| Popis: |
The mammalian hypothalamo-neurohypophysial complex6 contains a group of well defined neurons whose cell bodies lie in the anterior hypothalamus and whose axons extend into the neurohypophysis; they are responsible for the elaboration of the polypeptide hormones, oxytocin and vasopressin. These neurons fulfill the morphological and functional criteria of neurosecretory cells. The most distinguishing morphological features of these neuron sare that their axon endings (in the neural lobe) about on blood vessel s rather than on other nerve cells, and that their axoplasm usually abounds with dense granules about O.1 to O.3 [i in diameter. These granules were presumed to contain the polypeptide hormones, oxytocin and vasopressin and therefore were termed “neurosecretory granules” (NSG) by morphologists. Since these NSG appeared to move in a proximo-distal direction, it was postulated that the synthesis of the hormones takes place in the perikaryon within the NSG, which then move in a protoplasmic flow along the axon to the region of the nerve endings. It is in this region that, in response to appropriate stimuli, the release of the NSG, or their contents, into the blood stream is thought to occur (2). The rudimentary features of this “neurosecretory process” are represented schematically in Fig. 1. Studies in our own and other laboratories have begun to outline some of the cellular mechanisms involved in the intermediate neurosecretory stages. In this manuscript, we report on some of our recent findings on the biosynthesis, storage, and release of vasopressin. |
