| 1. |
- Dock, Hua, et al.
(author)
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DNA Methylation Inhibitor Zebularine Confers Stroke Protection in Ischemic Rats
- 2015
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In: TRANSLATIONAL STROKE RESEARCH. - : Springer Verlag (Germany). - 1868-4483 .- 1868-601X. ; 6:4, s. 296-300
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Journal article (peer-reviewed)abstract
- 5-Aza-deoxycytidine (5-aza-dC) confers neuroprotection in ischemic mice by inhibiting DNA methylation. Zebularine is another DNA methylation inhibitor, less toxic and more stable in aqueous solutions and, therefore more biologically suitable. We investigated Zebularines effects on brain ischemia in a rat middle cerebral artery occlusion (MCAo) model in order to elucidate its therapeutic potential. Male Wistar wild-type (WT) rats were randomly allocated to three treatment groups, vehicle, Zebularine 100 mu g, and Zebularine 500 mu g. Saline (10 mu L) or Zebularine (10 mu L) was administered intracerebroventricularly 20 min before 45-min occlusion of the middle cerebral artery. Reperfusion was allowed after 45-min occlusion, and the rats were sacrificed at 24-h reperfusion. The brains were removed, sliced, and stained with 2 % 2,3,5-triphenyltetrazolium chloride (TTC) before measuring infarct size. Zebularine (500 mu g) reduced infarct volumes significantly (p less than 0.05) by 61 % from 20.7 +/- 4.2 % in the vehicle treated to 8.1 +/- 1.6 % in the Zebularine treated. Zebularine (100 mu g) also reduced infarct volumes dramatically by 55 to 9.4 +/- 1.2 %. The mechanisms behind this neuroprotection is not yet known, but the results agree with previous studies and support the notion that Zebularine-induced inhibition of DNA methyltransferase ameliorates ischemic brain injury in rats.
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| 2. |
- Ingberg, Edvin, 1988-
(author)
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Challenges in experimental stroke research : The 17β-estradiol example
- 2016
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Doctoral thesis (other academic/artistic)abstract
- Ischemic stroke causes millions of deaths around the world each year, and surviving patients often suffer from long-term disability. Hundreds of promising drug candidates have been identified in animal models, but the clinical trials have repeatedly failed. Lack of methodological quality in the animal studies, e.g. low statistical power as a result of small group sizes in combination with high outcome variability and high mortality, has been suggested to in part explain the lack of translational success. In the meta-analytical Papers II and Paper V, we therefore investigated how method parameters impact infarct size variation and mortality in rodent stroke studies. These findings can help researchers to optimize their animal models or to more exactly predict variability and mortality given a certain experimental setup.The relation between ischemic stroke and estrogens is complex. Premenopausal women have a lower risk of stroke than men of the same age, suggesting that female sex hormones provide protection against cerebrovascular events. The idea of a beneficial effect on the brain of estrogens was also supported by epidemiological studies showing that estrogens given as postmenopausal hormone replacement therapy decreased the risk of stroke. However, subsequent clinical trials reported the opposite, an increased risk. Interestingly, discrepancies exist also in the animal stroke literature. The majority of the rodent studies on the effects of estrogens have shown protection, but there are also several examples of increased damage. Based on experimental results and a meta-analysis, it was hypothesized that differences in hormone administration methods and their resulting plasma concentrations of estrogens might explain the previous discordant animal findings. Paper I investigated the commonly used methods for 17β-estradiol administration and found that the popular slow-release pellets produced high and unpredictable serum concentrations. A novel method with 17β-estradiol administered orally in Nutella® was also evaluated with promising results. Paper III extracted data regarding methodological choices from all previously published estrogen-stroke studies, and showed through metaanalysis that slow-release pellets are more prone to render estrogens damaging. Finally, Paper IV tested whether estrogens could both exert neuroprotection and promote detrimental effects merely depending on dose and irrespective of the administration route. Surprisingly, and in contrast to the hypothesis, a significant negative correlation was found between 17β-estradiol dose group and infarct size meaning that the higher the dose, the smaller the infarcts.In summary, this thesis does not confirm the hypothesis of dose-related neuroprotective vs neurodamaging effects of estrogens on ischemic stroke. If high estrogen doses/plasma concentrations per se can cause increased stroke damage, such a phenomenon is not very robust, and seems to depend on tight dose ranges and/or other experimental circumstances. Although not directly applicable to the clinical situation, hopefully in a long-term perspective these findings may contribute in elucidating when estrogens are beneficial and when they are harmful. Further, it adds to the growing literature on how the quality of experimental stroke research can be increased to try to overcome translational difficulties.
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| 3. |
- Ingberg, Edvin, 1988-, et al.
(author)
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Effect of laser Doppler flowmetry and occlusion time on outcome variability and mortality in rat middle cerebral artery occlusion : inconclusive results
- 2018
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In: BMC Neuroscience. - London : BioMed Central. - 1471-2202. ; 19:1
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Journal article (peer-reviewed)abstract
- BACKGROUND: Stroke is among the leading causes of death and disability. Although intense research efforts have provided promising treatment options in animals, most clinical trials in humans have failed and the therapeutic options are few. Several factors have been suggested to explain this translational difficulty, particularly concerning methodology and study design. Consistent infarcts and low mortality might be desirable in some, but not all, studies. Here, we aimed to investigate whether the use of laser Doppler flowmetry (LDF) and the occlusion time (60 vs. 45 min) affected outcome variability and mortality in a rat stroke model. Eighty ovariectomized female Wistar rats were subjected to ischemic stroke using intraluminal filament middle cerebral artery occlusion with or without LDF and with occlusion times of 45 or 60 min. Outcome was evaluated by triphenyl tetrazolium chloride staining of brain slices to measure infarct size and a modified sticky tape test.RESULTS: Neither LDF nor occlusion times of 45 versus 60 min significantly affected mortality, outcome variability or outcome severity.CONCLUSIONS: Due to the unexpectedly high mortality and variability the statistical power was very low and thus the results were inconclusive.
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| 4. |
- Ingberg, Edvin, et al.
(author)
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Effects of high and low 17 beta-estradiol doses on focal cerebral ischemia in rats
- 2016
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In: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 6:20228
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Journal article (peer-reviewed)abstract
- The majority of the numerous animal studies of the effects of estrogens on cerebral ischemia have reported neuroprotective results, but a few have shown increased damage. Differences in hormone administration methods, resulting in highly different 17 beta-estradiol levels, may explain the discrepancies in previously reported effects. The objective of the present study was to test the hypothesis that it is the delivered dose per se, and not the route and method of administration, that determines the effect, and that high doses are damaging while lower doses are protective. One hundred and twenty ovariectomized female Wistar rats (n = 40 per group) were randomized into three groups, subcutaneously administered different doses of 17 beta-estradiol and subjected to transient middle cerebral artery occlusion. The modified sticky tape test was performed after 24 h and the rats were subsequently sacrificed for infarct size measurements. In contrast to our hypothesis, a significant negative correlation between 17 beta-estradiol dose and infarct size was found (p = 0.018). Thus, no support was found for the hypothesis that 17 beta-estradiol can be both neuroprotective and neurotoxic merely depending on dose. In fact, on the contrary, the findings indicate that the higher the dose of 17 beta-estradiol, the smaller the infarct.
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| 5. |
- Ingberg, Edvin, 1988-, et al.
(author)
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Effects of high and low 17β-estradiol doses on focal cerebral ischemia in rats
- 2016
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In: Scientific Reports. - London, United Kingdom : Nature Publishing Group. - 2045-2322. ; 6
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Journal article (peer-reviewed)abstract
- The majority of the numerous animal studies of the effects of estrogens on cerebral ischemia have reported neuroprotective results, but a few have shown increased damage. Differences in hormone administration methods, resulting in highly different 17β-estradiol levels, may explain the discrepancies in previously reported effects. The objective of the present study was to test the hypothesis that it is the delivered dose per se, and not the route and method of administration, that determines the effect, and that high doses are damaging while lower doses are protective. One hundred and twenty ovariectomized female Wistar rats (n = 40 per group) were randomized into three groups, subcutaneously administered different doses of 17β-estradiol and subjected to transient middle cerebral artery occlusion. The modified sticky tape test was performed after 24 h and the rats were subsequently sacrificed for infarct size measurements. In contrast to our hypothesis, a significant negative correlation between 17β-estradiol dose and infarct size was found (p = 0.018). Thus, no support was found for the hypothesis that 17β-estradiol can be both neuroprotective and neurotoxic merely depending on dose. In fact, on the contrary, the findings indicate that the higher the dose of 17β-estradiol, the smaller the infarct.
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| 6. |
- Ingberg, Edvin, 1988-, et al.
(author)
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Elevated body swing test after focal cerebral ischemia in rodents : methodological considerations
- 2015
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In: BMC Neuroscience. - : Springer Science and Business Media LLC. - 1471-2202. ; 16
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Journal article (peer-reviewed)abstract
- Background: The elevated body swing test (EBST) is a behavioral test used to evaluate experimental stroke in rodents. The basic idea is that when the animal is suspended vertically by the tail, it will swing its head laterally to the left or right depending on lesion side. In a previous study from our lab using the EBST after middle cerebral artery occlusion (MCAo), rats swung contralateral to the infarct day 1 post-MCAo, but ipsilateral day 3 post-MCAo. This shift was unexpected and prompted us to perform the present study. First, the literature was systematically reviewed to elucidate whether a similar shift had been noticed before, and if consensus existed regarding swing direction. Secondly, an experiment was conducted to systematically investigate the suggested behavior. Eighty-three adult male and female Sprague-Dawley rats were subjected to MCAo or sham surgery and the EBST was performed up to 7 days after the lesion.Results: Both experimentally and through systematic literature review, the present study shows that the direction of biased swing activity in the EBST for rodents after cerebral ischemia can differ and even shift over time in some situations. The EBST curve for females was significantly different from that of males after the same occlusion time (p = 0.023).Conclusions: This study highlights the importance of adequate reporting of behavioral tests for lateralization and it is concluded that the EBST cannot be recommended as a test for motor asymmetry after MCAo in rats.
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| 7. |
- Ingberg, Edvin, 1988-, et al.
(author)
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Method parameters' impact on mortality and variability in mouse stroke experiments : a meta-analysis
- 2016
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In: Scientific Reports. - London, England : Nature Publishing Group. - 2045-2322. ; 11:SUPP 3, s. 108-108
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Journal article (peer-reviewed)abstract
- Although hundreds of promising substances have been tested in clinical trials, thrombolysis currently remains the only specific pharmacological treatment for ischemic stroke. Poor quality, e.g. low statistical power, in the preclinical studies has been suggested to play an important role in these failures. Therefore, it would be attractive to use animal models optimized to minimize unnecessary mortality and outcome variability, or at least to be able to power studies more exactly by predicting variability and mortality given a certain experimental setup. The possible combinations of methodological parameters are innumerous, and an experimental comparison of them all is therefore not feasible. As an alternative approach, we extracted data from 334 experimental mouse stroke articles and, using a hypothesis-driven meta-analysis, investigated the method parameters' impact on infarct size variability and mortality. The use of Swiss and C57BL6 mice as well as permanent occlusion of the middle cerebral artery rendered the lowest variability of the infarct size while the emboli methods increased variability. The use of Swiss mice increased mortality. Our study offers guidance for researchers striving to optimize mouse stroke models.
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| 8. |
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| 9. |
- Ivars, Katrin, et al.
(author)
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Development of Salivary Cortisol Circadian Rhythm and Reference Intervals in Full-Term Infants
- 2015
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In: Plos One. - San Francisco, USA : Public Library of Science (PLoS). - 1932-6203. ; 10:6
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Journal article (peer-reviewed)abstract
- Background Cortisol concentrations in plasma display a circadian rhythm in adults and children older than one year. Earlier studies report divergent results regarding when cortisol circadian rhythm is established. The present study aims to investigate at what age infants develop a circadian rhythm, as well as the possible influences of behavioral regularity and daily life trauma on when the rhythm is established. Furthermore, we determine age-related reference intervals for cortisol concentrations in saliva during the first year of life. 130 healthy full-term infants were included in a prospective, longitudinal study with saliva sampling on two consecutive days, in the morning (07:30-09:30), noon (10:00-12:00) and evening (19:30-21:30), each month from birth until the infant was twelve months old. Information about development of behavioral regularity and potential exposure to trauma was obtained from the parents through the Baby Behavior Questionnaire and the Life Incidence of Traumatic Events checklist. A significant group-level circadian rhythm of salivary cortisol secretion was established at one month, and remained throughout the first year of life, although there was considerable individual variability. No correlation was found between development of cortisol circadian rhythm and the results from either the Baby Behavior Questionnaire or the Life Incidence of Traumatic Events checklist. The study presents salivary cortisol reference intervals for infants during the first twelve months of life. Cortisol circadian rhythm in infants is already established by one month of age, earlier than previous studies have shown. The current study also provides first year age-related reference intervals for salivary cortisol levels in healthy, full-term infants.
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| 10. |
- Ivars, Katrin, 1978-, et al.
(author)
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Development of salivary cortisol circadian rhythm in preterm infants
- 2017
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In: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 12:8
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Journal article (peer-reviewed)abstract
- Objectives: To investigate at what age preterm infants develop a salivary cortisol circadian rhythm and identify whether it is dependent on gestational age and/or postnatal age. To evaluate whether salivary cortisol circadian rhythm development is related to behavioral regularity. To elucidate salivary cortisol levels in preterm infants during the first year of life.Methods: This prospective, longitudinal study included 51 preterm infants. 130 healthy full-term infants served as controls. Monthly salivary cortisol levels were obtained in the morning (07:30-09:30), at noon (10:00-12:00), and in the evening (19:30-21:30), beginning at gestational age week 28-32 and continuing until twelve months corrected age. Behavioral regularity was studied using the Baby Behavior Questionnaire.Results: A salivary cortisol circadian rhythm was established by one month corrected age and persisted throughout the first year. The preterm infants showed a cortisol pattern increasingly more alike the full-term infants as the first year progressed. The preterm infants increase in behavioral regularity with age but no correlation was found between the development of salivary cortisol circadian rhythm and the development of behavior regularity. The time to establish salivary cortisol circadian rhythm differed between preterm and full-term infants according to postnatal age (p = 0.001) and was dependent on gestational age. Monthly salivary cortisol levels for preterm infants from birth until twelve months are presented. Additional findings were that topical corticosteroid medication was associated with higher concentrations of salivary cortisol (p = 0.02) and establishment of salivary cortisol circadian rhythm occurred later in infants treated with topical corticosteroid medication (p = 0.02).Conclusions: Salivary cortisol circadian rhythm is established by one month corrected age in preterm infants. Establishment of salivary cortisol circadian rhythm is related to gestational age rather than to postnatal age. Salivary cortisol circadian rhythm development is not related to behavioral regularity.
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