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Biomedical subjects

P Lessard

Publications and source records attributed to P Lessard.

At least 19 recordsLinked to original sources
PubMed2006

Effect of algal incorporation on growth, survival and carcass composition of rainbow trout (Oncorhynchus mykiss) fry.

A nutritional assay has been conducted with rainbow trout fry (Oncorhynchus mykiss) using a biomass of photosynthetic micro-organisms. The algal biomass was incorporated in the feed at increasing levels (12.5%, 25% and 50%) in order to verify the effects on survival (%), growth (length and mass) and carcass quality of the fish (skin color, water, protein and lipid content). Two commercial feeds (CF, as sold, and 0% A, reprocessed without algae) have been used as controls. After eight weeks at 10 degrees C, the growth has been significantly reduced in fish fed the feeds containing 25% and 50% algae diets (P<0.01). Moreover, an incorporation of algae higher than 12.5% in the feed led to a increase of water content (CF versus other diets; P<0.01) and TL (CF versus 50% A; P<0.01) (wet basis) content of carcasses. Survival was 100% in all treatment groups. Under the experimental conditions used, the results obtained show that a maximum of 12.5% of algal biomass can be incorporated in the feed for rainbow trout fry (O. mykiss) without negative consequences on growth and body content in lipids and energy of fish.

Analysis of Variance↗
PubMed2005

Nitrogen elimination mechanisms in an organic media aerated biofilter treating pig manure.

Biofilters using organic media are known to procure efficient treatment for different types of wastewater, but the nitrogen removal pathways implied are still not well understood. In this study, a lab-scale aerated biofilter using peat and treating pig manure was operated for 180 days, in order to quantify the nitrogen transformations occurring in it. It was shown that stripping was important during the start-up, until nitrification took place. Simultaneous nitrification and denitrification, proved by N2 production, became the principal mechanism after some time. The production of N2O did not seem to come only from heterotrophic denitrification, but also from chemodenitrification and autotrophic denitrification. It has also been found that part of the influent nitrogen was retained in the system during the first 150 days, due to filtration, sorption and assimilation. During the last periods of operation, the nitrogen previously retained has been used by microorganisms, leading to an excessive N2 discharge.

Animals↗
PubMed2003

Determination of the hydraulic residence time in a trickling biofilter filled with organic matter.

Biofiltration process using peat as media has been shown to be efficient for the treatment of agroindustrial, chemical and municipal effluents. However, determining the hydraulic retention time of this process is difficult due to many factors. Generally tracer techniques are used, but they measure the molecular retention time instead of the hydraulic retention time; and depending on the case, the results can be wrong. In order to contribute to solving this problem, the objective of this research was to find a trustworthy and adequate technique to determine the hydraulic retention time for a process using a very adsorbent filter bed material (peat). An overview of the hydraulic behaviour of a peat bed filter related to their particular structural composition is presented. Then, based on these characteristics, two different techniques to determine the hydraulic retention time were developed and tested. The first, an indirect modified tracing technique and, the second, a direct one which determines the volume of liquid in treatment into the filter bed through the establishment of a relation between the volume of porosity and the volume of empty spaces (or not occupied by liquid) into the filter bed. The results obtained showed that the proposed techniques gave similar results and proved adequate.

Biodegradation, Environmental↗
PubMed2002

Decay rate variability of active heterotrophic biomass.

Hypotheses of the ASM 1 model state that the specific respiration rate of heterotrophic active biomass is a constant. It thus becomes possible to assess the active heterotrophic biomass decay rate (bH) during starvation. The object of this study is to verify if the specific respiration rate of heterotrophic biomass remains constant throughout starvation, and if it is typical of global metabolic biomass activity, as proposed by the model hypotheses. The decay rate bH was evaluated using respirometric and enzymatic measurements. Measurement of bH through respirometry on various sludges varied between 0.28 and 0.76 d(-1). According to the enzyme and respirometric measurements carried out, a large portion of this value is related to enzymatic regulation. During starvation, when initial active biomass activity is high, down regulation of the respiratory chain results in a decrease in the specific heterotrophic active biomass respiration rate, thus creating an overevaluation of the decay rate as measured by respirometry. Thus a high decay rate used in the ASM 1 model could eventually lead to a poor forecast of biomass production.

Bacteria↗
PubMed2001

Modeling of a reactive primary clarifier.

Even though many models have been proposed for primary clarification, none is directly compatible with the ASM1. The objective of this paper is to present the development of a reactive primary clarifier model to be used in a wastewater treatment plant simulator (WEST). A model simulating COD behavior has been developed based on the Takacs model, and was tested with full-scale data. Particulate effluent COD was well described but problems occurred predicting the underflow suspended solids concentration. The model had to be upgraded with a residence time and a flocculation term to simulate the behavior of soluble COD. An ammonification term was added to the model, resulting in an improved model fit on effluent ammonium.

Belgium↗
PubMed2000

Comparison of equine amnion and a nonadherent wound dressing material for bandaging pinch-grafted wounds in ponies.

OBJECTIVE: To evaluate healing of pinch-grafted wounds on the distal aspect of the limbs of ponies bandaged with equine amnion or a standard nonadherent wound dressing material. ANIMALS: 6 ponies. PROCEDURE: A 2.5x2.5-cm full-thickness section of skin was removed from the dorsal aspect of each limb at the midpoint of the metacarpus or metatarsus. Six days later, wounds were grafted with partial-thickness pinch grafts. Half the wounds were bandaged with amnion, and the other half were bandaged with a nonadherent dressing. Bandages were changed every 3 days until wound healing was complete. At each bandage change, numbers of grafts lost were recorded, and wounds were measured. RESULTS: Percentage of grafts lost from wounds bandaged with amnion was not significantly different from percentage lost from wounds bandaged with the nonadherent dressing. Median healing time for wounds bandaged with amnion (30 days) was significantly less than median healing time for wounds bandaged with the nonadherent dressing (39 days). All wounds were healed by day 45. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that amnion can be used for bandaging pinch-grafted wounds on the distal aspect of the limbs of ponies.

Amnion↗
PubMed1999

Identification of cdc2cAt: a new cyclin-dependent kinase expressed in Arabidopsis thaliana flowers.

In the present paper, the isolation of a third cyclin-dependent kinase gene and its cognate cDNA from Arabidopsis thaliana is described. Whereas other characterised cdc2 genes are ubiquitously expressed in Arabidopsis, expression of cdc2cAt is restricted to flowers. This gene, named cdc2cAt, differs from the two previously reported cdc2 genes in its organisation. Comparison with other cdc2 genes suggests that the deduced protein belongs to a new family of CDC2-like proteins related to the human CHED protein kinase.

Amino Acid Sequence↗
PubMed1999

Arabidopsis thaliana proteins related to the yeast SIP and SNF4 interact with AKINalpha1, an SNF1-like protein kinase.

AKINalpha1, a Ser/Thr kinase from Arabidopsis thaliana belongs to the highly conserved SNF1 family of protein kinases in eukaryotes. Recent data suggest that the plant SNF1-related kinases (SnRK1 family) are key enzymes implicated in the regulation of carbohydrate and lipid metabolism. In Saccharomyces cerevisiae and mammals, the SNF1 and AMPKalpha protein kinases interact with two other families of proteins, namely SNF4/AMPKgamma and SIP1/SIP2/GAL83/AMPKbeta, to form active heterotrimeric complexes. In this paper, we describe the characterisation of three novel cDNAs. AKINbeta1 and AKINbeta2 encode proteins similar to SIP1, SIP2 and GAL83 and AKINgamma codes for a protein showing similarity with SNF4. Using the two-hybrid system, specific interactions have been shown between A. thaliana AKINbeta1/beta2, AKINgamma and AKINgamma as well as between the A. thaliana and S. cerevisiae subunits. Interestingly, AKINbeta1, AKINbeta2 and AKINgamma mRNAs accumulate differentially in A. thaliana tissues and are modulated during development and under different growth conditions. These data suggest the presence in higher plants of a conserved heterotrimeric complex. Moreover, the differential transcription of different non-catalytic subunits can constitute a first level of regulation of the SNF1-like complex in plants.

Amino Acid Sequence↗
PubMed1998

Sensitivity and specificity of antigen-capture ELISAs for diagnosis of Trypanosoma congolense and Trypanosoma vivax infections in cattle.

Sensitivity and specificity of the FAO/IAEA antigen-ELISA kits for diagnosis of bovine trypanosomosis were investigated using sera from experimental cattle infected by tsetse challenge with cloned populations of Trypanosoma congolense (three populations) or T. vivax (one population). The kits are based on monoclonal antibodies that recognise internal antigens of tsetse-transmitted trypanosomes. Ten cattle were infected with each trypanosome population for at least 60 days, and in combination with uninfected cohorts (n = 16) were used in a double-blind study design. Sensitivity and specificity of the tests depended on the choice of positive-negative thresholds expressed as percent positivity with respect to the median OD of four replicates of the strong positive reference serum provided with the kit. In general, while overall specificities were high, sensitivities of the antigen-ELISAs were poor. For example, at a cut-off of 5% positivity, the sensitivities of the antigen-ELISAs were 11% for samples (n = 1162) from T. congolense infected cattle (n = 30), and 24% for samples (n = 283) from T. vivax infected cattle (n = 10). The corresponding specificity values were 95% and 79%, respectively. At a cut-off of 2.5% positivity sensitivity for T. congolense was 25%, and for T. vivax 35%; corresponding specificity values were 85% and 63% respectively. There were no values of the positive-negative threshold at which both sensitivity and specificity were satisfactory. Restricting the analyses to samples taken more than 2 weeks after tsetse challenge did little to improve sensitivity estimates. Trypanosome species specificities of the antigen-ELISAs were also poor. Sensitivity and species specificity of the antigen-ELISA for Trypanosoma brucei infections were not investigated. In contrast to the antigen-ELISA, the sensitivity of the buffy-coat technique when applied to the same experimental animals was fairly high at 67% for T. congolense infections and 60% for T. vivax infections. For samples taken more than 2 weeks after tsetse challenge, high sensitivity estimates of 96% for T. congolense and 76% for T. vivax infections were obtained.

Africa South of the Sahara↗
PubMed1997

[Protein phosphatases and protein kinases in higher plants].

The recent gain in knowledge concerning enzymes involved in signal transduction pathways is a direct consequence of the considerable advances made in molecular biology. Protein kinases and protein phosphatases, the two major enzymes implicated in post-translational modifications, have been studied in particular. The number of characterized plant genes and/or cDNAs encoding these enzymes is increasing everyday. Since 1991, 26 genes and cDNAs coding for plant protein phosphatases have been isolated and characterized. The huge number of protein kinases (estimated at several thousands) makes it impossible to give an exhaustive list of the genes already identified, but a classification of these enzymes, based on phylogenetic criteria, allows us to appreciate the range of functions this protein family may play in plants.

Molecular Biology↗
PubMed1997

Prospective study of equine colic incidence and mortality.

A prospective study of one year was conducted on 31 horse farms to obtain population based estimates of incidence, morbidity and mortality rates of equine colic. Farms with greater than 20 horses were enrolled by randomly selecting horse owners from 2 adjacent counties of Virginia and Maryland. Descriptive information for 1427 horses was collected at the initiation of the study and updated at 3 month intervals. Time on the farm during the study was tabulated for each horse. When colic was reported by the owner, investigators visited the farm to obtain information about the colic. The crude incidence density rate of colic was 10.6 colic cases/100 horse-years, based on 104 cases/358,991 horse-days. The median farm specific incidence density rate was 7 cases/100 horse-years, and the range for individual farms varied from 0 to 30 colic cases/100 horse-years. A specific diagnosis was not made for 84 (81%) of colic episodes. Seventy colic episodes (67%) were treated by a veterinarian. Drugs were used in 83 (80%) colic episodes, and 78 (75%) of colic cases were mild, requiring no treatment or resolving after only one treatment. Four horses required colic surgery. Fourteen (13%) horses had more than one episode of colic during the year. Mortality from all causes of death was 2.5 deaths/100 horse-years, mortality rate for colic was 0.7 deaths/100 horse-years. Proportional mortality rate of colic, 28%, was higher than for any other cause of death. Horses less than age 2 years or greater than age 10 years had lower incidence than horses age 2-10 years. No difference in colic risk between genders was identified. Arabian horses had the lowest and Thoroughbreds the highest breed specific incidence rates. Horses used for eventing, or in training had a statistically significant higher incidence rate of colic compared to mature horses with no use (pets, retired, on pasture with no stated purpose). Horses used for lessons or with no use had the lowest incidence rates.

Age Factors↗
PubMed1997

Prospective study of equine colic risk factors.

A 1 year prospective study was conducted on 31 horse farms to identify risk factors for equine colic. Farms were randomly selected from a list from 2 adjacent counties of Virginia and Maryland, USA. The association between colic and farm or individual horse risk factors related to management, housing, pasture, use, nutrition, health and events was first examined by univariate statistical analysis. Individually significant (P < = 0.25 for farm factors, P < = 0.10 for horse factors) variables were used in a stepwise multivariable forward logistic regression to select explanatory factors (P < = 0.05). Analysis was conducted at 2 levels: farm and individual horse with farm specified as a random effects variable. No farm-level variables were significant. Significant horse-level variables included: age, odds ratio (OR) = 2.8 for horses age 2-10 years compared to < 2 years; history of previous colic, OR = 3.6 relative to no colic; changes in concentrate feeding during the year (1 per year, OR = 3.6, more than 1, OR = 2.2) relative to no changes; more than 1 change in hay feeding during the year, OR = 2.1 relative to no changes; feeding high levels of concentrate (> 2.5 kg/day dry matter, OR = 4.8, > 5 kg/day dry matter, OR = 6.3) relative to feeding no concentrate; and vaccination with monocytic ehrlichiosis vaccine during the study, OR = 2.0 relative to no vaccination. Feeding a whole grain with or without other concentrate components reduced risk, OR = 0.4, relative to feeding no whole grain. Results of the study suggest that diet and changes in diet are important risks for colic in a population of horses on farms.

Analysis of Variance↗
PubMed1993

Comparison of intradermal allergy test and enzyme-linked immunosorbent assay in dogs with allergic skin disease.

Results of an ELISA for allergen-specific IgE were compared with results of an intradermal (ID) allergy test in 5 clinically normal dogs and 36 dogs referred for evaluation of allergic dermatitis. The ELISA had a sensitivity of 100% and a specificity of 0%. Agreement between ID allergy test and ELISA for positive and negative results ranged from 44 to 56% for pollens, 39% for house dust/dust mite, 22% for fungi, and 54% for fleas. Agreement between ID allergy test and ELISA scores for all pollens was only 10% greater than that expected by chance alone, and a kappa value of 0.17 confirmed poor test agreement. The greatest disparity in results was seen in dogs with negative ID and positive ELISA results. Median ELISA absorbance values for 15 groups of related allergens were compared in 4 groups of dogs: clinically normal dogs, atopic dogs with positive ID reactivity, suspected atopic dogs with negative ID reactivity, and flea-allergic dogs. There was no significant difference in median ELISA values between clinically normal dogs and flea-allergic dogs, or clinically normal dogs and atopic dogs for any allergen group. Although the ELISA absorbance value for fungal antigens was significantly higher in dogs suspected of being atopic than in clinically normal dogs, there was no significant difference in median ELISA values for any other allergen group. These findings suggested the disparity between ID allergy test and ELISA results was primarily attributable to false-positive ELISA reactions rather than greater ELISA sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Dietary addition of cellular metabolic intermediates and carcass fat deposition in broilers.

Ninety-six 1-day-old male broilers were fed a diet containing 0, 2, 4, 6, 8, or 10% of a 1:1 mixture of pyruvic acid (PY) and dihydroxyacetone (DH) for ad libitum consumption for 42 days. Feed intake, body weight gain, and feed efficiency decreased linearly (P < .001) with increasing levels of PY and DH. There were no significant differences among treatments for abdominal fat percentage. Carcass chemical analysis revealed small but significant (P < .05) differences among dietary treatments for protein and fat percentages. In a second experiment, 192 1-day-old male broilers were fed diets containing 5% of PY, lactic acid (LA), citric acid (CI), DH, or glycerol (GY) or mixtures (1:1) of DH or GY in combination with each organic acid. Bird performance was impaired (P < .05) by PY or CI but not by DH or GY. Lactic acid reduced (P < .05) feed intake by 9% without affecting weight gain. Lactic acid plus DH, CI plus DH, and CI plus GY mixtures decreased (P < .05) bird performance but other combinations had no effect. Pyruvic acid or CI decreased abdominal fat and carcass lipid percentages. Dihydroxyacetone increased (P < .05) carcass lipid percentage and GY increased (P < .05) abdominal fat percentage. Lactic acid plus DH increased (P < .05) carcass lipid percentage. Only PY and CI decreased carcass fat deposition, but they also impaired broiler performance.

Adipose Tissue↗
PubMed1992

Effect of tiletamine/zolazepam sedation on intradermal allergy testing in atopic dogs.

Seven atopic dogs underwent intradermal allergy testing with 46 inhalant antigens before and after administration of a tiletamine/zolazepam solution (4 mg/kg of body weight, IV). This anesthetic protocol had no significant effect on the intradermal response caused by histamine, whole flea extract, or various inhalant allergens. Short-acting chemical restraint induced by the drug combination facilitated the intradermal testing procedure.

Animals↗
PubMed1991

Possible effect of altered management practices on seroprevalence of bovine leukemia virus in heifers of a dairy herd with history of high prevalence of infection.

A bovine leukemia virus (BLV) control program was instituted at a high-prevalence, purebred Holstein dairy. The specific control program required single use of needles and obstetrical sleeves, disinfection of tattoo equipment before use, dehorning by use of electrical burning devices, replacement of whole milk feeding with high-quality milk replacer, and heat treatment of colostrum before feeding. The effect of the program was estimated by comparing the pre- (1987) and postintervention (1989) prevalences of BLV-agar gel immunodiffusion titers within particular heifer age cohorts (0 to 90, 91 to 180, 181 to 360 days, and 361 days to parturition). Random serologic testing was conducted quarterly within each cohort, but was analyzed on a combined yearly basis. Seroprevalence of BLV decreased in all age cohorts greater than 180 days old, with significant decreases in the 361 days to parturition (P = 0.003) and the combined 181 days to parturition cohorts (P = 0.0004). Prevalence within the latter cohort decreased from 0.44 in 1987 to 0.17 in 1989. These results were obtained without either culling or segregation of BLV-agar gel immunodiffusion-positive cattle.

Animal Husbandry↗
PubMed1990

Geographical information systems for studying the epidemiology of cattle diseases caused by Theileria parva.

Data on selected variables which influence the epidemiology of cattle diseases caused by Theileria parva were assembled and entered in a computerised geographical information system. Variables studied included the distributions of major hosts (cattle and buffalo), the vector ticks (Rhipicephalus appendiculatus and related species) and the reported presence of East Coast fever, corridor disease and January disease. In addition, the distribution of climatic suitability for R appendiculatus was assessed using the model CLIMEX run on an interpolated climate database developed for Africa. Distribution maps of each variable were produced. The potential value of geographical information systems in studies of disease epidemiology and control is discussed, with examples of how sensitivity may be enhanced by the inclusion of additional variables. In addition, subject areas in which poor data quality and inadequate data standardisation may limit the use of these systems are identified and discussed.

Africa↗