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J Gabrion

Publications and source records attributed to J Gabrion.

72 records · Page 4Linked to original sources
PubMed1981

Influence of collagen gel on the orientation of epithelial cell polarity: follicle formation from isolated thyroid cells and from preformed monolayers.

The influence of collagen gels on the orientation of the polarity of epithelial thyroid cells in culture was studied under four different conditions. (a) Isolated cells cultured on the surface of a collagen gel formed a monolayer. The apical pole was in contact with the culture medium and the basal membrane was attached to the substratum. (b) Isolated cells embedded inside the gel organized within 8 into follicles. The basal pole was in contact with collagen and the apical pole was oriented towards the interior of the follicular lumen. (c) Cells were first organized into floating vesicles, structures in which the apical surface is in contact with the culture medium, and the vesicles were embedded inside the collagen gel. After 3 d, cell polarity was inverted, the apical pole being oriented towards the cavity encompassed by cells. Vesicles had been transformed into follicles. (d) Monolayers formed on collagen gels as in a were overlaid with a second layer of collagen, which was polymerized in contact with the apical cell surface. A disorganization of the continuous pavement occurred within 24 h; cells attached to the upper layer of collagen and reorganized into follicles in the collagen sandwich within 4-8 d. A similar process occurred when the monolayer was grown on plastic and overlaid with collagen, or grown on collagen and covered with small pieces of glass cover slips. No reorganization was observed between two glass surfaces. In conclusion, first, a basal pole was always formed in the area of contact between the cell membrane and an adhesive surface and, second, the interaction of a preformed apical pole with an adhesive surface was not compatible with the stability of this domain of the plasma membrane. The interaction of the cell membrane with extracellular components having adhesive properties appears to be a determinant factor in the orientation and stabilization of epithelial cell polarity.

Animals↗
PubMed1980

[Reorganisation of thyroid follicular cells in culture. Effect of collagen on the orientation of cell polarity].

In contact with a collagen gel, thyroid follicular cells form a basal pole. A monolayer, with the apical side facing the culture medium is formed when cells are seeded on a collagen layer. In contrast cells reorganize into follicle-like structures when they are embedded in the collagen gel. If vesicles which have their apical pole in contact with the culture medium are embedded in the gel, collagen-cell interaction induced the inversion of cell polarity giving follicular structures. In addition after being overlaid with a collagen layer, cells forming a monolayer reorgnaize into follicles. The apical pole is formed on the free surface of the monolayer or on the internal side of structures embedded in collagen which differentiate into follicles.

Animals↗
PubMed1980

Characterization of actin microfilaments at the apical pole of thyroid cells.

In thyroid cells (rat or hog), actin has been detected by immunofluorescence with an antiactin antibody and, in electron microscopy by decoration "in situ" with heavy meromyosin. The antibody as the heavy meromyosin method have shown that actin microfilaments are especially localized at the apical pole of the cells, in a region where thin filaments are usually observed by conventional methods of electron microscopy. These microfilaments are attached to the apical membrane at the ends of the microvilli and form dense bundles at their cores. They are polarized towards the interior of the cell. Decorated filaments are also organized in a clear network, parallel to the apical membrane; they are associated with microvillar bundles, but also with small apical vesicles and lateral membranes, in tight or gap junctions.

Actins↗
PubMed1979

[Identification of actin microfilaments in the neurosecretory axons of rat neural lobe].

Incubation of rat neural lobes with heavy meromyosin (HMM) after prolonged glycerination, induced characteristic arrowhead decoration of a number of microfilaments at different levels of the neurosecretory axons. In non terminal sections of axons the labelled microfilaments showed preferential relationships with microtubules in addition to occasional contacts with the axolemma and various axonal organelles. In axonal endings, they were mainly associated to microvesicles and appeared to be anchored on the axolemma facing the perivascular space at the level of membranous densifications.

Actins↗
PubMed1979

Hair cell degeneration in guinea pigs intoxicated with kanamycin during intrauterine life; a structural and ultrastructural study.

The structural ototoxic effect of kanamycin during intrauterine life has been shown in guinea pigs. The extent of the loss mostly affected the outer hair cells of the basal part of the cochlea. Ultrastructural studies demonstrated a hair cell degeneration pattern similar to that previously described in adult animals following antibiotic intoxication.

Animals↗
PubMed1979

[Thyroid incorporation of radioactive iodine in neotenic tritons (Triturus helveticus Raz.). In vivo studies by high resolution radioautography. Comparison of iodine incorporation in adults and larvae].

In vivo kinetics of radioiodine incorporation have been established for 70 newts, collected from Triturus helveticus Raz. populations where spontaneous neoteny occurs. Fifty of these newts which appeared to present four degrees of neoteny (more or less metamorphosed), have been studied. Main results obtained were: 1) The intensity of the iodine incorporation varies according to the degree of neoteny. The higher is this one, the lower is the intensity. 2) In general, iodine uptake rates are more or less similar to these of adults, but more often the evolution of the 125I uptake approaches a plateau-curve. From thyroid radioautographies on some animals (17 neotenic and 2 adult newts) for which in vivo iodine kinetics have been examined and on 9 normal larvae in premetamorphosis or in metamorphosis, we have noticed in those neotenic thyroids, a very small number of silver grains on apical vesicles and colloidal lumina when the degree of neoteny is the highest. This number of marked apical vesicles and colloid is more important in the neotenics which have lost some larval characters. Silver grains on colloid droplets indicating thyroid hormone excretion are inexistent in the most larval neotenics, more numerous in most metamorphosed neotenics. But they always are less numerous than in metamorphosing larvae. For a few animals, the fixation curve is very high, probably because of a stimulation of thyroid function, induced by the test and not because of a goitrous tendancy, as radioautographic observation of their thyroid shows. Thyroid function and its relation with the origin of this total and accidental neoteny are discussed.

Aging↗
PubMed1977

[Determination of the relative iodine concentration in the lumens of thyroid follicles of normal and neotenic Triturus helveticus, and evaluation of the halogen content of the thyroid colloid. Electron microprobe study (author's transl)].

The stable, bound iodine in the thyroid colloid of Triturus helveticus has been studied with the electron microprobe. Some animals show a normal development. Others are accidentally neotenic due to certain ecological conditions. The values of punctate iodine concentrations (CPI) have been computed and expressed in relative units (counts/s). The mean CPI per lumen is very variable from one follicle to another in the same thyroid section. During normal development, the mean CPI per animal is generally higher in metamorphosing individuals than in larvae. During development with neoteny, the mean CPI per animal attains high values if the larval state is maintained in its totality; the CPI decreases in partially metamorphosed animals, but increases again after metamorphosis. The amount of halogen contained in the thyroid colloid has been computed in relative units (colloid iodine pool). Throughout normal development, the pool remains small if the animals have not attained the adult state. In increases considerably in entirely larval neotenic newts, decreases during metamorphosis but increases afterwards. In totally neotenic newts, the thyroid gland receives only a low hypophyseal stimulation and reacts as the thyroid gland of various hypophysectomized Urodeles. Our results pose the problem as to whether TSH regulates the transepithelial iodine flows, which permit the expansion of the colloid iodine pool, when this hormone is secreted at a very low levels.

Animals↗
PubMed1976

[Relationship between the presence of microfilaments and the cell cycle of HeLa cells in synchronus culture].

Some cytoplasmic organelles have showed characteristic variations which are related to the different cell cycle phases, in thymidine synchonized HeLa cells in culture. In these cells, the most modified organelles were intracytoplasmic membranes (endoplasmic reticulum) and microfilament arrangements. Microfilaments were numerous under the cell membrane, but also some of them were dispersed in dense bundles. These structures were seen around the nucleus, 12-14 h after removal of excess thymidine (G1). They migrated to the periphery of the cell during S and G2. During mitosis, they were directly under superficial membrane-associated microfilaments.

Cell Division↗
PubMedDate not supplied

Choroidal responses in microgravity. (SLS-1, SLS-2 and hindlimb-suspension experiments).

Fluid and electrolyte shifts occurring during human spaceflight have been reported and investigated at the level of blood, cardiovascular and renal responses. Very few data were available concerning the cerebral fluid and electrolyte adaptation to microgravity, even in animal models. It is the reason why we developed several studies focused on the effects of spaceflight (SLS-1 and SLS-2 programs, carried on NASA STS 40 and 56 missions, which were 9- and 14-day flights, respectively), on structural and functional features of choroid plexuses, organs which secrete 70-90% of cerebrospinal fluid (CSF) and which are involved in brain homeostasis. Rats flown aboard space shuttles were sacrificed either in space (SLS-2 experiment, on flight day 13) or 4-8 hours after landing (SLS-1 and SLS-2 experiments). Quantitative autoradiography performed by microdensitometry and image analysis, showed that lateral and third ventricle choroid plexuses from rats flown for SLS-1 experiment demonstrated an increased number (about x 2) of binding sites to natriuretic peptides (which are known to be involved in mechanisms regulating CSF production). Using electron microscopy and immunocytochemistry, we studied the cellular response of choroid plexuses, which produce cerebrospinal fluid (CSF) in brain lateral, third and fourth ventricles. We demonstrated that spaceflight (SLS-2 experiment, inflight samples) induces changes in the choroidal cell structure (apical microvilli, kinocilia organization, vesicle accumulation) and protein distribution or expression (carbonic anhydrase II, water channels,...). These observations suggested a loss of choroidal cell polarity and a decrease in CSF secretion. Hindlimb-suspended rats displayed similar choroidal changes. All together, these results support the hypothesis of a modified CSF production in rats during long-term (9, 13 or 14 days) adaptations to microgravity.

Adaptation, Physiological↗
PubMedDate not supplied

Heart and plasma atrial natriuretic peptide (ANP) in response to long-term endurance training in rats.

Long-term endurance training effects on heart and plasma ANP were investigated in male Wistar rats. Maximal O2 uptake (VO2max) was significantly higher in trained groups, when they are used as their own control. After 3, 4, and 5 weeks of endurance training, VO2max was respectively increased by 7.7% (p less than 0.05), 13.7% (p less than 0.01), and 18.4% (p less than 0.001). Plasma ANP and glomerular ANP receptor density showed no clear variations in trained rats. However, cardiac ANP content decreased significantly in left and right atrial tissues by 35-36% (p less than 0.05) after 5 weeks of training. ANP immunoreactivity was investigated to show the distribution of ANP within the atria. ANP was found in diffuse and granular forms. The diffuse pattern (immature ANP) disappeared in cardiocytes of trained rats, while the granular form persisted, especially in the left atrial tissue. These data suggest that chronic endurance training might cause a decrease in ANP synthesis with no change in ANP storage. Such results are in agreement with the hypothesis that the left atrium could be especially involved in long-term fluid volume control.

Animals↗
PubMedDate not supplied

Effects of hypothyroidism on the structural development of the organ of Corti in the rat.

The structural development of the organ of Corti was studied in 30 rat pups rendered hypothyroid by daily administration of propylthiouracil during the first 35 days after birth. Cochlear changes were observed by light microscopy and electronmicroscopy. Hypothyroid rat pups were found to have severe abnormalities in the organ of Corti. There was an abnormally prolonged persistence of Kölliker's organ and striking distortion of the tectorial membrane. The sensory epithelium exhibited marked signs of immaturity: the tunnel of Corti has not opened yet in animals 35 days old, sensory and supporting cells presented immature characteristics with abnormal persistence of the kinocilium. It is suggested that hypothyroidism results in an overall retardation of the maturation of cochlear structures and ultrastructural changes that appear to be significant enough to account for the hearing loss.

Animals↗