bluuebunny/crossref_metadata_2025_split huggingface dataset:
Disulfide bond assignment, lipid transfer activity and secondary structure of a 7‐kDa plant lipid transfer protein, LTP2
Authors: Douliez Jean‐Paul , Pato Christine , Rabesona Hanitra , Mollé Daniel , Marion Didier 
Published: March 2003

The 7‐kDa lipid transfer proteins, LTP2s, share some amino‐acid sequence similarities with the 9‐kDa isoforms, LTP1s. Both proteins display an identical cysteine motif and, in this regard, LTP2s have been classified as lipid transfer proteins. However, in contrast with LTP1s, no data are available on their structure, cysteine pairings, lipid transfer and lipid binding properties. We reported on the isolation of two isoforms of 7‐kDa lipid transfer protein, LTP2, from wheat seeds and showed for the first time that they indeed display lipid transfer activity. Trypsin and chymotrypsin digestions of the native LTP2 afforded the sequence of both isoforms and assignment of disulfide bonds. The cysteine pairings, Cys10–Cys24, Cys25–Cys60, Cys2–Cys34, Cys36–Cys67, revealed a mismatch at the Cys34‐X‐Cys36 motif of LTP2 compared to LTP1. Moreover, the secondary structure as determined by circular dichroism suggested an identical proportion of α helices, β sheets and random coils. By analogy with the structure of the LTP1, we discussed what structural changes are required to accommodate the LTP2 disulfide pattern.
Tyrosine phosphorylation‐dependent activation of NF‐κB
Authors: Livolsi Antonia , Busuttil Valère , Imbert Véronique , Abraham Robert T. , Peyron Jean‐François 
Published: March 2003

Phosphorylation of the N‐terminal domain of IκB inhibitory subunits induces activation of the transcription factor NF‐κB. Although serine phosphorylation has been shown to induce ubiquitination and subsequent proteasome‐mediated degradation of IκB‐α, little is known about the mechanisms that lead to release of active NF‐κB in T cells as a consequence of tyrosine phosphorylation of IκB‐α[Imbert, V., Rupec, R.A., Livolsi, A., Pahl, H.L., Traenckner, B.M., Mueller‐Dieckmann, C., Farahifar, D., Rossi, B., Auberger, P., Baeuerle, P. & Peyron, J.F. (1996) Cell86, 787–798]. The involvement of the tyrosine kinases p56lck and ZAP‐70 in this reaction is demonstrated here using specific pharmacological inhibitors and Jurkat mutants unable to express these kinases. Although the inhibitors prevented both pervanadate‐induced phosphorylation of IκB‐α on Tyr42 and NF‐κB activation, we observed that, in p56lck‐deficient Jurkat mutants, NF‐κB could still associate with IκB‐α despite phosphorylation on Tyr42. Furthermore, the SH2 domain of p56lck appeared to be required for pervanadate‐induced NF‐κB activation but not for Tyr42 phosphorylation. These results show that p56lck and ZAP‐70 are key components of the signaling pathway that leads to phosphotyrosine‐dependent NF‐κB activation in T cells and confirm that tyrosine kinases must control at least two different steps to induce activation of NF‐κB. Finally, we show that H2O2, which stimulates p56lck and ZAP‐70 in T cells, is an activator of NF‐κB through tyrosine phosphorylation of IκB‐α.
A new structural type for Haemophilus influenzae lipopolysaccharide
Authors: Månsson Martin , Bauer Sebastian H. J. , Hood Derek W. , Richards James C. , Moxon E. Richard , Schweda Elke K. H. 
Published: March 2003

Structural elucidation of the sialylated lipopolysaccharide (LPS) of non‐typeable Haemophilus influenzae (NTHi) strain 486 has been achieved by the application of high‐field NMR techniques and ESI‐MS along with composition and linkage analyses on O‐deacylated LPS and oligosaccharide samples. It was found that the LPS contains the common element of H. influenzae, l‐α‐d‐Hepp‐(1→2)‐[PEtn→6]‐l‐α‐d‐Hepp‐(1→3)‐[β‐d‐Glcp‐(1→4)]‐l‐α‐d‐Hepp‐(1→5)‐[PPEtn→4]‐α‐Kdop‐(2→6)‐Lipid A, but instead of glycosyl substitution of the terminal heptose residue (HepIII) at the O2 position observed in other H. influenzae strains, HepIII is chain elongated at the O3 position by either lactose or sialyllactose (i.e. α‐Neu5Ac‐(2→3)‐β‐d‐Galp‐(1→4)‐β‐d‐Glcp). The LPS is substituted by an O‐acetyl group linked to the O2 position of HepIII and phosphocholine (PCho) which was located at the O6 position of a terminal α‐d‐Glcp residue attached to the central heptose, a molecular environment different from what has been reported earlier for PCho. In addition, minor substitution by O‐linked glycine to the LPS was observed. By investigation of LPS from a lpsA mutant of NTHi strain 486, it was demonstrated that the lpsA gene product also is responsible for chain extension from HepIII in this strain. The involvement of lic1 in expression of PCho was established by investigation of a lic1 mutant of NTHi strain 486.
Characterization and reconstitution of functional hemagglutinin of the Clostridium botulinum type C progenitor toxin
Authors: Kouguchi Hirokazu , Watanabe Toshihiro , Sagane Yoshimasa , Ohyama Tohru 
Published: March 2003

The purified progenitor toxin of Clostridium botulinum type C strain 6814 (C‐6814) forms a large complex composed of 150‐kDa neurotoxin (NT), 130‐kDa nontoxic‐nonhemagglutinin (NTNHA), and hemagglutinin (HA) components. The HA component consisted of a mixture of several subcomponents with molecular masses of 70, 55, 33, 26–21 and 17 kDa. We isolated the HA subcomponents from the progenitor toxin by chromatography in the presence of denaturants. The isolated HA subcomponents, designated as i‐HA‐33, i‐HA‐55, i‐HA‐70 and i‐HA‐33/17, were nearly homogenous on SDS/PAGE, but the HA‐17 and HA‐26–21 components were not purified. Some HA subcomponents, designated as f‐HA‐33 and f‐HA‐33/17 complex, existed free of the progenitor toxin in the culture medium and they were separately purified. Every HA subcomponent so far isolated shows binding activity to erythrocytes. The hemagglutination activities of each HA subcomponent had a titer of 25 for the f‐HA‐33/17 complex, and below 23 for the other f‐ and i‐HA subcomponents, while the parent progenitor L toxin was 28. The reconstitution of various combinations of f‐ and i‐HA subcomponents was attempted via mixing and tested for hemagglutination activity. When the i‐HA‐33/17 complex and i‐HA‐55 were mixed, the hemagglutination activity was recovered to a titer of 29, which was slightly higher than that of the parent toxin. These data imply that a combination of at least HA‐33, ‐17 and ‐55 subcomponents is required for full hemagglutination activity of the botulinum progenitor toxin, but each single HA subcomponent shows weak or no aggregation of erythrocytes.
Investigation of a functional requirement for isoprenylation by the human prostacyclin receptor
Authors: Miggin Sinead M. , Lawler Orlaith A. , Kinsella B. Therese 
Published: March 2003

In the current study, we have established that the human (h) prostacyclin receptor (IP) is isoprenylated in whole cells. Through site directed mutagenesis and generation of the isoprenylation defective hIPSSLC, it was established that while isoprenylation of hIP does not influence ligand binding, it is obligatory for agonist activation of adenylyl cyclase and cAMP generation. Overexpression of GαS significantly augmented cAMP generation by the hIP but not by the hIPSSLC. Moreover, GαS co‐immunoprecipitated with hIP following agonist activation but did not co‐immunoprecipitate with hIPSSLC. Whereas hIP mediated concentration‐dependent activation of phospholipase C (PLC); the extent of PLC activation by hIPSSLC was impaired compared to hIP. Co‐expression of Gαq significantly augmentated intracellular calcium mobilization by the hIP but not by hIPSSLC. Moreover, whereas Gαq co‐immunoprecipitated with hIP, it failed to co‐immunoprecipitate with hIPSSLC. While both the hIP and hIPSSLC underwent agonist‐induced internalization, the kinetics and extent of hIPSSLC internalization was impaired compared to hIP. Altering the CAAX motif of the hIP from a farnesyl (–CSLC) to a geranylgeranyl (–CSLL) isoprene acceptor, to generate hIPCSLL, did not affect ligand binding and yielded a receptor that exhibited identical signalling through both Gs‐ and Gq‐coupled effectors to that of hIP.Thus, whereas isoprenylation of hIP does not influence ligand binding, it is functionally imperative in regulating post‐receptor events including agonist‐activation of adenylyl cyclase, for efficient activation of PLC and for receptor internalization. Though the nature of the isoprenoid attached to hIP does not act as a major determinant, the presence of an isoprenoid group, for example farnesyl or geranylgeranyl, is required for functional receptor–G protein interaction and coupling and for efficient agonist‐ induced receptor internalization.
Frogs Have Rules: Selective Attention Algorithms Regulate Chorusing in Physalaemus pustulosus (Leptodactylidae)
Authors: Greenfield Michael D. , Rand A. Stanley 
Published: March 2003

In various acoustic insects and frogs, females preferentially orient towards the leading of two or more males' advertisement signals that occur closely in time. Such preferences in receivers have apparently selected for timing mechanisms whereby male signallers actively refrain from calling immediately following the onset of a neighbour's call and thereby increase their production of leading calls. However, indiscriminate application of this inhibitory mechanism to all neighbours might severely reduce a male's calling rate, particularly in high density. Consequently, mechanisms of selective attention to only a subset of signalling neighbours are expected.Female Túngara frogs (Physalaemus pustulosus) exhibit strong preferences for leading male calls, and males refrain from calling immediately following a neighbour. Four‐loudspeaker playback experiments demonstrated that males do selectively apply this inhibitory mechanism to only a subset of close signalling neighbours. Selective attention is regulated by a combination of sliding threshold and fixed number rules: (i) Attend to the loudest (nearest) conspecific neighbour and those additional ones whose calls are within 6–8 dB of the loudest one; (ii) attend to only two neighbours in total when the calls are weak or the second one is much farther than the first; (iii) attend to three neighbours when the calls are loud or all neighbours are approximately equidistant. The means by which such plasticity may be achieved and its potential adaptiveness are discussed.
Predation–Reproduction Conflict Resolution in the Hermit Crab, Clibanarius vittatus
Authors: Hazlett Brian A. , Rittschof Daniel 
Published: March 2003

AbstractActivities associated with courtship are often in conflict with avoiding elevated predation risk. In polygamous species with temporally restricted mating seasons, males should be less responsive to interruption of courtship by detection of elevated predation risk compared to females. We tested this prediction with the hermit crab Clibanarius vittatus. Courting males continued to execute pre‐copulatory behavior patterns when exposed to predator odors. However, in the presence of predator odors, fewer pairs were established. Exposing previously paired males and females to predator cues showed that males were unaffected in their motivation to form pairs, whereas females were no longer attractive to males following exposure to predator cues.
Effects of Pair‐Bond and Social Context on Male–Female Interactions in Captive Titi Monkeys (Callicebus moloch, Primates: Cebidae)
Authors: Fernandez‐Duque Eduardo , Valeggia Claudia R. , Mason William A. 
Published: March 2003

AbstractIn monogamous species, an abiding relationship between a specific adult male and a specific adult female is a defining feature of the social system. The interactions between these individuals are influenced by many factors, including not only the history of their relationship (for example, development of a mutual bond), but also the immediate effects of the prevailing social context (for example, presence and sex of extra‐pair conspecifics). In this study we examined the effects of an existing bond and of social context on interactions between adult heterosexual pairs of the monogamous titi monkeys (Callicebus moloch). Twelve adult males and 12 adult females were tested with their cagemates and with an unfamiliar partner of the opposite sex in five social contexts: (1) mated male–female pair; (2) unfamiliar pair; (3) single female; (4) single male; and (5) empty stimulus cage. Results show that mated pairs were more affiliative than unfamiliar pairs and differentiated social contexts more sharply. Males were more responsive to context than females. Distance between mates was less and physical contact was more frequent in the presence of male–female pairs or a single male, than in the presence of a single female or an empty cage. These findings suggest that the presence and sex of strangers have a stronger influence on male–female interactions when the pair has an existing relationship.
Scent Marking in Female Prairie Voles: a Test of Alternative Hypotheses
Authors: Wolff Jerry O. , Mech Stephen G. , Thomas Shawn A. 
Published: March 2003

We conducted three experiments with females in different stages of reproductive condition to test alternative hypotheses for the function of scent marking in female prairie voles, Microtus ochrogaster. The three reproductive categories were isolated females prior to sexual stimulation (anoestrous), sexually stimulated (oestrous) and lactating. Females in different reproductive condition were given the opportunity to scent mark clean unmarked substrate or areas that had previously been marked by adult females or adult males. The numbers of scent marks deposited by females did not differ statistically for females in different reproductive condition. However, there was a trend for anoestrous females to mark the most, oestrous females less, and lactating females the least. The lack of scent marking by lactating females might be to reduce conspicuousness to conspecifics or predators. Oestrous females tended to mark the most in the area marked previously by males, although the difference was not statistically significant.Our results provide some support for a mate‐attraction hypothesis and a territorial‐defense hypothesis, but were most consistent with a self‐advertisement hypothesis. Over marking was uncommon and did not differ by experiment or sex of previous donor. Our results suggest that the number and placement of scent marks by females are highly variable and function primarily to convey individual identity.
Interactions between Males of the Lizard Liolaemus tenuis: Roles of Familiarity and Memory
Authors: Trigosso‐Venario Rodrigo , Labra Antonieta , Niemeyer Hermann M. 
Published: March 2003

AbstractFor territorial organisms, recognition of familiar individuals can reduce the frequency and intensity of aggressive encounters (‘dear enemy’ phenomenon), stabilize social systems, and reduce the cost of territory maintenance. Here, we investigated the behavioural events displayed during contests between familiar and unfamiliar individuals in the lizard Liolaemus tenuis (Liolaemidae), a species in which males are territorial. The behaviours recorded were attack, warning, evasion, and submission, and the latencies to the first aggressive (attack or warning) behaviour. Additionally, we assessed the ability of individuals to remember a familiar conspecific after a period without social interaction. Individual males reduced and delayed aggressive behaviour directed towards socially familiar individuals compared with unfamiliar ones. These results suggest that males distinguished between familiar and unfamiliar conspecific males and are in agreement with the ‘dear enemy’ phenomenon. Other behaviours were similar in the contests between familiar and unfamiliar individuals. Recognition of familiar conspecifics was lost after 20 d without social interactions. This may be relevant for interactions with floater males or with neighbours that lose their territory and subsequently attempt to fight for their ex‐neighbour's territory.
Scrounging Tactics in Free‐Ranging Ravens, Corvus corax
Authors: Bugnyar Thomas , Kotrschal Kurt 
Published: March 2003

AbstractSocial foraging allows individuals to scrounge, i.e. to exploit the food others have made available. The conditions promoting scrounging as an alternative foraging tactic have yet received limited attention. We presently examine whether ravens, as opportunistic scavengers, adjust their foraging tactics according to the potential costs involved in accessing a particular food source. We observed wild ravens foraging in a game park, at the enclosures of wolves, Canis lupus, and wild boars, Sus scrofa. Wolves may aggressively defend their food and even kill ravens, whereas wild boars do not. When co‐feeding with wolves, the ravens showed higher scrounging rates than with wild boars. Only at the wolves, they tended to specialize either on scrounging or on getting food directly from the site. However, scrounging techniques differed in relation to the state of food depletion. Early on, after food became available, the ravens most frequently displaced others from food, whereas towards the end, stealing, solicited sharing, and cache raiding became prevalent. These techniques differed in their profitability and their use was related to the scroungers’ age, social status and affiliative relationships. This suggests that ecological conditions, such as co‐feeding with potential predators, may influence the individuals’ decision whether or not to scrounge in competition for food. Social conditions, on the other hand, may affect the way how to get at food possessed by others and may thus, to a large extent, determine the profitability of scrounging.
Etiology of oak decline in Spain
Authors: Gallego F. J. , de Algaba A. Perez , Fernandez‐Escobar R. 
Published: March 2003

SummaryIn different areas of Extremadura, Western Spain, soil samples were taken at the bottom of holm oak (Quercus ilex) trees that were showing decline symptoms. Half of each sample was sterilized, and acorns were sown in both sterilized and nonsterilized soil samples. The resulting seedlings were used as baits for the isolation of fungi. Seedlings growing on the natural, nonsterilized substrate were characterized by having a lower vegetative growth than the ones growing on the sterilized soil samples, and most of them died. Phytophthora dnnamomi was consistently isolated from their roots. Fusarium oxysporum was also isolated as well as different species of Pythium, although to a lesser extent. Pathogenicity tests were performed on holm oak seedlings with five different isolates of P. chinnamomi, with F. oxysporum, Pythium and with a mixture of the three fungi. All the inoculated seedlings with P. chinnamomi developed root rot and grew slowly, and 35.7% of them died up to the end of the experiments. P. chinnamomi was consistently isolated from their roots, indicating that this fungus is the causal agent of holm oak decline. However, F. oxysporum caused similar symptoms on oak seedlings as P. chinnamomi, and was isolated also from the roots, although its frequency was lower than that of. P. cinnamomi.
Detecting changes in tree health and productivity of silver fir in Slovenia
Authors: Torelli N. , Shortle W. C. , Cufar K. , Ferlin F. , Smith K. T. 
Published: March 2003

SummaryCambial electrical resistance (CER) was used as an objective measure of vitality of silver fir (Abies alba) in the forests of Slovenia. Trees were rated during the growing season by CER and a subjective crown status index (CSI). Both CER and CSI were inversely correlated to annual ring width increment. Using both CER and CSI, fir were assigned to vitality and vigour categories. Inferences made from these categories and radial growth trends indicated that ring growth decreased prior to the development of canopy symptoms. This decrease in ring growth would have been detected as an increase in CER. This pattern of decline is consistent with the decline of trees due to chronic below‐ground stress. Variation in CER was due both to the vascular cambium and to the thickness of the nonconducting phloem.
Induced resistance of Norway spruce, variation of phenolic compounds and their effects on fungal pathogens
Authors: Evensen P. C. , Solheim H. , Høiland K. , Stenersen J. 
Published: March 2003

SummaryThree clones of Norway spruce (Picea abies) were studied for their response to mass‐inoculation with the blue‐stain fungus Ceratocystis polonica. The effect of different pretreatments (fungal inoculation and wounding) before mass‐inoculation was investigated for their possible role in an acquired resistance reaction. Pretreated trees showed enhanced resistance to the subsequent mass‐inoculation relative to control trees that received no pretreatment. Furthermore, the fungal colonization of inoculated trees was less than that of wounded trees. The phenolic content of the bark, analysed by RP‐HPLC, was compared in trees receiving different treatments. Trees inoculated with C. polonica had higher average concentration of (+)‐catechin, taxifolin and trans‐resveratrol than wounded trees. Both inoculated and wounded trees had higher average concentrations of these compounds than control trees. The effect of the phenolic extract of Norway spruce bark on the growth of the root rot fungus Heterobasidion annosum and the blue‐stain fungi C. polonica and Ophiostoma penicillatum were investigated in vitro. Heterobasidion annosum was not negatively affected, and the extracts had fungistatic effects on the blue‐stain fungi. The growth of O. penicillatum was more inhibited than the growth of the more aggressive C. polonica.
UV‐B radiation constrains the photosynthesis of Quercus robur through impacts on the abundance of Microsphaera alphitoides
Authors: Newsham By K. K. , Oxborough K. , White R. , Greenslade P. D. , McLeod A. R. 
Published: March 2003

Summary Quercus robur saplings were exposed at an outdoor facility in the UK to supplemental levels of UV‐B radiation (280–315 nm) under arrays of cellulose diacetate‐filtered fluorescent lamps which also produced UV‐A radiation (315–400 nm). Saplings were also exposed to supplemental UV‐A radiation under arrays of polyester‐filtered lamps and to ambient levels of solar radiation under arrays of unenergized lamps. The UV‐B treatment was modulated to maintain a 30% elevation above the ambient level of erythemally weighted UV‐B radiation. Naturally occurring infections by oak powdery mildew (Microsphaera alphitoides) were more abundant, and developed more rapidly, on lammas leaves of saplings which were exposed to treatment levels of UV‐B radiation than on leaves of saplings exposed to supplemental UV‐A or to ambient levels of solar radiation over 12 weeks in summer and autumn 1996. An analysis of leaf photosynthetic capacities revealed that M. alphitoides infection reduced the quantum efficiency of photosystem (PS) II by 14% at moderate irradiance. Although there was no direct effect of UV‐B radiation on PSII photochemistry, exposure of saplings to supplemental UV‐A radiation under polyester‐filtered lamps resulted in a 17.5% decrease in PSII quantum efficiency, compared with saplings exposed to ambient solar radiation. The results from our study suggest that photosynthesis of Q. robur may be constrained by exposure to UV‐B radiation in the natural environment through impacts on the abundance of M. alphitoides.