Morphological alterations in oxidative muscles and mitochondrial structure associated with equine atypical myopathy

REASONS FOR PERFORMING STUDY: There is a lack of well documented studies about muscular lesions in equine atypical myopathy (EAM). OBJECTIVES: To characterise morphopathological changes of striated muscles and myocardium, to progress understanding of this disease. METHODS: Thirty-two horses age 0.5-7 years kept on pasture were referred for a sudden ataxia/myoglobinuria syndrome. Clinical examination (stiffness, muscle pain, muscle fasciculations, abnormal gait, recumbency, myoglobinuria, tachycardia, sweating) and plasma CPK, LDH and AST levels were consistent with extensive myonecrosis and, together with anamnestic data, with so-called 'equine atypical myopathy' (EAM), a disease of unknown aetiology reported since 1939. Macroscopic and microscopic (histology, histoenzymology, ultrastructure) lesions were evaluated. RESULTS: Necropsic examination revealed large areas of muscle necrosis, the extent and severity of which varied between cases and muscles, but which were clearly more constant and severe in respiratory and postural muscles and in the myocardium. Histology highlighted a multifocal and monophasic process compatible with Zenker degeneration/necrosis that mostly and segmentally affected type 1 fibres. Histochemical evaluation revealed a weak and disorganised pattern of NADH tetrazolium reductase staining, the absence of calcium salts precipitates and a dramatic accumulation of lipid droplets. Ultrastructural examination often revealed fibres of which the sole modifications were altered mitochondria and sarcoplasmic lipidosis. CONCLUSIONS: Taken together, the data suggest that a primary alteration of mitochondria should be considered, although secondary mitochondrial abnormalities have yet to be ruled out. POTENTIAL RELEVANCE: The morphological features gathered here reveal that EAM shares most of the characteristics of toxic myopathies.     

Morphologic alterations observed during experimental ischemia of the equine large colon

Morphologic changes that develop sequentially in the large colon during experimentally induced ischemia were documented in 14 halothane-anesthetized horses. Colonic ischemia was induced by 4 types of vascular occlusion, 24 cm proximal and distal to the pelvic flexure. The effect of transmural (colonic wall) vascular compression combined with either venous occlusion (3 horses, group A) or venous and arterial occlusion (3 horses, group B) of the colonic vessels was studied for 1, 2, and 6 hours of occlusion. Also observed was the effect of reperfusion for 0.5 hour after release of the clamps for the 1- and 2-hour occlusions and for 1 hour after release of the clamps for the 6-hour occlusion. Effects of occluding only the colonic veins (4 horses, group C), or the colonic veins and arteries (4 horses, group D) were studied for 0.5, 1, 1.5, and 2 hours of occlusion and during reperfusion for 0.5 hour. Full-thickness intestinal biopsy specimens were obtained from the antimesenteric border of the pelvic flexure at 0, 0.25, 0.5, 0.75, 1, 1.5, and 2 hours during occlusion and at 0.5 hour after release of vascular occlusion. Biopsy specimens were obtained at hourly intervals from the 2 horses in which 6-hour occlusion was performed and at 1 hour after release of vascular occlusion. Macroscopic changes (serosal color, mucosal color, serum leakage) in the colon were recorded.(ABSTRACT TRUNCATED AT 250 WORDS)     

Laboratory methods of equine pregnancy diagnosis.

Rectal examination is a reliable method of diagnosing pregnancy in the mare. Also, test kits are available for the simple quick detection of pregnant mare serum gonadotrophin. Nevertheless there is a considerable demand by practitioners for an independent laboratory service in equine pregnancy diagnosis, particularly during the gestational phase when placental gonadotrophin is concentrated in the blood. An initial attempt to provide a service by means of the agar gel diffusion test was disappointing and alternatives were sought. The primary requirements for an ideal alternative technique were defined as: accuracy, sensitivity, applicability to the optimum request period, elimination of subjective interpretation and a minimal inconclusive rate. Additional considerations included cost, practicality and test duration. The various tests available are summarised and their published accuracies are discussed. It was decided to reverse the current trend from biological to immunological techniques and to modify the test by which Cole and Hart announced the discovery of PMSG in 1930. The utero-ovarian response in the immature female mouse was quantified simply to produce a numerical result. The reason for this is explained, the method is described and its accuracy is evaluated. The primary requirements, defined above, were achieved.     

Endocrine changes associated with cystic ovarian degeneration in sows.

Endocrine changes in sows with ovarian cysts were determined to be comparable with those in sows in diestrus. Blood samples were collected at frequent intervals from 5 sows affected with cystic ovaries. Concentrations of serum luteinizing hormone, progesterone, estradiol-17 beta, and cortisol were determined by use of established radioimmunoassays. The development of ovarian cysts has been proposed to be associated with a deficiency of luteinizing hormone rather than an intrinsic ovarian abnormality. In contrast, the results of this study demonstrated that tonic and pulsatile luteinizing hormone release were not affected adversely in sows with cystic ovaries.     

Meningoencephalomyelitis in horses associated with equine herpesvirus 1 infection.

During an outbreak of abortion caused by equine herpesvirus 1, a neurologic disease characterized clinically by dullness and ataxia occurred in several mares. Equine herpesvirus 1 was isolated from brain and lung of two severely affected mares. Histologically, both mares had disseminated meningoencephalomyelitis characterized by necrotizing arteritis, focal malacia in grey and white matter of brain and spinal cord, and accumulation of lymphocytes and neutrophils in paravertebral ganglia. Eosinophilic intranuclear inclusion bodies occurred in foci of necrosis in thyroid adenomas of both mares.     

Effects of the dam on equine chorionic gonadotropin concentrations during pregnancy

Breeding trials were designed to determine the influence of the mare on serum concentrations of equine chorionic gonadotropin (eCG) from Day 39 to Day 104 of gestation. Sires were ranked according to mean eCG concentrations found in the groups of randomly selected mares to which they were mated in 1983. Mares were ranked according to their mean eCG concentrations on Days 55, 71 and 85 of gestation (Day 0 = mating), in 1983 and 1985. In the 1986 breeding season, mares that had pregnancies characterized by high eCG levels were mated to sires previously associated with low eCG concentration pregnancies and low producing mares were mated to sires associated with high eCG concentration pregnancies. The highest eCG concentrations (12.8 ug/ml serum) were detected on Day 55 of gestation in mares mated to the low-ranked sire (P<0.01), indicating an influence of the mare on serum eCG concentration. A comparison of eCG production by individual mares in 1985, 1986 and 1987 showed that mares retained the same rank (P<0.001), regardless of the rank of the sire to which they were mated. It was concluded that the influence of the mare predominates in determining eCG concentration. In 1987, the highest ranked sire was mated to the highest eCG producing mares (ranked 1–20) and the second highest ranked sire was mated to mares ranked 21–40. Two distinct subgroups resulted, suggesting that the selection of sires and mares could be used to maximize the production of eCG.     

Complications associated with immunotherapy of equine phycomycosis

Five horses with pythiosis of the limbs were treated unsuccessfully by surgery or topical application of amphotericin B, or both. Follow-up immunotherapy resulted in 1 horse responding favorably. Three horses were cured of the fungal infection but developed osteitis or deep-seated laminitis, which necessitated their destruction. The remaining horse, which had severe anemia, died before the course of vaccination was completed.     

Abnormal canine bone development associated with hypergravity exposure.

Chronic centrifugation of 85- to 92-day-old Beagles at 2.0 X g and 2.6 X g for 26 weeks during the time of active skeletal growth caused skeletal abnormalities in the radius and the ulna of ten of 11 dogs. The pattern of change mimicked that found in naturally occurring and experimentally induced premature distal ulnar physeal closure or delayed growth at this physis. Minimal changes in bone density were detected by sensitive photon absorptiometric techniques. Skeletal abnormalities also were found in five of the six cage-control dogs, although the run-control dogs were radiographically normal.     

Funisitis associated with leptospiral abortion in an equine placenta

Funisitis, inflammation of the umbilical cord, is well recognized in human placentas. This report describes a case of funisitis associated with leptospiral infection in the placenta of a Thoroughbred foal born prematurely. The umbilical cord had diffuse superficial yellow discoloration along its entire length. Microscopic evaluation showed an exudate of neutrophils admixed with fibrin on the surface. Warthin-Starry staining showed spirochetes in the Wharton's jelly of the umbilical cord. A locally extensive, severe placentitis not involving the star and allantoic cystic hyperplasia were the other lesions observed in the allantochorion. Leptospira funisitis is similar to the funisitis of congenital syphilis in humans, although there are some major microscopic differences. In Leptospira funisitis, lesions were limited to the cord surface, whereas in lesions in human umbilical cords with Treponema pallidum infection, the changes are observed mostly around the vessels and in the Wharton's jelly.