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Biomedical subjects

L Edelmann

Publications and source records attributed to L Edelmann.

At least 55 records · Page 3Linked to original sources
PubMed1986

Freeze-dried embedded specimens for biological microanalysis.

The main problems associated with freeze-drying of biological material for electron microscopy concern the freeze-drying temperatures and times necessary to minimize artifacts. Due to the many parameters involved these problems have to be resolved experimentally. It can be shown that good morphological preservation of chemically unfixed material is possible when freeze-drying is done exclusively in a temperature range between -80 degrees C and -50 degrees C. OsO4 vapour fixation of the freeze-dried tissue is not necessary and should be avoided because it may cause ion redistribution artifacts. Embedding at low temperature of properly freeze-dried material does not seem to disturb structure and ion distribution of the freeze-dried material. Hence, sections of such freeze-dried material and embedded biological material seem to be suitable for microanalysis. Preliminary micro-analytical results obtained from sections of freeze-dried and Lowicryl K11M embedded muscle reveal an uneven distribution of potassium in the sarcomeres similar to the visualized uneven distribution of the electron dense thallium (potassium surrogate) in frozen hydrated cryosections. A comparison of different cryomethods shows that freeze-drying and embedding is the simplest way to obtain stable thin sections of chemically unfixed biological material which, for instance, may be used for future microanalytical investigation of the interaction of proteins with physiological and non-physiological ions.

Animals↗
PubMed1985

Fibrinogen distribution on surfaces and in organelles of ADP stimulated human blood platelets.

The fibrinogen distribution in platelet organelles after ADP-stimulation was investigated with anti-human fibrinogen using protein A-gold applied to serial sections. Fibrinogen was detected in the so-called alpha-granules of platelets and also in granule protrusions which were observed after ADP-stimulation. The ends of these protrusions were formed as coated membranes and the tips were often in apposition to the surface connected membranes or the plasmalemma. At such places fusion events and hence signs of an exocytosis could be demonstrated by means of cryofixation and cryosubstitution. Examination of serial sections revealed fibrinogen on all these granule profiles. Surface connected membranes, free surfaces and the characteristic structure of the contact zones of aggregated platelets were also labelled by gold particles but less than anticipated. On the platelet surfaces and surface connected membranes fibrinogen was rarely demonstrable with ferritin-labelled anti-human fibrinogen on washed or thrombin-stimulated, almost fibrinogen free platelets. After addition of human fibrinogen to the thrombin stimulated and disaggregated platelets a part of the platelets aggregated spontaneously and formed characteristic contact zones. Anti-human fibrinogen was observed on the free surfaces, in filamentous bridges between the contact spaces and in a tubular surface connected membrane system with involvement of coated membranes at the central ends of these structures. The results indicate the following: all alpha-granules contain fibrinogen; after ADP-stimulation secretion takes place with involvement of coated membranes; during aggregation fibrinogen binds to platelet surfaces and forms contact spaces; fibrinogen is taken up by the surface connected system with involvement of coated membranes.

Adenosine Diphosphate↗
PubMed1984

Potassium efflux from frog oocytes: effects of temperature, preincubation and injection of a gelatin bead.

42K efflux was studied in frog oocytes. 17 of 43 cells had only a single slow exponential exchange of 42K, while the remainder had a curvature of 42K exchange with one or more fast fractions preceding the slow exponential one. This variability in the characteristic of 42K efflux is not associated with evident damage, occurs at both 5 degrees and 25 degrees C., is independent of the method of preincubation, and occurs whether or not the cells are injected with a gelatin bead. Most of the fast-exchange fraction of K is not caused by follicle cells or other extraoocytic sources. These results may help explain some of the apparently conflicting results reported in studies of K exchange in amphibian oocytes.

Animals↗
PubMed1984

Subcellular distribution of potassium in striated muscles.

Microanalytical experiments have been performed to answer the question whether the main cellular cation, K+, follows the water distribution in the striated muscle cell or whether K+ follows the distribution of negative fixed charges (beta- and gamma-carboxyl groups of aspartic and glutamic acid residues). Subcellular localization of K and/or of the K surrogates Rb, Cs, and Tl has been investigated by the following methods: Chemical precipitation of K with tetraphenylborate. Autoradiography of alkali-metals and Tl in air-dried and frozen-hydrated preparations. TEM visualization of electron dense Cs and Tl in sections of freeze-dried and plastic embedded muscle. X-ray microanalysis of air-dried myofibrils and muscle cryosections. The experiments consistently show that K, Rb, Cs, and Tl do not follow the water distribution but are mainly accumulated in the A band, especially in the marginal regions, and at Z lines. The same sites preferentially accumulate Cs or uranyl cations when sections of freeze-dried, embedded muscle are exposed to these electron microscopic stains. It is concluded that the detected uneven distribution of K, Rb, Cs, and Tl in muscle is neither a freeze-drying artifact nor an embedding artifact and may result from a weak ion binding to the beta- and gamma-carboxyl groups of cellular proteins.

Animals↗
PubMed1983

Electron probe X-ray microanalysis of K, Rb, Cs, and T1 in cryosections of striated muscle.

Muscles containing the normal amount of K+ or loaded with Rb+, Cs+, or T1+ were cryofixed, cryosectioned and analysed by electron probe X-ray microanalysis. Previously reported results obtained with independent methods were confirmed: The alkali-metals and T1 are mainly localized in the A bands and at Z lines of the striated muscle. The results are in accordance with the association-induction hypothesis and the concept that K+ is physically adsorbed onto beta- and gamma-carboxyl side chains of myosin and other proteins.

Animals↗
PubMed1980

Potassium binding sites in muscle: electron microscopic visualization of K, Rb, and Cs in freeze-dried preparations and autoradiography at liquid nitrogen temperature using 86Rb and 134Cs.

Normal frog sartorius muscles and muscles in which a major portion of the intracellular K+ was reversibly replaced by Rb+ or Cs+ were frozen, freeze-dried and embedded without chemical fixation or staining. Dry-cut sections of these preparations reveal striation patterns with higher contrast than those of wet-cut sections of the same preparation. The results suggest that in the living state the alkali metal ions are mainly localized in the A bands and Z lines of myofibrils. This idea is confirmed by a new autoradiographic technique by means of which the distribution of Rb+ and Cs+ in frozen-hydrated single muscle fibers has been investigated. The findings support the association-induction hypothesis according to which most cell K+ and other alkali-metal ions are not free in cell water but are adsorbed to beta- and gamma-carboxyl groups of cell proteins.

Animals↗
PubMed1980

Preferential localized uptake of K+ and Cs+ over Na+ in the A-band of freeze-dried embedded muscle section: detection by x-ray microanalysis and laser microprobe mass analysis.

Sections of freeze-dried embedded frog muscle were exposed to aqueous solutions containing various combinations of the salts LiCl, NaCl, KCl, and CsCl. Energy dispersive X-ray microanalysis and laser microprobe mass analysis of these sections showed selective and preferential accumulation of K+ (and Cs+) over Na+ on specific protein sites in the A-bands. The selectivity coefficient exceeded 10 and involved a total K+ accumulation of about 40 mmoles/kg (in comparison with a value of about 80 mmoles/kg in normal living frog muscle). These findings support the view that selective K+ adsorption on intracellular proteins is the primary cause of selective accumulation of K+ in living cells.

Animals↗
PubMed1977

Potassium adsorption sites in frog muscle visualized by cesium and thallium under the transmission electron microscope.

Frog muscles in which a major portion of the intracellular K+ was reversibly replaced by Cs+ or Tl+ were frozen, freeze-dried, and embedded in Spurr medium. Electron microscopic observation revealed a well-stained striation pattern of myofibrils, indicating that in the living state heavy tracers of K+ are mainly located in the A bands and Z lines. The findings contradict the membrane theory but are in accordance with the association-induction hypothesis.

Adsorption↗