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Biomedical subjects

P Delorme

Publications and source records attributed to P Delorme.

At least 19 recordsLinked to original sources
PubMed1992

In vitro adhesion of human epidermal Langerhans cells to laminin and fibronectin occurs through beta 1 integrin receptors.

Human epidermal Langerhans cells are dendritic cells that can capture, process, and present antigens to T cells. It was previously shown that these Langerhans cells express the very late activation antigen (VLA) protein family of beta 1 integrins. beta 1 integrins mainly mediate the adhesion of cells to a number of extracellular components, such as laminin, fibronectin, and collagen, which are present in the skin. In this report, we demonstrate that a large percentage of the Langerhans cell population was able in vitro to attach to laminin and fibronectin but not to collagen. An ultrastructural study of adherent Langerhans cells showed that they were spread largely on laminin, with a loss of their round shape, and partially on fibronectin. Langerhans cell binding to laminin or fibronectin induced a decrease of the Birbeck granule number. Specific inhibitions of cell adhesion were performed, and it was demonstrated that VLA-6 was the major receptor involved in Langerhans cell adhesion to laminin. This adhesion was not RGD dependent and was slightly enhanced by Mn2+. VLA-3 and especially VLA-5 mediated Langerhans cell binding to fibronectin through the RGDS sequence of the protein. Mn2+ sharply increased the Langerhans cell adhesion to fibronectin. VLA-6 mediated in vitro Langerhans cell adhesion to laminin, which suggests that in vivo VLA-6 could permit Langerhans cells to attach and migrate through the basement membrane. Moreover, VLA-5 and VLA-3 take part in the in vitro Langerhans cell binding to fibronectin, suggesting that in vivo these fibronectin receptors could facilitate Langerhans cell passage throughout the fibronectin network of the dermis before migration to lymph nodes.

Amino Acid Sequence↗
PubMed1992

In vitro HIV-1 entry and replication in Langerhans cells may clarify the HIV-1 genome detection by PCR in epidermis of seropositive patients.

Being dendritic antigen-presenting cells in skin and mucous membrane, Langerhans cells (LC) occur in areas at risk for inoculation by human immunodeficiency virus (HIV), and the question whether LC act as a target, reservoir, or vector for transmission of HIV has given rise to much controversy. To address this question, we first analyzed the epidermal compartment of skin from patients seropositive for HIV DNA. Second, we tested the susceptibility of each cell type normally found in this compartment to in vitro infection by HIV-1. A non-denatured DNA was obtained from epidermal sheets after a thermochemical treatment of biopsies (0.5 M ethylenediaminetetraacetic acid (EDTA), pH 7.5 at 60 degrees C for 90 seconds). Optimization of amplification of viral genome was performed with three primer pairs derived from gag, env, and pol sequences. Polymerase chain reaction (PCR) products were analyzed by Southern blot. Viral genome was found in five of 11 HIV-seropositive patients. To control the permissivity of epidermal cell population for HIV, cells isolated from the epidermal sheet of normal skin by trypsinization were co-cultured with HIV-1-carrying promonocytic cells (U937) and observed by electron microscopy. After 3-6 h of co-culture, numerous virions were either tightly bound or apparently engaged in the process of internalization through receptor-mediated endocytosis. At day 4 of co-culture, some infected LC appeared to release mature viral particles through bud formation. The in vitro HIV-1 entry and replication in LC may confirm the presence of the HIV-1 genome by PCR in epidermis of seropositive patients. The consequences of the permissivity of LC for HIV on the antigen-presenting function remain to be determined.

DNA, Viral↗
PubMed1991

Biochemical and ultrastructural study of glycogen in cultured astrocytes submitted to the convulsant methionine sulfoximine.

The convulsant methionine sulfoximine is a potent glycogenic agent in the central nervous system of rodents in vivo. This investigation was undertaken to look for the basic mechanism underlying this property. Astrocytes were cultivated from newborn rat neopallium and glycogen was studied by both biochemical and ultrastructural methods. When the astrocytes were incubated in a medium containing 5.55 mM glucose, methionine sulfoximine (0.55 mM) induced a significant increase in their glycogen content. Glucose content did not change in astrocytes, but it diminished in the medium in all cases. When the decrease in glucose level in the medium was limited, the same glycogenic effects of methionine sulfoximine were observed, but the glycogen contents were higher. The augmentation of the concentration of the convulsant enhanced its glycogenic effect, but this was not directly dose dependent. When the flat and polygonal astrocytes were transformed into process-bearing astrocytes by dibutyryl cyclic AMP methionine sulfoximine always induced an increase in glycogen content. In this case, the values of glycogen contents were lower. In electron microscopy, no glycogen particles were present in the astrocytes even after methionine sulfoximine treatment, contrary to the case in vivo. These results show that the convulsant does not need the presence of neuronal cells to induce glycogen accumulation and that astrocytes may be the direct cell targets. The apparent discrepancy between the biochemical and ultrastructural data is probably due to the relatively low concentration of glycogen in cultured astrocytes.

Animals↗
PubMed1991

Human epidermal Langerhans cells express integrins of the beta 1 subfamily.

The expression of VLA integrins on human epidermal Langerhans cells (LC) was investigated by indirect immunogold labeling on transmission electron microscopy, followed by a quantitative analysis. Labelings on suspensions enriched in freshly isolated LC were carried out with an antibody recognizing the beta 1 subunit, common to all members of the VLA family, and with antibodies specific for the six different alpha subunits, alpha 1 to alpha 6. Normal human epidermal LC were all beta 1 positive, of which 60% were highly positive. By labelings with different VLA-alpha-chain MoAb, there appeared two subpopulations of LC: one positive and one negative. On average 40% of LC bore small amounts of VLA-1 and VLA-3, 53% and 77% of LC expressed moderate amounts of VLA-2 and VLA-5, respectively, and VLA-4 and VLA-6 were expressed by 67% and 90% of LC, respectively. VLA proteins are mainly extracellular matrix protein receptors. VLA-6 (laminin receptor) and VLA-5 (fibronectin receptor) are expressed mainly by LC, and in this way could subserve LC to leave the epidermal compartment through the basement membrane, to migrate throughout the fibronectin network of the dermis before migrating via the afferent lymphatics to the regional lymph nodes, where they present antigen to T cells. VLA proteins such as VLA-4, VLA-3, or VLA-2, which are found involved in cell-cell contacts, could contribute to the promotion of T-cell activation by facilitating adherence between LC and T cells.

Humans↗
PubMed1990

Kinetic study of esterification by immobilized lipase in n-hexane.

The kinetic of the esterification of oleic acid by ethanol catalyzed by immobilized lipase of Mucor miehei in n-hexane as a solvent has been completely studied. The kinetics of the reaction are suggested to agree with a Ping-Pong Bi Bi mechanism in which only inhibition by excess of ethanol has been identified. Values of all apparent kinetic parameters were computed. No evidence of any significant external diffusional limitation which could account for these values has been detected. Optimization of water content through distribution ratio of water between solvent and support was examined.

Enzymes, Immobilized↗
PubMed1990

Possible involvement of indolamines in the glycogenic effect of the convulsant methionine sulfoximine in rat brain.

The aim of the present investigation was to look for the mechanisms causing disturbances in carbohydrate metabolism during the action of the epileptogenic agent methionine sulfoximine. The levels of glucose, glycogen, and indolamines were measured in seven different regions of rat brain. Methionine sulfoximine induced a decrease in serotonin level which was roughly dose-dependent. There were no obvious changes in tryptophan and 5-hydroxyindoleacetic levels in any area. Methionine sulfoximine induced the known increase in glucose and glycogen levels. The direct precursor of serotonin. 5-hydroxytryptophan, and benserazide (a decarboxylase inhibitor) were then injected into rats in association with methionine sulfoximine. In this case, methionine sulfoximine failed to induce seizures. Moreover, the serotonin level was unchanged and the carbohydrate content did not significantly increase. There was only a rise in 5-hydroxyindoleacetic acid level. This work shows a striking parallelism between serotonin decrease and glycogen increase.

Animals↗
PubMed1990

Basic Training Program in Medical Pedagogy: a 1-year program for medical faculty.

In 1979 université de Montréal developed the Basic Training Program in Medical Pedagogy; the program has since been offered at two other Canadian medical schools. The learning activities are spread over an academic year so that the teachers are able to continue their clinical or research duties. The program, which follows a model of systematic instruction, comprises 17 self-instructional modules on basic educational topics adapted to medical teaching. The topics are related to four components of an integrated system: student needs and learning objectives, instructional methods, student evaluation and program evaluation. The instructional format is aimed at three levels--understanding, analysis and application--to which assignments and assessments are related. In addition to the modules, the program offers 15 half-day sessions for small groups (five participants and one instructor) to discuss aspects of the program, especially home assignments and the application of personal educational projects. A minimum of 100 hours of personal time is requested. The program's main goal is that students be placed at the centre of the educational process. Of 215 participants since 1979, 171 (80%) have completed the program and reported high satisfaction. Issues related to any faculty development program are discussed.

Attitude of Health Personnel↗
PubMed1990

Correlation between carbohydrate and catecholamine level impairments in methionine sulfoximine epileptogenic rat brain.

This work shows that the convulsant methionine sulfoximine induces an increase in glucose and glycogen levels and a parallel decrease in norepinephrine and dopamine levels in rat brain. Among the epileptogenic agents, methionine sulfoximine is known to have a glycogenic property in the central nervous system. The aim of this work is to look for the neurochemical mechanism underlying this property. For this, catecholamines, glucose, and glycogen were measured at the same time in different areas of the brain in rats submitted to methionine sulfoximine. The convulsant induced an increase in glucose and glycogen levels as previously described and a decrease in dopamine and norepinephrine levels in all the areas of the rat brain. These changes were roughly dose dependent. When L-dihydroxyphenylalanine and benserazide (a decarboxylase inhibitor) were administered with methionine sulfoximine, the latter failed to induce seizures in rat up to 8 h after dosing. Moreover, the glucose and glycogen amounts did not increase. In all these experiments, there was an obvious evidence of parallelism between seizures, increase in carbohydrate levels, and decrease in catecholamine levels. These results allow to conclude that the glycogenic property of methionine sulfoximine in the central nervous system probably results from its ability to decrease norepinephrine and dopamine levels. Because the effect of the convulsant on the catecholamine levels persisted for long, it is normal that glucose and glycogen levels increased during preconvulsive, convulsive and postconvulsive period. Methionine sulfoximine is probably glycogenic in rat brain because it decreases catecholamine levels for a long time.

Animals↗
PubMed1990

An easier, reproducible, and mass-production method to study the blood-brain barrier in vitro.

To provide an "in vitro" system for studying brain capillary function, we have developed a process of coculture that closely mimics the "in vivo" situation by culturing brain capillary endothelial cells on one side of a filter and astrocytes on the other. Under these conditions, endothelial cells retain all the endothelial cell markers and the characteristics of the blood-brain barrier, including tight junctions and gamma-glutamyl transpeptidase activity. The average electric resistance for the monolayers was 661 omega cm2. The system is impermeable to inulin and sucrose but allows the transport of leucine. Arabinose treatment increases transcellular transport flux by 70%. The relative ease with which such monolayers can be produced in large quantities would facilitate the "in vitro" study of brain capillary functions.

Animals↗
PubMed1990

Humanism in medical education: a study of educational needs perceived by trainees of three Canadian schools.

The authors examined how medical trainees and recent graduates of three Quebec medical schools value 16 dimensions of medical competence classified in four broad categories: clinical, technological, humanistic, and social and preventive. To assess perceived educational needs, the trainees' perceptions of the importance that medical faculties attribute to these same dimensions in the education of physicians were also examined. The survey was conducted in 1986-87 via a questionnaire mailed to 2,030 individuals, including freshmen, juniors, interns, residents, and newly practicing generalists; 80.3% responded. Compared with the views attributed to the faculty, the medical trainees gave more importance to basic diagnostic and therapeutic skills such as the medical history, the physical examination, and the treatment of common diseases. They also valued to a greater extent non-biological dimensions of clinical competence, such as communication with patients, patient education, the social context of disease, and the multidisciplinary nature of patient care, while they ascribed less importance to medical technology and rare diseases. The study raises the question of the relevance of medical education to medical practice by suggesting that those who are preparing themselves to become doctors may not be receiving the training they wish to receive.

Attitude of Health Personnel↗
PubMed1989

Bovine brain endothelial cells express tight junctions and monoamine oxidase activity in long-term culture.

The passage of substances across the blood-brain barrier is regulated by cerebral capillaries which possess certain distinctly different morphological and enzymatic properties compared to capillaries of other organs. Investigations of the functional characteristics of brain capillaries have been facilitated by the use of cultured brain endothelial cells, but in most studies a number of characteristics of the in vivo system are lost. To provide an in vitro system for studies of brain capillary functions, we developed a method of isolating and producing a large number of bovine brain capillary endothelial cells. These cells, absolutely free of pericyte contamination, are subcultured, at the split ratio of 1:20 (20-fold increase of the cultured surface), with no apparent changes in cell morphology up to the fiftieth generation (10 passages). Retention of endothelial-specific characteristics (factor VIII-related antigen, angiotensin-converting enzyme, and nonthrombogenic surface) is shown for brain capillary-derived endothelial cells up to passage 10, even after frozen storage at passage 3. Furthermore, we showed that bovine brain capillary endothelial cells retain, up to the fiftieth generation, some of the characteristics of the blood-brain barrier: occurrence of tight junctions, paucity of pinocytotic vesicles, and monoamine oxidase activity.

Animals↗
PubMed1988

Catecholamine and indoleamine levels in chick cultured neurons and embryonic brain.

Catecholamine and indoleamine levels were determined in cultured neurons from chick embryos and in the "homologous" embryonic cerebral hemispheres in order to study their neurotransmission systems. The seeding of a large number of cells resulted in a pure neuronal culture made of clusters interconnected by processes. Norepinephrine, which was absent from the starting material of the culture, appeared on the 2nd day and then decreased. A small amount of epinephrine was present on the 2nd day and decreased thereafter. Dopamine was not detected. In the cerebral hemispheres of chick embryos, dopamine appeared on the 10th day in ovo and increased steadily up to the 18th day. Epinephrine was also present in the cerebral hemispheres. Its level increased up to the 14th day and then decreased. Indoleamines were measured in the same material. The level of serotonin was markedly higher than that of catecholamines and it increased during cultivation. Tryptophan was already present in the starting material and its amount increased during cultivation. The level of 5-hydroxyindoleacetic acid changed like that of serotonin. In the embryonic cerebral hemispheres, the concentration of serotonin was highest on the 12th day after incubation and then decreased. Tryptophan level decreased steadily all during the embryogenesis. These results were discussed on the ground of differences in the synthesized neurotransmitters.

Animals↗
PubMed1986

Glycogen synthesis and immunocytochemical study of fructose-1,6-biphosphatase in methionine sulfoximine epileptogenic rodent brain.

The effects of the convulsant methionine sulfoximine (MSO) on the glucose pathway have been investigated in mouse and rat brain. The key gluconeogenic enzyme fructose-1,6-biphosphatase (FBPase) (EC 3.1.3.11) was immunostained by rat anti-FBPase antibody. The rat cortex slices were very lightly stained, almost unstained in controls. After MSO injection, there was a marked staining only in astrocytes (perikarya, processes, and end feet). The activity of this enzyme also increased. MSO induced an increase of 63% in the stability at heating (47 degrees C) and of 36% in the stability at proteolysis (trypsin, 10 micrograms/ml) of FBPase. The convulsant had no effect on the concentrations of the metabolites related to the FBPase-phosphofructokinase step, i.e., fructose-1,6-biphosphate, glyceraldehyde-3-phosphate, and dihydroxyacetone phosphate, before, during, or after the convulsions. These results show that the cellular site of glucose pathway impairment induced by MSO in rodent brain is presumably the astroglial cells and that one mechanism of glycogenesis could be the reinforcement of the molecules of FBPase, which enhances gluconeogenesis. A hypothetical diagram of glucose metabolism under the effect of MSO has been proposed.

Animals↗
PubMed1979

Ultrastructural and biochemical studies of the swelling of developing chick telencephalic slices.

An ultrastructural and biochemical study of the importance and localization of tissue swelling was performed on telencephalic slices of 1- and 30-day-old chicks incubated in an oxygenated or a non-oxygenated physiological medium. The swelling of slices is greater for 30-day-old chick material than for that from 1-day-old chicks. It also reaches higher values in the non-oxygenated than in the oxygenated medium. When the 30-day-old chick telencephalic slices are incubated in an oxygenated medium, swelling mainly affects astrocytes, and especially the astrocytic endfeet. When they are incubated in a non-oxygenated medium, the astrocytes and astrocytic endfeet are very swollen and in addition the swelling also affects the neurons and their organelles. Extracellular space is increased. When 1-day-old chick telencephalic slices are incubated in a non-oxygenated medium, the tissue structures are well preserved. Swelling predominantly affects astrocytes and astrocytic endfeet. Neurons are not affected and the extracellular space is reduced. However, when they are incubated in an oxygenated medium, tissue structures are greatly affected showing a high degree of disorganization. Extracellular space is greatly increased. This study thus indicates that the best incubation conditions are an oxygenated medium for 30-day-old chick telencephalic slices which are characterized by an aerobic metabolism, and a non-oxygenated medium for 1-day-old chick telencephalic slices which have a predominantly anaerobic metabolism.

Aerobiosis↗
PubMed1978

An autoradiographic study on the biosynthesis of the capillary basal lamina in the chick embryo telencephalon.

The elaboration of the basal lamina of telencephalic capillaries has been studied by autoradiography in chick embryos from day 16 to 19 of incubation. The cerebral vascular basal lamina is actively synthesized during the period of these stages of development. The animals were sacrificed 2, 15, 40 and 180 min after intravenous injection of 3H-proline. The hydroxylation of proline to hydroxyproline in the "secretory" cells permits their identification. Our observations suggest that endothelial cells, pericytes and perhaps glial cells participate in this elaboration. The various stages of the synthesis are performed sequentially in the ergastoplasm and then in the Golgi apparatus before the secretory material is released by exocytosis.

Animals↗