bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relationships between head size, bite force, prey handling efficiency and diet in two sympatric lacertid lizards
Authors: Verwaijen D. , Van Damme R. , Herrel A. 
Published: March 2003

Summary

Relationships between morphology, bite force capacity, prey handling efficiency and trophic niche were explored in two sympatric species of lacertid lizards, Podarcis melisellensis (Braun 1877) and Lacerta oxycephala Duméril & Bibron 1839.
Head shape showed little variation, but head size (absolute and relative to snout–vent length, SVL) differed between species and sexes. Males have larger heads than females, both absolute and relative to their SVL. In absolute terms, male P. melisellensis have larger heads than male L. oxycephala, but the reverse case was true for the females. Relative to SVL, L. oxycephala have larger heads than P. melisellensis.
Bite force capacity was estimated by having the lizards bite on two metal plates, connected to a piezoelectric force transducer. Differences in maximal bite force between species and sexes paralleled differences in absolute head size. Differences in body size and head size explain the higher bite force of males (compared with females), but not the higher bite force of P. melisellensis (compared with L. oxycephala). Among individual lizards, bite force correlated with body size and head size.
Prey handling efficiency, estimated by the time and number of bites needed to subdue a cricket in experimental conditions, also showed intersexual and interspecific variation. This variation corresponded to the differences in maximal bite capacity, suggesting that bite force is a determining factor in prey handling. Among individual lizards, both estimates of handling efficiency correlated with maximal bite force capacity.
Faecal pellet analyses suggested that in field conditions, males of both sexes select larger and harder prey than females. There was no difference between the species. The proportion of hard‐bodied and large‐sized prey items found in a lizard's faeces correlated positively with its bite force capacity.
It is concluded that differences in head and body size, through their effect on bite force capacity, may affect prey selection, either directly, or via handling efficiency.
Energy balance in the Whitebellied Sunbird Nectarinia talatala: constraints on compensatory feeding, and consumption of supplementary water
Authors: Nicolson S. W. , Fleming P. A. 
Published: March 2003

Summary

Avian nectarivores consume a simple food which is generally dilute, but may vary widely in concentration and thus in water content.
Energy intake over 24 h was investigated in the Whitebellied Sunbird Nectarinia talatala (A. Smith) (mean mass 9·3 ± 1·0 SD g, n = 7) fed a wide range of sucrose concentrations (0·07–2·5 m), with and without access to supplementary water.
On diet concentrations between 0·25 and 2·5 m sucrose, birds showed perfect compensatory feeding by adjusting volumetric intake to maintain constant energy intake.
However, reduced intake on the two lowest concentrations of 0·07 and 0·1 m meant that the birds could not meet their energetic requirements and lost mass. We propose that physiological constraints associated with ingestion of large volumes of preformed water restrict intake at these very low concentrations.
Drinking of supplementary water varied greatly among individuals, but increased as diet concentration increased. This free water consumption effectively diluted the most concentrated diets of 1·5–2·5 m sucrose to an average value of 1·05 m, thus providing an indirect assessment of the birds’ concentration preferences.
Drosophila dSmad2 and Atr‐I transmit activin/TGFβ signals
Authors: Das Pradeep , Inoue Hirofumi , Baker Julie C. , Beppu Hideyuki , Kawabata Masahiro , Harland Richard M. , Miyazono Kohei , Padgett Richard W. 
Published: March 2003

BackgroundMuch is known about the three subfamilies of the TGFβ superfamily in vertebrates—the TGFβs, dpp/BMPs, and activins. Signalling in each subfamily is dependent on both shared and unique cell surface receptors and Smads. In invertebrates, mutants for BMP pathway components have been extensively characterized, but thus far, evidence for an activin‐ or TGFβ‐like pathway has been lacking, preventing the use of the extensive genetic tools available for studying several key issues of TGFβ signalling.ResultsHere we report the identification of dSmad2, a new Drosophila Smad which is most related to the activin/TGFβ‐pathway Smads, Smad2 and Smad3. We show that dSmad2 induces activin responsive genes in Xenopus animal cap assays. dSMAD2 is phosphorylated by ATR‐I and PUNT, but not by activated THICK VEINS, and translocates to the nucleus upon activation. Furthermore, we show that dSMAD2 complexes with MEDEA only in the presence of ATR‐I and PUNT. dSmad2 is expressed in the imaginal disks and in the outer proliferation centre of the larval brain, suggesting that it may have important proliferative and patterning roles during Drosophila development.ConclusionOur data provide evidence for the existence of an activin/TGFβ pathway in Drosophila. We show that dSmad2 participates in this pathway, and that it functions with Atr‐I and punt. We show that Medea also participates in this pathway, indicating the conservation of roles for Co‐Smads in diverse phyla. Expression patterns of dSmad2 suggest that it functions in imaginal disks and in the brain, in tissues that undergo extensive patterning and proliferation.
kel‐1, a novel Kelch‐related gene in Caenorhabditis elegans, is expressed in pharyngeal gland cells and is required for the feeding process
Authors: Ohmachi Mitsue , Sugimoto Asako , Iino Yuichi , Yamamoto Masayuki 
Published: March 2003

BackgroundKelch‐related proteins constitute an expanding family, members of which carry two conserved motifs named the BTB/POZ and the kelch repeat domains. The best‐characterized member, Drosophila Kelch, constitutes the ring canals in the egg chamber in association with actin. However, physiological and biochemical functions of the members of this family remain largely uncharacterized.ResultsWe identified the kel‐1 gene encoding a Kelch‐related protein in the nematode Caenorhabditis elegans. The deduced KEL‐1 protein had 618 amino acid residues and was most similar to Drosophila Kelch. Loss of kel‐1 function caused growth arrest at an early larval stage, most likely at the beginning of L2. The kel‐1 deletion mutant appeared normal in morphology, movement and pumping action for the initial two to three days after hatching, but it failed to convey foods effectively to intestine and could hardly increase in body size. Analyses using immunostaining and reporter gene expression indicated that kel‐1 was expressed almost exclusively in the g1 pharyngeal gland cells during late embryogenesis and at all developmental stages thereafter.Conclusions C. elegans KEL‐1 protein is essential for the larval development, probably performing a function required for feeding in the pharyngeal g1 gland cells, which are supposed to secrete materials aiding digestion.
Overproduction of elongation factor 1α, an essential translational component, causes aberrant cell morphology by affecting the control of growth polarity in fission yeast
Authors: Suda Masako , Fukui Mikiko , Sogabe Yuki , Sato Kazuhito , Morimatsu Akeshi , Arai Ritsuko , Motegi Fumio , Miyakawa Tokichi , Mabuchi Issei , Hirata Dai 
Published: March 2003

BackgroundElongation factor 1α (EF1α), an essential component of the eukaryotic translational machinery, has been shown to possess various biochemical and biological activities, including F‐actin‐binding and ‐bundling, microtubule‐ severing, and the activity of making fibroblasts highly susceptible to transformation. However, our understanding of the biological significance of EF1α with respect to these various biochemical or biological activities remains limited. Here we report the identification of EF1α‐encoding genes as genes whose over‐expression causes aberrant cell morphology in fission yeast.ResultsOverproduction of EF1α caused aberrant cell morphology—elliptic, curved or branched—and growth defects in yeast cells at high temperatures. EF1α‐overproducing cells showed a supersensitivity to the actin inhibitor cytochalasin D and to the tubulin inhibitor thiabendazole. Genetic analyses using cdc mutants suggested that excess EF1α disturbed the establishment and the maintenance of growth polarity in the G1 phase by pre‐ venting the localization of F‐actin to the polarized growing site and the organization of microtubules. Results from DNase I column chromatography indicated that EF1α was bound to G‐actin. Indeed, the fission yeast actin was immunoprecipitated along with EF1α. Moreover, the temperature sensitivity caused by the overproduction of EF1α was restored by co‐overproduction of actin.ConclusionsFission yeast EF1α has the ability to alter the cell morphology of yeast by affecting the control of actin and microtubule cytoskeletons.
Bloom's syndrome gene suppresses premature ageing caused by Sgs1 deficiency in yeast
Authors: Heo Seok‐Jin , Tatebayashi Kazuo , Ohsugi Itaru , Shimamoto Akira , Furuichi Yasuhiro , Ikeda Hideo 
Published: March 2003

BackgroundBloom's syndrome (BS) is an autosomal recessive disorder causing short stature, immunodeficiency, and an increased risk of cancer. Increased rates of sister chromatid exchange and chromosomal aberration have been observed in cells having defects in the BLM gene. Among five kinds of human RecQ helicases cloned, the mutations in WRN and RecQL4 have been known as the causes of premature ageing. Little is, however, known about the function of BLM helicase in ageing.ResultsWe show that human BLM, but not WRN can prevent the premature ageing and the increased homologous recombination at the rDNA loci caused by sgs1 mutation. Unexpectedly, the levels of ERCs (extrachromosomal rDNA circles), the products of homologous recombination, formed in 7‐generation cells of the wild‐type or the sgs1::BLM strain were comparable with those of the sgs1 or the sgs1::WRN age‐matched‐old cells.ConclusionThese results imply that BLM helicase may have an important role in human ageing. In addition, these data suggest that the accumulated ERCs per se may be not the cause of premature ageing in yeast, inconsistent with the model proposed by Sinclair & Guarente. We discuss a new model, which explains how Sgs1 or BLM helicase suppresses premature ageing in yeast.
Mutation enhancement by DINB1, a mammalian homologue of the Escherichia coli mutagenesis protein DinB
Authors: Ogi Tomoo , Kato Tomohisa , Kato Takesi , Ohmori Haruo 
Published: March 2003

BackgroundThe Escherichia coli dinB gene is an SOS gene known to be required for λ phage untargeted mutagenesis. When over‐expressed, it exhibits a potent mutagenic activity without any exogenous treatment to damage DNA. Frameshift mutations at a run of identical bases are most enhanced. The product DinB is structurally related to the E. coli UmuC protein and the Saccharomyces cerevisiae Rev1 and Rad30 proteins, all of which are shown to be involved in bypass synthesis at a DNA lesion.ResultsWe have cloned and sequenced human and mouse cDNAs encoding a DinB homologue. Their products are highly similar to DinB and less similar to UmuC, Rev1 or Rad30, and hence the genes were named DINB1 for human and Dinb1 for mouse. Both genes were expressed most abundantly in testis. Transient expression of the mouse cDNA in cultured mouse cells resulted in a nearly 10‐fold increase in the incidence of point mutations, among which about 30% were frameshift mutations.ConclusionsThe above results suggest that a mutagenic mechanism, a so‐called untargeted type, also operates in mammalian cells. Taken together with recent findings that human cells have multiple DNA polymerases for translesion synthesis which are homologous to the S. cerevisiae Rev3 and Rad30 proteins, our results imply that multiple mutagenic pathways are conserved from bacteria to higher eukaryotes.
The whorl‐specific action of a petunia class B floral homeotic gene
Authors: Tsuchimoto Suguru , Mayama Tomoko , Van Der Krol Alexander , Ohtsubo Eiichi 
Published: March 2003

Background GREEN PETAL (GP) is thought to be a petunia class B floral homeotic gene, because the gp mutant flower displays a severe homeotic conversion of petals into sepals in the second whorl. However, since the third whorl stamens remain unaffected in the gp null mutant, gp is different from class B mutants in Arabidopsis and Antirrhinum, which also show a conversion of the third whorl stamens into the carpelloid tissue. BLIND (BL) is thought to be a petunia class A floral homeotic gene, because the bl mutant flower displays homeotic conversions of sepals into the stigmatoid tissue in the first whorl and of the corolla limb into antheroid structures in the second whorl.ResultsA double mutant line homozygous for both bl and gp mutations was constructed. The bl gp double mutant flower displays homeotic conversions of sepals into the stigmatoid tissue in the first whorl and of the corolla limb into antheroid structures with stigmatoid tips in the second whorl. In the third and fourth whorls of the mutant flower, organs remained unchanged. In the gp flower, a petunia B‐type gene FBP1 is expressed strongly in the third whorl organs, but much more weakly in the second whorl organs. In the bl gp flower, FBP1 was found to be expressed strongly in the second whorl organs as well as in the third whorl organs.ConclusionsPetunia has a class B gene other than GP that determines organ identities, both in the second and third whorls of the double mutant flower, and the action of the postulated class B gene (here called PhBX) is prevented by the BL gene in the second whorl of the gp flower. PhBX appears to be a gene that specifically interacts with the FBP1 gene, and is involved in the up‐regulation of FBP1.
Large‐scale screening of intracellular protein localization in living fission yeast cells by the use of a GFP‐fusion genomic DNA library
Authors: Ding Da‐Qiao , Tomita Yuki , Yamamoto Ayumu , Chikashige Yuji , Haraguchi Tokuko , Hiraoka Yasushi 
Published: March 2003

BackgroundIntracellular localization is an important part of the characterization of a gene product. In an attempt to search for genes based on the intracellular localization of their products, we constructed a green fluorescent protein (GFP)‐fusion genomic DNA library of S. pombe.ResultsWe constructed the S. pombe GFP‐fusion genomic DNA library by fusing, in all three reading frames, random fragments of genomic DNA to the 5′ end of the GFP gene in such a way that expression of potential GFP‐fusion proteins would be under the control of the own promoters contained in the genomic DNA fragments. Fission yeast cells were transformed with this plasmid library, and microscopic screening of 49 845 transformants yielded 6954 transformants which exhibited GFP fluorescence, of which 728 transformants showed fluorescence localized to distinct intracellular structures such as the nucleus, the nuclear membrane, and cytoskeletal structures. Plasmids were isolated from 516 of these transformants, and a determination of their DNA sequences identified 250 independent genes. The intracellular localizations of the 250 GFP‐fusion constructs was categorized as an image database; using this database, DNA sequences can be searched for based on the localizations of their products.ConclusionsA number of new intracellular structural components were found in this library. The library of GFP‐fusion constructs also provides useful fluorescent markers for various intracellular structures and cellular activities, which can be readily used for microscopic observation in living cells.
Blockade of cadherin‐6B activity perturbs the distribution of PSD‐95 family proteins in retinal neurones
Authors: Honjo Yasuko , Nakagawa Shinichi , Takeichi Masatoshi 
Published: March 2003

BackgroundSynaptic junctions have cadherin–catenin complexes, but their functions are poorly understood. Using retinal neurones, we investigated the role of this adhesion machinery in synaptic organization.ResultsIn cultures of chicken retinal cells, cadherin‐6B (cad6B) and cadherin‐7 (cad7) are expressed by distinct neurones, each being distributed in a punctate pattern along their neurites as well as in the soma. Double‐immunostaining for cad6B and PSD‐95/SAP90 or other PSD‐95 family members, known to localize in the postsynaptic density, showed that their distributions overlapped each other. To assess the role for cad6B, we incubated retinal cells with antibodies that could specifically block cad6B‐mediated adhesion. In the antibody‐treated neurones, the localization pattern of PSD‐95 family proteins was altered, that is, their staining signals tended to be reduced or disarranged. We then examined whether cadherins interacted molecularly with PSD‐95: Cadherin immunoprecipitates from brain lysates did not contain PSD‐95; nevertheless, this protein was co‐precipitated with αN‐ and β‐catenins. When PSD‐95 proteins were ectopically expressed in epithelial cells, some of these molecules were concentrated in cell–cell junctions, co‐localizing with E‐cadherin, and this junctional localization of PSD‐95 was abolished by blocking of E‐cadherin activity.ConclusionThese results suggest that cadherins play a role in the subcellular organization of postsynaptic density components through some, perhaps indirect, molecular interactions.
Modulation of TFIIH‐associated kinase activity by complex formation and its relationship with CTD phosphorylation of RNA polymerase II
Authors: Watanabe Yoshinori , Fujimoto Hiroyuki , Watanabe Tomomichi , Maekawa Takafumi , Masutani Chikahide , Hanaoka Fumio , Ohkuma Yoshiaki 
Published: March 2003

BackgroundThe general transcription factor TFIIH plays important roles in initiation and the transition to elongation steps of transcription by RNA polymerase II (PolII). Both roles are dependent on the protein kinase, DNA‐dependent ATPase and DNA helicase activities of TFIIH. However, how these enzyme activities of TFIIH contribute to transcription has remained elusive. TFIIH consists of nine subunits, and one of them, Cdk7, possesses kinase activity. Here the substrate specificities of TFIIH and two forms of the Cdk7‐containing kinase complex are compared, and the relationship between transcription activity and the TFIIH‐dependent phosphorylation of the carboxy terminal domain of the largest subunit of PolII (CTD) is studied.ResultsWe prepared TFIIH and two Cdk7‐containing kinase complexes, Cdk7/Cyclin H and CAK (Cdk7/Cyclin H/MAT1). Consistent with previous reports, CAK strongly phosphorylated Cdk2, Cdk4, CTD and intact PolII. In contrast, Cdk7/Cyclin H, which lacks MAT1, did not phosphorylate these substrates, except for weak phosphorylation of Cdk2. The kinase activity of TFIIH displayed stronger substrate preference for Cdk4 than did CAK. In addition, TFIIH phosphorylation of PolII was stimulated by TFIIE both in solution and during preinitiation complex formation, whereas Cdk7/Cyclin H and CAK phosphorylation of PolII was not. In combination with other general transcription factors, TFIIH, but not Cdk7/CycH or CAK, promoted transcription on a linear DNA template. This transcription was well correlated with TFIIE stimulated TFIIH phosphorylation of serine at position 5 (Ser‐5) within the heptapeptide repeat of the PolII CTD.ConclusionThese results provide clues about the roles of CTD phosphorylation at Ser‐5 in transcription.
Adaptor protein Shc undergoes translocation and mediates up‐regulation of the tyrosine kinase c‐Src in EGF‐stimulated A431 cells
Authors: Sato Ken‐ichi , Kimoto Miwa , Kakumoto Miki , Horiuchi Dai , Iwasaki Tetsushi , Tokmakov Alexander A. , Fukami Yasuo 
Published: March 2003

BackgroundShc is the adaptor protein that exists in three isoforms, P46, P52 and P66, and acts as a bridge between activated cell surface receptors and downstream signalling molecules which act in extracellular signal‐regulated cell events such as cell cycle progression. In our previous studies, Shc was shown to be a substrate of the tyrosine kinase c‐Src in vitro and in vivo.ResultsUsing green fluorescent protein‐fusion Shc (GFP‐Shc), we have shown that following epidermal growth factor (EGF) stimulation of A431 cells, all Shc isoforms were rapidly recruited from the cytoplasm to the plasma membrane (within 5 min) and then redistributed to the cytoplasmic vesicle structures (in the next 10–20 min). Indirect immunofluorescent study demonstrated that all Shc isoforms co‐localize with EGF receptor (EGFR) and activated c‐Src in both plasma membranes and cytoplasmic vesicle structures. Our previous study has shown that EGF induces the indirect association of EGFR and c‐Src and activation of c‐Src in A431 cells. An immunoprecipitation study demonstrated that the EGFR–Src association and c‐Src activation are augmented in cells expressing GFP‐Shc P52 or P66, but not P46. In addition, P52 and P66, but not P46, are in association with EGFR‐Src complex. We also found that EGFR and Shc can be dissociated from c‐Src by the addition of a synthetic peptide that corresponds to the autophosphorylation site of c‐Src. Interestingly, the peptide‐induced dissociation of the complex was not affected by the tyrosine phosphorylation state of the peptide.ConclusionThese results demonstrated a dynamic subcellular movement of Shc in response to EGF, and suggested a hitherto unknown scheme whereby Shc can work not only as a substrate of c‐Src but also as a mediator of the EGF‐induced activation of c‐Src in an isoform‐specific manner.
The absence of ribonuclease H1 or H2 alters the sensitivity of Saccharomyces cerevisiae to hydroxyurea, caffeine and ethyl methanesulphonate: implications for roles of RNases H in DNA replication and repair
Authors: Arudchandran Arulvathani , Cerritelli Susana , Narimatsu Scott , Itaya Mitsuhiro , Shin Deug‐Yong , Shimada Yuji , Crouch Robert 
Published: March 2003

BackgroundRNA of RNA‐DNA hybrids can be degraded by ribonucleases H present in all organisms including the eukaryote Saccharomyces cerevisiae. Determination of the number and roles of the RNases H in eukaryotes is quite feasible in S. cerevisiae.ResultsTwo S. cerevisiae RNases H, related to Escherichia coli RNase HI and HII, are not required for growth under normal conditions, yet, compared with wild‐type cells, a double‐deletion strain has an increased sensitivity to hydroxyurea (HU) and is hypersensitive to caffeine and ethyl methanesulphonate (EMS). In the absence of RNase H1, RNase H2 activity increases, and cells are sensitive to EMS but not HU and are more tolerant of caffeine; the latter requires RNase H2 activity. Cells missing only RNase H2 exhibit increased sensitive to HU and EMS but not caffeineConclusionsMutant phenotypes infer that some RNA‐DNA hybrids are recognized by both RNases H1 and H2, while other hybrids appear to be recognized only by RNase H2. Undegraded RNA‐DNA hybrids have an effect when DNA synthesis is impaired, DNA damage occurs or the cell cycle is perturbed by exposure to caffeine suggesting a role in DNA replication/repair that can be either beneficial or detrimental to cell viability.