bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations on the Non-calcareous Component of the Shell of the Lamellibranchia
Authors: Beedham G. E.
Published: April 2021

A comparison has been made between the staining reactions and histochemical properties of the non-calcareous material (conchiolin) from the different layers of the shells of Anodonta cygnea, Mytilus edulis, and Ostrea edulis. Acid hydrolysates of the conchiolin protein have been analysed qualitatively by paper chromatography.

The composition of the conchiolin in Anodonta confirms the view that corresponding layers of the valves and ligament represent modifications of the same layers of the shell. In this bivalve, the properties of the outer layers of the valves and ligament are closely comparable with each other, and also with those of the periostracum and the fusion layer of the ligament. All these regions consist of a quinone-tanned protein, hydrolysates of which are rich in phenolic amino-acids, especially tyrosine, and in glycine.

Much of the periostracal conchiolin in Mytilus shows basically the same properties as the periostracum in Anodonta. However, the outer layers of the valves and ligament in Ostrea and Mytilus each exhibit progressively greater specialization compared with the situation in Anodonta. This is most marked in Mytilus where these components differ completely in character.

The conchiolin in the inner shell layers differs markedly in composition from that in the outer layers in Anodonta and Ostrea and from the periostracum in Mytilus. Hydrolysates of its protein constituent contain appreciably more aspartic acid and glutamic acid but much smaller amounts of phenolic amino-acids. The protein is only lightly tanned. Although in these properties the corresponding inner layers of the valves and ligament appear fundamentally alike, each component has certain specialized features. It is suggested that the modifications shown by the protein of the inner ligament layer, which is characterized by a high content of proline and methionine, are correlated with the specialized function of this region of the shell.
Some Aspects of Cuticular Organization of the Branchiopod, Streptocephalus dichotomus
Authors: Krishnan G.
Published: April 2021

The structural features of the cuticle of Streptocephalus are described. The epicuticle and endocuticle, unlike those of other Crustacea, stain alike and show similar chemical characters (apart from the absence of chitin in the epicuticle). This feature appears to be related to the absence of tanning of the cuticle, which remains soft and colourless in all stages of growth. In the epicuticle the outermost very thin layer, whose presence can be inferred from chemical tests, seems to correspond to the outer epicuticle of Crustacea, but this layer lacks histological distinctness. The protein constituent of the cuticle is unlike that of other arthropod cuticles so far studied. It differs markedly from arthropodin or sclerotin and recalls collagen. The significance of the peculiarities of the cuticle is discussed. It is suggested that the structure and chemical characteristics of the cuticle may indicate that it represents a generalized and unspecialized condition of the arthropod cuticle.
Observations on the Genital System and Alimentary Canal of a Lamiid Beetle, Nupserha bicolor
Authors: Dutt N.
Published: April 2021

The genital system and alimentary canal of both sexes of adult Nupserha bicolor s.sp. postbrunnea have been examined. In the female, the posterior end of the rectum is enclosed within a membranous jacket. The membranous jacket represents the tenth segment and is much more prominent than in the male. The jacket enclosing the rectal end runs a short course parallel with the vaginal passage through a common chitinous capsule representing the ninth segment, in which the openings of the anus and the genital passage lie. The chitinous capsule thus looks like a ‘cloacal chamber’. It disappears when the ovipositor is shot out. In the male, the posterior end of the rectum runs straight to the anus. The anus is located within the membranous remnant of the tenth segment. In the genitalia of the female, one remarkable peculiarity is observed distally in the eighth tergite of the adult female. At this level, the eighth tergite and the dorsal portion of the intersegmental membrane between the eighth and ninth segments lie superimposed upon one another and unite medially. On one side a condyle and an oblique socket are formed. The condyle of each side projects into the socket of the other side to form a ball-and-socket apparatus. The mechanism disappears proximally in the eighth tergite. The structure is absent in the male.
Studies on the growth of tissues In Vitro
Authors: Willmer E. N.
Published: April 2021

Experiments are described which demonstrate the importance of standardising the coagulum for the growth of tissues in vitro in respect to (a) depth and (b) plasma content, in order to obtain, by daily measurements of the area of the cultures, a true indication of the actual rate of growth of the tissues.
Metabolic Changes Associated with Endocrine Activity and the Reproductive Cycle in Xenopus Laevis
Authors: Zwarenstein H. , Shapiro H. A.
Published: April 2021

Throughout the normal reproductive cycle in Xenopus laevis the serum calcium level is higher in females than in males. The reproductive cycle in females is associated with changes in the serum calcium level and in ovarian activity. In male toads the serum calcium remains remarkably constant except for a slight rise during the breeding season. Captivity first causes a rise and then a steady decline in the serum calcium level of females. Both phases are accompanied by a progressive involution of the ovaries. The serum calcium of males is unaffected by captivity. It is suggested that seasonal variations in the amount of solar radiation and inadequate illumination during captivity are the main agencies influencing serum calcium (through the pituitary and parathyroid glands) and ovarian activity (through the anterior lobe of the pituitary).
Ultraviolet Sensitivity and Spectral Opponency in the Locust
Authors: Osorio D.
Published: April 2021

Intracellular recordings in the medulla of the locust optic lobe reveal units showing u.v. sensitivity and spectral opponency. Previously only a single population of photoreceptors had been recorded in the locust retina, with peak sensitivity from 450—480 nm. Behavioural measurements show that the dorsal light response is elicited only by u.v. light, unlike the optomotor response whose spectral sensitivity is probably attributable to inputs from the green-sensitive cells. The possibility that the cells described may be involved in maintenance of level flight is discussed.
The in vivo Regeneration of Goldfish Rhodopsin and Porphyropsin
Authors: Tsin Andrew T. C. , Flores Janie M.
Published: April 2021

Goldfish with retinas rich in either rhodopsin or porphyropsin were illuminated with bright light and then placed in the dark room to allow visual pigment regeneration. The kinetics of this in vivo pigment regeneration were followed by sampling these animals at regular time intervals. The first-order kinetic rate constant for the initial period of porphyropsin regeneration at 20°C was 8·3 × 10−3 nmol kg−1 body weight min−1 and the half-life of this reaction was 83 min. At 30°C, the rate constant was increased to 1·4 × 10−2nmol kg−1 body weight min−1, yielding a reduced half-life of 49 min. This suggests that the Q10 of porphyropsin regeneration is about 1·7. In goldfish retinas enriched with rhodopsin (62% rhodopsin and 38% porphyropsin), the initial phase of visual pigment regeneration (at 30°C) proceeded at a slower rate (first-order rate constant: 6·5 × 10−3 nmol kg−1 body weight min−1; half-life of reaction = 106 min) than the rate of porphyropsin regeneration. This suggests that the high proportion of rhodopsin in the retina of goldfish held at 30°C is not a direct result of a faster rate of regeneration of rhodopsin than of porphyropsin.
Swim Initiation in the Leech by Serotonin-Containing Interneurones, Cells 21 and 61
Authors: Nusbaum Michael P. , Kristan William B.
Published: April 2021

Two pairs of serotonin-containing neurones, designated cells 21 and 61, were characterized physiologically and anatomically in the hirudinid leeches Macrobdella decora and Hirudo medicinalis. Both of these cells are bilaterally paired interneurones and each cell is weakly electrically coupled to the other serotonin-containing cells both intra- and interganglionically. Cells 21 and 61 are excited polysynaptically by individual identified mechano-sensory neurones. Segmental nerve shock sufficient to elicit an episode of swimming strongly excites cells 21 and 61, which then tend to generate bursts of impulses that are phase-locked to the swim motor pattern. Intracellular stimulation of either cell 21 or cell 61 often causes the initiation of swimming, acting in parallel with the nonserotonergic swim-initiator cell 204. Cells 61 and 204 are also weakly electrically coupled. The latency to swim onset by stimulating cell 21 or 61 is similar to that of cell 204 and different from that of the serotonergic Retzius cell. This result, with those in the accompanying paper (Nusbaum, 1986), suggests that unlike the Retzius cell and similar to cell 204, cells 21 and 61 synaptically contact cells of the swim central pattern generator (CPG).
Spontaneous Locomotor Activity in Arctic Charr Measured by a Computerized Imaging Technique: Role of Brain Serotonergic Activity
Authors: Winberg Svante , Nilsson Göran E. , Spruijt Berry M. , Höglund Urban
Published: April 2021

Using a computerized video-image analysis system, spontaneous locomotor activity was measured in dominant and subordinate individuals of Arctic charr (Salvelinus alpinus) and in individuals treated with inhibitors of serotonin (5-HT) synthesis and re-uptake. Arctic charr were put together in pairs. After 1 week, subordinate individuals were found to have elevated brain levels of 5-hydroxyindoleacetic acid, a major 5-HT metabolite, suggesting an increase in serotonergic activity. The subordinate individuals had significantly lower spontaneous locomotor activity than the dominant fish. Similarly, Arctic charr displayed a significantly reduced locomotor activity when their serotonergic activity was stimulated by the specific 5-HT re-uptake inhibitor zimeldine. In contrast, fish treated with the 5-HT synthesis inhibitor p-chlorophenylalanine showed a significant increase in locomotor activity. Dominant, subordinate and pharmacologically treated fish all had very similar activity rhythms for the 18h test period. Thus, neither the previous social experience nor the pharmacological treatment seemed to affect the diurnal activity rhythm per se. Taken together, these results suggest that the brain serotonergic system inhibits locomotor activity and support the possibility that 5-HT is involved in the inhibition of locomotor activity displayed by subordinate fish.
Adaptations to a Terrestrial Existence by the Robber Crab Birgus Latro: VIII. Osmotic and Ionic Regulation on Freshwater and Saline Drinking Regimens
Authors: Taylor H. H. , Greenaway P. , Morris S.
Published: April 2021

Crabs supplied with deionized water (DIW) and food maintained constant haemolymph osmolality, [Na] and [Cl]. Drinking of 300, 600 or 1000mosmolkg−1 sea water (300SW, 600SW, 1000SW) elevated Na and Cl concentrations, which restabilized by 12 days on the 300SW and 600SW regimens but continued to rise on the 1000SW regimen. [Ca] increased slightly on all regimens. [K] changed only on the 1000SW regimen. Haemolymph [Mg] was poorly regulated on all saline regimens, doubling after 47 days on the 1000SW regimen.

Urine was always isosmotic to haemolymph, had twice the [K] and a lower [Ca]. Changes in urinary ion concentrations paralleled those in the haemolymph, indicating that the antennal organs are unimportant in ionic regulation. Changes in ionic composition of the branchially modified urine (P) reflected drinking water concentrations on a mole-for-mole basis (except for [Mg]), confirming the regulatory role of P. Water and ion budgets indicate reingestion of 70–90% of filtered urine. Branchial ion uptake and reingestion allow variable reclamation of 70–99.9% of filtered Na, Ca, Mg and Cl and 37–96% of K. Crabs drank DIW daily (mean rate, 16.2 g kg−1 day−1) and released P intermittently (intervals ranged from less than 1 to more than 6 days; mean 5.8 g kg−1 day−1). Provision of 300SW and 600SW doubled drinking rate and trebled P output. Intense initial drinking of 1000SW (58.1 g kg−1 day−1) was not maintained. Return to DIW after 1000SW stimulated very high drinking rates initially (119 g kg−1 day−1).

Birgus can vary P composition rapidly and widely (less than 100mosmolkg−1 and 20mmol l−1 [NaCl] to more than 1000mosmolkg−1 and 500mmol l−1 [NaCl] within 1 day) and sometimes produce P that is hyperosmotic to the haemolymph. Production of P hyperosmotic to the drinking water and increased drinking rate permit a gain of osmotically free water to balance evaporation when drinking 300SW and 600SW, but not 1000SW. Adjustments to the volume and composition of the P appear to be more important than ‘behavioural osmoregulation’.
Inhibition of The Respiratory Pattern-Generating Neurons by an Identified Whole-Body Withdrawal Interneuron of Lymnaea Stagnalis
Authors: Inoue T. , Takasaki M. , Lukowiak K. , Syed N. I.
Published: April 2021

Respiration and the whole-body withdrawal are two incompatible behaviors in the freshwater snail Lymnaea stagnalis. Whole-body withdrawal behavior is believed to be higher on the behavioral hierarchy than respiratory behavior. A central pattern generator (CPG) underlies respiratory behavior; whole-body withdrawal is mediated by a network of electrically coupled neurons. In this study, we provide evidence that the behavioral hierarchy between the whole-body withdrawal and the respiratory behaviors is established at the interneuronal level. We demonstrate that an identified whole-body withdrawal interneuron inhibits both muscular and neuronal components of the respiratory behavior in Lymnaea stagnalis.

A pair of identified, electrically coupled interneurons, termed left and right pedal dorsal 11 (L/RPeD11), coordinates the whole-body withdrawal behavior in Lymnaea stagnalis. In the present study, RPeD11 inhibited spontaneously occurring respiratory CPG activity in isolated brain preparations. In addition, electrical stimulation of RPeD11 in a semi-intact preparation also inhibited respiratory CPG interneuron RPeD1.

The synaptic connections between RPeD11 and the respiratory CPG neurons RPeD1 and visceral dorsal 4 (VD4) persisted in the presence of high-Ca2+/high-Mg2+ saline, suggesting the possibility that they may be monosynaptic.

In a semi-intact preparation (lung–mantle, pneumostome and central nervous system), electrical stimulation of RPeD11 induced pneumostome and columellar muscle contractions while inhibiting the activity of RPeD1. Moreover, mechanical stimulation of the respiratory orifice, the pneumostome, excited RPeD11, while its effects on the respiratory CPG neuron (RPeD1) were inhibitory.

To determine the monosynaptic nature of connections between RPeD11 and the respiratory CPG neurons in the intact nervous system, we constructed these synapses in culture. RPeD11 and individual respiratory interneurons were isolated from their respective ganglia and co-cultured under conditions that support neurite outgrowth. Following neuritic overlap, RPeD11 was found to establish inhibitory synapses with the respiratory interneurons, supporting the hypothesis that these synaptic connections are likely to be monosynaptic in the intact central nervous system.
Environmental Acidity and White Muscle Recruitment During Swimming in the Brown Trout (Salmo Trutta)
Authors: Day N. , Butler P. J.
Published: April 2021

Electromyographic recordings show that, for adult brown trout swum up to their critical swimming speed (Ucrit) in a flume at neutral pH, white muscle recruitment occurred when speeds approached 1 body length s−1 (BL s−1) and continued to Ucrit (approximately 2 BL s−1) at both winter (5 °C) and summer (15 °C) acclimation temperatures. However, in the majority of fish swum up to Ucrit at sublethal acidic pH, continuous white muscle recruitment did not occur, although all swam above 1 BL s−1. Any observed electrical activity of the white muscle in these individuals was, at best, intermittent. Consequently, the mean Ucrit of these fish was approximately half that of fish swum at neutral pH. In all fish at sublethal pH, red muscle activity was observed for the whole duration of the exercise period, showing that swimming speeds greater than 1 BL s−1 were achieved largely aerobically. Fish that were chased around a tank at sublethal pH appeared lethargic in their escape response, exhibiting little or no burst swimming. Other observed effects of exposure to sublethal pH, which may have affected swimming capacity, included increases in the resting levels of blood and muscle ammonia, reduced muscle glycogen stores and reduced muscle ion concentrations.
Sexual Signalling in Bladder Grasshoppers: Tactical Design for Maximizing Calling Range
Authors: Van Staaden Moira J. , Römer Heiner
Published: April 2021

Pair formation in the bladder grasshopper (Bullacris membracioides) is by duetting and male phonotaxis. Low-frequency stridulatory signals are emitted by an abdominal resonator in the male and are answered by females using a species-specific time delay. Acoustic transmission in the natural environment was studied using playback of sexual signals over distances of 450 m under two atmospheric conditions (day and night). Upward-refracting sound conditions and a sound shadow zone beyond approximately 50 m prevailed during the day. Acoustic enhancement was demonstrated at night when downward-refracting temperature inversions created a tunnel effect with sound caught between the ground and zones of different temperatures. Transmission conditions are almost ideal at night when the species actually calls; calling distances of 150 m for the male signal in the afternoon increased to 1.5–1.9 km at night, arguably the largest calling distance yet reported for insects. In contrast, female calls transmit over a maximum of 50 m, signifying a marked discrepancy in the active space of sex-specific signals. Transmission distance may, however, be profoundly affected by levels of masking noise. Adaptations to increase the signal range may variously be found in the signal itself, in behaviour patterns or in the sensory system. Here we demonstrate aspects of the first two types of adaptation in the sexual signalling system of a grasshopper in which maximizing the calling range appears to be the major selection pressure, with lesser effects imposed by inter-and intraspecific pressures and by the transmission channel.
The Effect Of Metamorphosis On The Repeatability Of Maximal Locomotor Performance In The Pacific Tree Frog Hyla Regilla
Authors: Watkins Timothy B.
Published: April 2021

Measuring the repeatability of inter-individual differences in locomotor performance is an important first step in elucidating both the functional causes and the ecological consequences of performance variation. Thus, repeatability of whole-animal performance traits provides a crucial link between functional and evolutionary biology. In the present study, repeatability of maximal burst locomotor performance was estimated for a single population of the Pacific tree frog Hyla regilla.

Animals were reared individually from eggs through metamorphosis in the laboratory. Maximum burst swimming speed of tadpoles was measured before metamorphosis (Gosner stage 37) and again at the onset of the metamorphic climax (stage 42). Maximum jump distance was measured on the same individuals as juvenile frogs.

Locomotor performance was repeatable over a 24 h period for both premetamorphic tadpoles and juvenile frogs. Performance was not repeatable across metamorphosis or between any two of the three developmental stages investigated. A high-performance individual at one developmental stage does not necessarily retain that performance advantage at another stage. This lack of repeatability contrasts sharply with several previous studies on non-metamorphosing vertebrates, but concurs with a single previous study on a metamorphosing salamander. Metamorphosis appears to place strict temporal constraints on individual consistency in locomotor ability.
Vascular control in larvalXenopus laevis: the role of endothelial-derived factors
Authors: Schwerte Thorsten , Printz Eva , Fritsche Regina
Published: April 2021

We used novel digital contrasting methods to measure the effects of endothelin-1 (ET-1, 10–6 to 10–8 mol l–1), the nitric-oxide-releasing agent sodium nitroprusside (SNP, 10–2 mol l–1) and Nω-nitro-l-arginine methyl ester hydrochloride (l-NAME, 10–4 mol l–1), a non-selective inhibitor of nitric oxide synthase, on the diameter of tiny arteries and veins of the head in anaesthetized Xenopus laevis tadpoles (stage NF 50–53). Perfusion of the main artery and vein supplying the head with ET-1 caused an immediate, significant and dose-dependent vasoconstriction. While preincubation with l-NAME caused no significant change in vessel diameter, the constriction provoked by subsequent endothelin administration was significantly enhanced. Application of SNP caused a vasodilation that was significant only after preconstriction with ET-1 (10–6 mol l–1). Our results provide strong evidence that the vasculature of developing Xenopus laevis tadpoles (NF stage 50–53) is influenced by endogenously released nitric oxide and endothelin. Vasoactive mediators released from vascular endothelial cells could be particularly important in vascular control in early embryos when the autonomic innervation is undifferentiated, poorly developed or even absent.
The archaeogastropod molluscHaliotis iris: tissue and blood metabolites and allosteric regulation of haemocyanin function
Authors: Behrens Jane W. , Elias John P. , Taylor H. Harry , Weber Roy E.
Published: April 2021

We investigated divalent cation and anaerobic end-product concentrations and the interactive effects of these substances and pH on haemocyanin oxygen-binding (Hc-O2) in the New Zealand abalone Haliotis iris. During 24 h of environmental hypoxia (emersion), d-lactate and tauropine accumulated in the foot and shell adductor muscles and in the haemolymph of the aorta, the pedal sinus and adductor muscle lacunae, whereas l-lactate was not detected. Intramuscular and haemolymph d-lactate concentrations were similar, but tauropine accumulated to much higher levels in muscle tissues. Repeated disturbance and short-term exposure to air over 3 h induced no accumulation of d- or l-lactate and no change in [Ca2+], [Mg2+], pH and O2-binding properties of the native haemolymph.

The haemolymph showed a low Hc-O2 affinity, a large reverse Bohr effect and marked cooperativity. Dialysis increased Hc-O2 affinity, obliterated cooperativity and decreased the pH-sensitivity of O2 binding. Replacing Mg2+ and Ca2+ restored the native O2-binding properties and the reverse Bohr shift. l- and d-lactate exerted minor modulatory effects on O2-affinity. At in vivo concentrations of Mg2+ and Ca2+, the cooperativity is dependent largely on Mg2+, which modulates the O2 association equilibrium constants of both the high-affinity (KR) and the low-affinity (KT) states (increasing and decreasing, respectively). This allosteric mechanism contrasts with that encountered in other haemocyanins and haemoglobins. The functional properties of H. iris haemocyanin suggest that high rates of O2 delivery to the tissues are not a priority but are consistent with the provision of a large O2 reserve for facultatively anaerobic tissues during internal hypoxia associated with clamping to the substratum.
The Co-Ordination of Insect Movements
Authors: Hughes G. M.
Published: April 2021

The effects of limb amputation and the cutting of commissures on the movements of the cockroach Blatta orientalis have been investigated with the aid of cinematography. Detailed analyses of changes in posture and rhythm of leg movements are given. It is shown that quite marked changes occur following the amputation of a single leg or the cutting of a single commissure between the thoracic ganglia. Changes following the amputation of a single leg are immediate and are such that the support normally provided by the missing leg is taken over by the two remaining legs on that side. Compensatory movements are also found in the contralateral legs. When two legs of opposite sides are amputated it has been confirmed that the diagonal sequence tends to be adopted, but this is not invariably true. Besides alterations in the rhythm which this may involve, there are again adaptive modifications in the movements of the limbs with respect to the body. When both commissures between the meso- and metathoracic ganglia are cut, the hind pair of legs fall out of rhythm with the other four legs. The observations on the effects of cutting commissures stress the importance of intersegmental pathways in co-ordination. It is shown that all modifications following the amputation of legs may be related to the altered mechanical conditions. Some of the important factors involved in normal co-ordination are discussed, and it is suggested that the altered movements would be produced by the operation of these factors under the new conditions. It is concluded that the sensory inflow to the central nervous system is of major importance in the co-ordination of normal movement.
A Neuropharmacologically Active Substance from Jellyfish Ganglia
Authors: Barnes W. J. P. , Horridge G. A.
Published: April 2021

A substance which is extractable with acetone from the marginal ganglia of the jellyfish Aurelia causes acceleration of the rhythm of intact ganglia used as test preparations in concentrations of under 50 ganglia/ml., while higher concentrations cause inhibition. As comparable extracts of non-nervous tissue had no effect, the active substance probably originates from nervous tissue. It is distinct from sub-stances extractable from mesogloea. The RF lies near 0·85 in tert.-butanol-methanol-water (40:50:10 by vol.). The chemical nature of the acceleratory substance is unknown though it is certainly none of the known or suspected neurohumours of other organisms. The active substance has no effect on crustacean or clam hearts or upon crustacean hindgut assay preparations but it does accelerate the rhythm of a hydromedusan Phialidium.
Central Blood Pressure and Heart Output in Surfaced and Submerged Frogs
Authors: Shelton G. , Jones D. R.
Published: April 2021

The systemic blood pressure of Rana pipiens and R. temporaria is slightly higher than the pulmocutaneous pressure at systole and much higher at diastole. The pulses differ in shape and a conus component can be seen in the systemic wave. Submersion of the animal causes a fall in systolic pressure in both arches, the diastolic pressure remaining relatively constant. The shape of the pulse wave changes, the conus component being accentuated and visible in recordings from both arches. Heart rate and stroke volume fall during submersion so that after 30 min. under water the minute volume may be 20-50% of the value at the surface. The heart becomes increasingly full of blood. The differences in systemic and pulmocutaneous pressures are explained in terms of resistance, compliance and flow in lung and body circuits. The same general relationships persist during submersion but selective increases in peripheral resistance must occur to maintain the central blood pressure in face of falling heart output.
Water balance across the cuticle of a soil insect
Authors: Galbreath R.A.
Published: April 2021

The water regime in soil commonly approaches equilibrium of water potential with the insects living there. Even under these conditions, non-equilibrium processes have a significant effect on water movement through the cuticle of soil insects. Measurements of water potential on either side of the cuticle of Costelytra zealandica larvae showed that equilibrium is not reached while the insect is alive. There is an active outward flow of water by thermoosmosis associated with the flow of heat from the insect.
The length-tension relationship of the dorsal longitudinal muscle of a leech
Authors: Miller J.B.
Published: April 2021

The length-tension relationship of a preparation of the dorsal body wall of the leech Haemopis sanguisuga was determined.

Passive tension is low except at very long lengths of the preparation, when it rises steeply. It is due mainly to the epidermis present in the preparation.

The active tension curve is very flat, with tension being reduced only at very short and very long lengths. This shape is explained in the context of the myofilament arrangement of the muscle fibres. It may be that thin filaments can form cross-bridges with different thick filaments at different lengths of the preparation.
The uptake of L-glutamate by the central nervous system of the cockroach, Periplaneta americana
Authors: Evans P.D.
Published: April 2021

A concentrative uptake mechanism for L-glutamate with the following characteristics has been identified in the abdominal nerve cord :

The uptake can be divided into Na+-sensitive and Na+-insensitive components. The Na+-sensitive component showed the typical saturation kinetics of a carrier mediate process. It had a V of 15·9 × 10 −6μM/mg wet weight/min and a Km of 0·33 mm. Its magnitude was proportional to the first power of the Na+ concentration of the medium. The uptake was specific for L-di-carboxylic amino acids and was sensitive to the presence of metabolic inhibitors. The Na+-insensitive component was linearly related to the glutamate concentration of the medium.

An isosmotic saline is described for use with the isolated intact abdominal nerve cord of P. americana.
The mechanical properties of the abdominal cuticle of Rhodnius larvae
Authors: Reynolds S.E.
Published: April 2021

The mechanical properties of loops of cuticle cut from the abdomens of 5th instar Rhodnius have been investigated. The cuticle shows pronounced viscoelastic behaviour. Stress-relaxation tests show a continuously falling modulus over a wide range of times after the imposition of a strain. Plasticized samples of cuticle show stress-relaxation curves which are shifted along the time axis towards earlier times by up to ×103. The modulus at any particular time after the imposition of strain is about 10 times lower than that of the unplasticized cuticle. It is concluded that the mechanical properties of this cuticle are determined, at least for maintained stresses, largely by the matrix material. Chitin microfibrils may act as a reinforcing filler for short-term, rapid stresses. The cuticular macromolecules are probably not extensively cross-linked by primary bonds, though secondary interactions between them are probably important in the viscoelastic properties of the cuticle. Plasticization probably involves a change in either the number or the strength of secondary interactions between the cuticle macromolecules, or both.
Studies on Locust Rectum
Authors: Spring J. H. , Phillips J. E.
Published: April 2021

The unidirectional fluxes of 36Cl− and 22Na+ across short-circuited locust recta bathed in a simple NaCl saline were followed with time. Unidirectional fluxes and net flux of 22Na+ to the haemocoel side all remained constant for at least 4 h and were unaffected by either corpora cardiaca homogenate (CC) or cAMP. Both CC and cAMP stimulated influx and net flux of 36Cl− to the haemocoel side. Over the whole time course of the experiment, i.e. both before and after stimulation, net Cl− flux approximately equalled the shortcircuit current (Zgc). Neither CC nor cAMP caused substantial stimulation of or trans-epithelial electropotential difference (PD) if all Cl − in the bathing saline was replaced by either sulphate or nitrate or acetate. Acetate saline sustains Isc, PD and transepithalial resistance (R) at higher levels than does simple Cl-saline. Experiments with Cl-free, SO4-salines suggest that alternate electrogenic transport processes can be slowly turned on when Cl− is absent, provided a complex saline which contains several organic constituents, or simple acetate saline, is present.
The Electrical Constants of the Skeletal Muscle Fibres of the Stick Insect, Carausius Morosus
Authors: Ashcroft Frances M.
Published: April 2021

The electrical constants of the ventral longitudinal muscle fibres of the stick insect Carausius morosus were determined by analysing the low-frequency cable properties of the fibre using short cable theory. At 20 °C in normal Ringer the membrane conductance (Gm) was 0·32 mmho.cm’, the sarcoplasmic conductivity (Gi) was 6·69 mmho/cm and the membrane capacity (Cm) was 12·2 μF/cm2. In this solution the length constant (λ) was 2·13 mm and averaged 130% of the fibre length. Hypertonic ( × 2) Ringers had no significant effect on Gt but increased the membrane conductance by about 35%. The effect of temperature on the electrical constants was also investigated: the temperature coefficient (Q10) of Gm was 1·44 and that of Gi was 1·41. The Q10 of the membrane capacity was1 ·11.
Competition Between Potassium and Rubidium Ions for Penetration of the Midgut of Hyalophora Cecropia Larvae
Authors: Zerahn Karl
Published: April 2021

The midgut of the American silkworm transports potassium actively from blood-side to lumen (Harvey and Nedergaard 1964). The use of radiopotassium to study this process is limited by the short half-life of 42K (12·4 h). 86Rb which has a half-life of 19 days has, therefore, been used in place of potassium on the assumption that Rb and K can substitute for each other. This assumption was tested by Harvey, Haskell & Nedergaard (1968) who showed that the short-circuit current does not change significantly when all K in the bathing solution is substituted by Rb. This experiment does not, in fact, prove that the two ions compete equally. However, Nedergaard and Harvey (1968) measured the net flux of Rb and K by means of absorption spectrophotometry and found that with a K/Rb concentration ratio of 1·1 the mean K/Rb flux ratio was 1·4 (5 determinations). The difference was disregarded and the conclusion made ‘the midgut is unable to distinguish between potassium and rubidium’.
Electrical Characteristics of the Membrane of An Identified Insect Motor Neurone
Authors: Gwilliam G. F. , Burrows M.
Published: April 2021

The electrical properties of the membrane of an identified locust motor neurone, the fast extensor tibiae in the metathoracic ganglion, have been investigated to determine : the distribution of excitable and inexcitable membrane; the impulse initiation zone; and the conduction velocity of the spike in the ganglion and in the axon. The waveform of extracellularly recorded spikes indicates that the transition from inactive to active membrane occurs along the region of the neurite which bears many arborizations within the neuropile. Measurements of the delay between orthodromically or antidromically evoked spikes, recorded at the soma and other points along the neurite, place the impulse initiating zone close to the transition between active and inactive membrane. Within the ganglion, the spike is conducted at different velocities over different parts of the neurite. The average velocity within the ganglion is, however, only about a seventh of that in the axon (0· 54 m.s-1 against 4· 1 m.s-1).
Extracellular Receptor Potentials from the Lateral-Line Organ of Xenopus Laevis
Authors: Kroese Alfons B. A. , Van Den Zalm Johan M. , Van Den Bercken Joep
Published: April 2021

The response of the epidermal lateral-line organ of Xenopus laevis to stimulation was studied by recording extracellular receptor potentials from the hair cells in single neuromasts in isolated preparations. One neuromast was stimulated by local, sinusoidal water movements induced by a glass sphere positioned at a short distance from the neuromast. The amplitudes of the extracellular receptor potentials were proportional to the stimulus amplitude over a range of 20 dB. The phase of the extracellular receptor potentials with respect to water displacement was independent of the stimulus amplitude. With large stimulus amplitude, and stimulus frequencies between 0·5 Hz and 2 Hz, the extracellular receptor potentials, and responses of single afferent nerve fibres, showed a phase lead of 1 ·2 π radians with respect to water displacement, i.e. they were almost in phase with water acceleration. It is concluded that under conditions of stimulation with small-amplitude water movements, the hair cells respond to sensory hair displacement, whereas under conditions of stimulation with large-amplitude water movements they respond to sensory hair velocity.
The Scaling of the Thermal Inertia of Lizards
Authors: Bell C. J.
Published: April 2021

The thermal status of an animal is the result of a combination of physical and physiological factors. In poikilotherms, it may be possible to separate these more easily than in homeotherms, where the presence of control mechanisms can mask the processes occurring. The thermal time constant of a poikilotherm has been shown to be a useful measure of its thermal behaviour, and to vary with the physiological status of the animal. A simple model is developed to show how the thermal time constant is related to the physics of heat exchange. The derived thermal time constant is shown to scale as body mass raised to the power 2/3, and this is compared with results on lizards heating and cooling in water, taken from the literature.

When heat exchange in air is considered, the concept of boundary layer resistance leads to a useful simplification. The thermal time constants in air taken from the literature show that the boundary layer resistance is approximately constant.
Dynamic Effects on the Product Distribution of the Photoreaction of s-cis-1,3-Butadiene: A Nonadiabatic Molecular Dynamics Study
Authors: Matsubara Toshiaki
Published: April 2021

A dynamic factor that determines the product distribution of the photochemical reaction of S2-excited s-cis-1,3-butadiene is examined using the nonadiabatic molecular dynamics method. The excited S2 state of s-cis-1,3-butadiene is relaxed via the S2/S1 and subsequent S1/S0 conical intersections (CIs). After the S1/S0-CI, several products including the trans and cis isomers, cyclobutene, bicyclobutane, and the methylenecyclopropyl diradical, are generated by six identified reaction channels. Channel 6 is another new channel leading to bicyclobutane. The ratio of each product is understood in terms of the allowed range of the ∠C–C–C–C dihedral angle at the S1/S0-CI for each product. When 2,3-dimethyl-1,3-butadiene is used instead of 1,3-butadiene, the product ratio changes because due to the dynamic effects of the Me groups the rotational motion around the central C–C bond slows down and consequently the fluctuation of the ∠C–C–C–C dihedral angle at the S1/S0-CI becomes smaller. Thus, our molecular dynamics simulations show that the fluctuation of the ∠C–C–C–C dihedral angle is an important factor to determine the product distribution.
Do Injury-Resistant Runners Have Distinct Differences in Clinical Measures Compared with Recently Injured Runners?
Authors: DILLON SARAH , BURKE AOIFE , WHYTE ENDA F. , O’CONNOR SIOBHÁN , GORE SHANE , MORAN KIERAN A.
Published: April 2021

Introduction

Although lower extremity muscle strength, joint motion, and functional foot alignment are commonly used, time-efficient clinical measures that have been proposed as risk factors for running-related injuries, it is unclear if these factors can distinguish injury resistance in runners.

Purpose

This study compares clinical measures, with consideration of sex, between recently injured runners (3 months to 1 yr prior), those with a high level of injury resistance who have been uninjured for at least 2 yr, and never-injured runners.

Methods

Averaged bilateral values and between-limb symmetry angles of lower limb isometric muscle strength, joint motion, navicular drop, and foot posture index (FPI) were assessed in a cohort of recreational runners, and their injury history was recorded. Differences in clinical measures between injury groupings were examined, with consideration of sex.

Results

Of the 223 runners tested, 116 had been recently injured, 61 had been injured >2 yr ago and were deemed to have acquired reinjury resistance, and 46 were never injured. Plantarflexion was greater in both recently injured (P = 0.001) and acquired reinjury resistance runners (P = 0.001) compared with never-injured runners. Recently injured runners displayed higher hip abduction strength compared with never-injured runners (P = 0.019, η
2 = 0.038, small effect size). There were no statistically significant differences in the remaining measures between the injury groupings. With the exception of FPI, there was no interaction between sex and injury grouping for any of the measures.

Conclusion

Commonly used clinical measures of strength, joint motion, and functional foot alignment were not superior in injury-resistant runners compared with recently injured runners, questioning their relevance in identifying future injury resistance of runners.
Effect of Aerobic Exercise-induced Weight Loss on the Components of Daily Energy Expenditure
Authors: BROSKEY NICHOLAS T. , MARTIN CORBY K. , BURTON JEFFREY H. , CHURCH TIMOTHY S. , RAVUSSIN ERIC , REDMAN LEANNE M.
Published: April 2021

Introduction

Exercise usually results in less weight loss than expected. This suggests increased energy intake and/or deceased expenditure counteract the energy deficit induced by exercise. The aim of this study was to evaluate changes in components of daily energy expenditure (doubly labeled water and room calorimetry) after 24 wk of exercise training with two doses of aerobic exercise.

Methods

This was an ancillary study in 42 (29 women, 13 men) sedentary, middle-age (47.8 ± 12.5 yr) individuals with obesity (35 ± 3.7 kg·m−2) enrolled in the Examination of Mechanisms of Exercise-induced Weight Compensation study. Subjects were randomized to three groups: healthy living control group (n = 13), aerobic exercise that expended 8 kcal·kg−1 of body weight per week (8 KKW, n = 14), or aerobic exercise that expended 20 kcal per kilogram of weight per week (20 KKW, n = 15). Total daily energy expenditure (TDEE) was measured in free-living condition by doubly labeled water and in sedentary conditions in a metabolic chamber over 24 h (24EE). Energy intake was calculated over 14 d from TDEE before and after the intervention using the intake-balance method.

Results

Significant weight loss occurred with 20 KKW (−2.1 ± 0.7 kg, P = 0.04) but was only half of expected. In the 20 KKW group free-living TDEE increased by ~4% (P = 0.03), which is attributed to the increased exercise energy expenditure (P = 0.001), while 24EE in the chamber decreased by ~4% (P = 0.04). Aerobic exercise at 8 KKW did not induce weight change, and there was no significant change in any component of EE. There was no significant change in energy intake for any group (P = 0.53).

Conclusions

Structured aerobic exercise at a dose of 20 KKW produced less weight loss than expected possibly due to behavioral adaptations leading to reduced 24EE in a metabolic chamber without any change in energy intake.
Exploring advanced nursing practice in stroke services: a scoping review
Authors: Bailey Joe , Tod Angela , Robertson Steve , King Rachel
Published: April 2021

Background:

Stroke care is becoming increasingly reliant on advanced nursing practice (ANP); however, little is known about these roles within the stroke specialty.

Aims:

To explore the current knowledge of advanced nursing practice in stroke services internationally, specifically, the conceptualisation of ANP and the rationale for its implementation.

Methods:

Arskey and O'Malley's scoping review methodology was employed, and six academic databases were used.

Findings:

Two key themes were identified; ‘role development’ and ‘four pillars of advanced practice’. The review identifies that ANP is implemented primarily to provide acute stroke care.

Conclusions:

Current research does not clarify the rationale for implementing these posts or how ANP is conceptualised. This review does identify that stroke ANP incorporates the four pillars of advanced practice (clinical, research, leadership and education) and was implemented to improve the quality of stroke care. Barriers and facilitators to implementation were also identified.
The legal, ethical and welfare implications of feeding vegan diets to dogs and cats
Authors: Bennett Lauren Katie
Published: April 2021

Veganism is on the rise both in humans and in companion animals, with many owners citing animal welfare as their primary reason for adopting a vegan lifestyle. Feeding vegan diet to dogs and cats significantly impacts their welfare as it puts them at undue risk of developing diet-induced disorders, leaving owners liable to prosecution if they are unwilling to adhere to expert recommendations. As commercial vegan diets are a relatively new phenomena, more research needs to be conducted to understand the full effects. In the meantime, veterinary professionals should continue to educate owners on suitable diets based on the individual's requirements.
Optimising the feline environment
Authors: Heath Sarah
Published: April 2021

In this workshop Sarah Heath explored the five pillars of feline environmental needs.
The dominantly expressed class II molecule from a resistant MHC haplotype presents only a few Marek’s disease virus peptides by using an unprecedented binding motif
Authors: Halabi Samer , Ghosh Michael , Stevanović Stefan , Rammensee Hans-Georg , Bertzbach Luca D. , Kaufer Benedikt B. , Moncrieffe Martin C. , Kaspers Bernd , Härtle Sonja , Kaufman Jim
Published: April 2021

Viral diseases pose major threats to humans and other animals, including the billions of chickens that are an important food source as well as a public health concern due to zoonotic pathogens. Unlike humans and other typical mammals, the major histocompatibility complex (MHC) of chickens can confer decisive resistance or susceptibility to many viral diseases. An iconic example is Marek’s disease, caused by an oncogenic herpesvirus with over 100 genes. Classical MHC class I and class II molecules present antigenic peptides to T lymphocytes, and it has been hard to understand how such MHC molecules could be involved in susceptibility to Marek’s disease, given the potential number of peptides from over 100 genes. We used a new in vitro infection system and immunopeptidomics to determine peptide motifs for the 2 class II molecules expressed by the MHC haplotype B2, which is known to confer resistance to Marek’s disease. Surprisingly, we found that the vast majority of viral peptide epitopes presented by chicken class II molecules arise from only 4 viral genes, nearly all having the peptide motif for BL2*02, the dominantly expressed class II molecule in chickens. We expressed BL2*02 linked to several Marek’s disease virus (MDV) peptides and determined one X-ray crystal structure, showing how a single small amino acid in the binding site causes a crinkle in the peptide, leading to a core binding peptide of 10 amino acids, compared to the 9 amino acids in all other reported class II molecules. The limited number of potential T cell epitopes from such a complex virus can explain the differential MHC-determined resistance to MDV, but raises questions of mechanism and opportunities for vaccine targets in this important food species, as well as providing a basis for understanding class II molecules in other species including humans.