SEARCH · PubMed Health

Results for “Microscopy, Polarization”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 361 records · Page 20Linked to original sources

PubMed1982

The role of liquid crystalline behaviour of adrenocortical lipids in the control of steroidogenesis.

The physical state of rat adrenocortical lipids was studied by applying temperature-dependent techniques, including polarization microscopy and differential scanning calorimetry. Freeze-fracture detection was used for electron microscopic examinations. Temperature-dependent multiple phase transitions of adrenocortical lipids and their lamellar submicroscopic structure suggest a liquid crystalline state. This provides a possible explanation for the transition of storage lipids into liquid state, a precondition for their mobilization and processing by hydrolyzing enzyme system.

Adrenal Cortex↗

PubMed1996

Chemical composition of gallbladder sludge in patients after marrow transplantation.

OBJECTIVES: Gallbladder sludge develops in approximately 70% of patients after bone marrow transplantation (BMT). Sludge often develops in these patients without known predisposing factors, such as fasting or narcotic use. In this study, we examined the chemical composition of sludge in BMT patients. METHODS: Gallbladder content samples from 15 patients were obtained at autopsy. Presence or absence of sludge was determined by examination of gallbladder contents. Sludge samples were examined with direct and polarizing microscopy and assayed for cholesterol, bilirubin, and calcium content and for the presence of a calcium-binding protein. RESULTS: On microscopic examination, cholesterol monohydrate crystals were almost completely absent. Calcium bilirubinate crystals were present in large amounts in all samples. Calcium-ceftriaxone crystals were found in two patients who had received ceftriaxone. A large proportion of the sludge (84.6%) was found to be "unmeasurable residue." Of this part, 5-30% was accounted for by a calcium-binding protein. CONCLUSIONS: We conclude that gallbladder sludge in patients after marrow transplantation consists primarily of "unmeasurable residue," calcium bilirubinate, and a calcium-binding protein. Cholesterol crystals are almost absent. We conclude that formation of gallbladder sludge in these patients could serve as a model for studying the pathogenesis of pigment gallstones.

Autopsy↗

PubMed1995

[An experimental study of the effects of stress-relaxation plate on bone remodeling].

An ideal bone plate would provide rigid fixation to ensure stabilization of bone fragments at the early stage after fracture, while at the late stage osteoporosis induced by stress shielding effect of the plate should be prevented. However, there is no report of such a plate that could meet with all these requirements. Twenty-eight adult New Zealand rabbits were used in this experiment. Ordinary stainless-steel plate (no washer plate) and similar plate padded with ultrahigh molecular polyethylene washers in its screw holes (washer plate) were fixed respectively on mid-shelf of each side of tibiae. The animals were killed at 2, 4, 8, 12, 16, 20 and 24 weeks after operation, and the fixed bone segments of both tibiae were removed for light microscopy, polarized light microscopy and fluoroscopy. The results showed that the tibiae fixed with plate fixation both appeared bone resorption, but there was more severe resorption in bone with no washer plate fixation than that with washer plate fixation. Cancelization of cortical bone was seen in the former but not in the latter at 12 weeks postopertively. This demonstrated that the washer might creep and damage with fixation time, resulting in gradual decrease in the rigidity of the plate-screw system and thus reducing bone resorption as caused by stress shielding.

Animals↗

PubMed1997

[Regeneration osteohistogenesis in the healing of gunshot fractures (an optical polarization analysis of the collagen fibers in the intercellular substance)].

Bone tissue intercellular substance was studied in healing of a tibial gunshot fracture in dog. The method of scanning polarization microscopy was used with cytospectrophotometer signal registration and the following three-dimensional computer reconstruction of indexes of the process which was monitored from days 15 to 120 of the experiment. By the end of the experiment optic anisotropy indexes of collagen fibres from proximal and distal bone fragments were 96 and 80 respectively as related to intact bone. Character of scanogrammes and increasing values of anisotropy indexes of fibrous component of the regenerate intercellular substance indicate changing and normalizing fibrillar architectonics of newly formed bone tissue on the site of preceding fracture and serve as one of criteria for regenerative osteogenesis phases.

Animals↗

PubMed1997

Histiocytosis of regional lymph nodes associated with hip replacement.

Five cases of pronounced histiocytic reaction in pelvic lymph nodes after hip replacement are demonstrated. Two patients subsequently underwent radical prostatectomies with bilateral lymph node dissections for adenocarcinoma. In three patients, the change was found during autopsy. The sinuses and interfollicular spaces were distended by numerous large macrophages that had bulky eosinophilic cytoplasm. The cells displayed immunoreactivity to KP1 antigen, alpha-1-antitrypsin and lysozyme, providing support for their histiocytic derivation. Polarization microscopy revealed birefringent needle-like particles in their cytoplasm. We think that the histologic appearance of lymph nodes represents a foreign body reaction to fragments of polyester or polyethylene derived from joint prostheses. It is necessary to be aware of this characteristic foreign body reaction in order to avoid confusion with other types of lymph node histiocytosis or with a metastatic tumor.

Adenocarcinoma↗

PubMed1998

Image analysis of dermal collagen changes during skin aging.

OBJECTIVE: To determine progressive quantitative, directional and textural changes in dermal collagen as a function of age and sex and to estimate their evolutive trend with appropriate regression models. STUDY DESIGN: Ninety-six samples of abdominal skin from autopsy cases were analyzed. The ages ranged from 3.5 months to 86 years. Picro-Sirius-stained slides were examined by polarizing microscopy, and spatial density, directional features and texture of collagen were measured by computerized image analysis. Nonlinear regression models were built to estimate evolutive changes with respect to age. The relationship between spatial orientation of collagen bundles and age was best modeled by linear regression. RESULTS: The evolutive patterns of dermal thickness and spatial density of collagen bundles correspond to a second-order polynomial model with a progressive increase from childhood to middle age and a relatively sharp decrease after the seventh decade. The evolution of textural pattern of dermal collagen, defined by gradient analysis, depicts a sort of inverted U. Its complexity is maximum in the first year of life, decreases until the period 25-50 years and increases progressively after the sixth decade. The horizontal orientation of collagen bundles with intermingled fascicles oriented in other directions, shown by young individuals, is progressively simplified with aging. In elderly subjects, collagen bundles have a horizontal orientation. No significant sex-related differences were found. CONCLUSION: Dermal collagen changes related to aging are apparently independent of sex, at least in abdominal skin, and show characteristic curvilinear evolutive trends defined by decreased dermal thickness in the elderly, decrease in the spatial density of collagen bundles and increase in textural heterogeneity of the dermis. Progressive simplification in the orientation of collagen bundles leading to a predominant horizontal disposition followed a linear trend. These changes could contribute to providing a substantial morphologic basis to age-associated biomechanical alterations in the skin.

Abdomen↗

PubMed2002

Detection of collagens in hypertrophic scars by picrosirius polarization method.

OBJECTIVE: To find a simple method to detect the collagens in human hypertrophic scars. METHODS: The content and distribution of collagen in human hypertrophic scars were observed with both conventional light and polarization microscopy combined with image analysis of hypertrophic scar sections stained with picrosiriusred. RESULTS: Polarization microscopy revealed closely packed thick fibrils of type I collagen fibers that showed either red or yellow intense birefringence in the hypertropic tissue, whereas type III collagen fibers consisted mainly of green thin fibril with weak greenish birefringence. The hypertrophic scar, as indicated by image analysis, contained (73.95+/-3.22)% type I collagen and (21.13+/-3.57)% type III collagen. CONCLUSION: Polarization microscopy and sirius red staining is an ideal method in analyzing the distribution and arrangement of the collagen in hypertrophic scars.

Azo Compounds↗

PubMed1968

DNA organization in the mature sperm of several orthoptera by the method of polarized fluorescence microscopy.

Mature sperm of Acheta domesticus, Acheta assimilis, Nemobius fasciatus, Nemobius confusus, Melanoplus femur-rubrum, Romalea microptera, Scudderia curvicauda, and Ceuthophilus nigricans were examined for DNA configuration by means of polarized fluorescence microscopy. In all cases, the results suggest that the DNA lies in unsupercoiled array, predominantly parallel to the elongate sperm head axes. Detailed calculations of the factors influencing the degree of polarization of the fluorescent emission from supercoiled DNA are contained in an appendix.

Animals↗

PubMed2000

Polarization confocal microscopy and congo red fluorescence: a simple and rapid method to determine the mean cellulose fibril orientation in plants.

The mean or net preferential orientation of cellulose fibrils in plant cell walls is detected with polarization confocal laser scanning microscopy using the fluorescence dichroism of Congo Red. Single cells, arrays of cells in a tissue, or the epidermis of whole organs can be assayed in vivo. Aerial parts require an extra pectinase treatment because of the cuticle, which is impermeable to aqueous solutions. Peeling off the epidermis can be an elegant alternative, especially for leaves. With this method the net preferential fibril orientation can be related to the symmetry axis of the cell in quantitative terms. Data issuing from this approach are useful in current research on plant biomechanics.

Cell Wall↗

PubMed2003

Quantitative polarized light microscopy.

We describe a simple modification to a confocal microscope, which analyses the state of polarization of light emerging from the specimen so as to permit quantitative polarized light microscopy to be performed. The system uses a novel form of rotating analyser which, together with lock-in detection, permits images to be obtained where the image contrast corresponds to both specimen retardance and orientation (e.g. in the case of a birefringent specimen). Images are presented from a wide range of specimens and the origin of the contrast observed from simple point scatterers is investigated both theoretically and experimentally.

Journal Article↗

PubMed1991

Layered collagen fabric of cerebral aneurysms quantitatively assessed by the universal stage and polarized light microscopy.

We evaluated the effectiveness of the Universal stage, an instrument for measuring three-dimensional orientation of birefringent materials, for studying the collagen fabric in the wall of brain aneurysms. Vessels from autopsy were fixed at normal arterial distending pressure with 10% formalin, and prepared for polarized light microscopy, with paraffin embedding and staining with picrosirius red for birefringent enhancement. Quantitative data were obtained from tangential and oblique sections (7 microns thickness) of an intact 8 mm aneurysm, a 1.5 mm aneurysm, and a tangential section (3 microns thickness) of a cerebral artery. Sections of full-size aneurysms seen through the microscope, adjusted either for plane or circularly polarized light, revealed distinctive layers of collagen across the aneurysmal wall, which at higher magnification were further subdivided. Three-dimensional measurements, numbering 1,082, were made by use of the Universal stage attachment to the polarizing microscope. They were plotted by computer-controlled graphics on Lambert projections and analyzed by circular statistics. When assessed layer by layer, the collagen spanned a full range of orientations relative to the tangential plane. The circular standard deviation, a measure of the spread of alignment about the mean, was as low as 10 degrees for coherently organized collagen and as high as 40 degrees for the least coherently organized collagen, values characteristic of either the organized tunica media, or the least organized tunica adventitia of cerebral arteries. Although there was a marked thinning of the wall of one aneurysm, there was no evidence of structural weakness based only on the directional organization assessed by our measurements.

Autopsy↗

PubMed2004

Automated description of colours in polarized-light surface microscopy images of melanocytic lesions.

The aim of this study was to develop a computerized method for the identification and description of colour areas in melanocytic lesion images based on an approach mimicking the human perception of colours. A colour palette comprising six colour groups (black, dark brown, light brown, blue-grey, red and white) was created by selecting single colour components within melanocytic lesion images acquired using a digital videomicroscope, and was implemented in the image analysis program. For each colour region, the area, the distance from the lesion centroid, the spread, the colour area distribution in the internal and the external part of the lesion, and asymmetries were assessed on 604 melanocytic lesion images in our image database. Black, white and blue-grey colour areas were detected more frequently in melanomas compared with naevi. Moreover, significant differences in colour descriptors were observed for each colour group, showing that colour areas are more unevenly distributed in melanomas compared with naevi. Using a discriminant analysis approach, the extension of dark, white and blue-grey areas and some descriptors of the distribution of the colour areas were identified as the most relevant colour parameters for differentiating between benign and malignant lesions. In conclusion, our automatic procedure breaks down the image into the colour areas used in the clinical examination process, and also supplies a description of their extension and distribution, with parameters that correlate with the clinical concepts of regularity and homogeneity.

Automation↗

PubMed1951

[Phase contrast microscopy in polarized light].

Explore the source record for details and available documents.

Microscopy↗

PubMed1984

[Structural changes in muscle fiber contractile proteins studied by polarization ultraviolet fluorescence microscopy. VIII. The effect of glutaraldehyde and phalloidine on F-actin conformation].

Conformational changes in F-actin, induced by glutaraldehyde or phalloidin, were found in glycerinated m. psoas rabbit fibres (ghost and reconstructed fibres). It is shown that the conformational changes of F-actin decreased the thin filament flexibility as well as weakened fibre's contractility. It is assumed that the stabilization in F-actin structure may be an important factor involved in the mechanism of muscle contraction regulation.

Actins↗

PubMed2005

In situ study of water-induced segregation of bromide in bromide-doped sodium chloride by scanning polarization force microscopy.

The adsorption of water on Br-doped NaCl crystals has been studied in situ using scanning polarization force microscopy, a noncontact electrostatic atomic force microscopy operation mode. Both topography and contact potential images were acquired as a function of relative humidity at room temperature, from 0% to more than 55%. It was found that the surface of the freshly cleaved crystal has an inhomogeneous electrical surface potential distribution with the steps more negative than the terraces below 40% relative humidity. This difference disappears when the humidity reaches 40% and higher. Below 40% the step morphology experiences only small changes due to water adsorption; however, above 40% major changes take place due to solvation, segregation, and redistribution of lattice ions. Bromide-rich islands and crystallites segregate to the surface above 40% relative humidity followed by drying. These islands and crystallites have a negative surface potential relative to the rest of the surface. These effects are attributed to the preferential solvation and segregation of Br- ions.

Journal Article↗

PubMed1987

The Dictyostelium discoideum 30,000-dalton protein is an actin filament-bundling protein that is selectively present in filopodia.

The interaction with actin and intracellular localization of the 30,000-D actin-binding protein from the cellular slime mold Dictyostelium discoideum have been investigated to analyze the potential contributions of this protein to cell structure and movement. The formation of anisotropic cross-linked filament networks (bundles) containing actin and the 30,000-D protein has been observed by electron microscopy, light scattering, viscometry, and polarization microscopy. Cosedimentation experiments indicate that a maximum of one molecule of the 30,000-D protein can bind to 10 actin monomers in filaments with an apparent association constant of 1 X 10(7) liters/mol. Inhibition of the interaction of the 30,000-D protein with actin by either magnesium or calcium was observed by viscometry, light scattering, polarization microscopy, and direct binding assays. However, the concentration of magnesium required to diminish the interaction is greater than 100 times greater than that of calcium. The association constant of the 30,000-D protein for actin is 4.2 X 10(6) liters/mol, or less than 1 X 10(5) liters/mol in the presence of increased concentrations of either Mg2+ or Ca2+, respectively. Enzyme-linked immunoassays indicate that the 30,000-D protein comprises 0.04% of the protein in D. discoideum. Extensive interaction of the 30,000-D protein with actin in cytoplasm is predicted from these measurements of the concentration of this protein and its affinity for actin. The distribution of the 30,000-D protein was analyzed by immunofluorescence microscopy using mono-specific affinity-purified polyclonal antibody. The 30,000-D protein exhibits a diffuse distribution in cytoplasm, is excluded from prominent organelles, and is quite prominent in fine extensions protruding from the cell surface. The number, length, and distribution of these extensions containing the 30,000-D protein are similar to those of filopodia observed by scanning electron microscopy. To analyze the effects of cell thickness and the distribution of organelles on the immunofluorescence localization, fluorescein-labeled BSA was incorporated into the cytoplasm of living cells before fixation and staining using a sonication loading technique. The results indicate that the 30,000-D protein is selectively incorporated into filopodia. These results provide a clear distinction between the multiple actin-cross-linking proteins present in D. discoideum, and suggest that the 30,000-D protein contributes to organization of bundles of actin filaments in filopodia.

Actins↗

PubMed2006

Structural insights into yeast septin organization from polarized fluorescence microscopy.

Septins are polymerizing GTPases that function in cortical organization and cell division. In Saccharomyces cerevisiae they localize at the isthmus between the mother and the daughter cells, where they undergo a transition from a non-dynamic hourglass-shaped assembly to two separate rings, at the onset of cytokinesis. Septins form filaments as pure protein and in vivo, but the filament organization within the hourglass and ring structures is controversial. Here, we use polarized fluorescence microscopy of orientationally constrained green fluorescent protein to determine septin filament organization and dynamics in living yeast. We found that the hourglass is made of filaments aligned along the yeast bud neck. During the transition from hourglass to rings the filaments rotate through 90 degrees in the membrane plane and become circumferential. These data resolve a long-standing controversy in the field and provide strong evidence that septins have a mechanical function in cell division.

Cell Cycle Proteins↗

PubMed2001

Limited recovery of meiotic spindles in living human oocytes after cooling-rewarming observed using polarized light microscopy.

BACKGROUND: Spindles are formed from microtubules and are exquisitely sensitive to changes in temperature. An orientation-independent polarized light microscope, the Polscope, can be used to image spindles in living oocytes allowing analysis of spindle kinetics in the living state. This study examined the effects of cooling on spindle disassembly in living human oocytes and spindle recovery after rewarming. METHODS: Oocytes were imaged continuously with the Polscope during cooling and rewarming. The quantity of microtubules in the spindles was measured by its birefringence using the Polscope. RESULTS: Spindles had completely disassembled by 5 min after cooling and recovered by 20 min after rewarming to 37 degrees C if rewarming started soon after the oocyte's temperature dropped to room temperature. However, when oocytes were cooled and kept at 33, 28 or 25 degrees C for 10 min and then warmed, it was found that warming allowed 5/5, 2/5 and 0/5 oocytes of the spindles to recover respectively. CONCLUSIONS: These results indicate that human meiotic spindles are exquisitely sensitive to alterations in temperature. The maintenance of temperature at 37 degrees C during in-vitro manipulation is important for spindle integrity and, therefore, is likely to be important for normal fertilization and subsequent embryo development.

Cold Temperature↗