Studies on the cardiac physiology of Onychophora and Chilopoda

Cardiac physiology in Onychophora and Chilopoda has not yet been studied by electrophysiological methods. Here we present ECGs and the first intracellular recordings from dorsal vessel muscle cells in Scolopendra cingulata, Lithobius forficatus and Peripatopsis sp. In Onychophora, a myogenic automatism generates the heart function. In the Chilopoda examined, heartbeat is triggered by a neurogenic automatism that is superimposed over a basic myogenic rhythm, which occurs under experimental conditions. The neuropeptide proctolin and the head peptide have no significant effects in the species investigated. The results are discussed from the viewpoints of comparative physiology and phylogenetics.     

Cardiac transplantation and resistance artery myogenic tone

Transplantation is an effective treatment for end-stage heart disease; however, most grafts eventually fail by progressive cardiac failure. Primarily, failure is ischemic due to the occlusive nature of transplant vascular disease (TVD). Early after transplantation and preceding TVD, alterations in coronary physiology such as reduced vascular myogenic tone occur. Resistance arteries possess an inherent ability to constrict in response to transmural pressure; this constrictive response (myogenic tone) is important in fluid homeostasis. Recent evidence suggests that a decline in myogenic tone leads to deficits in cardiac contractility. Factors that reduce myogenic tone in transplantation include constitutive nitric oxide synthase and inducible nitric oxide synthase catalyzed, NO-mediated vasodilation as well as deficits in arterial contractile function. Reduced myogenic tone in allograft resistance arteries increases coronary blood flow such that hydrostatic pressure surpasses oncotic pressure, causing cardiac interstitial edema. This generalized edema decreases ventricular compliance leading to heart failure during the course of acute immune rejection of the graft. Cyclosporine A treatment reduces immune mediated dysregulation of myogenic tone, resulting in reduced interstitial edema and improved cardiac function. In this review, we discuss aspects of TVD and myogenic tone signaling mechanisms and how aberrations in myogenic regulation of arterial tone contribute to functional changes observed in cardiac transplant.     

Apoptosis signal-regulating kinase 1 is an intracellular inducer of p38 MAPK-mediated myogenic signalling in cardiac myoblasts

Myogenic differentiation is an essential process for the myogenesis in response to various extracellular stimuli. p38 MAPK is a core signalling molecule in myogenic differentiation. The activation of p38 MAPK is required for myogenic differentiation; however, the mechanism for this activation remains undefined. ASK1 is a member of the MAP3K family that activates both JNK and p38 MAPK pathways in response to an array of stresses such as oxidative stress, endoplasmic reticulum stress and calcium influx. Here, we reported that TNFα was significantly released from H9c2 cardiac myoblast in differentiation medium. Furthermore, the oxidant H₂O₂ acted as a messenger in the TNFα signalling pathway to disrupt the complex of ASK1-Trx, which was followed by the activation of ASK1 in cardiac myogenic differentiation. Subsequently, the activated ASK1 stimulated MKK3/6-p38MAPK signalling cascade to induce specific myogenic differentiation. In addition, exogenous TNFα added to the medium at physiological levels enhanced the ASK1-p38 MAPK signalling pathway through the increased generation of H₂O₂. Interestingly, inhibition of p38 MAPK abrogated the production of H₂O₂, suggesting that there might be a positive feedback loop in the myogenic-redox signalling pathway. These results indicate that ASK1 is a new intracellular regulator of activation of the p38 MAPK in cardiac myogenic differentiation.     

Some observations on cardiac automatism in certain animals

Certain aspects of the acetylcholine hypothesis of cardiac automaticity have been tested in vitro with spontaneously beating cardiac tissue from rabbits, rats, dams, and hagfish. The beat of atria from rabbits and rats may be depressed or excited by acetylcholine, depending upon the state of the tissue. Proguanil and cocaine inhibition of the beat in the rat may be antagonized by acetylcholine so that reversal of the depression occurs. The action of acetylcholine on the hearts of clams was found to be strictly inhibitory. Proguanil and cocaine, in contrast to their action on mammalian atria, exert a stimulatory effect on the heart of the molluscs studied. In fact, cocaine stimulated these hearts when they were inhibited by acetylcholine. Studies on the non-innervated hagfish heart revealed that this tissue is completely insensitive to the action of acetylcholine. Extracts prepared from beating hearts of this species will accelerate hypodynamic hearts of the hagfish as well as of the mussel. An extract of the neurogenic lobster heart was without effect on the hagfish heart. Proguanil was likewise ineffective in concentrations which produced inhibition and excitation in rat and clam hearts respectively. It was concluded that acetylcholine does not play a role in the myogenic automatism of all species, and that another mechanism is responsible is suggested on the basis of results obtained in the hagfish hearts.     

刺激豚鼠中脑对化学诱发的踏步的易化作用

用电刺激和踏车相结合的方法对“踏步自动作用”的研究,曾在去大脑猫上证明有一个位于下丘下面的楔状核的“中脑运动区域”的存在。但未见关于前后肢踏步运动控制差别的报道。豚鼠脑内是否存在中脑运动区域也未有过研究。本研究利用我们发现的“踏步诱发物质”(SIS)诱发的豚鼠踏步模型,在整体豚鼠上实验,观察电刺激 A_(9.0—3.0),R_(0.5—3.5),H_(8—0)(Tindal,1965)间对踏步的影响。结果表明,在豚鼠上丘下面的 A_(6.0—5.0),R_(1.0),H_(4.0)区域存在一个主要兴奋前肢踏步的“中脑踏步易化区域”。同时也观察到下丘下面的网状结构中有一个明显增强后肢踏步的区域。     

Autonomy of spontaneous rhythmogenesis of perivesicular area of cat ureter

The work presents data indicating no dependence of the pacemaker activity located in the zone of junction of cat ureter with urinary bladder on genesis of the main perirenal pacemaker. Data are presented on effect of clamping the renal artery supplying with blood flow the renal area on rhythmogenesis of the ureter perivesicular area. An inhibition of the pacemaker activity of the pyeloureteral anastomosis is observed. At the same time, no marked effect on automatism of the low organ area is revealed. Data of morphological studies of the vascular bed providing blood supply of various ureter areas are presented.     

Transient induction of Cdk9 in the early stage of differentiation is critical for myogenesis

Cdk9 is a serine-threonine protein kinase that has been recognized as a regulator of cardiac differentiation. Recently, we have reported that transient induction of Cdk9 using noncoding RNA targeting Cdk9 sequences results in efficient cardiac differentiation. Concerning Cdk9 regulatory roles, here, we proposed whether constant overexpression of Cdk9 might influence the differentiation of myoblast C2C12 cells into myotubes. We overexpressed Cdk9 in mouse myoblast C2C12 cells to investigate its regulatory roles on myogenic differentiation. Upon Cdk9 overexpression, the expression level of myogenic regulatory factors was determined. Moreover, the expression profile of three important myomiRs consist of miR 1, 133 and 206 was examined during the differentiation process. Although Cdk9 expression is necessary for inducing differentiation in the early stage of myogenesis, continuous Cdk9 expression inhibits differentiation by modulating myomiRs and myogenic gene expression. Our results indicate that the transient induction of Cdk9 in the early stage of differentiation is critical for myogenesis.     

Effect of sulfhydryl compounds on the automatism of the pacemakers]

Experiments were performed on the isolated rabbit hearts and also on the hearts with complete atrioventricular block; a study was made of the effect of an excess or deficiency of the sulfhydryl groups on the automatism of the cardiac pace makers. Unithiol and cysteine in concentrations of 1-10(-6)-1-10(-4) g/ml were used as donors of sulfhydryl groups; deficiency of these groups was induced by the alloxan administration in concentrations of 1-10(-5)-5-10(-5) g/ml. Changes in the sulfhydryl group content produced no marked effect on the automatism of the synoatrial node. An excess of sulfhydryl groups promoted poststimulation depression of the automatism of the potential pace makers of the cardiac ventricles and could lead to the origination of Luciani's periods. On the contrary, in case of a deficiency of the sulfhydryl groups there was a sharp elevation of the automatism of the ventricular pace makers, the atrioventricular conduction became disturbed, and the poststimulation depression of the automatism became considerably diminished. Disturbances of the cardiac activity caused by the sulfhydryl group deficiency were completely eliminated by unithiol or cysteine.     

New models for the wing extension in pterosaurs

All powered flying animals have to face the same energetic problems: operating the wings during steady flight with muscles that require constant energy input and neural control to work. Accordingly the extant flying vertebrates have apparently found very similar solutions to parts of these issues – the biomechanical automatism built in their skeletal, muscular and connective tissue system. Based on these extant analogues (birds and bats) two new models are presented here for the mechanism of the distal wing extension in pterosaurs, an extinct group of flying vertebrates. The elongate fourth finger which solely supported their extensive flight membrane was a long lever arm that experienced significant loads and for which a reduction in muscle mass through automatisation would have been strongly beneficial. In the first model we hypothesize the presence of a propatagial ligament or ligamentous system which, as a result of the elbow extension, automatically performs and maintains the extension of the wing finger during flight and prohibits the hyperextension of the elbow. The second model has a co-operating bird-like propatagial ligamentous system and bat-like tendinous extensor muscle system on the forearm of the hypothetical pterosaur. Both models provide strong benefits to an animal with powered flight: (1) reduction of muscles and weight in the distal wing; (2) prevention of hyper extension of the elbow against drag; (3) automating wing extension and thereby reducing metabolic costs required to operate the pterosaurian locomotor apparatus. These models, although hypothetical, fit with the existing fossil evidence and lay down a basis for further biomechanical and/or aerodynamical investigations.     

Spontaneous high-frequency action potential

Action potential, which is the foundation of physiology and electrophysiology, is most vital in physiological research. This work starts by detecting cardiac electrophysiology (tachyarrhythmias), combined with all spontaneous discharge phenomena in vivo such as wound currents and spontaneous neuropathic pain, elaborates from generation, induction, initiation, to all of the features of spontaneous high-frequency action potential—SSL action potential mechanism, i.e., connecting-end hyperpolarization initiates spontaneous depolarization and action potential in somatic membrane. This work resolves the conundrums of in vivo spontaneous discharge in tachyarrhythmias, wounds, denervation supersensitivity, neurogenic pain (hyperalgesia and allodynia), epileptic discharge and diabetic pain in pathophysiological and clinical researches that have puzzled people for a hundred years.     

The myriapodological legacy of Victor Ivanovich Motschoulsky (1810–1871)

The little that remains of Motschoulsky’s myriapodological legacy in the collection of Moscow’s Zoological Museum proves to be of very limited value. Only one species of Diplopoda described by Motschoulsky, the Caucasian Hirudisoma roseum (Victor, 1839), is still in use, yet requiring a neotype designation, whereas the remaining few myriapod names he proposed are either nomina dubia or nomina nuda. The former include Scolopendra pentagramma Motschoulsky, 1866 (Chilopoda, Scolopendromorpha, Scolopendridae) and Strongylosoma carinulatum Motschoulsky, 1866 (Diplopoda, Polydesmida, Paradoxosomatidae), both from Japan, as well as Julus costulatus Motschoulsky, 1851 (Diplopoda, Callipodida, Schizopetalidae?), from Montenegro, because their type material is either inadequate or missing.     

Myriapod (Arthropoda,Myriapoda) diversity and distribution in a floodplain forest of the Brazilian Pantanal

This study presents the diversity and distribution of myriapod species associated with different habitats in a seasonally flooded forest composed predominantly of Vochysia divergens Pohl. (Vochysiaceae) in the Brazilian Pantanal. We evaluated species richness distribution across habitats and over different seasonal periods, and also identified possible survival strategies employed during periodic flooding that occur within this forest. A total of 1505 myriapods were sampled, representing four classes and 15 species. Diplopoda and Chilopoda were the most abundant and rich taxa. Pauropoda and Symphyla were represented by only one species each. Species richness was distinctly distributed across habitats evaluated in this forest, as well as over the different seasonal periods. Survival strategies observed in Diplopoda and Chilopoda were primarily associated with vertical migration ranging from the edaphic environment to tree trunks and canopies, and horizontal migration associated with water level before and during the flood period. Species richness was considered low; however, the survival strategies, especially vertical and horizontal migration, demonstrate the adaptation of these species to the seasonal floods of this ecosystem.     

Coronary artery myogenic response in a genetic model of hypertrophic cardiomyopathy

Hypertrophic cardiac myopathy (HCM) is the leading cause of mortality in young athletes. Abnormalities in small intramural coronary arteries have been observed at autopsy in such subjects. The walls of these intramural vessels, especially in the ventricular septum, are thickened, and the lumen frequently appears narrowed. Whether these morphological characteristics have functional correlates is unknown. We studied coronary myogenic tone in a transgenic mouse model of HCM that has mutations in the cardiac alpha-myosin heavy chain gene. This transgenic mouse has a cardiac phenotype that resembles that occurring in humans. We examined the possible vascular contributions to the pathology of HCM. Septal arteries from 3- and 11-mo-old wild-type (WT) and transgenic (TG) mice were studied on a pressure myograph. The myogenic response to increased intravascular pressure in older animals was significantly reduced [maximal constriction: 32 +/- 4% (TG) and 46 +/- 4% (WT), P < 0.05]. After inhibition of endothelin receptors with bosentan, both WT and TG mice had similar increases in myogenic constriction. The sensitivity to exogenous endothelin was significantly reduced in TG mice, suggesting that the reduced myogenic constriction in HCM was due to reduced receptor sensitivity. In conclusion, we show for the first time that 1) myogenic tone in the coronary septal artery of the mouse is regulated by a basal release of endothelin, and 2) pressure-induced myogenic activation is attenuated in HCM, possibly consequent to a reduction in endothelin responsiveness. The associated reduction in coronary vasodilatory reserve may increase susceptibility to ischemia and arrhythmias.     

Changes in Different Trophic Levels of Litter-dwelling Macrofauna Associated with Giant Knotweed Invasion

Abstract The highly invasive giant knotweed (Reynoutria spp.) often displaces nettle (Urtica dioica) dominated stands in European floodplains. Urtica-dominated stands differ from the monospecific Reynoutria stands in plant species richness and stand structure. We thus hypothesize that Reynoutria invasion profoundly alters ecosystem structure and function, with negative effects cascading up through the food chain. We performed a paired sampling design in six sites belonging to two different locations and studied effects on the soil and the litter-dwelling fauna. Reynoutria stands differed in habitat structure and were characterized by decreased soil pH and potassium depletion. The faunal analysis is based on model groups of herbivore generalists (Gastropoda), detritivores (Isopoda and Diplopoda), and predators (Opiliones). The gastropod assemblages from Reynoutria stands were severely impoverished subsets of those from Urtica stands with reduced densities, species richness and diversity. In general, snails were more sensitive to Reynoutria invasion than slugs such as the invasive Arion 'lusitanicus’. Among detritivores, the abundance of the Isopoda decreased, whereas Diplopoda were not affected by Reynoutria invasion. Yet, the relative abundance of detritivores was significantly higher within the Reynoutria stands. Abundance, species richness and diversity of the predatory Opiliones were higher in the relatively sparse Reynoutria stands. We conclude that ecosystem changes associated with Reynoutria invasion are characterized by shifts from a plant-based to a detritus-based food chain and that Reynoutria invasion primarily enhances predators that profit from the simplified vegetation structure. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Modulation of heart activity during withdrawal reflexes in the snail <Emphasis Type="Italic">Helix aspersa</Emphasis>

The beating activity of the molluscan heart is myogenic, but it is influenced by nervous signals of central origin. Previous studies have demonstrated changes in cardiac output during feeding and other behaviors. Here, we describe a short latency, transient cardiac response that accompanies withdrawal reflexes. When evoked by electrical stimulation of peripheral nerves, the response was detected within one or two heartbeats. Beat amplitudes increased on average 11.6%, and inter-beat intervals decreased on average 2.1%. The mean duration of the response was 28.1 s. A transient inhibitory phase often preceded the excitatory response. Results from testing various nerves and tissues show that the cardiac responses invariably occur whenever contractions of the tentacle retractor muscle are elicited. Even stimulation of the ovotestis and the kidney elicit responses despite their protected locations within the mantle cavity. Three excitatory cardioactive neurons are identified in the central nervous system of Helix aspersa, and their involvement in the reflex response is documented. The results suggest that the heart output is initially inhibited to relax the hydroskeleton and thereby aid withdrawal movements. A delayed increase in cardiac output then facilitates the re-inflation, hence eversion, of the withdrawn body parts.