| 1. |
- Cheng, Chee-Wai, et al.
(författare)
-
Dosimetric comparison of treatment planning systems in irradiation of breast with tangential fields
- 1997
-
Ingår i: International Journal of Radiation Oncology, Biology, Physics. - 0360-3016. ; 38:4, s. 835-842
-
Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: The objectives of this study are: (1) to investigate the dosimetric differences of the different treatment planning systems (TPS) in breast irradiation with tangential fields, and (2) to study the effect of beam characteristics on dose distributions in tangential breast irradiation with 6 MV linear accelerators from different manufacturers. METHODS AND MATERIALS: Nine commercial and two university-based TPS are evaluated in this study. The computed tomographic scan of three representative patients, labeled as "small", "medium" and "large" based on their respective chest wall separations in the central axis plane (CAX) were used. For each patient, the tangential fields were set up in each TPS. The CAX distribution was optimized separately with lung correction, for each TPS based on the same set of optimization conditions. The isodose distributions in two other off-axis planes, one 6 cm cephalic and the other 6 cm caudal to the CAX plane were also computed. To investigate the effect of beam characteristics on dose distributions, a three-dimensional TPS was used to calculate the isodose distributions for three different linear accelerators, the Varian Clinac 6/100, the Siemens MD2 and the Philips SL/7 for the three patients. In addition, dose distributions obtained with 6 MV X-rays from two different accelerators, the Varian Clinac 6/100 and the Varian 2100C, were compared. RESULTS: For all TPS, the dose distributions in all three planes agreed qualitatively to within +/- 5% for the "small" and the "medium" patients. For the "large" patient, all TPS agreed to within +/- 4% on the CAX plane. The isodose distributions in the caudal plane differed by +/- 5% among all TPS. In the cephalic plane in which the patient separation is much larger than that in the CAX plane, six TPS correctly calculated the dose distribution showing a cold spot in the center of the breast contour. The other five TPS showed that the center of the breast received adequate dose. Isodose distributions for 6 MV X-rays from three different accelerators differed by about +/- 3% for the "small" patient and more than +/- 5% for the "large" patient. For two different 6 MV machines of the same manufacturer, the isodose distribution agreed to within +/- 2% for all three planes for the "large" patient. CONCLUSION: The differences observed among the various TPS in this study were within +/- 5% for both the "small" and the "medium" patients while doses at the hot spot exhibit a larger variation. The large discrepancy observed in the off-axis plane for the "large" patient is largely due to the inability of most TPS to incorporate the collimator angles in the dose calculation. Only six systems involved agreed to within +/- 5% for all three patients in all calculation planes. The difference in dose distributions obtained with three accelerators from different manufacturers is probably due to the difference in beam profiles. On the other hand, the 6 MV X-rays from two different models of linear accelerators from the same manufacturer have similar beam characteristics and the dose distributions are within +/- 2% of each other throughout the breast volume. In general, multi-institutional breast treatment data can be compared within a +/- 5% accuracy.
|
|
| 2. |
- Hallengren, Bengt, et al.
(författare)
-
No increase in fracture incidence in patients treated for thyrotoxicosis in Malmo during 1970-74. A 20-year population-based follow-up
- 1999
-
Ingår i: Journal of Internal Medicine. - : Wiley. - 0954-6820 .- 1365-2796. ; 246:2, s. 139-144
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives. To study whether there is an increased fracture incidence following thyrotoxicosis. Design. A case-control study. Setting. Malmo University Hospital, Malmo, Sweden. Subjects: All patients (n = 333) from the population of Malmo who were treated for thyrotoxicosis for the first time during the 5-year period 1970-74. A total of 618 controls were selected from the local municipality registry in Malmo. For each case the aim was to randomly select two age- and gender-specific controls, alive in 1993 and born the same year and month as the case. Main outcome measures. Fracture incidence. Results. Comparing survivors, there were no differences in the percentage of individuals with fractures (all, fragility, non-fragility) between the patients and the controls. Comparing all individuals and including all fractures, the percentage of individuals with fractures in the entire female patient group (24.6%) was lower (P < 0.05) than in female controls (33.1%). There was a similar but non-significant pattern between male patients and controls. The mean number of all fractures was lower in male patients than in controls (P < 0.05), but no significant difference was noted between female patients and controls. For fragility fractures, there were no significant differences in the percentage of individuals with fractures or in the mean number of fractures between female or male patients and controls. Conclusion. In conclusion we found no increased incidence of fragility fractures in patients with previous thyrotoxicosis as compared with controls. Our results do not support the suggestion that screening for osteoporosis should be performed in patients with previous thyrotoxicosis.
|
|
| 3. |
- Islam, M. Shahidul, et al.
(författare)
-
In situ activation of the type 2 ryanodine receptor in pancreatic beta cells requires cAMP-dependent phosphorylation
- 1998
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 95:11, s. 6145-6150
-
Tidskriftsartikel (refereegranskat)abstract
- Molecular mechanisms that regulate in situ activation of ryanodine receptors (RY) in different cells are poorly understood. Here we demonstrate that caffeine (10 mM) released Ca2+ from the endoplasmic reticulum (ER) in the form of small spikes in only 14% of cultured fura-2 loaded beta cells from ob/ob mice. Surprisingly, when forskolin, an activator of adenylyl cyclase was present, caffeine induced larger Ca2+ spikes in as many as 60% of the cells. Forskolin or the phosphodiesterase-resistant PKA activator Sp-cAMPS alone did not release Ca2+ from ER. 4-Chloro-3-ethylphenol (4-CEP), an agent that activates RYs in other cell systems, released Ca2+ from ER, giving rise to a slow and small increase in [Ca2+]i in beta cells. Prior exposure of cells to forskolin or caffeine (5 mM) qualitatively altered Ca2+ release by 4-CEP, giving rise to Ca2+ spikes. In glucose-stimulated beta cells forskolin induced Ca2+ spikes that were enhanced by 3,9-dimethylxanthine, an activator of RYs. Analysis of RNA from islets and insulin-secreting betaTC-3-cells by RNase protection assay, using type-specific RY probes, revealed low-level expression of mRNA for the type 2 isoform of the receptor (RY2). We conclude that in situ activation of RY2 in beta cells requires cAMP-dependent phosphorylation, a process that recruits the receptor in a functionally operative form.
|
|
| 4. |
- Karsten, Stanislav L., et al.
(författare)
-
Two distinct deletions in the IDS gene and the gene W : a novel type of mutation associated with the Hunter syndrome
- 1997
-
Ingår i: Genomics. - : Elsevier BV. - 0888-7543 .- 1089-8646. ; 43:2, s. 123-129
-
Tidskriftsartikel (refereegranskat)abstract
- A novel mutation has been identified in a patient with the Hunter syndrome (mucopolysaccharidosis type II), in whom the disorder is associated with two distinct deletions separated by 30 kb. The deletions were characterized by Southern blot and PCR analyses, and the nucleotide sequences at both junctions were determined. The first deletion, corresponding to a loss of 3152 bp of DNA, included exons 5 and 6 of the iduronate-2-sulfatase (IDS) gene. The second deletion was 3603 bp long and included exons 3 and 4 of geneW, which is located in the DXS466 locus telomeric of theIDSgene. Both deletions are the result of nonhomologous (illegitimate) recombination events between short direct repeats at the deletion breakpoints. An interesting finding was the presence of the heptamer sequence 5′-TACTCTA-3′ present at both deletion junctions, suggesting that this motif might be a hot spot for recombination. We propose that the double deletion is the result of homology-associated nonhomologous recombinations caused by the presence of large duplicated regions in Xq27.3–q28.
|
|
| 5. |
- Potts, Barbara C.M., et al.
(författare)
-
1H NMR assignments of apo calcyclin and comparative structural analysis with calbindin d(9k) and s 100β
- 1996
-
Ingår i: Protein Science. - : Wiley. - 0961-8368 .- 1469-896X. ; 5:11, s. 2162-2174
-
Tidskriftsartikel (refereegranskat)abstract
- The homodimeric S100 protein calcyclin has been studied in the apo state by two-dimensional 1H NMR spectroscopy. Using a combination of scalar correlation and NOE experiments, sequence-specific 1H NMR assignments were obtained for all but one backbone and >90% of the side-chain resonances. To our knowledge, the 2 x 90 residue (20 kDa) calcyclin dimer is the largest protein system for which such complete assignments have been made by purely homonuclear methods. Sequential and medium-range NOEs and slowly exchanging backbone amide protons identified directly the four helices and the short antiparallel β-type interaction between the two binding loops that comprise each subunit of the dimer. Further analysis of NOEs enabled the unambiguous assignment of 556 intrasubunit distance constraints, 24 intrasubunit hydrogen bonding constraints, and 2 x 26 intersubunit distance constraints. The conformation of the monomer subunit was refined by distance geometry and restrained molecular dynamics calculations using the intrasubunit constraints only. Calculation of the dimer structure starting from this conformational ensemble has been reported elsewhere. The extent of structural homology among the apo calcyclin subunit, the monomer subunit of apo S100β, and monomeric apo calbindin D(9k) has been examined in detail by comparing 1H NMR chemical shifts and secondary structures. This analysis was extended to a comprehensive comparison of the three-dimensional structures of the calcyclin monomer subunit and calbindin D(9k), which revealed greater similarity in the packing of their hydrophobic cores than was anticipated previously. Together, these results support the hypothesis that all members of the S100 family have similar core structures and similar modes of dimerization. Analysis of the amphiphilicity of Helix IV is used to explain why calbindin D(9k) is monomeric, but full-length S100 proteins form homodimers.
|
|
| 6. |
|
|
