bluuebunny/crossref_metadata_2025_split huggingface dataset:
The enterins inhibit the contractile activity of the anterior aorta of Aplysia kurodai
Authors: Sasaki Kosei , Fujisawa Yuko , Morishita Fumihiro , Matsushima Osamu , Furukawa Yasuo 
Published: April 2021

SUMMARY
The anterior aorta is one of the largest blood vessels in the marine mollusc Aplysia kurodai. We examined the actions of recently identified neuropeptides, the enterins, on this blood vessel. Immunohistochemistry revealed that the enterin-immunopositive nerve fibers and varicosity-like structures are abundant in the aorta. When the enterins were applied to the aorta, the basal tonus of the arterial muscles was diminished. The enterins also decreased the contraction amplitude of the anterior aorta evoked either by the application of an Aplysia cardioactive peptide,NdWFamide, or by the stimulation of a nerve innervating the aorta (the vulvar nerve). We found that the enterins activate the 4-aminopyridine(4-AP)-sensitive K+ channels, and thereby hyperpolarize the membrane potential of the aortic muscles. In the presence of 4-AP, the enterins failed to inhibit the muscle contraction evoked by the vulvar nerve stimulation, suggesting that the inhibition is mainly due to the activation of the 4-AP-sensitive K+ channels. The inhibition of the NdWFamide-evoked contraction by the enterin was not, however, affected by 4-AP. These results suggest that the enterins are involved in inhibitory regulation of the contractile activity of the anterior aorta, and that the inhibition could be due to multiple mechanisms.
Low temperature X-ray microanalysis of calcium in a scleractinian coral:evidence of active transport mechanisms
Authors: Clode Peta L. , Marshall Alan T. 
Published: April 2021

SUMMARY
Element concentrations were measured by X-ray microanalysis in seawater(SW) compartments and mucocytes in bulk, frozen-hydrated preparations of the scleractinian coral Galaxea fascicularis. Quantitative X-ray microanalysis of polyps sampled in the daytime revealed that concentrations of the elements Na, S, K and Ca were all significantly higher in a thin (10-20μm) external SW layer adjacent to the oral ectoderm (P&lt;0.05,&lt;0.05, &lt;0.0001 and &lt;0.01, respectively) than in standard SW. In polyps sampled during night-time, concentrations of Ca and S in this external SW layer were significantly reduced (P&lt;0.05). Ca concentration in the coelenteron and extrathecal coelenteron was significantly higher(P&lt;0.001) than in the external SW layer, regardless of time of sampling, suggesting that Ca2+ transport across the oral epithelium occurs via an active, transcellular route. X-ray microanalyses of mucocytes revealed that the concentration of S was high and did not vary between epithelial layers, while that of Ca increased in an inward gradient toward the skeleton. We suggest that throughout the day, secreted mucus behaves as a Donnan matrix at the oral ectoderm—SW interface,facilitating intracellular Ca2+ uptake. The accumulation within internal SW compartments of high concentrations of Ca relative to standard SW levels, however, appears to be independent of mucus secretion and is likely to be a consequence of active transport processes.
Aerobic capacities in the skeletal muscles of Weddell seals: key to longer dive durations?
Authors: Kanatous S. B. , Davis R. W. , Watson R. , Polasek L. , Williams T. M. , Mathieu-Costello O. 
Published: April 2021

SUMMARYIn contrast to terrestrial animals that function under hypoxic conditions but display the typical exercise response of increasing ventilation and cardiac output, marine mammals exercise under a different form of hypoxic stress. They function for the duration of a dive under progressive asphyxia,which is the combination of increasing hypoxia, hypercapnia and acidosis. Our previous studies on short-duration, shallow divers found marked adaptations in their skeletal muscles, which culminated in enhanced aerobic capacities that are similar to those of atheltic terrestrial mammals. The purpose of the present study was to assess the aerobic capacity of skeletal muscles from long-duration divers. Swimming and non-swimming muscles were collected from adult Weddell seals, Leptonychotes weddelli, and processed for morphometric analysis, enzymology, myoglobin concentrations and fiber-type distribution. The results showed that the skeletal muscles of Weddell seals do not have enhanced aerobic capacities compared with those of terrestrial mammals but are adapted to maintain low levels of an aerobic lipid-based metabolism, especially under the hypoxic conditions associated with diving. The lower aerobic capacity of Weddell seal muscle as compared with that of shorter-duration divers appears to reflect their energy-conserving modes of locomotion, which enable longer and deeper dives.
Electroreception in juvenile scalloped hammerhead and sandbar sharks
Authors: Kajiura Stephen M. , Holland Kim N. 
Published: April 2021

SUMMARY
The unique head morphology of sphyrnid sharks might have evolved to enhance electrosensory capabilities. The `enhanced electroreception' hypothesis was tested by comparing the behavioral responses of similarly sized carcharhinid and sphyrnid sharks to prey-simulating electric stimuli. Juvenile scalloped hammerhead sharks Sphyrna lewini and sandbar sharks Carcharhinus plumbeus oriented to dipole electric fields from the same maximum distance (approximately 30 cm) and thus demonstrated comparable behavioral-response thresholds (&lt;1 nV cm-1). Despite the similarity of response threshold, the orientation pathways and behaviors differed for the two species. Scalloped hammerheads typically demonstrated a pivot orientation in which the edge of the cephalofoil closest to the dipole remained stationary while the shark bent its trunk to orient to the center of the dipole. By contrast, sandbars swam in a broader arc towards the center of the dipole. The different orientation patterns are attributed to the hydrodynamic properties of the cephalofoil, which enables the hammerheads to execute sharp turns at high speed. The greater trunk width of the sandbar sharks prevented them from demonstrating the same degree of flexibility. Therefore, although the sphyrnid head morphology does not appear to confer a greater sensitivity to prey-simulating dipole electric fields, it does provide(1) a greater lateral search area, which may increase the probability of prey encounter, and (2) enhanced maneuverability, which may aid in prey capture.
Elevated dietary intake of L-tryptophan counteracts the stress-induced elevation of plasma cortisol in rainbow trout (Oncorhynchus mykiss)
Authors: Lepage Olivier , Tottmar Olof , Winberg Svante 
Published: April 2021

SUMMARYJuvenile rainbow trout were isolated in individual compartments and allowed to acclimate for 1 week, during which they were fed commercial trout pellets. The feed was then replaced by pelleted feed supplemented with L-tryptophan(TRP) at two, four or eight times the concentration in the commercial feed. Fish were fed these supplemented feeds daily to satiety for 1 week, after which half of the fish were stressed, by lowering the water level for 2 h,while the remaining fish were left undisturbed. In undisturbed fish,supplementary dietary TRP resulted in slightly elevated plasma cortisol levels. In response to the stress, fish that had been fed control feed showed elevated plasma cortisol levels, but fish fed the TRP-supplemented feed displayed a significant reduction in this stress-induced elevation of plasma cortisol levels. Plasma and brain TRP levels were elevated in fish fed TRP-supplemented feed. TRP is the precursor of the monoamine neurotransmitter serotonin. Brain serotonergic activity was elevated by stress and also tended to be increased by elevated dietary TRP intake. The central serotonergic system is involved in the control of the hypothalamic—pituitary—interrenal axis, the action of serotonin being to stimulate or inhibit this neuroendocrine axis through different projections.
Gliclazide increases insulin receptor tyrosine phosphorylation but not p38 phosphorylation in insulin-resistant skeletal muscle cells
Authors: Kumar Naresh , Dey Chinmoy S. 
Published: April 2021

SUMMARYSulfonylurea drugs are used in the treatment of type 2 diabetes. The mechanism of action of sulfonylureas is to release insulin from pancreatic cells and they have been proposed to act on insulin-sensitive tissues to enhance glucose uptake. The goal of the present study was to test the hypothesis that gliclazide, a second-generation sulfonylurea, could enhance insulin signaling in insulin-resistant skeletal muscle cells. We demonstrated that gliclazide enhanced insulin-stimulated insulin receptor tyrosine phosphorylation in insulin-resistant skeletal muscle cells. Although insulin receptor substrate-1 tyrosine phosphorylation was unaffected by gliclazide treatment, phosphatidylinositol 3-kinase activity was partially restored by treatment with gliclazide. No increase in 2-deoxyglucose uptake in insulin-resistant cells by treatment with gliclazide was observed. Further investigations into the mitogen-activated protein kinase (MAPK) pathway revealed that insulin-stimulated p38 phosphorylation was impaired, as compared with extracellular-signal-regulated kinase (ERK) and c-Jun N-terminal kinase(JNK), which were phosphorylated normally in insulin-resistant cells. Treatment with gliclazide could not restore p38 phosphorylation in insulin-resistant cells. We propose that gliclazide can regulate part of the insulin signaling in insulin-resistant skeletal muscle, and p38 could be a potential therapeutic target for glucose uptake to treat insulin resistance.
The notochord of hagfishMyxine glutinosa: visco-elastic properties and mechanical functions during steady swimming
Authors: Long John H. , Koob-Emunds Magdalena , Sinwell Benjamin , Koob Thomas J. 
Published: April 2021

SUMMARYTo determine the possible locomotor functions of the hagfish notochord, we measured its flexural stiffness EI (N m-2) and flexural damping C (kg m3 s-1), under in vitroconditions that mimicked the body curvature and bending frequency measured during steady undulatory swimming. To assess the notochord's contribution to the mechanical behavior of the whole body, we also measured EI and C of the whole body, the body with skin removed, and the notochord with the outer fibrous sheath removed. When subjected to dynamic bending at angular frequencies from π to 6π rad s-1 and midline curvatures from 11 to 40 m-1, 1 cm in situ body segments(N=4), located at an axial position of 37% of the body length, showed significant changes in EI, C, the Young's modulus or material stiffness (E, MPa), the net work to bend the body over a cycle(W, J) and resilience (R, % energy return). When skin,muscles and the outer fibrous sheath of the notochord were removed sequentially, each structural reduction yielded significant changes in mechanical properties: C decreased when the skin was removed, E increased when the muscles were removed, and EI and R decreased when the outer fibrous sheath was removed. Although occupying only a small portion of the cross-sectional area, the notochord provides the body with 75% of its total EI and 80% of total C, by virtue of its high E, ranging from 4 to 8 MPa, which is an order of magnitude greater than that of the whole body. Thus, as the body's primary source of EI and C, the notochord determines the passive (i.e. internal, non-muscular) mechanical behavior of the swimming hagfish. EI and C covary inversely and non-linearly such that as C increases, EI decreases. However, the bending moments M (Nm) produced by each property increase proportionally, and the ratio of stiffness to damping moments, also known as the amplification ratio at resonance, is nearly invariant (approximately 7) with changes in driving frequency. If the body operates in life at or near resonance, the variables EI and C interact over a range of swimming speeds to produce passive mechanical stability.
How the viewing of familiar landscapes prior to release allows pigeons to home faster: evidence from GPS tracking
Authors: Biro Dora , Guilford Tim , Dell'Omo Giacomo , Lipp Hans-Peter 
Published: April 2021

SUMMARYProviding homing pigeons with a 5 min preview of the landscape at familiar sites prior to release reliably improves the birds' subsequent homing speeds. This phenomenon has been taken to suggest that the visual panorama is involved in familiar-site recognition, yet the exact nature of the improvement has never been elucidated. We employed newly developed miniature Global Positioning System (GPS) tracking technology to investigate how access to visual cues prior to release affects pigeons' flight along the length of the homing route. By applying a variety of novel analytical techniques enabled by the high-resolution GPS data (track efficiency, virtual vanishing bearings,orientation threshold), we localised the preview effect to the first 1000 m of the journey. Birds denied preview of a familiar landscape for 5 min before take-off flew an initially more tortuous path, including a high incidence of circling, possibly as part of an information-gathering strategy to determine their position. Beyond the first 1000 m, no differences were found in the performance of birds with or without preview. That the effect of the visual treatment was evident only in the early part of the journey suggests that lack of access to visual cues prior to release does not result in a non-specific effect on behaviour that is maintained throughout the flight. Instead, it seems that at least some decisions regarding the direction of home can be made prior to release and that such decisions are delayed if visual access to the landscape is denied. Overall, the variety of approaches applied here clearly highlight the potential for future applications of GPS tracking technology in navigation studies.
Effects of waterborne exposure of octylphenol and oestrogen on pregnant viviparous eelpout (Zoarces viviparus) and her embryos in ovario
Authors: Rasmussen Tina H. , Andreassen Thomas K. , Pedersen Søren N. , Van der Ven Leo T. M. , Bjerregaard Poul , Korsgaard Bodil 
Published: April 2021

SUMMARY
Exposure to oestrogenic chemicals (xeno-oestrogens) may have severe effects on embryonic development. The present study investigates whether the oestrogenic endocrine disruptor 4-tert-octylphenol (4-tOP) or 17β-oestradiol (E2) is accumulated in the viviparous fish the eelpout (Zoarces viviparus) and transferred to the embryos in ovario and subsequently affects embryonic development, including gonadal differentiation. Pregnant eelpouts were exposed to nominal concentrations of 25 μgl-1 or 100 μgl-1 4-tOP (OP25 or OP100,respectively) or 0.5 μgl-1 E2 in water. During 4-tOP exposure, the compound accumulated in both plasma and ovarian fluid in a concentration-dependent manner. In the mother fish, the oestrogenic biomarkers, vitellogenin (Vtg) in plasma, Vtg mRNA in liver and oestrogen-binding activity in liver, were all induced by 4-tOP (and by E2) at an actual concentration of 14 μgl-1. E2 and 4-tOP were examined for their potency to disturb the maternal—foetal trophic relationship by disturbing the physiology of the ovary and by changing the distribution of essential nutrients normally transported to embryos during pregnancy. After exposure to E2 or 4-tOP, calcium was depleted from the ovarian fluid and the level of free amino acids available in maternal plasma was decreased. A marked overall effect on ovarian components, including the ovarian sac, ovarian fluid and embryonic mass, was evident. Embryonic growth was significantly decreased, which might in part be attributed to disturbances of the maternal—foetal trophic relationship. Marked inductions of Vtg mRNA and Vtg protein, determined by RT-PCR and immunohistochemistry, respectively, were found in embryos from the OP100 group — the only group to show considerable accumulation of an oestrogenic compound in the ovarian fluid. A different pattern of gonadal development was found in embryos from the OP100 group compared with embryos from the control, OP25 or E2 groups, in which approximately 50% had normal ovaries and 50% had normal presmptive male gonads. In the OP100 group,46% had normal ovaries but, in contrast to controls, only 22% had normal presumptive male gonads, whereas the remaining 32% had abnormal male gonads with structures resembling the endo-ovarian cavity of a female gonad. As oestrogen receptor (ER) expression was detected by in situhybridisation in early differentiating gonads, these effects could be mediated by direct interaction of the xeno-oestrogens with gonadal ER. In conclusion,this study indicates that the xeno-oestrogen 4-tOP can be transferred from the water via the mother fish to the ovarian fluid and can subsequently disturb the maternal—foetal trophic relationship and cause severe effects on embryonic development, including gonadal differentiation in ovario.
Levamisole receptor phosphorylation: effects of kinase antagonists on membrane potential responses inAscaris suumsuggest that CaM kinase and tyrosine kinase regulate sensitivity to levamisole
Authors: Trailovic Sasa M. , Robertson Alan P. , Clark Cheryl L. , Martin Richard J. 
Published: April 2021

SUMMARYA two-micropipette current-clamp technique was used to record electrophysiological responses from the somatic muscle of Ascaris suum. Levamisole and acetylcholine were applied to the bag region of the muscle using a microperfusion system. Depolarizations produced by 10 s applications of 10 μmol l-1 levamisole or 20 s applications of 10 μmol l-1 acetylcholine were recorded. The effect on the peak membrane potential change of the kinase antagonists H-7, staurosporine, KN-93 and genistein was observed. H-7 (30 μmol l-1), a non-selective antagonist of protein kinases A, C and G but which has little effect on Ca2+/calmodulin-dependent kinase II (CaM kinase II), did not produce a significant effect on the peak response to levamisole or acetylcholine. Staurosporine (1 μmol l-1), a non-selective kinase antagonist that has effects on protein kinases A, C and G, CaM kinase and tyrosine kinase, reduced the mean peak membrane potential response to levamisole from 6.8 mV to 3.9 mV (P&lt;0.0001) and the mean response to acetylcholine from 5.5 mV to 2.8 mV (P=0.0016). The difference between the effects of H-7 and staurosporine suggested the involvement of CaM kinase II and/or tyrosine kinase. KN-93, a selective CaM kinase II antagonist,reduced the mean peak response to levamisole from 6.2 mV to 2.7 mV(P=0.035) and the mean peak response of acetylcholine from 4.7 mV to 2.0 mV (P=0.0004). The effects indicated the involvement of CaM kinase II in the phosphorylation of levamisole and acetylcholine receptors. The effect of extracellular Ca2+ on the response to levamisole was assessed by comparing responses to levamisole in normal and in low-Ca2+ bathing solutions. The response to levamisole was greater in the presence of Ca2+, an effect that may be explained by stimulation of CaM kinase II. Genistein (90 μmol l-1), a selective tyrosine kinase antagonist, reduced peak membrane potential responses to levamisole from a mean of 6.4 mV to 3.3 mV (P=0.001). This effect indicated the involvement of tyrosine kinase in maintaining the receptor.
The influence of visual landscape on the free flight behavior of the fruit flyDrosophila melanogaster
Authors: Tammero Lance F. , Dickinson Michael H. 
Published: April 2021

SUMMARYTo study the visual cues that control steering behavior in the fruit fly Drosophila melanogaster, we reconstructed three-dimensional trajectories from images taken by stereo infrared video cameras during free flight within structured visual landscapes. Flies move through their environment using a series of straight flight segments separated by rapid turns, termed saccades, during which the fly alters course by approximately 90° in less than 100 ms. Altering the amount of background visual contrast caused significant changes in the fly’s translational velocity and saccade frequency. Between saccades, asymmetries in the estimates of optic flow induce gradual turns away from the side experiencing a greater motion stimulus, a behavior opposite to that predicted by a flight control model based upon optomotor equilibrium. To determine which features of visual motion trigger saccades, we reconstructed the visual environment from the fly’s perspective for each position in the flight trajectory. From these reconstructions, we modeled the fly’s estimation of optic flow on the basis of a two-dimensional array of Hassenstein–Reichardt elementary motion detectors and, through spatial summation, the large-field motion stimuli experienced by the fly during the course of its flight. Event-triggered averages of the large-field motion preceding each saccade suggest that image expansion is the signal that triggers each saccade. The asymmetry in output of the local motion detector array prior to each saccade influences the direction (left versus right) but not the magnitude of the rapid turn. Once initiated, visual feedback does not appear to influence saccade kinematics further. The total expansion experienced before a saccade was similar for flight within both uniform and visually textured backgrounds. In summary, our data suggest that complex behavioral patterns seen during free flight emerge from interactions between the flight control system and the visual environment.
Tissue- and development-specific induction and turnover of hsp70 transcripts from loci 87A and 87C after heat shock and during recovery inDrosophila melanogaster
Authors: Lakhotia S. C. , Prasanth K. V. 
Published: April 2021

SUMMARYThe haploid genome of Drosophila melanogaster normally carries at least five nearly identical copies of heat-shock-inducible hsp70 genes, two copies at the 87A7 and three copies at the 87C1 chromosome sites. We used in situ hybridization of the cDNA, which hybridizes with transcripts of all five hsp70 genes, and of two 3′ untranslated region (3′UTR; specific for the 87A7- and 87C1-type hsp70 transcripts) riboprobes to cellular RNA to examine whether all these copies were similarly induced by heat shock in different cell types of D. melanogaster. Our results revealed remarkable differences not only in the heat-shock-inducibility of the hsp70 genes at the 87A7 and 87C1 loci, but also in their post-transcriptional metabolism, such as the stability of the transcripts and of their 3′UTRs in different cell types in developing embryos and in larval and adult tissues. Our results also revealed the constitutive presence of the heat-shock-inducible form of Hsp70 in a subset of late spermatogonial cells from the second-instar larval stage onwards. We suggest that the multiple copies of the stress-inducible hsp70 genes do not exist in the genome of D. melanogaster only to produce large amounts of the Hsp70 rapidly and at short notice, but that they are specifically regulated in a developmental-stage-specific manner. It is likely that the cost/benefit ratio of not producing or of producing a defined amount of Hsp70 under stress conditions varies for different cell types and under different physiological conditions and, accordingly, specific regulatory mechanisms operating at the transcriptional and post-transcriptional levels have evolved.