Imaging: Nuclear*

In this paper an overview of principles involved in nuclear imaging is presented. Nuclear images are picotrial representations of the distribution of systemically administered radiopharmaceuticals. Although many radionuclides are available. ^99mTc is the most commonly used radionuclide, either in ionic form (^99mTcO₄) or bound to other pharmaceuticals. Distribution within the body is by physiologic processes, dependent on the radiopharmaceutical used. Most distribution processes are organ specific rather than disease specific. Scintillation detectors are used to record the activity and disribution of an administered radiopharmaceutical and to create a representative image on film. A rectilinear scanner is an imaging system with a small detector that moves systematically, point by point, over an organ of interest. A gamma (scintillation) camera is an imaging system with a large stationary detector that encompasses a larger field of view. Nuclear imaging provides information based primarily on physiologic principles, and radiography provides infromation based primarily on anatomic or geometric principles. Examples of some scanning procedures are discussed.     

Diagnosis of Aelurostrongylus abstrusus and Dirofilaria immitis infections in cats from a human shelter

During a 6-month period, 108 sexually mature stray cats were euthanatized at a humane shelter in Alabama. Aelurostrongylus abstrusus was identified in 20 of the cats (18.5%) by Baermann fecal examination, necropsy, or histologic examination. The Baermann fecal examination was a more sensitive test for aelurostrongylosis than was necropsy or histologic examination. Thoracic radiography was useful in identifying infected cats, but was a less sensitive and more nonspecific method of detection than was the fecal examination. Changes in CBC and serum protein concentrations were not helpful identifying cats with aelurostrongylosis. Six of 17 (35%) heartworm-free, lungworm-infected cats had antibodies to Dirofilaria immitis, as determined by an ELISA method, but none had circulating D immitis antigen, as determined by an ELISA method. Three (2.8%) cats had D immitis. Two of the heartworm-infected cats had no detectable antemortem radiographic or clinicopathologic evidence of the infection. Results of ELISA were positive for antibodies to adult heartworms in 2 cats and for circulating heartworm antigen in 2 cats. One cat that had only one heartworm had no detectable circulating heartworm antigen.     

Comparison of the agar gel immunodiffusion test and ELISA in the detection of bovine leukosis virus antibody in cattle persistently infected with bovine virus diarrhoea virus

When six cattle persistently infected with bovine virus diarrhoea virus (BVDV) were inoculated with lymphocytes infected with bovine leukosis virus (BLV), a depressed antibody response to BLV was observed by ELISA which was due to a decrease in IgG1 synthesis. The ELISA was more sensitive and more reliable than the agar gel immunodiffusion (AGID) test in detecting BLV infection in cattle persistently infected with BVDV. Decreased antibody responses were manifested in the AGID test by negative, inconclusive or weakly positive reactions: only two of the six cattle developed antibodies that generated positive AGID reactions.     

Scrotal hernia in rams. A case report

Scrotal hernia in rams is relatively rare. This report would indicate the condition is probably inherited as a recessive character similar to other domestic animals.     

The metabolism of the herbicide flamprop-isopropyl in barley

The metabolism of the wild oat herbicide, flamprop-isopropyl, [Barnon, isopropyl (±) N-benzoyl-N-(3-chloro-4-fluorophenyl)-2-aminopropionate] in barley grown to maturity has been examined under glass-house and outdoor conditions. [¹⁴C]Flamprop-isopropyl labeled separately in two positions was used. The major metabolic route of the herbicide was by hydrolysis to the corresponding carboxylic acid, II, which occurred in free and conjugated forms. Flamprop-isopropyl also underwent hydroxylation in the 3 and 4 positions of the benzoyl group, and the 3-hydroxybenzoyl analogue of II was detected. The hydroxylated metabolites were also present in the plants as conjugates. Additional minor metabolites detected only in glass-house samples were N-benzoyl-3-chloro-4-fluoroaniline, 2-[3-chloro-4-fluorophenylamino]-propionic acid, and benzoic acid. The soil in which the plants were grown received part of the spray application of the herbicide. Residues in the 0–10-cm layer at barley harvest comprised the unchanged herbicide, the carboxylic acid II, and unidentified polar material.     

A re-evaluation of the D (+) xylose absorption test in the horse

The absorption of d-xylose forms the basis of a useful screening test in the investigation of small intestinal disorders in the horse. A comparison has been made of different assay methods and there was no significant difference between the results obtained with the parabromoaniline (PBA) method or the ferric chloride-orcinol (FCO) method. The orthotoluidine method was unsatisfactory. The anticoagulant agent did not affect the test. A dose of 0.5 g commercial grade xylose/kg body weight as a 10 per cent solution given by stomach tube, produced a peak plasma xylose level after 90 min and should discriminate normal from abnormal absorption. The FCO method was preferred for the occasional test performed in practice, and a 2-hour sampling period would be adequate.     

The vaginal mucus agglutination test in the diagnosis of bovine brucellosis

Of 1140 vaginal mucus agglutination tests (VMAT) on specimens obtained in 1971-72 from 663 dairy cows in seven herds infected with brucellosis, 97 were positive. When the VMAT was positive one or more serological tests were also positive. Of the 97 corresponding serum agglutination tests 80 sera had titres of more than 533 international units. Only 69.8 per cent of VMAT from serologically positive cows were positive. No evidence was found of non-specific agglutinins in vaginal mucus and positive VMAT reactions appeared to be specific for field infection. Three cows showed evidence of local agglutinins in the vagina. Hence herd testing by VMAT has no advantage over tests of blood serum but the test could be an aid in establishing whether individual cattle are infected.