Linear energy transfer characterization of five gel dosimeter formulations for electron and proton therapeutic beams.

Gel dosimeters, including radiochromic types like Fricke, as well as polymer formulations, are considered to be the only reliable option for accurate 3D dosimetry. Nevertheless, their implementation in daily clinical quality assurance still remains strongly limited for a few high specialized radiotherapy centres. Although gel dosimeters present very good water-equivalence due to their inherent chemical and isotopic compositions, addressing the corresponding dosimetry outputs is highly challenging, needing careful assessment in terms of the different radiation qualities involved in the mixed field. Accurate estimations of the linear energy transfer for each gel dosimeter formulation stands as a baseline for further accurate dose deconvolution in mixed radiation fields. The present study reports on the linear energy transfer characterization of five different gel dosimeter formulations, Fricke, Itabis, Magic, Nipam, and Pagat, for electron and proton therapeutic beams as obtained by Monte Carlo approaches, along with experimental results for validation purposes. The linear energy transfer, as a function of beam quality and penetration depth, is obtained for electron and proton therapeutic beams remarking the presence of non-negligible variations, which need to be accounted for a further accurate implementation of gel dosimetry as well as for precise dose deconvolution in mixed radiation fields.

Raman spectroscopy as a tool to evaluate oxygen effects on the response of polymer gel dosimetry.

Currently, advanced dosimeters like polymer gels are capable of obtaining reliable and accurate 3D dose distributions from correlations with the different polymerization degrees induced by incident radiation. Samples of polymer gel dosimeters are commonly read out using magnetic resonance imaging or optical methods like visible light transmission or laser computed tomography. Alternatively, this work proposes and evaluates the implementation of Raman spectroscopy to provide direct information on the effect of oxygen permeating through the walls of phantoms on the polymerization initiated by irradiation in three types of polymer gel dosimeters, namely NIPAM, ITABIS and PAGAT. The aim of the present study is to provide better and complete interpretations using three different containers, adequate for integral, 2D and 3D dose mapping. Moreover, Raman spectroscopy has been used to analyze the well-known effect of oxygen inhibition on the different polymer gel dosimeters remarking the importance of avoiding air exposition during sample storage and readout. Dose-response curves for different polymer gels were obtained in terms of measurements with a calibrated ionization chamber. Additionally, dedicated Monte Carlo simulations were performed aimed at characterizing dose for different X-ray irradiation setups, providing also suitable information to evaluate oxygen diffusion through the sample wall. The obtained results were contrasted with optical transmission readout as well as Monte Carlo simulations attaining very good agreements for all dosimeter types.

Feasibility of dose enhancement assessment: Preliminary results by means of Gd-infused polymer gel dosimeter and Monte Carlo study.

This work reports the experimental development of an integral Gd-infused dosimeter suitable for Gd dose enhancement assessment along with Monte Carlo simulations applied to determine the dose enhancement by radioactive and X-ray sources of interest in conventional and electronic brachytherapy. In this context, capability to elaborate a stable and reliable Gd-infused dosimeter was the first goal aimed at direct and accurate measurements of dose enhancement due to Gd presence. Dose-response was characterized for standard and Gd-infused PAGAT polymer gel dosimeters by means of optical transmission/absorbance. The developed Gd-infused PAGAT dosimeters demonstrated to be stable presenting similar dose-response as standard PAGAT within a linear trend up to 13 Gy along with good post-irradiation readout stability verified at 24 and 48 h. Additionally, dose enhancement was evaluated for Gd-infused PAGAT dosimeters by means of Monte Carlo (PENELOPE) simulations considering scenarios for isotopic and X-ray generator sources. The obtained results demonstrated the feasibility of obtaining a maximum enhancement around of (14 ±â€¯1)% for 192Ir source and an average enhancement of (70 ±â€¯13)% for 241Am. However, dose enhancement up to (267 ±â€¯18)% may be achieved if suitable filtering is added to the 241Am source. On the other hand, optimized X-ray spectra may attain dose enhancements up to (253 ±â€¯22) %, which constitutes a promising future alternative for replacing radioactive sources by implementing electronic brachytherapy achieving high dose levels.

Water-equivalence of gel dosimeters for radiology medical imaging.

International dosimetry protocols are based on determinations of absorbed dose to water. Ideally, the phantom material should be water equivalent; that is, it should have the same absorption and scatter properties as water. This study presents theoretical, experimental and Monte Carlo modeling of water-equivalence of Fricke and polymer (NIPAM, PAGAT and itaconic acid ITABIS) gel dosimeters. Mass and electronic densities along with effective atomic number were calculated by means of theoretical approaches. Samples were scanned by standard computed tomography. Photon mass attenuation coefficients and electron stopping powers were examined. Theoretical, Monte Carlo and experimental results confirmed good water-equivalence for all gel dosimeters. Overall variations with respect to water in the low energy radiology range (up to 130 kVp) were found to be less than 3% in average.

A four-gene LincRNA expression signature predicts risk in multiple cohorts of acute myeloid leukemia patients.

Prognostic gene expression signatures have been proposed as clinical tools to clarify therapeutic options in acute myeloid leukemia (AML). However, these signatures rely on measuring large numbers of genes and often perform poorly when applied to independent cohorts or those with older patients. Long intergenic non-coding RNAs (lincRNAs) are emerging as important regulators of cell identity and oncogenesis, but knowledge of their utility as prognostic markers in AML is limited. Here we analyze transcriptomic data from multiple cohorts of clinically annotated AML patients and report that (i) microarrays designed for coding gene expression can be repurposed to yield robust lincRNA expression data, (ii) some lincRNA genes are located in close proximity to hematopoietic coding genes and show strong expression correlations in AML, (iii) lincRNA gene expression patterns distinguish cytogenetic and molecular subtypes of AML, (iv) lincRNA signatures composed of three or four genes are independent predictors of clinical outcome and further dichotomize survival in European Leukemia Net (ELN) risk groups and (v) an analytical tool based on logistic regression analysis of quantitative PCR measurement of four lincRNA genes (LINC4) can be used to determine risk in AML.

Enfermedad extramamaria de Paget, revisión bibliográfica y reporte de caso / Extramammary Paget's disease, literature review and case report

La enfermedad de Paget es un adenocarcinoma intraepidérmico poco frecuente que se presenta en el complejo areola-pezón o en su forma extramamaria en áreas como las regiones anogenital, perineal y axilar. La enfermedad de Paget extramamaria es un carcinoma epidérmico de diferenciación apocrina que se origina en la epidermis o secundario a la diseminación epidermotropa de neoplasias adyacentes o a distancia. Caracterizado histológicamente por la presencia de células tumorales típicas, denominadas células de Paget...

Fibronectin and vitronectin promote human fetal osteoblast cell attachment and proliferation on nanoporous titanium surfaces.

Improvements in osteoconduction of implant biomaterials require focusing on the bone-implant interface, which is a complex multifactorial system. Surface topography of implants plays a crucial role at this interface. Nanostructured surfaces have been shown to promote serum protein adsorption and osteoblast adhesion when compared to micro-structured surfaces for bone-implant materials. We studied the influence of the serum proteins fibronectin and vitronectin on the attachment and proliferation of osteoblasts onto nanostructured titania surfaces. Human fetal osteoblastic cells hFOB 1.19 were used as model osteoblasts and were grown on nanoporous TiO2 templates, using Ti6AI4V and commercially pure Ti substrates as controls. Results show a significant increase in cell proliferation'on nanoporous TiO2 over flat substrates. Initial cell attachment data exhibited a significant effect by either fibronectin or vitronectin on cell adhesion at the surface of any of the tested materials. In addition, the extent of cell adhesion was significantly different between the nanoporous TiO2 and both Ti6AI4V and commercially pure Ti substrates, with the first showing the highest surface coverage. There was no significant difference on osteoblast attachment or proliferation between the presence of fibronectin or vitronectin using any of the material substrates. Taken together, these results suggest that the increase in osteoblast attachment and proliferation shown on the nanoporous TiO2 is due to an increase in the adsorption of fibronectin and vitronectin because of the higher surface area and to an enhanced protein unfolding, which allows access to osteoblast binding motifs within these proteins.

Removal of triazine herbicides from aqueous systems by a biofilm reactor continuously or intermittently operated.

The impact of pesticide movement via overland flow or tile drainage water on the quality of receiving water bodies has been a serious concern in the last decades; thus, for remediation of water contaminated with herbicides, bioreaction systems designed to retain biomass have been proposed. In this context, the aim of this study was to evaluate the atrazine and terbutryn biodegradation capacity of a microbial consortium, immobilized in a biofilm reactor (PBR), packed with fragments of porous volcanic stone. The microbial consortium, constituted by four predominant bacterial strains, was used to degrade a commercial formulation of atrazine and terbutryn in the biofilm reactor, intermittently or continuously operated at volumetric loading rates ranging from 44 to 306 mg L(-1) d(-1). The complete removal of both herbicides was achieved in both systems; however, higher volumetric removal rates were obtained in the continuous system. It was demonstrated that the adjuvants of the commercial formulation of the herbicide significantly enhanced the removal of atrazine and terbutryn.

Cyanuric acid biodegradation by a mixed bacterial culture of Agrobacterium tumefaciens and Acinetobacter sp. in a packed bed biofilm reactor.

Cyanuric acid (1,3,5-triazine-2,4,6-triol [OOOT]) is a common biodegradation byproduct of triazinic herbicides, frequently accumulated in soils or water when supplementary carbon sources are absent. A binary bacterial culture able to degrade OOOT was selected through a continuous selection process accomplished in a chemostat fed with a mineral salt (MS) medium containing cyanuric acid as the sole carbon and nitrogen source. By sequence comparison of their 16S rDNA amplicons, bacterial strains were identified as Agrobacterium tumefaciens, and Acinetobacter sp. When the binary culture immobilized in a packed bed reactor (PBR) was fed with MS medium containing OOOT (50 mg L(-1)), its removal efficiencies were about 95%; when it was fed with OOOT plus glucose (120 mg L(-1)) as a supplementary carbon source, its removal efficiencies were closer to 100%. From sessile cells, attached to PBR porous support, or free cells present in the outflowing medium, DNA was extracted and used for Random Amplification of Polymorphic DNA analysis. Electrophoretic patterns obtained were compared to those of pure bacterial strains, a clear predominance of A. tumefaciens in PBR was observed. Although in continuous suspended cell culture, a stable binary community could be maintained, the attachment capability of A. tumefaciens represented a selective advantage over Acinetobacter sp. in the biofilm reactor, favoring its predominance in the porous stone support.

A procedure for the efficient selection of piezoelectric ceramics constituting high-power ultrasonic transducers.

The most characteristic narrow-band transducer structure for high-power ultrasonic applications is the well known piezoelectric sandwich which is reminiscent of the Langevin transducer. Such structure is generally used jointly with other components in the construction of industrial high-power transducers. One of the main objectives in the design and construction of such high-power transducers is to minimize energy losses. To that purpose the selection of the piezoelectric ceramic rings forming the sandwich requires clear and specific criteria. This paper deals with a numerical and experimental procedure for the accurate selection of the piezoelectric rings constituting high-power transducers, based on the analysis of the mechanical Q, the frequency and the resonance curve. The procedure was experimentally checked by constructing and characterizing several transducer structures.

Low-dose continuous oral fosfestrol is highly active in 'hormone-refractory' prostate cancer.

BACKGROUND: Although not clearly defined, 'hormone refractory' prostate cancer implies disease progression after orchiectomy +/- antiandrogens. Patients in this setting are usually offered chemotherapy protocols which often lead to significant toxicity and expense. In search of a well-tolerated, active, third-line treatment, we have attempted to prolong hormonal maneuvers by using low-dose estrogen therapy. DESIGN: Thirty-eight patients with evidence of disease progression (as indicated by 2 consecutively rising PSA determinations) after > or = 2 hormonal treatments (including surgical or chemical orchiectomy and a median of 3 prior treatment lines) received fosfestrol 100 mg t.i.d. per os in a continuous schedule until the appearance of progressive disease or excessive toxicity. Response was assessed by serial PSA levels. Complete response (CR) was defined as normalisation and partial response (PR) as a > or = 50 decrease of PSA levels for longer than one month. The median duration of prior treatment was 20 months and the median PSA at fosfestrol start was 126 ng/ml (range 8-12,800); symptoms (pain) were present in 73% of patients. RESULTS: CR + PR were observed in 79% (95% confidence interval: 66%-92%). The median time to progression was seven months. Pain remained stable or improved in 34% and 53%, respectively, of symptomatic patients with PSA response. Toxicity included worsening of gynecomastia, peripheral edema, and deep vein thrombosis (8%). No treatment-related deaths occurred. Uni- and multivariate analyses failed to identify predictive factors for response. PSA response was associated with significantly longer survival (13 vs. 7 months, P < 0.05 by Mantel-Haentzel). CONCLUSIONS: FOSF produces high rates of PSA-determined and symptomatic response in 'hormone-refractory' prostate cancer. Toxicity and ease of administration compare favorably with those reported for CHT regimens used in this setting. The role of estrogens in prostate cancer should be redefined.

Detection of respiratory syncytial virus in nasopharyngeal secretions by 24-well plate precentrifugation assay using a monoclonal antibody against F protein.

BACKGROUND: Respiratory syncytial virus (RSV) is responsible for 50% of all bronchiolitis and 25% of pneumonia cases during the first month of life. Detection of the RSV antigen by immunofluorescence in exfoliated nasal epithelium or by other methods in nasopharyngeal swabs is useful in the potentially infected patient because results are available within a few hours. In contrast, RSV antigen detection in cell culture may require as much as 3 weeks. METHODS: Three methods for detection of respiratory syncytial virus in 131 clinical respiratory specimens from patients with acute respiratory disease and bronchiolitis were compared utilizing the following: a precentrifugation immunofluorescence assay using Hep-2 cells, indirect immunofluorescence assay, and conventional tube cell culture using Hep-2 cells. RESULTS: Respiratory syncytial virus was identified in 36 specimens by the three methods previously described. The virus was recovered in 41 (31.3%) samples by precentrifugation immunofluorescence assay, 40 (30.5%) were identified by the immunofluorescence technique, and 38 (29.0%) cases were positive by conventional cell culture. The sensitivity of the precentrifugation assay in relation to the immunofluorescence technique was 90%, the specificity 94.5%, and the agreement, 96.2%. A positive predictive value of 90.2% was obtained. Sensitivity, specificity, agreement, and positive predictive values obtained by the precentrifugation assay variant compared to the conventional cell were 90.8%, 94.5%, 93.1%, and 87.8%, respectively. CONCLUSIONS: The precentrifugation immunofluorescence assay method was as sensitive as the remainder of the methods used in our study and represents a valid alternative for rapid detection of respiratory syncytial virus in clinical samples.

Antigenic and genetic characterization of twenty-six strains of human respiratory syncytial virus (subgroup A) isolated during three consecutive outbreaks in Havana city, Cuba.

Twenty-six human respiratory syncytial virus strains (subgroup A) isolated from three outbreaks in Havana City during the period 1994/95, 1995/96 and 1996/97 were analyzed to determine their antigenic and genetic relationships. Analyses were performed by monoclonal antibodies and restriction mapping (N gene) following amplification of the select region of the virus genome by polymerase chain reaction. All isolated strains were classified as subgroup A by monoclonal antibodies and they showed a restriction pattern NP4 that belonged to subgroup A. Thus the results obtained in this work, showed a close relation (100%) between antigenic and genetic characterization of the isolated strains in our laboratory. These methods permit the examination of large numbers of isolates by molecular techniques, simplifying the researchs into the molecular epidemiology of the virus.

[Fast detection and characterization of influenza A and B viruses in nasopharyngeal secretions by the immunoperoxidase method]. / Detección y caracterización rápida de los virus de influenza A y B en secreciones nasofaríngeas mediante el método de la inmunoperoxidasa.

One hundred and fourty eight samples from patients with a symptomatology compatible with the influenza virus were studied aimed at identifying in a fast way these viruses. A rapid MDCK-L cell culture was developed on 96 well plates, where nasopharingeal exudates or gargarisms were inoculated and incubated all night long at 37 degrees C. The medium was removed and cells were washed with PBS and fixed with methanol. Viral antigens were detected through the immunoperoxidase staining by using two monoclonal antibody pools for the identification of influenza A and influenza B viruses. The HA1-71 monoclonal antibody, specific for influenza A (H3N2) and the HA2-76, which react with both A (H3N2) and A (H1N1) were used for subtyping. Of all the positive samples (136), 72% corresponded to type A while 34.6% and 37.5% corresponded to subtypes H1 and H3, respectively. Influenza B was detected in 27.9% of the 148 samples studied. Only 12 were negative (8.1%). The use of this technique is recommended as a rapid, convenient and sensitive method that is easy to carry put and to interpretate for the detection and characterization in type and subtype of the influenza viruses starting from the nasopharyngeal exudates or gargarisms.

Molecular characterization of an outbreak of respiratory syncytial virus (subgroup A) in Havana, Cuba, by monoclonal antibodies and restriction mapping (N gene).

Twenty-one respiratory syncytial virus (RSV) strains isolated from one outbreak in Havana, Cuba (1994 to 1995), were analyzed to determine their relatedness. All isolated strains were classified as subgroup A by monoclonal antibodies. Of 21 RSV strains examined, 20 were classified as having restriction pattern NP4 and only 1 was classified as having restriction pattern NP5.

Analysis of respiratory syncytial virus in clinical samples by reverse transcriptase-polymerase chain reaction restriction mapping.

The aim of this study was to develop a polymerase chain reaction (PCR) for the detection of respiratory syncytial virus (RSV) genomes. The primers were designed from published sequences and selected from conserved regions of the genome encoding for the N protein of subgroups A and B of RSV. PCR was applied to 20 specimens from children admitted to the respiratory ward of "William Soler" Pediatric Hospital in Havana City with a clinical diagnosis of bronchiolitis. The PCR was compared with viral isolation and with an indirect immunofluorescence technique that employs monoclonal antibodies of subgroups A and B. Of 20 nasopharyngeal exudates, 10 were found positive by the three assayed methods. In only two cases, samples that yielded positive RNA-PCR were found negative by indirect immunofluorescence and cell culture. Considering viral isolation as the "gold standard" technique, RNA-PCR had 100% sensitivity and 80% specificity. RNA-PCR is a specific and sensitive technique for the detection of the RSV genome. Technical advantages are discussed.

[Application of the polymerase chain reaction for detecting respiratory syncytial virus]. / Aplicación de la reacción en cadena de la polimerasa para la identificación del virus sincitial respiratorio.

The polymerase chain reaction (PCR) was developed in order to identify the respiratory syncytial virus by using the reference strain. The high sensitivity and specificity obtained show the PCR utility for detecting the RSV genoma and its application on the diagnosis.

[Evaluation of a mouse anti-IgG-fluorescein conjugate using indirect immunofluorescence and flow cytometry techniques]. / Evaluación de un conjugado anti-IgG de ratón-fluoresceína mediante técnicas de inmunofluorescencia indirecta y citometría de flujo.

An immunoglobulin G of mouse was purified from sera by affinity chromatography in protein A. The rabbits whose sera were able to recognize the antigen injected by double immunodiffusion were immunized with this preparation. The antibodies were precipitated from the rabbit's serum and purified by ion exchange chromatography. This preparation was conjugated to fluorescin isothiocyanate according to the conventional technique. The conjugated obtained was evaluated with the reference strains of Parainfluenza virus 1, 2, 3; Adenovirus; respiratory syncytial virus; and influenza virus A and B, by an indirect immunofluorescence technique and HIV positive samples by flow citometry. Specific monoclonal antibodies were used in both cases. Clinical specimens of patients with acute respiratory infection were evaluated.

Reproduction and conservation of the leatherback turtle Dermochelys coriacea (Testudines: Dermochelyidae) in Gandoca, Costa Rica.

The leatherback turtle was studied in Gandoca, an important nesting beach on the southeastern Caribbean coast of Costa Rica (82 degrees 37' W; 09 degrees 37' N). In 1994, a total of 530 nests was recorded during the nesting season (February/July) and 160 leatherbacks were tagged; five were remigrants from the 1992 season and 15 carried tags from elsewhere. Eighty eight females only nested once. Mean curve carapace measurements were length 153.8 cm and width 112.0 cm. A hatchery received 82 clutches, with 6277 normal eggs. Their mean incubation period was 62.24 days (range: 56-68 days). Average hatching rate was 55.10% (S.D.: 25.04, range 15-96%). Extensive erosion, beach debris and poaching activity represent the main hazards for nesting in Gandoca.