Biomedical subjects

J C Garaud

Publications and source records attributed to J C Garaud.

At least 19 recordsLinked to original sources

PubMed2002

Expansion of marginal zone B cells is not sufficient for the development of renal disease in NZBxNZW F1 mice.

The mechanisms which govern the production of autoantibodies and of tissue damage during systemic lupus (SLE) are still unclear. In the NZBxNZW F1 (BW) model of SLE glomerulonephritis, the activation and commitment of B cells are thought to play a major role in disease progression. Previous analysis has suggested that these mice have a substantial increase of marginal zone (MZ) B cells before the occurrence of the disease. Owing to the probable role of this B cell subset in autoantibody production, it was important to define the possible link between this abnormality and the occurrence of kidney damage. Using cytofluorometry analysis, we followed the splenic MZ B cell phenotype in different series of mice with shared autoimmune genetic background and histologically defined renal status. By comparing BW females and BW males, NZB and NZW mice, we confirm that BW mice have an increase in MZ B cells but this MZ B cells expansion is not directly linked to tissue lesions. Genetically modified BW female mice with a restricted repertoire of B and T cell antigen receptors, and which do not develop nephritis, exhibit the same increase of MZ B cells, suggesting that this increase does not depend on a specific set of antigens. Moreover, our analysis brings to light a pre-disease state in BW males, with autoantibody production and mesangial deposits.

Animals↗

PubMed2001

Natural autoreactive B cells in transgenic mice reproduce an apparent paradox to the clonal tolerance theory.

Naturally occurring autoreactive B cells are thought to be physically eliminated or rendered functionally silent through different mechanisms of tolerance. However, multireactive low affinity natural autoantibody-producing B cells seem to escape these mechanisms in normal adults and could constitute the B cell pool from which pathological autoantibodies can emerge. To analyze this apparent paradox to the clonal tolerance theory, we have made two transgenic mouse lines (mu(k), mudelta(k)) producing a natural low affinity multireactive human autoantibody. These models enable us to test both the central tolerance mechanisms (reactivity with single-stranded DNA) and the peripheral tolerance mechanisms after Ag administration. Not only are the multireactive B cells not deleted in the bone marrow, they circulate and remain in the periphery even after the prolonged administration of Ag, the presence of membrane IgD increasing the number of mature autoreactive B cells. Self-reactive B cells are shown to be autoantigen ignorant both in vivo and in vitro, but they are not anergic because they can be easily activated through both B cell receptor-dependent and -independent pathways. Thus, these mouse lines reproduce an apparent paradox to the clonal tolerance theory meriting further investigation of the biological significance of this phenomenon.

Animals↗

PubMed1995

Aphid transmission of beet western yellows luteovirus requires the minor capsid read-through protein P74.

Beet western yellows luteovirus is obligately transmitted by the aphid Myzus persicae in a circulative, non-propagative fashion. Virus movement across the epithelial cells of the digestive tube into the hemocoel and from the hemocoel into the accessory salivary glands is believed to occur by receptor-mediated endocytosis and exocytosis. Virions contain two types of protein; the major 22 kDa capsid protein and the minor read-through protein, P74, which is composed of the major capsid protein fused by translational read-through to a long C-terminal extension called the read-through domain. Beet western yellows virus carrying various mutations in the read-through domain was tested for its ability to be transmitted to test plants by aphids fed on agro-infected plants and semi-purified or purified virus preparations. The results establish that the read-through domain carries determinants that are essential for aphid transmission. The findings also reveal that the read-through domain is important for accumulation of the virus in agro-infected plants.

Amino Acid Sequence↗

PubMed1994

Detection by immunogold labelling of P75 readthrough protein near an extremity of beet necrotic yellow vein virus particles.

RNA 2 of beet necrotic yellow vein virus carries the cistron for the 21 kd coat protein at its 5'-extremity. During translation, the coat protein cistron termination codon is suppressed about 10% of the time so that translation continues into the adjacent open reading frame to produce a 75 kd species, known as P75, which contains the coat protein sequence at its N-terminus. Immunoblotting experiments with a P75-specific antiserum showed that P75 is present in only trace amounts in purified virus preparations. Electron microscopic visualization of immunogold-labelled virions in crude tissue extracts has provided evidence for an association between P75 and at least a fraction of the BNYVV particles, with P75 being predominantly located near one end of the rod-shaped virions. This finding is discussed in the context of the current model for the role of P75 in virus assembly and vector transmission.

Capsid↗

PubMed1993

Alpha IIb beta 3 integrin dissociation induced by EDTA results in morphological changes of the platelet surface-connected canalicular system with differential location of the two separate subunits.

Treatment of human platelets by EDTA (5 mM at 37 degrees C and pH 7.4 for 30 min) induces ultrastructural morphological changes of the surface-connected canalicular system (SCCS). The first consists in dilations of some portions of the channels, whereas the second is represented by collapse of parts of the canaliculi. The collapsed elements of the EDTA treated SCCS are made up of two parallel limiting membranes and a central striated zone. Some of the EDTA treated platelets form microaggregates, the cohesion of which is apparently due to the appearance of pentalaminar interplatelet structures. EDTA treatment is known to induce an irreversible loss of platelet aggregability which is due to irreversible dissociation of the membrane GPIIb-IIIa complexes. In the present study, we looked for involvement of GPIIb-IIIa in the formation of these pentalaminar structures, and were able to demonstrate that the morphological changes described are in fact directly dependent on the EDTA induced dissociation of GPIIb-IIIa complexes. Indeed, we observed that these changes (a) cannot be induced in type I Glanzmann's thrombasthenia, where GPIIb-IIIa complexes are absent, (b) do not appear when human platelets are preincubated with monoclonal anti-GPIIb-IIIa complex-dependent (CD41a) antibodies, which protect the complex from EDTA induced dissociation, (c) appear only at alkaline pH and at 37 degrees C, which corresponds to the range of pH and temperature where EDTA can dissociate GPIIb-IIIa complexes, (d) are accompanied by the disappearance in fluorescence flow cytometry of the heterodimer complex-dependent epitopes, when using anti-CD41a antibodies and (e) do not appear in rat platelets, where GPIIb-IIIa does not dissociate after EDTA treatment. Furthermore, using gold-labeled mAbs concomitantly with the addition of EDTA, we observed that almost only GPIIb was present in the collapsed regions of the canaliculi. Using double labeling studies with polyclonal anti-GPIIb antibodies coupled to 10 nm gold particles and polyclonal anti-GPIIIa antibodies coupled to 20 nm gold particles, we observed that while both 10 and 20 nm particles were present in the dilated portions of the canaliculi almost only the small particles, coupled to the anti-GPIIb antibodies, labeled the collapsed portions of the SCCS. On Lowicryl thin sections, polyclonal antibodies against GPIIb labeled the central striated zone while both GPIIb and GPIIIa were found in the dilated portions of the SCCS. All these observations lead us to suggest that homopolymers of GPIIb could be responsible for "zipping" of the SCCS.

Blood Platelets↗

PubMed1993

Inhibition of growth of a transplanted rat pancreatic acinar carcinoma with CCK-8.

Gastrointestinal hormones and neuropeptides are known to regulate growth of various normal gastrointestinal tissues and many cancers. Since cholecystokinin (CCK) is considered the most potent trophic factor for the exocrine pancreas, we studied its effect on growth of an acinar cell tumor, initially induced by azaserine and transplanted to the rat, in comparison with the normal pancreas. When tumors became palpable, rats were treated three times daily for 12 or 14 days with CCK-8 or NaCl 0.9% (controls) alone or in combination with the CCK receptor antagonist CR1409 (10 mg/kg) administered subcutaneously twice daily. Then tumors and pancreata were analyzed for their size, composition, and CCK receptors. Tumor volume, weight, and protein content, RNA, DNA, and enzymes decreased after CCK-8 treatment in a dose-dependent manner, the maximal effect being observed with 4-micrograms/kg treatment. This inhibitory effect was partially suppressed by CR1409, which by itself also reduced tumor growth, but to a lesser degree. CCK-8 exerted a stimulating effect on growth of the normal pancreas with low doses (1 and 2 micrograms/kg) and an inhibitory effect or no effect with a higher dose (4 micrograms/kg). CR1409 prevented this latter effect, but did not affect by itself the normal pancreas. These findings suggest that CCK-8 inhibits growth of an acinar cell tumor grafted to the rat; this effect is mediated by the occupation of specific CCK receptors present in high density on these cells. In contrast, CCK-8 exerts a biphasic effect on the normal pancreas as a function of its dose.

Animals↗

PubMed1993

Epidermal growth factor and the maturation of intestinal sucrase in suckling rats.

The regulatory effect of epidermal growth factor (EGF) on the postnatal maturation of sucrase was investigated in the small intestine of suckling and weanling rats. Administration of EGF (0.5 micrograms.g body wt-1.day-1) to suckling rats caused a slight precocious induction of sucrase expression. In weanling rats EGF markedly stimulated sucrase activity; however, at both ages, the effect of hydrocortisone was more potent. When the glucocorticoid antagonist RU-38486 was administered to sucklings, the precocious induction of sucrase activity by hydrocortisone was inhibited by 80%. However, RU-38486 or adrenalectomy did not prevent the inductive effect of EGF, indicating that EGF acts in a glucocorticoid-independent manner. EGF also potentiated the effect of hydrocortisone and dietary sucrose on the precocious induction of sucrase activity in the sucklings. At weaning, administration of an antiserum specific to rat EGF significantly decreased sucrase activity. This study shows the involvement of EGF in the postnatal maturation of intestinal sucrase in the rat.

Aging↗

PubMed1992

Gastrin-releasing peptide: in vivo and in vitro growth effects on an acinar pancreatic carcinoma.

The mammalian gastrin-releasing-peptide (GRP) and its structural amphibian analogue, bombesin, are known to be trophic factors for the normal exocrine pancreas. This work investigates the possible role of GRP in the growth of an acinar pancreatic cancer transplanted to the rat and in primary tumor cell cultures. Moreover, this adenocarcinoma was tested for its content of specific bombesin/GRP receptors by using autoradiographic technics and in vitro binding assays with tumor cells. In Lewis rats bearing the pancreatic carcinoma transplanted s.c. in the scapular region, chronic administration of GRP at the dose 30 micrograms/kg/day for 15 successive days significantly increased the tumor volume, the final tumor weight, and amylase, protein, RNA and DNA contents. Autoradiographic studies showed that tumor tissue was GRP receptor positive with a high density. The biochemical characterization indicated that receptor positive tumor tissue had saturable and high affinity receptors with pharmacological specificity for GRP and its bioactive analogues. In primary tumor cell cultures, GRP increased the incorporation of [3H] thymidine in DNA in a dose- and time-dependent manner. There was a good correlation between the ability of GRP and its COOH terminal analogues to elicit DNA synthesis and their affinity for 125I-GRP binding sites. These results from in vivo and in vitro experiments demonstrated that GRP induces growth of pancreatic carcinoma by acting directly on specific membrane receptors present on the tumor cells.

Adenocarcinoma↗

PubMed1988

Localization of immunoreactive gastrin-like cells in the alimentary tract of the ascidian Styela plicata.

The occurrence of a gastrin-like immunoreactivity in the alimentary tract of the ascidian Styela plicata has been investigated using immunocytochemical methods. Gastrin-like cells are present only in the gastric epithelium among the cell types responsible for digestion and absorption of food. The physiological role played by the ascidian gastrin-like peptides is discussed together with the evolutionary history of peptides of the gastrin/cholecystokinin family.

Animals↗

PubMed1988

Appearance of Birbeck granule-like structures in anti-T6 antibody-treated human epidermal Langerhans cells.

We have previously demonstrated by immunogold labeling techniques that the T6 surface antigen of living human Langerhans cells (LC) of the skin is internalized by a process of receptor-mediated endocytosis (RME). Receptor-mediated endocytosis induced by the binding of the monoclonal anti-T6 antibody BL6 involves coated pits, coated vesicles, endosomes, the smooth endoplasmic reticulum, and lysosomes. After RME, gold-labeled Birbeck granules (BGs) appear in the cell center. In the present study, by modifying the experimental conditions but retaining the presence of gold-labeled BL6, we have observed (in addition to the above-mentioned gold-labeled organelles) images that appear to correspond to BG-like structures. These structures, like the intracytoplasmic BGs, are pentalaminar and gold-labeled, but they differ from the intracytoplasmic BGs by their attachment to the cell membrane, their length, the frequent presence of a coat, and by prolongation by one or more coated pits. Birbeck granule-like structures seem to result, at the ultrastructural level, from receptor ligand interactions and from modifications of the LC shape.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1987

Human epidermal Langerhans cells cointernalize by receptor-mediated endocytosis "nonclassical" major histocompatibility complex class I molecules (T6 antigens) and class II molecules (HLA-DR antigens).

HLA-DR and T6 surface antigens are expressed only by Langerhans cells and indeterminate cells in normal human epidermis. We have previously demonstrated that T6 antigens are internalized in Langerhans cells and indeterminate cells by receptor-mediated endocytosis. This process is induced by the binding of BL6, a monoclonal antibody directed against T6 antigens. In the present study, using a monoclonal antibody directed against HLA-DR antigens, on human epidermal cells in suspension, we show that the surface HLA-DR antigens are also internalized by receptor-mediated endocytosis in Langerhans and indeterminate cells. Moreover, using immunogold double labeling, we demonstrate that T6 and HLA-DR antigens are internalized through common coated regions of the membrane of Langerhans or indeterminate cells. The receptor-mediated endocytosis that is induced involves coated pits and vesicles, receptosomes, lysosomes, and also, in Langerhans cells, the Birbeck granules. Thus, T6 antigens, which are considered to be "unusual" or "nonclassical" major histocompatibility complex class I molecules, and the major histocompatibility complex class II molecules, HLA-DR, are internalized in Langerhans and indeterminate cells through common receptor-mediated endocytosis organelles.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1987

Human epidermal Langerhans cells internalize by receptor-mediated endocytosis T6 (CD1 "NA1/34") surface antigen. Birbeck granules are involved in the intracellular traffic of the T6 antigen.

Using immunogold staining of a suspension of living human epidermal cells to identify the Langerhans cell membrane-associated antigen T6 (revealed by the monoclonal antibody BL6), we have observed internalization of T6 antigen in Langerhans cells. This phenomenon is at least partly due to receptor-mediated endocytosis involving coated pits, coated vesicles, endosomes, the smooth endoplasmic reticulum, and lysosomes. These ultrastructural results suggest that T6 antigen may be part of a receptor site. Following receptor-mediated endocytosis, the appearance in the cell center of the first labeled Birbeck granules suggests that Birbeck granules could represent T6 intracellular transport organelles carrying T6 from the central part of the cell to an unknown destination.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1987

Internalization by receptor-mediated endocytosis of T6 (CD1 "NA1/34") surface antigen in T6 positive human cord blood cells (Langerhans cell precursors?).

A subset of T6 positive cells was recently separated from normal human cord blood mononuclear cells. It was shown to coexpress HLA-DR and myeloid differentiation antigens (Mo1, MY4). The phenotype and ultrastructure of the cells suggested that these T6 positive cells might be the precursors of the Langerhans cells of the skin. We have previously demonstrated by immunogold labeling techniques that the T6 surface antigen of human Langerhans cells of the skin is internalized in unfixed Langerhans cells or indeterminate cells by a process of receptor-mediated endocytosis. This process involved the formation of coated pits, coated vesicles, endosomes and lysosomes. Following this process, in Langerhans cells, gold labeled Birbeck granules appeared in the cell center often in continuity with endosomes. In the present study, we used an indirect immunogold labeling technique to reveal the T6 antigen present on the surface of living T6 positive cord blood mononuclear cells. We observed the internalization of the T6 surface antigen by a process of receptor-mediated endocytosis similar to that described in Langerhans cells of the skin. This process, however, was not followed by the appearance of intracytoplasmic Birbeck granules.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1986

Calmodulin in epithelial intestinal cells during rat development.

Calmodulin was immunocytochemically localized in the brush borders of rat intestinal epithelial cells from the tip to the base of the villi, from day 18 of fetal life up to the adult stage. The early (14th day) fetal cells, like the adult crypt cells, were not immunoreactive, although their calmodulin content was equal to that of the mature cells from the tips of the villi.

Animals↗

PubMed1985

Immunocytochemical evidence for intragranular processing of pro-opiomelanocortin in the melanotropic cells of the rabbit.

The immunogold technique, employing antisera with clear-cut specificities, was used to localise different processing stages of pro-opiomelanocortin (POMC) in rabbit melanotropic cells. While the antiserum against gamma 3-MSH labelled all the secretory granules including intrasaccular condensations in the Golgi apparatus, antisera against alpha-MSH only labelled extra-Golgi secretory vesicles (SV). All extra-Golgi SV were likewise labelled with the three antisera against alpha-MSH used, despite their different specificities for the deacetylated, N-acetylated or C-amidated forms of the peptide. The antibody against beta-endorphin also labelled the extra-Golgi SV, while only some SV were labelled with the antibody against gamma-endorphin. These results correlate with biochemical data in favour of mainly--if not exclusively--intragranular processing of POMC. Except for gamma 3-MSH, the cleavage of which could coincide with Golgi packaging of secretory material, other post-translational modifications of the precursor seem to occur when SV are discharged outside the Golgi area. The cleavage of gamma-endorphin appears to be a later step in POMC processing, occurring in some mature SV.

Animals↗

PubMed1984

Coexistence of substances related to enkephalin and somatostatin in granules of the guinea-pig median eminence: demonstration by use of colloidal gold immunocytochemical methods.

Using two different immunocytochemical approaches at the electron microscopic level, it was shown that substances related to enkephalin and somatostatin coexist in the same granules in the median eminence of the guinea-pig. This finding means that the two neuropeptides are simultaneously released. The possible inhibiting action of enkephalins on somatostatin release is discussed related to other data.

Animals↗

PubMed1984

[Immunohistochemical arguments in favor of co-localization of neuropeptides in hypothalamo-infundibular neuron systems].

Light and electron microscope methods which can be used to examine the possibilities of co-occurrence of peptides are reviewed. The results obtained using some of them are exposed and discussed, concerning i/the light microscope demonstration of the CRF/vasopressin coexistence in rat and guinea-pig. ii/the electron microscope demonstration of the granular colocalization of LH-RH/C-terminal ACTH and somatostatin/enkephalin in the guinea-pig median eminence.

Adrenalectomy↗

PubMed1983

Oxytocin-immunoreactive nerve fibers in the pars intermedia of the pituitary in the rabbit and hare.

The pars intermedia of the pituitary in the rabbit and hare is abundantly innervated by axons reacting selectively with antibodies against oxytocin. These axons contain dense secretory vesicles about 140 nm in diameter, i.e., smaller than those in the neurosecretory axons of the neural lobe. No fiber elements staining for other peptides (vasopressin, somatostatin, substance P) were observed in the pars intermedia, except rare leu-enkephalin axons restricted to the rostral zone of the gland. Dopaminergic innervation appears to be completely absent from the intermediate lobe. This was shown by the lack of reaction with an antibody against tyrosine-hydroxylase, which did reveal a well-developed tubero-infundibular system of nerve fibers. Axons reacting with an antibody against serotonin were irregularly distributed in the pars intermedia. In the absence of dopaminergic axons, the extensive oxytocin-like innervation may play a major role in regulating the melanotrophic cell activity in the Leporidae.

Animals↗