bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neuro-Muscular Control of Dipteran Flight
Authors: Nachtigall Werner , Wilson Donald M. 
Published: April 2021

ABSTRACT
Electrical activity from the indirect, myogenic muscles of calliphorid flies was recorded during flight. The animals were suspended from an aerodynamic balance in the laminar air-stream from a wind-tunnel. Muscle action potentials, recorded with 25 μ wire, were 5−7 msec, in duration, up to 10 mV. in amplitude and positive in sign. Frequencies were mostly under 20/sec. Frequencies in all the indirect muscles were similar, but these varied together with changes in aerodynamic power. Frequencies in the indirect muscles of the two sides varied by no more than ±10% during extreme turns to right or left (only left or only right wing beating). Electrical records from the non-myogenic direct muscles were made during tethered flight. The potentials were 2−4 msec, in duration, up to 2 mV. positive and had frequencies up to 180/sec. A nearly linear positive correlation exists between impulse frequency in the musculus latus (pleurostemal muscle), the inward movement of the pleural wall, and the wingbeat frequency, suggesting that this muscle is the basic frequency determiner. Strong turning behaviour is associated with opposed frequency changes in the pairs of antagonistic adductor and abductor muscles of the wings on the two sides of the body. The musculus dorsoventralis IV (tergo-trochanteral) is activated by a short impulse burst at the beginning of flight. It apparently acts as an oscillation starter. Flight initiation normally requires 30−60 msec. Usually activity begins in the musculus latus, which stiffens the thorax. Then simultaneously the myogenic muscles are activated and the ‘starter’ muscle causes a jump and the beginning of oscillation of the thorax. Then the wings are drawn gradually forward and full wingbeat amplitude develops within the first six wingbeats. Flight begins with maximal lift and wingbeat frequency and a nearly synchronous burst discharge in all the indirect muscles. Power production and the transmission and distribution of power are under separate control. The myogenic indirect motor varies only in total power output, this being influenced by its own state of excitation and by a muscle-controlling wingbeat frequency. Steering is accomplished by non-myogenic direct muscles which are capable of differentially engaging the two wings with the motor.
Thermodynamic Aspects of Flagellar Activity
Authors: Holwill M. E. J. , Silvester N. R. 
Published: April 2021

ABSTRACT
The frequencies of the beat of cilia and flagella from various organisms have been determined at temperatures in the range 5–35° C. Values of the activation enthalpy (ΔH‡, kcal./mole) and activation entropy (ΔS‡, e.u.) derived from the thermal dependence of frequency show a linear correlation of the form, ΔS‡ = 3·25 ΔH‡ – 50·75. The corresponding isokinetic activation free energy is 15·6 kcal./mole. The results support a hypothesis that the breakdown of an ATP-ATPase complex could be the common rate-limiting reaction for flagellar activity. Values of AH* and AS* for the decay of length or tension in striated muscles also fall on the same regression line but some smooth muscles show deviations.
Visual Pigments in a Tropical Freshwater Fish Etroplus Maculatus (Teleostei)
Authors: Virabhadrachari V. , Krishnamoorthy R. V. , Parvatheswararao V. 
Published: April 2021

ABSTRACT
In its natural habitat (fresh water) E. maculatus had VP 5152 (porphyropsin) as the predominant visual pigment. On acclimation to 100% sea water VP 495! (rhodopsin) was found to be predominant. On acclimation to 50 % sea water the visual pigment system of the fish presented a transitory phase. The significance and implications of these results in relation to the earlier work is discussed.
Impulse Identification and Axon Mapping of the Nine Neurons in the Cardiac Ganglion of the Lobster Homarus Americanus
Authors: Hartline Daniel K. 
Published: April 2021

ABSTRACT
The isolated cardiac ganglion of the lobster is an autonomous, integrating system containing only nine neurons. Its physiology was first investigated by Welsh & Maynard (1951) and has been reviewed by Hagiwara (1961). Its component cells, when isolated from synaptic input, are usually either quiescent or fire nerve impulses at a uniform low frequency but, when connected normally in the ganglion, they periodically fire short, high-frequency trains of impulses. The periods of activity in all cells are approximately coincident, producing what is collectively termed the ‘burst’, which is followed by a quiescent period in all units (Maynard, 1955). Evidence so far accumulated indicates that the four posteriorly located ‘small cells’ or ‘pacemaker cells ‘control the burst timing, one of them initiating the normal burst. These interact strongly with the five anterior ‘large cells ‘or ‘follower cells ‘, producing firing in them. Output from these goes to the heart muscle, causing heart contraction. Pacemakerpacemaker interactions are presumed but not rigorously demonstrated; followerfollower interactions via impulses are present but weak (Otani & Bullock, 1959); long-lasting potential changes in followers affect pacemaker firing and intracellular potentials of other followers (Watanabe & Bullock, 1960). As a step toward the more exact determination of the means by which the over-all ganglionic behaviour derives from the synaptic interactions of its component cells, the paths of the axons of the large and small cells within the ganglion have been determined physiologically, and a means for identifying the nerve impulses produced by each during a burst has been developed.
Microelectrode Study of the Resting and Action Potentials of the Cockroach Giant Axon with Special Reference to the Role Played by the Nerve Sheath
Authors: Pichon Y. , Boistel J. 
Published: April 2021

ABSTRACT
The use of very fine-tipped and mechanically strong microelectrodes has allowed reliable recordings of resting and action potentials to be made in cockroach giant axons in sheathed and desheathed nerve cords. When the microelectrode was withdrawn from a giant axon in an intact connective the first positive change in the potential from the resting level, was in most cases followed by a negative deflexion to the original zero level, the ‘sheath potential’. The values of this ‘sheath potential ‘together with the resting potential, the action potential, the maximum rate of rise and maximum rate of fall of the action potential have been measured in three different salines. In normal saline, resting potentials were lower in sheathed preparations (58·1 ± 5·4 mV.) than in desheathed ones (67·4 ± 6·2 mV.), whereas action potentials were higher in the former (103 ± 5·9 mV.) than in the latter (85·9 ± 4·6 mV.). Elevation of K+ and Ca2+ concentrations in the saline to the haemolymph level resulted in a decrease of resting and action potentials in desheathed cords, to 57·3 ± 5·3 mV. and 36·5 ± 7·6 mV. respectively. No alterations in the membrane potentials were recorded in intact connectives bathed in this saline, the mean resting potential being 55·6 ± 4·2 mV. and the mean action potential 107·9 ± 6·0mV. Local desheathing of the nerve cord led only to local disturbance of the resting and action potentials, thus indicating that diffusion processes along the extracellular spaces were very slow. The use of a saline in which cation concentrations have been elevated to the extracellular level resulted in normal resting potentials (64·6 ± 3·3 mV.) and action potentials (90·9 ± 7·2 mV.) in desheathed cords, despite the relatively high potassium concentration (17·1 mM./L). Recordings of the maximum rates of rise and rates of fall showed that there was no significant modification in the shape of the action potential in these different experimental conditions. The values of the ‘sheath potential’ were very variable from one impalement to another and it is suggested that this potential might be related to variations of the microelectrode tip potential bathed in different ionic solutions. The low resting potentials and high action potentials of giant axons in intact nerve cords may result from an excess of inorganic cations in the extracellular fluid.
An Electrophysiological Study of the Tentacle-Regulating Potentials in Noctiluca
Authors: Sibaoka Takao , Eckert Roger 
Published: April 2021

ABSTRACT
The duration and frequency of tentacle-regulating potentials (TRPs) recorded from the vacuole of Noctiluca miliaris were modified by both steady and abrupt changes in the vacuolar potential. The spike frequency increased linearly with an increase in the vacuolar negativity over the range of o to −50 mV. A transient decrease of impedance across the soma occurs coincidentally with the negative-going TR spike recorded from the vacuole. Local measurements of impedance changes as well as local surface potential recordings indicate that the TR spike does not propagate over the remainder of the cell from its region of origin near the base of the tentacle. Specimens without visible tentacles exhibited TRPs of normal shape. Concurrent potential recordings from the vacuole and the perinuclear cytoplasm indicate that the vacuolar membrane bordering that portion of the cell is inactive. Except for a relatively more pronounced post-spike hyperpolarization the TRP shape and polarity in the perinuclear cytoplasm, referred to the sea-water bath, are similar to those recorded from the vacuole, but are of smaller amplitude. The TRP appears to consist of a pre-spike pacemaker potential and an action potential having a prolonged post-spike plateau, the pattern recorded from the vacuole being the approximate inverse of that which would be recorded if a microelectrode could be introduced into the cytoplasm adjacent to the electrically active portion of membrane. Several of the findings indicate that the active membrane faces the vacuole and is electrotonically isolated from the perinuclear cytoplasm except through the vacuole.
Sodium and Water Balance in the Cichlid Teleost, Tilapia Mossambica
Authors: Potts W. T. W. , Foster M. A. , Rudy P. P. , Howells G. Parry 
Published: April 2021

ABSTRACT
The total body sodium increases from 45·9 μM/g. fish in fresh water to 59·9 μM/g. fish in 200 % sea water. The rate of exchange of sodium increases from 2 μM/g./hr. in fresh water to 60 μM/g./hr. in 100% sea water. The rate of drinking increases from o·26%/hr. fresh water to 1·6%/hr. in 400% sea water. Even in 200% sea water drinking accounts for only a quarter of the total sodium influx. The permeability to water, as measured by tritiated water, is highest in fresh water and lowest in 200% sea water. The permeabilities to water measured in this way are consistent with the drinking rates determined in sea water and 200% sea water.
Studies on Freshwater Osmoregulation in the Ammocoete Larva of Lampetra Planeri (BLOCH)
Authors: Bull J. M. , Morris R. 
Published: April 2021

ABSTRACT
Measurements have been made of a number of basic parameters related to osmoregulation in the ammocoete larva of the brook lamprey (Lampetra planeri Bloch). There is no significant variation in the water content of whole animals or their tissues between animals analysed during November and July, but the fat content rises in July and the majority of fat storage takes place in the muscles. Analyses have been made of the major osmotically active ions in whole animals, in muscle and in blood. Unlike previous investigators we found no significant seasonal variation in any of these components. The freezing-point depression of ammocoete blood (113–119 mM/1. NaCl) is lower than that of adult river lampreys (140 mM/1. NaCl), but apart from higher potassium values, monovalent ions contribute nearly the same proportion to the total osmotic pressure in both animals. The muscle analyses indicate that the ammocoete has a higher ratio of potassium to sodium (14·8:1) than other vertebrates. Measurements of the fluid and ionic compartments have been made on whole animals and on muscle using isotopic dilution techniques and conventional analyses. The extracellular space of muscle is about half that of whole animals (24·4% body weight) and contains all the chloride and 69 % of the sodium within whole muscle. Potassium almost completely replaces sodium within the cells and part of this may be bound sodium in some tissues. The urine output of the ammocoete amounts to 198 ml. per kg. per day and is similar to the values previously obtained from other lampreys in fresh water. The high potassium to sodium ratio within cells, together with the lack of seasonal variation and low variability in ionic analyses, is taken as an indication of the presence of very efficient controlling mechanisms operating on extracellular fluids and within the cells themselves.
On the Eyespot of the Dinoflagellate, Nematodinium
Authors: Francis David 
Published: April 2021

ABSTRACT
Nematodinium possesses an eyespot which consists of a lens closely apposed to a pigment cup containing a supposedly light-sensitive retinoid. The shape of the lens is described and its refractive index measured. From these data it is concluded that light from sources outside the cell will be brought to focus on the retinoid. The quality of the image formed is assessed. A variety of functions are possible to the organelle. It is suggested that functions involving image formation may be realized, even in the absence of a true retina and nervous system.
The Osmotic Behaviour of a Number of Grapsoid Crabs with Respect to their Differential Penetration of an Estuarine System
Authors: Barnes R. S. K. 
Published: April 2021

ABSTRACT
The effect of salinity upon five Australian grapsoid crabs exhibiting differential penetration of an estuarine system has been investigated. The salinity tolerances over a range of 2–70‰ (approx.) salinity, the acclimation times, and the osmoregulatory capabilities of these species have been determined. It is concluded that for four of the five species salinity is probably a limiting factor in hyposaline conditions; whilst for only one species is salinity probably a limiting factor in hypersaline conditions. The relative abundances of two species in the estuary appears to be a function of their capabilities for osmoregulation. Habitat preferences probably limit the upstream penetration of one species, and may limit the downstream penetration of a second.
The Pedal Neurons of Aplysia punctata
Authors: Dorsett D. A. 
Published: April 2021

ABSTRACT
Three classes of neurons have been identified in the pedal ganglia of Aplysia punctata. The motor neurons, which may be unipolar or bipolar, have the axon passing into one of the pedal nerves and in the case of the bipolars, the other branch entering the pedal commissure. This synapses with neurons on the opposite side, thus providing an integrative link between the ganglia. The interneurons are without axons in the pedal nerves or commissure, although afferent pathways to these cells and the motor neurons occur in the pedal nerves in a variety of combinations. The pathways in the ipsilateral nerves are for the most part excitatory, but inhibitory fibres occur in the posterior pedal nerve. Inhibitory potentials were often obtained in the interneurons by stimulation of the pedal commissure. A second type of coordinative pathway is provided by fibres which enter the CNS in one of the pedal nerves and terminate on neurons in both pedal ganglia.
Urine Formation by the Malpighian Tubules of Calliphora
Authors: Berridge M. J. 
Published: April 2021

ABSTRACT
Rate of urine formation is very sensitive to potassium concentration. Potassium is concentrated in the urine by a mechanism which is independent of other monovalent cations. Rubidium, caesium and sodium are also capable of maintaining a flow of urine. At low external potassium concentrations, sodium stimulates potassium secretion. Rate of urine secretion is stimulated by low osmotic pressures; the osmotic pressure of urine was slightly hypertonic throughout the range of external osmotic pressure employed. Addition of sucrose depresses rate of urine secretion; the potassium concentration of the urine increased by 1 mM/l. for each 2 mM/l. of sucrose added to the bathing medium. Urine formation is insensitive to sulphanilamide, acetazolamide, ouabain and a wide variation of pH. These observations are discussed in relation to the hypothesis that potassium secretion takes place across both surfaces of the cell. The pump on the basal surface may be a coupled sodium-potassium pump, whereas that on the apical surface may be electrogenic. Microvilli at the apical surface or channels formed by a complex infolding of the basal plasma membrane may represent structural devices by which standing osmotic gradients can be established during solute-linked water transport across the cells of Malpighian tubules.
The Influence of Environment and Heredity on Flight Activity in the Milkweed Bug Oncopeltus
Authors: Dingle Hugh 
Published: April 2021

ABSTRACT
Most long flights of Oncopeltus, tested using tethered flight in the laboratory, took place during the middle of the day. This is consistent with field data from other Heteroptera. In bugs reared at 23° C., regardless of length of photoperiod, 20% of males and 30% of females were migrants. Temperatures of 19° and 27° C. reduced these proportions. A short photoperiod of 12 hr. of light failed to increase the proportion of migrants over that present at 16 hr. The period in the life-history during which migration took place, however, was lengthened considerably. In spite of the lengthened flight period and a delay in oviposition, migrants arrive at their destinations with reproductive value high and are therefore colonizers. Food deprivation may increase somewhat the proportion of migrants if it occurs shortly after eclosion, although most of the extra activity seems to be due to additional non-migratory flight. If it occurs after oviposition has begun, food deprivation can result in migration at a time when it would ordinarily have ceased. The proportion of migrants could be significantly increased by appropriate selection and breeding. The basis for migratory behaviour is thus, in part at least, genetic. The data in general support the hypothesis that migration is elicited, enhanced, or suppressed in genotypical migrants by those environmental factors which influence ovary (and corpus allatum) development.
Hearing in Terrestrial Urodeles: A Vibration-sensitive Mechanism in the Ear
Authors: Smith J. J. B. 
Published: April 2021

ABSTRACT
Sinusoidal vibrations delivered to the ventral surface of the urodeles Salamandra salamandra and Triturus cristatus result in sinusoidal displacements of the fluid in the perilymph foramen. The displacing force is transmitted either via the cranial cavity or via the ear capsule. The displacements are of considerably greater amplitude than those of the skull at frequencies between 50 and 400 Hz. These large displacements are explained in terms of a hydraulic system, based on the dimensions of structures associated with the ear. This system, together with a suitably located receptor organ, the amphibian papilla, provides a vibration-detection system of potentially greater sensitivity than one relying on otolith granules. The perilymph duct may act as a shunt pathway, allowing gross low-frequency displacements of the perilymph to bypass the amphibian papilla.
A Simple Electrolytic Respirometer for the Continuous Recording of Oxygen Consumption Under Constant and Natural Conditions
Authors: Chase Ann M. , Unwin D. M. , Brown R. H. J. 
Published: April 2021

ABSTRACT
The principles involved in the design of an electrolytic respirometer are set out. A respirometer is described for air-breathing animals which allows the continuous recording over long periods (up to two weeks) of oxygen consumption at rates of the order of 10-100 μl. per hour. Provision is made for maintaining the temperature, pressure, and carbon dioxide and oxygen levels constant and at atmospheric values. A new design of recorder displays the results directly as rate of oxygen consumption. The features of the apparatus are discussed with reference to specific requirements.
Respiratory Physiology of House Sparrows in Relation to High-Altitude Flight
Authors: Tucker Vance A. 
Published: April 2021

ABSTRACT
Some birds perform the strenuous activity of flapping flight at altitudes in excess of 6100 m. (20,000 ft.), an altitude at which resting, unacclimated man is in a state of incipient hypoxic collapse. This study investigates the respiratory problems associated with avian flight at 6100 m. House sparrows and white mice were exposed to a simulated altitude of 6100 m. for an hour. Their metabolic rates were kept above the basal level by regulating environmental temperature at 5°C. At 6100 m. the sparrows consumed oxygen at 2.2 times the basal rate, used more oxygen and had higher heart and respiratory rates than at sea level. Body temperature decreased 2°C., but the birds were normally active. In contrast, the mice at 6100 m. were moribund and had body temperatures 10°C. below normal after 1 hr. Oxygen consumption and respiratory rates were less than at sea level. At 6100 m. sparrows ventilated the respiratory parts of their lungs 77% more than at sea level. At sea level and 6100 m. respectively, the partial pressure of carbon dioxide in the lungs dropped from 39.5 to 27.2 mm. Hg, and the partial pressure of oxygen in the lungs dropped from 100 to 28 mm. The sparrows removed a greater proportion of the oxygen from the air ventilating the lungs at 6100 m. than they did at sea level. Oxygen dissociation curves were determined for sparrow blood at various pH values. At 6100 m. the arterial blood of sparrows appears to be less than 24% saturated with oxygen. For the cardiovascular system to transport adequate oxygen to the tissues at this low level of saturation house sparrows must have a cardiac output that is at least triple the maximum known for mammals. House sparrows in a hypobaric chamber could fly 2.5 m. and gain altitude at a simulated altitude of 6100 m. but not at 7620 m. (25,000 ft.). Budgerigars trained to fly in a wind tunnel in the hypobaric chamber could fly more than 20 min. at sea level and a maximum of 3 min. at an altitude of 3660 m. (12,000 ft.). A budgerigar trained to wear an oxygen mask while flying in the wind tunnel could fly at an altitude of 6100 m. Calculations based on our present knowledge of avian physiology suggest how birds could be capable of flying at 6100 m. The possible advantages of flight at high altitudes are discussed.
Transpiration Through the Slifer’s Patches of Acrididae (Orthoptera)
Authors: Makings P. 
Published: April 2021

ABSTRACT
Transpiration through the Slifer’s patches of the desert locust (Schistocerca gregaria) was demonstrated experimentally, and was found to be greater than that through the normal cuticle at room temperature (20° C.). The difference increases at higher temperatures. Similar results were obtained with other acridids. Death of the animal appeared to have no effect on the phenomenon. Tentative estimations of the patch transpiration rate gave very high values, probably exaggerated by pinhole diffusion. The surprising figure of 169 ±52 mg./ cm.2/hr. at about 45° C. was obtained with living preparations. With dead ones and a different method, the values were smaller, being near-zero below 40° C but increasing fairly steeply from 45° to 60° C. It is suggested that the patches might show a transition effect at 40° C. Some superficial lipid which appears to melt at 45° C. all over the cuticle may be connected with the high permeability of the patches. The structural peculiarities of the patches can be explained as adaptations to a high transpiration rate. The patches may form an emergency cooling system, but other functions are not excluded.