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R Eckert

Publications and source records attributed to R Eckert.

At least 127 records · Page 7Linked to original sources
PubMed1976

A voltage-sensitive persistent calcium conductance in neuronal somata of Helix.

1. An intracellular voltage clamp in conjunction with a patch pipette utilizing feed-back to monitor local current from the soma membrane were used to analyse transient and stationary currents in bursting pacemaker neurones in Helix pomatia and H. levantina. 2. A weak, net inward current flows during small (less than or equal 20 mV) depolarizations. This current exhibits slow activation kinetics, persistence during prolonged depolarization, and slow turning off at end of depolarization. Consequently, the steady-state current-voltage curve exhibits a region of negative resistance from about -55 to -35 mV. 3. The slow inward current and the negative resistance characteristic are rapidly and completely abolished by substitution of Co2+ or La3+ for Ca2+ and are partially blocked by the Ca-blocking drug D-600. Substitution of Tris or glucose for Na+ significantly reduces the inward current only after 15-20 min exposure, recovery being equally slow. 4. The inward current and the negative resistance characteristic of the I-V curve are greatly enhanced by Ba2+ substitution for Ca2+. This is ascribed in part to Ba2+ carrying current through the slow inward current channels and in part to a suppression of the late K+ current by Ba2+. 5. The inward current is also present in many non-bursting neurones but fails to appear as a net inward current due to short circuiting by a leakage current or by the delayed potassium current. In these cells the slow inward current contributes to inward going rectification. Replacement of Ca2+ with Ba2+ enhances the current so as to produce a net inward current during small depolarizations in these neurones. 6. It is concluded that the slow inward current is carried primarily by Ca2+ in the soma membrane of bursting pace-maker neurones and a number of non-bursting cells examined in the parietal ganglion of Helix. 7. The sensitivity to small depolarizations and persistence during prolonged depolarization suggests two roles for the Ca system in the generation of slow pace-maker oscillations. In this model the Ca system contributes to the slow depolarization which constitutes the onset of the pace-maker wave, and also contributes to the increment in [Ca] in which activates the Ca-sensitive K+ conductance responsible for repolarization. The inhibition of spontaneous bursting by Ca-blocking agents supports this model.

Animals↗
PubMed1975

Ureteroduodenal fistula.

A patient with pneumaturia was found to have a ureteroduodenal fistula, only the fourth such lesion reported. However, this patient is unique in that a fistula developed between the stump of a ureter and the duodenum in the absence of a kidney on that side. This case was namaged with a distal skin ureterostomy, thereby avoiding extremely hazardous surgery in the area of the duodenum. This successful conservative managemant offers a sharp contrast to the recommended management of reno-alimentary fistulas. The possible cause in this case based on roentgenographic analysis is discussed.

Duodenum↗
PubMed1975

[On the mode of action of heterologous antileukemic sera. Growth of syngeneically transplanted leukemia cells on serum treated neonatally thymectomized mice (author's transl)].

A heterologous antiserum against a Nitrosomethylurea--induced mouse leukemia prevented the outgrowth of syngeneically transplanted leukemia cells in neonatally thymectomized mice. After subcutaneous challenge with 50 000 leukemia-ascites cells thymectomized CBA mice at the age of 8 weeks were given 5 intraperitoneal injections each of 0,1 ml of the heterologous serum. While the antileukemic serum protected 9 out of 11 mice all of the 11 mice treated with normal rabbit serum developed a tumor. The absence of the thymus was confirmed by macroscopic control and by the absence of antibodies against the injected rabbit serum. With regard to previous findings showing a cooperation of heterologous antibodies with host cells as responsible for the antileukemic effect this result indicates that the effector cells are thymus-independent.

Animals↗
PubMed1975

[Methods for the separation of lymphocytes].

The paper reviews the currently available methods for lymphocyte separation, with particular reference to their effectiveness. Procedures based on density and size, such as density gradient centrifugation and sedimentation and size filtration on columns, allow accumulation of lymphocytes of different degree of differentiation, but do not permit any quantitative separation of distinct lymphocyte populations, because density and size of cells are properties strongly varying with the degree of development and physiological state of the cells. Differences of the cells' net potential cause differential adhesion of lymphoid cells to glass or other materials, and lead to varying migration speeds in the electric field. Adherence columns afford only partial separation of T and B cells, whereas favourable results have been obtained by preparative cell electrophoresis. Special membrane structures, such as differentiation antigens including membrane-bound immunoglobulins, cell receptors and transplantation antigens make possible a specific separation of lymphocytes. Essentially, the following 5 methods are being used: 1. Cytolytic treatment of the cells with antisera against differentiation antigens in the presence of complement. 2. Rosette separation 2.1 Rosette formation with sheep erythrocytes (SE) or with antigen-coaded SE for the isolation of antigen-binding lymphocytes. 2.2 Rosette formation by antigen-antibody-complement complexes (B rosettes) 2.3 Rosette formation with SE by human T lymphocytes (T rosettes) 2.1--2.3. Separation of the rosettes from the free lymphocytes by centrifugation or sedimentation.

Animals↗
PubMed1975

[The function of different lymphocyte groups and methods for their separation (author's transl)].

A review is given of the participation of T- and B-lymphocytes in the three most important lymphocyte functions: antibody formation, cellular effector reactions, especially cytotoxicity and regulator functions, with particular reference to the concept of "lymphocyte population". The most commonly used methods for the separation of T- and B-lymphocytes and of lymphocytes with the same function are described.

Agglutination↗
PubMed1973

Electrophysiological control of reversed ciliary beating in Paramecium.

Quantitative relations between ciliary reversal and membrane responses were examined in electrically stimulated paramecia. Specimens bathed in 1 mM CaCl(2), 1 mM KCl, and 1 mM Tris-HCl, pH 7.2, were filmed at 250 frames per second while depolarizing current pulses were injected. At current intensities producing only electrotonic shifts the cilia failed to respond. Stimuli which elicited a regenerative response were followed by a period of reversed ciliary beating. With increasing stimulus intensities the latency of ciliary reversal dropped from 30 to 4 ms or less, and the duration of reversal increased from 50 ms to 2.4 s or more; the corresponding regenerative responses increased in amplitude and rate of rise. With progressively larger intracellular positive pulses, electric stimulation became less effective, producing responses with a progressive increase in latency and decrease in duration of reversed beating of the cilia. When 100-ms pulses shifted the membrane potential to +70 mV or more, ciliary reversal was suppressed until the end of the pulse. "Off" responses then occurred with a latency of 2-4 ms independent of further increases in positive potential displacement. These results suggest that ciliary reversal is coupled to membrane depolarization by the influx of ions which produces the regenerative depolarization of the surface membrane. According to this view suppression of the ciliary response during stimulation occurs when the membrane potential approaches the equilibrium potential of the coupling ion, thereby retarding its influx. Previous data together with the present findings suggest that this ion is Ca(2+).

Animals↗