Storage and secretion of neurohypophyseal hormones

1968 ◽  
Vol 46 (2) ◽  
pp. 335-345 ◽  
Author(s):  
Frank S. LaBella
Keyword(s):  
Gradient Centrifugation ◽  
Cholinergic Neurons ◽  
Chemical Extraction ◽  
Nerve Terminals ◽  
Posterior Pituitary ◽  
Highly Active ◽  
Pituitary Glands ◽  
Posterior Pituitary Gland

Investigations in the author's laboratory which bear upon several fundamental aspects of the mammalian neurohypophysis were reviewed and related to well-established or currently accepted concepts, (a) The separation of vasopressin-rich from oxytocin-rich neurosecretory granules (NSG) from posterior pituitary homogenates was achieved. (b) The hormone and amino acid composition of isolated NSG was found to be almost identical to that of the van Dyke protein, prepared by chemical extraction of posterior pituitary glands, indicating that the protein is synonymous with the NSG carrier protein to which vasopressin (VP) and oxytocin (OT) are bound. (c) Pinched-off nerve terminals (neurosecretosomes) were isolated from homogenates by centrifugation and shown to be metabolically and morphologically intact. The hexosemonophosphate shunt was highly active in the nerve terminals, where the peptide hormones are stored and secreted, but not in the cell bodies within hypothalamic nuclei, where they are synthesized. (d) Neurosecretosomes relatively enriched in VP were separated from those rich in OT by density-gradient centrifugation, providing support for the concept that a given neurohypophyseal neuron stores and secretes only one of the hormones. (e) Electron microscopy indicated that microvesicles, about 50 mμ in diameter, and called "synaptic" vesicles by some workers, are derived from membranes of depleted NSG and are not of the type that contain neurotransmitter. (f) Acetylcholine (ACh), choline acetyltransferase, and acetylcholinesterase were identified in the posterior pituitary gland and are present in about the same proportions but 1/5 to 1/10 the activity as in whole brain. ACh was found in the neurosecretosome and microvesicle centrifugation fractions. The three cholinergic components in the posterior pituitary are believed to be constituents, not of neurosecretory nerve endings which contain VP or OT, but of specific cholinergic neurons whose role in neurohypophyseal physiology remains to be elucidated. (g) VP and OT are generally released together from the gland in vivo and from posterior pituitary tissue or NSG in vitro. However, exceptions can occur both in vivo and in vitro in which one of the hormones is apparently released exclusively. Studies on the release of VP and OT in vitro show that the NSG–hormone complex is more labile in the case of OT than of VP, an observation that suggests a molecular basis for numerous in vivo findings in which a preponderance of OT over VP is secreted in response to a wide variety of stimuli.

IN VITRO STUDIES OF THE RELEASE MECHANISM FOR VASOPRESSIN IN RATS

1966 ◽  
Vol 53 (4) ◽  
pp. 644-654 ◽  
Author(s):  
N. A. Thorn
Keyword(s):  
Release Mechanism ◽  
Posterior Pituitary ◽  
High Concentration ◽  
Vasopressin Release ◽  
Pituitary Glands ◽  
Posterior Pituitary Gland ◽  
Stimulation Period ◽  
Releasing Effect

ABSTRACT A study was made of the release of vasopressin activity from groups of isolated posterior pituitary hemilobes of rats, incubated in media with different ionic compositions and with different drugs added to the medium. Nicotine, amyl nitrite and ATP, which have been reported to cause a large in vivo release of hormone had no significant releasing effect in vitro. Caffeine too did not cause any release of hormone activity. About 5% of the vasopressin activity extractable from the isolated posterior pituitary hemilobes was released during stimulation with a high concentration of potassium in the medium. No more than this percentage could be mobilized during such a stimulation, even after further subdivision of the posterior pituitary glands, prolongation of the stimulation period or after increasing the calcium concentration in the medium five-fold. No release into the medium of vasopressin binding protein could be demonstrated during stimulation of vasopressin release. The results seem to be in agreement with the hypothesis that the release of vasopressin is intimately associated with arrival of impulses to the nerve endings in the posterior pituitary gland and that it takes place from a small pool of readily available hormone, presumably by dissociation of the hormone from the carrier protein.

SUCKLING IN THE GUINEA-PIG: THE EFFECTS OF PASSIVE IMMUNIZATION WITH AN ANTISERUM TO OXYTOCIN

1981 ◽  
Vol 90 (2) ◽  
pp. 237-244 ◽  
Author(s):  
I. C. A. F. ROBINSON ◽  
J. A. PARSONS
Keyword(s):  
Mammary Gland ◽  
Passive Immunization ◽  
High Titre ◽  
Immune Serum ◽  
In Vitro Experiments ◽  
Posterior Pituitary ◽  
Milk Ejection ◽  
Posterior Pituitary Gland

Lactating guinea-pigs were passively immunized with an antiserum to oxytocin of high titre, specificity and avidity. Single i.v. injections of 0·1–0·4 ml antiserum produced high titres which decayed slowly (half-life ≃7 days). Passively administered antiserum was effective in vivo; the clearance of exogenous oxytocin from plasma was greatly slowed in immunized animals. Passive immunization with 0·4 ml antiserum reduced milk transfer to the litter during suckling episodes of 10 min, and overall litter growth rates were significantly decreased. Non-immune serum was without effect. Plasma neurophysin levels showed the same large rises during suckling in immunized animals, indicating that neurohypophysial activation was unimpaired. Despite the presence of high titres of antiserum, some milk transfer still occurred at milk ejection. In-vitro experiments showed that more than 25% of oxytocin remained free 20 s after mixing with plasma taken from passively immunized animals. It is probable that the antiserum in the circulation was unable to bind all the oxytocin released from the posterior pituitary gland before it reached the mammary gland.

Effect of Estrogen on Melanocortin-3 Receptor mRNA Expression in Mouse Pituitary Glands in vivo and in vitro

2004 ◽  
Vol 80 (3) ◽  
pp. 143-151 ◽  
Author(s):  
Ryusei Matsumura ◽  
Sakae Takeuchi ◽  
Sumio Takahashi
Keyword(s):  
Mrna Expression ◽  
Receptor Mrna ◽  
Pituitary Glands ◽  
Mouse Pituitary

In-vivo and in-vitro secretion of prolactin by lactating rat adenohypophyses as a function of intracellular age

1984 ◽  
Vol 101 (1) ◽  
pp. 27-32 ◽  
Author(s):  
F. Mena ◽  
G. Martínez-Escalera ◽  
C. Clapp ◽  
C. E. Grosvenor
Keyword(s):  
Pituitary Gland ◽  
Incubation Period ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Polyacrylamide Gel ◽  
Pituitary Glands ◽  
H 26

ABSTRACT Adenohypophysial prolactin of lactating rats was pulse-labelled by [3H]leucine injected i.v. at the time of removal of the pups. The [3H]prolactin concentration in the pituitary gland, analysed by polyacrylamide-gel electrophoresis, progressively fell as the time from labelling to removal of the pituitary gland increased from 8 to 24 h, which suggests that there was a loss of hormone as it aged within the gland. Suckling effectively provoked the depletion–transformation of total and [3H]prolactin (extracted at pH 7·2) when applied after 8 h but not when applied after either 16 or 24 h after removing the pups. In rats whose pups were removed for 8 h, suckling also depleted–transformed [3H]prolactin labelled 4 h, but not that labelled 1 h before suckling. The pituitary glands of other lactating rats were labelled with [3H]leucine injected i.v. at various times before removing the glands and incubating them in medium 199. The secretion into the medium of [3H]prolactin labelled either 4, 8, 16 or 24 h beforehand was maximal during the first 30 min then declined from 30 to 240 min of incubation. However, secretion of prolactin labelled 1 h and 10 min beforehand reached a maximum after 0·5–1 h and 2 h of incubation respectively, then remained constant during the remainder of the 4-h incubation period. The total 4-h secretion of [3H]prolactin was greatest (65% of preincubation concentration) from those glands labelled 4 h before in contrast to those labelled 10 min (15%) or 1 (38%), 8 (34%), 16 (18%) or 24 h (26%) before incubation. Taken together, these data suggest that prolactin synthesized 4 h earlier is more likely to be released in response to physiological stimuli than is more recently formed prolactin or prolactin which has remained in the pituitary gland for 16 h or longer. J. Endocr. (1984) 101, 27–32

The centriolar complex isolated from starfish spermatozoa

1981 ◽  
Vol 49 (1) ◽  
pp. 33-49 ◽  
Author(s):  
R. Kuriyama ◽  
H. Kanatani
Keyword(s):  
Gradient Centrifugation ◽  
Sucrose Density Gradient ◽  
Microtubule Assembly ◽  
High Concentration ◽  
Microtubule Organization ◽  
Sucrose Density Gradient Centrifugation ◽  
The Difference ◽  
Distal Centriole

Centrioles from spermatozoa of the starfish, Asterina pectinifera, were isolated and partially purified by solubilization of chromatin followed by sucrose density-gradient centrifugation. The ultrastructure of the isolated centriolar complex was investigated in whole mount preparations by electron microscopy. The complex unit was composed of a pair of centrioles and a pericentriolar structure, which associated with the distal end of the distal centriole by 9 spoke-like satellites extending radially to a marginal ring. Each satellite bifurcated at a dense node forming 2 fan-like shapes with a periodic striated pattern. The tubular structure of the centrioles easily disintegrated, leaving the pericentriolar structure or axonemal microtubules intact. The distal centriole in a spermatozoon served as an initiating site for flagellar microtubule assembly; that is, a number of “9 + 2′ axonemal tubules were observed adhering just beneath the distal end of the basal body. In experiments in vitro, polymerization of microtubule proteins purified from porcine brain was initiated by the structure at the ends of both proximal and distal centrioles, but not from the satellites or the marginal ring. Also, few if any microtubules were formed from the sides of each centriole, even in the presence of a high concentration of exogenous tubulin. On the other hand, centrioles of spermatozoa, when they were in mature ooplasm, could initiate the formation of sperm asters by microtubules. Therefore, centrioles in spermatozoa seem to be able to initiate microtubules in a 2 ways. A possible explanation of the difference between the 2 types of microtubule organization in vivo, i.e. in the sperm cell itself and in the ooplasm, it discussed.

scholarly journals Senescence of canine biotinylated erythrocytes: increased autologous immunoglobulin binding occurs on erythrocytes aged in vivo for 104 to 110 days

Blood ◽  
1993 ◽  
Vol 82 (11) ◽  
pp. 3469-3473 ◽  
Author(s):  
JA Christian ◽  
AH Rebar ◽  
GD Boon ◽  
PS Low
Keyword(s):  
Life Span ◽  
Cell Sorting ◽  
Gradient Centrifugation ◽  
Magnetic Cell Sorting ◽  
Autologous Plasma ◽  
Low Degree ◽  
La Jolla ◽  
Immunoglobulin Binding

Abstract We have evaluated senescence related changes in canine red blood cells (RBCs) using the biotinylation system, where RBCs are labeled in vivo with biotin at the beginning of their life span, and retrieved from circulation on immobilized avidin at the end of their life span. This approach avoids the controversial use of density gradient centrifugation to collect presumably old RBCs. Furthermore, the dog is an appropriate model for human RBC senescence because it has a low degree of random RBC loss and a similarly long RBC life span (approximately 110 days). Two dogs had 97% to 100% of their circulating RBCs biotinylated by infusion of N-hydroxysuccinimido biotin (Clontech, Palo Alto, CA; Calbiochem, La Jolla, CA) dissolved in dimethyl sulfoxide. At postbiotinylation days 104 and 107 for one dog and day 110 for the other dog, biotinylated RBCs were isolated by magnetic cell sorting and analyzed for the presence of autologous IgG using 125I- labeled sheep-antidog IgG (SAD IgG). On all 3 days, there were at least three times more SAD IgG molecules per RBC on senescent biotinylated RBCs than on control (unfractionated) RBCs (day 104: 11,677 v 3,399; day 107: 6,710 v 2,115; day 110: 6,042 v 1,838 molecules of SAD IgG per senescent v control RBC). Furthermore, it is unlikely that an immune response to the conjugated biotin had been elicited, because fresh in vitro biotinylated RBCs that were incubated in autologous plasma (taken after exposure to circulating biotinylated RBCs for 113 days) and then exposed to the SAD IgG showed no increase in antibody binding over control (non-biotinylated) RBCs (1,431 v 1,378 cpm/10(8) biotinylated v control RBCs; P > .20). These results suggest that senescence of canine biotinylated RBCs is characterized by binding of autologous IgG and that antibiotin antibodies do not contribute to this process.

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