Precision measurement of the neutral pion lifetime.

The explicit breaking of the axial symmetry by quantum fluctuations gives rise to the so-called axial anomaly. This phenomenon is solely responsible for the decay of the neutral pion π0 into two photons (γγ), leading to its unusually short lifetime. We precisely measured the decay width Γ of the [Formula: see text] process. The differential cross sections for π0 photoproduction at forward angles were measured on two targets, carbon-12 and silicon-28, yielding [Formula: see text], where stat. denotes the statistical uncertainty and syst. the systematic uncertainty. We combined the results of this and an earlier experiment to generate a weighted average of [Formula: see text] Our final result has a total uncertainty of 1.50% and confirms the prediction based on the chiral anomaly in quantum chromodynamics.

Promotion of medial collateral ligament healing using a high-voltage electrical field.

PURPOSE: To assess the biomechanical and histological effects of a high-voltage electrical field on ligament healing. METHODS: 54 male Wistar rats were used. The medial collateral ligaments (MCLs) of 6 rats were measured for normal biomechanical failure load and stiffness. MCLs of the remaining 48 rats were transected and randomly assigned; half were subjected to a high-voltage electrical field for 8 hours a day (experimental group), and the other half were kept under normal conditions (control group). Eight rats from each group were killed 2, 4, and 6 weeks after the transection and their MCLs were tested biomechanically and histologically. RESULTS: Failure load and stiffness of the MCLs in the experimental group were significantly higher than those in the control group 2 weeks after transection, but not thereafter. At week 2, the granulation tissue completely occupied the space between the cut ends of the MCL in the experimental group, whereas some gaps remained in the control group. CONCLUSION: A high-voltage electrical field appear to accelerate ligament healing in the initial 2 weeks. Earlier initial healing may allow earlier start of the rehabilitation.

Evaluation of tibial bone-tunnel changes with X-ray and computed tomography after ACL reconstruction using a bone-patella tendon-bone autograft.

Thirteen patients who underwent anterior cruciate ligament (ACL) reconstruction with bone-patella tendon-bone autografts (BTB) using interference screws were the subjects of this study. We analysed the relationship between bone-tunnel changes and clinical results 2 years after ACL reconstruction. To investigate changes, X-ray images were used to evaluate bone-tunnel enlargement, and computed tomography (CT) was used to evaluate the sclerotic area around the bone tunnel. The KT-2000 was used to measure the discrepancy of tibial anterior displacement between the affected and nonaffected sides (DTAD). There was no correlation between bone-tunnel enlargement and DTAD. On the other hand, in the CT evaluation, there was a significant correlation between the sclerotic area and DTAD. Our results suggest that it is more significant to analyse the area of sclerotic change than bone-tunnel enlargement for clinical evaluation. We cannot evaluate bone-tunnel changes correctly with two-dimensional X-rays and cannot analyse the sclerotic area using X-rays. Therefore, we recommend that CT, with which it is possible to analyse the sclerotic area, be used to evaluate bone-tunnel changes and clinical results.

Morphological and biochemical re-evaluation of the process of cavitation in the rat knee joint: cellular and cell strata alterations in the interzone.

To assess the contribution of apoptosis to the mechanism of synovial joint cavitation, and to clarify morphological cellular changes during cavitation, we investigated the development of the rat knee joint by light and electron microscopy, TUNEL methods, and electrophoresis of DNA fragments. Although cavitation occurred within the interzone, which consists of 2 outer and a middle layer termed the intermediate zone, no morphological or biochemical signs of cell death, in particular apoptosis, were seen in the interzone at any embryonic stage. Microscopic and ultrastructural alterations affecting cell differentiation were clearly observed in the interzone, i.e. mesenchymal cells gradually showed elongation, cytoplasmic vacuolation and pyknosis in the intermediate zone where the elongated cells were arranged in parallel in some strata. Some of these cells were further flattened into spindle cells and the number of strata decreased to 2. The rest of the cells were incorporated secondarily into the outer layers, becoming chondroblasts. Collagen fibrils were arranged in a network structure in the outer layers, which obviously differed from the directional pattern parallel to the long axis of elongated cells in the intermediate zone. In addition, the density of collagen fibrils was higher in the outer layers than in the intermediate zone. During cavitation, the initial separation was detected between the elongated cells in the intermediate zone in paraffin sections at E16.5 and the spindle cells in epoxy sections at E18.5. The spindle cells lining the cavity, namely, the surfaces of the epiphysis and meniscus, finally became chondrocytes. The diminution of proteoglycans and collagen fibrils and the synthesis of hyaluronan in the extracellular matrix are now generally believed to be parts of the mechanism for cavitation based on the concept of 'loss of cohesion'. The microscopic and ultrastructural alterations in the interzone seemed to reflect differences in the arrangement and density of collagen fibrils and the developmental condition of the extracellular matrix between layers. Also it did not seem likely that these alterations inhibit the synthesis of hyaluronan at the presumptive joint line because this synthesis takes place at the plasma membrane. Separation between spindle cells should therefore represent the mechanism for developmentally programmed cavitation. Reorganization of the extracellular matrix is probably necessary for the cellular metamorphoses in the interzone involved in the process of cavitation.

Length and width of the tendinous portion of the palmaris longus: a cadaver study of adult Japanese.

We examined 72 forearms of 36 cadavers to measure the length and width of the tendinous portion of the palmaris longus in adult Japanese. The palmaris longus muscles were absent in both arms in 1 cadaver and in a unilateral arm in 1 cadaver. Double palmaris longus muscles were found in 1 arm in another cadaver. Most cadavers had a typical palmaris longus muscle and tendon shape. The mean length and width of the tendons were 124.6 +/- 17.0 and 4.5 +/- 0.7 mm, respectively, in male specimens and 108.3 +/- 16.4 and 4.0 +/- 0.7 mm in female specimens, respectively. The mean lengths of the forearms were 240.0 +/- 12.6 mm in male specimens and 218.8 +/- 14.6 mm in female specimens. There was a statistically significant correlation between the lengths of the palmaris longus tendon and forearm. These results indicate that one can estimate the length of palmaris longus tendons before surgical intervention.

The optimal equilibration time for mouse embryos frozen by vitrification with trehalose.

To determine the best equilibration time in the cryoprotectant before rapid cooling, 8-cell mouse embryos were exposed to a vitrification solution containing ethylene glycol, Ficoll and trehalose in modified phosphate-buffered saline at 5 degrees C for varying periods of time. They were frozen using an ultra rapid freezing method, thawed in a 20 degrees C water bath and cultured for 24 h with 5-bromo-2-deoxyuridine. Embryo development and the number of sister chromatid exchanges, a sensitive indicator of genetic damage, were observed. The results demonstrated that embryo development after freezing and thawing was similar among the groups exposed for periods of 5-40 min. However, the number of sister chromatid exchanges was significantly smaller in the group exposed for 5 min, indicating that this was the safest equilibration time in the vitrification solution.

Expression of CD44 in human cumulus and mural granulosa cells of individual patients in in-vitro fertilization programmes.

CD44 is a polymorphic and polyfunctional transmembrane glycoprotein widely expressed in many types of cells. Here, the expression of this protein on human membrana granulosa was studied by two techniques. Using confocal laser scanning microscopy (CLSM) with the mouse monoclonal antibody to human CD44 (clone G44-26), cells immunoreactive for CD44 were observed in both cumulus and mural granulosa cell masses. On the other hand, using monoclonal antibody to human CD44v9, goat polyclonal antibody to human CD44v3-10 and the clone G44-26, no immunoreactivity for CD44v9 and/or CD44v3-10 was observed in either cell group by flow cytometry. In the flow cytometric analysis of 32 patients, the incidence of CD44 expression in cumulus cells (62.6+/-1.3%) was significantly higher than that in mural granulosa cells (38.5+/-3.2%) (P<0.0001). In the comparison of CD44 expression by flow cytometry according to the maturation of each cumulus-oocyte complex, the incidence of CD44 expression of cumulus cells was significantly higher in the mature group than in the immature group (P<0.05). In a flow cytometric analysis, patients with endometriosis showed a significantly lower incidence of CD44 expression in cumulus cells compared to the infertility of unknown origin group (P<0.05), and compared to both the male infertility group and the unknown origin group in mural granulosa cells (P<0.01). These findings suggest that the standard form of CD44 is expressed in human membrana granulosa with polarity and may play an important role in oocyte maturation.

Leucoencefalopatia multifocal progressiva / Progressive multifocal leucoencephalopathy

A ocorrência de infecções oportunistas no sistema nervoso central, em pacientes imunossuprimidos é comum e reconhecida há longo tempo. Relata-se caso de Leucencefalopatia Multifocal Progressiva em paciente de 28 anos, HIV positivo, doença em estágio terminal. São discutidos os aspectos clínico-radiológicos, imunopatológicos e prognósticos dessa afecção, apoiados na literatura especializada