Evidence that thyroid hormone induces olfactory cellular proliferation in salmon during a sensitive period for imprinting
Evidence that thyroid hormone induces olfactory cellular proliferation in salmon during a sensitive period for imprinting
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DOI：
10.1242/jeb.01143
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发表时间：
2004-09-01
影响因子：
2.8
通讯作者：
Nevitt, GA
中科院分区：
文献类型：
--
作者：
Lema, SC;Nevitt, GA
鲑鱼很早以前就知道会在出生时留下气味印记，但导致嗅觉印记的机制仍然不清楚。印记的时机与血浆甲状腺激素水平的升高有关，可能会对周围嗅觉系统的生长和增殖产生影响。在这里，我们开始测试这一想法，确定实验中升高的血浆3，5，3‘-三碘甲状腺原氨酸(T-3)水平是否会影响5-溴-2’-脱氧尿苷(BrdU)细胞出生测定技术检测到的幼鱼(Oncorhynchus Kisutch)嗅觉上皮细胞的增殖。我们还探讨了在帕尔斯莫尔特转化过程中，甲状腺激素(T-4)的自然波动如何与上皮细胞的增殖有关。在这两项研究中，我们发现BrdU既标记单个有丝分裂细胞，也标记成簇的有丝分裂细胞。与安慰剂对照组相比，人工升高T-3的FISH组嗅觉上皮中BrdU标记细胞的总数显著增加。这种增殖的差异仅限于嗅觉上皮的基底区域，在那里多能前体细胞分化为嗅觉感受器神经元。在T-3和安慰剂治疗中，有丝分裂簇大小的分布与泊松分布显著不同，这表明增殖倾向于非随机的。在Parr-smolt转化过程中，BrdU细胞密度的变化与血浆T-4的自然波动呈正相关。这种关系表明，即使是甲状腺活动的微小变化也可以刺激鲑鱼上皮中神经前体细胞的增殖。综上所述，我们的结果建立了甲状腺激素轴和外周嗅觉系统可测量的解剖学变化之间的联系。
Salmon have long been known to imprint and home to natal stream odors, yet the mechanisms driving olfactory imprinting remain obscure. The timing of imprinting is associated with elevations in plasma thyroid hormone levels, with possible effects on growth and proliferation of the peripheral olfactory system. Here, we begin to test this idea by determining whether experimentally elevated plasma levels of 3,5,3'-triiodothyronine (T-3) influence cell proliferation as detected by the 5-bromo-2'-deoxyuridine (BrdU) cell birth-dating technique in the olfactory epithelium of juvenile coho salmon (Oncorhynchus kisutch). We also explore how natural fluctuations in thyroxine (T-4) relate to proliferation in the epithelium during the parr-smolt transformation. In both studies, we found that BrdU labeled both single and clusters of mitotic cells. The total number of BrdU-labeled cells in the olfactory epithelium was significantly greater in fish with artificially elevated T-3 compared with placebo controls. This difference in proliferation was restricted to the basal region of the olfactory epithelium, where multipotent progenitor cells differentiate into olfactory receptor neurons. The distributions of mitotic cluster sizes differed significantly from a Poisson distribution for both T-3 and placebo treatments, suggesting that proliferation tends to be non-random. Over the course of the parr-smolt transformation, changes in the density of BrdU cells showed a positive relationship with natural fluctuations in plasma T-4. This relationship suggests that even small changes in thyroid activity can stimulate the proliferation of neural progenitor cells in the salmon epithelium. Taken together, our results establish a link between the thyroid hormone axis and measurable anatomical changes in the peripheral olfactory system.