bluuebunny/crossref_metadata_2025_split huggingface dataset:
Walking on inclines: energetics of locomotion in the antCamponotus
Authors: Lipp Alexandra , Wolf Harald , Lehmann Fritz-Olaf 
Published: February 2005

SUMMARYTo assess energetic costs during rest and locomotion in a small insect, we measured metabolic rate in freely moving ants Camponotus sp.(average body mass 11.9 mg). The animals ran in a straight respirometric chamber in which locomotor speed and CO2 release were monitored simultaneously using flow-through respirometry and conventional video analysis. In resting intact ants, standard metabolic rate was on average 0.32 ml CO2 g-1 body mass h-1. During walking, the ants breathed continuously and metabolic rate increased between 4.3 times(level walking at 0-5 mm s-1) and 6.9 times (30° ascent at 85-95 mm s-1) over resting rates. Metabolic rate increased linearly with increasing walking speed but superficially leveled off beyond speeds of about 70 mm s-1. Walking on incline (uphill) or decline slopes(downhill) of up to 60° had only a small effect on energy consumption compared to level walking. During slope walking, total metabolic rate averaged over all running speeds ranged from a minimum of 1.55±0.4 (horizontal running) to a maximum of 1.89±0.7 ml CO2 h-1g-1 body mass (30° downhill). The mean cost of transport in Camponotus was approximately 130 J g-1 km-1. The metabolic requirements in the comparatively small insect Camponotus for walking were mostly in the range expected from data obtained from other insects and small poikilotherms, and from allometric scaling laws.
Intracellular calcium and survival of tadpole forebrain cells in anoxia
Authors: Hedrick Michael S. , Fahlman Christian S. , Bickler Philip E. 
Published: February 2005

SUMMARYThe frog brain survives hypoxia with a slow loss of energy charge and ion homeostasis. Because hypoxic death in most neurons is associated with increases in intracellular calcium ([Ca2+]i), we examined the relationship between [Ca2+]i and survival of a mixed population of isolated cells from the forebrain of North American bullfrog Rana catesbeiana tadpoles. Forebrain cells from stage V-XV tadpoles were isolated by enzymatic digestion and loaded with one of three different calcium indicators (Fura-2, Fura 2-FF and BTC) to provide estimates of [Ca2+]i accurate at low and high[Ca2+]i. Propidium iodide (PI) fluorescence was used as an indicator of cell viability. Cells were exposed to anoxia (100%N2) and measurements of [Ca2+]i and cell survival made from 1 h to 18 h. Intracellular [Ca2+] increased significantly after 3-6 h anoxia (P&lt;0.05), regardless of the type of Ca2+ indicator used; however, there were substantial differences in the measurements of [Ca2+]i with the different indicators, reflecting their varying affinities for Ca2+. Resting[Ca2+]i was approximately 50 nmol l-1 and increased to about 9-30 μmol l-1 after 4-6 h anoxia. The significant increase in [Ca2+]i during anoxia was not associated with significant increases in cell death, with 85-95% survival over this time period. Cells exposed to anoxia for 18 h, or those made anoxic for 4-6 and reoxygenated for 12 h to 16 h, had survival rates greater than 70%,but survival was significantly less than normoxic controls. These results indicate that large increases in [Ca2+]i are not necessarily associated with hypoxic cell death in vertebrate brain cells.
Lifespan extension and elevatedhspgene expression inDrosophilacaused by histone deacetylase inhibitors
Authors: Zhao Yanmei , Sun Hui , Lu Jun , Li Xiaoxue , Chen Xia , Tao Dan , Huang Weifeng , Huang Baiqu 
Published: February 2005

SUMMARYThe heat shock proteins (Hsps) play a positive role in lifespan determination, and histone acetylation has been shown to be involved in transcription of hsp genes in Drosophila. To further determine if hsp22 and hsp70 expression is correlated with lifespan, and if histone acetylation participates in this process, RNA levels for hsp22 and hsp70 were analyzed throughout the lifespan in the long-lived and short-lived iso-female lines. The results showed that hsp22 and hsp70 RNA levels were higher in long-lived line than in short-lived line and that the long-lived flies responded more rapidly to heat but were more tolerant to high temperature. Moreover, we investigated the influences of histone acetylation modification on longevity and on hsp gene expression by using histone deacetylase (HDAC) inhibitors TSA and BuA. The results demonstrated that both inhibitors were able to extend the lifespan and promote hsp22 and hsp70 expression. However, the optimal concentrations of these inhibitors, and probably the mechanisms of their actions, vary with the genetic background. In addition, we showed that HDAC inhibitors caused the hyperacetylation of core histone H3,implicating the involvement of chromatin modulation in hsp gene transcription. These data suggested a close correlation among histone acetylation, hsp gene expression and longevity in D. melanogaster.
Increased Oxidative DNA Damage, as Assessed by Urinary 8-Hydroxy-2′-Deoxyguanosine Concentrations, and Serum Redox Status in Persons Exposed to Mercury
Authors: Chen Chunying , Qu Liya , Li Bai , Xing Li , Jia Guang , Wang Tiancheng , Gao Yuxi , Zhang Peiqun , Li Mei , Chen Wei , Chai Zhifang 
Published: February 2005

Abstract
Background: Mercury is a ubiquitous and highly toxic environmental pollutant. In this study, we evaluated the relationship between mercury exposure and oxidative stress, serum and urinary mercury concentrations, oxidative DNA damage, and serum redox status in chronically mercury-exposed persons compared with healthy controls.
Methods: We measured urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG), which we used as a biomarker of oxidative DNA damage in the mercury-exposed persons, by HPLC with electrochemical detection (ECD). We evaluated antioxidant status by measuring the activities of superoxide dismutase and glutathione peroxidase and the concentrations of total reduced glutathione and protein-bound thiols in serum.
Results: The significant increase in 8-OHdG concentrations in urine indicated that mercury-induced oxidative damage to DNA occurred in vivo. Differences in body mercury burden and antioxidant enzyme activities were statistically significant between the mercury-exposed persons and controls. Serum and urinary mercury concentrations in the mercury-exposed persons were more than 40-fold higher than in controls.
Conclusions: Mercury exposure can induce oxidative DNA damage, whereas the antioxidative repair systems can be expected to minimize DNA lesions caused by mercury. Measurement of urinary 8-OHdG could be useful for evaluating in vivo oxidative DNA damage in mercury-exposed populations.
Dual concentration-dependent activity of thyroglobulin type-1 domain of testican: specific inhibitor and substrate of cathepsin L
Authors: Meh Primož , Pavšič Miha , Turk Vito , Baici Antonio , Lenarčič Brigita 
Published: February 2005

AbstractThe thyroglobulin type-1 (Tg-1) domain is a protein module that occurs in a variety of secreted and membrane proteins and is recognised as a potent inhibitor of cysteine peptidases. We present here some properties of the Tg-1 domain of human testican, a modularly organised proteoglycan secreted mainly by brain cells, the exactin vivofunction of which is not yet clear. The domain was prepared as a recombinant protein in aPichia pastorisexpression system and its activity was demonstrated by specific and selective inhibition of cathepsin L (Ki=0.14 nM). Interaction at high enzyme and inhibitor concentrations resulted in degradation of the domain by cathepsin L, which was not observed under conditions used for the determination of kinetic parameters. No inhibitory activity could be detected for cathepsin K, but it exhibited a very similar degradation pattern. Homology modelling provided a good explanation for the different behaviour observed with the two enzymes. Firstly, the steric fit between the interfaces of testican domain and cathepsin L is stabilised by numerous favourable forces, while no such interactions are evident in the complex with cathepsin K, and repulsive interactions even prevent access of the domain to the active site of papain. Secondly, the prolonged first loop of the domain occupies a position near the catalytic cysteine residue in a more substrate-like manner, enabling cleavage of the Gly22-Ala23bond.
50 Jahre Entdeckung des piezoresistiven Effekts – Geschichte und Entwicklungsstand piezoresistiver Sensoren (50 Years of Piezoresistive Sensors – History and State of the Art of Piezoresistive Sensors)
Authors: Gerlach Gerald , Werthschützky Roland 
Published: February 2005

Abstract
Am 1. April 1954 erschien in der Zeitschrift Physical Review ein Aufsatz von Charles S. Smith , in dem erstmalig über den piezoresistiven Effekt berichtet wurde, den er bei den kubischen Halbleitern Germanium und Silizium beobachtet hatte [1]. Mit dieser Entdeckung begann die Entwicklung diskreter Silizium-Dehnmessstreifen, die gegenüber Metall-DMS einen bis zu einem Faktor von 20...50 größeren K-Faktor aufweisen. Mit der Integration diffundierter Widerstände direkt in das Silizium und der Schaffung lokal abgedünnter Bereiche im Silizium, die dann als drucksensitiver Verformungskörper wirkten, wurden neben den piezoresistiven Wandlereigenschaften nun auch die ausgezeichneten mechanischen Eigenschaften von Silizium ausgenutzt. Rund zwei Jahrzehnte haben dann piezoresistive Sensoren die Entwicklung der Mikrosystemtechnik mit ihren vielfältigen Fertigungsverfahren mitbestimmt und damit vielen anderen mikroelektromechanischen Systemen (MEMS) den Weg bereitet [2;3;4] (Tabelle 1). Auch nach 50 Jahren der Entwicklung piezoresistiver Aufnehmer stellt diese Sensorklasse noch ein wissenschaftlich interessantes Gebiet dar.
Messunsicherheit piezoresistiver Sensoren (Uncertainty in the Measurement of Piezoresistive Sensors)
Authors: Hoa Phan L. P. , Suchaneck Gunnar , Gerlach Gerald 
Published: February 2005

Abstract
Dieser Beitrag betrachtet die Messunsicherheit piezoresistiver Drucksensoren entsprechend dem von der ISO herausgegebenen Guide to the „Expression of Uncertainty in Measurement“, kurz GUM genannt. Es wird gezeigt, dass das Rauschen im Sensor stark durch die Sensorpassivierung beeinflusst wird. Neben der Temperatur erwies sich die Feuchtigkeit als zweite bedeutsame Ursache der Messunsicherheit.
Developmental Roles of the Mi-2/NURD-Associated Protein p66 in Drosophila
Authors: Kon Charlene , Cadigan Kenneth M , da Silva Sofia Lopes , Nusse Roel 
Published: February 2005

Abstract
The NURD and Sin3 histone deacetylase complexes are involved in transcriptional repression through global deacetylation of chromatin. Both complexes contain many different components that may control how histone deacetylase complexes are regulated and interact with other transcription factors. In a genetic screen for modifiers of wingless signaling in the Drosophila eye, we isolated mutations in the Drosophila homolog of p66, a protein previously purified as part of the Xenopus NURD/Mi-2 complex. p66 encodes a highly conserved nuclear zinc-finger protein that is required for development and we propose that the p66 protein acts as a regulatory component of the NURD complex. Animals homozygous mutant for p66 display defects during metamorphosis possibly caused by misregulation of ecdysone-regulated expression. Although heterozygosity for p66 enhances a wingless phenotype in the eye, loss-of-function clones in the wing and the eye discs do not have any detectable phenotype, possibly due to redundancy with the Sin3 complex. Overexpression of p66, on the other hand, can repress wingless-dependent phenotypes. Furthermore, p66 expression can repress multiple reporters in a cell culture assay, including a Wnt-responsive TCF reporter construct, implicating the NURD complex in repression of Wnt target genes. By co-immunoprecipitation, p66 associates with dMi-2, a known NURD complex member.
Transient Receptor Potential-Like Channels Are Essential for Calcium Signaling and Fluid Transport in a Drosophila Epithelium
Authors: MacPherson Matthew R , Pollock Valerie P , Kean Laura , Southall Tony D , Giannakou Maria E , Broderick Kate E , Dow Julian A T , Hardie Roger C , Davies Shireen A 
Published: February 2005

Abstract
Calcium signaling is an important mediator of neuropeptide-stimulated fluid transport by Drosophila Malpighian (renal) tubules. We demonstrate the first epithelial role, in vivo, for members of the TRP family of calcium channels. RT-PCR revealed expression of trp, trpl, and trpγ in tubules. Use of antipeptide polyclonal antibodies for TRP, TRPL, and TRPγ showed expression of all three channels in type 1 (principal) cells in the tubule main segment. Neuropeptide (CAP2b)-stimulated fluid transport rates were significantly reduced in tubules from the trpl302 mutant and the trpl;trp double mutant, trpl302;trp343. However, a trp null, trp343, had no impact on stimulated fluid transport. Measurement of cytosolic calcium concentrations ([Ca2+]i) in tubule principal cells using an aequorin transgene in trp and trpl mutants showed a reduction in calcium responses in trpl302. Western blotting of tubule preparations from trp and trpl mutants revealed a correlation between TRPL levels and CAP2b-stimulated fluid transport and calcium signaling. Rescue of trpl302 with a trpl transgene under heat-shock control resulted in a stimulated fluid transport phenotype that was indistinguishable from wild-type tubules. Furthermore, restoration of normal stimulated rates of fluid transport by rescue of trpl302 was not compromised by introduction of the trp null, trp343. Thus, in an epithelial context, TRPL is sufficient for wild-type responses. Finally, a scaffolding component of the TRPL/TRP-signaling complex, INAD, is not expressed in tubules, suggesting that inaD is not essential for TRPL/TRP function in Drosophila tubules.
Gal80 Dimerization and the Yeast GAL Gene Switch
Authors: Pilauri Vepkhia , Bewley Maria , Diep Cuong , Hopper James 
Published: February 2005

Abstract
The Saccharomyces cerevisiae Gal80 protein has two binding partners: Gal4 and Gal3. In the absence of galactose, Gal80 binds to and inhibits the transcriptional activation domain (AD) of the GAL gene activator, Gal4, preventing GAL gene expression. Galactose triggers an association between Gal3 and Gal80, relieving Gal80 inhibition of Gal4. We selected for GAL80 mutants with impaired capacity of Gal80 to bind to Gal3 or Gal4AD. Most Gal80 variants selected for impaired binding to Gal4AD retained their capacity to bind to Gal3 and to self-associate, whereas most of those selected for impaired binding to Gal3 lost their ability to bind to Gal4AD and self-associate. Thus, some Gal80 amino acids are determinants for both the Gal80-Gal3 association and the Gal80 self-association, and Gal80 self-association may be required for binding to Gal4AD. We propose that the binding of Gal3 to the Gal80 monomer competes with Gal80 self-association, reducing the amount of the Gal80 dimer available for inhibition of Gal4.
Mitochondrial Translation
Authors: Chiron Stéphane , Suleau Audrey , Bonnefoy Nathalie 
Published: February 2005

AbstractThe translation elongation factor EF-Tu is a GTPase that delivers amino-acylated tRNAs to the ribosome during the elongation step of translation. EF-Tu/GDP is recycled by the guanine nucleotide exchange factor EF-Ts. Whereas EF-Ts is lacking in S. cerevisiae, both translation factors are found in S. pombe and H. sapiens mitochondria, consistent with the known similarity between fission yeast and human cell mitochondrial physiology. We constructed yeast mutants lacking these elongation factors. We show that mitochondrial translation is vital for S. pombe, as it is for human cells. In a genetic background allowing the loss of mitochondrial functions, a block in mitochondrial translation in S. pombe leads to a major depletion of mtDNA. The relationships between EF-Ts and EF-Tu from both yeasts and humans were investigated through functional complementation and coexpression experiments and by a search for suppressors of the absence of the S. pombe EF-Ts. We find that S. cerevisiae EF-Tu is functionally equivalent to the S. pombe EF-Tu/EF-Ts couple. Point mutations in the S. pombe EF-Tu can render it independent of its exchange factor, thereby mimicking the situation in S. cerevisiae.
Processivity Clamp gp45 and ssDNA-Binding-Protein gp32 Modulate the Fidelity of Bacteriophage RB69 DNA Polymerase in a Sequence-Specific Manner, Sometimes Enhancing and Sometimes Compromising Accuracy
Authors: Bebenek Anna , Carver Geraldine T , Kadyrov Farid A , Kissling Grace E , Drake John W 
Published: February 2005

Abstract
Numerous studies of the impact of accessory proteins upon the fidelity of DNA synthesis have provided a complex and sometimes discordant picture. We previously described such an analysis conducted in vitro using various bacteriophage RB69 gp43 mutator DNA polymerases with or without the accessory proteins gp32 (which binds single-stranded DNA) plus gp45/44/62 (processivity clamp and its loaders). Mutations were scored at many sites in the lacZα mutation reporter sequence. Unexpectedly, the accessory proteins sometimes decreased and sometimes increased fidelity at a handful of specific sites. Here, we enlarge our analysis with one particular mutator polymerase compromised in both insertion accuracy and proofreading and also extend the analysis to reactions supplemented only with gp32 or only with gp45/44/62. An overall 1.56-fold increase in mutation frequencies was produced by adding single or multiple accessory proteins and was driven mainly by increased Ttemplate•Gprimer mispairs. Evidence was found for many additional sites where the accessory proteins influence fidelity, indicating the generality of the effect. Thus, accessory proteins contribute to the site-specific variability in mutation rates characteristically seen in mutational spectra.
A Systematic High-Throughput Screen of a Yeast Deletion Collection for Mutants Defective in PHO5 Regulation
Authors: Huang Sidong , O'Shea Erin K 
Published: February 2005

Abstract
In response to phosphate limitation, Saccharomyces cerevisiae induces transcription of a set of genes important for survival. One of these genes is PHO5, which encodes a secreted acid phosphatase. A phosphate-responsive signal transduction pathway (the PHO pathway) mediates this response through three central components: a cyclin-dependent kinase (CDK), Pho85; a cyclin, Pho80; and a CDK inhibitor (CKI), Pho81. While signaling downstream of the Pho81/Pho80/Pho85 complex to PHO5 expression has been well characterized, little is known about factors acting upstream of these components. To identify missing factors involved in the PHO pathway, we carried out a high-throughput, quantitative enzymatic screen of a yeast deletion collection, searching for novel mutants defective in expression of PHO5. As a result of this study, we have identified at least nine genes that were previously not known to regulate PHO5 expression. The functional diversity of these genes suggests that the PHO pathway is networked with other important cellular signaling pathways. Among these genes, ADK1 and ADO1, encoding an adenylate kinase and an adenosine kinase, respectively, negatively regulate PHO5 expression and appear to function upstream of PHO81.
RacGap50C Negatively Regulates Wingless Pathway Activity During Drosophila Embryonic Development
Authors: Jones Whitney M , Bejsovec Amy 
Published: February 2005

Abstract
The Wingless (Wg)/Wnt signal transduction pathway directs a variety of cell fate decisions in developing animal embryos. Despite the identification of many Wg pathway components to date, it is still not clear how these elements work together to generate cellular identities. In the ventral epidermis of Drosophila embryos, Wg specifies cells to secrete a characteristic pattern of denticles and naked cuticle that decorate the larval cuticle at the end of embryonic development. We have used the Drosophila ventral epidermis as our assay system in a series of genetic screens to identify new components involved in Wg signaling. Two mutant lines that modify wg-mediated epidermal patterning represent the first loss-of-function mutations in the RacGap50C gene. These mutations on their own cause increased stabilization of Armadillo and cuticle pattern disruptions that include replacement of ventral denticles with naked cuticle, which suggests that the mutant embryos suffer from ectopic Wg pathway activation. In addition, RacGap50C mutations interact genetically with naked cuticle and Axin, known negative regulators of the Wg pathway. These phenotypes suggest that the RacGap50C gene product participates in the negative regulation of Wg pathway activity.
Single molecule raman spectroscopy and local work function fluctuations
Authors: Haran Gilad 
Published: February 2005

AbstractSingle molecule Raman spectroscopy provides information on individual molecules with vibrational‐level resolution. The unique mechanisms leading to the huge Raman cross‐section enhancement necessary for single molecule sensitivity are under intense investigation in several laboratories. We recently published an analysis of large spectral fluctuations in single molecule spectra of Rhodamine 6G on silver surfaces. The appearance of the fluctuations in two particular vibrational bands, and their dependence on several parameters, suggested that they originate in a charge transfer interaction of an adsorbed molecule with the surface. We argued that the fluctuations are due to variations of the local work function at the position of the molecule. In the current paper the fluctuations are further analyzed in terms of the intensity ratio between a fluctuating and a quiescent band, and it is found that the distribution of this ratio is independent of laser power, unlike the correlation time of the fluctuations. We show that a simple model, based on the energetics of charge transfer, can be used to extract the local work function distribution from the intensity ratio distribution. In a second experiment, single molecule spectra are collected from colloids immersed in water and in glycerol and a threefold decrease in fluctuation rate is found in the more viscous fluid. This indicates that surface dynamics are indeed responsible for the fluctuations, involving the motion of the adsorbed molecule and possibly also that of surface silver atoms around it.
Fluctuations and single molecules
Authors: Plakhotnik Taras 
Published: February 2005

AbstractThe fluorescence of single molecules coupled to a thermal bath is studied both experimentally and theoretically. The effect of different fluctuations on the coherence properties of resonance fluorescence is considered first. Coherence is measured in an interference experiment where a single molecule is used as a light source. A standard approach based on the optical Bloch equations apparently provides quite an accurate description of the interference experiment. Systems with long correlation times (where spectra are time dependent on any timescale) are considered next. It is shown that intensity—time—frequency correlation spectroscopy, which provides both high signal‐to‐noise ratio and high time resolution, is very suitable for such a case. The Bloch equations are further tested in an experiment where the shape of an excitation spectral line of a single molecule is accurately measured over six orders of magnitude of the exciting laser power. Significant deviations from the predictions of the Bloch equations are found. The role of critical parameters—the correlation time of the bath, the Rabi oscillation period, and the coupling constant between the bath and the molecule—is discussed. The paper also includes a short general introduction to the methodology of single‐molecule studies.