Frankfurt (Main), Univ., Diss., 2004. / Erscheinungsjahr an der Haupttitelstelle: 2003. Computerdatei im Fernzugriff.

Berlin, Freie Universiẗat, Diss., 2002. / Dateiformat: zip, Dateien im PDF-Format.

Frankfurt (Main), University, Diss., 2004. / Erscheinungsjahr an der Haupttitelstelle: 2003.

No / The study investigated the role of endothelin (ET) and the ET receptor subtypes ETA and ETB in mediating longitudinal contraction in the mouse proximal and distal colon. Cumulative concentration¿response curves to a range of ET agonists (ET-1, ET-2, ET-3, (Ala1,3,11,13) ET and IRL 1620) were established by administering concentrations ranging from 0.01nM to 0.3¿M. Concentration¿response curves to ET-1, which exhibits a high affinity for both ETA and ETB receptor subtypes, were also established in the presence of the ETA antagonist BMS 182874 and the ETB antagonist IRL1038. The addition of the selective ETA receptor antagonist BMS 182874 caused a rightward shift of the concentration¿response curve to ET-1 in both sections of the colon. The ETB receptor antagonist IRL1038 (0.3¿1¿M) did not significantly effect the response to ET-1 in the proximal colon but caused a significant decrease in response towards higher concentrations ranges (3nM) in the distal colon. A comparison of the concentration¿response curves to ET-1, ET-2 and ET-3 showed a rank order of potency ET-1ET-2ET-3 in the proximal colon and ET-1ET-2ET-3 in the distal colon. The selective ETB receptor agonists, (Ala1,3,11,13) ET and IRL 1620 did not produce any response in the proximal sections of the colon but produced a smaller contraction in the distal segments. The data indicate that ET can contract the proximal tissues of the mouse colon predominantly via ETA receptors and in the distal tissues via ETA and ETB receptors.

Inherited photoreceptor degenerations (IPDs) are the most common monogenic cause of blindness in humans. To discover genes that may influence the risk of death in IPDs, microarray studies were used, and ET-2 was identified as the most differentially expressed transcript. ET-2 mRNA was 32-fold (p< 0.004), 70-fold (p< 0.009) and 72-fold (p<0.0009) increased in the Rds+/- , Tg(RHO P347S) and Rd1-/- mouse models of IPD, respectively, and the ET-2 peptide was minimally three-fold upregulated in Rds+/- retinas. The increased ET-2 transcript was detected solely in the photoreceptors (PRs) of Rds+/- and Tg(RHO P347S) retinas, but not in wild-type (wt) retinas by in situ hybridization. To determine the biological role of ET-2 in IPDs, mouse IPD models were crossed to ET-2-null mice. At age 40 and 15 days, ET-2-/-; Tg(RHO P347S) and ET-2-/-;Rd1-/- retinas showed, respectively, a 41% (n=6;p<0.003) and 49% rescue of PR degeneration (n=5;p<0.007). Unexpectedly, however, the PRs in ET-2-/- Rd1-/-retinal explants were not rescued (n=6;p>0.05), suggesting that the rescue observed in vivo might be due to extraocular mechanisms. Additionally, the expression of ET-2 mRNA from an rAAV5-CBA-ET-2 vector in ET-2-/-; Rd1-/- retinas did not restore PR degeneration (n=6;p>0.05). A survey of the extraocular phenotypes of ET-2 null mice showed them to be hypoxic owing to aberrant lung development, with a loss of normal alveolarization of the lung. Erythropoietin (EPO) levels were 11-fold elevated in the serum of ET-2 null mice (n=7;p<0.05) and retinal vascular endothelial growth factor (VEGF) was increased 4-fold (n=4;p<0.05). To examine the role of hypoxia in PR degeneration and to exclude increased EPO levels as the sole factor accounting for the rescue of mutant PRs in ET-2-/-; Tg(RHO P347S) and ET-2-/-;Rd1-/- mice in vivo, the effect of hypoxia on PR death in Rd1-/- retinal explants was examined. Rd1-/- explants cultured in 6% O2 from PN10 to PN17 showed a 32% rescue of PR death (n=5;p<0.05). Although ET-2 may mediate PR death through a direct role in mutant PRs, the PR rescue observed in ET-2-/-; Tg(RHO P347S) and ET-2-/-;Rd1-/-retinas may also result from systemic hypoxia due to poor lung function in ET-2-/- animals.

Inherited photoreceptor degenerations (IPDs) are the most common monogenic cause of blindness in humans. To discover genes that may influence the risk of death in IPDs, microarray studies were used, and ET-2 was identified as the most differentially expressed transcript. ET-2 mRNA was 32-fold (p< 0.004), 70-fold (p< 0.009) and 72-fold (p<0.0009) increased in the Rds+/- , Tg(RHO P347S) and Rd1-/- mouse models of IPD, respectively, and the ET-2 peptide was minimally three-fold upregulated in Rds+/- retinas. The increased ET-2 transcript was detected solely in the photoreceptors (PRs) of Rds+/- and Tg(RHO P347S) retinas, but not in wild-type (wt) retinas by in situ hybridization. To determine the biological role of ET-2 in IPDs, mouse IPD models were crossed to ET-2-null mice. At age 40 and 15 days, ET-2-/-; Tg(RHO P347S) and ET-2-/-;Rd1-/- retinas showed, respectively, a 41% (n=6;p<0.003) and 49% rescue of PR degeneration (n=5;p<0.007). Unexpectedly, however, the PRs in ET-2-/- Rd1-/-retinal explants were not rescued (n=6;p>0.05), suggesting that the rescue observed in vivo might be due to extraocular mechanisms. Additionally, the expression of ET-2 mRNA from an rAAV5-CBA-ET-2 vector in ET-2-/-; Rd1-/- retinas did not restore PR degeneration (n=6;p>0.05). A survey of the extraocular phenotypes of ET-2 null mice showed them to be hypoxic owing to aberrant lung development, with a loss of normal alveolarization of the lung. Erythropoietin (EPO) levels were 11-fold elevated in the serum of ET-2 null mice (n=7;p<0.05) and retinal vascular endothelial growth factor (VEGF) was increased 4-fold (n=4;p<0.05). To examine the role of hypoxia in PR degeneration and to exclude increased EPO levels as the sole factor accounting for the rescue of mutant PRs in ET-2-/-; Tg(RHO P347S) and ET-2-/-;Rd1-/- mice in vivo, the effect of hypoxia on PR death in Rd1-/- retinal explants was examined. Rd1-/- explants cultured in 6% O2 from PN10 to PN17 showed a 32% rescue of PR death (n=5;p<0.05). Although ET-2 may mediate PR death through a direct role in mutant PRs, the PR rescue observed in ET-2-/-; Tg(RHO P347S) and ET-2-/-;Rd1-/-retinas may also result from systemic hypoxia due to poor lung function in ET-2-/- animals.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Thesis / Master of Science (MS)

Das akute Lungenversagen ist gekennzeichnet durch eine schwere Störung des Gasaustausches mit ausgeprägter arterieller Hypoxämie. Die inhalative Gabe von Stickstoffmonoxid (iNO) erfolgt in der Therapie zur Verbesserung der arteriellen Oxygenierung, der Effekt ist jedoch variabel. Bisher existieren nur wenige Studien zur Identifikation von Faktoren, die die Effektivität von iNO bestimmen. Die positive Wirkung von iNO auf den Gasaustausch lässt eine Vasokonstriktion in beatmeten Lungenarealen vermuten. Wir untersuchten eine mögliche Wechselwirkung zwischen dem endogenen Vasokonstriktor Endothelin-1 (ET-1) und iNO in einem tierexperimentellen Modell des akuten Lungenversagens. Sechzehn Schweine wurden narkotisiert, invasiv beatmet und nach Induktion des akuten Lungenschadens (ALI) mittels repetitiver Surfactantauswaschung (Lavagemodell nach Lachmann) zwei Gruppen zugeteilt. Die NO-Gruppe (n=8) erhielt eine Inhalation von 30ppm NO, die Kontrolltiere (CTR-Gruppe, n=8) blieben ohne weitere Intervention. Während der nächsten vier Stunden wurden Messungen von Gasaustausch und ET-1 Konzentrationen im arteriellen Blut durchgeführt. Bei allen Tieren führte die Induktion des ALI zu einer signifikanten Verschlechterung des Gasaustausches. Die Gabe von iNO bewirkte in der NO-Gruppe eine signifikante Erhöhung des PaO2. Die ET-1 Plasmaspiegel stiegen im Verlauf an und waren nach drei Stunden in der NO-Gruppe signifikant niedriger als in der CTR-Gruppe. Dabei zeigte sich eine signifikante, moderate Korrelation zwischen den ET-1 Plasmaspiegeln und den durch iNO induzierten Änderungen in PaO2 und Shunt. Damit konnte ET-1 als ein Einflussfaktor auf die durch iNO induzierte Verbesserung des Gasaustausches identifiziert werden.

Diss. (sammanfattning) Stockholm : Karol. inst., 2002. / Härtill 5 uppsatser.