| 1. |
- Immerstrand, Charlotte, 1974-, et al.
(författare)
-
Altered impedance during pigment aggregation in Xenopus laevis melanophores
- 2003
-
Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 41:3, s. 357-364
-
Tidskriftsartikel (refereegranskat)abstract
- Melanophores are dark-brown pigment cells located in the skin of amphibia, fish and many invertebrates. The skin colour of these organisms is regulated by the translocation of pigment organelles, and the pigment distribution can be altered by external stimuli. The ability to change colour in response to stimuli makes these cells of interest for biosensing applications. It was investigated whether pigment aggregation in Xenopus laevis melanophores can be detected by impedance measurements performed in transparent microvials. The results show that cell attachment, cell spreading and pigment aggregation all resulted in impedance changes, seen particularly at the highest frequency tested (10 kHz). The mechanisms behind the impedance changes were investigated by the addition of latrunculin or melatonin, both of which cause pigment aggregation. The latrunculin-induced aggregation was associated with cell area decrease and filamentous actin (F-actin) breakdown, processes that can influence the impedance. Lack of F-actin breakdown and an increase in cell area during melatonin-induced aggregation suggest that some other intracellular process also contributes to the impedance decrease seen for melatonin. It was shown that impedance measurements reflect not only cell attachment and cell spreading, but also intracellular events.
|
|
| 2. |
- Immerstrand, Charlotte, 1974-
(författare)
-
Biophysical studies of pigment transport in frog melanophores : impedance measurements and advanced microscopy analyses
- 2003
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Small proteins, other molecules and large organelles are frequently transported from one location to another within cells. These transports employ cytoskeletal networks and enable cells to maintain regions with different functions and attain an asymmetrical shape.The aim of this work was to explore biophysical methods for monitoring intracellular transport processes and associated structural changes. For these studies we have used pigment cells, melanophores, from the African clawed frog Xenopus laevis. In response to external stimuli, these cells can change colour by redistributing pigment granules in the cytoplasm.Transparent "cell clinics" equipped with gold electrodes were developed for impedance studies. The results show that impedance measurements at different frequencies not only can be used to monitor cell attachment and spreading, but also events like pigment aggregation. Significant F-actin breakdown and a cell area decrease may explain the impedance decrease seen during latrunculin-induced aggregation. In aggregation induced by melatonin there was, however, a small increase of the cell area, no F-actin breakdown and still lowered impedance, indicating that some other, likely intracellular mechanism is involved. In addition, confocal laser scanning microscopy (CLSM) studies showed that aggregation was associated with an increase in the cell height, more prominent for latrunculin than for melatonin. This height increase did not seem to involve influx of water through aquaporin channels at the cell membrane, or newly formed or remodelled microtubules in the cells.Besides impedance measurements, Image Correlation Spectroscopy (ICS) was applied to analyse pigment aggregation. The study shows for the first time that ICS can be used to analyse aggregation of non-fluorescent particles and suggests that the method may provide new information on the state of aggregation of granules in pigment cells.
|
|
