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At least 919 records · Page 51Linked to original sources
PubMed2006

Glycocalyx-mimetic dextran-modified poly(vinyl amine) surfactant coating reduces platelet adhesion on medical-grade polycarbonate surface.

A dextran-modified poly(vinyl amine) comb-like surfactant polymer, poly(N-vinyl dextran aldonamide-co-N-vinyl hexanamide), that can surface-adsorb on hydrophobic polymeric substrates, was designed to improve the interfacial blood-compatibility of polymeric biomaterials. Medical-grade polycarbonate was selected as a model substrate because of its extensive use in blood-contacting biomedical devices like hemodialyzers, blood pumps and oxygenators. The surfactant polymer was physisorbed from aqueous solution onto the polycarbonate substrate. The surfactant coating was stable under dynamic shear conditions in whole blood, as confirmed by fluorescence microscopy and total internal reflection fluorescence (TIRF) experiments with fluorescein-labeled surfactant polymer. The coated disks and uncoated control disks were exposed to platelet-rich plasma (PRP) and whole human blood in a rotating disk system (RDS) to study platelet-adhesion under dynamic shear stress environments. Adhered platelets were stained with fluorescein isothiocyante (FITC)-tagged anti-CD41a monoclonal antibody and imaged by epifluorescence microscopy. Complimentary images were obtained by phase-contrast microscopy. Platelet adhesion on the surfactant-coated disks was reduced by approximately 90%, compared with uncoated disks. The images also showed a concomitant reduction in platelet-derived microparticles on surfactant-coated disks, compared with uncoated disks. The results suggest potential application of carbohydrate-modified surfactant polymers as a glycocalyx-mimetic non-thrombogenic interfacial coating for blood-contacting biomaterials.

Adult↗
PubMed1997

Retinol influences contractile function and exerts an anti-proliferative effect on vascular smooth muscle cells through an endothelium-dependent mechanism.

Rat aortic rings maintained in organ culture for as little as 24 h show significant loss of contractile responsiveness to different agonists. Smooth muscle cells (SMC) in culture quickly de differentiate into a non-contractile phenotype with a marked capacity for proliferation. Rat aortic ring segments cultured in retinol supplemented (10(-6) M) medium showed significantly increased active tension development in response to 80 mM K+ depolarization compared with 7-day cultured control rings. The improvement of contractile performance of the cultured aorta segments in retinol-supplemented media was lost when rings were denuded of endothelium prior to culture, suggesting the endothelial cell layer as the mediator of this effect. Retinol at concentrations up to 10(-5) M was found to have no direct effect on proliferation of cells of the A7r5 SMC. However, retinol was found to augment significantly the growth inhibition of A7r5 cells grown in co-culture with bovine aortic endothelial cells (BAEC). It was further observed that media conditioned with BAEC treated with 10(-6) M retinol expressed SMC growth inhibitory properties compared with media conditioned by untreated BAEC cells or unconditioned media. Examination of cultured rat aortic ring segments by electron microscopy and BAEC cells with phase contrast microscopy revealed that retinol had obvious effects on endothelial cell morphology and ultrastructure. These results indicate that retinol exerts its effects primarily on the endothelium, which in turn secretes stable factors that directly affect SMC proliferation and contractility.

Animals↗
PubMed1987

Identification and electrophysiological investigations of embryonic mammalian motoneurones in culture.

The retrograde transport of fluorochromes from muscle was used to label embryonic rat motoneurones in vivo. The fluorescent motoneurones were subsequently detected in cultures of dissociated spinal cord neurones using an image-intensification video camera, the images from which allowed identification of the motoneurones under phase-contrast microscopy. Such motoneurones were mostly phase dark, often with a multipolar appearance and were detectable for up to 4 days in culture. Whole-cell patch-clamp recordings from these motoneurones demonstrated mean input resistances of 635 M omega and resting membrane potentials of -65 mV; action potentials could be evoked and, under voltage-clamp, inward and outward currents were present.

Animals↗
PubMed1987

Medical aspects of haematuria.

Haematuria is always a significant finding that requires proper evaluation, and investigations may need to be initiated based on an adequate history. A careful urine microscopy of the urine using phase contrast microscopy is essential, and may predict the source of the haematuria based on red cell morphology, and point the direction that appropriate investigation should take. Infection tumours, obstruction; and calculi account for most cases of gross haematuria in adults. In paediatric patients, the causes of gross haematuria are readily apparent in half of the cases, but further investigations are necessary in the other half. All cases of haematuria require prompt evaluation and appropriate investigations to ensure correct and early treatment.

Hematuria↗
PubMed2006

An efficient way of high-contrast, quasi-3D cellular imaging: off-axis illumination.

An imaging system enabling a convenient visualisation of cells and other small objects is presented. It represents an adaptation of the optical microscope condenser, accommodating a built-in edge (relief) diaphragm brought close to the condenser iris diaphragm and enabling high-contrast pseudo-relief (quasi-3D) imaging. The device broadens the family of available apparatus based on the off-axis (or anaxial, asymmetric, inclined, oblique, schlieren-type, sideband) illumination. The simplicity of the design makes the condenser a user-friendly, dedicated device delivering high-contrast quasi-3D images of phase objects. Those are nearly invisible under the ordinary (axial) illumination. The phase contrast microscopy commonly used in visualisation of phase objects does not deliver the quasi-3D effect and introduces a disturbing 'halo' effect around the edges. The performance of the device presented here is demonstrated on living cells and tissue replicas. High-contrast quasi-3D images of cell-free preparations of biological origin (paper fibres and microcrystals) are shown as well.

Animals↗
PubMed1988

The Bacteroides glycocalyx as visualized by differential interference contrast microscopy.

The glycocalyx of eight strains representing six species of Bacteroides was examined by differential interference contrast microscopy. Wet mounts in India ink were prepared from bacteria cultured in broth and on an agar medium; the wet mounts were observed by phase-contrast microscopy and differential interference contrast microscopy. With differential interference contrast microscopy, all bacteria demonstrated a glycocalyx, which included capsules surrounding single cells and microcolonies, strands of glycocalyx connecting cells and microcolonies, detached slime, and solid masses of glycocalyx in which innumerable bacteria were enmeshed. Bacteria showed comparable amounts of glycocalyx by visual observation with differential interference contrast microscopy whether grown on plates or in broth. Serial transfers of cultures did not diminish the amount of glycocalyx. Differential interference contrast microscopy proved to be a superior method to phase contrast for examining wet preparations of Bacteroides.

Bacteroides↗
PubMed1990

Expression of CD4 by human megakaryocytes.

The CD4 antigen, which serves as the receptor for human immunodeficiency virus type 1 (HIV-1) on T cells, has been detected on human megakaryocytes. Recent evidence of impaired thrombopoiesis in HIV-1-related thrombocytopenia suggested that these cells could be directly infected by the virus and prompted a search for a receptor on megakaryocytes of normal subjects that could permit entry of HIV-1. Bone marrow specimens from uninfected normal control subjects were centrifuged over Ficoll-Hypaque (1.077 g/ml) and analyzed by three-color analysis with a flow cytometer utilizing monoclonal antibodies against CD4 and a glycoprotein present on the surface of megakaryocytes and platelets (GPIIb/IIIa; CD41), as well as 7-aminoactinomycin D, a stain for DNA. Cells presumed to be megakaryocytes were identified by having a DNA content greater than tetraploid and staining brightly with anti-CD41. Approximately 0.4% of the nucleated cells of the marrow met these criteria. Twenty-five percent of these megakaryocytes stained as brightly as CD4+ T cells. Several clones of antibody recognizing different epitopes of the CD4 molecule gave similar results. Platelets were CD4-. Staining of megakaryocytes with anti-CD4 was confirmed by direct microscopic examination of Percoll-gradient-enriched megakaryocytes employing two-color (CD4-phycoerythrin and CD41-fluorescein) immunofluorescence analysis and phase-contrast microscopy. The proportion of double-labeled cells among 112 phase-contrast-identifiable megakaryocytes from five bone marrow specimens varied between 20% and 26% with a mean and SD of 22% +/- 2.5%. Thus some human megakaryocytes express CD4 on their surface that should be capable of binding the HIV-1 gp120 envelope protein. This could serve as a portal of entry for HIV-1.

Antibodies, Monoclonal↗
PubMed1987

Rapid detection of leukemia cells by use of a complement-mediated cytolytic reaction and an imaging sensor system.

We describe a system for detection of leukemia cells involving complement-mediated cytotoxic reaction and an image processing system, consisting of a charge-coupled-device image sensor, an image memory board, a personal computer, and a phase-contrast microscope. Then added to a cell suspension, monoclonal antibody specific to the fetal thymus antigen-1 of the mouse leukemia GRSL cell produced cytolysis of only GRSL cells. This cytolysis decreased the brightness of the cells observed by phase-contrast microscopy. The remaining brightness was subtracted from that of the phase-contrast image of the cells before cytolysis, which had been converted to a digital signal and stored in computer memory. Measurement time is 2 s. The time course for complete GRSL cytolysis, as measured with this system, is 12 min; overall measurement time, including reaction time, is approximately 15 min. GRSL cells in a suspension of mixed cells were determined specifically by the system.

Cell Count↗
PubMed2003

Asbestos release during removal of resilient floor covering materials by recommended work practices of the resilient floor covering institute.

The release of asbestos during maintenance and removal of resilient floor covering is of concern to health professionals and many regulators. This study assesses the asbestos levels observed during removal of resilient floor covering products using the "Recommended Work Practices" (1995) of the Resilient Floor Covering Institute or other methods requiring containment (Controls). The 1995 "work practices" require wet removal or dry heat removal but do not require the use of respirators. Wet removals of sheet vinyl/separated backing, 12" x 12" vinyl asbestos tile/mastic, and 9" x 9" asphalt tiles/mastic were conducted and the air was sampled during each procedure. Settled dust samples were collected at the sites of RFCI square tile removal and pieces of each type of tile were broken in a mini-enclosure to evaluate asbestos emissions. Analyses of the air samples collected during the removals showed that the RFCI methods did not produce asbestos counts significantly different from the Control methods requiring containment. Only a small number (0.7%) of fibers and structures, counted and measured by Analytical Transmission Electron Microscopy, would have been counted using the rules for Phase Contrast Microscopy in the 7400 method specified by Occupational Safety and Health Administration regulations. This indicates workers in similar situations without respirators are likely to have unknown exposure levels. A high percentage of these fibers and structures are 5 micrometers or less in length, smaller than 0.5 micrometer in diameter, and are easily inhaled. The RFCI air sample and settled dust data may cause regulators to consider requiring respiratory protection, cleanup procedures, and methods to control asbestos migration. Other areas that might be addressed are clearance levels and their measurement, removal area size, bulk sample analysis by transmission electron microscopy if polarized light microscopy reports less than 1 percent asbestos, better worker exposure evaluation, and supervisor/worker training in accordance with the Model Accreditation Plan.

Air Pollutants, Occupational↗
PubMedDate not supplied

Phase contrast visualization of squamous cell microridges.

A successful attempt has been made to identify microridges on squamous cells in routine smears using phase contrast microscopy. Microridges may be identified on mature cells of buccal mucosa and in cervical smears, either alcohol or spray fixed, and even in smears up to five years old. The features identified with phase contrast may also be observed with scanning electron microscopy. Identification of microridges may be of diagnostic interest in the evaluation of cervical smears.

Cell Membrane↗
PubMed1976

Degranulation of chicken heterophil leucocytes during phagocytosis, studied by phase contrast and interference microscopy.

The dynamic aspects of degranulation of chicken heterophil leucocytes during phagocytosis have been studied by phase contrast and interference microscopy. Both standard (8 fps) and high-speed (400 fps) cine-photomicrographic recordings of this process under phase contrast are presented. Lysis of individual granules is usually completed in less than 60 milliseconds. During lysis of each granule a rounded phase dense body is ejected into the phagocytic vacuole. Measurements made by interference microscopy show that there is usually a substantial fall from a protein concentration of c. 100 per cent. w/v for intact granules to a concentration of 16 per cent. w/v for the vacuole resulting from their lysis; this can only be explained by a rapid intake of water into the granule matrix following membrane fusion. The intake of water that accompanies granule lysis causes swelling of the granule matrix, and is thought to explain the mechanism of ejection of the phase dense body. Granule lysis is not dependent on the intake of water, since occasional vacuoles have been observed which showed no fall in protein concentration relative to the intact granules. The membrane around the intact granule effectively excludes the entry of water into the concentrated hygroscopic granule matrix, but once membrane fusion occurs this barrier to the entry of water is usually lost.

Animals↗
PubMed1982

Effect of epidermal growth factor on membrane motility and cell locomotion in cultures of human clonal glioma cells.

Two clones, designated Cl 2 and Cl 3, were established from the human malignant glioma line U-343 MGa. The astrocytic origin of the cells was proven by the presence in virtually 100% of the cells of the astrocyte marker glial fibrillary acidic protein. The addition of 10 ng epidermal growth factor (EGF) per milliliter to Cl 2 and Cl 3 cells resulted in the rapid appearance of large cell surface ruffles, visualized by scanning electron microscopy. A time course study by phase contrast microscopy showed that the maximal ruffling activity occurred 5 minutes after addition of EGF. Under basic culture conditions (Eagle's MEM, 10% fetal calf serum), Cl 2 and Cl 3 cells were essentially immobile and formed tightly packed, well demarcated colonies. In the presence of 10 ng EGF per milliliter, no defined colonies were formed and the cells seemed to move around freely. The stimulatory effect of EGF on cell migration was confirmed by growing the cells on a deposit of colloidal gold; in the absence of EGF, the cells remained immobile whereas cells grown at 10 ng EGF per ml formed long phagokinetic tracks. The effect of EGF on membrane motility and cell locomotion occurred in the absence of any effect of EGF on growth rate; both clones multiplied at the same rate in the absence as in the presence of EGF. Binding experiments using 125I-labeled EGF demonstrated a single class of high affinity receptors. The number of 180,000 receptors per cell was estimated in both clones. The finding that human glioma cells in culture require EGF for their migration raises the interesting possibility that tumor cells in vivo may respond in a similar fashion, and in that case require a growth factor for migration and for the expression of their infiltrative growth potential. Furthermore, the present findings strengthen the notion that glial cells should be recognized as targets for EGF.

Cell Division↗
PubMed2004

Associative phase separation of beta-lactoglobulin/pectin solutions: a kinetic study by small angle static light scattering.

Interpolymer complexation between beta-lactoglobulin (beta-lg) and pectin led to phase separation. Small angle static light scattering and phase contrast microscopy were used to monitor the phase separation of beta-lg/low-methoxyl or high-methoxyl-pectin (LM- or HM-pectin) dispersions as they were slowly acidified from pH 7 to 4 with glucono-delta-lactone (GDL). The monotonic decrease in scattered light intensity with the wave vector was associated with a nucleation and growth phase separation mechanism. Microscopic observations and turbidity measurements showed the increase of complex amounts with lower pH and at higher beta-lg/pectin ratios. The formation of intrapolymer complexes was initiated at pH 6.4 with the LM-pectin and at pH 5.0 with the HM-pectin. Local ordering with increasing amounts of small complexes was observed as scattered light intensity increased at intermediate q values. The beta-lg/LM-pectin complexes at the 5:1 and the 2:1 weight ratios and the beta-lg/HM-pectin complexes at 5:1 weight ratio have fractal structures. The formation of large amounts of small assemblies and sedimentation would be responsible for the decrease in the number and volume mean diameters and fractal dimension of beta-lg/LM-pectin complexes over time.

Kinetics↗