Ultrastructure, membrane

Fujikawa, S. Miura, K. (1986). Plasma membrane ultrastructural changes caused by mechanical stress in the formation of extracellular ice as a primary cause of slow freezing injury in fhiit-bodies of basidiomycetes (Lyophyllum ulmarium [Fr.J KOhner). Cryobiol. 23,371-382. 

Our knowledge of biological membrane ultrastructure has increased considerably over the years as a result of rapid advances in instrumentation. Although there is still controversy over the most correct biological membrane model, the concept of membrane structure presented by Davson and Danielli of a lipid bilayer is perhaps the one best accepted [12,13]. The most current version of that basic model, illustrated in Fig. 7, is referred to as the fluid mosaic model of membrane structure. This model is consistent with what we have learned about the existence of specific ion channels and receptors within and along surface membranes. 

The present report elaborates the ozone-induced changes in the fine structure of bean leaf mesophyll cells with particular reference to both the crystalline bodies in the chloroplasts and early changes in membrane ultrastructure. 

As discussed below, new knowledge about cell membrane ultrastructure emphasizes the importance of a layer of stranded glycoprotein material external to the lipid bilayer in a wide range of functions. These functions range from modulation of transmembrane ion fluxes through membrane ion channels to formation of receptor sites for antibody molecules. These capabilities depend in great measure on the polyanionic terminal structure of these stranded protrusions. Clearly, the two examples cited present extremes in the complexities of membrane organization. Nevertheless, both types of process exhibit similar sharp transitions as a function of temperature that are consistent with cooperative processes. 

In a recent review numerous examples were given of membrane ultrastructural textures consistent with the conformation discussed here [64]. Another obvious case of a conformation will be mentioned. The brain astrocytes are rich in potassium channels, which appear to play an important role in the regulation of the ion concentrations in the brain. Freeze-fracture electron micrographs of the outer astrocyte membrane contain patches of a periodic structure [65]. These ordered assemblies are thought to be potassium channels. In our membrane description these channels serve to plug the "holes" of a C D bilayer, whereas the rest of the membrane is in the conformation. 

It appears that the immature T-tubule membrane exhibits polymorphism. In newly developed invaginations of the PM, it is apparently able to adopt other cubic membrane ultrastructures than the gyroid. The membrane morphology seen in Figs. 7.17(a) and (b) seems to be described by a P-PCS, rather than a G-PCS. These particular sections are similar to sections through a P-PCS in which two indices are zero, or close to zero. However, gyroid-like structural elements... 

McNutt, M.S. and Winstein. R.S. (1973). Membrane ultrastructure at mammalian intercellular junction. Prog. Biophys. Mol. Biol. 26, 45—101. 

Dudkina, N.V., Sunderhaus, S., Braun, H.P. and Boekema, E.J., Characterization of dimeric ATP synthase and cristae membrane ultrastructure from Saccharomyces and Polytomella mitochondria, FEBS Lett 580 (2006) 3427-3432. 

Martinez-Palomo a, Benitez D and Alanis J (1973) Selective deposition of lanthanum in mammalian cardiac cell membranes. Ultrastructural and electrophysiological evidence. J Cell Biol 58 1-10. 

Coleman, R. Membrane-bound enzymes and membrane ultrastructure. Biochim. biophys. Acta (Amst.) 300, 1-30 (1973)... 

Thimon, L., Peypoux, F, Wallach, J., Michel, G. Effect of hpopeptide antibiotic iturin on morphology and membrane ultrastructure of yeast cells. FEMS Microbiol Lett. 1995, 128,101-106. 

Since further detail observable by magnification of this simple picture may have no direct relevance to membrane ultrastructure, the credibility limit roughly corresponds to about a 75 X 10 order of... 

Knoll G and Plattner H 1989 Ultrastructural analysis of biological membrane fusion and a tentative correlation with biochemical and biophysical aspects Electron Microscopy of Subcellular Dynamics ed H Plattner (London CRC) pp 95-117... 

The procedure for purification of Na,K-ATPase in membrane-bound form from the outer renal medulla of mammalian kidney offers the opportunity of exploring the structure of the Na,K-pump proteins in their native membrane environment. The protein remains embedded in the membrane bilayer throughout the purification procedure thus maintaining the asymmetric orientation of the protein in the baso-lateral membrane of the kidney cell in the purified preparation. This preparation has been particularly useful in studies of ultrastructure, protein conformation and for... 

The reported (14) mechanisms of action of allelochemlcals Include effects on root ultrastructure and subsequent Inhibition of Ion absorption and water uptake, effects on hormone-induced growth, alteration of membrane permeability, changes In lipid and organic acid metabolism, inhibition of protein synthesis and alteration of enzyme activity, and effects on stomatal opening and on photosynthesis. Reduced leaf water potential Is one result of treatment with ferulic and p-coumaric acids (15). Colton and Einhellig (16) found that aqueous extracts of velvetleaf (Abutllon theophrastl Medic.) Increased diffusive resistance In soybean fGlycine max. (L.) Merr.] leaves, probably as a result of stomatal closure. In addition, there was evidence of water stress and reduced quantities of chlorophyll In Inhibited plants. 

Myelin facilitates conduction 51 Myelin has a characteristic ultrastructure 52 Myelin is an extension of a glial plasma membrane 55 Myelin affects axonal structure 56... 

FIG. 4. Ultrastructure of vascular smooth muscle of the rabbit inferior vena cava revealed with electron microscopy. Serial cross-sections of VSMCs are shown in series 1 (panel A—D) and series 2 (panel E—G). Series 1 illustrates the close spatial apposition between the superficial SR sheet and the PM with the apices of the caveolae perforating through the superficial SR sheets to come into contact with the bulk cytoplasm. The membranes of the PM (dotted line) and the SR (solid line) in panel A-D are outlined to the right of the respective panels. The close apposition between the superficial SR sheet, the PM and the neck region of the caveolae creates a narrow and expansive restricted space. Series 2 illustrates the perpendicular sheets of SR, which appear to arise from the superficial SR sheets. Mitochondria also come into close contact with the perpendicular SR sheets. Panel H contains a stylized illustration of the close association between the superficial SR sheet, which is continuous with the perpendicular sheet, the perforating caveolae (C), the PM and a mitochondrion (M). Panel I shows calyculin-A mediated dissociation of the superficial SR sheets from the PM (see arrows). The black scale bar indicated represents 200 nm of distance. 

Epi-illumination Subcellular imaging structures Freeze fracture Preparation of cellular ultrastructures in frozen-hydrated and living state for electron microscopy macromolecular organization of bilayer membranes... 

It is contended that the renal slice technique measures primarily basolateral uptake of substrates or nephrotoxins, based on histological evidence of collapsed tubular lumens. This results in the inaccessibility of brush-border surfaces for reabsorptive transport (Burg and Orloff, 1969 Cohen and Kamm, 1976). This observation limits the ability of this model to accurately reflect reactions to nephrotoxins that occur as the result of brush-border accumulation of an injurious agent. Ultrastructurally, a number of alterations, particularly in the plasma membrane and mitochondrial compartments, have been shown to occur over a 2-h incubation period (Martel-Pelletier et al., 1977). This deterioration in morphology is very likely a consequence of the insufficient diffusion of oxygen, metabolic substrates, and waste products in the innermost regions of the kidney slice (Cohen and Kamm, 1976). Such factors also limit the use of slices in studying renal metabolism and transport functions. 

Many UVB-induced physiological effects such as declining photosynthetic rates can be related not only to damaged biomolecules, but also to ultrastructural changes in organelles or membranes (Holzinger and Lutz 2006). Typical alterations include... 

Linner, J. (1990). Ultrastructural localization of cytochrome b in the membranes of resting and phagocytosing human granulocytes. J. Clin. Invest. 85, 821-35. 

Ultrastructural examination of nuclei in situ showed they were not surrounded by a continuous double-layered membrane, but that the membrane was interrupted by pores (Callan and Tomlin, 1950). These were not holes but were highly organized structures involved in transport between the nucleus and the cytosol. 

Figure 11.1 Ultrastructure of the human lung alveolar barrier. The tissue specimen is obtained via lung resection surgery. (A) Section through a septal wall of an alveolus. The wall is lined by a thin cellular layer formed by alveolar epithelial type I cells (ATI). Connective tissues (ct) separate ATI cells from the capillary endothelium (en) within which an erythrocyte (er) and granulocyte (gc) can be seen. The minimal distance between the alveolar airspace (ai) and erythrocyte is about 800-900 nm. The endothelial nucleus is denoted as n. (B) Details of the lung alveolar epithelial and endothelial barriers. Numerous caveolae (arrows) are seen in the apical and basal plasma membranes of an ATI cell as well as endothelial cell (en) membranes. Caveolae may partake transport of some solutes (e.g., albumin). (C) ATII cells (ATII) are often localised in the comers of alveoli where septal walls branch off. (D) ATII cells are characterised by numerous multilamellar bodies (mlb) which contain components of surfactant. A mitochondrion is denoted as mi.

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