Biomedical subjects

Perikles Simon

Publications and source records attributed to Perikles Simon.

5 recordsLinked to original sources

PubMed2004

Early transcriptional changes of retinal and choroidal TGFbeta-2, RALDH-2, and ZENK following imposed positive and negative defocus in chickens.

PURPOSE: Imposing defocus to the retina results in compensatory changes of axial eye growth. It is not clear which factors initially contribute to this process and whether they act on the post-translational, translational, or transcriptional level. We have measured early changes in mRNA levels, in response to imposed negative and positive defocus, of the transcription factor ZENK, the retinoic acid synthesis enzyme RALDH-2, and the growth factor TGFbeta-2. METHODS: Chickens 11 days of age were unilaterally treated with positive or negative spectacle lenses of 7 D power. After 0, 15, 30, and 120 min, mRNA was extracted from retina and choroid, and the concentration of the mRNAs of the three candidates was measured by quantitative real time PCR in both eyes. RESULTS: ZENK in the retina and RALDH-2 in the choroid displayed parallel signs of defocus dependent changes in mRNA levels after 15 or 30 min, respectively. ZENK mRNA levels were reduced in the retina after 15 min with both types of lenses but were then up regulated at 30 min with positive lenses and down regulated with negative lenses, similar to the previously observed changes in ZENK protein levels. Changes of RALDH-2 and TGFbeta-2 mRNA levels were confined to the choroid. Treatment with negative lenses resulted in a rapid (15 min) and persistent decrease in TGFbeta-2 mRNA concentration in the choroid. Negative lenses provoked parallel but less pronounced alterations in the open fellow eyes. CONCLUSIONS: Imposed defocus triggers extensive transcriptional changes of ZENK in the retina, and of TGFbeta-2 and RALHD-2 in the choroid. Changes in retina and choroid are rapid, show no phase delay with respect to each other, and can be considered, in the case of RALDH-2 and ZENK, as specific for the sign of imposed defocus. They occur prior to any morphological changes. This is consistent with a role in causing or controlling later changes in eye growth.

Aldehyde Oxidoreductases↗

PubMed2004

Posttranscriptional regulation of the immediate-early gene EGR1 by light in the mouse retina.

Synaptic plasticity is modulated by differential regulation of transcription factors such as EGR1 which binds to DNA via a zinc finger binding domain. Inactivation of EGR1 has implicated this gene as a key regulator of memory formation and learning. However, it remains puzzling how synaptic input can lead to an up-regulation of the EGR-1 protein within only a few minutes. Here, we show by immunohistochemical staining that the EGR-1 protein is localized in synapses throughout the mouse retina. We demonstrate for the first time that two variants of Egr-1 mRNA are produced in the retina by alternative polyadenylation, with the longer version having an additional 293 base pairs at the end of the 3'UTR. Remarkably, the use of the alternative polyadenylation site is controlled by light. The additional 3'UTR sequence of the longer variant displays an even higher level of phylogenetic conservation than the coding region of this highly conserved gene. Additionally, it harbours a cytoplasmic polyadenylation element which is known to respond to NMDA receptor activation. The longer version of the Egr-1 mRNA could therefore rapidly respond to excitatory stimuli such as light or glutamate release whereas the short variant, which is predominantly expressed and contains the full coding sequence, lacks the regulatory elements for cytoplasmic polyadenylation in its 3'UTR.

Animals↗

PubMed2004

Effects of positive and negative lens treatment on retinal and choroidal glucagon and glucagon receptor mRNA levels in the chicken.

PURPOSE: It has been found in the chicken that the amount of retinal glucagon mRNA increases during treatment with positive lenses. Pharmacological studies support the idea that glucagon may act as a stop signal for visually induced eye growth. To gain more insight into the functional role of glucagon, the changes of glucagon and glucagon receptor mRNA concentrations in retina and choroid over time were studied. Furthermore, the abundance of glucagon and the glucagon receptor was studied in different fundal layers (retina, retinal pigment epithelium[RPE], choroid) and the blood. METHODS: Semiquantitative real-time RT-PCR was used to measure glucagon and glucagon receptor mRNA levels in retina and choroid after positive and negative lens treatment for 2, 6, or 24 hours, by unilateral -7- or +7-D lenses. Contralateral eyes served as the control, and completely untreated animals provided further reference data. Intravitreal colchicine injections (which are known to reduce the number of glucagon cells sharply) were used to verify that the related decline in glucagon mRNA could be measured by real-time RT-PCR. RESULTS: In the retina, treatment with -7-D lenses induced an initial upregulation of glucagon mRNA in both eyes, followed by a significant downregulation. The treatment with +7-D lenses showed a significant but transient downregulation in the control eye superimposed on a trend toward upregulation in the treated eye. However, the changes in glucagon mRNA expression were not confined to the lens-treated eyes but were also found, although sometimes to a lesser extent, in the non-lens-covered fellow eyes. There was evidence of a transient increase in glucagon receptor mRNA levels in lens-treated eyes after either -7- or +7-D lens wear. In the choroid, no effect of imposed defocus was detected. The injection of colchicine led to the destruction of approximately 75% of the glucagon amacrine cells but the mRNA level of retinal glucagon decreased by only approximately 50%. Glucagon receptor expression was found to be higher in the RPE than the retina and choroid whereas, in the blood, glucagon and glucagon receptor mRNA expression was below detection level. CONCLUSIONS: The observed bidirectional regulation of glucagon mRNA in correlation with the sign of imposed defocus supports the idea that glucagon may act as a stop-and-go signal for eye growth. This is in line with a previous proposal based on studies of changes of the glucagon peptide content.

Animals↗

PubMed2003

Q-Gene: processing quantitative real-time RT-PCR data.

SUMMARY: Q-Gene is an application for the processing of quantitative real-time RT-PCR data. It offers the user the possibility to freely choose between two principally different procedures to calculate normalized gene expressions as either means of Normalized Expressions or Mean Normalized Expressions. In this contribution it will be shown that the calculation of Mean Normalized Expressions has to be used for processing simplex PCR data, while multiplex PCR data should preferably be processed by calculating Normalized Expressions. The two procedures, which are currently in widespread use and regarded as more or less equivalent alternatives, should therefore specifically be applied according to the quantification procedure used. AVAILABILITY: Web access to this program is provided at http://www.biotechniques.com/softlib/qgene.html

Algorithms↗

PubMed2003

Molecular biology of myopia.

Experiments in animal models of myopia have emphasised the importance of visual input in emmetropisation but it is also evident that the development of human myopia is influenced to some degree by genetic factors. Molecular genetic approaches can help to identify both the genes involved in the control of ocular development and the potential targets for pharmacological intervention. This review covers a variety of techniques that are being used to study the molecular biology of myopia. In the first part, we describe techniques used to analyse visually induced changes in gene expression: Northern Blot, polymerase chain reaction (PCR) and real-time PCR to obtain semi-quantitative and quantitative measures of changes in transcription level of a known gene, differential display reverse transcription PCR (DD-RT-PCR) to search for new genes that are controlled by visual input, rapid amplification of 5' cDNA (5'-RACE) to extend the 5' end of sequences that are regulated by visual input, in situ hybridisation to localise the expression of a given gene in a tissue and oligonucleotide microarray assays to simultaneously test visually induced changes in thousands of transcripts in single experiments. In the second part, we describe techniques that are used to localise regions in the genome that contain genes that are involved in the control of eye growth and refractive errors in mice and humans. These include quantitative trait loci (QTL) mapping, exploiting experimental test crosses of mice and transmission disequilibrium tests (TDT) in humans to find chromosomal intervals that harbour genes involved in myopia development. We review several successful applications of this battery of techniques in myopia research.

Animals↗