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Now showing items 594-598 of 598
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(2018)Gut inflammation and permeability is speculated to play a major role in the pathophysiology of several human diseases. Signs of a low-grade gut inflammation in patients with type 1 diabetes (T1D) have been found. Focus of this study was to understand the role of gut inflammation and increased gut permeability in the development of diabetic complications, especially nephropathy. Approximately, one-third of Finnish patients with T1D develop kidney disease during their lifetime. Inflammatory mechanisms may have an essential role in the pathophysiology of the disease. Lipopolysaccharide, LPS, is found in the outer membrane of gram-negative bacteria. LPS activates innate immune system and triggers the activation of inflammatory cytokines, neutrophils and macrophages as well as many pathophysiological processes in vivo, for instance fever and endotoxic shock. Aim of this study was to establish a zebrafish gut inflammation model using fluorophore conjugated endotoxin, LPS. We hypothesized that delivery of LPS in addition to EDTA in the gut of zebrafish triggers inflammation and increased gut permeability which may lead to leakage of LPS to blood stream and potentially kidney injury. This novel zebrafish inflammation model could possibly be used for studying the pathophysiological mechanisms of gut inflammation and possible kidney injury as well as for screening new anti-inflammatory drugs. In addition, this animal model can be used for studying intestinal alkaline phosphatase (IAP) in reducing gut permeability and LPS-mediated kidney damage. IAP is an enzyme produced in small-intestinal epithelium. IAP can detoxify several bacterial endotoxins including LPS and thus protect against the induction of intestinal inflammation. LPS and EDTA were delivered in the gut of 6 days old zebrafish larvae using microgavage injection. Fluorescence microscopy imaging of live zebrafish enabled following the same individual at different timepoints after injections. Paraffin sectioning of the small larvae was promising for investigating the morphology and permeability of the gut as well as possible immunostaining for detection of IAP. L-phenylalanine was used for inhibition of IAP enzyme. Using the novel method of microinjection to gut on zebrafish larvae the timing and amount of delivered materials to gut can be controlled well. The anatomy and function of the gut in zebrafish is very similar to small intestine of mammals and the highly developed vertebrate immune system makes zebrafish an interesting model organism for studying gut inflammation and permeability. In addition, inflammatory processes can be visualized in live, intact transparent zebrafish larvae. However, the technique has a lot of challenges including small size of the fish and possible tissue damage of the fish while performing injection. More experiments need to be carried out to establish the model for drug screening. Also, along with microscopy images, a more precise way for quantification the gut permeability is needed. Based on the images it’s not yet possible to conclude whether LPS increased gut permeability or if IAP inhibition with L-phenylalanine worked in zebrafish larvae. Using adult zebrafish in the future will give more information about the chronic gut inflammation and development of possible kidney injury.
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(2014)Zebrafish (Danio rerio) is a vertebrate model organism. It is suited for many phases of drug development process like toxicological studies. The major advantage of using zebrafish is the possibility to conduct high-throughput screens on a whole vertebrate animal. However, there is not as much knowledge about zebrafish as there is about other model organisms. Therefore there might be differences between zebrafish and humans that affect the use of zebrafish as a model in the drug development process. The purpose of this thesis was to characterize the structure of the zebrafish oxytocin system and assess the role of oxytocin on zebrafish behaviour. In humans defects in the oxytocin system have been linked to many psychiatric disorders like autism. If the mammalian and zebrafish oxytocin systems resembled each other functionally and structurally, it would enable the use of zebrafish as a model when studying the role of oxytocin in pathophysiology of diseases and also in oxytocin system related drug development. The structure and development of zebrafish oxytocin system was studied by staining adult zebrafish brain cryosections and larval brains with antibodies made against mammalian oxytocin. The specificity of the antibodies to recognize zebrafish oxytocin was determined by absorption and cross-reactivity controls. The role of oxytocin on zebrafish locomotion was studied by inhibiting the splicing of oxytocin messenger RNA with morpholino oligonucleotides (MOs). The MOs were used to address the relevance of the model in pharmacology, since the zebrafish oxytocin receptors have not been expressed and pharmacologically characterized. In zebrafish oxytocin was produced in the cells of the preoptic nucleus. There were thick oxytocin fibers towards the pituitary and also thinner fibers into areas in the telencephalon, diencephalon, mesencephalon and rhombencephalon. One of the MOs was able to inhibit the production of oxytocin with a dose that did not cause morphological abnormalities. The MO reduced the locomotor activity of the fish, but the specificity of the MO has to be determined. The structure of the zebrafish oxytocin system resembles mammalian oxytocin system in terms of the location of oxytocin cells and fiber projections. Therefore zebrafish seems a suitable model organism for oxytocin research. However, the structure of the zebrafish oxytocin receptor system and the effect of oxytocin on other behavioural aspects have to be determined in order to further evaluate the applicability of zebrafish for oxytocin research.
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(2017)The α5 subunit of nicotinic acetylcholine receptors forms functional receptors with other subunits as a structural subunit. It affects the structural and functional properties of the nicotinic receptor by increasing calcium permeability and accelerating desensitization. In the mammalian brain, the α5 mRNA is widely expressed, mostly in substantia nigra pars compacta, ventral tegmental area and interpeduncular nucleus. Its protein has been identified in various distinct brain areas, such as striatum, cortex and medial habenula. In the dorsal striatum partaking in motor functions, the α5 subunit modulates the release of dopamine, thus it is believed to have an impact on motor function. In the experimental part of the thesis mice lacking the α5 subunit were injected unilaterally with neurotoxin 6-hydroxydopamine (6-OHDA) in the striatum. The purpose was to determine the importance of the subunit with regard to the lesion extent and motor function. The motor functions of α5-deficient and wild type control mice were assessed in amphetamine- and apomorphine-induced rotametry. After the tests the mice were euthanized and their substantia nigra and striatal brain samples were collected for further analysis. The number of dopamine cells in the medial and dorsal tier of substantia nigra were determined, so as to quantify the extent of the lesions and to explain the research group's previous finding about the α5-deficient mice spinning less ipsilaterally in amphetamine induced rotametry. The α5-deficient mice were found to turn less ipsilaterally compared to the control mice in the amphetamine-induced rotametry and in the apomorphine-induced rotametry, first less contralaterally and subsequently more contralaterally than the control mice. The results of male mice, that were less in number, were excluded from the results as the difference between genders was significant in the wild type mice in the amphetamine-induced rotametry. There was no significant difference in the number of remaining dopamine cells between the genotypes after the lesioning in either of the areas of interest. However, the wild type mice tended to have less cells remaining in the medial tier of the substantia nigra. The observed differences between the genotypes in the rotametries could be accounted by differences in the amount of dopamine released from striatal neurons or differences in striatal dopamine receptor quantities or function. The results support the hypothesis about the contribution of the α5 subunit containing acetylcholine nicotinic receptors in motor function.
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(2013)Parkinson's disease is a neurodegenerative disease which is characterized by progressive loss of dopaminergic neurons in the substantia nigra and formation of intracellular Lewy bodies. α-synuclein is an essential part of Lewy bodies. In addition, mutations in the α-synuclein gene have been found to cause rare familial forms of Parkinson's disease. Animal models of Parkinson's disease are created by neurotoxins, transgenic animals and viral vectors. Transgenic animal models and viral vector models seem to reflect the pathology of Parkinson's disease better than the traditional neurotoxin models. In the transgenic animal models, the transgene and the promoter used in the expression of the transgene guide the pathology and motor dysfunctions that the animal model exhibits. In the viral vector models, it is important to use a suitable animal strain and a correct viral serotype in order to express the transgene sufficiently enough in the laboratory animals. The aim of the study was to investigate the ability of adeno-associated viral vector (AAV1-vector) to transfect WT- or A53T-α-synuclein gene into the striatum or the substantia nigra, and the effects of their overexpression on motor functions and concentrations of striatal dopamine and its metabolites in mice. In addition, the effect of a prolyl endopeptidase (PREP) inhibitor on the overexpression of A53T-α-synuclein in the mouse nigrostriatal pathway was studied, as PREP has been found to stimulate the aggregation of α-synuclein and therefore perhaps to increase neurotoxicity of α-synuclein. There were no statistically significant differences between the groups in the motor function tests (locomotor activity, rotarod and balance beam walk). Green fluorescent protein immunostaining showed that the GFP gene was weakly transfected into the striatum by the AAV1-vector, and no overexpression was observed. There were only minor differences in the striatal concentrations of dopamine and its metabolites. Finally, PREP-activity measurements showed that PREP-inhibitor (KYP-2047) treatment had poorly reduced PREP-activity. In this study, the viral vectors did not induce the overexpression of α-synuclein, although previously AAV2- and AAV6-vectors have been efficient in mice and rats. High PREP-activities that were found in most of the samples probably resulted from failed installations of mini-pumps that delivered the PREP-inhibitor. While in this study the viral vectors were not a successful attempt in the creation of an animal model of Parkinson's disease, they are an important method to model Parkinson's disease in the future.
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(2017)lcohol addiction is a significant public health problem worldwide, and its treatment is extremely challenging. One major problem in the treatment of alcohol addiction are the later relapses to uncontrollable drinking. Approximately 60-70 % of addicts relapse to drinking within a year from the beginning of the treatment. The current treatment of alcohol addiction is based on a combined psychotheraphy and pharmacological treatments, but even at the best the efficacy remains quite modest. This is why further studies on the underlying mechanisms behind alcohol addiction and development of more effective pharmaceuticals to treat it are an important field of research. Chronic exposure to the rewarding effects of alcohol causes neurochemical adaptations in the brain reward system. These adaptations strive to restrain the recurring rewarding signals caused by alcohol and lead eventually to increased reward thresholds in the reward system. As the reward thresholds increase, the individual develops tolerance to the rewarding effects of alcohol, but also craving for the substance and a dysphoric mental state which are highlighted especially during periods of abstinence. It is known that the increase in reward thresholds is an important factor leading to relapses, but the exact nature of the neurochemical adaptations behind it are not known. According to recent studies dynorphin -peptides (DYN) and κ-opioid receptors (KOR) of the endogenous opioid system seem to have an important role in these neurochemical adaptations. It has been shown that chronic alcohol exposure increases the activity of DYN/ KOR -system especially within the nucleus accumbens (NAc), which is an essential structure of the brain reward system. The increased activity of the DYN/ KOR -system in the NAc has been shown to inhibit the development of rewarding signals. Previous studies have shown that inhibiting the increased activity of the DYN/ KOR -system with a selective KOR-antagonist, reduces voluntary alcohol intake and relapse-like alcohol seeking behavior during periods of abstinence, especially in physically addicted animals. In this study we studied the relapse-like alcohol drinking of Long-Evans rats in the alcohol deprivation effect (ADE) model. The effects of selective and long-acting KOR-antagonists, JDTic and nor-BNI, were tested on the ADE-effect which occurs after a period of deprivation. The ADE is defined as a transient increase in alcohol intake after a forced period of abstinence and it has been shown both in rodents with a history of alcohol consumption, and human alcohol addicts. In this study the rats were allowed to consume alcohol (10% ethanol-water solution) voluntarily during 90 minutes for 10 consecutive days after which followed a six days long deprivation period. According to results, both intra-accumbally (15 µg/ 0,3 µl/min/ site) or subcutaneously (10 mg/kg) administered JDTic decreased the ADEeffect significantly compared to vehicle, when administered 24 hours prior the end of the deprivation period. Also intra-accumbally administered nor-BNI (3 µg/0,3 µl/min/site) decreased the ADE-effect significantly compared to vehicle when administered 24 hour prior the end of deprivation. The results are in line with the theory that alcohol induces sensitization of the DYN/ KOR -system within the brain structures involved in reward. In theory it can be speculated that by suppressing the activity of the DYN/ KOR -system, KOR-antagonists can relieve craving for alcohol. This can be seen as a decrease in relapse-like consumption of alcohol. In conclusion, it can be suggested that by suppressing the increased activity of the DYN/ KOR -system induced by chronic alcohol exposure with a selective KOR-antagonist, like JDTic or nor-BNI, it could be possible to reduce the risk of relapse during abstinence and thus improve the efficacy of treatments for alcohol addiction.
Now showing items 594-598 of 598