Cystic fibrosis, vasoactive intestinal polypeptide, and active cutaneous vasodilation.

The transmitter substance for the active cutaneous vasodilation that accompanies sweating during hyperthermia in humans is unknown. H?kfelt et al. (Nature Lond. 284: 515-521, 180) hypothesized that it is vasoactive intestinal polypeptide (VIP) that is cotransmitted with acetylcholine. Heinz-Erian et al. (Science Wash. DC 229: 1407-1408, 1985) reported that VIP innervation is sparse in the skin of persons with cystic fibrosis (CF). A corresponding attenuation of active vasodilation in these subjects would be evidence that VIP is involved in this effector mechanism of human thermor-regulation. Immunocytochemical analysis of skin biopsies from four men with CF confirmed that VIP innervation was sparse. We also analyzed immunoreactivity for calcitonin gene-related peptide (CGRP; normal), substance P (normal), and neuropeptide Y (low). VIP-immunoreactive Merkel cells were abnormal. Despite sparse VIP-immunoreactive innervation, our CF subjects' cutaneous vascular responses to hyperthermia were normal. Because VIP was not completely absent, this evidence is insufficient to rule out VIP as the vasodilator transmitter. However, the CGRP and substance P innervation we observed could mean that release of one or both of these peptides was the mechanism of the fully developed active cutaneous vasodilation.     

Neurotransmission in the vestibular endorgans--glutamatergic transmission in the afferent synapses of hair cells.

In the sensory pathways the first synapse is that between hair cells and primary afferent neurons and its most likely neurotransmitter candidate has long been thought to be glutamate. A number of pharmacological and electrophysiological studies have lent credence to this theory (reviewed by Bledsoe et al. 1988, Bobbin 1979, Ehrenberger and Felix 1991, Puel et al. 1991; Puel 1995) as has recent neurochemical and immunocytochemical work (reviewed by Ottersen et al. 1998; Usami et al. 2000). These recent studies reveal that the afferent hair cell synapse resembles the central glutamate synapses in many ways. Of the proteins confirmed to be involved in signal transduction and transmitter metabolism at most central synapses, many are also seen in the afferent hair cell synapse, and have an analogous compartmentation. On the other hand, there are also important differences, especially those related to the molecular mechanisms that underlie transmitter release.     

Neonatal lesions of catecholaminergic system prevents maturation of cholinergic innervation of the rat neocortex

The influence ofcatecholaminergic system on functioning of the somatosensory and cholinergic systems in early ontogenesis in rats was studied. The neonatal systemic administration of the neurotoxin 6-hydroxydopamine modifies sensitivity of neurons in the somatosensory cortex to peripheral stimulation (stimulation of the sciatic nerve). It is shown that in animals with lesions, catecholaminergic system reduces the number of the cortical neurons responsive to stimulation of ascending cholinergic pathways. The sensitivity of these neurons to acetylcholine does not change. The damage in the early ontogeny catecholaminergic mechanisms seems to prevent maturation of cholinergic afferents in the neocortex.     

Electrophysiological actions of VIP in rat somatosensory cortex.

Electrophysiological and biochemical studies suggest that VIP may exert a facilitating action in the neocortical local circuitry. In the present study, we examined the actions of VIP and VIP + norepinephrine (NE) on somatosensory cortical neuron responses to direct application of the putative transmitters acetylcholine (ACh) and gamma-aminobutyric acid (GABA). Spontaneous and transmitter-induced discharges of cortical neurons from halothane-anesthetized rats were monitored before, during and after VIP, NE and VIP + NE iontophoresis. In 57 VIP-sensitive cells tested, VIP application (5-70 nA) increased (n = 18), decreased (n = 36) or had biphasic actions (n = 3) on background firing rate. In a group of 20 neurons tested for NE + VIP, the combined effect of both peptide and bioamine was predominantly (70%) inhibitory. On the other hand, inhibitory and excitatory responses of cortical neurons to GABA (11 of 15 cases) and ACh (10 of 18 cases), respectively, were enhanced during VIP iontophoresis. Concomitant application of VIP and NE produced additive (n = 2) or more than additive (n = 3) enhancing effects on GABA inhibition. NE administration reversed or enhanced further VIP modulatory actions on ACh-induced excitation. These findings provide electrophysiological evidence that NE and VIP afferents may exert convergent influences on cortical neuronal responses to afferent synaptic inputs such that modulatory actions are anatomically focused within the cortex.     

Sleepy dialogues between cortex and hippocampus: who talks to whom?

During NREM sleep, neocortical neurons undergo near-synchronous transitions, every second or so, between UP states, during which they are depolarized and fire actively, and DOWN states, during which they are hyperpolarized and completely silent. In this issue of Neuron, Isomura et al. report that slow oscillations of membrane potential occur near-synchronously not only in neocortex but also in entorhinal cortex and subiculum. Within the hippocampus proper, pyramidal neurons lack the bistability of UP and DOWN states, but their firing is strongly modulated by cortical activity during the UP state. Intriguingly, many hippocampal neurons fire during the cortical DOWN state. Thus, during sleep UP states, the cortex can talk to the hippocampus, but it is unclear whether the hippocampus talks back.     

Microstructure of the neocortex: Comparative aspects

The appearance of the neocortex, its expansion, and its differentiation in mammals, represents one of the principal episodes in the evolution of the vertebrate brain. One of the fundamental questions in neuroscience is what is special about the neocortex of humans and how does it differ from that of other species? It is clear that distinct cortical areas show important differences within both the same and different species, and this has led to some researchers emphasizing the similarities whereas others focus on the differences. In general, despite of the large number of different elements that contribute to neocortical circuits, it is thought that neocortical neurons are organized into multiple, small repeating microcircuits, based around pyramidal cells and their input-output connections. These inputs originate from extrinsic afferent systems, excitatory glutamatergic spiny cells (which include other pyramidal cells and spiny stellate cells), and inhibitory GABAergic interneurons. The problem is that the neuronal elements that make up the basic microcircuit are differentiated into subtypes, some of which are lacking or highly modified in different cortical areas or species. Furthermore, the number of neurons contained in a discrete vertical cylinder of cortical tissue varies across species. Additionally, it has been shown that the neuropil in different cortical areas of the human, rat and mouse has a characteristic layer specific synaptology. These variations most likely reflect functional differences in the specific cortical circuits. The laminar specific similarities between cortical areas and between species, with respect to the percentage, length and density of excitatory and inhibitory synapses, and to the number of synapses per neuron, might be considered as the basic cortical building bricks. In turn, the differences probably indicate the evolutionary adaptation of excitatory and inhibitory circuits to particular functions.     

Potassium stimulated calcium dependent release of immunoreactive somatostatin from incubated rat hypothalamus

S omatostatin (somatotropin release inhibiting factor, SRIF) is present in the median eminence of the hypothalamus in high concentration (K ronheim et al., 1976), is visualized in nerve endings (H ökfelt et al., 1974) and has been found to be concentrated in the synaptosome fraction of hypothalamic homogenates (E pelbaum et al., 1977; B erelowitz et al., 1978), suggesting a true neurosecretory role. To further explore this possibility we have studied the release of immunoreactive SRIF from the incubated rat hypothalamus (B radbury et al., 1974: R otsztein et al., 1977), basally and in response to depolarising concentrations of potassium, and have assessed the calcium dependence of this release.     

Cholinergic Surface Antigen Chol-1 Is Present in a Subclass of VIP-Containing Rat Cortical Synaptosomes

The colocalization of vasoactive intestinal polypeptide (VIP) with the cholinergic specific surface antigen Chol-1 was investigated in synaptosomes derived from the rat cerebral cortex. Immunoaffinity purification of cortical synaptosomes using antisera to Chol-1 resulted in the copurification of VIP and cholinergic nerve terminals. VIP was purified with a yield of 75% of that of choline acetyltransferase (ChAT). These results suggest that approximately 53% of the cortical cholinergic terminals contain VIP, whereas 75% of the cortical VIP content is present in these cholinergic terminals. Both hypotonic lysis and depolarization of the nerve terminals resulted in the differential release of VIP and acetylcholine (ACh), indicating the different compartmentalization in the same nerve terminal. Complement-mediated lysis of cholinergic nerve terminals, using antisera to Chol-1, resulted in the release of 64% of the ChAT, 71% of ACh, and 27% of the VIP. The application of our method enables quantifying and mapping, with a fast, efficient, and specific technique, the coexisting peptides in cholinergic neurons of distinct brain areas.     

喀麦隆塞玛岭地区溪流中的水生丝孢菌区系

Aquatic hyphomycetes on submerged fallen leaves and deadwoods have been numerously reported in fast running streams in temperate countries(Ingold,1976;Ingold,1979;Chauvet,1990;Barlocher & Rosset,1987;Barlocher et al.,1995;Descals et al.,1995).However,documented information is considerably limited in African countries(Ingold,1956;Dixon,1959;Le-John,1965;Ferreira et al.,1981),and unavailable in Cameroon,a country mostly covered with heavy tropical forests(Loung,1980).This paper is to present a list of aquatic and aeroaquatic hyphomycetes identified from foam samples collected in Cameroon during a two-year survey.     

Tangential migration and proliferation of intermediate progenitors of GABAergic neurons in the mouse telencephalon

In the embryonic neocortex, neuronal precursors are generated in the ventricular zone (VZ) and accumulate in the cortical plate. Recently, the subventricular zone (SVZ) of the embryonic neocortex was recognized as an additional neurogenic site for both principal excitatory neurons and GABAergic inhibitory neurons. To gain insight into the neurogenesis of GABAergic neurons in the SVZ, we investigated the characteristics of intermediate progenitors of GABAergic neurons (IPGNs) in mouse neocortex by immunohistochemistry, immunocytochemistry, single-cell RT-PCR and single-cell array analysis. IPGNs were identified by their expression of some neuronal and cell cycle markers. Moreover, we investigated the origins of the neocortical IPGNs by Cre-loxP fate mapping in transgenic mice and the transduction of part of the telencephalic VZ by Cre-reporter plasmids, and found them in the medial and lateral ganglionic eminence. Therefore, they must migrate tangentially within the telencephalon to reach the neocortex. Cell-lineage analysis by simple-retrovirus transduction revealed that the neocortical IPGNs self-renew and give rise to a small number of neocortical GABAergic neurons and to a large number of granule and periglomerular cells in the olfactory bulb. IPGNs are maintained in the neocortex and may act as progenitors for adult neurogenesis.     

Choline acetyltransferase-containing neurons in the human parietal neocortex

A number of immunocytochemical studies have indicated the presence of cholinergic neurons in the cerebral cortex of various species of mammals. Whether such cholinergic neurons in the human cerebral cortex are exclusively of subcortical origin is still debated. In this immunocytochemical study, the existence of cortical cholinergic neurons was investigated on surgical samples of human parietal association neocortex using a highly specific monoclonal antibody against choline acetyltransferase (ChAT), the acetylcholine biosynthesising enzyme. ChAT immunoreactivity was detected in a subpopulation of neurons located in layers II and III. These were small or medium-sized pyramidal neurons which showed cytoplasmic immunoreactivity in the perikarya and processes, often in close association to blood microvessels. This study, providing demonstration of ChAT neurons in the human parietal neocortex, strongly supports the existence of intrinsic cholinergic innervation of the human neocortex. It is likely that these neurons contribute to the cholinergic innervation of the intracortical microvessels.     

Target influences on transmitter choice by sympathetic neurons developing in the anterior chamber of the eye

In contrast to the majority of sympathetic neurons which are noradrenergic, the sympathetic neurons which innervate sweat glands are cholinergic. Previous studies have demonstrated that during development the sweat gland innervation initially contains catecholamines which are lost as cholinergic function appears. The neurotransmitter phenotype of sweat gland neurons further differs from the majority in that they contain vasoactive intestinal peptide (VIP) rather than neuropeptide Y (NPY). In the experiments described here, we addressed the question of whether sympathetic targets influence the neurotransmitter-related properties of the neurons which innervate them; in particular, do sweat glands play a role in reducing the expression of noradrenergic properties and inducing the expression of cholinergic properties and VIP in sympathetic neurons? This was accomplished by cotransplanting to the anterior chamber of the eye of host rats the superior cervical ganglia (SCG) which contains neurons that normally innervate targets other than the sweat glands and differentiate noradrenergically and footpad tissue from neonatal rats. Sweat glands developed in the transplanted footpad tissue and became innervated by the cotransplanted SCG neurons. The transplanted neurons and sweat gland innervation initially exhibited catecholamine histofluorescence which declined with further development in the anterior chamber. After 4 weeks, choline acetyltransferase (ChAT) and VIP immunoreactivities were evident. These observations suggest that as in the neurons which innervate the glands in situ, noradrenergic properties were suppressed and cholinergic function was induced in the neurons which innervated the glands in oculo. To distinguish a specific influence of the sweat glands on transmitter choice, SCG were also cotransplanted with the pineal gland, a normal target of the ganglion. Neurons cotransplanted with the pineal gland continued to exhibit catecholamine histofluorescence and contained NPY immunoreactivity. At least some neurons in SCG/pineal cotransplants, however, developed ChAT immunoreactivity. The target-appropriate expression of catecholamines and peptides in these experiments is consistent with the hypothesis that some transmitter properties are influenced by target tissues. The indiscriminant expression of ChAT, however, suggests that at least in oculo, additional factors can influence transmitter choice.     

Different long-term effects of bilateral and unilateral nucleus basalis lesions on rat cerebral cortical neurotransmitter content

Young adult rats received either unilateral or bilateral ibotenic acid infusions in their nucleus basalis, destroying most of the cholinesterase-staining neurons in that region. Cerebral cortex levels of choline acetyltransferase, somatostatin, neuropeptide Y, and monoamines were then assayed 2.5 and 10 months after bilateral lesions, or, 2.5, 10, and 14 months after unilateral lesions. Entorhinal and cerebral cortex levels of several amino acid transmitters were also measured. As expected, choline acetyltransferase activity was decreased in the frontal cortex ipsilateral to the ibotenic acid infusion in unilaterally or bilaterally lesioned animals. Parietal cortex concentrations of somatostatin and neuropeptide Y were altered by lesioning in a complicated, time-dependent manner. Thus, while unilateral lesions transiently decreased or had no effect on these neuropeptide levels, bilateral lesions elevated the level of each neuropeptide by over 100% at 10 months. Other cortical transmitter systems investigated appeared to be less affected by nucleus basalis-lesions. Unilateral lesions had no effect on prefrontal cortex norepinephrine, serotonin, or dopamine content at 14 months post-lesioning. These different neurochemical effects of unilateral and bilateral nucleus basalis lesions may be important for developing a model for the trans-synaptic effects of cortical cholinergic deafferentation.     

Induction of micronuclei in mouse bone-marrow cells by the flavonoid 5,3′, 4′-trihydroxy-3,6,7,8-tetramethoxy-flavone (THTMF)

Flavonoids obtained from various plant species are an important source of food additives and drugs. The finding that several compounds of this group had mutagenic activity in microbial tests (Hardigree and Epler, 1978; MacGregor and Jurd, 1978; Seino et al., 1978; Takahashi et al., 1979), induced cytological alterations in plant cells (Segawa and Kondo, 1978) and increased the frequency of micronuclei in mice (Sahu et al., 1981) revealed the importance of flavonoids as environmental mutagens.THTMF was isolated from the Compositae Gutierrezia resinosa (H. et A.) Blake as part of a screening of Chilean plants for anti-cancer activity, and it exhibited an anti-tumor effect in KB cells (Bhakuni et al., 1976; Bittner et al., 1982). Because a large number of anti-cancer compounds are well-known chromosome-breaking agents, we assayed THTMF with the micronucleus test as a prelilminary study on the biological properties of the drug.     

The characteristic three-banded birefringence of ligamentum nuchae elastic fibres indicates ordered micellar texture

The ultrastructural organization of the elastic fibres of bovine ligamentum nuchae is still controversial (Kádár 1979; Sandberg 1976; Sandberg et al. 1981; Quintarelli et al. 1973; Gosline 1976). Polarization microscopy demonstrated convincingly, contrary to a recent negative report (Aaron and Gosline 1980), an ordered birefringent micellar texture (Schmidt 1939; Romhányi 1965; Fischer 1979). The three-banded anisotropic pattern of the fibres can be explained by the optical interference of two micellar textures of opposite orientation, one arranged circularly in the surface layer and the other oriented longitudinally in the axial core of the fibres (Romhányi 1965). Analysis of the underlying molecular mechanism for the anisotropic staining reaction of these fibres with Congo red led to the conclusion that this is due to a definite structural order of specific cross-linking segments within the random network of elastin. The anisotropic staining reaction of the elastic fibres with Congo red is described as the most simple method to demonstrate the three-banded birefringent pattern of ligamentum nuchae elastic fibres even in histologic sections.     

The Effects of Praziquantel on the Monogenean Gill Parasite Pseudodactylogyrus Bini

The anthelminthic Praziquantel is found to be effective against trematodes and cestodes (for a comprehensive review of various aspects of this drug, see Andrews et al. 1983). Praziquantel has been reported to affect fish cestodes (Pool et al. 1984, Moser et al. 1986, Ward et al. 1986), fish digeneans (Bylund & Sumari 1981) and fish monogeneans (Schmahl & Mehlhorn 1985). Therefore Praziquantel could be a potential drug against Pseudodactylogyrus spp. parasitizing the gills of eels. Infections with these monogeneans cause problems in eel farms (Ogawa & Egusa 1976, Egusa 1979, Chan & Wu 1984, Mellergaard & Dalsgaard 1986). Köhler & Bachmann (1978) tested the effect of Praziquantel on the activity of succinate dehydrogenase and NADH-diaphorase (NADH-oxidase) from Ascaris suum and reported that the latter enzyme was inhibited by Praziquantel.     

Sequential phases of cortical specification involve Neurogenin-dependent and -independent pathways

Neocortical projection neurons, which segregate into six cortical layers according to their birthdate, have diverse morphologies, axonal projections and molecular profiles, yet they share a common cortical regional identity and glutamatergic neurotransmission phenotype. Here we demonstrate that distinct genetic programs operate at different stages of corticogenesis to specify the properties shared by all neocortical neurons. Ngn1 and Ngn2 are required to specify the cortical (regional), glutamatergic (neurotransmitter) and laminar (temporal) characters of early-born (lower-layer) neurons, while simultaneously repressing an alternative subcortical, GABAergic neuronal phenotype. Subsequently, later-born (upper-layer) cortical neurons are specified in an Ngn-independent manner, requiring instead the synergistic activities of Pax6 and Tlx, which also control a binary choice between cortical/glutamatergic and subcortical/GABAergic fates. Our study thus reveals an unanticipated heterogeneity in the genetic mechanisms specifying the identity of neocortical projection neurons.     

Involvement of Pituitary Adenylate Cyclase-Activating Polypeptide II Vasoactive Intestinal Peptide 2 Receptor in Mouse Neocortical Astrocytogenesis

Abstract: At the end of neuronal migration, the neopallial germinative zone produces glial cells destined to colonize the upper layers of neocortex. High densities of binding sites for vasoactive intestinal peptide (VIP) have been found in the rodent germinative zone just after completion of neuronal migration, suggesting a possible role of VIP in neocortical astrocytogenesis. In the present study, administration of a VIP antagonist at embryonic days 17 and 18 to pregnant mice was followed by a dramatic depletion of astrocytes in the upper cortical layer of the offspring. The depletion of astrocytes was dose-dependent, with a 42% reduction in the density of astrocytes observed with 50 µg of antagonist. The antagonist effect was reversed by cotreatment with VIP or pituitary adenylate cyclase-activating polypeptide (PACAP), suggesting the involvement of a receptor common to these two neuropeptides. VIP antagonist-induced inhibition of astrocytogenesis was also blocked by Ro 25-1553, a long-acting cyclic VIP analogue selective for the PACAP II VIP2 receptor subclass. Our results demonstrate that VIP and/or PACAP play a crucial physiological role in neocortical astrocytogenesis, possibly through interaction with PACAP II VIP2 receptors.     

Neurons with different neurotransmitters in embryonic neocortical allografts in the rat sciatic nerve

Different subsets of interneurons in the Wistar rat neocortex and in neocortical transplants developing in a damaged nerve were identified by the following immunohistochemical markers: glutamate decarboxylase (GAD 67) for GABAergic nerve cells, NO-synthase (NOS) for NO-ergic neurons, choline acetyltransferase (ChAT) for cholinergic cells, and tyrosine hydroxylase for catecholaminergic structures. Twentyeight days after surgery, individual GAD 67-ir, NO-ir, ChAT-ir, and very rarely TH-ir cells were detected in the graft. It was shown that the number of GAD 67-ir neurons per unit area in the grafts was less than in the rat neocortex P20.