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PubMed1982

The grid sectioning technique: a study of catalase platelets.

The grid sectioning technique has been used to obtain the two missing principal axis projections of orthorhombic catalase platelets and to measure directly the unit cell c-value. The negatively stained platelets have a unit cell c-dimension of half that proposed by Unwin (1975) from powder X-ray diffraction. The precision of the grid sectioning technique in positioning sections along a specimen axis shows that the growth fault lines usually observed on negatively stained catalase platelets are rows of missing molecules filled with stain. From these sections conclusions are drawn concerning the action of negative stain on a specimen, the microtomy process, and the specimen/supporting film interaction. Finally the value of microtomy for detailed structural analysis of biological objects is emphasized.

Catalase↗

PubMed1995

Rotavirus shedding in feces of gnotobiotic calves orally inoculated with a commercial rotavirus-coronavirus vaccine.

The purpose of this study was to monitor by negative stain electron microscopy the shedding of rotavirus in the feces of gnotobiotic calves orally inoculated with a commercial modified live bovine rotavirus-bovine coronavirus vaccine. Negative stain electron microscopic examination detected vaccine rotavirus in only 1 of 41 daily fecal specimens collected from 3 gnotobiotic calves during the 2 weeks following oral inoculation with a US Department of Agriculture-licensed modified live bovine rotavirus-bovine coronavirus vaccine. In contrast, rotavirus was demonstrable by the same negative stain electron microscopic examination procedure in 17 of 19 fecal specimens collected from diarrheic gnotobiotic or colostrum-deprived calves during the first 8 days after inoculation with virulent bovine rotavirus field strains. Rotavirus was also detected by this procedure in 4 enzyme-linked immunosorbent assay positive fecal specimens collected from naturally-infected diarrheic dairy calves. These results suggest that fecal shedding of vaccine rotavirus demonstrable by electron microscopic examination is uncommon following oral inoculation of calves with the bovine rotavirus-bovine coronavirus vaccine.

Animals↗

PubMed1997

Three-dimensional cryoelectron microscopy of 16-protofilament microtubules: structure, polarity, and interaction with motor proteins.

We present a three-dimensional (3D) map, reconstructed from electron microscope (EM) images of naturally occurring 16-protofilament (PF) microtubules (MTs) in ice. We compare it with the tubulin in six 3D maps of MTs decorated with motor domains, three from frozen MTs decorated with kinesin or ncd in the tightly bound AMP-PNP state, and three from negatively stained MTs decorated with kinesin in different nucleotide states. The comparison confirms that kinesin and ncd bind to identical sites and interact with both monomers of a tubulin dimer. Maps of specimens in negative stain and in ice are similar except that the protein in the top half of a motor domain appears denser in negative stain. The interactions have only a small effect on tubulin structure; the outward appearance is unchanged, but there seems to be a small internal rearrangement. The relative polarity of undecorated and decorated MTs is evident from their 3D structures. This agrees with the absolute polarities indicated by the orientations of motors in decorated specimens and by polar superposition patterns calculated for undecorated MTs. An image of tubulin PFs in zinc-induced sheets has been tentatively oriented by similar criteria.

Adenylyl Imidodiphosphate↗

PubMed1977

The arrangement of lipopolysaccharides on the outer membrane of Yersinia enterocolitica: an electron microscopic study.

One the cell surface of smooth of Yersinia enterocolitica 75 (Ye 75 S), and electron-lucent layer was identified in thin sections after incubation with Ye 75 S-antiserum. It is adjacent to the "double track" of the outer membrane. This layer does not appear on the analogously treated rough mutant (Ye 75 R), whose lipopolysaccharide (LPS) does not contain O-specific polysaccharides. It could be shown that this layer is formed by the O-specific side chains of LPS, which are unstained by routine methods. As the side chains of LPS obviosly make it difficult to visualize the LPS-strands in the outer membrane of rough strands was investigated. On Ye 75 R, the LPS-strands could be demonstrated only after treatment of cells with polymyxin B. After short time of exposure, the LPS appeared as contigous strand-like structures (diameter roughly 60 A) on the cell surface of cells which were negatively stained or dried by the critical-point-method. After prolonging polymyxin B treatment, "blebs" or "protrusions" appeared on the surface of Ye 75 cells, which were in negatively stained preparations and in thin sections identified as partly loosened LPS. The demonstration of LPS-strands in untreated cells was possible only on a "deep rough" mutant (Ye 161-45 a R), whose LPS contains only glucosamine and KDO besides lipid A. It is suggested that the LPS form a layer of contiguous strands (mid-to-distance 62 +/- 3 A) on the surface of negatively stained cells. According to this view, on the Ye 75 S, the O-specific side chains extend from this layer into the medium.

Cell Membrane↗

PubMed2006

Distorted rectal tissue on prostate needle biopsy: a mimicker of prostate cancer.

Rectal tissue is often seen in needle biopsies of the prostate gland. On rare occasion distorted rectal glands can mimic prostatic adenocarcinoma, an issue not previously addressed in the peer-reviewed literature. We evaluated 16 prostate needle biopsies received in consultation where the submitting pathologist questioned whether a focus of rectal tissue was prostate cancer. In addition to the distorted architecture, features mimicking prostate cancer included: (1) blue-tinged intraluminal mucinous secretions in 10 cases (63%), (2) prominent nucleoli in 6 cases (37%), (3) mitotic activity in 6 cases (37%), (4) extracellular mucin in 5 cases (31%), and (5) adenomatous changes of the rectal tissue in 1 case (6%). Immunohistochemical results further mimicked prostate cancer with negative stains for the basal cell markers high-molecular weight cytokeratin (n=6) and p63 (n=4), and positive stains for racemase in 4 of 5 biopsies. Diagnostic clues to recognizing that these foci were distorted rectal fragments were the presence of (1) lamina propria in 12 cases (75%), (2) rectal tissue located on a detached fragment of tissue in 10 biopsies (63%), (3) associated inflammation in 10 cases (63%), (4) goblet cells in 7 cases (44%), and (5) muscularis propria in 6 cases (37%). In 2 cases, there was negative staining for prostate specific antigen (PSA) and in 1 case negative staining for cytokeratin 7 and positivity for cytokeratin 20. Rectal glands are associated with many of the classical features of prostate cancer, and immunohistochemistry may be misleading. Recognition of these features mimicking prostate cancer and awareness of other findings that are diagnostic of rectal tissue on biopsy can prevent a misdiagnosis of atypical prostate glands or prostate cancer.

Adenocarcinoma↗

PubMed1980

Intracellular structures of Mycoplasma pneumoniae revealed after membrane removal.

Mycoplasma pneumoniae was grown on Formvar- and carbon-coated electron microscope grids and treated with the nonionic detergent Triton X-100 to gently remove the membrane and cytoplasm. The detergent mixture was composed of 0.5% Triton X-100 in SSR-2 broth base. After this treatment, the grids were rinsed in a mixture of 0.1 M KCl, 5 mM MgCl2, and 6 mM potassium phosphate buffer (pH 7.05) and negatively stained with uranyl acetate. The Triton X-100-resistant remains of M. pneumoniae after gentle removal of the membrane and cytoplasm consisted of fibrous structures oriented similarly to the undisrupted cells. The thin fibers displayed a negative staining quality and diameter analogous to that of rabbit muscle F-actin. The fibrous moieties ended in rodlike condensations which appeared striated in negatively stained and shadowed preparations. These striations were regular, and the majority of rod structures had lengths of 220 to 300 nm and widths of 50 to 80 nm. Specific antibody to rabbit muscle actin, produced in guinea pigs, was used in indirect immunofluorescence of the M. pneumoniae colonies. Fluorescence was detected, with concentrations at the colony center and at the tips of filamentous cells.

Actins↗

PubMed1988

Gap junction structures. VIII. Membrane cross-sections.

Profiles of negatively stained gap junctions have been measured by grid sectioning. After normal levels of electron irradiation, the membrane thickness shrinks to about half that of unirradiated controls, but no shrinkage occurs in the hexagonal lattice plane. Even under low irradiation conditions, there is significant thinning of the membranes. Edge views, in which rows of connexons are aligned parallel to the beam, were obtained from grid sections, folds in normal negatively stained specimens, and sections of a positively stained specimen. Averaging these micrographs with the translational and mirror symmetry of the projected lattice image displays conserved and variable features in the stain distribution of different specimens. Variations in the relative amount of negative stain in the gap at the surfaces and in the channel are uncorrelated with the irradiation but appear to depend on the local staining conditions and the integrity of the connexons. The dimensions measured from previously unirradiated grid sections, folds, and positively stained sections are in accord with x-ray diffraction measurements. Radiation-induced shrinkage can be accounted for by mass loss principally from the membrane bilayer. Disordering of the surface structure appears to be correlated with the radiation sensitivity of the bilayer; in contrast, the gap structure is well preserved under a variety of conditions.

Animals↗

PubMed1976

Regular structures in unit membranes. III. Further observations on the particulate component of the suckling rat ileum endocytic membrane complex.

Further morphological observations on the particulate components decorating the lumenal surfaces of membranes of the endocytic complex of the epithelial cells of the suckling rat ileum are presented. The particles each measure approximately 7.5 nm across and give the appearance of the capital letter H in frontal view. They consist of the enzyme n-acetyl-beta-glucosaminidase (NAG). They are arranged in rows called "decorated strips" with the symmetrical lateral bars in register and spaced approximately 14.5 nm apart. Decorated strips lie side-by-side in the external (lumenal) surface of the membrane. They are parallel and sometimes spaced approximately 14.5 nm apart making an orthogonal lattice. The lateral spacing between the decorated strips under certain conditions is reduced and sometimes there is shear between the adjacent ones. Occasionally, shear is present within the decorated strips themselves, with slight displacement of the two sides of each H-shaped particle. A purified preparation of these membranes has been studied by electron microscopy using thin sectioning, negative stain, Markham translation and optical diffraction computer image reconstruction methods. The individual particles comprising the array can be seen in the membrane surface in profile view when dried in a pool of negative stain. They appear either triangular or diamond-shaped in such views. If triangular, they appear to consist of three domains at the corners of an equilateral triangle. One side of each triangular figure is parallel to the membrane surface but separated from it by a dense band of negative stain approximately 2 nm thick that runs along the surface of the membrane. Sometimes a fourth symmetrical domain is visible within this dense band, giving a diamond-shaped figure. This fourth domain connects the particle to the membrane. Thus, each H-shaped particle is a double structure, with each half in profile view appearing as a diamond figure of four symmetrical domains. Each H-shaped particle is believed to consist of either two or four molecules of NAG.

Animals↗

PubMed1990

Solution structure of bacteriophage T4D and icosahedral capsid geometry visualized in freeze-fractured, deep-etched replicas.

The prolate icosahedral capsid geometry of wild type bacteriophage T4D has been determined by direct visualization of the triangular faces in stereoimages of transmission electron micrographs of phage particles. Bacteriophage T4 was prepared for transmission electron microscopy (TEM) following a protocol of freeze-fracturing, deep-etching (FDET) and replication by vertical deposition (80 degrees angle) of a thin platinum-carbon (Pt-C) metal layer of 1.01 nm. From direct statistical measurements of the ratio of the head length to width and of stereometric angles on T4 heads, we have estimated a Q number of 21. This confirms previous indirect studies on T4 and agrees with determinations on bacteriophage T2. Many of the structural features of T4 observed in FDET preparations differ significantly from those observed by classical negative staining methods for TEM imaging. Most important among the differences are the conformation of the baseplate (a closed rosebud) and the positioning of the tail fibers (retracted). The retracted position of the tail fibers in the FDET preparations has been confirmed by negatively staining phage previously fixed suspended in solution with 2% glutaraldehyde. The FDET protocols appear to reveal important structural features not seen in negative stained preparations. These have implications for bacteriophage T4 conformation in solution, viral assembly and phage conformation states prior to tail contraction and DNA ejection.

Capsid↗

PubMed1986

AN ultrastructural study of cross-bridge arrangement in the frog thigh muscle thick filament.

We have developed thick filament isolation methods that preserve the relaxed cross-bridge order of frog thick filaments such that the filaments can be analyzed by the convergent techniques of electron microscopy, optical diffraction, and computer image analysis. Images of the filaments shadowed by using either unidirectional shadowing or rotary shadowing show a series of subunits arranged along a series of right-handed near-helical strands that occur every 43 nm axially along the filament arms. Optical filtrations of images of these shadowed filaments show 4-5 subunits per half-turn of the strands, consistent with a three-stranded arrangement of the cross-bridges, thus supporting our earlier results from negative staining and computer-image analysis. The optical diffraction patterns of the shadowed filaments show a departure from the pattern expected for helical symmetry consistent with the presence of cylindrical symmetry and a departure of the cross-bridges from helical symmetry. We also describe a modified negative staining procedure that gives improved delineation of the cross-bridge arrangement. From analysis of micrographs of these negatively stained filament tilted about their long axes, we have computed a preliminary three-dimensional reconstruction of the filament that clearly confirms the three-stranded arrangement of the myosin heads.

Actin Cytoskeleton↗

PubMed1976

Ultrastructural characterization of capsulated Haemophilus influenzae type b and two spontaneous nontypable mutants.

Capsulated Haemophilus influenzae type b and two spontaneous mutants (classes I and II variants) were characterized by transmission and scanning electron microscopy. When cells were treated with type b-specific antiserum prior to manipulations for electron microscopy, sectioned capsulated cells had electron-dense, fibrous capsular antigen-antibody complexes around them. In negatively stained preparations, the complexes appeared as electron-transparent zones surrounding cells. In contrast, only residual electron-dense, extracellular material was seen in sectioned, untreated, capsulated cells, and electron-dense "bridges" connected adjacent cells in negatively stained preparations. No extracellular capsular material was seen around the class I and II variants. Characteristic electron-translucent regions were always observed within the cytosol of the class I cells, both in thin sections and by negative staining. These areas were located adjacent to the cell envelope separating the plasma membrane from the dense cytoplasmic matrix. At times, electron-dense, thread-like material extended from the dense cytoplasmic matrix to the plasma membrane. No such regions were seen in the capsulated and class II cells. Class I cells fixed with methanol or suspended in NaCl or phosphate-buffered saline prior to treatment with fluorescein-tagged type b-specific antiserum (FTA reagent) exhibited, by immunofluorescence, patches of capsular antigen along their sides. However, when fixed with glutaraldehyde or OsO4 or suspended in tris-(hydroxymethyl)aminomethane plus Ca2+ buffer prior to treatment with FTA reagent, no patches of capsular antigen were seen. Subsequent exposure of the latter cells to methanol followed by treatment with FTA reagent resulted in the reappearance of the patches of capsular antigen. Thus, in the class I variant the capsular antigen is unlikely to be surface located. Scanning electron microscopy revealed that class I and II variant cells within undisturbed colonies were regularly aligned side-by-side, whereas cells within colonies of the capsulated strain were randomly distributed.

Antigen-Antibody Complex↗

PubMed1982

Adrenal chromaffin granules: evidence for an ultrastructural equivalent of the proton-pumping ATPase.

Adrenal chromaffin granules are known to possess an F1-ATPase which according to biochemical criteria is very similar to the mitochondrial one. To find a morphological equivalent for this enzyme chromaffin granules from bovine adrenal medullar were subjected to negative staining and freeze-etching. With both methods globular particles of 8 to 9 min diameter could be demonstrated on the surface of these organelles. A single granule possessed on average 22 particles. In negative staining the particles appeared separated from the membrane by a stalk of 8 nm. This typical morphological appearance was independent from a great variety of experimental procedures. After freeze-etching the particles were closely apposed to the membrane without any evidence for an interposed stalk. Pretreatment of chromaffin granules with pronase or trypsin led to a time dependent disappearance of the surface particles. In negative staining the stalked of chromaffin granules were found to be very similar in structure and size to those of mitochondria which have already been identified as F1-complexes. Based on this observation and other lines of evidence we suggest that the stalk particles found on the surface of chromaffin granules represent the F1-complex of the proton-pumping ATPase of these organelles.

Adenosine Triphosphatases↗

PubMed1984

Morphology and ultrastructure of Lymphocystis disease virus, a fish iridovirus, grown in tissue culture.

The morphology and the ultrastructure of the Lymphocystis disease virus (LDV) strain Leetown , a fish iridovirus , was studied by electron microscopy. The virus was grown on bluegill fry (BF-2) cells at 21 degrees. LDV showed an icosahedral shape by ultrathin sections and negative staining, with a diameter of about 200 nm. The shell of the virion seemed to be composed of two unitary membranes with a total diameter of 16 nm. The outer membrane demonstrated swelling in negative staining, exhibiting a central core and the presence of globular subunits at its external surface organized in geometrical arrays of 60 and 90 degrees. Glutaraldehyde fixation preserved very effectively the icosahedral structure with the subunits remaining invisible. The internal structure of the virions was composed of osmiophilic threads or granules of 6 to 8 nm in diameter surrounded by an amorphous material of 10 to 20 nm in thickness. External filaments were observed at the surface of the particles in ultrathin sections, giving the appearance of a halo surrounding the shell. In negative staining these filaments were rarely observed; in one virus preparation, they appeared in bundles.

Animals↗

PubMed1990

An ultrastructural study of the guinea pig tectorial membrane 'type A' protofibril.

Fine structural features of the 'type A' protofibrils in the guinea pig tectorial membrane were examined using negative staining and deep-etching techniques. Negative-stained samples of fragmented tectorial membrane were composed of several fine filamentous subunits showing the clear banding pattern of the type A protofibrils. Deep-etched replicas of the EGTA (ethylene glycol bis-N,N,N',N'-tetraacetic acid)-treated samples showed fine surface structure consisting of several linear arrays of filamentous elements on the extracellular fibrils, which is interpreted to be type A protofibrils.

Animals↗

PubMed1979

Bridging structures spanning the junctioning gap at the triad of skeletal muscle.

The membrane systems of skeletal muscle were examined after tannic acid fixation. A new structure consisting of bridges spanning the junctional gap is described, and a model is proposed in which the cytoplasmic but not the luminal membrane leaflets of the transverse tubule and of the junctional sarcoplasmic reticulum (SR) are continuous. The globular particles (presumably the Ca-binding proteins) within the terminal cisternae were arranged in longitudinal rows and appeared adherent to the junctional membrane. The junctional gap was present in negatively stained, frozen thin sections of fixed muscles. Negatively staining material occured within the junctional gap. The cytoplasmic leaflets of the longitudinal, intermediate, and terminal cisterna regions of the SR exhibited a thick coat of densely staining material compatible with the presence of the Ca-ATPase. Similar bridges were also observed at the surface membrane-SR close coupling sites of vascular smooth muscle.

Animals↗

PubMed1984

Zonulae occludentes in junctional complex-enriched fractions from mouse liver: preliminary morphological and biochemical characterization.

A bile canaliculus-derived preparation containing junctional complexes has been obtained from mouse livers using subcellular fractionation techniques. The junctional complexes include structurally intact zonulae occludentes (ZOs). Extraction of this preparation with the anionic detergent sodium deoxycholate (DOC) left junctional ribbons, the detergent-insoluble zonular remnants of the junctional complexes. When visualized in negative stain electron microscopy, each of these ribbons contained a branching and anastomosing network of fibrils which appears similar to that of ZOs in freeze-fractured whole liver. Comparative measurements of freeze-fracture and negative stain fibril diameters and network densities support this relationship. SDS polyacrylamide gel analysis shows the DOC-insoluble junctional ribbons to be characterized by major polypeptides at 37,000 and at 48,000, with minor bands at 34,000, 41,000, 71,000, 86,000, 92,000, and 102,000. The ZO-containing membrane fractions have been isolated in the presence of EGTA in concentrations and under conditions shown by others to disrupt normal ZO morphology and physiology in whole living epithelia. The network of fibrils visualized in these fractions by negative staining is structurally resistant to treatment with DOC, but is either solubilized or disrupted by N-lauroylsarcosine.

Animals↗

PubMed1994

Tubular carcinoma of the breast: cytologic features in fine-needle aspirations and application of monoclonal anti-alpha-smooth muscle actin in diagnosis.

Twenty fine-needle aspirations (FNAs) of histologically proven tubular carcinoma of the breast (TCB) were reviewed, and the staining distribution of alpha-smooth muscle actin (SMA) was evaluated to see if this improved FNA sensitivity. In 18 cases, the aspirates were cellular, consisting predominantly of epithelial cells arranged in cohesive tubular structures that appeared angular or twisted. Single epithelial cells were present in varying numbers in 14 cases (70%). Cribriform fragments corresponding to in situ ductal carcinoma were noted in 9 cases (45%). Individual, bare nuclei were present in seven cases (35%). The initial cytologic diagnoses were 10 carcinomas, eight suspicious for carcinoma, and two cases were misinterpreted as fibroadenoma. In 8 of 14 cases, the epithelial fragments stained negatively for SMA, whereas in six cases some fragments (< 10%) stained positively. These findings were in contrast to a reticulated staining pattern noted in almost all of the epithelial fragments in nine fibroadenomas and three fibrocystic changes. Eighteen well-differentiated invasive ductal carcinomas stained negatively, whereas four had occasional positively staining fragments. We conclude that TCB displays distinct cytomorphologic features that can be recognized or at least suggested by FNA. Awareness of the cytologic characteristics--angulated tubular structures with or without single epithelial cells--coupled with mammographic/ultrasound findings, is necessary to avoid a misdiagnosis. Alpha-smooth muscle actin staining may help in selected cases.

Actins↗

PubMed1983

Morphology of isolated triads.

The triad is the junctional association of transverse tubule with sarcoplasmic reticulum terminal cisternae. A procedure for the isolation of highly enriched triads from skeletal muscle has been described in the previous paper. In the present study, the structural features of isolated triads have been examined by thin-section, negative-staining, and freeze-fracture electron microscopy. In isolated triads, key features of the structure observed in situ have been retained, including the osmiophilic "feet," junctional structures between the transverse tubule and terminal cisternae. New insight into triad structure is obtained by negative staining, which also enables visualization of feet at the junctional face of the terminal cisternae, whereas smaller surface particles, characteristic of calcium pump protein, are not visualized there. Therefore, the junctional face is different from the remainder of the sarcoplasmic reticulum membrane. Junctional feet as viewed by thin section or negative staining have similar periodicity and extend approximately 100 A from the surface of the membrane. Freeze-fracture of isolated triads reveals blocklike structures associated with the membrane of the terminal cisternae at the junctional face, interjunctional connections between the terminal cisternae and t-tubule, and intragap particles. The intragap particles can be observed to be closely associated with the t-tubule. The structure of isolated triads is susceptible to osmotic and salt perturbation, and examples are given regarding differential effects on transverse tubules and terminal cisternae. Conditions that adversely affect morphology must be considered in experimentation with triads as well as in their preparation and handling.

Animals↗