bluuebunny/crossref_metadata_2025 huggingface dataset:
Toward a catalog for the transcripts and proteins (sialome) from the salivary gland of the malaria vectorAnopheles gambiae
Authors: Francischetti Ivo M. B. , Valenzuela Jesus G. , Pham Van My , Garfield Mark K. , Ribeiro José M. C.
Published: April 2021

Hundreds of Anopheles gambiae salivary gland cDNA library clones have been sequenced. A cluster analysis based on sequence similarity at e-60 grouped the 691 sequences into 251 different clusters that code for proteins with putative secretory, housekeeping, or unknown functions. Among the housekeeping cDNAs, we found sequences predicted to code for novel thioredoxin, tetraspanin, hemopexin, heat shock protein, and TRIO and MBF proteins. Among secreted cDNAs, we found 21 novel A. gambiaesalivary sequences including those predicted to encode amylase, calreticulin,selenoprotein, mucin-like protein and 30-kDa allergen, in addition to antigen 5- and D7-related proteins, three novel salivary gland (SG)-like proteins and eight unique putative secreted proteins (Hypothetical Proteins, HP). The electronic version of this paper contains hyperlinks to FASTA-formatted files for each cluster with the best match to the nonredundant (NR) and conserved domain databases (CDD) in addition to CLUSTAL alignments of each cluster. The N terminus of 12 proteins (SG-1, SG-1-like 2, SG-6, HP 8, HP 9-like, 5′nucleotidase, 30-kDa protein, antigen 5- and four D7-related proteins) has been identified by Edman degradation of PVDF-transferred, SDS/PAGE-separated salivary gland proteins. Therefore, we contribute to the generation of a catalog of A. gambiae salivary transcripts and proteins. These data are freely available and will eventually become an invaluable tool to study the role of salivary molecules in parasite-host/vector interactions.
Three-dimensional launch kinematics in leaping, parachuting and gliding squirrels
Authors: Essner Richard L.
Published: April 2021

Leaping, parachuting and gliding are the primary means by which arboreal squirrels negotiate gaps in the canopy. There are notable differences among the three locomotor modes with respect to mid-air postures and aerodynamics,yet it is unclear whether variation should also be expected during the launch phase of locomotion. To address this question, launch kinematic profiles were compared in leaping (Tamias striatus), parachuting (Tamiasciurus hudsonicus) and gliding (Glaucomys volans) squirrels. Animals were filmed launching to the ground from a platform using high-speed video. Statistical comparisons among taxa indicated that only six out of 23 variables were significantly different among the three species. Two were associated with tail kinematics and were a consequence of tail morphology. Two were forelimb-related and discriminated gliding from non-gliding taxa. The remaining two variables were performance attributes, indicating significant variation among the species in take-off velocity and horizontal range. The absence of significant differences in hindlimb kinematics indicates that propulsion is essentially identical in leaping, parachuting and gliding squirrels.
Scaling bat wingbeat frequency and amplitude
Authors: Bullen R. D. , McKenzie N. L.
Published: April 2021

Wingbeat frequency (fw) and amplitude(θw) were measured for 23 species of Australian bat,representing two sub-orders and six families. Maximum values were between 4 and 13 Hz for fw, and between 90 and 150° forθ w, depending on the species. Wingbeat frequency for each species was found to vary only slightly with flight speed over the lower half of the speed range. At high speeds, frequency is almost independent of velocity. Wingbeat frequency (Hz) depends on bat mass (m, kg) and flight speed (V, ms-1) according to the equation: fw=5.54-3.068log10m-2.857log10V. This simple relationship applies to both sub-orders and to all six families of bats studied. For 21 of the 23 species, the empirical values were within 1 Hz of the model values. One species, a small molossid, also had a second mode of flight in which fw was up to 3 Hz lower for all flight speeds.

The following relationship predicts wingbeat amplitude to within±15° from flight speed and wing area (SREF,m2) at all flight speeds:θ w=56.92+5.18V+16.06log10SREF. This equation is based on data up to and including speeds that require maximum wingbeat amplitude to be sustained. For most species, the maximum wingbeat amplitude was 140°.
Branchial expression of an aquaporin 3 (AQP-3) homologue is downregulated in the European eelAnguilla anguillafollowing seawater acclimation
Authors: Cutler Christopher P. , Cramb Gordon
Published: April 2021

A cDNA encoding the homologue of mammalian aquaporin 3 (AQP-3) was isolated by reverse transcription—polymerase chain reaction from the gill of the European eel. The derived amino acid sequence shares 67-70% homology with other vertebrate AQP-3 homologues. Northern blot analysis revealed two AQP-3-specific mRNA species of 2.4 kb and 7 kb. AQP-3 mRNA is expressed predominantly in the eye, oesophagus, intestine (as found in mammals) and the gill; no expression could be demonstrated in the stomach and only low and sporadic levels in the kidney. Quantitative studies demonstrated that,following the 3-week acclimation of freshwater (FW)-adapted yellow and silver eels to seawater (SW), transcript abundance in the gill was reduced by 76% and 97%, respectively. The half time of branchial AQP-3 mRNA downregulation in yellow eels was approximately 10 h, with a maximal 94% decrease in expression after 2 days in SW (compared to time-matched FW controls). However, in fish acclimated to SW for more than 4 days, the fall in AQP-3 mRNA abundance recovered slightly, such that after 3 weeks, expression was 16% of that in time-matched FW controls. The potential roles for this aquaporin isoform in water or solute transport in the eel gill are discussed.
Immunolocalisation of aquaporin 3 in the gill and the gastrointestinal tract of the European eelAnguilla anguilla(L.)
Authors: Lignot Jean-H. , Cutler Christopher P. , Hazon Neil , Cramb Gordon
Published: April 2021

The expression of a putative water channel protein, aquaporin 3 (AQP-3),has been localised within branchial and intestinal tissues from the `silver'life stage of the European eel Anguilla anguilla, using a specific polyclonal antibody directed against the C-terminal of the amino acid sequence. Western blots using the AQP-3 antiserum identified the presence of a major immunoreactive protein of 24 kDa in extracts of gills from both freshwater (FW) and 3 week seawater (SW)-acclimated eels. SW acclimation induced a 65 % reduction in AQP-3 protein abundance in the gill extracts. AQP-3 immunoreactivity was apparent throughout the branchial epithelium from both FW and SW-acclimated fish, but especially so within the chloride cells,which also stained heavily with specific antisera for the β-subunit of the Na, K-ATPase. AQP-3 immunoreactivity not only colocalised with Na,K-ATPase within the basolateral tubular network but also stained the apical regions of the chloride cell where Na, K-ATPase was absent. Although there were no obvious differences in expression between the chloride cells of FW and SW-acclimated fish, considerably higher intensities of immunoreactivity were apparent near the periphery of the non-chloride cells of FW fish, especially within cells forming the base of the primary filaments and the branchial arch. AQP-3 immunoreactivity was also detected in intra-epithelial macrophage-like cells within the intestine of FW and SW-acclimated eels and in the mucous cells of the rectal epithelium of SW-acclimated fish. These results suggest that AQP-3 may play an important functional role in osmoregulation the teleostean gill but is unlikely to be responsible for the increases in intestinal water absorption that occur following SW acclimation.
Otolith growth in troutOncorhynchus mykiss: supply of Ca2+ and Sr2+ to the saccular endolymph
Authors: Payan P. , Borelli G. , Priouzeau F. , De Pontual H. , Bœuf G. , Mayer-Gostan N.
Published: April 2021

Kinetic and pharmacological characteristics of Ca2+ fluxes across the saccular epithelium of trout were studied using a perfused isolated inner ear. 45Ca2+ influx from the Ringer solution to the endolymph was 3-4 nmoles h-1μl-1 endolymph, which corresponds to a global turnover rate of the endolymph calcium of 200 %h-1. Ca2+ entry into the proximal endolymph was faster than into the distal fluid. Net Ca2+ movement across the saccular epithelium depended on the direction and intensity of the chemical gradient of calcium between the Ringer solution and the endolymph. Increasing the calcium concentration in the Ringer solution up to 4.4 mmol l-1 provoked an accumulation of Ca2+ in both proximal and distal endolymphs, and equilibrium was reached about 30 min after the beginning of perfusion. Perfusion with calcium-free Ringer partially emptied the proximal compartment of calcium, whereas the calcium levels in the distal endolymph did not vary during 70 min of perfusion. Verapamil (10-5 mol l-1) and cyanide (CN, 10-3 mol l-1) did not modify the accumulation of Ca2+ within the endolymph in the presence of a favourable calcium chemical gradient. Furthermore the relationship between Ca2+ net fluxes and the chemical calcium gradient across the saccular epithelium was linear, indicating a passive diffusional mechanism via a paracellular pathway. Similar relationships were found for Sr2+ fluxes across the saccular epithelium in the presence of positive chemical gradients (1, 2 and 4 mmol l-1 Sr2+). In vivo experiments in which trout were intraperitoneously injected with CaCl2 solution confirmed the tight relationship between the calcium levels in plasma and endolymph (both proximal and distal). Sampling proximal and distal endolymphs in trout and turbot saccules revealed a decreasing proximo—distal calcium gradient in endolymph of both fish species. The present results strongly suggest that the endolymph is supplied with Ca2+ and Sr2+via a paracellular pathway located in the proximal area of the saccular epithelium.
Effects of extracellular purines on ion transport across the integument ofHirudo medicinalis
Authors: Schnizler Mikael , Buss Mirjam , Clauss Wolfgang
Published: April 2021

Little is known about the long-term regulation of epithelial ion transport in invertebrates and the specific mediators involved. For some years, we have been investigating the short-term regulation of transepithelial ion transport across the dorsal integument of the leech Hirudo medicinalis, and we have established a model of Na+ uptake. In the present study, we investigated the effect of long-term acclimation on transintegumental ion transport by adapting leeches to high-salinity conditions. We dissected segments of dorsal integument and measured ion currents in Ussing chamber experiments. Electrophysiological variables, such as transepithelial potential(VT) and short-circuit-current (Isc),were profoundly affected by adaptation to high-salinity conditions. The total transepithelial Na+ current (INa) decreased from 7.66±0.82 to 4.6±0.54 μA cm-2 in preparations adapted to high salinity. The involvement of epithelial Na+channels was determined as current inhibition (Iami) by apical application of amiloride; Na+ channels were equally active in control epithelia and epithelia from leeches adapted to high salinity. Removal of Ca2+ from the apical solutions, which is believed to reduce intracellular Ca2+ concentrations, equalized transepithelial variables between high-salt-adapted integuments and control integuments.

Extracellular purines regulate transepithelial Cl- secretion and Na+ absorption. In a variety of tissues we tested ATP and adenosine for their effects on epithelial transport. Examination of integuments from pondwater- and high-salinity-adapted leeches revealed different sensitivities for these purines. Apical and basolateral application of ATP both stimulated transepithelial Na+ uptake and Iami. Adenosine upregulated non-Na+ currents and acted from the basolateral side only. Apical Ca2+-free conditions attenuated these effects of purines on transepithelial currents. Extracellular UTP had no effect on ion transport.
Mechanism allowing an insect to survive complete dehydration and extreme temperatures
Authors: Watanabe M. , Kikawada T. , Minagawa N. , Yukuhiro F. , Okuda T.
Published: April 2021

Cryptobiosis describes the state of an organism whose body water is completely dehydrated and metabolic activity has become undetectable. Our study aimed to elucidate the physiological mechanism of cryptobiosis in the highest cryptobiotic invertebrate, Polypedilum vanderplanki. Larvae of this insect rapidly accumulated a large amount of the carbohydrate,trehalose, (18% of dry body mass) during desiccation for 2 days, suggesting that a high level of trehalose accumulation contributed to the successful induction of cryptobiosis in P. vanderplanki as well as in other lower cryptobiotic organisms. When larvae deprived of the brain,suboesophageal ganglion (SG) and thoracic ganglia (TG) were completely dehydrated and then rehydrated, they were able to recover and move actively. During desiccation, such larvae also accumulated trehalose, although only about half as much as the intact larvae. It is concluded that the brain, SG and TG do not affect the induction and termination of cryptobiosis, and hence in this higher multicellular animal cryptobiosis is independent of brain, SG and TG regulation, just as in plants or in unicellular organisms.
The locust frontal ganglion: a central pattern generator network controlling foregut rhythmic motor patterns
Authors: Ayali Amir , Zilberstein Yael , Cohen Netta
Published: April 2021

The frontal ganglion (FG) is part of the insect stomatogastric nervous system and is found in most insect orders. Previous work has shown that in the desert locust, Schistocerca gregaria, the FG constitutes a major source of innervation to the foregut. In an in vitro preparation,isolated from all descending and sensory inputs, the FG spontaneously generated rhythmic multi-unit bursts of action potentials that could be recorded from all its efferent nerves. The consistent endogenous FG rhythmic pattern indicates the presence of a central pattern generator network. We found the appearance of in vitro rhythmic activity to be strongly correlated with the physiological state of the donor locust. A robust pattern emerged only after a period of saline superfusion, if the locust had a very full foregut and crop, or if the animal was close to ecdysis. Accordingly,haemolymph collected at these stages inhibited an ongoing rhythmic pattern when applied onto the ganglion. We present this novel central pattern generating system as a basis for future work on the neural network characterisation and its role in generating and controlling behaviour.
Energy metabolism of male and female tarantulas (Aphonopelma anax) during locomotion
Authors: Shillington Cara , Peterson Charles C.
Published: April 2021

We examined aerobic performance traits in male and female tarantulas(Aphonopelma anax). Reproductive fitness in these males relies heavily on locomotory searching to locate receptive females, which are fossorial and sedentary. Because of this dimorphism in life history, we predicted that selection in males would enhance their ability to sustain high levels of aerobic metabolism (compared with females) to support increased locomotory activity during the mating season. Rates of carbon dioxide production were measured in an enclosed variable-speed treadmill. Steady-state rates of carbon dioxide production increased linearly within the range of sustainable aerobic speeds for both males and females. Although there was substantial variation in physiological performance traits among individuals,there were no detectable intersexual differences in maximal rates of carbon dioxide production, maximal aerobic speed, minimum transport or factorial scope.
Mechanisms of ion transport inPotamotrygon, a stenohaline freshwater elasmobranch native to the ion-poor blackwaters of the Rio Negro
Authors: Wood Chris M. , Matsuo Aline Y. O. , Gonzalez R. J. , Wilson Rod W. , Patrick Marjorie L. , Val Adalberto Luis
Published: April 2021

Stingrays of the family Potamotrygonidae are the only stenohaline freshwater elasmobranchs. Potomotrygon sp. collected from the ion-poor blackwaters ([Na+], [Cl-] and[Ca2+]=10-30 μmol l-1, pH 6.1) of the Rio Negro,Amazonas, Brazil, were ammoniotelic (91% ammonia-N, 9% urea-N excretion) and exhibited blood chemistry (Na+, Cl-, urea, ammonia and glucose levels and osmolality) typical of freshwater teleosts. Unidirectional Na+ and Cl- influx rates, measured with radiotracers,displayed saturation kinetics. The relationships for Cl- and Na+ had similar Km values (300-500 μmol l-1), but Jmax values for Cl-(approximately 950 μmol kg-1 h-1) were almost twice those for Na+ (approximately 500 μmol kg-1h-1). Cl- efflux rates varied with external concentration, but Na+ efflux rates did not. There were no differences in the kinetic variables (Km, Jmax) for influx between animals acclimated to their native ion-poor blackwater or to ion-rich hard water, but efflux rates for both Na+ and Cl- were lower in the former, yielding much lower balance points (external Na+ or Cl- levels at which influx and efflux were equal). Na+, Cl- and Ca2+ uptake were all strongly inhibited by acute exposure to pH 4.0, but efflux rates and Ca2+ binding to the body surface did not change. Na+ influx was inhibited by amiloride (10-4 mol l-1) and by two of its analogs, phenamil (4×10-5mol l-1) and HMA (4×10-5 mol l-1), with the latter being slightly more potent, while Cl- fluxes were unaffected. Cl- fluxes were insensitive to DIDS(2×10-5 mol l-1 or 10-4 mol l-1) and SITS (10-4 mol l-1), but both influx and efflux rates were strongly inhibited by DPC (10-4 mol l-1) and thiocyanate (10-4 mol l-1). Ammonia excretion was unresponsive to large changes in water Na+concentration, but was elevated by 70% during acute exposure to pH 4.0 and transiently inhibited by approximately 50% by amiloride and its analogues. The strategy of adaptation to ion-poor blackwater appears similar to that of some Rio Negro teleosts (Cichlidae) in which low-affinity transport systems are relatively sensitive to inhibition by low pH but are complemented by low diffusive loss rates. Ionic transport systems in these freshwater elasmobranchs, although superficially similar to those in some freshwater teleosts, may bear more resemblance to their presumed evolutionary precursors in marine elasmobranchs.
Enhanced haemolymph circulation by insect ventral nerve cord: hormonal control byPseudaletia unipunctaallatotropin and serotonin
Authors: Koladich P. M. , Tobe S. S. , McNeil J. N.
Published: April 2021

The ventral diaphragm (VD) in many insects is a muscular membrane that essentially partitions a perineural sinus from the rest of the abdomen. In the true armyworm moth Pseudaletia unipuncta (Lepidoptera: Noctuidae) we describe how the VD is characterized by a series of aliform muscles inserted into a tissue matrix that is fused to the dorsal surface of the ventral nerve cord (VNC) itself. Because of this arrangement, the abdominal VNC can attain high rates of lateral oscillation, and is capable of directing haemolymph flow. We have previously demonstrated Manduca sexta allatotropin(Manse-AT)-like immunoreactivity throughout the central nervous system (CNS)in P. unipuncta, and that both Manse-AT and serotonin (5-HT) are dose-dependent stimulators of the dorsal vessel. Here we describe both Manse-AT- and 5-HT-like immunoreactivity associated with the VD. Furthermore,both Manse-AT and 5-HT are dose-dependent stimulators of the rates of VNC oscillation, and together are capable of maintaining highly elevated rates of VNC oscillation for extended periods of time. These data indicate that both the dorsal vessel and the VD/VNC are similarly modulated by both Manse-AT and 5-HT, and that VNC oscillations play a more active role in overall haemolymph circulation than previously recognized.
Regulation of early embryonic behavior by nitric oxide in the pond snailHelisoma trivolvis
Authors: Cole Alison G. , Mashkournia Aniseh , Parries Shawn C. , Goldberg Jeffrey I.
Published: April 2021

Helisoma trivolvis embryos display a cilia-driven rotational behavior that is regulated by a pair of serotonergic neurons named ENC1s. As these cilio-excitatory motor neurons contain an apical dendrite ending in a chemosensory dendritic knob at the embryonic surface, they probably function as sensorimotor neurons. Given that nitric oxide (NO) is often associated with sensory neurons in invertebrates, and has also been implicated in the control of ciliary activity, we examined the expression of NO synthase (NOS) activity and possible function of NO in regulating the rotational behavior in H. trivolvis embryos. NADPH diaphorase histochemistry on stage E25-E30 embryos revealed NOS expression in the protonephridia, buccal mass,dorsolateral ciliary cells and the sensory dendritic knobs of ENC1. At stages E35-40, the pedal ciliary cells and ENC1's soma, apical dendrite and proximal descending axon were also stained. In stage E25 embryos, optimal doses of the NO donors SNAP and SNP increased the rate of embryonic rotation by twofold, in contrast to the fourfold increase caused by 100 μmol l-1serotonin. The NOS inhibitors L-NAME (10 mmol l-1) and 7-NI (100μmol l-1) decreased the rotation rate by approximately 50%,whereas co-addition of L-NAME and SNAP caused a twofold increase. In an analysis of the surge and inter-surge subcomponents of the rotational behavior, the NO donors increased the inter-surge rotation rate and the surge amplitude. In contrast, the NO inhibitors decreased the inter-surge rotation rate and the frequency of surges. These data suggest that the embryonic rotational behavior depends in part on the constitutive excitatory actions of NO on ENC1 and ciliary cells.
Vibrometric studies of the middle ear of the bullfrogRana catesbeianaII. The operculum
Authors: Mason Matthew J. , Narins Peter M.
Published: April 2021

The operculum and stapes footplate, the two moveable elements within the oval window of the frog, have been thought to function independently. In this study, laser interferometry was used to record the vibrations of both structures in response to free-field airborne sound. Contrary to expectation,the operculum appears to be coupled to the footplate. Coupling is achieved both by means of ligaments and by a cartilaginous flange of the footplate that underlies the operculum. The stapes footplate rotates about an axis located ventrolaterally, but the axis for the operculum is dorsomedial. As a result of this unusual morphology, the opercularis muscle, which connects the operculum and shoulder girdle, can potentially affect the movements of both the operculum and footplate. The proposed roles of the opercularis system in seismic signal detection and extratympanic sound transmission are critically reviewed in the light of this new evidence. An alternative or additional role for the opercularis system is proposed, involving the protection of the inner ear from high-amplitude displacements of the stapes footplate during breathing and vocalisation.
Does reflection polarization by plants influence colour perception in insects? Polarimetric measurements applied to a polarization-sensitive model retina ofPapiliobutterflies
Authors: Horváth Gábor , Gál József , Labhart Thomas , Wehner Rüdiger
Published: April 2021

Using imaging polarimetry, we have measured some typical reflection-polarization patterns of plant surfaces (leaves and flowers) under different illuminations. Using a quantitative model to determine photon absorptions in the weakly polarization-sensitive (PS≈2)photoreceptors of Papilio butterflies, we have calculated the influence of reflection polarization on the colours of leaves and flowers perceived by Papilio. Compared with a retina containing polarization-blind colour receptors, the colour loci of specularly reflecting and, thus, strongly polarizing areas on a plant are slightly shifted, which could cause the perception of false colours. However, the colour of specularly reflecting surfaces is strongly masked by white glare, which may prevent the perception of polarization-induced hue shifts. Although the perception of polarizational false colours by Papilio butterflies was previously demonstrated with artificial, strongly colour-saturated and totally linearly polarized stimuli, we expect that the weak polarization sensitivity of Papilio photoreceptors hardly influences colour perception under natural conditions.
Ultraviolet colour perception in European starlings and Japanese quail
Authors: Smith Emma L. , Greenwood Verity J. , Bennett Andrew T. D.
Published: April 2021

Whereas humans have three types of cone photoreceptor, birds have four types of single cones and, unlike humans, are sensitive to ultraviolet light(UV, 320-400 nm). Most birds are thought to have either a violet-sensitive single cone that has some sensitivity to UV wavelengths (for example, many non-passerine species) or a single cone that has maximum sensitivity to UV(for example, oscine passerine species). UV sensitivity is possible because,unlike humans, avian ocular media do not absorb UV light before it reaches the retina. The different single cone types and their sensitivity to UV light give birds the potential to discriminate reflectance spectra that look identical to humans. It is clear that birds use UV signals for a number of visual tasks,but there are few studies that directly demonstrate a role for UV in the detection of chromaticity differences (i.e. colour vision) as opposed to achromatic brightness. If the output of the violet/UV cone is used in achromatic visual tasks, objects reflecting more UV will appear brighter to the bird. If, however, the output is used in a chromatic mechanism, birds will be able to discriminate spectral stimuli according to the amount of reflected light in the UV part of the spectrum relative to longer wavelengths. We have developed a UV `colour blindness' test, which we have given to a passerine(European starling) and a non-passerine (Japanese quail) species. Both species learnt to discriminate between a longwave control of orange vs red stimuli and UV vs `non-UV' stimuli, which were designed to be impossible to differentiate by achromatic mechanisms. We therefore conclude that the output of the violet/UV cone is involved in a chromatic colour vision system in these two species.
Sexual maturation and reproductive zinc physiology in the female squirrelfish
Authors: Thompson E. David , Mayer Gregory D. , Walsh Patrick J. , Hogstrand Christer
Published: April 2021

Female squirrelfish (Holocentridae) accumulate higher concentrations of hepatic zinc than any other known organism. In the liver cells, up to 70% of zinc is bound to metallothionein (MT), which is expressed at extremely high levels. These attributes are related to reproduction in ways that have not been fully characterized. In the present study, we have demonstrated that female-specific zinc and MT accumulation and distribution are strongly correlated to the onset of sexual maturity in Holocentrus adsenscionis. Sexual maturation not only resulted in increased concentrations of zinc in the liver and plasma, but also increased levels of hepatic MT mRNA. Furthermore, mature female squirrelfish exhibited greater proportions of MT protein in the nuclear liver cell fractions. To characterize the physiology further, we have examined the influence of the female sex hormone 17 β-estradiol (E2). E2 was not sufficient to elicit an increase in hepatic zinc concentrations or MT mRNA levels. E2 administration did, however, result in increased levels of MT in the nuclear fraction as well as overall hepatic MT protein. E2 also increased concentrations of zinc in the plasma. The changes in zinc concentration in the bloodstream followed the same time course as vitellogenin(VTG) transport from the liver. However, the high ratio of molar concentrations of zinc to VTG in the bloodstream suggest that VTG may not be the primary vehicle for hepato-ovarian zinc transport in squirrelfish.
Pendular energy transduction within the step in human walking
Authors: Cavagna G. A. , Willems P. A. , Legramandi M. A. , Heglund N. C.
Published: April 2021

During walking, the centre of mass of the body moves like that of a `square wheel': with each step cycle, some of its kinetic energy, Ek, is converted into gravitational potential energy, Ep, and then back into kinetic energy. To move the centre of mass, the locomotory muscles must supply only the power required to overcome the losses occurring during this energy transduction. African women carry loads of up to 20% of their body weight on the head without increasing their energy expenditure. This occurs as a result of an unexplained, more effective energy transduction between Ek and Ep than that of Europeans. In this study we measured the value of the Ek to Ep transduction at each instant in time during the step in African women and European subjects during level walking at 3.5-5.5 km h-1, both unloaded and carrying loads spanning 20-30% of their body weight. A simulation of the changes in Ek and Ep during the step by sinusoidal curves was used for comparison. It was found that loading improves the transduction of Ep to Ek during the descent of the centre of mass. The improvement is not significant in European subjects, whereas it is highly significant in African women.
Use of sonomicrometry demonstrates the link between prey capture kinematics and suction pressure in largemouth bass
Authors: Sanford Christopher P. J. , Wainwright Peter C.
Published: April 2021

Suction feeding in fishes is the result of a highly coordinated explosive expansion of the buccal cavity that results in a rapid drop in pressure. Prey are drawn into the mouth by a flow of water that is generated by this expansion. At a gross level it is clear that the expansion of the buccal cavity is responsible for the drop in pressure. However, attempts using high-speed video recordings to demonstrate a tight link between prey capture kinematics and suction pressure have met with limited success. In a study with largemouth bass Micropterus salmoides, we adopted a new technique for studying kinematics, sonomicrometry, to transduce the movement of skeletal elements of the head during feeding, and synchronized pressure recordings at a sampling rate of 500 Hz. From the positional relationships of six piezoelectric crystals we monitored the internal movements of the buccal cavity and mouth in both mid-sagittal and transverse planes. We found that peak subambient pressure was reached very early in the kinematic expansion of the buccal cavity, occurring at the time when the rate of percentage change in buccal volume was at its peak. Using multiple regression analyses we were consistently able to account for over 90%, and in the best model 99%, of the variation in buccal pressure among strikes using kinematic variables. Sonomicrometry shows great promise as a method for documenting movements of biological structures that are not clearly visible in the external view provided by film and video recordings.
Adaptive responses of vertebrate neurons to hypoxia
Authors: Bickler Philip E. , Donohoe Paul H.
Published: April 2021

The damage caused to mammalian neurons during ischaemic events in the brain(e.g. following a stroke), is an area of major interest to neuroscientists. The neurons of hypoxia-tolerant vertebrates offer unique models for identifying new strategies to enhance the survival of hypoxia-vulnerable neurons. In this review, we describe recent advances in our understanding of how hypoxia-tolerant neurons detect decreases in oxygen and create signals that have immediate and long-term effects on cell function and survival. Sensing and adapting to low oxygen tension involves numerous modalities with different times of activation and effect. Sensors include membrane proteins such as ionotropic ion channels, membrane or cytosolic heme proteins,mitochondrial proteins and/or oxygen sensitive transcription factors such as HIF-1α and NFκB. Signaling molecules involved in O2sensing include mitogen-activated protein kinases, ions such as Ca2+ and metabolites such as adenosine. These signals act rapidly to reduce the conductance of ion channels (ion flux arrest) and production of energy (metabolic arrest), and slowly to activate specific genes. The ability to construct an energy budget, illustrating which physiological processes are depressed during both long-term and acute metabolic suppression in hypoxia-tolerant neurons, would be of significant value in devising new strategies for neuroprotection. Additionally it is not known how metabolism is regulated at `pilot-light' levels at which energy-producing and energy-consuming processes are balanced. The regulation of organelle and cell fate during long-term hypoxia is almost completely unexplored, and whether programmed cell death and regeneration of lost neurons occur following protracted dormancy is also of considerable interest.
GABA-like immunoreactivity in nonspiking interneurons of the locust metathoracic ganglion
Authors: Wildman M. , Ott S. R. , Burrows M.
Published: April 2021

Nonspiking interneurons are important components of the premotor circuitry in the thoracic ganglia of insects. Their action on postsynaptic neurons appears to be predominantly inhibitory, but it is not known which transmitter(s) they use. Here, we demonstrate that many but not all nonspiking local interneurons in the locust metathoracic ganglion are immunopositive for GABA (γ-aminobutyric acid). Interneurons were impaled with intracellular microelectrodes and were shown physiologically to be nonspiking. They were further characterized by defining their effects on known leg motor neurons when their membrane potential was manipulated by current injection. Lucifer Yellow was then injected into these interneurons to reveal their cell bodies and the morphology of their branches. Some could be recognised as individuals by comparison with previous detailed descriptions. Ganglia were then processed for GABA immunohistochemistry. Fifteen of the 17 nonspiking interneurons studied were immunopositive for GABA, but two were not. The results suggest that the majority of these interneurons might exert their well-characterized effects on other neurons through the release of GABA but that some appear to use a transmitter other than GABA. These nonspiking interneurons are therefore not an homogeneous population with regard to their putative transmitter.
Physiological changes of sturgeon Acipenser naccarii caused by increasing environmental salinity
Authors: Martínez-Álvarez R. M. , Hidalgo M. C. , Domezain A. , Morales A. E. , García-Gallego M. , Sanz A.
Published: April 2021

The possible repercussions of osmoregulatory processes on some indicators of classical and oxidative stress were examined during gradual acclimation of sturgeons (Acipenser naccarii) to full seawater (35% salinity) and after a period of 20∼days at this salinity. Erythrocyte constants and levels of cortisol, protein and glucose in the plasma were determined. In addition, plasma osmolality and muscle-hydration values, as well as liver and heart protein, were determined. Catalase, glutathione peroxidase and superoxide dismutase activities and lipidperoxidation levels were measured in blood (plasma and red blood cells) and tissue (liver and heart). A number of physiological responses, such as disturbance in body fluid, activation of osmoregulatory mechanisms, augmented antioxidant defences in blood and alteration of energy metabolites, were detected with increasing environmental salinity. After 20 days at 35% salinity, plasma osmolality, erythrocyte constants and muscle water content all returned to values usual for low environmental salinity, indicating that osmoregulatory processes have achieved their objective. However, cortisol values, antioxidant enzyme activities in the blood (plasma and red blood cells), lipid peroxidation in plasma, and hepatic proteins did not return to initial values, showing that osmoregulatory processes cause major physiological changes in the fish.
Changes in locomotor activity parameters with variations in cycle time in larval lamprey
Authors: Boyd Malinda R. , McClellan Andrew D.
Published: April 2021

In larval lamprey, locomotor activity recorded from whole animals and in vitro brain/spinal cord preparations was analyzed to determine how two parameters of locomotor activity, burst proportion (BP; relative duration of motor burst activity) and intersegmental phase lag (ϕ; normalized delay of burst activity along one side of the body), vary with changes in cycle time(T). In individual animals, the slopes of BP and ϕ versus T were compared using linear regression analysis, followed by statistical analysis of the slopes to determine whether the parameters changed significantly with variations in cycle time.

For locomotor muscle activity in whole animals, the BP values increased significantly with decreases in T (i.e. negative slopes), while the slopes for ϕ values versus T were not significantly different from zero. For locomotor activity in preparations in vitro, the mean slopes for BP values versus T, although negative, were not significantly different from zero, and phase lags were also relatively constant with changes in cycle time.

Increases in BP with decreases in cycle time and increases in swimming speed can be expected to generate proportionately more force per cycle,presumably to compensate for the increase in viscous resistance of moving the body more rapidly through water. By contrast, constant intersegmental phase lags will ensure that the relative timing of locomotor burst activity is constant and that an approximately single S-wave along the body is retained during different swimming speeds.
Epithelial interactions inHydra: apoptosis in interspecies grafts is induced by detachment from the extracellular matrix
Authors: Kuznetsov Sergey G. , Anton-Erxleben Friederike , Bosch Thomas C. G.
Published: April 2021

Apoptosis plays an important role in immunity and is widely used to eliminate foreign or infected cells. Cnidaria are the most basal eumetazoans and have no specialised immune cells, but some colonial cnidarians possess a genetic system to discriminate between self and non-self. By grafting epithelia of different species we have previously shown that the freshwater polyp Hydra eliminates non-self cells by phagocytosis. Here we have investigated whether apoptosis is involved in the histocompatibility reactions. We studied epithelial interactions between Hydra vulgaris and Hydra oligactis and show that a large number of apoptotic cells accumulate in the contact region of interspecies grafts. Histological analysis of the graft site revealed that displacement of the endodermal layer of Hydra vulgaris by endoderm from Hydra oligactis coincided with impaired cell—cell and cell—matrix contacts. We therefore suggest that in interspecies grafts, apoptosis is induced by the detachment of epithelial cells from the extracellular matrix(anoikis) and not by a discriminative allorecognition system.
Two sniffing strategies in palinurid lobsters
Authors: Goldman J. A. , Patek S. N.
Published: April 2021

Most studies of lobster chemoreception have focused on the model systems of Panulirus argus (Palinuridae) and Homarus americanus(Nephropidae). We compare antennule morphology across lobsters and conduct the first kinematic study of antennule flicking in a palinurid species other than P. argus. High-speed video analysis shows that Palinurus elephas flicks at a rate more than an order of magnitude higher than in P. argus. However, both species flick their antennular flagella at a Reynolds number (Re) of approximately one, such that an asymmetry in the speed of the flick phases causes both species to have a leaky closing flick phase and a non-leaky opening phase. The antennular flagella of P. argus are nearly seven times longer than those of P. elephas,and, when compared across palinurid genera, Panulirus species sample far greater areas of water over greater spatial and time scales than do any other palinurid genera. Palinurid lobsters appear to have two sniffing strategies: low flick rates over a large area of water (e.g. P. argus) or high flick rates over a small area of water (e.g. P. elephas). P. argus is a highly informative model system in which to study aquatic chemoreception; however, its antennule anatomy and kinematics suggest a separate strategy, unique to Panulirus species, for sensing chemical plumes in fluid environments.
`Fixed-axis' magnetic orientation by an amphibian: non-shoreward-directed compass orientation, misdirected homing or positioning a magnetite-based map detector in a consistent alignment relative to the magnetic field?
Authors: Phillips John B. , Borland S. Chris , Freake Michael J. , Brassart Jacques , Kirschvink Joseph L.
Published: April 2021

Experiments were carried out to investigate the earlier prediction that prolonged exposure to long-wavelength (>500 nm) light would eliminate homing orientation by male Eastern red-spotted newts Notophthalmus viridescens. As in previous experiments, controls held in outdoor tanks under natural lighting conditions and tested in a visually uniform indoor arena under full-spectrum light were homeward oriented. As predicted, however,newts held under long-wavelength light and tested under either full-spectrum or long-wavelength light (>500 nm) failed to show consistent homeward orientation. The newts also did not orient with respect to the shore directions in the outdoor tanks in which they were held prior to testing. Unexpectedly, however, the newts exhibited bimodal orientation along a more-or-less `fixed' north-northeast—south-southwest magnetic axis. The orientation exhibited by newts tested under full-spectrum light was indistinguishable from that of newts tested under long-wavelength light,although these two wavelength conditions have previously been shown to differentially affect both shoreward compass orientation and homing orientation. To investigate the possibility that the `fixed-axis' response of the newts was mediated by a magnetoreception mechanism involving single-domain particles of magnetite, natural remanent magnetism (NRM) was measured from a subset of the newts. The distribution of NRM alignments with respect to the head—body axis of the newts was indistinguishable from random. Furthermore, there was no consistent relationship between the NRM of individual newts and their directional response in the overall sample. However, under full-spectrum, but not long-wavelength, light, the alignment of the NRM when the newts reached the 20 cm radius criterion circle in the indoor testing arena (estimated by adding the NRM alignment measured from each newt to its magnetic bearing) was non-randomly distributed. These findings are consistent with the earlier suggestion that homing newts use the light-dependent magnetic compass to align a magnetite-based `map detector'when obtaining the precise measurements necessary to derive map information from the magnetic field. However, aligning the putative map detector does not explain the fixed-axis response of newts tested under long-wavelength light. Preliminary evidence suggests that, in the absence of reliable directional information from the magnetic compass (caused by the 90° rotation of the response of the magnetic compass under long-wavelength light), newts may resort to a systematic sampling strategy to identify alignment(s) of the map detector that yields reliable magnetic field measurements.
Hyperpnea training attenuates peripheral chemosensitivity and improves cycling endurance
Authors: McMahon Michael E. , Boutellier Urs , Smith Richard M. , Spengler Christina M.
Published: April 2021

Well-trained endurance athletes frequently have a lower peripheral chemoreceptor (pRc) sensitivity and a lower minute ventilation(V̇E) during exercise compared to untrained individuals. We speculated that the decreased pRcresponse may be specifically associated with repeated exposure to the high rates of ventilation occurring during exercise training. We therefore examined the effect of respiratory muscle training (RMT; 20× 30 min sessions of voluntary normocapnic hyperpnea) on the pRc sensitivity during exercise and on cycling performance. RMT was chosen to achieve a high V̇E, similar to that of heavy exercise,while avoiding the other accompanying effects of whole body exercise. 20 trained male cyclists were randomized into RMT (N=10) or control(N=10) groups. Subjects' pRc response was assessed by a modified Dejours O2 test (10-12 breaths of 100% O2,repeated 4-6 times) during cycling exercise at 40% of the maximal work capacity (Ẇmax). Cycling performance was measured during a cycling test to exhaustion (85%Ẇmax). The RMT group exhibited a significantly reduced pRc sensitivity (mean ±S.D.) compared to the control group (-5.8±6.0% versus0.1±4.6%, P<0.5). Cycling endurance improved significantly after RMT in comparison to the control group (+3.26±4.98 versus -1.46±3.67 min, P<0.05). However, these changes in pRc response were not significantly correlated with exercise ventilation or cycling endurance time. We conclude that the high levels of ventilation achieved during exercise, as simulated by RMT in this study, appear to be accompanied by a reduction in pRc sensitivity;however, the role of the pRc in the control of ventilation during exercise seems to be minor.
Maternal and direct effects of the intestinal nematode Heligmosomoides polygyrus on offspring growth and susceptibility to infection
Authors: Kristan Deborah M.
Published: April 2021

The laboratory mouse (Mus musculus) has a naturally occurring intestinal nematode (Heligmosomoides polygyrus) that induces an immune response, causes phenotypic plasticity in metabolism and in organ structure and function, and results in changes in host reproductive output. The objectives of the present study were to determine (1) whether pups infected with parasites at weaning grew differently and had a different body composition at adulthood compared with uninfected pups, (2) whether offspring from parasitized mothers grew differently and had a different body composition at adulthood compared with offspring from unparasitized mothers, (3) whether parasite effects on body composition of pups varied under different infection intensities and (4) whether maternal parasite infection affected susceptibility, duration and intensity of offspring parasite infection. H. polygyrus had direct and maternal effects on offspring growth, but final adult mass was not affected by parasites. Parasite infection in offspring had no effect on overall fat mass, but mass changes for some organs were greater for mice that had a high infection intensity compared with mice that had a low infection intensity. Only offspring from parasitized mothers cleared their parasite infection; however, if the infection was not cleared, the final infection intensity was greater for offspring born to parasitized mothers than to unparasitized mothers. This study shows that chronic, sublethal parasite infection with H. polygyrus has both maternal and direct effects that induce physiological changes in growing mice sufficient to alter host growth trajectories, morphology and susceptibility to parasite infection.