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| 2. |
- Ersson, Lisa, 1985-
(författare)
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β-N-methylamino-L-alanine (BMAA)-induced neurotoxicity : Studies in vitro and in vivo
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- β-N-methylamino-L-alanine (BMAA) is a neurotoxic non-proteinogenic amino acid produced naturally by cyanobacteria, diatoms and dinoflagellates and it has been detected in samples from fresh and marine water from all over the world. It can bioaccumulate in fish and shellfish, and has a potential to biomagnify in a terrestrial food chain. BMAA was first discovered in the search for a neurotoxin related to the amyotrophic lateral sclerosis/Parkinsonism-dementia complex (ALS/PDC) found among the Chamorro people in Guam. This non-proteinogenic amino acid has also been suggested to contribute to sporadic neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD) and Alzheimer's disease (AD). BMAA can induce neurotoxicity via multiple mechanisms. It can act as an excitotoxin by activating glutamate receptors and to induce oxidative stress. It has also been suggested to be misincorporated into proteins leading to misfolded protein aggregates. Previous studies have demonstrated a specific damage in the hippocampus, including intracellular fibril formation, in adult rats following neonatal exposure to BMAA. In this thesis both in vitro and in vivo models were used to characterize the uptake, transport and effects of BMAA in cultured cell lines and in neonatal rodent brain tissue. The uptake of radiolabeled BMAA, as well as the effects of various amino acids and transporter antagonists on the uptake were studied in human mammary epithelial cells, intestinal epithelial cells, glioblastoma and neuroblastoma cells. Based on the obtained results a potential human mother-to-infant transfer of BMAA was suggested. BMAA-induced metabolic changes in a differentiated human neuroblastoma cell line were also characterized. The results revealed a plentitude of altered metabolites, many of them involved in amino acid metabolism and the TCA cycle. Of special interest were the perturbations in alanine, aspartate and glutamate metabolism as this pathway is involved in neurotransmission. The results revealed that BMAA can interfere with fundamental metabolic and neurotransmission pathways. Finally, the levels of free and protein-associated BMAA in the brain and peripheral tissues in neonatal rats exposed to BMAA were analysed. The results revealed high levels of free BMAA in some brain regions, thus demonstrating that the neonatal brain is not protected from BMAA by the blood-brain barrier. The results also revealed a protein-association of BMAA in the neonatal hypothalamus and hippocampus. Although the total amount of BMAA in the hippocampus was not high compared to other brain regions, the percentage of protein-associated BMAA was significantly higher. The results suggest that the protein-association of BMAA may play a role in the long-term effects in the hippocampus following neonatal exposure to BMAA. The studies in this thesis have demonstrated 1) a potential transfer of BMAA via breast milk to the brain of the nursing infant, 2) BMAA-induced metabolic alterations related to neurotransmission in human neuroblastoma cells and 3) that both free and protein-associated BMAA can be detected in the neonatal rat brain.
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| 3. |
- Granholm, Linnea
(författare)
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Neurobiological Consequences of Social Conditions and Alcohol Exposure in Adolescent rats
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Adolescence represents a time of extensive reorganisation and maturation of brain circuits involved in emotions, motivation and cognition and it is a period particular sensitive for external stimuli. External stimuli can be both socio-environmental factors and exposure to exogenous compounds such as drugs of abuse (e.g. alcohol). If these stimuli are of an adverse nature the probability of develop neuropsychiatric diseases or addiction is increased. To study the neurobiological consequences of adverse events during adolescence animal models are crucial since they give the opportunity of providing an environment where the exposure of the stimuli is controlled and also enable a detailed analysis of the effects in the brain. The overall aim of in this thesis was to investigate how environmental factors, social conditions or alcohol exposure, during adolescence affect the brain and/or drug-taking in rats. Rats are very sensitive for dis- turbances in their social conditions and to induce an adverse social environment, early adolescent rats where single-housed for either a short or prolonged time. A short period of single housing induced an acute stress response and increased levels of nociceptin/orphanin FQ in brain areas associated with stress. Prolonged single housing reduced the levels of Met-enkephalin-Arg6Phe7 in several brain areas. Rats exposed to alcohol during adolescence had an altered dopamine response in dorsal striatum after an am- phetamine challenge but displayed similar amphetamine intake-behaviour as water controls. However, animals exposed to a combination of adolescent alcohol exposure and subsequent amphetamine intake had a more efficient removal of dopamine in dorsal striatum after an amphetamine challenge. This thesis demonstrates how two different environmental stimuli are able to alter the neurobiology in adolescent rats. The results further support the notion that environmental conditions are of importance for normal brain maturation and provide new evidence that endogenous opioids are severely affected by social dis- turbances during adolescence. Furthermore, additional information is provided to the existing literature of how alcohol exposure during adolescence affects dopamine dynamics and drug-taking behaviour. In the literature, the majority of the studies of adolescent alcohol exposure have focused on the nucleus accum- bens, a brain area important in the processing of rewards. The results herein provide evidence that dorsal striatum, a brain area involved in the transition into habitual drug use is also affected by adolescent alco- hol exposure. An altered drug response in dorsal striatum may affect habit formation and contribute to a heightened susceptibility for high drug consumption later in life.
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| 4. |
- Lundberg, Stina
(författare)
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Examining Female Resilience to Early Environmental Influences : Short- and long-term consequences on behaviour, HPA axis activity and alcohol intake after prolonged maternal separation
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Early-life experiences are an important factor influencing further development of the individual. Adverse experiences early in life, such as various kinds of abuse or neglect, are types of early-life stress that can adversely affect an individuals health, as well as contribute to the development of an array of disorders later in life. Most prominent is the increased risk for psychiatric disorders, primarily depression, anxiety-related and substance use disorders. Many of the implicated disorders also exhibit sex-dependent differences in prevalence and severity. Thus, it is important to consider sex-dependent effects when modeling early-life stress and its consequences. A common animal model for early-life stress is prolonged maternal separation (MS). MS is an umbrella term for different manipulations of the early environment of rodent pups. In this thesis, a prolonged MS condition with separation of rat litters from their dams for six hours per day during the first three weeks of life (MS360) was used. In male offspring MS360 have been associated with early-life stress and negative effects apparent during both adolescence and adulthood. The literature regarding female offspring is not as substantial as for the males, but it seems that females’ exhibit less pronounced or no effect after prolonged MS independent of separation time. In addition, the studies that have examined female offspring have done so in adulthood and thus, short-term consequences of prolonged MS possibly present during adolescence have not been investigated. The aim of this thesis is to provide a broad investigation into the consequences of prolonged MS in female offspring, in both adolescence and adulthood. As stated above, MS360 was used as the adverse rearing condition in this thesis. As control, daily short MS (15 min; MS15) was used; this ensured that all animals were handled equally, except for the length of separation. Any detected differences are thus due to the length of separation only. Three categories of assessments were used to evaluate short- and long-term consequences: 1) hypothalamus-pituitary-adrenal (HPA) axis assessments, 2) behavioral assessments and 3) assessment of voluntary alcohol consumption. HPA axis reactivity was assessed in adolescent and adult offspring by blood sampling before and after challenge. HPA activity was also evaluated after long-term alcohol consumption by measurement of the fecal corticosterone content. Behavior was assessed in adolescence by registration of social play behavior and in adulthood by generation of behavioral profiles in the multivariate concentric square fieldTM (MCSF). Alcohol consumption was evaluated using the modified intermittent alcohol access schedule with the two- (20% alcohol) and three- bottle (5% and 20% alcohol) free-choice paradigms. Female offspring did not differ depending on rearing condition in HPA reactivity in adolescence or adulthood. However, after the long-term alcohol intake, MS360 females had increased levels of corticosterone in their feces compared to MS15 females. No difference was detected in adolescent social play among female offspring and only a minor alteration was detected in the adult behavioral profile, where MS360 females had increased risk assessment compared to MS15 females. No effect of rearing condition was seen during the two-bottle choice paradigm of alcohol intake, while whole- group differences over time were discovered. Alcohol intake and preference were highest the first week of access and directly after a two-week deprivation period, apart from those time-points, intake and preference were maintained on a stable level. In the three-bottle choice, an interaction with rearing condition was revealed for the total alcohol preference, however this only translated to a minor group-dependent difference. In conclusion, females reared under a prolonged MS paradigm exhibited no or only minor basal changes in HPA axis reactivity, behavior and alcohol consumption. However, after long-term alcohol intake females subjected to prolonged MS had increased corticosterone excretion into feces. That differences only emerge after long-term perturbation can be a sign that females have higher buffering capabilities than males after early-life adversity, as modeled through prolonged MS, and thus require additional challenges before consequences become apparent. This thesis highlights the importance of considering sex when studying the impact of early-life stress, and that the choice of animal model needs to be considered carefully in relation to the research question posed.
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| 6. |
- Thunander Sundbom, Lena, 1970-
(författare)
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The influence of gender and psychological distress on adherence to prescribed medication
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: The lack of adherence to drug therapy is a major problem; it can contribute to significant deterioration of disease and increased health-care costs. Improving medication adherence is a big challenge; there is no simple solution to the problem. It is thus essential to improve our knowledge of non-adherence (NA) and its causes.Aims: The aims of the thesis were to study the influence of gender and psychological distress on self-reported, intentional and unintentional non-adherent behaviour, and to investigate the reasons for NA.Methods: A population-based study that included a postal questionnaire was carried out in a cross-section of the general Swedish population (n=7,985, aged 18-84 years). The response rate was 61.1% (n=4,875) and current prescription drug use was reported by 2,802 participants. The questionnaire covered use of prescription drugs, NA to the drug regimens, reasons for NA, economic status, attitudes to drugs, and the presence of somatic or mental problems, and also included the Hospital Anxiety and Depression Scale questionnaire.Results: The results showed differences in various self-reported non-adherent behaviour patterns and reasons for NA between the genders. In most cases, these remained after controlling for confounders such as socioeconomic factors and attitudes to drugs that are known to differ between women and men. Associations were also found between symptoms of anxiety and/or depression and the presence of intentional or unintentional non-adherent behaviour (with a stronger average association for intentional NA), and between anxiety/depression and some of the reasons given for NA, e.g. adverse drug reactions (ADRs).Conclusions: Although it was not possible to confirm causal relationships, this thesis emphasises the effects of gender and psychological distress on NA. In summary, both gender and anxiety and/or depression influenced non-adherent behaviour and the reasons given for NA. For instance, ADRs seemed to influence the decision not to take the drug as prescribed, especially among women and participants under psychological distress. It is suggested that a deep understanding of the causes of NA and of the impact of gender and psychological distress on the outcomes would help those aiming to improve adherence to prescribed medication.
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| 7. |
- Zayny, Ahmad
(författare)
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Vitamin D metabolism in osteoblast-like cells : effects of drugs on inactivation by CYP24A1
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Vitamin D is essential for bone function, and deficiency in active vitamin D hormone can lead to bone disorders. Long-term treatment with glucocorticoids and antiretroviral drugs used to treat HIV infection, results in osteoporosis and increased risk of fractures. Much remains unclear regarding the effects of these compounds in bone cells. In the current study, human osteosarcoma Saos-2 cells and primary human osteoblasts were found to express mRNA for the vitamin D receptor as well as activating and deactivating enzymes in vitamin D3 metabolism. These bone cells exhibited CYP24A1-mediated 24-hydroxylation, involved in deactivation of the active vitamin form. However, bioactivating vitamin D3 hydroxylase activities were not detected in either of these cells, indicating that local vitamin D bioactivation is not significant in osteoblasts.Several glucocorticoids and antiretroviral drugs, including prednisolone, efavirenz and ritonavir, down regulated CYP24A1 mRNA expression. Prednisolone and ritonavir also down regulated CYP24A1-mediated 24-hydroxylase activity in both Saos-2 and primary human osteoblasts.Also, prednisolone significantly suppressed a human CYP24A1 promoter-luciferase reporter gene in Saos-2 cells co-transfected with the glucocorticoid receptor. Thus, the results of the present study show suppression by glucocorticoids on CYP24A1 mRNA, CYP24A1-mediated metabolism and CYP24A1 promoter activity in human osteoblast-like cells. Interestingly, ritonavir markedly potentiated the induction of CYP24A1 mRNA expression by 1,25-dihydroxyvitamin D3 suggesting that ritonavir may have different regulatory effects depending on the vitamin D3 metabolite levelsAs part of this study, we examined if glucocorticoids are formed locally in Saos-2 cells. The experiments indicate formation of 11-deoxycortisol, a steroid with glucocorticoid activity, which can bind the glucocorticoid receptor. Our findings showing effects of glucocorticoids and antiretroviral drugs on CYP24A1 expression in human osteoblasts indicate a previously unknown mechanism for effects of glucocorticoids and antiretroviral drugs in human bone, where effects of these drugs may lead to altered levels of active vitamin D3.
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