bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical Efficiency and Efficiency of Storage And Release Of Series Elastic Energy In Skeletal Muscle During Stretch–Shorten Cycles
Authors: Ettema G. J. C. 
Published: April 2021

ABSTRACT
The mechanical energy exchanges between components of a muscle–tendon complex, i.e. the contractile element (CE) and the series elastic element (SEE), and the environment during stretch–shorten cycles were examined. The efficiency of the storage and release of series elastic energy (SEE efficiency) and the overall mechanical efficiency of the rat gastrocnemius muscle (N=5) were determined for a range of stretch–shorten contractions. SEE efficiency was defined as elastic energy released to the environment divided by external work done upon the muscle–tendon complex plus internal work exchange from the CE to the SEE. Mechanical efficiency is external work done by the muscle–tendon complex divided by the external work done upon the muscle–tendon complex plus work done by the CE.
All stretch–shorten cycles were performed with a movement amplitude of 3 mm (6.7 % strain). Cycle frequency, duty factor and the onset of stimulation were altered for the different cycles. SEE efficiency varied from 0.02 to 0.85, mechanical efficiency from 0.43 to 0.92. SEE efficiency depended on the timing of stimulation and net muscle power in different ways. Mechanical efficiency was much more closely correlated with net power.
The timing of muscle relaxation was crucial for the effective release of elastic energy. Simulated in vivo contractions indicated that during rat locomotion the gastrocnemius may have a role other than that of effectively storing elastic energy and generating work.
Computer simulations showed that the amount of series elastic compliance can affect the internal energetics of a muscle contraction strongly without changing the muscle force generation dramatically.
Fictive locomotion induced by octopamine in the earthworm
Authors: Mizutani Kenji , Ogawa Hiroto , Saito Junichi , Oka Kotaro 
Published: April 2021

SUMMARY
We investigated the function of octopamine (OA) as a motor pattern inducer in the earthworm Eisenia fetida. We used semi-intact preparations, consisting of 20 sequential segmental ganglia of the ventral nerve cord (VNC) together with the body wall from the middle of the animal. Bath-application of 10–4 mol l–1 OA to the semi-intact preparation induced phasic muscle contractions, which are consistent with crawling. In the isolated VNC, OA induced bursts of motor neuron activity in the first lateral nerves. Burst frequency increased with OA concentration, with a large increase in activity observed in the range 10–6–10–4 mol l–1. At 10–4 mol l–1, the coefficient of variation of burst periods (BPs) was smaller than that seen upon application of OA at other concentrations, which is indicative of rhythmic bursts. These rhythmic bursts propagated along the VNC from the anterior to posterior, with a propagation velocity ranging from 60 to 110 mm s–1. This velocity is consistent with the propagation velocity of muscle contraction during crawling behavior in the intact earthworm. From these results, we conclude that fictive crawling motor patterns are observed at 10–4 mol l–1 OA, and that OA can induce rhythmic bursts in the isolated VNC of the earthworm.
Copper metabolism in actively growing rainbow trout (Oncorhynchus mykiss): interactions between dietary and waterborne copper uptake
Authors: Kamunde Collins , Grosell Martin , Higgs Dave , Wood Chris M. 
Published: April 2021

SUMMARYJuvenile rainbow trout Oncorhynchus mykiss were exposed to diets with low (12.6 nmol g–1), normal (50.4 nmol g–1) or elevated (4437.5 nmol g–1) Cu concentrations in combination with either low (5.8 nmol l–1) or normal (48.5 nmol l–1) waterborne Cu levels over a 50-day period, during which body mass increased up to fivefold. A nutritional requirement for Cu was demonstrated based on growth response and whole body and tissue Cu status. Simultaneous low Cu levels in both the water and the diet depressed growth by 31 % over 7 weeks. There were reductions in both specific growth rate (SGR, 1.95 versus 2.55 % day–1) and food conversion efficiency (FCE, 53–59 % versus 75–80 %) over weeks 0–4, but these effects disappeared in weeks 4–7. Elevated concentrations of dietary Cu did not affect SGR or FCE. Low levels of dietary and waterborne Cu decreased, and high levels of dietary Cu increased, the Cu concentrations in whole body, liver, carcass, gut and gills. Copper levels in the liver strongly reflected the exposure conditions with a corresponding fivefold decrease and a 22-fold increase in Cu concentration. Restricting available Cu caused an exponential decline in whole body Cu concentration from 0.0175 to 0.0069 μmol g–1 and increased the uptake of waterborne Cu (measured with 64Cu) by the gills. Conversely, high levels of dietary Cu caused a linear increase in whole body Cu concentration to approximately 0.170 μmol g–1 and depressed the uptake of waterborne Cu. Waterborne Cu uptake contributed the majority (60 %) of the body’s Cu accumulation under Cu-deficient conditions while dietary Cu contributed the majority (99 %) at high dietary levels of Cu. True bioavailability of dietary Cu decreased with increasing levels of dietary Cu concentration, although the absolute amount retained increased. These findings demonstrate an important interaction between dietary and waterborne Cu uptake in fish and provide compelling evidence of a key role for the gill in Cu homeostasis.
Studies on Possible Serological Blocks to Species Hybridization in Poultry
Authors: Ryle Margaret 
Published: April 2021

ABSTRACT
It is suggested that normal heteroantibodies may contribute to the difficulties of species hybridization by damaging heterologous spermatozoa and/or by reducing hybrid embryonic viability. Techniques are described for titrating yolk antibody and for agglutination tests with fowl spermatozoa. Plasma samples from several breeds of chickens were titrated with turkey erythrocytes in order to study the variability of normal heteroagglutinin titres. Turkey spermatozoa were agglutinated in vitro by chicken plasma. Absorption tests showed that the same antigens, reacting with the normal heteroagglutinin of chicken plasma, occur on turkey spermatozoa and turkey erythrocytes. Further work is required on the agglutination of chicken sperm by turkey plasma. Low titres of anti-turkey-erythrocyte agglutinin in the blood of domestic hens did not promote interspecific fertility. Immunization of domestic hens with the erythrocytes of the cockerel with which they were mated did not induce infertility. It is nevertheless considered that an investigation of normal incomplete antibody in relation to inter- and intraspecific fertility might prove fruitful. Normal heteroagglutinins occur in turkey and chicken yolk. The titre of anti-turkey agglutinin in chicken yolk is very close to that in the hen’s plasma. Antigens reacting with the normal heteroagglutinin of turkey plasma appear on chick embryo erythrocytes after 4–5 days’ incubation; there seems to be little quantitative increase thereafter. They occur on both primitive and definitive erythrocytes. Normal anti-turkey agglutinin derived from the egg yolk was detected in the blood plasma of a few chick embryos after 13 days’ incubation or more. The latter results are discussed in relation to other published work both on the effects of antisera on embryogenesis and on the ontogeny of antigenic properties.
On A Peculiar Type of Intersexuality in the Guinea-Pig
Authors: Lipschutz Alexander 
Published: April 2021

ABSTRACT
An abnormal condition of the external genital organs in 16 otherwise normal female guinea-pigs is described. They possessed an hypertrophied penis-like clitoris and horny styles similar to those in the intromittent sac of the normal male penis.
The abnormalities are often asymmetrical, the clitoris and the horny style on one side being more developed than on the other. They may even be absent on one side.
It is suggested that the malformation is a peculiar type of “partial somatic intersexuality,” the external genital organs resembling those in the male guinea-pig.
The condition is identical with that described in the castrated female guineapig experimentally masculinised by testicular transplantation.
There was no indication of the ovaries producing simultaneously female and male sexual hormones :
The ovaries were histologically normal. The ovaries when engrafted into castrated males produced the typical female hormonic effect on the mammary glands and had no influence on the penis or on the horny styles. The clitoris and the horny styles of the intersexual females were not affected by removal of the ovaries, whereas in the male removal of the testes caused a pronounced regression of the horny styles even in fully grown animals. The horny styles when cut regenerated even after removal of the ovaries ; there is never a regeneration in the castrated male, but only in the normal male.
The question is discussed whether the described type of intersexuality might be a case of “successive hormonic intersexuality,” both kinds of sexual hormones having been produced simultaneously for a certain time whereas at a later stage only female hormones were secreted. The hypertrophied clitoris and the horny styles would then be considered as “fixed” sex characters persisting after the disappearance of the male sexual hormones. The problem of fixation of sex characters by sexual hormones is considered on experimental lines. The facts observed are rather against the suggestion that the intersexuality described is a case of successive hormonic intersexuality.
Other possibilities of explaining the morphogenetic basis of this peculiar type of intersexuality are also discussed.
The intersexuality described is of an hereditary nature.
Studies on the Influence of the Surrounding Medium on the Activity of Cells in Tissue Culture
Authors: Willmer E. N. 
Published: April 2021

ABSTRACT
A suitable saline medium for the survival of intestinal tissues from the embryo chick was found to be the following: NaCl 0.8 per cent., KCl 0.025 per cent., CaCl2 0.025 per cent., NaHCO3 0.02 per cent., glucose 0.8 per cent. In this medium the concentration of NaCl could be varied from 0.4 per cent to 1 per cent. and still allow of an active migration of cells to take place. Outside these limits migration occurred fairly freely as far as 0.2 per cent. and 1.2 per cent., but was then either reduced in extent or abnormal in character. When the concentration of NaCl was low the cells became abnormal and vacuolated. This is assumed to be due to low osmotic pressure and not specifically to lack of NaCl. Fibroblasts grew most extensively when the sodium chloride concentration was 0.7 per cent. This was considered to be due to the stimulus given to amoeboid movement by hypotonic solutions, while the cells were still in a fairly normal condition. For good epithelial growth a salt concentration of 0.9 per cent. was found to be most satisfactory. A higher percentage of cultures showed epithelial growth in 0.7 per cent. solutions, but the extent was greatest in 0.9 per cent. The hypotonic solution at first stimulated the cells to migrate, but at the same time caused some abnormality, as they always perished before those in 0.9 per cent. NaCl media. Glucose was found to be a necessary constituent and, other things being equal, the amount of cell migration was found to be directly dependent on the amount of glucose present, up to a concentration of I per cent. Above that limit, glucose appeared to become slightly toxic. 0.9 per cent. NaCl can therefore be regarded as the optimum concentration of this salt in an otherwise normal medium, but in these cultures the amount of glucose necessary to support continued growth leads to too high an osmotic pressure, so that for general purposes the ideal standard solution contains 0.8 per cent. NaCl and 0.8 per cent, glucose. In this solution growth is steady and normal throughout.
An Examination of Nostoc for Nuclear Materials
Authors: Mockeridge F. A. 
Published: April 2021

ABSTRACT
The literature concerning the presence or absence of nuclear material in the cyanophycean cell is too well known to need review ; it is sufficient to say that there is a consensus of opinion in favour of the presence of granules of chromatin, or what Miss Acton (1914) and others prefer to call “metachromatin” (a substance of less complex organisation than chromatin), scattered through the central region of the cell. Since chromatin is of the nature of a nucleo-protein, it seemed worth while investigating the Cyanophyceae for nucleic acid content, in order to determine whether any appreciable quantities of this substance could be extracted.
Campaniform Sensilla on the Tactile Spines of the Legs of the Cockroach*
Authors: Chapman K. M. 
Published: April 2021

ABSTRACTThe failure to record receptor potentials from cut ends of the large tactile spines of the legs of the cockroach Periplaneta americana has prompted a histological and electrophysiological search for the sensory unit of these tactile spines. Histological sections, made with a cuticle-softening fixative containing tetrahydrofuran, and cleared whole-cuticle preparations reveal a single campaniform sensillum in the thick cuticular wall of the spine at its junction with the soft cuticle of its socket. Punctate stimulation in the same region reveals a highly mechanosensitive region similar in size, shape, orientation and location to the campaniform sensillum. Movement of the spine during after-discharges which sometimes follow punctate stimulation does not produce a second impulse train, but modulates the after-discharge. It is concluded that the campaniform sensillum is the sensory structure of the tactile spines of the cockroach, and is responsible for the normal discharge that occurs on contact with the spine. Strong stimulation causes a failure of the afferent discharge, resembling the ‘overstretch’ phenomena seen with other mechanoreceptors. Spike wave-form analysis suggests that impulse initiation may occur at more than one site on the sensory neuron or in more than one manner, and includes the possibility of a delayed, non-propagated discharge of the soma of the sensory neuron.
Accessibility of the Central Nervous Connectives ofAnodonta Cygneato a Compound of Large Molecular Weight
Authors: Lane N. J. , Treherne J. E. 
Published: April 2021

ABSTRACTUltrastructural observations on the uptake of an exogenous tracer substance, horseradish peroxidase (M.W. 40,000), have shown that this large molecule can penetrate the neural lamella in intact cerebro-visceral connectives of the lamellibranch, Anodonta cygnea. Peroxidase molecules were also observed to penetrate between the intercellular clefts formed by adjacent membranes of the underlying peripheral glial cell layer and to move extensively into the underlying extracellular spaces. These observations confirm the results of previous electrophysiological, radio-isotopic and ultrastructural investigations indicating that a relatively rapid exchange of water-soluble ions and molecules occurs between the blood, or bathing medium, and the extracellular fluid bathing the axon surfaces in intact connectives.
Convergence of olfactory inputs from both antennae in the brain of the honeybee
Authors: Suzuki H. 
Published: April 2021

ABSTRACT
Electrical activities of the olfactory neurones in the brain of the honeybee were investigated. Odorous stimuli were given to each antenna separately or to both simultaneously. The inputs from the antennae affected both the impulse frequency and the latency of the olfactory interneurones in the protocerebrum. The predominant response was to the stimulation of the ipsilateral antenna. Input from the contralateral antenna produced mainly excitatory effects, although a few inputs gave inhibitory effects.
No particular relationships between the loci of the units in the brain and the types of responses produced were found. Most of the units were located in the protocerebral lobe and in the central commissure. The units in the deutocerebrum responded only to the stimulation of the ipsilateral antenna, and the magnitude of response and the latency were not different with respect to unilateral or bilateral stimulation of the antennae. Differences in latency between unilateral and bilateral stimulation were observed in some of the units in the protocerebrum.
Neural models which explain these phenomena are postulated.
The relationship between transepithelial sodium movement and potential difference in the larva of Camptochironomus tentans (Fabr.) and some observations on the accumulation of other ions
Authors: Wright D.A. 
Published: April 2021

ABSTRACT
In fourth instar larvae of Camptochironomus tentans, net sodium uptake from 2 mm-NaCl has an elect ogenic component. During net uptake the transepithelial potential (TEP) alters from a value of ˜ – 40 mV (sign refers to haemolymph), in depleted animals, to ˜0 mV. The TEP in depleted larvae is dependent upon external sodium concentration above about 1 mm-Na+, becoming increasingly electropositive (haemolymph relative to medium) at high sodium concentrations. This effect is exaggerated in Na2SO4 compared with NaCl. At an external concentration of 2 mm-NaCl, chloride is carried by an electroneutral mechanism, probably a closely coupled Cl−/ anion exchange. However, it is possible that chloride transport could become somewhat electrogenic at higher concentrations.
Lithium competes with sodium for the electrogenic pump.
Observed TEPs differ greatly from those required to maintain passively the haemolymph concentrations of sodium and chloride.
Directional Hearing in the Japanese Quail (Coturnix Coturnix Japonica)
Authors: Hill K. G. , Lewis D. B. , Hutchings M. E. , Coles R. B. 
Published: April 2021

ABSTRACT
The auditory tympana in the quail, Coturnix coturnix japonica (L.) are internally coupled by an interaural air space. Unilaterally applied sound causing vibration of the ipsilateral tympanum is conducted through the interaural cavity to the inside surface of the contralateral tympanum. In a free sound field at frequencies up to 3150 Hz, sound pressure at the external surface of the tympanum contralateral to the source is within about 3 dB of the pressure exterior to the ipsilateral tympanum. Sound pressures developed at the inner surfaces of the tympana are of similar amplitude to the external pressures at several frequencies in the range 800–6300 Hz. In addition, pressure at each side of the tympanum ipsilateral to the source are generally out of phase, whereas pressures at each side of the contralateral tympanum are relatively close to the same phase. From measurements of amplitude and phase of the interacting pressures at the tympanum, the calculated driving pressure at the ipsilateral tympanum exceeds that at the contralateral tympanum by 10–20 dB over a range of frequencies. The auditory tympana in quail have considerable inherent directionality, therefore, due to their function as pressure-gradient receivers. Anatomical analogies with anurans and reptiles indicate that they derive directional hearing from the same acoustic mechanism that operates in the quail.
Body Fluid Pools, Kidney Function, and Acid-Base Regulation in the Freshwater Catfish Ictalurus Punctatus*
Authors: Cameron James N. 
Published: April 2021

ABSTRACT
Resting catfish excreted a urine with electrolyte concentrations about that of blood, with very low concentrations of ammonia and lactic acid, only slightly acid pH, and a small resultant net base excretion.
At 26 °C, the intracellular pH was normally 0·51 units lower than the extracellular pH. Both were depressed following the onset of hypercapnia, but there was compensation for both by 24 h, so that pHi was near control values. Consequently the whole body CO2 pool increased from 195 to 4·77 m-equiv kg−1 during hypercapnia, with about 1·50 m-equiv by active means, and the other 1·32 by passive (non-bicarbonate) buffering.
The renal response to hypercapnic acidosis was to switch from a small net base excretion to a net acid excretion, which persisted for up to 10 h, and accounted for about 14% of the total active bicarbonate compensation.
There was no statistically significant renal response to an infused HC1 load, but the whole body base excretion rate declined so as to indicate that about 25 % of the infused load was excreted in the first 2 h, presumably by the gills.
The catfish kidney appears to participate in acid-base regulation in a sig- nificant, but quantitatively minor way, implying that the gills are the principal site of ion transfer in regulating the whole body SID.
Haemoglobin-Oxygen Binding Properties in the Blood of Xenopus Laevis, With Special Reference to the Influences of Aestivation and of Temperature and Salinity Acclimation
Authors: Jokumsen Alfred , Weber Roy E. 
Published: April 2021

ABSTRACT
The oxygen equilibrium properties of blood and of solutions of haemoglobin from Xenopus laevis are reported. At pH 7·6 the oxygen affinity of the blood, expressed as half saturation oxygen tension (P50) amounts to 27·0 mm and 13·7 mmHg (3·60 and 1·83 kPa) when measured at 25 and 10 °C, while the Bohr factor (Δ log P50/ΔpH) was – 0·40, and the Hill’s cooperativity coefficient, n, averaged 2·1. These data reflect an overall heat of oxygenation, AH, of – 7·9 kcal. mol−1, which decreased to – 6·3 kcal. mol−1 when the live animals were acclimated to each measuring temperature. Xenopus blood showed a high O2 capacity (15 vol.%) compared to that of other amphibians.
Acclimation to water of increased salinity (12‰), and aestivation, raised blood O2 affinity; at 25 °C and pH 7·6, P50 decreased to 21·1 and 25·2 mmHg (2·81 and 3·36 kPa), respectively. These changes were concomitant with increases in the blood levels of urea. In contrast to NaCl and ATP, urea increased O2 affinity of the purified haemoglobin, suggesting that oxygenation-linked binding to haemoglobin is involved in the modulations of the blood O2 affinity during aestivation and acclimation to salt water.
Xenopus haemoglobin consists of two components. The major component is electrophoretically anodal, and has O2 binding properties similar to those of the haemolysate; the minor component is cathodal, and shows extremely low P50, pH sensitivity and cooperativity.
Rhythmic Electrical Activity in Stomach and Intestine of Toad
Authors: Mangel Allen , Prosser C. Ladd 
Published: April 2021

ABSTRACT
The intact stomach of the toad initiates rhythmic slow-spikes of 5–15 s duration and frequency of 3–5 min-1. The spontaneous electrical waves originate in the longitudinal muscle layer; isolated circular muscle is quiescent. Aboral conduction velocity is 0·12–0·9 mm s-1. Reduction of external sodium concentration from 89·5 to 15 mM produced no effect on slow spikes, although further reduction to 1·5 mM increased frequency and decreased amplitude. Slow-spikes were unaffected by ouabain or by incubation in potassium-free solution. When calcium in the medium was reduced, slow-spike amplitude and frequency decreased. Slow-spikes exhibited a change in amplitude of 16 mV per decade change in Ca02+; slow-spikes were eliminated at 10−8 M and by blockers of calcium conductance channels.
Intact intestine of toad demonstrated slow-waves which resembled those of mammalian intestine. These were sensitive to changes in external sodium and were eliminated by 1 × 10−4 M ouabain.
It is suggested that rhythmic slow-spikes of longitudinal smooth muscle of amphibian stomach may result from periodic changes in Ca conductance whereas endogenous electrical waves of intestine may result from rhythmic extrusion of sodium.