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Query: UMLS:C0276640 (TEM)
 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Vesicle-micelle transition structures of egg phosphatidylcholine (PC) and octyl glucoside (OG) mixtures were observed in the vitrified hydrated state by cryo-transmission electron microscopy (cryo-TEM) and correlated with the macroscopic and molecular changes previously associated with micellization monitored by 90 degrees light scattering and resonance energy transfer between fluorescent lipid probes. Several distinct structural changes occurred as OG was added to the PC vesicles. First, the average vesicle size decreased from 160 nm to less than 66 nm with no apparent change or decrease in optical density (OD). Then, associated with a small rise in OD, samples with open vesicles were observed coexisting with pieces of lamellae and long cylindrical micelles; more micelles were seen at higher [OG]. This mixture of vesicles and cylindrical micelles occurred in the region of the phase diagram previously attributed to vesicle opening, and possibly vesicle size increase. At higher [OG], small spheroidal micelles coexisting with cylindrical micelles correlated with a decrease in OD and changes in the fluorescence signal. At high [OG] when the solution appeared clear, spheroidal micelles were the dominant structure. By using cryo-TEM, a technique which preserves the original microstructure of fluid systems and provides direct images at 1 nm resolution, we have elucidated the vesicle-micelle transition and identified intermediates not known previously in the PC/OG system.
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PMID:Vesicle-micelle transition of phosphatidylcholine and octyl glucoside elucidated by cryo-transmission electron microscopy. 281 33

A method using low concentrations of formaldehyde and dithiothreitol was applied to obtain 'right-side out' luminal plasmalemma-derived vesicles from bovine aortic endothelial cells (EC) in culture, and from human umbilical vein and bovine or porcine aortas perfused ex vivo with the vesiculation solution. Vesicle formation and shedding were examined by phase-contrast microscopy and by transmission (TEM) and scanning electron microscopy (SEM). Vesicles showed the characteristic trilaminar pattern of the unit membrane and did not contain cellular organelles. As detected in freeze-fracture preparations, vesicle membrane displayed intramembrane particles and filipin-detectable cholesterol. Like EC plasmalemma, vesicle surface was heavily stained by Ruthenium Red and bound under a normal pattern cationized ferritin and ferritin hydrazide. As indicated by lectin agglutination assays and by ultrastructural cytochemistry, vesicles maintained on their ectodomains glycoconjugates bearing monosaccharides such as N-acetyl-neuraminic acid, beta-N-acetylglucosamine and beta-D-galactose, and expressed 5'-nucleotidase activity. The electrophoretic profiles of externally disposed 125I-labelled polypeptides of vesicles were found to be similar to those of intact EC. Chemically-induced vesiculation appears as a suitable method to obtain EC plasmalemma for studying its composition and functions in various vascular beds.
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PMID:Endothelial cell plasma membrane obtained by chemically induced vesiculation. 359 39

Normal and virus-infected (lymphocystis disease) integument from five species of teleosts was examined by light and TEM autoradiography and SEM to establish metabolic-morphologic characteristics of integument with mature lymphocystis cells (LC's). LC's with numerous morphologic attributes of a late developmental stage showed highest incorporation of [3H]-thymidine in vivo (1-91 h) above the intracytoplasmic inclusion body (ci) with little radiolabel in nuclei, cytoplasmic icosahedral deoxyriboviruses (ICDV's) or capsule. Analysis by quantitative autoradiography revealed that the % total cell label in ci and cytoplasm did not vary appreciably from 1-91 h and was corroborative with morphologic criteria of maturity. A possibly phylogenetic difference was noted between teleosts, wherein normal integument showed uptake of [3H]-thymidine in vivo (1 h) by cells at all levels of the epidermis, and cyclostomes (Spitzer et al. 1979) wherein labeling was confined to the basal third of the epidermis. Among four infected teleost species, the mean diameters of the ICDV's measured under the same conditions, ranged from 259.5 nm to 290.0 nm with the mean for each species differing significantly (p less than 0.01) from each of the other means. Ruptured LC's were shown by TEM and SEM to have released ICDV's onto the lesions and integument. Various stages of LC degeneration, host response, and integumental repair processes were documented. An evaluation of labeling in vivo of the capsular matrix was compatible ([3H]-D-galactose greater than [3H]-L-lysine much greater than [3H]-L-fucose) with a glycosaminoglycan-protein structure.
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PMID:Metabolic-morphologic characteristics of the integument of teleost fish with mature lymphocystis nodules. 628 67

This paper is a review discussing the cytomolecular structure of the rods, retinal photoreceptor cells, whose structural uniformity contributed to the progress in studies of their structure and morphogenesis in the vertebrate eye. Recent studies of protein and phospholipid metabolism in the rod inner segment have been reviewed. The structure of the outer segment connecting cilium is discussed with reference to the TEM and SEM, freeze-fracture, biochemical and immunological studies. The membranes of the rod outer segment undergo continuous renewal. The use of fine biochemical methods permitted to find differences in the structure of the plasma membrane surrounding the rod outer segment and the membrane discs, that fill this segment. Recent hypotheses dealing with morphogenesis of the rod outer segment membrane discs are also discussed. Special attention is paid to actin and myosin, as well as a small transient fraction of galactose-containing rhodopsin.
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PMID:[The cytostructure and morphogenesis of the rod outer segments]. 770 81

The class C tetracycline/H+ antiporter, TetA(C), confers nine distinct phenotypes in Escherichia coli: resistance to tetracycline, reduced culture density at stationary phase (growth yield), increased supercoiling of plasmid DNA, delayed growth in succinate minimal medium, complementation of potassium uptake defects, increased susceptibility to cadmium, increased susceptibility to fusaric acid, increased susceptibility to bleomycin and increased susceptibility to several classes of cationic aminoglycoside antibiotics. These nine phenotypes were resolved into three 'linkage' groups based on their patterns of suppression by mutations of the tetA(C) gene of plasmid pBR322. Group I includes resistance to tetracycline, increased susceptibility to cadmium and reduced growth yield. Group II includes delayed growth in succinate minimal medium and complementation of potassium uptake defects. Group III includes increased supercoiling of plasmid DNA and increased susceptibilities to fusaric acid, bleomycin and cationic aminoglycosides. Phenotypes of Groups II and III, but not Group I, also were conferred by a chimeric gene encoding a fusion between the N-terminal 34 residues of TetA(C) and the C-terminal 429 residues of a structurally-similar protein, the E. coli galactose/H+ symporter, GalP. In contrast, none of these phenotypes was conferred by a chimeric gene encoding a fusion between the N-terminal 34 residues of TetA(C) and a structurally-dissimilar protein, TEM beta-lactamase. These results demonstrate that the three groups of linked phenotypes are dependent on different elements of the TetA(C) amino acid sequence, implying that TetA(C) confers these phenotypes by at least three independent mechanisms.
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PMID:Structure and function of the class C tetracycline/H+ antiporter: three independent groups of phenotypes are conferred by TetA (C). 771 37

A series of double-tailed hydrocarbon and/or fluorocarbon glycolipids derived from galactose and glucose have been prepared. These compounds were obtained upon opening a lactono- and maltonolactone moiety by the amino group of either a glycine, glycylglycine or lysine residue. The carboxyl terminus of the glycyl and glycylglycine conjugates was further reacted with the appropriate double-tailed amine. In the case of lysine, the lactonamide conjugate was functionalized with a hydrocarbon and/or fluorocarbon fatty amine and acid, respectively. The ability of such glycolipids to disperse in water, the morphology of self-assemblies formed and the stability of the supramolecular structure obtained were shown to depend on the presence or absence and on the nature of the aminoacid spacer. Most of the compounds described were shown by conventional techniques (TEM, Cryo-TEM, LLS, etc.) to produce stable vesicular systems.
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PMID:Vesicles and other supramolecular systems from biocompatible synthetic glycolipids with hydrocarbon and/or fluorocarbon chains. 795 77

The floc-forming ability of flocculent strains of Kloeckera apiculata, isolated from musts, was tested for susceptibility to proteinase and sugar treatments. Three different flocculation phenotypes were discriminated by protease digestion, whereas the inhibition of flocculation by sugars distinguished two definite patterns: one mechanism of flocculation involved a galactose-specific protein and the other a broad-specificity lectin. SEM and TEM observation of the cell surface of two different Kloeckera strains revealed fine fibrils and a diffuse structure at the point of contact in one strain, and thick masses of mucus on the cell wall of the other strain.
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PMID:The flocculation of wine yeasts: biochemical and morphological characteristics in Kloeckera apiculata. 874 Sep 10

The effects of benanomicin A, a mannose-binding antifungal antibiotic, on yeast cells of Saccharomyces cerevisiae were studied by electron microscopy. Cytological studies using vital stain with methylene blue demonstrated that benanomicin A at 20 and 80 microg/ml killed buds in preference to parent cells. In confirmation, examination by TEM revealed that benanomicin A at 80 microg/ml damaged buds more severely than parent cells. The major effect on the ultrastructure was characterized by severe damage to the cell membrane. In addition, it caused expansion and vacuolation of the endoplasmic reticulum (ER), and partial fragmentation and disappearance of nuclear membranes. The membrane-disruptive activity of benanomicin A may be closely associated with its membrane affinity.
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PMID:Morphological alterations of Saccharomyces cerevisiae induced by benanomicin A, an antifungal antibiotic with mannan affinity. 965 68

The ability of an exopolymer of glycoproteic character (GP) excreted by a new gram-negative specie Pseudoalteromonas antarctica NF3, to coat phosphatidylcholine (PC) liposomes and to protect these bilayers against the action of the nonionic surfactant octyl glucoside (OG) has been investigated. TEM micrographs of freeze-fractured liposome/GP aggregates reveal that the addition of GP to liposomes led to the formation of a covering structure (polymer adsorbed onto the bilayers) that tightly coated PC bilayers. The complete coating was already achieved when the proportion of GP assembled with liposomes was approximately 10% (wt% vs total PC). Higher GP amounts resulted in a growth of this coating structure which exhibited at the highest GP proportion in the system (31% of assembled GP) a multilayered structure. An increasing resistance of PC liposomes to be affected by OG both at sublytic and lytic levels occurred as the proportion of GP in the system rose; this protective effect being more effective when the proportion of assembled GP was 10-20% in weight. Thus, although a direct dependence was found between the growth of the enveloping structure and the resistance of the coated liposomes to be affected by OG, the best protection occurred when the proportion of assembled GP was about 10 wt%.
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PMID:Ability of the exopolymer excreted by Pseudoalteromonas antarctica NF3, to coat liposomes and to protect these structures against octyl glucoside. 1035 66

The study reports on secretion production and composition in the tubular glands of the canine anal sacs. For this purpose, light and electron microscopical (TEM, SEM) as well as several histochemical methods for the demonstration of lysosomal acidity, lipofuscin, and complex carbohydrates were used. The glandular tubules exhibited a pseudostratified epithelium with secretory cells of a different shape as related to secretion production activity, and regionally varying amounts of basal cells. Flat, cuboidal or columnar cells with or without apocrine-like protrusions were assembled in one glandular endpiece, although grouping of these cell types often occurred. Active secretory cells were columnar with many cytoplasmic vesicles and a typically merocrine and/or micro-apocrine exocytosis of vesicle contents. Additionally, many lysosomes of different sizes could be found, whereby in aged cells giant secondary lysosomes (autophagolysosomes, about 7 microm in diameter) occupied the major cell part. These giant lysosomes were shed by an apocrine-like process forming a final bottleneck stage of the upper cell part, and consisted of ceroid-type lipofuscin. The general carbohydrate histochemical and the lectin histochemical methods revealed that the secretion produced was composed of strongly concentrated neutral glycoproteins with the following saccharide residues: alpha-D-mannose, beta-D-galactose, beta-N-acetyl-D-glucosamine, alpha-L-fucose and N-acetyl-neuraminic acid (sialic acid); the luminal secretion contained only beta-D-galactose and, especially, N-acetyl-neuraminic acid. This luminal secretion showed a spatially orientated maturation beginning in terminal tubular regions and finishing near the excretory duct, independent of the different secretory cell types. The results obtained demonstrated highly active secretion production, with a regional variation in the glandular tubule, and at least three different modes of secretion by the secretory cells, whereby the shedding of giant lipofuscin granules seems to be very specific. The high amounts of sialic acids in the glycoproteins found may influence the rheological properties of the secretion by their water-binding capacities.
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PMID:Cytological and lectin histochemical characterization of secretion production and secretion composition in the tubular glands of the canine anal sacs. 1117 5


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