4,081 research outputs found
Suppression of SIV-specific CD4+ T cells by infant but not adult macaque regulatory T cells: implications for SIV disease progression.
The impact of regulatory T cells (T reg cells) on the course of HIV and SIV disease is unknown. T reg cells could suppress protective antiviral responses and accelerate disease progression. Alternatively, these cells might block T cell activation and thereby limit viral replication as well as activation-associated immunopathology. Given the higher frequency of T reg cells known to be present during human fetal ontogeny, such influences may be most important in the context of perinatal infection. We found that infant macaques had higher fractions of CD4(+)CD25(+)CD127(low)FoxP3(+) T reg cells in the peripheral blood and in lymphoid tissues, and that these T reg cells showed greater in vitro suppressive activity on a per cell basis. Infant and adult macaques were infected with SIVmac251 to test the influence of the T reg cell compartment on SIV-specific immune responses. After infection with SIV, most (three out of four) infant macaques had persistently high viral loads, weak and transient SIV-specific CD4(+) and CD8(+) T cell responses, and rapid disease progression. T reg cells in the infant but not in the adult directly suppressed SIV-specific CD4(+) T cell responses, which were detectable only after depletion of T reg cells. In the case of both the infant and the adult macaque, T reg cells were not able to directly suppress SIV-specific CD8(+) T cell responses and had no apparent effect on T cell activation. In aggregate, these observations suggest that the T reg cell compartment of the infant macaque facilitates rapid disease progression, at least in part by incapacitating SIV-specific CD4(+) T cell responses
A Comparison Between Physiological and Perceived Exertion During Maximal and Submaximal Treadmill Exercise at Three Menstrual Cycle Phases
The purpose of this study was to investigate the differences in physiological and subjective perceived exertion levels at maximal and submaximal treadmill exercise between three phases of the menstrual cycle in eumennorheic women.
Nine females of varying fitness levels were subjects in the study. None of the subjects were using oral contraception or hormone altering medications at the time of the study.
The subjects performed three separate maximal graded exercise tests (GXT) using the Balke protocol. During each GXT, oxygen uptake (VO2), heart rate (HR), blood pressure (BP), respiratory quotient (RQ), rate of perceived exertion, and total time to exhaustion were recorded. During an eight minute recovery period, RQ, HR, and BP were recorded. These GXTs were performed beginning with either onset of menses, at ovulation, (as determined by oral temperature), or at cycle end chosen in random order.
Group mean values for each menstrual cycle phase were calculated for VO2, HR, RQ, and time to exhaustion. Means were compared between the three phases using a multivariate analysis of variance for repeated measures with an alpha of 0.05. It was found that at 75% maximal exertion and at maximal exertion, the ovulation phase means tended to be highest for the parameters of VO2 (75% mean =26.662 ± 6.281 ml · kg-1· min-1, maximal mean = 35.32± 6.711 ml · kg-1· min-1), HR (75% mean - 153.25± 7.146 bpm, maximal mean = 175.75 ± 13.573 bpm), and time to exhaustion (15.205± 3.902 minutes). The lowest mean values for these same parameters were found at the menses phase at the 75% and maximal exertion levels of intensity (mean VO2 75% = 26.109 ± 5.063 ml·kg-1· min-1, mean VO2 max = 34.826 ± 6.799 ml·kg-1· min-1; mean HR at 75% = 152.625 ± 16.928 bpm, mean HR at maximal =171.25± 14.23 bpm; mean time to exhaustion = 14.845 ± 3.125 minutes). However, these differences were found not to be satistically significant (p=\u3c0.05) between any of the menstrual phases.
It was concluded that the physiological responses which occur during submaximal and maximal exercise do not differ between menstrual cycle phases. However, trends were evident to indicate that ovulation produced the highest mean values for those parameters, and the menses phase produced the lowest. Further investigation of these trends is recommended
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Indirect induction of radiation lymphomas in mice. Evidence for a novel, transmissible leukemogen.
The transmission of a lymphomagenic agent(s) from the bone marrow of irradiated mice to thymic target cells has been demonstrated by: (a) the induction of T cell lymphomas in nonirradiated thymic grafts implanted in irradiated, Thy-l-congenic mice, (b) the induction of T cell lymphomas of host origin in mice infused with bone marrow from irradiated, Thy-l-congenic donors. The latter procedure also yields an appreciable number of pre-B cell lymphomas of uncertain origin. The results confirm Kaplan's theory that radiation induces thymic lymphomas in mice by an indirect mechanism. However, the previously described radiation leukemia virus is clearly not involved in the majority of transferred lymphomas. We propose that the mediating agent in radiation lymphomagenesis is a novel, transmissible agent induced in the bone marrow, but exerting its transforming activity on cells in the thymus. The nature and mode of action of the agent are under investigation
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Human immunodeficiency virus infection of the human thymus and disruption of the thymic microenvironment in the SCID-hu mouse.
Infection with the human immunodeficiency virus (HIV) results in immunosuppression and depletion of circulating CD4+ T cells. Since the thymus is the primary organ in which T cells mature it is of interest to examine the effects of HIV infection in this tissue. HIV infection has been demonstrated in the thymuses of infected individuals and thymocytes have been previously demonstrated to be susceptible to HIV infection both in vivo, using the SCID-hu mouse, and in vitro. The present study sought to determine which subsets of thymocytes were infected in the SCID-hu mouse model and to evaluate HIV-related alterations in the thymic microenvironment. Using two different primary HIV isolates, infection was found in CD4+/CD8+ double positive thymocytes as well as in both the CD4+ and CD8+ single positive subsets of thymocytes. The kinetics of infection and resulting viral burden differed among the three thymocyte subsets and depended on which HIV isolate was used for infection. Thymic epithelial (TE) cells were also shown to endocytose virus and to often contain copious amounts of viral RNA in the cytoplasm by in situ hybridization, although productive infection of these cells could not be definitively shown. Furthermore, degenerating TE cells were observed even without detection of HIV in the degenerating cells. Two striking morphologic patterns of infection were seen, involving either predominantly thymocyte infection and depletion, or TE cell involvement with detectable cytoplasmic viral RNA and/or TE cell toxicity. Thus, a variety of cells in the human thymus is susceptible to HIV infection, and infection with HIV results in a marked disruption of the thymic microenvironment leading to depletion of thymocytes and degeneration of TE cells
Control of poultry disease outbreaks (1990)
"Poultry owners should immediately begin an investigation if a disease is suspected in a flock. Obvious disease signs and symptoms can be identified on the farm while others may require laboratory assistance for proper diagnosis."--First page.E.L. McCune (School of Veterinary Medicine), and J.M. Vandepopuliere (Animal Sciences Department)Revised 5/90/4
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