FEASIBILITY FOR USING HYPOFRACTIONATED STEREOTACTIC VOLUMETRIC MODULATED ARC RADIOTHERAPY (VMAT) WITH ADAPTIVE PLANNING FOR TREATMENT OF THYMOMA IN RABBITS: 15 CASES

Thymoma is a relatively common tumor in rabbits. Treatment with surgery, radiation therapy, and chemotherapy alone or in combination has been reported with varying outcomes. Stereotactic volumetric modulated arc radiotherapy delivered in a hypofractionated manner allows high doses of radiation to be delivered to the target volume while allowing sparing of adjacent critical structures. This therapy is ideally suited for thymomas in rabbits given their size, the difficulty of multiple anesthesia episodes and the complexity of the radiotherapy plans required due to the tumor's proximity to the heart, lungs, and mediastinal structures. Fifteen rabbits with thymoma were prospectively recruited for this observational, single institution, single arm clinical study. All rabbits were imaged with both computed tomography (CT) and magnetic resonance imaging (MRI). A total dose of 40 Gy in six fractions was delivered using a single arc over an 11‐day period with repeat CT simulation done every other fraction for adaptive planning. Follow‐up evaluation was done through repeat CT and MRI imaging and revealed complete responses using the Response Evaluation Criteria in Solid Tumors (RECIST) criteria. Two rabbits had died at 618 and 718 days, 10 were alive and three were lost to follow‐up. Observed acute and late effects were graded according to the Veterinary Radiation Therapy Oncology Group (VRTOG) criteria and were found to be minimal.     

Alkyl aryl ketone oxime O-ethers: A novel group of pyrethroids

The alkyl phenyl ketone oxime O-benzyl ethers are a new group of insecticidal compounds. Although they lack the ester linkage, they resemble the pyrethroids in general, and the esters of 2-phenylalkanoic acids, in particular fenvalerate, because they show similar physiological effects on isolated nerve preparations and on whole insects; they also show a similar pattern of change of biological activity in response to structural change. The compounds may exist as two geometric isomers, of which only the (E) series shows significant biological activity; this observation appears to have some bearing on the relationship between conformation and activity in the pyrethroid series as a whole.     

Estimation of repeatability of blood constituents in gestating beef cattle on protein- and energy-restricted diets

Repeatabilities of blood constituents were calculated for 104 Angus heifers on two separate experiments fed adequate, protein-deficient, energy-deficient, or both protein- and energy-deficient diets. Four statistical methodologies were compared including analysis of variance, principal component (structural) analysis based on the sample covariance and sample correlation matrix, and maximum likelihood. Of 12 blood constituents tested only seven were considered sufficiently important to be included in the analysis. These blood constituents included blood urea nitrogen (BUN), creatinine (Creat), alkaline phosphatase (Alk Phos), total protein (T Prot), total bilirubin (T Bil), cholesterol (Chol) and Iron (Fe). If the standard linear model assumptions were met for heifers on the adequate diet, the estimators appeared to be quite similar for both years except when the correlation coefficient was relatively small. If the assumption of homogeneity of the variance-covariance matrix (compound symmetry) was relaxed, the structural analysis method based on the sample correlation matrix appeared preferable. However, when combining all diets, the maximum likelihood methodology was preferred. Among the specific blood constituents, Alk Phos had the highest repeatability, not only for the heifers on the adequate diet, but also for heifers on other treatments in both years. Repeatabilities for T Prot appeared to be the most consistent over all rations in both years. Repeatability estimates for Fe were high and relative rankings were consistent for both years, while repeatabilities for the other variables were either low and(or) inconsistent.     

Deposition and clearance of radiolabelled monodisperse polystyrene spheres in the calf lung

Two groups of three calves were exposed to monodisperse aerosols of radiolabelled polystyrene spheres measuring 3.3 microns in aerodynamic diameter (SD 0.3 micron). Although the spheres preferentially deposited in the trachea and major bronchi, 72 per cent of the total radioactivity deposited was found in lung tissue beyond the major bronchi. Mean alveolar deposition, estimated from the end retention value after mucociliary clearance, was 34 per cent in the group of bull calves and 52 per cent in the group of heifer calves. Alveolar deposition increased from 47 to 56 per cent (P less than 0.05) in heifer calves treated with oestradiol. Mucociliary clearance of the spheres was unaffected by repeated exposure to the experimental aerosol and the overall mean mucociliary clearance rate constant was 1.28 (+/- 0.43) h-1 (half-life 32 minutes). Clearance curve profiles tended to be characteristic for individual calves but variation in mucociliary clearance rates within calves was high and on occasions clearance rate inexplicably fell to 10 to 50 per cent of the maximum achievable value for the calf. Neither mucociliary clearance rate nor alveolar deposition was affected by a change in climate from 14 degrees C, 87 per cent relative humidity to 5 degrees C, 75 per cent relative humidity. Both alveolar deposition and mucociliary clearance of the spheres could be manipulated using a beta-adrenergic treatment.