Biomedical subjects

C Landry

Publications and source records attributed to C Landry.

At least 19 recordsLinked to original sources

PubMed2004

Effects of gamma- and hydroxypropyl-gamma-cyclodextrins on the transport of doxorubicin across an in vitro model of blood-brain barrier.

Association between doxorubicin (DOX) and gamma-cyclodextrin (gamma-CD) or hydroxypropyl-gamma-CD (HP-gamma-CD) has been examined to increase the delivery of this antitumoral agent to the brain. The stoichiometry and the stability constant of gamma-CD or HP-gamma-CD and DOX complexes were determined in physiological medium by UV-visible spectroscopy. By using an in vitro model of the blood-brain barrier (BBB), endothelial permeability and toxicity toward the brain capillary endothelial cells of DOX, gamma-CD, and HP-gamma-CD were performed. For each CD, endothelial permeability was relatively low and a disruption of the BBB occurred at 20 microM, 20 mM, and 50 mM DOX, gamma-CD, and HP-gamma-CD, respectively. Increasing amounts of CDs were added to a fixed DOX concentration. Addition of gamma-CD or HP-gamma-CD, up to 15 and 35 mM, respectively, decreased the DOX delivery, probably due to the low complex penetration across the BBB and the decrease in free DOX concentration. Higher CD concentrations increased the DOX delivery to the brain, but this effect is due to a loss of BBB integrity. In contrast to what was observed on Caco-2 cell model with various drugs, CDs are not able to increase the delivery of DOX across our in vitro model of BBB.

ATP Binding Cassette Transporter, Subfamily B↗

PubMed2004

Transport screening of drug cocktails through an in vitro blood-brain barrier: is it a good strategy for increasing the throughput of the discovery pipeline?

PURPOSE: The objective of the current study was to investigate whether blood-brain barrier (BBB) permeability studies in vitro could be accelerated by running several compounds together in the same experiment. METHODS: To address this question, we compared the transport of six compounds run separately with the results of the same compounds run together (cocktails). RESULTS: The study clearly demonstrated that the outcome of the experiments were totally different depending on the strategy used. Furthermore, the study highlights the importance of having the resistance to drug transport offered by filters without cells under control, as the filter membrane itself can be the rate-limiting step for some compounds; in addition, there is always a potential risk of interactions between molecules in cocktails as well as drug-drug interaction at the level of BBB transporters. In this study, the presence of several P-glycoprotein substrates in the drug cocktail was found to cause breakdown of the BBB. CONCLUSIONS: The results demonstrate that unless a strategy that involves running several compounds in the same experiment is properly validated, the results are of little predictive value.

ATP Binding Cassette Transporter, Subfamily B↗

PubMed2003

Recent speciation in the Indo-West Pacific: rapid evolution of gamete recognition and sperm morphology in cryptic species of sea urchin.

The rich species diversity of the marine Indo-West Pacific (IWP) has been explained largely on the basis of historical observation of large-scale diversity gradients. Careful study of divergence among closely related species can reveal important new information about the pace and mechanisms of their formation, and can illuminate the genesis of biogeographic patterns. Young species inhabiting the IWP include urchins of the genus Echinometra, which diverged over the past 1-5 Myr. Here, we report the most recent divergence of two cryptic species of Echinometra inhabiting this region. Mitochondrial cytochrome oxidase 1 (CO1) sequence data show that in Echinometra oblonga, species-level divergence in sperm morphology, gamete recognition proteins and gamete compatibility arose between central and western Pacific populations in the past 250 000 years. Divergence in sperm attachment proteins suggests rapid evolution of the fertilization system. Divergence of sperm morphology may be a common feature of free-spawning animals, and offers opportunities to simultaneously understand genetic divergence, changes in protein expression patterns and morphological evolution in traits directly related to reproductive isolation.

Animals↗

PubMed2003

MHC studies in nonmodel vertebrates: what have we learned about natural selection in 15 years?

Elucidating how natural selection promotes local adaptation in interaction with migration, genetic drift and mutation is a central aim of evolutionary biology. While several conceptual and practical limitations are still restraining our ability to study these processes at the DNA level, genes of the major histocompatibility complex (MHC) offer several assets that make them unique candidates for this purpose. Yet, it is unclear what general conclusions can be drawn after 15 years of empirical research that documented MHC diversity in the wild. The general objective of this review is to complement earlier literature syntheses on this topic by focusing on MHC studies other than humans and mice. This review first revealed a strong taxonomic bias, whereby many more studies of MHC diversity in natural populations have dealt with mammals than all other vertebrate classes combined. Secondly, it confirmed that positive selection has a determinant role in shaping patterns of nucleotide diversity in MHC genes in all vertebrates studied. Yet, future tests of positive selection would greatly benefit from making better use of the increasing number of models potentially offering more statistical rigour and higher resolution in detecting the effect and form of selection. Thirdly, studies that compared patterns of MHC diversity within and among natural populations with neutral expectations have reported higher population differentiation at MHC than expected either under neutrality or simple models of balancing selection. Fourthly, several studies showed that MHC-dependent mate preference and kin recognition may provide selective factors maintaining polymorphism in wild outbred populations. However, they also showed that such reproductive mechanisms are complex and context-based. Fifthly, several studies provided evidence that MHC may significantly influence fitness, either by affecting reproductive success or progeny survival to pathogens infections. Overall, the evidence is compelling that the MHC currently represents the best system available in vertebrates to investigate how natural selection can promote local adaptation at the gene level despite the counteracting actions of migration and genetic drift. We conclude this review by proposing several directions where future research is needed.

Animals↗

PubMed2002

Influence of the embryonic preplate on the organization of the cerebral cortex: a targeted ablation model.

Transgenic mice were generated to permit the targeted ablation of cortical preplate cells at the time they are born. In these mice, the 1.3 kb golli promoter of the myelin basic protein gene was used to drive the herpes simplex virus thymidine kinase (TK) transgene in cortical preplate cells. Heterozygous transgenic pairs were bred, and pregnant dams were treated with ganciclovir at embryonic days 11-12 to ablate preplate cells at the time the preplate was forming. This paradigm exposed control (TK-) and experimental (TK+) littermates to exactly the same conditions. Embryological ablation of preplate cells led to an early disruption of the radial glial framework and subplate structure in the developing cortex and dramatically altered the cellular lamination and connectivity of the cortical plate. The disturbed radial glial network contributed to an impaired radial migration of neurons into the cortical plate from the ventricular zone. The cortical plate became dyslaminated, and there was a substantial reduction in short- and long-range cortical projections within the cortex and to subcortical regions. Cell death within the cortical plate and the proliferative zones was substantially increased in the ablated animals. After birth, a cortical lesion developed, which became exacerbated with the secondary onset of hydrocephaly in the second postnatal week. The results underscore the critical importance of the preplate in cortex formation, mediated through its guidance of the formation of radial glial scaffolding, subsequent neuronal migration into the incipient cortical plate, and the final arrangement of its vertical organization and cellular connectivity.

Animals↗

PubMed2001

A monoclonal cytolytic T-lymphocyte response observed in a melanoma patient vaccinated with a tumor-specific antigenic peptide encoded by gene MAGE-3.

Vaccination of melanoma patients with tumor-specific antigens recognized by cytolytic T lymphocytes (CTL) produces significant tumor regressions in a minority of patients. These regressions appear to occur in the absence of massive CTL responses. To detect low-level responses, we resorted to antigenic stimulation of blood lymphocyte cultures in limiting dilution conditions, followed by tetramer analysis, cloning of the tetramer-positive cells, and T-cell receptor (TCR) sequence analysis of the CTL clones that showed strict specificity for the tumor antigen. A monoclonal CTL response against a MAGE-3 antigen was observed in a melanoma patient, who showed partial rejection of a large metastasis after treatment with a vaccine containing only the tumor-specific antigenic peptide. Tetramer analysis after in vitro restimulation indicated that about 1/40,000 postimmunization CD8(+) blood lymphocytes were directed against the antigen. The same TCR was present in all of the positive microcultures. TCR evaluation carried out directly on blood lymphocytes by PCR amplification led to a similar frequency estimate after immunization, whereas the TCR was not found among 2.5 x 10(6) CD8(+) lymphocytes collected before immunization. Our results prove unambiguously that vaccines containing only a tumor-specific antigenic peptide can elicit a CTL response. Even though they provide no information about the effector mechanisms responsible for the observed reduction in tumor mass in this patient, they would suggest that low-level CTL responses can initiate tumor rejection.

Antigens, Neoplasm↗

PubMed2001

'Good genes as heterozygosity': the major histocompatibility complex and mate choice in Atlantic salmon (Salmo salar).

According to the theory of mate choice based on heterozygosity, mates should choose each other in order to increase the heterozygosity of their offspring. In this study, we tested the 'good genes as heterozygosity' hypothesis of mate choice by documenting the mating patterns of wild Atlantic salmon (Salmo salar) using both major histocompatibility complex (MHC) and microsatellite loci. Specifically, we tested the null hypotheses that mate choice in Atlantic salmon is not dependent on the relatedness between potential partners or on the MHC similarity between mates. Three parameters were assessed: (i) the number of shared alleles between partners (x and y) at the MHC (M(xy)), (ii) the MHC amino-acid genotypic distance between mates' genotypes (AA(xy)), and (iii) genetic relatedness between mates (r(xy)). We found that Atlantic salmon choose their mates in order to increase the heterozygosity of their offspring at the MHC and, more specifically, at the peptide-binding region, presumably in order to provide them with better defence against parasites and pathogens. This was supported by a significant difference between the observed and expected AA(xy) (p = 0.0486). Furthermore, mate choice was not a mechanism of overall inbreeding avoidance as genetic relatedness supported a random mating scheme (p = 0.445). This study provides the first evidence that MHC genes influence mate choice in fish.

Alleles↗

PubMed2001

Factors affecting the sterility of work areas in barrier isolators and a biological safety cabinet.

Factors affecting the sterility of the work area in barrier isolators and a biological safety cabinet (BSC) were studied. A study in a mother-and-child tertiary care teaching hospital in Canada examined the effects of a range of variables on the sterility of work areas in four barrier isolators and a standard BSC. The variables consisted of type of equipment (barrier isolator or BSC), day of the week (Monday through Thursday), time of day (0800-1000, 1000-1200, 1200-1400, and 1400-1600), sampling site (16 surfaces and 5 air sedimentation zones), type of product prepared (antimicrobial, total parenteral nutrient solution, etc.), cleaning procedure (before or after primary cleaning), and level of product preparation activity (none to intense). A total of 657 surface and air sedimentation samples, 327 plated onto Trypticase soy agar (TSA) and 330 onto Sabouraud dextrose agar (SAB-D), were taken during a 20-day period. Thirty-three (5%) of the samples yielded microbial growth when cultured (24 on TSA and 9 on SAB-D). A total of 74 isolates were identified, including Bacillus, Staphylococcus, Penicillium, Micrococcus, Corynebacterium, and Mucor species. Single-variable analysis showed that sampling site, sample type, the time of day samples were taken, and the types of equipment contributed significantly to microbial growth in the samples taken. Several variables were associated with microbial growth in samples from the work areas of barrier isolators and a BSC. More study is needed to compare BSCs and barrier isolators with respect to sterility.

Air↗

PubMed2001

An alternative open reading frame of the human macrophage colony-stimulating factor gene is independently translated and codes for an antigenic peptide of 14 amino acids recognized by tumor-infiltrating CD8 T lymphocytes.

We show that cytotoxic T lymphocytes (CTLs) infiltrating a kidney tumor recognize a peptide encoded by an alternative open reading frame (ORF) of the macrophage colony-stimulating factor (M-CSF) gene. Remarkably, this alternative ORF, which is translated in many tumors concurrently with the major ORF, is also translated in some tissues that do not produce M-CSF, such as liver and kidney. Such a dissociation of the translation of two overlapping ORFs from the same gene is unexpected. The antigenic peptide encoded by the alternative ORF is presented by human histocompatibility leukocyte antigen (HLA)-B*3501 and has a length of 14 residues. Peptide elution indicated that tumor cells naturally present this 14 mer, which is the longest peptide known to be recognized by CTLs. Binding studies of peptide analogues suggest that it binds by its two extremities and bulges out of the HLA groove to compensate for its length.

Amino Acid Sequence↗

PubMed2001

Comparative analysis of population structure across environments and geographical scales at major histocompatibility complex and microsatellite loci in Atlantic salmon (Salmo salar).

Evidence of selection acting on major histocompatibility complex (MHC) genes has been illustrated with the analysis of their nucleotide sequences and allele frequency distribution. Comparing the patterns of population differentiation at neutral markers and MHC genes in the wild may provide further insights about the relative role of selection and neutrality in shaping their diversity. In this study, we combine both methods to assess the role of selection on a MHC gene in Atlantic salmon. We compare variation at a MHC class II B locus and microsatellites among 14 samples from seven different rivers and seven subpopulations within a single river system covering a variety of habitats and different geographical scales. We show that diversifying selection is acting on the sites involved in antigen presentation and that balancing selection maintains a high level of polymorphism within populations. Despite important differences in habitat type, the comparison of the population structure at MHC and microsatellites on large geographical scales reveals a correlation between patterns of differentiation, indicating that drift and migration have been more important than selection in shaping population differentiation at the MHC locus. In contrast, strong discrepancies between patterns of population differentiation at the two types of markers provides support for the role of selection in shaping population structure within rivers. Together, these results confirm that natural selection is influencing MHC gene diversity in wild Atlantic salmon although neutral forces may also be important in their evolution.

Alleles↗

PubMed2000

Monoclonal antibody 57B stains tumor tissues that express gene MAGE-A4.

Monoclonal antibody (Mab) 57B, which was raised against a recombinant MAGE-A3 protein, was tested for its ability to stain cells expressing various members of the MAGE-A gene family. COS-7 cells transfected with cDNAs encoding MAGE-A1, A2, A3, A4, A6, or A12 were stained, whereas those transfected with MAGE-A8, A9, A10, or A11 cDNAs were not. However, in tissue sections, we observed a different pattern of staining: the antibody effectively stained the tumors that expressed MAGE-A4 and only these tumors, regardless of the expression of the other MAGE-A genes. It seems, therefore, that at the level of MAGE gene expression found in tumors, a level clearly lower than that observed in transfected COS cells, only the MAGE-A4 protein can be reliably detected. We conclude that the 57B Mab should be useful for tumor diagnosis related to therapeutic vaccination involving MAGE-A4.

Animals↗

PubMed2000

High frequency of autologous anti-melanoma CTL directed against an antigen generated by a point mutation in a new helicase gene.

We have identified an Ag recognized by autologous CTL on the melanoma cells of a patient who enjoyed an unusually favorable clinical evolution. The antigenic peptide, which is presented by HLA-A28 molecules, is encoded by a mutated sequence in a new gene. This gene, which was named MUM-3, is expressed ubiquitously and shows homology with the RNA helicase gene family. Limiting dilution analysis indicated that at least 0.15% of the blood CD8 T cells were tumor-specific CTL precursors. The MUM-3 Ag was recognized by 90% of these CTL, indicating that it is the dominant target Ag of the tumor-specific CTL response. The high frequency of anti-MUM-3 CTL was confirmed with tetramers of soluble HLA-A28 molecules loaded with the antigenic peptide. MUM-3 tetramers stained 1.2% of blood CD8 cells, a frequency that has never been reported for T cells directed against a strictly tumor-specific Ag. To confirm these results, the CD8 T cells that were clearly labeled with tetramers were restimulated in clonal conditions. About 90% of these cells proliferated, and all the resulting clones proved lytic and MUM-3 specific. By improving the conditions used for the in vitro restimulation of CTL precursors by the tumor cells, the same frequency could be obtained in limiting dilution analysis. These results show that some cancer patients have a high frequency of circulating CTL that are directed against a strictly tumor-specific Ag. These CTL are responsive to restimulation in vitro and are easily detected with tetramers. Such responses may therefore be an achievable goal for therapeutic vaccination with tumor-specific Ags.

Amino Acid Sequence↗

PubMed2000

3D reconstruction method from biplanar radiography using non-stereocorresponding points and elastic deformable meshes.

Standard 3D reconstruction of bones using stereoradiography is limited by the number of anatomical landmarks visible in more than one projection. The proposed technique enables the 3D reconstruction of additional landmarks that can be identified in only one of the radiographs. The principle of this method is the deformation of an elastic object that respects stereocorresponding and non-stereocorresponding observations available in different projections. This technique is based on the principle that any non-stereocorresponding point belongs to a line joining the X-ray source and the projection of the point in one view. The aim is to determine the 3D position of these points on their line of projection when submitted to geometrical and topological constraints. This technique is used to obtain the 3D geometry of 18 cadaveric upper cervical vertebrae. The reconstructed geometry obtained is compared with direct measurements using a magnetic digitiser. The order of precision determined with the point-to-surface distance between the reconstruction obtained with that technique and reference measurements is about 1 mm, depending on the vertebrae studied. Comparison results indicate that the obtained reconstruction is close to the actual vertebral geometry. This method can therefore be proposed to obtain the 3D geometry of vertebrae.

Cervical Vertebrae↗

PubMed1999

APH-1, a POU homeobox gene expressed in the salt gland of the crustacean Artemia franciscana.

We characterized the first POU-homeoprotein in a crustacean (designated APH-1 for Artemia POU-Homeoprotein, EMBL Y15070). The amino acid sequence of the APH-1 POU-domain is identical, except for two residues, to that of the two class III POU proteins Cf1-a (Drosophila) and POU-M1 (Bombyx mori). Southern blot analysis suggests that crustaceans have only one class III POU gene. RT-PCR and whole-mount in situ hybridization show that APH-1 mRNA is present in larvae specifically in the salt gland, an organ which is involved in osmoregulation, and disappears in the adult.

Amino Acid Sequence↗

PubMed1999

Comparison between a short and a conventional blade periodontal curet: an in vitro study.

This in vitro study was done to compare a short-blade, long-shank (test) curet designed for deeper pockets of incisors and a conventional Gracey 1/2 curet regarding (a) their ability to remove root surface material at different pocket depths, and (b) their effect on root surface roughness. 2 groups of 12 senior dental hygiene students used either the randomly assigned test or conventional curet for a defined period on maxillary and mandibular incisors in a cross-over experimental design. Extent of root debridement was determined by assessing the removal of black enamel paint on root surfaces within pockets using a computerized video routine and root surface roughness measured using a profilometer. When each surface of the root was analyzed separately at 2-mm increments, the test instrument exhibited superior material removal on all surfaces at the 4-6 mm CAL (p-values<0.001). However, the test curet caused a rougher surface than the conventional curet on all surfaces (p<0.001), with a mean difference of 0.27 microm. While it is assumed that the ability of the test instrument to debride the root surface of deeper pockets more thoroughly is clinically more important than the rougher root surfaces it produces, this can only be assessed by further studies in vivo.

Analysis of Variance↗

PubMed1999

[Overuse of psychotropic drugs in seniors].

Seniors take three times as many drugs as the general population and are the group most vulnerable to the adverse effects of drug therapy. For this reason, it is extremely important that they receive support to help them understand and manage their medications. To highlight the major problems in managing medication, determine the risk factors and prevent overdosing of psychotropic drugs in seniors, the authors carried out a study of 549 senior rural residents living at home. The study findings indicate that 19 per cent of people aged 65 or over take no drugs at all, while 24 per cent have five prescriptions or more. Two thirds of respondents (65.7%) who had only one prescription were well informed about their medication, compared with just 14 per cent of those taking five drugs or more. One quarter (27%) said they never received information about their prescription, while 17.3 per cent reported that the labels on their prescription bottles were useless because the print was too small, too pale or because they could not read them. Close to half the respondents (42.6%) reported occasionally forgetting whether they had taken their medication. The findings also indicate that the respondents' sex, their perception of their personal state of health, the population density, and the depression index are all major variables that significantly relate to use of psychotropic drugs. All of the findings identify the specific needs of seniors and suggest a focus for nursing intervention.

Aged↗

PubMed1998

Functional analysis of the Numb phosphotyrosine-binding domain using site-directed mutagenesis.

The Numb protein is involved in cell fate determination during Drosophila neural development. Numb has a protein domain homologous to the phosphotyrosine-binding domain (PTB) in the adaptor protein Shc. In Shc, this domain interacts with specific phosphotyrosine containing motifs on receptor tyrosine kinases and other signaling molecules. Residues N-terminal to the phosphotyrosine are also crucial for phosphopeptide binding to the Shc PTB domain. Several amino acid residues in Shc have been implicated by site-directed mutagenesis to be critical for Shc binding to receptor tyrosine kinases. We have generated homologous mutations in Numb to test whether, in vivo, these changes affect Numb function during Drosophila sensory organ development. Two independent amino acid changes that interfere with Shc binding to phosphotyrosine residues do not affect Numb activity in vivo. In contrast, a mutation shown to abrogate the ability of the Shc PTB domain to bind residues upstream of the phosphotyrosine virtually eliminates Numb function. Similar results were observed in vitro by examining the binding of the Numb PTB domain to proteins from Schneider S2 cells. Our data confirm the importance of the PTB domain for Numb function but strongly suggest that the Numb PTB domain is not involved in phosphotyrosine-dependent interactions.

Amino Acid Sequence↗

PubMed1998

Postnatal localization and morphogenesis of cells expressing the dopaminergic D2 receptor gene in rat brain: expression in non-neuronal cells.

The cellular localization of the dopaminergic D2 receptor (D2R) mRNA and protein was determined during postnatal development, from birth to 35 days, in the rat neostriatum by in situ hybridization histochemistry and immunohistochemistry. To localize and identify more precisely the morphology of cells expressing the D2R mRNA, nonradioactive, digoxigenin in situ hybridization was performed. Throughout this period of development, D2R mRNA and protein were widely expressed by neostriatal cells, adjoining forebrain cells and small cellular processes. Within morphologically identifiable neurons, the expression of the D2 receptor appeared to occur after cell division ceased. D2R gene expression appeared during neuronal migration and followed the developmental pattern of neuronal settling within the neostriatum. Both D2R mRNA and protein appeared to colocalize in neostriatal cells and the labeling of both appeared to accumulate within the cells progressively with age. The structural phenotypes of neostriatal neurons bearing D2R mRNA and protein were diverse throughout postnatal development. The most frequently stained cells were a heterogeneous group of medium spiny and aspiny neurons. Large cells corresponding to aspiny neurons were less frequently stained. Both phenotypes exhibited considerable postnatal growth of their cell bodies. In addition to neurons, other cell types were also observed to express the D2R mRNA and protein over the developmental period studied. These other cells included patches of ciliated ependymal cells lining the lateral ventricles and many interfascicular oligodendroglia of forebrain fiber tracts. These results demonstrate the unexpected expression of the dopaminergic D2 receptor in non-neuronal cells within the brain. They provide a novel morphologic suggestion that the dopaminergic D2 receptor may support unrecognized, nonsynaptic functions in specific non-neuronal cell populations in the nervous system.

Animals↗