bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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
Cytolysis and Protoplasmic Structure
Authors: Page Irvine H. , Clowes G. H. A. 
Published: April 2021

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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.