Proposal for an electron antineutrino disappearance search using high-rate 8Li production and decay.

This paper introduces an experimental probe of the sterile neutrino with a novel, high-intensity source of electron antineutrinos from the production and subsequent decay of 8Li. When paired with an existing ∼1 kton scintillator-based detector, this = 6.4 MeV source opens a wide range of possible searches for beyond standard model physics via studies of the inverse beta decay interaction ν(e) + p → e+ + n. In particular, the experimental design described here has unprecedented sensitivity to ν(e) disappearance at Δm2 ∼ 1 eV2 and features the ability to distinguish between the existence of zero, one, and two sterile neutrinos.

Secretagogin expression in the mouse olfactory bulb under sensory impairments.

The interneurons of the olfactory bulb (OB) are characterized by the expression of different calcium-binding proteins, whose specific functions are not fully understood. This is the case of one of the most recently discovered, the secretagogin (SCGN), which is expressed in interneurons of the glomerular and the granule cell layers, but whose function in the olfactory pathway is still unknown. To address this question, we examined the distribution, generation and activity of SCGN-positive interneurons in the OB of two complementary models of olfactory impairments: Purkinje Cell Degeneration (PCD) and olfactory-deprived mice. Our results showed a significant increase in the density of SCGN-positive cells in the inframitral layers of olfactory-deprived mice as compared to control animals. Moreover, BrdU analyses revealed that these additional SCGN-positive cells are not newly formed. Finally, the neuronal activity, estimated by c-Fos expression, increased in preexisting SCGN-positive interneurons of both deprived and PCD mice -being higher in the later- in comparison with control animals. Altogether, our results suggest that the OB possesses different compensatory mechanisms depending on the type of alteration. Particularly, the SCGN expression is dependent of olfactory stimuli and its function may be related to a compensation against a reduction in sensory inputs.

Acceleration of uranium at the bevalac.

Recent upgrading projects have extended the mass range of particles that can be accelerated at the Bevalac to include any element of the periodic table to energies above 1 billion electron volts per atomic mass unit. This capability was verified on 11 May 1982 with the production of a uranium beam at 147.7 million electron volts per atomic mass unit.

Olfactory bulb plasticity ensures proper olfaction after severe impairment in postnatal neurogenesis.

The olfactory bulb (OB) neurons establish a complex network that ensures the correct processing of the olfactory inputs. Moreover, the OB presents a lifelong addition of new neurons into its existing circuitry. This neurogenesis is considered essential for the OB function. However, its functional impact on physiology and behavior is still unclear. Here, we investigate the mechanisms of OB plasticity that underlie bulbar physiology in relation to severe damage of neurogenesis. The neurogenesis of young mice was altered by ionizing radiation. Afterwards, both multi-channel olfactometry and electrophysiological studies were performed. Furthermore, neurogenesis and differentiation of the newly formed cells were assessed using bromodeoxyuridine labeling combined with a wide battery of neuronal markers. Our results demonstrate a reduction in both neurogenesis and volume of the OB in irradiated animals. The number of neuroblasts reaching the OB was reduced and their differentiation rate into interneurons selectively changed; some populations were noticeably affected whereas others remained preserved. Surprisingly, both olfactory detection and discrimination as well as electrophysiology presented almost no alterations in irradiated mice. Our findings suggest that after damaging postnatal neurogenesis, the neurochemical fate of some interneurons changes within a new biological scenario, while maintaining homeostasis and olfaction.

Differential effects of unilateral olfactory deprivation on noradrenergic and cholinergic systems in the main olfactory bulb of the rat.

The lack of environmental olfactory stimulation produced by sensory deprivation causes significant changes in the deprived olfactory bulb. Olfactory transmission in the main olfactory bulb (MOB) is strongly modulated by centrifugal systems. The present report examines the effects of unilateral deprivation on the noradrenergic and cholinergic centrifugal systems innervating the MOB. The morphology, distribution, and density of positive axons were studied in the MOBs of control and deprived rats, using dopamine-beta-hydroxylase (DBH)-immunohistochemistry and acetylcholinesterase (AChE) histochemistry in serial sections. Catecholamine content was compared among the different groups of MOBs (control, contralateral, and ipsilateral to the deprivation) using high-performance liquid chromatography analysis. Sensory deprivation revealed that the noradrenergic system developed adaptive plastic changes after olfactory deprivation, including important modifications in its fiber density and distribution, while no differences in cholinergic innervation were observed under the same conditions. The noradrenergic system underwent an important alteration in the glomerular layer, in which some glomeruli showed a dense noradrenergic innervation that was not detected in control animals. The DBH-positive glomeruli with the highest noradrenergic fiber density were compared with AChE-stained sections and it was observed that the strongly noradrenergic-innervated glomeruli were always atypical glomeruli (characterized by their strong degree of cholinergic innervation). In addition to the morphological findings, our biochemical data revealed that olfactory deprivation caused a decrease in the content of dopamine and its metabolite 3,4-dihydroxyphenylacetic acid in the ipsilateral MOB in comparison to the contralateral and control MOBs, together with an increase in noradrenaline levels in both the ipsilateral and contralateral MOBs. Our results show that regulation of the noradrenergic centrifugal system in the MOB depends on environmental olfactory stimulation and that it is highly reactive to sensory deprivation. By contrast, the cholinergic system is fairly stable and does not exhibit clear changes after the loss of sensory inputs.

Heterogeneous targeting of centrifugal inputs to the glomerular layer of the main olfactory bulb.

The centrifugal systems innervating the olfactory bulb are important elements in the functional regulation of the olfactory pathway. In this study, the selective innervation of specific glomeruli by serotonergic, noradrenergic and cholinergic centrifugal axons was analyzed. Thus, the morphology, distribution and density of positive axons were studied in the glomerular layer of the main olfactory bulb of the rat, using serotonin-, serotonin transporter- and dopamine-beta-hydroxylase-immunohistochemistry and acetylcholinesterase histochemistry in serial sections. Serotonin-, serotonin transporter-immunostaining and acetylcholinesterase-staining revealed a higher heterogeneity in the glomerular layer of the main olfactory bulb than previously reported. In this sense, four types of glomeruli could be identified according to their serotonergic innervation. The main distinctive feature of these four types of glomeruli was their serotonergic fibre density, although they also differed in their size, morphology and relative position throughout the rostro-caudal main olfactory bulb. In this sense, some specific regions of the glomerular layer were occupied by glomeruli with a particular morphology and a characteristic serotonergic innervation pattern that was consistent from animal to animal. Regarding the cholinergic system, we offer a new subclassification of glomeruli based on the distribution of cholinergic fibres in the glomerular structure. Finally, the serotonergic and cholinergic innervation patterns were compared in the glomerular layer. Sexual differences concerning the density of serotonergic fibres were observed in the atypical glomeruli (characterized by their strong cholinergic innervation). The present report provides new data on the heterogeneity of the centrifugal innervation of the glomerular layer that constitutes the morphological substrate supporting the existence of differential modulatory levels among the entire glomerular population.

Transdentinal cell photobiomodulation using different wavelengths.

OBJECTIVE: The aim of this study was to investigate the effects of transdentinal irradiation with different light-emitting diode (LED) parameters on odontoblast-like cells (MDPC-23). METHODS AND MATERIALS: Human dentin discs (0.2 mm thick) were obtained, and cells were seeded on their pulp surfaces with complete culture medium (Dulbecco modified Eagle medium). Discs were irradiated from the occlusal surfaces with LED at different wavelengths (450, 630, and 840 nm) and energy densities (0, 4, and 25 J/cm(2)). Cell viability (methyltetrazolium assay), alkaline phosphatase activity (ALP), total protein synthesis (TP), and cell morphology (scanning electron microscopy) were evaluated. Gene expression of collagen type I (Col-I) was analyzed by quantitative polymerase chain reaction (PCR). Data were analyzed by the Mann-Whitney test with a 5% significance level. RESULTS: Higher cell viability (21.8%) occurred when the cells were irradiated with 630 nm LED at 25 J/cm(2). Concerning TP, no statistically significant difference was observed between irradiated and control groups. A significant increase in ALP activity was observed for all tested LED parameters, except for 450 nm at 4 J/cm(2). Quantitative PCR showed a higher expression of Col-I by the cells subjected to infrared LED irradiation at 4 J/cm(2). More attached cells were observed on dentin discs subjected to irradiation at 25 J/cm(2) than at 4 J/cm(2). CONCLUSION: The infrared LED irradiation at an energy density of 4 J/cm(2) and red LED at an energy density of 25 J/cm(2) were the most effective parameters for transdentinal photobiomodulation of cultured odontoblast-like cells.

Organization of the septal region in the rat brain: a Golgi/EM study of lateral septal neurons.

The combined Golgi/electron microscope (EM) technique was used to analyze the fine structure and synaptic organization of the various types of neurons in the rat lateral septum (LS), i.e., in the dorsolateral (LSd), intermediolateral (LSi), and ventrolateral (LSv) nuclei of the septal complex. Two characteristic cell types were observed in the LSd: type I with thick, short dendrites densely covered with short spines, and type II with longer and thinner dendrites exhibiting fewer but longer spines. This latter type was by far the most frequently impregnated cell type in the LSd and was also present in the LSi. Synaptic contacts on spines of either cell type were asymmetric; the majority of the presynaptic boutons contained clear round synaptic vesicles. Occasionally terminals were found that contained both clear and dense-core vesicles. Typical fusiform neurons with a low number of spines and rather long dendrites, sometimes invading other LS nuclei, were found in the LSi. The LSv contained numerous small neurons with small dendritic fields. A relatively large number of terminals with dense-core vesicles were found to establish synaptic contacts with identified LSv neurons. The morphological heterogeneity of LS neurons is discussed with regard to other studies on afferent and efferent fiber systems as well as immunohistochemical studies of this particular region of the septal complex.

Cholinergic innervation of the primate hippocampal formation. I. Distribution of choline acetyltransferase immunoreactivity in the Macaca fascicularis and Macaca mulatta monkeys.

The cholinergic innervation of the hippocampal formation of Macaca fascicularis (cynomolgus) and Macaca mulatta (rhesus) monkeys was investigated by immunohistochemical procedures using a monoclonal antibody directed against choline acetyltransferase. The distribution of choline acetyltransferase in the monkey demonstrated both similarities and differences with the staining patterns observed in the rat or with acetylcholinesterase in the monkey. While both of these latter preparations demonstrated labeled cells, for example, no choline acetyltransferase labeled neurons were observed in the monkey hippocampal formation. Choline acetyltransferase activity was restricted to fibers which varied in thickness and number of varicosities and in their regional and laminar distribution. The highest densities of labeled fibers were observed in the uncal portion of the hippocampus, in the parasubiculum, and in the entorhinal cortex; the lowest densities of labeled fibers were observed in CA1 and in midrostrocaudal levels of the dentate gyrus. In the dentate gyrus, immunoreactive fibers were densely distributed in the molecular layer and in an infragranular plexus. One of the few striking noticeable interspecies differences was observed in the dentate gyrus. In the rhesus monkey, labeled fibers in the molecular layer were divided into a superficial denser and an inner lighter lamina, whereas in M. fascicularis, the cholinergic fibers were distributed more homogeneously throughout the molecular layer. In the hippocampus proper, there was a progressive decrease in the density of ChAT-immunoreactive fibers from CA3/CA2 into CA1. The subiculum also demonstrated modest labeling which was nonetheless higher than in CA1; the border of these fields demonstrated increased fiber labeling. The density of choline acetyltransferase staining was high in the presubiculum and parasubiculum. In the entorhinal cortex, a relatively clear boundary was observed between the more heavily stained superficial layers (I, II, and III) and the more weakly labeled deep layers (V and VI), especially in the intermediate and caudal fields. A transverse decreasing gradient was observed with the densest plexus of cholinergic fibers found in the medially situated olfactory field of the entorhinal cortex and the lowest density in the laterally located caudal and lateral fields.

Distribution of NADPH-diaphorase and nitric oxide synthase in relation to catecholaminergic neuronal structures in the brain of the lizard Gekko gecko.

A recent study of the distribution of NADPH-diaphorase (NADPHd) and nitric oxide synthase (NOS) in a turtle brain (Brüning et at. [1994]: J. Comp. Neurol. 348:183-206) has revealed that these enzymes are not only widely distributed throughout the brain, but also seem to be colocalized with other classical neurotransmitters, such as catecholamines and acetylcholine. The main goals of the present study were 1) to determine sites of colocalization of NADPHd/NOS with tyrosine hydroxylase (TH, as marker for catecholamines), and 2) by studying a representative of another reptilian radiation, to assess primitive and derived traits of the distribution of NADPHd and NOS in the brains of reptiles. For that purpose, single (NADPHd or NOS) and double staining (NADPHd with TH, or NOS with TH) techniques were applied to the brains of adult gekkonid lizards (Gekko gecko). The distribution of NADPHd and NOS in Gekko was largely comparable to that in turtles, which implies involvement in certain functions of these enzymes. Notable differences, however, were observed in the thalamus and pretectum. Colocalization was observed in numerous cells of the ventral tegmental area, the substantia nigra, and the retrorubral dopaminergic cell group. In other catecholaminergic cell groups, e.g., the locus coeruleus and the solitary tract nucleus, TH-immunoreactive cells and NADPHd/NOS-positive cells were closely intermingled, but not double-stained. From the present evidence, it is concluded that extensive colocalization of NADPHd/NOS with catecholamines occurs in the midbrain dopaminergic cell groups of reptiles and birds, but not (or only sparsely) in the corresponding cell groups of amphibians and mammals.

Cholinergic innervation of the primate hippocampal formation: II. Effects of fimbria/fornix transection.

The distribution of choline acetyltransferase (ChAT)-immunoreactive and acetylcholinesterase (AChE)-positive fibers and terminals was analyzed in the hippocampal formation of macaque monkeys subjected to transection of the fimbria/fornix. Cases with either unilateral or bilateral transections were prepared, with post transection survival times ranging from 2 weeks to 1.5 years. The fimbria/fornix transection resulted in a dramatic decrease in the number of cholinergic fibers in most regions of the hippocampal formation. Some hippocampal regions, however, showed relatively greater sparing of ChAT- or AChE-positive fibers. In practically all regions of the hippocampal formation, residual AChE-positive fibers were more abundant than ChAT-immunoreactive fibers. In animals with unilateral lesions, the distribution patterns and density of AChE and ChAT staining on the side contralateral to the lesion were generally similar to those of sections from unlesioned control brains. The largest decreases in the densities of positive fibers were observed in the dentate gyrus, CA3 and CA2 fields of the hippocampus, subiculum, parasubiculum, and medial and caudal parts of the entorhinal cortex. Fibers were relatively better preserved in the rostral or uncal portion of the hippocampus and dentate gyrus and in the rostral portion of the entorhinal cortex. The presubiculum demonstrated remarkable sparing that contrasted with the almost complete loss of fibers in the parasubiculum. Interestingly, animals killed approximately 1.5 years after the fornix transection showed essentially the same pattern of fiber loss as the cases with shorter survival periods. This indicates that the residual ChAT-immunoreactive fibers, many of which reach the hippocampal formation through a ventral cholinergic pathway, are not capable of reinnervating the denervated portions of the hippocampal formation. This appears to distinguish the monkey from the rat, for which substantial sprouting and reinnervation of cholinergic fibers have been reported after similar lesions.

NADPH-diaphorase active and calbindin D-28k-immunoreactive neurons and fibers in the olfactory bulb of the hedgehog (Erinaceus europaeus).

The hedgehog, a macrosomatic insectivore with an extraordinary development of the olfactory structures, has a crucial value for any phylogenetic or comparative study in mammals. The distribution pattern and morphology of NADPH-diaphorase-active and calbindin D-28k-immunoreactive neurons were studied in the main and accessory olfactory bulbs of the hedgehog. NADPH-diaphorase (ND) staining was carried out by a direct histochemical method, and the calbindin D-28k (CaBP) immunoreaction by using a monoclonal antibody and the avidin-biotin-immunoperoxidase method. The possible coexistence of both markers was determined by sequential histochemical-immunohistochemical double labeling of the same sections. Specific neuronal populations were positive for both ND and CaBP markers. No cell colocalized both stains in the hedgehog olfactory bulb. A subpopulation of olfactory fibers, and a subpopulation of olfactory glomeruli, located on the medial side, were positive for ND. Surrounding both the ND-positive and ND-negative glomeruli, there were ND- and CaBP-positive periglomerular cells, the latter group being much more abundant. A subpopulation of superficial short-axon cells was CaBP positive but, contrary to what is observed in rodents, this neuronal type was always ND negative. In addition, three neuronal types were observed in the GL-EPL border after CaBP immunostaining. These neuronal types have not been previously described either in the hedgehog or in the rodent olfactory bulb. Horizontal cells and vertical cells of Cajal were also observed after both ND and CaBP labeling. Distinct groups of ND- and CaBP-positive cells, differing in size, shape, dendritic branching pattern, and staining intensity, were distinguished in the granule cell layer and in the white matter. The large and medium-sized cells were identified as a very heterogeneous population of deep short-axon cells, whereas a subpopulation of granule cells was ND positive. The accessory olfactory bulb showed ND staining in all vomeronasal fibers and glomeruli, and in subpopulations of periglomerular cells, granule cells, and deep short-axon cells. The CaBP immunolabeling was more restricted and located in subpopulations of periglomerular cells and in deep short-axon cells. These results indicate different and more complex ND and CaBP staining patterns in the hedgehog olfactory bulb than those previously described in rodents, including the presence of specific, chemically and morphologically defined new neuronal types.

Chemical organization of the macaque monkey olfactory bulb: II. Calretinin, calbindin D-28k, parvalbumin, and neurocalcin immunoreactivity.

The distribution and morphologic features of calcium-binding protein- (calbindin D-28k, calretinin, neurocalcin, and parvalbumin) immunoreactive elements were studied in the macaque monkey olfactory bulb by using specific antibodies and the avidin-biotin-immunoperoxidase method. A characteristic laminar pattern of stained elements was observed for each marker. Scarce superficial short-axon cells and superficial stellate cells demonstrated calbindin D-28k immunoreactivity in the outer layers, whereas a moderate number of calbindin D-28k-immunoreactive granule cells and scarce deep short-axon cells were observed in the inner layers. Calretinin-staining demonstrated abundant periglomerular cells and granule cells and a scarce number of other interneuronal populations. Most neurocalcin-immunopositive elements were external and medial tufted cells and periglomerular cells, although other scarcer interneuronal populations were also immunostained. A few superficial and deep short-axon cells as well as small interneurons in the external plexiform layer were the only elements immunoreactive to parvalbumin. The distribution of the immunoreactive elements in the olfactory bulb of the macaque monkey showed a high similarity to that reported in the human, whereas it demonstrated a different and simpler pattern to what has been reported in the olfactory bulb of macrosmatic animals. It suggests more homogeneous calcium-mediated cell responses after stimulation that could be correlated to the lower capability to modulate olfactory signals in microsmatic animals. In addition, these results indicate that experimental models in rodents do not provide an accurate estimation of calcium-binding protein-immunoreactive neuronal populations in the primate olfactory system.

Calretinin-, neurocalcin-, and parvalbumin-immunoreactive elements in the olfactory bulb of the hedgehog (Erinaceus europaeus).

The distribution pattern and morphology of calretinin-, neurocalcin-, and parvalbumin-immunoreactive neurons were studied in the main and accessory olfactory bulbs of the hedgehog. The detection of these markers was carried out by using monoclonal or polyclonal antibodies and the avidin-biotin-immunoperoxidase method. Specific neuronal populations were positive for these calcium-binding proteins in the hedgehog olfactory bulb, revealing both similarities to and differences from the data reported in the olfactory bulb of rodent species. The distribution pattern of each calcium-binding protein studied in the accessory olfactory bulb was highly similar to that described in other macrosmatic species. However, in the main olfactory bulb, the markers analyzed were expressed in similar interneuronal populations as they are in the rodent olfactory bulb, whereas cell groups categorized as projecting neurons demonstrated striking differences in the expression of these calcium-binding proteins. These results suggest that the expression of calcium-binding proteins in a given brain region is not a constant feature among species despite a similar organization but that different factors could influence their expression. Thus, the accessory olfactory system involved in the processing of specific and similar olfactory cues among species demonstrates a more constant organization among species. By contrast, the functionally important role of the main olfactory system in the hedgehog is accompanied by a more complex organization, which is reflected in an increased diversity of calcium-buffering systems.

Topographical distribution of NADPH-diaphorase activity in the central nervous system of the frog, Rana perezi.

The distribution of NADPH-diaphorase (ND) activity was histochemically investigated in the brain of the frog Rana perezi. This technique provides a highly selective labeling of neurons and tracts. In the telencephalon, labeled cells are present in the olfactory bulb, pallial regions, septal area, nucleus of the diagonal band, striatum, and amygdala. Positive neurons surround the preoptic and infundibular recesses of the third ventricle. The magnocellular and suprachiasmatic hypothalamic nuclei contain stained cells. Numerous neurons are present in the anterior, lateral anterior, central, and lateral posteroventral thalamic nuclei. Positive terminal fields are organized in the same thalamic areas but most conspicuously in the visual recipient plexus of Bellonci, corpus geniculatum of the thalamus, and the superficial ventral thalamic nucleus. Labeled fibers and cell groups are observed in the pretectal area, the mesencephalic optic tectum, and the torus semicircularis. The nuclei of the mesencephalic tegmentum contain abundant labeled cells and a conspicuous cell population is localized medial and caudal to the isthmic nucleus. Numerous cells in the rhombencephalon are distributed in the octaval area, raphe nucleus, reticular nuclei, sensory trigeminal nuclei, nucleus of the solitary tract, and, at the obex levels, the dorsal column nucleus. Positive fibers are abundant in the superior olivary nucleus, the descending trigeminal, and the solitary tracts. In the spinal cord, a large population of intensely labeled neurons is present in all fields of the gray matter throughout its rostrocaudal extent. Several sensory pathways were heavily stained including part of the olfactory, visual, auditory, and somatosensory pathways. The distribution of ND-positive cells did not correspond to any single known neurotransmitter or neuroactive molecule system. In particular, abundant codistribution of ND and catecholamines is found in the anuran brain. Double labeling techniques have revealed restricted colocalization in the same neurons and only in the posterior tubercle and locus coeruleus. If ND is in amphibians a selective marker for neurons containing nitric oxide synthase, as generally proposed, with this method the neurons that may synthesize nitric oxide would be identified. This study provides evidence that nitric oxide may be involved in novel tasks, primarily related to forebrain functions, that are already present in amphibians.

NADPH-diaphorase in the central nervous system of the tench (Tinca tinca L., 1758).

The distribution and morphological characterization of nicotinamide adenine dinucleotide phosphate-diaphorase (ND)-positive cells and fibers in the tench central nervous system was mapped by using a direct histochemical method. This enzyme was observed in specific cell populations throughout all main divisions of the tench brain. In the telencephalon, we found strongly labeled olfactory fibers, as well as positive cells and fibers in the area ventralis of the telencephalic lobes. Positive staining was observed in the following diencephalic nuclei: nucleus preopticus magnocellularis pars magnocellularis, nucleus recessus lateralis, nucleus recessus posterioris, nucleus posterior tuberis, and nucleus diffusus torus lateralis, as well as small cells with a diffuse distribution surrounding the diencephalic ventricle. In the mesencephalon, heavily stained ND-positive neurons were observed in the nucleus fasciculi longitudinalis medialis, nucleus nervi oculomotorius, and nucleus nervi trochlearis. In the hindbrain the most evident staining was observed as large neurons located in the nuclei of the cranial nerves, scattered positive cells located between the negative fibers of the cranial nerves, and in the nucleus fasciculi solitari. Finally, in the spinal cord, ND-positive cells and fibers were mainly located in the ventral horn. This distribution of ND labeling in the brain of the tench is significantly different from previous data on ND activity in the brain of terrestrial vertebrates and does not correlate with the presence and distribution patterns of several neurotransmitters and neuroactive substances in the teleost brain.

Distribution of parvalbumin immunoreactivity in the brain of the tench (Tinca tinca L., 1758).

The distribution of parvalbumin (PV) immunoreactivity in the tench brain was examined by using the avidin-biotin-peroxidase immunocytochemical method. This protein was detected in neuronal populations throughout all main divisions of the tench brain. In the telencephalic hemispheres, PV-immunopositive neurons were distributed in both the dorsal and ventral areas, being more abundant in the area ventralis telencephali, nucleus ventralis. In the diencephalon, the scarce distribution of PV-containing cells followed a rostrocaudal gradient, and the most evident staining was observed in the nucleus periventricularis tuberculi posterioris and in a few nuclei of the area praetectalis. In the mesencephalon, abundant PV-immunoreactive elements were found in the tectum opticum, torus semicircularis, and tegmentum. In the tectum opticum, PV-immunoreactivity presented a laminar distribution. Three PV-containing neuronal populations were described in the torus semicircularis, whereas in the tegmentum, the PV staining was mainly located in the nucleus tegmentalis rostralis and in the nucleus nervi oculomotorii. In the metencephalon, Purkinje cells were PV-immunopositive in the valvula cerebelli, lobus caudalis cerebelli, and in the corpus cerebelli. In the myelencephalon, PV immunoreactivity was abundant in the nucleus lateralis valvulae, in the nucleus nervi trochlearis, nucleus nervi trigemini, nucleus nervi abducentis, nucleus nervi glossopharyngei, and in the formatio reticularis. Mauthner cells were also PV immunostained. By contrast to other vertebrate groups, only a restricted population of PV-containing neurons was GABA-immunoreactive in the tench, demonstrating that this calcium-binding protein cannot be considered a marker for GABAergic elements in the teleost brain. This study demonstrates a low phylogenetic conservation of the distribution of PV comparing teleosts and tetrapods.

Distribution of acetylcholinesterase and choline acetyltransferase in the main and accessory olfactory bulbs of the hedgehog (Erinaceus europaeus).

The distribution of cholinergic markers was studied in the main olfactory bulb (MOB) and accessory olfactory bulb (AOB) of the western European hedgehog (Erinaceus europaeus) by using choline acetyltransferase (ChAT) immunocytochemistry and acetylcholinesterase (AChE) histochemistry. A dense network of AChE-containing and ChAT-immunoreactive fibers was observed innervating all layers of the MOB except the olfactory nerve layer, where neither AChE- nor ChAT-labeled elements were found. The highest density of AChE- and ChAT-positive axons was found in the glomerular layer (GL)/external plexiform layer (EPL) boundary, and in the internal plexiform layer. This general distribution pattern of ChAT- and AChE-stained axons resembled the distribution pattern found in rodents. Nevertheless, some interspecies differences, such as the lack of atypical glomeruli in the hedgehog, were also found. In addition to fibers, a population of noncholinergic and presumably cholinoceptive AChE-active neurons was observed in the hedgehog. All mitral and tufted cells of the hedgehog MOB showed a dark AChE staining unlike previous observations in the mitral and tufted cells of rodents. As in other species previously reported, subpopulations of external tufted cells and short-axon cells were also AChE-active. Finally, a population of small AChE-containing cells was observed in the EPL of the hedgehog MOB. The size, shape, and location of these cells coincided with those of satellite and perinidal cells, two neuronal types described previously in the EPL of the hedgehog and not present in the rodent MOB. The AOB of the hedgehog showed a distribution of AChE- and ChAT-positive fibers similar to the rodent AOB. Nevertheless, a heterogeneous innervation of vomeronasal glomeruli by bundles of AChE- and ChAT-labeled axons found in the hedgehog has not been previously found in any other species. As in the MOB, all mitral cells in the AOB showed a strong AChE activity. These results demonstrate some similarities but also important differences between the distribution of ChAT and AChE in the MOB and AOB of rodents and this primitive mammalian. These variations may indicate a different organization of the cholinergic modulation of the olfactory information in the insectivores.

Chemical anatomy of the macaque monkey olfactory bulb: NADPH-diaphorase/nitric oxide synthase activity.

The distribution and the morphology of nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase (ND)-active and neuronal nitric oxide synthase (NOS)-immunoreactive neurons and fibers were studied in the olfactory bulb of three species of primates, i.e., the cynomolgus macaque monkey (Macaca fascicularis), the Japanese macaque monkey (Macaca fuscata), and the pig-tail macaque monkey (Macaca nemestrina). The ND staining was carried out by means of a direct histochemical method with beta-NADPH as cosubstrate and nitro blue tetrazolium as chromogen. The NOS immunostaining was carried out by using a polyclonal antibody and the avidin-biotin peroxidase method. Similar results were found in the three species, where a distinct distribution pattern of ND/NOS-stained neurons and fibers was observed. All olfactory fibers demonstrated ND-positive labeling but they were NOS-immunonegative. In the superficial modulatory area of the olfactory bulb, a few weakly ND- and NOS-positive periglomerular cells, stellate cells, and darkly stained superficial short-axon cells were observed. In the inframitral layers, granule cells, deep stellate cells, and deep short-axon cells were distinguished. Short-axon cells had oriented morphologies and spiny dendrites. Many thick, varicose ND/NOS-stained fibers identified as centrifugal fibers were observed in the white matter, granule cell layer, internal plexiform layer, mitral cell layer, and external plexiform layer. This distribution of ND activity and NOS immunoreactivity showed similarities to and differences from what has been reported in the olfactory bulb of macrosmatic mammals including rodents (rat, mouse, and hamster) and insectivores (hedgehog). These data confirm that the complexity of the ND/NOS staining in the olfactory bulb of one species correlates with the importance of olfaction in the biology of such species.

Topographical distribution of reduced nicotinamide adenine dinucleotide phosphate-diaphorase in the brain of the Japanese quail.

The distribution of reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase activity was histochemically investigated in the Japanese quail brain. This enzyme is now considered responsible for the synthesis of nitric oxide, a novel neural messenger whose distribution has not been described in the avian brain until now. The histochemical technique provides a simple and reliable method for staining selected populations of neurons throughout the avian brain. In the telencephalon several regions showed heavily stained NADPH-diaphorase positive neurons and processes. In particular the paleostriatal-paraolfactory lobe complex showed the greatest presence of both positive cells and processes. Neurons and processes were also observed in several regions of the hyperstriatum as well as in the archistriatal nucleus taeniae. Some regions, such as the ectostriatum and the hippocampus, had no positive elements. In the diencephalon, the magnocellular hypothalamic system, which in mammals shows NADPH-diaphorase activity, did not show any particular accumulation of reaction product. On the contrary, retinorecipient areas, such as the visual suprachiasmatic nucleus and the lateral geniculate complex, displayed a composite structure of both positive neurons and processes. The brainstem revealed a large NADPH-diaphorase positive population extending through the tegmental nuclei to the locus coeruleus and subcoeruleus. A complex organization was also observed in the optic lobe, where fusiform elements were distributed within the stratum griseum and superficialis of the tectum. In the medulla, a dense terminal field was observed at the level of the nucleus of the solitary tract, whereas scattered neurons were located within the reticular nuclei. Although the staining of neurons and tracts was highly selective, the positive cells did not correspond to any single known neurotransmitter, neuropeptide, or neuroactive molecule system. Several sensory pathways were heavily stained for the NADPH-diaphorase, including part of the olfactory, visual, and auditory pathways. The findings of the present study reveal that the NADPH-diaphorase-containing systems in the avian brain are organized according to a pattern comparable, because of its complexity, to that observed in mammals. However, important interspecific differences suggest that this novel neural system might be involved in diverse tasks.