bluuebunny/crossref_metadata_2025 huggingface dataset:
Receptor Elements in the Thoracic Muscles of Homarus vulgaris and Palinurus vulgaris
Authors: Alexandrowicz J. S.
Published: April 2021

In the thoracic muscles of Homarus vulgaris and Palinurus vulgaris the presence of receptor elements of various kinds has been recorded. Muscle receptor organs belonging to the same category as described previously in the abdomen have been found in the two posterior (7th and 8th) thoracic segments. According to their situation one lateral and one median receptor may be distinguished on each side of each segment. Like those in the six abdominal segments they are linked with the system of the extensor muscles. The topography of these organs in relation to that of the thoracico-abdominal muscles is described. There are certain differences in their location between the two species. Receptor organs of this category, with one exception, are composed of a special thin muscle and a nerve-cell ending in connective tissue intercalated in this muscle. The lateral receptor of the 7th thoracic segment in Homarus has no muscle of its own and terminates on connective tissue fibres accompanying an ordinary muscle. In the nerve supply of these receptors in the thorax the same elements as in the abdomen, i.e. the motor nerves and the two accessory nerves, can be distinguished, but their distribution in the thorax has certain special features. It is assumed, in view of certain differences in the appearance of the nerve-cells and their processes, that the muscle receptor organs of this category are of two types in each of the segments. Nerve-cells regarded as receptors of a different category have been found in some of the muscles inserting in the median surface of the epimeral plate. These cells, termed ‘N-cells’, are smaller elements than those of the first category and have not a special muscle of their own, but end with long processes between the fibres of the ordinary muscles. In each of the species investigated five such elements have been found. No evidence is as yet available as to whether they are present exclusively in the thoracic region or are more generally distributed. It is suggested that the N-cells may represent more primitive forms of muscle receptors, and that the receptor organs of the extensor muscles in the thorax and abdomen are more highly evolved forms.
A Comparison of some Aspects of the Retinae of the Manx Shearwater, Fulmar Petrel, and House Sparrow
Authors: Lockie James D.
Published: April 2021

Most birds are either diurnal or nocturnal. The Manx shearwater is one of the very few that regularly perform such normal activities as feeding, hunting, and flying by day, and other activities, such as homing to the nest, by night. The retinal structure of the Manx shearwater is compared with that of a diurnal passerine (house sparrow) and a diurnal sea-bird (fulmar petrel), in order to determine what features are common to sea-birds and what, if any, may be specific adaptations to vision over a wide range of light intensity. Both sea-birds have a linear area centralis but lack a fovea. The rods of the dark-adapted fulmar and shearwater show great difference of shape from those of the light-adapted. The shearwater has more rods at the area centralis, a larger rodparaboloid in the dark adapted retina, and a greater ratio of total number of visual cells to ganglion nuclei than has the fulmar.
A New Type of Light Source for Phase-Microscopy
Authors: A.Kempson D.
Published: April 2021

The method described here is a modification of the system of phasemicroscopy described by Kempson, Thomas, and Baker (1948) and Baker, Kempson, and Brunet (1949). In this system the phase-plate is placed behind (above) the rear focal plane of the objective. A large illuminating annulus is placed immediately in front of the microscope lamp, and an image of it is made to coincide with the phase-plate annulus by lowering the substage condenser and adjusting the mirror.
A simple Technique for direct Observation of the Effect of Radiation on living Cells in Vitro
Authors: Lajtha L. G. , Phil. D. , Oliver R. , Inst.P. A.
Published: April 2021

A Technique has been devised in our laboratory for irradiating living cells while they are being observed under the phase-contrast microscope.
Phase Contrast and Electron Microscope Studies of the Appearance and Behaviour of the White Cells of Normal Human Blood
Authors: Marchant June
Published: April 2021

The phase-contrast microscope has been used to study form and movement of human leucocytes and blood platelets in three types of preparation ; (a) warm sealed blood drops, (b) warm sealed films of leucocytes adhering to coverslips after incubation of blood drops at 37° C. for 30 minutes or more, and (c) warm sealed films of blood platelets obtained by similarly incubating drops of saline suspensions of these cells. Similar preparations to (b) and (c) were obtained on formvar films and studied in the electron microscope. Phagocytosis was studied in all the above preparations after adding suspensions of collodion particles or of Staphylococcus albus. The neutrophils were the most versatile cells seen in the above preparations. The amoeboid forms were the most mobile and phagocytic. Another form showed rapidly waving processes which gradually spread into a flat membrane on the glass. Flattened immobile neutrophils were still capable of phagocytosis. Bacteria which adhered to the cell surface moved over it towards the thicker central region of the cell where ingestion occurred. Eosinophils showed a mobile amoeboid form and flattened forms which were often very bizarre in shape. They did not phagocytose readily. Monocytes showed slowly moving amoeboid forms or forms with ruffle-like membranes around the cell. They were phagocytic. Lymphocytes were capable of amoeboid movement but did not flatten on glass and were not phagocytic.
Amoeba hugonis n.sp.: Life-history
Authors: Taylor Monica
Published: April 2021

Material collected in Loch Tannoch was allowed to macerate in a chemical nutrient. A rich crop of Euglena gracilis as well as other infusoria resulted. Eight months later, when the Euglena had encysted, many amoebae were found at the bottom of the receptacle. They constitute a new species, here named Amoeba hugonis. An average adult specimen, when extended, measures about 104 × 5· 2μ. The nucleus consists of a central karyosome lying in the nuclear sap, separated from the cytoplasm by a well-marked nuclear membrane. Between the latter and the karyosome is situated an achromatic ‘collar’ with chromatin particles embedded in it.

Fission is described, but a study of mitosis has been deferred. The life-history of this small amoeba is very similar to that of the large A. proteus, &c The cycle occupies two months. Chromidia begin to appear in the cytoplasm of the early adult. They give rise to spores, out of which amoebulae hatch.
Trimorphism in the Ichneumonid Parasite Geliscorruptor
Authors: SALT GEORGE
Published: April 2021

The ichneumonid parasite Gelis corruptor is trimorphic in the development of wings: females are invariably apterous; males may be either macropterous or micro-pterous. Females show no trace of wing-buds in the pupa and are without wing-disks in the late larval stage. The female apteryis a sex-limited character and is of genetic origin. All male larvae have wing-disks and are potentially fully winged males. On a host providing adequate nourishment, the male larva develops into the macropterous form; on a host providing meagre nourishment, it develops into the micropterous form. Eggs or young larvae transferred from a small to a large host develop into macropterous males ; larvae removed from large hosts before they have finished feeding develop into micropterous males. The dimorphism of the male sex is therefore controlled by the host viewed as a quantity of food. The two forms of males differ not only in the development of the wings but also in the structure of the thorax, the size of the ocelli, the form of the endoskeleton, and the development, innervation, and tracheal supply of the thoracic muscles. The trimorphism is strict, since all females are apterous and (with the exception of one abnormal specimen) all the males examined belong without intermediates to either the macropterous or the micropterous form. The principal differences observed between the three forms all appear to be bound up with the condition of the wings. How the development of this complex of characters is organized, particularly in the two forms of males, presents an interesting problem of morphogenesis.
Enucleation of Sea-Urchin Blastomeres with or without Removal of Asters
Authors: Lorch I. Joan
Published: April 2021

The following experiments were carried out on one blastomere at the two-cell stage of the sea-urchin egg:

1.Removal of the nucleus.

2.Removal of the nucleus and surrounding cytoplasm (centrosphere).

3.Attempted removal of the centrosphere only.

In cells from which the nucleus had been removed the asters multiplied for up to 7 hours and then disappeared. During the period of aster multiplication, cleavage furrows often appeared between the asters but did not succeed in dividing the cell. After about 8 hours, cleavage into a large number of spheroidal cells occurred.

When the nucleus and centrosphere were removed no asters were formed and no cleavage furrows were observed until after about 8 hours, when division into a large number of spheroidal cells occurred.

When attempts were made to remove the centrosphere, leaving the nucleus intact, asters were always eventually re-formed. Before the re-formation of asters neither the nucleus nor the cytoplasm divided although dissolution of the nuclear membrane, followed by its reappearance, occurred. After re-formation of the asters cleavage appeared to be normal.
Some Structural Proteins of Mytilus Edulis
Authors: Brown C. H.
Published: April 2021

The byssus threads, periostracum, hinge, ground substance of the shell, and the supporting material of the gills of Mytilus edulis, have been examined by physical, chemical, and histochemical means. The byssus threads, periostracum, and hinge have been shown to consist of a quinone-tanned protein. The byssus threads are formed in the posterior groove of the foot from the secretions of two glands, the ‘white ‘gland which supplies the bulk of the protein of the thread, and the ‘purple ‘gland which supplies the aromatic material responsible for the tanning. The periostracum is secreted by gland cells in the epithelium of the outer lobe of the mantle edge. The supporting material of the gills is a fibrous protein without quinone-tanning. This protein is in some respects similar to the untanned protein of the byssus.
Studies of the Mesogloea of Coelenterates: I. Histology and Chemical Properties
Authors: Chapman Garth
Published: April 2021

Evidence is presented to show that the mesogloea of the coelenterates examined, including Aequorea, Aurelia, Cyanea, Chrysaora, Calliactis, and Metridium contains collagen-like material in the form of fibres of varying sizes. Cells are also present in the mesogloea of some species but there is little evidence concerning their functions.

In Aequorea and the Scyphozoa examined the fibres appear to be straight and very transparent in life but on injury and fixation they adopt a convoluted and irregular appearance. Cells are present in Aurelia and form about 0· per cent, of the mesogloea by volume but are absent from the other medusae examined. The mesogloea of actinians is of a more densely fibrous character than that of medusae. In Calliactis and Metridium the crossed fibrillar structure present is determined by mechanical forces acting on the tissue.

Reference is made to the physical properties of Calliactis mesogloea, which are described in another paper. The material is tough, almost resembling cartilage in its consistency, and has considerable tensile strength.

The chemical nature of the mesogloea is shown to be primarily that of a protein of which the amino-acid composition is similar to that of vertebrate collagen.

The role of the mesogloea in the life of the animal is that of a base for the muscles, a limiter of the body volume, and a resister of rapid movements, both those caused by the musculature and those enforced by the environment without. Its viscous-elastic properties are well adapted to this role since the elastic component, having a short timescale, can provide a restoring force for rapid deformations.
The Ability to Differentiate, and the Size of Regenerated Cells, after repeated Regeneration in Spongilla Lacustris
Authors: Brøndsted H. V.
Published: April 2021

The findings presented here have a bearing on regeneration in general. They show that even in simply organized animals, the number of totipotent cells which are able to differentiate decreases as the individual ages. In older specimens it takes longer for the totipotent cells to differentiate than in younger ones ; at the same time the nuclear and cytoplasmic volume of these cells is reduced.

The expanded basal epithelium of sponges germinating from gemmules is an organ necessary to establish the tension in the body which is indispensable for the functioning of the sponge. Sponges that have germinated from gemmules can be forced to regenerate a basal epithelium. The materials for this regeneration is furnished by the archaeocytes, which are embryonic, totipotent amoebocytes. The number of archaeocytes that are able to perform this regeneration decreases with time, i.e. as the differentiation of the entire body proceeds.

On the other hand, the ability of the sponge to expand repeatedly on its own basal epithelium after being pushed away from it is limited only by the onset of cytolysis.

The ability of the archaeocytes to regenerate new typical basal epithelial cells is reduced after repeated regeneration.

The size of both nucleus and cytoplasm is reduced more and more during repeated regeneration. The nucleo-cytoplasmic ratio is thus kept fairly constant.
Cytological Studies of the Neurones of Locusta migratoria Part III. Histochemical Investigations, with Special Reference to the Lipochondria
Authors: Shafiq Saiyid Ahmad , Casselman W. G. Bruce
Published: April 2021

The motor neurones of the thoracic ganglia of adult Locusta migratoria have been studied by in situ histochemical techniques. Phospholipides and unsaturated cerebrosides are concentrated in the lipochondria; acetalphosphatides, cholesterol, protein, and ribonucleic acid are diffusely present throughout the cytoplasm; little nucleic acid is demonstrable in the nuclei.
Acetylated Sudan Black B as a More Specific Histochemical Reagent for Lipides
Authors: Casselman W. G. Bruce
Published: April 2021

Sudan black B is treated with an equivalent of acetic anhydride. The acetylated product is more specific for lipides than the parent dye.
Lead Tetra-Acetate/Schiff Tests in Histochemistry
Authors: Casselman W. G. Bruce
Published: April 2021

Certain polysaccharides, such as starch and glycogen, do not give consistently positive or negative reactions with all lead tetra-acetate/Schiff techniques. This depends upon the conditions under which the oxidant is used. A simple glacial acetic acid solution of lead tetra-acetate is least active but most specific. Added potassium acetate acts as a catalyst. Dilution with water not only increases the activity of the reagent but also decreases the specificity of the test.
The Histochemical Déphosphorylation of Riboflavin Phosphate (Flavin Mono-nucleotide) and Pyridoxal Phosphate (Co-decarboxylase)
Authors: Bourne Geoffrey H.
Published: April 2021

The histochemical dephosphorylation of riboflavin phosphate and pyridoxal phosphate has been studied at pH 9·0 and pH 5·0. The results have been compared with those obtained with glycerophosphate. It was concluded that these substrates are dephosphorylated by enzymes or enzyme systems differing from each other and from that which dephosphorylates glycerophosphate. The vitamin substrates undergo some dephosphorylation by all tissues examined at pH 9·0. At pH 5·0, however, no reaction is given by any tissue with riboflavin phosphate as a substrate, but all tissues give some reaction at this pH with pyridoxal phosphate. The reaction at both acid and alkaline pHs with pyridoxal phosphate is in some tissues located in bodies resembling mitochondria: the sarcosomes of heart-muscle in particular give a strong reaction. This is true at pH 9·0, to a lesser extent, with riboflavin phosphate. It is possible that the sites of dephosphorylation shown by the histochemical tests may also be the sites of phosphorylation of these vitamins. Intercalated disks of heart-muscle show an intense dephosphorylating activity for riboflavin phosphate and glycerophosphate. Pyridoxal phosphate and riboflavin phosphate are dephosphorylated at the same sites (differentiating regions) as glycerophosphate in rat embryos.
The Epicuticle of an Arachnid, Palamneus swammerdami
Authors: Krishnan G.
Published: April 2021

The epicuticle of Palamneus swammerdami in the unhardened condition is homogeneous. It stains uniformly red with Mallory. When hardened, it comprises an internal unstained region, giving evidence of —S—-S— bonding, and is bounded externally by a very thin membrane which stains blue with Mallory.

The protein of the inner basal layer differs from its counterpart in the insect epicuticle in the absence of tyrosine, in the occurrence of cystine and cysteine, and in being resistant to the action of hot alkalis. Though apparently related to the keratin of vertebrates, it is not identical with it. The outer thin membrane is lipide in nature. X-ray diffraction studies show that the epicuticular protein is unique: it is unlike both arthropodin and the keratin of vertebrates. However, the outer membrane of the epicuticle yields a diffraction pattern indicating the presence of long-chain paraffins and is similar to the outer epicuticle of the blowfly larva. The chitin of the cuticle appears to be identical in pattern with that of insects.

In spite of differences in structural and chemical constitution, the epicuticle of the scorpion shows a resemblance to the basic pattern of the insect epicuticle. The differences may be attributed to the absence of phenolic tanning and the occurrence of —S—S— bonding. The possible role of the purines present in the cuticle of the scorpion is discussed in relation to —S—S— bonding.
A Study of the Osmium Techniques for the ‘Golgi Apparatus’
Authors: Baker John R.
Published: April 2021

The paper is concerned with the action of the osmium techniques for the ‘Golgi apparatus’ on the intestinal epithelial cell of the mouse. It is shown that, when the fixative has acted, there are many separate lipide spheres in the ‘Golgi’ region. During postosmication the spaces between these spheres are filled up with a black precipitate. This black precipitate does not represent the distribution of lipide material.
The Action of Fixatives on the Ultra-violet-absorbing Components of Chick Fibroblasts
Authors: Davies H. G.
Published: April 2021

This paper describes an investigation by ultra-violet spectrometry of the physical and chemical changes caused by treating interphase chick heart fibroblasts, grown in tissue culture, with a variety of fixatives. The same cells, before and after fixation, were photographed either at 265 and 313 mμ or at a series of wavelengths required for an absorption spectrum. The nucleus of the living interphase cell, apart from nucleoli, is nearly homogeneous, and non-specific light loss measured by the optical extinction at 313 mμ (E313) is not detectable. After fixation the nuclear material is redistributed into filamentous and rounded structures. These nuclear structures are least apparent after osmium tetroxide, methanol freezing-substitution, and freezing-drying; may be more marked after 10 per cent, neutral formalin; and are very marked after Carnoy fixation. E313 is measurable in a fixed nucleus and the ratio of optical extinctions E313/E265 is always less than about 15 per cent. E265 increases as a result of the shrinkage of the nuclear area which ranges from about 8 to 16 percent, for osmium tetroxide, about 5 to 35 percent, for neutral formalin, about 19 to 47 per cent, for Carnoy, and about 20 to 40 per cent, for freezing-substitution. Apart from occasional cracks in cells, freezing-substitution and freezing-drying preserved nuclear and cytoplasmic structure as well as osmium tetroxide. (i) Total nuclear extinction is defined as average nuclear extinction times nuclear projected area. Decreases in total nuclear extinction at 265 mμ, after fixation in Carnoy and neutral formalin, range from 10 to 35 per cent, and may be attributed to losses of absorbing material. After formalin fixation there is a decrease of approximately 40 per cent, in the total cytoplasmic extinction at 265 mμ. The method of correcting for non-specific light loss and other possible sources of error are discussed. (ii) Osmium tetroxide itself absorbs in the ultra-violet and ‘stains’ the cell, thereby increasing the optical extinction. The staining reaction was studied by fixing films of protein, fat, and nucleic acid. (iii) After methanol freezing-substitution the total extinction of the nucleus increases slightly. The ratio of optical extinctions E265,/E280 for the living nucleus is about 2·0 and by applying the methods of curve analysis due to Caspersson it is concluded that the amount of ‘standard protein’ in the nucleus is small compared with the amount of nucleic acid. After all methods of fixation E265/E280 decreases to about 13 and similarly it is concluded that the fixed nucleus contains about ten to twenty times as much ‘standard protein’ as nucleic acid. This curious result is discussed and several possible explanations suggested. It is concluded that the derivation of relative amounts of protein and nucleic acid by analysis of the absorption spectra of either living or fixed cells should be treated with caution.
On the Structure and Adaptations of Pandora inaequivalvis and P. pinna
Authors: Allen J. A.
Published: April 2021

The two British species of Pandora are adapted for life on muddy-sand. P. inaequivalvis is taken from very sheltered shores at low-water mark and down to 10 fathoms. P. pinna is taken from depths of over 40 fathoms.

Both species are markedly inequivalve. This is probably connected with the habit of lying horizontally.

The mantle muscles and the ciliary mechanisms of the mantle and gills are described.

An account of the morphology and the functioning of the stomach is given and various modifications, due to the reduced typhlosole, are described.
Refractometry of Living Cells Part II. The Immersion Medium
Authors: Barer R. , Joseph S.
Published: April 2021

This paper continues the discussion of an immersion method of refractometry of living cells, the basic principles of which were given in Part I (Barer and Joseph, 1954). A suitable immersion medium should be non-toxic, must not penetrate the cell, and must be in osmotic equilibrium with it so that no change in volume (and hence in concentration) occurs. These requirements are best met by solutions of substances of high molecular weight. The effects observed when cells become freely permeable to such substances are described. An account of tests with various immersion media is given. The main substances tried have been peptone, proteose, protein hydrolysate, dextran, polyvinyl alcohol, polyvinylpyrrolidone, acacia gum, egg albumin, bovine gamma globulins, carboxyhaemoglobin, and bovine plasma albumin. Of these, bovine plasma albumin has proved to be most generally useful though acacia gum may be a good inexpensive substitute for some cells, particularly fungi.

The osmotic properties of the immersion medium are most important and must be carefully controlled if true determinations of solid concentration are to be made. Some of the many difficulties in defining an isotonic physiological medium are reviewed. It is suggested that the best practical definition is that such a medium should be innocuous and should not change the cell volume. A method of adjusting the salt content of the medium, based on this definition, is described, and the possibility that some cells may exhibit a degree of osmotic regulation is discussed. Finally, evidence is presented to demonstrate the harmlessness of the isotonic protein medium to many types of cells. Photomicrographs of cell division over a period of 48 hours in a protein medium are shown.
Neoteny with Goitre in Triturus helveticus
Authors: Dodd J. M. , Callan H. G.
Published: April 2021

A population of newts from a pond near Crail, Fife, was found to contain neotenic and goitrous specimens of Triturus helveticus in 1951 and 1952 but not in 1953 and 1954. This is a unique record of goitre among amphibians.

The thyroid glands of normal adult and neotenic non-goitrous T. helveticus are paired spheroidal or ellipsoidal bodies whose longest dimension varies between 300 and 700 ft. They consist of a few large follicles. The thyroid glands of the goitrous neotenic specimens may be as much as 4 mm. long. They are extremely hyperplastic and hyperaemic and for the most part consist of follicles smaller than those charac- teristic of normal newt thyroids. These goitrous thyroids produce major displacement of other structures in the throat region but do not invade other tissues.

It is suggested that the goitres result from the exposure of overwintering newt larvae to the ‘brassica factor’ carried to the pond in the faeces of rabbits feeding on turnips and kale in neighbouring fields.
The Histochemical Localization of β-Glucuronidase in the Digestive Gland of the Roman Snail (Helix pomatia)
Authors: Billett F. , Mcgee-Russell S. M.
Published: April 2021

A modification of the histochemical technique for the localization of β-glucuronidase originally suggested by Friedenwald and Becker (1948) has been applied to the digestive gland of the gastropod Helix pomatia. In the original technique the ferric 8-hydroxyquinoline formed by the enzymic hydrolysis of quinolyl-8-glucuronide, in a saturated golution of ferric 8-hydroxyquinoline, was converted to Prussian blue. The Prussian blue conversion is omitted in the technique described in this paper as it appears to introduce errors in localization. The ferric 8-hydroxyquinoline crystals are sufficiently characteristic to be used as the end-point of the technique. The results obtained suggest that β-glucuronidase is confined to the digestive cells in the digestive gland of the snail, and is associated with secretory granules in them.
Respiratory and Cardiac Performance inLolliguncula Brevis(Cephalopoda, Myopsida): The Effects of Activity, Temperature and Hypoxia
Authors: Wells M. J. , Hanlon R. T. , Lee P. G. , Dimarco F. P.
Published: April 2021

Lolliguncula brevis Blainville is a small euryhaline squid found at temperatures between 11 and 31 °C. Changes in heartbeat and ventilation frequencies were observed throughout this temperature range and under a variety of conditions, including acute hypoxia and swimming by jet propulsion in a tunnel respirometer. Resting showed a Q10 of 1·47, and heart rate and ventilation rate Q10 values of 1·92 and 1·73, respectively; oxygen uptake could exceed 1·01kg−1h−1 at 30°C even at rest. The squids regulated their oxygen uptake at all temperatures. Oxygen extraction rates were in the region of 5-10% in saturated water, increasing to 15-20% in hypoxic water or after exercise. One effect of this variability is that ventilation stroke volume can remain constant throughout the range of temperatures and oxygen concentrations that the animal is likely to encounter, a necessary condition since the ventilation stream is also the principal mode of locomotion by jet propulsion. Blood oxygen-carrying capacity (from the copper concentration) was 4·6 ± 1·8 vols%. Cardiac output and stroke volume were estimated from the observed values and heartbeat frequencies. Resting at 25°C, the output was close to ll-51kg−1bodymassh−1. The systemic heart of Lolliguncula weighed only 2·06 ± 0·62 g kg−1. In exercise the cardiac output must exceed 14x 1031kg−1 heart mass h−1, pumping more than the heart’s own mass of blood at each stroke.
The Action of Vasoactive Intestinal Peptide Antagonists On Peptidergic Modulation of the Squid Schwann Cell
Authors: Evans Peter D. , Villegas Jorge
Published: April 2021

The effects of two specific antagonists of vasoactive intestinal peptide (VIP) receptors were investigated on the VIP-induced hyperpolarization of the membrane potential of the Schwann cell of the giant nerve fibre of the tropical squid. Both (pCl-D-Phe6,Leu17)VIP and (N-Ac-Tyr1,D-Phe2)-GRF(l-29)amide competitively and reversibly blocked the effects of VIP in this preparation with the former compound being more potent than the latter. The blocking actions of both antagonists were specific for the responses of this preparation to VIP. They did not block the actions of carbachol, DL-octopamine or substance P. Both antagonists also reduced the effectiveness of an endogenous VIP-like component in the normal hyperpolarizing action of giant axon activity on the membrane potential of the Schwann cell, with the same potency ratio as for their actions on the effects induced by the exogenous application of VIP.
Kinematics of Swimming in Two Species ofIdotea(Isopoda: Valvifera)
Authors: Alexander David E.
Published: April 2021

Individuals of Idotea resecata and I. wosnesenskii were videotaped at 200 frames s∼1 while swimming freely. Propulsion is provided by the first three pairs of abdominal appendages (pleopods), which may also function as gills. Unlike typical crustacean metachronal beating, in Idotea all three pairs of propulsive pleopods begin their recovery strokes simultaneously. Each pair then carries out its power stroke in sequence: third pleopods have a short power stroke, then second pleopods have an intermediate power stroke, finally first pleopods have a long power stroke. After these power strokes, there is a pause before the next recovery stroke begins. The duration of the power stroke of any pair of pleopods, as well as the overlap with other pleopods’ power stroke, is variable and is not directly related to swimming speed. Stroke amplitude is approximately constant, but stroke frequency is significantly correlated with swimming speed. Other stroke variables which could affect swimming speed are also loosely correlated with frequency, but it appears that frequency is the most important determinant of swimming speed. The unusual stroke pattern in Idotea may be related to the respiratory function of the pleopods.
Calcium-Dependent Action Potentials in Giant Salivary Gland Cells of the LeechHaementeria Ghilianii: Calcium Removal Induces Dependence on Sodium
Authors: Wuttke Werner A. , Berry Michael S.
Published: April 2021

An electrophysiological study was made of the giant, non-coupled salivary gland cells of the leech Haementeria ghilianii (de Filippi, 1849). Resting membrane potential (−40 mV to −80 mV) was primarily dependent on K+, with a small contribution from a Na+ conductance and an electrogenic Na+ pump. Resting Cl− permeability was low. The cells generated overshooting action potentials (70-110 mV, 100-400 ms) which appeared to be mediated exclusively by Ca2+ because they were unaffected by removal of external Na+ and were blocked by 5 mmol 1−1 Co2+. Removal of external Ca2+ and addition of 1 mmol 1−1 EGTA produced spontaneous action potentials of reduced amplitude (peaking at about OmV) and greatly increased duration [typically tens of seconds but sometimes resulting in sustained depolarizations (plateau potentials) extending up to 30min or more]. Action potential amplitude was then dependent on external Na+ concentration, and action potentials were abolished by removal of Na+. The responses were blocked by 5 mmol 1−1 Co2+, indicating that they were produced by Na+ flowing through Ca2+ channels. Addition of micromolar concentrations of Ca2+ to Ca2+-free saline de-creased spike duration and amplitude, suggesting a competition between Na+ and Ca2+. An electrogenic Na+ pump was activated by removal of Ca2+, presumably as a result of the influx of Na+ during spiking; this produced large increases in membrane potential which occurred spontaneously or when Ca2+ was reintro-duced. In normal saline, spike overshoot and duration were increased when the temperature was lowered by 10°C, whereas in Ca2+-free solution, they were reduced by this change. This suggests that the Ca2+ channel may be differentially affected by cooling, depending on the presence or absence of Ca2+
Exercising with and Without Lungs: I. The Effects of Metabolic Cost, Maximal Oxygen Transport and Body Size on Terrestrial Locomotion in Salamander Species
Authors: Full Robert J. , Anderson Bruce D. , Finnerty Casey M. , Feder Martin E.
Published: April 2021

Metabolic cost, oxygen consumption , respiratory structure and body size interact to determine the capacity of salamanders for terrestrial locomotion. Salamanders respiring via both lungs and skin, Ambystoma laterale and A. tigrinum, or with skin alone, Desmognathus ochrophaeus and D. quadramaculatus, attained a steady-state , during exercise in a treadmill respirometer. Endurance was correlated with the speed at which maximal was attained Low aerobic costs of transport (60-80% lower than reptiles of similar mass) increased . However, in lungless salamanders a low maximum , decreased significantly. increased only 1·6-to 3·0-fold above resting rates in active lungless salamanders, whereas it could increase 3·5- to 7·0-fold in active lunged salamanders. Lungless salamanders attained maximal at half to one-tenth the speed of lunged animals. Lungless salamanders fatigued in 20 min or less at speeds that lunged salamanders could sustain for 1-2 h. Body size also affected the capacity for oxygen uptake during activity and locomotor performance. The large lungless salamander D. quadramaculatus attained maximum , even at its lowest rate of travel. Cutaneous gas exchange does not provide lungless salamanders with gas transport capacities found in lunged animals. However, only small increases in , may be required for modest levels of activity.
Exercising With and Without Lungs: II. Experimental Elimination of Pulmonary and Buccopharyngeal Gas Exchange in Individual Salamanders (Ambystoma Tigrinum)
Authors: Feder Martin E.
Published: April 2021

To ascertain whether the presence of lungs per se, or some other physiological feature, might account for the differences in oxygen consumption and stamina previously observed in an interspecific comparison (Full et al. 1988), individual salamanders (Ambystoma tigrinum) were exercised on a treadmill before and after their nares and mouth had been sealed. After airway closure, animals behaved normally and suffered no mortality. Airway closure reduced the routine (rate of oxygen consumption) by an average of 47% in six of seven individuals. Animals with open airways increased their 2- to 4-fold during locomotion at 11 cm s−1, and did not fatigue in 22 min of exercise at this speed. Animals with closed airways managed only small increases above the routine during exercise at 11 cm s−1, and none could sustain activity for more than 10 min. Thus, exclusively skinbreathing Ambystoma cannot increase cutaneous gas exchange to compensate for the elimination of pulmonary and buccopharyngeal respiration; locomotor stamina suffers accordingly. Small salamanders can apparently increase cutaneous gas exchange during activity, although large salamanders cannot, because cutaneous diffusing capacity and the resting oxygen requirement approach one another with increasing body size; the skin of large salamanders apparently has a limited scope for aerobic activity.
‘Steady’ Swimming Kinematics of Tiger Musky, an Esociform Accelerator, and Rainbow Trout, a Generalist Cruiser
Authors: Webb Paul W.
Published: April 2021

Locomotor kinematics of tiger musky (Esox sp.) and rainbow trout (Salmo gairdneri) were measured at ‘steady’ swimming speeds of up to 85 cm s−1. Tail beat frequencies of musky were approximately 2 Hz higher than those of trout at any swimming speed, but tail beat amplitudes were 0·04L (where L is total body length) smaller. The product of these two variables was similar for the two species at any speed. The length of the propulsive wave was independent of speed, and was 0·8L for musky, somewhat smaller than the value for trout, 0·9L. The depth of the caudal fin trailing edge of trout was greater than that of musky, but the greater depth of the posteriorly located median fins of musky also contributed to thrust production. The cosine of the angle of the trailing edge to its beat plane showed the same phase relationship with lateral displacement in both musky and trout. It increased with speed for both species, and values for musky were slightly smaller. Thrust power requirements of musky and trout were similar. Thrust (= drag) coefficients of musky were 1·55 times larger than those for trout: this is roughly as expected on the basis of the larger proportion of the total area of musky located caudally and the higher drag coefficients in this region of the body. Lateral recoil movements of musky were unexpectedly smaller than for trout and were associated with smaller energy wastage from undamped recoil movements. The large recoil expected for the body form of musky was damped to some extent by higher tail beat frequencies, although this entailed some loss in Froude efficiency. Otherwise, no hydrodynamic explanation for the small recoil movements of musky was apparent. It is suggested that the myotomal muscles could be involved in minimizing recoil. The esociform morphology incurs costs in steady swimming, in comparison with generalist cruises, because of reduced sprint speeds for fish of a given length or increased power requirements for fish of a given mass.
Actions of dendrotoxin on K+ channels and neuromuscular transmission in Drosophila melanogaster, and its effects in synergy with K+ channel-specific drugs and mutations
Authors: Wu Chun-Fang , Tsai Ming-Cheng , Chen Mai-Lei , Zhong Yi , Singh Satpal , Lee C. Y.
Published: April 2021

The blockade of K+ channels and enhancement of neuromuscular transmission by dendrotoxin (DTX), a convulsant peptide from mamba snake venom, were examined in normal and mutant larval preparations of Drosophila. Two-microelectrode voltage-clamp experiments showed that DTX reduced the transient K+ current, IA, in muscle membrane. This effect was suppressed by raising the Mg2+ concentration or by lowering the temperature. The interaction of DTX with Mg2+ was further analyzed at a low cation concentration, at which DTX reduced both IA and the delayed rectifier IK. These results were correlated with the action of DTX on the neuromuscular junction. Its facilitatory effect on excitatory junctional potentials (EJPs) was relatively mild but the effect was drastically enhanced when combined with certain mutations and K+ channel blocking drugs, leading to repetitive or prolonged giant EJPs. Only the mutations or drugs that reduced IK or the Ca2+-dependent K+ current, ICF, could yield these synergistic effects with DTX. In contrast, the abnormal EJPs caused by the mutation or drug that blocked IA were not further enhanced by DTX, indicating that DTX also affects IA at the neuromuscular junction. Thus, the A-type K+ channels in muscle and nerve terminals appeared very similar in their sensitivity to the specific toxin, drugs and mutations examined here.
Interactions Between ion Exchange and Metabolism in Erythrocytes of the Rainbow TroutOncorhynchus Mykiss
Authors: Tufts B. L. , Boutilier R. G.
Published: April 2021

Experiments were carried out to investigate the relationship between ion exchange and energy metabolism in rainbow trout erythrocytes in vitro. Under resting conditions, the sodium/potassium pump accounts for 20% of the cellular energy budget. In the presence of the β-adrenergic agonist isoproterenol, however, this increases to 43%. Inhibition of the sodium/potassium pump with ouabain results in greater increases in erythrocyte water content and sodium and chloride concentrations and a greater decrease in erythrocyte potassium concentration following stimulation by isoproterenol. Moreover, the decrease in erythrocyte NTP levels observed following adrenergic stimulation does not occur when the sodium/potassium pump is inhibited with ouabain. Inhibition of the sodium/ potassium pump also abolishes the increase in oxygen consumption by the cells which normally takes place following adrenergic stimulation. Finally, depletion of erythrocyte NTP levels by the sodium ionophore monensin or by previous incubation with nitrogen does not result in a significant increase in oxygen consumption. Thus, catecholamines appear to be crucial for the metabolic-membrane coupling that occurs following adrenergic stimulation in rainbow trout erythrocytes.
Activities of Enzymes for Glucose Catabolism in the Swimbladder of the European EelAnguilla Anguilla
Authors: Pelster Bernd , Scheid Peter
Published: April 2021

Gas secretion into the swimbladder of the eel relies on the production of CO2 and lactic acid from glucose in the swimbladder epithelium. The activities of the enzymes involved in glucose catabolism have been measured and compared with those in the rete mirabile, the liver and white skeletal muscle to evaluate whether the pentose phosphate shunt may contribute to glucose metabolism in the swimbladder tissue. The activities of enzymes of the pentose phosphate shunt were higher in the swimbladder epithelium than in white muscle, and close to those in the liver. The activities of the enzymes of anaerobic glycolysis were 2–5 times higher in the swimbladder epithelium than in the rete mirabile, reaching or even exceeding the levels in liver and white muscle, whereas the activities of the enzymes of oxidative metabolism were extremely low. Compared to enzymes of the other tissues, swimbladder phosphofructokinase and glucose-6-phosphate dehydrogenase showed no special adaptation to low pH values. The results show that the swimbladder epithelium is equipped with enzymes that produce CO2 from glucose without the removal of O2, which is particularly advantageous for creating the high gas partial pressures needed for filling the swimbladder at great depth.
Desensitization of Adrenaline-Induced Red Blood Cell H+ Extrusion in Vitro After Chronic Exposure of Rainbow Trout to Moderate Environmental Hypoxia
Authors: Thomas S. , Kinkead R. , Walsh P. J. , Wood C. M. , Perry S. F.
Published: April 2021

The sensitivity of red blood cell Na+/H+ exchange to exogenous adrenaline was assessed in vitro using blood withdrawn from catheterized rainbow trout (Oncorhynchus my kiss) maintained under normoxic conditions [water or after exposure to moderate hypoxia for 48 h, which chronically elevated plasma adrenaline, but not noradrenaline, levels. Peak changes in whole-blood extracellular pH over a 30 min period after adding 50–1000 nmol l−1 adrenaline were employed as an index of sensitivity; the blood was pre-equilibrated to simulate arterial blood gas tensions in severely hypoxic fish . Blood pooled from normoxic fish displayed a dose-dependent reduction in whole-blood pH after addition of adrenaline. Blood pooled from three separate groups of hypoxic fish, however, displayed diminished sensitivity to adrenaline, ranging from complete desensitization to a 60% reduction of the response. Subsequent experiments performed on blood from individual (i.e. not pooled) normoxic or hypoxic fish demonstrated an inverse correlation between the intensity of H+ extrusion (induced by exogenous adrenaline addition) and endogenous plasma adrenaline levels at the time of blood withdrawal. However, acute increases in plasma adrenaline levels in vitro did not affect the responsiveness of the red blood cell to subsequent adrenergic stimulation. The intensity of H+ extrusion was inversely related to the in vivo between 2.67 and 10.66 kPa, and directly related to the logarithm of the endogenous plasma adrenaline level. The results suggest that desensitization of Na+/H+ exchange in chronically hypoxic fish is related to persistent elevation of levels of this catecholamine. This desensitization can be reversed in vitro as a function of time, but only when blood is maintained under sufficiently aerobic conditions.
Hydrodynamics of Rapid Shell Closure in Articulate Brachiopods
Authors: Ackerly Spafford C.
Published: April 2021

The rapid shell-closing mechanism in articulate (hinged) brachiopods is subject to important hydrodynamic constraints related to expulsion of water from the shell. Fluid forces influence, for example, the speeds of shell closure and the mass flux rates of water from the shell. The principal hydrodynamic forces acting on a shell during rapid closure are (1) inertial reactions, due to the acceleration of water (=acceleration reaction), and (2) water pressure forces which develop as water is expelled from the shell. A generalized hydrodynamic model describes the relative magnitudes of the acceleration and pressure forces as functions of the shell’s angular acceleration, velocity and gape. In general, the acceleration reaction dominates the kinematics of shell closure during the initial phases of a closing event, whereas pressure forces dominate towards the later phases of shell closure. Solutions of the general model predict how variables such as the closing speed and the mass flux of water depend on shell size, initial shell gape and on the magnitude of the closing force. Results indicate that inertial reactions (due to acceleration of water) dominate the mechanics of shell closure in articulate brachiopod taxa.
Effect of γ-Aminobutyric Acid on Intracellular pH in the Crayfish Stretch-Receptor Neurone
Authors: Voipio J. , Pasternack M. , Rydqvist B. , Kaila K.
Published: April 2021

The effect of γ-aminobutyric acid (GABA) on intracellular pH (pHi) was examined in the crayfish stretch-receptor neurone using H+-selective microelectrodes and a two-microelectrode voltage clamp. In the presence of 30 mmol I−1 HCO3− (pH 7.4), application of GABA (0.5 mmol I−1) produced a mean fall in pHi of 0.26 units. The initial rate of fall of pHi was attributable to a net influx of acid equivalents of 6.3 mmol I−1 min−1. In the nominal absence of HCO3−, GABA had little effect on pHi. The HCO3−-dependent acidosis caused by GABA was inhibited by picrotoxin (0.1 mmol I−1) but not by depletion of extracellular and intracellular Cl−. Acetazolamide (0.1 mmol I−1) decreased the rate of fall of pHi caused by a step increase in CO2 partial pressure as well as by GABA, which indicates that the neurone contains carbonic anhydrase. In the presence of both Cl− and HCO3−, the reversal potential of the GABA-activated current was more positive than under nominally HCO3−-free conditions. In line with this, GABA induced a marked HCO3−-dependent depolarization, and this depolarizing action was enhanced in the absence of Cl− so as to lead to triggering of action potentials. All these observations support the conclusion that the GABA-induced fall in pHi is due to a net efflux of HCO3− through the inhibitory anion channels.
Microcalorimetric Investigations on the Energy Metabolism of Lizards
Authors: Lamprecht I. H. D. , Matuschka F.-R. , Schaarschmidt B.
Published: April 2021

The energy metabolism of three lizard species (Podarcis milensis, Podarcis muralis and Lacerta agilis) was investigated by means of microcalorimetry and polarography over the range of environmental temperatures between 17 and 35 °C encountered by active lizards during summer in Europe. In non-stimulated animals, the maximum and mean heat production rates were highest around 30°C for all species and amounted to 3.9±l.lmWg−1 and 2.1±0.5mWg−1, respectively. Resting metabolism contributed approximately 60% to the mean routine heat dissipation; the remainder originated from locomotory activity, 43% of which was based on anaerobic energy metabolism. From simultaneous determinations of heat dissipation and oxygen consumption, an average oxycaloric equivalent of 18.6±3.2 J ml−1O2 was calculated, which rose to 26.6±7.1 J ml−1O2 during short bursts of locomotion.