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Biomedical subjects

T A Holliday

Publications and source records attributed to T A Holliday.

At least 19 recordsLinked to original sources
PubMed1998

Interictal paroxysmal discharges in the electroencephalograms of epileptic dogs.

Paroxysmal discharges (PD) consisting of spikes, multiple spike complexes, sharp waves, multiple sharp-wave complexes, and spike-and-slow-wave complexes can be recorded in the interictal electroencephalograms of sedated epileptic dogs. With appropriate methods, focal PD can be detected and the hemisphere of origin and rostrocaudal location of their sources identified. Electrode montages that permit ready recognition of so-called instrumental phase reversal are especially helpful. PD that are presumably generalized can be recorded from dogs with signalments suggesting inherited/"idiopathic" epilepsy. These PD are described as "presumably" generalized because of the lack of recordings from ventral and ventrolateral cerebral regions. Further study is necessary, attempting to correlate types of PD with types of epilepsy.

Animals↗
PubMed1993

Brainstem auditory evoked potential interwave intervals are prolonged in vitamin B-6-deficient cats.

Vitamin B-6 deficiency has been reported to produce behavioral, neurophysiological and neuropathological abnormalities in a variety of species. In this investigation we used brainstem auditory evoked potentials (BAEP) to determine if vitamin B-6 deficiency in cats affected peripheral and brainstem auditory pathways. Brainstem auditory evoked potentials were recorded from growing cats as they developed vitamin B-6 deficiency, which was confirmed using clinical, hematological and urinary criteria. The BAEP interwave intervals measured from early (wave 1 or 1N) to late waves (5N) or from middle (wave 3) to late waves increased significantly, whereas interwave intervals from early to middle waves did not differ significantly. These results indicate that vitamin B-6 deficiency affects one or more structures of the brainstem that generate the later parts of the BAEP. The finding of prolonged interwave intervals in vitamin B-6-deficient animals is consistent with slowed axonal conduction velocity secondary to defective myelination. Recording BAEP provided a noninvasive means of detecting effects of vitamin B-6 deficiency on specific parts of the central nervous system.

Acoustic Stimulation↗
PubMed1990

Hyperkalemic periodic paralysis in horses.

Eleven horses (3 mares, 7 stallions, 1 gelding) with clinical and biochemical evidence of hyperkalemic periodic paralysis were studied. Each horse had history of episodic weakness, muscular tremors, or collapse, which lasted for periods of a few minutes to hours. Diagnosis was based on hyperkalemia in association with a spontaneous episode of paralysis or by precipitation of an episode by oral administration of potassium chloride. Clinical and biochemical events were documented during spontaneous and induced episodes of muscular weakness. During episodes, electrocardiographic findings were consistent with hyperkalemia. Electromyography performed between episodes revealed fibrillation potentials and positive sharp waves, complex repetitive discharges, and myotonic discharges. Histologic changes in muscle biopsy specimens varied from no overt changes in some horses to vacuolation in type-2B fibers with mild degenerative changes in other horses. Electron microscopy of myofibers revealed dilatations of the sarcoplasmic reticulum. Analysis of blood samples taken serially during induced attacks in 5 horses revealed marked hyperkalemia (5.5 to 9.0 mEq/L), with normal acid-base status, hemoconcentration, and modest changes in muscle-derived enzymes. Close correlation (r2 = 0.882) between total plasma protein and plasma potassium concentrations was observed and indicated a shift of fluid out of the extracellular fluid compartment. Treatment of either spontaneous or induced episodes by IV administration of calcium, glucose, or bicarbonate resulted in rapid recovery. Dietary management or daily administration of acetazolamide effectively controlled episodes. An affected mare was bred to an affected stallion, and 3 affected offspring were produced by embryo transfer. Blood samples from another extended family of affected horses were analyzed for identification of a genetic marker.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Correlation of sensory electroneurographic recordings and myelinated fiber diameters of the superficial peroneal nerve of dogs.

The compound nerve action potential (CNAP) of the superficial peroneal nerve of dogs was investigated to determine: (1) the influence of the stimulation technique on the configuration of the CNAP, with particular attention to late components; (2) the fiber diameter (FD) distribution; and (3) the relationship between FD distribution and CNAP configuration, by reconstruction of CNAP made on the basis of FD distributions. The CNAP were evoked in 9 dogs under halothane anesthesia by 2 stimulation methods: percutaneous needle electrode stimulation and direct stimulation of the exposed superficial peroneal nerve. Recordings were made with percutaneous needle electrodes. Full nerve cross sections of 7 superficial peroneal nerves were prepared for FD morphometric analysis. Reconstruction of CNAP were made on the basis of the FD distributions. Late components of the CNAP could be evoked with either stimulation method, but only with a stimulus intensity of 3 to 5 times maximal for the main (early) component of the CNAP. The FD histograms of 7 analyzed nerves had bimodal distribution. In 5 nerves, peaks were at 4.2 to 4.5 microns and 9.0 to 10.0 microns, with 60% of the fibers in the small-diameter group. In 2 nerves with lower maximal conduction velocities, peaks were shifted toward smaller values. The CNAP reconstructions made by use of FD data closely resembled actual recordings when a fifth-order polynomial function was applied to the relationship between nerve conduction velocity and FD. Reconstructions made by use of 1 or 2 linear functions did not accurately resemble actual recordings.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1989

A necrotizing meningoencephalitis of pug dogs.

Clinical and pathologic features of a sporadic, necrotizing meningoencephalitis affecting adolescent and mature pug dogs are described. Many of the affected animals were closely related. Acute and chronic forms occur, with clinical signs reflecting the pathologic affinity of the disease for the cerebral hemispheres. No etiologic agent has been identified. The extensive necrosis and affinity for the cerebral hemispheres are similar to alphatype herpesvirus encephalitides of other species.

Acute Disease↗
PubMed1987

Neuromuscular abnormalities associated with hypothyroidism and lymphocytic thyroiditis in three dogs.

Various degrees of persistent or paroxysmal paresis involving only the hindlimbs or all four limbs were observed in 3 dogs with hypothyroidism and lymphocytic thyroiditis. Clinical features included lethargy, obesity, alopecia, insidious and progressive paresis, hypotonia, and slow segmental reflexes in 2 dogs. Obesity, alopecia, paroxysmal paresis, and behavior change were observed in the third dog. Laboratory tests indicated that thyroid function was less than normal in all 3 dogs. Abnormal electromyographic potentials and slow motor nerve conduction velocities were found in each dog. Muscle biopsy specimen abnormalities included selective type-II myofiber atrophy in all dogs, whereas one dog had angular atrophy of type-I and type-II myofibers indicative of denervation. A substance that stained with para-aminosalicylic acid was observed within vacuoles of type-I myofibers in one dog. Lymphocytic thyroiditis characterized by lymphocytic infiltration of excised thyroid glands was observed in all dogs.

Animals↗
PubMed1986

Diagnosis and management of an atypical case of canine hydrocephalus, using computed tomography, ventriculoperitoneal shunting, and nuclear scintigraphy.

Hydrocephalus was diagnosed in a 4-month-old Staffordshire Terrier with gastrointestinal and neurologic signs and cervical pain, using computed tomography. A ventriculoperitoneal shunt was used to manage the hydrocephalus. Ventriculoperitoneal shunt patency was assessed, using nuclear scintigraphy. Because of expense and potential shunt complications, a ventriculoperitoneal shunt might not always be practical; however, this mode of diagnosis and management was successful.

Animals↗
PubMed1985

Brain stem auditory-evoked potentials of dogs: wave forms and effects of recording electrode positions.

Wave forms of canine brain stem auditory-evoked potentials (BAEP) and the effects of electrode positions on the wave forms were studied as a basis for experimental and clinical use of BAEP recording. The BAEP regularly consisted of 5 waves (I to V) with latencies and polarities similar to those of other species. In some dogs, waves II, III, and IV contained distinct subpeaks (a, b, c). Waves similar to waves VI and VII of other species were recorded in some dogs. With respect to BAEP, no site on the head was electrically inactive and BAEP could be recorded as far caudally as the caudal cervical region in some dogs. Wave I, positive in recordings from the dorsal midline of the calvaria (vertex) underwent polarity reversal and increased amplitude and duration in recordings made from caudal ventrolateral regions of the head (mastoid region). As a result, wave I partially or totally obscured wave II so that the latter could no longer be clearly identified. Waves IIIa and IIIb were differentially affected by moving the recording site, indicating that their generators were spatially separated. Waves IV and V were also affected by electrode site, consistent with previous reports that they have spatially separated generators in other species. In recordings made with vertex electrodes referenced to the mastoid region ipsilateral to the stimulated ear, wave I appeared as a high-amplitude positive peak with onset latency equalling that in noncephalic reference recordings, but with somewhat later peak latency and longer duration. As a result, wave II was partially or totally obscured so that only 4 major peaks were evident in the BAEP. In contralateral mastoid reference recordings, latency to peak of wave I was unchanged; however, amplitude of all waves was reduced and waves IIa and IIb were not as clearly differentiated as they were in noncephalic reference recordings.

Acoustic Stimulation↗
PubMed1984

Pathways of ascending evoked spinal cord potentials of dogs.

Pathways of the ascending evoked potentials (AEPs) of the spinal cord of the dog were investigated by stimulating rear leg nerves and recording at thoracic levels before and after making selective partial or complete transections of topographic regions of the spinal cord in the L-1 segment: hemisection; ventral quadrant (VQ); dorsal quadrant (DQ); dorsolateral fasciculus (DLF); dorsal columns (DCs). The AEPs were found to be propagated in all topographic areas of the spinal cord. The contribution by the DQ ipsilateral to the stimulated nerve appeared to be the largest. Within the DQ, both the DLF and the DC participated in the AEP but the DLF contribution tended to predominate in the earliest parts while the DC contribution tended to lag somewhat behind that of DLF. The predominance of DLF activity in early phases of the AEP probably reflected the influence of high conduction velocities in muscle afferents and in postsynaptic DLF axons having connections with muscle afferents or with cutaneous afferents. The VQ contribution to the AEP appeared to arise from both crossed and uncrossed pathways but was not otherwise defined. Based on the results and on data in the literature, important considerations in interpretation of AEPs are: the relative numbers of muscle or cutaneous afferent fibers in the stimulated nerves; temporal dispersion of action potentials associated with differences in conduction velocities; conduction distances in the stimulated primary afferent axons and in postsynaptic spinal cord axons.

Animals↗
PubMed1983

Sensory nerve conduction velocities in forelimb of ponies.

Normal nerve conduction velocity values in 10 ponies were determined for sensory nerve fibers in the median and ulnar nerves. A percutaneous signal-averaging technique was developed and used. Medial and lateral palmar digital nerves on the abaxial surface of the proximal sesamoid bones were used as the sites for percutaneous stimulation, whereas recording sites included the medial and lateral palmar nerves just distal to the carpus and the median and ulnar nerves in the middle of the radius. Sensory nerve conduction velocities can be evaluated simply and clinically in the limbs of horses, using percutaneous signal-averaging techniques.

Action Potentials↗
PubMed1982

Indirect imaging of the canine optic nerve, using metrizamide (optic thecography).

Between the optic nerve and its sheath is a small, CSF-filled space that communicates with the subarachnoid space of the brain. A technique for the radiographic opacification of the optic nerve subarachnoid space following the intrathecal injection of metrizamide was investigated in 8 dogs. The technique enabled indirect visualization of the optic nerves from the optic chiasm to the eyeball and of structures within the subarachnoid basal cisterns of the brain, including the optic chiasm, hypophysis, and blood vessels of the cerebral arterial circle. Displacement and obstruction of the optic nerve subarachnoid space were demonstrated after surgically creating optic nerve lesions to simulate orbital tumors and trauma. The technique was found to be safe, effective, and advantageous over other techniques currently available for the visualization of these structures.

Animals↗
PubMed1980

Critical evaluation of creatine phosphokinase in cerebrospinal fluid of dogs with neurologic disease.

Creatine phosphokinase (CPK) concentrations in CSF and in serum of dogs with a variety of neurologic diseases were evaluated. Concentrations of CPK in CSF and serum were diagnostically nonspecific. Although a diagnostic advantage was not found in measurement of CPK concentrations in CSF and serum, it appeared that increased CPK concentration in CSF was associated more frequently with a guarded-to-poor prognosis. The concentration of CPK in CSF was statistically independent of CPK concentration in serum. Cerebrospinal fluid CPK concentration was significantly (P = 0.01) correlated to the number of RBC in CSF. However, CSF concentration of CPK was not significantly correlated to serum, blood, or CSF variables evaluated.

Animals↗
PubMed1979

Percutaneous recording of evoked spinal cord potentials of dogs.

Using a signal-averaging system, potentials evoked by stimulation of nerves in the limbs or tail of dogs were recorded through needle electrodes placed adjacent to the vertebral column. Cord dorsum potentials (consisting of a small triphasic wave followed by a large negative peak and a subsequent slow positive phase) were recorded at the level of the lumbar enlargement after stimulating nerves in the pelvic limb or tail, and at the cervical enlargement after forelimb nerve stimulation. Ascending volleys were recorded from appropriate levels of the spinal cord or from regions of the cauda equina. After forelimb nerve stimulation, a large slow potential, reflecting activation of an unidentified neuronal pool, was recorded at the level of the first cervical vertebra. Percutaneously recorded potentials were closely similar to those recorded directly from the dura mater, suggesting that the method accurately recorded spinal cord electrical events and, therefore, might be of use in studying clinical or experimental spinal cord disease.

Animals↗