Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.3.1.51 (HDR)
605 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Groups of LAF1 mice were given thoracic irradiation using 60Co gamma-rays at dose-rates of 0.05 Gy/min (LDR) or 1.1 Gy/min (HDR) and the death of the animals was monitored as a function of time. It was found that the time pattern of animal deaths was similar for the two different dose-rates. Dose response curves for animals dying at various times up to 500 days after irradiation were calculated and the LD50 values determined. The curves for the LD50 values, plotted as a function of the time at analysis for treatment at HDR or LDR, were essentially parallel to each other but separated by a factor (LDR/HDR) of about 1.8. This indicates that the sparing effect of LDR treatment is the same for deaths occurring during the early pneumonitis phase or during the late fibrotic phase of lung damage. The available information on the response of patients to whole thoracic irradiation, given for either palliation or prior to bone marrow transplantation, suggests that for similar dose-rates to those studied here the ratio (LDR/HDR) is only 1.2-1.3. This difference between the animal and human data may reflect the modifying effect of the large doses of cytotoxic drugs used in combination with the irradiation of bone marrow transplant patients.
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PMID:Response of mouse lung to irradiation at different dose-rates. 686 71

Cholangiocarcinoma at the confluence of the hepatic ducts (Klatskin tumor) is a slowly growing malignancy with early onset of symptoms and poor outcome since surgery allows radical resection in only a minority of cases. Percutaneously placed biliary stents offer a good palliation, but tend to obstruct after 6-8 months; then, retreatment requires exchange of the endoprosthesis or establishment of a permanent external-internal biliary drainage which offers, in some patients, a relatively long survival. Percutaneous intraluminal HDR brachytherapy might be a valid alternative as a definitive therapy or as a method to keep metallic stents patent for a long time. Five patients with hilar cholangiocarcinoma, diagnosed by means of ultrasound, Computed Tomography, percutaneous transhepatic cholangiography and transluminal biopsy, underwent double percutaneous external-internal biliary drainage. Dummy sources were introduced into the drainage catheters to allow dose distribution planning. The stepwise progression of the miniaturized high activity Iridium source inside the applicators, introduced into the drainage catheters, was controlled and monitored by a computer equipped with dedicated software. In the radiotherapy bunker, using the remote loading technique, percutaneous intracavitary high dose rate brachytherapy was delivered at the rate of 750 cGy per fraction, prescribed at 1 cm from the center of the catheter, once a week, for 4 weeks. Nevertheless, only 4 of 5 patients underwent the complete treatment. In one case, radiation treatment was discontinued after the first session because of digestive bleeding from a duodenal ulcer, supposingly as a consequence of the decubitus of a catheter tip. CT demonstrated rapid progression of the disease with neoplastic spread to the omentum and gallbladder wall thickening; a gallbladder malignancy was then suspected and the patient was no more eligibile for brachytherapy. Subsequently, Carey-Coons endoprostheses were inserted to prevent post-actinic strictures and removed after three months. After completing radiation therapy, control cholangiograms demonstrated in all cases improvement of neoplastic strictures. The first two patients we treated show no signs of tumor recurrence at 4 and 1 months, respectively, after endoscopic removal of the stents. The third patient is still bearing 2 Carey-Coons endoprostheses to be removed after 3 months. The last patient with supposingly partial success of bracytherapy, was treated with two Strecker nitinol stents.
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PMID:[Percutaneous treatment of hilar cholangiocarcinoma completed by high-dose rate brachytherapy. Experience in the first 5 cases]. 752 May 94

In April 1988 the Christie Hospital started using the microSelectron-HDR machine to deliver intraluminal radiotherapy (ILT) to inoperable bronchial carcinomas causing symptoms due to endobronchial disease. Results of treatment in the first 406 patients with primary non-small-cell carcinoma are presented. Three main categories of patient were defined. Category 1 consisted of 324 patients (79.8%) who were previously unirradiated and received a single fraction of ILT as their primary treatment, mostly to a dose of 1500 cGy (76%) or 2000 cGy (23%) at 1 cm from the centre of the iridium-192 treatment source. The percentage of these patients whose symptoms or signs were improved at 6 weeks following ILT were as follows: stridor 92%, haemoptysis 88%, cough 62%, dyspnoea, 60%, pain, 50% and pulmonary collapse, 46%. Approximately two-thirds of these patients (67.3%) derived long lasting palliation and required no further treatment during their lifetime. The other third of patients needed subsequent treatment at some stage because of recurrence of their symptoms and in this situation external beam radiotherapy (EB) or a repeat ILT treatment was effectively utilised. Category 2 consisted of 65 patients (16%) who had previously received EB but required ILT when their tumour recurred. At 6 weeks post-ILT levels of symptom palliation were broadly similar to those obtained if ILT was used in previously unirradiated individuals, although the improvement was not so well sustained with time and only 7% showed improvement in pulmonary collapse at 6 weeks. Category 3 consisted of 17 patients (4.2%) in whom ILT was used concurrently with EB as a combined initial treatment. Similar levels of palliation were seen when compared with patients who received a single ILT treatment only. Overall, ILT was well tolerated in terms of early and late morbidity. In conclusion, the efficiency of a single ILT treatment in palliating symptoms due to endobronchial tumour in previously unirradiated individuals is comparable with that reported in series where treatment for advanced lung cancer combines a prolonged course of EB concurrently with several ILT treatments.
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PMID:High dose rate intraluminal radiotherapy for carcinoma of the bronchus: outcome of treatment of 406 patients. 753 4

The coplanar polycentric multiple 180 degrees single arc and narrow beams technique (PMA) allows high radiation doses to be delivered to the target, with similar dose distribution to that of brachytherapy. Since 1990, more than 100 patients have been treated: 80 had NSCLC, 12 had epidermoid head and neck (oral cavity and oropharynx) cancers, 8 brain tumors, 4 esophageal cancers and, sporadically, other patients had many other kinds of tumors, e.g., Hodgkin's and non-Hodgkin's lymphomas and sarcomas. X photons of a 12-MV Linac have always been used. NSCLC patients are assessable for local control, toxicity and survival, while the other patients only for local control and/or toxicity. As for 31 stage I-II lung cancer patients, CR has been observed in 82.8% of them and PR in 13.8%; the response was always assessed with chest radiography, CT, FBS, cytology and/or histology. The overall actuarial survival rate is 71% at 40 months, the disease-free survival rate is 75% and the local progression-free survival rate is 94%. As for 49 stage-III patients, CR has been observed in 40% of them and PR in 56%. The overall disease-free survival is 10% at 28 months (median survival: 14.37 +/- 0.6 months). The disease-free survival rate is 23%. The local progression-free survival rate is similar to the overall survival rate, which seems to prove the very high metastatic spread of this disease in advanced stages. Twelve head and neck cancer patients have been treated, 5 of them in stage II and 7 in stage IV. CR has been observed in all the patients in lower stages (100%), in 4/7 patients in stage IV (57%) and in 4/5 patients (80%) in the T4N0 subgroup. The response of brain tumors treated with the PMA technique is difficult to assess because radiographic, CT and MR images are difficult to correlate with patients clinical status. The patients in our series are still alive, with a medium follow-up of 7 months (range: 2-16 months). A longer follow-up is necessary before any other considerations on the effectiveness of this method can be made. This technique was used on the patients who were not eligible for the other techniques with high doses delivered to the tumor, because of its volume and/or shape. Four esophageal cancers were treated with palliative intent, because of absolute dysphagia, in alternative to HDR brachytherapy. All these patients have obtained symptom remission.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:[The polycentric multiple arc complanar technic, or telebrachytherapy. A 4-year experience (an innovative way for the local control of solid neoplasms)]. 756 75

Last month, the authors presented the principles of high-dose-rate intraoperative radiation therapy (HDR-IORT), a new approach to intraoperative radiation delivery, as well as their criteria for patient selection, the goals of surgery, and their approach to minimizing surgical morbidity. This month, the authors present the technical aspects of delivering HDR intraoperative brachytherapy, their dosimetry atlas, and their results using HDR-IORT in the treatment of patients with colorectal cancer.
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PMID:High-dose-rate intraoperative radiation therapy for colorectal cancer. 757 74

Late renal damage after total body irradiation (TBI) and bone marrow transplantation (BMT) is a recently recognised morbidity. We have tested the effect of single fraction TBI given at two different dose rates on late kidney damage in a mouse model. TBI was given at either high dose rate (HDR; 0.71 Gy/min) or low dose rate (LDR; 0.08 Gy/min). Transplantation with syngeneic marrow cells was done 4-6 h after TBI. Kidney damage was tested using 51CrEDTA residual activity, blood urea nitrogen (BUN) and percentage haematocrit (Hct). TBI alone given at HDR or LDR caused progressive renal damage with no evidence of recovery or plateau. The time latency before the expression of damage was dependent on both dose and the end point used. It was shorter the higher the dose. 51CrEDTA detected renal damage at the same doses as BUN but earlier in time, while %Hct showed evidence of renal damage at doses lower than both BUN and 51CrEDTA. Using the 51CrEDTA the dose-response curves for renal damage were steep and continuously shifting towards lower doses as follow-up time after treatment increased. There was a sparing effect of reducing the dose rate that was more evident at follow-up times of less than a year than at 66 weeks after TBI. Thus, the dose modifying ratio (DMF), defined as the dose needed to cause renal damage in 50% of irradiated animals (ED50) using LDR divided by the ED50 using HDR, was dependent on the time of evaluation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Renal damage after total body irradiation in a mouse model for bone marrow transplantation: effect of radiation dose rate. 763 Oct 26

A 3D-simulation model made with a milling system was applied to HDR-brachytherapy. The 3D-simulation model is used to simulate the 3D-structure of the lesion and the surrounding organs before the actual catheterization for brachytherapy. The first case was recurrent prostatic cancer in a 61-year-old man. The other case was lymph node recurrence of a 71-year-old woman's upper gum cancer. In both cases, the 3D-simulation model was very useful to simulate the 3D-conformation, to plan the treatment process and to avoid the risk accompanying treatment.
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PMID:[Planning for brachytherapy using a 3D-simulation model]. 763 59

The effect of progesterone (Pg), medroxyprogesterone acetate (MPA), estradiol (E2), dihydrotestosterone (DHT) and dexamethasone (DEXA) was studied on the in vitro growth rate of a progestin-dependent (PD), estrogen-sensitive mammary tumor line originated in an MPA-treated BALB/c mouse (C4-HD), and on its estrogen-resistant variant (C4-HDR). The specificity of hormone action was further investigated using the anti-hormones RU-486 and hydroxyflutamide (FLU). Cell growth was evaluated in epithelial and fibroblast-enriched cultures using 3H-thymidine and/or autoradiography and immunocytochemistry. The results indicate that cell growth is directly stimulated by MPA and Pg at concentrations ranging from 10(-11) to 10(-7) M. RU486 prevented MPA-induced stimulation in concentrations 10 to 100 fold lower than those of MPA. When used alone, it inhibited cell proliferation only in concentrations higher than 10(-11) M. At nM concentrations, neither DEXA nor DHT stimulated 3H-thymidine uptake except DEXA at 100 nM. MPA-induced stimulation was not reverted by micromolar concentrations of FLU. As for E2 (10(-7)-10(-9) M) it prevented MPA stimulation only in cultures of estrogen-sensitive tumors. Progesterone receptors (PR) (475 +/- 115 fmoles/10(5) cells, n = 5) and estrogen receptors (ER) (ND-115 fmoles/10(5) cells, n = 5) were detected only in epithelial-enriched cultures. Serum from 7 day-MPA-treated mice induced a significant increase of 3H-thymidine uptake; an increase was also obtained with serum from untreated ovariectomized animals to which 1 nM-100 nM concentrations of MPA had been added. The stimulatory effect of the exogenous MPA was much lower than that of the serum obtained from MPA-treated animals. It is concluded that MPA stimulates cell growth of primary cultures of MPA-induced PD tumors via PR. The results provide support for a direct effect of MPA which may be mediated or potentiated by serum factors.
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PMID:Effect of medroxyprogesterone acetate (MPA) and serum factors on cell proliferation in primary cultures of an MPA-induced mammary adenocarcinoma. 764 39

The aim was to determine whether peripheral blood lymphocytes can be used retrospectively to detect hypersensitivity to radiation in breast cancer patients who had exhibited severe reactions to radiotherapy. Blood samples were obtained from patients who developed both acute and late complications. For comparison, samples were also taken from a group of normal individuals, ataxia-telangiectasia (A-T) patients, A-T gene carriers and breast cancer patients previously treated with radiotherapy who failed to develop treatment-related complications. Radiosensitivity was assessed using a limiting dilution clonogenic assay following both high (HDR) and low (LDR) dose-rate irradiation. Following HDR irradiation, only lymphocytes from individuals with A-T were significantly more radiosensitive than those from normal donors. In contrast, at LDR, lymphocytes from A-T heterozygotes and breast cancer over reactors were also, on average, more sensitive than those from normal donors. Lymphocytes from breast cancer patients treated with radiotherapy without developing complications showed no significant differences in radiosensitivity compared with normals. This work has shown that peripheral blood lymphocytes from cancer patients who suffered severe reaction to radiotherapy are, on average, more radiosensitive than those from normal donors, and suggests that lymphocytes may be useful in the future for the development of rapid predictive assays for normal tissue tolerance to radiotherapy.
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PMID:A comparison of the radiosensitivity of lymphocytes from normal donors, cancer patients, individuals with ataxia-telangiectasia (A-T) and A-T heterozygotes. 765 45

A modified Standard Imaging HDR 1000 re-entrant ion chamber has been used with an NE 2570/1 electrometer as part of a quality-assurance programme for checking 192Ir source strengths and for source localization studies. The chamber measurements correlate well with in-air calibration measurements made over a three-month source-decay period; the maximum discrepancy between the in-air measurement and the re-entrant chamber measurement was 0.9%. The source position may be determined with an uncertainty of lower than 0.5 mm. The reproducibility of measurements made with each of four electrometers used with the reentrant ion chamber was typically 0.1% (1 sigma).
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PMID:HDR microSelectron quality-assurance studies using a well-type ion chamber. 770 48


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