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Biomedical subjects

D Bingmann

Publications and source records attributed to D Bingmann.

At least 73 records · Page 4Linked to original sources
PubMed1986

pO2-dependent distribution of potassium in hippocampal slices of the guinea pig.

The distribution of extracellular K+-concentration (cK+s) in 200-1000-micron thick hippocampal slices was studied with ion-selective microelectrodes. In ca. 500-micron thick slices cK+s increased from the surface to the innermost layers by ca. 2 mmol/liter if the pO2 of the bath (pBO2) ranged from 300-600 mm Hg and if the temperature was 28 degrees C. In thicker slices and lowered pO2-values further elevations of cK+s were observed. In vital slices thinner than 500 micron cK+s-values exceeded the potassium-concentration of the bath (cK+B) only when pBO2 was markedly lowered. When pBO2 was reincreased in such thin slices, cK+s rapidly declined and often decreased transiently below ck+B. Similar undershoots of cK+s were observed when cK+B was lowered from high to normal levels. The rapid decline was blocked by hypoxia, ouabain, antimycine and a temperature of 18 degrees C. A stepwise rise of cK+B also caused rapid changes of cK+s in vital thin slices. The rates of changes, however, were hardly affected e.g. by a transient hypoxia. Diffusion did not contribute significantly to these steep changes of cK+s. These rapid distribution modes were widely missing in slices thicker than 500 micron. Therefore in such preparations, the extracellular microenvironment of neurons may markedly differ from the ionic concentrations in the bath.

Animals↗
PubMed1986

Actions of pentylenetetrazol (PTZ) on CA3 neurons in hippocampal slices of guinea pigs.

The actions of the convulsant drug pentylenetetrazol (PTZ) were studied on CA3 neurons of hippocampal slices (300-400 microns thick). In 9 out of 109 neurons, epileptic reactions were elicited during a single application of PTZ. After repeated applications of PTZ, 53 neurons showed periodic paroxysmal activity. They developed according to the following sequence: (i) Paroxysmal hyperpolarizations, (ii) burst activity, and (iii) typical paroxysmal depolarization shifts (PDS). The rate of occurrence was about 8/min. Paroxysmal hyper- and depolarizations appeared synchronously in pairs of neurons. The developmental sequence occurred in reverse during washing. After the onset of paroxysmal activity, bursts and PDS persisted if PTZ concentration in tissue ranged between about 2 and 10 mmol/l. When this range was exceeded in either direction, epileptic activity was abolished at a calcium concentration of 2.75 mmol/l. Decreasing and increasing the calcium concentration shifted the epileptogenic concentration range to lower and higher levels, respectively. It is concluded that repetition of PTZ application alters membrane properties of neurons and thus leads to paroxysmal events triggered by synaptic processes.

Animals↗
PubMed1985

[A simple electronic delay line that facilitates the incomplete display of spontaneous bioelectric signals on an oscilloscope].

A simple electronic delay line is described which is appropriate to delay bioelectric events like action potentials of neurons up to 100 ms. Thus, the device allows to use untriggered potentials as trigger signals and thereafter to display the delayed events including possible prepotentials in toto on an oscilloscope. The delay line mainly consists on charge coupled devices (CCD) in which samples of potentials to be delayed are transported like in "bucket-chain". Thereby the delay time at a given number of CCD elements only depends on the frequency of a clock which drives the chain. As long as action potentials and other bioelectric events have to be delayed up to ca. 0,1 s this device may be used as an alternative to transient recorders or other apparatus which are far more expensive than the presented delay line.

Action Potentials↗
PubMed1982

PO2-profiles in hippocampal slices of the guinea pig.

For a detailed analysis of the oxygen supply of hippocampal slices, tissue PO2 (Pt,O2) was recorded polarographically in the neural layers of thick and thin slice preparations from the guinea pig. The experiments showed that the Pt,O2-gradients were extremely steep in the outer zones of vital slices. In an air equilibrated salt solution the surface PO2 was reduced to less than 50% within ca. 25 micron. Minimum values were measured at a depth of ca. 150 micron. A rise of temperature lowered the oxygen supply in the deeper layers of the excised tissue. An elevation of the surface PO2 hardly improved Pt,O2 in the deep structures, because the O2-consumption of the hippocampal slices increased with rising PO2.

Animals↗