Bovine aortic arch variant in humans: clarification of a common misnomer.

The term "bovine arch" is widely used to describe a common anatomic variant of the human aortic arch branching. This so-called bovine aortic arch has no resemblance to the bovine aortic arch. We describe the most common human aortic arch branching patterns and compare these with the bovine aortic arch.

Prevalence of atretic corpora lutea in ovaries of bovine fetuses.

Both ovaries from 88 bovine fetuses in the fifth month or later of gestation were studied histologically to determine the prevalence, origin, and time of appearance of atretic corpora lutea (ACL). Ovaries from 36 (41%) fetuses had ACL; fetuses < 6 months of gestation did not have ACL. Six fetuses had more than 25 ACL, but there was no apparent relationship between fetal age and number of ACL. Formation of ACL involved disintegration of the stratum granulosum of secondary follicles, concomitant with proliferation and invasion by vascularized elements of the theca. Fully developed ACL consisted of a large primary oocyte surrounded by a prominent zona pellucida and encased in a well-vascularized, largely thecal, fibrocellular wall. They measured approximately 0.5 to 1.0 mm in diameter. Empty, collapsed zona pellucidas were seen in many of the degenerating ACL.

Radiographic interpretation of endodontic file length.

The purpose of this study was to evaluate the accuracy of examiners when asked to make file length adjustments with only a radiograph. The examiners viewed several radiographs under proper viewing conditions but without the aid of measuring devices. Two files of varying lengths (sizes 10 and 15) were placed in maxillary and mandibular premolars and molars from cadavers. The nine examiners were 67.91% in agreement of actual file length adjustment needed when adjustments of up to 0.5 mm were needed, 17.76% when adjustments of from 0.5 up to 1.0 mm were needed, and 14.33% when adjustments of greater than 1.0 mm were needed.

Left cranial vena cava in a horse.

A complete left cranial vena cava (LCVC) was found in a normal horse. The LCVC was well developed, but there was a complete absence of the right cranial vena cava. The azygous vein was normally distributed on the right side of the thoracic vertebral bodies but passed ventral to the aortic arch to empty into the cranial vena cava on the left close to the origin of the aortic arch. The LCVC passed over the dorsal aspect of the left atrium to reach the coronary sulcus on the caudal aspect of the heart. The LCVC opened into the right atrium via a 5 cm diameter orifice (orifice of coronary sinus). The vena cordis magna joined the LCVC 6 cm from the orifice of the coronary sinus. Complete dissection of the horse revealed no other developmental abnormalities. This case is compared with similar cases in the literature.

Nonsystemic causes of the downer cow syndrome.

Traditionally, the downer cow has been considered a metabolic problem. This viewpoint cannot account for the pelvic limb predilection of the condition. Whatever the primary cause of recumbency, all recumbent animals are susceptible to pressure damage. The extensive literature on pressure damage in human beings and horses is reviewed. Miscellaneous causes of and contributing factors to bovine recumbency are reviewed. Concepts and details of diagnosis, prevention, management, and therapy are discussed.

Hepatic necrosis following halothane anesthesia in goats.

One goat anesthetized with thiamylal sodium, xylazine, and halothane for repair of an abominal hernia, and 7 of 29 goats similarly anesthetized for an experiment unrelated to considerations of anesthesia, developed signs of hepatic failure within 24 hours of anesthesia. Affected goats had high values for serum aspartate transaminase and serum total bilirubin by 12 to 24 hours after induction of anesthesia. Necropsy of the 8 affected goats revealed centrilobular to massive hepatic necrosis (8 of 8), brain lesions consistent with hepatic encephalopathy (3 of 4), and acute renal tubular necrosis (6 of 6). Two unaffected goats had no hepatic necrosis. Causes of hepatic necrosis other than those related to anesthesia (eg, infectious agents, toxins) were ruled out by lack of supporting necropsy findings or were considered unlikely because of lack of opportunity for exposure. Hepatic lesions in these goats closely resembled those described in human beings with halothane-associated hepatic injury, although in both species these lesions are nonspecific at the gross and light microscopic levels. The pathogenesis of halothane-associated hepatic injury in goats, as in human beings, remains to be determined.

Pressure-induced changes in fibular motor nerve conduction velocity and fibularis (peroneus) tertius muscle-evoked potentials in a goat model of the downer cow syndrome.

A study was conducted to determine the acceptable fibular motor nerve conduction velocity (NCV) in goats and to characterize pressure-induced changes in conduction velocity and muscle-evoked potentials (MEP). The acceptable motor NCV in the adult goat was determined to be 95.9 +/- 6.8 m/s. Limb compression in recumbent cows was modeled by application of external compression to the goat pelvic limb to increase IM pressure to a minimum of 50 mm of Hg. This pressure, when applied for a 6-hour period, caused a 30% to 100% reduction of fibular motor NCV and a 10% to 100% reduction of amplitude of MEP measured from fibularis (peroneus) tertius muscle. The reduction of motor NCV and MEP was associated with clinically evident limb dysfunction. The changes detected by the electrodiagnostic tests were proportional to the magnitude and duration of the locomotor deficits. The limb dysfunction was accompanied by muscular damage indicated by an increase of serum creatine kinase activity.

Canine cryptorchism and subsequent testicular neoplasia: case-control study with epidemiologic update.

A retrospective study of 2,912 cryptorchid dogs identified 14 breeds with significantly high risk. Among six distinct closely interrelated breed groups (e.g., toy, miniature, and standard poodles), the risk in the smaller breed was always greater than that in the larger relative, suggesting that genetically influenced maldescent could be, in part, related to physical size or the rate of growth of the involved structures. Testicular tumors were diagnosed in 5.7% of the cryptorchid dogs; half had only Sertoli cell tumors, one-third had only seminomas. The relative risk for Sertoli cell tumor or seminoma was not directly related to a familial risk for cryptorchism. Using the health experience of a control population composed of male dogs with anal sac disease (N = 4,184), there is an estimated relative risk of 9.2 in cryptorchid dogs to develop a testis tumor (95% confidence interval, 5.9-14.3) and 4.2 in dogs with inguinal hernia (95% confidence interval, 1.8-9.5). Considering that the anatomical development of the genital tract, testis descent, and tunic relationships in dog are very similar to that in man, and that the associations of cryptorchism and inguinal hernia with testis neoplasms are also similar, the dog should be an excellent model system to further investigate the causes of human cryptorchism.

Pathogenesis of the downer cow syndrome.

A historical review of the downer cow literature is presented in order to provide a background for understanding current research. Initially thought to be an entity separate from parturient paresis, the condition has eventually come to be regarded as a complication of parturient paresis. Since many other factors also contribute to the syndrome, it is difficult to define precisely what is meant by the term 'downer cow'. A hypothesis that many primary factors, including parturient paresis, may cause the initial stage of recumbency is presented. This is followed by secondary muscle and nerve damage caused by tissue compression. This damage leads to permanent recumbency even if the primary factors have been ameliorated by therapeutic measures. Support for this hypothesis is given from the literature on cattle and other species and from recent experiments on cows. The concepts are applied to a discussion of prevention and therapy of downer cow cases.

The role of pressure damage in pathogenesis of the downer cow syndrome.

Experimental downer cows were produced by maintaining healthy cows in sternal recumbency for 6, 9, or 12 hours with the right pelvic limb positioned under the body. Halothane anesthesia was used to create this artificial parturient paresis-like position. In 8 of 16 experiments, cows were able to stand within 3 hours after anesthesia, but the others remained recumbent until death or euthanasia. There was no correlation between duration of the treatment and ability to stand after enforced recumbency. The appearance of the right pelvic limb of downer cows resembled the injured limbs of human patients with compartmental/crush syndrome, as well as the limbs of clinical downer cows. The affected limbs were swollen and held in rigid extension. Some animals which were able to stand also had swollen right pelvic limbs. Systemic signs of crush syndrome included dark yellow or brown urine suggestive of myoglobinuria, and marked elevation of serum creatine kinase enzyme levels. Highest creatine kinase levels were observed at 24 hours in the ambulatory group and at 48 hours in the downer group. Necropsy of downer animals revealed ischemic necrosis of the caudal thigh muscles and inflammation of the sciatic nerve caudal to the proximal end of the femur. Evidence of peroneal nerve damage was observed in at least 9 animals.

Hereditary esophageal dysfunction in the Miniature Schnauzer dog.

Miniature Schnauzers maintained in a colony for 9 years were used to study the inheritance of esophageal dysfunction (canine achalasia, megaesophagus). All dogs were evaluated radiographically, using a barium swallow contrast technique which clearly distinguished normal and affected pups. At 4 to 6 months of age, all affected dogs had recovered clinically except one, and radiographic evidence of dysfunction was markedly diminished. None of the affected dogs required a special feeding regimen. Analysis of breeding pairs revealed a ratio of 9 affected/11 normal dogs when an affected male was mated with a normal female, and a 13/3 ratio was observed when two affected dogs were mated. These ratios were compatible with a simple autosomal dominant or a 60% penetrance autosomal-recessive mode of inheritance. Outbreeding to an affected Miniature Schnauzer/Poodle crossbred dog resulted in only two of 30 affected pups, indicating a polygenic mode of inheritance in outbred populations.

An anatomic and genetic study of canine cryptorchidism.

Twelve cases of cryptorchidism were found in a colony of Minature Schnauzer purebred and crossbred dogs. At least nine affected dogs were derived from the same sire directly or indirectly. Of 12 affected dogs, five cases were unilateral and seven were bilateral. Eight of the 12 cases were subjected to anatomic study. Fixation of affected organs was by vascular perfusion or immersion. Testes were separated from epididymides and both were weighed. All unilateral retained testicles were on the right side, and right sided bilaterally retained testes were always smaller than their left sided counterparts. With only one exception, ectopic testes were in the abdominal positon. Developmentally, the morphologic appearance of the epididymis of abdominal testes was very primitive in bilateral cases but nearly normal in the unilateral cases. Degree of inbreeding was greater for bilateral cases than unilateral cases. High incidence of cryptorchidism in this colony provided good evidence for hereditary nature of the condition in the Miniature Schnauzer dog. Morphologic observations were suggestive of a multiple gene defect.

Ultrastructure of the axon reaction in the immature rat thalamus.

The axon reaction was studied using immature rats aged 4 or 14 days at the time of unilateral removal of the cingulate cortex. After survival times of one to 5 days they were sacrificed and the anterior thalamic nucleus was examined using ultrastructural methods. The degree of degenerative change was much more intense in the 4-day group where the center of the reactive area was characterized by pronounced lysis of the neuropil and the loss of most neurons. Dark neurons were observed in both groups but mitochondrial proliferation was restricted to the 14-day group. Evidence for microglial formation from pericytes was observed in the 4-day group while reactive astrocytes were observed in both groups. It was concluded that a rapid maturation of the thalamic injury response occurs between the 4th and the 14th day in the rat so that by the 14th day the response is similar in many respects to that of mature animals.

Peroneal nerve paralysis in a heifer.

Peroneal nerve paralysis in a heifer developed during an 11-day period of recumbency following dystocia. The condition did not improve during the next 42 days and the heifer was slaughtered. On the basis of microscopic findings, it was concluded that 3 to 4 months would have been required to reestablish normal limb function.

Surgical and anatomic study of calving paralysis.

Dissections of the bovine pelvic inlet region were made to determine which nerves were vulnerable to fetal-induced traumatic damage. Surgical sections of the obturator nerves and the lumbar roots of the sciatic (ischiatic) nerves were done to determine a possible cause of calving paralysis. Only 1 of 11 cattle in which bilateral obturator nerve section was done was unable to stand after the operation, and in this individual, secondary stifle injuries were found on necropsy. Subsequent surgical operations were performed on some of these cattle in order to section the lumbar root of the sciatic nerve. Of 6 cattle prepared, 2 were unable to rise after surgery and another 2 became "downer" cattle after 30 to 45 minutes of forces exercise. Also, some of these cattle were very ataxic and had intermittent fetlock flexion.