bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diel Changes in Potassium Activity in the Haemolymph of the Cockroach Leucophaea Maderae
Authors: Lettau Janine , Foster W. A. , Harker J. E. , Treherne J. E. 
Published: April 2021

ABSTRACT
A technique is described for continuous measurement, with ion-selective microelectrodes, of K+ and Na+ activity in the blood of a free-walking cockroach Leucophaea maderae(Fab.).Measurements can be made for periods of up to 96 h. In LD 16:8, there is a marked and consistent pattern in the diel variation of K+ activity, with minima 1 h before dusk and 2 h after dawn. The mean diel range in K+ activity covers a drop of 67 % below the maximum daily value. The maximum range in K+ activity for an individual cockroach in 24 h was from 4·5 to 25·0 mm-K+. Simultaneous records of K+ activity and locomotor activity show that the first minimum in K+ activity occurs 1–2 h before the main, sharp peak in locomotor activity at dusk, and the second minimum 1–3 h after the subsidiary, broad peak in locomotor activity at dawn. Diel fluctuations in whole-blood potassium concentration follow a roughly similar pattern to the K+ activity changes. Comparison of the concentration and activity changes allows some speculations about the diel movements of potassium within the blood. Diel fluctuations in Na+ activity show no clear overall pattern.
The Swimming of Nymphon Gracile (Pycnogonida): the Vertical Lift Forces Generated While Swimming at Constant Depth
Authors: Morgan Elfed , Hayes Stephen V. 
Published: April 2021

ABSTRACT
The vertical lift forces generated by the legs of Nymphon while swimming at constant depth have been estimated graphically using drag constants determined by a sedimentation method. Drag both normal and tangential to the different segments of the leg has been considered. When holding station Nymphon characteristically employs a low elevation beat in which the upward force produced during the power stroke of each leg only just exceeds the predominantly downward force generated during the recovery. An upward lift component is also produced late during the recovery stroke. The legs beat in a vertical plane and an investigation of the moments at the joints of the leg suggests that much of the power stroke is gravity assisted. The upward lift produced by all eight legs agreed fairly well on average with the sinking force due to the animal ‘s weight in water, and the vertical lift fluctuates rhythmically throughout the leg beat cycle. The relationship between the swimming gait and the amplitude of these fluctuations has been investigated. During the gait most frequently used by the animal fluctuations in vertical lift were found to be minimal.
The Swimming of Nymphon Gracile (Pycnogonida): The Energetics of Swimming At Constant Depth
Authors: Morgan Elfed 
Published: April 2021

ABSTRACT
The mechanical power required by Nymphon for swimming at constant depth has been calculated from drag forces acting on the legs. For an adult male this was found to be 3·4 W kg. Only about 60 % of this is used to support the animal’s weight in water. The metabolic rate fluctuates spontaneously over a tidal cycle, being greatest during the ebb-tide period. The mean rate of oxygen consumption during the animals least active phase was found to be about 0·1 µl O2 mg−1 h−1. The total carbohydrate and lipid immediately available for combustion have been estimated at 4·64 and 16 µg/mg wet wt respectively. These quantities should be adequate for about 42 h periodic swimming in an adult Nymphon.
Electrophysiology and Luminescence of An Ophiuroid Radial Nerve
Authors: Brehm Paul 
Published: April 2021

ABSTRACT
All-or-none single unit spikes were recorded from an ophiuroid radial nerve cord. The spikes propagate non-decrementally over the entire radial nerve cord (RNC) length at rates as rapid as 78 cm−1. The neurones responsible for single unit activity reach lengths of 4−6 cm. Therefore, interneural transmission must occur for single units to be recorded over 315 cm long RNC. The electrical activity in the RNC is not affected by the removal of Na. However, all recordable electrical activity is blocked by the removal of Ca and restored by return of Ca or addition of Ba. A number of cells within and surrounding the RNC are capable of luminescing. These cells flash all along the RNC in response to RNC stimulation. The propagation of the flash is non-decremental along the RNC and travels at a rate similar to electrically recorded single unit activity in the RNC. The luminescence within the RNC and surrounding tissue requires Ca and does not require Na. Membrane fractions prepared from luminescent tissue flash in response to depolarization by KC1 or addition of the ionophore A23187 only in the presence of Ca or Sr. Neither Mn, Mg, nor Na will activate the luminescence and Ba will only slightly activate the luminescence. The coexistence of both neurones and luminescent cells within the RNC, the similar morphology of the two, and the similar ionic dependency of luminescence propagation and recorded electrical activity suggests that luminescent cells may be modified neurones. The rapid conduction velocity of both recorded spikes and propagated luminescence suggests that large neurones are present in the RNC. A small number of neurones were identified in the RNC which are 8 µm in diameter, which is considerably larger than any axons described in asteroids or echinoids. The large neurones themselves, however, have never been observed to be luminescent.
Peripheral Control of Responsiveness to Auditory Stimuli in Giant Fibres of Crickets and Cockroaches
Authors: Orida N. , Josephson R. K. 
Published: April 2021

ABSTRACT
Auditory stimuli initiate ascending activity in large fibres of the ventral nerve cord of the cricket, Acheta domesticus, and the cockroach, Periplaneta americana. This auditory responsiveness is reduced during locomotion. An earlier study concluded that the depression of responsiveness was mediated by descending inhibition. However, the auditory responsiveness is reduced during locomotion even after section of the ventral nerve cord anterior to the abdominal recording electrodes. Further, auditory responsiveness of isolated abdomens attached to intact animals is inhibited during locomotion of their hosts. Laminar wind streams over the cerci depress responsiveness to sound, but only at velocities markedly higher than those encountered by freely walking animals. Although the exact mechanism is not known, the depressed auditory responsiveness can occur independently of any descending influences.
Ion-Selective Electrode Studies on the Effects of 5-Hydroxytryptamine on the Intracellular Level of Potassium in an Insect Salivary Gland
Authors: Berridge M. J. , Schlue W. R. 
Published: April 2021

ABSTRACT
Potassium-sensitive microelectrodes were used to measure the intracellular level of potassium in Calliphora salivary glands. During stimulation with 1·10−8 M 5-HT, the potassium concentration increased from a resting level of 133·2 to 139·0 mm. When the external concentration of potassium was reduced below 2 mm there was a rapid loss of potassium which could be partially reversed by 5-HT. During 5-HT stimulation, the addition of ouabain had no effect on a number of parameters including the rate of fluid secretion, the ionic composition of the saliva and the intracellular level of potassium. The possibility that potassium enters the cells passively is discussed.
Respiratory Mechanics of Sound Production in Chickens and Geese
Authors: Brackenbury J. H. 
Published: April 2021

ABSTRACT
Air flow, air sac pressure and tracheal pressure were measured in chickens and geese during a variety of different vocal and non-vocal activities. Air flow and air sac pressure may rise to 500 ml s−1 and 60 cmH2O (6 × 10s N/m3) respectively during a crow in the chicken. During a sequence of honks in the goose the corresponding values are 650 ml s−1 and 25 cmH2O (2· 5 × 103 N/m2) respectively. The volume of air delivered through the respiratory system during a single crow is more than 400 ml, almost equivalent to the total volume of the lung air sac system. The efficiency of the chicken syrinx as a sound producing instrument, estimated by comparing the sound energy radiated with the energy consumed in the expulsion of air during a crow, appears to be less than 2 %. Cutting the paired sternotrachealis muscles had no effect on vocalization. The measured rates of clucking, cheeping and honking in adult chickens, young chicks and adult geese respectively are comparable to the characteristic rates of panting in these animals. This points to a similarity in the nature of the respiratory movements involved in each case. Simultaneous measurement of tracheal flow and pressure indicate that the glottis is capable of controlling air flow over a wide range of values in the presence of high pressures. During defaecation the valve is closed whilst during coughing it is wide open.
Electron Microprobe and Ion-Selective Microelectrode Studies of Fluid Secretion in the Salivary Glands of Calliphora
Authors: Gupta Brij L. , Berridge M. J. , Hall T. A. , Moreton R. B. 
Published: April 2021

ABSTRACT
The concentrations of sodium, potassium, chloride and water in the cells, secretory canaliculi and the lumen of Calliphora salivary glands have been measured by microprobe analysis of frozen-hydrated sections. Free concentrations of K+ and Cl- in all three compartments were measured with ion-selective microelectrodes. Most of the quantitative data from the two techniques are in close agreement. Microprobe values for the cytoplasm are (mm kg−1 wet weight):Na 20, K 115, Cl 33 in unstimulated glands and Na 15, K 125, Cl 23 after stimulation with 10−8 M 5-hydroxytryptamine (5-HT). The water content is 85% and 77·5% respectively. The highest concentrations are found in the canaliculi. The results indicate that the fluid in the canaliculi is 60–80 m-osmol more concentrated, thus supporting the hypothesis that canaliculi are the sites of solute-water coupling by some form of local osmosis. Both the microprobe and microelectrode measurements show that 5-HT stimulation causes a rise in the level of intracellular potassium and a fall in that of chloride. On 5-HT stimulation there is a rise in the luminal concentrations of K and Cl and little change in sodium level. In K-free medium the potassium in all tissue compartments is replaced with sodium; nearly normal rates of fluid secretion are maintained. The possible routes for the entry of K, Cl and H2O into the canaliculi are discussed.
Acoustics of Sound Production and of Hearing in the Bladder Cicada Cystosoma Saundersii (Westwood)
Authors: Fletcher N. H. , Hill K. G. 
Published: April 2021

ABSTRACT
The male cicada of the species Cystosoma saundersii has a grossly enlarged, hollow abdomen and emits a loud calling song with a fundamental frequency of about 800 Hz. At the song frequency, its hearing is non-directional. The female of C. saundersii lacks sound producing organs, has no enlargement of the abdomen, but possesses an abdominal air sac and has well developed directional hearing at the frequency of the species’ song.
Physical mechanisms are proposed that explain these observations in semi-quantitative detail using the standard method of electrical network analogues. The abdomen in the male, with its enclosed air, is found to act as a system resonant at the song frequency, thus contributing a large gain in radiated sound intensity. Coupling between this resonator and the auditory tympana accounts for the observed hearing sensitivity in the male, but destroys directionality. In the female, the abdominal cavity acts in association with the two auditory tympana as part of a phase shift network which results in appreciable directionality of hearing at the unusually low frequency of the male song.
Aspects of the Physiology of Terrestrial Life in Amphibious Fishes
Authors: Gordon Malcolm S. , Ng Wilson W.-s. , Yip Alice Y.-w. 
Published: April 2021

ABSTRACTAspects of the physiological adaptations for terrestrial life possessed by the Chinese mudskipper fish, Periophthalmus cantonensis have been studied. The basic amphibious features were comparable to those found earlier in the East African mudskipper species, Periophthalmus sobrinus. The fish can survive for up to days out of water, under moderate environmental conditions, and did not drown in aerated water. Durations of voluntary periods out of contact with water, in nature, were short. Evaporative water loss rates while out of water were relatively low, substantially below those of frogs of much larger size. The ‘diving syndrome’ was absent, metabolic rates, heart rates, and blood lactic acid levels all being unaffected by shifts of fish between water and air. During slow desiccation of intact fish, water was lost from the internal organs in the following sequence (from greatest to least proportional water losses): heart, blood, white muscle, brain, liver. Rapid desiccations withdrew water from the blood and heart, leaving hydration levels of other organs unaffected. Metabolic rates were only moderately sensitive to temperature in the range 10° – 20 °C (Q10 ≅ 1·5), but were highly temperature sensitive in the range 20° – 30 °C (Q10 ≅ 2·6). Measurements of routine metabolic rates of fish in water indicate that active metabolism at 20 °C can reach at least 5 times the standard rate. Measurements of blood levels of ammonia and urea, and of ammonia and urea excretion rates, showed that starvation for 9·5 days did not affect blood levels of these compounds, but did reduce urea excretion rates by 40% below rates for recently fed fish. Ammonia excretion was unaffected. Similar measurements on fish starved for 9·5 days, then kept out of water for 16·5 h, then returned to water, indicated that waste nitrogen produced by fish out of water was retained in their bodies until they returned to water. Fish out of water produced waste nitrogen 40% less rapidly than fish in water, and strongly shifted toward ureotelism. These experiments, however, did not permit fish to retain and renew water in their mouths, as they would have done in nature. The water in mudskipper burrows was found to be anoxic or nearly so. Mudskipper tolerance for hypoxia was, however, limited. Fish became inert at dissolved oxygen levels of about 20% saturation.
Unusual Step Patterns in the Free Walking Grasshopper Neoconocephalus Robustus
Authors: Graham D. 
Published: April 2021

ABSTRACT
The free walking step patterns of the tettigonid Neoconocephalus robustus are described and compared with the predictions of a model for walking co-ordination developed for the stick insect. Regular absences of rear leg protractions are found when the animal has walked for some minutes. The relative phasing of leg protractions before and after isolated absences suggests that an absence is created by a failure to meet all the conditions required for a protraction and that a ‘central oscillator’ maintains its intrinsic rhythm during such an absence.
Carbonic Anhydrase (Acetazolamide-Sensitive Esterase) Activity in the Blood, Gill and Kidney of the Thermally Acclimated Rainbow Trout, Salmo Gairdneri*
Authors: Houston A. H. , McCARTY L. S. 
Published: April 2021

ABSTRACT
Gill, kidney and blood levels of acetazolamide-sensitive esterase (carbonic anhydrase) activity were estimated at acclimation temperature and at a common temperature (25°C) in rainbow trout acclimated to 2, 10 and 18 °C. Plasma levels of sodium, potassium and chloride were also examined for possible acclimatory variations. Plasma sodium and chloride levels, and the sodium: chloride ratio were unaffected by thermal acclimation; potassium concentrations were significantly elevated at 18°C. Significant, but modest changes in renal and branchial carbonic anhydrase activity were observed under physiologically realistic incubation temperature conditions. Blood carbonic anhydrase activity was sharply elevated at higher acclimation temperatures. The data are discussed in relation to the hypothesis that carbonic anhydrase in this relatively stenothermal freshwater salmonid, through its intimate association with the coupled and exchange systems may provide for relatively thermostable basal rates of sodium and chloride uptake from the medium and recovery from urine. The renal, and more notably the branchial (Na+/K+)-stimulated ATPase systems, and erythrocytic carbonic anhydrase may then serve primarily as high-temperature amplifiers of sodium and chloride recruitment respectively.
Intrinsic Rhythm and Basic Tonus in Insect Skeletal Muscle
Authors: Hoyle Graham 
Published: April 2021

ABSTRACT
The jumping muscle of orthopterous insects contains fibres that possess an intrinsic rhythm (IR) of slow contraction. The contributing fibres are generally synchronized, but as many as three or four pacemakers are present. The frequency, amplitude and duration of IR contractions fluctuate erratically over a 24 h period. Metathoracic DUM neurone bursts suppress IR for a few minutes. Other, unidentified dorsal neurones enhance its amplitude. In addition to IR, the extensor tibiae shows intrinsic basic tonus (BT). BT is relaxed for several s by low-frequency burst output from unidentified metathoracic dorsal neurones. DUM neurone bursts may enhance extensor BT, relax it, or leave it unaffected.
The effects on IR of various regimes of activity in the slow extensor tibiae (SETi) and the common inhibitor (CI) axons were examined.
CI affects IR when stimulated at frequencies above 2 Hz. It causes amplitude depression and reduced duration of individual IR contractions as well as increased frequency. At 30 Hz and above, CI completely suppresses IR. An enhanced IR contraction starts within a few milliseconds of the termination of a CI train.
At low frequencies (below 10 Hz) SETi causes increased frequency and decreased amplitude of IR, with a depressed IR contraction following cessation of the SETi burst. At frequencies above 15 Hz the SETi-evoked contraction dominates tension development, though IR summates with it during the rising phase. In quiescent preparations not showing IR, SETi stimulation at 10 Hz often started up IR.
Single SETi or FETi impulses can initiate an IR contraction, and cause altered phasing, with up to a quintupling of frequency.
After a critical period has elapsed following the onset of an IR contraction, a single impulse in any one of the three axons will terminate it abruptly. The early termination is followed by a reduced interval which is proportional to the reduced IR contraction time. The rhythm of accumulated readiness to go into an IR contraction is independent of the pacemaker rhythm that initiates the contraction.
The Identification of An Octopaminergic Neurone and the Modulation of A Myogenic Rhythm in the Locust
Authors: Evans Peter D. , O’shea Michael 
Published: April 2021

ABSTRACT
An octopaminergic neurone in an insect is demonstrated. This cell (DUMETi) is the dorsal unpaired median neurone which projects to the extensor tibiae muscle of the locust metathoracic leg. Its soma was physiologically identified, isolated and shown to contain about 0·1 pmol of octopamine. Octopamine is about four times more concentrated in the axon than in the soma. The concentration in the soma is at least 800 times more than that in the soma of an identified motoneurone (which controls the fast extensor of the tibia). The effects of DUMETi on a myogenic rhythm in the extensor muscle of the locust metathoracic leg can be mimicked by superfusion with low concentrations of octopamine. The myogenic bundle possesses at least two types of aminergic receptor: one which slows the rhythm (and has a high-affinity for octopamine) and a second which accelerates the rhythm (and has a low-affinity for octopamine but a high-affinity for the indolalkylamine, 5-hydroxytryptamine). The roles of the two receptor types in modulating the rhythm are discussed in relation to the function of the rhythm.
Endothermy in African Dung Beetles During Flight, Ball Making, and Ball Rolling
Authors: Bartholomew George A. , Heinrich Bernd 
Published: April 2021

ABSTRACT
Body temperatures of diurnal and nocturnal ball-rolling and non ball-rolling dung beetles (in particular the genera Scarabaeus, Kheper, Gymno-pleurus and Heliocopris) were studied in the field in Kenya. The beetles were conspicuously endothermic during flight, ball making, and ball rolling. When at rest, their body temperatures did not differ significantly from that of their surroundings. They did not always generate high body temperatures while walking. However, they sometimes warmed up prior to walking and subsequently maintained a large difference between body and ambient temperatures. The nocturnal species, 5. laevistriatus, was conspicuously endothermic during ball making and ball rolling, often maintaining thoracic temperatures of 40°C or more in an ambient temperature of 25−26°C. In this species, the velocity of ball rolling increased linearly with body temperature from 5 cm/sec at 28°C to 18 cm/sec at 40°C. The take-off temperatures of dung beetles increased with body mass up to 2·5 g. In beetles larger than 2·5 g metathoracic temperatures at take-off ranged from 40 to 44°C and were independent of mass. Flight temperatures showed essentially the same pattern as take-off temperatures, increasing with mass up to about 42°C at 2·5 g and being independent of mass thereafter. Both flight and take-off temperatures increased with wing-loading up to about 35 N/m2, but were independent of wing loading from 35 to 65 N/m2. In each of the species for which we had an adequate sample, wing loading increased linearly with body mass. Partial correlation analysis suggests that metathoracic temperature is more dependent on body mass than on wing-loading. During periods of endothermy, metathoracic temperature exceeded prothoracic temperature, and abdominal temperature was lower than that of either the prothorax or metathorax. Cooling rate was inversely related to body mass. The removal of elytra and wings caused the cooling rate to increase by about one-quarter. Elevated body temperatures in dung beetles during terrestrial activity is probably selectively advantageous in competition for food. A high metathoracic temperature is a necessary condition for take-off and flight in the larger species. Mechanisms of heat production and the evidence for thermoregulation are discussed.
Pharmacological Study of the Reciprocal Dual Innervation of the Lateral Ciliated Gill Epithelium by the Cns of Mytilus Edulis (Bivalvia)
Authors: Catapane Edward J. , Stefano George B. , Aiello Edward 
Published: April 2021

ABSTRACT
The function of the CNS of Mytilus edulis was investigated for its role in the control of lateral ciliary activity. Ciliary beating rates were directly measured by stroboscopic microscopy of gill preparations which had the ipsilateral visceral ganglion (VG) attached. Low frequency electrical stimulation of the cerebrovisceral connective (CVC) or superfusion of the VG with serotonin increased lateral ciliary activity. This response could be antagonized by pretreating the gill with BOL or methysergide (MS), or by pretreating the VG with BOL, MS or ergonovine (ERG). High frequency stimulation of the CVC or superfusion of the VG with dopamine or epinephrine decreased lateral ciliary activity. This response could be antagonized by pretreating the gill with ERG or by pretreating the VG with ERG or MS. Acetylcholine and its mimetic acetylmethylcholine were found to be non-effective in altering ciliary activity in this study. The study demonstrates a reciprocal serotonergic-dopaminergic innervation of lateral gill ciliated cells originating in the CNS.