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Biomedical subjects

C Orton

Publications and source records attributed to C Orton.

6 recordsLinked to original sources
PubMed1991

Initial experience with a practical hyperfractionated accelerated radiotherapy regimen.

This paper presents early results of a trial of a three-fractions-per-day (TID) regimen that is more convenient to schedule than the Continuous Hyperfractionated Accelerated Radiotherapy (CHART) protocol currently being tested in Europe. The treatment schedule used in the CHART regimen has been modified from 36 fractions of 1.5 Gy TID in 12 days to 72 fractions of 1.1 Gy in 24 treatment days, with all fractions delivered during normal working hours. With no weekend treatments, the entire course of radiotherapy is completed in less than 5 weeks. The doses used were determined using the L-Q model, with correction for incomplete repair between fractions and for accelerated repopulation of cancer cells. Comparison with historical controls shows statistically significant improvements both in CR rates for the primary tumor and in acute toxicity, as measured by reduced treatment interruptions. L-Q model calculations predict that, compared to the highest dose achieved in previous studies without exceeding tolerance, we are able to obtain a 12% increase in bioeffect dose to the primary tumor due to accelerating the treatment. An analysis of the potential tumoricidal effectiveness of this new treatment regimen shows that it should be better than several other accelerated fractionation schedules being tested for all values of Tpot. For short Tpot times, the advantage may be as much as one log cell kill, corresponding to a 10-15% potential improvement in local control.

Aged↗
PubMed1991

Neonatal calves develop airflow limitation due to chronic hypobaric hypoxia.

Neonates and infants presenting with pulmonary hypertension and chronic hypoxia often exhibit airway obstruction. To investigate this association, we utilized a system in which neonatal calves are exposed to chronic hypobaric hypoxia and develop severe pulmonary hypertension. For the present study, one of each pair of six age-matched pairs of neonatal calves was continuously exposed to hypobaric hypoxia at 4,500 m (CH); the other remained at 1,500 m. At 2 wk of age, mean pulmonary arterial pressure (MPAP), dynamic lung compliance (Cdyn), resistance (RL), and static respiratory system compliance (Crs) were measured at 4,500 m in both CH and control calves exposed acutely to hypoxia (C). These measurements were repeated after cumulative administrations of nebulized methacholine (MCh). Tissues were removed for histological examination and assessment of bronchial ring contractility to MCh and KCl. After 2 wk of hypobaric hypoxia, MPAP (C 35 +/- 1.7 vs. CH 120 +/- 7 mmHg, P less than 0.001) and RL (C 2.64 +/- 0.16 vs CH 4.99 +/- 0.47 cmH2O.l-1s, P less than 0.001) increased. Cdyn (C 0.100 +/- 0.01 vs. CH 0.082 +/- 0.007 l/cmH2O) and Crs (CH 0.46 +/- 0.003 vs. C 0.59 +/- 0.009 l/cmH2O) were not significantly different. Compared with airways of C calves, airways of CH animals did not exhibit in vivo or in vitro MCh hyperresponsiveness; however, in vitro contractility to KCl of airways from CH animals was significantly increased. Histologically, airways from the CH calves showed increases in airway fibrous tissue and smooth muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1975

Venous diversion trapping and growth of blood-borne cancer cells en route to the lungs.

A proportion of W-256 tumour cells injected intravenously into a tail vein of the rat are diverted into venous plexuses en route to the lungs; here tumour cells remain trapped, proliferate and form invasive solid tumours in the pelvis and hindquarters, which cause paraplegia, metastases and death. Also, cells trapped in veins produce tumour nodules distributed along the length of the tail; this effect in markedly enhanced by temporarily arresting the outflow of blood from the tail for a few seconds only immediately after cells are injected. Continous monitoring of the radioactive signal over the lungs after W-256 cells labelled with 125IUDR were injected showed that massaging the tail or intravenously injecting isotonic saline into the tail dislodged cells trapped in veins. In heparinized rats, tail trapping was markedly reduced, although not entirely abolished, and venous trapping in vertebral and pravertebral regions was decreased. The anatomical distribution of growth of the trapped cells in rats closely resembled metastases involving dissemination via the "vertebral venous system" produced by certain cancers in man. Labelled tumour cells trapped in the lungs of untreated mature rats commenced dying rapidly in situ wiht 1-2 h after injection; the majority had disappeared within 24 h, and less than 1% of the injected tumour cells survived to form lung colonies. Experimental evidence is presented which indicates that the lungs play a vital role in rapidly eliminating a high proportion of blood-borne cancer cells in the adult individual.

Animals↗
PubMedDate not supplied

Radiation exposure to patients receiving routine scoliosis radiography measured at depth in an anthropomorphic phantom.

Concern about the amount of radiation received during scoliosis evaluation and treatment led us to measure radiation exposure in an anthropomorphic phantom to determine the increased risk of breast cancer in young women with scoliosis. Assuming that 22 radiographic examinations were performed over the course of scoliosis treatment, the increased relative risk of breast cancer was determined to be 0.22% in these patients.

Adolescent↗