Fukuzawa T, Bagnara J T
Department of Anatomy, College of Medicine, University of Arizona, Tucson 85724.
Pigment Cell Res. 1989 May-Jun;2(3):171-81. doi: 10.1111/j.1600-0749.1989.tb00183.x.
A ventrally localized melanization inhibiting factor (MIF) has been suggested to play an important role in the establishment of the dorsal-ventral pigment pattern in Xenopus laevis [Fukuzawa and Ide:Dev. Biol., 129:25-36, 1988]. To examine the possibility that melanoblast expression might be controlled by local putative MIF and melanogenic factors, the effects of alpha-melanocyte stimulating hormone (alpha-MSH), a serum melanization factor (SMF) from X. laevis or Rana pipiens, and MIF on the "outgrowth" and "melanization" of Xenopus neural crest cells were studied. Outgrowth represents the number of neural crest cells emigrating from cultured neural tubes, and melanization concerns the percentage of differentiated melanophores among the emigrated cells. MSH or SMF stimulate both outgrowth and melanization. The melanogenic effect of Xenopus serum in this system is more than twice that of Rana serum. The actions of MSH and Xenopus serum on melanization seem to be different: 1) Stronger melanization is induced by Xenopus serum than by MSH, and the onset of melanization occurs earlier with Xenopus serum; 2) MSH stimulates melanization only in the presence of added tyrosine; and 3) MSH causes young melanophores to assume a prominent state of melanophore dispersion during culture, while Xenopus serum (10%) had only a slight dispersing effect and not until day 3. A fraction of Xenopus serum presumably containing molecules of a smaller molecular weight (MW less than 30 kDa) than that of a pigment promoting factor reported in calf serum [Jerdan et al.: J. Cell Biol., 100:1493-1498, 1985] produces the same remarkable melanogenic effects as does intact serum. While this fraction stimulates outgrowth, another fraction presumably containing larger molecules (MW greater than 100 kDa) does not. MIF contained in Xenopus ventral skin conditioned medium (VCM) inhibits both outgrowth and melanization dose dependently. When VCM is used in combination with MSH, the stimulating effects of MSH on both outgrowth and melanization are completely inhibited. In contrast, the stimulatory effects of Xenopus serum are not completely inhibited when combined with VCM, although melanization is reduced to approximately 40% that of controls. MIF activity was also found to be present in ventral, but not in dorsal, skin conditioned media of R. pipiens when tested in the Xenopus neural crest system.(ABSTRACT TRUNCATED AT 400 WORDS)
一种位于腹侧的黑化抑制因子（MIF）被认为在非洲爪蟾背腹色素模式的形成中起重要作用[Fukuzawa和Ide：《发育生物学》，129:25 - 36，1988]。为了研究黑素母细胞的表达是否可能受局部假定的MIF和黑素生成因子的控制，研究了α - 黑素细胞刺激素（α - MSH）、来自非洲爪蟾或豹蛙的血清黑化因子（SMF）以及MIF对非洲爪蟾神经嵴细胞“生长”和“黑化”的影响。生长代表从培养的神经管中迁出的神经嵴细胞数量，黑化涉及迁出细胞中分化黑素细胞的百分比。MSH或SMF刺激生长和黑化。在该系统中，非洲爪蟾血清的黑素生成作用是豹蛙血清的两倍多。MSH和非洲爪蟾血清对黑化的作用似乎不同：1）非洲爪蟾血清诱导的黑化比MSH更强，且非洲爪蟾血清引起黑化的起始更早；2）MSH仅在添加酪氨酸的情况下刺激黑化；3）MSH使年轻黑素细胞在培养过程中呈现出显著的黑素细胞分散状态，而非洲爪蟾血清（10%）只有轻微的分散作用且直到第3天才出现。非洲爪蟾血清中一部分可能含有分子量（MW小于30 kDa）比小牛血清中报道的色素促进因子更小的分子，其产生的黑素生成作用与完整血清相同。虽然这一部分刺激生长，但另一部分可能含有较大分子（MW大于100 kDa）的则不然。非洲爪蟾腹侧皮肤条件培养基（VCM）中含有的MIF剂量依赖性地抑制生长和黑化。当VCM与MSH联合使用时，MSH对生长和黑化的刺激作用被完全抑制。相反，非洲爪蟾血清与VCM联合使用时，其刺激作用并未被完全抑制，尽管黑化程度降至对照组的约40%。当在非洲爪蟾神经嵴系统中进行测试时，还发现豹蛙腹侧而非背侧皮肤条件培养基中存在MIF活性。（摘要截于400字）
