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Biomedical subjects

C Lavallée

Publications and source records attributed to C Lavallée.

12 recordsLinked to original sources
PubMed1991

Interactions of copolymeric poly(glyceryl methacrylate)-collagen hydrogels with neural tissue: effects of structure and polar groups.

In a previous study we developed copolymeric glyceryl methacrylate-collagen hydrogels for implantation in surgical lesions of the rat brain. Such materials provide porous matrices that can serve as support systems for oriented growth of scar tissue and axonal growth. In the present work, we have investigated the effect of structural modifications (studied by mercury porosimetry) of polymeric matrices and the effect of polar groups on the response of the brain tissue. The findings show that the fractional porosity and the pore size distribution of matrices are critical for tissue ingrowth and that negative charges, i.e. carboxylic acid groups, incorporated in the polymer have a strong influence on reactive astrocytosis.

Animals↗
PubMed1990

Intracerebral implantation of synthetic polymer/biopolymer matrix: a new perspective for brain repair.

Various poly (2-hydroxyethyl methacrylate)-collagen and poly (glyceryl methacrylate)-collagen composite hydrogels with varying porosities and cross-linking densities were implanted into the cortex of adult rat brains to provide mechanical guiding substrates for wound healing and tissue ingrowth. The hydrogels were well tolerated by the neural tissue. After 2 and 3 month, hyper- and macroporous hydrogels (poly(glyceryl methacrylate)) with interconnected channel systems were penetrated by neural tissue and elements of extracellular matrices, with differences in the degree and the topographic patterning of tissue ingrowth according to the type of samples. These differences were ascribed to the geometry, size of the pore interconnections and the mechanical properties of the polymers. Hyper- and microporous hydrogels (poly(2-hydroxyethyl methacrylate)) and hydrogels without collagen were not penetrated by the host tissue. The compatibility of the polymers with the neural tissue was also tested in vitro. This study suggests a new approach to repair brain lesions consisting of loss of tissue volume.

Animals↗
PubMed1990

The eastern Cree bush-kit program evaluation; its usefulness.

In 1982 the Cree Board of Health and Social Services of James Bay in northern Quebec created the bush-kit program to provide hunters and trappers with the technical skills to handle medical problems in the bush. A formative evaluation of the program revealed a decrease in calls and in medical evacuations from the bush and high levels of satisfaction among the participants, health professionals and community leaders. However, specific service accessibility problems were identified at the time of the evaluation as indicated by participation rates of only 50% of the targeted hunters and trappers. These findings as well as discussions with bush-kit administrators led to subsequent improvements in the program and an increased participation rate the following year.

Community Health Workers↗
PubMed1989

A simplified method for the characterization of nuclear polyhedrosis virus genomes.

A simplified restriction endonuclease analysis procedure is described which allows the characterization of baculovirus DNA obtained directly from a single larvae without purification of virus. This rapid method was used to demonstrate the genomic stability of nuclear polyhedrosis viruses (NPVs) from Agrotis segetum, Euxoa messoria and Mamestra brassicae after several passages in Euxoa scandens.

Animals↗
PubMed1988

Molecular cloning and characterization of cytoplasmic polyhedrosis virus polyhedrin and a viable deletion mutant gene.

The double-stranded RNA genome of Bombyx mori cytoplasmic polyhedrosis virus (CPV) was converted to double-stranded DNA and cloned into plasmid pBR322. The complete nucleotide sequence of cloned genome segment 10, which encodes virus polyhedrin polypeptide, was determined. The CPV polyhedrin gene consists of 942 based pairs and possesses a long open reading frame that codes for a polypeptide of 248 amino acids (molecular weight, 28,500), consistent with an apparent molecular weight of 28,000 previously determined for purified polyhedrin. No sequence homology was found between CPV polyhedrin and polyhedrins from several nuclear polyhedrosis viruses. In addition to the polyhedrin gene, we completed the sequence analysis of a small deletion mutant gene derived from the polyhedrin gene. This mutant gene consists of two subset domains of the polyhedrin gene, i.e., the 5'-terminal 121 base pairs and the 3'-terminal 200 base pairs. An in vitro transcription demonstrated that the small mutant gene is transcribed by virion-associated RNA polymerases. These data confirm the importance of CPV terminal sequences in virus genome replication.

Amino Acid Sequence↗
PubMed1987

Antibiotic interaction of amoxycillin and clavulanic acid against 132 beta-lactamase positive Haemophilus isolates: a comparison with some other oral agents.

We studied the specific beta-lactamase inhibitory activity of clavulanic acid in association with amoxycillin against 132 beta-lactamase producing Haemophilus isolates. Inhibitory synergy between amoxycillin and clavulanic acid (ratio 2:1) was found in 131/132, partial synergy or antagonism in none; bactericidal synergy was found in 124/131, partial synergy in 4 and antagonism in 1. In comparison, inhibitory synergy between trimethoprim and sulphamethoxazole (ratio 1:19) was found in only 39/104 beta-lactamase positive strains, partial synergy in 42 and antagonism in 3 and bactericidal synergy in 18/104, partial synergy in 8 and antagonism in 3. The amoxycillin-clavulanic acid combination expressed significantly (P less than 0.001) more frequent synergy, at both inhibitory and bactericidal levels, than the trimethoprim-sulphamethoxazole combination. The synergy of amoxycillin-clavulanic acid resulted in a significant decrease of MIC90 (greater than or equal to 32.0-2.0 mg/l) and MBC90 (greater than or equal to 32.0-4.0 mg/l) of amoxycillin; the synergy of trimethoprim-sulphamethoxazole resulted in a significant decrease of MIC90 (8.0-2.0 mg/l) of trimethoprim but did not change MBC90. The amoxycillin-clavulanic acid combination was also more active than cefaclor or erythromycin alone against the 132 beta-lactamase producing strains.

Amoxicillin↗
PubMed1987

Roxithromycin alone and in combination with sulphamethoxazole against Haemophilus influenzae.

Haemophilus influenzae is only moderately susceptible to erythromycin but previous studies in vitro and in vivo have shown that it is fully susceptible when erythromycin is combined with sulphonamides. The purpose of this study was to evaluate whether the activity of the new macrolide antibiotic roxithromycin was improved after combination with sulphamethoxazole. One hundred and eighty fresh clinical isolates of Haemophilus influenzae, comprising 74 ampicillin-susceptible, beta-lactamase negative, and 106 ampicillin-resistant, beta-lactamase positive, strains, were tested for their susceptibility to erythromycin, roxithromycin, sulphamethoxazole, erythromycin-sulphamethoxazole and roxithromycin-sulphamethoxazole in a fixed ratio of 1:19. Bacteriostatic and bactericidal synergy was found between roxithromycin and sulphamethoxazole more commonly than between erythromycin and sulphamethoxazole. Antagonism, was less common between roxithromycin and sulphamethoxazole than erythromycin and sulphamethoxazole. These results suggest that the in-vitro activity of roxithromycin is improved by combination with sulphamethoxazole, making this combination more attractive in the oral therapy of infections due to H. influenzae.

Culture Media↗
PubMed1986

In vitro comparison of ampicillin-chloramphenicol and ampicillin-cefotaxime against 284 Haemophilus isolates.

Since November 1982 at the Sainte-Justine Hospital in Montreal, ampicillin and cefotaxime were used in association as initial treatment (greater than or equal to 48 h) for childhood bacterial meningitis. In this report is described the in vitro interaction of the new regimen in comparison with that of the previous ampicillin-chloramphenicol combination against 284 Haemophilus isolates. Among the 156 ampicillin-susceptible, beta-lactamase-negative isolates, synergy was detected in 13 with ampicillin-cefotaxime, and antagonism was detected in only 1; in contrast, synergy was found in only 2 strains with ampicillin-chloramphenicol, and antagonism was found in 15. These differences were statistically significant (P less than 0.01). Such significant differences were not observed among the 128 ampicillin-resistant, beta-lactamase-positive Haemophilus isolates. The synergy of ampicillin-cefotaxime did not contribute to a decrease of the MIC of cefotaxime for 90% of isolates tested, whereas the antagonism of ampicillin-chloramphenicol did not contribute to increase the MIC of ampicillin for 90% of isolates tested.

Ampicillin↗
PubMedDate not supplied

Intracerebral implantation of ionic synthetic hydrogels: effect of polar substrata on astrocytosis and axons.

In previous studies, hyperporous synthetic hydrogels of poly(glyceryl methacrylate) or p(GMA), containing bioadhesive substrates of collagen, were implanted into rat cerebral tissue in order to provide systems of oriented guidance channels for directing the growth of the scar and axons /28/. In the present study, ionic p(GMA)-collagen hydrogels containing polar chemical groups, either basic amino groups or acidic carboxyl groups, were evaluated for their tolerance and their effects on the brain scarring response and axonal reactivity after long-term implantation in the cerebral cortex. In all animals, the implants were well tolerated. Although both types of gels influenced the astroglial reaction near the bioimplant, hydrogels carrying carboxyl groups had the strongest influence on the elongation, the direction and the organization of astrocytic processes so that a glial matrix could form in regions of the gel. Extracellular material (e.g. reticulin) was also deposited into the gels carrying carboxyl groups. Although cortical nerve fibers in the surrounding tissue showed a regenerative response, extending onto or into the matrices, this behavior seemed to depend more on the organization of the astrocytic scar imposed by the gel than on the type of gel. We conclude that matrices carrying negatively charged groups influence favorably the astrocytosis and the deposition of connective tissue, and that this approach represents a new avenue in attempting to modulate the brain scar formation.

Animals↗
PubMedDate not supplied

Evaluation of a community health representative program among the Cree of northern Quebec.

The James Bay Cree Community Health Representative (CHR) program was implemented in 1984 to train persons from the Cree population of northern Quebec to act as health care advocates and educators, as intermediaries between the Cree population, health services and local organizations, and as participants in assessing health needs. A formative evaluation was initiated which included quantitative analysis of the daily tasks of CHRs and a qualitative component based on documentary research, observation and semi-structured interviews. The evaluation revealed that CHRs actively participated in the ongoing community health programs mainly through health education; the people interviewed showed a high level of satisfaction. However, direct supervision, sufficient continuing education for the CHRs and better integration into health care teams are long-term goals which need to be emphasized in the program.

Attitude of Health Personnel↗