Biomedical subjects

M Wienrich

Publications and source records attributed to M Wienrich.

23 records · Page 2Linked to original sources

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↗

PubMed1989

Activation of substance P receptors leads to membrane potential responses in cultured astrocytes.

Cultured astrocytes from rat cortex and spinal cord responded with different types of membrane potential changes upon brief (10 seconds) applications of the natural neurokinin agonists substance P and neurokinin A. The most prominent type of response was a long-lasting membrane depolarization. In some cells, an initial rapid depolarization followed by a partial repolarization preceded the slow depolarizing event. Few astrocytes responded with a hyperpolarization of the membrane. Selective agonists at the NK-1 receptive site, substance P-methyl ester (SP-OME) and septide, mimicked the response to the natural neurokinins as did DiMe-C7, a selective NK-3 receptor agonist. A putative neurokinin antagonist, (D-Arg1,D-Pro2,D-Trp7,9,Leu11)SP (DADPDT) partially blocked membrane potential responses induced by substance P, SP-OME, septide, DiMe-C7, and NKA. The authors conclude that astrocytes express NK-1 and NK-3 receptors, which upon activation affect the electrical properties of these cells.

Animals↗

PubMed1989

Effects of receptor-selective neurokinin agonists and a neurokinin antagonist on the electrical activity of spinal cord neurones in culture.

1. Rat spinal cord neurones grown in tissue culture were used to examine the electrophysiological effects of the neurokin in (NK)-selective agonists (pGlu6, Pro9) substance P(6-11) (septide; NK1, 10(-6)M) and (pGlu5, MePhe8, MeGly9)SP(1-7) (DiMe-C7; NK3, 10(-6)M). In addition, the effect of the neurokinin antagonist (D-Arg1, D-Pro2, D-Trp7,9, Leu11)SP (10(-5)M) on the neurokinin-evoked responses was investigated. 2. Neurokinin-evoked responses consisted of an increase in neuronal activity with or without long-lasting (mean: 50s) depolarizations of the membrane potential of up to 25mV. The latter also occurred in the presence of tetrodotoxin (10(-7)M) (direct response). 3. In a number of spinal cord neurones (n = 17) only septide induced a membrane depolarization while DiMe-C7 elicited no response. On the other hand, in 2 neurones a response was exclusively evoked by DiMe-C7. 4. The neurokinin antagonist (D-Arg1, D-Pro2, D-Trp7,9, Leu11)SP had no effect of its own but blocked the septide- and DiMe-C7-induced depolarizations. It had no effect on the glutamate (10(-5)M)-evoked depolarization. 5. It is concluded that by the use of neurokinin receptor-selective agonists, subpopulations of spinal cord neurones in primary dissociated cell culture can be differentiated which express the NK1 or the NK3 receptor. Cells expressing only the NK1 receptor outnumber those expressing only the NK3 receptor subtype. Both receptors can be blocked by the neurokinin antagonist (D-Arg1, D-Pro2, D-Trp7,9, Leu11)SP.

Animals↗

PubMed1984

Cone mechanisms and their colour-opponent interaction in monkeys and cat.

Cone mechanisms and colour opponency were investigated in 108 recordings from tonic ganglion cells of the rhesus monkey retina and 265 recordings from ganglion cells of the cat retina. Colour-opponent cells input from short and longer wavelength sensitive cones can be found in both species in about equal proportions (6-8%). Although cells with opponency between middle and long-wavelength sensitive cones are very common in monkey (49%), they are rare in the cat (4%); usually the opponency of the latter can only be detected with strong chromatic adapting lights suppressing the dominant mechanism, while in monkey colour opponency is usually revealed under neutral adapting conditions. These differences between both species in processing chromatic stimuli can help to explain certain types of colour vision deficiencies in man.

Animals↗

PubMed1983

Antibody L1 ejected from a micropipette identifies neurons without altering electrical activity.

Antibody L1 which reacts specifically with the cell surface of central nervous system neurons was pressure ejected from a micropipette into the vicinity of a cultured neuron, or applied to the bathing fluid during intracellular recording of activity. No alterations in membrane potential, shape of action potential, firing rates and postsynaptic activities were observed. Binding of antibody was observed by indirect immunofluorescence after injection of Lucifer Yellow. Bath application of antibody resulted in a uniform neuronal staining over the entire culture, whereas pressure ejected antibodies were limited to neuronal structures within about 200 micron of the cell recorded from. Live, L1 antigen-positive neurons could be identified by indirect immunofluorescence prior to recording.

Animals↗