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Biomedical subjects

G Olson

Publications and source records attributed to G Olson.

At least 37 records · Page 2Linked to original sources
PubMed1990

Growth, feed efficiency and carcass composition of finishing Friesian steers fed the beta-adrenergic agonist L-644,969.

The beta-adrenergic agonist L-644,969 was evaluated to determine its effects on growth performance and carcass composition of Friesian steers. L-644,969 is the R,R isomer of 6-amino [[(1-methyl-3-phenylpropyl) amino] methyl]-3-pyridine methanol dihydrochloride. Four groups of 18 steers, averaging 380 kg body weight, were individually given ad libitum access to a pelleted concentrate diet that contained either 0, .25, 1.0 or 4.0 ppm L-644,969 for the final 12 wk of the finishing period. Live weight gain was not affected by L-644,969, but feed consumption was linearly reduced (5.5, 6.3 and 15.7%; P less than .01) and feed conversion efficiency was linearly increased (16, 25 and 31%; P less than .01) relative to unmedicated controls, respectively. In addition, L-644,969 quadratically increased carcass weight (3.7, 9.3 and 8.5%; P less than .01) and dressing percentage (2.7, 7.9 and 7.9%; P less than .001). The proportion of trimmed fat in the carcass was quadratically reduced (14.5, 29 and 36%; P less than .001) and yield of lean meat quadratically increased (6.7, 13 and 15.6%; P less than .001). beta-adrenergic agonist treatment altered the distribution of lean meat such that a greater (P less than .001) proportion of the total lean was in the hind portion of carcasses from treated animals. Based on these findings, we suggest that L-644,969 may have utility as an agent to improve efficiency of production of lean beef.

Adrenergic beta-Agonists↗
PubMed1990

Hepatic steatosis during convalescence from influenza B infection in ferrets with postprandial hyperinsulinemia.

The possibility that postprandial hyperinsulinemia could play a role in the development of hepatic lipid disturbances during convalescence from influenza B infection was explored in the ferret as a possible model of the steatosis of Reye's syndrome. Postprandial hyperinsulinemia was produced by feeding young ferrets glucose/water and a regular diet (glucose-treated group), as reflected by the mean serum insulin levels attained, which were 57 and 135 microU/ml during control and postinfluenza periods, respectively. By comparison, ferrets fed water and a regular diet (untreated group) had mean insulin levels of 19 and 22 microU/ml, while postprandial glucose levels were comparable in the two groups of animals for each period. In contrast to untreated animals, grossly visible fatty livers were found in glucose-treated ferrets during convalescence. The total lipid content of these livers had doubled compared with preinfection samples and compared with livers of untreated ferrets. By electron microscopy hepatic mitochondria showed striking changes with diminution of matrix density and reduction in cristae surface area only in convalescent samples from glucose-treated animals. Serum free fatty acid (FFA) levels were considerably higher in the glucose-treated animals during fasting before influenza and also after feeding during convalescence. Serum triglyceride (TG) levels were also high during convalescence in the glucose-treated group. Adipose tissue lipoprotein lipase activities were similar between groups, but hormone-sensitive lipase activity was twelvefold higher in glucose-treated ferrets before and after influenza B. These findings indicate that for a given stimulus, glucose-treated ferrets would mobilize more FFA than untreated ferrets. The total capacity for beta-oxidation of FA by the mitochondrial pathway was identical in all groups of animals. Total carnitine palmitoyl transferase (CPT) activity was the same in both control groups, but was significantly diminished in glucose-treated animals during convalescence. As CPT regulates the entry of FA into the mitochondrial matrix, its reduction in response to higher insulin concentrations would limit the oxidation of FA and stimulate TG accumulation. Therefore, the accumulation of lipid in the liver in this model is regarded to have been caused by the simultaneous occurrence of increased lipolysis and increased hepatic TG synthesis owing, in part, to diversion of activated FA by CPT, which is reduced in activity due to the regulatory action of insulin. These findings may have pathophysiologic relevance for the lipid changes that occur in Reye's syndrome and to fatty liver formation in hyperinsulinemic states.

Adipose Tissue↗
PubMed1988

Effect of efrotomycin in feed on the quantity, duration, and prevalence of shedding and antibacterial susceptibility of Salmonella typhimurium in experimentally infected swine.

The influence of efrotomycin administered at the rate of 16 mg/kg of feed in 10 Salmonella typhimurium-inoculated pigs was determined by comparing this group with a group of 10 pigs inoculated with S typhimurium that were given nonmedicated feed. Two control groups of 4 noninoculated pigs each, 1 group medicated with efrotomycin at 16 mg/kg of feed, the other nonmedicated, also were evaluated. An inoculum of 1.7 x 10(10) colony-forming-units/pig induced colonization of S typhimurium in all 20 pigs. Evaluation of the quantity of shedding did not reveal a clear or consistent treatment-related increase in S typhimurium counts; mean differences between the nonmedicated and medicated groups never exceeded 1 log unit. On the last day of the study (day 56 of the medication), 8 nonmedicated and 9 medicated pigs were determined to be infected with S typhimurium via enrichment procedures, so there was no difference in duration of shedding, and there were no significant differences in prevalence of shedding between the nonmedicated and medicated groups at any of the sampling times. Of 1,340 S typhimurium colonies isolated from the nonmedicated and medicated groups, 1,330 were susceptible to all 12 antibacterials tested, indicating no treatment-related effect on susceptibility. At necropsy, S typhimurium was not isolated from any liver or spleen specimens, and was isolated from only 2 of 20 lymph nodes. However, S typhimurium was isolated via enrichment from the cecal contents from all 20 pigs. There were no treatment-related differences in feed consumption, weight gain, or feed efficiency. Appreciable differences in the measurements were not found between the efrotomycin-medicated and nonmedicated pigs.

Animal Feed↗
PubMed1987

The carcinogenicity of trichloroethylene and its metabolites, trichloroacetic acid and dichloroacetic acid, in mouse liver.

Trichloroethylene (TCE) has previously been shown to be carcinogenic in mouse liver when administered by daily gavage in corn oil. The metabolism of TCE results, in part, in the formation of trichloroacetic acid (TCA) as a major metabolite and dichloroacetic acid (DCA) as a minor metabolite. These chlorinated acetic acids have not been shown to be genotoxic, although they have been shown to induce peroxisome proliferation. Therefore, we determined the ability they have been shown to induce peroxisome proliferation. Therefore, we determined the ability of TCE, TCA, or DCA to act as tumor promoters in mouse liver. Male B6C3F1 mice were administered intraperitoneally 0, 2.5, or 10 micrograms/g body wt ethylnitrosourea (ENU) on Day 15 of age. At 28 days of age, the mice were placed on drinking water containing either TCE (3 or 40 mg/liter), TCA (2 or 5 g/liter), or DCA (2 or 5 g/liter). All drinking waters were neutralized with NaOH to a final pH of 6.5-7.5. The animals were killed after 61 weeks of exposure to the treated drinking water (65 weeks of age). Both DCA and TCA at a concentration of 5 g/liter were carcinogenic without prior initiation with ENU, resulting in hepatocellular carcinomas in 81 and 32% of the animals, respectively. DCA and TCA also increased the incidence of animals with adenomas and the number of adenomas/animal in those animals that were not initiated with ENU. While 2.5 micrograms/g body wt ENU followed by NaCl in the drinking water resulted in only 5% of the animals with hepatocellular carcinomas, 2.5 micrograms/g body wt ENU followed with 2 or 5 g/liter DCA resulted in a 66 or 78% incidence of carcinoma, respectively, or, followed with 2 or 5 g/liter TCA, resulted in a 48% incidence at either concentration. None of the untreated animals had hepatocellular carcinomas. Therefore our results demonstrate that DCA and TCA are complete hepatocarcinogens in B6C3F1 mice.

Acetates↗
PubMed1984

Purification and properties of chicken growth hormone and the development of a homologous radioimmunoassay.

Highly purified growth hormone (GH) has been isolated from pituitary glands of chicken (Gallus domesticus), and a specific homologous radioimmunoassay (RIA) has also been developed. The purified chicken GH was active in the rat tibia bioassay and it gave a dose-dependent response which paralleled that of the bovine GH standard. High pressure liquid chromatography revealed that the purified chicken GH was homogenous. Chicken GH had an Rf value of 0.2 in disc electrophoresis, and a MW of 26,000 from sodium dodecyl sulfate-gel electrophoresis. The isoelectric point was estimated to be 7.6 by gel isoelectric focusing. The amino acid composition of chicken GH was found to be similar to that of mammalian GH, and the NH2-terminal amino acid was threonine. Partial sequencing (114 amino acids) of the chicken GH showed 79% homology with bovine GH. An antiserum was developed to the purified chicken GH in a rabbit, and it was used to develop a homologous RIA using 125I-labeled chicken GH as the ligand. The purified chicken GH was iodinated via the lactoperoxidase method to a specific activity of approximately 100 microCi/micrograms. Plasma from chickens, medium from incubation of pituitary glands, and homogenates of pituitary glands gave parallel dilution-response curves with the chicken GH standard. Mammalian GH, prolactin (PRL), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) showed no cross-reaction with the 125I-labeled chicken GH. Purified turkey GH showed parallel dose response with the chicken GH, but purified turkey PRL did not cross-react. Chicken FSH and LH also showed no inhibition of binding. The minimum detectable concentration of the assay was 0.93 ng/tube, and the intraassay and interassay coefficients of variation were 9 and 16%, respectively. The specific binding of 125I-labeled chicken GH to a microsomal fraction isolated from chicken liver was identified, and the specific binding was generally low (1-4%). Turkey PRL, and chicken LH and FSH showed no inhibition of the 125I-labeled chicken GH hepatic binding and the ontogeny of the hepatic GH receptor binding sites in male and female chickens was examined.

Aging↗
PubMed1984

The antifertility and antiadrenergic actions of thiocarbamate fungicides in laying hens.

The effects of the thiocarbamate fungicides, thiram, ziram, ferbam, maneb, and zineb, on norepinephrine synthesis by laying hens were investigated. Inhibition experiments with dopamine beta-hydroxylase purified from chicken adrenals indicated that thiram, ziram, and ferbam are potent competitive inhibitors with the substrate the substrate ascorbate. Maneb and zineb were without effect at comparable concentrations. Experiments investigating the interaction of thiram, ziram, and ferbam with cupric ions suggested that these compounds probably inhibit the enzyme by complexing the fully oxidized copper at its active site. Maneb and zineb also complexed cupric ions in solution and thus their failure to inhibit is not due to their inability to complex copper. When tested in vivo, thiram, ziram, and ferbam at po doses of 2.5 mg/kg or greater significantly reduced the conversion of radioactive dopa, given systemically, to brain norepinephrine. Since they did not affect the uptake of radioactive dopa by the brain or its subsequent decarboxylation within the brain to yield dopamine, these three compounds inhibit cerebral dopamine beta-hydroxylase in vivo. In contrast maneb and zineb at a po dose of 20 mg/kg had no significant effect on brain norepinephrine synthesis. Previously published results (Weppelman et al., Biol. Reprod. 23, 40-46, 1980) demonstrated that thiram, ziram, and ferbam (but not maneb or zineb) have antifertility action in laying hens. The correlation between this action and inhibition of dopamine beta-hydroxylase suggests that the antifertility effects of thiram, ziram, and ferbam might result from their antiadrenergic action. The observation that all doses of thiram in the diet which caused significant antigonadal action when fed to laying hens for 1 week also significantly decreased central and peripheral stores of norepinephrine supports this conclusion.

Administration, Oral↗
PubMed1984

Development of encephalopathic features similar to Reye syndrome in rabbits.

The progression of neurological abnormalities through four or five clinically distinguishable levels of deepening coma and the development of a fatty liver are the hallmarks of Reye syndrome. A number of animal models have been described that result in fatty liver formation with minimal, static, or catastrophic neurological changes. In this study, we attempted to produce neurological features in rabbits that reflected a rostral-caudal progression of abnormalities that could be categorized into clinically distinguishable levels reminiscent of Reye syndrome. This was accomplished by the intracisternal administration of 0.5-25 mg of 11,14-icosadienoic acid (20:2 omega 6) suspended in a mixture of rabbit serum and isotonic saline solution. A reproducible, dose-titratable spectrum of at least four levels of deepening coma could be produced at will. Increases in serum glutamate-oxaloacetate transaminase and creatine kinase and changes in serum glucose resulted 1-2 hr after the neurological abnormalities were evoked. Other unsaturated fatty acids produced similar responses. Those tested included 18:1 omega 9, 18:2 omega 6, 18:3 omega 3, 20:3 omega 6, 20:4 omega 6, and 22:4 omega 6 fatty acids. Saturated fatty acids, including 6:0, 8:0, 16:0, 18:0, and 20:0, failed to elicit these effects. The abnormalities were sustained for 30-120 min after a single dose. Full recovery was observed in some animals that had not reached the fourth level of our grading system for coma. Pretreatment of the rabbits with aspirin modulated the neurological abnormalities. Twenty micrograms of bee venom melittin, which activates endogenous phospholipase A2, administered intracisternally into rabbits also produced signs of level 3 (our grading system) coma for several hours. These findings suggest a possible role for polyunsaturated fatty acids in the development of Reye syndrome and offer a means of producing the neurological components of that syndrome in a laboratory animal.

Acetaminophen↗
PubMed1983

Elevation of sperm adenosine 3':5'-monophosphate concentrations by a fucose-sulfate-rich complex associated with eggs: I. Structural characterization.

A fucose-sulfate-rich complex (F-SP) capable of causing up to 400-fold elevations of sperm cyclic AMP concentrations was isolated from Strongylocentrotus purpuratus egg jelly and characterized with respect to the relationship of composition to its ability to elevate cyclic AMP. The composition of F-SP varied between different preparations and consisted of, by weight, 32-45% fucose, 36-44% sulfate, 2.5-29% protein, and less than 1% other carbohydrate. The remainder of the weight (approximately 10% in most cases) was accounted for by Na+ or Cs+. The complex caused 45Ca2+ uptake and induced acrosome reactions in addition to its effect on cyclic AMP. The percentage of endogenous protein and sulfate in F-SP were highly correlated with the potency to elevate cyclic AMP with optimal activity observed at the highest relative percentage protein and sulfate. Treatment with NaOH and NaBH4 resulted in the release of most of the protein associated with F-SP but did not reduce sulfate content by more than 1%. The amino acid composition of the total acid hydrolysate did not change after the base treatment, suggesting the absence of serine or threonine O-glycosidic linkages. The NaOH treatment, however, resulted in significant reductions in both the potency and maximal ability of F-SP to elevate cyclic AMP, although it did not totally destroy activity even after treatments for up to 72 h at 37 degrees C. Pronase caused the release of a majority of the protein associated with F-SP and it also significantly reduced both the potency and maximal ability of the complex to elevate cyclic AMP. In contrast to base treatment, HCl (0.1 N) rapidly destroyed F-SP activity and caused a shift in the apparent molecular size of F-SP. Large quantities of fucose were removed from F-SP by the acid prior to a change in the elution position of protein and biological activity was lost, suggesting that the F-SP structure is essential for elevations of cyclic AMP. These results suggest that the fucose-sulfate-rich complex capable of markedly elevating sperm cyclic AMP concentrations requires both protein and sulfate for optimal activity and that protein is either attached to the carbohydrate by a base-labile bond not involving serine or threonine, or is associated with the F-SP structure in a noncovalent manner.

Amino Acids↗
PubMed1981

Purification and characterization of avian dopamine beta-hydroxylase.

Dopamine beta-hydroxylase (EC 1.14.17.1) has been purified from the chromaffin granules of avian adrenals. The enzyme has a molecular mass of approximately 320K daltons and consists of four apparently identical subunits joined in pairs by disulfide bonds. Analysis of the products formed from dopamine tritiated in the beta position indicated that 1.72 times as much tritium was retained in norepinephrine as was released as water. Ferrocyanide could serve as a reductant, but ascorbate at equal concentrations afforded higher rates. The enzyme had a pH optimum of 5-6 and was activated by either fumarate or acetate, with fumarate being far more effective. Kinetic experiments varying the concentrations of the substrates ascorbate and dopamine and those of the products dehydroascorbate and norepinephrine suggested that the mechanism was un-uni bi-uni ping pong. By this mechanism, the enzyme released dehydroascorbate after being irreversibly reduced by ascorbate and then sequentially bound oxygen and dopamine and released the product norepinephrine. The enzyme was inhibited by high but probably physiological concentrations of the substrate ascorbate and was activated by low concentrations of the product dehydroascorbate. Ascorbate inhibition was noncompetitive with dopamine, and dehydroascorbate activation was due to an increase in the enzyme's affinity for ascorbate with little or no change in its Vmax. Substrate inhibition by ascorbate and product activation by dehydroascorbate might together ensure that the rate of norepinephrine synthesis in vivo remains relatively unaffected by changes in the ratio of ascorbate to dehydroascorbate within chromaffin granules.

Adrenal Medulla↗
PubMed1981

Antifertility effects of clonidine in laying hens.

Clonidine was anovulatory and markedly antigonadal in laying hens when infused for 1 week from minipump implants at daily rates of 1.08 mg per hen or greater. The ovaries of hens treated with clonidine responded to FSH injections which suggests that the antigonadal effect of clonidine resulted from a reduction in the output of gonadotropin by the pituitary. These data suggest that alpha 2 receptors may be important in regulating avian fertility.

Animals↗
PubMed1981

Isomeric phenylthioimidazo[1,2-alpha]pyridines as anthelmintics.

A series of isomeric imidazo[1,2-alpha]pyridine-2-carbamates was prepared for testing as anthelmintics. The analogues were synthesized by reacting the appropriate 2-aminopyridine and methyl chloroacetylcarbamate. Steric hindrance in the 2,6-disubstituted derivative resulted in the formation of the isomeric 3-substituted analogue as the major product. Carbon-13 NMR proved useful in the structural assignments in this series. None of the analogues exhibited the potency of methyl 6-(phenylsulfinyl)imidazo[1,2-alpha]pyridine-2-carbamate when tested against Nematospiroides dubius in mice.

Animals↗
PubMed1981

Substituted imidazo[2,3-alpha]pyridine-2-carbamate anthelmintics.

Anthelmintic efficacies of a series of 6-substituted methyl imidazo[1,2-alpha]pyridine-2-carbamates were compared to similarly substituted benzimidazole-2-carbamates. With only one exception, methyl 6-benzoylimidazo[1,2-alpha]pyridine-2-carbamate, both classes of compounds exhibited similar activity vs. Nematospiroides dubius in mice. Preliminary screening indicated methyl 6-(1,2,2-trichloroethenyl)imidazo[1,2-alpha]pyridine-2-carbamate to be the most potent derivative in the series. However, evaluation in sheep indicated that its anthelmintic spectrum was inferior to methyl 6-(phenylsulfinyl)imidazo[1,2-alpha]pyridine-2-carbamate.

Animals↗
PubMed1980

Effects of arprinocid on developmental stages of Eimeria tenella.

Restricted medication experiments were done to correlate time of arprinocid medication with developmental stages of the life cycle of Eimeria tenella. By the criterion of histopathology and using a massive inoculum (10(6) sporulated oocysts), 50 ppm was partially active and 70 ppm was fully active against the first asexual generation when medication was delayed until day 1. When medication was delayed until day 2, full activity was demonstrated against the late, first asexual generation. When medication was delayed until day 3, definite but less complete activity was shown against the late, second asexual generation. Using the conventional efficacy parameters and with an inoculum of 5 X 10(4), full activity occurred with 50 ppm when medication was started up to day 2. Essentially full activity was observed with 60 ppm started at day 3. The combined results of the two tests are interpreted to indicate high activity against both the first and second asexual generations. Medication with 70 ppm changed the wall-forming bodies of the macrogamete. They were indistinct and less intensely eosinophilic than controls.

Adenine↗
PubMed1979

Avermectins, new family of potent anthelmintic agents: producing organism and fermentation.

The avermectins are a complex of chemically related agents which exhibit extraordinarily potent anthelmintic activity. They are produced by a novel species of actinomycete, NRRL 8165, which we have named Streptomyces avermitilis. The morphological and cultural characteristics which differentiate the producing organism from other species are described. The avermectins have been identified as a series of macrocyclic lactone derivatives which, in contrast to the macrolide or polyene antibiotics, lack significant antibacterial or antifungal activity. The avermectin complex is fully active against the gastrointestinal nematode Nematospiroides dubius when fed to infected mice for 6 days at 0.0002% of the diet. Fermentation development, including medium modification and strain selection, resulted in increasing the broth yields from 9 to 500 mug/ml.

Anthelmintics↗