Total skin electron therapy treatment verification: Monte Carlo simulation and beam characteristics of large non-standard electron fields

Total skin electron therapy (TSET) is a complex technique which requires non-standard measurements and dosimetric procedures. This paper investigates an essential first step towards TSET Monte Carlo (MC) verification. The non-standard 6 MeV 40 x 40 cm2 electron beam at a source to surface distance (SSD) of 100 cm as well as its horizontal projection behind a polymethylmethacrylate (PMMA) screen to SSD = 380 cm were evaluated. The EGS4 OMEGA-BEAM code package running on a Linux home made 47 PCs cluster was used for the MC simulations. Percentage depth-dose curves and profiles were calculated and measured experimentally for the 40 x 40 cm2 field at both SSD = 100 cm and patient surface SSD = 380 cm. The output factor (OF) between the reference 40 x 40 cm2 open field and its horizontal projection as TSET beam at SSD = 380 cm was also measured for comparison with MC results. The accuracy of the simulated beam was validated by the good agreement to within 2% between measured relative dose distributions, including the beam characteristic parameters (R50, R80, R100, Rp, E0) and the MC calculated results. The energy spectrum, fluence and angular distribution at different stages of the beam (at SSD = 100 cm, at SSD = 364.2 cm, behind the PMMA beam spoiler screen and at treatment surface SSD = 380 cm) were derived from MC simulations. Results showed a final decrease in mean energy of almost 56% from the exit window to the treatment surface. A broader angular distribution (FWHM of the angular distribution increased from 13 degrees at SSD = 100 cm to more than 30 degrees at the treatment surface) was fully attributable to the PMMA beam spoiler screen. OF calculations and measurements agreed to less than 1%. The effect of changing the electron energy cut-off from 0.7 MeV to 0.521 MeV and air density fluctuations in the bunker which could affect the MC results were shown to have a negligible impact on the beam fluence distributions. Results proved the applicability of using MC as a treatment verification tool for complex radiotherapy techniques.     

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.     

t(10;16)(q22;p13) and MORF-CREBBP fusion is a recurrent event in acute myeloid leukemia

Recently, it was shown that t(10;16)(q22;p13) fuses the MORF and CREBBP genes in a case of childhood acute myeloid leukemia (AML) M5a, with a complex karyotype containing other rearrangements. Here, we report a new case with the MORF-CREBBP fusion in an 84-year-old patient diagnosed with AML M5b, in which the t(10;16)(q22;p13) was the only cytogenetic aberration. This supports that this is a recurrent pathogenic translocation in AML.     

Bone mass,bone strength,muscle-bone interactions,osteopenias and osteoporoses

Densitometrically, the skeleton is currently conceived as 'a systemically regulated mass of mineralized material that is born, grows, reaches a more or less high peak, and then declines faster or slower as to develop a correspondingly high or low fracture risk'. Alternatively, from a biomechanical point of view, the skeleton can be conceived as 'a biomechanically-regulated structure that can be systemically disturbed (in the cybernetic sense), the strength of which depends on the intrinsic stiffness (material properties) and the spatial distribution (architectural properties) of the mineralized tissue'. The biomechanical feedback system involved (bone 'mechanostat') would not control bone mass to optimize bone strength; it would rather control bone material quality and architecture (through a modulation of bone modeling and remodeling) in order to optimize bone stiffness. The natural stimuli for the bone mechanostat would be the customary strains of bone tissue (sensed by osteocytes) that are induced by gravitational forces and, more importantly, the contractions of regional muscles. According to this view, the development of any bone-weakening disease should be related to either (1) an intrinsic illness of the system (primary disturbances of bone cells), (2) a lack of mechanical stimulation (disuse-induced bone losses), or (3) a systemically-induced shift of the system's setpoint (systemic or secondary bone diseases). This short review aims to conciliate those views: (1) taking profit of the diagnostic possibilities provided by densitometric bone 'mass' determinations; (2) proposing other resources to assess bone mechanical properties; and (3) analyzing the muscle-bone interactions. These are crucial for achieving a differential diagnosis between disuse and primary or secondary bone disturbances, based either (1) on the densitometric determination of bone and muscle masses that would provide an anthropometric diagnosis of osteopenia (not osteoporosis because no extrapolations to bone strength can be made this way) or (2) on the cross-sectional analyses of bone structure or strength and muscle strength provided by bone tomography, magnetic resonance or other techniques that could afford a diagnosis of osteoporosis according to biomechanical criteria.     

Risk factors for incident HIV infection among anonymous HIV testing site clients in Santos,Brazil: 1996-1999

OBJECTIVES: To determine temporal trends in HIV infection and risk factors among persons seeking anonymous HIV testing in Santos, Brazil. METHODS: Data and sera from persons testing for HIV from 1996 to 1999 were used. Exposures were abstracted from HIV testing risk assessments. Stored HIV-positive sera were tested to identify recently acquired HIV infection using a serologic testing algorithm for detecting recent HIV seroconversion (STARHS). Independent associations between exposures and recently acquired HIV infection were determined using multivariate analyses. RESULTS: Overall, estimated HIV incidence was 2.0% (95% CI: 1.1-3.5) for the 4-year period: 1.2% (95% CI: 0.5-2.6) in women and 2.7% (95% CI: 1.3-5.0) in men. Incidence increased among women but remained stable among men. Exposures independently associated with incident infection included a history of sex work (OR= 5.4, 95% CI: 1.5-18.7), concurrent syphilis infection (OR =4.1, 95% CI: 1.4-11.9), anal sex (OR = 3.0, 95% CI: 1.3-7.1), and having an HIV-positive sexual partner (OR= 1.4, 95% CI: 1.1-1.9). CONCLUSIONS: This study further demonstrates the public health utility of using the STARHS for the assessment of emerging trends in the HIV epidemic. Results from this study will help to target appropriate prevention strategies directed toward at-risk populations in Santos.     

Mutations of CD40 ligand in two patients with hyper-IgM syndrome

Two patients with the X-linked form of the hyper-IgM syndrome have been studied. Both patients present: 1. Mutations in the CD40L gene (a nonsense point mutation that introduces a termination codon at the extracellular domain of the protein, and a deletion that eliminates exon 4 as consequence of an abnormal splicing). 2. Lack of CD40L expression on the lymphocyte surface after stimulation with ionomycin and PMA. 3. Altered lymphocytic proliferation in response to anti-CD3. 4. Hyper IgM, low IgG and IgA levels and neutropenia. One of the patients shows, in addition, low Natural Killer cell numbers and severe herpetic infections, which distinguishes this case from the common hyper-IgM syndrome phenotype. Finally, a hyper-IgM stable phenotype has been immortalized by Herpes virus Saimiri for the first time.     

Somatic Exocytosis of Serotonin Mediated by L-Type Calcium Channels in Cultured Leech Neurones

We studied somatic exocytosis of serotonin and its mediation by L-type calcium (Ca²⁺) channels in cultured Retzius neurones of the leech. Exocytosis was induced by trains of impulses at different frequencies or by depolarisation with 40 m m potassium (K⁺), and was quantified by use of the fluorescent dye FM 1–43. Stimulation increased the membrane fluorescence and produced a pattern of FM 1–43 fluorescent spots of 1.28 ± 0.01 μm in diameter, provided that Ca²⁺ was present in the bathing fluid. Individual spots lost their stain during depolarisation with 40 m m K⁺. Electron micrographs showed clusters of dense core vesicles, some of which were in contact with the cell membrane. Presynaptic structures with clear vesicles were absent from the soma. The number of fluorescent spots per soma, but not their diameter or their fluorescence intensity, depended on the frequency of stimulation. Trains at 1 Hz produced 19.5 ± 5 spots per soma, 77.9 ± 13.9 spots per soma were produced at 10 Hz and 91.5 ± 16.9 spots per soma at 20 Hz. Staining patterns were similar for neurones in culture and in situ . In the presence of the L-type Ca²⁺ channel blocker nimodipine (10 μ m ), a 20 Hz train produced only 22.9 ± 6.4 spots per soma, representing a 75 % reduction compared to control cells (   P < 0.05  ). Subsequent incubation with 10 m m caffeine to induce Ca²⁺ release from intracellular stores increased the number of spots to 73.22 ± 12.5. Blockers of N-, P-, Q- or invertebrate Ca²⁺ channels did not affect somatic exocytosis. Our results suggest that somatic exocytosis by neurones shares common mechanisms with excitable endocrine cells.     

Tissue microarray immunohistochemical expression analysis of mismatch repair (hMLH1 and hMSH2 genes) in endometrial carcinoma and atypical endometrial hyperplasia: relationship with microsatellite instability.

Alterations in the mismatch repair genes (hMLH1 and hMSH2) play an important role in the development of microsatellite instability in sporadic endometrial cancer. Tissue microarray technology allows molecular profiling of tumor samples at the DNA, RNA, and protein levels. We analyzed hMLH1 and hMSH2 expression by immunohistochemistry in a group of atypical endometrial hyperplasias (n = 10), endometrioid endometrial carcinomas (n = 58), and nonendometrioid endometrial carcinomas (n = 27) on tissue microarray. The results were correlated with microsatellite instability status as evaluated by BAT-25 and BAT-26. Overall, 29.4% of lesions showed microsatellite instability. Loss of nuclear hMLH1 and hMSH2 protein expression was seen in 22.3% and 6.5% of cases, respectively. Immunohistochemistry for hMLH1 and hMSH2 showed lack of protein expression in 64% and 16.6% of microsatellite instability-positive endometrial lesions, respectively. Taken together, hMLH1 or hMSH2 protein expression was absent in 18 of 24 microsatellite instability-positive cases (75% sensitivity). A high level of concordance was found between immunohistochemistry for hMLH1 and hMSH2 and microsatellite instability status evaluated by BAT-25 and BAT-26 (kappa value of 0.7). Of the 57 cases found to be microsatellite instability negative, 53 showed normal expression of both proteins (93% specificity). The observed predictive value of absence of expression of hMLH1 for predicting microsatellite instability-positive status was 82%. The predictive value of normal expression of both proteins for predicting microsatellite instability-negative status was 90%. These results are consistent with those previously reported in whole tissue sections. Therefore, immunohistochemical analysis of hMLH1 and hMSH2 expression on tissue microarray provides an accurate technique for screening for tumors with microsatellite instability. Tissue microarrays represent an ideal approach for comparing different diagnostic or predictive markers with one another in consecutive tissue microarray sections.     

Experimental autoimmune myasthenia gravis in naive non-obese diabetic (NOD/LtJ) mice: susceptibility associated with natural IgG antibodies to the acetylcholine receptor

Naive non-obese diabetic (NOD/LtJ) mice spontaneously produce natural IgG autoantibodies against self-antigens associated with the experimental autoimmune diseases to which they are susceptible: insulin-dependant diabetes mellitus, systemic lupus erythematosus and experimental autoimmune encephalomyelitis. We discovered recently that NOD/LtJ mice also spontaneously produce IgG antibodies to the acetylcholine receptor (AchR), an antigen that can induce experimental autoimmune myasthenia gravis (EAMG) in susceptible rodents. However, there are no reports indicating that NOD/LtJ mice are susceptible to EAMG. To test whether the presence of spontaneous IgG autoantibodies can predict susceptibility to an autoimmune disease, we challenged NOD/LtJ mice using a standard protocol to induce EAMG. We now report that NOD/LtJ mice developed EAMG, although to a somewhat lesser degree than did C57BL/6 mice, a strain regarded as highly susceptible to the disease. Both strains produced comparable levels of immune antibodies to AchR of the complement-fixing isotypes IgG2a and IgG2b; however, NOD/LtJ mice produced significantly more IgG1. An antigen-specific T cell proliferative response to AchR of the same magnitude was detected in both strains, together with the secretion of similar amounts of IFN-gamma. Thus, NOD/LtJ mice are susceptible to EAMG and disease induction is accompanied by immune responses comparable to those seen in the susceptible strain C57BL/6. These results support the association between specific, natural IgG autoantibodies and susceptibility to the induction of a particular autoimmune disease.