PubMed Health⌕ Search

Biomedical subjects

M R Irwin

Publications and source records attributed to M R Irwin.

At least 37 records · Page 2Linked to original sources
PubMed1988

Adaptation to chronic stress. Temporal pattern of immune and neuroendocrine correlates.

Stress-inducing stimuli are associated with a suppression of immune function. In this study, the relationship between pituitary-adrenal hormone release and natural cytoxicity was examined in the rat during single and repeated instances of chronic stress. Increased plasma concentrations of both adrenocorticotropic hormone (ACTH) and beta-endorphin/lipotropin were correlated with increases in natural killer (NK) activity following a single period of immobilization. After 4 days of repeated daily immobilization (2.5 hours/day), the secretory response of beta-endorphin/lipotropin was similar to that on day 1, but NK activity was lower than on day 1. These observations suggest a complex interaction between pituitary-adrenal responses to stress and changes in natural cytoxicity.

Adrenocorticotropic Hormone↗
PubMed1987

L-5-hydroxytryptophan attenuates positive psychotic symptoms induced by D-amphetamine.

Brain serotonin has been hypothesized to be involved in the modulation of psychotic symptoms in at least some forms of schizophrenia. We examined the effects of the serotonin precursor L-5-hydroxytryptophan (5HTP) on D-amphetamine induction of acute psychotic symptoms in schizophrenic patients. Preadministration with 5HTP significantly antagonized amphetamine-elicited elevations in thought disturbance, activation, and hallucinations.

5-Hydroxytryptophan↗
PubMed1987

Central corticotropin-releasing factor suppresses natural killer cytotoxicity.

Corticotropin-releasing factor (CRF) administered as a single dose intraventricularly produces a dose-dependent suppression of rat splenic natural killer (NK) cell activity. Neither systemic CRF nor CRF in vitro significantly altered NK activity. The immunosuppressive effect of central CRF was antagonized by central, but not by systemic, preadministration of the CRF antagonist, alpha-helical oCRF residues 9-41. These data suggest that CRF released in the brain may have a role in the central modulation of natural killer cytotoxicity.

Animals↗
PubMed1979

Poor growth performance associated with hypocupremia in Hawaiian feedlot cattle.

Poor feedlot performance in native Hawaiian feedlot cattle was investigated. Cattle were first noticed to be affected 40 to 60 days after arrival at the feedlot, as judged by their retarded growth, when compared with penmates. Marked hypocupremia was detected in all 10 cattle examined, irrespective of time in the feedlot. Clinical signs and upper digestive tract lesions in 8 of the 10 cattle suggested secondary involvement of bovine papular stomatitis. The poor performance was attributed primarily to the hypocupremia, as a result of molybdenum-accentuated copper deficiency in forage on the ranch of origin.

Animal Feed↗
PubMed1979

Roles of predisposing factors and gonadal hormones in the buller syndrome of feedlot steers.

In a study of the role of predisposing factors and gonadal hormones in the buller syndrome, it was found that weather, amount of space available to each steer, and entry weights of the steers were not associated with increased occurrence of bulling; however, the type and timing of administration of the hormonal implant, the number of steers in a pen, and the manner in which the steers were grouped after arrival at the feedlot were found to influence the incidence of the syndrome. Serum concentrations of estradiol and testosterone in the buller steers were found to be lower during bulling than after a short period of isolation and apparent recovery from the syndrome. It was concluded that the occurrence of bulling is related to the use of hormonal implants and certain feedlot management procedures but that it is apparently not related to increased serum estrogen or testosterone concentrations.

Animal Feed↗
PubMed1976

Effects of vaccination infectious bovine rhinotracheitis and simultaneous administration of levamisole on primary humoral responses in calves.

In a study on the primary humoral response of calves vaccinated against infectious bovine rhinotracheitis (IBR) and simultaneously given levamisole, mild but consistent suppression of the group's geometric mean serum-neutralization titer to IBR virus occurred between 12 and 59 days later. The quantitative determination of circulating immunoglobulins (Ig) over the same period indicated a slight decrease in the IgG concentrations from an initial geometric mean concentration of 18.28 mg/ml before calves were vaccinated to 15.29 mg/ml after vaccination, and the control calves (vaccinated and given saline solution only) maintained their prevaccination IgG geometric mean concentration of 20.92 mg/ml. Difference was not observed in the circulating IgM values of the 2 groups. Levamisole had no apparent effect on the circulating Ig-bearing lymphocyte values when compared with control calves during the 24 hours of treatment. It was concluded that a single treatment of levamisole may mildly suppress the primary humoral response to IBR vaccination in calves, but it is unlikely that this would affect the animal's capability to recover from, or maintain resistance to, IBR infection.

Animals↗
PubMed1975

Abnormal bone development and lameness associated with secondary copper deficiency in young cattle.

Lameness in a group of 5- to 12-month-old calves was found to be clinically, radiographically, and pathologically associated with abnormal bone development of the distal growth plates of the metacarpus and metatarsus. Copper concentrations in serum and liver were low. Serum calcium, phosphorus, and alkaline phosphatase values were normal. In pasture forage samples, sulfate, zinc, and molybdenum concentrations were high, whereas copper, calcium, and phosphorus concentrations were normal. Red blood cell (RBC) counts and hemoglobin values were within normal limits. Radiographic findings included a widened zone of cartilage and lipping of the medial and lateral areas of the physeal plate. Histologic findings included focal widenings of the growth plate consisting of tongues of uncalcified cartilage.

Animal Feed↗
PubMed1975

Enhanced resistance to Corynebacterium pseudotuberculosis infections associated with reduced serum immunoglobulin levels in levamisole-treated mice.

The effect of levamisole (1-2,3,5,6-tetrahydro-6-imidazo[2,1-b]thiazole monohydrochloride) treatment on the course of a Corynebacterium pseudotuberculosis infection and the ability of either vaccinated or unvaccinated randomly bred mice to resist challenge were investigated. It was found that either a double treatment of levamisole administered with or without a sublethal inoculation of C. pseudotuberculosis or a single treatment of levamisole alone had a significant effect on the ability of mice to resist challenge with virulent C. pseudotuberculosis. This prolonged, enhanced nonspecific and specific resistance was associated with a quantitative reduction in the geometric mean serum immunoglobulin levels, with the immunoglobulin G2 and immunoglobulin A levels being more severely affected. As the enhanced nonspecific resistance to C. pseudotuberculosis was associated with depressed serum immunoglobulin levels in the mice pretreated with levamisole alone, it was suggested that the cell-mediated immunity may play a more important role than the humoral immunity in the resistance to C. pseudotuberculosis infection.

Animals↗
PubMed1972

Evolution in Columbidae: additional relationships among the antigenic specificities produced by gene interaction.

Two of the antigenic characters of erythrocytes, that in either identical or related forms differentiate four species of Streptopelia (chinensis, humilis, orientalis, and senegalensis) from a fifth (S. risoria) by interaction of the causative genes, are involved in the appearance in backcross hybrids of additional antigenic specificities to those of the parental species. The cells of backcross hybrids, resulting from matings of S. chinensis x S. risoria and backcrossing to S. risoria, in which the two independently inherited antigenic characters (ch-4 and ch-8 peculiar to S. chinensis) are combined as homozygotes, exhibit an antigenic specificity not present in backcross birds carrying separately these two characters. This result indicates an interaction within S. chinensis of the genes for these two antigenic characters. An antigen (C(g)) by which Columba guinea differs from C. livia has behaved as a unit in over 400 backcross offspring. It is antigenically related to both ch-4 and ch-8 of S. chinensis. It is also related to, but not identical with, this interaction antigen of S. chinensis. Further, the C(g) character is also related to an interaction product that appears in all backcross offspring carrying the group-4 antigen in a S. risoria genome. Genes related to those that in modern species or in species hybrids interact to effect new antigenic specificities presumably possessed the same abilities in ancestral forms of Columbidae.

Agglutination Tests↗