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At least 433 records · Page 24Linked to original sources
PubMed1983

Trophospongium-like structures in an insect eye: response of retinula cells of Papilio xuthus (Lepidoptera) to irradiation with ultraviolet light.

Presumably, as a consequence of a 3-h exposure to light of 350-nm wavelength (1.5 X 10(15) photons/cm2 sec) followed by a period of 20 h of rest in the dark, the four smaller retinula cells in each ommatidium of the eye of the butterfly Papilio xuthus contain a structure in the peripheral regions of their cytoplasm that resembles a portion of a rhabdom. Evidence for and against the view that this unusual, highly ordered arrangement of membranes represents a trophospongium is presented. In view of the fact that the structure in question only occurred at the same time when rhabdomeres were in a process of disintegration or reformation, the authors conclude that the structure in question is involved in the supply or removal of substances during a period of considerable activity of the retinula cell.

Animals↗
PubMed1988

Ultrastructural changes produced in Ehrlich ascites carcinoma cells by ultraviolet-visible radiation in the presence of melanins.

Irradiation of Ehrlich ascites carcinoma (EAC) cells in the presence of pheomelanin, i.e., red hair melanin (RHM), has been reported to produce extensive cell lysis. Irradiation in the presence of eumelanin, i.e., black hair melanin (BHM), or irradiation in the absence of either type of melanin did not produce this effect. We observed that RHM particles penetrated the cell membrane without apparent structural damage to the cell or the cell membrane. Irradiation of the cells in the absence of melanin did not produce any changes in the ultrastructure of the cells. Incubation of the cells in the dark in the presence of RHM produced only minor structural, mainly cytoplasmic changes. Irradiation of the cells in the presence of RHM produced extensive ultrastructural changes prior to complete cell lysis; these changes were more severe than the effects of incubation of the cells in the dark in the presence of RHM. When the cells incubated in the dark or irradiated in the presence of latex particles or either one of the eumelanins particles, viz. BHM or synthetic dopa melanin, these particles did not penetrate into the cells or produce any ultrastructural changes. These particles were in fact not even ingested by the cells.

Animals↗
PubMedDate not supplied

Perfusion culture enhances osteogenic differentiation of rat mesenchymal stem cells in collagen sponge reinforced with poly(glycolic Acid) fiber.

The objective of this study was to obtain fundamental knowledge about in vitro culture systems to enhance the proliferation and differentiation of mesenchymal stem cells (MSCs) in collagen sponge reinforced by the incorporation of poly(glycolic acid) (PGA) fiber. A collagen solution with PGA fiber homogeneously localized at PGA:collagen weight ratios of 0.67, 1.25, 2.5, and 5 was freezedried, followed by cross-linking of combined dehydrothermal, glutaraldehyde, and ultraviolet treatment. Scanning electron microscopy revealed that collagen sponges exhibited homogeneous and interconnected pore structures with an average size of 180 microm, irrespective of PGA fiber incorporation. When rat MSCs were seeded into collagen sponge with or without PGA fiber incorporation, more attached cells were observed in collagen sponge incorporating PGA fiber than in collagen sponge without PGA fiber incorporation, irrespective of the PGA:collagen ratio. The proliferation and osteogenic differentiation of MSCs in PGA-reinforced sponge at a weight ratio of 5 were greatly influenced by the culture method and growth conditions. Alkaline phosphatase (ALP) activity and osteocalcin content of MSCs cultured in PGA-reinforced sponge by the perfusion method became maximum at a flow rate of 0.2 mL/min, although they increased with culture time period. It may be concluded that appropriate perfusion conditions enable MSCs to positively improve the extent of proliferation and differentiation.

Alkaline Phosphatase↗
PubMed1982

New melanogenesis and photobiological processes in activation and proliferation of precursor melanocytes after UV-exposure: ultrastructural differentiation of precursor melanocytes from Langerhans cells.

Photobiological processes involving new melanogenesis after exposure to ultraviolet (UV) light were experimentally studied in C57 black adult mice by histochemistry, cytochemistry, and autoradiography. The trunk and the plantar region of the foot, where no functioning melanocytes were present before exposure, were exposed to UV-A for 14 consecutive days. Both regions revealed a basically similar pattern for new melanogenesis which involved an activation of precursor melanocytes. Essentially all of "indeterminate" cells appeared to be precursor melanocytes, the fine structure of which could be differentiated even from poorly developed Langerhans cells. New melanogenesis was manifested by 4 stages of cellular and subcellular reactions of these cells as indicated by histochemistry of dihydroxyphenylalanine (dopa) and autoradiography of thymidine incorporation: (a) an initial lag in the activation of precursor melanocytes with development of Golgi cisternae and rough endoplasmic reticulum followed by formation of unmelanized melanosomes (day 0 to 2); (b) synthesis of active tyrosinase accumulated in Golgi cisternae and vesicles with subsequent formation of melanized melanosomes in these cells (day 3 to 5); (c) mitotic proliferation of many of these activated cells, followed by an exponential increase of new melanocytes (day 6 to 7); and (d) melanosome transfer with differentiation of 10 nm filaments and arborization of dendrites, but without any significant change in the melanocyte population (day 8 to 14). The melanosome transfer was, however, not obvious until after 7 days of exposure. The size of newly synthesized melanosomes was similar to that of tail skin where native melanocytes were present before exposure.

Animals↗
PubMed1994

Long-term ultraviolet B-induced impairment of Langerhans cell function: an immunoelectron microscopic study.

The influence of low-dose, long-term ultraviolet B (UVB) light exposure on HLA class II-positive human epidermal Langerhans cells (LC) was studied using a sensitive immunoelectron microscopic technique for the ultrastructural assessment of HLA class II expression on LC and for quantification of these cells in situ. Six healthy Caucasian volunteers participated in the experiments and received thrice weekly UVB treatments for 4 weeks. The initial dose ranged from 30 to 50 mJ/cm2 and the total dose from 600 to 3500 mJ/cm2, depending on skin type. Suction blisters and biopsies were obtained before the start of the UVB protocol and 48 h after the last UVB irradiation, and processed for the mixed epidermal cell-lymphocyte reaction (MECLR) and electronmicroscopy, respectively. The MECLR was used as a measure of the immune response. The distribution of HLA class II molecules on LC was studied by incubating ultrathin cryosections of human skin tissue with an anti-HLA class II MoAb that was conjugated to 10 nm colloidal gold. Furthermore, the number of LC was assessed ultrastructurally, when they could be recognized by their unique cytoplasmic organelle, the Birbeck granule (BG). The UVB protocol that was employed caused a marked suppression of the MECLR responses. This UVB-induced reduction of the immune response was not paralleled by changes in HLA class II expression on LC, nor in the number of epidermal LC. These findings are further support for our hypothesis that UVB-induced immune suppression in the skin is not due to a depletion of local LC.

Histocompatibility Antigens Class II↗
PubMed1997

A modified confocal laser scanning microscope allows fast ultraviolet ratio imaging of intracellular Ca2+ activity using Fura-2.

A confocal, ultraviolet laser scanning microscope (LSM) for reliable ratio measurements of localized intracellular Ca2+ gradients using the Ca2+-sensitive dye Fura-2 was developed. In a commercial LSM, the filter wheels for the excitation band-pass filters and the grey filters were replaced by acousto-optic tunable filters (AOTF) for rapid switching (</=1.5 micros) of the ultraviolet (351 and 364 nm) and the visible (457, 476, 488, 514 nm) excitation light. This enabled dual wavelength excitation of Fura-2, or 2'7'-biscarboxyethyl-5(6)-carboxyfluorescein (BCECF) for pH measurements. Changing to a transmitted-light detector of high sensitivity allowed for simultaneous recording of differential interference contrast images of the preparation with the excitation light. The AOTF fine control of the intensity of the excitation light and improvements in the emission detector sensitivity enabled the acquisition of up to 120 ratio pairs of high-quality images from a single cell. The optical capabilities and limitations of the instrument were evaluated with fluorescent beads and dye-loaded cultured cells. Agonist-induced intracellular Ca2+ transients in HT29 cells were recorded to test for the instrument's ability to measure changes in [Ca2+]i. Ratio z-sections from Fura-2-loaded cells showed an inhomogeneity of the Fura-2 loading with an accumulation of the dye mostly in the mitochondria. We show, as an example of the microscope's achievable resolution, the spatial and temporal heterogeneity of [Ca2+]i signals in mitochondria and the cytosol in response to agonist-evoked stimulation of HT29 cells. In addition, we show that the lipophilic, membrane-bound Fura-2 derivative Fura-C18, for measurements of near-membrane Ca2+ changes, can be used with this confocal microscope. This new LSM is expected to deepen our understanding of localized [Ca2+]i signals; for example, the nuclear Ca2+ signalling or the [Ca2+]i changes that occur during stimulation of ion secretion in polarized epithelial cells.

Calcium↗
PubMed2002

Aspiration cytology of elastofibroma dorsi: case report with ultrastructural and immunohistochemical findings.

Elastofibroma is a well-recognized tumor-like process which typically occurs in the soft tissue of the shoulder. Although fine-needle aspiration (FNA) represents a quick and simple method for definitive diagnosis, the possibility of a false-negative diagnosis is high due to the hypocellularity of the smears. However, a high index of suspicion based on the clinical presentation of a firm mass in a typical location in an elderly person, usually female, aids in the diagnosis. We describe the FNA findings of elastofibroma dorsi in an 89-yr-old woman which, although hypocellular, contained diagnostic aggregates of petaloid globules within a collagenous matrix. The cytologic material showed a green-yellow autofluorescence of the altered elastic fibers with ultraviolet light. Transmission electron microscopy revealed an elongated beaded appearance with small electron densities and obliteration of the central elastin core. The presence of a hypocellular aspirate with autofluorescent elastic fibers should suggest the possibility of elastofibroma dorsi.

Aged↗
PubMed1980

Intestinal ceroid deposition - "brown bowel syndrome". A light and electron microscopic study.

Thirteen cases classified in our files as ceroid pigmentation of the intestinal wall ("brown bowel syndrome") are described. Clinically, all patients in this series had some symptoms of chronic bowel disease. The gut in this condition grossly demonstrates a variable orange-brown coloration. The ceroid pigment is difficult to identify in routine hematoxylin-eosin sections but may be demonstrated by a variety of special stains. In addition, ceroid may be identified by its golden-yellow autofluorescence under ultraviolet light. By electron microscopy, the deposited granules resemble ceroid deposits described in experimental animals. In addition to its occurrence in cases of chronic bowel disease, ceroid pigment was also found in 36 of 90 cases of cystic fibrosis (40%) and in 7 of 13 cases of congenital biliary atresia (54%). On the basis of pigment distribution and staining characteristics, brown bowel syndrome may be differentiated from melanosis coli and rectal ceroid histiocytosis.

Ceroid↗
PubMed1984

Psoralen-DNA crosslink repair in human lymphocytes. Comparison of alkaline elution with electron microscopy.

Much interest has surrounded the question of the removal of psoralen interstrand crosslinks in DNA of eukaryotic organisms. A commonly employed method for the study of psoralen repair is alkaline elution. In this study we have used alkaline elution to assess psoralen crosslink repair in human lymphocytes. The lymphocytes were treated with 8-methoxypsoralen or 4,5',8-trimethylpsoralen and allowed to repair for different periods of time. Analysis by alkaline elution showed elution patterns compatible with crosslink removal. When the crosslink removal under comparable conditions was studied by the use of electron microscopy under totally denaturing conditions, no repair of the crosslinks could be detected.

DNA↗
PubMed1982

Depth of information in photoelectron microscopy.

The depth of information is defined as the distance below the surface of a specimen from which information is contributed at a specific resolution. A simplified model of photoemission is used to explore the relationship between electron escape depths and depth of information in photoelectron microscopy (PEM or photoemission electron microscopy). The depth of information is equal to the escape depth when the escape depth is small relative to the instrument resolution. When the escape depth is large compared to the instrument resolution or when information is carried for example by reflected light, the image consists of well resolved surface detail at the instrument resolution and dimmer, more diffuse, images of detail below the surface. Thus the same sample can exhibit different depths of information depending on the image details of interest. Other mechanisms of transmitting information to the surface, for example induced topography, are discussed, and experimental examples are given.

Electrons↗
PubMed1978

The isolation of DNA from agarose gels by electrophoretic elution onto malachite green-polyacrylamide columns.

Electrophoretic elution of DNA coupled with direct adsorption onto malachite green-polyacrylamide columns was used to isolate double- and single-stranded DNA from agarose gels. Subsequently, DNA was eluted with a high salt buffer and filtered through Sephadex which permitted recovery of the DNA in a low salt buffer at concentrations suitable for heteroduplex analysis by electron microscopy. This method was tested by examining heteroduplexes formed from the isolated complementary single strands of T7 wild type DNA and a T7 deletion mutant. More than 80% of the reannealed molecules were intact heteroduplexes showing the deletion loop. Irradiation of single-stranded DNA with 254 nm light resulted in distorted, convoluted heteroduplexes while 366 nm light did not show this effect.

Coliphages↗
PubMed1991

Synergism between electricity and ionizing radiation.

Weak direct electric currents which produce little (or no) lethal damage to Escherichia coli bacteria are shown to act synergistically with ionizing radiation, both electromagnetic radiation (X-ray) and charged particles (beta radiation). This synergism greatly enhances the lethal effect of ionizing radiation on bacteria. This is possibly due to increased single-strand breaks in DNA, as detected by the alkaline sucrose gradient method. It is also shown that in cells with thymidine-3H incorporated into their DNA and treated with electricity, the radioactivity is released from the acid-insoluble fraction to the acid-soluble fraction, so that the ratio of radioactivity in the soluble fraction to that in the insoluble fraction increases from 0.47 in the non-treated control cells to 3.46 in the cells treated with an electric current of 1.0 mA (3.0 V) for 30 min, which indicates extensive degradation of cellular DNA. No synergism is detected between electricity and 254 nm UV radiation nor between electricity and X-rays, when these two agents are used sequentially in any order. Electricity alone produces lesions in cell membranes, as shown by electron microscopy.

Beta Particles↗
PubMed2004

A novel sub-population of bone marrow-derived myocardial stem cells: potential autologous cell therapy in myocardial infarction.

BACKGROUND: Several studies have identified beta2-microglobulin-negative (beta2M(-)) cells as a potential stem cell fraction in the bone marrow of rats and humans. We studied the ability of bone marrow-derived beta2M(-) cells to differentiate into cardiomyocytes and reconstitute the myocardium in a model of myocardial infarction. METHODS: beta2M(-) cells were purified from bone marrow of Lewis rats using a magnetic activated cell-sorting technique. beta2M(-) cells, 2.5 x 10(6) cells in 100 microl of phosphate-buffered saline (PBS), were transplanted 7 days after infarction into a transmural myocardial scar induced by cryoinjury in Lewis rats (n = 9). Control Group 1(n = 10) received a 100-microl injection of PBS, and Control Group 2 (n = 15) received no injection. The beta2M(-) cells were labeled before transplantation, using the membrane fluorescent intercalated dye, PKH26. Repopulation was examined at 6 and 8 weeks after transplantation. Differentiation of beta2M(-) cells into cardiac myocytes was determined by the colocalization of troponin and PKH26 to the same cell, utilizing immunohistochemistry, ultraviolet photomicroscopy and fluorescence microscopy on 6-microm serial sections. Area of engraftment within the scar was calculated by planimetry. RESULTS: The treatment group had multiple islands of de novo-formed myocardium within the fibrous matrix of the transmural scar (mean area 35 +/- 4.2% of scar area at 6 and 8 weeks). These cells colocalized cardiac-specific troponin and PKH26. Using these techniques, no myocardial islands were seen in the control groups. Before transplantation, beta2M(-) cells were troponin-negative. CONCLUSIONS: This study demonstrates that beta2M(-) cells represent a novel sub-population of bone marrow-derived stem cells capable of successful and substantial engraftment in areas of transmural myocardial scar, with de novo formation of cardiac myocytes. The functional significance of this observation is being studied.

Animals↗
PubMed2006

Degradation of 2,4-dichlorophenol by using glow discharge electrolysis.

Degradation of 2,4-dichlorophenol (2,4-DCP) in aqueous by glow discharge electrolysis (GDE) has been investigated. Ultraviolet (UV) absorption spectra, atomic force microscopy (AFM), high performance liquid chromatography (HPLC) and gas chromatogram-mass spectrum (GC/MS) are used to monitor the degradation process and to identify the major oxidation intermediate products. It has been found that 2,4-DCP undergoes a series of intermediate step, which leads to form a number of intermediate products, mainly isomeric chlorophenols and aliphatic acids. These products are further oxidized, eventually, mineralized into CO(2) and Cl(-). A degradation pathway for 2,4-DCP is proposed on the basis of detection of intermediate compounds.

Chlorophenols↗
PubMed1975

Improved isolation, separation and cytochemistry of living cells.

1. This paper describes improved methods of obtaining, purifying and studying bulk suspensions of isolated living hepatocytes and other cells of adult rats and urodeles. 2. The cells were isolated largely by dissolving the hepatic ground substance through the extracorporeal portal perfusion and further incubation of the excised liver with 0.05% collagenase and 0.1% hyaluronidase. The different kinds of cells were then separated from one another by counter-current centrifugation. The isolated cells were examined by differential interference, phase-contrast, amplitude-contrast, ultraviolet, fluorescence and electron microscopy. Various cytochemical tests were carried out. Whenever possible, for each method of examination, the isolated cells were compared with cells of the same kind which had not undergone isolation. 3. Dye-exclusion, lysochromy, fluorescence and differential interference microscopical analysis indicated viability rates between 75 and 99%. Succinate dehydrogenase activity was preserved at a high level in nearly all isolated cells. In hepatocytes, the essentially extracellular cells. In hepatocytes, the essentially extracellular 'soluble' alkaline phosphatase activity of bile canaliculi was retained. Living hepatocytes were studied by super-modulating methods of microscopy for the first time, with somewhat unexpected findings. It now seems probable that previous methods of tissue preparation produced gross alterations in hepatocyte mitochondria. The assessment of the viability of isolated cells was re-examined. 4. The methods described may permit a more meaningful correlation between biochemical, cytochemical, ultrastructural and biophysical findings than that obtainable by the use of current methods.

Acid Phosphatase↗
PubMed2003

Preparation and antibacterial effects of Ag-SiO2 thin films by sol-gel method.

In the present study, silver-doped silica thin films were successfully prepared by sol-gel method to apply for antibacterial materials. The starting solution was prepared from 1:0.24:3.75:2.2 molar ratios of Si(OC2H5)4):AgNO3:H2O:C2H5OCH2CH2OH and then the pH value controlled at 3 with 0.5 N HNO3 solution. The formation of silver-doped glassy silica thin films at various temperatures was investigated through infrared spectroscopy, ultraviolet-visible, scanning electron microscopy and X-ray diffraction. From these analysis data, it was found that silver ions were completely trapped in the silica matrix and their reduction could be achieved at 600 degrees C annealing temperature. The antibacterial effects of silica thin films against Escherichia coli and Staphylococcus aureus were examined by film attachment method. The coating films had an excellent antibacterial performance.

Anti-Bacterial Agents↗