Fluid secretion by the malpighian tubules of the tsetse fly Glossina morsitans: the effects of ouabain, ethacrynic acid and amiloride.
The effects of three inhibitors of sodium transport on the secretion of fluid by the Malpighian tubules of Glossina morsitans have been observed. The cardiac glycoside, ouabain, affects neither the rate of secretion nor the sodium concentration of the fluid secreted when isolated tubules are bathed by solutions containing a range of sodium and potassium concentrations. Secretion is inhibited, however, by ethacrynic acid and amiloride. The results confirm that fluid secretion by the Malpighian tubules of this insect is dependent on the active transport of sodium ions and show that Na+/k+ exchange pumps are not involved in this process. (+info)
Sodefrin: a novel sex pheromone in a newt.
The abdominal gland in the male red-bellied newt, Cynops pyrrhogaster, is the source of a female-attracting pheromone. An attempt was made to isolate and characterize the female-attracting pheromone in the abdominal glands of male newts. The active substance, named sodefrin (from the Japanese 'sodefuri' which means 'soliciting') has been isolated and shown to be a novel decapeptide with the sequence, Ser-Ile-Pro-Ser-Lys-Asp-Ala-Leu-Leu-Lys. Its minimum effective concentration in water is 0.1-1.0 pmol 1-1. Synthetic sodefrin shows a female-attracting activity similar to that of the native peptide, and acts through the olfactory organ of female newts. Electrophysiological studies reveal that sodefrin evokes a marked electroolfactogram response in the vomeronasal epithelium in sexually mature females and in ovariectomized females treated with prolactin and oestrogen. The pheromonal activity of sodefrin appears to be species-specific since it does not attract females of a congeneric species, the sword-tailed newt C. ensicauda. However, C. ensicauda has a variant of sodefrin differing from that in C. pyrrhogaster by substitutions of Leu for Pro at position 3 and Gln for Leu at position 8. The C. ensicauda variant sodefrin does not attract C. pyrrhogaster females. Genes encoding the sodefrin precursor protein have been cloned in both C. pyrrhogaster and C. ensicauda. Immunostaining of the abdominal gland using the antiserum against sodefrin shows that sodefrin occurs in the epithelial cells, predominantly within the secretory granules. Sodefrin content, detected by immunoassay, in C. pyrrhogaster males decreases after castration and hypophysectomy and increases markedly in the castrated and hypophysectomized newts after treatment with androgen and prolactin. This combination of hormones also enhances sodefrin mRNA content in the abdominal gland as assessed by northern blot analysis using sodefrin cDNA. (+info)
Chick Barx2b, a marker for myogenic cells also expressed in branchial arches and neural structures.
We have isolated a new chicken gene, cBarx2b, which is related to mBarx2 in sequence, although the expression patterns of the two genes are quite different from one another. The cBarx2b gene is expressed in craniofacial structures, regions of the neural tube, and muscle groups in the limb, neck and cloaca. Perturbation of anterior muscle pattern by application of Sonic Hedgehog protein results in a posteriorization of cBarx2b expression. (+info)
Ortho- and paramyxoviruses from migrating feral ducks: characterization of a new group of influenza A viruses.
Ortho- and parainfluenza viruses isolated from the cloacas of migrating feral ducks shot on the Mississippi flyway included three strains of influenza. A virus (Hav6 Nav1, Hav6 Nl, Hav7 Neq2) as well as Newcastle disease virus. One influenza virus, A/duck/Memphis/546/74, possessed Hav3 haemagglutinin, but the neuraminidase was not inhibited by any of the known influenza reference antisera. The neuraminidase on this virus was related to the neuraminidases on A/duck/GDR/72 (H2 N?), A/turkey/Ontario/7732/66 (Hav 5 N?), A/duck/Ukraine/1/60 (Hav3 N?) and A/turkey/Wisconsin/68. We therefore propose that the neuraminidase on this group of influenza viruses be designated Nav6. The A/duck/Memphis/546/74 influenza virus caused an ocular discharge in 1 of 5 ducks and was shed in faeces for 10 days; it was stable in faecal samples for up to 3 days at 20 degrees C. These results suggest that ecological studies on influenza in avian species should include attempts to isolate virus from faeces. Faecal-oral transmission is an attractive explanation for the spread of influenza virus from feral birds to other animals. (+info)
Innervation of NADPH diaphorase-containing neurons correlated with acetylcholinesterase, tyrosine hydroxylase, and neuropeptides in the pigeon cloaca.
The motility of the avian cloaca is under neural control, but little is known about the neural network that accomplishes this function. This present study was designed to determine the distribution of nitric oxide-synthesising neurons in the pigeon cloaca by enzyme histochemistry for reduced nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d). NADPH-d-positive staining was seen in the neurons and fibres in the cloaca. The highest density of nerve fibres was noted in the coprodeum and the lowest in the proctodeum. In the coprodeum, NADPH-d neurons were found singly, formed small groups of 2-10 neurons, or were seen in plexuses in the muscle layer, lamina propria, or around the arterioles. Several NADPH-d-positive neurons were also observed in the ganglia of the cloaca. NADPH-d fibres ran in the muscle layer, lamina muscularis mucosae and lamina propria, or surrounded blood vessels. The distribution pattern of acetylcholinesterase (AChE)-stained neurons and fibres in the cloaca was similar to that of NADPH-d. Double staining for NADPH-d and AChE showed colocalisation of the 2 enzymes in many neurons of the cloaca. Tyrosine hydroxylase (TH)-immunoreactive nerve fibres originating outside the cloaca were also noted. In the urodeum and proctodeum, neurons or fibres positive for NADPH-d, AChE or TH were scattered in the lamina propria. Nerve fibres immunoreactive for calcitonin-gene related peptide, galanin, methionine-enkephalin, substance P, and vasoactive intestinal peptide were found sparsely in the cloaca. Our results demonstrate that nitrergic neurons constitute a subpopulation which is closely associated with the cholinergic system in the pigeon cloaca. (+info)
Anorectal malformations caused by defects in sonic hedgehog signaling.
Anorectal malformations are a common clinical problem affecting the development of the distal hindgut in infants. The spectrum of anorectal malformations ranges from the mildly stenotic anus to imperforate anus with a fistula between the urinary and intestinal tracts to the most severe form, persistent cloaca. The etiology, embryology, and pathogenesis of anorectal malformations are poorly understood and controversial. Sonic hedgehog (Shh) is an endoderm-derived signaling molecule that induces mesodermal gene expression in the chick hindgut. However, the role of Shh signaling in mammalian hindgut development is unknown. Here, we show that mutant mice with various defects in the Shh signaling pathway exhibit a spectrum of distal hindgut defects mimicking human anorectal malformations. Shh null-mutant mice display persistent cloaca. Mutant mice lacking Gli2 or Gli3, two zinc finger transcription factors involved in Shh signaling, respectively, exhibit imperforate anus with recto-urethral fistula and anal stenosis. Furthermore, persistent cloaca is also observed in Gli2(-/-);Gli3(+/-), Gli2(+/-);Gli3(-/-), and Gli2(-/-);Gli3(-/-) mice demonstrating a gene dose-dependent effect. Therefore, Shh signaling is essential for normal development of the distal hindgut in mice and mutations affecting Shh signaling produce a spectrum of anorectal malformations that may reveal new insights into their human disease equivalents. (+info)
Excretory role of the midgut in larvae of the tobacco hornworm, Manduca sexta (L.).
Caterpillars of Manduca sexta use two distinct transport mechanisms for the excretion of dyes. One pump (Type A) has a high affinity for acid (anionic) dyes and occurs in the midgut and medial Malpighian tubules. Acid dyes accumulate rapidly in the lumen of the midgut while the Malpighian tubules appear to play only a minor role in the excretion of these dyes. The other pump (Type B) excretes basic (cationic) dyes and is located primarily in the proximal Malpighian tubules. Evidence is presented that hippuric acid competes with acid dyes for excretion by both midgut and Malpighian tubules. After the final-instar larva purges its gut the ability of the midgut and Malpighian tubules to excrete dyes gradually decreases. Sixty hours after the purge only the Malpighian tubules retain some dye excreting activity. (+info)
The removal of sulphate by the excretory apparatus of the blowfly Calliphora vomitoria.
The excretion of sulphate by the isolated Malpighian tubules of Calliphora vomitoria has been investigated. Contrary to expectation, it was found that the isolated tubules are freely permeable to sulphate. The rate of sulphate secretion is comparable to the rates of secretion of both phosphate and chloride. The excretion of sulphate by the intact fly has also been verified. (+info)