ISSN:
0021-9541
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
The melanocytes of isolated fish scales (Fundulus heteroclitus) immersed in 0.1 M aqueous KCl solution and in deuterated KCl solutions, in which 50-70% of the H2O was replaced by D7O, were observed at 300× magnification while they were subjected to increasing hydrostatic pressure, raised in increments of 1,000 psi in the range up to 16,000 psi. In one series of experiments the temperature was maintained at 20°C (± 0.2°), whereas in the other it was kept at 25°C (± 0.2).Initially, all the melanocytes in the KCl media displayed a contracted, or punctate, form. With increasing pressures, gradually, expansion, or pigment granule dispersal, occurred but the degree of expansion at a given pressure depended upon the percentage of deuteration and the temperature. At 20°C in aqueous medium, total expansion, in which the pigment extended all the way out into the peripheral tips of melanocyte branches, occurred at 8,000-9,000 psi. At lower pressure, the intermediate values, expressed as a percentage of the total, fell along a smooth, slightly sigmoid curve. In the deuterated media, similar curves were obtained, but the pressure levels required to produce a given degree of expansion were significantly higher. Thus, maximum expansion required the imposition of 14,000 psi in the 50% D2O medium and of 16,000 psi in the 70%. Upon decompression, at the end of each experiment, the melanocytes quickly contracted, reaching a completely punctate form within 3-4 minutes.Similar relationships were found at 25°C, except that all the pressure values were significantly higher than those at 20°C. In fact the values for 25°, with 50% deuteration, were very similar to those for 20°, with 70% D2O.The evidence tends to confirm conclusions, previously submitted, namely, that, as expansion occurs, the cytoplasm of the unicellular pigmentary effectors of the fish undergoes a progressive process of solation and that contraction involves a reestablishment of the original firm gel structure. Thus the well known solational effects of high pressure tend to be counteracted by agencies, such as increasing deuteration and temperature, which are known to foster protoplasmic gelations generally.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcp.1040700211
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