Stephen D. Lenz

Prevalence of antibodies to Neospora Caninum in dogs

An IFAT was used to determine the prevalence of Neospora-specific IgG antibodies in serum from Alabama horses. Serum samples (n = 536) were from asymptomatic horses routinely submitted for equine infectious anaemia virus infection testing. We also subjected a 13-year-old horse with CNS disease to necropsy examination for isolation and in vitro cultivation of protozoal organisms. In antemortem tests, this horse was positive for antibodies to Neospora sp. in the IFAT and western immunoblot. Results of the prevalence survey indicated that IgG antibodies to Neospora were present in 62 (11.5%) of the 536 serum samples. Endpoint titres for the positive samples were 1:50 (35/6.5%), 1:100 (19/3.5%), 1:200 (7/1.3%) and 1:1600 (1/0.2%). Tachyzoites were first seen in cultured bovine turbinate cells 32 days after inoculation with spinal cord homogenates from the horse with CNS disease. Tachyzoites reacted with known N. caninum-positive serum from horses, cows, dogs and mice, but did not react with murine anti-Toxoplasma gondii or equine anti-Sarcocystis neurona serum. Ultrastructural features of tachyzoites and results of comparison of tachyzoite immunodominant proteins revealed that they were identical to those of N. hughesi, a species described recently from a naturally infected horse. The isolate recovered from the naturally infected horse in the present study (designated NA1) is thought to be an isolate of N. hughesi, although confirmation of this awaits additional molecular characterisation. These results provide some additional evidence that N. hughesi is a valid species and that Neospora infections in horses may occur in widely separated geographic regions of the United States.

The quantity of nitric oxide released by macrophages regulates Chlamydia-induced disease

Intracellular bacteria of the genus Chlamydia cause numerous typically chronic diseases, frequently with debilitating sequelae. Genetic determinants of disease susceptibility after infection with Chlamydia bacteria are unknown. C57BL/6 mice develop severe pneumonia and poor immunity against Chlamydia after moderate respiratory infection whereas BALB/c mice are protected from disease and develop vigorous Th1 immunity. Here we show that infected C57BL/6 macrophages release more NO synthesized by NO synthase 2 (NOS2) than BALB/c macrophages and have lower mRNA concentrations of arginase II, a competitor of NOS2 for the common substrate, l-arginine. Reduction, but not elimination, of NO production by incomplete inhibition of NOS2 abolishes susceptibility of C57BL/6 mice to Chlamydia-induced disease. Thus, the quantity of NO released by infected macrophages is the effector mechanism that regulates between pathogenic and protective responses to chlamydial infection, and genes controlling NO production determine susceptibility to chlamydial disease.

EXPERIMENTAL INFECTION OF CATTLE WITH A FELINE ISOLATE OF TRITRICHOMONAS FOETUS

Tritrichomonas foetus is the causative agent of bovine trichomoniasis, a sexually transmitted disease in cattle that can result in large profit losses for cattle producers. Increasing reports have suggested that T. foetus is also the causative agent of large-bowel diarrhea in cats. To determine if the trichomonads recovered from the reproductive tract of cattle and the large intestine of cats can thrive in the same host, 2 groups of virgin Angus heifers were inoculated with T. foetus. The first group of heifers was inoculated with a bovine T. foetus isolate cultured from a naturally infected cow, and heifers in the second group were inoculated with T. foetus organisms cultured from the feces of a naturally infected cat. Over an 11-wk period, vaginal, cervical, and uterine mucus samples were analyzed, along with a single transcervical uterine biopsy sample, to determine organism and disease presence. The mucus and biopsy samples collected from each group indicate that the disease caused by feline and bovine isolates of T. foetus are comparable, but not identical.

Sphingolipid levels in catfish consuming Fusarium moniliforme corn culture material containing fumonisins

Fumonisin, a secondary metabolite of Fusarium moniliforme, is frequently found in foods and feeds of humans and animals. Fumonisins are specific inhibitors of sphinganine (sphingosine) N-acyltransferase, a key enzyme in the pathway for de novo sphingolipid biosynthesis and reacylation of sphingosine derived from dietary sources or complex sphingolipid turnover. The objective of this study was to evaluate the effect of F. moniliforme toxins on sphingolipids in year-2 channel catfish. In a 12-week feeding trial, four groups of catfish per treatment were fed pelleted balanced diets containing F. moniliforme cultured corn. The fumonisin B1 (FB1) concentrations in diets were 0.3 (control), 2.5, 5, 10, 20, 40, 80 and 240 mg/kg. The free sphinganine to free sphingosine ratio was significantly (P < 0.05) elevated (with exception of brain) at 10, 20, 40 and 80 mg FB1 per kg diet in kidney, serum, liver and muscle, respectively. The increase in free sphingolipid ratios observed were found to be due to increases in the levels of free sphinganine in tissues. These results demonstrate that a mode of action of F. moniliforme toxins in catfish is similar to other species (ponies, pigs, rats), and is suggestive of fumonisin toxicity. It also demonstrated the potential diagnostic value of ratios of free sphingolipids in catfish.

Early ultrastructural lesions of diphenylamine-induced renal papillary necrosis in Syrian hamsters

The ultrastructural lesions of diphenylamine-induced renal papillary necrosis in Syrian hamsters were characterized by transmission electron microscopy. Twenty-four male Syrian hamsters were orally administered 600 mg diphenylamine/kg body weight as a single dose. At 30 minutes and at 1, 2, 4, 8, 16 and 24 hours after administration of diphenylamine, three hamsters were anesthetized with pentobarbital, perfused via the left ventricle with half-strength KARNOVSKYs fixative, and the renal papilla and outer medulla collected. Three hamsters administered 0.5 ml peanut oil/kg body weight (vehicle controls) were anesthetized at 24 hours, perfused, and the renal papilla and outer medulla collected. Initial ultrastructural lesions were observed in the endothelial cells of the ascending vasa recta in the proximal portion of the renal papilla at 1 hour after diphenylamine administration. The endothelial cell basal plasma membrane was elevated from the basal lamina, forming large subendothelial vacuoles. Alterations in inner medullary interstitial cells, endothelial cells of the descending vasa recta, and the epithelial cells of the thin limbs of Henle and the medullary collecting tubules were observed subsequent to the lesion in the ascending vasa recta. It was concluded that the endothelial cell of the ascending vasa recta is the target cell in diphenylamine-induced renal papillary necrosis in Syrian hamsters.

In vitro assessment of in vivo damage to the barrier properties of pig skin caused by a complex mixture

AbstractThe purpose of this study was to determine if an in vitro method can be used to measure changes in the barrier properties of skin caused by in vivo or in vitro topical exposure to a test chemical. The effect of a test chemical (liquid gun propellant [LP], a highly irritating mixture of hydroxylammonium nitrate, triethanolammonium nitrate, and water) on the barrier function of skin was assessed in vitro by measuring the penetration of [14C]benzoic acid following exposure to LP. Weanling pigs were topically exposed to single doses (25μl/cm2) of saline (control) or LP. LP-induced changes in the barrier properties of the skin were determined by measuring the permeability to [14C]benzoic acid. After 1-5 days, pigs were euthanized and skin sections excised from the sites of application. Skin sections were mounted in in vitro penetration chambers to measure cumulative 24 hr penetration of [14C]benzoic acid. Topical treatment with undiluted LP resulted in an 8.2-fold increase in permeability to [14C]benzo...