bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-Release of Lactic Acid From Anaerobic Swimming Muscle of Plaice Pleuronectes Platessa L. : A Stress Reaction
Authors: Wardle C. S.
Published: April 2021

Plaice caught by trawl net and plaice exercised in laboratory tanks all show high levels of lactic acid (33–44 mmol/kg) in the anaerobic swimming muscle. During exhausting exercise 2 moles of lactate are formed from 1 mole of glycogen glucose. After an 8 h rest 50–80% of the muscle glycogen is restored. Blood lactate levels remain low (0·5–2 mmol/1) in the majority of plaice caught by trawl. In a small number of plaice, peak levels over 5 mmol/1 are reached 2–4 h after capture. Low blood lactate levels could be guaranteed in all fish exercised 24 h after the stress of capture and in tank-adapted fish exercised and injected with the β-adrenergic stimulating drug, isoxsuprine hydrochloride. The blood lactate in plaice, tank-adapted for more than 8 days and then exercised, may reach peak levels up to 5 mmol/l 2–4 h later. High blood lactate levels were obtained by injecting the β-adrenergic block propranolol to stressed exercised fish. The a-adrenergic block did not have this effect. All plaice with blood lactate levels reaching 5–12 mmol/1 died. The results indicate that the muscle cells regulate the release or nonrelease of their lactate load to the blood stream and increases in the blood circulating to the muscle do not influence this release. The non-release mechanism may be actived by a catecholamine circulated in the blood stream following a stress.
Reproduction Versus Somatic Growth: Hormonal Control in Octopus Vulgaris
Authors: ’Dor R. K. O , Wells M. J.
Published: April 2021

Octopus vulgaris can be forced into precocious maturity by removal of the subpedunculate lobe from the brain, an operation that releases the optic glands from inhibition, and allows them to secrete a gonadotropin. 14C-leucine was injected into the bloodstream of immature animals and its subsequent incorporation into muscle protein followed by taking successive samples from the arms. The optic glands were then activated, and a further injection of 3H-leucine given and followed by means of further arm samples. Optic gland secretion suppresses protein synthesis in the muscles. This is associated with an increase in the total amino acid pool in the muscles and with a considerable increase in the concentration of free amino acids circulating in the blood. If an ovary is present these events are associated with a rapid growth of the ovary and its ducts, and a loss of weight elsewhere. In ovariectomized animals the ducts grow, but there is no yolk to absorb the large pool of free amino acids, and the animals gain weight by osmotic uptake of water into the muscles. The developing ovary may produce a hormone that increases the release of amino acids from muscle, since the concentration circulating in the blood of intact animals remains at least as high as in ovariectomized octopuses, despite the demands of the developing ovary. These matters are discussed in relation to other evidence for a gonadial hormone and in relation to the ‘self-destruct’ effect of the optic gland secretion in determining the post-reproductive death of octopuses.
Electrophysiological Correlates of Ionic and Osmotic Stress In An Osmoconforming Bivalve (Mytilus Edulis)
Authors: Willmer P. G.
Published: April 2021

Mytilus edulis suffered reductions in trans-membrane sodium concentration gradient during dilute salinity acclimation. Nevertheless the nerves of this osmoconformer had a conventional basis for their excitability, irrespective of the salinity to which they were adapted, and could produce full-sized spikes after acclimation to 25 % media. The connectives showed rapid and predictable responses to sodium and to potassium ions, and the time-courses of these effects were unrelated to the presence or absence of the neural sheath at either of the acclimation salinities tested. Neural adaptation was therefore not a consequence of restricted access after acclimation to dilute media. Classic pharmacological agents (tetrodotoxin, tetra-ethyl ammonium ions, 2,4-dinitrophenol and ouabain) elicited the expected responses, but invariably required rather high concentrations and long exposures for full effect. Acute exposures of the connectives to hyposmotic or isosmotic dilutions resulted in changes in polarization accompanying the decline of the action potential. These were attributed to losses of potassium and of chloride from the axons, with a net loss of anion (and hence depolarization) during naturally occurring hyposmotic stress. Mytilus connectives exhibited a critical salinity, with hyposmotic exposure below this level producing irreversible impairment of function. This salinity occurred at 20 % S.w. for 100 %-adapted tissues, and at 3-25 % s.w. (i.e. 15% initial concentration) for 25%-adapted nerves. Gross isosmotic dilutions produced no permanent decrements in axonal function. The observed patterns of response to chronic and acute osmotic stress in Mytilus are contrasted with those reported in annelid and crustacean conformers, and possible adaptations which might underlie these responses are discussed.
Improved Flame Photometry
Authors: Fletcher C. R.
Published: April 2021

Flame photometry is now the usual means of measuring sodium and potassium, and commercially made flame photometers will measure about 0·2 μmol of either ion in about 2 ml of solution to about 1 %. However, the prior dilution of biological samples is necessary and the minimum quantity for measurement is set by the time constant of the measuring circuit. Specialized flame photometers have been described which extend the detection limit to 10−14 mol (Müller, 1958; Ramsay, Brown & Falloon, 1953), but these are hardly suitable for routine work. This communication describes inexpensive modifications for use with commercial flame photometers which avoid prior dilution of the samples and give a tenfold improvement in the detection limit, defined as the smallest quantity of an ion which may be detected with a 95 % certainty.
A Model for Extracellular Sodium Regulation in the Central Nervous System of An Insect (Periplaneta Americana)
Authors: Treherne J. E. , Schofield P. K.
Published: April 2021

The ionic composition of the immediate fluid environment of insect nerve cells is regulated so as to maintain concentrations which may differ considerably from those of the blood. The regulation of the extracellular sodium in the cockroach central nervous system has been suggested to result from a glial-mediated transport of this cation (cf. Treherne, 1974). We here propose a model system for sodium regulation, incorporating such transport, that accounts for the salient experimental observations (Fig. 1).
Biological and Chemical Studies of Extracts of the Anterior Lobe Pituitary
Authors: Spaul E. A. , Myddleton W. W.
Published: April 2021

A buff-coloured precipitate is obtained by the addition of N/20 iodine solution to dilute acetic acid extracts of fresh anterior lobe substance. The volume of the precipitate depends upon the volume of the iodine solution added. Similar acetic acid extracts of tissues and extracts of the anterior lobes prepared with other extracting media do not give the same precipitate with iodine. The precipitate indicates the presence and, within limits, gives an approximate measure of the metamorphic factor in fresh gland extracts of the anterior lobe. Dilute acetic acid extracts of the precipitates after removal of the iodine by shaking with alcohol are biologically active and characterised by their phosphate content. Similar extracts of the posterior lobe give an iodine precipitate but the phosphate content is much lower than that of the anterior lobe precipitate. The iodine in these precipitates is adsorbed or loosely combined. The adsorbed iodine is chemically more reactive than dissolved iodine or iodine crystals giving rapid evolution of nitrogen from sodium azide compared with the failure of the others. The biological activity of anterior lobe extracts varies with the time of extraction and the concentration of the extracts. There is a maximum for the time of extraction at any particular concentration and acid strength after which a loss of potency occurs. There is a continuous extraction—rapid at first—of the melanophore stimulant. The amount increases with the period of extraction and concentration, but is independent of the strength of the acid used in extraction. The metamorphic factor is slowly destroyed by pepsin but rapidly by trypsin. The biological activity is diminished by boiling, or by boiling with dilute hydrochloric acid, sodium hydroxide, or sodium carbonate.
The Phosphate Content and the Biological Activity of the Anterior Lobe Pituitary
Authors: Spaul E. A. , Myddleton W. W.
Published: April 2021

Qualitative and quantitative studies of the active substance in the anterior lobe of the pituitary gland stimulating amphibian metamorphosis have suffered considerable restriction on account of the limitations of the animal test, in which the specific response—the production or acceleration of metamorphosis— is confined to a small range, and the lack of information upon its chemical nature and relationships (Spaul, 1930). Attempts have been made in recent work to overcome these difficulties by seeking for an interpretation of this biological activity in chemical terms, and so establish a chemical test having wider application. Little progress has been made so far, but a correlation of the biological activity with chemical methods, providing also a means of studying chemically the activity itself, has been discovered (Spaul and Myddleton, 1930).
The Adaptation of Gunda Ulvae to Salinity
Authors: Pantin C. F. A.
Published: April 2021

In previous papers (Pantin, 1931 ; Weil and Pantin, 1931) the environment and water exchange of the estuarine flatworm, Gunda ulvae, have been described. It is found on the sea shore at the mouths of small streams, where it is subject to violent salinity changes.
Detour Experiments With Sticklebacks (Gasterosteus Aculeatus L.)
Authors: Russell E. S.
Published: April 2021

The six individuals of Gasterosteus aculeatus tested learned to find their way into a small jar or bottle for food, and also learned how to come out. One failed in the standard test, with the jar upright. The solution was found at first by chance, but after a few trials the behaviour became definitely directed towards finding the solution. This change was accompanied by a sudden drop in the time taken; the jar also acquired significance, ceasing to be an indifferent object. The mode of solution was retained for over 3 months. The bearing of these results on the theory of learning is briefly discussed.

The flight reaction shown by sticklebacks on sudden illumination is described.
A New Approach to Animal Flight Mechanics
Authors: Rayner J. M. V.
Published: April 2021

The mechanics of lift and thrust generation by flying animals are studied by considering the distribution of vorticity in the wake. As wake generation is not continuous, the momentum jet theory, which has previously been used, is not satisfactory, and the vortex theory is a more realistic model.

The vorticity shed by the wings in the course of each powered stroke deforms into a small-cored vortex ring; the wake is a chain of such rings. The momentum of each ring sustains and propels the animal; induced power is calculated as the rate of increase of wake kinetic energy.

A further advantage of the vortex theory is that lift and induced drag coefficients are not required; estimated instantaneous values of these coefficients are generally too large for steady state aerodynamic theory to be appropriate to natural flapping flight.

The vortex theory is applied to hovering of insects and to avian forward flight. A simple expression for induced power in hovering is found. Induced power is always greater than simple momentum jet estimatés, and the discrepancy becomes substantial as body mass increases.

In hovering the wake is composed of a stack of horizontal, coaxial, circular vortex rings. In forward flight of birds the rings are elliptic; they are neither horizontal nor coaxial because the momentum of each ring balances the vector sum of parasite and profile drag and the bird’s weight. Total power consumption as a function of flight velocity is calculated and compared for several species. Power reduction is one of the major factors influencing the choice of flight style.

A large body of data is used to obtain an approximate scaling between stroke period and the body mass for birds. Together with relations between other morphological parameters, this is used to estimate the variation of flight speed and power with body mass for birds, and on this basis deviations from allometric scaling can be related to flight proficiency and to the use of such strategies as the bounding flight of small passerines.
Thermoregulation of African and European Honeybees during Foraging, Attack, and Hive Exits and Returns
Authors: Heinrich Bernd
Published: April 2021

While foraging, attacking, or leaving or returning to their hives, both the African and European honeybees maintained their thoracic temperature at 30 °C or above, independent of ambient temperature from 7 to 23 °C (in shade). Thoracic temperatures were not significantly different between African and European bees. Thoracic temperatures were significantly different during different activities. Average thoracic temperatures (at ambient temperatures of 8–23 °C) were lowest (30°C) in bees turning to the hive. They were 31–32 °C during foraging, and 36–38 °C in bees leaving the hive, and in those attacking. The bees thus warm up above their temperature in the hive (32 °C) before leaving the colony. In the laboratory the bees (European) did not maintain the minimum thoracic temperature for continuous flight (27 °C) at 10 °C. When forced to remain in continuous flight for at least 2 min, thoracic temperature averaged 15 °C above ambient temperature from 15 to 25 °C, and was regulated only at high ambient temperatures (30–40 °C). At ambient temperatures > 25 °C, the bees heated up during return to the hive, attack and foraging above the thoracic temperatures they regulated at low ambient temperatures to near the temperatures they regulated during continuous flight. In both African and European bees, attack behaviour and high thoracic temperature are correlated. The data suggest that the bees regulate thoracic temperature by both behavioural and physiological means. It can be inferred that the African bees have a higher metabolic rate than the European, but their smaller size, which facilitates more rapid heat loss, results in similar thoracic temperatures.
Classes of Light-Evoked Response in the Retina of Strombus
Authors: Quandt Frederick N. , Gillary Howard L.
Published: April 2021

Two general classes of light-evoked responses were recorded intracellularly from the retina of Strombus luhuanus. In one class, retinal illumination caused depolarization, the amplitude of which was graded with light intensity. In the other, it produced hyperpolarization and concomitant inhibition of repetitive action potentials.

There were two types of depolarizing waveform. Each was associated with a different type of intracellular recording site, characterized on the basis of electrical properties in the dark. In general, the type of response with a more rapid rate of decay was recorded from a site which exhibited a lower resting potential, higher input resistance, and longer ‘membrane charging time. ‘

The two depolarizing responses and the hyperpolarizing response apparently each arose from a different type of neurone. The depolarizing types, at least one of which is a photoreceptor, apparently give rise to the cornea-negativity of the electroretinogram and ‘on’ activity in the optic nerve fibres. The hyperpolarizing type apparently mediates ‘off’ activity in the optic nerve..
An Analysis of the Shape and Propagation of Waves on the Flagellum of Crithidia Oncopelti
Authors: Johnston D. N. , Silvester N. R. , Holwill M. E. J.
Published: April 2021

Ciné micrographs were taken of the flagellated protozoan Crithidia oncopelti under dark-ground illumination. Coordinates of images of the flagella were obtained from the ciné frames by back-projection and automatic data acquisition. The flagellar waveforms of proximally directed waves were characterized using a Fourier-series method and compared by this means with a number of analytical curves. The shape of a wave remained constant as it was propagated and, of the curves suggested, a wave consisting of circular arcs connected by straight lines gave the best fit. The variation of bend curvature as bends moved along the flagellum was also found, for both proximally and distally directed waves. The wavelengths and speeds of proximally directed waves increased linearly with distance as they approached the base of the flagellum, while in distally directed bends the curvature remained constant but the velocity increased as bends moved away from the base. Causes of the above behaviour are discussed and it is concluded from the variation of curvature with time for proximally directed flagellar waves that unbending must be an active process.
On The Endogenous Bursting Properties of ‘Light Yellow’ Neurosecretory Cells in the Freshwater Snail Lymnaea Stagnalis (L.)
Authors: van Swigchem Harm
Published: April 2021

Intracellular microelectrodes were used to study a cluster of neurosecretory ‘Light Yellow’ Cells (LYC) in the central nervous system of Lymnaea stagnalis. LYC usually have a spontaneous firing pattern of bursts, lasting 10-600 s, alternating with periods of silence. Experiments on isolated single cells showed that the bursting activity has an endogenous origin.

Each action potential is followed by a depolarizing afterpotential (DAP), with an amplitude of about 10 mV, lasting several seconds. Bursts end with a subthreshold DAP. It is concluded that two pace-maker mechanisms are responsible for the bursting properties, one initiating and the other (the DAP) maintaining the burst.

The relationship between the electrical and the neurosecretory properties of the cells is discussed.
A Comparative Survey of the Function, Mechanism and Control of Cellular Oscillators
Authors: Berridge M. J. , Rapp P. E.
Published: April 2021

This review attempts to survey in a uniform manner the available evidence concerning the generation and behaviour of several well-investigated cellular oscillators. Members of two broad classifications are contrasted: (i) cytoplasmic oscillations, where the periodic phenomena is generated by an instability in a metabolic pathway and (ii) membrane oscillators in which a membrane potential rhythm is generated at the membrane. Interactions between the cytoplasmic and membrane compartments are considered and the effects of these interactions on oscillatory behaviour is discussed. Because of their biological importance and the greater body of experimental results, particular attention is directed to a study of membrane potential oscillations. These systems can be approximately classified in two groups: (i) systems in which a periodic potential results from oscillatory changes in permeability and (ii) systems in which potential oscillations result from the periodic activity of an electrogenic pump.

The examples considered include the glycolytic oscillator, oscillations in vein contraction in the slime mould Physarum polycephalum, rhythmic aggregation in Dictyostelium discoideum, neural oscillators, the periodic potential in Purkinje fibres and the sino-atrial node and rhythmic behaviour in smooth muscle. Questions considered include the generation of periodic activity, the modulation of the oscillation by drugs and other metabolic and membrane effectors and the question of the functional role of these oscillations.
Oscillations of Cyclic Nucleotide Concentrations in Relation to the Excitability of Dictyostelium Cells
Authors: Gerisch Günther , Malchow Dieter , Roos Werner , Wick Ursula
Published: April 2021

Aggregating cells of Dictyostelium discoideum are able to release cyclic AMP periodically. The oscillations of cAMP generation are associated with changes in adenylate cyclase activity. Cyclic AMP receptors on the cell surface are functionally coupled to the oscillating system as evidenced by phase shifts that are induced by small pulses of extracellular cAMP. An important element of the oscillating system is the signal processing from surface receptors to the adenylate cyclase. This pathway exhibits adaptation resulting in the suppression of responses to constant, elevated concentrations of cAMP. The signal input for adenylate cyclase activation is, therefore, a change in the extracellular cAMP concentration with time.

Oscillations in the absence of detectable changes of intra- or extracellular cAMP concentrations suggest the possibility that there is a metabolic network in D. discoideum cells that undergoes oscillations without coupling to adenylate cyclase. Cyclic GMP concentrations oscillate with a slight phase difference in advance of that of cAMP, suggesting that the two nucleotide cyclases might not be activated by the same mechanism. Elevation of extracellular calcium exerts an inhibitory effect on the accumulation of cAMP and on the second of the two cGMP peaks.
The Effect of Air Resistance On the Jumping Performance of Insects
Authors: Bennet-Clark H. C. , Alder G. M.
Published: April 2021

A spring gun was constructed to propel objects at known velocities of between 1 and 4·5 m.s-1. This was used to project insects and various models in a vertical trajectory. By comparing the height attained in air by the insects or models with the height theoretically possible in vacuo, the energy lost against air resistance was observed. Small insects have a higher frontal area to mass ratio than larger ones so have relatively more aerodynamic drag and attain lower heights.

The observed effect may be expressed in terms of the drag coefficient, CD. Fleas and locusts have CD of about 1. Winged flies have CD of about 1·5 which falls to about 1 when the wings are amputated and to about 0·8 when the legs are amputated. Aptery is advantageous in jumping insects.

From experiments with models, it appears that the optimal condition for small jumping insects is that the body should be as compact as possible to reduce the frontal area to mass ratio. Thus dense spherical bodies are favoured. Some species of jumping insect have densities of about 1 mg.mm−3 while some flying beetles and flies have densities between 0·3 and 0·8 mg.mm−3.

The Reynolds number at which the experiments were performed was from 65–205 for fleas up to 740–2340 for locusts. The models operated in similar ranges.

At a velocity which would propel a larger animal to a height of 1 m, fleas weighing 0·4 mg only reach about 0·4 m. At lower initial velocities, proportionately less energy is wasted against air resistance so the jump efficiency is higher. Most fleas jump to a height of about 0·1 m with an efficiency of 0·8 while locusts jump to a height of 0·35 m with an efficiency of over 0·9. Air resistance is thus an important scale effect in jumping insects and provides its own design constraints.
Acid-Base Relationships in the Blood of the Toad, Bufo Marinus
Authors: Boutilier R. G. , Randall D. J. , Shelton G. , Toews D. P.
Published: April 2021

An abrupt increase in ambient CO2 resulted in a marked respiratory acidosis which took place within 30 min. During this time there was a considerable reduction in the difference between arterial blood and inspired gas caused by an increase in ventilations. Prolonged CO2 exposure (24 h) showed that there was some compensation for the acidosis in that plasma bicarbonate concentrations increased substantially. At the same time, however, the of arterial blood always rose so that the net result was usually only a small increase in pH. Upon return to air, the blood was backtitrated along a buffer line elevated above and parallel to that seen during the initial response to hypercapnia. The fall in arterial blood during the early stages of recovery often led to pH values higher than those seen in the untreated animal. After 48 h in air, recovery had gone further with pH and [HCO3−] levels approaching but rarely reaching the pre-exposure values.
Ionic Selectivity of the Calcium Channels in Insect Larval Muscle Fibres
Authors: Yamamoto Daisuke , Washio Hiroshi
Published: April 2021

It is well known that the action potentials of insect muscle fibres are generally Ca-dependent (Washio, 1972; and others). The calcium channels involved in these spikes have recently been shown to pass Na as well as Ca ions in the larvae of the beetle Tenebrio molitor (Yamamoto & Washio, 1979) and in the locust (Mathers & Thesleff, 1979). In this report we examine whether the Ca channels of Tenebrio can pass Li+, NH4+, guanidine, choline and TEA. Li+, NH4+ and guanidine have been shown to negotiate Na channels (Binstock & Lecar, 1969; Hille, 1971, 1972).
Voltage Clamp Studies on Insect Skeletal Muscle
Authors: Yamamoto Daisuke , Fukami Jun-Ichi , Washio Hiroshi
Published: April 2021

Membrane currents in the muscle fibre of larval mealworm, Tenebrio molitor were investigated under voltage-clamp conditions. An initial inward current, a transient outward current and a delayed outward current were distinguished. Increasing external calcium concentration increased the size of the inward current and shifted the reversal potential in a positive direction. The inward current persisted in Na-free media and TTX-saline. However, the current was suppressed by 15 mm-cobalt ions. Therefore, it was concluded that the inward current was carried by calcium ions. Although the inward current was markedly reduced when external sodium was replaced with glucose, it was concluded that the contribution of Na ions to the current was small. Calcium conductance showed voltage and time dependence. The inactivation variable fell below unity with increasing strength of hyperpolarizing prepulses.
Physiology of Water Motion Detection in the Medicinal Leech
Authors: Friesen W. Otto
Published: April 2021

Neuronal activity resulting from stimulation by water waves occurs in ventral nerve cord-body wall preparations of the medicinal leech, Hirudo medicinalis. In segmental nerves, this activity consists of afferent compound action potentials with graded amplitudes resulting from simultaneous action potentials in many small sensory axons. Afferent input impinging on one segmental ganglion activates neuronal activity along much of the ventral nerve cord. Previously identified tactile mechanoreceptors are insensitive to low-amplitude wave stimulation. Touch-cell impulse activity can be evoked by moderate or strong wave stimulation, but these impulses appear to arise near the cell body, not from the peripheral receptor endings. The transduction sites for wave stimulation are localized at or very near the segmental sensilla. Because of their location and modality the receptors were named ‘sensillar movement receptors’ (SMR). S cells (Rohde’s fibre) receive suprathreshold excitatory input during SMR activation without concomitant activity in the tactile mechanoreceptors. The annulus erector motor neurones contralateral to the afferent SMR inflow are inhibited by SMR activation. This inhibition is also observed in ganglia adjacent to the ganglion receiving the afferent input and provides a neuronal basis for reflexive smoothing of the leech body wall. Two neurones in the anterior median packet of segmental ganglia receive powerful synaptic input during SMR activation. One, cell 202, receives 10 mV excitatory potentials while the other, cell 201, receives 10 mV inhibitory potentials.
The Modulatory Action of Dopamine On Crustacean Foregut Neuromuscular Preparations
Authors: Lingle Chris
Published: April 2021

Effects of dopamine (DA) on contractile and electrical properties of decapod foregut neuromuscular preparations were examined. Dopamine produced dramatic increases in nerve-evoked contractions and, in particular muscles, contractures and spontaneous contractions. These effects were observed at concentrations as low as 5 × 10−9 M-DA. The DA-produced enhancement of nerve-evoked contractions was associated with an increase in amplitude of excitatory junctional potentials (EJPs). The increase in EJPs resulted in part from an increase in muscle fibre membrane resistance that was particularly prominent over depolarized membrane potentials. A presynaptic action of dopamine cannot be as yet excluded. In fibres from the muscle in which dopamine produced a contracture, dopamine also produced a depolarization. In fibres from the muscle in which dopamine activated spontaneous contractions, dopamine also produced spontaneous rhythmic action potentials. Dopamine also accelerated the half-time of muscle relaxation following muscle contraction
Fish Branchial Na+/NH4+ Exchange is Via Basolateral Na+-K+-Activated ATPase
Authors: Claiborne J. B. , Evans David H. , Goldstein Leon
Published: April 2021

Krogh (1939) first proposed that freshwater organisms extract needed Na+ in exchange for to maintain near-electroneutrality across the skin or gills. Maetz & Garcia-Romeu (1964) provided an indirect demonstration of exchange in the goldfish (Carassius auratus) by showing that injected NH4C1 stimulated Na+ uptake, but addition of NH4C1 to the freshwater inhibited Na+ uptake. They proposed that exchange was apical (on the mucosal surface of the transporting epithelium, facing the fresh water) and that blood NH3 entered the basolateral surface of the cell, combined with a proton generated by the carbonic anhydrase hydration of CO2 (and the subsequent dissociation of carbonic acid), and left the cell in exchange for Na+. The role for carbonic anhydrase was indicated by their finding that injection of acetazolamide inhibited Na+ uptake. Subsequently, Kerstetter, Kirschner & Rafuse (1970) demonstrated that acetazolamide injection inhibited the influx of Na+ into the irrigated gills of the trout (Salmo gairdneri). However, ammonia efflux was not significantly inhibited, while acid efflux was. They concluded that Na+/H+, rather than exchange, occured at the apical surface. More recent evidence supporting the model for basolateral uptake of NH3 and apical exchange was presented by Payan (1978). He used the isolated, perfused, head of the trout (Salmo gairdneri) and showed that: (1) addition of amiloride to the solution irrigating the gills inhibited both Na+ influx and ammonia efflux, (2) acetazolamide added to the perfusate inhibited ammonia efflux, and (3) reduction in the NH3 concentration of the perfusate (by lowering pH) inhibited ammonia efflux as well as Na+ influx. Furthermore, addition of ouabain to the perfusate inhibited ammonia efflux, presumably because Na+-K+-activated ATPase at the basolateral surface mediates the final transfer of Na+ into the serosal medium, and is ultimately limiting in the regulation of apical exchange.
Mechanisms of Acid Extrusion by Two Marine Fishes: The Teleost,Opsanus Beta, and the Elasmobranch,Squalus Acanthias
Authors: Evans David H.
Published: April 2021

Rates of efflux of H+ and ammonia from a marine teleost and an elasmobranch were measured. Hypercapnia stimulated H+; efflux from both species, stimulated ammonia efflux from the elasmobranch, and inhibited ammonia efflux from the teleost. In both species the H+; and ammonia efflux were predominantly across the branchial epithelium. In Na+-free sea water, the H+ efflux from both species was completely abolished and the ammonia efflux was inhibited by approximately 50%. Injection of an acid load stimulated H+; efflux, which continued for 2-5 h until more than the injected acid load was excreted. It therefore appears that injection of an acid load also produces a metabolic acid load which must be excreted. The H+ efflux from mineral/metabolic acidotic fish is entirely branchial and dependent upon external Na+. The data support the conclusion that marine teleosts and elasmobranchs possess branchial Na+/NH4+ and Na+/H+; ionic exchange mechanisms and that Na+/H+; exchange plays a major role in the response to acidosis in both groups. The possible evolution of these ionic exchange systems is discussed.
Osmotic Tolerance of Ca-Dependent Excitability in the Marine Ciliate Paramecium Calkinsi
Authors: Deitmer Joachim W. , Machemer Hans
Published: April 2021

The electrical membrane properties of the marine (brackish-water) ciliate Paramecium calkinsi were investigated under constant-current and voltage-clamp conditions, using two intracellular microelectrodes. The action potential and membrane currents were extremely tolerant to changes in the salinity of the bathing medium. Current-voltage relationships exhibited a moderate inward-going rectification of the membrane upon hyperpolarization, and a prominent outward-going rectification upon depolarization of the membrane. Ion substitution experiments showed that the electrically excitable response is a graded Ca2+-action potential, similar to that found in freshwater ciliates.
Energetics and mechanics of terrestrial locomotion. III. Energy changes of the centre of mass as a function of speed and body size in birds and mammals
Authors: Heglund N. C. , Cavagna G. A. , Taylor C. R.
Published: April 2021

This is the third in a series of four papers examining the link between the energetics and mechanics of terrestrial locomotion. It reports measurements of the mechanical work required (ECM,tot) to lift and reaccelerate an animal’s centre of mass within each step as a function of speed and body size during level, constant average speed locomotion. A force platform was used in this study to measure ECM,tot for small bipeds, quadrupeds and hoppers. We have already published similar data from large animals. The total power required to lift and reaccelerate the centre of mass (ĖCM,tot) increased nearly linearly with speed for all the animals. Expressed in mass-specific terms, it was independent of body size and could be expressed by a simple equation :

where ĖCM,tot/Mb has the units of W kg−1 and vg is speed in m s−1.

Walking involves the same pendulum-like mechanism in small animals as has been described in humans and large animals. Also, running, trotting and hopping produce similar curves of ECM,tot as a function of time during a stride for both the small and large animals. Galloping, however, appears to be different in small and large animals. In small animals the front legs are used mainly for braking, while the back legs are used to reaccelerate the Centre of mass within a stride. In large animals the front and hind legs serve to both brake and reaccelerate the animal; this difference in mechanics is significant in that it does not allow the utilization of elastic energy in the legs of small animals, but does in the legs of large animals.
Electrical Properties of Fibres from Stridulatory and Flight Muscles of a Tettigoniid
Authors: Josephson Robert K. , Stokes Darrell R.
Published: April 2021

The mesothoracic dorsal longitudinal muscle (DLM) of the katydid Neoconocephahts robustas is used in stridulation and flight; the metathoracic DLM is used in flight only. The DLM’s in the two segments have radically different maximum operating frequencies, 200 Hz for the mesothoracic muscle during stridulation and 20 Hz for the metathoracic muscle during flight. Cable analysis was used to determine the passive electrical properties of mesothoracic and metathoracic DLM fibres. Fibres in the two segments are of similar diameter and have similar sarcoplasmic resistivity. The apparent membrane resistance is lower, the apparent membrane capacitance higher, and the time constant shorter in mesothoracic fibres than in the metathoracic homologues. The depolarization evoked by neural stimulation in both mesothoracic and metathoracic fibres is principally an excitatory junctional potential (e.j.p.) with little or no contribution from voltage-dependent, inward current channels. At shqrt interstimulus intervals the second e.j.p. of a pair is reduced in amplitude relative to the first e.j.p. The period of e.j.p. depression is shorter in mesothoracic than in metathoracic fibres. It is suggested that the faster recovery of e.j.p.’s in mesothoracic fibres is due to more rapid recovery of the transmitter release mechanism in their motorneurones. In mesothoracic but not metathoracic fibres the voltage response to large depolarizing currents is usually oscillatory, and the recovery of e.j.p. amplitude as a function of time in paired shock experiments is sometimes oscillatory. The oscillation frequency is 250–300 Hz (35 °C) which is higher than the natural operating frequency of the muscle.
Electrical Activity and Structure of Retinal Cells of the Aplysia Eye: I. Secondary Neurones
Authors: Jacklet Jon W. , Schuster Lesley , Rolerson Celine
Published: April 2021

Intracellular recordings were made from secondary neurones and photoreceptors of the Aplysia eye concurrently with extracellular recordings from the optic nerve. These cells were injected with Lucifer yellow to reveal their structure after they were typed according to electrical activity. Secondary neurones are described in this paper. All secondary neurones injected with Lucifer yellow were in the outer, non-receptor layer of the retina. Each had an axon in the optic nerve, short dendritic processes on the soma, but no distinct photoreceptive apparatus. Dye coupling between secondary neurones and between secondary neurones and photoreceptors was observed. Secondary neurones had pacemaker potentials and action potentials (APs) correlated 1 :1 with the optic nerve compound action potentials (CAPs) during spontaneous dark and light evoked activity. It is deduced that the secondary neurones are the output neurones of the circadian clock system of the eye. Secondary neurones appear to be electrically coupled to each other and to some photoreceptors, since blocking chemical synapses with high Mg2+ saline did not block the spontaneous or light evoked activities, and antidromic activation of the secondary neurones produced a compound input dependent in amplitude on stimulus voltage. Backfilling the optic nerve with cobalt revealed filled secondary neurones, 2 photoreceptor types and a small non-receptor cell type suggesting that most of these retinal cells have axons in the optic nerve.
Prevalence of Prediabetes and Type-2 Diabetes Mellitus in Cricket Players: Multi-Cricket Clubs Cross Sectional Study
Authors: Meo Sultan Ayoub , Abukhalaf Abdulelah Adnan , Alomar Ali Abdullah , Sami Waqas , Meo Anusha Sultan
Published: April 2021

Background & Objectives: Sports activities are highly beneficial for improving the human health and reducing the risk of diseases. This cross sectional study aimed to investigate the prevalence of prediabetes and Type-2 diabetes mellitus in cricket players compared to population based non-elite athlete control subjects.

Methods: The present matched cross sectional study was conducted in the Department of Physiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia during the period October 2019 to February 2020. Initially, 700 volunteer males, (300) cricket players and (400) population based non-elite athlete control subjects were interviewed. After socio-demographic and medical history, (200) nonsmoker cricket players and (300) nonsmoker control subjects were recruited. The age of cricket players was 34 (32-37) years, weight 81 (76-84) kg, height 1.79 (1.74-1.84) meters, and body mass index (BMI) was 25.09 (23.66-26.76) kg/m2. The cricket players have been playing cricket for 4 (3-4) hours per day; 3.50 (3-4) days per week; for the total period of 24 (12-36) months. American Diabetes Association (ADA) based criteria on Glycated Hemoglobin (HbA1c) was used to investigate the prediabetes and Type-2 diabetes mellitus.

Results: In cricket players, the prevalence of prediabetes was 23 (11.5%) and Type-2 diabetes mellitus (T2DM) was 7 (3.5%) compared to population based matched non-elite athlete control subjects the prediabetes was 73 (24.34%) and T2DM was 63 (21.1%) (p=0.001). Among cricket players, there was a 6-folds decrease in T2DM compared to control subjects.

Conclusions: The cricket sports activities decrease the prevalence of prediabetes and Type-2 diabetes mellitus (T2DM) among the cricket players compared to population based matched non-elite athlete control subjects. The study findings demonstrate the urgent need for promoting sports activities, more cricket grounds as a physiological preventive strategy against the global growing diabetes epidemic.

doi: https://doi.org/10.12669/pjms.37.4.4128

How to cite this:Meo SA, Abukhalaf AA, Alomar AA, Sami W, Meo AS. Prevalence of Prediabetes and Type-2 Diabetes Mellitus in Cricket Players: Multi- Cricket Clubs Cross Sectional Study. Pak J Med Sci. 2021;37(4):959-965. doi: https://doi.org/10.12669/pjms.37.4.4128

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
CURRENT STATE OF THE HUMAN RESOURCES POTENTIAL OF AGRICULTURE OF THE REPUBLIC OF TATARSTAN
Authors: Gaynutdinov Ilgizar , Kurakova Chulpan , Gabdulhaev Ralif , Gubaydullin Rashit
Published: April 2021

The research was carried out in order to study the state of human resource development in agriculture of the Republic of Tatarstan, the current causes and factors affecting the training of personnel and the provision of them in the industry. The work was carried out on the basis of data from the state statistics bodies, the Ministry of Agriculture and Food of the Republic of Tatarstan, as well as the results of their own observations and surveys. In 2015-2019, the number of employees in agricultural enterprises of the republic decreased by 5.9 %. The largest decrease during this period occurred in such professions as tractor drivers (by 24.3%), machine milking operators (25.5%), pig workers (26.3 %) and sheep workers (57.5 %). In general, the number of people employed in agriculture decreased by 34.5 thousand people, which, on the one hand, was the result of the processes of consolidation and automation of production, on the other, due to the ongoing urbanization. In the last 5 years alone, the city's population has grown by 3.6 %, while the rural population has decreased by 0.6 %. There are also problems in the higher education system. Today, about 25 % of the chief specialists (agronomists, veterinarians, accountants) do not have a higher education. There is an increase in the number of bachelor's degree students in the humanities and social areas to 37.5 and 32.7%, respectively, with the share of graduates in agricultural areas of training about 3 % of all graduates. According to the authors ' personal opinion, the increase in the active load on university teachers, as well as their distraction from the main educational classroom work, as well as the lack of professional standards in agricultural specialties that take into account the specifics of the industry, do not contribute to the training of competent specialists
POLICY OF THE SOCIALIST REPUBLIC OF VIETNAM ON RURAL DEVELOPMENT
Authors: Grigor'ev Vladimir , Nugen Van Lok , Nizamov Rustam , Grigorev Igor
Published: April 2021

In connection with the development of the Republic of Vietnam, which is accompanied by the growth of its importance in the Asia-Pacific region, it becomes relevant to analyze the current state and prospects of the republic in various industries and regions, including in agriculture. In order to eliminate the imbalance between the declining share of agricultural production in the national economy and more than 60% of the population living in rural areas, a competent state policy in the field of integrated rural development is necessary. In addition to this disparity, there are growing problems associated with the income gap between the peasantry and urban residents, with a strong orientation of agriculture towards exports, and with the implementation of the idea of creating peasant cooperative farms. To date, the basis for working with rural areas is the resolution of the Communist Party of Vietnam “Agriculture, farmers and rural areas” adopted in August 2008. On its basis, the “National target program - New rural development” was created, designed for the period from 2010 to 2020. Data analysis showed that the area of agricultural land in the Socialist Republic of Vietnam gradually increase, and the cropping pattern change, for example, reduces the area of rice fields and increases the area occupied by permanent crops, especially fruit. Production of grain per capita has been steadily decreasing. In animal husbandry, there is a gradual transition from small-scale dispersed production to its concentration on large farms. The measures taken for the development of agriculture are aimed, among other things, at minimizing the negative impact on the environment and introducing modern achievements of science and technology in order to increase the economic efficiency of production. At the same time, Vietnam’s food security in general cannot be called sustainable, especially because of the need to import barley, without which Vietnam’s livestock farms cannot feed their existing livestock
PEST- ANALYSIS OF THE DIGITAL TRANSFORMATION OF PUBLIC ADMINISTRATION
Authors: Kurakova Chulpan , Safiullin Niyaz
Published: April 2021

The article is dedicated to researching the impact of environmental factors on the processes of digital transformation of public administration. In today's digital economy, the effectiveness of the executive branch providing public services to citizens and organizations largely depends on the political will of the country's leadership, the socio-economic situation, as well as the technological and technological development of the public sphere. The authors to assess the impact of environmental factors were pest analysis, which reveals the most significant aspects of the impact of the macro environment and develop a strategy for the development of public authorities in the context of the digital transformation of their activities. The methodological basis is research into the problems of the system of providing electronic public services, the regulatory framework for their digitalization, the study of statistics, indicating the level of quality of the provision of public services. The results of the study revealed the most significant political, economic, social and technological factors of the macro environment and presented the main directions for improving the processes of digital transformation of public administration. Specific measures have been proposed for each group of factors to enable the executive branch to adapt to the external environment, thereby improving their performance. The results of the study can be used to develop programmes and plans for government agencies to digitize their public services