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PubMed1984

Microtubule coils in spread blood platelets.

The fate of the circumferential bundle of microtubules in activated platelets has been a subject of disagreement. Thin sections of stimulated platelets fixed at multiple intervals following exposure to aggregating agents have revealed that the circumferential band is constricted into a tight ring around centrally concentrated organelles. However, studies of detergent-resistant platelet cytoskeletons fixed and either negatively stained or critical point dried after activation on polylysine-coated grids have revealed that microtubule rings disappear, leaving only fragments in the peripheral cytoplasm of spread cells. The present study has employed immunofluorescence on glass slides and the whole mount technique with detergent extraction and either negative staining or critical point drying to evaluate the fate of microtubules in surface-activated platelets treated with or without the microtubule stabilizing agent, taxol. Significant numbers of microtubule coils were visible in control and taxol-treated platelets stained indirectly with a fluorescein-coupled antibody to tubulin 30 to 60 minutes after surface activation on glass. Coils of microtubules were also visible in dendritic forms and in significant numbers of spread platelets on negatively stained or critical point dried whole mounts in the electron microscope. The findings support the concept that microtubule disassembly is not an integral step in early phases of platelet activation.

Alkaloids↗
PubMed1988

Structure and mass of mammalian respiratory ciliary outer arm 19S dynein.

Mammalian respiratory ciliary outer arm dyneins isolated as the major ATPase peak migrating at 19S on sucrose density gradients were examined by transmission electron microscopy of negatively stained samples and scanning transmission electron microscopy of unstained samples. The predominant discrete particle structure observed was composed of two globular heads apparently connected by amorphous or indistinct material. The heads were either circular or slightly elliptical of mean 13 +/- 1 X 10 +/- 2 nm dimensions. The mass of this structure averaged 1.22 +/- 0.34 million daltons with the individual globular heads averaging 310 +/- 77 kilodaltons (kD). Negative staining revealed that one or both of the globular heads often contained a central accumulation of stain measuring 2.5 +/- 1 nm across. A second type of structure, appearing with lesser frequency in the 19S fraction than in the unfractionated dynein preparation loaded onto the sucrose gradient, was a single globular head of 13 +/- 1 X 10 +/- 2 nm often with 2 +/- 1 nm centrally accumulated stain and with or without an appendage. This one-headed particle thus resembled one-half of the two-headed particle. Mass measurements were lower, however, for isolated, single globular heads, averaging 220 +/- 111 kD. A third type of particle observed was a ring-like structure with 4 +/- 1 nm centrally accumulated stain and without appendages. The ring structure was slightly larger in diameter, 14 +/- 1 nm, and had a greater peripheral accumulation of negative stain than either of the one- or two-headed particles, suggesting that it was not derived therefrom.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed1973

Localization of Na + , K + -ATPase and other enzymes in teleost pseudobranch. II. Morphological characterization of intact pseudobranch, subcellular fractions, and plasma membrane substructure.

The pseudobranch of the pinfish Lagodon rhomboides is an unusually homogeneous and structurally simple tissue, well suited to cell fractionation studies. Its principal cell type, closely related to the chloride cells of teleost gill, is characterized by numerous mitochondria in close association with abundant tubular invaginations of the plasma membrane. Other cytoplasmic organelles are rarely encountered. In broken fresh pseudobranch cells negatively stained with ammonium molybdate, a 40 A particulate layer was observed on the intracellular surface of the tubular plasma membrane fragments. Nuclear (N), mitochondrial-light mitochondrial (M+L), and microsomal (P) fractions, obtained by differential centrifugation, were characterized by examination of fixed, embedded pellets and unfixed preparations negatively stained with ammonium molybdate and potassium phosphotung-state. Mitochondria, in orthodox configuration and retaining their outer membranes, were observed in M+L and N. Significant amounts of tubular, sheetlike, or vesicular membrane fragments were observed in all three fractions. Many such fragments, when negatively stained, showed the 40 A particulate surface layer characteristic of plasma membrane invaginations, and in some cases 20-A projections could be resolved on the opposite (extracellular) surface. Since these morphological observations, together with previously presented biochemical data, suggest a plasma membrane localization of Na(+), K(+)-ATPase, the possible association of the enzyme with membrane projections is discussed.

Adenosine Triphosphatases↗
PubMed1994

Local immune response to tumor invasion in esophageal squamous cell carcinoma. The expression of human leukocyte antigen-DR and lymphocyte infiltration.

BACKGROUND: The purpose of this study was to investigate the local immune response to tumor invasion in esophageal squamous cell carcinoma by using an immunohistochemical examination of the expression of human leukocyte antigen- (HLA) DR and lymphocyte infiltration. METHODS: The paraffin embedded sections from 108 patients with esophageal squamous cell carcinoma were studied immunohistochemically, using the streptavidin biotin peroxidase method with monoclonal antibody (HLA-DR, T-cell, and B-cell) in the 68 noninvasive sites of cancer (intraepithelial carcinoma) and the 108 invasive sites of cancer. RESULTS: The expression of HLA-DR antigen was detected in 49 of 108 cases (45%) of esophageal cancer. The expression of this antigen was more predominant in intraepithelial carcinoma than at the invasive sites of cancer (60% versus 22%, P < 0.01). Among the 40 cases with positive staining for HLA-DR antigen in intraepithelial carcinoma, negative staining of the invasion portion was shown in 27 (67.5%) cases. On the other hand, in the 28 cases with negative staining in intraepithelial carcinoma, 27 cases (96.4%) were also negative at the invasive sites. T-cell infiltration was significantly recognized at the area of HLA-DR antigen expression at the sites of both intraepithelial carcinoma and tumor invasion. However, no significant relationship was observed between the HLA-DR antigen expression and long term survival at this time. CONCLUSIONS: These results suggest that the local immune response to the HLA-DR may prevent tumor invasion, whereas the negative expression of HLA-DR antigen is a significant factor facilitating tumor invasion in esophageal squamous cell carcinoma.

Adult↗
PubMed1999

Tropomyosin positions in regulated thin filaments revealed by cryoelectron microscopy.

Past attempts to detect tropomyosin in electron micrograph images of frozen-hydrated troponin-regulated thin filaments under relaxing conditions have not been successful. This raised the possibility that tropomyosin may be disordered on filaments in the off-state, a possibility at odds with the steric blocking model of muscle regulation. By using cryoelectron microscopy and helical image reconstruction we have now resolved the location of tropomyosin in both relaxing and activating conditions. In the off-state, tropomyosin adopts a position on the outer domain of actin with a binding site virtually identical to that determined previously by negative staining, although at a radius of 3.8 nm, slightly higher than found in stained filaments. Molecular fitting to the atomic model of F-actin shows that tropomyosin is localized over sites on actin subdomain 1 required for myosin binding. Restricting access to these sites would inhibit the myosin-cross-bridge cycle, and hence contraction. Under high Ca(2+) activating conditions, tropomyosin moved azimuthally, away from its blocking position to the same site on the inner domain of actin previously determined by negative staining, also at 3.8 nm radius. These results provide strong support for operation of the steric mechanism of muscle regulation under near-native solution conditions and also validate the use of negative staining in investigations of muscle thin filament structure.

Actins↗
PubMed1986

Staining for factor VIII related antigen and Ulex europaeus agglutinin I (UEA-I) in 230 tumours. An assessment of their specificity for angiosarcoma and Kaposi's sarcoma.

In this study we examined the staining reactivity of commercially available antisera to factor VIII related antigen (F VIII RAg) and Ulex europaeus agglutinin I (UEA-I) on sections from 230 formalin fixed paraffin embedded tumours. These included 196 sarcomas, 20 carcinomas and 14 angiomas. All angiomas showed positive staining for F VIII RAg; all carcinomas showed negative staining; the vasoformative areas of all angiosarcomas stained positively but only four of six angiosarcomas showed positive staining of their solid areas; of seven Kaposi's sarcomas, all showed positive staining of vessels and six showed positive staining of the spindle cell component. In the remaining 181 non-vascular sarcomas there was a false positive result in four tumours (2.2%), three of which had a history of irradiation. Pre-radiotherapy biopsies of these three tumours stained negatively with anti-F VIII RAg. UEA-I was demonstrated in all the angiomas studied, in all angiosarcomas (including the solid components) and in well-formed vessels of all Kaposi's sarcomas, but only in the spindle cell component of 3/6. However, there was an unacceptably high rate of false positive staining amongst the carcinomas and non-vascular sarcomas. In conclusion, F VIII RAg is a specific but not a sensitive marker of angiosarcomas; UEA-I is a sensitive but not a specific marker of angiosarcomas.

Adolescent↗
PubMed1983

Molecular morphology of the tetrodotoxin-binding sodium channel protein from Electrophorus electricus in solubilized and reconstituted preparations.

The appearance of detergent-solubilized voltage-regulated sodium channel protein was recently characterized by this laboratory. Negative-staining revealed rod-shaped particles measuring 40 X 170 A. Further studies have suggested that the actual configuration of this protein may be quite different from the rod-shaped structures. Freeze-fracture and freeze-etch images of the protein in reconstituted membranes indicated that the channel is cylindrical with a diameter of 100 A and a minimum length of 80 A. Experiments with two detergent systems (Lubrol-PX and sodium cholate) enabled us to explain the discrepancy between this structure and the rod-shaped particles visualized earlier. Negative staining in either detergent at low pH (4.5) produced rod-shaped structures. As the pH was increased, doughnut-shaped particles, consistent with the structure of the protein in freeze-etch, appeared in negative stain. The tendency of the protein to change shape under different pH conditions appears to be a peculiar property of this protein.

Animals↗
PubMed2004

Rapid constriction of lipid bilayers by the mechanochemical enzyme dynamin.

Dynamin, a large GTPase, is located at the necks of clathrin-coated pits where it facilitates the release of coated vesicles from the plasma membrane upon GTP binding, and hydrolysis. Previously, we have shown by negative stain electron microscopy that wild-type dynamin and a dynamin mutant lacking the C-terminal proline-rich domain, DeltaPRD, form protein-lipid tubes that constrict and vesiculate upon addition of GTP. Here, we show by time-resolved cryo-electron microscopy (cryo-EM) that DeltaPRD dynamin in the presence of GTP rapidly constricts the underlying lipid bilayer, and then gradually disassembles from the lipid. In agreement with the negative stain results, the dynamin tubes constrict from 50 to 40 nm, and their helical pitch decreases from approximately 13 to 9.4 nm. However, in contrast to the previous results, examination by cryo-EM shows that the lipid bilayer remains intact and small vesicles or fragments do not form upon GTP binding and hydrolysis. Therefore, the vesicle formation seen by negative stain may be due to the lack of mobility of the dynamin tubes on the grid during the GTP-induced conformational changes. Our results confirm that dynamin is a mechanochemical enzyme and suggest that during endocytosis dynamin is directly responsible for membrane constriction. In the cell, other proteins may enhance the activity of dynamin or the constraints induced by the surrounding coated pit and plasma membrane during constriction may cause the final membrane fission event.

Animals↗
PubMed1991

Neurofilament reassembly in vitro: biochemical, morphological and immuno-electron microscopic studies employing monoclonal antibodies to defined epitopes.

The reassembly process of purified native (phosphorylated) and enzymatically dephosphorylated bovine neurofilament (NF) subunits was studied to delineate how NF triplet proteins assemble together into intermediate-size filaments in vitro. We determined the time course for reassembly, the ultrastructural characteristics of reassembled NFs, and the topographical disposition of NF protein subdomains within reassembled NFs using quantitative biochemical techniques, negative staining and immunoelectron microscopy. Our data indicate that: (1) approximately 50% of the purified NF subunit proteins assembled within 30 min from the start of reassembly into 10- to 12-nm filaments, and by 90 min approximately 85-90% of the NF proteins reassembled, (2) low concentrations (0.15-0.5 mg/ml) of purified NF proteins were able to reassemble into long filaments, (3) the rate and ability of native phosphorylated and dephosphorylated NF proteins to assemble into NFs were comparable, (4) negative staining revealed a periodicity of approximately 18-22 nm and a protofilamentous substructure in reassembled NFs, (5) immunoelectron microscopy using domain specific anti-NF monoclonal antibodies (mAbs) to all 3 NF proteins demonstrated specific labeling patterns corresponding to the spatial relationships of subdomains within reassembled NFs, and (6) negative staining and immunolabeling revealed that reassembled NFs are very similar to isolated native NFs. We conclude that purified mammalian axonal NF triplet proteins, independent of their phosphorylation state, rapidly and efficiently reassemble in vitro to generate characteristic 10-nm filaments. Furthermore, immunological analysis reveals that the rod domains of NF-H, NF-M and NF-L are buried within the reassembled NF, whereas the head domain of NF-M and the tail domains of all 3 NF proteins remain exposed following reassembly.

Animals↗
PubMed1998

Breast carcinoma associated with necrotic granulomas in axillary lymph nodes.

From a series of 100 consecutive breast carcinomas with axillary lymph node metastases, two cases of necrotic granulomas in the nodes are presented. Lymph nodes in each case were characterized by areas of necrosis surrounded by a palisade of cells resembling histiocytes as seen in a rheumatoid nodule. Although the initial impression was that of a reactive granuloma, when immunostained for keratin and EMA, the areas of necrosis showed positive staining for keratin and EMA in a cytoplasmic pattern. The surrounding palisade of cells stained with histiocyte markers, while the necrotic area itself was negative. Staining for both estrogen and progesterone markers was also negative. Staining of nine lymph nodes with caseating granulomas not associated with carcinoma with the same panel of antibodies revealed no staining except for irregular, noncellular staining with EMA. This pattern of necrosis in axillary lymph nodes from two cases of breast carcinoma was interpreted as evidence of necrotic metastatic tumor cells. Necrosis in axillary lymph nodes associated with invasive breast cancer should arouse suspicion for metastasis.

Axilla↗
PubMed2000

Polymerization of deoxy-sickle cell hemoglobin in high-phosphate buffer.

Deoxy-sicklecell hemoglobin (HbS) polymerizes in 0.05 M phosphate buffer to form long helical fibers. The reaction typically occurs when the concentration of HbS is about 165 mg/ml. Polymerization produces a variety of polymorphic forms. The structure of the fibers can be probed by using site-directed mutants to examine the effect of altering the residues involved in intermolecular interactions. Polymerization can also be induced in the presence of 1.5 M phosphate buffer. Under these conditions polymerization occurs at much lower concentrations (ca. 5 mg/ml), which is advantageous when site-directed mutants are being used because only small quantities of the mutants are available. We have characterized the structure of HbS polymers formed in 1.5 M phosphate to determine how their structures are related to the polymers formed under more physiological conditions. Under both sets of conditions fibers are the first species to form. At pHs between 6.7 and 7.3 fibers initially form bundles and then crystals. At lower pHs fibers form macrofibers and then crystals. Fourier transforms of micrographs of the polymers formed in 1.5 M phosphate display the 32- and 64-A(-1) periodicity characteristic of fibers formed in 0.05 M phosphate buffer. The 64-A(-1) layer line is less prominent in Fourier transforms of negatively stained fibers formed in 1.5 M phosphate possibly because salt interferes with staining of the fibers. However, micrographs and Fourier transforms of frozen hydrated fibers formed in high and low phosphate display the same periodicities. Under both sets of reaction conditions HbS polymers form crystals with the same unit cell parameters as Wishner-Love crystals (a = 64 A, b = 185 A, c = 53 A). Some of the polymerization intermediates were examined in the frozen-hydrated state in order to determine whether their structures were significantly perturbed by negative staining. We have also carried out reconstructions of the frozen-hydrated fibers in high and low phosphate to compare their molecular coordinates. The helical projection of the reconstructions in low phosphate shows the expected 14-strand structure. In high phosphate the 14-strand fibers are also formed and their molecular coordinates are the same (within experimental error) as those of fibers formed in 0.05 M phosphate. In addition, the reconstructions of high-phosphate fibers reveal a new minor variant of fiber containing 10 strands. The polymerization products in 1.5 M phosphate buffer were generally indistinguishable from those formed in 0.05 M phosphate buffer. Micrographs of frozen hydrated specimens have facilitated the interpretation of previously published micrographs using negative staining.

Biopolymers↗
PubMed1987

Rhodamine 123 as a cytoplasmic stain for mammalian zygotes.

A mitochondrion-specific fluorescent dye, rhodamine 123, stains the cytoplasm of ova from mice, rabbits, sheep, cattle and pigs. Mouse zygotes stained with rhodamine 123 are often observed with areas of negative stain where the pronuclei are located. However, such areas of negative staining are not observed in zygotes from rabbits, sheep or cattle. In vitro viability of mouse zygotes stained with rhodamine 123 is high if observed with fluorescent microscopy for 5 min or less. Observation for more than 5 min results in a significant effect on embryo developmental potential in vitro.

Journal Article↗
PubMedDate not supplied

Prognostic factors in resectable pancreatic cancer: p53 and bcl-2.

The p53 tumor suppressor gene and the Bcl-2 proto-oncogene regulate cell cycle progression and apoptosis. We evaluated the expression of these molecular markers with standard pathologic prognostic variables in patients who received multimodality therapy for resectable adenocarcinoma of the pancreas to study the effect of p53 and Bcl-2 on survival duration. Immunohistochemical staining of archival material was performed to determine levels of expression of p53 and Bcl-2 proteins in 70 patients with adenocarcinoma of pancreatic origin. All patients underwent a potentially curative pancreaticoduodenectomy and standardized pathologic analysis of resected specimens. Potential pathologic and molecular prognostic variables were assessed for their effect on survival duration. Nuclear staining for p53 was observed in 33 (47%) of 70 specimens. Immunostaining for Bcl-2 was observed in 23 specimens (33%). A trend toward improved survival duration was seen in patients whose tumors stained positive for either p53 or Bcl-2. Negative staining for both markers predicted short survival (P = 0.01). By univariate and multivariate analyses, no single pathologic factor was associated with survival duration. Immunohistochemical staging using both p53 and Bcl-2 significantly predicted survival duration by univariate and multivariate analysis; patients whose tumors stained positively for p53 and/or overexpressed Bcl-2 had a significantly longer survival than those whose tumors stained negative for both proteins.

Adenocarcinoma↗
PubMed1968

Rabbit skeletal muscle glycogen. A morphological and biochemical study of glycogen beta-particles isolated by the precipitation-centrifugation method.

Glycogen in its particulate beta-form is localized in the sarcoplasm close to the sarcoplasmic reticulum. Some particles are in close contact with the membranes, on the outer side of the vesicles. The mild technique of differential precipitation-centrifugation has been adapted to the preparation of glycogen from adult skeletal muscle. A preliminary low-speed centrifugation which eliminates the contractile protein structures and the cell debris is followed by a high-speed centrifugation which produces pellets containing glycogen mixed with smooth-walled vesicles, the glycogen-sarcovesicular fraction. The glycogen obtained after treatment of this fraction with deoxycholate and two washings contains 3% protein. A similar protein content contaminates glycogen banded in a linear sucrose gradient. The glycogen-sarcovesicular fraction and the purified glycogen have been examined, under the electron microscope, in sections of fixed and embedded material or with the negative staining technique. The glycogen beta-particles in negatively stained preparations have an average diameter of 39.4 mmicro. The largest particles present irregular outlines, suggesting the presence of conglomerated subunits, about 20 mmicro in diameter. These subunits seem to fall apart under the influence of concentrated potassium hydroxide. The mean sedimentation coefficients calculated for infinite dilution vary from 115 to 135S. The spectrophotometric analysis of the glycogen-iodine complex indicates the presence of long end-chains in the molecule.

Animals↗
PubMed1970

Tubules of globoid leukodystrophy: a right-handed helix.

Morphologic similarity between the cytoplasmic tubules of globoid leukodystrophy and Gaucher's disease (as demonstrated by thin sectioning, negative staining, and shadowing techniques) and their resemblance to negatively stained beef cerebroside are presented as evidence favoring the accumulation of cerebrosides in globoid cells. The tubules of globoid leukodystrophy have a 60-angstrom periodic banding similar to the tubules of Gaucher's disease. A right-handed helical twisting of the tubules is observed in both diseases.

Animals↗
PubMed2003

Novel enzymatic isolation of an entire viable human limbal epithelial sheet.

OBJECTIVE: To develop a reproducible method of isolating an intact viable human limbal epithelial sheet. METHODS: Human pigmented limbus was incubated at 4 degrees C for 18 hours in supplemental hormonal epithelial medium (SHEM) containing 50 mg/mL dispase II and 100 mM sorbitol. A loose limbal epithelial sheet was separated by a spatula. The remaining stroma was digested and subcultured. The viability of isolated cells was assessed. Isolated epithelial sheets and remaining stroma were subjected to immunostaining. Sheets 1.5 mm in length were cultured in SHEM on plastic until confluence, and cell extracts were subjected to Western blot analysis. RESULTS: Intact limbal epithelial sheets were consistently isolated. Pigmented palisades of Vogt revealed large superficial squamous cells and small basal cuboidal cells. No epithelial cells grew from the remaining stroma. Mean viability was 80.7% +/- 9.1%. The basal epithelium was negative to keratin 3 and connexin 43, but was scatter positive for p63. The epithelial sheet showed negative staining for laminin 5 and collagen VII, but interrupted linear basal staining for collagen IV. The remaining stroma showed negative staining for laminin 5, positive linear staining for collagen IV in the basement membrane, and diffuse staining for collagen VII in the superior stroma subjacent to the basement membrane. Western blot analysis revealed that cells originating from the limbal sheets expressed keratin 3 and p63. CONCLUSIONS: An intact limbal epithelial sheet can be consistently and reproducibly isolated and contains stem cell characteristics in the basal epithelium by degrading laminin 5 and part of collagen IV, and disassembling collagen VII.

Adult↗
PubMed1977

[Ultrastructural study of lipopolysaccharide and of polymyxin B-induced changes of the outer membrane of Serratia marcescens (author's transl)].

Electron micrographs of lipopolysaccharide (LPS) from Serratia marcescens which have been extracted with phenol/water, suspended in dist. water and subsequently negatively stained reveale round to ovoid particles besides singular ribbon-like structures. These structures are interpreted as collapsed LPS-strands of the outer membrane (OM). Fine structure investigations were carried out on strand-like structures which had been obtained by light alcalization of the particle suspension. Partial denaturation of LPS in ethylene-diaminotetracetic acid with polymyxin B (PB) gave rise to broad bends with periodic 180 degrees-torsions, indicating a helical structure. Chemically fixed LPS in phosphate buffer which were only partial transformed into LPS-strands, additionally revealed that a given LPS-strand consists of two electron-microscopic identical sub-strands which form a double helix. After short times of exposure to PB, negatively stained cells of Serratia marcescens show strand-like cell wall components on the cell surface consisting of longitudinal fibrils. In a further stage of denaturation, the strand-like structures form "projections" of the OM or are completely loosened. Based on a helical arrangement in the negative staining preparations as well as in the thin sections, they are identified as LPS-strands. Presumably, the LPS in the OM exists as contiguous strains. The development of the "double track"-aspect of the LPS in thin sections may be explained as a result of the projections of the helical longitudinal fibrils into the image plane.

Cell Membrane↗
PubMed1999

Fibrillar array in the cell wall of a gliding filamentous cyanobacterium.

The cell walls of a number of filamentous, gliding cyanobacteria of the genus Oscillatoria were examined by transmission electron microscopy of ultrathin sections, of freeze-etched replicas, and of whole cells crushed between glass slides and negatively stained. All three techniques revealed the presence of a highly ordered array of parallel fibrils, seen in transverse sections to be situated between the peptidoglycan and the outer membrane. Approximately 200 individual fibrils, each 25 to 30 nm in width, form a parallel, helical array that completely surrounds each cyanobacterial filament, running at an angle of 25 to 30 degrees to its long axis. This highly regular arrangement of the fibrillar layer may imply some underlying symmetry responsible for its organization. A possible source of such symmetry would be the peptidoglycan, and some form of interaction between this layer and the fibrils might provide the necessary scaffolding for the fibrillar array. In crushed, negatively stained samples of fresh cells, individual fibrils were seen outside the filament, released from the cell wall. These released fibrils were of the same width as those observed in situ but were in short lengths, mostly of 100 to 200 nm, and were invariably bent, sometimes even into U shapes, implying great flexibility. Negative staining of released fibrils showed no evidence that they were hollow tubes but did give some indication of a substructure, implying that they were composed of many subunits. The function of this fibrillar array is unknown, although its position in the cell wall, as well as the correspondence between the angle of the fibrils with respect to the long axis of the filament and the rotation of the filament during gliding, may imply an involvement in gliding motility.

Cell Membrane↗