bluuebunny/crossref_metadata_2025_split huggingface dataset:
Behaviour and Motor Output of Stick Insects Walking on a Slippery Surface: I. Forward Walking
Authors: Epstein S. , Graham D. 
Published: April 2021

ABSTRACT
The walking coordination and motor output of intact adult stick insects was examined when they were supported above an oiled glass surface. The viscosity of the silicone oil was adjusted so that the animal walked with either tripod or slow-walk coordination. In the absence of mechanical coupling through the substrate, the legs typically moved at different speeds in retraction. If these differences were not too large the walks were well-coordinated in the transitions from stance to swing phase. Motor output was variable and sometimes showed periods of very weak activity in depressors and retractors. Under these conditions an individual leg moved much more slowly than its neighbours, producing 2:1 coordination patterns.
Bony Nares Air Pressure And Nasal Plug Muscle Activity During Click Production in the Harbour Porpoise, Phocoena Phocoena, and the Bottlenosed Dolphin, Tursiops Truncatus
Authors: Amundin M. , Andersen S. H. 
Published: April 2021

ABSTRACT
Sound production mechanisms have been studied in two delphinid species - the harbour porpoise, Phocoena phocoena (L.), and the bottlenosed dolphin, Tursiops truncatus (Montagu). It was found that, in both species, the click sound production was coupled to a considerable pressure increase in the bony nares. The maximum pressure recorded in Phocoena was approximately 54kPa and in Tursiops close to 81 kPa; it was equal in time and amplitude in both nares. The nasal plug muscle was found to be active up to 450 ms prior to and during sound production. Sound production without such activity was not seen. The results suggest that an identical mechanism underlies click production in both species, with, pressurized air being the driving force and the nasal plug muscle having some active regulating function.
Probes were inserted into the bony nares of three harbour porpoises, Phocoena phocoena, and one bottlenosed dolphin, Tursiops truncatus, in order to record air pressure variations together with sound production. Sounds were picked up by a hydrophone manually held to the forehead of the animals. In several of the Phocoena recordings, electromyographic activity in the nasal plug muscle was also recorded.
Aquatic and Aerial Respiration Rates,Muscle Capillary Supply and Mitochondrial Volume Density in the Air-Breathing Catfish (Clarias Mossambicus)Acclimated to Either Aerated or Hypoxic Water
Authors: Johnston Ian A. , Bernard Lynne M. , Maloiy Geoffrey M. 
Published: April 2021

ABSTRACT
Specimens of the African air-breathing catfish Clarias mossambicus were acclimated to either aerated (15·3KPa) or hypoxic ( 2·4KPa) water for up to 27 days at 20 °C. Routine respiration rate for fish acclimated to aerated water was 85·7 mlO2 (kg bodyweight) −1 h−1. Gas exchange across the suprabranchial chambers accounted for 25% of the total. In aerated water the interval between air-breaths varied from 1·4 to 30·6 min. On acute exposure to hypoxia air-breathing frequency was unaltered (6·3 h−1) although aerial respiration rate increased by 70%. This suggests that ventilation of the suprabranchial chambers is variable and that air-breathing frequency is a poor measure of air-breathing effort. Total respiration decreased by 46% on acute exposure to hypoxia ( 2·4 KPa), reflecting a reduction in routine activity. Following acclimation to hypoxia, airbreathing frequency (84 h−1) was higher and total routine respiration rate increased from 46·3 to 67·8 mlO2kg−1 h−1. The increased oxygen consumption with hypoxia acclimation was largely the result of an increase in aquatic respiration from 10·4 to 27·5 mlO2kg−1 h−1
Measurements were made of mitochondrial volume densities [Vv(mt,f)] and capillary supply to fast and slow myotomal muscles. The fraction of fibre volume occupied by mitochondria was 15% for slow and 2·5% for fast muscles. Values for [Vv(mt,f)] obtained for fish slow fibres are much higher than for homologous muscles in birds and mammals and show a good correlation with capillary density [NA(c,f)].
Hypoxia acclimation did not result in changes in either muscle Vv(mt,f) or NA(c,f). It is suggested that increased ventilation of the suprabranchial chambers and greater oxygen extraction across the gills obviates the need for modifications in these parameters.
Fluid Transport by Gallbladder Epithelium
Authors: Spring Kenneth R. 
Published: April 2021

Abstract
The absorption of fluid by epithelial tissues is thought to be due to the existence of hypertonic regions within the epithelium. The magnitude of the required hypertonicity as well as its localization have been the subject of considerable experimental and theoretical effort. Model calculations demonstrated the need for knowledge of the water permeability of the membranes of epithelial cells for the purpose of estimation of the osmotic gradients required for fluid absorption. We measured the hydraulic water permeability of the individual cell membranes of Necturus gallbladder by quantitative light microscopy. The water permeabilities were sufficiently high so that small osmotic gradients were required to achieve normal rates of fluid transport. The cell osmolality was calculated to exceed that of the mucosal bathing solution by about 2 mosmol kg−1, and the basolateral interstitial osmolality was calculated to be about 1 mosmol kg−1 greater than that of the cell. The fluid absorbed by the epithelium must be slightly hypertonic to the bathing solutions. Knowledge of the apical cell membrane water permeability and the relative area of the cell and tight junction allow a calculation of the relative flow of fluid across both pathways. It can be readily shown that osmotically induced flow across the epithelium occurs predominantly transcellularly because of the small area of the junctional pathway and the high water permeability of the cell membranes.
Syncytial Epithelia: Transport in the Absence of Paracellular Pathways
Authors: Podesta Ron B. 
Published: April 2021

Abstract
The syncytial epithelium of parasitic flatworms offers the opportunity to examine epithelial transport physiology in the absence of paracellular pathways. The asymmetric enzymatic and permeability properties of the apical and basal membranes confirm the transepithelial transport function of the syncytial epithelium. Although the absence of a paracellular pathway has led to the suggestion that the syncytium is a ‘tight’ epithelium, which would be consistent with its low osmotic and diffusive water permeability, the ion transport mechanisms in the apical membrane are more consistent with those predominating in ‘leaky’ epithelia. Contrary to that expected of an animal covered with a ‘tight’ epithelium, the parasitic flatworms are not good ion regulators. The apical membrane contains a Cl−: Na+ co-transport system characteristic of ‘leaky’ epithelia. Although external acidification occurs by an active H+ extrusion mechanism, a large part of H+ secretion is coupled to Na+ influx as in ‘leaky’ epithelia. Categorization of the syncytial epithelium as ‘tight’ or ‘leaky’ will have to await electrical potential profile determinations which are made difficult by the electrical coupling of the syncytium to the underlying nerve-muscle syncytium.
Occluding Junctions and Paracellular Pathways Studied in Monolayers of Mdck Cells
Authors: Cereijido M. , González-Mariscal L. , Borboa L. 
Published: April 2021

Abstract
MDCK cells (epithelioid, derived from the kidney of a normal dog) cultured in monolayers on a permeable support, exhibit properties of natural transporting epithelia. Comparisons of the electrical resistance across the plasma membrane of MDCK cells (as studied with microelectrodes) and the resistance across the whole monolayer, (mounted as a flat sheet between two chambers) indicate that most of the current flows through an extracellular pathway. Scanning of the electrical field over the apical surface shows that this pathway is located at the intercellular space. Yet conductance is not evenly distributed along the intercellular space as in leaky epithelia, but is restricted to sites scattered irregularly along the intercellular space. Studies of freeze fracture electron microscopy indicate that the number of strands of the junctions is also distributed irregularly, varying from 1 to 10 in a few nanometers. This suggests that regions with few strands would correspond to spots with high conductance and vice versa. However, in this preparation the sealing property of the junction bears little relationship to its structure. Thus by changing the temperature from 37 to 3 °C and back, the electrical resistance increases reversibly by 306%, while the number and arrangement of the strands show no significant modification. The resistance of the monolayer varies also with the age of the cells, suggesting that sealing and ion-permeating components of the junction may be dynamic entities that are not permanently installed, but can be accommodated to the requirements of the tissue.
Functional Properties of the Paracellular Pathway in Some Leaky Epithelia
Authors: Kottra Gabor , Frömter Eberhard 
Published: April 2021

Abstract
We here review the functional properties of the paracellular pathway of leaky epithelia such as gallbladder and renal proximal tubule. These epithelia are characterized by leaky terminal bars between adjacent cells which allow small ions, non-electrolytes and water to leak from lumen to interstitial fluid or back. In the past 10 years a great deal of information has been obtained about the properties of the misnamed ‘tight’ junctions in the terminal bars, by assuming that the overall permeation pattern reflected predominantly the junctional permeation properties. Although recent trans- and intraepithelial impedance analyses indicate that this assumption is not always justified (the contribution of the lateral intercellular space to the paracellular shunt resistance is not negligible, when the spaces are collapsed) it seems that the major conclusions are correct. The properties of the terminal junctions may thus be summarized as follows. (1) Large molecules such as horseradish peroxidase are not able to pass. (2) Passage of lipophilic substances is insignificant, as these substances permeate by the cellular route. (3) Depending on the tissue, ion permeation is either governed by channels with negative fixed charges, or positive fixed charges, or both. As inferred from ion selectivity patterns the channels of different epithelia are either wide and highly hydrated or narrow and poorly hydrated, thus allowing more or less water molecules to pass besides the ions. In narrow channels singlefile diffusion may occur. (4) Besides the selective channels a free solution shunt seems to be present in some epithelia. (5) When applied in millimolar concentrations 2,4,6-triaminopyrimidinium and amiloride block negatively charged junctional channels. However these substances do not simply turn leaky epithelia into tight epithelia, because they have additional effects on the cell membranes. (6) As observed in cell cultures, formation of tight junctions requires connecting particles to be present on the cell surface – which seems to be controlled by the cytoskeleton – and requires the presence of calcium ions as ligands. (7) Cellular control over paracellular permeability may be exerted through changes of intracellular calcium concentration.
Use of Cultured Epithelia to Study Transport and its Regulation
Authors: Handler Joseph S. 
Published: April 2021

ABSTRACT
Epithelial cells from a variety of species and organs form polarized epithelia in culture. When epithelia are grown on a porous surface, such as a millipore filter, transport can be studied using adaptations of standard techniques. In the few years in which cultured epithelia have been studied by transport physiologists, most work has been focused on identification and description of the differentiated transport exhibited by cultured epithelia. Epithelia formed by a continuous line of cells derived from pig kidney (LLC-PK1) exhibit sodium-coupled glucose transport similar to that of the proximal tubule and have vasopressin-sensitive adenylate cyclase that has been studied in great detail. Also of interest are epithelia formed by con tinuous lines of cells derived from amphibian kidney (A6) and from am phibian urinary bladder (TBM). Each line forms epithelia that have high electrical resistance and amiloride-sensitive sodium transport. Transport is stimulated by aldosterone and by cAMP or hormones that raise cell cAMP levels. In LLC-PK1 and in A6 epithelia, transport and the response to hormones can be manipulated by manipulating the culture conditions. Cultured epithelia have also been used to explore the cell biology of epithelia. Most interesting in this regard are studies of the development and maintenance of epithelial cell polarity. This approach should be especially valuable.
Potassium Ion Transport Atpase in Insect Epithelia
Authors: Harvey William R. , Cioffi Moira , Dow Julian A. T. , Wolfersberger Michael G. 
Published: April 2021

ABSTRACT
K+ transport by the epithelia of midgut, salivary glands, Malpighian tubules, sensory sensilla, possibly rectum, and other organs of certain insects appears to use a unique K+ ATPase. Ouabain inhibition of transport-related events has not been demonstrated in these epithelia. The K+ pump is unlike the Na+, K+ pump but resembles the H+ pump of phosphorylating membranes in its transport orientation, efficient thermodynamics, speculated two K+ per one MgATP2− stoichiometry, electrogenicity, and structure. Older electrochemical, tracer flux, and conductance evidence suggested that the K+ pump was on the apical plasma membrane of transporting cells in these epithelia. New X-ray microanalytical studies (XMA), reveal that the K+ concentration in all cells is more than 100 mm. Together with new microelectrode data these XMA results confirm the apical K+ pump location, resolve the K+ transport route, and suggest that the goblet cell cavity facilitates the generation of a large apical PD which may be used in nutrient absorption and pH regulation. K+ portasomes, which resemble F1-F0 ATPase particles, stud these K+ transporting apical membranes and are thought to be the unit of active K+ transport. We have suggested a K+ transport mechanism in which two cations (2K+) are abandoned in an isolated domain of the portasomes during ATP2− hydrolysis and are repelled to the opposite membrane side via a K+ channel. Small peptides hydrolysed from the δ-endotoxin ot Bacillus thuringiensis inhibit the K+ transport and may be useful as K+ pump inhibitors, apical membrane probes and insecticides. Goblet cell apical membrane fragments (GCAM) as well as fragments from columnar cell apical membrane (CCAM), lateral membrane (LM) and basal membranes (BM) were isolated as clean fractions using ultrasound, aspiration, and both differential and density gradient centrifugation; purification was monitored by electron microscopy. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE) reveals that GCAM, CCAM, LM and BM have very different protein compositions. Preliminary enzymology is consistent with the K+ ATPase being on the apical plasma membrane of the goblet cells of midgut and enveloping cells of sensilla.
Symmetrical Giant Neurones in Asymmetrical Ganglia: Implications for Evolution of the Nervous System in Pulmonate Molluscs
Authors: Munoz Douglas P. , Pawson Peter A. , Chase Ronald 
Published: April 2021

ABSTRACT
Two of the largest neurones in the terrestrial snail Achatina fulica are RPrl, located in the right parietal ganglion, and VI, located in the visceral ganglion. Several characteristics of these cells were studied in detail, including morphology, passive and active electrical properties, synaptic inputs, sensory inputs, motor outputs and sensitivity to transmitter substances. The results suggest that RPrl and VI form a bilaterally homologous pair of cells, yet they reside in asymmetrically placed ganglia. An explanation of this paradox is offered in the proposal that RPrl and V1 were formerly located in the bilaterally symmetrical intestinal ganglia. Their contemporary asymmetrical locations are accounted for by the hypothesis that, during the evolution of the pulmonate nervous system, the supraintestinal ganglion fused with the right pallial ganglion and the subintestinal ganglion fused with the visceral ganglion.
CO2 and H+ Excretion By Swimming Coho Salmon, Oncorhynchus Kisutch
Authors: Thillart Guido Van Den , Randall David , Hoa-Ren Lin 
Published: April 2021

ABSTRACT
Coho salmon, Oncorhynchus kisutch (Walbaum), were swum at constant speed in a ‘Brett-type’ tunnel respirometer. Blood , and pH as well as total CO2 content and red blood cell pH were unchanged during swim ming. The RE (respiratory exchange ratio) was slightly less than 0·7 when the fish was swimming in normal sea water, indicating that some CO2 is retained by the fish. Lowering seawater bicarbonate concentration increased HCO3− transfer, presumably because of passive bicarbonate loss. A reduc tion in seawater pH from 7 ·95 to 7 ·1 sharply reduced both CO2 and hydrogen ion transfer, resulting in very low RE values of about 0 ·2. Hydrogen ion excretion was elevated during prolonged swimming following high speed swimming activity. It would appear that CO2 and hydrogen ion transfer by fish need not be matched and changing internal and external conditions can have a marked and separate effect on hydrogen ion and CO2 excretion and therefore on the RE value.
Diffusion of Oxygen Through the Mesogloea of the Sea Anemone Calliactis Parasitica
Authors: Brafield A. E. , Chapman G. 
Published: April 2021

ABSTRACT
The diffusion of oxygen through preparations of the mesogloea of Calliactis parasitica (Couch) has been measured with a custom-built diffusion cell and an oxygen microelectrode. The mean value for Fick’s diffusion coefficient was 7·29 × 10−6cm2s−1 and that for Krogh’s diffusion constant 10·00 × 10−6cm3 oxygen per min per cm2 area and cm thickness at a pressure difference of 1 atmosphere, at 25 °C. Comparison with the rather few values in the literature for oxygen diffusion through biological materials indicates that mesogloea is similar to connective tissue. The mesogloea of Calliactis seems to present a fairly significant barrier to the diffusion of oxygen between the two cell layers, and this is discussed in relation to the route whereby the endoderm obtains its oxygen.
Retinal Damage and Sensitivity Loss of A Light-Sensitive Crustacean Compound Eye (Cirolana Borealis): Electron Microscopy and Electrophysiology
Authors: Nilsson Heimo L. , Lindström Magnus 
Published: April 2021

ABSTRACT
The compound eye of the deep-water-living crustacean Cirolana borealis has been exposed to measured amounts of white light, and the effects have been analysed by electron microscopy and electrophysiology (ERG). The threshold for damage of the retinula cells lies between 117 lx (0·47Wm−2) and 1250 lx (4·9 Wm−2). With daylight exposures of more than 70 W m−2, there is severe structural derangement and the amplitude of the electroretinogram (ERG) is abolished. No recovery of the retinula cell organization or of the ERG occurs after daylight exposure and a dark period of up to 5 days. A novel type of photoreceptor membrane shedding is described for both dark-adapted and light-exposed eyes. Hence, morphologically and functionally, the Cirolana eye is strictly adapted to a dim-light environment and is destroyed by too intense illumination.
The Elicitation of the Predatory Labial Strike of Dragonfly Larvae in Response to A Purely Mechanical Stimulus
Authors: Kanou Masamichi , Shimozawa Tateo 
Published: April 2021

ABSTRACT
The predatory labial strike of dragonfly (Aeschna) larvae could be elicited by an artificial water jet stimulus.
The larvae showed fair prey-catching ability even when visually deprived, whereas when deprived of mechanosensory and visual information, the ability decreased sharply. Also, immobilized prey were unable to elicit a strike even from intact larvae.
The percentage of labial strike (PLS) increased in proportion to the logarithm of the water velocity at the body surface. Animals starved for 1 day or more showed higher PLS than satiated ones.
In addition to the water velocity, the movement of the jet nozzle (temporary change in the velocity) was also important in eliciting the labial strike. Although repetitive stimuli resulted in a rapid habituation of the labial strike, the second stimulus in a series was always the most effective: an arousal state to the newness was observed.
The anterior parts of the body surface (including the legs) showed higher sensitivity of PLS to the water jet stimulus, whereas the posterior parts elicited responses other than the labial strike: turning, head orientation and the setting of a posture.
These results explain nocturnal predation of larvae and predation in turbid pond beds where visual cues will be unavailable.
Effects of Osmolality and Potassium on Motility of Spermatozoa From Freshwater Cyprinid Fishes
Authors: Morisawa M. , Suzuki K. , Shimizu H. , Morisawa S. , Yasuda K. 
Published: April 2021

ABSTRACT
Spermatozoa of freshwater Cyprinidae (goldfish, carp, crucian carp and dace) remained immotile when the semen was diluted in solutions of NaCl, KC1, mannitol or glucose iso-osmolar to the seminal plasma (300mosmol kg−1). The spermatozoa became motile in media containing these solutes if the osmolality was lower than that of the seminal plasma, suggesting that motility is suppressed by the osmolality of the seminal plasma in the sperm duct and initiated by a decrease of osmolality upon spawning into fresh water. Potassium was a major component of seminal plasma, having a concentration 20–30 times higher than that in the blood plasma in goldfish and carp. Sodium concentration in seminal plasma was lower than that in blood plasma. Potassium increased viability and speed of sperm movement at a concentration below that in the seminal plasma, whereas sodium and the nonelectrolytes were less effective. Potassium released with spermatozoa at spawning may therefore stimulate motility which has already been initiated by the decrease of osmolality.
Acid-Base Regulation and Ion Transfers in the Carp (Cyprinus Carpio) During and After Exposure to Environmental Hypercapnia
Authors: Claiborne J. B. , Heisler Norbert 
Published: April 2021

ABSTRACT
Acid-base balance and ion transfers were studied in the carp, Cyprinus carpio L., during and after 48 h of exposure to environmental hypercapnia ( Torr). Plasma pH, [HCO3−], and net transfers of HCO3−, NH4+, Cl− and Na+ between the fish and the environmental water were measured periodically throughout the experiment.
Over the first 8 h of hypercapnia, plasma increased by 7·6 Torr with a concurrent decrease in plasma pH of 0·28 units. Plasma [HCO3−] was slowly elevated from about 14 to 22 mm after 48 h, at which point 50% of the pH depression expected at constant bicarbonate concentration had been compensated. The net amount of H+ transferred to the water was 3 ·3 mmol kg−1 fish, representing a 115 % increase in the rate of cumulative H+ efflux, and inducing an elevation of both intracellular and extracellular [HCO3−]. Cl− transfer was reversed from a net uptake to a net efflux, while net Na+ influx was increased slightly.
Following hypercapnia, plasma pH returned to control values within 1 h, while the plasma [HCO3−], which was elevated during hypercapnia, fell continuously to reattain pre-hypercapnic control values after 20 h. The [HCO3−] decrease was due to the net gain of H+ ions from the water during this period. Cl− transfer returned to a net uptake, while the original Na+ influx was reversed to a net loss.
Acid-base regulatory responses in the carp are qualitatively similar to those observed in other fish, though the time required for compensatory pH adjustment is longer. It is concluded that alterations in the rates of Cl −/HCO3− and Na+/H+ exchanges during hypercapnia and Na+/H+ exchange following hypercapnia, play a significant role in the compensation of respiratory acid-base disturbances in these animals.