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.

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.

Simultaneous minute by minute determination of unidirectional and net water fluxes in frog urinary bladder. A reexamination of the two barriers in series hypothesis.

Unidirectional and net water fluxes were simultaneously estimated in frog urinary bladder. The minute by minute tritiated water (3HOH) transepithelial flux and the net volume of fluid traversing the tissue were employed. It was observed that: (1) the time course of the increase in the 3HOH flux induced by antidiuretic hormone had a very similar pattern to that reported for the increase in the net movement. (2) Unstirred layers strongly affected the magnitude of the antidiuretic hormone-induced increase in 3HOH fluxes while the time course of the response was almost non-affected. In non-stimulated bladders 3HOH fluxes were poorly modified by medium stirring. New steady-state conditions for 3HOH fluxes were established 1 min after stirring rate modifications. (3) The simultaneously determined net water flux was not affected by a modification in the unstirred layers, indicating that the variations in the measured net water fluxes are a good estimation of the changes in the mucosal border permeability. (4) The presence of an osmotic gradient during hormonal challenge (implying net water fluxes, cell swelling and dilation of the intracellular spaces) did not modify the time course of 3HOH movements. These results suggest that the time course of the increase in water permeability is an intrinsic characteristic of the experimental system that could result from the addition of permeability units that increase in number during the development of the hormonal action.

Vesicles and particles of sodium bis(2-ethylhexyl) phosphate in binary and ternary systems.

Vesicles were identified in aqueous solution of pure sodium bis(2-ethylhexyl) phosphate, a short branched chain surfactant. Superficial tension measurements show that the vesicles appear above a molality of 0.02 (0.69 %w). These aggregates are equilibrium structures. The "packing parameter' theory established by Israelachvili et al. allows the prediction of the occurrence of such vesicles. If an organic solvent, such as xylene or ethylhexanoate, is added to the binary system, a different type of aggregate appears, the size of which is determined by several methods including electron microscopy and light scattering. Interfacial tension measurements show that these aggregates would be expected to form above a molality of 0.02. According to our experimental results, the microstructure of these aggregates can be described as micelles and/or vesicles, swollen or not.

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.

The role of microtubules and microfilaments in the hydrosmotic response to antidiuretic hormone.

To test the effects of colchicine and cytochalasin B on the ADH-induced response, unidirectional and net water fluxes were measured at one or two minutes intervals in frog urinary bladder. The action of these agents on the appearance of intramembrane particles aggregates in the luminal membrane of target cells under oxytocin stimulation and the changes in the tissue ultrastructure induced by cytochalasin B were also studied. It was observed that: the time-course of the response to oxytocin was strongly slowed by colchicine while the washout was not affected; the time-course of the 'on and off' of the response to oxytocin was not modified by cytochalasin B; cytochalasin B pretreatment proportionally reduced unidirectional and net water fluxes measured after glutaraldehyde fixation; the combined action of colchicine and cytochalasin B proportionally reduced the net water flux and the number of intramembrane particles aggregates, observed in freeze-fracture studies; after cytochalasin B action the dilation of intercellular spaces classically observed under oxytocin stimulation is strongly reduced. It is concluded that: microtubules probably play an important role in the water channels plug-in, but not in their removal; microfilaments integrity is necessary for the mechanisms inducing intercellular space dilation and the observed results confirm that water permeability is controlled by the number of permeation units present in the luminal border of granular cells and probably represented by the intramembrane particle aggregates.

The effect of hypertonic media on water permeability of frog urinary bladder. Inhibition by catecholamines and prostaglandin E 1 .

The frog urinary bladder undergoes, in some conditions, a marked increase of its water permeability when incubated in hypertonic media. This increase was observed with various nonpermeant solutes. It seems to result from the shrinkage of an osmo-sensitive compartment of the tissue, probably the epithelial cells. Many similarities were found between this effect and the physiological increase in water permeability (hydrosmotic response) elicited by antidiuretic hormone (ADH): both were dependent on the physiological state of the animals, and although the response was slower after hyperosmolar than after hormonal challenge, the patterns of response were similar, and in both cases markedly dependent on bathing solution temperature. Norepinephrine and prostaglandin E(1), which in this tissue reduce the hydrosmotic action of ADH, presumably by inhibiting the adenyl cylase also reduced the effect of hyperosmolarity. Conversely this effect was potentiated by incubation in the presence of oxytocin, exogenous cyclic AMP, and theophylline, conditions in which the intracellular concentration of cyclic AMP is increased. These data demonstrate that the response to hyperosmolarity is elicited, at least partly, by mechanisms also involved in the physiological hydrosmotic response to ADH.

The onset and offset of the hydrosmotic response in frog epithelia.

The onset and offset of the hydrosmotic responses elicited by different agonists in frog urinary bladder, frog skin and isolated frog skin epithelium were studied and compared. The removal of the frog skin supporting layers accelerated the onset of the reactions to oxytocin and 8-bromo-cyclic AMP (8-Br-cAMP), which, however, remained slower than the onset in the urinary bladder. The offset of these actions was not affected by corion removal and was also slower than in the bladder. A marked asymmetry between onset and offset of the hydrosmotic response was observed when the isolated skin epithelium was stimulated with 8-Br-cAMP. The results show that the increases in water permeability elicited by oxytocin and cyclic-AMP derivatives in frog skin and frog urinary bladder, although attributable to the same general mechanisms, present different specific characteristics.

[Supraventricular tachycardia due to simultaneous conduction in the rapid and slow nodal pathways. Treatment by ablation of the slow pathway]. / Tachycardie supraventriculaire due à une conduction simultanée dans la voie nodale rapide et lente. Traitement par ablation de la voie lente.

The authors report the case of a 70 year old woman with frequent attacks of supraventricular tachycardia resistant to antiarrhythmic therapy. The tachycardia was irregular with predominantly normal QRS complexes. Electrophysiological investigation showed dual conduction in the atrioventricular node and tachycardia was induced by atrial extrastimulus. However, reentrant tachycardia could not be induced, the refractory period of the slow pathway being much longer than that of the rapid pathway. The mechanism of the tachycardia was simultaneous conduction of the sinus rhythm through the two nodal conduction pathways. This was successfully treated by radiofrequency ablation of the slow pathway.

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.

[New method of deafness classification]. / Une nouvelle méthode de classification des surdités

Appreciating the difficulties in interpreting tonal audiograms using the classifications previously suggested, the authors, inspired by a paper by Wedenberg, have compared phonetic studies of phonemes and tonal audiograms. By this method they have obtained a simple audiometric pattern indicating both the degree of auditory loss and the rate of the curve. This is of value, from the point of view of classifying audiograms, for deciding on possible hearing-aids and for auditory education.

[Fronto-ethmoidal meningo-encephaloceles and nasal gliomas (author's transl)]. / Méningo-encéphalocèles fronto-ethmoïdales et gliomes nasaux.

Meningoencephalocoeles and nasal gliomas are congenital malformations rare in Europe but much better known in Morocco and in Thailand. These lesions have embryonic relations which are such that certain authors consider them to be only clinical varieties of the same malformation. They cause extra nasal, intra nasal or mixed tumours discovered most often at birth. Treatment is surgical either via a high intracranial approach or via a low facial approach (both approaches sometimes being used in association) and the prognosis is dominated by the problem of the dura mater if there are connections between the tumour mass and the subarachnoid spaces. When the problem is resolved by dural plasty, the later prognosis is excellent and, in particular, the psychomotor development of the children appears to be normal. Cosmetic problems, and in particular hypertelorism, may nevertheless require later surgery.

[Esophagotracheal fistula after tracheotomy and assisted ventilation (author's transl)]. / Les fistules oeso-trachéales après trachéotomie et ventilaltion assistée.

On the basis of 12 cases of oesophagotracheal fistula after tracheotomy and assisted ventilation, the authors discuss the etiopathogenesis and the diagnosis of this grave condition, emphasizing its inevitably surgical treatment, and the major value of prophylaxis which is nevertheless difficult to apply.

[The value of the treatment of post-radiotherapy hyposialorrhoea by dihydroergotamine (author's transl)]. / Intérêt du traitement des hyposialorrhées post-radiothérapiques par la dihydroergotamine.

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.

[On 30 cases of naso-pharyngeal fibromas (author's transl)]. / A propos de 30 fibromes naso-pharyngiens.

The authors report their experiments in the diagnosis and treatment of naso-pharyngeal fibromas. They point out:--the usefulness of tomo-densitometric and arteriographic examinations; but they are concerned by the neurological dangers of embolization;--the usefulness of surgical treatment in this condition, usually done by the infralabial route, in the Rouge-Denker technique.

[A description of surgery of the vidian nerve (author's transl)]. / A propos de la chirurgie du nerf vidien

The authors expound a method wihch is initially surgical, for approaching the vidian nerve while preserving the innermost periosteal lining of the pterygomaxillary fossa, thereby avoiding the disadvantages of cutting into the contents of this fossa.

[Exchanges of medical students from Rennes/Erlangen-Nuremberg: various considerations on these exchanges within the E.E.C. framework]. / Echanges d'étudiants en médecine Rennes/Erlangen-Nürnberg: de quelques considérations sur ces échanges dans le cadre de la C.E.E.

The current political trends of the European Economic Community (EEC) have made it more desirable than ever before for medical students to be able carry out part of their training in medical schools other than their Faculties of origin. The authors examine successively: 1) The results of 20 years of twinning-between the Medical Schools of Rennes (France) and Nürnberg-Erlangen (W. Germany). A considerable number of syllabuses and examinations are now recognized as equivalent. So far, nearly 500 students have taken advantage of the possibilities of exchanges lasting a few months or even a full University year. 2) The propositions submitted by the Medical Schools of Rennes and Strasbourg have been selected from the 800 presented by EEC Universities as port of the Erasmus programme. For the whole of the EEC, 12 medical projects have been started up since october 1989. Among the other projects accepted were those of Bonn and Hamburg, Ovideo and Valence, Naples and Barri, Dublin, Coïmbra, Brussels, Copenhagen, Leyden, etc. 3) In order to strengthen the North-South axis of the EEC and to widen further the horizons of European medical students (even beyond Europe), the Medical Facilities of Rennes and of Alcalà de Henares (University of Madrid) have just defined syllabus and examination equivalences as Rennes and Erlangen did some twenty years ago.