Visual Evoked Potentials in the Clinically Normal Dog

Visual evoked potentials (VEP) in response to flashes of white light were recorded from 15 adult beagles of both sexes to provide a normative data base. Separate recordings were taken by stimulating each eye of every dog. Responses were recorded from a needle electrode placed over the nuchal crest referenced to an electrode just caudal to the eyes. Five positive and negative peaks were present in each VEP; P1, N1, P2, N2, and P3. Peak P2 was the most prominent. Mean (+/- standard deviation [SD]) latencies for peaks P1, N1, P2, N2, and P3 were 14.3 +/- 2.4, 29.2 +/- 2.2, 54.5 +/- 7.4, 78.0 +/- 13.1, and 98.1 +/- 12.6 msec, respectively. Peak-to-peak mean amplitudes ranged from 5.88 to 13.30 microV. Recordings were accomplished without sedation, anesthesia, or mydriatic drugs.     

Magnetic Motor Evoked Potentials in Ponies

Magnetic stimulation of motor pathways was used to effect motor unit action potential recordings from forelimb and hindlimb muscles in unanesthetized ponies. Motor pathway conduction velocities to the forelimb and hindlimb were determined to be 53.8 ± 9.6 m/s^-1 and 63.4 ± 8.3 m/s^-1, respectively. This noninvasive technique will enable more precise evaluation of motor deficits in clinical patients than is possible with the neurological examination.     

Intraoperative Monitoring of Ischiatic Nerve Function with Sensory Evoked Potentials

Serial recordings of sensory evoked potentials (SEP) generated in response to stimulation of each tibial nerve were obtained from 23 anesthetized dogs. Five dogs were anesthetized for 3 hours to evaluate changes in serial SEP during general anesthesia. Nonsurgical and surgical manipulations were performed on one hind limb of five dogs to determine the effects of limb positioning and nerve retraction on SEP. In 13 dogs, the ischiatic nerve was exposed surgically and retracted until the SEP deteriorated and disappeared, to determine the relationship between amount of tension on the nerve and the time to complete deterioration of the SEP. Sensory evoked potential waveforms, which consisted of two to five peaks, were stable throughout the anesthetic period. The first two peaks were the most stable. Latency of the first two peaks was the easiest and most reliable parameter to evaluate. Although the peak latency in recordings from the superior hind limb was always slightly longer, SEP recordings from the inferior limb were good controls to monitor nerve function. There was considerable variation in sensitivity to nerve retraction. The technique proved to be a reliable way to monitor nerve function in normal anesthetized dogs.     

Aspects on Hormonal Control of Normal and Induced Parturition in the Dog

Average length of gestation on the dog is 63 ± 2 days but may vary between 57-71 days due to the long period of receptivity at oestrus and the extended period of sperm survival in the female genital tract. In contrast to other domestic animals progesterone- and oestrogen concentrations are almost identical in pregnant and non pregnant bitches, except for their rapid decline immediately prior to parturition. Control of luteolysis still poorly understood. Experiments with indomethacin leading to a blockade of the prepartal PgF_2α increase, which commences with the decrease of progesterone, point toward a role of PgF_2α at this stage of pregnancy, which was extended for several days. At physiological conditions first visible signs of parturition were observed at peak-PgF_2α levels, 33.6 ± 17.6 hours after onset of luteolysis, which lasted over 16.8 ± 3.4 hours. Pulse-type releases of oxytocin were only observed after this point of time. To test for the effect of progesterone-withdrawal, four 51-57 days pregnant bitches were treated with the antiprogestin RU 38486 which inhibits the activity of progesterone at the receptor level. In all dogs first visible signs of parturition were observed 33.5 ± 7.5 hours after onset of treatment. However, the process of parturition came to an end after cervical opening and totally only one puppy was born. Different to a normal parturition no increase of PgF_2α was observed. Relaxin levels were not influenced by treatment. These observations suggested that treatment with antiprogestin followed by PgF_2α might be an adequate method to induce parturition in the dog; first experiences seem to confirm this conclusion.     

孕激素诱导的生长激素与犬的乳腺肿瘤

乳腺肿瘤是犬的最常见的肿瘤，约占母犬肿瘤总数的一半；乳腺肿瘤约有一半是恶性肿瘤，发生转移的比率很高。犬乳腺肿瘤的发病原因还不很明确，它的形成都受哪些因子调节还未完全确定。孕激素能够诱导乳腺组织生成并蓄积生长激素，使乳腺增生，最终导致犬乳腺肿瘤的形成。在此过程中，雌激素受体、孕激素受体、生长激素结合蛋白和生长激素受体在乳腺癌的形成、发展中起关键作用。从内分泌的角度对犬乳腺肿瘤发病机理作了简单综述，以期为激素治疗乳腺肿瘤提供一些理论依据。     

Effects of Acute Hyperventilation on Serum Potassium in the Dog

The effects of increasing respiratory rates on arterial pH, PaCO2, HCO3, and potassium (K) were measured in normal anesthetized dogs. Hyperventilation resulted in increased pH, decreased PaCO2, decreased HCO3, and decreased K compared with those parameters in spontaneously breathing dogs. The changes were related quantitatively: each 10 mmHg decrease in PaCO2 was associated with a pH increase of 0.1, a HCO3 decrease of 2.0 mEq/L, and a K decrease of 0.4 mEq/L. There were no cardiac arrhythmias or clinical signs of hypokalemia. After termination of hyperventilation, serum K was slower to return to control values than PaCO2. The ratio of the duration of hyperventilation to the time required for return of serum K to control was 0.67.     

Temporary Bilateral Carotid Artery Occlusion During Surgical Exploration of the Nasal Cavity of the Dog

Surgical exploration of the nasal cavity and paranasal sinuses of dogs is often necessary to diagnose or treat conditions causing complete or partial nasal obstruction. Hemorrhage may obscure exploration and be detrimental to the patient. Temporary occlusion of both common carotid arteries reduces blood loss and enhances visualization during rhinotomy. Temporary bilateral common carotid artery occlusion was performed on 15 dogs subjected to nasal exploration. No obvious detrimental effects were noted.     

Suspected Phenobarbital‐Induced Pseudolymphoma in a Dog

Pseudolymphoma is a drug reaction to anti‐epileptics that is well recognized in humans; it has been reported in one cat but not dogs. In this report, lymphoma‐like clinical signs are suspected to be secondary to phenobarbital administration in a dog. A 2.5‐year‐old male, neutered Shepherd mix presented for a 3‐day history of progressive ataxia, dazed mentation, pyrexia, and lethargy. While hospitalized, the dog developed generalized lymphadenopathy and sustained pyrexia. The dog was receiving levetiracetam and phenobarbital for epilepsy, and serum concentrations of both were within standard therapeutic ranges. Abdominal ultrasound revealed hepatomegaly, splenomegaly, and generalized lymphadenopathy. Cytology of the peripheral lymph nodes was consistent with reactive lymph nodes, and aspirates of the liver and spleen revealed histiocytic‐neutrophilic inflammation. Phenobarbital was discontinued and replaced with zonisamide. Within 24 hours, the dog was normothermic, and other clinical signs resolved within a week. This case highlights a potentially serious yet reversible adverse reaction to phenobarbital in a dog. This idiosyncratic reaction could be mistaken for neoplasia and is an important differential for lymphoma‐like signs in any dog administered phenobarbital.     

Effects of Xylazine and Ketamine on Epinephrine-lnduced Arrhythmia in the Dog

Ten dogs were studied to determine the effects of xylazine, ketamine, and xylazine combined with ketamine on the dosage of epinephrine required to produce ventricular arrhythmia. Untreated dogs required an arrhythmogenic dose (AD) of 5.88 +/- 2.85 micrograms/kg/min. The AD was 4.28 +/- 3.25 micrograms/kg/min in xylazine-treated dogs, 3.05 +/- 2.3 micrograms/kg/min in ketamine-treated dogs, and 2.96 +/- 1.95 micrograms/kg/min in xylazine/ketamine-treated dogs. The latter two dosages were significantly less than that of the controls (p less than 0.025). The duration of increased arrhythmogenicity was also examined. Four hours after drug administration, the AD for xylazine-treated dogs was decreased further to 3.87 +/- 2.52 micrograms/kg/min (p less than 0.05). Ketamine-treated dogs had returned partially to normal with an AD of 4.09 +/- 3.09 micrograms/kg/min, as had xylazine/ketamine-treated dogs, at 4.22 +/- 2.71 micrograms/kg/min.     

德国牧羊犬持久性右主动脉弓的诊治

2009年6月收治1条作为肉犬父本的幼龄德国牧羊犬病犬,通过临床症状观察、血液常规指标检查、主要病原检查和影像学检查,确诊为持久性右主动脉弓。对其进行胸部手术治疗,经术后护理该犬恢复良好。     

Magnetic Motor Evoked Potentials for Assessing Spinal Cord Integrity in Dogs with Intervertebral Disc Disease

Magnetically elicited transcranial motor evoked potentials (MEPs) were studied in 37 dogs with type 1 intervertebral disc (IVD) disease. The waveforms were recorded from both cranial tibial muscles before and after surgery. The latencies and amplitudes obtained were compared to those of a control population (n = 14). MEPs were recordable in all dogs with mild or no neurologic deficits, but they were recordable in only 50% of ambulatory dogs that were severely ataxic. MEPs could not be elicited from nonambulatory dogs. There was a significant attenuation of the amplitudes in all clinical cases, even if the dogs demonstrated back pain alone. Significantly prolonged latencies were associated with neurologic deficits. MEPs were not good predictors of neurologic recovery. The responses obtained from the side where the disc material was found were not different from those recorded from the opposite side. MEPs were very sensitive to lesions of the spinal cord, as indicated by the significant changes in the waves in patients with mild or no neurologic deficits and in the loss of response in dogs that still demonstrated purposeful movement. Neurologic exams provided more accurate diagnoses and prognoses than did MEPs in dogs with IVD disease.