bluuebunny/crossref_metadata_2025 huggingface dataset:
Acid-Base and Ionic Exchanges at Gills and Kidney After Exhaustive Exercise in the Rainbow Trout
Authors: Wood Chris M.
Published: April 2021

Unidirectional Na+ and Cl− fluxes, net fluxes of Na+, Cl−, other ions, titratable acid (TA), ammonia and acidic equivalents (net H+) across the gills, together with the comparable renal fluxes, were monitored throughout a 24-h period after exhaustive exercise (simple chasing) in the rainbow trout. The gills were the major site of flux. The renal excretion of [TA—HCO3−], ammonia, lactate and most electrolytes increased after exercise, coincident with diuresis. Relative to the gills, the kidney accounted for only 8 % of net H+ flux, 0–15 %of net electrolyte losses and 50% of lactate loss, though the latter was negligibly small.

Approximately 1000 μequiv kg−1 of net H+ were transported across the gills to the water during the first 4h, and then fully recovered over the subsequent 8h, coincident with periods of extracellular acidosis and alkalosis recorded in previous studies. Ammonia efflux increased during the first 4h; changes in titratable acid flux and extracellular and NH4+ levels suggest that this elevation occurred partially as NH3 diffusion in the first hour, and thereafter mainly as NH4+ exchange. Small net Na+ losses (≈300 μequivkg−1), moderate net K+ losses (=600juequivkg−1) and large net Cl− losses (≈1200 μequiv kg−1) correlated well with previously reported plasma changes; only the Na+ deficit was fully corrected by 24 h. Na+ influx was stimulated and Cl− influx inhibited during the 0–4 h period of net H+ excretion, whereas Na+ influx returned to control levels and Cl− influx increased during the 4-12 h period of net H+ uptake. These data indicate dynamic modulation of Na+/NH4+,H+ and C1−/HCO3−,OH− exchanges; however, an excess of Cl− over Na+ efflux also contributed to net H+ excretion. Acidic equivalent flux correlated well with [Na+-Cl−] net flux, in accord with strong lon difference theory.
A Light, Portable Apparatus for The Assessment of Invertebrate Heartbeat Rate
Authors: Buchan Peter , Peck Lloyd , Tublitz Nathan
Published: April 2021

A major problem for invertebrate physiologists is that most measurements of physiological parameters are made in the laboratory, rather than in the field, often because of restrictions imposed by equipment size and sensitivity. It is questionable as to how representative such results are of animals in their natural environment. One technique that has been employed in the laboratory involves the measurement of electrical impedance, for example to monitor heartbeat (Hoggarth & Trueman, 1967; Ansell, 1973; Tublitz & Truman, 1985). To allow such measurements to be made in the field as well as the laboratory, a small, light and portable apparatus has been designed.
Ontogenesis of Contractile Properties of Skeletal Muscle and Sprint Performance in the Lizard Dipsosaurus Dorsalis
Authors: Marsh Richard L.
Published: April 2021

Ontogenetic allometries of running performance in 3-to 4-m burst runs (sprints) and of the contractile properties of the fast-twitch, glycolytic region of the iliofibularis muscle (FG-IF) were measured in Dipsosaurus dorsalis. This iguanid lizard hatches at a body mass of about 4 g and reaches adult masses of 40–70 g. Running velocity was little influenced by changes in body mass during development. Stride frequency (f) declines ontogenetically and was proportional to body mass (Mb) to approximately the −0·2 power (determined by regression analysis). Stride length (Ls) appeared to be related to the allometry of hindlimb length (LHL); both Ls and LHL were proportional to about Mb0·28. Intrinsic shortening velocity of the FG-IF decreased only slightly with increasing body mass, and was consequently not proportional to f as has been assumed by various models of running dynamics. In contrast, twitch time lengthened markedly with increasing body mass, and the ratio of twitch time to stride time remained approximately constant. These results suggest that the intrinsic velocity of the muscles does not directly or solely determine maximal f, but instead limb kinematics are determined in part by other biomechanical constraints related to body dimensions. Further, the allometry of twitch kinetics supports the idea that the properties of the muscles are adjusted to allow ample time for full activation and deactivation within the biomechanically determined stride time.
Regulation of Binding of Phosphofructokinase to Myofibrils in the Red and White Muscle of the Barred Sand Bass, Paralabrax Nebulifer (Serranidae)
Authors: Roberts Susan J. , Lowery Mary Sue , Somero George N.
Published: April 2021

The binding of phosphofructokinase (PFK) to myofibrils from the white muscle of the fish Paralabrax nebulifer (Girard, 1854) is sensitive to factors known to be allosteric regulators of PFK activity. PFK in Triton-X-100-extracted muscle remains bound to myofibrils at pH 7·0 and is fully solubilized by increasing the pH to 8-0. The curve describing the pH-dependence of PFK binding to myofibrils is similar in its steepness to pH versus activity curves of PFK at low temperature. Nucleotides are also potent modulators, preventing the association of PFK with myofibrils at concentrations between 20 and 60 μmol l−1 of ATP, ADP, MgATP or GTP, listed in order of effectiveness. PFKs in the red and white muscle extracts differ in their pH-dependence of binding to myofibrils, and their kinetic and regulatory properties (response to citrate, pH and fructose-2,6-bisphosphate). Reversible binding of PFK to myofibrils may be important in the control of glycolysis, especially in the highly glycolytic white muscle fibres.
Kinematics and Estimated Thrust Production of Swimming Harp and Ringed Seals
Authors: Fish Frank E. , Innes S. , Ronald K.
Published: April 2021

The propulsive motions of swimming harp seals (Phoca groenlandica Erxleben) and ringed seals (Phoca hispida Schreber) were studied by filming individuals in a flume. The seals swam at velocities ranging from 0·6 to 1·42 ms−1. Locomotion was accomplished with alternate lateral sweeps of the hind flippers generated by lateral flexions of the axial body in conjuction with flexion of the flippers. The frequency of the propulsive cycle increased linearly with the swimming velocity, and the maximum angle of attack of the flipper decreased, but the amplitude remained constant. The kinematics and morphology of this hind flipper motion indicated that phocid seals do not swim in the carangiform mode as categorized by Lighthill (1969), but in a distinct mode that mimics swimming by thunniform propulsors. The hind flippers acted as hydrofoils, and the efficiency, thrust power and coefficient of thrust were calculated from unsteady wing theory. The propulsive efficiency was high at approximately 0·85. The thrust power increased curvilinearly with velocity. The drag coefficient ranged from 0·012 to 0·028 and was found to be 2·8–7·0 times higher than the theoretical minimum. The drag coefficient was high compared with that of phocid seals examined during gliding or towing experiments, indicating an increased drag encumbered by actively swimming seals. It was determined that phocid seals are capable of generating sufficient power for swimming with turbulent boundary layer conditions.
Preferred Speeds in Terrestrial Vertebrates: Are They Equivalent?
Authors: Perry Andrew K. , Blickhan Reinhard , Biewener Andrew A. , Heglund Norman C. , Taylor C. Richard
Published: April 2021

Terrestrial animals have ‘preferred speeds’ within each gait, that are used much more frequently than others for moving along the ground. Energy costs reach minimal values at these speeds within each gait. In this study we asked whether these speeds are mechanically equivalent among different animals (i.e. speeds where the same levels of peak muscle stress occur). If so, this would help in establishing a link between the energetics and the mechanics of the active muscles at these speeds, providing a first step in understanding why energy costs are minimal. We also asked whether peak muscle stress reaches a similar fraction of the maximal isometric stress at these speeds. If so, this would suggest that muscles are structured so that a similar reserve capacity remains, with a similar safety factor for avoidance of injury in response to prolonged repetitive loading. We compared two species that use quite different locomotory methods at their preferred speeds: white rats that gallop and kangaroo rats that hop. We measured peak stress in the ankle extensor muscles of these two species, as they moved at their preferred speeds, using a force platform/ciné analysis technique. We also measured the maximum isometric force that this muscle group could develop in situ in the same individuals. We found the ankle extensors of white rats and kangaroo rats developed virtually identical levels of peak stress at their preferred speeds (70 ± 6 kPa and 69 ± 6 kPa, respectively, mean ± S.E.), despite a fourfold difference in peak ground reaction force per unit body mass exerted on each limb. The values of peak isometric stress in situ were also virtually identical (206 ±17 kPa and 200 ±9 kPa, respectively). Our finding that the peak muscle stress is about one-third of maximum isometric stress at the preferred speeds is consistent with the idea that these are mechanically equivalent speeds, where the same fraction of available muscle fibres is recruited. Finding nearly identical values in two species that move in such different ways (galloping vs hopping), and have such large differences in ground reaction force exerted by each limb, suggests this may be true more generally for terrestrial vertebrates.
Measured Behavioural Latency in Response to Sex-Pheromone Loss in the Large Silk Moth Antheraea Polyphemus
Authors: Baker T. C. , Vogt R. G.
Published: April 2021

Males of the giant silk moth Antheraea polyphemus Cramer (Lepidoptera: Saturniidae) were video-recorded in a sustained-flight wind tunnel in a constant plume of sex pheromone. The plume was experimentally truncated, and the moths, on losing pheromone stimulus, rapidly changed their behaviour from up-tunnel zig-zag flight to lateral casting flight. The latency of this change was in the range 300–500 ms. Video and computer analysis of flight tracks indicates that these moths effect this switch by increasing their course angle to the wind while decreasing their air speed. Combined with previous physiological and biochemical data concerning pheromone processing within this species, this behavioural study supports the argument that the temporal limit for this behavioural response latency is determined at the level of genetically coded kinetic processes located within the peripheral sensory hairs.
Wing Shape and Flight Behaviour in Butterflies (Lepidoptera: Papilionoidea and Hesperioidea): A Preliminary Analysis
Authors: Betts C. R. , Wootton R. J.
Published: April 2021

Representatives of six butterfly species, flying freely in the field or in simulated field conditions, were filmed with a high-speed ciné camera and subjected to kinematic and morphometric analysis. This is the first detailed investigation on an insect performing the varied patterns of ‘natural’ flight. Kinematic parameters in representative sequences of selected flight modes were calculated and compared, and wing shapes were characterized using aspect ratio and non-dimensional moment parameters.

The analyses and field observations of these and other butterflies suggest possible correlations between flight performance and wing shape. The behaviour of individual species conforms reasonably well with crude predictions based on aspect ratio, wing loading and wing inertia.
Quasielastic Laser Light Scattering and Laser Doppler Electrophoresis as Probes of Synaptic and Secretory Terminal Function
Authors: Sattelle David B.
Published: April 2021

The intensity fluctuations of scattered laser light provide a rapid, nondestructive probe of hydrodynamic size and polydispersity of nerve-ending subcellular particles. This method yields information on diffusive and directed motion of secretory granules and synaptic vesicles. It also enables accurate measurements of surface charge properties of isolated granules and plasma membranes. Recently, a fast, total intensity light-scattering change, sensitive to many of the factors that influence secretion, has been detected in neurosecretory terminals. Here a slower, but equally reversible, light-scattering change is detected using an intact invertebrate neurosecretory organ. Scattering at rest is dominated by particles of diameter similar to that of secretory vesicles detected in electron micrographs of the same tissue. Simultaneous release and light-scattering observations demonstrate an increase in the proportion of total scatter derived from mobile as opposed to fixed components, with no change in mean particle diameter. Since the major changes in intensity fluctuations are detected during the declining phase of the release of secretory product, they may represent longer term reorganization of terminals following intense secretory activity.

As a prelude to dissecting the origin of the fast light-scattering changes, the hydrodynamic properties of secretosomes and purified secretory granules from mouse neurohypophysis have been characterized. In this way, size, dispersity and aggregation can be followed, and subpopulations can be characterized. Application of an electric field to various subcellular fractions enables measurement of electrophoretic mobility, and hence calculation of surface-charge properties of granules and plasma membranes. The effects of divalent cations on granule surface charge in vitro indicate that surface-charge neutralization is not a calciumspecific event in exocytosis. The possibility that some of the light-scattering signal reflects dynamic changes in cytoskeletal components of the secretory terminal is examined.
The Cytoskeleton as a Barrier to Exocytosis in Secretory Cells
Authors: Aunis Dominique , Bader Marie-France
Published: April 2021

Chromaffin cells of the adrenal medulla synthesize, store and secrete catecholamines. These cells contain numerous electron-dense secretory granules which discharge their contents into the extracellular space by exocytosis. The subplasmalemmal area of the chromaffin cell is characterized by the presence of a highly organized cytoskeletal network. F-Actin seems to be exclusively localized in this area and together with specific actin-binding proteins forms a dense viscoelastic gel; fodrin, vinculin and caldesmon, three actin cross-linking proteins, and gelsolin, an actin-severing protein, are found in this subplasmalemmal region. Since fodrin-, caldesmon- and alpha-actinin-binding sites exist on secretory granule membranes, actin filaments can also link secretory granules. Chromaffin granules can be entrapped in this subplasmalemmal lattice and thus the cytoskeleton acts as a barrier preventing exocytosis. When cells are stimulated, molecular rearrangements of the subplasmalemmal cytoskeleton take place: F-actin depolymerizes and fodrin reorganizes into patches. In addition, introduction of monospecific antifodrin immunoglobulins into digitonin-permeabilized cells blocks exocytosis, demonstrating the crucial role of this actin-binding protein. In bacterial toxin-permeabilized chromaffin cells, experiments using actin-perturbing agents such as cytochalasin D and DNAase I suggest that exocytosis is in part controlled by the cytoskeleton. The intracellular signal governing the cytoskeletal reorganization (associated with exocytosis) is calcium. Calcium inhibits some and activates other actin-binding proteins and consequently causes dissolution of the subplasmalemmal cytoskeleton. This dissolution of cytoskeletal filaments should result in granule detachment and permit granules free access to exocytotic sites on the plasma membrane.
Electrophysiology of Neurosecretory Cells from the Pituitary Intermediate Lobe
Authors: Mcburney Robert N. , Kehl Steven J.
Published: April 2021

One of the goals in studying the electrical properties of neurosecretory cells is to relate their electrical activity to the process of secretion. A central question in these studies concerns the role of transmembrane calcium ion flux in the initiation of the secretory event.

With regard to the secretory process in pituitary cells, several research groups have addressed this question in vitro using mixed primary anterior pituitary cell cultures or clonal cell lines derived from pituitary tumours. Other workers, including ourselves, have used homogeneous cell cultures derived from the pituitary intermediate lobes of rats to examine the characteristics of voltagedependent conductances, the contribution of these conductances to action potentials and their role in stimulus-secretion coupling.

Pars intermedia (Pl) cells often fire spontaneous action potentials whose frequency can be modified by the injection of sustained currents through the recording electrode. In quiescent cells action potentials can also be evoked by the injection of depolarizing current stimuli. At around 20°C these action potentials have a duration of about 5 ms. Although most of the inward current during action potentials is carried by sodium ions, a calcium ion component can be demonstrated under abnormal conditions. Voltage-clamp experiments have revealed that the membrane of these cells contains high-threshold, L-type, Ca2+ channels and low-threshold Ca2+ channels.

Since hormone release from PI cells appears not to be dependent on action potential activity but does depend on external calcium ions, it is not clear what role these Ca2+ channels play in stimulus-secretion coupling in cells of the pituitary pars intermedia. One possibility is that the low-threshold Ca2+ channels are more important to the secretory process than the high-threshold channels.
The Role of Calcium in Stimulus-Secretion Coupling in Excitable and Non-Excitable Cells
Authors: Penner Reinhold , Neher Erwin
Published: April 2021

Secretion of vesicular contents by exocytosis is a common feature of excitable (neurones, chromaffin cells, beta cells) and non-excitable cells (platelets, neutrophils, mast cells). The simplistic view that the universal mechanism controlling secretion is elevation of [Ca2+]i -whatever the source of this second messenger may be -is no longer tenable in view of recent reports demonstrating secretion at basal or even reduced [Ca2+]i. It is nevertheless clear that in excitable cells an increase in [Ca2+]i is the triggering event that induces secretion. In non-excitable cells, secretion is presumably triggered by other second messengers, although [Ca2+]i appears to act as an important modulator of the rate of secretion. Conversely, these second messenger systems may serve a regulatory function in excitable cells.

Given the relative importance of [Ca2+]i in the regulation of cellular functions in excitable and non-excitable cells, it is not surprising that several mechanisms are expressed in these cells to regulate intracellular calcium concentration. The major pathway for Ca2+ in excitable cells is by voltage-activated Ca2+ channels, but release of Ca2+ from intracellular stores, via second messengers, predominates in non-excitable cells, and may also be important in excitable cells. In addition, receptor-operated channels and second messenger-gated conductances may prove to be important. All of these pathways are subject to regulation by a variety of interactive second messenger systems, which provide necessary tuning for an appropriate control of intracellular calcium level.
Pituicytes, Glia and Control of Terminal Secretion
Authors: Hatton Glenn I.
Published: April 2021

Once thought to be hormone-synthesizing cells, the pituicytes are now known to be the resident astroglia of the neurohypophysis (also referred to here as the posterior pituitary). Early investigators interpreted light microscopic observations as demonstrating pituicyte secretion, since pituicytes appeared to contain neurosecretory material when hormone demand was low and not when it was increased. Ultrastructural studies have shown that pituicytes actually engulf or completely surround neurosecretory axons and axonal endings under basal conditions, and release these neural processes when conditions require increased hormone output. Thus, the pituicytes appeared to the early workers to contain and release hormone when they actually contained and released axons and terminals in which the hormone was, in fact, contained. Dynamic interactions of pituicytes with various of the other elements in the gland have also been demonstrated. When hormone demand is low, the pituicytes not only engulf the neurosecretory processes but also interpose their own processes between the secretory endings and the basal lamina. Since any hormone that is secreted must pass through the basal lamina and into the perivascular spaces in order to enter the fenestrated capillaries, pituicyte interpositions form physical, and perhaps chemical, barriers to hormone entering the circulation. Increasing hormone demand results in retraction of pituicyte processes from the basal lamina, permitting increased neural contact. Studies of isolated neurohypophysis and of cultured adult rat pituicytes have shown that these glia undergo appropriate morphological changes in response to osmotic stimuli or to receptor-mediated activation of adenylate cyclase. Both these events are thought to be effectors of the alterations seen in vivo. Some possible mechanisms by which pituicytes may participate in the control of secretory events are discussed.
Capturing and Quantifying the Exocytotic Event
Authors: Morris John F. , Pow David V.
Published: April 2021

Although exocytosis is now known to be the universal method by which proteins are released from eukaryotic cells, we know surprisingly little of the mechanism by which exocytosis occurs. One reason for this is that it has proved difficult to capture sufficient of these evanescent events to permit their study. The difficulty with which exocytoses can be visualized with standard preparative techniques varies among tissues, but the problem is particularly apparent in the mammalian nervous system.

Tannic acid has recently been introduced as an agent by which exocytosed granule cores can be captured and visualized electron-microscopically. Application of tannic acid to the magnocellular neurosecretory system reveals exocytoses from all parts of their terminal arborization within the neural lobe, and also from their dendrites within the hypothalamus. Quantification of the exocytoses in unstimulated tissue and in tissue stimulated by a variety of exogenous and endogenous mechanisms indicates: (a) that exocytosis occurs equally from each unit of membrane of the perivascular nerve endings, and of the axonal swellings that were previously thought to be sites of granule storage, rather than release; (b) that, in the nerve endings, a greater proportion of the stored granules are exocytosed, and thus the endings are specialized for release not by any particular property of their membrane, but by a high surface membrane:volume ratio. Together, the data cast doubt on the hypothesis that exocytosis occurs only at some functionally specialized sites at certain loci in the membrane. Rather, the data favour the hypothesis that magnocellular granules can fuse with any part of the membrane, depending on constraints imposed by the cytoskeleton, and a local increase in cytosolic free calcium level.

When applied to hypothalamic central nervous tissue, tannic acid reveals that exocytosis of dense-cored synaptic vesicles occurs preferentially, but not exclusively, at the membrane apposed to the postsynaptic element. However, about half of all exocytoses from synaptic boutons occur at bouton membrane unrelated to the synaptic cleft.

In all tissues studied, tannic acid reveals a heterogeneity among secretory cells in the extent of exocytosis that occurs in response to stimulation, and permits an analysis of the degree to which secretion is polarized in any one direction.

These results question long-held assumptions concerning the site at which neurones release transmitters and modulators. Tannic acid seems likely to prove a potent tool in the investigation of both the mechanism of exocytosis and the ways in which different types of cells adapt the process to perform their physiological functions.
A Note on the Permeability of Trout Eggs to D2O AND H2O
Authors: Krogh August , Ussing Hans H.
Published: April 2021

Gray showed (1932) that the “vitelline membrane” of the trout’s egg is normally impermeable both to water and salts, while the tough “chorion” is freely permeable. In view of the fact that the eggs when squeezed out from the fish are somewhat permeable to water (Irving&Manery, 1934) and swell up to a certain extent and that the methods used by Gray might fail to reveal a very low grade of permeability, we found it worth while to utilize the “heavy” water now available for the study of permeability problems (Hevesy et al., 1935) for a few supplementary experiments on trout eggs.
Pseudo-Rheotropism in Fishes
Authors: Gray J.
Published: April 2021

Many species of pelagic fish tend to orientate their bodies so that their heads are directed upstream, and to maintain a fixed position in space although the surrounding water is in motion relative to the earth. As pointed out by Lyon (1904, 1909), it is impossible to attribute these phenomena to direct stimulation of the fish by the surrounding water, for they may occur under conditions in which there is no relative motion between the fish and its surrounding medium. Lyon showed that under normal circumstances certain fish orientate themselves by optical stimuli ; if such an animal is moved passively—either by a current of water or any other means—it responds by movements which are so adjusted as to maintain a stationary optical field ; in other words, any passive movement between the fish and its visual field calls forth compensatory movements equal and opposite to the passively induced motion. Although such phenomena undoubtedly occur in nature it is doubtful whether optical stimulation accounts for all the phenomena usually included under the term “rheotropism”. Both Steinmann (1914) and Schiemenz (1927) have shown that, in the absence of a moving visual field, fish show a marked tendency to maintain a fixed position in space when subjected to rotary movements on a turn-table. Steinmann rightly associated this behaviour with the activity of the semicircular canals of the labyrinth, but his interpretation also involves the belief that the relative motion of the fish and the water can be influenced by the motion of the water relative to the ground. This conclusion was very properly rejected by Schiemenz, who concluded that orientation was effected by an “unanalysierte Fähigkeit die Drehung an sich zu perzipieren”.
A New Form of Micro-Respirometer; With A Note on the Effect of Cleavage on the Respiration of the Egg ofRana
Authors: Stefanelli Alberto
Published: April 2021

In order to observe the respiration of single egg-cells it seemed desirable to construct a respirometer of greater sensitivity than those designed by Barcroft (1908) or Warburg (1926), or than that of any of the various modifications of these two instruments (Novy et al. 1925 ; Thunberg, 1905 ; Winterstein, 1911 ; Fenn, 1927–8 ; Fraps, 1930; and Krüger, 1934).
The Humidity Reactions of the African Migratory Locust,Locusta Migratoria MigratorioidesR. & F., Gregarious Phase
Authors: Kennedy John S.
Published: April 2021

Under the conditions of the experiments described, Locusta migratoria migratorioides shows a preference for dry air in all parts of the humidity range, although dry air is by no means optimal for development, maturation, and breeding. The strength of the reaction is correlated with the magnitude of the humidity difference available, but appears to be little dependent on the region of the humidity range. The mechanism of the reaction is hygrokinetic and possibly hygrophobotactic as well, but probably not hygrotropotactic.
The Gill Movements of NymphalEcdyonurus Venosus(Ephemeroptera) and the Currents Produced by Them in Water
Authors: Eastham L. E. S.
Published: April 2021

With further reference to the phenomena of mayfly gill movement (Eastham, 1932, 1934, 1936), an examination of the gills of Ecdyonurus venoms has been made.

The methods adopted for analysing gill movement and for observing the currents were similar to those employed for Caenis and Leptophlebia (Eastham, 1934, 1936) and need not be described here. It is perhaps sufficient to remark that the gills may be induced to oscillate at the rate of about seven per second thus making observation by means of the stroboscope possible (Gray, 1930).
The Dependence of Head Curvature on the Development of the Heart in the Chick Embryo
Authors: Waddington C. H.
Published: April 2021

At about the end of the second day of incubation, the anterior end of the embryonic axis of an embryo chick becomes twisted and bent. The twist, which is a simple rotation around the main embryonic axis, brings the left side of the head in contact with the yolk and raises the right side to point vertically upwards. The bending throws the embryonic axis into a rather complicated shape, the essential feature of which is that the anterior tip of the head remains comparatively near to a point just posterior to the ears, while the whole region of neural tube and brain which lies in between these two points is bent into an arc. The posterior part of the arc curves out slightly to the left of the main line of the embryonic axis but much the greater part lies to the right of this line. In the concavity of the curve, on the right side, lies the heart.
A Note On the Chitinous Nature of the Peritrophic Membrane ofMelanoplus BivittatusSay
Authors: Brown A. W. A.
Published: April 2021

A Previous communication (Brown, 1937) reported that the excreta of Melanoplus, after treatment by Campbell’s quantitative method for the estimation of chitin, yielded a residue which possessed a very low nitrogen content; it was suggested therefore that the peritrophic membrane here was not chitinous. Re-examination of this material showed, by the blue colour given with I2 and 75 per cent H2SO4, that its content of cellulose was very considerable; the chitinous portion, as indicated by the violet colour with I2 and 1 per cent H2SO4, consisted of small peripheral elements. This cellulose could be left behind by converting the chitin to chitosan, and extracting the latter in 3 per cent acetic acid (Hoppe-Seyler, 1894).
Studies on the Growth of TissuesIn Vitro
Authors: Jacoby F. , Trowell O. A. , Willmer E. N.
Published: April 2021

It has already been shown (1933, 1936) that chick fibroblasts (mesenchyme cells derived from the heart or from periosteal tissue) can be reduced to a state in which growth by cell division is almost at a standstill and that, by the addition to the medium of embryo tissue juice, the cells can be caused to divide again. The higher the concentration of embryo juice used, the greater is the number of cell divisions which occur. The addition of the embryo juice is followed within the first 2 hours by increased movement of the cells, which reaches its maximum in about 10 hours, but it is not until this latter time that cell divisions begin again.
The Spherical form of the Mammalian Erythrocyte
Authors: Ponder Eric
Published: April 2021

In a number of papers, I and my collaborators have considered various methods for measuring the volume of mammalian red cells, either in the discoidal 1 or in the spherical form (Ponder & Saslow, 1930a, b, 1931; Macleod & Ponder, 1933; Ponder & Robinson, 1934; Ponder, 1935 a, b). Some of these methods, such as the diffraction method, are applicable to spheres only, and others measure only changes in volume such as occur in hypotonic media. So far as this paper is concerned, the two most important conclusions of the investigations are (a) that the transformation from disk to sphere, whether effected by the addition of lecithin or one of the photodynamic dyes (Ponder, 1936), or by enclosing the cells between two closely opposed surfaces (Ponder, 1928-9), is accompanied by no change in volume, and (b) that at the “critical tonicity” in which haemolysis begins in hypotonic media, the percentage increase in volume is substantially the same irrespective of whether the cells are disks or spheres.
Permeability of Sanddollar Ova and ofModiolusandMytilusGills to Various Acids and Their Salts
Authors: Beck Lyle V. , Chambers Robert
Published: April 2021

The pH indicator, methyl red, as a vital stain (from a medium at pH 5.3) and having a relatively low pK value, was used for testing the penetration of acids and of salts of organic acids into cells. The cells were those of gill strips of Modiolus and Mytilus and the fertilized eggs of the sanddollar, Echinarachnius parma. The penetration of various acids into cells was studied by immersing the cells in artificial, unbuffered sea water acidified with the given acid at 3 ×10−3M concentration in experiments with gill strips and at 10 × 10−3M concentration in experiments with sanddollar eggs. The colour change indicating intracellular acidification was almost instantaneous with benzoic acid (5 sec. or less), slightly less rapid (5–20 sec.) with the fatty acids, valeric to acetic, and slow with HCl. The rate of the return of the methyl red to the original alkaline colour upon the transfer of the cells to artificial acid sea water (pH 5.3) was in the same order for the various acids. Intracellular acidification with a fatty acid was diminished when salts of the acid were present in the medium. Since the counteracting effect of the salts does not appear until the concentration of these salts exceeds that of the fatty acid by at least three times we may conclude that when both acid and salt are penetrating, the acid does so more rapidly than its salts. The penetration of salts of acetic, butyric and benzoic acids also occurred in the absence of added acid and at an alkaline pH approximating that of normal sea water. However, the rate of penetration was much slower than in the presence of added acid. Evidence for penetration of the salts in absence of added acid was obtained by exposing the cells to the salts prior to treatment with the corresponding acid. Effects obtained by prior treatment with the salts alone were enhanced by increasing the concentration of potassium in the medium.
The Behaviour of Epiblast Grafts Beneath the Primitive Streak of the Chick
Authors: Abercrombie M.
Published: April 2021

Grafts consisting of area opaca ectoderm, presumptive epidermis, presumptive neural tissue, or presumptive mesoderm (axial or side-plate), were transplanted to a position immediately under the primitive streak of chick blastoderms in the primitive streak stage. The grafts, though they sometimes remained as a non-neural epithelium, were usually neurally induced, contemporaneously and co-extensively with the neural induction of the host. The graft-derived neural tissue is often much thicker than the host neural tissue, and though usually forming an autonomous structure, it is frequently arranged with a high degree of symmetry relative to the host. If, however, the graft remains for a long time uninduced, lying in the host mesenchyme, it tends to break up into mesenchyme itself. It is probable that all parts of the epiblast, whatever their presumptive fate, are competent to form neural tissue, provided their epithelial structure is maintained ; and it is notable that this is true of presumptive mesoderm. The dorso-ventral polarity of the grafts is maintained whatever their orientation in the host; but the irreversible determination of this polarity was probably not tested. The antero-posterior polarity of the grafts was without effect on their differentiation. An elongation of the graft along the antero-posterior axis of the host usually occurred. It was often very marked, and generally consisted in the posterior end of the graft accompanying the host primitive node as it moved backwards. It is believed to be due to the induction of an active movement in the graft itself. The host is considerably modified by the presence of the graft. In particular, the head-fold is usually suppressed. The formation of the foregut is frequently upset, but the closed foregut shows a considerable power of regulation.
The Behaviour of Grafts of Primitive Streak Beneath the Primitive Streak of the Chick
Authors: Abercrombie M. , Waddington C. H.
Published: April 2021

Grafts consisting of pieces of primitive streak from blastoderms in the primitive streak stage were placed under the primitive streak of blastoderms also in this stage. Various effects of the host on the graft are described, particularly the reversal of the antero-posterior orientation of the graft, the alteration of the regional character of the graft so as to conform with the host tissues at the same level, the suppression of differentiation in the posterior end of the primitive streak, and the incorporation of the graft tissues into the host. A considerable number of inductions occurred, since the host axis often apparently shifts to one side of the graft. The inductions are of two kinds, the normal evocation by graft mesoderm, resulting usually in the formation of superfluous neural tissue; and the complementary induction of a normal secondary axis, which it is supposed is most often due to the preliminary induction of a primitive streak in the host. Various effects of the graft on the host occur. In particular the disturbance of the head mesenchyme suggests that foregut diverticula are produced where head mesenchyme joins lateral plate mesothelium.
Conversion of Presumptive Ectoderm to Mesoderm in the Chick
Authors: Waddington C. H. , Taylor Jean
Published: April 2021

Fragments of epiblast, or of epiblast together with endoderm, were placed in holes cut in the primitive streaks of young chick embryos, and the embryos then cultivated in vitro for about 24 hours. The grafts were sometimes extruded, but in many cases they healed more or less well. In those cases in which partial healing occurred the grafted presumptive ectoderm has usually developed into mesodermal structures, such as somites, though in a few cases it has been induced to form neural tissue. In some cases healing was so complete that no trace of the graft can be found, and in these embryos also the greater part of the presumptive ectoderm must have formed mesoderm. The conversion of presumptive ectoderm into mesoderm has only been accomplished by the method of the above experiments, which involves the performance by the graft of the normal gastrulation movements. In the Amphibia the performance of such movements is unnecessary, and it is suggested that in the chick the importance of the movements is not that they are a part of the gastrulation process but merely that they involve the breakdown of the epithelial structure of the grafted ectoderm. The relevance of these results to the germ-layer theory is discussed, and it is pointed out that, although it is clear that there is no fundamental physiological distinction between the ectoderm and mesoderm before invagination, it is still possible that such a distinction may exist between the endoderm and the ectodermmesoderm system.
The Water and Electrolyte Exchange ofNereis Diversicolor(Müller)
Authors: Ellis W. G.
Published: April 2021

It has been shown by McCutcheon & Lucke (1928) that in glucose solutions isotonic with 40 per cent sea water, the eggs of the sea-urchin Arbacia absorb twice as much water as they do from 40 per cent sea water, and that this increased imbibition is prevented by a small concentration of calcium ion in the glucose solution, even in the absence of the other cations of sea water. Pantin (1931 a) showed that the Platy-helminth, Procerodes (Gunda) ulvae, which in its estuarine habitat withstands tidal changes in osmotic pressure, is only able to survive in very dilute salt solutions if these contain calcium.
The Toxicity of Dissolved Metallic Salts toPolycelis Nigra(Muller) andGammarus Pulex(L.)
Authors: Jones J. R. Erichsen
Published: April 2021

A brief review is given of previous work on the toxic effect of aqueous solutions of metallic salts on living protoplasm and fresh-water animals. The behaviour of Polycelis nigra in aqueous solutions of metallic salts is described, survival curves for this animal in some variety of salts are given, and the mode of toxic action of these salts is discussed. It is shown that in the case of heavy metal salts the toxic effect at concentrations below isotonicity is due almost entirely to the cation, the toxicity of the anion being relatively small. At concentrations above isotonicity the anion and the osmotic pressure of the solution act as additional lethal factors. Salts of the metals of the alkalis and alkaline earths are shown to be comparatively harmless below isotonicity, with the exception of salts with a toxic anion such as potassium chromate. This salt is highly toxic at low concentrations. It is shown that in the case of the nitrates and sulphates of the heavy metals, the toxicity is determined by the product of the normality and the electrical conductance ratio at that normality. Recovery experiments with Polycelis are described and it is shown that these illustrate the above relationship between toxicity and conductivity. Survival curves for Gammaruspulex in salts of copper and zinc are described. Those for zinc exhibit the same relationship.
Wound Healing in an Insect (Rhodnius ProlixusHemiptera)
Authors: Wigglesworth V. B.
Published: April 2021

If the epidermis of an animal is injured so that its continuity is destroyed, the surrounding cells multiply and spread over the wound until the gap is filled. Then their growth ceases. The factors which initiate this renewed growth of “repair”, and the factors by which growth is arrested when the defect has been made good, are very incompletely known. The object of the present work was to re-investigate this old problem upon new material.
Stretch Receptors in the Muscles of Fishes
Authors: Fessard A. , Sand A.
Published: April 2021

The presence of stretch receptors in the muscles of Raja and Scylliwn has been physiologically demonstrated. Their morphology is unknown. The behaviour of a single end-organ in the radial muscles of the pelvic fin of Raja clavata has been examined in detail. The adaptation curve and the tension-frequency relationship have been determined. Under constant tension a single end-organ has continued to function rhythmically for over 1 hour. When tension is suddenly reduced, there follows a silent period before the frequency of discharge corresponding to the reduced tension appears. The quantitative aspects of the behaviour of the stretch receptor of Raja bear a closer resemblance to those of the receptors of the carotid sinus than to those of mammalian and amphibian limb muscles. The response of muscle receptors during a passive undulatory movement of the pectoral fin has been recorded, and their role in the swimming rhythm is discussed.
On the Eclipse Plumage of the Mallard (Anas Platyrhyncha Platyrhyncha)
Authors: Walton Arthur
Published: April 2021

The eclipse plumage of the male mallard (Anas platyrhyncha platyrhyncha) which normally appears in June and July has been produced prematurely in February and March by subjecting the birds to artificial light in addition to normal daylight.

Castration of male mallards did not prevent the assumption of eclipse in the first year but did so in the second year. Regenerated tissue was not found. It is concluded that the eclipse plumage is not caused by the direct action of a testicular hormone on the feather follicle, but that removal of the testis sooner or later produces an effect on some other endocrine organ or organs which consequently ceases to be sensitive to seasonal change (light) or fails to produce the hormones which bring about eclipse.
Studies on the Onychophora
Authors: Manton S. M. , Ramsay J. A.
Published: April 2021

All terrestrial animals have to solve the problem of resistance to desiccation, and adaptations associated with this difficulty are of two main types: (1) the development of waterproof external surfaces, and (2) the reduction of the amount of water lost by excretion. In some animals there is also an increase in the formation of metabolic water. In a previous paper it has been shown that the second method has been employed by the Onychophora (Manton& Heatley, 1937). A uricotelic metabolism has been acquired, and nitrogenous excretion by the intestine has reduced the water passing out by the segmental excretory organs to a minimum. The presence of large fat stores in the body may indicate that a fatty metabolism is also increasing the production of metabolic water.
Inositol Transport by Hepatopancreatic Brush-Border Membrane Vesicles of the Lobster Homarus Americanus
Authors: Siu Teva , Ahearn Gregory A.
Published: April 2021

The mechanism of [3H]myo-inositol transport by the lobster hepatopancreas was examined using purified brush-border membrane vesicles. Transport was stimulated by a 100 mmol 1−1 inward Na+ gradient, but other cation gradients were ineffective, suggesting a Na+-dependent transfer mechanism. The transport system was most efficient at pH7·0 (both sides), rather than in the presence of a pH gradient (pHin = 7·0; pHout = 5·5) or at bilaterally low pH (pHin = pHout = 5·5). The system was shown to be electrogenic in two different ways. First, myo-inositol uptake was stimulated by anions of increasing permeability (SCN− > Cl− > gluconate). Second, an outwardly directed, valinomycin-induced K+ diffusion potential (inside negative) enhanced uptake in comparison with vesicles lacking the ionophore. Myo-inositol was transported by a carrier mechanism with an apparent Kt of 0·79mmoll−1, a Jmax of 6·3pmolmg protein−1 s−1, and by apparent diffusion with a permeability coefficient of 5·92 pmol mg protein−1s−1 (mmoll−1)−1. D-Glucose was a noncompetitive inhibitor of myo-inositol uptake, but myo-inositol did not significantly reduce the transport of D-[3H]glucose. Vesicles preloaded with myo-inositol trans-stimulated [3H]myo-inositol uptake, whereas those preloaded with D-glucose did not, suggesting that the inositol carrier did not transport D-glucose. It is proposed that myo-inositol does not share the glucose carrier, and that D-glucose may modulate inositol influx by binding to a ‘regulator’ site on the inositol carrier.