bluuebunny/crossref_metadata_2025 huggingface dataset:
The Actions of L-Glutamate at the Postsynaptic Membrane of the Squid Giant Synapse
Authors: Adams D. J. , Gillespie J. I.
Published: April 2021

The actions of L-glutamate on the postsynaptic membrane of the squid giant synapse were investigated using two methods of application: ionophoresis and bath perfusion. Bath perfusion of 10 mmol l−1 sodium glutamate did not produce an appreciable depolarization of the postsynaptic membrane but reversibly blocked the neurally evoked postsynaptic potential (PSP). The postsynaptic membrane depolarized when L-glutamate was applied ionophoretically. The sensitivity to glutamate application was not uniform, but sharply localized to sites which may correspond to synaptic contacts made by branching colaterals from the postsynaptic axon. The relationship between membrane potential and amplitude of the glutamate-activated postsynaptic potential (PSP) examined under currentclamp conditions was linear over the voltage range studied (–110 to –60 mV) with an extrapolated reversal potential of –36mV. The amplitude of the glutamate-activated PSP was reduced either by replacing Na+ in the external solution with Tris+ (Na+-free) or by raising the extracellular K+ concentration to 20 mmol l−1 and was abolished by removing both Na+ and Ca2+ from the bath solution. The PSP amplitude was insensitive to changes in the extracellular Mg2+ concentration. The extrapolated reversal potential of the glutamate PSP was shifted to more positive potentials in both Na+-free and raised-K+ bathing solutions and was unchanged by anion substitution.

The depolarization induced by L-glutamate increased with increasing ionophoretic current and reached a maximum with large pulses. Double logarithmic plots of the coulomb dose-response relationship gave a limiting slope in the range 1·7–2·2, suggesting that two glutamate molecules are required for receptor activation. The time course of desensitization of the glutamate response was studied using a double-pulse method. The initial decrease in the ratio, PSP2/PSP1, is followed by a slower time-dependent recovery of the postsynaptic response with a time constant of 8·5 s. Prolonged perfusion of the squid giant synapse with concanavalin A failed to abolish desensitization of the glutamate-evoked PSP.
The Concentration Dependence of the Stimulatory Effects of Catecholamines on the Rate and Force of Contraction of the Heart of Dogfish (Scyliorhinus Canicula)
Authors: Van Vliet B. N. , Metcalfe J. D. , Butler P. J. , West N. H.
Published: April 2021

An adrenergic control of the elasmobranch heart has been inferred from pharmacological studies. Catecholamines have been repeatedly demonstrated to stimulate the frequency and/or force of the dogfish heart (MacDonald, 1925; Lyon, 1926; Hiatt, 1942; Ostlund, 1954; Fange & Ostlund, 1954; Capra & Satchell, 1977), and such effects have been shown to be reduced by propranolol, a beta-adrenergic antagonist (Capra & Satchell, 1977). However, the mechanism and functional significance of an adrenergic control of the elasmobranch heart remain to be demonstrated.
Synaptic Transmission Between Second- and Third-Order Neurones of Cockroach Ocelli
Authors: Mizunami Makoto , Tateda Hideki
Published: April 2021

The insect ocellus contains a large number of photoreceptors which converge on a small number of large second-order neurones, called L neurones. The L neurones exit from the ocellus and project into the ocellar tract of the brain, where they make synapses with third-order neurones (reviewed by Goodman, 1981). Response characteristics of L neurones have been well documented (Goodman, 1981; Mizunami et al. 1986), but less is known about ocellar third-order neurones. In locusts, three types of ocellar third-order neurones, which descend to the thoracic ganglia, have been found (Simmons, 1980,1981; Reichert et al. 1985), and the transmission characteristics between L neurones and some of these descending neurones have been documented (Simmons, 1981). In the present paper, we examine whether the transmission characteristics reported by Simmons (1981) are specific to descending ocellar third-order neurones or are generally applicable to a variety of ocellar third-order neurones, including those terminating within the brain. Experiments were made on cockroaches, Periplaneta americana.
Age-Dependent Changes in Volume and Haemoglobin Content of Erythrocytes in the Carp (Cyprinus Carpio L.)
Authors: Speckner W. , Schindler J. F. , Albers C.
Published: April 2021

Carp erythrocytes were fractionated by angle-head centrifugation which yielded fractions with a linear increase in density. Haematological examinations revealed that the heavier red blood cells of carp had greater volumes (MCV), more haemoglobin (MCH) and higher haemoglobin concentrations (MCHC) than light ones. The same experiments with human red cell fractions yielded a decrease in MCV, constant MCH and an increase in MCHC. Haemoglobin content in individual erythrocytes was also determined by scanning stage absorbance cytophotometry to establish the frequency distribution of the cellular haemoglobin contents. In carp, the distribution was symmetrical with the means increasing with density. No such change with cell density was found in human erythrocytes.

Both carp and human erythrocytes incorporated [2-14C]glycine in vitro. After gel filtration, radioactivity was detected in carp, but not in human, haemoglobin fractions. 14C was found in all three haemoglobin fractions, obtained by isoelectric focusing, and was present in the haem and in the globin. [2-14C]glycine-labelled erythrocytes were reinjected into chronically cannulated carp and followed in vivo for several months. With time, the main peak of scintillation counts shifted from red cell fractions of low to high density.

This is considered as evidence that density and age of red cells in carp are positively correlated and that erythrocytes can synthesize haemoglobin while circulating in the peripheral blood.
Ionic and Total Calcium Levels in the Blood of the European Eel (Anguilla Anguilla): Effects of Stanniectomy and Hypocalcin Replacement Therapy
Authors: Hanssen Robert G. J. , Lafeber Floris P. , Flik Gert , Bonga Sjoerd E. Wendelaar
Published: April 2021

Removal of the corpuscles of Stannius (STX) in the freshwater European eel causes a marked increase in the concentrations of blood ionic calcium and proteinbound calcium. The hypercalcaemia peaks 20 days after STX and lasts at least another 20 days. In stanniectomized eels hypocalcin decreased both blood ionic and total calcium concentrations. The reduction of plasma total calcium concentration by hypocalcin is attributed to a reduction in blood ionic calcium concentration. We conclude that hypocalcin regulates blood ionic calcium levels in fish.
Physical Properties, Sensory Receptors and Tactile Reflexes of the Antenna of the Australian Freshwater Crayfish Cherax Destructor
Authors: Sandeman David C.
Published: April 2021

The antennal flagellum of the crayfish Cherax destructor is very flexible, tapered and is almost as long as the body in mature animals. It consists of a series of short segments, oval in cross-section, that take the form of flattened rings at the base and slender tubes at the tip. There are no muscles in the flagellum. The flagellum’s mechanical resistance to being bent is not the same in all directions. It is most easily bent dorsally and least easily bent medially, when held stretched out horizontally in front of the animal. The resistance to bending is 10 times less than that of Astacus. The individual segments of the flagellum form curved articulating surfaces that may assist in reducing torsional movement of the flagellum when it is bent and, together with the tapered form, provide the flagellum with unique mechanical properties. Four main types of hairs are found on the flagellum. They are distributed in a specific manner, and total about 7000 hairs on the flagellum of a mature animal. Cross-sections through the sensory nerve reveal only about 2000 axons. Methylene blue applied to fresh preparations stains dendrites to all smooth hairs but never to procumbent feathered hairs. Physiological recordings from the sensory axons of the flagellar nerve allowed the characterization of the sensory hair response to displacement. Recordings were also made from slowly adapting receptors, sensitive to bending the flagellum in particular directions, but not related to mechanoreceptive hairs. Intracellular recordings from identified extensor and flexor motoneurones revealed the ordered projection of the inputs from the receptor hairs, and also provided a model that correlates specific receptor inputs with particular antennal reflexes, and links the unique mechanical properties of the flagellum with the detection of the distance of near objects.
Invariance of Oscillator Interneurone Activity During Variable Motor Output by Locusts
Authors: Reichert H. , Rowell C. H. F.
Published: April 2021

Simultaneous intracellular recordings were made in locusts from (a) flight motor neurones and (b) output interneurones of the flight oscillator. The insects were mounted with the head at the centre of rotation of an artificial horizon. During fictive flight, these animals responded to simulated deviations from course with the changes in motor output appropriate to course-correction manoeuvres, as previously described. In the motor neurone of depressor muscle MN98 (meso-thoracic second basalar) these changes take the form of systematic variation in amplitude in the cyclical depolarization seen in the neurone in flight which, in turn, leads to variation in the number of action potentials per cycle (from 0·3) and in the latency of the first spike (up to 19 ms difference). These changes are closely related to the perceived movement of the horizon. The oscillator output, as recorded in metathoracic interneurone 511, shows, in contrast, very little change. The fraction of its variation which is correlated with horizon movement is vanishingly small (e.g. for number of action potentials per burst r2 = 0·008). The exteroceptive sensory inputs which modify motor output during steering do not, therefore, affect the oscillator appreciably. Thus, by exclusion, the motor patterns of compensatory steering are due exclusively to summation of the oscillator drive with the sensory inputs. This takes place in the motor neurones and especially in the premotor interneurones, as previously described.
Skylight Polarization Patterns and the Orientation of Migratory Birds
Authors: Able Kenneth P.
Published: April 2021

Patterns of polarized light present in the clear dusk sky provide directional information relevant to the orientation behaviour of migratory birds. Experiments performed with white-throated sparrows (Zonotrichia albicollis) and American tree sparrows (Spizella arborea), North American night migrants, examined migratory orientation between the time of sunset and the first appearance of stars under several manipulations of skylight polarization patterns. Under clear skies, birds tested in Emlen funnel orientation cages oriented their hopping basically parallel to the E-vector of polarized light, with a bias towards the brightest part of the sky (sunset direction). Under solid, thick overcast conditions (no polarized light from the natural sky), birds showed axially bimodal hopping orientation parallel to an imposed E-vector. When birds were tested in cages covered with depolarizing material under a clear sky, their hopping orientation was seasonally appropriate and indistinguishable from controls viewing an unaltered clear sky. Skylight polarization patterns are not necessary for the occurrence of migratory orientation, but birds respond strongly to manipulations of the E-vector direction. The results reported here support the hypothesis that the relevant stimulus is the E-vector orientation rather than other parameters of skylight, e.g. intensity or colour patterns, degree of polarization. It appears that these night migrants are using skylight polarization at dusk as one of a set of multiple compass capabilities. Because of the necessarily artificial nature of the polarized light stimuli used in the experimental manipulations, it has not been possible to establish the relationship between this orientation cue and other known mechanisms (magnetic, sun and star compasses).
Water Balance in Manduca Sexta Caterpillars: Water Recycling from the Rectum
Authors: Reynolds Stuart E. , Bellward Karen
Published: April 2021

Tobacco hornworm (Manduca sexta) caterpillars are able to regulate the water content of their body when fed on diets of markedly different water content. This regulation extends to the water content of food within the gut. Regulation of body water is achieved by adjusting the amounts of water lost with the faeces. The rectum is shown to be the principal site of water reabsorption from the faeces. The rate of rectal water absorption is shown to vary with the water content of the food and thus according to need. Water reabsorbed from the rectal contents is recycled and added to the contents of the midgut. The ultrastructural appearance of epithelial cells in the rectal wall is that expected of a fluid-transporting tissue. The ileum appears to play little or no part in water recycling.
Circulating Catecholamines and Swimming Performance in the Atlantic Cod, Gadus Morhua
Authors: Butler P. J. , Axelsson M. , Ehrenström F. , Metcalfe J. D. , Nilsson S.
Published: April 2021

Sectioning the first four pairs of spinal nerves prevents the large increase in circulating catecholamine concentrations seen in Atlantic cod swimming at their critical velocity (Ucrit). There is also a significant reduction in the swimming performance of the fish. To test whether this reduced performance results from the lack of increase in plasma catecholamine levels or from the fact that other organs are also denervated by the operative procedure, a mixture of adrenaline and noradrenaline was infused into swimming, denervated fish. This caused a significant increase in their Ucrit-It is concluded, therefore, that the rise in plasma catecholamine levels seen in Atlantic cod swimming at their maximum sustainable velocity enhances the swimming performance of these fish.
Relationship Between Respiratory Pumping and Oxygen Consumption in Aplysia Depilans and Aplysia Fasciata
Authors: Levy Miriam , Achituv Yair , Susswein Abraham J.
Published: April 2021

Respiratory pumping in Aplysia is a well-characterized behaviour controlled by identified neurones, but its function is unknown. To gain insight into the function of this behaviour, respiratory pumping and oxygen consumption were examined under identical conditions, in Aplysia fasciata Poiret and in A. depilans Gmelin. A. fasciata is found in less turbulent environments than is A. depilans, suggesting that control of respiratory pumping may differ in the two species.

Rates of respiratory pumping and oxygen consumption were poorly correlated. The basal rate of respiratory pumping was similar in both species and was not significantly dependent on animal mass, but the resting rate of oxygen consumption was higher in A. depilans than in A. fasciata and was an inverse function of animal mass in both species. Brief, moderate hypercapnia led to an increase in oxygen consumption in both Aplysia species. In A. fasciata, the increase was much greater. Increase in oxygen consumed was not accompanied by changes in the rate of respiratory pumping. Longer, more severe periods of hypercapnia led to decreases in oxygen consumption in both Aplysia species, and an increase in the rate of respiratory pumping. Decreased oxygen consumption was more gradual in A. fasciata. Severe hypoxia produced a decrease in the rate of oxygen consumed, and an increase in the rate of respiratory pumping.
Acid-Base Regulation Following Exhaustive Exercise: a Comparison Between Freshwater-and Seawater-Adapted RainbowTrout (Salmo Gairdneri)
Authors: Tang Y. , Mcdonald D. G. , Boutilier R. G.
Published: April 2021

Blood acid-base regulation following exhaustive exercise was investigated in freshwater-(FW) and seawater-(SW) adapted rainbow trout (Salmo gairdneri) of the same genetic stock. Following exhaustive exercise at 10°C, both FW and SW trout displayed a mixed respiratory and metabolic blood acidosis. However, in FW trout the acidosis was about double that of SW trout and arterial blood pH took twice as long to correct. These SW/FW differences were related to the relative amounts of net H+ equivalent excretion to the environmental water, SW trout excreting five times as much as FW trout. The greater H+ equivalent excretion in SW trout may be secondary to changes in the gills that accompany the adaptation from FW to SW. It may also be related to the higher concentrations of HCO3− as well as other exchangeable counter-ions (Na+ and Cl−) in the external medium in SW compared to FW.
Adrenaline and Branchial Nerve Stimulation Inhibit 45Ca Influx into the Gills of Rainbow Trout, Salmo Gairdneri
Authors: Donald John A.
Published: April 2021

The tissues in the core of the gill filaments of Salmo gairdneri are innervated by cholinergic and adrenergic nerves (Donald, 1984, 1986, 1987). It is unlikely that the nerves are involved in vasomotor regulation, because the wall of the filament venous sinus of S. gairdneri is a simple endothelium, lacking any muscular elements (Donald, 1986). Since many of the nerves are closely associated with the filament epithelium (Donald, 1986), they might be involved in the regulation of some aspect of epithelial function.
Dye Transport Across the Retinal Basement Membrane of the Blowfly Calliphora Erythrocephala
Authors: Weyrauther E. , Roebroek J. G. H. , Stavenga D. G.
Published: April 2021

In the blowfly, Calliphora erythrocephala, transport of dye into or out of the retina, following injection into the eye or thorax, was investigated, mainly by microspectrophotometry and fluorimetry. After injection into the eye, Phenol Red, Trypan Blue, Lucifer Yellow and 9-amino-acridine were transported out of the retina; Procion Yellow and Rhodamine-123 stayed in it. The time constants of this transport process were in the range 45–80 min at 23°C, depending on the dye. When Lucifer Yellow was injected into the thorax, it was transported into the retina. The transport of these dyes across the retina was inhibited by nitrogen, ouabain and low temperature, indicating that active processes are involved.
The Effects of Hypersaline Exposure on Oxygen-Affinity of the Blood of the Freshwater Teleost Catostomus Commersoni
Authors: Walker R. L. , Wilkes P. R. H. , Wood C. M.
Published: April 2021

After 10 days’ exposure to an environmental salinity of 300mosmol kg−1 NaCl, the freshwater stenohaline teleost Catostomus commersoni exhibited an increase in plasma osmolality and a reduction in plasma strong ion difference (SID). There were reductions in plasma pH (pHe), red blood cell (RBC) pH (pHi), plasma total CO2 and erythrocyte nucleoside triphosphate (NTP) concentration, and increases in mean erythrocyte volume and plasma catecholamine levels. Despite the acidosis, the in vitro haemoglobin oxygen-affinity of blood from saline-acclimated fish was not significantly different from that of control fish (held in fresh water) which had higher pHe and pHi values at the tensions used. In vitro adjustment of SID of blood from control fish to approximate that of the saline-acclimated fish by the addition of NaOH and HC1 significantly reduced pHe, pHi and the haemoglobin oxygen-affinity. Adjustment of the plasma osmolality of blood from control fish to values identical to those of the saline-acclimated fish by the addition of NaCl in vitro did not alter the haemoglobin oxygen-affinity. An increase in catecholamine concentration and a decrease in red blood cell N IP concentration in the saline-acclimated fish may have been compensatory mechanisms to maintain haemoglobin oxygen-affinity against acidosis-induced Bohr and Root effects during saline exposure.
A New Analysis of Ammonia and Sodium Transport Through the Gills of the Freshwater Rainbow Trout (Salmo Gairdneri)
Authors: Avella Martine , Bornancin Michel
Published: April 2021

The mechanism of ammonia excretion and sodium absorption was re-examined in trout using the isolated-perfused head preparation. Preliminary experiments in which ammonia concentration was increased on the blood side (internal) showed that ammonia and sodium transport was uncoupled.

For ammonia excretion, our results showed that gill tissue endogenously produces ammonia. A correlation was demonstrated between ammonia excretion and the internal-external ammonia gradient. We conclude that diffusion in the form of NH3 was responsible for ammonia efflux and we were therefore able to estimate its diffusion coefficient and permeability coefficient (6 × 10−3cms−1). This ammonia diffusion was shown to be modified according to the external proton availability.

For sodium absorption, significant changes were caused by indirect modifications of intracellular pH brought about by addition of acetazolamide inside or ammonia outside or by acidification of the internal or external medium. The relationship between sodium and proton transport was further confirmed by the action of the drug amiloride and the measurement of H+ excretion.

A possible model representing sodium, proton and ammonia transport through the gill epithelium is proposed.
The Role Of Water In Tarsal Taste Thresholds To Sugar In The Blowfly Phormia Regina
Authors: Edgecomb Robert S. , Pyle Angela R. , Murdock Larry L.
Published: April 2021

Thirsty blowflies whose tarsi come into contact with water will respond with proboscis extension. When flies were exposed to high or low relative humidities (RH) prior to testing, the tarsal taste thresholds to sucrose in flies that were unresponsive to water alone increased or decreased, respectively. Evidently, thirst can also be subthreshold and recognizable only as a change in threshold to aqueous sucrose.

Thresholds to sucrose and fructose, which were in the millimolar range in 3-day-old adult flies held at 5–70% RH prior to testing, fell significantly after the flies had been held at low humidity (13–20% RH) for several hours. There was no low-humidity-dependent drop in threshold with galactose or xylose, sugars to which flies normally have thresholds in the 102mmoll−1 range.

Flies held at low relative humidity exhibited increased tarsal thresholds to sucrose when they were injected with water or were allowed to drink water ad libitum. When multiple injections of water were given, thresholds rose after successive injections. Changes in threshold to sucrose occurred after injection with aqueous NaCl, the direction and magnitude being dependent on the concentration injected. The threshold declined significantly after injection of 2μl of 75 mmol l−1 NaCl, remained unchanged after injection of 150 or 300 mmol l−1 NaCl, and increased after injection of 600 mmol l−1 NaCl.

Thirst in blowflies can affect thresholds to food stimuli. The changes in water content of the body resulting from a water-rich meal could contribute significantly to the normal post-meal rises in tarsal thresholds.
Intracellular Na+ and the Control of Amino Acid Fluxes in the Integumental Epithelium of a Marine Bivalve
Authors: Wright Stephen H. , Moon Debra A. , Silva Arnold L.
Published: April 2021

The accumulation of amino acids from sea water into the integumental epithelium of the bivalve gill can occur against chemical gradients in excess of 106 to 1. The energy to drive this transport has been proposed to come from the inwardly directed Na+ electrochemical gradient. The present study examined the influence of intracellular and extracellular [Na+] on influx and efflux of amino acids in gill tissue from the mussel, Mytilus californianus. Influx of alanine was inhibited by more than 90% when external [Na+] was reduced from 425 to 2 mmol l−1, and by 85% when intracellular [Na+] was increased from approximately 11 to approximately 100 mmol l−1 (by means of a 30-min exposure to the ionophore, nigericin). Efflux of taurine and alanine from gill tissue into normal-Na+ sea water was very low (<5% of the Jmax of the carrier-mediated influx pathways). Reducing the external Na+ from 425 to 2 mmol l−1 increased taurine efflux by only 20%. Raising cell [Na+] to approximately 100 mmol l−1 increased taurine efflux 2·7-fold; further increases in cell [Na+] increased taurine efflux another 7·5-fold. These data, in conjunction with results from earlier studies, suggest that activation of integumental amino acid transporters requires an interaction of multiple sodium ions with binding sites of low affinity for this ion. This set of characteristics results in transport systems that are well-adapted for the net accumulation of amino acids from sea water.
Insect Cardioactive Peptides: Neurohormonal Regulation Of Cardiac Activity By Two Cardioacceleratory Peptides During Flight In The Tobacco Hawkmoth, Manduca Sexta
Authors: Tublitz Nathan
Published: April 2021

The relationship between two cardioactive neuropeptides, the cardioacceleratory peptides (CAPs), and changes in heart rate during flight was investigated in the tobacco hawkmoth, Manduca sexta. In vivo heart recordings from intact, tethered adults revealed a marked increase in heart rate associated with flying. Both anterior-to-posterior and posterior-to-anterior contraction waves showed a measurable elevation in contraction frequency. These changes in heart activity were noted in animals engaged in short (20 min) or long (60 min) bouts of continuous flight. Bioassay of blood taken from flying animals revealed the presence of an activity-dependent, blood-borne cardioacceleratory factor(s). Biochemical analyses of the blood of flying insects on HPLC identified two cardioacceleratory factors which co-eluted with the two CAPs. A depletion in the ventral nerve cord levels of both CAPs was observed during flight. In vivo injections of an anti-CAP monoclonal antibody blocked the increase in cardiac activity associated with flight. These results confirm the hypothesis that both CAPs act as cardioregulatory neurohormones during flight in Manduca sexta.
A Kinetic Method for the Measurement of Zinc Influx in vivo in the Rainbow Trout, and the Effects of Waterborne Calcium on Flux Rates
Authors: Spry D. J. , Wood C. M.
Published: April 2021

Three methods were evaluated to measure rate of influx of Zn into rainbow trout. The first two, disappearance of 65Zn from the water and whole-body counting, overestimated influx when compared with a third method which used a terminal plasma sample to calculate influx. The cause of the overestimate was a short-term adsorption phenomenon to both the experimental apparatus and the exterior of the fish. The third method measured only Zn which entered the fish. This method entailed ‘calibration’ of cannulated trout by constant infusion of small amounts of radiolabelled Zn. This was analogous to the entry of Zn into fish across the gill. After 24-36 h of infusion, plasma radioactivity reached a steadystate concentration which was a simple linear function of the rate of infusion. This relationship was then used to predict influx from a single terminal plasma sample from uncannulated trout exposed to radiolabelled Zn in the water. Trout acclimated to tapwater (Ca2+= 2·0 mequiv P1) and exposed to Zn (1·5–45·9 /μequiv I−1; 0·05–1·5 mg I−1) showed saturable uptake which was apparently first order with no significant linear component. The apparent Jmax and Km were 314nequivkg−1 h−1 and 7·3iμequivl_1 (0·24mgl−1), respectively. Acutely raising the waterborne [Ca2+] (4·7 and 9·7 mequiv I−1) over the same range of [Zn] revealed a competitive type of interaction -little change in Jmax, with increased Km. When Ca2+ was acutely removed (0-05 and 1-02 mequiv I−1) by the use of artificial soft water, significant linear influx occurred in addition to the saturable uptake noted at higher [Ca2+], suggesting the opening of a paracellular leak. Calculation of the inhibitor constant for Ca2+ yielded a value of 0·48 mequiv I−1. This value is similar to the Km for Ca2+ when it was a transported substrate (0·28 ± 0·07 mequiv I−1). The true Km for Zn transport in the absence of Ca2+ was 1-Oqequivl−1 (0·06mgl−1). These data showed Zn influx to be saturable and strongly dependent upon waterborne [Ca2+], perhaps traversing the gill in a manner similar to Ca2+.
The Visual Acuity of Octopuses For Gratings of Different Orientations
Authors: Muntz W. R. A. , Gwyther J.
Published: April 2021

A recent study has shown that the minimum separable angle of visual acuity of Octopus pallidus and O. australis lies between 4·4′ and 9·7′ when vertical and horizontal gratings are used as test objects (Muntz & Gwyther, 1988). In view of other observations - the horizontal rectangular shape of octopus pupils, the pronounced astigmatism of the lens of Eledone cirrhosa (SroczyŃski & Muntz, 1985), the difficulty that O. vulgaris has in discriminating between oblique rectangles (Sutherland, 1957), and the vertically and horizontally arranged rectilinear organization of both retina and neurones in the optic lobe of O. vulgaris (Young, 1960) - it seemed worthwhile testing the effect of grating orientation on visual acuity in more detail, and in particular extending the measurements to include oblique gratings oriented at 45° with respect to gravity.
Small Cardioactive Peptide B Modulates Limax Feeding Motoneurones
Authors: Hess Stephen D. , Prior David J.
Published: April 2021

Although first described for its actions on the heart of the snail, Helix (Lloyd, 1978), small cardioactive peptide B (SCPB) has since received attention primarily for its neuronal effects. The effects of SCPB on the feeding neuronal networks of gastropods are particularly well characterized (e.g. Lloyd et al. 1984; Murphy et al. 1985; Sossin et al. 1987; Willows et al. 1988). However, less is known about cellular mechanisms by which the peptide enhances feeding responsiveness. The isolated central nervous system (CNS) preparation of the terrestrial slug Limax maximus is particularly useful for studies which examine the role of peptides in the expression of feeding, since the feeding motor programme can be reliably elicited by chemical stimulation of the lips (Gelperin et al. 1978) or electrical stimulation of the lip nerves (Phifer & Prior, 1985). SCPB increases both the responsiveness of the feeding motor programme and the burst frequency of the fast salivary burster neurone of Limax (Prior et al. 1985; Prior & Watson, 1988). We therefore used intracellular recordings to examine the membrane responses which underlie the ability of SCPB to increase the burst frequency of the fast salivary burster neurone (FSB). Portions of this work have appeared in an earlier abstract (Hess & Prior, 1986).
Length-Tension Relationships of Masseter and Digastric Muscles of Miniature Swine During Ontogeny
Authors: Anapol Fred , Herring Susan W.
Published: April 2021

At incremental whole muscle lengths, active isometric and passive elastic forces were recorded from the masseter and digastric muscles of anaesthetized miniature pigs (Hanford) weighing 2·0−20·0 kg. Wet muscle mass and maximum tetanic tension values for masseter exceed those for digastric and increase more rapidly with body mass (age). At any body mass, masseter exceeds digastric in the ratio of optimum length (that length at which maximum tetanic tension is produced) to in situ muscle length (that length which corresponds to the jaw in a closed position) and the proportion of passive tension comprising total (passive plus active) tension. Passive elastic tension begins to rise in masseter at lengths as short as 87 % of optimum (in younger pigs). In digastric, passive tension is absent until the muscle is stretched to a length slightly longer than optimum in younger pigs but occurs at shorter lengths in older pigs.

Contractile properties explain functional differences between masseter and digastric more clearly than they explain ontogenetic changes in either muscle. The behavioural transition from infant suckling to adult mastication of solid food is best characterized by a disproportionate increase in mass (and force) of the masseter, relative to digastric, and increased reliance upon active (rather than passive) tension.
Properties of a Set of Internal Receptors in the Medicinal Leech: The Nephridial Nerve Cells Monitor Extracellular Chloride Concentration
Authors: Wenning Angela
Published: April 2021

In the leech, Hirudo medicinalis, the functional properties of the peripheral nephridial nerve cells (NNCs) were investigated using long-term extracellular recordings from both intact and isolated preparations.

The NNCs respond selectively to changes in external Cl− concentration: their electrical activity is highest in fluid containing normal (i.e. low) extracellular [Cl−]. Their sensitivity to Cl− is confined to the dendritic tree. Extracellular [Cl−] is a control factor for ion homeostasis. It increases drastically after a blood meal, and after the animal has left the water or invaded brackish water. The NNCs continuously monitor the extracellular Cl− concentration: their burst rate changes, without adapting, by a factor of 4 in the physiological range between 40 and 90 mmoll−1.

Intracellular recordings from the NNC in isolated nephridial complexes suggest that a high Cl− conductance in combination with active transport of Cl− could be responsible for the observed Cl− sensitivity.
Energy Metabolism in Trout Red Cells: Consequences of Adrenergic Stimulation in Vivo and in Vitro
Authors: Ferguson R. A. , Tufts B. L. , Boutilier R. G.
Published: April 2021

β-Adrenergic stimulation of salmonid red cells results in a rapid decrease (within 5 min) in the nucleotide triphosphate: haemoglobin ratio (NTP:Hb), which is thereafter maintained at a constant level, presumably through increased ATP turnover via matched aerobic metabolism and energy-consuming processes. Addition of the β-adrenergic agonist isoproterenol to rainbow trout red cells in vitro leads to a rise in intracellular pH (pHi), a corresponding decrease in extracellular pH (pHe) and an increase in red cell oxygen consumption . Moreover, the extent to which red cell pHi is maintained constant in the face of an acute extracellular acidosis in vitro or in vivo is proportional to the adrenergically stimulated increase in red cell . In the absence of oxygen, these red cells remain capable of pH regulation, but cannot maintain NTP:Hb constant. As a result, membrane and metabolic functions become uncoupled in the stimulated deoxygenated cells.
Phosphocreatine Represents a Thermodynamic and Functional Improvement Over Other Muscle Phosphagens
Authors: Ellington W. Ross
Published: April 2021

In vertebrate tissues, the only phosphagen is phosphocreatine (PC), and the corresponding phosphotransferase is creatine phosphokinase (CPK). Among invertebrates, a variety of phosphotransferase reactions are found in addition to CPK, including arginine phosphokinase (APK), glycocyamine phosphokinase (GPK), taurocyamine phosphokinase (TPK) and lombricine phosphokinase (LPK). Although there is some uncertainty about the exact value, the apparent equilibrium constant for the CPK reaction ( = [creatine][ATP]/[PC][ADP]), under physiological conditions similar to those of vertebrate muscle, ranges from 100 to 160. The corresponding K′ value for the APK reaction is somewhat controversial, and K′ values for the GPK, TPK and LPK reactions are not known. In this study, conventional and 31P-NMR methods were used to evaluate the equilibrium constants for the APK, GPK, TPK and LPK reactions relative to that of CPK. The corresponding K′values for the APK, GPK, TPK and LPK reactions, expressed as a percentage of , are 13, 29, 29 and 32 %, respectively. The exclusively invertebrate phosphagens exist as a cohort of thermodynamically more stable compounds. Thus, PC constitutes a thermodynamic (and functional) improvement, in that the CPK reaction is able to buffer ATP at much higher ATP/ADP ratios than are other phosphagens. However, possession of a phosphagen system with a lower K′value may be advantageous under certain specific physiological conditions such as intracellular acidosis.
Hydrogen Ion Equilibria in Fish Haemoglobins
Authors: Jensen Frank B.
Published: April 2021

H+ titration studies on oxygenated and deoxygenated haemoglobins from carp, rainbow trout, spiny dogfish and pig are reported, and compared with Hb-H+ equilibria in other species and structural information deduced from amino acid sequences. The buffer values of oxygenated and deoxygenated teleost haemoglobins are low in comparison with elasmobranch and mammalian haemoglobins. This correlates with a much lower content of histidine residues and α-amino groups in teleost haemoglobins, than that in elasmobranch, dipnoan, amphibian, reptilian, avian and mammalian haemoglobins. The low total histidine content in teleost haemoglobins is paralleled by a reduced number of titratable histidine residues compared with that in mammals. An inverse relationship is observed between the magnitude of buffer values and the magnitude of fixed-acid Haldane effects. The largest Haldane effect and smallest buffer values are seen in carp, followed by trout, whereas the smallest Haldane effect and largest buffer values are seen in dogfish. The H+ equilibria of pig haemoglobin are intermediate between those of teleost and elasmobranch haemoglobins.
Oxidative Properties of Carp Red and White Muscle
Authors: Moyes C. D. , Buck L. T. , Hochachka P. W. , Suarez R. K.
Published: April 2021

Substrate preferences of isolated mitochondria and maximal enzyme activities were used to assess the oxidative capacities of red muscle (RM) and white muscle (WM) of carp (Cyprinus carpio). A 14-fold higher activity of citrate synthase (CS) in RM reflects the higher mitochondrial density in this tissue. RM mitochondria oxidize pyruvate and fatty acyl carnitines (8:0, 12:0, 16:0) at similarly high rates. WM mitochondria oxidize these fatty acyl carnitines at 35–70% the rate of pyruvate, depending on chain length. WM has only half the carnitine palmitoyl transferase/CS ratio of RM, but similar ratios of beta-hydroxyacyl CoA dehydro-genase/CS. Ketone bodies are poor substrates for mitochondria from both tissues. In both tissues mitochondrial alpha-glycerophosphate oxidation was minimal, and alpha-glycerophosphate dehydrogenase was present at low activities, suggesting the alpha-glycerophosphate shuttle is of minor significance in maintaining cytosolic redox balance in either tissue. The mitochondrial oxidation rates of other substrates relative to pyruvate are as follows: alpha-ketoglutarate 90% (RM and WM); glutamate 45% (WM) and 70% (RM); proline 20% (WM) and 45% (RM). Oxidation of neutral amino acids (serine, glycine, alanine, beta-alanine) was not consistently detectable. These data suggest that RM and WM differ in mitochondrial properties as well as mitochondrial abundance. Whereas RM mitochondria appear to be able to utilize a wide range of metabolic fuels (fatty acids, pyruvate, amino acids but not ketone bodies), WM mitochondria appear to be specialized to use pyruvate.
New Growth Elicited in Adult Leech Mechanosensory Neurones by Peripheral Axon Damage
Authors: Bannatyne B. A. , Blackshaw S. E. , Mcgregor M.
Published: April 2021

New growth in cutaneous mechanosensory neurones elicited by axotomy or axon crush was studied using intracellular injection of horseradish peroxidase at different times after the lesion, ranging from a few days to over a year. Cutting or crushing major, large-calibre axon branches of mechanosensory neurones elicits sprouting of new processes, either centrally within the ganglion neuropile or at the site of the lesion in the peripheral nerve. In contrast, cutting or crushing fine-calibre axon branches supplying accessory parts of the receptive field does not elicit sprouting of the main arbor or main axon branches. Different modalities of mechanosensory neurone respond differently to lesions of their axons. Cutting the axons of high-threshold units responding to noxious stimulation of the skin elicits sprouting of additional processes from the axon hillock region within the central nervous system (CNS), whereas cutting or crushing the axons of low-threshold cells responding to light touch of the skin elicits sprouting at the site of the lesion only, and not within the CNS. In addition to the new growth directed into the peripheral nerve, damaged nociceptive neurones also form new processes that wrap the somata of particular cells within the ganglion. Sprouted processes of axotomized neurones are retained for long periods after the lesion (up to 425 days). The electrical properties of touch and nociceptive cells were studied between 1 and 60 days after axotomy, by intracellular recording from the centrally located cell bodies. The amplitude, width and maximum dV/dt of the action potential and after-hyperpolarization, as well as the resting potential and input resistance, did not change significantly after axotomy, despite the considerable process sprouting known to occur during this time.
Neuromotor Bases of the Escape Behaviour of Nassa Mutabilis
Authors: Lemmnitz G. , Schuppe H. , Wolff H. G.
Published: April 2021

The complex sequence of movements in the escape behaviour of the snail Nassa mutabilis (L.) was described in detail and the neuromotor activity underlying the behaviour was investigated by extra- and intracellular recording. The escape reaction is triggered by a chemical stimulus to the animal ‘s foot, in these experiments either application of KC1 solution or contact with a starfish. It consists of a preliminary phase in which the shell tilts to its side, the actual locomotor phase, and a final righting movement. The snail performs leaps, in which the foot and the shell are repeatedly rotated with respect to one another. EMGs recorded from the columellar muscle during the escape reaction showed that bursts of potentials are coupled to the shell rotations. In the intact animal this burst activity ordinarily began 0 ·6 ± 0 ·3 s after stimulation with KC1. In an animal dissected for recording from the columellar nerve (which supplies the columellar muscle), KC1 stimulation of the dorsum of the foot induced burstlike neuronal activity with a latency of 0 ·5 ± 0 ·3 s. The dorsal foot region, the site at which the escape reaction can be triggered, was found to be supplied by the posterior pedal nerves; electrical stimulation of these nerves elicited bursts in the columellar nerve. The left pleural ganglion, which is known to contain neurones that project into the columellar nerve, was also found to contain neurones responsive to KC1 stimulation of the foot. These findings suggest that the left pleural ganglion contains a motor centre which is involved in control of activity of the columellar nerve, and is also active during the escape reaction.
A Note On The Diffusion of Water Across Oil And Wax Layers and Insect Cuticles
Authors: Croghan P. C. , Noble-Nesbitt J.
Published: April 2021

The terms diffusion and permeability are frequently confused and misused. For example, Barrer (1941) in the preface of his book defines permeability constant in contradictory ways in successive sentences and both are incorrect. In the case of diffusion of gases and water, confusing systems of units have been employed. Taylor et al. (1936) define a coefficient as g/hr/cm/mmHg and Barrer (1941) uses cc(vapour at N.T.P.)/sec/cm2/cmHg/mm thick. The use of more than one solidus leads to ambiguity and may, for example, disguise that the thickness term is in the numerator and Machin (1980) does, indeed, manage to invert this term. Other errors can also easily occur. Thus Beament (1958) writes mmHg when cmHg is intended and this is repeated by Machin (1980). Also Machin & Lampert (1987) use both the coefficients mg h−1 cm−2 torr−1 and cms−1 without relating them.
Intracellular Buffering by Dipeptides at High and Low Temperature in the Blue Crab Callinectes Sapidus
Authors: Cameron James N.
Published: April 2021

Intracellular buffering is provided mainly by bicarbonate, phosphates and proteins (see Burton, 1978). A part may also be played by free histidine and small peptides containing histidine. Although the free histidine content of most animal tissues is low, a variety have been found to possess substantial amounts of histidine-containing dipeptides, most commonly N-β-alanyl-L-histidine, either without substitutions (carnosine) or methylated at the 1-position (anserine) or at the 3-position (ophidine or balenine). At 25°C the pK of carnosine is 6·83 whereas that of anserine is 7·04, so the combination of appropriate pK and high concentration leads to significant intracellular buffer action.
Effects of Temperature on Gas Exchange and Acid-Base Balance in the Sea Turtle Caretta Caretta at Rest and During Routine Activity
Authors: Lutz Peter L. , Bergey Ann , Bergey Michael
Published: April 2021

Oxygen consumption, lung ventilation, plasma ion concentrations and osmolality, venous blood acid-base status and gas tensions were measured in unrestrained loggerhead sea turtles in sea water at 10, 15, 20 and 30 °C at rest and during routine activity. Moderate activity caused a threefold increase in oxygen consumption, accommodated by a twofold increase in ventilation (the result of increases in breathing frequency) and a 60% increase in lung oxygen extraction. There was an increase in oxygen consumption with temperature (Q10 = 2·4) also due primarily to an increase in oxygen extraction (decline in air convection requirement, ACR) since neither the tidal volume nor the breathing frequency changed.

Over the temperature range 15–30°C venous blood pH decreased by 0·017 units °C−1, indicating that the maintenance of constant relative alkalinity is not confined to species of low aerobic scope. Venous blood and increased with temperature. However, [HCO3−] decreased, suggesting that ventilatory adjustments alone are insufficient for regulating the thermally dependent shifts in blood pH. Plasma [K+] increased with temperature, which may be related to cellular-mediated adjustments in blood pH.

Temperature-related adjustments of blood pH in the loggerhead appear to be managed both at the lung (ACR-driven changes in blood ) and tissue (ion exchange) levels. This mixed regulation is associated with the unique mode of respiration of the sea turtle.
The Volume of Air Within the Swimbladder and Breathing Cavities of the Anabantoid Fish Colisa Laua (Perciformes, Belonthdae)
Authors: Schuster Stefan
Published: April 2021

The swimbladder volume and air volume within the breathing chambers of the anabantoid fish Colisa lalia have been measured. These data help in the understanding of some of the functions of these organs and are necessary for an analysis of their role in hearing and sound production. By means of a simple trick (based on new data) it was possible to analyse the time course of air volume changes in the breathing chambers at different temperatures. The results are well described by a simple diffusion model. The temperature-dependence of the time course suggests an interesting increase of the diffusion constant with temperature.

Under constant conditions the chambers were always filled with about the same volume of air. No excess pressure was found. Typical values of a single chamber’s air content range from 34 to 58 μl. Air content increases with about the third power of fish length. By using the present data, the time course of air volume changes in the chambers of a given fish can be estimated.

Swimbladder volumes, determined using Boyle’s law, ranged from 70 to 220 μ1 and were also found to increase with about the third power of fish length, in accordance with a simple estimation.

The data are discussed in relation to buoyancy, diffusion processes, blood circulation, hearing and sound production and suggest some interesting new work.