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Biomedical subjects

O Strauss

Publications and source records attributed to O Strauss.

29 records · Page 2Linked to original sources
PubMed1996

Activation of Cl- currents in cultured rat retinal pigment epithelial cells by intracellular applications of inositol-1,4,5-triphosphate: differences between rats with retinal dystrophy (RCS) and normal rats.

Using the whole-cell configuration of the patch-clamp technique, we studied the conditions necessary for the activation of Cl--currents in retinal pigment epithelial (RPE) cells from rats with retinal dystrophy (RCS) and nondystrophic control rats. In RPE cells from both rat strains, intracellular application of 10 microM inositol-1, 4,5-triphosphate (IP3) via the patch pipette led to a sustained activation of voltage-dependent Cl- currents, blockable by 1 mm 4, 4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS). IP3 activated Cl- currents in the presence of a high concentration of the calcium chelator BAPTA (10 mM) in the pipette solution, but failed to do so when extracellular calcium was removed. Intracellular application of 10(-5)M Ca2+ via the patch pipette also led to a transient activation of Cl- currents. When the cells were preincubated in a bath solution containing thapsigargin (1 microM) for 5 min before breaking into the whole-cell configuration, IP3 failed to activate voltage-dependent currents. Thus, IP3 led to release of Ca2+ from cytosolic calcium stores. This in turn activated an influx of extracellular calcium into the submembranal space by a mechanism as yet unknown, leading to an activation of calcium-dependent chloride currents. In RPE cells from RCS rats, which show an increased membrane conductance for calcium compared to normal rats, we observed an accelerated speed of Cl--current activation induced by IP3 which could be reduced by nifedipine (1 microM). Thus, the increased membrane conductance to calcium in RPE cells from RCS rats changes the response of the cell to the second messenger IP3.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1995

Incomplete belts of tight junctions in cultured non-pigmented human ciliary epithelial cells.

Tight junctions of cultured human non-pigmented ciliary epithelial cells were studied with the freeze-fracture technique and related to the transepithelial electrical resistance of these monolayers. Isolated tight junctional fibrils or small groups and networks of tight junctions sometimes associated with gap junctions were revealed in freeze-fracture images of the lateral plasma membrane. The tight junctions always formed incomplete belts, so that the apical and basolateral plasma membrane domains often were in continuity without morphological evidence of interposed intercellular junctions. The monolayers revealed a transepithelial resistance of 19.7 +/- 2.1 omega.cm2. Protamine induced a reversible increase of the transepithelial resistance of the cultures by 91 +/- 12%, but still the tight junctions formed incomplete belts. We conclude that contrary to complete networks of tight junctions in native non-pigmented ciliary epithelium, cultured monolayers only express incomplete belts of tight junctions which may be the morphological correlate of the relatively low transepithelial resistance of these monolayers. Interpretations on transepithelial transport and permeability characteristics of these cultures have to take into account the differences in junctional morphology from their native epithelium.

Cells, Cultured↗
PubMed1994

Ca(2+)-conductances in cultured rat retinal pigment epithelial cells.

Membrane conductances for Ca2+ in cultured rat pigment epithelial cells were studied in the whole-cell configuration of the patch-clamp technique using barium (10 mM) as a charge carrier. Two types of voltage-dependent and verapamil- and diltiazem-sensitive Ba2+ currents were observed. First, a nearly sustained current was activated by depolarization to potentials more positive than -30 mV and blocked by nifedipine (1 microM). This current was observed in cells of primary cultures less than 13 days old. Second, a transient nifedipine (1 microM) insensitive current was activated by depolarization to potentials more positive than -55mV in cultures which were more than 13 days old. This current was not carried by sodium and blocked by 1 microM tetrodotoxin (TTX). In summary, cultured rat retinal pigment epithelial cells in younger primary cultures express Ba2+ currents indicating the presence of L-type Ca2+ channels. In older primary cultures a low-voltage activated channel was observed with properties different from T-type calcium channels or TTX-sensitive calcium conducting sodium channels.

Aging↗
PubMed1994

Extracellular matrix proteins as substrate modulate the pattern of calcium channel expression in cultured rat retinal pigment epithelial cells.

We investigated the effect of different culture substrates on the expression of membrane conductances for calcium in cultured rat retinal pigment epithelial (RPE) cells using the perforated patch technique and barium as charge carrier. In younger cultures (up to 12 days old) the RPE cells expressed L-type calcium channels, in older cultures (more than 12 days old) LVA-type channels. The LVA-type channels have been characterized as a tetrodotoxin sensitive Ca2+ channels. Coating the culture substrate with laminin, shifted the culture age for expression of LVA-type channels to 7 days. When collagen type 4 was used as substrate LVA-type channels and L-type channels were expressed simultaneously in 7 days old cultures. We concluded that proteins of the extracellular matrix which are known to enhance cell differentiation in culture, enhance the expression of LVA-type channels in RPE cells.

Animals↗
PubMed1994

Potassium currents in cultured cells of the rat retinal pigment epithelium.

Whole-cell currents were investigated in cultured rat retinal pigment epithelial (RPE) cells. Two voltage-dependent conductances were discriminated. First, at potentials more positive than -30 mV, a time-dependent outward current was activated. Inhibition by Ba2+ (10 mM) and 4-aminopyridine (10 mM) indicated that this current was carried by potassium ions. This current showed no inactivation during 5 sec depolarizations. Second, an inward current, sensitive to Ba2+ (10 mM) and 4-aminopyridine (10 mM), was activated at potentials more negative than -70 mV. Under extra- and intracellular potassium-free conditions, both currents disappeared. In summary, cultured rat RPE cells expressed one potassium conductance similar to the delayed rectifier and one similar to the inward rectifier. The delayed rectifier expressed characteristics comparable with those known in mammalian species and different from those in non-mammalian species.

4-Aminopyridine↗
PubMed1993

Voltage-dependent potassium currents in cultured human retinal pigment epithelial cells.

Membrane currents in primary cultures of human retinal pigment epithelial cells were studied using the whole-cell configuration of the patch-clamp technique. Two types of voltage-dependent whole-cell currents were observed. First, a time- and voltage-dependent outward current, which was activated by depolarizing the cell to potentials more positive than -30mV, was sensitive to Ba2+ (10mM), 4-aminopyridine (10mM) and TEA+ (30mM). Tail-current analysis indicated that the current was mainly carried by K(+)-ions. Second, hyperpolarization of the cell to potentials more negative than -70mV led to a time- and voltage-dependent inward current which was blocked by Ba2+ (10mM) and 4-aminopyridine (10mM), but not by TEA+ (30mM). In summary, human retinal pigment epithelial cells in primary culture express currents which indicate the presence of a delayed rectifier K(+)-channel and an inward rectifier K(+)-channel.

4-Aminopyridine↗
PubMed1993

Cultured retinal pigment epithelial cells from RCS rats express an increased calcium conductance compared with cells from non-dystrophic rats.

The Royal College of Surgeon (RCS) rats suffer from a retinal dystrophy that is caused by a malfunction of the retinal pigment epithelium (RPE). We compared the membrane currents of cultured RPE cells from non-dystrophic and RCS rats by using the whole-cell configuration of the patch-clamp technique. Cultured RPE cells from RCS rats showed voltage-dependent, barium- and 4-aminopyridine-sensitive outward currents, which had characteristics of the delayed-rectifier and voltage-dependent, barium- and 4-aminopyridine-sensitive inward currents, which had characteristics of the inward rectifier. Differences between RPE cells from RCS rats and normal rats were as follows. (a) Cultured RCS rat RPE cells showed a resting potential and an activation threshold for the voltage-dependent outward current significantly more positive than that found in cells from non-dystrophic rats. (b) In the presence of 10 mM barium, the voltage-dependent outward current was reduced in both types of cells; in cells from RCS rats, an additional voltage-dependent inward current was observed. (c) This additional inward current had characteristics of L-type calcium channels and was reduced by verapamil (30 microM) and diltiazem (30 microM). In summary, we conclude that the membrane conductances of RPE cells from normal and RCS rats are dominated by potassium conductances. In contrast to cells from non-dystrophic rats, cells of RCS rats expressed an increased membrane conductance for calcium.

4-Aminopyridine↗
PubMed1992

Elevation of cytosolic free calcium in cultured ciliary epithelial cells by histamine: effects of verapamil and staurosporine.

Treatment with histamine (10(-4) M) of cultured non-pigmented human ciliary epithelial cells led to a biphasic elevation of free intracellular calcium mediated by H1-receptors. The initial transient increase was due to Ca(2+)-release from intracellular calcium stores and could be blocked with a high concentration of verapamil (10(-4) M). The subsequent sustained elevation of cytoplasmic calcium caused by an influx of extracellular calcium was reduced by staurosporine (10(-7) M). We conclude that the sustained increase of cytoplasmic calcium by histamine may be partially mediated by activation of protein kinase C. Since depolarization of the cells had no effect on intracellular calcium, we conclude that typical voltage-operated calcium channels do not significantly influence intracellular calcium.

Alkaloids↗
PubMed1991

Transepithelial resistance of ciliary epithelial cells in culture: functional modification by protamine and extracellular calcium.

1. Bovine pigmented and human non-pigmented ciliary epithelial cells were cultured on porous filter supports to obtain measurements of transepithelial electrical parameters. 2. The non-pigmented cells showed maximal transepithelial resistance of 15-30 omega cm2 from the third to seventh day in culture. 3. The pigmented ciliary cells reached maximal resistances of 9-20 omega cm2 after the fourth day in culture. 4. The transepithelial resistances of the cultured epithelia were functionally increased by protamine. This effect could be reversed by heparin. 5. We conclude that the range of resistances in cultured ciliary epithelial cells is the same as in whole ciliary preparations. Thus, cultured ciliary epithelial cells can be used for studies on transepithelial transport.

Animals↗
PubMed1982

[Prevalence and aetiology of respiratory symptoms and affections in adolescent school children in French Polynesia (author's transl)].

All the Tahitian school children from 3rd to final grade were questioned by an auto-questionnaire in May 1979. 93% replied to the questions asked (3,870). The prevalence of upper respiratory infections was increased as well as broncho-pulmonary symptoms (cough or other lung disease) during the year under study when compared to a control group in Metropolitan France. This prevalence was significantly increased both in boys and girls who smoked. The incidence of frequent or chronic cough was most increased in the older pupils, boarders, those followed a technical curriculum and belonging to the lower socio-professional categories. Asthma was very frequent at 11.5%, had an equal sex incidence and was not linked to any identifiable factor--the same enquiry was done in the Bas-Rhin department in France 3 years before; Tahitian school children, in general, have double the incidence of respiratory disease that is found in the Bas-Rhin.

Adolescent↗