bluuebunny/crossref_metadata_2025 huggingface dataset:
Cytological Studies of the Acinar Cells of the Pancreas of the Mouse: Part I. The Formation of Neutral Red Granules
Authors: Morgan Winfield S.
Published: April 2021

1. It has been found that during a 12-15 hour period after the subcutaneous injection of mice with a predetermined ‘optimum’ dose of neutral red, there occurs a definite series of changes in the pancreas acinar cell in which neutral red granules are formed as separate bodies, which subsequently come together as aggregates and then disappear from the cell.

2. The cell is not damaged by the cycle of events just described. The response to the presence of neutral red appears to be physiological, not pathological.

3. Evidence is brought forward showing that neutral red granules and aggregates are not vacuoles that pre-existed in the normal cell and were subsequently stained: they are new formations produced by the presence of neutral red in the cell.

4. Little more than one-quarter of the neutral red injected is excreted in unchanged form.
Macronuclear Regeneration in Epistylis Articulata
Authors: Seshachar B. R. , Dass C. M. S.
Published: April 2021

The reorganization of the macronucleus from the vegetative micronucleus is described in Epistylis articulata (Ciliophora, Peritricha). Individuals which have accidentally been deprived of a macronucleus during binary fission develop a new one from the micronucleus. In such amacronucleate animals, the micronucleus divides into two, one of them growing into a macronucleus, the other remaining as the micronucleus. The phenomenon throws new light on the relative importance of the two parts of the ciliate nuclear apparatus and brings into greater emphasis the undifferentiated nature of the micronucleus. It also establishes the possibility of de novo synthesis of DNA in the developing macronuclear rudiment.
The Ligament of Pecten
Authors: Trueman E. R.
Published: April 2021

The ligament of Pecten maximus consists of two layers, the outermost situated along the extensive dorsal margin of the valves, the inner between them at the umbo. The former, composed largely of tanned proteins, is laminated and is somewhat similar to the outer layer of other ligaments. The inner layer is divided into three parts, a large central non-calcified structure and two lateral calcified regions attaching the former to the valves. The lateral parts resemble the entire inner layer of the ligament of most other lamellibranchs, which is generally uniformly calcified. The central region, consisting mainly of a tanned protein complex, is gelatinous in appearance and is characteristic of P. maximus and associated species. This type of structure is particularly suitable for the rapid and frequent opening of the valves, and its relatively high efficiency may be largely attributed to the non-calcified region of the inner layer.
The Use of the Interference Microscope to Determine Dry Mass In Living Cells and as a Quantitative Cytochemical Method
Authors: Davies H. G. , Wilkins M. H. F. , Chayen J. , Cour L. F. La
Published: April 2021

The total mass M of substances other than water (the dry mass) in the living cell can be obtained from the expression M = ϕA/χ, where ϕis the optical path difference (o.p.d.) due to the cell and A its projected area. The method makes use of the fact that the refractive increments α (χ=100α) of most substances in cells are approximately the same, and independent of concentration. Values for χ have been tabulated. Inaccuracies in the measurement of dry mass due to variations in χ (using y average = 0·18) will be less than ± 10 per cent, in cells containing nucleic acids, proteins, and lipoproteins. When appreciable quantities of other substances are present the inaccuracy may be somewhat greater. When the total dry mass of living cells is determined in a medium other than water (e.g. isotonic solution), a correction term involving the thickness must be determined; this correction is often small. Optical path differences have been measured with the Dyson interference microscope, and different methods for doing this, together with the interpretation of the image in interference contrast, are discussed. The total dry masses and, in some cases, the concentrations of dry substance in a variety of biological objects including Amoebae, pollen grains at various stages of development, nuclei of cells in tissue culture, and sperm heads have been determined. In Tradescantia bracteata, during development from the microspore to the mature pollen grain, the dry mass increases by about tenfold. The dry masses of mature pollen grains were measured before and after successive digestion with ribonuclease, which removed about 4 to 14 per cent, of the dry mass, and with trypsin, after which about 40 per cent, of the original dry mass remained. In living ram sperm heads the ratio of deoxyribose nucleic acid to total dry mass determined by ultra-violet and interference microscopy respectively is 40 per cent. This is in good agreement with the value 45 per cent, obtained by bulk biochemical methods. The interference microscope has been used to measure the refractive index of cells and, hence, the concentrations of dry substances in them, by immersing them in media of different known refractive indices. The application of this method to fixed cells is discussed theoretically. In experiments on fixed ram sperm heads the expected linear relationship between o.p.d. and refractive index of the immersion medium was obtained. Data on the average concentration of dry substance in ram sperm heads, the localized refractive index, and concentration in the denatured submicroscopic particles in the head, the percentage of the head volume occupied by them, and. the geometrical thickness of the head were’obtained. : ‘ Factors affecting the accuracy of the measurements of o.p.d., such as glare in the microscope, light scatter or absorption by the object, &c., are outlined.
Refractometry of living cells part I. basic principles
Authors: Barer R. , Joseph S.
Published: April 2021

The principles underlying a new method of refractometry of living cells are discussed. The method was evolved from the chance observation that the amoebocytes of the blood of the earthworm, examined in their own blood, appeared bright instead of dark by positive phase-contrast microscopy. This was shown to be due to the presence of dissolved haemoglobin which raised the refractive index of the medium above that of the cytoplasm. In order to determine the refractive index of the latter it was only necessary to dilute the blood until the cytoplasm became virtually invisible. Non-pigmented proteins and other high molecular weight substances have now been substituted for haemoglobin.

The nature of the initial observations suggested that if the cell could be regarded to a first approximation as being composed entirely of proteins, the cytoplasmic protein concentration could be equated to the protein concentration of the immersion medium which made the cell appear with minimum contrast. This would only be true if equal concentrations of different proteins in solution had the same refractive index. The nature of refractive index and its relationship to density are discussed and it is shown that for nearly all unconjugated proteins so far investigated the specific refraction increments (i.e. the increase in refractive index per 1 per cent, increase in concentration) have almost the same values (00185±2 per cent.). The effects of many factors such as pH, salts, temperature, wavelength, concentration, and nature of the solvent are discussed. Since living cells contain substances other than proteins the specific refraction increments of protein derivatives, lipides, carbohydrates, and salts are considered and it is shown that the presence of moderate amounts of such substances is unlikely to affect the refractive index of cells to any great extent. It is suggested that the mean specific refraction increment of protoplasm should be taken as 0018 and that this value can be used in order to calculate the solid and water content of protoplasm from values of refractive index.
The Changes of Water Distribution in Cytoplasm and Nuclear Sap during Division as Indicated by Changes in their Refractive Indices
Authors: Ross K. F. A.
Published: April 2021

The changes in refractive index of the cytoplasm and nuclear sap of the dividing spermatocytes of Locusta migratoria were measured by the refractometric technique first employed by Barer and Ross in 1952. It was found that, while certain restricted regions behaved slightly differently, the refractive index of the greater part of the cytoplasm fell during the first part of prophase from 1·354 in the resting cell to about 1·346, and rose again steadily after the beginning of metaphase until it approximated to its original value at the end of telophase. These results did not accord very closely with previous refractometric measurements, but showed a marked agreement with a previous record of changes in viscosity made by Carlson in 1946. It is suggested that this parallel behaviour is best explained by assuming that shifts in water distribution occur in the dividing cell, and that during prophase the cytoplasm and nuclear sap become correspondingly more aqueous as the chromosomes become denser.
The Effect of Diet on Egg Maturation and Resorption in Mormoniella vitripennis (Hymenoptera, Pteromalidae)
Authors: Edwards Roy L.
Published: April 2021

M. vitripennis females have been treated in one of the following ways: (a) fed on honey, (b) starved, (c) fed on host blood. When fed on honey the ovaries contain 22 eggs after 2 days, then a slow cycle of maturation and resorption begins so that for 16 days their condition does not change. After 16 days resorption is more rapid and by 28 days there are only 1 or 2 mature eggs. When starved, the parasites die in 5 days. Rapid resorption occurs and at death there are only 3 eggs in the ovaries. When fed on host blood, eggs mature rapidly. After 5 days the ovaries contain 40 mature eggs even though 260 have been deposited. Parasites which are then starved, resorb eggs very rapidly and die in 48 hours, but those fed on honey live for at least 8 days and rapid resorption does not occur.
The Morphology of Peripheral Nerve Terminations in the Skin
Authors: Weddell G. , Pallie W. , Palmer Elisabeth
Published: April 2021

An account is given of the innervation of the skin from selected regions of the body in man, the rhesus monkey, and the rabbit. It is based on a critical evaluation of methylene blue and silver preparations in skin which had been treated with the enzyme hyaluronidase before removal from the body and in skin which had not thus been treated. The nerve fibres and terminals in preparations treated with hyaluronidase resemble those seen in fresh specimens of cornea under phase contrast conditions. The numerous artifacts seen in the cornea following methylene blue staining or silver impregnation, the origin of which is known, resemble those seen in specimens of skin not treated with hyaluronidase. It is shown that cutaneous nerves ultimately terminate in an arborization of fine naked axoplasmic filaments. The naked filaments always arise from ensheathed stem fibres of varying diameters and they all end freely and extracellularly in relation to a variety of tissue elements in the skin. The actual terminal filaments wherever they end in relation to the epidermis, dermal connective tissue, blood-vessels, sweat glands, hair follicles, or within capsules of epithelial cells, cannot be distinguished from one another on the basis of inherent morphological differences. Terminal filaments from neighbouring stem fibres are always intimately related to one another and to the tissues in which they lie. The stem fibres and axoplasmic filaments to which they give rise in encapsulated endings and hair follicles are so arranged that the slightest deformation of capsule or of follicle will alter the relationship of the terminal filaments to their stem fibres. Encapsulated nerve-endings may be served by more than one stem fibre but none of the terminals of these fuse with one another. Likewise, the terminals derived from individual stem fibres ending in relation to hair follicles do not enter into protoplasmic continuity with one another. The number and length of the axoplasmic filaments varies greatly from stem fibre to stem fibre. Our observations on the behaviour of the cutaneous nerve fibres and their terminals under different histological conditions provides us with a standard by which we can distinguish artifacts and thus re-evaluate the observations on cutaneous innervation which have been reported in the literature. Evidence is brought forward which suggests that the naked axoplasmic filaments derived from sensory stem fibres may be responsible for ‘flare* and other ‘nocifensor reactions’ (Lewis), in addition to and apart from their sensory functions. The relationship of these observations to the mechanism of cutaneous sensibility is discussed.
Experiments on the Mechanism of Silver Staining: II. Development
Authors: Peters A.
Published: April 2021

The effect of a series of photographic developers on the final silver-staining picture has been investigated. Ten common developers were used, but of these only hydroquinone, chloroquinol, pyrogallol, and p-aminophenol, were found to be of general use. The other developers were either so weak in their action that the final staining was light and incomplete, or so powerful that a differentiated nerve staining was not produced.

For silver staining to be effected nuclei of reduced silver should be present in the section. These nuclei act as centres for the deposition of additional silver reduced by the developer; the additional silver may either be derived from that combined with the sections during impregnation or from the developing solution itself. Whether or not the additional silver is deposited in such a way as to produce differentiated nerve staining depends on the properties of the developer and on the composition of the developing solution. The redox- and ‘bromide’-potentials, the sulphite and hydrogen ion concentrations in the developing solution, and the protective action of the tissue components of the section all play a part in determining the final staining picture.

A new glycine-containing physical developer and a gold thiocyanate physical developer are described.
The Significance of the Presence of Pollen in the Food of Worker Larvae of the Honey-bee
Authors: Simpson J.
Published: April 2021

1. From a study of the quantity of undigested shells of pollen grains in the gut of worker honey-bee larvae it is concluded that the larvae receive a variable quantity of pollen in their food in summer and sometimes none at all in winter.

2. Probably less than one-tenth of the nitrogen requirements of growing larvae are obtained from the pollen in their food.
Methyl Green and Pyronin Staining of Frozen-dried Tissue
Authors: Lavarack J. O.
Published: April 2021

Frozen-dried tissue stains readily with methyl green /pyronin. The gross in tracellular distribution of nucleic acids in frozen-dried pancreatic tissue stained with methyl green /pyronin corresponds with that found in chemically fixed tissue.
The Cytoplasmic Inclusions of a Mammalian Sympathetic Neurone: A Histochemical Study
Authors: Bruce Casselman W. G. , Baker John R.
Published: April 2021

1. The neurones studied were those of the anterior mesenteric and coeliac ganglia of immature rabbits.

2. Ectoplasm and endoplasm can be distinguished in these cells.

3. Two kinds of cytoplasmic inclusions occur. These are (a) spherical or spheroid lipid globules or lipochondria, which are confined to the endoplasm; and (b) very minute threads and granules, regarded as mitochondria.

4. A wide variety of histochemical tests was used. The results indicate that the lipo-chondria consist of galactolipid (cerebrosid) and phospholipid, though the smallest ones may perhaps consist of galactolipid only.

5. The objects regarded as mitochondria are too small for accurate investigation by in situ histochemical methods, but they give positive reactions for phospholipid and protein.
The Cytochemistry of the Amoebocytes and Intestinal Epithelium of Venus mercenaria (Lamellibranchiata), with Remarks on a Pigment resembling Ceroid
Authors: Zacks Sumner I.
Published: April 2021

The properties of the amoebocytes and intestinal epithelium of Venus mercenaria were studied by a variety of cytochemical procedures designed to demonstrate proteins, enzymes, carbohydrates, and lipids.

The cytoplasm of the amoebocytes contains specific granules which are constantly present and which are interpreted as being atypical mitochondria. Identification of their mitochondrial nature rests on their staining with Janus green B, their positive reaction for phospholipid by Baker’s test, and the presence of dehydrogenase activity. Unlike typical mitochondria, the specific granules are eosinophil. Protein-bound carbonyl groups and disulphide and sulphydryl groups are present in both the specific granules and the cytoplasm. The sulphydryl groups may in part be associated with the presence of dehydrogenase, lipase, and serum cholinesterase. Amoebocytes also contain glycogen and a material that is resistant to diastase and positive to the periodic acid /Schiff test; this material may be a neutral polysaccharide, unsaturated lipid, or mucoprotein.

Cytoplasmic structures which are inconstantly present in amoebocytes include sudanophil droplets, neutral red vacuoles, metachromatic granules, and granules of an excretory pigment resembling ceroid. The sudanophil droplets may be stored neutral fat or lipid associated with the Golgi apparatus. The neutral red vacuoles are not preformed inclusions, but form as the dye accumulates within the cells. Metachromatic granules, which are confined solely to the intestinal amoebocytes, consist of phagocytosed intestinal mucus liberated from goblet cells.

The histochemical reactions of the columnar intestinal epithelium suggest that these cells may be active in the digestion and absorption of nutrients, since eosinophil granules, lipid droplets, alkaline phosphatase, lipase, and serum cholinesterase are present in them.

Masses of a ceroid-like excretory pigment and goblet cells containing mucus are present between the columnar intestinal epithelial cells. The pigment contains phospholipid and apparently arises as an oxidized end-product of lipid metabolism.
Phylogenetic Plasticity of Crustacean Stomatogastric Circuits: I. Pyloric Patterns and Pyloric Circuit of the Shrimp Palaemon Serratus
Authors: Meyrand Pierre , Moulins Maurice
Published: April 2021

Recordings from the muscles of the pyloric chamber of the shrimp Palaemon display a rhythmic pattern which is either monophasic or biphasic, and is different from the triphasic pyloric pattern of large decapods. Identification of the pyloric neurones in the stomatogastric ganglion and study of their synaptic relationships indicate that the pyloric circuit of Palaemon is very similar to the pyloric circuit of large decapods. It is concluded that homologous neuronal circuits in related species, although similar in terms of their ‘wiring diagram’, are able to produce significantly different patterned outputs.
Phylogenetic Plasticity of Crustacean Stomatogastric Circuits: II. Extrinsic Inputs to the Pyloric Circuit of the ShrimpPalaemon Serratus
Authors: Meyrand Pierre , Moulins Maurice
Published: April 2021

The rhythmic motor patterns produced by the pyloric circuit of the shrimp Palaemon are substantially different from those of large decapods, although the homologous neuronal circuits are very similar (Meyrand & Moulins, 1988). The extrinsic inputs received by the Palaemon pyloric circuit were similar, at least qualitatively, to the extrinsic inputs known to impinge upon the pyloric circuit of large decapods. These include: rhythmic inputs that descend from another oscillator (the commissural pyloric oscillator, CPO) which appears to impose its own rhythm on neurones of the pyloric circuit; and inputs that have long-lasting effects and control the expression of endogenous burst-generating properties of individual neurones within the circuit via modulatory mechanisms.

The AB-PD neurones were not observed to oscillate, and so do not appear to act as pacemakers for the pyloric circuit as they do in large decapods, probably because of differences in the organization of the modulatory extrinsic inputs.

It is our conclusion that differences in the control of expression of intrinsic properties of neurones of homologous (and structurally similar) circuits belonging to related species can explain how such circuits produce widely different patterned motor outputs.
Ocular Tracking of Rapidly Moving Visual Targets by Stomatopod Crustaceans
Authors: Cronin Thomas W. , Nair Jaygopal N. , Doyle Robert D. , Caldwell Roy L.
Published: April 2021

Ocular tracking in two species of stomatopod crustaceans, Squilla empusa (Say) and Gonodactylus oerstedii (Hansen), was studied by presenting animals with small targets moving to their right and left. Squilla empusa showed no indication of ocular movement responses synchronized with the target’s motion, whereas Gonodactylus oerstedii often tracked the target through large angular amplitudes. The region of visual fixation in G. oerstedii is probably the ommatidial patches in line with the eyecup axis. This is suggested by the arrangement of ommatidial axes on the eye’s circumference, and by the alignment of the eyes and the rotational motions they make as they observe an approaching target. Tracking is irregular, probably because the animal pays attention to the target only intermittently. Targets are most stimulatory as they move nearly in front of an animal. Eye tracking responses become larger, more frequent and more accurate with increasingly anterior target positions. During visual tracking, the eyes perform both smooth and saccadic tracking movements. Eye movements in the size range 7·5°-15° are made to near the position of the target at movement onset, but are less accurate relative to the target’s position at the end of the movement. During visual tracking, the two eyes apparently act with complete independence. Movements of one eye are uncorrelated with movements of the other, both for extreme and central locations of the moving target. The existence of ocular independence during smooth pursuit and saccadic tracking in G. oerstedii may be possible because of the redundancy of visual fields existing in each eye, which could permit monocular measurements of distance to a viewed object. If so, each eye is capable of providing a complete description of the location of a target in space.
Behavioural Thermoregulation in the Freeze-Tolerant Arctic Caterpillar, Gynaephora Groenlandica
Authors: Kukal Olga , Heinrich Bernd , Duman John G.
Published: April 2021

Larvae of the high arctic caterpillar, Gynaephora groenlandica (Wöcke) (Lepidoptera: Lymantriidae) spent most (60%) of their time orienting towards the sun (i.e. basking) and only 20% feeding, primarily near midday. Larvae usually basked after feeding, then either fed again or moved to a new feeding site. Basking larvae reached their highest body temperatures (Tb) of ≈30°C (≈20°C in excess of the ambient temperature) when surrounded by snow on a calm day in the midday sun. Setae significantly decreased larval cooling rates. Maximal metabolic rates were attained in basking larvae, but at body temperatures below 10°C oxygen uptake was greatly reduced. Our studies indicate that G. groenlandica larvae are behaviourally adapted to utilize available solar radiation for growth and development.
Evidence That Histamine is a Neurotransmitter of Photoreceptors in the Locust Ocellus
Authors: Simmons Peter J. , Hardie Roger C.
Published: April 2021

The results presented here are consistent with the hypothesis that histamine is the major neurotransmitter released by photoreceptors of locust ocelli.

When histamine is injected by ionophoresis into the locust ocellar neuropile, large second-order neurones (L-neurones) hyperpolarize in a dose-dependent manner, and responses to light in these neurones are diminished in amplitude. Both histamine and the illumination of ocellar photoreceptors caused an outward current across the membrane. Hyperpolarizing potentials in L-neurones evoked by histamine had the same reversal potential as hyperpolarizing potentials evoked by photoreceptor illumi-nation. When applied ionophoretically in the ocellus, other biogenic amines, including octopamine, dopamine and noradrenaline, had no effect on the L-neurones. Both gamma-aminobutyric acid and acetylcholine, however, depolar-ized L-neurones and diminished responses to light. Curare blocked the L-neurone’s responses to histamine and light. The histamine response recovered fully. The initial peak hyperpolarizing response to increased light recovered, but the more sustained plateau hyperpolarizing potential did not. hexamethonium bromide prolonged the response of an L-neurone to histamine, and increased the tonic component of the response to light.
Effects of Antagonists On Putative Histamine Receptors in the First Visual Neuropile of the Housefly (Musca Domestica)
Authors: Hardie Roger C.
Published: April 2021

Intracellular recordings were made from the large monopolar cells (LMCs), which are the cells postsynaptic to photoreceptors, in the housefly Musca domestica. A multi-barrelled ionophoretic pipette glued to the recording electrode was used to apply a variety of cholinergic and histaminergic antagonists onto the recorded neurones. All substances which blocked the physiological response to light also antagonized the response to ionophoretically applied histamine, supporting the hypothesis that histamine is the neurotransmitter released by insect photoreceptors. In order of potency, the following drugs were found to block or reduce the LMC’s responses to light: benzoquinonium ⩾ gallamine > ranitidine ⩾ atropine ≈ cimetidine > metiamide≈SK&F93479 ⩾ mepyramine. Mecamylamine, scopolamine, dexetimide, nicotine, mequitazine, chlorpheniramine and clemastine were ineffective.

Two other cholinergic ligands, hexamethonium and decamethonium, were much more potent than even benzoquinonium, but had the effect of facilitating and greatly slowing down the responses to light. Responses evoked by acetylcholine showed a different pharmacology, being blocked by mecamylamine but unaffected by hexamethonium. Despite testing a number of known cholinergic and histaminergic agents, no effective agonist for histamine was found. The results indicate the existence of a novel class of histamine-sensitive receptor with nicotinic features. In addition the unusual effects of a traditional Hl agonist, 2-thiazolylethylamine, suggested the presence of a second, distinct class of histamine receptor.
Speed, Stride Frequency and Energy Cost Per Stride: How Do They Change With Body Size and Gait?
Authors: Heglund Norman C. , Taylor C. Richard
Published: April 2021

In this study we investigate how speed and stride frequency change with body size. We use this information to define ‘equivalent speeds’ for animals of different size and to explore the factors underlying the six-fold difference in mass-specific energy cost of locomotion between mouse-and horse-sized animals at these speeds. Speeds and stride frequencies within a trot and a gallop were measured on a treadmill in 16 species of wild and domestic quadrupeds, ranging in body size from 30 g mice to 200 kg horses. We found that the minimum, preferred and maximum sustained speeds within a trot and a gallop all change in the same rather dramatic manner with body size, differing by nine-fold between mice and horses (i.e. all three speeds scale with about the 0·2 power of body mass). Although the absolute speeds differ greatly, the maximum sustainable speed was about 2·6-fold greater than the minimum within a trot, and 2·1-fold greater within a gallop. The frequencies used to sustain the equivalent speeds (with the exception of the minimum trotting speed) scale with about the same factor, the -0·15 power of body mass. Combining this speed and frequency data with previously published data on the energetic cost of locomotion, we find that the mass-specific energetic cost of locomotion is almost directly proportional to the stride frequency used to sustain a constant speed at all the equivalent speeds within a trot and a gallop, except for the minimum trotting speed (where it changes by a factor of two over the size range of animals studied). Thus the energy cost per kilogram per stride at five of the six equivalent speeds is about the same for all animals, independent of body size, but increases with speed: 5·0 J kg−1 stride−1 at the preferred trotting speed; 5·3 J kg−1 stride−1 at the trot-gallop transition speed; 7·5 J kg−1 stride−1 at the preferred galloping speed; and 9·4J kg−1 stride−1 at the maximum sustained galloping speed. The cost of locomotion is determined primarily by the cost of activating muscles and of generating a unit of force for a unit of time. Our data show that both these costs increase directly with the stride frequency used at equivalent speeds by different-sized animals. The increase in cost per stride with increasing speed may be related to differences in mechanical advantage of the limb muscles (necessitating higher muscle forces for the same ground reaction force) as stride length increases both in the trot and in the gallop.
Ion Replacement as a Buoyancy Mechanism in a Pelagic Deep-Sea Crustacean
Authors: Sanders N. K. , Childress J. J.
Published: April 2021

Unlike most pelagic crustaceans, the deep-sea shrimp Notostomus gibbosus (A. Milne-Edwards) (Oplophoridae) is positively buoyant, possessing a dorsally enlarged carapace which contains a low-density fluid. This fluid comprises 43% of the animal’s wet mass, has a low pH, and gives a lift of 17·7mgml−1; when this fluid is drained, the animal sinks. Low density is achieved by the replacement of less buoyant ions with ions which reduce density via two mechanisms: a change in total solute mass by the use of ions of lesser mass, and an ion-specific disruption of the structure of water molecules (resulting in an increase in fluid volume) caused by ions having large, positive partial molal volumes. The presence of large amounts of trimethylamine (Me3NH+), a relatively large, heavy ion which, together with NH4+, replaces nearly 90% of the Na+ in the carapace fluid, results in little change in the total solute mass of the carapace fluid of N. gibbosus (33·2 ‰) relative to sea water (approximately 34·1 ‰). Reduced fluid density is primarily a result of the large, positive partial molal volumes of Me3NH+ and NH4+, rather than a function of reduced solute masses.
Postural Changes Occurring During One Month of Vestibular Compensation in Goldfish
Authors: Ott Janet F. , Platt Christopher
Published: April 2021

Postural behavioural changes during vestibular compensation were studied in goldfish. The tilting posture induced by directional light in the dorsal light reflex (DLR) was monitored by an automated camera system. Responses were measured over a 1-month period following a partial unilateral labyrinthectomy. After the fish had recovered from the ataxic stage, the first observable DLR had shifted strongly towards the operated side. This early bias decreased rapidly, then more gradually. Mean values for the DLR reached a steady state within 2 weeks. Recovery rates were slowest for DLR tilts elicited by light presented from the operated side. The DLR did not recover to preoperative control values for light from either the intact or operated side. Shortly after the operation, light from the operated side produced DLR values nearly double the normal; light from the intact side had an effect very little different from normal. At steady state, the light effect from the operated side had decreased from the high immediately postataxic levels to a level roughly 1·5 times normal, but the light effect from the intact side had increased, also reaching a level roughly 1·5 times normal. Thus the final values again show symmetry. Variability appears to be an important feature of the response.
Biomechanics of Frog Swimming I. Estimation of the Propulsive Force Generated byHymenochirus Boettgeri
Authors: Gal Julianna M. , Blake R. W.
Published: April 2021

Ciné films were used to study swimming in the frog, Hymenochirus boettgeri (Tornier) during near-vertical breathing excursions. The animals generally decelerated during hindlimb flexion (recovery phase) and accelerated throughout hindlimb extension (power phase). Body velocity patterns of frogs are distinct from those of other drag-based paddlers, such as angelfish and water boatman, where the body is accelerated and decelerated within the power stroke phase. The propulsive force, estimated for a single sequence from quasi-steady drag and inertial considerations, was positive throughout extension. The upper and lower bounds of this estimate were calculated by considering additional components of the force balance, including the net effect of gravity and buoyancy, and the longitudinal added mass forces associated with the body. Consideration of the force balance implies that simple drag-based propulsion may not be sufficient to explain the swimming patterns observed in frogs.
Biomechanics of Frog Swimming: II. Mechanics of the Limb-Beat Cycle in Hymenochirus Boettgeri
Authors: Gal Julianna M. , Blake R. W.
Published: April 2021

The hindlimb kinematics of Hymenochirus boettgeri (Tornier) were investigated using high-speed ciné films. The movement pattern was stereotypic, flexion and extension of the metatarsal-phalangeals and feet always lagging behind flexion and extension of the femora and tibiofibulae. The right hindlimb was modelled as a series of linked circular cylinders and a flat plate. A blade-element approach was used to calculate the quasi-steady drag-based and accelerative force components parallel to the direction of motion, based on the hindlimb kinematics of sequence 1 (see preceding paper). Positive thrust is generated primarily during the initial stages of extension (power stroke) because of unsteady (added mass) effects. Negative thrust occurs over the latter half of extension, despite the continued acceleration of the animal. Hindlimb interaction is thought to provide propulsive thrust for the latter half of the extension phase. It is suggested that a jet and/or reflective effect may be involved.
Mechanisms of Coupling Between the Ipsilateral Legs of a Walking Insect (Carausius Morosus)
Authors: Cruse H. , Schwarze W.
Published: April 2021

The mechanisms by which the legs of a stick insect influence one another during walking were investigated by running the animals on a horizontal plane covered with a thin film of silicone oil to prevent mechanical coupling between the legs. Coupling between ipsilateral legs was investigated by interrupting the retraction (power stroke) of a leg for a short time and observing how the legs return to normal coordination following this disturbance.

The results show that three ipsilateral coupling mechanisms exist: (a) a forward-directed influence that inhibits the start of a protraction of the leg as long as the posterior leg is performing a protraction; (b) a forward-directed influence that excites the start of a protraction of the leg when the posterior leg starts a retraction movement; (c) a backward-directed influence that excites the start of a protrac-tion, the influence being stronger the further the anterior leg has moved backwards during its retraction. The latter influence depends on the position but not the phase of the anterior leg.
Amino Acid Metabolism and Water Transport Across the Seawater Eel Intestine
Authors: Ando Masaaki
Published: April 2021

To elucidate how intracellular L-alanine enhances water transport across the seawater eel intestine, effects of various metabolic inhibitors were examined. The L-alanine-induced water flux was inhibited by amino-oxyacetate, an inhibitor of aminotransferase. After blocking the synthesis of pyruvate from L-alanine with this drug, water transport was stimulated with pyruvate, whose effects were inhibited by oxythiamine, an inhibitor of pyruvate dehydrogenase. 2,4-Dinitro-phenol (DNP) also inhibited the effects of L-alanine. Furthermore, L-alanine enhanced ouabain-sensitive O2 consumption in this tissue, and the enhancement in O2 consumption preceded that in the transepithelial potential difference (PD) and the net water flux. These results indicate that L-alanine is metabolized through the citric acid cycle to produce ATP, and that a metabolic product stimulates ion and water transport. L-Glutamine also seems to be metabolized just like L-alanine because: L-glutamine acted from inside the enterocyte; DNP inhibited the effects of L-glutamine; neither of the effects of L-glutamine and L-alanine were additive but they were mutually complementary; L-glutamine also enhanced ouabain-sensitive O2 consumption; and the increment in O2 consumption preceded that in the PD and the net water flux. The effects of L-glutamine on the PD and the net water flux depended on glutamine concentration and the concentration-response curve was of the Michaelis-Menten type, indicating that the rate of L-glutamine uptake into the enterocyte limits the overall rate of L-glutamine metabolism. A regulatory role of amino acids for ion and water transport is discussed.
Depression Of Whole-Body Calcium Uptake During Acute Hypercalcaemia In American Eel, Anguilla Rostrata, is Mediated Exclusively by Corpuscles of Stannius
Authors: Perry S. F. , Seguin D. , Lafeber F. P. J. G. , Bonga S. E. Wendelaar , Fenwick J. C.
Published: April 2021

The role of the corpuscles of Stannius (CS) in acute modulation of wholebody calcium influx in American eel, Anguilla rostrata, was investigated by (i) assessing the effects of stanniectomy on and plasma total calcium concentration ([Catot]), (ii) comparing the abilities of sham-operated and stanniectomized eels to reduce during artificially induced hypercalcaemia, and (iii) monitoring the effects of homologous hypocalcin (a 54×103Mr glycoprotein) injection on . Stanniectomy (STX) caused a pronounced elevation of and hypercalcaemia measured 7 days after surgery. When hypercalcaemia was induced by intra-arterial infusion of CaCl2, a treatment known to cause degranulation of the CS and the specific release of hypocalcin, was reduced significantly within 1 h in intact fish. NaCl infusion did not affect plasma [Catot] or in any group tested. Stanniectomy prevented the reduction of associated with the hypercalcaemia induced by CaCl2 infusion. Intra-arterial infusion of MgCl2 caused a significant elevation of plasma total magnesium concentration [Mgtot] but did not alter . Intra-arterial infusion of hypocalcin (18.5 nmol kg−1 body mass) into intact eels decreased to an extent similar to that seen following artificially induced hypercalcaemia. We conclude that the rapid reduction of during experimental hypercalcaemia is mediated by hypocalcin released from the corpuscles of Stannius and suggest that calcitonin, another putative hypocalcaemic hormone, is not involved. The results are discussed with respect to the relative importance of hypocalcin and calcitonin as hypocalcaemic hormones in fish.
Photosensitive and Photostable Pigments in the Retinae of Old World Monkeys
Authors: Bowmaker J. K. , Astell Susan , Hunt D. M. , Mollon J. D.
Published: April 2021

Microspectrophotometric measurements of retinal receptors are reported for eight species of Old World monkey. Although the animals vary greatly in size, colourings and habitat, they all appear to be trichromats and the peak sensitivities of their cones invariably lie near 430, 535 and 565 nm. This consistent pattern contrasts with the results reported earlier for New World monkeys and with the results reported here for Tupaia glis. The trichromacy of frugivorous catarrhine monkeys may have co-evolved with a particular class of coloured fruit.

Short-wave cones were rare in all species. The ratio of the numbers of middle-wave and long-wave cones varied between individual animals, but had an overall value close to unity.

In the case of all the species examined here, we have recorded a photostable pigment in the inner segments of rods and cones. The latter pigment has a peak sensitivity close to 420 nm and an absorbance spectrum that is narrower than that of a photosensitive visual pigment.
The Kinematics and Performance of the Escape Response in the Angelfish(Pterophyllum Eimekei)
Authors: Domenici Paolo , Blake Robert W.
Published: April 2021

The kinematics of turning manoeuvres and the distance-time performance in escape responses of startled angelfish (Pterophyllum eimekei) are investigated employing high-speed cinematography (400Hz). All escape responses observed are C-type fast-starts, in which the fish assumes a C shape at the end of the initial body contraction (stage 1). Kinematic analysis of the subsequent stage (stage 2) allows the response to be classified into two types: single bend (SB), in which the tail does not recoil completely after the formation of the C, and double bend (DB), in which it does.

The two types of response have different total escape angles (measured from the subsequent positions of the centre of mass, SB 120·0°; DB 73·3°, P<0·005), different stage 2 turning angles (in the same direction as stage 1 for SB, 11·0°; in the direction opposite to stage 1 for DB, –21·9°: P<0·0005) and different maximum angular velocities in the direction opposite to the initial one (SB –8·08 rads−1; DB –56.62rads−1: P<0·001). There are no significant differences in stage 1 kinematics for the two types of escape. Stage 1 turning angle is linearly correlated to stage 2 turning angle for DB only (P<0·0l; r2=0·60) and to total escape angle for both types of response (P<0·000l; r2=0·80). Stage 1 duration is linearly correlated to stage 1 turning angle (P<0.0001; r2=0.83) and to total escape angle (P<0·0001; =0·72) for both types of escape.

Distance-time performance is also different in the two response types, mainly because of differences in stage 2 (maximum velocity for SB 0<99ms−1; maximum velocity for DB 1·53ms−1: maximum acceleration for SB 34<1ms−2; maximum acceleration for DB 74<7 ms−2: P<0·000l in both cases). As a result, there are significant differences in the performance throughout the whole response (maximum velocity 1<02 ms−1 and 1<53 ms−1 for SB and DB fast-starts, respectively; maximum acceleration 63<2 ms−2 and 91<9 ms−2 for SB and DB fast-starts, respectively) as well as within a fixed time (0<03 s). Overall, higher distance-time performances associated with smaller angles of turn are found in DB than in SB responses. Comparison with previous studies reveals that angelfish have a good fast-start performance despite specializations for low-speed swimming. In addition, the angelfish turning radius (0·065 ±0·0063L, where L is body length; mean±2s.E.) is lower than that previously reported for any fish.
Proton-Equivalent Ion Transfer inSipunculus Nudusas a Function of Ambient Oxygen Tension: Relationships With Energy Metabolism
Authors: Pörtner H. O. , Andersen N. A. , Heisler N.
Published: April 2021

Proton-equivalent ion transfer processes between animals and ambient water were determined under normoxic control conditions during anaerobiosis and the subsequent recovery period in the marine worm Sipunculus nudus L. During anaerobiosis and recovery, transepithelial H+-equivalent ion transfer was generally correlated with changes in extracellular pH, with some disparities in ‘spring’ animals. The typical initial alkalosis induced by phosphagen cleavage during early anaerobiosis was reflected by a loss of basic equivalents. The acidosis, which developed later, reflecting production of acidic metabolic intermediates, resulted in a relatively small net extrusion of protons into the water. The coelomic acidosis during recovery was greatly exaggerated by the release of protons during phosphagen repletion and by the considerable elevation of after normoxia had been reattained. The acidosis stimulated the net release of H+ to the water at a rate several times higher than that during anaerobiosis. The efficient transfer of protons from the body fluids to the environmental water during recovery facilitated normalization of coelomic pH, long before protons dissociated from the large amounts of organic acids produced as anaerobic intermediates could be removed from the body fluids by metabolism.

Although the transfer of net H+ equivalents to the water coincided with coelomic acidosis, the rates of transfer during different periods of the experiment were primarily correlated with overall metabolic rate. Low net proton transfer rates associated with anaerobiosis were not sufficient to maintain acid-base parameters typical for normoxia, whereas re-establishment of aerobic conditions facilitated a greatly increased transepithelial H+ transfer rate. These data suggest that the transfer capacity of the energy-consuming translocation mechanism may primarily be determined by the rate of metabolic turnover and, accordingly, by the amount of available energy.
Receptive Fields and Properties of A New Cluster Of Mechanoreceptor Neurons Innervating the Mantle Region and the Branchial Cavity of the Marine MolluskAplysia California
Authors: Dubuc Bruno , Castellucci Vincent F.
Published: April 2021

The rostral LE cluster (rLE) is a new set of mechanoreceptor neurons of the abdominal ganglion innervating the mantle area, the branchial cavity, the gill and the siphon of the marine mollusk Aplysia californica Cooper. We have compared the organization of rLE cell receptive fields with that of three other clusters of sensory neurons in the abdominal ganglion (LE, RE and RF) that we have reanalysed. There is extensive overlap of receptive fields from the four populations of sensory cells, and the most exposed areas of the mantle are the most densely innervated. The sensory threshold is similar for all groups. The action potentials of the LE, rLE and RE neurons are broadened by serotonin and the peptide SCPB and narrowed by dopamine and FMRFamide. The RF group does not show the same kind of sensitivity to these neuromodulators. The synaptic outputs of the LE and rLE neurons undergo similar synaptic depression and homosynaptic and heterosynaptic facilitation. We estimate that 100 mechanoreceptor neurons innervate the entire mantle and siphon skin, gill and branchial cavity of Aplysia. The degree of their convergence onto various interneurons and motor neurons mediating the gill- and siphon-withdrawal reflex and other reflexes is under investigation.
Defense Mechanisms in Notaspid Snails: Acid Humor and Evasiveness
Authors: Gillette Rhanor , Saeki Mayuko , Huang Rong-Chi
Published: April 2021

Notaspid snails are known for their defensive skin secretion of sulfuric acid (pH 1–2) in response to noxious stimuli. We observed acid secretion and behavior in five notaspid species, and studied them in detail in Pleurobranchaea californica. All species secreted acid in response to skin abrasion or compression. Moreover, all species showed stereotypic avoidance behavior to acidified sea water less acidic (pH2–3) then their own secretions. In Pleurobranchaea, secretion could also be stimulated by dilute solutions of taurine, 10−5–10−2moll−1. Secretion began at the stimulated region and spread slowly for about a minute following stimulation. Local contraction and transient edema of the skin were associated with acid secretion. In de-ganglionated preparations secretion could be caused by orthodromic stimulation of body wall nerves, by mechanical stimulation or by taurine.

These data suggest that acid secretion is a positive feedback process modulated by inhibitory paths and coordinated by both central and peripheral nervous systems. A picture emerges of a defensive secretory response that provides an additional noxious stimulus initiating or potentiating avoidance behavior. The data also suggest a potential role for taurine release from injured tissue and the existence of specific nociceptive neural pathways regulating complex behavior. In addition to deterring extraspecific predation, acid secretion could regulate interactions between animals of the same species.