bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Electrical Properties of A Crustacean Sensory Dendrite
Authors: Mirolli Maurizio 
Published: April 2021

ABSTRACT
The input properties and the response to stretch of a coxal receptor, the S fibre of the crab Scylla serrata, were studied using two and three intracellular microelectrodes. In the relaxed receptor the transmembrane potential ranged from about –60 to –70 mV, and the input resistance, RT, from 1 to 3 MΩ. The input IV relationship, studied by injecting slow-rising current ramps, was not linear either in the hyperpolarizing or in the depolarizing quadrants. Low values of RT and a linear IV relationship were associated with a large leakage of the microelectrodes. The response to step stretches was complex, consisting of an initial depolarizing transient, Va, and a steady-state depolarizing plateau, Vs. Both Va and Va propagated with decrement in the fibre which was about 9 mm long. The spatial decrement of Va and Vs was equal to that of the response to distally injected current pulses of comparable duration and amplitude. On the basis of the spatial decrement of both Va and Vs the dendrite can be considered equivalent, for current flowing from its distal to its proximal end, to a semi-infinite cable having a length constant of between 4 and 6 cm. The voltage transients recorded in response to long current pulses reached 84% of their final value in a time (t84%)ranging from 150 to 180 ms in fibres in which RT was 2 MΩ or larger. t84% was smaller in fibres having a lower RT. The time course of the transients recorded in response to injected current pulses deviated from the semi-infinite cable model in a manner suggesting the presence of a partial short circuit. For this reason the membrane time constant of the fibre is considered larger (by an undetermined amount) than t84%. The fibre presented less resistance to current flowing from its proximal to its distal end than to current flowing in the opposite direction. For this reason, and also because of the time course of the voltage transient, it is concluded that the distal sensory endings of the fibre have the properties of a leaky end termination, even in the non-stimulated receptors.
Interlimb Coordination During Slow Walking in the Cockroach
Authors: Spirito Carl P. , Mushrush Daniel L. 
Published: April 2021

ABSTRACT
In this study, interlimb coordination in the cockroach during slow walking (2–7 steps/s) is described for a variety of substrate conditions. During normal free-walking, the animal utilizes an alternating tripod gait (both ipsilateral and contralateral phase close to 0·50). The protraction/ retraction ratio varies linearly with walking speed. When tethered on a supported ball, the ipsilateral phase ranges from 0·32 to 0·46 at walking speeds of 2–7 steps/s, and contralateral phase is constant at 0-53. Protraction/ retraction ratios are normal in this case. Blind free-walking animals use a gait which is indistinguishable from normal, but the protraction/retraction ratio is constant over speeds of 2–7 steps/s. When walking down an inclined plane (45°), the gait resembles ball-walking, with an average ipsilateral phase of 0·43 and contralateral phase of 0·53. These alterations of gait under different substrate conditions can be related to the animal’s responses to loading, gravity, and steering control system.
A Sliding Microtubule Model Incorporating Axonemal Twist and Compatible With Three-dimensional Ciliary Bending
Authors: Holwill M. E. J. , Cohen Howard J. , Satir Peter 
Published: April 2021

ABSTRACT
Equations are developed to calculate the relative displacements of the doublet microtubules at the tip of a cilium when the microtubules twist about the axis of the organelle. Displacements measured from electron micrographs show asymmetry (or skew) which can be matched quantitatively by the theoretical model with the appropriate selection of twist angle and orientation of the axoneme with respect to the plane of beat. For Elliptio cilia the experimental results are consistent with a planar effective stroke and a recovery stroke involving a three-dimensional bend. The plane of the effective stroke is not normal to a surface containing the central pair of microtubules but contains microtubule 2 to produce the observed skew. This model for the beat also explains the range of orientations of axoneme observed in sections through the metachronal wave.
Ionic Basis of Action Potentials and Bursting Activity in the Hydromedusan Jellyfish Polyorchis Penicillatus
Authors: Anderson Peter A. V. 
Published: April 2021

ABSTRACT
Knowledge of coelenterate cellular neurophysiology is extremely limited despite the amount of attention this phylum has received from physiologists (cf. Josephson, 1974). However, the recent discovery that reliable intracellular recordings can be obtained from motor neurones in the inner nerve ring of the hydromedusan jellyfish Polyorchis penicillatus (Anderson & Mackie, 1977) presents us with a preparation with which to study cellular events in these organisms. This report describes results from a series of experiments designed to investigate the ionic basis of action potentials in this preparation.
Fluorescence and Luminescence of Isolated Photophores of Porichthys
Authors: Baguet F. , Zietz-Nicolas A. M. 
Published: April 2021

ABSTRACT
Isolated photophores of Porichthys exposed to u.v. light (365 nm) exhibit a green fluorescence localized in the photocytes and a bluish fluorescence originating from the lens-like body. The luminescence of photophores evoked by epinephrine, nor-epinephrine or potassium cyanide decreases with the intensity of the green fluorescence of the photogenic tissue; the bluish fluorescence of the lens-like body does not chnge significantly. The total amount of light emitted is a linear function of the decrease of the greenish fluorescence intensity. The slope of the regression line is maximal in response to epinephrine or nor-epinephrine 5·10−4 M and potassium cyanide 10−3 M. It decreases significantly for higher concentrations. The decrease of fluorescence observed during the light emission is tentatively explained by oxidation of a luciferin present in a fluorescent form in a fresh photophore.
Eclosion Hormone and Bursicon Titres and the Onset of Hormonal Responsiveness During the Last Day of Adult Development in Manduca Sexta (L)
Authors: Reynolds Stuart E. , Taghert Paul H. , Truman James W. 
Published: April 2021

ABSTRACT
The blood titres of eclosion hormone in Manduca sexta indicate that the hormone is liberated into the blood during a span of about 20 min and then disappears with a half-life of about 45 min. Eclosion normally follows 2·5 h after the appearance of the hormone in the blood.
Bursicon appears in the blood within 2 min after the newly emerged moth comes to rest at a wing spreading site. Hormone is apparently released during the following 10 min and then disappears with a of 40–50 min.
The target tissues for the two hormones become responsive during the last day of development. The wing epidermis and nervous system appear to become sensitive to the eclosion hormone at about the same time, approximately 4 h before the hormone’s release. Wings become responsive to bursicon about 2 h earlier.
During the last day of adult development, Manduca show a precise onset of responsiveness to bursicon and eclosion hormone followed a few hours later by the gated release of the two hormones. This appearance of hormone sensitivity is likely to be due to a photoperiodically gated event which occurs late in adult development but prior to eclosion hormone release. The nature of this event is unknown.
The Effect of Epinephrine and Acetylcholine On the Distribution of Red Cells Within the Gills of the Channel Catfish (Ictalurus Punctatus)
Authors: Holbert P. W. , Boland E. J. , Olson K. R. 
Published: April 2021

ABSTRACT
The second pair of gill arches were perfused with 51Cr tagged red cells at constant pressure or constant flow and in the presence of 10−5 M epinephrine or 10−6 M acetylcholine. The tissues were quick frozen, lyophilized and the lamellae and alamellar filaments from the distal, mid and basal thirds of the filaments counted for radioactivity. At constant flow, epinephrine increased red cell space (RCS) in lamellae from basal and mid regions and decreased RCS in peripheral lamellae. The RCS in all alamellar filaments decreased. With constant pressure perfusion, epinephrine increased RCS in all lamellae while alamellar filamental RCS remained unchanged. Acetylcholine, at constant flow perfusion, decreased distal lamellar RCS and increased basal lamellar RCS. RCS decreased in distal and mid alamellar filaments during the same period. These data support the theory of lamellar recruitment as a means of increasing respiratory exchange and stress the importance of concomitant central cardiovascular changes in eliciting maximal response.
Water Exchange Across Fish Gills: The Significance of Tritiated-Water Flux Measurements
Authors: Loretz Christopher A. 
Published: April 2021

ABSTRACT
Branchial turnover rates of tritiated water in the cyprinid teleost Carassius auratus are temperature dependent and show temperature acclimation with time. Hypoxia produced abrupt increases in the rates of branchial water turnover. The evidence suggests the importance of branchial blood flow parameters and ventilation on turnover rate. Membrane resistance is not a major barrier to water diffusion in these small fish. Calculated apparent diffusional water permeabilities do not represent true branchial membrane permeabilities.
Respiration and Adaptation to the Terrestrial Habitat in the Land Hermit Crab Coenobita Clypeatus
Authors: McMahon Brian R. , Burggren Warren W. 
Published: April 2021

ABSTRACT
The frequencies of heart (fH) and scaphognathite (ventilatory = fsc) pumping, and responses to hypoxia, hypercapnia and wetting (simulated rain), as well as oxygen consumption pre-and postbranchial haemolymph oxygen tension oxygen content , carbon dioxide content and pH were measured in adult land crabs Coenobita clypeatus. There was a large increase in fsc in response to both hypoxia and wetting but a smaller increase in response to even severe hypercapnia. Some evidence suggests that ventilation via the scaphognathites may have been supplemented by a second (branchiostegal) pump when ventilatory requirement was high. fH was less responsive to either hypoxia or hypercapnia, but decreased with severe exposure to either. Haemolymph oxygen tensions were low but haemocyanin oxygen affinity was high in vivo (P50= 10 torr at 23°C) and postbranchial haemocyanin was 60–80% saturated. Oxygen content was also high allowing adequate oxygen release to the tissues despite the low oxygen tensions. ΔP50/Δt = 0·37 torr/Δ°C, log ΔP50/ΔpH = −0·84 torr/pH unit, both determined in vitro were lower than literature values for marine and littoral species. As in other terrestrial species, and (calculated) were high, as were both bicarbonate and non-bicarbonate buffering capacities. Water loss was less (0·08% body weight.h−1) in Coenobita than in other terrestrial crustaceans, this resulting from the protection of the adopted shell. Results obtained from Coenobita are compared with those from other terrestrial and littoral crabs to illustrate the influence of the adopted shell on the degree of modification needed to enter terrestrial habitats.
The Spawning of Echinus Esculentus and Some Changes in Gonad Composition
Authors: Stott F. C. 
Published: April 2021

ABSTRACT
The spring inshore migration of Echinus at Port Erin in 1930 started in early February and reached its maximum in the middle of March. Mature gonads were found at the end of February and throughout March and early April. At the end of June all gonads examined were spent. The sea temperature throughout this period was observed. It is probable that May was the chief month in which natural spawning took place. A cycle of changes in the composition of the gonad are recorded from November 1929 to July 1930. The chief of these are: In the males an increase in percentage dry weight as the gonads mature ; the opposite taking place in the females. A large and simultaneous decrease in percentage glycogen in both male and female gonads prior to spawning followed by a great post-spawning increase. The fatty acid content does not alter with the maturation of the gonad, but an indication is given that an increase in the percentage of carbohydrates other than glycogen occurs. Hence it is suggested that glycogen is transformed in the maturing gonad into carbohydrate food reserves for the ripe eggs and sperm.
Iodine Compounds and Fertilisation
Authors: Carter G. S. 
Published: April 2021

ABSTRACT
In the previous papers (Carter, 1930, 1931) results were recorded which led to the conclusion that the egg-secretions of these species of Echinus contain a substance which is similar to thyroxine in its action upon the activity of the sperm. The experiments to be discussed in the present paper were undertaken with the object of observing whether thyroxine is also able to produce effects in the cytoplasm of the egg similar to those normally produced by the secretions.
Observations on Living Cells, Made with the Microscope-Centrifuge
Authors: Harvey E. Newton 
Published: April 2021

ABSTRACT
The microscope-centrifuge, recently described by Harvey and Loomis (1930), was devised in collaboration with Mr Alfred L. Loomis and constructed in his private laboratory at Tuxedo Park, N.Y. It is a device by which living cells can be observed while they are being centrifuged at speeds of 1000 to 4000 R.P.M. at a distance of 11 cm. from the centrifuge axis. The instrument is really a special head, containing part of a microscope, built to fit a 12 in. shaft, the size of the type SB International Equipment Company electric centrifuge. The scheme is as follows.
The Relations Between Yolk and White in the Hen’s Egg
Authors: Smith Michael , Shepherd James 
Published: April 2021

ABSTRACT
The freezing-points of white and yolk in the hen’s egg gradually approach equality when the egg is kept for long periods ; and the rate of the process of equilibration is rapid at first but becomes very slow as equality is more closely approached. Between 0° and 25° C. the rate of equilibration has a temperature coefficient (Q 10) of from 1·5 to 2. At 25° C. equality of freezing-points is reached after about 70 days. Equilibration is achieved partly by the passage of water across the vitelline membrane from white to yolk, but partly also by more complicated changes of osmotic concentration occurring more or less independently in white and yolk. The recovery of hypertony by a yolk, previously diluted by immersion in water, when it is replaced in egg-white can be explained on the basis of a temporary heterogeneity of the diluted yolk, and this explanation is supported by experimental evidence. The rate of equilibration is much greater when the separated yolk is placed in mixed egg-white than in the intact egg, but since it is also greater in thin white than in thick white, and greater again in the white dialysate, the structure and viscosity of the white are probably important factors. There is evidence of an appreciable resistance to water-movement both in egg-white and in egg-yolk. In hypotonic or hypertonic aqueous solutions of glucose or glycerol, or in Ringer’s solution, the rate of equilibration is greater than in egg-white and many times greater than in the intact egg. Water is taken up by the yolk both from hypotonic and hypertonic solutions of Ringer, within the range Δ = 0·10° to 1·20° C., at a rate which increases the further the solution is removed from the point of isotony. Evidence that the apparent disequilibrium in intact eggs is not a steady state maintained by a “Lebenswirkung,” is afforded by: (i) the form of the equilibration curves, which strongly suggest the slow attainment of an equilibrium by diffusion, rather than a steady state terminated by death ; (ii) the temperature relations of equilibration, which are consistent with the former assumption, but which do not agree at all with the effect of temperature on the viability of fertile eggs ; (iii) the absence of any tendency of the yolk to maintain its hypertony when the white is concentrated by rapid evaporation ; (iv) the alternative explanation for the recovery of hypertony by diluted yolks, which was the most crucial evidence for the existence of a steady staté maintained by the expenditure of energy.
The Relations Between Yolk and White in the Hen’s Egg
Authors: Needham Joseph , Stephenson Marjory , Needham Dorothy Moyle 
Published: April 2021

ABSTRACT
The vitelline membrane of the infertile hen’s egg exhibits no dehydrase activity. The vitelline membrane has no measurable aerobic respiration in vitro, nor has the yolk of the infertile egg. This confirms the view that the carbon dioxide production of the intact egg is not the result of any true respiration. When incubated anaerobically in vitro, bacteriologically sterile yolk produces consistently small amounts of lactic acid. This glycolysis is not the result of any catalytic activity of the vitelline membrane, but takes place throughout the substance of the yolk. Under similar conditions, bacteriologically sterile yolk produces small amounts of a substance or substances estimatable as ethyl alcohol. If the yolk suspension is bacterially contaminated, however, lactic acid and alcohol are produced in amounts closely similar to those found by earlier workers on this subject. The heat of glycolysis, under anaerobic conditions, calculated from the amounts of lactic acid experimentally found to be formed, is of the same order as (a) the calculated requirement of the vitelline membrane (Straub), and (b) the observed heat production (Langworthy and Barott). Thus even if the vitelline membrane is capable of using energy to do osmotic work, the yolk is only capable of supplying it by means of its glycolytic mechanism if the whole energy output of the whole yolk can be made available for doing work at the membrane.
The Relations Between Yolk and White in the Hen’s Egg
Authors: Needham Joseph 
Published: April 2021

ABSTRACT
In a previous paper of this series it has been stated that yolk and white, separated only by a thin collodion membrane, come rapidly into osmotic equilibrium. The converse experiment to this would consist in isolating the vitelline membrane from the yolk and white and studying its osmotic properties in relation to solutions of simpler composition than the egg contents. Under such conditions, with a solution of salts equivalent to the yolk on one side, and a solution of salts equivalent to the white on the other side, would the membrane maintain the difference or not?
Respiratory, Ventilatory, and Cardiovascular Responses to Experimental Anaemia in the Starry Flounder, Platichthys Stellatus
Authors: Wood Chris M. , McMahon B. R. , McDonald D. G. 
Published: April 2021

ABSTRACT
Unrestrained, quiescent starry flounder maintained approximately normal levels of O2 uptake in the face of severe experimental anaemia. At haematocrits above about 5 %, the only major compensation was a reduction in venous O2 tension which lowered venous saturation and thereby kept a constant difference between arterial and venous O2 contents. Below a haematocrit of about 5 %, this difference decreased, and many additional compensations were invoked, including increases in ventilation, expired O2 tension, arterial O2 tension, and cardiac output, and decreases in systemic vascular resistance and blood pH. All changes could be reversed by restoration of haematocrit. Exercise performance and post-exercise changes in blood pH and lactate differed only slightly between anaemic and normal flounder. In wild flounder, anaemia commonly occurs and apparently only causes death at the haematocrit value (about 5 %) below which most major compensations are implemented. The respiratory strategy of the flounder during anaemia is compared with that of the rainbow trout.
The Roles of Endogenous Membrane Properties and Synaptic Interaction in Generating the Heartbeat Rhythm of the Leech, Hirudo Medicinalis
Authors: Calabrese Ronald L. 
Published: April 2021

ABSTRACT
Inhibitory synapses among the central neurones involved in the genera- tion of the heartbeat rhythm of the leech were blocked by either low Cl− physiological saline or presynaptic hyperpolarizing current. Low Cl− saline reversibly blocked inhibitory postsynaptic potentials (IPSPs) from the HN cells onto both other HN cells and HE cells but did not block electrical coupling among HN cells. The rhythmic bursts of impulses in HE cells were abolished when IPSPs were blocked by either low Cl− saline or hyperpolarization of HN cells. The rhythmic bursts of impulses in HN cells were not abolished (except in cell HN(5)) when IPSPs were blocked by low Cl− saline, but phase relations became unfixed (unless the cells were electrically coupled). Both brief depolarizing and hyperpolarizing current pulses reset the rhythm of HN cells whose IPSPs were blocked by low Cl− saline. The results indicate that the motor neurones to the heart (HE cells) produce rhythmic impulse bursts because their steady discharge is period- ically inhibited by the HN interneurones. The pattern generated by die HN cells originates from an endogenous rhythm co-ordinated by the inhibitory interactions and electrical coupling between these cells.
Biomodal Gas Exchange During Variation in Environmental Oxygen and Carbon Dioxide in the Air Breathing Fish Trichogaster Trichopterus
Authors: Burggren Warren W. 
Published: April 2021

ABSTRACT
Gas exchange in the gourami, Trichogaster trichopterus, an obligate air breather, is achieved both by branchial exchange with water and aerial exchange via labyrinth organs lying within the suprabranchial chamber.
Ventilation of the suprabranchial chamber, , gas exchange ratios of both gills and labyrinth organs, and air convection requirements have been measured under conditions of hypoxia, hyperoxia or hypercapnia in either water or air.
In undisturbed fish in control conditions (27 °C), air breathing frequency was 12 breaths/h, gas tidal volume 30 μl /g, total oxygen uptake 5· 2 μ/g/h and total carbon dioxide excretion 4·1 μ/g/h, indicating a total gas exchange ratio of approximately 0·8. The aerial labyrinth organs accounted for 40% of oxygen uptake but only 15% of carbon dioxide elimination.
Hypoxia, in either inspired water or air, stimulated air breathing. Total was continuously maintained at or above control levels by an augmentation of oxygen uptake by the labyrinth during aquatic hypoxia or by the gills during aerial hypoxia. Hypoxia had no effect on partitioning between air and water. Hypercapnia in water greatly stimulated air breathing. About 60 % of total then occurred via aerial excretion, a situation unusual among air breathing fish, enabling the overall gas exchange to remain at control levels. Aerial hypercapnia had no effect on air breathing or O2 partitioning, but resulted in a net aerial CO2 uptake and a decrease in overall gas exchange ratio.
Trichogaster is thus an air breathing fish which is able to maintain a respiratory homeostasis under varying environmental conditions by exploiting whichever respiratory medium at a particular time is the most effective for O2 uptake and CO2 elimination.