Search PubMed⌕ Search

Biomedical subjects

U Homberg

Publications and source records attributed to U Homberg.

At least 37 records · Page 2Linked to original sources
PubMed1994

Pigment-dispersing hormone-immunoreactive neurons in the cockroach Leucophaea maderae share properties with circadian pacemaker neurons.

Neurons immunoreactive with antisera against the crustacean peptide beta-pigment dispersing hormone fulfill several anatomical criteria proposed for circadian pacemakers in the brain of the cockroach Leucophaea maderae. These include position of somata, projections to the lamina and midbrain and possible coupling pathways between the two pacemakers through commissural fibers. In behavioral experiments combined with lesion studies and immunocytochemical investigations we examined whether the presence of pigment-dispersing hormone-immunoreactive arborizations in the midbrain of the cockroach correlates with the presence of circadian locomotor activity. No rhythm was detected after severing both optic stalks in any animal for at least 12 days. Within the same time pigment-dispersing hormone-immunoreactive fibers in the midbrain disappeared. Two to seven weeks after the operation some of the cockroaches regained circadian locomotor activity, while others remained arrhythmic. In all cockroaches which regained rhythmic behavior pigment-dispersing hormone-immunoreactive fibers had regenerated and had largely found their original targets within the brain. In all arrhythmic cockroaches either none or very little regeneration had occurred. The period of the regained circadian activity inversely correlated with the number of regenerated immunoreactive commissural fibers. These data provide further evidence for the involvement of pigment-dispersing hormone-immunoreactive neurons in circadian clocks of orthopteroid insects.

Animals↗
PubMed1993

Crustacean cardioactive peptide-immunoreactive neurons in the hawkmoth Manduca sexta and changes in their immunoreactivity during postembryonic development.

An antiserum against crustacean cardioactive peptide was used, in indirect immunocytochemistry on whole-mounts and Vibratome sections, to map immunoreactive neurons at various stages of postembryonic development of the hawkmoth Manduca sexta. About 90 immunoreactive neurons were identified. Many of these cells are immunoreactive at hatching and persist into the adult stage; others become immunoreactive late in postembryonic development. During adult development, transient immunoreactivity is expressed in several cells in the subesophageal and thoracic ganglia. Two sets of immunoreactive neurons are found in the protocerebrum of larvae, but only one of these sets persists into the adult stage. Paired lateral interneurons and neurosecretory neurons are segmentally repeated in the abdominal ganglia and are present from the first larval stage to the adult; the abdominal interneurons project contralaterally to arborizations in adjacent ganglia, and some ascend to tritocerebral arborizations. The abdominal neurosecretory cells, which correspond to a pair of cells reported to contain bursicon, project posteriorly to neurohemal release organs. Motor neurons of dorsal external oblique abdominal muscles become immunoreactive in the fourth larval stage. Paired median neurosecretory cells of abdominal ganglia become immunoreactive during the fifth larval stage. The immunoreactive median and lateral abdominal neurosecretory cells are a subset of a group of cells known to contain cardioactive peptides. Paired lateral neurosecretory cells of the subesophageal ganglion become immunoreactive during pupation and project to the corpora cardiaca and aorta of the adult. Many of the neurons identified here are comparable to crustacean cardioactive peptide-immunoreactive cells described previously in locusts and the mealworm beetle.

Animals↗
PubMed1993

Pigment-dispersing hormone-immunoreactive neurons in the nervous system of wild-type Drosophila melanogaster and of several mutants with altered circadian rhythmicity.

Antisera against the crustacean pigment-dispersing hormone (beta-PDH) were used in immunocytochemical preparations to investigate the anatomy of PDH-immunoreactive neurons in the nervous system of wild-type Drosophila melanogaster and in that of several brain mutants of this species, some of which express altered circadian rhythmicity. In the wild-type and in all rhythmic mutants (small optic lobes, sine oculis, small optic lobes; sine oculis), eight cell bodies at the anterior base of the medulla (PDFMe neurons) exhibit intense PDH-like immunoreactivity. Four of the eight somata are large and four are smaller. The four large PDFMe neurons have wide tangential arborizations in the medulla and send axons via the posterior optic tract to the contralateral medulla. Fibers from the four small PDFMe neurons ramify in the median protocerebrum dorsal to the calyces of the mushroom bodies. Their terminals are adjacent to other PDH-immunoreactive somata (PDFCa neurons) which send axons via the median bundle into the tritocerebrum. The results suggest a possible involvement of the PDFMe neurons in the circadian pacemaking system of Drosophila. The location and size of the PDFMe neurons are identical with those of neurons containing the period protein which is essential for circadian rhythmicity. Changes in the arborizations of the PDFMe neurons in small optic lobes; sine oculis mutants are suited to explain the splitting in the locomotor rhythm of these flies. In the arrhythmic mutant, disconnected, the PDFMe neurons are absent. The arrhythmic mutant per0, however, shows normal PDH immunoreactivity and therefore, does not prevent the expression of PDH-like peptides in these neurons.

Animals↗
PubMed1993

A simple method for immunofluorescent double staining with primary antisera from the same species.

We have developed a new double immunofluorescence technique by which two neuroactive substances in the same tissue section can be labeled with primary antisera raised in the same species. The optic lobes of the locust Schistocerca gregaria were used as a model system to develop the staining procedure. FMRFamide-immunoreactive neurons were detected by rabbit antisera against FMRFamide and FITC-conjugated secondary antibodies. Antibodies against the second peptide, pigment-dispersing hormone (PDH), also raised in rabbit, were biotinylated and detected via streptavidin-Texas Red. Crossreactivity of the PDH immunoglobulins with the FITC-conjugated secondary antiserum was prevented by pre-incubation with rabbit gamma globulins. The two peptide immunoreactivities could be conveniently observed on the same section with the different fluorescent markers. This double labeling technique with modified antibodies is easily performed and highly useful for co-localization studies with antisera raised in the same species.

Animals↗
PubMed1992

Immunocytochemistry of dopamine in the brain of the locust Schistocerca gregaria.

Catecholamine-induced histofluorescence studies have suggested a rich innervation of the locust brain by dopamine-containing neurons. To provide a basis for future studies on dopamine action in this insect, the location and morphology of neurons reacting with antisera against dopamine were investigated in the supraoesophageal ganglion of the locust, Schistocerca gregaria. In each brain hemisphere, about 100 interneurons in the midbrain and approximately 3,000 cells in the optic lobe show dopamine-like immunoreactivity. All major areas of the brain except the calyces of the mushroom body, the antennal lobe, large parts of the lobula, and some areas in the inferior lateral protocerebrum contain immunoreactive neuronal processes. The arborization patterns of most dopamine-immunoreactive cell types could be identified through detailed reconstructions. The central body exhibits the most intense immunostaining. It is innervated by at least 40 pairs of dopamine-immunoreactive neurons belonging to three different cell types. Additional arborizations of these neurons are in the superior protocerebrum and in the lateral accessory lobes. A group of 4 immunoreactive neurons with ramifications in the antennal mechanosensory and motor center gives rise to a dense meshwork of varicose fibers in the pedunculus and parts of the alpha- and beta-lobes of the mushroom body. Other cell types innervate the ventrolateral protocerebrum, the inferior protocerebrum and the posterior optic tubercles. Three descending neurons originating in the tritocerebrum exhibit dopamine-like immunoreactivity. In the optic lobe, about 3,000 columnar intrinsic neurons of the medulla and a group of centrifugal tangential cells with arborizations in the medulla and lamina are dopamine-immunoreactive.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

The roles of local interneurons in the processing of olfactory information in the antennal lobes of the moth Manduca sexta.

The antennal lobe (AL) of the sphinx month Manduca sexta is characterized by a typically glomerular neuropil and two principal classes to neurons local interneurons and projection neurons. The somata of these neurons reside in defined neural cell-body groups in the AL, and the neurons exhibit characteristic patterns of innervation of the glomeruli. Evidence gathered to date indicates that individual antennal olfactory receptor-cell axons project to single glomeruli in the ipsilateral AL and make excitatory, apparently cholinergic synapses with neurites of AL neurons (usually local neurons) innervating the target glomeruli. Much has been learned about the physiology of the projection neurons, but only recently have the physiological properties and functions of the local interneurons been examined systematically through the use of intracellular recording and staining methods. Immunocytochemical studies have shown that most of the local interneurons contain GABA as well as one or more putative neuropeptides. Physiological, pharmacological, and biochemical experiments support the view that GABAergic local interneurons are responsible for inhibitory synaptic inputs to projection neurons that predominate in shaping the activity of projection neurons conveying synaptically processed olfactory information to higher-order centers in the protocerebrum.

Animals↗
PubMed1991

Histamine-immunoreactive neurons in the midbrain and suboesophageal ganglion of sphinx moth Manduca sexta.

This paper describes the distribution of histamine-like immunoreactivity in the midbrain and suboesophageal ganglion of the sphinx moth Manduca sexta. Intense immunocytochemical staining was detected in ten bilateral pairs of neurons in the median protocerebrum and in one pair of neurons in the suboesophageal ganglion. Whereas most areas of the brain and suboesophageal ganglion are innervated by one or more of these neurons, typically no immunoreactive fibers were found in the mushroom bodies, the protocerebral bridge, and the lateral horn of the protocerebrum. The 11 histamine-immunoreactive neurons were reconstructed from serial sections. Ten neurons have bilateral arborizations, often with axonal projections in symmetric areas of both hemispheres. One neuron, whose soma resides in the lateral protocerebrum, has only unilateral projections. Of the 11 neurons, 6 occur in pairs with similar morphological features. In addition to these neurons, weak histamine-like immunoreactivity was detected in 7-13 interneurons that were not reconstructed individually. The central projections of the ocellar nerves from the intracranial ocelli also exhibit histamine-like immunoreactivity. The single-cell reconstructions reveal similarities between the organization of histamine- and serotonin-immunoreactive neurons in the brain and suboesophageal ganglion of this insect.

Animals↗
PubMed1991

Neuroarchitecture of the central complex in the brain of the locust Schistocerca gregaria and S. americana as revealed by serotonin immunocytochemistry.

The central complex is a prominent structure in the insect brain, yet its anatomical organization and functional role is still poorly understood. To facilitate investigations on the physiology of the central complex, this study describes its anatomical organization in the brain of locusts (Schistocerca gregaria and Schistocerca americana) based on an investigation of serotonin immunocytochemistry. Most subdivisions of the central complex including the protocerebral bridge, several layers in the upper division of the central body, and the noduli of the central body are innervated by serotonin-immunoreactive neurons, while the lower division of the central body does not exhibit serotonin-like immunoreactivity. Several types of serotonin-immunoreactive neurons can be distinguished. A system of about 60 columnar neurons innervates the protocerebral bridge, layer III of the upper division of the central body, and the noduli. A group of 15-20 bilateral pairs of serotonin-immunoreactive neurons connects the posterior optic tubercles with the protocerebral bridge. About ten pairs of neurons with somata in the inferior protocerebrum innervate layer Ia of the upper division of the central body. In addition, large-field neurons arborize in layers Ia and Ib of the upper division of the central body and in the lateral accessory lobes. The detailed mapping of serotonin immunoreactivity provides further insight into the anatomical organization of the central complex and suggests that serotonin is a major neuroactive substance within this brain structure.

Africa↗
PubMed1991

Peptide-immunocytochemistry of neurosecretory cells in the brain and retrocerebral complex of the sphinx moth Manduca sexta.

Antisera against a variety of vertebrate and invertebrate neuropeptides were used to map cerebral neurosecretory cells in the sphinx moth Manduca sexta. Intense immunoreactive staining of distinct populations of neurosecretory cells was obtained with antisera against locust adipokinetic hormone, bovine pancreatic polypeptide, FMRFamide, molluscan small cardioactive peptide (SCPB), leucine-enkephalin, gastrin/cholecystokinin, and crustacean beta-pigment dispersing hormone (beta PDH). Other antisera revealed moderate to weak staining. Each type of neurosecretory cell is immunoreactive with at least one of the antisera tested, and most of these neurons can be identified anatomically. The staining patterns provide additional information on the organization of cerebral neurosecretory cells in M. sexta. Based upon anatomical and immunocytochemical characteristics, 11 types of neurosecretory cells have been recognized in the brain, one type in the suboesophageal ganglion, and one in the corpus cardiacum. Extensive colocalization experiments show that many neurosecretory cells are immunoreactive with several different antisera. This raises the possibility that these cells may release mixtures of neuropeptides into the hemolymph, as has been demonstrated in certain other systems. The immunocytochemical data should be helpful in efforts to identify additional peptide neurohormones released from the brain of this and other insects.

Animals↗
PubMed1990

Acetylcholinesterase activity in antennal receptor neurons of the sphinx moth Manduca sexta.

We have used a cytochemical technique to investigate the distribution of acetylcholinesterase (AChE) activity in the antenna of the sphinx moth Manduca sexta. High levels of echothiophate-insensitive (presumably intracellular) AChE activity were found in six different types of antennal receptors localized in specific regions of the three antennal segments of the adult moth. Mechanosensory organs in the scape and pedicel, the Böhm bristles and Johnston's organ, are innervated by AChE-positive neurons. In each annulus of the antennal flagellum, AChE-positive neurons are associated with six sensilla chaetica and a peg organ, probably a sensillum styloconicum. At least 112 receptor neurons (8-10 per annulus) innervating the intersegmental membranes between the 14 distalmost annuli also exhibit high levels of echothiophate-resistant AChE. In addition, each annulus has more than 30 AChE-positive somata in the epidermis of the scale-covered (back) side of the flagellum, and 4 AChE-positive somata reside within the first annulus of the flagellum. Since none of the olfactory receptor neurons show a high level of echothiophate-resistant AChE activity, and all known mechanoreceptors are AChE-positive, apparently "intracellular" AChE activity in the antenna correlates well with mechanosensory functions and is consistent with the idea that these cells employ acetylcholine as a neurotransmitter.

Acetylcholinesterase↗
PubMed1990

Distribution of FMRFamide-like immunoreactivity in the brain and suboesophageal ganglion of the sphinx moth Manduca sexta and colocalization with SCPB-, BPP-, and GABA-like immunoreactivity.

Using an antiserum against the tetrapeptide FMRFamide, we have studied the distribution of FMRFamide-like substances in the brain and suboesophageal ganglion of the sphinx moth Manduca sexta. More than 2000 neurons per hemisphere exhibit FMRFamide-like immunoreactivity. Most of these cells reside within the optic lobe. Particular types of FMRFamide-immunoreactive neurons can be identified. Among these are neurosecretory cells, putatively centrifugal neurons of the optic lobe, local interneurons of the antennal lobe, mushroom-body Kenyon cells, and small-field neurons of the central complex. In the suboesophageal ganglion, groups of ventral midline neurons exhibit FMRFamide-like immunoreactivity. Some of these cells have axons in the maxillary nerves and apparently give rise to FMRFamide-immunoreactive terminals in the sheath of the suboesophageal ganglion and the maxillary nerves. In local interneurons of the antennal lobe and a particular group of protocerebral neurons, FMRFamide-like immunoreactivity is colocalized with GABA-like immunoreactivity. This suggests that FMRFamide-like peptides may be cotransmitters of these putatively GABAergic interneurons. All FMRFamide-immunoreactive neurons are, furthermore, immunoreactive with an antiserum against bovine pancreatic polypeptide, and the vast majority is also immunoreactive with an antibody against the molluscan small cardioactive peptide SCPB. Therefore, it is possible that more than one peptide is localized within many FMRFamide-immunoreactive neurons. The results suggest that FMRFamide-related peptides are widespread within the nervous system of M. sexta and might function as neurohormones and neurotransmitters in a variety of neuronal cell types.

Animals↗
PubMed1989

Serotonin immunoreactivity in the optic lobes of the sphinx moth Manduca sexta and colocalization with FMRFamide and SCPB immunoreactivity.

In the optic lobes (OLs) of the sphinx moth Manduca sexta, 300-350 neurons per hemisphere are immunoreactive with an antiserotonin antiserum. Two groups of weakly serotonin-immunoreactive cells (OL1) appear to be amacrine cells of the medulla, whereas more intensely immunoreactive cells (OL2) are probably centrifugal neurons that innervate the lobula, medulla, and lamina, as well as the superior protocerebrum. At least one other OL2 cell is a local optic-lobe interneuron with arborizations in the dorsal medulla and lobula. The serotonin-immunoreactive cells are also immunoreactive with an antiserum against Drosophila melanogaster DOPA decarboxylase. All OL2 cells, but not the OL1 cells, are furthermore immunoreactive with an anti-FMRFamide antiserum and an anti-SCPB antiserum. This suggests that neuropeptides related or identical to FMRFamide and SCPB are localized and may serve as cotransmitters with serotonin in OL2 optic-lobe interneurons.

Animals↗
PubMed1989

Serotonin-immunoreactive neurons in the median protocerebrum and suboesophageal ganglion of the sphinx moth Manduca sexta.

Serotonin-immunoreactive neurons in the median protocerebrum and suboesophageal ganglion of the sphinx moth Manduca sexta were individually reconstructed. Serotonin immunoreactivity was detected in 19-20 bilaterally symmetrical pairs of interneurons in the midbrain and 10 pairs in the suboesophageal ganglion. These neurons were also immunoreactive with antisera against DOPA decarboxylase. All major neuropil regions except the protocerebral bridge are innervated by these neurons. In addition, efferent cells are serotonin-immunoreactive in the frontal ganglion (5 neurons) and the suboesophageal ganglion (2 pairs of neurons). The latter cells probably give rise to an extensive network of immunoreactive terminals on the surface of the suboesophageal ganglion and suboesophageal nerves. Most of the serotonin-immunoreactive neurons show a gradient in the intensity of immunoreactive staining, suggesting low levels of serotonin in cell bodies and dendritic arbors and highest concentrations in axonal terminals. Serotonin-immunoreactive cells often occur in pairs with similar morphological features. With one exception, all serotonin-immunoreactive neurons have bilateral projections with at least some arborizations in identical neuropil areas in both hemispheres. The morphology of several neurons suggests that they are part of neuronal feedback circuits. The similarity in the arborization patterns of serotonin-immunoreactive neurons raises the possibility that their outgrowing neurites experienced similar forces during embryonic development. The morphological similarities further suggest that serotonin-immunoreactive interneurons in the midbrain and suboesophageal ganglion share physiological characteristics.

Animals↗
PubMed1989

Serotonin-immunoreactive neurons in the brain of Manduca sexta during larval development and larval-pupal metamorphosis.

The developing serotonergic system of the tobacco hornworm, Manduca sexta, has been studied immunocytochemically in whole mount preparations of brain-retrocerebral complexes. The distribution of serotonin-immunoreactive cell bodies, fibers and terminal fields has been analysed during larval and larval-pupal development using a specific rabbit antiserum against serotonin-hemocyanin conjugates. The serotonergic system was conserved from the fourth to the fifth larval stadium, with minimal changes occurring until the onset of pupal development. At this time, alterations in the distribution of serotonin-immunoreactive cells and processes were observed, including the apparent disappearance of some cell bodies and terminals. Nevertheless, the overall appearance of this system in the pupal brain was not significantly different from that in the larva. The larval pattern was characterized by eight bilateral groups of cell bodies which sent thick bridges of fibers across the midline, a feature strikingly similar to the serotonergic system in vertebrate embryos. In addition, three bilateral immunoreactive fields of arborization were observed around and ventral to these cell groups, together with regions of serotonin immunoreactivity in the medial and lateral protocerebral lobes. The central body, larval antennal centers, larval accessory lobes, and the tritocerebrum were also immunoreactive. Fibrous networks of serotonergic processes were usually observed around nerves emanating from the brain, including the connectives from the brain to the corpus cardiacum and corpus allatum. Smaller varicosities were observed in the interior of these neurohemal and glandular organs, and a network of 5-HT fibers was occasionally found around the corpus cardiacum and corpus allatum. The possible relationship of serotonin to cerebral neuroendocrine functions during the postembryonic development of M. sexta is discussed.

Animals↗
PubMed1988

Anatomy of antenno-cerebral pathways in the brain of the sphinx moth Manduca sexta.

In the moth Manduca sexta, the number and morphology of neuronal connections between the antennal lobes and the protocerebrum were examined. Cobalt injections revealed eight morphological types of neurons with somata adjacent to the AL neuropil that project in the inner, middle, and outer antenno-cerebral tracts to the proto-cerebrum. Neurons innervating the macroglomerular complex and many neurons with fibers in the inner antenno-cerebral tract have uniglomerular antennal-lobe arborizations. Most neurons in the middle and outer antenno-cerebral tracts, on the other hand, seem to innervate more than one glomerulus. Protocerebral areas receiving direct input from the antennal lobe include the calyces of the mushroom bodies, and circumscribed areas termed "olfactory foci" in the lateral horn of the protocerebrum and several other regions, especially areas in close proximity to the mushroom bodies. Fibers in the inner antenno-cerebral tract that innervate the male-specific macroglomerular complex have arborizations in the protocerebrum that are distinct from the projections of sexually non-specific neurons. Protocerebral neurons projecting into the antennal lobe are much less numerous than antennal-lobe output cells. Most of these protocerebral fibers enter the antennal lobe in small fiber tracts that are different from those described above. In the protocerebrum, these centrifugal cells arborize in olfactory foci and also in the inferior median protocerebrum and the lateral accessory lobes. The morphological diversity of connections between the antennal lobes and the protocerebrum, described here for the first time on a single-cell level, suggests a much greater physiological complexity of the olfactory system than has been assumed so far.

Animals↗
PubMed1987

Immunocytochemistry of GABA in the brain and suboesophageal ganglion of Manduca sexta.

We have used specific antisera against protein-conjugated gamma-aminobutyric acid (GABA) in immunocytochemical preparations to investigate the distribution of putatively GABAergic neurons in the brain and suboesophageal ganglion of the sphinx moth Manduca sexta. About 20,000 neurons per brain hemisphere exhibit GABA-immunoreactivity. Most of these are optic-lobe interneurons, especially morphologically centrifugal neurons of the lamina and tangential neurons that innervate the medulla or the lobula complex. Many GABA-immunoreactive neurons, among them giant fibers of the lobula plate, project into the median protocerebrum. Among prominent GABA-immunoreactive neurons of the median protocerebrum are about 150 putatively negative-feedback fibers of the mushroom body, innervating both the calyces and lobes, and a group of large, fan-shaped neurons of the lower division of the central body. Several commissures in the supra- and suboesophageal ganglion exhibit GABA-like immunoreactivity. In the suboesophageal ganglion, a group of contralaterally descending neurons shows GABA-like immunoreactivity. The frontal ganglion is innervated by immunoreactive processes from the tritocerebrum but does not contain GABA-immunoreactive somata. With few exceptions the brain nerves do not contain GABA-immunoreactive fibers.

Animals↗
PubMed1986

Immunocytochemistry of GABA in the antennal lobes of the sphinx moth Manduca sexta.

We have prepared and characterized specific rabbit antisera against gamma-aminobutyric acid (GABA) coupled covalently to bovine serum albumin and keyhole-limpet hemocyanin. Using these antisera in immunocytochemical staining procedures, we have probed the antennal lobes and their afferent and efferent fiber tracts in the sphinx moth Manduca sexta for GABA-like immunoreactivity in order to map putatively GABAergic central neurons in the central antennal-sensory pathway. About 30% of the neuronal somata in the large lateral group of cell bodies in the antennal lobe are GABA-immunoreactive; cells in the medial and anterior groups of antennal-lobe cells did not exhibit GABA-like immunoreactivity. GABA-immunoreactive neurites had arborizations in all of the glomeruli in the antennal lobe. Double-labeling experiments involving tandem intracellular staining with Lucifer Yellow and immunocytochemical staining for GABA-like immunoreactivity demonstrated that at least some of the GABA-immunoreactive cells in the antennal lobe are amacrine local interneurons. Several fiber tracts that carry axons of antennal-lobe projection neurons exhibited GABA-immunoreactive fibers. Among the possibly GABA-containing projection neurons are several cells, with somata in the lateral group of the antennal lobe, that send their axons directly to the lateral protocerebrum.

Animals↗