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     

The effect of exogenous catecholamines on the ventilatory and cardiac responses of normoxic and hyperoxic rainbow trout,Oncorhynchus mykiss

Ventilation frequency, opercular pressure amplitude, heart rate, dorsal aortic pressure, arterial pH, arterial O₂ tension, and plasma catecholamine levels were recorded in rainbow trout, Oncorhynchus mykiss, during normoxia (19.7 kPa, 148 mmHg) or hyperoxia (51.2 kPa, 384 mmHg) after injection of various concentrations of catecholamines. In normoxic fish, adrenaline injection resulted in a depression of arterial O₂ tension, hypoventilation due to a drop in ventilation frequency, and a drop in heart rate, while dorsal aortic pressure increased. Noradrenaline depressed ventilation frequency, but opercular pressure amplitude increased to a far greater extent, and dorsal aortic pressure increased. During hyperoxia, adrenaline injection lowered ventilation frequency, opercular amplitude and heart rate, but dorsal aortic pressure increased. The stimulatory effects of noradrenaline on ventilation were abolished during hyperoxia, but the cardiac responses were similar to those seen during normoxia. These results indicate that catecholamines can modify the ventilatory output from the respiratory centre, and modification of ventilation frequency can occur independently of opercular pressure amplitude.Abbreviations f _g ventilation frequency - HPLC high performance liquid chromatography - P _op opercular pressure amplitude - f _h heart rate - P _DA dorsal aortic pressure - pH_a arterial pH - P _aO₂ arterial oxygen tension - PO₂ oxygen tension     

Haemoglobin staining for in vivo portraying of functional vasculature in experimental zebrafish embryos

Characterization of functional vessels is required either for monitoring hemodynamics or patterning of functional vasculature in experimental models. Haemoglobin (Hb) staining is a traditionally used approach for determining the differentiation of erythroid cells. In this investigation, we tested if HB staining can be used for portraying of functional vasculature in experimental zebrafish embryos. The staining sufficiently revealed aortic arches, dorsal aorta, posterior cardinal vein, dorsal longitudinal anastomotic vessels, intersegmental vessels as well as subintestinal vessel basket. We conclude that Hb staining offers an informative and rapid method for in vivo portraying of functional vasculature in experimental zebrafish embryos. It is also suitable for large scale experiments.     

Graded intracellular acidosis produces extensive and reversible reductions in the effective free energy change of ATP hydrolysis in a molluscan muscle

Phosphorus nuclear magnetic resonance spectroscopy was used to evaluate the impact of experimental reductions of intracellular pH on in vitro preparations of the radula protractor muscle of the marine gastropod, Busycon canaliculatum. The intracellular pH of radula refractor muscle bundles superfused with buffered artificial sea water (pH=7.8) was 7.29. It was possible to clamp muscle intracellular pH at various acidotic states by changing the superfusate to 5, 10, and 15 mmol·l^-1 5,5-dimethyl-oxazolidine-2,4-dione in buffered artifical sea water (pH=6.5). Consistent and temporally stable reductions of intracellular pH were achieved (intracellular pH=6.98, 6.79, and 6.62, respectively). During the acidotic transitions, arginine phosphate concentrations decreased and inorganic phosphate concentrations increased in a reciprocal manner and remained essentially constant after the intracellular pH stabilized. The extent of changes in arginine phosphate and inorganic phosphate was directly proportional to the magnitude of the imposed acidosis. Total adenosine triphosphate concentrations remained unchanged in all treatments. However, the magnesium adenosine triphosphate to total adenosine triphosphate ratio declined in direct relation to the extent of the acidosis. Intracellular free Mg²⁺ fell incrementally with reduced intracellular pH. All of the above effects were rapidly reversed when the 5,5-dimethyl-oxazolidine-2,4-dione was washed out by changing the superfusate to buffered artificial sea water (pH=7.8). Mg-adenosine diphosphate concentrations were calculated in all treatments using equilibrium constants for the arginine kinase reaction corrected for pH and intracellular free [Mg²⁺]. The metabolite, intracellular pH, and [Mg²⁺] data were used to estimate the effective free energy of hydrolysis of adenosine triphosphate (dG/d_ATP) under most experimental conditions. Experimental acidosis resulted in dramatic reductions in dG/d_ATP which were fully reversible upon wash-out of 5,5-dimethyl-dioxazolidine-2,4-dione and recovery to normal intracellular pH conditions. Acidosis resulted in net hydrolysis of arginine phosphate, likely via a complex mechanism involving enhancement of rate of adenosine triphosphate hydrolysis and/or inhibition of adenosine triphosphate synthesis.Abbreviations ABRM anterior byssus retractor muscle - ADP, ATP adenosine di- and triphosphate - AP arginine phosphate - BASW buffered artificial sea-water - CP creatine phosphate - DMO 5, 5-dimethyl-oxazolidine-2, 4-dione - G _o ^obs standard free energy change of ATP hydrolysis - dG/d_ATP effective free energy change of ATP hydrolysis - HEPES 4-(2-hydroxyethyl)-piperazine-1-ethanesulphonic acid - K _obs equilibrium constant under specified conditions - MES 2-[N-morpholino] ethanesulphonic acid - [Mg²⁺]_i intracellular free magnesium concentration - NMR nuclear magnetic resonance - pH _i intracellular pH·P _i inorganic phosphate - PIPES piperazine-N,N-bis-2-ethane sulphonic acid - RPM radula protractor muscle - SR sarcoplasmic reticulum     

Evidence for multiple adrenoceptor sites in rainbow trout vasculature

The importance of neuronal and lumenal vascular adrenoceptors in the regulation of vascular reactivity was examined in rainbow trout (Oncorhynchus mykiss), in vivo and in vitro. In vivo, ganglionic blockade with hexamethonium or -adrenoceptor blockade, with either phentolamine or prazosin, produced similar (7 mmHg) decreases in dorsal aortic blood pressure. The drop in dorsal aortic pressure produced by phentolamine or prazosin was due to reduced systemic vascular resistance. Neither the -adrenoceptor antagonist, phenoxybenzamine nor chemical sympathectomy with 6-hydroxy-dopamine affected dorsal aortic pressure. However, after chemical sympathectomy, phenoxybenzamine lowered dorsal aortic pressure to levels similar to that produced by either phentolamine or prazosin. Plasma epinephrine and norepinephrine concentrations increased four- and twofold, respectively, in sympathectomized fish. Sympathectomy also produced a leftward shift in the epinephrine dose/response curve of the in vitro perfused splanchnic vasculature, placing the effective catecholamine concentration well within the in vivo plasma levels. These results indicate that following chemical sympathectomy arterial blood pressure is stabilized by circulating catecholamines through the combined effect of increased plasma catecholamine concentrations and increased sensitivity of vascular adrenoceptors. Phenoxybenzamine is incapable of blocking neuronal vascular adrenoceptors but is a potent antagonist of the up-regulated adrenoceptors, suggesting that the latter are localized on the lumenal side of the vessel.Abbreviations 6OH-DA 6-hydroxy dopamine - EC ₅₀ half-maximal response - EDTA ethylenediaminetetra-acetate - PE polyethylene - PBS phosphate-buffered saline - P _da dorsal aortic pressure - USP United States Pharmacopeia     

Osmoregulatory responses of glaucous-winged gulls (Larus glaucescens) to dehydration and hemorrhage

The effects of dehydration and hemorrhage on plasma ionic, osmotic, and antidiuretic hormone (arginine vasotocin) concentrations and of hemorrhage on salt gland secretion and glomerular filtration rate were evaluated in glaucous-winged gulls, Larus glaucescens. Dehydration for 24 h did not affect plasma ionic, osmotic or arginine vasotocin concentrations; 72 h dehydration significantly elevated plasma osmolality, plasma sodium and chloride concentrations, and plasma arginine vasotocin concentration, but did not affect plasma potassium concentration. Constant infusion of 0.8 mol·l^-1 NaCl increased plasma arginine vasotocin concentration and produced salt gland secretion in seven gulls; four secreted well, while three secreted less well. Removal of 20% blood volume during saline infusion immediately reduced (P<0.001) salt gland secretion rate in all gulls. After bleeding, good secretors maintained glomerular filtration rate and urine flow rate; the poorer secretors increased glomerular filtration rate and became diuretic. Blood replacement returned salt gland secretion rate to the prebleeding level (P<0.05) without affecting salt gland secretions sodium concentration in gulls which secreted well, but did not restimulate salt gland secretion in gulls which secreted poorly. Reinfusion of blood had no effect on glomerular filtration rate. Bleeding and blood replacement did not affect plasma arginine vasotocin concentration.Abbreviations AVT arginine vasotocin - ECF extracellular fluid - ECFV extracellular fluid volume - EDTA ethylenediaminetetra-acetate - EWL evaporative water loss - GFR glomerular filtration rate - Hct hematocrit - LB large blood sample - [Na⁺]_pl plasma sodium concentration - Osm_pl plasma osmolality - PEG polyethylene glycol - RH relative humidity - RIA radioimmunoassay - SB small blood sample - SGS salt gland secretion - T _a ambient temperature - TFA trifluoroacetic acid - UFR urine flow rate     

Embryonic vascular development: immunohistochemical identification of the origin and subsequent morphogenesis of the major vessel primordia in quail embryos

The development of the embryonic vasculature is examined here using a monoclonal antibody, QH-1, capable of labelling the presumptive endothelial cells of Japanese quail embryos. Antibody labelling is first seen within the embryo proper at the 1-somite stage. Scattered labelling of single cells appears ventral to the somites and at the lateral edges of the anterior intestinal portal. The dorsal aorta soon forms a continuous cord at the ventrolateral edge of the somites and continues into the head to fuse with the ventral aorta forming the first aortic arch by the 6-somite stage. The rudiments of the endocardium fuse at the midline above the anterior intestinal portal by the 3-somite stage and the ventral aorta extends craniad. Intersomitic arteries begin to sprout off of the dorsal aorta at the 7-somite stage. The posterior cardinal vein forms from single cells which segregate from somatic mesoderm at the 7-somite stage to form a loose plexus which moves mediad and wraps around the developing Wolffian duct in later stages. These studies suggest two modes of origin of embryonic blood vessels. The dorsal aortae and cardinal veins apparently arise in situ by the local segregation of presumptive endothelial cells from the mesoderm. The intersomitic arteries, vertebral arteries and cephalic vasculature arise by sprouts from these early vessel rudiments. There also seems to be some cell migration in the morphogenesis of endocardium, ventral aorta and aortic arches. The extent of presumptive endothelial migration in these cases, however, needs to be clarified by microsurgical intervention.     

Modulation of catecholamine storage and release by the pituitary-interrenal axis in the rainbow trout,Oncorhynchus mykiss

This study examined the effects of pituitary-interrenal hormones on catecholamine storage and release in the rainbow trout Oncorhynchus mykiss. An extract of trout pituitary elicited the release of adrenaline, but not noradrenaline, using an in situ perfusion preparation. A variety of doses of adrenocorticotropic hormone (2–2000 mU) caused the release of both catecholamines in situ which was unaffected by pre-treatment with the ganglion blocker, hexamethonium, or the serotonergic receptor antagonist, methysergide, but was abolished in calcium-free media. Intra-arterial injections of adrenocorticotrophic hormone in vivo caused an elevation of plasma adrenaline but not noradrenaline levels. Injections of cortisol in situ did not elicit catecholamine release. Trout given an intraperitoneal implant of cortisol (50 mg·kg^-1 body weight) had significantly higher plasma cortisol concentrations when compared to controls after 7 days of implantation. Increases in the levels of stored catecholamines were observed in various regions of the kidney and posterior cardinal vein following 3 and 7 days of cortisol treatment. The ability of the chromaffin cells to release catecholamines in response to cholinergic stimulation was assessed in situ after 7 days of treatment. Basal (non-stimulated) adrenaline outflowing perfusate levels were greater in the cortisol-treated fish. Cortisol treatment increased the responsiveness of the catecholamine release process to low doses of the cholinoceptor agonist carbachol. Three or 7 days of cortisol treatment did not alter the in vitro activity of the enzyme phenylethanolamine-N-methyl-transferase. The results of this study demonstrate that interactions within the pituitary-adrenal axis can influence both catecholamine storage and release in the rainbow trout.Abbreviations ACTH adrenocorticotropic hormone - AK anterior third of the kidney - APCV anterior third of the PCV - HPLC high performance liquid chromatography - MK middle third of the kidney - M1 maximum value - MPCV middle third of the PCV - MS222 ethyl-aminobenzoate - P1 pre value - PCA perchloric acid - PCV posterior cardinal vein - PK posterior third of the kidney - PNMT phenylethanolamine-N-methyltransferase - PPCV posterior third of the PCV - rbc red blood cells - SEM standard error of the mean - TK total kidney (i.e. the sum of the AK, MK, and PK) - TPCV total PCV (i.e. the sum of the APCV, MPCV and PPCV)     

Haemodynamic effects of adenosine on gills of the trout (Salmo gairdneri)

Summary The haemodynamic effects of adenosine on gills of the trout (Salmo gairdneri) were studied with in vitro and in vivo preparations.On the isolated head preparation, adenosine induced a decrease of the ventral aortic inflow and of the dorsal aortic outflow. Simultaneously the venous outflow increased. These effects were antagonized by theophylline. Adenosine induced a vasoconstriction in gill arches without filaments perfused by the afferent or the efferent branchial arteries. The efferent vessels were more sensitive to adenosine than afferent vessels. The whole systemic circulation of the isolated trunk did not show any response to adenosine. When adenosine was infused into the ventral aorta of living trout, the gill resistance to blood flow was greatly increased.These results suggest that adenosine is able to control the arterious and venous blood pathways in the trout gills by modulating their vascular resistance.     

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     

Loss of unc45a precipitates arteriovenous shunting in the aortic arches

Aortic arch malformations are common congenital disorders that are frequently of unknown etiology. To gain insight into the factors that guide branchial aortic arch development, we examined the process by which these vessels assemble in wild type zebrafish embryos and in kurzschluss^tr12 (kus^tr12) mutants. In wild type embryos, each branchial aortic arch first appears as an island of angioblasts in the lateral pharyngeal mesoderm, then elaborates by angiogenesis to connect to the lateral dorsal aorta and ventral aorta. In kus^tr12 mutants, angioblast formation and initial sprouting are normal, but aortic arches 5 and 6 fail to form a lumenized connection to the lateral dorsal aorta. Blood enters these blind-ending vessels from the ventral aorta, distending the arteries and precipitating fusion with an adjacent vein. This arteriovenous malformation (AVM), which shunts nearly all blood directly back to the heart, is not exclusively genetically programmed, as its formation correlates with blood flow and aortic arch enlargement. By positional cloning, we have identified a nonsense mutation in unc45a in kus^tr12 mutants. Our results are the first to ascribe a role for Unc45a, a putative myosin chaperone, in vertebrate development, and identify a novel mechanism by which an AVM can form.     

The whole-body shortening reflex of the medicinal leech: motor pattern,sensory basis,and interneuronal pathways

The leech whole-body shortening reflex consists of a rapid contraction of the body elicited by a mechanical stimulus to the anterior of the animal. We used a variety of reduced preparations — semi-intact, body wall, and isolated nerve cord — to begin to elucidate the neural basis of this reflex in the medicinal leech Hirudo medicinalis. The motor pattern of the reflex involved an activation of excitatory motor neurons innervating dorsal and ventral longitudinal muscles (dorsal excitors and ventral excitors respectively), as well as the L cell, a motor neuron innervating both dorsal and ventral longitudinal muscles. The sensory input for the reflex was provided primarily by the T (touch) and P (pressure) types of identified mechanosensory neuron. The S cell network, a set of electrically-coupled interneurons which makes up a fast conducting pathway in the leech nerve cord, was active during shortening and accounted for the shortest-latency excitation of the L cells. Other, parallel, interneuronal pathways contributed to shortening as well. The whole-body shortening reflex was shown to be distinct from the previously described local shortening behavior of the leech in its sensory threshold, motor pattern, and (at least partially) in its interneuronal basis.Abbreviations conn connective - DE dorsal excitor motor neuron - DI dorsal inhibitor motor neuron - DP dorsal posterior nerve - DP:B1 dorsal posterior nerve branch 1 - DP:B2 dorsal posterior nerve branch 2 - MG midbody ganglion - VE ventral excitor motor neuron - VI ventral inhibitor motor neuron     

Cholinoceptor-mediated control of catecholamine release from chromaffin cells in the American eel,Anguilla rostrata

The cholinergic agonist-induced secretion of catecholamines from chromaffin cells in the American eel, Anguilla rostrata, was assessed using a salineperfused posterior cardinal vein preparation. Direct membrane depolarization with 60 mmol·l^-1 K⁺ caused a significant release of catecholamines (adrenaline + noradrenaline) into the perfusate which was unaffected by pre-treatment with the ganglion blocker, hexamethonium (final concentration = 10^-3 mol · l^-1). The nicotinic receptor agonist, 1,1-dimethyl-4-phenylpiperazinium iodide, evoked catecholamine release in response to several doses exceeding 10^-7 mol; at 10^-5 mol the response was abolished by pre-treatment with the ganglion blocker, hexamethonium (final concentration = 10^-3 mol · l^-1). The muscarinic receptor agonist, pilocarpine, did not elicit catecholamine release in response to any of the doses administered (10^-8–10^-4 mol). A single injection of the mixed nicotinic/muscarinic cholinoceptor agonist, carbachol (10^-5 mol), caused the release of catecholamines which was abolished by pre-treatment with hexamethonium but which was unaffected by pre-treatment with the muscarinic receptor antagonist atropine (final concentration = 10^-5 mol · l^-1). The results of this study indicate that the process of cholinergic agonist-induced catecholamine secretion from the chromaffin cells in the American eel is mediated exclusively by activation of nicotinic receptors with no involvement of the muscarinic receptor.Abbreviations DMPP 1,1-dimethyl-4-phenylpiperazinium iodide - MS222 ethylaminobenzoate - HPLC high-performance liquid chromatography - PCV posterior cardinal vein - SEM standard error of the mean     

Antennal circulatory organs in Onychophora,Myriapoda and Hexapoda: Functional morphology and evolutionary implications

Summary A comparative investigation of the antennal circulatory organs in representatives of the Onychophora, all subtaxa of the Myriapoda and numerous taxa of the Hexapoda (comprising a total of 54 species) revealed an unexpected diversity in structure and function.In the Onychophora, antennal vessels exist which are connected to the enlarged anterior end of the aorta dorsal to the brain.In the Chilopoda, Diplopoda and Symphyla, antennal vessels exist which originate from the dorsal vessel caudal to the brain. They extend under the optic lobes, lateral to the circumoesophageal connectives, into the antennae.In the Hexapoda, the investigations include representatives of all higher taxa, apart from the Paraneoptera and the Holometabola. Generally, antennal vessels exist. In the Diplura, they originate from the anterior end of the aorta in front of the brain. In all other insects the antennal vessels are separate from the dorsal vessel. Their proximal ends form ampullary enlargements which are attached to the frontal cuticle near the antenna bases. They communicate via valved ostia with the haemolymph sinus in front of the brain. In the Archaeognatha, Zygentoma, Odonata, certain Plecoptera and the Notoptera, no muscles are connected to these organs. In all other groups the ampullae are pulsatile as a result of associated muscles (antennal hearts). These muscles diverge widely in their attachments and act either as compressors (Dermaptera) or dilators of the ampullae (Embioptera, Blattopteroidea, Orthopteroidea, and some Plecoptera).In the Collembola and Ephemeroptera, special antennal circulatory organs are lacking. In some forms the anatomical arrangement of the inner organs, in conjunction with short diaphragms at the antenna bases, apparently leads to a channelling of haemolymph flow. This condition may be explained by the very short antennae of these insects and is considered as a convergent and apomorphic state in these taxa.The antennal vessels are supposed to be homologous within the Tracheata and to represent the lateral arteries of the antenna segment. An origin from the dorsal vessel is considered an ancestral state, which was lost in the stem lineage of the Ectognatha. Specific space constraints within the cephalic capsule are discussed as the possible reason for this loss. The evolution of pulsatile antennal circulatory organs in the Neoptera is the result of the association of muscles with the proximal ampullary ends of the antennal vessels. The attachments and innervation of these muscles indicate a derivation from precerebral pharyngeal dilators.Abbreviations Amp ampulla - Ant antenna - ant anterior - AN antennal nerve - Ao aorta - AV antennal vessel - Br brain - BrSi brain sinus - CC corpora cardiaca - CoeC circumoesophageal connectives - CM compressor muscle of ampulla - CT connective tissue - Dia diagphragm - do dorsal - DM dilator muscle of ampulla - DM1 ampullo-ampullary dilator muscle - DM2 ampullo-pharyngeal dilator muscle - DM3 ampullo-frontal dilator muscle - DM Acc accessory dilator muscle of ampulla - DV dorsal vessel - EB elastic band - FbDM fronto-buccal pharynx dilator muscle - FG frontal ganglion - FSa frontal sac - FSe frontal septum - FSi frontal sinus - Lb labium - LV lateral vessel of aorta - MA mouth-angle - Nr nervus recurrens - Oc ocellus - Oe oesophagus - OeSi oesophageal sinus - Ost ostium - Ph pharynx - Pl labial palpus - RM retractor muscle of mouth-angle - RMl lateral retractor of mouth-angle - RMm medial retractor of mouth-angle - SceSi supracerebral sinus - SD salivary duct - T tentorium     

The energetic cost of protein synthesis in isolated hepatocytes of rainbow trout (Oncorhynchus mykiss)

Summary To establish the energetic cost of protein synthesis, isolated trout hepatocytes were used to measure protein synthesis and respiration simultaneously at a variety of temperatures. The presence of bovine serum albumin was essential for the viability of isolated hepatocytes during isolation, but, in order to measure protein synthesis rates, oxygen consumption rates and RNA-to-protein ratios, BSA had to be washed from the cells. Isolated hepatocytes were found to be capable of protein synthesis and oxygen consumption at constant rates over a wide range of oxygen tension. Cycloheximide was used to inhibit protein synthesis. Isolated hepatocytes used on average 79.7±9.5% of their total oxygen consumption on cycloheximide-sensitive protein synthesis and 2.8±2.8% on maintaining ouabain-sensitive Na⁺/K⁺-ATPase activity. The energetic cost of protein synthesis in terms of moles of adenosine triphosphate per gram of protein synthesis decreased with increasing rates of protein synthesis at higher temperatures. It is suggested that the energetic cost consists of a fixed (independent of synthesis rate) and a variable component (dependent on synthesis rate).Abbreviations BSA bovine serum albumin - dpm disintegrations per min - k _s fractional rate of protein synthesis - HEPES N-2-hydroxyethylpiperazine-N-2-ethane sulphonic acid - PHE phenylalanine; PO₂ oxygen tension - PCA perchloric acid     

On the evolution of arterial vascular patterns of tetrapods

The factors that explain the diverse arrangement of the major arteries of tetrapods are not known. Here, I aim to illuminate some of the underpinnings of these patterns. I review the variation in the sauropsid left, right, and dorsal aortae regarding the origin of the gastrointestinal blood vessels and the relative diameters of left and right aortae where they join together to form the dorsal aorta. I focus on these features because the quality of blood that flows through these aortae can vary depending on the state of cardiac shunting and the size of the vessel can provide insight into the quantity of blood borne by the vessels. I then place the information in a phyletic, historical, and ecological context. The plesiomorphic pattern is for the gastrointestinal vessels to arise as segmental arteries from the dorsal aorta, which is formed from the confluence of left and right aortae with similar diameters. The pattern is well conserved with only two major variations. First, in several clades of reptiles (testudines, crocodilians, lizards of the genera Varanus and Hydrosaurus) a substantial portion of the gastrointestinal arteries arises from the left aorta, leaving the diameter of the left aorta smaller than the right at their confluence. I hypothesize that this vascular arrangement facilitates growth by allowing more alkaline blood to flow to the somatic (body wall) and appendicular circulations, which may promote bone deposition and inhibit resorption, whereas hypercapnic, acidic blood flows to the digestive viscera, which may provide CO₂ as a substrate for the synthesis of gastric acid, bicarbonate, fatty acids, glutamine, purine rings, as well as glucose from lactate. Second, in some snakes and lizards with snake‐like body forms, such as Amphisbaenidae, the diameters of left and right aortae are asymmetrical at their confluence with the left aorta exceeding the right, but in members of the amphibian order Gymnophiona the right generally exceeds the left. This condition is associated with asymmetrical development of the lungs. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

Capacitance,short-circuit current and osmotic water flow across different regions of the isolated toad skin

Summary The amphibian antidiuretic hormone, arginine vasotocin, stimulated osmotic water flow across isolated skin from the pelvic but not the pectoral skin of the toad, Bufo woodhouseii. Changes in the apical membrane capacitance were not observed for either region of the skin following treatment with arginine vasotocin when there was an osmotic gradient across the tissue. In the absence of an osmotic pressure gradient, the apical membrane capacitance of the pelvic skin increased from 2.8±0.5 to 3.3±0.6 F · cm^-2 after treatment with 5 · 10^-8 M arginine vasotocin. Under these conditions, apical membrane capacitance of the pectoral skin was 1.8±0.1 F · cm^-2 and did not change significantly after arginine vasotocin treatment. The amiloride-sensitive short-circuit current across the pelvic skin was stimulated by arginine vasotocin as was the density of channels in the apical membrane as determined by fluctuation analysis. Values for channel density in the pelvic skin also correlated with apical membrane capacitance and increased from 90 to 273 channels per m² of estimated membrane area following arginine vasotocin treatment. In the pectoral skin the stimulation of short-circuit current following arginine vasotocin treatment was small and an increase in channel density could not be demonstrated. The current through single Na⁺ channels in both regions of the skin did not different either before or after arginine vasotocin treatment.Abbreviations A amiloride - ADH antidiuretic hormone - AVT arginine vasotocin - C capacitance - C _a capacitance of apical membrane - f _c corner frequency - i single-channel current - osmotic water flow - IMP intramembrane particles - I _sc short-circuit current - amiloride-sensitive short-circuit current - M channel density - P _o probability of a channel being open - R channel receptor - R _a apical resistance - R _p paracellular resistance     

Influence of long-term hypoxia on the energy metabolism of the haemoglobin-containing bivalve Scapharca inaequivalvis: critical O2 levels for metabolic depression

Summary The oxygen consumption rate of Scapharca inaequivalvis measured under normoxic conditions over 48 h showed a significant daily cycle with lowest values occurring shortly after the dark period; all hypoxia exposure experiments were carried out during the declining part of the cycle. Animals were exposed to a constant level of hypoxia for a 12-h period in a series of 14 experiments, each at a different oxygen tension. The oxygen consumption was measured continuously, and the extent of accumulation of end-products (succinate and propionate), and the inhibitory effect of adenosine triphosphate on phosphofructokinase were determined at the end of exposures. All three parameters (oxygen consumption, end-product accumulation, phosphofructokinase inhibition) showed a remarkable correlation with major changes occurring between 2.5 and 1.5 ppm (7 and 4 kPa) O₂. The oxygen consumption rates showed a drop to 6% of the normoxic rate, but a consistent low consumption remained below 2 ppm (5.5 kPa) which partly recovered over the 12-h exposure period by about three-fold. Succinate and propionate accumulated progressively between 2.5 and 1.5 ppm (7 and 4 kPa); at [O₂]<1.5 ppm (4kPa) the concentration did not increase further, indicating that anaerobic metabolism had reached a maximum. Over the same range, phosphofructokinase showed an increased sensitivity for adenosine triphosphate, the lower inhibitor concentration at 50% V _max value pointing to depression of glycolytic rate. Despite the activation of anaerobic metabolism and the evident depression of aerobic metabolism, simple calculation demonstrates that Scapharca inaequivalvis relies mainly on aerobic metabolism even during severe hypoxia. It is assumed that the occurrence of haemoglobin in this species is essential for its capacity to survive long periods of hypoxia.Abbreviations ATP adenosine triphosphate - I₅₀ inhibitor concentration at 50% V _max - PFK phosphofructokinase - P _c critical PO₂ - SEM standard error of mean - VO₂ oxygen consumption rate - ww wet weight     

A radiological study of the central circulation in the lungfish, Protopterus aethiopicus

The dipnoan heart is only in part structurally developed to support a separated circulation in pulmonary and systemic circuits. In the present investigation biplane angiocardiography has been used to describe the extent of such a double circulation and the factors which may modify it in the African lungfish, Protopterus aethiopicus. Contrast injections in the pulmonary vein revealed a clear tendency for aerated blood returing from the lungs to be selectively dispatched to the anterior branchial arteries giving rise to the major systemic circulation. Contrast injections in the vena cava delineated the sinus venosus as a large receiving chamber for systemic venous blood. Contraction of the sinus venosus discharged blood into the right, posterior part of the partially divided atrial space. Contrast injection in the pulmonary vein showed that vessel to pass obliquely from right to left such that blood was emptied distinctly into the left side of the atrium. During contraction the atrial space tended to retain a residual volume in its anterior undivided part which minized mixing. Ventricular filling occurred through separate right and left atrio-ventricular connections. Right-left separation in most of the ventricle was maintained by the partial ventricular septum, the trabeculated, spongelike myocardium and the mode of inflow from the atria. Mixing in the anterior undivided portion of the ventricle during the ejection phase was slight due to a streamlined ejection pattern. The outflow through the bulbus cordis occurred in discrete streams which in part were structurally separated by well developed spiral folds. In the anterior bulbus segment the spiral folds are fused and make completely separate dorsal and ventral outflow tracts. The ventral bulbus channel provides blood to the three anterior branchial arteries. The second and third branchial arteries are large and represent direct shunts to the dorsal aorta. The fourth and fifth branchial arteries are gill bearing and receive blood form the dorsal bulbus channel. The most posterior epibranchial vessels give rise to the pulmonary arteries.     

The effects of endogenous or exogenous catecholamines on blood respiratory status during acute hypoxia in rainbow trout (Oncorhynchus mykiss)

Summary An extracorporeal circulation of rainbow trout (Oncorhynchus mykiss) was utilized to continuously monitor the rapid and progressive effects of endogenous or exogenous catecholamines on blood respiratory/acid-base status, and to provide in vivo evidence for adrenergic retention of carbon dioxide (CO₂) in fish blood (cf. Wood and Perry 1985). Exposure of fish to severe aquatic hypoxia (final P _wO₂=40–60 torr; reached within 10–20 min) elicited an initial respiratory alkalosis resulting from hypoxia-induced hyperventilation. However, at a critical arterial oxygen tension (P _aO₂) between 15 and 25 torr, fish became agitated for approximately 5 s and a marked (0.2–0.4 pH unit) but transient arterial blood acidosis ensued. This response is characteristic of abrupt catecholamine mobilization into the circulation and subsequent adrenergic activation of red blood cell (RBC) Na⁺/H⁺ exchange (Fievet et al. 1987). Within approximately 1–2 min after the activation of RBC Na⁺/H⁺ exchange by endogenous catecholamines, there was a significant rise in arterial PCO₂ (P _aCO₂) whereas arterial PO₂ was unaltered; the elevation of P _aCO₂ could not be explained by changes in gill ventilation. Pre-treatment of fish with the -adrenoceptor antagonist phentolamine did not prevent the apparent catecholamine-mediated increase of P _aCO₂. Conversely, pre-treatment with the -adrenoceptor antagonist sotalol abolished both the activation of the RBC Na⁺/H⁺ antiporter and the associated rise in P _aCO₂, suggesting a causal relationship between the stimulation of RBC Na⁺/H⁺ exchange and the elevation of P _aCO₂. To more clearly establish that elevation of plasma catecholamine levels during severe hypoxia was indeed responsible for causing the elevation of P _aCO₂, fish were exposed to moderate hypoxia (final P _wO₂=60–80 torr) and then injected intraarterially with a bolus of adrenaline to elicit an estimated circulating level of 400 nmol·l^-1 immediately after the injection. This protocol activated RBC Na⁺/H⁺ exchange as indicated by abrupt changes in arterial pH (pHa). In all fish examined, P _aCO₂ increased after injection of exogenous adrenaline. The effects on P _aO₂ were inconsistent, although a reduction in this variable was the most frequent response. Gill ventilation frequency and amplitude were unaffected by exogenous adrenaline. Therefore, it is unlikely that ventilatory changes contributed to the consistently observed rise in P _aCO₂. Pretreatment of fish with sotalol did not alter the ventilatory response to adrenaline injection but did prevent the stimulation of RBC Na⁺/H⁺ exchange and the accompanying increases and decreases in P _aCO₂ and P _aO₂, respectively. These results suggest that adrenergic elevation of P _aCO₂, in addition to the frequently observed reduction of P _aO₂ are linked to activation of RBC Na⁺/H⁺ exchange. The physiological significance and the potential mechanisms underlying the changes in blood respiratory status after addition of endogenous or exogenous catecholamines to the circulation of hypoxic rainbow trout are discussed.Abbreviations P _aCO₂ arterial carbon dioxide tension - P _aO₂ arterial oxygen tension - P _da dorsal aortic pressure - pHa arterial pH - P _wO₂ water oxygen tension - RBC red blood cell - V _f breathing frequency