Characterisation of flattening filter free (FFF) beam properties for initial beam set-up and routine QA, independent of flattened beams.

Flattening filter free (FFF) beams have reached widespread use for clinical treatment deliveries. The usual methods for FFF beam characterisation for their quality assurance (QA) require the use of associated conventional flattened beams (cFF). Methods for QA of FFF without the need to use associated cFF beams are presented and evaluated against current methods for both FFF and cFF beams. Inflection point normalisation is evaluated against conventional methods for the determination of field size and penumbra for field sizes from 3 cm × 3 cm to 40 cm × 40cm at depths from dmax to 20 cm in water for matched and unmatched FFF beams and for cFF beams. A method for measuring symmetry in the cross plane direction is suggested and evaluated as FFF beams are insensitive to symmetry changes in this direction. Methods for characterising beam energy are evaluated and the impact of beam energy on profile shape compared to that of cFF beams. In-plane symmetry can be measured, as can cFF beams, using observed changes in profile, whereas cross-plane symmetry can be measured by acquiring profiles at collimator angles 0 and 180. Beam energy and 'unflatness' can be measured as with cFF beams from observed shifts in profile with changing beam energy. Normalising the inflection points of FFF beams to 55% results in an equivalent penumbra and field size measurement within 0.5 mm of conventional methods with the exception of 40 cm × 40 cm fields at a depth of 20 cm. New proposed methods are presented that make it possible to independently carry out set up and QA measurements on beam energy, flatness, symmetry and field size of an FFF beam without the need to reference to an equivalent flattened beam of the same energy. The methods proposed can also be used to carry out this QA for flattened beams, resulting in universal definitions and methods for MV beams. This is presented for beams produced by an Elekta linear accelerator, but is anticipated to also apply to other manufacturers' beams.

Beam characteristics of energy-matched flattening filter free beams.

PURPOSE: Flattening filter free (FFF) linear accelerators can increase treatment efficiency and plan quality. There are multiple methods of defining a FFF beam. The Elekta control system supports tuning of the delivered FFF beam energy to enable matching of the percentage depth-dose (PDD) of the flattened beam at 10 cm depth. This is compared to FFF beams where the linac control parameters are identical to those for the flattened beam. All beams were delivered on an Elekta Synergy accelerator with an Agility multi-leaf collimator installed and compared to the standard, flattened beam. The aim of this study is to compare "matched" FFF beams to both "unmatched" FFF beams and flattened beams to determine the benefits of matching beams. METHODS: For the three modes of operation 6 MV flattened, 6 MV matched FFF, 6 MV unmatched FFF, 10 MV flattened, 10 MV matched FFF, and 10 MV unmatched FFF beam profiles were obtained using a plotting tank and were measured in steps of 0.1 mm in the penumbral region. Beam penumbra was defined as the distance between the 80% and 20% of the normalized dose when the inflection points of the unflattened and flattened profiles were normalized with the central axis dose of the flattened field set as 100%. PDD data was obtained at field sizes ranging from 3 cm × 3 cm to 40 cm × 40 cm. Radiation protection measurements were additionally performed to determine the head leakage and environmental monitoring through the maze and primary barriers. RESULTS: No significant change is made to the beam penumbra for FFF beams with and without PDD matching, the maximum change in penumbra for a 10 cm × 10 cm field was within the experimental error of the study. The changes in the profile shape with increasing field size are most significant for the matched FFF beam, and both FFF beams showed less profile shape variation with increasing depth when compared to flattened beams, due to consistency in beam energy spectra across the radiation field. The PDDs of the FFF beams showed less variation with field size, the d(max) value was deeper for the matched FFF beam than the FFF beam and deeper than the flattened beam for field sizes greater than 5 cm × 5 cm. The head leakage when using the machine in FFF mode is less than half that for a flattened beam, but comparable for both FFF modes. The radiation protection dose-rate measurements show an increase of instantaneous dose-rates when operating the machines in FFF mode but that increase is less than the ratio of MU/min produced by the machine. CONCLUSIONS: The matching of a FFF beam to a flattened beam at a depth of 10 cm in water by increasing the FFF beam energy does not reduce any of the reported benefits of FFF beams. Conversely, there are a number of potential benefits resulting from matching the FFF beam; the depth of maximum dose is deeper, the out of field dose is potentially reduced, and the beam quality and penetration more closely resembles the flattened beams currently used in clinical practice, making dose distributions in water more alike. Highlighted in this work is the fact that some conventional specifications and methods for measurement of beam parameters such as penumbra are not relevant and further work is required to address this situation with respect to "matched" FFF beams and to determine methods of measurement that are not reliant on an associated flattened beam.

The amino acid sequence GPLY is not necessary for normal endocytosis of the human insulin receptor B isoform.

The human insulin receptor (hIR) cytoplasmic juxtamembrane domain contains two tyrosine (Y) residues which exist in GPLY and NPEY motifs that have been implicated in endocytic function. We have previously shown that the NPEY motif is not necessary for endocytosis of the B isoform (exon 11+) of hIR. To examine the role of the GPLY sequence in transmembrane insulin signaling and endocytic functions of hIR-B, we constructed a mutant receptor, hIR delta GPLY, that lacks the GPLY sequence (residues 962-965), and stably expressed it in CHO cells. When compared to wild type hIR-B (hIR-WT) similarly expressed in CHO cells, the hIR delta GPLY mutant exhibited higher insulin binding affinity (EC50 of 1.0 vs 3.5 nM) and normal insulin-stimulated receptor tyrosine autophosphorylation and kinase activity towards the endogenous 185 kDa insulin receptor substrate. The hIR delta GPLY receptor also exhibited normal endocytic functions as hIR-WT in that: a) the internalization of surface photoaffinity labeled hIR delta GPLY was similar to that of hIR-WT, and b) the rate and extent of 125I-insulin internalization and degradation at 37 degrees C were also unimpaired. Therefore, these results demonstrate that the GPLY sequence is not necessary for transmembrane insulin signaling and endocytic functions of the hIR-B isoform.

Influence of selenium status in merino weaners on resistance to trichostrongylid infection.

Weaned merino lambs, grazing pastures low in selenium, were used to investigate the effect of selenium status on immunity to trichostrongylids. Six weeks following selenium supplementation to 14 of the 27 sheep using intraruminal selenium pellets, 5000 Ostertagia circumcincta and 5000 Trichostrongylus colubriformis larvae were administered orally to all sheep. At four weeks after infection, the mean total worm burden in the selenium supplemented sheep (5537 +/- 343, n = 14) was not significantly different (P greater than 0.05) from that in the unsupplemented sheep (5614 +/- 374, n = 12) and faecal worm egg concentrations were also similar in the two treatment groups. At this time, mean red cell glutathione peroxidase activities in the supplemented and unsupplemented groups were 430 and 11 U g-1 haemoglobin, respectively, and clinical white muscle disease had been observed in the latter group. These results suggest that increasing selenium status of selenium deficient sheep by the use of intraruminal selenium supplementation, has a negligible effect on resistance to an artificial challenge infection of O circumcincta and T colubriformis.

Evaluation of the use of an oxygen conservation device in long-term oxygen therapy.

An oxygen-conserving delivery system employing a flow reducing oxygen pendant (OP) cannula was evaluated during home use for oxygen savings, cost reduction, and patient acceptance. Twenty-one male outpatients receiving home oxygen from liquid systems by conventional nasal cannula (NC) were fitted with OP and followed for 1 month. Oxyhemoglobin saturations (SaO2) were successfully maintained with a threefold reduction in mean O2 flow rate from 1.45 to 0.46 L/min. Exercise testing demonstrated no change between the 2 systems in either degree of desaturation or duration of exercise. Because the same benefit was achieved at lower O2 flow with the OP, 14 patients were able to utilize their O2 for longer periods of time without refilling their portable liquid units. Liquid O2 use per patient was reduced from 200 pounds/month with NC to 135 pounds/month with OP. In 12 patients who reported full compliance during the study period; a net savings of $141/month/patient was realized. However, 9 of the 21 patients stopped using the OP before completing the study. Patient evaluations of the OP identified several factors leading to poor compliance, including bulkiness and/or poor fit (16 patients), ear discomfort (8 patients), nasal discomfort (6 patients), and required nasal breathing (6 patients). While significant savings were achieved with OP, problems with patient acceptance may limit its practicality, particularly in continuous use situations. The primary benefit of the OP may be in extending the range of portable oxygen systems.

Crystal-associated cholangiohepatopathy and photosensitisation in lambs.

Four outbreaks of hepatogenous photosensitisation occurred in weaned lambs in north eastern Victoria during the summers of 1985 and 1986. Attack rates varied between 7% and 43% and case fatality rates between 60% and 71%. Clinical signs included photosensitisation and jaundice. Serum biochemistry suggested hepatobiliary and hepatoparenchymal damage with impaired renal function. At necropsy livers were an ochre colour and kidneys a mottled brown to khaki. Histopathologically, needle-shaped to lenticular clefts were observed in and around bile ducts and in hepatocytes, hepatic sinusoidal macrophages and renal tubules. Optically active rhomboidal crystals were present in bile sediments. Panicum schinzii was identified as a possible cause in 2 of the 4 outbreaks. The clinical disease was reproduced in 2 of 6 lambs grazed on a toxic paddock. The disease was indistinguishable from geeldikkop except for the fact that Tribulus terrestris was not present on any of the 4 farms.

Age-related changes in activities of the superoxide dismutase enzymes in tissues of the sheep and the effect of dietary copper and manganese on these changes.

Activities of the copper-zinc- and manganese-containing superoxide dismutase enzymes (CuSOD and MnSOD) were studied in tissues of the sheep to determine the dependence of these activities on sheep age, and their relationship to tissue and dietary mineral concentrations. Tissue samples were obtained from day-old through 16-week-old lambs from flocks grazing pastures normal or high in copper and manganese, and from adult sheep. In liver, lung, heart, kidney and skeletal muscle, activities of CuSOD and MnSOD in day-old and week-old lambs were only half those measured in 16-week-old and adult sheep. Activities in 4-week-old lambs were intermediate between these two groups except for heart tissue, in which activities were not increased until lambs were 16 weeks old. For all age groups, heart and skeletal muscle had low activities of CuSOD. Minimal age-related changes were observed for CuSOD activities in erythrocyte and brain tissues. The low enzyme activities evident in most tissues of day-old lambs, occurred in the presence of apparently adequate tissue copper and manganese concentrations. Concentrations of these minerals in lamb tissues were equal to or greater than those observed in older sheep and although these concentrations increased considerably with increased pasture mineral concentrations, enzyme activities were unchanged. Age-related increases in tissue CuSOD and MnSOD activities, occurring as normal developmental processes, may be important factors in diseases attributed to uncontrolled tissue peroxidation in sheep.

Differences between serum and plasma ceruloplasmin activities and copper concentrations: investigation of possible contributing factors.

Values for ceruloplasmin activities and copper concentrations were found to be lower in serum than in paired samples of plasma in both sheep and cattle. Ceruloplasmin activities in serum were 13-40% lower relative to plasma for nine different groups of animals, and 10-65% lower for individual animals (n = 112). As the values are not directly interchangeable, plasma rather than serum should be used when estimating copper nutrition in these animals. Maximum effects in serum were apparent 3-4 h after collection, the earliest time at which serum could be obtained. Lower ceruloplasmin and copper values in serum could not be attributed to the type of blood collection vessel used, subsequent storage of samples, the methods used for measuring ceruloplasmin activities and copper concentrations, the formation of fibrin in blood, or to the effects of dietary molybdenum. In contrast, the addition of neuraminidase to whole blood before clotting decreased the differences between serum and plasma ceruloplasmin activity and copper concentration in a dose-dependent manner. Of the two major copper-containing enzymes present in blood, effects of clotting were only evident with ceruloplasmin. Cu-Zn-containing superoxide dismutase activity in erythrocytes was unaffected by clot formation. The results indicate that ceruloplasmin and the copper associated with this protein are sequestered into the clot during clot formation by attachment of the enzyme to the blood cellular fraction. The minimizing of this effect by the addition of neuraminidase suggests that this attachment may be through sialic acid residues.

Investigations into combined dietary deficiencies of copper, selenium, and vitamin E in the rat.

Interactions between dietary Cu, Se, and vitamin E in ascorbate-induced hemolysis of erythrocytes obtained from rats fed diets deficient or adequate in these elements were investigated. Hemolysis was affected by all three dietary factors, through closely interrelated but distinct mechanisms. In vitamin E-deficient cells, hemolysis was increased and the amount of hemolysis was directly related to the amount of hemoglobin breakdown. Deficiency of Cu or Se decreased hemolysis, but only in vitamin E-deficient cells. Vitamin E did not affect the breakdown of hemoglobin, but Cu and Se did. Hemolysis and hemoglobin breakdown were decreased by the addition of glucose, through mechanisms independent of that involving reduced glutathione metabolism. These results suggest that vitamin E acts within erythrocyte membranes to prevent products of hemoglobin breakdown from initiating peroxidation and subsequent hemolysis. Effects of Cu and Se are linked with that of vitamin E by the involvement of glutathione peroxidase and Cu superoxide dismutase in the cytoplasmic breakdown of hemoglobin, rather than by a direct effect of these enzymes on lipid peroxidation. It is concluded that the erythrocyte, because of its high heme content, probably represents a special system in terms of peroxidative pathways, and these findings may not be directly applicable to other tissues.

The role of dietary copper, manganese, selenium, and vitamin E in lipid peroxidation in tissues of the rat.

The role of dietary Cu and Mn in maintaining tissue integrity, through the effects of these metals on activity of the superoxide dismutase (SOD) enzyme, and their interactions in peroxidative pathways involving Se and vitamin E was investigated. Weanling rats were fed diets deficient in Mn, Cu, Se, and/or vitamin E for 35 days, in a factorial experimental design. Dietary effects on peroxidation, measured in mitochondrial fractions prepared from liver and heart tissue, were compared with changes in the activities of glutathione peroxidase and the Cu and MnSOD enzymes.Decreased heart MnSOD and CuSOD activities, resulting from dietary Mn and Cu deficiencies, were both associated with increased peroxidation. Adequate Se (and glutathione peroxidase activity) prevented the peroxidation associated with either of these deficiencies, but was ineffective with a combined Cu-Mn deficiency. These effects of Se were only observed in tissue lacking glutathione transferase activity. Effects of Cu, Mn, and Se on peroxidation appeared to be present at both levels of vitamin E, although in both tissues, vitamin E deficiency greatly increased the overall peroxidation. Comparison of these in vitro peroxidation results with the deficiency associated lesions observed in vivo indicates that changes in SOD activities and peroxidation pathways may be the dominant cause of these lesions in only some cases. In others, the roles of Cu and Mn in different metabolic pathways appear to be of greater importance.

Changes in activity of the Cu-Zn superoxide dismutase enzyme in tissues of the rat with changes in dietary copper.

The effects of dietary copper level on tissue activities of the copper containing superoxide dismutase (CuSOD) were investigated, and these activities related to those of other copper containing enzymes particularly cytochrome oxidase. Male weaning rats were fed a basal diet (containing 0.8 mg Cu/kg) or this diet supplemented with 4 or 24 mg Cu/kg. After 6 weeks, rats fed the basal diet were then repleted using the high copper diet. In the two copper supplemented groups, no differences were observed in any of the parameters measured. In these groups, tissue activities of CuSOD were in the order of liver greater than kidney greater than RBC greater than testis greater than heart greater than brain greater than lung greater than muscle. In the basal group, CuSOD activity decreased in liver; RBC and heart to 14, 25, and 61%, respectively, of control activities after 6 weeks' depletion; tissues other than brain or muscle showed smaller but significant changes. Conversely, heart and muscle cytochrome oxidase activities decreased to 30 and 45% of control activity and liver to 70%. With repletion, CuSOD activities in liver and heart increased more rapidly than did cytochrome oxidase activities. It is concluded that liver CuSOD activity, which is normally high, is greatly reduced with little change in cytochrome oxidase activity; the reverse is found for heart and muscle tissue. The relevance of these changes to the maintenance of tissue integrity is discussed.

Response of immunosympathectomized rats to training.

The influence of chronic exercise was investigated with male rats assigned to normal (N) and sympathectomized (IS) groups. Animals in the latter group were injected daily for 5 days with the antiserum to the nerve growth factor beginning 24 h after birth. Training was introduced when the animals were 35--45 days old and lasted for 12 wk. The exercise program used by both groups was progressive in nature and modified in accordance with the performance capability of the IS animals. When IS and N rats performed a standardized treadmill test, the IS rats had significantly higher rectal temperatures than normal animals. Significant training differences were observed in resting heart rate and in mean blood pressures, but only in the N animals. However, both trained groups exhibited significantly less vasoconstricting ability to conditions of lower body negative pressure than their nontrained controls. Varied doses of epinephrine and norepinephrine were injected into both groups and training per se had no significant influence on the responses recorded. However, both IS group had changes which indicated that a supersensitivity to catecholamines had occurred. Although selective training adaptations can occur without sympathetic nerves, it was concluded that an intact nervous system was essential for maximal training effects to occur.

Comparative Enzymology of the Adenosine Triphosphate Sulfurylases from Leaf and Swollen Hypocotyl Tissue of Beta vulgaris: Multiple Enzyme Forms in Hypocotyl Tissue.

ATP sulfurylase activity was partially purified from the swollen hypocotyl of beetroot (Beta vulgaris); activity was measured by sulfate-dependent PPi-ATP exchange. The ATP sulfurylase activity was separated from pyrophosphatase and ATPase activities which interfere with the assay of ATP sulfurylase activity. The ATP sulfurylase activity from hypocotyl tissue was invariably resolved into two approximately equal activities (hypocotyls I and II) by ion exchange chromatography and polyacrylamide gradient gel electrophoresis. Both enzymes catalyzed selenate- and sulfate-dependent PPi-ATP exchange; the affinity of hypocotyl II for these substrates was greater than for hypocotyl I. It is unlikely that the two activities arise by allelic variation or as an artifact of purification; they are most probably isoenzymes. Studies of the subcellular localization of the two hypocotyl enzymes were inconclusive.ATP sulfurylase was also purified from leaf tissue. Ion exchange chromatography resolved the ATP sulfurylase from leaf tissue into a major activity (which accounted for 98% of the total leaf activity) and a minor activity. The major leaf and hypocotyl II ATP sulfurylases were indistinguishable as judged by the properties investigated.