Fate of descending interneurons in the metamorphosing brain of an insect, the beetle Tenebrio molitor L.

The fate of descending brain-thoracic neurons in the metamorphosing supraoesophageal ganglion of the mealworm beetle, Tenebrio molitor, is described. Comparison of the descending neurons of the larval, various pupal, and adult stages outlines a high degree of topological invariance in the structure of descending interneurons; i.e., the basic organization of the imaginal set of descending neurons is anticipated by the structure of the larval neurons. Single descending neurons of analogous clusters of larval and imaginal neurons outline a virtual identical structural organization in both the larval and imaginal brain. There is a quantitative increase from approximately 70 to approximately 120 brain-thoracic interneurons during metamorphosis. This increase does not cause complex transformations in the structural organization of the descending interneurons. Experiments with the DNA-inhibitor hydroxyurea prove that the described topological invariant structure of the set of descending neurons is based on the persistence of individually descending neurons. There is evidence that the whole set of larval interneurons persists throughout the beetles' metamorphosis. The essential characteristics of the later imaginal set of descending neurons are qualitatively and quantitatively established within the first 10% of pupation. Structural invariance of the set of descending neurons is discussed with regard to the significance of cellular interaction for the mechanisms of metamorphic reorganization of nervous tissue.

Reorganization of persistent motoneurons in a metamorphosing insect (Tenebrio molitor L., Coleoptera).

The present analysis outlines how the shape of motoneurons which persist through metamorphosis in the beetle Tenebrio molitor is regulated by cellular interactions. This study focused on the structural changes of prothoracic leg motoneurons. The fate of these neurons is described in normal metamorphic development, so as to provide a basis for experimental analysis. In a first experiment the prothoracic leg imaginal discs or part of these were extirpated in the prepupa or early pupa. In a second experiment the leg imaginal discs were rotated by 180 degrees in early larval instars of Tenebrio; the procedure caused a threefold leg anlage. Thereafter, the treated individuals continued to develop. In both experiments the effect of the operation on the structure of the dendritic trees of the persisting motoneurons was analyzed at the imaginal stage. In the first experiment the dendritic tree of the motoneurons is locally deleted. In the second experiment the branching index (quantitative description of dendritic arborization pattern) of the dendritic tree of the persisting motoneurons increased. Both experiments provided evidence that the shape of persistent leg motoneurons is stabilized and even regulated by cellular interactions during metamorphosis. Evidence is presented that sensory neurons are effective both in stabilization and regulation of the shape of persistent motoneurons.

Structural homology of identified motoneurones in larval and adult stages of hemi- and holometabolous insects.

The set of neurones innervating the dorsal longitudinal muscles was studied with cobalt and nickel backfills in: (1) larval and adult locusts (Schistocerca gregaria and Locusta migratoria), (2) the larval and adult beetle (Zophobas morio), and (3) various segments of these insect species. In all specimens 11 neurones were encountered, which can be subdivided into a group of 7 motoneurones that stem from the next anterior ganglion and 4 neurones located in the ganglion of the segment containing the muscles. The latter group comprises 2 contralateral and 2 medial somata, of which one is a dorsal unpaired median neurone. The results were analysed under different aspects. This neural set and the basic structure of the dendritic fields is similar in: (1) different segments (serial homology), (2) the larval stage and imago of the same species with or without a pronounced metamorphosis (ontogeny), and (3) the studied hemi- and holometabolous insects (phylogeny). Our results support the notion that the structure of these neurones is conserved irrespectively of changes in the periphery and strategy of postembryonic development.

Development of locustatachykinin immunopositive neurons in the central complex of the beetle Tenebrio molitor.

Locustatachykinin-immunoreactive (LomTK-IR) interneurons were found to be associated with the central complex, a prominent neuropil region of the insect brain. The structures and development of this set of brain interneurons was studied from the embryo onward in the beetle Tenebrio molitor, showing individual neurons that persist from the late embryo to the adult stage. Their essential structural characteristics were already present in the late embryo, but distinct parts of their arborization patterns became newly formed throughout development. Using a combination of immunohistochemistry and single-cell injection, we demonstrated minute structural changes, allowing a characterization of structural plasticity of identifiable, persistent, neuropeptidergic neurons throughout ontogenesis. Furthermore, this study has provided new information about basic principles of central brain neuroanatomy and the development of a distinct midbrain region of the insect brain, the central complex. The development of its basic connections, the connections between the fan-shaped body and the protocerebral bridge, and the compartmentation of these neuropil regions were shown, using LomTK-IR neurons as marker structures. These basic features of the central complex-associated LomTK-immunopositive neurons were formed in the embryonic brain, whereas in metamorphosis, reorganization of these persistent interneurons was restricted to the formation of a precisely defined projection of their side branches.

Embryonic and postembryonic development of serial homologous neurons in the subesophageal ganglion of Tenebrio molitor (Insecta: Coleoptera).

Neuroblast pattern, engrailed expression and proliferation in the subesophageal neuromers of the beetle Tenebrio molitor are characterized throughout embryogenesis. The proliferation of neuroblasts has been studied throughout postembyronic development. Serotonin, crustacean cardioactive peptide and tyrosine hydroxylase-like-immunoreactive neurons are characterized and their neuronal development has been studied. There is an initial posterior-anterior gradient in neuroblast segregation leading to a reduced number of neuroblasts in the frontal subesophageal neuromer. The study of the engrailed expression shows that only the anterior subfraction of the neuromeral neuroblast configuration is reduced, whereas the posterior two rows of engrailed-positive neuroblasts are not affected during the first 40% of embryogenesis. The overall number of proliferations in the first subesophageal neuromer reaches only 30-50% of the value found in each of the other two neuromers. The analysis of serotonin and crustacean cardioactive peptide immunoreactivity allows the identification of serial homologous neurons which persist from the early embryo to the adult stage. In the different gnathal neuromers, these neurons form structurally highly similar projection patterns, but show different extensions of their arborizations, corresponding to the relative size of each neuromer. Structural homologies between subesophageal and thoracic neuromers are discussed.

Application of scanning electron microscopy in an analysis of the retina of lower vertebrates.

The scanning electron microscope (SEM) is a useful tool in the study of the retina of lower vertebrates. SEM analysis (preparation over the critical point) offers a useful addition to the existing histological preparations. It is suitable for a comparative analysis, in which the arrangement of different cellular elements and their overall distribution is studied.

Intracellular dye injection of previously immunolabeled insect neurons in fixed brain slices.

Our method combines intracellular dye injection and immunohistochemistry. Under optical control, Lucifer Yellow was injected into immunohistochemically identified neurons that reside in fixed tissue. The technique allows visualization of the complete arborization patterns of immunostained neurons. Injections were performed on small neurons (somata < 10 microns in diameter). The technique works on microslices of insect brain. Standard immunohistochemical procedures have only been varied slightly, omitting Triton X-100 treatment. Anti-Lucifer Yellow immunohistochemistry, or alternatively the photoconversion technique, enables extension of the morphological analysis of these cells to the electron microscopic level. In the present study, Lucifer Yellow injections were performed on immunohistochemically pretreated brain microslices (anti-Locusta tachykinin II antiserum) of the beetle Tenebrio molitor.

Spectral analysis of electroencephalogram during sleep-related apneas in pre-term and term born infants in the first weeks of life.

OBJECTIVES: A correlation between sudden infant death syndrome (SIDS) and apnea has been discussed in a variety of studies. We analyzed polysomnographic data in 51 infants and investigated correlations between the manifestation of apneas and changes in EEG pattern. METHODS: Measurements were performed by means of the commercial polysomnographic device 'ALICE III'. Spectral analysis of certain parts of the registered EEG was performed. RESULTS: During apnea a reduction of the EEG amplitude was seen. The extent of the decrease differed slightly between the frequency bands. CONCLUSIONS: According to the widespread agreement that a lower voltage of electrical brain activity is a fundamental sign of waking up, we hypothesize that the observed change might be an immature type of arousal reaction.

Clinical relevance of age-dependent EEG signatures in the detection of neonates at high risk for apnea.

Age dependent EEG signatures were detected in the EEG of 71 neonates of 28-100 weeks of conceptional age (CA). Using the new method presented, neonates were automatically classified in three age groups (28-35 weeks CA), (36-40 weeks CA) and (41-100 weeks CA). Analysis was performed employing relative distance functions for the complete frequency spectra of the EEG registered by electrodes in C3 and C4 positions. The analysis was successful in automatic identification of individuals showing EEG anomalies. Polysomnographic analysis demonstrated these to be apnea risk patients. Accordingly, a purely EEG based detection of neonates that are medically at risk becomes feasible.

Evidence for the expression of a glucuronic acid-containing epitope in the central nervous system of two insects (Calliphora vicina, Diptera; Tenebrio molitor, Coleoptera).

The monoclonal antibody CAF-I recognises a glucuronic acid-containing epitope present on various acidic glycosphingolipids of Calliphora vicina. Immunohistochemistry was performed on CAF-I-labelled whole-mount preparations of the central nervous system, visualised by peroxidase-conjugated second antibody. A differential, temporal and spatial expression of this epitope in metamorphosing nervous tissue was outlined, that apparently characterises homologous neuronal populations in two phylogenetically distinct holometabolous insects, i.e. Calliphora vicina and Tenebrio molitor. Implications for a functional interpretation of insect glyco(sphingo)lipids in tissue development are discussed.

Insect glial cells show differential expression of a glycolipid-derived, glucuronic acid-containing epitope throughout neurogenesis: detection during postembryogenesis and regeneration in the central nervous system of Tenebrio molitor L.

The monoclonal antibody CAF-1 recognises a glucuronic acid-containing epitope present on insect acidic glycolipids. Immunohistochemical analysis of the CAF-1 epitope has revealed its differential, temporal and spatial expression during postembryogenesis of the midbrain of Tenebrio molitor. Electron microscopic resolution demonstrated, that the CAF-1 epitope is expressed on glial cells that ensheath the glomeruli of the central body. Concomitantly, a differential pattern of expression was observed in the ventral nerve cord, exhibiting a serially homologous display on glial cells that ensheath neuronal somata in the cell body layer of the thoracic ganglia and ventral associative neuropil. Prominent, topologically restricted CAF-1 immunoreactivity was monitored in termination areas of sensory neurons in the ventral associative neuropil and corresponding nerves 6-48 h after extirpation of the respective sensory neuron somata. CAF-1 expression is correlated with structural reorganisation in postembryonic nervous tissue of T. molitor.

Brain dysmaturity index for automatic detection of high-risk infants.

The definition of an electroencephalographic (EEG)-based brain dysmaturity index that could allow automatic detection of neonates who deviate from expected ontogenetic patterns is proposed. The investigation was performed in a group of 94 term and preterm infants (28-112 weeks postconceptional age). For each neonate, one continuous two-channel EEG of 1-6 hours was recorded. The cluster analysis of different age groups was performed with a self-referential neural network. The network performed a nonlinear discriminant analysis; the synaptic strength of input nodes indicates the relevance of an individual EEG feature. The most relevant EEG features are given by the average amplitude in the delta and theta bands and by the relative amplitudes of beta-1/theta and beta-1/delta, respectively. The correlation between the frequency shifts and the postconceptional age agreed with measures of brain dysmaturity in healthy preterm neonates. Thus the presented trend in early EEG development demonstrates that it is possible to establish clinically relevant age dysmaturity scores.

Studies on the stridulation of Hylotrupes Bajulus (L.) (Cerambycidae, Coleoptera): Communication through support vibration - Morphology and mechanics of the signal.

The stridulation of Hylotrupes bajulus (L.) is examined with respect to ethology and functional morphology. The morphology outlines a defined species-specific structure. Biophysical aspects of sound emission are discussed. The sound pattern of stridulation is described. Its time structure is species-specific. Only the vibrational component of stridulation is an effective signal in the intraspecific communication of H. bajulus . It is a part of aggressive behaviour, where it constitutes menacing or impressing elememts. It is also found within the mating behaviour, where it forms a part of the tactile stimulation of the female by the male beetle. The 'open' organisation of the behaviour analysed is of interest. This open arrangement of the behaviour is somewhat surprising in view of the complex differentiation of the morphology. The specifity of the ethological structure is discussed.

Understanding the functional architecture of cortical tissue in the XIXth century.

This paper outlines the historical development of the idea that the cerebral cortex is responsible for the integration of sensory information and the co-ordination of complex movement patterns. The concept of a functional compartmentalisation of the cortex was developed in the 19th century, based on electrophysiological experiments. In spite of conceptual frameworks like those of Meynert and Wernicke, neuroanatomy did not contribute significantly to the conceptual development of neurobiology during the end of the 19th century. For electrophysiologists, an analysis of neuronal connections in the cortex was of minor interest. Data about the fine texture of the brain did not significantly influence the development of early 20th century neurobiology.

Constant topological organization of the coleopteran metamorphosing nervous system: analysis of persistent elements in the nervous system of Tenebrio molitor.

Evidence is provided that the topological organization of the larval neuropil is preserved during metamorphosis of Tenebrio molitor. Constancies in neuronal organization were due in part to persistence of individual neurons whose morphologies were individually followed. It appears that the phenomenologically static situation of the metamorphosing neuropil is achieved by stabilization and regulation due to cellular interactions. Comparisons are made with features of hemimetabolan postembryogenesis.

A rapid methylene blue staining procedure for the ventral nerve cord of holometabolous insects.

The author describes a modification of the methylene blue technique that stains neurons dark blue against a clear background. The resolution of the dendritic tree attains Golgi-like quality. The procedure offers a rapid, easily adaptable alternative to the reduced silver procedures in holometabolous insects.

[Jena philosophies of nature around 1800]. / Jenaer Naturphilosophien um 1800.

This paper describes the situation and the outline of positions in philosophy of nature in Jena about 1800, in focusing on research other than the key figures Schelling and Hegel. In 1789, Schelling introduced philosophy of nature into the course program of Jena University. Already in 1800, two young scientists--a mathematician (Fischer) and a physiologist--reacted, announcing lectures on Schellingian topics. But only in late 1802, younger philosophers offered courses on those topics. From 1802 onwards, lectures were announced by Schad, Krause, Henrici, Hegel, Oken and the botanist Schelver. Apart from the Fisher lecture from 1800, the program of these presentations was based on Schellingian principles. Analyses of the ideas of Schad, Krause and Schelver show that, about 1800, philosophy of nature in Jena conserved basic ideas of the early philosophy of nature of Schelling. Thus, philosophy of nature in this period of Jena University seemed to follow just one line of reasoning.

The controversy on stain technologies--an experimental reexamination of the dispute on the cellular nature of the nervous system around 1900.

The controversy of neuroanatomy on the principal structure of the nervous systems, which took place at the end of the nineteenth century, is described. Two groups of scientists are identified: one that favoured the idea of a discrete cellular organization of the nervous tissue, and one that favoured a syncytial organization. These two interpretations arose from different histological techniques that produced conflicting pictures of the organization of the nervous tissue. In an experimental reexamination of the techniques used at the end of the nineteenth century, the present study concerns the impact of these different histological procedures on the controversy about the principle nature of the nervous tissue. This controversy could not be resolved by neuroanatomy itself until the 1950s when electron microscopy was introduced into neurobiology. Thus, in a critical period of the conceptual development of neurosciences, neuroanatomy failed to establish a proper base for an interpretation of the functional morphology of nervous tissues.

Analytical description of the evolution of neural networks: learning rules and complexity.

We present the foundation of a physical formalism that allows us to characterize the dynamics of the evolution of neural networks both in regard to the network configuration and to network performance. Model runs were performed on a simple network consisting of six neurons, allowing complete analytical description of the network's behaviour. Order parameters are characterized that allow an analytical description of critical periods in network evolution. Thus, correlations of the local dynamics and the system's global behaviour could be computed. It is shown that local learning rules are sufficient to model complex dynamical aspects of the evolution of networks. It is demonstrated in how far novel statistical formalisms, e.g. neural complexity, can be employed to evaluate the system's dynamics. The introduction of order parameters allows an analytical characterization of transient phases in the network's behaviour, correlating network connectivity with neuronal firing patterns. The relevance of this approach for the interpretation of physiological data is discussed.

Common general morphological pattern of peptidergic neurons in the arachnid brain: crustacean cardioactive peptide-immunoreactive neurons in the protocerebrum of seven arachnid species.

A polyclonal antiserum raised against crustacean cardioactive peptide labels 14 clusters of immunoreactive neurons in the protocerebrum of the spiders Tegenaria atrica and Nephila clavipes, and the harvestman (opilionid) Rilaena triangularis. In all species, these clusters possess the same number of neurons, and share similar structural and topological characteristics. Two sets of bilateral symmetrical neurons associated with the optic lobes and the arachnid "central body" were analysed in detail, comparing the harvestman R. triangularis and the spiders Brachypelma albopilosa (Theraphosidae), Cupiennius salei (Lycosidae), Tegenaria atrica (Agelenidae), Meta segmentata (Metidae) and Nephila clavipes (Araneidae). Sixteen neurons have been identified that display markedly similar axonal pathways and arborization patterns in all species. These neurons are considered homologues in the opilionid and the araneid brains. We presume that these putative phylogenetically persisting neurons represent part of the general morphological pattern of the arachnid brain.