An alternative methodology to determine 210Pb activity soil profiles.

Unsupported 210Pb (Pbexc) is generated in air and is subsequently deposited on soil surface. The Pbexc can be used for sediment dating, soil erosion/sedimentation and air mass studies. In many cases, 210Pb activity determination (gamma ray 46.5 keV) cannot be performed due to the lack of efficiency calibration curve, especially when radioactive patron source is not available. This work presents an alternative methodology to obtain the 210Pb activity values, based on the activity definition and the attenuation coefficient determinations and assuming that soil samples coming from depth higher than 25 cm only contain 210Pb generated in the soil (Pbexc free, i.e., for those soil layers the 210Pb activity is equal to the 226Ra activity, at secular equilibrium). The proposed methodology was evaluated using soils from La Plata region, Argentina. The same soil samples were also analyzed in a second laboratory by the conventional methodology. The obtained results indicated that the proposed procedure can be used as a good alternative in cases where a calibration sample is not available.

Annual variation of (7)Be soil inventory in a semiarid region of central Argentina.

Reliable information on environmental radionuclides atmospheric entrance, and their distribution along the soil profile, is a necessary condition for using these soil and sediment tracers to investigate key environmental processes. To address this need, (7)Be content in rainwater and the wet deposition in a semiarid region at San Luis Province, Argentina, were studied. Following these researches, in the same region, we have assessed the (7)Be content along a soil profile, during 2.5 years from September 2009 to January 2012. As expected, the specific activity values in soil samples in the wet period (November-April) were higher than in the dry period (May-October). During the investigated period (2009 - beginning 2012) and for all sampled points, the maximum value of the (7)Be specific activity (Bq kg(-1)) was measured at the surface level. A typical decreasing exponential function of (7)Be areal activity (Bq m(-2)) with soil mass depth (kg m(-2)) was found and the key distribution parameters were determined for each month. The minimum value of areal activity was 51 Bq m(-2) in August, and the maximum was 438 Bq m(-2) in February. The relaxation mass depth ranges from 2.9 kg m(-2) in March to 1.3 kg m(-2) in August. (7)Be wet deposition can explain in a very significant proportion the (7)Be inventory in soil. During the period of winds in the region (September and October), the (7)Be content in soil was greater than the expected contribution from wet deposition, situation that is compatible with a higher relative contribution of dry deposition at this period of the year.

Using (222)Rn as a tracer of geodynamical processes in underground environments.

Radon levels in two old mines in San Luis, Argentina, were measured and analyzed, with the aim to assess the potential use of this radioactive noble gas as a tracer of geological processes in underground environments. La Carolina gold mine and Los Cóndores tungsten mine are today used as tourism mines. CR-39 nuclear track detectors were used for this purpose. Measurements were performed during both winter and summer seasons. The findings show that in these environments, significant radon concentrations are subject to large seasonal fluctuations, due to the strong dependence on natural ventilation with the outside temperature variations. For both mines, higher concentration values of (222)Rn were observed in summer than in winter; with an extreme ratio of 2.5 times between summer and winter seasons for Los Cóndores mine. The pattern of radon transport inside La Carolina mine revealed, contrary to what was believed, that this mine behaves as a system with two entrances located at different levels. However, this feature can only be observed in the winter season, when there is a marked difference between the inside and outside temperatures of the mine. In the case of Los Cóndores mine, the radon concentration pattern distribution is principally established by air current due to chimney-effect in summer and winter seasons. In both cases, the analyses of radon pattern distribution appear as a good method to trace air currents, and then localize unknown ducts, fissures or secondary tunnels in subterranean environments.

Temporal evolution of ¹³7Cs⁺, K⁺ and Na⁺ in fruits of South American tropical species.

Concentrations of (137)Cs, K and Na in fruits of lemon (Citrus limon B.) and of K and Na in fruits of coconut (Cocos nucifera L.) trees were measured by both gamma spectrometry and neutron activation analysis, with the aim to understand the behaviour of monovalent inorganic cations in tropical plants as well as the plant ability to store these elements. Similar amounts of K(+) were incorporated by lemon and coconut trees during the growth and ripening processes of its fruits. The K concentration decreased exponentially during the growth of lemons and coconuts, ranging from 13 to 25 g kg(-1) dry weight. The incorporation of Na(+) differed considerably between the plant species studied. The Na concentration increased linearly during the lemon growth period (0.04 to 0.70 g kg(-1) d.w.) and decreased exponentially during the coconut growth period (1.4 to 0.5 g kg(-1) d.w.). Even though radiocaesium is not an essential element to plants, our results have shown that (137)Cs incorporation to vegetable tissues is positively correlated to K distribution within the studied tropical plant species, suggesting that the two elements might be assimilated in a similar way, going through the biological cycle together. A mathematical model was developed from the experimental data allowing simulating the incorporation process of monovalent inorganic cations by the fruits of such tropical species. The agreement between the theoretical approach and the experimental values is satisfactory along fruit development.

Assessment of 7Be content in precipitation in a South American semi-arid environment.

There are two naturally occurring radiogenic isotopes of beryllium, 7Be and ¹°Be. These are produced when cosmic radiation interacts with oxygen and nitrogen in the atmosphere. After production, these radionuclides are input to ecosystems through wet and dry deposition. In recent years 7Be and ¹°Be have proved to be powerful tools for studying dynamic processes that occur on the surface of the earth. We measured the 7Be content in precipitation at a semiarid location in central Argentina. From November 2006 to March 2009, 68 precipitation events were collected. Measured 7Be content ranged from 0.7±0.4 Bq L⁻¹ to 3.2±0.7 Bq L⁻¹, with a mean of 1.7 Bq L⁻¹ ±0.6 Bq L⁻¹. Beryllium-7 content of rainfall did not show clear relationships with amount of rainfall (mm), mean intensity (mm h⁻¹) or duration (h⁻¹), or elapsed time between events (day). The general results indicate that for the typical range of precipitation there was no atmospheric washout and that the reload of the atmosphere is not a relevant factor, but when the amount of precipitation is very high washout may occur. On the other hand, when the 7Be content was measured during single rain events, a high content of this radionuclide was found to be associated with very low rainfall intensity (≈3 mm h⁻¹), this suggests that rain intensity could affect the 7Be content. Using all data, a good linear relationship between 7Be deposition and rain magnitude was obtained (r²=0.82, p<0.0001). Because of this, the slope of this linear regression equation may be applied as a tool for tracing environmental processes that affect the surface of the earth. We can do this by directly estimating erosion/sedimentation processes using 7Be or by estimating the input of ¹°Be in the environment with the aim to evaluate land degradation phenomena.

Variability of 137Cs and 40K soil-to-fruit transfer factor in tropical lemon trees during the fruit development period.

In this investigation we evaluate the soil uptake of (137)Cs and (40)K by tropical plants and their consequent translocation to fruits, by calculating the soil-to-fruit transfer factors defined as F(v) = [concentration of radionuclide in fruit (Bq kg(-1) dry mass)/concentration of radionuclide in soil (Bq kg(-1) dry mass in upper 20 cm)]. In order to obtain F(v) values, the accumulation of these radionuclides in fruits of lemon trees (Citrus limon B.) during the fruit growth was measured. A mathematical model was calibrated from the experimental data allowing simulating the incorporation process of these radionuclides by fruits. Although the fruit incorporates a lot more potassium than cesium, both radionuclides present similar absorption patterns during the entire growth period. F(v) ranged from 0.54 to 1.02 for (40)K and from 0.02 to 0.06 for (137)Cs. Maximum F(v) values are reached at the initial time of fruit growth and decrease as the fruit develops, being lowest at the maturation period. As a result of applying the model a decreasing exponential function is derived for F(v) as time increases. The agreement between the theoretical approach and the experimental values is satisfactory.

External gamma-ray dose rate and radon concentration in indoor environments covered with Brazilian granites.

Health hazard from natural radioactivity in Brazilian granites, covering the walls and floor in a typical dwelling room, was assessed by indirect methods to predict external gamma-ray dose rates and radon concentrations. The gamma-ray dose rate was estimated by a Monte Carlo simulation method and validated by in-situ measurements with a NaI spectrometer. Activity concentrations of (232)Th, (226)Ra, and (40)K in an extensive selection of Brazilian commercial granite samples measured by using gamma-ray spectrometry were found to be 4.5-450 Bq kg(-1), 4.9-160 Bq kg(-1) and 190-2029 Bq kg(-1), respectively. The maximum external gamma-ray dose rate from floor and walls covered with the Brazilian granites in the typical dwelling room (5.0 m × 4.0 m area, 2.8 m height) was found to be 120 nGy h(-1), which is comparable with the average worldwide exposure to external terrestrial radiation of 80 nGy h(-1) due to natural sources, proposed by United Nations Scientific Committee on the Effects of Atomic Radiation. Radon concentrations in the room were also estimated by a simple mass balance equation and exhalation rates calculated from the measured values of (226)Ra concentrations and the material properties. The results showed that the radon concentration in the room ventilated adequately (0.5 h(-1)) will be lower than 100 Bq m(-3), value recommended as a reference level by the World Health Organization.

Short-term seasonal variability in 7Be wet deposition in a semiarid ecosystem of central Argentina.

The (7)Be wet deposition has been intensively investigated in a semiarid region at San Luis Province, Argentina. From November 2006 to May 2008, the (7)Be content in rainwater was determined in 58 individual rain events, randomly comprising more than 50% of all individual precipitations at the sampling period. (7)Be activity concentration in rainwater ranged from 0.7+/-0.3 Bq l(-1) to 3.2+/-0.7 Bq l(-1), with a mean value of 1.7 Bq l(-1) (sd=0.53 Bq l(-1)). No relationship was found between (7)Be content in rainwater and (a) rainfall amount, (b) precipitation intensity and (c) elapsed time between events. (7)Be ground deposition was found to be well correlated with rainfall amount (R=0.92). For the precipitation events considered, the (7)Be depositional fluxes ranged from 1.1 to 120 Bq m(-2), with a mean value of 32.7 Bq m(-2) (sd=29.9 Bq m(-2)). The annual depositional flux was estimated at 1140+/-120 Bq m(-2)y(-1). Assuming the same monthly deposition pattern and that the (7)Be content in soil decreases only through radioactive decay, the seasonal variation of (7)Be areal activity density in soil was estimated. Results of this investigation may contribute to a valuable characterization of (7)Be input in the explored semiarid ecosystem and its potential use as tracer of environmental processes.

Influence of crop types and soil properties on radionuclide soil-to-plant transfer factors in tropical and subtropical environments.

This paper presents a descriptive statistical analysis of radionuclide soil-to-plant transfer factors (Fv) for tropical and subtropical environments. These values were collected from previous databases and standard publications with the objective of contributing to the IAEA Technical Report Series: Handbook of parameter values for the prediction of radionuclide transfer to humans in terrestrial and freshwater environments. More than 2200 Fv values of different radionuclides were gathered and arranged into specific databases, detailing relevant information regarding the environments where this parameter was calculated. This study explores the dependence of Fv values to crop types, and soil properties. The wide variability and uncertainty observed in calculated Fv values were considerably reduced when the data was independently grouped into clusters containing the same radionuclide/plant group/soil type combinations. For each cluster the principal statistical quantities were determined. Using these quantities, the Fv distributions of each data set was explored. Fv probability distribution is discussed to clarify the use of this empirical parameter in radioecological and radiological assessment models.

Analysis of radionuclide transfer factors from soil to plant in tropical and subtropical environments.

In this study, the factors that influence the variability of soil to plant radionuclide transfer factors (TF) in tropical and subtropical environments were statistically analyzed. More than 2,700 TF values were obtained from the literature, and from this four broad soil groups and 13 plant groups were investigated. Additionally, different plant compartments were distinguished. The wide variability and uncertainty observed in TF is considerably reduced when data are independently grouped into groups of plant/plant part/soil type combinations. In most plant groups Zn and Sr have the highest transfer values. TFs are lower for Cs and the lowest TFs were found for Ra, U and Pb.

Subunit interaction in B19 parvovirus empty capsids.

B19 parvovirus is a small single-stranded DNA virus with a genome that encodes only two structural proteins, designated VP1 and VP2. 60 copies of the structural proteins assemble into the viral capsid, with approximately 95% VP2 and 5% VP1. Recombinant empty capsids composed of VP2 alone or of VP2 and VP1 self-assemble into particles that are morphologically indistinguishable from full virions. Empty capsids containing both VP2 and VP1 elicit a strong neutralizing antibody response when used to immunize rabbits. Capsids containing only VP2 are similarly antigenic but elicit only weak neutralizing activity. We performed fine structure epitope mapping by measuring the reactivity of antisera raised against capsids composed of VP2 and VP1 or VP2 alone against 85 overlapping peptides spanning the sequence of the two structural proteins. A profile of the antigenic difference between empty capsids with and without VP1 was produced from the resulting data. This profile divided the sequence of the structural proteins into four regions that correlated well with expected viral structures. Thus, the addition of a small number of VP1 residues altered the antigenicity of the entire capsid. The major area of enhanced antigenicity is homologous to the spike of canine parvovirus, an area known to contain both neutralizing and host-range determinants. Our data are consistent with a model in which the unique region of VP1 is necessary for the virus to assume its mature capsid conformation.

Important aspects concerning evaluation of renal function and blood pressure. Kinins, prostaglandins, lead.

The kallikrein-kinin and prostaglandin-thromboxane-leukotriene systems and the body lead burden all influence renal function and systemic blood pressure to some extent. Because these systems may become generally accepted as more important in assessing renal function and blood pressure in the future, a brief overview of each has been given.

Survival after first recurrence of breast cancer. The Miami experience.

BACKGROUND: Four hundred thirty-three patients with recurrent breast cancer were treated by the authors at a large medical breast oncology facility from 1976-1982. The median survival time from first relapse (MSFR) for the 193 patients whose survival experience was not confounded by lead-time bias was 26 months. This MSFR is similar to that of most series published in the 1970s and 1980s and is approximately double that of series published in the 1960s. METHODS: In this series, regression analysis identified disease-free interval (DFI), estrogen receptor (ER) status, and dominant disease site as significant prognostic variables, similar to other published series. RESULTS: In 113 patients with known ER values, DFI, and dominant metastatic sites, a prognostic spectrum of MSFR patterns was identified among combinations of these three variables. The MSFR ranged from 15 months for poor risk patients with negative ER values, visceral dominant sites, and DFI of less than 24 months, to more than 90 months for good risk patients with positive ER values, soft tissue dominant sites, and DFI of more than 24 months. Although menopausal status alone was not a significant prognostic variable in regression analysis, 66% of premenopausal patients had a constellation of "poor" prognostic variables. CONCLUSIONS: This type of prognostic factor analysis at first relapse could help identify subsets of patients who might be considered for aggressive investigational therapies such as high-dose chemotherapy with autologous bone marrow reconstitution.

Nosocomial human parvovirus B19 infection: lack of transmission from a chronically infected patient to hospital staff.

OBJECTIVE: To assess the potential for nosocomial spread of parvovirus B19 from a chronically infected patient. DESIGN: Employees exposed to the index case and control (unexposed) employees were evaluated by baseline and follow up parvovirus B19 serologies and hematologic assessments, and completed baseline and follow up epidemiologic questionnaires. SETTING: A chronically infected patient was hospitalized on a hematology ward in a research referral hospital for 3.5 weeks prior to a diagnosis of parvovirus B19 infection and the institution of isolation precautions. METHODS: Sera were screened for parvovirus B19 DNA (dot blot analysis), and IgG and IgM anti-B19 antibodies (capture immunoassay). Hematologic assessment included CBC, differential, and reticulocyte count. RESULTS: The index case had parvovirus B19 DNA at approximately 10(6) genome copies per ml of serum, elevated IgM and low levels of IgG B19 antibodies. Of the 21 exposed staff, 11 (52%) had IgG B19 antibodies and were immune; of the 8 unexposed staff, 6 (75%) had IgG B19 antibodies. No employees developed IgM B19 antibodies, B19 DNA, hematologic abnormalities, or clinical symptoms. CONCLUSIONS: In contrast to reports of documented nosocomial transmission of B19 parvovirus from patients in transient aplastic crisis, nosocomial transmission did not occur--even in the absence of isolation precautions--presumably from the lower level of B19 viremia in our chronically infected (rather than acutely infected) patient.

Translational regulation of B19 parvovirus capsid protein production by multiple upstream AUG triplets.

The B19 parvovirus produces two capsid proteins in strikingly different quantities (VP1 less than 4%, VP2 greater than 96%) from overlapping RNAs that are derived from the same transcription unit. Immediately upstream from the VP1 translation initiation site is an unusual sequence containing multiple ATG triplets. During RNA processing this sequence is spliced out of VP2 RNA. To test the regulatory role on translation of this sequence containing upstream AUGs, synthetic RNAs were produced in vitro by T7 RNA polymerase from various plasmid constructions. Translation of VP1 RNA was very inefficient compared to VP2 RNA in a cell-free system, indicating that capsid protein production was regulated at the level of translation. Removal of upstream AUG sequences from VP1 RNA greatly increased the efficiency of translation. Conversely, the addition of the same AUG-rich sequence upstream of the initiation site of VP2 decreased its translation. These data indicate that an upstream AUG-rich region acts as a negative regulatory element in the translational control of B19 capsid protein production.

The gene encoding the nonstructural protein of B19 (human) parvovirus may be lethal in transfected cells.

The B19 parvovirus is a cause of bone marrow failure in humans. B19 is toxic to erythroid progenitor cells in vitro. Viral products possibly responsible for toxicity were explored by transfection of cloned B19 genome into HeLa cells. The nonstructural (NS) protein was detected in cells 30 h after transfection. Plasmids containing the B19 genome were transfected with selectable marker genes in stable transformation assays. Plasmids that contained the left side of the B19 genome, which encodes the NS protein of the virus, inhibited antibiotic-resistant colony formation. Transformation occurred when NS protein expression was blocked by mutation. Suppression of transformation by NS protein was not tissue specific, suggesting a role for NS protein in toxicity for nonpermissive cells without parvovirus replication or virion accumulation.

Functional mapping of the genome of the B19 (human) parvovirus by in vitro translation after negative hybrid selection.

We have analyzed the coding capacity of B19 parvovirus transcripts by in vitro translation using the negative hybrid selection technique. Five different antisense oligonucleotides (18-mers) corresponding to different portions of the B19 genome were hybridized to RNA samples extracted from human erythroid bone marrow cells infected with B19 parvovirus in vitro, and RNase H was added to cleave specific B19 RNA molecules at selected sites. B19-specific translation products of these RNA samples were determined by immunoprecipitation. We localized the B19 nonstructural protein to the left-side transcript and the two capsid proteins to overlapping transcripts from the right side of the genome.

Novel transcription map for the B19 (human) pathogenic parvovirus.

The B19 parvovirus, a small single-stranded DNA virus of 5.4 kilobases, is pathogenic in humans. B19 has remarkable specificity for erythroid progenitor cells and has been propagated in vitro only with human erythroid bone marrow. Replication of viral DNA and the viral protein products of B19 appear similar to those of other animal parvoviruses. However, B19 transcription had unusual features in comparison with that in other animal parvoviruses. At least nine overlapping poly(A)+ transcripts were identified in infected cells; all but one contained large introns. B19 differed from other parvoviruses in the initiation of all transcripts at a strong left side promoter (p6) and the absence of a functional internal promoter; the presence of short 5' leader sequences of about 60 bases and very large introns for RNAs encoded by the right side of the genome; two separate transcription termination sites, in contrast to cotermination at the far right side of the genome for other parvoviruses; the probable utilization by three transcripts of a variant polyadenylation signal (ATTAAA or AATAAC) in the middle of the genome; and the abundance of two unique transcripts from the middle of the genome which did not code for capsid proteins. The unusual transcription map of B19 suggests that regulation of the relative abundance of transcripts occurs by splicing and termination-polyadenylation events rather than by promoter strength. In combination with the published nucleotide sequence, the novel transcription map separated the pathogenic B19 virus at a molecular level from other animal parvoviruses and human adeno-associated virus.

Danazol therapy for autoimmune hemolytic anemia.

We evaluated the use of danazol in 15 patients with autoimmune hemolytic anemia of the warm antibody type. Danazol, 600 to 800 mg/d, was added to previous regimens or given initially in conjunction with high-dose prednisone treatment. Twelve patients with autoimmune hemolytic anemia associated with nonmalignant disorders or idiopathic autoimmune hemolytic anemia and 1 of 3 patients with underlying neoplasms showed a rise in hematocrit within 1 to 3 weeks. Thereafter, glucocorticoid doses were tapered to a minimum requirement or stopped. Once remission was sustained, the dose of danazol was reduced to 200 to 400 mg/d. Although levels of erythrocyte-bound IgG antibody and C3 decreased with therapy, only the decrease in C3 was statistically significant (p less than 0.05) in this limited study. Danazol was effective regardless of the severity of the disorder and success or failure of previous treatments. Danazol is valuable in the treatment of autoimmune hemolytic anemia and may be better suited than glucocorticoids for long-term management.