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- Ericsson, Rolf
(författare)
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A Comparative Study of Head Development in Mexican Axolotl and Australian Lungfish: Cell Migration, Cell Fate and Morphogenesis
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of the vertebrate head is a complex process involving interactions between a multitude of cell types and tissues. This thesis describes the development of the cranial neural crest and of the visceral arch muscles in the head of two species. One, the Mexican axolotl (Ambystoma mexicanum), is a basal tetrapod, whereas the other, the Australian lungfish (Neoceratodus forsteri), belongs to the Dipnoi, the extant sister group of the Tetrapoda. The migration of neural crest cells, which form most of the bones and connective tissues in the head, and the morphogenesis of the jaw, was determined in the Mexican axolotl. It was shown that both the upper and lower jaws form from ventral condensations of neural crest cells in the mandibular arch. The dorsal condensation, earlier considered to give rise to the upper jaw, was shown to form the trabecula cranii.The normal spatio-temporal development of visceral arch muscles was investigated in both the Mexican axolotl and the Australian lungfish. In axolotl, the muscles tended to start forming almost simultaneously in all visceral arches at their future origins and extend towards their future insertions at the onset of muscle fibre formation. In lungfish, fibres formed simultaneously throughout most of each muscle anlage in the first and second visceral arch, but were delayed in the branchial arches. The anlagen were first observed at their future insertion, from which they developed towards future origins. To test the ability of neural crest cells to pattern the visceral arch muscles, migrating crest cells were extirpated from axolotl embryos, which resulted in a wide range of muscle malformations. In most cases, the muscles appeared in the right position but were small and extended in abnormal directions. This shows that neural crest cells are responsible not for the position of the muscles but for their correct anatomical pattern. Fate mapping showed that connective tissue surrounding myofibers is, at least partly, neural crest derived.In conclusion, the work presented in this thesis shows that although early development may map out the patterns of later development, the differences between axolotl and lungfish head development are not seen until during morphogenesis. Further investigation of morphogenesis is needed to explain the great variation of head morphology seen in vertebrates today.
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| 2. |
- South, Nicholas, et al.
(författare)
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Väderradarteknik inom VA-området : Test av metodik
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The report consists of a literature study of X-band weather radar technology, a comparison of rain data between an X-band radar facility near Lund and rain gauges, an analysis of flow- and sewage overflow data during rain events and implementation ideas of the X-band radar.
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| 3. |
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| 4. |
- Andersson, Sarah, et al.
(författare)
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Malmbanan Diaries
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This booklet is a report for a case study visit during four day field trip, a group of nine PhD students and their supervisors – all part of the National Research School for Architecture and Planning in the Urban Landscape, APULA – set out to explore what may be considered the outback of Western Europe’s conurbations, the transnational region of Kiruna -Narvik.Both “remote” and “resourceful”, “threatened” and “thriving” (equally relative notions), this region seemed to offer possibilities to reflect upon many of the current tendencies influencing contemporary planning practice and research.
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| 5. |
- Backofen, Rolf, et al.
(författare)
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Requirements and specification of bioinformatics use cases
- 2005
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This deliverable specifies use cases based on bioinformatics research carried out by members ofA2. The use cases involve the use of rules to reason over ontologies and pathways (Dresden,Edinburgh, Paris, Linköping) and rules to specify workflows to integrate bioinformatics data (Lisbon, Skövde, Jena, Bucharest). The use cases are designed as a reference point to foster the take up of A2 use cases by I-work packages. Most notably, many of the use cases specify the need for querying and reactivity with languages like Xcerpt (I4), Erus (I5) and Prova (I5). The use cases range from basic research applications to fully deployed software with an international user base.
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| 6. |
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| 7. |
- Backofen, Rolf, et al.
(författare)
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Usage of bioinformatics tools and identification of information sources
- 2005
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Bioinformatics is an important application area for semantic web technologies as much of the data is online and accessible in XML format, as some sites already support web services, and as ontologies are widely used to annotate data. In this deliverable, we give a survey over 18 of the most important bioinformatics resources and discuss their availability and accessibility, which are two of the main criteria for these resources to act as bases for later demonstrators.
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| 10. |
- Boisvert, Catherine Anne, 1978-
(författare)
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The Origin of Tetrapod Limbs and Girdles: Fossil and Developmental Evidence
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Around 375 million years ago, the first tetrapods appeared, marking one of the most important events in vertebrate evolutionary history. The fin to limb transition saw the appearance of fingers and a weight bearing pelvic girdle. While very little research has been done on the evolution of the tetrapod pelvic girdle, a fair amount has been done on the origins of fingers but some aspects remained controversial. A combination of palaeontology, developmental biology and comparative morphology was therefore used in this thesis to better understand the fin to limb transition. The pectoral fin of Panderichthys, a sarcopterygian fish closely related to tetrapods was CT-scanned and modeled in three dimensions and its pelvic girdle and fin were examined with traditional techniques. This information from the fossil record was integrated with comparisons of the development of the Australian lungfish, Neoceratodus forsteri, our closest living fish relative and the axolotl (Ambystoma mexicanum), a salamander representing well the condition of early tetrapods. Development of bone and cartilage was studied through clearing and staining and development of skeletal muscles through immunostaining. In situ hybridizations were performed on the lungfish to study the expression of Hoxd13, associated with the formation of digits in tetrapods. This work shows that the late expression phase of Hoxd13 is present in Neoceratodus and is associated with the formation of radials. Redescription of the pectoral fin of Panderichthys reveals that distal radials are present, which, in addition to other information, lead us to conclude that digits are not novelties in tetrapods but rather have evolved from the distal radials present in the fins of all sarcopterygian fish. The earliest tetrapods lack a full set of wrist + carpals/ankle + tarsal bones. Here, we propose that this region of the limbs evolved after fingers and toes through an expansion of the region between the proximal limb bones and the digits. As for the pelvic girdle, it is very primitive in Panderichthys but comparison of its development in Neoceratodus and Ambystoma suggest that the ischium evolved through the posterior expansion of the pubis and the ilium, through an elongation of the iliac process already present in sarcopterygian fishes. The results of this thesis help to better understand the fin to limb transition and show that it is more gradual than previously believed.
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