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Biomedical subjects

L Bilodeau

Publications and source records attributed to L Bilodeau.

At least 19 recordsLinked to original sources
PubMed2005

Effects of recombinant bovine somatotropin on growth and abundance of mRNA for IGF-I and IGF-II in channel catfish (Ictalurus punctatus).

Research was conducted to examine growth rates, circulating concentrations of IGF-I, and mRNA abundance levels of IGF-I and IGF-II in channel catfish (Ictalurus punctatus) given recombinant bovine ST (rbST; Posilac, Monsanto Co., St. Louis MO). In the first study, juvenile catfish (5.5 +/- 0.5 g) were randomly assigned to one of three treatments: 1) sham-injected control (one needle puncture per week); 2) rbST (30 microg x g BW(-1) x wk(-1); Posilac); and 3) nonhandled control (control). At the end of the 6-wk study, the fish were weighed, measured for length, and G:F was determined. Compared with sham and control treatments, rbST-treated fish had 48% greater final BW, 14% greater total length, and 52% greater G:F (P < 0.001). In the second study, juvenile catfish (41.1 +/- 1.5 g) were assigned randomly to one of two treatments: 1) sham or 2) rbST. Eight fish per treatment were sampled on d 0, 1, 2, 7, 14, and 21 for blood, muscle, and liver. Relative expression of IGF-I and IGF-II mRNA was determined by real-time PCR and plasma concentrations of IGF-I were measured using a validated fluoroimmunoassay. Circulating concentrations of IGF-I were increased (37.9 +/- 5.5 vs. 22.0 +/- 6.6 ng/mL; P < 0.05) in rbST-injected fish compared with sham-injected controls by d 14. Liver IGF-I and IGF-II mRNA was increased 4.3-and 14.4-fold, respectively, by d 1 in rbST-injected fish compared with controls (P < 0.05); however, abundance of liver IGF-I and IGF-II mRNA did not differ from controls on d 0, 2, 7, 14, and 21. Abundance of muscle IGF-I and IGF-II mRNA did not differ in rbST-injected fish compared with controls throughout the study. Results of the first study demonstrated that rbST improves growth performance of channel catfish. Results of the second study showed that the growth-promoting effects of rbST were not mediated by the expression of IGF-I or IGF-II mRNA in the muscle. Instead, the results suggest that rbST promotes growth by stimulating plasma IGF-I release, possibly through its direct effect on the liver or on local tissues to synthesize IGF-I. The changes in mRNA abundance and plasma concentrations of IGF-I support the role of IGF-I in growth regulation of channel catfish.

Animals↗
PubMed2004

Early quantitative coronary angiography of saphenous vein grafts for coronary artery bypass grafting harvested by means of open versus endoscopic saphenectomy: a prospective randomized trial.

OBJECTIVE: Endoscopic saphenectomy is associated with a decreased incidence of wound complications without an increase in histologic trauma or endothelial dysfunction in published reports. Concern remains about the patency of saphenous vein grafts harvested endoscopically and the development of early intimal hyperplasia. The purpose of this study was to compare early quantitative coronary analysis of saphenous vein grafts used for coronary artery bypass grafting harvested with the open versus endoscopic techniques. METHODS: Forty patients undergoing primary coronary artery bypass grafting surgery with at least 1 saphenous vein graft were randomized preoperatively to open versus endoscopic saphenectomy with bipolar cauterization of side branches. Quantitative coronary angiography was performed a mean of 3 months (range, 1-9 months) after the operation. RESULTS: There was no statistically significant difference in the patency rates of internal thoracic artery grafts between the open and endoscopic groups and no statistically significant difference in the patency rates of saphenous vein grafts between both groups (85.2% vs 84.4%, P =.991). Quantitative coronary angiography showed no difference in graft stenosis (>or=50% of the internal diameter of the graft) in the body of the saphenous vein grafts in the open versus endoscopic saphenectomy groups (3.7% vs 0%, P =.280). CONCLUSION: Angiographic appearance and patency rates of saphenous vein grafts harvested with the endoscopic technique are similar to those of saphenous vein grafts harvested with the open technique. These results support the use of endoscopic saphenectomy because of the known lower incidence of wound and infectious complications and superior functional results.

Coronary Angiography↗
PubMed2002

Nitinol versus stainless steel stents: acute thrombogenicity study in an ex vivo porcine model.

Acute and subacute stents thrombosis along with thrombus mediating neointimal proliferation within the stent struts remain major concerns in coronary stenting. Up to date, there is an obvious lack of data on the thrombogenicity of stent materials in physiological conditions. This study was performed to compare the relative thrombogenicity of nitinol versus stainless steel stents. Nitinol stents were laser cut to reproduce the exact geometry of the stainless steel Palmaz stents and tested in an ex vivo AV shunt porcine model under controlled conditions. Nitinol stents presented only small amounts of white and/or red thrombus principally located at the strut intersections while Palmaz stents clearly exhibited more thrombus. As a result, 125I-fibrin(ogen) adsorption and (111)I-platelets adhesion were significantly lower on nitinol than on stainless steel devices (36%, p = 0.03 for fibrin(ogen) and 63%, p = 0.01 for platelet). These results were confirmed by scanning electron observations showing different thrombus morphologies for nitinol and stainless steel. Along with the unique mechanical properties of nitinol, its promising haemocompatibility demonstrated in our study may promote their increasing use for both peripheral and coronary revascularization procedures.

Alloys↗
PubMed2001

Stent placement to prevent restenosis after angioplasty in small coronary arteries.

BACKGROUND: Lesions in small-diameter vessels (<3 mm) define a group with distinct clinical and morphological characteristics. There is an inverse relationship between vessel size and angiographic restenosis rate. This study assessed whether stents reduce angiographic restenosis in small coronary arteries compared with standard balloon angioplasty. METHODS AND RESULTS: We randomly assigned 351 symptomatic patients needing dilatation of 1 native coronary vessel between 2.3 and 2.9 mm in size to angioplasty alone (n=182) or stent implantation (n=169). The primary end point was angiographic restenosis at 6 months. Secondary end points included death, myocardial infarction, bypass surgery, and target vessel revascularization in hospital and at 6 months. There were no significant differences between groups in terms of major in-hospital complications. There was a trend toward fewer in-hospital events in the stent group (3% versus 7.1% in angioplasty group, P=0.076). Crossovers to stent occurred in 37 patients (20.3%). Repeat angiography at 6-month follow-up was performed in 85.3% of patients. Angiographic restenosis occurred in 28% of the stent group and 32.9% of the angioplasty group (P=0.36). Target vessel revascularization was required in 17.8% versus 20.3% of patients (P=0.54), respectively. CONCLUSIONS: Stenting and standard coronary angioplasty are associated with equal restenosis rate in small coronary arteries. With a lower in-hospital complication rate, stenting may be a superior strategy in small vessels.

Angioplasty, Balloon, Coronary↗
PubMed2001

Complications of cardiac catheterization in the current era: a single-center experience.

Consecutive cardiac catheterization procedures done over a 2-yr period (April 1996 to March 1998) were prospectively analyzed to determine and characterize procedure-related complications (in-hospital and 1-mo follow-up), as they occur at present. During the study period, 11,821 procedures (7,953 diagnostic and 3,868 therapeutic) were performed. The majority of procedures (> 60%) were done in high-risk patients. Stents were implanted in 33% of patients, and adjunctive abciximab was used in 6.6% of therapeutic procedures. The overall complication rate was 8% (3.6% of diagnostic procedures and 15.1% of therapeutic procedures). The procedure-related mortality rates were 0.2%, 0.1%, and 0.5% for total, diagnostic, and therapeutic procedures, respectively. Cardiac complications were seen in 3.9% (1.5% of diagnostic and 9% of therapeutic procedures). Emergency cardiac surgery was required in 0.05% of the diagnostic procedure group and 0.3% of the therapeutic procedure group (total, 0.1%). Despite marked changes in patient population and practice, the complication rates of cardiac catheterization remain very low.

Abciximab↗
PubMed2001

Influence of stent expansion states on platelet deposition in an extracorporeal porcine arteriovenous shunt model using a multichannel perfusion chamber.

Limited data are available about incomplete stent expansion (SE) on platelet deposition (PD). We examined PD following different SE using an extracorporeal porcine arteriovenous shunt model to which a perfusion chamber with four parallel silastic tubes were connected. Blood flow was set at a 20 and 100 mL/min in 1.8 and 3.1 mm diameter tubes, respectively. P154 stents were deployed completely (Group A, n=15) or incompletely (Group B, n=15) in 1.8 mm (n=13) and 3.1 mm (n=17) tubes. 51Cr-labelled platelet autologous blood was injected 1 hr before the perfusion. After 15 min-perfusion, the testing tubes were assessed for radioactivity counts. In-stent cross sectional area was measured by intravascular ultrasound. There was a significant difference in PD between group A and B regardless of channel size (118+/-18.4 vs 261.4+/-52.1 pits x 10(6)/cm2, p<0.05). With adjusted shear rate and similar stenosis, PD was similar in both tubes. In smaller 1.8 mm tubes, a stenosis as subtle as 10% was associated with a significant PD difference (226.1+/-20 vs 112.9+/-20.5 plts x 10(6)/cm2, p<0.005). This model enabled a repetitive, simultaneous comparison of PD following different SE states. It seems that the quality of SE remains crucial in smaller channels.

Animals↗
PubMed2001

Impact of residual plaque burden after balloon angioplasty in the MultiVitamins and Probucol (MVP) trial.

BACKGROUND: It has been shown in the MultiVitamins and Probucol (MVP) trial that probucol reduces angiographic lumen loss by 68% after percutaneous transluminal coronary angioplasty (PTCA). Restenosis occurred in 40% of patients not treated with probucol and in 20% of those in the probucol alone group. OBJECTIVE: To determine the morphological predictors of restenosis in patients treated with probucol. PATIENTS AND METHODS: Beginning 30 days before angioplasty, 317 patients were randomly assigned to receive probucol, multivitamins, the combined treatment or placebo. Patients were then treated for six months after angioplasty. Intravascular ultrasound (IVUS) examination was performed immediately after angioplasty and at follow-up in 94 patients (108 segments). The angioplasty operator was blinded to the IVUS results. The cross-section selected for serial analysis was the one at the angioplasty site with the smallest lumen area at follow-up. Receiver operating characteristic curves were used to determine the performance of criteria to predict angiographic restenosis at follow-up. RESULTS: In probucol-treated patients, the cross-sectional area (CSA) narrowing of 67.6% or less was the best IVUS predictor for the absence of restenosis (P=0.03). Diameter stenosis of 35% or less almost reached significance as a predictor in these patients (P=0.056). The restenosis rate when either of these predictors was met was less than 13%. Rates of repeat PTCA in patients treated with probucol were 9.7% when CSA narrowing was 67.6% or less on IVUS and 3.1% with a post-PTCA stenosis of 35% or less on quantitative coronary angiography (QCA). No predictor of the absence of restenosis in patients not treated with probucol was identified. CONCLUSIONS: The presence after balloon angioplasty of a CSA narrowing of 67.6% or less on IVUS or a diameter stenosis of 35% or less on QCA is associated, in patients treated with probucol, with extremely low rates of coronary restenosis and repeat angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed2000

Randomized trial comparing intravenous nitroglycerin and heparin for treatment of unstable angina secondary to restenosis after coronary artery angioplasty.

BACKGROUND: The treatment of unstable angina targets the specific pathophysiological thrombotic process at the site of the active culprit lesion. In unstable angina due to a restenotic lesion, smooth muscle cell proliferation and increased vasoreactivity may play a more important role than thrombus formation. Therefore, the relative benefits of nitroglycerin and heparin might differ in unstable angina associated with restenosis compared with classic unstable angina. METHODS AND RESULTS: We randomized 200 patients hospitalized for unstable angina within 6 months after angioplasty (excluding those with intracoronary stents) to double-blind administration of intravenous nitroglycerin, heparin, their combination, or placebo for 63+/-30 hours. Recurrent angina occurred in 75% of patients in the placebo and heparin-alone groups, compared with 42.6% of patients in the nitroglycerin-alone group and 41.7% of patients in the nitroglycerin-plus-heparin group (P<0.003). Refractory angina requiring angiography occurred in 22.9%, 29.2%, 4. 3%, and 4.2% of patients, respectively (P<0.002). The odds ratios for being event free were 0.24 (95% CI, -0.13 to 0.45, P=0.0001) for nitroglycerin versus no nitroglycerin and 0.98 (95% CI, -0.55 to 1. 73, P=NS) for heparin versus no heparin. No patient died or suffered myocardial infarction. CONCLUSIONS: Intravenous nitroglycerin is highly effective in preventing adverse ischemic events (recurrent or refractory angina) in patients with unstable angina secondary to restenosis, whereas heparin has no effect.

Aged↗
PubMed2000

A Ras-dependent chloride current activated by adrenocorticotropin in rat adrenal zona glomerulosa cells.

In the present study, we report that ACTH induces a transient chloride current. The lack of correlation between ACTH-induced cAMP production and amplitude of the Cl- current, as well as the absence of stimulation by forskolin or 8Br-cAMP indicated that the ACTH-induced current was not cAMP-dependent. We explored the possibility that one or several elements of the Ras/Raf MAPK cascade were involved. Indeed, we found that ACTH at 10(-10) M induced activation of Ras. Inhibition of the current by QEHA peptide, a Gbetagamma sequestrant, demonstrated that Gbetagamma subunits transduced the message. Blockage of the Ras activation using an inhibitor of farnesyl transferase (BZA-5B) or the monoclonal antibody H-Ras(259) abrogated the current. Moreover, the addition of Ras-GTPyS in the pipette medium gave rise to the Cl- current. Treatment of the cells with BZA decreased the aldosterone secretion induced by 10(-10) M ACTH but not that induced by 10(-8) M ACTH, confirming the involvement of Ras in steroid secretion. We conclude that ACTH triggers a Cl- current through the activation of the Ras protein by Gbetagamma subunits. This current, activated at physiological ACTH concentrations (1 to 100 pM) where cAMP production is very low, could play a significant role in aldosterone production.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2000

Transverse chromatic aberration and colour-defined motion.

A number of recent studies have explored the role of the chromatic system in motion processes using the isoluminance paradigm. A major concern when using such methodological procedures is potential artefacts produced by chromatic aberrations. In the present study we address the problem of optically induced luminance artefacts produced by transverse chromatic aberrations (TCA), which may contaminate the results obtained in chromatic motion-nulling experiments. Results show that different TCA levels artificially increase chromatic motion sensitivity values to varying degrees above 0.5 cpd for red/green gratings. The data also suggest the notion that naturally occurring TCA can decrease motion-nulling thresholds for chromatic gratings at high spatial frequencies. Furthermore, our data show that the motion-nulling paradigm for chromatic gratings may in fact be an efficient functional method for assessing the amount of TCA produced by optical factors.

Adult↗
PubMed1999

Preliminary investigation of the effects of surface treatments on biological response to shape memory NiTi stents.

Nickel-titanium (NiTi) offers many advantages for the fabrication of coronary stents: shape memory, superelasticity, and radiopacity. However, many authors highlighted the selective dissolution of Ni from the alloy during the corrosion process that could lead to potential toxicity. The improvement of the NiTi stent's corrosion resistance by different surface treatments (electropolishing, heat treatment, and nitric acid passivation) was reported in a previous article. In the present study a comparative biocompatibility evaluation of such stents was performed through in vitro and in vivo assays. A cell proliferation test was completed to evaluate the cytotoxicity of surface treated NiTi using human fibroblasts. Then a stent implantation was performed in rabbit paramuscular muscle to study the inflammatory response generated by the same implants. Cell proliferation tests generally indicated an in vitro biocompatibility of our samples similar to the control group. An in vivo implantation study demonstrated the gradual overall reduction with time of the fibrocellular capsule thickness surrounding the implants. After a 12-week implantation period, the fibrous capsules surrounding the different implants tended toward the same value of 0.07 mm, which suggested that all surface treatments produced a similar biological response. This low value of the fibrocellular capsule indicated that our NiTi surface treated implants were relatively inert.

Animals↗
PubMed1999

Repair of left anterior descending coronary artery perforation by Magic Wallstent implantation.

Coronary rupture is a rare complication of percutaneous coronary intervention. However, it may be associated with serious hemodynamic consequences often leading to tamponade, myocardial infarction, emergency surgical intervention, or death. We report a successful percutaneous repair of a brisk left anterior descending coronary artery perforation by the implantation of a Magic Wallstent.

Angioplasty, Balloon, Coronary↗
PubMed1999

The oblique effect with colour defined motion throughout the visual field.

We assessed the extent of the oblique effect (OE) and the meridional orientation effect (MOE) for a chromatic motion task using red/green gratings throughout an 80 degrees visual field. Four different stimulus orientations were tested. Generally, sensitivity to chromatic motion decreased with increasing eccentricity regardless of the visual field meridian. Also, sensitivity was highest for horizontal or vertical gratings, thus supporting the presence of an OE rather than of a MOE. The strength of the OE varied between subjects, but was present from the fovea to 20 degrees of eccentricity. At 40 degrees of eccentricity, chromatic motion was always perceived but the grating orientation did not consistently influence chromatic motion sensitivity. The present study confirmed our previous results on chromatic motion sensitivity and isoluminance ratios throughout the visual field. In addition, our data show that the chromatic system can exhibit OEs at lower spatial frequencies than is observed for the achromatic system.

Analysis of Variance↗
PubMed1999

Characterization of an ACTH-induced chloride current in rat adrenal zona glomerulosa cells.

Adrenocorticotropic hormone (ACTH) is one of the principal activator of aldosterone secretion in rat zona glomerulosa cells, but its action on chloride currents is not well established. Here, we demonstrate that the hormone provoked a transient increase in a chloride current with a small unitary conductance estimated at 3.35 pS. Amplitude, as well as time-dependent increase of the ACTH-induced chloride current was independent of the intracellular cAMP concentration. In contrary, its decrease was sensitive to alkaline phosphatase and PKA-inhibitor H-89, indicating that protein phosphorylation, at least in part via PKA, is involved in the decline of the current.

1-Methyl-3-isobutylxanthine↗
PubMed1999

Global motion cues and the chromatic system.

The capacity of the isolated chromatic system to perceive global motion was tested in a 40-deg visual field by use of random-dot kinematograms. The method of equivalent cone contrasts was used to directly compare the chromatic and the achromatic systems. The minimum number of dots necessary to correctly identify the motion direction was on the order of 20% for the isochromatic conditions, whereas thresholds were rarely obtained in the chromatic conditions. For both the isochromatic and the chromatic conditions, the central visual field was the most sensitive area, whereas the periphery was slightly less sensitive. This study suggests that the chromatic system does not efficiently integrate local motion cues to generate a global motion percept.

Analysis of Variance↗
PubMed1998

Prevention of restenosis after angioplasty in small coronary arteries with probucol.

BACKGROUND: Restenosis remains the major limitation of coronary angioplasty. Coronary stents have reduced the incidence of restenosis in selected patients with relatively large vessels. No strategies to date have demonstrated a beneficial effect in vessels < 3.0 mm in diameter. We have shown in the MultiVitamins and Probucol (MVP) Trial that probucol, a potent antioxidant, reduces restenosis after balloon angioplasty. The purpose of this study was to determine whether the benefit of probucol therapy is maintained in the subgroup of patients with smaller coronary vessels. METHODS AND RESULTS: We studied a subgroup of 189 patients included in the MVP trial who underwent successful balloon angioplasty of at least one coronary segment with a reference diameter < 3.0 mm. One month before angioplasty, patients were randomly assigned to one of four treatments: placebo, probucol (500 mg), multivitamins (beta-carotene 30000 IU, vitamin C 500 mg, and vitamin E 700 IU), or probucol plus multivitamins twice daily. The treatment was maintained until follow-up angiography was performed at 6 months. The mean reference diameter of this study population was 2.49+/-0.34 mm. Lumen loss was 0.12+/-0.34 mm for probucol, 0.25+/-0.43 mm for the combined treatment, 0.35+/-0.56 mm for vitamins, and 0.38+/-0.51 mm for placebo (P=.005 for probucol). Restenosis rates per segment were 20.0% for probucol, 28.6% for the combined treatment, 45.1% for vitamins, and 37.3% for placebo (P=.006 for probucol). CONCLUSIONS: Probucol reduces lumen loss and restenosis rate after balloon angioplasty in small coronary arteries.

Aged↗
PubMed1998

Effect of modification of oxide layer on NiTi stent corrosion resistance.

Because of its good radiopacity, superelasticity, and shape memory properties, nickel-titanium (NiTi) is a potential material for fabrication of stents because these properties can facilitate their implantation and precise positioning. However, in vitro studies of NiTi alloys report the dependence of alloy biocompatibility and corrosion behavior on surface conditions. Surface oxidation seems to be very promising for improving the corrosion resistance and biocompatibility of NiTi. In this work, we studied the effect on corrosion resistance and surface characteristics of electropolishing, heat treatment, and nitric acid passivation of NiTi stents. Characterization techniques such as potentiodynamic polarization tests, scanning electron microscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy were used to relate corrosion behavior to surface characteristics and surface treatments. Results show that all of these surface treatments improve the corrosion resistance of the alloy. This improvement is attributed to the plastically deformed native oxide layer removal and replacement by a newly grown, more uniform one. The uniformity of the oxide layer, rather than its thickness and composition, seems to be the predominant factor to explain the corrosion resistance improvement.

Alloys↗