Evaluation of neutrophil oxidative metabolism in canine monocytic ehrlichiosis.

BACKGROUND: Canine monocytic ehrlichiosis (CME) is a tick-borne disease caused by Ehrlichia canis, a rickettsia that infects the monocytes of dogs. This infection can result in a chronic and life-threatening disease. Thrombocytopenia, mild anemia, and leukopenia are the most common hematologic findings in CME. OBJECTIVE: To investigate the role of peripheral blood neutrophils in CME, an evaluation was conducted of their functional state during the acute phase of the disease in dogs experimentally infected by E canis. METHODS: Seven dogs were inoculated with E canis, and 3 remained as uninfected controls. All dogs had physical exams and hematologic tests (CBC and nitroblue tetrazolium [NBT] reduction) during a 6-week period. RESULTS: There was no difference (P > .05) in spontaneous NBT reduction results between the 2 groups of dogs throughout the 6-week period of observation. Nevertheless, when stimulated, the neutrophils showed higher activity in the infected group (P = .01) on weeks 4 and 5 after infection. CONCLUSION: Infection by E canis has no influence on neutrophil oxidative metabolism even though during the remission period of the acute phase of the disease, the neutrophils seem to be more reactive under stimulation.

Cohabitation with a sick cage mate: consequences on behavior and on ehrlich tumor growth.

The present study analyzed the effects of cohabitation for 11 days with a sick cage mate on behavior and Ehrlich tumor growth in mice. Pairs of female mice were divided into one control and one experimental group. One mouse of each control pair was kept undisturbed and called 'healthy companion' (HC). One animal of each experimental pair of mice was inoculated (i.p.) with 5 x 10(6) Ehrlich tumor cells, and the other, the object of this study, was called 'sick companion' (SC). The SC mice presented: (1) increased activity in an open field, (2) increased number of entries and of movements within the plus-maze open arms, (3) similar levels of plus-maze closed-arm exploration, (4) a decrease in the exploratory activity in a hole board, (5) a decrease in the number of white but not red blood cells, and (6) similar corticosterone serum levels. Eleven days after cohabitation with a conspecific, HC and SC mice were injected with 5 x10(6) Ehrlich tumor cells. Results showed that SC animals presented decreased resistance to the ascitic form of the Ehrlich tumor. The observed data provide experimental evidence that psychosocial stress induced by cohabitation with a sick cage mate changed at the same time some behavioral and physiological parameters, and decreased resistance to Ehrlich tumor. These data are discussed in the light of a possible neuroimmune system interaction.

Effects of acute and long-term diazepam administrations on neutrophil activity: a flow cytometric study.

This study analyzed the effects of acute and long-term diazepam treatments on rat peripheral blood neutrophil activity and cortisol serum levels. Rats were acutely and long-term (21 days, once daily) treated with diazepam (10 mg/kg) or its vehicle (1.0 ml/kg). Blood was collected 1 h after treatments for flow cytometric analysis of neutrophil oxidative burst and phagocytosis. Corticosterone and diazepam concentrations were also determined. Results showed that: (1) both diazepam treatments increased lipopolysaccharide (LPS) and phorbol myristate acetate (PMA)-induced neutrophil oxidative burst; (2) the increase in oxidative burst after Staphylococcus aureus induction in acutely treated animals was higher than that observed after long-term treatment; (3) phagocytosis is increased by acute diazepam treatment and decreased by a long-term regimen; (4) acute, but not long-term, diazepam treatment increased corticosterone levels; (5) diazepam plasmatic levels after acute and long-term treatments were not different. These results indicate the development of tolerance to diazepam effects on corticosterone serum levels but not on neutrophil activity.

Effects of in ovo and acute diazepam treatments on peripheral benzodiazepine receptors and cutaneous basophil hypersensitivity in chickens.

Prenatal diazepam treatment impairs immune responses in mammals, but chicken embryos allow experimental manipulation isolated from maternal influences on embryo development. In ovodiazepam treatment in chickens decreased macrophage spreading and phagocytosis. In the present experiment, we investigated the effects of in ovoand/or acute diazepam treatments on phytohemagglutinin (PHA)-induced cutaneous basophil hypersensitivity (CBH) response in chickens. Forty day-old chickens, treated in ovo with 8 mg diazepam/kg, 2 ml diazepam vehicle/kg, or sham-manipulated. were subsequently treated po with 2 mg diazepam/kg or with diazepam's vehicle 1 h before PHA injection. The existence of an interaction between diazepam treatments was shown. Birds acutely treated with diazepam exhibited an increment in CBH response. In contrast, in ovo diazepam treatment per se did no change animals' response to PHA, but antagonized acute diazepam effects on CBH response. The results occurred through direct and/or indirect action of diazepam on cytokine and/or glucocorticoid hormone production and release. In the former case, the effects might be related to stimulation of peripheral benzodiazepine receptors (PBR) on immune cells, thus changing the cytokine cascade, while in the latter instance they might be mediated through glucocorticoid hormones via PBR stimulation in the adrenal gland cells.