The electric charge of pigment granules in pigment cells

Testorf, Martin F.; Lundström, Ingemar; Öberg, Peter

doi:10.1016/s0956-5663(00)00130-5

Cited by 5 publications

(6 citation statements)

References 14 publications

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“…The absence of statistically significant differences between field and control experiments tells us that aggregation of melanophores is not affected by homogenous static magnetic fields with flux densities of 8 and 14 T. More specifically, the charge or speed of granules [Testorf et al, 2000] is apparently too small to give a Lorentz force big enough to alter the aggregation, and so is the strength of the reported paramagnetic centers (free radicals) [Cope et al, 1963]. Microtubules do not seem to reorient in a way affecting the aggregation and this may be explained by high intracellular viscosity.…”

Section: Discussionmentioning

confidence: 87%

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Melanophore aggregation in strong static magnetic fields

Testorf

Öberg

Iwasaka

et al. 2002

Bioelectromagnetics

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Contradicting results can be found in the literature on effects from magnetic exposure to pigment cells. We have studied the influence of strong, static, homogenous magnetic fields of 8 and 14 T on melanophore aggregation during exposure to the field. Melanophores, black pigment cells, in fish are large flat cells having intracellular black pigment granules. Due to large size, high optical contrast, and quick response to drugs, melanophores are attractive as biosensors as well as for model studies of intracellular processes. This is especially true for modeling nerve cells, since melanophores share stem cells with axons. Twenty experiments on black tetra fish fins were carried out in the two magnetic flux densities. The same number of control experiments were carried out in the magnet with the magnetic field turned off. Several factors, such as the degree of maximal aggregation, speed of aggregation, and irregularity of the speed, were examined. The statistical analysis showed no significant field effects on the aggregation, with one exception: the irregularity in aggregation speed in the 8 T field, compared to control. The believed reorientation of the cytoskeleton (microtubules) in the field or the induced Lorentz force on moving pigment granules, did not affect the aggregation.

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Section: Discussionmentioning

confidence: 87%

“…Pigment granules have paramagnetic centers [Cope et al, 1963] and a negative electric charge [Testorf et al, 2000]. Reorientation of microtubules due to their diamagnetic anisotropy has been reported [Vassilev et al, 1982;Bras et al, 1998].…”

Section: Introductionmentioning

confidence: 99%

Melanophore aggregation in strong static magnetic fields

Testorf

Öberg

Iwasaka

et al. 2002

Bioelectromagnetics

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“…Because melanosomes are negatively charged (TESTORF et al, 2001), the translocation ofmelanosomes could alter the charge distribution within the cells, yielding an impedance change, it has been shown that negatively charged cell components can be monitored by the measuring of electrical parameters; the varying amount of negatively charged DNA during the cell cycle was detected by flowing cells across a 1 kHz electric field (SOHN et al, 2000).…”

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confidence: 99%

Altered impedance during pigment aggregation inXenopus laevis melanophores

Immerstrand

Jager

Magnusson

et al. 2003

Med. Biol. Eng. Comput.

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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.

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“…In a similar manner the microtubules may provide tracks for the pigment granules to be transported vertically by motor proteins at the cell centre. Since melanin and the pigment granules are negatively charged (Riley, 1997;Testorf et al, 2001) their repulsion inside the plasma membrane could also facilitate the elevation of the membrane.…”

Section: Introductionmentioning

confidence: 99%

Height Changes Associated with Pigment Aggregation inXenopus laevisMelanophores

et al. 2004

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Melanophores are pigment cells found in the skin of lower vertebrates. The brownish-black pigment melanin is stored in organelles called melanosomes. In response to different stimuli, the cells can redistribute the melanosomes, and thereby change colour. During melanosome aggregation, a height increase has been observed in fish and frog melanophores across the cell centre. The mechanism by which the cell increases its height is unknown. Changes in cell shape can alter the electrical properties of the cell, and thereby be detected in impedance measurements. We have in earlier studies of Xenopus laevis melanophores shown that pigment aggregation can be revealed as impedance changes, and therefore we were interested in investigating the height changes associated with pigment aggregation further. Accordingly, we quantified the changes in cell height by performing vertical sectioning with confocal microscopy. In analogy with theories explaining the leading edge of migrating cells, we investigated the possibility that the elevation of plasma membrane is caused by local swelling due to influx of water through HgCl2-sensitive aquaporins. We also measured the height of the microtubule structures to assess whether they are involved in the height increase. Our results show that pigment aggregation in X. laevis melanophores resulted in a significant height increase, which was substantially larger when aggregation was induced by latrunculin than with melatonin. Moreover, the elevation of the plasma membrane did not correlate with influx of water through aquaporins or formation of new microtubules, Rather, the accumulation of granules seemed to drive the change in cell height.

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The electric charge of pigment granules in pigment cells

Cited by 5 publications

References 14 publications

Melanophore aggregation in strong static magnetic fields

Melanophore aggregation in strong static magnetic fields

Altered impedance during pigment aggregation inXenopus laevis melanophores

Height Changes Associated with Pigment Aggregation inXenopus laevisMelanophores

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