bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heterothermy and the water economy of free-living Arabian oryx (Oryx leucoryx)
Authors: Ostrowski Stéphane , Williams Joseph B. , Ismael Khairi 
Published: March 2003

SUMMARY
To test the idea that large, free-living, desert ungulates use heterothermy to reduce water loss, we measured core body temperature(Tb) of six free-ranging, adult Arabian oryx (Oryx leucoryx) during 2 years in the arid desert of west-central Saudi Arabia. We report the first case of heterothermy in a free-living ruminant in a desert environment: Tb varied by 4.1±1.7°C day–1 during summer (June to September) and by 1.5±0.6°C day –1 during winter (November to March). Over both seasons, mean Tb was 38.4±1.3°C. During the day in both summer and winter, Tb increased continually, suggesting that oryx store heat instead of dissipating it by evaporation, whereas at night Tb decreased. The minimum Tb was lower in summer (36.5±1.16°C) than in winter (37.5±0.51°C)despite the fact that the temperature gradient between Tband air temperature (Ta) was larger and solar radiation was lower in winter. Throughout the year, daily variation in Tb appeared to reflect thermal load(Ta,max–Ta,min) rather than an endogenous rhythm. Behavioural thermoregulation was used by oryx to cope with thermal stress during summer: animals lay down in shade in the morning shortly before Ta exceeded Tb and remained there until evening when Tb–Tabecame positive. The use of heterothermy by oryx resulted in storage ofandwould672.4 kJ day–1 animal–1258.6 kJ day–1 animal–1in winter, if heat storage is based on calculations involving mean Tb. Todissipaterequirethisheatin summerby evaporation0.28 litres H2O day–1 animal–1and0.11 litres H2O day–1 animal–1 in summer and winter,respectively. Without heat storage in summer, we estimated that oryx would have to increase their water intake by 19%, a requirement that would be difficult to meet in their desert environment. If heat storage was calculated based on the daily change in Tb rather than on heat storage above mean Tb then we estimated that oryx saved 0.538 litres H2O day–1 animal–1during summer.
The energetics of the trot–gallop transition
Authors: Wickler Steven J. , Hoyt Donald F. , Cogger Edward A. , Myers Gregory 
Published: March 2003

SUMMARYTwo studies have focused on potential triggers for the trot–gallop transition in the horse. One study concluded that the transition was triggered by metabolic economy. The second study found that it was not metabolic factors but, rather, peak musculoskeletal forces that determine gait transition speeds. In theory, peak musculoskeletal forces should be the same when trotting up an incline as when trotting at the same speed on the level. Assuming this is the case, we hypothesized that if peak forces determine gait transition speeds then horses should switch from a trot to a gallop at the same speed (i.e. the same critical force) regardless of incline. The aim of the present research was to examine the effects of incline on the trot–gallop transition speed in horses and to re-examine the role of metabolism in determining the trot–gallop transition. Horses (Equus caballus) were conditioned to run on a high-speed treadmill prior to data collection. Gait changes were recorded for each horse using a standardized testing protocol on the level and when trotting up a 10% incline. Both maximum sustained trotting speeds and minimum sustained galloping speeds, representing the lower and upper limits of the trot–gallop transition, respectively,were significantly slower when trotting up an incline. After completing collection of gait transition data, the horses were trained to extend their gaits beyond the normal transition speeds, and metabolic data were collected. Maximum sustained trotting speeds were not different from the energetically optimal transition speeds, i.e. the speed at which metabolic rates are the same for both gaits.
Insights into the evolution of human bipedalism from experimental studies of humans and other primates
Authors: Schmitt Daniel 
Published: March 2003

SUMMARYAn understanding of the evolution of human bipedalism can provide valuable insights into the biomechanical and physiological characteristics of locomotion in modern humans. The walking gaits of humans, other bipeds and most quadrupedal mammals can best be described by using an inverted-pendulum model, in which there is minimal change in flexion of the limb joints during stance phase. As a result, it seems logical that the evolution of bipedalism in humans involved a simple transition from a relatively stiff-legged quadrupedalism in a terrestrial ancestor to relatively stiff-legged bipedalism in early humans. However, experimental studies of locomotion in humans and nonhuman primates have shown that the evolution of bipedalism involved a much more complex series of transitions, originating with a relatively compliant form of quadrupedalism. These studies show that relatively compliant walking gaits allow primates to achieve fast walking speeds using long strides, low stride frequencies, relatively low peak vertical forces, and relatively high impact shock attenuation ratios. A relatively compliant, ape-like bipedal walking style is consistent with the anatomy of early hominids and may have been an effective gait for a small biped with relatively small and less stabilized joints, which had not yet completely forsaken arboreal locomotion. Laboratory-based studies of primates also suggest that human bipedalism arose not from a terrestrial ancestor but rather from a climbing, arboreal forerunner. Experimental data, in conjunction with anatomical data on early human ancestors, show clearly that a relatively stiff modern human gait and associated physiological and anatomical adaptations are not primitive retentions from a primate ancestor, but are instead recently acquired characters of our genus.
Regulation of L-alanine transport systems A and ASC by cyclic AMP and calcium in a reptilian duodenal model
Authors: Gómez Tomás , Medina Virtudes , Ramírez Cristina M. , Dópido Rosa , Lorenzo Antonio , Díaz Mario 
Published: March 2003

SUMMARYThe regulation of neutral amino acid transport by cyclic AMP (cAMP) and calcium across the isolated duodenum of the lizard Gallotia gallotihas been studied under short-circuit conditions. Active L-alanine transport was stimulated by forskolin, theophylline and dibutyryl cyclic AMP (db-cAMP). All these agents increased transmural potential difference (PD) and short-circuit current (Isc) in a manner consistent with the activation of a chloride secretory pathway. Both forskolin and theophylline increased intracellular cAMP levels in the lizard duodenal mucosa. Addition of calcium ionophore A23187 rapidly reduced mucosa-to-serosa L-alanine fluxes and diminished net L-alanine transport. Despite the reduction of alanine fluxes by A23187, transepithelial PD and Iscvalues were increased by the ionophore. Analyses of the responses of isolated transport pathways indicated that the Na+-independent L-alanine transport system was unaffected by db-cAMP or calcium ionophore. By contrast,Na+-dependent transport activities were profoundly modified by these agents. Thus, while system A [α-methylamino-isobutiric acid(MeAIB)-transporting pathway] was stimulated by increased calcium, system ASC activity was nearly abolished. Calcium ionophore also potentiated the electrogenic response of system A. Forskolin strongly stimulated system ASC activity but left system A activity unchanged. Activation of system ASC by forskolin was clearly electroneutral, as pre-incubation of the tissues with the chloride channel blocker diphenylamine-2-carboxilic acid (DPC) completely prevented forskolin-induced transepithelial electrical responses. It is concluded that intracellular messengers cAMP and calcium oppositely modulate active Na+-dependent L-alanine transport in the lizard intestine. The different sensitivity exhibited by individual transport pathways may well account for the changes observed in overall alanine transport.
Evolution of glutamine synthetase in vertebrates: multiple glutamine synthetase genes expressed in rainbow trout (Oncorhynchus mykiss)
Authors: Murray Brent W. , Busby Ellen R. , Mommsen Thomas P. , Wright Patricia A. 
Published: March 2003

SUMMARYGlutamine synthetase (GSase) is a key enzyme in nitrogen metabolism and encoded by a single gene in mammals. Using PCR cloning techniques, including RT-PCR from total RNA and PCR from a cDNA library, we find evidence of four expressed GSase mRNAs for the tetraploid rainbow trout. For two of these mRNAs(Onmy-GS01, -GS02) we characterize the full-length coding regions,and for two others (Onmy-GS03, -GS04), we describe partial sequences. Northern analysis of Onmy-GS01, -GS02, -GS03 and -GS04 indicates that (1) Onmy-GS02 is expressed at higher levels relative to the other transcripts in most adult tissues, with the exception of brain and gill, where Onmy-GS01 is at the highest level,and (2) the tissue with the highest level of expression of all four transcripts is the brain, with decreasing levels in the intestine, liver, red muscle, gill/kidney, white muscle and heart. Clearly, rainbow trout possess multiple GSase genes with differing levels of tissue expression, implying manifold potential routes of regulation for this octameric enzyme. Our data also indicate that caution should be taken when interpreting mRNA expression data of a single gene, unless multiple genes have been ruled out. Consistent with a southern blot, phylogenetic and intron sequence analyses imply that the trout genes are encoded by at least four separate loci, belonging to two distinct evolutionary branches. Our data on rainbow trout, together with those from two full-length zebrafish Danio rerio GSase genes compiled from GenBank ESTs, support the idea that fish GSases are polyphyletic and that gene duplications have occurred at multiple points and in independent lineages throughout the evolution of bony fishes.
Regulation of Na+/K+-ATPase activity by nitric oxide in the kidney and gill of the brown trout (Salmo trutta)
Authors: Tipsmark Christian K. , Madsen Steffen S. 
Published: March 2003

SUMMARYIn teleost fish, successful osmoregulation involves controlled ion transport mechanisms in kidney and gill epithelia. In this study, the effect of nitric oxide (NO) on Na+/K+-ATPase was investigated in vitro in these two tissues in brown trout (Salmo trutta)acclimated to freshwater. The NO donor sodium nitroprusside (SNP) inhibited in situ Na+/K+-ATPase activity, measured as ouabain-sensitive Rb+ uptake, in both samples of kidney and gill tissue and in isolated gill cells. The effect was dose-dependent in both tissues, with a maximal observed inhibition of approximately 40–50% (1 mmol l –1 SNP). The time-course of inhibition revealed a maximum effect with 10 min pre-incubation. The effect of SNP was reproduced with another NO donor, papa-nonoate (NOC-15; 200 μmol l–1), and was prevented by the NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO; 1 mmol l–1). To further investigate the mechanism of the NO effect,whole-tissue Na+ and K+ levels were analysed. In kidney,SNP (1 mmol l–1) led to an increase in tissue Na+levels and a decrease in K+ levels in a 3:2 ratio. In gill tissue,no change in either ion was observed. These observations indicate that the effect on Na+/K+-ATPase is direct rather than due to a decrease in intracellular Na+, its rate-limiting substrate. SNP elevated the level of cyclic GMP (cGMP) in both kidney and gill tissue. Dibutyryl cyclic GMP (db-cGMP; 1 mmol l–1) also inhibited Na+/K+-ATPase activity in both tissues. Hence, a possible mechanism may involve the cGMP-activated kinase, even though other mechanisms cannot be excluded.
Regulation of promoter occupancy during activation of cryptobiotic embryos from the crustacean Artemia franciscana
Authors: Martinez-Lamparero Ana , Casero Marie-Carmen , Ortiz-Caro Javier , Sastre Leandro 
Published: March 2003

SUMMARY
Artemia franciscana embryos can suspend their development and metabolism at the gastrula stage to enter a state of cryptobiosis, forming cysts. Embryonic development and metabolism can be resumed under favorable environmental conditions to give rise to free-swimming larvae or nauplii. The mechanisms that mediate these processes are not completely known. Here, we report our studies of the mechanisms that regulate transcriptional activation upon exiting cryptobiosis. Regulatory regions of several A. franciscana gene promoters were identified. Functional analyses in mammalian cells allowed the identification of transcriptional activator regions in the Actin302 promoter and in promoter 2 of the sarco/endoplasmic reticulum Ca2+-ATPase-encoding gene. These regions were shown to specifically bind protein factors from nuclear extracts of A. franciscana nauplii by means of electrophoretic mobility shift assays. Several protein-binding regions were also detected by DNase I protection analysis in the promoters of the genes encoding the α1 subunit of Na+/K+-ATPase, actin 302 and sarco/endoplasmic reticulum Ca2+-ATPase. Specific DNA-binding proteins in nauplius nuclear extracts were detected for all the promoter regions analyzed. These proteins were either not present in cyst nuclear extracts or were present in much smaller concentrations. Three of the five regions analyzed also bound proteins present in cyst nuclear extracts. These data indicate that transcriptional activation upon exiting cryptobiosis in A. franciscana involves the expression/activation of DNA-binding transcription factors that are not present in cyst nuclei
Behavioral attraction of Leach's storm-petrels (Oceanodroma leucorhoa) to dimethyl sulfide
Authors: Nevitt Gabrielle A. , Haberman Karen 
Published: March 2003

SUMMARY
A recent model for olfactory foraging by procellariiform seabirds suggests that these birds use biogenic sulfur compounds to locate productive areas for foraging in the southern oceans. The present study refines a simple approach to test birds' responses to odors on land and extends our knowledge to a northern species, the Leach's storm-petrel (Oceanodroma leucorhoa). Rather than working at sea, we tested the behavioral response to dimethyl sulfide (DMS) at night in breeding colonies on Kent Island, New Brunswick,Canada. Birds were presented with either 5 ml DMS (100 μmol l–1 concentration) or control (water) solutions from a platform 1.5 m in height positioned in a flyway 10 m from a breeding colony. We also tested birds' responses to cod liver oil, a well-established olfactory attractant of procellariiforms foraging at sea. Leach's storm-petrels approached DMS presentations nearly twice as frequently as they approached controls. We next compared the distribution of approaches against a Poisson process to test for evidence of social cueing. We found that approaches to DMS were significantly clustered. By contrast, the distribution of approaches did not depart significantly from a Poisson distribution for either cod liver oil or control presentations. Taken together, these results suggest that Leach's storm-petrels can smell DMS and potentially use it as a foraging cue. The results are consistent with the hypothesis that the detection of biogenic sulfur compounds in combination with other cues assists birds in locating foraging hotspots.
Twilight orientation to polarised light in the crepuscular dung beetleScarabaeus zambesianus
Authors: Dacke Marie , Nordström Peter , Scholtz Clarke H. 
Published: March 2003

SUMMARYThe polarisation pattern of skylight offers many arthropods a reference for visual compass orientation. The dung beetle Scarabaeus zambesianusstarts foraging at around sunset. After locating a source of fresh droppings,it forms a ball of dung and rolls it off at high speed to escape competition at and around the dung pile. Using behavioural experiments in the field and in the laboratory, we show that the beetle is able to roll along a straight path by using the polarised light pattern of evening skylight. The receptors used to detect this skylight cue can be found in the ommatidia of the dorsal rim area of the eye, whose structures differ from the regular ommatidia in the rest of the eye. The dorsal rim ommatidia are characterised by rhabdoms with microvilli oriented at only two orthogonal orientations. Together with the finding that the receptors do not twist along the length of the rhabdom, this indicates that the photoreceptors of the dorsal rim area are polarisation sensitive. Large rhabdoms, a reflecting tracheal sheath and a lack of screening pigments make this area of the eye well adapted for polarised light detection at low light levels. The fan-shaped arrangement of receptors over the dorsal rim area was previously believed to be an adaptation to polarised light analysis, but here we argue that it is simply a consequence of the way that the eye is built.
Functional consequences of a gene duplication and fusion event in an arginine kinase
Authors: Compaan Deanne M. , Ellington W. Ross 
Published: March 2003

SUMMARYArginine kinase (AK) from the foot of the razor clam Ensis directus consists of two full-length AK domains, denoted D1 and D2, fused in a single polypeptide chain. The full-length cDNA for Ensis AK was obtained and its deduced amino acid sequence was analyzed in the context of the X-ray crystal structure of a typical, monomeric AK. Both domains of Ensis AK contain most of the residues currently thought to be critical in catalysis, suggesting that both AK domains are catalytically competent. The full-length Ensis AK, a D2–NusA–His-tag fusion protein and a D2-truncated AK (enterokinase cleavage product of the fusion protein) were expressed in Escherichia coli and purified. All recombinant AK constructs displayed high enzyme activity. Attempts at expressing active D1 alone, D2 alone or a D1–NusA–His-tag fusion protein were unsuccessful. The catalytic properties of the active proteins were compared with the corresponding properties of recombinant AK from the horseshoe crab Limulus polyphemus, which is a typical monomeric AK. In contrast to expectations, the kinetic results strongly suggest that Ensis AK has only one active domain, namely D2. The Kcat values for all Ensis constructs were roughly twice that of typical AKs, indicating higher overall catalytic throughput at the competent active site. Furthermore, both the full-length and truncated D2 Ensis AKs showed no synergism of substrate binding unlike typical AKs. The D2–NusA–His-tag fusion construct actually displayed negative synergism of substrate binding, which means that, in effect, the first substrate bound acts as a competitive inhibitor of the second. The conservation of the structure of the apparently inactive D1 may be related to constraints imposed by structural changes that could potentially impact substrate binding in D2 and/or possibly influence the proper folding of the enzyme during synthesis. Overall, the results from the present study indicate that the AK contiguous dimer from Ensis directus functions with activity in only the second domain. Although lacking activity in D1, D2 appears to compensate by having a higher intrinsic catalytic throughput than typical 40-kDa monomeric AKs.
Adaptation in pheromone-sensitive trichoid sensilla of the hawkmoth Manduca sexta
Authors: Dolzer Jan , Fischer Karin , Stengl Monika 
Published: March 2003

SUMMARY
In extracellular tip recordings from long trichoid sensilla of male Manduca sexta moths, we studied dose–response relationships in response to bombykal stimuli of two different durations in the adapted and the non-adapted state. Bombykal-responsive cells could be distinguished from non-bombykal-sensitive cells in each trichoid sensillum because the bombykal-responsive cell always generated the action potentials of larger initial amplitude. The bombykal cell, which was recorded at a defined location within a distal flagellar annulus, can resolve at least four log10-units of pheromone concentrations but is apparently unable to encode all stimulus durations tested. Parameters of the amplitude-modulated sensillar potential and the frequency-modulated action potential responses were examined in different states of adaptation. Evidence is presented for the existence of several mechanisms of adaptation, which affect distinct steps of the transduction cascade. After adapting pheromone stimuli, the sensillar potential rises to a lower amplitude and declines faster compared with the non-adapted response. In addition, the frequency of the adapted action potential response is reduced. Only the time of rise of the sensillar potential is differentially affected by adapting pheromone stimuli of different duration. The time of rise does not increase after short, but only after long, adapting stimuli. Both short and long adapting stimuli shift the dose–response curves of the sensillar potential amplitude, as well as the initial slope of its rising phase, to higher stimulus concentrations by approximately one log10-unit. The shift in the dose–response curve of the action potential response is larger than for the sensillar potential response, suggesting that an additional adaptation mechanism acts at the level of action potential generation. Furthermore, a faster decline of the sensillar potential after short and long adapting stimuli suggests that the resting potential of the olfactory receptor neuron is stabilized.
A mobile-bearing total knee prosthesis compared with a fixed-bearing prosthesis
Authors: Price A. J. , Rees J. L. , Beard D. , Juszczak E. , Carter S. , White S. , de Steiger R. , Dodd C. A. F. , Gibbons M. , McLardy-Smith P. , Goodfellow J. W. , Murray D. W. 
Published: March 2003

Before proceeding to longer-term studies, we have studied the early clinical results of a new mobile-bearing total knee prosthesis in comparison with an established fixed-bearing device. Patients requiring bilateral knee replacement consented to have their operations under one anaesthetic using one of each prosthesis. They also agreed to accept the random choice of knee (right or left) and to remain ignorant as to which side had which implant. Outcomes were measured using the American Knee Society Score (AKSS), the Oxford Knee Score (OKS), and determination of the range of movement and pain scores before and at one year after operation. Preoperatively, there was no systematic difference between the right and left knees. One patient died in the perioperative period and one mobile-bearing prosthesis required early revision for dislocation of the meniscal component. At one year the mean AKSS, OKS and pain scores for the new device were slightly better (p < 0.025) than those for the fixed-bearing device. There was no difference in the range of movement. We believe that this is the first controlled, blinded trial to compare early function of a new knee prosthesis with that of a standard implant. It demonstrates a small but significant clinical advantage for the mobile-bearing design.
Relationship between outcome and annual surgical experience for the Charnley total hip replacement
Authors: Fender D. , van der Meulen J. H. P. , Gregg P. J. 
Published: March 2003

Using a regional arthroplasty register, we assessed the outcome, at five years, of 1198 primary Charnley total hip replacements (THRs) undertaken across a single health region in England in 1990. An independent clinical and radiological assessment was completed for 497 operations, carried out in 18 different hospitals, under the care of 56 consultants and by differing grades of surgeon. The overall number of failures in this group was 44 (8.9%). We found that the risk of failure in patients operated on by a consultant whose firm carried out 60 or more THRs in 1990 was 25% of that of patients under the care of a consultant whose firm undertook less than 30, adjusting for a number of patient, surgeon and hospital characteristics (16% v 4%; p < 0.001 for linear trend). Our study shows that the early outcome of hip replacement surgery varies with the number of replacements undertaken by the consultant firm. A national arthroplasty register would be a convenient source for such data.