RESUMEN
BACKGROUND: The modulating effect of vitamin D on cytokine concentrations in severe coronavirus disease 2019 (COVID-19) remains unknown. OBJECTIVES: We aimed to investigate the effect of a single high dose of vitamin D3 on cytokines, chemokines, and growth factor in hospitalized patients with moderate to severe COVID-19. METHODS: This is a post hoc, ancillary, and exploratory analysis from a multicenter, double-blind, placebo-controlled, randomized clinical trial. Patients with moderate to severe COVID-19 were recruited from 2 hospitals in São Paulo, Brazil. Of 240 randomly assigned patients, 200 were assessed in this study and randomly assigned to receive a single oral dose of 200,000 IU vitamin D3 (n = 101) or placebo (n = 99). The primary outcome was hospital length of stay, which has been published in our previous study. The prespecified secondary outcomes were serum concentrations of IL-1ß, IL-6, IL-10, TNF-α, and 25-hydroxyvitamin D. The post hoc exploratory secondary outcomes were IL-4, IL-12p70, IL-17A, IFN-γ, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-8, IFN-inducible protein-10 (IP-10), macrophage inflammatory protein-1ß (MIP-1ß), monocyte chemoattractant protein-1 (MCP-1), vascular endothelial growth factor (VEGF), and leukocyte count. Generalized estimating equations for repeated measures, with Bonferroni's adjustment, were used for testing all outcomes. RESULTS: The study included 200 patients with a mean ± SD age of 55.5 ± 14.3 y and BMI of 32.2 ± 7.1 kg/m2, of which 109 (54.5%) were male. GM-CSF concentrations showed a significant group-by-time interaction effect (P = 0.04), although the between-group difference at postintervention after Bonferroni's adjustment was not significant. No significant effects were observed for the other outcomes. CONCLUSIONS: The findings do not support the use of a single dose of 200,000 IU vitamin D3, compared with placebo, for the improvement of cytokines, chemokines, and growth factor in hospitalized patients with moderate to severe COVID-19.This trial was registered at clinicaltrials.gov as NCT04449718.
Asunto(s)
Tratamiento Farmacológico de COVID-19 , Quimiocinas/efectos de los fármacos , Colecalciferol/administración & dosificación , Citocinas/efectos de los fármacos , Factor Estimulante de Colonias de Granulocitos y Macrófagos/efectos de los fármacos , Factor A de Crecimiento Endotelial Vascular/efectos de los fármacos , Vitaminas/administración & dosificación , Adulto , Anciano , Brasil , COVID-19/inmunología , Método Doble Ciego , Femenino , Humanos , Péptidos y Proteínas de Señalización Intercelular/sangre , Masculino , Persona de Mediana Edad , SARS-CoV-2/inmunologíaRESUMEN
UNLABELLED: Eosinophilic nasosinusal polyposis is a chronic inflammatory infection with elevated infiltration of eosinophils, which presents high rate of recurrence after surgical treatment. The continuous inflammatory process that leads to the formation of polyps requires constant clinical treatment. Contributing to the maintenance of eosinophilia are cytokines IL5 (interleukin-5) and GM-CSF (granulocyte macrophages colony-stimulating factor), which show up in elevated concentrations. These oligoproteins diminish the rate of apoptosis and prolong the survival of eosinophils. AIM: By diminishing these cytokines, the action of Mitomycin C (MMC), an antineoplastic drug which inhibits the synthesis of DNA, was studied. In a recent study the power of this drug to cause apoptosis in eosinophils, in vitro, of nasal polyps was verified. METHODOLOGY: A biopsy of the nasal polyps was undertaken in 15 patients carriers of eosinophilic nasosinusal polyposis 24 hours after applying 0.5 mg/ml of MMC during five minutes. RT-PCR (reverse transcription of polymerase chain reaction) for IL5 and GM-CSF was the method used to obtain the results. RESULTS: The comparison of the results of GM-CSF pre- and post-application of MMC, when the paired T-test was used, showed p=0.041 and for IL5 we found p<0.001. CONCLUSION: Topic use of MMC in patients with eosinophilic nasosinusal polyposis shows statistically significant reduction for GM-CSF and significant and important reduction for IL5.
Asunto(s)
Eosinofilia/tratamiento farmacológico , Factor Estimulante de Colonias de Granulocitos y Macrófagos/efectos de los fármacos , Interleucina-5/metabolismo , Mitomicina/uso terapéutico , Pólipos Nasales/tratamiento farmacológico , Inhibidores de la Síntesis del Ácido Nucleico/uso terapéutico , Adulto , Eosinofilia/metabolismo , Eosinófilos/efectos de los fármacos , Eosinófilos/metabolismo , Femenino , Factor Estimulante de Colonias de Granulocitos y Macrófagos/metabolismo , Humanos , Masculino , Persona de Mediana Edad , Pólipos Nasales/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factores de TiempoRESUMEN
Megakaryopoiesis and platelet production are driven by transcription factors and cytokines present in bone marrow environment. Essential thrombocythemia (ET) is a chronic myeloproliferative disorder characterized by high platelet count and megakaryocytic hyperplasia. In the present work we evaluated plasmatic levels of cytokines involved in megakaryocytic development in a group of patients with ET that were not on treatment, as well as thrombopoietin (TPO) levels before and during anagrelide treatment. The assays were carried out using ELISA techniques. Among the cytokines mainly involved in proliferation of megakaryocytic progenitors, interleukin 3 (IL-3) levels were found increased in patients compared to normal controls (p = 0.0383). Granulocyte-macrophage colony stimulating factor and stem cell factor levels were normal. Interleukin 6, as well as interleukin 11 and erythropoietin (EPO), cytokines mainly related to megakaryocytic maturation, were normal. Plasma TPO levels before treatment were within the normal range and increased during treatment but the difference was not statistically significant. Patients who displayed spontaneous platelet aggregation had higher plasma TPO levels compared to those who did not (p = 0.049). We did not find any relationship between cytokine levels and clinical or laboratory parameters. The high IL-3 levels seen in some patients with ET could contribute to megakaryocytic proliferation. The simultaneous occurrence of higher TPO levels and elevated platelet count could be a predisposing factor for the development of spontaneous platelet aggregation in ET patients.
Asunto(s)
Megacariocitos/fisiología , Trombocitemia Esencial/sangre , Trombopoyesis/fisiología , Trombopoyetina/sangre , Ensayo de Inmunoadsorción Enzimática , Factor Estimulante de Colonias de Granulocitos y Macrófagos/sangre , Factor Estimulante de Colonias de Granulocitos y Macrófagos/efectos de los fármacos , Humanos , Interleucina-3/sangre , Megacariocitos/efectos de los fármacos , Agregación Plaquetaria/efectos de los fármacos , Agregación Plaquetaria/fisiología , Inhibidores de Agregación Plaquetaria/uso terapéutico , Quinazolinas/uso terapéutico , Estudios Retrospectivos , Estadísticas no Paramétricas , Factor de Células Madre/sangre , Factor de Células Madre/efectos de los fármacos , Trombocitemia Esencial/tratamiento farmacológico , Trombocitosis/inducido químicamente , Trombopoyesis/efectos de los fármacos , Trombopoyetina/efectos de los fármacosRESUMEN
La megacariocitopoyesis y la producción de plaquetas están regidas por factores de transcripción y citoquinas presentes en el microambiente medular. La trombocitemia esencial (TE) es una enfermedad mieloproliferativa crónica caracterizada por aumento del recuento de plaquetas e hiperplasia megacariocítica. En el presente trabajo se evaluaron los niveles de las citoquinas que participan en el desarrollo megacariocítico en plasma de pacientes con TE que se encontraban sin tratamiento y los de trombopoyetina (TPO) antes y durante el tratamiento con anagrelide. Las determinaciones se realizaron por técnica de ELISA. Dentro de las citoquinas involucradas en la etapa de proliferación, los niveles de interleuquina 3 (IL-3) se encontraron aumentados en los pacientes (p=0.0383) respecto al grupo control. Los niveles de factor estimulante de colonias granulocito-macrofágico y stem cell factor fueron normales. Dentro de las citoquinas con acción sobre la maduración megacariocítica, tanto la interleuquina 6 como la interleuquina 11 y la eritropoyetina estuvieron normales. Los niveles de TPO antes del tratamiento no difirieron del grupo control y durante el tratamiento aumentaron de manera no significativa. Los pacientes que presentaron agregación espontánea tuvieron niveles más altos de TPO que los que no lo hicieron (p=0.049). Los niveles de las citoquinas no tuvieron relación con ninguno de los parámetros clínicos ni de laboratorio evaluados. El aumento de los niveles de IL-3 podría contribuir al incremento en la proliferación megacariocítica en este grupo. La presencia simultánea de niveles más altos de TPO y trombocitosis sería un factor predisponente para la ocurrencia de agregación espontánea en los pacientes con TE (AU)
Megakaryopoiesis and platelet production are driven by transcription factors and cytokines present in bone marrow environment. Essential thrombocythemia (ET) is a chronic myeloproliferative disorder characterized by high platelet count and megakaryocytic hyperplasia. In the present work we evaluated plasmatic levels of cytokines involved in megakaryocytic development in a group of patients with ET that were not on treatment, as well as thrombopoietin (TPO) levels before and during anagrelide treatment. The assays were carried out using ELISA techniques. Among the cytokines mainly involved in proliferation of megakaryocytic progenitors, interleukin 3 (IL-3) levels were found increased in patients compared to normal controls (p=0.0383). Granulocyte-macrophage colony stimulating factor and stem cell factor levels were normal. Interleukin 6, as well as interleukin 11 and erythropoietin (EPO), cytokines mainly related to megakaryocytic maturation, were normal. Plasma TPO levels before treatment were within the normal range and increased during treatment but the difference was not statistically significant. Patients who displayed spontaneous platelet aggregation had higher plasma TPO levels compared to those who did not (p=0.049). We did not find any relationship between cytokine levels and clinical or laboratory parameters. The high IL-3 levels seen in some patients with ET could contribute to megakaryocytic proliferation. The simultaneous occurrence of higher TPO levels and elevated platelet count could be a predisposing factor for the development of spontaneous platelet aggregation in ET patients(AU)
Asunto(s)
Humanos , Megacariocitos/fisiología , Hematopoyesis/fisiología , Trombopoyetina/sangre , Trombocitemia Esencial/sangre , Megacariocitos/efectos de los fármacos , Hematopoyesis/efectos de los fármacos , Trombopoyetina/efectos de los fármacos , Interleucina-3/sangre , Trombocitemia Esencial/tratamiento farmacológico , Factor Estimulante de Colonias de Granulocitos y Macrófagos/sangre , Factor Estimulante de Colonias de Granulocitos y Macrófagos/efectos de los fármacos , Factor de Células Madre/sangre , Factor de Células Madre/efectos de los fármacos , Quinazolinas/uso terapéutico , Inhibidores de Agregación Plaquetaria/uso terapéutico , Trombocitosis/inducido químicamente , Agregación Plaquetaria/efectos de los fármacos , Agregación Plaquetaria/fisiología , Ensayo de Inmunoadsorción Enzimática , Estudios Retrospectivos , Estadísticas no ParamétricasRESUMEN
La megacariocitopoyesis y la producción de plaquetas están regidas por factores de transcripción y citoquinas presentes en el microambiente medular. La trombocitemia esencial (TE) es una enfermedad mieloproliferativa crónica caracterizada por aumento del recuento de plaquetas e hiperplasia megacariocítica. En el presente trabajo se evaluaron los niveles de las citoquinas que participan en el desarrollo megacariocítico en plasma de pacientes con TE que se encontraban sin tratamiento y los de trombopoyetina (TPO) antes y durante el tratamiento con anagrelide. Las determinaciones se realizaron por técnica de ELISA. Dentro de las citoquinas involucradas en la etapa de proliferación, los niveles de interleuquina 3 (IL-3) se encontraron aumentados en los pacientes (p=0.0383) respecto al grupo control. Los niveles de factor estimulante de colonias granulocito-macrofágico y stem cell factor fueron normales. Dentro de las citoquinas con acción sobre la maduración megacariocítica, tanto la interleuquina 6 como la interleuquina 11 y la eritropoyetina estuvieron normales. Los niveles de TPO antes del tratamiento no difirieron del grupo control y durante el tratamiento aumentaron de manera no significativa. Los pacientes que presentaron agregación espontánea tuvieron niveles más altos de TPO que los que no lo hicieron (p=0.049). Los niveles de las citoquinas no tuvieron relación con ninguno de los parámetros clínicos ni de laboratorio evaluados. El aumento de los niveles de IL-3 podría contribuir al incremento en la proliferación megacariocítica en este grupo. La presencia simultánea de niveles más altos de TPO y trombocitosis sería un factor predisponente para la ocurrencia de agregación espontánea en los pacientes con TE
Megakaryopoiesis and platelet production are driven by transcription factors and cytokines present in bone marrow environment. Essential thrombocythemia (ET) is a chronic myeloproliferative disorder characterized by high platelet count and megakaryocytic hyperplasia. In the present work we evaluated plasmatic levels of cytokines involved in megakaryocytic development in a group of patients with ET that were not on treatment, as well as thrombopoietin (TPO) levels before and during anagrelide treatment. The assays were carried out using ELISA techniques. Among the cytokines mainly involved in proliferation of megakaryocytic progenitors, interleukin 3 (IL-3) levels were found increased in patients compared to normal controls (p=0.0383). Granulocyte-macrophage colony stimulating factor and stem cell factor levels were normal. Interleukin 6, as well as interleukin 11 and erythropoietin (EPO), cytokines mainly related to megakaryocytic maturation, were normal. Plasma TPO levels before treatment were within the normal range and increased during treatment but the difference was not statistically significant. Patients who displayed spontaneous platelet aggregation had higher plasma TPO levels compared to those who did not (p=0.049). We did not find any relationship between cytokine levels and clinical or laboratory parameters. The high IL-3 levels seen in some patients with ET could contribute to megakaryocytic proliferation. The simultaneous occurrence of higher TPO levels and elevated platelet count could be a predisposing factor for the development of spontaneous platelet aggregation in ET patients
Asunto(s)
Humanos , Hematopoyesis/fisiología , Megacariocitos/fisiología , Trombocitemia Esencial/sangre , Trombopoyetina/sangre , Ensayo de Inmunoadsorción Enzimática , Factor Estimulante de Colonias de Granulocitos y Macrófagos/sangre , Factor Estimulante de Colonias de Granulocitos y Macrófagos/efectos de los fármacos , Hematopoyesis/efectos de los fármacos , /sangre , Megacariocitos/efectos de los fármacos , Inhibidores de Agregación Plaquetaria/uso terapéutico , Agregación Plaquetaria/efectos de los fármacos , Agregación Plaquetaria/fisiología , Quinazolinas/uso terapéutico , Estudios Retrospectivos , Estadísticas no Paramétricas , Factor de Células Madre/sangre , Factor de Células Madre/efectos de los fármacos , Trombocitemia Esencial/tratamiento farmacológico , Trombocitosis/inducido químicamente , Trombopoyetina/efectos de los fármacosRESUMEN
La megacariocitopoyesis y la producción de plaquetas están regidas por factores de transcripción y citoquinas presentes en el microambiente medular. La trombocitemia esencial (TE) es una enfermedad mieloproliferativa crónica caracterizada por aumento del recuento de plaquetas e hiperplasia megacariocítica. En el presente trabajo se evaluaron los niveles de las citoquinas que participan en el desarrollo megacariocítico en plasma de pacientes con TE que se encontraban sin tratamiento y los de trombopoyetina (TPO) antes y durante el tratamiento con anagrelide. Las determinaciones se realizaron por técnica de ELISA. Dentro de las citoquinas involucradas en la etapa de proliferación, los niveles de interleuquina 3 (IL-3) se encontraron aumentados en los pacientes (p=0.0383) respecto al grupo control. Los niveles de factor estimulante de colonias granulocito-macrofágico y stem cell factor fueron normales. Dentro de las citoquinas con acción sobre la maduración megacariocítica, tanto la interleuquina 6 como la interleuquina 11 y la eritropoyetina estuvieron normales. Los niveles de TPO antes del tratamiento no difirieron del grupo control y durante el tratamiento aumentaron de manera no significativa. Los pacientes que presentaron agregación espontánea tuvieron niveles más altos de TPO que los que no lo hicieron (p=0.049). Los niveles de las citoquinas no tuvieron relación con ninguno de los parámetros clínicos ni de laboratorio evaluados. El aumento de los niveles de IL-3 podría contribuir al incremento en la proliferación megacariocítica en este grupo. La presencia simultánea de niveles más altos de TPO y trombocitosis sería un factor predisponente para la ocurrencia de agregación espontánea en los pacientes con TE (AU)
Megakaryopoiesis and platelet production are driven by transcription factors and cytokines present in bone marrow environment. Essential thrombocythemia (ET) is a chronic myeloproliferative disorder characterized by high platelet count and megakaryocytic hyperplasia. In the present work we evaluated plasmatic levels of cytokines involved in megakaryocytic development in a group of patients with ET that were not on treatment, as well as thrombopoietin (TPO) levels before and during anagrelide treatment. The assays were carried out using ELISA techniques. Among the cytokines mainly involved in proliferation of megakaryocytic progenitors, interleukin 3 (IL-3) levels were found increased in patients compared to normal controls (p=0.0383). Granulocyte-macrophage colony stimulating factor and stem cell factor levels were normal. Interleukin 6, as well as interleukin 11 and erythropoietin (EPO), cytokines mainly related to megakaryocytic maturation, were normal. Plasma TPO levels before treatment were within the normal range and increased during treatment but the difference was not statistically significant. Patients who displayed spontaneous platelet aggregation had higher plasma TPO levels compared to those who did not (p=0.049). We did not find any relationship between cytokine levels and clinical or laboratory parameters. The high IL-3 levels seen in some patients with ET could contribute to megakaryocytic proliferation. The simultaneous occurrence of higher TPO levels and elevated platelet count could be a predisposing factor for the development of spontaneous platelet aggregation in ET patients(AU)
Asunto(s)
Humanos , Megacariocitos/fisiología , Hematopoyesis/fisiología , Trombopoyetina/sangre , Trombocitemia Esencial/sangre , Megacariocitos/efectos de los fármacos , Hematopoyesis/efectos de los fármacos , Trombopoyetina/efectos de los fármacos , Interleucina-3/sangre , Trombocitemia Esencial/tratamiento farmacológico , Factor Estimulante de Colonias de Granulocitos y Macrófagos/sangre , Factor Estimulante de Colonias de Granulocitos y Macrófagos/efectos de los fármacos , Factor de Células Madre/sangre , Factor de Células Madre/efectos de los fármacos , Quinazolinas/uso terapéutico , Inhibidores de Agregación Plaquetaria/uso terapéutico , Trombocitosis/inducido químicamente , Agregación Plaquetaria/efectos de los fármacos , Agregación Plaquetaria/fisiología , Ensayo de Inmunoadsorción Enzimática , Estudios Retrospectivos , Estadísticas no ParamétricasRESUMEN
Chlorella vulgaris extract (CVE) was examined for its effects on the Ehrlich ascites tumor-induced suppression in the numbers of bone marrow and spleen granulocyte-macrophage progenitor cells (CFU-GM) in mice. No effects on bone marrow and spleen CFU-GM, as compared to controls, were observed in normal mice given 50, 100 and 200 mg/kg CVE orally for 5 days. In tumor-bearing mice, myelosuppression concomitant with increased number of spleen CFU-GM were observed. The number of CFU-GM in the bone marrow was restored to control levels after the administration of CVE (50, 100 and 200 mg/kg) to tumor-bearing mice, and a slight reduction in spleen colony formation was observed in these animals. In addition, CVE significantly prolonged the survival of mice inoculated with the Ehrlich ascites tumor. These results suggest a protective antitumor effect of CVE which might be attributable, at least in part, to the stimulation of the production and, possibly, maturation of granulocytes and macrophages.
Asunto(s)
Células de la Médula Ósea/efectos de los fármacos , Carcinoma de Ehrlich/inmunología , Chlorella , Factor Estimulante de Colonias de Granulocitos y Macrófagos/efectos de los fármacos , Células Madre Hematopoyéticas/efectos de los fármacos , Leucopoyesis/efectos de los fármacos , Extractos Vegetales/farmacología , Administración Oral , Animales , Células Cultivadas , Ensayo de Unidades Formadoras de Colonias , Vida Libre de Gérmenes , Hematopoyesis Extramedular/efectos de los fármacos , Inyecciones Intraperitoneales , Masculino , Ratones , Ratones Endogámicos BALB C , Trasplante de Neoplasias , Extractos Vegetales/análisis , Proteínas Recombinantes , Bazo/citología , Tasa de SupervivenciaRESUMEN
In this study we have investigated the effects of Petiveria alliacea on the hematopoietic response of mice infected with Listeria monocytogenes. Our results demonstrate a protective effect of the crude extract of P. alliacea since the survival of the treated/infected was higher than that in the infected group. Moreover, the number of granulocyte/macrophage colonies (CFU-GM) and the serum colony stimulating activity levels were increased in the treated/infected mice in relation to the infected group. These results suggest an immunomodulation of Petiveria alliacea extract on hematopoiesis, which may be responsible, at least in part, for the increased resistance of mice to Listeria monocytogenes infection.
Asunto(s)
Allium/química , Células de la Médula Ósea/efectos de los fármacos , Listeria monocytogenes/efectos de los fármacos , Listeriosis/prevención & control , Extractos Vegetales/uso terapéutico , Células Madre/efectos de los fármacos , Animales , Células de la Médula Ósea/microbiología , Diferenciación Celular/efectos de los fármacos , Ensayo de Unidades Formadoras de Colonias , Factor Estimulante de Colonias de Granulocitos y Macrófagos/efectos de los fármacos , Granulocitos/efectos de los fármacos , Granulocitos/microbiología , Macrófagos/efectos de los fármacos , Macrófagos/microbiología , Masculino , Ratones , Ratones Endogámicos BALB C , Extractos Vegetales/toxicidad , Células Madre/microbiologíaRESUMEN
1. The effects of deltamethrin on mouse bone marrow and spleen progenitor cell responsiveness to granulocyte and macrophage colony-stimulating factors (CSFs) were evaluated. 2. Deltamethrin (1-5 mg/kg) was administered four times subcutaneously on alternate days for one week to male BALB/c mice, 5-8 weeks old (N = 6 mice/group), raised under pathogen-free conditions and maintained in conventional animal rooms for four weeks before use. Soft agar colony formation (CFU-C), marrow and spleen cell counts as well as body, spleen and thymus weights were determined. 3. Although treatment with the lowest dose (1 mg kg-1 48 h-1) produced no significant effect on CFU-C, the administration of 3 and 5 mg kg-1 48 h-1 caused a more than two-fold increase in the formation of granulocyte and macrophage colonies in the marrow, but not in the spleen (control value = 100.5 +/- 12 for N = 6). Colony numbers returned to normal values within five days after the end of deltamethrin administration. 4. No changes were observed in the total (range: 1-3 x 10(8) per spleen) and differential marrow and spleen cell counts, nor was there any alteration in spleen weight. However, treatment with the three doses resulted in a dramatic reduction in thymus weight. 5. These effects were not due to the liberation of endotoxin, because if endotoxin had been present it would have been < 0.060 ng/ml, a concentration that would not have a biological effect. 6. In vitro addition of 0.10 to 10 microM deltamethrin to marrow cell cultures obtained from untreated mice did not induce any response. 7. These data indicate that the CSF-driven granulocyte and macrophage development provides a useful model for the study of the effects of toxicants on myelopoiesis.
Asunto(s)
Células de la Médula Ósea , Células Madre Hematopoyéticas/efectos de los fármacos , Piretrinas/toxicidad , Bazo/citología , Animales , Médula Ósea/efectos de los fármacos , Diferenciación Celular/efectos de los fármacos , División Celular/efectos de los fármacos , Factor Estimulante de Colonias de Granulocitos y Macrófagos/efectos de los fármacos , Factor Estimulante de Colonias de Macrófagos/efectos de los fármacos , Masculino , Ratones , Nitrilos , Tamaño de los Órganos/efectos de los fármacos , Piretrinas/administración & dosificación , Bazo/efectos de los fármacosRESUMEN
1. The effects of deltamethrin on mouse bone marrow and spleen progenitor cell responsiveness to granulocyte and macrophage colony-stimulating factors (CSFs) were evaluated. 2. Deltamethrin (1-5 mg/kg) was administered four times subcutaneously on alternate days for one week to male BALB/c mice, 5-8 weeks old (N = 6 mice/group), raised under pathogen-free conditions and maintained in conventional animal rooms for four weeks before use. Soft agar colony formation (CFU-C), marrow and spleen cell counts as well as body, spleen and thymus weights were determined. 3. Although treatment with the lowest dose (1 mg kg-1 48 h-1) produced no significant effect on CFU-C, the administration of 3 and 5 mg kg-1 48 h-1 caused a more than two-fold increase in the formation of granulocyte and macrophage colonies in the marrow, but not in the spleen (control value = 100.5 +/- 12 for N = 6). Colony numbers returned to normal values within five days after the end of deltamethrin administration. 4. No changes were observed in the total (range: 1-3 x 10(8) per spleen) and differential marrow and spleen cell counts, nor was there any alteration in spleen weight. However, treatment with the three doses resulted in a dramatic reduction in thymus weight. 5. These effects were not due to the liberation of endotoxin, because if endotoxin had been present it would have been < 0.060 ng/ml, a concentration that would not have a biological effect. 6. In vitro addition of 0.10 to 10 microM deltamethrin to marrow cell cultures obtained from untreated mice did not induce any response. 7. These data indicate that the CSF-driven granulocyte and macrophage development provides a useful model for the study of the effects of toxicants on myelopoiesis