bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects Of Repeated Physical Stress On The β-Adrenergic Response Of The Rainbow Trout Red Blood Cell
Authors: Perry Steve F. , Reid Stephen G. , Salama Annika
Published: April 2021

The effects of a 7-day period of daily physical stress (chasing until exhaustion) on the β-adrenergic response of the rainbow trout (Oncorhynchus mykiss) red blood cell (rbc) were examined in vitro. Physical stress was associated with pronounced increases in the circulating levels of the catecholamine hormones (adrenaline and noradrenaline) measured on days 1, 3 and 7 of the stress regime. After 7 days, the numbers of high-affinity cell surface β-adrenoceptors were reduced in the physically stressed fish when measured in vitro under conditions of normoxia (20 % reduction) or hypoxia (30 % reduction). Under hypoxic conditions, the binding affinity of the rbc β-adrenoceptor was significantly higher in the stressed fish.

Although the stressed fish had fewer β-adrenoceptors, rbc adrenergic responsiveness was enhanced after 7 days of physical stress as determined from dose–response curves relating noradrenaline concentration to water and Na+ accumulation (indices of rbc adrenergic Na+/H+ exchange activity). The EC50 values (concentrations yielding half-maximal responses) for noradrenaline were lowered significantly by 1.7-to 3.9-fold in the blood from physically stressed fish. The enhanced adrenergic responsiveness of the rbcs appeared to be unrelated to changes in the initial steps of the -adrenergic signal transduction pathway leading to cyclic AMP production because physical stress was without effect on the magnitude or the dose-dependency of rbc cyclic AMP accumulation.

To determine whether post-cyclic-AMP events were affected by physical stress, water and Na+ accumulation were measured in rbcs that had been incubated with the permeable cyclic AMP analogue 8-bromo cyclic AMP. The EC50 values for 8-bromo cyclic AMP were lowered by 1.6-to 1.7-fold in the blood from stressed fish.

These experiments demonstrate that repeated physical stress significantly enhances the adrenergic responsiveness of the rainbow trout rbc, presumably by modifying the sensitivity of the Na+/H+ exchanger (or the steps immediately preceding exchanger activation) to cyclic AMP. The results are discussed with respect to the interrelationships between chronic and acute stress responses in fish.
Operant Conditioning of Aerial Respiratory Behaviour in Lymnaea Stagnalis
Authors: Lukowiak Ken , Ringseis Erika , Spencer Gaynor , Wildering Wic , Syed Naweed
Published: April 2021

In this study, we operantly conditioned the aerial respiratory behaviour of the freshwater snail Lymnaea stagnalis. Aerial respiration in Lymnaea stagnalis is accomplished by the spontaneous opening and closing of its respiratory orifice, the pneumostome, at the water surface. Weak tactile stimulation of the pneumostome area, when the pneumostome is open, evoked only the pneumostome closure response, which is one aspect of the escape–withdrawal reflex. Pneumostome stimulation resulted in its closure and the termination of aerial respiratory activity. A contingent tactile stimulation paradigm was used to operantly condition the animals. Stimulation of the pneumostome whenever the animal attempted to breathe resulted in significantly fewer attempts to open the pneumostome as training progressed. The latency of the first breath (subsequent to stimulation), the number of breaths and the total breathing time were measured before and after each training period. Significant, quantifiable changes in these behavioural parameters were observed only in the operant conditioning group animals. Control animals receiving tactile stimulation to their pneumostome not contingent upon pneumostome opening movements (yoked controls) or those that were physically prevented from surfacing to breathe (hypoxic controls), did not exhibit significant changes in these behavioural parameters. Our data provide the first direct evidence for operant conditioning of respiration in any animal.
Locomotory behavior in the hawkmoth Manduca sexta: kinematic and electromyographic analyses of the thoracic legs in larvae and adults
Authors: Johnston Rebecca M. , Levine Richard B.
Published: April 2021

During metamorphosis in Manduca sexta, muscles and most sensory structures of the thoracic legs undergo extensive changes while the motor neurons that are present in the larva persist into the adult. The main goal of this work was to identify similarities and dissimilarities in thoracic leg movements during crawling in larvae and walking in adults. This information provides a foundation for understanding the extent to which centrally located neural elements are reorganized during metamorphosis to accommodate changes in locomotion. Analysis of electromyographic activity from leg muscles synchronized with video-taped recordings of the leg movements during larval crawling and adult walking revealed differences in cycle periods as well as intersegmental and intrasegmental patterns of coordination. Larval crawling was characterized by synchronous movements of segmental pairs of legs as activity proceeded slowly from the more posterior to the more anterior segments. During crawling, antagonistic muscles maintained a strict reciprocity. In contrast, walking in adults was characterized by fast, alternating movements of the left and right prothoracic legs and more variable coordination patterns in the mesothoracic and metathoracic legs (ranging from synchrony to alternation). In adults, sensory information, possibly associated with the weight-bearing or postural demands of walking on an incline, contributed to a strong dependence between the duration of muscle activity and cycle period and to the extent that the muscle activity overlapped during walking.
Effects of Pineal Indoles and Parachlorophenylalanine on Seasonal Reproduction in the Pigeon
Authors: Ramachandran A. V. , Patel M. M. , Patel C. S.
Published: April 2021

The effect of melatonin, methoxytryptophol (ML), methoxytryptamine (MT) and parachlorophenylalanine (p-CPA) on the mass and histology of the testes and the adrenal and thyroid glands and on serum thyroid hormone levels have been studied in the recrudescent phase of the feral pigeon Columba livia. All the pineal indoles showed a common anti-gonadal effect, resulting in the arrest of spermatogenesis and the degeneration of germ cells. Treatment with melatonin resulted in adreno-cortical enlargement and medullary hypertrophy, whereas ML, MT and p-CPA induced medullary enlargement and hypertrophy without having much influence on the cortex. Treatment with melatonin and ML brought about colloid retention in the thyroid follicles, while MT and p-CPA induced colloid depletion and hypertrophy of the follicular epithelium. From the present study, it can be concluded that both pineal indoles and p-CPA induce testicular regression in the breeding phase but do so by different mechanisms.
The Peripheral Auditory Characteristics of Noctuid Moths: Responses to the Search-Phase Echolocation Calls of Bats
Authors: Waters Dean A. , Jones Gareth
Published: April 2021

The noctuid moths Agrotis segetum and Noctua pronuba show peak auditory sensitivity between 15 and 25 kHz, and a maximum sensitivity of 35 dB SPL. A. segetum shows a temporal integration time of 69 ms. It is predicted that bats using high-frequency and short-duration calls will be acoustically less apparent to these moths. Short-duration frequency-modulated (FM) calls of Plecotus auritus are not significantly less acoustically apparent than those of other FM bats with slightly longer call durations, based on their combined frequency and temporal structure alone. Long-duration, high-frequency, constant-frequency (CF) calls of Rhinolophus hipposideros at 113 kHz are significantly less apparent than those of the FM bats tested. The predicted low call apparency of the 83 kHz CF calls of R. ferrumequinum appears to be counteracted by their long duration. It is proposed that two separate mechanisms are exploited by bats to reduce their call apparency, low intensity in FM bats and high frequency in CF bats. Within the FM bats tested, shorter-duration calls do not significantly reduce the apparency of the call at the peripheral level, though they may limit the amount of information available to the central nervous system.
Retinal Development and Visual Sensitivity of Young Pacific Sockeye Salmon (Oncorhynchus Nerka)
Authors: Flamarique Iñigo Novales , Hawryshyn Craig W.
Published: April 2021

The development of photoreceptor cell types and the visual sensitivity of young sockeye salmon were examined. In contrast to previous findings from rainbow trout, rod outer segments were observed in the embryo 1.5 weeks before hatching. At this stage, a full square mosaic with accessory corner cones was visible in the central retina. Post-hatching retinal development is similar to that of other fish species. During the first 11 months of development, the fibrous and interplexiform layers, the outer nuclear layer, the visual cell layer and the retinal pigment epithelium thicken. The ganglion cell layer and the inner nuclear layer regress. In addition, the mean diameter of the cones increases, with that of double cones increasing faster than that of either of the single cone types. As is the case for other salmonids, the density of accessory corner cones diminishes after smoltification (a developmental stage in salmonids). The retina of smolts exhibits a full square mosaic pattern in some peripheral areas and near the central embryonic fissure. However, unlike findings from rainbow trout, compound action potential recordings from the optic nerve of smolt sockeye reveal the presence of four cone mechanisms with sensitivity maxima at 380 (ultraviolet), 425 (short), 520 (middle) and 635 nm (long wavelength). There is also a rod mechanism with maximum sensitivity around 530 nm. Smolts also exhibit polarization sensitivity to 380 nm light under a white crepuscular background.
Differential Protein Profiles Reflect the Different Lifestyles of Symbiotic and Aposymbiotic Anthopleura Elegantissima, a Sea Anemone from Temperate Waters
Authors: Weis Virginia M. , Levine R. Paul
Published: April 2021

Mutualistic associations are prevalent in virtually all environments yet relatively little is known about their complex biochemical and molecular integration and regulation. The endosymbiosis between cnidarians such as the sea anemone Anthopleura elegantissima and the photosynthetic dinoflagellate Symbiodinium californium, in which the algal symbionts are housed in vacuoles within animal endodermal cells, is an ideal model for the study of highly integrated associations at the biochemical and molecular levels. This study describes differential protein synthesis between symbiotic A. elegantissima, collected from environments with high levels of light in the intertidal zone and A. elegantissima that naturally lack symbionts (aposymbiotic), collected from nearby deep-shade habitats. Two-dimensional gel electrophoresis profiles of both steady-state and newly synthesized proteins were compared between the two types of animals using scanning densitometry and image analysis. Symbiotic and aposymbiotic animals share a majority of proteins; however, striking differences in several abundant proteins in steady-state profiles occur. Two proteins are unique to symbiotic animals, one at 32 kDa with an isoelectric point (pI) of 7.9 and another at 31 kDa, pI 6.3. Levels of six proteins with an apparent molecular mass of 25 kDa and pI values ranging from 4.8 to 5.5 are greatly enhanced in aposymbiotic animals. Furthermore, profiles of newly synthesized proteins from symbiotic animals contain a unique cluster of proteins ranging from 25 to 30 kDa and pI 6.6 to 6.9. These marked differences in protein profiles must be a reflection either of underlying differences in the regulation of gene expression or in post-translational modification of common proteins. Identifying the symbiosis-specific products present in A. elegantissima and identifying the inter-partner signaling and cues that result in differential expression will provide an insight into the understanding of these highly integrated associations.
Continuous Tracer Infusion to Measure in Vivo Metabolite Turnover Rates in Trout
Authors: Haman François , Weber Jean-Michel
Published: April 2021

This paper describes a double dorsal aorta catheterization technique allowing the measurement of substrate turnover rates by continuous infusion of metabolic tracers in rainbow trout. The placement of both catheters can be performed in about 30 min with minimal surgical training. As a practical example of a routine substrate flux measurement, glucose turnover rate of resting trout was measured by primed continuous infusion of 6-[3H]glucose through one of the catheters and blood sampling from the other. The animals maintained resting metabolic rate, normal blood glucose and low blood lactate concentrations throughout the experiments. Glucose isotopic steady state was achieved in less than 40 min, and mean turnover rate was 9.0±0.7 μmol kg-1 min−1 (N=8). Comparison with published glucose turnover rates measured in trout and other teleost species suggest that values previously obtained using the ‘bolus injection technique’ are underestimates of true flux rates. We conclude that the simple surgical technique presented here opens the door to the dynamic study of substrate kinetics under a variety of experimental conditions and that it can be adapted to the investigation of most metabolic substrates, including fatty acids, glycerol, amino acids and lactate, in addition to glucose. Future application of the continuous infusion technique under steady-state as well as non-steady-state conditions will add a new dimension to the general understanding of fish metabolism.
The Discharge Mechanism of Acontial Nematocytes Involves the Release of Nitric Oxide
Authors: Salleo Alberto , Musci Giovanni , Barra Paolo F. A. , Calabrese Lilia
Published: April 2021

The events which trigger the activation of nematocytes are still poorly understood, and no evidence has been presented so far on either the nature of the activatory signal for the nematocyte or the transduction mechanism. In this paper, we present evidence for a role of NO in the discharge of acontial nematocytes. A citrulline-forming enzymatic activity, significantly decreased by the NO synthase inhibitor Nw-nitro-L-arginine (L-NNA) and by the Ca2+-chelating agent EGTA, was found in the acontial tissue of Aiptasia diaphana. Staining for NADPH diaphorase suggested that NO synthase is localized in supporting cells surrounding the nematocytes. The ability of K+ to induce the discharge of nematocytes in situ could be abolished by preincubation of acontia with L-NNA and restored by addition of excess L-arginine. Direct measurements on K+-induced discharging nematocytes in situ confirmed that NO was released by stimulated acontia. Both in situ and isolated acontial nematocytes promptly discharged when perfused with an aqueous solution of NO. The responsiveness to NO of isolated nematocytes was not abolished in Ca2+-free medium or by treatment with La3+, a well-known Ca2+ channel inhibitor. Since the discharge of in situ nematocytes is known to be Ca2+-dependent, it is proposed that activation of in situ acontial nematocytes is triggered by a Ca2+-dependent release of NO from supporting and/or sensory cells.
Sulfide May Directly Modify Cytoplasmic Hemoglobin Deoxygenation in Solemya Reidi Gills
Authors: Kraus David W. , Doeller Jeannette E. , Powell C. Stephen
Published: April 2021

The clam Solemya reidi, which survives in sulfide-rich sediments, houses intracellular sulfide-oxidizing bacteria as symbionts in its gills. The gill bacteriocytes also contain a high concentration of cytoplasmic hemoglobin. Although the in situ hemoglobin optical spectrum was not altered in the presence of hydrogen sulfide, hemoglobin deoxygenation was significantly slowed and incomplete when sulfide was present. A sulfide-mediated decrease in oxygen consumption rate, a shift in intracellular pH or the conversion of hemoglobin to an unusual derivative could all slow in situ hemoglobin deoxygenation. However, under low sulfide levels at which deoxygenation is incomplete, oxygen consumption rate was not inhibited, intracellular pH decreased by less than 0.1 units and the only hemoglobin derivatives present were deoxyhemoglobin and oxyhemoglobin. These results and preliminary measurements of the isolated gill hemoglobin dissociation rate constants suggest that sulfide or a rapidly formed oxidation product may directly influence the rate of Solemya reidi gill hemoglobin deoxygenation.
Molecular Mechanisms Underlying the Plasticity of Muscle Contractile Properties With Temperature Acclimation in the Marine Fish Myoxocephalus Scorpius
Authors: Ball Derek , Johnston Ian A.
Published: April 2021

Single fibres were isolated from the fast myotomal muscle of the short-horned sculpin (Myoxocephalus scorpius L.). Fish were acclimated to either 5 °C (10 h:14 h light:dark) or 15 °C (12 h:12 h light:dark) for 1–2 months. Isometric tension (Fmax) and unloaded contraction velocity (Vslack) were determined in maximally activated skinned fibres over the range 0 to 20 °C. Fibres isolated from 5 °C-acclimated and 15 °C-acclimated fish failed to relax completely following activations at 15 °C and 20 °C respectively. In 5 °C-acclimated fish, Fmax increased from 75 kN m-2 at 0 °C to 123 kN m-2 at 10 °C and was not significantly higher at 15 or 20 °C. The relationship between Fmax and temperature was not significantly different for cold- and warm-acclimated fish. Vslack was around 2.8 fibre lengths s-1 in both acclimation groups at 0 °C, but it increased at a significantly faster rate with temperature in 15 °C-than in 5 °C-acclimated fish. At 20 °C, Vmax was significantly higher in 15 °C-acclimated (8.7 fibre lengths s-1) than in 5 °C-acclimated fish (5.3 fibre lengths s-1). In order to investigate the molecular mechanism(s) underlying changes in Vmax, myosin was purified by ion-exchange chromatography. No difference in myosin heavy chain composition could be detected on the basis of peptide mapping with four different proteolytic enzymes. Two-dimensional polyacrylamide gel electrophoresis revealed no myofibrillar protein isoforms unique to either acclimation temperature. However, the ratio of myosin alkali light chain contents (LC3f:LC1f), as determined by capillary electrophoresis, was significantly lower in muscle from 15 °C-acclimated (0.73) than from 5 °C-acclimated fish (1.66). The results suggest that changes in Vmax are achieved via altered expression of myosin light chains independently of myosin heavy chain composition. In support of this hypothesis, the myofibrillar ATPase activity of fast muscle was not altered by temperature acclimation.
Recovery of the Flight System Following Ablation of the Tegulae in Immature Adult Locusts
Authors: Gee Christine E. , Robertson R. Meldrum
Published: April 2021

The capacity of the flight system to recover from ablation of the tegulae was studied in immature adult Locusta migratoria and compared with recovery in mature adults. We ablated the hindwing tegulae or all tegulae in adult locusts either 1 day after the imaginal moult (immature locusts) or 2 weeks after the imaginal moult (mature locusts). We monitored recovery throughout the recovery period by using a stroboscope to measure the wingbeat frequency of tethered locusts. In addition, we measured other parameters of the flight motor pattern using electromyographic electrodes implanted into recovered locusts. Both methods of monitoring recovery yielded the same results. There was no reduction, during adult maturation, in the capacity of the locust flight system to recover from the loss of these proprioceptors. Plasticity of the locust flight system was therefore maintained in the mature adult locust. This suggests that the flight system is not fixed and simply implemented when the locust reaches adulthood, but that the circuitry can be remodelled throughout the animal’s life to produce behaviour adapted to the needs and constraints of the individual.
The Mechanism of Cardiac Shunting in Reptiles: a New Synthesis
Authors: Hicks James W. , Ishimatsu Atsushi , Molloi Sabee , Erskin Atilla , Heisler Norbert
Published: April 2021

The mechanism of cardiac shunting in reptiles is controversial. Recent evidence suggests that a right-to-left shunt in turtles results primarily from a washout mechanism. The mechanism that accounts for left-to-right (L–R) shunting is unresolved. This study used haemodynamic analysis and digital subtraction angiography to determine the mechanism of L–R cardiac shunting in the turtle Trachemys (Pseudemys) scripta. Animals were instrumented with ultrasonic blood flow probes (Transonic Systems, Inc.) for the measurement of total pulmonary blood flow and total systemic blood flow. In addition, catheters were inserted into the common pulmonary artery (PA), the systemic arteries, the left atrium and right atrium. These catheters were used for the measurement of blood pressure or for the infusion of radio-opaque material. Haemodynamic conditions were altered by electrical stimulation of the afferent (VAF) or efferent vagal nerves or by infusion of vasoactive drugs. Under control conditions, the peak systolic pressure in the systemic arteries was slightly higher than that in the PA (30.6 versus 28.3 mmHg; 4.08 versus 3.77 kPa), whereas diastolic pressure in the PA was significantly less than that in the systemic arteries (9.8 versus 24.4 mmHg; 1.31 versus 3.25 kPa). During VAF stimulation, the peak systolic pressures in the PA and aortae almost doubled. Diastolic pressure in the systemic arteries also doubled, but it increased by only 45 % in the PA. Ejection of blood into the PA preceded that into the left aorta by 53 ms under control conditions. This difference increased (by as much as 200 ms) as the difference in the diastolic pressures between the two circulations increased during VAF stimulation. This resulted in the development of a large net L–R shunt. Under these conditions, digital subtraction angiography showed that the L–R shunt resulted from a combination of both washout and pressure mechanisms.
Curve Walking in Crayfish
Authors: Cruse Holk , Saavedra Manuel G. Silva
Published: April 2021

Curve walking of crayfish Astacus leptodactylus was investigated by exploiting their optomotor response. The animal walked while spatially fixed on a motor-driven treadmill and turning behaviour was induced by an optical stimulus, a pattern consisting of vertical stripes moving in a horizontal direction. In this open-loop situation, the crayfish maintains the same step frequency for the legs on both sides of the body for low and intermediate turning speeds, but increases the step amplitude of the outer legs 2, 3 and 4 by shifting the posterior extreme position (PEP) of these legs in a posterior direction and reduces the step amplitude of inner leg 5 by shifting the PEP of this leg in an anterior direction. Furthermore, the main movement direction of the legs can change relative to the body. This was observed for outer leg 5 and also, at higher turning speeds, for outer leg 2. As coordinating influences between contra-and ipsilateral legs were found directly to influence only the anterior extreme position of the legs, these results indicate that the mechanisms controlling curve walking may be different from those controlling normal leg coordination.
Comparison of the Expression Patterns of Five Developmentally Regulated Genes in Manduca Sexta and Their Regulation By 20-Hydroxyecdysone In Vitro
Authors: Mészáros Melinda , Morton David B.
Published: April 2021

A previous study, using subtractive hybridization, identified five genes (esr16, esr20, Mng10, Mng14 and tps9) whose transcripts were up-regulated prior to metamorphosis in Manduca sexta nervous tissue. The developmental time points chosen for subtraction suggested that expression could be coordinately regulated and should be negatively regulated by the steroid hormones, the ecdysteroids. In the present paper, we present an analysis of the expression patterns of these five genes, using reverse transcription–polymerase chain reaction (RT-PCR), at various times during development and assess the effects of 20-hydroxyecdysone and cycloheximide on their expression in vitro. This analysis revealed that with the exception of esr20 all transcripts were detectable at all times and that all but one of the genes were up-regulated in vivo and in vitro in the absence or in the presence of low levels of the ecdysteroids. In the absence of ecdysteroids, cycloheximide blocked the accumulation of only two transcripts, esr16 and esr20. These results reveal a much more complex pattern of gene expression in the central nervous system prior to metamorphosis than previously imagined.
Kinematics of Feeding in the Lizard Agama Stellio
Authors: Herrel Anthony , Cleuren Johan , Vree Frits De
Published: April 2021

The kinematics of prey capture, intraoral transport and swallowing in lizards of the species Agama stellio (Agamidae) were investigated using cineradiography (50 frames s-1) and high-speed video recordings (500 frames s-1). Small metal markers were inserted into different parts of the upper and lower jaw and the tongue. Video and cineradiographic images were digitized, and displacements of the body, head, upper and lower jaw and the tongue were quantified. Twenty additional variables depicting displacements and timing of events were calculated. A factor analysis performed on the kinematic data separates prey capture and swallowing cycles from intraoral transport bites. However, the intraoral transport stage cannot be separated into chewing (reduction) and transport bites. The effect of prey type and size on the feeding kinematics of intraoral transport and swallowing cycles was investigated. During the intraoral transport stage, distinct aspects (e.g. durations, maximal excursions) of the gape and tongue cycle are modulated in response to both the size and type of the prey item. The results for A. stellio generally agree with a previous model, although it is the entire slow opening phase rather than solely the duration of the second part of this phase that is affected by the size of the prey. The intraoral transport cycles in A. stellio show the two synapomorphic characteristics of tetrapods (tongue-based terrestrial intraoral prey transport and the existence of a long preparatory period of prey compression). However, not all five characters of the feeding cycle previously proposed for amniotes are present in A. stellio. One major difference is that in A. stellio the recovery of the hyolingual apparatus does not take place during the slow opening phase but during the slow closing/powerstroke phase.
Morphology and Biomechanics of the Microfibrillar Network of Sea Cucumber Dermis
Authors: Thurmond Frederick A. , Trotter John A.
Published: April 2021

The principal component of the body wall of the sea cucumber Cucumaria frondosa is a dermis consisting of collagen fibrils, microfibrils, proteoglycans and other soluble and insoluble components. A major structural constituent of the dermis is a network of 10–14 nm diameter microfibrils, which surrounds and penetrates bundles of collagen fibrils. This network has been extracted and purified using guanidine and bacterial collagenase. Tensile testing of the microfibrillar network in artificial sea water demonstrates that it is reversibly extensible up to approximately 300 % of its initial length. It behaves like a viscoelastic solid, having a long-range elastic component as well as a time-dependent viscous component. Reduction and alkylation of the cysteine residues in the network do not change its breaking strain or strength, but greatly increase the compliance of the network until, near the breaking strain, the tensile resistance rapidly increases.

These data suggest that the strength of the network is due to non-reducible crosslinks, while its elasticity is dependent upon disulfide bonds. In deionized water, the network becomes swollen and, although it remains elastic, is much more compliant than when tested in artificial sea water. Examination of whole tissues and purified networks with the electron microscope reveals structures similar to vertebrate fibrillin-containing microfibrils. Considering that the dermis of C. frondosa is a mechanically mutable tissue in which elongation is accompanied by the sliding of collagen fibrils past one another, the microfibrillar network may act to maintain the orientation of fibrillar components during movement and may also provide a long-range restoring force.
Effect of Engineering Hsp70 Copy Number on Hsp70 Expression and Tolerance of Ecologically Relevant Heat Shock in Larvae and Pupae of Drosophila Melanogaster
Authors: Feder Martin E. , Cartaño Noemi V. , Milos Lukasz , Krebs Robert A. , Lindquist Susan L.
Published: April 2021

To determine how the accumulation of the major Drosophila melanogaster heat-shock protein, Hsp70, affects inducible thermotolerance in larvae and pupae, we have compared two sister strains generated by site-specific homologous recombination. One strain carried 12 extra copies of the Hsp70 gene at a single insertion site (extra-copy strain) and the other carried remnants of the transgene construct but lacked the extra copies of Hsp70 (excision strain). Hsp70 levels in whole-body lysates of larvae and pupae were measured by ELISA with an Hsp70-specific antibody. In both extra-copy and excision strains, Hsp70 was undetectable prior to heat shock. Hsp70 concentrations were higher in the extra-copy strain than in the excision strain at most time points during and after heat shock. Pretreatment (i.e. exposure to 36 °C before heat shock) significantly improved thermotolerance, and this improvement was greater and more rapid in larvae and pupae of the extra-copy strain than in those of the excision strain. The experimental conditions resemble thermal regimes actually experienced by Drosophila in the field. Thus, these findings represent the best evidence to date that the amount of a heat-shock protein affects the fitness of a complex animal in the wild.
On The Determination of the Percentage of Abortive Pollen in Plants
Authors: Ferguson Nesta
Published: April 2021

It has long been known that, in many species of plants, a proportion of the pollen grains in the anther of a given flower is abortive. This is true for plants in Nature, as well as for cultivated varieties. It is not possible to give a single or a simple explanation of this sterility and probably a large number of causes have to be considered. One cause has been frequently emphasised: as far back as 1832, Dutrochet 5 pointed out that pollen abortion is a criterion of hybridism, a view supported by Gaertner 6, Many subsequent investigators have also adopted this view, but some more recent studies have shown that pollen sterility in a plant does not necessarily indicate a hybrid origin, although pollen sterility is frequently associated with hybridity.7,9,12
The Growth Rate in Hypophysectomised Salamander Larvæ
Authors: Greenwood A. W.
Published: April 2021

The ablation of the pituitary gland in the Axolotl larva of Amblystoma tigrinum at an age when the thyroid gland has developed does not produce any significant alteration in the growth rate when compared to the growth rate of the normal animal.
Gonad Grafts in Embryonic Chicks and Their Relation to Sexual Differentiation
Authors: Greenwood A. W.
Published: April 2021

An experimental study on the effects of gonad grafts in the embryo chick was undertaken in an attempt to reproduce the results obtained by Minoura and to define the bearing of this experiment on Lillie’s theory of the free-martin in cattle. Eggs from a sex-linked cross were used so as to be able to identify the original sex of the embryos. In the majority of cases the egg received the graft at the seventh day of incubation and was examined at the seventeenth day, at which stage the progress of sexual differentiation is almost as complete as at the time of hatching. In all 540 embryos were operated on. Of this number 233 received testis grafts and 168 ovary grafts. Other tissues grafted were thyroid, adrenal, pancreas, spleen, gall-bladder, liver, Wolffian body, kidney, lung, lens, and heart. The age of the grafted tissue varied from the fourteenth day of incubation up to ten weeks old. Of the gonad grafts, 150 survived the operation, 71 ♂ and 79 ♀. 47 ♀ chicks were obtained after testis grafts, and 27 ♂ chicks were obtained after ovary grafts. Healthy active testis grafts were found in 20 ♀ and 5 ovary grafts in ♂. The sex ratio in the surviving chicks showed no deviation from the normal. Macroscopical examination of the urogenital system showed no deviation from the typical structure consonant with the sex of the chick as determined by its plumage colour. Microscopical examination of the gonads revealed no abnormalities in histological structure. These results lend no confirmation to the view that the process of sexual differentiation in the chick can be profoundly modified by the specific physiological activity of a gonad graft of the opposite sex. Minoufa’s interpretation of his results are criticised. The grafting of gonad tissue in the embryo chick does not reproduce experimentally the conditions existing in the bovine free-martin in that in the former the embryo is exposed to the specific action of the grafted gonad alone, whereas in the latter the female co-twin is exposed to the action of all the internal secretions from the male.
Cytolysis and Protoplasmic Structure
Authors: Page Irvine H. , Clowes G. H. A.
Published: April 2021

The starfish (Asterias forbesii) egg is unusual in that it is very resistant to cytolysis by Quillaja saponin but possesses little resistance to hypotonic solutions (Page and Clowes1).

Inasmuch as the point of attack of saponin and hypotonic solutions is quite unknown, the fact that the effect of hypotonic solutions is related to the fixing action of saponin in different kinds of protoplasm becomes of much interest. Such a selective increase in resistance to hypotonic solutions is conferred by saponin as the following experiments demonstrate.
Absorption of Volatile Acids From the Alimentary Tract of the Sheep and Other Animals
Authors: Barcroft J. , Mcanally R. A. , Phillipson A. T.
Published: April 2021

It has long been known that volatile fatty acids are among the chief non-gaseous products of bacterial breakdown of carbohydrate in the rumen; however, in spite of the fact that the ruminant apparently subsists to a large extent upon the carbohydrates which are so broken down, investigators have been loath to admit the value of these to the animal. Instead, therefore, of following up the subsequent fate of the volatile acids they have concentrated more upon searching for unsuspected bacterial products which might make possible an explanation of ruminant carbohydrate metabolism more in line with the better known processes of absorption of sugars in non-ruminant animals.
Modeling Seasonal Changes in Intracellular Freeze-Tolerance of Fat Body Cells of the Gall Fly Eurosta Solidaginis (Diptera, Tephritidae)
Authors: Bennett Valerie A. , Lee Richard E.
Published: April 2021

Although seasonal changes in the freeze-tolerance of third-instar larvae of Eurosta solidaginis have been well documented for the whole organism, the nature of this cold-hardiness at the cellular level has not been examined. Seasonal changes in the survival of fat body cells from E. solidaginis larvae were assessed using fluorescent vital dyes after freezing at −10, −25 or −80 °C for 24 h both in vivo and in vitro. Cells frozen in vitro were frozen with glycerol, with sorbitol (both of which enhanced cell survival) or without cryoprotectants. Both cellular and organismal survival were low in August when larvae were not freeze-tolerant, then increased dramatically during September and October before leveling off from November to January. This observation for cells frozen without cryoprotectants indicates that the cells themselves have adapted. The single most important factor influencing cell survival, as determined by logistic regression modeling, was the time of larval collection, which reflects the level of cold-hardiness achieved by field acclimation. Cells frozen in vivo exhibited greater survival than did those frozen in vitro, even with the addition of cryoprotectants. Since no differences were observed between cells frozen with glycerol or sorbitol, the role of the multi-component cryoprotectant system present in E. solidaginis should be investigated.
Intraoperative Sarcomere Length Measurements Reveal Differential Design of Human Wrist Extensor Muscles
Authors: Lieber Richard L. , Ljung Björn-ove , fridén Jan
Published: April 2021

The design of the wrist extensor muscles was studied using a combination of intraoperative laser diffraction and biomechanical modelling of data obtained from human patients and previously published data. Intraoperatively, the change in sarcomere length per degree joint angle rotation (i.e. dSL/dω) was measured as the wrist was moved from neutral to full flexion in both the extensor carpi radialis brevis (ECRB) and extensor carpi radialis longus (ECRL) muscles. Sarcomere length change per degree rotation was approximately twice as great for the ECRB compared with the ECRL muscle (9.06±1.06 versus 4.69±1.20 nm degree−1, mean ± S.E.M., N=7). Muscle fibre length and wrist extensor moment arms were obtained from published data and dSL/dω calculated. The experimental values for dSL/dω were extremely close to the calculated values. These data demonstrate that architectural differences between the ECRB and ECRL are accentuated by differences between their wrist extensor moment arms. This differential design may permit the extensor muscles, as a group, to generate high force over a wider range of velocities than would be possible with a single muscle or it may permit conservation of mass such that the two muscles together can generate approximately the same force and excursion as a single muscle but with approximately 30 % less mass.
Mitochondria-Rich Cells in Gills of Tilapia (Oreochromis Mossambicus) Adapted to Fresh Water or Sea Water: Quantification by Confocal Laser Scanning Microscopy
Authors: Van Der Heijden A. J. H. , Verbost P. M. , Eygensteyn J. , LI J. , Bonga S. E. Wendelaar , Flik G.
Published: April 2021

We used confocal laser scanning microscopy to validate a new and fast co-labelling method to study the distribution of mitochondria-rich (MR) cells in gill filaments and to differentiate between MR cells that are in contact with the water (cells labelled with both DASPMI and Concanavalin-A) and those that are not (DASPMI-positive only). This method was used to describe differences in MR cell density that occur in the gills of tilapia Oreochromis mossambicus adapted to fresh water or sea water. In fresh water, the total MR cell density was 6233 cells mm−2 and the density of the subpopulation of MR cells that are in contact with the water was 3458 mm−2. After seawater adaptation, cell density decreased to 3061 cells mm−2 for all MR cells of which 2445 cells mm−2 were in contact with water. The percentage of double-labelled MR cells in the total MR cell population had increased from 55 to 80 %. MR cell size (measured as the maximal cross-sectional area) increased from 87 μm2 in fresh water to 217 μm2 in sea water.

Biochemical determination of specific and total Na+/K+-ATPase activity in gill homogenates showed no difference between freshwater- and seawater-adapted fish. Quantification of ‘mature’ chloride cell density in fixed gill filaments using scanning electron microscopy resulted in an overestimate of chloride cell density due to shrinkage of the sample.
Sulphide Oxidation and Oxidative Phosphorylation in the Mitochondria of the Lugworm Arenicola Marina
Authors: Völkel Susanne , Grieshaber Manfred K.
Published: April 2021

Oxygen consumption, ATP production and cytochrome c oxidase activity of isolated mitochondria from body-wall tissue of Arenicola marina were measured as a function of sulphide concentration, and the effect of inhibitors of the respiratory complexes on these processes was determined. Concentrations of sulphide between 6 and 9 μmol l−1 induced oxygen consumption with a respiratory control ratio of 1.7. Production of ATP was stimulated by the addition of sulphide, reaching a maximal value of 67 nmol min−1 mg−1 protein at a sulphide concentration of 8 μmol l−1. Under these conditions, 1 mole of ATP was formed per mole of sulphide consumed. Higher concentrations of sulphide led to a decrease in ATP production until complete inhibition occurred at approximately 50 μmol l−1. The production of ATP with malate and succinate was stimulated by approximately 15 % in the presence of 4 μmol l−1 sulphide, but decreased at sulphide concentrations higher than 15–20 μmol l−1. Cytochrome c oxidase was also inhibited by sulphide, showing half-maximal inhibition at 1.5 μmol l−1 sulphide. Sulphide-induced ATP production was inhibited by antimycin, cyanide and oligomycin but not by rotenone or salicylhydroxamic acid. The present data indicate that sulphide oxidation is coupled to oxidative phosphorylation solely by electron flow through cytochrome c oxidase, whereas the alternative oxidase does not serve as a coupling site. At sulphide concentrations higher than 20 μmol l−1, oxidation of sulphide serves mainly as a detoxification process rather than as a source of energy.
Modulation of Ciliary Beat Frequency by Neuropeptides From Identified Molluscan Neurons
Authors: Willows A. O. Dennis , Pavlova Galina A. , Phillips Nicole E.
Published: April 2021

Prior work in the nudibranch Tritonia diomedea indicated that certain identifiable pedal ganglion neurons (Pd5 and 6) innervating the foot synthesize three novel peptides (TPeps) that resemble Pedal peptide (Pep) identified in the sea hare Aplysia californica. We report here that when TPeps are applied directly to isolated ciliated patches of Tritonia diomedea foot epithelium, there is an increase in ciliary beating that normally drives locomotion. Exposure to TPeps also increases the ciliary beat frequency of cells isolated from the pedal epithelium, suggesting that the observed ciliomotor effects are direct and not mediated by intervening cells. Antibodies to TPep bind to specific cells of the brain and foot and to ciliated peripheral tissues in Tritonia diomedea and in the pulmonate gastropod Lymnaea stagnalis. We suggest, therefore, that TPeps may regulate the activity of ciliated cells responsible for pedal locomotion and other functions in gastropod molluscs.
Brightness Discrimination Ability in the West Indian Manatee (Trichechus Manatus)
Authors: Griebel Ulrike , Schmid Axel
Published: April 2021

Two manatees were tested on their ability to discriminate brightness using a series of 30 shades of grey varying from white to black. The animals were trained to discriminate between different shades of grey in a twofold simultaneous-choice situation. Their ability to discern brightness differences correlates with Weber’s law, and the calculated Weber fraction is 0.35.
What a Drag it is Getting Cold: Partitioning the Physical and Physiological Effects of Temperature on Fish Swimming
Authors: Fuiman Lee A. , Batty Robert S.
Published: April 2021

The influence of temperature-induced changes in water viscosity on the swimming performance and kinematics of larval Atlantic herring (Clupea harengus) was examined using high-speed video recording. The physical effects of viscosity were measured separately from the physiological (Q10) effects of temperature by increasing the viscosity using methyl cellulose. Voluntary swimming speeds of large larvae (18.2 mm total length) were characterized by Reynolds numbers based on length (ReL) between 100 and 500 and varied with temperature and viscosity. Speeds of small larvae (9.6 mm) at ReL between 25 and 125 were strongly affected by viscosity, but virtually unaffected by temperature at equal viscosities. Speeds of large larvae were modulated by transverse tail speed. Small (viscosity-dominated) larvae altered both transverse tail speed and tail amplitude to vary their swimming speed. Stride lengths for both sizes of larvae followed predictions for viscous-regime swimming until ReL>450. The combined data suggest that the viscous hydrodynamic regime for larval herring extends to at least ReL=300 and that viscosity could be important up to ReL of approximately 450. Because the physical effects of viscosity supplement the physiological effects of temperature on locomotor performance (when ReL is below approximately 300), indices such as Q10 can greatly overestimate the dependence of physiological processes on temperature, as demonstrated by an example.
Physiological Mechanisms of Evolved Desiccation Resistance in Drosophila Melanogaster
Authors: Gibbs Allen G. , Chippindale Adam K. , Rose Michael R.
Published: April 2021

We investigated physiological characters associated with water balance in laboratory populations of Drosophila melanogaster selected for resistance to desiccating conditions for over 100 generations. Five replicate, outbred, desiccation-selected (D) populations were compared with their control (C) populations. Water loss rates of female D flies were approximately 40 % lower than those of C females. Although excretory water loss was reduced in desiccation-selected flies, it comprised less than 10 % of total water loss, indicating that the D populations have evolved reduced cuticular and/or respiratory water loss rates. Total surface lipid amounts did not differ between the C and D flies. Cuticular hydrocarbons from D flies were longer than those from C flies and melted at slightly higher temperatures, possibly contributing to reduced water loss rates. Desiccation-selected flies contained approximately 30 % more bulk water than controls, as well as more glycogen. However, total metabolic water stores did not differ between the stocks owing to higher lipid levels in the C populations. The ability to tolerate water loss, as measured by water content at the time of death, did not differ between D and C flies. Thus, evolution of increased desiccation resistance has occurred by multiple physiological mechanisms, but some potential adaptive differences have not evolved.
Changes in Na+/K+-Atpase Expression During Adaptive Cell Differentiation In Avian Nasal Salt Gland
Authors: Hildebrandt Jan-Peter
Published: April 2021

Chronic salt stress in ducklings (Anas platyrhynchos) resulted in a sustained accumulation of cyclic AMP in the secretory cells of the nasal salt glands. Adaptive increases in the activity of the Na+/K+-ATPase, measured as ATP hydrolysis rates in freshly isolated tissue, were observed after 12 h of salt stress. This change in enzyme activity was associated with increases in protein abundance in the α-as well as in the β-subunit of Na+/K+-ATPase and an increase in β-subunit glycosylation. We investigated whether the increase in the cytosolic cyclic AMP concentration and the adaptive changes in Na+/K+-ATPase activity were causally related.

Using an organotypic tissue culture system for salt gland slices from unstressed (naive) ducklings, we produced similar changes in Na+/K+-ATPase activity and subunit abundance by treating cultured tissue with drugs that elevate cytosolic cyclic AMP levels (forskolin, 8-CPT-cAMP) during a 15 h culture period. Protein synthesis assays using cultured tissue revealed that elevations in cytosolic cyclic AMP level mediate increases in Na+/K+-ATPase subunit abundance by slowing down the degradation of ATPase subunits. This increase in the amount of enzyme protein was associated with a significant increase in Na+/K+-ATPase activity in tissue homogenates. The time course of these changes in cyclic-AMP-treated cultured tissue resembled that observed in salt-stressed intact animals, indicating that the elevation in cyclic AMP level in salt gland tissue may constitute a portion of the signalling events ultimately leading to the adaptive increase in Na+/K+-ATPase activity in vivo.