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Biomedical subjects

G Geyer

Publications and source records attributed to G Geyer.

At least 91 records · Page 5Linked to original sources
PubMed1981

[Genesis of microcytes in hemodialysis patients with chronic uremia].

The study is concerned with factors that may reduce the life time of erythrocytes of patients under intermittent haemodialysis. The red cell population of these patients consisted of micro-, normo-, macro- and megalocytes. The classification of the cell size was shiftet to greater diameters in comparison with healthy donors. The evaluation of the biological half time of erythrocytes labelled with 51Cr resulted in a decrease of about 16 days. The autoradiographic evaluation of the erythrocyte size-distribution patterns 1 and 24 hours after the injection of labelled red cells into the donors circulation clearly demonstrated a decrease of macro- and megalocytes. Simultaneously, the number of microcytes rose considerably. The measurement of erythrocyte deformability could demonstrate a clearcut relationship of flexibility for a) disturbed erythropoiesis resulting in the production of macro- and megalocytes, and b) fragmentation and premature elimination from the circulation due to unfavourable rheologic properties of erythrocytes of abnormal big and small sizes.

Autoradiography↗
PubMed1981

[Electron microscopic autoradiography of semithin sections].

Semithin sections are useful for electron microscopic autoradiography. Compared with highest power electron microscopic autoradiography the employment of thicker sections is connected with the following advantages: a) a decrease of exposition time, b) lower intensity of isotope labelling, c) restriction of chemographic processes. Quantifying big series of radioautograms is facilitated.

Autoradiography↗
PubMed1981

[Echography in rhinogenic orbital complications (author's transl)].

Echography in 1273 patients with suspicious orbital tumor revealed in 5.4% a rhinogenic disease causing proptosis. Muco- and pyoceles, hemorrhages of the orbit following paranasal trauma, orbital inflammation in sinusitis and rhinogenic tumors invading the orbit could be detected echographically by specific criteria. Because of its simple, reproducable and riskless appliance, echography of the orbit and paranasal region is a screening-method in the differential diagnosis of proptosis.

Diagnosis, Differential↗
PubMed1980

Lipid segregation from the maturing erythroid cell membrane.

Vesicles attached to the cell membrane of enucleating normoblasts and reticulocytes are considered indicative of the segregation of plasmalemmal components. The vesicles are obviously free from haemoglobin. They bind cationized ferritin and autologous immunoglobulin G. This segregation of plasmalemmal constituents is suggested to be one line of erythroid cell maturation.

Animals↗
PubMed1980

DNase--a likely probe of juxtatranscriptional DNP.

The acridine orange-DNase sequences applied to rat lymphoid cells resulted in granular products within the cell nucleus. Staining with uranyl acetate rendered the granules very opaque. Most of the coarse deposits lay adjacent to condensed chromatin. Minute granules were found in dispersed chromatin as well as in the nucleolus and in heterochromatin regions. Phosphotungstic acid staining revealed the protein constituents of these deposits. The procedure is suggested an electron microscopic demonstration of DNase protein bound to acridine orange modified beaded chromatin juxtaposed to transcription units.

Acridine Orange↗
PubMed1980

Erythrocyte hypotonic lesion stimulates plasmalemmal acetylcholine esterase.

Contrary to the rather high amount of acetylcholine esterase, histochemical methods revealed only an insignificant activity of that enzyme in the erythrocyte plasmalemma. Following hypotonic incubation many damaged red cells whether or not hemolyzed were heavily loaded with reaction products on the outer aspect of their membrane. The findings are consistent with a suggested allosteric activation of acetylcholine esterase in the moderately disintegrated cell membrane. Thus, the cytochemical demonstration of acetylcholine esterase is considered a means to assess the plasmalemmal integrity of individual red cells.

Acetylcholinesterase↗
PubMed1980

Erythrocyte membrane topo-optical staining reflects glycoprotein conformational changes.

The study is concerned with the relationship of induced birefringence to conformational alterations of glycocalyx glycoproteins. Human erythrocytes washed with phosphate-buffered saline (PBS) and fixed with glutaraldehyde exhibit the most intense topo-optical staining, which is thought to reflect the lipid bound state of glycophorins. Incubations at reduced pH, in hypotonic media or in the presence of procaine resulted in a significant decline of induced anisotropy. The effects were not due to degradation of glycocalyx constituents. Erythrocytes subjected to treatments with procaine or at pH 6x2 suffered from loss of electrophoretic velocity, a finding indicative of rearrangement of cell surface glycoproteins. by example of the red blood cell the findings of this study confirm the premised suggestion of the sensible detection by topo-optical toluidine blue staining of the conformational state of glycoproteins of the glycocalyx.

Birefringence↗
PubMed1980

How sensitive may cytochemical methods detect alterations of the glycocalyx?

This review reports on the relationship of light and electron microscopic cytochemical staining and chemo-affinity labelling to the conformational state of the human erythrocyte glycocalyx glycophorin. According to a recent suggestion, primary glycophorin conformation is associated with binding to the lipid bilayer of this glycoprotein's N-terminal segment. Pretreatment of cells prior to fixation may cause this segment of detach from the lipid lamella and to acquire a less orientation. Alterations of the glycocalyx were sensitively demonstrated by topo-optical staining and by the labelling of unmasked binding sites.

Antigens, Surface↗
PubMed1980

[Changes in shape and plasticity of preserved erythrocytes].

The present study is concerned with alterations of erythrocyte shape and deformability during banking of ACD-AG blood samples. Highly diluted blood plasma suspensions of erythrocytes previously stored for 1 and 43 days, respectively, were employed for a) the microscopic evaluation of cell shapes, and b) measurement of the negative pressure pt essential for a cell's complete transit of a cylindrical micropipette 3.2 micrometers in diameter. Each of the blood samples was studied in an air equilibrated state either prior and following the fractionation of light and heavy cells. The classification of cell shapes was accomplished by a particular index. The findings are in accord with the banking related transformation of erythrocytes as known from recent studies. Although, exept of spheroechinocytes and spherocytes, a significant decline of deformability of stored red cells was found only in the case of discocytes and type 3 echinocytes, all types of heavy erythrocytes were shown less deformable in comparison with light cells equally banked for 43 days. The relation between our pt values and published data is discussed, and a crude estimate of the trapping time of the most rigid cells by the spleen after retransfusion is presented.

Blood Preservation↗
PubMed1980

[Inverse pH-dependent shape changes of erythrocytes in the presence of albumin].

A comparative study on the shape of human erythrocytes suspended in 7 different media showed, contrary to the well-known albumin-free case, an enhancement of the number of discocytes and stomatocytes for pH rising in all HSA containing media applied. At the same time, the transmembrane potential as determined by extra- and intracellular pH was lowered in all of 6 media tested. Consequently, there is no simple relationship between the pH-dependent behaviour of cell shape and corresponding changes of transmembrane potential.

Culture Media↗
PubMed1980

[Protein changes of the erythrocyte membrane during blood preservation].

The present study was conducted on erythrocytes banked in ACD-AG medium for 1, 21, or 42 days at 4 degrees C. Erythrocyte membrane proteins were analysed by means of SDS-polyacrylamide gel electrophoresis in relation to the action of beta-mercaptoethanol. Under banking conditions proteins of the erythrocyte membrane formed 380 000--420 000 daltons aggregates, presumably heterodimers of spectrin I and II, and very high molecular weight aggregates (MG > 600 000 daltons). Part of the aggregated proteins were cross-linked by disulfide bridges, which are subject of the reduction by beta-mercaptoethanol. The nonreducible components were considered an irreversible alteration of the erythrocyte membrane. Many samples of banked erythrocytes exhibited an increase of protein band II.3 (MG = 185 000 daltons) and band IV.2 (MG = 72 000 daltons). The amount of protein band VI (GAPDH) was shown to depend on both banking time and conditions of haemolysis. A modified hypotonic haemolysis with an additional intermediate alkaline incubation of ghosts resulted in a considerable decline of protein band VI of banked erythrocytes. Substraterich incubation of banked erythrocytes, which raised the ATP level well above normal, could only partially restore the membrane bound portion of protein band VI.

Blood Preservation↗
PubMed1980

Alteration by procaine of spectrin cross-links, deformability, and fluidity related properties of the erythrocyte membrane.

The study on procainized human erythrocytes revealed a) temperature dependent changes of cellshapes, b) a significant increase of deformability, c) low amounts of cross-linked membrane proteins, d) a mean cell volume identical with the volume of nonprocainized cells, e) severe reduction of induced anisotropy, f) no loss of negatively charged groups of the glycocalyx, g) decrease of electrophoretic velocity, h) a significant rise of adhesiveness to glass, and i) increase of agglutinability with antiserum and lectin. The findings are discussed in their relationships to alterations of the molecular structure of the red cell membrane.

Adhesiveness↗
PubMed1980

Conformational calculations of the N-terminal hydrophilic segment of human erythrocyte glycophorin.

The study is focused on the secondary structure of the external N-terminal segment of human erythrocyte glycophorin A (NN) which was determined by applying methods of CHOU et FASMAN and LIM. This hydrophilic glycophorin segment is assumed to consist of 48.5% ordered (alpha-helix, beta-sheet, beta-turn) and 51.5% unordered sequences. From the secondary structure suggestions are made concerning (i) peptide interaction and (ii) binding to the lipid bilayer of the N-terminal segment.

Amino Acid Sequence↗
PubMed1980

IgG binding sites of the enucleating normoblast membrane.

The binding of autologous immunoglobulin G to the membrane of the enucleating rabbit normoblast was studied by means of light and electron microscopic immunohistochemical methods. In comparison with the future reticulocyte membrane, the plasmalemmal envelope of the normoblast nucleus under extrusion displays a high affinity to IgG.

Animals↗
PubMed1980

[Immunological and enzymatical activity after dimiimidoester fixation (author's transl)].

The paper is concerned with the capability of diimidoesteras as histochemical fixatives. findings of diimidoester-fixed human erythrocytes show the receptor activity these cells had retained. Due to these properties amidinated red cells proved well suited as storable immunosorbens for ensuing tests of haemagglutination. Following immunisation with horseradish peroxidase of rats, diimidoester-fixed plasma cells were highly reactive towards HRP in contrast to only moderately stained glutaraldehyde fixed cells.

Animals↗
PubMed1980

[Inverse binding of lectin to either area of the plasmalemma of the enucleating normoblast (author's transl)].

The study was concerned with properties of either area of the cell membrane of the enucleating erythroblast, i.e. the plasmalemma envelope of the nucleus under extrusion and the future membrane of the reticulocyte. The findings did not corroborate the notion of a decline of the negative surplus charge of the plasmalemmal envelope. At this area of the erythroblast membrane it was demonstrated an increased lectin binding associated with the loss of toluidine blue induced anisotropy.

Cell Nucleus↗
PubMed1980

Cell organelles--fact or fancy.

The paper reappraises a definition of cell organelles previously suggested as part of a general classification of cellular components. According to that scheme cellular components are subdivided in a) nuclear and cytoplasmic organelles, b) groundplasm and nuclear sap, and c) inclusions. Cell organelles, defined as entities characterized by specific morphologic, chemical, and physical features, are considered representatives of particular subcellular functions. Functional energy consumption, though unequivocally associated with the activity of some organelles, is not a general criterium of cell organelles. The application of these criteria is outlined in the case of chromosomes, polysomes, microtubules, and myofilaments.

Cells↗