A 10-day toxicity study of toltrazuril 5% suspension in the horse.

Equine protozoal myeloencephalitis (EPM) is a serious disorder of the nervous system of horses caused by Sarcocystis neurona. Recently, toltrazuril has begun to be used for treatment of EPM. The purpose of this study was to evaluate the potential toxicity of toltrazuril in horses when administered at a dose of 50 mg/kg for 10 days. Five horses were given 50 mg/kg of toltrazuril once daily for 10 days by nasogastric tube. Complete blood cell counts, serum chemistry values, and coagulation panels were evaluated before and after treatment; then a full postmortem examination was completed on day 11. Results of the study show that only mild clinical signs (i.e., anorexia, weight loss, and colic in one of the five horses) were observed after treatment. Minimal changes were noted in the serum chemistry analysis (i.e., increased bilirubin and serum protein, mildly increased hematocrit and hemoglobin concentration, and mildly increased albumin). Renal medullary congestion was noted on gross postmortem examination; however, no microscopic changes due to compound administration were noted in the kidneys or other tissue. Results of this study suggest that administration of toltrazuril at 50 mg/kg (5x to 10x anticipated clinical dosage) for 10 days resulted in only mild clinical abnormalities.

Use of polypentapeptides of elastin to prevent postoperative adhesions: efficacy in a contaminated peritoneal model.

We investigated the use of a sheet of polypentapeptide of elastin as a physical barrier to adhesion formation in a contaminated peritoneal wound model. A total of 88 rats were studied with random assignment of animals to three study groups; control (29), polypentapeptide steam sterilized (30), and polypentapeptide gas sterilized (29). Animals were anesthetized and a laparotomy was conducted to reveal the cranial portion of the ileum. The abdominal wall muscle peritoneum was excoriated until hemorrhage was noted. In sham animals, there was no physical barrier placed between bowel loop and the abdominal wall. In two of the study groups, the polypentapeptide sheet was placed directly over the excoriated area. The intestinal loop was then loosely secured to excoriated area with 2-O nylon (stay suture) which was tied subcutaneously in all groups. Four puncture wounds were made with a 20-gauge hypodermic needle in the bowel that was apposed to the excoriated peritoneal musculature which allowed leakage of intestinal contents and contamination. On Day 7 postsurgery, the animals were anesthetized and the stay suture was removed. On Day 14, all animals were sacrificed and adhesions were graded. The incidence of significant adhesions was 28% for the barrier group versus 90% for control animals (P < 0.05). The results of this study indicate that the polypentapeptide of elastin sheet is an effective physical barrier in this surgically induced contaminated wound model.

Lipopolysaccharide detoxification by endotoxin neutralizing protein.

Endotoxin neutralizing protein (ENP), a recombinant form of the anti-lipopolysaccharide factor that was isolated from amebocytes of the American horseshoe crab, Limulus polyphemus, detoxifies lipopolysaccharide (LPS) both in vitro and in vivo. Using the Limulus amebocyte lysate assay, LPS was detoxified by ENP at a 1 to 1 weight ratio (1:1). When isolated rat aortic rings were preincubated for 16 hr with either LPS or LPS/ENP (1:5), only aortas in the LPS/ENP group contracted normally under norepinephrine stimulation. To show that detoxification of a lethal amount of LPS (18 mg/kg, LD50 at 48 hr) persists in vivo, LPS/albumin (1:1) or LPS/ENP (1:1) mixtures were preincubated (30 min, 37 degrees C) and then injected intravenously into rats. In the 8 hr after injection, LPS/ENP challenged rats, in contrast to their LPS/albumin injected counterparts, had significantly fewer physical signs of acute LPS toxicity (P < 0.001). At 48 hr after challenge, all LPS/ENP treated rats survived (P < 0.01 vs LPS/albumin), and with significantly less weight loss (P < 0.001 vs LPS/albumin challenged survivors). At necropsy, the LPS/ENP group was free of typical LPS-induced gross organ lesions, notably in the liver, spleen, gut-associated lymphoid tissue (GALT), and small intestine. By microscopic examination, lymphocytic necrosis in the spleen and GALT of the LPS/ENP treated survivors was significantly milder than that in the LPS/albumin challenged survivors, although the degree of hepatocellular necrosis and small intestinal enteritis was similar. LPS-neutralizing proteins such as ENP may be useful in treating LPS toxicity.

Pentoxifylline treatment of sepsis in conscious Yucatan minipigs.

Recent evidence suggests that pentoxifylline (PTX) may be useful in the treatment of sepsis. We examined effects of PTX in a conscious swine model of sepsis. Yucatan minipigs (20-30 kg) were anesthetized and instrumented with catheters in the vena cava, aortic arch, pulmonary artery (Swan-Ganz thermodilution catheter), and peritoneum. Twenty-four hours after surgery, sepsis was induced by intraperitoneal (ip) injection of Escherichia coli bacteria (2 x 10(10) cfu/kg). Nonseptic pigs received intraperitoneal saline (5 ml/kg). PTX treatment (3 mg/kg/hr, iv; 1 mg/ml in 0.9% saline) and maintenance fluid (5 ml/kg/hr, iv) were started with bacterial infusion. An additional 60 cc/kg 0.9% saline bolus was administered iv at 1 hr. Pigs were monitored before and 1, 2, 5, and 24 hr after bacterial injection. Intraperitoneal injection of bacteria led to significant reductions in blood pressure and cardiac output and elevations in pulmonary wedge pressure and pulmonary vascular resistance. These effects were attenuated by PTX treatment. All septic animals demonstrated elevated creatinine, blood urea nitrogen, circulating endotoxin (LPS), and tumor necrosis factor concentrations, reductions in white blood cell and platelet counts, and peritonitis. None of these responses was altered by PTX treatment. We conclude that PTX may prove to be a useful therapeutic tool in the early treatment of septic shock but is limited in the scope of its effects.

The surgical significance of Persian Gulf sand.

Foreign bodies, in particular sand and soil particles, can cause considerable reaction in wounds and remain in tissues indefinitely. The introduction of foreign material as a contaminant in wounds and intracavitary injuries to military personnel deployed in the Persian Gulf region can be a complicating factor in treatment. Samples of desert sand from the military operational areas of the Persian Gulf were analyzed and the acute local and systemic responses of intraperitoneal contamination determined in an experimental rat model.

Further evaluation of a mutagen-attenuated Rift Valley fever vaccine in sheep.

A previous study demonstrated that a mutagen-attenuated Rift Valley fever virus (RVFV) vaccine, RVF MP-12, was immunogenic and non-abortogenic when ewes, 90-110 days pregnant, were inoculated with 5 x 10(5) plaque-forming units (p.f.u.) of the virus strain. The ewes delivered live, healthy lambs that had no neutralizing antibody to RVFV until after they had ingested colostrum. To assess further the safety and protective capability of this candidate vaccine, six pregnant ewes were inoculated with 5 x 10(3) p.f.u. of RVF MP-12 and challenged with 5 x 10(5) p.f.u. of virulent ZH-501 strain of RVFV 30 days later. No viraemia was detected after vaccination or challenge and all six ewes delivered live, healthy lambs. Those lambs tested before their nursing did not have neutralizing antibody to RVFV but quickly acquired antibody titres of 1:320 to greater than or equal to 1:10,240 after ingesting colostrum. To test the safety of the RVF MP-12 immunogen in neonates, lambs less than or equal to 7 days old, born to unvaccinated ewes, were inoculated with 5 x 10(5) p.f.u. of RVF MP-12. With the exception of brief pyrexia in 18 of 26 lambs, and a transient low-titred viraemia in 16 of 26 lambs after inoculation, no untoward effects were observed. Serum-neutralizing antibody to RVFV was detected 5-7 days after inoculation. Lambs vaccinated with either 5 x 10(5) or 5 x 10(3) p.f.u. of RVF MP-12 were protected against virulent RVFV challenge at 14 days postvaccination.

Adrenal cortical necrosis caused by T-2 mycotoxicosis in female, but not male, mice.

Experimentally, adrenal cortical parenchymal cell necrosis was induced by T-2 mycotoxin in female, but not male, mice. The lesion occurred in the adrenal glands in 11 of 11 female and 0 of 10 male mice given a nose-only aerosol exposure to T-2 mycotoxin. The necrosis, restricted to the zona fasciculata, began at the X zone interface and extended peripherally to involve 15% to 70% of the zone. Both light and transmission electron microscopies were used to determine whether the cellular and subcellular damage involved parenchymal cells of the zona fasciculata. Extensive necrosis of cortical thymocytes and necrosis of lymphoid cells in follicles of the spleen, lymph nodes, and intestine-associated lymphoid tissue were observed in both sexes. This is the first report to describe adrenal gland necrosis associated with exposure to T-2 mycotoxin.

Enzyme synthesis in the cellular slime mould Dictyostelium discoideum during the differentiation of myxamoebae grown axenically.

1. Myxamoebae of the cellular slime mould Dictyostelium discoideum Ax-2 were grown on different media, and were harvested either in the stationary or exponential phases of the growth cycle to yield samples of myxamoebae differing in enzymic composition. 2. Morphogenesis and cell differentiation phenomena in D. discoideum appear to be similar in myxamoebae grown and harvested under different conditions. 3. The specific activity of the enzymes beta-N-acetylglucosaminidase, acid phosphatase, alpha-mannosidase, beta-glucosidase and alkaline phosphatase have been determined during cell differentiation of myxamoebae grown and harvested under different conditions. 4. The pattern of synthesis of these enzymes, all of which have been claimed to be part of the ;developmental programme', either remains unaffected despite the origin of the myxamoebae (alkaline phosphatase) or is qualitatively similar but quantitatively affected (acid phosphatase, beta-glucosidase) or is both qualitatively and quantitatively affected by changes in the myxamoebae (alpha-mannosidase, beta-N-acetylglucosaminidase). 5. The implications of these results for the concept of a ;developmental programme' are discussed.

Enzyme synthesis in myxamoebae of the cellular slime mould Dictyostelium discoideum during growth in axenic culture.

1. The specific activities of beta-N-acetylglucosaminidase, acid phosphatase, alpha-mannosidase, beta-glucosidase, UDP-glucose pyrophosphorylase and alkaline phosphatase have been determined in myxamoebae of the cellular slime mould Dictyostelium discoideum Ax-2 grown on different media and in different phases of the growth cycle. 2. Variations in enzymic composition occur with changes in growth medium and phase of the growth cycle. 3. The intracellular location of the enzymes studied has been determined. 4. Two enzymes, beta-N-acetylglucosaminidase and alpha-mannosidase, are not only synthesized preferentially as the myxamoebae enter the stationary phase of growth but they are also excreted. The excretion process appears to be specific, because other enzymes that occur in the same intracellular fraction are not excreted.

Biochemical and cytological heterogeneity of the differentiating cells of the cellular slime mould Dictyostelium discoideum.

1. The slug stage of the cellular slime mould Dictyostelium discoideum has been shown to contain two types of cell, which differ in buoyant density. 2. These two cell types also differ in cytological appearance and histochemical behaviour and have very different enzymic activities. 3. Evidence is presented suggesting that the lighter of these two cell types corresponds to cells from the posterior region of the slug (pre-spore cells) and the heavier of the two to cells from the anterior region of the slug (pre-stalk cells).