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M R Irwin

Publications and source records attributed to M R Irwin.

47 records · Page 3Linked to original sources
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The identification of the neonatal NBXFO hybridoma cell and its mediator.

The neonatal spleen:myeloma hybridoma cell, NBXFO, with immunosuppressive properties supported rodent hematopoietic colony formation. We identified this hybridoma to be an undifferentiated fibroblast that produced macrophage colony-stimulating factor (M-CSF). The bone marrow cells that grew in the presence of the NBXFO supernate were macrophages and were immunosuppressive towards lymphocytes. Neutralizing anti-M-CSF antibody partially inhibited the actions of the neonatal splenic suppressor cells. Neonatal splenocytes, but not the other parental cell line, FO, induced macrophage colony formation, possessed surface-associated M-CSF, and possessed M-CSF-specific transcripts. Therefore, we believe that the M-CSF-producing phenotype was contributed by a fibroblastic stromal cell and that these stromal cells could be responsible for the in situ generation of neonatal splenic suppressor cells.

Animals↗
PubMedDate not supplied

Possible effect of a sex chromosome on reproductive performance in Columbidae.

In comparison with the reproductive performance of matings within Streptopelia risoria, the species hybrid males, from matings to S. risoria of males of S. chinensis or S. senegalensis, displayed increased infertility, but not an increase of embryo mortality. Previous findings of a high percentage of sperm abnormalities provide a basis that explains in part the infertility of the species hybrid males. The infertility and embryo mortality of both kinds of species hybrid females, the heterogametic sex, was much higher than in the S. risoria X S. risoria matings. The reproductive performance of the backcross females of the first, second and third backcross generations, having either species hybrid or backcross hybrid males as parents, could be divided into two classes, differing significantly either in percentage of infertility or embryo mortality, or in both categories. The backcross females producing the lower reproductive performance presumably carried the X chromosome of the wild parental species. Limited date obtained following a mating between a S. senegalensis female and a S. chinensis male showed a very low percentage of infertility of eggs from two species hybrid females and a backcross female (1/4-S. chinensis), indicating that the adverse effect of changes affecting infertility, presumably on the X-chromosome of these two wild species, towards S. risoria, had occurred in parallel during their evolution. The genetic changes affecting embryo mortality, and particularly the death of the squabs before becoming adults, are located on somatic chromosomes.

Animals↗
PubMedDate not supplied

Chronic life stress alters sympathetic, neuroendocrine, and immune responsivity to an acute psychological stressor in humans.

OBJECTIVE: Life stress is hypothesized to alter the dynamic regulation of the autonomic, neuroendocrine, and immune systems. This study examined the effects of antecedent chronic life stress on psychological and physiological responsivity after acute challenge with a psychological stressor. METHOD: Using a within-subject mixed design, male volunteers with (N = 12) and without chronic life stress (N = 11) were administered a 12-minute laboratory stressor (mental arithmetic) vs a video control. RESULTS: Acute psychological stress induced subjective distress, increases of circulating concentrations of epinephrine, norepinephrine, beta-endorphin, adrenocorticotropic hormone (ACTH), and cortisol, and a selective redistribution of natural killer (NK) cells into the peripheral blood as compared with the video control condition. Although the two groups were almost identical at baseline in psychological, sympathetic, neuroendocrine, and immune domains, the chronic stress group showed greater subjective distress, higher peak levels of epinephrine, lower peak levels of beta-endorphin and of NK cell lysis, and a more pronounced redistribution of NK cells in response to the acute psychological challenge than the controls. Furthermore, the acute stressor induced a protracted decline in NK lysis per NK cell in the chronic stress group but had no effect in the controls. CONCLUSIONS: In summary, when persons who are undergoing chronic life stress are confronted with an acute psychological challenge, an exaggerated psychologic and peak sympathomedullary reactivity occurs that is associated with decrements in individual NK cell function and is protracted beyond termination of the stressor and sympathomedullary recovery.

Adrenal Medulla↗
PubMedDate not supplied

Interleukin-6 and tumor necrosis factor-alpha production after acute psychological stress, exercise, and infused isoproterenol: differential effects and pathways.

OBJECTIVE: The aim of the study was to assess the effects of three different methods of acute activation of the sympathetic nervous system on lipopolysaccharide-induced in vitro production of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha). METHODS: Thirty-two healthy volunteers performed speech and exercise tasks and underwent a 30-minute infusion of isoproterenol. RESULTS: As expected, acute activation of the sympathetic nervous system led to leukocytosis, including increases in lymphocyte, monocyte, and granulocyte populations (p values <.05). Lipopolysaccharide-induced IL-6 production was increased after both the speaking and exercise tasks (p values <.001), whereas TNF-alpha production was elevated only after exercise (p<.05). In contrast, infusion of isoproterenol inhibited TNF-alpha production (p<.001) and caused no change in IL-6 production. CONCLUSIONS: In response to the challenges, IL-6 and TNF-alpha production showed different profiles. Purely beta-agonist stimulation led to downregulation of TNF-alpha production, providing evidence of the antiinflammatory effect of in vivo beta-receptor activation. The enhanced production of both cytokines after exercise, and of IL-6 after the speech task, can be best explained by a simultaneous upregulation of proinflammatory and inflammation-responding mediators. These effects may have an important role in controlling the immune response to acute psychological and physical stress.

Adult↗