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Biomedical subjects

C J Howard

Publications and source records attributed to C J Howard.

At least 181 records · Page 10Linked to original sources
PubMed1976

Experimentally produced calf pneumonia.

Experimental pneumonia was produced in calves by the endobronchial inoculation of pneumonic lung homogenates. Irradiated homogenates produced minimal pneumonia. Ampicillin treatment of the homogenates and the experimental calves reduced the extent of pneumonia. Treatment with tylosin tartrate prevented experimental pneumonia. These results suggest that the total pneumonia was due to organisms susceptible to tylosin tartrate and that the residual pneumonia remaining after ampicillin treatment was due to organisms susceptible to tylosin tartrate but not to ampicillin. Of the organisms isolated from the lungs, the ones in this latter category most likely to be responsible are Mycoplasma dispar and ureaplasmas (T-mycoplasmas).

Acholeplasma laidlawii↗
PubMed1976

Pathogenicity of certain Mycoplasma species in the bovine mammary gland.

Strains of three of the species of mycoplasmas isolated from pneumonic calf lungs, Mycoplasma dispar, Mycoplasma bovirhinis and Acholeplasma laidlawii, were inoculated into the bovine mammary gland. Pathogenicity of the species was monitored by counting the inflammatory cells and mycoplasmas in milk. Six of the seven M dispar strains produced clinical mastitis, but the seventh strain, Vic12, was apparently avirulent. The four strains of M bovirhinis caused subclinical mastitis. None of the four strains of A laidlawii multiplied and they produced only a transient cell response in the milk.

Acholeplasma laidlawii↗
PubMed1976

Induction of pneumonia in gnotobiotic calves following inoculation of Mycoplasma dispar and ureaplasmas (T-mycoplasmas).

Cloned cultures of Mycoplasma dispar and of Ureaplasma sp were inoculated endobronchially into gnotobiotic calves. The resulting pneumonia was estimated to involve 2 to 10 per cent of the lung although no clinical signs were observed. The histopathological lesions consisted of infiltration with mononuclear cells, cuffing (peribronchiolar lympho-reticular hyperplasia), catarrhal bronchiolitis and atelectasis. The results indicate that both M dispar and Ureaplasma sp are capable of causing sub-clinical cuffing pneumonia in calves.

Animals↗
PubMed1975

Presence of a dialysable fraction in normal bovine whey capable of killing several species of bovine mycoplasmas.

Most normal bovine whey samples contain a fraction that survives heating at 56 degrees C. for 30 min., passes through a dialysis membrane and kills a maximum of seven out of ten of the different bovine mycoplasma species tested. Some whey samples appear more active than other but not all affect the same strains of mycoplasma indicating some specificity in their action. Absorption of the active factor from whey by heterologous and homologous mycoplasmas and by erythrocytes was observed. Binding of the factor to mycoplasmas appears to be temperature-dependent and non-specific, but subsequent mycoplasmacidal action shows some specificity.

Absorption↗
PubMed1975

Production of mastitis in mice with human and bovine ureaplasmas (T-mycoplasmas).

Five ureaplasmas (T-mycoplasmas) of human origin and four of bovine origin were inoculated into the mammary glands of mice. The strains multiplied and neutrophils were observed in sections of infected glands. Some of the glands were macroscopically inflamed, albeit slightly, at necropsy but none of the mice showed any sign of disease during the course of the experiments. All nine ureaplasma strains produced mastitis in BSVS mice and the mammary glands of mice appear more susceptible to ureaplasmas than the udders of cows or goats. Mouse mastitis is suggested as being a suitable small animal model for studying ureaplasma infections.

Animals↗
PubMed1975

Localized immunity in experimental bovine mastitis caused by Mycoplasma dispar.

Development of immunity to reinfection with Mycoplasma dispar occurred in the bovine mammary gland and appeared to be confined to the quarter or quarters previously infected with this mycoplasma; it was not generalized throughout the gland. Immunity followed the inoculation of virulent strains of M. dispar but not of an avirulent strain. The immunity engendered protected against both homologous and heterologous strains of M. dispar. Challenge of immune quarters with virulent M. dispar resulted in a transient polymorphonuclear cell response greater than that observed in previously uninoculated quarters.

Animals↗
PubMed1974

Mycoplasmacidal activity of bovine milk for T-mycoplasmas.

Normal bovine milk and whey was mycoplasmacidal for 6 of the 13 strains of bovine T-mycoplasmas examined. The in vitro assay used also demonstrated no killing of the human, canine and simian T-mycoplasma strains after 4 hr. incubation. However, there appeared to be some cow-to-cow variation in possession of this activity, and following E. coli endotoxin stimulation of the mammary gland the activity was considerably reduced.Whey from three normal cows was fractionated on a Bio-Gel A 1.5 m. column and the mycoplasmacidal activity of the resulting five peaks assayed. Only the second peak, peak B, contained activity and was characterized as the only peak containing bovine IgA. The active component in whey, however, was found to be heat stable at 60 degrees C. for 60 minutes and to pass through a dialysis membrane. This is inconsistent with it being immunoglobulin.

Animals↗
PubMed1974

Serological comparison and haemagglutinating activity of Mycoplasma dispar.

A comparison of twelve strains of Mycoplasma dispar by the metabolism inhibition and indirect haemagglutination tests has shown them to form a serologically homogeneous group of micro-organisms. The twelve strains vary in their haemagglutinating activity against erythrocytes from different animal species, and certain of the strains can be distinguished by the erythrocytes they agglutinate. Haemagglutination may thus provide a method by which certain strains can be typed. The erythrocyte receptor site does not appear to contain sialic acid and is not sensitive to proteolytic enzymes. On the mycoplasma cell two attachment sites have been demonstrated. One, by which it attaches to sheep and bovine erythrocytes, is a protein or contains a protein moiety. The chemical nature of the other attachment site, by which M. dispar attaches to rabbit erythrocytes, is unknown.

Animals↗
PubMed1974

Immunity in experimental T-mycoplasma mastitis.

Immunity to reinfection with the homologous T-mycoplasma strain has been demonstrated in the bovine mammary gland. This immunity was generalized throughout the udder and was not confined to previously infected quarters. Two out of three cows which were immune to reinfection with the homologous strain were not immune to reinfection with a serologically distinct T-mycoplasma strain. Animals varied in their ability to resolve experimental mastitis with T-mycoplasmas: those which resolved the initial infection without antibiotic therapy were immune to challenge with the homologous strain, but those which needed to be given antibiotics to clear the first infection were not all immune to such challenge.

Animals↗
PubMed1973

The virulence of T-mycoplasmas, isolated from various animal species, assayed by intramammary inoculation in cattle.

The virulence of T-mycoplasmas for cattle was tested by examining their ability to produce mastitis in cows. It was found that both virulent and avirulent strains of T-mycoplasmas can be isolated from cattle. All of four strains from pneumonic calf lungs and a strain from a case of bovine kerato-conjunctivitis caused mastitis but only two of four strains isolated from the urogenital tract of cows were virulent. None of the human, simian or canine T-mycoplasmas examined were able to cause mastitis in cattle. However, a bovine strain was found to be capable of causing mastitis in goats. Virulent and avirulent strains from the same and different species contain common antigens detected by the metabolic inhibition test. Pathogenicity could not be shown to be characteristic of any particular serotype. The possibility is raised of some species barrier being responsible for the inability of non-bovine strains to infect cattle.

Animals↗