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Biomedical subjects

D Landry

Publications and source records attributed to D Landry.

At least 19 recordsLinked to original sources
PubMed2003

Isolation and characterisation of Nocardioides sp. SP12, an atrazine-degrading bacterial strain possessing the gene trzN from bulk- and maize rhizosphere soil.

We report the characterisation of Nocardioides sp. SP12, an atrazine-degrading bacteria isolated from atrazine-treated bulk- and maize rhizosphere soil. Based on 16S rDNA alignment, strain SP12 showed close phylogenic relationships with Nocardioides sp. C157 and Nocardioides simplex. Internal transcribed spacer (ITS) sequences of strain SP12 were longer than those of other Nocardioides sp. and present Ala- and Ile-tRNA unlike Actinomycetales. Nocardioides sp. SP12 presents a novel atrazine catabolic pathway combining trzN with atzB and atzC. Atrazine biodegradation ends in a metabolite that co-eluted in HPLC with cyanuric acid. This metabolite shows an absorption spectrum identical to that of cyanuric acid with a maximal absorption at 214.6 nm. The mass of the atrazine metabolite is in concordance with that of cyanuric acid according to mass spectrometry analysis. Quantitative PCR revealed that the ITS sequence of Nocardioides sp. SP12 was at a lower number than the one of trzN in atrazine-treated soil samples. It suggests that trzN could also be present in other atrazine degrading bacteria. The numbers of trzN and ITS sequences of Nocardioides sp. SP12 were higher in the maize rhizosphere than in bulk soil.

Actinomycetales↗
PubMed2003

Endometrioid adenocarcinoma of the uterus with a minimal deviation invasive pattern.

AIMS: Minimal deviation adenocarcinoma of endometrioid type is a rare pathological entity. We describe a variant of typical endometrioid adenocarcinoma associated with minimal deviation adenocarcinoma of endometrioid type. METHODS AND RESULTS: One 'pilot' case of minimal deviation adenocarcinoma of endometrioid type associated with typical endometrioid adenocarcinoma was encountered at our institution in 2001. A second case of same type was received in consultation. We reviewed 168 consecutive hysterectomy specimens diagnosed with 'endometrioid adenocarcinoma' specifically to identify areas of minimal deviation adenocarcinoma of endometrioid type. Immunohistochemistry was done with the following antibodies: MIB1, p53, oestrogen receptor (ER), progesterone receptor (PR), cytokeratin 7 (CK7), cytokeratin 20 (CK20), carcinoembryonic antigen (CEA), and vimentin (VIM). Four additional cases of minimal deviation adenocarcinoma of endometrioid type were identified. All six cases of minimal deviation adenocarcinoma of endometrioid type were associated with superficial endometrioid adenocarcinoma. In two cases with a large amount of minimal deviation adenocarcinoma of endometrioid type, the cervix was involved. The immunoprofile of two representative cases was ER+, PR+, CK7+, CK20-, CEA-, VIM+. MIB1 immunostaining of four cases revealed little proliferative activity of the minimal deviation adenocarcinoma of endometrioid type glandular cells (0-1%) compared with the associated 'typical' endometrioid adenocarcinoma (20-30%). The same four cases showed no p53 immunostaining in minimal deviation adenocarcinoma of endometrioid type compared with a range of positive staining in the associated endometrioid adenocarcinoma. CONCLUSIONS: Minimal deviation adenocarcinoma of endometrioid type more often develops as a result of differentiation from typical endometrioid adenocarcinoma than de novo. Due to its deceptively benign microscopic appearance, minimal deviation adenocarcinoma of endometrioid type may be overlooked and may lead to incorrect assessment of tumour depth and pathological stage. There was a tendency for tumour with a large amount of minimal deviation adenocarcinoma of endometrioid type to invade the cervix.

Aged↗
PubMed2003

Controlled release of anti-cocaine catalytic antibody from biodegradable polymer microspheres.

Recent reports have shown that anti-cocaine catalytic monoclonal antibody 15A10 reduces the toxic effect of cocaine by increasing its breakdown to systemically inert products ecgonine methylester and benzoic acid. This study reports the microencapsulation of antibody 15A10 using biodegradable poly (lactic-glycolic) acid (PLGA) by double emulsion technique. Formulation parameters such as protein loading, polymer molecular weight and the presence of zinc carbonate were studied for their effects on in-vitro release of antibody from microspheres. The initial burst release was decreased by the reduction of the protein (as % of total ingredients) in the formulation. Although changing the polymer molecular weight did not cause a reduction in initial burst release, it was effective in improving the release rate. The inclusion of zinc carbonate in microsphere preparation resulted in increase in initial burst release. An in-vivo study in mice revealed the presence of antibody in blood up to ten days following subcutaneous injections. These data demonstrate a potential for a sustained-release formulation of monoclonal antibody 15A10 for treatment of cocaine addiction.

Animals↗
PubMed2002

Pagetoid variant of actinic keratosis with or without squamous cell carcinoma of sun-exposed skin: a lesion simulating extramammary Paget's disease.

BACKGROUND: Extramammary Paget's disease usually occurs in anogenital skin. We present five cases of squamous cell carcinoma in situ of sun-exposed skin and non-squamous cell carcinoma in situ actinic keratosis that displayed atypical keratinocytes disposed in intraepithelial cell nests and immunohistochemical staining simulating extramammary Paget's disease. METHODS AND RESULTS: Two pilot cases--one squamous cell carcinoma in situ and one non-squamous cell carcinoma in situ actinic keratosis with formation of intra-epidermal nests of atypical keratinocytes with a pagetoid spread pattern--were encountered at our institution. Fifty-four consecutive cases of squamous cell carcinoma in situ including bowenoid actinic keratosis and 34 cases of non-squamous cell carcinoma in situ actinic keratosis were reviewed to identify pagetoid spread of atypical cells. Representative sections of all cases with pagetoid spread of atypical keratinocytes were submitted for special stains for mucin, and immunostaining for cytokeratin 7 (CK7), cytokeratin 20 (CK20), cytokeratin CAM 5.2 (CAM 5.2), carcinoembryonic antigen (CEA), vimentin and S100 protein. In the group of squamous cell carcinoma in situ, 10 cases displayed pagetoid spread of atypical keratinocytes with cytoplasm ranging from clear to pale and atypical hyperchromatic nuclei. One review squamous cell carcinoma in situ was multicentric with three separate lesions. The atypical keratinocytes tended to form well to poorly defined cell groups extending from the basal cell layer to the corneal layer. No similar cases were identified in the group of non-squamous cell carcinoma in situ actinic keratosis. Two pilot cases and three of 10 review cases with a total of seven separate lesions displayed a moderate to marked immunohistochemical reactivity for CK7 similar to extramammary Paget's disease. CEA immunoreactivity was also detected in two of these cases. In addition, two of 44 squamous cell carcinomas in situ without pagetoid spread of atypical keratinocytes showed a moderate reactivity for CK7 in very occasional atypical keratinocytes. The remaining seven squamous cell carcinomas in situ with pagetoid spread of atypical keratinocytes were not immunoreactive for CEA and CK7. Immunostaining for CK20, vimentin, S100 protein was negative in all atypical cells in all study cases. CONCLUSIONS: Actinic keratosis, particularly squamous cell carcinoma in situ of sun-exposed skin, may have histopathological and immunohistochemical features similar to extramammary Paget's disease and probably represents a variant of actinic keratosis. Awareness of the pagetoid variant of actinic keratosis arising in sun-exposed skin is helpful to avoid the over-diagnosis of extramammary Paget's disease.

Adult↗
PubMed2001

Penicillin concentrations in serum, milk, and urine following intramuscular and subcutaneous administration of increasing doses of procaine penicillin G in lactating dairy cows.

Eight healthy, non-pregnant, crossbred Holstein dairy cows (557-682 kg) within their first 3 months of lactation (13-21.5 kg of milk/day) were used. Cows were kept in tie stalls for the whole experiment. The 8 cows were randomly assigned to 2 (IM and SC) 4 x 4 balanced Latin square design experiments. Doses of procaine penicillin G (PPG) (300000 IU/mL) in each square were 7000, 14000, 21000 and 28000 IU/kg and were injected IM or SC once daily for 5 consecutive days. Volumes of PPG per site of injection never exceeded 20 mL. Blood was collected to determine the Cmax, Tmax, and AUC; urine and milk were also taken to measure the persistence of PPG in these fluids. Results show that serum Cmax and Tmax were only slightly affected by increasing the doses or the route of administration, whereas the AUC was linearly increased in relation to the dose injected in both modes of injection. In the urine, Cmax varied from 160 to 388 IU/mL and Tmax from 72-120 h during 5 consecutive days of PPG injection. A dose effect in Cmax was observed only for the IM route of administration and no variation (P > 0.05) was found between the IM and SC routes. Milk Cmax concentrations were only increased by the dose regimen in the IM group. At doses of 21000 and 28000 IU/kg, the IM group had a higher (P > 0.05) Cmax when compared with the SC groups. Milk PPG residues were not detectable over 96 h following the last IM injection, independently of the dose injected. However milk PPG residues were detected for up to 132 h following the last SC injection. These results show that when PPG is injected IM once daily in volumes not exceeding 20 mL/site at doses as high as 28000 IU/kg, the withdrawal period should be at least 96 h. Therefore, in the present model, there was no advantage to inject PPG by SC route to improve PPG kinetic parameters as the AUC, Cmax, or Tmax.

Animals↗
PubMed2000

Renal blood flow regulation, autoregulation, and vasomotor nephropathy.

Renal blood flow and renal perfusion pressure are regulated by two control mechanisms. The first, extrinsic, actually involves a complex interaction of vasomotor effects between opposing neurohormonal systems. The second, intrinsic mechanism, renal autoregulation, depends on changes in afferent arteriolar tone in response to the renal perfusion pressure itself. This article reviews these two mechanisms, how they normally respond to stress, and the clinical implications of certain situations in which these control mechanisms are disrupted.

Cardiopulmonary Bypass↗
PubMed1997

Human thymic dendritic cells.

ABSTRACT Human thymic dendritic cells (DC) represent a member of the bone marrow-derived dendritic cell family. They have a dendritic shape and are found in small numbers mainly at the corticomedullary border and in medullary regions of the thymus. Human thymic DC were isolated by density gradient separation, followed by treatment with CD2, CD7, CD1, and CD11b mAb and immunobeads magnetic separation. The resulting population contains 60-75% brightly HLA-DR+ cells which present the morphological characteristics of DC observed in situ. Extensive phenotypic analysis confirmed that they are of mesenchymal origin and that some express CD11a and CD54 molecules. Freshly isolated DC do not stain with a wide variety of anti-T-B and -monocyte or -macrophage mAb. However, they acquire the CD1 molecule after a few days in culture. By using a cell sorter we obtained 90-95% of purified human thymic DC. Functional studies have shown that human thymic DC are potent activators in mixed lymphocyte reactions, act as accessory cells in mitogenic thymocyte proliferation, increase the thymocyte proliferative response to a toxin signal, and produce IL-1. They also formed spontaneous physical associations with thymocytes, which raises questions about the implication of DC in differentiation and/or maturation processes of thymocytes.

Dendritic Cells↗
PubMed1997

Single-column purification of free recombinant proteins using a self-cleavable affinity tag derived from a protein splicing element.

A novel protein purification system has been developed which enables purification of free recombinant proteins in a single chromatographic step. The system utilizes a modified protein splicing element (intein) from Saccharomyces cerevisiae (Sce VMA intein) in conjunction with a chitin-binding domain (CBD) from Bacillus circulans as an affinity tag. The concept is based on the observation that the modified Sce VMA intein can be induced to undergo a self-cleavage reaction at its N-terminal peptide linkage by 1,4-dithiothreitol (DTT), beta-mercaptoethanol (beta-ME) or cysteine at low temperatures and over a broad pH range. A target protein is cloned in-frame with the N-terminus of the intein-CBD fusion, and the stable fusion protein is purified by adsorption onto a chitin column. The immobilized fusion protein is then induced to undergo self-cleavage under mild conditions, resulting in the release of the target protein while the intein-CBD fusion remains bound to the column. No exogenous proteolytic cleavage is needed. Furthermore, using this procedure, the purified free target protein can be specifically labeled at its C-terminus.

Affinity Labels↗
PubMed1996

In vitro characterization of purified human thymic dendritic cells infected with human immunodeficiency virus type 1.

In the thymus, dendritic cells (DC) are functionally associated with thymocytes and are recognized to play a major role in the intrathymic differentiation of T cells. Several studies have previously investigated the role of DC during HIV-infection, but the status of thymic DC in HIV-1 pathogenesis remains unclear. In this study, we investigated the susceptibility of purified human thymic DC to HIV-1 infection in vitro. HIV-1 was not detected in cell-free supernatants collected from HIV-infected DC. However, these cultures were shown to transmit HIV-1 infection since coculture with permissive MT4 cells resulted in virus production. The exposure of DC in culture to HIV-1 was shown to promote severe DC morphological changes and killing. We also found that one or several heat labile soluble cytotoxic agents present in the HIV-1-infected DC supernatant mediated the killing of thymocytes. Our observations raise the possibility that (1) the HIV-1-induced DC killing, (2) the capacity of DC to transmit viral infection, and/or (3) the release of HIV-1-mediated cytotoxic agent(s) from DC may contribute to AIDS pathogenesis in vivo.

Animals↗
PubMed1996

The role of catecholamines in cocaine toxicity: a model for cocaine "sudden death".

Sudden death associated with cocaine abuse is preceded by a state of agitated delirium. We postulated that release of catecholamines associated with this stress enhanced toxicity from cocaine. Thus we investigated the effect of catecholamine infusion [(epinephrine (7.25 ugml-1), norepinephrine (4.4 ugml-1) and dopamine (8.0 ugml-1), infused at 6 ml h-1] on the toxicity from concomitant infusion of cocaine (1 mg-kg-1 min-1). Two groups of rats were studied in order to isolate distinct toxicity endpoints: convulsions and respiratory arrest in conscious, and, circulatory arrest in anesthetized and ventilated rats. Catecholamines were administered at either full or 1/2 strength to establish a dose response effect on cocaine toxicity. Catecholamine infusion in a dose dependent fashion provoked earlier convulsions and respiratory arrest in conscious rats and circulatory arrest in anesthetized and ventilated rats. Despite lower cocaine cumulative dose administration, rats receiving catecholamines had similar plasma cocaine concentrations at the onset of convulsions and respiratory arrest compared to those with cocaine infusion alone. The data suggest that catecholamines enhance the convulsive, respiratory and circulatory toxicity of cocaine by a pharmacokinetic interaction.

Animals↗
PubMed1995

Molecular characterization of a cyclosporin A-insensitive cyclophilin from the parasitic nematode Brugia malayi.

The cyclophilins are a family of proteins that exhibit peptidyl-prolyl cis-trans isomerase (PPIase, EC 5.2.1.8) activity and bind the immunosuppressive agent cyclosporin A (CsA) to varying degrees. We have isolated a cDNA clone encoding a novel cyclophilin from the human filarial parasite Brugia malayi. This gene possesses an N-terminal domain homologous to cyclophilins from diverse phyla (49-60% amino acid sequence identity) and a hydrophilic C-terminal domain. The cyclophilin domain was overexpressed in Escherichia coli and found to possess peptidyl-prolyl cis-trans isomerase (PPIase) activity, with a kcat/Km value of 7.9 x 10(6) M-1 s-1. A histidine residue in lieu of tryptophan in the highly conserved CsA-binding site suggests that B. malayi cyclophilin is more closely related to the cyclophilin-like proteins described recently from natural killer (NK) cells, plants, and the 40 kDa cyclophilins from mammals. In accordance with the histidine-containing CsA-binding domain, the B. malayi enzyme was relatively insensitive to inhibition by CsA, since an IC50 value of 860 nM (compared to 19 nM for human cyclophilin A) was determined.

Amino Acid Isomerases↗
PubMed1995

An improved method for purifying human thymic dendritic cells.

Thymic dendritic cells (DC) play a prominent role in the immune response as they constitute a key element involved in the maturation of thymocytes in the thymus. Human thymic DC, like DC from other lymphoid organs, represent a minor cell population (< 2%) of the thymus. Since these cells cannot replicate in vitro, the development of efficient purification methods is an essential prerequisite for extensive functional studies. DC express high levels of HLA-DR, a cell surface marker of the MHC class II antigen which is not exclusive to DC. Since no specific human thymic DC marker has been identified so far, DC purification methods are mainly based on depletion of particular subgroups of cells. We report here an improved method for purifying human thymic dendritic cells. In contrast to prior work, CD2+ thymocytes were first depleted by rosetting with neuraminidase treated sheep red blood cells. The nonrosetted cells were separated in a Percoll gradient, and the low-density cells were subsequently depleted of nondendritic cells by using thymocyte and macrophage specific monoclonal antibodies and either magnetic bead depletion or cytofluorometry. Cell populations (18-55 x 10(6) cells) obtained following magnetic bead purification were at least 80% HLA-DR+/CD2- and exhibited ultrastructural morphological features and functional activities such as those described previously for thymic DC. This improved method was compared with different purification approaches that use various combinations of cell density-based separation techniques and cell surface specific markers antibody reactivity. The magnetic beads depletion approach provided higher yields.

Antibodies, Monoclonal↗
PubMed1995

Purification and characterization of novel glycosidases from the bacterial genus Xanthomonas.

Enzymatic analysis of oligosaccharides using exoglycosidases has become a powerful tool for determining the sequence and structure of sugar chains. The principal limitation to these methods has been the lack of highly purified and well-characterized enzymes. Using fluorescently labelled carbohydrate substrates and TLC, we have developed a method to identify glycosidases with novel specificities. This screening method led to the discovery that bacteria of the genus Xanthomonas are a rich source of exoglycosidases. From Xanthomonas manihotis, eight novel exoglycosidases have been isolated and characterized. A novel beta-N-acetylglucosaminidase has been purified that, unlike those previously described, will cleave N-acetylglucosamine without cleaving N-acetylgalactosamine residues. A novel beta-galactosidase has been isolated that preferentially hydrolyses beta(1-->3) galactosyl linkages. Three alpha-mannosidases have been isolated that serve as useful reagents in the analysis of high-mannose oligosaccharide structures: alpha 1-3,6 mannosidase, alpha 1-6 mannosidase and alpha 1-2,3 mannosidase. An alpha 1-3,6 galactosidase has been purified that does not hydrolyse terminal alpha 1-4 galactose residues. Two fucosidases, alpha 1-3,4 fucosidase and alpha 1-2 fucosidase, are similar to enzymes purified from other sources. Together, these glycosidases provide powerful reagents for determining the sequence of complex carbohydrates. Equally important is their usefulness in selectively removing specific sugar residues and thereby creating novel carbohydrates for analysing the biological roles of oligosaccharides.

Acetylglucosaminidase↗
PubMed1994

Genetic relatedness of toxic and nontoxic isolates of the marine pennate diatom Pseudonitzschia (Bacillariophyceae): phylogenetic analysis of 18S rRNA sequences.

The nuclear small subunit (SSU) rRNA genes from several marine diatoms, including 2 species that have been responsible for toxic blooms, were amplified from total DNA by the polymerase chain reaction (PCR), and the sequences analysed to determine their genetic relatedness. The isolates investigated include 2 morphologically similar forms of the pennate diatom Pseudonitzschia pungens: (1) P. pungens f. multiseries, a known producer of the toxin domoic acid, and (2) P. pungens f. pungens, which is not toxic. Strains of a second toxin-producing species, P. australis, and a nontoxic Thalassiosira species were also included in this study. Phylogenetic analyses of sequences by both distance and parsimony methods clearly distinguished the 2 forms of P. pungens and the 2 Pseudonitzschia species from other diatoms for which sequence data are available. Differences in the nucleotide sequences of the 2 forms of P. pungens permitted the design of PCR primers that allowed discrimination between them. This may prove a valuable tool in identifying toxic and nontoxic forms of closely related and morphologically similar diatom species.

Base Sequence↗
PubMed1993

Molecular cloning and characterization of p64, a chloride channel protein from kidney microsomes.

Chloride channels were previously purified from bovine kidney cortex membranes using a drug affinity column. Reconstitution of the purified proteins into artificial liposomes and planar bilayers yielded chloride channels. A 64-kDa protein, p64, identified as a component of this chloride channel was used to generate antibodies which depleted solubilized kidney membranes of all chloride channel activity. This antibody has now been used to identify a clone, H2B, from a kidney cDNA library. Antibodies, affinity-purified against the fusion protein of H2B also depleted solubilized kidney cortex from all chloride channel activity. The predicted amino acid sequence of p64 shows that it contains two and possibly four putative transmembrane domains and potential phosphorylation sites by protein kinase A, protein kinase C, and casein kinase II. There was no significant homology to other protein (or DNA) sequences in the data base. The protein is expressed in all cells tested. Expression of its mRNA in Xenopus laevis oocytes led to the insertion of a protein with the appropriate molecular mass in microsomes but not in the plasma membrane. It is likely that p64 represents the chloride channel of intracellular organelles.

Amino Acid Sequence↗
PubMed1993

Brugia malayi and Brugia pahangi: synthetic biotin labeling of oligonucleotide probes for use in species-specific detection assays.

We have developed a novel, high-yield synthetic approach for the incorporation of multiple biotin residues into a series of species-specific oligonucleotide probes for the detection of filarial parasites. The probes are designed to detect species-specific regions of a highly repeated DNA sequence (HhaI repeat) found in all species of Brugia. The synthetic method described in this paper was used to construct oligomer probes tailed on the 5' end with 1 to 46 biotinylated uridine residues. Probes with 46 biotins were found to be more sensitive than probes with 30 or fewer biotins. We also found that alternating the biotinylated uridine residues with nonbiotinylated thymidine residues improved the sensitivity of the probes. Melting temperature studies indicated that the long tails (up to 91 nucleotides) had only a minimal effect on the Tm of the probes. Conditions were found that optimized the sensitivity of the probes while maintaining their species specificity. Using these conditions, the probes were shown to be sensitive enough to detect single parasites in blood using a chemiluminescent detection system. This method of nonradioactively labeling oligonucleotides for the detection of infectious agents will enable the use of such probes in endemic regions in developing countries.

Animals↗