bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of total immunoglobulin levels, mass and condition on the first‐year survival of Grey Seal pups
Authors: Hall A. J. , McConnell B. J. , Barker R. J. 
Published: March 2003

Summary1. A joint live‐recapture/live‐resighting/dead‐recovery mark–recapture model was used to investigate the effect of serum gammaglobulin (IgG) levels, sex, mass and condition (mass/length as a surrogate for total body fat) at weaning on the probability of survival from weaning to age 1, in Grey Seal (Halichoerus grypus Fabricius 1791) pups born at two different breeding colonies (Isle of May and Farne Islands) in two different years (1997 and 1998).2. It was found that increased mass or condition at weaning had a positive effect on the first year survival of Grey Seal pups born at both colonies. Males had a lower probability of survival than females.3. Higher postweaning circulating IgG concentrations also decreased the probability of survival. It is not known if those pups with high IgG were individuals with naturally higher circulating concentrations or because titres were elevated due to antigenic challenge.
Does flight morphology relate to flight performance? An experimental test with the butterflyPararge aegeria
Authors: Berwaerts K. , Van Dyck H. , Aerts P. 
Published: March 2003

Summary1. The relationship between maximal acceleration capacity and flight morphology was tested experimentally in the butterflyPararge aegeria. Such relations are often assumed but seldom tested.2. In both sexes acceleration capacity was positively correlated with total body mass, thorax mass, forewing area, forewing length, wing loading, aspect ratio and centre of forewing area (centroid). Relationships with total body mass, forewing area, forewing length and wing loading were stronger in males. This can be explained by different mass allocation: males allocate proportionally more mass to the thorax, females more to the abdomen.3. Evidence for the combined effect of morphological traits on acceleration capacity was found by multivariate analysis. In males and females, a more distant relative centroid and higher relative thorax mass were related to a higher flight capacity. In addition, aspect ratio was positively related to acceleration capacity in males only.4. Our results support the assumed mechanism behind the relationship between flight morphology and mate‐locating behaviour.
Feeding methods, visual fields and vigilance in dabbling ducks (Anatidae)
Authors: Guillemain M. , Martin G. R. , Fritz H. 
Published: March 2003

Summary 1. Visual fields were determined in two species of dabbling ducks (Anatini): Shoveler Anas clypeata L. (planktivore whose foraging is guided mainly by tactile cues) and Wigeon A. penelope L. (herbivore whose foraging is guided mainly by visual cues). 2. The binocular fields of Shoveler and Wigeon are of similar maximum width (20°), but they differ in their position and vertical extent. The bill of the Shoveler lies in the very periphery of its frontal binocular field, which extends through 220° thus providing comprehensive visual coverage about the head. In Wigeon the bill is positioned more centrally in the frontal binocular field, which extends through 150° and results in the birds having a narrow blind area behind the head. 3. The vigilance behaviour of Shoveler and Wigeon when foraging simultaneously was studied using a focal observation procedure at sites where the two species winter in sympatry. Focal Wigeon almost only fed by grazing. Only Shoveler feeding by dabbling (filtering the first centimetres of water) were used in the analyses. Wigeon spent significantly more time in head‐up vigilance than Shoveler (F1,75 = 14·70, P = 0·0003). 4. It is proposed that this interspecific difference in the proportion of time spent in vigilance behaviour may be an adaptive response to differences in the visual field topography of these species, particularly with respect to the presence/absence of a blind area to the rear of the head. 5. The ability of foragers to combine part of their vigilance behaviour with head‐down feeding has recently been recognized as influencing the trade‐offs related to vigilance while foraging. This study shows that this ability may vary significantly between species, even within the same genus, and that these variations are likely to be due to contrasted visual fields, themselves related to the type of feeding techniques employed by the different duck species.
Comparative elemental stoichiometry of ecologically diverseDrosophila
Authors: Jaenike J. , Markow T. A. 
Published: March 2003

SummaryChemical analyses of ecologically diverse species ofDrosophilareveal substantial variation among them in their nitrogen and phosphorus contents, determined as a percentage of adult dry mass. AcrossDrosophilaspecies, the nitrogen content of flies is positively correlated with phosphorus content.For both N and P, the concentration in the flies is correlated with that of their breeding sites. The variation in the elemental composition of breeding sites, and therefore of the flies themselves, may affect the ecology and life‐history variation ofDrosophila.The range of variation in N and P contents and the N : P ratio is considerably less amongDrosophilathan among their breeding sites, indicating that there is substantial constancy for elemental composition acrossDrosophilaspecies. The N : P ratio varies somewhat among species, indicating that the nitrogen and phosphorus contents do not change in perfect proportion across species.An important, but unanswered, question concerns the relation between intraspecific homeostasis and interspecific constancy for elemental composition. Three possible mechanisms by which such interspecific constancy is brought about are discussed.
Cold acclimation enhances cutaneous resistance to inoculative freezing in hatchling painted turtles, Chrysemys picta
Authors: Packard G. C. , Packard M. J. 
Published: March 2003

Summary

Neonatal Painted Turtles, Chrysemys picta (Schneider 1783), typically spend the first winter of their life inside the shallow, subterranean nest where they completed incubation the preceding summer. This behaviour commonly causes hatchlings in northerly populations to be exposed in mid‐winter to life‐threatening conditions of ice and cold. Neonates apparently withstand such exposure by remaining unfrozen and becoming supercooled.
Recently hatched turtles are unable to resist freezing by inoculation (i.e. freezing that is induced by the penetration of ice crystals through the integument and into body compartments from frozen soil). Consequently, newly hatched animals that make contact with ice are highly susceptible to freezing when temperature goes below the equilibrium freezing point for their body fluids (c. −0·7 °C). Freezing is fatal, even when temperature does not go below −2 °C, so newly hatched turtles have only a very limited tolerance for exposure to ice and cold.
Acclimation (or acclimatization) by neonatal turtles to low temperatures in the interval between hatching and the start of winter elicits an increase in effectiveness of the cutaneous barrier to the penetration of ice into body compartments from the environment. Acclimated hatchlings coming into contact with ice in frozen soil usually remain unfrozen and supercooled, and survival by supercooled turtles is uniformly high. This thermally induced enhancement of the cutaneous barrier to inoculation is key to an overwintering strategy based on supercooling.
Are bacteria more like plants or animals? Growth rate and resource dependence of bacterial C : N : P stoichiometry
Authors: Makino W. , Cotner J. B. , Sterner R. W. , Elser J. J. 
Published: March 2003

Summary

We examined the relative importance of resource composition (carbon : phosphorus molar ratios which varied between 9 and 933) and growth rate (0·5–1·5 h−1) to biomass carbon : nitrogen : phosphorus stoichiometry and nucleic acid content in Escherichia coli grown in chemostats, and in other heterotrophic prokaryotes using published literature.
Escherichia coli RNA content and the contribution of RNA‐P to total cellular P increased with increasing growth rate at all supply C : P ratios. Growth rate had a much stronger effect on biomass C : P than did supply C : P, and increased RNA content resulted in low biomass C : P and N : P ratios.
However, we observed only twofold variations in biomass C : P and N : P ratios in the experiments, despite a difference of two orders of magnitude in C : P and N : P supply. The response of biomass C : P and N : P ratios to alteration of the supply C : P and N : P ratios revealed that E. coli was strongly homeostatic in its elemental composition.
This result, and a literature survey, suggest that each heterotrophic bacterial strain regulates its elemental composition homeostatically within a relatively narrow range of characteristic biomass C : P and N : P ratios.
Thus shifts in the dominance of different bacterial strains in the environment are probably responsible for the large variation in bacterial biomass C : P, as has been suggested for crustacean zooplankton. These findings indicate that bacteria are more like animals than plants in terms of biomass C : P and N : P homeostasis.
A new sigma factor, SigD, essential for stationary phase is also required for multicellular differentiation in Myxococcus xanthus
Authors: Ueki Toshiyuki , Inouye Sumiko 
Published: March 2003

Background: Myxococcus xanthus is a gram‐negative bacterium that undergoes spectacular development to form multicellular fruiting bodies under nutrient deprivation. Inside a fruiting body, vegetative cells differentiate into spores. A number of sigma factors have been shown to play roles in the regulation of gene expression in the M. xanthus life cycle. Additional sigma factors were searched to further explore the M. xanthus life cycle.Results:A new sigma factor was identified, SigD, which consists of 297 amino acid residues. Two transcription initiation sites for the sigD gene were detected by primer extension analysis using total RNA from the vegetative and developmental cells, one of which was specific for development. The characterization of sigD‐lacZ fusion strains demonstrated that sigD expression increased during entry into stationary phase of vegetative growth and during early development. A deletion mutant of sigD exhibited growth defects during the late‐log phase and stationary phase, with dramatically reduced cell viability. The patterns of protein synthesis at late log phase of vegetative growth and at early development on CF agar plates were significantly different between the deletion mutant and the wild‐type strain. The deletion mutant was more sensitive to various stresses when compared with the wild‐type strain and did not accumulate trehalose in response to osmotic stress. The deletion mutant also showed a significant delay in fruiting body formation and sporulation and yielded fewer spores than the wild‐type strain.Conclusions:SigD shows characteristic features of the stationary phase sigma factors and also plays important roles in multicellular differentiation of M. xanthus.
In vitro assembly of the CENP‐B/α‐satellite DNA/core histone complex: CENP‐B causes nucleosome positioning
Authors: Yoda Kinya , Ando Satoshi , Okuda Asuko , Kikuchi Akihiko , Okazaki Tuneko 
Published: March 2003

BackgroundWe have studied the nucleosome structure formed from α‐satellite DNA bound with CENP‐B and core histones, in order to develop a previous proposal that the CENP‐B dimer may play a critical role in the assembly of higher order structures of the human centromere by juxtaposing CENP‐B boxes in long α‐satellite arrays.ResultsThe dimeric structure of CENP‐B was sufficiently stable to bundle together two 3.5 kbp DNA fragments when each DNA contained a CENP‐B box. When the same length of DNA included two CENP‐B boxes, the intra–molecular interaction with the CENP‐B dimer predominated, resulting in the formation of loop structures. The in vitro assembly of CENP‐B/α‐satellite DNA/core histone complexes with the aid of nucleosome assembly protein‐1 (NAP‐1) permitted an investigation into the nucleosome arrangement in α‐satellite DNA with CENP‐B bound to CENP‐B boxes. Footprint analyses with micrococcal nuclease (MNase) revealed that CENP‐B causes nucleosome positioning between pairs of CENP‐B boxes with unique hypersensitive sites created on both sides.ConclusionWe propose that CENP‐B functions as a structural factor in the centromere region in order to establish a unique, centromere specific pattern of nucleosome positioning.
Mutational analysis on structure–function relationship of a Holliday junction specific endonuclease RuvC
Authors: Ichiyanagi Kenji , Iwasaki Hiroshi , Hishida Takashi , Shinagawa Hideo 
Published: March 2003

Background Escherichia coli RuvC protein is a specific endonuclease that resolves Holliday junctions during homologous recombination. For junction resolution, RuvC undergoes distinct steps such as dimerization, junction‐specific binding and endonucleolytic cleavage. The crystal structure of RuvC has been revealed.ResultsTo identify functionally important residues, we isolated a large number of mutant ruvC genes created by random mutagenesis and characterized their properties in vivo and in vitro. The mutations which were isolated most frequently were mapped to the four acidic residues constituting the catalytic centre. Amongst the several mutant proteins affected in the dimer interface, only one could not form a dimer. The others were able to form a dimer but were defective in cleavage. F69L and K118R mutant proteins could not cleave the junction, but they were able to form a dimer and bind the junction DNA.ConclusionsRandom mutagenesis highlighted many structurally and functionally important residues of RuvC, most of which are highly conserved among RuvC homologues. Dimer formation and also conservation of intact interface interactions between the subunits are important for junction binding and subsequent cleavage. Phe‐69 and Lys‐118 are critically important for the interactions which lead to junction cleavage.
Spatio‐temporally regulated expression of receptor tyrosine kinases, mRor1, mRor2, during mouse development: implications in development and function of the nervous system
Authors: Oishi Isao , Takeuchi Shigeto , Hashimoto Ryuju , Nagabukuro Akira , Ueda Takahiro , Liu Zhao‐Jun , Hatta Toshihisa , Akira Shizuo , Matsuda Yoichi , Yamamura Hirohei , Otani Hiroki , Minami Yasuhiro 
Published: March 2003

BackgroundsDrosophila neurospecific receptor tyrosine kinases (RTKs), Dror and Dnrk, as well as Ror1 and Ror2 RTKs, isolated from human neuroblastoma, have been identified as a structurally related novel family of RTKs (Ror‐family RTKs). Thus far, little is known about the expression and function of mammalian Ror‐family RTKs.ResultsWe have identified murine Ror‐family RTKs, mRor1 and mRor2. Both mRor1 and mRor2 genes are induced upon neuronal differentiation of P19EC cells. During neuronal differentiation in vitro, the expression of mRor2 is transiently induced, although that of mRor1 increases continuously. During embryogenesis, the mRor1 gene is expressed in the developing nervous system within restricted regions and in the developing lens epithelium. The expression of mRor1 is sustained in the nervous system and is also detected in non‐neuronal tissues after birth. In contrast, the expression of mRor2 is detected mainly in the developing nervous system within broader regions and declines after birth. Possible relationships of mRor1 and mRor2 genes with previously identified mutants have also been examined.ConclusionsThe developmental expressions of mRor1 and mRor2, in particular in the nervous system, are differentially regulated, reflecting their expression patterns in vitro. mRor1 and mRor2 may thus play differential roles during the development of the nervous system.
A mammalian ortholog of Drosophila timeless, highly expressed in SCN and retina, forms a complex with mPER1
Authors: Takumi Toru , Nagamine Yasuko , Miyake Shigeru , Matsubara Chiaki , Taguchi Kouji , Takekida Seiichi , Sakakida Yoko , Nishikawa Kazuko , Kishimoto Toshihiko , Niwa Shin‐ichiro , Okumura Ko , Okamura Hitoshi 
Published: March 2003

Background:It is now becoming clear that the circadian rhythm of behaviours and hormones arises from a rhythm at the level of gene expression, and that mammals and Drosophila essentially use homologous genes as molecular gears in the control of circadian oscillation. In Drosophila, the period and timeless genes form a functional unit of the clock and its autoregulatory feedback loop for circadian rhythm. However, in mammals, the counterpart of timeless has not been found.Results:We have isolated a mammalian homologue of timeless, mTim, from the mouse brain. mTim is highly expressed, with a weak or absent rhythm in the suprachiasmatic nucleus, the mammalian circadian centre. In the retina, mTim mRNA was found to be expressed with a circadian rhythm, and a particularly robust cycle was observed in the presence of light/dark cycles. We demonstrated that mTIM physically associates with mPER1 in vitro and in the nuclei of cultured COS7 cells.Conclusions:We have reported the isolation of the mouse timeless cDNA, the expression of the mTim mRNA and an interaction of mTIM with mPER1. These results indicate that the autoregulatory feedback mechanism of circadian oscillation of the period gene may also be conserved in mammals.
Nps1/Sth1p, a component of an essential chromatin‐remodeling complex of Saccharomyces cerevisiae, is required for the maximal expression of early meiotic genes
Authors: Yukawa Masashi , Katoh Soko , Miyakawa Tokichi , Tsuchiya Eiko 
Published: March 2003

BackgroundThe NPS1/STH1 gene of Saccharomyces cerevisiae is essential for mitotic growth, especially for the progression through the G2/M phase. It encodes a major component of the chromatin‐remodelling complex, RSC, of unknown function. We attempted to address the function of NPS1 in meiosis.ResultsThe homozygote of the temperature sensitive nps1 mutant, nps1‐105, showed reduced and delayed levels of sporulation, accompanied with a notable decrease and delay of the expression of several early meiotic genes (IME2, SPO11 and SPO13). Deletion analysis of the IME2 promoter revealed that the defect in the gene expression occurred through the URS1 site. The sporulation defect of nps1‐105 was alleviated by the over‐expression of either IME1 or IME2. However, over‐expression of IME1 did not permit the full expression of IME2, SPO11 and SPO13 in nps1‐105. In addition, the expression of NPS1 itself increased transiently upon initiation of meiosis, before the appearance of the IME2 message but after that of IME1. The impaired increase in NPS1 transcription led to inefficient sporulation.ConclusionThe results suggest that Nps1p/RSC is required for the activation of gene expression at the initiation of meiosis.
Cytokine‐inducible SH2 protein‐3 (CIS3/SOCS3) inhibits Janus tyrosine kinase by binding through the N‐terminal kinase inhibitory region as well as SH2 domain
Authors: Sasaki Atsuo , Yasukawa Hideo , Suzuki Asuka , Kamizono Shintaro , Syoda Takanori , Kinjyo Ichiko , Sasaki Mika , Johnston James A. , Yoshimura Akihiko 
Published: March 2003

BackgroundThe Janus family of protein tyrosine kinases (JAKs) regulate cellular processes involved in cell growth, differentiation and transformation through their association with cytokine receptors. We have recently identified the JAK‐binding protein, JAB that inhibits various cytokine‐dependent JAK signalling pathways. JAB inhibits JAK2 tyrosine kinase activity by binding to the kinase domain (JH1 domain) through the N‐terminal kinase inhibitory region (KIR) and the SH2 domain. The SH2 domain of JAB has been shown to bind to the phosphorylated Y1007 in the activation loop of JH1. We also identified another JAK‐binding protein, CIS3 (cytokine‐inducible SH2‐protein 3, or SOCS3) that inhibits signalling of various cytokines. However, the mechanism of JAK signal inhibition by CIS3 has not been clarified.ResultsWe showed that endogenous CIS3 bound to JAK2 in intact cells. The CIS3‐SH2 domain bound to the phosphorylated Y1007 of JH1, and inhibited tyrosine kinase activity through the N‐terminal KIR. Therefore, CIS3 and JAB inhibit JAK2 tyrosine kinase activity by an essentially similar mechanism. However, we found that the affinity of the SH2 domain of CIS3 to Y1007 was weaker than that of JAB. In contrast, the KIR of CIS3 showed stronger potential for both binding to JH1 and inhibition of JAK kinase activity than that of JAB. Consistent with this notion, chimeras containing CIS3‐KIR and JAB‐SH2 domain inhibited JAK2 kinase activity more efficiently than the wild‐type CIS3 or JAB.ConclusionCIS3 inhibits JAK2 kinase activity by binding to the activation loop through the SH2 domain, and KIR is necessary for kinase inhibition. Although the inhibitory mechanism by CIS3 is similar to that by JAB, the contributions of the SH2 domain and KIR for binding are different between JAB and CIS3. Our study defined the inhibitory mechanism of CIS3 and provides a useful information for creating a novel tyrosine kinase inhibitor.
Changes in nuclear morphology during apoptosis correlate with vimentin cleavage by different caspases located either upstream or downstream of Bcl‐2 action
Authors: Morishima Nobuhiro 
Published: March 2003

BackgroundUpon Fas stimulation, procaspase‐8 is recruited to the death‐inducing signalling complex where autoactivation of caspase‐8 occurs. Active caspase‐8 can directly activate downstream caspases (e.g. caspase‐3, 6, and 7) for the execution of apoptosis (mitochondria‐independent pathway), while caspase‐8 can also lead to executioner caspase activation through mitochondrial damage (mitochondria‐dependent pathway). Caspase activation results in the dismantling of intracellular structure through specific proteolysis.ResultsWe have found that an intermediate filament protein, vimentin, is cleaved at multiple sites by caspases at an early stage of apoptosis in Jurkat cells. The sequences of the two major cleavage sites in vimentin (IDVD/V and DSVD/F) suggested that these sites are cleaved by caspase‐8 and caspase‐3, respectively, or by close homologues of these proteases. The IDVD/V site can be cleaved by caspase‐8 in vitro, and its cleavage is less sensitive to DEVD‐CHO and Bcl‐2 over‐expression than that of the DSVD/F site in Jurkat cells. Over‐expression of a mutant vimentin which was insensitive to caspase cleavage at these sites delayed the appearance of apoptotic nuclei in Jurkat cells.ConclusionThe specific cleavage of vimentin can be used as an apoptotic marker of both apical‐ and mitochondria‐dependent caspase activation. Apoptotic cleavage of vimentin most likely results in disruption of its filamentous structure, which may facilitate nuclear condensation and subsequent fragmentation through disruption of the cytoskeletal network.