Characterization of Newly Formed and Aged Granules in the Neurohypophysis

Abstract

Neurosecretory granules from the rat and bovine neurohypophysis were isolated and some of their biochemical and biophysical properties studied. Neurosecretory granules (NSG) from rat neurohypophysis were labeled, in vivo, with [35S]cysteine and isolated on isoosmotic gradients. Whereas 1 day after labeling most of the radioactivity was found in the lower part of the gradient, 35 days later the isotope was also located in the lighter NSG-containing fraction. Different analytical procedures showed that the lighter fraction, both in bovine and rat NSG, contain more subpopulations of neurophysin-like material than the heavier fraction. The first material to be released during stimulation of secretion, in vivo or in vitro, is mobilized from the heavy NSG. Isolation of rat NSG, at different times during and after dehydration of the animals, reveals that the newly synthesized material is found in the heavy NSG-containing fraction. Furthermore, the results indicate that the newly synthesized NSG are more resistant to lysis than the lighter granules. The results are discussed in relation to the maturation and degradation processes of the granule content and to the functional state of the NSG.

Ca2+‐regulated, neurosecretory granule channel involved in release from neurohypophysial terminals

“…Neurosecretory granules (NSG) were purified from bovine neurohypophyses (see Methods). The purity (90–95 %) of the NSG preparation has been confirmed in previous biochemical and morphological studies (Nordmann et al 1979; Nordmann & Cazalis, 1986; Lemos et al 1989). The identity of the proteins included in the NSG preparation was further verified by immunoblotting (Fig.…”

Autoradiographic evidence that transport of newly synthesized neuropeptides is directed to release sites in the X-organsinus gland of Cardisoma carnifex

“…Whether or not release occurs from swellings as well as endings, the smaller volume and larger surface of endings would predict a more rapid turnover of material in them and opportunistic "parking" of granules in available space could account for the autoradiographic observations without requiring that granules remain fixed to a transporter out to the endings (Morris et al 1988). Biochemical changes with aging of granules (Nordmann and Cazalis 1986) that reduce their probability of release could provide an alternative or additional mechanism for the preferential secretion of the most recently synthesized material. Reconciliation of the new with the earlier observations on the neurohypophysis is incomplete.…”

“…Observations from two groups suggest that release occurs from pretcrminal axons and swellings, as well as endings in the neurohypophysis (Morris et al 1988;Nordmann and Dayanithi 1988). Further, biochemical differences between old and new granules have been demonstrated in the neurohypophysis (Nordmann and Cazalis 1986) that could provide an alternative to spatial arguments in explaining selective release of the contents of newer granules.…”

Presynaptic Aspects of Cotransmission: Relationship Between Vesicles and Neurotransmitters

“…This may occur with respect to degree of peptide processing, as mentioned previously. Changes with age have been directly demonstrated with respect to the neurosecretory granules of the neural lobe of the pituitary, where granules that do not secrete their contents are stored and undergo major physical and biochemical changes over a period of days (Nordmann and Cazalis, 1986).…”