PubMed Health⌕ Search

Biomedical subjects

D Cremaschi

Publications and source records attributed to D Cremaschi.

At least 73 records · Page 4Linked to original sources
PubMed1979

Post-natal development of amiloride sensitive sodium transport in pig distal colon.

1. Both electrophysiological properties and unidirectional Na and Cl fluxes have been determined across distal colons taken from pigs during early post-natal development. 2. The transmural potential difference (Vms) was 5 mV in the new-born and 10 mV in the 4 day old colon. The short circuit current (Scc) showed a three to sixfold increase during the first 10 days of post-natal life. The microvillar membrane potential (Vm) fell from about -45 mV in the new-born to -40 mV in the 4 day old colon. 3. Amiloride had no effect on Vms, Scc or Vm, measured in the new-born animal. It reduced Vms and Scc, caused a hyperpolarization of Vm and increased the microvillar membrane/basolateral membrane resistance ratio (Rm/Rs) in colons taken from older animals. 4. The Scc of distal colons taken from new-born and 1 day old pigs was only half that predicted from unidirectional measurements of Na flux. This discrepancy, which could not be completely accounted for by net CL absorption, disappeared in the older animals. 5. Net transport of Na doubled during the first 24 h of post-natal life. Part of this transport took place through an amiloride sensitive, non-electrogenic, pathway. 6. It is suggested that Na uses mainly a non-electrogenic pathway to cross the mucosa of the new-born pig. This pathway is replaced by an electrogenic amiloride sensitive mechanism in older animals. Aldosterone is thought to initiate these changes in Na tranport.

Amiloride↗
PubMed1977

Electrical parameters in gallbladders of different species. Their contribution to the origin of the transmural potential difference.

Amphotericin B enhances Na+ conductance of the mucosal membrane of gallbladder epithelial cells and in such a way it modifies the brush border electromotive force. On this basis a method to measure cell and shunt resistances by comparing changes of the mucosal membrane potential (Vm) and of the transmural p.d. (Vms) is developed. This method is applied in gallbladders of different vertebrate species (i.e. rabbit, guinea pig, goose, tortoise, toad, trout). The two tested mammals, rabbit and guinea pig, exhibited a lower shunting percentage (89--93%) than the nonmammals (96--97%), but this fact did not bring about a homogeneous positive Vms. This means that shunting percent contributes, but it is not the only source of differences in Vms, in accordance with that reported by Gelarden and Rose (J. Membrane Biol. 19:37, 1974). Moreover, mammals exhibited a lower luminal resistance and a lower ratio between luminal and basolateral resistance than nonmammals. Possible causes of these differences are discussed.

Amphotericin B↗
PubMed1976

Facilitated transport of urea across the toad gallbladder.

The toad gallbladder epithelium is much more selective than that of the rabbit especially as to the permeability of two molecules like urea and thiourea. These observations can probably be attributed to different permeation mechanisms of the 2 molecules. Neither active transport nor solvent drag can explain these phenomena. 10(-4) M phloretin strongly inhibits urea movement, but does not alter either thiourea fluxes or isotonic net water transport: these results suggest that a specific mechanism is involved in urea movement. The urea transport shows saturation kinetic which is consistent with the presence of a facilitated mechanism.

Animals↗
PubMed1975

Na+ and Cl- transepithelial routes in rabbit gallbladder: tracer analysis of the transports.

The reported experiments demonstrate that in rabbit gallbladder epithelium: a) the mucosa-cell Na+ and Cl- influxes (45 sec long) are reduced in Cl- -free and Na+ -free bathing solutions respectively; transconcentration effects are observed. b) Cell Cl- labelling through the luminal membrane, with 36Cl- (1 hr incubation), is nearly abolished if a Na+ -free bathing solution is used; but cell Na+ labelling with 22Na+ in the lumen (1 hr incubation) does not change if a Cl- -free bathing solution is employed. c) Cell Na+ and Cl- labelling through the basolateral membrane (1 hr incubation) is negligible; some Cl- labelling is obtained only when the intracellular electrical potential is artificially reduced. d) SO 2 4- is found to abolish net water transport, to cross the epithelium, but not to enter the cell. On the basis of these data a paracellular pathway for net Cl- transport is ruled out, a Na+ and Cl- cotransport through the cell luminal barrier and a Na+ active extrusion through the basolateral membrane are suggested. No definitive conclusion about Cl- extrusion is possible.

Animals↗
PubMed1975

Electrical resistance and ATPase levels in the cecal wall of germ free and conventional rats.

(a) Electrical resistance across the cecal wall of germfree rats is higher than in conventional controls when the luminal fluid is a physiological solution. Transmural resistance of the cecum increases both in germfree and conventional rats when the supernatant from cecal contents of germfree rats is used as luminal fluid. These phenomena might be due to an effect of germfree intestinal contents on the ionic composition and/or on the dimensions of intercellular pathways within the intestinal epithelium. (b) Total and Na+ and K+ stimulated ATPase show higher levels in mucosal scrapings from the ileum and cecum of germfree rats than in conventional controls. This characteristic of the germ-free lower bowel may be associated with the greater "absorptive efficiency" which it was found to display when relieved from luminal inhibitory substances.

Adenosine Triphosphatases↗