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B J Hoffman

Publications and source records attributed to B J Hoffman.

At least 19 recordsLinked to original sources
PubMed1992

Expression cloning of a reserpine-sensitive vesicular monoamine transporter.

A cDNA for a rat vesicular monoamine transporter, designated MAT, was isolated by expression cloning in a mammalian cell line (CV-1). The cDNA sequence predicts a protein of 515 amino acids with 12 putative membrane-spanning domains. The characteristics of [3H]serotonin accumulation by CV-1 cells expressing the cDNA clone suggested sequestration by an intracellular compartment. In cells permeabilized with digitonin, uptake was ATP dependent with an apparent Km of 1.3 microM. Uptake was abolished by the proton-translocating ionophore carbonylcyanide p-trifluoromethoxyphenylhydrazone and with tri-(n-butyl)tin, an inhibitor of the vacuolar H(+)-ATPase. The rank order of potency to inhibit uptake was reserpine > tetrabenazine > serotonin > dopamine > norepinephrine > epinephrine. Direct comparison of [3H]monoamine uptake indicated that serotonin was the preferred substrate. Photolabeling of membranes prepared from CV-1 cells expressing MAT with 7-azido-8-[125I]iodoketanserin revealed a predominant tetrabenazine-sensitive photolabeled glycoprotein with an apparent molecular mass of approximately 75 kDa. The mRNA that encodes MAT was present specifically in monoamine-containing cells of the locus coeruleus, substantia nigra, and raphe nucleus of rat brain, each of which expresses a unique plasma membrane reuptake transporter. The MAT cDNA clone defines a vesicular monoamine transporter representing a distinct class of neurotransmitter transport molecules.

Affinity Labels↗
PubMed1992

A human serotonin 1D receptor variant (5HT1D beta) encoded by an intronless gene on chromosome 6.

An intronless gene encoding a serotonin receptor (5HT1D beta) has been cloned and functionally expressed in mammalian fibroblast cultures. Based on the deduced amino acid sequence, the gene encodes a 390-amino acid protein displaying considerable homology, within putative transmembrane domains (approximately 75% identity) to the canine and human 5HT1D receptors. Membranes prepared from CHO cells stably expressing the receptor bound [3H]serotonin with high affinity (Kd 4 nM) and displayed a pharmacological profile consistent, but not identical, with that of the characterized serotonin 5HT1D receptor. Most notably, metergoline and serotonergic piperazine derivatives, as a group, display 3- to 8-fold lower affinity for the 5HT1D beta receptor than for the 5HT1D receptor, whereas both receptors display similar affinities for tryptamine derivatives, including the antimigraine drug sumatriptan. Northern blot analysis revealed an mRNA of approximately 5.5 kilobases expressed in human and monkey frontal cortex, medulla, striatum, hippocampus and amygdala but not in cerebellum, olfactory tubercle, and pituitary. The 5HT1D beta gene maps to human chromosome 6. The existence of multiple neuronal 5HT1D-like receptors may help account for some of the complexities associated with [3H]serotonin binding patterns in native membranes.

Amino Acid Sequence↗
PubMed1992

Molecular pharmacological differences in the interaction of serotonin with 5-hydroxytryptamine1C and 5-hydroxytryptamine2 receptors.

5-Hydroxytryptamine (5HT)1C and 5HT2 receptors appear to be closely related, from a molecular viewpoint, displaying similar second messenger systems and a high degree of sequence homology. However, there are striking differences in the interactions of 5HT with 5HT1C and 5HT2 receptors; 5HT is generally more potent in stimulating responses mediated through 5HT1C receptors than responses mediated through 5HT2 receptors. Also [3H]5HT labels 5HT1C receptors and not 5HT2 receptors. In order to explore more fully the molecular rationale for these differences, radioligand binding studies were performed in rat, human, and porcine brain and choroid plexus tissues and in mammalian cells transfected with rat 5HT1C or 5HT2 receptors; second messenger studies (inositol phosphate accumulation) were performed in the transfected cells. The second messenger studies confirmed the approximately 10-fold higher potency of 5HT in stimulating intracellular responses through 5HT1C receptors (EC50 = 8.3 nM) than in stimulating intracellular responses through 5HT2 receptors (EC50 = 101 nM). An agonist radioligand selective for the 5HT1C and 5HT2 receptors, 2,5-dimethoxy-(4-[125I]iodo)phenylisopropylamine, was used, as well as [3H]5HT, [3H]mesulergine (antagonist radioligand for 5HT1C receptors), and [3H]ketanserin (antagonist radioligand for 5HT2 receptors). Computer-assisted analyses of the binding data revealed two agonist affinity states for the 5HT1C receptor. The agonist high affinity state of the receptor was modifiable by guanyl nucleotides. The proportion of agonist high affinity states, relative to the total receptor population, was approximately 10% for both receptors. The apparent higher affinity of 5HT for the radiolabeled 5HT1C receptors was due to the higher affinity 5HT displayed for the agonist low affinity state of the 5HT1C receptor, compared with the affinity of 5HT for the agonist low affinity state of the 5HT2 receptor. The correspondence between the higher affinity of 5HT for the agonist low affinity state of the 5HT1C receptor, relative to the 5HT2 receptor, and the higher potency of 5HT in stimulating 5HT1C responses indicates that 5HT interacts with the agonist low affinity state of the 5HT1C and 5HT2 receptors in initiating its biological effects. These observations indicate that guanine nucleotide-binding protein (G protein)-coupled receptors can exhibit high affinity for neurotransmitters in both the free receptor and the G protein-coupled states and that receptors exhibiting this property may represent a novel subfamily of G protein-coupled receptors.

3T3 Cells↗
PubMed1992

Radiation exposure during gastroenterologic fluoroscopy: risk assessment for pregnant workers.

With more females in childbearing years participating in fluoroscopic examinations, safety guidelines need to be evaluated. Present recommendations suggest limiting fetal irradiation to less than 500 mrem (0.5 rad) during gestation, and to avoid doses above 100 mrem (0.1 rad) from 8 to 15 wk postconception. The average radiation dose delivered per case was monitored during 10 therapeutic biliary procedures with lithium fluoride dosimeters worn at the endoscopist's collar, over the suprapubic region outside a knee-length 0.5-mm leaded equivalent apron, and inside the apron over the mid-pelvis. A short survey of 15 female technicians and physicians was conducted to gather their opinions about working in fluoroscopy during pregnancy. We found that radiation doses beneath the leaded apron were comparable to environmental exposure. The dose measured at the endoscopist's collar was 0.083 mrem/min. The dose over the pelvis was 0.044 mrem/min. The survey revealed that 13 of those interviewed would not feel safe working near fluoroscopy, and 12 wished to be excluded from fluoroscopy if they became pregnant. We conclude that a high level of anxiety regarding fetal safety exists among females participating in fluoroscopic procedures. In this study, with proper use of standard safety equipment, radiation exposure does not exceed those levels currently recommended to avoid during pregnancy.

Adult↗
PubMed1991

Cloning of the cocaine-sensitive bovine dopamine transporter.

A cDNA encoding the dopamine transporter from bovine brain substantia nigra was identified on the basis of its structural homology to other, recently cloned, neurotransmitter transporters. The sequence of the 693-amino acid protein is quite similar to those of the rat gamma-aminobutyric acid, human norepinephrine, and rat serotonin transporters. Dopamine transporter mRNA was detected by in situ hybridization in the substantia nigra but not in the locus coeruleus, raphe, caudate, or other brain areas. [3H]Dopamine accumulation in tissue culture cells transfected with the cDNA was inhibited by amphetamine, cocaine, and specific inhibitors of dopamine transport, including GBR12909.

Amino Acid Sequence↗
PubMed1991

Cloning of a serotonin transporter affected by antidepressants.

A complementary DNA clone for a serotonin (5HT) transporter has been isolated from rat basophilic leukemia cells. The complementary DNA sequence predicts a 653-amino acid protein with 12 to 13 putative transmembrane domains. The 5HT transporter has significant homology to the gamma-aminobutyric acid, dopamine, and norepinephrine transporters. Uptake by CV-1 cells expressing the transporter complementary DNA resembles 5HT uptake by platelets and brain synaptosomes; it is sensitive to antidepressants, amphetamine derivatives, and cocaine.

Amino Acid Sequence↗
PubMed1991

The mouse 5-HT1C receptor contains eight hydrophobic domains and is X-linked.

The neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) exerts diverse physiological effects in the central and peripheral nervous systems and in smooth muscle by interacting with pharmacologically distinct membrane receptors. We report here the cDNA cloning of the mouse 5-HT1C receptor and its functional expression in Xenopus oocytes. This receptor possesses the unusual feature of containing eight hydrophobic domains capable of forming membrane-spanning alpha-helices, contrary to the usual '7-helix' paradigm for other membrane receptors that function through coupling to GTP-binding proteins. By hybridization analysis of Chinese hamster x mouse somatic cell hybrid lines, the gene for the receptor, designated Htr1c, has been assigned to the mouse X chromosome.

Amino Acid Sequence↗
PubMed1990

Cardiomyopathy unrecognized as a cause of hepatic failure.

Two patients with similar symptoms referred for diagnosis and treatment of hepatic failure subsequently proved to have cardiomyopathy as the cause of their hepatic decompensation. Except for fatigue and edema, symptoms of congestive heart failure were absent and no history of dyspnea, orthopnea, or paroxysmal nocturnal dyspnea could be elicited. Hepatomegaly was present in both patients, but neck venous distension and hypotension were not apparent, and both patients were able to lie flat. The diagnosis of cardiomyopathy was made by echocardiogram showing global hypokinesis and low ejection fractions; right atrial pressures were markedly increased. Liver biopsies demonstrated centrilobular necrosis and congestion. Treatment for heart failure led to a prompt response in both patients with rapid return of all hepatic parameters toward normal. Paradoxically, our patients had striking evidence of hepatic failure and a notable absence of symptoms and signs of congestive heart failure. An awareness of this unique presentation may avoid prolonged evaluations in such critically ill patients.

Adult↗
PubMed1990

4-[125I]iodo-(2,5-dimethoxy)phenylisopropylamine and [3H]ketanserin labeling of 5-hydroxytryptamine2 (5HT2) receptors in mammalian cells transfected with a rat 5HT2 cDNA: evidence for multiple states and not multiple 5HT2 receptor subtypes.

Evidence has accumulated indicating that the radioactive hallucinogens 4-bromo-[3H](2,5-dimethoxy)phenylisopropylamine ([3H]DOB) and 4-[125I]iodo-(2,5-dimethoxy)phenylisopropylamine ([125I]DOI) label an agonist high affinity state of the 5-hydroxytryptamine2 (5HT2) receptor and [3H]ketanserin labels both agonist high and low affinity states. Recently, an alternative hypothesis has been put forward proposing that the radioactive hallucinogens are labeling a 5HT2 receptor subtype distinct from the receptor labeled by [3H]ketanserin. In order to provide definitive evidence as to which of these hypotheses is correct, the rat 5HT2 receptor gene was transfected into NIH-3T3 (mammalian fibroblast) cells and COS (green monkey kidney) cells. Neither nontransfected cell type expresses 5HT2 receptors; the transfected cells expressed high affinity binding sites for both [125I] DOI (KD = 0.8 nM and Bmax = 363 fmol/mg in NIH-3T3 cells; KD = 0.2 nM and Bmax = 26 fmol/mg in COS cells) and [3H]ketanserin (KD = 0.4 nM and Bmax = 5034 fmol/mg in NIH-3T3 cells; KD = 1.0 nM and Bmax = 432 fmol/mg in COS cells). The affinities of agonists and antagonists for the [125I]DOI-labeled receptor were significantly higher than for the [3H]ketanserin-labeled receptor. The affinities of agonists and antagonists for these binding sites were essentially identical to their affinities for the sites radiolabeled by these radioligands in mammalian brain homogenates. The [125I]DOI binding was guanyl nucleotide sensitive, indicating a coupling to a GTP-binding protein. These data indicate that the 5HT2 receptor gene product contains both the guanyl nucleotide-sensitive [125I]DOI binding site and the [3H]ketanserin binding site. Therefore, these data indicate that the 5HT2 receptor gene product can produce a high affinity binding site for the phenylisopropylamine hallucinogen agonists as well as for the 5HT2 receptor antagonists. These results strongly support the two-state hypothesis for the 5HT2 receptor and do not support the multiple 5HT2 receptor subtype hypothesis.

Amphetamines↗
PubMed1990

Hepatic infarction associated with eclampsia.

Pregnancy-related liver diseases are complex in presentation and oftentimes confusing to clinicians, leading to misdiagnoses and unwarranted or delayed therapies. The exact pathogenesis of these disorders and their relationship to pre-eclampsia/eclampsia is unclear, thus making categorization difficult. We present a patient who in the third trimester of pregnancy developed severe abdominal pain, fever and transaminases greater than 30 times normal. The patient's laboratory data, abdominal CT scan, abdominal MRI scan, liver-spleen scan and liver biopsy performed 28 days postpartum subsequently confirmed the diagnosis of hepatic infarction. Hepatic infarction is a rare complication of late pregnancy usually associated with severe eclampsia that has distinctive histologic and laboratory findings. Recognition of infarction as a separate entity among the spectrum of the pregnancy-related liver disorders should help avoid unneeded delay in diagnosis or inappropriate treatment of these critically ill patients.

Adolescent↗
PubMed1990

Endoscopic management of biliary fistulas with small caliber stents.

Biliary fistulas have in the past been managed by a variety of methods, including surgical correction or endoscopic sphincterotomy. From 1984 to 1989, we used endoscopic indwelling biliary stents in seven consecutive patients with and without sphincterotomy and have attained fistula closure in all patients studied. The etiologies of the fistulous tracts varied, as did the type and number of stents used. The duration of time between stent placement and observed closure of the fistulous tracts ranged from 3 days to 5 months. Of note, all patients had a dramatic reduction of drainage within the first week. From our study we conclude that surgical correction of biliary fistulas is not required, that sphincterotomy is not mandatory for stent placement or fistula management in patients without distal obstruction, and that a single, small caliber stent alone may be effective.

Biliary Fistula↗
PubMed1989

Distribution of serotonin 5-HT1C receptor mRNA in adult rat brain.

Based on in situ hybridization histochemistry (ISHH), we describe the anatomical distribution of the serotonin 5-HT1C receptor mRNA. In addition to the very high levels in epithelial cells of the choroid plexus, 5-HT1C receptor mRNA is found throughout the limbic system, in catecholaminergic cells and in serotonergic neurons. Receptor transcripts are also present in the hypothalamus, numerous motor nuclei and the subthalamus. Our results correlate well with serotonin (5-HT) innervation and receptor binding. Receptor mRNA is present in many brain structures in addition to regions previously shown to have 5-HT1C receptor binding. The distribution of this receptor mRNA suggests that the 5-HT1C receptor may mediate a number of the central effects of 5-HT.

Animals↗
PubMed1989

Synthesis and in vivo characterization of D-(+)-(N1-[11C]methyl)-2-Br-LSD: a radioligand for positron emission tomographic studies of serotonin 5-HT2 receptors.

D-(+)-N1-Methyl-2-Br-LSD (MBL), which displays high affinity and selectivity for serotonin receptors in vitro, has been labeled with carbon-11 for localization of cerebral serotonin 5-HT2 receptors by positron emission tomography. [11C]MBL was prepared from [11C]iodomethane and D-(+)-2-Br-LSD within 20 min from end of bombardment. The average specific activity of [11C]MBL was 2300 mCi/mumol and the average radiochemical yield was 17%, both at end of synthesis. The in vivo regional distribution of radioactivity in brain after i.v. administration of [11C]MBL to mice paralleled the known density of serotonin 5-HT2 receptors. The maximum specific binding, defined by a frontal cortex to cerebellum radioactivity concentration ratio of 5.4 to 1, was reached 30 min postinjection. Administration of ketanserin, a potent serotonin 5-HT2 receptor antagonist, markedly blocked radioligand binding in all brain regions examined except cerebellum.

Animals↗
PubMed1987

Localization of serotonin 5-HT2 receptors in living human brain by positron emission tomography using N1-([11C]-methyl)-2-Br-LSD.

N1-([11C]-Methyl)-2-Br-LSD ([11C]-MBL) has been developed as a positron emission tomography (PET) imaging agent for serotonin 5-HT2 receptors. In vitro receptor binding assays with nonradioactive MBL show high-affinity binding to serotonin 5-HT2 receptors (Ki = 0.5 nM), a secondary interaction of 8-fold lower affinity with dopamine D2 receptors, and low-affinity interactions with alpha 1-adrenergic as well as serotonin 5-HT1 receptors. Intravenous injection of [11C]-MBL in a baboon led to selective labeling of cortical regions that was markedly blocked by prior administration of ketanserin, a selective 5-HT2 receptor antagonist. Clinical trials with [11C]-MBL have been conducted in seven normal human volunteers, and the regional distribution of radioactivity in the brain was distinctly serotonergic. Labeling was highest in frontal, temporal, and parietal cortex with lower levels observed in caudate and putamen. The tracer rapidly washed from the cerebellum and the low levels of activity in this brain region were used to define nonspecific binding. The maximum specificity was reached between 30 and 60 minutes postinjection when frontal cortex to cerebellum ratios ranged from 1.7 for a 52-year-old male to 2.7 for a 30-year-old male. In agreement with previous studies, a trend towards lower ratios (lower serotonin 5-HT2 receptor levels) was observed in older volunteers. These studies indicate that [11C]-MBL is a selective radioligand that can be used to monitor serotonin 5-HT2 receptor densities in vivo in most regions of the human brain.

Animals↗
PubMed1987

cDNA cloning of a serotonin 5-HT1C receptor by electrophysiological assays of mRNA-injected Xenopus oocytes.

We describe a strategy for the cloning of neurotransmitter-receptor and ion-channel cDNAs that is based on electrophysiological assays of mRNA-injected Xenopus oocytes. This procedure circumvents the purification of these membrane proteins, which is hindered by their low abundance and their hydrophobic nature. It involves methods for RNA fractionation by high-resolution gel electrophoresis, directional cDNA cloning in a single-stranded vector, and screening of the cDNA library by voltage-clamp measurements of currents induced by serotonin in mRNA-injected oocytes. The applicability of our approach is demonstrated by the isolation of a serotonin receptor cDNA clone from a mouse choroid plexus papilloma. The clone was identified by hybrid-depletion and hybrid-selection procedures. The receptor expressed in oocytes injected with hybrid-selected RNA is fully functional, indicating that it is composed of a single subunit encoded by a 5-kilobase RNA. The pharmacology of the hybrid-selected receptor confirms that we have successfully cloned a serotonin 5-HT1C receptor cDNA.

Animals↗
PubMed1987

N1-methyl-2-125I-lysergic acid diethylamide, a preferred ligand for in vitro and in vivo characterization of serotonin receptors.

Methylation of 2-125I-lysergic acid diethylamide (125I-LSD) at the N1 position produces a new derivative, N1-methyl-2-125I-lysergic acid diethylamide (125I-MIL), with improved selectivity and higher affinity for serotonin 5-HT2 receptors. In rat frontal cortex homogenates, specific binding of 125I-MIL represents 80-90% of total binding, and the apparent dissociation constant (KD) for serotonin 5-HT2 receptors is 0.14 nM (using 2 mg of tissue/ml). 125I-MIL also displays a high affinity for serotonin 5-HT1C receptors, with an apparent dissociation constant of 0.41 nM at this site. 125I-MIL exhibits at least 60-fold higher affinity for serotonin 5-HT2 receptors than for other classes of neurotransmitter receptors, with the dopamine D2 receptor as its most potent secondary binding site. Studies of the association and dissociation kinetics of 125I-MIL reveal a strong temperature dependence, with very slow association and dissociation rates at 0 degree C. Autoradiographic experiments confirm the improved specificity of 125I-MIL. Selective labeling of serotonin receptors was observed in all brain areas examined. In vivo binding studies in mice indicate that 125I-MIL is the best serotonin receptor label yet described, with the highest frontal cortex to cerebellum ratio of any serotonergic radioligand. 125I-MIL is a promising ligand for both in vitro and in vivo labeling of serotonin receptors in the mammalian brain.

Animals↗