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At least 19 recordsLinked to original sources
PubMed1997

Sound emission from cochlear filters and foveae--does the auditory sense organ make sense?

Sense organs filter relevant information from a broad background of physical interactions and discard possible perceptual input that has not proven useful during the course of biological evolution. Sense organs not only limit the access to physical reality, under certain conditions they have a life of their own and produce responses even in the absence of physical stimulation. As a perfect example, the inner ear, the cochlea, in addition to detecting incoming sound waves, it also is capable of producing sound energy. Such "active" processes, however, seem to be necessary to push detection thresholds close to physical limits. The price that has to be paid are "cochlear artifacts" like otoacoustic emissions. In the following, measurement of sound that is emitted by the ear will be introduced as a noninvasive means to assess cochlear function and to help to unravel the mechanical interaction between sensory cells and supporting structures that ultimately leads to sensitive and sharply tuned auditory perception. One focus will be on the cochlea of echo-locating bats that use audition as the main window of perception to their environment and therefore have highest demands on cochlear performance.

Animals↗
PubMed1999

Prospero distinguishes sibling cell fate without asymmetric localization in the Drosophila adult external sense organ lineage.

The adult external sense organ precursor (SOP) lineage is a model system for studying asymmetric cell division. Adult SOPs divide asymmetrically to produce IIa and IIb daughter cells; IIa generates the external socket (tormogen) and hair (trichogen) cells, while IIb generates the internal neuron and sheath (thecogen) cells. Here we investigate the expression and function of prospero in the adult SOP lineage. Although Prospero is asymmetrically localized in embryonic SOP lineage, this is not observed in the adult SOP lineage: Prospero is first detected in the IIb nucleus and, during IIb division, it is cytoplasmic and inherited by both neuron and sheath cells. Subsequently, Prospero is downregulated in the neuron but maintained in the sheath cell. Loss of prospero function leads to 'double bristle' sense organs (reflecting a IIb-to-IIa transformation) or 'single bristle' sense organs with abnormal neuronal differentiation (reflecting defective IIb development). Conversely, ectopic prospero expression results in duplicate neurons and sheath cells and a complete absence of hair/socket cells (reflecting a IIa-to-IIb transformation). We conclude that (1) despite the absence of asymmetric protein localization, prospero expression is restricted to the IIb cell but not its IIa sibling, (2) prospero promotes IIb cell fate and inhibits IIa cell fate, and (3) prospero is required for proper axon and dendrite morphology of the neuron derived from the IIb cell. Thus, prospero plays a fundamental role in establishing binary IIa/IIb sibling cell fates without being asymmetrically localized during SOP division. Finally, in contrast to previous studies, we find that the IIb cell divides prior to the IIa cell in the SOP lineage.

Animals↗
PubMed1998

Patterning an epidermal field: Drosophila lozenge, a member of the AML-1/Runt family of transcription factors, specifies olfactory sense organ type in a dose-dependent manner.

Sense organ development in the Drosophila antenna is initiated by the selection of a founder cell from an epidermal field. This cell is believed to recruit neighbours to form a cluster of cells which then divides to form a mature sense organ. In most systems so far studied, sense organ type appears to be specified by the identity of proneural genes involved in the selection of precursors. The regulation of proneural gene expression is, in turn, controlled by the prepatterning genes. In the antenna, the only known proneural function is that of atonal, a gene that is involved in founder cell choice in the sensilla coeloconica, and no prepatterning gene function has yet been demonstrated. In this study, we show that Lozenge, a protein which possesses a DNA binding domain similar to that of the Acute myeloid leukemia-1/Runt transcription factors, functions in a dose-dependent manner to specify the fate of the other two types of sense organs in the antenna: the sensilla trichoidea and the sensilla basiconica. Our results suggest that Lozenge may act on the epidermal field, resulting in founder cells acquiring specific cell fates that lead to the development of an appropriate type of sense organ.

Animals↗
PubMed1973

Development of locomotor patterns in the absence of peripheral sense organs and muscles.

The role of peripheral sense organs and muscles in specifying the circuitry of the central nervous system during ontogeny was tested in larval lobsters. Presumptive locomotor appendages, the abdominal swimmerets, were extirpated before their differentiation. Electrophysiological recordings made 2-4 weeks later from the corresponding motor nerves showed that, despite the absence of the target muscles and sense organs, normal reflexes and normal patterns of rhythmic locomotor output appeared in the swimmeret motoneurons at the usual developmental stage. Therefore, target muscles and sense organs are unnecessary to the differentiation of normal motor output patterns in this simple invertebrate locomotor system.

Action Potentials↗
PubMed1998

The specificity of proneural genes in determining Drosophila sense organ identity.

The proneural genes (atonal and the genes of the achaete-scute complex (AS-C)) are required for the selection of sense organ precursors. They also endow these precursors with sense organ subtype information. In most of the ectoderm, atonal is required for precursors of chordotonal sense organs, whereas AS-C are required for those of most external sense organs, such as bristles. To address the question of how proneural genes influence subtype identity, we have made use of the Gal4/UAS system of misexpression. Unlike previous misexpression experiments, we found that under specific conditions of misexpression, atonal shows high subtype specificity of ectopic sense organ formation. Moreover, atonal can even transform wild-type external sense organs to chordotonal organs, although scute cannot perform the reciprocal transformation. Our evidence demonstrates that atonal's subtype determining role is not to activate directly chordotonal fate, but to repress the activation of cut, a gene that is necessary for external sense organ fate, thereby freeing its precursors to follow the alternative chordotonal organ fate.

Animals↗
PubMed2001

Organisation of the praesoma of Paratenuisentis ambiguus (Van Cleave, 1921) (Acanthocephala: Eoacanthocephala), with special reference to the lateral sense organs and musculature.

The praesoma of the acanthocephalan parasite Paratenuisentis ambiguus was studied at the light and the electron microscope level, with special reference to the lateral sense organs and the musculature, in order to substantiate the basal pattern of the Acanthocephala and to analyse the phylogeny of the taxon. The study includes the first ultrastructural description of a lateral sense organ in the Acanthocephala. Two sensory support cell ducts extend from the binucleate pericaryon of the sensory support cell to the lateral sense organs. On their way to the lateral sense organs the ducts penetrate the receptacle and join the anterior ventral nerves. Each lateral sense organ consists of a conical termination of one of the sensory support cell ducts, in which the neuronal fibres and dendritic terminations of the equilateral anterior ventral nerve are embedded. An analysis of the available data of praesomal sense organs in Acanthocephala suggests that lateral and apical sense organs are absent in the basal pattern of the Acanthocephala. It is likely that two lateral sense organs, a binucleate sensory support cell with two ducts and two anterior ventral nerves evolved within the stem-line of some Palaeacanthocephala, all Eoacanthocephala and all Archiacanthocephala, whereas two apical sense organs, a quadrinucleate sensory support cell with four ducts and two apical sensory nerves presumably represent an autapomorphic character of the Archiacanthocephala. Furthermore, it can be derived from data in the literature and the present study that the praesomal hooks are totally covered by epidermis in the basal pattern of the Acanthocephala, whereas the ontogenetic loss of the epidermal covering can be regarded as an autapomorphy of the Archiacanthocephala.

Acanthocephala↗
PubMed2005

The structure and development of avian lumbosacral specializations of the vertebral canal and the spinal cord with special reference to a possible function as a sense organ of equilibrium.

The avian lumbosacral vertebral column and spinal cord show a number of specializations which have recently been interpreted as a sense organ of equilibrium. This sense organ is thought to support balanced walking on the ground. Although most of the peculiar structures have been described previously, there was a need to reevaluate the specializations with regard to the possible function as a sense organ. Specializations were studied in detail in the adult pigeon. The development of the system was studied both in the pigeon (semiprecocial at hatching) and in the chicken (precocial). Specializations in the vertebral canal consist of a considerable enlargement, which is not due to an increase in the size of the spinal nervous tissue, but to a large glycogen body embedded in a dorsal rhomboid sinus. The dorsal wall of the vertebral canal shows segmented bilateral dorsal grooves, which are covered by the meninges towards the lumen of the vertebral canal leaving openings in the midline and laterally. This results in a system of lumbosacral canals which look and may function similar to the semicircular canals in the inner ear. Laterally these canals open above ventrolateral protrusions or accessory lobes of the spinal cord which contain neurons. There are large subarachnoidal cerebrospinal fluid spaces, lateral and ventral to the accessory lobes. Movement of this fluid is thought to stimulate the lobes mechanically. As to the development of avian lumbosacral specializations, main attention was given to the organization of the lobes and the adjacent fluid spaces including the dorsal canals. In the pigeon the system is far from being adult-like at hatching but maturates rapidly after hatching. In the chicken the system looks already adult-like at hatching. The implications derived from the structural findings are discussed with regard to a possible function of the lumbosacral specializations as a sense organ of equilibrium. The adult-like organization in the newly hatched chickens, which walk around immediately after hatching, supports the assumed function as a sense organ involved in the control of locomotion on the ground.

Animal Structures↗
PubMed2003

The capsular organ of Chelyosoma productum (Ascidiacea: Corellidae): a new tunicate hydrodynamic sense organ.

Chelyosoma has about 200 sense organs in the atrial wall of the branchial sac that show structural features suggestive of a role in hydrodynamic sensing. They consist of a fluid-filled capsule with an acellular diaphragm spanning an opening in the top. The floor of the capsule is a sensory macula, with 5-6 primary sensory neurons whose cilia project into the capsular cavity and whose axons go to the brain. Animals were tested for vibrational sensitivity using a loudspeaker probe. They responded by muscular contractions of the siphons and/or arrests of the branchial cilia, both of which caused changes in water flow velocity through the siphons, which were monitored non-invasively using a thermistor flow meter. The animals showed peak sensitivity at 240-260 Hz. Subsequent calibration of the loudspeaker probe indicated that the animals could detect 104 decibels re 1 microPa from a source 80 cm away. The majority of axons leaving the capsular organs go to the brain via the visceral nerve. Cutting this nerve abolished or greatly reduced responses. Electrophysiological recordings from the distal nerve stump showed bursts of electrical events following vibrational stimulation. No such records could be obtained from other major nerves and cutting them did not affect responsivity. Corella inflata, a close relative of Chelyosoma, lacks capsular organs and failed to show any responses when the source was more than 3.5 cm away. We conclude that Chelyosoma's vibration-sensing ability is due to its capsular organs and is adaptive in terms of detecting the movements of objects in the vicinity. The findings are discussed in relation to the evolution of hydrodynamic mechanoreceptors in tunicates, amphioxus and craniates.

Animals↗
PubMed1997

Atonal is a proneural gene for a subset of olfactory sense organs in Drosophila.

BACKGROUND: The antenna of the adult fruit fly, Drosophila melanogaster, is covered with three morphologically distinct types of olfactory sense organs. In addition, mechano- and hygro-sensitive receptors are also present on its surface. While much has been learnt about the development of peripheral nervous system in Drosophila, the mechanisms underlying the development of olfactory sensilla are just beginning to be unraveled. The antennal sense organs have several properties that make them distinct from other sense organs. While each sensillum type is arranged in a well-defined region of the antenna, the position of an individual sensillum is not fixed. The development of these sense organs appears to combine an initial step of cell recruitment, as in photoreceptors, followed by cell lineage mechanisms, as in the development of other external sense organs. The earliest step in development, the selection of a sensory organ precursor, involves the interaction of proneural and neurogenic genes. The proneural gene for the antennal sense organs has been elusive so far. RESULTS: We show that the basic helix-loop-helix (bHLH) transcription factor encoded by atonal (ato) is a proneural gene for one morphological type of olfactory sensilla on the antenna and for all the olfactory sensilla on the maxillary palp. Loss of function and overexpression experiments together reveal that ato is both necessary and sufficient to specify these sensilla. Immunohistochemical experiments show that Ato expresses in a dynamic pattern in the developing antennal disc. CONCLUSIONS: Our results demonstrate that ato acts solely in the specification of antennal sensilla coeloconica. This along with our previous observation that the AS-C genes do not function in antenna allows us to suggest that other proneural genes must operate in the specification of sensilla basiconica and trichoidea. Our experiment involving overexpression of extramacrochaetae, a negative regulator of bHLH encoding genes, results in a significant reduction in the number of all three types of antennal sensilla. This suggests that the unidentified proneural gene(s) possibly encode bHLH factors.

Animals↗
PubMed1999

Antagonism of EGFR and notch signalling in the reiterative recruitment of Drosophila adult chordotonal sense organ precursors.

The selection of Drosophila melanogaster sense organ precursors (SOPs) for sensory bristles is a progressive process: each neural equivalence group is transiently defined by the expression of proneural genes (proneural cluster), and neural fate is refined to single cells by Notch-Delta lateral inhibitory signalling between the cells. Unlike sensory bristles, SOPs of chordotonal (stretch receptor) sense organs are tightly clustered. Here we show that for one large adult chordotonal SOP array, clustering results from the progressive accumulation of a large number of SOPs from a persistent proneural cluster. This is achieved by a novel interplay of inductive epidermal growth factor-receptor (EGFR) and competitive Notch signals. EGFR acts in opposition to Notch signalling in two ways: it promotes continuous SOP recruitment despite lateral inhibition, and it attenuates the effect of lateral inhibition on the proneural cluster equivalence group, thus maintaining the persistent proneural cluster. SOP recruitment is reiterative because the inductive signal comes from previously recruited SOPs.

Animals↗
PubMed2006

External sense organs in freshwater oligochaetes (Annelida, Clitellata) revealed by scanning electron microscopy.

Freshwater oligochaetes have at least two kinds of external sense organs: multiciliate organs of short cilia (also present in earthworms) and sense organs with one to three long cilia (unknown in earthworms and possibly acting as rheoreceptors). Ciliate sense organs of freshwater oligochaetes are distributed over their entire body surface, including the clitellum. They are scattered on the prostomium and pigidium and are arranged into a transversal chaetal row and dispersed or forming a few other discrete transversal rows on chaetal segments. Three species display very prominent sense organs (sensory buds in Protuberodrilus tourenqui and papillae in Ophidonais serpentina and Spirosperma velutinus). The number of cilia per organ at the prostomium of freshwater families appears to be fewer than that of terrestrial ones. It is suggested that the total number of cilia at the prostomium of the freshwater species could be related to their habitat, evolving from an epibenthic to an endobenthic way of life.

Animals↗
PubMed2001

Anatomy and histology of the brain and sense organs of the Antarctic eel cod Muraenolepis microps (Gadiformes; Muraenolepididae).

Brain regions, cranial nerves, and sense organs in Muraenolepis microps, an Antarctic gadiform fish, were examined to determine which features could be attributed to a gadiform ancestry and which to habitation of Antarctic waters. We found that the central nervous system and sense organs are well developed, showing neither substantial regression nor hypertrophy. A detailed drawing of the brain and cranial nerves is provided. The rostral position of the olfactory bulbs and telencephalic size and lobation are common for the order. The optic tectum and corpus cerebelli are smaller than in most other gadiforms. The shape of the corpus cerebelli is not distinctive among gadiforms. The lateral line region is moderately well-developed, but not hypertrophied to the extent seen in deep-sea gadiforms. As is the case in gadids possessing barbels and elongated pelvic rays, Muraenolepis has well-developed facial lobes, although these are smaller and more laterally positioned. The vagal lobes are deeply placed in the rhombencephalon and project into the fourth ventricle. The brain of Muraenolepis resembles that of a phyletically derived gadoid, especially a phycid, more than it resembles the brain of a phyletically basal macrourid. Two histological features of the diencephalon of Muraenolepis appear to be unique among gadiforms: a well-organized thalamic central medial nucleus and subependymal expansions. Muraenolepis has a pure rod retina like many deep-sea species but lacks the superimposed layers of rod outer segments. The histology of the nonvisual sense organs, especially the olfactory and external taste systems, are well-developed in Muraenolepis but not hypertrophied. We relate our findings to what is known about neural morphology in other gadiforms and in phyletically distant notothenioids and liparids that are sympatric with Muraenolepis on the Antarctic shelf. The only feature that reflects an Antarctic existence is the diencephalic subependymal expansions, which within notothenioids mirror the habitation of cold waters and have been found in every Antarctic species examined to date. Although the waters of the Antarctic shelf are cold, dark, and deep, brain and sense organ morphology in Muraenolepis are remarkably free of extreme specialization.

Animals↗
PubMed1992

The determination of sense organs in Drosophila: a search for interacting genes.

The determination of sense organs in Drosophila requires the concerted action of a battery of genes, several of which have been identified. Previous experiments revealed that flies doubly heterozygous for mutations in two of these genes have a reduced number of sense organs, suggesting the existence of a direct interaction between the corresponding genes and/or their products. We have now used this observation to search for mutations in additional genes that would show similar interactions. We have detected 10 recessive mutations that show a dominant reduction in the number of bristles when simultaneously heterozygous for either Df(2)J27 or Df(4)M62f. Among these mutations, 3 are homozygous viable and show striking defects in their bristle patterns, confirming that the genes thus identified play a role in the patterning of sense organs. We conclude that the "gene dose titration" method (Botas et al., 1982) is an efficient method for identifying interacting genes involved in a common process, provided one can identify a well-defined phenotype to look at, and at least one mutation that alters the process. Our experience suggests that its efficiency should be substantially improved by the use of insertional mutagenesis.

Animals↗
PubMed1977

Labial sense organs of the nematode, Heterakis gallinarum.

The labial sense organs of Heterakis gallinarum (Schrank 1788) were examined by scanning and transmission electron microscopy. Two large doublet papillae are visible externally on the dorsal lip while a single doublet papilla, a short peglike ventrolateral papilla, and the opening of the amphid are visible on each subventral lip. Internal anatomy of these papillae indicates that the doublet papillae are probably pressure receptors while the ventrolateral papillae may be combined mechano- and chemoreceptors. Amphids resemble the structure of amphids of several previously studied nematodes. Six internal labial receptors, two at the inner edge of each lip, can be identified by transmission microscopy. They may be mechanoreceptors recording cuticular stresses during feeding. Each sense organ is associated with a complexly folded system of membranes delimiting extracellular space continuous with space surrounding the dendritic process of the receptor.

Nematoda↗