Protocols for the dosimetry of high-energy photon and electron beams: a comparison of the IAEA TRS-398 and previous international codes of practice. International Atomic Energy Agency

A new international Code of Practice for radiotherapy dosimetry co-sponsored by several international organizations has been published by the IAEA, TRS-398. It is based on standards of absorbed dose to water, whereas previous protocols (TRS-381 and TRS-277) were based on air kerma standards. To estimate the changes in beam calibration caused by the introduction of TRS-398, a detailed experimental comparison of the dose determination in reference conditions in high-energy photon and electron beams has been made using the different IAEA protocols. A summary of the formulation and reference conditions in the various Codes of Practice, as well as of their basic data, is presented first. Accurate measurements have been made in 25 photon and electron beams from 10 clinical accelerators using 12 different cylindrical and plane-parallel chambers, and dose ratios under different conditions of TRS-398 to the other protocols determined. A strict step-by-step checklist was followed by the two participating clinical institutions to ascertain that the resulting calculations agreed within tenths of a per cent. The maximum differences found between TRS-398 and the previous Codes of Practice TRS-277 (2nd edn) and TRS-381 are of the order of 1.5-2.0%. TRS-398 yields absorbed doses larger than the previous protocols, around 1.0% for photons (TRS-277) and for electrons (TRS-381 and TRS-277) when plane-parallel chambers are cross-calibrated. For the Markus chamber, results show a very large variation, although a fortuitous cancellation of the old stopping powers with the ND,w/NK ratios makes the overall discrepancy between TRS-398 and TRS-277 in this case smaller than for well-guarded plane-parallel chambers. Chambers of the Roos-type with a 60Co ND,w calibration yield the maximum discrepancy in absorbed dose, which varies between 1.0% and 1.5% for TRS-381 and between 1.5% and 2.0% for TRS-277. Photon beam calibrations using directly measured or calculated TPR20,10 from a percentage dose data at SSD = 100 cm were found to be indistinguishable. Considering that approximately 0.8% of the differences between TRS-398 and the NK-based protocols are caused by the change to the new type of standards, the remaining difference in absolute dose is due either to a close similarity in basic data or to a fortuitous cancellation of the discrepancies in data and type of chamber calibration. It is emphasized that the NK-ND,air and ND,w formalisms have very similar uncertainty when the same criteria are used for both procedures. Arguments are provided in support of the recommendation for a change in reference dosimetry based on standards of absorbed dose to water.     

Interpopulation variability among Panstrongylus megistus (Hemiptera: Reduviidae) from Brazil

Comparisons were made among Panstrongylus megistus (Burmeister) from three areas of Brazil (Bahia, Minas Gerais, and Santa Catarina), where populations differ with regard to their degree of association with human dwellings. The following characters were studied: morphology of the eggs and the male genitalia; morphometry of the head and thorax; isoenzyme profile; enzymatic activity of the alpha-glycerophosphate dehydrogenase (alpha-GPDH); and cytogenetics. In general, differences were observed in the weight, diameter, and length of the egg among Bahia, Minas Gerais, and Santa Catarina populations. Differences were not observed in the architecture of the egg exochorion. The size of the median process of the pygophore of the male genitalia of individuals from Bahia differed from the other two populations. The Minas Gerais population presented the largest number of denticles in the endosome process. The morphometry of the head and thorax differentiated Santa Catarina from the Bahia and Minas Gerais populations. Phosphoglucomutase (EC 5.4.2.2., PGM) was the only enzyme out of 11 that showed polymorphism; the population from Minas Gerais was most polymorphic, whereas the population from Santa Catarina was monomorphic. Study of the alpha-GPDH activity and cytogenetics did not reveal differences among the three populations. Analysis of all the characters studied together with information on these three populations from previous publications allowed a phenogram to be constructed. Two distinct groups were evident, one represented by Santa Catarina and the other by Bahia and Minas Gerais. Considering the greater variability of the Minas Gerais and Bahia populations, we propose the inclusion of these states within the area of origin of P. megistus.     

Antibody response after RSV infection in children younger than 1 year of age living in a rural area of Mozambique

Serological responses have been studied in respiratory syncytial virus (RSV) infected children < 1 year of age attending the outpatient department of the Manhiça District Hospital (Mozambique). Molecular characterization of viral RNA in nasopharyngeal aspirates from the infected children indicated a high level of genetic uniformity among the infecting viruses, all of which belonged to a single genotype of RSV group A. A representative virus strain, Moz00, was isolated from one of the infants and was used, together with the group A strain A2 and the group B strain 8/60, as antigens in the quantification of infant antibody responses. In this study, 97.5% (39/40) and 96.4% (27/28) of infected children produced an antibody response against Moz00 detected by the membrane fluorescent antibody test (MFAT) and the neutralization test (NT), respectively. Seroconversion rates decreased when the A2 and 8/60 strains were used as antigen in MFAT (95.4% and 88.2%, respectively) or NT (81.8% and 54.5%, respectively), indicating that antibody responses had both group‐ and strain‐specific components. Antibodies in convalescent sera of infected children were compared with maternally derived antibodies detected in a group of children also < 1 year of age, but with no evidence of RSV infection. The convalescent sera exhibited reduced neutralizing capacity when the 8/60 strain was used as antigen (P = 0.028), suggesting that the infant antibody response lacks neutralizing capacity against strains of the heterologous virus group. Restricted cross‐reactivity and neutralizing capacity of antibodies generated by young children might be expected to induce only moderate protection in subsequent epidemics against genetically distant strains. J. Med. Virol. 69:579–587, 2003. © 2003 Wiley‐Liss, Inc.     

ICAM-3, the third LFA-1 counterreceptor,is a co-stimulatory molecule for both resting and activated T lymphocytes

Optimal activation of human T cells mediated by ligation of CD3/T cell receptor (TcR) complex requires co-stimulatory signals. These can be provided by the adhesive interaction between receptor molecules on T cells and their counter-receptors on antigen-presenting cells. Soluble ICAM-3, anti-ICAM-3 and anti-CD3 mAb were utilized to address the role of the ICAM-3/LFA-1 pathway in TcR/CD3-dependent or -independent T cell activation. Immunoaffinity-purified ICAM-3 co-immobilized with suboptimal concentrations of anti-CD3 monoclonal antibody (mAb) stimulated T lymphocytes as monitored by the expression of the lymphocyte activation antigens CD25 and CD69. The mechanism underlaying this activation appear to involve the interaction of ICAM-3 with a β2 integrin, likely to be LFA-1, since mAb to the CD18 chain completely inhibited T cell activation. Similar experiments demonstrated that anti-ICAM-3 mAb were able to co-stimulate both resting (cord blood) and activated (T cell clones) T lymphocytes. On the contrary, anti-ICAM-1 mAb were only co-stimulatory for CD25 expression on activated but not on resting T cells. In addition, we have found that some γδ T cell clones bearing the Vδ1 segment were activated by direct mAb engagement of ICAM-3 in the absence of TcR/CD3 occupancy. Furthermore, immobilized anti-ICAM-3 mAb also induced development of dentritic processes. In conclusion, our data suggest that ICAM-3 on the surface of both T cells and antigen-presenting cells plays an essential role in the initiation of the immune response.     

Correction to: Longitudinal associations of physical fitness and affect with depression,anxiety and life satisfaction in adult women with fibromyalgia

Quality of Life Research -     

Genetic association of the PERIOD3 (PER3) Clock gene with extreme obesity

BackgroundObesity has reached epidemic proportions worldwide, affecting life quality and span. Susceptibility to obesity is partly mediated by genetic differences. Indeed, several genes from the clock gene family have already been shown to be intimately associated with obesity in diverse ethnic groups. In the present study, an association between BMI and the rs707467, rs228697 and rs228729 PER3 (Period Circadian Clock 3) polymorphisms in subjects with class II (BMI ≥ 35.0–39.9 kg/m²) and class III obesity (>40 kg/m², extreme obesity) were carried out using TaqMan real-time PCR. Overall, 259 Brazilian adults were genotyped, of whom 122 had class II or III obesity (BMI ≥ 35.0 kg/m²) and 137 were controls having normal weight (BMI > 18.5 and <24.9 kg/m²).ResultsPER3 tag SNP (rs228729) shows a significant association with extreme obesity (1000 permutation p = 0.03 and p = 0.04), for genotype and allele frequency respectively) and a haplotype among the three assessed SNPs (alleles G/T/A, rs228697, rs228729, and rs707467, respectively, 1000 permutation p = 0.03) was significantly more prevalent in the group with obesity.ConclusionThis exploratory association study suggests that PER3 rs228729 may be associated with extreme obesity in Brazilian adults, however, replication is needed.     

Body Composition Changes after a Weight Loss Intervention: A 3-Year Follow-Up Study

Studies comparing different types of exercise-based interventions have not shown a consistent effect of training on long-term weight maintenance. The aim of this study was to compare the effects of exercise modalities combined with diet intervention on body composition immediately after intervention and at 3 years’ follow-up in overweight and obese adults. Two-hundred thirty-nine people (107 men) participated in a 6-month diet and exercise-based intervention, split into four randomly assigned groups: strength group (S), endurance group (E), combined strength and endurance group (SE), and control group (C). The body composition measurements took place on the first week before the start of training and after 22 weeks of training. In addition, a third measurement took place 3 years after the intervention period. A significant interaction effect (group × time) (p = 0.017) was observed for the fat mass percentage. It significantly decreased by 5.48 ± 0.65%, 5.30 ± 0.65%, 7.04 ± 0.72%, and 4.86 ± 0.65% at post-intervention for S, E, SE, and C, respectively. Three years after the intervention, the fat mass percentage returned to values similar to the baseline, except for the combined strength and endurance group, where it remained lower than the value at pre-intervention (p < 0.05). However, no significant interaction was discovered for the rest of the studied outcomes, neither at post-intervention nor 3 years later. The combined strength and endurance group was the only group that achieved lower levels of fat mass (%) at both post-intervention and 3 years after intervention, in comparison with the other groups.