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PubMed1994

The immunocytochemical localization of glutamate in the electrosensory system of the gymnotiform fish, Apteronotus leptorhynchus.

The first processing station of the electrosensory system is the medullary electrosensory lateral line lobe. The electrosensory lateral line lobe of gymnotiform fish is a laminated structure with three anatomically distinct excitatory inputs: primary afferents from electroreceptors, the direct feedback from n. praeminentialis and indirect feedback from n. praeminentialis via a cerebellar lobe--the eminentia granularis posterior. We utilized immunocytochemistry on L-R White-embedded semithin sections, and immunogold on thin sections to localize glutamate and aspartate in the electrosensory lateral line lobe, its afferent inputs and efferent targets. The excitatory inputs and the electrosensory lateral line lobe projection neurons are immunopositive for glutamate only, suggesting that glutamate rather than aspartate is the excitatory transmitter of the electrosensory system.

Animals↗
PubMed1998

Morphological and cytological ontogenesis of the ampullae of lorenzini and lateral line canals in the Oman shark, Iago omanensis Norman 1939 (Triakidae), from the Gulf of Aqaba, Red Sea.

The Oman shark, Iago omanensis, is a small, placental viviparous species encountered in great numbers in the deeper waters of the Gulf of Aqaba, Red Sea. It reproduces year-round, providing an opportunity to study ontogenesis of organ systems at various stages of development. This study examines the morphological and cytological development of the mechanoreceptive lateral line (LL) system and the electrosensory Ampullae of Lorenzini. Female I. omanensis were collected bimonthly from the Gulf of Aqaba at depths of 300-800 m and sacrificed with an overdose of MS222. Their uteri were dissected and the embryos separated and fixed for light and electron microscopy. A total of 260 embryos of varying dimensions were studied. The first primordia of neuroectodermal LL neuromasts are seen in embryos of 18 mm TL. These then sink into the dermis, ripen, and develop tubuli that join to form the LL canal systems, especially developed on the head. In contrast, the primordia of Ampullae of Lorenzini start out as groups of embryonic cells situated subdermally. In embryos of 24-26 mm TL initially they develop into tubuli. With growth, the ampullar alveoli gradually widen at their ends to form the sensory epithelium. The ampullar tubuli elongate, bringing the alveoli to sites over the rostrum and head, where the ampullar capsules are formed. The presynaptic electrosensory cells are attached to afferent neural extensions forming sensory rami which extend, as in adult sharks, to the dorsal nucleus in the medulla. In preterm juveniles of 150-160 mm TL, the LL system and the Ampullae of Lorenzini are fully developed cytologically. The results of this study support the hypothesis that the LL system and electrosensory Ampullae of Lorenzini develop as separate modalities and that their structural similarity is due to the origin from the embryonic neuroectoderm. The dichotomy of their evolution occurred in very early ancestry as an ecomorphological adaptation to different sensory functions.

Animals↗
PubMed2006

Reproducibility of two four-point clinical severity scores for lateral canthal lines (crow's feet).

BACKGROUND: Several clinical scoring systems have been used to evaluate the efficacy of botulinum toxin A in the treatment of hyperkinetic wrinkles. So far very few have been investigated for their reproducibility. OBJECTIVE: The aim of this study was to investigate the reproducibility of two clinical four-point scales for lateral canthal lines (crow's feet), at rest and at maximum smile. MATERIAL AND METHODS: Based on standardized photographs, a consensus atlas depicting the different severity grades [from 0 (none) to 3 (severe)] was developed. After training based on the atlas, 49 photographs at rest and 48 at maximum smile were graded by the same group of investigators on 2 consecutive days (n=9 on Day 1; n=8 on Day 2). The scores were compared for reproducibility using kappa statistics. RESULTS: Overall, reproducibility was good for both scales. Interobserver reproducibility showed an agreement of 0.6 at rest and 0.58 at maximum smile (unweighted kappa). Intraobserver reproducibility showed an agreement between 0.47 and 0.86 at rest and between 0.62 and 0.81 at maximum smile (unweighted kappa). Using weighted kappa analysis, the agreement ranged between 0.63 and 0.91 at rest and between 0.71 and 0.85 at maximum smile. CONCLUSION: The clinical scales using scores of 0 to 3 for crow's feet, both at rest and at maximum smile, show a good inter- and intraobserver reproducibility. The use of these scores in clinical trials can be recommended.

Cosmetic Techniques↗
PubMed1996

Glial cell line-derived neurotrophic factor: the lateral cerebral ventricle as a site of administration for stimulation of the substantia nigra dopamine system in rats.

The direct application of recombinant human glial cell line-derived neurotrophic factor (rhGDNF) to the deep structures of the nigrostriatum has been shown previously to augment dopamine function and inhibit loss of substantia nigra neurons in rodent models of Parkinson's disease. The present studies were designed to determine whether administration of rhGDNF into the lateral ventricle, a more clinically accessible intracranial target, is capable of augmenting dopamine function of the nigrostriatal pathway in normal rats. Single bolus intracerebroventricular (i.c.v) injections of rhGDNF increased locomotor activity and decreased food and water consumption and body weight gain in a dose-dependent manner. rhGDNF increased concentrations of dopamine and dopamine metabolites in the substantia nigra, ventral tegmental area and hypothalamus, but had no significant effects in the striatum. rhGDNF had no effect on striatal or substantia nigral serotonin (5-HT) and 5-hydroxyindoleacetic acid levels, but these levels were significantly increased in the ventral tegmental area and hypothalamus respectively. The augmentation of the dopamine and 5-HT systems was detected 2 weeks but not 3 days or 6 weeks after rhGDNF administration. After a repeat injection of i.c.v rhGDNF (6 weeks after the initial injection), substantia nigral dopamine, 5-HIAA and noradrenalin levels were increased. These results indicate that i.c. v administration of rhGDNF has an influence on adult rat dopamine neurons. This route of administration may be useful for stimulating dopamine neurons in Parkinson's disease.

Animals↗
PubMed1996

Structural diversity of the ordinary and specialized lateral line organs.

Lateral line organ, a superficial sensory system in amphibia and fish which provides the animal with information about its surrounding environment, is divided classically into two main different types, ordinary and specialized, whose functions are mechanoreceptive and electroreceptive, respectively. Although it has great diversity, the basic sensory unit, which is usually called "neuromast," is composed of sensory cells embedded in accessory cells. The functions of the latter are to support the sensory cells and to secrete the material that covers the organs, forming a cupular structure or filling a canal which enables the organ to communicate with the exterior. Sensory cells of mechanoreceptive neuromasts have a tuft of processes included in the cupular material; these are a kinocilium and a group of stereocilia with a typical staircase arrangement. The displacement of the stereocilia towards or away from the kinocilium produces different stimuli. The electroreceptive organs are more diverse. They include ampullary and tuberous organs. The latter can be subdivided into different types: knollenorgans, mormyromasts, gymnarchomasts, etc. All of these present a great diversity among species, but their morphology is less reported than that of the mechanoreceptive organs. This paper summarizes the structural features of the main different types of lateral line organs, as well as their taxonomic distribution and different patterns of distribution along the surface of the animal.

Amphibians↗
PubMed2006

Myelin structure and composition in zebrafish.

To establish a standard for genotype/phenotype studies on the myelin of zebrafish (Danio rerio), an organism increasingly popular as a model system for vertebrates, we have initiated a detailed characterization of the structure and biochemical composition of its myelinated central and peripheral nervous system (CNS; PNS) tissues. Myelin periods, determined by X-ray diffraction from whole, unfixed optic and lateral line nerves, were approximately 153 and approximately 162 Angstrom, respectively. In contrast with the lability of PNS myelin in higher vertebrates, zebrafish lateral line nerve myelin exhibited structural stability when exposed to substantial changes in pH and ionic strength. Neither optic nor lateral line nerves showed swelling at the cytoplasmic apposition in CaCl(2)-containing Ringer's solution, in contrast with nerves from other teleost and elasmobranch fishes. Zebrafish optic nerve showed greater stability against changes in NaCl and CaCl(2) than lateral line nerve. The nerves from zebrafish having mutations in the gene for myelin basic protein (mbpAla2Thr and mbpAsp25Val) showed similar myelin periods as the wildtype (WT), but gave approximately 20% less compact myelin. Analysis of proteins by SDS-PAGE and Western blotting identified in both CNS and PNS of WT zebrafish two orthologues of myelin P0 glycoprotein that have been characterized extensively in trout--intermediate protein 1 (24 kDa) and intermediate protein 2 (28 kDa). Treatment with endoglycosidase-F demonstrated a carbohydrate moiety of approximately 7 kDa, which is nearly threefold larger than for higher vertebrates. Thin-layer chromatography for lipids revealed a similar composition as for other teleosts. Taken together, these data will serve as a baseline for detecting changes in the structure and/or amount of myelin resulting from mutations in myelin-related genes or from exogenous, potentially cytotoxic compounds that could affect myelin formation or stability.

Animals↗
PubMedDate not supplied

Some features of the medium surrounding the mechano- and electroreceptors of the acousticolateral system of the ray Raja clavata.

The degree of binding of K ions has been investigated and the contents of free Ca ions and of glycosaminoglycans have been determined in the medium surrounding the mechano- and electroreceptors of the acousticolateral system of the ray Raja clavata; in addition, electrical phenomena in solutions of K hyaluronate in solutions of the media investigated have been studied. A comparison of the results of electrometric and chemical analysis has shown that the proportions of bound K ions as percentages of the total amounts of these ions are 36.4 in the endolymphatic jelly, 39.6 in the ampullar jelly, and 21.9 in the liquid of the lateral canals. The amount of Ca ions in the media investigated is 3.6-4.4 meq/liter and is close to the concentration of these ions in sea water--3.4 meq/liter. In the endolymphatic jelly the amount of glycosaminoglycans is 0.30+/-0.022% of the wet weight, in the liquid of the lateral canals 0.21+/-0.026%, and in the jelly of the ampullae of Lorenzini 2.79+/-0.28%. Some characteristics of the "displacement potentials" of solutions of K hyaluronate and solutions of the jelly of the ampullae of Lorenzini have been determined, and some hypotheses have been put forward on the possible role of these potentials in the activity of the ampullar formations of the systems of organs of the lateral line.

Animals↗
PubMed1992

Characterization of inner ear sensory hair cells after rapid-freezing and freeze-substitution.

In order to determine the ultrastructural organization of normal cells and to understand better the anatomical substrates for outer hair cell motility, cryofixation was performed on the sensory epithelium of the inner ear of guinea pigs prior to substitution of frozen water with organic solvents containing chemical fixatives. In this way cells would not be altered by the direct application of the chemicals commonly used for preservation, which are also known to cause fixation-induced shape changes in outer hair cells. Following rapid freezing and freeze-substitution, preservation of cells within the isolated sensory epithelium containing the organ of Corti was similar to that seen in conventionally fixed cells. However, in rapidly frozen and freeze-substituted outer hair cells the cytoplasm and the cellular membranes differed from those seen in conventionally fixed preparations. The cytoplasmic matrix was densely packed with filaments and stained homogeneously, suggesting better preservation of the cytoskeleton and less extraction of the soluble ground substance. Cell membranes were smooth, indicating that fixation-induced shape changes and shrinkage had been avoided. The subsurface cisternal system of intracellular membranes lining the lateral wall of the outer hair cells was composed of continuous, tightly packed, parallel rows of membranous lamellae. Thus rapid-freezing and freeze-substitution are important techniques by which structural alterations correlated with outer hair cell motility can be separated from fixation-induced cell shape changes.

Animals↗
PubMed1985

Multisensory interaction in the torus semicircularis of the clawed toad Xenopus laevis.

Interactions between the lateral-line, general somatosensory and auditory system were studied using field potential analysis and single unit recordings in the torus semicircularis of the clawed toad Xenopus laevis. As a response to paired stimuli (electric shocks applied to the peripheral nerves or acoustic clicks), in all systems a reduction of the second evoked potential occurred for intervals of up to 5 s. Following consecutive stimulation of two different systems, the amplitude of the second evoked potential was also reduced, indicating mutual interaction of different systems. Single unit recordings revealed the existence of both inhibitory and excitatory interaction between different modalities.

Afferent Pathways↗
PubMed1989

Ganglion cell arrangement and axonal trajectories in the anterior lateral line nerve of the weakly electric fish Apteronotus leptorhynchus (Gymnotiformes).

To determine the organizational principles underlying the peripheral electrosensory nervous system of weakly electric gymnotiform teleosts we labelled each of the four anterior lateral line nerve branches with HRP. We determined the position of labelled cell bodies within the ganglion and followed anterogradely filled fibers to their termination sites in one of the four somatotopic maps in the electroreceptive lateral line lobe (ELL). Within the ganglion, cell bodies exhibit a loose somatotopy based on nerve branch position: trunk electroreceptors have their cell bodies located in the caudal ganglion; cell bodies to the head receptors are rostral. Cell bodies to the head exhibit a rough dorsoventral polarity, supraorbital cells tend to be located dorsally, infraorbital cells centrally, and mandibular cells ventrally. Despite this general somatotopy there is substantial overlap (up to 30%) of cell bodies among regions. There appears to be no rostrocaudal topography within nerve branch regions. Iontophoretic WGA-HRP injected into the medial segment of the ELL retrogradely labelled cell bodies that innervate ampullary organs. These cell bodies were dispersed throughout the ganglion, indicating that cell bodies do not cluster by receptor type. Peripherally directed axons from the ganglion appear to undergo an active reorganization in order to form the nerve branches. Within nerve branches, axons to a particular area of skin do not cluster together. Centrally from the ganglion, axons retain the position of their cell body until they reach the ELL border. Once in the ELL, fibers become sorted in the deep fiber layer according to receptor type and the map they terminate in. This reorganization involves rearrangement of fascicles and axons within fascicles. In toto, proceeding from peripheral to central, the electrosensory periphery loses at least a portion of its receptor topography in the distal nerve and ganglion and then acquires both a functional and somatotopic organization after reaching the ELL; conceptually it is torn down and rebuilt again. From an ontogenetic perspective, axonal growth occurs from the ganglion outward; the fact that ganglion cell bodies are not highly organized while the receptors they innervate and their central processes are suggests that active axonal guidance mechanisms are involved.

Animals↗
PubMed1993

The octavolateral systems in the stingray, Dasyatis sabina. I. Primary projections of the octaval and lateral line nerves.

The central projections of the electrosensory, mechanosensory, and octaval nerves of the Atlantic stingray were examined by transganglionic transport of horseradish peroxidase. Particular attention was paid to the relation of the projections to cell plates C1 and C2, and to a newly described cell plate, C3. The electroreceptors in the stingray are found in three groups on the dorsal and ventral sides of the body. The electroreceptors are represented topographically on the ipsilateral dorsal nucleus. Those of the rostral part of the head and pectoral fins are represented on the rostroventral part of the nucleus, and those on the caudal part of the head and the pectoral fin on the dorsocaudal part of the nucleus. Mechanosensory lateral line afferents terminate within the ipsilateral intermediate and caudal nuclei, and the lateral granular mass of the vestibulocerebellum. Anterior lateral line afferents also project to the magnocellular octaval nucleus. A topographic representation of the mechanosensory lateral line periphery is present on the intermediate and caudal nuclei. Mechanoreceptors on the trunk are represented laterally and those on the head medially. The terminal field of the anterior lateral line afferents on the intermediate nucleus surrounds cell plates C1 and C2. The anterior lateral line afferents also project to the medial part of the lateral granular mass, whereas the posterior lateral line afferents project to the lateral portion. Sparse projections of anterior lateral line afferents to the periventricular octaval nucleus were also observed. The octaval nerve afferents terminate largely within the octaval column. Octaval nerve projections were also observed to the reticular formation, the periventricular octaval nucleus, the deep cerebellar nucleus, the vestibulocerebellum, particularly the lower lip and medial granular mass, and the intermediate nucleus. A sparse projection to cell plate C3 was found. The relation between cell plates C1 and C2 and the anterior lateral line afferents suggests that these cell plates are related to processing lateral line information. While the relationship between cell plate C3 and the octaval afferents is not strong, the sparse octaval projection C3 receives suggests that it is relaying octaval information.

Afferent Pathways↗
PubMed1976

A rocking motion sensor for the blind.

Rocking motion is an unconscious and often unwanted phenomenon exhibited by the blind. It is usually manifested in oscillatory back and forth, side to side, or rotatory movements of the upper torso or head at about 1 Hz rate. Subjects desiring to function unobtrusively in the world of the sighted need to be alerted when rocking so they can control it. The rocking motion sensor incorporates biofeedback and records rock occurrences. A miniature body mounted accelerometer senses body accelerations exceeding 0.1g. These motions during a given period, compared with a presettable "rock threshold", discriminate rocking from normal activities. Sound biofeedback alerts the subject that he has exceeded threshold. Another counting and timing subsystem determines "end of rock" and resets the system. A recorder is provided that records signals only during rocking. Timing information is provided on a separate channel to permit later time line analysis. The rocking motion sensor system utilizes primarily solid state CMOS circuits with a combination of synchronous-asynchronous timing. The recorder is a modified commercial unit. The two units are separate, portable, and belt mounted. Tests have been made and results will be presented.

Biomedical Engineering↗
PubMed2000

Xenopus cadherin-6 is expressed in the central and peripheral nervous system and in neurogenic placodes.

We have cloned the cDNAs encoding the two Xenopus laevis cadherin-6 pseudoalleles (Xcad-6 and Xcad-6'), which belong to the classical type II cadherin subfamily. During embryogenesis, Xcad-6 expression starts at early neurula and increases dramatically until tadpole stages. Whole-mount in situ hybridization revealed that the transcripts are localized in the developing brain and eye. However, most prominent expression was found in the peripheral nervous system, including a major proportion of lateral line structures. Our results implicate an important contribution of cadherin-6 to the formation of placode derived nerves in Xenopus, an observation which has not been described for other species.

Amino Acid Sequence↗
PubMed2005

Ptena and ptenb genes play distinct roles in zebrafish embryogenesis.

PTEN is a tumor suppressor gene associated with multiple tumor types. PTEN function is essential for early embryonic development and is involved in the regulation of cell size, number, and survival. By dephosphorylating PIP(3), PTEN normally acts to inhibit the PI3-Kinase/AKT pathway. Here we have identified two zebrafish orthologs, ptena and ptenb, of the single mammalian PTEN gene and analyzed the role of these genes in zebrafish development. Ptena transcripts were expressed throughout the embryo at early somitogenesis. By 24 hpf, expression was predominant in the central nervous system, axial vasculature, retina, branchial arches, ear, lateral line primordium, and pectoral fin bud. Ptenb was also ubiquitously expressed early in somitogenesis, but transcripts became more restricted to the somites and central nervous system as development progressed. By 48 hpf, ptena and ptenb were expressed predominantly in the central nervous system, branchial arches, pectoral fins, and eye. Antisense morpholinos were used to knock down translation of ptena and ptenb mRNA in zebrafish embryos. Knockdown of either pten gene caused increased levels of phosphorylated Akt in morphant embryos, indicating that Ptena and Ptenb each possess PIP(3) lipid phosphatase activity. Ptena morphants had irregularities in notochord shape (73%), vasculogenesis (83%), head shape (72%), and inner ear development (59%). The most noticeable defects in ptenb morphants were upward hooked tails (73%), domed heads (83%), and reduced yolk extensions (90%). These results indicate that ptena and ptenb encode functional enzymes and that each pten gene plays a distinct role during zebrafish embryogenesis.

Amino Acid Sequence↗
PubMed2002

Tactile hairs on the postcranial body in Florida manatees: a Mammalian lateral line?

Previous reports have suggested that the sparsely distributed hairs found on the entire postcranial body of sirenians are all sinus type tactile hairs. This would represent a unique arrangement because no other mammal has been reported to possess tactile hairs except on restricted regions of the body, primarily the face. In order to investigate this issue further, hair counts were made systematically in three Florida manatees (Trichechus manatus latirostris), and hair follicle microanatomy was studied in 110 specimens gathered from 9 animals. We found that the postcranial body possesses approximately 1500 hairs per side, and hair density decreases from dorsal to ventral. External hair length ranged from 2-9 mm, and most hairs were separated from their nearest neighbor by 20-40 mm, resulting in an independent domain of movement for each hair. All hairs exhibited the anatomical characteristics of follicle-sinus complexes typical of tactile hairs, including a dense connective tissue capsule containing an elongated circumferential blood sinus and innervation by 20-50 axons which ascend the mesenchymal sheath. We conclude that this represents a unique distributed underwater tactile system capable of conveying detailed and significant external information concerning approaching animals, water currents and possibly the presence of large stationary features of the environment. Such a system would be analogous to the lateral line in fish, and would be particularly useful in the turbid habitat frequented by Florida manatees.

Animals↗
PubMed1962

Synaptic structures in the lateral line canal organ of the teleost fish Lota vulgaris.

This paper is a preliminary report on some of the results of electron microscopic studies on the lateral line canal organ of the teleost fish Lota vulgaris. It deals with the ultrastructure of the synaptic area on the hair cells of the sensory epithelium and describes the nerve endings as well as a complicated system of foldings of the hair cell plasma membranes enclosing portions of the hair cell cytoplasm in the synaptic area. These findings are discussed in the light of present knowledge of the ultrastructure of other receptoneuronal synapses.

Animals↗
PubMed1978

Frequency response of the lateral-line organ of Xenopus laevis.

The stimulus response relation of the epidermal lateral-line organ of Xenopus laevis was studied by recording activity of single afferent nerve fibres in isolated preparations. Linear frequency response analysis over a frequency range of 0.1--100Hz was performed under steady-state conditions, using small amplitude, sinusoidal water displacements produced by a glass sphere at a short distance from the skin. Period histograms of afferent nerve activity were computed, and amplitude, phase and mean activity of the response were determined by means of Fourier analysis. A standardization procedure at the start of each experiment made scaling of the frequency responses of different preparations unnecessary. The results show that for small stimulus amplitudes the response of the lateral-line organ over the whole range of frequencies studied can adequately be described as a modulation of the spontaneous activity. The amplitude of the response is proportional to the stimulus amplitude, and the phase of the response is independent of stimulus amplitude. The lateral-line organ of Xenopus laevis can thus be regarded as a linear system for stimuli which produce modulation of the spontaneous activity. The frequency response demonstrates unequivocally that the lateral-line organ of Xenopus laevis functions as a water velocity detector. For frequencies of stimulation from 0.1--20Hz the gain increases with a slope of 7.5 dB/oct, and up to 5Hz the response is almost in phase with the water velocity. The extent to which the different transmission steps between stimulus and response will contribute to the frequency response is discussed.

Animals↗
PubMedDate not supplied

Type I burst excitability.

We introduce the concept of "type I burst excitability", which is a generalization of the "normal" excitability that is well-known in cardiac and neural systems. We demonstrate this type of burst excitability in a specific model system, a pyramidal cell from the electrosensory lateral line lobe of the weakly electric fish Apteronotus leptorhynchus. As depolarizing current is increased, a saddle-node bifurcation of periodic orbits occurs, which separates tonic and burst activity. This bifurcation is responsible for the excitable nature of the system, and is the basis for the "type I" designation. We verify the existence of this transition from in vitro recordings of a number of actual pyramidal cells. A scaling relationship between the magnitude and duration of a current pulse required to induce a burst is derived. We also observe this type of burst excitability and the scaling relationships in a multicompartmental model that is driven by realistic stochastic synaptic inputs mimicking sensory input. We conclude by discussing the relevance of burst excitability to communication between weakly electric fish.

Action Potentials↗