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Background Previous study of the diagnostic validity of electroencephalography (EEG) to detect abnormalities in equine cerebral cortical function relied on the administration of various drugs for sedation, induction, and maintenance of general anesthesia but used identical criteria to interpret recordings. Objectives To determine the effects of 2 inhalation anesthetics on the EEG of healthy horses. Animals Six healthy horses. Methods Prospective study. After the sole administration of one of either isoflurane or halothane at 1.2, 1.4, and 1.6 times the minimum alveolar concentration, EEG was recorded during controlled ventilation, spontaneous ventilation, and nerve stimulation. Results Burst suppression was observed with isoflurane, along with EEG events that resembled epileptiform discharges. Halothane results were variable between horses, with epileptiform-like discharges and bursts of theta, alpha, and beta recorded intermittently. One horse died and 2 were euthanized as the result of anesthesia-related complications. Conclusions and Clinical Importance The results of this study indicate that the effects of halothane and isoflurane on EEG activity in the normal horse can be quite variable, even when used in the absence of other drugs. It is recommended that equine EEG be performed without the use of these inhalation anesthetics and that general anesthesia be induced and maintained by other contemporary means.

Background Brainstem auditory evoked response has been an underused diagnostic modality in horses as evidenced by few reports on the subject. Hypothesis/Objectives To describe BAER findings, common clinical signs, and causes of hearing loss in adult horses. Animals Study group, 76 horses; control group, 8 horses. Methods Retrospective. BAER records from the Clinical Neurophysiology Laboratory were reviewed from the years of 1982 to 2013. Peak latencies, amplitudes, and interpeak intervals were measured when visible. Horses were grouped under disease categories. Descriptive statistics and a posthoc Bonferroni test were performed. Results Fifty-seven of 76 horses had BAER deficits. There was no breed or sex predisposition, with the exception of American Paint horses diagnosed with congenital sensorineural deafness. Eighty-six percent (n = 49/57) of the horses were younger than 16 years of age. The most common causes of BAER abnormalities were temporohyoid osteoarthropathy (THO, n = 20/20; abnormalities/total), congenital sensorineural deafness in Paint horses (17/17), multifocal brain disease (13/16), and otitis media/interna (4/4). Auditory loss was bilateral and unilateral in 74% (n = 42/57) and 26% (n = 15/57) of the horses, respectively. The most common causes of bilateral auditory loss were sensorineural deafness, THO, and multifocal brain disease whereas THO and otitis were the most common causes of unilateral deficits. Conclusions and Clinical Importance Auditory deficits should be investigated in horses with altered behavior, THO, multifocal brain disease, otitis, and in horses with certain coat and eye color patterns. BAER testing is an objective and noninvasive diagnostic modality to assess auditory function in horses.

Author(s): Williams, DC; Brosnan, RJ; Fletcher, DJ; Aleman, M; Holliday, TA; Tharp, B; Kass, PH; LeCouteur, RA; Steffey, EP | Abstract: BackgroundThe effects of anesthesia on the equine electroencephalogram (EEG) after administration of various drugs for sedation, induction, and maintenance are known, but not that the effect of inhaled anesthetics alone for EEG recording.ObjectiveTo determine the effects of isoflurane and halothane, administered as single agents at multiple levels, on the EEG and quantitative EEG (qEEG) of normal horses.AnimalsSix healthy horses.MethodsProspective study. Digital EEG with video and quantitative EEG (qEEG) were recorded after the administration of one of the 2 anesthetics, isoflurane or halothane, at 3 alveolar doses (1.2, 1.4 and 1.6 MAC). Segments of EEG during controlled ventilation (CV), spontaneous ventilation (SV), and with peroneal nerve stimulation (ST) at each MAC multiple for each anesthetic were selected, analyzed, and compared. Multiple non-EEG measurements were also recorded.ResultsSpecific raw EEG findings were indicative of changes in the depth of anesthesia. However, there was considerable variability in EEG between horses at identical MAC multiples/conditions and within individual horses over segments of a given epoch. Statistical significance for qEEG variables differed between anesthetics with bispectral index (BIS) CV MAC and 95% spectral edge frequency (SEF95) SV MAC differences in isoflurane only and median frequency (MED) differences in SV MAC with halothane only.Conclusions and clinical importanceUnprocessed EEG features (background and transients) appear to be beneficial for monitoring the depth of a particular anesthetic, but offer little advantage over the use of changes in mean arterial pressure for this purpose.

Background Reports of the use of brainstem auditory evoked response (BAER) as a diagnostic modality in foals have been limited. Hypothesis/Objectives To describe BAER findings and associated causes of hearing loss in foals. Animals Study group 18 foals (15 neonatal, 3 nonneonatal), control group (5 neonatal foals). Methods Retrospective. BAER records from the Clinical Neurophysiology Laboratory were reviewed from the years of 1982 to 2013. Peak latencies, amplitudes, and interpeak intervals were measured when visible. Clinical data were extracted from the medical records. Foals were grouped under disease categories. Descriptive statistics were performed. Results Ten neonatal foals had complete absence of BAER bilaterally and 5 had findings within reference range. Abnormalities were associated with common neonatal disorders such as sepsis, neonatal encephalopathy, neonatal isoerythrolysis, and prematurity. BAER loss also was observed in foals with specific coat color patterns such as completely or mostly white with blue irides or lavender with pale yellow irides. An American Miniature foal with marked facial deformation also lacked BAER bilaterally. One nonneonatal foal with an intracranial abscess had no detectable BAER peaks bilaterally, and 2 older foals, 1 with presumed equine protozoal myeloencephalitis and the other with progressive scoliosis and ataxia, had BAER within normal limits. Conclusions and Clinical Importance In neonatal foals, BAER deficits commonly are complete and bilateral, and associated with common neonatal disorders and certain coat and eye color patterns. Sepsis, hypoxia, bilirubin toxicity, and prematurity should be investigated as potential causes of auditory loss in neonatal foals.

Sensitive analytical methods indicate the presence of hundreds of chemical contaminants in our environment. However, concentration of these pollutants is usually at the low parts per million or parts per billion level. At such low levels, toxicants induce long-term (chronic) rather than short-term (acute) toxicities. Experiments are designed to evaluate chronic toxicity using early bioindicators. Recently, fish have been used as experimental animals because some species show early (weeks as opposed to years in other research animals), sensitive responses. Thus, medaka (Oryzias latipes), following exposure to diethylnitrosamine (DEN), exhibited liver tumors in several weeks; more interestingly its DNA was modified (to a 'DNA-adduct') after only 24-48 hours exposure. Such adducts show promise as early bioindicators because they are formed within hours of exposure. The formation of DNA-adducts were monitored in medaka and rainbow trout (Salmo gairdneri) exposed to DEN by aqueous or intra-peritoneal routes. Using HPLC-Fluorimetry, O (6)-ethylguanine (O (6)-EtGua) was detected and monitored in acid thermal hydrolysates of DNA isolates. (Detection limit for O (6)-EtGua was as low as 3 ng, 1.7×10(-11) moles). Fourier transform cyclotron resonance mass spectrometry with IR laser desorption/ionization was used advantageously to establish the structure of nucleotides, bases and nucleosides directly, without further cumbersome derivatizations. Other aspects of DNA-adducts are discussed.

Background Idiopathic headshaking (HSK) in horses is a distressing disorder in which the etiology and pathophysiology are unknown. Hypothesis Differences in sensory function of the trigeminal nerve exist between healthy and affected horses. Animals Six healthy mature geldings and 6 mature geldings with idiopathic HSK. Methods Prospective study. Sensory nerve action and somatosensory evoked potentials studies were performed. The stimulus site comprised the gingival mucosa dorsal to the maxillary canine. A pair of recording electrodes was placed along the sensory pathway of the trigeminal complex at the infraorbital nerve (R1), maxillary nerve (R2), spinal tract of trigeminal (R3), and somatosensory cortex (R4). Sensory nerve action potential latency (ms), amplitude (μV), duration (ms), area under the curve (μVms), and conduction velocity (m/s) were calculated. Results Threshold for activation of the infraorbital branch of the trigeminal nerve was significantly different between 5 affected (≤5 mA) and 6 control horses (≥10 mA). After initiation of an action potential, there were no differences in all parameters measured and no differences between left and right sides. A horse with seasonal HSK tested during a time of no clinical manifestations showed a threshold for activation similar to control horses. Conclusions and Clinical Importance This study confirms involvement of the trigeminal nerve hyperexcitability in the pathophysiology of disease. Further, results might support a functional rather than a structural alteration in the sensory pathway of the trigeminal complex that can be seasonal. The horse could serve as a natural animal model for humans with idiopathic trigeminal neuralgia.

Background The administration of certain sedatives has been shown to promote sleep in humans. Related agents induce sleep-like behavior when administered to horses. Interpretation of electroencephalograms (EEGs) obtained from sedated horses should take into account background activity, presence of sleep-related EEG events, and the animal's behavior. Hypothesis Sedatives induce states of vigilance that are indistinguishable on EEGs from those that occur naturally. Animals Six healthy horses. Methods Digital EEG with video was recorded after administration of 1 of 4 sedatives (acepromazine, butorphanol, xylazine, or detomidine). Serum drug concentrations were measured. Recordings were reviewed, states were identified, and representative EEG samples were analysed. These data were compared with data previously obtained during a study of natural sleep. Results Butorphanol was associated with brief episodes resembling slow wave sleep in 1 horse. Acepromazine led to SWS in 3 horses, including 1 that also exhibited rapid eye movement sleep. Periods of SWS were observed in all horses afer xylazine or detomidine administration. Normal sleep-related EEG events and heart block, occurred in association with SWS regardless of which sedative was used. Spectral data varied primarily by state, but some differences were observed between sedative and natural data. Conclusions and Clinical Importance Qualitatively, EEG findings appeared identical whether sedation-induced or naturally occurring. The startle response and heart block associated with some sedatives may be related to sleep. Alpha2 agonists can be used to obtain high quality EEGs in horses, but acepromazine does not promote a relaxed state in all animals.

The anatomic/physiologic basis and uses of somatosensory evoked potential recordings are presented. A brief summary of the use of electromyography in spinal cord diseases is included.

In a survey of 900 Dalmatian dogs, brainstem auditory-evoked responses (BAER) and clinical observations were used to determine the incidence and sex distribution of bilateral and unilateral BAER abnormalities and their association with heterochromia iridis (HI). To assess the efficacy of BAER testing in guiding breeding programs, data from 749 dogs (subgroup A), considered to be a sample of the population at large, were compared with data from a subgroup (subgroup B; n = 151) in which selection of breeding stock had been based on BAER testing from the beginning of the 4-year survey. Brainstem auditory-evoked responses were elicited by applying click stimuli unilaterally, while applying a white noise masking sound to the contralateral ear. Under these conditions, BAER were either normal, unilaterally absent, or bilaterally absent. Dogs with bilaterally absent BAER were clinically deaf; dogs with unilaterally absent BAER were not clinically deaf but appeared dependent on their BAER-normal ears for their auditory-cued behavior. Dogs with unilaterally absent BAER often were misidentified as normal by uninformed observers. Among the 900 dogs, 648 (72.0%) were normal, 189 (21.0%) had unilateral absence of BAER, and 63 (7.0%) had bilateral absence of BAER or were clinically deaf and assumed to have bilaterally absent BAER (n = 4). Total incidence in the population sampled was assumed to be higher, because some bilaterally affected dogs that would have been members of subgroup A undoubtedly did not come to our attention. Among females, 24.0% were unilaterally abnormal and 8.2% were bilaterally abnormal whereas, among males, 17.8% were unilaterally abnormal and 5.7% were bilaterally abnormal.(ABSTRACT TRUNCATED AT 250 WORDS)

Background: Facial and vestibulocochlear nerve dysfunction occurs commonly in horses with temporohyoid osteoarthropathy (THO); however, auditory dysfunction has not been thoroughly assessed. Objective: To determine if auditory abnormalities occur in horses with THO. Animals: Eleven diseased and 8 control horses. Methods: This is a prospective study in which brainstem auditory-evoked responses (BAER) were recorded in 11 horses diagnosed with THO through neurologic, endoscopic, radiographic, or computed tomographic examinations. BAER findings were compared with those recorded from 8 adult control horses. Results: All horses with THO were found to have BAER abnormalities that included complete unilateral BAER loss (82%, n = 9/11), partial unilateral BAER loss (18%, n = 2/11) on the most affected side, and contralateral partial BAER loss (46%, n = 5/11). Nine horses had bilateral THO based on diagnostic imaging findings; of these, 5 (56%) horses also had bilateral BAER abnormalities. The complete absence of BAER in affected horses was most consistent with peripheral sensorineural hearing loss. There was a significant association between complete BAER loss and neurologic and diagnostic abnormalities. Conclusions and Clinical Importance: Auditory abnormalities such as complete or partial BAER loss are common in horses with THO. The BAER test is an objective diagnostic tool that can aid along with other diagnostic modalities in the assessment, management, and follow-up of horses with THO. Furthermore, BAER studies may help to elucidate the pathophysiology of THO in horses.

Background: The influence of sleep on the equine electroencephalogram (EEG) has not been well documented. Hypothesis: The objectives were to develop a noninvasive method of electrode placement for recording the EEG in horses and to establish normal EEG parameters for the various states of vigilance. Findings are compared with previously published reports on equine sleep based on electrocorticography (ECoG). Animals: Five neurologically normal horses. Methods: Overnight EEGs were recorded digitally in association with simultaneous videotaping of the horses' behavior. Data were analyzed by visual inspection, states of vigilance were identified, and representative segments were quantitatively processed. Transient EEG events were examined. Results: Slow wave sleep (SWS) was significantly different (P < .05) in frequency and power from drowsiness and rapid eye movement (REM) sleep. Second-degree heart block was associated with SWS as were transient events commonly recognized in EEGs of humans. Drowsiness and REM sleep were similar. In both, background activity was low-amplitude β activity admixed with prominent activity of approximately 4 Hz. Standing REM sleep was associated with numerous partial collapses in 1 horse. Conclusions and Clinical Importance: Normative data for several states were described and probable benign variants identified. This information will serve as control data for sedative and anesthetic studies in this species. The sleep patterns observed during this study are those of horses removed from their usual surroundings, and thus may represent those encountered in a clinical environment.

Background:Epilepsy is relatively uncommon in horses compared with other species and limited information is available. Hypothesis:The objectives of the study were to describe the age of onset, clinical signs, clinicopathologic data, electroencephalographic findings, treatment, and outcome, including long-term prognosis in Arabian foals with idiopathic epilepsy. Animals:Twenty-two foals were included in the study. Materials and Methods: Medical records from 1985 to 2005 were reviewed. Results:The age of onset of affected foals ranged from 2 days to 6 months. Seizures were characterized by generalized tonic and clonic motor activity, staring, and loss of consciousness. The most common postictal signs were transient blindness and abnormal mental status. The interictal neurologic examination was otherwise normal. Clinicopathologic data and imaging diagnostics were normal except in 4 foals that developed complications. Electroencephalography revealed epileptiform activity in 9 of 13 foals. Foals were treated with benzodiazepines for the short-term; whereas phenobarbital was used over the long-term. Potassium bromide was added in 3 foals in which seizures were multiple, frequent, and difficult to control. The long-term prognosis was favorable with cessation of seizures by 1 year of age. The most common complication was head trauma. The most common concurrent disease was pneumonia. Conclusions and Clinical Importance: Juvenile idiopathic epilepsy of Egyptian Arabian foals has an early clinical onset but appears to be self-limiting. Information obtained from this study strongly suggests a heritable condition that merits further investigation.

A discriminant function analysis based on seven postcranial measurements for the metric assessment of race is presented. A sample from the Terry Collection (NMNH) was used to create independent functions for African-American males and females, and European-American males and females. The functions were tested using known forensic cases from the Maxwell Museum of Anthropology and the C.A. Pound Human Identification Laboratory. Based on the Terry Collection sample, correct classification of race for males was 87.0%, and for females 100.0%. For the independent test population, correct classification for males was 81.8%, and for females only 57.1%. The low classification for females is most likely due to sample bias.

The low brachial and crural indices of the European Neandertals have long been considered indicative of cold adaptation. Recent work has documented lower limb/trunk ratios and deeper chests (anterior-posterior diameter) in European Neandertals than among their successors. The present study uses variables reflective of limb length, body mass and trunk height, and compares European Neandertals to 15 globally diverse recent human samples (1 "Eskimo," 3 North African, 4 sub-Saharan African and 7 European). Bivariate plots, as well as principal components analysis plots of log shape-transformed data, indicate that European Neandertals had an overall body shape that falls at the extreme end of modern higher latitude groups' range of variation. Cluster analysis (minimum spanning tree on a principal coordinates plot) indicates that the Neandertals are closest in body shape to modern "Eskimos," but even in this dendrogram, they are joined to the "Eskimo" via a long branch. In fact, it appears that European Neandertals were "hyperpolar" in body shape, likely due to two factors: 1) the extremely cold temperatures of glacial Europe and 2) less effective cultural buffering against cold stress.

In our previous study, we proposed a unique sampling technique for mutagens in marine environment by suspending an absorbent, blue rayon, selective to polycyclic mutagens with three or more fused rings. By using this technique, we were able to bring back a small amount of adsorbent, weighing less than 10 g, from remote sampling sites, rather than large volumes of water. In the summer of 1990, a collision of barge tankers occurred in Galveston Bay and approximately 500,000 gal of oil were spilled into the Bay. Several sites in Galveston Bay were sampled 5-7 d after the oil sill. We characterized the pollutants chemically and detected the mutagenicity. We designed the present study to examine the applicability of our technique from two points of view. One was to determine if there was a correlation between mutagenicity of blue rayon-adsorbed compounds and the level of known mutagens detected in water samples from the same site. The other was to certify if the sampling technique provided a convenient method for handling water samples collected at remote sites. The chemical analysis was carried out in Texas (U.S.A.) an the mutagenicity testing was done in Okayama (Japan). 7 refs., 2 figs., 1 tab.

A useful and important addition to characterization of identification of plastic explosives, especially ultra-low levels, by these analytical methods would be the ability to obtain their molecular weight or a pseudomolecular mass. This is difficult or impossible to do using conventional techniques since these compounds have low vapor pressures and are thermally labile. Using Fourier Transform--Ion Cyclotron Resonance--Mass Spectrometry, we have obtained molecular mass or pseudo-molecular mass information on some common explosives, viz. RDX, PETN and TNT.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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.

The anatomic/physiologic basis and uses of somatosensory evoked potential recordings are presented. A brief summary of the use of electromyography in spinal cord diseases is included.

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)

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)

In the acquired form of myasthenia gravis in dogs, there are circulating antibodies to acetylcholine receptors (AChRs) and a reduction in the number of AChRs in the postsynaptic membrane. In this study, immune complexes were localized at the neuromuscular junctions in biopsy samples from 10 myasthenic dogs by immunocytochemical means employing conjugates of staphylococcal protein A and horseradish peroxidase. Immune complexes were observed in approximately 70% of the neuromuscular junctions studied in both type 1 and type 2 myofibers. Thus, acquired canine myasthenia gravis appears to involve immune-mediated mechanisms that destroy AChRs in a manner similar to myasthenia gravis in humans. Protein A was also observed to bind principally to elastic fibers in small arteries and arterioles of some myasthenic and control dogs; however, the significance of that localization is unknown.

The literature contains many descriptions of clinical signs observed in animals following experimental injury of the cerebellum or its parts. These descriptions are a valuable source of information for clinicians dealing with animals afflicted with neurological disease. In this paper, this literature is reviewed, and then discussed in the light of its clinical significance. Outstanding in the latter regard are: the marked changes and improvement in clinical signs that occur with time following cerebellar injuries; the similarity of the posture immediately after certain cerebellar lesions to that seen in decerebrate rigidity or in Schiff-Sherrington rigidity; the deficiency of placing reactions after cerebellar lesions, a sign usually taken to indicate abnormality in the corticorubrospinal systems; the occurrence of so-called “paradoxical” vestibular syndromes following certain cerebellar lesions; and the occurrence of anisocoria and inequality of width of the palpebral fissures after certain cerebellar lesions, despite the lack of direct damage to parasympathetic or sympathetic pathways to ocular structures.

In affected muscles of dystrophic chickens, electromyography with needle electrodes revealed hyperexcitability to mechanical stimuli such as electrode movement (prolonged "insertion activity"), spontaneous potentials, and polyphasic motor unit potentials. In agreement with pathological findings in this and previous studies, the light breast muscles exhibited more extensive electromyographic abnormalities than the more distally placed light muscles of the wings, whereas the dark muscles of the legs showed little or no electromyographic abnormality. Electrode movement in the muscles of 5-day-old chickens evoked a discharge of high-frequency, low-amplitude potentials which continued for several seconds. In normal chickens the duration of this discharge diminished with age and reached the adult level, 1 sec, at 30 days of age. Breast muscles of dystrophic chickens first exhibited distinct electromyographic abnormalities at I6 days of age. It is possible that onset occurred earlier but was obscured by the high-frequency discharges normally observed during this period of life.

Because of the universal interest of all engineers in safety in aircraft, this article presents a summary of the conference on aircraft safety sponsored by the committee on air transportation at the 1947 AIEE winter general meeting in New York. It is to be noted that a number of conflicting points of view were expressed at this conference, which are summarized herein. Further comments are invited.

As a national defense problem of primary importance, the needs of the aviation industry offer a challenge to the designers and manufacturers of electrical equipment. The author lists the following as some of the important needs already recognized, and warns that others may be expected to develop.

AN ENGINEER needs a goal. In this respect he is no different from the follower of any other profession, art, or trade. Having a goal, every effort and project becomes a step in the final achievement. It is the purpose of this paper to suggest some goals which are on the horizon today. When these goals are reached, it is quite likely that new horizons can be seen. However, let tomorrow take care of itself.

THE MATERIAL that is presented in this paper was gathered during an engineering study on the same subject which was made for the Air Research and Development Command of the United States Air Force. The objective of the study was preparation of recommendations for needed development in the area of ground support for secondary power. In aviation terminology, secondary power is defined as that power which is used for purposes other than the propulsion of aircraft and missiles. Aircraft and missiles are defined as weapons, and a weapon system includes everything that is needed for maintenance, calibration, testing, and training during operational use of the weapon. ?Ground power? substitutes for air-borne secondary power during tests. The familiar secondary power systems are electric, hydraulic, and pneumatic. During the study, it was found desirable to treat air conditioning as a fourth and newly important type of secondary power.

Rapid advances in aviation have created a whole series of new problems for electrical engineers and aviation designers. The electrical and aviation industries must work together to develop satisfactory aircraft electric equipment, standardize minimum requirements for such equipment, and educate members of both industries to comply with these standards.

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.

The dielectric behavior of cerium dioxide with calcium concentrations ranging up to 8 mole % were investigated from 50 to 600 kHz and from room temperature to 1000 deg C. At temperatures less than 500 deg C and calcium concentrations less than 1.0 mole %, barrier layer polarization seemed responsible for the observed dielectric behavior. At larger calcium concentrations and higher temperatures, where ionic conduction predominated, the dielectric behavior was rationalized on the basis of a space charge polarization model involving mobile ionic point defects, which were blocked or partially blocked at the specimen electrodes, and electronic carriers, which were able to freely pass through the electrodes. The effective dielectric constant was found to increase exponentially with temperature with an activation energy of approximately 0.74 eV.

Ascending paralysis developed in 3 dogs, 12 to 14 days following inoculation with a modified live virus, chicken embryo origin, low egg passage, Flury strain rabies vaccine. The paralysis began in the inoculated limb but rapidly involved both hindlimbs. Partial paresis of the forelimbs was seen several days following the hindlimb paralysis in all 3 dogs, and in 1 of these dogs the infection ascended rapidly to the brain as well. Two of the dogs recovered within 1 and 2 months, respectively, but the 3rd dog died within 5 days of the onset of paralytic signs. The fatal case was complicated by naturally acquired coincidental distemper. Serologic studies in 2 dogs and virus isolation from the 3rd dog indicated that rabies virus was the cause of the paralysis in 2 of the dogs and contributed to the disease syndrome in the 3rd dog. Virus could not be isolated from the saliva of CSF of the 2 surviving dogs. The virus isolated in the fatal case appeared to have some of the characteristics of the vaccine virus, as determined by its behavior in mice, cell culture, and embryonating chicken eggs and by its failure to produce Negri bodies in the brain of the infected dog.

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.

Urethral pressure and electromyographic profiles were recorded in 10 healthy adult male cats before and after perineal urethrostomy. There was a significant decrease (P = 0 at 1 week after surgery, P = 0.002 at 3 weeks after surgery) in the mean maximum urethral pressure profile with associated loss of periurethral striated muscle activity.

Systemic lupus erythematosus with polymyositis and polyarthritis was diagnosed in a 7-year-old female Standard Poodle. Pertinent clinical signs included extreme muscular weakness, muscle wasting, atrial fibrillation, and dysphagia due to megaesophagus. Aspiration pneumonia secondary to the megaesophagus contributed to the death of the dog. Serum muscle enzyme activities were increased. Electromyographic findings included fibrillation potentials, positive sharp waves, increased insertional activity, and bizarre high-frequency repetitive potentials. Histopathologic findings in skeletal muscle included myofiber necrosis and phagocytosis; regeneration of myofibers; perivascular and interstitial infiltrations of macrophages, lymphocytes, and plasma cells; and type I and II myofiber degeneration and vacuolation.

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.

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.

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.

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.

The similarity of certain animal diseases to human epilepsy has been recognized for at least 300 years. In the seventeenth century Paracelsus said that epilepsy “exists not only in man but in all living creatures.” Paracelsus also recognized the disease could be inherited and, in stating that “some species of animals suffer the disease by heredity,” has permitted us to deduce that he believed some species might suffer diseases now termed “acquired epilepsy” (for Paracelsus’ quotations, see Lennox and Lennox 1960).

Pathologic findings in mature dogs with old dog encephalitis were compared with the findings in multiple sclerosis, subacute sclerosing panencephalitis and neuromyelitis optica in man. Fluorescent antibody studies in animal and human tissues were compared. Optic neuritis in dogs with chronic distemper shows changes similar to those in the optic tract of human patients with severe demyelinating disease. The pathologic changes in multiple sclerosis, such as perivascular infiltration with lymphocytes, plasma cells and demyelination are similar to those seen in old dog encephalitis. Demyelination in old dog encephalitis is usually diffuse. The findings strongly support a possible relationship of old dog encephalitis to multiple sclerosis, subacute sclerosing panencephalitis, and neuromyelitis optica.

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.