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Biomedical subjects

G M Strain

Publications and source records attributed to G M Strain.

At least 37 records · Page 2Linked to original sources
PubMed1991

Comparison of nerve regeneration through different types of neural prostheses.

Rat sciatic nerve regeneration through three synthetic neural prostheses was compared with regeneration through nerve allografts. The synthetic prostheses were either nonpermeable nonabsorbable (Silastic), permeable absorbable (polyglactin mesh), or permeable nonabsorbable (polypropylene mesh). Animals were evaluated at 10, 24, and 90 days. Functional analysis of nerve regeneration was performed by noninvasive methods: electromyography and walking tracks. Nerve tissue was examined with routine histologic and immunofluorescent techniques. A compressive neuropathy developed with the use of the Silastic implant. A neutrophilic inflammatory infiltrate was consistently associated with implantation of the polyglactin mesh. A strong connective tissue response was noted around the polypropylene mesh. Early recovery of nerve function was seen with the Silastic implants, however, overall nerve function was best in the nerve allograft and polypropylene mesh groups. Polyglactin implantation increases the local inflammatory response and should not be used for nerve anastomoses. If Silastic entubulation is used, it should be removed between 24 and 90 days.

Animals↗
PubMed1991

Hyperbaric oxygen effects on brown recluse spider (Loxosceles reclusa) envenomation in rabbits.

Human loxoscelism was modeled in albino rabbits by injection of brown recluse spider (Loxosceles reclusa) venom, and the effects of daily or twice-daily hyperbaric oxygen treatment on wound healing were investigated. Lesions similar to those seen in humans were produced in rabbits by intradermal injection of 200 microliters of a venom extract (0.21 microgram protein per microliter), including edema and erythema, ischemia and cyanosis in the first 12 hr, extensive purpura by 24 hr, and crateriform ulcer formation by day four, with induration and eschar formation. Hyperbaric oxygen treatments, consisting of two atmospheres absolute (2 ATA) for 60 min, were applied daily (n = 8) or twice daily (n = 8), while control animals (n = 8) received no treatment. Treatments were initiated 72 hr after venom injection (day 3) to duplicate typical clinical treatment delays, and were administered for seven consecutive days. No significant effects of hyperbaric oxygen treatment on lesion healing were seen as measured by lesion area. However, histologic evaluation of wound tissue collected at euthanasia on day 24 showed clear differences between rabbits receiving twice-daily treatments and those receiving daily or no treatment. The former showed complete re-epithelization or slight ulceration, while the latter usually had necrotic cavities extending into the dermis, with myonecrosis and inflammatory cell accumulation. Thus, no superficial differences were seen between groups, but twice-daily treatments resulted in enhanced recovery at the histologic level.

Animals↗
PubMed1991

Electroretinogram and visual-evoked potential measurements in sheep.

Electroretinogram (ERG) and visual-evoked potential (VEP) recordings were taken from ten Suffolk-cross sheep. Stimuli for VEP were 1.5 flashes of white light/s; ERG stimuli were single flashes. The ERG measurements of the a and b wave latencies and a-to-b amplitude were measured between the lower eyelid and the vertex, with ground on the nuchal crest. The VEP after monocular stimulation were measured between the nuchal crest and the interorbital line, with ground on the vertex. Measurements consisted of the latencies to seven alternating positive and negative peaks P1, N1, P2, N2, P3, N3 and P4, and six amplitudes, P1-N1, N1-P2, P2-N2, N2-P3, P3-N3 and N3-P4. Average latencies for the a and b waves were 13.6 and 28.2 ms; the mean ab amplitude was 131.68 microV. Average latencies for the seven VEP peaks were 35.0, 43.1, 52.8, 64.1, 74.5, 90.4 and 112.2 ms. Mean amplitudes ranged from 3.90 to 8.29 microV.

Animals↗
PubMed1991

Postnatal development of the visual-evoked potential in dogs.

Recordings of visual-evoked potentials that were induced by flashes of white light were obtained from 13 Beagle pups to document the development of the response from age 7 to 100 days. Responses were recorded between needle electrodes placed on the nuchal crest and the interorbital line, with ground at the vertex. Five alternating positive (P) and negative (N) peaks were observed in most visual-evoked potentials: P1, N1, P2, N2, and P3. Responses were recorded from 2 pups prior to opening of the eyelids. Recordings were performed without sedation or dark adaptation. Peak latencies were essentially mature (equal to those of adult dogs) by day 11 for P1, and by day 38 for N1 and P2. The latencies to N2 and P3 did not reach adult values by day 100, but did reach plateau values by day 43. The P1-N1 amplitude measurements reached mature levels by day 14, whereas N1-P2 amplitudes were mature by day 32. The P2-N2 and N2-P3 amplitudes reached plateaus that greatly exceeded adult amplitudes by days 50 and 58, respectively. Maturation of visual-evoked potential responses paralleled reported morphologic development of the visual cortex. All of the measured latency and amplitude values had significant (P less than or equal to 0.004) linear regression lines of latency vs age or amplitude vs age.

Animals↗
PubMed1991

Postnatal development of the brain stem auditory-evoked potential in dogs.

Recordings of averaged brain stem auditory-evoked potentials were obtained from 13 Beagle pups of both genders to document the postnatal development of the response from age 1 to 76 days. Responses were recorded between needle electrodes placed on the vertex and the ipsilateral ear, with ground at the interorbital line. Recordings were performed without sedation. Low-amplitude responses to high-intensity stimuli could be recorded from animals prior to opening of the ear canals. Peak latencies did not change after day 20 for peak I, day 30 for peaks II and III, and day 40 for peak V. As a result, the interpeak latencies between peaks I and III did not change after day 30, but continued to decrease until day 40 for peaks III-V and I-V. Peak amplitudes reached plateau values by day 20 (peak I) or day 30 (peaks II, III, and V). All of the measured latency and amplitude values had significant (P less than 0.001) linear regression lines of latency vs age and amplitude vs age. The brain stem auditory-evoked potential thresholds were mature by day 20.

Animals↗
PubMed1990

Antibodies to the neural cell adhesion molecule disrupt functional recovery in injured nerves.

Tubes containing specific monoclonal antibodies to the neural cell adhesion molecule (N-CAM) were applied to transected sciatic nerves to attempt to perturb the recovery of muscle function. Physiological recordings were used to estimate the return of function. The decline of implanted antibody over 28 days was estimated and negatively correlated with the degree of functional recovery. No significant immune responses were detected in response to the implanted material. The data implicated N-CAM as a significant component of nerve regeneration.

Animals↗
PubMed1990

Visual-evoked potentials and electroretinograms in ruminants with thiamine-responsive polioencephalomalacia or suspected listeriosis.

Electrodiagnostic visual testing (electroretinogram [ERG] and visual-evoked potential [VEP]) was performed on 5 ruminants (3 lambs, 1 kid, and 1 steer) with thiamine-responsive polioencephalomalacia (PEM) and on 2 sheep with listeriosis. The lambs and kid had typical clinical signs of PEM, especially blindness. In these animals, the ERG was normal but the VEP was abnormal. Follow-up recordings in the kid and 1 lamb indicated an improvement in VEP recordings accompanying a gradual return of vision after thiamine treatment. Possible subtle changes in VEP peak latencies could not be assessed because of lack of normative VEP data for sheep and goats. All animals had complete return of vision (owner-assessed). The steer did not have signs of blindness, and the ERG and VEP were normal. Changes in VEP accompanying permanent PEM blindness are not known. One sheep with suspected listeriosis had lack of menace response and palpebral and corneal reflexes, but had intact vision. The ERG and VEP were normal. The second sheep with suspected listeriosis had intact menace response and vision, but became acutely blind and died; the ERG was normal, but VEP amplitudes were depressed.

Animals↗
PubMed1989

Simple aliphatic diamines: acute neurotoxicity.

The acute neurotoxicity of a homologous series of diamines (ethylenediamine to 1,6-diaminohexane) was tested by injection into the lateral ventricle of conscious rats, documented as changes in behavior and electroencephalogram (EEG). Three distinct response patterns were seen ranging from prostration and EEG depression, to EEG seizures and convulsions, to a mixture of the patterns. All compounds were acutely lethal after micromole doses.

Animals↗
PubMed1988

Cortical somatosensory-evoked potentials in the horse.

Cortical somatosensory-evoked potentials (SEP) were recorded from thoracic and pelvic limbs in 15 horses (13 Thoroughbreds and 2 Quarter Horses). Ulnar nerve SEP were evoked by electrical stimulation of the lateral palmar branch of the ulnar nerve at the level of the metacarpophalangeal joint. Recordings were taken between electrodes at 2 cm lateral to the vertex (contralateral to the stimulated limb) and the midpoint of the interorbital line. Four peaks were found in all recordings: N1, P1, N2, and P2. Latencies to the peaks were 39.0 +/- 2.7, 45.5 +/- 5.3, 50.4 +/- 5.2, and 62.3 +/- 3.7 ms (mean +/- SD), respectively. Tibial nerve SEP were evoked by stimulation of the lateral plantar nerve branch of the tibial nerve at the level of the metatarsophalangeal joint. Recordings were taken between electrodes at the vertex (contralateral to the stimulated limb) and the midpoint of the interorbital line. Four peaks were also found in all tibial nerve SEP recordings: N1, P1, N2, and P2. Latencies to the peaks were 64.6 +/- 11.8, 84.5 +/- 9.7, 121.2 +/- 11.6, and 134.0 +/- 11.1 ms, respectively. Amplitude variability was high for the ulnar nerve and the tibial nerve SEP. There was no effect of sex seen on peak latency or amplitude, and peak latencies were not affected by body length.

Animals↗
PubMed1987

Diagnosis of partial epilepsy in a goat.

A seizure disorder of 4.5 years' duration in a 6-year-old female Nubian goat was diagnosed as partial epilepsy on the basis of history, focal electroencephalogram (EEG) abnormalities, convulsive response to ketamine, and necropsy findings. The goat appeared to maintain consciousness during her seizures. A 1.5-day period of continuous seizures during a pregnancy at age 1.5 years may have resulted in a postanoxic seizure focus responsible for the seizures. A morphologic cause for the seizures was not detected. Two spontaneous seizures and 2 drug-induced seizures were detected during 1 month of observation after donation. The amplitude of the EEG over the left frontocentral cortex was depressed, and periodic bursts of high-frequency interictal spiking were detected over the same site. Acepromazine, intermittent photic stimulation, or ketamine after acepromazine failed to elicit seizures or EEG abnormalities, but ketamine alone (50 mg, IV) twice elicited seizures. Seizure severity appeared to parallel plasma estrogen concentration.

Animals↗
PubMed1987

Diagnosis of primary generalized epilepsy in a cow.

On the basis of history, electrodiagnostic and neuropharmacologic studies, and results of laboratory testing and necropsy, a seizure disorder of 1.5 years' duration in an 8-year-old Hereford cow was diagnosed as primary generalized epilepsy. Evidence of metabolic, toxicologic, head trauma, or genetic cause of the seizures was not found. A morphologic cause for the convulsions also was not detected. One naturally occurring seizure was recorded electroencephalographically, but interictal EEG abnormalities were not seen. Attempts to evoke a seizure with photostimulation or therapeutic doses of acepromazine, ketamine, tripelennamine, and estradiol cypionate were unsuccessful. The seizure threshold for the CNS stimulant pentylenetetrazol was found to be less than 6 mg/kg, IV; the seizure threshold in a control cow was found to be greater than 12 mg/kg, IV. The pharmacologic protocol used for this cow may be useful for diagnosis of epilepsy in other animals.

Animals↗
PubMed1987

Atraumatic loop electrodes for electroretinography.

A simple method is described for producing inexpensive, atraumatic electrodes for electroretinography. Scleral contact is obtained by a loop of ultra-lightweight stainless steel wire placed between the eye and lower lid. Recordings obtained by this method in animals are equal to those recorded with needle electrodes from the same ophthalmologically normal dog are presented.

Animals↗
PubMed1987

Brain-stem auditory evoked potentials in the alligator. Effects of temperature and hypoxia.

Brain-stem auditory evoked potentials (BAEPs) were recorded from young alligators (Alligator mississippiensis), and the effects of hypothermia, hyperthermia and hypoxia on the wave forms were determined. The wave form shape was similar to the human BAEP, although extra waves were routinely seen. The responses were highly repeatable and varied in a predictable manner as a function of stimulus frequency, polarity, intensity, and body temperature. Rarefaction clicks produced longer wave form latencies than condensation clicks. BAEPs were present over the entire temperature range studied (0-36 degrees C). In contrast, mammalian BAEPs disappear over the temperature range of 20-27 degrees C, and seizures occur at 20-21 degrees C. At temperatures below 20 degrees C, the alligator BAEP peak amplitudes decreased with decreased temperature, but latencies only decreased slightly. At temperatures above 20 degrees C the peak amplitudes increased, and the latencies decreased with temperature. Peak I was largely unaffected by temperature change, while peaks IIIa and V increased 0.015 and 0.018 msec/degree C, respectively, at temperatures above 24 degrees C. Transient brain hypoxia, achieved by inverting the alligator, produced a progressive decrease in BAEP waves to an isoelectric amplitude without greatly altered latencies. The reverse sequence of changes was seen during recovery. Postural effects on blood flow were documented in two alligators with implanted flow probes. Carotid artery blood flow decreased 43% with body inversion, in both anesthetized and unanesthetized alligators, but no sequelae from the hypoxia could be detected. Metabolic differences between mammals and the alligator may account for the alligator's resistance to hypothermia, hyperthermia and hypoxia.

Alligators and Crocodiles↗
PubMed1987

Evoked potential and electroencephalographic assessment of central blindness due to brain abscesses in a steer.

Central blindness in a 3.5-year-old crossbred steer was evaluated by electrodiagnostic techniques. When admitted the steer was depressed, head pressed, and circled to the left. Ptosis and absence of menace response were seen with the right eye, while the left eye was normal; direct and consensual pupillary light responses were normal in both eyes. Brainstem auditory evoked potentials and electroretinograms were essentially normal. The flash visual evoked potential (VEP) was greatly reduced upon stimulation of the right eye, while no VEP peaks could be recognized after flash stimuli were presented to the left eye. The amplitude of the electroencephalogram was depressed over right occipital cortex. Multiple brain abscesses were detected on postmortem examination adjacent to the left thalamus, in the left caudal cerebrum, and right frontal cerebrum. Corynebacterium pyogenes was cultured from abscess exudate; however, no origin for the infection could be determined. Both eyes were microscopically normal. The thalamic abscesses were postulated to have produced the EEG depression. Correlations between the VEP abnormalities and the abscess locations are discussed, based on proposed central nervous system generators of the VEP.

Animals↗
PubMed1986

Electroretinogram and visual-evoked potential measurements in Holstein cows.

The electroretinogram (ERG) and flash visual-evoked potential (FVEP) were recorded from 25 Holstein cows in a clinical setting without dark adaptation. Latencies to the a and b waves of the ERG were measured bilaterally. The ERG recordings were between the lower eyelid of the stimulated eye and the vertex, with ground on the nuchal crest. Stimuli for ERG and FVEP were 1.5 flashes of white light/s. Recorded ERG were highly consistent and repeatable. The average latencies for the a and b waves were 14 and 30 ms; the mean ab amplitude was 43 microV. The FVEP were recorded bilaterally between the middle of the interocular line and the midpoint of the nuchal crest, with ground on the vertex. The FVEP measurements included latencies to 5 alternating positive and negative peaks (P1, N1, P2, N2, and P3) and 4 peak-to-peak amplitudes (P1 to N1, N1 to P2, P2 to N2, and N2 to P3). The P2 peak was consistently the most prominent. Average latencies for the 5 peaks were 46, 64, 86, 106, and 137 ms for P1, N1, P2, N2, and P3, respectively. The FVEP peak-to-peak amplitudes had a high variability.

Animals↗
PubMed1986

Electroencephalogram and evoked potentials in naturally occurring scrapie in sheep.

Electroencephalogram (EEG), brain stem auditory-evoked potential, and flash visual-evoked potential recordings were taken from healthy sheep and from 3 sheep with scrapie, a CNS slow virus infection. The EEG changes included semi-periodic, polyphasic, high-voltage sharp waves (bilaterally synchronous and symmetric in all channels), and a cyclic alternating pattern consisting of a high-voltage low-frequency phase, followed by a low-voltage high-frequency phase. The high-voltage phase occurred with increased arousal, and the low-voltage phase occurred with decreased arousal. Myoclonic jerks were coincident with EEG sharp waves in one sheep with scrapie. Several spontaneous focal seizures were observed. Wave-form amplitudes were greatly reduced in the brain stem auditory-evoked potential and flash visual-evoked potential; degree of reduction did not always correlate with disease severity. The EEG and evoked potential changes were seen in an exposed sheep that had not yet developed clinical signs of scrapie.

Animals↗
PubMed1984

Narcolepsy in a Brahman bull.

Behavioral, electrophysiologic, and pharmacologic tests were performed on a 2 1/2-year-old Brahman bull suspected of having narcolepsy. Placement on a tilt table or electroejaculation induced apparent sleep and cataplexy. Electrophysiologic recordings during the episodes revealed the low-voltage, high-frequency electroencephalogram, reduced electromyogram amplitude, and rapid eye movements in the electrooculogram associated with rapid eye movements sleep. Physostigmine salicylate appeared to elicit and potentiate the episodes, whereas atropine sulfate and imipramine reduced or blocked them. The combined results of the tests supported the diagnosis of narcolepsy.

Animals↗