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C Duch

Publications and source records attributed to C Duch.

18 recordsLinked to original sources
PubMed2006

Developmental relocation of presynaptic terminals along distinct types of dendritic filopodia.

Dendritic filopodia are long thin protrusions occurring predominantly on developing neurons. Data from different systems suggest a range of crucial functions for filopodia in central circuit formation, including steering of dendritic growth, branch formation, synaptogenesis, and spinogenesis. Are the same filopodia competent to mediate all these processes, do filopodia acquire different functions through development, or do different filopodial types with distinct functions exist? In this study, 3-dimensional reconstructions from confocal image stacks demonstrate the existence of two morphologically and functionally distinct types of filopodia located on the dendritic tips versus the dendritic shafts of the same developing motoneuron. During dendritic growth, both filopodial types undergo a process of stage-specific morphogenesis. Using novel quantification strategies of 3-dimensional co-localization analysis for immunocytochemically labeled presynaptic specializations along postsynaptic filopodia, we find that presynaptic terminals accumulate along filopodia towards the dendrites at both stable dendritic shafts and on growing dendritic tips. On tips, this is likely to reflect synaptotrophic growth of the dendrite. At stable shafts, however, presynaptic sites become relocated along filopodia towards dendritic branches. This indicates the interactive growth of both pre- and postsynaptic partner towards one another during synaptogenesis, using filopodia as guides.

Animals↗
PubMed2006

A steroid hormone affects sodium channel expression in Manduca central neurons.

Neuronal differentiation is characterized by stereotypical sequences of membrane channel and receptor acquisition. This is regulated by the coordinated interactions of a variety of developmental mechanisms, one of which is the control by steroid hormones. We have used the metamorphosis of the holometabolous insect, Manduca sexta, as a model to study effects of 20-hydroxyecdysone on the maturation of thoracic neuron membrane channel expression. To test for direct hormone action, neurons were dissociated into primary cell culture on the first day of pupal life. In situ hybridization demonstrated that the amount of expression of the acetylcholine receptor alpha subunit, MARA1, was not affected by 20-hydroxyecdysone. Immunocytochemistry with an antibody directed against the SP19 segment of voltage-gated sodium channels revealed no effect of 20-hydroxyecdysone treatment during the first 6 days in culture. SP19 sodium channel protein was evenly distributed along all neurites. In contrast, after 8 days in culture, 20-hydroxyecdysone increased the amount of SP19 protein expression and strongly affected its distribution in differentiating neurons. In the presence of 20-hydroxyecdysone, patches of high densities of SP19 sodium channel protein were found in growth cones close to the base of filopodia. This is a further step toward unraveling the blend of membrane proteins under the control of steroids during the development of the central nervous system of postembryonic Manduca. Our results, taken together with previous studies, indicate that 20-hydroxyecdysone does not affect the expression of potassium membrane current or of the nicotinic acetylcholine receptor but instead regulates the amplitude of the calcium membrane current and the amount and distribution of SP19 sodium channel protein.

Animals↗
PubMed2006

Developmental changes of CaMKII localization, activity and function during postembryonic CNS remodelling in Manduca sexta.

Insect metamorphosis is a compelling example of postembryonic remodelling of neuronal structure and synaptic connectivity as larval and adult behaviours place distinct demands on the CNS. Holometabolous insects such as the moth Manduca sexta have long served as suitable models for the study of steroid effects on CNS remodelling, but activity and calcium-dependent mechanisms have been found to act in concert with hormonal signals. This study examines developmental changes in the localization and the activational state of CaMKII during postembryonic Manduca CNS remodelling. Western blotting, CaMKII purification and autophosphorylation with gamma(32)P-ATP indicate that the lepidopteran CNS may contain only one CaMKII isoform. In situ immunohistochemistry reveals developmental changes in the expression patterns of CaMKII in different types of thoracic neurons and in different neuronal compartments. Early pupal life is characterized by an increase in postsynaptic CaMKII localization, which coincides with a developmental increase in CaMKII activation. Both events correlate temporally with motoneuron dendritic filopodia collapse and rapid synaptogenesis, indicating a possible functional role for CaMKII for the postembryonic development of invertebrate motor circuitry. Substrate phosphorylation assays demonstrate that CaMKII activity in the ventral nerve cord reflects changes in calcium influx through voltage-activated channels as occurring in vivo during normal development.

Animals↗
PubMed2004

Progress in functional neuroanatomy: precise automatic geometric reconstruction of neuronal morphology from confocal image stacks.

Dendritic architecture provides the structural substrate for myriads of input and output synapses in the brain and for the integration of presynaptic inputs. Understanding mechanisms of evolution and development of neuronal shape and its respective function is thus a formidable problem in neuroscience. A fundamental prerequisite for finding answers is a precise quantitative analysis of neuronal structure in situ and in vivo. Therefore we have developed a tool set for automatic geometric reconstruction of neuronal architecture from stacks of confocal images. It provides exact midlines, diameters, surfaces, volumes, and branch point locations and allows analysis of labeled molecule distribution along neuronal surfaces as well as direct export into modeling software. We show the high accuracy of geometric reconstruction and the analysis of putative input synapse distribution throughout entire dendritic trees from in situ light microscopy preparations as a possible application. The binary version of the reconstruction module is downloadable at no cost.

Animals↗
PubMed2004

Neuromodulatory octopaminergic neurons and their functions during insect motor behaviour. The Ernst Florey memory lecture.

In this article we describe recent advances in functional studies on the role of octopamine released in the periphery by efferent dorsal or ventral unpaired median neurons. In addition to the previously described modulatory effects on the neuromuscular junction, we describe a metabolic regulatory role for these neurons. Due to their activity glycolytic rates in target tissues, such as muscles, are increased. In flight muscles that use carbohydrate catabolism only at take-off but have to switch to lipid oxidation during prolonged flight, these neurons are only active at rest but are inhibited as soon as flight motor patterns are selected.

Animals↗
PubMed2003

Stage-specific activity patterns affect motoneuron axonal retraction and outgrowth during the metamorphosis of Manduca sexta.

During the metamorphosis of holometabolous insects, most larval muscles and sensory neurons are replaced by new adult elements, whereas most motoneurons persist and are remodelled to serve new adult functions. In Manduca sexta, the formation of the anlagen of the adult dorsal longitudinal flight muscle (DLM) is characterized by retraction of axonal terminals and dendrites of persisting larval motoneurons, partial target muscle degeneration and myoblast accumulation during late larval life. Most of these structural changes have been attributed to hormonal control, not only because ecdysteroids govern metamorphosis, but also because motoneurons express ecdysteroid receptors and experimental manipulations of ecdysteroid titres perturb normal development. To test whether activity-dependent mechanisms also came into play, chronic extracellular recordings were conducted in vivo from the five future DLM motoneurons throughout the last 3 days of larval life. Motoneuron activity is regulated developmentally. The types of motoneurons recruited, the number of motor spikes and the duration of bursts change in a stereotypical fashion during different stages, indicating an internal control of motor activity. A characteristic cessation in the activity of the five future DLM motoneurons coincides in time with the retraction of their dendrites and their terminal arborizations, whereas their activation during ecdysis coincides with the onset of new outgrowth. Inducing advanced activity by stimulating the motoneurons selectively with ecdysis-like patterns results in significant outgrowth of their terminal arborizations. Therefore, steroids might act in concert with activity-dependent mechanisms during the postembryonic modifications of neuromuscular systems.

Animals↗
PubMed2002

Changes in calcium signaling during postembryonic dendritic growth in Manduca sexta.

Activity-dependent Ca(2+) influx plays crucial roles in adult and developing nervous systems through its influence on signal processing, synaptic plasticity, and neuronal differentiation. The responses to internal Ca(2+) elevations vary depending on the spatial distribution of Ca(2+) accumulation in different cell compartments. In this study, the mechanisms and the distribution of Ca(2+) accumulation are addressed by in situ Ca(2+) imaging of an identified insect motoneuron, MN5, at critical stages of postembryonic life. During metamorphosis of Manduca sexta, MN5 undergoes extensive dendritic regression followed by regrowth. The time course, amplitude, and distribution of Ca(2+) accumulation within MN5 change during development. During the initial stage of rapid dendritic growth and branching, dendritic growth cones are present, and voltage-dependent Ca(2+) currents are small. At this stage, activity-induced elevations of internal Ca(2+) are largest in the distal dendrites, suggesting that the density of voltage-gated Ca(2+) channels is highest in these regions. Later phases of dendritic growth are accompanied by the transient occurrence of prominent Ca(2+) spikes. Single Ca(2+) spikes cause robust Ca(2+) influx of similar amplitudes and time courses in all central compartments of MN5. The resting Ca(2+) levels also increase during development. Ca(2+)-induced Ca(2+) release from intracellular stores did not contribute to the elevations measured at either stage, although Ca(2+) stores are present in the dendrites. These developmental changes of the internal Ca(2+) signaling are consistent with a regulatory role for activity-dependent Ca(2+) influx in postembryonic dendritic growth.

Action Potentials↗
PubMed2001

Nerve-muscle interactions regulate motor terminal growth and myoblast distribution during muscle development.

Interactions between motoneurons and muscles influence many aspects of neuromuscular development in all animals. These interactions can be readily investigated during adult muscle development in holometabolous insects. In this study, the development of the dorsolongitudinal flight muscle (DLM) and its innervation is investigated in the moth, Manduca sexta, to address the specificity of neuromuscular interactions. The DLM develops from an anlage containing both regressed larval template fibers and imaginal myoblasts. In the adult, each fiber bundle (DLM1-5) is innervated by a single motoneuron (MN1-MN5), with the dorsal-most fiber bundle (DLM5) innervated by a mesothoracic motoneuron (MN5). The DLM failed to develop following complete denervation because myoblasts failed to accumulate in the DLM anlage. After lesioning MN1-4, MN5 retained its specificity for the DLM5 region of the anlage and failed to rescue DLM1-4. Thus specific innervation of the DLM fiber bundles does not depend on interactions among motoneurons. Myoblast accumulation, but not myonuclear proliferation, increased around the MN5 terminals, producing a hypertrophied adult DLM5. Therefore, motoneurons compete for uncommitted myoblasts. MN5 terminals subsequently grew more rapidly over the hypertrophied DLM5 anlage, indicating that motoneuron terminal expansion is regulated by the size of the target muscle anlage.

Animals↗
PubMed2000

Behavioral transformations during metamorphosis: remodeling of neural and motor systems.

During insect metamorphosis, neural and motor systems are remodeled to accommodate behavioral transformations. Nerve and muscle cells that are required for larval behavior, such as crawling, feeding and ecdysis, must either be replaced or respecified to allow adult emergence, walking, flight, mating and egg-laying. This review describes the types of cellular changes that occur during metamorphosis, as well as recent attempts to understand how they are related to behavioral changes and how they are regulated. Within the periphery, many larval muscles degenerate at the onset of metamorphosis and are replaced by adult muscles, which are derived from myoblasts and, in some cases, remnants of the larval muscle fibers. The terminal processes of many larval motoneurons persist within the periphery and are essential for the formation of adult muscle fibers. Although most adult sensory neurons are born postembryonically, a subset of larval proprioceptive neurons persist to participate in adult behavior. Within the central nervous system, larval neurons that will no longer be necessary die and some adult interneurons are born postembryonically. By contrast, all of the adult motoneurons, as well as some interneurons and modulatory neurons, are persistent larval cells. In accordance with their new behavioral roles, these neurons undergo striking changes in dendritic morphology, intrinsic biophysical properties, and synaptic interactions.

Animals↗
PubMed2000

Remodeling of membrane properties and dendritic architecture accompanies the postembryonic conversion of a slow into a fast motoneuron.

The postembryonic acquisition of behavior requires alterations in neuronal circuitry, which ultimately must be understood as specific changes in neuronal structure, membrane properties, and synaptic connectivity. This study addresses this goal by describing the postembryonic remodeling of the excitability and dendritic morphology of an identified motoneuron, MN5, which during the metamorphosis of Manduca sexta (L.) changes from a slow motoneuron that is involved in larval-crawling behavior into a fast adult flight motoneuron. A fivefold lower input resistance, a higher firing threshold, and an increase in voltage-activated K(+) current contribute to a lower excitability of the adult MN5, which is a prerequisite for its newly acquired behavioral role. In addition, the adult MN5 displays larger Ca(2+) currents. The dendrites of MN5 undergo extensive remodeling. Drastic regression of larval dendrites during early pupal stages is followed by rapid growth of new dendrites. Critical changes in excitability take place during the onset of adult dendrite formation. Larval Ca(2+) currents are absent when dendritic remodeling is most dramatic but increase markedly during later development. Changes in Ca(2+) and K(+) currents follow different time courses, allowing the transient occurrence of Ca(2+) spikes during pupal stages when new dendritic branching ceases. The adult MN5 can produce prolonged Ca(2+) spikes after K(+) currents are reduced. We suggest that alterations in Ca(2+) and K(+) currents are necessary for the participation of MN5 in flight behavior and that the transient production of Ca(2+) spikes may influence postembryonic dendritic remodeling.

Action Potentials↗
PubMed2000

Postembryonic development of the dorsal longitudinal flight muscle and its innervation in Manduca sexta.

The neuromuscular systems of holometabolous insects must be remodeled during metamorphosis to allow striking behavioral changes, such as the acquisition of flight. The fast contracting dorsal longitudinal flight muscle (DLM) of Manduca arises from an anlage containing both remnants of specific larval dorsal body wall muscles and extrinsic myoblasts. In the mesothorax, the DLM is innervated by five persisting larval motoneurons: one in the mesothoracic and four in the prothoracic ganglion. These motoneurons innervate two slowly contracting body wall muscles in the larva. 2 days before pupation, the DLM template fibers begin to degenerate, whereas other muscles remain intact until pupation. Correspondingly, the motor terminals retract from the template fibers while they remain on other muscle fibers until pupation. Accumulation and proliferation of putative myoblasts also starts 2 days before pupation in close spatial relationship to the retracted motor tufts around the degenerating larval template fibers. Proliferation increases through the early pupal stages, and is detected within the anlage until the ninth day after pupation. 2 days after pupation, the anlage splits into five bundles, each innervated by one motoneuron. Striations occur on the seventh day after pupation when the growing motor axons reach the attachment sites. Subsequently, the muscle grows in volume and higher-order motor branches are formed. Within the central nervous system, there is dramatic regression of larval dendrites followed by growth of new dendrites as the persistent motoneurons assume their new role in flight behavior. Both central and peripheral remodeling follow similar time courses.

Animals↗
PubMed2000

The functional role of octopaminergic neurons in insect motor behavior.

The role of efferent, octopaminergic dorsal unpaired median (DUM) neurons in insects is examined by recording from them during motor behaviour. This population of neuromodulatory neurons is divided into sub-populations which are specifically activated or inhibited during ongoing motor behavior. These neurons are always activated in parallel to the respective motor circuits, and in addition to their modulatory effects on synaptic transmission may also cause metabolic changes in their target tissues.

Animals↗
PubMed1999

Distribution and activation of different types of octopaminergic DUM neurons in the locust.

The first part of this study describes the distribution of all different types of octopaminergic, efferent dorsal unpaired median (DUM) neurons in the first two thoracic ganglia by immunocytochemistry, retrograde labeling, and intracellular staining. The prothoracic ganglion contains five different types of 10 DUM neurons. The mesothoracic ganglion has 21 octopaminergic somata in the DUM neuron cluster. Retrograde labeling and intracellular staining show that 19 of these 21 somata belong to five different types of efferent DUM neurons. In both ganglia, the number and the distribution of all types of DUM neurons are completely described. Differences in the distribution of efferent DUM neurons between the thoracic ganglia are discussed as functional segmental specializations. In the second part, we show that, in contrast to previous suggestions, DUM neurons are not recruited as a homogeneous population mediating general arousal but differentially, thus forming subpopulations of specific types. The existence or the absence of commonly occurring postsynaptic potentials in paired recordings clearly shows that only specific types of DUM neurons are targeted by the same presynaptic pathways. Within the thoracic ganglia, different subpopulations of DUM neurons can be distinguished by their different local inputs. Furthermore, only specific subpopulations of DUM neurons receive common intersegmental drive and inputs from the subesophageal ganglion. As a result of all our recordings, we propose a scheme for the differential activation of efferent DUM neurons. This scheme is sufficient to explain DUM neuron activity during principal motor programs.

Animals↗
PubMed1999

Differential activation of octopaminergic (DUM) neurones via proprioceptors responding to flight muscle contractions in the locust

The synaptic potentials generated in neuromodulatory octopaminergic dorsal unpaired median (DUM) neurones by afferents excited by twitch contractions of a dorso-ventral flight muscle were investigated in the locust. Responses to stimulation of the metathoracic wing elevator muscle 113 were obtained in locusts in which all sensory feedback from the thorax had been removed, except for feedback from the thoracic chordotonal organs, the axons of which enter via the purely sensory nerve 2. Afferents in nerve 2C, which originates from two chordotonal organs, responded reliably to twitch contractions of this flight muscle. Octopaminergic neurones innervating leg muscles (DUM5 neurones) received depolarising inputs and often spiked following stimulation of the muscle. In contrast, those innervating the wing muscles themselves (DUM3 and DUM3,4 neurones) received inhibitory inputs. The responses of DUM3,4,5 neurones, which project mainly to leg muscles, were more complex: most were excited by twitch contractions of M113 but some were inhibited. DUMDL, which innervates the dorsal longitudinal indirect flight muscles, showed no clear response. Direct stimulation of nerve 2C evoked depolarising inputs and spikes in DUM5 neurones and hyperpolarising inputs in DUM3 and DUM3,4 neurones. Our data suggest that sensory feedback from thoracic chordotonal organs, which are known to be activated rhythmically during flight, contributes to the differential activation of efferent DUM neurones observed during flight.

Journal Article↗
PubMed1998

Coupling of efferent neuromodulatory neurons to rhythmical leg motor activity in the locust.

The spike activity of neuromodulatory dorsal unpaired median (DUM) neurons was analyzed during a pilocarpine-induced motor pattern in the locust. Paired intracellular recordings were made from these octopaminergic neurons during rhythmic activity in hindleg motor neurons evoked by applying pilocarpine to an isolated metathoracic ganglion. This motor pattern is characterized by two alternating phases: a levator phase, during which levator, flexor, and common inhibitor motor neurons spike, and a depressor phase, during which depressor and extensor motor neurons spike. Three different subpopulations of efferent DUM neurons could be distinguished during this rhythmical motor pattern according to their characteristic spike output. DUM 1 neurons, which in the intact animal do not innervate muscles involved in leg movements, showed no change apart from a general increase in spike frequency. DUM 3 and DUM 3,4 neurons produced the most variable activity but received frequent and sometimes pronounced hyperpolarizations that were often common to both recorded neurons. DUM 5 and DUM 3,4,5 neurons innervate muscles of the hindleg and showed rhythmical excitation leading to bursts of spikes during rhythmic activity of the motor neurons, which innervate these same muscles. Sometimes the motor output was coordinated across both sides of the ganglion so that there was alternating activity between levators of both sides. In these cases, the spikes of DUM 5 and DUM 3,4,5 neurons and the hyperpolarization of DUM 3 and DUM 3,4 neurons occurred at particular phases in the motor pattern. Our data demonstrate a central coupling of specific types of DUM neurons to a rhythmical motor pattern. Changes in the spike output of these particular efferent DUM neurons parallel changes in the motor output. The spike activity of DUM neurons thus may be controlled by the same circuits that determine the action of the motor neurons. Functional implications for real walking are discussed.

Animals↗
PubMed1995

Motor patterns for horizontal and upside down walking and vertical climbing in the locust

The motor patterns of the locust's flexor tibiae and metathoracic subcoxal joint muscles were compared during unrestrained horizontal walking, vertical climbing and walking upside-down hanging from a branch. Combining anatomical and structural data with the results from myographic recordings revealed the role of these muscles during walking and their functional adjustments to different loads and gravity effects caused by changes in walking conditions. Motor patterns are remarkably constant during a given walking situation even at quite different walking speeds. In all walking situations, changes in step duration correlate strongly with changes in the duration of retraction but only weakly with the duration of protraction. Different motor units of one muscle can be distinguished by their spike amplitude. They may be active simultaneously or they may alternate and then fire in different phases of the step cycle. For example, during horizontal walking, the small unit of the first abductor (M125) is active during protraction and the large one during retraction. During retraction, the coxal muscles serve two functions: (1) the joint has to be brought back to the posterior extreme position by retractor muscles; (2) the joint has to be stabilized, that is held 'stiffly', by co-activity of functional antagonists. During protraction, it is moved to the anterior extreme position by powerful contractions of protractor muscles. The muscular activity patterns show marked differences depending on the walking situation. Some large motor units spike only sporadically during horizontal walking but burst during vertical climbing and upside-down walking (muscle M121p, the large units of muscles M126 and M120). During upside-down walking, muscles M120 and M121 and the large unit of muscle M125 are active during opposite phases of the step cycle when compared with horizontal walking and vertical climbing (for example, during walking and climbing, muscle M120 is active at the transition between retraction and protraction, whereas during upside-down walking, activity occurs during late protraction and early retraction). The results describe how motor patterns are adjusted to the different requirements of various walking situations.

Journal Article↗
PubMed1992

Changes in depressive status associated with topical beta-blockers.

Depression and sexual dysfunction have been related to side effects of topical beta-blockers. We performed a preliminary study in order to determine any difference between a non selective beta-blocker (timolol) and a selective beta-blocker (betaxolol) regarding CNS side effects. Eight glaucomatous patients chronically treated with timolol 0.5%/12h, suffering from depression diagnosed through DMS-III-R criteria, were included in the study. During the six-month follow up, depression was quantified through the Beck and Zung-Conde scales every two months. In a double blind cross-over study with control group, the patients under timolol treatment presented higher depression values measured through the Beck and the Zung-Conde scales (p < 0.001 vs control). These results suggest that betaxolol could be less of a depression-inducer than timolol in predisposed patients.

Adult↗