Inelastic neutron scattering measurements and Ab initio calculations of hydrogen in single-crystal palladium

Using a single-crystal sample of PdH, we have measured the inelastic form factor for exciting the proton from its ground state to various excited states as a function of crystal orientation. Because of the anharmonicity of the potential well which splits otherwise degenerate states, each inelastic form factor could be measured individually. Agreement between theory and experiment is excellent, both with regard to the transition energies and to the modulation of the intensity, giving confidence in the quantum treatment of the proton and hence in the use of the model to predict other properties of the system.

The asymmetry of the habenular nuclei of female and male frogs in spring and in winter

Male and female frog brains stained according to the Nissl method and cut transversely, 15 microns thick, at the level of the habenular nuclei, were investigated in spring and winter. Right and left habenular nuclei were examined. The volume and the standard deviations were calculated in each portion of the habenular nuclei investigated. The frog habenula consists of a single cell group: one on the right and two on the left side of the brain which differ, among themselves, both in the volumes of the neuropil and of the cellular ring. Functional corollaries of this striking asymmetry are still unknown. However, female and male frogs' habenular nuclei are longer and larger in spring--when frogs are sexually active--than in winter. We propose that structural brain asymmetries may be sex linked and may be induced by steroid hormonal effect in the central nervous system.

Lithium decreases retinal melatonin levels in the frog

The effect of the acute i.p. administration of lithium chloride (1 mg/kg) and of haloperidol (1 mg/kg) on retinal melatonin levels was studied in light-adapted and dark-adapted frogs of the species Rana esculenta. Two hours following drug administration, animals were killed by decapitation and a single retina from each frog was collected and homogenized in 1 ml of chilled 0.1 N HCl. After centrifugation, the pH of the supernatant was adjusted to 7.0. Melatonin was extracted by diethylether and assayed by double antibody radioimmunoassay (RIA). Lithium induced a significant decrease of retinal melatonin levels both in light-adapted (P less than 0.006) and in dark-adapted (P less than 0.01) animals, whereas no change was observed after haloperidol treatment. These results suggest that the scleral aggregation of pigment granules induced by lithium in the frog retina is not mediated by a stimulation of melatonin synthesis.

Substance P and hydra: an immunohistochemical and physiological study

1. The distribution of substance P-like immunoreactivity was studied in Hydra attenuata using the peroxidase-antiperoxidase technique. 2. Positive immunoreactivity was observed in ectodermal nerve cells and fibers as well as in nematoblasts at various stages of differentiation. 3. Administration of synthetic substance P to regenerating hydra did not affect regeneration rates. Exogenous substance P administration stimulated tentacle contraction and nematocyst displacement within battery cells. 4. It is suggested that substance P acts on the contractile apparatus of Hydra tissues.

A horseradish peroxidase study of the olfactory system of the frog, Rana esculenta

The olfactory system of the frog Rana esculenta was studied by using horseradish peroxidase (HRP) tracing of axonal pathways. Injections of HRP were made in the main olfactory bulb (MOB), accessory olfactory bulb (AOB), anterior olfactory nucleus (AON), the amygdala (AMY), and in a zone of the leteral wall of the telencephalic hemisphere immediately posterior to the AOB. Projections from these sites are described and are generally similar to those obtained by degeneration methods. However, HRP reveals more extensive olfactory connections than previously reported. Ipsilateral, contralateral, and bilateral projections are described. The MOB, AOB, and AON have ipsilateral connections to each other. The MOB and AOB have very different projections. The MOB and AON project via the habenular commissure (HC) to the contralateral medial wall of the telencephalon. Ipsilateral MOB fibers also terminate in this cell-free zone where the medial forebrain bundle (MFB) originates. The AOB projects to the lateral cortex of the contralateral telencephalic hemisphere via the HC and also to the ipsilateral AMY and lateral forebrain bundle (LFB) from where some fibers project contralaterally. HRP injections in the AMY retrogradely fill cells in the ipsilateral AOB, two nuclei of the ipsilateral hypothalamus and a nucleus of cells caudal to the ipsilateral nucleus isthmi. Fibers are also labeled that project to the contralateral AMY. Few fibers were observed to decussate in the interpeduncular nucleus or optic chiasma. No olfactory fibers were found to project to the habenular nuclei, and no labeled neurons were found to project to the olfactory bulbs. No morphological asymmetry was observed qualitatively in the distribution of olfactory fibers in the two halves of the brain.

Lithium and melatonin: morphological modifications induced in frog retina pigment screening

Pigment screening (PS) is a phenomenon occurring in the retina of lower vertebrates, which consists in the dispersion, induced by the light, of melatonin granules into processes of the pigment epithelium which extend between photoreceptors, and in the aggregation, induced by the dark, of the same granules within the cell bodies of the pigment epithelium. It has been hypothesized that this phenomenon might be modulated by melatonin, which is present not only in the pineal but also in the retina, and whose retinal content is high in the dark and low in the light. In the present study we demonstrate that a single intraperitoneal injection of lithium chloride affects in a peculiar way PS of light-adapted frogs and of frogs subjected to natural day/night conditions, but not that of dark-adapted frogs. The implications of this findings are briefly discussed, also in view of the reported effect of lithium on the 24-hour rhythm of retinal melatonin, and of the possible relationship between this effect and the altering properties of lithium on other biological rhythms.

Frog retinal pigment screening and lithium

The effect of the intraperitoneal injection of lithium on the pattern of the pigment screening (PS) of the frog retina has been studied in various illumination conditions. Lithium enhances the PS pattern induced by dark and it substantially modifies the PS pattern induced by the other light conditions. The dark-induced PS pattern is very stable and might be regulated by a single factor. The PS of light-adapted frogs is easily modified by drug administration and probably depends on a variety of factors which may be affected differently by the various injected substances. The possibility that lithium, melatonin and darkness might act in the same way or on the same system which regulates the PS in dark-adaptation must not be disregarded.

Anatomical localisation of neuromelanin in the brains of the frog and tadpole. Ultrastructural comparison of neuromelanin with other melanins

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Substance P-like immunoreactivity in the frog dorsal root ganglia

The distribution of substance P-like immunoreactivity was studied in the thoracic dorsal root ganglia of the frog Rana esculenta by immunohistochemistry. Substance P-like immunoreactivity was contained in approximately 50% of primary sensory neurons. The immunoreactive fibers arising from the cell bodies are collected in small bundles within the ganglia neuropil before entering the central and peripheral roots.

Cobalt injected into the right and left fasciculi retroflexes clarifies the organization of this pathway

A cobaltic lysine complex was injected separately into the right and left fasciculi retroflexes of the frog. This tracing technique labeled, in a Golgi-like manner, the neurons which initiate the fasciculi retroflexes and revealed details of their morphological pattern. The fasciculi retroflexes originate from various neurons distributed in the diencephalon and mesencephalon, but their main source is the habenular nuclei. In the frog there are dorsal and ventral habenulae which are homologous to the medial and lateral habenulae, respectively, of mammals. In the frog the dorsal habenulae are strikingly asymmetric. Our study shows that the fasciculus retroflexus is composed of several compact separated bundles of fibers and that the fibers originating from the dorsal habenular nuclei project to the interpeduncular nucleus, while those originating from the ventral habenular nuclei project beyond the interpeduncular nucleus, but so far we have not been able to show the exact site of their termination. The labeling of cells within the interpeduncular nucleus raises the possibility that the habenulo-interpeduncular tract is reciprocal in function. The finds support our previously reported hypothesis on the theoretical interpretation of the functional circuitry of the frog habenulo-interpeduncular system.

The distribution of substance P in the habenulo-interpeduncular system of the frog shown by an immunohistochemical method

The distribution of substance P(SP)-like immunoreactivity was studied in the habenulo-interpeduncular (HAB-ITP) complex of the frog Rana esculenta by means of the immunohistochemical peroxidase-antiperoxidase (PAP) method. The HAB of the frog were subdivided into dorsal and ventral nuclei, corresponding to the medial and lateral HAB of mammals respectively. In addition, the dorsal HAB of the frog were morphologically asymmetric, since only the left has a lateral and a medial subnucleus. SP-like immunoreactive cells were found in the right dorsal HAB, in the lateral subnucleus of the left dorsal HAB and in a nucleus of scattered cells located rostrodorsally to the ITP. However, the medial subnucleus of the left dorsal HAB and a portion of the right dorsal HAB facing the 3rd ventricle, did not show SP immunoreactivity. Immunoreactive fibers were found in the medial subnucleus of the left dorsal HAB, in the two fasciculi retroflexes and in the ITP. Moreover, immunoreactive terminals were observed in the ventral HAB of both sides, in the ITP and on the blood vessels which cross the ITP. It is assumed that a portion of fibers connecting the various structures of the HAB-ITP complex belongs to the SP peptidergic system as suggested for mammals. However, in contrast to the mammals, the results on the frog are in favour of an histochemical asymmetry of the SP-like immunoreactivity, since a different distribution of this peptide was found between the right and left side of the brain. Such histochemical asymmetry was less pronounced than the morphological asymmetry and its functional meaning is unknown.

Drugs and the frog retina. Effect of dopaminergic agents on the pigment screening of light- and dark-adapted frogs

This is a study, using the light and electron microscope, of the action of a dopamine agonist (apomorphine) and of a dopamine antagonist (haloperidol) on the retinal pigment screening (PS) of light- and dark-adapted frogs. Pigment screening is a phenomenon which consists of the migration of melanin granules into processes of the pigment epithelium that extend between photoreceptors, in response to changes in the conditions of illumination. In the light the pigment migrates vitreally , in the dark it aggregates sclerally . A single intravenous injection of apomorphine (0.15 mg/kg) and of haloperidol (1 mg/kg) did not induce substantial modifications in the pattern of pigment screening which was similar to that of controls both in light- and dark-adapted frogs. This suggests that dopamine is probably not directly involved in the phenomenon of pigment screening in the retina of the frog.

The extracranial portion of the pineal complex of the frog (frontal organ) is connected to the pineal, the hypothalamus, the brain stem and the retina

The central connections of the frontal organ of the frog Rana esculenta were studied by means of the cobalt-filling technique using the cobaltic lysine complex. The results showed that the frontal organ has surprisingly more extended connections than those demonstrated after the application of other techniques. In fact, we found that it is connected to the pineal, the hypothalamus, the brain stem and the retina. These connections, which neuroanatomically have not been reported before, suggest that the frontal organ of the frog participates, in some way, in several different functions, such as neuroendocrine activities, motor responses and lateral eyes photoreception interaction.

Modification of the pigment screening of the frog retina following administration of neuroactive drugs

Pigment screening (PS) occurs in the retina of lower vertebrates and consists of the bidirectional migration (vitreally or sclerally) of melanin granules into processes of the pigment epithelium that extend between photoreceptors, in response to changes in the illumination conditions. We have studied the effect of some neuroactive drugs on the PS of frogs maintained under cyclic lighting conditions or dark-adapted. The drugs, administered intravenously were: lysergic acid diethylamide (LSD), mescaline, d-amphetamine, the LSD analogue lisuride and the LSD derivative 2-bromolysergic acid (BOL). All the drugs used--with the exception of mescaline--modify the bidirectional migration of the pigment induced by the two illumination conditions in a different way. This suggests that in general these substances interact in some way with those processes which normally produce the well-defined PS pattern. It has been possible to discriminate two opposite effects on the retinal PS induced by two chemically related substances (LSD and lisuride) only one of which (LSD) has potent hallucinogenic properties.

Neuroanatomical asymmetry in the telencephalic hemispheres of the frog Rana esculenta

The frog's brain postfixed with osmium tetroxide and stained with uranyl acetate was examined for asymmetries. Examination with the light microscope of serial semithin sections of the telencephalon revealed a nucleus of dark cells located in the lateral cortex of only the left hemisphere in a region close to the 'porcion arqueada' of Pedro Ramón y Cajal. Electron microscopy of ultrathin sections suggests that the cells of this asymmetric nucleus are neurons with a coarse cytoplasmic texture, where large inclusions occur, and with broad cisternae of endoplasmic reticulum.

The action of LSD on the isolated frog spinal cord: electrophysiological and ultrastructural data

In the isolated hemisected frog spinal cord, LSD induced a substantial enhancement of spontaneous dorsal and ventral root activity and a general decrease of both orthodromic and antidromic root potentials. 2. These electrophysiological modifications were reversible. The LSD homologue compound--Lisuride--was without effect. 3. Electron microscopy of the LSD-treated spinal cord revealed synaptic "omega" figures and terminals almost depleted of vesicles. 4. The results suggest that LSD acts at the synaptic level favouring the spontaneous release of transmitters from those involved in the pathways tested.

Third ventricle suprachoroidal cells

Using transmission electron microscopy two types of cells on the choroid plexus of the third ventricle of the frog Rana esculenta have been located. They lie on the microvilli and cilia of the choroid epithelium. Their free surface is in contact with the cerebrospinal fluid. One type, Kolmer-like, has large, dense bodies in its cytoplasm. The cytoplasm of the other type is completely filled by large, ovoidal structures which have a limiting membrane and a polymorphic filamentous content. Their functional significance is unknown.

Substance P-, met-enkephalin- and somatostatin-like immunoreactivity distribution in the frog spinal cord

The distribution of substance P-, Met-enkephalin- and somatostatin-like immunoreactivity was studied in the thoracic spinal cord of the frog using immunohistochemical techniques. In fibres, probably nerve terminals, immunoreactivity was greatest in the grey matter (mainly dorsal horn), but it was also present in white matter regions. While substance P- and, perhaps, somatostatin-like immunoreactivity appeared to be contained in primary afferents, the presence of all 3 peptides in neuronal cells of the grey matter indicates the existence of a propriospinal peptidergic system.

Large granular vesicles in the frog spinal cord

Two types of large granular vesicles have been demonstrated in the spinal cord of the frog Rana esculenta. Each type is contained in different fibres located in the neuropil of the ventral horn. The two types of vesicles differ in their diameter and quantity, in the smoothness of their limiting membrane and the electron density of their core. The possibility that they contain peptides is discussed.

Neuroanatomical identification of the frog habenular connections using peroxidase (HRP)

A study of the habenular nuclei connections by means of horseradish peroxidase (HRP) has never been carried out in amphibia. In the present paper we have investigated the afferent projections of the left and right habenular nuclei of the frog Rana esculenta using this technique. Cells, labelled by HRP, were either in a Golgi-like pattern or in a granular pattern. It appears that the habenular nuclei on the two sides of the epithalamus do not show different connections even though they are morphologically asymmetric. In fact, each habenula is connected bilaterally with the septal area and the bed nucleus of the hippocampal commissure, and ipsilaterally with the hypothalamic areas, the entopeduncular nucleus, the periventricular gray of the third ventricle and the interpeduncular nucleus. However, the habenular commissure has typical commissural fibres which apparently do not involve the medial portion of the left habenula. The habenular connections in the frog are generally similar to those reported in the literature for mammals. In addition, our results show the possibility that HRP is transported both retrograde and anterograde.

Asymmetry of the habenulae in the elasmobranch "Scyllium stellare". II. Electron microscopy

The structure of the habenular nuclei of the elasmobranch Scyllium stellare has been examined with the electron microscope. There is asymmetry of the left and right habenulae; difference is manifest in their cell types and myelin distribution. The presence in only the left habenula of cells bearing large granules - probably secretory - and of cells with myelinated perikarya suggest a functional diversification of the habenulae. A large variety of synaptic vesicles occur in the habenulae of both sides but we could not demonstrate a preferential localization of one particular type in specific habenular subnuclei. A feature common to all portions of the habenular complex is the presence of multilamellar astroglial formations wrapping cell bodies and synapses.

Lysergic acid diethylamide: morphological study of its effect on synapses

A morphometric analysis of the effect of LSD on synapses was performed in the habenulae and the interpeduncular nucleus of the frog. The OsO4-fixed nervous tissue was treated with ethanol phosphotungstic acid (EPTA). Intersection of lattice lines with synapses were counted as a proportion of the total length of lines. LSD-treated frogs had a higher total area of synaptic contact than control frogs. Exocytosis profiles were observed only in LSD-treated frogs Other qualitative changes in the ultrastructural characteristic of synapses were appreciable after LSD administration.

Light- and electron-microscopic structure of cells protruding into the mesencephalic ventricle of Scyllium stellare (Elasmobranchii, Selachii)

In the elasmobranch fish, Scyllium stellare, a complex group of cells protrudes into the cavity of the mesencephalic ventricle of the optic tectum. It consists of six to seven large spherical perikarya which resemble neurons of the mesencephalic nucleus of the Vth cranial nerve. The bundled processes of these cells form a stalk connecting the protrusion with the brain tissue. The protrusion is located in the region where the mesencephalic ventricle joins the cerebral aqueduct. This complex was not found in all specimens examined in the present study. The functional role of this peculiar group of cells, which contain dense core granules and are bathed in the cerebrospinal fluid, is open to discussion.

The habenular nuclei of the elasmobranch "Scyllium stellare": myelinated perikarya

Some habenular cells of the elasmobranch, Scyllium stellare, have a perikaryon completely enveloped by myelin of the compact type. They are found only in the left habenula and not in the right. The myelin sheath accompanies the proximal segment of the process arising from the perikaryon, in a node of Ranvier-like pattern. The identity of these myelinated cells and the functional significance of their myelination are unknown.

Non-ependymal cilia in the habenulae and the interpeduncular nucleus of the frog tadpole

Cilia of the 9 + 2 pattern are found electron microscopically in nonependymal cells of the habenulae and the interpeduncular nucleus of the tadpole of Rana esculenta at an early stage of development (8 mm length, head to tip of tail). A comparison is made between these and the ependymal and sensory cilia in the same specimens. The cilia project into the neuropil emerging from a perikaryon rich in free ribosomes and displaying a prominent Golgi apparatus. These perikarya contain dense core vesicles. Synapses with vesicles of the clear spherical type have been observed along the ciliary shaft. On a purely morphologic basis the authors hypothesize that these cilia, at least in this early ontogenetic stage, may extend considerably the conducting surface of the cell and represent a sensory structure which could be stimulated by terminal processes belonging to distantly located cells. In addition, they could also be involved in the trophic exchange of material with the adjacent structures.

An electron microscope observation of the right and the two left portions of the habenular nuclei of the frog

The right dorsal habenula (RDH), the left dorsal habenula, lateral portion (LDH-LP) and the left dorsal habenula, medial portion (LDH-MP) of the adult frog Rana esculenta have been studied by the electron microscope with the use of three types of fixatives: osmium tetroxide, aldehydes and potassium permangarate. The study has demonstrated in the habenulae of both sides a variety of syraptic vesicles, special synaptic patterns (en passant, serial, axo-somatic) containing small spherical transparent vesicles, never mixed with other types of vesicles, and large pale processes containing big granules. However, a particular type of synaptic vesicles characterized by small clear spherical vesicles with a tiny dark granule revealed by potassium permanganate fixition has been demonstrated only in the neuropil of the LDH and not in the RDH. Further, a peculiar type of intracytoplasmic inclusion appears in the form of myelin-like and crystal-like formations only in the LDH-MP. On the basis of these consistent ultrastructural differences, the dorsal habenular nuclei of the frog can be considered as composed of three individual nuclei, each with its own morphological characterization, dislocated, for some unknown reason, one on the right and two on the left side of the epithalamus. The results suggest that the LDH-MP is a nucleus metabolically different from the others and that the projections to the dorsal habenular nuclei are different on the right and left sides of the brain.

The interpeduncular nucleus (ITP). Ultrastructure data indicative of a possible neurosecretory activity

Special types of cells of the interpeduncular nucleus (ITP) in the fog, Rana esculenta, are described after three typed of fixation: osmium tetroxide, aldehydes and potassium permanganate. Large granules with a sub-unit structure occurring together with bundles of filaments and elongated mitochondria are illustrated in the processes of cells, the perikarya of which lie distant from the ependymal lining of the aqueduct of Sylvius. Such processes cross the ITP in a dorso-ventral direction perpendicular to the fibers which traverse the nucleus in a horizontal and frontal plane. They reach the subpial ventral surface of the nucleus ending in foot-like expansions where granules and mitochondria are assembled. The secretory nature of the granules is assumed. The release of possible peptide hormones into the interpeduncular cistern, where a pool of cerebrospinal fluid and large blood vessels occur, cannot be excluded.

A modification of the rapid Golgi method

An extremely rapid Golgi procedure for immersion impregnation of the whole brain of the frog Rana esculenta is described. It uses an isotonic 2% osmium tetroxide solution buffered with sodium barbital at pH 7.2 that has previously been used for electron microscopy. To 15 ml of this solution 85 ml 3% potassium dichromate is added just before use. Twelve-hour treatments (6 hr in the chrome-osmium solution plus 6 hr in 0.75% silver nitrate) are sufficient to obtain consistently excellent impregnations of external brain formations. Twenty-four-hour treatments (12 hr in the chrome-osmium solution and 12 hr in the silver solution) impregnate also the deeper regions of the brain. The results show neuronal details on a clear background.

Topological analysis of the brain stem of the frogs Rana esculenta and Rana catesbeiana

The ventricular sulcal pattern and the cytoarchitectonic organization of the brain stem of the frogs Rana esculenta and Rana catesbeiana have been studied in transversely cut, Nissl stained serial sections. Four longitudinal sulci, the sulcus medianus inferior, the sulcus intermedius ventralis, the sulcus limitans and the sulcus medianus superior could be distinguished in both species. A fifth longitudinal groove, the sulcus intermedius dorsalis, was found only in Rana esculenta. With the aid of the usual cytoarchitectonic criteria 25 cell masses have been delineated in Rana esculenta and 27 in Rana catesbeiana. These cell masses can be distributed over the following categories (numbers added in brackets for Rana catesbeiana, if different from those in Rana esculenta): primary efferent or motor, 8; primary afferent or sensory, 4(6); "relay" centers, 7. Contrary to statements in the literature the reticular formation can be divided into six separate cell groups. The majority of the nuclei form part of the central gray, which constitutes a rather wide zone in anurans; three reticular nuclei lie partly within the stratum griseum and partly within the stratum album; six nuclei are entirely embedded in the stratum album. The morphological pattern of the cell masses and their relationship to the ventricular sulci were studied with the aid of a graphical reconstruction procedure termed topological analysis (cf. Nieuwenhuys, '74 and figs. 15, 16). This analysis yielded the following results: The sulcus limitans extends throughout the rhombencephalon, dividing this brain part into a basal plate and an alar plate. The cell masses in the basal plate fit into two longitudinal zones, a medial area ventralis and a lateral area intermedioventralis. The area ventralis contains three somatic motor nuclei (IV, VI and XII) and the rhombencephalic medial reticular zone. The latter may be primarily considered as a somatic motor coordinating center. The area intermedioventralis contains the visceral motor nuclei of V, VII, IX and X. However, the basal plate also contains a number of non-motor centers, for example the superior olive. The alar plate contains visceral sensory, general somatic sensory and special somatic sensory centers. Two cell masses, the nucleusfasciculi solitarii and the nucleus visceralis secundarius, represent together a discontinuous visceral sensory zone. Both of these nuclei are situated immediately dorsal to the sulcus limitans. The special somatic sensory area, i.e., the area of termination of the eighth nerve, occupies a considerable part of the alar plate. This area comprises, apart from a large zone of diffuse gray, three distinct cell masses...