RESUMEN
The performance of commercially available microtiter plate enzyme-linked immunosorbent assays (ELISA) kits specific for the determination of triazines (atrazine), chlorpyrifos, and diazinon was evaluated for sensitivity, intra-assay repeatability, and accuracy using samples of known concentration in aqueous solution. Mean percent recovery values were not significantly different among concentrations for diazinon (One-way parametric ANOVA, P=0.46, n=72). However, mean percent recovery values were significantly different among concentrations for both atrazine and chlorpyrifos analyses (One-way parametric ANOVA, P<0.0001, n=36 for both analyses), and were highly dependent on concentrations for chlorpyrifos (% recovery=-0.155 (concentration)+238.448, r(2)=0.91, P<0.0001, n=36). All methods demonstrated a high degree of statistical separation between readings at various concentrations (One-way parametric ANOVA followed by Student-Neuman-Keuls (SNK) multiple range test, P<0.0001 for all analyses) and a close correlation between known concentrations and concentrations derived from ELISA for all three analytes (diazinon, r=0.985, P<0.0001, n=72; atrazine r=0.967, P<0.0001, n=36; chlorpyrifos r=0.947, P<0.0001, n=36). Statistical comparisons between known concentrations and concentrations derived from ELISAs showed that diazinon values were significantly (P<0.01, n=12 per concentration level) overestimated for all concentration levels. Chlorpyrifos concentrations were significantly (P<0.01, n=6 per concentration level) overestimated at lower concentrations and significantly (P<0.01, n=6 per concentration level) underestimated at higher concentrations. ELISA-derived atrazine concentrations were statistically similar to known concentrations for most concentration levels (P>0.05, n=6 per concentration level). Results indicate that ELISA kits are excellent for screening purposes, although consistent overestimation of ELISA for diazinon at all concentration levels and chlorpyrifos at lower concentrations levels must be resolved before the kits can be used routinely for regulatory compliance monitoring.
RESUMEN
Hepatitis B virus (HBV) replicates by the reverse transcription of the 3.5-kb viral pregenomic RNA. Therefore, the regulation of the transcription of the pregenomic RNA is a critical step in the viral life cycle. Various ubiquitous and liver-enriched transcription factors have been shown to modulate the level of RNA synthesis from the core promoter. The nuclear hormone receptors HNF4 and RXRalpha plus PPARalpha appear to have a critical role in governing pregenomic RNA synthesis from the core promoter in cell culture and probably represent a major determinant governing the hepatotropism of this virus. The level of 3.5-kb HBV RNA synthesis is approximately proportional to the level of viral replication in cell culture; however, this is not the case in the liver of HBV transgenic mice. Directly modulating the levels or activities of specific transcription factors known to regulate HBV transcription in cell culture can increase viral replication in HBV transgenic mice without greatly changing the levels of HBV transcripts. Various immune stimuli that alter transcription factor activities involved in regulating viral RNA synthesis can negatively affect viral replication without affecting HBV transcription. These observations suggest that in vivo very subtle changes in HBV transcription may contribute to large alterations, either negative or positive, in viral replication. Investigation of transcription factor-null HBV transgenic mice under various physiological conditions will be required to establish the putative role of specific transcription factors in regulating viral replication in vivo.
RESUMEN
We examined the role of the dopamine projection to the medial prefrontal cortex in amphetamine-induced sensitization of meso-nucleus accumbens dopamine function. In the first experiment, male rats received bilateral microinfusions either of 6-hydroxydopamine or of vehicle (sham) into prefrontal cortex. Six weeks later animals from both groups were injected once daily for 5 consecutive days with either amphetamine or saline. Two days after the last daily injection, all the animals were each implanted with a voltammetric electrode into nucleus accumbens. Increases in dopamine-dependent electrochemical signals elicited by amphetamine were monitored 3-4 days later using chronoamperometry. The results showed that amphetamine stimulates dopamine efflux to a greater extent in the nucleus accumbens of lesioned than of sham-lesioned animals. Furthermore, of the animals with prefrontal cortical lesions, amphetamine-induced dopamine efflux was greater in animals previously treated with the drug than in animals with no prior drug experience. In a second experiment, sensitization to the acute locomotor-stimulant effect of amphetamine was examined in prefrontal cortex-lesioned and sham-lesioned animals. The locomotor response of all animals to a test dose of amphetamine was first monitored and then on each of the subsequent 5 days, lesioned and sham-lesioned animals received an injection either of amphetamine or of saline. Five and then 13 days later, the locomotor response of all animals to the test dose of amphetamine was again measured. The results of this study showed that prefrontal cortex-lesioned animals were less responsive to the first amphetamine injection than sham-lesioned animals. However, after repeated daily administration, the acute locomotor response of lesioned animals to amphetamine was significantly greater than that of sham-lesioned animals with the same drug history. These findings are generally consistent with evidence from other sources suggesting that the dopamine input to medial prefrontal cortex exerts an indirect, inhibitory influence on mesolimbic dopamine transmission. They also suggest that long-term changes to a dopamine-sensitive mechanism in prefrontal cortex may contribute to the development of stimulant-induced sensitization of mesolimbic dopamine function.