Cell Membrane Morphology Research Articles

Toxicological approaches to streptothricin antibiotics. IV. Toxicity of streptothricin antibiotics to the blood.

The hematoxicity of a streptothricin antibiotic was investigated in rats by blood morphological examination by scanning electron microscopic observation of changes in the erythrocytic membrane and by means of the coil planet centrifuge (CPC) technique to detect alterations in erythrocytic membrane dysfunction. The administration of the antibiotic caused no appreciable hematological change, nor any alteration in the morphology or function of the red blood cell membrane. The results indicate that the streptothricin antibiotic has no hematotoxic potential.

Freeze-Fracture Study of the Morphology of Cell Membranes in Hepatocytes Following Extrahepatic Cholestasis

The technique of freeze-fracture electron microscopy was used to examine the morphology of plasma membranes of hepatocytes after bile duct ligation. Freeze fracturing splits cell membranes along a central hydrophobic plane producing two fracture faces, the E face directed toward the exterior of the cell and the P face directed toward the cytoplasm. The P and E fracture faces of the plasma membranes are studded with intramembranous particles (IMPs). The intramembranous particles seen on these fracture faces presumably correspond to integral membrane proteins. They are uniformly and randomly distributed, but in normal liver cells P faces show 6 times more particles than E faces (PF: 2560 IMP/μm 2; EF: 427 IMP/μm 2). The density of IMPs on the P face is much higher in the lateral than in the luminal region of the plasmalemma (2180 IMP/μm 2). The latter is also characterized by the presence of microvilli. Plasma membranes are readily identified in freeze-fracture replicas by the presence of characteristic structures representing intercellular contacts within these membranes. Liver cells are connected by tight junctions which separate the lumen of the bile canaliculus from the intercellular space. In the P face the tight junctions appear as ridges. In the E face complementary grooves are observed. In the normal adult liver, tight junctions are limited to a narrow band of hepatocyte membrane on each side of the bile canaliculus. The tight junction includes continuous parallel strands surrounded by an abluminal, looser network of variable orientation. The abluminal strands are interrupted from time to time by open-ended spurs.

Electron microscopy of hepatitis B virus components in chronic active liver disease.

Eighteen liver biopsy specimens from patients with hepatitis B surface antigen (HBsAg) positive chronic aggressive hepatitis were studied by electron microscopy. All cases were selected on the basis of positive liver cell membrane fluorescence for HBsAg on immunohistochemical investigation. Striking changes in the morphology of the liver cell membrane were observed in nearly all cases. Furthermore, a dual aspect of hepatitis B core antigen (HBcAg) is described. HBcAg particles may occur as either 'naked' or 'cloudy' particles surrounded by semi electron dense material. The nature of the 'cloud' remains to be identified.

Herpes simplex virus induced alterations of membrane morphology and permeability of cells

Infection of HEp-2 cells with HSV-1 results in an increased stability of the cell membrane in comparison to uninfected cells. This effect is characterized by a reduced release of 51Cr, by an increased resistance against the non-ionic detergent Triton-X-100 and by a protection from complement mediated immune cytolysis with anti-HSV-1 antibodies. Infection with other viruses however (Poliomyelitis type 1, Mouse Elberfeld, Coxsackie B 6, Vesicular stomatitis) leads to opposite results with an enhancement of the 51Cr-release. - Comparative experiments with 7 other cell lines (Chang liver, FL, BHK21, primary rabbit kidney, HeLa, KB, primary embryonic chick fibroblasts) confirmed the above mentioned HSV-induced stability of the cell membrane with one exception: in embryonic chick fibroblasts (ECF), HSV-1 infection leads to an enhanced release and uptake of 51Cr as well as to an increased sensitivity to Triton-X-100, and the complement mediated immune cytolysis clearly can be demonstrated (Table 1).

Effects of pronase and concanavalin A upon the freeze-etch morphology of cell membranes of intact human erythrocytes.

Freeze-etch studies reveal that mild pronase treatment with subsequent incubation in concanavalin A induces aggregation of intramembranous particles (IMP) in intact human erythrocytes. This alteration in particle distribution is accompanied by a change in the distribution of the Con A molecules such that they also become clustered on the extracellular etch face. If divalent succinyl Con A is used after pronase instead of tetravalent Con A the IMPs still become clustered. Pronase only, Con A only, or succinyl Con A only does not cause the IMPs to become aggregated. Most surprising is the finding that pronase followed by Con A causes partial haemolysis of the cells whereas pronase only, Con A only, or pronase+succinyl Con A do not cause this haemoglobin loss. These perturbations of the erythrocyte plasma membrane appear to be a result of the pronase+Con A exerting a transmembrane effect on the spectrin. This conclusion is supported by sodium dodecylsulphate polyacrylamide gel electrophoresis of material crosslinked with dimethyl adipimidate dihydrochloride, which indicates that spectrin is more susceptible to being cross-linked after pronase+Con A; i.e. the spectrin is probably aggregated by the enzyme and lectin incubation.

Spontaneous, reversible protein cross-linking in the human erythrocyte membrane. Temperature and pH dependence.

Changes in pH significantly affect the morphology and physical properties of red cell membranes. We have explored the molecular basis for these phenomena by characterizing the pattern of protein disulfide cross-linkages formed spontaneously in ghost exposed to acid pH or elevated temperature (37 degrees C). Protein aggregation was analyzed by two-dimensional polyacrylamide gel electrophoresis in sodium dodecyl sulfate. incubation of ghosts at pH 4.0 to 5.5 (0-4 degrees C) yielded (i) complexes of spectrin and band 3, (ii) complexes of actin and band 3, (iii) band 3 complexes, i.e. dimer and trimer, and (iv) heterogeneous aggregates involving spectrin, band 3, band 4.2, and actin in varying proportions. Aggregation was maximal near the isoelectric points of the major membrane proteins, and appeared to reflect (i) the aggregation of intramembrane particles including band 3 and (ii) more intimate contact between spectrin-actin meshwork and band 3.

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Abstract Positions Available. Postdoctoral Position. Ph.D. in biochemistry with strong background in immunochemistry (or immunology) or Ph.D. in immunology with strong background in lipid biochemistry. Study concerns the relationship of red cell membrane composition, structure, morphology, and immunologic behavior. Antigenicity of liposomes. Experience in membrane biophysics, membrane immunology, hematology very desirable. Start: As soon as possible; funds secure for 3 years. For information contact R. Ostwald, Department of Nutritional Sciences, University of California, Berkeley, Calif. 94720, (415-642-0750). First Class Mail Service. Many of our contributors who are using the U.S. Postal Service to mail their manuscripts to us are not getting the First Class service they are paying for. If you mail your manuscripts in large (i.e. 9 × 12 inch) manila envelopes and do not specifically write the words “FIRST CLASS” on the envelope, the package usually goes third class no matter how much postage is on the envelope.

Age-related refractoriness of PHA-induced lymphocyte transformation. II. 125I-PHA binding to spleen cells from young and old mice

Using 125I-labeled red kidney bean phytohemagglutinin ( 125I-PHA), we have found that spleen cells from old BC3F 1 mice bind this plant mitogen equally well, if not better, than spleen cells from young BC3F 1 mice, although PHA-induced blastogenesis of spleen cells from old mice is sharply reduced. Analyses demonstrated that there is neither significant alteration of binding affinity nor decreased total number of membrane receptor sites for PHA in senescing mouse spleen cells. The amount of PHA which was initially bound to spleen cells in serum-free medium appeared to be insufficient for a subsequent full stimulation of blastogenesis ([ 3H]thymidine incorporation) in either young or old mouse spleen cells; when washed free of unbound extracellular PHA and upon cultivation in serum-containing culture medium, spleen cells rapidly released more than 90% of the bound PHA. Also, temperatures which change cell membrane morphology played a significant role in the binding and retention of PHA. However, no difference was observed between young and old mouse spleen cells in all these phenomena of PHA-cell membrane interaction.

Divalent cations in cerebral impedance and cell membrane morphology

Electrical impedance of cerebral cortex was measured at 1.0 kHz with low current levels (10 −13 A per square micron of electrode surface). Changes in impedance were observed after topical application of calcium and magnesium solutions. These modifications were further evaluated by asphyxiation, and by dehydration with intravenous urea. Asphyxiation of untreated cortex caused an initial fall in resistance and raised capacitance rapidly followed by raised resistance and reduced capacitance. Repeated topical application of small amounts of calcium solutions induced a progressive rise in resistance, typically between 20 and 30% of baseline values 10–20 KΩ. This increased impedance reached a plateau after 30–50 min, and further application of calcium was without effect. By contrast with untreated cortex, asphyxiation was followed by a rapid fall in resistance to values around baseline levels. This impedance curve was thus biphasic, with an inverse relationship between the size of the calcium-induced rise and the ensuing fall during asphyxiation. On the other hand, magnesium ions in equivalent amounts exerted only minor effects on cortical impedance, and subsequent asphyxiation produced a large impedance increase, as in untreated cortex. However, magnesium ions produced effects similar to calcium in normal and asphyxiated cortex, if the cortex was first dehydrated with intravenous urea, and even though urea alone was without major effects on impedance. Prior dehydration with urea had no effect on the course of impedance changes produced by calcium. These findings are interpreted in terms of conductance of impedance measuring currents mainly through an extracellular space containing a hydrated network of macromolecules that blend with similar external coats on cell membrane, and which bear numerous cationic binding sites. Evidence is presented in electron micrographs prepared with aldehyde fixation that excess calcium ions narrow intercellular spaces and that these changes reverse with asphyxiation. No such narrowing was induced by urea. On the other hand, magnesium ions were associated with much augmented intercellular spaces. It is proposed that conductance in the extracellular space is determined by the state of its structural elements, including interdependent factors such as hydration and divalent cation binding, as well as by changes in its cross-sectional area. The preeminent role of calcium ions in altering tissue impedance is discussed in relation to membrane excitation, with competitive binding of calcium and hydrogen ions to anionic macromolecular sites. Evidence relating these results to information storage at the neuronal surface is discussed.