bluuebunny/crossref_metadata_2025_split huggingface dataset:
A functional model for maximum growth of Atlantic Salmon parr, Salmo salar, from two populations in northwest England
Authors: ELLIOTT J. M. , HURLEY M. A. 
Published: November 2003

1. The chief objective was to develop a functional model for the growth of parr (0+, 1+) of Atlantic Salmon, Salmo salar, from two populations (Rivers Leven and Lune in northwest England), using a model similar to that developed previously for Brown Trout, Salmo trutta. Parr bred from Leven parents were acclimatized to nine fairly constant temperatures (two 0+, two 1+ parr per temperature) in the range 3·8–21·7 °C (variation ± 0·3 at 3·8 °C to ± 1·0 at 21·7 °C). Each fish was kept in a separate tank and fed to satiation on shrimps. The mass and length of each fish was recorded at the start and finish of a growth period of 30 days. Parr (0+, 1+) bred from Lune parents were separated into slow and fast growers, and acclimatized to six very constant temperatures. There were three slow and three fast growers at each of 5·0, 10·0, 15·0 °C for 0+ parr and each of 5·0, 10·0, 13·0, 15·0, 18·0, 20·0 °C for 1+ parr. Procedures were the same as for Leven parr except that the growth period lasted 30 days for the 18 0+ parr and 42 days for the 36 1+ parr. 2. The growth model was an excellent fit (P < 0·001) with no significant differences between parr from the two rivers, fast‐growing parr of different ages (0+, 1+), or fast‐ and slow‐growing 1+ parr. The optimum temperature for the combined data (81 parr) was 15·9 °C with a range for growth of 6·0–22·5 °C. The model failed to fit the data for slow‐growing 0+ Lune parr in experiments from November to February. Growth was reduced in these fish, even though the temperatures were suitable for growth (10, 15°C). 3. The model described approximately the growth of three year‐classes of Atlantic Salmon parr in the River Eden in northwest England. Some of the discrepancies between actual masses and those predicted from the model were consistent and possible reasons for this are discussed.
The optimal shape of avian eggs
Authors: BARTA Z. , SZÉKELY T. 
Published: November 2003

1. The shape of avian eggs is often explained by involving the mechanical properties of eggshell such as resistance to breakage or invoking physiological forces operating during egg development. 2. Here we take a different approach and investigate the efficient use of space. According to this approach the optimal egg shape is the one that produces the most compact fit under the incubating parent. 3. We extend the model of Andersson (1978) and use a numerical technique to investigate egg shapes in clutches of 1 to 10 eggs. In our model the shape of eggs is described by four parameters in a two‐dimensional space. These parameters are free to vary – but eggs cannot be concave. 4. The optimal egg shape for each clutch size was found by a genetic algorithm. 5. The model predicts that egg shape should depend on clutch size. In particular, if the clutch consists of one egg then this egg should be spherical; whereas in clutches of two or three eggs the eggs should be biconical. In clutches of four the eggs should be pointed. The model also predicts that in clutches of over seven eggs the optimal egg shape should be approximately spherical. 6. These predictions are valuable because they point out that some of the variation in avian egg shapes may be explained solely by the efficient use of the brood patch area of the incubating parent.
The influence of the rate of temperature change on the activation of dormant seeds of Rumex obtusifolius L.
Authors: VAN NERUM J. A. VAN ASSCHE & D. M. 
Published: November 2003

1. One temperature shift from 20 to 30°C in darkness induces 30–40% germination in Rumex obtusifolius seeds. The same germination percentages are found with heat treatment varying between 1 and 6h duration, indicating that the total heat sum of the temperature shift is not important. 2. Germination is greatly enhanced by three consecutive heat shifts of 1h at 30°C separated by 1h periods at 20°C. 3. The seeds are activated to a small extent after a slow warming (+2°Ch–1) from 20 to 30°C, followed by incubation for 1h at 30°C. Germination is much higher after rapid heating (+10°Ch–1) to 30°C, followed by 1h incubation at this temperature. Repeated fast heating treatments on four consecutive days enhances germination. Moderately rapid heatings (+3·3°Ch–1) give intermediate results. 4. The rate of cooling does not influence the germination percentage. Cooling alone cannot induce germination. 5. Heating alone from 15 to 25°C without cooling also activates germination. In this temperature range the seeds are more activated by rapid warming than by slow warming. 6. The ecological relevance of the response to different warming rate is discussed. The insensitivity of seeds to a slow warming might keep deeply buried seeds in a dormant stage.
Changes in haematological parameters in relation to prey switching in a wild population of harbour seals
Authors: THOMPSON P. M. , TOLLIT D. J. , CORPE H. M. , REID R. J. , ROSS H. M. 
Published: November 2003

1. Previous studies have found marked inter‐annual variation in winter food availability, diet composition and body condition in a population of harbour seals (Phoca vitulina L.) in Northeast Scotland. This study aimed to determine whether there were other physiological consequences of prey switching by comparing haematological parameters in years when the clupeids herring and sprat dominated the diet and in years when seals switched to alternative prey. 2. There were significant differences in leukocyte and erythrocyte parameters in relation to diet composition. In contrast, indices of body condition did not explain the variation in haematological parameters, suggesting that the observed changes did not result from differences in the energetic content of the prey. 3. Leukocyte counts were significantly higher after ‘good’ clupeid years, although the differences in mean counts were small. Such differences could have resulted either from immuno‐suppression, for example because of differences in prey nutrient or contaminant levels, or from differences in the pathogen challenge resulting from geographical variations in water quality. 4. The differences in erythrocyte parameters were more marked, and there was evidence of widespread macrocytic anaemia when seals switched from clupeids to alternative prey. Such differences could result either from acclimation, as a result of prey‐specific foraging strategies, or from differences in the nutritional quality of prey. 5. These results indicate that generalist predators such as the harbour seal may exhibit physiological responses to changes in the composition of their diet. These data highlight the need to consider the long‐term physiological effects of variations in food availability on the population dynamics of generalist marine top predators. In particular, it is hypothesized that fish‐induced anaemia may be responsible for declines in certain pinniped populations.
Identical origin of adrenal cortex and gonad revealed by expression profiles of Ad4BP/SF‐1
Authors: Hatano Osamu , Takakusu Akira , Nomura Masatoshi , Morohashi Ken‐ichirou 
Published: November 2003

Background: Ad4BP/SF‐1 was originally identified as a steroidogenic tissue‐specific transcription factor. Recent gene disruption studies with the mammalian Ftz‐F1 gene encoding Ad4BP/SF‐1 clearly revealed the essential function of the factor for adrenal and gonadal differentiation. Results: In this study, we examined the early development of these tissues using Ad4BP/SF‐1 as the marker. In rat foetuses of 11.5 days post‐coitum (d.p.c.), a cell population designated adreno‐genital primordium was firstly observed on symmetrical lines extending from the dorsal aorta to the dorsal coelomic epithelia of the primitive urogenital ridges. From 12.5 d.p.c., the rostral half of the adreno‐genital primordium started to separate into two distinct cell populations. Judging from the distribution of primordial germ cells, the cell population on the dorsal aortal side is a primordium for the adrenal cortex whereas that on the coelomic epithelial side is for the gonads. At 13.5 d.p.c., these two primordia have separated completely. Conclusion: These observations clearly identified a novel adreno‐genital primordium from which both the adrenal cortex and the gonads originate. An RT‐PCR study conducted to detect adrenal‐ and gonad‐specific mRNAs supported the above observations.
Sensing of DNA non‐homology lowers the initiation of meiotic recomination in yeast
Authors: Rocco Vincenzo , Nicolas Alain 
Published: November 2003

Background: Meiotic recombination between homologous chromosomes in the yeast Saccharomyces cerevisiae is initiated by the formation of DNA double‐strand breaks (DSBs). The mechanism of DSB formation and the factors that determine their frequency and location have yet to be elucidated. Current studies of meiotic recombination are also concerned with the question of the functional relationship between DSB formation and the other meiotic processes of homology searching, pairing and synapsis of homologues. Results: To test if DNA identity is required for high levels of DSBs and recombination, we have asked whether small DNA heterologies (140–547 bp) located within the well characterized ARG4 initiator of meiotic recombination, can affect DSB formation and gene conversion events in the ARG4 locus. The present physical and genetic analyses show that some heterologies reduced recombination frequencies without altering DSB formation, whereas others reduced both DSB and gene conversion frequencies. Conclusions: These results suggest that DNA heterologies overlapping a recombination initiator impair meiotic gene conversion at two levels. First, some heterologies affect the level of DSB formation, revealing the existence of an anti‐initiation process sensing the presence of sequence non‐homology between the homologous chromosomes. Second, heterologies can impair the successful processing of the recombination intermediates once DSBs are made. We present a model for interhomologue cross‐talks involving chromosomal and DNA/DNA interactions.
D‐type cyclin expression is decreased and p21 and p27 CDK inhibitor expression is increased when tsBN462 CCG1/TAFII250 mutant cells arrest in G1 at the restrictive temperature
Authors: Sekiguchi Takeshi , Noguchi Eishi , Hayashida Toshiro , Nakashima Torahiko , Toyoshima Hideo , Nishimoto Takeharu , Hunter Tony 
Published: November 2003

Background: The tsBN462 temperature‐sensitive mutant hamster cell line exhibits cell cycle arrest and apoptosis at the restrictive temperature of 39.5 °C, due to a point mutation in the CCG1/TAFII 250 gene, which encodes a component of the general transcription factor TFIID. Results: We now report that CCG1/TAFII 250 persisted as a complex with TBP and associated proteins (TAFs) in tsBN462 cells at the restrictive temperature. FACScan analysis revealed that the tsBN462 mutation resulted in a failure to progress out of G0 into G1. Using two‐dimensional gel electrophoresis we observed a decrease in the synthesis of several proteins, starting in the middle of the G1 phase, becoming very pronounced during late G1. The expression of the immediate early genes c‐fos, c‐jun and c‐myc was normally induced by serum treatment of quiescent cells at the restrictive temperature, whereas expression of cyclins A, D1 and D3 was reduced. Expression of the cyclin‐dependent kinase (CDK) inhibitor proteins p21 and p27 was enhanced. Consistent with the decreased cyclin D and increased p21/p27 expression, we found that phosphorylation of Rb was decreased at 39.5 °C. Cyclin A‐, E‐ and Cdk2‐associated histone H1 kinase activity was reduced concomitantly with the increase in p21 protein. Conclusion: Decreased cyclin/Cdk kinase activity and decreased Rb phosphorylation are possible causes of G1 cell cycle arrest in tsBN462 cells at the restrictive temperature.
Phosphorylation of Ser‐3 of cofilin regulates its essential function on actin
Authors: Moriyama Kenji , Iida Kazuko , Yahara Ichiro 
Published: November 2003

Background:  Cofilin is a low‐molecular weight actin‐modulating protein, and is structurally and functionally conserved in eucaryotes from yeast to mammals. The functions of cofilin appear to be regulated by phosphorylation and dephosphorylation. Results:  A proteolytic study of phosphorylated porcine cofilin and expression of a mutated cofilin in cultured cells revealed that Ser‐3 is the unique phosphorylation site. Phosphorylated cofilin was found not to bind to either F‐or G‐actin while unphosphorylated cofilin binds to both. S3D‐cofilin, in which Ser‐3 was replaced with Asp, did not bind in vitro to actin while S3A‐cofilin did. The transient overexpression of wild‐type or S3A‐cofilin in cultured cells caused disruption of pre‐existing actin structures and induced cytoplasmic actin bundles. Heat shock‐induced nuclear or NaCl buffer‐induced cytoplasmic actin/cofilin rods contained the expressed cofilin. In contrast, the overexpression of S3D‐cofilin did not alter the actin structures. Induced actin rods did not contain S3D‐cofilin. S3D‐porcine cofilin did not complement the lethality associated with Δcof1 mutations in Saccharomyces cerevisiae while wild‐type and S3A‐cofilin did. Furthermore, we found that S2A/S4D‐ and S2D/S4D‐yeast cofilin mutants were not viable. Conclusion:  We conclude that the function of cofilin is negatively regulated in vivo by phosphorylation of Ser‐3 and that cells require the functions of unphosphorylated cofilin for viability.
HALF‐1, a bZIP‐type protein, interacting with the wheat transcription factor HBP‐1a contains a novel transcriptional activation domain
Authors: Okanami Masahiro , Meshi Tetsuo , Tamai Hiroki , Iwabuchi Masaki 
Published: November 2003

Background: Nuclear factors bind to cis‐acting elements and mediate transcriptional regulation through protein–protein interactions with other factors. The bZIP‐type wheat nuclear protein HBP‐1a(17) is a putative transcriptional activator specifically binding to the Hex (ccACGTCA) and G‐box (CCACGTGG) motifs, which are often found in the cis‐acting elements critical for various responses in plants. Results: In order to investigate the mechanisms for gene expression mediated via the Hex and G‐box motifs, we attempted to isolate proteins interacting with HBP‐1a(17) based on protein–protein interactions. A cDNA expression library from wheat seedlings was screened with 32P‐labelled HBP‐1a(17), and a bZIP‐type protein, termed HALF‐1 (HBP‐1‐associated leucine‐zipper factor‐1), was isolated. GST‐pulldown assay, yeast two‐hybrid system and EMSA showed that HALF‐1 and HBP‐1a(17) interact with each other through their leucine‐zipper regions. Dissection experiments showed that HALF‐1 has at least one potential trans‐activation domain which includes a nine amino acid motif conserved between several plant bZIP‐type proteins. This motif, named GCB (GBF‐conserved box; consensus, NLNIGMDXW), activated the expression of a reporter gene, when fused to the GAL4 DNA‐binding domain. The corresponding region of Arabidopsis GBF1 also stimulated transcription. However, the trans‐activation domain of HALF‐1 did not function in yeast. Conclusions: We identified a novel trans‐activation domain which contains the GCB motif conserved among plant bZIP‐type factors. The trans‐activation appears to be mediated by interaction between the GCB motif and a factor conserved in plants.
The sbcC and sbcD genes of Escherichia coli encode a nuclease involved in palindrome inviability and genetic recombination
Authors: Connelly John C. , Leach David R. F. 
Published: November 2003

Background: Long DNA palindromes have the potential to adopt hairpin or cruciform secondary structures that inhibit DNA replication. In Escherichia coli, this palindrome‐mediated inviability results from the activity of the sbcC and sbcD genes, and genetic observations have suggested that they may encode a nuclease. Mutations in these genes also restore the defect in genetic recombination associated with recBC sbcB mutants.Results: We have purified the E. coli SbcCD protein from an overexpressing strain and have shown that it has an ATP‐dependent DNA double‐strand exonuclease activity. Co‐purification of nuclease with protein, antibody inhibition and the absence of activity in extracts lacking the sbcCD genes confirm that the activity is intrinsic to SbcCD. The purified protein also has an ATP‐independent single‐strand DNA endonuclease activity.Conclusions: We have shown that sbcCD encodes a nuclease. The purified protein has double‐strand DNA exonuclease and single‐strand DNA endonuclease activities. We propose that SbcCD cleaves secondary structures formed at replication forks and that the broken forks can be repaired by homologous recombination.
Mechanism responsible for glucose–lactose diauxie in Escherichia coli: challenge to the cAMP model
Authors: Inada Toshifumi , Kimata Keiko , Aiba Hiroji 
Published: November 2003

Background : The inhibition of β‐galactosidase expression in glucose–lactose diauxie is a typical example of the glucose effect in Escherichia coli. It is generally believed that glucose exerts its effect at least partly by reducing the intracellular cAMP level. However, there is no direct evidence that the inhibitory effect of glucose on the expression of the lac operon is mediated by a reduction of the cAMP level in the glucose–lactose system.Results : To examine the roles of cAMP and the cAMP receptor protein (CRP) in the glucose effect, the intracellular levels of these factors were determined during diauxic growth in a glucose–lactose medium. We found that the levels of cAMP and CRP in a lactose‐grown phase were not higher than those in a glucose‐grown phase, although the cAMP levels increased transiently during the lag phase. The addition of exogenous cAMP eliminated diauxic growth but did not eliminate glucose repression. Glucose repression and diauxie were observed in cells which lack cAMP but produce a cAMP‐independent CRP. In addition, inactivation of the lac repressor by the disruption of the lacI gene or the addition of IPTG, eliminated glucose repression.Conclusion : We conclude that the repression of β‐galactosidase expression by glucose is not due to the reduction of the cAMP‐CRP level but due to an inducer exclusion mechanism which is mediated by the phosphoenolpyruvate‐dependent sugar phosphotransferase system.
RNA‐dependent association of the Drosophila maleless protein with the male X chromosome
Authors: Richter Liz , Bone James R. , Kuroda Mitzi I. 
Published: November 2003

Background: Dosage compensation results in equivalent X‐linked gene expression in males (XY) and females (XX). In Drosophila, both X chromosomes are active in females, and the single male X must double its transcriptional activity to allow male development. Four proteins (encoded by the male‐specific lethal genes) are required for dosage compensation and associate with the X chromosome in males but not in females.Results : In this report, we focus on the maleless (MLE) protein. The MLE protein sequence contains motifs common to members of a family of RNA‐dependent ATPases. We have found that association of MLE with the male X chromosome is RNase sensitive, and that mutations in the ATPase motifs affect MLE function. Overexpression of MLE or its carboxyl terminus, which includes glycine‐rich repeats, reveals an RNase‐sensitive affinity for all chromosome arms.Conclusions: Our results suggest that nascent transcripts or a hypothetical RNA component of chromatin play a critical role in the biochemical mechanism of dosage compensation. The potential relationship between interaction with RNA and transcriptional control of the X chromosome suggests that the mechanism of dosage compensation is distinct from classical models for transcriptional activation.
The Schizosaccharomyces pombe mra1 gene, which is required for cell growth and mating, can suppress the mating inefficiency caused by a deficit in the Ras1 activity
Authors: Hakuno Fumihiko , Hughes David A. , Yamamoto Masayuki 
Published: November 2003

Background
Schizosaccharomyces pombe Ras1 regulates two downstream pathways, namely the Byr2/Byr1/Spk1 mitogen‐activated protein kinase cascade and the Cdc42sp small G protein pathway. The former is relevant to mating and sporulation, whereas the latter is relevant to mating, cell growth and cell morphology. We addressed whether Ras1 has any additional role in the regulation of cell physiology.Results: Using a specific mutation in the effector region of Ras1, we isolated a high‐copy‐number suppressor of the mating deficiency caused by a decrease of the Ras1 activity. The isolated gene, named mra1, encodes a novel protein of 359 amino acids, which has apparent homologues in rice and budding yeast. Disruption of mra1 indicated that it is essential for cell growth, and mutational analysis indicated that it is required for the promotion of mating. These two functions could be separated by mutations, suggesting that Mra1 is bifunctional. Overexpression of mra1 could also suppress the mating inefficiency caused by either overexpression of gap1, which is a downregulator of Ras1, or loss of function of zfs1, which is a gene relevant to the mating pheromone signalling. However, it could not suppress null mutations in genes involved in the two known pathways downstream of Ras1.Conclusions: Mra1 is an apparent downstream factor of Ras1, which is essential for cell growth and relevant to mating but is not involved in the maintenance of cell morphology. Mra1 is unlikely to interact directly with the known pathways downstream of Ras1, implying that it may be a factor constituting a third pathway regulated by Ras1.
A single Drosophila melanogaster myosin light chain kinase gene produces multiple isoforms whose activities are differently regulated
Authors: Kojima Shin‐ichiro , Mishima Masanori , Mabuchi Issei , Hotta Yoshiki 
Published: November 2003

Background: Myosin light chain kinase (MLCK) specifically phosphorylates the myosin regulatory light chain in a calcium/calmodulin (Ca2+/CaM)‐dependent manner in animal cells. The roles of MLCK are not fully understood, particularly in nonmuscle cells. Therefore, we cloned and characterized a Drosophila MLCK gene as the first step in a genetic analysis of this process. Results: Four transcripts are produced from this gene. These transcripts encode at least three isoforms (isoform‐I, ‐II and ‐III), which share a kinase domain, a fibronectin type III motif and an immunoglobulin C2 motif. However, regulatory regions differ between isoform‐I/II and ‐III due to the alternative splicing of the exon encoding a CaM‐binding domain. As a result, isoform‐I and ‐II are Ca2+/CaM‐dependent forms, whereas isoform‐III is a Ca2+/CaM‐independent form. Northern blotting and in situ hybridization showed that the expressions of these isoforms are distinctly regulated in stage‐ and tissue‐dependent manners. Isoform‐I seems to be expressed ubiquitously, while isoform‐III is expressed predominantly in muscle tissues. In contrast to these isoforms, isoform‐II is specific to late pupa and adult. Conclusion: In Drosophila, a single MLCK gene produces multiple isoforms whose regulatory regions and expression patterns are different. These differences suggest various cellular functions of MLCK in Drosophila.