Cardiovascular responses of semi-arboreal snakes to chronic,intermittent hypergravity

Cardiovascular functions were studied in semi-arboreal rat snakes (Elaphe obsoleta) following long-term, intermittent exposure to +1.5G _z (head-totail acceleration) on a centrifuge. Snakes were held in a nearly straight position within horizontal plastic tubes during periods of centrifugation. Centrifugal acceleration, therefore, subjected snakes to a linear force gradient with the maximal force being experienced at the tail. Compared to non-centrifuged controls,G _z-acceimated snakes showed greater increases of heart rate during head-up tilt or acceleration, greater sensitivity of arterial pressure to circulating catecholamines, higher blood levels of corticosterone, and higher blood ratios of prostaglandin F₂/prostaglandin E₂. Cardiovascular tolerance to increased gravity during gradedG _z acceleration was measured as the maximum (caudal) acceleration force at which carotid arterial blood flow became null. When such tolerances were adjusted for effects of body size and other continuous variables incorporated into an analysis of covariance, the difference between the adjusted mean values of control and acelimated snakes (2.37 and 2.84G _z, respectively) corresponded closely to the 0.5G difference between the acelimationG (1.5) and Earth gravity (1.0). As in other vertebrates, cardiovascular tolerance toG _z stress tended to be increased by acclimation, short body length, high arterial pressure, and comparatively large blood volume. Voluntary body movements were important for promoting carotid blood flow at the higher levels ofG _z stress.Abbreviations bpm heat beats per minute - FV fluid volume - G gravitational or acceleration force - G _z gravitational or acceleration force in the head-to-tail direction - Hct hematocrit - HIP hydrostatic indifferent point - PGE prostaglandin E₂ - PGF prostaglandin F_2a - PGFM stable metabolite of PGF - RCV red cell volume - RIA radioimmunoassay - SAS statistical analysis system - TBV total blood volume     

Neural regulation of the pulmonary vasculature in a semi-arboreal snake,Elaphe obsoleta

Summary The innervation of the pulmonary vasculature of the semi-arboreal rat snake,Elaphe obsoleta, was examined with glyoxylic acid-induced catecholamine histochemistry, peptide immunohistochemistry, and in vitro perfusion of the pulmonary vasculature. An adrenergic innervation was present on the pulmonary artery, the smaller pulmonary arteries, the veins draining the lung, and the main pulmonary vein. Vasoactive intestinal polypeptide-like immunoreactive axons were observed on the pulmonary artery and vein, small arteries, and occasionally small veins within the lung parenchyma. A dense plexus of substance P-like immunoreactive (SP-LI) axons was observed on the distal extrinsic pulmonary artery. SP-LI axons were found on the more distal arteries within the lung parenchyma, but not on the veins. The distribution of calcitonin gene-related peptide- and SP-LI axons was similar suggesting that the axons are sensory nerves. In the perfused pulmonary vasculature, vagal stimulation caused a predominant vasoconstriction which was abolished by atropine indicating it was cholinergic in nature. A post-stimulus vasodilatation was abolished by bretylium and propranolol indicating it was adrenergic in nature. The responses to nerve stimulation were located in both the extrinsic and intrinsic pulmonary vasculature. No evidence for non-adrenergic, noncholinergic transmission to the vascular smooth muscle was found. The extensive, functional innervation of the main pulmonary artery, as well as the more distal vasculature within the lung, may reflect adaptation to cardiovascular problems imposed by an elongated body and arboreal habits.Abbreviations VIP vasoactive intestinal polypeptide - VIP-LI vasoactive intestinal polypeptide-like immunoreactive - SP substance P - SP-LI substance P-like immunoreactive - SOM somatostatin - SOM-LI somatostatin-like immunoreactive - CGRP calcitonin gene-related peptide - CGRP-LI calcitonin gene-related peptide-like immunoreactive - NANC non-adrenergic noncholinergic - PI perfusion inflow     

The distribution and colocalization of neuropeptides in perivascular nerves innervating the large arteries and veins of the snake,Elaphe obsoleta

Summary Single- and dual-labelling immunohistochemistry were used to determine the distribution and coexistence of neuropeptides in perivascular nerves of the large arteries and veins of the snake, Elaphe obsoleta, using antibodies for vasoactive intestinal polypeptide, substance P, calcitonin gene-related peptide, neuropeptide Y, galanin, somatostatin, and leu-enkephalin. Blood vessels were sampled from four regions along the body of the snake: region 1, arteries and veins anterior to the heart; region 2, central vasculature 5 cm anterior and 10 cm posterior to the heart; region 3, arteries and veins in a 30-cm region posterior to the liver; and region 4, dorsal aorta and renal arteries, renal and intestinal veins, 5–30 cm cephalad of the vent. A moderate to dense distribution of vasoactive intestinal polypeptide-like immunoreactive fibres was found in most arteries and veins of regions 1–3, but fibres were absent from the vessels of region 4. The majority of vasoactive intestinal polypeptide-like immunoreactive fibres contained colocalized substance P-like immunoreactivity, and these fibres were unaffected by either capsaicin or 6-hydroxydopamine (6-OHDA) pretreatment. In the anterior section of the snake, the vagal trunks contained many cell bodies with colocalized vasoactive intestinal polypeptide and substance P-like immunoreactivity. It is suggested that the vasoactive intestinal polypeptide/substance P-like immunoreactive cell bodies and fibres are parasympathetic postganglionic nerves. Neuropeptide Y-like immunoreactive fibres were observed in all arteries and veins, being most dense in regions 3 and 4. The majority of these fibres also contained colocalized galanin-like immunoreactivity, and were absent in tissues from 6-OHDA pretreated snakes, suggesting that neuropeptide Y and galanin are colocalized in adrenergic nerves. A small number of neuropeptide Y-like immunoreactive fibres contained vasoactive intestinal polypeptide but not galanin, and were unaffected by 6-OHDA treatment. All calcitonin gene-related peptide-like immunoreactive fibres contained colocalized substance P-like immunoreactivity, and these fibres were observed in all vessels, being particularly dense in the carotid artery and jugular veins. All calcitonin gene-related peptide/substance P-like immunoreactive fibres appeared damaged after capsaicin treatment suggesting they represent fibres from afferent sensory neurons. A sparse plexus of somatostatin-like immunoreactive fibres was observed in the vessels only from region 4. No enkephalin-like immunoreactive fibres were found in any blood vessels from any region. This study provides morphological evidence to suggest that there is considerable functional specialization within the components of the rat snake peripheral autonomic system controlling the circulation, in particular the regulation of venous capacitance.     

Bothrops jararaca fibrinogen and its resistance to hydrolysis evoked by snake venoms

Fibrinogen is an essential protein involved in several steps of hemostasis, being associated with the final steps of the blood coagulation mechanism. Herein, we describe the purification and characterization of a reptile fibrinogen, obtained from Bothrops jararaca plasma. Native B. jararaca fibrinogen showed a molecular mass of 372 kDa, and the reduced and alkylated fibrinogen molecule showed three chains of 71, 60 and 55 kDa, which are similar to the molecular masses of human and bovine Aα, Bβ and γ fibrinogen chains. Remarkably, B. jararaca fibrinogen was clotted by bovine thrombin, but B. jararaca, Crotalus durissus terrificus and Lachesis muta rhombeata venoms could not induce its clotting or hydrolysis. Thus, despite the similarities between B. jararaca and mammalian fibrinogens, the former shows distinctive features, which protect B. jararaca snakes from accidental envenomation.     

Vasoactive intestinal polypeptide-immunoreactive nerves in the pulmonary vasculature of the aquatic file snake Acrochordus granulatus

Summary The indirect immunofluorescence technique was used to determine the distribution of vasoactive intestinal polypeptide-immunoreactive and somatostatin-immunoreactive axons in the pulmonary vasculature of the aquatic file snake Acrochordus granulatus. A dense distribution of vasoactive intestinal polypeptide-immunoreactive axons was found on the common pulmonary artery, the anterior and posterior pulmonary arteries, and the smaller arteries branching to the lung. The density of these axons appeared greater in arterial preparations taken from more distal regions of the lung. The densest distribution of vasoactive intestinal polypeptide-immunoreactive axons was observed on the larger pulmonary veins in all regions of the lung. These axons were observed on the larger veins within the lung parenchyma but not on the smaller veins. Axons and cell bodies were observed in the vagal nerve trunks which run parallel to the pulmonary arteries and veins. In contrast, no somatostatin-immunoreactive axons were observed in any region of the pulmonary vasculature. It is proposed that the perivascular plexus of vasoactive intestinal polypeptide-immunoreactive axons may represent part or all of the vagal postganglionic innervation of the pulmonary vasculature.     

内蒙古蛇类新纪录——双斑锦蛇

2007年8月17日在内蒙古赤峰市巴林右旗北部的赛罕乌拉国家级自然保护区进行野生动物多样性调查时,首次发现双斑锦蛇(Elaphe bimaculata),随后又分别于2008年8月、2009年10月4次在保护区内发现该蛇种,2次为成年个体,1次为幼体,经核查鉴定该蛇为内蒙古蛇类新纪录。     

Podocytes in the blood vessel linings of Phoronis muelleri (Phoronida,Tentaculata)

Summary In several metasomal blood vessels of Phoronis muelleri myofilament-containing podocytes are the predominant cell-type. In some regions the podocytes can build a labyrinth resembling e.g. the glomerular epithelium of Enteropneusta and the axial organ of Asteroidea.Financially supported by DFG (Sto 75/4)     

Toxoplasma gondii: effects of neuwiedase, a metalloproteinase from Bothrops neuwiedi snake venom, on the invasion and replication of human fibroblasts in vitro

The major aim to the present study was to determine the effects of neuwiedase, a metalloproteinase isolated from Bothrops neuwiedi snake venom, on invasion and replication of Toxoplasma gondii in human fibroblasts in vitro. Neuwiedase treatment was done on host cells previously infected with T. gondii or on parasite before fibroblast infection. When treatments were done after or before infection, infection rates were inhibited in 71% and 61%, respectively. Considering that therapy protocols currently used in T. gondii infection cause considerable side effects, particularly in immunocompromised individuals and pregnant women, the results of neuwiedase treatment described herein could be taken into account for the development of new synthetic therapeutic agents, mainly due to the capacity of this enzyme to degrade extracellular matrix components, such as laminin, fibronectin and type I collagen, which is important to interfere in T. gondii host cell invasion.     

Primary structure characterization of Bothrops jararacussu snake venom lectin

The complete amino acid sequence of the lectin from Bothrops jararacussu snake venom (BJcuL) is reported. The sequence was determined by Edman degradation and amino acid analysis of the S-carboxymethylated BJcuL derivative (RC-BJcuL) and from its peptides originated from enzymatic digestion. The sequence of amino acid residues showed that this lectin displays the invariant amino acid residues characterized in C-type lectins. Amino acids analysis revealed a high content of acidic amino acids and leucine. These findings suggest that BJcuL, like other snake venom lectins, possesses structural similarities to the carbohydrate recognition domain (CRD) of calcium-dependent animal lectins belonging to the C-type -galactoside binding lectin family.     

Aquatic surface respiration,a widespread adaptation to hypoxia in tropical freshwater fishes

Synopsis Use of the surface water for aquatic respiration (aquatic surface respiration, ASR) is one of the few alternatives to aerial respiration which allow fish to survive extreme hypoxia, yet it has received very little attention. This report examines three generalizations concerning ASR on a phylogenetically and geographically diverse range of tropical freshwater fishes. It demonstrates that ASR greatly enhances survival in hypoxic water, even in fish not morphologically specialized to use the surface film, that ASR is initiated at a distinct threshold oxygen concentration, with time spent at the surface increasing rapidly as O₂ declines, and that with extreme deoxygenation fish perform ASR over 90% of the time. Ninety-four percent of the 31 species of non-air breathing fish tested showed ASR., with the threshold oxygen concentration ranging from 6 to 40 torr.Present address correspondence and reprint requests to D.L. Kramer.     

Antioxidant activity in Spalax ehrenbergi: a possible adaptation to underground stress

The blind subterranean mole rat Spalax ehrenbergi superspecies has evolved adaptive strategies to cope with underground stress. Hypoxia is known to stimulate reactive oxygen species generation; however, mechanisms by which Spalax counteracts oxidative damage have not been investigated before. We studied in Spalax the oxidative status of the Harderian gland (HG), an organ which is particularly vulnerable to oxidative stress in many rodents. With regard to the sexual dimorphism found in this gland, differences between males and females were determined and compared to the surface-dwelling Syrian hamster. Our results show, for the first time, that Spalax exhibits remarkably low biomolecular damage, which implies the existence of physiological strategies to avoid oxidative damage under fluctuating O₂ and CO₂ levels existing in the mole rat’s subterranean niche. Correspondingly, main antioxidant enzymes, such as superoxide dismutase (SOD), catalase, and glutathione reductase (GR), exhibited high activities in both genders; in particular, remarkably high levels were measured in SOD. SOD and GR activities showed statistically significant differences between sexes. Melatonin, an important circadian agent is also a very important antioxidant molecule and is synthesized in the Harderian glands (HGs) of Spalax. Therefore, the possible interaction between antioxidant enzymes and melatonin is suggested.Joint senior authorship: Aaron Avivi and Ana Coto-Montes     

Compliance and smooth muscle reactivity of rainbow trout (Oncorhynchus mykiss) vessels in vitro

Systemic veins have a profound influence on cardiac output in mammals. Venoregulatory mechanisms have not been adequately studied in fish and their existence has been questioned. In the present study, two characteristics of vascular mechanics, compliance and agonist-induced tension development, were investigated in rainbow trout vessels in vitro. Rapid compliance in the anterior cardinal vein and efferent branchial artery was calculated from step-wise changes in the volume-pressure curve of isolated vessel segments. Agonist-induced tension development was examined in four veins; anterior and posterior cardinals, intestinal and duct of Cuvier. Venous compliance was not altered in response to epinephrine, norepinephrine or angiotensin II, while efferent branchial artery compliance was decreased by 10^-6 mol·l^-1 epinephrine and norepinephrine but not angiotensin II. The ratios of venous to arterial compliance in vessels from two rainbow trout strains were similar (21:1 and 32:1) and consistent with the ratio reported for mammalian viens (24:1). Trout veins contracted in response to agonists in both an, agonist- and vesselspecific manner. The greatest tension per vessel wet weight was produced in anterior cardinal vein. The response pattern of anterior cardinal vein and duct of Cuvier were similar; acetylcholine, arginine vasotocin, epinephrine and norepinephrine, and the thromboxane A₂ agonist, U-44,069, produced approximately identical contractions, whereas angiotensin II was virtually ineffective. Conversely, angiotensin II was more potent than epinephrine in posterior cardinal vein. In cumulative dose-response experiments, epinephrine was equipotent in anterior cardinal vein and duct of Cuvier, whereas the latter was less sensitive to acetylcholine. Both atrial natriuretic peptide and sodium nitroprusside relaxed precontracted veins. This is the first study to determine compliance in fish vessels and the contractile nature of different rainbow trout veins. These findings suggest that venous tone and therefore cardiac output in fish may be regulated by neural or humoral mechanisms.Abbreviations ACH acetylcholine - ACV anterior cardinal vein - ANG II salmon asn¹-val⁵ angiotensin II - ANP rat atrial natriuretic peptide - AVT arginine vasotocin - DNR Department of Natural Resources - DOC duct of Cuvier - EBA efferent branchial artery - EC₅ threshold dose producing 5% maximal contraction - EC₅₀ dose producing 50% maximal contraction - EPI epinephrine - HI K⁺ 80 mmol·l^-1 - KCl IV, intestinal vein - NEPI norepinephrine - PBS phosphate buffered saline - PCV posterior cardinal vein - SNP sodium nitroprusside - U-44,069 thromboxane A₂ agonist     

Old pythons stay fit; effects of haematozoan infections on life history traits of a large tropical predator

We document the impact of blood parasite infections caused by Hepatozoon sp. on water python (Liasis fuscus) life history traits such as growth rates, condition, reproductive output and survival. Individual snakes maintained similar among-year parasite loads. Hepatozoon infections affected python growth rate, i.e. snakes suffering from high infection levels exhibited significantly slower growth compared to individuals with low parasite loads. Our results suggest that the parasites also affected the pythons nutritional status (condition), as snakes with low condition scores suffered from higher parasite infection levels than snakes with high scores. Furthermore, our data suggest that parasitaemia may affect female reproductive output, as reproductive female pythons harboured lower parasite loads compared to non-reproductive adult females. High levels of parasite infections also affected juvenile python survival, as recaptured snakes harboured significantly lower parasite loads compared to non-recaptured yearling pythons. In our study area, water python have very few natural predators and, hence, experience low mortality rates and commonly reach an age of >15 years. In contrast to results obtained in other studies, parasite loads in larger/older pythons were lower compared to younger snakes, suggesting that only snakes harbouring lower levels of parasitaemia were able to survive to old age. We suggest that a possible cause for the opposing results regarding parasite prevalence and host age may be due to different levels of extrinsic mortality rates and longevity. Long-lived organisms, such as water pythons, may invest relatively more into crucial self-maintenance functions such as parasite defence, compared to short-lived organisms.     

Catecholamine fluorescence in the pituitary of the eel,Anguilla anguilla,with special reference to its variation during background adaptation

Summary In the neuro-intermediate lobe (NIL) of the eel, Anguilla anguilla, a specific formaldehyde-induced fluorescence, indicating a catecholamine (CA) innervation, has been demonstrated in the neural lobe processes. Microspectrofluorimetric analyses and pharmacological treatments indicate noradrenaline or dopamine or both to be responsible for the fluorescence.The fluorescence in the NIL has displayed a definite tendency toward variation during the adaptation to a white and to a black background. The highest amounts of fluorescence were generally found in animals adapted to a black background, especially when adapted for a rather long period, and in animals recently transferred to a white background. The lowest amounts of fluorescence were generally found in animals adapted to a white background.This and the result of injections of CA-depleting drugs suggest that the monoaminergic nerves are active when the animal is on a white background, inhibiting the MSH release directly or indirectly or both, or in co-operation with other factors.Specific green fluorescent structures were also found in other parts of the neural lobe supplying the pars distalis.In some pharmacologically untreated specimens and in animals treated with CA-depleting drugs, the intermedia cells fluoresced. Microspectrofluorimetric analyses indicated that this fluorophore was not a CA.We wish to express our sincere thanks to Miss Ingrid Carlsen for excellent technical assistance, Mr. Lajos Erdös for the photography and the technical staff of the Department of Histology in Lund. We are also indepted to Dr. Anders Björklund for valuable discussion and advice.Supported by grants from the Swedish Natural Science Research Council, the University of Lund, and the Royal Physiographic Society of Lund.     

Adrenergic nerves and 5-hydroxytryptamine-containing cells in the pulmonary vasculature of the aquatic file snake Acrochordus granulatus

Summary The adrenergic innervation of the pulmonary vasculature of the file snake Acrochordus granulatus was examined by use of glyoxylic acid-induced fluorescence. Perivascular plexuses of blue-green fluorescent nerves are observed around the common pulmonary artery, the anterior and posterior pulmonary arteries, the arterioles leading to the gas exchange capillaries of the lung, the venules draining the lung, and the anterior and posterior pulmonary veins. Adrenergic nerves are also associated with the visceral smooth muscle of the lung septa and other tissues. Thus, adrenergic control of pulmonary blood flow may occur either at the common pulmonary artery or more regionally within the lung. Regional control of blood flow in the elongate lung of this snake may be important in matching pulmonary perfusion with the distribution of respiratory gas. Glyoxylic acid-histochemistry and immunohistochemistry revealed that populations of cells located in the common pulmonary artery contain the indoleamine 5-hydroxy-tryptamine. Many of the cells are intimately associated with varicose blue-green fluorescent nerves. It is proposed that the 5-hydroxytryptamine-containing cells may be involved in intravascular chemoreception.     

Cranial adaptation to a high attrition diet in Japanese macaques

Primates with diets that require greater occlusal forces to process exhibit anteroposteriorly shorter, vertically deeper faces, more anteriorly placed masseter attachment areas, and broader, taller mandibular corpora compared to closely related species/populations. Japanese macaques (Macaca fuscata)eat different, perhaps mechanically tougher to process, foods than other macaques do. Accordingly, they should exhibit structural features of the skull related to dissipating great occlusal loads. To test this hypothesis I compared cranial variables amongst wild-caught, adult female skulls (n = 85) of M. fuscataand three other macaque species (M. mulatta, M. fascicularis,and M. nemestrina)and applied least-squares and reduced-major-axis regression analysis and principal components analysis (PCA) to 17 cranial variables reflecting facial, vault, and mandibular dimensions. When scaled for size, the Japanese macaque has a vertically deeper and anteroposteriorly shorter face,a broader but not taller mandibular corpus, and a more anteriorly placed masseter muscle than the other three macaques do. The first PCA axis isolates variation due to a suite of characters related to mechanical efficiency in dissipating occlusal loads (vertically deep face and broad corpus) and differentiates the Japanese macaques from the other species. This, coupled with reported dietary differences among species, suggests that Japanese macaques are selected for dissipating greater occlusal loads than other macaques are. The presence of a narrow mandible relative to cranial breadth and a hyperrobust mandibular corpus width suggests that axial torsion is a significant influence in the masticatory regime of M. fuscata.The lack of an increase in corpus height indicates that parasagittal bending is not as significant an influence. Geographic and climatic influences cannot account for the patterns of variation between M. fuscataand the other macaques.     

Atlantic snake pipefish (<Emphasis Type="Italic">Entelurus aequoreus</Emphasis>) extends its northward distribution range to Svalbard (Arctic Ocean)

Ecological forecasts predict the immigration of boreal species into Arctic waters as one consequence of rising sea temperatures. Here, we report the finding of Atlantic snake pipefish (Entelurus aequoreus) off the western coast of Spitsbergen at 79°N in August 2006. This syngnathid fish species, which was presumed to be confined to waters south of Iceland, has dramatically increased in population size in its core distribution area in the northeastern Atlantic since 2002, probably in response to greater reproduction success due to higher water temperatures. We conclude that our finding is an indication of the predicted northward extension of the distribution range of boreal species.     

Blood parasites and male fitness in the pied flycatcher

In vertebrates the effect of parasites on host ecology has almost been ignored. Recently the view that well-adapted parasites do not harm their hosts has been challenged and there is growing evidence that parasites do have a present-day effect on a great variety of host fitness components. The pied flycatcher is a small migratory passcrine bird. Any decrease in condition caused by disease should affect its ability to cope with physical demands of migration. Here we examine whether blood parasites have any effect on male arrival time. Males infected with Trypanosoma arrived on average 2 days later than males with no Trypanosoma infection. Infected males also had shorted tails and tended to have shorter wings. By contrast, there was no difference in male arrival time between males infected with Haemoproteus and healthy males. It seems that Trypanosoma infection lowered male condition and consequently the ability to moult and migrate. The difference in length of feathers may have generated the difference in arrival times. Early arrival is highly important for males, since only the first males become polygynous and breeding prospects deteriorate rapidly with any delay in egg laying. Estimated reduction in breeding success for infected males was about 20%.     

Local adaptation to serpentine soils in Pinus ponderosa

Local adaptation to serpentine soils is studied using both transplant experiments and molecular genetic techniques. In long-lived species, such as pines, it is unclear how soon after germination local adaptation becomes detectable. Here I present results of a 36-year reciprocal transplant experiment using Pinus ponderosa, along with allozyme analyses from the same trees. Using a repeated measures analysis of variance, there is evidence for adaptation to serpentine soils; however, significant differences between source soil types do not become apparent until 20 years after the start of the experiment. Analysis of allozyme data showed no evidence for differentiation between the serpentine and non-serpentine populations. Comparing the performance of families over the course of the experiment found that there was little correlation between performance after 1 or 4 years of growth in the field and performance after 36 years. This suggests that short-term transplant experiments may not provide definitive evidence for adaptation to serpentine soils. A literature survey of all transplant studies using pine species growing on and off of serpentine soils found that studies that lasted fewer than 2 years showed no evidence for adaptation. However, in the two experiments (this one included) that lasted more than 2 years, both showed evidence for adaptation to serpentine soils. More long-term experiments are required to validate these results.