Trilobites within nautiloid cephalopods

'Sheltered preservation' of the remains of trilobites within the shells of nautiloid cephalopods is not especially uncommon. In most cases, of course, both the trilobites and the nautiloids were dead, and the association, merely due to post-mortem happenstance. However, on the basis of state of preservation and occurrence, a number of live individuals of the trilobite genera Acidaspis, Flexicalymene, and Isotelus from the Ordovician of the United States and of Alcymene and Encrinuraspis from the Silurian of Wales and the Czech Republic seem to have entered conchs of dead cephalopods, presumably for refuge.     

Auditory brain stem responses in characterization of dolphin hearing

Summary Auditory brain stem responses (ABR) were recorded from the head surface of non-anesthetized and non-relaxed bottle-nosed dolphins, Tursiops truncatus. The region of best ABR recording was shown to be located 6–9 cm caudal to the blowhole. The threshold values were about 1 mPa for noise bursts and –3 dB re 1 mPa for tone bursts of the optimal frequency (80 kHz). The maximum frequency at which ABR could be evoked was 140 kHz. The duration of temporal summation reached 0.5 ms at intensities near the threshold and decreased with an increase in intensity. When the stimuli were paired clicks of the same intensity, the time to complete recovery from the second response was about 5 ms, while that to its 50% recovery was 0.7 ms. When the conditioning click exceeded the testing one in intensity, prolongation of the recovery period was observed. A 40-dB intensity difference led to an approximately 10-fold prolongation of this period.Abbreviations ABR auditory brain stem response - EP evoked potential     

Infrasound sensitive neurones in the pigeon cochlear ganglion

Summary The cochlear ganglion of the pigeon contains neurones sensitive to sound frequencies below 20 Hz (infrasound). They are characterized by a high spontaneous discharge rate (mean 115 imp/s). In contrast to ordinary auditory units, the mean discharge rate of these neurones is not increased by infrasound or sound stimuli, but modulated by these stimuli at levels comparable to the behavioural thresholds of pigeon reported by Kreithen and Quine (1979).     

Ethical and welfare considerations when using cephalopods as experimental animals

When using cephalopods as experimental animals, a number of factors, including morality, quality of information derived from experiments, and public perception, drives the motivation to consider welfare issues. Refinement of methods and techniques is a major step in ensuring protection of cephalopod welfare in both laboratory and field studies. To this end, existing literature that provides details of methods used in the collection, handling, maintenance, and culture of a range of cephalopods is a useful starting point when refining and justifying decisions about animal welfare. This review collates recent literature in which authors have used cephalopods as experimental animals, revealing the extent of use and diversity of cephalopod species and techniques. It also highlights several major issues when considering cephalopod welfare; how little is known about disease in cephalopods and its relationship to senescence and also how to define objective endpoints when animals are stressed or dying as a result of the experiment.     

Precision medicine in hearing loss

Precision medicine (PM) proposes customized medical care based on a patient's unique genome, biomarkers, environment and behaviors. Hearing loss (HL) is the most common sensorineural disorder worldwide and is frequently caused by a single genetic mutation. With recent advances in PM tools such as genetic sequencing and data analysis, the field of HL is ideally positioned to adopt the strategies of PM. Here, we review current and future applications of PM in HL as they relate to the four core qualities of PM (P4): predictive, personalized, patient-centered, and participatory. We then introduce a strategy for effective incorporation of HL PM into the design of future research studies, electronic medical records, and clinical practice to improve diagnostics, prognostics, and, ultimately, individualized patient treatment. Finally, specific anticipated ethical and economic concerns in this growing era of genomics-based HL treatment are discussed. By integrating PM principles into translational HL research and clinical practice, hearing specialists are uniquely positioned to effectively treat the heterogeneous causes and manifestations of HL on an individualized basis.     

Lung-based hearing in an “earless” anuran amphibian

The mechanisms of hearing in the fire-bellied toad Bombina orientalis, an “earless” species of amphibian that lacks a standard tympanic middle ear, were studied using laser Doppler vibrometric and neurophysiological techniques. Laser vibrometry demonstrated that the anterolateral body wall overlying the lung is much more responsive to sound than the lateral head surface overlying the inner ear. Covering the lateral body wall with silicone grease dramatically decreased auditory midbrain sensitivity at all frequencies examined, elevating thresholds by 20–25 dB. Filling the lungs with oxygenated saline produced similar decrements in hearing sensitivity, and both manipulations strongly suggest that the lung is the primary route of sound reception in this species. The precise route of transfer of sound energy from the body wall and lungs to the inner ear remains unclear. The lung-based hearing system of “earless” fire-bellied toads may represent the retention of the first auditory mechanism used by early tetrapod vertebrates for detection of airborne sound. Accepted: 10 December 1998     

Neuroethology of ultrasonic hearing in nocturnal butterflies (Hedyloidea)

Nocturnal Hedyloidea butterflies possess ultrasound-sensitive ears that mediate evasive flight maneuvers. Tympanal ear morphology, auditory physiology and behavioural responses to ultrasound are described for Macrosoma heliconiaria, and evidence for hearing is described for eight other hedylid species. The ear is formed by modifications of the cubital and subcostal veins at the forewing base, where the thin (1–3 μm), ovoid (520 × 220 μm) tympanal membrane occurs in a cavity. The ear is innervated by nerve IIN1c, with three chordotonal organs attaching to separate regions of the tympanal membrane. Extracellular recordings from IIN1c reveal sensory responses to ultrasonic (>20 kHz), but not low frequency (<10 kHz) sounds. Hearing is broadly tuned to frequencies between 40 and 80 kHz, with best thresholds around 60 dB SPL. Free flying butterflies exposed to ultrasound exhibit a variety of evasive maneuvers, characterized by sudden and unpredictable changes in direction, increased velocity, and durations of ∼500 ms. Hedylid hearing is compared to that of several other insects that have independently evolved ears for the same purpose-bat detection. Hedylid hearing may also represent an interesting example of evolutionary divergence, since we demonstrate that the ears are homologous to low frequency ears in some diurnal Nymphalidae butterflies.     

ABR frequency tuning curves in dolphins

Tone-tone masking was used to determine auditory brain-stem response tuning curves in dolphins (Tursiops truncatus) in a simultaneous-masking paradigm. The Q ₁₀ of the curves was as large as 16–19 in the frequency range 64–128 kHz. In the range 45–16 kHz, Q ₁₀ decreased proportionally to the frequency with the bandwidth of the curves being constant, about 3.5–4 kHz at the 10-dB level. Tuning curves below 45 kHz are supposed to reflect broad spectral bandwidth of the probe's effective part which is no longer than 0.5 ms, irrespective of actual probe duration. Tuning curves above 64 kHz are supposed to reflect the real frequency tuning of the dolphin's auditory system.Abbreviations ABR auditory brain stem response - AP action potential     

The role of aquaporins in hearing function and dysfunction

The inner ear is composed by tiny and complex structures that, together with peripheral and central auditory pathways, are responsible for hearing processing. However, not only the anatomy of the cochlea, its compartments and related structures are complex. The mechanisms involved in the regulation of homeostasis in the inner ear fluid, which determines the ionic gradient necessary for hearing and balancing sensory excitability, is an intricate phenomenon that involves several molecules. Among them, Aquaporins (AQP) play a significant role in this process. AQP are part of a family of small, integral membrane proteins that regulate different processes, including bidirectional water and ionic flow in the inner ear. Changes in the expression of these proteins are essential to auditory physiology and several pathophysiological processes in the inner ear. This review focuses on the role of AQP in health and disease of the auditory system.     

Frequency tuning curves of the dolphin's hearing: envelope-following response study

Simultaneous tone-tone masking in conjunction with the envelope-following response (EFR) recording was used to obtain tuning curves in dolphins (Turslops truncatus). The EFR was evoked by amplitude-modulated probes of various frequencies. A modulation rate of 600 Hz was found to fit the requirement to have a narrow spectrum and evoke EFR of large amplitude. Tuning curves were obtained within the frequency range from 11.2 to 110 kHz. The Q₁₀ values of the obtained tuning curves varied from 12–14 at the 11.2 kHz center frequency to 17–20 at the 64–90 kHz frequencies.Abbreviations ABR auditory brainstem response - EFR envelope following response - ERB equivalent rectangular bandwidth     

Detection of frequency modulation in the FM-bat Phyllostomus discolor

In a two-alternative forced-choice procedure lesser spear-nosed bats, Phyllostomus discolor, had to discriminate between a pure tone stimulus and a sinusoidally frequency-modulated signal generated at the same carrier frequency as the tone. Modulation depths of the SFM stimuli were reduced until the animals' performance dropped below the 75%-correct level which was used to determine difference limens for detection of frequency modulation (FMDL). The dependence of FMDLs on modulation and carrier frequency was systematically investigated. For a carrier frequency of 18.5 kHz, average FMDLs increased from 95 Hz at a modulation frequency of 10 Hz to 820 Hz at a modulation frequency of 2000 Hz which corresponds to Weber ratios (2f/f) of 0.005 and 0.044 respectively. Further, difference limens were found to increase linearly in proportion to carrier frequency throughout a major part (9–74 kHz) of the species' hearing range. In comparison to other mammals, P. discolor has a pronounced capability for frequency discrimination which might be related to the extensive use of individually distinct frequency-modulated communication calls and audio-vocal learning.Abbreviations FM frequency modulation - SFM sinusoidal frequency modulation - FMDL frequency modulation difference limen - CF constant frequency - DLF difference limen for frequency - VCO voltage-controlled oscillator - SPL sound pressure level - WR Weber ratio     

头足类神经肽研究进展

神经肽是一类由神经内分泌组织分泌的小分子多肽。近年来随着头足类的经济价值越来越受到人们的重视,其神经肽的研究也日趋深入。通过高效液相色谱分离纯化、质谱鉴定、免疫组化定位和分子克隆等技术方法发现神经肽对头足类的生殖调控等具有重要意义。本文就目前已发现的7类头足类神经肽的种类、分布、结构与功能进行了综述,同时,展示了目前头足类神经肽研究存在的问题,并对头足类神经肽的发展趋势和应用前景进行了展望。     

Modulation rate transfer functions in bottlenose dolphins (<Emphasis Type="Italic">Tursiops truncatus</Emphasis>) with normal hearing and high-frequency hearing loss

Envelope following responses were measured in two bottlenose dolphins in response to sinusoidal amplitude modulated tones with carrier frequencies from 20 to 60 kHz and modulation rates from 100 to 5,000 Hz. One subject had elevated hearing thresholds at higher frequencies, with threshold differences between subjects varying from ±4 dB at 20 and 30 kHz to +40 dB at 50 and 60 kHz. At each carrier frequency, evoked response amplitudes and phase angles were plotted with respect to modulation frequency to construct modulation rate transfer functions. Results showed that both subjects could follow the stimulus envelope components up to at least 2,000 Hz, regardless of carrier frequency. There were no substantial differences in modulation rate transfer functions for the two subjects suggesting that reductions in hearing sensitivity did not result in reduced temporal processing ability. In contrast to earlier studies, phase data showed group delays of approximately 3.5 ms across the tested frequency range, implying generation site(s) within the brainstem rather than the periphery at modulation rates from 100 to 1,600 Hz. This discrepancy is believed to be the result of undersampling of the modulation rate during previous phase measurements.     

Functional correlates of characteristic frequency in single cochlear nerve fibers of the Mongolian gerbil

Summary Single-unit recordings obtained from the auditory nerve of the Mongolian gerbil, Meriones unguiculatus, revealed functional differences in the response properties of neurons tuned to low and high frequencies. The distribution of neural thresholds displayed a distinct rise for auditory nerve fibers with characteristic frequencies] (CFs) between 3–5 kHz. This frequency band also marked abrupt changes in both the distribution of spontaneous discharge rates and the shape of the neural tuning curve. For neurons of all CFs, spontaneous firing rates were inversely related to neural threshold but unrelated to sharpness of neural tuning. The range of CF thresholds encountered, even when data from many animals were combined, rarely exceeded 20 dB, suggesting that cochlear nerve responses obtained from this species display little inter-animal variability. These results are compared with similar data from other species and discussed in terms of recent studies on sound communication and cochlear anatomy in gerbils.Abbreviations CF characteristic frequency - SR spontaneous discharge rate     

A comparative study of hearing ability in fishes: the auditory brainstem response approach

Auditory brainstem response (ABR) techniques, an electrophysiological far-field recording method widely used in clinical evaluation of human hearing, were adapted for fishes to overcome the major limitations of traditional behavioral and electrophysiological methods (e.g., invasive surgery, lengthy training of fishes, etc.) used for fish hearing research. Responses to clicks and tone bursts of different frequencies and amplitudes were recorded with cutaneous electrodes. To evaluate the effectiveness of this method, the auditory sensitivity of a hearing specialist (goldfish, Carassius auratus) and a hearing generalist (oscar, Astronotus ocellatus) was investigated and compared to audiograms obtained through psychophysical methods. The ABRs could be obtained between 100 Hz and 2000 Hz (oscar), and up to 5000 Hz (goldfish). The ABR audiograms are similar to those obtained by behavioral methods in both species. The ABR audiogram of curarized (i.e., Flaxedil-treated) goldfish did not differ significantly from two previously published behavioral curves but was lower than that obtained from uncurarized fish. In the oscar, ABR audiometry resulted in lower thresholds and a larger bandwidth than observed in behavioral tests. Comparison between methods revealed the advantages of this technique: rapid evaluation of hearing in untrained fishes, and no limitations on repeated testing of animals. Accepted: 8 August 1997     

Hsp70 inhibits aminoglycoside-induced hearing loss and cochlear hair cell death

Sensory hair cells of the inner ear are sensitive to death from aging, noise trauma, and ototoxic drugs. Ototoxic drugs include the aminoglycoside antibiotics and the antineoplastic agent cisplatin. Exposure to aminoglycosides results in hair cell death that is mediated by specific apoptotic proteins, including c-Jun N-terminal kinase (JNK) and caspases. Induction of heat shock proteins (Hsps) can inhibit JNK- and caspase-dependent apoptosis in a variety of systems. We have previously shown that heat shock results in robust upregulation of Hsps in the hair cells of the adult mouse utricle in vitro. In addition, heat shock results in significant inhibition of both cisplatin- and aminoglycoside-induced hair cell death. In this system, Hsp70 is the most strongly induced Hsp, which is upregulated over 250-fold at the level of mRNA 2 h after heat shock. Hsp70 overexpression inhibits aminoglycoside-induced hair cell death in vitro. In this study, we utilized Hsp70-overexpressing mice to determine whether Hsp70 is protective in vivo. Both Hsp70-overexpressing mice and their wild-type littermates were treated with systemic kanamycin (700 mg/kg body weight) twice daily for 14 days. While kanamycin treatment resulted in significant hearing loss and hair cell death in wild-type mice, Hsp70-overexpressing mice were significantly protected against aminoglycoside-induced hearing loss and hair cell death. These data indicate that Hsp70 is protective against aminoglycoside-induced ototoxicity in vivo.     

Aroclor 1254 impairs the hearing ability of Xenopus laevis

In this study we assessed the effects of chronic, dietary exposure of Aroclor 1254 (A1254) on the hearing of Xenopus frogs. We used the auditory brainstem response (ABR) to assay changes in hearing physiology; ABR thresholds, as well as latency-intensity and amplitude-intensity profiles of the initial positive (P1) and negative (N1) peaks were measured. Two groups of animals that received 50 ppm and 100 ppm of A1254 in their diet from 5 days post-fertilization through metamorphosis were compared to a control group that received untreated chow. The results showed significant threshold elevations in the 3–4 kHz range and significantly delayed peak latencies and reduced amplitudes at these frequencies in A1254 treated animals as compared to control animals. These findings indicate that A1254 selectively damages the high-frequency sensorineural hearing system associated with the basilar papilla of frogs. This preferential damage may be related to inherent differences in the vulnerability of the basilar versus amphibian papilla in the frog. The overall results of this study are also consistent with the reported A1254-induced auditory deficits in mammals indicating that the basilar papilla of the Xenopus frog may serve as an effective model for studying the effects of A1254 on the auditory system.     

Skin color in the squids Loligo pealii and Loligo opalescens

Summary Rapid, physiological color changes seen in the skin of cephalopods are due to a unique anatomical system composed of chromatophore organs and iridophores. The morphology and ultrastructure of the chromatophores was studied in the squids Loligo pealii Lesueur and Loligo opalescens Berry. A three-dimensional model of a brown chromatophore was reconstructed from serial sections for the electron microscope.The chromatophore organ is composed of a central nucleated pigment cell, 10–30 obliquely striated muscle cells (radially arranged on the equator of the pigment cell), axons, Schwann cells, and sheath cells. The pigment cell consists of a central aggregation of pigment granules and surrounding peripheral cytoplasmic compartments. These regions are incompletely separated by an electron-dense, sac-like structure, the pigment container. Proximal portions of a muscle cell contact the pigment cell in regions called myo-chromatophore junctions. Neuromuscular and myo-muscular junctions are also present.The results presented are discussed in terms of previous morphological and physiological studies of chromatophores.Part of a study submitted in partial fulfillment of the requirement for the degree of Ph. D. (Anatomy), the Graduate School of Basic Medical Sciences, New York Medical College, New York, N.Y. 10029.The research reported here was in part supported by grants from the Health Research Council of the City of New York (U-1008) and United States Public Health Service, General Research Grant No. FR-05398.Report on some of this material was given at the Annual Meeting of the American Association of Anatomists, Philadelphia, Pennsylvania, April 19–22, 1971.     

Global burden of ototoxic hearing loss associated with platinum-based cancer treatment: A systematic review and meta-analysis

Platinum-based chemotherapeutic agents cisplatin and carboplatin are widely used in cancer treatment worldwide and may result in ototoxic hearing loss. The high incidence of cancer and salient ototoxic effects of platinum-based compounds pose a global public health threat. The purpose of this study was twofold. First, to estimate the prevalence of ototoxic hearing loss associated with treatment with cisplatin and/or carboplatin via a systematic review and meta-analysis. Second, to estimate the annual global burden of ototoxic hearing loss associated with exposure to cisplatin and/or carboplatin. For the systematic review, three databases were searched (Ovid Medline, Ovid Embase, and Web of Science Core Collection) and studies that reported prevalence of objectively measured ototoxic hearing loss in cancer patients were included. A random effects meta-analysis determined pooled prevalence (95% confidence intervals [CI]) of ototoxic hearing loss overall, and estimates were stratified by treatment and patient attributes. Estimates of ototoxic hearing loss burden were created with published global estimates of incident cancers often treated with platinum-based compounds and cancer-specific treatment rates. Eighty-seven records (n = 5077 individuals) were included in the meta-analysis. Pooled prevalence of ototoxic hearing loss associated with cisplatin and/or carboplatin exposure was 43.17% [CI 37.93–48.56%]. Prevalence estimates were higher for regimens involving cisplatin (cisplatin only: 49.21% [CI 42.62–55.82%]; cisplatin & carboplatin: 56.05% [CI 45.12–66.43%]) versus carboplatin only (13.47% [CI 8.68–20.32%]). Our crude estimates of burden indicated approximately one million individuals worldwide are likely exposed to cisplatin and/or carboplatin, which would result in almost half a million cases of hearing loss per year, globally. There is an urgent need to reduce impacts of ototoxicity in cancer patients. This can be partially achieved by implementing existing strategies focused on primary, secondary, and tertiary hearing loss prevention. Primary ototoxicity prevention via otoprotectants should be a research and policy priority.