bluuebunny/crossref_metadata_2025 huggingface dataset:
Tumor Cells Utilize Multiple Pathways to Down‐modulate Apoptosis: Lessons from a Mouse Model of Islet Cell Carcinogenesis
Authors: HAGER JEFFREY H. , HANAHAN DOUGLAS
Published: July 2010

Apoptosis, the process of programmed cell death, plays a critical role in many normal and pathological (disease) processes.1In normal tissues, apoptosis functions in the homeostatic maintenance of proper tissue and organ size by eliminating aged cells to offset the birth of new cells that arise by mitosis. In disease, apoptosis can affect the pathological process is two disparate ways. There are diseases that have too much apoptosis such as autoimmune diabetes and Alzheimer's, or those that have too little apoptosis, such as cancer. This review will focus on the latter and, more specifically, detail and summarize some important lessons learned about apoptosis and cancer from studying a transgenic mouse model of islet cell carcinoma, RIP‐Tag, as outlined below.
Hyperoxia in Cell Culture: A Non‐apoptotic Programmed Cell Death
Authors: KAZZAZ JEFFREY A. , HOROWITZ STUART , LI YUCHI , MANTELL LIN L.
Published: July 2010

Here we discuss the morphological features and our current understanding of the pathways involved in non‐apoptotic cell death from O2 toxicity. Preliminary data on hyperoxic signaling indicate that NF‐κB translocation (and presumptive activation) is not a result of the p42/p44 MAPK pathway, but a likely downstream consequence of activation of the JNK pathway. Our observations suggest the existence of multiple signal transduction pathways in hyperoxia‐induced cell death: one involved in the stress response which appears to be NF‐κB‐dependent and another in cell death.
Apoptosis in Coxsackievirus B3‐induced Myocarditis and Dilated Cardiomyopathy
Authors: HUBER S. A. , BUDD R. C. , ROSSNER K. , NEWELL M. K.
Published: July 2010

Group B coxsackieviruses (CVB), which infect the myocardium, cause myocarditis and dilated cardiomyopathy. However, not all infections of the myocardium result in disease. In the mouse model, CVB infection stimulates autoimmune T cell response to cardiac antigens, and these autoimmune effectors cause myocyte necrosis and cardiomyopathy. Induction of pathogenic autoimmunity depends upon CD4+ Thl (interferon‐γ positive) cells while Th2 (IL‐4 positive) cell responses promote disease resistance. T lymphocytes expressing the γ‐δ T cell receptor (γδ+) constitute up to 12% of the inflammatory cells in the heart and are crucial to maintaining a dominant Th1 response phenotype. γδ+ lymphocytes modulate T cell responses by selectively lysing CD4+ Th2 cells. Thl cells are not killed by γδ+ cells. Lysis requires direct cell:cell interaction between the γδ+ cell and CD4+ Th2 target and is most likely mediated through Fas: FasL interaction. These studies demonstrate a novel mechanism for immune modulation of cytokine responses in vivo.
The Role of Melanocortins in Adipocyte Function
Authors: BOSTON BRUCE A.
Published: July 2010

ABSTRACT: It has been demonstrated that adipocytes express high affinity ACTH and α‐MSH binding sites, and that ACTH, α‐MSH, and β‐LPH are potent lipolytic Hormones. Considerable species variability exists in the lipolytic response to melanocortins, however. Recently, MC2 and MC5 receptor‐MRNA was found in both murine adipocytes and in the 3T3‐L1 murine embryonic fibroblast cell line, but only after the 3T3‐L1 cells had differentiated into adipocytes. The 3T3‐L1 cell line was used to characterize the pharmacological properties of both MC2 and MC5 receptors in situ. Both murine MC2 and MC5 receptors are functional in the adipocyte, although the MC5 receptor required high doses of α‐MSH to activate cylase. ACTH potently stimulates cyclase with EC50 values that are consistent with the hypothesis that the murine MC2 receptor, not the MC5 receptor, mediates stress‐induced lipolysis via release of ACTH from the pituitary.
An Immunocytochemical Approach to the Study of β‐Endorphin Production in Human Keratinocytes using Confocal Microscopy
Authors: ZANELLO SUSANA B. , JACKSON DAVID M. , HOLICK MICHAEL F.
Published: July 2010

ABSTRACT: Proopiomelanocortin (POMC) is a protein that is posttranslationally processed to yield POMC peptides. The main site of POMC expression is the anterior pituitary lobe but many other sources have been identified. There is evidence that the skin produces POMC peptides, although their roles have not yet been defined. In the skin, regulation of POMC gene expression is known to be hair‐cycle dependent, and it is localized to the sebaceous gland. In particular, β‐endorphin, a POMC peptide, has been shown to be modulated by TPA, IL‐1α, and ultraviolet radiation in keratinocytes. These results were obtained by examination of POMC mRNA levels using the Northern blot method; β‐endorphin protein production by the Western blot method on cultured cells; and immunocytochemistry for tissue preparations. This report represents an approach to use immunocytochemistry to quantify β‐endorphin production in cultured human keratinocytes. Additionally, we examined whether exposure to 20 mJ ultraviolet B radiation (UVB) and/or UVA could influence β‐endorphin production in these cells. Keratinocytes were grown in monolayers, in serum‐free medium, fixed, and incubated with antiserum to whole synthetic β‐endorphin. Fluorescence microscopy was performed with a confocal laser scanning microscope. The integrated level of fluorescence was evaluated in n= 18 ± 8 individual cells, and this was assumed to be proportional to β‐endorphin content. High variability was observed in the fluorescence intensity among cells. No significant differences between control and UVB‐ or UVA+UVB‐treated cells was found. Similar results were produced by using brefeldin A, a compound that disrupts the secretory pathway, eliminating the possibility that the absence of a difference between β‐endorphin content in the treated and control cells was due to secretion of the peptide into the medium. We conclude that: (1) β‐endorphin or β‐endorphin‐like peptides are produced in human keratinocytes and are readily detected by immunocytochemistry; (2) under the conditions tested, UVA and/or UVB did not increase β‐endorphin‐like immunoreactivity in these cells.
UV Light and MSH Receptors
Authors: CHAKRABORTY ASHOK K. , FUNASAKA YOKO , SLOMINSKI ANDRZEJ , BOLOGNIA JEAN , SODI STEFANO , ICHIHASHI MASAMITSU , PAWELEK JOHN M.
Published: July 2010

ABSTRACT:Ultraviolet B (UVB) radiation in the skin induces pigmentation that protects cells from further UVB damage and reduces photocarcinogenesis. Although the mechanisms are not well understood, our laboratory has shown that UVB radiation causes increased MSH receptor activity by redistributing MSH receptors from internal pools to the external surface, with a resultant increase in cellular responsiveness to MSH. By this means, UVB and MSH act synergistically to increase melanin content in the skin of mice and guinea pigs. In humans, MSH causes increased skin pigmentation, predominantly in sun‐exposed areas. We have shown recently that UVB irradiation and exposure to MSH or to dbcAMP, stimulates production of mRNAs for both αMSH receptors and POMC in human melanocytes and keratinocytes. This indicates that at least one action of UVB on the pigmentary system is mediated through increased MSH receptor production, as well as through the production of the signal peptides, MSH and ACTH, that can further activate MSH receptors. The results add support to the hypothesis that the effects of UVB on cutaneous melanogenesis are mediated through a series of coordinated events in which MSH receptors and POMC‐derived peptides play a central role.
The Melanocortin‐1 Receptor and Human Pigmentation
Authors: ABDEL‐MALEK ZALFA , SUZUKI ITARU , TADA AKIHIRO , IM SUNGBIN , AKCALI CAN
Published: July 2010

ABSTRACT: α‐Melanocyte stimulating hormone (α‐MSH) is known to be the main physiologic regulator for integumental pigmentation of various vertebrate species. However, the role of α‐MSH and related melanocortins in the regulation of human cutaneous pigmentation is only beginning to be understood. Cloning of the melanocortin‐1 receptor (MC1R), and the feasibility of establishing normal human epidermal melanocyte cultures have made it possible to demonstrate direct and specific biological effects of α‐MSH on these cells. It is now recognized that both α‐MSH and ACTH have similar mitogenic and melanogenic effects on human epidermal melanocytes. These effects are mediated by binding of these hormones to the specific MC1R that recognizes them both with similar affinity. Human MC1R is homologous to its mouse counterpart in that its activation leads to stimulation of eumelanin synthesis. MC1R is also the binding site for agouti signaling protein (ASP), the product of the agouti locus. Human epidermal melanocytes respond to purified recombinant mouse or human ASP, with a reduction in basal tyrosinase activity, and complete abrogation of the mitogenic and melanogenic effects of α‐MSH. These results suggest that ASP induces pheomelanin synthesis by competing with α‐MSH for binding to the MC1R. This receptor seems to be subject to regulation by a variety of paracrine and/or autocrine factors that are synthesized in response to exposure of the skin to ultraviolet radiation (UVR). Activation of MC1R seems to be pivotal for UV‐induced melanogenesis, since stimulation of the cAMP pathway plays a key role in the melanogenic response of human epidermal melanocytes. The melanogenic response to UVR might be influenced by the presence of allelic variants of the MC1R gene. Allelic variants have been identified and shown to be associated with red hair, poor tanning ability, and possibly melanoma. The possible influence of these variants on the function of the MC1R needs to be investigated, in order to understand the physiological consequence of these mutations. Also, the interaction of α‐MSH with other factors that are known to affect pigmentation needs to be better understood in order to define the role possible of this hormone and its receptor in acquired human cutaneous hyper‐ or hypopigmentation.
Molecular Pharmacology of Agouti Protein in Vitro and in Vivo
Authors: BARSH GREGORY S. , OLLMANN MICHAEL M. , WILSON BRENT D. , MILLER KIMBERLY A. , GUNN TERESA M.
Published: July 2010

ABSTRACT: Agouti protein and Agouti‐related protein (Agrp) are paracrine signaling molecules that act by antagonizing the effects of melanocortins, and several alternatives have been proposed to explain their mechanisms of action. Genetic crosses in a sensitized background uncover a phenotypic difference between overexpression of Agouti and loss of Mc1r function, demonstrate that a functional Mc1r is required for the pigmentary effects of Agouti, and suggest that Agouti protein can act as an agonist of the Mc1r in a way that differs from α‐MSH stimulation. In vitro, Agouti protein inhibits melanocortin action by two mechanisms: competitive antagonism that depends on the carboxy‐terminus of the protein, and downregulation of melanocortin receptor signaling that depends on the aminoterminus. Our findings provide evidence of a novel signaling mechanism whereby α‐MSH and Agouti protein function as independent ligands that inhibit each other's binding and transduce opposite signals through a single receptor.
Mechanisms of Antiinflammatory Action of α‐MSH Peptides: In Vivo and in Vitro Evidence
Authors: LIPTON J. M. , ZHAO H. , ICHIYAMA T. , BARSH G. S. , CATANIA A.
Published: July 2010

ABSTRACT: α‐Melanocyte stimulating hormone (α‐MSH) modulates all forms of inflammation by acting on peripheral inflammatory cells, glial inflammatory cells, and on CNS receptors that activate descending antiinflammatory neural pathways. The multiple actions of this ancient peptide suggest that there is no singular biochemical mechanism through which it exerts its antiinflammatory activity. However, research on IL‐10 deficient and Agouti protein hypersecreting mice provide new insights into the actions of the peptide in living animals. Studies of cultured human astrocytes, whole murine brain, and human monocyte/macrophages indicate that a primary effect of the peptide is modulation of activation of the nuclear transcription factor κB. The latter influence may underlie the established reduction of gene expression and production of proinflammatory peptides and inducible nitric oxide by α‐MSH peptides.
α‐MSH and the Regulation of Melanocyte Function
Authors: THODY ANTHONY J.
Published: July 2010

ABSTRACT: α‐MSH, has numerous actions in the skin and by activating the MC1 receptor (MC1‐R) on melanocytes it stimulates melanogenesis. Rather than producing large increase in melanin production α‐MSH acts specifically to stimulate eumelanin synthesis. Although this could be important in determining skin color and tanning there is debate as to the pigmentary significance of α‐MSH in humans. Circulating levels of α‐MSH are negligible and although it is produced in the skin by different cell types, including melanocytes, the major skin form is desacetyl α‐MSH, and this is a weak agonist at MC1‐R. Certain ACTH peptides, notably ACTH1–17, are more potent agonists at the MC1‐R and, since their skin concentrations exceed those of α‐MSH, they could serve as natural ligands at this receptor an regulate pigmentary responses in humans. Activation of MC1‐R does, however, produce other responses in human melanocytes. Thus, α‐MSH stimulates melanocyte dendricity and attachment to extracellular matrix proteins. It also protects melanocytes from the damaging effects of oxidative stress, and regulates their production of NO by modulating the induction of iNOS‐as it does within macrophages. α‐MSH clearly affects various aspects of melanocyte behavior and its melanogenic effects could be the consequence of a more fundamental role in the melanocyte. The precise nature of this role is unclear, but it could be part of a generic role that α‐MSH and other POMC peptides have in skin homeostasis.
Expression of Functional Melanocortin Receptors and Proopiomelanocortin Peptides by Human Dermal Microvascular Endothelial Cells
Authors: SCHOLZEN THOMAS E. , BRZOSKA THOMAS , KALDEN DIRK‐HENNER , HARTMEYER MECHTHILD , FASTRICH MICHAELA , LUGER THOMAS A. , ARMSTRONG CHERYL A. , ANSEL JOHN C.
Published: July 2010

ABSTRACT: Human dermal microvascular endothelial cells (HDMEC) are capable of mediating leukocyte‐endothelial interactions by the expression of cellular adhesion molecules and the release of proinflammatory cytokines and chemokines during cutaneous inflammation. Recent studies support the important role for proopiomelanocortin (POMC) peptides, such as α‐melanocyte stimulating hormone (α‐MSH), as immunomodulators in the cutaneous immune system. The purpose of the studies described here was to determine whether HDMEC serves as both target and source for POMC peptides. RT‐PCR and Northern blot studies demonstrated the constitutive expression of mRNA for the adrenocorticotropin (ACTH) and α‐MSH‐specific melanocortin receptor 1 (MC‐1R) in HDMEC, and the microvascular endothelial cell line HMEC‐1 that could be upregulated by stimulation with IL‐1β and α‐MSH. HDMEC responded to stimulation by α‐MSH with a dose‐ and time‐dependent synthesis and release of the CXC chemokines, IL‐8 and GROα. Likewise, α‐MSH augmented HDMEC chemokine release induced by TNF or IL‐1. HDMEC were found to constitutively express POMC and prohormone convertase 1 (PC‐1); the latter being required to generate ACTH from the POMC prohormone. POMC and PC‐1 mRNA expression are increased as a result of stimulation with UVB and UVA1 radiation, IL‐1, and α‐MSH. In addition, UV‐radiation is capable of inducing the release of HDMEC, ACTH, and α‐MSH in a time‐ and dose‐dependent fashion. Thus, these data provide evidence that HDMEC are capable of expressing functional MC‐1R, POMC, and PC‐1 mRNA; and of releasing POMC peptides with UV light, IL‐1, and α‐MSH as regulatory factors. The expression and regulation of these peptides may be of importance, not only for the autocrine or paracrine regulation of physiologic functions of dermal endothelial cells, but also for the regulation of certain microvascular‐mediated cutaneous or systemic inflammatory responses.
α‐MSH Can Control the Essential Cofactor 6‐Tetrahydrobiopterin in Melanogenesis
Authors: SCHALLREUTER KARIN U. , MOORE JEREMY , TOBIN DESMOND J. , GIBBONS NICHOLAS J.P. , MARSHALL HARRIET S. , JENNER TRACEY , BEAZLEY WAYNE D. , WOOD JOHN M.
Published: July 2010

ABSTRACT: In the human epidermis both keratinocytes and melanocytes express POMC m‐RNA. Immunohistochemical studies of both cell types demonstrate significantly higher levels of α‐MSH in melanocytes than in keratinocytes. Both cell types also hold the full capacity for de novo synthesis/recycling of the essential cofactor (6R)‐l‐erythro‐5,6,7,8‐tetrahydrobiopterin (6BH4). 6BH4 is critical for the hydroxylation of the aromatic amino acids l‐phenylalanine, l‐tyrosine, and l‐tryptophan, for nitric oxide production and in various immune modulatory processes. Recently it was shown that tyrosinase activity is regulated by 6BH4 through a specific allosteric inhibition. The tyrosinase/6BH4 inhibition can be activated by 1:1 complex formation between 6BH4 and α‐MSH, but an excess of α‐MSH over 6BH4 can inhibit tyrosinase due to complex formation by tyr2 in the α‐MSH sequence. In both melanocytes and keratinocytes 6BH4 controls the l‐tyrosine supply via phenylalanine hydroxylase (PAH). Recently we were able to show that the cellular uptake of l‐phenylalanine and its intracellular turnover to l‐tyrosine is crucial for melanogenesis. α‐MSH can promote the production of l‐tyrosine via PAH due to activation of the PAH tetramer to the more active dimer by removing 6BH4 from the regulatory binding domain on the enzyme. In conclusion, α‐MSH can control (1) intracellular l‐tyrosine formation from l‐phenylalanine in both melanocytes and keratinocytes, and (2) tyrosinase activity, directly, in melanocytes.
Probing the Role of the Dopamine D1 Receptor in Psychostimulant Addiction
Authors: ZHANG JIANHUA , WALSH RYAN R. , XU MING
Published: July 2010

Pharmacological studies have shown that blockade of the dopamine D1 receptor attenuates locomotor behaviors and prevents sensitization to psychostimulants. However, due to possible cross‐reactivities of the D1 receptor antagonists, the exact role of the D1 receptor in response to psychostimulants is still not definitive. To address this issue, we used D1 receptor mutant mice and tested locomotor responses of the mutant mice and wild‐type control mice after cocaine and amphetamine treatments. We found that the D1 receptor mutant mice exhibit significantly reduced locomotor responses to repeated cocaine administration compared to wild‐type mice. Moreover, D1 receptor mutant mice were less sensitive than the wild‐type mice to acute amphetamine administration over a dose range, although they exhibited apparently similar behavioral responses to those of the wild‐type mice after repeated amphetamine administration at the 5 mg/kg dose. These studies suggest that the D1 receptor plays an essential role in mediating cocaine‐induced locomotor responses in mice. In addition, the D1 receptor also participates in behavioral responses induced by amphetamine administration. Further molecular studies are in progress to address the intracellular signaling mechanisms in response to D1 receptor activation by psychostimulants.
C‐fosandegr‐1Immediate‐early Gene Induction by Cocaine and Cocaethylene in Rat Brain: A Comparative Study
Authors: THIRIET NATHALIE , AUNIS DOMINIQUE , ZWILLER JEAN
Published: July 2010

The induction of immediate‐early genes can now be considered as a tool to study neuronal activation in different brain structures. These genes, which are rapidly and transiently induced in response to diverse extracellular stimulation, coordinate alterations in gene expression underlying neuronal plasticity. Usingin situhybridization, we found that acute i.p. cocaine (20 mg/kg) injection produced a strong expression ofegr‐1andc‐fosgenes in the nucleus accumbens, caudate‐putamen, and frontal cortex in the rat. Cocaethylene is an active metabolite of cocaine that is formed when cocaine is consumed together with ethyl alcohol. Injection of cocaethylene at a dose equivalent to cocaine induced the expression of the two immediate‐early genes in the same brain structures, but to a lesser extent. A high dose of ethanol increasedegr‐1andc‐fosexpression in the frontal cortex and in the lateral part of the caudateputamen. Since cocaine is known to potently inhibit both dopamine and serotonin transporters, whereas cocaethylene only inhibits the dopamine transporter, our results strongly suggest that the serotonergic system participates in the mode of action of cocaine in its ability to trigger immediate‐early gene transcription.
Methamphetamine Dependence: Medication Development Efforts Based on the Dual Deficit Model of Stimulant Addiction
Authors: ROTHMAN RICHARD B. , PARTILLA JOHN S. , DERSCH CHRISTINA M. , CARROLL F. IVY , RICE KENNER C. , BAUMANN MICHAEL H.
Published: July 2010

Converging lines of evidence indicate that withdrawal from prolonged exposure to stimulants and alcohol results in synaptic deficits of both dopamine (DA) and serotonin (5‐HT). According to the dual deficit model proposed by the authors, DA dysfunction during cocaine or alcohol withdrawal underlies anhedonia and psychomotor retardation, whereas 5‐HT dysfunction gives rise to depressed mood, obsessional thoughts, and lack of impulse control. This model predicts that pharmacotherapies which correct only one of the two neurochemical deficits will not be effective. On the other hand, pharmacotherapies which “correct” both of the proposed DA and 5‐HT abnormalities should be effective in treating stimulant and alcohol dependence. This paper reviews two approaches, based on the dual deficit model, taken by our laboratory to develop medications to treat stimulant abuse.
Serum Withdrawal Potentiates the Toxic Effects of Methamphetaminein Vitro
Authors: CADET JEAN LUD , ORDONEZ SONIA
Published: July 2010

Methamphetamine (METH) has been shown to cause neurotoxic damage bothin vitroandin vivo. The mechanisms of action are thought to involve the production of pathophysiologic concentration of free radicals. The present study was undertaken to assess the toxic effects of METH caused dose‐dependent increased production of reactive oxygen species (ROS) and cell death. Cell death caused by METH was characterized by cytoplasmic vacuolar formation, shrinkage of cytoplasm and nuclear dissolution. Flow cytometric evaluation also revealed that this toxin causes changes similar to those observed in cells undergoing apoptosis. When taken together these observations suggest the METH can cause these cells to die via apoptosis. Further experiments indicated that growth of these cells in low (1%) serum or in the absence of serum markedly enhanced the apoptotic effects of METH. These data provide further support for the ideas that METH can cause ROS‐mediated apoptosis.
Restorative Effects of GDNF on Striatal Dopamine Release in Rats Treated with Neurotoxic Doses of Methamphetamine
Authors: CASS WAYNE A. , MANNING MICHAEL W. , BAILEY SHERRY L.
Published: July 2010

Repeated methamphetamine (METH) administration to animals can result in long‐lasting decreases in striatal dopamine (DA) release and content. Glial cell line‐derived neurotrophic factor (GDNF) has pronounced effects on dopaminergic systemsin vivo, including neuroprotective effects against METH. The present experiments were designed to examine the ability of GDNF to reverse, or accelerate recovery from, METH‐induced alterations in striatal DA release. Male Fischer‐344 rats were administered METH (5 mg/kg, s.c.) or saline 4 times in one day at 2‐hour intervals. Seven days later the animals were anesthetized and given a single injection of 10 μg GDNF, or vehicle, into the right striatum. Three weeks later microdialysis experiments were carried out in both the right and left striata to examine basal and evoked levels of DA and its metabolites 3,4‐dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA). In animals treated with METH followed by vehicle 7 days later, there were significant reductions in potassium‐ and amphetamine‐evoked overflow of DA, and in basal levels of DOPAC and HVA, compared to control animals. In rats treated with METH followed 7 days later with GDNF, there were significant increases in potassium‐ and amphetamine‐evoked overflow of DA on the right, GDNF‐treated, side of the brain compared to the left side. Basal levels of DOPAC and HVA were also elevated on the GDNF‐treated side of the brain. These results suggest that GDNF can accelerate recovery of dopaminergic release processes in the striatum of rats treated with neurotoxic doses of METH.
Methamphetamine‐induced Oxidative Stress in Cultured Mouse Astrocytes
Authors: LAU JOSEPHINE W.S. , SENOK SOLOMON , STADLIN ALFREDA
Published: July 2010

Methamphetamine (METH) is a monoaminergic toxin that destroys dopamine terminals and causes astrogliosisin vivo. Oxidative stress has been shown to play an important role in the toxic effects of METH. In the present study, we sought to determine whether astrocytes are involved in METH‐induced oxidative stress. Reactive oxygen species (ROS), ATP, and change in mitochondria membrane potential (ΔΨm) were examined in cultured striatal, mesencephalic, and cortical astrocytes after 4 to 48 h of 4 mM METH treatment. Results showed that only striatal and mesencephalic astrocytes showed a significant increase in ROS formation from 8 and 12 h, respectively. At 48 h treatment, there was a 55 and 53% increase in ROS content in striatal and mesencephalic astrocytes, respectively, whereas cortical astrocytes showed only a 25% (not significant) increase. JC‐1, a ΔΨm‐sensitive dye, showed a decrease in ΔΨm at 8 h treatment for striatal and mesencephalic astrocytes and at 12 h for cortical astrocytes. Astrocytes from all three regions showed a similar pattern of initial increase followed by a decrease in ATP content, with striatal astrocytes resulting in a maximum depletion (39% of control value) at 48 h treatment. These findings showed that METH treatment resulted in the formation of ROS in the order of striatal > mesencephalic > cortical astrocytes. Although the formation of ROS did not severely interfere with ATP production, a depolarization of mitochondria was observed. The present study suggested that astrocytes may be an important element governing the selective vulnerability to the striatum to METH‐induced oxidative stress.
Pharmacology of MDMA in Humans
Authors: DE LA TORRE R. , FARRÉ M. , ROSET P. N. , LÓPEZ C. HERNÁNDEZ , MAS M. , ORTUÑO J. , MENOYO E. , PIZARRO N. , SEGURA J. , CAMÍ J.
Published: July 2010

MDMA given at recreational doses (range tested 50 to 150 mg) to healthy volunteers, produced mydriasis and marked increases in systolic and diastolic blood pressure, heart rate, and pupillary diameter. MDMA induced changes on oral temperature. The time course of this observation was biphasic, as a slight decrease at 1 h and a slight increase at 2 and 4 h were observed. MDMA induced a slight dose‐dependent impairment on psychomotor performance. MDMA produced a marked rise in plasma cortisol and prolactin concentrations. The elimination half‐life of MDMA was about 8‐9 h. Drug concentrations increased, and a parallel increase in physiologic and hormonal measures was observed. Both peak concentrations and peak effects were obtained between 1 and 2 h and decreased to baseline values 4‐6 h after drug administration.
Susceptibility to Subsequent Episodes in Spontaneous Recurrence of Methamphetamine Psychosis
Authors: YUI KUNIO , ISHIGURO TAKEO , GOTO KIMIHIKO , IKEMOTO SHIGENORI
Published: July 2010

The relation is examined between increased sensitivity to stress associated with noradrenergic hyperactivity and dopaminergic changes, and susceptibility to subsequent spontaneous recurrences of methamphetamine (MAP) psychosis (i.e., flashbacks). Plasma monoamine metabolite levels were assayed in 23 flashbackers, 19 nonflashbackers with a history of MAP psychosis, 10 subjects with persistent MAP psychosis, and 21 MAP user and 9 nonuser controls. All 23 flashbackers had undergone frightening stressful experiences during previous MAP use. Mild psychosocial stressors then triggered flashbacks. The 12 flashbackers with further episodes had markedly increased norepinephrine levels and slightly increased plasma levels of 3‐methoxytyramine, an index of dopamine release. While the 11 flashbackers with a single episode displayed small increases in norepinephrine and 3‐methoxytyramine levels. Thus, robust noradrenergic hyperreactivity, involving increased dopamine release in response to mild stress may predispose to further episodes of flashbacks.
Behavioral Responses to Repeated Cocaine Exposure in Mice Selectively Bred for Differential Sensitivity to Pentobarbital
Authors: PARK KWANKYUN , HUBER JASON , KOLTA MALAK G. , STINO FARID K.R. , SAMAAN SABER S. , SOLIMAN KARAM F.A.
Published: July 2010

Mice from the 20th generation of three lines divergently selected for response to pentobarbital‐induced sedation times [long‐sedation time (LST), short sedation time (SST), and randomly bred control (RBC)] were used to study cocaine‐induced behavioral sensitization. These lines showed variable degrees of locomotor activities in response to cocaine. At a low cocaine dose and long withdrawal period (10 mg/kg, twice a day for 5 days followed by a 14‐day withdrawal), the LST mice showed tolerance development. In response to cocaine, the locomotor activities of the SST were not significantly different from the RBC group. At a higher dose and a shorter withdrawal period (20 mg/kg, daily for 7 days followed by a 3‐day withdrawal), the SST mice showed behavioral sensitization similar to the RBC mice, but the LST mice did not develop sensitization. The different responses in locomotor activity induced by cocaine suggest that genetic factors may play a role in determining the magnitude of response to this drug. Dopamine (DA) levels did not differ significantly in either striatum (STR) or nucleus accumbens (NAC) for the cocaine‐treated animals to their corresponding saline‐treated controls. The affinity (Kd) of D2in the NAC decreased significantly, without changes in density (Bmax), in the cocaine‐treated SST and RBC mice. On the other hand, the density of D2binding sites in the SST and the RBC mice in the STR was significantly increased in cocaine‐treated groups without change in Kd. The LST mice did not show any changes in the Kdand Bmaxin either the STR or the NAC. Taken together, these findings suggest that the changes in the Kdof D2in the NAC and the Bmaxof D2in the STR may contribute to the differences in locomotor responses to cocaine exposure in these mouse lines.
Effects of Neonatal Exposure to Cocaine in the Development of the Neurotransmitters Retinal Systems: An Immunocytochemical and Neurochemical Study
Authors: SUMMAVIELLE TERESA , SILVA‐ARAÚJO ANTÓNIO , SILVA MARIA C. , TAVARES MARIA AMÉLIA
Published: July 2010

The visual system of rodents is affected if exposure to drugs, e.g., cocaine, occurs during prenatal or early postnatal development. This study aims to evaluate, in an experimental model of neonatal exposure to cocaine in the rat, the immunocytochemical expression of tyrosine hydroxylase in the retina and the levels of different neurotransmitters and its metabolites. Male Wistar rats were given 15 mg cocaine hydrochloride/kg body weight/day, subcutaneously, in two daily doses, from the day after birth (PND1) to PND6, 13, and 29. Controls were given 0.9% saline. Groups of rats were perfused at PND7, 14, and 30 with fixative, and the retinas were processed as wholemounts, and immunostained with the antibody anti‐TH. Other groups were decapitated, and the retinas were dissected and processed by high performance liquid chromatography with electrochemical detection (HPLC‐EC) for determination of dopamine and metabolites (DOPAC and HVA). A reduction in the retinal surface area was detected in the PND30 cocaine group, and a decrease in the density of the small TH‐IR cells was found in the PND14 cocaine group although not reaching significant levels. The other quantitative parameters did not differ between the control and cocaine groups. The levels of neurotransmitters did not significantly differ between the groups at any age. These results show a differential vulnerability of the dopaminergic system of rats exposed neonatally to cocaine when compared with the effects found after prenatal exposure to the same drug.
Cl‐Dependent Na‐H Exchange: A Novel Colonic Crypt Transport Mechanism
Authors: BINDER HENRY J. , RAJENDRAN VAZHAIKKURICHI M. , GEIBEL JOHN P.
Published: July 2010

Abstract: This communication summaries a series of observations of the transport function of the crypt of the rat distal colon. Development of methods to study both 22Na uptake by apical membrane vesicles prepared from crypt cells and intracellular pHi (pHi), fluid movement (Jv), and bicarbonate secretion during microperfusion of the crypt has led to the identification of (1) a novel Cl‐dependent Na‐H exchange (Cl‐NHE) that most likely represents the coupling of a Cl channel to a Na‐H exchange isoform that has not as yet been identified and (2) bicarbonate secretion that appears to be most consistent with HCO3 uptake across the basolateral membrane by a mechanism that is closely linked to Cl transport and its movement across the apical membrane via an anion channel. Na‐dependent fluid absorption is the constitutive transport process in the crypt, while fluid secretion is regulated by one or more neurohumoral agonists. Cl‐NHE is responsible for both the recovery/regulation of pHi in crypt cells to an acid load and fluid absorption.
Coupling between Na+, Sugar, and Water Transport across the Intestine
Authors: WRIGHT ERNEST M. , LOO DONALD D. F.
Published: July 2010

Abstract: Water is absorbed across the small intestine in the absence of external driving forces. However, it has been established that water transport is secondary to active sodium transport. In the upper intestine both sodium and water absorption are largely dependent on the presence of D‐glucose. The link between active sodium transport and glucose is the coupled transport of sodium and glucose across the brush border membrane of enterocytes by the Na+/ glucose cotransporter (SGLT1). Na+ that enters the cells with glucose is pumped out towards the blood by 3Na+/2K+ pumps on the basolateral membrane, and glucose passes out across the basolateral membrane by facilitated diffusion, the net result being that glucose and sodium are transported across the epithelium. The coupling between Na+, glucose, and water transport is less well understood. It is commonly thought that Na+ transport increases the local osmotic pressure in the lateral intercellular spaces, and that this in turn generates osmotic water flow across the epithelium. Recent work suggests a more direct link between Na+, glucose, and water transport; that is, water is cotransported along with Na+ and sugar through SGLT1. Here we review the evidence for Na+/glucose/water cotransport.
Three 5′‐Variant mRNAs of Anion Exchanger AE2 in Stomach and Intestine of Mouse, Rabbit, and Rat
Authors: ROSSMANN HEIDI , ALPER SETH L. , NADER MANUELA , WANG ZHUO , GREGOR MICHAEL , SEIDLER URSULA
Published: July 2010

Abstract: AE2 is one of three known isoforms of the anion exchanger (AE) gene family. The use of alternative promoters, resulting in a tissue‐specific transcript pattern, was reported for all AE genes. Three N‐terminal variant AE2 subtypes are described: AE2a, AE2b, and AE2c. Although the basolaterally located parietal cell anion exchanger is known to be an AE2, the molecular identity of the basolateral and apical anion exchangers throughout the gut are still unknown. This article summarizes functional, immunohistochemical, and Western blot data demonstrating the basolateral localization of the gastric and intestinal AE2 in rabbit, mouse, and rat, and showing the AE2 subtype mRNA expression pattern in the stomach and along the intestine of rabbit and mouse: AE2a is expressed in all studied tissues, but most strongly in the colon; AE2b is expressed mainly in the stomach; and AE2c is detected nearly exclusively in the stomach. Further investigation is necessary to characterize the apical anion transport protein involved in NaCl absorption and HCO3− secretion in the gut.
Stimulation by Portal Insulin of Intestinal Glucose Absorption via Hepatoenteral Nerves and Prostaglandin E2 in the Isolated, Jointly Perfused Small Intestine and Liver of the Rat
Authors: STÜMPEL FRANK , SCHOLTKA BETTINA , JUNGERMANN KURT
Published: July 2010

Abstract: Insulin infused into the portal vein acutely enhanced intestinal glucose and galactose absorption via the sodium‐dependent glucose cotransporter‐1 in the isolated, jointly perfused small intestine and liver of the rat. Atropine and tetrodotoxin infused into the superior mesenteric artery completely prevented the portal insulin‐dependent increase in intestinal glucose absorption, and carbachol caused an increase similar to that of portal insulin. Thus, a signal was transmitted against the bloodstream in a retrograde direction from the portal vein to the small intestine via hepatoenteral cholinergic nerves. The intracellular messenger in the enterocytes was cAMP, and the link between the muscarinic receptors, which do not increase cAMP concentrations, and adenylate cyclase was found to be prostaglandin E2.
The Structure and Function of Claudins, Cell Adhesion Molecules at Tight Junctions
Authors: TSUKITA SHOICHIRO , FURUSE MIKIO
Published: July 2010

Abstract: Tight junctions (TJs) play a pivotal role in compartmentalization in multicellular organisms by sealing the paracellular pathway in epithelial and endothelial cell sheets. Recently, novel integral membrane proteins, claudins, have been identified as major cell adhesion molecules working at TJs. Claudins comprise a multigene family, and each member of ~23 kDa bears four transmembrane domains. To date, 15 members of this gene family have been identified. When expression vectors of each species of claudins were transfected into fibroblasts lacking endogenous claudins or TJs, well‐developed TJs were observed between adjacent transfectants. Furthermore, claudins were shown to be directly involved in the barrier function of TJs by experiments using Clostridium perfringens enterotoxin. Now that claudins have been identified, the structure and functions of TJs should be determined in detail in molecular terms.
Intestinal Cell Adhesion Molecules: Liver‐Intestine Cadherin
Authors: GESSNER REINHARD , TAUBER RUDOLF
Published: July 2010

Abstract: The cadherin superfamily comprises a large number of cell adhesion molecules, several of which are expressed in the gastrointestinal tract. LI‐cadherin represents a novel type of cadherin within the cadherin superfamily distinguished from other cadherins by structural and functional features described in this review. In the mouse and human, LI‐cadherin is selectively expressed on the basolateral surface of enterocytes and goblet cells in the small and large intestine, whereas in the rat this cadherin is additionally detectable in hepatocytes. LI‐cadherin is capable of mediating Ca2+‐dependent homophilic cell‐cell adhesion independent of interactions with the cytoskeleton, indicating that the adhesive function of this novel cadherin is complementary to that of E‐cadherin and desmosomal cadherins co expressed in the intestinal mucosa.
Expression and Function of Death Receptors and Their Natural Ligands in the Intestine
Authors: STRÄTER JÖRN , MÖLLER PETER
Published: July 2010

Abstract: The tumor necrosis factor receptor (TNFR) family is a still‐growing group of homologous transmembrane proteins, some of which bear an intra‐cellular “death domain” and are able to directly mediate apoptosis. Apoptosis is induced upon trimerization of the receptors by their natural ligands' constituting the complementary TNF family. The best‐characterized apoptosis‐mediating TNFR family member is CD95 (APO‐1/Fas). CD95 is functionally expressed on the basolateral surface of colonic epithelial cells regardless of their position along the crypt axis. The biological significance of this CD95 expression in the gut, however, is still under discussion. Although it is unlikely that the CD95/CD95L system is involved in the physiologic regeneration of the intestinal epithelium, this system may play an important role in the pathogenesis of inflammatory bowel diseases. In contrast to the normal epithelium, colon carcinoma cell lines are mostly resistant to CD95‐induced apoptosis. The detection of CD95L expression in colon carcinoma cell lines has led to the concept of carcinomas as “immunoprivileged sites,” where invading immune cells are killed by CD95L‐expressing tumor cells. A more recently described member of the TNF family is TRAIL, which is also able to induce apoptosis. As yet, four TRAIL receptors have been cloned, two of which (TRAIL‐R1 and 2) bear a death domain and mediate apoptosis, whereas two others (TRAIL‐R3 and 4) lack (functional) death domains and are supposed to act as decoy receptors. Because many tumor cell lines in vitro are sensitive to TRAIL‐induced apoptosis while their normal counterparts are not, TRAIL is currently under discussion as a possible anticancer therapeutic agent.
Regulation of Intercellular Tight Junctions by Zonula Occludens Toxin and Its Eukaryotic Analogue Zonulin
Authors: FASANO ALESSIO
Published: July 2010

Abstract: The intestinal epithelium represents the largest interface between the external environment and the internal host milieu and constitutes the major barrier through which molecules can either be absorbed or secreted. There is now substantial evidence that tight junctions (tj) play a major role in regulating epithelial permeability by influencing paracellular flow of fluid and solutes. Tj are one of the hallmarks of absorptive and secretory epithelia. Evidence now exists that tj are dynamic rather than static structures and readily adapt to a variety of developmental, physiological, and pathological circumstances. These adaptive mechanisms are still incompletely understood. Activation of PKC either by Zonula occludens toxin (Zot) or by phorbol esters increases paracellular permeability. Alteration of epithelial tj is a recently described property for infectious agents. Clostridium difficile toxin A and B and influenza and vesicular stomatitis viruses have been shown to loosen tj in tissue culture monolayers. Unlike what occurs after the Zot stimulus, these changes appear to be irreversible and are associated with destruction of the tj complex. On the basis of this observation, we postulated that Zot may mimic the effect of a functionally and immunologically related endogenous modulator of epithelial tj. We were able to identify an intestinal Zot analogue, which we named zonulin. It is conceivable that the zonulins participate in the physiological regulation of intercellular tj not only in the small intestine, but also throughout a wide range of extraintestinal epithelia as well as the ubiquitous vascular endothelium, including the blood‐brain barrier. Disregulation of this hypothetical zonulin model may contribute to disease states that involve disordered intercellular communication, including developmental and intestinal disorders, tissue inflammation, malignant transformation, and metastasis.
Cytokine‐Induced Alteration of the Epithelial Barrier to Food Antigens in Disease
Authors: HEYMAN M. , DESJEUX J. F.
Published: July 2010

Abstract: The alteration of the intestinal epithelial barrier is often a consequence of various intestinal diseases but may also be the starting point of these diseases. Undigested food antigens are transported across the intestinal epithelium by a transcytotic mechanism, including a processing within the enterocytes, and leading to the passage of intact proteins, peptides, and amino acids to the underlying mucosa. Inflammation and infection lead to the upregulation of the transport and processing of food proteins; for example, IFNγ increases the rate of transcytosis and alters, like TNF a, the tight junction permeability. Infection of gastric digestive epithelia with Helicobacter pylori also increases the antigenic load transmitted to the underlying immune system by inhibiting the enterocytic lysosomal degradation of proteins. In allergic diseases, such as cow's milk allergy, TNFα may be involved in the intestinal dysfunction and the associated enteropathy.
Protecting Health, Facilitating Trade, or Both?
Authors: THIERMANN ALEJANDRO B.
Published: July 2010

Abstract: The General Agreement on Tariffs and Trade (GATT) has existed and dealt with trade issues since 1947. However, to take on the question of to what extent can we set fair and science‐based rules allowing countries to have the sovereign right to set measures for protecting public, animal and plant health and food safety, while not creating unjustified barriers to trade was the challenge of the Uruguay Round negotiators. The outcome of this seven‐year exercise was the SPS agreement discussed here. A number of key issues are addressed: transparency including notification, special and differential treatment for developing countries, harmonization, equivalence, regionalization, risk analysis, and other matters. Early warning and exposure of these issues has encouraged countries to resolve their problems quickly. Some of the issues that should be taken into consideration during this next round are the following: biotechnology, aquaculture, consumer concerns, animal welfare, the environment, organic foods, morality in trade, compliance with the WTO, compensation, and the precautionary principle. Compliance with the decision of the WTO is an area of grave concern, especially if developed and powerful countries continue to threaten the survival of the WTO system through lengthy and costly legal interpretations and appeals of dispute settlements without serious efforts by all parties to find win‐win solutions. In spite of these problems, over all we must recognize the significant gains in trade thanks to the SPS agreement. The most flagrant trade violations have been eliminated as a result of improved transparency in the process. Consumers are in general better off, since they have greater diversity and increased safety in what they can buy.
International Trade: Multinational Aspectsa
Authors: OZAWA YOSHIHIRO
Published: July 2010

Abstract: Of numerous regional economic agreements, the European Union (EU), the North American Free Trade Agreement (NAFTA), South American Common Market (MERCOSUR), the Association of Southeast Asian Nations (ASEAN), the South Asian Association for Regional Cooperation (SAARC) and the Australia‐New Zealand Closer Economic Relations Agreement are examples that are actively pursuing regional integration for freer trade of animals and animal products. The World Trade Organization (WTO) believes that regional and multinational integration initiatives are complements rather than alternatives in the pursuit of more open trade. in the efforts to harmonize SPS standards among multilateral trading nations, it is recommended that national requirements meet the standards developed by the OIE and the FAO/WHO Codex Alimentarius Commission as the minimum requirements rather than adopting the standards of the lowest common denominator. Regional grouping may hinder multilateral or bilateral trade between the countries of a group and those of the other groups. How to eliminate such non‐tariff barriers as traditional trade custom remains to be examined. Ongoing activities of VICH (Harmonisation of Technical Requirements for Registration of Veterinary Medical Products) may pave the way for more open trade in pharmaceutical products between multilateral regional groups.