J. Neurochem. (2010) 115, 585–594. Abstract In mammals, the retina contains a clock system that oscillates independently of the master clock in the suprachiasmatic nucleus and allows the retina to anticipate and to adapt to the sustained daily changes in ambient illumination. Using a combination of laser capture micro‐dissection and quantitative PCR in the present study, the clockwork of mammalian photoreceptors has been recorded. The transcript amounts of the core clock genes Clock, Bmal1, Period1 (Per1), Per3, Cryptochrome2, and Casein kinase Iε in photoreceptors of rat retina have been found to undergo daily changes. Clock and Bmal1 peak with Per1 and Per3 around dark onset, whereas Casein kinase Iε and Cryptochrome2 peak at night. As shown for Clock, Per1, and Casein kinase Iε, the oscillation of transcript amounts results in daily changes of the protein products. The in‐phase oscillation of Clock/Bmal1 with Pers and the rhythmic expression of Casein kinase Iε do not occur in molecular clocks of other tissues including the suprachiasmatic nucleus. Therefore, the findings presented suggest that the photoreceptor clock is unique not only in its position outside the clock hierarchy mastered by the suprachiasmatic nucleus, but also with regard to the intrinsic rhythmic properties of its molecular components.

No abstract

No abstract

The retinal photopigment melanopsin (Opn4) mediates photoentrainment of the circadian system. In the present study, seasonal regulation of the melanopsin gene was investigated in comparison with the arylalkylamine N-acetyltransferase (AA-NAT) gene as an indicator of retinal pacemaker output. For this purpose, the daily profiles in the amount of melanopsin mRNA and AA-NAT mRNA were monitored under 8 : 16 h light/dark, 12 : 12 h light/dark and 16 : 8 h light/dark photoperiods using real-time polymerase chain reaction analysis. We found that, under all of the lighting regimes, melanopsin and AA-NAT expression oscillated with a peak around dark onset and the middle of the dark phase, respectively. The lighting regime influenced both genes, but in an opposing manner. Under long photoperiods, the duration of peak expression was prolonged for melanopsin, whereas it was shortened for AA-NAT. Under constant darkness, the rhythm of mRNA was abolished for melanopsin, but persisted for AA-NAT whereas, under constant light, the rhythm of mRNA was abolished for both genes. Our findings suggest that, in contrast to the AA-NAT gene, the daily and photoperiod-dependent regulation of the melanopsin gene does not rely on a circadian oscillator but is directly illumination-dependent.

No abstract

2-Aminobutylamino-4-ethylamino-6-isopropylamino-1,3,5-triazine (ABA-atrazine) has been synthesized and used as a coating hapten in an immunoassay with a monoclonal antibody against terbutryn. Coating was achieved by covalently linking ABA-atrazine to a glutaraldehyde polymer network directly bound to the polystyrene surface of a standard 96-well microtiter plate. The assay was carefully optimized. In particular, the coating hapten concentration had a strong effect on the ELISA sensitivity. By including a pre-incubation step a low test midpoint (IC50-value) of 0.130 microg L(-1) was achieved. As far as we are aware this is the most sensitive ELISA for terbutryn yet reported. The coating-hapten-format presented is proposed as generally applicable, because the glutaraldehyde-modified microtiter plate surface enables stable immobilization of a broad variety of coating haptens.

No abstract

No abstract