bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Mechanisms of RET Activation in Human Cancer
Authors: SANTORO MASSIMO , MELILLO ROSA MARINA , CARLOMAGNO FRANCESCA , FUSCO ALFREDO , VECCHIO GIANCARLO
Published: July 2010

Abstract: Mutations that produce oncogenes with dominant gain of function target receptor protein tyrosine kinases (PTKs) in cancer and confer uncontrolled proliferation, impaired differentiation, or unrestrained survival to the cancer cell. However, insufficient PTK signaling may be responsible for developmental diseases. Gain of function of the RET receptor PTK is associated with human cancer. At the germline level, point mutations of RET are responsible for multiple endocrine neoplasia type 2 (MEN2A, MEN2B, and FMTC). Mutations of extracellular cysteines are found in MEN2A patients, and a Met918Thr mutation is responsible for most MEN2B cases. At the somatic level, gene rearrangements juxtaposing the tyrosine kinase domain of RET to heterologous gene partners are found in papillary carcinomas of the thyroid. These rearrangements generate the chimeric RET/PTC oncogenes. Both MEN2 mutations and PTC gene rearrangements potentiate the intrinsic tyrosine kinase activity of RET and, ultimately, the RET downstream signaling events. A multidocking site of the C‐tail of RET is essential for both mitogenic and survival RET signaling. Such a site is involved in the recruitment of several intracellular molecules, such as the Shc, FRS2, IRS1, Gab1/2, and Enigma. The different activating mutations not only potentiate the enzymatic activity of the RET kinase but also may alter qualitatively RET signaling properties by: (1) altering RET autophosphorylation (in the case of the MEN2B mutation), (2) modifying the subcellular distribution of the active kinase, and (3) providing the active kinase with a scaffold for novel protein‐protein interactions (as in the case of RET/PTC oncoproteins). This review describes the molecular mechanisms by which the different genetic alterations cause the conversion of RET into a dominant transforming oncogene.
Nutrition and Prostate Cancer
Authors: COHEN LEONARD A.
Published: July 2010

Abstract: Despite intense efforts, little is known about the etiology of prostate cancer, and treatment of advanced forms of the disease has had limited success. Nonetheless, epidemiologic studies combined with animal model and in vitro experiments indicate that natural components of the diet, including n‐3 PUFA, the carotenoid lycopene, and the trace element selenium, may serve as chemopreventive agents that suppress the growth and dissemination of neoplastic prostate cells. Until further study, however, soy isoflavones should be viewed with some caution, especially as adjuvant's to chemotherapy, in patients with hormone‐refractory prostate cancer. Future studies, using different forms and doses of selenium and tomato carotenoids, may shed new light on the etiology and prevention of prostate cancer.
Precancerous Lesions and Conditions of the Prostate
Authors: MONTIRONI RODOLFO , MAZZUCCHELLI ROBERTA , SCARPELLI MARINA
Published: July 2010

Abstract: Prostatic intraepithelial neoplasia (PIN) is composed of dysplastic cells with a luminal cell phenotype, expressing the androgen receptor as well as prostate‐specific antigen. PIN is characterized by progressive abnormalities of phenotype that are intermediate between normal prostatic epithelium and cancer, indicating impairment of cell differentiation and regulatory control with advancing stages of carcinogenesis. High‐grade PIN is considered the most likely precursor of prostatic carcinoma, according to virtually all available evidence. Androgen deprivation decreases the prevalence and extent of PIN and the degree of capillary vascularization (e.g., angiogenesis) in the surrounding stroma via suppression of vascular endothelial growth factor production. Prostatic carcinoma is also likely to arise from precursor lesions other than high‐grade PIN such as low‐grade PIN, atypical adenomatous hyperplasia, malignancy‐associated foci, and atrophy.
Anti‐Aromatase Chemicals in Red Wine
Authors: ENG E. T. , WILLIAMS D. , MANDAVA U. , KIRMA N. , TEKMAL R. R. , CHEN S.
Published: July 2010

Abstract: Estrogen synthesized in situ plays a more important role in breast cancer cell proliferation than does circulating estrogen. Aromatase is the enzyme that converts androgen to estrogen and is expressed at a higher level in breast cancer tissue than in surrounding noncancer tissue. A promising route of chemoprevention against breast cancer may be through the suppression of in situ estrogen formation using aromatase inhibitors. A diet high in fruits and vegetables may reduce the incidence of breast cancer, because they contain phytochemicals that can act as aromatase inhibitors. In our previous studies, we found that grapes and wine contain potent phytochemicals that can inhibit aromatase. We show that red wine was more effective than white wine in suppressing aromatase activity. Interestingly, our results from white wine studies suggest a weak inductive effect of alcohol on aromatase activity. On the other hand, the potent effect of anti‐aromatase chemicals in red wine overcomes the weak inductive effect of alcohol in wine. Several purification procedures were performed on whole red wine to separate active aromatase inhibitors from non‐active compounds. These techniques included liquid‐liquid extraction, silica gel chromatography, various solid phase extraction (SPE) columns, and high performance liquid chromatography. An active Pinot Noir red wine SPE C18 column fraction (20% acetonitrile:water) was more effective than complete Pinot Noir wine in suppressing aromatase assay. This red wine extract was further analyzed in a transgenic mouse model in which aromatase was over‐expressed in mammary tissue. Our gavaged red wine extract completely abrogated aromatase‐induced hyperplasia and other neoplastic changes in mammary tissue. These results suggest that red wine or red wine extract may be a chemopreventive diet supplement for postmenopausal women who have a high risk of breast cancer. Further research is underway to purify and characterize the active compounds in red wine that are responsible for the inhibition of aromatase.
Murine Models of Paroxysmal Nocturnal Hemoglobinuria
Authors: ROSTI VITTORIO
Published: July 2010

Abstract: Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal disorder characterized by chronic intravascular hemolysis, cytopenia, and an increased tendency to thrombosis. All patients with PNH studied so far have a somatic mutation of phosphatidyl inositol glycan complementation group A (PIG‐A), an X‐linked gene involved initially in the biosynthesis of the glycosyl phosphatidylinositol (GPI) molecule, which serves as an anchor for many cell surface proteins. The mutation occurs in a hematopoietic stem cell, and consequently, all cells derived from the mutated stem cell are devoid of GPI‐linked proteins. The absence of GPI‐linked proteins explains some clinical symptoms of the disease but not the mechanism that allows the expansion of the mutated clone. By using targeted disruption of the PIG‐A gene in mouse embryonic stem cells, some mice models of PNH have been generated. These animals have a discrete proportion of blood cells devoid of GPI‐linked proteins, and although not anemic, they have evidence of hemolysis. The clinical course of these animals is benign, and there are no signs of a substantial expansion of the PNH clone, as observed in human patients. The fact that these animals do not develop the disease strongly supports the notion that a mutation of PIG‐A is not sufficient per se to cause PNH and that another factor, namely, bone marrow failure, is necessary to allow proliferation and expansion of the PNH clone.
Identification of Chronic Cocaine‐Induced Gene Expression Through Dopamine D1 Receptors by Using cDNA Microarrays
Authors: ZHANG JIANHUA , ZHANG DONGSHENG , XU MING
Published: July 2010

Abstract:A major goal of drug abuse research is to understand the molecular mechanisms underlying the behavioral changes caused by repeated exposure to cocaine. Enduring behavioral changes, such as behavioral sensitization, can be induced in rodents by repeated cocaine administration. The neurobiological mechanisms underlying such behavioral changes are associated with the brain mesocorticolimbic dopamine (DA) pathway. Moreover, the DA D1 receptors are involved in mediating the long‐term behavioral effects of cocaine. The long‐lasting behavioral effects of repeated cocaine exposure are highly likely to be associated with underlying changes in gene expression. To examine this possibility, we have started to combine the use of D1 receptor mutant mice with cDNA microarrays to identify gene expression changes mediated through the D1 receptors induced by repeated cocaine administration. Our initial experiments focused on a target of the mesocorticolimbic DA pathway, the nucleus accumbens (NAc), which is the primary neural substrate for mediating the long‐term effects of cocaine. We found that multiple genes are differentially expressed in wild‐type and D1 receptor mutant mice after chronic cocaine treatment. Further studies are in progress to determine the physiological significance of the differential expression of these genes in chronic cocaine‐induced behaviors.
A Single Dose of Methamphetamine Rescues the Blunted Dopamine D1‐Receptor Activity in the Neocortex of D2‐ and D3‐Receptor Knockout Mice
Authors: SCHMAUSS CLAUDIA , GLICKSTEIN SARA B. , ADLERSBERG MELLA , HSIUNG SHU‐CHI , TAMIR HADASSAH
Published: July 2010

Abstract: Knockout mice deficient for dopamine D2 and D3 receptors exhibit blunted c‐fos responses to D1‐agonist stimulation. A single dose of methamphetamine (METH), however, leads to a long‐term reversal of these blunted c‐fos responses in both mutants, and the same effect is obtained with a single administration of a full D1‐agonist. Consistent with the predominant c‐fos expression in the neocortex induced by METH itself, METH pretreatment leads to the largest D1‐agonist‐stimulated c‐fos responses in the neocortex of these mutants. For example, a pronounced blunting of neocortical c‐fos responses is detected in the prefrontal cortex, a region in which D1 receptors play a critical role in working memory. METH pretreated mutants, however, exhibit robust c‐fos responses in this region that are indistinguishable from wild type. Recent studies indicate that different mechanisms operate in brains of D2 and D3 mutants to lead to decreased D1‐receptor activity. For example, drug‐naive D2, but not D3, mutants show significantly decreased G protein activation in response to D1‐agonist stimulation, and METH pretreatment also rescues this abnormal molecular phenotype. Moreover, although the protein phosphatases (PP) 1/2A and 2B play a critical role in modulating G protein activation in wild type, their effect is either diminished (PP1/2A) or abolished (2B) in D2 mutants. Interestingly however, METH pretreatment does not rescue the activities of these phosphatases in the mutants, suggesting that the long‐term effects of a single dose of METH are mediated via effector systems that act downstream of G protein activation.
The Nitric Oxide Releasing Agent Sodium Nitroprusside Modulates Cocaine‐Induced Immediate Early Gene Expression in Rat Brain
Authors: THIRIET NATHALIE , AUNIS DOMINIQUE , ZWILLER JEAN
Published: July 2010

Abstract:The nitric oxide (NO)/cGMP pathway triggers key events in synaptic phenomena involved in learning and memory. Usingin situhybridization, the present report demonstrates that NO released by sodium nitroprusside regulatesegr‐1, c‐fos, andjunBimmediate early gene expression in rat forebrain. These genes, which are rapidly and transiently induced in response to diverse extracellular stimulation, coordinate alterations in gene expression underlying neuronal plasticity. Intracerebroventricular injection of sodium nitroprusside induced immediate early gene expression, which was highest in the nucleus accumbens. On the other hand, sodium nitroprusside abolished the cocaine‐induced early gene expression in the dopaminergic projection fields nucleus accumbens, caudate‐putamen, and frontal cortex. Further studies are warranted to explore the potential of the NO/cGMP/cGMP‐dependent protein kinase pathway to modify cocaine‐related behavioral effects.
Preclinical Evaluation of GBR12909 Decanoate as a Long‐Acting Medication for Methamphetamine Dependence
Authors: BAUMANN MICHAEL H. , PHILLIPS JENNIFER M. , AYESTAS MARIO A. , ALI SYED F. , RICE KENNER C. , ROTHMAN RICHARD B.
Published: July 2010

Abstract:Methamphetamine (METH) abuse is a growing health problem, and no treatments for METH dependence have been identified. The powerful addictive properties of METH are mediated by release of dopamine (DA) from nerve terminals in mesolimbic reward pathways. METH stimulates DA release by acting as a substrate for DA transporter (DAT) proteins, thereby triggering efflux of DA from cells into the synapse. We have shown that blocking DAT activity with high‐affinity DA uptake inhibitors, like GBR12909, can substantially reduce METH‐evoked DA releasein vitro, suggesting GBR12909 may have potential as a pharmacotherapy for METH dependence. The purpose of the present study was to examine the neurobiological effects of a long‐acting oil‐soluble preparation of GBR12909 (1‐[2‐[bis(4‐fluorophenyl)methoxy]ethyl]‐4‐(3‐hydroxy‐3‐phenylpropyl) piperazinyl decanoate, or GBR‐decanoate). Male rats received GBR‐decanoate (480 mg/kg, i.m.) or its oil vehicle, and were tested using a variety of methods one and two weeks later.Ex vivoautoradiography showed that GBR‐decanoate decreases DAT binding in DA‐rich brain regions.In vivomicrodialysis in the nucleus accumbens revealed that GBR‐decanoate elevates baseline levels of extracellular DA and antagonizes the ability of METH to evoke DA release. The dopaminergic effects of GBR‐decanoate were sustained, lasting for at least two weeks. Rats pretreated with GBR‐decanoate displayed enhanced locomotor responses to novelty at one week, but not two weeks, postinjection. Administration of the D2/D3receptor agonist quinpirole (10 and 100 μg/kg, s.c.) decreased locomotor activity and suppressed plasma prolactin levels; quinpirole‐induced responses were not altered by GBR‐decanoate. Thus, GBR‐decanoate is able to elevate basal synaptic DA levels and block METH‐evoked DA release in a persistent manner, without significant perturbation of DA receptor function. The findings suggest that GBR‐decanoate, or similar long‐acting agents, should be evaluated further as potential treatment adjuncts in the management of METH addiction in humans.
Effects of Cocaine Administration on VTA Cell Activity in Response to Prefrontal Cortex Stimulation
Authors: ALMODÓVAR‐FÁBREGAS L. J. , SEGARRA O. , COLÓN N. , DONES J. G. , MERCADO M. , MEJÍAS‐APONTE C. A. , VÁZQUEZ R. , ABREU R. , VÁZQUEZ E. , WILLIAMS J. T. , JIMÉNEZ‐RIVERA C. A.
Published: July 2010

Abstract:The repeated use of psychostimulants in humans has been associated with progressive enhancement of anxiety, panic attacks, and eventually paranoid psychosis. The appearance of such behaviors has been termed behavioral sensitization, which forms part of the basic pathological mechanisms involved in drug addiction. Psychostimulants act via a circuit involving the ventral tegmental area (VTA), prefrontal cortex (PFC), and nucleus accumbens. The PFC sends glutamatergic projections that activate dopaminergic neurons in the VTA. These projections provide an extremely important excitatory drive necessary for the development of sensitization. The effects of cocaine administration on the response of dopaminergic VTA cells to activation of the PFC have not been reported. Here the effects of acute cocaine administration on VTA cell response to PFC stimulation are examined. Statistical analysis of the changes in spontaneous activity and evoked response revealed a significant decrease in spontaneous activity at 1.0 mg/kg i.v. after cocaine treatment compared to baseline levels. The net effect was an increase in signal‐to‐noise ratio. Treatment with MK‐801 at a dose of 2 mg/kg showed that the excitatory response was, at least partially, NMDA‐mediated. Prazosin pretreatment (0.5 mg/kg i.p.) did not prevent a significant decrease in spontaneous activity brought about by cocaine (15 mg/kg, i.p.). Nonetheless, prazosin alone induced a significant decrease in the response to PFC stimulation when compared to baseline. In addition, iontophoretic application of norepinephrine (NE) onto VTA cells revealed that NE potentiated (19.2%), enhanced (26.9%), or suppressed (46.2%) the glutamate‐evoked response in VTA cells. The results suggest that a possible role of cocaine in the process of sensitization might be to amplify the PFC‐induced excitation at the VTA. Since the iontophoretic release of NE in almost half of the sampled cells produced similar effects to those of cocaine it may suggest a possible NE‐mediated mechanism for cocaine actions.
Neurochemical Changes and Neurotoxic Effects of an Acute Treatment with Sydnocarb, A Novel Psychostimulant
Authors: BASHKATOVA V. , MATHIEU‐KIA A.‐M. , DURAND C. , PENIT‐SORIA J.
Published: July 2010

Abstract:Sydnocarb [(phenylisopropyl)N‐phenylcarbamoylsydnonimine; SYD] was introduced to clinical practice in Russia as a psychostimulant drug used for the treatment of asthenia and apathy, which accompany schizophrenia and manic depression. It has been described as a psychostimulant with addiction liability and toxicity less than amphetamine (AMPH). The precise cellular mechanisms by which sydnocarb elicits its psychostimulant effect are still unclear. At present its neurochemical and neurotoxic effects are compared to those of AMPH in the striatum, the main input structure of the basal ganglia. The expression of c‐fos protein in striatal neurons was much more increased after a single injection of d‐AMPH (5 mg/kg) than after an equimolar concentration of SYD (23.8 mg/kg) in both the anterior and the posterior part of the striatum. Usingin situhybridization on striatal slices, we observed that AMPH increased the striatal levels of preprodynorphin (PPDYN) mRNAs in both parts of the striatum, while SYD did not affect basal levels of PPDYN mRNAs. Furthermore, AMPH and SYD increased striatal preprotachykinin (PPT‐A) and preproenkephalin (PPE) mRNA levels. The effects of AMPH and SYD on PPT‐A‐mRNA levels were similar. A differential effect of AMPH and SYD was observed only on the PPE‐mRNA levels measured in the anterior striatum where SYD increased these levels more than AMPH. The acute neurotoxicity of these two psychostimulants was analyzed by measuring their effects on the parameters of oxidative stress, such as nitric oxide (NO) generation, as well as specific indices of lipid peroxidation (i.e., thiobarbituric acid reactive substances; TBARS), while, on the other hand, the alpha‐tocopherol level was taken as an index of antioxidant defense processes. Measuring generation of NO directly by electron paramagnetic resonance, it was observed that AMPH shows a more pronouced increase in comparison to SYD, in the striatum and in cortex. TBARS levels in the striatum and cortex were significantly less enhanced than AMPH after a single injection of SYD. Similarly, the alpha‐tocopherol level was decreased only by AMPH in the striatum, and neither AMPH nor SYD had any effect in the cortex. Results show that a single injection of a high dose of AMPH is able to induce several neurotoxic effects. The study also demonstrates that SYD has mild neurochemical effects as well as fewer neurotoxic properties than AMPH.
Methamphetamine‐Induced Dopaminergic Neurotoxicity and Production of Peroxynitrite Are Potentiated in Nerve Growth Factor Differentiated Pheochromocytoma 12 Cells
Authors: IMAM SYED Z. , NEWPORT GLENN D. , DUHART HELEN M. , ISLAM FAKHRUL , SLIKKER WILLIAM , ALI SYED F.
Published: July 2010

Abstract:Methamphetamine (METH) is a widely abused psychomotor stimulant known to cause dopaminergic neurotoxicity in rodents, nonhuman primates, and humans. METH administration selectively damages the dopaminergic nerve terminals, which is hypothesized to be due to release of dopamine from synaptic vesicles within the terminals. This process is believed to be mediated by the production of free radicals. The current study evaluates METH‐induced dopaminergic toxicity in pheochromocytoma 12 (PC12) cells cultured in the presence or absence of nerve growth factor (NGF). Dopaminergic changes and the formation of 3‐nitrotyrosine (3‐NT), a marker for peroxynitrite production, were studied in PC12 cell cultures grown in the presence or absence of NGF after different doses of METH (100‐1,000 μM). METH exposure did not cause significant alterations in cell viability and did not produce significant dopaminergic changes or 3‐NT production in PC12 cells grown in NGF‐negative media after 24 hours. However, cell viability of PC12 cells grown in NGF‐positive media was decreased by 45%, and significant dose‐dependent dopaminergic alteration and 3‐NT production were observed 24 hours after exposure to METH. The current study supports the hypothesis that METH acts at the dopaminergic nerve terminals and produces dopaminergic damage by the production of free radical peroxynitrite.
Methylphenidate‐Evoked Potentiation of Extracellular Dopamine in the Brain of Adolescents with Premature Birth
Authors: NETO PEDRO ROSA , LOU HANS , CUMMING PAUL , PRYDS OLE , GJEDDE ALBERT
Published: July 2010

Abstract: Perinatal anoxia/ischemia or premature birth increases the risk of developing attention deficit/hyperactivity disorder (ADHD). Brain imaging studies of idopathic ADHD reveal elevated dopamine transporter density in striatum of patients, predicting abnormal response to a challenge with methylphenidate in this population. We hypothesized that the severity of attention deficit in adolescents should correlate with the sensitivity to psychostimulant‐evoked dopamine release. To test this hypothesis, we investigated six adolescent subjects (mean age 14.2 ± 2.4 yr) with documented birth trauma and/or low birth weight and a diagnosis of ADHD. Using positron emission tomography (PET), we measured the relative binding of [11C]raclopride to dopamine receptors in striatum, first in the baseline condition and again after methylphenidate challenge at a therapeutic dose for ADHD (0.3 mg/kg, p.o.) in order to map the altered dopamine release evoked by the psychostimulant challenge. Neuropsychological measurements of impulsivity and inattention were also performed. We found a positive correlation between commission errors and the methylphenidate‐evoked decrease in [11C]raclopride binding, thought to reflect the balance of dopamine release and reuptake. The greater the decline in the [11C]raclopride binding, the greater the ability of methylphenidate to block the reuptake of dopamine. As the ability to block the reuptake depends on the relative dopamine concentration, the result suggests that the impulsivity in these adolescents is associated with abnormally low extracellular dopamine concentration.
Repeated Administration of Gamma‐Hydroxybutyric Acid (GHB) to Mice
Authors: ITZHAK YOSSEF , ALI SYED F.
Published: July 2010

Abstract:Because of the sedative/hypnotic and euphoric effects of gamma‐hydroxybutyric acid (GHB), the recreational use of the drug has increased significantly. In the current study we investigated the sedative and rewarding effects of GHB in Swiss Webster mice. Although the acute administration of GHB (200 mg/kg) caused marked hypolocomotion, repeated administration of the drug for 6 or 14 days produced tolerance to this effect. In addition, the administration of GHB 300 mg/kg to naive mice caused catalepsy, which dissipated in mice pre‐exposed to GHB (200 mg/kg). Consequently, after repeated treatment with GHB, tolerance developed to both the hypolocomotion and cataleptic effects of the drug. The administration of GHB or its precursor gamma‐butyrolactone for 14 days increased the striatal content of dopamine. The sedative effects of GHB may be due to hypodopaminergic activity from inhibition of dopamine release and a subsequent increase in the intraneuronal dopamine level. The rewarding effect of GHB was assessed in the conditioned place preference paradigm. Mice treated repeatedly with 250 mg/kg for 7 days developed conditioned preference for the GHB‐paired compartment of the cage, suggesting that the GHB cue is rewarding. The development of tolerance to the sedative effects of GHB coupled with the rewarding properties of the drug support the abuse potential of GHB. Further studies are necessary to determine the mechanism underlying the development of tolerance to GHB and the rewarding effect of the drug.
Cell Signaling as a Target and Underlying Mechanism for Neurobehavioral Teratogenesis
Authors: YANAI JOSEPH , VATURY ORI , SLOTKIN THEODORE A.
Published: July 2010

Abstract:A wide variety of drugs and chemicals elicit neurobehavioral teratogenesis. Surprisingly, however, despite the obvious differences among unrelated compounds, the behavioral outcomes often display striking similarities, such as cognitive and attentional deficits. Recent studies of drugs of abuse (heroin, nicotine, barbiturates) and environmental toxins (environmental tobacco smoke, pesticides, metals) suggest that, regardless of the originating mechanism for perturbation of brain development, disparate neuroteratogens converge downstream on common families of alterations, characterized by changes in the expression and/or activity of the cell‐signaling molecules that are essential to neuronal differentiation and synaptic communication. Identification of these common targets may help in the design of pharmacologic interventions that, administered in adulthood, can reverse the impact of exposure to neurobehavioral teratogens.
Neonatal Exposure to Cocaine
Authors: SUMMAVIELLE TERESA , MAGALHÃES ANA , CASTRO‐VALE IVONE , DE SOUSA LILIANA , TAVARES MARIA AMÉLIA
Published: July 2010

Abstract:The amygdala is a brain region that is known to be implicated in the development of behavioral sensitization to cocaine. This area is often related to conditioned associations, stress responses, and anxiety; and these behaviors are usually posited to be due to altered dopamine levels. This study aimed to evaluate the effects of neonatal exposure to cocaine on the levels of neurotransmitters in the amygdala of developing rats and to relate these levels with open‐field observations, mainly rearing behavior, that is regarded to reflect emotional components. Male and female Wistar rats were given 15 mg of cocaine hydrochloride/kg body weight, subcutaneously, in two daily doses, from postnatal day 1 (PND1) to PND30. Controls were given 0.9% saline. Open‐field activity was registered on PND14, 21, and 30 in three sessions of 15 min each. In PND30, rats were decapitated, and the amygdala dissected from both brain hemispheres and processed for determination of dopamine (DA) and metabolites by high‐performance liquid chromatography with electrochemical detection (HPLC‐EC). Results show that in PND14 and 21 all registered activity behaviors were increased in male and female cocaine‐exposed animals. In PND30, there was a significant decrease in rearing and in global activity in the group exposed to cocaine, and DA levels were significantly decreased in the amygdala of the same group. No differences were found between the left and right amygdala. These results suggest that chronic neonatal cocaine administration leads to depletion of DA levels in the amygdala, which is consistent with previous findings. Furthermore, the lower levels of DA are associated with decreased rearing behavior, which may indicate emotional depression. These results can help to clarify the role of amygdala in cocaine‐induced behavioral sensitization in the developing rat.
SREBP‐1: Gene Regulatory Key to Syndrome X?
Authors: MÜLLER‐WIELAND DIRK , KOTZKA JÖRG
Published: July 2010

Abstract: Combined appearance of different cardiovascular risk factors seems to be more prevalent in individuals with decreased insulin sensitivity and increased visceral obesity, thereby being components of the so‐called metabolic syndrome or syndrome X. Alterations in the abundance and activity of transcription factors lead to complex dysregulation of gene expression, which might be a key to understand insulin resistance‐associated clinical clustering of coronary risk factors at the cellular or gene regulatory level. Recent examples are members of the nuclear hormone receptor superfamily—for example, peroxisome proliferator‐activated receptors (PPARs) and sterol regulatory element‐binding proteins (SREBPs). Besides their regulation by metabolites and nutrients, these transcription factors are also targets of hormones (like insulin and leptin), growth factors, inflammatory signals, and drugs. Major signaling pathways coupling transcription factors to extracellular stimuli are the MAP kinase cascades. We have recently shown that SREBPs appear to be substrates of MAP kinases and propose that SREBP‐1 might play a role in the development of cellular features belonging to lipid toxicity and possibly syndrome X. Thus, the metabolic syndrome appears to be not only a disease or state of altered glucose tolerance, plasma lipid levels, blood pressure, and body fat distribution, but rather a complex clinical phenomenon of dysregulated gene expression.
Sterol Regulatory Element‐Binding Proteins (SREBPs) as Regulators of Lipid Metabolism
Authors: KIM HYOUN‐JU , MIYAZAKI MAKOTO , MAN WENG CHI , NTAMBI JAMES M.
Published: July 2010

Abstract: Cellular cholesterol and fatty acid metabolism in mammals is controlled by a family of transcription factors called sterol regulatory element‐binding protein isoforms, three of which (SREBP‐1a, 1c, and 2) are well characterized. These proteins, which are synthesized as precursors, are inserted into the endoplasmic reticulum (ER) membrane with both the amino and carboxylic acid domains facing the cytosolic face of the membrane. In sterol‐deficient cells, proteolytic cleavage of SREBPs occurs, thereby releasing their N‐terminal mature and active forms and enabling them to enter the nucleus, where they bind to the sterol regulatory response element (SRE) and/or E‐box sequences and activate genes involved in cholesterol, triglyceride, and fatty acid biosynthesis. Of the three SREBP isoforms, SREBP‐1c gene expression is induced by cholesterol and repressed by polyunsaturated fatty acids (PUFA). We have examined the changes in SREBP‐1c mRNA and protein levels as well as the mRNA levels of several SREBP‐1c target genes when a high‐cholesterol diet is combined with diets rich in PUFA of the n‐6 series. Our studies show that PUFA oppose the cholesterol‐mediated SREBP‐1 maturation without affecting the cholesterol‐mediated increase of SREBP‐1c mRNA and precursor protein. The decrease in SREBP‐1 mature protein paralleled the decrease in mRNAs for genes of fatty acid and cholesterol biosynthesis, such as HMG‐CoA synthase and fatty acid synthase, but interestingly gene expression of stearoyl‐CoA desaturase 1 (SCD1) was instead induced. These studies suggest that the main point of control of PUFA‐mediated suppression of lipogenic gene expression is the inhibition of SREBP‐1 maturation. The studies also reveal that the induction of SCD1 gene expression by cholesterol occurs through a mechanism independent of SREBP‐1 maturation.
An Increase in Peroxisomal Fatty Acid Oxidation Is Not Sufficient to Prevent Tissue Lipid Accumulation in hHTg Rats
Authors: UKROPEC J. , KLIMEŠ I. , GAŠPERÍKOVÁ D. , DEMCÁKOVÁ E. , DREVON C. A. , RESELAND J. E. , ŠEBÖKOVÁ E.
Published: July 2010

Abstract: We observed earlier that increased skeletal muscle lipid content in the hereditary hypertriglyceridemic (hHTg) rat is accompanied by a decline in plasma leptin. Leptin has recently been shown to enhance peripheral insulin sensitivity by decreasing the tissue triglyceride accumulation, possibly through regulation of fatty acid oxidation and lipogenesis. Thus, to test the hypothesis that insulin resistance and increased skeletal muscle lipid accumulation in hHTg rats are due to a defect in lipid catabolism, we measured mitochondrial and peroxisomal fatty acid oxidation and malonyl‐CoA and acetyl‐CoA carboxylase‐2 content in skeletal muscles of these animals. In addition, we investigated possible molecular mechanisms responsible for the lower leptin levels in hHTg rats by measuring leptin and leptin‐receptor (Ob‐Ra) mRNA levels. We found the following: (1) in spite of a higher skeletal muscle malonyl‐CoA content and an increased sensitivity of carnitine palmitoyltransferase‐1 to malonyl‐CoA, carnitine palmitoyltransferase‐1 activity in muscle of hHTg rats was normal; (2) increased peroxisomal fatty acid oxidation did not seem to be sufficient to prevent the tissue lipid accumulation in these animals; (3) both lower leptin production by white adipose tissue and increased leptin uptake seem to be responsible for lower circulating leptin levels and therefore lower fatty acid catabolism.
Modulation of Lipid Metabolism by Energy Status of Adipocytes
Authors: KOPECKÝ JAN , FLACHS PAVEL , BARDOVÁ KRISTINA , BRAUNER PETR , PRAŽÁK TOMÁŠ , ŠPONAROVÁ JANA
Published: July 2010

Abstract: It is becoming evident that insulin resistance of white adipose tissue is a major factor underlying the cardiovascular risk of obesity. Impaired fat storage rather than altered glucose metabolism in adipocytes probably contributes to development of insulin resistance in muscle and other tissues, in particular via increased delivery of nonesterified fatty acids into circulation. Lipid metabolism of adipose tissue is affected by the energy status of fat cells. In vitro experiments indicated the dependence of both lipogenesis and lipolysis on ATP levels in adipocytes. Thus, respiratory uncoupling in adipocytes that results in stimulation of energy dissipation and depression of ATP synthesis may contribute to the control of lipid metabolism, adiposity, and insulin sensitivity. This notion is supported by the expression of UCPs in adipocytes, for example, UCP2, UCP5, as well as some protonophoric anion transporters, and by induction of UCP1 and UCP3 in white fat by pharmacological treatments that reduce adiposity. A negative correlation between expression of UCPs in adipocytes and accumulation of white fat was also found. Expression of UCP1 from the adipose‐specific promoter in the aP2‐Ucp1 transgenic mice mitigated obesity induced by genetic or dietary factors. The obesity resistance, accompanied by respiratory uncoupling in adipocytes and increased energy expenditure, resulted from ectopic expression of UCP1 in white, but not brown fat. Probably due to depression of the ATP/ADP ratio, both fatty acid synthesis and lipolytic action of norepinephrine in adipocytes of transgenic mice were relatively low. Expression of regulatory G‐proteins, which are essential for both catecholamine and insulin signaling in adipocytes, was also altered by ectopic UCP1. These results support the role of protonophoric proteins in adipocytes in the control of adiposity and insulin sensitivity. Antidiabetic effects of thiazolidinediones, fibrates, β3‐adrenoreceptor agonists, dietary n‐3 PUFAs, and leptin may be explained at least partially by their effects on the energy and hence also the lipid metabolism of fat cells.
Evaluation of Free Fatty Acid Metabolism in Vivo
Authors: OAKES NICHOLAS D. , FURLER STUART M.
Published: July 2010

Abstract: In order to enable detailed studies of free fatty acid (FFA) metabolism, we recently introduced a method for the evaluation of tissue‐specific FFA metabolism in vivo. The method is based on the simultaneous use of 14C‐palmitate (14C‐P) and the non‐β‐oxidizable FFA analogue, [9,10‐3H]‐(R)‐2‐bromopalmitate (3H‐R‐BrP). Indices of total FFA utilization and incorporation into storage products are obtained from tissue concentrations of 3H and 14C, respectively, following intravenous administration of 3H‐R‐BrP and 14C‐P and their disappearance from plasma into tissues. This review covers the basis for, and developments in, the methodology, as well as some of the applications to date. In the rat, the method has been used to characterize tissue‐specific alterations in FFA metabolism in various situations, including skeletal muscle contraction, fasting, hyperinsulinemia, and various pharmacological manipulations. The results of all these studies clearly demonstrate tissue‐level control of FFA utilization and metabolic fate, refuting the traditional view that FFA utilization is simply supply‐driven. Recent developments enable the simultaneous evaluation of both tissue‐specific FFA and glucose metabolism by integrating the use of 2‐deoxyglucose and stable isotope‐labeled glucose tracers. In conclusion, the 3H‐R‐BrP methodology, especially in combination with other tracers, represents a powerful tool for elucidation of tissue‐specific fatty acid metabolism in vivo.
Eicosanoids and the Regulation of Cardiac Glucose Transport
Authors: DRANSFELD OLAF , RAKATZI IRINI , SASSON SHLOMO , ECKEL JÜRGEN
Published: July 2010

Abstract: Intact actin microfilaments are necessary for insulin‐regulated GLUT4 translocation from intracellular pools to the plasma membrane. Products of the lipoxygenase (LO) pathway were shown to be implicated in the regulation of actin cytoskeleton rearrangement. The aim of this study was to examine the role of these LO products for cardiac insulin signaling and glucose uptake, GLUT4 translocation, and actin‐based cytoskeleton structure. Exposure of cardiomyocytes to esculetin or NDGA, two structurally different LO inhibitors, induced a complete inhibition of insulin‐stimulated glucose uptake, whereas control cells showed a threefold stimulation by insulin. Addition of 12(S)‐HETE rendered the NDGA‐treated cells insulin‐sensitive. Early insulin signaling was not changed in cells exposed to LO inhibitors. Cell surface biotinylation of control cells showed a twofold increase of GLUT4 at the cell surface after insulin stimulation. In contrast, the LO inhibitors induced a complete inhibition of insulin‐stimulated GLUT4 translocation. Labeling of the F‐actin cytoskeleton revealed a prominent disassembly of actin fibers in cells exposed to the LO inhibitors. In conclusion, we show here that products of the LO reaction participate in the organization of the actin network in ventricular cardiomyocytes. Inhibition of LO blocks GLUT4 translocation without affecting insulin signaling events. These data suggest that products of the LO reaction participate in the regulation of glucose transport by contribution to a rearrangement of actin cytoskeletal elements.
Dietary Fat as a Risk Factor for Type 2 Diabetes
Authors: HOWARD BARBARA V.
Published: July 2010

Abstract: Too much information is missing for a definitive recommendation to be made concerning the role of diet in the development of diabetes. Although studies in certain population subgroups show a positive correlation between amount of dietary fat intake and occurrence of type 2 diabetes, these cannot be considered definitive, in part because they are confounded by many other variables that might relate to the development of diabetes. Furthermore, dietary fat intake has not been correlated with certainty to diabetes risk factors. With regard to diabetes risk, type of dietary fat consumed may be more important than total dietary fat intake. Several studies suggest that diets higher in saturated fat may pose a higher diabetes risk than those higher in unsaturated fat. Although there is a general consensus that reduced consumption of saturated fat and cholesterol reduces CVD risk, there are no definite nutrition recommendations to prevent diabetes. The most important recommendation may be for health‐care providers to carefully assess diabetes risk in their patients and institute dietary changes on an individual basis as needed to achieve and maintain body weight.
Erythrocyte Membrane Ion Transport in Offspring of Hypertensive Parents
Authors: SUCHÁNKOVÁ GABRIELA , VLASÁKOVÁ ZUZANA , ZICHA JOSEF , VOKURKOVÁ MARTINA , DOBEŠOVÁ ZDENA , PELIKÁNOVÁ TEREZIE
Published: July 2010

Abstract: Some patients with essential hypertension exhibit insulin resistance (IR) and several red blood cell (RBC) ion transport abnormalities. The aims of the study were to assess RBC ion transport acitivities under basal conditions, to test in vivo the effect of acute hyperinsulinemia, and to evaluate the relationship to IR in the offspring of hypertensive parents (n= 12; OHP) and healthy controls (n= 14; C). Activities of the Na+‐K+ pump, Na+‐K+ cotransport, Na+‐Li+ countertransport (SLC), and Na+, Rb+, and Li+ leaks (passive membrane permeability) were measured before and after a hyperinsulinemic (75 μU/mL) euglycemic clamp (HIC) and compared to those found under isoinsulinemic isovolumic conditions in OHP and C. An insulin action was calculated as glucose disposal and insulin sensitivity index (M/I) after HIC. OHP were characterized by lower M/I (0.12±0.07 vs. 0.20±0.09 mg/kg/min/μU/mL; p < 0.05) and elevated SLC and Li+ and Rb+ leaks (p < 0.05) compared with C. Although acute hyperinsulinemia did not modify significantly any ion transport parameter studied, negative correlation was observed between insulin action and membrane cation leaks. Glucose disposal correlated with an Li+ leak in C (r=−0.736; p < 0.01) and all subjects (r=−0.424; p < 0.05) after HIC and in OHP with an Na+ leak (r=−0.727; p < 0.05) before HIC. In conclusion, OHP displayed higher insulin resistance, enhanced activity of SLC, and augmented Li+ and Rb+ leaks. Acute hyperinsulinemia did not modify any ion transport parameter studied, although negative correlation was observed between insulin action and membrane leaks.
Terguride Treatment Attenuated Prolactin Release and Enhanced Insulin Receptor Affinity and GLUT 4 Content in Obese Spontaneously Hypertensive Female, but Not Male Rats
Authors: ZORAD S. , GOLDA V. , FICKOVA M. , MACHO L. , PINTEROVA L. , JURCOVICOVA J.
Published: July 2010

Abstract: Glucose tolerance, serum insulin, insulin receptors in epididymal fat tissue, and GLUT 4 content in muscle, as well as serum prolactin, were studied in obese and lean spontaneously hypertensive rats (SHRs) of both sexes. Obese animals displayed insulin resistance and decreased capacity of high‐affinity binding sites of insulin receptors in fat tissue plasma membranes. GLUT 4 content in musculus quadriceps was diminished only in obese females. Terguride treatment lowered prolactin serum levels, which was concomitant with ameliorated insulin sensitivity in obese animals of both sexes. Similarly, only in obese females, terguride significantly increased the affinity of high‐affinity insulin‐binding sites and normalized GLUT 4 content. Our results document downregulation of insulin receptors and GLUT 4 in obesity and suggest a role for prolactin in obesity‐induced insulin resistance, particularly in female rats.
Effects of Selected Anthropometric Parameters on Plasma Lipoproteins, Fatty Acid Composition, and Lipoperoxidation
Authors: ŽÁK ALEŠ , TVRZICKÁ EVA , VECKA MAREK , ROMANIV SEVERYN , ZEMAN MIROSLAV , KONÁRKOVÁ MARTA
Published: July 2010

Abstract: Four anthropometric parameters (body mass index, waist‐to‐hip circumference ratio, waist circumference, and ratio of subscapularis to triceps skinfold thickness), cutoff values being set according to the WHO guidelines, were compared as discriminative parameters for anthropometric, hemodynamic, and metabolic data relevant as risk factors of coronary heart disease. Waist circumference reflected differences between below and above cutoff values throughout all parameters, with the highest “effect size” values being for fat mass; blood pressure; glucose homeostasis parameters; plasma and LDL cholesterol; plasma, LDL, and VLDL apo B; and LDL oxidability (cumulative effect size value: 2777). Body mass index reflected most significantly plasma, LDL, and VLDL triglyceride; HDL and VLDL cholesterol; and content of linoleic acid in LDL phosphatidylcholine (cumulative effect size value: 2016). Waist‐to‐hip ratio dominated in effect size value only in VLDL oxidability (cumulative effect size value: 1497). Subscapularis to triceps skinfold thickness ratio had the lowest discriminating ability in all data.
Multiple Modes of Regulation of Na+/H+ Exchangers
Authors: HAYASHI HISAYOSHI , SZÁSZI KATALIN , GRINSTEIN SERGIO
Published: July 2010

Abstract: Mammalian Na+/H+ exchangers (NHE) mediate electroneutral countertransport of H+ for Na+ across the plasmalemmal and organellar membranes. They contribute to cellular and organellar pH and volume regulation and transepithelial Na+ transport. The aim of this review is to illustrate the complex regulation of these transporters by focusing on the multiple mechanisms controlling the epithelial isoform, NHE3. A variety of agents and conditions (e.g., hormones, growth factors, cellular pH, and medium osmolarity) act in concert to achieve short‐term and long‐term regulation of this isoform. The underlying mechanism involves changes in the number of transporters on the cell surface and/or altered activity of the individual exchangers due to allosteric activation by intracellular protons, phosphorylation and interaction with accessory proteins and the cytoskeleton. A similar regulatory versatility probably applies to other NHE isoforms, and the lessons learned from studying members of the NHE family could serve as a useful reference when exploring the modes and levels of regulation of other transporters.
Role of Sodium‐Calcium Exchanger (Ncx1) in Embryonic Heart Development
Authors: CONWAY SIMON J. , KRUZYNSKA‐FREJTAG AGNIESZKA , WANG JIAN , ROGERS RHONDA , KNEER PAIGE L. , CHEN HONGMEI , CREAZZO TONY , MENICK DONALD R. , KOUSHIK SRINAGESH V.
Published: July 2010

Abstract: Na+/Ca2+ exchanger (Ncx‐1) is highly expressed in cardiomyocytes, is thought to be required to maintain a low intracellular Ca2+ concentration, and may play a role in excitation‐contraction coupling. Significantly, targeted deletion of Ncx‐1 results in Ncx1‐null embryos that do not have a spontaneously beating heart and die in utero. Ultrastructural analysis revealed gross anomalies in the Ncx1‐null contractile apparatus, but physiologic analysis showed normal field‐stimulated Ca2+ transients, suggesting that Ncx‐1 function may not be critical for Ca2+ extrusion from the cytosol as previously thought. Using caffeine to empty the intracellular Ca2+ stores, we show that the sarcoplasmic reticulum is not fully functional within the 9.5‐dpc mouse heart, indicating that the sarcoplasmic reticulum is unlikely to account for the unexpected maintenance of intracellular Ca2+ homeostasis. Using the Ncx1‐lacZ reporter, our data indicate restricted expression patterns of Ncx1 and that Ncx1 is highly expressed within the conduction system, suggesting Ncx1 may be required for spontaneous pacemaking activity. To test this hypothesis, we used transgenic mice overexpressing one of the two known adult Ncx1 isoforms under the control of the cardiac‐specific a‐myosin heavy chain promoter to restore Ncx1 expression within the Ncx1‐null hearts. Results indicate that the transgenic re‐expression of one Ncx1 isoform was unable to rescue the lethal null mutant phenotype. Furthermore, our in situ results indicate that both known adult Ncx1 isoforms are coexpressed within the embryonic heart, suggesting that effective transgenic rescue may require the presence of both isoforms within the developing heart.