bluuebunny/crossref_metadata_2025_split huggingface dataset:
Catalyzing “Hot” Reactions: Enzymes from Hyperthermophilic Archaea
Authors: Imanaka Tadayuki , Atomi Haruyuki 
Published: October 2002

AbstractWe reflect on some of our studies on the hyperthermophilic archaeon, Thermococcus kodakaraensis KOD1 and its enzymes. The strain can grow at temperatures up to the boiling point and also represents one of the simplest forms of life. As expected, all enzymes displayed remarkable thermostability, and we have determined some of the basic principles that govern this feature. To our delight, many of the enzymes exhibited unique biochemical properties and novel structures not found in mesophilic proteins. Here, we focus on a few enzymes that are useful in application, and whose three‐dimensional structures are characteristic of thermostable enzymes. © 2002 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 2: 149–163, 2002: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.10023
Fostering students' knowledge and argumentation skills through dilemmas in human genetics
Authors: Zohar Anat , Nemet Flora 
Published: October 2002

AbstractThis study examined the outcomes of a unit that integrates explicit teaching of general reasoning patterns into the teaching of a specific science content. Specifically, this article examined the teaching of argumentation skills in the context of dilemmas in human genetics. Before instruction only a minority (16.2%) of the students referred to correct, specific biological knowledge in constructing arguments in the context of dilemmas in genetics. Approximately 90% of the students were successful in formulating simple arguments. An assessment that took place following instruction supported the conclusion that integrating explicit teaching of argumentation into the teaching of dilemmas in human genetics enhances performance in both biological knowledge and argumentation. An increase was found in the frequency of students who referred to correct, specific biological knowledge in constructing arguments. Students in the experimental group scored significantly higher than students in the comparison group in a test of genetics knowledge. An increase was also found in the quality of students' argumentation. Students were able to transfer the reasoning abilities taught in the context of genetics to the context of dilemmas taken from everyday life. The effects of metacognitive thinking and of changing students' thinking dispositions by modifying what is considered valuable in the class culture are discussed. © 2002 John Wiley & Sons, Inc. J Res Sci Teach 39: 35–62, 2002
Talipes equinovarus and maternal smoking: A population‐based case‐control study in Washington state
Authors: Skelly Andrea C. , Holt Victoria L. , Mosca Vincent S. , Alderman Beth W. 
Published: October 2002

AbstractBackgroundTalipes equinovarus (TEV), also called congenital idiopathic clubfoot, true clubfoot and common clubfoot, is one of the most common major birth defects. Its correction is often difficult and expensive. Its etiology is poorly understood and few analytic epidemiological studies have been devoted to exploring specific risk factors for TEV.MethodsOur population‐based study consists of 239 documented cases of idiopathic TEV obtained from hospital and outpatient sources and 365 controls identified via random digit dialing from five Western Washington counties. Structured maternal interviews were conducted by trained interviewers and multiple logistic regression used to evaluate associations between maternal smoking and birth of a child with TEV.ResultsOur study shows strong associations between maternal smoking and idiopathic TEV. Case mothers were more likely to have smoked during pregnancy (OR = 2.2; 95% CI = 1.5, 3.3). Increased TEV risk was seen with increased smoking and estimates ranged from 1.5 for the lightest smokers to 3.9 for the heaviest smokers. Gender specific differences in risk were also noted with risk estimates of 1.8 (95% CI = 1.2, 3.0) for boys whose mothers smoked during pregnancy and 2.8 (95% CI = 1.4, 5.4) for girls. Trends for increased risk with higher numbers of cigarettes were noted for both genders. For isolated TEV, the overall odds ratio (OR) for smoking was 2.4 (95% CI = 1.6, 3.6) with a range from 1.4–4.6. No confounders were noted.ConclusionsAs postulated, maternal smoking during pregnancy appears to increase the risk of having a child with idiopathic clubfoot and the number of cigarettes smoked influence that risk. Further delineation of dose‐response is warranted as are continued efforts to decrease maternal smoking during pregnancy. Teratology 66:91–100, 2002. © 2002 Wiley‐Liss, Inc.
Applications of MALDI‐TOF MS analysis in cyanotoxin research
Authors: Welker Martin , Fastner Jutta , Erhard Marcel , von Döhren Hans 
Published: October 2002

AbstractRecent advances in analytical chemistry have provided an array of techniques to analyze cyanotoxins in a variety of samples. Mass spectral analysis by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) has proven to be a reliable and rapid tool to detect and identify microcystin variants in very small samples such as single Microcystis colonies. Mass signals presumptive of microcystin variants can be characterized further and identified by postsource‐decay fragmentation and comparison of observed fragment spectra with theoretical ones or with those of pure reference compounds. By analyzing Microcystis colonies from water blooms, the high metabolic diversity among individual colonies in the communities could be established. For monitoring microcystins in environmental samples, MALDI‐TOF MS can provide considerable support to HPLC by identifying microcystin variants not available as purified standards, especially in Planktothrix‐dominated blooms in which demethylated variants are predominant. A short description of the principles of MALDI‐TOF MS is provided, followed by examples of its application and a discussion of its potential use in cyanotoxin research. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 367–374, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10073
Scale‐invariant segmentation of dynamic contrast‐enhanced perfusion MR images with inherent scale selection
Authors: Janssen J. P. , Egmont‐Petersen M. , Hendriks E. A. , Reinders M. J. T. , van der Geest R. J. , Hogendoorn P. C. W. , Reiber J. H. C. 
Published: October 2002

AbstractSelection of the best set of scales is problematic when developing signal‐driven approaches for pixel‐based image segmentation. Often, different possibly conflicting criteria need to be fulfilled in order to obtain the best trade‐off between uncertainty (variance) and location accuracy. The optimal set of scales depends on several factors: the noise level present in the image material, the prior distribution of the different types of segments, the class‐conditional distributions associated with each type of segment as well as the actual size of the (connected) segments. We analyse, theoretically and through experiments, the possibility of using the overall and class‐conditional error rates as criteria for selecting the optimal sampling of the linear and morphological scale spaces. It is shown that the overall error rate is optimized by taking the prior class distribution in the image material into account. However, a uniform (ignorant) prior distribution ensures constant class‐conditional error rates. Consequently, we advocate for a uniform prior class distribution when an uncommitted, scale‐invariant segmentation approach is desired. Experiments with a neural net classifier developed for segmentation of dynamic magnetic resonance (MR) images, acquired with a paramagnetic tracer, support the theoretical results. Furthermore, the experiments show that the addition of spatial features to the classifier, extracted from the linear or morphological scale spaces, improves the segmentation result compared to a signal‐driven approach based solely on the dynamic MR signal. The segmentation results obtained from the two types of features are compared using two novel quality measures that characterize spatial properties of labelled images. Copyright © 2002 John Wiley & Sons, Ltd.
Multi‐carrier platform for wireless communications. Part 1: High‐performance, high‐throughput TDMA and DS‐CDMA via multi‐carrier implementations
Authors: Nassar Carl R. , Natarajan Bala , Wu Zhiqiang 
Published: October 2002

AbstractMulti‐carrier technologies in general, and OFDM and MC‐CDMA in particular, are quickly becoming an integral part of the wireless landscape. In this first of a two‐part survey, the authors present the innovative transmit/receive multi‐carrier implementation of TDMA and DS‐CDMA systems. Specifically, at the transmit side, the pulse shape (in TDMA) and the chip shape (in DS‐CDMA) corresponds to a linear combining of in‐phase harmonics (called a CI signal). At the receiver side, traditional time‐domain processing (equalization in TDMA and RAKE reception in DS‐CDMA) is replaced by innovative frequency based processing. Here, receivers decompose pulse (or chip) shapes into carrier subcomponents and recombine these in a manner achieving both high frequency diversity gain and low MAI. The resulting system outperforms traditional TDMA and DS‐CDMA systems by 10–14 dB at typical BERs, and, by application of pseudo‐orthogonal pulse shapes (chip shapes), is able to double system throughput while maintaining performance gains of up to 8 dB. Copyright © 2002 John Wiley & Sons, Ltd.
Distribution of acetylated tubulin in cultured cells and tissues from the Atlantic cod (Gadus morhua). Role of acetylation in cold adaptation and drug stability
Authors: Rutberg M. , Billger M. , Modig C. , Wallin M. 
Published: October 2002

AbstractThe Atlantic cod (Gadus morhua) is a poikilothermic animal living at temperatures between 2‐15°C. Isolated cod brain tubulin is, in contrast to mammalian brain tubulin, posttranslationally modified by acetylation to a high extent. To investigate the role of acetylation in cold adaptation, microtubules were isolated by a taxol‐dependent procedure from different organs of the cod, and cells from different tissues were cultured. All cells from skin and brain were able to grow between 4°C and room temperature. Microtubules in the cultured cells were sometimes severed near the periphery of the cells. Microtubules in brain cells were in general more stable to vinblastine and colchicine, when compared to skin cells. Acetylated microtubules were found only in brain cells, in peripheral nerves on scales and in nerves of the intestinal tract and in microtubules isolated from neuronal tissue. Our results show that acetylated microtubules are found both in the central and peripheral nervous system, but that there is no correlation between acetylation and cold‐adaptation.
STRUCTURAL BIOLOGY OF THE FIBRES OF THE COLLAGENOUS AND ELASTIC SYSTEMS
Authors: MONTES GREGORIO S. 
Published: October 2002

AbstractThe different types of fibres of the collagenous and elastic systems can be demonstrated specifically in tissue sections by comparing the typical ultrastructural picture of each of the fibre types with studies using selective staining techniques for light microscopy. A practicalmodus operandi, which includes the recommended staining procedures and interpretation of the results, is presented. Micrographs and tables are provided to summarize the differential procedures. Reticulin fibres display a distinct argyrophilia when studied by means of silver impregnation techniques, and show up as a thin meshwork of weakly birefringent, greenish fibres when examined with the aid of the Picrosirius‐polarization method. In addition, electron‐microscopic studies showed that reticulin fibres are composed of a small number of thin collagen fibrils, contrasting with the very many thicker fibrils that could be localized ultrastructurally to the sites where non‐argyrophilic, coarse collagen fibres had been characterized by the histochemical methods used. The three different fibre types of the elastic system belong to a continuous series: oxytalan—elaunin—elastic (all of the fibre types comprising collections of microfibrils with, in the given sequence, increasing amounts of elastin). The three distinct types of elastic system fibres have different staining characteristics and ultrastructural patterns. Ultrastructurally, a characteristic elastic fibre consists of two morphologically different components: a centrally located solid cylinder of amorphous and homogeneous elastin surrounded by tubular microfibrils. An oxytalan fibre is composed of a bundle of microfibrils, identical to the elastic fibre microfibrils, without amorphous material. In elaunin fibres, dispersed amorphous material (elastin) is intermingled among the microfibrils.
α‐KETOGLUTARATE UPTAKE IN HUMAN FIBROBLASTS
Authors: AUSSEL C. , COUDRAY‐LUCAS C. , LASNIER E. , CYNOBER L. , EKINDJIAN O. G. 
Published: October 2002

AbstractGlutamine requirements are increased during injury, in particular to sustain the needs of rapidly growing cells. This includes fibroblasts involved in wound healing. α‐Ketoglutarate (α‐KG) has been proved to be a potent precursor of glutamine. However, little is known about the process of its cell uptake. Since this first step could be crucial in α‐KG metabolism, we have characterized α‐ketoglutarate uptake in fibroblasts. Total uptake of α‐ketoglutarate was linear up to 1mmol and temperature independent. Rate of uptake was independent of the presence of Na+in the medium. Competition studies with another ketoacid demonstrated the non‐specificity of α‐ketoglutarate uptake. In addition, 4‐hydroxy‐α‐cyanocinnamate, a known inhibitor of anion transport, was ineffective on α‐ketoglutarate uptake. Taken as a whole, these data provide evidence that α‐ketoglutarate uptake in fibroblast occurs by an unmediated diffusion process. This suggests that α‐ketoglutarate uptake is not the controlling step in fibroblasts, i.e. only the availability of extracellular α‐ketoglutarate. This could be an advantage since during injury, cell membrane depolarization and dissipation of Na+gradient may limit cellular glutamine uptake.
CONNEXIN43 GAP JUNCTION LEVELS DURING DEVELOPMENT OF THE THORACIC AORTA ARE TEMPORALLY CORRELATED WITH ELASTIC LAMINAE DEPOSITION AND INCREASED BLOOD PRESSURE
Authors: BLACKBURN J.P , CONNAT J.‐L , SEVERS N.J , GREEN C.R 
Published: October 2002

AbstractA characteristic property of the vascular smooth muscle cell is its ability to modulate between a contractile phenotype, responsible for control of vascular tone and tension, through to a synthetic phenotype, capable of migration and synthesis of extracellular matrix molecules. Smooth muscle cells are coupled by gap junctions, the membrane structures which permit direct intercellular passage of ions and small molecules, and which play a role both in electrical coupling and intercellular communication during patterning and development. We have previously found that connexin43 type gap junction expression is upregulated in the synthetic phenotype smooth muscle cellin vitroand during atherosclerotic plaque formation in human coronary arteries. On the basis of immunohistochemical labelling, confocal laser scanning microscopy and digital image analysis, we now report that relatively high levels of connexin43 are expressed during development of the rat thoracic aorta, temporally correlating with reported periods of smooth muscle cell proliferation and secretion of elastic laminae. A major peak in expression occurs at seven days post‐natal, with a second less pronounced peak at 72 days post‐natal. The principal peak in gap junction levels appears to coincide with increased post‐natal blood pressure and aorta media thickening. The amount of gap junction labelling falls off to normal adult levels as the smooth muscle cells modulate towards the contractile phenotype and growth is completed. The results indicate an association between direct cell‐to‐cell communication and synthetic phenotype smooth muscle cell activity during aortic growth and patterning.
ADHESION‐DEPENDENT F‐ACTIN PATTERN INAMOEBA PROTEUSAS A COMMON FEATURE OF AMOEBAE AND THE METAZOAN MOTILE CELLS
Authors: GREBECKA LUCYNA , POMORSKI PAWEŁ , GRE ANDRZEJ , ŁOPATOWSKA ANNA 
Published: October 2002

AbstractAdhesion and movement ofAmoeba proteusare both dependent on the appropriate arrangement of the F‐actin cytoskeleton and on the presence of the cell nucleus. In this study the F‐actin organization was examined by routine FITC‐phalloidin staining and confocal laser microscopy in intact amoebae and in their nucleated and anucleated fragments, at different levels of cell adherence to the substratum. In the adhering and migrating intact cells and nucleated cell fragments dot‐like aggregates of F‐actin are scattered over the ventral side at sites close to the substratum. In the case of de‐adhesion of nucleated specimens this pattern disappears and F‐actin is accumulated in the cell centre and/or dispersed in the cytoplasm. The same actin distribution, without ventral dots, is found in the anucleated fragments which usually fail to attach to the substratum. Re‐adhesion of anucleated fragments, induced by a modified substratum or spontaneous, is accompanied by restoration of actin dots at the lower cell side. It is concluded that: (1) adhering specimens ofA. proteusdisplay the same dot‐like actin pattern on the ventral cell side, as many metazoan motile cells; (2) organization or disorganization of this pattern may occur independently of the presence of the cell nucleus, under the control of cell adhesion to the substratum.
DNA PLASMID TRANSMISSION IN YEAST IS ASSOCIATED WITH SPECIFIC SUB‐NUCLEAR LOCALISATION DURING CELL DIVISION
Authors: Scott‐Drew Suzanna , Wong C. Michael V. L. , Murray James A. H. 
Published: October 2002

AbstractCircular plasmids in yeast carrying only an origin of DNA replication (ARS) exhibit maternal inheritance bias (MIB) and are poorly transmitted from mother to daughter cell during division. A variety of different sequences that overcome MIB have been described, including centromeric sequences (CEN), telomere‐associated repeats, silencer sequences and a specific system encoded by the endogenous 2μ circle plasmid requiring the cis‐acting locus STB and the proteins Rep1 and Rep2. In each case, DNA segregation between mother and daughter cells is dependent on DNA‐protein interactions. Using plasmids carrying multiple copies of a lac repressor binding sequence, we have localised DNA molecules in the yeast nucleus using a green fluorescent protein (GFP)‐lac repressor fusion protein. We compared GFP localised plasmids carrying a centromere sequence with plasmids based on 2μ circle carrying or lacking the STB sequences required for their segregation. We show that GFP localised plasmid carrying the complete STB locus co‐localises with the plasmid proteins Rep1 and Rep2 to discrete chromatin sites. These sites are distinct from both the telomeres and from sites of cohesin binding. Deletion of the region of STB essential for the stability of the plasmid, leads to a loss of plasmid association with chromatin, relocalisation of plasmids towards the nuclear periphery, and a decrease in the Rep1 protein associated with the plasmid. We conclude that specific plasmid localisation is likely to be important in the overcoming of MIB in yeast.
Glacial-Lake Outburst Erosion of the Grand Valley, Michigan, and Impacts on Glacial Lakes in the Lake Michigan Basin
Authors: Kehew Alan E. 
Published: October 2002

AbstractGeomorphic and sedimentologic evidence in the Grand Valley, which drained the retreating Saginaw Lobe of the Laurentide Ice Sheet and later acted as a spillway between lakes in the Huron and Erie basins and in the Michigan basin, suggests that at least one drainage event from glacial Lake Saginaw to glacial Lake Chicago was a catastrophic outburst that deeply incised the valley. Analysis of shoreline and outlet geomorphology at the Chicago outlet supports J H Bretz's hypothesis of episodic incision and lake-level change. Shoreline features of each lake level converge to separate outlet sills that decrease in elevation from the oldest to youngest lake phases. This evidence, coupled with the presence of boulder lags and other features consistent with outburst origin, suggests that the outlets were deepened by catastrophic outbursts at least twice. The first incision event is correlated with a linked series of floods that progressed from Huron and Erie basin lakes to glacial Lake Saginaw to glacial Lake Chicago and then to the Mississippi. The second downcutting event occurred after the Two Rivers Advance of the Lake Michigan Lobe. Outbursts from the eastern outlets of glacial Lake Agassiz to glacial Lake Algonquin are a possible cause for this period of downcutting at the Chicago outlets.
Late Quaternary Lacustrine Pollen Records from Southwestern Beringia
Authors: Lozhkin Anatoly V. , Anderson Patricia M. , Eisner Wendy R. , Ravako Lilia G. , Hopkins David M. , Brubaker Linda B. , Colinvaux Paul A. , Miller Michael C. 
Published: October 2002

AbstractSediment cores from three lakes in the Upper Kolyma region, northeast Russia, provide the first well-dated continuous record of late Quaternary vegetation change from far southwestern Beringia. The oldest pollen zone, tentatively assigned to the Karginsk (mid-Wisconsinan) Interstade, indicates anArtemisiashrub tundra withPinus pumila,Betula, andAlnusat mid- to low elevations. With the onset of the Sartan (late Wisconsinan) Stade,Pinusdisappeared, probably indicating severely cold, dry winters and cool summers. As conditions deteriorated further, anArtemisia-Gramineae tundra developed.Selaginella rupestrisand minor herb taxa indicate the presence of poor soils and disturbed ground. This herb tundra was replaced by a short-lived (< 1000 yr)Betula-Alnusshrub tundra followed by the rapid establishment of aLarix dahuricaforest with aBetula exilis-ericales-lichen understory.Populus suaveolensandChoseniamay have formed limited hardwood gallery forests at this time. Modern vegetation associations probably developed during the early Holocene with the arrival ofPinus pumilaca. 9000 yr B.P. This shrub became important in the forest understory and, withB. exilis, formed a belt of shrub tundra beyond altitudinal treeline. Comparison of the Upper Kolyma and Alaskan pollen records indicates that important differences in vegetation types and timing of vegetation change occurred across Beringia during the late Quaternary.
Late Pleistocene Climate Record in the Eustis Loess Section, Nebraska, Based on Land Snail Assemblages and Magnetic Susceptibility
Authors: Rousseau Denis-Didier , Kukla George 
Published: October 2002

AbstractBased on multivariate analysis of mollusk assemblages and magnetic susceptibility of the Eustis section in western Nebraska, the climate of the Peoria loess steppe was relatively mild and, in terms of annual precipitation, relatively moist during the advance stages of Woodfordian ice. It was cold and dry during ice retreat. The diversity and composition of mollusk species indicates that the extreme cold and dry climate was reached during the late phase of Peoria time, in mollusk zone MZ3. Although soil moisture during the growing season at that time was high, the growing season was short and annual precipitation totals were low. Low values of magnetic susceptibility imply relatively rapid dust deposition during this interval, Judging from the current ecological tolerance of the species, no closed forest existed in the area. Only scattered shrubs or isolated tree stands may have been present. The late Peoria MZ3 assemblage compares favorably with theColumellafauna of Europe. In contrast, the early Peoria mollusk assemblages MZ1 and MZ2 compare well with the European pleniglacialPupillaassociations. Based on available14C dates from the studied region and on assumed relation of magnetic susceptibility to sedimentation rates, the estimated age of the MZ1 and MZ2 zones is 24,000 to 16,000 yr, whereas that of MZ3 is 16,000 to 12,000 yr.