bluuebunny/crossref_metadata_2025_split huggingface dataset:
Specificity of Connections Formed by Nociceptive Cells of the Leech in Tissue Culture
Authors: Vyklicky L. , Nicholls J. 
Published: April 2021

ABSTRACT
Individual medial and lateral nociceptive (N) cells of the leech have been paired with a variety of different target cells to determine the patterns and the properties of the connections made in culture.
Lateral nociceptive N cells did not make electrical or chemical connections with other N cells or with P sensory cells. N cells made electrical connections with Retzius cells, anterior pagoda cells (AP) and annulus erector (AE) and L motor neurones in culture. Lateral and medial N cells, which differ in the animal, exhibited consistent differences in culture. Well-established electrical junctions made by lateral N cells showed clear rectification. In contrast, medial N cells could make either non-rectifying or rectifying connections with target cells. In spite of the presence of strong electrical coupling, evidence for chemically mediated synaptic interactions between N cells and other neurones was obtained on occasion. These findings emphasize the specific nature of connections formed in culture. Unlike P sensory cells, N cells in culture did become electrically connected to Retzius cells and could make both rectifying and non-rectifying electrical junctions with appropriate targets.
Indoor Flight Experiments with Trained Kestrels:II. The Effect of Added Weight on Flapping Flight Kinematics
Authors: Videler J. J. , Groenewegen A. , Gnodde M. , Vossebelt G. 
Published: April 2021

ABSTRACT
A male and a female kestrel were trained to fly over a mirror in a corridor, with lead weights attached to the feet to increase weight in the range 0–0·6 N (0–61 g). Films taken at 200 frames s−1 allowed three-dimensional analysis of the displacements of the head, tail and wingtips. A kinematic analysis, based on Fourier series, was made of the displacements in three perpendicular directions and of periodic changes of wing areas and tail areas.
With increased mass, there was a decrease in flight speed, increase in wing beat frequency, increase in vertical wing beat amplitude, and an increase in the inclination of the tail. The shorter wing beat cycle under load was mainly due to a decreased upstroke duration, implying that the relative importance of the down-stroke was increased. The tail area and to a lesser extent the wing areas were enlarged during flights with the largest added weight.
Functional Design of the Feeding Mechanism in Salamanders: Causal Bases of Ontogenetic Changes in Function
Authors: Lauder George V. , Reilly Stephen M. 
Published: April 2021

ABSTRACT
Many correlated changes in the structure and function of the skull occur during metamorphosis in salamanders. To separate correlated from causal changes in form and function, we experimentally converted the unidirectional flow feeding system in axolotls (Ambystoma mexicanum) to a bidirectional system by suturing closed the gill slits. This mimics one of the major structural changes in the feeding mechanism that occur at metamorphosis. Eleven variables were measured from the intra-oral pressure traces recorded during feeding. The major changes in buccal pressure produced by suturing the gill slits were in the duration and area of the negative pressure traces. In addition, the ratio of positive to negative pressure areas increased by four times following closure of the gill slits. In contrast to pressure changes during metamorphosis in tiger salamanders, increases in the positive portion of the pressure traces occur in axolotls. These data corroborate the hypothesis that the decreased feeding performance after metamorphosis is a direct consequence of the change from a unidirectional to a bidirectional feeding mechanism, and demonstrate the causes of ontogenetic changes in function.
Potency of Adrenaline and Noradrenaline for β-Adrenergic Proton Extrusion From Red Cells of Rainbow Trout, Salmo Gairdneri
Authors: Tetens Vilhelm , Lykkeboe Gunnar , Christensen Niels Juel 
Published: April 2021

ABSTRACT
The red cell adrenoceptor affinity for the unspecific agonists adrenaline and noradrenaline and the specific β-agonist isoprenaline was studied in vitro on whole blood of rainbow trout, Salmo gairdneri at 15°C. The erythrocytic adrenoceptors could be pharmacologically characterized as β-receptors of the ‘noradrenaline’-type (β1-type), with an order of potency of isoprénaline &gt; noradrenaline ⪢ adrenaline. The adrenoceptor affinities, expressed as agonist concentrations for 50% response (ECSo), were 1·3×10−8 and 7·6× 10−7 mol I−1 for noradrenaline and adrenaline, respectively. Winter fish showed a red cell adrenergic response identical to that of summer-acclimated fish. It is concluded that most red cell β-adrenergic responses in vivo are exclusively elicited by noradrenaline.
Chromatophore Motor Fields in the Squid, Lolliguncula Brevis
Authors: Ferguson Graham P. , Martini Frank M. , Pinsker Harold M. 
Published: April 2021

ABSTRACT
Chromatophore motoneurones in Lolliguncula brevis are known to originate in the suboesophageal lobes of the brain and to project directly to the mantle and fin through bilateral stellate ganglia and fin nerves. The chromatophore motor fields of stellar and fin nerves were investigated by stimulation of the cut end of individual nerves in a semi-intact preparation. This elicited expansion of yellow and brown chromatophores in distinct motor fields. Brown chromatophores extended over the entire mantle, whereas yellow chromatophores were limited to the dorsal and lateral mantle areas. Combined nerve stimulation and lesions demonstrated substantial overlap between adjacent chromatophore motor fields and innervation of individual chromatophores by different stellar nerves.
Mechanics of Jet Propulsion in the Hydromedusan Jellyfish, Polyorchis Penicillatus: I. Mechanical Properties of the Locomotor Structure
Authors: Demont M. Edwin , Gosline John M. 
Published: April 2021

ABSTRACT
A non-destructive test was developed to measure the static mechanical properties of the locomotor structure (bell) in the hydromedusan jellyfish, Polyorchis penicillatus (Eschscholtz, 1829). A nonlinear stress-strain relationship was found, and the mean static structural stiffness of the bell was 150 N m−2. Visualization procedures that showed the natural changes in the geometry of the deformation of the bell were used to calculate the static modulus of elasticity of the mesoglea, and gave a modulus of 400 N m−2. Dynamic measurements on isolated samples of mesoglea gave a mean storage modulus of 1000 Nm−2. The resilience of the material was about 58%. These data were integrated to imply that the dynamic structural stiffness of the bell is at least 400 N m−2. Attempts to measure the dynamic structural stiffness directly indicate that the dynamic stiffness of the intact bell lies between 400 and 1000 N m−2. All, or most, of the potential energy stored in the mesoglea during contractions of the bell is stored as strain energy in the radial mesogleal fibres.
Cardiovascular and Respiratory Responses in Thoroughbred Horses During Treadmill Exercise
Authors: Evans D. L. , Rose R. J. 
Published: April 2021

ABSTRACT
Six detrained Thoroughbred horses performed incremental treadmill tests. Maximal oxygen uptake was measured during exercise by analysis of expired gas. The relationships between oxygen consumption and work rate, heart rate (HR), cardiac output (Q̇), stroke volume (SV) and arteriovenous oxygen content difference were examined during submaximal and maximal exercise. The relative contributions of blood flow and extraction of oxygen from muscle capillaries were assessed during exercise at . Mean was 129·7 ± 2·9 (mean ± S.E.M.) ml kg−1 min−1, which occurred at a mean speed of 8·0ms−1, with the treadmill set at a slope of 10%. At the mean HR was 222± 7 beats min−1. Maximal Q̇ was 534 ± 22 ml kg−1 min−1 and mean SV was 2·4 ± 0·1 ml kg−1. Mean was 24·5 ± 1·2 ml 100 ml−1 blood. Linear relationships were found between and work rate, HR, Q̇ and . Stroke volume did not increase significantly during exercise. Increasing metabolic rate during exercise was associated with linear increases in arterial haemoglobin concentration and oxygen content, and decreases in arterial oxygen partial pressures and haemoglobin saturation. We conclude that the relatively high in the detrained Thoroughbred racehorse is dependent on the generation of a large , despite development of hypoxaemia and haemoglobin desaturation, during strenuous exercise.
An in vitro and in vivo Study of the Distribution of Ammonia Between Plasma and Red Cells of Rainbow Trout (Salmo Gairdneri)
Authors: Wright P. A. , Wood C. M. , Randall D. J. 
Published: April 2021

ABSTRACT
Fish are ammoniotelic animals and therefore produce ammonia as the end-product of protein metabolism. (The term ammonia or Tamm will be used to indicate the total ammonia concentration, while NH4+ and NH3 will refer to ammonium ion and ammonia, respectively.) Ammonia is a weak base that is produced as NH3 or NH4+ depending on the biochemical reaction and exists in solution as NH3 and NH4+. Owing to the relatively high pK of ammonia (pK = 9-7 at 10°C) and the physiological pH of body fluids, the predominant form of ammonia in tissue compartments is the ionic form, NH4+. Biological membranes are highly permeable to NH3 and much less permeable to NH4+ (Klocke, Andersson, Rotman & Forster, 1972; Castell & Moore, 1971; Bown et al. 1975; Boron, 1980; Lockwood, Finn, Campbell & Richman, 1980), which requires ion carriers for transport. Thus, the extent of movement of NH4+ between tissue compartments depends on the availability of these carriers and their affinity for NH4+. Transfer of ammonia between tissue compartments is largely determined by NH3 gradients (see Randall & Wright, 1987), but NH4+ electrochemical gradients may also be important (Thomas, 1974; Boron & DeWeer, 1976). The purpose of this study was to determine whether ammonia was passively distributed between red cells and plasma at rest and during an extracellular acidosis. Protons are passively distributed across red cell membranes over a range of pH values in trout (Heming et al. 1986). Thus, if ammonia is passively distributed, the distribution will be determined by red cell-to-plasma pH gradients.
A Simple, Sensitive and Versatile Solid-State Pressure Transducer
Authors: Lighton John R. B. 
Published: April 2021

ABSTRACT
Sensitive and accurate pressure transducers are useful in many areas of biology. Two common applications are the measurement of pressure changes within the respiratory system of an animal, and quantification of the small pressure fluctuations that accompany the humidification and warming of inspired air in whole-body closed-system or open-system flow-through plethysmography (see Malan, 1973; Bucher, 1981). The design of such transducers is often complicated by the requirement to measure very small pressure fluctuations in the presence of a substantial pressure offset. Moreover, such pressure offsets often vary slowly with time. Frequent adjustments are then required to keep the output of the pressure transducer from saturating in either direction.
Behavioural Responses to Light in Paramecium Bursaria in Relation to its Symbiotic Green Alga Chlorella
Authors: Iwatsuki Kenji , Naitoh Yutaka 
Published: April 2021

ABSTRACT
The behavioural responses to light in the ciliate Paramecium bursaria Focke, which normally contains hundreds of the symbiotic green alga Chlorella in its cytoplasm, were analysed quantitatively to clarify the mechanisms governing photoreception in the cell. P. bursana was found to possess three kinds of photoreceptor systems for (1) the step-up photophobic response (system I), (2) the step-down photophobic response (system II), and (3) the photokinetic response (system III). Under the influence of light, the symbiotic algae inhibited systems I and HI, but activated system II. Thus the cells showed the avoiding reaction when they encountered shade (the step-down photophobic response), and consequently gathered in the light region (photoaccumulation). Inhibition of system I and activation of system II were assumed to be mediated by products of the blue-light effect of the algae, while inhibition of system III was due to photosynthetic products of the algae. The cells whose algae were experimentally removed gathered in the shade (photodispersal) due to the avoiding reaction exhibited by them when they encountered a lighted region (the step-up photophobic response mediated by system I). Lowered swimming velocity and increased frequency of spontaneous changes in the swimming direction in the shade (photokinetic responses mediated by system III) also caused photodispersal.
Heart Rate and Gas Exchange in Freely Diving American Mink (Mustela Vison)
Authors: Stephenson R. , Butler P. J. , Dunstone N. , Woakes A. J. 
Published: April 2021

ABSTRACT
Several studies have shown that the diet of the North American mink can vary according to habitat, season and sex (Gerell, 1967;Akande, 1972; Day & Linn, 1972; Birks & Dunstone, 1985; Dunstone & Birks, 1987). It is clear that at times, particularly in autumn and winter, both male and female mink may obtain over 50 % of their food (as fish and crustaceans) from an aquatic environment. Thus, mink will readily take to water and dive to capture prey despite the fact that they possess very few anatomical adaptations which enhance their ability to hunt underwater. Indeed, the unusually high resting metabolic rate of mustelids (Iversen, 1972) and the high energetic cost of transport during surface swimming (Williams, 1983) argue against the successful use of a diving foraging strategy. Brown & Lasiewski (1972) proposed that the adaptive advantage of the elongated body shape of mink (which is energetically expensive because of high rates of heat loss as a result of the high surface area to body volume ratio) lies in the increased ability to capture prey in confined spaces (e.g. lagomorphs in their burrows; Dunstone & Birks, 1987). Perhaps an enhanced ability to capture fish and crustaceans in underwater hides (e.g. Dunstone, 1978) compensates for their presumed locomotory inefficiency underwater.
Non-Spiking Interneurones in the Pedal Ganglia of a Swimming Mollusc
Authors: Spencer Andrew N. 
Published: April 2021

ABSTRACT
Neurones that produce graded potentials and not action potentials are found in a diverse range of species (Roberts & Bush, 1981), and are usually associated with situations where sensory information is being integrated, for example in the vertebrate retina. Nevertheless, in several arthropod species, non-spiking interneurones can participate in the production of a centrally generated motor pattern (Mendelson, 1971; Pearson & Fourtner, 1975; Heitler & Pearson, 1980; Simmers & Bush, 1980; Takahata, Nagayama & Hisada, 1981; Paul & Mulloney, 1985). Surprisingly, such interneurones with similar functions have not been reported for other phyla. In this study, non-spiking interneurones are described in the pedal ganglia of a mollusc that are probably the source of the motor pattern controlling swimming.
Some Motor Neurones of the Abdominal Longitudinal Muscles of Grasshoppers and Their Role in Steering Behaviour
Authors: Baader A. 
Published: April 2021

ABSTRACT
The abdomen is used by acridid grasshoppers for steering during flight (Camhi, 1970a ; Gewecke & Philippen, 1978; Taylor, 1981 ; Altman, 1982; Arbas, 1986; for a review see Rowell, Reichert & Bacon, 1985). The aim of the present study is to characterize some of the various motor neurones innervating the dorsal and ventral longitudinal muscles of the previously undescribed second abdominal segment (ASG2) of Locusta and to describe their activity during steering.
High Blood CO2 Levels in Rainbow Trout Exposed to Hypercapnia In Bicarbonate-Rich Hard Fresh Water - A Methodological Verification
Authors: Dimberg Kenth 
Published: April 2021

ABSTRACT
Heisler (1984, 1986) suggested that fish have a maximum extracellular bicarbonate concentration of about 30 mmol l−1, which can be attained and used for the compensation of blood acidosis induced during environmental hypercapnia. In contrast, Börjeson (1977) and Dimberg & Höglund (1987) reported HCO3−concentrations, analysed using Astrup’s tonometric method (Astrup, 1956), of 40–50 mmol l−1 in venous blood drawn by a syringe from captured fish. However, blood pH in rainbow trout is greatly affected by sampling stress induced by venous puncture (Railo, Nikinmaa & Soivio, 1985). This may introduce error into the determination of blood [HCO3−] when using a tonometric technique based on pH measurements. Consequently, the present study was performed to determine whether the maximal blood HCO3− level in hypercapnic fish is limited to 30 mmol l−1, and if the higher reported blood bicarbonate values could be the result of sampling and/or analytical errors. Rainbow trout (Salmo gairdneri) were exposed to different levels of hypercapnia and acid-base variables were analysed either in venous blood taken with a syringe in the ductus Cuvieri from captured fish or in blood sampled via a dorsal aortic catheter from undisturbed fish. In addition, tonometry and gasometry were carried out separately to determine total blood CO2 concentration.
Acid–Base Regulation and Blood Gases in the Anuran Amphibian, Bufo Marinus, During Environmental Hypercapnia
Authors: Boutilier R. G. , Heisler N. 
Published: April 2021

ABSTRACT
Specimens of Bufo marinus were exposed to aerial and aquatic hypercapnia (5 % CO2) in a closed, water recirculation system to evaluate mechanisms involved in the compensation of a respiratory acidosis in these animals. Arterial was elevated from about 9 mmHg (1 mmHg = 133·3 Pa) to 35 (1h) and 37 mmHg (2h), and gradually approached about 40mmHg (24h of hypercapnia). The typical hypercapnia-induced reduction in plasma pH from about 7·9 to below 7·4 was partially offset, at least during the first hours of hypercapnia, by a reduction in the inspired/arterial difference, presumably brought about by pulmonary hyperventilation. The predominant contributor to extracellular pH compensation, however, was a net gain of bicarbonate from the environment, mainly facilitated by ammonia excretion. Bicarbonate originating from the environment was accumulated in the body fluids, increasing the plasma concentration from the control of about 9 to 36 mmol 1-1 after 24 h. Extracellular pH was compensated to only about 30% of the shift expected at constant bicarbonate level and, according to the steady reduction of pH, non-bicarbonate buffering of CO2 also contributed significantly to the elevation of bicarbonate. This relatively poor pH compensation (compared with fishes) could not be improved either by direct administration of bicarbonate into the bloodstream or by increased environmental ion concentrations. It is concluded that the availability of bicarbonate is not a limiting factor for pH compensation during hypercapnia, and that the inability of Bufo to accumulate bicarbonate to concentrations sufficient for better hypercapnia compensation is based on a constitutional ‘bicarbonate threshold’ of the resorbing and retaining structures for acid-base-relevant ions.
Angiotensin Converting Enzyme in Brush-Border Membranes of Avian Small Intestine
Authors: Stevens Bruce R. , Fernandez Alarico , Del Rio Carlos Martinez 
Published: April 2021

ABSTRACT
Angiotensin converting enzyme activity was identified in brush-border membranes purified from the small intestinal epithelium of the common grackle, Quiscalus quiscula. Angiotensin converting enzyme was enriched 20-fold in the membrane preparation, compared with intestinal epithelial cell scrapes, and was coenriched with the brush-border markers, alkaline phosphatase and aminopeptidase N. The kinetics of hydrolysis of N-[3-(2-furyl)acryloyl]-L-phenylalanylglycylglycine (FAPGG) gave a Vmax of 907 ± 41 units g−1 and a Km of 55 ± 6μmol I−1. The avian intestinal angiotensin converting enzyme was inhibited by the antihypertensive drug, Ramipril, with a median inhibitory concentration (IC50) of 1 nmol I−1. In the light of previous studies on angiotensin converting enzyme in mammalian epithelia, these results may implicate a physiological role for angiotensin converting enzyme in regulating electrolyte and fluid uptake in bird small intestines.
Changes In Electrical Connection During Cell Fusion In The Heliozoan, Echinosphaerium Akamae
Authors: Nishi Takako , Gotow Tsukasa , Kobayashi Makoto 
Published: April 2021

ABSTRACT
The electrophysiology of cell fusion in the heliozoan, Echinosphaerium akamae, was studied by intracellular recording from two unicellular organisms undergoing fusion. Fusion was preceded by the electrical connection of axopodia of each cell to the cell body of the other. In the early stages of the fusion process, spikes evoked in one cell body failed to invade the other, but electrotonic potentials (subthreshold depolarizations) did pass to the other cell. When background depolarizing currents were injected into the organism into which the potentials had invaded, these potentials developed into spikes. In advanced stages of fusion, spikes were transmitted in both directions from one organism to the other, in the absence of polarizing current. At this time, application of appropriate hyperpolarizing currents to either of the two organisms prevented spikes produced in one from invading the other. These results suggest that in the early stage of fusion, relatively few axopodia were bridged by membrane fusion between paired cell bodies, and that the number of such bridged axopodia increased as fusion proceeded, allowing spikes to be transmitted between the two organisms.
Effects Of Acid-Base Variables On in vitro Hepatic Metabolism In Rainbow Trout
Authors: Walsh Patrick J. , Mommsen Thomas P. , Thomas W. Moon , Steve F. Perry 
Published: April 2021

ABSTRACT
The effects of hypercapnia (1 % CO2), and the independent effects of changes in extracellular pH (pHe), and [HCO3−] on intracellular pH (measured by the DMO method) and lactate metabolism (measured by utilization of 14C-labelled lactate), were examined in rainbow trout hepatocytes in vitro. Simulated uncompensated hypercapnia (high , low pHe, moderately increased [HCO3−] led to a substantial depression in the production of CO2 (44%) and glucose (51%) from lactate. In simulated compensated hypercapnia (high normal pHe, high [HCO3−], metabolism was still significantly inhibited (18–33%). Subsequent multifactorial design experiments determined that variations in , pH and [HCO3−] independently affected metabolism; increased and decreased pH inhibited metabolism, but increased [HCO3−] stimulated metabolism. These results are interpreted in terms of the effects of acid-base variables on enzymatic and transport pathways, and the possible causes of decreased hepatic glycogen stores during in vivo hypercapnia are discussed.
Perfusion-Independent Oxygen Extraction in Myoglobin-Rich Hearts
Authors: Bailey John R. , Driedzic William R. 
Published: April 2021

ABSTRACT
Cardiac myoglobin plays a role in oxygen consumption and has a protective effect during periods of hypoxia, but little is known about the role of myoglobin during periods of ischaemia. Myoglobin-rich sea raven hearts and myoglobin-poor ocean pout hearts were isolated and perfused at varying flow rates and under conditions of low and high oxygen demand to assess the role of myoglobin in oxygen extraction. In the myoglobin-rich hearts, oxygen extraction remained constant over the flow range. In the myoglobin-poor hearts, oxygen extraction was significantly elevated, relative to controls, at the lower flow rates but decreased as the flow rate increased. In hearts where myoglobin was inactivated by an oxidizing agent, oxygen extraction was similar to that observed in myoglobin-poor hearts. Under conditions of high oxygen demand, myoglobin-rich hearts again showed a constant oxygen extraction over the flow range. Myoglobin-inactivated hearts had a significantly elevated oxygen extraction at low flows, and this decreased as flow rate increased. These data suggest that myoglobin renders oxygen extraction by fish hearts independent of the rate of perfusion.