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Biomedical subjects

G Geyer

Publications and source records attributed to G Geyer.

At least 127 records · Page 7Linked to original sources
PubMed1978

[Conformational alteration of the Antennulae microvillares (author's transl)].

Brush border cells of the rectal mucosa of the rat previously fixed with glutaraldehyde and OsO4 exhibit branched antennulae microvillares. This regular type of antennulae changes to become a cap-like layer at the tip of the microvilli following the incubation in 100 mM EDTA and 1 M guanidinium hydrochloride, respectively, of the native mucosa. During an incubation in isotonic sucrose the antennulae are transformed to moderately branched rod-like forms. The findings suggest a collaps of antennulae whose anchoring at the membrane of the microvilli appears to be resistant and, presumably, may prevent the loss of this mucosubstance.

Animals↗
PubMed1978

[Stimulation of prolactin secretion by drugs].

Intravenous administration of metaclopramide and cimetidine provokes an immediate rise in serum prolactin concentration. The results are compared with the response of serum prolactin to arginine, insulin and TRH.

Animals↗
PubMed1978

[Peroxidase distribution pattern and cochlear microphonics in the impulse-noise exposed cochlea of the guinea pig (author's transl)].

Morphological findings evidenced the impulse noise trauma primarily a mechanical lesion of cells. The loss of mechanically damaged sensory cells results in the initial decline of cochlear microphonics. Due to mechanical lesions many sites of leakage in the wall of the cochlear duct give way to the diffusion of components of either lymph, which will produce a general functional disturbance associated with additional decline of microphonics. The functional restoration of the inner ear requires the previous repair of the endo/perilymphatic barrier.

Animals↗
PubMed1978

[Environmentally dependent erythrocyte membrane permeability as a source of error in the determination of hematocrit].

The volume of human red blood cells (RBC) was evaluated by means of the centrifugation method (hematocrit) and 131-J-labelled human serum albumin, respectively. Both of the methods yielded an identical volume of about 107 micron3 of the single RBC, provided the evaluation was performed in autologous plasma. Contrary to the 131-J-albumin method the results of which were found independent of various pretreatments of RBC, the centrifugation hematocrits of RBC previously washed with PBS and resuspended in PBS or saline protein media resulted in a mean cell volume of about 86 micron3. The decrease of the cell volume was associated with an efflux of K+ ions. If the RBC are centrifuged at 800 g instead of 15000 g, their volume will remain unchanged. The assessment of cytodeformability has shown, that RBC in PBS by loss of cell volume could enter a 2.3 micron micropipette completely. RBC in plasma, though traversing a 2.9 micron micropipette were incapable of entering a 2.3 micron channel completely. With pressures ranging from 300 to 350 mm H2O the processes of these cells undergo microspherulation.

Cell Membrane Permeability↗
PubMed1978

Electron microscopic toluidine blue staining of the erythrocyte membrane.

Incubation in ferricyanide medium of toluidine blue stained erythrocytes produces opaque precipitates lining either aspect of the cell membrane. In addition, granular and needle-shaped precipitates occupy an intra- or extracellular position. Staining of the outer aspect of the membrane may reflect toluidine blue binding of the erythrocyte glycocalyx. Precipitates at the inner leaflet resemble Ca2+ affinity sites which were considered phosphorylated spectrins. Comparison with the light microscopic topo-optical toluidine blue reaction proved most of the electron dense precitates noncontributive to anisotropic staining.

Erythrocyte Membrane↗
PubMed1978

Glutaraldehyde mediated echinocyte/discocyte transformation is Ca2+ dependent.

Echinocytes, which were produced from freshly banked blood by repeated washes in phosphate buffered saline, undergo a transformation to the discoid shape within less than 30 seconds of incubation in isotonic 0.05% glutaraldehyde pH 7.4. This echinocyte/discocyte transformation is not associated with a change of cell volume or critical hemolysis volume although a slight decrease of cellular deformability and a 4-8 fold increase of K+ efflux within 1 hour after glutaraldehyde incubation provide evidence of the fixative's attack on the cell membrane. Trypsination prior to the incubation in isotonic glutaraldehyde could not inhibit the shape change. Hypertonic glutaraldehyde solutions partially prevent the E/D transformation with regard to both the osmolarity of the medium and the permeability of the cell membrane. The glutaraldehyde stimulated transformation is entirely inhibited in the presence of a chelating agent the efficiency of which is overcome by addition of a more-than-equivalent amount of Ca2+. The mutual action of either agent is discussed, however, the mechanism of the phenomenon remains unclear.

Aldehydes↗
PubMed1978

[Modification of sialic acid determination in erythrocytes].

Various chromophores impair the evaluation of N-acetyl-neuraminic acid (NANA) of red blood cells by means of the thiobarbituric acid method according to WARREN. Therefore, a time consuming isolation of erythrocyte membranes is essential in order to avoid these shortcomings. The procedure was simplified by fixation with glutaraldehyde of washed red blood cells.

Erythrocyte Membrane↗
PubMed1978

[Distribution pattern in the guinea pig cochlea of intravitally injected peroxidase].

Following perilymphatic perfusion and injection into the cisterna cerebello-medullaris, respectively, the distribution pattern of horseradish peroxidase in the cochlea of the guinea pig was studied light and electron microscopically. The findings prove effective tight junctions (zonulae occludentes) between the cells of the epithelial lining of the endolymphatic compartment. At the level of the reticular membrane the tight junctions are far more extended than elsewhere at the cochlear duct epithelium. From the findings a fairly rapid exchange is suggestive between the lymphatic space of the organ of Corti and the tympanic scale. Various types of cells of the cochlear duct actively take up considerable amounts of peroxidase. However, endocytosis of peroxidase by hair cells and particularly by the outer ones is rather scanty. Passive permeation of the tracer through the membran of undamaged hair cells was disproven.

Animals↗
PubMed1977

[The clinical relevance of scintigraphic adrenal imaging (author's transl)].

Labelled steroid precursors have been found to be valuable in scintigraphic imaging of localized adrenal disease or even in adrenal hyperplasia. Scanning procedures are non-invasive diagnostic methods and, in the case of the adrenals the images reflect anatomical as well as functional changes in the organs, constituting an advantage over angiographic methods. However, careful preparation of the patient, sophisticated technical prerequisites and a case-oriented programme of the procedure favouring either dexamethasone suppression, comparsion with phantom measurements adrenal profiles and/or multichannel analysis are necessary for the attainment of optimum results on scintigraphy.

Adrenal Gland Diseases↗
PubMed1977

[Investigations on the glycocalyx with toluidin blue staining (author's transl)].

The study was concerned with the molecular structure of the erythrocyte membrane and its anisotropic staining with toluidine blue. Enzymatic or chemical degradation impairs the topo-optical staining. Decreased anisotropy results also from digitonin treatment of glutaraldehyde fixed cells. Incubation in a mixture of chloroform and methanol abolishes the anisotropic staining with toluidine blue, but it has been restored by the aldehyde bisulfite-procedure. The efficacy of a treatment with chloroform-methanol is greatly reduced int eh case of agglutinated erythrocytes. The reversibly collapsed glycocalyx is devoid of topo-optical staining. The findings refer to the spatial orientaiton of glycoproteins at the cell surface. Degradation or loss and rearrangement, respectively, change the glycocalyx structure and likewise deteriorate the condition for the anisotropic staining. Alterations of the lipid layer of the membrane may result in similar effects. There was, however, no indication of an intercalation into the lipid layer of dyestuff molecules. In conclusion, the topo-optical toluidine blue staining is considered a powerful method aiding studies of the glycocalyx of erythrocytes (and presumably of other types of cells too).

Birefringence↗
PubMed1977

Reversible conformational changes of plasmalemmal glycoproteins.

Repeated incubations of human red blood cells in low ionic isotonic sucrose result in an instantaneous agglutination. In the same medium which had caused the agglutination, erythrocytes completely disagglutinate within 60 to 90 min. Disagglutination is accompanied by the efflux of cellular ions, which causes a 500-fold increase of extracellular K+. Decomposition of agglutinates occurs at once upon addition to the medium of about 3 mM KCL. It will be inhibited for hours, if the medium is renewed twice an hour. Erythrocytes washed successively with phosphate buffered saline and isotonic sucrose are devoid of adhering blood plasma proteins. If these cells were fixed with glutaraldehyde in isotonic sucrose they had lost a) their anisotropic staining with toluidine blue, and b) most of their colloidal iron binding capacity. The staining with ruthenium red and the electrophoretic velocity of these erythrocytes apparently were identical with the controls. The findings are considered evidence of the reversible unfolding of glycocalyx glycoproteins in the low ionic medium.

Animals↗
PubMed1977

Adsorbed proteins mask negatively charged sites of the erythrocyte glycocalyx.

Protein masking of charged sites of the erythrocyte glycocalyx was studied by means of the colloidal iron affinity. Washed red cells were fixed with glutaraldehyde such as to stabilize their glycocalyx and to inhibit conformational changes during posttreatment. Following the incubation in an ionic protein solution, proteins adsorbed to the cell surface were insolubilized by repeated treatment with low ionic isotonic surcose. Erythrocytes coated with precipitated proteins exhibited a rough surface. Their iron binding capacity was reduced considerably. In comparison with serum albumin, masking by gamma globulin was more efficient, apparently, because of its insolubility in low ionic media. High ionic incubation of coated erythrocytes resolubilized adsorbed proteins and unmasked negatively charged groups of the glycocalyx.

Erythrocyte Membrane↗
PubMed1977

Ultrahistochemical demonstration of cations in the guinea pig organ of Corti.

The distribution of cations in the guinea pig organ of CORTI was studied by means of the ultrahistochemical pyroantimonate method. In the outer hair cells precipitates were localized at the cell membrane, at stereocilia, in the subplasmalemmal cisterns, in the the nucleus, in mitochondria and within the ground plasm. Coarse precipitates at the cell membrane may consist mainly of cations other than calcium ions. The subplasmalemmal cisterns are suggested to sequester cations in the outer hair cells. The mechanism of the trapping reaction and factors injuring this histochemical method are discussed.

Animals↗
PubMed1977

[Electronmicroscopic detection of cation binding sites on the erythrocyte membrane].

Numerous Ca2+-binding sites were localized ultrahistochemically at the inner surface of the erythrocyte membrane and small amounts at the outer surface. La3+-binding sites were demonstrated at the outer surface only. The results were discussed in relationship to the binding capacity of the filamentous matrix and the glycocalyx of the human erythrocyte membrane.

Binding Sites↗
PubMed1977

[Agglutination of the red blood cells after experimental glycolytic alteration].

The present findings proved Alcian Blue as hemagglutinin suitable for the specific demonstration of negatively charged sites of the cell surface. Erythrocytes with reduced surface charge because of previous trypsination or desialization exhibited decreased Alcian Blue agglutination. On the other hand, Alcian Blue agglutinates more intensely red blood cells with a high surface charge (reticulocytes). Findings with A antiserum or the lectins prepared from Lens culinaris and Helix pomatia indicate a masking of glycolipidic group A receptors by glycoproteins of the erythrocyte membrane. Effects of enzymatic degradation (neuraminidase, trpysin, pronase) combined with incubation in NaF-medium for the deprivation of ATP could be explained by a rearrangement of receptors resulting in altered agglutinability of erythrocytes.

ABO Blood-Group System↗
PubMed1977

[Alcian blue induced mixed cell agglutination--short communication].

Because of its specific affinity to negatively charged sites of the cell surface, alcian blue is suitable to effect mixed cell agglutination between human erythrocytes and peritoneal macrophages of guinea pigs. This effect could be inhibited by adding heparin molecules which were negatively charged as well.

Agglutination↗
PubMed1977

[The possibility of use of amidinated human erythrocytes as agglutinin adsorbents in hemagglutination tests].

This study is concerned with the agglutinability of amidinated human erythrocytes. Amidinated erythrocytes behave like an immuno-adsorbent. Following the adsorption of an agglutinin, amidinated erythrocytes agglutinate specifically with native red blood cells or with native eukaryotic cells, if the glycocalyx of these native cells is provided with the respective agglutinin receptor groupings.

Amidines↗