| 31. |
- Larsson, Kjell, 1958-, et al.
(author)
-
Population differentiation in the redshank (Tringa totanus) as revealed by mitochondrial DNA and amplified fragment length polymorphism markers
- 2005
-
In: Conservation Genetics. - : Springer Science and Business Media LLC. - 1566-0621 .- 1572-9737. ; 6:3, s. 321-331
-
Journal article (peer-reviewed)abstract
- The redshank (Tringa totanus) is declining throughout Europe and to implement efficient conservation measures, it is important to obtain information about the population genetic structure. The aim of the present study was two-fold. First, we analysed the genetic variation within and between populations in the Baltic region in southern Scandinavia. Evidence of genetic structure would suggest that different populations might require separate management strategies. Second, in an attempt to study large-scale genetic structure we compared the Baltic populations with redshanks from northern Scandinavia and Iceland. This analysis could reveal insights into phylogeography and long-term population history. DNA samples were collected from six breeding sites in Scandinavia presumed to include two subspecies (totanus and britannica) and a further sample from Iceland (subspecies robusta). Two methods were used to study the population genetic structure. Domain II and III of the mitochondrial control region was analysed by DNA sequencing and nuclear DNA was analysed by screening amplified fragment length polymorphism (AFLP) markers. Mitochondrial DNA showed no variation between individuals in domain II. When analysing an 481 bp fragment of domain III seven haplotypes were found among birds. On the basis of mtDNA sequences, redshanks showed some evidence of a recent expansion from a bottlenecked refugial population. Bayesian analyses of AFLP data revealed a significant genetic differentiation between suggested subspecies but not between populations within the Baltic region. Our results indicate that populations of redshanks in Europe constitute at least three separate management units corresponding to the recognised subspecies.
|
|
| 32. |
- Modig, Carina, et al.
(author)
-
Analysis of vitelline envelope synthesis and composition during early oocyte development in gilthead seabream (Sparus aurata)
- 2008
-
In: Molecular Reproduction and Development. - New York : Wiley-Liss. - 1040-452X .- 1098-2795. ; 75:8, s. 1351-1360
-
Journal article (peer-reviewed)abstract
- The oocyte vitelline envelope (VE) of gilthead seabream is composed of four known zona pellucida (ZP) proteins, ZPBa, ZPBb, ZPC, and ZPX. We have previously shown that the gilthead seabream ZP proteins are differentially transcribed in liver and ovary, with the expression in liver being under estrogenic control. However, although mRNA was found in both liver and ovary, only low ZPBa protein levels were detected in liver and plasma. Using isoform-specific ZP antibodies we show that ZPBa and ZPX translation products are present in the cytosol of stage I and II oocytes. In addition, the zpBa and zpX mRNAs were detected in early developing oocytes. During oocyte growth (vitellogenesis), the VE increased in thickness (>10 µm), and we show that the four ZP isoforms are present in different regions of the VE. ZPX was detected closest to the oocyte plasma membrane while the intermediate region was composed of ZPBa, ZPBb, and ZPC. At the outer layer, only ZPC was detected. When oocytes reach the fully grown stage they resume meiosis and hydration. As the oocyte expands, thinning to 4 µm, the VE acquire a striped and compact appearance at the electron microscopy level. This study provides further evidence for the oocyte origin of some ZP proteins in the gilthead seabream and suggests that the ZP proteins are differentially distributed within the VE. Mol. Reprod. Dev. 75: 1351-1360, 2008.
|
|
| 33. |
- Nilsson, P. O., et al.
(author)
-
Electronic structure of buried Si layers in GaAs(001) as studied by soft-x-ray emission
- 1995
-
In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 52, s. R8643-
-
Journal article (peer-reviewed)abstract
- It is demonstrated that it is possible to investigate details of the electronic structure of an internal atomic monolayer using soft-x-ray-emission spectroscopy. The local and partial density of states of one monolayer and three monolayers of Si, embedded deep below a GaAs(001) surface, was extracted. Clear differences to the density of states for bulk Si were observed.
|
|
| 34. |
|
|
| 35. |
- Orban, Laszlo, et al.
(author)
-
Long and winding roads : testis differentiation in zebrafish
- 2009
-
In: Molecular and Cellular Endocrinology. - Amsterdam : Elsevier BV. - 0303-7207 .- 1872-8057. ; 312:1-2, s. 35-41
-
Journal article (peer-reviewed)abstract
- Zebrafish sex determination, gonad differentiation and reproduction are far from being fully understood. Although the mode of sex determination is still being disputed, most experimental data point towards the lack of sex chromosomes and a multigenic sex determination system. Secondary effects from the environment and/or (xeno)hormones may influence the process, resulting in biased sex ratios. The exact time point of sex determination is unknown. Gonad differentiation involves a compulsory 'juvenile ovary' stage with subsequent transformation of the gonad into a testis in males. As the latter is a late event, there is a delay between sex determination and testis differentiation in zebrafish, in contrast to mammals. Information on the expression of several candidate genes thought to be involved in these processes has been supplemented with data from large-scale gonadal transcriptomic studies. New approaches and methodologies provide hope that answers to a number of important questions will be deciphered in the future.
|
|
| 36. |
- Paccagnini, Eugenio, et al.
(author)
-
New findings on sperm ultrastructure in thrips (Thysanoptera, Insecta)
- 2009
-
In: Arthropod structure & development. - : Elsevier BV. - 1467-8039 .- 1873-5495. ; 38:1, s. 70-83
-
Journal article (peer-reviewed)abstract
- Sperm ultrastructure of several species in each of the two suborders of Thysanoptera Tubulifera and Terebrantia shows a distinctive and unusual architecture. Members of the whole order share a bizarre axoneme consisting of 27 microtubular elements derived from the amalgamation of 3 (9+0) axonemes present in each spermatid at the beginning of spermiogenesis. The reciprocal shifting of these axonemes along the length of the sperm, together with their possible shortening and overlapping for short distances, could explain why in some species it is never possible to observe the complete set of 27 microtubular elements in any one cross section. Tubuliferan sperm have a small elliptical (in cross section) acrosome extending the length of the sperm. In Bolothrips insularis and Compsothrips albosignatus this structure is larger and is associated with an external, flattened vesicle throughout its length. Terebrantian sperm lack an acrosome, but display for half their length a dense body running parallel to the nucleus. The sperm, in members of this suborder, are also characterized by possession of a small mitochondrion and by the unusual bilobed outline of cross sections through the anterior sperm region, with the nucleus located in one of the two lobes. Structures serving to anchor sperm to the inner surface of the cyst cell have been observed at their anterior tips in the testes of tubuliferans. In B. insularis, an anterior appendage is formed in immature sperm and is maintained in the mature spermatozoon parallel to its long axis in the most anterior region. Such an anchoring structure has not been observed in sperm of the terebrantian species examined, probably because the testis of terebrantians contains only a single cyst of developing gametes.
|
|
| 37. |
- Sköld, Helen Nilsson, et al.
(author)
-
Hormonal regulation of female nuptial coloration in a fish.
- 2008
-
In: Hormones and behavior. - : Elsevier BV. - 1095-6867 .- 0018-506X. ; 54:4, s. 549-56
-
Journal article (peer-reviewed)abstract
- Physiological color change in camouflage and mating is widespread among fishes, but little is known about the regulation of such temporal changes in nuptial coloration and particularly concerning female coloration. To better understand regulation of nuptial coloration we investigated physiological color change in female two-spotted gobies (Gobiusculus flavescens). Females of this species develop an orange belly that acts as an ornament. The orange color is caused by the color of the gonads combined with the chromathophore based pigmentation and transparency of the skin. Often during courtship and female-female competition, a rapid increase in orange coloration, in combination with lighter sides and back that increases skin and body transparency, gives the belly an intense 'glowing' appearance. To understand how this increased orange coloration can be regulated we analysed chromatic and transparency effects of neurohumoral agents on abdominal skin biopsies in vitro. We found prolactin and alpha-melanocyte stimulating hormone (MSH) to increase orange coloration of the skin. By contrast, melatonin and noradrenaline increased skin transparency, but had a negative effect on orange coloration. However, mixtures of melatonin and MSH, or melatonin and prolactin, increased both orange coloration and transparency. This effect mimics the chromatic 'glow' effect that commonly takes place during courtship and intra sexual aggression. Notably, not only epidermal chromatophores but also internal chromatophores lining the peritoneum responded to hormone treatments. There were no chromatic effects of the sex steroids 17beta-estradiol, testosterone or 11-ketotestosterone. We hypothesize that similar modulation of nuptial coloration by multiple hormones may be widespread in nature.
|
|
| 38. |
- Strand, Tanja, et al.
(author)
-
The MHC class II of the Black grouse (Tetrao tetrix) consists of low numbers of B and Y genes with variable diversity and expression
- 2007
-
In: Immunogenetics. - : Springer Science and Business Media LLC. - 0093-7711 .- 1432-1211. ; 59:9, s. 725-734
-
Journal article (peer-reviewed)abstract
- We found that the Black grouse (Tetrao tetrix) possess low numbers of Mhc class II B (BLB) and Y (YLB) genes with variable diversity and expression. We have therefore shown, for the first time, that another bird species (in this case, a wild lek-breeding galliform) shares several features of the simple Mhc of the domestic chicken (Gallus gallus). The Black grouse BLB genes showed the same level of polymorphism that has been reported in chicken, and we also found indications of balancing selection in the peptide-binding regions. The YLB genes were less variable than the BLB genes, also in accordance with earlier studies in chicken, although their functional significance still remains obscure. We hypothesize that the YLB genes could have been under purifying selection, just as the mammal Mhc-E gene cluster.
|
|
| 39. |
- Svensson, Maria
(author)
-
Studies of genes involved in regulating flowering time in Arabidopsis
- 2006
-
Doctoral thesis (other academic/artistic)abstract
- Transition from a vegetative growth phase to flowering in plants occurs in response to both environmental conditions and endogenous signals. Identification of genes that are involved in regulating the time of flowering is of great importance in agri- and horticulture. Flowering-time genes can be used for crop improvement by, for instance, engineering plants to flower earlier. This shortening of the time to flowering could result in an extended growing season that could enable farmers to grow more than one crop each year. In this work, a gene knockout approach using T-DNA tagging and in vivo gene fusion has been employed to identify and characterise genes that are involved in regulating flowering time in the model plant Arabidopsis thaliana. This approach resulted in the identification of two genes, At4g20010 and its homologue At1g31010. Expression studies and GUS histochemical analysis of a reporter gene revealed that At4g20010 is mainly expressed in rapid growing tissues such as root tips, shoot apex, flowers and stem nodes. T-DNA insertional mutants of At4g20010 and At1g31010 exhibit a late-flowering phenotype that can largely be repressed by application of gibberellin. Plants with an insertional mutation in At4g20010 contain a reduced amount of the bioactive gibberellin GA4 compared to wild-type plants. The decreased level of GA4 is not due to a transcriptional repression of the GA-biosynthetic genes AtGA3ox1 or AtGA20ox1, since their expressions were increased in the mutant plants. In silico analyses revealed that the C-terminal protein sequences encoded by At4g20010 and At1g31010 contain RNA-binding motifs, whereas the N-terminal sequences have three-dimensional structures similar to single stranded nucleic acid-binding proteins. To conclude, At4g20010 and At1g31010 may encode two RNA-binding proteins that are involved in regulating flowering time in A. thaliana by affecting the metabolism of GA. This can be possible either by a positive regulation of GA3ox at the post-transcriptional level or by a negative regulation of GA2ox.
|
|
| 40. |
- Valdiosera, Cristina, et al.
(author)
-
Typing single polymorphic nucleotides in mitochondrial DNA as a way to access Middle Pleistocene DNA
- 2006
-
In: Biology Letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 2:4, s. 601-603
-
Journal article (peer-reviewed)abstract
- In this study, we have used a technique designed to target short fragments containing informative mitochondrial substitutions to extend the temporal limits of DNA recovery and study the molecular phylogeny of Ursus deningeri. We present a cladistic analysis using DNA recovered from 400 kyr old U. deningeri remains, which demonstrates U. deningeri's relation to Ursus spelaeus. This study extends the limits of recovery from skeletal remains by almost 300 kyr. Plant material from permafrost environments has yielded DNA of this age in earlier studies, and our data suggest that DNA in teeth from cave environments may be equally well preserved.
|
|
