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Biomedical subjects

R Turcotte

Publications and source records attributed to R Turcotte.

At least 19 recordsLinked to original sources
PubMed2003

Thermal hazard assessment of AN and AN-based explosives.

Ammonium nitrate (AN) is an essential ingredient in most fertilizers. It is also widely used in the commercial explosives industry. In this latter application, it is mostly mixed with fuel oil to form the most popular commercial explosive: ANFO. In both the fertilizer and the explosive industry, aqueous AN solutions (ANS) of various concentrations are processed. These solutions also form the basis of ammonium nitrate emulsion explosives (also called ammonium nitrate emulsions or ANE), which are produced either in bulk or in packaged form. For all these AN-based products, quantities of the order of 20,000kg are being manufactured, transported, stored, and processed at elevated temperatures and/or elevated pressures. Correspondingly, major accidents involving overheating of large quantities of these products have happened in several of these operations. In comparison, convenient laboratory quantities to investigate thermal decomposition properties are generally less than 1kg. As a result, in order to provide information applicable to real-life situations, any laboratory study must use techniques that minimize heat losses from the samples to their environment. In the present study, two laboratory-scale calorimeters providing an adiabatic environment were used: an accelerating rate calorimeter (ARC) and an adiabatic Dewar calorimeter (ADC). Experiments were performed on pure AN, ANFO, various ANS systems, and typical bulk and packaged ANE systems. The effects of sample mass, atmosphere, and formulation on the resulting onset temperatures were studied. A comparison of the results from the two techniques is provided and a proposed method to extrapolate these results to large-scale inventories is examined.

Atmosphere↗
PubMed2002

Function and health status outcomes in a randomized trial comparing preoperative and postoperative radiotherapy in extremity soft tissue sarcoma.

PURPOSE: Morbidity associated with wound complications may translate into disability and quality-of-life disadvantages for patients treated with radiotherapy (RT) for soft tissue sarcoma (STS) of the extremities. Functional outcome and health status of extremity STS patients randomized in a phase III trial comparing preoperative versus postoperative RT is described. PATIENTS AND METHODS: One hundred ninety patients with extremity STS were randomized after stratification by tumor size dichotomized at 10 cm. Function and quality of life were measured by the Musculoskeletal Tumor Society Rating Scale (MSTS), the Toronto Extremity Salvage Score (TESS), and the Short Form-36 (SF-36) at randomization, 6 weeks, and 3, 6, 12, and 24 months after surgery. RESULTS: One hundred eighty-five patients had function data. Patients treated with postoperative RT had better function with higher MSTS (25.8 v 21.3, P <.01), TESS (69.8 v 60.6, P =.01), and SF-36 bodily pain (67.7 v 58.5, P =.03) scores at 6 weeks after surgery. There were no differences at later time points. Scores on the physical function, role-physical, and general health subscales of the SF-36 were significantly lower than Canadian normative data at all time points. After treatment arm was controlled for, MSTS change scores were predicted by a lower-extremity tumor, a large resection specimen, and motor nerve sacrifice; TESS change scores were predicted by lower-extremity tumor and prior incomplete excision. When wound complication was included in the model, patients with complications had lower MSTS and TESS scores in the first 2 years after treatment. CONCLUSION: The timing of RT has minimal impact on the function of STS patients in the first year after surgery. Tumor characteristics and wound complications have a detrimental effect on patient function.

Adult↗
PubMed2001

Sciatic nerve resection in the thigh: a functional evaluation.

Patients with a soft tissue malignancy involving the sciatic nerve who present with neurologic loss generally are advised to have an amputation. Twenty patients who underwent limb-sparing procedures with complete resection of the sciatic nerve as treatment for neurofibrosarcomas (12 patients), liposarcomas (four patients), malignant fibrous histiocytomas (two patients), recurrent desmoid tumor (one patient), and epithelioid hemangioendothelioma (one patient) were reviewed retrospectively. The mean age of these nine women and 11 men at the time of surgery was 51 years (range, 28-84 years). The right sciatic nerve was affected in 12 patients. These tumors were large and high grade. A mean of 22 cm of the nerve had to be resected (range, 8-42 cm). Ten patients received preoperative radiotherapy and 16 patients had intraoperative or postoperative radiotherapy. At a mean followup of 35 months (range, 7-97 months), 14 of the 20 patients were alive. Two patients had local recurrences develop (10%), whereas 12 patients had distant metastases. The function of the 10 patients as assessed by the Toronto Extremity Salvage Score averaged 74%. Most patients indicated that walking in the house is not difficult, but walking is compromised as soon as an effort is needed. Four patients walk without a cane, four needed one cane, and two needed two canes. The patients experienced stiffness, a sense of numbness, and premature fatigue. The use of analgesics was infrequent. Generally, patients rated themselves to be mildly to moderately disabled. From this small number of patients, it is shown that a tumor involving the sciatic nerve can be treated by limb-sparing surgery, including complete nerve resection, as an alternative to hip disarticulation or hindquarter amputation because the limb salvage option provides an acceptable functional outcome.

Activities of Daily Living↗
PubMed1997

Exercise-induced oxyhemoglobin desaturation and pulmonary diffusing capacity during high-intensity exercise.

The purpose of this investigation was to examine if exercise-induced arterial oxyhemoglobin desaturation selectively observed in highly trained endurance athletes could be related to differences in the pulmonary diffusing capacity (DL) measured during exercise. The DL of 24 male endurance athletes was measured using a 3-s breath-hold carbon monoxide procedure (to give DLCO) at rest as well as during cycling at 60% and 90% of these previously determined VO2max. Oxyhemoglobin saturation (SaO2%) was monitored throughout both exercise protocols using an Ohmeda Biox II oximeter. Exercise-induced oxyhemoglobin desaturation (DS) (SaO2% < 91% at VO2max) was observed in 13 subjects [88.2 (0.6)%] but not in the other 11 nondesaturation subjects [NDS: 92.9 (0.4)%] (P < or = 0.05), although VO2max was not significantly different between the groups [DS: 4.34 (0.65) l/min vs NDS: 4.1 (0.49) l/min]. At rest, no differences in either DLCO [ml CO.mmHg-1.min-1: 41.7 (1.7) (DS) vs 41.1 (1.8) (NDS)], DLCO/VA [8.2 (0.4) (DS) vs 7.3 (0.9) (NDS)], MVV [l/min: 196.0 (10.4) (DS) vs 182.0 (9.9) (NDS)] or FEV1/FVC [86.3 (2.2) (DS) vs 82.9 (4.7) (NDS)] were found between groups (P > or = 0.05). However, VE/VO2 at VO2max was lower in the DS group [33.0 (1.1)] compared to the NDS group [36.8 (1.5)] (P < or = 0.05). Exercise DLCO (ml CO.mmHg-1.min-1) was not different between groups at either 60% VO2max [DS: 55.1 (1.4) vs NDS: 57.2 (2.1)] or at 90% VO2max [DS: 61.0 (1.8) vs NDS: 61.4 (2.9)]. A significant relationship (r = 0.698) was calculated to occur between SaO2% and VE/VO2 during maximal exercise. The present findings indicate that the exercise-induced oxyhemoglobin desaturation seen during submaximal and near-maximal exercise is not related to differences in DL, although during maximal exercise SaO2 may be limited by a relatively lower exercise ventilation.

Adolescent↗
PubMed1995

Cellular target of in vitro-induced suppressor cells derived from the spleen of Mycobacterium lepraemurium-infected mice and role of IFN-gamma in their development.

Unfractionated spleen cells from C3H mice infected a few weeks before with Mycobacterium lepraemurium developed a suppressor activity after overnight culture. This requires contact of plastic adherent cells with nonadherent cells distinct from T, B, or natural killer cells. The present study demonstrates that anti-interferon-gamma (IFN-gamma) monoclonal antibody and indomethacin totally abrogate the expression, although not the induction, of this activity. Furthermore, culture-induced suppressor cells selectively inhibit T lymphocyte proliferation, probably by altering the generation of interleukin-2 (IL-2) responsiveness through reduction of the affinity and density of high-affinity IL-2 receptors on activated cells. These and other previously determined properties of culture-induced suppressor cells, similar to those of adherent suppressor cells detected in freshly harvested spleen cells at a later stage of M. lepraemurium infection, suggest a common precursor. If so, the present observations should help in defining a strategy to prevent the impairment of cell-mediated immunity in infected mice.

Animals↗
PubMed1995

Phenotypic characterization of two cell populations involved in the acquisition of suppressor activity by cultured spleen cells from Mycobacterium lepraemurium-infected mice.

The impairment of cellular immunity in mice infected with Mycobacterium lepraemurium was shown to correlate with the development of suppressor cells. We have previously reported that before suppressor activity is detectable in freshly harvested cell suspensions, suppressor cell precursors accumulate in the spleen of infected mice. Upon overnight culture in the presence of a regulatory cell subset, these precursor cells acquire the capacity to impair the concanavalin A (Con A)-induced proliferation of normal spleen cells. The purpose of this study was to determine the phenotype of the cells involved in this phenomenon. This was done by following the development of suppressor activity in spleen cell suspensions depleted of defined cell subsets of the adherent or the non-adherent cell fractions with selected MoAbs and immunomagnetic beads or by in vivo treatment. Our results indicate that the acquisition of suppressor activity requires the interaction of Ia+CD11b+Fc gamma R+IgG- asialo GM1- adherent cells with Thy1-CD4-CD8-IgG-Ia- asialo GM1-Fc gamma R+CD11b+ non-adherent cells. It is also shown that the development of suppressor activity is impaired by preventing cell-cell contact between these two cell subsets through coculture in 'Transwell chambers'. These observations support the conclusion that the in vitro acquisition of suppressor activity is a consequence of the maturation of suppressor cell precursors of the monocytic lineage induced by a receptor-ligand type interaction with a non-adherent cell subset that is clearly distinct from mature T, B and natural killer (NK) cells.

Animals↗
PubMed1995

Effects of physical conditioning on endogenous nitric oxide output during exercise.

Nitric oxide (NO) has been detected in the expiratory air of normal animals and human subjects. Recent experiments revealed that expiratory NO production rises during exercise and correlates well with O2 consumption (VO2) and heart rate. Whether physical conditioning influences expiratory NO output production remains unclear. In this study, NO concentration in expired gas was measured in 18 healthy male volunteers subdivided into three groups (sedentary, intermediate, and athletic) on the basis of the subjects' state of physical conditioning. Measurements were taken at rest and during two steady-state exercise bouts on a bicycle ergometer designed to elicit VO2 of 1 and 2 l/min with the athletes performing an additional bout at VO2 of 4 l/min. In the sedentary and intermediate groups, expired NO concentrations declined significantly with increasing VO2. In contrast, expired NO levels declined only slightly with increasing VO2 in the athletes. At a VO2 of 2 l/min, expired NO concentrations were significantly higher in the athletes compared with values in the other groups. When correlated with minute ventilation (VE), expired NO concentrations declined linearly with the increase in VE in sedentary and intermediate groups but not in the athletes. Only the athletes had a significant linear increase in NO output (expired NO x VE) with increasing VO2 (P < 0.001). These results support the notion that physical conditioning increases expiratory NO output during exercise. We speculate that the rise in expiratory NO output in the athletes might be due to increased vascular and/or epithelial production of NO. Enhanced vascular NO production may be the result of increased shear stress and/or upregulation of endothelial NO synthase gene expression.

Adult↗
PubMed1994

Influence of the Ity/Lsh/Bcg gene on the development of suppressor cell precursors in the early phase of the infection of mice with Mycobacterium lepraemurium.

In vitro inducible suppressor cell precursors were detected in the spleen of BALB/c but not in DBA/2 mice infected intraperitoneally with 10(8) Mycobacterium lepraemurium bacilli, thus suggesting that their development is genetically controlled. Two pairs of mouse strains congenic at the Ity/Lsh/Bcg locus (BALB/c-C.D2 and B10.A-B10.A.Bcgr) were used to investigate whether this phenomenon is influenced by this gene known to control the relative susceptibility of mice to Myco. lepraemurium infection. This seems likely, as the detection of culture-induced suppressor activity was delayed for 5-6 weeks in C.D2 and B10.A.Bcgr mice infected intravenously with 10(4) Myco. lepraemurium bacilli. However, despite the retardation in the detection of suppressor cell precursors, the level of in vitro induced suppressor activity at onset in spleen cell suspensions of mice carrying the resistant allele was higher than in cell cultures derived from susceptible mice. As the resistant allele has a different effect when found on BALB/c or DBA/2 background, other genetic factors are apparently involved in the development of suppressor cell precursors. We finally observed that, in spleen cell cultures from intravenously infected Ity/Lsh/Bcg congenic mice on the BALB/c background, adherent and non-adherent cells were required in the inductive phase of suppressor cell development, whereas in vitro induced suppressor activity was found exclusively in the adherent cell fraction. Given these properties, we thus conclude that suppressor cell precursors detected in the spleen of these intravenously infected mice are similar to those previously observed in C3H mice infected intraperitoneally with a thousand times more bacilli.

Animals↗
PubMed1994

Malignant fibrous histiocytoma in a patient with Blackfan-Diamond anemia.

Blackfan-Diamond anemia, a chronic, pure red cell aplasia, is rare. Malignant fibrous histiocytoma is also uncommon; it can arise in pre-existing bone lesions. The authors describe a 23-year-old man with Blackfan-Diamond anemia complicated by hemochromatosis in whom malignant fibrous histiocytoma developed in the distal femur.

Adult↗
PubMed1992

Cyclophosphamide treatment antagonizes the in vitro development of Mycobacterium lepraemurium-induced suppressor cell precursors.

The in vitro-inducible maturation of splenic suppressor cell precursors detected during the early phase of Mycobacterium lepraemurium infection can be abrogated when a high dose of cyclophosphamide (Cy) is inoculated to infected mice 2 days before assay. The drug does not act directly on adherent suppressor cell precursors, but rather inhibits their activation by a non-adherent cell subset whose phenotype has not yet been elucidated. It was established by flow cytometry analyses, that despite a marked increase in the total number of splenic non-adherent cells following M. lepraemurium infection, the effect of Cy on Ia+, Thy-1+, CD4+ and CD8+ cells in infected mice was comparable to that observed in normal controls. It was not possible to determine the duration of the inhibiting effect of Cy on non-adherent regulatory cells, because the drug was itself inducing suppressor cells from 7 days after inoculation. By the time spleen cell suspensions were totally free of Cy-induced suppressor cells, infection-dependent suppressor cell precursors were once again detected, indicating that Cy treatment did not prevent their in vivo accumulation. Therefore, even though M. lepraemurium-induced adherent suppressor cell precursors are themselves fully resistant to Cy, their development is transiently abrogated by the drug, most probably through the impairment of a non-adherent cell subset regulating their maturation.

Animals↗
PubMed1991

TTX-induced muscle disuse alters Ca2+ activation characteristics of myofibril ATPase.

1. Previous reports of the effects of disuse induced by tetrodotoxin (TTX) have demonstrated alterations in muscle function suggesting changes in the quality of contractile proteins. 2. We extended these studies to the effects of TTX-induced disuse on the Ca2+ activation characteristics of myofibrillar ATPase of the rat gastrocnemius. 3. Atrophic responses were as previously reported (St-Pierre, D.M.M. and Gardiner P.F. (1985) Effect of disuse on mammalian fast-twitch muscle: joint fixation compared with neurally applied tetrodotoxin. Exp. Neurol. 90, 635-651; St-Pierre, D.M.M. et al. (1987). Recovery of muscle from tetrodotoxin-induced disuse and the influence of daily exercise; 1. Contractile properties. Exp. Neurol. 98, 472-488.) with a significant decrease in left gastrocnemius weight compared to control (C) (1.25 +/- 0.06 for C vs 0.72 +/- 0.04 for TTX, X +/- SEM, P less than or equal to 0.01). 4. Myofibrillar protein yield (mg/g wet weight) was also depressed (92.8 +/- 4.5 for C vs 70.3 +/- 3.7 for TTX; P less than or equal to 0.01). 5. Maximum ATPase of myofibrils (nmol Pi/mg/min) was decreased (441 +/- 28 for C vs 181 +/- 30 for TTX, P less than or equal to 0.01). 6. Furthermore, the Hill n which reflects the cooperative aspects of Ca2+ activation of the myofibrillar ATPase was depressed (1.58 +/- 0.07 for C vs 1.29 +/- 0.09 for TTX; P less than or equal to 0.01). 7. The results suggest that muscle perturbations resulting from disuse are partially related to changes in the myofibril.

Adenosine Triphosphatases↗
PubMed1991

A role for gamma interferon, tumor necrosis factors, and soluble T-cell receptors in the depressed blastogenic response of spleen cells of Mycobacterium lepraemurium-infected mice.

Spleen cells of Mycobacterium lepraemurium-infected mice were cultured on petri dishes coated with mycobacterial antigens, and antigen-reactive cells were isolated. Upon incubation in mitogen- or antigen-free culture medium, these cells released mediators capable of depressing the in vitro proliferative response of normal splenocytes to specific antigen and to concanavalin A and lipopolysaccharide. One of these mediators was identified with gamma interferon (IFN-gamma), mainly on the basis that treatment of supernatants with monoclonal anti-IFN-gamma antibodies markedly reduced the suppressive activity contained therein. Detectable levels of tumor necrosis factor alpha (TNF-alpha) and TNF-beta were present in spleen cell culture supernatants of infected mice. Moreover, low doses of recombinant TNF-alpha and TNF-beta were found to potentiate the suppressive activity of exogenous IFN-gamma. Soluble T-cell receptors beta were also detected in the culture supernatants. The elimination of these molecules with monoclonal anti-T-cell receptor beta (F23.1) antibodies immobilized on a plastic surface partially reversed the depression of the response to mycobacterial antigen but did not affect the response to mitogens. These results revealed the complex nature of suppressor mediators that are produced by mycobacterial antigen-reactive cells and that regulate the in vitro proliferative response.

Animals↗
PubMed1990

Early accumulation of suppressor cell precursors in the spleen of Mycobacterium lepraemurium-infected mice and analysis of their in vitro-induced maturation.

Spleen cells harvested from mice infected intraperitoneally with M. lepraemurium 11-17 weeks prior to harvest acquired the capacity to inhibit concanavalin A (Con A) induced proliferation of normal spleen cells when precultured for up to 24 h in mitogen-free medium. The in vivo induced suppressor activity correlated with the length of the preculture period, the time post-infection and the infecting dose. These findings were interpreted as an indication that suppressor cell precursors accumulated in the spleen of infected mice during the early phase of the disease. The interaction of infection-dependent adherent suppressor cell precursors and infection-independent, non-adherent regulatory cells is necessary for the suppressor activity to develop. Both the cells which transmit the inductive signal and the precursor cells which mature into active suppressor cells are radiosensitive, whereas suppressor activity itself is a function of radioresistant adherent cells. Preculture of cells for a short period, before they were cocultured with Con A-stimulated normal spleen cells, allowed the detection of suppressor cells before they were deleterious to the infected host and also turned out to be a relevant in vitro model for characterization of suppressor cell development during M. lepraemurium infection.

Animals↗
PubMed1990

Biological properties of factors secreted by antigen-reactive suppressor cells in mice infected with Mycobacterium lepraemurium.

Antigen-reactive cells were isolated from the spleens of Mycobacterium lepraemurium-infected C57BL/6 mice on petri dishes coated with mycobacterial antigens. When adoptively transferred to syngeneic mice, the mycobacterial antigen-reactive cells were found to depress the induction and expression of the delayed-type hypersensitivity (DTH) reaction to M. lepraemurium antigens. The adoptive transfer of soluble suppressor factors (SF) secreted by these cells inhibited only the expression of DTH. The cells depressing the induction of DTH mainly belonged to the L3T4+ (CD4+) T-lymphocyte subset, whereas those depressing its expression differed from the L3T4+ and Lyt-2+ (CD8+) subsets. Treatment of M. lepraemurium-infected mice with SF reduced their mean survival time and enhanced the multiplication of bacilli at the site of infection and their dissemination to the spleen and liver. In vitro at least, SF appeared to interfere at the level of mycobacterial antigen recognition by T lymphocytes rather than at the levels of antigen processing and presentation by macrophages.

Animals↗
PubMed1990

Hip fractures and Parkinson's disease. A clinical review of 94 fractures treated surgically.

A series of 87 parkinsonian patients with 94 hip fractures were reviewed to reexamine the evidence for internal fixation versus hemiarthroplasty. Forty-seven subcapital Garden Type I and Type II fractures and transcervical fractures were treated by nailing, and 47 Garden Type III and Type IV fractures were treated by hemiarthroplasty. There were twice as many complications in the hemiarthroplasty group as in patients treated by nailing, including four wound infections and five dislocations, all with uniformly bad results. Patients treated by nailing regained greater ambulatory independence than those with a hemiarthroplasty. The parkinsonian patients with hip fractures treated by internal fixation had better results than those treated by hemiarthroplasty; hemiarthroplasty may be even contraindicated.

Aged↗
PubMed1989

Unresponsiveness to Con A in spleen cell cultures of M. lepraemurium-infected mice is dependent on a defective expression of high-affinity IL-2 receptors rather than on a lack of IL-2 production.

The production of interleukin-2 (IL-2) by Con A-activated spleen cells (SC) progressively declined and reached negligible values during the course of infection of C57BL/6 mice with Mycobacterium lepraemurium. In addition, the capacity of cultured SC to utilize IL-2 was highly reduced, as demonstrated by the accumulation of IL-2 activity in culture supernatants at 48 and 72 h after Con A activation. The depressed IL-2 utilization started to be observed about 1 to 2 weeks prior to the onset of the depressed IL-2 production and was not reversed by the addition of exogenous IL-2; thus implying that a lack of IL-2 utilization rather than a lack of IL-2 production could be directly responsible for the inhibition of T-cell proliferative responses to Con A in SC cultures of infected mice. The utilization of IL-2 was found to be down-regulated, at least in part, by splenic suppressor cells since, in mixed-culture experiments, SC from infected mice actively depressed the capacity of normal splenocytes to consume IL-2. Finally, the depressed IL-2 utilization would result from a 2- to 3-fold reduction of either or both the density of high-affinity IL-2 receptors and their affinity for IL-2.

Animals↗
PubMed1988

Partial characterization of suppressor factors in spleen cell culture supernatants of Mycobacterium lepraemurium-infected mice.

Suppressor factors (SF) were released into the culture supernatant when spleen cells from M. lepraemurium-infected C57BL/6 mice were incubated at 37 degrees C in the absence of any inducing agents. Some of the SF appeared to be specific in that they inhibited the blastogenic response to mycobacterial antigens by opposition to the others which inhibited the blastogenic responses to PHA, Con A and LPS. All SF seemed to be produced in a cyclic manner. In mice infected 9 weeks earlier, the release of "specific" SF occurred early (4-8 h) during the incubation period whereas, the nonspecific SF were released later on (12-32 h). Adoptive transfers of SF-containing culture supernatants depressed the expression of DTH to M.1m antigens but not its induction.

Animals↗