| 1. |
- Asnake, Solomon, 1985-
(författare)
-
Interaction of brominated flame retardants with the chicken and zebrafish androgen receptors
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The survival of organisms depends on their ability to use different signaling pathways to adapt to the environment. The endocrine system consists of glands that release hormones to the blood stream. Male reproductive functions are regulated by androgens through interactions with the androgen receptor (AR). AR has been characterized in chicken and zebrafish where they use testosterone and 11-ketotestosterone as their primary androgens, respectively. AR function has been disturbed by different endocrine disrupting compounds (EDCs) present in the environment causing detrimental effects on avian and fish species. Brominated flame retardants (BFRs) are a group of EDCs that are ubiquitous in the environment. Molecular modeling techniques using computer simulations such as docking and molecular dynamics are a useful tool in the identification of EDCs. The capacity to test thousands of compounds at once has helped in the early identification of EDCs that interact with AR. Two groups of BFRs, the 1,2-dibromo-4- cyclohexane diastereomers (TBECH) and the compounds synthesized from 2, 4, 6-tribromophenol, allyl 2,4,6-tribromophenyl ether (ATE), 2-bromoallyl 2,4,6- tribromophenyl ether (BATE) and 2,3-dibromopropyl 2,4,6-tribromophenyl ether (DPTE) interact and alter AR activity in human in vitro studies. As models for avian and fish species, chicken and zebrafish were used to test these BFRs. TBECH diastereomers were able to bind to the AR, estrogen receptors and thyroid receptors in the chicken and to the AR in zebrafish. ATE, BATE and DPTE were also able to interact with the chicken AR and zebrafish AR. Activation studies using cell lines showed that TBECH diastereomers acted as agonists to the cAR and zAR while ATE, BATE and DPTE acted as antagonists. The BFRs also altered multiple signaling pathways such as the apoptotic, antiapoptotic, immune, drug metabolizing and DNA methylation systems and in vivo studies resulted in physiological effects on zebrafish.
|
|
| 2. |
|
|
| 3. |
- Rahman, Aminur, 1984-
(författare)
-
Bioremediation of Toxic Metals for Protecting Human Health and the Ecosystem
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Heavy metal pollutants, discharged into the ecosystem as waste by anthropogenic activities, contaminate drinking water for millions of people and animals in many regions of the world. Long term exposure to these metals, leads to several lethal diseases like cancer, keratosis, gangrene, diabetes, cardio- vascular disorders, etc. Therefore, removal of these pollutants from soil, water and environment is of great importance for human welfare. One of the possible eco-friendly solutions to this problem is the use of microorganisms that can accumulate the heavy metals from the contaminated sources, hence reducing the pollutant contents to a safe level.In this thesis an arsenic resistant bacterium Lysinibacillus sphaericus B1-CDA, a chromium resistant bacterium Enterobacter cloacae B2-DHA and a nickel resistant bacterium Lysinibacillus sp. BA2 were isolated and studied. The minimum inhibitory concentration values of these isolates are 500 mM sodium arsenate, 5.5 mM potassium chromate and 9 mM nickel chloride, respectively. The time of flight-secondary ion mass spectrometry and inductively coupled plasma-mass spectroscopy analyses revealed that after 120 h of exposure, the intracellular accumulation of arsenic in B1-CDA and chromium in B2-DHA were 5.0 mg/g dwt and 320 μg/g dwt of cell biomass, respectively. However, the arsenic and chromium contents in the liquid medium were reduced to 50% and 81%, respectively. The adsorption values of BA2 when exposed to nickel for 6 h were 238.04 mg of Ni(II) per gram of dead biomass indicating BA2 can reduce nickel content in the solution to 53.89%. Scanning electron micrograph depicted the effect of these metals on cellular morphology of the isolates. The genetic composition of B1-CDA and B2-DHA were studied in detail by sequencing of whole genomes. All genes of B1-CDA and B2-DHA predicted to be associated with resistance to heavy metals were annotated.The findings in this study accentuate the significance of these bacteria in removing toxic metals from the contaminated sources. The genetic mechanisms of these isolates in absorbing and thus removing toxic metals could be used as vehicles to cope with metal toxicity of the contaminated effluents discharged to the nature by industries and other human activities.
|
|
| 4. |
- Stighäll, Kristoffer, 1971-
(författare)
-
Habitat composition and restocking for conservation of the white-backed woodpecker in Sweden
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In Sweden, intense human land use, especially forestry, has led to profound changes in the landscape over time, especially within the forest ecosystems. A consequence of this is that several specialist species have become endangered. One group of specialists is the woodpeckers. The middle spotted woodpecker became extinct in Sweden in 1982 and the white-backed woodpecker is today Sweden’s most critically endangered forest-living bird. The white-backed woodpecker is dependent on old deciduous forests, rich in dead wood. The woodpecker is areademanding and hence one of the best indicators or umbrella species for biodiversity in this region. A long-term goal within the conservation of the species is to be able to make more accurate predictions of what is needed in the species habitat to establish a viable population, both in terms of composition of landscape and breeding territories. In addition to earlier studies better tools are needed for measuring the distribution of suitable and potential habitats and finding faster ways of creating optimal habitats. In an attempt to secure the future existence of the white-backed woodpecker in Sweden, restocking of birds are carried out. This presupposes availability of suitable habitats as well as strong enough landscape. Due to intense forestry the presumption for the species is, as stated above, alarming. Comparing the different populations around the Baltic Sea and Norway, great differences but also similarities can be seen, in landscape as well as in territory composition. It seems that fragmentation of foraging patches as well as amount of dead deciduous wood within the breeding territory is critical matters. Grey alder stands in Sweden should have high priority in conservation of habitat for the species.
|
|
