Studies on the neuronal circuits involved in the discriminative stimulus effects of 5-hydroxytryptamine1A receptor agonists in the rat

Rats were trained to discriminate 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 0.1 mg/kg i.p.) or 5-methoxy-N,N-dimethyltryptamine (5-OMe-DMT, 1.25 mg/kg i.p.), a selective and nonselective 5-hydroxytryptamine1A (5-HT, serotonin) receptor agonist, respectively, from saline in a two-lever procedure. The selective 5-HT1A receptor agonist ipsapirone substituted completely for 8-OH-DPAT (ED50, 1.52 mg/kg) and 5-OMe-DMT substituted partially for 8-OH-DPAT, whereas 8-OH-DPAT (ED50, 0.07 mg/kg) and ipsapirone (ED50, 4.15 mg/kg) substituted completely for 5-OMe-DMT. These results suggest that the discriminative stimulus properties of both 8-OH-DPAT and 5-OMe-DMT are 5-HT1A receptor mediated, although 5-OMe-DMT may involve an additional interaction with other 5-HT receptor subtypes. 5-OMe-DMT substituted for 8-OH-DPAT after application in the lateral ventricle (ED50, 3.0 micrograms/rat) and the dorsal raphe nucleus (DRN, 1.1 micrograms/rat). After application in the DRN (ED50 range, 1.4-5.0 micrograms/rat) and the median raphe nucleus (2.3 micrograms/rat), and after bilateral application into the CA-4 region of the dorsal hippocampus (4.1 micrograms/rat), 8-OH-DPAT also produced responding on the 8-OH-DPAT lever. Ipsapirone also substituted for 8-OH-DPAT after application into the DRN and the hippocampus (ED50S, 38 and 62 micrograms/rat, respectively). The 5-HT1A mixed agonist-antagonist (1-(2-methoxyphenyl) 4-[4-(2-pthalimido)butyl]piperazine, i.p. NAN-190) attenuated the discriminative stimulus effects of 8-OH-DPAT injected i.p. (0.1 mg/kg), into the DRN (10 micrograms) or into the hippocampus (2 x 10 micrograms).(ABSTRACT TRUNCATED AT 250 WORDS)     

Temperature-dependent resistivity measurements on polycrystalline SiO2-covered thin nickel films

The resistivity of thin nickel films is studied as a function of temperature from 4 to 320 K. Both as-deposited and heat-treated samples with thicknesses ranging from 10 to 80 nm are studied. The resistivity can be analysed taking only grain boundary scattering into account, using the theory of Mayadas and Shatzkes. The bulk residual resistivity of the as-deposited films appears to be dominated by grain boundary scattering. No clear evidence for surface scattering could be found.     

Surface losses in transmission lines

Two derivations of the loss parameter R, entirely from wave considerations in the presence of a metallic interface, are presented. R, which represents surface losses, occurs in transmission line equations for propagation of the voltage across the plates and of the current in the plates. Explanation of the surface losses involves some radiation of the interior fields into the metallic surfaces that absorb electromagnetic energy, and that ultimately convert it into ohmic losses (heat). Although the approach may restrict the derivation to a planar interface, i.e., to a parallel-plate transmission line, that restriction is not so essential that it cannot be softened     

Cimaterol and clenbuterol residue analysis by HPLC-HPTLC in liver.

A method has been developed for the analysis of cimaterol and clenbuterol residues in liver, with detection limits of 0.25 micrograms/kg and 0.5 micrograms/kg, respectively. The recovery varied from 55% to 60%. After extraction, a clean-up procedure with Baker-spe C-18 columns was performed. The two chemical compounds of interest were eluted with methanol. Cimaterol and clenbuterol were quantitatively determined by high-performance liquid chromatography (HPLC) using an RP-Select B (5 microns) column and a post-column reaction procedure. The positive results were confirmed by high-performance thin-layer chromatography (HPTLC) as this technique reaches the same level of sensitivity as the HPLC method.     

Comparative toxicity of organotin compounds to rainbow trout (Oncorhynchus mykiss) yolk sac fry

The comparative toxicity of various organotin compounds was investigated in early life stages of the rainbow trout. Beginning with yolk sac fry, trout were continuously exposed for 110 days to tributyl- (TBTC), triphenyl- (TPhTC) or tricyclohexyltin chloride (TCHTC) at concentrations of 0.12-15 nM, to trimethyltin chloride (TMTC) at concentrations of 3-75 nM or to dibutyl- (DBTC) or diphenyltin chloride (DPhTC) at 160-4000 nM. The diorganotin compounds DBTC and DPhTC were about three orders of magnitude less toxic than the triorganotin homologs TBTC and TPhTC. Both for DBTC and DPhTC, a no-observable-effect concentration (NOEC) of 160 nM was established, corresponding to 40 and 60 ppb, respectively. Of the triorganotin compounds, TCHTC appeared to be the most toxic, inducing 100% mortality within 1 week at a concentration of 3 nM. Only a few trout survived exposure to 0.6 nM TCHTC for 110 days. TBTC and TPhTC caused acute mortality at a concentration of 15 nM. For both TBTC and TPhTC a NOEC of 0.12 nM was established, corresponding to water concentrations of 40 and 50 ppt, respectively. Histopathological examination revealed depletion of glycogen in liver cells of both di- and triorganotin exposed fish, except in the case of TMTC. No signs of toxicity were observed in fish exposed to up to 75 nM TMTC, the highest concentration tested. Atrophy of the thymus, the most prominent sign of toxicity of di- and tributyltin compounds in mammalian species, was not observed in early life stages of rainbow trout. Tail melanization was observed in the groups exposed to 3 nM TPhTC, 3 nM TBTC, 800 nM DBTC and 800 nM DPhTC. At the end of the exposure period, resistance to infection was examined by an intraperitoneal challenge with Aeromonas hydrophila, a secondary pathogenic bacterium to fish. Resistance of bacterial challenge was found to be decreased even at the lowest-effect concentration of both di- and triorganotin compounds.     

Linguistic Knowledge, Processing Speed, and Metacognitive Knowledge in First- and Second-Language Reading Comprehension: A Componential Analysis.

The authors report results of a study into the role of components of first-language (L1; Dutch) and second-language (L2; English) reading comprehension. Differences in the contributions of components of L1 and L2 reading comprehension are analyzed, in particular processing speed in L1 and L2. Findings indicate that regression weights of the L1 and L2 components are different. Although correlations between most processing speed components and reading comprehension are substantial, there are no unique contributions to the explanation of either L1 or L2 reading comprehension when linguistic and metacognitive knowledge are accounted for. In addition, L1 reading comprehension is shown to have a large contribution to L2 reading comprehension, supporting theories of L1-L2 transfer of reading skills. Results are discussed from a developmental perspective. (PsycINFO Database Record (c) 2010 APA, all rights reserved)