In vitro effect of diacetoxyscirpenol and deoxynivalenol on microbicidal activity of murine peritoneal macrophages.

Diacetoxyscirpenol and deoxynivalenol, two trichothecene mycotoxins shown previously to exert immunosuppressive effects on the immune system were examined for their in vitro effects on some functions of murine peritoneal macrophages. The cells were pre-incubated for 4 hr with the mycotoxin concentrations of 0.1 ng/ml-1 micrograms/ml. At concentrations that did not affect the cell viability (Specific Lactate Dehydrogenase test), diacetoxyscirpenol and deoxynivalenol suppress microbicidal activity of phagocytic cells. The diacetoxyscirpenol concentrations, which reduce phagocytosis (2 ng/ml), microbicidal activity (1 ng/ml), superoxide anion production (1 ng/ml) and phagosome-lysosome fusion (0.1 ng/ml), indicate that the inhibition of killing mechanism arise from both oxidative and non-oxidative pathways. Phagocytosis, microbicidal activity and superoxide anion production are inhibited by deoxynivalenol at 1 ng/ml whereas phagosome-lysosome fusion is reduce above 100 ng/ml. These results suggest that microbicidal activity inhibition by deoxynivalenol did not depend on non-oxidative pathway (phagosome-lysosome fusion) impairment.

Patulin production by Penicillium granulatum and inhibition of ruminal flora.

The maximum patulin production by Penicillium granulatum was obtained during the 16th day of culture at 26 degrees C (2.9 g/L) on liquid Czapek medium (+ 8 p. 1000 glucose), followed by 32 degrees C after 24 days and 20 degrees C after 32 days. At 26 degrees C patulin production was maximum before the greatest rate of sporulation when the pH of the medium was about 4. Toxin production was studied by anaerobic culture for 75 days and then the cultures were exposed to ambient air. P. granulatum did not produce its toxin under anaerobic conditions. An in vitro fermentation model with rumen liquor was used, and within 4 hr acetic acid production declined and dose-dependent protein synthesis was inhibited with 20, 100, and 300 microgram patulin/mL rumen liquid.

Interactions between neuropeptides and dexamethasone on the mitogenic response of rabbit spleen lymphocytes.

The interactions between vasoactive intestinal peptide (VIP), substance P (SP), a somatostatin analog (SMS 201-995) and dexamethasone have been investigated on the Con A mitogenic response of rabbit spleen cells. The neuropeptide regulatory effects appeared to be time dependent: when added with the Con A mitogen, they inhibited (VIP) or did not modulate (SMS and SP) the rabbit lymphocyte proliferation and did not change the inhibitory effect induced by a dexamethasone preincubation. When added 18 h before the mitogen, they all induced an increase of the proliferative response at high concentration. The mitogenic response observed when adding dexamethasone to lymphocytes previously preincubated in the presence of neuropeptides was not different from control response except with SMS 10(-10) M. The similar lymphocyte responses obtained whatever the neuropeptide suggested that the immunomodulatory effect induced by a neuropeptide preincubation might be mediated by the induction of common effector(s).

Dual effect of vasoactive intestinal peptide on the mitogenic response of rabbit spleen lymphocytes.

The effects of vasoactive intestinal peptide (VIP) have been investigated on the mitogenic response of rabbit spleen cells. Specific binding of 125I-VIP to these mononuclear cells is rapid and saturable. Analysis of binding reveals two classes of binding sites, a class of high-affinity binding sites with KD = 0.93 +/- 0.11 nM and maximal binding capacity of 2000 +/- 560 sites/cell, and a class of low-affinity binding sites with KD = 225 +/- 58 nM and maximal binding capacity of 280,000 +/- 60,000 sites/cell. The VIP regulatory effect on mitogen-stimulated rabbit spleen cell proliferation appears to be time dependent and bimodal. When VIP was added simultaneously with mitogens, it induced an inhibition of the proliferative response. With concanavalin A (Con A) or pokeweed mitogen (PWM), addition of 10(-8) M VIP resulted in a maximal 30% inhibition of [3H]thymidine incorporation after 96 h of culture. This inhibitory effect was significant at concentrations from 10(-8)-10(-6) M and half-maximal inhibition was obtained with 1.2 x 10(-9) M VIP. By contrast, when rabbit spleen cells were preincubated for 18 h with VIP alone, the lymphocyte proliferative response to Con A was increased. However, this increase was mitogen-selective, since it was only observed when the T-cell mitogen Con A was used. The maximal response was obtained after 96 h of culture in the presence of Con A. The VIP stimulatory effect was dose-dependent with a maximal effect at 10(-7) M and a half-maximal effect at 1.7 x 10(-9) M VIP. The effect of VIP was also time-dependent, since a 6 h preincubation was sufficient to induce a significant increase in the proliferative response which was maximal after an 18 h preincubation.

Effect of patulin on microbicidal activity of mouse peritoneal macrophages.

Patulin, a fungal metabolite shown previously to exert immunosuppressive effects on the cellular and humoral immune systems, was examined for its in vitro effects on some functions of murine peritoneal macrophages. The cells were pre-incubated for 2 hr with mycotoxin concentrations of 0.01-2 micrograms/ml. Phagocytosis and phagosome-lysosome fusion were diminished above 0.1 microgram patulin/ml and lysosomal enzymes and microbicidal activity above 0.5 microgram/ml, whereas O2- production was inhibited only above 2 micrograms/ml. This indicated that the killing mechanism did not depend on products of the oxidative burst. The concentrations used did not decrease the cell viability. Under natural circumstances, patulin may constitute a health risk for animals.

[Immunopharmacologic study in mice of 2 beta-1, 3, beta-1, 6 polysaccharides (scleroglucan and PSAT) on the activation of macrophages and T lymphocytes]. / Etude immunopharmacologique chez la souris de deux polysaccharides beta 1-3, beta 1-6 (scléroglucane et PSAT) sur l'activation des macrophages et des lymphocytes T et B.

The immunopotentiating activity and mechanisms of PSAT and scleroglucan, two beta 1-3, beta 1-6 glucan, were investigated in mice: these polysaccharides increase the chemiluminescence of peritoneal phagocytes and the serum C3 level. Augmentation of DNA synthesis of spleen cells was induced in vivo by injecting PSAT or scleroglucan. An additional proliferative effect of these polysaccharides was observed when spleen cells were incubated with mitogens. Moreover, PSAT enhances the number of Thy1 lymphocytes and increases the ratio of lymphocytes L3T4/Lyt2 in mice infected with Toxoplasma gondii. No significant changes in immunoglobulin levels were found. These data indicate that PSAT and scleroglucan favorably affect the non-specific host defense and cellular immune response in mice.

Enhancing resistance and modulation of humoral immune response to experimental Candida albicans infection by patulin.

Mice receiving patulin (10 mg/kg) from 1 to 4 days showed enhancing resistance to intraperitoneal challenge with 10(8) viable Candida albicans at day 2. Resistance to C. albicans infection (10(6) blastospores) appeared to be unchanged after cyclophosphamide oral administration (60 mg/kg). Immunoglobulins levels (IgA, IgM, IgG) are marked depressed (10 to 75%) in mice infected and/or treated by patulin and cyclophosphamide. The results show that an increase of neutrophil count may be among the factor underlying the late increase in resistance to C. albicans after administration of patulin.

Patulin immunotoxicology: effect on phagocyte activation and the cellular and humoral immune system of mice and rabbits.

Patulin is a mycotoxin frequently found in rotten apples or molded corn. We have investigated the effect of sublethal doses of patulin on the immune system in mice and rabbits. A significant suppression of the chemiluminescence response of peritoneal leucocytes was observed in both species. Mouse spleen lymphocytes showed a decrease in absolute number, most pronounced for the B-cell population whereas the Ts population showed a relative increase after patulin treatment. The mitogenic response to PHA, Con A and, in particular, PWM was also depressed by patulin. This was paralleled by decreasing serum immunoglobulin levels in the mice and rabbits. The immunosuppressive effect of patulin is reversible and is probably due to interaction with cellular free SH groups since the action of patulin can be circumvented, at least partially, by the prior administration of cystein. Under natural circumstances, patulin may constitute a health risk for animals.

[Enhancement of resistance of mice Toxoplasma gondii by 2 polysaccharides beta 1-3, beta 1-6 (PSAT and Scleroglucan)]. / Augmentation de la résistance des souris à Toxoplasma gondii par deux polysaccharides beta 1-3, beta 1-6 (le PSAT et le Scléroglucane).

The protective effect of PSAT and Scleroglucan (beta 1-3, beta 1-6 polysaccharides), has been studied in mice infected with different strains of Toxoplasma gondii (RH, attenuated RH or Prugniaud strains). Intramuscular or intravenous administration of PSAT before infection of mice by the attenuated RH strain, resulted in a significant enhancement of survival: 100% of survival in the treated group, compared to 33% in controls and 50% in mice pretreated with Scleroglucan (10 mg/kg, intravenously). In contrast, there was no difference in the survival rate between the group treated with PSAT (1 mg/kg, IV) and the control in mice infected with the virulent RH strain: all mice died between day 7 and day 8. In mice infected with 15 cysts of the Prugniaud strain a decrease in the chemiluminescence (CL) of peritoneal macrophages and of the number of cysts in the brain of mice were observed in mice treated either with PSAT (1 mg/kg, IM) or scleroglucan (10 mg/kg, IM).

Ampicillin inactivation in the caecum of axenic, gnotoxenic and conventional lambs: interaction with resistant or sensitive Escherichia coli.

The fate of orally administered ampicillin was studied in axenic lambs, in gnotoxenic lambs given a complex microflora and a mixture of ampicillin resistant and/or sensitive strains of Escherichia coli, and in conventional lambs. In axenic lambs or animals with a sensitive microflora, antibiotic concentrations of 500-1600 micrograms ml-1 were detected in the intestine, and most of the ampicillin passed through the small intestine and entered the large intestine, within 12-15 h of administration. These antibiotic concentrations were sufficient to decrease the numbers of ampicillin-sensitive E. coli from 10(8)-10(9) bacteria ml-1 to about 10(5)-10(6) bacteria ml-1 by 8 h after ampicillin administration. Second and third doses of antibiotic had no further effect on the bacterial count. Administration of ampicillin to animals hosting ampicillin-resistant E. coli resulted in a significant inactivation of the antibiotic in the intestine. As might be expected there was little reduction in the numbers of these organisms. These results are similar to those observed in conventional lambs hosting resistant E. coli as the dominant colibacillary flora.

Small filter membrane bags for the study of antibiotic action in the digestive tract: bioavailability and in situ activity of oxytetracycline, chloramphenicol, neomycin and gentamicin in the pig caecum.

Observations were made for two consecutive days on the disposition of oxytetracycline, chloramphenicol, neomycin and gentamicin through the digestive tract of pigs given an oral drench. The effect of these antibiotics upon the colibacilli flora and upon an Escherichia coli 127 strain in small filter membrane bags placed into the caecum was also investigated. For chloramphenicol, inactivation by antibiotic resistant colibacilli and, for neomycin, losses of activity by digestive content may explain the lower concentrations obtained in the gut and the correlative lack of curative or preventive action against E coli 127 in small bags. Tetracycline and gentamicin prevented growth of E coli 127 from the second day.

[In vitro interaction between an ampicillin-colistin combination and ampicillin-resistant Escherichia coli]. / Interaction in vitro entre lássociation ampicilline-collistine et Escherichia coli resistant à lámpicilline.

In this work, the authors studied in vitro potential interactions between bacteria and antibiotics. Colistin and ampicillin were introduced to ampicillin-resistant Escherichia coli and ampicillin activity was measured. Two layers of agar media were used. The lower layer contained E. coli and colistin. The superficial layer was sown with indicating bacteria (ampicillin-sensitive Proteus mirabilis). Ampicillin activity was evaluated on the upper layer with impregnated disks. By this technique, it was ascertained that ampicillin degradation increased with colistin concentration. In this case, colistin may favour interactions of intracellular beta-lactamases on ampicillin.

Pharmacokinetics of [3H]levamisole in pigs after oral and intramuscular administration.

A single oral (10 mg/kg of body weight) or IM (7.5 mg/kg) dose of [3H]levamisole was administered to pigs. Liquid scintillation counting and high performance liquid chromatography were used to determine total radioactivity and drug levels in plasma, duodenal and cecal contents, bile, and urine for 24 and 72 hours after dosing. Pharmacokinetic analysis indicated a 1-compartment open model with higher plasma bioavailability of levamisole after IM injection. Biological half-lives for elimination of the drug were 9.3 and 6.9 hours after oral and IM administration, respectively. Anthelmintic concentrations were higher in intestinal contents after oral gavage than after IM injection. The drug appeared extensively metabolized in all body fluids and particularly in bile, regardless of the route of administration. Biliary excretion of radioactivity and unchanged levamisole represented only slight percentages of the administered dose (approx 0.4% and 4.2%, respectively, in 72 hours). In contrast, about 60% and 20% of the dose were eliminated via urine as tritiated materials and unchanged drug. The choice of the most efficacious route of administration is discussed in regard to localization of helminthic disease.

Small filter membrane bags for the study of antibiotic action in the digestive tract: bioavailability and in situ efficacy of ampicillin in the pig caecum.

Bioavailability and activity of ampicillin were evaluated in the pig after preventive and curative doses by using small filter membrane bags containing strains of Escherichia coli placed into the caecum. A peak concentration of 720 micrograms ampicillin per ml was obtained in caecal liquor which was effective against E coli K82 and E coli 127 in the bags, in pigs orally administered with 20 mg/kg of the drug. After intramuscular injection of ampicillin with 40 mg/kg, the peak concentration in caecum reached 15 micrograms/ml but no activity against the strains of E coli K82 and 127 was recorded.

Effect of carbohydrates on the antibacterial activity of patulin on Streptococcus bovis.

The antibiotic activity of patulin on Streptococcus bovis varied in the presence of different sugars in the incubation medium. The 50% inhibitory concentration (IC50) of patulin was 4.5 times greater in the medium containing glucose than in the lactose-containing medium (100.5 versus 22 micrograms/mL). The addition of two sugars (glucose plus lactose) to the medium was followed by the utilization of glucose only when patulin was present; lack of growth on lactose was not due to beta-galactosidase inactivation by patulin.

[Effect of route and place of minocycline administration on the zootechnical performance of rabbits]. / Influence de la voie et du lieu d'administration de la minocycline sur les performances zootechniques du lapin.

Minocycline administered to rabbits per os or intramuscularly (30 mg/kg) over a period of three days led neither to digestive problems nor mortality. Administration per os left the growth curve unchanged. Intramuscular administration reduced rate of growth, and on the 15th day weight loss compared to controls was 3.2% or 11.7% depending on whether the place of administration was in the back muscles or in the thigh, and this despite a normal food intake. Minocycline did not modify microbial flora and level of ammonia in the caecum. Level of acetic acid was reduced by 50% on the fourth and 15th day after intramuscular administration of minocycline into the thigh. The depressive effect of minocycline on growth remains unexplained.

Enhancement of spiramycin concentration by bromhexin in the bovine nasal secretions.

Intramuscular injection of bromhexin (Quentan) results in increased bioavailability of spiramycin in nasal secretions. In the presence of a mucolytic agent, the area under the curve calculated according to spiramycin concentrations found in nasal secretions increases by 6%, 41% and 32% respectively in the course of three days of treatment. This potentiation reveals the interest involved in administering a combination of bromhexine and antibiotics in the treatment of infectious diseases of the respiratory tract.

[Bioavailability of erythromycin and colistin in calves (author's transl)]. / Biodisponibilité de l'association érythromycine-colistine chez les veaux.

Bioavailability of erythromycin and colistin was studied in plasma, ruminal liquid and nasal mucus after simultaneous injection by intraruminal or intramuscular route. After intramuscular injection, erythromycin was found in plasma and respiratory tract, colistin in plasma. After oral administration, only erythromycin was found in nasal cavity secretions but nitrogen metabolism and volatile fatty acid production were modified in rumen.

[Sensibility of rabbits to treatment with ampicillin and gentamycin (author's transl)]. / Sur la sensibilité du lapin a l'association ampicilline-gentamicine.

Ampicillin administered to rabbits (20 mg/kg per day) over a period of three days subsequently provoked a death rate of 40%. No deaths were observed after treatment with gentamycin (10 mg/kg per day) or with a combination of ampicillin and gentamycin. On the fourth day weight loss in the three treated groups was 12%, 11% and 9%, respectively, compared to controls. At the same time food intake in the treated groups was only 15% to 20% of the amount consumed by controls. In the caecum, ampicillin treatment resulted in dominance of a strain of Enterobacter aerogenes. Gentamycin had no effect on bacterial flora, although in combination with ampicillin, the number of caecal bacteria (aerobic and anaerobic) was reduced. Flora modification might be responsible for accumulation of NH3 and an unbalance of free acids. Caecotrophy was inhibited by administration of ampicillin. When administered intramuscularly, ampicillin produced results comparable with those obtained orally, although gentamycin was ineffective.

Comparative bioavailability of levamisole in non lactating ewes and goats.

An original HPLC assay enabled the quantitation of levamisole in biological fluids of ewes (n = 4) and goats (n = 4). An open two compartment model showed the development of the drug in animals after oral (10 mg X kg -1) intramuscular (7.5), and subcutaneous (7.5) administrations by veterinary therapeutic forms. Greater efficiency was obtained in both species after intramuscular rather than subcutaneous or oral administrations. After intramuscular injection, levamisole levels in nasal secretion and saliva were five to 20 times higher than in plasma. Because of the high susceptibility of goats to levamisole, the subcutaneous route is preferred in this animal.