| 1. |
- Erlöv, Tobias, et al.
(författare)
-
Automatic Measurements of Diameter, Distension and Intima Media Thickness of the Aorta in Premature Rabbit Pups Using B-Mode Images.
- 2014
-
Ingår i: Ultrasound in Medicine and Biology. - : Elsevier BV. - 0301-5629. ; 40:2, s. 371-377
-
Tidskriftsartikel (refereegranskat)abstract
- To improve cardiovascular research, there is a growing need for arterial characterization in small animals. We developed a method, ARTIC (arterial characterization) for measuring lumen diameter, distension and intima media thickness (IMT). In this study ARTIC was used to automatically characterize the aorta of premature rabbit pups. Automatic measurements were compared with manual measurements, both performed by three observers. Diameter was 769 ± 140 μm (manual) and 766 ± 142 μm (automatic), distension was 35 ± 15 μm (manual) and 40 ± 12 μm (automatic) and IMT was 84 ± 11 μm (manual) and 88 ± 8 μm (automatic) (mean ± standard deviation). The variation in the measured diameter, distension and IMT ranged from 1.1% to 26.0% (manual) and from 1.0% to 9.0% (automatic). The intra-class correlation coefficient ranged from 33.0% to 99.3% (manual) and from 76.9% to 99.6% (automatic). The evaluation revealed that it is feasible to use ARTIC on B-mode images of arteries with small dimensions, which makes it a useful tool for arterial characterization in small animals.
|
|
| 2. |
- Karlsson, Patrik Milton
(författare)
-
Plastidial phosphate transport in plants
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Phosphorus is an essential element for all living organisms and is central to the genetics and energetics of life. Inorganic phosphate (Pi) is recurrently involved in protein regulation and signal transduction but also in energy transfer as a component of the ATP-molecule. When cells and cell organelles commence a plethora of energy-demanding processes associated with ATP hydrolysis to ADP and Pi, a balancing of the Pi content between compartments is crucial to prevent the ATP hydrolysis to be stalled from accumulation of Pi. The transport of Pi via specialized protein(s) is therefore essential for cellular Pi homeostasis since biological membranes are impermeable to Pi (Paper I, III). This thesis shows that the plastid-localized Pi transporter PHT4;2 in Arabidopsis thaliana is nearly restricted to roots during vegetative growth, where it regulates plastid homeostasis by a Na+-dependent Pi efflux. The accumulation of Pi in the root plastids of pht4;2 loss-of function-mutants yields a reduced starch accumulation in roots, which is consistent with the inhibition of starch synthesis by a deficient Pi export. However, the pht4;2 mutants display a 40% increased rosette area and a twofold larger shoot biomass as compared to wild type (WT) plants, indicating an involvement of PHT4;2 in signaling between roots and leaves. The larger leaf area and biomass accounts from an increased cell proliferation in pht4;2 mutants compared to the WT plants. Nevertheless, the cell size and the photosynthetic electron transport rate are similar in all genotypes. (Paper I). Another Pi transporter, PHT4;1, is located in the chloroplast thylakoid membrane of Arabidopsis. By using homology modeling, site directed mutagenesis and functional characterization in Escherichia coli, several residues important for Pi transport and its sodium dependency have been identified in PHT4;1 (Paper II). Rosette area and biomass of the pht4:1 mutants are reduced to 70-80% of the WT plants. Absence of PHT4;1 does not affect the relative electron transport rates, pigment composition, and the expression of photosynthesis-related proteins. However, the ΔpH contribution to the protonmotive force across the thylakoid membrane is significantly higher in the pht4;1 mutants as compared to the WT plants. Non-photochemical quenching kinetics in pht4;1 mutants is transiently increased at the initial phase and declines to WT levels during the plateau phase. Moreover, the Pi content is elevated in the pht4;1 mutants whereas the total Phosphor content is similar to the WT (Paper III). This thesis shows that, through their activity, plastidial Pi transporters play role in plant growth and behavior under different environmental conditions. This is a subject still in its cradle of being understood. The data acquired in this work not only strengthen the importance for a normal daily life of plants, but also the relevance of Pi transporters as a research field.
|
|
| 3. |
- Karlsson, Patrik Milton, et al.
(författare)
-
The Arabidopsis thylakoid transporter PHT4;1 influences phosphate availability for ATP synthesis and plant growth
- 2015
-
Ingår i: The Plant Journal. - : Wiley. - 0960-7412 .- 1365-313X. ; 84:1, s. 99-110
-
Tidskriftsartikel (refereegranskat)abstract
- The Arabidopsis phosphate transporter PHT4;1 was previously localized to the chloroplast thylakoid membrane. Here we investigated the physiological consequences of the absence of PHT4;1 for photosynthesis and plant growth. In standard growth conditions, two independent Arabidopsis knockout mutant lines displayed significantly reduced leaf size and biomass but normal phosphorus content. When mutants were grown in high-phosphate conditions, the leaf phosphorus levels increased and the growth phenotype was suppressed. Photosynthetic measurements indicated that in the absence of PHT4;1 stromal phosphate was reduced to levels that limited ATP synthase activity. This resulted in reduced CO2 fixation and accumulation of soluble sugars, limiting plant growth. The mutants also displayed faster induction of non-photochemical quenching than the wild type, in line with the increased contribution of ΔpH to the proton-motive force across thylakoids. Small-angle neutron scattering showed a smaller lamellar repeat distance, whereas circular dichroism spectroscopy indicated a perturbed long-range order of photosystem II (PSII) complexes in the mutant thylakoids. The absence of PHT4;1 did not alter the PSII repair cycle, as indicated by wild-type levels of phosphorylation of PSII proteins, inactivation and D1 protein degradation. Interestingly, the expression of genes for several thylakoid proteins was downregulated in the mutants, but the relative levels of the corresponding proteins were either not affected or could not be discerned. Based on these data, we propose that PHT4;1 plays an important role in chloroplast phosphate compartmentation and ATP synthesis, which affect plant growth. It also maintains the ionic environment of thylakoids, which affects the macro-organization of complexes and induction of photoprotective mechanisms.
|
|
| 4. |
- Segstedt, Simon, et al.
(författare)
-
Arterial diameter change measurements in premature rabbit pups using B-Mode images
- 2012
-
Ingår i: 2012 IEEE International Ultrasonics Symposium (IUS). ; , s. 922-924
-
Konferensbidrag (refereegranskat)abstract
- To further promote cardiovascular research there is a growing need for arterial characterization on small animals. Arterial wall movement measurements form the basis for most stiffness related parameters. As far as we know, previous reports on lumen diameter change measurements in small animals have required ECG triggering and cross-correlation techniques on the RF-signal using extremely high frame rate. The first aim of this study was to evaluate a novel method, ARTerIal Characterization (ARTIC), for robust diameter measurements in premature rabbit pups using conventional scanning technique (B-mode, 230 Hz). Although blood pressure is important for arterial stiffness measurements, it is often impossible to obtain without affecting the animal setup. However, arterial stiffness can also be assessed by measuring the pressure independent transition strain as recently proposed by Danpinid et al. (Ultrasonics 50, 2010: 654-665). The second aim was to investigate the feasibility of measuring transition strain in premature rabbit pups using the obtained diameter curve. The diameter was 874/82 mu m (mean/SD), CV 2.9%. The distension was 24+/-3 mu m, CV 7.3%. The transition strain was 1.55+/-0.46%, CV 12.8%. In summary, ARTIC can measure arterial diameter and distension in small animals using B-Mode images at regular frame rates. ARTIC also has a low computation time suitable for real-time implementation. Measurements of transition strain on premature rabbit pups are feasible using B-Mode images at regular frame rate. (Abstract)
|
|
