bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Molecular Basis for Synexin-Driven, Calcium-Dependent Membrane Fusion
Authors: Pollard Harvey B. , Burns A. Lee , Rojas Eduardo 
Published: April 2021

ABSTRACT
Membranes of secretory vesicles fuse with each other and with plasma membranes during exocytosis in many different cell types. The probable role of calcium in the process is now widely accepted, and it is possible that at least one cytosolic mediator of calcium action is synexin. Synexin is a 47 000 Mr calcium-binding protein, initially discovered in the bovine adrenal medulla, which binds to granule membranes and to inner aspects of chromaffin cell plasma membranes. Synexin causes chromaffin granules to aggregate, and such aggregates can be caused to fuse in the additional presence of arachidonic acid. Synexin also mediates the direct fusion of liposomes and chromaffin granule ghosts. To understand better the mechanisms of membrane fusion promoted by synexin we have attempted to define the primary sequence of the protein. Our initial efforts were directed towards purification of bovine synexin in sufficient amounts to allow us to sequence tryptic peptides. However, as the project progressed we also directed our attention to human synexin, preparing peptides from this protein as well. From analysis of bovine peptides we learned that the synexin molecule might be closely related to a class of proteins including lipocortin I, calpactin (p36), endonexin II, protein II and calelectrin 67K. Complete analysis of a human synexin cDNA clone revealed strong homology with bovine synexin. The analysis also showed that synexin contained a unique, long, highly hydrophobic N-terminal leader sequence followed by a characteristic four-fold repeat homologous with those found in other members of the synexin gene family. The highly hydrophobic character of synexin seems consistent with information previously obtained that synexin is able to insert directly into the interior of bilayers prepared not only from purified phosphatidylserine but also from biological membranes. The evidence for such insertions is a dramatic increase in the capacitance of the membrane, formed at the tip of a patch pipette, when calcium-activated synexin is applied to the bilayer. Additional evidence is the fact that synexin also forms calcium-selective channels when the protein is applied to the cytosolic aspect of the plasmalemma when that side is also exposed to calcium at sub-millimolar concentrations. Thus, the synexin molecule not only enters the membrane, but also spans it. From these and other data we have developed the concept that the fusion process may involve synexin forming a ‘hydrophobic bridge’ between two fusing membranes. Lipid movement across this bridge may then be the material basis for final fusion. We have termed this concept the ‘hydrophobic bridge hypothesis’, and have developed the predictive properties of this hypothesis in considerable detail.
The Mechanism of Urine Formation in Invertebrates
Authors: Picken L. E. R. 
Published: April 2021

ABSTRACT
In Anodonta cygnea: The blood has a vapour pressure equivalent to that of a solution of ca. 0.10 per cent sodium chloride. The pericardial fluid is isotonic with the blood. The urine has a vapour pressure equivalent to that of a solution of ca. 0.06 per cent sodium chloride. The hydrostatic pressure of the blood is ca. 6 cm. of water. The calculated colloid osmotic pressure is ca. 3.8 mm. of water. The average rate of filtration of fluid into the pericardium is ca. 250 c.c. in 24 hours. The salt uptake from ingested phytoplankton is estimated as equivalent to 0.012. g. sodium chloride in 24 hours. The loss of osmotically active substance in the urine is estimated as equivalent to 0.15 g. sodium chloride in 24 hours. In Limnaea peregra the vapour pressure of the blood is equivalent to that of a solution of ca. 0.43 per cent sodium chloride. The pericardial fluid is isotonic with the blood, and the urine has a concentration equivalent to ca. 0.30 per cent sodium chloride. In Limnaea stagnalis the hydrostatic pressure of the blood is ca. 8 cm. of water. The colloid osmotic pressure of the blood is ca. 2.5 cm. of water (calculated); that of the pericardial fluid is ca. 0.7 cm. of water.
The Oxygen Consumption of Ephemerid Nymphs From Flowing and From Still Waters in Relation to the Concentra-Tion of Oxygen in the Water
Authors: Fox H. Munro , Wingfield C. A. , Simmonds B. G. 
Published: April 2021

ABSTRACTFox & Simmonds (1933) and Fox et al. (1935) have shown that certain may-fly nymphs, a caddis larva and an isopod from swift streams have a higher oxygen consumption than nearly related forms from still waters or slow-flowing streams. Their results were summarized in Table IV1 of Fox et al. (1935). It has since been shown by Washbourn (1936) that the oxygen consumption of trout fry reared in swiftly flowing water is greater than that of fry reared in slow water.Wolsky & Holmes (1933) found the oxygen consumptions of four individuals of the crayfish Astacus leptodactylus Eschscholtz, from Lake Balaton, to be 90, 103, 104 and 105 mg. of oxygen per kg. of animal per hour at 19–21° C., the animals weighing 16, 22, 36 and 64 g. respectively. The mean of these values for oxygen consumption is 101. Without studying the problem we are now considering, Wolsky (1934) later found that the oxygen consumptions of seven individuals of A. torren-tium (Schrank), living in a swift stream in Hungary, were 160, 188, 157, 157, 170, 102 and 137 mg. oxygen per kg. of animal per hour at 19–21° C., the animals weighing 8, 8, 15, 17, 17, 21 and 32 g. respectively. The mean of these values for oxygen consumption is 153. The oxygen consumption of A. torrentium is thus 50 per cent greater than that of A. leptodactylus, and the relation between oxygen consumption and weight suggests that habitat, not size, was responsible for this difference.
The Absorption of Water and the Associated Volume Changes Occurring in the Eggs ofNotostira ErraticaL. (Hemiptera, Capsidae) During Embryonic Development Under Experimental Conditions
Authors: Johnson C. G. 
Published: April 2021

ABSTRACTThe eggs of Notostira erratica L. (Hemiptera) swell during embryonic development. Increase in wet weight accompanies swelling.Under the conditions of the experiments described in this paper the gross increase in wet weight of the eggs from oviposition till hatching is due entirely to the increase in amount of water. The weight of water per egg is, however, slightly greater than the increase in wet weight of the same egg, since the amount of dry matter per egg decreases slightly during development.The increased amount of water must be largely due to absorption from the external environment: a certain amount, however, is probably metabolic water, which if due to oxidation of fat in the yolk would result in an increase in wet weight of the egg. This increase due to metabolic water will tend to be balanced by the decrease in dry matter during embryonic development.The increase in volume of an egg during embryonic development is directly proportional to its increase in wet weight during the same period. Theoretically it would be more accurate to correlate volume change with the amount of water in the egg; this cannot be done accurately enough, however, with the present methods.The embryonic development and the extrusion of the subopercular yolk-plug in relation to water absorption are briefly described. The work of other authors concerned with water-absorbing insect eggs is discussed.The method used for finding the volume of the eggs (which does not involve their death) is described in detail.
Quantitative Studies on the CiliateGlaucoma
Authors: Harding J. P. 
Published: April 2021

ABSTRACTGlaucoma was cultured in various concentrations of bacteria which were kept as constant as possible. The rate of disappearance of the bacteria was a function of the concentration of the Glaucoma. In low concentrations of bacteria the rate of feeding of the Glaucoma was a function of the concentration of bacteria. In high concentrations of bacteria the Glaucoma were able to find almost as much food as they could take in; so that the rate of feeding tended to become independent of the concentration of bacteria. Counts of food vacuoles showed that the rate of feeding never became quite independent of the concentration of bacteria. For every increase in the concentration, up to at least 8,000,000 bacteria per cu. mm., there was an increase in the rate of formation of food vacuoles. High concentrations of bacteria did not inhibit the growth or the reproduction of the Glaucoma. When the concentration of bacteria was less than 600,000 per cu. mm. the Glaucoma were semi-starved and both their size and their rate of fission was dependent on the concentration. Between concentrations of 600,000 and 7,000,000 bacteria per cu. mm. the rate of growth in size, but not the rate of fission of Glaucoma, was influenced by the concentration. The generation-time was constant throughout this range at between 2-3 and 2-4 hours.
The Tonic Function of the Horizontal Semicircular Canals in Fishes
Authors: Löwenstein Otto 
Published: April 2021

ABSTRACTAn operative technique is described, which makes possible the elimination of a single horizontal semicircular canal in the pike (Esox lucius). Such an operation, carried out unilaterally, leads to a lasting tonic asymmetry of the eye muscle apparatus. Hence a tonic function of the horizontal semicircular canals must be assumed. The eye reactions of the pike during and after rotation in a horizontal plane are in complete agreement with the properties of the ampullary sense organ of the dogfish described by Löwenstein & Sand (1936). It is demonstrated that a single horizontal semicircular canal can give rise to reflex responses of the eyes on both clockwise and anti-clockwise rotation of the fish in the horizontal plane.
Preservation of Glucose Transport and Enzyme Activity in Fish Intestinal Brush-Border and Basolateral Membrane Vesicles
Authors: Reshkin Stephan J. , Cassano Giuseppe , Womersley Christopher , Ahearn Gregory A. 
Published: April 2021

ABSTRACT
The preservation of glucose transport and membrane-bound enzyme activity in intestinal brush-border and basolateral membrane vesicles from the euryhaline teleost, Oreochromis mossambicus, was examined. Transport was well-preserved when the vesicles were either frozen in liquid nitrogen or lyophilized and stored in the presence of trehalose. Transport activity was not well-maintained when vesicles were lyophilized with mannitol as the protective carbohydrate. Enzyme activities were reduced by liquid nitrogen storage or by lyophilization with mannitol. However, enzyme enrichments of all treatments remained fairly constant over storage time, suggesting similar functional and perhaps structural changes in the different membrane fractions in response to preservation. These techniques provide a simple way to obtain functionally similar vesicles over a relatively long period of storage, permitting improved comparisons of transport properties. These results extend for the first time to vertebrate epithelial membranes the finding that trehalose preserves transport activity during lyophilization, storage and rehydration.
The Importance of Torsion in the Design of Insect Wings
Authors: Ennos A. Roland 
Published: April 2021

ABSTRACT
A model insect wing is described in which spars of corrugated membrane which incorporate stiffening veins branch serially from a V-section leading edge spar. The mechanical behaviour of this model is analysed.
The open, corrugated spars possess great resistance to bending, but are compliant in torsion. Torsion of the leading edge spar will result in torsion and relative movement of the rear spars. As a result camber will automatically be set up in the wing as it twists.
Aerodynamic forces produced during the wing strokes will result in torsion and camber of the wing which should improve its aerodynamic efficiency.
The effects of varying parameters of the wing model are examined. For given wing torsion, higher camber is given by spars branching from the leading edge at a lower angle, by spars which curve posteriorly, and by spars which diverge from each other.
Wings of three species of flies were each subjected to two series of mechanical tests. Application of a force behind the torsional axis caused the wings to twist and to develop camber. Immobilizing basal regions of the leading edge greatly reduced compliance to torsion and camber, as predicted by the theoretical model. Aerodynamic forces produced during a half-stroke are sufficient to produce observed values of torsion and camber, and to maintain changes in pitch caused by inertial effects at stroke reversal.
The Inertial Cause of Wing Rotation in Diptera
Authors: Ennos A. Roland 
Published: April 2021

ABSTRACT
The cause of the changes in wing pitch at stroke reversal in Diptera has been investigated. The high compliance of the wing base makes it seem unlikely that pitch changes are caused by active torsion at the wing articulation.
The centre of mass of insect wings tends to be behind the centre of torsion of the wing, and it is proposed that wing inertia about the torsional axis alone is responsible for pitch changes as the wing is accelerated at stroke reversal. A simplified inertial model is developed to calculate the angular velocity about the torsional axis that would be caused by wing inertia.
The mass distribution and the torsional axis of the wings of two species of flies was found and it was shown that in these animals inertial causes alone could develop the angular velocity in the pitching plane that is observed at stroke reversal.
Analysis of the movement of individual regions of the wing shows further that inertial effects will produce the tip to base ‘torsion wave’ seen in the wing at stroke reversal.
Parallel Inhibition of the Motor Giant, Segmental Giant and Fast Flexor Neurones of the Hermit Crab
Authors: Fraser K. , Heitler W. J. 
Published: April 2021

ABSTRACT
Previous work has shown that the giant fibres (GFs) of the hermit crab make excitatory electrical connections with the motor giant (MoG) and segmental giant (SG) neurones, and that the SGs in turn make connections to fast flexor (FF) motor neurones. In this paper we show that synchronous or almost-synchronous IPSPs can be elicited in all three classes of neurone by electrical stimulation of the connectives or roots. These IPSPs are depolarizing in the MoG and SG, and hyperpolarizing in the FFs. The IPSPs can functionally disconnect the MoG, SG and FF neurones from the GF command. Several interneurones have been found which initiate the IPSPs when driven with injected current. These are referred to collectively as inhibitory driver neurones (IDNs). In some cases IPSPs follow IDN spikes 1:1; in others more than one IDN spike is required to produce a single IPSP.
The Mechanical Power Output of a Crab Respiratory Muscle
Authors: Stokes Darrell R. , Josephson Robert K. 
Published: April 2021

ABSTRACT
The mechanical power output was measured from scaphognathite (SG = gill bailer) muscle L2B of the crab Carcinus maenas (L.). The work was determined from the area of the loop formed by plotting muscle length against force when the muscle was subjected to sinusoidal length change (strain) and phasic stimulation in the length cycle. The stimulation pattern (10 stimuli per burst, burst length = 20% of cycle length) mimicked that which has been recorded from muscle L2B in intact animals. Work output was measured at cycle frequencies ranging from 0·5 to 5 Hz. The work output at optimum strain and stimulus phase increased with increasing cycle frequency to a maximum at 2-3 Hz and declined thereafter. The maximum work per cycle was 2·7 J kg−1 (15 °C). The power output reached a maximum (8·8 W kg−1) at 4 Hz. Both optimum strain and optimum stimulus phase were relatively constant over the range of burst frequencies examined.
Based on the fraction of the total SG musculature represented by muscle L2B (18%) and literature values for the oxygen consumption associated with ventilation in C. maenas and for the hydraulic power output from an SG, we estimate that at a beat frequency of 2 Hz the SG muscle is about 10% efficient in converting metabolic energy to muscle power, and about 19% efficient in converting muscle power to hydraulic power.
Gliding Birds: Descending Flight Of The White-Backed Vulture, Gyps Africanus
Authors: Tucker Vance A. 
Published: April 2021

ABSTRACT
The air speeds and sinking speeds of birds gliding at equilibrium fall in a performance area when these quantities are plotted against one another. Three curves bound the performance area: (i) a curve for minimum sinking speed at each air speed, (ii) a curve for maximum sinking speed at each air speed, and (iii) a curve dependent on the maximum lift coefficient of the wings. I have discussed curve i in a previous paper. This paper discusses the theory of curves ii and iii, which describe rapid descent in gliding birds. I used an optical tracking device (an ornithodolite) to measure air speeds and sinking speeds of 16 African white-backed vultures (Gyps africanus Salvadori) descending rapidly from altitudes 200–500 m above the ground. The ornithodolite measured the polar coordinates of a bird’s position in space (relative to the ground) and recorded them on magnetic tape. The vultures had air speeds between 5·4 and 39·1 ms−1, and sinking speeds between 0·2 and 8·3 ms−1. Most of the observations fell within the theoretical boundaries of the performance area. These data are consistent with a maximum lift coefficient of 2·2 for the wings of white-backed vultures.
Predominance of Vagal Bradycardia Mechanism in the Brain Stem of Turtles
Authors: Hsieh J. H. , Pan C. M. , Kuo J. S. , Chai C. Y. 
Published: April 2021

ABSTRACT
Cardiovascular parameters of spontaneously breathing pond turtles (Cyclemys flavomarginata) anaesthetized with chloralose (4 mg 100 g−1) and urethane (40 mg 100 g−1), were examined during exploratory electrical stimulation of the brain stem. Turtles exhibited a low mean systemic arterial blood pressure (MSAP, average 25 mmHg) and slow heart rate (average 24 beats min−1). Upon stimulation, pressor (sympathetic), depressor (sympathetic inhibition), bradycardia and hypotensive (vagal) responses were elicited from regions of the brain stem extending from the hypothalamus to the medulla, principally in the medial region. The pressor response appeared after a longer latency than did the bradycardia and hypotensive responses. It developed rather slowly, and rarely attained a magnitude double its resting value. In contrast, stimulation of many points in the brain stem produced marked slowing or even cessation of the heart beat, and thus resulted in an immediate fall of the blood pressure even to zero. This cardio-inhibitory response depended on the integrity of the vagus nerves and was particularly marked upon stimulation in the caudal medulla, the areas of the ambiguus, solitary and dorsomotor nuclei of the vagus and the midline structures. When such an area was stimulated continuously the heart stopped beating throughout the stimulation. The longest period of cardiac arrest before the appearance of escape was 35 min. With continuous stimulation of the peripheral end of the cut vagus, the earliest escape beat occurred even later (65min). Epinephrine given intravenously produced an increase of MSAP and force of cardiac contraction, although the slope of pressor rise was shallow. Reflex bradycardia, however, was not observed. These experiments show that a very prominent vagal bradycardia can be evoked from the turtle brain stem, which may contribute to its well-known capacity for tolerating anoxia.
Motor Activity in the Stump of an Amputated Leg During Free Walking in Cockroaches
Authors: Delcomyn Fred 
Published: April 2021

ABSTRACT
A rhythmic pattern of motor activity was recorded in the stump of an amputated leg during free walking in cockroaches. During relatively rapid walking, extensor (depressor) and flexor (elevator) muscles in the intact coxa of the amputated leg showed one burst of activity during each cycle of bursting in an adjacent, intact leg. However, during slower walking these muscles could show two or three bursts of activity during each cycle of bursting in an intact leg. Motor bursts in the stump of an amputated leg showed features similar to those of bursts recorded from intact legs. Burst duration increased with an increase in period, and the bursts generally showed consistent timing (phase) relative to bursts in most of the intact legs. The motor pattern recorded in a stump was very like that recorded in an intact leg during walking, and unlike that recorded during searching for a foothold (defined in the text). It is concluded that after the amputation of most of a leg, motor neurones innervating muscles in the stump of the amputated leg continue to be driven by the interneurones that normally drive the intact leg during walking. Analysis of the motor pattern in the stump may therefore reveal important features of the locomotor control system.
The Pars Intercerebralis Neurone PI(2)5 of Locusts: Convergent Processing of Inputs Reporting Head Movements and Deviations from Straight Flight
Authors: Hensler Klaus 
Published: April 2021

ABSTRACT
The pars intercerebralis neurone PI(2)5 of Locusta migratoria is a descending large-field deviation detector (DN), projecting from the brain to the fused abdominal ganglia. It responds with bursts of action potentials (1) to specific movements of an artificial horizon, simulating deviations from course (preferred deviations are roll and yaw to the side of the axon, and pitch-up), and (2) to proprioceptive input from neck receptors signalling head movements in either direction. During compensatory head movements both inputs act together so that the deficit in visual information is balanced by proprioceptive input.
The number of spikes elicited by roll deviations depends on the sector of the visual vield initially covered by the horizon (sector specificity), increasing the more the horizon is oriented in the visually preferred direction. Hence, sector specificity involves information about the absolute orientation with respect to the horizon. The number of spikes depends further on the roll position of the head with respect to the prothorax. The response is amplified when the head is oriented in the visually preferred direction, and is attenuated when the head is oriented in the visually antipreferred direction. Visual and proprioceptive modulatory effects balance each other so that sector specificity relates to the body (i.e. the aerodynamic organs) even when head and body are rotated against each other.
During flight, the excitability of PI(2)5 is further influenced by tonic inhibition from frontal wind (no directionality), which is overriden by tonic excitation of central origin.