| 1. |
- Gunnarsson, David, et al.
(författare)
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Cadmium-induced decrement of the LH receptor expression and cAMP levels in the testis of rats
- 2003
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Ingår i: Toxicology. - 0300-483X .- 1879-3185. ; 183:(1-3), s. 57-63
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Tidskriftsartikel (refereegranskat)abstract
- Cadmium (Cd) is a widespread environmental pollutant, characterized by its ability to affect various organs. Adverse effect of Cd on the testis including decreased testosterone production are well-known phenomena, but the cellular events explaining these effects have not yet been established. In the present study the initial steps of gonadotropin mediated testosterone biosynthesis were examined in vivo in rats, in relation to Cd dose and time after injection. In the dose–response experiment Male Sprague–Dawley rats received a single subcutaneous (sc) injection of CdCl2 (1, 5 or 10 μmol/kg body weight) and were sacrificed 48 h after injection. A statistically significant decrease in luteinizing hormone (LH) receptor mRNA level in the testicular tissue was demonstrated at the highest dose (10 μmol/kg). In the temporal–response experiment rats were given 10 μmol/kg of CdCl2 sc and sacrificed 0.48, 4.8, 48 or 144 h after injection. LH receptor mRNA levels as well as cyclic adenosine monophosphate (cAMP) levels were found to be significantly lowered at 48 and 144 h. These observations of the mechanisms whereby Cd exerts its effect on the initial steps of testosterone biosynthesis are the first from in vivo experiments.
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| 2. |
- Gunnarsson, David, et al.
(författare)
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Differential effects of cadmium on the gene expression of seven-transmembrane-spanning receptors and GAPDH in the rat testis.
- 2007
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Ingår i: Toxicology letters. - : Elsevier BV. - 0378-4274 .- 1879-3169. ; 168:1, s. 51-7
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Tidskriftsartikel (refereegranskat)abstract
- Cadmium (Cd) is a widely spread toxicant with endocrine disrupting properties. Under experimental conditions it suppresses sex steroid synthesis in the male as well as the female. Testicular steroidogenesis is primarily regulated by gonadotropins, but is also influenced by catecholamines. We have previously shown that Cd exposure affects rat testosterone synthesis by down-regulating luteinizing hormone (LH) receptor mRNA expression. In this study, rats were given 10 micromol/kg Cd subcutaneously and sacrificed 0.48-144 h later. We investigated the effects of Cd on testicular gene expression of two adrenergic receptors. In addition, mRNA levels of the androgen-regulated house keeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were measured. In contrast to the suppressive influence on LH receptor expression Cd lacked effect on the expression of alpha(1A)- and beta(2)-adrenergic receptors. GAPDH gene expression, on the other hand, was up-regulated 1.6-fold after exposure to 10 micromol/kg Cd. These data suggest that the influence of Cd on testicular gene expression involves a specific effect on the LH receptor and not a general effect on seven-transmembrane-spanning receptors. Also, data indicate that the increased expression of GAPDH may be secondary to Cd-induced testosterone deprivation, suggesting future studies of androgen-regulated genes in the toxicity of Cd.
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| 3. |
- Gunnarsson, David, et al.
(författare)
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Pronounced induction of testicular PGF(2 alpha) and suppression of testosterone by cadmium-prevention by zinc.
- 2004
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Ingår i: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 200:1, s. 49-58
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Tidskriftsartikel (refereegranskat)abstract
- In order to investigate the effects of cadmium (Cd) on testicular prostaglandin F(2 alpha) (PGF(2 alpha)) production, adult male Sprague-Dawley rats were exposed to CdCl(2) by subcutaneous injections. Dose-response as well as temporal-response experiments were performed, and PGF(2 alpha) levels were determined by radioimmunoassay (RIA). The highest cadmium dose (10 micromol/kg) caused a dramatic elevation of testicular PGF(2 alpha), which was established to occur 48 h after exposure. At this point of time, cadmium-treated animals displayed PGF(2 alpha) levels 16.7 times higher than saline-injected controls. No significant differences were found with the lower doses used (1 and 5 micromol/kg). In addition, the influence of pre-treatment with zinc (Zn) was assessed. The very strong stimulatory effect on PGF(2 alpha) synthesis (22.3-fold) detected after exposure to 20 micromol/kg cadmium, was completely absent in the group given zinc (1 mmol/kg) prior to cadmium exposure. Plasma testosterone concentrations were determined in the three experiments, and all groups with strongly elevated PGF(2 alpha) levels showed drastically lowered concentrations of testosterone. Zinc pre-treatment abolished not only the cadmium-induced rise in PGF(2 alpha) but also the testosterone reduction. Additionally, cadmium was found to inhibit the expression of steroidogenic acute regulatory protein (StAR), which is responsible for the rate-limiting step in steroidogenesis. The present findings establish that cadmium can cause a strong induction of testicular PGF(2 alpha) production, which might help to explain the well-known antisteroidogenic effect of this heavy metal. Such an inhibitory effect could be due to reduced levels of StAR.
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| 4. |
- Gunnarsson, David, 1975-
(författare)
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Reproductive toxicology of endocrine disruptors : effects of cadmium, phthalates and phytoestrogens on testicular steroidogenesis
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A number of investigations during the last two decades describe adverse trends in male reproductive health, which have been proposed to be caused by environmental factors with endocrine disrupting properties. In contrast to many other toxicants, endocrine disruptors often do not show linear dose-response relationships typical of those found in traditional toxicological studies. For many compounds, low-dose exposure causes effects opposite to the ones seen after high-dose exposure. In addition, the timing of exposure has been found to be critical. Hence, to correctly assess the impact of endocrine disruptors on reproductive health requires in-depth knowledge of their mechanisms of action. This thesis aimed at identifying the mechanisms underlying the effects of cadmium (Cd), phthalates and phytoestrogens on testicular steroidogenesis. For this purpose, in vitro as well as in vivo models were used. Cd was found to inhibit testosterone synthesis in vivo by down-regulating LH receptor gene expression and reducing the testicular levels of cAMP and StAR protein. In addition, Cd caused a pronounced increase in testicular prostaglandin F2ɑ (PGF2ɑ), suggesting that Cd exerts its suppressive effect on steroidogenesis also by inducing the inhibitory PKC pathway. Pre-treatment with zinc (Zn) protected completely against Cd-induced effects on testosterone and PGF2ɑ. Furthermore, we observed that Cd exposure increased glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA expression in the testis. GAPDH is a potent coactivator of androgen receptor-mediated transcription and the up-regulation found in our study is probably a compensatory response to reduced testosterone concentrations. This finding is interesting since GAPDH has been proposed to have an important role in the regulation of apoptosis as well as sperm motility. We discovered that mono-(2-ethylhexyl) phthalate (MEHP), the active metabolite of the frequently used phthalate di-(2-ethylhexyl) phthalate (DEHP), stimulates Leydig cell steroidogenesis in vitro, by a cAMP- and StAR-independent mechanism. MEHP exposure caused a similar effect in granulosa cells. Gene expression analysis revealed that MEHP is likely to stimulate steroidogenesis by increasing the amount of cholesterol available for steroid synthesis. In the last investigation, we examined the effects of low-dose phytoestrogen exposure on testosterone synthesis during puberty in male goats. Isoflavones present in clover increased plasma concentrations of testosterone and free as well as total triiodothyronine (T3). T3 has previously been shown to induce testosterone synthesis and it is possible that an elevated T3 secretion underlies the increased plasma testosterone levels. Reduced fertility and reproductive tract malformations affect both the individual and the society. Hence, a sound knowledge of reproductive toxicants is of crucial importance. The findings presented in this thesis provide new insights into the reproductive toxicology of endocrine disruptors and may be valuable for risk assessment purposes.
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| 5. |
- Arend, Andres, et al.
(författare)
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Electron microscope immunocytochemical localization of cyclooxygenase-1 and-2 in pseudopregnant rat corpus luteum during luteolysis
- 2004
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Ingår i: Prostaglandins & other lipid mediators. - New York : Elsevier. - 1098-8823 .- 2212-196X. ; 74:1-4, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Prostaglandins converted from arachidonic acid by cyclooxygenases play an important regulatory role in regression of the corpus luteum. To reveal luteal distribution of cyclooxygenase isoforms during luteolysis, an electron microscope immunocytochemical study was performed. Cyclooxygenase-1 and -2 were found both in luteal steroid-producing and interstitial cells on days 13, 15 and 18 of the adult pseudopregnant rat. Cyclooxygenase-2 immunolabelling was predominantly seen in non-luteal cells. The two enzymes were localized in similar fashion to the plasma membrane, rough and smooth endoplasmic reticulum, lipid bodies and mitochondria, but differently in the nuclear compartment. Cyclooxygenase-1 labelling was found only in the perinuclear region, while cyclooxygenase-2 was localized to the nuclear envelope, region of condensed heterochromatin as well as at the perimeter of the heterochromatin. Nuclear residence may indicate additional roles for cyclooxygenase-2 in regulating gene expression. Identification of both enzymes on lipid bodies suggests that these inclusions may be involved in luteal prostanoid production.
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| 6. |
- Arend, A, et al.
(författare)
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Prostaglandins of the E-series inhibit connective tissue proliferation in the liver wound of the rat
- 2005
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Ingår i: Annals of Anatomy. - Jena : Urban & Fischer. - 0940-9602 .- 1618-0402. ; 187:1, s. 57-62
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Tidskriftsartikel (refereegranskat)abstract
- The present study was undertaken to relate wound heating of an internal organ to prostaglandins of the E and F series. A small liver wound was induced by a galvanic cauter via the abdominal route under general anesthesia and prostaglandin E-1, E-2 and F-2 alpha were injected twice daily at a dose of 250 mu g/kg. Proliferation of the connective tissue in the liver wound was estimated morphometrically 6 days after liver wound infliction. Levels of prostaglandins E-2 and F-2 alpha were measured in the liver wound as well as in normal liver tissue from adjacent lobes using radioimmunoassay. The results show that exogenous prostaglandins of the E-series suppress connective tissue proliferation. Three minutes after the last prostaglandin E-2 injection, high prostaglandin concentrations were measured both in the tiver wound and in the liver tissue of the adjacent lobe. Prostaglandin F-2 alpha injections had no effect on wound heating. We believe that the rat thermic liver wound model can be used for different studies on wound heating mechanisms and that prostaglandins of the E-series are involved in wound heating in the specific time period studied.
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| 7. |
- Damber, Jan-Erik, et al.
(författare)
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Rhythmical oscillations in rat testicular microcirculation as recorded by laser Doppler flowmetry
- 1983
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Ingår i: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 118:2, s. 117-123
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Tidskriftsartikel (refereegranskat)abstract
- We have earlier reported that local testicular blood flow, recorded by laser Doppler flowmetry, shows large oscillations with a frequency of 5-10 min-1. In the present study it is proposed that the recorded oscillations represent mainly local microvascular blood flow variations rather than variations in total testicular blood flow or tissue movements. The reasons for this are: (a) Blood flow simultaneously measured at two separate sites showed oscillations with different frequencies. (b) A local subcapsular injection of room-tempered saline under one probe site eradicated oscillations under that probe but not under another adjacent probe. (c) When the testicular capsule was split open, recordings of blood flow continued to show oscillations. (d) The amplitude of the oscillations was rather large (peak to peak value about 50% of mean flow value). No movements of the testicular surface were seen. A 20 min continuous infusion of 0.4 microgram/min noradrenaline did induce a decrease in plasma testosterone concentration, but did not change the mean blood flow. However, the oscillations nearly completely disappeared during the infusion period. The present study also shows that laser Doppler flowmetry is a versatile method and the rat testis provides a suitable organ in the study of the origin and functional importance of these oscillations
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| 8. |
- Damber, Jan-Erik, et al.
(författare)
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Testicular blood flow measured with a laser Doppler flowmeter : acute effects of catecholamines.
- 1982
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Ingår i: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 115:2, s. 209-215
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Tidskriftsartikel (refereegranskat)abstract
- Laser Doppler flowmetry was used to continuously measure testicular blood flow in rats. The method was found applicable on surgically exposed testes. Regular oscillations in blood flow, with a periodicity of 8.6 +/- 0.7 cycles per minute (mean +/- SD), were observed in recordings from 22 to 23 rats. Clamping of the testicular artery reduced the blood flow signal to background values. Effects of catecholamines administered into the tail artery on testicular blood flow together with systemic effects on mean arterial blood pressure and heart rate were measured. It was found that noradrenaline as well as adrenaline caused a significant decrease in blood flow when 10 micrograms was injected. Only noradrenaline decreased the blood flow when 1 microgram was given. The large oscillations detected in the blood flow recordings disappeared quickly when 10 or 1 micrograms of both hormones was administered. It was concluded that catecholamines can exert rapid effects on testicular blood flow
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| 9. |
- Gunnarsson, David, et al.
(författare)
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Effects of dietary phytoestrogens on plasma testosterone and triiodothyronine (T3) levels in male goat kids
- 2009
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Ingår i: Acta Veterinaria Scandinavica. - : Springer Science and Business Media LLC. - 0044-605X .- 1751-0147. ; 51
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Exposure to xenoestrogens in humans and animals has gained increasing attention due to the effects of these compounds on reproduction. The present study was undertaken to investigate the influence of low-dose dietary phytoestrogen exposure, i.e. a mixture of genistein, daidzein, biochanin A and formononetin, on the establishment of testosterone production during puberty in male goat kids. METHODS: Goat kids at the age of 3 months received either a standard diet or a diet supplemented with phytoestrogens (3-4 mg/kg/day) for approximately 3 months. Plasma testosterone and total and free triiodothyronine (T3) concentrations were determined weekly. Testicular levels of testosterone and cAMP were measured at the end of the experiment. Repeated measurement analysis of variance using the MIXED procedure on the generated averages, according to the Statistical Analysis System program package (Release 6.12, 1996, SAS Institute Inc., Cary, NC, USA) was carried out. RESULTS: No significant difference in plasma testosterone concentration between the groups was detected during the first 7 weeks. However, at the age of 5 months (i.e. October 1, week 8) phytoestrogen-treated animals showed significantly higher testosterone concentrations than control animals (37.5 nmol/l vs 19.1 nmol/l). This elevation was preceded by a rise in plasma total T3 that occurred on September 17 (week 6). A slightly higher concentration of free T3 was detected in the phytoestrogen group at the same time point, but it was not until October 8 and 15 (week 9 and 10) that a significant difference was found between the groups. At the termination of the experiment, testicular cAMP levels were significantly lower in goats fed a phytoestrogen-supplemented diet. Phytoestrogen-fed animals also had lower plasma and testicular testosterone concentrations, but these differences were not statistically significant. CONCLUSION: Our findings suggest that phytoestrogens can stimulate testosterone synthesis during puberty in male goats by increasing the secretion of T3; a hormone known to stimulate Leydig cell steroidogenesis. It is possible that feedback signalling underlies the tendency towards decreased steroid production at the end of the experiment.
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| 10. |
- Gunnarsson, David, et al.
(författare)
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Mono-(2-ethylhexyl) phthalate stimulates basal steroidogenesis by a cAMP-independent mechanism in mouse gonadal cells of both sexes
- 2008
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Ingår i: Reproduction. - 1470-1626 .- 1476-3990. ; 135:5, s. 693-703
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Tidskriftsartikel (refereegranskat)abstract
- Phthalates are widely used as plasticizers in a number of daily-life products. In this study, we investigated the influence of mono-(2-ethylhexyl) phthalate (MEHP), the active metabolite of the frequently used plasticizer di-(2-ethylhexyl) phthalate (DEHP), on gonadal steroidogenesis in vitro. MEHP (25–100 µM) stimulated basal steroid synthesis in a concentration-dependent manner in immortalized mouse Leydig tumor cells (MLTC-1). The stimulatory effect was also detected in KK-1 granulosa tumor cells. MEHP exposure did not influence cAMP or StAR protein levels and induced a gene expression profile of key steroidogenic proteins different from the one induced by human chorionic gonadotropin (hCG). Simultaneous treatment with MEHP and a p450scc inhibitor (aminoglutethimide) indicated that MEHP exerts its main stimulatory effect prior to pregnenolone formation. MEHP (10–100 µM) up-regulated hormone-sensitive lipase and 3-hydroxy-3-methylglutaryl coenzyme A reductase, suggesting that MEHP increases the amount of cholesterol available for steroidogenesis. Our data suggest that MEHP, besides its known inhibitory effect on hCG action, can directly stimulate gonadal steroidogenesis in both sexes through a cAMP- and StAR-independent mechanism. The anti-steroidogenic effect of DEHP has been proposed to cause developmental disorders such as hypospadias and cryptorchidism, whereas a stimulation of steroid synthesis may prematurely initiate the onset of puberty and theoretically affect the hypothalamic–pituitary–gonadal axis.
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| 11. |
- Hendrickson, Luke, et al.
(författare)
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Cold acclimation of the Arabidopsis dgd1 mutant results in recovery from photosystem I-limited photosynthesis.
- 2006
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793. ; 580:20, s. 4959-68
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Tidskriftsartikel (refereegranskat)abstract
- We compared the thylakoid membrane composition and photosynthetic properties of non- and cold-acclimated leaves from the dgd1 mutant (lacking >90% of digalactosyl–diacylglycerol; DGDG) and wild type (WT) Arabidopsis thaliana. In contrast to warm grown plants, cold-acclimated dgd1 leaves recovered pigment-protein pools and photosynthetic function equivalent to WT. Surprisingly, this recovery was not correlated with an increase in DGDG. When returned to warm temperatures the severe dgd1 mutant phenotype reappeared. We conclude that the relative recovery of photosynthetic activity at 5 °C resulted from a temperature/lipid interaction enabling the stable assembly of PSI complexes in the thylakoid.
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| 12. |
- Ivanov, Alexander G, et al.
(författare)
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Digalactosyl-diacylglycerol deficiency impairs the capacity for photosynthetic intersystem electron transport and state transitions in Arabidopsis thaliana due to photosystem I acceptor-side limitations.
- 2006
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Ingår i: Plant Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 47:8, s. 1146-57
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Tidskriftsartikel (refereegranskat)abstract
- Compared with wild type, the dgd1 mutant of Arabidopsis thaliana exhibited a lower amount of PSI-related Chl–protein complexes and lower abundance of the PSI-associated polypeptides, PsaA, PsaB, PsaC, PsaL and PsaH, with no changes in the levels of Lhca1–4. Functionally, the dgd1 mutant exhibited a significantly lower light-dependent, steady-state oxidation level of P700 (P700+) in vivo, a higher intersystem electron pool size, restricted linear electron transport and a higher rate of reduction of P700+ in the dark, indicating an increased capacity for PSI cyclic electron transfer compared with the wild type. Concomitantly, the dgd1 mutant exhibited a higher sensitivity to and incomplete recovery of photoinhibition of PSI. Furthermore, dgd1 exhibited a lower capacity to undergo state transitions compared with the wild type, which was associated with a higher reduction state of the plastoquinone (PQ) pool. We conclude that digalactosyl-diacylglycerol (DGDG) deficiency results in PSI acceptor-side limitations that alter the flux of electrons through the photosynthetic electron chain and impair the regulation of distribution of excitation energy between the photosystems. These results are discussed in terms of thylakoid membrane domain reorganization in response to DGDG deficiency in A. thaliana.
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| 13. |
- Ivanov, Alexander G, et al.
(författare)
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Iron deficiency in cyanobacteria causes monomerization of photosystem I trimers and reduces the capacity for state transitions and the effective absorption cross section of photosystem I in vivo.
- 2006
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 141:4, s. 1436-45
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Tidskriftsartikel (refereegranskat)abstract
- The induction of the isiA (CP43') protein in iron-stressed cyanobacteria is accompanied by the formation of a ring of 18 CP43' proteins around the photosystem I (PSI) trimer and is thought to increase the absorption cross section of PSI within the CP43'-PSI supercomplex. In contrast to these in vitro studies, our in vivo measurements failed to demonstrate any increase of the PSI absorption cross section in two strains (Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803) of iron-stressed cells. We report that iron-stressed cells exhibited a reduced capacity for state transitions and limited dark reduction of the plastoquinone pool, which accounts for the increase in PSII-related 685 nm chlorophyll fluorescence under iron deficiency. This was accompanied by lower abundance of the NADP-dehydrogenase complex and the PSI-associated subunit PsaL, as well as a reduced amount of phosphatidylglycerol. Nondenaturating polyacrylamide gel electrophoresis separation of the chlorophyll-protein complexes indicated that the monomeric form of PSI is favored over the trimeric form of PSI under iron stress. Thus, we demonstrate that the induction of CP43' does not increase the PSI functional absorption cross section of whole cells in vivo, but rather, induces monomerization of PSI trimers and reduces the capacity for state transitions. We discuss the role of CP43' as an effective energy quencher to photoprotect PSII and PSI under unfavorable environmental conditions in cyanobacteria in vivo.
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| 14. |
- Ivanov, Alexander G., et al.
(författare)
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The decreased PG content of pgp1 inhibits PSI photochemistry and limits reaction center and light-harvesting polypeptide accumulation in response to cold acclimation
- 2022
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Ingår i: Planta. - : Springer. - 0032-0935 .- 1432-2048. ; 255:2
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Tidskriftsartikel (refereegranskat)abstract
- Main conclusion: Decreased PG constrains PSI activity due to inhibition of transcript and polypeptide abundance of light-harvesting and reaction center polypeptides generating a reversible, yellow phenotype during cold acclimation of pgp1.Cold acclimation of the Arabidopsis pgp1 mutant at 5 °C resulted in a pale-yellow phenotype with abnormal chloroplast ultrastructure compared to its green phenotype upon growth at 20 °C despite a normal cold-acclimation response at the transcript level. In contrast, wild type maintained its normal green phenotype and chloroplast ultrastructure irrespective of growth temperature. In contrast to cold acclimation of WT, growth of pgp1 at 5 °C limited the accumulation of Lhcbs and Lhcas assessed by immunoblotting. However, a novel 43 kD polypeptide of Lhcb1 as well as a 29 kD polypeptide of Lhcb3 accumulated in the soluble fraction which was absent in the thylakoid membrane fraction of cold-acclimated pgp1 which was not observed in WT. Cold acclimation of pgp1 destabilized the Chl–protein complexes associated with PSI and predisposed energy distribution in favor of PSII rather than PSI compared to the WT. Functionally, in vivo PSI versus PSII photochemistry was inhibited in cold-acclimated pgp1 to a greater extent than in WT relative to controls. Greening of the pale-yellow pgp1 was induced when cold-acclimated pgp1 was shifted from 5 to 20 °C which resulted in a marked decrease in excitation pressure to a level comparable to WT. Concomitantly, Lhcbs and Lhcas accumulated with a simultaneous decrease in the novel 43 and 29kD polypeptides. We conclude that the reduced levels of phosphatidyldiacylglycerol in the pgp1 limit the capacity of the mutant to maintain the structure and function of its photosynthetic apparatus during cold acclimation. Thus, maintenance of normal thylakoid phosphatidyldiacylglycerol levels is essential to stabilize the photosynthetic apparatus during cold acclimation.
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| 15. |
- Ivanov, Alexander G, et al.
(författare)
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The induction of CP43' by iron-stress in Synechococcus sp. PCC 7942 is associated with carotenoid accumulation and enhanced fatty acid unsaturation.
- 2007
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Ingår i: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002 .- 0005-2728. ; 1767:6, s. 807-13
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Tidskriftsartikel (refereegranskat)abstract
- Comparative lipid analysis demonstrated reduced amount of PG (50%) and lower ratio of MGDG/DGDG in iron-stressed Synechococcus sp. PCC 7942 cells compared to cells grown under iron sufficient conditions. In parallel, the monoenoic (C:1) fatty acids in MGDG, DGDG and PG increased from 46.8%, 43.7% and 45.6%, respectively in control cells to 51.6%, 48.8% and 48.7%, respectively in iron-stressed cells. This suggests increased membrane dynamics, which may facilitate the diffusion of PQ and keep the PQ pool in relatively more oxidized state in iron-stressed compared to control cells. This was confirmed by chlorophyll fluorescence and thermoluminescence measurements. Analysis of carotenoid composition demonstrated that the induction of isiA (CP43′) protein in response to iron stress is accompanied by significant increase of the relative abundance of all carotenoids. The quantity of carotenoids calculated on a Chl basis increased differentially with nostoxanthin, cryptoxanthin, zeaxanthin and β-carotene showing 2.6-, 3.1-, 1.9- and 1.9-fold increases, respectively, while the relative amount of caloxanthin was increased only by 30%. HPLC analyses of the pigment composition of Chl–protein complexes separated by non-denaturating SDS-PAGE demonstrated even higher relative carotenoids content, especially of cryptoxanthin, in trimer and monomer PSI Chl–protein complexes co-migrating with CP43′ from iron-stressed cells than in PSI complexes from control cells where CP43′ is not present. This implies a carotenoid-binding role for the CP43′ protein which supports our previous suggestion for effective energy quenching and photoprotective role of CP43′ protein in cyanobacteria under iron stress.
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| 16. |
- Jiguet, Frédéric, et al.
(författare)
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An update of the European breeding population sizes and trends of the Ortolan Bunting (Emberiza hortulana)
- 2016
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Ingår i: Ornis Fennica. - : University of Helsinki. - 0030-5685. ; 93:3, s. 186-196
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Forskningsöversikt (refereegranskat)abstract
- Following recent updates proposed by BirdLife International and further updates across Europe gathered in the context of a continent-wide study of the migration strategy of the species, we propose here an update of national population sizes and associated recent trends of the Ortolan Bunting (Emberiza hortulana). Previous estimates for the period 1999-2002 reported 5,200,000 to 16,000,000 breeding pairs, for an area extending east to European Russia, and south to the Caucasus and Turkey. The countries holding the largest populations were Turkey (3-10 million pairs) and Russia (1.5-5.0 million pairs). The updated results give approximately 3,319,000 to 7,057,000 pairs in Europe (for the period 2012-2014), representing a c. 50% decrease in numbers over the last decade. This decrease is partly due to overestimates proposed in previous reports for the key country, Turkey, which is now considered to support only 500,000 to 1,000,000 pairs. Russia still holds 2.0-4.3 million pairs, although with an estimated decline of c.15-30% since 2000. Overall, within the 39 European countries assessed here, recent decadal trends (on average 2000-2012) in population size are reported as unknown in 15 countries, increasing in 2 countries (Germany and Serbia), stable or fluctuating in 6 countries, and decreasing in 16 countries including recent extinctions in Belgium, Hungary, Slovakia and the Netherlands. Overall, declining populations are mostly located in northern Europe, and fourteen of the 15 northern European countries with a known national trend have declining breeding populations, suggesting that northern breeders are of particular conservation concern.
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| 17. |
- Jiguet, Frederic, et al.
(författare)
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Desert crossing strategies of migrant songbirds vary between and within species
- 2019
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Each year, billions of songbirds cross large ecological barriers during their migration. Understanding how they perform this incredible task is crucial to predict how global change may threaten the safety of such journeys. Earlier studies based on radar suggested that most songbirds cross deserts in intermittent flights at high altitude, stopping in the desert during the day, while recent tracking with light loggers suggested diurnal prolongation of nocturnal flights and common non-stop flights for some species. We analyzed light intensity and temperature data obtained from geolocation loggers deployed on 130 individuals of ten migratory songbird species, and show that a large variety of strategies for crossing deserts exists between, but also sometimes within species. Diurnal stopover in the desert is a common strategy in autumn, while most species prolonged some nocturnal flights into the day. Nonstop flights over the desert occurred more frequently in spring than in autumn, and more frequently in foliage gleaners. Temperature recordings suggest that songbirds crossed deserts with flight bouts performed at various altitudes according to species and season, along a gradient ranging from low above ground in autumn to probably >2000 m above ground level, and possibly at higher altitude in spring. High-altitude flights are therefore not the general rule for crossing deserts in migrant songbirds. We conclude that a diversity of migration strategies exists for desert crossing among songbirds, with variations between but also within species.
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| 18. |
- Jiguet, Frédéric, et al.
(författare)
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Unravelling migration connectivity reveals unsustainable hunting of the declining ortolan bunting
- 2019
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 5:5
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Tidskriftsartikel (refereegranskat)abstract
- In France, illegal hunting of the endangered ortolan bunting Emberiza hortulana has been defended for the sake of tradition and gastronomy. Hunters argued that ortolan buntings trapped in southwest France originate from large and stable populations across the whole of Europe. Yet, the European Commission referred France to the Court of Justice of the European Union (EU) in December 2016 for infringements to legislation (IP/16/4213). To better assess the impact of hunting in France, we combined Pan-European data from archival light loggers, stable isotopes, and genetics to determine the migration strategy of the species across continents. Ortolan buntings migrating through France come from northern and western populations, which are small, fragmented and declining. Population viability modeling further revealed that harvesting in southwest France is far from sustainable and increases extinction risk. These results provide the sufficient scientific evidence for justifying the ban on ortolan harvesting in France.
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| 19. |
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| 20. |
- Liu, Lian, et al.
(författare)
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Infertility caused by retardation of follicular development in mice with oocyte-specific expression of Foxo3a
- 2007
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Ingår i: Development. - : The Company of Biologists. - 0950-1991 .- 1477-9129. ; 134:1, s. 199-209
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, mammalian oocytes have been proposed to have important roles in the orchestration of ovarian follicular development and fertility. To determine whether intra-oocyte Foxo3a, a component of the phosphatidylinositol 3-kinase (PI3K) signaling pathway, influences follicular development and female fertility, a transgenic mouse model was generated with constitutively active Foxo3a expressed in oocytes. We found that the female transgenic mice were infertile, which was caused by retarded oocyte growth and follicular development, and anovulation. Further mechanistic studies revealed that the constitutively active Foxo3a in oocytes caused a dramatic reduction in the expression of bone morphogenic protein 15 (Bmp15), connexin 37 and connexin 43, which are important molecules for the establishment of paracrine and gap junction communications in follicles. Foxo3a was also found to facilitate the nuclear localization of p27(kip1) in oocytes, a cyclin-dependent kinase (Cdk) inhibitor that may serve to inhibit oocyte growth. The results from the current study indicate that Foxo3a is an important intra-oocyte signaling molecule that negatively regulates oocyte growth and follicular development. Our study may therefore give some insight into oocyte-borne genetic aberrations that cause defects in follicular development and anovulation in human diseases, such as premature ovarian failure.
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| 21. |
- Liu, Lian, et al.
(författare)
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Phosphorylation and inactivation of glycogen synthase kinase-3 by soluble kit ligand in mouse oocytes during early follicular development.
- 2007
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Ingår i: Journal of Molecular Endocrinology. - : Bioscientifica. - 0952-5041 .- 1479-6813. ; 38:1-2, s. 137-146
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Tidskriftsartikel (refereegranskat)abstract
- Communication between mammalian oocytes and their surrounding granulosa cells through the Kit-Kit ligand (KL, or stem cell factor, SCF) system has been shown to be crucial for follicular development. Our previous studies (Reddy et al. 2005, Liu et al. 2006) have indicated that the intra-oocyte KL-Kit-PI3 kinase (PI3K)-Akt-Foxo3a cascade may play an important role in follicular activation and early development. In the present study, using in situ hybridization and in vitro culture of growing oocytes from 8-day-old postnatal mice, we have demonstrated that another Akt substrate, glycogen synthase kinase-3 (GSK-3), is expressed in growing oocytes. Also, treatment of cultured mouse oocytes with soluble KL not only leads to increased Akt kinase activity in the oocytes, which can phosphorylate recombinant GSK-3 in vitro, but also leads to phosphorylation of oocyte GSK-3alpha and GSK-3beta, which can result in the inactivation of GSK-3 function in oocytes. In addition, we have shown that the regulation of GSK-3alpha and GSK-3beta in cultured oocytes by soluble KL is accomplished through PI3K, since the PI3K-specific inhibitor LY294002 completely abolished the KL-induced phosphorylation of GSK-3alpha and GSK-3beta. Moreover, blockage of the Kit signaling pathway by a Kit function-blocking antibody, ACK2, resulted in reduced phosphorylation of GSK-3. Taken together, our data suggest that the cascade from granulosa cell-derived KL to Kit-PI3K-Akt-GSK-3 in oocytes may take part in regulation of oocyte growth and early ovarian follicular development.
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| 22. |
- Moussy, Caroline, et al.
(författare)
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The genetic structure of the European breeding populations of a declining farmland bird, the ortolan bunting (Emberiza hortulana), reveals conservation priorities
- 2018
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Ingår i: Conservation Genetics. - : Springer. - 1566-0621 .- 1572-9737. ; 19:4, s. 909-922
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic activities, such as agricultural intensification, caused large declines in biodiversity, including farmland birds. In addition to demographic consequences, anthropogenic activities can result in loss of genetic diversity, reduction of gene flow and altered genetic structure. We investigated the distribution of the genetic variation of a declining farmland and long-distance migratory bird, the ortolan bunting Emberiza hortulana, across its European breeding range to assess the impact of human-driven population declines on genetic diversity and structure in order to advise conservation priorities. The large population declines observed have not resulted in dramatic loss of genetic diversity, which is moderate to high and constant across all sampled breeding sites. Extensive gene flow occurs across the breeding range, even across a migratory divide, which contributes little to genetic structuring. However, gene flow is asymmetric, with the large eastern populations acting as source populations for the smaller western ones. Furthermore, breeding populations that underwent the largest declines, in Fennoscandia and Baltic countries, appear to be recently isolated, with no gene exchange occurring with the eastern or the western populations. These are signs for concern as declines in the eastern populations could affect the strength of gene flow and in turn affect the western populations. The genetic, and demographic, isolation of the northern populations make them particularly sensitive to loss of genetic diversity and to extinction as no immigration is occurring to counter-act the drastic declines. In such a situation, conservation efforts are needed across the whole breeding range: in particular, protecting the eastern populations due to their key role in maintaining gene flow across the range, and focussing on the northern populations due to their recent isolation and endangered status.
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| 23. |
- Porankiewicz, J, et al.
(författare)
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Membrane lipid composition and restoration of photosynthesis during low temperature acclimation in Synechococcus sp. strain PCC 7942
- 1998
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Ingår i: Physiologia Plantarum. - 0031-9317 .- 1399-3054. ; 104:3, s. 405-412
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Tidskriftsartikel (refereegranskat)abstract
- We compared temperature acclimation of the cyanobacterium Synechococcus sp. strain PCC 7942 and two psbA inactivation mutants, R2K1 and R2S2C3, following shifts from 37 to 25 degrees C. Wild-type cultures incubated in the dark at 25 degrees C showed no chill-induction of lipid desaturation, probably because the lipid acclimation is dependent on photosynthesis. Incubation in the light at 25 degrees C, however, induced considerable increases in membrane lipid desaturation, and within 24 h the monoenoic fatty acids increased from about 46 to about 57%. In parallel with this desaturation the ratio of monogalactosyldiacylglycerol to digalactosyldiacylglycerol (MGDG/DGDG) increased. Both of these lipid changes increase the repulsive forces of the hydrophobic chains of the membrane lipids and thereby alter the physical properties of the membrane. As expected, under irradiation this temperature shift also induced a reversible replacement of the constitutive photosystem II protein, D1:1, with an alternative stress form, D1:2. Photosynthesis decreased to 42% of the control level within the initial 2 h of cold incubation. but later recovered. The D1:2 protein accumulated to high levels between 2 and 4 h after the temperature shift, when desaturation of membrane lipids and MGDG/DGDG ratio had not yet increased significantly. Much of this accumulated D1:2 protein was in a higher molecular mass form, termed D1:2*, which is probably an unprocessed precursor form of the protein. In contrast to the wild-type cells the psbA inactivation mutants, R2K1 and R2S2C3 did not accumulate any precursor form of D1 protein either at the optimal or low growth temperature. The R2S2C3 mutant strain expresses only the constitutive D1:1 protein and suffered severe photoinhibition following the temperature shift. Nevertheless; R2S2C3 eventually recovered some photosynthetic activity, induced lipid desaturation and slowly resumed growth ar 25 degrees C, thus demonstrating acclimation to the lower growth temperature. The R2K1 mutant synthesizes only the D1:2 stress form of D1 protein and maintained oxygen evolution at a high level (ca 70% of a control rate) after the low temperature shift. Chill-induced lipid desaturation and increase in MGDG/DGDG ratio did proceed but, for unknown reasons the strain did nor resume growth at the lower temperature. The physical properties of the membrane lipids were not the limiting factor for growth resumption. Our results demonstrate that in the wild-type the chill-induced desaturation of membrane lipids follows after the exchange of the two forms of the D1 proteins, but the D1 exchange results in accumulation of unprocessed D1:2* polypeptides until the lipid composition later acclimates. We also show that the lipid desaturation process in Synechococcus sp. strain PCC 7942 is dependent upon photosynthetic activity.
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| 24. |
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| 25. |
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| 26. |
- Simovart, Helle Evi, et al.
(författare)
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Experimental sepsis : characteristics of activated macrophages and apoptotic cells in the rat spleen.
- 2006
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Ingår i: Ann N Y Acad Sci. - 0077-8923. ; 1090, s. 253-64
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Tidskriftsartikel (refereegranskat)abstract
- Sepsis, being characterized by massive translocation of bacteria into tissues, induces the suppression of the function of both leukocytes and macrophages. The aim of the study was to count activated macrophages (AMs) and apoptotic (Ao) cells in the rat spleen during the period of experimental sepsis and to clarify the associations of these parameters with each other and with leukocyte migration and bacterial translocation into different organs. The Wistar rats were intraperitoneally inoculated with Escherichia coli (E. coli) and were sacrificed after 2, 6, 24, 48, and 120 h. Bacteria and leukocytes in tissues were specifically stained. AMs were identified by immunohistological staining and Ao cells by the TUNEL assay. The high counts of E. coli at 6 h were strongly associated with a low level of the total counts of leukocytes, accompanied by the high translocation of microbes into tissues. In the spleen, lymphocytes, macrophages, and neutrophils with pyknotic nuclei were identified. The count of AMs was highest at 24 h after the inoculation with E. coli; at the same time the Ao cell count began to rise and achieved the highest level 24 h later. Our investigation indicates that the molecular peculiarities of macrophages and their responses to the inflammation process are tissue-specific. In the spleen the activation process involving hematopoietic cells and macrophages was remarkable at the late stage of sepsis, characterized by a high count of Ao cells.
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| 27. |
- Suutre, Siim, et al.
(författare)
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Bone tissue content of TGF-2 changes with time in human heterotopic ossification after total hip arthroplasty
- 2009
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Ingår i: Growth Factors. - : Taylor & Francis. - 0897-7194 .- 1029-2292. ; 27:2, s. 114-120
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Tidskriftsartikel (refereegranskat)abstract
- Transforming growth factor beta isoforms (TGF-1, TGF-2, and TGF-3) most likely play a role in bone physiology, but little is known about their relative importance in normal as well as in heterotopic bone. This study focused on possible differences in the localization and relative content of different TGF beta isoforms in heterotopic ossifications (HO) by comparing HOs, which have developed less than 17 months (immature HOs) with those developed 3-9 years (mature HOs). The HOs were harvested after total hip arthroplasty (THA) during revision surgery. The HO samples were decalcified, embedded in paraffin and sectioned. Azan staining was used to evaluate histological structure of the ossifications and immunohistochemical analysis was performed to estimate the localization of three TGF beta isoforms in the HOs. Comparison of different TGF beta isoforms in the immature and the mature ossifications showed that the content of TGF-2 was decreased by almost three times in the mature HO as compared to the immature HO (p=0.0064). The proportions of other isoforms in HOs did not differ significantly. This study shows that the relative importance of TGF betas change with HO development.
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| 28. |
- Suutre, S, et al.
(författare)
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Involvement of BMP-2, TGF-beta 2 and TGF-beta 3 signaling in initial and early stages of heterotopic ossification in a rat experimental model
- 2010
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Ingår i: Scandinavian Journal of Laboratory Animal Science. - 0901-3393. ; 37:1, s. 31-40
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Tidskriftsartikel (refereegranskat)abstract
- This study focused on the localization and expression of bone morphogenetic protein 2 (BMP-2) and different isoforms of transforming growth factor beta (TGF-beta(1), TGF-beta(2) and TGF-beta(3)) in the initial and early stages of heterotopic ossification (HO) employing an animal model mimicking the situation after total hip arthroplasty (THA). Bone growth was induced in rats using beta-tricalcium phosphate implants immersed either in osteoinductive rhBMP-2 solution or in saline and implanted at the site where the HO is usually expected to develop after THA. Implants were removed at 3 or 21 days after the operation and handled according to stereology principles. mRNA expression and protein staining of growth factors in different types of tissues was determined by in situ hybridization and immunohistochemistry, respectively. After three days, TGF-beta(3) content in the undifferentiated mesenchymal-like cells in the rhBMP-2 treated implants was, as assessed by immunohistochemistry, 49.6% higher compared to the saline treated group (p=0.024). This was also supported by in situ hybridization of mRNA of TGF-beta(3), which showed stronger expression in rhBMP-2 treated group. Immunohistochemical investigation showed that after 21 days the connective tissue in the rhBMP-2 treated implants contained more TGF-beta(1),TGF-beta(2) and TGF-beta(3), compared to BMP-2 and osteoblasts contained significantly (27.2%) more TGF-beta(3) compared to TGF-beta(1) (p=0.045). In the formed HO the proportion of the TGF-beta(2) and TGF-beta(3), producing bone tissue was increased by 32.1% and 47.8% respectively, compared to the TGF-beta(1) producing bone tissue (p=0.007 and p=0.006) and although this difference was not so clear at mRNA level, this suggests that TGF-beta(2) and TGF-beta(3) signaling seem to play an important role during initial and early stages of HO formation.
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| 29. |
- Toom, A., et al.
(författare)
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Bone formation zones in heterotopic ossifications : histologic findings and increased expression of bone morphogenetic protein 2 and transforming growth factors beta2 and beta3
- 2007
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Ingår i: Cell Calcium. - 0143-4160 .- 1532-1991. ; 80:4, s. 259-67
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Tidskriftsartikel (refereegranskat)abstract
- Heterotopic ossifications (HOs) formed after total endoprosthetic replacement of the hip joint were collected during revision surgery (n = 7). Tissues collected during regular hip arthroplasty (n = 12) were used as reference. Histomorphometric analysis was performed for assessment of bone formation activity in HOs and reference bone. HOs were dissected with histological guidance into three zones: formed bone, zone of active bone formation, and zone with fibrous connective and fibrocartilagineous tissue. Relative expression of the mRNA for bone morphogenetic protein 2 (BMP-2), transforming growth factor beta2 (TGF-beta2), and TGF-beta3 was determined by reverse-transcription polymerase chain reaction relative to beta-actin. Expression of all three growth factors was higher than in orthotopic bone. Similarly, the osteoid surface density was increased in HOs. The levels of all growth factors were higher in the zone of active bone formation or remodeling than in the zone of formed bone. In matured HOs, the osteoid surface density as well as mRNA levels were lower, although still significantly raised, indicating that bone formation slows down after 2 years. Immunohistochemical analysis demonstrated the presence of TGF-beta1, TGF-beta2, TGF-beta3, and BMP-2 proteins in the zone of bone formation. We conclude that bone formation after heterotopic bone induction is initially intense, slows down within 2 years, and thereupon continues as active remodeling mainly on the border of HO. Our data indicate that BMP-2, TGF-beta2, and TGF-beta3 are involved in bone formation in HO.
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| 30. |
- Toom, A., et al.
(författare)
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Lack of a central role for osteoprogenitor cells from the femoral canal in heterotopic ossification of the hip : An experimental study in a rat model
- 2010
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Ingår i: Journal of Bone and Joint Surgery. - : British Editorial Society of Bone and Joint Surgery. - 0301-620X .- 2044-5377. ; 92:2, s. 298-303
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Tidskriftsartikel (refereegranskat)abstract
- We have developed an animal model to examine the formation of heterotopic ossification using standardised muscular damage and implantation of a beta-tricalcium phosphate block into a hip capsulotomy wound in Wistar rats. The aim was to investigate how cells originating from drilled femoral canals and damaged muscles influence the formation of heterotopic bone. The femoral canal was either drilled or left untouched and a tricalcium phosphate block, immersed either in saline or a rhBMP-2 solution, was implanted. These implants were removed at three and 21 days after the operation and examined histologically, histomorphometrically and immunohistochemically. Bone formation was seen in all implants in rhBMP-2-immersed, whereas in those immersed in saline the process was minimal, irrespective of drilling of the femoral canals. Bone mineralisation was somewhat greater in the absence of drilling with a mean mineralised volume to mean total volume of 18.2% (SD 4.5) versus 12.7% (SD 2.9, p < 0.019), respectively. Our findings suggest that osteoinductive signalling is an early event in the formation of ectopic bone. If applicable to man the results indicate that careful tissue handling is more important than the prevention of the dissemination of bone cells in order to avoid heterotopic ossification. © 2010 British Editorial Society of Bone and Joint Surgery.
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