Dosimetric effect by shallow air cavities in high energy electron beams.

This study evaluates the dosimetric impact caused by an air cavity located at 2 mm depth from the top surface in a PMMA phantom irradiated by electron beams produced by a Siemens Primus linear accelerator. A systematic evaluation of the effect related to the cavity area and thickness as well as to the electron beam energy was performed by using Monte Carlo simulations (EGSnrc code), Pencil Beam algorithm and Gafchromic EBT2 films. A home-PMMA phantom with the same geometry as the simulated one was specifically constructed for the measurements. Our results indicate that the presence of the cavity causes an increase (up to 70%) of the dose maximum value as well as a shift forward of the position of the depth-dose curve, compared to the homogeneous one. Pronounced dose discontinuities in the regions close to the lateral cavity edges are observed. The shape and magnitude of these discontinuities change with the dimension of the cavity. It is also found that the cavity effect is more pronounced (6%) for the 12 MeV electron beam and the presence of cavities with large thickness and small area introduces more significant variations (up to 70%) on the depth-dose curves. Overall, the Gafchromic EBT2 film measurements were found in agreement within 3% with Monte Carlo calculations and predict well the fine details of the dosimetric change near the cavity interface. The Pencil Beam calculations underestimate the dose up to 40% compared to Monte Carlo simulations; in particular for the largest cavity thickness (2.8 cm).

Overland flow computations in urban and industrial catchments from direct precipitation data using a two-dimensional shallow water model.

This paper presents the experimental validation and the application to a real industrial catchment of a two-dimensional depth-averaged shallow water model used for the computation of rainfall-runoff transformation from direct precipitation data. Instead of using the common approach in flood inundation modelling, which consists in computing the water depth and velocity fields given the water discharge, in this study the rainfall intensity is imposed directly in the model, the surface runoff being generated automatically. The model considers infiltration losses simultaneously with flow simulation. Gullies are also included in the model, although the coupling between the surface runoff and the sewer network is not considered. Experimental validation of the model is presented in several simplified laboratory configurations of urban catchments, in which the surface runoff has been measured for different hyetographs. The application to a real industrial catchment includes a sewer network flow component, which is solved with the SWMM model. The numerical predictions of the discharge hydrograph generated by a 12 hours storm event are compared with field measurements, providing encouraging results.

Estimulación iterativa (EI) de TSH endógena (TSH-En) mediante el uso de la hormona liberadora de tirotrofina (TRH) en pacientes portadores de carcinoma diferenciado de tiroides / Rapid iterative stimulation (IS) of endogenous tsh (En-TSH) utilizing thyrotropin releasing hormone (TRH) in patients with differentiated thyroid carcinoma (DTC)

En el CDT es indispensable elevar los valores de TSH para efectuar Tg y barrido (RCT) con 131I, debiéndose suspender la opoterapia (HT) durante 4/5 sem. con el consecuente hipotiroidismo (H) y los trastornos que conlleva. Nuestro objetivo fue incrementar en forma rápida TSH-E acortando el tiempo de abstinencia. Se efectuaron 43 estudios en 37 pacientes con CDT (G-1); de entre 19 y 78 años, 34 con forma papilar y 3 folicular de CDT, 12 de sexo masculino y 25 femenino Se consideraron 2 subgrupos, G-1A, 7 p. para ablación (A); G-1B, 36 p. para seguimiento (S) y/o tratamiento (T) entre 6 meses y 5 años poscirugía; 6 p. efectuaron dos estudios, 4 para A y S y 2 para 2 veces S. Como comparación se revisaron 41 estudios en 35 p (G-2) que efectuaron suspensión de opoterapia por 4/5 semanas, entre 18 y 81 años; 28 de sexo femenino y 7 masculino; 32 papilares y 3 foliculares; 18 para A (G-2 A) y 21 para S, primer control (G-2B); 4 p. efectuaron 2 estudios, A y S. G-1A: entre 8/10 días poscirugía se les administra TRH 200 mcg i.v los días 1, 3, 5 y 6. A los 30 min de la 3ra aplicación, determinación de TSH y RCT con 370 MBq de 99mT; a igual lapso en la 4ta aplicación determinación de TSH, Tg y antiTg y 5,55 o 7,4 GBq de 131I, para A; a los 8 días RCT con 131I. G-1B: se suspende T4 y reemplaza por T3 por 3 semanas. Se suspende T3; a las 24 horas se inicia el esquema indicado para G-1A . A la 4ta aplicación de TRH, se administra el 131I, 14,8 MBq y RCT a las 48 horas en S o la actividad terapéutica indicada para T. En ambos grupos se indicó dieta hipoyódica. Resultados: En G-1, los valores de TSH ascendieron a 26-360 UI/L; promedio 83 UI/L ± 54; G-1A : 137 ±109; G-1B 7, 62 ± 52 . Los RCT no mostraron diferencias con ambos trazadores. En G-1A todos los p presentaron remanentes tiroideos y Tg positivas. En G-1B, 21 p. mostraron RCT y Tg negativas; 7 áreas activas y Tg positivas y 8 p RCT negativos con valores elevados de Tg . En G-2, TSH, 23-170 UI/L ( 63 ± 3 UI/L) ; G-2 A: 71 ± 41 ; G-2B, 63 ± 42. Conclusiones: Estos hallazgos indican que a) la metodología propuesta es adecuada para acortar sensible-mente el tiempo de abstinencia de opoterapia y reducir la sintomatología del H que pasa desapercibida en la mayoría de los casos; b) los valores de TSH-En obtenidos son similares y aun superiores a los alcanzados por suspensión de opoterapia por lapsos prolongados; c) el empleo del RCT con 99mTc como indicador de tejido captante disminuye el uso terapéutico a ciegas de 131I al señalar casos de ausencia de concentración y permite, cuando sea necesario, obtener anticipadamente 131I para su empleo terapéutico.

In the follow up (F) of p with DTC it is necessary to obtain high figures of serum TSH for determination of serum Tg and 131I scan (WBS). For this object, he method, for a long time, was to withdrawal thyroid hormone therapy (generally l-T4) that produce hypothyroidism with the inconvenient for the p, dramatics in certain cases. Our objective was to increase TSH by IS to shortening time of L-T4 withdrawal for F, ablation (A) or treatment (T) with 131I. In 37 p. with DTC (G-1), aged 19-78 y., 34 with pap. DTC and 3 with foll. form, 25 females, 12 males, 43 studies were carried out; 6 p carried 2 studies. The group was divided in 2 sub-groups: G-1A,7 p derived for A; G-1 B 36 p. for F or T with 131I. Six p carried out 2 studies; 4 of them for A and for F and 2 realizes 2 times F. All p treated with l-T4 replaced this hormone for T3 during 3 weeks ,that was withdrawal the day before IS. In G-1A, between 8/10 days after surgery they begin IS. IS: At days 1, 3, 5 and 6, the p were injected i.v. with 200 mcg of TRH; at 30 minutes of the 3rd injec. blood TSH determination ; immediately 370 MBq of 99mT was administered and at 30 minutes a WBS was carried out. At 30 minutes of the 4th injec. blood figures of TSH, Tg and Tg-ab were determined; immediately the activity of 131I indicated for each group was given to the p; in G-1A, at 8 days and in G1-B, at 48 hours WBS were carried out. As a control group (G-2) 41 studies in 35 DTC p. that withdrawal l-T4 for 4/5 weeks, were studied, aged 18-81 years, 31 females and 4 males; 32 with pap. and 3 folli.c form; 18 for A (G-2A) and 23 for F (G-2B); 6 p carried out 2 studies. One for A and the second as the first control. In G-1, TSH values obtained were 26-360 UI/L ( 83 ± 54. In G-1A : 137 ± 109 and in G-1B 62 ± 52). The 2 tracers 131I and 99mTc-Tc, produce show similar figures. In G-1A all p present thyroid remnants and elevated Tg. In G-1B, 7 p showed positive WBS and Tg; 8 p present Tg positive and WBS negative and 21 WBS and Tg negative. In G-2, the TSH values obtained were 23-179 UI/L (63 ± 39 ); G-2A 71 ± 41 and G-2B 63 ± 42. These findings indicate that the methods is adequate to shortened the time of withdrawal of l-T4 and reduce the signs/symptoms of hypothyroidism to an acceptable status. Also allow us to considered the use of 99mTc as an indicator of existence of remnants, relapses or metastases and avoid blind use of therapeutic activities of 131I.

Cloning and sequence analysis of a low temperature-induced gene from trifoliate orange with unusual pre-mRNA processing.

Exposure of cold-hardy Rubidoux trifoliate orange [Poncirus trifoliata (L) Raf.] plants to temperatures from 28 degrees C to -5 degrees C enabled us to isolate and characterize a novel citrus low-temperature gene (CLT) with two transcripts, called CLTa and CLTb, from leaves and stems. CLTa was produced when plants were subjected to low temperatures (starting at 10 degrees C), while CLTb was constitutively expressed. Both CLTa and CLTb have the same open reading frame (ORF) of 165 nucleotides and encode a small (54 deduced amino acid) protein. However, CLTa has an additional 98 nucleotides in the 3'-untranslated region (UTR) that are absent in CLTb. Expression analysis using relative quantitative RT-PCR demonstrated that CLTa is expressed exclusively at low temperatures, while CLTb is expressed constitutively (expression verified from 33 degrees C to -5 degrees C). A GenBank database search identified 61 nucleotides inside of the ORF that are highly similar to low-temperature-responsive genes from Arabidopsis thaliana and Solanum tuberosum. The deduced amino acid sequence revealed similarity with low-temperature-responsive proteins from A. thaliana, Oryza sativa, and S. tuberosum of 77%, 81%, and 73.9%, respectively. A genomic clone was isolated, and the genome organization revealed the presence of three exons and two introns, the second of which is in the 3' UTR and participates in alternative 3' splice site selection. One of the 3' splice sites of the second intron was located immediately before the additional 98-bp non-coding fragment of CLTa, and the second at the very end of the 98-bp fragment. Additionally, the presence of the tetranucleotides TCTT and TTCT, which are involved in the regulation of transcript processing in animals and possibly also active in peach, was found in this intron. Competition for splicing sites on the pre-mRNA in the spliceosome, which is induced by low temperature, may be involved in the production of the two transcripts of the CLT gene.

Radioactivity in bottled waters sold in Mexico.

Measurements of gross alpha and beta activities were made on 21 domestic and international brands of bottled (purified and mineral) water sold in the Mexican market to assess its radiological quality. Alpha and beta activities were determined using a liquid-scintillation detector with pulse-shape analysis feature. All the purified water had values of beta activity lower than the limit for potable drinking water (1.0 Bq/l), while three brands surpassed the limit of alpha activity (0.1 Bq/l). The limit for alpha radioactivity content was exceed by three mineral waters; the results show a correlation between radioactivity content and mineral salts, which are related with the origin and treatment of the waters.

Mining DNA microarray data using a novel approach based on graph theory.

The recent demonstration that biochemical pathways from diverse organisms are arranged in scale-free, rather than random, systems [Jeong et al., Nature 407 (2000) 651-654], emphasizes the importance of developing methods for the identification of biochemical nexuses--the nodes within biochemical pathways that serve as the major input/output hubs, and therefore represent potentially important targets for modulation. Here we describe a bioinformatics approach that identifies candidate nexuses for biochemical pathways without requiring functional gene annotation; we also provide proof-of-principle experiments to support this technique. This approach, called Nexxus, may lead to the identification of new signal transduction pathways and targets for drug design.

Community structure of denitrifiers, bacteria, and archaea along redox gradients in Pacific Northwest marine sediments by terminal restriction fragment length polymorphism analysis of amplified nitrite reductase (nirS) and 16S rRNA genes.

Steep vertical gradients of oxidants (O(2) and NO(3)(-)) in Puget Sound and Washington continental margin sediments indicate that aerobic respiration and denitrification occur within the top few millimeters to centimeters. To systematically explore the underlying communities of denitrifiers, Bacteria, and Archaea along redox gradients at distant geographic locations, nitrite reductase (nirS) genes and bacterial and archaeal 16S rRNA genes (rDNAs) were PCR amplified and analyzed by terminal restriction fragment length polymorphism (T-RFLP) analysis. The suitablility of T-RFLP analysis for investigating communities of nirS-containing denitrifiers was established by the correspondence of dominant terminal restriction fragments (T-RFs) of nirS to computer-simulated T-RFs of nirS clones. These clones belonged to clusters II, III, and IV from the same cores and were analyzed in a previous study (G. Braker, J. Zhou, L. Wu, A. H. Devol, and J. M. Tiedje, Appl. Environ. Microbiol. 66:2096-2104, 2000). T-RFLP analysis of nirS and bacterial rDNA revealed a high level of functional and phylogenetic diversity, whereas the level of diversity of Archaea was lower. A comparison of T-RFLPs based on the presence or absence of T-RFs and correspondence analysis based on the frequencies and heights of T-RFs allowed us to group sediment samples according to the sampling location and thus clearly distinguish Puget Sound and the Washington margin populations. However, changes in community structure within sediment core sections during the transition from aerobic to anaerobic conditions were minor. Thus, within the top layers of marine sediments, redox gradients seem to result from the differential metabolic activities of populations of similar communities, probably through mixing by marine invertebrates rather than from the development of distinct communities.

99mTc-ENS ventilation scintigraphy: preliminary study in human volunteers.

Exogenous natural surfactant (ENS) labeled with (99m)Tc ((99m)Tc-ENS, 900-1110 MBq), a new radiopharmaceutical for ventilation scintigraphy, was nebulized during 3 min to five volunteers. For comparative purposes, (99m)Tc-diethylenetriamine pentaacetic acid (DTPA) was studied in the same way. (99m)Tc-ENS images were of at least the same quality as (99m)Tc-DTPA images. However, in smoking volunteers, the (99m)Tc-DTPA images show some areas that seemed to be not well-ventilated, although these areas appeared well-ventilated when the study was performed with (99m)Tc-ENS. These results suggest that (99m)Tc-ENS can be used for ventilation scintigraphy to allow the observation of some areas that cannot been visualized using (99m)Tc-DTPA as ventilation agent.

Bioavailability of microencapsulated ferrous sulfate in fluid milk studies in human beings.

Iron deficiency is one of the most important nutritional problems in the world. The best method to overcome this problem is the fortification of foods with highly bioavailable iron. Fluid milk is a massive consumption food with an easy access and which is generally the only food intake during the first months of life. Therefore the fortification of fluid milk with highly bioavailable iron and no detectable alterations of its sensorial characteristics was studied in the present work. This procedure was made possible using a new type of ferrous sulfate, stabilized and microencapsulated with soy lecitin (SFE-171). The iron concentration of the fortified milk is 12 mg per liter. In order to study the iron absorption from milk fortified with this product, SFE-171 was labeled with 59Fe and given to 29 volunteers with a normal iron status, each of which received an iron quantity of 3 mg in 250 ml of fluid milk. The average iron absorption was (10.2 +/- 4.7) %. This result shows that the iron given in this physicochemical form has the advantage of a high bioavailability and it is possible that this product will be the first attempt for an adequate solution of iron deficiency.

[Tc-99-sestamibi scan in the preoperative localization of abnormal hyperfunctioning parathyroid glands]. / Uso del Tc-99m-sestamibi en la localización preoperatoria de paratiroides anormales hiperfuncionantes.

Hyperparathyroidism is a relatively frequent condition mostly due to a solitary parathyroid adenoma. Although it has been claimed that surgical exploration is the best way to visualize the abnormal parathyroid gland, several imaging techniques have been proposed to localize it in order to simplify and shorten the surgical procedure. Echography, thalium-technetium scintigraphy, computerized tomography and nuclear magnetic resonance have shown a mean sensitivity of 75% which can be increased to about 90% by combining 2 or more of these procedures. In this study, we evaluated the utility of Tc-99m-sestamibi scintigraphy in 13 patients with hyperparathyroidism (11 primary, 2 secondary). High resolution neck echography was carried out in all of the cases. Cervical scans were obtained 10-15 min and 3 hours after giving an i.v. injection of 25 mCi Tc-99m-sestamibi in all the patients; suppression studies with combined 131-I were also done. Positive scans were obtained in 11 out of the 13 patients. Abnormal parathyroid glands were found and surgically excised in all the cases (10 adenomas, 1 carcinoma, 2 hyperplasias). Echographic localization had a sensitivity of only 33.3%. On the contrary, Tc-99m-sestamibi showed a sensitivity of 56% for the whole group, increasing to 82% in the 11 patients with primary hyperparathyroidism whereas the positive predictive value was of 91% and 90%, respectively. We conclude that Tc-99m-sestamibi is a very useful tool in localizing abnormal parathyroid glands and should be the first choice before reoperation after surgical failure or before the first parathyroid surgery whenever it is desired to shorten the surgical and anesthetic duration.

Serum kinetics, bioavailability and bone scanning of 99mTc-labelled sodium olpadronate in patients with different rates of bone turnover.

The activity of olpadronate labelled with technetium-99m(99mTc) was monitored in plasma and urine samples after single oral (925 MBq 99mTc/10 mg, coadministered with 50 mg cold drug) and intravenous (925 MBq 99mTc/5 mg) administrations to two groups of patients with different rates of bone turnover. The first group comprised high bone turnover (HBTO) patients suffering from Paget's bone disease; the second group comprised patients with normal to low bone turnover (NBTO) having the diagnosis of rheumatoid arthritis and secondary osteoporosis. Kinetic variables were correlated with anthropomorphometric variables, biological markers of bone metabolism and plasma proteins. Data were also obtained after repeatedly dosing the HBTO patients. Additionally, Paget's bone and healthy bone (PB/HB) uptake before and after low-dose oral treatment were assessed by means of scintigraphy. Results showed that most of the kinetic variables did not differ between the two groups of patients, except for a greater Vss and smaller blood area under the curve AUC in the patients with HBTO. After a repeated-dose administration period, the blood AUC activity and Whole Body Retention (WBR) of the HBTO patients tended to be similar to those of the NBTO patients. In both groups, after oral dosing, the Cmax was 20 times lower than the C0.5 after i.v. injection, and the oral bioavailability ranged from 3% to 4%. Finally, the plasma t1/2 beta ranged from 9 to 14 h. Correlation coefficients were obtained from multiple regression analysis; kinetic variables showed very low correlations with anthropomorphometric measurements. In contrast the Vss and WBR were significantly correlated with serum alkaline phosphatase levels and the Vss also with urine hydroxyproline levels. Plasma protein concentration was also correlated with excretion parameters such as CLP and plasma t1/2 beta after an oral dose. Scintigraphic studies in the HBTO group allowed bone selectivity to be seen through skeletal drug uptake. The 15 Pagetic lesions analysed in the HBTO group showed a decrease in PB/HB ratio from 3.8 in the basal study to 2.7 after olpadronate administration for 30 days at the rate of 50 mg/day. In conclusion, the kinetic profile of 99mTc-labelled olpadronate, mainly AUC and WBR, showed a dependence upon bone metabolism and seemed unrelated to body size variables. HBTO patients showed a lower blood AUC but a higher Vss. Both variables may have been reflecting the fact that the drug binds selectively with calcified tissues and, in turn, with the target compartment. Scintigraphy confirmed the labelled-compound bone selectivity as a desirable feature for a bone-scanning agent.

Natural and synthetic oviposition stimulants forCatolaccus grandis (Burks) females.

Oviposition behavior was elicited fromCatolaccus grandis (Burks) (Hymenoptera: Pteromalidae) females, an ectoparasitoid of the boll weevil,Anthonomus grandis Boheman (Coleoptera: Curculionidae), by smears of freshly cut cotton bolls or smears of extracts prepared with boll weevil damaged or undamaged cotton boll tissues. Oviposition behavior was also elicited fromC. grandis females by smears made withn-pentane,n-hexane,n-heptane, and isooctane. This is the first report of oviposition behavior elicited for any parasitoid by these short-chain saturated hydrocarbons (alkanes), introducing a new concept on the chemical mediation of parasitoid behavior during host selection. Oviposition behavior was also elicited fromC. grandis females by volatiles emanating from an artificial diet devoid of insect components that was specifically developed for the in vitro rearing of ectoparasitoids. The possible use of a synergistic combination ofn-hexane and diet to optimize the mechanized production of noncontaminated eggs is also discussed.

[Serum thyroglobulin and whole-body scanning as markers in the follow-up of differentiated thyroid carcinomas]. / La tiroglobina sérica y el rastreo corporal total como indicadores en el seguimiento del carcinoma diferenciado de tiroides.

We have compared two "markers" in the follow up of post treatment (surgery and therapeutical use of I-131) differentiated thyroid carcinoma. In 153 patients, thyroglobulin (Tg) serum levels were measured after withdrawal of I-thyroxine therapy, before performing a whole-body scan (WBS) with iodine-131; in 55 of these patients, Tg was measured again after at least 45 days of I-thyroxine treatment. The patients were followed between 3 and 10 years, and there were 2713 matched studies. Our results indicate for both parameters, false positive and negative values; sensitivity (SE) for WBS was 89% and specificity (SP) 83%; Tg presents a SE of 86% and SP of 83%. Matching both parameters, SE was 95% and SP 98%. The causes of false results are discussed. Tg determinations under I-thyroxine treatment do not permit the establishment of absence of illness; 37.7% of patients with demonstrated metastases or relapse showed negative Tg values that reached pathological values after suspension of I-thyroxine treatment; another 41.4% with elevated Tg values under therapy reached these values after suspension of I-thyroxine. Both markers, when utilized at the same time, offer the best possibilities in the follow-up of differentiated thyroid carcinoma, when determinations are carried out after suspension of hormonal treatment.

La tiroglobulina sérica y el rastreo corporal total como indicadores en el seguimiento del carcinoma diferenciado de tiroides / Serum thyroglobulin and whole-body scan as markers in the follow up of differentiated thyroid carcinomas

Hemos comparado el valor de los indicadores en el seguimiento del carcinoma tiroideo diferenciado (CaDT): tiroglobulina sérica (Tg) y rastreo corporal total con I-131 (RCT), que fueron realizados entre 3 y 10 años después del tratamiento quirúrgico más dosis terapéutica de I-131. Se realizaron en 153 pacientes 2713 estudios apareados, que se efectuaron con suspensión de la opoterapia por más de 30 días. En 55 pac. se realizaron determinaciones de Tg bajo opoterapia y en 18 en las mismas condiciones, determinaciones seriadas durante 6 meses. Los resultados indican que ambos parámetros pueden presentar falsos positivos y negativos, discutiéndose las razones de los mismos. La sensibilidad (S) para RCT fue de 89% y la especificidad (E) de 83% y para Tg S de 86% y E de 83%; si se consideran ambos parámetros en forma conjunta, S 95% y E 98%. La determinación de Tg bajo opoterapia no permite estabelecer la existencia de metástasis o recidivas con iguales posibilidades que luego de suspensión de la misma. El 37,7% de los casos con enfermedad demostrable, presentaron valores negativos de Tg bajo opoterapia que se elevaron a valores patológicos ...

La tiroglobina sérica y el rastreo corporal total como indicadores en el seguimiento del carcinoma diferenciado de tiroides. / [Serum thyroglobulin and whole-body scanning as markers in the follow-up of differentiated thyroid carcinomas]

We have compared two [quot ]markers[quot ] in the follow up of post treatment (surgery and therapeutical use of I-131) differentiated thyroid carcinoma. In 153 patients, thyroglobulin (Tg) serum levels were measured after withdrawal of I-thyroxine therapy, before performing a whole-body scan (WBS) with iodine-131; in 55 of these patients, Tg was measured again after at least 45 days of I-thyroxine treatment. The patients were followed between 3 and 10 years, and there were 2713 matched studies. Our results indicate for both parameters, false positive and negative values; sensitivity (SE) for WBS was 89

and specificity (SP) 83

; Tg presents a SE of 86

and SP of 83

. Matching both parameters, SE was 95

and SP 98

. The causes of false results are discussed. Tg determinations under I-thyroxine treatment do not permit the establishment of absence of illness; 37.7

of patients with demonstrated metastases or relapse showed negative Tg values that reached pathological values after suspension of I-thyroxine treatment; another 41.4

with elevated Tg values under therapy reached these values after suspension of I-thyroxine. Both markers, when utilized at the same time, offer the best possibilities in the follow-up of differentiated thyroid carcinoma, when determinations are carried out after suspension of hormonal treatment.