bluuebunny/crossref_metadata_2025 huggingface dataset:
The fine structure of the secondary lamellae of the gills of Gadus pollachius
Authors: Hughes G. M. , Grimstone A. V.
Published: April 2021

The structure of the leaf-like secondary lamellae, across which gaseous exchange takes place, is described on the basis of an electron-microscope study of sectioned material. The epithelial layers on the two sides of the secondary lamellae are separated by widely spaced pillar cells, of characteristic form. These have a central cell body with wide flanges at each end which spread out below the epithelia. The flanges of adjacent pillar cells meet and connect, delimiting an extensive blood space between the pillar cell bodies. Pillar cells contain abundant mitochondria and membranes, and their cytoplasmic matrix is largely occupied by finely fibrous material. They appear to be responsible for the formation of a thick, collagen-containing basement membrane which lies between them and the overlying epithelia. There are also columns of basement membrane material which run transversely across the secondary lamellae, set in deep infoldings in the surface of the pillar cell bodies. Pillar cells appear to combine the functions of fibroblasts and the endothelial cells of true capillaries. The epithelium forming the outer surface of the secondary lamellae is one or more cells thick and consists of cells with large nuclei and abundant mitochondria and cytoplasmic membranes. The water/blood pathway across which gaseous exchange takes place consists of the epithelium, basement membrane and pillar cell flange and has a total thickness of 1 to 3μ.
The Use of Cajuput Oil in Microscopy
Authors: Brug S. L.
Published: April 2021

During the world war 1914-18 our stock of xylene (xylol) in Java ran low; moreover, the small quantity that was left changed into a thick syrupy fluid which was useless as a medium for mounting water-fixed preparations in balsam. Chemists told us that the xylene had polymerized. In text-books of microscopical technique cedar-wood oil is recommended as a substitute for xylene in some cases. However, this oil was still scarcer in Java than xylene; therefore we resolved to try another ethereal oil, namely, cajuput oil. Of this oil, a product of the Malay Archipelago, unlimited quantities were available. It soon, proved to be not only a good substitute for xylene, but in some cases superior to it.
The Experimental Production of Goblet Cells and Inclusion Bodies
Authors: Meirowsky E. , Behr G. , Keys S.
Published: April 2021

1. Goblet cells have been produced experimentally in rabbits’ and guineapigs’ corneae by ten methods.

2. Goblet cells can develop from ordinary epithelial cells.

3. The secretion antecedents originate in the nucleus.

4. Intranuclear and cytoplasmic inclusions can be produced experimentally and form the response mechanism of the cell towards animate and inanimate stimuli.
The Localization of Dehydrogenase Activity and Sulphydryl Groups in Wool and Hair Follicles by the use of Tetrazolium Salts
Authors: Rogers G. E.
Published: April 2021

Three tetrazolium salts are used as histochemical indicators of dehydrogenase activity in the skin of sheep and other mammals. Of these compounds 2-(p-iodophenyl) -3-(p-nitrophenyl)-5-phenyl-tetrazolium chloride (INT) is shown to be the most satisfactory. It enables various histological structures of the wool follicle to be conveniently demonstrated.

In the presence of appropriate substrates and DPN and ATP, the intracellular deposition of the granular formazan in frozen sections has revealed the distribution of succinic, αglycerophosphoric, lactic, and malic dehydrogenases, and regions where some phosphorylated carbohydrate intermediates promote reduction. Metabolic activity in the Malpighian layers and in the undifferentiated epidermal cells of the hair matrix reduces INT enzymatically up to the pre-keratinous zone. Here the proteinbound sulphydryl groups reduce INT and produce intense red staining which is easily distinguished from the granular enzymic staining.

The distribution of cytochrome oxidase in the wool follicle resembles the distribution of dehydrogenase activity.

INT is used for the estimation of succinic dehydrogenase in skin and kidney tissues.
A Sharpening Machine for a New Type of Microtome Knife
Authors: Dilworth S. , Appleyard H. M.
Published: April 2021

A description is given of the manufacture of a new type of microtome knife made from selected portions of discarded low tungsten steel power hacksaw blades. A machine for sharpening this type of knife is described. Its main feature is a lapping plate of 14 in. plate glass which can be adjusted for height to give cutting angles ranging from 24 to 32°, these angles being accurately reproducible on resharpening. Results of tests with a series of knives covering this range of cutting angles is given.
Studies of the Development of the imaginal Cuticle of Calliphora erythrocephala
Authors: Wolfe L. S.
Published: April 2021

The development of the imaginal cuticle has been studied with particular emphasis on the microtrichia and the pupal moulting fluid.

The microtrichia are formed from acidophil filaments of epidermal cytoplasm which remain as the cuticular pore canals after secretion of the endocuticle. Microtrichia at the base of the bristles are associated with nerves.

The cuticle before emergence consists of a single-layered epicuticle less than 1 μ thick and an endocuticle 3–5 μ thick. The epicuticle and the endocuticle of the sclerites are completely sclerotized after emergence.

The pupal moulting fluid was found to be a clear, salt-free, watery liquid containing protein and lipoid and devoid of proteinases or chitinases. No evidence of dissolution was found in the pupal cuticle. The aqueous part of the moulting fluid is absorbed before emergence and this may be prevented by the addition of salts.

Evidence is presented for the formation of a denatured, hydrophobic, protein-lipoid film from the moulting fluid on the surface of the epicuticle after emergence.

Resistance to water loss develops after emergence and is not entirely dependent on cuticle darkening and hardening. A film of moulting fluid spread and dried on natural and artificial membranes lowers the rate of water permeation. Such films possibly are operative in regulation of water loss from the imaginal cuticle immediately after emergence. Waxy materials appear on the cuticle surface during the hardening phase. Their possible origin is discussed.
On the Relationship between Mammary, Sweat, and Sebaceous Glands
Authors: Carlisle D. B.
Published: April 2021

Stages are described in the development of the mammae of male rabbits responding to regular injections of oestrogen and progesterone. It is suggested that the extra mammary lobes which develop under this treatment are derived from hair follicles and sebaceous glands by the loss of the hairs from the follicles and the proliferation of sebaceous glands and ducts. This may throw light on the phylogenetic origin and homology of the mammary gland.
The Post-embryonic Development of the Tracheal System in Drosophila melanogaster
Authors: Whitten Joan M.
Published: April 2021

The fate of the tracheal system is traced from the first larval instar to the adult stage. The basic larval pattern conforms to that shown for other Diptera Cyclorrhapha (Whitten, 1955), and is identical in all three instars.

According to previous accounts the adult system directly replaces the larval: the larval system is partly shed, partly histolysed, and the adult system arises from imaginai cell clusters independently of the preceding larval system.

In contrast, it is shown here that in the cephalic, thoracic, and anterior abdominal region there is a definite continuity in the tracheal system, from larval, through pupal to the adult stage, whereas in the posterior abdominal region the larval system is histolysed, and the adult system is independent of it in origin. Moreover, in the pupal stage this region is tracheated by tracheae arising from the anterior abdominal region and belonging to a distinct pupal system.

Moulting of the tracheal linings is complete at the first and second larval ecdyses, but incomplete at the third larval-pupal and pupal-adult ecdyses. In consequence, in both pupal and adult systems there are tracheae which are secreted around preexisting tracheae, others formed as new ‘branch’ tracheae, and those which have been carried over from the previous instar. In the adult the newly formed tracheae of the posterior abdominal region fall into a fourth category. Most of the adult thoracic air sacs correspond to new ‘branch’ tracheae of other instars.

The pre-pupal moult and instar are discussed with reference to the tracheal system and tentative suggestions are made concerning the true nature of the pre-pupal cuticle. There is no pre-pupal tracheal system.

Events traced for Drosophila would seem to be general for Cyclorrhapha, both Acalypterae and Calypterae. The separate fates of the anterior and posterior abdom inal systems, in contrast with the straightforward development in Dipterc Nematocera, would appear to mark a distinct step in the evolution of the system in Diptera.
The Fixation of Adipose Fat by Potassium Dichromate
Authors: Chou J. T. Y.
Published: April 2021

Ordinary adipose fat globules can be rendered resistant to paraffin embedding by the immersion of suitably fixed tissues in a saturated solution of potassium dichromate at 37° C for 7 weeks. Xylene has less tendency to remove the postchromed fat than chloroform, benzene, or toluene.

Adipose fat is usually dissolved out of the tissues during dehydration or embedding. Empty spaces are therefore usually seen in paraffin sections wherever fat globules were present during life. Several authors (Kaufmann and Lehmann, 1926 a, b; 1928; Smith, Mair, and Thorpe, 1909) have claimed that potassium dichromate can in certain circumstances be used to fix adipose fat in such a way that it is retained in paraffin sections, but a full study of this subject has not previously been made. My object has been to find a reliable method of fixing adipose fat by potassium dichromate in such a form that it is not dissolved away when paraffin sections are made.
The Role of Carbonic Anhydrase in Respiration, ion Regulation and Acid-Base Balance in the Aquatic Crab Callinectes Sapidus and the Terrestrial Crab Gecarcinus Lateralis
Authors: Henry Raymond P. , Cameron James N.
Published: April 2021

The enzyme carbonic anhydrase (CA), which is concentrated mainly in the osmoregulatory tissue of the gills, appears to be required for ion regulation but not for CO2 excretion. An injection of the CA inhibitor acetazolamide produced an inhibition of between 90 and 100 %, which took 6 h to be fully effective, and 48 –96 h to wear off. During the period of inhibition in Callinectes sapidus there was no change in either O2 uptake or CO2 excretion, nor was there any increase in blood In blue crabs acclimated to 250mosM salinity, at which the animals are ion regulators, inhibition of CA caused both Na+ and Cl− concentrations in the blood to be lowered, with Cl− being lowered to a greater degree. As a result of an increase in the Na+–Cl− difference the animal experienced a ‘metabolic’ alkalosis: elevated blood pH and HCO3− at constant The data are consistent with the hypothesis that branchial CA functions in providing H+ and HCO3− as counterions for Na+ and Cl− transport through the hydration of respiratory CO2.

In the terrestrial Gecarcinus lateralis, inhibition of CA caused an increase in blood but did not alter O2 uptake or CO2 excretion. After an initial acidosis, blood pH and HCO2− increased and remained elevated. Blood osmolality, Na+, Cl− and Ca2+ concentrations all increased, and the animals experienced a high rate of mortality. These data suggest that CA in the land crab is also important in blood ion regulation, probably to combat desiccation.
The Transition Between Branchial Pumping and Ram Ventilation in Fishes: Energetic Consequences and Dependence on Water Oxygen Tension
Authors: Steffensen John Fleng
Published: April 2021

Ram ventilation has been demonstrated in rainbow trout, Salmo gairdneri. The swimming speed eliciting the transition in mode of ventila-tion increased with declining ambient water oxygen tension . The mode of ventilation of fish swimming at a constant speed could be altered by controlled variations in . Oxygen consumption decreased by 10·2% when rainbow trout, swimming at a constant speed, shifted from active to ram ventilation. This difference can be ascribed to a lowering of the energetic cost of active ventilation as well as improved drag characteristics. Water velocity required for the transition from active to ram ventila-tion in the resting sharksucker, Echeneis naucrates, increased with decreas-ing . The results show that water oxygen tension is an important stimulus for setting the ventilatory mode in rainbow trout and sharksucker.
Kinetics of Branchial Calcium Uptake in the Rainbow Trout: Effects of Acclimation to Various External Calcium Levels
Authors: Perry S. F. , Wood C. M.
Published: April 2021

Calcium uptake in freshwater rainbow trout (Salmogairdnert) under control conditions (external [Ca2+] ≃ 1·8mequivl−1, [NaCl] ≃ 0·8mequiv 1−1) occurred at approximately equal rates (12–15 equiv kg−1 h−1) through the gills and the general body surface in vivo. The gut was not involved. Under the same conditions, in vitro branchial in an isolated, saline-perfused head preparation was equal to that in vivo. The cells involved in are mainly located on lamellae rather than on filaments since ∼ 95 % of occurred across the arterio-arterial circulation of the gill. in vitro, displayed Michaelis-Menten kinetics. Acclimation to low external [Ca2+] (50μequivl−1; unchanged [NaCl]) for 1 day caused a five-fold stimulation of characterized by decreased Km and increased Jmax Longer periods of low [Ca2+] acclimation resulted in changes of Jmax only. Jmax gradually returned towards control levels as acclimation time increased, but was still elevated after 30 days. Acclimation to low ambient [Ca2+] caused proliferation and increased exposure of lamellar chloride cells which were correlated with increased Jmax. Fish exposed to high external [Ca2+] (10 μequiv 1−1; unchanged [NaCl]) displayed reduced Similar changes in were observed during in vivo experiments. Plasma Ca2+ concentration remained constant regardless of external [Ca2+], while plasma Na+ and Cl− levels were transiently reduced at 1 day low [Ca2+] exposure but had recovered by 7 days. A possible role for cortisol in Ca2+ regulation is discussed based on observations of cortisol-stimulated lamellar chloride cell proliferation and and elevated plasma [cortisol] in low-[Ca2+] acclimated fish.
Epithelial Amino Acid Transport in Marine Mussels: Role in net Exchange of Taurine Between Gills and Sea water
Authors: Wright Stephen H. , Secomb Timothy W.
Published: April 2021

The exchange of taurine across epidermal epithelia of Mytilus edulis and M. califonianus was studied using radiotracer and chromatographic (HPLC) methods. Gill levels of taurine in both species ranged from 60 to 70μmol g −1 wet weight. Net uptake of taurine, determined using HPLC, occurred down to ambient concentrations as low as 10 nmol 1 −1. The rate of taurine loss from mussels was about 0·02 μmolg −1 wet body weight h −1, and when exposed to amino-acid-free sea water, external taurine concentration increased until a steady-state of about 15 nmol 1 −1 was achieved. Mussels accumulated inhibitors of taurine transport at rates which were directly related to their relative inhibitory capacities: β-alanine>β-aminobutyric acid ≃ γ-aminobutyric acid (GABA). Addition of large concentrations (50–200 μmoll −1) of GABA resulted in a rapid increase in taurine concentration in test solutions. This increase was consistent with a model in which GABA both competitively inhibits the reaccumulation of endogenous taurine lost from epidermal tissues, and accelerates the exchange diffusion of taurine from surface cells. We suggest that epidermal taurine transport in Mytilus assists in the maintenance of large intracellular taurine concentrations, and can serve to reaccumulate up to 30% of the taurine lost from surface tissues by passive processes.
The Effects of Forced and Voluntary Diving on Ventilation, Blood Gases and Ph in the Aquatic Amphibian, Xenopus Laevis
Authors: Boutilier Robert G. , Shelton Graham
Published: April 2021

Pre-and post-dive breathing patterns, blood oxygenation and acid-base balance have been examined in voluntarily and forcibly submerged Xenopus laevis. Enforced 30-min dives led to a large acidosis with both respiratory (CO2) and metabolic (lactic acid) components. Complete recovery of the arterial blood variables after such dives took more than 4h. Lung ventilation (measured by a pneumotachograph) following enforced dives was always markedly elevated compared with levels either before or after voluntary dives of the same duration. In undisturbed Xenopus, diving freely for periods of 30 min or more, there was no accumulation of lactic acid and the fall in blood oxygen, increase in CO2 and the associated respiratory acidosis were all corrected within the first few breaths upon surfacing. The evidence presented here leads us to conclude that anaerobiosis is unimportant during voluntary dives, even when these are of considerable duration.
Recovery From Anaerobiosis in the Intertidal Worm Sipunculus Nudus: I. Restoration of Aerobic, Steady-State Energy Metabolism
Authors: Pörtner H. O. , Vogeler S. , Grieshaber M. K.
Published: April 2021

Recovery from 24 h of anaerobiosis was investigated in Sipunculus nudus L. by monitoring changes in the concentrations of anaerobic metabolites in the musculature and in the coelomic plasma. The metabolic events in animals collected during March and October were compared.

Anaerobiosis led to an increase of succinate, propionate and acetate in the muscle tissues and the coelomic plasma. Strombine, octopine and alanine (predominantly L-rather than D-alanine) accumulated in the musculature, whereas aspartate and phospho-L-arginine levels decreased. A higher metabolic rate was observed during anaerobiosis in October than in March animals, as indicated by the higher amounts of strombine, octopine and acetate formed. An increase in metabolic rate appears to entail an increase of flux through the Embden–Meyerhof pathway which favours the accumulation of direct derivatives of pyruvate.

During recovery, regeneration of phospho-L-arginine occurred during the first 3 h, whereas disposal of succinate, octopine and propionate was observed during the entire 24-h period of recovery. Strombine, alanine and, to a lesser extent, acetate contents remained elevated. The concentration of D-alanine approached that of L-alanine during recovery, indicating the activity of alanine racemase. Malate levels increased transiently, possibly linked to the repletion of the aspartate pool.

In October animals, strombine seemed to accumulate transiently during initial recovery, indicating that the energy demand was not met by aerobic metabolism alone. In contrast to the situation in March animals, however, anaerobic glycolysis during recovery obviously becomes important only when the metabolic rate during anaerobiosis was high enough.
Oviposition Digging in the Grasshopper: II. Descending Neural Control
Authors: Thompson Karen J.
Published: April 2021

Transection of the ventral nerve cord of female grasshoppers activates the rhythmical motor programme for oviposition digging. Electrical stimulation of the cut nerve cord had the following effects on elicited oviposition motor activity: (i) short- and long-lasting inhibition of activity, (ii) phase resetting and (iii) modulation of burst frequency. Cold saline applied to the nerve cord reversibly elicited the oviposition motor programme. The effects of transection and stimulation at different levels of the nerve cord indicate that the higher neural control of the motor pattern is not confined to the head ganglia, but includes a thoracic component. In intracellular recordings of ventral opener motoneurones, stimulus-related IPSPs were observed in response to stimulation of the cut nerve cord. Stimulation also abolished slow wave synaptic input to the motoneurones during inhibition of the oviposition motor programme. It is suggested that oviposition digging behaviour is initiated and maintained by a mechanism of ‘release’ from descending neural inhibition.
Resting Potential and Potassium-Selective Electrode Measurements in Locust Skeletal Muscles
Authors: Leech C. A.
Published: April 2021

The membrane of locust skeletal muscle fibres is permeable to both potassium and chloride ions in the resting state and has a potassium selectivity similar to that of a potassium electrode (Usherwood, 1967). The experiments described here were performed on the isolated retractor unguis muscle of the locust Schistocerca gregaria. The composition of the standard locust saline was similar to that of Hoyle (1953) except that in most experiments the HPO4/HCO3 buffer was replaced by Tris-maleate (pH 6·8). Conventional electrophysiological techniques were used and electrodes had tip potentials of less than 5 mV.
Release of Octopamine From the Photomotor Neurones of the Larval Firefly Lanterns
Authors: Carlson Albert D. , Jalenak Mary
Published: April 2021

The biogenic amine, octopamine, has been proposed as the transmitter in the firefly light organ (Evans, 1980; Robertson, 1981). Whereas initial studies implicated adrenaline (Smalley, 1965; Carlson, 1968a), octopamine was found to be more potent in inducing luminescence than any amine other than synephrine (Carlson, 1968b). Octopamine, but not synephrine, was found in adult lantern segments (Robertson & Carlson, 1976; Copeland & Robertson, 1982) and in larval lantern tissue (Christensen, Sherman, McCaman & Carlson, 1983). Evidence that cyclic nucleotides mediate the effect of octopamine was obtained by Oertel & Case (1976). An octopamine-sensitive adenylate cyclase has been found in the larval lantern and application of exogenous octopamine strongly stimulates cyclic AMP production in adult (Nathanson, 1979) and larval (Nathanson & Hunnicutt, 1979) light organs.
Amino Acid Receptor-Mediated Transmission at Primary Afferent Synapses in Rat Spinal Cord
Authors: Jessell T. M. , Yoshioka K. , Jahr C. E.
Published: April 2021

Intracellular recording techniques have been used to provide information on the identity of excitatory transmitters released at synapses formed between dorsal root ganglion (DRG) and spinal cord neurones in two in vitro preparations. Explants of embryonic rat DRG were added to dissociated cultures of embryonic dorsal horn neurones and synaptic potentials recorded intracellularly from dorsal horn neurones after DRG explant stimulation. More than 80% of dorsal horn neurones received at least one fast, DRG-evoked, monosynaptic input. In the presence of high divalent cation concentrations (5 mmoll−1 Ca2+, 3mmoll−1 Mg2+) the acidic amino acid receptor agonists, L-glutamate, kainate (KA) and quisqualate (QUIS) excited all dorsal horn neurones which received a monosynaptic DRG neurone input, whereas L-aspartate and.V-methyl-D-aspartate (NMDA) had little or no action. 2-Amino-5-phosphonovalerate (APV), a selective NMDA receptor antagonist, was relatively ineffective at antagonizing DRG-evoked synaptic potentials and L-glutamate-evoked responses. In contrast, kynurenate was found to be a potent antagonist of amino acid-evoked responses and of synaptic transmission at all DRG-dorsal horn synapses examined. The blockade of synaptic transmission by kynurenate appeared to result from a postsynaptic action on dorsal horn neurones.

Intracellular recordings from motoneurones in new-born rat spinal cord were used to study the sensitivity of the la excitatory postsynaptic potential (EPSP) to antagonists of excitatory amino acids. Superfusion of the spinal cord with APV did not inhibit the la EPSP but did suppress later, polysynaptic components of the afferent-evoked response. Kynurenate was a potent and selective inhibitor of the la EPSP, acting via a postsynaptic mechanism. These findings indicate that L-glutamate, or a glutamate-like compound, but not L-aspartate, is likely to be the predominant excitatory transmitter that mediates fast excitatory postsynaptic potentials at primary afferent synapses with both dorsal horn neurones and motoneurones.
Regulation of Ion Channels By Inositol Trisphosphate and Diacylglycerol
Authors: Berridge Michael J.
Published: April 2021

Calcium-mobilizing receptors function to regulate ion channels located not only in the plasma membrane but also across the membranes of intracellular organelles, particularly the endoplasmic reticulum. A characteristic feature of such receptors is that they stimulate the hydrolysis of an inositol lipid to generate a pair of second messengers. Diacylglycerol remains within the plasma membrane where it activates protein kinase C leading to the phosphorylation of proteins some of which may regulate specific ionic channels, such as the calcium-dependent potassium channel or the Na+/H+ exchanger which regulates intracellular pH. The inositol trisphosphate (Ins l,4,5P3) released to the cytosol functions as a second messenger to release calcium from the endoplasmic reticulum. The Ins 1,4,5P3 acts on a specific receptor to enhance the passive efflux of calcium while having no effect on the active calcium pump. There are indications that this Ins 1,4,5P3-induced release of calcium from an internal membrane store might provide an explanation of excitation-contraction coupling in skeletal muscle. Skinned skeletal muscle cells can be induced to contract by adding Ins l,4,5P3. Mobilization of calcium from intracellular reservoirs by Ins l,4,5P3 may thus prove to be a ubiquitous and fundamental mechanism for regulating cellular activity.
The Acid–Base Balance of the Outer Mantle Epithelium of Anodonta Cygnea
Authors: Machado J. , Ferreira K. G. , Ferreira H. G. , Fernandes P. L.
Published: April 2021

Under short-circuit conditions the outer mantle epithelium of Anodonta cygnea is known to produce an acidification of the solution bathing the shell side and an alkalinization of the solution bathing the haemolymph side. At steady state, the rates of secretion of acid and base were numerically equal to the simultaneously measured short-circuit current, expressed in the same units. The rates of acid and base secretion, and the short-circuit current, showed close similarity in the reductions caused by anoxia, diamox, DIDS (from haemolymph side), DNP and iodoacetamide. The short-circuit current (Isc) was sensitive to the concentration of CO2, bicarbonate or protons in the solution on the shell side. The short-circuit current was insensitive to vanadate or oligomycin, was slowly inhibited by DCCD added under anoxia to the shell side, and was almost completely inhibited within seconds by TBTO (shell side) which also caused a 40% reduction in transepithelial conductance. It is suggested that Isc is due to a Cl−/HCO3−exchange shunted by a Cl− recirculation across the basolateral membrane and to the operation of an electrogenic proton pump located in the apical membrane.
Lethal and Quasi-Lethal Effects Produce by Monochromatic Ultra-Violet Irradiation
Authors: McAulay A. L. , Taylor M. C.
Published: April 2021

Lethal and quasi-lethal effects produced by monochromatic ultra-violet irradiation of biological material representing the phyla Bacteria, Fungi, Angiospermae, Protozoa and Arthropoda have been observed and recorded over a range of wavelengths from 254 to 365 mµ. Although the materials represent high and low forms in both vegetable and animal kingdoms, there is a striking similarity in their behaviour. There is a sudden increase in the lethal effect between 313 and 297 mµ in every case.

Although the curves connecting lethal dose with wave-length are closely similar in all cases, the absolute magnitudes of doses are widely different. The ratio of lethal doses for different material may be as high as two hundred to one at corresponding wave-lengths. The ratio of the greatest to the least dose recorded is of the order of a million to one.

Tables and curves are given recording lethal and quasi-lethal doses for the different materials at different wave-lengths, and brief accounts of the conditions in which the experiments were conducted are given in the text.

An interesting correlation is exhibited between the form of the lethal dose curves and the ultra-violet radiation in daylight.
Energy-Saving Mechanisms in Walking and Running
Authors: Alexander R. McN.
Published: April 2021

Energy can be saved in terrestrial locomotion in many different ways. The maximum shortening speeds (vmax) of the muscles can be adjusted to their optimum values for the tasks required of them. The moments exerted by the muscles at different joints can be adjusted to keep the ground force in line with the leg so that muscles do not work against each other. The joints of the legs can be kept as straight as possible, minimizing muscle forces and work requirements. Walking gaits should be selected at low Froude numbers (a dimensionless speed parameter) and running gaits at high Froude numbers. Tendon and other springs can be used to store elastic strain energy and to return it by elastic recoil. This paper aims to show how these energy-saving mechanisms work and to what extent mammals exploit them. Arguments based on our rather limited knowledge of the relationship between the mechanical performance of muscle and its metabolic energy consumption are used throughout. They suggest that muscles that are optimally adapted for their tasks in running should do positive work with constant efficiency.
A Model of Rapid-Start Swimming at Intermediate Reynolds Number: Undulatory Locomotion in the Chaetognath Sagitta Elegans
Authors: Jordan Christopher E.
Published: April 2021

The mechanics and kinematics of accelerational undulatory locomotion by the chaetognath Sagitta elegans (Verrill, 1873) are studied with a combination of highspeed cinematography (200 frames s−1) and mathematical modeling. The model is constructed such that it predicts body velocity for an organism starting from rest and accelerating rapidly by swimming with prescribed wave kinematics. The speed of the undulatory propulsive waves and the number of these waves on the body is highly conserved across 11 individuals, while the wave amplitude is positively related to distance traveled in the first 65 ms of swimming. There is excellent agreement between these data and predictions of body translations that are based on a mathematical model for this mode of locomotion. The model also shows that instantaneous forces generated by the undulating body are much larger than average forces and consist of non-trivial inertial terms, even for such small organisms. The model also shows that the distance traveled over a fixed time interval is limited by the maximum muscle stress that can be physiologically generated. Peak instantaneous force represents a mechanical upper boundary to thrust production and, hence, a limit to performance.
Regulation of Pulmonary Blood Flow and of Blood Pressure in a Mangrove Crab (Goniopsis Cruentata)
Authors: Wilkens J. L. , Young R. E.
Published: April 2021

The air-breathing mangrove crab Goniopsis cruentata ventilates the branchial chambers with its scaphognathites (SG). Ventilation is predominantly in the forward direction, but is punctuated by bouts of reversed pumping. Reversals are more frequent when crabs are in air than in water, and yet more frequent during respiratory stress (hypoxia or exercise). Reversed SG pumping is tightly coupled with bursts of impulses to the dorsal-ventral muscles (DVM) which span the anterolateral thorax. Phasic contractions of the DVMs increase the hemolymph pressure in the dorsal sinuses. These pressure pulses help drive hemolymph through the lungs. The coupled SG reversed ventilation and DVM-assisted increases in lung perfusion appear to be an adaptation to increase gas exchange at the lungs.

When crabs are made hyper-or hypotensive by changes in hemolymph volume, the EMG activity of the DVMs dramatically decreases or increases, respectively. The resultant expansion or constriction of the dorsal sinuses is an effective baroreceptor reflex producing short-term adjustments in hemolymph pressure.
Pectoralis Muscle Force and Power Output During Flight in the Starling
Authors: Biewener Andrew A. , Dial Kenneth P. , Goslow G. E.
Published: April 2021

Force recordings of the pectoralis muscle of European starlings have been made in vivo during level flight in a wind tunnel, based on bone strain recordings at the muscle’s attachment site on the humerus (deltopectoral crest). This represents the first direct measurement of muscle force during activity in a live animal based on calibrated bone strain recordings. Our force measurements confirm earlier electromyographic data and show that the pectoralis begins to develop force during the final one-third of the upstroke, reaches a maximal level halfway through the downstroke, and sustains force throughout the downstroke. Peak forces generated by the pectoralis during level flight at a speed estimated to be 13.7ms−1 averaged 6.4N (28% of maximal isometric force), generating a mean mass-specific muscle power output of 104 W kg−1. Combining our data for the power output of the pectoralis muscle with data for the metabolic power of starlings flying at a similar speed yields an overall flight efficiency of 13 %. The force recordings and length changes of the muscle, based on angular displacements of the humerus, indicate that the pectoralis muscle undergoes a lengthening-shortening contraction sequence during its activation and that, in addition to lift and thrust generation, overcoming wing inertia is probably an important function of this muscle in flapping flight.
Kinematics of Aquatic Prey Capture in the Snapping Turtle Chelydra Serpentina
Authors: Lauder G. V. , Prendergast T.
Published: April 2021

The kinematics of feeding on two prey types is studied quantitatively in the common snapping turtle, Chelydra serpentina, to provide a description of prey capture mechanisms and to determine whether kinematic patterns can be altered in response to prey that vary in escape capability. High-speed video recordings of prey capture (200 fields s-1) provide data for field-by-field analysis of 12 kinematic variables characterizing head and neck movement. Feedings on fish were accomplished in 78 ms, with peak head extension velocities of 152.5 cm s-1. Worm feedings lasted 98 ms with maximum head extension velocities of 54cms-1. Both univariate and multivariate statistical analyses demonstrate significant differences in kinematic patterns between fish and earthworm feedings: Chelydra serpentina possesses the ability to modulate its kinematic pattern depending on the prey. The pattern of bone movement during the fast opening phase of the gape cycle is similar to that found in ray-finned fishes, lungfishes and aquatic salamanders. However, movements of the cranium and lower jaw during the closing phase are markedly different. Our data show Chelydra to be predominantly a ram-feeder, with any intraoral negative pressures generated during the strike having a negligible effect on the prey, which remains largely stationary relative to a fixed background. Hyoid and esophageal expansion during the closing phase may function to allow a unidirectional flow of water and prey into the mouth until the gape closes and to delay reverse flow until the prey has been trapped inside the mouth. The independent evolutionary acquisition of aquatic feeding in fishes and turtles reveals some kinematic similarities that may be the result of hydrodynamic constraints on aquatic prey capture systems, as well as kinematic differences that result from the fundamentally different morphological design of the prey capture apparatus.
Antibodies to Mammalian and Plant V-Atpases Cross React With the V-Atpase of Insect Cation-Transporting Plasma Membranes
Authors: Russell Virginia E. W. , Klein Ulla , Reuveni Moshe , Spaeth Daniel D. , Wolfersberger Michael G. , Harvey William R.
Published: April 2021

In immunobiochemical blots, polyclonal antibodies against subunits of plant and mammalian vacuolar-type ATPases (V-ATPases) cross-react strongly with corresponding subunits of larval Manduca sexta midgut plasma membrane V-ATPase. Thus, rabbit antiserum against Kalanchoe daigremontiana tonoplast V-ATPase holoenzyme cross-reacts with the 67, 56, 40, 28 and 20kDa subunits of midgut V-ATPase separated by SDS-PAGE. Antisera against bovine chromaffin granule 72 and 39 kDa V-ATPase subunits cross-react with the corresponding 67 and 43 kDa subunits of midgut V-ATPase. Antisera against the 57 kDa subunit of both beet root and oat root V-ATPase cross-react strongly with the midgut 56 kDa V-ATPase subunit.

In immunocytochemical light micrographs, antiserum against the beet root 57 kDa V-ATPase subunit labels the goblet cell apical membrane of both posterior and anterior midgut in freeze-substituted and fixed sections. The plant antiserum also labels the apical brush-border plasma membrane of Malpighian tubules. The ability of antibodies against plant V-ATPase to label these insect membranes suggests a high sequence homology between V-ATPases from plants and insects.

Both of the antibody-labelled insect membranes transport K+ and both membranes possess Frlike particles, portasomes, on their cytoplasmic surfaces. This immunolabelling by xenic V-ATPase antisera of two insect cation-transporting membranes suggests that the portasomes on these membranes may be V-ATPase particles, similar to those reported on V-ATPase-containing vacuolar membranes from various sources.
The Synchronization of Ventilation and Locomotion in Horses (Equus Caballus)
Authors: Young Iain S. , Alexander R. McN. , Woakes A. J. , Butler P. J. , Anderson Lloyd
Published: April 2021

Ciné film and synchronized records of respiratory flow were obtained from Thoroughbred racehorses cantering on a treadmill at speeds of 9 and 11ms−1.

Horses and some other galloping and hopping mammals link their breathing and locomotion, taking exactly one breath per stride. Three theoretical mechanisms by which the movements of locomotion might drive ventilation are considered.

(i) Flexion of the lumbosacral joint and the resulting forward sweep of the pelvis pushes the viscera against the diaphragm. However, back flexion lags behind ventilation at 11ms−1 and could not exclusively drive ventilation at this speed. (ii) Loading of the thorax by the impact of the forelimbs with the ground might force air out of the lungs. If the respiratory system were damped sufficiently to perform as this mechanism requires, the work of driving ventilation would make up approximately 15 % of the total work of running. In comparison with other estimates of the work of ventilation this seems improbably high, (iii) The observed phase relationship between displacements of the viscera, caused by the accelerations of the body during running, and respiratory airflow is not consistent with a tuned visceral piston mechanism driving breathing.

Thus, it would seem likely that back flexion is likely to contribute towards driving ventilation but loading of the thorax and the visceral piston mechanism do not.
An Analysis of Control of the Ventricle of the Mollusc Mercenaria
Mercenaria: II. Ionic Mechanisms Involved in Excitation By 5-Hydroxytryptamine
Authors: Devlin C. Leah
Published: April 2021

This study focuses on the ionic mechanisms involved in serotonergic control of the ventricle from the mollusc MercenariaMercenaria. The effects of calcium (Ca2+), sodium (Na+), potassium (K+), magnesium (Mg2+) and chloride (Cl−) ions on the action of 5-hydroxytryptamine (5-HT) were tested using a sucrose-gap technique. 5-HT increased the amplitude and frequency of the cardiac action potentials (APs) and coupled systolic force in a range of concentrations from the threshold, at 10−10 mol l−1, to 10−6 mol l−1. Low, physiological doses of 5-HT increased the rate of rise and amplitude of the fast rising phase of the AP, and hastened the process of repolarization. Doses of 5-HT higher than 10−5mol l−1caused systolic arrest.

The action of 5-HT was highly dependent on the presence of physiological levels of extracellular Ca2+. It had a maximal effect on systolic activity in a calcium chloride concentration range of 9–18mmol l−1. The activity of 5-HT was blocked by treatment with Ca2+-free saline, with inorganic Ca2+ blockers (lanthanum or cobalt) or with an organic Ca2+ entry blocker (verapamil). The effects of 5-HT were potentiated by treatment with barium ions (Ba2+), by a dihydropyridine-sensitive Ca2+ agonist, Bay K 8644, or by a vertebrate Ca2+ entry blocker, diltiazem.Removal of extracellular Na+ or treatment with a Na+ ionophore, monensin, did not significantly affect excitation by 10−6 mol l−15-HT; nor did the removal of Cl− or Mg2+. Unlike Ca2+, these three ions probably did not have a critical role during the excitatory action of 5-HT.

The excitatory action of 5-HT was not significantly altered by treatment with K+-free saline. When the membrane was depolarized by high-K+ salines, however, 5-HT was unable to elicit any APs or systolic contractions, suggesting that its mechanism may involve voltage-sensitive channels.
Anomalous Glutamate/Alkali Cation Symport In Larval Manduca Sexta Midgut
Authors: Xie Tao , Parthasarathy R. , Wolfersberger Michael G. , Harvey William R.
Published: April 2021

Rapid filtration assays were used to characterize glutamate/cation uptake in brush-border membrane vesicles from the larval midgut of the lepidopteran Manduca sexta. At pH 10.5, which is close to the physiological pH in the midgut of M. sexta, an inwardly directed K+ gradient stimulated glutamate uptake, suggesting that glutamate was symported. Gradients of Na+ or Li+ were less effective. Neither Rb+ nor Cs+ stimulated glutamate uptake. Anion-specificity was less pronounced: the accumulation maximum was only slightly higher with thiocyanate (SCN−) than with Cl−, although initial uptake was noticeably faster with thiocyanate.

A distinct set of amino acids that would cis-inhibit or trans-elicit glutamate uptake was not found. Even L-glutamate itself did not elicit accumulations of labeled glutamate. Taken together, these results suggest that a glutamate-specific symporter may not be present. Moreover, because glutamate symport was found to be electroneutral in vitro whereas amino acid uptake is electrophoretic in vivo, we infer that symport with K+ may not be an important mechanism of glutamate translocation by M. sexta midgut.
Transepithelial Potential And Alkalization in an in Situ Preparation of Tobacco Hornworm (Manduca Sexta) Midgut
Authors: Moffett David F. , Cummings Stacey Ann
Published: April 2021

The midgut of larval lepidopteran insects rapidly raises the pH of the entering food from approximately neutral values to as high as pH 12 in some species (Waterhouse, 1949; Dow, 1984). These values are among the highest achieved by biological systems and are all the more remarkable in view of the high rate of food consumption relative to body mass in lepidopteran larvae.
Head Waving in Aplysia Californica: I. Behavioural Characterization of Searching Movements
Authors: Kuenzi Frederick M. , Carew Thomas J.
Published: April 2021

Searching is an important component of several types of goal-directed behaviour. In soft-bodied animals, searching behaviour can appear quite complex because the range of body movement is not constrained by joints, limbs or muscles with discrete areas of origin and insertion. In addition, animals exhibiting this type of behaviour utilize their maximum freedom of movement. In this paper, we describe the head-waving searching behaviour of the sea hare Aplysia californica by characterizing patterns of movements and the changes in body shape that underlie these movements. A bout of head waving consists of a series of discrete movements separated by pauses. Each discrete movement lasts 4–10 s and is directed either horizontally or vertically with respect to the stationary part of the animal. Large movements, such as bending from the extreme right to the extreme left, consist of a series of these shorter movements separated by pauses lasting 1–2 s. In all head-waving movements, the transverse axis of the head is kept relatively parallel with the substratum. Thus, vertical movements require only bending of the body, whereas horizontal movements require twisting of the body, particularly when the posture is more erect. During head waving, the anterior two-thirds of the body is free to move, but most of the bending occurs immediately posterior to the head region. There is no periodicity of movements within a bout of head waving, although isolated instances of repeated movements are sometimes observed. Therefore, although the individual movements during head waving are relatively simple, the absence of a patterned sequence accounts for the complexity of the overall behaviour. These observations both constrain models of the neural organization of head waving and provide criteria for categorizing head-waving movements in further behavioural and physiological studies.
Physiological Modelling of Oxygen Consumption In Birds During Flight
Authors: Bishop C. M. , Butler P. J.
Published: April 2021

This study combines data on changes in cardiovascular variables with body mass (Mb) and with exercise intensity to model the oxygen supply available to birds during flight. Its main purpose is to provide a framework for identifying the factors involved in limiting aerobic power input to birds during flight and to suggest which cardiovascular variables are the most likely to have been influenced by natural selection when considering both allometric and adaptive variation.

It is argued that natural selection has acted on heart rate (fh) and cardiac stroke volume (Vs), so that the difference in the arteriovenous oxygen content in birds, both at rest and during flight, is independent of Mb. Therefore, the Mb exponent for oxygen consumption during flight can be estimated from measurements of heart rate and stroke volume. Stroke volume is likely to be directly proportional to heart mass (Mh) and, using empirical data, values for the Mb coefficients and exponents of various cardiovascular variables are estimated. It is concluded that, as found for mammals, fh is the main adaptive variable when considering allometric variation, although Mh also shows a slight scaling effect. Relative Mh is likely to be the most important when considering adaptive specialisations.

The Fick equation may be represented as:

where w, x, y, z are the body mass exponents for each variable and the terms in parentheses represent the Mb coefficients. Utilising this formula and data from the literature, the scaling of minimum during flight for bird species with a ‘high aerobic capacity’ (excluding hummingbirds) is calculated to be:

and for hummingbirds (considered separately owing to their unique wing kinematics) it is:

These results are largely dependent on the cardiovascular values obtained from pigeons flying near to the minimum power speed of 10 m s-1, but would appear to provide realistic values. Both the measured and the estimated for hummingbirds appear to scale with a larger Mb exponent than that for all other birds, and it is suggested that this is as a result of the larger Mb exponent for flight muscle mass as the larger species of hummingbirds try to maintain hovering performance. It is proposed that estimated for birds during flight, which is based on Mh in combination with estimates of fh and , gives an indirect measure of relative aerobic power input and, when corrected for the estimated scaling influences of the mechano-chemical conversion efficiency and lift generation with respect to Mb, may be a useful indicator of the relative capacity of the muscle to sustain power output and lift production during flight.