Tonotopic organization of auditory receptors of the bushcricket Pholidoptera griseoaptera (Tettigoniidae, Decticinae)

The peripheral and central tonotopy of auditory receptors of the bushcricket Pholidoptera griseoaptera is described. Out of 24 auditory receptor cells of the crista acustica 18 were identified by single-cell recordings in the prothoracic ganglion and complete staining with neurobiotin. Proximal receptor cells of the crista acustica were most sensitive to 6 kHz, with medial cells being sensitive to 20–30 kHz, whereas distal cells were most sensitive to frequencies higher than 50 kHz. Projection areas within the auditory neuropile in the prothoracic ganglion were to- notopically arranged. Proximal cells projected anteriorly, medial cells ventrally and posteriorly, and distal cells to more dorsal regions. Identified receptor cells revealed an interindividual variability of tuning and central projections. Receptor cells from the intermediate organ of a bushcricket were identified for the first time. Receptors of the distal intermediate organ were broadly tuned and less sensitive than those of the crista acustica. Receptor cells of the proximal intermediate organ were most sensitive to frequencies below 10 kHz. They projected in anterior portions of the auditory neuropile, whereas cells of the distal intermediate organ had terminations spread over almost the whole auditory neuropile.     

Intraspinal organ in man]

In the ependymal zone of the spinal cord at the LI-SIII level an ependymal glandular organ has been described. Its highest secretory activity coincides with the period of the greatest functional activity of the human reproductive system functioning. Certain stages in development of the organ, its cell composition, blood supply, afferent and efferent innervation have been studied. In secretory cells of the organ peptide with cardio- and vasotonic properties has been identified immunochemically. The action of the organ is considered in connection with role, which the ependymal glands of the brain play in regulation of the organism's function.     

Structure and synaptic organization of the osphradium of the lamellibranch mollusk Unio pectorum

The osphradial organ has been studied in Lamellibranchia--Unio pectorum--by means of scanning and transmissive electron microscopy. On the surface of the distal part of this hemosensory organ there is a distinct division into zones. The central part of the osphradial torus is occupied by the receptory zone, formed predominantly by supporting cells with microvilli and by peripheral processes of the subepithelial receptory cells. The lateral surfaces are occupied with ciliar areas of the ciliar supporting cells. In the receptory zone two types of the peripheral processes of the receptory cells are identified; they differ by the number of kinocilia and by ultrastructural organization of the apical part. Axon-like processes of the receptory cells interact with axons and dendrites of the ganglionic cells, forming axo-axonal, axodendritic and axosomatic synapses. The facts revealed demonstrate a high level of specialization of the osphradial receptory surface, connected with polymodality of this organ.     

Critical role for TSLC1 expression in the growth and organ infiltration of adult T-cell leukemia cells in vivo

Adult T-cell leukemia (ATL) is associated with human T-cell leukemia virus type 1 infection. The tumor suppressor lung cancer 1 (TSLC1) gene was previously identified as a novel cell surface marker for ATL, and this study demonstrated the involvement of TSLC1 expression in tumor growth and organ infiltration of ATL cells. In experiments using NOD/SCID/γc^null mice, both leukemia cell lines and primary ATL cells with high TSLC1 expression caused more tumor formation and aggressive infiltration of various organs of mice. Our results suggest that TSLC1 expression in ATL cells plays an important role in the growth and organ infiltration of ATL cells.     

Fine structural studies of the nervous system and the apical organ in the planula larva of the sea anemone Anthopleura elegantissima

The nervous system of the planula larva of Anthopleura elegantissima consists of an apical organ, one type of endodermal receptor cell, two types of ectodermal receptor cells, central neurons and nerve plexus. Both interneural and neuromuscular synapses are found in the nerve plexus. The apical organ is a collection of about 100 long, columnar cells each bearing a long cilium and a collar of about 10 microvilli. The cilia of the apical organ are twisted together to form an apical tuft. The ciliary rootlets of the apical organ cells are extremely long, reaching to the basal processes of the cells adjacent to the mesoglea. All three types of sensory cells are tall and slender in profile and are identified by the presence of one or more of the following features: microtubules, small vesicles, membrane-bound granules and synapses. The interneurons are bipolar cells with somas restricted to the aboral end, adjacent to the apical organ. All synapses observed are polarized or asymmetrical. A diagram including all the elements of the nervous system is presented and the possible functions of the nervous system are discussed in relation to larval behavior.     

Intracellular recording from a spider vibration receptor

The present study introduces a new preparation of a spider vibration receptor that allows intracellular recording of responses to natural mechanical or electrical stimulation of the associated mechanoreceptor cells. The spider vibration receptor is a lyriform slit sense organ made up of 21 cuticular slits located on the distal end of the metatarsus of each walking leg. The organ is stimulated when the tarsus receives substrate vibrations, which it transmits to the organ’s cuticular structures, reducing the displacement to about one tenth due to geometrical reasons. Current clamp recording was used to record action potentials generated by electrical or mechanical stimuli. Square pulse stimulation identified two groups of sensory cells, the first being single-spike cells which generated only one or two action potentials and the second being multi-spike cells which produced bursts of action potentials. When the more natural mechanical sinusoidal stimulation was applied, differences in adaptation rate between the two cell types remained. In agreement with prior extracellular recordings, both cell types showed a decrease in the threshold tarsus deflection with increasing stimulus frequency. Off-responses to mechanical stimuli have also been seen in the metatarsal organ for the first time.     

Fiddlehead: an Arabidopsis mutant constitutively expressing an organ fusion program that involves interactions between epidermal cells.

In most circumstances plant epidermal cells do not respond to surface contact with adjacent plant parts. We have identified and characterized a mutant of Arabidopsis thaliana, designated fiddlehead, where lateral appendages of the shoot fuse with one another. While fusion between floral organs is most frequent, leaf fusions also occur. Using scanning and transmission electron microscopy, we show that adhesion takes place between epidermal cells and does not involve cytoplasmic union. We also show that the frequency of organ fusion is dictated by organ proximity. In wildtype Arabidopsis, postgenital fusion takes place exclusively in the gynoecium, whereas in the fiddlehead mutant, this program becomes expressed constitutively. The existence of such a mutant demonstrates that postgenital fusion is a genetically distinct program superimposed upon other aspects of gynoecial development in Arabidopsis.     

Detection of gill-associated virus (GAV) by in situ hybridization during acute and chronic infections of Penaeus monodon and P. esculentus

Chronic and acute gill-associated virus (GAV) infections were examined by in situ hybridization (ISH) using a DNA probe targeting a 779 nucleotide region of the ORF1b-gene. Chronic GAV infections were observed in healthy Penaeus monodon collected from farms and healthy P. esculentus surviving experimental infection. During chronic-phase infections in both species, GAV was detected only in partitioned foci of cells with hypertrophied nuclei (spheroids) within the lymphoid organ. Acute-phase infections were observed in moribund P. monodon and P. esculentus infected experimentally with a high dose of GAV, and in moribund P. monodon collected from farms during outbreaks of disease. During acute experimental infections in P. monodon, ISH detected GAV throughout the lymphoid organ, in gills and in connective tissues throughout the cephalothorax. In moribund P. monodon collected from natural outbreaks of disease, GAV was also detected in the gills and in connective tissues of the cephalothorax, but the distribution of virus within the lymphoid organ varied. In acutely infected P. esculentus, GAV was detected in connective tissues, but was restricted to the inner stromal matrix cells and endothelial cells of intact lymphoid organ tubules. The tissue distribution of GAV identified by ISH suggests that shrimp are able to control and maintain chronic asymptomatic infection by a process involving lymphoid organ spheroids. Acute phase infections and the development of disease appear to be dose-related and involve the systemic distribution of virus in connective tissues throughout the cephalothorax.     

Organ culture of the goldfish pineal body

Summary The ultrastructure and biochemistry of the goldfish pineal organ were examined in expiants cultured for 1, 3, and 6 days. All four cell types (photoreceptor, supportive, ganglion, phagocytic) were identified; they exhibited many of the characteristics of these cells in vivo. Exceptions included a gradual disorganization of the outer segments and reduction of synaptic ribbons in photoreceptors with time in culture. In addition, there was a marked proliferation of endoplasmic reticulum in both photoreceptor and supportive cells. The indoles 5-hydroxytryptophan, serotonin, 5-hydroxyindoleacetic acid, 5-methoxytryptophol, and melatonin were separated in expiants by high performance liquid chromatography using electrochemical detection. Serotonin levels could be depleted by p-chlorophenylalanine and elevated by nialamide or by adding 5-hydroxytryptophan to the culture medium. These findings suggest that organ culture may be a useful model for study of regulatory processes related to the photoneuroendocrine functions of the teleost pineal organ.     

Characterization of different microenvironments at the surface of the frog's taste organ

We used a panel of histochemical techniques to identify and characterize the cell-associated extracellular material at the surface of the frog's taste organ. We employed morphological and histochemical techniques using both the light microscope and the electron microscope. Results show that the apical, external aspect of cells reaching the surface of the taste organ is in close contact with a layer of amorphous material. The histochemical characteristics of this material vary according to the cell type with which it is in contact. Three different microenvironments can be identified at the surface of the frog's taste organ: type 1 microenvironment is associated with the superficial layer of mucus (secretory) cells; type 2 microenvironment characterizes the surface of the so-called wing cells, which reach the surface of the taste organ as thin laminae running among mucus cells; and type 3 microenvironment shrouds the free endings of putative taste cells and is rich in calcium and lipids. Type 2 and type 3 microenvironments fix peroxidase (a sapid macromolecule) with increasing affinity. We conclude that highly differentiated microenvironments exist at the surface of the frog's taste organ, and these could play a role in the chain of biological events leading to the taste sensation. Furthermore, characterization of the cell-associated, specific microenvironments can help clarify the role of the different cell types in the frog's taste organ.     

Characterization of Mesonephric Cells That Migrate into the XY Gonad during Testis Differentiation

In mouse fetal gonads, sex differentiation begins at 10.5-11.5 days postcoitum (dpc). With XY gonads of 12.5 dpc, cord-like structures are visible and stromal cells migrate from adjacent mesonephros, unlike in XX gonads. However, the migrated mesonephric cells, except for the endothelial cells, have not been specifically identified because they have not expressed differentiation markers over the course of organ coculture in previous experiments. In this study, we have for the first time succeeded in isolating only the mesonephric cells that migrate into the XY gonad from the mesonephros with alive and then cultured these cells in vitro through the use of an organ coculture system using EGFP-transgenic mice and a FACS Vantage. The migrated and isolated cells were used for morphological and molecular characterization. The migrated mesonephric cells contained three cell forms; a sharp cell form, a round cell form, and a cluster-forming cell. The sharp cells have the characters of peritubular myoid cells. The round cells and cluster-forming cells have the potential to differentiate into Leydig cells, as some of them are 3beta-HSD-positive. In in vitro culture of migrated mesonephric cells, the cluster-forming cells proliferated well and then differentiated into round cells, suggesting that the cluster-forming cells may be stem or precursor cells for the round cells. Thus, our findings provide important information related to the migration and differentiation of migrated mesonephric cells in the XY gonad.     

A gain-of-function screen for genes that affect the development of the Drosophila adult external sensory organ

The Drosophila adult external sensory organ, comprising a neuron and its support cells, is derived from a single precursor cell via several asymmetric cell divisions. To identify molecules involved in sensory organ development, we conducted a tissue-specific gain-of-function screen. We screened 2293 independent P-element lines established by P. Rorth and identified 105 lines, carrying insertions at 78 distinct loci, that produced misexpression phenotypes with changes in number, fate, or morphology of cells of the adult external sensory organ. On the basis of the gain-of-function phenotypes of both internal and external support cells, we subdivided the candidate lines into three classes. The first class (52 lines, 40 loci) exhibits partial or complete loss of adult external sensory organs. The second class (38 lines, 28 loci) is associated with increased numbers of entire adult external sensory organs or subsets of sensory organ cells. The third class (15 lines, 10 loci) results in potential cell fate transformations. Genetic and molecular characterization of these candidate lines reveals that some loci identified in this screen correspond to genes known to function in the formation of the peripheral nervous system, such as big brain, extra macrochaetae, and numb. Also emerging from the screen are a large group of previously uncharacterized genes and several known genes that have not yet been implicated in the development of the peripheral nervous system.     

Spatial distribution of the medullary command signal within the electric organ of Gymnotus carapo

The pacemaker nucleus of Gymnotus carapo contains two types of neurons: pacemaker cells which set up the frequency of the electric organ discharge (EOD) and relay cells which convey the command signal to the spinal cord. Direct activation of a single relay cell provides enough excitation to discharge a pool of spinal electromotor neurons and electrocytes, generating a small EOD (unit EOD). Different relay cells generate unit EODs of variable size and waveform, indicating the involvement of different groups of electrocytes. A special technique of EOD recording (multiple air-gap) was combined with intracellular stimulation of relay cells to study the spatial distribution within the electric organ (EO) of the command signal arising from different relay cells. Three types of relay cells could be identified: type I commanding the rostral 10% of the EO, type II which distribute their command all along the EO and type III driving the caudal 30%. Waveform analysis of unit EODs indicates that doubly innervated electrocytes which are the most relevant for attaining the specific EOD waveform, receive a favored command from the pacemaker nucleus.Abbreviations CV conduction velocity - EMF electromotive force - EMN electromotor neuron - EO electric organ - EOD electric organ discharge - PN pacemaker nucleus - uEOD unit electric organ discharge     

The infundibular organ of the lancelet (Branchiostoma lanceolatum,Acrania): an immunocytochemical study

Reissner's fibers are secretions produced by different ependymal areas of the chordate brain, viz., in adult vertebrates, by the dorsal subcommissural organ, and in all stages of cephalochordates (Branchiostoma lancelets), by the ventral infundibular organ. Fibers produced by these different organs are seemingly identical and the two fiber sources also share some immunocytochemical and lectin-binding properties. The secretions in these two glands are, however, not identical; the infundibular organ cells are strongly reactive with antibodies against vertebrate Reissner's fibers, but they do not react with antibodies raised against the source of the vertebrate fibers, viz., the subcommissural organ. The results support the possibility that, in adult vertebrates, the Reissner's fibers are composed of material not only from the subcommissural organ, but also from another, not yet identified, source that is identical or equivalent to the infundibular organ of the lancelet. There are indications that the infundibular organ is immunocytochemically closely akin to some secretory cells in the vertebrate embryonic brain and also to those that produce the juvenile vertebrate Reissner's fibers, viz., secretory cells in the flexural organ.     

A dual function of phyllopod in Drosophila external sensory organ development: cell fate specification of sensory organ precursor and its progeny

During Drosophila external sensory organ development, one sensory organ precursor (SOP) arises from a proneural cluster, and undergoes asymmetrical cell divisions to produce an external sensory (es) organ made up of different types of daughter cells. We show that phyllopod (phyl), previously identified to be essential for R7 photoreceptor differentiation, is required in two stages of es organ development: the formation of SOP cells and cell fate specification of SOP progeny. Loss-of-function mutations in phyl result in failure of SOP formation, which leads to missing bristles in adult flies. At a later stage of es organ development, phyl mutations cause the first cell division of the SOP lineage to generate two identical daughters, leading to the fate transformation of neurons and sheath cells to hair cells and socket cells. Conversely, misexpression of phyl promotes ectopic SOP formation, and causes opposite fate transformation in SOP daughter cells. Thus, phyl functions as a genetic switch in specifying the fate of the SOP cells and their progeny. We further show that seven in absentia (sina), another gene required for R7 cell fate differentiation, is also involved in es organ development. Genetic interactions among phyl, sina and tramtrack (ttk) suggest that phyl and sina function in bristle development by antagonizing ttk activity, and ttk acts downstream of phyl. It has been shown previously that Notch (N) mutations induce formation of supernumerary SOP cells, and transformation from hair and socket cells to neurons. We further demonstrate that phyl acts epistatically to N. phyl is expressed specifically in SOP cells and other neural precursors, and its mRNA level is negatively regulated by N signaling. Thus, these analyses demonstrate that phyl acts downstream of N signaling in controlling cell fates in es organ development.     

Photoreceptor cells and neural elements with long axonal processes in the pineal organ of the lamprey,Lampetra japonica,identified by use of the horseradish peroxidase method

Summary Horseradish peroxidase (HRP) was applied to the transected end of the pineal tract of the lamprey, Lampetra japonica. Distinct reaction products of HRP were observed in 2 types of cell other than ganglion cells. The first type of cell protrudes a knob-like process into the pineal lumen. This type of cell was clearly identified by electron microscopy as a photoreceptor cell; its outer segment was connected to the ellipsoid through a sensory cilium. The other type of cell was located among photoreceptor and supporting cells. The processes of these cells were thin and slender, and they obviously did not represent photoreceptor, supporting, or conventional ganglion cells. The present results indicate that, in the lamprey, some of the photoreceptor cells of the pineal organ project their axon-like processes toward the posterior commissure, but that there is also another type of cell displaying long axonal projections. HRP-containing cells were distributed randomly over the pineal organ and were occasionally also observed in the parapineal organ.