bluuebunny/crossref_metadata_2025_split huggingface dataset:
Male Accessory Gland Factors Elicit Change From ‘Virgin’ to ‘Mated’ Behaviour in the Female Corn Earworm Moth Helicoverpa Zea
Authors: Kingan Timothy G. , Thomas-Laemont Patricia A. , Raina Ashok K. 
Published: April 2021

ABSTRACT
After mating, the females of many species of moths become depleted of sex pheromone, calling behaviour is terminated, and they become transiently or permanently unreceptive to additional matings. In the corn earworm moth, Helicoverpa zea, we have found that the male accessory gland/duplex is required for evoking the post-mating depletion of sex pheromone but apparently not for the cessation of calling. The latter change requires the receipt of a spermatophore or a chemical messenger derived from non-accessory gland/duplex sources. Desalted extracts of combined accessory glands and duplexes caused a depletion of pheromone in injected females. Proteinaceous components in extracts purified by fractionation in cation-exchange cartridges and by reverse-phase high-performance liquid chromotography retain their pheromonostatic activity. In addition, this fractionated material shuts off calling behaviour and prevents mating in injected females, raising the possibility that redundant mechanisms exist in eliciting the different components of ‘mated’ behaviour.
Stimulus–Secretion Coupling In Excitable Cells: A Central Role For Calcium
Authors: Cheek Timothy R. , Barry Victoria A. 
Published: April 2021

ABSTRACTSecretion of vesicular contents by exocytosis is a common feature of neuroendocrine secretory cells such as adrenal chromaffin cells and PC12 cells. Although it is clear that in these cells an elevation in intracellular calcium concentration, [Ca2+]i, is the triggering event that induces secretion, recent studies using video-imaging, patch-clamp and flash photolysis techniques have all indicated that the Ca2+ signal that triggers secretion is in fact very complex, with the subcellular distribution of Ca2+ being of particular importance along with the magnitude of the rise.It has become evident that Ca2+ signals with different spatial profiles can be triggered in the same cell by a given stimulus, depending upon the nature of the Ca2+ signalling pathway activated, and that this ability to be able to vary the method of delivery of Ca2+ into the cell is important physiologically, because it provides a means of obtaining differential activation of Ca2+-dependent processes.
Imaging Calcium Waves in Eggs and Embryos
Authors: Gillot Isabelle , Whitaker Michael 
Published: April 2021

ABSTRACT
Sea urchin eggs and those of most other deuterostomes are activated at fertilization by an increase in cytoplasmic free calcium concentration ([Ca2+]i) that triggers the onset of the embryonic cell division cycles. We can image the calcium wave using fluorescent calcium indicator dyes and confocal microscopy. There are two components to the [Ca2+]i increase at fertilization. The first is due to a rapid calcium influx caused by a calcium action potential; this leads to a small increase in [Ca2+]i just beneath the plasma membrane with spherical symmetry. After a latent period of some 15s, there is a second large and rapid increase in [Ca2+]i localized to the region of sperm–egg contact: during the latent period [Ca2+]i does not change but within 1s of the end of the latent period [Ca2+]i reaches 2 μmol l-1. The calcium wave then spreads across the egg with a velocity of 5 μms-1. Behind the advancing wavefront, the calcium concentration is uniformly high, even within the egg nucleus, though there are no indications that intranuclear calcium concentration differs from [Ca2+]i. [Ca2+]i falls uniformly towards resting levels over the next 500s. In cases where there is an apparent inhomogeneity in [Ca2+]i in either the cortex or the nucleus, we find that the calcium indicator dye is inhomogeneously distributed. This appears to be due to uptake of the indicator dye (Fluo-3), probably into mitochondria. The artefact can be avoided by using a dextran-conjugated dye.
The Effect of Graded Methaemoglobin Levels on the Swimming Performance of Chinook Salmon (Oncorhynchus Tshawytscha)
Authors: Brauner C. J. , Val A. L. , Randall D. J. 
Published: April 2021

ABSTRACT
Nitrite oxidizes haemoglobin (Hb) to methaemoglobin (MetHb), which is unable to bind oxygen. Nitrite exposure can therefore be used as a tool to manipulate the oxygen-carrying capacity of the blood without changing haematocrit. The objective of this study is to examine the relationship between the critical swimming velocity (Ucrit) and the functional haemoglobin concentration ([Hb]) of the blood in adult chinook salmon. Functional [Hb] was reduced by increasing MetHb levels through intraperitoneal administration of a mass-dependent volume of sodium nitrite. In resting fish, MetHb levels were found to stabilize at 25% of total [Hb] 3h after the injection of 30mgkg−1 sodium nitrite. Methaemoglobin levels increased in proportion to the amount of sodium nitrite injected and reached a maximum (following the injection of 90mgkg−1 sodium nitrite) of 51.8% in resting fish and 72% in fish forced to swim to Ucrit. At 60 and 90mgkg−1 sodium nitrite, MetHb formation was greater in exercised than in resting fish. A second-order regression revealed that Ucrit was virtually independent of functional [Hb] between 51 and 100% of control functional [Hb], but was positively correlated with functional [Hb] below 51% of total [Hb] (4.5 g dl−1). The insensitivity of Ucrit to a functional [Hb] greater than 51% may be partly due to the exponential increase in aerobic metabolism required to provide the power to overcome hydrodynamic drag at higher water velocities. There were no significant changes in intraerythrocytic organic phosphate (adenylates and guanylates) concentrations standardized to [Hb] in swimming or resting fish over the range of MetHb levels induced in this study. Fish may encounter nitrite naturally; if MetHb levels become severely elevated as a result, swimming ability will be significantly impaired.
Effects of Temperature on Mitochondria From Abalone (Genus Haliotis): Adaptive Plasticity and its Limits
Authors: Dahlhoff Elizabeth , Somero George N. 
Published: April 2021

ABSTRACT
The effects of temperature on mitochondrial oxygen consumption, membrane fluidity and cytochrome c oxidase activity were measured for five species of eastern Pacific abalone (genus Haliotis) found at different latitudes and tidal heights. Mitochondria were isolated from freshly collected individuals and from specimens that had been acclimated in the laboratory to temperatures spanning the extremes of each species’ known habitat temperature range. The temperatures at which Arrhenius plots of respiration rate of mitochondria from freshly collected abalone exhibited sharp breaks in slope were found to correlate with the habitat temperature at the time of capture of each species. Membranes isolated from freshly collected abalone living at warm temperatures (Haliotis cracherodii and H. corregata) were significantly less fluid (as determined by the fluorescence polarization of the probe 1,6-diphenyl 1,3,5-hexatriene) than were membranes from species captured at cooler temperatures (H. rufesens and H. kamtschatkana kamtschatkana). Laboratory acclimation significantly shifted the temperature of mitochondrial thermal inactivation in an adaptive manner in the eurythermal species, H. fulgens, H. corregata and H. rufesens, but did not alter this property significantly for mitochondria from the stenothermal species, H. k. kamtschatkana. Laboratory acclimation resulted in temperature-compensatory changes in membrane fluidity in all species except H. rufesens. The temperatures at which cytochrome c oxidase activity was inactivated also shifted in an adaptive manner in some species. Acclimation of mitochondrial respiration, membrane fluidity and cytochrome c oxidase activity occurred only over the ranges of temperature at which each species is common, suggesting that there is a relationship between acclimatory ability and the biogeographical distribution of congeneric species.
Differential Effects of Acetylcholine on Coronary Flow in Isolated Hypothermic Hearts From Rats and Ground Squirrels
Authors: Burlington Roy F. , Milsom William K. 
Published: April 2021

ABSTRACT
This study was designed to determine whether cholinergic receptors are operative in the coronary vessels of a hibernating species (golden mantled ground squirrel, Spermophilus lateralis) and a nonhibernating species (rat, Rattus norvegicus) under normothermic and hypothermic conditions. Coronary flow and left ventricular systolic pressure were measured in isolated perfused hearts from squirrels at 37, 20 or 7°C and from rats at 37 and 20°C. During cooling, rat hearts became arrhythmic and failed between 15 and 12°C. Squirrel hearts remained functional at 7°C. Bolus injections of acetylcholine (&gt;1.0 μg) caused significant coronary vasoconstriction in rat hearts at 37 and 20°C. Similar treatment caused mild coronary vasodilation in squirrel hearts at both temperatures. Squirrel hearts did not respond to acetylcholine at 7°C. The responses in both species were blocked by atropine. Rat coronary vessels appear to contain muscarinic constrictor receptors similar to those described in humans, sheep, cattle and pigs. The coronary vessels of squirrels, by contrast, do not. In this latter species there appears to be a preponderance of muscarinic (possibly endothelial-relaxing-factor-linked) dilator receptors. Given that acetylcholine acts only as a mild vasodilator at higher temperatures in squirrels, parasympathetic regulation of coronary flow in the squirrel heart is unlikely, especially during hibernation.
Efficiency of Energy Conversion During Sinusoidal Movement of Red Muscle Fibres from the Dogfish Scyliorhinus Canicula
Authors: Curtin N. A. , Woledge R. C. 
Published: April 2021

ABSTRACT
Bundles of red myotomal muscle fibres isolated from dogfish were electrically stimulated at 12°C. Peak twitch force was 54% of that produced by a brief isometric tetanus. Relaxation was slower than in white fibres, but much faster than would be expected for the tonic fibres found in amphibian muscle. These two results indicate that the red fibres in dogfish are slow, but not tonic, in their behaviour.
Net work output and heat production were measured during complete cycles of sinusoidal movement. The following variables were kept constant: peak-to-peak movement, about 7% of the muscle fibre length; tetanus duration, 33% of the mechanical cycle time; stimulus frequency, 40Hz. The frequency of movement and the timing of the stimulation were varied for each preparation to find the conditions optimal for power output and those optimal for efficiency (the ratio of net work output to total energy output as heat+work). To achieve either maximum power or maximum efficiency, the tetanus must start while the muscle fibres are being stretched, before the beginning of the shortening part of the mechanical cycle. The highest power output was produced during movement at 1.02Hz. The highest efficiency, 0.507±0.045 (±S.E.M., N=9), was at 0.61–0.95Hz. The efficiency is higher than that previously measured during sinusoidal movement of white fibres; the difference, 0.095±0.045 (±S.E.M. of the difference, d.f. 20), is statistically significant at the 5% level.
Vagal Influence on Heart Rate in Hibernating Ground Squirrels
Authors: Milsom William K. , Burlington Roy F. , Burleson Mark L. 
Published: April 2021

ABSTRACT
The heart rate of anesthetized golden mantled ground squirrels (Spermophilus lateralis) falls from 372±20 to 37±9beatsmin−1 during hibernation at 7°C body temperature. Heart rate in the hibernating animals often waxed and waned in a fashion that was not clearly linked to the breathing pattern. Similar observations have been made on unanesthetized ground squirrels. Under anesthesia, the effects of vagotomy were small in both euthermic and hibernating animals and led to a 6–8% increase in heart rate. Vagotomy also eliminated the cyclic fluctuations of heart rate in hibernating animals exhibiting this phenomenon. The post-vagotomy heart rate exhibited by these individuals suggested that both sympathetic excitation and parasympathetic depression were involved in producing these cyclic changes. Vagal stimulation reduced mean heart rate by at most 60–80% in euthermic and hibernating animals. The strength of the stimulus required to elicit a maximal response in the hibernating animals was 35–45% greater than that required in euthermic animals. Comparisons of mean heart rates obtained from euthermic and hibernating animals which were vagotomized, intact or stimulated to produce a maximum bradycardia produced temperature quotients of 2.21, 2.15 and 2.31, respectively. In this species, both resting vagal tone and the effects of vagal stimulation decrease in parallel with decreasing temperature over the range studied.
A Method For Long-Term Multiple-Channel Recording of Oxygen Consumption in Aquatic Animals
Authors: Nordtug Trond , Olsen Anders Johny 
Published: April 2021

ABSTRACT
The objective of the present work has been to develop a method for measuring the rate of oxygen consumption on a routine basis during toxicity testing and environmental monitoring. This requires a method that is reliable over long periods and can be used with a minimum of maintenance work in a variable environment. The system should consist of a compact unit easily transported and available at a reasonable cost. Visual updated records of the oxygen consumption should be available at all times.
Running Springs: Speed and Animal Size
Authors: Farley Claire T. , Glasheen James , Mcmahon Thomas A. 
Published: April 2021

ABSTRACT
Trotting and hopping animals use muscles, tendons and ligaments to store and return elastic energy as they bounce along the ground. We examine how the musculoskeletal spring system operates at different speeds and in animals of different sizes. We model trotting and hopping as a simple spring-mass system which consists of a leg spring and a mass. We find that the stiffness of the leg spring (kleg) is nearly independent of speed in dogs, goats, horses and red kangaroos. As these animals trot or hop faster, the leg spring sweeps a greater angle during the stance phase, and the vertical excursion of the center of mass during the ground contact phase decreases. The combination of these changes to the spring system causes animals to bounce off the ground more quickly at higher speeds.
Analysis of a wide size range of animals (0.1–140kg) at equivalent speeds reveals that larger animals have stiffer leg springs (kleg∝M0.67, where M is body mass), but that the angle swept by the leg spring is nearly independent of body mass. As a result, the resonant period of vertical vibration of the spring-mass system is longer in larger animals. The length of time that the feet are in contact with the ground increases with body mass in nearly the same way as the resonant period of vertical vibration.
Switching in the activity state of an interneuron that controls coordination of the hearts in the medicinal leech (Hirudo medicinalis)
Authors: Gramoll S. , Schmidt J. , Calabrese R. L. 
Published: April 2021

ABSTRACT
The rhythmically active heart interneuron HN(5) in the medicinal leech exhibits two distinct activity states, which have been associated with different coordination states of the two hearts. During the active state, it discharges high-frequency bursts of action potentials interrupted by rhythmic inhibitory input from other interneurons. In the inactive state, the same cell receives rhythmic inhibition but the membrane potential remains subthreshold between these volleys, producing few or no action potentials. We investigated differences in the membrane properties of the cell during the active and inactive states. The membrane potential in the active state oscillates on average between about -56±6 mV (S.D.) and -45±7 mV; the mean oscillation amplitude is 11±4 mV. In the inactive state, the membrane potential oscillates on average between -58±6 mV and -55±6 mV with a mean amplitude of 3±1 mV. The overall conductance of an HN(5) interneuron during the active state is approximately 10 nS lower than that during the inactive state, indicating that an outward current is turned off during the active state or turned on during the inactive state. This outward current is not voltage-dependent in the range -80 mV to -10 mV, as shown in voltage-clamp experiments by a linear current–voltage relationship. The reversal potential of this current is approximately -60 mV, indicating that chloride or potassium ions underlie the current. Using dynamic-clamp, we show that by adding an artificial current with a linear voltage-dependence (leak conductance) to an HN(5) interneuron (conductance 15 nS, reversal potential -60 mV), the cell can be transferred from its active to its inactive state.
Ultraviolet photoreception contributes to prey search behaviour in two species of zooplanktivorous fishes
Authors: Browman Howard I. , Novales-Flamarique Iñigo , Hawryshyn Craig W. 
Published: April 2021

ABSTRACT
We tested the hypothesis that ultraviolet photoreception contributes to prey search in small juvenile rainbow trout (Oncorhynchus mykiss) and pumpkinseed sunfish (Lepomis gibbosus) while foraging on Daphnia pulex. Small individuals of these species are ultraviolet-photosensitive zooplanktivores. For both species, prey pursuit distances and angles were larger under full-spectrum illumination than under ultraviolet-absent illumination. The same was true for the distances and angles associated with repositioning movements (i.e. those not leading to the location of a prey item). Thus, ultraviolet photoreception contributes to prey search and detection in these fishes. We argue that the most likely mechanism underlying this enhancement of prey search abilities is improved target contrast.
Down-regulation of red blood cell β-adrenoreceptors in response to chronic elevation of plasma catecholamine levels in the rainbow trout
Authors: Gilmour Kathleen M. , Didyk Nicole E. , Reid Steve G. , Perry Steve F. 
Published: April 2021

ABSTRACT
In many teleost fish, including the rainbow trout, Oncorhynchus mykiss, catecholamines are mobilized into the blood in situations when enhanced oxygen transport is necessary, such as hypoxia, anaemia, hypercapnia and strenuous exercise (see review by Thomas and Perry, 1992). These hormones initiate a series of integrated physiological responses that optimize cardiovascular and respiratory functions (see reviews by Perry and Wood, 1989; Randall and Perry, 1992; Thomas and Perry, 1992). Stimulation of red blood cell β-adrenoreceptors leads to the activation of a red blood cell membrane Na+/H+ antiporter which extrudes protons in exchange for plasma Na+, thereby elevating intracellular pH (pHi) (Baroin et al. 1984; Cossins and Richardson, 1985; see review by Nikinmaa, 1992). The binding of catecholamines to - βadrenoreceptors, which are coupled to adenylate cyclase, engenders the formation of cyclic AMP. This second messenger, in turn, presumably initiates a phosphorylation cascade which ultimately activates the Na+/H+ antiporter. Erythrocyte alkalization can increase haemoglobin oxygen-binding affinity and capacity via the Bohr and Root effects, thus increasing the ability of the blood to transport oxygen (Tufts and Randall, 1989; see also reviews by Nikinmaa and Tufts, 1989; Perry and Wood, 1989; Randall and Perry, 1992; Thomas and Perry, 1992).
Two distinct receptors are activated by arecoline on cockroach sixth abdominal ganglion DUM neurones
Authors: Tribut F. , Duval A. , Lapied B. 
Published: April 2021

ABSTRACT
During the last decade, extensive biochemical and electrophysiological studies have been performed to characterize the pharmacological properties of cholinergic receptors of insect neurone somata (Sattelle, 1985; Breer and Sattelle, 1987; Benson, 1992). Although most of these studies have been focused on the pharmacological characterization of the cell body nicotinic receptors (Lane et al. 1982; Harrow and Sattelle, 1983; David and Sattelle, 1984; Benson, 1992), evidence for a population of acetylcholine (ACh) receptors exhibiting muscarinic and ‘mixed’ (nicotinic/muscarinic) properties has been reported on insect neurone somata (Benson and Neumann, 1987; Knipper and Breer, 1988; Benson, 1989, 1992, 1993; Trimmer and Weeks, 1989; David and Pitman, 1990, 1992, 1993). One group of insect neurones, called dorsal unpaired median (DUM) neurones, expresses functional cholinergic receptors that differ from the classic vertebrate ACh receptors in that, although DUM neurones were sensitive to ACh, the nicotinic and/or muscarinic nature of these receptors has not been resolved since the cholinergic antagonists α-bungarotoxin and atropine were relatively ineffective in blocking the ACh response (Goodman and Spitzer, 1980; Lane et al. 1982; Lapied et al. 1990). However, using a range of cholinergic antagonists known to be selective for vertebrate ACh receptors, it has recently been possible to demonstrate the diversity of functional ACh receptors; these include nicotinic, ‘mixed’ and muscarinic receptors mediating specific responses elicited by different cholinergic agonists, such as nicotine, muscarine, oxotremorine and McN-A-343, on both isolated and in situ DUM neurones (Lapied et al. 1990, 1992; Bai et al. 1992). Extending these studies, we report in this paper that another cholinergic ligand, arecoline, which is known to act preferentially as a muscarinic agonist in vertebrate preparations (Wess et al. 1990), induced a complex response mediated by both nicotinic and muscarinic receptors on DUM neurones.
Effects of zinc on the kinetics of branchial calcium uptake in freshwater rainbow trout during adaptation to waterborne zinc
Authors: Hogstrand C. , Wilson R. W. , Polgar D. , Wood C. M. 
Published: April 2021

ABSTRACT
The effects of sublethal waterborne Zn2+ (150 µg l-1=2.3 µmol l-1) on the kinetics of unidirectional Ca2+ influx were studied in juvenile freshwater rainbow trout during chronic exposure (60 days) at a water [Ca2+] of 1.0 mmol l-1. An unexposed group held under identical conditions served as control. The presence of Zn2+ in the water increased the apparent Km for Ca2+ influx by up to 300 % with only a small inhibitory effect (35 % at most) on the maximum rate of uptake (Jmax). These results, in combination with earlier data showing that Ca2+ competitively inhibits Zn2+ uptake, suggest that Zn2+ and Ca2+ compete for the same uptake sites. Acute withdrawal of Zn2+ after 3 h of exposure resulted in a 23-fold reduction in Km for Ca2+, but a persistent small depression of Jmax. During prolonged exposure to Zn2+, the apparent Km for Ca2+ remained greatly elevated and Jmax remained slightly depressed. The actual Ca2+ influx in hard water ([Ca2+]=1.0 mmol l-1) decreased marginally and paralleled the small changes in Jmax. The increases in apparent Km had a negligible influence on the actual Ca2+ influx because Km values (38–230 µmol l-1), even when elevated by Zn2+, remained below the water [Ca2+] (1000 µmol l-1). Rainbow trout exposed to Zn2+ exhibited a slower rate of protein synthesis in the gills (measured on day 23) and an increased tolerance to Zn2+ challenge (measured on both days 27 and 50). Unidirectional Zn2+ influx, measured at the end of the exposure period, was significantly reduced in the Zn2+-exposed fish. There were no changes in hepatic or branchial Zn2+, Cu2+ or metallothionein concentrations. We hypothesize that, during exposure to sublethal [Zn2+] in hard water, the fish may change the Km for a mutual Ca2+/Zn2+ carrier so as to reduce markedly Zn2+ influx without greatly altering Ca2+ influx. This reduced Zn2+ influx, rather than metallothionein induction, may be the basis of adaptation to elevated concentrations of waterborne Zn2+.