The prevalence of serum precipitating antibody to Aspergillus fumigatus in adult cattle in Britain

The prevalence of precipitating antibody to A. fumigatus in 3509 sera from adult cattle in 44 herds was 25 per cent. Only 19 per cent of sera from grazing or recently housed animals were positive compared with 30 per cent of those taken towards the end of the winter. Mouldy hay was the most likely source of A. fumigatus antigens although a positive correlation between the prevalence of precipitins and either the mouldiness of the hay or the frequency of coughing in the springtime was not established. However, there was a positive correlation between the age of cattle sampled and the prevalence of antibodies. Mycotic abortion had been confirmed in only one of 6 herds in which more than 80 per cent of the cows were seropositive and so it can be inferred that the presence of serum precipitating antibody is of very little value in the diagnosis of mycotic abortion resulting from A. fumigatus infection.

Experimental production of bovine pneumonic pasteurellosis

Pneumonic pasteurellosis has been reproduced in conventional, weaned, Friesian-cross calves using a strain of Pasteurella haemolytica biotype A, serotype 1 (P haemolytica A1) isolated from a pathologically confirmed incident of bovine pneumonic pasteurellosis. The major clinical findings were pyrexia, hyperpnoea, tachypnoea, nasal discharge and reduced appetite. Fibrinous pneumonia was present in the lungs of animals at necropsy on days 2 and 3 after initial infection while by days 9 and 10 after initial infection many of the areas of fibrinous pneumonia were confined by a fibrous capsule forming well defined nodules. During the experiment natural transmission of the infecting strain of P haemolytica A1 occurred in two control calves which developed a condition identical to that in the artificially infected calves. P haemolytica A1 was repeatedly recovered from the nasopharynx of infected calves and at necropsy throughout the upper and lower respiratory tracts. Seroconversion, as measured by indirect haemagglutination, to the organism developed in all infected calves by days 9 and 10 after initial infection. The clinical, microbiological and pathological findings were identical to those seen in field incidents of bovine pneumonic pasteurellosis involving recently housed, weaned, single-suckled calves.

Effect of anti-prostaglandin therapy in experimental parainfluenza type 3 pneumonia in weaned, conventional calves

An acute pneumonia was induced experimentally in 10, 10- to 12-week-old conventional calves by administration into the upper airways of a pathogenic strain of parainfluenza type 3 (PI3) virus. The experimental calves had been selected on the basis of freedom from clinical evidence of respiratory and other diseases, freedom from current infection by PI3 virus as judged by repeated nasopharyngeal swabbing and freedom from earlier PI3 virus infection as judged by their lack of significant levels of serum antibody to that virus. The infection procedure was deemed to have been successful in that infection was established with subsequent seroconversion, clinical signs of a febrile pneumonia arose soon after the administration of virus, histopathological changes characteristic of PI3 pneumonia developed and the presence of PI3 virus antigen was demonstrated by immunofluorescence in association with those lesions. Treatment of five of the pneumonic calves was carried out on days 1, 2 and 3 of the trial using the anti-prostaglandin compound flunixin meglumine and that treatment appeared to be of benefit in that in the test calves there was a prompt cessation of coughing with fewer fevers and lower respiratory rates as compared with the untreated controls. The drug did not appear to influence PI3 infection rates but its administration was associated with a marked reduction in the extent of pulmonary consolidation, probably as the result of its known ability to limit the acute inflammatory response.

Studies on the properties of highly purified cytochrome P-448 and its dependent activity benzo[a]pyrene hydroxylase, from Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae, produces a cytochrome P-450 enzyme with a Soret peak in the reduced-CO difference spectrum at 448 nm. The enzyme purified to homogeneity (88-97% pure on a specific content basis) has a molecular wt. of 55 500 as determined by SDS-PAGE. Amino acid analysis of yeast cytochrome P-448 revealed 407 amino acid residues per molecule with a 43% complement of hydrophobic residues. Although the number of residues is smaller than cytochrome P-448 enzymes from mammalian sources, the percentage of hydrophobic residues is almost identical. Estimation of the haem content of yeast cytochrome P-448 showed that one haem group was present per molecule. Phospholipid was present at very low levels. The molecular wt. of the polypeptide chain plus an estimated 5-6 units of hexose and of hexosamine is in good agreement with the molecular wt. value obtained from SDS-PAGE. A reconstituted system of purified cytochrome P-448, purified NADPH-cytochrome P-450 (c) reductase and phospholipid showed aryl hydrocarbon hydroxylase activity towards benzo[a]pyrene. Both protein components, NADPH and dilauroyl phosphatidylcholine (or emulgen 911) were necessary for full activity. The NADPH requirement could be replaced by cumene hydroperoxide or H2O2 generated in situ from a glucose oxidase system; in each case Vmax is increased, but the apparent affinity for benzo[a]pyrene, as measured by an increased Km, is lowered. The spin state of purified yeast cytochrome P-448 was 94% low spin (22 degrees C) as determined from the temperature-dependent spin-state equilibrium. The addition of benzo[a]pyrene to this enzyme resulted in a change to higher spin state (18% high spin at 22 degrees C). Equilibrium gel filtration analysis of the number of benzo[a]pyrene binding sites per mole of enzyme monomer showed a value of 1 for purified yeast cytochrome P-448 and 6 for this enzyme in microsomal form. The corresponding values for purified and microsomal cytochrome P-450 from phenobarbital-pretreated rats are 1 and 6, respectively. However, purified cytochrome P-448 from beta-naphthoflavone-induced rats gave a value of 6 benzo[a]pyrene binding sites. Type I binding spectra with purified yeast cytochrome P-448 were observed with benzo[a]pyrene, lanosterol, ethylmorphine, dimethylnitrosamine, sodium phenobarbitone and perhydrofluorene. Type II spectral changes were observed with imidazole, aniline and benzphetamine. Cytochrome P-448 from Saccharomyces cerevisiae is identified as a distinct enzyme of the P-450 family. This enzyme however has many properties in common with cytochrome P-448 from mammalian sources.(ABSTRACT TRUNCATED AT 400 WORDS)

Isolation and uptake characteristics of human cell variants resistant to the antiproliferative effects of methylglyoxal bis(guanylhydrazone)

Four variants (VA2/MGBG) of the human cell line, VA2, have been isolated which are 10- to 20-fold more resistant than the parent line to the antiproliferative effects of the anticancer agent, methylglyoxal bis(guanylhydrazone) (MGBG). Drug resistance was not cytoplasmically transmitted by cytoplast cell fusion for any of the four sublines, suggesting that the genes responsible for resistance may be of nuclear rather than mitochondrial origin. Uptake properties were characterized in the VA2 cells and two of the four variant lines. Uptake of [14C]MGBG during long-term (0.5 to 28 hr) incubations was 3 to 4 times greater in the VA2 cells than in the VA2/MGBG sublines. However, during short-term (2 to 60 min) incubations, the uptake of [14C]MGBG or [3H]spermidine (which competes for MGBG uptake) was similar for all cell lines. This was further supported by kinetic data which indicated that, for [14C]MGBG uptake at 4 min, the apparent Km for all cell lines was 5.8 to 13.4 microM, and the Vmax, 44 to 53 pmol/mg/min. For [3H]spermidine uptake, the apparent Km values were approximately 1 microM and Vmax, 54 to 69 pmol/mg/min. Efflux studies performed on cells incubated for 30 min in 10 microM [14C]MGBG revealed that the two VA2/MGBG sublines released drug much more rapidly than did VA2 cells over an 8-hr period. Thus, while the variants may transport MGBG at a rate similar to VA2 cells, the drug is not accumulated to the same extent during long-term incubations, probably because of altered intracellular binding sites for MGBG. The identification of these sites may provide insight into the basis for antiproliferative action of MGBG.

Biochemical and ultrastructural characterization of human cell variants resistant to the antiproliferative effects of methylglyoxal bis(guanylhydrazone)

Stable variants of the human cell line, VA2-B, have been developed which are 10- to 20-fold less sensitive to the antiproliferative effects of methylglyoxal bis(guanylhydrazone) (MGBG) than the parent cell lines and which are not drug transport deficient. The lines were characterized biochemically giving particular attention to parameters related to the two known sites of MGBG action, mitochondria and polyamine metabolism. Dose-response studies with MGBG (0 to 30 microM for 40 to 48 hr) revealed that, of the parameters related to polyamine metabolism (i.e., polyamine pools, S-adenosylmethionine, and ornithine decarboxylase activities), only spermine pool size reduction seemed to correlate with inhibition of cell growth by MGBG. By contrast, decreases in pyruvate oxidation (used here as a measure of mitochondrial function) closely paralleled growth inhibition in all cell lines. Similarly, MGBG-induced changes in mitochondrial ultrastructure were less conspicuous in the variants than in the parent cell line and also corresponded with growth inhibition. Respiration of isolated mitochondria from one of the variant lines was about 2-fold more resistant to the inhibitory effects of MGBG than mitochondria from the VA2 cells. Finally, treatment with alpha-difluoromethylornithine, a potent inhibitor of polyamine biosynthesis having no known effect on mitochondrial function, resulted in comparable inhibition of growth in variant and parent cell lines. Overall, the data suggest that a phenotypic alteration in mitochondrial function, rather than in polyamine metabolism, may represent the basis for MGBG resistance in these variant cell lines.

Studies on the genetic regulation of cytochrome P-450 production in Saccharomyces cerevisiae

An initial survey of 18 haploid strains of Saccharomyces cerevisiae revealed that only 3 of these strains could produce a detectable level of cytochrome P-450. A cross between a cytochrome P-450 producing strain of S. cerevisiae (B/B) and a non-producing strain (D22) gave a diploid which was a non-producer and a 2:2 segregation of producers to non-producers in meiotic tetrads. Of the two producers in each tetrad, one produced a higher level of cytochrome P-450 than the other. We deduce that cytochrome P-450 production in S. cerevisiae is regulated by a single nuclear gene and that a modifier gene is also involved which can enhance the amount of cytochrome P-450 synthesized. Benzo(a)pyrene (an inducer of P-450 in yeast) had no effect on the action of the regulatory gene.

Purification of cybrids by fluorescence-activated cell sorting

A general method to isolate and purify substantial numbers of viable cybrids from cultured mammalian cells immediately following cytoplast-cell fusion is described. This method uses cytoplasts whose mitochondria are selectively stained in vivo by the cationic fluorescent rhodamine dye, rhodamine 123. Large numbers of highly purified, rhodamine-stained cytoplasts are fused to appropriate recipient cell lines and then the fusion mixture is sorted based on forward angle scatter and fluorescence parameters. Plating the positively sorted population in culture for as short as 12 h eliminates contaminating cytoplasts which, lacking a nucleus, are unable to adhere or survive. The resultant population, based on an analysis of genetic markers, is 75-100% cybrids, an enrichment of 1000- to 10,000-fold over the initial fusion mixture. Cybrids purified by cell sorting may be useful for detailed molecular studies of mitochondrial DNA gene expression and in the specific induction of new mitochondrial DNA mutants.

Reactivation and shedding of bovine herpesvirus 1 following Dictyocaulus viviparus infection

Three groups of 4 bullocks which had recovered from infectious bovine rhinotracheitis (IBR) were infected 5 months later with Dictyocaulus viviparus larvae. Bovine herpesvirus 1 was recovered from days 7 to 21 post-infection from the nasal secretions of the group given 50 larvae per kilogram and on one occasion from those given 1000 larvae per animal (less than 5 L3 per kg). Virus was not isolated from the animals given 1000 irradiated larvae. Typical clinical signs and lesions of IBR developed in the group from which the virus was isolated regularly.

A comparison of the virulence of three strains of infectious bovine rhinotracheitis virus

The virulence of three strains of infectious bovine rhinotracheitis (IBR) virus was compared in six-month-old Ayrshire-cross calves. The strains were an isolate from a recent severe outbreak of IBR in Scotland (Strichen strain), the prototype British strain (Oxford strain) and a North American isolate (Colorado strain). The Colorado and Strichen strains produced the characteristic clinical signs and pathological lesions of severe IBR three to four days post infection (p.i.). The Strichen strain was slightly more virulent, possibly as a result of its having been passaged fewer times in tissue culture. In contrast, the Oxford strain produced a mild clinical response with minimal pathological lesions. Virus was recovered from nasal swabs for a longer-period from the calves infected with the Strichen strain (up to 13 days p.i.) and Colorado strain (up to 12 days p.i.) than from the animals infected with the Oxford strain (up to 10 days p.i.). These findings support the suggestion that the recent epidemic of severe IBR in Britain had resulted from the importation of a "new" strain of virus.

Experimental infection of cattle of different ages with infectious bovine rhinotracheitis virus (Strichen strain)

The clinical signs and pathological lesions which developed in various ages of cattle experimentally infected intranasally with the "Strichen" strain of IBR virus were similar to, but generally milder than, those of the field disease. The clinical signs were most severe 4 days after infection and had almost wholly regressed after 12 days. Serum neutralizing antibodies were detected in every animal. Virus was isolated from nasal and ocular swabs for up to 13 days and 10 days, respectively, after infection. The clinical signs and the pathological lesions were more severe in the younger animals.

Human cell variants resistant to methylglyoxal-bis(guanylhydrazone) display increased sensitivity to chloramphenicol

Four variants of the cultured human cell line VA2 have been isolated which are resistant to the antiproliferative and antimitochondrial effects of methylglyoxal-bis(guanylhydrazone) (MGBG). Each of the four variants is two- to fivefold more sensitive to the mitochondrial protein synthesis inhibitor chloramphenicol (CAP) than wild type when grown in the absence of MGBG, and five- to tenfold more sensitive to CAP when grown in the presence of MGBG. Uptake studies demonstrate that each MGBG-resistant variant cell line is freely permeable to CAP. The in vivo rates of mitochondrial protein synthesis are significantly reduced in each of the variants whether pregrown and labeled in the presence or absence of MGBG. When cytoplasts from a cytoplasmically inherited CAP-resistant mutant are fused to an MGBG-resistant recipient cell line, cybrid clones can be isolated which are functionally resistant to low levels of CAP. With continued growth, the levels of resistance to CAP do not, however, approach the levels of resistance of the CAP-resistant donor cell line. When CAP resistance is subsequently transferred from a CAP/MGBG-resistant cybrid by enucleation and fusion to other human cell lines, then CAP-resistant cybrids can be readily selected in high levels of CAP. It is possible that the substantial decrease in mitochondrial protein synthesis observed in the variants fully accounts for their increased sensitivity to CAP, although the basis for this decreased rate of mitochondrial protein synthesis is not understood.

Experimental production of diffuse pulmonary fibrosis and alveolitis in cattle: the effects of repeated dosage with 3, methyl indole

Eleven Friesian steers were given 3, methyl indole (3MI) orally at dose rates ranging from 0.1 to 0.3 g/kg. Three of these (group B) received a single oral dose of 0.2 g/kg and subsequently developed respiratory distress. Their plasma 3MI concentrations six hours after dosing were between 2.25 and 7.23 micrograms/ml. The steer with the highest six-hour plasma value died at this stage and the dominant pathological feature was severe pulmonary oedema. The other two steers survived until they were slaughtered 96 hours after dosing; the major pathological findings in them were interstitial emphysema, hyaline membranes and alveolar epithelial hyperplasia. The other eight steers (group C) each received weekly oral doses of 0.1 g 3MI/kg for 10 weeks. One animal died after developing severe respiratory distress following its third dose. Thereafter, the others developed two separate patterns of response. Three steers (subgroup C1) became progressively more tolerant to oral 3MI, even in the face of dose rates increased to 0.2 and 0.3 g/kg during the 11th to 14th weeks of the study and also in the presence of relatively high plasma 3MI concentrations after dosing. One animal was slaughtered after its 10th dose and two after their 14th dose of 3MI; post mortem examinations revealed that their lungs were macro- and microscopically normal. The other steers (subgroup C2) all continued to react after each weekly oral dose of 3MI and their post-dosing plasma 3MI concentrations consistently remained relatively low. Latterly, each of the three steers which survived to the 14th week also exhibited persistent tachypnoea and marked hyperpnoea between dosings. On post mortem examination, in addition to the signs generally associated with acute 3MI toxicity (see above), each of the subgroup C2 steers were found to have diffuse pulmonary fibrosis and an alveolitis. While certain cattle appear to become tolerant to the effects of repeated doses of 3MI, the results of this study clearly demonstrated that, in others, such treatment eventually gives rise to diffuse pulmonary fibrosis and alveolitis.

Bovine nasal granuloma (atopic rhinitis) in Britain

During three successive summer grazing periods, several young Friesian cross heifers developed an increasingly severe upper respiratory syndrome which improved soon after the animals were housed. The major clinical signs during the third summer episode were: ocular and nasal discharge; ulceration of the nasal mucosa, which was swollen, causing obstruction of the nasal passages; and the presence of large numbers of small, hard, white nodules in the nasal vestibules. From these clinical and epidemiological findings, a diagnosis of atopic rhinitis was made.