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Biomedical subjects

D F Mahoney

Publications and source records attributed to D F Mahoney.

At least 55 records · Page 3Linked to original sources
PubMed1980

The irradiation of Babesia bovis. 1. The difference in pathogenicity between irradiated and non-irradiated populations.

Babesia bovis parasites attenuated by 35 krads gamma irradiation and parasites not exposed to irradiation, were injected into intact 2-year-old Hereford steers. All five animals receiving non-irradiated blood died but the five animals which received irradiated blood were only mildly affected. Highly significant differences were observed in changes to plasma fibrinogen, serum fibrinogen-like proteins, packed cell volume, partial thromboplastin time, prothrombin time, blood kinins, and plasma kininogen levels in the control animals but non-significant changes in these parameters occurred in the group receiving iradiated blood. Significant changes in the antiplasmin alpha 2M, and the antithrombin levels occurred in control cattle but not in the group receiving irradiated blood. Parasite multiplications rates and maximum parasitaemias were similar in both groups. Irradiation reduced the dose of living parasites from 1 x 10(8) to 2.5 x 10(3), but this was not the reason for the mild reactions. It was concluded that irradiation had selected an avirulent parasite population.

Animals↗
PubMed1980

Babesia bovis (Argentina): analysis of paracoagulation proteins in acutely infected cattle.

The proteins in plasma and serum from cattle infected with Babesia bovis that react with protamine sulphate and ethanol have been characterized. Their sizes and chain structures suggest they are intermediates in the conversion of fibrinogen to cross-linked fibrin. In addition, comparison with reference proteins and in vitro systems strongly indicate the proteins are, in the main, the products of thrombin activation in vivo and not those of fibrinolysis.

Animals↗
PubMed1979

Evaluation of an indirect fluorescent antibody test to diagnose Babesia equi infection in horses.

An indirect fluorescent antibody (IFA) test for the diagnosis of Babesia equi infections was evaluated. Antigen prepared by conventional methods was of high quality in one instance and of lesser quality in a second when possible autofluorescence of the horse blood caused inconvenience in reading tests. Tests on 14 horses shown by parasitological means to be either infected (9) or uninfected (5) produced reactions at dilutions of 1/270 to 1/7290 for infected and at 1/10 to 1/90 for uninfected animals. The accuracy of the test was further demonstrated during investigations of 701 horses in 3 states of Australia. The 30 horses reacting at 1/270 to 1/2430 were from 33 imported to 3 different farms in Australia from a common source. Investigations of crossreactivity between B. equi and B. bovis of cattle suggested that B. bovis would not interfere with the test for B. equi, but that the reverse was possible.

Animals↗
PubMed1979

Immunity in cattle to Babesia bovis after single infections with parasites of various origin.

Sixty calves, 3 to 6 months old, were vaccinated once against Babesia bovis in groups of 10, by the following methods: (a) tick infestation; (b) inoculation of virulent parasites obtained from the tick-infested animals immediately after infection; (c) inoculation of the parasites used in (b) attenuated by passage through splenectomised calves; (d) inoculation of commercially-available, living, attenuated vaccine; (e) inoculation of virulent parasites obtained from the tick-infested animals in (a) one year after infection; (f) inoculation of the parasites used in (e) attenuated by passage. All vaccinated animals were maintained tick-free and were strongly immune to challenge with a heterologous strain of B. bovis approximately 4 years after vaccination. There was no difference in immunogenicity between any of the B. bovis populations.

Animals↗
PubMed1979

Lack of correlation between beta-lactamase production and susceptibility to cefamandole or cefoxitin among spontaneous mutants of Enterobacteriaceae.

A large number of cultures of gram-negative bacteria were examined for their susceptibility to various concentrations of cefamandole, cefoxitin, carbenicillin, and nalidixic acid. Heterogeneity of susceptibility was demonstrated in individual cultures to all of these antibiotics. Resistant clones isolated from cefamandole or cefoxitin plates were examined for beta-lactamase production. Approximately 13% of 262 resistant clones acquired the ability to produce a beta-lactamase. Examination of the substrate profile of the beta-lactamases from some of these clones revealed no change in the specific activity of these enzymes for cefamandole, cephaloridine, or compound 87/312 as compared with their parental enzymes. This study clearly shows that some resistant clones do not produce beta-lactamases, whereas some susceptible strains produced significant amounts of these enzymes. We conclude from these findings that little correlation exists between beta-lactamase production and decreased susceptibility to cefamandole or cefoxitin. The results suggest the possibility that characteristics other than beta-lactamase production may be responsible for resistance in Enterobacteriaceae.

Cefamandole↗
PubMed1979

A note on the transmission of Babesia bovis (syn B argentina) by the one-host tick, Boophilus microplus.

Boophilus microplus infected with Babesia bovis were transferred artificially from one splenectomised calf to another during each moult in the parasitic life cycle of the tick. Eggs from the engorged female ticks recovered at the end of the cycle were incubated and the resulting larvae used to infest more splenectomised calves. Babesia bovis was transmitted only by the original larvae used at the commencement of the experiment and it was concluded that the protozoan parasite did not persist in an infective form in the ticks beyond the larval stage.

Animals↗
PubMed1978

Babesia bovis (argentina): components of the cryofibrinogen complex and their contribution to pathophysiology of infection in splenectomized calves.

A cryofibrinogen complex, found in the plasma of cattle acutely infected with Babesia bovis (argentina), was characterized. The fibrinogen-like proteins of the complex were isolated and the structure of their polypeptide chains analysed. In general, the chain structure was similar to that of soluble non-crosslinked fibrin (fibrinogen) although chains indicating some degree of fibrin crosslinking were often detected. Only rarely did the chain structure suggest that fibrinolysis occurred. It was concluded that the complex was produced by activation of the coagulation system but that fibrinolysis did not occur to any marked degree. The complex was implicated in assistance to the sludging of erythrocytes in the internal organs which is a feature of the pathogenesis of the disease.

Animals↗
PubMed1977

The identification of Babesia equi in Australia.

A Babesia parasite, isolated from the blood of a horse at Bowral, New South Wales, was identified on the basis of its morphological features, host specificity and serological reactions, as Babesia equi (Laveran 1901). The case was originally reported by Churchill and Best (1976, Aust. vet. J. 52: 487) and is the first record of equine babesiosis in Australia. In preliminary studies, the organism produced only a mild disease in an intact horse, but caused the typical clinical syndrome of acute babesiosis in a splenectomised horse, which died 19 days after the intravenous inoculation of the parasites.

Animals↗
PubMed1977

The selection of larvae of Boophilus microplus infected with Babesia bovis (syn B argentina).

Observations on the dynamics of the transovarial transmission of Babesia bovis by Boophilus microplus showed that, at 28 degrees C and 90--95 per cent relative humidity, a low proportion of the eggs laid during the first five days' incubation of the engorged female ticks were infected with the Babesia. However, the eggs laid on the sixth and seventh days of incubation were heavily infected. This was the basis of a method for selecting larval cultures of B microplus which contained up to five times the infection rate of B bovis obtained if the entire egg mass of the tick were used. The technique has been used to obtain larval cultures with infection rates exceeding 20 per cent and should facilitate studies on the life cycle and immunology of the invertebrate stages of B bovis.

Animals↗
PubMed1976

Substrate inhibition of beta-lactamases, a method for predicting enzymatic stability of cephalosporins.

Selected cephalosporins, including cefamandole, cephaloridine, cephaloglycin, and cefoxitin, were examined for their ability to inhibit the enzymatic activity of and act as substrates for beta-lactamases produced by Enterobacter cloacae and Staphylococcus aureus. Enzyme inhibition was determined by Michaelis-Menten kinetic measurements and by a spot plate assay using a chromogenic substrate (Glaxo compound 87/312). These two methods provide comparable estimates of kinetic parameters. Inhibition of beta-lactamase, as measured by these two methods, was generally found to correlate with resistance to hydrolysis and is proposed as a preliminary method of assessing susceptibility of cephalosporins to beta-lactamase hydrolysis. Four 7-alphaOCH(3), 7-alphaH cephalosporin analogue pairs were also examined. The presence of the 7-alphaOCH(3) substituent invariably resulted in reduced susceptibility to enzymatic hydrolysis, regardless of the other C7 substituent. The 7-alphaOCH(3) compounds were also better inhibitors than were their 7-alphaH analogues, with the exception that 7-alphaOCH(3) compounds having C7 adipic acid substituents were less inhibitory to the S. aureus enzyme than were the corresponding 7-alphaH analogues. Response of these two enzymes to 7-alphaOCH(3) and 7-alphaH cephalosporins suggests that beta-lactamase hydrolysis of these compounds involves attack at the alpha side of the betalactam ring.

Amidohydrolases↗