bluuebunny/crossref_metadata_2025 huggingface dataset:
D3Receptors and the Actions of Neuroleptics in the Ventral Striatopallidal System of Schizophrenics
Authors: JOYCE JEFFREY N. , GUREVICH EUGENIA V.
Published: February 2006

ABSTRACT:The mesolimbic dopamine (DA) system and an important target receptor, the D3receptor, have been implicated in schizophrenia. We have identified, using non‐radioactivein situhybridization histochemistry, that D3mRNA‐positive neurons are highly concentrated in the ventral striatum, efferents of the ventral striatum (globus pallidus internal, ventral palladium, substantia nigra pars reticulata), and in regions projecting to the ventral striatum (medial dorsal thalamus, nucleus basalis, extended amygdala). D3receptors are also highly enriched in the “limbic” striatal‐pallidal‐thalamic loop, exhibiting segregation from the D2receptor‐enriched “motor loop.” This supports data developed in rats showing that the D3receptor is a target of the mesolimbic DA system that can modulate the limbic striato‐palladial‐thalamic loop. However, D2and D3receptors and their mRNAs are co‐localized in many sensory regions (lateral and medial geniculate nuclei, basolateral and basomedial amygdala, regions of thalamus), suggesting mechanisms of cross‐talk. We have also demonstrated that there are 45% elevations in D3receptor number in ventral striatal neurons and their striatopalladial targets in schizophrenics that is reduced by concurrent antipsychotic treatment. Chronic haloperidol treatment to rats for 6 months with a 2‐month withdrawal does not result in elevated D3receptor number. We hypothesize that antipsychotic treatment via D3receptors returns balance to limbic efferents of the ventral striatum. We established that early neonatal damage to the nigrostriatal DA system in rats produces characteristic adaptations in the pre‐ and post‐synaptic components of the mesolimbic DA system that can provide a model to explore regulation by antipsychotics. This includes elevated release of DA from the mesolimbic DA terminals, elevated D3receptor mRNA in the Islands of Calleja and nucleus accumbens, and enhanced behavioral response to psychostimulants.
On Some Clinical Implications of the Ventral Striatum and the Extended Amygdala: Investigations of Aggression
Authors: TRIMBLE MICHAEL R. , VAN ELST LUDGER TEBARTZ
Published: February 2006

ABSTRACT: In this paper, we have first reviewed the animal studies which suggest an association between the amygdala and aggressive behavior. This is followed by a review of the literature of aggression in epilepsy, emphasizing the less controversial peri‐ictal aggressions, with the more controversial assertion that temporal lobe epilepsy in particular is associated with an increase in interictal aggression. We then go on to describe the results of some investigations using the MRI to examine amygdala pathology in a group of patients presenting with affective aggression in comparison with a control group. The main findings are that the patients with aggression tend to have lower IQs and more psychopathology than the control group. There is no difference in amygdala T2 and volumetric assessments between the groups, but a sub‐group of patients are defined with aggression, left‐sided amygdala atrophy, and a history of encephalitis.
Novel Selective Compounds for the Investigation of Imidazoline Receptorsa
Authors: HUDSON A. L. , GOUGH R. , TYACKE R. , LIONE L. , LALIES M. , LEWIS J. , HUSBANDS S. , KNIGHT P. , MURRAY F. , HUTSON P. , NUTT D. J.
Published: February 2006

ABSTRACT: Over several years our group has sought to synthesize and identify selective ligands for imidazoline (I) receptors, in particular the I2 binding site. As a consequence, [3H]2‐(2‐benzofuranyl)‐2‐imidazoline (2BFI) has proved extremely useful for binding and autoradiographic studies. More recently we have synthesized a BU series of compounds and examined these for their affinities for both I1 and I2 binding sites. BU224 (2‐(4,5‐dihydroimidaz‐2‐yl)‐quinoline) shows high affinity for I2 receptors with a Ki of 2.1 nM. BU226 (2‐(4,5‐dihydroimidaz‐2‐yl)‐isoquinoline) demonstrated slightly higher affinity (Ki 1.4 nM) for I2 receptors, but overall BU224 displayed greater selectivity for I2 over I1 receptors (832‐fold) than BU226 (380‐fold). Both compounds showed low (μM) affinity for α2‐adrenoceptors. Given BU224's ability to cross the blood brain barrier, we predict that its in vivo effects are likely to be mediated via I2 receptors. Brain dialysis revealed BU224 to dose dependently (0–20 mg/kg ip) elevate basal noradrenaline in rat frontal cortex and basal dopamine in striatum. In a rat model of opiate withdrawal, behavioral studies showed that BU224 (10 mg/kg, sc) was able to reduce acute weight loss and diarrhea, but not the number of wet dog shakes associated with the withdrawal syndrome.
Identification of I1 and I2 Imidazoline Receptors in Striatum Membranes from Different Speciesa
Authors: VAUQUELIN GEORGES , DE BACKER JEAN‐PAUL , LADURE PHILIPPE , FLAMEZ ANJA
Published: February 2006

ABSTRACT: The α2‐adrenergic agonist [3H]clonidine and antagonist [3H]idazoxan also label I1 and I2 imidazoline receptors in striatum membranes. They are investigated here in striata from the dog, rat, mouse, rabbit, calf, monkey, and human. I1 receptors were barely detected in the dog, rat, and mouse and only further examined by competition binding experiments in calf, rabbit, and human. I2 receptors were further examined in all species. The centrally acting vasodilators clonidine and rilmenidine were more potent than moxonidine at the I1 receptors. They displayed low potency for the I2 receptors in all species except the rat. In all species examined, the nonsubstituted imidazoline derivatives idazoxan and RX801077 displayed high affinity for the I1 and I2 receptors. Conversely, both stereoisomers of the alkoxy‐substituted imidazoline‐derivative efaroxan displayed low affinity. The matching binding characteristics of these compounds further stress the structural similarity of the ligand binding sites of I1 and I2 receptors.
Pharmacologic and Molecular Discrimination of I2‐Imidazoline Receptor Subtypesa
Authors: OLMOS GABRIEL , ALEMANY REGINA , BORONAT M. ASSUMPCIÓ , GARCÍA‐SEVILLA JESÚS A.
Published: February 2006

ABSTRACT: I2‐imidazoline receptors (I2‐IR) are characterized by their high affinity for imidazolines and guanidines and medium affinity for imidazolidines. The differential recognition of I2‐IR by amiloride led to subtype these sites as amiloride‐sensitive (I2A ‐IR) and amiloride‐insensitive (I2B‐IR). I2‐IR labeled with [3H] cbidazoxan or [3H]2‐BFI in the rabbit cerebral cortex (I 2A ‐IR) displayed higher affinities for amiloride and amiloride analogs than in the rat cerebral cortex (I2B‐IR). Other drugs tested displayed biphasic curves in competition experiments, indicating the existence of high and low affinity sites for both I2‐IR subtypes. The drugs (+)‐ and (−)‐medetomidine, bromoxidine, moxonidine, and clorgyline were more potent on the high and/or low affinity sites of I2B‐IR than on I2A‐IR. Preincubation (30 min at 25°C) with 10 −6 M isothiocyanatobenzyl imidazoline (IBI) or with 10−6 M clorgyline reduced by 40% and 26%, respectively, the binding of [3H]‐BFI to I2B‐IR, but it did not alter the binding of the radioligand to I2A‐IR. These results indicated that the I2‐IR subtypes differ in their pharmacologic profiles and in the nature of the imidazoline binding site involved in clorgyline and IBI alkylation. In rat cortical membranes, western blot detection of immunoreactive imidazoline receptor proteins revealed a double band of ∼29/30 kD and three less intense bands of ∼45, ∼66, and ∼85 kD. In rabbit cortical membranes the antibody detected proteins of ∼30, ∼57, ∼66, and ∼85 kD. It is suggested that I2‐IR may be related to more than one receptor protein and that I2‐IR subtypes differ in the nature of the proteins implicated.
Presynaptic Imidazoline Receptors: New Developments in Characterization and Classificationa
Authors: GÖTHERT M. , BRÜSS M. , BÖNISCH H. , MOLDERINGS G. J.
Published: February 2006

ABSTRACT: Presynaptic imidazoline receptors (IRs) which inhibit norepinephrine (NE) release from sympathetic nerve endings have been identified in cardiovascular tissue of man, rabbit, rat, and guinea pig. They do not belong to one of the classical presynaptic inhibitory receptor classes such as α2‐adrenoceptors or H3 histamine receptors, and there is also no relation to I1‐ and I2‐imidazoline binding sites. Segments of human right atrial appendages preincubated with [3H]NE were used to determine unknown pharmacologic properties of the presynaptic IRs. In the presence of 1 μM rauwolscine, S23230, the (−)‐enantiomer of the racemic oxazoline derivative S22687 (5‐(2(methyl‐phenoxy‐methyl)‐1,3‐oxazoline‐2‐yl)amine) exhibited low potency in inhibiting the electrically evoked [3H]NE release (pIC30%= 4.96), whereas the (+)‐enantiomer S23229 and the racemate S22687 were ineffective. The IR‐mediated inhibitory effect of the imidazoline BDF 6143 (4‐chloro‐2‐(2‐imidazolin‐2‐ylamino)‐isoindoline) and the guanidine aganodine on evoked [3H]NE release from sympathetic nerves in human atrial appendages was counteracted by rauwolscine (with very low potency) and by the cannabinoid CB1‐receptor antagonist SR141715A (N‐[piperdin‐1‐yl]‐5‐[4‐chlorophenyl]‐2,4‐dichlorophenyl]‐4‐methyl‐1H‐pyrazole‐3‐carboxamide). The inhibitory effect of moxonidine on evoked [3H]NE release (which is exclusively mediated via activation of α2‐autoreceptors) was antagonized with high potency by rauwolscine, but not by SR141716A. The cannabinoid CB1 receptor agonists CP55,940([(−)‐Cis‐3‐[2‐hydroxy‐4‐(1,1‐dimethylheptyl)phenyl]‐trans‐4‐(3‐hydroxy‐propyl)cyclohexane]) and anandamide inhibited evoked [3H]NE release. Inhibition by CP55,940 and anandamide was abolished by 1 μM SR141716A as well as by 30 μM rauwolscine. In radioligand binding experiments on membranes from human atrial appendages (α2‐and σ‐binding sites were masked), cannabinoid receptor ligands and IR agonists displaced the radiolabeled guanidine derivative [3H]DTG (1,3‐di‐o‐tolyguanidine, an agonist at presynaptic IRs) from its binding sites. Comparison of the potencies of these drugs determined in the competition experiments with [3H]DTG with those in inhibiting NE release via activation of the presynaptic IRs in the same tissue revealed a correlation. The present results suggest, e.g., that the presynaptic IRs may have certain binding domains in common with presynaptic cannabinoid receptors or that both receptors are different proteins which interact with each other in an unknown manner.
Imidazolines and Pancreatic Hormone Secretiona
Authors: MORGAN NOEL G. , CHAN SUE L. F. , MOURTADA MIRNA , MONKS LARA K. , RAMSDEN CHRISTOPHER A.
Published: February 2006

ABSTRACT: A range of imidazoline derivatives are known to be effective stimulators of insulin secretion, and this response correlates with closure of ATP‐sensitive potassium channels in the pancreatic β‐cell. However, mounting evidence indicates that potassium channel blockade may form only part of the mechanism by which imidazolines exert their effects on insulin secretion. Additionally, it remains unclear whether members of this class of drugs can bind directly to potassium channel components and whether occupation of a single binding site accounts for their functional activity. This review considers recent developments in the field and highlights evidence that does not fit readily with the concept that a single mechanism of action is sufficient to mediate the effects of imidazolines on pancreatic hormone secretion.
Imidazolines and the Pancreatic B‐Cell: Actions and Binding Sites
Authors: RUSTENBECK I. , KÖPP M. , RATZKA P. , LEUPOLT L. , HASSELBLATT A.
Published: February 2006

ABSTRACT: Stimulation of insulin secretion by imidazoline compounds displays variable characteristics. Phentolamine (10–100 μM) increased secretion of perifused mouse islets at nonstimulatory glucose concentrations (5 mM) and even in the absence of glucose. Idazoxan (20–100 μM) elicited a moderate increase in insulin secretion, which required the presence of a stimulatory glucose concentration (10 mM). Phentolamine is therefore a stimulator of secretion in its own right, whereas idazoxan may be termed an enhancer of secretion. Both compounds inhibited the activity of ATP‐dependent K+ channels in inside‐out patches from B‐cells; however, idazoxan achieved only an incomplete block. Both compounds depolarized the B‐cell plasma membrane to an extent that permitted the opening of voltage‐dependent Ca2+ channels (−40 to −30 mV). An increase in cytoplasmic Ca2+ concentration was induced by phentolamine and much less so by idazoxan. Activation of protein kinase C, a possible mechanism to amplify Ca2+‐induced secretion, could not be verified for phentolamine. It thus appears that stimulation of insulin secretion by phentolamine is due to its blocking effect on KATP channels, which may be the correlate of non‐adrenergic imidazoline binding sites which were characterized in insulin‐secreting HIT cells. Whether incomplete closure of KATP channels by idazoxan or additional effects are responsible for the requirement of high glucose to stimulate secretion remains to be clarified.
Different Modes of Action of the Imidazoline Compound RX871024 in Pancreatic β‐Cells: Blocking of K+ Channels, Mobilization of Ca2+ from Endoplasmic Reticulum, and Interaction with Exocytotic Machinerya
Authors: ZAITSEV S. V. , EFANOV A. M. , RAAP A. , EFANOVA I. B. , SCHLOOS J. , STECKEL‐HAMANN B. , LARSSON O. , ÖSTENSON C.‐G. , BERGGREN P.‐O. , MEST H.‐J. , EFENDIC S.
Published: February 2006

ABSTRACT: The imidazoline compound RX871024 glucose‐dependently potentiates the release of insulin in pancreatic islets and β‐cell lines. This activity of the compound is not related to its action by stimulating α2‐adrenoceptors and I1‐ and I2‐imidazoline receptors. There are at least three modes of action of RX871024 in β‐cells: (1) RX871024 blocks the ATP‐dependent, Ca+‐activated, and delayed rectifier K+ channel activity; (2) RX871024 causes mobilization of Ca2+ from thapsigargin‐sensitive intracellular stores, the effect probably controlled by cytochrome P450; and (3) the stimulatory activity of RX871024 on insulin release involves interaction of the compound with the exocytotic machinery, unrelated to the changes in membrane potential and cytoplasmic‐free Ca2+ concentration, whereas protein phosphorylation plays an important role in this process. The maximal insulinotropic effect of RX871024 is much higher than that of the sulfonylurea glibenclamide. RX871024 stimulates insulin release and normalizes blood glucose levels in rats in vivo without affecting blood pressure and heart rate.
Participation of Imidazoline Receptors and Alpha2−‐Adrenoceptors in the Central Hypotensive Effects of Imidazoline‐Like Drugs
Authors: BOUSQUET P. , BRUBAN V. , SCHANN S. , GRENEY H. , EHRHARDT J. D. , DONTENWILL M. , FELDMAN J.
Published: February 2006

ABSTRACT: The central hypotensive effect of imidazoline‐like drugs (IMs) involves non‐adrenergic imidazoline receptors (IRs). IMs cause hypotension irrespective of their affinity and selectivity for one or the other α‐adrenoceptor subtypes. LNP 509, which binds to I1Rs (Ki= 5.10−7 M) but roughly not to α2‐adrenoceptors (A2Rs) (Ki >10−5 M), causes hypotension when injected alone into the brainstem. As far as hybrid drugs, that is, those with mixed binding profiles (I1/α2), are concerned, a significant correlation was reported between their central hypotensive effect and their affinity for IRs. Imidazoline antagonists such as idazoxan competitively antagonized the centrally induced hypotensive effect of IMs. Yohimbine, an A2Rs antagonist, blocks the hypotensive effect of hybrids but usually in a noncompetitive manner. Mutation of A2Rs prevented the hypotensive effects of drugs highly selective for A2Rs, but also that of hybrids such as clonidine. These data indicate that triggering of the hypotensive effects of IMs (1) needs implication of IRs; (2) appears to be facilitated by additional activation of A2Rs; and (3) requires integrity of A2Rs along the sympathetic pathways.
Novel Targets and Techniques in Imidazoline Receptor Researcha
Authors: MUSGRAVE IAN F. , HUGHES RICHARD A.
Published: February 2006

ABSTRACT:Imidazoline binding sites are now generally accepted as being receptors. Despite this acceptance, the molecular structure and signal transduction mechanisms of these receptors are still poorly understood. The I1‐imidazoline binding site (I1‐receptor) is localized to the plasma membrane, but it is not clear if this represents a conventional receptor. It is also not clear if there are multiple forms of the I1‐receptor. The signal transduction mechanisms of I1‐receptors are similarly unclear, but much progress has been made. Evidence clearly indicates that ligands with high affinity for I1‐receptors stimulate a novel signal transduction pathway, phosphatidylcholine‐selective phospholipase C, in the rat adrenal medullary tumor cell line PC‐12. However, this may not be the case in all cell types as microphysiometry, a novel technique for determining cellular activation, could not detect receptor activation in cultured bovine adrenal medullary cells exposed to a number of imidazolines considered to be agonists at the I1‐receptor. This suggests that there is no I1‐receptor mediated stimulation of phosphatidylcholine‐specific phospholipase C in these cells. By contrast, nicotine‐stimulated increases in ion entry were blocked by clonidine. Ion channels have been suggested as another possible I1‐imidazoline “receptor” family and may represent the low affinity I1‐receptor. I1‐Receptor ligands can be shown to bind to, or block, the following members of the ligand‐gated ion channel super family, the 5HT3, K+ATP, NMDA, and nicotinic acetylcholine receptors. The site of action appears to be the phencyclidine binding site in these channels, but other possibilities cannot be excluded. Molecular modeling suggests that I1‐receptor selective ligands share a common three‐dimensional structure with phencyclidine, providing a basis for these actions. This suggests that a phencyclidine‐binding site motif may represent a novel site of action for I1‐receptor ligands and that searches for receptors based on this motif may reveal novel imidazoline “receptors.”
Modulation of MAO Activity by Imidazoline and Guanidine Derivatives
Authors: RAASCH W. , MUHLE H. , DOMINIAK P.
Published: February 2006

ABSTRACT: I2‐binding sites (I2‐BS) are attributed to be a regulative site on monoamine oxidase (MAO). The in vivo and in vitro effects of various imidazoline and guanidine derivatives on MAO activity and on mitochondrial respiration were studied. Substances with high affinity for I2‐BS (antazoline, idazoxan, and cirazoline: IC50= 20.3, 33.8, and 43.4 μM) had a stronger inhibitory effect on MAO activity than did I1‐ligands (efaroxan, rilmenidine, clonidine, and moxonidine: IC50= 277, 801, 1,224, and >10,000 μM). Substances with the highest inhibitory effects were BDF8082 (IC50= 1.7 μM) and 2‐(2‐benzofuranyl)‐2‐imidazoline (BFI; IC50= 4.0 μM). The enzyme is inhibited noncompetitively and is reversible, because its activity is completely or partially restored after dialysis. Agmatine, the putative endogenous ligand for IBS, also decreased MAO activity (IC50= 168 μM), whereas its precursor, l‐arginine, and its metabolite, putrescine, had no effects. In vitro inhibition of MAO and mitochondrial respiration by the IBS‐ligands tested could not be correlated, suggesting no link between the function of the inner and outer mitochondrial membrane. MAO activity in vivo was significantly reduced only by pargyline (−95%), BDF8082 (−68%), BFI (−43%), and 1‐(m‐chlorophenyl)‐biguanide (−28%). Catecholamine content of livers obtained from animals treated with different IBS‐ligands was consequently increased. In conclusion, the strong inhibitory effects of I2 selective imidazoline ligands confirm the existence of I2‐BS as a regulatory site on MAO.
Moxonidine Acting Centrally Inhibits Airway Reflex Responsesa
Authors: HAXHIU MUSA A. , DRESHAJ ISMAIL A. , McFADDEN CHRISTOPHER B. , EROKWU BERNADETTE O. , ERNSBERGER PAUL
Published: February 2006

ABSTRACT: We examined the role of I1‐imidazoline (I1‐IR) receptors in control of airway function, by testing the effects of systemic administration of the I1‐IR agonist moxonidine on reflex responses of tracheal smooth muscle (TSM) tone to either lung deflation or mechanical stimulation of intrapulmonary rapidly adapting receptors. Experiments were performed in either α‐chloralose anesthetized or decorticate, paralyzed, and mechanically ventilated beagle dogs. Moxonidine (10 ‐ 100 μg/kg) administered via three different routes (femoral vein, muscular branch of superior thyroid artery, and vertebral artery) attenuated TSM responses to stimulation of airway sensory nerve fibers by two different ways and caused a decrease in arterial pressure and heart rate. These effects were dose dependent and were significantly reversed by efaroxan (an I1‐IR and α2‐adrenergic blocker) administered via the vertebral artery. Intravertebral efaroxan abolished the hemodynamic effects of moxonidine. Intravenous moxonidine (10 ‐ 100 μg/ kg) did not alter airway smooth muscle responses to electrical stimulation of the peripheral vagus nerve. In addition, in vitro moxonidine (1 ‐ 100 μg/ml) had no effect on contractile responses to increasing doses of acetylcholine. These findings indicate that moxonidine may act at a central site to suppress reflex airway constriction, even when given into the systemic circulation. Given the presence of I1‐IR sites and α2‐adrenergic receptors in brain regions participating in airway reflexes, these receptor classes may be involved in brainstem control of the cholinergic outflow to the airways.
Telomerase: A Target for Anticancer Therapy
Authors: LICHTSTEINER SERGE P. , LEBKOWSKI JANE S. , VASSEROT ALAIN P.
Published: February 2006

Abstract: Telomerase is absent in most normal tissues, but is abnormally reactivated in all major cancer types. Telomerase enables tumor cells to maintain telomere length, allowing indefinite replicative capacity. Albeit not sufficient in itself to induce neoplasia, telomerase is believed to be necessary for cancer cells to grow without limit. The presence of telomerase has been detected in virtually all cancer types including the most prevalent cancers of the prostate, breast, lung, colon, bladder, uterus, ovary, and pancreas as well as in lymphomas, leukemias, and melanomas. In addition, data from cancer patients indicate that telomerase levels correlate with clinical outcome in neuroblastomas, leukemias, and prostate, gastric, and breast cancers. Studies using an anti‐sense to the human telomerase RNA component demonstrate that telomerase in human tumor lines can be blocked ex vivo. In these experiments, telomerase inhibition led to telomere shortening and cancer cell death, validating telomerase as a target for anticancer therapy. Telomerase is a uniquely appealing target for drug discovery because its dichotomic expression in normal versus cancer cells suggests that no serious side effects would result from a treatment abrogating telomerase activity. A variety of approaches to telomerase inhibition are being investigated and are discussed.
Trichostatin and Leptomycin: Inhibition of Histone Deacetylation and Signal‐Dependent Nuclear Export
Authors: YOSHIDA MINORU , HORINOUCHI SUEHARU
Published: February 2006

Abstract: Trichostatin A (TSA), an inhibitor of the eukaryotic cell cycle and an inducer of morphological reversion of transformed cells, inhibits histone deacetylase (HDAC) at nanomolar concentrations. Recently, trapoxin, oxamflatin, and FR901228, antitumor agents structurally unrelated to TSA, were found to be potent HDAC inhibitors. These inhibitors activate expression of p21Waf1 and 16INK4A in a p53‐independent manner. Changes in the expression of these cell cycle regulators by an increase in histone acetylation may be responsible for cell cycle arrest and antitumor activity by HDAC inhibitors. The target molecule of leptomycin B (LMB), a potent antitumor agent, was genetically and biochemically identified as CRM1, a protein reported as being required for chromosome structure control. We showed that CRM1 was a receptor for the nuclear export signal (NES) and that LMB inhibited nuclear export of proteins. Using LMB, we identified a novel NES in fission yeast transcription factor Pap1, the function of which is abolished by oxidative stress in a manner conserved in eukaryotes.
The Dual Role of Cytoskeletal Anchor Proteins in Cell Adhesion and Signal Transduction
Authors: BEN‐ZE'EV AVRI
Published: February 2006

Abstract: β‐Catenin and plakoglobin are homologous proteins having a dual role in cell adhesion and in transactivation together with LEF/TCF transcription factors. Overexpression of plakoglobin suppresses tumorigenicity, whereas increased β‐catenin levels are considered oncogenic. We compared the nuclear translocation and transactivation by β‐catenin and plakoglobin. Overexpression of each protein resulted in nuclear translocation and formation of structures that also contained LEF‐1 and vinculin with β‐catenin, but not with plakoglobin. Transfection of LEF‐1 translocated endogenous β‐catenin, but not plakoglobin into the nucleus. Chimeras of the Gal4 DNA‐binding domain and the transactivation domains of either plakoglobin or β‐catenin were equally potent in transactivation, but induction of LEF‐1‐responsive transcription was higher with β‐catenin. Overexpression of wt plakoglobin or mutant β‐catenin lacking the transactivation domain induced nuclear accumulation of the enodogenous β‐catenin and LEF‐1‐responsive transactivation. The nuclear localization and constitutive β‐catenin‐dependent transactivation in SW480 cancer cells were inhibited by overexpressing cadherin or α‐catenin. Moreover, transfecting the cytoplasmic tail of cadherin inhibited transactivation, by competition with LEF‐1 in the nucleus for β‐catenin binding. The results indicate that (1) plakoglobin and β‐catenin differ in nuclear translocation and complexing with LEF‐1 and vinculin, (2) LEF‐1‐dependent transactivation is mainly driven by β‐catenin, (3) cadherin and α‐catenin can sequester β‐catenin, inhibit its transcriptional activity, and antogonize its oncogenic action.
Cytoskeletal Tumor Suppressors That Block Oncogenic RAS Signaling
Authors: MARUTA HIROSHI , HE HONG , TIKOO ANJALI , NUR‐E‐KAMAL MSA
Published: February 2006

Abstract: Several distinct peptides or drugs that block the Rho family GTPases‐mediated pathways were found to suppress RAS‐induced malignant phenotype. They include (1) C3 enzyme that selectively inactivates Rho, (2) ACK42, a peptide that blocks the interaction of CDC42 with its effectors such as ACKs, (3) PAK18, a peptide that blocks the activation of PAK and membrane ruffling, and (4) actin‐binding drugs, chaetoglobosin K (CK) and MKT‐077, that block membrane ruffling by capping and bundling actin filaments, respectively.
Immunotherapy of Cancer
Authors: JAFFEE ELIZABETH M.
Published: February 2006

Abstract: The goal of cancer treatment is to develop modalities that specifically target tumor cells, thereby avoiding unnecessary side effects to normal tissue. Vaccine strategies that result in the activation of the immune system specifically against proteins expressed by a cancer have the potential to be effective treatment for this purpose. An early vaccine approach that was developed by our group involves the insertion of the granulocyte‐macrophage colony stimulating factor (GM‐CSF) gene into cancer cells that are then used to immunize patients. These genetically modified tumor cells produce the immune activating protein GM‐CSF in the local environment of the tumor cells, specifically activating the patient's T cells to eradicate cancer at metastatic sites. We have performed many studies that demonstrate that this vaccine can cure mice of cancer. We recently demonstrated that this approach can activate an immune response in patients with renal cell carcinoma. We are currently testing a similar approach in patients with pancreatic cancer. Until recently, whole tumor cells were used to produce the vaccine because the proteins expressed by the tumor cells that can be recognized by the immune system were unknown. However, recent advances have allowed the identifiation of many of the proteins expressed by some cancers. In addition, significant attention has been focused on the mechanisms by which antitumor immunity can be modulated. These active areas of research will undoubtably lead to the devleopment of more specific and more potent vaccine strategies in the near future. The first part of this paper focuses on data from two recent clinical trials that evaluated the whole tumor cell approach. The second part of this paper discusses some of the more exciting antigen‐specific vaccine approaches that are under development for the treatment of cancer.
Bacterial Toxins Inhibiting or Activating Small GTP‐Binding Proteins
Authors: BOQUET PATRICE
Published: February 2006

Abstract: Amino acids located on the switch 1 or switch 2 domains of small GTPases of the Ras and Rho family are targets of several bacterial toxins. Exoenzyme C3 from Clostridium botulinum ADP‐ribosylates specifically Rho at R43 and prevents the recruitment of Rho on the cell membrane. This blocks the downstream effects of the Rho GTPase. However, exoenzyme C3 is not a toxin, and chimeric proteins fusing C3 with the B moiety of either diphtheria toxin or Pseudomonas aeruginosa exotoxin A have been produced to intoxicate cells with low concentration of C3. C. difficile toxin B modifies by glucosylation Rho on T37 and Rac and Cdc42 on T35. Glucosylation of Rho, Rac, and Cdc42 blocks the binding of these GTPases on their downstream effectors. C. sordellii lethal toxin modifies Ras, Rap, and Rac on T35 by glucosylation. Cytotoxic necrotizing factor 1 (CNF1), from uropathogenic Escherichia coli strains, deamidates Q63 of Rho into E63, thereby blocking the intrinsic or GAP‐mediated GTPase of Rho. This allows permanent activation of Rho. Thus, Rho GTPases are targets for three different toxin activities. Molecular mechanisms of these toxins are discussed.
Selective Inhibition of ras‐Transformed Cell Growth by a Novel Fatty Acid‐Based Chloromethyl Ketone Designed to Target Ras Endoprotease
Authors: CHEN YULONG
Published: February 2006

A novel fatty acid‐based chloromethyl ketone, UM96001, which was designed to be a Ras C‐terminal sequence‐specific endoprotease inhibitor, at low micromolar concentrations (1 ∼ 5.0 μM), potently inhibits ras‐transformed rat kidney cell growth, whereas the growth of untransformed normal rat kidney cells is not affected under the same conditions. UM96001 almost completely blocks the anchorage‐independent clonogenic growth of ras‐transformed rat and human cancer cells at low micromolar concentrations. Inhibition of ras‐transformed rat and human cancer cell growth by UM96001 may occur via the mechanism of selective induction of apoptosis of the cells. Furthermore, TPCK and BFCCMK, the known selective inhibitors of Ras C‐terminal sequence‐specific endoprotease, also yield similar inhibition results. These results provide the first experimental evidence that the endoproteolysis of Ras oncoproteins may be important for Ras‐mediated cell growth and apoptosis. Therefore, the Ras C‐terminal sequence‐specific endoprotease may be a potential anticancer target.
Azatyrosine: Mechanism of Action for Conversion of Transformed Phenotype to Normal
Authors: MONDEN YOSHIAKI , HAMANO‐TAKAKU FUMIE , SHINDO‐OKADA NOBUKO , NISHIMURA SUSUMU
Published: February 2006

Abstract: Azatyrosine [L‐β‐(5‐hydroxy‐2‐pyridyl)‐alanine] has the unique property of converting ras‐ or c‐erbB‐2 transformed phenotype to normal. The administration of azatyrosine also inhibits tumor formation in transgenic mice harboring the normal human c‐Ha‐ras which is mutated during treatment with various chemical carcinogens. To elucidate the molecular mechanism, we investigated how azatyrosine functions and what are its major targets. Azatyrosine functions downstream of ras; azatyrosine does not alter either the level of GTP‐bound Ras or the total amount of Ras. Instead, azatyrosine inhibits the activation of c‐Raf‐1 kinase by oncogenic c‐ErbB‐2, resulting in inactivation of AP1. It is interesting that azatyrosine also restores the expression of the rhoB gene, the product of which regulates the formation of actin stress fibers. Azatyrosine is incorporated into cellular proteins to replace tyrosine. Several experiments indicate that replacement of tyrosine is likely to be a cause for its conversion of ransformed phenotype to normal. To prove this hypothesis, we are attempting to develop a mutant of tyrosyl‐tRNA synthetase that, unlike wild type, can aminoacylate azatyrosine more efficiently than can tyrosine.
Application of Linear Circuit Models to Impedance Spectra in Irradiated Musclea
Authors: OSTERMAN K. SUNSHINE , PAULSEN KEITH D. , HOOPES P. JACK
Published: February 2006

Abstract: We have applied a number of modeling schemes to previously reported in vivo electrical impedance measurements on irradiated and normal muscle in the hind legs of rats. Specifically, seven‐parameter parallel pathways and embedded membrane circuit models have been fit to group averages of impedance spectra measured at different doses and time points. Correlations between histologically scored tissue sections and model parameters have also been determined. The results show that both models produce good fits to the experimental observations, especially in the case of the irradiated tissues. The correlations between histology scores and circuit parameters were, however, higher with the embedded model. Trends in the spectra and the model parameters were found to agree with the expected changes in tissue pathophysiology associated with the progression of tissue injury from radiation exposure. Quantitative correlations with specific histological criteria were less conclusive, suggesting that more information may be needed to refine the model architecture if model parameters are to be explicitly related to the types and extent of tissue damage induced by radiation treatments.
Ex Vivo Discrimination between Normal and Pathological Tissues in Human Breast Surgical Biopsies Using Bioimpedance Spectroscopy
Authors: CHAUVEAU N. , HAMZAOUI L. , ROCHAIX P. , RIGAUD B. , VOIGT J. J. , MORUCCI J. P.
Published: February 2006

Abstract: Ex vivo bioimpedance data measured on normal and cancerous female breast tissues are reported. They clearly show that the electrical properties of normal tissues, surrounding tissues, and carcinoma are different. These differences lie in the conductivity, in the characteristic frequency (frequency of the maximum of the imaginary part of the bioimpedance), and also in the shape of the Bode plots. Modeling using an R‐S‐Zcpe model is reported as well as indexes extracted from the real and imaginary parts of the bioimpedance. Even if a classification of the different types of tissues remains a difficult task and leads to much less precise diagnosis than microscopic examination, the electrical behavior of mammary tissue could be used to develop a noninvasive technique for early breast cancer detection.
Dielectric Properties of Skeletal Muscle during Ischemia in the Frequency Range from 50 Hz to 200 MHz
Authors: SCHÄFER M. , KIRLUM H.‐J. , SCHLEGEL C. , GEBHARD M. M.
Published: February 2006

Abstract: The complex dielectric properties of canine skeletal muscles were measured at 25 °C during ischemia in the frequency range from 50 Hz to 200 MHz. The dielectric spectrum of skeletal muscle shows an α‐dispersion below 1 kHz and a β‐dispersion with a relaxation frequency of about 100 kHz. The α‐dispersion disappears between 450 and 500 min of ischemia time, the same time during which mechanical contraction was observed, and was restored later. During ischemia, the β‐dispersion is shifted continuously to higher frequencies; and at frequencies above 50 MHz, a decrease of the real part of the dielectric permittivity was measured. The dielectric loss factor decreases during ischemia at frequencies below 500 kHz, only interrupted by a short increase, coinciding with the disappearance of the α‐dispersion. The principal processes that happen during ischemia inside the skeletal muscle tissues were studied with the help of a model especially designed to simulate membrane effects on the dielectric spectrum. The disappearance of the α‐dispersion is explained by an increase of conductivity in the membrane of the sarcoplasmic reticulum. Shifting β‐dispersion to higher frequencies is a result of metabolically produced ions and therefore increasing conductivity of the intracellular medium. Decreasing dielectric permittivity at frequencies above 50 MHz and decreasing dielectric loss factor at low frequencies are caused by the cell edema.
Study of the Relation between Fluid Distribution Change in Tissue and Impedance Change during Hemodialysis by Frequency Characteristics of the Flowing Blood
Authors: SAKAMOTO K. , SUNAGA R. , NAKAMURA K. , SATO Y. , FUJII M. , KANAI H. , TSUCHIDA T. , UENO A. , KANAI N. , HASEGAWA K.
Published: February 2006

Abstract: Erythrocyte orientation and deformation cause differences in impedance between flowing and resting blood. Through theoretical calculation and experimental measurements, we studied the effects of these factors on blood impedance. The size and shape of the erythrocyte and the conductivity of the interior medium of the erythrocyte change when the osmotic pressure of plasma is changed. From experimental results, we obtained the following: when the size of the erythrocyte becomes larger than the normal size due to the osmotic pressure change, the β dispersion frequency decreases and the intra‐ and extracellular fluid resistance increase. These experimental results corroborate that the change of tissue impedance like muscle impedance during hemodialysis is caused by the change of the fluid distribution and the change of ionic concentration of the electrolyte in tissues during hemodialysis. Also, we could estimate the relative change value of the intra‐ and extracellular fluid volume by the impedance method, if there were no ionic concentration change in the electrolyte. It would be very difficult to estimate the absolute change value of them because a shadow effect due to the cells depends greatly upon the shape and size of the cells and the cell concentration.
Bioimpedance: Is It a Predictor of True Water Volume?
Authors: THOMAS B. J. , CORNISH B. H. , WARD L. C. , JACOBS A.
Published: February 2006

Abstract: Bioelectrical impedance analysis (BIA) has been reported to be insensitive to changes in water volumes in individual subjects. This study was designed to investigate the effect on the intra‐ and extracellular resistances (Ri and Re) of the segments of subjects for whom body water was changed without significant change to the total amount of electrolyte in the respective fluids. Twelve healthy adult subjects were recruited. Ri and Re of the leg, trunk, and arm of the subjects were determined from BIA measures prior to commencement of two separate studies that involved intervention, resulting in a loss/gain of body water effected either by a sauna followed by water intake (study 1) or by ingestion (study 2). Ri and Re of the segments were also determined at a number of times following these interventions. The mean change in body water, expressed as a percentage of body weight, was 0.9% in study 1 and 1.25% in study 2. For each study, the results for each subject were normalized for each limb to the initial (prestudy) value and then the normalized results for each segment were pooled for all subjects. ANOVA of these pooled results failed to demonstrate any significant differences between the normalized mean values of Ri or Re of the segments measured through the course of each study. The failure to detect a change in Ri or Re is explained in terms of the basic theory of BIA.
Measurement of Leg Arterial Compliance of Normal Subjects and Diabetics Using Impedance Plethysmography
Authors: KIM DEOK WON , KIM SOO CHAN
Published: February 2006

Abstract: In this study, compliance, a mechanical characteristic of the lower leg arteries, was measured noninvasively. Changes in blood volume and pressure were measured using impedance plethysmography and a mercury sphygmomanometer, respectively. Compliance was calculated by dividing the change in blood volume by the change in pulse pressure (systolic‐diastolic pressure). Subjects were 24 asymptomatic persons ranging from 30 to 58 years and 14 diabetics ranging from 41 to 59 years. Peak compliance, mean pressure, and systolic pressure were statistically analyzed using a t test between the asymptomatic and diabetic groups. The average peak compliance of the asymptomatic and diabetic groups was measured as 2.79 and 1.82 μL/mmHg/cm, respectively, and these were significantly different (p < 0.01). It was also found that compliance is a better parameter in differentiating vascular disease than the mean or systolic blood pressure.
Towards a Theoretical Understanding of Stroke Volume Estimation with Impedance Cardiographya
Authors: FAES TH. J C. , RAAIJMAKERS E. , MEIJER J. H. , GOOVAERTS H. G. , HEETHAAR R. M
Published: February 2006

Abstract: In electrical impedance cardiography, Kubicek's formula is often used to measure stroke volume from thoracic impedance variations synchronously to heart activity. To calculate stroke volume from impedance variations, the so‐called outflow problem should be adequately solved. This outflow problem refers to the joint causes of impedance change due to blood entering the aorta from the heart, as well as blood leaving the aorta due to arterial runoff. The aim of this study was to investigate the Kubicek formula as a solution of the outflow problem. Kubicek's formula was theoretically investigated using a simple model of the volume‐conducting properties of the thorax (two‐cylinder model), as well as the hemodynamics of the systemic circulation (three‐element “windkessel” model). The mathematical analysis showed that the outflow problem was not solved by the Kubicek formula. Moreover, this theoretical result was experimentally confirmed.
Impedance Stroke Volume Compared with Dye and Electromagnetic Flowmeter Values during Drug‐Induced Inotropic and Vascular Changes in Dogs
Authors: PATTERSON ROBERT P. , WITSOE DAVID A. , FROM ARTHUR
Published: February 2006

Abstract: Stroke volumes measured by impedance were compared with values obtained by dye dilution and an electromagnetic flowmeter (EMF) on 14 dogs during drug‐induced changes in cardiac contraction strength and peripheral resistance changes. Grouping all data for a total of 305 points showed correlations between dye and EMF, dye and impedance, and EMF and impedance of 0.89, 0.68, and 0.72, respectively. Correlations for individual dogs between dye and EMF, dye and impedance, and EMF and impedance ranged from 0.60 to 0.99, −0.39 to 0.96, and −0.26 to 0.89, respectively. These data suggest that the use of impedance cardiac output measurements to make treatment decisions about individual patients could result in serious error.
A Comparison of Bioimpedance and Echocardiography in Measuring Systolic Heart Function in Cardiac Patients
Authors: JURN KERKKAMP H. J. , HEETHAAR ROB M.
Published: February 2006

Abstract: To investigate the ability of bioimpedance cardiography to assess left ventricular systolic function in comparison with known echocardiographic parameters and to establish the most informative bioimpedance parameter, 28 cardiac patients were submitted to simultaneous echocardiography and bioimpedance cardiography. Bioimpedance systolic time ratio, Heather index, acceleration index, and index of contractility were compared with echocardiographically obtained left ventricular dimensions, 2D left ventricular ejection fraction, fractional shortening, and mean velocity of circumferential shortening. The systolic time ratio and Heather index correlated significantly well with, respectively, 2D ejection fraction (r= ‐0.73) and, respectively, fractional shortening (r= 0.69). The systolic time ratio was the best parameter in recognizing impaired left ventricular systolic function (F= 12.6) in comparison with the Heather index (F= 6.5). This study demonstrates the applicability of bioimpedance cardiography in assessing left ventricular systolic function similar to echocardiography in clinical cardiology.
In Vivoac Impedance Spectroscopy of Human Skin: Theory and Problems in Monitoring of Passive Percutaneous Drug Delivery
Authors: LACKERMEIER A. H. , McADAMS E. T. , MOSS G. P. , WOOLFSON A. D.
Published: February 2006

Abstract:The use of impedance spectroscopy to evaluate transdermal drug delivery is discussed and new techniques and protocols are suggested to avoid or minimize potential problems. A novel multichannel impedance analyzer, exploiting the advantages of the “three‐electrode” configuration, was employed to measure the effects of differing topically applied concentrations of the percutaneous local anesthetic amethocaine on the electrical properties of the treated skin sites. Each measured impedance spectrum was modeled by an equivalent circuit consisting of a resistor in series with the parallel combination of a pseudocapacitance and a resistor. Due to differences in skin sites and to the finite times taken to apply each electrode, it was difficult to satisfactorily compare and contrast the results obtained from adjacent skin sites. Normalization of data highlighted differences in relative impedance changes and aided the meaningful comparison of treated skin sites.
On Assessment of Skin Reactivity Using Electrical Impedancea
Authors: NYRÉN MIRUNA , HAGSTRÖMER LENA , EMTESTAM LENNART
Published: February 2006

Abstract: Pathophysiological events in biological tissue are characterized by a shift in electrical impedance spectra of the tissue under study. In this paper, techniques based on electrical impedance are reviewed with emphasis on their possible role in evaluating the skin reactivity of an individual, including results from impedance measurement studies on patients with allergic contact reactions, wheals, tuberculin tests, and irritant contact reactions and on an appropriate number of controls. The results show that, compared to relevant controls, at different types of experimental cutaneous reactions, both of allergic and irritant type, statistically significant changes of the impedance parameters have been detected. Each reaction type had a specific impedance index pattern. Data up to now indicate that the improved impedance technique offers not only a noninvasive alternative for characterization and perhaps differentiation between the skin responses induced by either an allergen or an irritant, but also a capability to distinguish responses induced by chemically different irritants.
Orientation and Deformation of Erythrocytes in Flowing Blood
Authors: FUJII MAMIKO , NAKAJIMA KENGO , SAKAMOTO KATSUYUKI , KANAI HIROSHI
Published: February 2006

Abstract: The effects of flow on the changes of electrical resistivity and light‐scattering characteristics of blood are experimentally and theoretically discussed. Studies indicate that most erythrocytes deform and orient themselves in the flow direction when blood flows in a conduit. Such oriented blood shows anisotropic properties. Anisotropic electrical resistivity of flowing blood is measured in three rectangular directions with a measurement cell of coaxial cylindrical type. From these experimental results, the orientation and deformation of erythrocytes are discussed. The orientation ratio and the deformation are calculated using a simplified spheroidal model of an erythrocyte. Calculated results show that the fractions of erythrocytes with their short axis parallel to each direction and the equivalent axis ratio for a simplified spheroidal model change with the shear rate of flow.