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Biomedical subjects

J A Cameron

Publications and source records attributed to J A Cameron.

At least 73 records · Page 4Linked to original sources
PubMed1984

Increase in the haemolytic complement activity of dogs affected with cyclic haematopoiesis.

Cyclic haematopoiesis (CH) is an inherited disorder which occurs in both humans and Grey Collie dogs. The disease is characterized by fluctuations in the numbers of peripheral blood leucocytes, reticulocytes and platelets at regular intervals and is associated with a variety of clinical signs. The most prominent cycle observed is that of neutrophils. The 12-day neutropenic cycle includes a period of relatively normal neutrophil counts, a period of neutropenia and generally a period in which neutrophil counts greatly exceed the normal range. In this study the daily serum haemolytic complement activity (classical pathway CH50) of CH and normal Collie dogs was assayed. The serum CH50 of normal Collie dogs was relatively stable throughout the test period. In contrast, the serum CH50 of CH dogs fluctuated extensively and the mean serum CH50 of CH dogs during the neutropenic cycle greatly exceeded that of normal Collie dogs over the same test period. A close temporal relationship between the stage of the CH neutropenic cycle and the serum CH50 was observed. The mean serum CH50 during neutropenia was not significantly different from that observed when neutrophil counts were within normal range, both values being significantly higher than that of normal dogs. However, the mean serum CH50 during the period of neutrophil rebound was significantly (P less than 0.01) higher than that during the period of neutropenia or normal neutrophil counts. These data suggest that alterations in the production of complement components or regulatory proteins occur at regular intervals in CH dogs.

Animals↗
PubMed1983

Muscle and cartilage differentiation in axolotl limb regeneration blastema cultures.

A tissue culture system is described for explants of mesenchyme from Ambystoma mexicanum limb regeneration blastemas. Explants were cultured on collagen substrate for 3 weeks in minimal essential medium supplemented with the hormones insulin, thyroxine, somatotropin, and hydrocortisone, plus beef embryo extract (EE), 2%. This medium supported extensive cell migration onto the substrate followed by cell proliferation and differentiation of both cartilage matrix and myotubes. Cultures on plastic substrate, rather than on collagen, displayed similar cell outgrowth and cartilage formation, but relatively little myotube formation. Differentiation in EE-supplemented medium was compared with that in two defined media: Explants in medium containing only the hormones showed little outgrowth or cartilage development and never formed myotubes; medium containing the hormones plus fibroblast growth factor, 50 ng/ml, supported an intermediate degree of outgrowth and cartilage development and occasional myotube formation. Explant size was also a factor: Smaller explants survived and formed myotubes less frequently, even when on collagen in EE-supplemented medium.

Ambystoma↗
PubMed1983

Regeneration of adult newt skeletal muscle tissue in vitro.

Explants and cells of forelimb muscle from adult Notophthalmus viridescens were cultured for periods up to 160 days in MEM-based medium supplemented with serum, hormones, and antibiotics. Explants which were not minced prior to culture contained muscle fibres with healthy myonuclei and no evidence of dedifferentiation after four weeks. Explants which were minced prior to culture contained degenerated muscle fibres after 1 day and no evidence of dedifferentiation after four weeks. Mononucleated cells from both minced and non-minced explants proliferated. Cell proliferation and myotube formation was greater in the minced muscle cultures. Proliferation and fusion of myoblasts and subsequent formation of myofibrils were observed on the plate in primary cultures. Secondarily transferred cells proliferated and fused into myotubes. Although adult newt muscle does not contain satellite cells, myogenesis in this amphibian followed the same course as all other vertebrate skeletal muscle: proliferation of mononucleated myogenic cells, fusion of the myoblasts to form syncytia, and eventual accumulation of myofibrils. The ultimate source of the myogenic cells was not identified; however, the absence of dedifferentiation of the mature fibres and the occurrence of myogenesis in cultures of minced muscle explants demonstrated that the regenerated muscle developed from a population of mononucleated cells whose origin did not depend upon dedifferentiation of intact fibres.

Animals↗
PubMed1981

Inflammatory toxin from Mycoplasma bovis: isolation and characterization.

An inflammatory toxin was extracted from Mycoplasma bovis with 75 percent aqueous ethanol. The toxin is a complex polysaccharide composed of glucose, glucosamine or galactosamine, and a heptose, is heat-stable, devoid of protein and lipid, and has a molecular weight of 73,000. The holotoxin in the cell membrane is a glycoprotein; however, it is the polysaccharide portion that is toxic. This inflammatory toxin increases vascular permeability and is capable of activating complement. Infusion of 0.9 milligram of toxin into the bovine udder resulted in the characteristic eosinophilic mastitis produced by Mycoplasma bovine.

Animals↗
PubMed1979

Effects of cyclic AMP altering drugs on endotoxin-induced termination of pregnancy.

The effects of dibutyryl-cyclic AMP (DBcAMP), propranolol, and theophylline on endotoxin (LPS) challenged pregnant mice was determined by comparing the patterns of termination and times of fetal expulsion. Endotoxin isolated from wild type (WT) and Re chemotype mutant cells of Salmonella typhimurium was used. Wild type LPS caused the expulsion of the fetuses, while Re LPS primarily caused the resorption of the fetuses. The major change in pattern occurred in the propranolol treated Re LPS challenged group with a trend toward more expulsions and a decrease in uterine cyclic AMP (cAMP) levels to that approaching the group challenged with wild type LPS. The time of expulsion was also affected in the wild type LPS treated group, with propranolol hastening and DBcAMP and theophylline delaying the expulsion. These results support the hypothesis that uterine cAMP is involved in the expulsion of the fetuses.

Abortion, Spontaneous↗
PubMed1978

Effect on particle size of solubilization of wild-type and Re chemotype lipopolysaccharides solubilized with bovine serum albumin and triethylamine.

Disaggregation of wild-type and Re chemotype lipopolysaccharides (LPS) has been accomplished by solubilization with triethylamine followed by stabilization with bovine serum albumin in order to determine the degree of aggregation. Solubilization with 1.5% triethylamine was found to be more effective than with lower concentrations, as judged by permeation chromatography. Chromatographic analysis of triethylamine-bovine serum albumin-disaggregated LPS showed a range of particle sizes. Wild-type LPS yielded size classes of 1 X 10(6) to 4 X 10(6) daltons, 250,000 daltons, and 20,000 daltons. Re LPS yielded size classes of 1 X 10(6) to 4 X 10(6) daltons and 20,000 daltons. Untreated LPS was always greater than 4 X 10(6) daltons. Chemical characterization of the size classes revealed 3-keto-2-deoxyoctonate in all size classes and suggests that the O-antigenic side chain length may determine the aggregate size in solubilized LPS.

Carbohydrates↗
PubMed1978

Effect of endotoxin on uterine cycle AMP in pregnant mice.

The effect of endotoxin (LPS) on uterine cAMP was determined by measuring the levels of cAMP and cAMP phosphodiesterase after challenge. Two LPS preparations, isolated from wild type (WT) and Re chemotype mutant cells of Salmonella typhimurium were used. The pattern of termination differed with WT LPS resulting in expulsion of the fetuses, and Re LPS primarily causing the resorption of the fetuses. The animals challenged with WT LPS showed a decrease in uterine cAMP when the mice were starting to expel the fetuses while the Re LPS treated group maintained control levels of cAMP. Cyclic AMP phosphodiesterase also decreased in WT LPS and not the Re LPS group. These results suggest the possibility that uterine cAMP is involved in the expulsion of the fetuses.

3',5'-Cyclic-AMP Phosphodiesterases↗