respectively. In a separate experiment, NE (3 mM) application on the capillary 500 microns away from the draining venule (capillary occluded) caused a 19% venular constriction (i.e., similar to a reported 21% arteriolar constriction caused by the NE stimulus). We concluded that (i) K+ channels were present on the capillary and (ii) capillary communication was bidirectional. We interpreted these results to be consistent with the above hypothesis of membrane potential change and electrotonic spread.

Acetylcholine↗
PubMed1991

[A lot in common].

Since 1978, the Faculty of Nursing at Sherbrooke University has been offering courses that stress the interdisciplinary approach and the notion of teamwork. In the early 1980s, students were given the opportunity to participate in a pilot program, working as an interdisciplinary team and choosing their own clients. Three different disciplines took part: nursing, psychology and social science. In 1989 and again in 1990, nearly 200 medical students and more than 50 nurses were involved in a joint interdisciplinary project. The article recaps these experiences and describes the two programs recently put in place by the Faculty of Medicine, to benefit future nurses and doctors. The process is well under way towards planning a complete course of 45 hours, with six hours of joint experience already factored in. The teaching methods used in both programs are explained, the two-year program is evaluated, and conclusions and recommendations put forth.

Curriculum↗