Substance P-like immunoreactive nerve fibers in the pars distalis of the anterior pituitary in the dog

Summary The pars distalis of the anterior pituitary is known to be regulated by hypothalamic hormones. Recently, we have discovered the presence of substance P-like immunoreactive nerve fibers in the pars distalis of the monkeys. Substance P-like immunoreactivity in the pars distalis of the dog was investigated in this study. A substantial amount of substance P-like immunoreactive nerve fibers with a large amount of varicosities were found. They were widely distributed in the gland, more abundant along its periphery. Most of them were closely related to the glandular tissue, some were located on vascular walls. Substance P-like immunoreactive nerve fibers were also found in the meningeal sheath of the anterior pituitary. They could be followed into the parenchyma of the gland.     

Substance P Enhances Desensitization of the Nicotinic Response in Bovine Chromaffin Cells but Enhances Secretion upon Removal

A fundamental process in neurosecretion is desensitization, or a declining response to a stimulus. The response of chromaffin cells to continuous nicotinic stimulation, secretion of catecholamines, desensitizes within a few minutes. The neuropeptide substance P (SP) has been reported to prevent desensitization in culture dish experiments and to enhance desensitization in patch clamp studies. In the present study, these contradictory responses have been demonstrated and the apparent contradictions resolved. We have measured catecholamine secretion by on-line electrochemical detection in a constant-pressure flow system. Isolated chromaffin cells cultured on quartz plates were stimulated with the nicotinic agonist 1,1-dimethyl-4-phenylpiperazinium (DMPP) in the presence and absence of SP. SP inhibited secretion and increase the rate of desensitization compared with stimulation by DMPP alone. However, when the cells were stimulated a second time with DMPP alone immediately after 5-min stimulation with SP + DMPP, the rate of desensitization was markedly lower than the control. Removal of SP after a desensitizing stimulation with SP + DMPP caused a slow secondary release of catecholamine in response to the continued stimulation with DMPP. The kinetic analysis of the secretory response shows that the primary response to SP is enhanced desensitization, but that upon removal of SP the response to DMPP desensitizes less rapidly. We suggest that SP protects some receptors from nicotinic desensitization while holding them in an inactive state, and that upon removal of SP these receptors can slowly respond to DMPP.     

Denver Papillae Protocol for Objective Analysis of Fungiform Papillae

The goal of the Denver Papillae Protocol is to use a dichotomous key to define and prioritize the characteristics of fungiform papillae (FP) to ensure consistent scoring between scorers. This protocol builds off of a need that has arisen from the last two decades of taste research using FP as a proxy for taste pore density. FP density has historically been analyzed using Miller & Reedy’s 1990 characterizations of their morphology: round, stained lighter, large, and elevated. In this work, the authors forewarned that stricter definitions of FP morphology needed to be outlined. Despite this call to action, follow up literature has been scarce, with most studies continuing to cite Miller & Reedy’s original work. Consequently, FP density reports have been highly variable and, combined with small sample sizes, may contribute to the discrepant conclusions on the role of FP in taste sensitivity. The Genetics of Taste Lab explored this apparent inconsistency in counting and found that scorers were individually prioritizing the importance of these characteristics differently and had no guidance for when a papilla had some, but not all, of the reported qualities of FP. The result of this subjectivity is highly variable FP counts of the same tongue image. The Denver Papillae Protocol has been developed to remedy this consequence through use of a dichotomous key that further defines and prioritizes the importance of the characteristics put forth by Miller & Reedy. The proposed method could help create a standard way to quantify FP for researchers in the field of taste and nutritional studies.     

Calcitonin gene-related peptide and substance P in the pharynx and lung of the bullfrog,Rana catesbeiana

Indirect double immunofluorescence labelling in the pharynx and lung of the bullfrog, Rana catesbeiana, demonstrated the occurrence, distribution, and coexistence of two neuropeptides. In the pharynx, immunoreactive calcitonin gene-related peptide (CGRP) and substance P (SP) were localized in nerve fibers distributed within and just beneath the ciliated epithelium. In the lung, CGRP and SP were localized in nerve fibers in five principal locations: 1) within the smooth muscle layer in the interfaveolar septa; 2) in the luminal thickened edges of the septa; 3) around the pulmonary vasculature; 4) within, and 5) under the ciliated epithelium. Within the smooth muscle layer in the septa, luminal thickened septa, and around blood vessels, almost all fibers showed coexistence of CGRP and SP. Within and just beneath the ciliated epithelium in the thickened septa, all fibers showed coexistence of CGRP and SP. No immunoreactivity for vasoactive intestinal polypeptide, neuropeptide Y, galanin, somatostatin, FMRFamide, and leucine-and methionine-enkephalins was detected in the nerve fibers within the larynx and the lung. Together with our previous data, the present findings suggest that peptidergic mechanisms are involved in the regulation of amphibian respiratory systems throughout their life.     

Acute effect of substance P in immunologic vasculitis in the rat colon

Substance P has been implicated as a neuronal mediator of inflammation in various inflammatory conditions. However, the exact role played by substance P in inflammatory bowel diseases or in experimental colonic vasculitis has not been clearly understood. In this study, we examined the effect of close superior mesenteric artery injection of substance P under prevailing inflammatory conditions induced by intravenous human albumin antialbumin immune complex followed by intracolonic perfusion of 2.5% formaldehyde in rats or intracolonic perfusion of 5% alcohol alone. The immune complex- and formaldehyde-treated rats showed severe microvascular changes such as microvascular plugging by red blood cells, endothelial breakage and extravasation of plasma proteins and red blood cells. The bolus injection of 10⁻⁸ M substance P reduced extravasation of Evans blue dye by 50% and the tissue wet to dry ratio by 20% in immune complex- and formaldehyde-perfused rats. Myeloperoxidase activity was not changed. Substance P also significantly inhibited (44%) the extravasation in alcohol-perfused rats. Pretreatment of immune complex- and formaldehyde-treated rats with substance P antagonist reversed the effect of substance P. These findings suggest that the most immediate effect of substance P may be vasodilation and clearing of vascular plugs induced by immune complex and formaldehyde. This effect of substance P differs from its chronic effect, which causes vasodilation and extravasation.     

Neurokinin A-like immunoreactivity in feline dental pulp: its distribution,origin and coexistence with substance P-like immunoreactivity

Summary The distribution and origin of neurokinin A (NKA)-like immunoreactivity were investigated in feline dental pulp by an indirect immunofluorescence method. NKA-containing nerve fibres with varicosities, which entered the dental pulp via apical foramen, were distributed throughout this tissue. Many NKA-containing nerve fibres were localized around blood vessels, but some were observed apart therefrom. At the odontoblastic layer, thin NKA-containing nerve fibres were observed running straight toward the pulp-predentinal border between odontoblasts. After inferior alveolar nerve section, all NKA-containing nerve fibres disappeared in the dental pulp, while the removal of the superior cervial ganglion resulted in no change in the distribution of these fibres. The correlation of NKA-like immunoreactivity and substance P (SP)-like immunoreactivity was also investigated by double-immunofluorescence technique. The distribution of NKA-containing nerve fibres was very similar to that of SP-containing nerve fibres; it appeared that all NKA-containing nerve fibres contained SP.     

Untersuchungen an den Geschmacksknospen der Barteln von Corydoras paleatus Jenyns

Zusammenfassung Der Bau der Geschmacksknospen auf den Barteln von Corydoras paleatus Jen. wurde elektronenmikroskopisch untersucht. Jede Geschmacksknospe ist aus 2 Zelltypen aufgebaut: den Rezeptorzellen und den sie umhüllenden Stützzellen. Die sich von der Geschmacksknospenbasis bis zur Oberfläche erstreckenden Stützzellen tragen einen Mikrovillibesatz. — Die einheitlich gestalteten Rezeptoren, die im Längsschnitt spindelförmig, im Querschnitt rund sind, besitzen zum Unterschied von den Stützzellen zahlreiche Mitochondrien und peripher gelagerte Vesikel sowie 2 Typen von Tubuli. Der Zellapex trägt einen über die freie Oberfläche senkrecht hinausragenden, schlankkegelförmigen Fortsatz mit rundem oder ovalem Querschnitt. — Innerhalb der Bindegewebspapille befindet sich dicht unter der Geschmacksknospenbasis ein Plexus von Axonbündeln, von dem aus die Axone meist einzeln an das Perikaryon der Rezeptorzellen herantreten. In der Nähe der Kontaktstelle mit dem Rezeptor sind häufig Tubulibündel zu finden. — Die meisten Geschmacksknospen enthalten einzelne degenerierende Zellen. — Im Epithel zwischen den Geschmacksknospen wurde ein besonderer Sekretzellentyp nachgewiesen.

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Investigation of taste buds of barbels in Corydoras paleatus JenynsI. Ultrastructure of the taste buds

Summary The taste buds of the barbels of Corydoras paleatus have been studied with the electron microscope. Each taste bud is composed of two cell types: receptor cells and supporting cells. The supporting cells extend from the base of the taste bud to the surface where they bear microvilli. The apex of the uniform, spindle shaped receptor cells has a free, cone-shaped appendage. The receptor cells, unlike the supporting cells, contain numerous mitochondria, peripherally-located vesicles, and two types of tubuli. Single axons project from a nerve plexus close to the base of the taste bud and run to perikarya of the receptor cells. Frequently bundles of tubuli lie close to the area of contact between axon and receptor cell membranes. Most of the taste buds contain individual degenerating cells. A special type of secretory cell is present in the epithelium of the barbels.

     

大鼠初级感觉神经元P2X3受体的表达及其与SP的关系

目的研究在大鼠初级感觉神经元细胞上P2X3受体的表达情况及其与P物质的关系。方法取SD大鼠背根神经节(DRG)和三叉神经节(TG)固定后切片;用抗P2X3受体抗体和抗SP抗体进行免疫组织化学反应,并通过两种不同的显色方法同时进行P2X3受体和SP的双标。结果P2X3免疫反应阳性细胞主要集中在小细胞和中等细胞(其中在TG,P2X3-ir阳性神经元约占整个细胞的24.8%;在DRG约31.7%的神经元是P2X3-ir阳性),并且在DRG和TG细胞上均存在有P2X3受体和SP共存(TG上的双标细胞占P2X3-ir阳性细胞总数的36.26%,DRG上占46.81%)。结论由于ATP门控阳离子通道受体P2X3本身就与伤害性感受的初级传入有关,而它与SP的共存可提示当组织中的ATP释放时可以通过P2X3受体作用于含SP的伤害性感觉神经末梢上,促使SP释放引起痛觉过敏。     

Multiple Shh signaling centers participate in fungiform papilla and taste bud formation and maintenance

The adult fungiform taste papilla is a complex of specialized cell types residing in the stratified squamous tongue epithelium. This unique sensory organ includes taste buds, papilla epithelium and lateral walls that extend into underlying connective tissue to surround a core of lamina propria cells. Fungiform papillae must contain long-lived, sustaining or stem cells and short-lived, maintaining or transit amplifying cells that support the papilla and specialized taste buds. Shh signaling has established roles in supporting fungiform induction, development and patterning. However, for a full understanding of how Shh transduced signals act in tongue, papilla and taste bud formation and maintenance, it is necessary to know where and when the Shh ligand and pathway components are positioned. We used immunostaining, in situ hybridization and mouse reporter strains for Shh, Ptch1, Gli1 and Gli2-expression and proliferation markers to identify cells that participate in hedgehog signaling. Whereas there is a progressive restriction in location of Shh ligand-expressing cells, from placode and apical papilla cells to taste bud cells only, a surrounding population of Ptch1 and Gli1 responding cells is maintained in signaling centers throughout papilla and taste bud development and differentiation. The Shh signaling targets are in regions of active cell proliferation. Using genetic-inducible lineage tracing for Gli1-expression, we found that Shh-responding cells contribute not only to maintenance of filiform and fungiform papillae, but also to taste buds. A requirement for normal Shh signaling in fungiform papilla, taste bud and filiform papilla maintenance was shown by Gli2 constitutive activation. We identified proliferation niches where Shh signaling is active and suggest that epithelial and mesenchymal compartments harbor potential stem and/or progenitor cell zones. In all, we report a set of hedgehog signaling centers that regulate development and maintenance of taste organs, the fungiform papilla and taste bud, and surrounding lingual cells. Shh signaling has roles in forming and maintaining fungiform papillae and taste buds, most likely via stage-specific autocrine and/or paracrine mechanisms, and by engaging epithelial/mesenchymal interactions.     

Ago-Allosteric Modulation and Other Types of Allostery in Dimeric 7TM Receptors

Conventionally, an allosteric modulator is neutral in respect of efficacy and binds to a receptor site distant from the orthosteric site of the endogenous agonist. However, recently compounds being ago-allosteric modulators have been described i.e., compounds acting both as agonists on their own and as enhancers for the endogenous agonists in both increasing agonist potency and providing additive efficacy—superagonism. The additive efficacy can also be observed with agonists, which are neutral or even negative modulators of the potency of the endogenous ligand. Based on the prevailing dimeric concept for 7TM receptors, it is proposed that the ago-allosteric modulators bind in the orthosteric binding site, but–importantly–in the “other” or allosteric protomer of the dimer. Hereby, they can act both as additive co-agonists, and through intermolecular cooperative effects between the protomers, they may influence the potency of the endogenous agonist. It is of interest that at least some endogenous agonists can only occupy one protomer of a dimeric 7TM receptor complex at a time and thereby they leave the orthosteric binding site in the allosteric protomer free, potentially for binding of exogenous, allosteric modulators. If the allosteric modulator is an agonist, it is an ago-allosteric modulator; if it is neutral, it is a classical enhancer. Molecular mapping in hetero-dimeric class-C receptors, where the endogenous agonist clearly binds only in one protomer, supports the notion that allosteric modulators can act through binding in the “other” protomer. It is suggested that for the in vivo, clinical setting a positive ago-allosteric modulator should be the preferred agonist drug.