bluuebunny/crossref_metadata_2025_split huggingface dataset:
Arg2074Cys missense mutation in the C2 domain of factor V causing moderately severe factor V deficiency: molecular characterization by expression of the recombinant protein
Authors: Duga Stefano , Montefusco Maria Claudia , Asselta Rosanna , Malcovati Massimo , Peyvandi Flora , Santagostino Elena , Mannucci Pier Mannuccio , Tenchini Maria Luisa 
Published: December 2002

AbstractFactor V (FV) deficiency is a rare bleeding disorder whose genetic basis has been described in a relatively small number of cases. Among a total of 12 genetic defects reported in severely or moderately severe deficient patients, 3 were missense mutations and in no case was the mechanism underlying the deficiency explored at the molecular level. In this study, a homozygous missense mutation at cDNA position 6394 in exon 23 of the FV gene was identified in a 22-year-old Italian patient. This mutation causes the replacement of arginine 2074 with a cysteine residue (Arg2074Cys) in the C2 domain of the protein. The effect of the Arg2074Cys mutation on FV secretion, stability, and activity was investigated. Site-directed mutagenesis of FV cDNA was used to introduce the identified mutation, and wild-type as well as mutant FV proteins were expressed by transient transfection in COS-1 cells. An enzyme immunoassay detected low FV antigen levels both in the conditioned media of cells expressing the mutant protein and in cell lysates. Metabolic labeling and pulse-chase experiments confirmed that the mutation caused an impaired secretion of FV associated with rapid intracellular degradation. In addition, evaluation of wild-type and mutant coagulant activity demonstrated that the FV molecules carrying the Arg2074Cys mutation have reduced activity. These findings, beside confirming the structural and functional importance of the arginine 2074 residue, demonstrate that its substitution with a cysteine impairs both FV secretion and activity.
Mac-1 (CD11b/CD18) is crucial for effective Fc receptor–mediated immunity to melanoma
Authors: van Spriel Annemiek B. , van Ojik Heidi H. , Bakker Annie , Jansen Marco J. H. , van de Winkel Jan G. J. 
Published: December 2002

AbstractAntibody-reliant destruction of tumor cells by immune effector cells is mediated by antibody-dependent cellular cytotoxicity, in which Fc receptor (FcR) engagement is crucial. This study documents an important role for the β2 integrin Mac-1 (CD11b/CD18) in FcR-mediated protection against melanoma. CD11b-deficient mice, those that lack Mac-1, were less protected by melanoma-specific monoclonal antibody TA99 than wild-type (WT) mice. Significantly more lung metastases and higher tumor loads were observed in Mac-1−/− mice. Histologic analyses revealed no differences in neutrophil infiltration of lung tumors between Mac-1−/− and WT mice. Importantly, Mac-1−/−phagocytes retained the capacity to bind tumor cells, implying that Mac-1 is essential during actual FcR-mediated cytotoxicity. In summary, this study documents Mac-1 to be required for FcR-mediated antimelanoma immunity in vivo and, furthermore, supports a role for neutrophils in melanoma rejection.
GA-binding protein (GABP) and Sp1 are required, along with retinoid receptors, to mediate retinoic acid responsiveness of CD18 (β2 leukocyte integrin): a novel mechanism of transcriptional regulation in myeloid cells
Authors: Bush Thomas S. , St. Coeur Michele , Resendes Karen K. , Rosmarin Alan G. 
Published: December 2002

AbstractCD18 (β2 leukocyte integrin) is transcriptionally regulated in myeloid cells, but the mechanisms that increase its expression in response to retinoic acid (RA) have not been defined. The CD18 promoter was activated by RA treatment in stably transfected U937 myeloid cells. We identified a retinoic acid response element (RARE) that lies nearly 900 nucleotides upstream of the CD18 transcriptional start site that was bound by the RA receptors, retinoic acid receptor (RAR) and retinoic X receptor (RXR). This RARE accounted for one half of the RA responsiveness of CD18. However, unexpectedly, one half of the dynamic response to RA was mediated by the 96-nucleotide CD18 minimal promoter, which lacks a recognizable RARE. Binding sites for the ets transcription factor, GA-binding protein (GABP), and Sp1 were required for full RA responsiveness of both the CD18 minimal promoter and the full-length promoter. The ets sites conferred RA responsiveness on an otherwise unresponsive heterologous promoter, and RA responsiveness was directly related to the number of ets sites. The transcriptional coactivator p300/CBP physically interacted with GABP in vivo, and p300 increased the responsiveness of the CD18 promoter to RA. These studies demonstrate a novel role for non-RAR transcription factors in mediating RA activation in myeloid cells. They support the concept that transcription factors other than RARs are required for RA-activated gene expression. We hypothesize that a multiprotein complex—an enhanceosome—that includes GABP, other transcription factors, and coactivators, dynamically regulates CD18 expression in myeloid cells.
Prey-capture success revealed by echolocation signals in pipistrelle bats (Pipistrellus pygmaeus)
Authors: Surlykke Annemarie , Futtrup Vibeke , Tougaard Jakob 
Published: December 2002

SUMMARYThree Pipistrellus pygmaeus bats were trained to capture prey on the wing while flying in the laboratory. The bats' capture behaviour and capture success were determined and correlated with acoustic analyses of post-buzz echolocation signals. Three acoustic parameters revealed capture success: in case of success, post-buzz pauses (pbP) were longer, interpulse intervals (IPI) of the post-buzz signals were longer and, most notably, the spectra of the echolocation signals showed a number of notches that were absent after unsuccessful attempts. If the bats touched the prey without seizing it, pbP was significantly increased, but by less than was seen following a successful capture. Thus, acoustic recordings can be used to determine the outcome of a capture attempt with 72-75% correct using IPI or pbP, and with 78% correct using notches. Even more trials (&gt;85%) were classified correctly by using the first canonical discriminant factor from principal component analysis combining the three parameters. Four types of prey were used, of 7-22 mm length and 7-240 mg mass. After successful captures, interpulse intervals, post-buzz pause and notches all depended on prey type, but not in a way that was systematically related to size, indicating that acoustic parameters cannot reveal prey size.
Tension sensitivity of the heart pacemaker neurons in the isopod crustaceanLigia pallasii
Authors: Sakurai Akira , Wilkens Jerrel L. 
Published: December 2002

SUMMARYIn the crustacean neurogenic heart, the cardiac ganglion (CG) acts as a peripherally located central pattern generator (CPG) by producing rhythmic motor output that initiates the heartbeat. In the isopod Ligia, the CG consists of six electrically coupled neurons that all function both as endogenous oscillators and as glutamatergic motoneurons innervating heart muscle. In the present study, we present several lines of evidence to suggest that the CG neurons are sensitive to passive stretch and active tension of the heart muscle. Stretching the heart wall caused a sustained decrease in the burst frequency of the CG neuron. Releasing from the stretch caused a rebound increase in burst frequency above the control rate. A brief stretch (200-300 ms duration) caused either phase advance or phase delay of the following CG bursts, depending on the timing at which the stretch was applied. Repeated brief stretches could entrain the CG bursts to either higher or lower frequencies than the free-run burst frequency. Intracellular recording from one of the CG neurons revealed that it exhibited hyperpolarization during the stretch. The stretch-induced hyperpolarization was followed by a burst discharge upon release from the stretch. With increased stretch amplitude, the amplitude of hyperpolarizing response increased and the timing of the following burst was advanced. When the myogenic activity of the heart muscle was pharmacologically isolated from the ganglionic drive by applying a glutamatergic antagonist, Joro spider toxin (JSTX), the spontaneous muscle contraction caused a hyperpolarizing deflection in the CG neuron. Under specific conditions made by JSTX and tetrodotoxin, the CG burst became entrained to the myogenic rhythm. These results suggest that the Ligia CG neurons have tension sensitivity in addition to their pacemaker and motoneuronal functions. Such multifunctional neurons may form a single neuron reflex arc inside the heart.
Proliferation of myogenic progenitor cells following feeding in the sub-antarctic notothenioid fishHarpagifer bispinis
Authors: Brodeur Julie C. , Calvo Jorge , Johnston Ian A. 
Published: December 2002

SUMMARYFeeding metabolism and the activation of myogenic progenitor cells were investigated in the fast myotomal muscle of the sub-Antarctic fish Hapagifer bispinis acclimatized to either simulated summer (10°C; 18 h:6 h light:dark) or simulated winter (5°C; 6 h:18 h light:dark) conditions. Ingestion of a single meal equivalent to 10% and 15% of body mass in simulated winter and summer groups, respectively, resulted in an average 2.6-fold and 3.6-fold increase in oxygen consumption, declining to 75% of peak values after 63 h and 46 h. In fasted individuals, the number of myogenic progenitor cells, identified by the expression of c-met, was not significantly different between simulated summer and winter fish, representing 6.6% and 5.8% of total myonuclei, respectively. However, the number of cells expressing myogenin was higher whereas the expression of MyoD was lower in winter than in summer groups. The ingestion of a single meal under winter and summer treatment regimes resulted in a significant increase in the number of cells expressing MyoD (51% and 111%) and PCNA (88% and 140%, respectively). This was followed by an increase in the abundance of c-met (74 and 85%) and myogenin (42 and 97%, respectively) positive cells, indicating the production of new myogenic progenitor cells and the commitment to differentiation of a number of them. These results show that the proliferation of myogenic progenitor cells can be induced by feeding in teleost fishes and that temperature and photoperiod influence the expression of myogenic regulatory factors.
Differential expression of voltage-sensitive K+ and Ca2+ currents in neurons of the honeybee olfactory pathway
Authors: Grünewald Bernd 
Published: December 2002

SUMMARYIn order to understand the neuronal processes underlying olfactory learning, biophysical properties such as ion channel activity need to be analysed within neurons of the olfactory pathway. This study analyses voltage-sensitive ionic currents of cultured antennal lobe projection neurons and mushroom body Kenyon cells in the brain of the honeybee Apis mellifera. Rhodamine-labelled neurons were identified in vitro prior to recording, and whole-cell K+ and Ca2+ currents were measured. All neurons expressed transient and sustained outward K+ currents, but Kenyon cells expressed higher relative amounts of transient A-type K+ (IK,A) currents than sustained delayed rectifier K+ current (IK,V). The current density of the IK,V was significantly higher in projection neurons than in Kenyon cells. The voltage-dependency of K+ currents at positive membrane potentials was linear in Kenyon cells, but N-shaped in projection neurons. Blocking of voltage-sensitive Ca2+ currents transformed the N-shaped voltage-dependency into a linear one, indicating activation of calcium-dependent K+ currents (IK,Ca). The densities of currents through voltage-sensitive Ca2+ channels did not differ between the two neuron classes and the voltage-dependency of current activation was similar. Projection neurons thus express higher calcium-dependent K+ currents. These analyses revealed that the various neurons of the honeybee olfactory pathway in vitro have different current phenotypes, which may reflect functional differences between the neuron types in vivo.
Metabolic plasticity and critical temperatures for aerobic scope in a eurythermal marine invertebrate (Littorina saxatilis, Gastropoda: Littorinidae) from different latitudes
Authors: Sokolova Inna M. , Pörtner Hans-Otto 
Published: December 2002

SUMMARYEffects of latitudinal cold adaptation and cold acclimation on metabolic rates and aerobic scope were studied in the eurythermal marine gastropod Littorina saxatilis from temperate North Sea and sub-arctic White Sea areas. Animals were acclimated for 6-8 weeks at control temperature (13°C) or at 4°C, and their respiration rates were measured during acute temperature change (1-1.5°C h-1) in a range between 0°C and 32°C. In parallel, the accumulation of anaerobic end products and changes in energy status were monitored. Starting from 0°C, aerobic metabolic rates of L. saxatilis rose quickly with increasing temperatures up to a point at or slightly above the respective acclimation temperature. Beyond this value, thermal sensitivity of oxygen consumption rate (V̇O2) greatly decreased in a wide, 15°C range of experimental temperatures. This change in metabolic regulation was also reflected in the activation energy of aerobic metabolism (Ea), which was approximately seven times lower at temperatures above Arrhenius breakpoint temperatures (ABTs) than at temperatures below ABTs. Warming progressively led to a discrepancy between energy demand and energy production, as demonstrated by a decrease in the levels of high-energy phosphates [phosho-L-arginine (PLA) and ATP], and resulted in the onset of anaerobiosis at critically high temperatures, indicating a limitation of aerobic scope. The comparison of aerobic and anaerobic metabolic rates in L. saxatilis in air and water suggests that the heat-induced onset of anaerobiosis is due to the insufficient oxygen supply to tissues at high temperatures. Cold acclimation led to an increase in aerobic metabolic rates and a considerable downward shift of the upper critical temperature in North Sea L. saxatilis but not in White Sea L. saxatilis. Limited metabolic plasticity in response to cold acclimation in sub-arctic White Sea snails as compared with their temperate North Sea counterparts suggests that metabolic depression occurs during overwintering under the more extreme winter conditions at the White Sea.
Fluid mechanics produces conflicting, constraints during olfactory navigation of blue crabs,Callinectes sapidus
Authors: Weissburg M. J. , James C. P. , Smee D. L. , Webster D. R. 
Published: December 2002

SUMMARYForaging blue crabs must respond to fluid forces imposed on their body while acquiring useful chemical signals from turbulent odor plumes. This study examines how blue crabs manage these simultaneous demands. The drag force, and hence the cost of locomotion, experienced by blue crabs is shown to be a function of the body orientation angle relative to the flow. Rather than adopting a fixed orientation that minimizes the drag, blue crabs decrease their relative angle (increase drag) when odor is present in low speed flow, while assuming a drag-minimizing posture under other conditions. The motivation for crabs to adopt an orientation with larger drag appears to relate to their ability to acquire chemical signal information for odor tracking. In particular, when orienting at a smaller angle relative to the flow direction, more concentrated odor filaments arrive at the antennules to mediate upstream movement, allowing a more useful bilateral comparison between the appendage chemosensors to be made. Blue crabs respond to conflicting demands by weighting the degree of drag minimization in proportion to the potential magnitude of the drag cost and the potential benefit of acquiring chemosensory cues. Higher flow velocity magnifies the locomotory cost of a high drag posture, thus in swift flows crabs minimize drag and sacrifice their ability to acquire olfactory cues.
Rheotaxis and prey detection in uniform currents by Lake Michigan mottled sculpin(Cottus bairdi)
Authors: Kanter Max J. , Coombs Sheryl 
Published: December 2002

SUMMARYLake Michigan mottled sculpin, Cottus bairdi, exhibit a lateral-line mediated, unconditioned orienting response, which is part of the overall prey capture behavior of this species and can be triggered in visually deprived animals by both live (e.g. Daphnia magna) and artificial (e.g. chemically inert vibrating sphere) prey. However, the extent to which background water motions (e.g. currents) might mask the detection of biologically significant stimuli like these is almost entirely unknown, despite the fundamental nature and importance of this question. To examine this question, the orienting response of mottled sculpin was used to measure threshold sensitivity to a nearby artificial prey (a 50 Hz vibrating sphere) as a function of background noise level (unidirectional currents of different flow velocities). Because many fish show unconditioned rheotaxis to uniform currents, we also measured the fish's angular heading relative to the oncoming flow in the absence of the signal. Frequency distributions of fish headings revealed positive rheotaxis to flows as low as 4 cm s-1 and an increasing degree of alignment with the oncoming flow as a function of increasing flow velocity. Sculpin positioned in the upstream direction were able to detect relatively weak signals (estimated to be approx. 0.001-0.0001 peak—peak cm s-1 at the location of the fish) in the presence of strong background flows (2-8 cm s-1), and signal levels at threshold increased by less than twofold for a fourfold increase in flow velocity. These results are consistent with the idea that lateral line canals behave as high-pass filters to effectively reject low frequency noises such as those caused by slow d.c. currents.
Transient peripheral warming accompanies the hypoxic metabolic response in the golden-mantled ground squirrel
Authors: Tattersall Glenn J. , Milsom William K. 
Published: December 2002

SUMMARY
The hypoxic metabolic response of mammals involves a reversible metabolic suppression, possibly brought about by a reduction in the body temperature set-point. In the present study we tested the hypothesis that this is accompanied by a transient increase in heat loss that facilitates the decline in body temperature and metabolic rate. Peripheral heat distribution was assessed using infrared thermography to measure the surface temperatures of the golden-mantled ground squirrel at three different ambient temperatures (10, 22 and 30°C). During early hypoxic exposure, surface temperatures increased dramatically in the feet, ears and nose, and this increase was more dramatic and prolonged at 22°C than at the other two temperatures. These increases were associated with a fall in metabolic rate. Following this initial increase, surface temperatures decreased back to control values, and at 10°C, the surface temperatures of the eyes and body decreased below normoxic levels. Subsequent normoxic recovery was not accompanied by transient changes in surface temperatures, despite large increases in metabolic rate associated with post-hypoxic shivering and thermogenesis. The temporal changes in surface temperature suggest that peripheral blood flow is initially increased during hypoxia, shifting heat away from the core to the periphery and thus facilitating cooling. These results are consistent with the hypothesis that hypoxia leads to a regulated fall in body temperature.
Amino acids modulate ion transport and fluid secretion by insect Malpighian tubules
Authors: Hazel Matthew H. , Ianowski Juan P. , Christensen Robert J. , Maddrell Simon H. P. , O'Donnell Michael J. 
Published: December 2002

SUMMARYInsect haemolymph typically contains very high levels of free amino acids. This study shows that amino acids can modulate the secretion of ions and water by isolated Malpighian tubules of Rhodnius prolixus and Drosophila melanogaster. Secretion rates of Rhodnius tubules in amino-acid-free saline increase after addition of serotonin to a peak value, then slowly decline to a plateau. Addition of glutamine, glutamate or aspartate to such tubules increases secretion rates dramatically relative to the controls in amino-acid-free saline, and these increases are sustained for 1-2h. Seven other amino acids have more modest stimulatory effects, whereas lysine and arginine are inhibitory. Secreted fluid pH and Na+ concentration increase and K+ concentration decreases in response to glutamine. Pre-incubation of unstimulated tubules in saline solutions containing amino acids followed by stimulation with serotonin in amino-acid-free saline shows that the effects of amino acids far outlast the duration of exposure to them. Amino acids do not appear to be important as metabolites in Rhodnius tubules, nor do they act to draw significant amounts of water into the lumen by osmosis. Significant stimulation of fluid secretion can be achieved by physiological levels of particular amino acids, whereas those amino acids that inhibit fluid secretion only do so at concentrations much above those at which they occur naturally in the haemolymph. Secretion rates of unstimulated or stimulated Drosophila tubules are increased by pre-incubation in saline solutions containing glutamine or methionine or by continuous exposure to glutamine, methionine or tyrosine. Cysteine dramatically inhibited fluid secretion by Drosophila tubules, but only at concentrations well above the physiological range. We suggest that the amino acids probably function as compatible intracellular osmolytes that are necessary for sustained secretion at high rates by the Malpighian tubules.
Energetics of diving in macaroni penguins
Authors: Green J. A. , Butler P. J. , Woakes A. J. , Boyd I. L. 
Published: December 2002

SUMMARYHeart rate (fH), abdominal temperature (Tab) and diving depth were measured in thirteen free-ranging breeding female macaroni penguins. Measurement of these variables allowed estimation of the mass-specific rate of oxygen consumption (V̇O2) while diving and investigation of the physiological adjustments that might facilitate the diving behaviour observed in this species. In common with other diving birds, macaroni penguins showed significant changes in fH associated with diving, and these variables accounted for 36% of the variation in dive duration. When V̇O2 was calculated for dives of different durations, 95.3% of dives measured were within the calculated aerobic dive limit (cADL) for this species. Mean fH for all complete dive cycles was 147±6 beats min-1. When this fH is used to estimate V̇O2 of 26.2±1.4 ml min-1 kg-1 then only 92.8% of dives measured were within the cADL. Significant changes in abdominal temperature were not detected within individual dives, though the time constant of the measuring device used may not have been low enough to record these changes if they were present. Abdominal temperature did decline consistently during bouts of repeated diving of all durations and the mean decrease in Tab during a diving bout was 2.32±0.2°C. There was a linear relationship between bout duration and the magnitude of this temperature drop. There was no commensurate increase in dive duration during dive bouts as Tab declined, suggesting that macaroni penguins are diving within their physiological limits and that factors other than Tab are important in determining the duration of dives and dive bouts. Lowered Tab will in turn facilitate lower metabolic rates during diving bouts, but it was not possible in the present study to determine the importance of this energy saving and whether it is occurs actively or passively.