Biomedical subjects

M Bergeron

Publications and source records attributed to M Bergeron.

At least 19 recordsLinked to original sources

PubMed1996

Maleate modifies apical endocytosis and permeability of endoplasmic reticulum membranes in kidney tubular cells.

Previous studies have shown that histochemical modifications of the endoplasmic reticulum in epithelial cells might be related to their transport function. We have examined the effect of sodium maleate, which produces generalized transport derangement reminiscent of Fanconi syndrome, on the organization, morphology and enzyme activities of endoplasmic reticulum in rat kidney cells. The osmium impregnation technique has revealed that apical vacuoles increase in volume and in number in most proximal tubule cells, and contain osmium deposits. Osmium impregnation of the endoplasmic reticulum is much reduced. In vitro studies, performed with isolated microsomes, show NADPH cytochrome c reductase activity in both normal and maleate-treated rats. As revealed by vanadate, Ca+-ATPase activity in isolated microsomes is unnaffected by maleate but the vanadate-insensitive or passive component of calcium uptake increases particularly later in the response. Therefore, the remaining calcium uptake in the presence of vanadate is indeed passive; in vivo maleate administration also appears to increase the passive entry of calcium into the microsomal compartment. The morphological and histochemical alterations of the endoplasmic reticulum cisternae occur rapidly and with a similar time course to the transport defects, suggesting that this organelle plays a role in transcellular transport. Maleate may directly affect the endoplasmic reticulum membranes whereby passive permeability to calcium is increased. The endocytotic apparatus and possibly exocytosis phenomena are modified by maleate as shown by the increased vacuolization and the presence of black osmium deposits in vacuoles.

Animals↗

PubMed1996

Mechanism of heat shock protein 72 induction in primary cultured astrocytes after oxygen-glucose deprivation.

Induction of stress proteins is thought to be important in the protection of cells from a variety of environmental insults including heat, hypoxia and ischemia. The aim of this study was to compare the mechanism of induction of heat shock protein 72 (HSP72) in primary cultures of murine cortical astrocytes by heat and combined oxygen-glucose deprivation (OGD), a model of in vitro ischemia. 35S-methionine labeling and immunoblotting showed increased HSP72 synthesis and accumulation lasting for up to 24 h following heat or OGD. Heat induced a markedly greater amount of HSP72 mRNA and protein than did OGD. We then sought evidence of heat shock transcription factor-1 (HSF-1) activation. An increase in apparent molecular weight of nuclear HSF-1 after heat or OGD was observed, consistent with increased phosphorylation. To seek an explanation of the difference between heat and OGD as inducers of HSP72 we examined the binding activity of HSP72 + 73 to other proteins. More cellular protein was found to co-immunoprecipitate with HSP72 + 73, and more HSP72 + 73 was found in the pellet fraction after heat shock compared to OGD. These results suggest that HSP72 induction is regulated in astrocytes at least in part at the level of HSF activation, by both heat and OGD. Reduced availability of free HSP72 + 73 in heated cells could be responsible for the greater magnitude of HSP72 induction after heat compared to OGD.

Animals↗

PubMed1995

Reversible histochemical modifications of endoplasmic reticulum following arginine vasopressin stimulation of granular cells of toad bladder.

The endoplasmic reticulum is generally absent from schematic representations of transport phenomena, although it shows a well-organized network in most transport epithelial cells. In order to examine the correlation between this organelle and cellular activity, bladders of Bufo marinus were studied under different experimental conditions and fixed by immersion in glutaraldehyde, followed by OsO4 impregnation for 3 days. Normal granular and mitochondria-rich cells showed a rich cytoplasmic network of canaliculi, well-impregnated by osmium deposits. Following a 2 to 15-min stimulation (serosal bath) with arginine vasopressin, the V2 receptor agonist dD-arginine-vasopressin or cyclic AMP (cAMP), the staining of endoplasmic reticulum in granular cells disappeared. After washing out of the hormone or the agonist, impregnation of the endoplasmic reticulum could be observed once again. Arginine vasopressin did not modify the impregnation of endoplasmic reticulum of either mitochondria-rich or basal cells. Our data indicate a correlation between the reactivity of endoplasmic reticulum to osmium, and a cAMP-dependent effect of arginine vasopressin through its V2 receptors. Incubation of arginine vasopressin through its V2 receptors. Incubation of toad bladders carried out with agents interfering with cellular calcium (calcium ionophores, high or low bath calcium) or with calcium release from the endoplasmic reticulum (TMB-8, thapsigargin) suggested that an early step in the cAMP-dependent effect of arginine vasopressin must involve the release of intracellular calcium from the endoplasmic reticulum. However, calcium ATPases in this organelle do not seem to participate in the hormonal effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Effect of probenecid on 5-hydroxyindoleacetic acid in cisternal cerebrospinal fluid of rats with portacaval anastomosis.

Portal-systemic encephalopathy (PSE) is characterized by a neuropsychiatric disorder progressing through personality changes, to stupor and coma. Previous studies have revealed alterations of serotonin and of its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in brain tissue and CSF in experimental (rat) and human PSE. Increased brain 5-HIAA concentrations could result from its decreased removal rather than to increased serotonin metabolism. In order to evaluate this possibility, CSF 5-HIAA concentrations were measured using an indwelling cisterna magna catheter technique at various times following end-to-side portacaval anastomosis in rats (the most widely used animal model of PSE) treated with probenecid, a competitive inhibitor that blocks the active transport of acid metabolites out of the brain and CSF. Following portacaval anastomosis and probenecid treatment, CSF concentrations of 5-HIAA were increased to a greater extent than in sham-operated controls. When data were expressed as per-cent baseline values, the relative increase of CSF 5-HIAA in portacaval shunted rats following probenecid treatment was not significantly different from sham-operated controls. These findings confirm that increased 5-HIAA in the CNS in experimental PSE results from increased 5HT metabolism or turnover and that the probenecidsensitive acid metabolite carrier is intact in PSE.

Animals↗

PubMed1995

Regional alterations of dopamine and its metabolites in rat brain following portacaval anastomosis.

Hyperammonemia and changes in brain monoamine metabolism have been proposed to contribute to the pathogenesis of the neuropsychiatric symptoms characteristic of human portal-systemic encephalopathy (PSE) resulting from chronic liver disease. Portacaval anastomosis (PCA) in the rat leads to sustained hyperammonemia and mild encephalopathy. In order to evaluate the role of dopamine (DA) metabolism in PSE, levels of DA and its metabolites were measured by HPLC with electrochemical detection in brain regions of rats with PCA at various stages of encephalopathy precipitated by ammonium acetate administration. Following ammonium acetate administration, rats with PCA rapidly develop severe neurological signs of encephalopathy progressing through loss of righting reflex to coma; sham-operated control animals administered ammonium acetate showed no such neurological deterioration. Concentrations of the DA metabolites DOPAC and HVA as well as [DA metabolites]/[DA] ratios, an indirect measure of DA turnover in brain, were increased in caudate-putamen, in cingulate and pyriform entorhinal cortices as well as in raphe nucleus and locus coeruleus. Increased DA metabolites, however, did not worsen at coma stages of PSE. Increased DA turnover thus appears to relate to early neuropsychiatric and extrapyramidal symptoms of PSE.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1995

A simple technique for staining of cell membranes with imidazole and osmium tetroxide.

We describe a simple new technique based on the affinity of imidazole and osmium tetroxide for unsaturated lipids. Organs (e.g., kidney, liver, intestine) were perfused in vivo with a glutaraldehyde solution. Tissue fragments were then immersed in a solution containing imidazole and OsO4 and are further stained with a double lead and copper citrate solution. Ultra-thin (0.06 microns) or thick (0.1-0.3 microns) sections were observed with transmission electron microscopy (80-100 kV). The method presented permits excellent visualization of cell membranes (e.g., endoplasmic reticulum, endocytotic apparatus) because it favors good resin penetration and the alkaline pH preserves cell volume. A better stereomicroscopic analysis of the relationship between cell organelles can be carried out with thick sections. The imidazole/osmium can be used routinely because the technical steps are easy and simple to follow. Furthermore, it can complement other cytochemical methods.

Animals↗

PubMed1995

[Tetanus vaccination. Evaluation of a program of health promotion in a family medicine unit].

OBJECTIVE: To assess the effectiveness of a tetanus immunization poster at a medical clinic in encouraging patients to request immunization against tetanus with d2T5. DESIGN: Quasi-experimental study. SETTING: The Family Medicine Unit (F.M.U.) at the Centre hospitalier de l'Université Laval (C.H.U.L.), a tertiary hospital in the region of Quebec City. PARTICIPANTS: All patients over 7 years of age at CHUL's FMU between February 22 and March 19, 1993. INTERVENTIONS: Poster promoting tetanus immunization displayed in waiting room during test weeks 2 and 4 and withdrawn during control weeks 1 and 3. MAIN OUTCOME MEASURE: Proportion of patients vaccinated with d2T5. RESULTS: The proportion of patients vaccinated during the test weeks was the same as the proportion vaccinated during the control weeks. Week 1: 1/507 (0.20); Week 2: 1/394 (0.25); Week 3: 1/441 (0.23); Week 4: 1/486 (0.21). CONCLUSION: The presence of the posters in the waiting room had no impact on tetanus immunization at CHUL's FMU.

Adolescent↗

PubMed1994

Organization of the endoplasmic reticulum in renal cell lines MDCK and LLC-PK1.

The spatial organization of the endoplasmic reticulum has been studied in two renal cell lines, MDCK and LLC-PK1, which originate from the distal and proximal portions of the mammalian nephron, respectively, and which form a polarized epithelium when they reach confluence in tissue culture. The two renal cell lines, grown to confluence on either solid or permeable supports, were investigated by fluorescence microscopy, confocal microscopy, and transmission electron microscopy. Fluorescence labeling of the endoplasmic reticulum was achieved using the cationic fluorescent dye DIOC6 (3). In order to differentiate fluorescent labeling of the endoplasmic reticulum from that of the mitochondria, cells were also labeled with rhodamine 123. For electron microscopy, the spatial organization of the endoplasmic reticulum was examined in thick sections using the long-duration osmium impregnation technique or the ferrocyanide/osmium technique. In both cell lines, the endoplasmic reticulum formed an abundant tubular network of canaliculi that frequently abutted the basolateral domain of the plasma membrane and occasionally the apical membrane. Elements of the endoplasmic reticulum were also found in close proximity to mitochondria that, as in the nephron, formed branched structures. Canaliculi appeared circular or flattened and had an inner diameter of 10-70 nm for MDCK cells and 20-90 nm for LLC-PK1 cells. Such a three-dimensional organization might facilitate the translocation of defined lipid species between the endoplasmic reticulum and the plasma membrane, and between the endoplasmic reticulum and mitochondria.

Animals↗

PubMed1993

[Factors associated with at-risk anal relations in homosexual HIV-seropositive men].

This pilot study proposes an index to quantify the intensity of high-risk anal sex and presents factors associated with this practice among 65 homosexual men with HIV infection. All of them answered a self-administered questionnaire. Using multiple logistic regression, we first compared those who had had safe sex in the past six months to those who had had unsafe sex. Variables significantly associated with unsafe sex are: drugs and/or alcohol use with sex, and less favorable attitude towards condom use. Finally, multiple linear regression analysis among respondents who had had unsafe sex indicated that the following factors are associated with higher levels of unsafe sex: men between the ages of 32 and 38, satisfied with their social life, non-smokers, with a less favorable attitude towards condom use, and with few social relationships. These results must be interpreted with caution because of the small number of respondents.

Attitude↗

PubMed1992

A simultaneous three-color T cell subsets analysis with single laser flow cytometers using T cell gating protocol. Comparison with conventional two-color immunophenotyping method.

We describe a method for simultaneous analysis of CD3, CD4, and CD8 positive cells from whole blood utilizing single laser flow cytometers. All three T cell values are attained from a single test tube. CD4 and CD8 positive cells are identified only if they are CD3 positive. Thus the values obtained by this method for T helper/inducer and T cytotoxic/suppressor cells can be reported directly as a percentage of T lymphocytes. Analysis for CD4 and CD8 positive cells is accomplished, by first gating on CD3 positive T lymphocytes, hence the approach is referred to as a T gating method. As the third dye, conjugated to anti-CD3 monoclonal antibodies (MAbs), we utilized peridinin chlorophyll protein (PerCP), a new red fluorochrome. The proposed method may prove to be practical for monitoring disease progression in AIDS, where longitudinal T helper/inducer and T cytotoxic/suppressor cell enumeration must be performed unambiguously by a simple, reproducible, and fast method.

CD3 Complex↗

PubMed1992

Monitoring of neurotransmitter amino acids by means of an indwelling cisterna magna catheter: a comparison of two rodent models of fulminant liver failure.

Alterations of brain and cerebrospinal fluid amino acids have consistently been described in human and experimental fulminant liver failure. To evaluate the significance of such changes in the pathogenesis of hepatic encephalopathy in fulminant liver failure, brain and cerebrospinal fluid amino acids (glutamate, aspartate, GABA, glycine, taurine) were measured at various stages during the development of neurological dysfunction in rats after hepatic devascularization or thioacetamide treatment to induce acute liver failure. To facilitate repetitive removal of cerebrospinal fluid, a technique employing long-term implantation of cisterna magna catheters in conscious, freely moving rats was developed. Brain but not cerebrospinal fluid concentrations of the excitatory amino acids glutamate and aspartate were reduced in both animal models of fulminant liver failure in parallel with deterioration of neurological status. Brain and cerebrospinal fluid GABA levels were not significantly altered. Cerebrospinal fluid glycine levels were increased two to three times in parallel with increasing brain glycine content in the devascularized rat but were unchanged in thioacetamide-induced liver failure, suggesting distinct pathophysiological mechanisms in these two experimental situations. On the other hand, onset of coma in both animal models of fulminant liver failure was accompanied by significantly increased cerebrospinal fluid taurine levels. We suggest that such changes result from taurine release from astrocytes in brain into the extracellular fluid; this is consistent with taurine's role in the regulation of intracellular osmolarity in brain. Sequential measurements of amino acids in the cerebrospinal fluid of small rodents with indwelling cisterna magna catheters adds a useful new approach for exploring the neurobiology of hepatic encephalopathy in fulminant liver failure.

Amino Acids↗

PubMed1991

Influence of calcium and amino acids on the osmium impregnation of the endoplasmic reticulum.

The aim of this study was to define further the interaction between osmium and organelle content in cells prefixed with glutaraldehyde. We have studied the reaction of osmium with divalent or trivalent cations (calcium, barium, zinc, aluminum, and iron) and various amino acids in the same conditions prevalent in histological techniques, in particular with Thiéry's technique of metal impregnation. Experiments were carried out in vitro in test tubes, on cellulose acetate discs, or with an immunodiffusion apparatus. Some experiments were also carried out with tissue extracts (kidney and intestine). Our studies suggest that calcium is in general essential for the formation of osmium black, but also that lysine is reactive even in the absence of calcium and that a few amino acids--such as tryptophan, ornithine, cysteine, and aspartic acid--are only slightly reactive in the absence of calcium. Other amino acids do not seem to participate in the endoplasmic reticulum osmium impregnation even in the presence of calcium ions. Our studies also suggest that osmium reactivity reflects calcium binding sites and not only calcium content.

Amino Acids↗

PubMed1990

Morphogenesis of endoplasmic reticulum in Xenopus oocytes after microinjection of rat liver smooth microsomes.

We have determined the kinetics of endoplasmic reticulum (ER) reconstitution following insertion of rat-liver smooth microsomes (SM) into Xenopus oocyte cytoplasm using electron microscopy as well as cytochemistry and thick-section 3-dimensional reconstruction. Oocytes were fixed 0, 10, 20, 40, 80, and 120 min after microinjection with SM and processed for thin- and thick-section electron microscopy. At 0 min postinjection, rat liver SM were observed as small vesicles and were loosely dispersed amongst oocyte organelles. At 10 min, tubules were discerned among many elongate vesicles; and these structures comprised large cytoplasmic regions delimited by mitochondria and yolk platelets. By 20 min, segregation of transplanted organelles yielded yolk-platelet-free regions composed of few vesicles but increasingly numerous, long and anastomosing tubules. By 40 min, a network with numerous tubular branches and fenestrations was observed among the few remaining vesicles. By 80 min, transformation of rat liver SM into a complex network of branching and anastomosing tubules was complete. Three-dimensional reconstruction revealed the network to be composed of interconnecting elements consisting of anastomosing tubules. The reconstituted network of anastomosing tubules in Xenopus oocytes was compared to the network of anastomosing tubules in rat liver hepatocytes and was found to be essentially identical. Network formation occurred in oocytes pretreated with either vinblastine (40 microM) or nocodazole (0.166 microM), and network organization was maintained in oocytes treated with the same drugs after microinjection and reconstitution. We conclude that SM retain sufficient molecular information for rapid self-assembly into structures resembling those in the cells from which they were derived. Both the assembly and maintenance of ER structure in oocyte cytoplasm are microtubule-independent. The formation of such structures following microinjection of SM into living cells provides a unique assay for this type of membrane subfraction.

Animals↗

PubMed1990

Fasting induces modifications of the endoplasmic reticulum in intestinal cells.

The polymorphism of the endoplasmic reticulum (ER) in epithelial cells with different transport functions such as the enterocyte suggests that the ER may be involved in some way in molecular transport. To further access this possibility, we examined the ER from the intestine of winter flounder, Pseudopleuronectes americanus, a species which undergoes an annual fast of approximately 6 months' duration, a time during which previous work indicates nutrient carrier number does not change. Fish from June (feeding) and January (8-10 weeks fasted) were sampled. Tissues from the pyloric caeca, foregut, midgut, and hindgut were prepared for electron microscopy using two techniques of staining. Cell height was unaltered in any section, although microvillar length shortened variably. Cellular organization, including position of nuclei, number and distribution of mitochondria, and presence of basolateral membranes, did not change. The ER appeared equally abundant in June and January. However, use of the osmium impregnation technique, which is specific for ER cisternal contents, revealed a change in the impregnation of ER, from a heavily impregnated network in summer to little or no impregnation in winter. These results suggest that a shift in function of the ER had occurred when nutrient transport ceased, and supports a role of the ER in nutrient transport.

Animals↗

PubMed1990

Protein phosphorylation in developing and regenerating rat kidney.

Renal cytosolic extracts from rats of different ages and mononephrectomized rats were incubated with gamma-[32P]ATP and analysed by high resolution two-dimensional electrophoresis and autoradiography. Extracts from new-born and young rats showed a great number of phosphorylated proteins migrating between the origin and Mr 52,000. Among these proteins, the group co-migrating with phosphorylase b (Mr 97,000) was particularly evident in new-born and days-old rats. In extracts from mature rats, other proteins of lower molecular weight, particularly those migrating between Mr 60,000 and 44,000, became intensely phosphorylated. The number and intensity of phosphorylated proteins from extracts of normal and nephrectomized rats, however, did not vary. Activity of cAMP-dependent protein kinase and [3H]cAMP binding was also modified during neonatal development but not in compensatory renal growth. Since cAMP-PK and protein phosphorylation are known to be regulated in response to hormonal stimulations, these results may provide good indications for the understanding of hormonal involvement in kidney growth.

Animals↗

PubMed1990

Effect of ammonia on brain serotonin metabolism in relation to function in the portacaval shunted rat.

Four weeks following portacaval anastomosis (PCA) in the rat, severe liver atrophy, sustained hyperammonemia, and increased plasma and brain tryptophan are observed. Administration of ammonium acetate (NH4Ac) to rats with PCA precipitates severe signs of hepatic encephalopathy (HE) (loss of righting reflex progressing to loss of consciousness and ultimately deep coma). To evaluate the relationship between the deterioration of neurological status in HE and serotonin (5-HT) metabolism, the levels of 5-HT, its precursor 5-hydroxytryptophan, and its major metabolite 5-hydroxy-indole-3-acetic acid (5-HIAA) were measured by HPLC with ion-pairing and electrochemical detection in three well-defined areas of the cerebral cortex: anterior cingulate, piriform and entorhinal, and frontoparietal; as well as in the caudate-putamen, the raphe nuclei, and the locus ceruleus in rats with PCA at different stages of HE, before and after injection of NH4Ac, as well as in sham-operated controls. The results demonstrate increased 5-HIAA/5-HT ratios after PCA and NH4Ac loading, suggesting increased 5-HT turnover in the brains of these animals. However, these changes do not appear to be related to the precipitation of coma as no significant difference in 5-HT turnover was observed between precoma and coma stages of HE. Increased 5-HT turnover in brain of shunted rats may be related to early symptoms of HE such as altered sleep patterns and disorders of motor coordination.

5-Hydroxytryptophan↗

PubMed1990

Brief inhalation of asbestos compromises superoxide production in cells from bronchoalveolar lavage.

Production of superoxide (O-.2) was measured in alveolar macrophages (AM) exposed to asbestos in vitro and in cells obtained from bronchoalveolar lavage (BAL) of rats inhaling asbestos. Steady state levels of O-.2 released by AM in vitro were dose and time dependent in response to crocidolite, chrysotile, and opsonized zymosan, a particulate used to trigger O-.2 generation. In contrast, an inhalation exposure for 1 h to crocidolite or for 6 days to either crocidolite or chrysotile asbestos resulted in a decreased production of O-.2 by BAL cells. Likewise, BAL cells from rats inhaling chrysotile for 1 h or crocidolite for 9 days exhibited a diminished capacity to secrete O-.2 when challenged with the particulate opsonized zymosan. Diminished generation of O-.2 by asbestos occurred in BAL cell populations containing either significantly increased numbers of polymorphonuclear leukocytes and lymphocytes (6- and 9-day exposures) or 99% AM (1-h exposure). Thus, these novel observations suggest that short-term inhalation of asbestos compromises the ability of BAL cells to produce O-.2 in the presence or absence of an additional phagocytic stimulus.

Administration, Inhalation↗

PubMed1990

A new method based on cobalt for histochemical and cytochemical demonstration of glucose-6-phosphatase activity.

We describe a novel technique for the histochemical and cytochemical demonstration of glucose-6-phosphatase activity. In this method, lead is replaced by cobalt. After activity of glucose-6-phosphatase, cobalt phosphate Co3(PO4)2 is formed, and in the presence of ammonium sulfide (NH4)2S, the precipitate is transformed into a sulfide that fixes osmium and provides good electron density. Glucose-6-phosphatase activity was determined mostly in rat kidney cells, but controls were also performed in liver cells. A strong reaction was seen in proximal tubule cells, but the reaction was weak in distal convoluted tubule cells. This technique showed the same endoplasmic reticulum (ER) organization in proximal and distal nephron as that seen with the osmium impregnation technique. In collecting tubules, intercalated cells had irregular reactivity, while principal cells had none. Our results indicate that the cobalt technique is valid, reliable, and sensitive enough to detect low glucose-6-phosphatase activity. Moreover, the technique can be used with 1-mm-thick specimens and obviates the need for use of frozen tissue sections.

Animals↗