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Biomedical subjects

R B Atwell

Publications and source records attributed to R B Atwell.

At least 55 records · Page 3Linked to original sources
PubMed1987

Use of an antigen detection assay to determine mortality of Dirofilaria immitis after thiacetarsamide therapy.

The use of an antigen detection enzyme immunoassay (EIA) to determine the post-treatment infection status of 16 dogs naturally infected with Dirofilaria immitis was investigated. Dogs were treated with thiacetarsamide at a dose rate of 12mg/4.5kg twice daily for 2 days, bled at regular intervals and necropsied 9 weeks later. The infection status of all dogs at necropsy was compared to the ratios of optical density (OD) values from the EIA using fresh plasma samples (day 60/day 0 = R60) and dogs were divided into 2 groups. Using the R60 ratios, those dogs with fewer than 2 live adult worms or immature worms at necropsy ("cleared" dogs) could be differentiated with 95% confidence from those dogs with more than 1 live adult worm ("non-cleared" dogs). Changes in the average OD values from the plasma of "cleared" dogs and "non-cleared" dogs were similar up to 46 days after treatment but diverged significantly thereafter. The efficacy of thiacetarsamide was 50% if all worms were considered and 75% if the presence of immature worms was ignored. The benefits of antigen detection assays for diagnosis and improved patient assessment and the use of an R60 ratio to assess the efficacy of adulticides such as thiacetarsamide are discussed in relation to their practical significance for clinicians.

Animals↗
PubMed1986

The ability of microfilariae to evade in vitro cell-mediated cytotoxicity.

When microfilariae (Mf) of Dirofilaria immitis, both uterine and systemic, were incubated in an in vitro cytotoxicity assay with neutrophils and sera from dogs with occult infections, some Mf remained free of adherent cells and consequently evaded cytotoxicity. The ability to evade cytotoxicity could not be related to the age of the Mf, and host albumin was not detected on any Mf, either uterine or systemic. However, it was shown that some Mf failed to bind IgM, IgG and C3 when incubated with occult sera. It is suggested that the ability of some Mf to evade serum-dependent, neutrophil-mediated cytotoxicity in vitro was related to differences in their antigenicity.

Age Factors↗
PubMed1986

Inoculation of dogs with artificial larvae similar to those of Dirofilaria immitis: distribution within the pulmonary arteries.

Two hundred artificial larvae, similar in size to those of Dirofilaria immitis, were inoculated into the venous system of 20 clinically healthy dogs and the distribution pattern was evaluated. One hundred forty-four (73%) of the larvae were located in the right lung and fifty-one (26%) in the left lung. Of those larvae in the lung, 50% were in the right caudal branch and 21% in the left caudal branch of the pulmonary artery. These findings help to explain why the right caudal lung lobe usually is more affected in canine dirofilariasis.

Animals↗
PubMed1986

Early pulmonary lesions caused by dead Dirofilaria immitis in dogs exposed to homologous antigens.

Dead adult D. immitis were inserted into the pulmonary arteries of 10 healthy pups, five of which were given a crude antigenic extract of D. immitis subcutaneously. Two dogs, one from each group were then killed 1, 3, 5, 7 and 9 days after the insertion of filariae and the associated pulmonary artery pathology examined. Microscopically, haemorrhage was evident at day 1, followed by suppuration and organization at days 5 to 7, with organization, fibrosis and focal pleural retraction evident on days 7 to 9. Within arteries haemorrhage and thrombosis was evident, particularly on days 1, 3 and 5. Histology confirmed the extent of haemorrhage evident grossly and, as no rupture was evident, suggested it to be due to diapedesis. Wall disruption occurred due to the local pressure effects of impacted filariae, but also due to inflammation, which was initially suppurative, later being replaced by plasma cell and lymphocyte involvement. Maximal wall disruption occurred at day 5 followed by organization and fibrosis. After day 5 there was more intense organization in the dogs given antigen, in association with the development of interstitial thickening, a finding previously reported in dogs with similar antigenic exposure.

Animals↗
PubMed1985

Experimental production of lesions in canine pulmonary arteries similar to those produced by Dirofilaria immitis infection.

Pulmonary arterial disease was produced by the placement of flexible polyvinyl chloride threads (similar in size, shape and flexibility to adult female Dirofilaria immitis) in the pulmonary arteries of dogs. Several different types of pathological change were apparent ranging from subendothelial oedema and endothelial loss, mild intimal proliferation and thrombus formation to organised fibrous encasement of the threads in areas where they had become impacted in the lumen of the artery. This range of pathological changes is very similar to that produced by D immitis and suggests that the intima of the canine pulmonary artery may react to different insults in a similar way.

Animals↗
PubMed1985

Liver changes, following diethylcarbamazine administration, in microfilaremic dogs infected with Dirofilaria immitis.

Livers of dogs which were microfilaremic due to infection with Dirofilaria immitis were studied after the administration of diethylcarbamazine. Most dogs had a severe shock-like clinical reaction. The main hepatic features were congestion and hemorrhage around the central vein and irregularly scattered foci of inflammation. The severity of the vascular reaction was associated with the number of microfilariae in the livers. Mast cells associated with the vascular reaction were not degranulated, suggesting that histamine-mediated anaphylaxis was not the cause of the reaction. The observations suggest that the mediator of the hepatic vascular reaction originates from the microfilariae and is influenced or activated by diethylcarbamazine.

Animals↗
PubMed1984

The effectiveness of levamisole hydrochloride against the microfilaria of Dirofilaria immitis.

Levamisole hydrochloride was an efficient microfilaricide when used in dogs at a dosage of 10 mg/kg twice daily for 14 days. Increasing the dose rate every 3 days to 10 mg/kg twice daily and maintaining it at 10 mg/kg twice daily for a further 8 days, was also effective but a dosage of 5 mg/kg twice daily for 21 days was less effective and a dose rate of 20 mg/kg was efficient, but toxic.

Animals↗
PubMed1984

A survey of heartworm in dogs in Australia.

A survey conducted throughout Australia indicated that Dirofilaria immitis was far more widespread than previously described. It was prevalent throughout Queensland and New South Wales, including the western regions and was increasing in incidence. Confusion exists as to which diagnostic tests to use and the methods of treatment are extremely variable.

Animals↗
PubMed1983

Suspect three chambered right atrium in a pup.

The necropsy results from a puppy with decompensated heart failure suggested that deformities of the right atrium, consisting of triple chamber development and venous obstruction, were the cause of cardiac failure.

Animals↗