Showing papers on "Ultraviolet light published in 1994"

Ultraviolet light and ozone stimulate accumulation of salicylic acid, pathogenesis-related proteins and virus resistance in tobacco

Abstract: In tobacco (Nicotiana tabacum L. cv. Xanthinc), salicylic acid (SA) levels increase in leaves inoculated by necrotizing pathogens and in healthy leaves located above the inoculated site. Systemic SA increase may trigger disease resistance and synthesis of pathogenesis-related proteins (PR proteins). Here we report that ultraviolet (UV)-C light or ozone induced biochemical responses similar to those induced by necrotizing pathogens. Exposure of leaves to UV-C light or ozone resulted in a transient ninefold increase in SA compared to controls. In addition, in UV-light-irradiated plants, SA increased nearly fourfold to 0.77 μg·g−1 fresh weight in leaves that were shielded from UV light. Increased SA levels were accompanied by accumulation of an SA conjugate and by an increase in the activity of benzoic acid 2-hydroxylase which catalyzes SA biosynthesis. In irradiated and in unirradiated leaves of plants treated with UV light, as well as in plants fumigated with ozone, PR proteins 1a and 1b accumulated. This was paralleled by the appearance of induced resistance to a subsequent challenge with tobacco mosaic virus. The results suggest that UV light, ozone fumigation and tobacco mosaic virus can activate a common signal-transduction pathway that leads to SA and PR-protein accumulation and increased disease resistance.

Ecology of Free-Living Amoebae

Abstract: Small free-living amoebae (FLA) are the main predators controlling bacterial populations in soils. They are distributed in the rhizospheric zone and the surrounding bulk soil; however, they may spread deeper, reaching the vadose zone of groundwater systems, especially where bacterial populations get to high densities. Soil texture is the physical factor controlling the distribution of FLA because it determines the mean bore pore of soil aggregates and other important physical factors. FLA help maintain the high bacterial mineralization rate of organic matter through predation. As attachment onto a surface is necessary for feeding, the quantity of available surfaces is very important for developing this activity. However, the role of protozoa on plant growth promotion is still unclear because they may increase this effect by feeding on both fungi and bacteria. Small FLA are found in soils or sediments, as well as attached to suspended particulate matter in water columns, in the first 30 pm of water surface, or on the bodies of submerged animals and plants. These microor- ganisms do not distinguish between terrestrial or aquatic environments because they live in the interfaces between them. However, their importance in aquatic systems has been considered as negligible because they are outcompeted by free swimmers. The water conditions affecting amoebae survival are pH, temperature, concentration of sulfhydric acid and salinity. These factors have a strong influence on the structure of amoebae communities in aquatic environments. FLA are considered cosmopolitan as a group, and they live inside vertebrates, in soils, freshwater, marine waters, and on the aerial parts of plants and animals. These microbes, are spread by wind and water currents. Once in the air, cysts and trophozoites behave like any other suspended particulate matter. Therefore, suspension, transportation, and removal depend on atmospheric dynamics rather than on their own mechanisms. Ultraviolet light and drought are the main causes of losing viability, but much needs to be learned about the effects of air contaminants on amoebal survival. Naked amoebae also live in the phyllosphere as part of phylloplane community, but their importance and participation in this environment remain unknown. Some species belonging to the genera Acantharnoebae, Naegleria, and Balamuthia cause fatal diseases in humans and are carriers of other pathogens such as Legionella pneumophilia. However, FLA communities can be of some utility in sewage treatment works based in soil filters. %A's predatory activity in the root zone method may be of greater importance than previously thought, because this is their natural or more favorable environment. Research on the feeding behavior of FLA species, their rate of biomass transformation, and growth rate changes in response to environmental stresses are still needed in order to clarify their importance in both sewage system works and agricultural fields, where both bacteria and amoebae are involved.

Characterization of broadly pleiotropic phenotypes caused by an hfq insertion mutation in Escherichia coli K‐12

Abstract: The region immediately downstream from the miaA tRNA modification gene at 94.8 min contains the hfq gene and the hflA region, which are important in the bacteriophage Q beta and lambda life cycles. The roles of these genes in bacteria remain largely unknown. We report here the characterization of two chromosomal hfq insertion mutations. An omega (omega) cassette insertion near the end of hfq resulted in phenotypes only slightly different from the parent, although transcript mapping demonstrated that the insertion was completely polar on hflX expression. In contrast, an equally polar omega cassette insertion near the beginning of hfq caused pronounced pleiotropic phenotypes, including decreased growth rates and yields, decreased negative supercoiling of plasmids in stationary phase, increased cell size, osmosensitivity, increased oxidation of carbon sources, increased sensitivity to ultraviolet light, and suppression of bgl activation by hns mutations. hfq::omega mutant phenotypes were distinct from those caused by omega insertions early in the miaA tRNA modification gene. On the other hand, both hfq insertions interfered with lambda phage plaque formation, probably by means of polarity at the hflA region. Together, these results show that hfq function plays a fundamental role in Escherichia coli physiology and that hfq and the hflA-region are in the amiB-mutL-miaA-hfq-hflX superoperon.

Proopiomelanocortin-derived peptides are synthesized and released by human keratinocytes

Abstract: Proopiomelanocortin (POMC), the precursor for melanotropic, corticotropic, and opioid peptides such as alpha-melanocyte-stimulating hormone (alpha MSH), ACTH, and other related peptides, was originally identified as a product of the pituitary gland. However, recent evidence shows that POMC products can also be produced by nonpituitary tissues. Because keratinocytes, the major constituent of the epidermis exhibit the capacity to release a variety of proinflammatory and immunomodulatory mediators, the present study was performed to investigate whether human keratinocytes are able to produce POMC-derived peptides. Supernatants of human normal keratinocytes and an epidermal carcinoma cell line (A431) contained significant levels of immunoreactive alpha MSH and ACTH. Upon immuneprecipitation and size-exclusion chromatography, keratinocyte-derived alpha MSH exhibited a molecular mass of approximately 1 kD and was biologically active as demonstrated in a tyrosinase bioassay. Northern blot analysis revealed the expression of POMC-specific transcripts (1.3 kb) in both normal keratinocytes and A431 cells. The production of alpha MSH and ACTH could be significantly upregulated both at the protein and mRNA level upon treatment with phorbol myristate acetate, ultraviolet light, or interleukin 1. These data provide first evidence that human keratinocytes produce POMC-derived peptides such as alpha MSH and ACTH. Because POMC-derived peptides recently have been recognized as potent immunomodulatory mediators, their presence in the epidermis may have a major impact on the skin immune system.

Immunotoxicology and immunopharmacology

Abstract: The second edition of this text has been revised and refocused to reflect the transformation of immunotoxicology from a subdiscipline of toxicology to an independent area of research that can best be described as "environmental immunology" New chapters discuss the role of immune mediators in liver, lung, and skin toxicity, in regulating chemical- metabolizing enzymes, and in the immunosuppression produced by ultraviolet light More emphasis is placed on the clinical consequences of immunotoxicity, as well as the interpretation of experimental data for predicting, human health risk; The second edition is divided into three major sections: immunosuppression, autoimmunity, and hypersensitivity This new organization of the text allows for a more thorough treatment of these phenomena, with greater attention to test methods, theoretical considerations, and clinical implications The book includes many chapters on specific environmental agents, therapeutic drugs, biological agents, and drugs of abuse, as well as on immune-mediated toxicity in specific organ systems

Oxidation of humic substances by manganese oxides yields low-molecular-weight organic substrates

Abstract: MANY bacteria oxidize thermodynamically unstable manganese(II) to Mn oxides and deposit the oxides on their surfaces1,2, a process that appears to account for most Mn oxidation in natural waters3–5 and sediments6. Among the reasons that have been proposed for the evolutionary selection of this process are protection from damage by toxic metals and oxygen species, protection from ultraviolet light, and strengthening of the bacterial sheath or capsule1,7. Mn oxides may promote harmful free radical reactions, however, and marine Mn-oxidizing bacteria are particularly susceptible to photoinhibition8. Here we report that Mn oxides lyse complex humic substances, which in general cannot be used by microorganisms directly9–11, to form low-molecular-weight organic compounds that can be used as substrates for microbial growth. Mn-oxidizing bacteria may thus be able to use the carbon pool in humic substances, which represent one of the largest organic reservoirs in natural waters, sediments and soils.

Sunlight, Vitamin D, and Ovarian Cancer Mortality Rates in US Women

Abstract: Background In general, ovarian cancer incidence and mortality is higher in northern than southern latitudes. This ecologic study tests the hypothesis that vitamin D produced in the skin from sunlight exposure may be associated with a protective action in ovarian cancer mortality. Methods The association between average annual sunlight energy and age-specific ovarian cancer mortality rates in counties containing the 100 largest US cities was evaluated for 1979-1988. Simple linear regression was performed by decade using sunlight and ozone as independent variables and ovarian cancer rates as the dependent variable. Multiple regression was used to adjust for ozone and sulphur dioxide, since these atmospheric components may absorb ultraviolet light. Results Fatal ovarian cancer in these areas was inversely proportional to mean annual intensity of local sunlight in a univariate analysis (P = 0.0001), and in a regression adjusted for air pollution (P = 0.04). The association was also seen when restricted to 27 major urban areas of the US; however, probably due to a small sample size, this statistic did not reach significance. Conclusions This ecologic study supports the hypothesis that sunlight may be a protective factor for ovarian cancer mortality.

Slow Repair of Pyrimidine Dimers at p53 Mutation Hotspots in Skin Cancer

Abstract: Ultraviolet light has been linked with the development of human skin cancers. Such cancers often exhibit mutations in the p53 tumor suppressor gene. Ligation-mediated polymerase chain reaction was used to analyze at nucleotide resolution the repair of cyclobutane pyrimidine dimers along the p53 gene in ultraviolet-irradiated human fibroblasts. Repair rates at individual nucleotides were highly variable and sequence-dependent. Slow repair was seen at seven of eight positions frequently mutated in skin cancer, suggesting that repair efficiency may strongly contribute to the mutation spectrum in a cancer-associated gene.

Optimization of photopolymerized bioerodible hydrogel properties for adhesion prevention.

Abstract: The aim of this study was to optimize the properties of a lubricious bioerodible hydrogel barrier for the prevention of postoperative adhesions. Water-soluble macromers based on block copolymers of poly(ethylene glycol) (PEG) and poly(lactic acid) or poly(glycolic acid) with terminal acrylate groups were used, and these macromers were gelled in vivo by exposure to long wavelength ultraviolet light. The precursor was photopolymerized from buffered saline solution while in contact with the tissues. This resulted in the conformal coating of the tissue with an adherent hydrogel film, while forming a nonadhesive barrier at the free surface, on the treated wound site. The hydrogels were evaluated in two animal models of postsurgical adhesions, first in a rat cecum abrasion model and then in a rabbit uterine horn ischemia model. In the rat cecum model, six of seven animals treated with a hydrogel, with glycolide in the precursor as the comonomer, showed no adhesions; untreated animals and animals treated with precursor, but not gelled with light, showed consistent dense adhesions. In the rabbit uterine horn ischemia model, using hydrogels with lactide in the precursor as the comonomer, and PEG of molecular weight from 6,000 to 18,500 Da, adhesions were dramatically reduced, with occurrence in none of seven animals treated with a gel containing PEG 10,000. By contrast, the seven animals in the control group demonstrated a mean of 35% involvement of the horn length in dense, fibrous adhesions. These materials, photopolymerized in vivo in direct contact with the tissues, appear to form an adherent hydrogel barrier that is highly effective in reducing postoperative adhesions in the models used.(ABSTRACT TRUNCATED AT 250 WORDS) [on SciFinder (R)]

Ultraviolet light‐induced free radical formation in skin: an electron paramagnetic resonance study

Abstract: It has been suggested that ultraviolet light induces free radical formation in skin, leading to photoaging and cancer. We have demonstrated by electron paramagnetic resonance that the ascorbate free radical is naturally present in unexposed skin at a very low steady state level. When a section of SKH-1 hairless mouse skin in an EPR cavity is exposed to UV light (4,500 J m-2.s-1, Xe lamp, 305 nm cutoff and IR filters), the ascorbate free radical signal intensity increases. These results indicate that UV light increases free radical oxidative stress, consistent with ascorbate's role as the terminal, small-molecule antioxidant. The initial radicals produced by UV light would have very short lifetimes at room temperature; thus, we have applied EPR spin trapping techniques to detect these radicals. Using alpha-[4-pyridyl 1-oxide]-N-tert-butyl nitrone (POBN), we have for the first time spin trapped a UV light-produced carbon-centered free radical from intact skin. The EPR spectra exhibited hyperfine splittings that are characteristic of POBN/alkyl radicals, aN = 15.56 G and aH = 2.70 G, possibly generated from membrane lipids as a result of beta-scission of lipid alkoxyl radicals. Iron can act as a catalyst for free radical oxidative reactions; chronic exposure of skin to UV radiation causes increased iron deposition. Using our spin trapping system, we have shown that topical application of the iron-chelator, Desferal, to a section of skin reduces the UV light-induced POBN adduct radical signal.(ABSTRACT TRUNCATED AT 250 WORDS)

Phenolic components of the plant cell wall.

Abstract: Publisher Summary This chapter focuses on phenolic components of the plant cell wall. Phenol is the structural component common to all phenolic compounds. Both lignin and suberin are phenolic, or phenol-rich polymers, and their role in the life of the plant is well established. The chapter discusses lignin and phenolic acids in detail. There is also a description of other phenolic components in the plant cell wall such as cutin and suberin, which are lipophilic polymers. Sporopollenin is a highly resistant polymer found in the outer pollen wall of higher plants. Lignin is often present in the primary cell walls of fibers, xylem vessels, and tracheids. Lignin can be stained cytochemically by using a range of relatively specific reagents, including phloroglucinol-HCl, which responds to the cinnamaldehyde groups present in lignin. Phenolic compounds can also be detected in situ by their autofluorescence under ultraviolet light. During development, lignification often begins in the middle lamellae and primary cell walls and only later spreads into the secondary wall layers; in other tissues, however, only the secondary walls lignify. The lignin content of tissues can change quantitatively and qualitatively in response to various stimuli.

Synthesis and processing of silicon nanocrystallites using a pulsed laser ablation supersonic expansion method

Abstract: We report the preparation of nanometer sized crystallites of silicon by a pulsed laser ablation supersonic expansion technique. High resolution transmission electron microscopy is used to verify that particles with diameter in the range of ∼3 nm and greater are produced. Glancing angle x‐ray diffraction results confirm that the particles formed have the silicon diamond cubic crystal structure. Visible photoluminescence emission from self‐supporting thin films of agglomerated nanocrystallites is observed under excitation with ultraviolet light.

Luminescent microbanding in speleothems: High-resolution chronology and paleoclimate

Abstract: When illuminated by ultraviolet light, many calcite speleothems (stalagmites, stalactites, flowstones) display luminescence caused by the presence of organic (humic) substances occluded in the calcite. The amplitude of luminescence varies in a banded pattern parallel to growth layering. Through 14 C and thermal ionization mass spectrometry uranium-series dating, we show that cyclical oscillations in the luminescence have periodicities ranging from a few days to ≥10 5 yr. A well-defined annual cycle is present in many vadose-zone speleothems and can be used to define the chronology of short-term events. This cycle is probably a response to hydrological events in the recharge to the cave. Longer term oscillations are inferred to be controlled by climate, through its effect on organic activity in the overlying soil.

Accumulation of UV-absorbing flavonoids induced by UV-B radiation in Arabidopsis thaliana L.

Abstract: Irradiation of Arabidopsis with ultraviolet (UV) light resulted in intensity- and wavelength-dependent increases in the levels of a small family of UV-absorbing flavonoids, which accumulate in the aerial parts of the plants. A gradient of sensitivity to UV-B radiation is described in the different leaves of developingArabidopsis plants whereby the earliest formed leaves become damaged by UV-B faster and more extensively than later formed leaves. This UV-sensitivity gradient tightly parallels differences in constitutive as well as UV-induced levels of flavonoid accumulation among the various leaves, suggesting a direct role of flavonoids in protection against damage by UV radiation. The level of accumulated flavonoids, both constitutive and UV-induced, in each leaf appear to be dependent on the specific developmental state of each leaf as well as the overall developmental state of the plant. The UV-mediated flavonoid response, along with the observed UV-induced damage, appear not to be systemic in Arabidopsis but restricted very closely to the irradiated areas of leaves.

Fiber optic microcable produced with fiber reinforced ultraviolet light cured resin and method for manufacturing same

Abstract: The invention provides a fiber reinforced optical microcable comprised of a buffered optical waveguide coated with a fiber reinforced protective sheath made of a fiber reinforced, ultraviolet light cured resin over which is formed an ultraviolet light cured resin overcoat. The protective sheath is manufactured by soaking reinforcing fibers in the UV curable resin, placing the wetted fibers around the buffered optical waveguide, feeding both the fibers and buffered optical waveguide through a die, and curing the resin with ultraviolet light. Then, an ultraviolet light cured resin is flow coated over the protective sheath and cured with ultraviolet light to complete the microcable.

Effect of Noble Gas Doping in Single-Bubble Sonoluminescence

Abstract: The trillionfold concentration of sound energy by a trapped gas bubble, so as to emit picosecond flashes of ultraviolet light, is found to be extremely sensitive to doping with a noble gas. Increasing the noble gas content of a nitrogen bubble to about 1% dramatically stabilizes the bubble motion and increases the light emission by over an order of magnitude to a value that exceeds the sonoluminescence of either gas alone. The spectrum also strongly depends on the nature of the gas inside the bubble: Xenon yields a spectral peak at about 300 nanometers, whereas the helium spectrum is so strongly ultraviolet that its peak is obscured by the cutoff of water.

Armoire adaptable to a sauna, drum dryer, and tubular lighted clothing dryer with humidity damper control of exhaust gases

Abstract: A dryer has an internal drying chamber for accommodating articles that are subjected to heated circulating air to remove moisture from the articles. An air mixing chamber contains a first fan for moving air through a heater into the drying chamber. A second fan draws air out of the drying and mixing chambers and discharges air back into the mixing chamber through a filter into the external environment. The heated air in the drying chamber is mixed with fresh air and recirculated through the drying chamber to minimize heat losses and increase drying effectiveness. Ultraviolet lamps within the drying chamber destroy contaminants in the air and articles within the chamber. A boot dryer, located in the drying chamber, has fans that move air through tubes used to support boots, shoes, skates and socks. Ultraviolet light in the boot chamber destroys contaminants in the air in the boot chamber. One modification of the dryer has a bench to permit the dryer to be used as a dry sauna. A further modification of the dryer has a rotatable tumbler for accommodating articles to be dried.

Bone Cell Expression on Titanium Surfaces is Altered by Sterilization Treatments

Abstract: Phenotypic responses of rat calvarial osteoblast-like cells (RCOB) were evaluated on commercially pure titanium (cpTi) surfaces when cultured at high density (5100 cells/mm2). These surfaces were prepared to three different clinically relevant surface preparations (1-micron, 600-grit, and 50-microns-grit sand-blast), followed by sterilization with either ultraviolet light, ethylene oxide, argon plasma-cleaning, or routine clinical autoclaving. Osteocalcin and alkaline phosphatase, but not collagen expression, were significantly affected by surface roughness when these surfaces were altered by argon plasma-cleaning. In general, plasma-cleaned cpTi surfaces demonstrated an inverse relationship between surface roughness and phenotypic markers for a bone-like response. On a per-cell basis, levels of the bone-specific protein, osteocalcin, and the enzymatic activity of alkaline phosphatase were highest on the smooth 1-micron polished surface and lowest on the roughest surfaces for the plasma-cleaned cpTi. Detectable bone cell expression can be altered by clinically relevant surfaces prepared by standard dental implant preparation techniques.

DNA repair rates mapped along the human PGK1 gene at nucleotide resolution.

Abstract: The repair of cyclobutane pyrimidine dimers (CPDs), DNA lesions induced by ultraviolet light, was studied at nucleotide resolution. Human fibroblasts were irradiated with ultraviolet light and allowed to repair. The DNA was enzymatically cleaved at the CPDs, and the induced breaks along the promoter and exon 1 of the PGK1 gene were mapped by ligation-mediated polymerase chain reaction. Repair rates within the nontranscribed strand varied as much as 15-fold, depending on nucleotide position. Preferential repair of the transcribed strand began just downstream of the transcription start site but was most pronounced beginning at nucleotide +140 in exon 1. The promoter contained two slowly repaired regions that coincided with two transcription factor binding sites.

Method and apparatus for reducing etching erosion in a plasma containment tube

Abstract: A method and apparatus is provided for reducing wall erosion in a plasma containment tube (20), such as, for example, a quartz plasma tube (20) used in a microwave-induced plasma reaction process for etching semiconductor wafers. A pure benign or non-corrosive gas (Ar) is introduced into the "upstream" section (22a) of the tube (22), where the microwave energy is imparted to create a plasma. The activated benign gas flows "downstream" through a flange (28), preferably made of quartz, which is seated on o-rings (50) inside a water-cooled metal flange (48). These sealing o-rings (50) are thus cooled and removed from the ultraviolet light created by the plasma. The corrosive etchant gas (SF6) is introduced into the "downstream" section (22b) of the tube (22) beyond the flange (28), where it is activated by the benign gas (Ar). The benign gas (Ar) flows principally along the inner sidewalls of the tube (22), and the etchant gas (SF6) is thus principally contained by the benign gas (Ar) in the center of this section (22b) of the tube. This "downstream" section (22b) of the tube (22) is surrounded by a water jacket (24), which channels coolant around the outer surface of the tube (22b). Consequently, etching erosion of the inner surface of the tube (22) is minimized in the "upstream" or microwave section (22a) where the plasma is hottest, and also in the "downstream" section (22b) where the corrosive etchant gas (SF6) is activated.

Nitric oxide and human skin blood flow responses to acetylcholine and ultraviolet light.

Abstract: Nitric oxide (NO) is a potent endogenous vasodilator of large blood vessels but its role in the physiological and pathological control of the human microcirculation is not known. This study was designed to assess whether NO contributes to the control of blood flow in the human skin microcirculation in vivo. Local changes in blood flow were measured in the forearm skin microcirculation of normal volunteers. The responses to agents injected intradermally were assessed with a laser Doppler flow probe. NO was generated in local areas of skin by the injection of the NO donor, sodium nitroprusside. Endogenous NO was generated by the injection of acetylcholine and the exposure of skin to ultraviolet light (UVB) to stimulate the constitutive and inducible forms of nitric oxide synthase (NOS), respectively. The skin microvasculature was comparatively insensitive to exogenous NO derived from the NO donor sodium nitroprusside, being 10,000-fold more sensitive to the vasodilator prostaglandin PGE2 (P < 0.001). However, the rapid onset, dose-dependent local vasodilation caused by acetylcholine was blocked by the NOS inhibitor NG-monomethyl-L-arginine, L-NMMA (P < 0.05), but not by the cyclooxygenase inhibitor indomethacin. The delayed local blood flow response to UVB was attenuated by either L-NMMA or indomethacin (P < 0.05 in each case). The UVB response was abolished by a combination of L-NMMA and indomethacin or by local, topical corticosteroid treatment (P < 0.01 in each case). This study indicates that NO increases blood flow in the human microcirculation in vivo. NOS inhibition attenuated both the rapid blood flow response to acetylcholine and the delayed response to UVB. Both NOS and cyclooxygenase contributed to the erythema response to UVB, and dual inhibition of both enzymes would explain the mechanism of action of the corticosteroid in this model of inflammation.