| 1. |
- Carlsson, Björn, 1958, et al.
(författare)
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Obese (ob) gene defects are rare in human obesity
- 1997
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Ingår i: Obesity Research. - 1071-7323 .- 1550-8528. ; 5:1, s. 30-5
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Tidskriftsartikel (refereegranskat)abstract
- Our knowledge of the role of the recently cloned ob-protein (leptin) in the regulation of body fat stores is largely derived from experiments performed in mice. Different mouse models exhibit abnormalities in ob-gene expression, with extreme overexpression in mice which lack bioactive ob-protein, have nonfunctional ob-receptors or hypothalamic lesions, and undetectable expression in mice with suggested defects in regulatory elements. The aim of this study is to examine if defects, corresponding to those in mice, exist in human obesity. Adipose tissue was obtained from 94 adult obese subjects and from six children who had developed obesity after surgery in the hypothalamic region. Total RNA was isolated and ob-gene expression was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) and Northern blot. The coding region of the ob-gene was sequenced in both directions in the 94 obese adults. No mutations were detected in the coding region of the ob-gene and ob-gene expression was detectable in all subjects and none of the subjects had an extreme overexpression. There was no systematic increase in ob-expression in obese children with hypothalamic disease compared to their healthy brothers and sisters. These results show that severe abnormalities involving the ob-gene, analogous to those described in mouse models, are rare in human obesity. We therefore conclude that the cloning and subsequent analysis of the ob-gene has not provided information that can, by itself, explain the genetic component in the development of human obesity.
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| 2. |
- Karlsson, Lars, 1968-
(författare)
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Actions, interactions and narratives
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The area of reasoning about action and change is concerned with the formalization of actions and their effects as well as other aspects of inhabited dynamical systems. The representation is typically done in some logical language. Although there has been substantial progress recently regarding the frame problem and the ramification problem, many problems still remain. One of these problems is the representation of concurrent actions and their effects. In particular, the effects of two or more actions executed concurrently may be different from the union of the effects of the individual actions had they been executed in isolation. This thesis presents a language, TAL-C, which supports detailed and flexible yet modular descriptions of concurrent interactions. Two related topics, which both require a solution to the concurrency problem, are also addressed: the representation of effects of actions that occur with some delay, and the representation of actions that are caused by other actions.Another aspect of reasoning about action and change is how to describe higher-level reasoning tasks such as planning and explanation. In such cases, it is important not to just be able to reason about a specific narrative (course of action), but to reason about alternative narratives and their properties, to compare and manipulate narratives, and to reason about alternative results of a specific narrative. This subject is addressed in the context of the situation calculus, where it is shown how the standard version provides insufficient support for reasoning about alternative results, and an alternative version is proposed. The narrative logic NL is also presented; it is based on the temporal action logic TAL, where narratives are represented as first-order terms. NL supports reasoning about (I) metric time, (II) alternative ways the world can develop relative to a specific choice of actions, and (III) alternative choices of actions.
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| 3. |
- Karlsson, Lars, 1968-, et al.
(författare)
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Delayed effects of actions
- 1998
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Ingår i: Proceedings of the 13th European Conference on Artificial Intelligence (ECAI). - Chichester : John Wiley & Sons. - 9780471984313 ; , s. 542-546
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Konferensbidrag (refereegranskat)
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| 4. |
- Loo, Lars-Ove, 1954, et al.
(författare)
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Passive suspension feeding in Amphiura filiformis (Echinodermata: Ophiuroidea): Feeding behaviour in flume flow and potential feeding rate of field populations
- 1996
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Ingår i: Mar Ecol-Progr Ser. - 0171-8630. ; 139:1-3, s. 143-155
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Tidskriftsartikel (refereegranskat)abstract
- Experimental studies in a laboratory flume show that the sediment-living brittle-star Amphiura filiformis captures suspended particles. Feeding activity is a function of now velocity with few animals extending feeding arms in still water. Flow velocity also affects the orientation of feeding arms, and we suggest that this orientation is partly controlled by A. filiformis. By combining field measurements of current velocity and seston concentration with morphometrics and filtration models, a theoretical encounter rate of suspended particles was calculated for A. filiformis. In terms of organic content, A. filiformis can potentially balance growth and respiration with ingested seston although balance will strongly depend on retention efficiency and particle quality. Detailed measurements of flow around feeding arms revealed complex now patterns that will limit the applicability of available models of food encounter for passive suspension feeders, but our sensitivity analysis indicates that suspended aggregates may be especially important in the nutrition of this species.
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