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Biomedical subjects

J Bourguet

Publications and source records attributed to J Bourguet.

At least 55 records · Page 3Linked to original sources
PubMed1983

The single file hypothesis and the water channels induced by antidiuretic hormone.

Unidirectional and net water movements were determined at minute intervals in frog urinary bladders. The changes in both parameters were followed, during the action of antidiuretic hormone (ADH), at different temperatures and stirring conditions. After correction for external unstirred layer effects, the ratio of the osmotic (Pf) and diffusional (Pd) permeability coefficients was remarkably constant, at different times and in different experimental conditions. In the presence of ADH the delta Pf/delta Pd ratio in the mucosal border was probably greater than 9. On the other hand, in nonstimulated preparations the ratio was smaller, and probably not different from 1. These results, together with previous observations indicating that other small molecules (like urea) are excluded from the ADH-induced channel, might indicate that single-file water movement can occur through this structure. Alternatively, the delta Pf/delta Pd ratio could result from a complex geometric arrangement in series with the aqueous pore.

Animals↗
PubMed1983

Intracellular pH, transepithelial pH gradients, and ADH-induced water channels.

Urinary bladders of frogs were exposed to a transepithelial proton and osmotic gradient (serosal pH 8.1, Tris or bicarbonate buffer; mucosal pH 5.8, unbuffered) while the alkalinization rate of the mucosal bath and the net water movement were simultaneously monitored. It was observed that 1) the mucosal alkalinization rate was dependent on serosal pH and buffer; 2) oxytocin increased the mucosal alkalinization rate only when serosal bicarbonate was employed, whereas the net water movement augmented both when serosal bicarbonate or Tris buffers were used; 3) amiloride did not modify the mucosal alkalinization rate either before or after oxytocin; 4) the increases in the mucosal alkalinization rate and in the net water movement induced by oxytocin (serosal bicarbonate) were negatively correlated. In other experiments intracellular pH (pHi) was estimated with the DMO distribution technique with the following results. 1) Oxytocin increased the pHi when either serosal bicarbonate or Tris buffers was used and even in the presence of a low mucosal pH (Tris buffer, pH 5.8). 2) Important cellular acidification was observed when CO2 was bubbled (to pH 5.8), whereas the hydrosmotic response to 8-bromo-cAMP was clearly inhibited. These results indicate that cellular alkalinization could play a pivotal role in action of ADH, show that ADH can modify the transepithelial pH equilibrium mechanism, and suggest that intracellular pH regulation and water permeability control can be linked regulatory processes.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1983

[Traumatic lesions of the nose-ethmoid-forehead region].

The treatment of this kind of lesion further remains difficult and requires work of several specialists: Neurosurgeon, Ophthalmologist, and ENT-surgeon. As for our opinion the reconstruction of anatomy and normal function of the frontal sinus is unequivocal, and performing it in the majority of cases renders in outstanding results.

Ethmoid Bone↗
PubMed1982

Detergent extraction of membrane proteins related to the action of antidiuretic hormone.

Antidiuretic hormone (ADH) induces, in the apical plasma membrane of target cells, the insertion of intramembranous particle aggregates that probably contain water channels. A mild attack of this membrane by a polyoxyethylene nonylphenyl detergent, which reversibly depressed ADH-induced water permeability, has been found to modify aggregate structure while extracting additional proteins. This simple procedure could be a valuable approach to the problem of aggregate isolation and characterization.

Animals↗
PubMed1982

Retention of antidiuretic hormone-induced particle aggregates by luminal membranes separated from toad bladder epithelial cells.

Aggregates of intramembrane particles appear in the luminal membranes of renal collecting duct and amphibian bladder cells after stimulation by antidiuretic hormone (ADH). We undertook this freeze-fracture study to determine whether particle aggregates, once in place, remain in the luminal membrane of the amphibian bladder after the membrane is physically separated from the rest of the cell. We found that the aggregates do remain in high yield in isolated membranes stabilized with a bifunctional imidoester (DTBP) followed by fixation with glutaraldehyde, or unfixed but stabilized with DTBP. These findings support the view that the particles are intrinsic membrane components and that their organization in the form of aggregates does not depend on the presence of the intact cell. In addition, the availability of isolated membranes containing particle aggregates provides a starting point for the isolation of the water-conducting proteins.

Animals↗
PubMed1981

Cellular pH and water permeability control in frog urinary bladder. A possible action on the water pathway.

Mucosal acidification (from pH 8.1 to 6.0) reversibly inhibited the hydroosmotic responses to oxytocin, cyclic AMP and 8-bromo-cyclic AMP in frog urinary bladder. These inhibitory effects were only observed in the presence of a permeant buffer in the apical medium and could also be elicited by CO2 bubbling, even when the mucosal pH was clamped at 8.1. Acid pH reduced the oxytocin-induced net water flux faster than norepinephrine or oxytocin removal and the difference was especially important at low temperature. The time course of recovery from acid pH inhibition was, at 20 degree C, similar to that of the hormonal action, but when the medium temperature was reduced to 6-7 degrees C, the recovery from acid pH inhibition paradoxically became faster while the oxytocin action was markedly slowed down (t 1/2 of changes in net water fluxes (expressed in min): oxytocin addition at 20 degrees C, 6.2 +/- 0.9; at 6 degrees C, 24 +/- 3; oxytocin removal at 20 degrees C, 4.7 +/- 0.8; at 6 degrees C, 22 +/- 3; pH inhibition at 20 degrees C, 2.6 +/- 0.2, at 6 degrees C 2.5 +/- 0.2; recovery from pH 6 at 20 degrees C 6.5 +/- 0.9; at 6 degrees C, 2.7 +/- 0.3). These results can be explained by accepting two main loci sensitive to medium acidification: (1) the cyclase system and (2) an intracellular, temperature-independent, post-cyclic AMP site. The fact that the intramembranous particle aggregates associated with the oxytocin-induced water permeability increase did not disappear after the flow inhibition by acid pH at low temperature suggests that the second effect could be located at the water channel itself.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1981

Fine structure of intramembranous particle aggregates in ADH-treated frog urinary bladder and skin: influence of glutaraldehyde and N-ethyl maleimide.

The fine structure of ADH-induced intramembrane particle aggregates has been studied in different tissues and under different experimental conditions. Particle aggregates similar to those previously observed in the amphibian urinary bladder and in the mammalian collecting duct were also found in the frog skin, another ADH target tissue. In the frog urinary bladder, typical aggregates were observed in the absence of glutaraldehyde fixation. Two experimental approaches were used 1) the absence of both fixative and cryoprotectant treatments and b) the absence of only glutaraldehyde treatment. In the latter case the reversal of hydrosmotic action was prevented by exposing the preparations to N-ethyl maleimide. In specimens of frog urinary bladder conventionally fixed with glutaraldehyde, two fracture levels could be observed in the aggregates, suggesting that the aggregated particles span an appreciable part of the membrane thickness.

Aldehydes↗
PubMed1981

Effects of pentoxifylline and various methylxanthine derivatives on transepithelial water permeability of frog urinary bladder.

Theophylline, pentoxifylline and MIX (isobutyl methylxanthine) increase the water permeability of frog urinary bladder when added to the serosal side of the epithelium; this hydrosmotic effect is explained by an inhibition of adenylate cyclase. Both pentoxifylline and MIX exhibit an higher biological activity than theophylline. In contrast to theophylline, pentoxifylline and MIX stimulate the water permeability when added to the mucosal side of the epithelium; this probably results from a better penetration of these drugs into cells.

Animals↗
PubMed1981

[Role of ADH-induced intramembrane particle aggregates (author's transl)].

In certain epithelial tissues, water permeability is markedly increased by antidiuretic hormone. This so-called hydrosmotic effect has been shown to be mediated by 3'-5' cyclic adenosine monophosphate, which, in turn, alters the permeability o the luminal membrane of receptor cells. This review deals wity ultrastructural alterations occurring in the membrane, as observed with freeze-fracture electron microscopy. Basically, these alterations consist of organized particle aggregates which appear in the apical membrane. In all experimental conditions, similar aggregates can be observed in the membrane of cytoplasmic vesicles. ADH stimulation triggers the fusion of these vesicles with the apical membrane resulting in the concomitant transfer of particle aggregates. It has been shown, in a wide range of experimental conditions, that both number and total area of the aggregates are directly proportional to the water permeability of the tissue. It is generally assumed that particle aggregates contain transmembrane channels that are selectively to water.

Amphibians↗
PubMed1981

[The value of the treatment of post-radiotherapy hyposialorrhoea by dihydroergotamine (author's transl)].

This study of the Rennes anti-cancer Center reports the results of a clinical and isotope scan study of Dihydroergotamine-Sandoz in the treatment of post-radiotherapy hyposialorrhoea. Dihydroergotamine was used at an initial dose of 100 drops 3 times per day for two weeks, then 60 drops 3 times per day. Treatment must be continued for several months. The results of such treatment given to 11 patients in comparison with a "control" group of 19 patients were evaluated objectively using isotope studies of salivary function. It was found, in addition, that the interruption of treatment might be associated with a relapse of symptoms, reversible when the drug was restarted. Finally, and in the light of the results of this study, it would appear to be logical to treat patients immediately following the end of radiotherapy without awaiting the first symptoms of hyposialorrhoea.

Dihydroergotamine↗