Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cellular Structures”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,513 records · Page 84Linked to original sources
PubMed1981

Isolation and Characterization of Chloroplast DNA from the Marine Chromophyte, Olisthodiscus luteus: Electron Microscopic Visualization of Isomeric Molecular Forms.

Chloroplast DNA (ctDNA) from the marine chromophytic alga, Olisthodiscus luteus, has been isolated using a whole cell lysis method followed by CsCl-Hoechst 33258 dye gradient centrifugation. This DNA, which has a buoyant density of 1.691 grams per cubic centimeter was identified as plastidic in origin by enrichment experiments. Inclusion of the nuclease inhibitor aurintricarboxylic acid in all lysis buffers was mandatory for isolation of high molecular weight DNA. Long linear molecules (40 to 48 micrometers) with considerable internal organization comprised the majority of the ctDNA isolated, whereas supertwisted ctDNA and open circular molecules averaging 46 micrometers were occasionally present. Also observed in this study were folded ctDNA molecules with electron dense centers ("rosettes") and plastid DNA molecules which have a tightly wound "key-ring" center. The ctDNA of Olisthodiscus has a contour length that is median to the size range reported for chlorophytic plants.A minor component of the total cellular DNA, which originates from a DNase insensitive cellular structure, has a buoyant density of 1.694 grams per cubic centimeter. This DNA consists predominantly of linear molecules, but open circles 11.5 micrometers in length and rare 22-micrometer dimers were also present.This study represents the first analysis of the extranuclear DNA of a chromophytic alga.

Journal Article↗
PubMed2006

Plastic-embedded protein crystals.

Rapid vitrification followed by the replacement of the vitrified water by a solvent (freeze substitution) and then resin is a widely used procedure for preparing biological samples for electron microscopy. The resulting plastic-embedded samples permit convenient room-temperature sectioning (microtomy) and can yield well preserved cellular structures. Here this procedure has been applied to crystalline protein samples, and it is shown that it is possible to freeze-substitute vitrified crystals while preserving some of their original diffraction properties. The plastic-embedded crystals were used to collect a series of complete room-temperature data sets at a powerful macromolecular crystallography synchrotron beamline. Whereas one normally observes specific damage to disulfide bonds upon X-ray radiation, no such damage was seen for the plastic-embedded sample. The X-ray diffraction data allowed an initial atomic analysis to be made of the effects of freeze-substitution and plastic embedding on biological samples.

Acrylic Resins↗
PubMed1975

A comparative study of allergic and primary irritant contact dermatitis with dinitrochlorobenzene (DNCB) in dogs.

Attempts were made to induce allergic contact dermatitis in dogs, a species generally considered poorly responsive to experimental allergic contact dermatitis. Yound Beagles were sensitized to 2,4 dinitrochlorobenzene (DNCB) by multiple intradermal injections. Two weeks after sensitization, these dogs were challenged topically with 0.1% DNCB by a standard closed-patch technique. Sensitization evidenced by various degrees of reaction following challenge was established in all of 14 pups used, while 7 nonsensitized control pups did not react to challenge. Primary irritant contact dermatitis was induced in the skin of nonsensitized Beagle pups by 1%, 5%, and 10% solutions of DNCB. In allergic contact dermatitis the sites of challenge were grossly indurated, erythematous, and edematous. Histologically at these sites there was an infiltration of mononuclear cells which reached maximum intensity at 3 to 4 days. Accumulations of lymphoid cells were marked around sweat galnds and hair follicles. Penetration of leukocytes into these cutaneous adnexa was associated with degenerative processes in their cellular structures. Mononuclear cell infiltration into the epidermis was mild. Spongiosis was observed in the epidermis, but vesicle formation was rare. In primary irritant contact dermatitis gross lesions were characterized by severe erythema, edema, and gangreen of the skin. Microscopically, the main lesions were necrosis of the epidermal cells, separation of the epidermis from the dermis, dermal edema, and massive infiltration of the dermis with polymorphonuclear cells.

Administration, Topical↗
PubMed2004

Evaluation of the penetration of 5-aminolevulinic acid through basal cell carcinoma: a pilot study.

Aminolevulinic acid (ALA) is a charged, hydrophilic molecule that penetrates poorly through cellular structures. This property has been implicated in the poor clinical response of non-superficial basal cell carcinomas (BCCs) to photodynamic therapy (PDT). Release of ALA hydrochloride from a 20% w/w formulation was found to be incomplete and that approximately 36.8% of the total dose is released during the application period of 4 h. Using scintillation spectroscopy and a precise tissue sectioning protocol, it was demonstrated that depths of penetration of at least 2 mm from the lesion surface had been reached. Using cumulative stratal ALA concentrations, it was found that 10% of the total applied dose permeated into the lesion. In spite of this, comparisons drawn with photodynamic concentrations used in tissue culture work reported elsewhere revealed that estimations of the ALA concentration at 2 mm were sufficient to elicit a possible therapeutic response. Results from this work question the reasons given for poor outcomes of PDT in nodular BCC based solely on depth as a hindering factor.

Aged↗
PubMed2000

Size conversion of a linear plasmid in the relapsing fever agent Borrelia duttonii.

Borreliae have genomes composed of both linear and circular replicons. We have characterized the organization of linear DNA molecules from the Borrelia duttonii strain Ly. It contains a linear one megabase chromosome and 12 linear plasmids of 11 to 200 kb in size. A variant of the strain obtained after successive in vitro cultivation in BSKII medium had a 69 kb molecule instead of the 44 kb linear plasmid. No detectable differences in the growth rates and cellular structures were found. Southern hybridization using the vsp33 gene sequence from Borrelia hermsii as a probe showed that both plasmids (69 and 44 kb molecules) contained a similar part of the sequence. The spirochetes of the parental strain cause erythrocytes to aggregate in mice blood, but the variant did not form such aggregates and seemed to have lost its infectivity in mice. Size conversion of the linear plasmid may be associated with the host-parasite relationship in mammals.

Animals↗
PubMed1985

The effect of anthralin (dithranol) on mitochondria.

The short-term effect of topical application of anthralin (dithranol) on normal human skin was investigated by electron microscopy. Mitochondria appeared markedly damaged. By contrast other cellular structures, particularly the nuclear and cytoplasmic membranes were unchanged. In vitro experiments were therefore performed on isolated rat liver mitochondria and it was shown that anthralin acts as an uncoupler of oxidative phosphorylation. These results suggest that anthralin can inhibit the adenosine triphosphate supply in epidermal cells. This loss of energy supply in keratinocytes could explain, at least in part, the therapeutic efficiency of anthralin in psoriasis.

Animals↗
PubMed2004

Expression of the peripheral benzodiazepine receptor is decreased in skin cancers in comparison with normal skin.

BACKGROUND: The peripheral benzodiazepine receptor (PBR) is an 18-kDa protein receptor mainly found on the outer mitochondrial membrane of cells. The PBR plays a role in several cellular functions including haem synthesis, steroidogenesis, DNA synthesis, cell growth and differentiation, and apoptosis. PBR expression in normal skin correlates with proliferating, secretory and differentiated cellular structures. Increased or aberrant expression of PBR has been associated with aggressive behaviour in several tumour types including ovarian, colon and breast adenocarcinomas and glioblastoma. OBJECTIVES: To determine whether changes in normal PBR distribution would be useful as markers for skin cancers or possible target sites for therapies such as photodynamic therapy (PDT), we used immunohistochemistry to evaluate PBR expression and distribution in normal and photodamaged skin (actinic keratoses), skin cancers (in situ and invasive squamous cell carcinomas and superficial, nodular, morphoeiform and mixed pattern basal cell carcinomas) and several benign epithelial proliferations. METHODS: A rabbit polyclonal antibody to a synthetic peptide fragment of the PBR was developed and characterized by enzyme-linked immunosorbent assay and Western blot analysis. The antibody was used to stain formalin-fixed and paraffin-embedded tissue samples (n = 157) by a routine avidin-biotin immunohistochemical technique. Sections were evaluated for antibody localization, distribution (0-4+) and reaction intensity (negative to strong). RESULTS: Normal skin stained with a strong homogeneous positive reaction (3-4+) in the spinous and granular layers (with a gradient corresponding to increasing differentiation), the pilosebaceous units, eccrine gland ducts, endothelial cells and pilar muscle. In cutaneous neoplasms and other skin diseases, a heterogeneous pattern (0-4+) of PBR expression at lower intensity was seen depending on tumour type and degree of differentiation. PBR expression was greatest in well-differentiated tumours, synonymous with the PBR expression gradient seen in normal skin; and least in poorly differentiated and infiltrative tumour types. CONCLUSIONS: The haem biosynthetic pathway has been harnessed for PDT of skin carcinomas by application of exogenous aminolaevulinic acid to generate the endogenous photosensitizer protoporphyrin IX (PpIX). Owing to the role of PBR as a transporter of haem precursors in haem synthesis, PBR density and distribution in skin cancers could be a predictor of the capacity for PpIX production and subsequent response to PDT in skin cancers.

Biomarkers, Tumor↗
PubMed1978

Localization and role of calcium in the erythrocyte coat: effects of enzymes and storage.

The effects of various treatments on erythrocyte shape, surface, cell coat and calcium binding sites have been investigated by means of high voltage electron microscopy (HVM), scanning electron microscopy (SEM) and conventional electron microscopy (TEM). Papain caused the formation of small blisters within the cellular surface as well as crenation and 'budding' of the erythrocytes. After neuraminidase treatment, long filaments were observed to radiate from the surface of the erythrocyte. The other enzymes investigated, RNA'se DNA'se, phospholipase, protease and trypsin, produced no demonstrable effect on the cellular structure, nor (with the possible exception of trypsin) on the cell coat as seen by subsequent staining with ruthenium red. Putative calcium binding sites on and in the erythrocyte membrane were demonstrated. Following incubation with radioactive calcium, activity was found in the erythrocyte membranes. Calcium binding could be reduced by prior treatment of the erythrocyte with EDTA, neuraminidase, and to a lesser extent, by papain and trypsin. Other enzymes had no demonstrable effect. Stored erythrocytes showed a progressive diminution in calcium binding over a period of up to 4 weeks.

Binding Sites↗
PubMed1992

The B cell repertoire in patients with systemic autoimmune diseases: analysis of Epstein-Barr virus (EBV)-inducible circulating precursors that produce autoantibodies against nuclear ribonucleoprotein (nRNP).

Peripheral blood B cells from patients with systemic autoimmune disease and healthy volunteers were immortalized using EBV and the frequencies of B cell precursors that produced immunoglobulin class-specific antibodies against anti-nRNP, a specific marker for mixed connective tissue disease, were assessed using limiting dilution analysis. The frequencies of EBV-induced B cell precursors that produced IgG anti-nRNP were correlated closely with the serum titres of the corresponding autoantibodies, which indicates that B cell precursors that produced potentially pathogenic autoantibodies could be immortalized from the peripheral blood of the patients by EBV. In contrast, the frequency of EBV-induced B cell precursors that produced IgM anti-nRNP in patients with systemic autoimmune disease was comparable to that in healthy volunteers and greater than those that produced IgG and IgA anti-nRNP. Moreover, many of the clones that produced IgM antibodies against nRNP reacted with other autoantigens, such as double-stranded DNA, single-stranded DNA and rabbit IgG. These polyreactive IgM antibodies are believed to belong to the 'natural antibodies', to be coded by the germline immunoglobulin V genes, and to react with evolutionarily conserved structural cellular components, including nRNP. Our finding that nRNP is one of the target antigens for this polyreactive autoantibody may lead to the elucidation of the origin of the pathogenic IgG and IgA anti-nRNP antibodies found in sera from patients with systemic autoimmune diseases.

Adult↗
PubMed1994

E-cadherin as a functional marker of the differentiation and invasiveness of squamous cell carcinoma of the head and neck.

The cell-cell-adhesion molecule E-cadherin is necessary for the maintenance of the epithelial cellular structure. We were able to show a correlation between decreasing E-cadherin expression, dedifferentiation and increased invasiveness in a cell line model. We studied 73 squamous cell carcinomas from the upper aerodigestive tract using the immunofluorescent method to demonstrate expression of E-cadherin. Decreased E-cadherin expression correlated with a decreased grade of differentiation and an increased lymph node metastatic rate. This confirms the significance of E-cadherin as a marker for differentiation and invasiveness of squamous cell carcinoma of the pharynx and larynx.

Cadherins↗
PubMed1994

Adhesion of Helicobacter pylori and Escherichia coli to human and bovine surface mucus cells in vitro.

Helicobacter pylori shows in vivo a specific affinity for epithelial surface mucus cells (SMC) of the human stomach. We studied the in vitro adhesion of five different H. pylori strains and one non-pathogenic Escherichia coli-strain to (a) human antral SMC, obtained during gastroscopy; (b) human tumour SMC, from a carcinoma cell line (CRL 1739 AGS); and (c) bovine SMC, obtained from the abomasum. SMC of different origin were characterized by means of electron microscopy and immunohistochemistry, and showed similar main features: all cells showed intra-cellular structures like zymogens and PAS-positive mucin granules. HSMC were antibody-positive against epithelial cell markers. All five H. pylori strains adhered to human SMC (HSMC) and tumour SMC (TSMC). Only one strain additionally adhered to bovine SMC (BSMC). No adhesion to any of these cells was observed with E. coli. Adhesion in vitro is characterized by a close membrane-to-membrane association between H. pylori and the target cells. This phenomenon suggests a specific receptor-ligand interaction.

Adenocarcinoma↗
PubMed1976

A copper block method for freezing non-cryoprotected tissue to produce ice-crystal-free regions for electron microscopy. II. Evaluation using freeze fracturing with a cryo-ultramicrotome.

Two methods are described for fracturing unfixed, uncryoprotected mouse liver that had been frozen by contact with a copper block at liquid nitrogen temperature. The best method involved precise fracturing of a few microns of surface tissue with a cooled glass knife, using the Cryokit attachment of the LKB III ultramicrotome. The resulting replicas were free from electron microscopically-visible ice crystals. A noticeable feature of replicas from unfixed, uncryoprotected tissue was the extent of plastic deformation of certain cellular structures. Cytoplasmic macromolecules, and to a lesser extent intramembranous particles, often appeared to be 'stretched' to form fibrils.

Animals↗
PubMed1978

Cryofracture of paraffin-embedded heart muscle cells.

A comparative study of internal cellular structures of the sheep ventricular myocardium has been conducted by scanning electron microscopy (SEM) and by transmission electron microscopy (TEM). Access to the cell interior for three-dimensional studies was obtained by cryofracturing paraffin-embedded tissue frozen in liquid nitrogen. For accurate localization of structures of special interest thick paraffin sections were examined in the light microscope (LM). Based on the information gained, it was possible to fracture the block in a desired plane. The fracturing was carried out by a light blow to a precooled scalpel held against the surface of the block, which was immersed in liquid nitrogen. After thawing and deparaffinizing at room temperature in several baths of xylene, the tissue pieces were critical point dried using CO2. As xylene was found to be miscible with CO2, it also served as an intermediate fluid. This method resulted in good preservation fo the myofibrils, mitochondria, sarcoplasmic reticulum and transverse tubules (T-tubules), which was confirmed by TEM studies of conventionally prepared tissue and of tissue originally prepared for SEM.

Animals↗
PubMed1979

Effect of sodium azide on the ultrastructural preservation of tissues.

An electron microscopic study was carried out to examine the quality of ultrastructural preservation of parenchymatous and mesenchymatous tissues and isolated cells fixed in glutaraldehyde with sodium azide (NaN3) as an additive. The dense tissues fixed with conventional glutaraldehyde containing calcium chloride demonstrated only a narrow zone of good tissue preservation on the surface of the specimens. Addition of azide at a concentration of 0.1% greatly improved the cellular preservation in the deeper region of tissues, in particular with respect to the mitochondrial morphology. There was no adverse effect on other cell organelles. The improvement in mitochondrial preservation and the enhancement of penetration of the fixative is presumably due to selective and instantaneous inhibition of mitochondrial metabolic activity by the azide, thus retarding anoxic degenerative effects on cellular structures until permanent fixation is completed by the comparatively slow-acting aldehyde. However, the addition of azide offers no significant improvement in the ultrastructural preservation of isolated lymphocytes and liver cells, or fibroblasts maintained in culture.

Animals↗
PubMed1981

The fixation, dehydration, drying and coating of cultured cells of SEM.

Cultivated cells form a valuable model system for studies on the effects of various preparative protocols for scanning electron microscopy (SEM). The various effects of each preparative step can be followed in detail in the light microscope and no diffusion gradients complicate the fixation and other procedures as in the case of solid tissues. Studies on cultivated cells indicate that the glutaraldehyde component of a glutaraldehyde-based fixative does not contribute to the effective osmotic pressure of the fixative and thus the osmolarity of the buffer, and other components, must be equalized to that of the medium in which the cells grow. Even small deviations from this ideal effective osmotic pressure will result in osmotically induced artefacts. Disturbances of pH and temperature of the cultures prior to and during fixation will result in changes in the appearance of many cellular structures such as microspikes and ruffles. We find that osmium fixation is advisable in most instances for best possible membrance preservation and that even long periods of glutaraldehyde fixation do not compensate for osmium fixation. Dehydration always results in shrinkage. Freeze drying (FD) and critical point drying (CPD) also give rise to shrinkage, the former to a lesser degree than the latter. A gold-palladium alloy gives a less granular coating that does gold alone. When cultured cells are studied, a metal thickness of between 5 and 15 nm is usually sufficient to give rise to an adequate secondary electron production and to avoid charging even at accelerating voltages of 30-40 kV. Without treatment with OsO4 a thicker metal coating is required.

Cells, Cultured↗
PubMed1991

Cryosputtering--a combined freeze-drying and sputtering method for high-resolution electron microscopy.

Preparing cellular structures for visualization by high-resolution scanning electron microscopy (SEM) is a multi-step process which includes fixation, dehydration, drying and metal coating. Drying and metal coating are limiting for high-resolution work. Commonly, the dried samples are exposed to the air before they are inserted into a metal coating apparatus, thereby exposing them to moisture and the accompanying risk of rehydration, which may cause changes in the supramolecular structure. We have modified a freeze-dryer to accommodate a magnetron sputtering head, in order to sputter-coat the frozen-dried samples while still in the drying chamber in the cold, a process we call cryosputtering. A layer of 1.5 nm of tungsten was cryosputtered onto whole mounts of cytoskeletons from detergent-extracted human glioma cells or fibroblasts and the specimens were examined by high-resolution SEM and transmission electron microscopy (TEM). To reduce the effects of backstreaming oil from the vacuum system, a turbomolecular pump backed by a two-stage rotary vane pump was connected to the drying-coating chamber. This pump system provides a high vacuum, making it possible to dry the specimens at -90 degrees C/183 K, thus reducing the risk for recrystallization of water. Furthermore, the high vacuum minimizes the negative effects of contaminants, which can be deposited onto the specimen surface and affect the quality of the metal coat formed during sputtering.

Cell Line↗
PubMed1991

Elemental composition of pyroantimonate precipitates analysed by electron spectroscopic imaging (ESI) and electron energy-loss spectroscopy (EELS) in vitellogenic ovarian follicles of Drosophila.

Ca2+ was precipitated with potassium antimonate in vitellogenic follicles of the fruit fly Drosophila melanogaster and the distribution of the precipitates formed was studied by electron microscopy. The microvilli of the oolemma in mid- and late vitellogenic follicles were lined with precipitates. The chemical composition of the precipitates was analysed by electron spectroscopic imaging (ESI). The images produced by inelastically scattered electrons at specific ionization edges were compared, and the non-specific background signals were subtracted by an image processing system. The presence of Ca2+, antimony and oxygen in the precipitates formed could be demonstrated. The elemental composition of the precipitates and of yolk spheres was also analysed by electron energy-loss spectroscopy (EELS). With respect to the precipitates, signals at the calcium L2,3-edge, the oxygen K-edge and the antimony M4,5-edge were recorded without deconvolution and background subtraction. The yolk spheres, which were free of precipitates, gave the characteristic signal of the nitrogen K-edge. The applied techniques combine good ultrastructural resolution with the possibility of analysing the elemental composition of histochemical reaction products and cellular structures.

Animals↗
PubMed1995

Backscattered electron imaging of the undersurface of resin-embedded cells by field-emission scanning electron microscopy.

In this study backscattered electron (BSE) imaging was used to display cellular structures stained with heavy metals within an unstained resin by atomic number contrast in successively deeper layers. Balb/c 3T3 fibroblasts were cultured on either 13-mm discs of plastic Thermanox, commercially pure titanium or steel. The cells were fixed, stained and embedded in resin and the disc removed. The resin block containing the cells was sputter coated and examined in a field-emission scanning electron microscope. The technique allowed for the direct visualization of the cell undersurface and immediately overlying areas of cytoplasm through the surrounding embedding resin, with good resolution and contrast to a significant depth of about 2 microm, without the requirement for cutting sections. The fixation protocol was optimized in order to increase heavy metal staining for maximal backscattered electron production. The operation of the microscope was optimized to maximize the number of backscattered electrons produced and to minimize the spot size. BSE images were collected over a wide range of accelerating voltages (keV), from low values to high values to give 'sections' of information from increasing depths within the sample. At 3-4 keV only structures a very short distance into the material were observed, essentially the areas of cell attachment to the removed substrate. At higher accelerating voltages information on cell morphology, including in particular stress fibres and cell nuclei, where heavy metals were intensely bound became more evident. The technique allowed stepwise 'sectional' information to be acquired. The technique should be useful for studies on cell morphology, cycle and adhesion with greater resolution than can be obtained with any light-microscope-based system.

3T3 Cells↗