bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physiological Modulation of Gap Junction Permeability
Authors: Neyton Jacques , Trautmann Alain 
Published: April 2021

ABSTRACT
In many tissues cells communicate directly through arrays of intercellular channels which are organized to form gap junctions. These channels are permeant to inorganic ions as well as to small hydrophilic molecules up to Mr2000. The electrical and chemical coupling provided by such junctions is under the control of intracellular and, in many cases, extracellular substances. The latter (hormones or neurotransmitters) function via the activation of intracellular second messengers. These can rapidly affect the state of opening of the junctions, or induce long-term modulation of the coupling. What are the second messengers and how do they control the functional state of the junctions? These questions′ remain largely unanswered, although several internal molecules are thought to be involved in these modulations (e.g. Ca2+, H+ or cyclic AMP). The double patch-clamp technique which enables control of both the intracellular milieu and high resolution measurement of transjunctional currents, has recently been applied to study these problems. In particular, it is now possible to examine at the single channel level how junctional conductance is modulated in terms, for example, of the number of open channels or channel elementary properties.
Physics of the Hen’s Egg
Authors: Moran T. , Hale H. P. 
Published: April 2021

ABSTRACTThis paper is an account of observations made on the composition and behaviour of certain of the membranes in the hen’s egg. The composition is based on the examination of stained sections; the results should, however, give pointers in a purely chemical survey. Needham (1) has reviewed the work—chemical and histological—that has been carried out on the nature of the yolk and shell membranes. The common constituent appears to be keratin, but as he points out, this protein can exist in different forms with somewhat different properties.
The Excretion of Ammonia and Uric Acid During The Larval Life of Certain Muscoid Flies
Authors: Brown A. W. A. 
Published: April 2021

ABSTRACT
In the early years of this century Weinland (1906) conclusively showed that ammonia constitutes the bulk of the nitrogenous excreta of larvae of the blow-fly, Calliphora vomitoria. This was a remarkable observation in a subphylum that was, and still is, considered essentially uricotelic. Pupae and imagines of this species excrete uric acid; Weinland was therefore led to postulate that pupation was basically a physiological change, the change from ammonia to uric acid as the protein catabolite. Twenty-five years later Delaunay (1931), reviewing protein catabolism in invertebrates, quotes Weinland’s work and states that “les larves de Calliphora…n’excrètent pas d’acide urique”.
Studies on the Growth of Tissues in Vitro
Authors: Willmer E. N. , Jacoby F. 
Published: April 2021

ABSTRACT
In a previous number of this Journal (8) a method was described for measuring the growth rates of tissues in vitro. The colonies of fibroblasts were grown in modified Carrel flasks and photographed from below at regular intervals, so that a continuous record was obtained of the behaviour of the more peripheral cells of the colony over long periods of time. Mitoses could be easily observed, and the total number of cells on the field fairly accurately estimated. In this way the percentage of cells dividing per hour, or “mitotic index “, was calculated, and thereby a measure obtained of one of the more important factors concerned in the growth of tissues. By the use of this method it is possible to investigate the reaction of tissues to various growth-promoting or growth-inhibiting media, and to gain some insight into the general behaviour of growing tissues.
Apparatus for Investigating the Reactions of Land Arthropods to Humidity
Authors: Gunn Donald L. , Kennedy John S. 
Published: April 2021

ABSTRACTApparatus for the investigation of the reactions of land arthropods to air humidity is described.A(1). A straight line gradient of humidity is obtained with a long closed channel, into which water vapour is diffusing at one end, while being absorbed from it at the other end.The undesirable ends present in the above apparatus are eliminated by constructing the channel in the form of a ring.A (2). Any two humidities may be presented to an animal as alternatives in a simple chamber which has the advantage of providing space in which the animal can manœuvre, as well as being very cheap and easy to make. The exact form of the gradient is not, however, known in this chamber.B (1). The effect of different air humidities on the general state of activity of an insect may be investigated in an “Aktograph” consisting of a delicately balanced box; the movements of an insect inside the box cause it to tip to one side or the other, and this tipping is recorded by a lever writing on a drum.B (2). The existence of an avoiding reaction to humidity may be determined in the apparatus described under A (2), arranged so as to provide a wall of suddenly rising humidity across the centre of the dish.B (3). A straight line gradient, which for convenience must be shorter than A (1), may be obtained across a wide area, suitable for the study of directed reactions.
The Role of the Fins in the Equilibrium of the Swimming Fish
Authors: Harris J. E. 
Published: April 2021

ABSTRACT
An attempt was made to determine the relationship of the fins to the equilibrium of the swimming dogfish. Two factors at least are involved in this equilibrium; passive mechanical forces and reflex motions of the fins themselves. The part played by the automatic (passive) components was estimated by experimenting on a model of Mustelus canis mounted in a wind tunnel tested at a suitable air speed. The equilibrium in the horizontal plane (yawing equilibrium--for turning movements) is unstable without fins, completely stable only in the absence of the first dorsal fin, and is neutral when all fins are present. In the vertical plane (pitching equilibrium--for rising and diving turns) the equilibrium is unstable without fins, and this instability is greatly increased by the presence of the pectorals. The pelvics have little or no effect. Stability and controllability are inversely related. The fish is comparatively stable in the horizontal plane, extremely controllable in the vertical plane. This fact is closely related to the flexibility of the body for lateral movements. The results obtained in the wind tunnel were confirmed by amputation of the fins of the living dogfish. The normal equilibrium of the swimming dogfish in the vertical plane is determined largely by the pectoral fins and the heterocercal tail. The relationship of these facts to the problem of the evolution of the swimming chordates is considered.
Distribution of Na+ and K+ Currents in Soma, Axons and Growth Cones of Leech Retzius Neurones in Culture
Authors: García U. , Grumbacher-Reinert S. , Bookman R. , Reuter H. 
Published: April 2021

ABSTRACTLeech Retzius neurones were isolated by a new technique which allowed investigation of macroscopic currents over the surface of the cell body and the axons using loose patch-clamp. The distribution of ion current densities was measured for neurones that had just been removed from the CNS, and for cultured cells in which neurite outgrowth had begun. To standardize the mapping procedure, the same patch electrode was used at various sites along the neurone. Immediately after isolation of the cell, rapidly activating and inactivating Na+ currents were recorded from distal segments of the axons, but not from the soma or the proximal segment. Na+ currents were isolated by using patch electrodes containing tetraethylammonium (TEA+) and 4-aminopyridine (4-AP) to block K+ channels and Cd2+ to block calcium channels. Na+ currents in all regions of the neurone where they could be recorded were similar in their voltage dependence and kinetics. The Na+ current density was highest at the broken tips of the axon stumps. Neurites began to extend from the broken axon tips approximately 30 min after isolation. Newly grown processes showed a high density of Na+ currents at their growth cones. After 2 days in culture the current densities became more uniformly distributed and Na+ currents could then be recorded in the soma and proximal axon segments. In agreement with earlier studies made with conventional two-electrode voltage-clamp, three principal K+ currents were detected in Retzius cells: a rapidly activating and inactivating A-type current blocked by 4-AP (IA); a more slowly activating and inactivating delayed K+ current blocked by TEA+ (IK1) ; and a Ca2+-activated K+ current (Ic). Immediately after isolation of the Retzius cell, both rapid A-type and slow delayed K+ currents were distributed more uniformly than Na+ currents over the soma and axons. In their voltage sensitivities and kinetics, these two K+ currents were markedly different from each other; their characteristics were, however, constant in different regions of the cell. Ca2+ currents were too small to be measured directly during depolarizing pulses. However, tail currents were large enough to demonstrate the presence of Ca2+ channels in the proximal segment of the axon and in the soma; the currents were not sufficiently large to resolve their spatial distribution. It is concluded that ion channels are present in newly grown membranes and that the density of Na+ channels is highest in the tips of distal axon stumps from which outgrowth begins. By contrast, K+ currents are distributed more uniformly along the neurone.
Biomechanics of Flight in Neotropical Butterflies: Morphometries and Kinematics
Authors: Dudley Robert 
Published: April 2021

ABSTRACTWing and body kinematics of free cruising flight are described for 37 species of Panamanian butterflies ranging over two orders of magnitude in body mass. Butterflies exhibit considerable diversity in body and wing shape, but morphological design is, in general, isometric. Wing loading and mean body diameter show positive allometry. The cruising flight of butterflies is characterized by low wingbeat frequencies (here averaging 11 Hz), stroke amplitudes averaging 103°, and forward speeds in excess of 1ms−1. Body angles during flight are close to horizontal, and stroke plane angles are correspondingly high. Advance ratios are typically greater than 0.9, indicating that the forward and flapping velocity vectors are of comparable magnitude. Flight speed scales with morphological parameters in general accordance with predictions based on isometric design. Interspecifically, no consistent correlation exists between wing kinematics and absolute flight speed. However, maximum positional angle and stroke amplitude tend to increase while body angle decreases with increased relative flight speed.
Taurine accumulation by the heart of embryonic skates,Raja eglanteria
Authors: Goldstein L , Luer CA , Blum PC 
Published: April 2021

ABSTRACTThe hearts of elasmobranchs, like those of other vertebrates, contain high concentrations of the β-amino acid taurine, which is thought to play an osmoregulatory role in cardiac tissue. Although mammals and certain invertebrates can synthesize taurine from sulfur-containing precursors, e.g. cysteine, fish are unable to do so since they lack at least one enzyme involved in taurine biosynthesis: cysteine sulfinate decarboxylase (Jacobsen and Smith, 1968). Therefore, taurine must be acquired by fish via their diet (King et al. 1986). This poses a problem for the embryos of those fish that lay eggs and, for the early period of development at least, have no direct contact with amino acids in the external environment. Although solutes in the egg-case fluids can exchange with the sea water (Evans, 1981), the taurine concentration gradient between the egg case and the environment actually favors outward movement of taurine rather than uptake (L. Golstein, unpublished results). Therefore, we chose to study the mechanism by which the embryonic skate heart accumulates and maintains elevated trations of taurine in its heart. Concentrations of about 50 mmol l−1 taurine are typically found in cardiac muscle of adult specimens of the little skate Raja erinacea (Boyd et al. 1977).
Short Communication: Proline Transport by Brush-Border Membrane Vesicles of Starfish Pyloric Caeca
Authors: Ahearn Gregory A. 
Published: April 2021

ABSTRACTStarfish, unlike other echinoderms such as sea cucumbers and sea urchins, lack an effective intestine for nutrient absorption. Instead, they possess digestive diverticula called pyloric caeca which extend from the stomach wall into each arm and branch laterally into numerous blind-ended, epithelial-lined tubules. These tubules exhibit a number of physiological activities including the secretion of extracellular proteolytic enzymes (Lawrence, 1982), the storage of carbohydrates and lipids as energy reservoirs (Lawrence and Lane, 1982) and the absorption of low molecular weight organic solutes resulting from digestive activities in the diverticulum lumen (Ferguson, 1979, 1982; Jangoux, 1982; Lawrence, 1982). While it is clear from these studies that starfish pyloric caeca participate in nutrient absorption, there has been no direct physiological characterization of a transapical or transcellular transport process for amino acids or sugars by the epithelial cells of this organ. The present investigation is the first to show, using purified brushborder membrane vesicles from asteroid pyloric caeca, that amino acids can be transported across this membrane by at least one carrier-mediated process that displays properties in common with gastrointestinal absorptive organs of animals from a variety of phyla.
On the Function of a Locust Flight Steering Muscle and its Inhibitory Innervation
Authors: Wolf Harald 
Published: April 2021

ABSTRACTIn tethered flying locusts, the pleuroalar (or pleuroaxillary) muscle of the forewing (M85) was stimulated via its efferent nerve. The effect on the angular setting of the wing was observed using photogrammetry. Maximal tetanic contraction of the muscle reduced downstroke pronation and upstroke supination by more than 25°. A more physiological stimulus regime resulted in angular changes of about 7°, which is near the range observed during steering manoeuvres. This confirms that the pleuroalar muscle plays an important role in adjusting the wing’s aerodynamic angle of attack, as proposed in anatomical studies by Pfau (1978). Unit a of the pleuroalar muscle was found to be innervated by the common inhibitor neurone 1 (CI) of the segmental ganglion. IJPs with amplitudes between 2 and 10mV were elicited by action potentials in CI. A basic tonus was observed in the pleuroalar muscle in the absence of activity in excitatory motoneurones. CI input reduced this basic contracture but did not affect EJPs or muscle twitches elicited by excitatory input. Activity of the common inhibitor was recorded intracellularly and with nerve electrodes in tethered flying locusts. Tonic discharges were observed with spike frequencies ranging from 5 to 35 Hz, 25 Hz being a typical value. EMG recordings from the two units of the pleuroalar muscle showed that only unit a was active during most horizontal flight sequences. While its discharge was modulated in response to imposed roll movements, unit b was recruited primarily during ipsilateral roll.These results indicate functional specialization between pleuroalar muscle units a and b and suggest that the inhibitory innervation of unit a functions in the fine adjustment of wing pronation.
A Comparison of the Respiratory Function of the Haemocyanins of Vertically Migrating and Non-Migrating Pelagic, Deep-Sea Oplophorid Shrimps
Authors: Sanders N. K. , Childress J. J. 
Published: April 2021

ABSTRACTThe effects of temperature and pH on haemocyanin oxygen-binding were compared for three species of diurnally vertically migrating and two species of non-migrating, pelagic oplophorid shrimps from the deep sea off the Hawaiian island of Oahu. The effects of L-lactate were also measured for three of these species. Haemocyanin concentrations were higher in the haemolymphs of oplophorids that migrate vertically (39.4, 46.8 and 57.6 mg ml−1) than in those of non-migrators (26.0 and 36.4 mg ml−1). Moderately high Bohr effects were found for vertically migrating and non-migrating oplophorids at all temperatures examined (5−25°C, ϕ= −0.46 to −0.80, and −0.55 to −0.88, respectively). The vertically migrating species had temperature-sensitive haemocyanins (ΔH=−23.1 to −41.2 kJ mol−1) across the normal temperature range (5–25 °C) encountered during diurnal vertical migration. This results in haemocyanins that have relatively high affinities (P50=0.80–1.06 kPa at pH 7.8,5 °C) at the low temperatures and low O2 partial pressures (approximately 2.66kPa O2 at 5°C) found at depth, and low affinities (P50=4.00–4.66kPa at pH 7.5, 25°C) at the higher temperatures and higher O2 partial pressures (approximately 13.33–17.50 kPa at 25°C) found in the near-surface waters. In contrast, the non-migrating species, which live within a narrower temperature range (3–6°C) and at a constant, low partial pressure of O2 (2.66–4.00 kPa), have haemocyanins with a high affinity for oxygen (P50=0.67–0.93 kPa at pH 7.8, 5°C) and lower sensitivity to temperature (ΔH−4.2 to −21.6kJ mol−1). The effects of temperature on the haemocyanin oxygen-affinities of the vertical migrators appear to be highly adaptive, enabling these haemocyanins to be functional across the entire depth (and thus, temperature and oxygen partial pressure) range encountered.
Autonomic regulation of cutaneous vascular resistance in the bullfrogRana catesbeiana
Authors: Malvin G. M. , Riedel C. 
Published: April 2021

ABSTRACTTo gain a better understanding of the regulation of cutaneous blood flow in the bullfrog, the vascular innervation, vasoactivity and adrenoceptor types of the cutaneous vasculature were investigated using a pump-perfused skin preparation. Stimulation of cranial nerve I, the vagal ganglion, sympathetic ganglion 1 and sometimes sympathetic ganglion 2 caused cutaneous vascular resistance (CVR) to increase. Stimulation of cranial nerve IX and spinal nerves 1 and 2 had no effect on CVR. The response to stimulation of sympathetic ganglion 1 was antagonized by phentolamine but not by atropine. Phentolamine, atropine and α, β-methylene ATP had no effect on the response to vagal stimulation. Both epinephrine (EPI) and norepinephrine (NE) increased CVR, with EPI being more potent than NE. The minimum concentrations of EPI and NE required for a significant change in CVR were much higher than plasma catecholamine levels reported for resting bullfrogs. Phentolamine antagonized, but propranolol had no effect on, the responses to the catecholamines. Isoproterenol caused small decreases in CVR which were abolished by propranolol. Acetylcholine was a weak vasodilator. The results indicate that the cutaneous vasculature has two types of vasomotor nerves: sympathetic nerves that are probably adrenergic, and other nerves that are non-adrenergic/non-cholinergic and which do not use ATP as a transmitter. Although catecholamines are vasoactive, the sensitivity of the cutaneous vasculature to EPI and NE is probably too low to allow a direct regulatory role of these hormones on CVR. There is no evidence for cholinergic regulation of CVR. Both α- and β- adrenoceptors are present in the cutaneous vasculature, α-Adrenoceptors mediate the constrictor responses to sympathetic nerve stimulation and catecholamine administration. It is unlikely that β-adrenoceptors play a significant role in regulating CVR.
The Importance of Vascular Elasticity in the Circulatory System of the CephalopodOctopus Vulgaris
Authors: Shadwick R. E. , Nilsson E. K. 
Published: April 2021

ABSTRACTThe passive mechanical properties of the dorsal aorta and the vena cava of Octopus vulgaris were investigated in vitro. Both vessels are highly distensible structures that exhibit non-linear elasticity, but have substantially different material properties. The volume compliance of each vessel is maximal within the resting physiological pressure range (2–3 kPa in the aorta and 0–0.5 kPa in the vena cava) but is five times greater in the vena cava than in the aorta. The aorta is mechanically suited to function as an elastic storage reservoir in the arterial circulation, while the vena cava is appropriately designed to be a low-pressure capacitance element.Pressure wave velocity in the aorta was calculated from the elastic modulus to be 1.8ms−1 under resting conditions. Therefore, pressure changes will occur almost simultaneously throughout the arterial tree and pressure wave transmission properties can be described by a two-element Windkessel model. Predictions of vascular impedance amplitude made from this model are presented.The effectiveness of the aorta as an elastic reservoir appears to be severely reduced during exercise in Octopus. Because blood pressure increases while heart rate does not, the efficiency of the Windkessel will be diminished as the time constant of the system decreases and the pulsatile work of the heart subsequently increases.
The Actions of Proctolin, Octopamine and Serotonin on Crustacean Proprioceptors Show Species and Neurone Specificity
Authors: Pasztor Valerie M. , Macmillan David L. 
Published: April 2021

ABSTRACTA comparative survey is presented of the responsiveness of crustacean mechanoreceptors to the neurohormones proctolin, octopamine and serotonin. Seven identifiable primary afferents were examined in the crayfish Cherax destructor and the lobster Homarus americanus: three from the oval organ (OO) of the second maxilla, two from the non-spiking stretch receptor (NSSR) of the swimmeret and two from the muscle receptor organ (MRO) of the abdomen. Proctolin modulation was observed in 10 of the 14 fibres tested and was invariably potentiating, resulting in enhanced receptor potential amplitudes and increased firing. Octopamine and serotonin each modulated 8 of the 14 fibres and their effects were excitatory or depressive depending upon the target fibre. In the latter case the receptor potentials became attenuated, often to subthreshold levels, with loss of spiking.A comparison of results from Cherax with those of Homarus shows that there is species specificity in the responses of homologous neurones. Neurohormones that are excitatory in one species may be ineffective or depressive in the other.The broad distribution of modulatory effects observed here suggests that sensitivity to biogenic amines and peptides is a general property of proprioceptors.
Substratum Slope and the Alignment of Acute Zones in Semi-Terrestrial Crabs (Ocypode Ceratophthalmus)
Authors: Zeil Jochen 
Published: April 2021

ABSTRACTThe organisation of the visual system in semi-terrestrial crabs is related to the three-dimensional structure of the environment (Zeil et al. 1986; Nalbach and Nalbach, 1987; Nalbach et al. 1989a,b;Zeil et al. 1989). In species that Eve in flat habitats - like sandy ocean beaches or mudflats - we find: (1) long, vertically oriented eye stalks; (2) a small separation between the eyes; (3) an acute zone for vertical resolving power with its maximum along the eye equator; and (4) a specific gradient of vertical resolution towards more dorsal and more ventral directions of view. Species that live in three-dimensionally more complex worlds - like rocky shorelines and within mangrove forests - have short eye stalks far apart at the lateral corners of the carapace and lack prominent acute zones.