Light microscope radioautographic study of glycoprotein secretion in the hypothalamic-neurohypophysial system of the rat, after L-fucose-3H injection

Age-associated changes in neuroaxonal transport in the hypothalamo-neurohypophysial system of the mouse

In this study, we investigated age-associated changes in neuroaxonal transport of the hormone vasopressin (AVP) and its associated neurophysin (NPII), from the supraoptic nucleus (SON) of the hypothalamus to the neurohypophysis. C57BL/Icrfat male mice of 6 and 28 months of age were injected in the hypothalamus with L-[35S]cysteine. Animals were killed up to 2.25 h after injection and NPII and AVP from the SON and neurohypophysis were separated using HPLC, and the fractions counted for radioactivity. In the SON, radiolabelled NPII and AVP were first detected after 0.50 h in both young and old mice. There was no significant difference between the age-groups in the incorporation of radiolabel over the time course studied. Radiolabelled NPII in the neurohypophysis was significantly above background after 1.25 h in the young, and after 1.50 h in the old mice. The differences between the two age groups was significant (P = 0.05). Radiolabelled AVP followed a similar trend, but was not significantly above background until 1.50 h in the young and 1.75 h in the old. The differences between the two age groups was on the point of significance (P = 0.056). These results indicate a significant reduction of up to 25% in the rate of axonal transport of neurohypophyseal peptides with advancing age.

Glial and glycoconjugate boundaries during postnatal development of the central nervous system

The localization of glycosylated molecules and glia has been studied during early postnatal development in the mouse central nervous system (CNS) using autoradiographic detection of radiolabeled fucose incorporation, and in sections processed either for histochemistry or immunocytochemistry following binding of labeled lectins or an antibody to glial fibrillary acidic protein. Radiolabeled sugar incorporation, lectin binding of glycoconjugates, and glial labeling all reveal borders between nuclei within the diencephalon, midbrain, and brainstem through the first postnatal week. Glycoconjugate and glial boundaries exist throughout the CNS during pattern formation events, and they also are seen in relation to fine aspects of developing functional organization within individual structures (e.g. segmentation associated with the representation of mystacial vibrissae within the brainstem trigeminal complex). The observation that each of the probes employed in this study fails to label boundary organization during later postnatal times suggests that the distribution and chemistry of the glial/glycoconjugate network are dynamic, and they change in accordance with distinct maturational states of the nervous system.

Molecular organization of prolactin granules. III. Intracellular transport of sulfated glycosaminoglycans and glycoproteins of the bovine prolactin granule matrix

The intracellular transport of sulfated glycosaminoglycans (heparan sulfate and chondroitin sulfate) and glycoproteins of the prolactin (PRL) granule matrix, as well as that of PRL, was studied using a system of double-labeled bovine anterior pituitary slices. [(35)S]sulfate was used to label sulfated macromolecules and L-[(3)H]leucine to label PRL. In membraneless granules (isolated from a PRL granule fraction after solubilization of the membrane with Lubrol PX), sulfated glycosaminoglycans and glycoproteins were considerably labeled after a 15- min pulse, while the hormone was still unlabeled. During the chase incubation, the specific radioactivity of granule PRL and the various complex carbohydrate classes first increased, reaching a peak after approximately 40 min, and then began to decline. After 4 h of chase incubation the radioactivity remaining in granule PRL and sulfated complex carbohydrates was 50-60 percent of that observed at 40 min. Thus, in pituitary mammotrophs a pool of sulfated glycoproteins and glycosaminoglycans is transported intracellularly in parallel with PRL. This finding corroborates the previous conclusion (Zanini et al., 1980 J. Cell. Biol. 86:260-272) that sulfated macromolecules are structural components of the granule matrix. The discharge of labeled PRL and complex carbohydrates from the slices to the incubation medium was also investigated. [(35)S]-glycosaminoglycans and glycoproteins were released at a rapid rate during the first 30-40 min of chase incubation, when PRL granules had not yet attained maximum specific activities. By 40 min, their release tended to level off but the radioactivity accumulating in the incubation medium was still much larger (approximately a fourfold increase) than the losses observed concomitantly in PRL granules. These discharge kinetics contrast with that of [(3)H]PRL, which was not released during the 1st h of chase incubation but then began to accumulate at a high rate in the medium, in parallel with its decrease in granules. Dopamin (5 x 10(-7) M) strongly inhibited the release of labeled PRL but had no detectable effect on the release of labeled glycosaminoglycans and glycoproteins or on the discharge of (35)S-macromolecules as revealed by SDS polyacrylamide gel electrophoresis of incubation media. Thus the releases of PRL and sulfated macromolecules have different kinetics and can be dissociated from each other. These data indicate that much of the flycosaminoglycans and glycoproteins release form pituitary slices originates from sites other than PRL granules, and that at least part of the complex carbohydrates of the PRL granule matrix might not be released with the hormone but rather remains associated with the mammotroph cells after exocytosis.