Feeding frequency does not interact with BPA exposure to influence metabolism or behaviour in zebrafish (Danio rerio)

Resource limitation can constrain energy (ATP) production, and thereby affect locomotion and behaviour such as exploration of novel environments and boldness. Consequently, ecological processes such as dispersal and interactions within and between species may be influenced by food availability. Energy metabolism, and behaviour are regulated by endocrine signalling, and may therefore be impacted by endocrine disrupting compounds (EDCs) including bisphenol A (BPA) derived from plastic manufacture and pollution. It is important to determine the impacts of these novel environmental contexts to understand how human activity alters individual physiology and behaviour and thereby populations. Our aim was to determine whether BPA exposure interacts with feeding frequency to alter metabolism and behaviour. In a fully factorial experiment, we show that low feeding frequency reduced zebrafish (Danio rerio) mass, condition, resting metabolic rates, total distance moved and speed in a novel arena, as well as anxiety indicated by the number of times fish returned to a dark shelter. However, feeding frequency did not significantly affect maximal metabolic rates, aerobic scope, swimming performance, latency to leave a shelter, or metabolic enzyme activities (citrate synthase and lactate dehydrogenase). Natural or anthropogenic fluctuation in food resources can therefore impact energetics and movement of animals with repercussions for ecological processes such as dispersal. BPA exposure reduced LDH activity and body mass, but did not interact with feeding frequency. Hence, behaviour of adult fish is relatively insensitive to disruption by BPA. However, alteration of LDH activity by BPA could disrupt lactate metabolism and signalling and together with reduction in body mass could affect size-dependent reproductive output. BPA released by plastic manufacture and pollution can thereby impact conservation and management of natural resources.

Bisphenol S reduces locomotor performance and modifies muscle protein levels but not mitochondrial bioenergetics in adult zebrafish

Human activity has now introduced novel chemicals into most aquatic ecosystems. Endocrine-disrupting compounds originating from plastic pollution and manufacture can have pronounced biological effects by disrupting hormone-mediated processes. Bisphenol A (BPA) is one of the most commonly produced endocrine-disrupting compounds, which interferes with signalling by a broad range of hormones. In recognition of its potentially harmful effects, BPA is being replaced by substitutes such as bisphenol S (BPS). However, toxicological studies revealed that BPS too can bind to hormone receptors and disrupt signalling, particularly of thyroid hormone. The aim of this study was to test whether BPS exposure impacts locomotor performance and muscle function in zebrafish (Danio rerio). Locomotor performance depends on thyroid hormone signalling, and it is closely related to fitness so that its disruption can have negative ecological and evolutionary consequences. BPS exposure of 15 μg l^-1 [∼60 nM] and 30 μg l^-1 (but not 60 μg l^-1) decreased sustained swimming performance (U_crit), but not sprint speed. In a fully factorial design, we show that living in flowing water increased U_crit compared to a still water control, and that BPS reduced U_crit under both conditions but did not eliminate the training effect. In a second factorial experiment, we show that BPS did not affect mitochondrial bioenergetics in skeletal muscle (state 3 and 4 rates, respiratory control ratios, ROS production), but that induced hypothyroidism decreased state 3 and 4 rates of respiration. However, both hypothyroidism and BPS exposure decreased activity of AMP-activated protein kinase (pAMPK:total AMPK) but increased protein levels of myocyte enhancer factor 2, and slow and fast myosin heavy chains. Our data indicate that BPS is not a safe alternative for BPA and that exposure to BPS can have ecological consequences, which are likely to be at least partly mediated via thyroid hormone disruption.

Bisphenols impact hormone levels in animals: A meta-analysis

Bisphenols are used in the manufacture of plastics and are endocrine disrupting compounds detectable in free living organisms and environments globally. The original bisphenol, bisphenol A (BPA), is best known as a xenoestrogen, but it also disrupts other steroid hormones and other classes of hormones including thyroid and pituitary hormones. When its toxicity became better known, BPA was replaced by presumably less toxic alternatives, including bisphenols S, F, and AF. However, recent data suggest that all bisphenols can have endocrine disrupting effects, although their impacts remain unresolved particularly in non-human animals. Our aim was to establish the current state-of-knowledge of the effects of different bisphenols on circulating hormone levels in non-human animals. Our meta-analysis showed that a diverse range of hormones (including thyroid hormones, corticosterone, follicle stimulating hormone, luteinizing hormone, and estradiol) are strongly impacted by exposure to any bisphenol type, and that in laboratory rats (Rattus norvegicus) the effect was modified by life-stage. Although there were qualitative differences, BPA alternatives had as great or greater effects on hormone levels as BPA. However, data coverage across hormones was uneven, and most studies measured the effects of BPA on vertebrate reproductive hormones. Similarly, taxonomic coverage was poor. Over 80% of data originated from laboratory rats and zebrafish (Danio rerio) and there are no data for whole classes of invertebrates and vertebrates (e.g., amphibians). Our results show that all bisphenols alter circulating levels of a broad range of hormones. However, the current state-of-knowledge is incomplete so that the ecological impacts of bisphenols are difficult to gauge, although based on the available data bisphenols are likely to be detrimental to a broad range of taxa and ecosystems.

Suboptimal Embryonic Incubation Temperature Has Long-Term, Sex-Specific Consequences on Beak Coloration and the Behavioral Stress Response in Zebra Finches

Secondary sex characteristics, like beak color in some avian species, have indirect impacts on reproductive success, as they are considered to be honest indicators of condition, immunocompetence, and developmental history. However, little is known about the long-term effects of environmental perturbations on the production and maintenance of these secondary sex characteristics in avian species. In zebra finches (Taeniopygia guttata), redder beaks indicate increased carotenoid expression and implantation into beak tissue, and female zebra finches prefer males with pronounced bright red beaks as a mate. The present study examines the long-term effects of embryonic incubation temperature on the maturation of beak color in zebra finches. We also investigated the effects of embryonic incubation temperature on sensitivity to a handling and restraint stressor in adulthood. Specifically, the aims of this study were to examine: (1) whether suboptimal incubation temperatures affect the timing of beak color development and color characteristics before and after sexual maturity, (2) if repeated handling causes short-term changes in beak color and whether color changes are related to embryonic thermal environment, and (3) how thermal stress during incubation alters future responses to a repeated handling stressor. Zebra finch eggs were randomly assigned to one of three incubators: “Control,” “Low,” or “Periodic Cooling.” Beak color (hue, saturation, and value) was quantified before [45, 60, 75 days post-hatch (dph)] and after sexual maturity (95 dph), as well as after repeated handling stress later in adulthood (avg of 386 dph). We found that there were age- and sex- specific effects of incubation treatment on beak hue, where females from periodically cooled eggs had decreased hues (redder) in adulthood. Additionally, eggs laid later in a clutch had decreased beak saturation levels throughout life regardless of incubation environment. We found that females had lower beak hue and saturation following a capture and restraint stressor, while males showed increased beak saturation. Lastly, males subjected to the Low incubation treatment had relatively higher activity levels during restraint than those in the Control group. Overall, these findings suggest that fluctuating incubation temperatures combined with repeated, short-term stressors can have significant, sex-specific effects on sexual ornamentation and behavior.

Postnatal expression of IGF2 is the norm in amniote vertebrates

The insulin and insulin-like signalling (IIS) network plays an important role in mediating several life-history traits, including growth, reproduction and senescence. Although insulin-like growth factors (IGFs) 1 and 2 are both key hormones in the vertebrate IIS network, research on IGF2 in juveniles and adults has been largely neglected because early biomedical research on rodents found negligible IGF2 postnatal expression. Here, we challenge this assumption and ask to what degree IGF2 is expressed during postnatal life across amniotes by quantifying the relative gene expression of IGF1 and IGF2 using publicly available RNAseq data for 82 amniote species and quantitative polymerase chain reaction on liver cDNA at embryonic, juvenile and adult stages for two lizard, bird and mouse species. We found that (i) IGF2 is expressed postnatally across amniote species and life stages-often at a higher relative expression than IGF1, contradicting rodent models; (ii) the lack of rodent postnatal IGF2 expression is due to phylogenetic placement, not inbreeding or artificial selection; and (iii) adult IGF2 expression is sex-biased in some species. Our results demonstrate that IGF2 expression is typical for amniotes throughout life, suggesting that a comprehensive understanding of the mechanisms mediating variation in life-history traits will require studies that measure both IGFs.

Endocrine disruption from plastic pollution and warming interact to increase the energetic cost of growth in a fish

Energetic cost of growth determines how much food-derived energy is needed to produce a given amount of new biomass and thereby influences energy transduction between trophic levels. Growth and development are regulated by hormones and are therefore sensitive to changes in temperature and environmental endocrine disruption. Here, we show that the endocrine disruptor bisphenol A (BPA) at an environmentally relevant concentration (10 µgl^-1) decreased fish (Danio rerio) size at 30°C water temperature. Under the same conditions, it significantly increased metabolic rates and the energetic cost of growth across development. By contrast, BPA decreased the cost of growth at cooler temperatures (24°C). BPA-mediated changes in cost of growth were not associated with mitochondrial efficiency (P/O ratios (i.e. adenosine diphosphate (ADP) used/oxygen consumed) and respiratory control ratios) although BPA did increase mitochondrial proton leak. In females, BPA decreased age at maturity at 24°C but increased it at 30°C, and it decreased the gonadosomatic index suggesting reduced investment into reproduction. Our data reveal a potentially serious emerging problem: increasing water temperatures resulting from climate warming together with endocrine disruption from plastic pollution can impact animal growth efficiency, and hence the dynamics and resilience of animal populations and the services these provide.

Genetic contribution to high temperature tolerance in Cryptococcus neoformans

The human fungal pathogen Cryptococcus neoformans relies on a complex signaling network for the adaptation and survival at the host temperature. Protein phosphatase calcineurin is central to proliferation at 37°C but its exact contributions remain ill-defined. To better define genetic contributions to the C. neoformans temperature tolerance, 4031 gene knockouts were screened for genes essential at 37°C and under conditions that keep calcineurin inactive. Identified 83 candidate strains, potentially sensitive to 37°C, were subsequently subject to technologically simple yet robust assay, in which cells are exposed to a temperature gradient. This has resulted in identification of 46 genes contributing to the maximum temperature at which C. neoformans can proliferate (Tmax). The 46 mutants, characterized by a range of Tmax on drug-free media, were further assessed for Tmax under conditions that inhibit calcineurin, which led to identification of several previously uncharacterized knockouts exhibiting synthetic interaction with the inhibition of calcineurin. A mutant that lacked septin Cdc11 was among those with the lowest Tmax and failed to proliferate in the absence of calcineurin activity. To further define connections with calcineurin and the role for septins in high temperature growth, the 46 mutants were tested for cell morphology at 37°C and growth in the presence of agents disrupting cell wall and cell membrane. Mutants sensitive to calcineurin inhibition were tested for synthetic lethal interaction with deletion of the septin-encoding CDC12 and the localization of the septin Cdc3-mCherry. The analysis described here pointed to previously uncharacterized genes that were missed in standard growth assays indicating that the temperature gradient assay is a valuable complementary tool for elucidating the genetic basis of temperature range at which microorganisms proliferate.

Periodic Cooling during Incubation Alters the Adrenocortical Response and Posthatch Growth in Zebra Finches

AbstractIn birds, incubation temperature is critically deterministic for a range of traits. When parents leave the nest to forage, developing embryos can be exposed to cooling events that represent thermal stress. To investigate the consequences of periodic cooling on offspring development and physiology, we exposed zebra finch embryos to cooling events throughout the incubation period. We then compared embryonic survival, egg mass change, incubation duration, posthatch growth, and adrenocortical response of these individuals with embryos reared at a constant optimal temperature of 37.4°C and embryos reared at a constant suboptimal temperature of 36.4°C, the mean incubation temperature of periodically cooled embryos. There were no differences in embryonic survival or egg mass change during incubation, but individuals exposed to periodic cooling had longer incubation periods than those from the 37.4°C treatment and shorter incubation periods than those from the 36.4°C treatment. Periodically cooled individuals showed slower posthatch growth in comparison with both constant-temperature treatments, but this did not impact adult body size. Treatment groups did not differ in their adrenocortical response, but embryos exposed to periodic cooling and a constant temperature of 37.4°C were able to habituate to repeated capture and restraint stress, while individuals exposed to the constant temperature of 36.4°C were not. These results point to the differential impacts of cooling events versus constant low temperatures during incubation on posthatch growth and physiology and may represent a way for parents to devote less energy toward incubation while still ensuring offspring success.

Tinnitus: etiology and management

Tinnitus is the perceived sensation of sound in the absence of acoustic stimulation. Individuals who suffer from it are commonly between the ages of 40 and 80 years. Tinnitus is often classified as objective or subjective, yet the pathophysiologic cause is still unknown. Subjective tinnitus is largely identified with hearing loss. Management of tinnitus is based on an individual approach; there is no single treatment or regimen for it.

Otolaryngologic management of dizziness in the older patient

Studies report that dizziness is the most common presenting symptom in older patients who seek primary care. To understand the causes of dizziness, which is one of the major risk factors in causing falls in the older population, basic anatomy and physiology are reviewed in this article. Age-specific histopathologic changes occur in the labyrinth of the inner ear. To display evidence of the patient's symptoms, evaluation must include a comprehensive history, neurotologic examination, and diagnostic testing. There are common disorders associated with dizziness; thus, management depends on the cause. Once a diagnosis is secured, treatment is instituted based on sound medical principles.

Astrocyte reaction in the rat vestibular nuclei after unilateral removal of Scarpa's ganglion

Unilateral vestibular ganglionectomy (UVG) results in a complete degeneration of vestibular nerve fibers and terminals in the ipsilateral vestibular nuclear complex (VNC). A subsequent glial reaction may affect the activities of VNC neurons and thereby influence compensation for lesion-induced vestibular disorders. Expression of glial fibrillary acidic protein (GFAP), a specific marker for reactive astrocytes, was demonstrated immunohistochemically in the rat VNC at 7, 14, and 35 days after UVG. An increased GFAP-positive astrocytic response was evident at 7 days after lesion in all the VNC regions on the lesioned side and in some regions on the unlesioned side and remained through 35 days. The glial response included hypertrophy, which was more prominent at 7 days than at 14 days or 35 days, and proliferation, more prominent at the later times, of GFAP-positive astrocytes. Astrocytic projections around VNC neuron somata and proximal dendrites increased in number and became thicker and more elongated, especially at 14 days, in the lateral vestibular nucleus. It is suggested that UVG results in a bilateral astrocytic reaction in the VNC that would affect the subsequent compensation.

Quantitative autoradiography of 5-[3H]6-cyano-7-nitro-quinoxaline-2,3-dione and (+)-3-[3H]dizocilpine maleate binding in rat vestibular nuclear complex after unilateral deafferentation, with comparison to cochlear nucleus

The distributions of non-N-methyl-D-aspartate and N-methyl-D-aspartate receptors in the rat vestibular nuclear complex were estimated by quantitative autoradiography of 5-[3H]6-cyano-7-nitro-quinoxaline-2,3-dione and (+)-3-[3H]dizocilpine maleate binding, respectively. The binding of 5-[3H]6-cyano-7-nitro-quinoxaline-2,3-dione in the vestibular nuclear complex was also compared with that in the cerebellar cortex and cochlear nucleus. Measurements were made in control rats and in rats with unilateral destruction of the inner ear and removal of the vestibular ganglion. Compared to the unlesioned side, 5-[3H]6-cyano-7-nitro-quinoxaline-2,3-dione binding in the lesioned-side vestibular nuclear complex was decreased significantly in all regions at two to four postoperative days. However, the bilateral asymmetry disappeared in most regions by 30 days. 5-[3H]6-Cyano-7-nitro-quinoxaline-2,3-dione binding increased in the molecular layer of the cerebellar cortex at 30 days after lesion, although there were no clear changes at two to seven days. 5-[3H]6-Cyano-7-nitro-quinoxaline-2,3-dione binding in the cochlear nucleus decreased on the lesioned side, compared to the unlesioned side, in regions receiving significant auditory nerve innervation, but increased in the molecular layer of the dorsal cochlear nucleus. (+)-3-[3H]Dizocilpine maleate binding in regions of the vestibular nuclear complex was reduced on the lesioned side, compared to the unlesioned side, after deafferentation, with the largest reductions usually at 30 postoperative days. It is suggested that: (i) non-N-methyl-D-aspartate receptors are involved in synaptic transmission for both vestibular and auditory nerve fibers, while the involvement of N-methyl-D-aspartate receptors is less certain; (ii) unilateral deafferentation of the vestibular nuclear complex can result in bilateral asymmetries for non-N-methyl-D-aspartate and N-methyl-D-aspartate receptors, which are most prominent at earlier and later survival times, respectively; and (iii) vestibular compensation may involve regulation of both non-N-methyl-D-aspartate and N-methyl-D-aspartate receptors in the vestibular nuclear complex and activation of non-N-methyl-D-aspartate receptor-related processes in cerebellar cortex.

Effects of oral propafenone on defibrillation and pacing thresholds in patients receiving implantable cardioverter-defibrillators. Propafenone Defibrillation Threshold Investigators

OBJECTIVES

The effects of propafenone, a predominantly class IC antiarrhythmic drug, on defibrillation and pacing thresholds were evaluated in patients undergoing cardioverter-defibrillator implantation.

BACKGROUND

Previous studies have shown that the class IC agents encainide and flecainide may increase the energy requirements for pacing and defibrillation. Animal studies with propafenone have shown inconsistent results regarding its effect on defibrillation energy requirements. This report investigated the effects of propafenone on defibrillation and pacing thresholds in humans.

METHODS

After cardioverter-defibrillator implantation, 47 patients were enrolled in a double-blind, three-way parallel, randomized trial of 450 mg/day (Group 1) or 675 mg/day (Group 2) of oral propafenone or placebo (Group 3) for 3 to 7 days. Predischarge defibrillation and pacing thresholds after treatment were compared with baseline thresholds obtained at implantation.

RESULTS

There was no statistically significant difference between implantation and predischarge defibrillation thresholds in the three groups (Group 1: [mean +/- SE] 11.0 +/- 1.3 vs. 12.1 +/- 1.5 J; Group 2: 11.5 +/- 1.1 vs. 13.6 +/- 1.3 J; Group 3: 12.5 +/- 1.2 vs. 13.3 +/- 1.6 J), and no significant difference between treatment groups was found with a 0.86 power to detect a 5-J difference between groups. Paired pulse width pacing thresholds at 2.8 V were compared in 14 patients. A small increase of 0.02 ms was noted at predischarge testing in patients treated with propafenone and placebo.

CONCLUSIONS

Short-term oral propafenone (450 and 675 mg/day) does not significantly affect defibrillation or pacing thresholds. Concomitant use of propafenone in patients with implantable cardioverter-defibrillators with recurrent ventricular or atrial tachyarrhythmias should not interfere with proper device function.

Quantitative changes of amino acid distributions in the rat vestibular nuclear complex after unilateral vestibular ganglionectomy

Changes of amino acid concentrations in the vestibular nuclear complex (VNC) during lesion-induced vestibular compensation were studied in rats after unilateral vestibular ganglionectomy. Distributions of 12 amino acids within the VNC were measured at 2,4,7, and 30 days after surgery, using microdissection of freeze-dried brain sections and HPLC. Glutamate decreased on the lesioned side in nearly all VNC regions. Changes were fully developed 2 days after lesion and persisted through 30 days. In some regions, glutamate decreased also on the unlesioned side, especially at longer survival times, so that bilateral asymmetries became reduced. Aspartate changes were similar to those of glutamate on either side. Lesion-induced glutamine asymmetry was usually opposite to that of glutamate. Although GABA concentration decreased at early survival times, it recovered at later times and sometimes increased in dorsal parts of lateral and medial nuclei. Taurine changes were similar to those of GABA in most regions. Glycine change was primarily limited to a bilateral decrease in the dorsal part of the lateral vestibular nucleus. Concentrations of other amino acids were much lower, but some showed postlesion changes.

Monomorphic right ventricular tachycardia in a patient with mitral valve prolapse

A patient with mitral valve prolapse and symptomatic ventricular ectopy underwent an electrophysiological study during which a sustained monomorphic ventricular tachycardia with a left bundle branch block/right axis deviation morphology was induced. This morphology was replicated by pace mapping at the right ventricular outflow tract. To the best of our knowledge, this finding has not been previously described and suggests that the association between ventricular arrhythmias and mitral valve prolapse may not necessarily be causal.

Comparison of surgeries for removal of primary vestibular inputs: a combined anatomical and behavioral study in rats

Unilateral removal of Scarpa's ganglion and neurectomy of the peripheral vestibular nerve branches were compared in rats as methods to eliminate primary vestibular input. Ocular nystagmus was consistently observed after both types of lesion, but it completely disappeared within 4 to 7 days. Imbalance and rotation were more serious and prolonged after ganglionectomy than after peripheral neurectomy. Corresponding with these differences in symptoms were differences in terminal degeneration. After ganglionectomy, degenerated axons and terminals were distributed throughout all terminal regions of primary vestibular fibers on the lesioned side, while after peripheral neurectomy, the degeneration was more limited. The results of this study suggest that vestibular ganglionectomy is a more successful approach than peripheral vestibular neurectomy for removing the primary vestibular input.

Postural stability following mild head or whiplash injuries

Studies of the sequelae of head injury suggest that cochlear and vestibular dysfunctions, comprise some of the most frequently reported delayed complications following head trauma. To date, little attention has been given to the relation between post-traumatic subjective symptoms of dizziness and the objective measures of postural stability or balance. The purpose of this study was to quantify the balance deficits in individuals who had developed symptoms of dizziness following mild head and whiplash injuries. The balance abilities of 29 patients, who developed dizziness following some type of mild head or whiplash injury, were compared to those of 51 healthy symptom-free subjects. Balance was assessed by examining the center-of-pressure movements, in the anterior-posterior and medial-lateral directions, and the total movement displacement. The isolated contributions of visual and somatosensory inputs were estimated by comparing the magnitudes of the center-of-pressure movements for the various sensory conditions. Data were collected from three 30-second trials of each combination of three visual conditions (accurate, absent, and inaccurate) and two somatosensory conditions (accurate and inaccurate), with the patient standing on a fixed-force platform. Univariate analyses of variance indicated that the group with head injury, compared to the control group, exhibited significantly greater anterior-posterior movements in four of the six sensory conditions and greater total movement displacement during the inaccurate vision/inaccurate somatosensation condition. These data suggest that patients who have sustained head or neck trauma exhibit increased reliance on accurate visual input and are unable to utilize vestibular orienting information to resolve conflicting information from the visual and somatosensory systems.

Sudden hearing loss and unstable angina pectoris

Acute sudden sensorineural hearing loss has been extensively described in the literature and is a well recognized clinical entity. The exact etiology for this entity has been difficult to ascertain. Multiple etiologies have been promoted including infectious agents, vascular abnormalities, acoustic trauma, metabolic disorders, and autoimmune syndromes. In some cases, neoplasms such as acoustic neurinoma can be identified. On occasion, ototoxic medications are present in the history. Moulonguet and Gougelot have associated mitral valve prolapse, microemboli, transient hemiparesis and sudden hearing loss. This report describes a patient who had sudden sensorineural hearing loss in conjunction with unstable angina pectoris, in whom coronary bypass surgery appeared to have resulted in acute and significant hearing improvement and stabilization.

Effect of left ventricular hypertrophy and its regression on ventricular electrophysiology and vulnerability to inducible arrhythmia in the feline heart

BACKGROUND

Left ventricular hypertrophy (LVH) is associated with an increased risk of death, susceptibility to ventricular arrhythmia, and multiple electrophysiological abnormalities. The purpose of the present study was to determine whether the susceptibility to arrhythmia and electrical abnormalities persists after regression of hypertrophy in an animal model of LVH.

METHODS AND RESULTS

We placed constricting bands on the ascending aorta of cats (n = 9) or performed sham operations (n = 9). Serial cardiac echocardiography was performed to measure left ventricular wall thickness. After LVH had developed in the banded animals, the constricting bands were removed and serial echocardiograms were used to monitor for regression of hypertrophy. Electrophysiological studies were performed in cats that showed regression of LVH (Regress, n = 5), those that showed no change in LV wall thickness (No Regress, n = 4), and in the sham-operated animals (Sham). Cats with persistent LVH had a higher incidence of inducible polymorphic ventricular tachycardia (4 of 4) compared with Regress (1 of 5) or Sham (1 of 9) cats (P < .05) and had lower ventricular fibrillation thresholds (9 +/- 2 mA) than Regress (17 +/- 4 mA) or Sham (16 +/- 3 mA) cats (P < .05). Persistent LVH in the No Regress group was associated with prolongation of epicardial monophasic action potential duration (MAPD) in the left but not the right ventricle. Dispersion of refractoriness was greater in the No Regress group (P < .05 versus Regress or Sham). Regress cats were identical to Sham cats in having a low incidence of inducible polymorphic ventricular arrhythmia, high fibrillation threshold, and MAPD measurements (P = NS versus Sham).

CONCLUSIONS

LVH produces multiple electrophysiological abnormalities and increased vulnerability to inducible polymorphic ventricular arrhythmia in this model of LVH. Cats that show regression of hyperthrophy have normal ventricular electrophysiology and have the same low vulnerability to inducible ventricular arrhythmia as Sham animals.

Quantitative distribution of amino acids in the rat vestibular nuclei

The normal concentrations of 12 amino acids in the vestibular nuclei of rats were quantitatively measured using microdissection of freeze-dried brain sections combined with high performance liquid chromatography (HPLC) analysis. Both excitatory amino acids, aspartate and glutamate, showed only small variation across the vestibular nuclei. The distribution of glutamine tended to parallel that of glutamate. The inhibitory amino acids, gamma-aminobutyrate (GABA) and glycine, were much more concentrated in some regions than in others. GABA tended to be more concentrated than glycine in dorsal and rostral nuclei, while glycine tended to be more concentrated than GABA in ventral and caudal nuclei. The distribution of taurine was comparable to that of GABA, suggesting a close relationship with GABA function. Asparagine, serine, threonine, arginine, alanine and tyrosine had relatively low concentrations without significant differences among vestibular nuclei. Our results suggest that (1) different parts of the vestibular nuclear complex may receive similar amounts of excitatory amino acid afferents, (2) there is predominance of GABA or glycine as an inhibitory transmitter in different parts of the vestibular nuclear complex, and (3) there may be a close functional relationship between taurine and GABA within the vestibular nuclear complex. These results provide data basic to further research on the details of amino acid functions in the normal and abnormal vestibular system, as well as studies of plasticity in this system.

Static stabilometry, transcranial Doppler, and single photon emission computed tomography in patients with central dizziness

Previous studies have found that transcranial doppler (TCD) and single photon emission computed tomography (SPECT) are effective means of diagnosing cerebral blood flow disorders in patients with central dizziness whose etiology was unknown by standard audiologic and/or vestibular assessment techniques. Also, static stabilometry, which measures a person's standing center of pressure (COP) movements, has been used to distinguish between patients with central neurologic and peripheral vestibular disorders. The purpose of this retrospective study was to examine the relation between TCD, SPECT, and stabilometry in patients with central dizziness attributable to cerebral blood flow disorders. Stabilometry testing was conducted on 50 normal subjects and 31 subjects with dizziness, the latter group consisting of persons with cerebral dysautoregulation, migraines, and unknown etiology with negative or positive SPECT results. The results indicated that patients with cerebral dysautoregulation were not significantly different from normal subjects or the other three groups in their COP movements. The other three groups exhibited significantly higher COP movements than the normal subjects, particularly when visual inputs were compromised. Patients with negative SPECT results were significantly different in their COP movements from the other three groups of subjects with dizziness. These results suggest that the pattern of COP movements may be useful in identifying patients with postural dysfunctions whose etiology may then be detected by TCD and SPECT.

Central dizziness associated with cerebral blood flow disorders

This retrospective study describes the use of transcranial Doppler (TCD) and history for further defining and diagnosing cerebral blood flow (CBF) disorders in patients with central dizziness. Central dizziness was defined as dizziness of nonlabyrinthine, non-peripheral causes. It was believed that at least some of the causes for central dizziness are not unknown but are associated with CBF disorders. Fifty patients who presented with central dizziness were examined and subsequently tested with TCD. In 33 of 50 cases (66%) a diagnosis could be assigned after TCD; whereas, on the basis of both history and TCD a diagnosis was assigned to 38 patients (76%).

Differentiation of balance deficits through examination of selected components of static stabilometry

Stabilometry, which measures the body's center of pressure (COP) movements, during relaxed standing, has been used to distinguish individuals with vestibular and neurologic dysfunctions from normal subjects. The purpose of this study was to determine whether mathematical differences in the magnitudes of the COP obtained from six somatosensory testing conditions could be used to discriminate between different types of balance deficits. Stabilometry measures, using a fixed force platform, were obtained from normal (N = 52) and dizzy (N = 149), peripheral vestibular dysfunction (PVD), post-concussion syndrome (PCS), psychogenic (PSG), and unknown/undetermined etiology (UNK). The data significantly differentiated CVD, PVD and PSG patients from normals and between some of the dizzy groups: CVD versus PVD, PCS; and PSG versus CVD, PVD, PCS and UNK. The measures of anterior-posterior COP movements provided the greatest discrimination.

Electrophysiologic testing in patients who respond acutely to intravenous amiodarone for incessant ventricular tachyarrhythmias

The outcome of patients who receive intravenous amiodarone for suppression of incessant ventricular tachyarrhythmia has not been studied conclusively. We conducted a prospective study in which all patients who responded acutely to intravenous amiodarone and went on to receive a subsequent oral loading dose were subjected to electrophysiologic testing before hospital discharge to determine whether additional or alternative therapy would be required. Among 18 patients (17 with ischemic heart disease) who entered the protocol, 16 had a clinical response to intravenous amiodarone alone (12 patients) or in combination with another antiarrhythmic drug (4 patients) and survived to study. Of these, 10 had monomorphic ventricular tachycardia (VT) when first seen, five had polymorphous VT or ventricular fibrillation (VF), and three had both. In seven patients sustained monomorphic VT was inducible (group 1), and in nine it was not (group 2). The only clinical factor that distinguished group 1 from group 2 was age (group 1 > group 2). Five patients in group 1 and one in group 2 received an implantable cardioverter defibrillator; one patient in group 1 had a successful endocardial resection. During a mean follow-up period of 11 months, four patients in group 1 have had appropriate implantable cardioverter defibrillator discharges, whereas only one patient in group 2 has had a clinical event (sudden death). We conclude that intravenous amiodarone is a highly effective drug used alone or in combination to suppress spontaneous incessant VT/VF. Predischarge electrophysiologic testing, even in patients who have polymorphous VT, has predictive value over and above the observed clinical response. These preliminary results favor predischarge testing and aggressive device treatment in this cohort.

Head-upright tilt-table testing: a useful tool in the evaluation and management of recurrent vertigo of unknown origin associated with near-syncope or syncope

Recurrent idiopathic vertigo associated with near-syncope and syncope is a common perplexing problem, some cases of which are considered autonomically mediated (vasovagal). Upright-tilt-table testing has emerged as a potential method to test for vasovagal episodes. This study evaluated the use of this technique in the evaluation and management of patients with recurrent idiopathic vertigo associated with near-syncope or syncope. Twenty-one patients with recurrent unexplained vertigo and syncope/near-syncope and 11 control subjects were evaluated by use of an upright-tilt-table test for 30 minutes, with or without a graded isoproterenol infusion (1 to 4 micrograms/min given intravenously), in an attempt to provoke hypotension, bradycardia, or both, which reproduced the patient's symptoms. The patients included 10 men and 11 women (mean age, 51 +/- 16 years). Eleven controls with no history of vertigo were also studied. Transcranial Doppler sonography was used to assess cerebral arteriolar blood flow during tilt. All tilt-positive patients were placed on therapy with either beta-blockers, disopyramide, or transdermal scopolamine, the effectiveness of which was determined with another tilt-table study. Symptoms occurred in seven patients (33%) during the baseline tilt and in eight patients (38%) during isoproterenol infusion (total positives, 71%). Transcranial Doppler sonography demonstrated a 225% +/- 192% increase in pulsatility index and a 70% +/- 29% increase in resistance index (indicative of cerebral arteriolar vasoconstriction) at the time of vertigo. No control subject experienced syncope during this test. Each tilt-positive patient eventually became tilt-negative with therapy, and over a mean follow-up period of 26 months, no further episodes have occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

The team approach to treatment of the dizzy patient

This report describes how a rehabilitation team treats dizziness and vestibular disorders. Team members include a nurse, physician, audiologist, physical therapist, occupational therapist, and a research scientist. Although unusual, this multidisciplinary approach, involving a close-knit group of professionals, is of great benefit in the treatment of vestibular and balance disorders.

Stabilometry in balance assessment of dizzy and normal subjects

Normal adults and patients referred to the Dizzy Clinic at the Medical College of Ohio had their standing balance assessed during combinations of normal and altered visual and somatosensory orientation conditions using a fixed-force platform to measure center-of-pressure translations. Significant differences were identified between normal subjects and dizzy patients, depending on the particular diagnostic category, the sensory condition tested, and the particular sway component being measured. Patients with central and peripheral vestibular dysfunctions had significantly greater sway than all other categories in most test conditions, especially with eyes closed and with a visual conflict dome while standing on a foam surface. The central vestibular dysfunction and peripheral vestibular dysfunction groups could be differentiated statistically under eyes-closed and visual conflict-foam conditions. The normal and psychogenic groups could not be differentiated statistically for any test conditions except one: there was significantly greater mean anterior/posterior sway displacement in the psychogenic group compared with all other diagnostic categories for the eyes-open foam test condition. Our results indicate that static stabilometry recordings of postural sway can be used to evaluate and quantify a dizzy patient's ability to receive and process vestibular, visual, and somatosensory-proprioceptive cues for postural stability. It can also be used to monitor patients with vestibular disorders and to document their responses to rehabilitation programs.

Enzymes of transmitter and energy metabolism in cat middle ear muscles

Activities of the enzymes choline acetyltransferase (ChAT) and acetylcholinesterase (AChE), which metabolize the neuromuscular transmitter acetylcholine, and malate and lactate dehydrogenase (MDH and LDH), enzymes of oxidative and glycolytic energy metabolism, respectively, were measured in the middle ear muscles of the cat. For comparison, the same enzyme activities were measured in extraocular muscle tissue and in three hindlimb muscles rich in either slow oxidative (soleus), fast glycolytic (white part of vastus lateralis), or fast oxidative glycolytic (plantaris) muscle fibers. ChAT and AChE activities were much higher in middle ear muscles than in hindlimb muscles, consistent with a denser neuromuscular innervation, as in extraocular muscles. By contrast, MDH and LDH activities were remarkably low in the middle ear muscles, lower than in any of the hindlimb muscles or the extraocular muscles. Denervation of the stapedius muscle by peripheral transection of the facial nerve resulted in decreases in all four enzyme activities without associated changes in the tensor tympani. Surgical ablation of the peripheral facial nerve supply to the stapedius muscle appears to be a feasible option for producing its denervation. The results suggest some rather specialized chemical characteristics for the middle ear muscles.

Myasthenia gravis with thymoma and pure red blood cell aplasia

A case of myasthenia gravis with histopathologic confirmation of spindle cell thymoma and pure red blood cell aplasia is reported. This is the twelfth case in the literature in which a simultaneous occurrence of all three disorders, with documented thymic pathology, is noted. Immunologic observations in this patient include an elevated acetylcholine receptor antibody and antinuclear antibody titer, agglutination of mouse red blood cells when combined with the patient's serum, and lack of inhibition of binding of radioactive erythropoietin to mouse red cell receptors when combined with the patient's serum. Although both myasthenia with thymoma and pure red blood cell aplasia may have a common immunologic denominator, our findings in this case indicate that inhibition of erythropoiesis is unrelated to erythropoietin receptor blockade. An alternative hypothesis is offered based on defective T-cell function.

Cerebral blindness and encephalopathy with cyclosporin A toxicity

We observed acute cerebral blindness and encephalopathy complicating cyclosporin A (CyA) toxicity in a 5-year-old transplantation patient. Serum CyA level was 1,704 ng/ml (normal, less than 300 ng/ml). Additional neurologic complications of CyA toxicity will be reviewed.

Contextual age as a life-position index

A contextual age construct was developed and examined as a transactional, life-position index of aging. The eighteen-item contextual age index included six interrelated dimensions: physical health, interpersonal interaction, mobility, life satisfaction, social activity, and economic security. In addition to the development of the index, associations among contextual age and sociodemographic characteristics were examined for a sample of 640 persons. Chronological age was correlated negatively with mobility and physical health, and positively with economic security, life satisfaction, and interpersonal interaction. Mobility, economic security, life satisfaction, physical health, and interpersonal interaction discriminated between chronological age groups. Interpersonal interaction, economic security, physical health, and social activity were predictors of life satisfaction. The contextual age construct raises questions concerning several negative myths about aging. The findings reflect the weak validity of chronological age as a unidimensional indicator of life-position and well-being.

The otolaryngologist's attitude to facial plastic surgery

Of 453 Canadian otolaryngologist, 226 responded to a questionnaire, indicating significant interest in the state of facial plastic and reconstructive surgery. The majority of these otolaryngologists practised in larger cities and one-quarter received foreign training. Half of the respondents had academic affiliations and three-quarters considered themselves general otolaryngologists. Almost all the otolaryngologists believed that cosmetic and reconstructive surgery should form a major part of their specialty, this being unanimous among current residents. A large majority felt there should be more facial plastic surgical training, this both at the residency and fellowship levels, preferably through increased surgical exposure. With respect to sub-certification, only the resident group was in favor.

Contextual age as a life-position index

A contextual age construct was developed and examined as a transactional, life-position index of aging. The eighteen-item contextual age index included six interrelated dimensions: physical health, interpersonal interaction, mobility, life satisfaction, social activity, and economic security. In addition to the development of the index, associations among contextual age and sociodemographic characteristics were examined for a sample of 640 persons. Chronological age was correlated negatively with mobility and physical health, and positively with economic security, life satisfaction, and interpersonal interaction. Mobility, economic security, life satisfaction, physical health, and interpersonal interaction discriminated between chronological age groups. Interpersonal interaction, economic security, physical health, and social activity were predictors of life satisfaction. The contextual age construct raises questions concerning several negative myths about aging. The findings reflect the weak validity of chronological age as a unidimensional indicator of life-position and well-being.

Mondini dysplasia--late complications

Mondini's deformity is the second most common malformation seen in congenital genetic deafness. It is characterized by bony and membranous abnormalities of the inner ear, with a wide range of morphological and functional abnormalities. The importance of the Mondini malformation is that the patient is at an increased risk of developing meningitis or bilateral total hearing loss (or both) at an early age. Six cases are presented which illustrate the various sequelae of the Mondini malformation including meningitis, vertigo, and auditory deterioration. Decompression of the endolymphatic sac was undertaken in three patients. Emphasis is placed on the danger of head trauma, even minor, in these patients. The necessity of early diagnosis with adequate patient counseling is stressed.

Optokinetic afternystagmus and post rotatory nystagmus in patients with unilateral labyrinthine lesions

The decay times of optokinetic afternystagmus (OKAN) and the vestibuloocular reflex (VOR) were measured in six subjects with chronic unilateral labyrinthectomy and in six age-matched controls. Both OKAN and VOR decay times showed parallel reduction following unilateral labyrinthectomy when the induced nystagmus beat toward the side of the lesion. The VOR decay time for nystagmus beating toward the contralateral side was also significantly reduced. Our findings support the view that the optokinetic system increases the vestibular decay time, that separate left and right velocity storage mechanisms do exist, but that the decoupling between the two sides is far from perfect.

Near-drowning, scuba diving: an unusual late sequela of bulbar polio

This case report illustrates an unusual hazard of underwater sports: vagal neuropathology secondary to early poliomyelitis which resulted in residual palato-pharyngeal paresis. Gag and swallowing reflexes appeared to function adequately but in fact were not normal. When stressed, during water aspiration, they were inadequate, resulting in great risk to the underwater enthusiast. A history of early viral myelitis must be considered as a potential hazard in underwater sports.

Parathyroid gland transplantation after total thyroidectomy with pharyngolaryngoesophagectomy

Surgical treatment of extensive hypopharyngeal carcinoma often includes total thyroidectomy together with resection of the primary disease. The risk of removing or damaging the parathyroid glands is considerable; this may render the patient permanently hypoparathyroid with all the problems of management. These patients must be on lifelong supplementation and at times, due to failure to take the medication, hypocalcemic crises are precipitated. To avoid this problem, we have been identifying the parathyroid glands intraoperatively and, after pathological confirmation, have transplanted them to the forearm. Three patients who underwent this procedure are presented. All are normocalcemic without supplementation and parathyroid hormone assays on serum from the transplanted forearm show significantly elevated levels.

Head and neck manifestations of mycobacteria in the absence of pulmonary disease

Mycobacterial infections, once relatively rare in North America have recently shown an upsurge with the influx of Asian and African immigrants. The infections are usually due to M. tuberculosis and present with pulmonary symptoms. However, an uncommon presentation is that of a mass in the head and neck region without any pulmonary manifestations. Although these infections are usually secondary to invasion by "atypical" mycobacteria, unusual presentations due to mycobacterium tuberculosis have been noted. Case reports depicting the very rare presentations of M. tuberculosis in the thyroglossal duct cyst, parotid, and submandibular lymph node are described. A very unusual case of atypical mycobacteria in the larynx is noted and cervical adenitis is also included. The initial subtle presentation emphasizes the importance of mycobacteria in the differential diagnosis of lesions in the head and neck region.

Limb input to the cat vestibular nuclei

The input from fore- and hindlimbs to the vestibular nuclear complex (VNC) was investigated in awake cats. Electrical stimulus was given to the sciatic, radial and vestibular nerves bilaterally and single unit responses were recorded in the VNC with extracellular technique. The position of the microelectrode was histologically confirmed. All four major vestibular nuclei received fore- as well as hindlimb input. Forty per cent of the neurons with limb input also received vestibular afferents. No major distinguishing features appeared between the different nuclei with regard to response characteristics. Certain differences in laterality of response, quantitative fore-hindlimb ratio and somatosensory-labyrinthine convergence were observed however. Response latencies to sciatic and radial nerve stimuli always exceeded a 3 msec and were grouped around 8 and 16 msec. A third population of vestibular neurons had latencies over 20 msec. Both excitatory and inhibitory responses were recorded, with the latter not always following an activation. The findings illustrate the complex nature of the ascending pathway to the VNC and the integrative properties of this complex.

Labyrinthine and somatosensory convergence upon vestibulospinal neurons

In awake cats cells forming the lateral (LVST) and medial (MVST) vestibulospinal tracts were identified by employing antidromic stimulation of the spinal cord. Neuronal responses to bilateral vestibular, forelimb, hindlimb, and neck electrical nerve stimulation were analysed. Extracellular recording in the vestibular nuclei was performed via a glass micropipette saturated with Fast Green, to aid in later histological tract identification. The number of cells projecting to cervical and lumbar regions in the dorsal and ventral division of Deiters' nucleus did not differ significantly. An unexpectedly large number of MVST units was found in the descending nucleus. Some MVST units projected to the lumbar cord but in both the medial and descending nuclei, projections to the cervical cord were in majority. Almost all spinal projecting vestibular neurons received labyrinthine input and more than half received somatosensory input. The units could be separated into several populations on basis of excitatory and inhibitory labyrinthine response latencies indicating multiple pathways. As regards labyrinthine-somatosensory integration the two tracts were found to be quite similar. The extent and complexity of labyrinthine-somatosensory convergence indicate the importance of feed-back mechanisms upon postural controls also at the level of the vestibular nuclei.

Vestibulothalamic projections in man--a sixth primary sensory pathway

1. Responses suggesting activation of the vestibular system, elicited by electrical stimulation of the human thalamus during 22 routine stereotaxic neurosurgical procedures, were examined in a retrospective study to determine the possible existence of vestibulothalamo-cortical projections in man. 2. Such responses were most frequently described as sensations of movement through space and were associated with two distinct vestibulothalamic projections: a) an anterior relay was situated ventral to the medial lemniscus, passing lateral to the red nucleus and dorsal to the subthalamic nucleus prior to terminating in the nucleus ventrointermedius (Vim) (comparable to VPLo in primates); b) a posterior relay associated with the auditory pathway (lateral lemniscus and brachium of the inferior colliculus) projected to the medial geniculate body. 3. The production of sensations of motion in conscious patients by stimulating areas that are similar to those reported constituting vestibulothalamic pathways in cats and primates implies a distinct primary sensory cortical projection for processing information from the vestibular receptors pertaining to the recognition of spatial movements.

Labyrinthine and somatosensory convergence upon vestibulo-ocular units

The vestibular nuclei were investigated in 18 adult cats. Vestibulo-oculo-motor neurons were identified by antidromic stimulation of the ascending medial longitudinal fasciculus (MLF). The neurons were subjected to various stimuli: vestibular, neck, forelimb and hindlimb nerve stimulation on both sides. The recording was extracellular with micropipettes containing Fast Green. Only the medial and the superior vestibular nuclei were found to project to the MLF. All projecting units had input from the labyrinths. Excitatory response latencies to ipsilateral labyrinth stimulation never exceeded 3 msec. Both excitatory and inhibitory response latencies could be distributed into different categories. The majority of the neurons did not receive a somatosensory input, and surprisingly few convergent units could be seen. Peripheral somatosensory information apparently plays a minor role in vestibulo-ocular relations.

Labyrinthine input to the vestibular nuclei of the awake cat

The labyrinthine input to the vestibular nuclei was investigated in 24 awake cats. Stimulus consisted of electrical shocks given through bipolar silver wire electrodes, implanted in the utricular and lateral ampullar nerves. Throughout the vestibular nuclei, single units were recorded extracellularly with glass micropipettes filled with Fast Green. The tracts of the penetrating electrodes were identified histologically. In all four nuclei units responding to both labyrinths outnumbered unilaterally responding neurones with certain differences between the individual nuclei. Excitatory as well as inhibitory responses were observed, polysynaptic being more common than mono- or disynaptic ones. No monosynaptic contralateral responses were seen. The latency distribution of contralateral responses closely mirrored that of ipsilateral responses within each nucleus. Both excitatory and inhibitory responses fell into relatively segregated populations, based upon latency distribution. This implies separate pathways for labyrinthine input to the vestibular nuclei.

Vestibular and somatosensory interaction in the cat vestibular nuclei

The vestibular nuclei of cats were explored extracellulary with micropipettes to locate units with a resting discharge rate which responded to rotation in the horizontal plane. These units were examined for somatosensory input from neck and limbs. Fewer than half responded to somatosensory stimulation. The neck region was the body area most effective in influencing unitary activity. The response pattern most often noted was an increase and decrease in discharge frequency when the body was moved towards and away from the recording electrode respectively. Change in discharge rate was observed to be primarily dependant upon neck velocity and not upon absolute neck position. Half of the somatosensory units received input from either the forelimbs or the hindlimbs, while the remaining half responded to both.

Hearing under stress: II. Effect of hyperventilation and hypercapnia on speech discrimination

Changes in the ability to discriminate speech from a eucapnic state to hyperventilation and hypercapnia were investigated. Standard speech audiometric techniques were employed to determine the speech reception threshold and the speech discrimination values, while respiratory conditions were varied and measured utilizing a mixed-gas breathing method. Respiratory parameters were similar to those encountered in aircraft personnel who experience oxygen/pressure system malfunction. The results of the study suggest no significant change in the speech reception threshold while in a hyperventilated or hypercapnic state. The speech discrimination results, however, suggest a significant performance decrement while in a state of hyperventilation.