Clinical dosimetry for implementation of a multileaf collimator.

In order to initiate the use of a multileaf collimator (MLC) in the clinic, a set of technical procedures needs to be available sufficient to create MLC leaf settings and to deliver an accurate dose of radiation through the MLC-shaped field. Dosimetry data for clinical use of the MLC were measured. Dosimetric characteristics included central axis percent depth dose, output factors, and penumbra. In this paper, it has been concluded that a dose control monitor unit calculation procedure that has been applied to the use of conventional secondary field-shaping blocks can be applied to the multileaf collimator dosimetry. The multileaf collimator penumbra (20% to 80%) is only slightly wider (1-3 mm) than the penumbra of the conventional collimator jaws. Beam's-eye-view comparisons made between the isodose curves in fields shaped by conventional Cerrobend blocks and isodose curves in fields shaped by the multileaf collimator demonstrated that the 50% isodose line at 10-cm depth exhibited the discrete steps of the multileaf collimator leaves, but that the 90% and 10% isodose curves of the multileaf were close to those shaped by Cerrobend blocks.     

Prevalence and distribution of osteoarthritis in a population from Georgian and early Victorian London.

The prevalence of osteoarthritis was calculated in adult skeletons excavated from the crypt of Christ Church, Spitalfields in east London, which was used for burial between 1729 and 1869. Age and sex specific prevalences were also calculated for a subsample of the group for whom age and sex were accurately known from surviving coffin plates. Prevalences were slightly higher in men than in women, except for generalised osteoarthritis. The principal sites affected were the acromioclavicular joints, the facet joints of the spine, and the hands. Osteoarthritis of the large joints was relatively uncommon; osteoarthritis of the hip occurred in 4/360 (1.1%) of men and 10/346 (2.9%) of women and of the knee in 3/360 (0.8%) of men and 18/346 (5.2%) of women. This last difference was statistically significant. A comparison with modern data suggests that the prevalence of osteoarthritis at Spitalfields was lower than in the contemporary population, and some explanations for this apparent difference are considered.     

Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability

X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG repeat expansion in the first exon of the androgen receptor (AR) gene. Disease-associated alleles (37-66 CAGs) change in length when transmitted from parents to offspring, with a significantly greater tendency to shift size when inherited paternally. As transgenic mice carrying human AR cDNAs with 45 and 66 CAG repeats do not display repeat instability, we attempted to model trinucleotide repeat instability by generating transgenic mice with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions in their genomic context. Studies of independent lines of AR YAC transgenic mice with CAG 45 alleles reveal intergenerational instability at an overall rate of approximately 10%. We also find that the 45 CAG repeat tracts are significantly more unstable with maternal transmission and as the transmitting mother ages. Of all the CAG/CTG repeat transgenic mice produced to date the AR YAC CAG 45 mice are unstable with the smallest trinucleotide repeat mutations, suggesting that the length threshold for repeat instability in the mouse may be lowered by including the appropriate flanking human DNA sequences. By sequence-tagged site content analysis and long range mapping we determined that one unstable transgenic line has integrated an approximately 70 kb segment of the AR locus due to fragmentation of the AR YAC. Identification of the cis - acting elements that permit CAG tract instability and the trans -acting factors that modulate repeat instability in the AR YAC CAG 45 mice may provide insights into the molecular basis of trinucleotide repeat instability in humans.      

Blinded comparison of a direct immunofluorescent monoclonal antibody staining method and a Giemsa staining method for identification of Pneumocystis carinii in induced sputum and bronchoalveolar lavage specimens of patients infected with human immunodeficiency virus.

A new direct immunofluorescence monoclonal antibody (DFA) method (Genetic Systems, Inc., Seattle, Wash.) for identification of Pneumocystis carinii in induced sputum and bronchoalveolar lavage specimens was compared in a blinded study with an established Giemsa stain method. We evaluated 148 consecutive clinical specimens from 104 patients with the following results. For the 67 patients (64%) infected with the human immunodeficiency virus (HIV), 49 were initially negative by both the DFA and the Giemsa methods, none were negative by DFA and positive by Giemsa, 6 were positive by DFA and negative by Giemsa, and 12 were positive by both methods, for a sensitivity and a negative predictive value of greater than 99%. For the six patients positive by DFA and negative by Giemsa, all were positive by both methods on evaluation of subsequently obtained clinical specimens, suggesting a specificity of greater than 99% and a false-positive rate of less than 1%. For 37 patients whose HIV status was negative or unknown, 35 were negative by both methods and 2 were positive by DFA and negative by Giemsa. The DFA method was simple to perform and required less time for scoring of stained slides than the Giemsa method, but care had to be taken to avoid false-positive readings due to extraneous fluorescence. This study indicates that the DFA method represents an advance as a sensitive, simple, and rapid way to identify P. carinii in induced sputum and bronchoalveolar lavage specimens from HIV-infected patients and suggests greater sensitivity of the DFA than the Giemsa method in this patient population.     

Interleukin-6, but not interleukin-4, is expressed by Reed-Sternberg cells in Hodgkin''s disease with or without histologic features of Castleman''s disease.

Hodgkin's disease (HD) is a neoplastic disease that is characterized by unbalanced and/or unregulated cytokine production. Information accumulated in our own and other laboratories indicates that the cytokines interleukin-1 (IL-1), IL-5, IL-9, tumor necrosis factor-alpha (TNF-alpha), granulocyte colony-stimulating factor (G-CSF), macrophage CSF (M-CSF), and transforming growth factor-beta (TGF-beta) are secreted by Hodgkin's and Reed-Sternberg (H-RS) cells. These and perhaps additional cytokines are likely to be responsible for the unique histopathologic and clinical alterations seen in patients with HD. In this study, we confirmed that IL-6 is produced by cultured H-RS cells as well as by H-RS cells in tissues. By using an enzyme-linked immunosorbent assay, we found that approximately 2 to 10 ng/ml of IL-6 was secreted by cultured H-RS cells (10(6) cells/ml). In tissues, we were able to immunolocalize IL-6 in the cytoplasm in 10 to 30% of H-RS cells by using rabbit polyclonal and mouse monoclonal anti-IL-6 antibodies. There was no correlation among the IL-6 staining intensity, number of H-RS cells stained, and the degree of plasma cell infiltration. However, in 3 of 17 cases studied, a large number (60%) of H-RS cells were positive for IL-6, and in these patients, abundant plasma cells were present. In one patient, the involved lymph node also showed histologic features similar to those of Castleman's disease. In this patient, we noted abundant IL-6 expression not only in H-RS cells, but also in most reactive histiocytes. The cultured H-RS cells did not express functional receptors for IL-6, and exogenously added IL-6 did not induce proliferation of these cells. We also conducted studies with specific anti-IL-4 antibodies, which did not show IL-4 production by H-RS cells in both cultures and tissues. In tissues, only rare IL-4 positive lymphoid cells or dendritic cells were identified. Thus, the study demonstrated that adequate amounts of IL-6 are required for an abundant plasma cell reaction, and that an additional source of IL-6 from histiocytes is essential for the formation of Castleman's disease-like changes in lymph nodes involved by HD. Furthermore, IL-4 is not likely to be responsible for the T-lymphocyte reaction in tissues, by a mechanism distinct from that in T-cell-rich B-cell lymphomas.     

Cryopreservation of human oocytes: a review of current problems and perspectives

It is well recognized that the ability to cryopreserve unfertilizedhuman oocytes would make a significant contribution to infertilitytreatment. However, despite considerable interest, very fewsuccessful pregnancies have arisen from cryopreserved oocytesafter thawing, insemination and transfer of the subsequent embryo.The reasons for this lack of progress may well result from adearth of information on how the various biophysical changesduring a cryopreservation regimen affect human oocyte function.Recently, fundamental studies on the effects of cooling, membranepermeability, cryoprotectant addition and ice formation havebeen performed on human oocytes by a number of groups, and theseform the basis of the current review. It is likely that successfulhuman oocyte cryopreservation will only follow once these factorsare fully understood, but the existing base of knowledge shouldprovide a platform for further improvements in the techniquescurrently employed.