bluuebunny/crossref_metadata_2025 huggingface dataset:
Cell cycle behavior of human HP1 subtypes: distinct molecular domains of HP1 are required for their centromeric localization during interphase and metaphase
Authors: Hayakawa Tomohiro , Haraguchi Tokuko , Masumoto Hiroshi , Hiraoka Yasushi
Published: July 2003

Heterochromatin protein 1 (HP1) plays an important role in heterochromatin formation. Three subtypes of HP1, namely HP1α, β, and γ, have been identified in humans. In this study, using yellow fluorescent protein(YFP) fusion constructs, we examined the intracellular localization of human HP1 subtypes during the cell cycle. During interphase, all three HP1 subtypes were localized to centromeric heterochromatin and to promyelocytic leukemia(PML) nuclear bodies. Different preferences, however, were observed among the subtypes: during interphase HP1β localized most preferentially to centromeric heterochromatin, whereas HP1α and γ were more preferentially localized to PML nuclear bodies. During metaphase, only HP1α, was localized to the centromere. We thus determined which molecular domains of HP1 were necessary for their intracellular localization. Our results showed that the C-terminal fragment (amino acid residues 101-180)of HP1α was necessary for localization to the metaphase centromere and the N-terminal fragment (amino acid residues 1-76) of HP1β was necessary for localization to the interphase centromere. Interestingly, simultaneous observations of residues 101-180 of HP1α and residues 1-76 of HP1βin living HeLa cells revealed that during late prophase, the HP1βfragment dissociated from centromeric regions and the HP1α fragment accumulated in centromeric regions. These results indicate that different specific regions of human HP1α and HP1β mediate localization to metaphase and interphase centromeric regions resulting in association of different subtypes of HP1 with the centromere at different times during the cell cycle.
Lack of plakophilin 1 increases keratinocyte migration and reduces desmosome stability
Authors: South Andrew P. , Wan Hong , Stone Michael G. , Dopping-Hepenstal Patricia J. C. , Purkis Patricia E. , Marshall John F. , Leigh Irene M. , Eady Robin A. J. , Hart Ian R. , McGrath John A.
Published: July 2003

Ablation of the desmosomal plaque component plakophilin 1 underlies the autosomal recessive genodermatosis, skin fragility-ectodermal dysplasia syndrome (OMIM 604536). Skin from affected patients is thickened with increased scale, and there is loss of adhesion between adjacent keratinocytes,which exhibit few small, poorly formed desmosomes. To investigate further the influence of plakophilin 1 on keratinocyte adhesion and desmosome morphology,we compared plakophilin 1-deficient keratinocytes (vector controls) with those expressing recombinant plakophilin 1 introduced by retroviral transduction. We found that plakophilin 1 increases desmosomal protein content within the cell rather than enhancing transcriptional levels of desmosomal genes. Re-expression of plakophilin 1 in null cells retards cell migration but does not alter keratinocyte cell growth. Confluent sheets of plakophilin 1-deficient keratinocytes display fewer calcium-independent desmosomes than do plakophilin 1-deficient keratinocytes expressing recombinant plakophilin 1 or keratinocytes expressing endogenous plakophilin 1. In addition electron microscopy studies show that re-expression of plakophilin 1 affects desmosome size and number. Collectively, these results demonstrate that restoration of plakophilin 1 function in our culture system influences the transition of desmosomes from a calcium-dependent to a calcium-independent state and this correlates with altered keratinocyte migration in response to wounding. Thus,plakophilin 1 has a key role in increasing desmosomal protein content, in desmosome assembly, and in regulating cell migration.
Altered connexin expression and wound healing in the epidermis of connexin-deficient mice
Authors: Kretz Markus , Euwens Carsten , Hombach Sonja , Eckardt Dominik , Teubner Barbara , Traub Otto , Willecke Klaus , Ott Thomas
Published: July 2003

To analyze the effect of connexin loss on the repair of wounded tail skin,we have studied the following transgenic mouse mutants: connexin30–/–, connexin31–/– and connexin43Cre-ER(T)/fl (for inducible deletion of the connexin43 coding region). Connexin43 and connexin31 are expressed in the basal and spinous layers of wild-type epidermis, whereas connexin31 and small amounts of connexin30, as well as connexin26 proteins,were found in the granulous layer. Connexin43 was downregulated in connexin31-deficient mice, whereas mice with reduced connexin43 exhibited an upregulation of connexin30. During wound healing, connexin30 and connexin26 proteins were upregulated in all epidermal layers, whereas connexin43 and connexin31 protein expression were downregulated. In connexin31–/– mice, reduced levels of connexin30 protein were observed on days 1 and 2 after wounding. The closure of epidermal wounds in mice with decreased amounts of connexin43 protein occurred one day earlier. Under these conditions the expression profiles of connexin30 and connexin31 were also temporarily shifted by one day. Furthermore, dye transfer between keratinocytes in skin sections from connexin43-deficient mice was decreased by 40%. These results suggest that downregulation of connexin43 appears to be a prerequisite for the coordinated proliferation and mobilization of keratinocytes during wound healing.
Regulation of neural markers nestin and GFAP expression by cultivated bone marrow stromal cells
Authors: Wislet-Gendebien S. , Leprince P. , Moonen G. , Rogister B.
Published: July 2003

Bone marrow stromal cells can differentiate into many types of mesenchymal cells, i.e. osteocyte, chondrocyte and adipocyte, but can also differentiate into non-mesenchymal cells, i.e. neural cells under appropriate in vivo experimental conditions (Kopen et al.,1999; Brazelton et al.,2000; Mezey et al.,2000). This neural phenotypic plasticity allows us to consider the utilization of mesenchymal stem cells as cellular material in regenerative medicine. In this study, we demonstrate that cultured adult rat stromal cells can express nestin, an intermediate filament protein predominantly expressed by neural stem cells. Two factors contribute to the regulation of nestin expression by rat stromal cells: serum in the culture medium inhibits nestin expression and a threshold number of passages must be reached below which nestin expression does not occur. Only nestin-positive rat stromal cells are able to form spheres when they are placed in the culture conditions used for neural stem cells. Likewise, only nestin-positive stromal cells are able to differentiate into GFAP (glial fibrillary acidic protein)-positive cells when they are co-cultivated with neural stem cells. We thus demonstrated that adult rat stromal cells in culture express nestin in absence of serum after passaging the cells at least ten times, and we suggest that nestin expression by these cells might be a prerequisite for the acquisition of the capacity to progress towards the neural lineage.
Involvement of connexin 43 in human trophoblast cell fusion and differentiation
Authors: Frendo Jean-Louis , Cronier Laurent , Bertin Gwladys , Guibourdenche Jean , Vidaud Michel , Evain-Brion Danièle , Malassiné André
Published: July 2003

The syncytiotrophoblast is the principal component of the human placenta involved in feto-maternal exchanges and hormone secretion. The syncytiotrophoblast arises from the fusion of villous cytotrophoblasts. We recently showed that functional gap junctional intercellular communication(GJIC) is an important prerequisite for syncytiotrophoblast formation and that connexin 43 (Cx43) is present in cytotrophoblasts and in the syncytiotrophoblast. To determine whether Cx43 is directly involved in trophoblast fusion, we used an antisense strategy in primary cultures of human villous cytotrophoblasts that spontaneously differentiate into the syncytiotrophoblast by cell fusion. We assessed the morphological and functional differentiation of trophoblasts by desmoplakin immunostaining, by quantifying hCG (human chorionic gonadotropin) production and by measuring the expression of specific trophoblast genes (hCG and HERV-W). Furthermore, we used the gap-FRAP (fluorescence recovery after photobleaching) method to investigate functional GJIC. Cytotrophoblasts treated with Cx43 antisense aggregated and fused poorly. Furthermore, less HERV-W env mRNA, hCGβ mRNA and hCG secretion were detected in Cx43 antisense-treated cytotrophoblasts than in cells treated with scrambled antisense. Treatment with Cx43 antisense dramatically reduced the percentage of coupled trophoblast cells. Taken together, these results suggest that Cx43 is directly involved in human trophoblast cell-cell communication, fusion and differentiation.
Superoxide signalling required for multicellular development ofDictyostelium
Authors: Bloomfield Gareth , Pears Catherine
Published: July 2003

Reactive oxygen species are known to have a signalling role in many organisms. In bacteria and yeast various response systems have evolved to combat oxidative stress which are triggered by reactive oxygen species. Mammals and plants are known to actively generate reactive oxygen species such as superoxide during signalling responses to a variety of extracellular factors. We report here the generation of superoxide as a signalling molecule in early development of Dictyostelium discoideum. Dictyostelium grows as single amoebae but, on starvation, the single cells aggregate to form a multicellular organism. Superoxide is generated in response to a secreted factor during the transition to the multicellular phase of development. Scavenging superoxide, either pharmacologically or by overexpressing the enzyme superoxide dismutase, inhibits the formation of the aggregate. This report of the use of superoxide as a signalling molecule in a lower eukaryote as it switches to a multicellular phase suggests that this signalling mechanism arose early in the evolution of multicellular organisms, perhaps as a necessary consequence of the need to diversify the number and type of signalling pathways available to facilitate intercellular communication.
Adhesion measurements on the attachment devices of the jumping spiderEvarcha arcuata
Authors: Kesel A. B. , Martin A. , Seidl T.
Published: July 2003

The feet of the jumping spider Evarcha arcuata attach to rough substrates using tarsal claws. On smooth surfaces, however, attachment is achieved by means of a claw tuft, the scopula. All eight feet bear a tarsal scopula, which is equipped with setae, these again being covered by numerous setules. In E. arcuata, an estimated 624 000 setules, with a mean contact area of 1.7×105 nm2, are present. The spider's entire contact area thus totals 1.06×1011nm2. Adhesion to the substrate does not depend on the secretion of an adhesive fluid. Analysis via atomic force microscopy (AFM) shows that a single setule can produce an adhesive force (Fa) of 38.12 nN perpendicular to a surface. Consequently, at a total Fa of 2.38×10–2 N and a mean body mass of 15.1 mg, a safety factor (SF; Fa/Fm, where Fm is weight) of 160 is achieved. Tenacity (τn; Fa/A, where A is area of contact) amounts to 2.24×105 N m-2.
Initial mechanical efficiency of isolated cardiac muscle
Authors: Barclay C. J. , Widén C. , Mellors L. J.
Published: July 2003

The aim of this study was to determine whether the initial mechanical efficiency (ratio of work output to initial metabolic cost) of isolated cardiac muscle is over 60%, as has been reported previously, or whether it is approximately 30%, as suggested by an estimate based on the well-established net mechanical efficiency (ratio of work output to total, suprabasal energy cost) of 15%. Determination of initial efficiency required separation of the enthalpy output (i.e. heat + work) into initial and recovery components. The former corresponds to energy produced by reactions that use high-energy phosphates and the latter to energy produced in the regeneration of high-energy phosphates. The two components were separated mathematically. Experiments were performed in vitro (30°C) using preparations dissected from rat left ventricular papillary muscles (N=13). Muscle work output and heat production were measured during a series of 40 contractions using a contraction protocol designed to mimic in vivopapillary muscle activity. Net mechanical efficiency was 13.3±0.7%. The total enthalpy output was 2.16 times greater than the initial enthalpy output,so that initial mechanical efficiency was 28.1±1.2%.
Comparative studies of high performance swimming in sharks I. Red muscle morphometrics, vascularization and ultrastructure
Authors: Bernal D. , Sepulveda C. , Mathieu-Costello O. , Graham J. B.
Published: July 2003

Tunas (family Scombridae) and sharks in the family Lamnidae are highly convergent for features commonly related to efficient and high-performance(i.e. sustained, aerobic) swimming. High-performance swimming by fishes requires adaptations augmenting the delivery, transfer and utilization of O2 by the red myotomal muscle (RM), which powers continuous swimming. Tuna swimming performance is enhanced by a unique anterior and centrally positioned RM (i.e. closer to the vertebral column) and by structural features (relatively small fiber diameter, high capillary density and greater myoglobin concentration) increasing O2 flux from RM capillaries to the mitochondria. A study of the structural and biochemical features of the mako shark (Isurus oxyrinchus) RM was undertaken to enable performance-capacity comparisons of tuna and lamnid RM. Similar to tunas, mako RM is positioned centrally and more anterior in the body. Another lamnid, the salmon shark (Lamna ditropis), also has this RM distribution, as does the closely related common thresher shark (Alopias vulpinus; family Alopiidae). However, in both the leopard shark(Triakis semifasciata) and the blue shark (Prionace glauca),RM occupies the position where it is typically found in most fishes; more posterior and along the lateral edge of the body. Comparisons among sharks in this study revealed no differences in the total RM quantity (approximately 2–3% of body mass) and, irrespective of position within the body, RM scaling is isometric in all species. Sharks thus have less RM than do tunas(4–13% of body mass). Relative to published data on other shark species,mako RM appears to have a higher capillary density, a greater capillary-to-fiber ratio and a higher myoglobin concentration. However, mako RM fiber size does not differ from that reported for other shark species and the total volume of mitochondria in mako RM is similar to that reported for other sharks and for tunas. Lamnid RM properties thus suggest a higher O2 flux capacity than in other sharks; however, lamnid RM aerobic capacity appears to be less than that of tuna RM.
Metabolic responses of shorebird chicks to cold stress: hysteresis of cooling and warming phases
Authors: Ricklefs Robert E. , Williams Joseph B.
Published: July 2003

We developed a protocol for determining the maximum rate of oxygen consumption of shorebird chicks (Scolopacidae and Charadriidae) in response to cold challenge. We first subjected the chicks to gradually decreasing temperatures until their metabolism peaked and began to decrease. We ended the cooling phase of a trial when a chick's body temperature Tb had declined typically to 32–34°C. After this point, we gradually increased the temperature in the metabolism chamber until normal Tb values and thermoneutral resting metabolism were restored. We refer to this cycle as the down–up (DU) protocol. We estimated instantaneous oxygen consumption(V̇O2) using the equation of Bartholomew et al.(1981). V̇O2 and Tb were monitored continuously during the trials.

Here, we illustrate typical temperature and metabolism dynamics of the DU protocol by describing several trials in detail, and we discuss the implications of these results for the control of metabolism and regulation of Tb. Chicks subjected to the DU protocol exhibited three distinct phases of metabolic response to ambient temperature(Ta). In Phase I, V̇O2 increase was directly related to the gradient between Tb and Ta, consistent with a Newtonian response to cooling. During Phase II, chicks sustained a maximum level of V̇O2 that decreased as Tb dropped, exhibiting a Q10 of approximately 2. Based on the slope of the relationship between V̇O2 and Tb during Phase II, we were able to estimate maximum V̇O2 at a standardized high Tb. Phase II continued until chick Tb began to rise as a result of the gradually increasing Ta. During Phase III, the Tb-adjusted rate of oxygen consumption decreased from the maximum level at low Tb to the resting level at high Tb in the thermoneutral zone. Further trials with faster and slower rates of chamber cooling showed that V̇O2 during Phase I varied in proportion to the difference between Tb and Ta (ΔT), whereas during Phase III it responded to Tb.

Even though chicks may be capable of generating enough heat to regulate Tb during the early part of Phase I of the DU protocol,the constantly decreasing Ta created a time lag between Ta and the chick's metabolic response, leading to body cooling. The hysteresis observed between Phase I and Phase III suggests that chicks rewarm passively while being brooded following the decrease in Tb experienced during active foraging. The results of the DU protocol suggest that Tb should be measured continuously during measurements of maximum oxygen consumption, and that peak values should be adjusted by Tb to make them comparable with other studies.
Oxidative stress stimulates multiple MAPK signalling pathways and phosphorylation of the small HSP27 in the perfused amphibian heart
Authors: Gaitanaki Catherine , Konstantina Stathopoulou , Chrysa Stavridou , Beis Isidoros
Published: July 2003

We investigated the activation of three subfamilies of MAPKs (ERK, JNKs and p38-MAPK) by oxidative stress in the isolated perfused amphibian heart. Activation of p43-ERK by 100 μmol l-1 H2O2was maximally observed within 5 min, remained elevated for 30 min and was comparable with the effect of 1 μmol l-1 PMA. p43-ERK activation by H2O2 was inhibited by PD98059 but not by SB203580. The p46 and p52 species of JNKs were maximally activated by 2.5- and 2.1-fold,respectively, by 100 μmol l-1 H2O2 within 2 min. JNK activation was still detectable after 15 min, reaching control values at 30 min of treatment. p38-MAPK was maximally activated by 9.75-fold by 100 μmol l-1 H2O2 after 2 min and this activation progressively declined thereafter, reaching control values within 45 min of treatment. The observed dose-dependent profile of p38-MAPK activation by H2O2 revealed that 30 μmol l-1 H2O2 induced maximal phosphorylation,whereas 100–300 μmol l-1 H2O2induced considerable activation of the kinase. Our studies also showed that the phosphorylation of MAPKAPK2 by H2O2 followed a parallel time-dependent pattern and that SB203580 abolished this phosphorylation. Furthermore, our experiments clearly showed that 30 μmol l-1 H2O2 induced a strong, specific phosphorylation of HSP27. Our immunohistochemical studies showed that immune complexes of phosphorylated forms of both p38-MAPK and HSP27 were strongly enhanced by 30 μmol l-1 H2O2 in the perinuclear region as well as dispersedly in the cytoplasm of ventricular cells and that SB203580 abolished this phosphorylation. These data indicate that oxidative stress is a powerful activator of all three MAPK subfamilies in the amphibian heart. Stimulation of p38-MAPK and the consequent phosphorylation of HSP27 may be important in cardioprotection under such conditions.
Biophysical properties of the pelt of a diurnal marsupial, the numbat(Myrmecobius fasciatus), and its role in thermoregulation
Authors: Cooper C. E. , Walsberg G. E. , Withers P. C.
Published: July 2003

Numbats are unusual marsupials in being exclusively diurnal and termitivorous. They have a sparse (1921 hairs cm-2) and shallow(1.19 mm) pelt compared with other marsupials. Coat reflectivity is low (19%)for numbats compared with nocturnal marsupials, but absorptivity is similar to that of diurnal North American ground squirrels (72%), indicating that the coat of the numbat may be adapted for acquisition of solar heat. Numbat coat thermal resistance decreases significantly with wind speed from 45.9 s m-1 (at 0.5 m s-1) to 29.8 s m-1 (at 3 m s-1). Erecting the fur significantly increases pelt depth (6.5 mm)and coat resistance (79.2–64.2 s m-1) at wind speeds between 0.5 m s-1 and 3 m s-1. Numbat coat resistance is much lower than that of other marsupials, and wind speed has a greater influence on coat resistance for numbats than for other mammals, reflecting the low pelt density and thickness.

Solar heat gain by numbats through the pelt to the level of the skin(60–63%) is similar to the highest value measured for any mammal. However the numbat's high solar heat gain is not associated with the same degree of reduction in coat resistance as seen for other mammals, suggesting that its pelt has structural and spectral characteristics that enhance both solar heat acquisition and endogenous heat conservation. Maximum solar heat gain is estimated to be 0.5–3.6 times resting metabolic heat production for the numbat at ambient temperatures of 15–32.5°C, so radiative heat gain is probably an important aspect of thermoregulation for wild numbats.
Acutely elevated vasopressin increases circulating concentrations of cortisol and aldosterone in fasting northern elephant seal (Mirounga angustirostris) pups
Authors: Ortiz Rudy M. , Wade Charles E. , Ortiz C. Leo , Talamantes Frank
Published: July 2003

The physiological actions of vasopressin (VP) in marine mammals are not well defined. To help elucidate its hormonal and renal effects in this group of mammals, northern elephant seal (Mirounga angustirostris) pups(N=7; 99±4 kg) were first infused with 0.9% saline (control;220 ml), followed 24 h later with VP (as a 20 ng kg-1 bolus, then 2 ng kg-1 min-1 for approximately 35 min in 225±16 ml saline). During both control and VP periods, blood samples were collected prior to infusion, and 15, 30, 60, 120 min and 24 h after infusion to examine the hormonal responses of the pups to VP. Renal responses were quantified from 24 h urine samples obtained prior to infusion (control) and 24 h post-infusion. Compared to the control period, infusion of VP increased plasma concentrations of cortisol over a 120 min period and aldosterone over 30 min,while plasma renin activity (PRA) was decreased for a 120 min period. The plasma urea:creatinine ratio was elevated following infusion of VP. Urine output and osmotic clearance were increased by 69±18% (mean ± s.e.m.) and 36±10%, respectively, but free water clearance and glomerular filtration rate were not significantly altered 24 h post-infusion of VP. Solute (osmolality, Na+, K+ and Cl-) excretion and fractional excretion of electrolytes were also increased when compared to control values. The increase in cortisol concentration suggests that VP may possess corticotropin releasing hormone-like activity in elephant seals. If osmotic diuresis and natriuresis are typical consequences of elevated [VP] in fasting pups, then not increasing VP normally during the fast may serve as a protective mechanism to avoid the potential loss of Na+ induced by elevated [VP]. Therefore, under natural fasting conditions, pups may be highly sensitive to small changes in[VP], resulting in the maintenance of water and electrolyte balance.
Ontogeny of baroreflex control in the American alligatorAlligator mississippiensis
Authors: Crossley Dane A. , Hicks James W. , Altimiras Jordi
Published: July 2003

Baroreflex regulation appears in different species at different points in embryonic development. This study was designed to understand the development of the baroreflex in embryos of the American alligator at four different points of embryonic development (60%, 70%, 80% and 90% of a total incubation period of 72 days) and in 1-week-old hatchlings. Data from a separate study on 1-year-old alligators were included for comparison. The gain of the cardiac limb of the baroreflex was calculated from heart rate changes triggered by pharmacological manipulation of arterial pressure with sodium nitroprusside and phenylephrine. The results demonstrated that a vagally mediated hypertensive baroreflex was present during the final 30% of alligator development. A hypotensive baroreflex was not present in embryos but appeared in hatchlings, mediated by a combined effect of vagal and sympathetic efferents. Absolute baroreflex gain was maximal at 80% of incubation (41.22 beats kPa–1 min–1) and dropped thereafter,reaching a minimum in 1-year-old alligators (9.69 beats kPa–1min–1). When the baroreflex gain was normalized to resting arterial pressure and heart rate, the maximum gain was observed in 1-year-old alligators (normalized index of 2.12 versus 0.75 in hatchlings and 0.69 as the highest gain in embryos). In conclusion, baroreflex regulation appeared during embryonic development with a substantial gain. These findings indicate that embryonic development is a period of preparation for cardiovascular regulatory mechanisms that will be necessary in adult life and that the baroreflex control mechanism is required for cardiovascular control during ontogeny.
Rapid mechano-sensory pathways code leg impact and elicit very rapid reflexes in insects
Authors: Höltje Markus , Hustert Reinhold
Published: July 2003

The temporal sequence of mechanoreceptor input arriving at the motoneuron level in the central nervous system (CNS) after distal mechanical contact was studied for the locust middle leg. Different types of afferent information from potential contact areas after selective stimulation showed propagation times of no less than 8 ms from mechanosensory hairs, campaniform sensilla(CS) and spurs of the distal leg segments. Impact of the same mechanical stimuli, even if very delicate, elicits strain that is transferred in less than 1 ms via the cuticle and stimulates proximal CS on the trochanter and femur. These propagate the afferents that code distal leg contact in about 1 ms to the CNS, where they connect mono- and polysynaptically to motoneurons of the depressor trochanteris system. The elicited excitatory postsynaptic potentials (EPSPs) contribute to rapid efferent commands, since single EPSPs already rise near firing threshold of the motoneurons. The short delays in this mechano-neuronal-muscular pathway from the tip of a leg to the neuromuscular synapses (5–7 ms) can very rapidly raise muscle tension in the trochanteral depressors at new leg contacts during locust landing and locomotion. At substrate contact, proximal leg CS contribute to very rapid motor responses supporting the body.
Polymorphism of red receptors: sensitivity spectra of proximal photoreceptors in the small white butterflyPieris rapae crucivora
Authors: Qiu Xudong , Arikawa Kentaro
Published: July 2003

The compound eye of the small white butterfly Pieris rapae crucivora contains three anatomically distinct types of ommatidia. They differ in pigmentation around the rhabdom, colour of tapetal reflection and violet light-induced autofluorescence, indicating physiological differences between them. We recently reported that the ommatidia are in fact spectrally heterogeneous: in the distal part of the tiered retina they contain different sets of the spectral receptors R1–4. This study examines whether the ommatidia in the proximal retinal tier also show the spectral heterogeneity for the receptors R5–8. We recorded the sensitivity spectra of the proximal photoreceptors, and subsequently injected the dye Alexafluor 568 into proximal photoreceptors, to localize the cell and identify the ommatidial type to which it belonged. We analysed 13 successfully labeled proximal photoreceptors, and found that the sensitivity spectrum of the proximal photoreceptors in types I and III ommatidia peaks at 620 nm, whereas that of type II ommatidia peaks at 640 nm. The difference in the sensitivity spectra can be explained by the anatomical characteristics of each ommatidial type. This is the first demonstration of red receptor polymorphism in insects. The polymorphic red receptor system most probably enhances contrast sensitivity and/or color discrimination in the long wavelength spectral region.
Swimming performance studies on the eastern Pacific bonitoSarda chiliensis, a close relative of the tunas (family Scombridae) Swimming performance studies on the eastern Pacific bonitoSarda chiliensis, a close relative of the tunas (family Scombridae) II. Kinematics
Authors: Dowis Hawkins J. , Sepulveda Chugey A. , Graham Jeffrey B. , Dickson Kathryn A.
Published: July 2003

The swimming kinematics of the eastern Pacific bonito Sarda chiliensis at a range of sustained speeds were analyzed to test the hypothesis that the bonito's swimming mode differs from the thunniform locomotor mode of tunas. Eight bonito (fork length FL 47.5±2.1 cm, mass 1.25±0.15 kg) (mean ± s.d.) swam at speeds of 50–130 cm s-1 at 18±2°C in the same temperature-controlled water tunnel that was used in previous studies of tunas. Kinematics variables, quantified from 60 Hz video recordings and analyzed using a computerized, two-dimensional motion analysis system, were compared with published data for similar sized tunas at comparable speeds. Bonito tailbeat frequency, tailbeat amplitude and stride length all increased significantly with speed. Neither yaw (6.0±0.6%FL) nor propulsive wavelength (120±65% fish total length) varied with speed,and there were no mass or body-length effects on the kinematics variables for the size range of bonitos used. Relative to similar sized yellowfin(Thunnus albacares) and skipjack (Katsuwonus pelamis) tunas at similar speeds, the bonito has a lower tailbeat frequency, a higher yaw and a greater stride length. The lateral displacement and bending angle of each intervertebral joint during a complete tailbeat cycle were determined for the bonito at a swimming speed of 90 cm s-1. The pattern of mean maximum lateral displacement (zmax) and mean maximum bending angle (βmax) along the body in the bonito differed from that of both chub mackerel Scomber japonicus and kawakawa tuna Euthynnus affinis; zmax was highest in the bonito. This study verifies that S. chiliensis is a carangiform swimmer and supports the hypothesis that the thunniform locomotor mode is a derived tuna characteristic associated with changes in this group's myotomal architecture. The finding that yaw and zmax were greater in the bonito than in both mackerels and tunas suggests that swimming kinematics in the bonito is not intermediate between that of tunas and mackerels, as would be predicted on the basis of morphological characteristics.
Swimming performance studies on the eastern Pacific bonitoSarda chiliensis, a close relative of the tunas (family Scombridae) I. Energetics
Authors: Sepulveda C. A. , Dickson K. A. , Graham J. B.
Published: July 2003

A large swim tunnel respirometer was used to quantify the swimming energetics of the eastern Pacific bonito Sarda chiliensis (tribe Sardini) (45–50 cm fork length, FL) at speeds between 50 and 120 cm s-1 and at 18±2°C. The bonito rate of oxygen uptake(V̇O2)–speed function is U-shaped with a minimum V̇O2 at 60 cm s-1, an exponential increase in V̇O2 with increased speed, and an elevated increase in V̇O2 at 50 cm s-1 where bonito swimming is unstable. The onset of unstable swimming occurs at speeds predicted by calculation of the minimum speed for bonito hydrostatic equilibrium (1.2 FL s-1). The optimum swimming speed (Uopt) for the bonito at 18±2°C is approximately 70 cm s-1 (1.4 FL s-1) and the gross cost of transport at Uopt is 0.27 J N-1m-1. The mean standard metabolic rate (SMR), determined by extrapolating swimming V̇O2 to zero speed, is 107±22 mg O2 kg-1 h-1. Plasma lactate determinations at different phases of the experiment showed that capture and handling increased anaerobic metabolism, but plasma lactate concentration returned to pre-experiment levels over the course of the swimming tests. When adjustments are made for differences in temperature,bonito net swimming costs are similar to those of similar-sized yellowfin tuna Thunnus albacares (tribe Thunnini), but the bonito has a significantly lower SMR. Because bonitos are the sister group to tunas, this finding suggests that the elevated SMR of the tunas is an autapomorphic trait of the Thunnini.
Evolved patterns and rates of water loss and ion regulation in laboratory-selected populations ofDrosophila melanogaster
Authors: Folk Donna G. , Bradley Timothy J.
Published: July 2003

We have investigated water loss from, and ion regulation within, the hemolymph and tissues of five replicate populations of Drosophila melanogaster that have undergone laboratory selection for enhanced desiccation resistance (i.e. the D populations). We compared the patterns and rates of water loss and the ion content of the D populations prior to and during desiccation with those of five replicate control (C) populations. The net rate of water loss in the C flies was ∼3-fold greater than that of the D flies during the initial hours of desiccation. After 8 h, both C and D flies had considerable reductions in water loss rate. During 24 h of desiccation,the tissue water content of the D flies was conserved, while the C flies were faced with significant loss of tissue water during the initial 8 h of desiccation. We propose that the increased hemolymph volume of the D flies plays a role in buffering water loss from the tissues. One consequence of this large hemolymph pool is that the hydrated D flies contained approximately seven times more sodium within the hemolymph than did the hydrated C flies. Despite a continual loss of hemolymph volume in the D flies during lengthy periods of desiccation, the sodium content of the hemolymph was significantly reduced only during a single event. We provide evidence that the regulation of extracellular sodium, as well as chloride, occurred via excretory processes during desiccation. In addition, whole-body potassium was not significantly decreased in the D flies during desiccation but was reduced(i.e. excreted) in the C flies; hence, we suggest that the potassium content paralleled tissue water level.
Regulation of urine reprocessing in the maintenance of sodium and water balance in the terrestrial Christmas Island red crabGecarcoidea natalisinvestigated under field conditions
Authors: Morris Stephen , Ahern Mark D.
Published: July 2003

Land crabs produce isosmotic urine but reduce salt loss by reabsorbing salt via the gills to produce a dilute excretory fluid (P). This branchial salt reclamation is regulated in response to changes in dietary salt availability. The regulation of branchial Na reabsorption and osmotic status was investigated in the terrestrial crab Gecarcoidea natalis on Christmas Island. Confinement within field enclosures had no general effect on salt and water balance compared with crabs free in the rainforest but there were seasonal effects. Extracellular fluid volume was 27.9% body mass during the wet season but only 22.7% in the dry season. Urine production was 53 ml kg-1 day-1 in the dry season but 111 ml kg-1day-1 in the wet season, while water flux rates were 140 ml kg-1 day-1 and 280 ml kg-1 day-1,respectively. Serotonin but not dopamine increased urine production by at least 16% but only during the dry season when rates were seasonally lowered. Crabs acclimated to drinking 50% seawater increased haemolymph osmotic pressure and downregulated branchial reabsorption of salt. Net Na flux(Jnet) and unidirectional Na influx(Jin) were investigated in branchial perfusion experiments. In red crabs acclimated to drinking freshwater, Jin, Jnet and the activity of the Na+/K+-ATPase were increased by serotonin, indicating that the increase of sodium absorption was due to a stimulation of the ATPase. Red crabs drinking 50% seawater reduced Jnet primarily due to increased passive loss (Jout), since both Jin and Na+/K+-ATPase were unchanged. Serotonin and dopamine abolished the increased diffusive loss and re-established Jnet with no change in Jin. G. natalis exhibits different regulatory systems. Branchial salt uptake can be adjusted via the leak component when adequate salt is available but also by stimulated active uptake under diluting conditions. The gills are important sites of ion pumping in euryhaline aquatic crabs, and the upregulation of Jnet in red crabs is reminiscent of that in marine crabs. Serotonergic stimulation of branchial uptake, independent of cAMP, and hormonally modulated ion leakage are presently unique to terrestrial species.
Geographic variation in energy storage and physiological responses to freezing in the gray treefrogsHyla versicolorandH. chrysoscelis
Authors: Irwin Jason T. , Lee Jr Richard E.
Published: July 2003

The physiological responses supporting freeze tolerance in anurans are well known, but the evolution of this trait remains little studied. This is the first common-garden study of geographic variation in cryoprotective responses to freezing and the degree of freeze tolerance. We studied the gray treefrogs(Hyla versicolor and H. chrysoscelis) from sympatric sites in Minnesota, Indiana and Missouri. Patterns in the literature suggest that northern frogs produce more cryoprotectants upon freezing, but we found no geographic variation in cryoprotective responses or degree of freeze tolerance. The concentration of glucose produced upon freezing was higher than previously reported for this species (liver: 475 μmol g–1dry mass). Unfrozen frogs had high levels of glycerol (liver: approx. 150μmol g–1 dry mass), and did not produce more upon freezing. Liver glycogen content (concentration multiplied by liver mass) was highest in frogs from Minnesota and Missouri, and was stored in preference to lipids in Minnesota frogs, possibly to provide energy for the longer northern winters. Minnesota frogs accumulated more ice (53.4±1.8%) after freezing to–2.5°C than Indiana frogs (45.5±3.3%). The two species differed in body size but not in any of the physiological parameters measured. We conclude that these populations show no adaptive variation in freeze tolerance and that comparing published studies may be misleading because of different acclimation and feeding regimes.
Dynamic flight stability in the desert locustSchistocerca gregaria
Authors: Taylor Graham K. , Thomas Adrian L. R.
Published: July 2003

Here we provide the first formal quantitative analysis of dynamic stability in a flying animal. By measuring the longitudinal static stability derivatives and mass distribution of desert locusts Schistocerca gregaria, we find that their static stability and static control responses are insufficient to provide asymptotic longitudinal dynamic stability unless they are sensitive to pitch attitude (measured with respect to an inertial or earth-fixed frame)as well as aerodynamic incidence (measured relative to the direction of flight). We find no evidence for a `constant-lift reaction', previously supposed to keep lift production constant over a range of body angles, and show that such a reaction would be inconsequential because locusts can potentially correct for pitch disturbances within a single wingbeat. The static stability derivatives identify three natural longitudinal modes of motion: one stable subsidence mode, one unstable divergence mode, and one stable oscillatory mode (which is present with or without pitch attitude control). The latter is identified with the short period mode of aircraft, and shown to consist of rapid pitch oscillations with negligible changes in forward speed. The frequency of the short period mode (approx. 10 Hz) is only half the wingbeat frequency (approx. 22 Hz), so the mode would become coupled with the flapping cycle without adequate damping. Pitch rate damping is shown to be highly effective for this purpose — especially at the small scales associated with insect flight — and may be essential in stabilising locust flight. Although having a short period mode frequency close to the wingbeat frequency risks coupling, it is essential for control inputs made at the level of a single wingbeat to be effective. This is identified as a general constraint on flight control in flying animals.
Comparative studies of high performance swimming in sharks II. Metabolic biochemistry of locomotor and myocardial muscle in endothermic and ectothermic sharks
Authors: Bernal D. , Smith D. , Lopez G. , Weitz D. , Grimminger T. , Dickson K. , Graham J. B.
Published: July 2003

Metabolic enzyme activities in red (RM) and white (WM) myotomal muscle and in the heart ventricle (HV) were compared in two lamnid sharks (shortfin mako and salmon shark), the common thresher shark and several other actively swimming shark species. The metabolic enzymes measured were citrate synthase(CS), an index of aerobic capacity, and lactate dehydrogenase (LDH), an index of anaerobic capacity. WM creatine phosphokinase (CPK) activity, an index of rapid ATP production during burst swimming, was also quantified. Enzyme activities in RM, WM and HV were similar in the two lamnid species. Interspecific comparisons of enzyme activities at a common reference temperature (20°C) show no significant differences in RM CS activity but higher CS activity in the WM and HV of the lamnid sharks compared with the other species. For the other enzymes, activities in lamnids overlapped with those of other shark species. Comparison of the HV spongy and compact myocardial layers in mako, salmon and thresher sharks reveals a significantly greater spongy CS activity in all three species but no differences in LDH activity. Adjustment of enzyme activities to in vivo RM and WM temperatures in the endothermic lamnids elevates CS and LDH in both tissues relative to the ectothermic sharks. Thus, through its enhancement of both RM and WM enzyme activity, endothermy may be an important determinant of energy supply for sustained and burst swimming in the lamnids. Although lamnid WM is differentially warmed as a result of RM endothermy, regional differences in WM CS and LDH activities and thermal sensitivities (Q10 values) were not found. The general pattern of the endothermic myotomal and ectothermic HV muscle metabolic enzyme activities in the endothermic lamnids relative to other active, ectothermic sharks parallels the general pattern demonstrated for the endothermic tunas relative to their ectothermic sister species. However, the activities of all enzymes measured are lower in lamnids than in tunas. Relative to lamnids, the presence of lower WM enzyme activities in the thresher shark (which is in the same order as the lamnids, has an RM morphology similar to that of the mako and salmon sharks and may be endothermic) suggests that other factors, such as behavior and swimming pattern, also affect shark myotomal organization and metabolic function.
Molecular diagnostics in routine practice: quality issues and application to complex disease
Authors: Ferns Gordon A.A. , O'Dowd David , Wark Gwen , Collins Nadine
Published: July 2003

The public already has concerns about 'the new genetics', and it is clear that confidence can only be maintained by scrupulous attention to quality. Standards can be improved by harmonization of methods, discouraging poor practice and using appropriate internal and external quality controls. At present, despite the profound implications of genetic test results, few genetic tests are subject to sufficient scrutiny. The Human Genome Project will lead to the identification of numerous genetic variations contributing to multifactorial diseases, and high-throughput technologies will permit the generation of disease-susceptibility profiles. Clinical laboratories will need to develop the wherewithal to handle these data and present them in a format that is clinically useful.
Pitfalls in the measurement of some intermediary metabolites
Authors: Carragher F. M. , Bonham J. R. , Smith J. M.
Published: July 2003

Lactate, pyruvate, 3-hydroxybutyrate, acetoacetate and non-esterified fatty acids are intermediary metabolites that normally occur in blood and all have a vital role in energy metabolism. Their relative concentrations are an expression of nutritional balance, providing a snapshot of the metabolic disturbances arising in a patient. They are therefore invaluable tools to investigate intermediary metabolism in health and disease, particularly in the fields of diabetes and inherited metabolic disease. Although the analysis of these key metabolites would appear to be straightforward, with apparently simple assays widely available, there are many pitfalls in their measurement. To compound this difficulty there is limited advice available for the optimum pre-analytical and analytical aspects of their measurement and also for the interpretation of results. In this personal view, we aim to highlight a number of these problems, such as sample stability, assay interference and availability of reference ranges, with the aim of producing guidelines for the measurement and interpretation of these metabolites.
Anabolic steroids in sport: biochemical, clinical and analytical perspectives
Authors: Kicman Andrew T. , Gower D. B.
Published: July 2003

International Olympic Committee accredited laboratories play a key role in upholding the principle of fair play and innate ability, as desired by the majority of sports competitors and spectators. Not only does doping damage the image of sport, but it can also be harmful to the individual. The great majority of samples test negative but, when an adverse finding is declared, the analytical data must be of a sufficiently high standard to withstand legal challenges by third parties. The most widely misused performance-enhancing drugs are the anabolic-androgenic steroids, commonly referred to as 'anabolic steroids'. This review attempts to address the complex issues concerning anabolic steroids in sport by considering the clinical, biochemical and analytical perspectives.
Towards complete and accurate reporting of studies of diagnostic accuracy: the STARD initiative
Authors: Bossuyt Patrick M. , Reitsma Johannes B. , Bruns David E. , Gatsonis Constantine A. , Glasziou Paul P. , Irwig Les M. , Lijmer Jeroen G. , Moher David , Rennie Drummond , de Vet Henrica C.W.
Published: July 2003

Background: To improve the accuracy and completeness of reporting of studies of diagnostic accuracy in order to allow readers to assess the potential for bias in a study and to evaluate the generalizability of its results.

Methods: The Standards for Reporting of Diagnostic Accuracy (STARD) steering committee searched the literature to identify publications on the appropriate conduct and reporting of diagnostic studies and extracted potential items into an extensive list. Researchers, editors and members of professional organizations shortened this list during a 2-day consensus meeting with the goal of developing a checklist and a generic flow diagram for studies of diagnostic accuracy.

Results: The search for published guidelines regarding diagnostic research yielded 33 previously published checklists, from which we extracted a list of 75 potential items. At the consensus meeting, participants shortened the list to 25 items, using evidence on bias whenever available. A prototypical flow diagram provides information about the method of patient recruitment, the order of test execution and the numbers of patients undergoing the test under evaluation, the reference standard or both.

Conclusions: Evaluation of research depends on complete and accurate reporting. If medical journals adopt the checklist and the flow diagram, the quality of reporting of studies of diagnostic accuracy should improve to the advantage of the clinicians, researchers, reviewers, journals and the public.