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P Greve

Publications and source records attributed to P Greve.

10 recordsLinked to original sources
PubMed1994

Regulation of hydroxyindole-O-methyltransferase gene expression in the pineal gland and retina.

Hydroxyindole-O-methyltransferase (HIOMT) catalyzes the final step of melatonin biosynthesis and appears to be specifically expressed in the pineal gland and in the retina. This review deals with the regulation of HIOMT by environmental light and with the developmental aspects of HIOMT expression in chicken and rat. Early studies based on HIOMT activity measurements and more recent studies involving cDNA hybridization to HIOMT mRNA are taken into consideration. Together, the data reveal that long term regulation of HIOMT by light would rely on a day/night rhythm of HIOMT gene transcription, coupled to a slow turnover of the protein. Rapid changes in HIOMT mRNA levels and early expression during embryonic development suggest that further studies on this gene may shed light on the molecular mechanisms involved in the differentiation of the melatoninergic function and in its regulation by light, both in the pineal gland and in the retina.

Acetylserotonin O-Methyltransferase↗
PubMed1993

Transcriptional regulation of hydroxyindole O-methyltransferase in the chicken pineal gland: day/night changes and long-term effects of light and darkness.

The indolic hormone melatonin is produced by the pineal gland according to a daily rhythm. The terminal step of melatonin synthesis is catalysed by hydroxyindole O-methyltransferase (HIOMT, EC 2.1.1.4). Adaptation to constant light or darkness modifies HIOMT activity and concentration. Using a cDNA probe encoding HIOMT, we investigated the effect of environmental lighting on HIOMT gene expression in the chicken pineal gland. HIOMT mRNA levels increased by 100% in constant light as compared with constant darkness. In addition, the present study disclosed the existence of a day/night rhythm of HIOMT gene transcription, with 3-fold higher mRNA levels at midday than at midnight. This transcriptional rhythm was not accompanied by day/night changes in HIOMT concentration, probably due to a slow turnover of this protein. Unexpected darkness did not prevent the daytime rise in HIOMT mRNA levels, whereas unexpected light prevented the night-time fall in HIOMT mRNA levels. Together, the data would suggest that the day/night rhythm of HIOMT gene transcription in the chicken pineal gland involves both a response to light and the activity of a biological oscillator.

Acetylserotonin O-Methyltransferase↗
PubMed1993

[Transcriptional regulation of an enzyme involved in the synthesis of melatonin].

The indolic hormone melatonin is produced by the pineal gland according to a daily rhythm. The terminal step of melatonin synthesis is catalyzed by hydroxyindole-O-methyltransferase (HIOMT, EC 2.1.1.4). Adaptation to constant light or darkness modifies HIOMT activity and concentration. Using a cDNA probe encoding HIOMT, we investigated the effect of environmental lighting on HIOMT gene expression in the chicken pineal gland. HIOMT mRNA levels increased by 100% in constant light as compared with constant darkness. In addition, the present study disclosed the existence of a day/night rhythm of HIOMT gene transcription, with 3-fold higher mRNA levels at midday than at midnight. Unexpected darkness did not prevent the daytime rise in HIOMT mRNA levels, whereas unexpected light prevented the night-time fall in HIOMT mRNA levels. Together, the data would suggest that the day/night rhythm of HIOMT gene transcription in the chicken pineal gland involves both a response to light and the activity of a biological oscillator.

Acetylserotonin O-Methyltransferase↗
PubMed1975

[Macular pucker after retinal detachment surgery (author's transl)].

A report is given on 6 cases of macular pucker after retinal detachment surgery. Two of these 6 patients were found only by a check up of 145 detachment patients one year after surgery. In accordance with the literature presumbly causative factors were present in 5 of the cases: vitreous hemorrhage (4), reoperations (3) vitreous loss (1). A 6Th case with very unusual centrally located retinal breaks was operated on with a silicone explant and was seen with a macular pucker 6 months later.

Adult↗
PubMedDate not supplied

Cellular and molecular regulation of serotonin N-acetyltransferase activity in chicken retinal photoreceptors.

Serotonin N-acetyltransferase (AA-NAT; arylalkylamine N-acetyltransferase; EC 2.3.1.87) is the penultimate enzyme in melatonin synthesis and large changes in the activity of this enzyme appear to regulate the rhythm in melatonin synthesis. Recent advances have made it possible to study the mRNA encoding chicken AA-NAT, which has only been detected in the retina and pineal gland. Within the retina, AA-NAT mRNA is expressed primarily in photoreceptors. The levels of chicken retinal AA-NAT mRNA and activity exhibit 24-hour rhythms with peaks at night. These rhythms appear to reflect circadian clock control of AA-NAT mRNA abundance and independent effects of light and darkness on both mRNA levels and enzyme activity. The effects of darkness and light may occur through alterations in cAMP-dependent protein phosphorylation, which increases AA-NAT activity in photoreceptor cell cultures. The cAMP-dependent increase of AA-NAT enzyme activity reflects, at least in part, increased mRNA levels and inhibition of enzyme inactivation by a posttranslational mechanism. This review discusses a hypothetical model for the cellular and molecular regulation of AA-NAT activity by circadian oscillators and light in chicken retinal photoreceptor cells.

Animals↗