Spaceflight affects numerous organ systems in the body, leading to metabolic dysfunction that may... more Spaceflight affects numerous organ systems in the body, leading to metabolic dysfunction that may have long-term consequences. Microgravity-induced alterations in liver metabolism, particularly with respect to lipids, remain largely unexplored. Here we utilize a novel systems biology approach, combining metabolomics and transcriptomics with advanced Raman microscopy, to investigate altered hepatic lipid metabolism in mice following short duration spaceflight. Mice flown aboard Space Transportation System -135, the last Shuttle mission, lose weight but redistribute lipids, particularly to the liver. Intriguingly, spaceflight mice lose retinol from lipid droplets. Both mRNA and metabolite changes suggest the retinol loss is linked to activation of PPARα-mediated pathways and potentially to hepatic stellate cell activation, both of which may be coincident with increased bile acids and early signs of liver injury. Although the 13-day flight duration is too short for frank fibrosis to de...
The influence of gravity on the formation of lignified vascular elements was investigated through... more The influence of gravity on the formation of lignified vascular elements was investigated through a comparison of leguminous seedlings raised in reduced gravity and controls raised on the ground in identical hardware. Tissues of 6-day-old alfalfa (Medicago sativa L.) cotyledons, hypocotyls, and roots taken from both experimental groups were sectioned and studied for evidence of distinctions in prevalence and arrangement of lignified vascular elements. Within hypocotyl tissue, the prevalence of lignified vessel elements was 20 % lower among flight seedlings than ground seedlings (P<0.05). Similarly, within root tissue, the flight samples incorporated 14% fewer lignified elements than ground controls (P<0.05). The prevalence of lignified vascular elements within tissue of cotyledons was not significantly different between seedlings from the two gravitational environments. The arrangement of lignified vascular cells within cotyledon and root was also constant between the two experimental populations. However. the organization of vascular elements within hypocotyl tissue taken from flight seedlings demonstrated a bias towards the triarch pattern while ground sections exhibited a tendency for the tetrarch arrangement at this location. Among the ground hypocotyls. 36 % (n = 18) exhibited a triarch arrangement of lignified vascular cells, while the same pattern was observed in 64 % (n = 19) of the flight hypocotyls. The data suggest that differentiation of lignified vascular elements for the developmental period studied may be lower in reduced gravity environments. This finding supports the hypothesis that the presence of gravity is a driver of lignification within leguminous plants.
To determine whether proton radiation can be used to treat chronic intractable pain. The focus of... more To determine whether proton radiation can be used to treat chronic intractable pain. The focus of this study was on the biological effects of spinal cord irradiation. Proton radiation (0-25 Gy, single fraction) was applied to the spinal cord within L3-L5 of Yucatan mini-pigs (n=20). Skin reaction, body mass and behavior were monitored. At euthanasia, blood and spinal cord were analyzed. Skin morbidity was mild and overall health for the 5-20 Gy-treated groups was good based on behavior and weight gain up to 8.5-9 months post-exposure. The 25 Gy-treated animals developed hind limb weakness at 2.5-3 months and were euthanized. Radiation had a significant effect on white blood cell count (p<0.05), with the 25 Gy-treated mini-pigs having the highest number of all three major leukocyte populations. A few differences were also noted for erythrocyte parameters, but the blood chemistry panel was normal. Apoptosis in the targeted portion of the spinal cord was elevated in the 20- and 25 G...
The goal of the study was to evaluate changes in lung status due to spaceflight stressors that in... more The goal of the study was to evaluate changes in lung status due to spaceflight stressors that include radiation above levels found on Earth. Within hours after return from a 13-day mission in space onboard the Space Shuttle Atlantis, C57BL/6 mice (FLT group) were euthanized; mice housed on the ground in similar animal enclosure modules served as controls (AEM group). Lung tissue was collected to evaluate the expression of genes related to extracellular matrix (ECM)/adhesion and stem cell signaling. Pathway analysis was also performed. In addition, immunohistochemistry for stem cell antigen-1 (SCA-1), the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay for apoptosis, and staining for histological characteristics were performed. There were 18/168 genes significantly modulated in lungs from the FLT group (p<0.05 vs. AEM); 17 of these were up-regulated and one was down-regulated. The greatest effect, namely a 5.14-fold increase, was observed on Spock1 (als...
The major goal was to determine whether variations in the method of CO2 euthanasia would induce s... more The major goal was to determine whether variations in the method of CO2 euthanasia would induce significant immunologic differences. Young adult C57BL/6 mice (n = 40) were euthanized, using four regimens: 70% CO2/30% O2; 70% CO2/30% O2-->100% CO2; 100% CO2-naïve chamber; and 100% CO2 pre-charged chamber. Time to recumbency and euthanasia and body, liver, lung, spleen, and thymus masses were determined. Blood and spleen were further evaluated for leukocyte, lymphocyte, and thrombocyte counts, erythrocyte characteristics, distribution of lymphocyte subpopulations, spontaneous and mitogen-induced blastogenesis, complement activity, and cytokine production. Time to euthanasia was five- to eightfold longer in mice exposed to 70% CO2/30% O2 than that for any other group. There were slight increases in mean erythrocyte volume (MCV) and mean erythrocyte hemoglobin (MCH) for all groups, compared with those for the 100% CO2 pre-charged group. Circulating cytotoxic T (CD8+) lymphocyte perce...
An effective countermeasure against radiation damage to normal tissues is urgently needed. The ma... more An effective countermeasure against radiation damage to normal tissues is urgently needed. The major goal of the present study was to determine if minocycline could modify the immunomodulatory effects of radiation on the brain. C57BL/6 mice were treated with minocycline intraperitoneally for 5 days beginning immediately before total-body exposure to 0, 1, 2 and 3 Gray (Gy) (60)Co γ-rays. Brains were collected on days 4 and 32 post-irradiation for cytokine and gene analyses. Minocycline treatment significantly increased the levels of interleukin (IL)-10, IL-15 and vascular endothelial growth factor (VEGF) in the brain on day 4 in one or more irradiated groups compared to radiation-alone (p<0.05). IL-10 is anti-inflammatory, IL-15 can prevent apoptosis and VEGF is nuroprotective. On day 32, the drug decreased IL-1β in the 2- Gy group (p<0.05 vs. 2-Gy alone); this cytokine is implicated in immune-related central nervous system pathologies. Microarray analysis of brains on day 32 ...
The goal of the present study was to obtain pilot data on the effects of protracted low-dose/low-... more The goal of the present study was to obtain pilot data on the effects of protracted low-dose/low-dose-rate (LDR) γ-rays on the skin, both with and without acute gamma or proton irradiation (IR). Six groups of C57BL/6 mice were examined: a) 0 Gy control, b) LDR, c) Gamma, d) LDR+Gamma, e) Proton, and f) LDR+Proton. LDR radiation was delivered to a total dose of 0.01 Gy (0.03 cGy/h), whereas the Gamma and Proton groups received 2 Gy (0.9 Gy/min and 1.0 Gy/min, respectively). Assays were performed 56 days after exposure. Skin samples from all irradiated groups had activated caspase-3, indicative of apoptosis. The significant (p<0.05) increases in immunoreactivity in the Gamma and Proton groups were not present when LDR pre-exposure was included. However, the terminal deoxynucleotidyl transferase dUTP nick-end labeling assay for DNA fragmentation and histological examination of hematoxylin and eosin-stained sections revealed no significant differences among groups, regardless of radi...
We previously found that minocycline enhanced the levels of several leukocyte populations and had... more We previously found that minocycline enhanced the levels of several leukocyte populations and had the capacity to induce secretion of certain cytokines early after irradiation. In the current study we further determined the drug's effect on hematopoietic recovery. Minocycline was injected intraperitoneally into C57BL/6 mice for 5 days, beginning immediately before exposure to (60)Co γ-rays (1, 2, 3 Gy). Thirty-two days post-irradiation, spleen and blood were collected to quantify cell populations, cytokines in splenic T-cell supernatants after anti-CD3 activation, and chromosomic status based on spectral karyotyping. While radiation resulted in significantly lower B-cell counts at 3 Gy in both blood and spleen, minocycline treatment increased the counts and/or percentages of splenic B-cells at 2 Gy and 3 Gy. In spleen supernatants, the drug-alone increased the levels of cytokines, including interleukin-1α (IL-1α) and IL-6 that are radioprotective, as well as granulocyte-macropha...
To evaluate the impact of an antibiotic, minocycline, on several immune parameters in response to... more To evaluate the impact of an antibiotic, minocycline, on several immune parameters in response to radiation in a mouse model. C57BL/6 mice were treated with minocycline (i.p.) for 5 days, beginning immediately before radiation with 1-3 Gy (60)Co γ-rays. Spleen and blood were collected on day 4 post-irradiation. Cell populations were determined in the blood and spleen. Splenocytes were activated with anti-CD3 antibody for 48 h and cytokines were quantified. Minocycline increased the counts and/or percentages of splenic macrophages, granulocytes, natural killer, T- and CD8(+) T-cells (p<0.05 versus radiation alone). Minocycline significantly increased the expression of interleukin-1α and β, which are radioprotective, as well as the ones of granulocyte-macrophage colony-stimulating factor and granulocyte colony-stimulating factor, which accelerate neutrophil recovery (p<0.05 versus radiation alone), while suppressing cytokines that could prevent hematopoiesis, e.g. macrophage inf...
The purpose of this study was to determine whether secondary immune responses to lipopolysacchari... more The purpose of this study was to determine whether secondary immune responses to lipopolysaccharide (LPS) were altered by exposure to radiation. C57BL/6 mice were irradiated (60Co, gamma-rays) to 0 or 3 Gray (Gy) and injected intraperitoneally with LPS on days 10 and 42 thereafter. Subsets were euthanized 0-14 days after the second injection for analyses. The data show numerous radiation-induced effects, as well as some significant interactions among radiation, LPS, and day of analysis. Among the most striking were changes in thymus mass, circulating lymphocytes, monocytes, granulocytes, and specific lymphocyte subpopulations, erythrocyte counts, hematocrit, and platelet counts and volume. Spontaneous blastogenesis and oxidative burst capacity of phagocytic cells, however, were relatively normal. The findings indicate that exposure to radiation at a spaceflight relevant dose can influence the distribution of certain leukocyte populations in response to a secondary challenge with LPS.
Lipopolysaccharide (LPS) is a major cause of septic shock and death due to infection with Gram-ne... more Lipopolysaccharide (LPS) is a major cause of septic shock and death due to infection with Gram-negative bacteria. The purpose of this study was to quantify the effects of whole-body irradiation on lymphocyte populations during response to challenge with LPS. C57BL/6 mice (n = 10/group) were irradiated whole-body with 3 gray (Gy) gamma-rays in a single fraction at 0.8 Gy/min. LPS (E. coli serotype 0111:B4) at 1 mg/kg was injected intraperitoneally 10 days later and mice were euthanized at 60 min and days 1, 7, and 14 post-inoculation for analyses. Significant interactions between radiation and LPS were noted in circulating and splenic lymphocyte subpopulations, including T-, B-, and NK-cells, particularly at the early time points. There were significant interactions on circulating, but not splenic, CD62L+ T-cell populations. However, there were no interactions on CD62L+ B-cells. Finally, there were significant interactions in both early and late blastogenic responses. The data suppor...
The major goal of this study was to determine whether radiation significantly alters bone marrow-... more The major goal of this study was to determine whether radiation significantly alters bone marrow-derived cell distribution and mass of sensitive organs after challenge with lipopolysaccharide (LPS). C57BL/6 mice were exposed whole-body to 0 or 3 gray (Gy) gamma-radiation (60Co) and injected intraperitoneally with 0.1 ml saline or 1 mg/kg LPS (E. coli serotype 0111:B4) 10 days later. Subsets from each group were euthanized at 60 min and 1, 7 and 14 days post-injection for analyses. Body mass was low 1 day after LPS, especially in irradiated animals. LPS-induced splenomegaly and hepatomegaly were attenuated by radiation, whereas thymic atrophy was enhanced. However, radiation had no effect on LPS-induced changes in oxygen radical production by liver phagocytes. The numbers of all major leukocyte populations (lymphocytes, monocyte-macrophages, granulocytes) were altered by both radiation and LPS at virtually all time points of testing. In general, the LPS-induced changes in leukocytes ...
The major aim of this study was to quantify long-term changes in bone marrow-derived cell populat... more The major aim of this study was to quantify long-term changes in bone marrow-derived cell populations after exposure to radiations of differing quality. Mice were whole-body irradiated to 2 Gy gamma, proton, carbon or iron radiation, and euthanized approximately 110 days later for immunocyte phenotyping. Splenic lymphocytes and mono/macrophages increased after gamma-rays when compared to 0 Gy and one or more of the other groups. There were high T cells (carbon vs. 0 Gy), high B cells (gamma-rays vs. 0 Gy), and low natural killer (NK) cells (proton and carbon vs. 0 Gy). All radiations, except gamma-rays, increased CD62L+ memory T cell counts, whereas CD62L+ B cells increased only after gamma-rays. There were significant aberrations in many immune parameters nearly 4 months after exposure to various forms of radiation. This suggests radiation exposure can have long-term health consequences.
The heads of Sprague-Dawley rats were irradiated with protons to total doses of 1.5, 3 and 4 Gy a... more The heads of Sprague-Dawley rats were irradiated with protons to total doses of 1.5, 3 and 4 Gy and euthanized 9-10 days later. Significant dose-dependent decreases were noted in thymus mass. Lymphocyte and platelet numbers were significantly reduced in blood. Flow cytometric analysis of blood and spleen showed that CD3+ T, CD3+/CD4+ TH, and CD3+/CD8+ TC cell numbers were low and proportions were significantly altered by radiation. CD4:CD8 ratios and CD45R+ B lymphocytes were unaffected. Spontaneous blastogenesis of blood and spleen leukocytes was significantly increased by radiation. Plasma TGF-beta 1 level in irradiated rats was consistently, but not significantly, higher than in non-irradiated animals. T and B cell proportions in lymph nodes from irradiated animals were similar to non-irradiated controls. Bone marrow from all irradiated groups had high CD90+/Gran+ cell numbers. The data show that head-localized proton irradiation at relatively modest doses can profoundly influenc...
Outside the protection of the terrestrial environment, astronauts on any long-term missions will ... more Outside the protection of the terrestrial environment, astronauts on any long-term missions will unavoidably be exposed to fields of charged particle radiation dominated by protons. These fields and their biological risks are modified in complex ways by the presence of protective shielding. To examine the long-term effects of space-like proton exposures on immune status, we treated female C57BL/6 mice with 3 or 4 Gy of 250 MeV monoenergetic protons or the complex space-like radiation field produced after 250 MeV protons are transported through 15 g x cm(-2) aluminum shielding. The animals were euthanized 122 d post-irradiation and lymphocyte phenotypes, hematological parameters, and lymphocyte blastogenesis were characterized. There were significant dose-dependent decreases in macrophage, CD3+/CD8+ T, NK, platelet, and red blood cell populations, as well as low hematocrit and hemoglobin levels. In contrast, dose-dependent increases in spontaneous, but not mitogen-induced, blastogene...
American journal of physiology. Regulatory, integrative and comparative physiology, 2002
Although the immune system is highly susceptible to radiation-induced damage, consequences of hig... more Although the immune system is highly susceptible to radiation-induced damage, consequences of high linear energy transfer (LET) radiation remain unclear. This study evaluated the effects of 0.1 gray (Gy), 0.5 Gy, and 2.0 Gy iron ion (56Fe(26)) radiation on lymphoid cells and organs of C57BL/6 mice on days 4 and 113 after whole body exposure; a group irradiated with 2.0 Gy silicon ions (28Si) was euthanized on day 113. On day 4 after 56Fe irradiation, dose-dependent decreases were noted in spleen and thymus masses and all major leukocyte populations in blood and spleen. The CD19(+) B lymphocytes were most radiosensitive and NK1.1(+) natural killer (NK) cells were most resistant. CD3(+) T cells were moderately radiosensitive and a greater loss of CD3(+)/CD8(+) T(C) cells than CD3(+)/CD4(+) T(H) cells was noted. Basal DNA synthesis was elevated on day 4, but response to mitogens and secretion of interleukin-2 and tumor necrosis factor-alpha were unaffected. Signs of anemia were noted. ...
American journal of physiology. Regulatory, integrative and comparative physiology, 2000
Spaceflight produces changes in the immune system. The mechanisms for the alterations in immune f... more Spaceflight produces changes in the immune system. The mechanisms for the alterations in immune function after spaceflight remain unclear due in part to the difficulties associated with conducting spaceflight research. The purpose of the following studies, therefore, was to create a ground-based protocol that can reproduce the immunological changes found after spaceflight, i.e., changes in splenic lymphocyte populations. Rats were exposed to either flight aboard the Space Shuttle Endeavor (STS-77) or ground-based simulations of various components of the spaceflight experience. The ground-based mock spaceflight was comprised of exposure to launch and landing loads and unloading of the hindlimbs. In addition, each component of this ground-based mock spaceflight was tested separately. The results were that spaceflight reduced splenic CD4(+) T (helper/inducer) cells and CD11b(+) (neutrophils/macrophages) cells. The ground-based simulations of spaceflight did not reproduce the same patte...
Spaceflight affects numerous organ systems in the body, leading to metabolic dysfunction that may... more Spaceflight affects numerous organ systems in the body, leading to metabolic dysfunction that may have long-term consequences. Microgravity-induced alterations in liver metabolism, particularly with respect to lipids, remain largely unexplored. Here we utilize a novel systems biology approach, combining metabolomics and transcriptomics with advanced Raman microscopy, to investigate altered hepatic lipid metabolism in mice following short duration spaceflight. Mice flown aboard Space Transportation System -135, the last Shuttle mission, lose weight but redistribute lipids, particularly to the liver. Intriguingly, spaceflight mice lose retinol from lipid droplets. Both mRNA and metabolite changes suggest the retinol loss is linked to activation of PPARα-mediated pathways and potentially to hepatic stellate cell activation, both of which may be coincident with increased bile acids and early signs of liver injury. Although the 13-day flight duration is too short for frank fibrosis to de...
The influence of gravity on the formation of lignified vascular elements was investigated through... more The influence of gravity on the formation of lignified vascular elements was investigated through a comparison of leguminous seedlings raised in reduced gravity and controls raised on the ground in identical hardware. Tissues of 6-day-old alfalfa (Medicago sativa L.) cotyledons, hypocotyls, and roots taken from both experimental groups were sectioned and studied for evidence of distinctions in prevalence and arrangement of lignified vascular elements. Within hypocotyl tissue, the prevalence of lignified vessel elements was 20 % lower among flight seedlings than ground seedlings (P<0.05). Similarly, within root tissue, the flight samples incorporated 14% fewer lignified elements than ground controls (P<0.05). The prevalence of lignified vascular elements within tissue of cotyledons was not significantly different between seedlings from the two gravitational environments. The arrangement of lignified vascular cells within cotyledon and root was also constant between the two experimental populations. However. the organization of vascular elements within hypocotyl tissue taken from flight seedlings demonstrated a bias towards the triarch pattern while ground sections exhibited a tendency for the tetrarch arrangement at this location. Among the ground hypocotyls. 36 % (n = 18) exhibited a triarch arrangement of lignified vascular cells, while the same pattern was observed in 64 % (n = 19) of the flight hypocotyls. The data suggest that differentiation of lignified vascular elements for the developmental period studied may be lower in reduced gravity environments. This finding supports the hypothesis that the presence of gravity is a driver of lignification within leguminous plants.
To determine whether proton radiation can be used to treat chronic intractable pain. The focus of... more To determine whether proton radiation can be used to treat chronic intractable pain. The focus of this study was on the biological effects of spinal cord irradiation. Proton radiation (0-25 Gy, single fraction) was applied to the spinal cord within L3-L5 of Yucatan mini-pigs (n=20). Skin reaction, body mass and behavior were monitored. At euthanasia, blood and spinal cord were analyzed. Skin morbidity was mild and overall health for the 5-20 Gy-treated groups was good based on behavior and weight gain up to 8.5-9 months post-exposure. The 25 Gy-treated animals developed hind limb weakness at 2.5-3 months and were euthanized. Radiation had a significant effect on white blood cell count (p<0.05), with the 25 Gy-treated mini-pigs having the highest number of all three major leukocyte populations. A few differences were also noted for erythrocyte parameters, but the blood chemistry panel was normal. Apoptosis in the targeted portion of the spinal cord was elevated in the 20- and 25 G...
The goal of the study was to evaluate changes in lung status due to spaceflight stressors that in... more The goal of the study was to evaluate changes in lung status due to spaceflight stressors that include radiation above levels found on Earth. Within hours after return from a 13-day mission in space onboard the Space Shuttle Atlantis, C57BL/6 mice (FLT group) were euthanized; mice housed on the ground in similar animal enclosure modules served as controls (AEM group). Lung tissue was collected to evaluate the expression of genes related to extracellular matrix (ECM)/adhesion and stem cell signaling. Pathway analysis was also performed. In addition, immunohistochemistry for stem cell antigen-1 (SCA-1), the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay for apoptosis, and staining for histological characteristics were performed. There were 18/168 genes significantly modulated in lungs from the FLT group (p<0.05 vs. AEM); 17 of these were up-regulated and one was down-regulated. The greatest effect, namely a 5.14-fold increase, was observed on Spock1 (als...
The major goal was to determine whether variations in the method of CO2 euthanasia would induce s... more The major goal was to determine whether variations in the method of CO2 euthanasia would induce significant immunologic differences. Young adult C57BL/6 mice (n = 40) were euthanized, using four regimens: 70% CO2/30% O2; 70% CO2/30% O2-->100% CO2; 100% CO2-naïve chamber; and 100% CO2 pre-charged chamber. Time to recumbency and euthanasia and body, liver, lung, spleen, and thymus masses were determined. Blood and spleen were further evaluated for leukocyte, lymphocyte, and thrombocyte counts, erythrocyte characteristics, distribution of lymphocyte subpopulations, spontaneous and mitogen-induced blastogenesis, complement activity, and cytokine production. Time to euthanasia was five- to eightfold longer in mice exposed to 70% CO2/30% O2 than that for any other group. There were slight increases in mean erythrocyte volume (MCV) and mean erythrocyte hemoglobin (MCH) for all groups, compared with those for the 100% CO2 pre-charged group. Circulating cytotoxic T (CD8+) lymphocyte perce...
An effective countermeasure against radiation damage to normal tissues is urgently needed. The ma... more An effective countermeasure against radiation damage to normal tissues is urgently needed. The major goal of the present study was to determine if minocycline could modify the immunomodulatory effects of radiation on the brain. C57BL/6 mice were treated with minocycline intraperitoneally for 5 days beginning immediately before total-body exposure to 0, 1, 2 and 3 Gray (Gy) (60)Co γ-rays. Brains were collected on days 4 and 32 post-irradiation for cytokine and gene analyses. Minocycline treatment significantly increased the levels of interleukin (IL)-10, IL-15 and vascular endothelial growth factor (VEGF) in the brain on day 4 in one or more irradiated groups compared to radiation-alone (p<0.05). IL-10 is anti-inflammatory, IL-15 can prevent apoptosis and VEGF is nuroprotective. On day 32, the drug decreased IL-1β in the 2- Gy group (p<0.05 vs. 2-Gy alone); this cytokine is implicated in immune-related central nervous system pathologies. Microarray analysis of brains on day 32 ...
The goal of the present study was to obtain pilot data on the effects of protracted low-dose/low-... more The goal of the present study was to obtain pilot data on the effects of protracted low-dose/low-dose-rate (LDR) γ-rays on the skin, both with and without acute gamma or proton irradiation (IR). Six groups of C57BL/6 mice were examined: a) 0 Gy control, b) LDR, c) Gamma, d) LDR+Gamma, e) Proton, and f) LDR+Proton. LDR radiation was delivered to a total dose of 0.01 Gy (0.03 cGy/h), whereas the Gamma and Proton groups received 2 Gy (0.9 Gy/min and 1.0 Gy/min, respectively). Assays were performed 56 days after exposure. Skin samples from all irradiated groups had activated caspase-3, indicative of apoptosis. The significant (p<0.05) increases in immunoreactivity in the Gamma and Proton groups were not present when LDR pre-exposure was included. However, the terminal deoxynucleotidyl transferase dUTP nick-end labeling assay for DNA fragmentation and histological examination of hematoxylin and eosin-stained sections revealed no significant differences among groups, regardless of radi...
We previously found that minocycline enhanced the levels of several leukocyte populations and had... more We previously found that minocycline enhanced the levels of several leukocyte populations and had the capacity to induce secretion of certain cytokines early after irradiation. In the current study we further determined the drug's effect on hematopoietic recovery. Minocycline was injected intraperitoneally into C57BL/6 mice for 5 days, beginning immediately before exposure to (60)Co γ-rays (1, 2, 3 Gy). Thirty-two days post-irradiation, spleen and blood were collected to quantify cell populations, cytokines in splenic T-cell supernatants after anti-CD3 activation, and chromosomic status based on spectral karyotyping. While radiation resulted in significantly lower B-cell counts at 3 Gy in both blood and spleen, minocycline treatment increased the counts and/or percentages of splenic B-cells at 2 Gy and 3 Gy. In spleen supernatants, the drug-alone increased the levels of cytokines, including interleukin-1α (IL-1α) and IL-6 that are radioprotective, as well as granulocyte-macropha...
To evaluate the impact of an antibiotic, minocycline, on several immune parameters in response to... more To evaluate the impact of an antibiotic, minocycline, on several immune parameters in response to radiation in a mouse model. C57BL/6 mice were treated with minocycline (i.p.) for 5 days, beginning immediately before radiation with 1-3 Gy (60)Co γ-rays. Spleen and blood were collected on day 4 post-irradiation. Cell populations were determined in the blood and spleen. Splenocytes were activated with anti-CD3 antibody for 48 h and cytokines were quantified. Minocycline increased the counts and/or percentages of splenic macrophages, granulocytes, natural killer, T- and CD8(+) T-cells (p<0.05 versus radiation alone). Minocycline significantly increased the expression of interleukin-1α and β, which are radioprotective, as well as the ones of granulocyte-macrophage colony-stimulating factor and granulocyte colony-stimulating factor, which accelerate neutrophil recovery (p<0.05 versus radiation alone), while suppressing cytokines that could prevent hematopoiesis, e.g. macrophage inf...
The purpose of this study was to determine whether secondary immune responses to lipopolysacchari... more The purpose of this study was to determine whether secondary immune responses to lipopolysaccharide (LPS) were altered by exposure to radiation. C57BL/6 mice were irradiated (60Co, gamma-rays) to 0 or 3 Gray (Gy) and injected intraperitoneally with LPS on days 10 and 42 thereafter. Subsets were euthanized 0-14 days after the second injection for analyses. The data show numerous radiation-induced effects, as well as some significant interactions among radiation, LPS, and day of analysis. Among the most striking were changes in thymus mass, circulating lymphocytes, monocytes, granulocytes, and specific lymphocyte subpopulations, erythrocyte counts, hematocrit, and platelet counts and volume. Spontaneous blastogenesis and oxidative burst capacity of phagocytic cells, however, were relatively normal. The findings indicate that exposure to radiation at a spaceflight relevant dose can influence the distribution of certain leukocyte populations in response to a secondary challenge with LPS.
Lipopolysaccharide (LPS) is a major cause of septic shock and death due to infection with Gram-ne... more Lipopolysaccharide (LPS) is a major cause of septic shock and death due to infection with Gram-negative bacteria. The purpose of this study was to quantify the effects of whole-body irradiation on lymphocyte populations during response to challenge with LPS. C57BL/6 mice (n = 10/group) were irradiated whole-body with 3 gray (Gy) gamma-rays in a single fraction at 0.8 Gy/min. LPS (E. coli serotype 0111:B4) at 1 mg/kg was injected intraperitoneally 10 days later and mice were euthanized at 60 min and days 1, 7, and 14 post-inoculation for analyses. Significant interactions between radiation and LPS were noted in circulating and splenic lymphocyte subpopulations, including T-, B-, and NK-cells, particularly at the early time points. There were significant interactions on circulating, but not splenic, CD62L+ T-cell populations. However, there were no interactions on CD62L+ B-cells. Finally, there were significant interactions in both early and late blastogenic responses. The data suppor...
The major goal of this study was to determine whether radiation significantly alters bone marrow-... more The major goal of this study was to determine whether radiation significantly alters bone marrow-derived cell distribution and mass of sensitive organs after challenge with lipopolysaccharide (LPS). C57BL/6 mice were exposed whole-body to 0 or 3 gray (Gy) gamma-radiation (60Co) and injected intraperitoneally with 0.1 ml saline or 1 mg/kg LPS (E. coli serotype 0111:B4) 10 days later. Subsets from each group were euthanized at 60 min and 1, 7 and 14 days post-injection for analyses. Body mass was low 1 day after LPS, especially in irradiated animals. LPS-induced splenomegaly and hepatomegaly were attenuated by radiation, whereas thymic atrophy was enhanced. However, radiation had no effect on LPS-induced changes in oxygen radical production by liver phagocytes. The numbers of all major leukocyte populations (lymphocytes, monocyte-macrophages, granulocytes) were altered by both radiation and LPS at virtually all time points of testing. In general, the LPS-induced changes in leukocytes ...
The major aim of this study was to quantify long-term changes in bone marrow-derived cell populat... more The major aim of this study was to quantify long-term changes in bone marrow-derived cell populations after exposure to radiations of differing quality. Mice were whole-body irradiated to 2 Gy gamma, proton, carbon or iron radiation, and euthanized approximately 110 days later for immunocyte phenotyping. Splenic lymphocytes and mono/macrophages increased after gamma-rays when compared to 0 Gy and one or more of the other groups. There were high T cells (carbon vs. 0 Gy), high B cells (gamma-rays vs. 0 Gy), and low natural killer (NK) cells (proton and carbon vs. 0 Gy). All radiations, except gamma-rays, increased CD62L+ memory T cell counts, whereas CD62L+ B cells increased only after gamma-rays. There were significant aberrations in many immune parameters nearly 4 months after exposure to various forms of radiation. This suggests radiation exposure can have long-term health consequences.
The heads of Sprague-Dawley rats were irradiated with protons to total doses of 1.5, 3 and 4 Gy a... more The heads of Sprague-Dawley rats were irradiated with protons to total doses of 1.5, 3 and 4 Gy and euthanized 9-10 days later. Significant dose-dependent decreases were noted in thymus mass. Lymphocyte and platelet numbers were significantly reduced in blood. Flow cytometric analysis of blood and spleen showed that CD3+ T, CD3+/CD4+ TH, and CD3+/CD8+ TC cell numbers were low and proportions were significantly altered by radiation. CD4:CD8 ratios and CD45R+ B lymphocytes were unaffected. Spontaneous blastogenesis of blood and spleen leukocytes was significantly increased by radiation. Plasma TGF-beta 1 level in irradiated rats was consistently, but not significantly, higher than in non-irradiated animals. T and B cell proportions in lymph nodes from irradiated animals were similar to non-irradiated controls. Bone marrow from all irradiated groups had high CD90+/Gran+ cell numbers. The data show that head-localized proton irradiation at relatively modest doses can profoundly influenc...
Outside the protection of the terrestrial environment, astronauts on any long-term missions will ... more Outside the protection of the terrestrial environment, astronauts on any long-term missions will unavoidably be exposed to fields of charged particle radiation dominated by protons. These fields and their biological risks are modified in complex ways by the presence of protective shielding. To examine the long-term effects of space-like proton exposures on immune status, we treated female C57BL/6 mice with 3 or 4 Gy of 250 MeV monoenergetic protons or the complex space-like radiation field produced after 250 MeV protons are transported through 15 g x cm(-2) aluminum shielding. The animals were euthanized 122 d post-irradiation and lymphocyte phenotypes, hematological parameters, and lymphocyte blastogenesis were characterized. There were significant dose-dependent decreases in macrophage, CD3+/CD8+ T, NK, platelet, and red blood cell populations, as well as low hematocrit and hemoglobin levels. In contrast, dose-dependent increases in spontaneous, but not mitogen-induced, blastogene...
American journal of physiology. Regulatory, integrative and comparative physiology, 2002
Although the immune system is highly susceptible to radiation-induced damage, consequences of hig... more Although the immune system is highly susceptible to radiation-induced damage, consequences of high linear energy transfer (LET) radiation remain unclear. This study evaluated the effects of 0.1 gray (Gy), 0.5 Gy, and 2.0 Gy iron ion (56Fe(26)) radiation on lymphoid cells and organs of C57BL/6 mice on days 4 and 113 after whole body exposure; a group irradiated with 2.0 Gy silicon ions (28Si) was euthanized on day 113. On day 4 after 56Fe irradiation, dose-dependent decreases were noted in spleen and thymus masses and all major leukocyte populations in blood and spleen. The CD19(+) B lymphocytes were most radiosensitive and NK1.1(+) natural killer (NK) cells were most resistant. CD3(+) T cells were moderately radiosensitive and a greater loss of CD3(+)/CD8(+) T(C) cells than CD3(+)/CD4(+) T(H) cells was noted. Basal DNA synthesis was elevated on day 4, but response to mitogens and secretion of interleukin-2 and tumor necrosis factor-alpha were unaffected. Signs of anemia were noted. ...
American journal of physiology. Regulatory, integrative and comparative physiology, 2000
Spaceflight produces changes in the immune system. The mechanisms for the alterations in immune f... more Spaceflight produces changes in the immune system. The mechanisms for the alterations in immune function after spaceflight remain unclear due in part to the difficulties associated with conducting spaceflight research. The purpose of the following studies, therefore, was to create a ground-based protocol that can reproduce the immunological changes found after spaceflight, i.e., changes in splenic lymphocyte populations. Rats were exposed to either flight aboard the Space Shuttle Endeavor (STS-77) or ground-based simulations of various components of the spaceflight experience. The ground-based mock spaceflight was comprised of exposure to launch and landing loads and unloading of the hindlimbs. In addition, each component of this ground-based mock spaceflight was tested separately. The results were that spaceflight reduced splenic CD4(+) T (helper/inducer) cells and CD11b(+) (neutrophils/macrophages) cells. The ground-based simulations of spaceflight did not reproduce the same patte...
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Papers by Michael Pecaut