Search PubMed⌕ Search

Biomedical subjects

B L Tempel

Publications and source records attributed to B L Tempel.

50 records · Page 3Linked to original sources
PubMed1990

A family of three mouse potassium channel genes with intronless coding regions.

To understand the molecular mechanisms responsible for generating physiologically diverse potassium channels in mammalian cells, mouse genomic clones have been isolated with a potassium channel complementary DNA, MBK1, that is homologous to the Drosophila potassium channel gene, Shaker. A family of three closely related potassium channel genes (MK1, MK2, and MK3) that are encoded at distinct genomic loci has been isolated. Sequence analysis reveals that the coding region of each of these three genes exists as a single uninterrupted exon in the mouse genome. This organization precludes the generation of multiple forms of the protein by alternative RNA splicing, a mechanism known to characterize the Drosophila potassium channel genes Shaker and Shab. Thus, mammals may use a different strategy for generating diverse K+ channels by encoding related genes at multiple distinct genomic loci, each of which produces only a single protein.

Amino Acid Sequence↗
PubMed1989

Dendrotoxin-binding brain membrane protein displays a K+ channel activity that is stimulated by both cAMP-dependent and endogenous phosphorylations.

The purified protein that binds the K+ channel ligands dendrotoxin I and mast cell degranulating peptide can be phosphorylated by cAMP-dependent protein kinase and by an endogenous protein kinase, which may be a specific K+ channel kinase. Phosphorylations take place on the toxin-binding subunit, a polypeptide of 76-80 kDa. Phosphorylation by both kinases leads to activation of the reconstituted dendrotoxin-sensitive K+ channel.

Animals↗
PubMed1989

Immunological evidence for a relationship between the dendrotoxin-binding protein and the mammalian homologue of the Drosophila Shaker K+ channel.

Polyclonal antibodies were raised against two synthetic peptides from different parts of the predicted amino acid sequence of the mouse homologue (MBK1) of the Drosophila Shaker K+ channel. The antibodies recognized the toxin-binding subunit of the dendrotoxin-binding proteins from rat and bovine brain. The results suggest that the dendrotoxin-binding protein is related to the expression products of the mammalian homologue of the Shaker gene.

Animals↗
PubMed1988

Cloning of a probable potassium channel gene from mouse brain.

Potassium channels comprise a diverse class of ion channels important for neuronal excitability and plasticity. The recent cloning of the Shaker locus from Drosophila melanogaster has provided a starting point for molecular studies of potassium channels. Predicted Shaker proteins appear to be integral membrane proteins and have a sequence similar to the sequence of the S4 segment of the vertebrate sodium channel, where the S4 segment has been proposed to be the voltage sensor. Expression studies in frog oocytes confirm that Shaker encodes a component of a potassium channel (the A channel) that conducts a fast transient potassium current. Here we report the isolation of complementary DNA clones from the mouse brain, the nucleotide sequences of which predict a protein remarkably similar to the Shaker protein. The strong conservation of the predicted protein sequence in flies and mammals suggests that these mouse clones encode a potassium channel component and that the conserved amino acids may be essential to some aspect of potassium channel function.

Amino Acid Sequence↗
PubMed1988

Expression of functional potassium channels from Shaker cDNA in Xenopus oocytes.

The Shaker gene of Drosophila melanogaster encodes a potassium-selective ion channel, the 'A' channel, or one of its subunits. A single Shaker messenger RNA species suffices to direct the synthesis of functional A channels in Xenopus oocytes. Physiological characteristics of the A currents induced by two different mRNA species are compared.

Animals↗
PubMed1987

Cloning of genomic and complementary DNA from Shaker, a putative potassium channel gene from Drosophila.

On the basis of electrophysiological analysis of Shaker mutants, the Shaker locus of Drosophila melanogaster has been proposed to encode a structural component of a voltage-dependent potassium channel, the A channel. Unlike sodium channels, acetylcholine receptors, and calcium channels, K+ channels have not been purified biochemically. To facilitate biochemical studies of a K+ channel, genomic DNA from the Shaker locus has been cloned. Rearrangements in five Shaker mutants have been mapped to a 60-kilobase segment of the genome. Four complementary DNA clones have been analyzed. These clones indicate that the Shaker gene contains multiple exons distributed over at least 65 kilobases of genomic DNA in the region where the mutations mapped. Furthermore, the gene may produce several classes of alternatively spliced transcripts. Two of the complementary DNA clones have been sequenced and their sequences support the hypothesis that Shaker encodes a component of a K+ channel.

Animals↗
PubMed1987

Sequence of a probable potassium channel component encoded at Shaker locus of Drosophila.

Potassium currents are crucial for the repolarization of electrically excitable membranes, a role that makes potassium channels a target for physiological modifications that alter synaptic efficacy. The Shaker locus of Drosophila is thought to encode a K+ channel. The sequence of two complementary DNA clones from the Shaker locus is reported here. The sequence predicts an integral membrane protein of 70,200 daltons containing seven potential membrane-spanning sequences. In addition, the predicted protein is homologous to the vertebrate sodium channel in a region previously proposed to be involved in the voltage-dependent activation of the Na+ channel. These results support the hypothesis that Shaker encodes a structural component of a voltage-dependent K+ channel and suggest a conserved mechanism for voltage activation.

Animals↗
PubMed1984

Mutations in the dopa decarboxylase gene affect learning in Drosophila.

Fruit flies synthesize several monoamine neurotransmitters. Dopa decarboxylase (Ddc) mutations affect synthesis of two of these, dopamine and serotonin. Both transmitters are implicated in vertebrate and invertebrate learning. Therefore, we bred flies of various Ddc genotypes and tested their learning ability in positively and negatively reinforced learning tasks. Mutations in the Ddc gene diminished learning acquisition approximately in proportion to their effect on enzymatic activity. Courtship and mating sequences of the mutants appeared normal, except for one aspect of male courtship that had previously been shown to be experience dependent. In contrast, the effect on behavior patterns that do not involve learning--phototaxis, geotaxis, olfactory acuity, responsiveness to sucrose--was relatively slight under these conditions. Moderate Ddc mutations affected the acquisition of learned responses while leaving memory retention unaltered. This is in contrast to the mutations dunce , rutabaga , and amnesiac , which primarily affect short-term memory.

Animals↗
PubMed1983

Reward learning in normal and mutant Drosophila.

Hungry fruit flies can be trained by exposing them to two chemical odorants, one paired with the opportunity to feed on 1 M sucrose. On later testing, when given a choice between odorants the flies migrate specifically toward the sucrose-paired odor. This appetitively reinforced learning by the flies is similar in strength and character to previously demonstrated negatively reinforced learning, but it differs in several properties. Both memory consolidation and memory decay proceed relatively slowly after training with sucrose reward. Consolidation of learned information into anesthesia-resistant long-term memory requires about 100 min after training with sucrose compared to about 30 min after training with electric shock. Memory in wild-type flies persists for 24 hr after training with sucrose compared to 4-6 hr after training with electric shock. Memory in amnesiac mutants appears to be similarly lengthened, from 1 hr to 6 hr, by substituting sucrose reward for shock punishment. Two other mutants, dunce and rutabaga, which were isolated because they failed to learn the shock-avoidance task, learn normally in response to sucrose reward but forget rapidly afterward. One mutant, turnip, does not learn in either paradigm. Reward and punishment can be combined in olfactory discrimination training by pairing one odor to sucrose and the other to electric shock. In this situation, the expression of learning is approximately the sum of that obtained by using either reinforcement alone. After such training, memory decays at two distinct rates, each characteristic of one type of reinforcement.

Animals↗
PubMedDate not supplied

BOLD-fMRI of PTZ-induced seizures in rats.

PURPOSE: To develop a non-invasive method for exploring seizure initiation and propagation in the brain of intact experimental animals. METHODS: We have developed and applied a model-independent statistical method--Hierarchical Cluster Analysis (HCA)--for analyzing BOLD-fMRI data following administration of pentylenetetrazol (PTZ) to intact rats. HCA clusters voxels into groups that share similar time courses and magnitudes of signal change, without any assumptions about when and/or where the seizure begins. RESULTS: Epileptiform spiking activity was monitored by EEG (outside the magnet) following intravenous PTZ (IV-PTZ; n=4) or intraperitoneal PTZ administration (IP-PTZ; n=5). Onset of cortical spiking first occurred at 29+/-16 s (IV-PTZ) and 147+/-29 s (IP-PTZ) following drug delivery. HCA of fMRI data following IV-PTZ (n=4) demonstrated a single dominant cluster, involving the majority of the brain and first activating at 27+/-23s. In contrast, IP-PTZ produced multiple, relatively small, clusters with heterogeneous time courses that varied markedly across animals (n=5); activation of the first cluster (involving cortex) occurred at 130+/-59 s. With both routes of PTZ administration, the timing of the fMRI signal increase correlated with onset of EEG spiking. CONCLUSIONS: These experiments demonstrate that fMRI activity associated with seizure activity can be analyzed with a model-independent statistical method. HCA indicated that seizure initiation in the IV- and IP-PTZ models involves multiple regions of sensitivity that vary with route of drug administration and that show significant variability across animal subjects. Even given this heterogeneity, fMRI shows clear differences that are not apparent with typical EEG monitoring procedures, in the activation patterns between IV and IP-PTZ models. These results suggest that fMRI can be used to assess different models and patterns of seizure activation.

Animals↗
PubMedDate not supplied

Genetic dissection of monoamine neurotransmitter synthesis in Drosophila.

The biogenic monoamine neurotransmitters octopamine, dopamine and serotonin have been detected in nervous tissue from many insects. We report here that intact Drosophila melanogaster brains, when incubated with the radioactive amino acids tyrosine and tryptophan, synthesized and accumulated labelled monoamines. In two mutant strains monoamine synthesis was abnormal. The per o mutation abolishes the normal circadian rhythm. Brains from per o flies, when incubated in tritiated tyrosine, accumulated one-third as much labelled octopamine as did brains from wild-type flies, but had normal dopamine and serotonin synthesis. In contrast, dopa decarboxylase (Ddc) mutations decreased dopamine and serotonin synthesis but did not affect octopamine synthesis. These results suggest that there are two different aromatic amino acid decarboxylases in Drosophila brains, one that decarboxylates L-dopa and 5-hydroxytryptophan and another that decarboxylates tyrosine. Direct measurement of L-dopa, 5-hydroxytryptophan and tyrosine decarboxylase activities in the different strains confirmed this suggestion.

Animals↗