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Y N Jan

Publications and source records attributed to Y N Jan.

At least 217 records · Page 12Linked to original sources
PubMed1987

Identification and purification of an irreversible presynaptic neurotoxin from the venom of the spider Hololena curta.

A search for potent toxins that inhibit neuronal calcium channels in Drosophila melanogaster has resulted in the identification of a presynaptic neurotoxin from the venom of the hunting spider Hololena curta. Using Drosophila neuromuscular junction as an assay, presynaptic inhibitory activity was purified using gel filtration and reverse-phase HPLC. Data from gel electrophoresis indicate that the toxin is composed of two different subunits of Mr 7000 and 9000. At nanomolar concentrations the toxin produced a complete and long-lasting inhibition of synaptic transmission at the Drosophila larval neuromuscular junction without affecting the amplitudes of the spontaneously occurring miniature junction potentials. The block of transmission produced by the toxin was observed even during the direct depolarization of the motor nerve terminal. These physiological results indicate that the terminal is the site of action for the toxin. Indirect evidence using abnormally excitable Drosophila mutants suggests that the toxin is inhibiting transmitter release by altering the electrical properties of the nerve terminal rather than by interfering with nonelectrical events that may occur subsequent to calcium influx. All of the actions of the Hololena toxin can be explained by a specific and direct effect on presynaptic calcium channels in Drosophila motor neurons.

Animals↗
PubMed1987

Neurotoxins from Plectreurys spider venom are potent presynaptic blockers in Drosophila.

Studies of presynaptic events in synaptic transmission may be facilitated through the use of specific ligands for functional components of the transmitter release mechanism and through the use of genetics. For this purpose, neurotoxins that affect neuromuscular transmission in Drosophila have been identified and purified from Plectreurys spider venom (PLTX). One class of toxins causes irreversible presynaptic block, probably by blocking calcium entry or by acting on other closely associated processes. These toxins have been highly purified and are peptides of about 7 kDa in molecular weight. They specifically block transmitter release at nanomolar concentrations and may be useful in further biochemical studies.

Animals↗
PubMed1986

Muscle connections between imaginal discs in Drosophila.

A comparison of the protein content of different imaginal discs of Drosophila revealed that among more than 600 protein species that can be detected, only three show differences in concentration among different types of discs. Two of them form a doublet that can be resolved only by using extended electrophoresis conditions. This doublet was also reported to have a nonhomogeneous distribution within some discs. Here we show that these two proteins are tropomyosin components, and that they are associated not with the discs themselves but with a new type of muscle that connects some of the discs together.

Antibodies, Monoclonal↗
PubMed1986

A substance P-like peptide in bullfrog autonomic nerve terminals: anatomy biochemistry and physiology.

Substance P immunoreactivity was localized to dense-cored vesicles in parasympathetic preganglionic nerve terminals in the bullfrog cardiac ganglion. Analysis with radioimmunoassay and high pressure liquid chromatography indicated that the immunoreactive substance was more similar to substance P than to substance K but was not identical to either. The bullfrog substance P was also shown to be different than kassinin, eledoisin, ranatensin, bombesin, neuromedin K and physalaemin. Although the peptide was present in most of the terminals in the ganglion and appeared to be releasable in a calcium-dependent manner, intracellular recordings from ganglion neurons during stimulation revealed no electrophysiological events that might be mediated by an endogenous peptide. In addition, the direct application of substance P to ganglion neurons generally produced no changes in membrane potential, membrane conductance, somal calcium spikes or nerve-evoked release of acetylcholine. High concentrations of substance P did cause an apparent increase in the rate of desensitization of the nicotinic receptors but there was little indication that this phenomenon would occur under physiological conditions. It is suggested that bullfrog substance P is released as a neurotransmitter but is involved in electrically silent events in the postsynaptic neurons or is acting on non-neuronal cells near the terminals. The possible implications of these results for peptidergic systems in general are discussed.

Animals↗
PubMed1985

Segmental determination in Drosophila central nervous system.

We have analyzed the control of two segment-specific features in the central nervous system of Drosophila larvae. One of them is present only in the thoracic ganglia of the larva, where it represents the anlage of the adult leg neuromeres; the other is found in the first abdominal, as well as in the thoracic, ganglia. We show that mutations within the bithorax complex have parallel but independent effects on these neural structures and on the larval epidermis. We also show that the central nervous system is very sensitive to mild perturbations of the bithorax complex, and in particular to haploinsufficiency.

Animals↗
PubMed1985

Formation of neuronal pathways in the imaginal discs of Drosophila melanogaster.

We have followed the formation of neuronal pathways in different imaginal discs of Drosophila. The pattern is highly reproducible for a given disc type but distinct for each type of discs: in leg discs, several neurons are present before metamorphosis and provide two major pathways that are joined by later neurons; in the wing and haltere discs, a few pairs of neurons appear after the onset of metamorphosis and pioneer the major pathways; in antenna discs, no pioneers are detected before massive neuronal differentiation begins. The mechanisms used for axonal guidance seem common to all discs, and the differences between discs can be accounted for simply by differences in the arrangement and birth time of pioneer neurons. Different subsets of pioneer neurons are deleted by mutations such as scute and engrailed.

Animals↗
PubMed1983

Coexistence and corelease of cholinergic and peptidergic transmitters in frog sympathetic ganglia.

Both acetylcholine (ACh) and a peptide that resembles luteinizing hormone-releasing hormone (LHRH) serve as transmitters in sympathetic ganglia of the bullfrog. Although ACh is contained and released from both preganglionic B fibers, which form synaptic contacts with only B cells in the ganglia, and preganglionic C fibers, which are in synaptic contact with C cells only, the LHRH-like peptide is contained and released exclusively from preganglionic C fibers. The same preganglionic C fibers appear to supply both ACh and the LHRH-like peptide because the thresholds for the cholinergic fast excitatory postsynaptic potential (EPSP) correlate well with the thresholds for the peptidergic late slow EPSP recorded in the same C cell. Further, anatomical studies showed that almost all nerve terminals on C cells contained the LHRH-like peptide. Some of these same terminals must also contain and release. ACh, mediating the cholinergic fast EPSPs with millisecond synaptic delays. Therefore at least some, if not all, terminals of preganglionic C fibers contain and release both cholinergic and peptidergic transmitters.

Acetylcholine↗
PubMed1982

Segmental differences in the protein content of Drosophila imaginal discs.

The protein content of various Drosophila imaginal discs was analysed by two-dimensional electrophoresis followed by silver-staining. Three proteins, identified as tropomyosins alpha and beta and actin I, are more abundant in the metathoracic discs (haltere and third leg) than in the mesothoracic discs (wing and second leg). In the case of the wing disc, these proteins are probably contributed by the adepithelial (muscle precursor) cells, as indicated by their non-uniform localisation within the disc. Mutations in the bithorax complex have no effect on the difference between second and third leg discs. We conclude that there is a segmental difference in the protein content of homologous discs, that this difference is probably localized in the adepithelial cells, and that it is not under the direct control of known alleles of the bithorax complex.

Journal Article↗
PubMed1982

Antibodies to horseradish peroxidase as specific neuronal markers in Drosophila and in grasshopper embryos.

Antibodies specific for horseradish peroxidase (HRPeroxase) bind to neuronal membranes in Drosophila and serve as a specific neuronal marker. Immunocytochemical staining with these antibodies marks sensory neurons, peripheral nerves, and fiber tracks in the central nervous system of embryos, larvae, and adult flies. Similar patterns of staining also were seen in embryos of the grasshopper. It appears that an antigen associated with the nervous system and appearing early in differentiation is recognized by antibodies to HRPeroxase. Using this staining method, we followed embryogenesis of the central nervous system in Drosophila and found that the organization of central fiber tracks resembled that in the previously well-characterized grasshopper. We have used the anti-HRPeroxase antibodies to show that mutations affecting segmentation in Drosophila affect the organization of the embryonic nervous system.

Animals↗
PubMed1982

Peptidergic transmission in sympathetic ganglia of the frog.

1. A slow synaptic potential recorded in neurones of sympathetic ganglia of bullfrog, the late slow e.p.s.p., is probably mediated by a peptide resembling luteinizing hormone-releasing hormone (LHRH), because (1). a LHRH-like peptide is contained in preganglionic nerve terminals and is released upon nerve stimulation, (2) application of LHRH to ganglion cells mimics the effects of the natural transmitter for the late slow e.p.s.p., and (3) the pharmacological properties of LHRH and the natural transmitter for the late slow e.p.s.p. are similar. 2. Neurones in frog sympathetic ganglia are also depolarized by substance P. The substance P receptors, unlike the LHRH receptors or the post-synaptic receptors for the late slow e.p.s.p., are not blocked by antagonist of LHRH. No cross-desensitization was found between the substance P-induced response and the LHRH-induced response or the late slow e.p.s.p. 3. Substance P-like immunoreactivity is contained in bundles of axons passing through the ganglia. This distribution is distinct from the distribution of LHRH-like immunoreactivity in preganglionic nerve terminals. Thus, substance P receptors and substance P-containing fibers are distinct from the post-synaptic receptors and preganglionic fibers responsible for the late slow e.p.s.p. 4. Physiological and anatomical evidence is presented which indicates that the peptidergic transmitter for the late slow e.p.s.p. can diffuse for many micrometres before acting on ganglion cells.

Animals↗
PubMed1981

Role of an LHRH-like peptide as a neurotransmitter is sympathetic ganglia of the frog.

In sympathetic ganglia of the bullfrog a peptide that resembles luteinizing hormone releasing hormone (LHRH) probably functions as the transmitter for the late slow excitatory postsynaptic potential (EPSP), a signal that lasts several minutes: 1) Radioimmunoassays indicated that the lumbar chain of sympathetic ganglia contains 100-800 pg of an LHRH-like peptide, which disappeared 5 days after preganglionic axons were cut, while by this time the LHRH-like immunoreactivity tripled in the spinal nerves proximal to the cut region. 2) Immunohistochemical studies demonstrated the presence of LHRH-like immunoreactivity in numerous nerve terminals around sympathetic neurons. 3) The LHRH-like peptide can be released from ganglia with isotonic KCI or with nerve stimulation, a release that requires Ca2+. 4) LHRH acts directly on sympathetic neurons and produces a depolarizing response lasting for minutes. 5) The LHRH response and the late slow EPSP are associated with similar membrane conductance changes. Further, they alter the excitability of the neuron and interact with the cholinergic EPSPs in a parallel manner. 6) Both responses are blocked by certain analogs of LHRH, which antagonize the effects of LHRH in the rat.

Action Potentials↗
PubMed1980

Peptidergic transmitters in synaptic boutons of sympathetic ganglia.

In sympathetic ganglia of the bullfrog, a slow synaptic potential lasting for minutes--the late slow excitatory postsynaptic potential (e.p.s.p.)--was discovered. This slow response, unlike other previously known synaptic potentials in the autonomic nervous system, is not mediated by acetylcholine or monoamines. Similar non-cholinergic, non-adrenergic slow synaptic potentials have since been found in several other vertebrate autonomic ganglia. We found that the late slow e.p.s.p. is probably mediated by a peptide that is identical to, or closely resembles, mammalian luteinizing hormone releasing hormone (LHRH), because (1) when applied directly to sympathetic neurones, LHRH and its agonists elicit a slow depolarization, associated with similar changes in membrane conductance and excitability as those occurring during the late slow e.p.s.p. Furthermore, both peptide-induced and nerve-evoked responses are blocked by antagonists of LHRH; and (2) radioimmunoassays indicate that a chain of sympathetic ganglia contains 100-800 pg of a LHRH-like peptide. Its distribution among spinal nerves, the great reduction of this substance following denervation, and its release from ganglia following isotonic KCl treatment or nerve stimulation suggest that the LHRH-like material is contained in preganglionic nerve fibres. Here we report that immunohistochemical staining of sympathetic ganglia shows that LHRH-like immunoreactivity is indeed present in synaptic boutons. We also show that the two types of ganglion cells (B cells and C cells) receive strikingly different patterns of peptidergic innervation.

Animals↗
PubMed1980

Further evidence for peptidergic transmission in sympathetic ganglia.

We previously proposed that, in sympathetic ganglia of the bullfrog, a peptide which resembles luteinizing hormone-releasing factor (LH-RF, luliberin) functions as the transmitter for the late slow excitatory postsynaptic potential (epsp), a signal that may last 5-10 min. To test this hypothesis further, we have compared the physiological andpharmacological effects of LH-RF with those of the natural transmitter and have found a close parallel. (i) LH-RF, when ejected with a brief pulse of pressure through a micropipette near a ganglion cell, produces a depolarizing response lasting for minutes. (ii) The LH-RF-induced response is associated with changes in input resistance similar to thoe during a late slow epsp. (iii) The amplitudes of the LH-RF-induced response and the late slow epsp vary in parallel as the membrane potential is shifted over a wide range. (iv) Both responses increase the excitability of ganglion cells. (v) The two responses interact with the cholinergic epsps in a parallel manner: they cause diminution of the slow epsp but not of the fast epsp. (vi) Both responses are blocked by an analog of LH-RF that antagonizes the effects of LH-RF in the rat.

Animals↗
PubMed1979

A peptide as a possible transmitter in sympathetic ganglia of the frog.

A search was made in sympathetic ganglia of the bullfrog for a noncholinergic, nonaminergic transmitter that is released by a distinct group of preganglionic axons. These initiate a late slow excitatory postsynaptic potential which lasts for many minutes. The most promising candidate for the role of transmitter is a peptide that resembles luteinizing hormone-releasing hormone (LHRH; luliberin). The reasons are: (i) LHRH (1 muM) and some of its analogs cause a slow depolarization of ganglion cells. (ii) Radioimmunoassays established that 100-800 pg of a LHRH-like substance is contained in the lumbar chain of sympathetic ganglia. (iii) The LHRH-like material is specifically distributed in those spinal nerves that contain axons that initiate the slow noncholinergic synaptic responses. (iv) Five days after ipsilateral preganglionic axons are cut, 95% of the LHRH-like substance disappears from ganglia, while the LHRH immunoreactivity triples in the spinal nerves proximal to the cut region. (v) About 0.6% of the LHRH-like material within ganglia can be collected from the perfusate after 30 min of incubation in isotonic KC1; this release is Ca dependent. (vi) The candidate for transmitter has several chemical characteristics of a peptide and has a Mr near 1000.

Animals↗