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Biomedical subjects

M Laurin

Publications and source records attributed to M Laurin.

17 recordsLinked to original sources
PubMed2005

Development of a total quality system for transfusion medicine services in Ontario hospitals.

TOTAL QUALITY SYSTEM: The purpose of the project was to develop a total quality system in Transfusion Medicine which would serve as a model for development of a provincial transfusion quality system. Pilot studies were carried out in Ottawa and Hamilton/Niagara. Each region was provided with resources to create a Quality Team. The Quality Team was comprised of several individuals including a Quality Team Leader, and a number of Quality Assistants. The responsibilities of the Quality Team included: working with Transfusion Medicine Laboratories in area hospitals to achieve a total quality system, identification, standardization and implementation of 'best transfusion practices' throughout the regional hospitals, development and implementation of standard operating procedures (SOP) based on best practices, development and implementation of transfusion/administration guidelines, assessment of blood utilization, education, training, non-conformance (error) management, and surveillance. Liaison was also established with the co-coordinator for the Transfusion Co-coordinator's Project (ONTRAC), the education coordinator for the Sunnybrook Project, the Public Health Agency of Canada, Quality Management Practice-Laboratory System, the Ontario Hospital Association and Laboratory Licensing. In Ottawa these activities resulted in the development of:

Blood Banks↗
PubMed2005

Transient and steady state CO oxidation kinetics on nanolithographically prepared supported Pd model catalysts: experiments and simulations.

Applying molecular-beam methods to a nanolithographically prepared planar PdSiO2 model catalyst, we have performed a detailed study of the kinetics of CO oxidation. The model catalyst was prepared by electron-beam lithography, allowing individual control of particle size and position. The sample was structurally characterized by atomic force microscopy and scanning electron microscopy before and after reaction. In the kinetic experiments, the O-rich and CO-rich regimes were investigated systematically with respect to their transient and steady-state behaviors, both under bistable and monostable reaction conditions. Separate molecular beams were used in order to supply the reactants, allowing individual control over the reactant fluxes. The desorbing CO2 was detected by both angle-resolved and angle-integrated mass spectrometries. The experimental results were analyzed using different types of microkinetic models, including a detailed reaction-diffusion model, which takes into account the structural parameters of the catalyst as well as scattering of the reactants from the support. The model quantitatively reproduces the results as a function of the reactant fluxes and the surface temperature. Various kinetic effects observed are discussed in detail on the basis of the model. Specifically, it is shown that under conditions of limited oxygen mobility, the switching behavior between the kinetic regimes is largely driven by the surface mobility of CO.

Journal Article↗
PubMed2005

Local reaction rates and surface diffusion on nanolithographically prepared model catalysts: experiments and simulations.

Combining molecular beam methods and angular resolved mass spectrometry, we have studied the angular distribution of desorbing products during CO oxidation on a planar Pd/silica supported model catalyst. The model catalyst was prepared by means of electron beam lithography, allowing individual control of particle size, position, and aspect ratio, and was characterized by atomic force microscopy and scanning electron microscopy before and after reaction. In the experiment, both oxygen and CO rich regimes were investigated using separate molecular beams for the two reactants. This allows exploration of diffusion effects of reactants on the particles and of shadowing and backscattering phenomena. A reaction-diffusion model was developed in order to extract information about local reaction rates on the surface of the catalyst nanoparticles. The model takes into account the structural parameters of the catalyst as well as the backscattering of the reactants and products from the support. It allows a quantitative description of the experimental data and provides a detailed understanding of temperature and reactant flux dependent effects. Moreover, information on the surface mobility of oxygen under steady-state reaction conditions could be obtained by comparison with the experimental results.

Journal Article↗
PubMed2005

Phylogenetic signal in bone microstructure of sauropsids.

In spite of the fact that the potential usefulness of bone histology in systematics has been discussed for over one and a half centuries, the presence of a phylogenetic signal in the variation of histological characters has rarely been assessed. A quantitative assessment of phylogenetic signal in bone histological characters could provide a justification for performing optimizations of these traits onto independently generated phylogenetic trees (as has been done in recent years). Here we present an investigation on the quantification of the phylogenetic signal in the following bone histological, microanatomical, and morphological traits in a sample of femora of 35 species of sauropsids: vascular density, vascular orientation, index of Haversian remodeling, cortical thickness, and cross-sectional area (bone size). For this purpose, we use two methods, regressions on distance matrices tested for significance using permutations (a Mantel test) and random tree length distribution. Within sauropsids, these bone microstructural traits have an optimal systematic value in archosaurs. In this taxon, a Mantel test shows that the phylogeny explains 81.8% of the variation of bone size and 86.2% of the variation of cortical thickness. In contrast, a Mantel test suggests that the phylogenetic signal in histological traits is weak: although the phylogeny explains 18.7% of the variation of vascular density in archosaurs, the phylogenetic signal is not significant either for vascular orientation or for the index of Haversian remodeling. However, Mantel tests seem to underestimate the proportion of variance of the dependent character explained by the phylogeny, as suggested by a PVR (phylogenetic eigenvector) analysis. We also deal with some complementary questions. First, we evaluate the functional dependence of bone vascular density on bone size by using phylogenetically independent contrasts. Second, we perform a variation partitioning analysis and show that the phylogenetic signal in bone vascular density is not a by-product of phylogentic signal in bone size. Finally, we analyze the evolution of cortical thickness in diapsids by using an optimization by squared change parsimony and discuss the functional significance of this character in terms of decreased buoyancy in crocodiles and mass saving in birds. These results are placed in the framework of the constructional morphology model, according to which the variation of a character in a clade has a historical (phylogenetic) component, a functional (adaptive) component, and a structural (architectural) component.

Analysis of Variance↗
PubMed2004

Fluctuations and bistabilities on catalyst nanoparticles.

We show that coverage fluctuations on catalyst particles can drastically alter their macroscopic catalytic behavior. Scrutinizing the occurrence of kinetic bistabilities, it is demonstrated by molecular beam experiments on model catalysts that macroscopically observable bistabilities vanish completely with decreasing particle size, as previously predicted by theory. The effect is attributed to fluctuation-induced transitions between two kinetic reaction regimes, with a transition rate controlled by both particle size and surface defects. These results suggest that fluctuation-induced effects represent a general phenomenon affecting the reaction kinetics on nanostructured surfaces.

Journal Article↗
PubMed2002

Molecular analysis of the stylar-expressed Solanum chacoense small asparagine-rich protein family related to the HT modifier of gametophytic self-incompatibility in Nicotiana.

Gametophytic self-incompatibility (GSI) systems involving the expression of stylar ribonucleases have been described and extensively studied in many plant families including the Solanaceae, Rosaceae and Scrophulariaceae. Pollen recognition and rejection is governed in the style by specific ribonucleases called S-RNases, but in many self-incompatibility (SI) systems, modifier loci that can modulate the SI response have been described at the genetic level. Here, we present at the molecular level, the isolation and characterization of two Solanum chacoense homologues of the Nicotiana HT modifier that had been previously shown to be necessary for the SI reaction to occur in N. alata (McClure et al., 1999). HT homologues from other solanaceous species have also been isolated and a phylogenetic analysis reveals that the HT genes fall into two groups. In S. chacoense, these small proteins named ScHT-A and ScHT-B are expressed in the style and are developmentally regulated during anthesis identically to the S-RNases as well as following compatible and incompatible pollination. To elucidate the precise role of each HT isoform, antisense ScHT-A and RNAi ScHT-B lines were generated. Conversion from SI to self-compatibility (SC) was only observed in RNAi ScHT-B lines with reduced levels of ScHT-B mRNA. These results confirm the role of the HT modifier in solanaceous SI and indicate that only the HT-B isoform is directly involved in SI.

Amino Acid Sequence↗
PubMed2001

The oldest stegocephalian from the Iberian peninsula: evidence that temnospondyls were euryhaline.

The previous fossil record of limbed vertebrates of the Iberian peninsula started in the Triassic (245 Ma). The discovery of a new temnospondyl from the Late Carboniferous (Stephanian C, 290 Ma) extends the fossil record of stegocephalians in this region by at least 45 Ma. Early stegocephalians are usually thought to have been unable to live in salt water, but the new temnospondyl described below appears to have lived in a coastal region, presumably in salt water.

Animals↗
PubMed2001

Molecular evidence for precambrian origin of amelogenin, the major protein of vertebrate enamel.

Although molecular dating of cladogenetic events is possible, no molecular method has been described to date the acquisition of various tissues. Taking into account the specificity of the major protein in enamel in formation (amelogenin), we were able to develop such a method for enamel. Indeed, because the amelogenin protein is exclusively involved in enamel formation and mineralization and because it lacks pleiotropic effects, this protein is a good candidate to estimate the date of acquisition of this highly mineralized tissue. We searched DNA banks for similarities between the amelogenin sequence and other sequences. Similarities were found only to exon 2 of SPARC (osteonectin) in two protostomians and in eight deuterostomians, and to exon 2 of three SPARC-related deuterostomian genes (SC1, hevin, and QR1). The other amelogenin exons did not reveal significant similarities to other sequences. In these proteins, exon 2 mainly encodes the peptide signal that plays the essential role in enabling the protein to be ultimately localized in the extracellular matrix. We tested the significance of the exon 2 similarities. The observed values were always significantly higher than the expected randomly generated similarities. This demonstrates a common evolutionary origin of this exon. The phylogenetic analyses of exon 2 sequences indicated that exon 2 was duplicated to amelogenin from an ancestral SPARC sequence in the deuterostomian lineage before the duplication of deuterostomian SPARC and SC1/hevin/QR1. We were able to date the origin of the latter duplication at approximately 630 MYA. Therefore, amelogenin exon 2 was acquired before this date, in the Proterozoic, long before the so-called "Cambrian explosion," the sudden appearance of several bilateralian phyla in the fossil record at the Proterozoic-Phanerozoic transition. This sudden appearance has been often suggested to reflect intensive cladogenesis during this period. However, molecular dating of protostomian-deuterostomian divergence and of the cladogenesis among several major clades of Bilateralia lead to a different conclusion: many bilateralian clades were already present during the late Proterozoic. It has previously been proposed that these bilateralians were not mineralized and that they had low fossilization potential. Our results strongly suggest that late Proterozoic fossils possessing a mineralized tissue homologous to enamel might be found in the future.

Amelogenin↗
PubMed2000

Arm morbidity after breast-conserving therapy for breast cancer.

This study reports on 110 consecutive patients, mean age 59 years, operated on for partial mastectomy and axillary dissection. Radiotherapy of 50 Gy was administered to 75 of the patients. Most tumours were T1 tumours and all patients were NO. Lymphoedema is defined as an increase in arm volume > 10% and impaired shoulder mobility as an impairment of 15 degrees compared with the preoperative value. After operation, 21 patients developed lymphoedema, 17 in the radiotherapy group and 4 in the group without radiotherapy; 49% of the patients had reduced shoulder mobility, and of these, 57% were in the radiotherapy group and 30% in the group without radiotherapy. We found a good correlation between the number of patients stating arm swelling and patients with registered lymphoedema. There were fewer patients stating limitation of movement than patients with registered impaired mobility; 31% of patients were still perceiving some pain five years after the operation. We conclude, that breast-conserving therapy in breast cancer is afflicted with a significant arm morbidity that persists for several years after surgery.

Adult↗
PubMed1999

[Problems with arms are common after breast surgery. Lymphedema is a frequent complication in elderly women treated for breast cancer].

75 women aged 70 years or more at the time of operation for breast carcinoma were monitored regarding arm morbidity; median follow-up was three years. 19 women (25%) developed lymphedema; of these, nine belonged to a group of 12 that had undergone both modified radical mastectomy and postoperative radiotherapy. Of this group of 12, ten had impaired arm mobility. Approximately 30% of those with lymphedema had not been identified at routine follow-up, while 20% reported moderate to severe pain. 15 of the 75 reported numbness and pricking sensations in the arm; of these, only one had lymphedema, while six had impaired arm mobility. Having thus found that a substantial number of elderly women experience complications in the upper extremity after primary treatment for breast carcinoma, we feel it essential to consider these factors when planning treatment protocols.

Aged↗
PubMed1998

Evolutionary analysis of "hagfish amelogenin".

Hagfishes lack mineralized tissues and teeth. Part of a cDNA strand, allegedly from amelogenin, the major gene involved in enamel formation in mammals, has recently been cloned in a hagfish (Slavkin and Diekwish, Anat. Rec., 1996;245:131-150). This cloning is of great interest because it could change the current view about the evolution of mineralized tissues, but no phylogenetic analysis of this piece of DNA has been made by the authors. Phylogenetic analysis of this part of cDNA has been conducted using both phenetic and cladistic methods. The cDNA amplified in hagfish does not fit with a nonmammalian origin but fits well with a degraded rodent sequence. The gene cloned in hagfish is probably of mammalian origin due to contamination during PCR.

Algorithms↗
PubMed1997

Identification of caries risk children and prevention of caries in pre-school children.

A special model for dental care in pre-school children was used in a small clinic in the county of Blekinge in southern Sweden. The model is based on screening of caries risk performed by a dental assistant before the caries attack. Any single risk factor or risk behavior in pre-school children was considered. The aim was to 1) evaluate the dental assistant's selection of caries risk children up to the age of three years, 2) compare dental health variables in 4 yr olds in the test clinic with those for the whole county in 1994 and 3) compare time spent by the dentist and the dental assistant in the test clinic and in the whole county per child up to the age of four. 102 children participated. One specially trained dental assistant screened all children using background factors combined with clinical examinations at ages 1, 2 and 3. Eighty-two children participated each year from one year. A systematized form for questioning the parents was used. Individual caries prevention was given including fluoride and antimicrobial treatments as well as fissure sealants in primary molars at caries risk. The proportion of children with caries lesions at four years and a caries risk assessment up to the age of two was 1.0 (sensitivity). The proportion of children with no caries lesions at four years and no caries risk assessment at year two was 0.7 (specificity). The most frequent risk factors found at 2 yrs were frequency order: lack of oral hygiene (visible plaque), deep fissures in molars and frequent intakes of sweet drinks. The proportion of children with no caries lesions at 4 yrs of age in the test clinic was 92.9% compared to a county mean of 76.4%. In the group of children where a risk assessment was made each year from one year the proportion of caries free children was 96.3%. The total time spent per child in the test clinic was 22 minutes more than the county mean. However, dentist's time, excluding assistance, was 28 minutes less in the test clinic. The results suggest that the model used for caries prevention in pre-school children is cost-effective, and that dental health can be remarkably improved.

Anti-Infective Agents↗
PubMed1985

[Infectious mononucleosis and splenic pseudocyst: presentation of a case].

The authors report the clinical case of an 18-year-old patient who presented with a symptomatic mass in the left upper quadrant 6 months after having infectious mononucleosis. The preoperative investigation consisted principally of echography and computerized axial tomography of the abdomen, which demonstrated a cystic mass of the lower pole of the spleen. Splenectomy was carried out. Histologic examination showed a pseudocyst of the spleen with a fibrous capsule without an epithelial lining. The treatment and pathogenesis of pseudocysts of the spleen secondary to infectious mononucleosis are discussed.

Adolescent↗
PubMed1984

Sympathetic uveitis 66 years after injury.

We report a case of sympathetic uveitis occurring 66 years after perforating trauma to the other eye. To our knowledge this is the longest interval ever cited in the literature.

Aged↗