bluuebunny/crossref_metadata_2025_split huggingface dataset:
Co-And Counter-Transport Mechanisms Inbrush Border Membranes and Basal-Lateralmembranes of Intestine and Kidney
Authors: Murer H. , Ahearn G. , Biber J. , Cassano G. , Gmaj P. , Stieger B. 
Published: April 2021

AbstractOne way to obtain a deeper understanding of the complex function of the small intestinal and renal proximal tubular epithelium is to dissect it into single components and then, having defined the components under well-controlled conditions, try to describe the behaviour of the whole system on the basis of the properties of the single components.Brush border and basal-lateral membranes can be isolated by different methods, including free flow electrophoresis, differential and gradient centrifugation. Transport can be analysed in vesiculated membrane fractions by tracer techniques and spectrophotometric techniques.Different sodium-solute co-transport mechanisms were identified in the brush border membrane. Until now, studies with vesicles failed to document a sodium-chloride co-transport mechanism satisfactorily. On the other hand, a sodium/proton and a chloride/hydroxyl exchange mechanism were documented. These two exchange mechanisms could represent partial reactions of the postulated electroneutral sodium-chloride co-transport. In addition to different sodium-independent transport systems, the basallateral membrane contains an ATP-driven transport system for calcium as well as a sodium/calcium exchange mechanism.Studies with membrane vesicles isolated from animals which have been exposed to different dietary conditions or in which the parathyroid hormone or 1·25(OH)2Vit D3 level has been altered show altered transport of calcium and inorganic phosphate. Thereby, it might be possible to identify the biochemical mechanisms involved in transport regulation.
Chloride Cells and the Hormonal Control of Teleost Fish Osmoregulation
Authors: Kevin Foskett J. , Bern Howard A. , Machen Terry E. , Conner Marilyn 
Published: April 2021

ABSTRACT
Teleost fish osmoregulation is largely the result of integrated transport activities of the gill, gut and renal system. The basic ‘epithelial fabric’ in each of these tissues is adapted to provide the appropriate transport mechanisms depending upon whether the fish is in fresh water or sea water. Net NaCl transport by the branchial epithelium reverses direction when euryhaline species migrate between the two media, providing a useful focus in experiments designed to elucidate mechanisms of differentiation and integration of transport function. Isolated opercular membranes and skins from certain seawater-adapted species are good models to study branchial salt extrusion mechanisms. These heterogeneous tissues generate short-circuit currents equal to net chloride secretion. The vibrating probe technique has allowed localization of all current and almost all conductance to the apical crypt of chloride cells. Area-specific surface current and conductance of chloride cells are 18mAcm−2 and 580mScm−2 (1·7Ωcm2), ranking them as one of the most actively transporting and conductive cells known. There is no net sodium transport under short-circuit conditions but the chloride secretion process is sodium-dependent and ouabain and ‘loop’-diuretic sensitive. Sodium fluxes through chloride cells are large (PNa = 5·2 × Ω 10−4cms−1) and appear passive and rate-limited by a single barrier. A link may exist between the active transport and leak pathways since sodium fluxes always account for 50% of chloride cell conductance. The sodium pathway is probably the chloride cell-accessory cell tight junction, although this is still unresolved. Chloride secretion can be rapidly modulated by several hormones, including catecholamines, somatostatin, glucagon, vasoactive intestinal polypeptide and urotensins I and II. Regulation by these hormones may be by rapid alterations of cellular cAMP levels. Differentiation of chloride cells and chloride secretion may be controlled by cortisol and prolactin. Cortisol stimulates chloride cell proliferation and differentiation and appears to interact with NaCl to initiate salt secretion. Prolactin appears to cause chloride cell dedifferentiation by reducing both the active-transport and leak pathways proportionately. Prolactin and cortisol also affect epithelial cell proliferation and differentiation in the other osmoregulatory tissues in fish, suggesting that these hormones are primary agents in the integration of transport activities to achieve whole animal osmoregulation.
Evolution of Control of Epithelial Transport in Vertebrates
Authors: Pang Peter K. T. 
Published: April 2021

ABSTRACT
In this review, the control of osmoregulation in the whole animal is discussed. Two main areas are considered: (i) the interaction between neural and hormonal control of osmoregulation and (ii) the relationship between vascular and osmoregulatory responses to these controlling factors. In the first area, the importance of neural influence on bullfrog kidney is described. The data suggest that a-adrenergic mechanisms are involved in glomerular as well as tubular functions. Innervation of tubular cells is seen in electron microscopic studies. Effects of neurotransmitters on fish gills and amphibian urinary bladder and skin transport are discussed. It is suggested that neural control in fish and amphibian epithelial transport might play an important role in osmoregulation. In the second area, a hypothesis is advanced for the evolution of renal function of arginine vasotocin (AVT). AVT probably first appeared as a vascular hormone. Its diuretic effect on fishes could be due to its systemic pressor action. During evolution, redistribution of vascular receptors, which became more numerous or more sensitive in the preglomerular circulation, resulted in glomerular anti-diuresis as seen in the mudpuppy and bullfrog. Tubular receptors to AVT, present in the bullfrog, enhanced the antidiuretic property of this peptide. Effects of neurotransmitters on gill transport could be due in part to their vascular action on the branchial vasculature. The intimate relationship between vascular and osmoregulatory responses to controlling factors could be important in our understanding of the evolution of the control of osmoregulation.
Na/K/Cl Co-Transport and its Regulation
Authors: Palfrey H. C. , Rao M. C. 
Published: April 2021

ABSTRACT
NaCl and Na/K/Cl co-transport systems in many cell types show a number of similarities, among which are sensitivity to ‘loop’ diuretic inhibition and extremely high anion selectivity. Avian erythrocytes possess a Na + K + 2C1 co-transporter that is stimulated by agents raising intracellular cAMP. The system is also inhibited following ATP-depletion of the cells, in agreement with results in other tissues; this nucleotide may exert a regulatory role on the operation of the co-transporter. A Na/K/Cl co-transport system is also present in flounder intestine, where it plays a central role in salt absorption at the luminal border of the tissue. In contrast to the avian erythrocyte this system is inhibited by raising intracellular cyclic nucleotide content, cGMP being more effective than cAMP. From these results it is concluded that second messenger regulation of Na/K/Cl cotransport processes is heterogeneous and may exhibit some tissue specificity.
Cellular Mechanisms and Control of KCL Absorption in Insect Hindgut
Authors: Hanrahan J. W. , PHILLIPS J. E. 
Published: April 2021

ABSTRACT
The hindgut of the desert locust possesses an unusual chloride transport system. The isolated locust rectum absorbs chloride from the mucosal (lumen) to the serosal (haemolymph) side at a rate which is equal to the short-circuit current (Isc). Net chloride transport persists in nominally Na-free or HCO3(CO2)-free saline, is insensitive to normal inhibitors of NaCl co-transport and anion exchange, and is independent of the net electrochemical gradient for sodium across the apical membrane. However, active chloride transport is strongly dependent on mucosal potassium (K2 = 5·3mm-K). Chloride entry across the apical membrane is active, whereas the net electrochemical gradient across the basal membrane favours passive Cl exit from the cell. Although mucosal potassium directly stimulates ‘uphill’ chloride entry, there is no evidence for coupled KCL co-transport, nor would co-entry with potassium be advantageous energetically.
Net chloride absorption and IK are stimulated by a peptide hormone from the central nervous system which acts via cyclic-AMP. Cyclic-AMP increases Isc and approximately 1000% and transepithelial conductance (Gt) ˜100%. Approximately half of the ΔGt during stimulation results from increased Cl conductance at the basal cell border. This increase is also reflected in a shift of the basal membrane e.m.f. towards the Nemst potential for chloride. The remainder of the cAMP-induced ΔGt is due to an elevation of apical membrane K conductance, which causes a 400% increase in transepithelial potassium permeability as estimated by radiotracer diffusion. Because of this stimulation of K conductance, potassium serves as the principal counterion for active chloride transport under open-circuit conditions. Very high luminal levels of K oppose the stimulatory actions of cAMP on active Cl transport and K conductance. These and other results have been incorporated into a cellular model for KCL absorption across this insect epithelium.
Control of Na+ and Water Absorption Across Vertebrate ‘Tight’ Epithelia By ADH and Aldosterone
Authors: Lewis Simon A. 
Published: April 2021

ABSTRACT
Salt and water balance in vertebrates is controlled by the release of two blood borne hormones: aldosterone and antidiuretic hormone (ADH). It is the purpose of this chapter to review the mechanisms (at the plasma membrane level) by which these hormones cause an increase in salt (sodium) and water movement in the target tissues. The primary effect of aldosterone is to increase the Na+ permeability of the lumen-facing (apical) membrane by activation of pre-existing quiescent channels at short times, and by the incorporation of newly synthesized channels after prolonged exposure. Other effects might involve an increase in energy supply and synthesis of Na+-K+ ATPase which is responsible for Na+ extrusion from cell cytoplasm to blood. Similarly, ADH stimulates pre-existing quiescent apical membrane Na+ channels. The second effect of ADH is to increase epithelial water permeability. Evidence strongly suggests that water channels exist in cytoplasmic vesicles which, upon ADH challenge, fuse into the apical membrane causing a rapid increase in apical membrane hydraulic conductivity. The movements of vesicles are dependent on an intact cytoskeleton. Regulation of electrolyte and non-electrolyte transport will be discussed in the light of the above two mechanisms.
Blood Pressure in the Leech Hirudo Medicinalis
Authors: Krahl Bodo , Zerbst-Boroffka Irene 
Published: April 2021

ABSTRACT
Intravascular pressure recordings in the lateral vessels of the leech, Hirudo medicinalis, show two distinct pressure patterns: high pressure phases (diastolic pressure: 5 ± 3 mmHg, systolic pressure: 48 ± 14mmHg) alternate with low pressure phases (diastolic pressure: 4 ± 2·5 mmHg, systolic pressure: 26 ± 11 mmHg). The lateral vessel of one side produces high pressure pulses during peristaltic action while the other vessel generates low pressure pulses during non-peristaltic action. After 20–60 pulses a transition occurs, which sometimes appears more gradually.
Quantitative Analysis of Walking in A Decapod Crustacean, the Rock Lobster Jasus Lalandii I. Comparative Study of Free and Driven Walking
Authors: Clarac F. , Chasserat C. 
Published: April 2021

ABSTRACT
The study compares the relative validity of the data obtained from two experimental situations, i.e. free walking and driven walking, in relation to leg coordination in Jasus lalandii (Milne-Edwards).
The relationship between ipsilateral and contralateral legs during the forward as well as the backward walking sequences has been analysed in the two situations. They operate roughly in opposition. Although little dif ference in the mean phase values has been observed in the two experimental situations, the strength of coupling is greater in the driven walking animals.
The power stroke (PS) duration correlates well with the period, but the return stroke (RS) is more variable and varies according to the leg considered. The phase does not appear to be correlated with the step period during free walking, but is correlated in the treadmill situation.
Initially, several of the properties of the single motor unit discharges correlated with movement have identical mean values in both free and driven walking. However, several significant differences have been observed in the intra-burst organization. These differences indicate that the constraint of the treadmill decreases the variability of all parameters and produces a stable and more stereotyped walking pattern.
The Mechanics of the Predatory Strike of the Praying Mantid Heirodula Membranacea
Authors: Gray P. T. A. , Mill P. J. 
Published: April 2021

ABSTRACT
The mechanics of the predatory strike of Heirodula membranacea (Burm.) have been studied using high speed ciné, electrophysiological and anatomical techniques. Calculations of the muscle output required to produce the strike suggest that muscle performance generally lies within the range observed elsewhere and that no specializations for prior energy storage, as are found in some other rapid insect movements, are necessary. This view is supported by simultaneous EMG and ciné studies showing no significant delay between the onset of EMG activity and the onset of stress development required by the direct action model. The apodemes of a number of forelimb muscles are found to have complex two-point suspensions; these have a significant role in determining the moment-arm/joint-angle relationships of the muscles. The parallel-fibred part of the tibial flexor muscle has a high strain rate, 17·5 s−1, at 27–30°C. This is the fastest recorded strain rate for an insect muscle, and approaches the fastest strain rates of mammalian muscles operating at 37 °C.
Nervous Control of the Salivary Glands of the Carnivorous Mollusc Philineaperta
Authors: Barber Andrew 
Published: April 2021

ABSTRACT
Evidence is presented to show that the electrical activity of the salivary glands of Philine aperta is controlled by two largely independent systems which elicit different responses from salivary acinar cells. The excitatory junction potentials (EJPs) recorded from salivary cells result from the activity of a pair of identified buccal ganglion neurones. Each of these salivary effector neurones innervates only the ipsilateral gland. The effector neurones are driven to fire by synaptic input which is timed to occur during the retraction phase of the feeding cycle. Gland cell excitatory post-synaptic potentials (EPSPs) and action potentials appear to be mediated by a small group of peripheral neurones located at the base of each salivary gland. These cells give rise to a tract of fibres which cross to the contralateral gland and which may be responsible for communicating EPSP/action potential activity between the glands. The possible functions of the EJP and EPSP/ spiking activities are discussed.
Graded Potentials and Spiking in Single Units of The Oval Organ, A Mechanoreceptor in the Lobster Ventilatory System: I. Characteristics of Dual Afferent Signalling
Authors: Pasztor V. M. , Bush B. M. H. 
Published: April 2021

ABSTRACT
The lobster oval organ sends three afferent fibres to the sub-oesophageal ganglion: X (mean diameter 41 μm), Y (32 μm) and Z (22 μm). The distance between the oval organ and the ganglion is 10–15 mm in animals of approximately 10 cm carapace length. The cell bodies of the sensory units lie centrally amidst the ventilatory motoneurones, and their central branches permeate the same lateral neuropile. Intracellular recordings from each fibre show that the afferent response to stretch has two components: overshooting, regenerative, TTX-sensitive impulses, and an underlying graded depolarization. The analogue signal has the characteristics of a receptor potential: a dynamic response with rapidly depolarizing initial component, some adaptive fall leading to a maintained static plateau, and a post-release hyperpolarizing undershoot. The two signals are not equally represented in the response of the three afferents. Fibre X has the largest graded potentials (up to 30 mV in recordings 6mm proximal to the confluence of the sensory dendrites). Fibre Z attains the highest firing frequencies (usually around 100 s−1). Fibre Y has intermediate properties. Both the amplitude of the graded potential and the number of spikes per response (in fibres Y and Z) relate linearly to pull amplitude. Estimates of length constant (approximately 10 mm) and specific membrane resistance (l00 kΩcm2) are consistent with the hypothesis that the graded potentials spread into the presynaptic terminals with sufficient magnitude to bring about postsynaptic events.
Labial Extension in the Dragonfly Larva Anax Imperator
Authors: Parry D. A. 
Published: April 2021

ABSTRACT
The extension mechanism of the larval dragonfly’s labium has been under discussion since Snodgrass (1954) drew attention to the absence of muscles at the head/postmentum joint (p–h, Fig. 1A) and proposed that it was extended by blood pressure, due to the abdominal muscles which also cause jet propulsion. This proposition is supported by evidence that the anus closes (Pritchard, 1965), and the abdominal muscles contract (Caillère, 1972; Olesen, 1972) during labial extension; and by reports of an increase in abdominal pressure of 5000 Pa (Olesen, 1979) and 4000—12000Pa (Tanaka & Hisada, 1980). From high-speed film of Aeschna nigroflava, Tanaka & Hisada (1980) calculate a maximum torque of 40 αN.m (neglecting water resistance) and state that this would require a joint pressure of 6000 Pa. They also claim that the labium extends normally when a pressure of 8000 Pa is applied to a dead animal under water, thus indicating the relatively small effect of water resistance. However, these conclusions raise a number of questions. In deriving the pressure of 6000 Pa, they appear to have used the torque/pressure characteristic of the postmentum/prementum joint (p–p, Fig. 1A). Had they used the p-h joint characteristic (their Fig. 6) a required pressure of 24 000 Pa would have been obtained. And the statement that 8000 Pa, applied to a head preparation under water, produces normal extension, is not borne out by a comparison of their Figs 5 and 8. which again only relates to the p–p joint. Confusion between the p–h and p–p joint may be due to the erroneous view that the torques at the two joints must, for mechanical reasons, be equal. Their data on labial movement is subject to large standard error and no estimate is made of the error caused by the use of a simplified model, which assumes that the mass of the prementum is concentrated at the end of the postmentum.
Intersegmental to Intrasegmental Conversion by Ganglionic Fusion in Lateral Giant Interneurones of Crayfish
Authors: Kondoh Yasuhiro , Hisada Mituhiko 
Published: April 2021

ABSTRACT
The central nervous system (CNS) of arthropods in general consists of a chain of ganglia in the form of a ladder. Each ganglion has a basically homologous neuronal organization and is contained in one body segment (Bullock & Horridge, 1965). This basic pattern is often modified by ganglionic fusion. What changes are caused by ganglionic fusion, particularly with regard to segmentally homologous neurones?
Photoperiodic Effects On Thermoregulation in A ‘Blind’ Subterranean Mammal
Authors: Haim A. , Heth G. , Pratt H. , Nevo E. 
Published: April 2021

ABSTRACT
Thermoregulatory responses to changes in photoperiod were studied in the ‘blind’ mole rat Spalax ehrenbergi (Nehring). Acclimation of coldsensitive individuals to short photoperiod (8L: 16D) at an ambient temperature (Ta) of 22 °C increased their thermoregulatory capacity in cold conditions, when compared to individuals which were acclimated to a photoperiod of 12L: 12D at the same Ta. Acclimation of cold-resistant individuals to Ta= 17 °C but with a photoperiod of 16L:8D caused a decrease in thermoregulatory capacity.
Evaluation of the visual pathway through the visual-evoked potentials showed that the mole rat does not respond to flash stimuli and can thus be considered to be effectively blind.
Comparison Between Active Transport of Tl+, K+ and Rb+ Across the Isolated Short-Circuited Frog Skin
Authors: Zerahn Karl 
Published: April 2021

ABSTRACT
Active transport of Tl+ by frog skin was compared with transport of K+ and Rb+. Tl+ was transported actively (using a Na,K-ATPase) by the epithelium and the adrenalin-stimulated glands.
In the epithelium, K+, Tl+ and Rb+ competed for transport in the ratio 1:1 ·7: 0· 9; in the glands the ratio was 1:1:1.
Nerve Nets and Conducting Systems in Sea Anemones: Two Pathways Excite Tentacle Contractions in calliactis Parasitica
Authors: Mcfarlane Ian D. 
Published: April 2021

ABSTRACT
Single shocks to the column sometimes evoke tentacle contractions, ranging from slight movement of a few scattered tentacles to rapid bending or shortening of all the tentacles. Some individuals are more responsive than others. Complex bursts of electrical activity follow single shocks, but only in tentacles that contract. These single shocks excite pulses in two conducting systems - the through-conducting nerve net (TCNN) and the ectodermal slow conduction system (SS1). When a single shock evokes contractions and bursts of electrical activity, these usually follow the SSI pulse, rarely the TCNN pulse. Stimulation of the SS1 alone causes tentacle contraction in responsive anemones. Fast tentacle contractions always follow the second of two closely-spaced TCNN pulses: the TCNN shows facilitation (Pantin, 1935a). An SSI pulse, however, does not facilitate subsequent pulses in either the SSI or TCNN. There are two pathways for activation of tentacle contractions. The TCNN pathway is mechano-sensitive and normally requires facilitation. The SS1 pathway is mechano- and chemosensitive, only requires a single SSI pulse to evoke contraction, but is very labile. It is proposed that the TCNN and the SS1 do not excite the ectodermal muscles directly, but via a multipolar nerve net.
Reversal of the Direction of Mucus-Flow on the Ciliated Pharynx of a Sea Anemone
Authors: Holley M. C. , Shelton G. A. B. 
Published: April 2021

ABSTRACT
The ciliated pharynx of the sea anemone Calliactisparasitica (Couch) acts as an independent selective barrier for the admission of material to the coelenteron. Direct observation shows that reversal of the direction of the mucus flow is effected by a reversal of the direction of the ciliary power-stroke. Reversal of the power-stroke can only be stimulated by food juices applied directly to the pharynx and it is not propagated to unstimulated areas. Reversal of the power-stroke occurs in the absence of all recordable electrical activity. This is one of the few examples among the Metazoa where it has been shown that a modification of the ciliary beating pattern is unlikely to be controlled by an electrical conduction system.