Osmiophilic membranes

There is general agreement that a surfactant film exists at the air-aqueous interface. It appears as a eontinuous amorphous or multilayered strueture (13,14,75). The sol and gel phases have also been reported to be separated by osmiophilic membranes that are thought to consist of surfactant and may act as a lubricant to facilitate sliding of the mucous blanket on the sol phase (6,85-... 

Fig. 4. An apoptotic peripheral blood eosinophil observed under EM. The apoptotic cell displays the characteristic condensation of nuclear chromatin into large, electron-dense masses surrounding the central, relatively electron-lucent nuclear matrix. The swelling and breakage of plasma and perinuclear membranes and the release of the contents of granules from swollen, enlarged, electron-lucent granule containers within secretory cells are also observed. A single osmiophilic lipid body is found in the cytoplasm (x 18,500) (D6). Reproduced with permission from Dvorak, A. M., Images in clinical medicine, an apoptotic eosinophil. N. Engl. J. Med. 340, 437 (1999).

An arresting finding, which strongly supports the structural evaluation, is that the so called "osmiophilic minute particles", which are 90-110 run in size [61], are in fact not particles. The particulate appearance in the micrograph simply arises as an effect of the electron density distribution of that particular section through the gyroid cubic membrane ... 

Accumulation of Flavonoids in the Plasmalemma Area With classical electron microscopy, in young cells osmiophilic sites have rarely been detected near the plasmalemma. Hence, without isolation of the plasmalemma, no information can be given about the possible flavonoid accumulation or transformation in contact with this membrane, although biochemical studies in Populus (Eef. 14) suggest a role of plasmalemma in flavonoid 0-methylation. In older cells, ER becomes closely connected to the extended plasmalemma invaginations, indicating that secretion proceeds. 

Elavonoid transport from the sites of biogenesis or from the sites of transitional accumulation takes place by diffusion or active transport across the closely connected membranes of smooth EE and associated organelles (plastids, vacuoles, plasmalemma), and through the EB. During the endoplasmic transfer, the osmiophilic properties of the secretion disappear. This characteristic may be related to the possible bonding of aglycons with proteins, vjith terpenoids or with phenolic acids. 

Polymeric silicic acid (3 mM) interacted directly with neonatal rat lung fibroblasts, which had a dramatic effect on the surface membrane, its subsequent internalisation, and cytoplasmic processing (Linthicum 2001). Polymeric silicic acid was the only treatment that caused the formation and appearance of numerous osmiophilic vesicles, lipoid bodies and multivesicular bodies during the entire 72-h time course. 

As a result of vascular or neurogenic alteration, amyotrophies and osteopathies have been observed in diabetes. The muscle atrophy involves the individual fibers and is usually not associated with an inflammatory reaction. The electron microscope may reveal a marked increase in the granular osmiophilic material between myofibrils. Frequently, the basement membrane of the capillaries nourishing the muscle is greatly thickened. Abnormalities of motor end plates resulting in a soap bubble appearance have been described in diabetes. 

Osmiophilic lipid-protein particles enriched in membrane lipid catabolites have been isolated from the cytosol of carnation petals and of cotyledons (Phaseolus vulgaris) by ultrafiltration or flotation centrifugation [2,3]. The particles are spherical in nature and range from 150 to 300 nm in diameter [Fig. 1]. Osmiophilic particles of similar size and shape are also detectable in the cell cytoplasm [3]. The particles contain phospholipid, but are enriched (10- to 100- fold) by comparison with membranes in free fatty acids, triacylglycerols, and steiyl and wax esters [Fig. 2]. 

The electron-cytochemical method for localization of DPP was optimized by Lojda (1981) and its modification for cytochemical reaction for DPP in glutaraldehyde prefixed yeast cells was described recently (Voffsek in preparation). In principle, the synthetic dipeptide substrate has its carboxyl terminus bound to 4-methoxy-2-naphthylamine. The primary reaction product was formed by coupling hexazonium pararosaniline (HPR) with the MNA liberated by DPP and was osmiophilic. Thus postfixation by osmium tetrox-ide revealed also the electron-dense final reaction product on the background of the general osmiophilia of the matrix phase and membranes. 

Excess amounts of plastoquinone-9 and of -tocopherol are stored outside the thylakoids in the osmiophilic plastoglobuli (2,23). The latter contain Kj and trace amounts. In fact, the prenylquinones and c/-TQ are minor but essential functional constituents of the photosynthetic membrane with a concentration similar to that of cytochroms and ferredoxin (24). In etiolated leaf tissue, they are presentjsimilar to B-carotene, only in trace amounts. During the light-induced thylakoid formation they are rapidly accumulated together with B-carotene, as indicated by the decreasing values of the ratios of PQ-9 to and to o -TQ (Table 4) the functional ratios with values of 5 to 6 for plastoglobuli-free thylakoids are reached after 36 h of illumination. 

Fig. 22. Dark-grown C. reinhardi y-1 exposed to the light for 5 h (chlorophyll concentration 5.3 Mg/10 cells). Note the increase in number and length of disc profiles (d) and disc pairing (dp), the still limited fusion of discs to form grana (g), and the chloroplast ribosomes (cr). mb, plasma membrane o, osmiophilic globules sg, starch granules. (78,500x for experimental details see ref. 63.)...

Fig. 2.17. Bottom left. Chloroplasts (P) in chlorenchyma of pea leaf. Note the large starch grains within the chloroplast (asterisks). IS, intercellular space V, vacuole. X 780. Right. Electron micrograph of a chloroplast of a leaf of spinach Spinacea oleracea). The chloroplast is surrounded by a double membrane (PM) and the internal membrane system is differentiated into grana (asterisks) and stroma lamellae (open arrows). Osmiophilic droplets (small black arrows) occur in the plastid stroma. The structure of the grana is shown in more detail in the inset top left) as are regions of continuity between the grana and stroma lamellae (large solid arrows). Key CM, cell membrane CW, cell wall SG, starch grain ...

Key CM, chloroplast double membrane (each 35—50 A thick) S, stroma G, granum (made up of a cylindrical pile of discs) SL, stroma lamella GL, grana lamella D, disc OD, osmiophilic droplet. 

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