Effects of colchicine on release of neurosecretory material from the posterior pituitary gland of the rat

An aromatase-associated cytoplasmic inclusion, the "stigmoid body," in the rat brain: II. Ultrastructure (with a review of its history and nomenclature)

The ultrastructure of aromatase-associated "stigmoid (dot-like) structures," which were detected in a previous study using light-microscopic immunohistochemistry (Shinoda et al.: J. Comp. Neurol. 322:360-376, '92), were examined in the rat medial preoptic region, bed nucleus of the stria terminalis, medial amygdaloid nucleus, and arcuate nucleus by pre- and post-embedding marking with a polyclonal antibody against human placental antigen X-P2 (hPAX-P2) for immuno-electron microscopic analysis. The immunoreactive stigmoid structure was identified as a distinct, non-membrane-bounded cytoplasmic inclusion (approximately 1-3 microns in diameter), which has a granulo-fuzzy texture with moderate-to-low electron density in non-immunostained preparations. It consists of at least four distinct granular and three distinct fibrillo-tubular elements forming a granulo-fibrillar conglomerate. This type of inclusions was formally termed the "stigmoid body" under the electron microscope. The stigmoid body is composed of the outer granulo-fibrillar and inner hyaloplasmic compartments. The immunoreactivity for hPAX-P2 is mainly localized to the former, especially to the low density granulo-fuzzy materials associated with the fibrillo-tubular elements. Identification of the ultrastructure of stigmoid body clarified their prevalence not only in the limbic and hypothalamic regions, but also in sex-steroid-sensitive peripheral tissues (e.g., peripheral sensory ganglia, ovary, testis) by consulting earlier electron-microscopic studies. Reviewing the history and nomenclature of this inclusion body, we reorganized the terminology of related neuronal cytoplasmic inclusions, the terms of which have often been confused, and discussed its functional significance on the basis of the present and previously accumulated data. In conclusion, we emphasized the importance of the stigmoid bodies in the sex-steroid-sensitive neural system because of their large size, high frequency, specific distribution in brains and peripheral tissues, effects of sex-steroids, and immunological and histochemical characteristics of the antibody marking the inclusion. The stigmoid bodies may provide a subcellular site for sex-steroid metabolism in their target tissues and play a critical role in cytosolic modulation of their actions (e.g., by aromatization) prior to their receptor binding.

Peptides and transmitter enzymes in hypothalamic magnocellular neurons after administration of hyperosmotic stimuli: comparison between messenger RNA and peptide/protein levels

In situ hybridization histochemistry and indirect immunofluorescence histochemistry were used to study changes in the expression of vasopressin (VP), oxytocin (OXY), tyrosine hydroxylase (TH), galanin (GAL), dynorphin (DYN) and cholecystokinin (CCK) in hypothalamic magnocellular neurons of the paraventricular (PVN) and supraoptic (SON) nuclei of rats. After prolonged administration of 2% sodium chloride as drinking water (salt-loading), the treatment increased the levels of VP, OXY, TH, GAL, DYN and CCK mRNA in the PVN and SON. The increase in CCK mRNA was, however, proportionally higher in the PVN than in the SON. Within cell bodies of the PVN and SON of salt-loaded rats, a depletion of VP- and OXY-like immunoreactivity (LI) and an increase in TH-LI were seen. In salt-loaded/colchicine-treated rats, a marked decrease in GAL- and DYN-LI, but no specific changes in CCK-LI were observed. Within nerve fibers of the posterior pituitary of salt-loaded rats, a marked depletion of VP-, GAL- and DYN-LI was found. Less pronounced depletion was observed in OXY- and CCK-LI, and no specific changes in TH-LI were seen. The results show that high plasma osmolality induces increased mRNA levels for VP, OXY, TH, GAL, DYN and CCK, presumably indicating increased synthesis, an increased export from cell somata of VP, OXY, GAL and DYN, and a decrease in levels of these peptides in the posterior pituitary, suggesting increased release. The catecholamine-synthesizing enzyme TH, however, which has a cytoplasmic localization and is not released from nerve endings, remains high in the cell bodies and nerve endings during this state of increased activity.

Ultrastructural and cytochemical studies of nucleolus-like bodies in neurons of rat sympathetic ganglia

Intracytoplasmic fibrillar inclusions, generally referred to as nucleolus-like bodies (NLBs) were studied by means of ultrastructural cytochemistry. The structure of these bodies was visualized by several different staining procedures: conventional electron microscopy and preferential staining methods for localization of various proteins including ribonucleoproteins, basic proteins, glycoproteins and phosphorylated proteins. The results of the cytochemical tests indicate that NLBs have an essentially proteinaceous nature. They consist of ribonucleoproteins, basic proteins and glycoproteins but do not contain phosphorylated proteins. These findings suggest that NLBs are, at least partially, of the same nature as nucleoli and coiled bodies. The origin of NLBs and their possible functional role is briefly discussed.

Effects of colchicine on the intraneuronal transport of secretory material prior to the axon: a morphofunctional study in hypothalamic neurosecretory neurons of the rat

The effects of colchicine on neurosecretory neurons of the rat hypothalamus were studied by immunocytochemistry, high-resolution radioautography, and conventional electron microscopy. In control rats, intraneuronal immunocytochemical labeling of vasopressin, oxytocin and somatostatin occurred essentially in the Golgi apparatus, the neurosecretory granules and to a lesser extent, the endoplasmic reticulum. These immunostaining patterns were dramatically modified 24 h after the administration of colchicine: immunoreactive peptides were located in granular or tubular structures accumulated at the periphery of the perikarya, but the Golgi stacks were not immunostained. Two h after the administration of tritiated leucine, quantitative analysis of radioautographic labeling of supraoptic perikarya revealed large amounts of radioactive protein in the Golgi saccules of neurosecretory neurons in control rats, but in the neurons of colchicine-treated rats, radioautographic labeling was mainly located in granular structures accumulated at the periphery of the perikarya, with no significant labeling on the Golgi stacks. Lastly, 3 noteworthy effects of colchicine on the ultrastructural morphological features of these neurosecretory neurons consisted in: (1) a dramatic disorganization of the Golgi complexes, (2) an accumulation of electron-dense proteic material within the lumen of cisternae of both the rough and smooth endoplasmic reticulum and, (3) a marked depolymerization of perikaryal microtubules, specifically those associated with the Golgi stacks. Taken together, these data do not fit the prevailing concept that the colchicine-induced accumulation of secretory material within the perikarya of neurosecretory neurons essentially results from the blockade of axoplasmic transport mechanisms. Instead, they support the idea that the effects of colchicine are related to the inhibition of the intraneuronal transport of newly synthesized secretory material from the endoplasmic reticulum to the Golgi apparatus, suggesting that the microtubules associated with the Golgi stacks are possible sites of colchicine action.

Degeneration of thalamic neurons in "Purkinje cell degeneration" mutant mice. II. Cytology of neuron loss

The cytology of thalamocortical relay neuron degeneration in the ventral medial geniculate nucleus (vMG) of mice homozygous for the autosomal recessive Purkinje cell degeneration (pcd) mutation has been studied by light and electron microscopy. More limited sampling of the submedial and mediodorsal nuclei suggested that cytological alterations in the vMG were typical of all degenerating thalamic nuclei. The number of vMG neurons in pcd mutants was comparable to controls at and prior to postnatal day 40 (P40). By P60 seventy percent, and by P90 approximately 90%, of the original complement of vMG neurons had degenerated in mutant mice. At P30, the general cytological organization of vMG neurons closely resembled that of neurons in littermate (+/+ or +/pcd) controls, but neurons in mutants were distinguished by the presence of small aggregates of fine granules (approximately 9 nm in diameter) that were commonly associated with otherwise normal cisternae of rough endoplasmic reticulum; neither the number nor the size of these granular aggregates increased in older mutants. By P50 cytoplasmic organelles were curiously distributed in more severely affected neurons: large areas of cytoplasm were occupied exclusively by polysomes, while profiles of endoplasmic reticulum and the Golgi apparatus appeared to be reduced. Before frank degenerative changes were apparent (at P50), all classes of synaptic terminals identified in normal mice were found to have made morphologically normal synaptic contacts on mutant vMG neuron dendrites. In contrast to the homologous nuclear complex in the cat, presynaptic dendrites were not apparent in synaptic glomeruli in wild-type or mutant murine vMG. Cytopathological alterations in the neuropil of P50 and older mutants were dominated by degenerating dendritic profiles; there was no evidence that the loss of thalamic neurons in pcd mutants was associated with synaptic agenesis or dysgenesis or the prior or concurrent degeneration of afferent synaptic terminals.

Reversible fine structural changes in the supraoptic nucleus of the rat following intraventricular administration of colchicine

A single low dose (3.5 micrograms or 7.0 micrograms) of colchicine injected intraventricularly into normally hydrated or dehydrated (7 or 4 days) and, subsequently, rehydrated (3 hours) rats caused a number of characteristic changes within the perikarya of the supraoptic nucleus. The temporary slow-down of axonal transport of neurosecretory granulated vesicles (NGVs) and their continued synthesis led to a perikaryal accumulation of NGVs, and changes in their electron-density are considered to be indicative of their continued maturation. In some neurons, the biosynthetic pathway appears to be interrupted or temporarily impaired as evidenced by the accumulation of material of varying electron-density and of granules within the cisternae of the rough ER. An increased number of varying types of lysosomes and phagolysosomes is indicative for the disposal of NGVs within the perikaryon. Most of them are, however, removed through resumption of axonal transport which leads to the reestablishment of pre-experimental fine structural characteristics within approximately 9 days. In the osmotically stressed groups, the fine structural changes are more pronounced but equally reversible.

The influence of age on the hypothalamo-neurohypophyseal system of the mouse: a quantitative ultrastructural analysis of the posterior pituitary

A quantitative ultrastructural study of the posterior pituitary was undertaken. The posterior pituitary is the storage of the hormones vasopressin and oxytocin. Female C57BL/Icrfat mice which were under conditions of normal hydration were sampled at 8 and 32 months of age. There was a slight age-related decline in the volume fraction of cellular components with a corresponding increase in perivascular space. The proportion of neurosecretory endings and swellings showing autophagic activity (Dellman type II Herring bodies) increased significantly in the senescent mouse. The total pituicyte population showed a significant decrease in volume fraction, but with a significant increase in electron-dense types. Of the subcellular parameters examined, only the diameter of the neurosecretory granules showed a significant age-related decrease, the volume fraction remaining unaltered. The animals used in this study were from stocks found to be in a constant oestrus-metoestrus-like state unlikely to obscure changes in pituitary morphology. Over-all, the morphology of the posterior pituitary of the senescent female mouse under physiologically defined resting conditions indicates maintenance of the status quo.

Ultrastructural observations on the hypothalamo-posthypophysical complex of the Brattleboro rat

The hypothalamo-posthypophysial complex of the homozygous Brattleboro rat is characterized by a hyperactivity of its neurons. The neurosecretory fibers, especially in the neurohypophysis, show numerous signs of autophagy and tubular proliferation of the axoplasmic reticulum. These structural alterations, as well as the nematosomes of nucleolus-like bodies encountered in the perikarya, may be related to the chronic hyperactivity of the neurons. They can be reduced by administration of exogenous vasopressin. The numerous liposomes in the pituicytes are paralleled in the neuronal perikarya by a great number of lysosomes. Small dense core vesicles observed in the neurosecretory endings and perikarya may indicate a secretory product distinct from oxytocin and vasopressin. In the homozygous Brattleboro rat, endings of the aminergic type are more numerous than in the normal rat. With respect to the role they may play in the secretory processes, their increase might be secondary to the vasopressin deficiency.

Cytoplasmic inclusions of neurons in the monkey visual cortex (area 19)

Several unusual neuronal inclusions were found in certain cells of the rhesus monkey visual cortex (Area 19): 1. Filamentous bodies, present in the small stellate cells of layer IV, globoid, 0.3-0.6 mum in diameter, consisting of fine 50 A filaments in a hexagonal meshwork. These are often associated with the labyrinthine bodies. 2. Labyrinthine bodies found exclusively in the small stellate cells of layer IV, including certain neurons with dispersed ribosomes. These are 0.4-0.7 mum in diameter and consist of 900 A wide tubes which interconnect with one another. The walls of these tubes are continuous and made up of a sheet or honeycomb lacework of small hexagonal 150 A subunits. 3. This inclusion, an aggregate 0.3-0.7 mum in size, consists of small membrane-bounded vesicles with a single dense granule associated with other non-membrane bound small dense droplets. The inclusions are always associated with the maturing face of the Golgi complex of certain layer IV pyramidal cells; as such, they may be an unusual product of the Golgi apparatus. These observations were confirmed by examination of stereo pairs of electron micrographs. Speculations are made with regard to possible functions for these inclusions.

Subcellular localization of calcium in the mouse hypophysis. I. Calcium distribution in the adeno- and neurohypophysis under normal conditions

Application of the K-pyroantimonate technique combined with glutaraldehydeosmium fixation results in a reproducible intracellular distribution of mineral precipitates in the mouse hypophysis. Control experiments--with chelators and electron probe microanalysis--reveal that these precipitates consist mainly of calcium. Regularly present in the mitochondria, Ca also seems to be stored in the Golgi apparatus of the glandular cells and in the axoplasmic reticulum and the "synaptic" vesicles of the neurosecretory fibres. These structures thus appear able to control intracytoplasmic calcium movements. These observations agree with physiological data showing the existence of an intracellular Ca pool that can be mobilized by specific stimulation. The presence of diffuse precipitates in the pituicytes, together with the existence of gap junctions between them, suggest that these cells regulate the ionic environment of the neurosecretory nerve fibres; in this way, they too might participate in neurohypophysial hormonal release.