Biomedical subjects

J Gabrion

Publications and source records attributed to J Gabrion.

At least 19 recordsLinked to original sources

PubMed2005

Aging affects choroidal proteins involved in CSF production in Sprague-Dawley rats.

Aging is currently associated with progressive declines of cerebral functions. From these, a decreased resistance to dehydration suggested alteration in choroidal control of brain homeostasis and reduced cerebrospinal fluid (CSF) production in old subjects. In the present study, choroid plexuses of 20-month old Sprague-Dawley rats were compared with those of 3- and 10-month old rats. Using ultrastructure analysis and immunodetection of ezrin, a protein associating cytoskeleton to membranes, we showed that progressive loss of microvilli and strong decrease in apical ezrin are evident in 20-month old rats. Using immunolabeling and confocal microscopy, we found reduction in expression of two choroidal proteins, carbonic anhydrase II and aquaporin 1, involved in CSF secretion. In addition, we confirmed previous studies indicating that choroidal Na,K-ATPase decreased with age. In situ hybridization analyses showed that mRNA levels for Na,K-ATPase and aquaporin 1 were significantly lowered in choroid plexus of old rats. These findings are consistent with a reduced secretory activity in choroid plexus and suggest that massive disorders could affect choroidal CSF production in aged rats.

Aging↗

PubMed2002

Influence of hypergravity on hypothalamic vasopressin and oxytocin neurons in rats.

This study was aimed to evaluate the reaction of the vasopressin (VP) and oxytocin (OT) neurons of the supraoptic nucleus (SON) in rats to single or repeated hypergravity (HG). Special attention was paid to the tyrosine hydroxylase (TH) expression in VP neurons as a marker of the neuron activation. Rats were revolved in a centrifuge with overloading 2G for 5 days or 34 days as well as for 34 days plus 5 days with an interval of 39 days between two rotations. Control rats were kept in a centrifuge room. Radioimmununoassay, quantitative and semi-quantitative immunocytochemistry and in situ hybridization were used to evaluate: a) VP concentration in the pituitary posterior lobe (PL) and in plasma; b) the number of VP-, OT- and TH-immunoreactive neurons in the SON; c) the optic density of VP-, OT- and TH-immunoreactive materials in cell bodies (SON) and distal axons (PL), d) the optic density of VP and OT mRNAs signals (S35) in the whole SON on microfilms. According to our data, VP neurons were strongly activated during HG (5 days or 34 days) that was manifested in the functional hypertrophy of the neurons, greatly increased concentrations of VP mRNA in the SON and VP in plasma, the onset of the TH expression. The neurons showed initially (5 days) the functional insufficiency (VP release > VP synthesis) followed by their adaptation (subsequent 29 days) to the increased need in VP (VP release < VP synthesis). No reaction of VP neurons was observed to repeated HG. In contrast to VP neurons, OT neurons did not react to short-term HG or showed functional depression after the long-term treatment.

Journal Article↗

PubMed2001

Persistence of tight junctions and changes in apical structures and protein expression in choroid plexus epithelium of rats after short-term head-down tilt.

Major alterations of choroidal cell polarity and protein expression were previously shown to be induced in rats by long-term adaptation to space flight (14 days aboard a space shuttle) or anti-orthostatic suspension (14 and 28 days) performed by tilting rats head-down (i.e. using a ground-based model known to simulate several effects of weightlessness). In rabbits, it was hypothesized that the blood-CSF barrier was opened in choroid plexus, after a short head-down suspension. To understand the early responses to fluid shifts induced by head-down tilts and evaluate the tightness of the choroidal junctions, we have investigated the effects of acute adaptations to anti-orthostatic restraints, using hindlimb-suspended Sprague-Dawley and Wistar rats. Ultrastructural and immunocytochemical studies were performed on choroid plexuses from lateral, third and fourth ventricles, after 30, 90 and 180 minutes of head-down tilt. Alterations were not perceptible at the level of choroidal tight junctions, as shown by freeze-fracture, claudin-1 and ZO-1 immunolocalizations and conventional electron microscopy, after intravenous injection of cytochrome C. The apical surface of choroidal cells was clearly more affected. Microvilli were longer and thinner and ezrin was over-expressed during all the periods of time considered, showing an early cytoskeletal response. Several proteins involved in the choroidal production of cerebrospinal fluid (sodium-potassium ATPase, carbonic anhydrase II, aquaporin 1) appeared first increased (30 minutes after the tilt), and then, returned to the control level or were lowered (after a 3-hour head-down suspension). Although head-down tilts do not seem to damage the blood-cerebrospinal fluid barrier in choroid plexus, it seemed that the expression of several apical proteins is affected very early.

Animals↗

PubMed2000

Altered gravity downregulates aquaporin-1 protein expression in choroid plexus.

Aquaporin-1 (AQP1) is a water channel expressed abundantly at the apical pole of choroidal epithelial cells. The protein expression was quantified by immunocytochemistry and confocal microscopy in adult rats adapted to altered gravity. AQP1 expression was decreased by 64% at the apical pole of choroidal cells in rats dissected 5.5-8 h after a 14-day spaceflight. AQP1 was significantly overexpressed in rats readapted for 2 days to Earth's gravity after an 11-day flight (48% overshoot, when compared with the value measured in control rats). In a ground-based model that simulates some effects of weightlessness and alters choroidal structures and functions, apical AQP1 expression was reduced by 44% in choroid plexus from rats suspended head down for 14 days and by 69% in rats suspended for 28 days. Apical AQP1 was rapidly enhanced in choroid plexus of rats dissected 6 h after a 14-day suspension (57% overshoot, in comparison with control rats) and restored to the control level when rats were dissected 2 days after the end of a 14-day suspension. Decreases in the apical expression of choroidal AQP1 were also noted in rats adapted to hypergravity in the NASA 24-ft centrifuge: AQP1 expression was reduced by 47% and 85% in rats adapted for 14 days to 2 G and 3 G, respectively. AQP1 is downregulated in the apical membrane of choroidal cells in response to altered gravity and is rapidly restored after readaptation to normal gravity. This suggests that water transport, which is partly involved in the choroidal production of cerebrospinal fluid, might be decreased during spaceflight and after chronic hypergravity.

Animals↗

PubMed1999

Cardiac atrial natriuretic peptide (ANP) in rat dams and fetuses developed in space (NIH-R1 and NIH-R2 experiments).

NIH-R1 and R2 missions, conducted by NASA, allowed us to study the effects of the microgravitational environment 1) on cardiac ANP in pregnant rats, spaceflown for 11 days and dissected after a 2-day readaptation to Earth's gravity, after natural delivery, and 2) on maturation of cardiac ANP system in rat fetuses developed for 11 days in space and dissected on the day of landing, 2 days before birth. Immunocytochemical and electron microscopy analyses showed a typical formation of ANP-containing granules in atrial myocytes, in both dams and fetuses. Using competitive RT-PCR and radioimmunoassays, we observed that, after 2 days of readaptation to Earth's gravity, cardiac ANP biosynthesis of rat dams flown in space was increased by about twice, when compared to Synchronous and Vivarium Control rats. More obviously, rat fetuses developed in space and dissected on the day of landing displayed an altered maturation of cardiac ANP, evidenced by an increased mRNA biosynthesis (by about 6 fold, p<0.05), whereas the cardiac ANP storage was slightly reduced (by about twice, p<0.05) in both Flight and Synchronous Control groups, in comparison with Vivarium Control rats. These last results suggest that ANP metabolism during development is impacted by the microgravitational environment, but also by the housing conditions designed for space flight.

Animals↗

PubMed1998

Presence of atrial natriuretic peptide in two desert rodents: comparison with rat.

Atrial natriuretic peptide (ANP) was characterized and assayed in plasmas, hearts, and brains of two Algerian desert rodents, Psammomys obesus and Meriones libycus along with vasopressin, which was assayed in hypophyses and hypothalami. Using reverse-phase high-performance liquid chromatography and radioimmunoassay, we showed, in plasmas and hearts of both species of desert rats, the presence of peptides similar to rat N- and C-terminal ANP but in lower amounts than in Wistar rats. Conversely, C-terminal ANP was abundantly detected in hypophyses from Meriones libycus rats. As these peptides, through their diuretic and natriuretic activities, are involved in body fluid regulation and electrolyte balance, the reduction of ANP stores in both plasmas and hearts suggests that diuresis and natriuresis are lowered in both species of mammals adapted to arid environments. This could occur because of the vasopressin-mediated adaptation, but also in response to the low ANP involvement in hydro-osmotic regulations, even in Psammomys, which has a dietary salt loading. On the other hand, the higher C-terminal ANP contents in the hypophysis of Meriones than in Psammomys and Wistar rats remain to be understood.

Acclimatization↗

PubMed1998

Phenotype modulation in primary cultures of aortic smooth muscle cells from streptozotocin-diabetic rats.

Diabetes mellitus is a major risk factor for atherosclerosis. In atherosclerotic lesions, arterial smooth muscle cells (SMC) change from a contractile to a synthetic phenotype characterized by active proliferation. A similar phenotype modulation occurs in vitro when isolated arterial SMC are grown in culture and is characterized by both changes in cell morphology and a typical switch in actin isoform expression. In this study, we examined the influence of streptozotocin (STZ)-induced diabetes on the differentiation state and the phenotype modulation of cultured rat aortic SMC. We used transmission electron microscopy to study the fine structure of STZ-diabetic and non-diabetic SMC in primary culture and immunological methods for the determination of the proportions of alpha-smooth muscle actin (alpha-SM) and nonmuscle beta-actin (beta-NM) isoforms. Cultured STZ-diabetic SMC exhibited a large cytoplasmic volume, rich in rough endoplasmic reticulum, when compared with cultured non-diabetic SMC. alpha-SM, organized in stress fibers, was less homogeneously and abundantly distributed and by contrast, beta-NM was more abundant in STZ-diabetic than in non-diabetic SMC. Cytofluorimetric analyses demonstrated that the alpha-SM content was reduced in freshly STZ-diabetic SMC. Furthermore, during logarithmic growth of cultured SMC, the decrease of alpha-SM was more important in STZ-diabetic than in non-diabetic SMC. Immunoblotting of actin isoforms confirmed that expression of beta-NM was more important in STZ-diabetic than in non-diabetic SMC even in freshly isolated cells. The results suggest that SMC from STZ-diabetic rats express a more dedifferentiated state and undergo a more rapid phenotypic modulation in primary cultures than SMC from non-diabetic rats. Therefore, diabetes could induce changes in the phenotype of arterial SMC which might be associated with the onset or progression of the atherogenic process.

Actins↗

PubMed1998

Choroidal readaptation to gravity in rats after spaceflight and head-down tilt.

To determine when choroidal structures were restored after readaptation to Earth gravity or orthostatic position, fine structure and protein distribution were studied in rat choroid plexus dissected either 6 h [Space Life Sciences-2 (SLS-2) experiments] or 2 days [National Institutes of Health-Rodent 1 (NIH-R1) experiments] after a spaceflight, or 6 h after head-down tilt (HDT) experiments. Apical alterations were noted in choroidal cells from SLS-2 and HDT animals, confirming that weightlessness impaired choroidal structures and functions. However, the presence of small apical microvilli and kinocilia and the absence of vesicle accumulations showed that the apical organization began to be restored rapidly after landing. Very enlarged apical microvilli appeared after 2 days on Earth, suggesting increased choroidal activity. However, as distributions of ezrin and carbonic anhydrase II remained altered in both flight and suspended animals after readaptation to Earth gravity, it was concluded that choroidal structures and functions were not completely restored, even after 2 days in Earth's gravity.

Adaptation, Physiological↗

PubMed1997

Effects of an 11-day spaceflight on the choroid plexus of developing rats.

Cellular distributions of ezrin, a cytoskeletal protein involved in apical cell differentiation in choroid plexus, and carbonic anhydrase II, which is partly involved in the cerebrospinal fluid production, were studied by immunocytochemistry, at the level of choroidal epithelial cells from the lateral, third and fourth ventricles in normal or experimental fetuses, in parallel with the ultrastructure of apical microvilli, observed by transmission electron microscopy. We compared choroid plexuses from developing normal rats (gestational day 15 to birth) with choroid plexuses from 20-day-old rat fetuses, developed for 11 days in space, aboard a space shuttle (NASA STS-66 mission, NIH-R1 experiments), from gestational day 9 to day 20. The main changes observed in fetuses developed in space were demonstrated by immunocytochemistry and concerned the distribution of ezrin and carbonic anhydrase II. Thus, in fetuses developing in space, ezrin was strongly detected in the choroidal cytoplasm and weakly associated to the membrane in the apical domain of the choroid plexus from the fourth ventricle. Such alterations suggested that choroid plexus from rat fetal brain displays a delayed maturation under a micro-gravitational environment. In contrast, intense immunoreactions to anti-carbonic anhydrase II antibodies showed that this enzyme is very abundant in rats developed in space, compared to ground control fetuses.

Animals↗

PubMed1996

Changes in apical organization of choroidal cells in rats adapted to spaceflight or head-down tilt.

Structural changes observed in choroid plexuses from rats dissected aboard a space shuttle, on day 13 of an orbital flight (NASA STS-58 mission, SLS-2 Experiments) demonstrated that choroidal epithelial cells display a modified organization in a microgravitational environment. Results were compared with ultrastructural observations of choroid plexus from rats maintained under anti-orthostatic restraint (head-down tilt) for 14 days. In both experiment types, the main alterations observed by transmission electron microscopy, at the level of choroidal epithelial cells from the third and fourth ventricles, concerned the formation and the organization of apical microvilli, whereas pseudopod-like structures appeared. Immunocytochemical distribution of ezrin, a cytoskeletal protein involved in apical cell differentiation in choroid plexus, confirmed the structural alteration of microvilli in head-down tilted rats, Kinocilia tended to disappear from the apical surface, suggesting a partial loss of cell polarization. In addition, large amounts of clear vesicles were gathered in the apical cytoplasm of choroidal epithelial cells. Disorganization of apical microvilli accumulations of apical vesicles and partial loss of cell polarity showed that long-stays in weightlessness induced alterations in the fine structure of choroid plexus, consistent with a marked reduction of cerebrospinal fluid production.

Adaptation, Physiological↗

PubMed1995

Progressive development of gap junctions during growth of human pancreatic duct cells (Capan-1) in vitro and in vivo.

Among their numerous functions, gap junctions play a crucial role in proliferation, differentiation and secretion processes, although their existence and potential role in ion secretion in human pancreatic ducts have yet to be established. To investigate the morphogenesis and the role of gap junctions in human pancreatic duct cells, the Capan-1 cell line maintained in culture or heterotransplanted into nude mice was employed as model system. Capan-1 cells polarize during their growth in vivo and in vitro forming duct-like structures. Furthermore in culture, after confluence, these cells form domes, which is indicative of ion exchange processes. After treatment with tannic acid and freeze-fracture, gap junctions were observed along the basolateral membranes of Capan-1 cells on electron microscopic examination. The presence of alkaline phosphatases on gap junctions was demonstrated cytoenzymatically. In addition, cell-to-cell communication was visualized by microinjection of Lucifer yellow. During differentiation of Capan-1 cells in culture, the frequency of intercellular communications increased markedly over the period (days 11-13) when the cells form duct-like structures. The increase in gap junctions was demonstrated by analysis of the polarized cells organized in duct-like structures that are commonly observed in the tumors formed by heterotransplantation of Capan-1 cells into nude mice. Furthermore, gap junctions associated with tight junctions were also observed in the cells forming such structures. The role of gap junctions in ion exchange was evaluated by counting the number of domes in cultures treated with heptanol. Heptanol (an uncoupling agent of gap junction communication) completely inhibited dome formation in a reversible way, and reduced the frequency of intracellular communications by 44%. These results suggest that the gap junctions expressed by Capan-1 cells are involved in ion secretion by the human cancerous pancreatic duct cell line, Capan-1. In the present study, we show that: i) the expression of gap junctions is linked to development of the spatial conformation of the cells; and ii) gap junctions may be involved in ion secretion.

Adenocarcinoma↗

PubMed1994

Cardiac and plasma atrial natriuretic peptide after 9-day hindlimb suspension in rats.

To determine atrial natriuretic peptide (ANP) adaptation to simulated weightlessness, immunoreactive plasma (ir-NH2- and ir-COOH-terminals) and atrial (ir-COOH-terminal) ANP levels, atrial mRNA expression, immunoreactive cardiocyte ANP levels (ir-NH2- and ir-COOH-terminals), and ultrastructural observations of granules in atrial cardiocytes were assessed in male Wistar rats after a 9-day hindlimb suspension. Plasma ir-NH2- and ir-COOH-terminal ANP concentrations decreased by 17 (P < 0.05) and 37% (P < 0.05), respectively, in suspended rats. A concomitant ir-COOH-terminal ANP content reduction was also observed in left (31%; P < 0.01) and right atria (25%; P < 0.05). Atrial ANP mRNA expression was severely depleted in the right atrium and less so in the left atrium after 9 days of hindlimb suspension. Immunocytochemistry observations demonstrated lowered NH2- and COOH-terminal ANP immunoreactivities in left and right atria from suspended rats. A reduced number of storage granules (dense granules) in both atria was also noted on ultrastructural analysis. It was concluded that ANP biosynthesis, storage, and release were decreased after a 9-day hindlimb suspension.

Animals↗

PubMed1994

ANP binding sites are increased in choroid plexus of SLS-1 rats after 9 days of spaceflight.

Specific alpha-rat 28-amino acid atrial natriuretic peptide [ANP(99-126)] (rANP) binding sites in choroid plexus and meningia of rats flown for 9 days on the mission STS-40 (SLS-1) carried on the space shuttle Columbia in June 1991 were analyzed after incubation of brain sections with 125I-rANP and autoradiography, using computer-assisted microdensitometric image analysis. The number of 125I-rANP binding sites (expressed by Bmax values) in the choroid plexus of lateral and third ventricles of these rats was significantly increased (x 1.5-2.5 times), as compared with that found in ground control rats. No differences in the binding affinity (deducible from Kd values) were observed at the level of these structures. The choroid plexus from the fourth ventricle of the same rats displayed no changes in the binding capacity or affinity after the spaceflight. Meningia from the rats flown in space did not demonstrate any significant modifications of the number of 125I-rANP binding sites, but displayed a significant increase in Kd values, which suggested a reduced affinity of the meningeal ANP receptors during a 9-d spaceflight. The possibility that atrial natriuretic peptide may be involved in the regulation of fluid and electrolyte fluxes in the brain, during adaptation to microgravity, through modified expression of specific high affinity receptors, mainly in choroid plexus from forebrain or in meningia, must be considered.

Animals↗

PubMed1991

Gap junctional intercellular communication between cultured ependymal cells, revealed by lucifer yellow CH transfer and freeze-fracture.

In order to analyze intercellular communication between ependymal cells in mammalian brain, we have studied gap junctional communication of ependymal and glial cells in long term primary cultures derived from fetal mouse or rat hypothalamus and choroid plexus obtained in serum supplemented media with two complementary methods: 1) dye transfer of Lucifer Yellow CH after intracellular microinjection of the different cellular types, and 2) freeze-fracture of the same cultured ependymal cells. In our culture conditions, we have shown that the GJIC capacity to transfer dye was very different according to cellular types microinjected with Lucifer Yellow CH in the following respects: 1) in ependymal cells, GJIC was always important: ciliated ependymal cells, which are numerous in hypothalamic ependymal cultures (10-120 coupled cells), choroidal ependymocytes in plexus cultures (15-250 coupled cells), and non-choroidal ependymocytes in diencephalic roof cultures (10-30 coupled cells), and 2) in astroglial cells found in these primary cultures, no GJIC was observed in spite of the presence of well-differentiated gap junctions revealed by freeze-fracture replicas. All these results show a strong GJIC in ependymal cells and indicate the very good functional state of these cells in vitro.

Animals↗

PubMed1991

Incorporation of D-[3H]-glucosamine and L-[3H]-fucose into the developing rat cochlea.

The uptake of two tritiated carbohydrates, D-[3H]-glucosamine and L-[3H]-fucose, to the developing rat cochlea was examined using light and electron microscopic radioautography. Both carbohydrates, administered to in vitro developing rat cochleas, shared a similar ultrastructural labeling pattern on the microvilli and apical cell region and on the tectorial membrane (TM) fibrils. On embryonic day 18, the radiolabeling appeared on the apical surface of the undifferentiated epithelium that will develop into both spiral limbus and Kölliker's organ (KO), while on postnatal day (PD) 1, it was only located on the apical surface of the KO. When D-[3H]-glucosamine was administered in vivo to newborn rats, the radiolabeling was observed in the TM covering the KO at PD 3. Lastly, D-[3H]-glucosamine administered in vivo to PD 7 rats, appeared at PD 9 in the TM region lying just above the organ of Corti. The present findings support the previously suggested leading role of the spiral limbus and KO in the secretion of the TM during cochlear development. The secretion of carbohydrates, and probably of other matrix components, starts on the spiral limbus and KO region and progressively extends to the organ of Corti.

Animals↗

PubMed1991

Distribution of arrestin-like protein and beta-subunit of GTP-binding proteins in quail choroid plexuses.

Monoclonal antibodies (Mabs) directed against retinal arrestin (S-antigen) were used to detect and characterize this protein in choroid plexus (CP) of quails maintained during eight days, either under long-day photoperiods or in constant darkness. Immunocytochemistry and Western blotting confirmed the presence and the distribution of an arrestin-like protein in quail CP. Arrestin-like immunoreactivities in CP were compared with those obtained with Mabs to beta 36-subunit of G proteins (G beta), alpha-subunit of transducin and rhodopsin. Rhodopsin-like and transducin-like proteins could not be detected in choroidal cells, whereas intense positive reactions were observed with anti-G beta and anti-arrestin Mabs. The strongest immunoreactivities were found in choroidal ependymocytes of the lateral and IIIrd ventricles. In CP epithelial cells lining the IVth ventricle, very weak or no immunoreactivity could be detected with Mabs to arrestin, while Mab against G beta subunit always provided a positive reaction. In quails maintained in constant darkness, arrestin- and G beta-immunoreactivities of CP epithelial cells displayed changes in cellular distribution and intensity (decrease or disappearance of the immunoreactions). The strong arrestin-like immunoreaction located in the apical region of ependymocytes suggests the preferential association of the protein with choroidal microvilli and a possible role in cerebrospinal fluid production assumed by CP cells.

Animals↗

PubMed1991

A common epitope is shared by ciliary rootlets and cell-cell adherens junctions in ciliated ependymal cells.

Using immunoblot, light and electron immunocytochemistry, we investigated the presence and the localization of polypeptides cross-reacting with the monoclonal antibody CC.310 (mAb CC.310), which is mainly directed against a 175K (K = 10(3) Mr) ciliary rootlet protein. In hypothalamic ependymal cultures, the unique antigen recognized by mAb CC.310 was associated with the Triton X-100-insoluble fraction in these cultures and electrophoretically migrated to these cultures and electrophoretically migrated to 94K. mAb CC.310, which appears to be a very suitable marker for ciliated ependymocytes, allowed us to observe ciliogenesis during the growth of the ependymal cultures, from a single spot in each undifferentiated ependymal cell to a massive labeling in ciliated ependymal cells. In fully differentiated ciliated ependymocytes, mAb CC.310 strongly reacted with fibrous structures corresponding to ciliary rootlets, as confirmed by ultrastructural observations. In addition, a weaker immunostaining was also found along the intercellular junctions, and showed that proteins sharing a common epitope are located in ependymal ciliary rootlets and near adherens-type junctional complexes. Immunofluorescence studies confirmed the presence of positive labeling at the level of junctional complexes between cells in two epithelial lines, HeLa and PtK2, in which mAb CC.310 mainly reacted with one polypeptide of 85K.

Animals↗

PubMed1991

[Monoclonal antibodies obtained against G-protein epitopes: comparison of immunoreactions seen in the brain, retina and striated muscular tissue].

Monoclonal antibodies have been obtained against a purified fraction of brain G proteins containing the Gi alpha, G0 alpha, G beta, and G gamma subunits. After characterization, two monoclonal antibodies have been used to detect the cellular distribution of the two epitopes in neural, retinal and muscular tissues: ELISA, cross-dot and Western blot demonstrated that F.IV.5 is an anti-G beta antibody specific for the 36 kDa beta-subunit. ELISA, cross-dot and immunocytochemical distribution of the epitopes recognized by F.VII.9 suggested that this antibody recognizes epitopes which are also detected with polyclonal anti-G0 alpha antibodies. With both monoclonal antibodies, we confirmed that G proteins demonstrated a sub-membranous distribution as well as extensively cytoplasmic, axoplasmic or sarcoplasmic distributions in different cell types.

Animals↗