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Search Results: 1 - 10 of 5072 matches for " Erik Olsson "
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Introduction
Erik Olsson, Fataneh Farahani
Nordic Journal of Migration Research , 2012, DOI: 10.2478/v10202-011-0031-z
Abstract:
UV-Deprived Coloration Reduces Success in Mate Acquisition in Male Sand Lizards (Lacerta agilis)
Mats Olsson,Staffan Andersson,Erik Wapstra
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0019360
Abstract: Recent work on animal signals has revealed a wide occurrence of UV signals in tetrapods, in particular birds, but also in lizards (and perhaps other Squamate reptiles). Our previous work on the Swedish sand lizard (Lacerta agilis) has verified, both in correlative selection analyses in the wild and with laboratory and field experiments, the importance of the green ‘badge’ on the body sides of adult males for securing mating opportunities, probably mostly through deterring rival males rather than attracting females. The role of UV in communication has, however, never been examined.
Zebrafish sex determination and differentiation: Involvement of FTZ-F1 genes
Jonas von Hofsten, Per-Erik Olsson
Reproductive Biology and Endocrinology , 2005, DOI: 10.1186/1477-7827-3-63
Abstract: Among mammals sex is usually defined by the presence or absence of the sex specific chromosome Y. In many, but not all, fish species there is also a chromosomal background to sex determination. Several fishes, including most salmonids, have heterogametic males and homogametic females, similar to the mammalian XY/XX-system [1-3]. Other species, such as Poecilia, have homogametic males and heterogametic females (ZZ/ZW), which also is the case for birds [4]. Some species of the Poecilid platyfish Xiphophorus, utilize a system with three sex chromosomes [5]. In yet other species sex determination is influenced by environmental factors such as the temperature surrounding the developing embryo [6-8]. Hermaphroditism is also a common feature of several fish species. Several studies have shown that species with genetic sex determination can be directed to produce genetically sex-reversed offspring. This is accomplished either by treating the fish with hormones, which can induce sex reversal in synchronous hermaphroditic fish [9,10] and masculinization/feminization in gonochoristic species, or by incubating embryos in certain temperatures or pH [11]. The proportion of males usually increases with temperature whereas lower temperatures favour females. In the case of pH, species differences have been observed.There are few studies of sex determination in fish and the genetic mechanisms behind sex determination in fish remain largely unknown. Environmental factors, including endocrine disrupters such as diethylstilbestrol, PCBs or dioxins, can affect both teleost and mammalian reproductive systems, but do not seem to alter sex ratios or cause sex reversals in mammals. This indicates that mammalian sex determination is more strictly genetic, and shows less gonad plasticity than teleosts. However, it has been observed that a number of genes, both sex-linked and autosomal, display dosage effects in mammals (Table 1), suggesting that allelic variants could account for differences i
Consistent Paternity Skew through Ontogeny in Peron's Tree Frog (Litoria peronii)
Craig D. H. Sherman,Erik Wapstra,Mats Olsson
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0008252
Abstract: A large number of studies in postcopulatory sexual selection use paternity success as a proxy for fertilization success. However, selective mortality during embryonic development can lead to skews in paternity in situations of polyandry and sperm competition. Thus, when assessment of paternity fails to incorporate mortality skews during early ontogeny, this may interfere with correct interpretation of results and subsequent evolutionary inference. In a previous series of in vitro sperm competition experiments with amphibians (Litoria peronii), we showed skewed paternity patterns towards males more genetically similar to the female.
Differential cytokine regulation by NF-κB and AP-1 in Jurkat T-cells
Hazem Khalaf, Jana Jass, Per-Erik Olsson
BMC Immunology , 2010, DOI: 10.1186/1471-2172-11-26
Abstract: Phorbol myristate acetate (PMA) exposure resulted in an up-regulation of AP-1 and down-regulation of NF-κB activity, however, exposure to heat killed (HK) Escherichia. coli MG1655 resulted in a dose-dependent increase in NF-κB activity without affecting AP-1. The cytokine profile revealed an up-regulation of the chemokine CXCL8 and the pro-inflammatory cytokines TNF, IL-2 and IL-6 following treatment with both PMA and HK E. coli, while the levels of the anti-inflammatory cytokine IL-10 were not affected by PMA but were significantly down-regulated by HK E. coli. AP-1 activation was significantly increased 2 h after PMA exposure and continued to increase thereafter. In contrast, NF-κB responded to PMA exposure by a rapid up-regulation followed by a subsequent down-regulation. Increased intracellular Ca2+ concentrations countered the down-regulation of NF-κB by PMA, while similar treatment with calcium ionophore resulted in a reduced NF-κB activity following induction with HK E. coli. In order to further study NF-κB activation, we considered two up-stream signalling proteins, PKC and Bcl10. Phosphorylated-PKC levels increased in response to PMA and HK E. coli, while Bcl10 levels significantly decreased following PMA treatment. Using an NF-κB activation inhibitor, we observed complete inhibition of IL-6 expression while CXCL8 levels only decreased by 40% at the highest concentration. Treatment of Jurkat T-cells with PMA in the presence of JNK-inhibitor suppressed both CXCL8 and IL-6 while PKC-inhibitor primarily decreased CXCL8 expression.The present study shows that NF-κB regulated IL-6 but not CXCL8. This complex regulation of CXCL8 suggests that there is a need to further evaluate the signalling pathways in order to develop new treatment for diseases with elevated CXCL8 levels, such as AIDS and autoimmune diseases.Cytokines and chemokines are important in immune cell recruitment and in regulation of inflammatory responses [1]. T-cells produce a broad range of inflam
17beta-estradiol induced vitellogenesis is inhibited by cortisol at the post-transcriptional level in Arctic char (Salvelinus alpinus)
Hakan Berg, Carina Modig, Per-Erik Olsson
Reproductive Biology and Endocrinology , 2004, DOI: 10.1186/1477-7827-2-62
Abstract: The major proteinaceous egg yolk precursor vitellogenin (Vtg) is a large complex lipoglycophosphoprotein produced under estrogenic control in the liver of sexually maturing female oviparous animals. The estrogenic control of Vtg is mediated by binding of the most potent estrogen, 17-β-estradiol (E2), to the hepatic estrogen receptor (ER) [1]. The ER-E2 complex activates the transcription of the Vtg-genes by binding to estrogen responsive elements [1]. Vtg is transported from the liver as a dimer via the circulation to the oocytes, where it is taken up by receptor mediated endocytosis [2,3] and proteolytically cleaved into the smaller yolk units lipovitelin, phosvitin [4,5] and phosvettes [6], which serve as a nutritional source for the growing embryos [7]. Studies have shown that Vtg bind metal-ions such as zinc, calcium [8,9] and magnesium [10]. It has been suggested that Vtg is involved in the transport of metal-ions, crucial for embryonic development, into the growing oocyte [11].A number of Vtg genes have been characterized in a wide variety of oviparous species and it has been shown that the Vtg genes are highly conserved [12,13]. The Vtg-genes belong to a small gene family where the number of genes varies depending on species [7,14,15]. The different genes give rise to multiple forms of the protein, which are expressed at different times during oogenesis. This indicates that Vtg isoforms may have different roles during oocyte maturation and embryonic development [5]. Vitellogenin genes are present in both females and males but the lack of estrogens in the males prevents the expression of the protein under normal conditions [16].In teleosts, cortisol (F) is released from interrenal cells in response to stress. It has been shown that F affects reproduction by decreasing the amount of gonadotropins produced by the pituitary, the amount steroids present in the plasma and by reducing gamete quality [17]. Earlier studies on stress responses on teleost reproduction a
Biochemical characterization of the Arctic char (Salvelinus alpinus) ovarian progestin membrane receptor
A H?kan Berg, Peter Thomas, Per-Erik Olsson
Reproductive Biology and Endocrinology , 2005, DOI: 10.1186/1477-7827-3-64
Abstract: Meiosis is arrested at prophase 1 in vertebrate oocytes during their growth phase and a surge in gonadotropin secretion is required to induce the resumption of meiosis and oocyte maturation (OM). It has been demonstrated that gonadotropin (luteinizing hormone, LH) initiates oocyte maturation and ovulation in teleost fish and amphibians by stimulating the production of a maturation inducing substance (MIS) by the ovarian follicles [1]. The MISs have been identified as progesterone in a variety of amphibians and as hydroxylated progestins in teleost fishes [2,3]. Two C21 steroids, 17, 20β-dihydroxy-4-pregnen-3-one (17,20β-P) [4] and 17, 20β, 21-trihydroxy-4-pregnen-3-one (20β-S) [5,6], have been positively identified as the MISs in amago salmon and Atlantic croaker, respectively. While 17,20β-P is the major MIS for salmonids and cyprinids [2], 20β-S has been shown to be the predominant MIS in sciaenids and some other perciform fishes [3].MIS does not induce OM in amphibians and teleosts by the classical mechanism of steroid action, instead it acts at the cell surface by binding to receptors located on the oocyte plasma membrane [3,7]. Activation of the MIS receptor results in induction of OM via a non-genomic mechanism [8] mediated by G-proteins and second messengers such as cAMP [9,10]. Progestin membrane receptors (mPRs) have been identified and characterized in several amphibian and teleost species [11-15]. Moreover, membrane progestin receptor (mPR) upregulation by gonadotropins during OM has been demonstrated in several teleost species [14,16] and has been associated with development of the ability of oocytes to become responsive to the MIS (oocyte maturational competence, OMC) and complete OM [17]. A two-stage model of the gonadotropic control of OM in teleosts has been proposed based on the results with several teleost species showing that priming of fully grown follicle-enclosed oocytes by gonadotropin is required to induce OMC [18]. Early studies in rainbow t
Hippocampal volumes in patients exposed to low-dose radiation to the basal brain. A case–control study in long-term survivors from cancer in the head and neck region
Olsson Erik,Eckerstr?m Carl,Berg Gertrud,Borga Magnus
Radiation Oncology , 2012, DOI: 10.1186/1748-717x-7-202
Abstract: Background An earlier study from our group of long time survivors of head and neck cancer who had received a low radiation dose to the hypothalamic-pituitary region, with no signs of recurrence or pituitary dysfunction, had their quality of life (QoL) compromised as compared with matched healthy controls. Hippocampal changes have been shown to accompany several psychiatric conditions and the aim of the present study was to test whether the patients’ lowered QoL was coupled to a reduction in hippocampal volume. Methods Patients (11 men and 4 women, age 31–65) treated for head and neck cancer 4–10 years earlier and with no sign of recurrence or pituitary dysfunction, and 15 matched controls were included. The estimated radiation doses to the basal brain including the hippocampus (1.5 – 9.3 Gy) had been calculated in the earlier study. The hippocampal volumetry was done on coronal sections from a 1.5 T MRI scanner. Measurements were done by two independent raters, blinded to patients and controls, using a custom method for computer assisted manual segmentation. The volumes were normalized for intracranial volume which was also measured manually. The paired t test and Wilcoxon’s signed rank test were used for the main statistical analysis. Results There was no significant difference with respect to left, right or total hippocampal volume between patients and controls. All mean differences were close to zero, and the two-tailed 95% confidence interval for the difference in total, normalized volume does not include a larger than 8% deficit in the patients. Conclusion The study gives solid evidence against the hypothesis that the patients’ lowered quality of life was due to a major reduction of hippocampal volume.
Differences in the Defense Mechanism Technique modified (DMTm) between Depressive and Somatoform Disorder Patients  [PDF]
Lars Olsson
Open Journal of Depression (OJD) , 2015, DOI: 10.4236/ojd.2015.41001
Abstract: Differences in the Defense Mechanism Technique modified (DMTm), a percept-genetic tachistoscopic technique, between 56 patients with a main diagnosis of mild, moderate or severe unipolar depression and 42 with a main diagnosis of somatoform disorder were studied. As expected, the affect defenses of inhibition, introaggression and barrier isolation—all through their specified motive related to the depressive position of the affect positions model of the Andersson developmental and psychodynamic model of the mind—appeared more often with the depressive than the somatoform patients. Repression scored at the place of the threatening person in the DMTm pictures (Pp-repression) was more often found with the depressive patients, projected introaggression and no Pp-repression but repression scored at the place of the non-threatening person (H-repression) with the somatoform. In total less than four scorings of affect anxiety and affect defense, seen to indicate alexithymia, characterized the somatoform patients and those with mild depression. Denial through reversal II 3 and denial through reversal IV were common with the somatoform patients and those with severe depression. Denial was uncommon with mild depression. Denial, denial through reversal II 3 and denial through reversal IV increased the more severe the depression. The findings were interpreted according to the Andersson model.
Androgen receptor-beta mRNA levels in different tissues in breeding and post-breeding male and female sticklebacks, Gasterosteus aculeatus
Erik Hoffmann, Anders Walstad, Johnny Karlsson, Per-Erik Olsson, Bertil Borg
Reproductive Biology and Endocrinology , 2012, DOI: 10.1186/1477-7827-10-23
Abstract: AR-beta mRNA levels were quantified in ten tissues; eye, liver, axial muscle, heart, brain, intestine, ovary, testis, kidney and pectoral muscle in six breeding and post-breeding males and females using reverse transcription quantitative PCR.Breeding in contrast to post-breeding males built nests and showed secondary sexual characters (e.g. kidney hypertrophy) and elevated androgen levels. Post-breeding females had lower ovarian weights and testosterone levels than breeding females. AR-beta was expressed in all studied tissues in both sexes and reproductive states with the highest expression in the gonads and in the kidneys. The kidney is an androgen target organ in sticklebacks, from which breeding males produce the protein spiggin, which is used in nest-building. There was also high AR-beta expression in the intestine, an organ that appears to take over hyperosmo-regulation in fresh water when the kidney hypertrophies in mature males and largely loses this function. The only tissue that showed effects of sex or reproductive state on AR-beta mRNA levels was the kidneys, where post-breeding males displayed higher AR-beta mRNA levels than breeding males.The results indicate that changes in AR-beta mRNA levels play no or little role in changes in androgen dependent traits in the male stickleback.Androgens stimulate masculine traits such as development of male secondary sexual characters, male reproductive behaviour and spermatogenesis via interactions with nuclear androgen receptors (AR). Among teleost fishes, complete AR cDNAs have been cloned in e.g. Japanese eel, Anguilla japonica [1], rainbow trout, Oncorhynchus mykiss [2] and red seabream, Pagrus major [3].In some teleost fishes, two different AR genes have been cloned e.g. Japanese eel [1], Burton's mouthbrooder, Astatotilapia burtoni [4] and Western mosquitofish, Gambusia affinis [5]. The nomenclatur used for AR subdivision into alpha and beta is based on the first report of two forms present in Japanese eel [6
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