| 51. |
|
|
| 52. |
|
|
| 53. |
- Theander, S, et al.
(författare)
-
Cl- transport in the lobster stretch receptor neurone
- 1999
-
Ingår i: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772. ; 167:4, s. 98-285
-
Tidskriftsartikel (refereegranskat)abstract
- Experiments were performed to identify mechanisms underlying non-leakage and non-H+/HCO3--linked transmembrane Cl- transports in the slowly adapting stretch receptor neurone of the European lobster, using intracellular microelectrode and pharmacological techniques. In methodological tests, it was established that direct estimates of intracellular Cl- with ion-sensitive microelectrodes are statistically identical with indirect estimates by means of a GABA method, where 1-2 mM GABA is transforming the cell's membrane voltage into its Cl- equilibrium voltage from which the Cl- concentration is inferred by the Nernst equation. From experiments using sodium orthovanadate and ethacrynic acid, supposed to block primary Cl- pumps, and bumetanide, supposed to block Na-K-Cl co-transporters, it appeared that neither of the two Cl- transport systems exists in the stretch receptor neurone. It could be shown, however, that the cell is equipped with an electroneutral K-Cl co-transporter that (a) is blockable by furosemide in high (Km approximately 350 microM), by 4-acetamido-4'-isothiocyanato-stilbene-2,2-disulphonic acid (SITS) in medium-high (Km approximately 35 microM), and by 4, 4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS) in low (Km approximately 15 microM) doses, (b) is (transiently) activatable by (1 mM) n-ethylmaleimide, (c) is not suppressed by extracellular Rb+ or NH4+, and (d) is not directly coupled to any transmembrane transports of Na+, H+ or HCO3-. From functional tests, with varying transmembrane K+ and Cl- gradients, evidence obtained that the K-Cl co-transporter is able to reverse its transport direction and to adjust its transport rate in a considerable range. As a whole, the results speak in favour of the K-Cl co-transporter being responsible (a) for normally keeping the intracellular Cl- concentration at low levels, for an optimization of the cell's inhibitory system, and (b) for achieving fast transmembrane shifts of K+ (and Cl-), as a means of stabilizing the cell's membrane excitability in conditions of varying extracellular K+ concentrations.
|
|
| 54. |
- Valente-Silva, Paula, et al.
(författare)
-
Effects of Tryptophan Supplementation and Exercise on the Fate of Kynurenine Metabolites in Mice and Humans.
- 2021
-
Ingår i: Metabolites. - : MDPI AG. - 2218-1989. ; 11:8
-
Tidskriftsartikel (refereegranskat)abstract
- The kynurenine pathway of tryptophan (TRP) degradation (KP) generates metabolites with effects on metabolism, immunity, and mental health. Endurance exercise training can change KP metabolites by changing the levels of KP enzymes in skeletal muscle. This leads to a metabolite pattern that favors energy expenditure and an anti-inflammatory immune cell profile and reduces neurotoxic metabolites. Here, we aimed to understand if TRP supplementation in untrained vs. trained subjects affects KP metabolite levels and biological effects. Our data show that chronic TRP supplementation in mice increases all KP metabolites in circulation, and that exercise reduces the neurotoxic branch of the pathway. However, in addition to increasing wheel running, we did not observe other effects of TRP supplementation on training adaptations, energy metabolism or behavior in mice. A similar increase in KP metabolites was seen in trained vs. untrained human volunteers that took a TRP drink while performing a bout of aerobic exercise. With this acute TRP administration, TRP and KYN were higher in the trained vs. the untrained group. Considering the many biological effects of the KP, which can lead to beneficial or deleterious effects to health, our data encourage future studies of the crosstalk between TRP supplementation and physical exercise.
|
|
| 55. |
|
|
| 56. |
- Wennmalm, S, et al.
(författare)
-
Conformational fluctuations in single DNA molecules
- 1997
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 94:20, s. 10641-10646
-
Tidskriftsartikel (refereegranskat)abstract
- Measurement of fluorescent lifetimes of dye-tagged DNA molecules reveal the existence of different conformations. Conformational fluctuations observed by fluorescence correlation spectroscopy give rise to a relaxation behavior that is described by “stretched” exponentials and indicates the presence of a distribution of transition rates between two conformations. Whether this is an inhomogeneous distribution, where each molecule contributes with its own reaction rate to the overall distribution, or a homogeneous distribution, where the reaction rate of each molecule is time-dependent, is not yet known. We used a tetramethylrhodamine-linked 217-bp DNA oligonucleotide as a probe for conformational fluctuations. Fluorescence fluctuations from single DNA molecules attached to a streptavidin-coated surface directly show the transitions between two conformational states. The conformational fluctuations typical for single molecules are similar to those seen in single ion channels in cell membranes.
|
|
| 57. |
|
|
| 58. |
- Yang, SZ, et al.
(författare)
-
Cxcl12/Cxcr4 signaling controls the migration and process orientation of A9-A10 dopaminergic neurons
- 2013
-
Ingår i: Development (Cambridge, England). - : The Company of Biologists. - 1477-9129 .- 0950-1991. ; 140:22, s. 4554-4564
-
Tidskriftsartikel (refereegranskat)abstract
- CXCL12/CXCR4 signaling has been reported to regulate three essential processes for the establishment of neural networks in different neuronal systems: neuronal migration, cell positioning and axon wiring. However, it is not known whether it regulates the development of A9-A10 tyrosine hydroxylase positive (TH+) midbrain dopaminergic (mDA) neurons. We report here that Cxcl12 is expressed in the meninges surrounding the ventral midbrain (VM), whereas CXCR4 is present in NURR1+ mDA precursors and mDA neurons from E10.5 to E14.5. CXCR4 is activated in NURR1+ cells as they migrate towards the meninges. Accordingly, VM meninges and CXCL12 promoted migration and neuritogenesis of TH+ cells in VM explants in a CXCR4-dependent manner. Moreover, in vivo electroporation of Cxcl12 at E12.5 in the basal plate resulted in lateral migration, whereas expression in the midline resulted in retention of TH+ cells in the IZ close to the midline. Analysis of Cxcr4-/- mice revealed the presence of VM TH+ cells with disoriented processes in the intermediate zone (IZ) at E11.5 and marginal zone (MZ) at E14. Consistently, pharmacological blockade of CXCR4 or genetic deletion of Cxcr4 resulted in an accumulation of TH+ cells in the lateral aspect of the IZ at E14, indicating that CXCR4 is required for the radial migration of mDA neurons in vivo. Altogether, our findings demonstrate that CXCL12/CXCR4 regulates the migration and orientation of processes in A9-A10 mDA neurons.
|
|
| 59. |
- Öborn, Ingrid, et al.
(författare)
-
A systems approach to assess farm-scale nutrient and trace element dynamics: A case study at the Ojebyn dairy farm
- 2005
-
Ingår i: Ambio: a Journal of Human Environment. - 0044-7447 .- 1654-7209. ; 34:4, s. 301-310
-
Tidskriftsartikel (refereegranskat)abstract
- A systems analysis approach was used to assess farmscale nutrient and trace element sustainability by combining full-scale field experiments with specific studies of nutrient release from mineral weathering and trace-element cycling. At the Ojebyn dairy farm in northern Sweden, a farm-scale case study including phosphorus (P), potassium (K), and zinc (Zn) was run to compare organic and conventional agricultural management practices. By combining different element-balance approaches (at farmgate, barn, and field scales) and further adapting these to the FARMFLOW model, we were able to combine mass flows and pools within the subsystems and establish links between subsystems in order to make farm-scale predictions. It was found that internal element flows on the farm are large and that there are farm internal sources (Zn) and loss terms (K). The approaches developed and tested at the Ojebyn farm are promising and considered generally adaptable to any farm.
|
|
