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Results for “Microscopy, Ultraviolet”

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At least 811 records · Page 45Linked to original sources
PubMedDate not supplied

[Localization of ribonucleases in the mycelium of the fungus Aspergillus clavatus].

The localization of ribonucleases in Aspergillus clavatus mycelium was studied using differential centrifugation of mycelial homogenates, preparation of protoplasts, by cytochemical and immunochemical studies. The RNase activity was represented mainly by guanylic and nonspecific RNases and was not associated with the intracellular structures. The cytochemical and immunochemical observations revealed the presence of a nonspecific RNase activity in the periplasm, mitochondria, perinuclear space and vesicular structures. The presence of this RNase in the periplasmic space and vesicular structures of A. clavatus suggests that it may be secreted through a fusion of the vesicular membranes with the cytoplasmic membrane, and then from the periplasm through the cell wall into the surrounding medium.

Aspergillus↗
PubMed1981

[Isolation and analysis of phage-resistant Pseudomonas putida mutants using new bacteriophages].

Three new bacteriophages of Pseudomonas putida PpG1 have been isolated. Bacteriophages differ in many characteristics and are unrelated. Phage-resistant mutants of Pseudomonas putida PpG1 are selected using these phages and pf16 bacteriophage. No lysogenic variants were detected among these mutants. They have been distributed in seven groups according to their resistance to bacteriophages. The resistance to PMW phage was caused by at least two different mutations. Some of the phage-resistant mutants seem to cause the killing effect on Pseudomonas putida PpG1 cells.

Bacteriophages↗
PubMedDate not supplied

[Sakhalin antigenic group (Bunyaviridae family)].

Serological study of viruses belonging to the Sakhalin group showed Paramushir virus isolated in the USSR and Avalon virus isolated in Canada to be identical in all the tests used. The data on the cultural properties of the Sakhalin group viruses, the virions buoyant densities in sucrose gradient, the data on thermal sensitivity and UV inactivation of the viruses, on their morphology and morphogenesis are presented.

Antigens, Viral↗
PubMed1978

The cytolytic effect of PUVA treatment on PHA-stimulated human peripheral lymphocytes.

The morphology of PUVA-treated and PHA-stimulated human peripheral lymphocytes in vitro was studied by means of the light and electron microscopes. Most cells showed signs of cytolysis, such as pyknotic nuclei and a swollen and decomposed cytoplasm; a few cells, however, appeared as normal lymphoblasts. In the latter, repair-enzyme mechanisms may successfully have rectified alterations in the DNS prior to the inception of S-phase. These findings are discussed with reference to the in vivo effect of PUVA treatment.

Cell Nucleus↗
PubMed1973

Cell culture studies of a neonatal calf diarrhea virus.

The effects of a neonatal calf diarrhea virus on cell cultures were investigated. Bovine embryonic kidney cell cultures were the most satisfactory for production of virus. Cytoplasmic changes detected after inoculation with a high multiplicity of virus were: 1) cytoplasmic vacuoles; 2) some eosinophilic cytoplasmic inclusions; and 3) some degeneration of cells and detachment from the monolayer. Cultures stained with fluorescein-labeled antibody showed cytoplasmic fluorescence as early as four hr after infection with the maximum fluorescence at five days. No cross reactions were observed between the neonatal calf diarrhea virus and reovirus type 1 or type 3 by the fluorescent antibody technique. Plaques were small and were not produced consistently. The optimal adsorption time was one to two hr. The maximum titer was reached at 18 hr, with the cell-associated titer remaining higher than the cell-free titer until that time. An interferon was produced by cultures infected with either ultraviolet-inactivated or untreated virus.

Adsorption↗
PubMed1972

Effects of growth inhibitors and ultraviolet irradiation on F pili.

The effects of chloramphenicol, nalidixic acid, mitomycin C, NaCN, and ultraviolet irradiation at 253.7 nm on F pili production by Escherichia coli cells was studied by electron microscopy. The results show that cells contain pools of pili protein, and that assembly does not require synthesis of protein or deoxyribonucleic acid (DNA). NaCN (2 x 10(-2)m) prevents the reappearance of pili and causes existing pili to disappear quickly from the cell surface. This suggests that energy is used in the assembly of pili and to retain pili on the cell. Cells irradiated with high doses (10(4)ergs/mm(2)) of 253. 7 nm light produce fewer pili, and these are shorter than normal. Dose-response curves for number of pili per cell and length of pili resemble single hit kinetics, showing 37% survival at 10(4) ergs/mm(2) and 2 x 10(4) ergs/mm(2), respectively. This suggests that DNA is at the site where pili are produced, and that it may be involved in the assembly of pili.

Bacterial Proteins↗
PubMed1995

Laser exposure of Parylene-C insulated microelectrodes.

The polymer, Parylene-C, has proven to be a biocompatible insulation for microelectrodes. However, due to its inert nature, the removal of the insulation from the tips of microelectrodes is difficult. This paper describes the use of an ultraviolet laser system to micromachine Parylene-C insulation with photoablation to precisely expose an arbitrary shape recording or stimulating surface.

Lasers↗
PubMedDate not supplied

Image enhancement of the in vivo leukocyte-endothelium contact zone using optical sectioning microscopy.

A major determinant of the strength of leukocyte [white blood cell (WBC)] to endothelium [endothelial cell (EC)] adhesion is the contact area formed between the two cells, which is often obscured by out-of-focus information inherent to intravital microscopy. To improve visualization of the WBC-EC contact zone, techniques of optical sectioning microscopy were developed to enhance brightfield images of WBC-EC adhesion in postcapillary venules of the mesentery of the rat. A 50x/1.0 NA objective was held in a piezoelectric mount that was computer-driven, and video images were obtained by digitizing images from a CCD camera while focusing through the vertical direction in 1 micron steps over a depth of 16 microns. Using measurements of the microscope's optical transfer function, deconvolution of the central image was performed in the Fourier domain using the technique of singular value decomposition with Tikhonov-Miller regulation to remove out-of-focus information. Measurement of the length of the WBC-EC contact zone (LC) in the original images yielded values on the order of 4.32 +/- 1.08 microns (mean +/- SD). The enhanced images showed a significantly 35% smaller LC equal to 2.78 +/- 0.70 micron. Topical application of the chemoattractant f-met-leu-phe resulted in a 26% increase in LC to 3.49 +/- 0.72 micron, thus suggesting that upregulation of adhesion molecules on the WBC membrane results in the recruitment of additional membrane area from surface ruffles into the zone of adhesion. Other advantages of the deconvolution were to visualize structural characteristics of the microvascular wall and parenchymal tissue in greater detail. Thus, brightfield optical sectioning microscopy may provide a valuable tool for in vivo studies of the microvasculature, and serves as a useful alternative to fluorescence microscopy without the undesirable effects of exogenous fluorophores and exposure to ultraviolet radiation.

Algorithms↗
PubMed1988

Ultrastructure and dynamics of selective mitochondrial injury in carcinoma cells after doxycycline photosensitization in vitro.

Mechanisms and intracellular sites of photosensitized damage were investigated in cultured MGH-U1 cells treated with doxycycline (DOTC). Cells were examined by phase-contrast, fluorescence, and electron microscopy at various times (15 minutes to 24 hours) after ultraviolet irradiation (320-400 nm). DOTC localized selectively within the mitochondria, as shown by colocalized fluorescence with rhodamine 123 (R123). Photosensitization at 1 J/sq cm caused striking swelling of the mitochondrial matrix and disruption of the cristae, accompanied by loss of the ability of mitochondria to concentrate R123. These changes progressed during the first hour after irradiation, and then were followed by partial recovery of mitochondrial ultrastructure and function. At no time were other organelles seen to be affected. It appears that this selective, photosensitized alteration was a consequence of localized and partially reversible damage to the mitochondrial inner membrane. In contrast, exposure to 2-6 J/sq cm caused irreversible injury and necrosis.

Doxycycline↗
PubMed2006

Effects of cellulose whiskers on properties of soy protein thermoplastics.

Environmentally-friendly SPI/cellulose whisker composites were successfully prepared using a colloidal suspension of cellulose whiskers, to reinforce soy protein isolate (SPI) plastics. The cellulose whiskers, having an average length of 1.2 microm and diameter of 90 nm, respectively, were prepared from cotton linter pulp by hydrolyzing with sulfuric acid aqueous solution. The effects of the whisker content on the morphology and properties of the glycerol-plasticized SPI composites were investigated by scanning electron microscopy, dynamic mechanical thermal analysis, differential scanning calorimetry, ultraviolet-visible spectroscopy, water-resistivity testing and tensile testing. The results indicated that, with the addition of 0 to 30 wt.-% of cellulose whiskers, strong interactions occurred both between the whiskers and between the filler and the SPI matrix, reinforcing the composites and preserving their biodegradability. Both the tensile strength and Young's modulus of the SPI/cellulose whisker composites increased from 5.8 to 8.1 MPa and from 44.7 to 133.2 MPa, respectively, at a relative humidity of 43%, following an increase of the whisker content from 0 to 30 wt.-%. Furthermore, the incorporation of the cellulose whiskers into the SPI matrix led to an improvement in the water resistance for the SPI-based composites.

Amino Acids↗