The Experts below are selected from a list of 1362 Experts worldwide ranked by ideXlab platform

Andreas Kimergård - One of the best experts on this subject based on the ideXlab platform.

  • identification and characterization by lc uv ms ms of melanotan ii skin tanning products sold illegally on the internet
    Drug Testing and Analysis, 2015
    Co-Authors: Torben Breindahl, Michael Evansbrown, Jim Mcveigh, Peter Hindersson, Allan Stensballe, Mark A Bellis, Andreas Kimergård
    Abstract:

    New methods were developed and validated to determine the identity, contents, and purity of samples of melanotan II, a synthetic Melanocortin Receptor Agonist, sold in vials as injectable skin-tanning products that were purchased from three online shops. Methods were based on liquid chromatography with ultra-violet detection (LC-UV) at wavelength 218 nm, and tandem mass spectrometric detection (MS/MS) after collision-induced fragmentation of the double charged [M+2H]2+ precursor ion (m/z 513). Identification of melanotan II was verified by correct chromatographic retention time, and relative abundance ratios of five qualifying fragment ions. LC-UV was used to quantify melanotan II as well as impurities. Method validation was performed with reference to guidelines for assessing active substances in authorized medicinal products to reach acceptable accuracy and precision. Vials from two shops contained unknown impurities ranging from 4.1 to 5.9%; impurities from one shop were below the quantification limit. The total amount of melanotan II in vials ranged between 4.32 and 8.84 mg, although each shop claimed that vials contained 10 mg melanotan II. A broad range of drugs used for enhancement purposes can be obtained from the illicit market. However, users of these drugs may be exposed to a range of potential harms, as shown in this study, given that these products are manufactured, distributed and supplied from an illicit market. Copyright © 2014 John Wiley & Sons, Ltd

  • identification and characterization by lc uv ms ms of melanotan ii skin tanning products sold illegally on the internet
    Drug Testing and Analysis, 2015
    Co-Authors: Torbe Eindahl, Jim Mcveigh, Allan Stensballe, Michael Evansbrow, Pete Hindersso, Mark A Ellis, Andreas Kimergård
    Abstract:

    New methods were developed and validated to determine the identity, contents, and purity of samples of melanotan II, a synthetic Melanocortin Receptor Agonist, sold in vials as injectable skin-tanning products that were purchased from three online shops. Methods were based on liquid chromatography with ultra-violet detection (LC-UV) at wavelength 218 nm, and tandem mass spectrometric detection (MS/MS) after collision-induced fragmentation of the double charged [M+2H](2+) precursor ion (m/z 513). Identification of melanotan II was verified by correct chromatographic retention time, and relative abundance ratios of five qualifying fragment ions. LC-UV was used to quantify melanotan II as well as impurities. Method validation was performed with reference to guidelines for assessing active substances in authorized medicinal products to reach acceptable accuracy and precision. Vials from two shops contained unknown impurities ranging from 4.1 to 5.9%; impurities from one shop were below the quantification limit. The total amount of melanotan II in vials ranged between 4.32 and 8.84 mg, although each shop claimed that vials contained 10 mg melanotan II. A broad range of drugs used for enhancement purposes can be obtained from the illicit market. However, users of these drugs may be exposed to a range of potential harms, as shown in this study, given that these products are manufactured, distributed and supplied from an illicit market.

Roger A.h. Adan - One of the best experts on this subject based on the ideXlab platform.

  • Reduced Anorexigenic Efficacy of Leptin, But Not of the Melanocortin Receptor Agonist Melanotan-II, Predicts Diet-Induced Obesity in Rats
    2016
    Co-Authors: Gertjan Van Dijk, Koert De Vries, Bauke Buwalda, Tiziana Adage, Csaba Nyakas, Roger A.h. Adan, Charles W Wilkinson, Martien J H Kas, Folkert Kuipers, Todd E Thiele
    Abstract:

    Leptin gains access to the central nervous system where it influences activity of neuronal networks involved in ingestive behavior, neuroendocrine activity, and metabolism. In par-ticular, the brain Melanocortin (MC) system is important in leptin signalingandmaintenanceof energybalance.Although leptin or MC Receptor insensitivity has been proposed to be associated with obesity, the present study compared central leptin and MC Receptor stimulation on some of the above-mentioned parameters and investigated whether these treat-ments predict proneness to diet-induced obesity (DIO) in out-bred Wistar rats. Third-cerebroventricular administration of equi-anorexigenic doses of leptin and of the MC Agonist mela-notan-II caused comparable increases in plasma ACTH and corticosterone levels and c-Fos-labeling in approximately 70% of paraventricular hypothalamic (PVN) neuronal cell bodie

  • inhibitory effect of the Melanocortin Receptor Agonist melanotan ii mtii on feeding depends on dietary fat content and not obesity in rats on free choice diets
    Frontiers in Behavioral Neuroscience, 2015
    Co-Authors: José K. Van Den Heuvel, Leslie Eggels, Andrea J. Van Rozen, Andries Kalsbeek, Roger A.h. Adan, Eric Fliers, Susanne E La Fleur
    Abstract:

    Introduction: Conflicting data exist on sensitivity changes of the Melanocortin system during diet-induced obesity. We hypothesized that Melanocortin sensitivity depends on diet composition, in particular on the fat content rather than the level of obesity. The aim of this study was to determine the influence of diet composition on feeding responses to a Melanocortin Receptor Agonist, using free-choice diets that differ in food components. Methods: Male Wistar rats were subjected to a chow (CHOW) diet or a free-choice (fc) diet of either chow, saturated fat and liquid sugar (fcHFHS), chow and saturated fat (fcHF), or chow and liquid sugar (fcHS) for 4 weeks. Melanocortin sensitivity was tested by measuring food intake following administration of the Melanocortin 3/4 Receptor Agonist melanotan II (MTII) or vehicle in the lateral ventricle. In a separate experiment, POMC and AgRP mRNA levels were determined in the arcuate nucleus with in situ hybridization in rats subjected to the free-choice diets for 4 weeks. Results: Rats on the fcHFHS diet for 4 weeks show increased caloric intake and body weight gain compared to rats on the CHOW, fcHS and fcHF diet. Caloric intake and body weight gain was comparable between rats on the fcHF, fcHS and CHOW diet. After 4 weeks diet, POMC and AgRP mRNA levels were not different between diet groups. MTII inhibited caloric intake to a larger extent in rats on the fcHF diet compared to rats on the CHOW, fcHFHS or fcHS diet. Moreover, the fat component was the most inhibited by MTII, and the sugar component the least. Conclusion: Rats on the fcHF diet show stronger food intake inhibition to the Melanocortin Receptor Agonist MTII than rats on the CHOW, fcHS and fcHFHS diet, which is independent of caloric intake and body weight gain. Our data point towards an important role for diet composition, particularly the dietary fat content, and not obesity in the sensitivity of the Melanocortin system.

  • reduced anorexigenic efficacy of leptin but not of the Melanocortin Receptor Agonist melanotan ii predicts diet induced obesity in rats
    Endocrinology, 2005
    Co-Authors: Gertjan Van Dijk, Koert De Vries, Bauke Buwalda, Tiziana Adage, Todd E Thiele, Csaba Nyakas, Roger A.h. Adan, Charles W Wilkinson, Anton J W Scheurink
    Abstract:

    Leptin gains access to the central nervous system where it influencesactivityofneuronalnetworksinvolvediningestive behavior, neuroendocrine activity, and metabolism. In particular, the brain Melanocortin (MC) system is important in leptinsignalingandmaintenanceofenergybalance.Although leptin or MC Receptor insensitivity has been proposed to be associated with obesity, the present study compared central leptin and MC Receptor stimulation on some of the abovementioned parameters and investigated whether these treatments predict proneness to diet-induced obesity (DIO) in outbred Wistar rats. Third-cerebroventricular administration of equi-anorexigenic doses of leptin and of the MC Agonist melanotan-II caused comparable increases in plasma ACTH and corticosterone levels and c-Fos-labeling in approximately 70% of paraventricular hypothalamic (PVN) neuronal cell bodies containing CRH. This reinforces involvement of paraventricular CRH neurons in the short-term neuroendocrine and ingestive effects of leptin and Melanocortins. In the DIO prediction study, anorexigenic efficacy of melanotan-II was not correlated with any parameter linked to DIO but was highly correlated with MC in situ binding (with labeled [Nle 4 ,DPhe 7 ]-MSH) as well as CRH immunoreactivity in the PVN of DIO rats. This suggests intricate relationships among MC signaling, the CRH system, and ingestive behavior unrelated to DIO. In the same animals, leptin’s anorexigenic efficacy was not correlated with PVN MC in situ binding or CRH immunoreactivity but correlated inversely to post-DIO plasma leptin, liver weight, and abdominal adiposity, the latter being correlated to insulin resistance. Thus, differences in leptin butnotMCsignalingmightunderlieDIO,visceralobesity,and insulin resistance. (Endocrinology 146: 5247–5256, 2005)

  • Differential regulation of agouti-related protein and neuropeptide Y in hypothalamic neurons following a stressful event.
    Journal of molecular endocrinology, 2005
    Co-Authors: Martien J H Kas, Adrie W. Bruijnzeel, Jurgen R. Haanstra, Victor M. Wiegant, Roger A.h. Adan
    Abstract:

    Stress affects eating behaviour in rodents and humans, suggesting that the regulation of energy balance and the stress response are coupled physiological processes. Neuropeptide Y (NPY) and agouti-related protein (AgRP) are potent food-stimulating neuropeptides that are highly co-localised in arcuate nucleus neurons of the hypothalamus. Recent studies have shown that NPY and AgRP mRNA levels in these neurons respond similarly to fasting and leptin, indicating functional redundancy of the neuropeptide systems in these orexigenic neurons. However, we have found that NPY and AgRP mRNA expression in arcuate nucleus neurons are dissociated immediately following a stressful event. Two hours following a brief session of inescapable foot shocks, AgRP mRNA levels are down-regulated (P < 0.0001). In contrast, NPY mRNA levels are up-regulated (P < 0.0001). To provide physiological relevance for this acute down-regulation of AgRP, an inverse Agonist of Melanocortin Receptors, we have shown that acute intracerebroventricular injection of a Melanocortin Receptor Agonist, alpha-melanocyte-stimulating hormone (alpha-MSH), caused a significantly stronger activation of the hypothalamus-pituitary-adrenal-cortical (HPA) axis following a stressful event than in controls. Thus, AgRP and NPY mRNA levels in similar arcuate nucleus neurons are differentially regulated following a stressful event. This may contribute to increased sensitivity for alpha-MSH to activate the HPA axis following a repeated stressful experience.

  • the potent Melanocortin Receptor Agonist melanotan ii promotes peripheral nerve regeneration and has neuroprotective properties in the rat
    European Journal of Pharmacology, 2003
    Co-Authors: M. Poort Ter Laak, Jan H. Brakkee, Roger A.h. Adan, Frank P T Hamers, Willem Hendrik Gispen
    Abstract:

    Abstract The neurotrophic and neuroprotective potential of the α-melanocyte-stimulating hormone (α-MSH) analog cyclo-[Ac-Nle4,Asp5, d -Phe7,Lys10]α-MSH-(4–10) amide (melanotan-II), a potent Melanocortin Receptor Agonist, was investigated. The sciatic nerve crush model was used as a paradigm to investigate the neurotrophic properties of melanotan-II. Melanotan-II significantly enhanced the recovery of sensory function following a crush lesion of the sciatic nerve in the rat at a dose of 20 μg kg−1 per 48 h, s.c., but not at a dose of 2 or 50 μg kg−1. In addition, we observed that melanotan-II also possesses neuroprotective properties, as it partially protected the nerve from a toxic neuropathy induced by cisplatin. Thus, the present data for the first time demonstrate the effectiveness of the potent α-MSH analog melanotan-II in nerve regeneration and neuroprotection.

Todd E Thiele - One of the best experts on this subject based on the ideXlab platform.

  • Reduced Anorexigenic Efficacy of Leptin, But Not of the Melanocortin Receptor Agonist Melanotan-II, Predicts Diet-Induced Obesity in Rats
    2016
    Co-Authors: Gertjan Van Dijk, Koert De Vries, Bauke Buwalda, Tiziana Adage, Csaba Nyakas, Roger A.h. Adan, Charles W Wilkinson, Martien J H Kas, Folkert Kuipers, Todd E Thiele
    Abstract:

    Leptin gains access to the central nervous system where it influences activity of neuronal networks involved in ingestive behavior, neuroendocrine activity, and metabolism. In par-ticular, the brain Melanocortin (MC) system is important in leptin signalingandmaintenanceof energybalance.Although leptin or MC Receptor insensitivity has been proposed to be associated with obesity, the present study compared central leptin and MC Receptor stimulation on some of the above-mentioned parameters and investigated whether these treat-ments predict proneness to diet-induced obesity (DIO) in out-bred Wistar rats. Third-cerebroventricular administration of equi-anorexigenic doses of leptin and of the MC Agonist mela-notan-II caused comparable increases in plasma ACTH and corticosterone levels and c-Fos-labeling in approximately 70% of paraventricular hypothalamic (PVN) neuronal cell bodie

  • evidence that Melanocortin Receptor Agonist melanotan ii synergistically augments the ability of naltrexone to blunt binge like ethanol intake in male c57bl 6j mice
    Alcoholism: Clinical and Experimental Research, 2015
    Co-Authors: Montserrat Navarro, Francisca Carvajal, Jose Manuel Lermacabrera, Inmaculada Cubero, Mitchell J. Picker, Todd E Thiele
    Abstract:

    Background The nonselective opioid Receptor antAgonist, naltrexone (NAL), reduces alcohol (ethanol [EtOH]) consumption in animals and humans and is an approved medication for treating alcohol abuse disorders. ProopioMelanocortin (POMC)-derived Melanocortin (MC) and opioid peptides are produced in the same neurons in the brain, and recent preclinical evidence shows that MC Receptor (MCR) Agonists reduce excessive EtOH drinking in animal models. Interestingly, there is a growing body of literature revealing interactions between the MC and the opioid systems in the modulation of pain, drug tolerance, and food intake. Methods In the present report, a mouse model of binge EtOH drinking was employed to determine whether the MCR Agonist, melanotan-II (MTII), would improve the effectiveness of NAL in reducing excessive binge-like EtOH drinking when these drugs were co-administered prior to EtOH access. Results Both NAL and MTII blunt binge-like EtOH drinking and associated blood EtOH levels, and when administered together, a low dose of MTII (0.26 mg/kg) produces a 7.6-fold increase in the effectiveness of NAL in reducing binge-like EtOH drinking. Using isobolographic analysis, it is demonstrated that MTII increases the effectiveness of NAL in a synergistic manner. Conclusions The current observations suggest that activators of MC signaling may represent a new approach to treating alcohol abuse disorders and a way to potentially improve existing NAL-based therapies.

  • reduced anorexigenic efficacy of leptin but not of the Melanocortin Receptor Agonist melanotan ii predicts diet induced obesity in rats
    Endocrinology, 2005
    Co-Authors: Gertjan Van Dijk, Koert De Vries, Bauke Buwalda, Tiziana Adage, Todd E Thiele, Csaba Nyakas, Roger A.h. Adan, Charles W Wilkinson, Anton J W Scheurink
    Abstract:

    Leptin gains access to the central nervous system where it influencesactivityofneuronalnetworksinvolvediningestive behavior, neuroendocrine activity, and metabolism. In particular, the brain Melanocortin (MC) system is important in leptinsignalingandmaintenanceofenergybalance.Although leptin or MC Receptor insensitivity has been proposed to be associated with obesity, the present study compared central leptin and MC Receptor stimulation on some of the abovementioned parameters and investigated whether these treatments predict proneness to diet-induced obesity (DIO) in outbred Wistar rats. Third-cerebroventricular administration of equi-anorexigenic doses of leptin and of the MC Agonist melanotan-II caused comparable increases in plasma ACTH and corticosterone levels and c-Fos-labeling in approximately 70% of paraventricular hypothalamic (PVN) neuronal cell bodies containing CRH. This reinforces involvement of paraventricular CRH neurons in the short-term neuroendocrine and ingestive effects of leptin and Melanocortins. In the DIO prediction study, anorexigenic efficacy of melanotan-II was not correlated with any parameter linked to DIO but was highly correlated with MC in situ binding (with labeled [Nle 4 ,DPhe 7 ]-MSH) as well as CRH immunoreactivity in the PVN of DIO rats. This suggests intricate relationships among MC signaling, the CRH system, and ingestive behavior unrelated to DIO. In the same animals, leptin’s anorexigenic efficacy was not correlated with PVN MC in situ binding or CRH immunoreactivity but correlated inversely to post-DIO plasma leptin, liver weight, and abdominal adiposity, the latter being correlated to insulin resistance. Thus, differences in leptin butnotMCsignalingmightunderlieDIO,visceralobesity,and insulin resistance. (Endocrinology 146: 5247–5256, 2005)

Jim Mcveigh - One of the best experts on this subject based on the ideXlab platform.

  • identification and characterization by lc uv ms ms of melanotan ii skin tanning products sold illegally on the internet
    Drug Testing and Analysis, 2015
    Co-Authors: Torben Breindahl, Michael Evansbrown, Jim Mcveigh, Peter Hindersson, Allan Stensballe, Mark A Bellis, Andreas Kimergård
    Abstract:

    New methods were developed and validated to determine the identity, contents, and purity of samples of melanotan II, a synthetic Melanocortin Receptor Agonist, sold in vials as injectable skin-tanning products that were purchased from three online shops. Methods were based on liquid chromatography with ultra-violet detection (LC-UV) at wavelength 218 nm, and tandem mass spectrometric detection (MS/MS) after collision-induced fragmentation of the double charged [M+2H]2+ precursor ion (m/z 513). Identification of melanotan II was verified by correct chromatographic retention time, and relative abundance ratios of five qualifying fragment ions. LC-UV was used to quantify melanotan II as well as impurities. Method validation was performed with reference to guidelines for assessing active substances in authorized medicinal products to reach acceptable accuracy and precision. Vials from two shops contained unknown impurities ranging from 4.1 to 5.9%; impurities from one shop were below the quantification limit. The total amount of melanotan II in vials ranged between 4.32 and 8.84 mg, although each shop claimed that vials contained 10 mg melanotan II. A broad range of drugs used for enhancement purposes can be obtained from the illicit market. However, users of these drugs may be exposed to a range of potential harms, as shown in this study, given that these products are manufactured, distributed and supplied from an illicit market. Copyright © 2014 John Wiley & Sons, Ltd

  • identification and characterization by lc uv ms ms of melanotan ii skin tanning products sold illegally on the internet
    Drug Testing and Analysis, 2015
    Co-Authors: Torbe Eindahl, Jim Mcveigh, Allan Stensballe, Michael Evansbrow, Pete Hindersso, Mark A Ellis, Andreas Kimergård
    Abstract:

    New methods were developed and validated to determine the identity, contents, and purity of samples of melanotan II, a synthetic Melanocortin Receptor Agonist, sold in vials as injectable skin-tanning products that were purchased from three online shops. Methods were based on liquid chromatography with ultra-violet detection (LC-UV) at wavelength 218 nm, and tandem mass spectrometric detection (MS/MS) after collision-induced fragmentation of the double charged [M+2H](2+) precursor ion (m/z 513). Identification of melanotan II was verified by correct chromatographic retention time, and relative abundance ratios of five qualifying fragment ions. LC-UV was used to quantify melanotan II as well as impurities. Method validation was performed with reference to guidelines for assessing active substances in authorized medicinal products to reach acceptable accuracy and precision. Vials from two shops contained unknown impurities ranging from 4.1 to 5.9%; impurities from one shop were below the quantification limit. The total amount of melanotan II in vials ranged between 4.32 and 8.84 mg, although each shop claimed that vials contained 10 mg melanotan II. A broad range of drugs used for enhancement purposes can be obtained from the illicit market. However, users of these drugs may be exposed to a range of potential harms, as shown in this study, given that these products are manufactured, distributed and supplied from an illicit market.

Allan Stensballe - One of the best experts on this subject based on the ideXlab platform.

  • identification and characterization by lc uv ms ms of melanotan ii skin tanning products sold illegally on the internet
    Drug Testing and Analysis, 2015
    Co-Authors: Torben Breindahl, Michael Evansbrown, Jim Mcveigh, Peter Hindersson, Allan Stensballe, Mark A Bellis, Andreas Kimergård
    Abstract:

    New methods were developed and validated to determine the identity, contents, and purity of samples of melanotan II, a synthetic Melanocortin Receptor Agonist, sold in vials as injectable skin-tanning products that were purchased from three online shops. Methods were based on liquid chromatography with ultra-violet detection (LC-UV) at wavelength 218 nm, and tandem mass spectrometric detection (MS/MS) after collision-induced fragmentation of the double charged [M+2H]2+ precursor ion (m/z 513). Identification of melanotan II was verified by correct chromatographic retention time, and relative abundance ratios of five qualifying fragment ions. LC-UV was used to quantify melanotan II as well as impurities. Method validation was performed with reference to guidelines for assessing active substances in authorized medicinal products to reach acceptable accuracy and precision. Vials from two shops contained unknown impurities ranging from 4.1 to 5.9%; impurities from one shop were below the quantification limit. The total amount of melanotan II in vials ranged between 4.32 and 8.84 mg, although each shop claimed that vials contained 10 mg melanotan II. A broad range of drugs used for enhancement purposes can be obtained from the illicit market. However, users of these drugs may be exposed to a range of potential harms, as shown in this study, given that these products are manufactured, distributed and supplied from an illicit market. Copyright © 2014 John Wiley & Sons, Ltd

  • identification and characterization by lc uv ms ms of melanotan ii skin tanning products sold illegally on the internet
    Drug Testing and Analysis, 2015
    Co-Authors: Torbe Eindahl, Jim Mcveigh, Allan Stensballe, Michael Evansbrow, Pete Hindersso, Mark A Ellis, Andreas Kimergård
    Abstract:

    New methods were developed and validated to determine the identity, contents, and purity of samples of melanotan II, a synthetic Melanocortin Receptor Agonist, sold in vials as injectable skin-tanning products that were purchased from three online shops. Methods were based on liquid chromatography with ultra-violet detection (LC-UV) at wavelength 218 nm, and tandem mass spectrometric detection (MS/MS) after collision-induced fragmentation of the double charged [M+2H](2+) precursor ion (m/z 513). Identification of melanotan II was verified by correct chromatographic retention time, and relative abundance ratios of five qualifying fragment ions. LC-UV was used to quantify melanotan II as well as impurities. Method validation was performed with reference to guidelines for assessing active substances in authorized medicinal products to reach acceptable accuracy and precision. Vials from two shops contained unknown impurities ranging from 4.1 to 5.9%; impurities from one shop were below the quantification limit. The total amount of melanotan II in vials ranged between 4.32 and 8.84 mg, although each shop claimed that vials contained 10 mg melanotan II. A broad range of drugs used for enhancement purposes can be obtained from the illicit market. However, users of these drugs may be exposed to a range of potential harms, as shown in this study, given that these products are manufactured, distributed and supplied from an illicit market.