Tachykinin receptors and the airways.

The tachykinins, substance P, neurokinin A and neurokinin B, belong to a structural family of peptides. In mammalian airways, substance P and neurokinin A are colocalized to afferent C-fibres. Substance P-containing fibres are close to bronchial epithelium, smooth muscle, mucus glands and blood vessels. Sensory neuropeptides may be released locally, possibly as a result of a local reflex, and produce bronchial obstruction through activation of specific receptors on these various tissues. Three types of tachykinin receptors, namely NK-1, NK-2 and NK-3 receptors, have been characterized by preferential activation by substance P, neurokinin A and neurokinin B respectively. NK-1 and NK-2 receptors were recently cloned. The determination of receptor types involved in the effects of tachykinins in the airways has been done with synthetic agonists and antagonists binding specifically to NK-1, NK-2 and NK-3 receptors. Although the existence of species differences, the conclusion that bronchial smooth muscle contraction is mainly related to activation of NK-2 receptors on bronchial smooth muscle cell has been drawn. The hypothesis of a NK-2 receptor subclassification has been proposed with NK-2A receptor subtype in the guinea-pig airways. Other effects in the airways are related to stimulation of NK-1 receptors on mucus cells, vessels, epithelium and inflammatory cells. A non-receptor-mediated mechanism is also involved in the effect of substance P on inflammatory cells and mast cells.     

Access to data and material for research: putting empirical evidence into perspective

The aim of this article is to put into critical perspective the empirical findings on secrecy and withholding in research. In other words, by taking existing empirical literature into account, it is intended that a crucial question is answered: Is secrecy and withholding in research harmful or innocuous to science? To understand how secrecy and withholding in research have affected academic science, empirical studies have been placed in the wider context of Mertonian underpinnings of the anticommons threat. The turning point in testing the effects of secrecy and withholding of data and material on scientific research was marked by statistical studies based on surveys and bibliometric measures. These two types of empirical studies have given answers to the basic question since academia was threatened by different modes of practicing science.     

Tachykinin receptors mediating airway macromolecular secretion.

Three tachykinin receptor types, termed NK1, NK2, and NK3, can be distinguished by the relative potency of various peptides in eliciting tissue responses. Airway macromolecular secretion is stimulated by the tachykinin substance P (SP). The purposes of this study were to determine the tachykinin receptor subtype responsible for this stimulation, and to examine the possible involvement of other neurotransmitters in mediating this effect. Ferret tracheal explants maintained in organ culture were labeled with 3H-glucosamine, a precursor of high molecular weight glycoconjugates (HMWG) which are released by airway secretory cells. Secretion of labeled HMWG then was determined in the absence and presence of the tachykinins SP, neurokinin A (NKA), neurokinin B (NKB), physalaemin (PHY), and eledoisin (ELE). All the tachykinins tested stimulated HMWG release to an approximately equal degree. Stimulation was concentration-related, with log concentrations giving half-maximal effects (EC50) as follows: SP -9.47, NKA -7.37, NKB -5.98, PHY -8.08, and ELE -7.68. This rank order of potency (SP greater than PHY greater than or equal to ELE greater than or equal to NKA greater than NKB) is most consistent with NK1 receptors. To evaluate the possible contribution of other mediators, tachykinin stimulation was examined in the presence of several receptor blockers. The potency of SP was not diminished by pretreatment with atropine, propranolol, or chlorpheniramine, and atropine actually increased the magnitude of the secretory response. The SP receptor antagonist [D-Arg1,D-Phe5, D-Trp7,9, Leu11]-SP blocked SP-induced secretion. These findings indicate that SP is a potent stimulus of airway macromolecular secretion. This effect occurs through the action of NK1 receptors, and is not dependent upon cholinergic, beta-adrenergic, or H-1 histamine receptors. The facilitation by atropine of SP stimulation suggests the existence of a mechanism of cholinergic inhibition of SP-induced stimulation.     

Evolutionary insights into umami,sweet, and bitter taste receptors in amphibians

Umami and sweet sensations provide animals with important dietary information for detecting and consuming nutrients, whereas bitter sensation helps animals avoid potentially toxic or harmful substances. Enormous progress has been made toward animal sweet/umami taste receptor (Tas1r) and bitter taste receptor (Tas2r). However, information about amphibians is mainly scarce. This study attempted to delineate the repertoire of Tas1r/Tas2r genes by searching for currently available genome sequences in 14 amphibian species. This study identified 16 Tas1r1, 9 Tas1r2, and 9 Tas1r3 genes to be intact and another 17 Tas1r genes to be pseudogenes or absent in the 14 amphibians. According to the functional prediction of Tas1r genes, two species have lost sweet sensation and seven species have lost both umami and sweet sensations. Anurans possessed a large number of intact Tas2rs, ranging from 39 to 178. In contrast, caecilians possessed a contractive bitter taste repertoire, ranging from 4 to 19. Phylogenetic and reconciling analysis revealed that the repertoire of amphibian Tas1rs and Tas2rs was shaped by massive gene duplications and losses. No correlation was found between feeding preferences and the evolution of Tas1rs in amphibians. However, the expansion of Tas2rs may help amphibians adapt to both aquatic and terrestrial habitats. Bitter detection may have played an important role in the evolutionary adaptation of vertebrates in the transition from water to land.     

Cellular senescence: putting the paradoxes in perspective

Cellular senescence arrests the proliferation of potential cancer cells, and so is a potent tumor suppressive mechanism, akin to apoptosis. Or is it? Why did cells evolve an anti-cancer mechanism that arrests, rather than kills, would-be tumor cells? Recent discoveries that senescent cells secrete growth factors, proteases and cytokines provide a shifting view--from senescence as a cell autonomous suppressor of tumorigenesis to senescence as a means to mobilize the systemic and local tissue milieu for repair. In some instances, this mobilization benefits the organism, but in others it can be detrimental. These discoveries provide potential mechanisms by which cellular senescence might contribute to the diverse, and seemingly incongruent, processes of tumor suppression, tumor promotion, tissue repair, and aging.     

Tachykinin peptide-induced activation and desensitization of neurokinin 1 receptors

The actions of four tachykinins on inhibition and desensitization of the M-current of bullfrog sympathetic neurons have been characterized. Radioligand binding parameters of the tachykinins were determined at a neurokinin receptor in a heterologous expression system. The correlation between binding, signaling and receptor regulation was investigated. A correlation between receptor binding and signaling was found between the peptides; however, their ability to produce desensitization was not correlated with binding and signaling. These results show that the ability of a tachykinin peptide to induce signal activation is not indicative of its ability to induce receptor regulation.     

Tachykinin receptors in the rat brain bind alpha-bungarotoxin

alpha-Bungarotoxin was found to inhibit effectively the binding of 125I-labelled substance P and eledoisin to membrane and to solubilize preparations of the rat brain. Other postsynaptic neurotoxins exerted similar but less pronounced influence on the interaction of tachykinins with their receptors. The obtained results suggest that some alpha-bungarotoxin-binding polypeptides in brain are components of tachykinin receptors.     

Historical perspective: Hormonal regulation of behaviors in amphibians

This review focuses on research into the hormonal control of behaviors in amphibians that was conducted prior to the 21st century. Most advances in this field come from studies of a limited number of species and investigations into the hormonal mechanisms that regulate reproductive behaviors in male frogs and salamanders. From this earlier research, we highlight five main generalizations or conclusions. (1) Based on studies of vocalization behaviors in anurans, testicular androgens induce developmental changes in cartilage and muscles fibers in the larynx and thereby masculinize peripheral structures that influence the properties of advertisement calls by males. (2) Gonadal steroid hormones act to enhance reproductive behaviors in adult amphibians, but causal relationships are not as well established in amphibians as in birds and mammals. Research into the relationships between testicular androgens and male behaviors, mainly using castration/steroid treatment studies, generally supports the conclusion that androgens are necessary but not sufficient to enhance male behaviors. (3) Prolactin acts synergistically with androgens and induces reproductive development, sexual behaviors, and pheromone production. This interaction between prolactin and gonadal steroids helps to explain why androgens alone sometimes fail to stimulate amphibian behaviors. (4) Vasotocin also plays an important role and enhances specific types of behaviors in amphibians (frog calling, receptivity in female frogs, amplectic clasping in newts, and non-clasping courtship behaviors). Gonadal steroids typically act to maintain behavioral responses to vasotocin. Vasotocin modulates behavioral responses, at least in part, by acting within the brain on sensory pathways that detect sexual stimuli and on motor pathways that control behavioral responses. (5) Corticosterone acts as a potent and rapid suppressor of reproductive behaviors during periods of acute stress. These rapid stress-induced changes in behaviors use non-genomic mechanisms and membrane-associated corticosterone receptors.     

PATIKAmad: putting microarray data into pathway context

High-throughput experiments, most significantly DNA microarrays, provide us with system-scale profiles. Connecting these data with existing biological networks poses a formidable challenge to uncover facts about a cell's proteome. Studies and tools with this purpose are limited to networks with simple structure, such as protein-protein interaction graphs, or do not go much beyond than simply displaying values on the network. We have built a microarray data analysis tool, named PATIKAmad, which can be used to associate microarray data with the pathway models in mechanistic detail, and provides facilities for visualization, clustering, querying, and navigation of biological graphs related with loaded microarray experiments. PATIKAmad is freely available to noncommercial users as a new module of PATIKAweb at http://web.patika.org.     

Insight into tachykinin-related peptides,their receptors,and invertebrate tachykinins: a review

Tachykinins (TKs) constitute the largest vertebrate neuropeptide family with multifunctions in central and peripheral tissues. In several invertebrate species, two types of structurally related peptides, 'tachykinin-related peptides (TKRPs)' and 'invertebrate tachykinins (inv-TKs)' have been identified. TKRPs, isolated from the nerve and/or gut tissues, contain the common C-terminal sequence -Phe-X-Gly-Y-Arg-NH(2) (X and Y are variable) analogous to the vertebrate TK consensus -Phe-X-Gly-Leu-Met-NH(2), and exhibit vertebrate TK-like contractile activity on invertebrate gut tissues. Inv-TKs have been shown to be present exclusively in the salivary gland of several species, to share vertebrate TK consensus motif, and to possess TK-like potencies on vertebrate, not invertebrate tissues. However, the functional and evolutionary relevance of TKRPs and inv-TKs to vertebrate TKs remains to be understood. Recent studies have revealed that TKRP precursors dramatically differ from vertebrate preprotachykinins in structural organization and that TKRP receptors share structural and functional properties with vertebrate TK receptors. Moreover, the C-terminal arginine in TKRPs has been shown to play an essential role in discriminating their receptors from vertebrate TK receptors. Such recent marked progress is expected to enhance further investigation of biological roles of TKRPs. This review provides an overview of the basic findings obtained previously and a buildup of new knowledge regarding TKRPs and inv-TKs. We also compare TKRPs and inv-TKs to vertebrate TKs with regard to evolutionary relationships in structure and function among these structurally related peptides.     

Positional orthology: putting genomic evolutionary relationships into context

Orthology is a powerful refinement of homology that allows us to describe more precisely the evolution of genomes and understand the function of the genes they contain. However, because orthology is not concerned with genomic position, it is limited in its ability to describe genes that are likely to have equivalent roles in different genomes. Because of this limitation, the concept of 'positional orthology' has emerged, which describes the relation between orthologous genes that retain their ancestral genomic positions. In this review, we formally define this concept, for which we introduce the shorter term 'toporthology', with respect to the evolutionary events experienced by a gene's ancestors. Through a discussion of recent studies on the role of genomic context in gene evolution, we show that the distinction between orthology and toporthology is biologically significant. We then review a number of orthology prediction methods that take genomic context into account and thus that may be used to infer the important relation of toporthology.     

Carbohydrate recognition systems in amphibians: primitive alpha 2-macroglobulin receptors

Two alpha-macroglobulins were isolated from the plasma of the frog. Murine clearance studies were performed with these proteins after they were reacted with proteinase. These studies indicated that clearance behavior was more complex than observed with avian or human homologues, since it involved not only specific receptors for the complex, but also carbohydrate recognition. Recognition of one of these macroglobulins by both the alpha-macroglobulin receptor and carbohydrate receptors required conformational change in the inhibitor. Clearance studies were then performed in frogs to probe the nature of carbohydrate receptor recognition. Model glycoproteins were employed to avoid the problem of heterogeneous carbohydrate end groups in the alpha-macroglobulins. These studies demonstrated that the N-acetylglucosamine/mannose receptor is the major carbohydrate recognition system in frogs.     

Atrial natriuretic peptides: receptors and second messengers

Atrial natriuretic peptides appear to elicit their actions in some target tissues by binding to a novel cell-surface transmembrane protein which possesses both peptide binding and guanylate cyclase activities. Ligand binding stimulates enzyme activity to produce increased intracellular concentrations of cyclic GMP which, in turn, mediates the cell's physiological response.     

An immimohistochemical study of regulatory peptides in lungs of amphibians

Summary The lungs of five species of European Anura and one species of Urodela (Triturus alpestris) have been studied by immunohistochemical methods to determine the occurrence, localization and distribution of serotonin, neuron-specific enolase, and eight regulatory peptides reported in the mammalian respiratory tract.Single and groups of serotonin-immunoreactive cells, corresponding to neuroendocrine cells of the mammalian lung, were identified in lungs of all amphibian species studied. Immunoreactivity for neuron-specific enolase was localized mainly in pulmonary nerves, nerve cell bodies and neuroendocrine cells. The localization and distribution of regulatory peptides varied among species. Bombesin and gastrin-releasing peptide immunoreactivities (predominant peptides in human lung) were localized mostly in submucosal nerves. Single bombesin-immunoreactive cells were found only in lungs of Urodela, i.e., Triturus alpestris. Occasional single cells, immunoreactive for somatostatin and leu-enkephalin were identified in lungs of Bombina variegata and a few cholecystokinin-immunoreactive cells in Hyla arborea. In all anuran species, numerous substance P-immunoreactive nerves were identified in submucosa, pulmonary septa and around blood vessels. No immunoreactive cells or nerves were demonstrated with antibodies against calcitonin and vasoactive intestinal peptide.The term pulmonary neuroendocrine (NE) cells (used here) does not imply neural origin or classical endocrine function for these cells, but rather indicates their potential involvement in neurohormonal regulation of pulmonary function (Cutz 1982)Supported by grant to E.C. from Medical Research Council of Canada (MT-7641)     

Breeding trees resistant to insects and diseases: putting theory into application

Tree species world-wide are under increasing threat from diseases and insects, many of which are non-native. The integrity of our natural, urban and plantation forest ecosystems, and the services they provide are seriously imperiled. Breeding programs that harness the natural genetic resistance within tree species can provide a durable solution to these threats. In many cases, genetic resistance offers the key to restoration of forests and may even prevent extinction of some tree species. The potential use of genetic resistance is often widely discussed, but the development of applied programs and use of resistant seed has only taken place in a relatively few species. The reflections here from some of the most advanced applied resistance programs, as well as some of the unknowns and limitations of implementing a resistance program will provide a guide to managers considering this approach. In any such program, there is a research component, a tree improvement component and a restoration and reforestation component. These three components, along with sustained management and public support, need to be linked for any genetic resistance program to be fully successful in facilitating the recovery of healthy forests. Other management activities and newly developing technologies may serve to complement genetic resistance or to expedite its development, but premature, over-emphasis on some of these may slow the operational program. An understanding of the level, frequency, durability and stability of resistance and its limitations are necessary to management planning.     

Interaction of antimicrobial peptides from Australian amphibians with lipid membranes

Solid-state NMR and CD spectroscopy were used to study the effect of antimicrobial peptides (aurein 1.2, citropin 1.1, maculatin 1.1 and caerin 1.1) from Australian tree frogs on phospholipid membranes. 31P NMR results revealed some effect on the phospholipid headgroups when the peptides interact with DMPC/DHPC (dimyristoylphosphatidylcholine/dihexanoylphosphatidylcholine) bicelles and aligned DMPC multilayers. 2H NMR showed a small effect of the peptides on the acyl chains of DMPC in bicelles or aligned multilayers, suggesting interaction with the membrane surface for the shorter peptides and partial insertion for the longer peptides. 15N NMR of selectively labelled peptides in aligned membranes and oriented CD spectra indicated an alpha-helical conformation with helix long axis approximately 50 degrees to the bilayer surface at high peptide concentrations. The peptides did not appear to insert deeply into PC membranes, which may explain why these positively charged peptides preferentially lyse bacterial rather than eucaryotic cells.