Resistance to schistosome infection in Biomphalaria glabrata induced by gamma radiation

Two strains of Biomphalaria glabrata were studied with respect to the effects of ionizing radiation on their susceptibility to Schistosoma mansoni infection. Gamma radiation at levels of 3.5 and 5 krad did not induce susceptibility in the resistant S-3 strain, but was found to initiate resistance in the susceptible PR-1 strain. In an attempt to understand the induced resistance in irradiated snails, histopathologic examinations and analyses of snail hemolymph were performed. Results indicated that miracidia invading irradiated snails were quickly surrounded and encapsulated by amoebocytes. Similarly, alterations in the hemolymph of irradiated snails suggested that radiation induced aging. It is suggested that radiation-altered snails may be of value in studying the defense mechanisms of these organisms.     

Mortality of plastic-ware workers exposed to radiofrequencies

The mortality experience of a cohort of Italian plastic-ware workers exposed to radiofrequency (RF)-electromagnetic fields generated by dielectric heat sealers was investigated. Follow-up extended from 1962 to 1992. The standardised mortality ratio (SMR) analysis was restricted to 481 women workers, representing 78% of the total person-years at risk. Mortality from malignant neoplasms was slightly elevated, and increased risks of leukemia and accidents were detected. The all-cancer SMR was higher among women employed in the sealing department, where exposure to RF occurred, than in the whole cohort. This study raises interest in a possible association between exposure to RF radiation and cancer risk. However, the study power was very small, and the possible confounding effects of exposure to solvents and vinyl chloride monomer (VCM) could not be ruled out. The hypothesis of an increased risk of cancer after radiofrequency exposure should be further explored by means of analytical studies characterised by adequate power and more accurate exposure assessment. Bioelectromagnetics 18:418–421, 1997. © 1997 Wiley-Liss, Inc.     

Question 2: Relation of Panspermia-Hypothesis to Astrobiology

In the answer to major questions of astrobiology and chirality, the panspermia-hypothesis is often discussed as the only proposal of transportation of life to the Earth. On the basis of the known presence of ionizing radiation in the space, assumed on the level calculated by Clark (Orig Life Evol Biosph 31:185–197, 2001), the hypothesis is rejected as the explanation of origins of life on Earth. In fact, comparatively low doses of radiation sterilize irreversibly all biological material. Sufficiently long sojourn in space of objects containing prebiotic chemical blocks also does not contribute to the origins of life on Earth, because of elimination of homochirality, if any, and of radiation induced reactions of dehydrogenation, decarboxylation and deamination of chemical compounds closing with complete decomposition of organics, leaving elementary nano-carbon and/or minerals like calcium carbonate. Presented at the International School of Complexity – 4th Course: Basic Questions on the Origins of Life; “Ettore Majorana” Foundation and Centre for Scientific Culture, Erice, Italy, 1–6 October 2006.     

Use of Radiation Hybrid panels to map genetic loci

The mapping of genetic loci within organisms has been accelerated by the advent of Radiation Hybrid (RH) panels. These panels are available for humans and non-humans including mice, baboon, rat, and canine. This article contains a general protocol for the use of the Genebridge 4 whole genome RH panel to map a human locus. This protocol may also be adjusted to suit the other RH panels currently available.     

In vitro fertilization of mouse ova by spermatozoa exposed isothermally to radio-frequency radiation

Mouse spermatozoa were exposed in vitro for 1 h to 27- or 2,450-MHz CW RF radiation at SARs of 0 to 90 W/kg under isothermal (37 +/- 0.2 degrees C) conditions. Exposure at either frequency to RF radiation at SARs of 50 W/kg or greater resulted in a statistically significant reduction in the ability of irradiated sperm to fertilize mouse ova in vitro (P less than .05). Over the range of SARs there was no apparent difference in the effects of 27- vs. 2,450-MHz RF radiation. There were no readily detectable exposure effects on spermatozoan morphology, ultrastructure, or capacitation. The reduction of in vitro fertilization is attributed to a direct effect of RF radiation on spermatozoa rather than to heating.     

Stomatal Responses of Bean (Phaseolus Vulgaris L.) Leaves to Changing Irradiance,Air Humidity,and Water Potential of Root Medium

Stomatal responses of attached bean (Phaseolus vulgaris L.) leaves to changing spectral composition ("white" - WL., blue - BL, or red - RL radiation), air humidity (100 % or about 4 % RH), and water potential of the root medium (close to 0 or −1.2 MPa) were determined by air flow porometer. Opening of stomata always increased under BL and decreased under RL. In response to decline in air humidity, leaf conductance showed transient increase before it reached lowered steady state. BL enhanced and RL diminished this response. This revised version was published online in June 2006 with corrections to the Cover Date.     

Stress proteins are not induced in mammalian cells exposed to radiofrequency or microwave radiation

The induction of stress proteins in HeLa and CHO cells was investigated following a 2 h exposure to radiofrequency (RF) or microwave radiation. Cells were exposed or sham exposed in vitro under isothermal (37 ± 0.2 °C) conditions. HeLa cells were exposed to 27- or 2450 MHz continuous wave (CW) radiation at a specific absorption rate (SAR) of 25 W/kg. CHO cells were exposed to CW 27 MHz radiation at a SAR of 100 W/kg. Parallel positive control studies included 2 h exposure of HeLa or CHO cells to 40 °C or to 45 μM cadmium sulfate. Stress protein induction was assayed 24 h after treatment by electrophoresis of whole-cell extracted protein labeled with [³⁵S]-methionine. Both cell types exhibited well-characterized responses to the positive control stresses. Under these exposure conditions, neither microwave nor RF radiation had a detectable effect on stress protein induction as determined by either comparison of RF-exposed cells with sham-exposed cells or comparison with heat-stressed or Cd⁺⁺ positive control cells. Bioelectromagnetics 18:499–505, 1997. © 1997 Wiley-Liss, Inc.     

Sediment-Associated Phototoxicity to Aquatic Organisms

Phototoxicity is a two to greater than 1000-fold increase in chemical toxicity caused by ultraviolet radiation (UV), which has been demonstrated in a broad range of marine and freshwater fish, invertebrates, and other aquatic organisms in water column exposures. Field collected sediments containing polycyclic aromatic hydrocarbons (PAHs) and other contaminants are phototoxic to sediment-dwelling organisms in laboratory tests, but in situ or field investigations of phototoxicity have not been reported. Sediment provides a pathway for the bioaccumulation of phototoxic chemicals through contact with and ingestion of bedded and suspended sediment, and maternal transfer, but risks are uncertain. Risks from sediment-associated phototoxicity will be greatest in areas of both high contaminant exposure (e.g., surficial and suspended sediments in harbors, outfall areas, and spill sites), and high UV exposure (e.g., high optical clarity or shallow depths). Organisms and life-stages most at risk will be those translucent to UV that inhabit the photic zone and near shore areas, but benthic organisms may have generally low UV exposure because of life history and morphological characteristics. Site-specific assessments are needed to characterize risks both spatially and temporally because of heterogeneous sediment contamination and large differences in species sensitivity and exposure pathways.     

Testicular function of rats following exposure to microwave radiation

Male Sprague-Dawley rats were exposed for 6 h per day for nine days to pulse-modulated microwave radiation (1.3 GHz, at 1-microseconds pulse width, 600 pulses per second). Exposures were carried out in cylindrical waveguide sections at a mean dose rate of 6.3 mW/g; sham controls were treated similarly and received no irradiation. At time periods corresponding to 0.5, 1.0, 2.0, and 4.0 cycles of the seminiferous epithelium, groups of four sham-irradiated and four irradiated rats were killed and the testes removed for analysis. Net mass of the testes, epididymides, and seminal vesicles; daily sperm production (DSP) per testis and per gram of testis; sperm morphology; and the number of epididymal sperm were determined. There were no statistically significant differences between the sham-irradiated and irradiated groups with respect to any measured variable. In a group of seven surrogate animals of similar body mass, the dose rate of 6.3 mW/g caused a net change in body temperature (via rectal probe) of 1.5 degrees C.     

Canopy photosynthesis of six major arable crops is enhanced under diffuse light due to canopy architecture

Diffuse radiation generally increases photosynthetic rates if total radiation is kept constant. Different hypotheses have been proposed to explain this enhancement of photosynthesis, but conclusive results over a wide range of diffuse conditions or about the effect of canopy architecture are lacking. Here, we show the response of canopy photosynthesis to different fractions of diffuse light conditions for five major arable crops (pea, potato, wheat, barley, rapeseed) and cover crops characterized by different canopy architecture. We used 13 years of flux and microclimate measurements over a field with a typical 4 year crop rotation scheme in Switzerland. We investigated the effect of diffuse light on photosynthesis over a gradient of diffuse light fractions ranging from 100% diffuse (overcast sky) to 11% diffuse light (clear‐sky conditions). Gross primary productivity (GPP) increased with diffuse fraction and thus was greater under diffuse than direct light conditions if the absolute photon flux density per unit surface area was kept constant. Mean leaf tilt angle (MTA) and canopy height were found to be the best predictors of the diffuse versus direct radiation effect on photosynthesis. Climatic factors, such as the drought index and growing degree days (GDD), had a significant influence on initial quantum yield under direct but not diffuse light conditions, which depended primarily on MTA. The maximum photosynthetic rate at 2,000 µmol m^?2 s^?1 photosynthetically active radiation under direct conditions strongly depended on GDD, MTA, leaf area index (LAI) and the interaction between MTA and LAI, while under diffuse conditions, this parameter depended mostly on MTA and only to a minor extent on canopy height and their interaction. The strongest photosynthesis enhancement under diffuse light was found for wheat, barley and rapeseed, whereas the lowest was for pea. Thus, we suggest that measuring canopy architecture and diffuse radiation will greatly improve GPP estimates of global cropping systems.     

Ultra-violet radiation damage to Metarhizium flavoviride conidia and the protection given by vegetable and mineral oils and chemical sunscreens

Metarhizium flavouiride conidia formulated in oil or water were exposed to simulated solar radiation. Radiation below 320 nm killed conidia and caused delays in the germination of survivors; germination was greater after 48 h of incubation than after 24 h. UV exposure of conidia formulated in oil for 2 h reduced germination from 99% to 37.5% after incubation for 48 h. Exposure of conidia in water to UV for 1 h resulted in 4.7% germination after 24 h incubation compared with 36.5% for conidia formulated in oil. The addition of 1% oxybenzone resulted in 81.9% conidial germination after 3 h exposure and 48 h incubation compared with 28.1% in oil without the sunscreen.     

The physiological response of winter wheat to reductions in plant density

The effects of reducing the plant density of winter wheat (cv. Haven) on canopy formation, radiation absorption and dry matter production and partitioning were investigated in field experiments in 1996/97 and 1997/98. Crop densities established ranged from 19 to 338 plants m^?2. Grain yield was maintained with large reductions in plant density. At low plant densities the relative growth rate of the crop increased allowing a maintenance of crop dry matter production. An 18 fold reduction in plant density led only to a six fold reduction in green area index at the beginning of stem extension and by anthesis the difference was less than two fold. Crops grown at low plant densities increased green area per plant through increased duration of tiller production, green area per shoot and shoot survival. Main stem leaf number, phyllochron and tiller production rate were not significantly affected by plant density. Radiation use efficiency was greater at the low plant densities. We propose that better radiation distribution through the canopy and increased canopy nitrogen ratio were the causative mechanisms for this increase in RUE. As a result of increased green area per shoot and a decrease in ear production, more radiation was absorbed per shoot at the low plant densities, allowing an increase in grain number per ear from 32 to 48.     

Response of 19 cultivars of soybeans to ultraviolet-B irradiance

Nineteen soybean cultivars were grown for four weeks in controlled environmental chambers with artificial daylight supplemented by five UV-B irradiance regimes to determine the range of growth and development responses of seedlings. Data from nine plant characteristics were assessed: leaf area, dry weight of leaves, stems and roots, total plant dry weight, height, ratio of roots to shoots and leaf area to weight and rating of leaves for damage. Significant differences were observed in the responses noted. Stunting, leaf chlorosis and loss of apical dominance were three general symptoms apparent on all cultivars which received UV-B irradiance. Varying degrees of reduced leaf area and dry weight of the plants and altered ratios of weights of leaves per unit area and weight of roots to shoots were also found. It was concluded that different soybean cultivars demonstrate a marked difference in sensitivity to UV-B radiation under the artificial conditions of controlled environmental growth chambers and this may indicate a genetic basis for variability in sensitivity of soybean cultivars to this waveband. However, the sensitivity to UV-B radiation was increased by the lower than normal photon fluence of photosynthetically active radiation (225 μE m⁻² s⁻¹).     

Morphological and physiological responses of bean plants to supplemental UV radiation in a Mediterranean climate

During the last few decades many experiments have been performed to evaluate the responses of plants to enhanced solar UV-B radiation (280–320 nm) that may occur because of stratospheric ozone depletion; most of them were performed in controlled environment conditions where plants were exposed to low photosynthetically active radiation (PAR) levels and high UV-B irradiance. Since environmental radiative regimes can play a role in the response of plants to UV-B enhancement, it appears doubtful whether it is valid to extrapolate the results from these experiments to plants grown in natural conditions. The objective of this work was to evaluate the effects on physiology and morphology of a bean (Phaseolus vulgaris L.) cultivar Nano Bobis, exposed to supplemental UV radiation in the open-air. UV-B radiation was supplied by fluorescent lamps to simulate a 20% stratospheric ozone reduction. Three groups of plants were grown: control (no supplemental UV), UV-A treatment (supplementation in the UV-A band) and UV-B treatment (supplemental UV-B and UV-A radiation). Each group was replicated three times. After 33 days of treatment plants grown under UV-B treatment had lower biomass, leaf area and reduced leaf elongation compared to UV-A treatment. No significant differences were detected in photosynthetic parameters, photosynthetic pigments and UV-B absorbing compounds among the three groups of plants. However, plants exposed to UV-A treatment showed a sort of 'stimulation' of their growth when compared to the control. The results of this experiment showed that plants may be sensitive to UV-A radiation, thus it is difficult to evaluate the specific effects of UV-B (280–320 nm) radiation from fluorescent lamps and it is important to choose the appropriate control. Environmental conditions strongly affect plant response to UV radiation so further field studies are necessary to assess the interaction between UV-B exposure and meteorological variability.     

Functional morphogenesis from embryos to adults: Late development shapes trophic niche in coral reef damselfishes

The damselfishes are one of the dominant coral reef fish lineages. Their ecological diversification has involved repeated transitions between pelagic feeding using fast bites and benthic feeding using forceful bites. A highly‐integrative approach that combined gene expression assays, shape analyses, and high‐speed video analyses was used to examine the development of trophic morphology in embryonic, larval, juvenile, and adult damselfishes. The anatomical characters that distinguish pelagic‐feeding and benthic‐feeding species do not appear until after larval development. Neither patterns of embryonic jaw morphogenesis, larval skull shapes nor larval bite mechanics significantly distinguished damselfishes from different adult trophic guilds. Analyses of skull shape and feeding performance identified two important transitions in the trophic development of a single species (the orange clownfish; Amphiprion percula): (a) a pronounced transformation in feeding mechanics during metamorphosis; and (b) more protracted cranial remodeling over the course of juvenile development. The results of this study indicate that changes in postlarval morphogenesis have played an important role in damselfish evolution. This is likely to be true for other fish lineages, particularly if they consist of marine species, the majority of which have planktonic larvae with different functional requirements for feeding in comparison to their adult forms.     

Changes in morphological, photosynthetic and physiological responses of Mono Maple seedlings to enhanced UV-B and to nitrogen addition

In the southeast of the Qinghai-Tibetan Plateau of China, Mono Maple is a common species in reforestation processes. The paper mainly investigated the changes in morphological, photosynthetic and physiological responses of Mono Maple seedlings to UV-B radiation, nitrogen supply and their combination. The experimental design included two levels of UV-B treatments (ambient UV-B, 11.02 KJ m⁻² day⁻¹; enhanced UV-B, 14.33 KJ m⁻² day⁻¹) and two nitrogen levels (0; 20 g N m⁻² a⁻¹)—to determine whether the adverse effects of UV-B on plants are eased by nitrogen supply. Enhanced UV-B caused a marked decline in growth parameters, net photosynthetic rate, and photosynthetic pigments, whereas it induced an increase in reaction oxygen species (hydrogen peroxide accumulation and the rate of superoxide radical production) and malondialdehyde content. Enhance UV-B also induced an increase in antioxidant compounds of Mono Maple, such as UV-B absorbing compounds, proline content, and activities of antioxidant enzymes (peroxidase, superoxide dimutase and catalase). On the other hand, nitrogen supply caused an increase in some growth parameters, net photosynthetic rate, photosynthetic pigments and antioxidant compounds (peroxidase, proline content and UV-B absorbing compounds), and reduced the content of reaction oxygen species (H₂O₂ accumulation, the rate of O₂⁻ production) and malondialdehyde content under ambient UV-B. However, under enhanced UV-B, nitrogen supply inhibited some growth parameters, and increased H₂O₂ accumulation, the rate of O₂⁻ production and MDA content, though proline content, UV-B absorbing compounds and activities of POD and SOD increased. These results implied that enhanced UV-B brought harmful effects on Mono Maple seedlings and nitrogen supply made plants more sensitive to enhanced UV-B, though increased some antioxidant activity.     

陆生植物体内酶系统对UV-B辐射增强的响应

臭氧层减薄导致地表中波紫外线UV-B(280～320 nm)辐射的增强,UV-B辐射能量远高于可见光,且能被植物体内蛋白质和核酸等生物大分子吸收.酶是植物体内起催化作用的一类蛋白质,酶的数量和活性对UV-B辐射增强有强烈的响应.本文将近年来增强UV-B辐射对植物体内酶影响的研究工作进行了综述.主要包括抗氧化酶、核酮糖-1,5-二磷酸羧化酶、硝酸还原酶和谷氨酰胺合成酶.并就今后该方面的研究提出建议.