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PubMed1996

Subcellular localization of Suppressor of Hairless in Drosophila sense organ cells during Notch signalling.

During imaginal development of Drosophila, Suppressor of Hairless [Su(H)], an evolutionarily conserved transcription factor that mediates intracellular signalling by the Notch (N) receptor, controls successive alternative cell fate decisions leading to the differentiation of multicellular sensory organs. We describe here the distribution of the Su(H) protein in the wing disc epithelium throughout development of adult sense organs. Su(H) was found to be evenly distributed in the nuclei of all imaginal disc cells during sensory organ precursor cells selection. Thus differential expression and/or subcellular localization of Su(H) is not essential for its function. Soon after division of the pIIa secondary precursor cell, Su(H) specifically accumulates in the nucleus of the future socket cell. At the onset of differentiation of the socket cell, Su(H) is also detected in the cytoplasm. In this differentiating cell, N and deltex participate in the cytoplasmic retention of Su(H). Still, Su(H) does not colocalize with N at the apical-lateral membranes. These observations suggest that N regulates in an indirect manner the cytoplasmic localization of Su(H) in the socket cell. Finally, the pIIb, shaft and socket cells are found to adopt invariant positions along the anteroposterior axis of the notum. This raises the possibility that tissue-polarity biases these N-mediated cell fate choices.

Animals↗
PubMed1990

Functions of a proprioceptive sense organ in freely moving insects: characteristics of reflexes elicited by stimulation of the locust metathoracic femoral chordotonal organ.

(1) The metathoracic femoral chordotonal organ is an identified joint angle receptor of the locust hindleg. In order to assess and quantify the functions of this sense organ in the control of posture, mechanical stimuli were applied to the main ligament of the receptor in freely standing locusts. These stimuli produced an afferent discharge that mimicked a sudden small (10-15 degree) change in the angle of the femoro-tibial joint of the hindleg. The reflex effects that resulted from afferent stimulation were monitored myographically in the tibial extensor and flexor muscles. The angle of the femoro-tibial joint at the onset of sensory stimulation was also recorded by still photography. (2) As previously reported, stimulation of the chordotonal organ in freely standing animals produced resistance reflexes in tibial muscles that opposed the apparent joint movement. However, we also found that, at certain joint angles, a different mode of reflex response was elicited in which motoneurons to the tibial flexor muscle fired in response to apparent movements in any direction. (3) In this study, characteristics of resistance reflexes in the tibial extensor muscle were analyzed quantitatively, as that muscle is innervated by only one slow excitatory motoneuron. The gain of the resistance reflex (ratio of the firing frequency during afferent stimulation versus the rate of activity prior to the stimulus) was quite high in all preparations, and represent a greater than two-fold increase in motoneuron frequency (mean 2.11 +/- 0.54 S.D.). The reflex gain was also highest at the lowest initial rates of motoneuron activity (circa 5 Hz) and declined for higher firing frequencies (maximum 35 Hz).(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1997

Evidence for the involvement of carbonic anhydrase and urease in calcium carbonate formation in the gravity-sensing organ of Aplysia californica.

To better understand the mechanisms that could modulate the formation of otoconia, calcium carbonate granules in the inner ear of vertebrate species, we examined statoconia formation in the gravity-sensing organ, the statocyst, of the gastropod mollusk Aplysia californica using an in vitro organ culture model. We determined the type of calcium carbonate present in the statoconia and investigated the role of carbonic anhydrase (CA) and urease in regulating statocyst pH as well as the role of protein synthesis and urease in statoconia production and homeostasis in vitro. The type of mineral present in statoconia was found to be aragonitic calcium carbonate. When the CA inhibitor, acetazolamide (AZ), was added to cultures of statocysts, the pH initially (30 min) increased and then decreased. The urease inhibitor, acetohydroxamic acid (AHA), decreased statocyst pH. Simultaneous addition of AZ and AHA caused a decrease in pH. Inhibition of urease activity also reduced total statoconia number, but had no effect on statoconia volume. Inhibition of protein synthesis reduced statoconia production and increased statoconia volume. In a previous study, inhibition of CA was shown to decrease statoconia production. Taken together, these data show that urease and CA play a role in regulating statocyst pH and the formation and maintenance of statoconia. CA produces carbonate ion for calcium carbonate formation and urease neutralizes the acid formed due to CA action, by production of ammonia.

Animals↗
PubMed1991

Structural and functional effects of heavy metals on the nervous system, including sense organs, of fish.

1. Today, fish in the environment are inevitably exposed to chemical pollution. Although most hazardous substances are present at concentrations far below the lethal level, they may still cause serious damage to the life processes of these animals. 2. Fish depend on an intact nervous system, including their sense organs, for mediating relevant behaviour such as food search, predator recognition, communication and orientation. 3. Unfortunately, the nervous system is most vulnerable and injuries to its elements may dramatically change the behaviour and consequently the survival of fish. 4. Heavy metals are well known pollutants in the aquatic environment. Their interaction with relevant chemical stimuli may interfere with the communication between fish and environment. 5. The affinity for a number of ligands and macromolecules makes heavy metals most potent neurotoxins. 6. The present Mini-Review highlights some aspects of how trace concentrations of mercury, copper and lead affect the integrity of the fish nervous system; structurally, physiologically and biochemically.

Animals↗
PubMed1991

The determination of sense organs in Drosophila: effect of the neurogenic mutations in the embryo.

We have examined the early pattern of sensory mother cells in embryos mutant for six different neurogenic loci. Our results show that the neurogenic loci are required to restrict the number of competent cells that will become sensory mother cells, but are not involved in controlling the localization or the position-dependent specification of competent cells. We conclude that these loci are involved in setting up a system of mutual inhibition, which transforms graded differences within the proneural clusters into an all-or-none difference between one cell, which becomes the sense organ progenitor cell, and the other cells, which remain epidermal.

Animals↗
PubMed2003

The formation of sense organs in Drosophila: a logical approach.

The genetic analysis of development has revealed the importance of small sets of interacting genes in most morphogenetic processes. The results of gene interactions have so far been examined intuitively. This approach is largely sufficient when one deals with simple interactions, a feedback circuit for example. As more components become involved, however, it is difficult to make sure that the intuitive approach gives a comprehensive view of the behaviour of the system. In this paper, we illustrate the use of a logical approach to describe the genetic circuit that underlies the singling out of sense organ precursor cells in Drosophila. We show how to apply logical modelling to a realistic problem, and how this approach allows an easy assessment of the dynamic properties of the system, i.e., of its possible evolutions and of its reactions to fluctuations and perturbations.

Animals↗
PubMed1999

Centrids, a pair of asymmetrically arranged sense organs in Ascaris suum (Nematoda, Ascaridoidea).

Two prominent, asymmetrically placed cuticular somatic sensilla, called centrids, are reported in Ascaris suum Goeze, 1782, the pig roundworm. The right centrid is situated much more anteriorly on the body than is the left one. The centrids are globular in the fourth-stage larva and obviously void of an apical pore, suggesting at least a tactile function. In adult worms, the centrids are platelike, lacking a globular expansion. The observation on the presence of asymmetrically placed centrids in A. suum gives further impetus to the importance assigned to sense organs in the classification and identification of nematodes. The name centrid was originally chosen to indicate the placement of the papillae in the midbody region of worms. The name centrid, rather than, e.g. postdeirid, is proposed to be used when denoting asymmetrically oriented midbody sensilla among the Ascaridida and papillae, when shown homologous to these, of species within the Rhabditea generally. This proposal is in line with the name "Mittelkörperpapillen" originally adopted to denote homologous sensillae in Cucullanidae (Seuratoidea) by Törnquist in 1931.

Animals↗
PubMed2003

Anatomy and histology of the brain and sense organs of the antarctic plunderfish Dolloidraco longedorsalis (Perciformes: Notothenioidei: Artedidraconidae), with comments on the brain morphology of other artedidraconids and closely related harpagiferids.

In the high-latitude shelf waters of Antarctica, fishes in the perciform suborder Notothenioidei dominate the fish fauna and constitute an adaptive radiation and a species flock. The 25 species of notothenioid plunderfishes, comprising four genera of the family Artedidraconidae, contribute substantially to fish species diversity on the high Antarctic shelf. A mental barbel is an autapomorphy for the family. Dolloidraco longedorsalis is the most abundant artedidraconid at depths over 400 m in these waters. In this article we present the anatomy and histology of the brain and special sense organs of Dolloidraco and compare it to the brains of other artedidraconids, closely related harpagiferids, and more generally to other notothenioids. We provide a detailed drawing of the brain and cranial nerves. The brain of Dolloidraco is simple, without external hypertrophy of sensory or motor regions, but contains several unusual features associated with the ventricular system and CSF, including well-developed circumventricular organs, subependymal expansions, and subarachnoid cisterns; and a ventricle in the corpus cerebellum. The brain of Dolloidraco also contains a lobed chief sensory nucleus of the trigeminal nerve that is correlated across species with barbel length. The eyes are large and contain a small choroid rete, a structure previously thought to be absent from members of this family. We document the histology of the duplex retina, olfactory apparatus, cutaneous taste buds, and barbel musculature and innervation. We discuss the role of pedomorphy in producing simplified brain morphologies. We consider the possibility that Dolloidraco is a somatosensory specialist-an unusual feature among vertebrates-and decide that this is unlikely.

Animals↗
PubMed1995

Cellular events during development of the olfactory sense organs in Drosophila melanogaster.

The olfactory sensilla on the antenna of adult Drosophila melanogaster develop during the first 36 hr after pupariation, from their anlagen in the cephalic disc. We have used tissue-specific beta-galactosidase expression in the enhancer trap strain A101.IF3 and the monoclonal antibody 22C10 as sensory cell markers, as well as the lineage tracer 5-bromo-2'-deoxyuridine (BrdU), to describe this process. The development of an olfactory sensillum begins with the selection of a "founder cell" (FC). These cells are distinct in that they possess large apically located nuclei revealed by beta-galactosidase expression in A101.IF3. In the following 6 hr, a few cells neighboring the FC also start expressing beta-galactosidase and together comprise a group. Cells of this group, denoted a "presensillum-cluster" (PSC), undergo at least one round of replication and give rise to all of the cells of a sensillum. A subset of the cells within each PSC and, later, all the sensory neurons are recognized by MAb22C10. The antennae of the mutant lozenge3 (lz3) lack all basiconic and some trichoid sensilla. The mutation apparently affects early steps in sensillum development and many of the FCs fail to form. Those that are present, however, proceed to form mature olfactory sensilla. Therefore, we conclude that the selection of an FC is the first step in olfactory sense organ development. Our study reveals novel aspects of sensory development in Drosophila.

Animals↗
PubMed1995

Limb deformity proteins during avian neurulation and sense organ development.

The nuclear Limb deformity (Ld) proteins (formins) are expressed during the avian primitive streak stages. Initially, they are detected predominantly in cells of the forming notochord, scattered mesodermal precursors and the induced neural plate. No expression is detected in endodermal cells. The subsequent graded distribution of Ld positive cells along the anterior-posterior axis of the neural tube follows the antero-posterior progression of its differentiation. The Ld proteins are also differentially expressed during induction and development of both the inner ear and eye. An unequal distribution of Ld proteins along the dorso-ventral axis of the otic vesicle is observed during its initial patterning. In the eye, the Ld proteins are expressed by the optic vesicle during secondary induction of the lens placode. Following induction, the proteins are also expressed by the newly formed lens placode, a process which is reminiscent of homeogenetic induction. During differentiation of the retina and lens, the Ld domains seem to demarcate territories, giving rise to specific eye structures. A comparative analysis of the Ld distribution and BrdU incorporation in the two sense organs indicates that the proteins are predominantly expressed by committed and/or differentiating (post-mitotic) cells. In general, expression of Ld proteins is induced during determination and remains during differentiation of particular cell-types. This study implies that the nuclear Ld proteins are involved in morphogenesis of both neuro-ectodermal and mesodermal structures.

Animals↗
PubMed1999

Schedule for rating disabilities; diseases of the ear and other sense organs. Department of Veterans Affairs. Final rule.

This document amends that portion of the Department of Veterans Affairs (VA) Schedule for Rating Disabilities that addresses the ear and other sense organs. The intended effect of this action is to update this portion of the rating schedule to ensure that it uses current medical terminology and unambiguous criteria, and that it reflects medical advances that have occurred since the last review.

Disability Evaluation↗
PubMed1998

Morphology of the brain and sense organs in the snailfish Paraliparis devriesi: neural convergence and sensory compensation on the Antarctic shelf.

The Antarctic snailfish Paraliparis devriesi (Liparidae) is an epibenthic species, inhabiting depths of 500-650 m in McMurdo Sound. Liparids are the most speciose fish family in the Antarctic Region. We examine the gross morphology and histology of the sense organs and brain of P. devriesi and provide a phyletic perspective by comparing this morphology to that of four scorpaeniforms and of sympatric perciform notothenioids. The brain has numerous derived features, including well-developed olfactory lamellae with thick epithelia, large olfactory nerves and bulbs, and large telencephalic lobes. The retina contains only rods and exhibits a high convergence ratio (82:1). Optic nerves are small and nonpleated. The tectum is small. The corpus of the cerebellum is large, whereas the valvula is vestigial. The rhombencephalon and bulbospinal junction are extended and feature expanded vagal and spinal sensory lobes as well as hypertrophied dorsal horns and funiculi in the rostral spinal cord. The lower lobes of the pectoral fins have taste buds and expanded somatosensory innervation. Although the cephalic lateral line and anterior lateral line nerve are well developed, the trunk lateral line and posterior lateral line nerve are reduced. Near-field mechanoreception by trunk neuromasts may have been compromised by the watery, gelatinous subdermal extracellular matrix employed as a buoyancy mechanism. The expanded somatosensory input to the pectoral fin may compensate for the reduction in the trunk lateral line. The brains of P. devriesi and sympatric notothenioids share well-developed olfactory systems, an enlarged preoptic-hypophyseal axis, and subependymal expansions. Although the functional significance is unknown, the latter two features are correlated with habitation of the deep subzero waters of the Antarctic shelf.

Animals↗
PubMedDate not supplied

Quantitative study of Scarpa's ganglion and vestibular sense organs in endolymphatic hydrops.

The density of vestibular hair cells and the number of neurons in Scarpa's ganglion were estimated for 11 temporal bones with endolymphatic hydrops. The ten subjects from which these bones were taken all exhibited decreased caloric response (when tested), fluctuating hearing loss, and episodic vertigo. The degeneration of vestibular sense organs was found within the "normal" range for all except one case, which showed total degeneration of the posterior crista ampullaris. Ganglion cell counts in all cases were low. In three of the ten subjects, counts fell below the lowest values seen in a sample of "normal" ears. These three subjects exhibited fluctuating hearing loss and episodic vertigo for more than six years prior to death. In cases of unilateral endolymphatic hydrops there was no significant difference between counts in the affected and unaffected ear. Thus, the apparent ganglion cell degeneration may be due to ear disease other than endolymphatic hydrops.

Aged↗