NADP+ -dependent isocitrate dehydrogenase isozymes from a psychrotrophic bacterium, Psychrobacter sp. strain 13A.

The genes encoding dimeric and monomeric isocitrate dehydrogenase (IDH) isozymes from a psychrotrophic bacterium, strain 13A (13AIDH-D and 13AIDH-M, respectively), were cloned and sequenced. The deduced amino acid sequences of these two IDHs showed high degrees of identity with those of bacteria of genus Psychrobacter. Analysis of the 16S ribosomal RNA gene of the strain 13A revealed that this bacterium is classified to genus Psychrobacter. The optimum temperatures for activities of 13AIDH-D and 13AIDH-M were 55°C and 45°C, respectively, indicating that they are mesophilic. On the contrary, 13AIDH-D maintained 90% of its maximum activity after incubation for 10 min at 50°C, while the 13AIDH-M activity was completely lost under the same condition. In addition, 13AIDH-D showed much higher specific activity than 13AIDH-M. From northern and western blot analyses, the 13AIDH-D gene was found to be not transcribed under the growth conditions tested in this study. However, the catalytic ability of the mesophilic 13AIDH-M was concluded to be enough to sustain the growth of strain 13A at low temperatures. Therefore, a novel pattern of the contribution of IDH isozymes in cold-living bacteria to their growth at low temperatures was confirmed in strain 13A.

Analysis of amino acid residues involved in the thermal properties of isocitrate dehydrogenases from a psychrophilic bacterium, Colwellia maris, and a psychrotrophic bacterium, Pseudomonas psychrophila.

Monomeric NADP+-dependent isocitrate dehydrogenase (IDH) from a psychrophilic bacterium, Colwella maris, (CmIDH) is a cold-adapted enzyme, whereas that of a psychrotrophic bacterium, Pseudomonas psychrophila, (PpIDH) is mesophilic. However, the amino acid sequence identity of the two IDHs is high (67%). To identify the amino acid residues involved in the differences in their thermal properties, such as optimum temperature and thermostability for activity, six amino acid residues located in the corresponding positions of their regions 2 and 3 were substituted by site-directed mutagenesis, and several thermal properties of the mutated IDHs were examined. CmIDH mutants, CmE538L, CmE596L and CmA741S, substituted at Glu538, Glu596 and Ala741 by the corresponding PpIDH residues of Leu, Leu and Ser, respectively, exhibited higher thermostability than wild-type CmIDH (CmWT). Furthermore, the specific activity of CmE596L and CmA741S was higher than that of CmWT. On the other hand, the corresponding mutants of PpIDH PpL536E, PpL594E and PpS739A were more thermolabile than wild-type PpIDH, and PpL594E had a lower specific activity at temperatures over 45°C. These results suggested that these amino acid residues of CmIDH and PpIDH are involved in their thermal properties.

Effects of the substituted amino acid residues on the thermal properties of monomeric isocitrate dehydrogenases from a psychrophilic bacterium, Psychromonas marina, and a mesophilic bacterium, Azotobacter vinelandii.

A cold-adapted monomeric isocitrate dehydrogenase from a psychrophilic bacterium, Psychromonas marina (PmIDH), showed a high degree of amino acid sequential identity (64%) to a mesophilic one from a mesophilic bacterium, Azotobacter vinelandii (AvIDH). In this study, eight corresponding amino acid residues were substituted between them by site-directed mutagenesis, and several thermal properties of the mutated IDHs were examined. In the PmIDH mutants, PmL735F, substituted Leu735 of PmIDH by the corresponding Phe of AvIDH, showed higher specific activity and thermostability of activity than wild-type PmIDH, while the H600Y and N741P mutations of PmIDH resulted in decreased specific activity and thermostability of activity. On the other hand, among the AvIDH mutants, AvP718T showed lower optimum temperature and thermostability of activity than wild-type AvIDH. In PmIDH variously combined the H600Y, L735F and N741P mutations, PmH600YL735F, including the H600Y and L735F mutations, showed higher specific activity than PmH600Y and similar optimum temperature and thermostability of activity to PmH600Y. Furthermore, PmL735FN741P exhibited higher specific activity and thermostability of activity than PmN741P. These results indicated that the effects of the three mutations of PmIDH are additive on the specific activity of both PmH600YL735F and PmL735FN741P and on thermostability of PmL735FN741P.

Contribution of Three Different Regions of Isocitrate Dehydrogenases from Psychrophilic and Psychrotolerant Bacteria to Their Thermal Properties.

Monomeric isocitrate dehydrogenases of a psychrophilic bacterium, Colwellia maris, and a psychrotolerant bacterium, Pseudomonas psychrophila, (CmIDH and PpIDH) are cold-adapted and mesophilic, respectively. On the other hand, previous studies revealed that the monomeric IDH of Azotobacter vinelandii (AvIDH) is also mesophilic and the regions 2 and 3 among three regions of this enzyme are involved in the thermal properties. Therefore, to examine whether the region(s) responsible for the mesophilic properties are common between PpIDH and AvIDH, the genes of chimeric IDHs exchanging three regions of PpIDH and CmIDH in various combinations were constructed and overexpressed as His-tagged recombinant proteins in the Escherichia coli cells, and the chimeric and wild-type PpIDH and CmIDH were purified with Ni-chelating affinity column chromatography. The swapping chimeras of the regions 2 or 3 in PpIDH and CmIDH showed lower and higher optimum temperatures for activities and their thermostabilities than the wild-type ones, respectively. On the other hand, the exchange of the respective region 1 hardly influenced these properties of the two IDHs. Therefore, the regions 2 and 3 of the two IDHs were confirmed to be involved in their thermal properties. These results were coincident with those of the previous study on chimeric IDHs between AvIDH and CmIDH, indicating that the common regions of AvIDH and PpIDH are responsible for their mesophilic properties and the amino acid residues involved in their thermal properties are present in the regions 2 and 3.

Pravastatin reduces radiation-induced damage in normal tissues.

Pravastatin is an inhibitor of 3-hydroxy-3-methyl- glutaryl-coenzyme A reductase that has been reported to have therapeutic applications in a range of inflammatory conditions. The aim of the present study was to assess the radioprotective effects of pravastatin in an experimental animal model. Mice were divided into two groups: The control group received ionizing radiation with no prior medication, while the pravastatin group received pravastatin prior to ionizing radiation. Pravastatin was administered orally at 30 mg/kg body weight in drinking water at 24 and 4 h before irradiation. Intestinal crypt epithelial cell survival and the incidence of apoptosis in the intestine and lung were measured post-irradiation. The effect of pravastatin on intestinal DNA damage was determined by immunohistochemistry. Finally, the effect of pravastatin on tumor response to radiotherapy was examined in a mouse mesothelioma xenograft model. Pravastatin increased the number of viable intestinal crypts and this effect was statistically significant in the ileum (P<0.0001). The pravastatin group showed significantly lower apoptotic indices in all examined parts of the intestine (P<0.0001) and tended to show reduced apoptosis in the lung. Pravastatin reduced the intestinal expression of ataxia-telangiectasia mutated and gamma-H2AX after irradiation. No apparent pravastatin-related differences were observed in the response of xenograft tumors to irradiation. In conclusion, pravastatin had radioprotective effects on the intestine and lung and reduced radiation-induced DNA double-strand breaks. Pravastatin may increase the therapeutic index of radiotherapy.

NADP+-dependent isocitrate dehydrogenase from a psychrophilic bacterium, Psychromonas marina.

The gene encoding NADP+-dependent isocitrate dehydrogenase (IDH; EC 1.1.1.42) of a psychrophilic bacterium, Psychromonas marina, was cloned and sequenced. The open reading frame of the gene encoding IDH of P. marina (PmIDH) was 2229 bp in length and corresponded to a polypeptide composed of 742 amino acids. The molecular mass of IDH was calculated as 80,426 Da. The deduced amino acid sequence of PmIDH exhibited high degrees of homology with the monomeric IDH from other bacteria such as Colwellia maris (62% identity) and Azotobacter vinelandii (AvIDH) (64%). His-tagged PmIDH overexpressed in Escherichia coli cells was purified and characterized. The optimum temperature of PmIDH activity was about 35 °C; however, the enzyme lost 74% of the activity after incubation for 10 min at 30 °C, indicating that this enzyme is thermolabile. Chimeric enzymes produced through domain swapping between PmIDH and mesophilic AvIDH were constructed and their optimum temperatures and thermostability were determined. The results suggest that regions 2 and 3, especially region 3, of the two IDHs are involved in their catalytic activities and optimum temperature and thermostability for activity.

Radiotherapy in late elderly (aged 75 or older) patients with paranasal sinus carcinoma: a single institution experience.

The purpose of our study was to assess the feasibility of radiotherapy (RT) for locally advanced paranasal sinus carcinomas in late elderly patients (aged ≥75 years) from a single institution in Japan. From 2000 to 2015, we retrospectively analyzed 14 patients (11 maxillary and 3 ethmoid sinus carcinoma patients) who underwent RT for pathologically confirmed paranasal sinus carcinomas. RT was performed without unexpected cessations. Two patients, however, developed Grade 3 mucositis. The median follow-up duration was 13 months (range 2-54 months). The 1- and 2-year overall survival (OS) rates were 81.8 and 54.5 %, respectively. The local response rate after the initial treatment was 85.7 %. The 1- and 2-year progression-free survival (PFS) rates were 46.2 and 24.8 %, respectively. Univariate analysis of different clinicopathological parameters was conducted to identify associations with OS and PFS. We demonstrated that intensity modulated radiation therapy (IMRT) of >60 Gy with concomitant intra-arterial (cisplatin-based) infusion chemoradiotherapy led to improved OS and PFS rates, although no statistical significance was observed. Moreover, none of the squamous cell carcinoma (SCC) patients who received 33 fractions of 66 Gy in IMRT died during the median follow-up period of 13 months (range 12-25 months). In conclusion, RT with concomitant intra-arterial (cisplatin-based) infusion chemoradiotherapy can be considered an effective, well-tolerated, and feasible treatment option for late elderly patients with paranasal sinus carcinomas. In addition, >60 Gy of RT in IMRT led to improved survival outcomes in elderly paranasal sinus carcinoma patients.

Characterization of NADP(+)-dependent isocitrate dehydrogenase isozymes from a psychrophilic bacterium, Colwellia psychrerythraea strain 34H.

NADP(+)-dependent isocitrate dehydrogenase (IDH) isozymes of a psychrophilic bacterium, Colwellia psychrerythraea strain 34H, were characterized. The coexistence of monomeric and homodimeric IDHs in this bacterium was confirmed by Western blot analysis, the genes encoding two monomeric (IDH-IIa and IDH-IIb) and one dimeric (IDH-I) IDHs were cloned and overexpressed in Escherichia coli, and the three IDH proteins were purified. Both of the purified IDH-IIa and IDH-IIb were found to be cold-adapted enzymes while the purified IDH-I showed mesophilic properties. However, the specific activities of IDH-IIa and IDH-IIb were lower even at low temperatures than that of IDH-I. Therefore, IDH-I was suggested to be important for the growth of this bacterium. The results of colony formation of E. coli transformants carrying the respective IDH genes and IDH activities in their crude extracts indicated that the expression of the IDH-IIa gene is cold-inducible in the E. coli cells.

The threshold of hypothyroidism after radiation therapy for head and neck cancer: a retrospective analysis of 116 cases.

The purpose of the present study was to determine the risk factors for developing thyroid disorders based on a dose-volume histograms (DVHs) analysis. Data from a total of 116 consecutive patients undergoing 3D conformal radiation therapy for head and neck cancers was retrospectively evaluated. Radiation therapy was performed between April 2007 and December 2010. There were 108 males and 8 females included in the study. The median follow-up term was 24 months (range, 1-62 months). The thyroid function was evaluated by measuring thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels. The mean thyroid dose, and the volume of thyroid gland spared from doses ≥10, 20, 30 and 40 Gy (VS10, VS20, VS30 and VS40) were calculated for all patients. The thyroid dose and volume were calculated by the radiotherapy planning system (RTPS). The cumulative incidences of hypothyroidism were 21.1% and 36.4% at one year and two years, respectively, after the end of radiation therapy. In the DVH analyses, the patients who received a mean thyroid dose <30 Gy had a significantly lower incidence of hypothyroidism. The univariate analyses showed that the VS10, VS20, VS30 and VS40 were associated with the risk of hypothyroidism. Hypothyroidism was a relatively common type of late radiation-induced toxicity. A mean thyroid dose of 30 Gy may be a useful threshold for predicting the development of hypothyroidism after radiation therapy for head and neck cancers.

Polaprezinc reduces the severity of radiation-induced mucositis in head and neck cancer patients.

Polaprezinc (PZ), an antiulcer drug, has been reported to have antioxidant properties. The aim of the present study was to assess the feasibility and efficacy of administering PZ for radiation-induced mucositis in head and neck cancer patients. Patients with newly diagnosed head and neck cancer were enrolled in this prospective study. PZ was prepared as an oral rinse. The PZ oral rinse was used four times per day during the course of radiotherapy. Sequential changes in radiation mucositis were assessed during and after radiotherapy according to the Common Terminology Criteria for Adverse Events, version 3.0. Furthermore, a retrospective comparison analysis was performed to assess the efficacy of PZ for radiation-induced mucositis. A total of 32 patients were enrolled in the prospective study of the PZ oral rinse. Radiotherapy was performed up to a total dose of 60-66 Gy using a conventional schedule combined with chemotherapy. Of the 32 patients, 30 (93.8%) reported no complaints due to the PZ oral rinse. In addition, PZ was not associated with severe adverse effects. Among the patients who received PZ, grade 3 mucositis was observed in 29.0% based on the mucosal findings and in 39.3% based on the symptoms. In the patients who did not receive PZ, the incidence of grade 3 mucositis was 40.0% based on the mucosal findings and 60.7% based on the symptoms. Moreover, PZ promoted the recovery from mucositis caused by chemoradiotherapy and was not associated with reduced tumor response to radiotherapy. Therefore, the PZ oral rinse was well tolerated and proved to be efficient for the treatment of radiotherapy-induced oral mucositis.

Arterial chemoradiotherapy for carcinomas of the external auditory canal and middle ear.

OBJECTIVES/HYPOTHESIS: The purpose of this study was to estimate the efficacy of superselective arterial chemoradiotherapy for locally advanced carcinomas of the external auditory canal and middle ear. STUDY DESIGN: A retrospective study of clinical data for consecutive patients with locally advanced carcinomas of the external auditory canal and middle ear. METHODS: Thirteen patients with locally advanced carcinomas of the external auditory canal and middle ear (T3: one patient, T4: 12 patients) were reviewed. The median follow-up duration in the living patients was 33 months. The total dose of radiation therapy was 60 Gy using conventional fractionation. Four, five, or six courses of a superselective arterial infusion (cisplatin 50 mg) were given weekly. RESULTS: The overall survival and progression-free survival rates at 2 years, calculated by the Kaplan-Meier method, were 58.7% and 53.8%, respectively. No late-phase adverse effects due to chemoradiation and no adverse effects due to catheterization were observed. CONCLUSIONS: These results suggest that superselective arterial chemoradiation can be a treatment option for locally advanced carcinomas of the external auditory canal and middle ear.

Characterization of chimeric and mutated isocitrate lyases of a mesophilic nitrogen-fixing bacterium, Azotobacter vinelandii, and a psychrophilic bacterium, Colwellia maris.

Chimeric enzymes between a cold-adapted isocitrate lyase (ICL) of a psychrophilic bacterium, Colwellia maris, (CmICL) and a mesophilic ICL of a nitrogen-fixing bacterium, Azotobacter vinelandii, (AvICL) were constructed by dividing the ICL genes into four regions of almost equal length and exchanging regions in various combinations. The chimeric ICL, which was replaced C-terminal region 4 of AvICL by the corresponding region of CmICL, showed much lower specific activity and lower optimum temperature and thermostability for activity than wild-type AvICL, indicating that region 4 is involved in its thermal properties. Furthermore, mutual substitution between the Met501 residue in region 4 of CmICL and the corresponding Ile504 residue of AvICL influenced the temperature dependence of their activities, suggesting that these amino acid residues are important to the respective mesophilic and cold-adapted properties of AvICL and CmICL.

Effects of the combined substitutions of amino acid residues on thermal properties of cold-adapted monomeric isocitrate dehydrogenases from psychrophilic bacteria.

In the two cold-adapted monomeric isocitrate dehydrogenases from psychrophilic bacteria, Colwellia maris and Colwellia psychrerythraea (CmIDH and CpIDH, respectively), the combined substitutions of amino acid residues between the Leu693, Leu724 and Phe735 residues of CmIDH and the corresponding Phe693, Gln724 and Leu735 residues of CpIDH were introduced by site-directed mutagenesis. A double mutant of CmIDH substituted its Leu724 and Phe735 residues by the corresponding ones of CpIDH, CmL724Q/F735L, and the triple mutant of CpIDH, CpF693L/Q724L/L735F, showed the most decrease and increase of activity, respectively, of each wild-type and its all mutated enzymes. In the case of CmIDH, the substitutions of these three amino acid residues resulted in the decrease of catalytic activity and thermostability for activity, but the combined substitutions of amino acid residues did not necessarily exert additive effects on these properties. On the other hand, similar substitutions in CpIDH had quite opposite effects to CmIDH, and the effects of the combined substitutions were additive. All multiple mutants of CmIDH and CpIDH showed lower and higher catalytic efficiency (k(cat)/K(m)) values than the respective wild-type enzymes. Single and multiple mutations of the substituted amino acid residues in the CmIDH and CpIDH led to the increase and decrease of sensitivity to tryptic digestion, indicating that the stability of protein structure was decreased and increased by the mutations, respectively.

Body mass index can affect gastrointestinal and genitourinary toxicity in patients with prostate cancer treated with external beam radiation therapy.

The aim of the present study was to determine the impact of obesity on radiation-induced gastrointestinal (GI) and genitourinary (GU) toxicity. The cases of 54 patients with prostate cancer, treated with three-dimensional conformal radiation therapy (RT), were reviewed. For each patient, the body mass index (BMI), distance between the prostate and rectum (D) on a computerised tomography scan and the dosimetric parameters of the rectum and bladder in the planning data of RT, were analyzed. GI and GU toxicity was assessed during and following RT. The results of the patients with a BMI of <25 (lower BMI) were compared with those of the patients with a BMI of ≥25 (higher BMI). The higher BMI group exhibited significantly lower doses of V60 and V65 in the rectum than the lower BMI group. No significant differences were found in D and bladder doses between the two groups. The incidence of acute GI and GU toxicity and late GI and GU toxicity were 41.7, 19.4, 35.3 and 5.7% in the lower BMI group, respectively, and 27.8, 27.8, 5.9 and 35.3% in the higher BMI group, respectively. In addition, a significant difference was found in the incidence of late GU toxicity between the two groups. Among patients who underwent RT for prostate cancer, those with higher BMIs had a tendency to show lower incidences of GI toxicity and higher incidences of GU toxicity than patients with lower BMIs. To conclude, an increased effort must be made to reduce rectal doses in patients with lower BMIs. Conversely, increased care for GU toxicity must be provided for overweight patients.

Analysis of amino acid residues involved in cold activity of monomeric isocitrate dehydrogenase from psychrophilic bacteria, Colwellia maris and Colwellia psychrerythraea.

Monomeric isocitrate dehydrogenases from psychrophilic bacteria, Colwellia maris and Colwellia psychrerythraea (CmIDH-II and CpIDH-M, respectively) are cold-adapted enzymes and show a high degree of amino acid sequential identity to each other (77%). However, maximum activity of CpIDH-M at optimum temperature is much less than that of CmIDH-II. In the C-terminal region 3 of these enzymes, which was suggested from previous study to be responsible for their distinct catalytic ability, several sequential differences of amino acid residue are present. Among them, ten amino acid residues were exchanged between them by site-directed mutagenesis and several properties of the mutated enzymes were examined in this study. The mutated enzymes of CmIDH-II substituted its Gln671, Leu724 and Phe735 residues with the corresponding residues of CpIDH-M (termed Q671K, L724Q and F735L, respectively) showed lower specific activity and thermostability for activity than the wild-type enzyme. Furthermore, the decreased specific activity was also observed in L693F. In contrast, the corresponding mutants of CpIDH-M, F693L, Q724L and L735F, showed the increased specific activity and thermostability for activity. The catalytic efficiency (k(cat)/K(m)) values of these mutated CmIDH-II and CpIDH-M were lower and higher than those of their wild-type IDHs, respectively. These results suggest that the Gln671, Leu693, Leu724 and Phe735 residues of CmIDH-II are important for exerting its high catalytic ability.

Three-dimensional radiochromic film dosimetry for volumetric modulated arc therapy using a spiral water phantom.

We validated 3D radiochromic film dosimetry for volumetric modulated arc therapy (VMAT) using a newly developed spiral water phantom. The phantom consists of a main body and an insert box, each of which has an acrylic wall thickness of 3 mm and is filled with water. The insert box includes a spiral film box used for dose-distribution measurement, and a film holder for positioning a radiochromic film. The film holder has two parallel walls whose facing inner surfaces are equipped with spiral grooves in a mirrored configuration. The film is inserted into the spiral grooves by its side edges and runs along them to be positioned on a spiral plane. Dose calculation was performed by applying clinical VMAT plans to the spiral water phantom using a commercial Monte Carlo-based treatment-planning system, Monaco, whereas dose was measured by delivering the VMAT beams to the phantom. The calculated dose distributions were resampled on the spiral plane, and the dose distributions recorded on the film were scanned. Comparisons between the calculated and measured dose distributions yielded an average gamma-index pass rate of 87.0% (range, 91.2-84.6%) in nine prostate VMAT plans under 3 mm/3% criteria with a dose-calculation grid size of 2 mm. The pass rates were increased beyond 90% (average, 91.1%; range, 90.1-92.0%) when the dose-calculation grid size was decreased to 1 mm. We have confirmed that 3D radiochromic film dosimetry using the spiral water phantom is a simple and cost-effective approach to VMAT dose verification.

Neoadjuvant short-course hyperfractionated accelerated radiotherapy (SC-HART) combined with S-1 for locally advanced rectal cancer.

The purpose of this study was to examine the safety and feasibility of a novel protocol of neoadjuvant short-course hyperfractionated accelerated radiotherapy (SC-HART) combined with S-1 for locally advanced rectal cancer. A total of 56 patients with lower rectal cancer of cT3N1M0 (Stage III b) was treated with SC-HART followed by radical surgery, and were analyzed in the present study. SC-HART was performed with a dose of 2.5 Gy twice daily, with an interval of at least 6 hours between fractions, up to a total dose of 25 Gy (25 Gy in 10 fractions for 5 days) combined with S-1 for 10 days. Radical surgery was performed within three weeks following the end of the SC-HART. The median age was 64.6 (range, 39-85) years. The median follow-up term was 16.3 (range, 2-53) months. Of the 56 patients, 53 (94.4%) had no apparent adverse events before surgery; 55 (98.2%) completed the full course of neoadjuvant therapy, while one patient stopped chemotherapy because of Grade 3 gastrointestinal toxicity (CTCAE v.3). The sphincter preservation rate was 94.6%. Downstaging was observed in 45 patients (80.4%). Adjuvant chemotherapy was administered to 43 patients (76.8%). The local control rate, disease-free survival rate and disease-specific survival rate were 100%, 91.1% and 100%, respectively. To conclude, SC-HART combined with S-1 for locally advanced rectal cancer was well tolerated and produced good short-term outcomes. SC-HART therefore appeared to have a good feasibility for use in further clinical trials.

Analysis of the amino acid residues involved in the thermal properties of the monomeric isocitrate dehydrogenases of the psychrophilic bacterium Colwellia maris and the mesophilic bacterium Azotobacter vinelandii.

Cold-adapted monomeric isocitrate dehydrogenase of a psychrophilic bacterium, Colwellia maris, (CmIDH) showed a high degree of amino acid sequential identity (69.5%) to a mesophilic nitrogen-fixing bacterium, Azotobacter vinelandii, (AvIDH). In this study, three Ala residues of CmIDH and the corresponding Pro residues of AvIDH were exchanged by site-directed mutagenesis, and several properties of single, double, and triple mutants of the two enzymes were investigated. The mutated CmIDHs, which replaced Ala719 with Pro, showed increased activity and elevation of the optimum temperature and thermostability for activity. In contrast, mutants of AvIDH, in which Pro717 was replaced by Ala, decreased the thermostability for activity. These results indicate that Ala719 of CmIDH and Pro717 of AvIDH are involved in thermostability. On the other hand, mutated CmIDH, in which Ala710 was replaced by Pro, and the corresponding AvIDH mutant, which replaced Pro708 with Ala, showed higher and lower specific activity than the corresponding wild-type enzymes, suggesting that Pro708 of AvIDH is involved in its high catalytic ability. Furthermore, the exchange mutations between Ala740 in CmIDH and the corresponding Pro738 in AvIDH resulted in decreased and increased thermostability for CmIDH and AvIDH activity respectively, suggesting that the native Ala740 and Pro738 residues make the enzymes thermostable and thermolabile.

Dosimetric and delivery characterizations of full-arc and half-arc volumetric-modulated arc therapy for maxillary cancer.

We compared the efficiency and accuracy of full-arc and half-arc volumetric-modulated arc therapy (VMAT) delivery for maxillary cancer. Plans for gantry rotation angles of 360° and 180° (full-arc and half-arc VMAT) were created for six maxillary cancer cases with the Monaco treatment planning system, and delivered using an Elekta Synergy linear accelerator. Full-arc and half-arc VMAT were compared with regard to homogeneity index (HI), conformity index (CI), mean dose to normal brain, total monitor units (MU), delivery times, root mean square (r.m.s.) gantry accelerations (°/s(2)), and r.m.s. gantry angle errors (°). The half-arc VMAT plans achieved comparable HI and CI to the full-arc plans. Mean doses to the normal brain and brainstem with the half-arc VMAT plans were on average 16% and 17% lower than those with the full-arc VMAT plans. For other organs at risk (OARs), no significant DVH differences were observed between plans. Half-arc VMAT resulted in 11% less total MU and 20% shorter delivery time than the full-arc VMAT, while r.m.s. gantry acceleration and r.m.s. gantry angle error during half-arc VMAT delivery were 30% and 23% less than those during full-arc VMAT delivery, respectively. Furthermore, the half-arc VMAT plans were comparable with the full-arc plans regarding dose homogeneity and conformity in maxillary cancer, and provided a statistical decrease in mean dose to OAR, total MU, delivery time and gantry angle error. Half-arc VMAT plans may be a suitable treatment option in radiotherapy for maxillary cancer.

Long-term sequential changes of radiation proctitis and angiopathy in rats.

The purpose of the present study was to establish an experimental rat model for late radiation proctitis, and to examine the assessment strategy for late radiation proctitis. A total of 57 Wistar rats were used. Fourty-five of the rats were exposed to selective rectal irradiation with a single fraction of 25 Gy. These rats were sacrificed at the 4(th), 12(th), 24(th), and 37(th) week following irradiation. The remaining 12 rats comprised the control group without irradiation. The rectal mucosa of each rat was evaluated macroscopically and pathologically. The number of vessels in the rectal mucosa was counted microscopically. In addition, the vascular stenosis was evaluated. In the results, the degree of clinical and macroscopic findings decreased following acute proctitis and developed later. In the pathological examination, mucosal changes and microangiopathy were followed up, as well. The absolute number of vessels in the rectum was the greatest at the 12(th) week following irradiation and was the lowest in the control group. The severity of the microangiopathy was also well evaluated. To conclude, we established an animal experimental model of late radiation proctitis, and also established an assessment strategy to evaluate objectively the severity of late radiation proctitis with focusing on microangiopathy using an animal experimental model. This model can be used as an animal experimental model of radiation-induced microangiopathy.