| 1. |
- Båmstedt, Ulf, et al.
(författare)
-
Fecundity and early life of the deep-water jellyfish Periphylla periphylla
- 2020
-
Ingår i: Journal of Plankton Research. - : OXFORD UNIV PRESS. - 0142-7873 .- 1464-3774. ; 42:1, s. 87-101
-
Tidskriftsartikel (refereegranskat)abstract
- Comparisons over 6 years of three Norwegian fjord populations of the deep-water scyphomedusa Periphylla periphylla are presented. A minor part of the population in Lurefjord is migrating to the surface during night, which benefits mating encounters by increasing abundance per unit volume and decreasing the distance between individuals. Simulations using a typical water-column density profile and Stoke's law show that fertilized eggs released in the surface quickly reach a depth where light is insufficient for visual predators. Consequently, the distribution of the smallest juveniles was strongly skewed towards higher depths in all three fjords studied. Mature females in Sognefjord were 4-5 times less abundant than in Lurefjord and Halsafjord, but due to a larger size and strong exponential relationship between size and number of mature oocytes, the potential recruitment rate as recruits m(-2) year(-1) was not much different from the other two fjords. Nevertheless, the observed number of small (<1 cm) juveniles was 18-31 times higher in Sognefjord than in the other two fjords, and it is assumed that the deeper habitat (up to 1300 m) compared to the other fjords (up to 440 and 530 m) is a superior habitat for the early development of P. periphylla.
|
|
| 2. |
- Hermann, Florian M., et al.
(författare)
-
An insulin hypersecretion phenotype precedes pancreatic beta cell failure in MODY3 patient-specific cells
- 2023
-
Ingår i: Cell Stem Cell. - : Elsevier. - 1934-5909 .- 1875-9777. ; 30:1, s. 38-51
-
Tidskriftsartikel (refereegranskat)abstract
- MODY3 is a monogenic hereditary form of diabetes caused by mutations in the transcription factor HNF1A. The patients progressively develop hyperglycemia due to perturbed insulin secretion, but the pathogenesis is unknown. Using patient-specific hiPSCs, we recapitulate the insulin secretion sensitivity to the membrane depolarizing agent sulfonylurea commonly observed in MODY3 patients. Unexpectedly, MODY3 patient -specific HNF1A+/R272C R cells hypersecrete insulin both in vitro and in vivo after transplantation into mice. Consistently, we identified a trend of increased birth weight in human HNF1A mutation carriers compared with healthy siblings. Reduced expression of potassium channels, specifically the KATP channel, in MODY3 0 cells, increased calcium signaling, and rescue of the insulin hypersecretion phenotype by pharmacological targeting ATP-sensitive potassium channels or low-voltage-activated calcium channels suggest that more efficient membrane depolarization underlies the hypersecretion of insulin in MODY3 0 cells. Our findings identify a pathogenic mechanism leading to 0 cell failure in MODY3.
|
|
| 3. |
- Hermann, Florian M., et al.
(författare)
-
An insulin hypersecretion phenotype precedes pancreatic β cell failure in MODY3 patient-specific cells
- 2023
-
Ingår i: Cell Stem Cell. - : Elsevier BV. - 1934-5909. ; 30:1, s. 8-51
-
Tidskriftsartikel (refereegranskat)abstract
- MODY3 is a monogenic hereditary form of diabetes caused by mutations in the transcription factor HNF1A. The patients progressively develop hyperglycemia due to perturbed insulin secretion, but the pathogenesis is unknown. Using patient-specific hiPSCs, we recapitulate the insulin secretion sensitivity to the membrane depolarizing agent sulfonylurea commonly observed in MODY3 patients. Unexpectedly, MODY3 patient-specific HNF1A+/R272C β cells hypersecrete insulin both in vitro and in vivo after transplantation into mice. Consistently, we identified a trend of increased birth weight in human HNF1A mutation carriers compared with healthy siblings. Reduced expression of potassium channels, specifically the KATP channel, in MODY3 β cells, increased calcium signaling, and rescue of the insulin hypersecretion phenotype by pharmacological targeting ATP-sensitive potassium channels or low-voltage-activated calcium channels suggest that more efficient membrane depolarization underlies the hypersecretion of insulin in MODY3 β cells. Our findings identify a pathogenic mechanism leading to β cell failure in MODY3.
|
|
| 4. |
- Sotje, I., et al.
(författare)
-
Trophic ecology and the related functional morphology of the deepwater medusa Periphylla periphylla (Scyphozoa, Coronata)
- 2007
-
Ingår i: Marine Biology. - 0025-3162 .- 1432-1793. ; 150:3, s. 329-343
-
Tidskriftsartikel (refereegranskat)abstract
- Remotely operated vehicle (ROV)-based field studies on the distribution and behaviour of Periphylla periphylla Péron and Lesueur (Ann Mus Hist Nat Marseille 14:316-366, 1809), from three Norwegian fjords have been combined with on-board experiments and morphological and histological studies in order to understand the trophic ecology of this species. Field studies from one of the fjords showed that the zooplankton biomass was negatively related with P. periphylla abundance, indicating a predatory effect. The majority of zooplankton biomass tended to be distributed above the aggregation of P. periphylla, which in turn showed highest abundance at 100-200 m depth. Observation on the orientation of medusae passing the ROV when descending down in the water column at dawn and dusk, showed no consistency with the theory of diel vertical migration. Estimated metabolic demand of P. periphylla indicated a daily predation impact on the prey assemblage of 13% as an average for the fjord. In situ behavioural observations showed that the dominant tentacle posture of large medusae was straight upward, with tentacles extended to the oral-aboral body axis. The hunting mode alternates between ambush and ramming, whereby tentacle posture minimises the water turbulence that may otherwise alarm the prey. The musculature of the tentacles is well developed, with an especially strong longitudinal muscle on the oral side, facilitating fast movement of the tentacle towards the mouth. In addition, ring-, radial-, and diagonal musculatures are also present. The diagonal is probably most important for the corkscrew retraction of the tentacle, used at the moment of prey capture. Results from laboratory experiments show that different body-parts of P. periphylla vary in sensitivity for chemical and mechanical stimuli, including hydrodynamic disturbance and vibration in the surrounding water. Feeding success is facilitated by combining the vibration-sense on the tentacle tips and the marginal lappets, the touch-sense on the tentacle bases and marginal lappets, and a taste control of the captured prey at the mouthlips.
|
|
| 5. |
- Tiemann, Henry, et al.
(författare)
-
Documentation of potential courtship-behaviour in Periphylla periphylla (Cnidaria : Scyphozoa)
- 2009
-
Ingår i: Journal of the Marine Biological Association of the United Kingdom. - 0025-3154 .- 1469-7769. ; 89:1, s. 63-66
-
Tidskriftsartikel (refereegranskat)abstract
- The distribution pattern and nocturnal surface behaviour of the deep-sea medusa Periphylla periphylla in a Norwegian fjord was studied. Medusa abundance, size distribution and condition were determined, using surface collections, net tows and ROV-based video profiles. Only larger, mature medusae reached the surface and aggregated into small groups of both sexes, whereas juvenile medusae remained in deeper waters. Observations on the behaviour and cytology of aggregated medusae suggested a mating strategy. We hypothesize that this behaviour is the by-product of a holopelagic life history, developed in a more oceanic deep environment with low species abundance, as surface aggregation increases the chance of encounter and mating.
|
|
