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K E Isenberg

Publications and source records attributed to K E Isenberg.

36 records · Page 2Linked to original sources
PubMed1992

Nonoxidative ethanol metabolism: expression of fatty acid ethyl ester synthase-III in cultured neural cells.

Alcohol metabolism in the human brain has been characterized as essentially nonoxidative in nature, with the esterification of ethanol with fatty acids via fatty acid ethyl ester synthase. This pathway of ethanol metabolism is related to end organ damage in the brain but the neural cell type expressing FAEES has not been identified. In this study human and rodent neuroblastoma and glioma cell lines are assayed for fatty acid ethyl ester synthase activity. Cells with neuronal properties demonstrated higher activity than glioma cell lines. We confirmed the presence of the mRNA for one type of synthase, fatty acid ethyl ester synthase-III in three neuronal cell lines--N1E115 cells, PC12 cells, and SK-N-MC cells. These results support the hypothesis that FAEES activity is expressed chiefly in cells with neuronal properties and suggest that non-oxidative ethanol metabolism is potentially related to the toxic effect of ethanol on the human brain.

Acyltransferases↗
PubMed1992

Volatile anesthetics gate a chloride current in postnatal rat hippocampal neurons.

A volatile anesthetic-gated current was characterized in patch-clamped cultured postnatal rat hippocampal neurons. In this preparation, the major volatile anesthetics, isoflurane, halothane, and enflurane, open an anion-selective conductance. This volatile anesthetic-gated current exhibits anion selectivity with a chloride-to-acetate permeability ratio of 15, shows outward rectification well described by the constant field equation, and is activated in a dose-dependent fashion with half-maximal response to isoflurane at 0.8 mM (0.032 atm). The current persists in the absence of external Ca2+ and is not blocked by strychnine, a glycine antagonist. However, the gamma-aminobutyric acidA (GABAA) antagonists, bicuculline and picrotoxinin, and the nonspecific anion channel blocker, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), completely block the response. These observations suggest that volatile anesthetics, like several other general anesthetics such as barbiturates, steroids, and etomidate, have a GABA-mimetic effect on vertebrate central neurons in culture. It is not clear whether this GABAA-gating property is a prerequisite for all general anesthetics. However, under normal physiological conditions of low intracellular Cl-, it is likely that drugs with both direct GABA agonist and GABA modulatory properties will produce overall depression of the central nervous system by increasing the normal inhibitory synaptic influence and by directly hyperpolarizing neurons.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1992

Effects of a benz[e]indene on gamma-aminobutyric acid-gated chloride currents in cultured postnatal rat hippocampal neurons.

Benz[e]indenes (BIs) are tricyclic molecules that can be envisioned as steroids without an A-ring. Because certain steroids are known to alter gamma-aminobutyric acid (GABA) responses in central neurons, we examined the effects of a substituted BI resembling 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha-OH-DHP) on GABA-gated chloride currents in cultured postnatal rat hippocampal neurons. The compound, BI-1, reversibly potentiated GABA currents at concentrations of > 10 nM, with an EC50 value of 0.2 microM. BI-1 increased the apparent affinity of GABA for its receptor, decreasing the GABA EC50 from 9 microM to 3 microM. BI-1 had no effect on the shape of the GABA current-voltage relationship and did not alter the GABA reversal potential. The effects of BI-1 were not altered by benzodiazepine or picrotoxin site antagonists. At concentrations up to 10 microM, where maximal effects on GABA currents were seen, BI-1 did not directly activate a membrane current. This contrasts with the effects of 3 alpha-OH-DHP, which activated chloride currents at concentrations that were subsaturating for GABA potentiation. These results suggest that the BIs may be useful for determining the mechanisms by which steroids potentiate GABA responses and directly gate chloride channels.

Animals↗
PubMed1992

Nicotinic acetylcholine currents in cultured postnatal rat hippocampal neurons.

Nicotinic acetylcholine (ACh) currents were studied in cultured postnatal rat hippocampal neurons, using whole-cell voltage-clamp techniques. In most cells, ACh produces one of two types of response. One class of ACh currents exhibits rapid and profound desensitization and is sensitive to inhibition by alpha-bungarotoxin (alpha BTXN). The second class activates slowly and exhibits no desensitization during prolonged agonist applications. This slow current is insensitive to alpha BTXN. Both the fast and slow responses exhibit inwardly rectifying current-voltage relationships and pass little current at positive membrane potentials. Both currents can be recorded in the presence of 1 microM atropine but are blocked by 0.1-1.0 mM d-tubocurarine and 0.1-1.0 mM mecamylamine. These observations suggest heterogeneity of nicotinic ACh receptors in rat hippocampal neurons and provide support for functional alpha BTXN-sensitive nicotinic receptors in this region.

Acetylcholine↗
PubMed1991

Insights into the structure and function of GABA-benzodiazepine receptors: ion channels and psychiatry.

OBJECTIVE: As a result of combined biophysical and molecular biological studies, important insights into the structure and function of gamma-aminobutyric acid (GABA) receptors have been achieved. These insights have helped to define the role of GABA receptors in synaptic inhibition and the ion channel mechanisms by which different neuropsychiatric drugs work. The authors' goal is to describe the actions of GABA as a neurotransmitter and discuss the modulation of receptor function by different drugs. DATA COLLECTION: The authors focus on more recent studies of the structure and physiology of the receptor-ion channel complex and the relevance of these studies to psychiatry. FINDINGS: The CNS effects of benzodiazepines, barbiturates, and alcohol have been linked to the GABA-chloride channel receptor complex. Multiple subunits of this complex have been cloned, sequenced, and expressed in heterologous systems. The results of cloning studies, coupled with membrane biophysics, have provided important insights into the structure and function of GABA receptors and their modulation by psychopharmacological agents. CONCLUSIONS: Future understanding of disease states, drug effects, and therapeutic successes and failures may be expressed in terms of differences in the structure and function of specific receptors and their associated ion channels. Furthermore, the ability to describe the molecular function of receptor subtypes offers the ability to tailor drug specificity by developing agents directed against a given receptor subtype. The current GABA studies also have important implications for the understanding of how neurotransmitter systems may be involved in illness.

Forecasting↗
PubMed1990

Genetic linkage is excluded for the D2-dopamine receptor lambda HD2G1 and flanking loci on chromosome 11q22-q23 in Tourette syndrome.

A genetic linkage study of fifteen families (n = 166) ascertained through probands diagnosed for Tourette syndrome was carried out for the D2-dopamine receptor and flanking loci on chromosome 11q22-q23. Tight linkage was excluded for all probes and regions of exclusion up to +/- 20% recombination were obtained. Overlapping regions of exclusion based upon primary map data permit exclusion of the entire region of the DRD2 locus in Tourette syndrome.

Chromosomes, Human, Pair 11↗
PubMed1990

No evidence for linkage between chromosome 5 markers and schizophrenia.

Linkage between chromosome 5 markers and schizophrenia has been proposed for a small number of Icelandic and English families. Three subsequent reports have failed to replicate this report. To increase the number of tested kindreds, we collected seven North American families with schizophrenia and genotyped them at 4 loci that span the region 5p13-5q11-14, including the two markers used in the single positive linkage report. The data were analyzed with models of affection status similar to those utilized in the positive report. We observed no evidence of linkage between these markers and psychiatric disorders, regardless of the definition of affection status. Additionally, we can exclude most of the region for linkage with schizophrenia in these families. This and other negative reports of linkage between schizophrenia and chromosome 5 markers suggest that genetic defects in this region are rarely, if ever, etiologically related to schizophrenia.

Chromosomes, Human, Pair 5↗
PubMed1989

Adaptive evolution of G-protein coupled receptor genes.

The phylogeny and patterns of nucleotide substitutions in the visual pigment genes, adrenergic receptor genes, muscarinic receptor genes, and in the human mas oncogene were studied by comparing their DNA sequences. The evolutionary tree obtained shows that the visual pigment genes and mas oncogene form one cluster and that the receptor genes form another. In the evolution of rhodopsin genes, synonymous substitutions outnumber nonsynonymous substitutions. This is consistent with the neutral theory of molecular evolution. However, the early evolutionary stages of alpha- and beta-adrenergic and muscarinic receptors are notable for significantly more nonsynonymous substitutions than synonymous substitutions, suggesting the acquisition of novel functional adaptations. Variable rates of nonsynonymous changes in different domains of these proteins reveal DNA segments that might have been important in their functional adaptations.

Amino Acids↗
PubMed1989

Schizophrenia and the question of genetic heterogeneity.

Despite major advances in psychiatric diagnosis during the past 20 years, boundaries of the schizophrenic syndrome remain elusive. Moreover, in pedigrees containing cases of schizophrenia there are marked between-pedigree differences with respect to prognosis, familial patterns of psychiatric illness, drug response, and especially association of affected status with a specific chromosomal locus. Such between-pedigree differences suggest the syndrome may be made up of several different diseases. Linkage of affected status to specific loci may aid in resolving genetic heterogeneity. Large multigenerational informative pedigrees may permit the separation into those that do and do not link to a genomic locus of interest. Admixture analysis of smaller informative pedigrees may permit separation of linked and unlinked pedigrees on the basis of differences in the recombination fraction. Finally, biological "markers" can be used before the genetic analysis to separate putative linked and unlinked pedigrees. The combined study of genetic linkage and clinical heterogeneity will aid in the resolution of etiological heterogeneity of schizophrenia and the delineation of meaningful diagnostic boundaries.

Genetic Linkage↗
PubMed1989

Cloning of a putative neuronal nicotinic acetylcholine receptor subunit.

A cDNA clone was isolated from a rat superior cervical ganglion cDNA library with an oligonucleotide that hybridized to muscle-like nicotinic acetylcholine receptor (nAChR) subunit cDNA. The deduced amino acid sequence possesses characteristics expected of a nAChR subunit that does not bind acetylcholine, in addition to distinctive features such as unique cysteine residues and N-linked glycosylation sites.

Amino Acid Sequence↗
PubMed1989

Linkage disequilibrium study of RFLPs detected at the human muscle nicotinic acetylcholine receptor subunit genes.

We screened DNA from unrelated individuals for RFLPs in the muscle nicotinic acetylcholine receptor (AcChoR) genes. These RFLP markers can be used for genetic linkage and association studies to test the hypothesis that receptor structure or regulation is involved in the development of myasthenia gravis (MG). The cDNAs from four subunits (alpha, beta, gamma, and delta) of the murine muscle AcChoR were used as probes to identify RFLPs in the homologous human genes. Digestion of DNA from 15 unrelated individuals with a set of 10 restriction enzymes revealed 11 RFLPs. At least one RFLP was found for each subunit gene. Eight RFLPs were found at the linked gamma and delta gene loci, six with minor allele frequencies greater than 15%, making that linkage group a very informative marker locus (PIC = .72). PIC values were calculated for the RFLPs from allele and haplotype frequency estimates obtained from a population sample of 53 individuals. The delta gene was assigned by in situ hybridization to region q31----q34 of chromosome 2. All pairs of RFLPs were analyzed for linkage disequilibrium. Of the 16 pairs of RFLPs from the same gene or from the linked gamma and delta genes, 13 pairs showed evidence of disequilibrium that was significant, with P less than .05. The implications of these results are discussed.

Chromosomes, Human, Pair 2↗
PubMed1984

Possible involvement of opiate receptors in the pharmacological profiles of antidepressant compounds.

Tricyclic antidepressants and selected hydroxylated metabolites were found to inhibit [3H]naltrexone binding in whole rat brain. The drug concentrations required to inhibit binding appeared to be within pharmacological relevant brain concentrations. Carbamazepine and several monoamine oxidase inhibitors (with the exception of clorgyline) were inactive in this regard. The relative potency of the tricyclic antidepressants with regard to inhibitions of opiate binding in brain did not correlate with their clinical efficiency as antidepressants, suggesting that these compounds probably do not exert their antidepressant effects through opioid peptidergic systems in brain. In addition, we found that imipramine (30 mg/kg) had antinociceptive properties, as assessed by the hot plate procedure, which were partially, but not significantly, reversed by naloxone (2 mg/kg). The possibility that opioid receptors may be involved in the analgesic properties of the tricyclic antidepressants has been discussed.

Animals↗
PubMed1984

Denervation supersensitivity in skeletal muscle: analysis with a cloned cDNA probe.

Motor neurons regulate the acetylcholine sensitivity of the muscles they innervate: denervated muscle fiber become "supersensitive" to acetylcholine, due to insertion of newly synthesized acetylcholine receptors (AChRs) in the plasma membrane. We used hybridization analysis with a cloned cDNA specific for AChR alpha-subunit to compare the abundance of AChR mRNA in innervated and denervated adult mouse muscles. Within 3 d of denervation, levels of AChR mRNA increased 100-fold; levels of actin mRNA changed little. The increase in AChR mRNA level was sufficiently large and rapid to account for denervation supersensitivity.

Actins↗
PubMedDate not supplied

Oligonucleotide pharmacotherapy: an antigene strategy.

Oligonucleotide pharmacotherapy, although in a very preliminary stage, promises to provide new, highly specific tools for the treatment of human diseases, such as viral illnesses and cancer. The agents have several proposed mechanisms of action, including inhibition of translation, splicing, and transcription. In addition, the bioefficacy of oligonucleotides may be enhanced by phosphorothioates, methylphosphonates, and alpha-oligonucleotides. The agents are delivered by the ex vivo or topical route, and new methods of administration are under study. It is predicted that within the decade these agents will be used routinely to treat several serious illnesses.

Drug Delivery Systems↗