Small beams are often applied in radiotherapy, e.g., in shrinking field and high-dose techniques with curative intent. For a given beam, measured field size factors (FSF) may vary with responses of different detectors to nonuniform radiation fluence. Dose rates of small photon and electron beams with diverse profiles were measured in polystyrene with 0.6- and 0.2-cm3 Farmer ionization chambers. FSF of 60Co, 4-, 8-, and 16-MV photon beams, and of 6-, 12-, and 20-MeV electron beams, were determined as ratios of dose rates of beams with differing field dimensions to dose rates of 10 X 10 cm beams. 60Co and 4-MV photon beam FSF were also determined in air using acrylic buildup caps. FSF obtained via 0.6- and 0.2-cm3 chambers are compared as functions of beam flatness and quality.. It is shown that notable discrepancies can exist between FSF for the same field obtained with different detectors, even when chamber volumes are well within nominal beam dimensions. Possible dose delivery errors arising from use of the 0.6-cm3 chamber were found to be from 0% to 2% for 4 X 4 to 5 X 5 cm photon beams, and from - 1% to 5% for electron beams 4 cm in diameter. Possible errors greater than 5% were noted for most beams less than 3.5 X 3.5 cm. Consequently, it is recommended that detectors smaller than the Farmer 0.6-cm3 chamber be employed in determining FSF of beams less than or equal to 5 X 5 cm.(ABSTRACT TRUNCATED AT 250 WORDS)

Calibration↗

PubMedDate not supplied

Arthroscopy of the elbow.

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Arthroscopy↗

PubMedDate not supplied

Effect of amlodipine on echocardiographic variables in cats with systemic hypertension.

Left ventricular hypertrophy signals a poor prognosis in hypertensive humans. Cardiac disease is common in cats with systemic hypertension. The aims of this study were to characterize the echocardiographic findings of cats with systemic hypertension and to determine if reducing the degree of hypertension is associated with resolution of cardiac hypertrophy. Echocardiographic examinations were performed on 19 cats with naturally occurring systemic hypertension. Fourteen of these cats were subsequently studied after a minimum of 3 months of treatment with the antihypertensive agent amlodipine. Hypertensive cats had a significantly thicker interventricular septum in both systole and diastole, thicker left ventricular free wall in both systole and diastole, and larger left atrium compared to the published normal values and 74% (14/19) of the cats met criteria for left ventricular hypertrophy (diastolic septal or free-wall thickness > 0.60 cm). Systolic blood pressure was lower after treatment (217 +/- 25 mm Hg, range: 180-275 mm Hg; and 142 +/- 27 mm Hg, range: 90-200 mm Hg). No difference was found in any of the echocardiographic measurements between the untreated and treated cats, although more cats had ventricular hypertrophy before treatment (11/14) than after initiating amlodipine (6/14; P = .006). Ventricular hypertrophy is common in hypertensive cats and may resolve after the initiation of amlodipine.

Amlodipine↗

PubMedDate not supplied

Postprandial venous ammonia concentrations in the diagnosis of hepatobiliary disease in dogs.

A postprandial ammonia tolerance test (PPATT) was performed on normal dogs and dogs with signs that suggested they may have liver disease. All dogs underwent transcolonic scintigraphy, liver biopsy, or both and were assigned to extrahepatic disease, primary hepatocellular, and congenital portosystemic vascular anomalies (PSVA) groups. Each dog was fed a chicken and rice diet providing 25% of its estimated daily metabolizable energy requirement (MER) as an ammonia challenge. This is practical in patients with liver disease because ammonium chloride administration often causes vomiting or ammonia toxicity. Venous ammonia concentrations were measured before feeding and every 2 hours after feeding for 8 hours. No difference in mean ammonia concentrations between dogs with extrahepatic disease and control dogs was found. Therefore, the specificity of the PPATT was 100%. Dogs with hepatocellular disease showed no change in mean ammonia concentration at any time point, before or after feeding, but sensitivity was greatest when venous ammonia was measured 6 hours after feeding (sensitivity before feeding, 28%, and after feeding, 36%). Among dogs with congenital PSVA, mean ammonia concentrations were higher than the reference range at all time points before and after feeding, and peak mean ammonia concentration occurred 6 hours after feeding. In this group, the sensitivity of the PPATT was 81% before feeding and 91% 6 hours after feeding. This study demonstrates that the measurement of venous ammonia concentration is a useful test to detect congenital PSVA, and the sensitivity of the test may be improved by sampling 6 hours after feeding. The PPATT has poor sensitivity in detecting primary hepatocellular disease.

Ammonia↗

PubMedDate not supplied

High-titer antisera production using three adjuvants and peptide conjugates derived from malarial surface antigen MSA-2.

We have identified a 51-kDa glycosylated myristoylated merozoite surface antigen as the target of a number of monoclonal antibodies that inhibit P. falciparum invasion. This antigen has been shown to exist in a limited number of strain-specific forms, but despite wide variation in the sequences of the internal repeat regions both N- and C-terminal elements of the protein are almost totally conserved. Accordingly, we prepared a large number of overlapping peptide constructs and demonstrated that one peptide, SNTFINNA (E-71), from the N-terminus and two peptides, QHG HMHGS (G-5) and NTSDSQKE (G-12), from the C-terminus were capable, when suitably conjoined to carrier protein diphtheria toxoid, of eliciting antibodies reactive with MSA-2 from diverse strains of P. falciparum. Here we compared the immunogenicity of the peptide constructs when formulated with a Freund's adjuvant, alum and algammulin. Both peptide constructs E-71 and G-5 elicit high-titer antibodies with all three adjuvants when tested by ELISA against the immunogens themselves and by Western blotting of whole parasite extracts from two distinct parasite strains.

Adjuvants, Immunologic↗

PubMedDate not supplied

High titer response against a malarial antigen depends on the flanking sequence of the immunizing peptide conjugate.

The immunogenicity of peptides conjugates containing the epitope STNS, recognized by inhibitory monoclonal antibodies directed against the Plasmodium falciparum merozoite surface antigen MSA2, was investigated. The sequence of the flanking regions was critical in determining the response against the central epitope. In the best immunogen tested, this flanking sequence was not related to the sequence of the surface antigen itself but nevertheless gave rise to a strong anti-MSA2 protein response as judged by Western blotting and immunofluorescence. This finding illustrates the importance of defining such flanking sequences in optimizing peptide based vaccines.

Animals↗