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Biomedical subjects

T Roeder

Publications and source records attributed to T Roeder.

18 recordsLinked to original sources
PubMed2000

The pharmacology of a dopamine receptor in the locust nervous tissue.

A dopamine receptor in the nervous tissue of the desert locust (Schistocerca gregaria Forskâl) was studied using ¿3Hlysergic acid diethylamide (LSD) as the radioligand. Its expression is almost entirely restricted to the mushroom bodies, centres for learning and memory in the insect brain. This G-protein coupled receptor is present in relatively low concentrations in the locust brain (35 fmol/mg protein). The pharmacological characterisation reveals high affinity for the putative natural agonist dopamine (K(i)=28 nM). Substances with high subtype specificity for vertebrate dopamine receptors such as SCH 23390 (K(i)=639 nM) and sulpiride (K(i)=21,200 nM) have low affinity for the locust neuronal dopamine receptor. In opposite, substances with a broad pharmacological profile such as LSD, spiperone (K(i)=7.26 nM), and chlorpromazine (K(i)=9.52 nM) have high affinity properties. Comparison of the pharmacological data reveals no significant homology to any vertebrate dopamine receptor class characterised so far. This uncertainty about the pharmacological relatedness of insect dopamine receptors mirrors the available molecular data. It is almost impossible to classify cloned insect dopamine receptors into vertebrate dopamine receptor schemes. This lack of pharmacological relatedness opens the opportunity to develop highly specific insecticides against insect dopamine receptors.

Animals↗
PubMed2000

Octopamine receptors in the honey bee and locust nervous system: pharmacological similarities between homologous receptors of distantly related species.

Honey bees are perhaps the most versatile models to study the cellular and pharmacological basis underlying behaviours ranging from learning and memory to sociobiology. For both aspects octopamine (OA) is known to play a vital role. The neuronal octopamine receptor of the honey bee shares pharmacological similarities with the neuronal octopamine receptor of the locust. Both, agonists and antagonists known to have high affinities for the locust neuronal octopamine receptor have also high affinities for the bee neuronal octopamine receptor. The distribution of receptors is more or less congruent between locusts and bees. Optic lobes and especially the mushroom bodies are areas of greatest octopamine receptor expression in both species, which mirrors the physiological significance of octopamine in the insect nervous system. The neuronal octopamine receptor of insects served as a model to study the pharmacological similarity of homologous receptors from distantly related species, because bees and locusts are separated by at least 330 million years of evolution.

Animals↗
PubMed1999

Verification of differential gene transcription using virtual northern blotting.

We introduce here an alternative to conventional northern blotting that requires only minute amounts of RNA. This has been achieved by modification of methods currently used for the mapping of mRNA 5'-terminal ends. The terminal desoxynucleotidyl transferase-mediated G-tailing, cap finder, ligation-anchored and RNA ligase-mediated approaches followed by polymerase chain reaction protocols all produced high quality cDNAs in large amounts. These cDNAs could be separated by electrophoresis to obtain virtual northern blots that could replace conventional northern blots. All the essential information, including transcript length and the expression pattern, are preserved in these cDNAs, even if the transcripts are long or GC-rich. In addition, minute amounts of material (less than 100 cells) are sufficient to produce more than 100 virtual northern blots, making this approach extremely versatile.

Animals↗
PubMed1999

Evolutionary consequences of selected locus-specific variations in epistasis and fitness contribution in Kauffman's NK model.

Mathematical analysis and computer simulations are used to evaluate three modifications to Kauffman's NK model in an attempt to incorporate unexplored aspects of epistatic interaction between loci in genome evolution. Two modifications--one to the amount and the other to the distribution of epistatic interaction--further support Kauffman's conclusion that high levels of epistatic interaction lead to a decrease in overall fitness of the genome. The third model, however, provides a condition under which increased epistatic interaction at certain loci results in higher genome fitness.

Alleles↗
PubMed1999

Octopamine in invertebrates.

Octopamine (OA), a biogenic monoamine structurally related to noradrenaline, acts as a neurohormone, a neuromodulator and a neurotransmitter in invertebrates. It is present in relatively high concentrations in neuronal as well as in non-neuronal tissues of most invertebrate species studied. It functions as a model for the study of modulation in general. OA modulates almost every physiological process in invertebrates studied so far. Among the targets are peripheral organs, sense organs, and processes within the central nervous system. The known actions of OA in the central nervous system include desensitization of sensory inputs, influence on learning and memory, or regulation of the 'mood' of the animal. Together with tyramine, OA it is the only neuroactive non-peptide transmitter whose physiological role is restricted to invertebrates. This focussed the interest on the corresponding OA receptors. They are believed to be good targets for highly specific insecticides as they are not found in vertebrates. All octopamine receptors belong to the family of G-protein coupled receptors. Four of them could be distinguished using pharmacological tools. They show different coupling to second messenger systems including activation and inhibition of adenylyl cyclase, activation of phospholipase C and coupling to a chloride channel. Recently, octopamine receptors from molluscs and insects have been cloned. Further studies of all aspects of octopaminergic neurotransmission should give deeper insights into modulation of peripheral and sense organs and within the central nervous system in general.

Animals↗
PubMed1998

Solid-phase cDNA library construction, a versatile approach.

A rapid and versatile method for cDNA library construction was developed. It is based on conventional cDNA library synthesis including all enzymatic steps usually required, but is performed on a solid support. The cDNA is immobilised via a biotin residue to streptavidin coupled magnetic beads, which allows rapid and easy to perform changes of buffers and enzymes. Therefore, it combines speed (library construction within a single day) with high quality libraries, making it ideally suited for most purposes.

Base Sequence↗
PubMed1998

Epinastine, a highly specific antagonist of insect neuronal octopamine receptors.

The tetracyclic compound epinastine (3-amino-9, 13b-dihydro-1H-dibenz(c,f)imidazo(1,5a)azepine hydrochloride) that was recently introduced as a vertebrate histamine H1 receptor antagonist has also high affinity for insect neuronal octopamine receptors. This holds true for the neuronal octopamine receptor from the locust (Ki = 2 Nm) as well as from the honey bee nervous system (Ki = 1.1 Nm). In addition to its high affinity, it has a high degree of specificity. Its affinity for other insect receptors for biogenic amines, such as 5-hydroxytryptamine, dopamine, histamine, and tyramine, is at least four orders of magnitude lower. Therefore, epinastine could serve as a highly specific antagonist of octopamine receptors that enables physiological dissection of octopaminergic neurotransmission within the nervous system of insects. To demonstrate these abilities, epinastine was used to inhibit the visually evoked activity of an identified interneuron in the visual pathway which is known to be modulated by octopamine.

Action Potentials↗
PubMed1998

Isolation of ultrapure supercoiled plasmid-DNA using preparative electrophoresis.

A large-scale preparative polyacrylamide gel electrophoresis (PAGE) system for the isolation of high-purity supercoiled plasmid-DNA is described. This method should prove suitable for the isolation of large DNA molecules, either plasmid or linear DNA, that is required for the production of transgenic animals, for instance. The efficiency of the method is illustrated by the isolation of the gene for the green fluorescent protein, cloned into a mammalian expression vector and used for transfection of eukaryotic cells.

Animals↗
PubMed1995

Pharmacology of the octopamine receptor from locust central nervous tissue (OAR3).

1. The present study characterized highly effective agonists from different classes of compounds for the neuronal octopamine receptor (OAR3) of the migratory locust (Locusta migratoria L.). Biogenic amines and phenyliminoimidazolidines (PIIs) were employed for the study of structure-activity relationships. 2. The highest affinity PIIs were predominantly those with substitutions at the positions 2 and 4 of the phenolic ring (e.g. NC 7, KI = 0.3 nM, NC 8, KI = 0.81 nM). Substitutions at these positions always had positive effects on the affinity of the respective agonists. 3. Substitutions at the positions 3, 5 and 6, however, always had negative effects on the affinity. At the position one of the phenolic ring, heterocyclic substituents are preferred. 4. Some PIIs had a more than 30 times higher affinity for OARs than for alpha-adrenoceptors which are the vertebrate homologues of the insect octopamine receptors. 5. The only non-PII with subnanomolar affinity was the aminooxazoline derivative AC 6 (KI = 0.92 nM). 6. A variety of substances with known insecticidal activity such as chlordimeform, demethylchlor-dimeform, amitraz or AC 6 had high affinity for the locust neuronal octopamine receptor.

Animals↗
PubMed1994

Photoaffinity labeling of a neuronal octopamine receptor.

The invertebrate aminergic neurotransmitter and neuromodulator octopamine (OA) acts at both neuronal and nonneuronal receptors that appear to have distinct pharmacological characteristics. The current work uses a potent and specific OA photoaffinity ligand, tritiated 2(2,6-diethyl-4-azidophenylimino)imidazolidine ([3H]NC-5Z), to identify and characterize a putative neuronal OA receptor protein in membranes from nerve tissue of the desert locust, Schistocerca gregaria. Under nonphotolyzing conditions, [3H]NC-5Z demonstrated high-affinity binding (KD = 2.5 +/- 0.3 nM; Bmax = 702 fmol/mg of protein) to a single class of noninteracting sites. The absolute and rank order potency of binding of both agonists and antagonists was highly correlated (r = 0.99) with their known ability to displace [3H]OA binding to locust neuronal membranes and was consistent with the labeling of a class 3 OA receptor. Under photolyzing conditions, [3H]NC-5Z demonstrated irreversible binding that was resistant to trichloroacetic acid and methanol, displaceable by OA and other octopaminergic agonists and antagonists, soluble in sodium dodecyl sulfate, and only sparingly soluble in nonionic detergents. Membrane-bound [3H]NC-5Z, solubilized with Nonidet P-40, bound specifically only to immobilized concanavalin A or lentil lectin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of photolyzed proteins under reducing conditions revealed a single peak of radioactivity with a molecular mass of 53 +/- 5 kDa. Taken together, these biochemical and pharmacological results support the identity of this protein peak as that of the neuronal OA3 receptor.

Affinity Labels↗
PubMed1993

Characterization of insect neuronal octopamine receptors (OA3 receptors).

Octopamine receptors in the nervous tissue of insects were investigated using a ligand-receptor assay with [3H]NC-5Z or [3H]octopamine as the radioligands. Both ligands recognized a homogeneous class of binding sites with the properties of an octopamine receptor. This receptor has been characterized pharmacologically. Both high-affinity agonists (e.g. NC 7, K1 = 0.3 nM) and antagonists (e.g. maroxepine, K1 = 1.02 nM) were investigated. The neuronal octopamine receptor belongs to a receptor class that can easily be distinguished from peripheral octopamine receptors. Initial investigations of the localization of octopamine receptors within the insect nervous tissue show the greatest receptor density in the optic lobes.

Animals↗
PubMed1992

Pharmacological characterization of a 5-HT receptor in locust nervous tissue.

A 5-HT receptor in the nervous tissue of the desert locust (Schistocerca gregaria Forsk.) was investigated, using [3H]LSD (lysergic acid diethylamide) as the radioligand. [3H]LSD labels in addition a putative dopamine receptor whose specific [3H]LSD binding nevertheless could easily be diminished by co-incubation with 1 microM dopamine. The binding site was characterized by a KD of 1.64 nM, and a maximal concentration of binding sites of 79.8 fmol/mg protein. Pharmacological investigation revealed a relatively low affinity for the putative natural agonist, serotonin (KI = 0.209 microM). In contrast to the high affinity of classical serotonergic antagonists (e.g. dihydroergotamine or (+)-butaclamol) substances with subtype specificity such as 8-OH-DPAT (8-hydroxyl-1-(N,N-dipropyl)-aminotetralin) or ketanserin have only moderate affinities. Quantitative comparison of the pharmacological data demonstrated that there is obviously no pharmacological homology with vertebrate 5-HT receptors characterized so far. The only receptors with a close pharmacological relationship to the 5-HT receptor of locusts are the 5-HTdro1 receptor expressed in Drosophila nervous tissue and a 5-HT receptor in snail nervous tissue which might be homologous to that of locusts. The 5-HT receptor investigated, was shown to be G-protein-coupled, as addition of stable GTP analogues or depletion of Mg2+ ions from the incubation medium led to agonist-specific lowering of the affinity.

Animals↗
PubMed1992

A new octopamine receptor class in locust nervous tissue, the octopamine 3 (OA3) receptor.

The insect neuronal 3H-octopamine binding site represents a new type of octopamine receptor. This receptor has pharmacological features that are characteristic for all known octopamine receptors, but it is possible to distinguish this receptor class from all others using either agonists or antagonists. The quantitative determination of the pharmacological relationships to the other octopamine receptor classes could demonstrate greatest homology with both class 2 (OA2A and OA2B) receptors. Therefore, the neuronal octopamine receptor should be named a class 3 receptor (OA3). A new and simple classification scheme for octopamine receptors which enables classification of the new receptor class is established using antagonists.

Adrenergic Agonists↗
PubMed1990

High-affinity antagonists of the locust neuronal octopamine receptor.

The pharmacological antagonistic properties of the invertebrate specific octopamine receptor were investigated using a conventional radio-receptor assay with [3H]octopamine as the radioligand. Among the antagonists with highest affinity of the locust (Locusta migratoria L.) neuronal octopamine receptor were tetracyclic substances like mianserin (K1 = 1.2 nM), some of its derivatives (8-hydroxymianserin; K1 = 1.68 nM), and maroxepine, which is the antagonist with the highest affinity ever reported (K1 = 1.02 nM) to this octopamine receptor class. Among the other antagonists tested only phentolamine (K1 = 19 nM) and promethazine (K1 = 31.2 nM) had high-affinity properties.

Animals↗
PubMed1990

Histamine H1-receptor-like binding sites in the locust nervous tissue.

The histamine H1-receptor-like binding sites in the nervous tissue of the locust Locusta migratoria were investigated with a conventional radio-receptor assay using [3H]mianserin as the radio ligand. Binding of [3H]mianserin to the binding site is sensitive to proteases and heat treatment. It shows the characteristics of ligand-receptor interactions. The single binding site has high affinity for mianserin (KD = 7.05 nM) and is present in high concentrations (Bmax = 1.53 pmol/mg) in the whole nervous tissue. All tested antihistamines have a high affinity for the binding site, which suggests that it represents an insect histamine receptor. Nevertheless, it shows its peculiarities distinguishing it from vertebrate histamine H1-receptors.

Animals↗
PubMed1990

Octopamine receptors in locust nervous tissue.

The octopamine binding site in the nervous tissue of the migratory locust Locusta migratoria is identified as an octopamine receptor of class 2. The binding of octopamine to the binding site is saturable, reversible, stereospecific and shows a pharmacological profile typical for octopamine receptors. Saturation analysis results in a single class of non-interacting binding sites (KD = 7.9 +/- 0.9 nM; Bmax = 160 fmol/mg). The pharmacological analysis shows that the phenyliminoimidazolidines NC7 and NC5 (Ki = 0.29 and 0.87 nM, respectively) are the most potent agonists, and that mianserin (Ki = 1.20 nM) is the most potent antagonist ever reported for octopamine receptors in direct binding studies.

Adrenergic Antagonists↗
PubMed1982

Demonstration of alpha 1-acid glycoprotein (orosomucoid) by double one-dimensional slab gel electrophoresis: evidence for intra- and interindividual variability of the microheterogeneity pattern in health and disease.

This double one-dimensional slab gel electrophoresis technique, in the sequence polyacrylamide gel electrophoresis followed by isoelectric focusing in polyacrylamide gels, permits the selective demonstration and comparison of the micro-heterogeneity pattern of alpha 1-acid glycoprotein (orosomucoid) in as many as 96 human plasma or serum samples on one gel. The electrophoretic analysis is performed on 8 microL of serum or plasma without prior purification. Several hundred samples can be analyzed by one investigator during a working day. Densitometric evaluation of the patterns revealed two new findings: 1) The microheterogeneity pattern can be described by a parameter that is independent of the concentration of orosomucoid in plasma: the center of density of the pattern, with the peak number as coordinate. 2) There is a considerable average shift of the center of density towards more basic components among the patterns obtained for samples from hospital patients. The results suggest that followup of the intra-individual variation of the orosomucoid pattern in health and disease might help in studying the still-uncertain function of this protein as well as the diseases affecting the pattern.

Adult↗