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Biomedical subjects

O Behnke

Publications and source records attributed to O Behnke.

At least 37 records · Page 2Linked to original sources
PubMed1981

Acetylcholinesterase in the platelet-megakaryocyte system. I. Structural localization in platelets of the rat, mouse, and cat.

The localization of acetylcholinesterase (AchE) (E. C. 3.7.1.7) and peroxidase was studied cytochemically in blood platelets from cat, rat, mouse, and man. In a fraction (less than 1%) of cat, rat, and mouse platelets AchE activity was demonstrated in the dense, tubular membrane system (DTS), but activity was not detectable in human platelets. Some platelets showed AchE activity in granules distinct from alpha-granules. A fraction of the human platelet population exhibited a peroxidase-like activity in the DTS, but peroxidase activity was not detectable in cat, rat, and mouse platelets. The observations are interpreted to suggest a functional heterogeneity of the platelet population.

Acetylcholinesterase↗
PubMed1981

Acetylcholinesterase in the platelet-megakaryocyte system. II. Structural localization in megakaryocytes of the rat, mouse, and cat.

Acetylcholinesterase (AchE) activity (EC 3.7.1.7) was demonstrated cytochemically in the megakaryocyte (MK) line of differentiation in the red bone marrow of rat, mouse, and cat. Activity was detected in the Golgi complexes of cells considered to be committed MK precursor cells, and was found in Golgi cisterns through all subsequent stages of MK maturation. In the early, basophilic stage of differentiation some MK showed AchE activity in the perinuclear cistern and in a few profiles of the granular endoplasmic reticulum, but reaction was absent from this location at later maturation stages. Concomitantly with the development of the demarcation membrane system, another membrane system appeared; this system consisted of smooth-surfaced, tortuous tubules and narrow cisterns, and it displayed AchE activity through cytoplasmic maturation. In thrombocytogenic MK, the smooth AchE-reacting membranes (SAM) became the AchE-reacting dense tubular system (DTS) of released MK cytoplasm. The MK of the species studied also contained a varying number of AchE-reacting granules (mouse greater than cat greater than rat) which were distinct from alpha-granules.

Acetylcholinesterase↗
PubMed1980

Membrane structure of nonactivated and activated human blood platelets as revealed by freeze-fracture: evidence for particle redistribution during platelet contraction.

The distribution of intramembrane particles of nonactivated and activated human blood platelets was studied by freeze-fracture under various experimental conditions to see whether morphological evidence for a structural coupling between the platelet actomyosin system and the fibrin network in a retracting clot could be established. Membrane particles were evenly distributed in nonactivated platelets; the total number (E + P faces) was approximately 1,500/micrometers 2 of membrane, and there were two to three times more particles present on the E face than on the P face. Transformation of discoid platelets to "spiny spheres" by cooling did not change the particle distribution. Platelet activation and aggregation by serum or ADP caused no change in membrane particle density or distribution. Particle distribution was not changed in Ca2+-activated platelets fixed immediately before fibrin formation, but after fibrin formation and during clot retraction, particles were sometimes most frequent on the P face and tended to form distinct clusters, and aggregates of E face pits were observed. Blood platelets contain contractile proteins that are distinct as filaments in platelets in retracting clots. We suggest that the redistribution of particles seen in activated platelets during clot retraction reflects the esablishment of mechanical transmembrane links between the platelet actomyosin system and the fibrin net. The P-face particle clusters may represent sites of force transmission between actin filaments bonded to the inside of the membrane and the fibrin network at the outside. Thus, whereas membrane particles may not be directly involved in the attachment of actin filaments to membranes, the transmission of the force of the contractile system to an exterior substrate apparently involves the intramembrane particles.

Adenosine Diphosphate↗
PubMed1978

Megathrombocytopenia associated with glomerulonephritis, deafness and aortic cystic medianecrosis.

Macrothrombocytopenia associated with glomerulonephritis and deafness has only been reported in a few patients since it was first described in 1972. We present a patient with macrothrombocytopenia, glomerulonephritis, progressive uraemia and progressive sensorineural deafness associated with cystic medianecrosis of the ascending aorta and malformation of the aortic valves. The patient had consistently low platelet counts but no clinical signs of a defect haemostasis. The giant platelets were characterized by their size, averaging 11 micron in diameter, elaborate maze-like membrane formations, abundance of microtubules, and the total absence of very dense granules.

Adolescent↗
PubMed1978

Harvesting of granulocytes for transfusion therapy by haemonetics 30. Yield, morphology and in vitro functions of collected granulocytes.

By means of a Haemonetics 30 blood cell separator white blood cells (WBC) were collected for transfusion purposes from 21 normal unstimulated donors. Citrated Hydroxyethyl Starch (HES) was used as anticoagulant. A mean yield of 1.13 x 10(10) WBC was obtained in 2 1/2-3 h. Half of the collected WBC were PMN cells containing a few per cent band forms, the other half lymphocytes and monocytes (12%). No shift in the distribution of WBC was found during the leucapheresis. Light and electron microscopy did not reveal any damage or changes in the structure of the processed granulocytes. The Trypan blue exclusion test showed 99% vital cells. In vitro assessment of the chemotactic and bactericidal activity of the collected granulocytes showed normal function. Also the content of myeloperoxidase was within normal range.

Blood Cell Count↗
PubMed1977

Electron microscopical identification of the committed precursor cell of the megakaryocyte compartment of rat bone marrow.

In the rat bone marrow, cells of the megakaryocyte line of differentiation are the only hemopoietic cells which show cytochemically demonstrable Acetylcholineesterase activity (AchE; EC 3.1.1.7). A small number of morphologically unrecognizable cells exhibit AchE activity in their Golgi complexes. These cells are identified as committed precursor cells of the MK compartment.

Acetylcholinesterase↗