bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of ammonia loading onPorcellio Scaber: Glutamine and glutamate synthesis, ammonia excretion and toxicity
Authors: Wright Jonathan C. , O’Donnell Michael J. , Reichert Johanna 
Published: April 2021

ABSTRACTThe effects of ammonia loading in the terrestrial isopod Porcellio scaber were studied by exposing animals to atmospheres of high . Isopods show a remarkable tolerance of elevated ambient , with an LD50 of 89 Pa for a 7-day exposure. However, haemolymph total ammonia concentrations generally remained below 5 mmol l−1 (=0.37 Pa) over the range of ambient ammonia levels used (6.6–165 Pa). Following a 7-day loading period, whole-animal glutamine (Gln) and glutamate (Glu) levels increased in direct proportion to ambient , reaching values of 35 μmol g−1 fresh mass for glutamine and 12 μmol g−1 fresh mass for glutamate in 99 Pa ; these correspond to control levels of 7.5 μmol g−1 fresh mass and 5.9 μmol g−1 fresh mass, respectively. Following transfer to ammonia-free chambers, NH3 excretion rates were augmented five-to sixfold relative to non-loaded controls. Ammonia volatilization subsequently declined, approaching control levels after 8–9 days. Levels of Gln and Glu showed a concomitant decline to 13.7 μmol g−1 fresh mass and 9.2 μmol g−1 fresh mass, respectively. The results suggest that these amino acids function in ammonia sequestration and, hence, detoxification. Calculations indicate that mobilization of amino groups by deamination of accumulated Gln and Glu could explain 35 % of the increased ammonia production. Implications of NH3 volatilization for acid–base balance are discussed.
Somatostatin-related peptides isolated from the eel gut: effects on ion and water absorption across the intestine of the seawater eel
Authors: Uesaka Toshihiro , Yano Keiichi , Yamasaki Motoo , Nagashima Kei , Ando Masaaki 
Published: April 2021

ABSTRACT
Four somatostatin-related peptides were isolated from eel guts. Two of them were the same as eel SS-25II (eSS-25II) and eel SS-25I (eSS-25I) isolated from European eel pancreas. The remaining two peptides were C-terminal tetradecapeptides (eSS-14II and eSS-14I) of eSS25II and eSS-25I, respectively. These four peptides all enhanced the serosa-negative transepithelial potential difference and short-circuit current across the seawater eel intestine after pretreatment with isobutylmethylxanthine, serotonin (5-HT) and methacholine, an agonist of acetylcholine (ACh). Among these peptides, eSS-25II was the most potent enhancer, followed by eSS-25I and eSS-14II. Since the large peptide (eSS-25II) acts at a lower concentration than the small somatostatin (eSS-14II), the 11 N-terminal amino acid residues seem to potentiate somatostatin action in the eel intestine. In contrast, eSS-14II was more potent than mammalian SS-14, indicating that the three amino acid residues (Tyr18, Gly21, Pro22) in the C-terminal portion also contribute to the potency of somatostatin. Endogenous somatostatin (eSS-25II) activated net Na+, Cl-and water fluxes across the seawater eel intestine. This stimulatory action was not inhibited by tetrodotoxin or yohimbine, an adrenergic antagonist, indicating that eSS-25II does not act through neuronal firing or through catecholamine release. Thus, eel somatostatins may act directly on the enterocytes, but on a distinct receptor from that for adrenaline, to antagonize the inhibition of NaCl and water absorption by 5-HT and ACh in the seawater eel intestine.
A mysid shrimp carrying a pair of binoculars
Authors: Nilsson Dan-E. , Modlin Richard F. 
Published: April 2021

ABSTRACT
Like other mysid shrimps, the tropical shallow-water species Dioptromysis paucispinosa possesses compound eyes of the refracting superposition type. In the rear of each eye, pointing backwards, is a single conspicuous facet almost three times the diameter of those in the rest of the eye. Underlying the large facet is an equally enlarged single crystalline cone, projecting an upright image onto a specialized retina of 120 densely packed and extremely narrow rhabdoms. This peculiar arrangement constitutes an acute zone which operates as a simple eye within a compound eye. Calculations of spatial sampling frequency and photon catch indicate that the centre of the acute zone resolves more than six times better than the normal eye, but it requires intensities more than a log unit higher – figures not unlike those of modern compact binoculars. The fact that the acute zone covers a visual field of 15–20°, with a large binocular overlap, strengthens the analogy with a pair of binoculars. The resolution of the acute zone is also remarkable in absolute terms: a rhabdom axis separation of 0.64° rivals foveal vision in large insects, although the entire eye of Dioptromysis measures only 0.4 mm. With the normal posture of the shrimp, the acute zone points backwards, about 12 ° above the horizon. Difficulties in understanding the animal’s use of such an acute zone were resolved by the discovery of large coordinated eye movements. The eyestalk can be rotated around its axis by at least 130 °. This makes the acute zone aim forwards and upwards, which is a more sensible direction for spotting and pursuing prey. The acute zone is probably held in the rest position aiming backwards only to avoid having an important part of the forward visual field constantly occupied by an eye region of inferior sensitivity.
Blood Sugar and the Follicles of Langerhans in the Ammocoete Larva
Authors: Barrington E. J. W. 
Published: April 2021

ABSTRACT
Glandular follicles, first described by Langerhans, develop in the wall of the alimentary canal of the ammocoete larva at the point of junction of fore- and midgut, and have often been compared with the pancreas of higher forms. They have been re-examined histologically, using Helly’s fixative and the ‘Azan’ stain, and the view of some recent workers, that they have the appearance of endocrine structures, is confirmed. They comprise only one type of cell, however, which shows no decisive resemblance in staining reaction to any of the cell types characteristic of typical islet tissue.
The injection of glucose into ammocoetes usually produces a marked response in these cells, involving extensive vacuolization, while destruction of the follicles by cautery induces a significant rise in blood sugar. These reactions, which imply that the follicles are involved in carbohydrate metabolism, are similar to those associated with the B cells of islet tissue.
It is concluded that the evidence, while not yet complete, suggests that the follicles represent a primitive stage in the evolution of the endocrine component of the vertebrate pancreas, and it is pointed out that ‘follicles of Langerhans ‘would be an apt designation for them. Further work will be necessary to Clarify their relationship to the islets of Langerhans of higher forms.
The Temperature and Humidity Relations of the Cockroach
Authors: Gunn D. L. , Cosway C. A. 
Published: April 2021

ABSTRACTThe carpet type of Barcroft respiration apparatus previously used by Gunn for cockroaches gives results comparable with those now obtained with a new basket type. Desiccated cockroaches use oxygen at the same rate per animal as undesiccated specimens. If, however, the rates are calculated with reference to the weight of the animal at the time of the experiment, since the desiccated animals tested had lost about 25 % of their original weight, their rates of oxygen consumption appeared to have gone up. Both normal and desiccated animals used oxygen slightly faster in moist air than in dry. Part of this increase must be attributed to a higher body temperature in moist air at 25° C. than in drier air at 25° C. Part of it may be due to greater activity in moist air than in dry, slight though the activity was in both cases. There is no reason to believe that, at a given body temperature, air humidity influences basal metabolic rate.
Shape Transformations in the Red Cells of Camels, Birds, Reptiles, Amphibia, and Fishes
Authors: Ponder Eric 
Published: April 2021

ABSTRACT
The bearing of shape changes on the problem of red-cell structure is so great that we cannot afford to omit studying the transformations which occur in oval nucleated red cells in order to compare them with those in the discoidal non-nucleated red cells of man and of most mammals. The purpose of this paper, accordingly, is to give a description of the shape changes observed in the erythrocytes of camels, birds, reptiles, amphibians, and fishes.
Narcosis and Asphyxiation in Some Species and Mutants of Drosophila
Authors: Kalmus Hans 
Published: April 2021

ABSTRACT
Narcosis and asphyxia in insects can be investigated by measuring the recovery time. This and other terms are defined, and suitable criteria of recovery are given. Simple techniques for the etherizing and gassing of Drosophila batches are described and the validity of the quantitative results obtained is shown. The recovery time is increased by the time of influx and by the concentration oj the narcotic. The shapes of the curves obtained in experimental Series are logarithmic (carbon dioxide asphyxiation), straight line (ether in some species), concave, convex or sigmoid (ether). It is suggested that the different forms of ether recovery curves are different parts of essentially similar curves, which one might explain by the joint action of two macrophases, one aqueous and one lipoid. Physiological factors determining recovery times are : (a) sex : females recover earlier from ether narcosis than males; (b) age: young flies recover earlier than older ones; (c) lack of food and moisture, which increases the recovery time ; and (d) chemical reaction: flies kept on acid food remain longer narcotized than flies-bred on an alkaline medium. Carbon dioxide lengthens recovery from ether narcosis and hydrocyanic acid immobilization when applied before the influx time and shortens it when applied during recovery-time. If administered during recovery, it also shortens the recovery from asphyxiation. Carbon monoxide and coal gas administered before narcotization can shorten the recovery time from ether narcosis. Under specified conditions corresponding to those, used during narcosis by Droso-phila-workers some differences in recovery time after etherization due to genetical differences could be established. Significant differences also exist between some Drosophila species, races and mutants in their resistance to carbon dioxide, asphyxiation and hydrocyanic acid.gas.
Scale effects on the stresses and safety factors in the wing bones of birds and bats
Authors: Kirkpatrick Sean J. 
Published: April 2021

ABSTRACT
The effects of scale on the estimated stresses and safety factors in the humeri of several bird and bat species were investigated. This was accomplished by estimating the lift distribution across the wings at two extremes of flight, gliding flight and the downstroke in hovering, finding the center of lift on the wings at these two extremes and calculating the applied bending and twisting moments. This information, along with measurements of mechanically important morphological variables, allowed for estimates of bending and shearing stresses in the humeri for both gliding flight and on the downstroke in hovering. The stresses in flapping flight other than hovering should fall somewhere between these two values. It was found that the stresses in the humeri are not scale-dependent and that the bending stresses are slightly lower than those found in the limbs of terrestrial animals, while the shearing stresses are larger than those in terrestrial limbs. The breaking stress of bird and bat wing bone was also investigated. Both materials were found to have a lower breaking stress than that of typical long bone material. The ratio between the breaking stress of the material and the estimated stresses was defined as the safety factor. Bird humeri have safety factors that are generally greater than those of bat humeri. This is because bat bone has a lower breaking stress than does bird bone, although the estimated stresses in the wings are similar. The mean safety factor against failure due to bending in gliding flight was 6.63 for birds and 3.99 for bats. In hovering, the mean safety factors against failure due to bending were 2.22 for birds and 1.41 for bats. The safety factors against failure due to shearing stresses were estimated to be seven time greater than those against failure due to pure bending stresses.
Comparative analysis of hyperexcitability and synaptic facilitation induced by nerve injury in two populations of mechanosensory neurones of Aplysia californica
Authors: Clatworthy Andrea L. , Walters Edgar T. 
Published: April 2021

ABSTRACT
Long-term effects of nerve injury on electrophysiological properties were compared in two populations of mechanosensory neurones in Aplysia californica: the J and K clusters in the cerebral ganglia and the VC clusters in the pleural ganglia. Following crush of cerebral nerves containing their axons, the cerebral J/K sensory neurones showed long-term changes that were quite similar to alterations previously described in the VC sensory neurones after either axonal injury or aversive learning. These changes include synaptic facilitation, an increase in soma excitability and spike duration, and a decrease in spike threshold and afterhyperpolarization. In addition, simultaneous crush of both the cerebral and pedal nerves in the same animals produced alterations in the cerebral J/K sensory neurones and pleural VC sensory neurones that were virtually identical. The incidence of hyperexcitability was the same in cerebral J/K and pleural VC sensory neurones when all their axons were crushed, even though the former population includes many neurones that probably have appetitive functions while the latter population appears to be made up exclusively of neurones with defensive functions. Long-term plasticity in both sensory populations failed to occur when nerves lacking axons of the tested neurones were crushed, even when the crush site was very close to the somata of the sensory neurones. This axonal specificity argues against a role for delayed activation of facilitatory interneurones in triggering the plasticity. Several observations are consistent with a triggering role for either (1) intracellular signals released directly by axonal injury or (2) extracellular signals released locally by other axons or injured support cells, or by immunocytes attracted to the injured site.
Blood pressure control in the antarctic fish Pagothenia borchgrevinki
Authors: Axelsson Michael , Davison Bill , Forster Malcolm , Nilsson Stefan 
Published: April 2021

ABSTRACT
The mechanisms of cardiovascular control in the Antarctic fish Pagothenia borchgrevinki were investigated during rest and swimming exercise using pharmacological tools to reveal the nature of the control systems involved. Simultaneous and continuous recordings of ventral and dorsal aortic blood pressure, heart rate and ventral aortic blood flow (cardiac output) were made using standard cannulation procedures and a single-crystal Doppler flowmeter.
Exercise produced a clear and consistent decrease in dorsal aortic blood pressure caused by a decrease in systemic vascular resistance. At the same time, ventral aortic blood pressure increased owing to the combined effects of a markedly increased cardiac output (by about 80 %) and branchial vasoconstriction. Judged from the effects of the α-adrenoceptor antagonist prazosin, control of the branchial vasculature involves an α-adrenoceptor-mediated vasoconstriction, in addition to more traditional cholinergic vasoconstrictor and β-adrenoceptor-mediated dilatory mechanisms.
The range of heart rates is large, from 3–4 beats min-1 in individual fish during hypertensive bradycardia to about 28 beats min-1 after atropine treatment. Both chronotropic and inotropic effects are responsible for a marked increase in cardiac output during exercise. The increase in blood pressure caused by adrenaline injection was due largely to an increase in cardiac output, while direct effects on the systemic vasculature were small and transient. The increase in cardiac output, in turn, was due solely to an adrenergic stimulation of stroke volume. A barostatic bradycardia, often seen in other vertebrates in response to adrenaline injection, was absent and it is possible that a decrease in heart rate was offset by direct adrenergic stimulation of the heart.
Angiotensin II (Ang II) produced consistent hypertension by systemic vasoconstriction. In contrast to the effects of adrenaline injection, the hypertension caused by Ang II was accompanied by a marked bradycardia. This could be abolished by atropine, suggesting a cholinergic vagal reflex of the type found in other vertebrates.
Angiotensin I also caused an elevated blood pressure, and this effect was abolished by the angiotensin converting enzyme inhibitor enalapril, demonstrating elements of an angiotensin-related cardiovascular control system.
Evidence of regulatory mechanisms for the distribution of blood between the arterial and the venous compartments in the hagfish gill pouch
Authors: Sundin L. , Axelsson M. , Nilsson S. , Davison W. , Forster M. E. 
Published: April 2021

ABSTRACT
Of the extant vertebrate animals, the hagfishes are generally considered to be the group which diverged first from the ancestral vertebrate lineage, although molecular sequence analysis has recently suggested that they form a monophyletic group with lampreys (Stock and Whitt, 1992). The circulatory system of hagfishes has features that have been described as ‘primitive’ (Burggren et al. 1985), but their gills are effective gas exchangers. The gills are contained within discrete muscular pouches, and the anatomy of the blood system and ventilatory ducts has an ideal countercurrent arrangement (Mallatt and Paulsen, 1986; Elger, 1987).
Motion analysis of escape movements evoked by tactile stimulation in the cockroach Periplaneta americana
Authors: Schaefer Paul L. , Kondagunta G. Varuni , Ritzmann Roy E. 
Published: April 2021

ABSTRACT
The escape behavior of the American cockroach, Periplaneta americana, has provided a large amount of neuroethological data on the control of orientation movements. In the typical behavior, the animal responds to gentle wind puffs by turning away from the wind source and running (Camhi and Tom, 1978). However, cockroaches also escape in a directional manner in response to tactile stimuli (Comer et al. 1989, 1993). This additional category of escape response raises two important questions. Do the neural circuits for wind-and tactile-evoked escape responses converge, and if so where? At one extreme, the two behaviors may be under the control of completely separate circuits. Alternatively, the two sensory pathways could converge on a single set of controlling interneurons.
The relative contributions of red and white blood cells to whole-blood energy turnover in trout
Authors: Wang Tobias , Nielsen Ole B. , Lykkeboe Gunnar 
Published: April 2021

ABSTRACT
Previous studies addressing energy turnover in fish blood have ignored the possible influence of white cells. The present investigation quantified the contribution of white and red cells to whole-blood energy turnover in trout (Oncorhynchus mykiss) before and after adrenergic stimulation. All experiments were carried out on cells kept in their native plasma. White cells were found to have an almost twenty times higher rate of oxygen consumption than red cells. Furthermore, white cells were responsible for essentially all whole-blood lactate production. Our data therefore show that white cells account for almost half of the energy turnover in trout blood. Adrenergic stimulation elicited a significant increase in total as well as ouabain-sensitive (a Na+/K+-ATPase inhibitor) red cell oxygen consumption. However, the ouabain-sensitive red cell oxygen consumption amounted to approximately 23 % of the total red cell oxygen consumption, regardless of adrenergic stimulation. Therefore, energy-consuming processes other than Na+/K+-ATPase activity are probably involved in the increased red cell oxygen uptake after adrenergic stimulation.
Mechanical Performance of anin SituPerfused Heart From the TurtleChrysemys ScriptaDuring Normoxia and Anoxia At 5°C and 15°C
Authors: Farrell A. P. , Franklin C. E. , Arthur P. G. , Thorarensen H. , Cousins K. L. 
Published: April 2021

ABSTRACTWe developed an in situ perfused turtle (Chrysemys scripta) heart preparation to study its intrinsic mechanical properties at 5°C and 15°C using normoxic and anoxic perfusion conditions. The in situ preparation proved durable and stable. At 15°C and a spontaneous heart rate of 23.4 beats min−1, maximum stroke volume was 2.54 ml kg−1 body mass, maximum cardiac output was 62.5 ml min−1 kg−1 and maximum cardiac myocardial power output was 1.50 mW g−1 ventricular mass. There was good agreement between these values and those previously obtained in vivo. Furthermore, since the maximum stroke volume observed here was numerically equivalent to that observed in ventilating C. scripta in vivo, it seems likely that C. scripta has little scope to increase stroke volume to a level much beyond that observed in the resting animal through intrinsic mechanisms alone. The ability of the perfused turtle heart to maintain stroke volume when diastolic afterload was raised (homeometric regulation) was relatively poor.At 5°C, the spontaneous heart rate (8.1 beats min−1) was threefold lower and homeometric regulation was impaired, but maximum stroke volume (2.25 ml kg−1) was not significantly reduced compared with the value at 15°C. The significantly lower maximum values for cardiac output (18.9 ml min−1 kg−1) and power output (0.39 mW g−1 ventricular mass) at 5°C were largely related to pronounced negative chronotropy with only a relatively small negative inotropy.Anoxia had weak negative chronotropic effects and marked negative inotropic effects at both temperatures. Negative inotropy affected pressure development to a greater degree than maximum flow and this difference was more pronounced at 5°C than at 15°C. The maximum anoxic cardiac power output value at 15°C (0.77 mW g−1 ventricular mass) was not that different from values previously obtained for the performance of anoxic rainbow trout and hagfish hearts. In view of this, we conclude that the ability of turtles to overwinter under anoxic conditions depends more on their ability to reduce cardiac work to a level that can be supported through glycolysis than on their cardiac glycolytic potential being exceptional.
Characterisation of Large Second-Order Ocellar Neurones of the Blowfly Calliphora Erythrocephala
Authors: Simmons Peter J. , Jian Shi , Rind F. Claire 
Published: April 2021

ABSTRACT
Blowflies have twelve large, second-order ocellar neurones (L-neurones) with axons in the single ocellar nerve. These neurones have fairly restricted arborizations in the posterior slope neuropile of the protocerebrum and cell bodies in the nerve, near to the fused ocellar retinae. Like ocellar L-neurones of other insects, or large second-order neurones of the fly compound eye, blowfly L-neurones hyperpolarise in response to increases in light intensity and depolarise in response to decreases in light intensity. Both polarities of response have a strong phasic component. Adaptation to sustained illumination shifts the intensity–response curve, with little change in its gradient. The maximum responses of blowfly L-neurones to sinusoidal changes in light intensity occur at stimulus frequencies of 5–10 Hz. Hyperpolarising an L-neurone with small currents causes an increase in input resistance. Larger hyperpolarising currents cause oscillations in the membrane potential. The amplitude of the oscillations increases with current strength. Repolarisation generates brief rebound spikes of variable amplitude. Injection of small hyperpolarising currents increases the amplitude of a response to a subsaturating pulse of light. This effect is not seen for saturating responses to light and is likely to be due to the increase in membrane resistance caused by hyperpolarisation.