Inhibitory influences of vagal afferences on the oesophageal EMG peristaltic pattern

The influence of vagal afferents on the EMG peristaltic pattern was studied in pigeon oesophagus. Bilateral vagotomy did not abolish the primary peristalsis, but induced significant modifications of the peristaltic pattern parameters. Vagal afferent stimulation induced an inhibitory effect consisting of a temporary break or definitive block of the EMG peristaltic activity already in progress. Vagal afferent stimulation also induced a reduction of the spontaneous EMG activity and this effect was abolished either by glossopharyngeal bilateral section or ganglionic block. Likewise vagal afferent stimulation, the crop distension caused inhibitory effects on EMG peristaltic pattern. This effect was abolished by bilateral vagotomy. These results indicate that vagal afferents, originating from the crop, could influence the central neurons responsible for the peristaltic motor programme.     

Pressure profile along the oesophagus during eructation in sheep.

The pressure profile along the oesophagus was recorded simultaneously with the flow rate of eructated gas in sheep to evaluate the oesophageal motor events leading to the relief of gas. All the eructation sequences started by a rise followed by a plateau of oesophageal pressure. The passage of gas at the tracheal level occurred during this plateau and not during the consecutive transient lowering of the oesophageal pressure. All eructation sequences ended by a peristaltic contraction of the oesophagus. The flow rate pattern of gas during eructation was affected by head position leading to different tensions of the oesophagus. We conclude that, despite the large volume of eructated gases, the eructation process is not significantly different in sheep compared to other animals. Therefore, by virtue of its unique physiological particularity, the sheep might be used as an experimental model for the evaluation of lower oesophageal sphincter (LOS) competence.     

Comparison of kinetic and regulatory properties of high S0.5 form of AMP deaminase from chicken and pigeon liver with AMP deaminase from rat and ox liver

1. The high S0.5 form of AMP deaminase from avian liver was shown to display a two times lower S0.5 value than the single mammalian enzyme form. 2. Avian enzymes showed several fold higher affinity to the activator (ATP) but lower affinity to inhibitors (GTP and Pi) than the mammalian AMP deaminases. 3. GTP was shown to exert a biphasic: activating and inhibitory effect on all the enzymes tested, the chicken and pigeon enzymes being activated within a much broader range of effector concentration. 4. In the presence of 3 mM ATP the activity of avian enzymes was not affected by high GTP and Pi concentrations, in contrast to AMP diaminase from rat liver which was strongly inhibited by GTP under the same experimental conditions. 5. The differences of the regulatory properties described are discussed in terms of adjustment of avian liver AMP deaminase to a faster adenylates' catabolism and thus urate synthesis.     

Identification and partial characterisation of a serum enzyme which hydrolyses epidermal inhibitory pentapeptide

We have identified an enzyme present in mammalian, avian, and reptilian serum which cleaves epidermal inhibitory pentapeptide (pGlu-Glu-Asp-Ser-GlyOH) to form a relatively stable tripeptide (pGlu-Glu-Asp). The enzyme has an inhibitor profile unlike any readily identifiable serum enzyme, and is stable at 4 degrees C for up to 3 months. As most experiments using the pentapeptide are carried out in the presence of serum this finding may have important implications on future research into the biological function of the pentapeptide.     

A novel family of diversified immunoregulatory receptors in teleosts is homologous to both mammalian Fc receptors and molecules encoded within the leukocyte receptor complex

Three novel and closely related leukocyte immune-type receptors (IpLITR) have been identified in channel catfish (Ictalurus punctatus). These receptors belong to a large polymorphic and polygenic subset of the Ig superfamily with members located on at least three independently segregating loci. Like mammalian and avian innate immune regulatory receptors, IpLITRs have both putative inhibitory and stimulatory forms, with multiple types coexpressed in various lymphoid tissues and clonal leukocyte cell lines. IpLITRs have an unusual and novel relationship to mammalian and avian innate immune receptors: the membrane distal Ig domains of an individual IpLITR are related to fragment crystallizable receptors (FcRs) and FcR-like proteins, whereas the membrane proximal Ig domains are related to several leukocyte receptor complex encoded receptors. This unique composition of Ig domains within individual receptors supports the hypothesis that functionally and genomically distinct immune receptor families found in tetrapods may have evolved from such ancestral genes by duplication and recombination events. Furthermore, the discovery of a large heterogeneous family of immunoregulatory receptors in teleosts, reminiscent of amphibian, avian, and mammalian Ig-like receptors, suggests that complex innate immune receptor networks have been conserved during vertebrate evolution.Electronic supplementary material Supplementary material is available for this article at and is accessible for authorized users. GenBank Submissions: The sequences presented in this article have been submitted to GenBank under the following accession numbers: AAW82352, IpLITR1; AAW82353, IpLITR2; AAW82354, IpLITR3.     

A dead giveaway: Foraging vultures and other avian scavengers respond to auditory cues

Carrion represents an unpredictable and widely distributed primary food source for vultures and other avian scavengers. Avian scavengers in African savanna ecosystems are reported to rely exclusively on visual stimuli to locate carcasses. However, carnivores’ predation of large mammalian herbivores and subsequent competition for access to the carcass can result in considerable noise, often audible over long distances and for prolonged periods. Vultures and other avian scavengers may therefore detect and respond to these auditory cues, as do the mammalian carnivores alongside which vultures have coevolved, but this has not been investigated to date. Working in the Serengeti ecosystem, Tanzania, we used diurnal auditory broadcasts to simulate predation and competitive carnivore feeding interactions. Based on the current understanding of avian scavenger ecology, we hypothesized that avian responses to call‐in stations would be evoked exclusively by visual, rather than auditory, cues. We therefore predicted that (a) the arrival of avian scavengers at call‐in stations should be preceded and facilitated by mammalian carnivores and that (b) the arrival of avian scavengers would be positively correlated with the number of mammalian scavengers present, which would increase detectability. We recorded 482 birds during 122 separate playback events. In 22% of these instances, avian scavengers arrived first, ruling out responses based exclusively on visual observations of mammalian carnivores, thereby contradicting our first prediction. Furthermore, the first avian arrivals at survey sessions were inversely related to the number of hyenas and jackals present, contradicting our second prediction. Since no bait or carcasses were used during the experiments, these responses are indicative of the birds’ ability to detect and respond to audio stimuli. Our findings challenge the current consensus of sensory perception and foraging in these species and provide evidence that avian scavengers have the ability to use sound to locate food resources.     

Production and characterization of a soluble, active form of Tva, the subgroup A avian sarcoma and leukosis virus receptor

The receptor for the subgroup A avian sarcoma and leukosis viruses [ASLV(A)] is the cellular glycoprotein Tva. A soluble form of Tva, sTva, was produced and purified with a baculovirus expression system. Using this system, 7 to 10 mg of purified sTva per liter of cultured Sf9 cells was obtained. Characterization of the carbohydrate modification of sTva revealed that the three N glycosylation sites in sTva were differentially utilized; however, the O glycosylation common to Tva produced in mammalian and avian cells was not observed. Purified sTva demonstrates significant biological activity, specifically blocking infection of avian cells by ASLV(A) with a 90% inhibitory concentration of approximately 25 pM. A quantitative enzyme-linked immunosorbent assay, developed to assess the binding of sTva to ASLV envelope glycoprotein, demonstrates that sTva has a high affinity for EnvA, with an apparent dissociation constant of approximately 0.3 nM. Once they are bound, a very stable complex is formed between EnvA and sTva, with an estimated complex half-life of 6 h. The soluble receptor protein described here represents a valuable tool for analysis of the receptor-envelope glycoprotein interaction and for structural analysis of Tva.     

Effect of guanabenz on the peristaltic reflex and on the spontaneous rhythmic movements of the ileum isolated from the rabbit: do the alpha-2-adrenoreceptors constitute a homogenous population?

The inhibitory effect of the predominantly alpha-2 adrenoceptor agonist, guanabenz, on the peristaltic reflex and on the pendular movements of the rabbit isolated ileum was investigated. Guanabenz depressed or abolished the peristaltic reflex as well as the pendular movements. These effects were concentration-dependent. Guanabenz is much more potent inhibiting the peristaltic reflex (IC50 1 X 10(-7) M) than the pendular movements (IC50 1 X 10(-5) M). The choline ester, acetylcholine restored the peristaltic reflex and the anticholinesterase, eserine, restored the pendular movements previously abolished by guanabenz. During the blockade of the peristaltic reflex produced by guanabenz, the pendular movements were virtually not changed. It is therefore reasonable to suppose that the inhibitory effect of guanabenz reflects the different properties of alpha-2 adrenoceptors associated with cholinergic nerve terminals within the myenteric plexus and the longitudinal smooth muscle subserving the peristaltic reflex and the pendular movements.     

Origin of the secondary peristalsis of the esophagus in sheep

Manometric and electromyographic methods were used for investigating oesophageal motor activity in conscious sheep. A contraction wave, the so-called "secondary peristalsis", was readily evoked by means of the fast inflation of a rubber balloon distending the oesophagus. This peristaltic wave travels onto the cardia at the same speed as the primary deglutitive peristalsis (28 m X sec-1, approximately). In that particular species, whose oesophageal muscular coat is all along entirely made of striated fibers, secondary peristalsis is always initiated at the origin of the cervical oesophagus, whatever the site, cervical or thoracic, of the distension.     

Electrical stimulation of glossopharyngeal nerve and oesophageal EMG response in the pigeon

The effects of the efferent glossopharyngeal nerve stimulation, on EMG activity of the pigeon cervical oesophagus, were studied. In control animals, stimulation caused a biphasic response characterized by an intra-stimulus excitatory component followed by a post-stimulus inhibitory one. The EMG response to glossopharyngeal stimulation appeared simultaneously throughout the cervical oesophagus. A bell-shaped mechanical wave was detected relating to the electrical excitatory component. Atropine administration antagonized the excitatory component, while the inhibitory one persisted. It occurs intra-stimulus, and its duration is increased, compared to control ones. A reduction in the oesophageal resting pressure was observed relating to the electrical inhibitory component. Hexamethonium caused complete disappearance of any EMG response to glossopharyngeal stimulation, as well as suppression of mechanical responses. The comparison between the EMG responses to swallow and to efferent glossopharyngeal stimulation suggests that in pigeon cervical oesophagus: primary peristalsis is central in origin; a dual system of glossopharyngeal fibres, excitatory and inhibitory, carries the central control for oesophageal motility; these excitatory and inhibitory fibres supply the oesophageal muscle via intramural neurons; the synaptic arrangement of the inhibitory pathway is more complex than the excitatory one.     

Inhibitory and excitatory effects of methionine-enkephalin in the isolated rabbit ileum

Methionine-enkephalin first inhibited and then stimulated the spontaneous rhythmic activity of the rabbit isolated ileum. The inhibitory effect of methionine-enkephalin was antagonized by naloxone. On the contrary, atropine did not change significantly either the inhibitory or the stimulatory action of this peptide. Furthermore, methionine-enkephalin inhibited the peristaltic reflex of the rabbit isolated ileum as well. Naloxone completely antagonized the inhibition of peristalsis produced by methionine-enkephalin. On the other hand, acetylcholine reversed only the propulsive activity and the back pressure, but not the peristaltic movements of the longitudinal muscle previously abolished by methionine-enkephalin. It appears, therefore, that only the inhibitory effects of methionine-enkephalin are mediated through opioid receptors in the intestine.     

The effect of leucine-enkephalin on the peristaltic reflex of the isolated guinea-pig ileum

Leucine (leu)-enkephalin depresses or inhibits the peristaltic reflex of the isolated guinea-pig ileum. Opiate antagonists (naloxone and nalorphine), choline esters (acetylcholine, methacholine and carbachol), cholinomimetics (muscarine and arecoline) and polypeptides which stimulate peristalsis (eledoisin and angiotensin) antagonize the peristaltic block caused by leu-enkephalin. On the other hand, nicotinic ganglionic stimulants (nicotine and dimethylphenylpiperazine) as well as muscarinic ganglionic stimulants (McN-A-343 and AHR-602) do not restore the peristaltic reflex abolished by leu-enkephalin. Thus the inhibitory effect of leu-enkephalin is due mainly to an action on myenteric ganglia as well as on axon terminals of the myenteric plexus subserving the peristaltic reflex. The inhibitory action of leu-enkephalin may be ascribed to the opiate as well as to the cholinoceptive sites in the nervous elements in the myenteric plexus. The blocking action of leu-enkephalin is not associated with ganglionic muscarinic M-1 receptors as well as with ganglionic nicotinic receptors in the myenteric plexus of the guinea-pig isolated ileum.     

Effectiveness of Hair Bundle Motility as the Cochlear Amplifier

The effectiveness of hair bundle motility in mammalian and avian ears is studied by examining energy balance for a small sinusoidal displacement of the hair bundle. The condition that the energy generated by a hair bundle must be greater than energy loss due to the shear in the subtectorial gap per hair bundle leads to a limiting frequency that can be supported by hair-bundle motility. Limiting frequencies are obtained for two motile mechanisms for fast adaptation, the channel re-closure model and a model that assumes that fast adaptation is an interplay between gating of the channel and the myosin motor. The limiting frequency obtained for each of these models is an increasing function of a factor that is determined by the morphology of hair bundles and the cochlea. Primarily due to the higher density of hair cells in the avian inner ear, this factor is ∼10-fold greater for the avian ear than the mammalian ear, which has much higher auditory frequency limit. This result is consistent with a much greater significance of hair bundle motility in the avian ear than that in the mammalian ear.     

Avian reticuloendotheliosis viruses: evolutionary linkage with mammalian type C retroviruses.

Reticuloendotheliosis viruses have been shown to be causative of tumors in a variety of avian species. The major structural protein of these non-genetically transmitted viruses is demonstrated to possess antigenic determinants common to those of all known mammalian type C viruses. These findings establish a mammalian origin for this oncogenic avian retrovirus group. None of the known mammalian type C virus groups demonstrated a closer immunological relationship to avian reticuloendotheliosis viruses. These results suggest that reticuloendotheliosis viruses have been non-genetically transmitted for a long period of evolution or that these viruses may have arisen by relatively recent infection of birds with an as yet undiscovered mammalian type C retrovirus.     

Specificity of desmin to avian and mammalian muscle cells.

The extent of invariance and heterogeneity in desmin, the major component of the muscle form of 100 Å filaments, has been investigated in avian and mammalian muscle and nonmuscle cells with two-dimensional gel electrophoresis and indirect immunofluorescence. Desmin from chick, duck and quail, smooth, skeletal and cardiac muscle cells is resolved into two isoelectric variants, α and β, with each possessing the same charge and electrophoretic mobility in all three avian species irrespective of muscle type. Guinea pig and rat muscle desmin resolves into only one variant; it also possesses the same charge and electrophoretic mobility in the two mammalian species, but it is more acidic and slower in electrophoretic mobility than the two avian variants.In immunofluorescence, desmin is localized together with α-actinin along myofibril Z lines. Antibodies to chick smooth muscle desmin, prepared against the protein purified by preparative SDS gel electrophoresis prior to immunization, cross-react with myofibril Z lines in all three avian species. These antibodies do not cross-react with either rat or guinea pig myofibril Z lines. Similarly, they do not cross-react with avian or mammalian nonmuscle cells grown in tissue culture and known to contain cytoplasmic 100 Å filaments.These results demonstrate that desmin is highly conserved within avian muscle cells and within mammalian muscle cells. It is, however, both biochemically and immunologically distinguishable between avian and mammalian muscle cells, and between muscle and nonmuscle cells. We conclude that there are biochemically and immunologically specific forms of desmin for avian and mammalian muscle cells. Furthermore, within a particular vertebrate species, there are at least two separate classes of 100 Å filaments: the muscle class whose major component is desmin, and the nonmuscle class whose major component is distinct from desmin. Taking into consideration the immunological specificity reported by other laboratories for the 100 Å filaments in glial cells, for neurofilaments and for the epidermal 80 Å keratin filaments, we propose that a given vertebrate species contains at least four major distinguishable classes of 100 Å filaments: muscle 100 Å filaments (desmin filaments), glial filaments, neurofilaments and epidermal keratin filaments.     

黑龙江凉水和丰林保护区鸟类和兽类多样性

2013年12月至2015年5月、2014年4月至2015年5月利用红外相机分别对黑龙江凉水保护区和丰林保护区鸟兽多样性进行研究:凉水保护区累计10736个捕获日,获得有效照片总数14726张,兽类独立照片514张,共4目7科11种,鸟类独立照片107张,共4目8科11种;丰林保护区累计7460个捕获日,获得有效照片总数13677张,兽类独立照片638张,共3目6科9种,鸟类独立照片166张,共4目10科16种。凉水保护区实际监测到的鸟兽物种数约为全部鸟兽物种的70%—78%;丰林保护区实际监测到的鸟兽物种数目全部鸟兽物种的80%—89%,保护区内大部分物种被监测到。凉水和丰林保护区兽类相对丰富度最高的均为松鼠(Sciurus vulgaris)和花鼠(Eutamias sibiricus),其次为西伯利亚狍(Capreolus capreolu),鸟类相对丰富度最高的普通鳾(Sitta europaea)和白腹鸫(Turdus pallidus);物种多样性指数显示鸟兽多样性无显著差异;鸟、兽群落相似性指数Cs=0.621,凉水和丰林保护区鸟兽物种有较多重叠。利用红外相机对凉水和丰林保护区鸟兽多样性进行研究发现,兽类中对夜行性小型啮齿类监测不足,监测到的鸟类以林下活动为主。