| 41. |
- Andersson, Kennet, 1979-
(författare)
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Assessment of cerebrospinal fluid system dynamics : novel infusion protocol, mathematical modelling and parameter estimation for hydrocephalus investigations
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Patients with idiopathic normal pressure hydrocephalus (INPH) have a disturbance in the cerebrospinal fluid (CSF) system. The treatment is neurosurgical – a shunt is placed in the CSF system. The infusion test is used to assess CSF system dynamics and to aid in the selection of patients that will benefit from shunt surgery. The infusion test can be divided into three parts: a mathematical model, an infusion protocol and a parameter estimation method. A non-linear differential equation is used to mathematically describe the CSF system, where two important parameters are the outflow conductance (Cout) and the Pressure Volume Index (PVI). These are used both for clinical and research purposes. The analysis methods for the non-linear CSF system have limited the infusion protocols of presently used infusion investigations. They come with disadvantages such as long investigation time, no estimation of PVI and no measure of the reliability of the estimates.The aim of this dissertation was to develop and evaluate novel methods for infusion protocols, mathematical modelling and parameter estimation methods for assessment of CSF system dynamics.The infusion protocols and parameter estimation methods in current use, constant pressure infusion (CPI), constant infusion and bolus infusion, were investigated. The estimates of Cout were compared, both on an experimental set-up and on 20 INPH patients. The results showed that the bolus method produced a significantly higher Cout than the other methods. The study suggested a method with continuous infusion for estimating Cout and emphasized that standardization of Cout measurement is necessary.The non-linear model of the CSF system was further developed. The ability to model physiological variations that affect the CSF system was incorporated into the model and it was transformed into a linear time-invariant system. This enabled the use of methods developed for identification of such systems. The underlying model for CSF absorption was discussed and the effect of baseline resting pressure (Pr) in the analysis on the estimation of Cout was explored using two different analyses, with and without Pr.A novel infusion protocol with an oscillating pressure pattern was introduced. This protocol was theoretically better suited for the CSF system characteristics. Three new parameter estimation methods were developed. The adaptive observer was developed from the original non-linear model of the CSF system and estimated Cout in real time. The prediction error method (PEM) and the robust simulation error (RSE) method were based on the transformed linear system, and they estimated both Cout and PVI with confidence intervals in real time. Both the oscillating pressure pattern and the reference CPI protocol were performed on an experimental set-up of the CSF system and on 47 hydrocephalus patients. The parameter estimation methods were applied to the data, and the RSE method produced estimates of Cout that were in good agreement with the reference method and allowed for an individualized and considerably reduced investigation time.In summary, current methods have been investigated and a novel approach for assessment of CSF system dynamics has been presented. The Oscillating Pressure Infusion method, which includes a new infusion protocol, a further developed mathematical model and new parameter estimation methods has resulted in an improved way to perform infusion investigations and should be used when assessing CSF system dynamics. The advantages of the new approach are the pressure-regulated infusion protocol, simultaneous estimation of Cout and PVI and estimates of reliability that allow for an individualized investigation time.
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| 42. |
- Andersson, Karin
(författare)
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Prefibrillar oligomeric Transthyretin mutants - amyloid conformation, toxicity and association with Serum amyloid P component
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Amyloidoses represent a heterogeneous group of diseases characterized by abnormal protein metabolism leading to extracellular deposition of fibrillar, proteinaceous amyloid in various tissues and organs of the body. To date more than 20 different proteins have been linked to diseases with amyloid depositions, of which Alzheimer’s disease and the prion-associated diseases are the most well known. Despite the origin of protein in the amyloid, the fibrils share some common biochemical and biophysical properties such as a diameter of 8-13 nm, a β-pleated sheet secondary structure packed in an ordered crystal-like way, Congo red and thioflavin binding with characteristic spectroscopic patterns and decoration of the fibrils with Serum amyloid P component and glycoseaminoglycans.The plasma protein transthyretin (TTR) is associated with familial amyloidosis with polyneuropathy (FAP) and senile systemic amyloidosis (SSA). FAP is a lethal, autosomal inherited disorder caused by point mutations in the TTR-gene. More than 80 different mutations have been associated with amyloid formation and linked to FAP. The interpretation is that amino acid replacements at different sites of the polypeptide lead to reduced stability. Mutant TTR were constructed that have a strong tendency to self-aggregate under physiological conditions. The precipitates were shown to be amyloid by staining with thioflavin T and Congo red. As the mutants were sensitive to trypsin cleavage compared to plasma TTR, we suggest that the mutants represent amyloid precursors or that they may share structural properties with intermediates on a pathway leading to amyloid deposition. Monoclonal antibodies were generated that exclusively recognize the amyloidogenic folding of TTR providing direct biochemical evidence for a structural change in amyloidogenic intermediates. Two cryptic epitopes were mapped to a domain of TTR, where most mutations associated with amyloidosis occur and is proposed to be displaced at the initial phase of amyloid formation. Amyloidogenic intermediates of TTR were shown to induce a toxic, free radical dependent, response in cultured neuroblastoma cells. Morphological studies revealed a correlation between toxicity (apoptosis) and the presence of immature amyloid suggesting that mature full-length fibrils represent an inert end stage, which might serve as a rescue mechanism.Serum amyloid P component (SAP) is a highly conserved plasma glycoprotein universally found associated with amyloid depositions independently of protein origin. SAP’s role in amyloid formation is contradictory since both inhibition and promotion of aggregation have been shown in the case of fibril formation from the Aβ peptide of Alzheimer’s disease. Amyloidogenic prefibrils of TTR were shown to bind SAP and no interference with aggregation was detected. SAP co-localize in patches with mutant TTR on the surface of neuroblastoma cells and prevent apoptosis induced by mutant TTR and Aβ peptide, while several other molecules known to decorate amyloid fibrils were without effect.
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| 43. |
- Andersson, Liselott, 1961-
(författare)
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Implications of psychiatric disorders during pregnancy and the postpartum period - A population-based study
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Depressive and anxiety disorders are common health problems, affecting women at least twice as often as men. Although some studies have been made on pregnant women or, especially, in the postpartum period, most of these studies have been performed on small samples, mainly specific risk groups such as teenage mothers, women of low socioeconomic status and certain ethnic groups. Also, there is a lack of studies on antenatal and postpartum depression and/or anxiety using diagnostic criteria adhering to the Diagnostic and Statistical Manual of Mental disorders, fourth edition (DSM-IV). Aims and methods: The aims were to estimate the point prevalence of mood, anxiety and eating disorders, based on DSM-IV criteria, in an unselected population during the second trimester of pregnancy, and to assess the obstetric and neonatal outcome, as well as the health care consumption during pregnancy, delivery and the early postpartum period among women with a psychiatric disorder, compared to healthy subjects. Finally, we aimed to investigate depression and anxiety, and associated maternal characteristics and events through pregnancy and the postpartum period in the same group of women. The Primary Care Evaluation of Mental Disorders (PRIME-MD) was used for assessment of psychiatric disorders during the second trimester of pregnancy and three to six months after delivery. From October 2nd, 2000, to October 1st, 2001 all women attending the second trimester routine ultrasound-screening at two different hospitals in northern Sweden (at Umeå University Hospital and at Sunderby Central Hospital) were approached for participation in the study. After delivery, data were extracted from the medical records of the mothers and their offspring to evaluate obstetric and neonatal outcome. Three to six months after delivery, the women who had an antenatal depression and/or anxiety were contacted for an assessment using the PRIME-MD. The same procedure was made in a control group, consisting of 500 women, randomly selected among those who did not have any psychiatric diagnosis according to the PRIME-MD investigation during the second trimester of pregnancy. Results and conclusions: Of the 1555 women in the study population, 220 (14.1%) had one or more PRIME-MD diagnoses. Living single, low socioeconomic status, smoking, multiparity and a body mass index of 30 or more were significantly associated with a psychiatric diagnosis in the second trimester of pregnancy. Women with antenatal depression and/or anxiety more often suffered from nausea and vomiting during pregnancy were more often on sick leave, and they visited their obstetrician more often than healthy subjects, specifically because of fear of childbirth and premature contractions. Also, they were more commonly delivered by elective caesarean section, had an increased use of epidural analgesia and reported a longer self-experienced duration of labor. Severe complications of pregnancy, delivery, and the early postpartum period were not affected by antenatal depression and/or anxiety. There was no significant difference in neonatal outcome depending on antenatal depressive or anxiety disorder. Fewer cases of depressive and/or anxiety disorders were prevalent postpartum, but there was a significant shift from a majority of sub-threshold diagnoses during pregnancy to full DSM-IV diagnoses during the postpartum period. Previous psychiatric disorder and living singly were significantly associated with both a new-onset and a postpartum continuation/recurrence of depression and/or anxiety. Postpartum continuation/recurrence of a psychiatric disorder was additionally associated with smoking, obesity, and adverse obstetric events.
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| 44. |
- Andersson, Marie, 1962-
(författare)
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Immunopathogenesis of relapsing fever borreliosis
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Relapsing fever (RF) is caused by different species of Borrelia transmitted by soft ticks or by the human body louse. Illness is characterized by reappearing peaks of high concentrations of spirochetes in blood, concordant with fever peaks separated by asymptomatic periods. Neuroborreliosis is one of the most severe manifestations of RF borreliosis. To understand the immune response during early RF, we analyzed immune cells in brain and kidney of mice infected with B. crocidurae during the acute infection. Our results indicate that brain defense is comprised primarily of innate immune cells. Despite the infiltration of innate immune cells, Borrelia was not completely eradicated. A failure of the host brain to clear the bacteria may give the pathogen a niche where it can persist. Using our mouse model, we revealed that Borrelia duttonii could persist in the mouse brain for up to 270 days, without being present in the circulation. The infection was silent with no change in host gene expression, and the spirochetes could re-enter the circulation after immunosuppression. We propose that the brain is used by the pathogen to evade host immunity and serves as a possible natural reservoir for B. duttonii, a spirochete that has rarely been found in any mammalian host other than man. Borrelia-induced complications during pregnancy have been reported, and are especially common in RF. In our established mouse model of gestational RF, we could show that the fetuses suffered from severe pathology and growth retardation, probably as a consequence of placental destruction. We could also show trans-placental transmission of the bacteria leading to neonatal RF. Surprisingly, pregnant dams had a lower bacterial load and less severe disease, showing that pregnancy has a protective effect during RF. We have used the gestational RF model to investigate host factors favoring disease resolution. Because the spleen is the primary organ responsible for trapping and removing blood-borne pathogens, we have compared temporal changes in spleen immune cell populations and cytokine/chemokine induction during the infection. Spleens of pregnant mice had earlier neutrophil infiltration, as well as faster and higher production of pro-inflammatory mediators. This rapid, robust response suggests a more effective host defense. Thus, an enhanced pro-inflammatory response during pregnancy imparts a distinct advantage in controlling the severity of relapsing fever infection.
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| 45. |
- Andersson, Nina, 1976-
(författare)
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Cerebrospinal fluid infusion methods : development and validation on patients with idiopathic normal pressure hydrocephalus
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cerebrospinal fluid (CSF) infusion tests can be used to estimate the dynamic properties of the CSF system. Idiopathic normal pressure hydrocephalus (INPH) is a syndrome signified by a disturbance to the CSF system, where the cause is unknown and the diagnosis is difficult to determine. As an aid in identifying patients with INPH who will improve after shunt surgery, infusion tests are commonly used to determine the outflow conductance (Cout), or outflow resistance (Rout=1/Cout), of the CSF system. The tests are also used to determine shunt function in vivo. The general aim of this thesis was to develop and validate CSF infusion methods, to investigate the dynamics of the CSF system. The methods should be applicable to patients with INPH, to aid in the quest to further improve the diagnosis and management of this syndrome.An existing mathematical model describing the dynamics of the CSF system was further developed. The characteristics of the model were verified and the effect of expanding intracranial air on the intracranial pressure (ICP) was simulated. The simulations supported the recommendation to maintain sea-level pressure during air ambulance transportation of patients with suspected intracranial air.A recently developed infusion apparatus was evaluated, on an experimental model as well as on a patient material. The repetitiveness in estimating Cout was found to be good. A statistically significant difference was found between the repeated Cout estimations in the patient group, indicating that there might have been a small physiological change introduced during the infusion test. A parameter, ∆Cout, was proposed and evaluated. It proved to reflect the reliability of individual Cout investigations in a clinically useful way, as well as to provide easily interpreted information.An adaptive algorithm for assessment of Cout was developed and evaluated on a patient group. The new algorithm was shown to reduce the investigation time, from 60 minutes, by 14.3 ± 5.9 minutes (mean ± SD), p<0.01, without reducing the reliability of the estimated Cout below clinically relevant levels.The relationship between ICP and CSF outflow was studied in a group of patients investigated for INPH. It was found that in the range of moderate increase from baseline pressure, the assumption of a pressure independent Rout was confirmed (p=0.5). However, at larger pressure increments, the relationship had a non-linear tendency (p<0.05). This indicates that the traditional view of a pressure independent Rout might have to be questioned in the region where ICP exceeds baseline pressure too much.Infusion tests can be performed in different ways, where three main categories may be distinguished. The bolus infusion method was compared to the constant pressure and constant flow infusion methods, on an experimental model as well as on a patient material. When physiological pressure fluctuations were added to the model, significant differences were found in the determination of Cout in the range of clinical importance, i.e. low Cout (p<0.05). The finding was supported by the patient investigations, the difference was however not significant.With the application of the new methods developed in this thesis, and the increased knowledge concerning relationships between CSF dynamic parameters, the CSF infusion test was further improved with the ability to increase measurement reliability in a reduced time. This constitutes a good basis to perform a large multi-centre study with the main goal to determine the predictive value of the parameter Cout.
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| 46. |
- Andersson, Sofia, 1972-
(författare)
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Vård i livets slutskede på särskilt boende för äldre personer : närstående och vårdpersonals skattade och berättade erfarenheter
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bakgrund I Europa, blir det allt vanligare att äldre personer dör på särskilt boende i stället för på sjukhus. Särskilda boenden spelar därför en viktig roll när det gäller vård i livets slutskede. Målet med palliativ vård för personer med livshotande sjukdom och deras närstående är att öka livskvaliteten och lindra lidande. Strukturerade vårdplaner såsom Liverpool Care Pathway for care of the dying (LCP) kan vara ett sätt att öka vårdkvaliteten. Det saknas dock forskning om vård i livets slutskede på särskilda boenden när en strukturerad vårdplan har använts.Syfte Det övergripande syftet med avhandlingen var att beskriva vård i livets slutskede på särskilt boende för äldre personer utifrån närstående och vårdpersonals skattade och berättade erfarenheter.Metod Avhandlingen baseras på två kvantitativa (I, II) och två kvalitativa (III, IV) studier. Studie I baseras på frågeformuläret Views of Informal Carers – Evaluation of Services (VOICES) som har besvarats av närstående (n = 189) efter att en anhörig har dött. Data har därefter analyserats med beskrivande och jämförande statistik. Studie II baseras på data om alla förväntade dödsfall (n = 22 855) som registrerats i Svenska palliativregistret (SPR). Dödsfallsenkäten har besvarats av vårdpersonal och svaren har sedan analyserats med beskrivande statistik och univariat och multipel logistisk regressionsanalys. Studie III baseras på fokusgruppsintervjuer och enskilda intervjuer med vårdpersonal. Studie IV baseras på enskilda intervjuer med närstående. Data från studie III och IV har analyserats med hjälp av kvalitativ innehållsanalys.Resultat Resultatet i studie I visar att majoriteten av de närstående skattade att den äldre personen fick tillräcklig hjälp såväl med personlig vård (78,5 %) som med sjukvård (93,0 %) de sista tre dagarna i livet. De närstående (86,2 %) rapporterade att de var informerade om att det var sannolikt att den äldre personen skulle avlida och majoriteten (94,1 %) av de äldre hade avlidit på önskad plats. Resultatet visade dock på hög förekomst av smärta (46,5 %) och andnöd (55,9 %). Det var ingen skillnad mellan åldersgrupperna när det gällde smärta men de äldre < 85 år hade signifikant högre förekomst av andnöd (70,6 %) jämfört med de äldre äldre, ≥ 85 år, (47,5 %). De äldre, < 85 år, hade signifikant oftare symtomlindring för andnöd (53,1 %) jämfört med äldre äldre, ≥ 85 år, (31,8 %).Resultatet i studie II visar hög förekomst av smärta (68,8 %) och ångest (44,0 %). Faktorer associerade med symtomlindring av smärta, illamående, ångest och andnöd var dels att validerat smärtskattningsinstrument hade använts, dels att munhälsan var bedömd. Starkast samband var det mellan symtomlindring av tre symtom (smärta, andnöd och ångest) och att injektioner var förskrivna vid behov.Resultatet i studie III visar att vårdpersonalen upplevde sig tryggare efter implementeringen av LCP genom att de hade fått ett gemensamt förhållningssätt, kände stöd att skräddarsy vården utifrån den döende personens individuella behov, kände stöd att involvera närstående i beslut och i vården samt hade blivit mer medvetna om vårdmiljön.Resultatet i studie IV visar att närstående upplevde sig tryggare i en välbekant och varm atmosfär, att vara kontra inte vara involverad i vård i livets slutskede och att bli tröstade genom att bevittna vårdpersonalens strävan att lindra lidande.Konklusion Resultatet från studierna i den här avhandlingen pekar på hög vårdkvalitet i livets slutskede på särskilt boende genom god omvårdnad, men resultatet pekar också mot förekomst av inadekvat symtomlindring och hög förekomst av smärta, andnöd och ångest de sista dagarna i livet. Det framkom ett tydligt samband mellan ordinerade injektioner vid behov och symtomlindring av smärta, illamående och ångest. Resultatet indikerar även vikten av att använda smärtskattningsinstrument och göra munhälsobedömningar för symtomlindring vid vård i livets slutskede. Således kan ett sätt att öka vårdkvaliteten för döende personer vara att det finns ordinerade injektionsläkemedel vid behov mot vanliga symtom, att använda validerade smärtskattningsinstrument och att göra munhälsobedömningar. Det framkom också att användandet av en standardiserad vårdplan såsom LCP kan vara ett sätt att förbättra vården för de äldre personerna i livets slutskede. Såväl vårdpersonalen som de närstående upplevde stöd av den struktur för bedömningar och vårdaktiviteter som LCP ger. Vårdpersonalen upplevde också stöd i att involvera närstående i vården och i vårdrelaterade beslut.
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| 47. |
- Andersson, Therese, 1983-
(författare)
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Acute Pulmonary Embolism : not just an acute condition after all
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Acute pulmonary embolism (PE) is the third most common cardiovascular disease following myocardial infarction and stroke. Despite diagnostic improvements, the diagnosis of PE is still associated with many difficulties, as the symptoms of an acute PE are nonspecific. Even though an acute PE is associated with a high short-term mortality, less attention has been given to long-term mortality. In addition, the clinical course following an acute PE may be accompanied by substantial morbidity, and one feared complication is chronic thromboembolic pulmonary hypertension (CTEPH), a progressive pulmonary vasculopathy. In addition to CTEPH, increasing evidence suggests that a large proportion of patients report persistent functional impairment several years after an acute PE. Recently, the term chronic thromboembolic pulmonary disease (CTEPD) has been proposed for those with remaining symptoms and signs of residual thrombotic material in the pulmonary arteries. Methods and Results: A nation-wide Swedish cohort of all patients (n= 5793) diagnosed with an acute PE in 2005 was identified. The incidence of PE was 0.6/1000 person-years, and during a 4-year follow-up, the mortality was more than doubled compared with an age- and sex-matched control group. We found that the acute PE associated with multiple comorbidities, and with cardiovascular diseases in particular. All surviving patients in 2007 (n=3510) were invited to answer a questionnaire regarding dyspnea and related comorbidities. We demonstrated a substantially higher prevalence of both exertional dyspnea (53.0% vs. 17.3%) and wake-up dyspnea (12% vs. 1.7%) in patients compared to controls from the Northern Sweden MONICA study. Furthermore, PE associated independently with dyspnea in a multivariable analysis. Through a manual review of approximately 10 % of the patient’s medical records, a positive predictive value of 79% was found for the PE diagnosis. Post-PE patients with remaining dyspnea and/or previously known risk factors for CTEPH development were referred for blood sampling and levels of N-terminal (NT)-prohormone (pro) brain-type natriuretic peptide (BNP) were determined. Thereafter, they were referred to their local hospital for a pulmonary ventilation/perfusion (V/Q) scintigraphy and echocardiography. Approximately 45% of the V/Q-scans showed perfusion defects and 27 % of echocardiographies showed signs of pulmonary hypertension. In total, 24 cases of CTEPH were identified, resulting in a prevalence of 0.4 % (95 % confidence interval 0.2 %–0.6 %). Conclusion: An acute PE is a serious event, associated with decreased survival, multiple comorbidities, frequent dyspnea, and pathological investigational findings. The term CTEPD seems reasonable as it captures that this is a disease of the pulmonary vasculature, and that pharmacological and surgical interventions used for CTEPH may be useful. Regardless, proper follow-up after acute PE is essential for timely identification of patients in need of appropriate investigations and care.
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| 48. |
- Andersson, Therése, 1978-
(författare)
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Estrogen and Glucocorticoid Metabolism
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Cardiovascular disease (CVD) is the leading cause of death among women in Sweden. The risk of CVD increases rapidly after the menopause. A major contributing factor may be the redistribution of adipose tissue, from the peripheral to central depots, associated with menopause. This change in body composition is commonly attributed to declining estrogen levels but may also be affected by tissue-specific alterations in exposure to other steroid hormones, notably glucocorticoids – mainly cortisol in humans. Indeed, adipose tissue-specific overexpression of the glucocorticoid-activating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) induces central obesity, insulin resistance and hypertension in mice. Interestingly, estrogen may regulate this enzyme. The aim of this thesis was to investigate putative links between estrogen and glucocorticoid activation by 11βHSD1. Materials and Methods: 11βHSD1 expression and/or activity in adipose tissue and liver, and adipose estrogen receptor α and β (ERα and ERβ) gene expression, were investigated in lean pre- and postmenopausal women and ovariectomized rodents with and without estrogen supplementation. In lean women measures of 11βHSD1 were correlated to risk markers for CVD. The association between adipose 11βHSD1 and ER mRNA expression was investigated in both lean women and rats and in an additional cohort of obese premenopausal women. In vitro experiments with adipocyte cell lines were used to explore possible pathways for estrogen regulation of 11βHSD1. Results: Subcutaneous adipose tissue transcript levels and hepatic activity of 11βHSD1 were higher in postmenopausal vs. premenopausal women. In rodents, estrogen treatment to ovariectomized rats decreased visceral adipose tissue 11βHSD1, resulting in a shift towards higher subcutaneous (vs. visceral) 11βHSD1 mRNA expression/activity. Increased adipose and hepatic 11βHSD1 were associated with increased blood pressure and a disadvantageous blood lipid profile in humans. We found significant positive associations between 11βHSD1 and ERβ transcript levels in adipose tissue. The in vitro experiments showed upregulation of 11βHSD1 mRNA expression and activity with estrogen or ERβ-agonist treatment at low (corresponding to physiological) concentrations. Conclusions: Our studies show for the first time increased local tissue glucocorticoid activation with menopause/age in women. This may contribute to an increased risk of CVD. Estrogen treatment in rodents induces a shift in 11βHSD1 activity towards the subcutaneous adipose tissue depots, which may direct fat accumulation to this metabolically “safer” depot. The in vitro studies suggest that low-dose estrogen treatment upregulates 11βHSD1 via ERβ. In summary, estrogen - glucocorticoid metabolism interactions may be key in the development of menopause-related metabolic dysfunction and in part mediate the beneficial effects of postmenopausal estrogen treatment on body fat distribution.
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| 49. |
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| 50. |
- Andersson, Ulrika, 1963-
(författare)
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Experimental studies in brain tumours : with special regard to multidrug resistance and the ErbB-family
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Primary brain tumours, and especially the most common form malignant gliomas, usually display a pronounced resistance to other treatment modalities when surgery fails to cure. Growth factors, such as EGF and its receptor, frequently amplified and overexpressed in malignant gliomas, and factors associated with multidrug resistance have been suggested to at least partially explain the poor outcome. The aim of this thesis was to characterise factors in primary brain tumours associated with the development of resistance with focus on the epidermal growth factor receptor (ErbB) family, and multidrug resistance (MDR). Influences of irradiation on the expression and activity of P-glycoprotein (Pgp) in malignant gliomas was evaluated. The effects showed that irradiation increased the efflux activity of Pgp in rat brain vascular endothelial cells, but not in glioma cells. In the intracranial BT4C glioma model, Pgp was detected in the capillary endothelium in the tumour tissue but not in glioma cells. Expression of several factors coupled to MDR (Pgp, MRP1, LRP, and MGMT) in primary brain tumours were analysed and correlated to clinical data. In gliomas, Pgp and MRP1 were predominantly observed in capillary endothelium and in scattered tumour cells, whereas LRP occurred only in tumour cells. In meningiomas, expression of the analysed markers was demonstrated in the capillary endothelium, with a higher expression of Pgp and MRP1 in transitional compared to meningothelial meningiomas. A pronounced expression of MGMT was found independently of the histopathological grade or tumour type. Survival analysis indicated a shorter overall survival for patients suffering from low-grade gliomas with high expression of Pgp. To explore the importance of the epidermal growth factor receptor (EGFR), expression levels of the family members (EGFR, ErbB2-4) were analysed and their relations to various clinical parameters were evaluated in gliomas and meningiomas. In gliomas, the highest EGFR expression was observed in high-grade tumours, while ErbB4 expression was most pronounced in low-grade tumours. In meningiomas, expression of EGFR, ErbB2, and ErbB4 was observed in the majority of the tumours. An intriguing observation in low-grade gliomas was a significantly decreased overall survival for patients with high EGFR protein expression. The effects of different time schedules for administration of the selective EGFR inhibitor ZD1839 in relation to irradiation of glioma cells were analysed. The analyses showed a heterogeneity in the cytotoxic effects of ZD1839 between cell lines, and it was obvious that some of the cell lines showed sensitivity to ZD1839 despite no or low expression of EGFR. The study also demonstrated the importance of timing of ZD1839 administration when this agent is combined with irradiation. In conclusion, in order to enhance the efficacy of radiotherapy by various drugs in malignant gliomas it may be essential to inhibit drug efflux activity in endothelial cells and to deliver drugs in an optimal timing in relation to radiotherapy. The heterogeneity in expression of drug resistance markers, as well as the ErbB family reflects the complexity in classification of primary brain tumours, and indicates that subgroups of patients with low-grade gliomas expressing Pgp and EGFR might benefit from more aggressive and individualised treatment.
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