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Biomedical subjects

R Dörner

Publications and source records attributed to R Dörner.

50 records · Page 3Linked to original sources
PubMed1990

Glutaminergic responses of neuropile glial cells and Retzius neurones in the leech central nervous system.

The effects of glutaminergic agonists on neuropile glial cells and on Retzius neurones in the central nervous system (CNS) of the leech, Hirudo medicinalis were investigated using double-barrelled ion-sensitive microelectrodes. In both types of cells, bath-application of L-glutamate (Glu), kainate (Ka) and quisqualate (Qui) elicited substantial membrane depolarizations which were accompanied by increases of the intracellular Na+ activity aiNa and by concomitant decrease of the intracellular K+ activity aiK. In the glial cells, these alterations of aiNa and aiK were preceded by a transient decrease of aiNa and an increase of aiK upon administration of Ka and Qui. In both glial cells and neurones, N-methyl-D-aspartate (NMDA) did not affect Em, aiK and aiNa. As found for Ka, the neuronal as well as the glial responses to glutaminergic agonists persisted during inhibition of synaptic transmission in high Mg2+, low Ca2+ solutions. The results indicate that leech neuropile glial cells have a Ka/Qui-preferring non-NMDA glutamate receptor similar to that in the Retzius neurones.

Animals↗
PubMed1989

Glutamate and kainate increase intracellular sodium activity in leech neuropile glial cells.

Na+-selective, double-barrelled microelectrodes were used to measure intracellular Na+ activity (aiNa) and membrane potential (Em) in neuropile glial cells of isolated segmental ganglia in the leech Hirudo medicinalis. Bath application of glutamate (10(-3) M) resulted in membrane depolarizations of about 5 mV and a concomitant increase of aiNa by between 2 and 10 mM. Kainate (10(-4) M) elicited depolarizations of up to 40 mV amplitude followed by a prominent after hyperpolarization. During kainate, aiNa increased by 7 to 25 mM. In contrast to glutamate, an initial decrease of aiNa was detected during the action of kainate. N-methyl-D-aspartate (NMDA, 10(-5)-10(-3) M) had no effect of Em and aiNa. The results indicate that leech glial cells have a kainate-preferring non-NMDA glutamate receptor.

Animals↗
PubMed1989

[Statistical analysis of parameters which determine yield in continuous centrifugal plateletpheresis].

In order to ensure the economical handling of thrombocyte preparations which cannot be dispensed of and provided in unlimited quantities as well as in the interest of an indulgent behaviour towards donors it is desirable to adjust the platelet content of preparations in such a way that it corresponds to a therapeutically required, but also sufficient concentration. For this purpose, it must be possible to assess the yield of an apheresis in advance. This can be made without any difficulties by applying an equation developed according to a mathematical-statistical analysis by a multiple and partial correlation from 120 cases of apheresis, which shows, however, that the yield does not depend on machine data, but in a decisive manner on the donor's initial platelet number and the separated total blood volume.

Blood Component Removal↗
PubMed1988

[Washed erythrocyte concentrates. A contribution to the problem of the effect of wash procedures and storage time on erythrocytes in the preparation of blood].

The question of how often erythrocytes should be washed in order to obtain a protein-free and therapeutically efficient unit of washed red blood cells is still controversial. To obtain more information regarding this problem, 6 X 15 units of whole blood were washed 1-6 times with a saline solution immediately and after 7, 14, 21, 28 and 35 days of storage. After each washing procedure the content of total protein, of immunglobulins A, G, and M and of complement factor C3 was determined in the supernatants, as well as the osmotic fragility in the corresponding erythrocyte sediments. The statistically analyzed results enabled us to describe the average degree of influences as equations and to recommend a preparation prescription. The results show that the protein levels decrease precipitously after the first and second washing procedures. The following 4 procedures have no significant effect. On the other hand, with increasing time of storage more washing procedures are necessary to reach the same results than with younger units. That is also true for the concentrations of immunoglobulins and complement C3. The osmotic fragility of the erythrocytes increases with each washing procedure as well as each day of storage. According to these results, an optimal, protein-free and effective unit of washed red blood cells is obtained when a 1-2-week-old unit of whole blood is washed 2-3 times.

Blood Preservation↗