Effect of Suckling and Parturition on Axonal Transport and Turnover of Neurohypophysial Proteins of the Rat

Norström, Anders; Sjöstrand, Johan

doi:10.1677/joe.0.0520107

Cited by 22 publications

(5 citation statements)

References 19 publications

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“…In normally hydrated animals, most or all of the neurosecretory vesicles are transported at a fixed velocity from the cell body to the axon terminals in the NL [15,16], Immunocytochemical evidence [20] suggests that vesicles may leave the main intra-axonal transport route and become arrested peripherally within dilatations or swell ings. Thus it appears that transport velocities vary along the length of the axon, the nondilated segments of the axon being regions of fast transport while dilatations are areas of slow transport, temporary storage or disposal of vesicles [3,13].…”

Section: Discussionmentioning

confidence: 99%

“…If arrested vesicles are not disposed of within dilata tions, they resume transport by reentering the main tran- sport route, and then continue to move at the same velocity as before. In long-term osmotically stimulated rats, axonal transport of neurohypophysial peptides proceeds at the same velocity as in normally hydrated and osmotically stimulated animals [15,16], but both the amount of material transported along the axons [6,13] and the number of axo nal microtubules [8] are increased. Because of the increased need for and thus elevated release of hormone, storage and disposal of vesicles within dilatations are decreased or even abolished.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Immunohistochemical Investigation of the Magnocellular Peptidergic Hypothalamo-Neurohypophysial System of the Rat Chronically Stimulated by Long-Term Administration of Hypertonic Saline

Peña

et al. 1988

Neuroendocrinology

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The hypothalamic supraoptic (SON) and paraventricular nuclei (PVN), median eminences (ME) and neural lobes (NL) of normally hydrated control rats (group 1), and of rats drinking 2% NaCl for 7 (group 2), 30 (group 3) or 90 days (group 4) were investigated using immunohistochemistry for neurophysins (NP), arginine vasopressin (AVP) or oxytocin (OXY). Animals from the 3 experimental groups showed equivalent decreased levels of immunoreactive NP in the SON and PVN, but the greatest decrease was in the SON. Dendrites of SON and PVN neurons became loaded progressively with immunoreactive NP, AVP and OXY as salt loading proceeded. In rats of group 2, axons leaving the SON and PVN showed a marked depletion of immunoreactive material. The latter was found mainly at the periphery of widely spaced axonal swellings, clearly contrasting with the small and narrowly spaced beads of the neurosecretory axons of control rats. In rats of groups 3 and 4, axons leaving the SON and PVN resembled those of control rats. In the ME of the animals in all experimental groups, the same degree of decrease of immunoreactive NP was observed. In rats of group 3, bundles of axons containing immunoreactive AVP and OXY frequently projected through the ependymal lining of the ME into the third ventricle. In the NL of all experimental animals, a marked decrease occurred in the amount of immunoreactive NP, AVP and OXY. The decrease of immunoreactive AVP, however, was more pronounced in rats of group 2 than in those of groups 3 and 4. The NL of rats in group 4 were approximately 80% larger than those of control rats. Particularly striking in these hypertrophied NL were networks of expanded perivascular basal lamina and large intra-axonal vacuoles. The survival of rats to the long-term salt loading and the changes observed in the hypothalamo-neurohypophysial system indicate that these animals have developed adaptive mechanisms to the salt load.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Immunohistochemical Investigation of the Magnocellular Peptidergic Hypothalamo-Neurohypophysial System of the Rat Chronically Stimulated by Long-Term Administration of Hypertonic Saline

Peña

et al. 1988

Neuroendocrinology

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“…"there is now substantial evidence to support the view that oxytocin and vasopressin are synthesized in separate neurons as well as in separate nuclei; oxytocin mainly in the PV nuclei and vasopressin in the SO nuclei, although there is overlapping between the nuclei." For more detailed discussion and references see Bissett et al (1971), Dyball (1971), Kalimo (1971) and Norstrom (1972).…”

Section: The Hypothalamo-neurohypophyseal Axis A) Neurons Of Thementioning

confidence: 99%

“…The functional significance of the neurosecretory cell as a centre of hypothalamic hormone synthesis is presently widely accepted. For example, the site of origin of the neurohypophyseal hormones oxytocin and vasopressin has long been associated with the supraoptic (SO) and paraventricular (PV) hypothalamic nuclei Bissett Clark and Errington (1971), Dyball (1971), Kalimo (1971), Kalimo and Rinne (1972), Norstrom (1972). However, the precise localization of hypothalamic nuclei responsible for the synthesis of those hormones associated with the control of adenohypophyseal activity remains more uncertain.…”

Section: Introductionmentioning

confidence: 99%

Ultrastructure of Hypothalamic Neurons and of the Median Eminence

Re¹

1974

Can. j. neurol. sci.

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SUMMARYOur light, and electron microscopic (EM) findings within the hypothalamic supraoptic (SO) and paraventricular (PV) nuclei of the normal female rabbit are in agreement with those reported earlier by other investigators for the same nuclei of the dog and rat. The neurons of these nuclei are the hypothalamic synthesis sites of the neurohypophyseal hormones.With the exception of the arcuate nucleus, none of the hypothalamic nuclei associated with the control of adenohypohpyseal function have been studied extensively with the electron microscope. On the basis of our EM findings within the female rabbit hypothalamus, all neurons observed within the preoptic (PO) and suprachiasmatic (SCH) nuclei of the non-mated control animal were morphologically identical to the conventional neuron as described by Peters, Palay and Webster (1970). However, following coitus, castration and laparotomy, many neurons of these nuclei showed subcellular changes that have been repeatedly associated with enhanced protein synthesis. These large ‘neurosecretory’ neurons were usually located near capillaries and characterized by their well developed Rough endoplasmic reticulum (RER) and Golgi profiles, dense populations of mitochondria and lysosomes and by the presence of a homogeneous population of densecore vesicles (DCV) showing a peak distribution of 120-140 nm. Since similar neurons were not observed within the PO and SCH of the normal control rabbit it is suggested that we were observing functional states of the same type of neuron and that these ultrastructural changes occur in response to endocrine manipulation.Two types of neurons described as ‘pale’ and ‘dark’ were observed within the arcuate nucleus of both the control and experimental female rabbit. Ultrastructurally, these neuron types were identical to those described by other investigators for the rat. It has been suggested that the ‘pale’ and ‘dark’ neurons of this hypothalamic nucleus represent functional states of the same type of cell. However, increases in the ratio of ‘dark’ to ‘pale’ neurons as observed within the arcuate nucleus of the rat following castration, were not seen in the rabbit. Similar findings were also not evident within the arcuate nucleus of the female rabbit following coitus.As far as could be determined, all neurons of the ventromedial (VMN) nuclei of both the control and experimental rabbit were morphologically identical to the smaller, conventional type neuron. Certainly, ultrastructural changes similar to those observed within the PO and SCH nuclei of the female rabbit following coitus, castration or laparotomy, were never observed.The basic zonation and subcellular organization of the female rabbit Median Eminence (ME) is similar to that described for other mammalian species. Our EM findings within the external layer of the rabbit ME, however, are not entirely in agreement with the earlier study of Duffy and Menefeef 1965). These investigators reported only one population of DCV within the axon terminals of the rabbit ME external layer. We feel that we have ultrastructural evidence for the presence of at least two distinct populations of DCV within this layer of the rabbit ME. Furthermore, since these vesicle populations occurred within separate axon profiles and terminals, differences in their content and origin are suggested.Certainly, the relationship between releasing factors (RF) and the various populations of DCV observed within the external layer of the mammalian ME is not well established. The smaller (90 nm - 100 nm) DCV we have observed probably contain the catecholamines, while those of larger (120 nm - 140 nm) diameters may well represent the carriers of the RF associated with gonadotropic activity. The latter view is based primarily on our finding or numerous ‘vesicle ghosts’ within the axon terminals abutting the perivascular space (PVS) of portal capillaries of rabbits sacrificed at 10 minutes post-coitus. The mean diameters of 137±14 nm obtained for these ghosts strongly supports the suggested depletion of only the larger of the two DCV populations. Similar changes were not apparent within the axon terminals containing homogenous populations of only the smaller DCV.Unquestionably, the precise hypothalamic synthesis sites for the RF associated with control of adenohypophyseal function, continues to provoke comment. From the results obtained from countless studies that have employed a variety of neuroendocrinilogical techniques, two main hypothalamic centers of RF synthesis have been suggested: a) the medial basal hypothalamus (MBH) or hypophysiotropic area (HTA) and b) the anterior hypothalamus. The ultrastructural studies carried out to date within this laboratoiy are in favour of the latter for the following reasons:1) — the presence of large DCV and ‘vesicle ghosts’ within the external layer of the rabbit ME with diameters similar to those of the large (120-150 nm) DCV synthesized within the PO and SCH nuclei of the same animal in response to coitus, castration and laparotomy.2) — the absence of evidence for the storage of these large DCV within the somata of PO and SCH nuclei, suggesting their immediate transport toward the ME.3) — the absence of any ultrastructural changes within neuron somata of the rabbit arcuate nuclei which might reflect enhanced neurosecretory activity in response to coitus and/or castration.These ultrastructural findings within the rabbit hypothalamus may, therefore, provide the first evidence of a morphological nature for the actual release of RF from their ME storage sites, as well as their synthesis within certain neurons of the anterior hypothalamus.

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“…In addition, the distribution of labelled neurophysin I and I1 in the tissues of the lactating mouse was examined, using whole-body autoradiography (Ullberg, 1954;Cross, Groves & Hesselbo, 1974) to determine the site of uptake. Since stimuli that release oxytocin and vasopressin also release neurophysins (Fawcett et al, 1968;Cheng, Martin & Friesen, 1972;Norstrom, 1972;Johnston et al, 1975), we were particularly interested to see whether, like oxytocin, the neurophysins are specifically taken up by the mammary gland during lactation and the pregnant uterus.…”

Section: Introductionmentioning

confidence: 99%

Clearance from the circulation of the rat and whole‐body autoradiography in the mouse of ¹²⁵I‐labelled neurophysins

Morris

Cross

Johnston

1975

Clin Exp Pharma Physio

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1. The rate of clearance of 125I-labelled porcine neurophysins I and II from the circulation of the rat has an initial fast component followed by a slower component. 2. In the initial phase of clearance the half-life of neurophysin I was 1.50 min (s.e.m. = 0.03) and for neurophysin II was 1.74 min (s.e.m. = 0.05). In the slower phase of clearance the half-life of neurophysin I was 22.6 min (s.e.m. = 2.2) and for neurophysin II was 27.3 min (s.e.m. = 5.8). 3. The first component had a volume of distribution similar to the blood volume and the second component had a volume of distribution similar to the volume of extracellular fuid of the rat. 4. The metabolic clearance rates per 200 g of body weight were 1.94 ml/min (s.e.m. = 0.12) for neurophysin I and 1.29 ml/min (s.e.m. = 0.15) for neurophysin II. 5. Using whole-body autoradiography, the kidney was shown to be the major site of uptake of radioactivity in both virgin female and lactating mice.

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Effect of Suckling and Parturition on Axonal Transport and Turnover of Neurohypophysial Proteins of the Rat

Cited by 22 publications

References 19 publications

Immunohistochemical Investigation of the Magnocellular Peptidergic Hypothalamo-Neurohypophysial System of the Rat Chronically Stimulated by Long-Term Administration of Hypertonic Saline

Immunohistochemical Investigation of the Magnocellular Peptidergic Hypothalamo-Neurohypophysial System of the Rat Chronically Stimulated by Long-Term Administration of Hypertonic Saline

Ultrastructure of Hypothalamic Neurons and of the Median Eminence

Clearance from the circulation of the rat and whole‐body autoradiography in the mouse of ¹²⁵I‐labelled neurophysins

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Effect of Suckling and Parturition on Axonal Transport and Turnover of Neurohypophysial Proteins of the Rat

Cited by 22 publications

References 19 publications

Immunohistochemical Investigation of the Magnocellular Peptidergic Hypothalamo-Neurohypophysial System of the Rat Chronically Stimulated by Long-Term Administration of Hypertonic Saline

Immunohistochemical Investigation of the Magnocellular Peptidergic Hypothalamo-Neurohypophysial System of the Rat Chronically Stimulated by Long-Term Administration of Hypertonic Saline

Ultrastructure of Hypothalamic Neurons and of the Median Eminence

Clearance from the circulation of the rat and whole‐body autoradiography in the mouse of 125I‐labelled neurophysins

Contact Info

Product

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Clearance from the circulation of the rat and whole‐body autoradiography in the mouse of ¹²⁵I‐labelled neurophysins