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Biomedical subjects

C M Cameron

Publications and source records attributed to C M Cameron.

At least 55 records · Page 3Linked to original sources
PubMed1983

Extracellular calcium ion concentration required for prolactin to express its actions on casein, ribonucleic acid, and lipid biosynthesis in mouse mammary gland explants.

The depletion of extracellular calcium ions by EGTA abolishes the PRL stimulation of [14C]acetate incorporation into lipids in mouse mammary gland explants. This abolition is reversed by the addition of calcium, but not magnesium. The chelation of calcium ions was similarly shown in earlier studies to abolish PRL's actions on RNA and casein synthesis. When the actions of PRL on lipid, RNA, and casein biosynthesis were tested when the extracellular calcium ion concentration was varied, it was observed that 5-10 microM calcium was required for PRL to manifest its actions. The calcium ionophore A23187 was unable, however, to mimic the PRL stimulation of lipid, RNA, or casein synthesis. Trifluoperazine, an inhibitor of calmodulin action had no effect on the PRL-induced synthesis of lipids, RNA, or casein, except at pharmacological levels.

Acetates↗
PubMed1983

Effects of cyclic nucleotides on lipid biosynthesis in mouse mammary gland explants.

The effects of dibutyryl cAMP, 1-methyl-3-isobutyl xanthine (MIX), cGMP, dibutyryl cGMP, and 8-bromo cGMP on the rate of lipid synthesis in mouse mammary gland explants were studied. Dibutyryl cAMP at 10(-4) M selectively inhibited the effect of prolactin on the rate of [14C]acetate incorporation into lipids. At 10(-3) M, dB-cAMP inhibited the effects of insulin, insulin plus cortisol, and prolactin. The phosphodiesterase inhibitor, MIX, inhibited both basal and prolactin-stimulated incorporation rates in a concentration-dependent fashion. These data suggest an inhibitory role for cAMP in the regulation of lipogenesis in the mammary gland. Cyclic GMP, db-cGMP, and 8-bromo cGMP were all without effect on either basal or prolactin-stimulated incorporation rates. Therefore, it appears that cGMP, by itself, is not involved in the regulation of lipogenesis in the mammary gland.

1-Methyl-3-isobutylxanthine↗
PubMed1983

Early action of prolactin on ornithine decarboxylase activity is not essential for the subsequent actions of prolactin on casein and lipid biosynthesis.

The actions of prolactin (PRL) on casein and lipid biosynthesis in cultured mouse mammary gland explants require the ongoing synthesis of the polyamines. This is supported by the fact that (MGBG) methylglyoxal bis(guanylhydrazone), a drug that inhibits the conversion of putrescine to spermidine, abolishes the effects of PRL on casein and lipid biosynthesis; the inhibitory effects of MGBG are reversed by the addition of spermidine to the culture medium. alpha-Difluoro methyl ornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase activity, reduces the PRL-stimulated ornithine decarboxylase (ODC) activity by more than 95%, and yet does not suppress the effects of PRL on RNA, casein or lipid synthesis. These observations suggest that PRL's early action on ODC activity is not essential for the subsequent actions of PRL on the synthesis of certain of the components of milk.

Acetates↗
PubMed1983

The inefficacy of polivalent Pasteurella multocida vaccines for sheep.

Immunity assays on sheep sera using passive mouse protection tests showed that vaccines containing more than 4 strains of Pasteurella multocida did not give a good immunity. The immune response was not enhanced by the use of an oil adjuvant, and high concentrations of bacteria had only a partial positive effect. Attempts to extract selectively the protection-inducing antigen(s) from P. multocida by veronal, phenol or potassium thiocyanate extraction were unsuccessful. Furthermore, it was found that sheep antisera to the recognized type strains of P. multocida afforded only limited protection against a number of field strains. We concluded from this that successful immunization against ovine pasteurellosis will depend on either the identification of a strain of P. multocida that gives a wide spectrum of immunity or the discovery of a live mutant suitable for vaccine production and the definition of cultural conditions that promote the expression of a common immunizing antigen.

Animals↗
PubMed1983

Comparison of oil adjuvant and aluminium phosphate-adsorbed toxoid for the passive immunization of lambs against tetanus.

Immunization of ewes with oil emulsion toxoid followed by an aluminium phosphate-adsorbed toxoid both containing 10 Lf per dose, resulted in a very high antitoxin level in their lambs. Two injections of aluminium phosphate-adsorbed toxoid also imparted a passive immunity to lambs which is considered to be adequate to protect them against tetanus for 4 weeks after birth.

Adjuvants, Immunologic↗
PubMed1981

Effect of various concentrations of prolactin and growth hormone on the magnitude of stimulation of RNA synthesis, casein synthesis and ornithine decarboxylase activity in mouse mammary gland explants.

The effects of various concentrations of prolactin and growth hormone on the rates of [3H]-uridine incorporation into RNA, [3H]-leucine incorporation into casein, and ornithine decarboxylase (ODC) activity were determined in mouse mammary gland explants. The lowest concentrations of prolactin which produced significant responses were between 5 and 25 ng/ml. Growth hormone, in contrast, produced significant response at concentrations between 250 and 1,000 ng/ml. The prolactin actions on RNA and casein synthesis were essentially all-or-none type responses, i.e. the magnitude of the responses were maximal at about 10 ng/ml prolactin. The action of prolactin on ODC activity was quite different; a concentration-response relationship was observed with prolactin at concentrations from 10 t 250 ng/ml. It is apparent from these studies that different concentrations of prolactin are required to produce optimal actions on different biochemical parameters in cultured mammary tissues.

Animals↗
PubMed1980

Lack of cross-immunity among Pasteurella multocida type A strains.

Active and passive protection studies in mice using sheep antisera revealed that the immunological relationship among Pasteurella multocida Type A strains could not be correlated with their serological relationship as determined by a haemagglutination or an agglutination test. Furthermore, strains possessing similar phenol extractable antigens or heat stable antigens did not provide complete cross-protection. The conclusion was reached that immunity to P. multocida Type A strains is induced by an antigen which is strain specific and not detectable by existing serological typing systems. The immunological relationship of strains can therefore not be predicted on the basis of their serological characteristics.

Animals↗
PubMed1980

Effective immunization of lambs against enterotoxaemia.

In contrast to adult sheep, 2- to 3-month-old lambs do not respond well to a single injection of Clostridium perfringens Type D oil adjuvant epsilon toxoid. This unresponsiveness can be overcome, however, by administering 2 injections of oil adjuvant vaccine or one injection of oil adjuvant followed 4 weeks later by an injection of alum-precipitated toxoid. The latter procedure evokes protective antitoxin levels which persist for 8 months, and a booster injection of alum-precipitated toxoid given at this stage results in an immunity which lasts for at least 1 year.

Age Factors↗
PubMed1979

Trout mortalities as a result of Streptococcus infection.

Excessive mortalities were experienced in the bigger rainbow trout (Salmo gairdneri) at an efficiently managed trout farm. All tests for known toxins in the feed and water proved to be negative. A faecal Streptococcus which belongs to the Lancefield group D but which could not be identified as belonging to any of the recognized species within this group, was isolated from the spleens, livers and kidneys of affected fish. Pathogenicity studies with this organism proved it to be highly fatal to trout but not to Mozambique bream (Sarotherodon mossambicus), banded bream (Tilapia sparrmenii), carp (Cyprinus carpio) or largemouth bass (Micropterus salmoides). The isolation and biochemical characteristics of the organism are described. The symptoms, gross- and histopathology of this disease are described and discussed. The disease resembles a haemorrhagic septicaemia and appears to be associated with intensification and conditions of stress.

Animals↗
PubMed1979

Composition and evaluation of the efficacy of Staphylococcus aureus vaccine.

An alum-precipitated Staphylococcus aureus vaccine, composed of a formalin-inactivated whole culture of a strain which produces Smith surface antigen and combined with the whole culture of a highly toxigenic strain, was found to afford a good immunity to staphylococcal skin infection in rabbits. Three injections of the vaccine provided immunity which lasted for at least 6 months against a primarily pyogenic strain of S. aureus and for at least 3 months against a toxigenic strain. From experiments using vaccines prepared from cells or toxoid only, it was deduced that, although there is a measure of strain specific immunity, a good heterologous immunity can be established with a combined product provided that it contains adequate quantities of toxoid. The use of such a vaccine as a potential aid in the control of bovine staphylococcal mastitis is discussed.

Adjuvants, Immunologic↗
PubMed1979

Production and application of a live Salmonella gallinarum vaccine.

The production and application of a freeze-dried Salmonella gallinarum vaccine are described in this report. The vaccine is stable when kept at 4 degrees C and a single injection elicits a good immunity for 2 months, though its effect gradually diminishes. Immunity is neither enhanced nor depressed by repeated injections of the live vaccine, and no interference effect was observed in experimentally infected chickens. Furazolidone therapy jeopardizes the immunogenicity of a live vaccine, but its effect can be countered by the administration of either an inactivated or a live vaccine when medication is commenced and this is followed by the application of live vaccine 6 days after cessation of medication.

Animals↗
PubMed1979

Comparative efficacy of six Brucella vaccines in guinea-pigs.

Immunity assays in guinea-pigs based on spleen mass: body mass ratios showed that live vaccines were markedly more effective than inactivated oil adjuvant vaccines in providing protection against challenge with 5 000 virulent organisms.

Adjuvants, Immunologic↗
PubMed1978

The serological and immunological relationship of type strains A and D of Pasteurella multocida to field isolates from sheep.

Investigations with antisera prepared in rabbits and sheep and active immunity experiments in mice showed that strains of Pasteurella multocida which, according to the haemagglutination test, are serologically related, do not necessarily give rise to cross immunity. Conversely, it was found that serologically unrelated strains may exhibit an appreciable degree of cross protection. The unreliability of the haemagglutination test as an indicator of immunological identity of strains was further confirmed in that peritoneal fluid from immunized mice showed passive protection properties despite the absence of haemagglutinating antibodies. There was no consistent agreement between the results obtained with antisera prepared in different species and active immunity experiments in mice, and this leads to the conclusion that different species probably vary quantitatively and qualitatively in their immune response to immunization with P. multocida. Attempts to determine whether combined bacterins afforded a better immunity than monovalent bacterins were inconclusive.

Animals↗
PubMed1977

Failure to induce in rabbits effective immunity to a mixed infection of Fusobacterium necrophorum and Corynebacterium pyogenes with a combined bacterin.

Failure to induce in rabbits effective immunity to a mixed infection of Fusobacterium necrophorum and Corynebacterium pyogenes with a combined bacterin. Onderstepoort Journal of Veterinary Research, 44 (4), 253--2;6 (1977). Rabbits were immunized with alum-precipitated, oil adjuvant and an untreated bacterin composed of F. necrophorum and C. pyogenes. Immunized rabbits were challenged intradermally with a mixture of F. necrophorum and C. pyrogenes. Immunized rabbits were challenged intradermally with a mixture of F. necorphorum and C. pyrogenes. Initially a low level of initial transient resistance could be demonstrated but a solid immunity could not be established.

Animals↗
PubMed1977

Effect of levamisole on immunity to Corynebacterium pseudotuberculosis in mice and sheep.

The stimulating effect of levamisole on immunity to Corynebacterium pseudotuberculosis in mice was marginal, while no enhancement of immunity could be detected in sheep. The conclusion was reached that, as levamisole has no potentiating effect on immunity to C. pseudotuberculosis in normal sheep, it is of no practical value as an immunostimulant in this instance.

Animals↗
PubMed1976

Immunization of mice and calves against Salmonella dublin with attenuated live and inactivated vaccines.

Previous findings, viz. that mice can be successfully immunized against infection with Salmonella dublin with either live or inactivated vaccine, were confirmed. Immunity lasted for at least 12 weeks in mice which had been immunized with inactivated alum-precipitated vaccine. The immunogenicity of inactivated vaccine gradually decreased on storage at 4 degrees C, but this was only detectable if a single injection was used for immunization: 2 injections virtually eliminated this phenomenon. The immunogenicity of live vaccine in mice was not enhanced by levamizole or the simultaneous injection of inactivated organisms. Both live and inactivated vaccines provided immunity in calves. A single injection of lyophilized vaccine, prepared from live rough Salmonella dublin strain (HB 1/17),protected 3 out of 6 calves, while 2 injections of a formalin-inactivated, alum-precipated vaccine, containing 1% packed cells of S. dublin strain 2652 V, protected 5 out of 6 calves against intraduodenal challenge with 2 x 10(9), S. dublin strain 2652 V. Two calves which had been immunized with an inactivated oil adjuvant vaccine were also solidly immune to this challenge. Serum antibody response in calves was poor when measured by the tube agglutination and the haemagglutination tests. Similarly, the sera had only marginal protective values when tested by means of a passive protection test in mice. Antibody titres alone are not a valid measure therefore, for the immune status of immunized animals.

Animals↗