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L Racine

Publications and source records attributed to L Racine.

At least 19 recordsLinked to original sources
PubMed1996

Adhesion of Helicobacter pylori to polarized T84 human intestinal cell monolayers is pH dependent.

Epithelial cells, which form tight polarized monolayers on porous substrates, constitute ideal model systems to study bacterial adhesion and invasion. The binding of Helicobacter pylori to the apical membrane of T84 cells, an epithelial cell line derived from a human colon carcinoma, was assessed biochemically and morphologically. Attachment was rapid, and binding remained constant over time, with a significant (P < 0.01, Mann-Whitney U test) ca. fourfold increase at pH 5.4 (76% +/- 22%) compared with pH 7.4 (18% +/- 7%). In contrast, adhesion of enteropathogenic Escherichia coli was not enhanced at pH 5.4. The transepithelial electrical resistance of the T84 cell monolayers was not affected by pH or by H. pylori. Following binding, H. pylori induced a reorganization of the brush border as reflected by actin condensation, facilitating the intimate association of the bacteria with the apical plasma membrane. H.pylori was not internalized, as shown by confocal microscopy. Some bacteria, found in deep invaginations of the apical membrane, were probably inaccessible to gentamicin, thus accounting for the observed tolerance to the antibiotic. These data provide the first evidence that an acidic environment favors Helicobacter adhesion and that binding is followed by survival of the survival of the bacteria in pockets of the apical membrane.

Bacterial Adhesion↗
PubMed1995

Distribution of albumin, alpha 1-inhibitor 3 and their respective mRNAs in periportal and perivenous rat hepatocytes isolated by the digitonin-collagenase technique.

The expression of albumin and alpha 1-inhibitor 3 genes was investigated in rat cell suspensions enriched in periportal (n = 10) and perivenous (n = 10) hepatocytes obtained by the digitonin-collagenase technique. The degree of enrichment of the cell suspensions was assessed: (1) by enzymic assays for the periportal marker alanine aminotransferase and for the perivenous marker glutamine synthetase; and (2) by their content of mRNAs for the periportal marker hepatic glutaminase and for glutamine synthetase. The existence of an antegrade intra-lobular gradient for albumin and alpha 1-inhibitor 3 mRNAs was demonstrated, with periportal:perivenous ratios of 2.33 and 3.80, respectively. However, no gradient was demonstrated for the respective protein contents with corresponding ratios of 0.98 and 1.21. A certain degree of overlap existed between periportal and perivenous suspensions for their content in albumin and alpha 1-inhibitor 3 mRNAs. A morphometrical analysis of the surface of digitonin-permeabilized hepatic tissue revealed that this overlap could be explained by a variable extent of permeabilization of the mediolobular zone from one rat to another and from one lobule to another in a given animal. These results suggest that while the digitonin-collagenase technique is well suited for studies in vitro of proteins expressed in sharp intra-lobular gradients or restricted to an intra-lobular compartment, it is not completely reliable for proteins distributed in continuous moderate intra-lobular gradients, such as albumin and alpha 1-inhibitor 3.

Acute-Phase Proteins↗
PubMed1994

Endothelial cell heterogeneity in the normal human liver acinus: in situ immunohistochemical demonstration.

While a certain degree of structural and functional intra-lobular heterogeneity of sinusoidal endothelial cells has been observed in rodents, little information is available about the zonal characteristics of sinusoidal endothelial cells in the human liver acinus. We have therefore examined the intra-acinar distribution of a panel of endothelial markers in the normal human liver, including: (a) structural markers of continuous and sinusoidal endothelia (PECAM-1, CD-34 protein, VE-cadherin, 1F10 antigen), (b) functional markers specific for sinusoidal endothelial cells, as previously determined in the laboratory (CD4 protein, the lipopolysaccharide-binding protein receptor (CD 14), aminopeptidase N, ICAM-1, receptors II and III for the Fc fragment of immunoglobulins G), (c) endothelial cell-matrix adhesion proteins and leukocyte-endothelial cell adhesion molecules. We observed a heterogeneous distribution for: (a) the 1F10 antigen, whose distribution in the human liver acinus was restricted to vessels situated along the axis of acinar zone 1, (b) the lipopolysaccharide-binding protein receptor and the receptor III for the Fc fragment of IgG, not expressed or only barely expressed in acinar zone 1. The distribution of the other markers tested did not display significant intra-lobular variation. Our in situ results suggest the existence of a degree of zonal heterogeneity in the structural and functional characteristics of sinusoidal endothelial cells in the human liver acinus. This might contribute to the constitution of distinct microenvironments within the human liver parenchyma.

Adult↗
PubMed1993

Parenchymal innervation of normal and cirrhotic human liver: a light and electron microscopic study using monoclonal antibodies against the neural cell-adhesion molecule.

Hepatic innervation participates in the control of sinusoidal blood flow and in the regulation of certain metabolic functions of the liver. The study of the distribution of hepatic nerves has been hampered by the lack of adequate markers. We therefore tested the value of the neural cell-adhesion molecule (NCAM) as a probe for the study of parenchymal nerves in the normal and cirrhotic human liver. Four antibodies against various epitopes of NCAM were tested by light and electron microscopic immunohistochemistry: Leu19, ERIC-1, VC1.1, and HNK-1. Their reactivity was compared with that of antibodies against the following neural cell markers: S100 protein, neurofilaments, and neuron-specific enolase (NSE). The tissue reactivity of anti-NCAM antibodies was variable, suggesting a microheterogeneity of the NCAM molecule in the normal liver. Clones Leu19 and ERIC-1 proved to be the most sensitive of the anti-NCAM antibodies. Their sensitivity was superior to that of the antibodies directed against the other neural cell markers tested. In the normal liver, both Leu19 and ERIC-1 demonstrated a heterogeneous distribution of nerve fibers inside the hepatic lobule. Intralobular nerve fibers predominated in Zone 1. This might contribute to the constitution of distinct zonal microenvironments inside the hepatic lobule. In cirrhosis, no nerve fiber was detected inside parenchymal nodules; no nerve plexus was visible at the contact of proliferating neoductules. These alterations might contribute to the pathogenesis of the hemodynamic and metabolic disorders observed in cirrhosis.

Antibodies, Monoclonal↗
PubMed1993

Effects of digitonin on the intracellular content of rat hepatocytes: implications for its use in the study of intralobular heterogeneity.

Anterograde or retrograde perfusion of rat liver with digitonin selectively permeabilizes the periportal or the perivenous zone of the hepatic lobule. Digitonin perfusion is used to analyze the effluents released by permeabilized hepatocytes or, combined with collagenase perfusion, to obtain cell suspensions enriched in either periportal or perivenous hepatocytes. Despite the wide use of digitonin to study lobular heterogeneity, its affects on rat hepatocytes are not well documented. We therefore analyzed the effects of digitonin perfusion on the intracellular content of rat hepatocytes by combining electron microscopy, histoenzymology, immunohistochemistry, and in situ hybridization. At the concentration currently used for the study of lobular heterogeneity, digitonin perfusion induced a marked cytosolic clarification of permeabilized hepatocytes, while most organelles except mitochondria were well preserved. In the digitonin-altered zones, there was no histochemical detection of non-membrane-bound enzymes (lactate dehydrogenase, glutamate dehydrogenase), whereas membrane-bound enzymes (succinate dehydrogenase, beta-hydroxybutyrate dehydrogenase, NADPH dehydrogenase, glucose-6-phosphatase) were still detected. Immunohistochemistry and in situ hybridization revealed significant amounts of several plasma proteins (albumin, alpha 2-macroglobulin, alpha 1-inhibitor 3, alpha 1-acid glycoprotein) and their respective mRNAs in digitonin-permeabilized hepatocytes. The demonstration that digitonin-permeabilized hepatocytes retain many intracellular constituents shows that biochemical analysis of cellular effluents released from digitonin-permeabilized hepatocytes must be interpreted with caution and that the apparent characteristics of cell suspensions obtained by the digitonin-collagenase technique might be significantly altered by contamination with permeabilized hepatocytes from the opposite zone.

Animals↗
PubMed1993

[Mitchell's osteotomy in the treatment of hallux valgus].

Ninety-one (91) Mitchell osteotomies on 63 patients (60 females and 3 males) were reviewed. The average follow-up was 40 months (min. 12, max. 70). The average age at the time of the surgery was 51 years (min. 20, max. 74). The presence of a apinful bunion justified the surgery in a majority of cases (92%). The clinical evaluation was done by an independent observer. Weight bearing X-rays of the feet were made in each case. The results show a satisfactory improvement of the pain in 92% of the cases. The patients were satisfied with the appearance of their foot in 93% of the cases. The average active articular range of motion was 47 degrees (min. 20 degrees, max. 120 degrees). The Das De scale showed 75% of excellent and good results. Twelve per cent (12%) of the patients presented residual metatarsalgia. We observed minor complications in 10 cases (11%). We report no cases of avascular necrosis, pseudarthrosis or infection. Clinico-radiological correlations were made. We obtained an average correction of 13 degrees (min. -5 degrees, max. 28 degrees) of the hallux valgus and 3.5 degrees (min. -7 degrees, max. 7 degrees) of the intermetatarsal angle. We recommend the Mitchell osteotomy as long as the indication criterias and the surgical technique are respected.

Adult↗
PubMed1992

Functional hepatocellular heterogeneity for the production of plasma proteins.

It is now well established that hepatocytes are the main liver cells responsible for the synthesis of plasma proteins produced by the liver. That these cells are not specialized in the production of the different plasma proteins is also well established. Presently the point still debated is whether a functional hepatocellular heterogeneity exists for plasma protein synthesis as for many other hepatocyte functions. Several physiological and pathological situations suggest that this heterogeneity takes place in the hepatocytes of two opposite hepatic lobular zones, the periportal and centrilobular zones. However, this zonal difference, which supposes different regulatory mechanisms, must be confirmed by techniques other than the now classical immunocytochemistry or the in situ hybridization technique recently proposed for the demonstration of mRNAs in hepatocytes. Another hepatocellular heterogeneity, the intercellular heterogeneity, which can be observed in the same lobular zone, is more difficult to analyze, but shows that from hepatocyte to hepatocyte a variation exists in the synthesis of a given plasma protein.

Animals↗
PubMed1991

Transfection of lipoma cells with papilloma bovine virus subgenomic fragment.

Lipoma cells with consistent chromosomal aberration have been transfected with plasmids carrying papilloma bovine virus subgenomic fragment (PBV 69). The successful transformation of the cells was ascerted on the changed growth pattern of the cells in liquid medium, colony formation in soft agar and modified cell appearance in electron microscopy; transfection with PBV 69 has not been, however, sufficient to immortalize lipoma cells.

Adipose Tissue↗
PubMed1990

HIV infection among Quebec women giving birth to live infants.

This is the first anonymous unlinked seroprevalence study in Canada to use serum samples from newborns to determine the seroprevalence rate of human immunodeficiency virus (HIV) infection among childbearing women. Of the 68,808 samples tested 42 were confirmed as positive, for an overall crude seroprevalence rate of 6.1 per 10,000 live births (95% confidence interval [CI] 4.4 to 8.3), or 1 woman in 1638. Women who lived on Montreal island had an overall rate of 17.9 per 10,000 live births (95% CI 12.2 to 25.4), or 1 woman in 559. We observed a significant association between revenue index and seroprevalence; the rates were as high as 46.4 per 10,000 live births (95% CI 18.7 to 95.3), or 1 woman in 216, for Montreal island postal code areas with revenue indexes 20% or more below the provincial median. Extrapolation of the data suggested that 56 women with HIV infection gave birth to a live infant during 1989 in Quebec. Even though attempts to generalize the data from childbearing women to women of childbearing age have an inherent conservative bias, the results of our study suggest that 988 women (95% CI 713 to 1336) aged 15 to 44 years in Quebec had HIV infection in 1989. The actual number is likely substantially higher. The need for well-designed, creative interventions to prevent further HIV transmission to women is evident. Planning for the provision of medical and psychosocial services sensitive to specific needs of women who are already infected should start immediately.

Adolescent↗
PubMed1990

Polarized transport of the polymeric immunoglobulin receptor in transfected rabbit mammary epithelial cells.

A cDNA for the rabbit low Mr polymeric immunoglobulin (poly-Ig) receptor was expressed in an immortalized rabbit mammary cell line. The intracellular routing of the receptor and its cell surface expression was analyzed in stably transfected cells grown on permeable supports. Initially the cells formed a monolayer with no transmural electrical resistance. All monolayer cells expressed the poly-Ig receptor and cytokeratin 7 filaments characteristic of luminal mammary cells but absent in myoepithelial cells. Within 7 d in culture, the cells underwent cytodifferentiation and formed a bilayer with a transepithelial electrical resistance of approximately 500 omega x cm2. Upper layer cells formed tight junctions with adjacent cells and gap junctions with basal cells. Expression of the poly-Ig receptor and cytokeratin 7 was restricted to the cells from the upper layer. The kinetics of receptor biosynthesis and processing was similar to that reported for rabbit mammary gland and rat liver. The receptor was cleaved at the apical cell surface and release of secretory component into the apical medium occurred with a half-time of approximately 2 h. Selective cell surface trypsinization combined with pulse-chase experiments served to determine at which cell surface domain newly synthesized receptor appeared first. The receptor was digested with a half-time of approximately 60 min with trypsin present in the basolateral medium and 90 min with apical trypsin. These data are consistent with selective targeting of newly synthesized receptor to the basolateral surface. The results indicate that transcytosis of the receptor from basolateral to apical membrane in the presence or the absence of its ligand requires approximately 30 min. Cleavage of the receptor by endogenous protease is not concomitant with its appearance at the apical surface, but requires additional time, thus explaining the presence of intact receptor on the apical membrane.

Animals↗
PubMed1989

Processing of the polymeric immunoglobulin receptor.

The transcellular transport of polymeric immunoglobulins (pIg) across mucosal epithelia is mediated by a membrane glycoprotein known as the polymeric immunoglobulin receptor (pIgR). The intracellular routing of the pIgR has been used as a model to study protein traffic. Examination of the biosynthesis and processing of the pIgR in mammary gland and liver have led to a working hypothesis for pIgR routing in the cell. These hypotheses are currently being tested in an immortalized cell line derived from rabbit mammary gland alveolar cells.

Animals↗
PubMed1986

Distribution and processing of the polymeric immunoglobulin receptor in the rat hepatocyte: morphological and biochemical characterization of subcellular fractions.

The transepithelial transport of polymeric immunoglobulins is an essential process in the mucosal immune system. Transport across the epithelial cells of mucous or exocrine glands is affected by an integral membrane glycoprotein receptor known as membrane secretory component (SCm) or as polymeric immunoglobulin receptor (pIgR). This receptor binds polymeric immunoglobulins at the basolateral cell surface and mediates their transcellular translocation and their release from the apical plasma membrane into external secretions. Release depends on cleavage of the membrane-anchoring domain of the receptor, resulting in liberation of polymeric immunoglobulin bound to the ectoplasmic domain of the receptor (secreted SC or SCs) into extracellular secretions. Using a monoclonal antibody directed against the cytoplasmic tail of the receptor and a polyclonal antibody directed against the secreted ectoplasmic domain, we have combined cell fractionation and Western blotting techniques to examine the fate of these receptor domains in the hepatocyte. In this study, we characterize biochemically and morphologically the various subcellular components separated by our fractionation scheme, and correlate this with biochemical analysis of the receptor in each fraction.

Animals↗
PubMed1983

Effect of cell shape change on the function and differentiation of rabbit mammary cells in culture.

We examined the role of cell shape, cytodifferentiation, and tissue topography on the induction and maintenance of functional differentiation in rabbit mammary cells grown as primary cultures on two-dimensional collagen surfaces or in three-dimensional collagen matrices. Mammary glands from mid-pregnant rabbits were dissociated into single cells, and epithelial cells were enriched by isopycnic centrifugation. Small spheroids of epithelial cells (approximately 50 cells) that formed on a rotary shaker were plated on or embedded in collagen gels. The cells were cultured for 1 d in serum-containing medium and then for up to 25 d in chemically defined medium. In some experiments, epithelial monolayers on gels were mechanically freed from the dishes on day 2 or 5. These gels retracted and formed floating collagen gels. On attached collagen gels, flat monolayers of a single cell type developed within a few days. The cells synthesized DNA until the achievement of confluence but did not accumulate milk proteins. No morphological changes were induced by prolactin (PRL). On floating gels, two cell types appeared in the absence of cell proliferation. The cells in direct contact with the medium became cuboidal and developed intracellular organelles typical of secretory cells. PRL-induced lipogenesis, resulting in large fat droplets filling the apical cytoplasm and accumulation of casein and alpha-lactalbumin in vesicles surrounding the fat droplets. We detected tranferrin in the presence or absence of PRL intracellularly in small vesicles but also in the collagen matrix in contact with the cell layer. The second cell type, rich in microfilaments and reminiscent of the myoepithelial cells, was situated between the secretory cell layer and the collagen matrix. In embedding gels, the cells formed hollow ductlike structures, which grew continuously in size. Secretory cells formed typical lumina distended by secretory products. We found few microfilament-rich cells in contact with the collagen gels. Storage and secretion of fat, caseins and alpha-lactalbumin required the presence of PRL, whereas the accumulation and vectorial discharge of transferrin was prolactin independent. There was no differentiation gradient between the tip and the cent of the outgrowth, since DNA synthesis and milk protein storage were random along the tubular structures. These results indicate that establishment of functional polarity and induction of cytodifferentiation are influenced by the nature of the interaction of the cells with the collagen structure. The morphological differentiation in turn plays an important role in the synthesis, storage, and secretion of fat and milk proteins.

Animals↗
PubMed1980

Attempts to quantitate immunocytochemistry at the electron microscope level.

The ability to localize intracellular macromolecules in situ by high resolution techniques has been made possible by the development of antibody labelling of thin sections obtained either from tissues embedded in an hydrophilic matrix, or by ultracryotomy or from conventional plastic embedded tissue. When particle-tagged immunological reagents are used to visualize intracellular antigens, quantitative information can be obtained by combining particle counts with morphometric estimations of compartment volume. Various detection systems have been used successfully for quantitation, which include ferritin-conjugated antibodies, biotin-avidin-ferritin complexes and, more recently, gold-protein A conjugates. Examples of the use of these techniques the localization of secretory proteins in pancreatic exocrine cells, opsin and a large membrane protein in photoreceptor cells of frog retina, and contractile proteins in skeletal muscle are given. Quantitative data obtained by morphometric analysis, both in bovine and rat pancreatic exocrine cells, are compared with values assessed by biochemical methods.

Amylases↗
PubMed1977

Immunocytochemical localization of secretory proteins in bovine pancreatic exocrine cells.

The bovine exocrine pancreatic cell produces a variety of enzymes and proenzymes for export. Biochemical studies by Greene L.J., C.H. Hirs, and G.E. Palade (J. Biol. Chem. 1963. 238:2054) have shown that the mass proportions of several of these proteins in resting pancreatic juice and zymogen granule fractions are identical. In this study we have used immunocytochemical techniques at the electron microscope level to determine whether regional differences exist in the bovine gland with regard to production of individual secretory proteins and whether specialization of product handling occurs at the subcellular level. The technique used is a modification of one previously reported (McLean, J.D., and S.J. Singer. 1970. Proc. Natl. Acad. Sci U.S.A. 69:1771) in which immunocytochemical reagents are applied to thin sections of bovine serum albumin-imbedded tissue and zymogen granule fractions. A double antibody technique was used in which the first step consisted of rabbit F(ab')2 antibovine secretory protein and the detection step consisted of sheep (F(ab')2 antirabbit F(ab')2 conjugated to ferritin. The results showed that all exocrine cells in the gland, and all zymogen granules and Golgi cisternae in each cell, were qualitatively alike with regard to their content of secretory proteins examined (trypsinogen, chymotrypsinogen A, carboxypeptidase A, RNase, and DNase). The data suggest that these secretory proteins are transported through the cisternae of the Golgi complex where they are intermixed before copackaging in zymogen granules; passage through the Golgi complex is apparently obligatory for these (and likely all) secretory proteins, and is independent of extent of glycosylation, e.g., trypsinogen, a nonglycoprotein vs. DNase, a glycoprotein.

Animals↗
PubMed1975

Localization of secretory IgA, secretory component, and alpha chain in the mammary gland of lactating rabbits by immunoelectron microscopy.

The different steps in the processing of secretory IgA (sIgA) of the mammary gland of lactating rabbits have been investigated with immunoelectron microscopy. The method employed consists of an indirect localization sequence, in which the immunologic reagents are allowed to diffuse into the fixed tissue prior to embedding and thin sectioning. In the first step, goat F(ab')2 fragments directed against sIgA, secretory component (SC), or alpha chain were used. To visualize the location of these first-step antibody fragments, a second Fab fragment directed against goat F(ab')2 antibody was prepared and coupled to a small heme octapeptide that possessed peroxidatic activity, the reaction product of which is visible by electron microscopy. Both the epithelial cell and the local plasmacytes of the mammary gland contain alpha chain, whereas SC is exclusively located in the epithelial cells. In the plasmacytes, both the cisternae of the rough endoplasmic reticulum and the saccules and vesicles of the Golgi complex contain alpha chain. In the epithelial cells, the elements of the Golgi complex and large apical vacuoles situated in the apical region of the cell. Based on these results, a model for processing of sIgA is proposed and discussed.

Animals↗