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L Lessard

Publications and source records attributed to L Lessard.

15 recordsLinked to original sources
PubMed2006

Simulation of special bubble detectors for PICASSO.

The PICASSO project is a cold dark matter (CDM) search experiment relying on the superheated droplet technique. The detectors use superheated freon liquid droplets (active material) dispersed and trapped in a polymerised gel. This detection technique is based on the phase transition of superheated droplets at about room temperature and ambient pressure. The phase transition is induced by nuclear recoils when an atomic nucleus in the droplets interacts with incoming subatomic particles. This includes CDM particles candidate as the neutralino (a yet-to-discover particle predicted in extensions of the standard model of particle physics). Simulations performed to understand the detector response to neutrons and alpha particles are presented along with corresponding data obtained at the Montreal Laboratory.

Computer Simulation↗
PubMed2006

Direct dark matter search using large-mass superheated droplet detectors in the PICASSO experiment.

The PICASSO experiment investigates the presence and nature of dark matter in the Universe. The experiment is based on the detection of acoustic signals generated in explosive phase transitions induced by dark matter particles. This technique is an alternative more traditional detection technique like scintillation and ionisation, which are largely employed for dark matter search. One of the main advantages of this technique, besides its sensitivity to very low nuclear recoil energies (few keV), is its excellent background suppression features. A pilot experiment consisting of six superheated droplet detectors (40 g of active mass) is presently taking data at the Sudbury Neutrino Observatory (SNO) at a depth of 2000 m. We discuss the operation, calibration and data acquisition of the experiment and also the ongoing work to increase the sensitivity and the active mass of the detectors.

Cosmic Radiation↗
PubMed2005

Nuclear localisation of nuclear factor-kappaB transcription factors in prostate cancer: an immunohistochemical study.

Several reports suggest that the canonical nuclear factor-kappaB (NF-kappaB) pathway is constitutively activated in a subset of prostate cancer cells. However, except for RelA (p65), little is known about the status of NF-kappaB transcription factors in prostate cancer tissues. To clarify the status of NF-kappaB subunits, we analysed the expression and subcellular localisation of RelA, RelB, c-Rel, p50, and p52 on tissue array sections containing respectively 344, 346, 369, 343, and 344 cores from 75 patients. The subcellular localisation of NF-kappaB factors was tested against relevant clinical parameters (preoperative prostate-specific antigen, pathological stage, and postoperative Gleason grade). With the exception of c-Rel, each subunit was detected in the nucleus of cancer cells: significant nuclear expression of RelB, RelA, p52, and p50 was seen in 26.6, 15.6, 10.7, and 10.5% of cores, respectively. Surprisingly, cores expressing both nuclear RelA and p50 canonical pathway proteins were less frequently observed than cores expressing other subunit combinations such as RelB-p52 and RelA-RelB. In addition, the nuclear localisation of RelB correlated with patient's Gleason scores (Spearman correlation: 0.167; P=0.018). The nuclear localisation of both canonical and noncanonical NF-kappaB subunits in prostate cancer cells suggests for the first time that different NF-kappaB pathways and dimers may be activated in the progression of the disease.

Adenocarcinoma↗
PubMed2003

NF-kappa B nuclear localization and its prognostic significance in prostate cancer.

OBJECTIVE: To detect the subcellular localization of NF-kappa B (p65) in human prostate cancer tissues of different histological grades, and to test whether NF-kappa B localization alone, or combined with the histological grade, can be used to predict patient outcome. PATIENTS AND METHODS: Prostate cancer tissues were obtained from radical prostatectomy specimens; the histological grade was determined using the Gleason grading system. Clinical outcomes were defined as good (5-year disease-free survival with undetectable levels of prostate specific antigen) or poor (progression to bone metastases). The subcellular localization of NF-kappa B was visualized by immunohistochemistry using an anti-p65 antibody. RESULTS: The NF-kappa B subcellular localization was initially assessed in 45 specimens; in these samples a nuclear localization of NF-kappa B was specific to cancer tissues, but did not correlate with the Gleason score (P = 0.089). NF-kappa B was then assessed as a prognostic marker to complement Gleason score in predicting cancer progression. Tumour tissues from 30 men with a known clinical outcome were included; 10 of 17 patients who had a poor outcome were positive for NF-kappa B nuclear staining, whereas only two of 13 with a good outcome were positive (P = 0.026). When NF-kappa B subcellular localization and Gleason score were combined, two risk categories of progression were defined. Eleven of 13 specimens from those with a good outcome were in the low-risk category (Gleason 2-4 or Gleason 5-7 with negative nuclear NF-kappa B) and 12 of 17 in the poor outcome group were in the high-risk category (Gleason 8-10 or Gleason 5-7 with positive nuclear NF-kappa B; P = 0.004). CONCLUSION: NF-kappa B is detectable in the nucleus in prostate cancer tissues and positivity can be used to help predict patient outcome. Multivariate analyses using other clinical and molecular variables are underway, and will validate the usefulness of NF-kappa B as a prognostic factor.

Aged↗
PubMed2001

Skull base meningioma: delayed extracranial presentation.

Meningiomas are common intracranial tumors that rarely extend to extracranial sites. When they occur extracranially near the skull base, their diagnosis and management represent tremendous challenges. Although the extracranial component tends to manifest at the same time as the intracranial component, this is not always the case. In the patient reported in this article, 13 years separated the diagnosis of the intracranial tumor from the appearance of an extracranial component. The clinical presentation, radiologic findings, and management of this large skull base meningioma are discussed with reference to the literature. A high index of suspicion and clinical acumen are needed to ensure that the extracranial component of these frequent tumors is discovered, especially when it presents later than the intracranial component.

Journal Article↗
PubMed2001

Host response to various treatments to reduce Salmonella infections in swine.

Host response was evaluated following the administration of various treatments, such as probiotics, prebiotics, and vaccination, to reduce Salmonella in swine. Response to the treatments were studied by the evaluation of phagocytosis rates by flow cytometry, by studying the activation of whole-blood phagocytes by bioluminescence, the production of IgA against S. Typhimurium, and by histopathology. Significant differences were observed in the activation of whole-blood phagocytes in all groups of treated pigs (P = 0.0001). In SC54 vaccinated pigs, a significant reduction of Salmonella in the ileum was observed (P < 0.05) and the production of IgA against S. Typhimurium was higher in this group in comparison to uninfected control pigs (P = 0.0007). Furthermore, significant histopathological (P < 0.05) changes were observed in SC54 vaccinated pigs. Villus height and mucus and goblet cells density in the small intestine were reduced in vaccinated pigs in comparison to infected control pigs. Taken together, these findings suggest that SC54 vaccine can stimulate local immunity and reduce the presence of Salmonella in the ileum in swine. Use of SC54 vaccine should thus be considered in further field experiments.

Animals↗
PubMed2000

Assessment of various treatments to reduce carriage of Salmonella in swine.

In this study, different strategies to reduce carriage of Salmonella spp. in pigs were evaluated. Probiotics, prebiotics, vaccination, and acidification of drinking water were assessed as means of reducing Salmonella. Acidification of water, use of egg yolk-specific immunoglobulins, and vaccination with an endotoxin vaccine did not reduce Salmonella excretion in experimentally infected pigs. A reduction of Salmonella in the colonization of mesenteric lymph nodes was observed with the use of bambermycins and a live attenuated vaccine. A reduction in the shedding of S. Typhimurium was also observed after supplementation with fructooligosaccharides in drinking water. The use of probiotics and prebiotics appeared to change the pig fecal bacterial flora as indicated by Gram staining of smears from rectal swabs.

Animals↗
PubMed1999

Characterization of the risk to human health of pathogenic Escherichia coli isolates from chicken carcasses.

The purpose of this study was to evaluate the risk for human health associated with pathogenic Escherichia coli isolated from airsacculitis and cellulitis in chickens, by comparing the genotypic and phenotypic profiles of avian E. coli isolates and E. coli strains isolated from sick humans during the same period and in the same geographical area as the avian isolates. A total of 96 isolates and 46 isolates from lesions of cellulitis and airsacculitis, respectively, were obtained. Isolates from the backs of some of the affected and healthy birds and 91 intestinal and extraintestinal isolates from humans with diarrhea, urinary tract infections, or septicemia were examined. The frequency of antimicrobial resistance was in general higher in the avian than in the human isolates. VT1-VT2-Eae and VT2-Eae, pathotypes associated with hemolytic and uremic syndrome and bloody diarrhea in humans, were the most frequently encountered pathotypes in human intestinal isolates but were not recovered from the avian isolates. Aero-Pap-TSH and Aero-TSH were the most frequently encountered pathotypes in avian isolates but were rarely observed in human isolates. No avian isolate was of serogroup O157, whereas many human isolates belonged to this O group. O78 and O2 were the most frequently observed O groups in avian isolates but were rarely found in human isolates. Only two avian isolates demonstrated possible relatedness to human isolates based on pulsed-field gel electrophoresis profiles, but they belonged to different pathotypes. Our results suggest that avian isolates recovered from cellulitis and air sacullitis possess very few of the attributes required to cause diseases in humans. It is also concluded that isolates from cellulitis and airsacculitis do not represent a greater hazard than isolates from the back of healthy birds.

Air Sacs↗
PubMed1995

EMG analysis of harmaline-induced tremor in normal and three strains of mutant mice with Purkinje cell degeneration and the role of the inferior olive.

1. The effects of intraperitoneal injections of 10 mg/kg harmaline were tested in normal mice and three strains of cerebellar mutant mice with Purkinje cell degeneration. Ten normal (wild-type) mice (+/+), as well as five lurcher (lc/+), six nervous (nr/nr), and eight Purkinje cell degeneration (pcd/pcd) mutants were implanted with chronic electromyogram (EMG) electrodes in the hamstring and quadriceps muscle groups of the right hindlimb. 2. EMGs were recorded in each of the mice during spontaneous activity before and after intraperitoneal injections of 0.3 ml harmaline (10 mg/kg). Spectral analysis was used to quantify the amplitude and frequency of tremor found in the EMGs after harmaline administration. Normal mice responded to harmaline with strong, continuous 11- to 14-Hz tremor. Mutants from the pcd/pcd strain also reacted with continuous tremor, but of lower amplitude and frequency. In contrast, nr/nr mutants exhibited intermittent paroxysmal tremor lasting for only a few seconds, and lc/+ mutants showed no evidence of tremor whatsoever. 3. In order to detect covert tremor that was possibly not revealed by focal intramuscular EMG recordings, several mutant and normal mice were also tested on a suspended platform to which an accelerometer was attached. The results confirmed the findings from EMG recordings. 4. An incidental observation made during the course of this study was that harmaline tremor disappeared from the normal mouse during swimming and reappeared when the animal was withdrawn from the water. 5. Although Purkinje cells appeared to increase both the depth of modulation and the frequency of tremor, the inhibitory action of the cerebellar cortex does not seem to be essential for the generation of tremor. 6. Parasagittal cerebellar sections of the normal, wild-type mice and the three strains of cerebellar mutant mice of various ages were stained with cresyl violet and examined for Purkinje cell degeneration. Purkinje cell degeneration was found to be complete in the pcd/pcd and lc/+ strains. Although an initial examination of parasagittal sections of the nr/nr strain failed to find any surviving Purkinje cells, further examination of sections cut in the coronal plane revealed small clusters of Purkinje cells in the vermal area of the posterior lobe. 7. The retrograde transport of wheat-germ-agglutinin-conjugated horseradish peroxidase (WGA-HRP) pressure-injected into the cerebellar cortex was used to study the olivocerebellar projections in the wild-type mice and the three strains of cerebellar mutant mice.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

The use of preformed HTR polymer implants for chin augmentation. A preliminary report.

Ten patients with microgenia had their chins augmented with HTR polymer implants. The implants were inserted intraorally and fixed rigidly with a titanium screw. The postoperative course was uneventful except in one patient who had wound dehiscence and was resutured. This patient and all the others were clinically and radiographically stable at one year follow up.

Adult↗
PubMed1986

Selective release of inner core proteins from intestinal microvillus membrane by lithium diiodosalicylate.

Lithium diiodosalicylate (LIS) was used to selectively solubilize proteins from purified intestinal brush border membrane vesicles. Incubation of the vesicles with increasing concentrations of LIS resulted in the progressive release of proteins with total disruption of the membranes being obtained at 200 mM. Maximum selectivity was observed at 20-30 mM LIS which preferentially released actin and other non-glycosylated proteins while all the glycoproteins remained associated with the membrane. Electron micrographs showed that, after LIS treatment, brush border vesicles are partially disrupted and have lost their inner core of microfilaments. Sucrase, trehalase, leucylnaphthylamide hydrolase, gamma-glutamyl transpeptidase and alkaline phosphatase all retained more than 70% of their activities and remained associated with the membrane fraction after LIS solubilization (30 mM). The results indicate that lithium diiodosalicylate treatment provides an efficient method for the separation of cytoskeletal proteins from intrinsic membrane glycoproteins and should be very useful for the purification of microvilli proteins and for the study of membrane-protein interactions.

Animals↗
PubMed1973

Prolonged and variable intervals between EEG complexes in subacute inclusion body encephalitis.

Should effective therapy of SIBE ever depend upon early diagnosis, periodic EEG complexes must be sought carefully when the condition is suspected, bearing in mind that initially the duration of intervals between complexes may be more prolonged and more variable than commonly appreciated. Prolonged, uninterrupted recording at reduced speed, taken both while the patient is awake and asleep, may well facilitate recognition of periodic events as unusual as those observed in the 20-year-old young man described in this paper, who was examined during the early stage of the disease. When initial EEG complexes are separated, as in our patient, by variable and prolonged intervals - up to 86 seconds' duration - their periodicity and diagnostic implication can be overlooked, particularly in a so-called routine electroencephalogram. Optimal dispaly of such unusual findings calls for suitable electroencephalographic techniques.

Adult↗