Die Rolle von Fgfs und Bmps in der frühen Schilddrüsenentwicklung des Zebrafisches

Die Schilddrüse ist ein endokrines Organ, das in allen Wirbeltieren vorkommt und das sich aus dem ventralen Bereich des Pharynx entwickelt. Über die Induktionsvorgänge, in dessen Verlauf ein Teil des anterioren Urdarms zur Schilddrüsenanlage spezifiziert wird, ist wenig bekannt. Der klassische Induktionsvorgang beinhaltet die Sekretion eines induzierenden Faktors aus umliegendem Gewebe, das ein kompetentes Gewebe zu einer bestimmten Organanlage spezifiziert. In dieser Arbeit wurde die Rolle des Fgf- und des Bmp-Signalweges in der frühen Schilddrüsenentwicklung des Zebrafisches und eine mögliche Involvierung der beiden Signalwege in der Induktion der Schilddrüsenanlage untersucht. In der embryonal-letalen Zebrafisch-Mutante hands off, die homozygot für das hanS6-Allel ist, ist der Genlokus für den Transkriptionsfaktor Hand2 vollständig deletiert. In früheren Versuchen wurde gezeigt, dass in der hanS6-Mutante die Expression schilddrüsenspezifischer Gene nicht vorhanden ist und daher die Schilddrüse fehlt. Da bereits gezeigt worden ist, dass Hand2 die Expression von Fgfs hochregulieren kann, wurden in dieser Arbeit Fgfs zum Zeitpunkt der Induktion der Schilddrüsenanlage im Bereich des anterioren Endoderms von hanS6-Mutanten ektopisch exprimiert. Die ektopische Exposition der Fgf-Signalmoleküle führt zur Wiederherstellung der Schilddrüsenentwicklung in hanS6-Mutanten. Die ubiquitäre Herrunterregulierung des Fgf-Signalweges durch den Fgf-Blocker SU5402 in Wildtyp-Embryonen führt zum Wegfall der schilddrüsenspezifischen Genexpression und damit zum Eingehen der Schilddrüse. Da die ektopische Exposition der Fgfs in hanS6-Mutanten kein ektopisches Schilddrüsengewebe induziert und die Herrunterregulierung des Fgf-Signalweges auch lange Zeit nach der Induktion der Schilddrüsenanlage zum Wegfall der Schilddrüse führt, ist vermutlich der Fgf-Signalweg für den Erhalt der Schilddrüse und nicht für deren Induktion notwendig. Experimente im Huhn und in der Maus haben gezeigt, dass Bmps die Expression schilddrüsenspezifischer Transkriptionsfaktoren beeinflussen können. Um eine Rolle des Bmp-Signalweges in der Schilddrüsenentwicklung des Zebrafisches zu untersuchen wurde der Ligand Bmp2b, sowie der Bmp-Inhibitor Noggin3 in hitzeschock-indzierbaren transgenen Linien zum Zeitpunkt der Schilddrüseninduktion hochreguliert. Die Überexpression von Bmp2b führt zu einer vergrößerten Schilddrüsenanlage, während die Überexpression von Noggin3 die Schilddrüsenentwicklung inhibiert. Da nach der Schilddrüseninduktion die Bmp2bÜberexpression keinen vergrößernden Effekt auf die Schilddrüse hat, sind vermutlich Bmps an der Induktion der Schilddrüsenanlage beteiligt

Ektoparaziti brancina u Bokokotorskom zalivu

The objective of this work has been to examine the presence, identify ectoparasite species and extensity and intensity of infection of Sea Bass (Dicentrarchus labrax) cultivated in cage systems of breeding in Boka Kotorska Bay during a production cycle. Additionally, pathomorphological and pathohistological changes in infected fish caused by parasites have been examined. The examination covered both juveniles and adult fish. The examinations were performed during three seasons: in the spring, summer and autumn of 2009. By examining ectoparasitic fauna in cage systems of Cogi in Boka Kotorska Bay, we found the presence of the following parasites: Diplectanum aequans, Trichodina spp., Amyloodinium ocellatum. The most important ectoparasitic species in Sea Bass in our examination was Diplectanum aequans – monogenean gill parasite. This parasite in a case of big infestation can cause disease diplectanosis. The extensity of infection caused by identified ectoparasite species varied depending on the season, but the biggest was during the summer, while the intensity was generally low. Therefore, no significant damage was noted in the cage systems. Minor pathomorphological and pathohistological changes were noted in the infected fish. Due to low intensity of parasitic fauna, no specific therapy administration was required. However, more intensive administration of prophylactic measures and regular veterinary surveillance could result in significant reduction in the presence of parasites and, consequently, more efficient performance

Early developmental specification of the thyroid gland depends on han-expressing surrounding tissue and on FGF signals

The thyroid is an endocrine gland in all vertebrates that develops from the ventral floor of the anterior pharyngeal endoderm. Unravelling the molecular mechanisms of thyroid development helps to understand congenital hypothyroidism caused by the absence or reduction of this gland in newborn humans. Severely reduced or absent thyroid-specific developmental genes concomitant with the complete loss of the functional gland in the zebrafish hands off (han, hand2) mutant reveals the han gene as playing a novel, crucial role in thyroid development. han-expressing tissues surround the thyroid primordium throughout development. Fate mapping reveals that, even before the onset of thyroid-specific developmental gene expression, thyroid precursor cells are in close contact with han-expressing cardiac lateral plate mesoderm. Grafting experiments show that han is required in surrounding tissue, and not in a cell-autonomous manner, for thyroid development. Loss of han expression in the branchial arches and arch-associated cells after morpholino knock-down of upstream regulator genes does not impair thyroid development, indicating that other han-expressing structures, most probably cardiac mesoderm, are responsible for the thyroid defects in han mutants. The zebrafish ace (fgf8) mutant has similar thyroid defects as han mutants, and chemical suppression of fibroblast growth factor (FGF) signalling confirms that this pathway is required for thyroid development. FGF-soaked beads can restore thyroid development in han mutants, showing that FGFs act downstream of or in parallel to han. These data suggest that loss of FGF-expressing tissue in han mutants is responsible for the thyroid defects

Influence of carbon dioxide content in the biogas to nitrogen oxides emissions

U radu je prikazano eksperimentalno istraživanje i analiza uticaja sadržaja ugljen-dioksida u biogasu na emisiju azotnih oksida. Sagorevanje biogasa različitog sastava vršeno je vihornim gorionikom sa pilot gorionikom. Rezultati pokazuju da postoji uticaj sadržaja ugljen-dioksida na emisiju azotnih oksida, i to tako da sa povećanjem sadržaja ugljen-dioksida emisija azotnih oksida opada. Ovakav trend je nepromenjen u opsegu koeficijenta viška vazduha (1,2-1,8) za koje je vršeno istraživanje. Utvrđeno je da pri nepromenjenom sastavu biogasa promena toplotne snage nema uticaja na emisiju azotnih oksida.Fuels derived from biomass are an alternative solution for the fossil fuel shortage. Usually fuels of this kind are called low calorific value fuels, due to the large proportion of inert components in their composition. The most common is carbon dioxide, and its proportion in biogas can be different, from 10 up to 40%, or even more. The presence of inert component in the composition of biogas causes problems that are related with flame blow off limits. One of the possibilities for efficient combustion of biogas is the combustion in swirling flow including a pilot burner, aimed to expand the borders of stable combustion. This paper presents an analysis of the influence of the carbon dioxide content on nitrogen oxides emissions. Laboratory biogas was used with different content of CO2 (10, 20, 30 and 40%). The investigation was carried out for different nominal powers, coefficients of excess air and carbon dioxide content. With increasing content of carbon dioxide, emission of nitrogen oxides was reduced, and this trend was the same throughout the whole range of excess air, carried out through measurements. Still, the influence of carbon dioxide content is significantly smaller than the influence of excess air. The coefficient of excess air greatly affects the production of radicals which are essential for the formation of nitrogen oxides, O, OH and CH. Also, the results show that the nominal power has no impact on the emission of nitrogen oxides

Research and development of efficient, environmentally improved household gas appliances

An experimental research and analysis of performance of three domestic house hold gas appliances was carried out. The objective of this work, based on the conducted analysis of the research data, was to improve the appliances’ performance, prefer ably through relative simple modifications, in order to satisfy DIN 4702 emissions and efficiency standards when using different fuels, including natural gas, liquefied petroleum gases and lower quality natural gas. This report summarizes details of this work and how the objectives were achieved

Using clinical research networks to assess severity of an emerging influenza pandemic

BACKGROUND: Early clinical severity assessments during the 2009 influenza A H1N1 pandemic (pH1N1) overestimated clinical severity due to selection bias and other factors. We retrospectively investigated how to use data from the International Network for Strategic Initiatives in Global HIV Trials, a global clinical influenza research network, to make more accurate case fatality ratio (CFR) estimates early in a future pandemic, an essential part of pandemic response. METHODS: We estimated the CFR of medically attended influenza (CFRMA) as the product of probability of hospitalization given confirmed outpatient influenza and the probability of death given hospitalization with confirmed influenza for the pandemic (2009-2011) and post-pandemic (2012-2015) periods. We used literature survey results on health-seeking behavior to convert that estimate to CFR among all infected persons (CFRAR). RESULTS: During the pandemic period, 5.0% (3.1%-6.9%) of 561 pH1N1-positive outpatients were hospitalized. Of 282 pH1N1-positive inpatients, 8.5% (5.7%-12.6%) died. CFRMA for pH1N1 was 0.4% (0.2%-0.6%) in the pandemic period 2009-2011 but declined 5-fold in young adults during the post-pandemic period compared to the level of seasonal influenza in the post-pandemic period 2012-2015. CFR for influenza-negative patients did not change over time. We estimated the 2009 pandemic CFRAR to be 0.025%, 16-fold lower than CFRMA. CONCLUSIONS: Data from a clinical research network yielded accurate pandemic severity estimates, including increased severity among younger people. Going forward, clinical research networks with a global presence and standardized protocols would substantially aid rapid assessment of clinical severity