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At least 829 records · Page 46Linked to original sources
PubMed2006

Colonization of barley (Hordeum vulgare) with Salmonella enterica and Listeria spp.

Colonization of barley plants by the food-borne pathogens Salmonella enterica serovar typhimurium and three Listeria spp. (L. monocytogenes, L. ivanovii, L. innocua) was investigated in a monoxenic system. Herbaspirillum sp. N3 was used as a positive control and Escherichia coli HB101 as a negative control for endophytic root colonization. Colonization of the plants was tested 1-4 weeks after inoculation by determination of CFU, specific PCR assays and fluorescence in situ hybridization (FISH) with fluorescently labelled oligonucleotide probes in combination with confocal laser scanning microscopy (CLSM). Both S. enterica strains were found as endophytic colonizers of barley roots and reached up to 2.3 x 10(6) CFU per g root fresh weight after surface sterilization. The three Listeria strains had 10-fold fewer cell numbers after surface sterilization on the roots and therefore were similar to the results of nonendophytic colonizers, such as E. coli HB101. The FISH/CSLM approach demonstrated not only high-density colonization of the root hairs and the root surface by S. enterica but also a spreading to subjacent rhizodermis layers and the inner root cortex. By contrast, the inoculated Listeria spp. colonized the root hair zone but did not colonize other parts of the root surface. Endophytic colonization of Listeria spp. was not observed. Finally, a systemic spreading of S. enterica to the plant shoot (stems and leaves) was demonstrated using a specific PCR analysis and plate count technique.

Hordeum↗
PubMed1997

Impact of nutrient composition on a degradative biofilm community.

A microbial community was cultivated in flow cells with 2,4,6-trichlorobenzoic acid (2,4,6-TCB) as sole carbon and energy source and was examined with scanning confocal laser microscopy and fluorescent molecular probes. The biofilm community which developed under these conditions exhibited a characteristic architecture, including a basal cell layer and conspicuous mounds of bacterial cells and polymer (approximately 20 to 30 (mu)m high and 25 to 40 (mu)m in diameter) occurring at 20- to 200-(mu)m intervals. When biofilms grown on 2,4,6-TCB were shifted to a labile, nonchlorinated carbon source (Trypticase soy broth), the biofilms underwent an architectural change which included the loss of mound structures and the formation of a more homogeneous biofilm. Neutrally charged fluorescent dextrans, which upon hydration become cationic, were observed to bind to mounds, as well as to the basal cell layer, in 14-day biofilms. In contrast, polyanionic dextrans bound only to the basal cell layer, indicating that this material incorporated sites with both positive and negative charge. The results from this study indicate that nutrient composition has a significant impact on both the architecture and the physicochemistry of degradative biofilm communities.

Journal Article↗
PubMed2004

Nanoscale analysis of biofunctional molecules and components.

In basic medical research, as well as in concrete clinical applications, the nanoscale analysis of biofunctional units is of strongly increasing relevance. Dedicated investigations on molecules, molecular composites or functional units can efficiently be performed ex or in situ by scanning probe methods and, namely, by scanning force microscopy. In the following investigations, the folding behavior of DNA is presented as an example of basic research in medicine. In contrast, the investigation of bioadsorption phenomena in systems on which apheresis therapies are based provides a real contribution to applied medicine.

Absorbable Implants↗
PubMed1984

Hydrolytic degradation of dental composites.

The leakage of filler elements from four composites after storage in water was investigated by use of atomic absorption spectrophotometry. The results confirmed previous findings that leaching of silicon from different composites is strongly dependent on filler composition. Consideration of the total filler surface of each composite material indicated that quartz as well as pyrolytic silica-containing composites leached less silicon than did composites containing fillers of strontium and/or barium glasses. A correlation between leakage and crack formation in the matrix appeared to exist for all composites except for the microfilled resin. These cracks were explained as a result of osmotic pressure built up at the matrix-filler interface due to hydrolytic degradation of the filler. Of the investigated materials, the microfilled resin was found to be the most stable material in a wet environment with respect to crack formation. This finding was explained by filler composition, filler form, and the specific structure of the microfilled resin.

Aluminum↗
PubMed1985

Microstructures of duplex (beta + gamma) silver-tin alloys.

The microstructures of (beta + gamma) silver-tin alloys are especially influenced by both homogenization temperature and subsequent heat treatment. When the alloy is cooled from homogenization temperatures above approximately 200 degrees C, lenticular regions of the ordered orthorhombic gamma phase precipitate from within the disordered h.c.p. beta phase on three structurally equivalent planes, (1210), (1120), and (2110), to form a Widmanstatten structure. When the duplex alloys were homogenized at temperatures below approximately 200 degrees C, where the beta/(beta + gamma) phase boundary is vertical, these structures were not observed.

Chemical Phenomena↗
PubMed1998

Surface chemistry of a high-copper dental amalgam.

In amalgam, mercury is intended to take the form of stable intermetallic compounds. Any mercury leakage must therefore come from free mercury not involved in such compounds. Thus, a knowledge of the exact surface chemistry of dental amalgam is necessary if this phenomenon is to be understood. From XPS and EDS analyses, a model of the surface chemistry of amalgam is proposed which fully characterizes all the phases that are present. The data show the surface to have a composition different from that of the bulk, being comprised of a hydrocarbon deposit and adsorbed water covering the intermetallic phase gamma2 (Sn(6-8)Hg), tin (iv) oxide, and mercury in a free state. After amalgamation, the amount of mercury at the surface decreases with time and eventually attains a constant concentration, where it is all involved in the gamma2 phase, leaving no free mercury. A model is proposed for the surface of amalgam and the changes in this model with time.

Copper↗
PubMed1992

SUPERMAN, a regulator of floral homeotic genes in Arabidopsis.

We describe a locus, SUPERMAN, mutations in which result in extra stamens developing at the expense of the central carpels in the Arabidopsis thaliana flower. The development of superman flowers, from initial primordium to mature flower, is described by scanning electron microscopy. The development of doubly and triply mutant strains, constructed with superman alleles and previously identified homeotic mutations that cause alterations in floral organ identity, is also described. Essentially additive phenotypes are observed in superman agamous and superman apetala2 double mutants. The epistatic relationships observed between either apetala3 or pistillata and superman alleles suggest that the SUPERMAN gene product could be a regulator of these floral homeotic genes. To test this, the expression patterns of AGAMOUS and APETALA3 were examined in superman flowers. In wild-type flowers, APETALA3 expression is restricted to the second and third whorls where it is required for the specification of petals and stamens. In contrast, in superman flowers, APETALA3 expression expands to include most of the cells that would normally constitute the fourth whorl. This ectopic APETALA3 expression is proposed to be one of the causes of the development of the extra stamens in superman flowers. The spatial pattern of AGAMOUS expression remains unaltered in superman flowers as compared to wild-type flowers. Taken together these data indicate that one of the functions of the wild-type SUPERMAN gene product is to negatively regulate APETALA3 in the fourth whorl of the flower. In addition, superman mutants exhibit a loss of determinacy of the floral meristem, an effect that appears to be mediated by the APETALA3 and PISTILLATA gene products.

Gene Expression Regulation↗
PubMed2005

Design and fabrication of a microlens on the sidewall of an optical fiber with a metallized 45 degrees end face.

We propose a method for designing a self-aligned microlens. We have improved its fabrication by employing metallization on a 45 degrees angled surface of the optical fiber. We designed the focal length of the microlens to be 14.0 microm, considering the dimensions of a scanning near-field optical microscopy (SNOM) probe, and we calculated possible dimensions of diameter and height by the ray-tracing method. The modeling of lens formation was also carried out with two assumptions: no volume change and no movement of peripheral parts of the photoresist (PR) on the substrate during reflow. To fabricate a microlens of diameter 16.0 microm and height 5.0 microm we exposed a coated PR to UV light guided into the optical fiber, followed by optimized reflow of 150 degrees C for 2 min. For this microlens the focal length and the beam waist were 14.0 and 1.4 microm, respectively. This lens can be used for compact optical data storage.

Journal Article↗
PubMed1998

Microscopic analysis of enzyme activity, mitochondrial distribution and hydrogen peroxide in two-cell rat embryos.

A developmental block is induced by phosphate in rat embryos at the late two-cell stage. The present study was designed to examine the energy metabolism of rat two-cell blocked and non-blocked embryos. Enzyme activity was measured in individual embryos by histochemical techniques. The activities of malate dehydrogenase, isocitrate dehydrogenase, lactate dehydrogenase, pyruvate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, glutamate dehydrogenase, glucose-6-phosphate dehydrogenase, glucose-6-phosphatase, and phosphorylase did not differ among non-blocked and blocked embryos. However, the activity of succinate dehydrogenase was significantly decreased in blocked embryos compared with non-blocked embryos. In blocked embryos, cytochrome oxidase activity was distributed homogeneously, but was located at the perinuclear region in non-blocked embryos. Active mitochondrial organization was visualized using the fluorescent probe rhodamine 123 and laser scanning confocal microscopy. In both non-blocked and blocked embryos, mitochondria were distributed homogeneously. The concentration of H2O2 measured fluorometrically in embryos cultured without phosphate did not change significantly during the culture period, but decreased in embryos cultured with phosphate. The timing corresponded to the occurrence of the two-cell block. In summary, these results suggest that the developmental block in rat two-cell embryos is induced by disturbance of mitochondrial energy metabolism.

Animals↗
PubMed2002

Photodynamic therapy with pyropheophorbide-a methyl ester in human lung carcinoma cancer cell: efficacy, localization and apoptosis.

Pyropheophorbide-a methyl ester (MPPa) is a semisynthetic photosensitizer derived from chlorophyll a. The absorption peak of MPPa in organic solvent and in cells was at 667 and 674 nm, respectively. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay showed that MPPa had no dark cytotoxicity. In vitro photodynamic activity was extensively evaluated using a human lung carcinoma cancer cell line (NCI-h446). MPPa exhibited no genotoxicity, as assayed by single-cell gel electrophoresis. Using confocal laser scanning microscopy and organelle-specific fluorescent probes, MPPa was found to localize in the intracellular membrane system, namely the endoplasmic reticulum, Golgi apparatus, lysosomes and mitochondria, in the NCI-h446 cells. Furthermore, nuclear staining and DNA gel electrophoresis revealed that DNA condensation and fragmentation occurred post-photodynamic therapy, indicating the cell death was in the apoptotic mode.

Apoptosis↗
PubMed2006

Effects of plaque control on the patency of dentinal tubules: an in vivo study in beagle dogs.

BACKGROUND: The aim of this in vivo study was to evaluate the effects of plaque control on the patency of dentinal tubules using vital teeth of beagle dogs. METHODS: Class V cavities were prepared on the cervical areas of the mandibular and maxillary molars in each dog with a diamond point. To simulate the state of dentinal hypersensitivity, the teeth were etched with 50% citric acid for 2 minutes to obtain patent dentinal tubules. Plaque control was achieved by brushing the left-side teeth every day, whereas no plaque control was performed for the right-side teeth. A dentin biopsy was performed after 1, 2, and 3 weeks using the cylindrical diamond point to obtain dentin specimens. RESULTS: In the plaque control group, some of the dentinal tubules were occluded with precipitate (Ca/P=1.49), and the diameter of the dentinal tubules decreased from 2.42+/-0.33 microm (mean+/-SD) to 1.11+/-0.51 microm after 7 days, although most of the dentinal tubules remained open. In contrast, no precipitate was observed in the dentinal tubules of the non-plaque control group. Also, the diameter of the dentinal tubules increased from 2.42+/-0.33 to 2.9+/-0.49 microm, due to the demineralization of the peritubular and intertubular dentin. CONCLUSION: Plaque control plays a key role in reducing the patency of dentinal tubules and, therefore, might promote the natural repair of dentinal hypersensitivity.

Analysis of Variance↗
PubMed2002

Efficacy enhancement of trisodium phosphate against spoilage and pathogenic bacteria in model biofilms and on adipose tissue.

A two-step approach for enhancing the efficacy of trisodium phosphate (TSP) was evaluated using meat spoilage and pathogenic bacteria in flow cell biofilms and adipose tissue model systems. The process was based on the plasmolysis of attached bacteria (biofilms) with a hyperosmotic solution (1.5 M NaCl) and the subsequent deplasmolysis of cells with a low-osmotic-strength solution containing different concentrations of TSP (0.1, 0.25, 0.5, 0.625, and 1.0 % [wt/vol]). Escherichia coli, Salmonella Enteritidis, Pseudomonas sp., Listeria monocytogenes, and Brochothrix thermosphacta strains were cultivated for 24 h as pure culture biofilms in glass flow cells with complex media and were then treated with either 0.1, 0.25, 0.5, 0.625, and 1.0% TSP, or the same TSP concentrations delivered in conjunction with plasmolysis-deplasmolysis (PDP). Confocal scanning laser microscopy, a commercial fluorescent viability probe, and image analysis were then used to quantify the relative abundances of living and dead cells remaining after the different treatment regimes. With the exception of L. monocytogenes (which was resistant to TSP concentrations of up to 5%), the PDP process increased the sensitivity of the test strains to TSP. However, when similar experiments were conducted with pork adipose tissue, it became evident that higher TSP concentrations were necessary to produce significant decreases in the number of viable cells and that the PDP process generally failed to enhance TSP efficacy. An exception was L. monocytogenes, which exhibited an increase in sensitivity to TSP when inoculated tissue was pretreated with 1.5 M NaCl. It is thought that factors contributing to the failure of the PDP process to enhance the activity of TSP in meat systems involves the mode of TSP antimicrobial activity, alkaline pH stress, and the chemically complex, buffered nature of meats. It remains to be determined whether the PDP process is suitable for use with other food grade antimicrobial agents or can be used in nonfood biofilm control applications.

Adipose Tissue↗
PubMed2001

Endogenous production of protoporphyrin IX induced by 5-aminolevulinic acid in leukemia cells.

AIM: To explore the photosensitization of 5-aminolevulinic acid (ALA) in myeloid leukemia cell line. METHODS: Using the technique of fluorescence spectra, the A LA induced protoporphyrin IX (Pp IX) was measured in myeloid leukemia JCS cells. Cofocal laser scanning microscopy (CLSM) combined with fluorescence organelle probe was used to detect the localization of Pp IX in JCS cells at the subcellular levels. MTT assay was used to measure the cell survival after light irradiation. RESULTS: ALA successfully produced endogenous PpI X in leukemia JCS cells. PpIX was observed to be distributed in the cytoplasm and mitochondria was exhibited as the one of binding sites of PpIX. As a photosensitizer, PpIX initiated photodynamic reaction after light irradiation and effectively photodamaged leukemia cells. CONCLUSION: ALA-based photosensitization could be used for inactivation of leukemia cells.

Aminolevulinic Acid↗
PubMed1992

Short-term plasma-cleaning treatments enhance in vitro osteoblast attachment to titanium.

The purpose of this research was to characterize the in vitro cellular behavior of osteoblast-like cells on titanium surfaces prepared with argon plasma-cleaning (PC) treatments for various lengths of time. The highest levels of cell attachment were observed for surfaces which had been plasma-treated for one min. Surface analyses indicated that although PC treatments dramatically improved surface wettability, the presence of inorganic contaminants was observed with longer treatment times and may have interfered with cell attachment. Further work is suggested to investigate the longer-term phenotypic expression of osteoblasts when grown on implant surfaces.

Analysis of Variance↗