Fejér Z, Röhlich P, Szél A, Dávid C, Zádori A, Manzano M J, Vígh B
Department of Human Morphology and Developmental Biology, Semmelweis University, Tüzoltó u. 58, 1094 Budapest, Hungary.
Microsc Res Tech. 2001 Apr 1;53(1):12-24. doi: 10.1002/jemt.1064.
The breeding of birds is expected to solve problems of nourishment for the growing human population. The function of the pineal organ synchronizing sexual activity and environmental light periods is important for successful reproduction. Comparative morphology of the avian pineal completes data furnished by experiments on some frequently used laboratory animals about the functional organization of the organ. According to comparative histological data, the pineal of vertebrates is originally a double organ (the "third" and the "fourth eye"). One of them often lies extracranially, perceiving direct solar radiation, and the other, located intracranially, is supposed to measure diffuse brightness of the environment. Birds have only a single pineal, presumably originating from the intracranial pineal of lower vertebrates. Developing from the epithalamus, the avian pineal organ histologically seems not to be a simple gland ("pineal gland") but a complex part of the brain composed of various pinealocytes and neurons that are embedded in an ependymal/glial network. In contrast to organs of "directional view" that develop large photoreceptor outer segments (retina, parietal pineal eye of reptiles) in order to decode two-dimensional images of the environment, the "densitometer"-like pineal organ seems to increase their photoreceptor membrane content by multiplying the number of photoreceptor perikarya and developing follicle-like foldings of its wall during evolution ("folded retina"). Photoreceptor membranes of avian pinealocytes can be stained by antibodies against various photoreceptor-specific compounds, among others, opsins, including pineal opsins. Photoreceptors immunoreacting with antibodies to chicken pinopsin were also found in the reptilian pineal organ. Similar to cones and rods representing the first neurons of the retina in the lateral eye, pinealocytes of birds possess an axonal effector process which terminates on the vascular surface of the organ as a neurohormonal ending, or forms ribbon-containing synapses on pineal neurons. Serotonin is detectable immunocytochemically on the granular vesicles accumulated in neurohormonal terminals. Pinealocytic perikarya and axon terminals also bind immunocytochemically recognizable excitatory amino acids. Peripheral autonomic fibers entering the pineal organ through its meningeal cover terminate near blood vessels. Being vasomotor fibers, they presumably regulate the blood supply of the pineal tissue according to the different levels of light-dependent pineal cell activity.
鸟类养殖有望解决不断增长的人类人口的营养问题。松果体器官同步性活动和环境光照周期的功能对于成功繁殖至关重要。鸟类松果体的比较形态学完善了一些常用实验动物关于该器官功能组织的实验所提供的数据。根据比较组织学数据，脊椎动物的松果体原本是一个双器官（“第三只眼”和“第四只眼”）。其中一个通常位于颅外，感知直接的太阳辐射，另一个位于颅内，据推测用于测量环境的漫射亮度。鸟类只有一个松果体，大概起源于低等脊椎动物的颅内松果体。鸟类松果体器官从间脑发育而来，在组织学上似乎不是一个简单的腺体（“松果体”），而是大脑的一个复杂部分，由各种松果体细胞和神经元组成，这些细胞和神经元嵌入室管膜/神经胶质网络中。与为了解码环境的二维图像而发育出大的光感受器外段的“定向视觉”器官（视网膜、爬行动物的顶松果体眼）不同，“密度计”样的松果体器官似乎在进化过程中通过增加每个光感受器核周体的数量并形成其壁的卵泡样折叠（“折叠视网膜”）来增加其光感受器膜含量。鸟类松果体细胞的光感受器膜可以被针对各种光感受器特异性化合物的抗体染色。其中包括视蛋白，包括松果体视蛋白。在爬行动物的松果体器官中也发现了与鸡视蛋白抗体发生免疫反应的光感受器。与代表侧眼中视网膜的第一级神经元的视锥细胞和视杆细胞类似，鸟类的松果体细胞具有一个轴突效应过程，该过程在器官的血管表面终止为神经激素末梢，或在松果体神经元上形成含带状突触。在神经激素末梢积累的颗粒小泡上可通过免疫细胞化学检测到血清素。松果体细胞的核周体和轴突末梢也能免疫细胞化学识别兴奋性氨基酸。通过其脑膜覆盖物进入松果体器官的外周自主神经纤维在血管附近终止。作为血管运动纤维，它们大概根据光依赖的松果体细胞活动的不同水平调节松果体组织中的血液供应。
