| 1. |
- Aagaard, Philip
(författare)
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Cardiovascular assessment in middle-aged male long distance runners
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Endurance events such as long distance running races are increasing in popularity and convey multiple health benefits. However, such exercise forms also represent a major challenge to human cardiovascular physiology and are associated with a momentarily increased risk for adverse cardiac events. Using the world’s largest cross-country running race Lidingöloppet as a model of endurance events, this thesis aims to: 1) investigate male and female participation and performance trends 2) detail the cardiovascular findings of a comprehensive cardiovascular preparticipation evaluation in novice male race participants aged 45 years and older 3) study the impact of race participation on cardiac autonomic tone and 4) assess features of cardiovascular function and vectorcardiography (VCG), and their response to endurance exercise in individuals with early repolarisation (ER). Study I: Participation and performance trends were investigated in >120,000 runners partaking in the Lidingöloppet between 1993 and 2007. In a subgroup of 249 middle-aged males, the association between the cardiac biomarker NT-proBNP and runtime was also studied. Participation increased over the study period, particularly in females and older males, while participants’ fitness deteriorated, as measured by an average increase in runtime of 21 ± 31 min. Longer runtimes were independently associated with higher levels of NT-proBNP. Study II: A preparticipation cardiovascular exam was performed in 153 middle-aged male first-time Lidingöloppet race participants. Runners were assessed by medical history and physical exam, 12-lead ECG, echocardiography, and blood tests. 9 % of runners required further diagnostic work-up and 2 % were discouraged from race participation due to cardiac abnormalities that could increase their risk of exercise- related cardiac events. Study III: Heart rate (HR) and heart rate variability (HRV) was continuously measured from 48 hours before until 96 hours after a Lidingöloppet 30km race. Compared to pre-race values, HR was elevated during the night after the race while HRV remained depressed for 64 [51 - 96] hours after the race. A reduced HR recovery and a greater fall in HRV post race were associated with higher levels of high-sensitivity troponin T (hsTnT). Study IV: The prevalence and associated cardiac features of ER, characterized by ST-segment elevation (STE) and/or J-waves, was investigated in 153 middle-aged males registered for first-time participation in the Lidingöloppet 10, 15 or 30km race. ER was present in 40 % and generally associated with features of better cardiovascular fitness. The cardiovascular effects of participating in the 30km race (n= 94) were also assessed after the race; runners with J-waves, but not with STE alone, showed changes of repolarisation parameters usually considered unfavourable (e.g. prolonged T peak-to-end (Tpe) and QTc). Conclusion: This thesis demonstrated that increased participation in a long distance running event (Lidingöloppet) was paralleled by deteriorating runtimes. In middle-aged men, longer runtimes were associated with higher levels of NT-proBNP. These findings may raise concern regarding the fitness and cardiovascular health of some of today’s race participants. A comprehensive preparticipation evaluation identified 9 % of first- time runners needing additional work-up and 2% who were ultimately discouraged from participating, suggesting that such a protocol is useful to identify individuals requiring further testing prior to vigorous exercise. After the race there was a prolonged depression of HRV. The magnitude and duration of HRV depression correlated with higher levels of hsTnT, suggesting that the degree of troponin (Tn) increase after strenuous exercise may reflect the level of exercise-induced cardiovascular stress. ER was generally associated with a benign cardiovascular profile, although subjects with J-waves showed post-race changes in some parameters of ventricular repolarisation that are usually associated with increased arrhythmia propensity. More research into the mechanisms and potential preventive measures of adverse exercise related effects on cardiac function is warranted.
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| 2. |
- Aanesen, Arthur
(författare)
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GABA and human spermatozoa : characterization and regulation of GABA transport proteins
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present project aimed at investigating the interaction between GABA and human spermatozoa under in vitro conditions. Our initial hypothesis was that human spermatozoa had specific binding proteins for GABA and that the binding of GABA to such binding sites could affect sperm function. Studies on swim-up preparations of human spermatozoa incubated with radiolabelled GABA in the presence of unlabelled GABA, alternatively displacers of GABAA/B receptors and GABA transport proteins, indicated that GABA specific binding sites were present on the surface of human spermatozoa. The potency of the different inhibitors indicated that the binding sites possibly represented GABA transport proteins. No effect on sperm motility or AR was observed following incubation with GABA. Further studies indicated that human spermatozoa are capable of a carrier mediated GABA uptake. The uptake is dependent on the concentration of chloride and sodium in the external medium, and the kinetic properties of the carrier resembled high affinity GABA transport proteins. Uptake of radiolabelled GABA into human spermatozoa in the presence of steroids was investigated. We examined progesterone, other steroids known to increase calcium influx, and steroids known to be ineffective as stimulators of calcium influx in human sperm. The results demonstrated a twofold increase in GABA uptake following preincubation with P or steroids known to stimulate calcium influx. In contrast, an inhibition of GABA uptake following preincubation with activators of protein kinase C was observed. The results suggest a role for PKC in the regulation of GABA transport in human spermatozoa. The reduced GABA uptake following incubation with phorbol esters and diacyl glycerol (DAG) analogues, as well as the lack of effect observed following addition of inactive DAG analogues, strongly indicate such a regulatory pathway. The existence of GABA transporter m-RNA and proteins in human testis and sperm was examined using RT-PCR, immunohistochemistry and immunoblotting. Oligonucleotide primer pairs were designed from nucleotide sequences for the three cloned GABA transport proteins identified in human brain: GAT-1, GAT-3 and BGT-1. From homogenized human testis, PCR products of predicted size and with homology to respective GABA transport proteins were identified. This finding indicates the MRNA expression of all three GABA transporters in human testicular tissue. Studies on the protein expression of GABA transporters in sperm cells were performed with SDS-PAGE and immunoblotting techniques. Immunoblots using polyclonal antibodies raised against rat GAT-1, GAT-2 and GAT-3 recognized bands of approximately 65kDa, indicating cross-reactivity to GABA transporters present in human sperm cells. Pharmacological characterization of GABA uptake with specific inhibitors of GABA transport revealed a unique sequence in the relative potencies of the inhibitors tested. The results may indicate the presence of more than one GABA transporter in the plasma membrane of human spermatozoa. Immunoblots and immunohistochemistry studies indicate the presence of one or several GABA transporters in human spermatozoa and testis, these results are supported by pharmacological studies using specific inhibitors of GABA transport. These studies add new information to the present knowledge concerning GABA and human spermatozoa. They also for the first time describe specific GABA transport proteins in the male reproductive tract. Further studies are however, required to elucidate the functional role for these proteins in terms of human reproduction.
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| 3. |
- Aarne, Päivikki
(författare)
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Self and other : socio-emotional aspects of development in children with language impairment
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis comprises four studies that focus on young children with language impairment (LI). The research focus was different aspects of socio-emotional development. In Study I visual check back behaviors were investigated in ten pre-school-aged children with LI and in two groups of children with typical development (TD); ten children that were matched with regard to age (AMC) and ten children matched with regard to language level (LMC). Play setting situations were designed to elicit the target behaviors of shared attention, intention and emotion. The children with lower language level (LI and LMC) gave visual check back significantly more seldom than children with a higher language level (AMC). In Study II, the association between communication and language level, and socio-emotional level was investigated by parent ratings. Pre-school-aged children with LI and children with TD were assessed by their respective parents using The MacArthur Communicative Development Inventories (Swedish version (SECDI) and Greenspan Socio Emotional Growth Chart, (GSEGC). An association between language and socio-emotional development was found. Children with LI were rated similar to the young language-matched children with TD, but significantly lower relative to age-matched TD children, particularly concerning symbolic stages of development. In Study III, a case study, the capacity to mentalize was explored in a primary-school-aged boy with a history of LI. In play situations, the child was presented story stems that he could complete by play actions or verbally. The mentalizing capacity was analyzed with respect to the organization and the content of his responses, as well as his observable behavior in the situation. The child had difficulties in affect regulation, i.e. self-oriented mentalizing, and his other-oriented mentalizing was limited as well. In Study IV, parental stress and the parents’ perception of their child’s behavioral as well as communication and language difficulties were investigated by Swedish Parenthood Stress Questionnaire (SPSQ), Swedish version of Strengths and Difficulties Questionnaire (SDQ-Swe) and the Swedish version of MacArthur Communicative Developmental Inventories (SECDI), in three groups of pre-school-aged children: children with LI, children with more extensive communication difficulties and suspected ASD (COM), and children with TD. Parental experience of stress differed significantly between the groups on total and specific aspects of stress. A significant association was found between parental stress and children’s behavioral difficulties in the total group, but not in the clinical groups. Parental stress and children’s communication and language difficulties were associated in the group COM with extensive communication difficulties.
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| 4. |
- Aarum, Johan
(författare)
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Interactions between mouse CNS cells : microglia and neural precursor cells
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The mammalian central nervous system (CNS) contains a variety of cells, all specialized to perform different functions. Most numerous are the three types of glia cells, whose basic role is to support the signaling units of the CNS, the neurons. The perspective of this thesis is from the glia cells; particularly the microglia cells, a non-neural population of cells that are spread throughout the CNS. In the healthy CNS these cells are resting, but as a consequence of various CNS disturbances they rapidly become activated, frequently together with astrocytes, the second type of glia cells (oligodendrocytes being the third). This can happen slowly, as in neurodegenerative diseases, or quickly as in acute CNS lesions such as stroke. Both processes involve microglia cells, and sometimes macrophages from the circulation. These latter cells are difficult to distinguish from the microglia cells. In an effort to generate microglia specific markers we used phage display technology to select microglia specific peptides from a random peptide library displayed on the phage surface. Two sets of selection strategies were compared with regard to phage-clone enrichment. The first strategy was based on phage binding to monolayers of primary microglia fixed to a solid surface, while the second strategy was based on fluorescence activated cell sorting (FACS) of microglia cells with bound phages. The latter protocol was found to be superior. Five phage-clones that preferentially bound to microglia cells were isolated. One of the selected clones was shown to be microglia specific by free peptide inhibition and selective in binding to microglia cells, as compared to blood-derived monocytes. Much of our current knowledge in neurobiology derives from studies of cells in culture, a less complex substitute for in vivo studies. As a bridge between monolayer CNS cell cultures and in vivo animal models we set up a three-dimensional culture system, so called aggregate cultures from mouse CNS cells. These aggregates were characterized in detail regarding cellular composition and dynamics, as well as the expression of several neuropeptides and neurotransmitters. All the principle brain cells were present in the aggregates and their numbers changed over time, neurons being the most numerous. The cells appeared to mature as judged by their morphology and, in the case of neurons, the increased expression of synapse specific proteins. Among the investigated neuropeptides, enkephalin and dynorphin were the most abundant followed by galanin, approximating their expression in CNS development. We also found that neural precursor cells, capable of self-renewal and differentiation into neurons, astrocytes and oligodendrocytes, were maintained in the aggregates, even after more than two months of culturing. Treating the aggregates with EGF led to the formation of an outer layer of nestin-positive precursor cells. Using the aggregate culture in part, we found that factor(s) secreted from microglia cells attracts neural precursor cells in a chemotactic manner. This finding may explain the preferred migration of precursor cells to sites of CNS injury. Furthermore, microglia derived factors could affect the differentiation of neural precursor cells, such that more neurons were formed. Together these results suggest important functions of microglia cells in CNS development and pathology. It is reasonable to believe that the migration of neural precursor cells is directed both by attractant and repellant cues. Reactive astrocytes are well known to inhibit growing axons and recently also suggested to inhibit the migration of neural precursor cells. We show that astrocytes in culture repel neural precursor cells and that this effect is mediated by secreted Slit proteins. This conclusion is based on several observations; astrocytes produce Slit and the astrocyte-repellant effect was blocked by the ectodomain of the Slit receptor, and finally, recombinant Slit could substitute for astrocyte derived Slit. Knowledge about the interplay between attractive and repulsive cues may be important for the manipulation of neural precursor cells for medical purposes.
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| 5. |
- Aas, Randi Wågö
(författare)
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Workplace-based sick leave prevention and return to work : exploratory studies
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Earlier research have revealed risk factors for sick leave in the workplace, and thus the workplace has become an important arena for sick leave prevention and return to work (RTW). Despite that, some of these aspects have received little attention in exploratory studies. Simultaneously, there is a need to translate and implement the growing knowledge base in this field in order to develop evidence-based practice (EBP). Aim: The aim of the present research was to explore some aspects of workplace-based sick leave prevention and RTW, such as workplace interventions (studies III, IV, and the appendix), leadership qualities (study I), and work demands (study II), and also to reveal challenges to translating scientific knowledge into intervention decisions in the RTW process, and possible solutions to these challenges (study III). Methods: Content analysis methods were applied on data from interview transcripts and documents. In addition, a Cochrane systematic review of the literature was conducted. Results: Study I identified 78 distinct leadership qualities and seven leadership types (n = 345 meaning units) perceived by 30 employees on long-term sick leave and their immediate supervisors. The three most valued leadership qualities were “ability to make contact”, “being considerate”, and “being understanding”. The three most valued leadership types were the Protector, the Problem-Solver, and the Contact-Maker. The subordinates gave more descriptions of the Encourager and the Recognizer, whereas the supervisors most often described the Responsibility-Maker and the Problem-Solver. The combination of leadership types reported most frequently was the Protector together with the Problem-Solver. In study II, eight employees on long-term sick leave due to musculoskeletal diseases and disorders described 51 work demands they had experienced. The demands were perceived in some cases as having only a negative or a positive impact on work performance, but in others as both. Only seven of the demands were physical in nature, and most involved emotional and cognitive challenges in mastering the work tasks. It was also experienced that most demands came from the employee (n = 36) and only a few from the employer/work environment (n = 7) or both those sources (n = 8). Study III was a hypothetical case study aimed at revealing the challenges associated with translating scientific evidence into intervention decisions in the RTW process. This investigation was performed according to EBP frameworks. The evidence seemed to differ depending on whether it came from preventive, curative, or rehabilitative interventions. Moreover, it appeared that evidence in some cases originated from “good-for-all” interventions but in others from “tailored-type” interventions. Thus, a need to differentiate the roles of evidence was revealed in terms of whether it inspired, challenged, enlightened, informed, or determined the intervention decision. In general, the evidence-based framework seemed to construct a confined decision process. Possible solutions, and revised EBP steps were suggested. In study IV, 15 workplace interventions were identified (n = 306 meaning units), which were intended to reduce sick leave rates in 12 municipalities. The interventions were divided into two groups according to their targets in the organizations: nine organizational-workplace interventions targeted structures, processes, and culture (n = 220 descriptions, 72%); six employee-workplace interventions targeted persons (n = 86 descriptions, 28%). Examples of organizational-workplace interventions were developing routines/systems, establishing cooperation/ collaboration, providing information/education, building culture/anchoring, and recruiting/staffing. Employee-workplace interventions involved well-being/lifestyle interventions, physical activity/exercise, redeployment, adaptation, follow-up of employees on sick leave, and RTW programmes. The intervention profiles varied considerably between the municipalities. In the appendix (study V), a Cochrane systematic review of the literature was conducted to reveal the content and effectiveness of workplace interventions for employees with neck pain. Of 1,995 references found, 10 randomized controlled trials (RCTs) were included. Two of the RCTs had low risk of bias, and eight of them examined office workers. Few were on sick leave. Only three of the ten studies assessed the outcome of sick leave. The workplace interventions varied considerably regarding complexity and content. Overall, evidence was of low quality and showed no significant impact of workplace interventions on pain reduction (seven RCTs, 2,368 workers). Furthermore, one RCT, with 415 workers revealed that workplace interventions were significantly more effective in reducing sick leave in the intermediate term (OR 0.56, 95% CI 0.33–0.95), but not in the short or the long term. Conclusions: The results reported in this thesis revealed a variety of terminology related to workplace interventions, leadership qualities, and work demands, which might contribute to more in-depth understanding of sick leave prevention and RTW at workplaces. It was a challenge to trying to use evidence from randomized controlled trials in the RTW process, and the results call for new EBP approaches to translate evidence into decisions concerning complex workplace interventions. The current research also revealed that knowledge about the effectiveness of workplace interventions is still limited.
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| 6. |
- Aasa, Mikael
(författare)
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Reperfusion therapy in acute ST-elevation myocardial infarction : a comparison between primary percutaneous intervention and thrombolysis in a short- and long-term perspective
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Approximately 35,000 people suffer from a heart attack in Sweden annually. Among them, approximately 8000 are diagnosed with a ST-elevation myocardial infarction (STEMI) where timely reperfusion has been shown to save lives. Previous studies that have compared the existing reperfusion strategies, thrombolysis (TL) and primary PCI (PPCI), made use of treatment regimens that since have been improved with the use of mechanical and medical adjunctives. The objective of this thesis was to compare both of these strategies employing updated regimens in accordance to current guidelines with respect to; 1) efficacy in restoring blood flow and myocardial perfusion, 2) clinical outcome and 3) cost-effectiveness. Methods and results: Between November 2001 and May 2003, 205 patients with STEMI were randomized to PPCI with adjunctive abciximab or TL. The low molecular weight heparin enoxaparin was used as anticoagulant in both groups. In 42% treatment was initiated in the pre-hospital phase. The primary end points were the rate of STsegment resolution (STRES) ≥ 50% 120 minutes after inclusion and the rate of normalized (TIMI 3) flow in the infarct related vessel 5-7 days after treatment, serving as surrogates for a beneficial outcome. Secondary end points were the ability to restore myocardial perfusion evaluated angiographically by TIMI Myocardial Perfusion Grade (TMPG) 5-7 days after inclusion in the study, clinical events at 30 days and one year cost-effectiveness. The patients were followed prospectively for one year and, in addition, information on survival status and major clinical events was collected from national registries for an extended follow up period of a median of 5.3 years. STRES≥ 50% was achieved in 68% following PPCI and 64% after TL (n.s.). However, the TIMI 3 rate was higher after PPCI compared to TL (71% vs. 54%, p=0.04). TMPG tended to be better in the PPCI group than in the TL group. An analysis of the evolution of TMPG in the PPCI cohort revealed that there was a significant improvement of myocardial perfusion in the week following PPCI. Thirty day mortality rates were low and similar in the groups. At one year PPCI was tended to be less costly ($-2,505) than TL ($-2,505; n.s.), mainly due to higher costs for re-hospitalizations in the TL group. Primary PCI also lead to an insignificant gain in quality-adjusted survival (0.031 QALYs). A bootstrap analysis indicated that PPCI has a high probability of being cost-effective when a threshold value of $50,000 is employed. A survival analysis at 5.3 years showed a significant benefit from PPCI in terms of the combination of all-cause death and recurrent infarction (p=0.03) as well as for cardiac mortality alone (p=0.02). Conclusion: Primary PCI is more efficient than thrombolysis in re-establishing antegrade flow in the infarct- related artery and offers a better long term clinical outcome with respect to major cardiac events without an increase in societal costs. Thus, based on the conditions under which this study was performed, primary PCI is a more efficient alternative than thrombolysis for the treatment of ST-elevation myocardial infarction.
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| 7. |
- Aase, Karin
(författare)
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On vascular endothelial growth factor B and platelet-derived growth factor C : two members of the VEGF/PDGF family of growth factors
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Vascular endothelial growth factors (VEGFs), platelet-derived growth factors (PDGFs) and their receptors are important for normal development. They have also been implicated in many pathological conditions. VEGFs have been shown to play an important role in the development of both blood and lymphatic vessels. PDGFs on the other hand, are important regulators of the connective tissue cells of both the vascular network and other organs systems. The focus of the work presented in this thesis has been to elucidate the role of two members of the VEGF/PDGF family of growth factors, namely VEGF-B and PDGF-C. Embryonic analysis at the mRNA and protein level showed that VEGF-B was expressed in several organs, with highest expression in the developing muscles. VEGF-B was not detected in endothelial cells, where its receptor VEGFR-1 is expressed, which suggested that VEGF-B acts in a paracrine way. The expression of the two isoforms, VEGF-B167 and VEGF-B186 were investigated using techniques that can distinguish the two isoforms. The results showed that the VEGF-B167 isoform is predominantly expressed in most tissues. The VEGF-B186 isoform is expressed at lower levels and only in a limited numbers of organs. Moreover, the VEGF-B186 isoform is upregulated in mouse and human tumour cell lines and primary tumours compared with their corresponding normal tissues. These data suggest a fine genetic control of the expression of the two isoforms of VEGF-B, implying tissue- and cell-specific roles for the two VEGF-B isoforms. To elucidate the function in vivo, a VEGF-B knockout mouse strain was generated. The results showed that VEGF-B is not required for normal development of the cardiovascular system or for angiogenesis in adults. However, adult VEGF-B deficient mice have an atrial conduction abnormality characterised by a prolonged PQ interval in the electrocardiogram; thus VEGF-B appears to be required for normal heart function in adult animals. The second growth factor, PDGF-C contains a domain structure not present in other members of the VEGF/PDGF family. Following the signal sequence, PDGF-C contains an N-terminal CUB-domain and, in the C-terminus, the VEGF/PDGF homology domain. PDGF-C is synthesised as an inactive precursor protein that has to be proteolytically processed in the N-terminus before it can bind and activate its receptor, PDGFR-a. Expression analysis during mouse development suggests that PDGF-C acts in both paracrine and autocrine ways.
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| 8. |
- Aasheim, Vigdis
(författare)
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Becoming a mother at an advanced age : pregnancy, outcomes, psychological distress, experience of childbirth and satisfaction with life
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The objectives of this thesis were to investigate adverse pregnancy outcomes, and pregnancy and psychological experiences in women who become mothers in the later phase of the reproductive period. The age of first-time mothers has increased in most high-income countries in recent decades. Research into the postponement of childbirth phenomenon has predominantly focused on pregnancy and infant outcomes, and only to a lesser degree on psychological aspects of postponement. Study I is a population-based register study including 955 804 primiparous women from the Swedish and Norwegian Medical Birth Registers who gave birth between 1990-2010. It investigates the risk for preterm birth, infants small for gestation age, low Apgar score, stillbirth and neonatal death in women aged 30-34 years, 35-39 years and ≥40 years compared with women aged 25-29 years. Study I also compares risks associated with advanced maternal age with those associated with smoking and being overweight or obese. The adjusted Odds Ratios (aOR) of all outcomes increased with maternal age in a similar way in Sweden and Norway and the risk of fetal death already at age 30-35 years (Sweden OR 1.24; 95% CI 1.13-1.37, Norway aOR 1.26; 95% CI 1.12-1.41). The Swedish data showed that a maternal age of ≥30 years was associated with the same number of additional cases of fetal deaths as being overweight/obesity (251) and a larger number than smoking (67) compared with normal weight, nonsmokers aged 25-29 years, and estimated over the entire time period. Studies II-IV are longitudinal prospective population-based cohort studies based on data from the National Norwegian Mother and Child Cohort Study conducted by the Norwegian Institute of Public Health. Study II investigated psychological distress in 19 291nulliparous women from mid pregnancy to 18 months after the birth, comparing women of ≥32 years with those of 25-31 years. It was found that women in the oldest group had a slightly increased risk of psychological distress during pregnancy and the first 18 months of motherhood. Study III investigated 30 065 women’s experience of childbirth at six months postpartum in relation to antenatal expectations, using the same age categories as in Study II. The oldest women had a marginally higher risk of experiencing childbirth as worse than expected. Older women seemed to manage better than younger women when having an operative delivery. Study IV investigated 18 565 women’s satisfaction with life during pregnancy and the first three years of motherhood, comparing women of 32-37 years and ≥38 years respectively with the same reference groups as above. Women in the two oldest age groups reported a slightly lower degree of satisfaction with life, and the age effect was greatest three years after the birth. In conclusion, this thesis shows that the postponement of childbirth in high-income countries may increase the risk of adverse pregnancy outcomes at an earlier age than has previously been reported, and that it may have marginal negative effects on women’s emotional wellbeing and satisfaction with life. These findings should be included when giving reproductive health information to young people.
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| 9. |
- Abate, Getahun
(författare)
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Drug resistance in mycobacterium tuberculosis
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Drug-resistant tuberculosis is a global public health problem. This investigation was performed to find ways of improving regimens that could be used for the treatment of drug- and multidrug-resistant TB and also to find a rapid method of diagnosis of drug resistant TB, particularly MDR-TB. Among 107 isolates of M. tuberculosis from re-treatment cases of pulmonary TB in Ethiopia (study 1), 48% were resistant at least to one of the four first-line drugs tested and 12 % were AMR. In this study, rifampicin resistance was a strong predictor of MDR-TB. The extended susceptibility of 35 polyresistant isolates including NMR isolates on ten other drugs showed that all were susceptible at least to five drugs (i.e., amikacin ciprofloxacin, clofazimine ethambutol, and ethionamide). The WHO re-treatment regimen would be effective in 86 % of cases. Moreover, the extended susceptibility pattern of MDR isolates indicated that it is possible to find a low-cost treatment regimen for patients at risk of harbouring MDR-TB by replacing very expensive drugs like amikacin and ciprofloxacin. The studies on ß-lactams showed that cefepime (study II) and amoxicillin-clavulanate (study 111) are effective on M. tuberculosis isolates including MDR-isolates. Cefepime at a concentration of 32 mg/L was active on 54 % of M. tuberculosis isolates. The minimum inhibitory concentration (MIC) of amoxicillin-clavulanate was 2 or 4 mg/L for 90 %the isolates tested. The MIC was reduced to 5 0.5 mg/L for 97 %of isolates when subinhibitory concentration of ethambutol was added. The results suggested that ß-lactams, particularly in combination with ethambutol, could be important for the treatment of MDR-TB. An assay based on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) was standardised in both microtiter (study and tube formats (study V) for the detection of rifampicin resistance in clinical isolates of M. tuberculosis. MTT is converted to a blue formazan by live cells and the amount of formazan formation was proportional to the number of viable bacilli. In suspensions containing mixed bacterial population, the assay could detect a resistant subpopulation of I%. The evaluation of the assay with the BACTEC method using 92 clinical isolates of M. tuberculosis showed that the result obtained by the MIT assay (both on the third and sixth day) matched with the result obtained by the BACTEC method. Seventy-eight strains were identified as susceptible, 13 strains as resistant and one strain as borderline resistant. In the MIT assay, resistant and susceptible stains were identified based on the relative optical density (RODU) values and changes in OD from the third to the sixth day. AD results were interpretable by the naked eye. NM assay is rapid, reliable, safe and inexpensive assay for the detection of rifampicin resistance. Rifampicin resistance is a strong predictor of MDR-TB and the assay is appropriate for clinical application in low-income countries. Fifty isoniazid-resistant strains of M. tuberculosis (study VI) were characterised based on the catalase activity, MIC of isoniazid, growth pattern in the presence of different concentrations of isomazid, and mutations in katG gene (codons 315 and 463). The MIC of 72 % of the strains was < 4 mg/L. The results also showed that these stains could be classified into three groups based on their growth pattern. A majority (80%) of stains with high MIC (>= 16 mg/L) of isoiazid had no catalase activity. Mutations in codons 315 and 463 of katG gene were detected in 91 % of strains with MIC < 8 mg/L but only in 28 % of strains with higher MlC. This study showed that mutations in codons 315 and 463 of katG gene failed to detect 72 % of clinically most important group with high MlC of isoniazid (>= 16 mg/L). The sensitivity of molecular methods based on mutations in these codons could be increased by combining with the results from the catalase activity. The majority of strains with high MIC had no catalase activity and could be detected by a simple catalase test. The results also indicated that isoniazid-resistant strains of M. tuberculosis could be characterized based on their growth pattern.
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| 10. |
- Abbas Ahmed M Gadeh EL Dum, Nagat
(författare)
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Immunomodulation of cytokine and chemokine production in animal models of neuroinflammatory and neurodegenerative disorders
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Experimental autoimmune neuritis (EAN) is a CD4+ T cell-mediated autoimmune disease of the peripheral nervous system (PNS) that can be actively induced in susceptible animal species and strains by active immunization with heterogeneous peripheral nerve myelin or its component P2 or PO proteins or their peptides emulsified in Freund's complete adjuvant. EAN represents an animal model for studying the immunopathogenesis and therapy of Guillain-Barré syndrome (GBS ) which is a major inflammatory demyelinating disease of the PNS in humans. The close clinical, histopathological, and electrophysiological similarities between EAN and GBS make EAN an especially suitable model, capable of offering insights into the pathophysiology of GBS. EAN is also considered to represent a general model for studying CD4+-mediated autoimmune diseases. Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia in the Western world. It is characterised neuropathologically by the deposition of extracellular amyeloid plaques containing aggregates of the amyloid protein beta (A-beta) peptide, as well as by intracellular aggregation of neurofibrillary tangles and selective neuronal loss accompanied by cerebrovascular amyloidosis. The mechanism of AD has not been completely defined. The inflammatory cytokines have been implicated as mediators in response to brain injury in AD. A-beta precursor protein APP transgenic mice (Tg2576) are one of the most widely used animal model for A-beta plaques in cortical regions of the brain, which over-expresses human APP with the Swedish double mutation. Peak numbers of macrophage inflammatory protein (MIP)- 1 alpha-positive cells in the sciatic nerve were seen on day 14 post-immunization (p.i.), which coincided with the development of severe clinical signs. Administration of an anti-MIP-1 alpha antibody suppressed clinical signs of EAN and inhibited inflammation and demyelination in the sciatic nerve. Peak numbers of monocyte chemotactic protein (MCP)-1-positive cells in the sciatic nerve were detected on day 7 p.i. (i.e., tile onset of clinical EAN). Administration of an anti-MCP-1 antibody caused a delay of onset of EAR The numbers of MIP-2-positive cells reached a maximum on day 21 p.i. Anti-MIP-2 antibody failed to suppress clinical signs of EAN and inflammation and demyelination in the sciatic nerve. EAN was strongly suppressed by Rolipram administered twice daily intraperitoneally from day 9 p.i., after onset of clinical EAN, to day 18 p.i., over 10 days. This clinical effect was associated with dose-dependent downregulation of interferon (IFN)-gamma and the chemokines MIP-1alpha, MIP-2 and MCP-1 as well as up-regulated interleukin (IL)-4 production in sciatic nerve sections from Rolipram-treated EAN rats at the maximum of clinical EAN, i.e., on day 14 p.i. These findings suggest that Rolipram could be useful in certain T cell-dependent autoimmune diseases and inflammatory neuropathies. ABR-215062, which is a new synthetic immunomodulatory compound derived from Linomide, administered daily subcutaneously from the day of inoculation strongly suppressed EAN in a dose-dependent manner. ABR215062 reduced the incidence of EAN, ameliorated clinical signs, and inhibited PO peptide 180-199-specific T and B cell responses and also decreased inflammation and demyelination in the peripheral nerves. The suppression of clinical EAN is associated with inhibition of the inflammatory cytokines IFN-gamma and tumor necrosis factor-alpha as well as the enhancement of the anti-inflammatory cytokine IL-4 in peripheral nerve tissues. The suppressive effects of ABR-215062 on EAN are quite similar to those of Linomide on EAN. These findings suggest that ABR-215062 could be useful in certain T cell-mediated autoimmune diseases. To elucidate the mechanisms involved in A-beta-mediated inflammation, we used immunocytochemistry and in situ hybridization to study the potential role of the cytokines interferon-gamma (IFN-gamma), interleukin (IL)-12 and IL-4 in transgenic mice Tg2576. Cytokine and cytokine mRNA expression was detected in brain sections from cortical regions at various postnatal ages ranging from 3 to 19 months. High levels of IFN-gamma and IL-12 mRNA expression, as well as their protein production appeared early at 9 months and peaked at 17-19 months in Tg2576 mice. Significantly increased transcripts of IFN-gamma and IL-12 genes were found in the reactive microglia. and astrocytes surrounding AP deposits. Both findings indicate a role for the pro-inflammatory cytokines IFN-gamma and IL-12 in early disease development and are consistent with microglial activation related to AP formation. In contrast, transcription and production of IL-4 in brain sections was almost undetectable in transgenic mice up to post-natal ages of 17-19 months. These results suggest a major pro-inflammatory role for IL-12 and IFN- gamma in Tg2576 transgenic mice that may provide the association between AP plaque formation, microglial and astrocyte activation in these animals. These observations call for further studies on the potential role of anti-inflammatory therapeutic strategies for AD.
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