Biomedical subjects

R Berdecia

Publications and source records attributed to R Berdecia.

5 recordsLinked to original sources

PubMed1990

Effect of PO2 and metabolic inhibitors on ionic fluxes across the isolated rabbit corneal endothelium.

Bicarbonate and sodium fluxes were measured across the isolated rabbit corneal endothelium under the influence of several inhibitors. Depression of PO2 in the bathing medium decreased net sodium movement but increased bicarbonate movement. Furosemide did not alter bicarbonate fluxes at either 10(-4) or 10(-5) M, but increased passive sodium flux leading to a decrease in net flux. Thiocyanate, at 5 x 10(-3) or 5 x 10(-2) M, decreased active bicarbonate flux and hence net flux, but had no effect on sodium fluxes. Dinitrophenol increased only the passive bicarbonate flux while decreasing both active and passive sodium fluxes, albeit unequally, leading to a decreased net flux. Ethacrynic acid affected only passive bicarbonate flux, while decreasing net sodium flux. The stilbene derivatives, SITS and DIDS caused opposite effects on both sodium and bicarbonate fluxes. SITS decreased net bicarbonate flux by decreasing active and increasing passive flux, yet increased net sodium flux. DIDS, however, increased net bicarbonate flux but decreased net sodium flux. The results may be explained by current models for endothelial ion transport that include a Na+/H+ antiport and a HCO3-/Na+ symport system in parallel with an independent pathway for HCO3- exit from the endothelial cells. When compared with prior corneal swelling data using these same inhibitors, the maintenance of corneal thickness appears to be dependent on the variation of ion fluxes from normal values, and the dissociation of the two active ion fluxes. In addition, there appears to be a significant ability of ion transport systems to compensate for disturbances to other ion exchange or transport mechanisms.

Animals↗

PubMed1987

Mussel adhesive protein: permeability characteristics when used as a basement membrane.

Mussel Adhesive Protein (MAP) was applied to either denuded rabbit cornea, or dialysis membrane with a 50,000 dalton molecular weight cut-off. The permeability of corneal endothelium or bare stroma was compared with demambranized stroma coated on one surface with MAP. The permeability of dialysis membrane, both in the presence and absence of MAP, was also determined to inulin (5,000 daltons) and dextran (40,000 daltons). Corneal endothelial permeability was much less than that of bare stroma, and coating denuded stroma with MAP on one surface had no effect on stromal permeability. Dialysis membrane permeability was not reduced after coating with different thickness of MAP, indicating that MAP offers little resistance to the passage of even large non-electrolytes and can serve as a basement membrane for cellular or tissue attachment without impairment of nutritional supply to the overlying cells.

Animals↗

PubMed1987

Corneal storage in MK medium and K-Sol. Effect on ionic and non-ionic fluxes.

Rabbit corneas were stored at 4 degrees C for 3, 7 or 14 days in either modified MK medium or K-Sol. Corneal endothelial permeability to inulin following storage in modified MK was significantly less at each time examined than that found in corneas stored for either 3, 7 or 14 days in K-Sol. Inulin permeability after storage in K-Sol was increased at all times relative to unstored control corneal tissue, but only at 7 and 14 days in MK medium. Dextran permeability was similar following 3 days of storage in either solution, but dextran permeability following storage in modified MK was significantly less than the values found in corneas stored for 7 and 14 days in K-Sol. Dextran permeability was not significantly increased relative to control, at any storage time in MK medium but was increased at 7 and 14 days in K-Sol. Inulin and dextran permeabilities after storage in MK medium were maintained more closely to values found in fresh tissue than corneas stored in K-Sol. Net endothelial sodium fluxes following storage in modified MK medium were markedly less than those found in corneas stored for 3, 7 and 14 days in K-Sol. Net sodium fluxes are maintained better in K-Sol than in MK medium relative to control values. Net bicarbonate fluxes following storage in modified MK medium were significantly less than the 3-day values in K-Sol, but similar to the values after 7 and 14 days of K-Sol storage.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Effect of dextran-bound acetazolamide on rabbit corneal endothelial ion fluxes.

The effects of a carbonic anhydrase inhibitor, acetazolamide, bound to a 72,000 dalton dextran (DBI) on bicarbonate and sodium fluxes across the isolated rabbit corneal endothelium have been examined. When DBI was present on the aqueous-facing endothelial surface, there was a marked inhibition of both the stromal to endothelial unidirectional and net flux of bicarbonate. This suggests that the exit of bicarbonate from the cell into the aqueous-facing solution is influenced by the enzyme carbonic anhydrase. No change was found in sodium fluxes under these same incubation conditions. When DBI was present on the stromal-facing surface of the endothelium, no changes were found in unidirectional or net bicarbonate fluxes; the sodium flux from stroma to endothelium was increased, however, with no change in net flux. This data implies that the link between sodium and bicarbonate movement across the endothelium is not a direct coupling between the transport of the two ions in the form of a symport (Na+:HCO3-) at the apical cell border.

Acetazolamide↗

PubMed1986

BSS and BSS-plus: effect on corneal endothelial ionic and non-ionic fluxes.

Rabbit corneas were mounted in water jacketed chambers and the endothelial surface perfused with either BSS (Balanced Salt Solution) or BSS-Plus for 3 hr. Unidirectional and net fluxes of sodium were similar in both groups of corneas. Bicarbonate fluxes in BSS-Plus were statistically similar to those in Krebs-Ringer solution. Bicarbonate fluxes could not be determined with BSS because the solution does not contain bicarbonate. In addition, there was no statistically significant alteration of inulin or dextran permeability when comparing perfusion with BSS and BSS-Plus. From this study it appears that BSS and BSS-Plus are comparable in their ability to maintain corneal endothelial physiologic function during in-vitro perfusion. This is in contrast to previous work which showed that BSS-Plus induced less endothelial morphologic change than BSS. It is concluded that morphologic alterations may be more sensitive parameters of endothelial stress than are fluxes and permeabilities.

Acetates↗