bluuebunny/crossref_metadata_2025 huggingface dataset:
Atmospheric pressure chemical ionisation normal phase liquid chromatography mass spectrometry and tandem mass spectrometry of chlorophyll a allomers
Authors: Jie Chi , Walker J. Stuart , Keely Brendan J.
Published: September 2002

Four oxidation products formed during the allomerisation reaction of chlorophyll a in methanol have been separated and identified using normal phase high‐performance liquid chromatography (NP‐HPLC) coupled with atmospheric pressure chemical ionisation (APCI) tandem mass spectrometry (MS/MS) and photodiode array detection. Fragmentation pathways of the main stereoisomers of the four major products, Mg‐purpurin‐7 dimethyl phytyl ester, 151‐MeO‐lact‐chl a, 132‐MeO‐chl a and 132‐HO‐chl a, have been assigned using APCI‐MSn aided by examination of deuteriated counterparts of the purpurin and the lactone. Diagnostic fragmentations have been determined, including those for Mg‐purpurin‐7 dimethyl phytyl ester and 151‐MeO‐lact‐chl a, which display very similar full MS and MS/MS spectra. The use of NP‐HPLC offers a rapid and efficient method which, combined with MS/MS, reduces reliance on precursor ion mass for assignment of structure in the allomerisation reaction where major and minor components are often isobaric. Copyright © 2002 John Wiley & Sons, Ltd.
Decentralized control of satellite formations
Authors: Russell Carpenter J.
Published: September 2002

A decentralized architecture is proposed for autonomous establishment and maintenance of satellite formations. Such an architecture does not require a central supervisor, as the spacecraft can cooperatively track planned maneuvers and trajectories in the face of disturbances and uncertainties, while processing only local measurement information. If the planned maneuvers and trajectories are themselves optimal, the decentralized framework generates a neighbouring optimal control. Use of such a controller simplifies and improves the robustness of formation operations, since it distributes an autonomous capability for orbit determination and relative navigation, formation maintenance, and maneuver trim among all of the spacecraft. In an example formation flying scenario, the decentralized approach successfully maintains the formation in the face of uncertainties and nonlinear perturbations, and produces identical results to those of a corresponding centralized controller. Published in 2002 by John Wiley & Sons, Ltd.
Simulation‐based actuator selection for redundantly actuated robot mechanisms
Authors: Lee Yong‐Hoon , Han Youngmo , Iuraşcu Cornel C. , Park Frank C.
Published: September 2002

This article presents a simulation‐based strategy for sizing the actuators of a redundantly actuated robotic mechanism. The class of robotic mechanisms we consider may contain one or more closed loops and possess an arbitrary number of active and passive joints, and the number of actuators may exceed the mechanism's kinematic degrees of freedom. Our approach relies on a series of dynamic simulations of the mechanism, by applying Taguchi's method to systematically perform the simulations. To efficiently perform each of the dynamic simulations, we develop, using tools from modern screw theory, new recursive algorithms for the forward and inverse dynamics of the class of redundantly actuated mechanisms described. © 2002 Wiley Periodicals, Inc.
Auditory scene analysis based on time‐frequency integration of shared FM and AM (II): Optimum time‐domain integration and stream sound reconstruction
Authors: Abe Mototsugu , Ando Shigeru
Published: September 2002

In the preceding paper, we have proposed a method for auditory scene analysis, in which the instantaneous frequency, frequency change rate, and amplitude change rate in time‐frequency space are intensified into a multipeak probability density distribution by voting method and the grouping into streams of mixed sounds is realized. In this paper, as the main point of the second half of this method, we will introduce the assumption that the stream parameters vary slowly according to the known dynamics and propose an integration method on the time axis, in which the probability density distribution of the stream parameters is optimally estimated in time series by a nonparametric Kalman filter. By doing so, the mechanism of higher auditory scene analysis such as enhancement of the accuracy of the stream parameters, interpolation and connection of the breaks of the streams, and introduction of a priori knowledge into stream selection can be realized. Moreover, the separation and reconstruction system of sounds which correspond to streams is constructed, and the proposed technique is verified by fundamental experiments for synthesized sounds or musical sounds and voices. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(10): 83–94, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1160
Efficiency comparisons of rank and permutation tests based on summary statistics computed from repeated measures data
Authors: Weinberg Janice M. , Lagakos Stephen W.
Published: September 2002

A popular method of using repeated measures data to compare treatment groups in a clinical trial is to summarize each individual's outcomes with a scalar summary statistic, and then to perform a two‐group comparison of the resulting statistics using a rank or permutation test. Many different types of summary statistics are used in practice, including discrete and continuous functions of the underlying repeated measures data. When the repeated measures processes of the comparison groups differ by a location shift at each time point, the asymptotic relative efficiency of (continuous) summary statistics that are linear functions of the repeated measures has been determined and used to compare tests in this class. However, little is known about the non‐null behaviour of discrete summary statistics, about continuous summary statistics when the groups differ in more complex ways than location shifts or where the summary statistics are not linear functions of the repeated measures. Indeed, even simple distributional structures on the repeated measures variables can lead to complex differences between the distribution of common summary statistics of the comparison groups. The presence of left censoring of the repeated measures, which can arise when these are laboratory markers with lower limits of detection, further complicates the distribution of, and hence the ability to compare, summary statistics. This paper uses recent theoretical results for the non‐null behaviour of rank and permutation tests to examine the asymptotic relative efficiencies of several popular summary statistics, both discrete and continuous, under a variety of common settings. We assume a flexible linear growth curve model to describe the repeated measures responses and focus on the types of settings that commonly arise in HIV/AIDS and other diseases. Copyright © 2001 John Wiley & Sons, Ltd.
Preferential action of gabapentin and pregabalin at P/Q‐type voltage‐sensitive calcium channels: Inhibition of K+‐evoked [3H]‐norepinephrine release from rat neocortical slices
Authors: Dooley David J. , Donovan Cindy M. , Meder Wolfgang P. , Whetzel Steven Z.
Published: September 2002

Gabapentin (GBP; Neurontin®) and pregabalin (PGB; CI‐1008), efficacious drugs in several neurological and psychiatric disorders, inhibit neurotransmitter release from mammalian brain slices at therapeutically relevant concentrations. A detailed investigation, exploring the basis for this in vitro phenomenon, focused on norepinephrine (NE) and rat neocortical tissue in complementary assays of neurotransmitter release and radioligand binding. The results are consistent with the hypothesis that GBP, PGB, and related substances decrease neocortical NE release by acting at the α2δ subunit of presynaptic P/Q‐type voltage‐sensitive Ca2+ channels (VSCC) subserving Ca2+ influx in noradrenergic terminals. The inhibitory action appears competitive with [Ca2+]o and preferential to those neurons undergoing prolonged depolarization. Other results indicate that the reduction of exocytotic NE release is independent of L‐ and N‐type VSCC, classical drug/peptide binding sites on VSCC, Na+ channels, α2‐adrenoceptors, NE transporter, and system L amino acid transporter. These findings suggest a selective modulation of P/Q‐type VSCC that are implicated in neurotransmission and several GBP‐responsive pathologies. Synapse 45:171–190, 2002. © 2002 Wiley‐Liss, Inc.
Sex differences in [123I]β‐CIT SPECT measures of dopamine and serotonin transporter availability in healthy smokers and nonsmokers
Authors: Staley Julie K. , Krishnan‐Sarin Suchitra , Zoghbi Sami , Tamagnan Gilles , Fujita Masahiro , Seibyl John P. , Maciejewski Paul K. , O'Malley Stephanie , Innis Robert B.
Published: September 2002

Nicotine and other constituents of tobacco smoke elevate dopamine (DA) and serotonin (5‐HT) levels in brain and may cause homeostatic adaptations in DA and 5‐HT transporters. Since sex steroids alter DA and 5‐HT transporter expression, the effects of smoking on DA and 5‐HT transporter availability may differ between sexes. In the present study, DA and 5‐HT transporter availabilities were quantitated using single photon emission computed tomography (SPECT) imaging approximately 22 h after bolus administration of [123I]β‐CIT, an analog of cocaine which labels DA and 5‐HT transporters. Forty‐two subjects including 21 pairs of age‐, race‐, and gender‐matched healthy smokers and nonsmokers (12 female and 9 male pairs) were imaged. Regional uptake was assessed by the outcome measures, V3″, which is the ratio of specific (i.e., ROI‐cerebellar activity) to nondisplaceable (cerebellar) activity, and V3, the ratio of specific to free plasma parent. Overall, striatal and diencephalic [123I]β‐CIT uptake was not altered by smoking, whereas brainstem [123I]β‐CIT uptake was modestly higher (10%) in smokers vs. nonsmokers. When subgrouped by sex, regardless of smoking status, [123I]β‐CIT uptake was higher in the striatum (10%), diencephalon (15%), and brainstem (15%) in females vs. males. The sex*smoking interaction was not significant in the striatum, diencephalon, or brainstem, despite the observation of 20% higher brainstem [123I]β‐CIT uptake in male smokers vs. nonsmokers and less than a 5% difference between female smokers and nonsmokers. The results demonstrate higher DA and 5‐HT transporter availability in females vs. males and no overall effect of smoking with the exception of a modest elevation in brainstem 5‐HT transporters in male smokers. Although these findings are preliminary and need validation with a more selective 5‐HT transporter radiotracer, the results suggest that brainstem 5‐HT transporters may be regulated by smoking in a sex‐specific manner. Synapse 41:275–284, 2001. © 2001 Wiley‐Liss, Inc.
Promoting understanding of chemical bonding and spontaneity through student explanation and integration of ideas
Authors: Teichert Melonie A. , Stacy Angelica M.
Published: September 2002

This article explores the effectiveness of intervention discussion sections for a college general chemistry course designed to apply research on student preconceptions, knowledge integration, and student explanation. Two interventions, on bond energy and spontaneity, were tested and intervention student performance was compared with that of a control group that did not use the experimental pedagogy. Results indicate that this instruction, which identifies students' initial conceptions and integrates those ideas into class discussion, leads to enhanced conceptual understanding. The intervention group outperformed the control group on a written course midterm, the thermodynamics portion of a standardized American Chemical Society examination, and an in‐depth interview. In interviews, the intervention group students explained the energetics of bond breaking and formation at a more sophisticated level than did the control students. In contrast, control students were more tenuous in their thinking, tended to contradict themselves more when discussing bond energy, and harbored more misconceptions about spontaneity. © 2002 Wiley Periodicals, Inc. J Res Sci Teach 39: 464–496, 2002
Complete nutrient composition of commercially raised invertebrates used as food for insectivores
Authors: Finke Mark D.
Published: September 2002

A variety of invertebrates are commonly fed to insectivorous animals by both zoos and hobbyists, but information as to the nutrient composition of most commercially raised species is limited. Adult house crickets, house cricket nymphs (Acheta domesticus), superworms (Zophobas morio larvae), giant mealworm larvae, mealworm larvae and adult mealworms (Tenebrio molitor), waxworm larvae (Galleria mellonella), and silkworm larvae (Bombyx mori) were analyzed for moisture, crude protein, crude fat, ash, acid detergent fiber (ADF), neutral detergent fiber (NDF), minerals, amino acids, fatty acids, and vitamins. Earthworms (Lumbricus terresstris) were analyzed for moisture, crude protein, crude fat, ash, ADF, NDF, minerals, amino acids, and vitamins A and D3. Proximate analyses were variable, with wide ranges found for moisture (57.9–83.6%), crude protein (9.3–23.7%), crude fat (1.6–24.9%), ADF (0.1–7.4%), NDF (0.0–11.5%), and ash (0.6–1.2%). Energy content ranged from a low of 674 kcal/kg for silkworms to 2,741 kcal/kg for waxworms.Using an amino acid scoring pattern for rats, the first limiting amino acid for all invertebrates tested was the total sulfur amino acid methionine+cystine. Deficiencies by nutrient (% of samples deficient vs. NRC requirements for rats on a dry matter (DM) basis) were as follows: calcium (100%), vitamin D3 (100%), vitamin A (89%), vitamin B12 (75%), thiamin (63%), vitamin E (50%), iodine (44%), manganese (22%), methionine‐cystine (22%), and sodium (11%). Deficiencies by invertebrate species (number of nutrients deficient vs. the NRC requirements for rats on a DM basis) were as follows: waxworms (9), superworms (8), giant mealworm larvae (7), adult mealworms (6), mealworm larvae (5), adult house crickets (4), house cricket nymphs (4), silkworms (4), and earthworms (4). These data provide a basis for determining nutrient intake of captive insectivores, and will aid in the development of gut‐loading diets to provide captive insectivorous animals with appropriate levels of necessary nutrients. Zoo Biol 21:269–285, 2002. © 2002 Wiley‐Liss, Inc.
Polycoccum crespoae sp. nov., the first report of a lichenicolous fungus on Chondropsis semiviridis (Parmeliaceae)
Authors: Váczi P. , Hawksworth D.L.
Published: September 2002

Polycoccum crespoae sp. nov. is described from thalli of Chondropsis semiviridis collected in Australia (Victoria). It has consistently 4-spored asci but differs from known 4-spored species in the size and shape of the ascospores. Attention is also drawn to another undescribed Polycoccum found on another genus of Parmeliaceae, Karoowia adhaerens, from South Africa (Cape Province).
Correlations Among Charcoal Records of Fires from the Past 16,000 Years in Indonesia, Papua New Guinea, and Central and South America
Authors: Haberle Simon G. , Ledru Marie-Pierre
Published: September 2002

Microscopic charcoal preserved in lake and swamp sediments from 10 sites in Indonesia and Papua New Guinea and from 5 sites in Central and South America have been used to reconstruct long-term fire histories for these two regions. Comparison of these records demonstrates that fire is promoted during periods of rapid climate change and high climate variability, regardless of the presence or absence of humans. Broad synchrony of changes in corrected charcoal values in each region supports an atmospheric transmission of the climate signal via the dominant large-scale atmospheric circulation systems (Walker Circulation) that appears to have persisted since 16,000 cal yr B.P. Altered climate boundary conditions under the influence of changing El Niño-related variability, insolation, sea level, and sea surface temperature all influenced the strength of this connection. Correlation of biomass burning records between the regions tends to increase in the Holocene. The main period of inverse correlation occurs during the Younger Dryas Stade, when extratropical climate most affected the tropics. The strongest correlation between the two regions postdates 5000 cal yr B.P., when El Niño-related variability intensified. Fluctuations in tropical biomass burning are at least partly controlled by orbital forcing (precession), although extratropical climate influences and human activity are also important.
Orexin signaling in recombinant neuron‐like cells
Authors: Holmqvist Tomas , Åkerman Karl E.O , Kukkonen Jyrki P
Published: September 2002

To assess the role of orexin receptor signaling in neuron‐like cells, Neuro‐2a murine neuroblastoma and PC12 human pheochromocytoma cells were stably transfected with human OX1 or OX2 receptors. Activation of both receptors strongly elevated cellular inositol phosphates and Ca2+. A difference in the potency between orexin‐A and ‐B was seen for OX1, but not OX2 receptors. Dependence of the orexin‐mediated Ca2+ response on extracellular Ca2+ and the observed Ba2+ influx indicate that in addition to phospholipase C, orexin receptors also may couple to similar non‐voltage‐gated Ca2+ channels in neuronal cells as previously characterized in non‐neuronal cells.
Divergent role of ceramide generated by exogenous sphingomyelinases on NF‐κB activation and apoptosis in human colon HT‐29 cells
Authors: Colell Anna , Coll Olga , Marı́ Montse , Fernández-Checa José C , Garcı́a-Ruiz Carmen
Published: September 2002

This study examined the role of ceramide generated by exogenous sphingomyelinases (SMases) on transcription nuclear factor‐κB (NF‐κB) activation and apoptosis in human colon epithelial HT‐29 cells. Exogenous neutral (N) and acidic (A) SMase activated NF‐κB with different kinetics, accounting for the diverse pattern of DNA binding of NF‐κB complexes activated by tumor necrosis factor‐α (TNF). NSMase activated predominantly RelA/p52 and RelA/p50 dimers within 30 min, while ASMase activated the p50/p50 homodimer by 20 h. The predominant activation of RelA‐containing κB complexes by TNF or NSMase paralleled the induction of interleukin‐8. HT‐29 cells were sensitive to ASMase and TNF but resistant to NSMase. However, the apoptotic potential of NSMase was masked by NF‐κB, as its prior inactivation sensitized HT‐29 cells to NSMase. Thus, the generation of ceramide by exogenous SMases participates differentially in inflammation and apoptosis.
Huperzine A attenuates apoptosis and mitochondria‐dependent caspase‐3 in rat cortical neurons
Authors: Zhou Jin , Tang Xi Can
Published: September 2002

The neuroprotection of huperzine A against apoptosis was investigated. In cultures of rat primary cortical neurons, neuronal apoptosis was induced by serum deprivation for 24 h, which was accompanied by enhanced caspase‐3 activity and the release of cytochrome c into the cytosol from mitochondria. Pretreating the neurons for 2 h with huperzine A (0.1–10 μM) improved neuronal survival. Huperzine A at a concentration of 1 μM significantly attenuated apoptosis by inhibiting the mitochondria–caspase pathway directly and indirectly.
Resistin expression and regulation in mouse pituitary
Authors: Morash Barbara A , Willkinson Diane , Ur Ehud , Wilkinson Michael
Published: September 2002

Resistin, a new adipocytokine, is expressed in human, rat and mouse adipose tissue. Its putative role as a mediator of insulin resistance is controversial. We hypothesized that resistin, in common with leptin, has multiple roles in non‐adipose tissues. Using reverse transcription polymerase chain reaction (RT‐PCR) we show that the resistin gene (Retn) is expressed in mouse brain (hypothalamus and cortex) and pituitary gland. Immunohistochemistry revealed resistin protein in the arcuate nucleus and pituitary gland. Semi‐quantitative RT‐PCR analysis indicated that Retn mRNA is developmentally regulated in the pituitary. Expression was lowest at birth, increased abruptly between postnatal days 14 and 25 (four‐fold; P<0.001), and declined thereafter. This peak in pituitary Retn mRNA was unaffected by early weaning but was abolished by neonatal treatment with monosodium glutamate, suggesting that the basal hypothalamus regulates pituitary Retn. Although the role(s) of endogenous resistin in mouse brain and pituitary remains to be determined, it may be distinct from its controversial involvement in insulin resistance. Our data suggest that local resistin expression could have functional implications during prepubertal maturation of the hypothalamic–pituitary system.
Mutagenic and functional analysis of the C‐terminus of Saccharomyces cerevisiae Pho84 phosphate transporter
Authors: Lagerstedt Jens O. , Zvyagilskaya Renata , Pratt James R. , Pattison-Granberg Johanna , Kruckeberg Arthur L. , Berden Jan A. , Persson Bengt L.
Published: September 2002

A widely accepted mechanism for selective degradation of plasma membrane proteins is via ubiquitination and/or phosphorylation events. Such a regulated degradation has previously been suggested to rely on the presence of a specific SINNDAKSS sequence within the protein. Modification of a partly conserved SINNDAKSS‐like sequence in the C‐terminal tail of the Pho84 phosphate transporter, in combination with C‐terminal fusion of green fluorescent protein or a MYC epitope, were used to evaluate the presence of this sequence and its role in the regulated degradation. The functional Pho84 mutants in which this SINNDAKSS‐like sequence was altered or truncated were subjected to degradation like that of the wild type, suggesting that degradation of the Pho84 protein is regulated by factors other than properties of this sequence.
Sustained activation of AMP‐activated protein kinase induces c‐Jun N‐terminal kinase activation and apoptosis in liver cells
Authors: Meisse Delphine , Van de Casteele Mark , Beauloye Christophe , Hainault Isabelle , Kefas Benjamin A , Rider Mark H , Foufelle Fabienne , Hue Louis
Published: September 2002

The aim of this work was to study the effect of a sustained activation of AMP‐activated protein kinase (AMPK) on liver cell survival. AMPK activation was achieved by incubating FTO2B cells with AICA‐riboside, which is transformed into ZMP, an AMP analogue, or by adenoviral transfection of hepatocytes with a constitutively active form of AMPK. Prolonged AMPK activation triggered apoptosis and activated c‐Jun N‐terminal kinase (JNK) and caspase‐3. Experiments with iodotubercidin, dicoumarol and z‐VAD‐fmk, which inhibited AMPK, JNK and caspase activation, respectively, supported the notion that prolonged AMPK activation in liver cells induces apoptosis through an activation pathway that involves JNK and caspase‐3.
Conversion of the dimeric D‐amino acid oxidase from Rhodotorula gracilis to a monomeric form. A rational mutagenesis approach
Authors: Piubelli Luciano , Caldinelli Laura , Molla Gianluca , Pilone Mirella S , Pollegioni Loredano
Published: September 2002

The relevance of the dimeric state for the structure/function relationships of Rhodotorula gracilis D‐amino acid oxidase (RgDAAO) holoenzyme has been investigated by rational mutagenesis. Deletion of 14 amino acids in a surface loop (connecting β‐strands 12 and 13) transforms RgDAAO from a dimeric protein into a stable monomer. The mutant enzyme is still catalytically competent and retains its binding with the FAD coenzyme. Dimerization has been used by this flavoenzyme in evolution to achieve maximal activity, a tighter interaction between the protein moiety and the coenzyme, and higher thermal stability.
A desaturase‐like protein from white spruce is a Δ9 desaturase
Authors: Marillia Elizabeth-France , Giblin E.Michael , Covello Patrick S , Taylor David C
Published: September 2002

Gymnospermae seed lipids are characterized by a high degree of desaturation, most having a Δ9 double bond. By degenerate polymerase chain reaction (PCR) we have isolated a white spruce (Picea glauca) cDNA clone that encodes an amino acid sequence sharing a high degree of homology with other putative plant acyl‐coenzyme A (CoA) Des9 desaturases. Both in vivo and in vitro expression studies in a Δ9 desaturase‐deficient yeast strain demonstrated the desaturation functionality of the white spruce clone, and gas chromatography‐mass spectrometry (GC‐MS) analyses confirmed the regioselectivity of the encoded enzyme. This is the first report of the functional characterization of a plant membrane‐bound acyl‐CoA‐like protein Δ9 desaturase by heterologous expression in yeast.
A tormentor in the quest for plant p53‐like proteins
Authors: Korthout Henrie A.A.J , Caspers Martien P.M , Kottenhagen Marijke J , Helmer Quinta , Wang Mei
Published: September 2002

Over the past few years the presence of p53‐like proteins in plants was frequently reported, by using the monoclonal antibody Pab240. By means of protein purification and screening a cDNA library, a Pab240 cross‐reacting protein and a cDNA clone were isolated from barley. Peptide‐ and DNA‐sequence analysis identified one and the same protein: 2‐oxoglutarate dehydrogenase. Sequence analysis of 2‐oxoglutarate dehydrogenase revealed that the protein contains a perfect Pab240 epitope. In barley, the 110 kDa oxoglutarate dehydrogenase was degraded during isolation to a 53 kDa Pab240 cross‐reacting polypeptide, thereby mimicking curiously p53‐like properties.
The micro domain responsible for ligand‐binding of guanylyl cyclase C
Authors: Hidaka Yuji , Matsumoto Yoshiko , Shimonishi Yasutsugu
Published: September 2002

Guanylyl cyclase C (GC‐C), a member of membrane‐bound guanylyl cyclases, is a receptor protein for guanylin and uroguanylin. The binding of a ligand to the extracellular domain of GC‐C (ECDGC‐C) triggers signal transduction, resulting in the regulation of intestinal fluids and electrolytes. A previous study proposed that a ligand‐binding site on GC‐C is localized near the transmembrane region. To further investigate the mechanism by which GC‐C is activated, the C‐terminal polypeptide (Met341–Gln407) of ECDGC‐C (the micro domain), which includes the ligand‐binding site, was over‐expressed in Escherichia coli and its ligand‐binding ability was examined. The micro domain showed ligand‐binding activity (IC50=1×10−8 M). This result clearly indicates that a ligand‐binding site is located in close proximity to the membrane‐bound region, and that the micro domain is capable of independently binding the ligand, without assistance from other domains. The use of this micro binding domain in the study of interactions between GC‐C and ligands could be a useful tool and could lead to a better understanding of GC‐C signal transduction.
MIZIP, a highly conserved, vertebrate specific melanin‐concentrating hormone receptor 1 interacting zinc‐finger protein1
Authors: Bächner Dietmar , Kreienkamp Hans-Jürgen , Richter Dietmar
Published: September 2002

Using the yeast‐two‐hybrid system a novel protein was identified from human brain that interacts with the C‐terminus of melanin‐concentrating hormone receptor 1 (MCH‐R1). This protein, characterized by a Myeloid translocation protein 8, Nervy, DEAF1 proteins (MYND) zinc‐finger domain, is termed MCH‐R1‐interacting zinc‐finger protein, MIZIP. It is fully conserved in man, rat, mouse and highly conserved in Xenopus and zebrafish, but not detectable in invertebrates. MIZIP gene organization in human (six exons on chromosome 9q34.3) and mouse is highly conserved, yet in rodents an additional exon is generated giving rise to alternatively spliced mRNAs. MIZIP is expressed in brain, testis and stomach, where expression of MCH and MCH‐R1 was previously reported. MIZIP interaction with MCH‐R1 was verified by overlay and pull‐down assays as well as by co‐transfection experiments in human embryonic kidney‐293 cells. MIZIP is cytoplasmically localized but gets recruted to the plasma membrane when cells are co‐transfected with MCH‐R1 supporting the notion that MIZIP is involved in the function of MCH‐R1.
Photoaffinity labeling of the uncoupling protein UCP1 with retinoic acid: ubiquinone favors binding
Authors: Tomás Paula , Ledesma Amalia , Rial Eduardo
Published: September 2002

Retinoic acid is a potent activator of the uncoupling protein‐1 (UCP1) both at the gene and mitochondrial level. Irradiation with ultraviolet light can be used to directly photolabel proteins with retinoic acid. The procedure has been applied to investigate its interaction with UCP1 isolated from brown adipose tissue mitochondria. All‐trans‐retinoic acid binds to UCP1 with high affinity and the labeling is only partially protected by guanosine diphosphate. Ubiquinone (UQ) has been described to be an obligatory cofactor for uncoupling protein function and we demonstrate that it greatly increases the affinity of UCP1 for retinoic acid. Data support the notion of a direct interaction between UQ and retinoic acid.
Domain structure and ATP‐induced conformational changes in Escherichia coli protease Lon revealed by limited proteolysis and autolysis
Authors: Vasilyeva Oxana V , Kolygo Kristina B , Leonova Yulia F , Potapenko Natalia A , Ovchinnikova Tatyana V
Published: September 2002

Escherichia coli protease Lon (La) is an adenosine triphosphate (ATP)‐regulated homo‐oligomeric proteolytic complex responsible for the recognition and selective degradation of abnormal and unstable proteins. Each subunit of the protease Lon appears to consist of three functional domains: the C‐terminal proteolytic containing a serine active site, the central displaying the ATPase activity, and the N‐terminal with still obscure function. We have used limited proteolysis to probe the domain structure and nucleotide‐induced conformational changes in the enzyme. Limited proteolysis of the native protease Lon generated a low number of stable fragments roughly corresponding to its functional domains. Conformational changes in the wild‐type enzyme and its mutant forms in the presence or absence of adenine and guanine nucleotides were investigated by limited proteolysis. The nucleotide character was shown to play a key role for susceptibility of the protease Lon to limited proteolysis, in particular, for resistance of the ATPase functional domain. ATP and adenosine diphosphate displayed a protective effect of the ATPase domain of the enzyme. We suggest that these nucleotides induce conformational changes of the enzyme, transforming the ATPase domain from the most vulnerable part of the molecule into a spatially inaccessible one. Both limited proteolysis and autolysis demonstrate that the most stable part of the protease Lon molecule is its N‐terminal region. Obvious resistance of the protease Lon C‐terminus to proteolysis indicates that this region of the enzyme molecule including its substrate‐binding and proteolytic domains has a well folded structure.
Characterization and thermodynamic properties of quadruplex/duplex competition
Authors: Li Wei , Wu Peng , Ohmichi Tastuo , Sugimoto Naoki
Published: September 2002

Structural characteristics and thermodynamic properties of dG3(T2AG3)3, d(C3TA2)3C3 and dG3(T2AG3)3/d(C3TA2)3C3 were intensively investigated. It was indicated that metal ions greatly affected the conformation and stability of the G‐quadruplex. A competition of a structure transition among the G‐quadruplex, I‐motif, and the duplex was confirmed to be dependent on both cation species and pH values. The structural competitive mechanism is discussed for the first time. This study shows an intriguing potential in modulating DNA structures in vivo, which is of great importance in drug design and cancer chemotherapy.
Ccz1p/Aut11p/Cvt16p is essential for autophagy and the cvt pathway
Authors: Meiling-Wesse Khuyen , Barth Henning , Thumm Michael
Published: September 2002

In a reverse genetics screen, we here identify Ccz1p as an essential component of the cvt pathway and autophagy. Ccz1p is identical with the so far unknown Cvt16p. GFP‐Aut7p, a specific cargo of autophagosomes, accumulates in ccz1Δ cells at punctate, vesicular structures in the cytosol, suggesting a block in the autophagic pathway prior to vacuolar fusion of autophagosomes. Proteinase protection experiments using hypotonically lysed ccz1Δ spheroplasts demonstrate that proaminopeptidase I, another specific cargo of autophagy and the cvt pathway, is trapped inside membrane‐enclosed vesicles. Taken together our findings are compatible with a function of Ccz1p in vacuolar fusion of cvt vesicles and autophagosomes.
Cyclin E and cyclin A are likely targets of Src for PDGF‐induced DNA synthesis in fibroblasts
Authors: Furstoss Olivia , Manes Gaël , Roche Serge
Published: September 2002

How tyrosine kinases of the Src family regulate platelet‐derived growth factor (PDGF)‐induced DNA synthesis remains elusive. Here we show that the E1A antigen of adenovirus 5 overrides the G1 block elicited by the kinase‐inactive mutant SrcK−. This was dependent upon the CR2 region of E1A that upregulated cyclin E and cyclin A and inactivated the pocket protein pRb. E1A rescue was independent of pRb. Expression of SrcK− in fibroblasts prevented PDGF‐induced expression of cyclins E and A. This effect was overcome by E1A. Constitutive expression of cyclins E and A, but not D1, restored mitogenesis that was inhibited by SrcK−. We conclude that both cyclin E and cyclin A are likely targets of Src mediating PDGF‐induced DNA synthesis.
Preimplantation‐embryo‐specific cell cycle regulation is attributed to the low expression level of retinoblastoma protein
Authors: Iwamori Naoki , Naito Kunihiko , Sugiura Koji , Tojo Hideaki
Published: September 2002

It is known that a characteristic of the mammalian preimplantation‐embryo‐specific cell cycle is the substantially shortened G1‐phase, although the regulation mechanisms of the unique cell cycle remain unclear. In the present study, we first examined the presence of retinoblastoma (RB) tumor suppressor gene product throughout mouse preimplantation embryo development and found that the RB expression was down‐regulated between the four‐cell and morula stages. Furthermore, the overexpression of RB protein in the mouse embryos during this phase inhibited their development significantly. These results suggest that the absence of RB protein contributes to the preimplantation‐embryo‐specific cell cycle.
Important amino acid properties for determining the transition state structures of two‐state protein mutants
Authors: Gromiha M.Michael , Selvaraj S
Published: September 2002

Understanding the mechanism in the folding pathways of proteins is an important problem in molecular biology. The Φ‐value analysis provides insight into the transition state structures during protein folding. In this work, we have analyzed the relationship between the observed Φ values upon mutations in two‐state proteins (FK506 binding protein, chymotrypsin inhibitor and src SH3 domain) and the changes in 48 various physico‐chemical, energetic and conformational properties. We found that the classification of mutations based on solvent accessibility improved the correlation significantly. The relationship between conformational properties and Φ values determines the presence/absence of secondary structures in the transition state. In buried mutations, the physical properties volume, shape and flexibility, and the thermodynamic properties enthalpy, entropy and free‐energy change have significant correlation with Φ. The short and medium‐range non‐bonded energy in partially buried mutations and average long‐range contacts in exposed mutations showed a strong correlation with Φ values. Multiple regression analysis incorporating combinations of three properties from among all possible combinations of the 48 properties increased the correlation coefficient up to 0.99, by an average rise of 20% for all the data sets. Information about local sequence and structure is more important in surface mutations than those in buried mutations for explaining the transition state structures of two‐state proteins. Further, the implications of our results for understanding the process of protein folding have been discussed.
Towards a new T‐fold protein?: The coproporphyrinogen III oxidase sequence matches many structural features from urate oxidase
Authors: Colloc'h Nathalie , Mornon Jean-Paul , Camadro Jean-Michel
Published: September 2002

Urate oxidase (UOX) and coproporphyrinogen III oxidase (CPO) are two unusual oxidases as they accomplish their catalytic act with no co‐factor nor metal ion. They both require molecular oxygen, and lead to hydrogen peroxide in addition to the product. UOX is composed of two contiguous Tunneling‐fold domains and CPO appears to be also divided into two structurally equivalent domains. Moreover, each of these putative domains can be coherently aligned on UOX domains. Although their sequences are very distant, we therefore suggest that functional CPO dimer is built around a tunnel, with the substrate sitting above it, on the N‐ and C‐terminal side. This overall model is supported by mutation data and is coherent with the chemical events expected for substrate processing by CPO.
Calnexin Δ185–520 partially reverses the misprocessing of the ΔF508 cystic fibrosis transmembrane conductance regulator1
Authors: Okiyoneda Tsukasa , Wada Ikuo , Jono Hirofumi , Shuto Tsuyoshi , Yoshitake Kazuhisa , Nakano Nahoko , Nagayama Shin-ichi , Harada Kazutsune , Isohama Yoichiro , Miyata Takeshi , Kai Hirofumi
Published: September 2002

Abnormal retention of ΔF508 CFTR (cystic fibrosis transmembrane conductance regulator) in the endoplasmic reticulum is a major cause of cystic fibrosis (CF). We show that calnexin Δ185–520 but not calnexin can partially reverse the mislocalization of ΔF508 CFTR. This 256‐amino acid protein has neither the transmembrane domain nor the P domain of calnexin. Calnexin Δ185–520 interacted with CFTR directly, and was secreted into the extracellular compartment over time. Forty‐eight hours after transfection into CHO cells, calnexin Δ185–520 increased the conversion of immature ΔF508 CFTR into mature ΔF508 CFTR. In immortalized human CF cell lines expressing ΔF508 CFTR, a halide efflux assay showed that calnexin Δ185–520 partially restored CFTR function. These data indicate that calnexin Δ185–520 may give a clue to develop the therapeutic way of cystic fibrosis with ΔF508 CFTR.
Only the soluble form of the scavenger receptor CD163 acts inhibitory on phorbol ester‐activated T‐lymphocytes, whereas membrane‐bound protein has no effect
Authors: Frings Werner , Dreier Jens , Sorg Clemens
Published: September 2002

The extracellular moiety of the hemoglobin/haptoglobin scavenger receptor CD163 (RM3/1 antigen) can be shed from monocytes and is a normal plasma component. We found that in a dose‐dependent manner soluble CD163 induces a decrease in CD69 expression, a reduced [3H]thymidine uptake and a down‐regulated matrix metalloproteinase‐9 RNA expression in phorbol myristate acetate‐stimulated T‐cells. Co‐culturing T‐cells on transgenic fibroblasts, expressing membrane‐bound CD163, yielded no differences compared to culture on non‐transfected cells. We conclude that CD163 has at least two distinct functions: the clearance of hemoglobin in its cell‐bound form and participation in anti‐inflammation as a soluble factor, exhibiting cytokine‐like functions.
Monte Carlo simulations of voltage‐driven translocation of a signal sequence
Authors: Efremov Roman G , Volynsky Pavel E , Nolde Dmitry E , van Dalen Annemieke , de Kruijff Ben , Arseniev Alexander S
Published: September 2002

Transmembrane potentials play important but poorly understood roles in many biological processes, including signal sequence‐mediated protein translocation across bacterial membranes. In this study we applied Monte Carlo techniques to simulate the way the potential acts on a signal sequence. The simulations demonstrate that in the absence of a potential the signal sequence prefers insertion in both helical hairpin and transmembrane α‐helical conformations. However, in the presence of a potential only the transmembrane α‐helical conformation is the state of lowest energy for the signal sequence. From these results it is concluded that the membrane potential stabilizes the transmembrane orientation of a signal sequence, explaining the membrane potential dependence of preprotein translocation.
Proteasome inhibitors stimulate activator protein‐1 pathway via reactive oxygen species production
Authors: Wu Hsiao-Mei , Chi Kwan-Hwa , Lin Wan-Wan
Published: September 2002

In this report we explored the effects of proteasome inhibitors (MG132, aLLN, lactacystin and MG262) on interleukin‐8 (IL‐8) induction. In HEK293 cells, proteasome inhibitors could concentration‐dependently increase IL‐8 promoter and activator protein‐1 (AP‐1) activities, but inhibited nuclear factor (NF)‐κB activation induced by cytokines. The stimulating effects on IL‐8 promoter and AP‐1 were reduced by N‐acetylcysteine, glutathione, diphenyleneiodonium, rotenone and antimycin A. Fluorescent analysis using 2′,7′‐dichlorodihydrofluorescin diacetate further confirmed the abilities of proteasome inhibitors to induce reactive oxygen species (ROS) production. These results suggest that ROS production by proteasome inhibitors leads to AP‐1 activation, which in the absence of NF‐κB activation still transactivates IL‐8 gene expression.
Intracellular redox regulation by a cystine derivative suppresses UV‐induced NF‐κB activation
Authors: Kitazawa Manabu , Nakano Takashi , Chuujou Hiromi , Shiojiri Eiji , Iwasaki Keiji , Sakamoto Kazutami
Published: September 2002

Nuclear factor (NF)‐κB pathways are influenced by the intracellular reduction–oxidation (redox) balance. While NF‐κB is activated through inhibitor (I)‐κB degradation by oxidative stress, its DNA binding is accelerated in the reduced state. We found that N,N′‐diacetyl‐L‐cystine dimethylester (DACDM) suppressed the UVB‐induced NF‐κB binding activity at a much lower concentration (50–100 μM) than N‐acetyl‐L‐cysteine (NAC, 10–30 mM). While NAC suppressed the I‐κB degradation but not the DNA binding, DACDM prevented the activated NF‐κB from binding DNA, without influencing the I‐κB degradation. These properties of DACDM make it possible to effectively regulate the intracellular redox balance.
PIAS3 (protein inhibitor of activated STAT‐3) modulates the transcriptional activation mediated by the nuclear receptor coactivator TIF2
Authors: Jiménez-Lara Ana M. , Heine Mattias J.S. , Gronemeyer Hinrich
Published: September 2002

PIAS3, a member of the protein inhibitor of activated STAT family, was found to interact in vivo and in vitro with TIF2, a previously described coactivator for nuclear receptors. The interaction is mediated by two distinct non‐contiguous regions of TIF2. We found that TIF2–PIAS3 interaction occurs through a unique domain of PIAS3, very rich in acidic residues and conserved throughout the PIAS family. PIAS3 modulates the ability of TIF2 to mediate ligand‐enhanced transcription activation positively or negatively, for different steroid receptors. Taken together, our results indicate a potential role of PIAS3 as transcriptional modulator of TIF2‐mediated signalling.
Why are sweet proteins sweet? Interaction of brazzein, monellin and thaumatin with the T1R2‐T1R3 receptor
Authors: Temussi Piero Andrea
Published: September 2002

Sweet tasting proteins interact with the same receptor that binds small molecular weight sweeteners, the T1R2–T1R3 G‐protein coupled receptor, but the key groups on the protein surface responsible for the biological activity have not yet been identified. I propose that sweet proteins, contrary to small ligands, do not bind to the ‘glutamate‐like’ pocket but stabilize the free form II of the T1R2–T1R3 receptor by attachment to a secondary binding site. Docking of brazzein, monellin and thaumatin with a model of the T1R2–T1R3 sweet taste receptor shows that the most likely complexes can indeed stabilize the active form of the receptor.
Arginine metabolism in Trypanosoma cruzi is coupled to parasite stage and replication
Authors: Pereira Claudio A , Alonso Guillermo D , Ivaldi Soledad , Silber Ariel , Alves Maria Júlia M , Bouvier León A , Flawiá Mirtha M , Torres Héctor N
Published: September 2002

L‐Arginine plays an essential role in the energetic metabolism of Trypanosoma cruzi. In this work we propose a relationship between L‐arginine uptake, arginine kinase activity and the parasite replication ability. In epimastigote cultures L‐arginine uptake decreases continuously accompanying a cell replication rate reduction. The use of conditioned or fresh medium mimics uptake variations. Interestingly, in non‐replicative trypomastigote cells, L‐arginine uptake was undetectable. The association between L‐arginine uptake and cell replication was demonstrated using the antimitotic agent hydroxyurea. Arginine kinase, the enzyme responsible for phosphoarginine and ATP synthesis, also shows a differential activity in epimastigote and trypomastigote parasite stages.
Characterization of deoxyuridine 5′‐triphosphate nucleotidohydrolase from Trypanosoma cruzi1
Authors: Bernier-Villamor Victor , Camacho Ana , Hidalgo-Zarco Fernando , Pérez Juana , Ruiz-Pérez Luis M , González-Pacanowska Dolores
Published: September 2002

We report the cloning and kinetic characterization of Trypanosoma cruzi deoxyuridine 5′‐triphosphate nucleotidohydrolase (dUTPase) whose coding sequence was isolated by genetic complementation in Escherichia coli. The deduced amino acid sequence was similar to Leishmania major dUTPase although it exhibits an amino acid insertion which is sensitive to protease inactivation. The catalytically active species of the enzyme is a dimer and a detailed kinetic characterization showed that it is highly specific for dUTP and dUDP. The general observation that dUTPases from the Trypanosomatidae differ in sequence, conformation and substrate specificity suggests that a different family of dUTPases exists in certain organisms, which may be exploited as drug targets against infectious diseases.
Restricted feeding induces daily expression of clock genes and Pai‐1 mRNA in the heart of Clock mutant mice
Authors: Minami Yoichi , Horikawa Kazumasa , Akiyama Masashi , Shibata Shigenobu
Published: September 2002

Plasminogen activator inhibitor‐1 (PAI‐1) is a key factor of fibrinolytic activity. The activity and mRNA abundance show a daily rhythm. To elucidate the mechanism of daily Pai‐1 gene expression, the expression of Pai‐1 and several clock genes was examined in the heart of homozygous Clock mutant (Clock/Clock) mice. Damping of the daily oscillation of Pai‐1 gene expression in Clock/Clock mice was accompanied with damped or attenuated oscillations of mPer1, mPer2, mBmal1, and mNpas2 mRNA. Daily restricted feeding induced a daily mRNA rhythm of all clock genes and Pai‐1 mRNA in Clock/Clock mice as well as wild‐type mice. The peaks of clock genes and Pai‐1 mRNA were phase‐advanced in the heart of both genotypes after 6 days of restricted feeding. The present results demonstrate that daily Pai‐1 gene expression depends on clock gene expression in the heart and that a functional Clock gene is not required for restricted feeding‐induced resetting of the peripheral clock.