Afferent connections of physiologically identified neuronal complexes in the paraventricular nucleus of conscious Pekin ducks involved in regulation of salt- and water-balance

Summary The afferent connections of the paraventricular nucleus (PVN) of the domestic mallard (Pekin duck), Anas platyrhynchos, were demonstrated by means of microiontophoretic injection of horseradish peroxidase (HRP). To place the HRP injection exactly into the PVN, its location was identified prior to the injection by observing antidiuretic reactions to electrostimulations within the rostral hypothalamus of conscious, hydrated animals. Antidiuresis was induced only when electrostimulation was applied to a distinct hypothalamic area. Two different patterns of antidiuresis were observed: (i) an immediate reduction in rate of production of urine, and (ii) antidiuresis preceded by a period of increase in production of urine. Repeated stimulation of the same site with the same parameters resulted in decreasing antidiuretic effects. At the site where stimulation had elicited the most pronounced antidiuresis of either response type, HRP was injected microiontophoretically.Histological examination after 3–8 days of survival revealed delicate injection sites located exclusively in the periventricular portion of the PVN. Adjacent to the dorsal portion of the PVN retrogradely labeled tanycytes and intraependymal neurons were scattered in the ventricular wall. As demonstrated in neurohistological and electron-microscopic investigations, this ependymal region exhibits a particular arrangement of tanycytes and small neurons (10–15 m in diameter), some of which belong to the neurosecretory type.Additional HRP-labeled neuronal perikarya afferent to the PVN were demonstrated in the contralateral PVN, and on the ipsilateral side in the lateral septum, lateral hypothalamic area and locus coeruleus. Within the nuclei of the solitary tract, stained nerve cells were found ipsilateral as well as contralateral to the injection site.Several of the neurons demonstrated may be considered as candidates for the transmission of signals originating from various receptive structures relevant for the control of avian salt- and water-balance. The physiological results conform to the concept that neurons of the PVN influence urine formation by controlling the release of arginine-vasotocin (AVT). Evidence that suggests additional modes of control exerted by these neurons in salt- and water-balance is presented.Supported by grants from the Deutsche Forschungsgemeinschaft (Ko 758/1; Si 230/4-4)Portions of these results were presented on the occasion of the 54th Meeting of the Deutsche Physiologische Gesellschaft (Korf et al. 1981 a) and the 76th Meeting of the Anatomische Gesellschaft (Korf et al. 1981 b)     

Use of [3H] Spiperone for Labelling Dopaminergic and Serotonergic Receptors in Bovine Caudate Nucleus

Abstract— [³H]Spiperone binding has been used to study neurotransmitter receptors in bovine caudate nucleus in displacement and saturation binding experiments. Displacement curves for several antagonists are biphasic and can be analysed into contributions from dopaminergic and serotonergic sites. Antagonist binding at each class of sites follows the simple mass action equations for binding at a homogeneous set of sites (slope factors close to unity). Agonist displacement curves also indicate complex behaviour, but agonist binding to the dopaminergic sites alone exhibits heterogeneous properties (slope factors less than unity). Saturation binding experiments have been conducted on each class of site, defining dopaminergic binding of [³H]spiperone as that binding displaced by 0.1 m m -dopamine and serotonergic binding as that displaced by 0.3 μ m -mianserin. In each case, a single class of binding sites was detected: the binding parameters derived in this way have been used to calculate the proportions of the two classes of binding site observed in displacement experiments. Good agreement was obtained between calculated and observed values.     

Catecholamine-Sensitive Guanylate Cyclase from Human Caudate Nucleus

Abstract: Partial purification of soluble guanylate cyclase on DEAE-Sephacel yields two separate peaks of guanylate cyclase activity. After 10-fold purification of the soluble enzyme, guanylate cyclase is markedly inhibited by micromolar concentrations of dopamine (I₅₀= 0.2 μm). Dopamine inhibition is observed whether the reaction is conducted with Mn²¹ or with Mg²⁺, under atmosphere or N₂(g), and using enzyme from either peak from the DEAESephacel column. Other catecholamines also inhibit partially purified guanylate cyclase with an order of potency at 1 μm of: dopamine =l -DOPA > norepinephrine = isoproterenol = adrenochrome > epinephrine. The structural requirements for inhibition are two free hydroxyl groups on the phenyl ring and an ethylamine side chain. Dopamine also inhibits the Triton X-100-solubilized microsomal guanylate cyclase after partial purification on DEAESephacel. Neither chlorpromazine, propranolol, nor phentolamine at 20 μm effectively block the dopamine inhibition of partially purified soluble guanylate cyclase. Micromolar concentrations of the reducing agents dithiothreitol and glutathione also inhibit partially purified guanylate cyclase, but unlike these agents, catecholamines can inhibit whether added in the reduced or the oxidized forms. Inhibition of enzyme activity by micromolar concentrations of dopamine, adrenochrome, or dithiothreitol is rapidly reversed by dilution and the dopamine inhibition is competitive with MgGTP. Inhibition does not appear to involve covalent binding or to result from the ability of catecholamines to reduce the concentrations of oxygen or free radicals in solution.     

Subsurface cisterns in paraventricular nuclei of the hypothalamus of the rat

Summary Structures identified as subsurface cisterns (SSC's) were found in neurons of the paraventricular nuclei of the rat hypothalamus. They appeared as cytoplasmic organelles consisting most often of stacks of parallel cisterns apposed to the neuronal plasmalemma. These SSC's were located in the interneurons of the parvocellular system, but not in neurosecretory cells and glial cells. SSC's were seen at zones of cytoplasm apposed to neuronal or glial cell processes, showing in some instances specific relationships with synaptic areas.The morphological features of these SSC's are described, and their possible functional significance is briefly discussed.     

A critical evaluation of the relationship between the presynaptic network,synaptic vesicles and dense projections in central synapses

Summary Synapses of the oculomotor nucleus of Echidna have been examined ultrastructurally with the aim of integrating data obtained from osmicated and nonosmicated PTA stained material. Particular emphasis has been laid on the relationship between the synaptic vesicles of the osmicated material and the presynaptic network and vesicular grid of the PTA material. This relationship has been explored qualitatively by examining osmicated material of varying qualities of fixation. Such material contains dense projections in addition to synaptic vesicles, and various vesicular network appearances. A variety of measurement techniques have shown that the PTA network is characterised by reticular strands, spaces, and regular hexagonal units smaller than vesicles, these observations prompting the formulation of a vesicle-network coincidence model of the presynaptic terminal. This model has been tested by tracing the profiles of vesicles within the PTA network and comparing their size and shape frequency distributions with those of osmicated synaptic vesicles. The distributions have been found to be essentially similar, suggesting that vesicles can be located within the network, and that the hexagonal network units are formed only in the presence of an underlying vesicular matrix.Additionally, the following points have emerged: 1) the dense projections in the two types of material appear to be equivalent; 2) a loose correlation exists between dense projections and vesicles in osmicated terminals, increase in the area of the dense projections being associated with a decrease in the area of the vesicles; 3) network and dense projection units are similar. In view of the similarity between network and dense projection units, the demonstrated vesicular basis of the network raises the question of whether dense projections are entirely independent structures, or whether they depend in part for their existence on the nearby presence of synaptic vesicles.This work was supported by the Arnold Yeldham and Mary Raine Research Foundation of the University of Western Australia and by the Australian Research Grants Committee and the Nuffield Foundation     

Cerebrospinal fluid-contacting neurons,ciliated perikarya and “peptidergic” synapses in the magnocellular preoptic Nucleus of teleostean fishes

Summary The magnocellular preoptic nucleus of fishes (Anguilla anguilla, Amiurus nebulosus, Cyprinus carpio, Carassius auratus, Ctenopharyngodon idella, Cichlasoma nigrofasciatum) has been studied by light and electron microscopy.Two kinds of neurons were found: a) large, electron-dense, Gomori-positive cells with moderate acetylcholinesterase (AChE) positivity which contain granulated vesicles of 1400 to 2200 Å (in average 1600 to 1800 Å), and b) small, strongly AChE-positive, electron-lucent neurons containing granulated vesicles of 900 to 1200 Å. The nerve cells are supplied with axo-somatic and axo-dendritic synapses. These are formed by axon terminals containing either 1. synaptic vesicles of 500 Å, or 2. synaptic vesicles of 500 Å and dense-core vesicles of 600 to 800 Å, or 3. synaptic vesicles of 600 Å and granulated vesicles of up to 1100 Å, or 4. synaptic vesicles of about 400 Å and granulated vesicles of up to 1800 Å. The presence of peptidergic and numerous other synapses shows the complexity of the organization and afferentation of the magnocellular preoptic nucleus.In the eel, both types of nerve cells form dendritic terminals within the cerebrospinal fluid (CSF). These CSF contacting dendrites are supplied with 9×2+0 cilia. In the other species investigated, only some large neurons build up intraventricular endings. The ependymofugal process of the CSF contacting neurons enters the preoptic-neurohypophysial tract.Perikarya of both the large and the small cells may give rise to single, paired or multiple 9×2+0 cilia extending into the intercellular space. The number of CSF contacting neurons is reciprocal to the number of perikarya with intercellular cilium. These latter cells may represent modified, more differentiated forms of the CSF contacting neurons. We think that atypical cilia protruding into the intercellular space may have the same significance for the intercellular fluid as the cilia of the intraventricular dendrites of the CSF contacting neurons for the CSF.Dedicated to Prof. Dr. W. Bargmann on the occasion of his 70th birthday.     

Light and electron microscopical study of Nosema eurytremae

A nuclear-polyhedrosis virus (NPV) of the silkworm, Bombyx mori, which forms an icosahedral inclusion body, was transmitted to larvae of the rice stem borer, Chilo suppressalis. Serial passages of Bombyx NPV in the alternate host by injecting the supernatant of diseased hemolymph produced inclusion bodies with cuboidal and other shapes that differed from the original shape formed in Bombyx. These different shapes increased with times of passages, and after the twelfth passage, only cuboidal inclusion bodies were formed. The icosahedral inclusion bodies in B. mori and the cuboidal inclusion bodies in C. suppressalis occluded singly enveloped virions of the same size (350 × 75 nm), but the cuboidal inclusion bodies contained only a few virions and a large number of membraneous spherical structures. The formation process of the cuboidal inclusion body differed from that of the icosahedral. At first, irregularly branched inclusion bodies containing “vacant” spaces appeared in the infected nuclei. The bodies grew larger with the deposition of protein in the spaces between the branches, and this was accompanied with the occlusion of a large number of membraneous structures formed in the vicinity of the inclusion bodies, which became cuboidal in shape.     

LAUDERIA ANNULATA—A MARINE CENTRIC DIATOM WITH AN ELONGATE BILOBED NUCLEUS1

Lauderia annulata Cleve is probably unique among marine centric diatoms in possessing an elongate dumbbell-shaped nucleus. A lobe at, each end of the nucleus lies adjacent to each valve during interphase and each lobe resembles a typical eucaryotic nucleus. The central portion of the thin strand, which passes through the vacuole connecting the two lobes is Feulgen positive and is nuclear membrane bounded. A group of micro tubules occurs in this strand clustered excentrically between, the nuclear membrane and the tonoplast. Evidence for the coordinated functioning of both nuclear lobes is suggested, by the aggregation of chloroplasts around, both lobes when shade-adapted cells are exposed, to intense white or blue (400–500 nm) light.     

大鼠尾壳核衰老变化定量分析：Ⅱ.多巴胺（DA）系统

本实验结果表明:衰老大鼠(26—27月龄)尾壳核多巴胺(DA)神经末梢膨体较成年组(3—4月龄)明显减少,而单个膨体内DA含量较成年组显著增多,提示纹状体DA系统在衰老过程中可能具有一定的代偿机制。本文对其意义进行了讨论。     

The endosperm development and the variations of structures of embryo sacs: unravelling the low fecundity of Zephyranthes candida (Amaryllidaceae)

To unravel a low fecundity in Zephyranthes candida (Lindl.) Herb., the development of the endosperm was studied using conventional paraplast section technique. The results show that the endosperm develops normally and comprises four major stages viz. syncytial, cellularization, differentiation and maturation. Both proliferation of antipodal cells and their close contact with the primary endosperm nucleus were observed, which should favor transportation of nutrients and accelerate development of embryo and endosperm. In Z. candida, at least four events of nuclear migration occurred during the course of embryogenesis and endosperm development. The 12.7% structurally and functionally abnormal ovules, along with the 22.3% collapsed and aborted ovules observed accounts for the low fecundity to some extent.