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Biomedical subjects

M Fournier

Publications and source records attributed to M Fournier.

At least 181 records · Page 10Linked to original sources
PubMed1993

Mercuric chloride affects protein secretion in rat primary hepatocyte cultures: a biochemical ultrastructural, and gold immunocytochemical study.

The toxicity of mercury on hepatocytes was studied at the ultrastructural, biochemical, and immunocytochemical levels. Albumin metabolism was examined because it is a representative liver-specific function. A novel cytochemical method using the protein A-gold technique for the in situ localization of albumin in hepatocyte cultures was applied. Primary rat hepatocyte cultures were exposed to increasing HgCl2 concentrations. Cytotoxicity was assessed by measuring the release of lactic dehydrogenase from the cells. At the highest exposure concentration tested (50 microM), Hg was found to be significantly cytotoxic in contrast to what occurred at 5.0 and 0.5 microM. The level of albumin secreted, as measured by ELISA, was decreased by approximately 38% at 5.0 microM HgCl2 and was found not to be different from that of controls at lower concentrations. The ultrastructural analysis showed that hepatocytes treated with 5.0 microM HgCl2 undergo drastic morphological changes such as a decreased number of ribosomes associated with the rough endoplasmic reticulum, and the disappearance of the latter organelle, proliferation of the smooth endoplasmic reticulum, and dilatation of both the Golgi apparatus and the biliary canaliculus-like structures. Immunocytochemical detection of albumin-immunoreactive sites using protein A-gold labeling further revealed that these were less abundant in hepatocytes treated with 5.0 microM HgCl2 (-64%) as compared to control preparations. These results suggest that one of the effects of mercury on hepatocytes is to affect liver-specific functions such as albumin production, possibly through interference with ribosomal function. This study also demonstrates for the first time the applicability of the high-resolution protein A-gold technique for toxicological investigations on hepatocytes in vitro.

Albumins↗
PubMed1993

Recovery potential of hepatocytes from inhibition of albumin secretion by cadmium.

The aim of this study was to examine albumin production, a typical liver-specific function, in hepatocytes treated with Cd and to examine the reversibility of the perturbations induced by the toxic metal. Cultures of freshly isolated rat hepatocytes were exposed to increasing amounts of Cd in modified Leibowitz L-15 medium for 20 h; the cells were then allowed to recover by further incubation in Cd-free medium for an additional period of 20 h. The levels of albumin secreted into the extracellular medium were determined by enzyme-linked immunosorbent assay and were found to be reduced by Cd in a concentration-dependent fashion over the first 20 h. Inhibition was seen at Cd concentrations that did not cause any loss of cellular viability (up to 0.5 microM Cd), as judged from the release of lactate dehydrogenase by the cells. After replacement of the exposure medium by Cd-free medium, the same pattern of diminished albumin secretion was obtained, revealing the persistence of the cytotoxic effects when recovery conditions were applied. Moreover, hepatocytes exposed to 0.5 microM Cd for 20 h and processed for visualization of albumin immunoreactive sites using protein A-gold and electron microscopy exhibited very low albumin-specific labeling as compared to the controls (0.6 +/- 0.05 vs. 20.0 +/- 2.6 gold particles/micron2). Intracellular glutathione levels were not significantly changed by Cd either after the initial exposure or after the incubation that followed in control medium. The accumulation of Cd by the cells, as measured by graphite furnace atomic absorption spectrophotometry, was concentration dependent. It remained stable after medium change, indicating that Cd efflux was negligible upon reestablishment of normal conditions. The present data show that the perturbations in albumin metabolism caused by Cd are not readily alleviated after the cells are returned to Cd-free medium, suggesting a limited short-term recovery potential against cytotoxic damage. The data also demonstrate that hepatocyte-specific functions can be used as sensitive indicators for the detection of cellular disturbances by hepatotoxins.

Albumins↗
PubMed1993

Cyclosporin A increases the pulmonary eosinophilia induced by inhaled Aspergillus antigen in mice.

We evaluated the effects of anti-inflammatory drugs in a murine model of allergic bronchopulmonary aspergillosis (ABPA). Mice instilled with 100 micrograms of Aspergillus fumigatus antigen (intranasally, 3 days a week for 3 weeks) developed pulmonary lesions, characterized by a perivascular and peribronchial eosinophil infiltration, a bronchoalveolar lavage (BAL) eosinophilia, and elevated levels of total IgE, total IgG1 and A. fumigatus-specific IgG1. Under the same conditions, groups of mice receiving a daily dose of 2 mg/kg dexamethasone showed decreased numbers of eosinophils and total cells in BAL, had less numerous eosinophils in their pulmonary infiltrates, and had lower levels of serum and BAL fluid total IgE, total IgG1 and A. fumigatus-specific IgG1. Conversely, groups of mice pretreated with an immunosuppressive agent, cyclosporin A (CsA) at a dose of 50 mg/kg, three times per week, developed pulmonary lesions with enhanced lung eosinophilic influx and increased total IgE levels, both in serum and in BAL fluid. These findings show that dexamethasone potently prevents the murine immunopathologic response to A. fumigatus. The effect of CsA on this inflammatory response was paradoxical, insofar as it suggests an activation of the T helper 2 subset, which up-regulates eosinophil recruitment and IgE production.

Administration, Inhalation↗
PubMed1993

Biochemical and electrophysiological properties of SR 57746A, a new, potent 5-HT1A receptor agonist.

SR 57746A (1-[2-(naphth-2-yl) ethyl]-4-(3-trifluoromethylphenyl)-1, 2, 5, 6 tetra-hydropyridine hydrochloride) binds competitively, and with high affinity (Ki = 2.0 +/- 0.7 nM) to 5-HT1A receptors from rat hippocampus in vitro, but has much less affinity for other 5-HT receptor subtypes (IC50 > 650 nM). SR 57746A produces a concentration-dependent inhibition of forskolin-stimulated adenylate cyclase activity in rat hippocampal homogenates, with a maximal effect identical to that of 8-OH-DPAT, suggesting that SR 57746A behaves as a full agonist in this experimental model. SR 57746A potently displaces [3H]8-OH-DPAT binding to rat hippocampal membranes ex vivo, with an ID50 of 11.1 mg/kg po, 30 min after administration, and 2.8 mg/kg po, 2 h after administration. This effect of SR 57746A is long-lasting (at least 24 hours at 10 mg/kg po). SR 57746A does not modify the levels of 5-HT or DA in various brain areas, but decreases the concentrations of 5-HIAA, and increases those of DOPAC, HVA and 3-MT. Following i.v. administration, SR 57746A (0.095 to 0.25 mg/kg) inhibits the spontaneous firing of dorsal raphe neurones, but does not modify the activity of DA neurones in the substantia nigra or ventral tegmental area. Thus, SR 57746A is a potent, selective and full agonist at 5-HT1A receptors in vitro and vivo.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1993

Effects of prenatal undernutrition on developing rat diaphragm.

The effects of maternal nutritional deprivation (ND) on the proportions and cross-sectional areas (CSAs) of type I and II fibers in the developing rat diaphragm (Dia) were examined. In addition, the effects of ND on in vitro contractile and fatigue properties were also studied. Compared with in the control (CTL) group (from pups of well-nourished mothers), proportions of type II fibers were significantly lower in the ND group during the first 3 postnatal wk. However, this difference did not persist into adulthood. CSAs of type I and II fibers were larger in ND Dia than in CTL Dia during early postnatal development, but in adults type I and II fiber CSAs were larger in CTL than in ND Dia. Interstitial space comprised a smaller fraction of total muscle area in ND Dia throughout postnatal development and persisted in adults. Estimated fiber density (no. of fibers/CSA muscle) was lower in ND groups at all ages. In addition, the total number of fibers was significantly lower in ND Dia at all ages. Optimal muscle fiber length for peak twitch and maximum isometric force generation was shorter in ND Dia at all ages. At postnatal days 7 and 14, specific force (maximum tetanic force in N/cm2) of ND Dia was significantly lower than that of CTL Dia. At day 21, Dia specific force was comparable between the two groups but was significantly lower in adult ND compared with adult CTL Dia. Except for days 0 and 14, ND Dia was more fatigue resistant than CTL Dia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

In vivo proliferative pattern of trembler hypomyelinating Schwann cells is modified in culture: an experimental analysis.

Trembler mouse, a Schwann cell mutation, is characterized by severe hypomyelination of peripheral nerves, high Schwann cell proliferation and the presence of a multilayered basal lamina which surrounds them. In contrast with their continuous in vivo division, mutant Schwann cells prepared from 15-day sciatic nerves display a lower proliferation rate in cell culture than normal Schwann cells. However, quiescent Trembler Schwann cells are still able to respond, as normal Schwann cells, to exogenous mitogens, such as nerve extracts and myelin-enriched fractions. In addition, both normal and Trembler Schwann cells proliferate in response to Trembler serum. Fibroblast growth factor is not the mitogenic factor which stimulates mutant Schwann cell proliferation in vivo, since it is absent in Trembler serum and poorly concentrated in Trembler adult sciatic nerves. Our results suggest that, in vivo, the serum of Trembler mouse probably contains mitogenic factors, not yet characterized, which may trigger the permanent division of mutant Schwann cells, in contrast to the quiescent state of these cells in the nerves of normal mice.

Aging↗
PubMed1993

Farmer's fever. Systemic manifestation of farmer's lung without lung involvement.

A 35-year-old dairy farmer presented with recurrent febrile episodes over more than three years. Fever up to 39 degrees C occurred only if he was in contact with the dairy barn and typically appeared at 4 to 8 h after an otherwise usual barn exposure. He had no dyspnea and throughout this period repeated physical examinations, chest roentgenograms, and lung functions remained normal. He was bronchoscoped and lavaged on three occasions, a lymphocytic alveolitis was always present and once, immediately after an acute episode, an important increase in lavage neutrophils was also found (47 percent). Transbronchial lung biopsy specimens showed a moderate cellular infiltrate but no granuloma or fibrosis. Three other persons who worked at the same farm had no similar manifestations or respiratory illnesses. The patient therefore had typical systemic manifestations of acute farmer's lung, but without the lung involvement required to confirm that diagnosis. Furthermore, his disease does not fit the entities known as grain fever and organic dust toxic syndrome. We believe that this patient presented a different entity that we coined "farmer's fever."

Adult↗
PubMed1993

Single-lung retransplantation for late graft failure.

In lung or heart-lung recipients, an irreversible graft-failure may develop in connection with chronic rejection, infection or bronchial complications. A limited number of transplant-recipients have undergone a retransplantation procedure in several centres. First results are discouraging, especially in the case of early retransplantation. We decided, 3 yrs ago, to evaluate the feasibility and benefits of single-lung retransplantation in lung-transplant recipients with late graft-failure. Eight consecutive single-lung retransplantations were performed in patients with previous single-lung (n = 7), or double-lung (n = 1) transplant. Primary graft and native lung were removed in 5 and 3 patients, respectively. The delay between the two surgical procedures was 16 +/- 10 months (range 6-37 months). Three patients died within 3 months. Long-term survivors experienced stable and satisfactory functional results (forced expiratory volume in one second (FEV1 63 +/- 21% predicted; range 40-103% predicted), with survival values ranging 8-20 months. One patient died of septic shock 16.5 months after retransplantation. The remaining four patients are alive. These data suggest that the retransplantation option could be considered in selected patients with late graft-failure. The final decision for retransplantation, however, is largely influenced by the current shortage of donor lungs.

Bronchiolitis Obliterans↗
PubMed1993

Modulation of experimental hypersensitivity pneumonitis by Sendai virus.

To evaluate the potential role of viruses in the pathogenesis of hypersensitivity pneumonitis (HP), we looked at the effect of challenging normal versus Sendai-injected mice with Saccharopolyspora rectivirgula (SR). In this model of HP, mice are nasally instilled with SR antigen three consecutive days per week of study. For this study virus was given after 3 weeks of SR. Two positive (SR alone, virus alone) and a negative (saline) control groups were done in parallel with the viral plus SR group. Lung response to these different conditions was evaluated by lung index, bronchoalveolar lavage (BAL) cell populations, lung histopathology, and BAL fluid fibronectin levels. SR challenge resulted in an increase in BAL cells, lung index, and BAL fibronectin levels and in a peribronchial inflammatory reaction. The virus alone produced a transient increase in BAL cells. The cellular response to SR, in virus-injected animals, was greater than the added effects of the virus and SR. Virus alone had no persistent effect on the other measured parameters and did not change the effect of SR on these variables. We conclude that the Sendai virus enhances the cellular response of the mouse lungs to an SR antigenic challenge.

Alveolitis, Extrinsic Allergic↗
PubMed1992

Fast separation of macrophages by retention on cross-linked amylose and release by enzymatic amylolysis of the chromatographic material.

Macrophages from mice peritoneal exudate were isolated on basis of specific adherence on epichlorohydrin cross-linked amylose (CLA), a chromatographic gel presenting a high susceptibility to advanced amylolysis with alpha-amylase. The cell suspension, containing predominantly macrophages and lymphocytes, was applied onto the column and incubated for 30 min at 37 degrees C for the adherence of macrophages. After this interval the non-adherent cells were eluted with buffered medium and the CLA support was incubated in the column with an alpha-amylase-buffered solution liquefying the matrix and releasing, in situ, the adherent cell population containing 90% macrophages with a viability higher than 90%.

Amylose↗
PubMed1992

[Therapeutic strategy].

The clinical manifestations of bronchial asthma fall into two categories: acute asthma which consists of asthmatic attacks and their variants, and chronic asthma. The treatment of acute asthma is now well established, while that of chronic asthma, more difficult to organize, is part of a true therapeutic strategy which has two aspects: 1. A more global approach to the treatment must be developed. This means full management of asthmatic patients who must be instructed and considered as active partners in the prevention of acute attacks, the evaluation of the severity of their disease and the application of the treatment prescribed. 2. An asthma severity scale must be devised and a specific therapeutic programme must be offered for each stage of the disease. The general principle, beside treatment of acute asthma, is to pay much attention to the intercritical situation and, in particular, to treat effectively the bronchial inflammation.

Asthma↗
PubMed1992

Interaction of tRNALys with the p66/p66 form of HIV-1 reverse transcriptase stimulates DNA polymerase and ribonuclease H activities.

The precursor homodimeric p66/p66 form of human immunodeficiency virus type-1 reverse transcriptase (HIV-1 RT) possesses the DNA polymerase and RNase H activities involved in the synthesis of the double-stranded provirus DNA. Reverse transcription is initiated from tRNALys in the case of HIV-1. The present study confirmed that interactions between HIV-1 RT and tRNALys induce protein conformational changes and demonstrated that these interactions stimulate the enzymatic activities associated with the p66 subunit. Thus, the p66/p66 form of the enzyme is strongly stimulated in both DNA polymerase and RNase H activities. Preincubation of the enzyme with tRNA is an obligatory step to obtain the stimulatory effect. The affinity of template, primer, or substrate for RT p66/p66 did not change when the enzyme was preincubated with tRNALys at stimulatory concentrations; the interaction of tRNA with p66/p66 has an effect only on the maximal rate of polymerization. It is further shown that the RNase H domain of RT is much more accessible to protease attack than the DNA polymerase active site.

Chymotrypsin↗
PubMed1992

Immunotoxicity of subchronic versus chronic exposure to aldicarb in mice.

In this study we compared the immunotoxicity of subchronic vs chronic exposure to the aldicarb insecticide at a relatively low, 0.1-10 ppb, level in drinking water. The immunotoxicity of aldicarb was evaluated in 28- and 90-day studies by determination of the humoral, cellular and nonspecific immunity in inbred C57BL/6 mice. Quantification of splenic plaque-forming cells (PFC) to sheep erythrocytes (SRBC), mitogen activation of spleen lymphocytes, mixed lymphocyte reaction (MLR) and the cytofluorometric assay of the phagocytic uptake of fluorescent beads were among the parameters studied. Neither the cell viability nor the splenic cell count was affected by the insecticide exposure. Immunophenotyping and cytometric determination of L3T4+, Lyt2+ and Ig+ cells revealed no effect of the insecticide exposure on the total count of cell subsets in the ungated splenocyte population. However, a marked shift in the percentages of L3T4+ and Lyt2+ cells was noted after subchronic exposure to 1 and 10 ppb aldicarb, possibly indicating activation of these splenic T-cell subsets. Subchronic aldicarb exposure significantly suppressed the splenic PFC response to SRBC at 1 ppb dose, however, no dose-effect correlation could be concluded. Similarly, no dose-effect correlation was observed for subchronic aldicarb-related changes in mitogen responses. Subchronic exposure to aldicarb had no statistically significant effect on the mixed lymphocyte reaction (MLR) or on the macrophage phagocytosis. Chronic exposure to 0.1-10 ppb aldicarb did not affect any of the parameters measured, including the cell subsets. Thus, aldicarb-related changes in immune parameters, noted after a 28-day exposure, were compensated over chronic exposure to the insecticide.

Aldicarb↗
PubMed1992

Combined effects of selected insecticides on humoral immune response in mice.

Biological effects data with single insecticides are far more abundant than with mixtures. These data cannot be used directly to predict the effects of insecticide mixtures. Three insecticides of different chemical classes: organochlorine; dieldrin, organophosphate; malathion, and carbamate; carbofuran, previously evaluated for their immunotoxic potential, were selected for studies of combined acute exposure in C57B1/6 inbred mice. The humoral response to sheep red blood cells (SRBC) and the functional activities of peritoneal macrophages, such as phagocytosis of fluorescent beads and presentation of a single protein antigen, avidin, were examined after in vivo exposure of mice to different combinations of the selected pesticides and compared with the vehicle controls. Regarding exposure to single substances, the data confirmed the immunosuppressive potential of dieldrin and carbofuran and the immunopotentiating effect of malathion. Following the acute concomitant exposure to dieldrin/carbofuran mixture, however, values for the parameters of antigen presentation, primary IgM antibody response to SRBC antigen, and macrophage phagocytosis, returned to control or above-control values, indicating a lack of any synergistic or additive effects of the chemicals on the immune response. Thus, it was concluded the dieldrin/carbofuran mixture had an antagonistic effect on the humoral response to SRBC and the macrophage phagocytic activity, in comparison with the action of administration of each of the insecticides alone.

Animals↗
PubMed1992

Limited immunotoxic potential of technical formulation of the herbicide atrazine (AAtrex) in mice.

Immunotoxicity of the technical atrazine formulation, AAtrex, was examined in C57Bl/6 female mice following a sublethal exposure to equivalent 1/2-1.64 LD50 doses of the herbicide. Animal weight was not affected by the herbicide exposure. No dose-related changes could be concluded for fluctuations in organ weight, changes in the spleen cell number and cell viability. Furthermore, cytofluorometric studies showed no significant changes in the frequency of L3T4-positive and Lyt-2-positive T-cells. Functional in vitro assays of mitogen activation showed no marked effects of AAtrex exposure on lymphocyte stimulation by lipopolysaccharide (LPS), phytohemagglutinin (PHA) and concanavalin A (Con-A). In addition, sublethal exposure to AAtrex did not affect interleukin-2 (IL-2) production by splenic cells. Furthermore, no dose-related effect could be concluded from a transient suppression of a primary humoral IgM response to sheep erythrocytes (SRBC) as well as from a transient inhibition of a specific T-cell response to alloantigens in mixed lymphocyte reaction (MLR). Exposure to equiv. 1/2-1/16 LD50 doses augmented phagocytic activity of peritoneal macrophages, without any visible AAtrex dose-related effect. Normal humoral and cellular responses were restored at 14-40 days after the herbicide exposure. Overall, transient and reversible immunosuppression of humoral-mediated and cell-mediated responses and activated macrophage phagocytic activity could not be attributed to the direct chemical-related effect of sublethal exposure to AAtrex.

Animals↗
PubMed1992

Immunosuppression by chronic exposure to N-nitrosodimethylamine (NDMA) in mice.

Immunosuppression of humoral and cellular responses following chronic oral exposure to 1, 5, 10, and 20 ppm N-nitrosodimethylamine (NDMA) was examined in CD-1 mice. Monitoring of cumulative mortality and the incidence of peritoneal ascites in animals showed an NDMA dose-related mortality and hepatotoxicity. No visible changes in immunological parameters were noted at the 1 ppm NDMA dose. Immunosuppression of immunoglobulin M (IgM) antibody response by NDMA to sheep red blood cells (SRBC) was time-related, dose-related, and could be reversed within 30 d by removal of the chemical from the drinking water. Cellular immune response, monitored by allogeneic stimulation of cells in mixed lymphocyte reaction (MLR), was markedly suppressed by 10 and 20 ppm NDMA. Thus, chronic exposure to NDMA, except for the low-hepatotoxic doses of nitrosamine, resulted in a marked and persistent immunosuppression of cellular and humoral responses in CD-1 mice. In conclusion, chronic exposure to the hepatotoxic (ascite-inducing) doses of NDMA suppressed humoral and cellular immunity. The persistent immunosuppression could be reversed after the removal of NDMA from the drinking water. Although no direct NDMA-related cancer was reported in humans, our data point to a potential epigenetic carcinogenicity of nitrosamines due to chronic immunosuppression.

Animals↗
PubMed1992

Colloidal gold ultraimmunocytochemical localization of DNA and RNA adducts in rat hepatocytes.

The localization of DNA and RNA adducts was studied at the ultrastructural level using antibodies directed against O6-methylguanine (O6-metG) and the protein A-gold technique. Primary rat hepatocyte cultures were exposed for 2 h to 5 mM N-nitrosodimethylamine (NDMA). In NDMA-treated cells, the O6-metG-induced immunoreactive sites do not appear at random but seem to be concentrated in the nucleus, and in the cytoplasm, in areas rich in rough endoplasmic reticulum (RER) elements. Mitochondria were not significantly labelled. Untreated control preparations showed no specific immunogold labelling. After RNase digestion of ultrathin sections obtained from cells exposed to NDMA and subsequent immunogold labelling, most of the immunolabelling in the cytoplasm had disappeared, and that over the nucleus had only been slightly reduced, as compared to undigested specimens from NDMA-treated cultures. After similar digestion with DNase, a strong reduction of the labelling of the nucleus was observed, but labelling of the cytoplasm was practically unaffected by this enzymatic treatment, as compared to what was observed in undigested preparations of NDMA-treated hepatocytes. The results provide evidence of preferential formation of O6-metG at the DNA and RNA levels, in the nucleus and cytoplasm RER, respectively. Furthermore, this study demonstrates the applicability of the high-resolution protein A-gold technique for ultrastructural detection of nucleic acid adducts in NDMA-treated hepatocytes using affinity-purified anti-O6-metG polyclonal antibodies.

Animals↗