Study about the radionuclides implanted on glass surfaces for the estimation of retrospective indoor radon concentrations.

Indoor radon retrospective dosimetry can be performed by measuring the 210Po activity concentration deposited on surfaces. An experimental study about the implantation of 210Po on mirrors exposed to radon has been performed. Two cases were studied: exposure to high and low 222Rn concentrations. Results were compared with those calculated by using the activity evolution equations. Experimental results can be only explained assuming additional deposition of the long-lived 222Rn descendants.

Measuring radon concentrations and estimating dose in tourist caves.

Caves and mines are considered to be places of especial risk of exposure to (222)Rn. This is particularly important for guides and workers, but also for visitors. In the Extremadura region (Spain), there are two cave systems in which there are workers carrying out their normal everyday tasks. In one, visits have been reduced to maintain the conditions of temperature and humidity. The other comprises several caves frequently visited by school groups. The caves were radiologically characterised in order to estimate the dose received by workers or possible hazards for visitors.

Radon in underground waters as a natural analogue to study the escape of CO2 in geological repositories.

Activity concentrations of dissolved (222)Rn and (226)Ra were measured in several underground aquifers, which are candidates for repositories or for the study of analogue natural escapes of CO2. The concentration of both radionuclides in water was determined using liquid scintillation counting. The values obtained for the (222)Rn concentrations varied from 0 to 150 Bq l(-1), while the levels of (226)Ra were in general very low. This indicates that (222)Rn is coming from the decay of the undissolved (226)Ra existing in the rocks and deep layers of the aquifers, being later transported by diffusion in water.

Experimental studies about the ratio between 210Po deposited on surfaces and retrospective indoor 222Rn concentrations.

Measurements of radon concentration may not be sufficiently representative for the cumulative total exposure suffered by a person throughout his life. Retrospective dosimetry can help estimating from the direct measurement of 210Po (descendant of 222Rn) implanted on surfaces, because this quantity is related (through the conversion factor) with the mean indoor 222Rn concentration existing in a room for long time. This factor depends on multiple variables. Theoretical models can provide some values. Experiments are tedious and very time consuming. The 210Po activity concentration was measured in mirrors, which were previously exposed to 222Rn concentrations under real environmental conditions. This work deals with the preliminary results in two known places (a room and a cave), which have very different characteristics, in order to show experimentally the large differences found in the values of this factor.

Influence of source composition and particle energy on the determination of gross alpha activity.

The influence of different source compositions and α-particle energies on the detection efficiency of a gas-flow proportional counter was examined using experimental measurements and Monte Carlo simulations. Efficiency variation with alpha-particle energy was very marked, being less significant with the substrate composition. These results show that the determination of gross alpha activity in an unknown sample must be carried out very carefully in order to give a correct estimation of its activity.

On the use of different scintillation cocktails for determining gross alpha and beta activities in water samples.

Gross alpha and beta indices for water samples are generally measured in environmental radioactivity laboratories. Liquid scintillation spectrometers can be used to determine these indices but different factors could affect the measurements. Several scintillation cocktails and different radionuclides have been used for calibration. Quenching effects must be considered for each cocktail because the results can be different depending of the calibration and cocktail used.

Gross alpha and beta indices in water samples revisited.

Gross α and ß indices for water samples are generally determined simultaneously when a gas-flow proportional counter is used. The thickness of the source and the α-particle energy are factors of great importance due to self-absorption or energy loss effects. Two variables have been studied: the use of different salts to produce standards with several thicknesses and the use of different radionuclides for the calibration process. Samples of known activity were prepared and measured for checking the procedures.

Additional contamination when radon is in excess.

A study of the behavior of the (222)Rn progeny on clothes, skin and hair has been performed in a place with very high radon concentration. In the past, radon concentration was established to be about 32 kBq/m(3) in a very high humidity environment inside a tourist cave in Extremadura (Spain). The results show that (222)Rn daughters are adhered on clothes, skin and hair, adding some radioactive concentration to that due to radon and its progeny existing in the breathable air.

Determination of alpha activity in solid samples by leaching or digestion.

The analysis of solid environmental samples by α-particle spectrometry generally involves processes requiring an initial treatment to destroy the complexes in the matrix, and dissolve the radionuclides of interest. This study compared the activities obtained for several natural radionuclides ((238)U, (234)U, (230)Th, (226)Ra, and (210)Po) in previously well-characterized materials, using two procedures: acid leaching and digestion in a microwave oven. The measured activities were in general very similar for the two procedures, with a strong statistical correlation between the two sets of values.

Radon in workplaces in Extremadura (Spain).

Indoor radon measurements are usually associated with housing. However, a typical person spends about one-third of the day at their workplace. A survey was made of radon levels in workplaces in Extremadura (Spain). More than 200 measurements were performed in some 130 firms and organizations of different sectors (urban wellness centres, spas, caves, mines, water management facilities, underground carparks, wine cellars, museums, etc.). Activated charcoal canisters and track detectors were used for sampling. The results indicated the importance of performing this type of measurement because the exposure of workers can reach high values in some cases.

Thermodynamics of cosolvent action: phenacetin, salicylic acid and probenecid.

The solubility of phenacetin, salicylic acid, and probenecid in ethanol-water and ethanol-ethyl acetate mixtures at several temperatures (15-40 degrees C) was measured. The solubility profiles are related to medium polarity changes. The apparent thermodynamic magnitudes and enthalpy-entropy relationships are related to the cosolvent action. Salicylic acid and probenecid show a single peak against the solubility parameter delta(1) of both solvent mixtures, at 40% (delta(1) = 21.70 MPa(1/2)) and 30% (delta(1) = 20.91 MPa(1/2)) ethanol in ethyl acetate, respectively. Phenacetin displays two peaks at 60% ethanol in ethyl acetate (23.30 MPa(1/2)) and 90% ethanol in water (delta(1) = 28.64 MPa(1/2)). The apparent enthalpies of solution display a maximum at 30% (phenacetin and salicylic acid) and 40% (probenecid) ethanol in water, respectively. Two different mechanisms, entropy at low ethanol ratios, and enthalpy at high ethanol ratios control the solubility enhancement in the aqueous mixture. In the nonaqueous mixture (ethanol-ethyl acetate) enthalpy is the driving force throughout the whole solvent composition for salicylic acid and phenacetin. For probenecid, the dominant mechanism shifts from entropy to enthalpy as the ethanol in ethyl acetate concentration increases. The enthalpy-entropy compensation plots corroborate the different mechanisms involved in the solubility enhancement by cosolvents.

Food-dependent exercise-induced anaphylaxis to pistachio.

We report the case of a 16-year-old male who, 30 minutes after beginning to play football with previous ingestion of pistachio nuts, experienced an anaphylactic reaction. Prick-by-prick test with roasted pistachios was negative. Specific IgE antibodies to pistachio, cashew nuts and mango were negative. An open oral challenge test with pistachio in resting conditions was negative. Treadmill ergonometric stress in a fasting state and 60 minutes after a meal without pistachio gave negative results. A specific food exercise challenge 60 minutes after ingestion of 50 g pistachio nuts was positive, showing mild diffuse erythema and small wheals in face and thorax. To the best of our knowledge, this is the first described case of specific food dependent exercise-induced anaphylaxis to pistachio. Negative allergologic tests is an unusual condition, since most cases appear to be IgE-mediated. In this case, a positive specific food exercise challenge test provided a definite diagnosis.

Visna/maedi virus Env protein expressed by a vaccinia virus recombinant induces cell-to-cell fusion in cells of different origins in the apparent absence of Env cleavage: role of glycosylation and of proteoglycans.

The in vivo productive infection by the ovine Visna/maedi lentivirus (VISNA) is restricted to cells of the monocyte/macrophage lineage. The basis for this restriction is not understood. Although the VISNA envelope (Env) glycoprotein is the main target for virus neutralization, studies on the role of this protein in virus infection are limited. A vaccinia virus recombinant (VV- env-MV) containing the entire VISNA env sequence was generated and shown to produce in infected cells a protein of about 165 kDa (referred to as gp150). During VV- env-MV infection, expression of env caused extensive cell-to-cell fusion in cell lines of different origins. Pulse-chase and Western blot analyses revealed that gp150 is not cleaved in VV- env-MV infected cells. The glycoprotein gp150 formed oligomers held by disulfide bonding. Cell-to-cell fusion was prevented in the presence of the inhibitor of glycosilation, tunicamycin, but it was markedly enhanced by an inhibitor of proteoglycan synthesis, beta-D-xyloside. These findings showed that the receptor for VISNA Env is widely distributed within cells, that fusion-from-within of cells can occur in the apparent absence of proteolytic cleavage of gp150, and that fusion require a glycosylated Env but not the addition of proteoglycan chains at the cell surface. This recombinant virus could have utility as a potential vaccine against VISNA.

Proteolytic processing in infectious bursal disease virus: identification of the polyprotein cleavage sites by site-directed mutagenesis.

The infectious bursal disease virus (IBDV), a member of the Birnaviridae family, is the causative agent of an immune depressive disease that affects domesticated and wild avian species. The expression strategy of IBDV includes the synthesis of a 110-kDa polyprotein containing the capsid precursor polypeptides. The polyprotein is autocatalitically processed rendering three polypeptides: NH2-VPX-VP4-VP3-COOH. We have carried out a systematic analysis, using a series of plasmids encoding polyproteins containing either deletions or single amino acid substitutions, to identify the processing sites. The results obtained showed the existence of two sites, 511LAA513 and 754MAA756, that are essential for the processing of the VPX-VP4 and VP4-VP3 precursors, respectively. These sequences are highly conserved among IBDV strains form serotypes 1 and 2. A secondary VPX-VP4 processing site was detected in a 19-amino acid stretch located upstream of the 511LAA513 site. Analyses using versions of the 754MAA756 VP4-VP3 processing site containing conservative and nonconservative amino acid substitutions demonstrated that the specificity of the cleavage is dictated by the conserved AA dipeptide.

Role of 5-lipoxygenase products in the local accumulation of neutrophils in dermal inflammation in the rabbit.

Studies were undertaken to define the role of 5-lipoxygenase (5-LO) products and, in particular, of leukotriene (LT) B4 in the polymorphonuclear leukocyte (PMN) emigration process using a rabbit model of dermal inflammation. Our results show that i.v. administration to rabbits of MK-0591, a compound that inhibits LT biosynthesis in blood and tissues when administered in vivo, significantly reduced 51Cr-labeled PMN accumulation in response to intradermally injected chemotactic agonists, including IL-8, FMLP, C5a, and LTB4 itself. In addition, pretreatment of the labeled PMN with MK-0591 ex vivo before their injection in recipient animals was equally effective in reducing 51Cr-labeled PMN emigration to dermal inflammatory sites. These results support a role for de novo synthesis of 5-LO metabolites by PMN for their chemotactic response to inflammatory mediators. Other studies demonstrated that elevated intravascular concentration of LTB4 interferes with PMN extravasation inasmuch as a continuous i.v. infusion of LTB4, in the range of 5-300 ng/min/kg, dose-dependently inhibited extravascular PMN accumulation to acute inflammatory skin sites elicited by the chemoattractants LTB4, FMLP, C5a, and IL-8 and by TNF-alpha, IL-1beta, and LPS; such phenomena may constitute a natural protective mechanism from massive tissue invasion by activated PMN in specific pathologic conditions such as ischemia (and reperfusion). These studies demonstrate additional functions of 5-LO products in the regulation of PMN trafficking, distinct from the well-characterized chemotactic activity of LTB4 present in the extravascular compartment.

Photoreactivation of ultraviolet radiation-induced skin and eye tumors of Monodelphis domestica.

Chronic exposure of the opossum Monodelphis domestica to UV radiation (UVR) leads to the formation of cutaneous and corneal tumors. Groups of shaved opossums were exposed 3 times/week to: (a) UVR alone; (b) UVR followed immediately by 1 h of photoreactivating light (PRL) (320-700 nm); (c) 1 h of PRL followed by UVR; and (d) 1 h of PRL alone. Exposures were terminated after 70 weeks of treatment. Analysis of data plotted as probability of tumor formation versus weeks from first exposure shows that post-UVR exposure to PRL significantly (P less than 0.005) delayed the time to appearance of cutaneous tumors from a 50% probability of tumor formation at 73 weeks for those animals exposed to UVR alone to 128 weeks for those animals exposed to PRL after UVR. Pre-UVR exposure to PRL delayed the appearance of tumors by 6 weeks when compared to the UVR alone group, but the difference between the two groups was not statistically significant. The yield (number of tumors/surviving animal) of cutaneous tumors at 70 and 110 weeks following initiation of treatments also was significantly less in those animals exposed to PRL after, but not before, UVR. Based on the specificity of the PR repair pathway to act only on pyrimidine dimers, these results suggest that dimers are involved in the induction of cutaneous tumors. The results obtained with the induction of corneal tumors are more difficult to interpret. While exposure to PRL significantly delayed the appearance of corneal tumors, the magnitude of the effect was the same regardless of whether the PRL was given before or after each UVR exposure.