published_or_final_version / Biological Sciences / Master / Master of Philosophy

This dissertation investigates the embryonic specification of a specific group of cells: the germ cells. Germ cells, which give rise to sperm and egg, are the only cells in sexually-reproducing animals that directly contribute hereditary information to the next generation. Germ cells are therefore a universal cell type across animals, and represent a profound novelty that likely arose near the base of the animal phylogeny. Yet despite their conserved, essential function in all animals, there is surprising diversity in the mechanisms that specify these cells during embryonic development. In this dissertation, I address the diversity of germ cell specification mechanisms in insects. I focus on two species, the milkweed bug Oncopeltus fasciatus (Hemiptera) and the cricket Gryllus bimaculatus (Orthoptera), which both branch basally to the Holometabola (those insects which undergo metamorphosis, including the well-studied fruit fly Drosophila melanogaster), and thus provide important phylogenetic breadth to our understanding of germ cell specification across insects. Using functional genetic approaches, I show that germ cell specification in both Oncopeltus and Gryllus differs fundamentally from germ cell specification in Drosophila. Specifically, I provide evidence that germ cells arise via inductive cell signaling during mid-embryogenesis, rather than via maternally-supplied cytoplasmic determinants localized in the oocyte, as is the case for Drosophila. These data suggest that Drosophila employs an evolutionarily derived mode of germ cell specification. In further support of this hypothesis, I show that several of the genes required for Drosophila germ cell specification perform other functions in both Oncopeltus and Gryllus. I demonstrate that one of these genes, oskar, which is the only gene both necessary and sufficient for germ cell specification in Drosophila, instead functions in nervous system of the cricket, both during embryonic development and in the adult brain. I suggest that the evolution of the derived mode of germ cell specification seen in Drosophila may have involved co-opting oskar into the germ cell specification pathway from an ancestral role in the nervous system.

published_or_final_version / Zoology / Master / Master of Philosophy

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Darbo tikslas: nustatyti antioksidacinį preparatų, turinčių omega – 3 riebalų rūgščių, aktyvumą, palyginti jį su preparatų sudėtimis, atlikti vaistinės asortimento analizę. Darbo uždaviniai: Atlikti preparatų antioksidacinio aktyvumo tyrimą DPPH metodu. Atlikti preparatų palyginamąją analizę vertinant sudėtis. Išnagrinėti omega – 3 riebalų rūgščių turinčių preparatų pasiūlą vaistinėse. Metodai: antioksidacinis aliejų aktyvumas tirtas spektrofotometriškai naudojant 2,2-difenil-1-pikrilhidrazilo (DPPH) laisvojo radikalo sujungimo metodą. Pasirinktų linų sėmenų, kanapių sėklų, judros, rapsų, kviečių gemalų, graikinių riešutų aliejų bei žuvų taukų sudėtys vertintos ir lygintos literatūros analizės metodu. Tyrime naudotų aliejų paplitimas vaistinės asortimente nustatytas renkant duomenis vaistinėse bei elektroninėse vaistinių parduotuvėse. Rezultatai: nustatytas antioksidacinis aktyvumas (išreikštas inaktyvuoto DPPH % ±SD) kviečių gemalų aliejaus 53,59 ± 9,45, žuvų taukų 22,58 ± 5,38, judros aliejaus 22,40 ± 4,74, linų sėmenų aliejaus 22,17 ± 2,64, kanapių sėklų aliejaus 19,05 ± 1,54, graikinių riešutų aliejaus 18,66 ± 4,10, rapsų aliejaus 17,04 ± 2,68. Palyginus rezultatus ir literatūroje pateiktus duomenis nustatyta, kad nėra ryšio tarp aliejuje esančio omega – 3 riebalų rūgščių kiekio ir antioksidacinio aktyvumo, tačiau yra statistiškai patikimas ryšys tarp antioksidacinio aktyvumo ir sudėtyje esančio vit.E kiekio. Įvertinus vaistinės asortimentą nustatyti 75 žuvų taukų... [toliau žr. visą tekstą] / Objective of work: To estimate the antioxidant activity of preparations containing omega - 3 fatty acids; compare it with constitution of preparations; to execute the analysis of pharmacy range. Main tasks: to estimate the antioxidant activity by using DPPH method. To compare preparations by evaluating their constitutions. To execute the analysis of pharmacy range. Methods: antioxidant activity determined by using 2,2 – diphenyl-1-picrylhidrazyl free radical scavenging method. The constituents of flax seed, hemp seed, camelina, rapeseed, wheat germ, walnut and fish oil were evaluated by literature analysis. The data of prevalence of selected oils in pharmacy range was collected in the pharmacies and their online-shops. Results: antioxidant activity of wheat germ oil was 53,59 ± 9,45%, fish oil 22,58 ± 5,38%, camelina oil 22,40 ± 4,74%, flax seed oil 22,17 ± 2,64%, hemp seed oil 19,05 ± 1,54%, walnut oil 18,66 ± 4,10%, rapeseed oil 17,04 ± 2,68%. A comparison of the results showed that there is no significant relationship between amount of omega – 3 fatty acids and the antioxidant activity of the oil, but there is a statistically significant relationship between the amount of tocopherols and the antioxidant activity. The evaluation of the pharmacy range showed 75 fish oil products, 10 products containing flax seed oil, 9 wheat germ oil, 6 hemp seed oil, 3 products with camelina oil, 2 rapeseed oil, and only one product containing walnut oil. Conclusions: The highest... [to full text]

The aim of this thesis work was to extract lipids and antioxidants from wheat germ using an ultrasonic bath. Alternative solvents: Ethanol, isopropanol and acetone were used for the extraction purposes and for the fat content determination hexane was used. Alternative solvents dissolve wax, phospholipids and some other proteins because of their polar nature which increased the yield. Since waxes and some proteins can be added to the soaps and creams which were made from carrier oils, obtaining these substances together with the oil in the extract was very useful. For isopropanol a linear relation was found between the extract ratio and ultrasonication time. The highest extract ratios were achieved with ethanol. For 30 minutes of ultrasonication 0.10 g extract / g germ was obtained. After the extraction in order to enhance the phase separation between the solid phase (germ and other solids) and the extract phase, combinations of centrifugation, storage in the refrigerator and decantation were tested. The technique involving storage the extracts in the refrigerator for 24 hours and centrifugation at 2800 rpm for 20 minutes gave the second highest yield but the best phase separation. Ethanol extracts from both roasted and nonroasted wheat germs were characterized in terms of their total polyphenol contents. For non roasted wheat germs total polyphenol contents of 200 mg gallic acid / L solution and for roasted wheat germs an average of 170 mg gallic acid / L solution were obtained for 30 minutes of ultrasonic extraction. For nonroasted wheat germs weak but significant linear relations were found between total polyphenol contents of the extracts and ultrasonication time.