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  • 1
    Electronic Resource
    Electronic Resource
    Naloxone effects on sucrose-motivated behavior (1996)
    Springer
    Psychopharmacology 126 (1996), S. 110-114 
    Details
    ISSN: 1432-2072
    Keywords: Motivation ; Naloxone ; Opioids ; Sucrose ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The opioid system plays an important role in feeding. In general, opioid agonists typically increase feeding and opioid antagonists decrease feeding in nonfood restricted animals. In food restricted animals the effects of these drugs are substantially reduced. Opioid antagonists have shown a marked effectiveness at reducing consumption of sweet foods. Explanations for this robust effect have typically focused on drug induced changes in taste, taste perception, or palatability. The current study relates the effects of the opioid antagonist naloxone on motivation to obtain different sucrose concentrations to the drug's effects on unrestricted sucrose solution consumption. Changes in motivation to respond were assessed under a progressive ratio reinforcement schedule (PR) which required increased response cost for each successive unit of sucrose solution. Motivation, as measured by the PR, increased as sucrose concentration increased and naloxone produced a dose-dependent decrease in motivation to respond for a given sucrose concentration. Thus, the effectiveness of naloxone was indirectly related to strength of the sucrose concentration. Under unrestricted access to sucrose solutions, naloxone reduced consumption greatest under the higher concentrations. The data suggest at least part of naloxone's effects on sweet tasting food may be mediated through endogenous opioid reward systems that are reflected in measures of motivation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02246345
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  • 2
    Electronic Resource
    Electronic Resource
    Naloxone administration following operant training of sucrose/water discrimination in the rat (1997)
    Springer
    Psychopharmacology 129 (1997), S. 289-294 
    Details
    ISSN: 1432-2072
    Keywords: Key words Discrimination ; Naloxone ; Opioids ; Taste ; Sucrose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The suppression of food intake observed following naloxone administration has often been ascribed to palatability or taste. Unfortunately, many confounds become apparent when attempts are made to isolate such factors in the investigation of ingestive behaviors. In the present study, rats (two groups) were trained to discriminate either a 10% or 5% sucrose solution from water (0.1 ml). These mildly food deprived subjects (95% of free-feeding weight) were trained to press the appropriate lever in a two-lever operant chamber following sampling of sucrose or water; successful responding was reinforced by delivery of a 45 mg grain food pellet. Following random exposure to reduced sucrose concentrations tested under extinction, a sucrose concentration gradient (1.0, 0.5, 0.1, 0.05, 0.01 and 0.005% sucrose solution) was established for both training groups under IP saline administration. Data collected under IP saline were then compared to those collected following random IP naloxone administration (3.0, 1.0, 0.3 and 0.1 mg/kg). No significant differences were observed between the sucrose concentration gradients obtained under saline and those obtained under naloxone, suggesting that the anorectic effect of naloxone is not primarily determined by discrimination of sweet taste.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050193
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of chimeric UmuC proteins: identification of regions inSalmonella typhimurium UmuC important for mutagenic activity (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 121-129 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; Salmonella typhimurium ; SOS mutagenesis ; Chimeric proteins ; UmuC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract UnlikeEscherichia coli, the closely related bacteriumSalmonella typhimurium is relatively unresponsive to the mutagenic effects of DNA-damaging agents. Previous experiments have suggested that these phenotypic differences might result from reduced activity of theS. typhimurium UmuC protein. To investigate this possibility, we have taken advantage of the high degree of homology between the UmuC proteins ofE. coli andS. typhimurium and have constructed a series of plasmid-encoded chimeric proteins. The possibility that the phenotypic differences might be due to differential expression of the respective UmuC proteins was eliminated by constructing chimeric proteins that retained the first 25 N-terminal amino acids of either of the UmuC proteins (and presumably the same translational signals), but substituting the remaining 397 C-terminal amino acids with the corresponding segments from the reciprocal operon. Constructs expressing mostlyE. coli UmuC were moderately proficient for mutagenesis whereas those expressing mostlyS. typhimurium UmuC exhibited much lower frequencies of mutation, indicating that the activity of the UmuC protein ofS. typhimurium is indeed curtailed. The regions responsible for this phenotype were more precisely localized by introducing smaller segments of theS. typhimurium UmuC protein into the UmuC protein ofE. coli. While some regions could be interchanged with few or no phenotypic effects, substitution of residues 212–395 and 396–422 ofE. coli UmuC with those fromS. typhimurium resulted in reduced mutability, while substitution of residues 26–59 caused a dramatic loss of activity. We suggest, therefore, that the primary cause for the poor mutability ofS. typhimurium can be attributed to mutations located within residues 26–59 of theS. typhimurium UmuC protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02172909
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  • 4
    Electronic Resource
    Electronic Resource
    Cells transformed by a wide variety of agents express higher abundance levels of some cellular RNA species (1982)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 19 (1982), S. 259-265 
    Details
    ISSN: 0730-2312
    Keywords: cytoplasmic RNA ; messenger RNA ; 3T3 cells ; C3HEF ; SV40 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A cDNA-cloned library was prepared from mRNA synthesized by SV40-transformed mouse cells. Eleven cDNA clones were selected based on their ability to hybridize higher levels of mRNA in SV40-transformed 3T3 cells than in 3T3 cells. These cDNA clones were employed to screen the steady-state levels of cytoplasmic RNAs in a wide variety of viral (SV40, polyoma, adenovirus, and Rous sarcoma virus) and nonviral (methylcholanthrene, embryonal carcinoma) transformed cell lines. Two of the cDNA clones - A17 and 104 - detected greater than 40-100-fold higher levels of mRNA in all the transformed cell lines tested when compared to nontransformed cells (3T3, C3HEF). The levels of mRNA complementary to these two cDNAs were regulated in a temperature-sensitive fashion (87-100-fold) in both SV40tsA- and RSV ts-src-transformed murine cell lines. These two cDNA clones detected greater than 100-fold, higher levels of complementary RNA derived from SV40 tumor tissue than in normal mouse liver. RNA species complementary to cDNA clones A17 or 104 were not detected in either actively growing nontransformed cells or in serum-stimulated 3T3 cells. The abundance levels of mRNAs detected by these two cDNA clones appear to be regulated 100-fold or greater by the transformed state, independent of the transforming agent. The higher levels of these RNA species detected in transformed mouse cells appear not to be solely regulated by the state of growth of nontransformed cells.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240190307
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    Paper (German National Licenses)
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