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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↗
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↗
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↗
PubMed1984

Sense organs of the nematodes Trichinella pseudospiralis Garkavi, 1972 and T. nativa Britov et Boev, 1972.

The structure and distribution of the sense organs of the head and the tail of two day-old Trichinella species (females) have been determined by transmission (TEM) and scanning (SEM) electron microscopy. In both species occur 16 cephalic sense organs, which contain three modified dendritic processes, in addition to the amphids. The nerve cell bodies are situated in the area above the nerve ring. The amphid contains ten dendritic processes. The sense organs open to the external environment by pores through the cuticle. Above the bulbous tip, the dendritic processes are surrounded by hypodermal cells. They enter posteriorly the pseudocoelom and join in subventral, subdorsal and two sublateral nerves, with transparent nuclei, in the area above the nerve ring. The distribution of the sense organs of larvae from the muscles and from the uterus is similar to that of the adults. The dendritic processes are short, most of their distal chamber is compacted with a dense, filamentous material. The rectum in the tail end of the female is innervated from the dorsal ganglion composed by multipolar cells with numerous dendrites and a single axon. Close to the excretory pore occurs a hemizonid which consists of six to eight dendrites and is situated between the hypodermis and the muscles. This organ has not been found in the larva.

Animals↗
PubMed1995

Genetic determinants of sense organ identity in Drosophila: regulatory interactions between cut and poxn.

Two genes involved in defining the type of sense organ have been identified in Drosophila. The gene cut differentiates the external sense organs (where it is expressed) from the chordotonal organs (where it is not); among the external sense organs poxn differentiates the poly-innervated organs (where it is expressed) from the mono-innervated organs (where it is not). Here we show that the expression of poxn in normal embryos does not depend on cut, and that poxn is capable of inducing the expression of cut. We have identified a small domain of the very large cut regulatory region as a likely target for activation by poxn.

Animals↗
PubMed1992

The paired box gene pox neuro: a determinant of poly-innervated sense organs in Drosophila.

This study describes the structure and function of pox neuro (poxn), a gene previously isolated by virtue of a conserved domain, the paired box, which it shares with the segmentation genes paired and gooseberry. Its expression pattern has been analyzed, particularly during development of the PNS. We propose that poxn is a "neuroblast identity" gene acting in both the PNS and the CNS on the basis of the following evidence. Its expression is restricted to four neuronal precursors in each hemisegment: two neuronal stem cells (neuroblasts) in the CNS, and two sensory mother cells (SMCs) in the PNS. The SMCs that express poxn produce the poly-innervated external sense organs of the larva. In poxn- embryos, poly-innervated sense organs are transformed into mono-innervated. Conversely, ectopic expression of poxn in embryos transformed with a heat-inducible poxn gene can switch mono-innervated to poly-innervated sense organs. Expression of poxn in the wing disc is restricted to the SMCs of the poly-innervated sense organs, suggesting that poxn also determines the lineage of poly-innervated adult sense organs.

Amino Acid Sequence↗
PubMed1977

Sense organs on the antennal flagellum of psocids (Insecta, Psocoptera).

The sense organs on the antennal flagella of five species of winged psocids belonging to two families of Psocoptera, Psocidae and Leptopsocidae, have been examined, All agree in possessing tactile hairs, thick-walled chemoreceptors and long, porous chemoreceptors. Thin-walled chemoreceptors were identified in all species except Metylophorous novaescotiae. Coeloconic chemoreceptors were present in all species except Echmepteryx hageni. Campaniform sense organs were found only in Metylophorus novaescotiae and Psocus leidyi.

Animals↗
PubMed1994

Position-reading and the emergence of sense organ precursors in Drosophila.

Genetic analysis of development in Drosophila melanogaster has advanced our understanding of "position reading", where the expression of particular genes informs a cell of its position in the developing animal. The first step in localization of fly sense organs is the local expression of a gene conferring neural competence on epidermal cells. The four genes of the achaete-scute (AS-C) complex play crucial roles in the localization of sense organs. The resolution of local expression of AS-C genes along one dimension is about 10%; accuracy is improved by the balancing local expression of AS-C antagonist genes such as extramacrochaete. Position reading seems to depend primarily on such patterns of gene expression, and not upon the compartmental identity of the cells. No evidence has been found for differing roles of the four AS-C genes in the generation of sense organ progenitor cells or in the specification of neuronal properties of innervating neurons. The formation of each sense organ may be a unique case where the different proneural and neurogenic gene products have varying importance, and fortuitous local effects acting on this complex combination of factors have come to be important. The fly may be evolving from a flexible regular pattern to an inflexible irregular pattern strongly dependent on local factors, turning the fly into a crystallized system. (Written by R. Wayne Davies.).

Animals↗
PubMed1995

Specification of sense-organ identity by a Caenorhabditis elegans Pax-6 homologue.

The Pax-6 transcription-factor gene, containing a paired domain and a paired-type homeodomain, is conserved in structure and ubiquitously present among Metazoa. It is required for development of the central nervous system, and is mutated in human aniridia, mouse and rat small eye and Drosophila eyeless. We identified the Pax-6 gene of the nematode Caenorhabditis elegans in genetic studies of male tail morphology. C. elegans Pax-6 encodes at least two independent genetic functions. One, like other Pax-6 genes, contains paired and homeodomains; this constitutes the genetic locus vab-3. The other, described here, is expressed from an internal promoter and contains only the homeodomain portion; this constitutes the genetic locus mab-18. The mab-18 form of the gene is expressed in a peripheral sense organ and is necessary for specification of sense-organ identity. Its function in this context could be to regulate the expression of cell recognition and adhesion proteins required for sense-organ assembly.

Amino Acid Sequence↗
PubMed1991

The emergence of sense organs in the wing disc of Drosophila.

We have examined the origin of a set of precisely located sense organs in the notum and wing of Drosophila, in transformant flies where lacZ is expressed in the progenitor cells of the sense organs (the sensory mother cells) and in their progeny. Here we describe the temporal pattern of appearance and divisions of the sensory mother cells that will form the eleven macrochaetes and the two trichoid sensilla of the notum, and five campaniform sensilla on the wing blade. The complete pattern of sensory mother cells develops in a strict sequence that extends over most of the third larval instar and the first 10 h after puparium formation. The delay between the onset of lacZ expression and the first differentiative division ranges from 30 h, in the case of the earliest mother cells, to 2 h for the latest mother cells. The first division shows a preferential orientation which is also specific for each sensory mother cell. Up to this stage, there is no marked difference between the three types of mechanosensory organs.

Animals↗