Structural and functional response of toad urinary bladder to LiCl

AbstractStructural and functional response of toad urinary bladder to LiCl. The physiological and morphological response of toad urinary bladder was examined during mucosal exposure of LiCl both with and without vasopressin (VP). With 20 or 100 mU/ml of VP in the serosal bath there was a decrease in Jv between the first and second VP stimulation in LiCl-treated bladders (VP20, -14 ± 6%; VP100, -16 ± 5%) that was not different from that observed without LiCl (VP20, -8 ± 3%, P = NS). However, with 1 mU/ml of VP, a significant decrease in Jv was evident in LiCl-treated (-30 ± 10%) versus control sacs (+6 ± 8%; P < 0.02). At all VP concentrations tested, a significant decrease in SCC and PD was observed between the first stimulation without LiCl and the second stimulation with LiCl. Both osmotic (Pf) and diffusional water permeability (Pd) were increased significantly with 11 mM LiCl only, while neither basal nor VP-stimulated urea permeability (Pu) was affected. Morphological changes paralleled the physiological alterations induced by LiCl. These data demonstrate that LiCl interferes with the osmotic response of the toad bladder to low concentrations of VP, and increases both Pf and Pd while leaving Pu unaffected. These findings coupled with the cell swelling and intracellular vacuolization suggest the presence of a defect in transepithelial water movement somewhere beyond the apical membrane of the granular cell exposed to LiCl.Réponse structurelle et fonctionnelle de la vessie de crapaud au LiCl. La réponse physiologique et morphologique de la vessie de crapaud a été examinée pendant exposition de la muqueuse à du LiCl en présence ou en l'absence de vasopressine (VP). Pour 20 ou 100 mU/ml de VP dans le bain séreux, il y avait une diminution de Jv entre la première et la seconde stimulation par VP dans les vessies traitées par le LiCl (VP20, -14 ± 6%; VP100, -16 ± 5%), qui n'étaient pas différentes de celles observées sans LiCl (VP20, -8 ± 3%; P = NS). Cependant, avec 1 mU/ml de VP, une diminution significative de Jv était évidente dans les sacs traités au LiCl (-30 ± 10%) par rapport aux sacs contrôles (+6 ± 8%; P < 0,02). Pour toutes les concentrations de VP testées, une diminution significative du SCC et de PD a été observée entre la première stimulation sans LiCl, et la seconde stimulation avec LiCl. Les perméabilités osmotiques (Pf) et diffusionnelles (Pd) à l'eau étaient augmentées significativement avec 11 mM de LiCl seulement tandis que la perméabilité à l'urée basale ou stimulée par la VP (Pu) n'était pas affectée. Des modifications morphologiques allaient de pair avec les altérations physiologiques induites par le LiCl. Ces données démontrent que LiCl interfère avec la réponse osmotique de la vessie de crapaud pour de faibles concentrations de VP, augmente Pf et Pd, mais laisse Pu inchangé. Ces résultats, couplés avec le gonflement cellulaire et la vacuolisation intracellulaire suggèrent la présence d'un défaut du mouvement transépithélial d'eau quelque part au delà de la membrane apicale de la cellule granulaire exposée au LiCl

Vasopressin (VP) induced changed in the epithelial surface of toad urinary bladder

SCOPUS: NotDefined.jinfo:eu-repo/semantics/publishe

Saccharomyces cerevisiae Vacuole in Zinc Storage and Intracellular Zinc Distribution▿ ‡

Previous studies of the yeast Saccharomyces cerevisiae indicated that the vacuole is a major site of zinc storage in the cell. However, these studies did not address the absolute level of zinc that was stored in the vacuole nor did they examine the abundances of stored zinc in other compartments of the cell. In this report, we describe an analysis of the cellular distribution of zinc by use of both an organellar fractionation method and an electron probe X-ray microanalysis. With these methods, we determined that zinc levels in the vacuole vary with zinc status and can rise to almost 100 mM zinc (i.e., 7 × 108 atoms of vacuolar zinc per cell). Moreover, this zinc can be mobilized effectively to supply the needs of as many as eight generations of progeny cells under zinc starvation conditions. While the Zrc1 and Cot1 zinc transporters are essential for zinc uptake into the vacuole under steady-state growth conditions, additional transporters help mediate zinc uptake into the vacuole during “zinc shock,” when zinc-limited cells are resupplied with zinc. In addition, we found that other compartments of the cell do not provide significant stores of zinc. In particular, zinc accumulation in mitochondria is low and is homeostatically regulated independently of vacuolar zinc storage. Finally, we observed a strong correlation between zinc status and the levels of magnesium and phosphorus accumulated in cells. Our results implicate zinc as a major determinant of the ability of the cell to store these other important nutrients

Calcium- and polyphosphate containing acido calcisomes in chicken egg yolk

14 p. : il., tabBackground information. Poly P (inorganic polyphosphate) is a polymer formed by Pi residues linked by high-energy phosphoanhydride bonds. The presence of poly P in bacteria, fungi, algae and protists has been widely recognized, but the distribution of poly P in more complex eukaryotes has been poorly studied. Poly P accumulates, together with calcium, in acidic vesicles or acidocalcisomes in a number of organisms and possesses a diverse array of functions, including roles in stress response, blood clotting, inflammation, calcification, cell proliferation and apoptosis. Results. We report here that a considerable amount of phosphorus in the yolk of chicken eggs is in the form of poly P. DAPI (4 ,6-diamidino-2-phenylindole) staining showed that poly P is localized mainly in electron-dense vesicles located inside larger vacuoles (compound organelles) that are randomly distributed in the yolk. These internal vesicles were shown to contain calcium, potassium, sodium, magnesium, phosphorus, chlorine, iron and zinc, as detected by X-ray microanalysis and elemental mapping. These vesicles stain with the acidophilic dye Acridine Orange. The presence of poly P in organellar fractions of the egg yolk was evident in agarose gels stained with Toluidine Blue and DAPI. Of the total phosphate (Pi) of yolk organelles, 16% is present in the form of poly P. Total poly P content was not altered during the first 4 days of embryogenesis, but poly P chain length decreased after 1 day of development. Conclusions. The results of the present study identify a novel organelle in chicken egg yolk comprising acidic vesicles with a morphology, physiology and composition similar to those of acidocalcisomes, within larger acidic vacuoles. The elemental composition of these acidocalcisomes is proportionally similar to the elemental composition of the yolk, suggesting that most of these elements are located in these organelles, which might be an important storage compartment in eggs