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Biomedical subjects

R Atwell

Publications and source records attributed to R Atwell.

10 recordsLinked to original sources
PubMed2006

Physiological and haematological findings and clinical observations in a model of acute systemic anaphylaxis in Dirofilaria immitis-sensitised cats.

OBJECTIVE: This study aims to understand the pathophysiology of anaphylaxis in Dirofilaria immitis-sensitised cats by analysing objective physiological and haematological measurements after challenge. DESIGN: Nineteen healthy D immitis-naive cats were sensitised using weekly injections of aluminium hydroxide-adjuvanted D immitis antigen, administered subcutaneously over 6 weeks. After sensitisation, cats (n = 16) were anaesthetised and challenged with intravenous D immitis antigen. A control group (n = 3) was sham-challenged using intravenous sterile 0.9% saline. Systolic blood pressure (measured non-invasively/indirectly), respiratory rate, degree of dyspnoea, blood O2 saturation, expired CO2, and heart rate and were measured immediately before and at 10 to 15 min intervals after challenge until terminal apnoea occurred or euthanasia at 140 mins post-challenge. Blood was collected for complete blood count immediately before and at 10, 20 and 35 mins after challenge. Clinical observations were recorded as they occurred. RESULTS: Antigen-challenged cats were divided into two groups: acute (apnoea occurred within 25 mins of challenge) and subacute (breathing at 25 mins after challenge). In both groups, the degree of dyspnoea increased and blood O2 saturation and blood pressure decreased. Respiratory rate increased in the subacute group. Expired CO2 decreased in both Ag-challenged and control groups. Haematocrit increased in the subacute group. Neutrophil count decreased in the acute group and platelet count decreased in the subacute group. Eosinophil count decreased in the subacute and control groups. Sustained dyspnoea and gastrointestinal signs were the most common clinical manifestations of anaphylaxis in the antigen-challenged cats. CONCLUSIONS: Intravenous challenge with D immitis antigen in sensitised cats results in dyspnoea, hypoxaemia and systemic hypotension accompanied by haemoconcentration.

Acute Disease↗
PubMed1995

Technical report. Using a world wide web server as a local organizer for protein and DNA sequences.

We have used a local World Wide Web (WWW) server to organize protein and DNA sequences that are used frequently in our laboratory. WWW server programs are available for most computer platforms and are easily set up with minimal computer skills. This approach allows for the easy retrieval of sequence data, which can then be used as input for other analysis programs. This format is especially simple to use in conjunction with WWW database searches. The sequence files may be served to the "public" Internet or kept private by requiring a password for access. Other advantages are (i) sequences can be accessed from multiple computer platforms using the appropriate WWW-browser; (ii) files can be accessed remotely from any computer on the Internet; (iii) only a single sequence format is used, simplifying the updating and archiving of data; and (iv) links to remote files can also be served in addition to local files.

Amino Acid Sequence↗
PubMed1993

The effect of ketoconazole on pulmonary pathology associated with dead Dirofilaria immitis.

The involvement of thromboxane and lipoxygenase in the regulation of pulmonary lesions and immune responses was investigated in dogs given ketoconazole and exposed to dead adult Dirofiliara immitis. Immunopathological reactions to the dead filariae were monitored by light and transmission electron microscopy and serology. When compared with control tissues, ketoconazole administration enhanced the level of pulmonary haemorrhage and early parenchymal fibrosis associated with dead adult filariae. Ultrastructurally, alveolar capillaries were filled with erythrocyte aggregations and proteinaceous material. These results suggested that an intact thromboxane and lipoxygenase pathway within the arachidonic acid system is necessary to minimize the effect of dead D. immitis in this pulmonary artery model.

Animals↗
PubMed1992

Cardiac beta-adrenoceptor changes in experimental hyperthyroidism in dogs.

1. Triiodothyronine (T3; 1.0 mg/kg per day subcutaneously) was administered to 10 dogs for 14 days; 10 saline-treated dogs served as controls. T3-treated dogs showed the expected physiological responses of hyperthyroidism; further, chronotropic responses to isoprenaline in vivo were significantly increased in T3-treated dogs. 2. Beta-adrenoceptor subtype density was measured in membrane preparations by displacement of 125I-iodocyanopindolol binding by the selective beta 2-adrenoceptor antagonist, ICI 118, 551. T3 treatment led to a 93% increase in right atrial beta 1-adrenoceptor density and a 141% increase in left ventricular beta 1-adrenoceptor density; beta 2-adrenoceptor densities in right atrial, left ventricular and lung membranes were unchanged. 3. T3-treatment did not change basal or maximally stimulated adenylate cyclase activities in left ventricular membranes. 4. Thus, the cardiovascular changes in experimental hyperthyroidism in dogs were accompanied by an increased chronotropic response in vivo to isoprenaline and an increased beta 1-adrenoceptor density in atrial and ventricular membranes. However, there was no corresponding change in basal or maximal responsiveness of adenylate cyclase in ventricular membranes.

Adenylyl Cyclases↗
PubMed1986

Stimulation of neutrophil respiratory burst and iodination reaction by opsonized microfilariae of Dirofilaria immitis.

It has been shown that the interaction of Dirofilaria immitis microfilariae (Mf) opsonized with sera from infected but amicrofilaraemic dogs (occult dogs) stimulated the respiratory burst and degranulation of neutrophils as measured by chemiluminescence and iodination. Sera from normal and microfilaraemic dogs gave either low level or non-significant reactions. Since the sera required were also those required for neutrophil-mediated cytotoxicity to D. immitis Mf in vitro, the results suggested that the products of oxygen reduction as well as the myeloperoxidase system could be involved in the killing of Mf by neutrophils. However, whether these pathways have a major role to play in neutrophil-mediated cytotoxicity to Mf is uncertain, as various chemical and enzymatic inhibitors of the products of the respiratory burst were unable to prevent or reduce cytotoxicity. Azide, which is a known inhibitor of the iodination reaction, also failed to reduce cytotoxicity.

Animals↗
PubMed1979

In vitro effect of branched chain amino acids on the ribosomal cycle in muscles of fasted rats.

1) The effect of a single i.p injection of branched chain amino acids on ribosomal profiles of psoas muscles was studied in rats after a 48--96 hour fast. Experimental and control animals received glucose and insulin 1--2 hours before killing. 2) The ratio of polysomes to subunits and monomers decreased progressively during the fast. 3) The administration of the three branched chain amino acids together or leucine alone significantly increased the proportion of polysomes. 4) This effect was not observed in rats fed ad libitum. 5) It is suggested that the branched chain amino acids and specifically leucine may be required for the full protein anabolic response of muscles to insulin during a prolonged fast.

Amino Acids↗