bluuebunny/crossref_metadata_2025 huggingface dataset:
Protein products of human Gas2-related genes on chromosomes 17 and 22 (hGAR17 and hGAR22) associate with both microfilaments and microtubules
Authors: Goriounov Dmitri , Leung Conrad L. , Liem Ronald K. H.
Published: February 2003

The human Gas2-related gene on chromosome 22 (hGAR22)encodes two alternatively spliced mRNA species. The longer mRNA encodes a protein with a deduced molecular mass of 36.3 kDa (GAR22α), whereas the shorter mRNA encodes a larger protein with a deduced molecular mass of 72.6 kDa (GAR22β). We show that both hGAR22 proteins contain a calponin homology actin-binding domain and a Gas2-related microtubule-binding domain. Using rapid amplification of cDNA ends, we have cloned the mouse orthologue of hGAR22, mGAR22, and found its protein products to be extremely well conserved. We also report the cDNA cloning of a human Gas2-related gene on chromosome 17(hGAR17). hGAR17 also encodes two protein isoforms. The overall cytoskeletal binding properties of the hGAR17 and hGAR22 proteins are remarkably similar. hGAR17 mRNA expression is limited to skeletal muscle. Although hGAR22 and mGAR22 mRNAs are expressed nearly ubiquitously, mGAR22 protein can only be detected in testis and brain. Furthermore, only the βisoform is present in these tissues. GAR22β expression is induced in a variety of cultured cells by growth arrest. The absolute amounts of GAR22β protein expressed are low. The β isoforms of hGAR17 and hGAR22 appear to be able to crosslink microtubules and microfilaments in transfected cells. This finding suggests that the physiological functions of these proteins may involve integration of these two components of the cytoskeleton.
Abnormal tissue-dependent polytenization of a block of chromosome 3 pericentric heterochromatin inDrosophila melanogaster
Authors: Koryakov Dmitry E. , Domanitskaya Elena V. , Belyakin Stepan N. , Zhimulev Igor F.
Published: February 2003

Heterochromatic DNA sequences in the polytene chromosomes of Drosophila melanogaster salivary glands are under-replicated in wild-type strains. In salivary glands of SuUR and in the nurse cells of otumutants, under-replication is partly suppressed and a banded structure appears within the centric heterochromatin of chromosome 3. This novel banded structure in salivary gland chromosomes was called Plato Atlantis. In order to characterize the heterochromatic component of Plato Atlantis, we constructed a fine-scale cytogenetic map of deletions with break points within centric heterochromatin (Df(3L)1-16, Df(3L)2-66, Df(3R)10-65, Df(3R)4-75 and Df(3L)6B-29 + Df(3R)6B-29). Salivary gland chromosomes show that Df(3L)1-16 removes the complete Plato Atlantis, while Df(3L)2-66 deletes the most proximal 3L regions. These deletions therefore show a substantial cytological overlap. However, in the chromosomes of nurse cells, the same deficiencies remove distinct heterochromatic blocks,with the region of overlap being almost invisible. Satellite (AATAACATAG,AAGAG) and dodecasatellite DNAs mapped in a narrow interval in salivary glands but were found in three clearly distinguishable blocks in nurse cells. The 1.688 satellite was found at a single site in salivary glands but at two sites in nurse cells. We show that newly polytenized heterochromatic structures include blocks h47-h50d of mitotic heterochromatin in salivary glands, but the additional blocks h50p, h53 and h57 are also included in nurse cell chromosomes. Tissue specificity of the patterns of abnormal heterochromatic polytenization implies differential control of DNA replication in somatic and germline cells.
In situ visualization of rDNA arrangement and its relationship with subnucleolar structural regions inAllium sativumcell nucleolus
Authors: Wei Tao , Baiqu Huang , Chunxiang Liu , Zhonghe Zhai
Published: February 2003

We used a DNA-specific staining technique to show the two states of DNA component distributed in the nucleolar region of Allium sativumcells. One state is the extended DNA fiber, and the other is the condensed DNA clump. In situ hybridization demonstrated that the extended DNA fiber was an rRNA gene. Anti-fibrillarin antibody immunolabeling revealed that these rRNA genes were located in the dense fibrillar component near the fibrillar center,including at the periphery of the fibrillar center. None was in the dense fibrillar component far away from the fibrillar center. The condensed DNA clump was located in the fibrillar center. Further observations showed that the rRNA genes in the nucleolus were all arranged around the fibrillar center and associated with the DNA clumps in the fibrillar center. Results of statistical analysis showed that the distribution region of rRNA genes occupied about one-third of the total dense fibrillar component region. Ag-NOR protein showed a similar distribution pattern to that of rDNA. Immunolabeling of an anti-RNA/DNA hybrid antibody demonstrated that the transcription sites of rRNA were located at the periphery of the fibrillar center and in the dense fibrillar component near the fibrillar center, and these sites were consistent with the location and arrangement of rDNA shown in situ. These results demonstrated that transcription of rRNA takes place around the fibrillar center and at the periphery, whereas the dense fibrillar component that was far away from fibrillar center was the non-transcription region. The DNA clumps within the fibrillar center were probably the anchoring sites for rDNA arrangement.
Reduced survival of lens epithelial cells in theαA-crystallin-knockout mouse
Authors: Xi Jing Hua , Bai Fang , Andley Usha P.
Published: February 2003

αA-Crystallin (αA) is a molecular chaperone expressed preferentially in the lens. αA transcripts are first detected during the early stages of lens development and its synthesis continues as the lens grows throughout life. αA–/– mouse lenses are smaller than controls, and lens epithelial cells derived from these mice have diminished growth in culture. In the current work, we tested the hypothesis thatαA prevents cell death at a specific stage of the cell cycle in vivo. Seven-day-old 129Sv (wild-type) and αA–/–mice were injected with 5-bromo-2′-deoxyuridine (BrdU) to label newly synthesized DNA in proliferating cells. To follow the fate of the labeled cells, wholemounts of the capsule epithelial explants were made at successive times after the BrdU pulse, and the labeling index was determined. Immunofluorescence and confocal microscopy showed that both wild-type andαA–/– cells had a 3-hour labeling index of 4.5%in the central region of the wholemount, indicating that the number of cells in S phase was the same. Twenty-four hours after the pulse, individual cells labeled with BrdU had divided and BrdU-labeled cells were detected in pairs. The 24-hour labeling index in the wild-type lens was 8.6%, but in theαA–/– lens it was significantly lower, suggesting that some of the cells failed to divide and/or that the daughter cells died during mitosis. TUNEL labeling was rarely detected in the wild-type lens, but was significant and always detected in pairs in theαA–/– wholemounts. Dual labeling with TUNEL and BrdU also suggested that the labeled cells were dying in pairs in theαA–/– lens epithelium. Immunolabeling of wholemounts with β-tubulin antibodies indicated that the anaphase spindle in a significant proportion of αA–/– cells was not well organized. Examination of the cellular distribution of αA in cultured lens epithelial cells showed that it was concentrated in the intercellular microtubules of cells undergoing cytokinesis. These data suggest that αA expression in vivo protects against cell death during mitosis in the lens epithelium, and the smaller size of theαA–/– lens may be due to a decrease in the net production of epithelial cells.
Deletion of proteasomal subunit S5a/Rpn10/p54 causes lethality, multiple mitotic defects and overexpression of proteasomal genes inDrosophila melanogaster
Authors: Szlanka Tamás , Haracska Lajos , Kiss István , Deák Péter , Kurucz Éva , Andó István , Virágh Erika , Udvardy Andor
Published: February 2003

The regulatory complex of the 26S proteasome is responsible for the selective recognition and binding of multiubiquitinated proteins. It was earlier shown that the subunit S5a/Rpn10/p54 of the regulatory complex is the only cellular protein capable of binding multiubiquitin chains in an in vitro overlay assay. The role of this subunit in substrate selection, however, is a subject of debate, following the observation that its deletion in Saccharomyces cerevisiae is not lethal and instead causes only a mild phenotype. To study the function of this subunit in higher eukaryotes, a mutant Drosophila strain was constructed by deleting the single copy gene encoding subunit S5a/Rpn10/p54. This deletion caused larval-pupal polyphasic lethality, multiple mitotic defects, the accumulation of higher multimers of ubiquitinated proteins and a huge accumulation of defective 26S proteasome particles. Deletion of the subunit S5a/Rpn10/p54 does not destabilise the regulatory complex and does not disturb the assembly of the regulatory complex and the catalytic core. The pupal lethality is a consequence of the depletion of the maternally provided 26S proteasome during the larval stages and a sudden increase in the proteasomal activity demands during the first few hours of pupal development. The huge accumulation of the fully assembled 26S proteasome in the deletion mutant and the lack of free subunits or partially assembled particles indicate that there is a highly coordinated accumulation of all the subunits of the 26S proteasome. This suggests that in higher eukaryotes, as with yeast, a feedback circuit coordinately regulates the expression of the proteasomal genes, and this adjusts the actual proteasome concentration in the cells according to the temporal and/or spatial proteolytic demands.
Metal vs bioabsorbable interference screws: Initial fixation
Authors: Beevers D J
Published: February 2003

Interference screws are used for graft fixation in anterior cruciate ligament reconstruction. There is current debate as to whether metal or bioabsorbable varieties provide the optimal results. This paper provides a critique of the single load-to-failure uniaxial tensile test data available in the literature, which provide the initial postoperative characteristics. Both metal and bioabsorbable screws were found to give similar levels of pull-out force and stiffness when used on similar types of graft material. Screws with bone-patellar tendon-bone grafts provided the greatest values, exceeding the forces transmitted through the native anterior cruciate ligament during normal daily activities. Hamstring grafts provided lower values, only being comparable with the forces of daily living. Consequently, this raises the question as to whether the rehabilitation regime of the hamstring patient must not be aggressive in the early postoperative stages when using either metal or bioabsorbable screws. This would ensure that the graft will not fail in the initial postoperative period before biological fixation occurs, which will then boost the strength to an acceptable level.
Enhanced Effect of Mesoporous Silica on Base-Catalyzed Aldol Reaction
Authors: Kubota Yoshihiro , Goto Kunio , Miyata Shintaro , Goto Yasutomo , Fukushima Yoshiaki , Sugi Yoshihiro
Published: February 2003

Aldol reaction of 4-nitrobenzaldehyde with acetone gives 4-(4-nitrophenyl)-4-hydroxy-2-butanone in high yield in the presence of both secondary amine and mesoporous silica, whereas the yield is low in the absence of the mesoporous silica.
Periodic Expansion-contraction Motion of Photoabsorbing Organic Droplets during Laser Photophoretic Migration in Water
Authors: Monjushiro Hideaki , Tanaka Makiko , Watarai Hitoshi
Published: February 2003

Laser photophoretic behavior of 2-benzylpyridine droplets including Co(III)-pyridylazo complex as a photoabsorber was examined in water by irradiating cw Ar+ ion laser. We have made a new observation like a “breathing” motion that the droplets repeated the expansion and the sudden contraction during laser photophoretic migration. The period of the motion decreased with increasing the Co complex concentration in the droplet and also with increasing the laser power. The origin of the motion is the water vaporization in the droplet by photothermal conversion.
Study on Thermal-addressing Characteristics of (Polymer Network/Liquid Crystals/Chiral Dopant) Composite
Authors: Yang Huai , Kikuchi Hirotsugu , Kajiyama Tisato
Published: February 2003

A [polymer network/liquid crystals (LCs)/chiral dopant] composite with a smectic A (Sa) ↔ chiral nematic (N*) phase transition is prepared. A very drastic change from the light-scattering Sa phase to the transparent N* one is achieved upon heating the composite. The transparent state of the N* phase is ‘frozen’ in the Sa phase upon cooling. When an ac electric field is applied to the composite, the transparent Sa phase is changed into the light-scattering Sa one again.
Potassium Triiodide. A New and Efficient Catalyst for Carbon–Carbon Bond Formation in Aqueous Media
Authors: Thakur Ashim J , Prajapati Dipak , Gogoi Baikuntha J , Sandhu Jagir S
Published: February 2003

Potassium triiodide catalyses the condensation of carbonyl compounds with active methylene compounds in aqueous media to afford E olefinic products in high yields.
Vapochromic Properties of Nafion Film Doped with Cationic Dyes
Authors: Matsushima Ryoka , Nishimura Naoko , Kohno Yoshiumi
Published: February 2003

Protonated Nafion thin film doped with cationic dyes such as flavylium and thionine revealed rapid and vapor-specific color changes (vapochromism) upon exposure to volatile organic compounds. The vapochromic performances were substantially retained after 10 repeated cycles of exposures, implying good reversibility.
Characterization of transgenic mice—a comparison of protocols for welfare evaluation and phenotype characterization of mice with a suggestion on a future certificate of instruction
Authors: Jegstrup I. , Thon R. , Hansen A. K. , Hoitinga M. Ritskes
Published: February 2003

A thorough welfare evaluation performed as part of a general phenotype characterization for both transgenic and traditional mouse strains could not only contribute to the improvement of the welfare of laboratory animals, but could also be of benefit to scientists, laboratory veterinarians and the inspecting authorities. A literature review has been performed to identify and critically evaluate already existing protocols for phenotype and welfare characterization. There are several relevant schemes available, among others the SHIRPA method, the modified score sheet of Morton and Griffiths, the FRIMORFO phenotype characterization scheme and the behavioural phenotype schemes as described by Crawley. These protocols have been evaluated according to four goals: Their ability (1) to reveal any special needs or problems with a transgenic strain, (2) to cover the informational needs of the purchaser/user of the strain, (3) to refine the welfare of the transgenic animal model by identifying relevant humane endpoints, (4) to prevent the duplication of animal models that have already been developed. The protocols described are useful for characterizing the phenotype and judging welfare disturbances, however the total amount of information and the degree of detail varies considerably from one scheme to another. We present a proposal regarding the practical application of the various schemes that will secure proper treatment and the identification of humane endpoints. It is advocated that with every purchase of a particular strain, an instruction document should accompany the strain. This document needs to give detailed descriptions of the typical characteristics of the strain, as well as necessary actions concerning relevant treatment and humane endpoints. At the moment no such documents are required. The introduction of these types of documents will contribute to improvements in animal welfare as well as experimental results in laboratory animal experimentation.
Interaction of biological membranes with the cytoskeletal framework of living cells
Authors: MANGEAT Paul‐Henri
Published: February 2003

The review is focused on the molecular structure and function of the proteins composing the actin‐based cytokeletal cortex, located at the cytoplasmic face of plasma membranes of eucaryotic cells, which stabilizes integral membrane proteins in separate domains of cell membranes. It includes a survey of the molecular properties of teh proteins of the erythrocyte membrane skeleton such as spectrin, ankyrin, protein 4.1, and adducin. The properties of the immunological counterparts of erythroid cortical proteins found in nonerythroid tissues and cells are compared. The structural organization and function of the newly discovered class of calcium‐binding proteins, nonerythroid peripheral membrane proteins, calpactins, are also described. Finally, the discussion of some experimental models illustrates that the membrane skeleton of living cells is actively involved in a wide variety of essential biological functions ranging from differentiation, to maintenance of cell polarity and cell shape, and regulation of exocytotic processes.
Effect of microtubule reactive drugs on steroid‐ and centrifugation‐induced germinal vesicle migration during goldfish oocyte meiosis
Authors: LESSMAN Charles A. , HABIBI Hamid R. , Macrae Thomas H.
Published: February 2003

During the process of progestogen‐induced meiotic maturation in the goldfish oocyte, the oocyte nucleus (germinal vesicle, GV) migrates to the sperm entry site or micropyle at the animal pole. Following GV migration (GVM) to the micropyle, the nuclear membrane undergoes dissolution (GVD) and the cell enters metaphase I in preparation to generate the first polar body. Microtubule destabilizing drugs including colcemid, nocodazole and vinblastine were found to elicit GVM, mimicking the process which occurs just prior to the prophase I‐metaphase I transition during steroid induced oocyte meiotic maturation. In addition, these drugs enhanced the induction of GVM by 17 alpha, 20 beta dihydroxy‐4‐pregnen‐3‐one, a potent, naturally occurring meiotogenic steroid in this species. By contrast, taxol, a microtubule stabilizing drug, was found to inhibit steroid induced GVM. A new assay for centrifugation induced GVM was applied to the goldfish oocyte in order to assess effects of steroids and drugs on GVM, without the complication of GVD or the restrictions imposed by the slow time course of naturally occurring GVM. The effective centrifugal force (ECF) required to elicit GVM in 50% of the oocytes (ECF50) decreased significantly after short incubations (1–5 hr) of oocytes with either 17 alpha, 20 beta dihydroxy‐4‐pregnen‐3‐one or microtubule disrupting drugs (i.e., colcemid, nocodazole, or vinblastine). A working hypothesis, modeled after the effects of microtubule disrupting agents on intermediate filament arrays in somatic cells, is proposed in which a small number of microtubules or other polymeric tubulin units are responsible for maintaining a cytoskeletal array. The net effect of progestogen or microtubule disrupting drugs would be to collapse or reorganize the array to allow GVM.
Secretion systems and membrane‐associated structures in rust fungi after high pressure freezing and freeze‐fracturing
Authors: KNAUF Gertrude M. , MENDGEN Kurt
Published: February 2003

Excellent preservation and new structural details can be demonstrated in rust‐infected leaf tissue after high pressure freezing and freeze‐fracturing. A tubular‐vesicular complex was the most remarkable cytoplasmic structure observed in cells of the bean rust fungus Uromyces appendiculatus var. appendiculatus during its establishement in its host Phaseolus vulgaris. In fungal cells undergoing intensive synthesis of wall material, this membranous system extended throughout the cytoplasm; in addition, vesicles were accumulated adjacent to the plasma membrane. Here, membrane‐associated configurations were observed which seem to be involved in exo‐ and/or endocytotic processes. It is assumed that the tubular‐vesicular complex belongs to the endomembraneous system of the bean rust fungus and that it is involved in the synthesis and secretion of wall material.
Swimming behaviour of the unicellular biflagellate Oxyrrhis marina: in vivo and in vitro movement of the two flagella
Authors: Cosson Jacky , Cachon Monique , Cachon Jean , Cosson Marie‐Paule
Published: February 2003

Summary— The movement of the 2 flagella of Oxyrrhis marina was examined with respect to their individual waveforms and the swimming behaviour of the organism. The longitudinal flagella propagated helicoidal waves whose amplitude decreased toward the tip of the flagellum. Their beat frequencies were 50–60 Hz. The transverse flagella beat helicoidally within a furrow. Sudden changes in the direction of the cell trajectories were generated by transient arrests of the longitudinal flagellum beat, which were accompanied by a switch from the backward orientation to a forward one. This sweeping motion generated the rotation of the cell body. Ca2+ ions highly stimulated the frequencies of this arrest response, which compared to the “walking‐stick” behaviour of sea urchin spermatozoa.

Isolated flagella were ATP‐reactivated after detergent treatment. They exhibited 2 types of motion within the same experimental conditions. A progressive helicoidal motion was generated upon longitudinal flagellum reactivation, whereas a rolling motion with little progression characterized transverse flagellum reactivation. The differences motile behaviour reflect regulations of flagellar movement which were not destroyed by the isolation procedure and may be indicative of regulation of accessory structures.
Microtubule cytoskeleton and morphogenesis in the amoebae of the myxomycete Physarum polycephalum
Authors: Wright Michel , Albertini Catherine , Planques Viviane , Salles Isabelle , Ducommun Bernard , Gely Catherine , Akhavan‐Niaki Haleh , Mir Luis , Moisand André , Oustrin Marie‐Louise
Published: February 2003

Summary— The amoebae of the myxomycete Physarum polycephalum are of interest in order to analyze the morphogenesis of the microtubule and microfilament cytoskeleton during cell cycle and flagellation. The amoebal interphase microtubule cytoskeleton consists of 2 distinct levels of organization, which correspond to different physiological roles. The first level is composed of the 2 kinetosomes or centrioles and their associated structures. The anterior and posterior kinetosomes forming the anterior and posterior flagella are morphologically distinguishable. Each centriole plays a role in the morphogenesis of its associated satellites and specific microtubule arrays. The 2 distinct centrioles correspond to the 2 successive maturation stages of the pro‐centrioles which are built during prophase. The second level of organization consists of a prominent microtubule organizing center (mtoc 1) to which the anterior centriole is attached at least during interphase. This mtoc plays a role in the formation of the mitotic pole. These observations based on ultrastructural and physiological analyses of the amoebal cystoskeleton are now being extended to the biochemical level. The complex formed by the 2 centrioles and the mtoc 1 has been purified without modifying the microtubule‐nucleating activity of the mtoc 1. Several microtubule‐associated proteins have been characterized by their ability to bind taxol‐stabilized microtubules. Their functions (e.g., microtubule assembly, protection of microtubules against dilution or cold treatment, phosphorylating and ATPase activities) are under investigation. These biochemical approaches could allow in vitro analysis of the morphogenesis of the amoebal microtubule cytoskeleton.
From cilia and flagella to intracellular motility and back again: a review of a few aspects of microtubule‐based motility
Authors: Huitorel Philippe
Published: February 2003

Summary— Ciliary or flagellar movement is the model of microtubule‐dependent motility, the best studied at the molecular level. It is based on the relative sliding of outer doublets of microtubules that are linked at their proximal end to the basal structure and interconnected by associated proteins, among which dynein ATPase is at the origin of the movement. It is regulated from inside and outside media by various diffusible factors such as Ca2+, cyclic adenosine monophosphate (cAMP), polypeptides and so on (see other conferences presented during this meeting).

Other motility processes are based on microtubules: vesicle and organelle transport through the cytoplasm (axonal flow in neurons, pigment granule movements in fish chromatophores, movements of particles along heliozoan axopods, etc.) could be mediated by microtubule motors such as kinesin or MAP 1C. Kinesin and MAP 1C, like dynein, are proteins that bind to microtubules and show an ATPase activity associated with force production. They differ from each other by their structure, and biochemical and pharmacological properties.

The movements of chromosomes during mitosis and melosis have long been studied, but are still poorly understood at the molecular level; this topic will be discussed in the light of recent data.

Other constituents of the cytoskeleton are certainly involved in cellular motility: actin microfilaments and their motor myosin, intermediate filaments, non‐actin filaments, all organized around te Microtubule Organizing Center (MTOC). As more information becomes available, it seems increasingly obvious that these various networks are closely interconnected and that each component probably modulates, resists, or favors properties of its partners, contributing to cellular and intracellular motility.
Expression of variant‐specific antigen genes in African trypanosomes
Authors: Pays Etienne
Published: February 2003

Among the large collection of antigen genes present in the Trypanosoma brucei genome, only one is usually transcribed at a time when the parasites develop in the mammalian bloodstream. The antigen gene is transcribed in a telometric expression site, together with other genes whose function is unknown. The nature of the RNA polymerase and transcription promoter, as well as the overall organization of the transcription unit, suggests that transcription of the antigen gene is of the ribosomal type. This transcription rapidly stops when the temperature of the parasite medium is lowered, probably accounting for the gene inactivation in the procyclic form of the insect midgut. Antigen gene expression resumes in 2 steps: first, induction of specific metacyclic variants occurs in the fly salivary glands, then injection into the blood reactivates the expression site silenced at the procyclic stage. Several telomeres can act as alternative expression sites, but the mechanism for expression‐site switching is unknown. In a given expression site, the specificity of the antigen gene can change following gene conversion, telomeric reciprocal recombination, or point mutation. The alternate use of these mechanisms leads to the successive appearance of a very high number of antigenic variants, as well as to rapid evolution of the antigen gene repertoire. The relative extent of homology between nontelomeric antigen genes and the expression site may condition the programming of antigenic variation late in chronic infection, as well as the generation of chimaeric antigen genes.
Activation of a Plasmodium falciparum protease correlated with merozoite maturation and erythrocyte invasion
Authors: Braun‐Breton Catherine , Da Silva Luis Pereira
Published: February 2003

Protease‐dependent processes of the P. falciparum schizogonic cycle are briefly described. The P. falciparum p76 protease is the first example of a biochemically regulated protease, the activation of which is related to merozoite maturation and/or erythrocyte invasion. The main known properties of the p76 protease are reviewed and some original results concerning its biosynthesis and biological properties are described.
Isolation and characterization of stable nuclear matrix preparations and associated DNA from avian erythroblasts
Authors: RZESZOWSKA‐WOLNY Joanna , RAZIN Serge , PUVION Edmond , MOREAU Jacques , SCHERRER Klaus
Published: February 2003

A novel procedure for isolation of nuclear matrices from chicken erythroblast cells was elaborated. The influence of variations in the isolation procedure on structural integrity and morphology of nuclear matrices as well as on properties of the nuclear matrix‐associated DNA fractions was investigated. The incubation of isolated nuclei in the presence of Cu2+ ions provided significant stabilization of the nuclear matrix. Copper treatment of nuclei did not affect the properties of the nuclear skeleton‐associated DNA fraction. In both copper‐stabilized as well as unstabilized nuclei, nuclear matrix‐attached DNA was digested to the same extent with nucleolytic enzymes, and could be totally removed from nuclear matrices by 2 M NaCl‐2 M urea treatment. The fine morphology of the nuclear matrix did not change after extraction of nuclear skeleton‐associated DNA fragments. In the presence or absence of copper ions, matrix DNA was found to be qualitatively different compared with total DNA, in particular with respect to the representation of specific repetitive sequences of the chicken beta globin gene domain.
Image analysis and three‐dimensional model of chymotrypsin‐transformed human alpha2‐macroglobulin complexed with a monoclonal antibody specific for this conformation
Authors: BOISSET Nicolas , TAVEAU Jean‐Christophe , BARRAY Martine , VAN LEUVEN Fred , DELAIN Etienne , LAMY Jean N.
Published: February 2003

Alpha2‐macroglobulin (α2M) is a plasma inhibitor of proteinases, the steric mechanism of which is based on a considerable conformational change. The typical and distinct H‐like shape of α2M‐chymotrypsin (α2M‐chy) complexes seen by electron microscopy led us to an ultrastructural study of the binding of a monoclonal antibody (Mab) specific for this conformation of α2M. The epitope of this Mab is located near the extremities of the 4 arms of the H‐like α2M‐chy, at a site that is not accessible on the native molecule. The identical binding of the Mab on the 4 arms of the tetrameric molecule demonstrates that these arms are equivalent portions of the 4 monomers. Various types of immune complexes between α2M and IgG are described, and images of individual immune complexes are processed by correspondence analysis. This extracts new information concerning the organization of chymotrysin‐transformed α2M. The molecule appears asymmetrical, presents 2 conformational states (which we describe as relaxed and twisted), and has flexible arms. These intramolecular motions are supposed to be related to IgG binding. The results are discussed in comparison with previously published models of proteinase‐transformed α2M.
Human keratinocyte membrane lectins: characterization and modulation of their expression by cytokines
Authors: Cerdan Dominique , Grillon Catherine , Monsigny Michel , Redziniak Gérard , Kieda Claudine
Published: February 2003

Summary— In an attempt to identify cell surface molecules involved in recognition phenomena between cells such as keratinocytes and melanocytes and putatively target biological responses modifiers to keratinocytes, we undertook the detection of cell surface sugar specific receptors: membrane lectins. Keratinocyte membrane lectins were found to bind synthetic glycoproteins (neoglycoproteins) carrying either α‐l‐fucosyl or α‐l‐rhamnosyl residues. Fluorescence microscopy observations indicate that cultured keratinocytes are able to bind these two neoglycoproteins while frozen sections of human skin labelled with neoglycoprotein‐coated covaspheres show that the selectivity of the binding to keratinocytes is restricted to α‐l‐rhamnosyl‐BSA. Keratinocytes were adapted to grow on collagen; harvesting conditions allowing the analysis of keratinocytes by flow cytometry are described. This technique allows the quantification of the binding at 4°C, and the estimation of the endocytosis of F‐, neoglycoproteins: F‐, α‐l‐Rha‐BSA and F‐, α‐l‐Fuc‐BSA were efficiently internalized. Thereafter, α‐l‐rhamnose‐substituted liposomes containing 5‐(6)carboxyfluorescein were prepared in order to follow the delivery of the fluorescent dye into cells. This was measured both by flow cytometry and by spectrofluorimetry. The expression of surface lectins was checked upon action of cytokines (IL1α, IL1β, IL2 and TNF) which are known as biological response modifiers of keratinocytes.
Low molecular weight DNA in the heteromeric macronuclei of two cyrtophorid ciliates
Authors: Lahlafi Touria , Méténier Guy
Published: February 2003

Summary— The size range of the native DNA molecules in the heteromeric macronuclei of two cyrtophorid ciliates (Trithigmostoma cucullulus, Chilodonella uncinata) was mainly investigated by using agarose gel electrophoresis. Numerous bands superimposed on a continuous spectrum of molecular sizes between about 0.35 kb and 30 kb were resolved by conventional electrophoresis. Species‐specific banding patterns indicate a variation between species in the copy number of individual DNA fragments. A slight intra‐specific variability of banding patterns can exist. Electrophoretic distributions for two strains of T cucullulus were indeed found to differ by at least one more intense band (‘overamplified’ sequences?). Fractionation by contour‐clamped homogeneous electric field (CHEF) gel electrophoresis revealed that the size continum of macronuclear DNA molecules does not extend beyond 60–70 kb. The average size was estimated to be around 4 kb. Unresolved DNA fraction (> 1000 kb) accounted for less than 10% of the mass of cellular DNA entering CHEF gels. Macronuclear ribosomal DNA of each cyrtophorid species was identified by Southern hybridization with a Tetrahymena rDNA probe. The hybridization signal was observed on a single band of low molecular weight DNA. The corresponding size was close to 14.5 kb in Trithigmostoma and 15.5 kb in Chilodonella, which is about twice the size of monomeric rDNA in hypotrichous ciliates. We showed that S1 nuclease resistant duplexes wit half the length of the native rDNA can be formed by rapid renaturation of heat‐denatured molecules and hybridized with native rDNA. This strongly suggests that the nucleotide sequence of this rDNA is a large palindrome. Unlike the hypotrichs, macronuclear rDNA in cyrtophorids should be organized into palindromic dimers as in Tetrahymena species.
Ca2+ ‐binding proteins and contractility of the infraciliary lattice in Paramecium
Authors: De Loubresse Nicole Garreau , Klotz Catherine , Vigues Bernard , Rutin Jacques , Beisson Janine
Published: February 2003

Summary— The infraciliary lattice (ICL) is the innermost cortical cytoskeletal network of Paramecium. Its meshes which run around the proximal end of basal bodies form a continuous contractile network beneath the cell surface. We had previously shown that the network, which could be recovered in a contracted form and selectively solubilized by EGTA from an ICL‐enriched cell fraction, was principally composed of 23–24 kDa polypeptides cross‐reacting with antibodies raised against the 22 kDa Ca2+ ‐binding proteins of the ecto‐endoplasmic boundary (EEB), a contractile cytoskeletal network of another ciliate Isotricha prostoma. We show here 1) that the ICL also comprises a 220 kDa polypeptide; 2) that the 23–24 kDa polypeptides are resolved in 2D gels into 11 spots of acidic pI, 7 of which are both Ca2+ ‐binding and cross‐reacting with the anti EEB polypeptides; 3) that the network displays a high Ca2+ ‐affinity as the treshold for solubilization/co‐precipitation of both high and low MW polypeptides is around 10−8 M free Ca2+; 4) that in vivo contraction of the network occurs upon physiological increase of internal calcium concentration. The likely phylogenetic relationships of the 23–24 kDa ICL polypeptides with the calmodulin related family of Ca2+ ‐modulated polypeptides and the functions of the ICL in cell contractility and Ca2+ homeostasis are discussed.
Post‐transcriptional analysis of rat mitochondrial D‐3‐hydroxybutyrate dehydrogenase control through development and physiological stages*
Authors: Bailly Anne , Lone Yu Chun , Latruffe Norbert
Published: February 2003

Summry— The nuclear encoded mitochondrial D‐3‐hydroxybutyrate dehydrogenase (BDH) is synthesized in the cytosal as a larger precursor. This membrane enzyme which requires lecithin for activity plays an essential role in energy metabolism as a ketone bodies‐converting enzyme. A cDNA clone of the rat liver enzyme encompassing an antigenic determinant peptide has been isolated after immunoscreening of a λ gt11 expression library. The nucleotide sequence of this 279‐base cDNA insert contains a single open reading frame of 93 amino‐acids, which represents about a third of the mature enzyme. Amino‐acid sequence analysis predicts a hydrophobic stretch of 29 amino‐acids long which probably functions as membrane anchor domain, or as an important region for the enzyme activation by phospholipid. By using this cDNA probe the BDH gene has been investigated at the mRNA level. There is only one mRNA (2‐kb size) for BDH whatever the studied tissue. The rat gene is differently expressed since its mRNA is already present in the foetus liver while the BDH polypeptide amount is low and its enzymatic activity is not detectable even in the late stage of foetal development. The mRNA content is higher in the liver than in extrahepatic tissues. Adrenalectomy and ovariectomy increase liver mRNA content and polypeptide level, as well as activity of BDH. These effects are totally or partially abolished by corticosterone and estradiol treatments respectively. In addition, a 15‐day hyperlipidic diet stimulates BDH gene expression. Present results show that the gene expression of this mitochondrial enzyme is modulated through development and hormonal and metabolic conditions mentioned above.
Membrane fluidity aspects in endocytosis; a study with the fluorescent probe trimethylamino‐diphenylhexatriene in L929 cells
Authors: Illinger Dominique , Poindron Philippe , Kuhry Jean‐Georges
Published: February 2003

Summary— The fluorescent hydrophobic plasma membrane probe, trimethylamino‐diphenylhexatriene (TMA‐DPH) was previously shown to follow the plasma membrane throughout its internalization and recycling process and thus to behave as a marker for endo‐ and exocytosis in living cell systems. In this paper, we made use of these properties to investigate membrane fluidity effects associated with endocytosis in L929 cells. For that purpose we performed TMA‐DPH fluorescence anisotrophy measurements which showed that endocytosis starts from particularly rigid regions of the plasma membrane (probably coated pits). The fluorescence anisotropy then continuously decreases to a lower limit corresponding to the membrane fluidity of the probe in the lysosomial membrane. Strikingly, the value of this limit is identical to the average anisotropy value in the peripheral membrane, which suggests that lysosomes and plasma membrane may have a similar phospholipidic composition and a possible common origin.
Phenological studies of Acrostichum danaeifolium (Pteridaceae, Pteridophyta) at a mangrove site on the Gulf of
Mexico
Authors: Mehltreter Klaus , Palacios-Rios Mónica
Published: February 2003

A population of the giant leather fern Acrostichum danaeifolium
was observed during an 18-mo period at La Mancha (19°36′00″N, 96°22′40″W), Veracruz, Mexico. The study site was 230 m from a brackish-water lagoon, in the understorey of the mangroves, which are dominated by Avicennia germinans (Avicenniaceae). Acrostichum danaeifolium showed a clumped distribution pattern, and one third of the population became fertile during this time. Plants had a mean number of 9.4 ± 0.45 sterile leaves, which developed continuously at a rate of 14.6 ± 0.44 leaves y-1. The mean life span of sterile leaves was 7.7 mo. Although soil water was always available, phenological patterns of fertility, leaf production and leaf growth were strongly correlated with the seasonal climate. Individual leaf growth and leaf size increased significantly during the rainy season. Fertile leaves emerged exclusively from April to August and had a mean life span of 4.1 mo. Spore release was restricted to the wet season, when conditions for germination were favourable. Environmental triggers of fertility are discussed and phenological patterns are compared with ferns and angiosperms from other habitats.
Woody plant damage by African elephants in relation to leaf nutrients in western Zimbabwe
Authors: Holdo Ricardo M.
Published: February 2003

The relationship between elephant damage and leaf nutrient concentration across tree species was investigated in a semi-arid savanna in western Zimbabwe with the purpose of investigating possible nutritional factors influencing elephant feeding preferences in Kalahari sand woodlands. The presence of elephant damage was recorded in all trees above 1 m in height, and leaf samples were collected from all tree species encountered in 12 vegetation plots during the late dry season. Elephant damage was positively correlated with leaf calcium, magnesium, potassium and protein concentration, but not with sodium, phosphorus or fibre. Tree species associated with sandy soils appeared to be less preferred by elephants and to have lower nutrient concentrations than species occurring on more fertile soils, such as species associated with termite mounds. Elephant damage may suppress recruitment in preferred tree species in these woodlands. This notion was supported by (1) the fact that 44% of all trees surveyed had had their main stems broken by elephants, a situation that leads to a multi-stemmed growth form with limited vertical growth; and (2) the negative correlation between the height of damaged trees and elephant damage across species.
Ecological and isotopic discrimination of syntopic rodents in a neotropical rain forest of French Guiana
Authors: Mauffrey Jean-François , Catzeflis François
Published: February 2003

Stable isotopes are commonly used in ecological studies to infer food resources (Ambrose & DeNiro 1986, Bocherens et al. 1990,1991,1994;Yoshinaga et al. 1991) since isotopic composition is conserved during the feeding process. Moreover,for herbivorous (sensu lato) species, it is often possible to identify the main resource because different photosynthetic pathways generate different values of carbon isotope ratios (Park & Epstein 1961, Sternberg et al. 1984). This allows the characterization of broad biota such as savannas or forest and discrimination of grazers from sympatric folivorous species (DeNiro & Epstein 1978).
The idea of an Institute of Advanced Study. Some reflections on education, science and art
Authors: WESSELING H. L.
Published: February 2003

The first Institute for Advanced Study was founded in Princeton, New Jersey in 1930. Several other institutes followed, both in America, Europe and, more recently, in Asia and Africa. This paper is not a history of such institutes, but is about the idea of an Institute for Advanced Study. Like John Henry Newman in his famous book, The Idea of a University, it offers some general reflections on education, science and art and their interrelationship. It underlines the importance of these institutes in an academic world increasingly dominated by notions of measured output and impact and of policies imposed from ‘above’.
The limits of historical knowledge
Authors: ELLIOTT JOHN
Published: February 2003

This paper sets out the limitations of knowledge from the past and the ways that knowledge can be used. The first part deals with the extent to which the past can be known and raises questions about the survival of evidence and also about the ways evidence is interpreted. The second part looks briefly at possible uses of the past and suggests, in particular, the importance of new interpretations challenging the received wisdom and thus giving societies new ways of looking at themselves and their histories.
Bias in species range estimates from minimum convex polygons: implications for conservation and options for improved planning
Authors: Burgman Mark A. , Fox Julian C.
Published: February 2003

Minimum convex polygons (convex hulls) are an internationally accepted, standard method for estimating species' ranges, particularly in circumstances in which presence‐only data are the only kind of spatially explicit data available. One of their main strengths is their simplicity. They are used to make area statements and to assess trends in occupied habitat, and are an important part of the assessment of the conservation status of species. We show by simulation that these estimates are biased. The bias increases with sample size, and is affected by the underlying shape of the species habitat, the magnitude of errors in locations, and the spatial and temporal distribution of sampling effort. The errors affect both area statements and estimates of trends. Some of these errors may be reduced through the application of α‐hulls, which are generalizations of convex hulls, but they cannot be eliminated entirely. α‐hulls provide an explicit means for excluding discontinuities within a species range. Strengths and weaknesses of alternatives including kernel estimators were examined. Convex hulls exhibit larger bias than α‐hulls when used to quantify habitat extent and to detect changes in range, and when subject to differences in the spatial and temporal distribution of sampling effort and spatial accuracy. α‐hulls should be preferred for estimating the extent of and trends in species' ranges.
Growth strains and losses in Nb−diffused LiTaO3 optical film waveguides
Authors: Ramaswamy V. , Standley R. D.
Published: February 2003

We have observed the formation of growth strains due to interfacial dislocations in thin films made by the diffusion of niobium into LiTaO3. These dislocations become significant for films wherein Δn0≳0.01; their effect is to increase the scattering loss of the optical guided waves in the film.
Pulse generation in a cw dye laser by mode−locked synchronous pumping
Authors: Harris J. M. , Chrisman R. W. , Lytle F. E.
Published: February 2003

A continuous train of <500 ps (detector limited) pulses has been produced with a cw dye laser pumped by a mode−locked argon ion laser. The cavity lengths of the dye laser and argon laser were made equal in order to synchronously amplify a single pulse oscillating in the dye laser. An intracavity acousto−optic modulator was used to dump dye laser pulses at rates as high as 10 MHz.
Absence of dynamic conversion of bubbles in Permalloy-coated garnet films of (YGdTm)3 (FeGa)5O12
Authors: Suzuki Ryo , Sugita Yutaka
Published: February 2003

The scatter in the bubble velocity has been investigated in Permalloy-coated garnet films of high-mobility (YGdTm)3 (FeGa)5O12. When Permalloy layers are 80 Å thick, the scatter does not exist even if the bias field is near the bubble run-out field. This shows that the dynamic conversion does not occur in these films. When Permalloy layers become thicker than 120 Å, however, bubble velocities deviate to low values and show large scatter. The scatter in this case is due to pinning of planar domain walls of the Permalloy layer associated with bubbles.
A new concept for solar energy thermal conversion
Authors: Cuomo J. J. , Ziegler J. F. , Woodall J. M.
Published: February 2003

A material has been developed which allows a new approach to be made to the conversion of solar energy to heat. It consists of a dense array of metal whiskers grown with spacings of a few wavelengths of visible light. The material selected has low emissivity, and achieves significant optical absorption by trapping the light by a geometric maze effect. We have deomonstrated that absorption of normal incidence light is greater than 98% from 0.5 to 40-μm wavelengths, and hemispherical emissivity at 550 °C can be made less than 0.26. Since surfaces can be made of a single refractory element, such as W, high-temperature solar conversion (550 °C) should be maintained with good surface stability.