bluuebunny/crossref_metadata_2025 huggingface dataset:
Antibodies that can discriminate between dynein heavy chains and their HUV1 photoproducts
Authors: Sperling Linda , Houari Abdellah , Moudjou Mohammed , Mazarguil Honoré , Wright Michel
Published: February 2005

Dyneins are multi‐subunit enzymes that transduce chemical energy into the mechanical energy that makes cilia and flagella beat and moves organelles towards the minus end of microtubules. The ATPase activity is borne by heavy chains, and recent molecular analysis indicates that dynein heavy chain genes form an ancient multigene family: the similarity between the same isoform of two distantly related species is greater than that between different isoforms of the same species. We have exploited sequence identities between a Paramecium axonemal dynein heavy chain gene cloned in our laboratory and sequences of dynein heavy chains from other species to prepare antibodies against active‐site peptides capable of recognizing dynein heavy chains regardless of species or isoform. One of the antibodies is perfectly specific for the larger product of V1 photolysis (HUV1) and thus incorporates a unique property of the hydrolytic ATP binding site of all known dynein heavy chains, the capacity for photocleavage in the presence of micromolar vanadate. Our characterization of these reagents suggests that they will be useful for biochemical and in situ studies of known dyneins as well as identification of potential new members of the family. © 1994 Wiley‐Liss, Inc.
Phosphoprotein phosphatase 1 (PP1) is a component of the isolated sea urchin mitotic apparatus
Authors: Johnston Jennifer A. , Sloboda Roger D. , Silver Robert B.
Published: February 2005

A protein component of isolated mitotic apparatus having a relative molecular mass of 62,000 (p62) is a substrate of a calcium/calmodulin dependent protein kinase, and the phosphorylation of p62 in vitro correlates directly with microtubule disassembly. In vivo experiments have determined the phosphorylation of p62 increases after fertilization; maximum incorporation of phosphate occurs during late metaphase/early anaphase and decreases thereafter. Because the level of p62 is constant throughout the cell cycle [Johnston and Sloboda, 1992: J. Cell Biol. 119:843–54] the decrease in phosphorylation of p62 observed after anaphase onset is most likely due to the action of a phosphatase. By examination of the relative amount of phosphorylated p62 which remained radiolabeled as a function of time using a standard in vitro phosphorylation assay, the activity of a phosphoprotein phosphatase capable of dephosphorylating p62 in the isolated mitotic apparatus was observed. To characterize the p62 phosphatase, okadaic acid and calyculin A were used to inhibit the dephosphorylation of p62 in vitro. It was found that specific concentrations of okadaic acid (50–500 nM) and of calyculin A (10–100 nM) were effective at inhibiting the dephosphorylation of p62 in vitro. Lower concentrations of either inhibitor had a negligible effect on dephosphorylation of p62. These data indicate the presence of phosphoprotein phosphatase type 1 activity associated with mitotic apparatus isolated from sea urchin embryos using the procedures described here. The implications of these findings relative to our understanding of the regulation of mitosis and cytokinesis are discussed. © 1994 Wiley‐Liss, Inc.
Characterization of a monoclonal antibody prepared against plant actin
Authors: Andersland John M. , Fisher Deborah D. , Wymer Carol L. , Cyr Richard J. , Parthasarathy M. V.
Published: February 2005

Anti‐actin monoclonal antibodies were prepared using phalloidin‐stabilized actin that was purified from pea roots by DNase I affinity chromatography. One monoclonal antibody, designated mAb3H11, bound plant actin in preliminary screenings and was further analyzed. Immunoblot analysis showed that this antibody had a high affinity for plant actin in crude and purified preparations but a low affinity for rabbit muscle actin. In immunoblots of plant extracts separated on two‐dimensional gels it appeared to bind all actin isoforms recognized by the JLA20 anti‐chicken actin antibody. Using immunofluorescent cytochemistry, the antibody was used to observe actin filaments in aldehyde‐fixed and methanol‐treated tobacco protoplasts. These results indicate that mAb3H11 should be a useful reagent for the study of plant actins. © 1994 Wiley‐Liss, Inc.
Myosin reorganization in activated RBL cells correlates temporally with stimulated secretion
Authors: Spudich Annamma
Published: February 2005

Rat basophilic leukemia cells secrete histamine and serotonin in response to cross‐linking of the IgE receptor by multivalent antigen [Metzger et al., 1986: Ann. Rev. Immunol. 4:419–470]. Receptor crosslinking also induces phosphorylation of the light and heavy chains of myosin II with kinetics similar to that of secretion [Ludowyke et al., 1989: J. Biol. Chem. 264:12492–12501]. Here we show that myosin II localization changes after activation with similar kinetics. Furthermore, these changes are coincident with changes in cell shape and increase in motile activity induced by activation. Within 2 min, activated cells begin to flatten, spread on their substratum, and extend lamellipodia which show active ruffling. Quantitation of the extent of cell spreading from video micrographs shows that 48% of the cells increase significantly in surface area by 5 min and 71% by 15 min. Myosin II is uniformly distributed in unactivated cells but is deficient in newly formed lamellipodia that start to appear at 2 min after activation. In contrast these lamellipodia show strong staining for actin. Further changes in myosin organization are detected by 15 min after activation when myosin reappears in the cell periphery, is concentrated in the perinuclear area, and is also organized in punctate linear arrays that extend from the nucleus to the cell periphery. The kinetics of the early cell shape changes and formation of the myosin‐deficient lamellipodia correlate well with, and may relate to, the increase in the level of myosin II phosphorylation reported by Ludowyke et al. [1989: J. Biol. Chem. 264:12492–12501]. Changes in the distribution of cell surface‐bound IgE also occur upon antigen activation, and they correlate with the myosin distribution in a manner that suggests that they may be driven by myosin II. © 1994 Wiley‐Liss, Inc.
Protein tyrosine phosphorylation during sea urchin fertilization: Microtubule dynamics require tyrosine kinase activity
Authors: Wright Shirley J. , Schatten Gerald
Published: February 2005

Protein tyrosine phosphorylation plays an important role in cell growth, mitosis, and tumorigenesis. It has also been implicated in meiotic maturation and fertilization. We have used anti‐phosphotyrosine immunofluorescence and immunoblotting to identify sperm and egg proteins which are phosphorylated on tyrosine residues prior to and during sea urchin fertilization. On immunoblots of sperm proteins, the monoclonal anti‐phosphotyrosine antibody detected three major proteins with molecular weights of 44, 82, and 100 kD, and six minor bands at 46, 48, 70, 76, 95, and 150 kD. These phosphotyrosyl proteins were localized to the sperm acrosomal and centriolar fossae. In contrast, staining was found globally in unfertilized eggs, and the antibody recognized two major egg phosphotyrosyl proteins of molecular weights 42 and 50 kD, and five minor bands at 40, 90, 116, 130, and 150 kD. While immunofluorescent staining remained throughout the fertilized egg cytoplasm, there were dynamic changes in the staining intensity of single bands. The 90 kD immunoreactive band increased in intensity, and the 40 and 42 kD bands disappeared by 15 min after fertilization. Loss of the 40 and 42 kD bands was due to dephosphorylation by okadaic acid‐sensitive phosphatase(s). The 50 kD immunoreactive protein was unchanged up to the 8‐cell stage and was still present in blastulae, indicating its importance throughout fertilization and early development. Alterations in the pattern of phosphotyrosine‐containing proteins during fertilization did not depend on nascent proteins and could not be completely mimicked by increasing intracellular calcium, pH, and protein kinase C activity alone. Since changes in the fertilization pattern of phosphotyrosyl proteins occurred during formation of the sperm aster and mitotic spindle, we analyzed the role of protein tyrosine kinase activity in these processes using the tyrosine kinase specific inhibitor, erbstatin. Both the sperm aster and mitotic spindle were disrupted, indicating an involvement of tyrosine phosphorylation in these processes during interphase and mitosis. We conclude that the changes in phosphotyrosyl proteins play an important role in fertilization and early development of sea urchin eggs. Control of microtubule assembly into the sperm aster and mitotic spindle of the first cell cycle are examples of such roles. © 1995 Wiley‐Liss, Inc.
Buckling of a single microtubule by optical trapping forces: Direct measurement of microtubule rigidity
Authors: Kurachi Masashi , Hoshi Masayuki , Tashiro Hideo
Published: February 2005

As major determinants of cell shape and polarity, microtubules are required to have suitable rigidity. However, our knowledge of the mechanical properties of microtubules is far from satisfactory. We report here a new method of measuring the flexural rigidity of a single microtubule by direct buckling using the optical trapping technique. Microtubule buckling was induced by applying a small longitudinal compressing force through an optically trapped microsphere that was firmly attached to the microtubule. Three ways of estimating the flexural rigidity of a continuous slender rod, one from the observed critical load of buckling and two from deflected lengths and angles of bending, yielded values which agreed well when applied to the analysis of buckling microtubules. Unexpectedly, we found that the rigidity was not constant as expected but was dependent on microtubule length. This length dependency explains the discrepancies among reported values of microtubule flexural rigidity measured by different methods. Comparing microtubules of identical lengths, microtubules assembled with brain‐derived associated proteins (4 × 10−23 Nm2 at around 10 m̈m in length) were four times more rigid than those assembled from purified tubulin and stabilized with taxol (1 × 10−23 Nm2). © 1995 Wiley‐Liss, Inc.
Protein substrates for CGMP‐dependent protein phosphorylation in cilia of wild type and atalanta mutants of Paramecium
Authors: Ann Kyoung‐Sook , Nelson David L.
Published: February 2005

In the ciliated protozoan Paramecium, swimming direction is regulated by voltage‐gated Ca2+ channels in the ciliary membrane. In response to depolarizing stimuli, intraciliary Ca2+ rises, triggering reversal of the ciliary power stroke and backward swimming. One class of Ca2+ ‐unresponsive behavioral mutants of Paramecium, atalanta mutants, cannot swim backward even though they have functional Ca2+ channels in their ciliary membrane. Several atalanta mutants were characterized with regard to several Ca2+ ‐dependent activities, but no significant difference between wild type and the mutants was detected. However, one allelic group, atalanta A (initially characterized by Hinrichsen and Kung [1984: Genet. Res. Camb. 43:11–20]), showed a helical swimming path of opposite handedness from that of wild‐type cells when detergent‐permeabilized cells (“models”) were reactivated with MgATP. When cGMP‐dependent protein kinase purified from wild‐type cells was added to atalanta A models, the handedness of the swimming path was reversed. Cyclic GMP stimulated in vitro phosphorylation of several proteins in isolated cilia, and the pattern of phosphoproteins was very similar for wild type and atalanta mutants, with one exception: a protein of 59 kDa was phosphorylated much less in the mutant ata A. When ciliary proteins were separated by gel electrophoresis and then phosphorylated “on blot” by purified cGMP‐dependent protein kinase, phosphoprotein patterns were similar in wild type and ata mutants except that a 48 kDa protein (p48) from ata A3 was more heavily phosphorylated. This difference in p48 phosphorylation was also observed with cGMP‐dependent protein kinase purified from ata A3 mutant cells. Ciliary p48 may be part of the mechanism that regulates the orientation of the ciliary power stroke. © 1995 Wiley‐Liss, Inc.
Differentiation dependent expression of tensin and cortactin in chicken osteoclasts
Authors: Hiura Kenji , Lim Soo‐Siang , Little Sheila P. , Lin Shin , Sato Masahiko
Published: February 2005

The expression and localization of tensin and cortactin were examined in osteoclast precursors in comparison with isolated osteoclasts on various substrates. Initially, the ability of hen monocytes to differentiate into osteoclasts was evaluated on plastic or glass, and compared to differentiation on bone. Specifically, monocytes were isolated from the medullary bones of egg‐laying hens maintained on a Ca‐deficient diet. Differentiation was monitored morphologically and by quantitation of the ability to form Howship's lacunae in bone slices or resorb radiolabeled bone particles of 20–53 m̈m diameter. These cells differentiated into tartrate resistant acid phosphatase (TRAP)‐positive, bone resorbing, multinucleated syncytia in the presence of cytosine‐1‐β‐D‐arabinofuranoside in a time dependent manner (day 1–6). Differentiation into osteoclast‐like cells was similar whether cultured on plastic, on glass, or on bone. When compared to GAP‐DH control levels, tensin and cortctin mRNA levels increased by 7‐ and 10‐fold, respectively, by day 6. Tensin and cortactin protein levels also increased by 6‐ and 15‐fold, respectively, by day 6. Immunofluorescence of differentiating precursors showed that tensin localized between regions of cell to cell contact and colocalized with vinculin in podosomes of osteoclast‐like cells and of real osteoclasts. Cortactin immunofluorescence was not detectable in monocytes but localized inside tensin/vinculin podosome structures after fusion into osteoclast‐like cells and in freshly isolated osteoclasts. Both tensin and cortactin were associated with attachment complexes used by osteoclast‐like cells and osteoclasts to resorb bone. Specifically, punctate cortactin staining was observed inside tensin staining which formed a double ring structure at the membrane/bone interface of resorbing osteoclasts. These data showed that tensin and cortactin can be used as osteoclast differentiation markers, that participate in attachment complexes used to resorb bone, and that tensin may participate in the fusion process of osteoclast precursors. © 1995 Wiley‐Liss, Inc.
Polylysine cross‐links axoplasmic neurofilaments into tight bundles
Authors: Brown Anthony , Lasek Raymond J.
Published: February 2005

We have used axoplasm from the squid giant axon to investigate the effects of anionic and cationic polypeptides on the mobility and organization of axonal neurofilaments (NFs). Intact cylinders of axoplasm were extruded from squid giant axons into an excess volume of artificial axoplasm solution. In a previous study on the mobility of NFs in extruded axoplasm, we showed that these polymers disperse freely and diffusively into the surrounding solution, thereby expanding the axoplasmic cross‐sectional area [Brown and Lasek, 1993: Cell Motil. Cytoskeleton 26:313–324]. In the present study, we found that 83nm‐long (“long‐chain”) polylysine, a synthetic multivalent cationic protein, inhibited the radial expansion of isolated axoplasm and condensed the axoplasm, thereby reducing the cross‐sectional area. Equivalent concentrations of a 7nm‐long (“short‐chain”) polylysine did not inhibit the expansion of axoplasm and did not cause the axoplasm to condense. Inhibition of the expansion of axoplasm by long‐chain polylysine was dependent on the polylysine concentration; condensation of axoplasm was observed at concentrations of 0.01 mg/ml (0.27 μM) or greater. Electron microscopy of the condensed axoplasm showed that the NFs were aligned side‐by‐side and in parallel in closely‐packed bundles. Equivalent concentrations of 91nm‐long (“long‐chain”) polyglutamate, a synthetic multivalent anionic protein, partially inhibited the expansion of axoplasm but did not cause the NFs to bundle and did not cause the axoplasm to condense. These studies indicate that cationic proteins bind tightly to the highly charged anionic surfaces of NFs and can link them together into compact bundles in a charge‐dependent and length‐dependent manner. The tightly packed organization of these cross‐linked NFs differs from the normal loose organization of NFs in healthy axons. However, tightly bundled NFs are sometimes found in certain neuropathologies, such as giant axonal neuropathy.
Outer arm dynein from newt lung respiratory cilia: Purification and polypeptide composition
Authors: Rupp Gerald , Hard Robert
Published: February 2005

Dyneins are multimeric ATPases that comprise the inner and outer arms of cilia and flagella. It previously has been shown that salt extraction of newt lung axonemes selectively removes >95% of the outer arm dynein (OAD), and that the beat frequency of OAD‐depleted axonemes cannot be activated as compared to controls [Hard et al., 1992: Cell Motil. Cytoskeleton 21:199–209]. Therefore, expression of the activated state appears to require the presence of outer dynein arms. The presen study was undertaken to ascertain basic information on the structure and molecular composition of newt OAD. Populations of demembranated axonemes were extracted with 0.375 M salt. Each lung released ∼ 1.4 × 107 axonemes during isolation, yielding ∼ 120 ng of salt extractable OAD. Electron microscopy of negatively stained samples revealed that newt OAD consisted of two globular heads joined together by a Y‐shaped stem, similar to sea urchin and trout sperm OAD. Each head appeared to be roughly spherical in shape, measuring ∼ 17 nm in diameter. Electrophoretic analysis of whole axonemes revealed more than six dynein heavy chains when resolved in silver stained 0–8 M urea, 3–5% acrylamide gradients. Extracted OAD, either crude in high salt or purified by alloaffinity, was composed of two heavy chains. UV‐induced (366 nm) photolytic cleavage at the V1 site, performed in the presence of Mg2+, vanadate, and ATP, produced four new polypeptides (Mr 234, 232, 197, and 189 kD). Photolysis was supported by Mg2+ and Ca2+, but did not occur in the presence of Mn2+. The apparent Mr of the dynein heavy chains was determined to lie between 430–420 kD. Eight discrete polypeptides (putative intermediate chains, IC1‐IC8, Mr 175–56 kD) copurified with the α‐ and β‐heavy chains by microtubule‐alloaffinity.

Based on its extraction characteristics, polypeptide composition in purified and crude samples, and structure, we conclude that this two‐headed particle represents the entire newt respiratory outer arm dynein.
Focal adhesion formation is associated with secretion of allergic mediators
Authors: Kawasugi Kazuo , French Peter W. , Penny Ronald , Ludowyke Russell I.
Published: February 2005

Adherence of cells to the extracellular matrix via focal adhesions is known to modulate many cellular functions. However, the role of focal adhesions in the regulation of secretion is unclear. To examine this we have used the RBL‐2H3 rat mast cell line, in which we and others have observed cytoskeletal rearrangements and increased cell spreading during secretion. All activators of secretion examined, whether acting specifically through or bypassing the IgE‐receptor, induced the assembly of focal adhesions, as defined by the localization of vinculin and talin. The extent of focal adhesion formation correlated with the extent of secretion and the time course of secretion also correlated with that of the assembly of focal adhesions. To examine the mechanism by which focal adhesion formation occurred, the protein kinase C inhibitor bisindolylmaleimide was used. Bisin‐dolylmaleimide caused complete inhibition of both secretion and focal adhesion formation induced by antigen or the calcium ionophore A23187. Although PMA did not induce secretion, it induced focal adhesion assembly which was inhibited by bisindolylmaleimide. The inhibitor had no effect on secretion or focal adhesion formation induced by the ATP analogue, ATPγS in permeabilized cells, indicating ATPγS acts after the activation of protein kinase C in the secretory pathway. These data provide novel evidence that the formation of focal adhesions may have a role in the process of secretion from mast cells.
In ascaris sperm pseudopods, msp fibers move proximally at a constant rate regardless of the forward rate of cellular translocation
Authors: Royal Dewey , Royal Maryanne , Soll David R. , Italiano Joseph , Roberts Tom
Published: February 2005

Computer‐assisted methods have been employed to obtain a high resolution description of pseudopod expansion, cellular translocation, and the subcellular dynamics of MSP fiber complexes in the motile sperm of the nematode Ascaris suum. Although Ascaris sperm translocating in a straight line or along a curved path do not retract their pseudopod or significantly alter pseudopod shape, they move in a cyclic fashion, with an average period between velocity peaks of 0.35 × 0.05 min, which is independent of the forward velocity of sperm translocation. Expansion is confined to a central zone at the distal edge of the pseudopod for sperm translocating in a straight line and to a left‐handed or right‐handed lateral zone in the direction of turning, for sperm translocating along a curved path. For cells translocating in a straight line, the branch points and kinks of MSP fiber complexes move in a retrograde direction in relation to the substratum at an average velocity of 11 μm per min which is independent of the forward velocity of sperm translocation. The distal (anterior) end of a fiber complex, however, moves distally at the speed of sperm translocation when it emanates from the expansion zone, but when it is displaced to a nonexpanding surface of the pseudopod, it stops moving distally. When a cell is anchored to the substratum and is, therefore, nonmotile, the velocity of fiber complexes moving in a retrograde direction doubles. The unique aspects of pseudopod and MSP fiber complex dynamics in Ascaris are compared to the dynamics of pseudopod formation and actin filament dynamics in traditional actin‐based amoeboid cells, and the treadmill model for MSP polymerization is reassessed in light of the discovery that fiber complex branch points move proximally (posteriorly) at a fixed rate.
Increasing intracellular concentrations of thymosin β4 in PtK2 cells: Effects on stress fibers, cytokinesis, and cell spreading
Authors: Sanger Jean M. , Golla Rajasree , Safer Daniel , Choi John K. , Yu Keh‐Ru , Sanger Joseph W. , Nachmias Vivianne T.
Published: February 2005

Thymosin β4 (Tβ4) binds to G‐actin in vitro and inhibits actin polymerization. We studied the effects of incresing Tβ4 concentration within living PtK2 cells, comparing its effects on the disassembly of stress fibers and membrane‐associated actin with its ability to inhibit cytokinesis and cell spreading after mitosis. We chose PtK2 cells for the study because these cells have many striking actin bundles in both stress fibers and cleavage furrows. They also have prominent concentrations of membrane‐associated actin and remain flattened during mitosis. We have found that PtK2 cells contain an endogenous homologue of Tβ4 at a concentration (approximately 28 μM) sufficient to complex a third or more of the cell's unpolymerized actin. Intracellular Tβ4 concentrations were increased by three different methods: (1) microinjection of an RSV vector containing a cDNA for Tβ4; (2) transfection with the same vector; and (3) microinjection of purified Tβ4 protein. The plasmid coding for Tβ4 was microinjected into PtK2 cells together with fluorescently labeled alpha‐actinin as a reporter molecule. Immediately after microinjection fluorescently labeled alpha‐actinin was detected in a periodic pattern along the stress fibers just as in control cells injected solely with the reporter. However, after 13 h, cells microinjected with reporter and plasmid showed marked disassembly of the fiber bundles. PtK2 cells transfected with this RSV vector for 2–3 days showed disassembly of stress fibers as detected by rhodamine‐phalloidin staining; in these cells the membrane actin was also greatly diminished or absent and the border of the cells was markedly retracted. Microinjection of pure Tβ4 protein into interphase PtK2 cells induced disassembly of the stress fibers within 10 min, while membrane actin appeared only somewhat reduced. If the PtK2 cells were mitotic, Similar microinjection of pure thymosin β4 protein at times from early prophase to metaphase resulted in an unusual pattern of delayed cytokinesis. Furrowing occurred but at a much slower rate than in controls and the amount of actin in the cleavage furrow was greatly reduced. The cells constricted to apparent completion, but after about 30 min the furrow re‐gressed, forming a binucleate cell, much as after treatment with cytochalasin B or D. Postcytokinesis spreading of these Tβ4‐injected cells was often inhibited. These experiments suggest that an insufficient number of actin filaments prolongs the contractile phase of cytokinesis and abolishes the final sealing process. © 1995 Wiley‐Liss, Inc.
Characterization of adhesion plates induced by the interaction of Entamoeba histolytica trophozoites with fibronectin
Authors: Váazquez Joséa , Franco Elizabeth , Reyes Guadalupe , Meza Isaura
Published: February 2005

Entamoeba histolytica trophozoites are pleiomorphic and highly motile cells. Although scarce fibrous material can be identified in the cytoplasm as elements of an organized cytoskeleton, clearly defined actin‐containing structures are formed at the sites of cell‐matrix contact upon the interaction of trophozoites with fibronectin (FN) and other extracellular matrix substrates. These structures are reminiscent of the adhesion plaques or focal contacts found in higher eukaryotic cells, where actin filament bundles insert into specialized regions of the plasma membrane and function as signal transduction organelles. Thus, the formation of adhesion plates in this parasitic ameba could be related to specific signaling responses involved in its invasive behavior. Here, we report the isolation of amebic adhesion plates and the results of their structural and molecular analyses. Filaments, with the characteristic diameter of F‐actin, radiating from an electrondense matrix, are the main feature. Actin is one of the main protein components of the plate; other proteins identified are a FN‐binding protein—previously reported as a “putative” FN receptor—the actin‐binding proteins myosin II, myosin I, α‐actinin, vinculin, and tropomyosin. The presence in the isolated plates of several proteases and protein kinases, in particular pp125FAK, is also demonstrated. Our results suggest that adhesion plates in amebas are dynamic membrane‐cytoskeletal complexes participating not only in the attachment to FN substrates but also providing the structural basis for their involvement in parasite locomotion and invasiveness. © 1995 Wiley‐Liss, Inc.
Cytochalasin J affects chromosome congression and spindle microtubule organization in PtK1 cells
Authors: Snyder Judith A. , Cohen Laura
Published: February 2005

PtK1 cells were treated with 10 μg/ml cytochalasin J (CJ) for 15 min at various stages of mitosis. When applied at nuclear envelope breakdown (NEB) chromosome congression was blocked or substantially slowed, and chromosomes failed to show organization patterns typical of prometaphase. Spindle microtubule (MT) numbers appeared unaffected as judged by the pattern of birefringent retardation. However, ultrastructural analysis showed MTs to be reorganized within the spindle domain with some exhibiting fragmentation and others failing to interact with poorly defined kinetochore laminae. The spindle domain took on a curved, almost banana‐like shape, as related to the position of the centrosomes and lack of orientation of chromosomes. Serial section analysis of kinetochore regions showed reduced contour length and maturation of the kinetochore plate with few MTs associated with this structure. Cells similarly treated with 10 μg/ml CJ at NEB for 15 min and then released into conditioned medium for 15 min showed that most chromosomes resumed congression to the metaphase plate. Ultrastructural analysis revelaed a more normal organization of spindle MTs, but kinetochore structure remained affected. CJ treatment of cells in prometaphase slightly affected chromosome congression with most chromosomes aligning at the metaphase plate after 10–15 min of treatment. Ultrastructural analysis showed that astral MTs were disrupted and spindle MTs were fragmented; few MTs coursed from kinetochore to pole. Kinetochore structure was also affected with only small numbers of short MTs seen associated with kinetochores. Application of CJ at anaphase onset had little effect on anaphase A and B, but cytokinesis failed to occur. Anti‐tubulin staining of a monolayer of cells treated with 10 μg/ml CJ for 15 min showed that over 60% of mitotic figures exhibited changes in MT organization. Cells showing the greatest effect of treatment had several foci of bundles of MTs, as if the spindle were multipolar. Chromosomes were arranged near the periphery of the spindle which could be a result of abnormalities of kinetochore structure. Improper association of spindle MTs with kinetochores and, thus, changes in kinetochore position could account for these changes in spindle architecture. © 1995 Wiley‐Liss, Inc.
Equilibrium and growth shapes of crystals: how do they differ and why should we care?
Authors: Sekerka Robert F.
Published: February 2005

Since the death of Prof. Dr. Jan Czochralski nearly 50 years ago, crystals grown by the Czochralski method have increased remarkably in size and perfection, resulting today in the industrial production of silicon crystals about 30 cm in diameter and two meters in length. The Czochralski method is of great technological and economic importance for semiconductors and optical crystals. Over this same time period, there have been equally dramatic improvements in our theoretical understanding of crystal growth morphology. Today we can compute complex crystal growth shapes from robust models that reproduce most of the features and phenomena observed experimentally. We should care about this because it is likely to result in the development of powerful and economical design tools to enable future progress. Crystal growth morphology results from an interplay of crystallographic anisotropy and growth kinetics by means of interfacial processes and long‐range transport. The equilibrium shape of a crystal results from minimizing its anisotropic surface free energy under the constraint of constant volume; it is given by the classical Wulff construction but can also be represented by an analytical formula based on the ξ‐vector formalism of Hoffman and Cahn. We now have analytic criteria for missing orientations (sharp corners or edges) on the equilibrium shape, both in two (classical) and three (new) dimensions. Crystals that grow under the control of interfacial kinetic processes tend asymptotically toward a “kinetic Wulff shape”, the analogue of the Wulff shape, except it is based on the anisotropic interfacial kinetic coefficient. If it were not for long range transport, crystals would presumably nucleate with their equilibrium shape and then evolve toward their “kinetic Wulff shape”. Allowing for long range transport leads to morphological instabilities on the scale of the geometric mean of a transport length (typically a diffusivity divided by the growth speed) and a capillary length (of the order of atomic dimensions). Resulting crystal growth shapes can be cellular or dendritic, but can also exhibit corners and facets related to the underlying crystallographic anisotropy. Within the last decade, powerful phase field models, based on a diffuse interface, have been used to treat simultaneously all of the above phenomena. Computed morphologies can exhibit cells, dendrites and facets, and the geometry of isotherms and isoconcentrates can also be determined. Results of such computations are illustrated in both two and three dimensions. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recent developments in modelling of liquid phase electroepitaxy under applied magnetic field
Authors: Dost S. , Sheibani H. , Liu Y. C. , Lent B.
Published: February 2005

Growth of single crystals under magnetic field is of interest for suppressing the adverse effect of natural convection and for better mixing in the liquid solution, which are the favorable conditions for prolonged growth and high quality crystals. In this short review article, recent developments in the modelling of electroepitaxy under magnetic field are presented. An application is given for the liquid phase electroepitaxial growth of GaAs bulk single crystals under a static magnetic field. Experimental results, that have shown that the growth rate under an applied static magnetic field is proportional to the applied magnetic field, and increases with the field intensity level, are predicted from the present model. The model also predicts growth interface shapes accurately. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Behavior of oxygen bubbles during crystal growth of Ca12Al14O33 by floating method in magnetic field
Authors: Park J. K. , Shimomura T. , Yamanaka M. , Watauchi S. , Kishio K. , Tanaka I.
Published: February 2005

Magnetic field generator using a helium‐free superconducting magnet was installed with an infrared light heating floating zone (FZ) apparatus. Single crystals of Ca12Al14O33, in which oxygen bubbles easily remain when it is grown by a conventional FZ, were grown in various magnetic conditions in order to investigate the behavior of oxygen bubbles in molten zone, and to research the magnetic effects on FZ growth. When the crystals were grown at the lower position than center of the magnet bore, where magnetic force to paramagnetic oxygen gas is upward, oxygen bubbles formed in the molten zone were inclined to go toward stronger field and the grown crystals were half transparent and half opaque. The distribution of remaining oxygen bubbles in crystals was rather lopsided than centered. These effects might be explained by the magnetic force effect and the magnetic convection effect driven by inhomogeneous heating of the melt.
3D global analysis of CZ‐Si growth in a transverse magnetic field with rotating crucible and crystal
Authors: Liu Lijun , Kakimoto Koichi
Published: February 2005

Three‐dimensional global simulations were carried out for a small Czochralski furnace for silicon crystal growth with a recently developed global model. The furnace is placed in a transverse magnetic field with rotating crucible and crystal. The convective, conductive and radiative heat transfers in the entire furnace were solved in a three‐dimensionally conjugated way. Three‐dimensional distributions of temperature and velocity were analyzed. The melt‐crystal interface was found to have nearly rotational symmetry, and the azimuthal non‐uniformity of temperature is much weaker on the crystal and crucible sidewalls in the case of high rotation rates of crucible and crystal than in the case of non‐rotating crucible and crystal. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In situ interferometric investigation of hillock morphology of the {100} and {101} faces of KDP growing in TMS gels
Authors: Krasiński M. J.
Published: February 2005

The results of an in situ interferometric study of the surface morphology of {100} and {101} faces of potassium dihydrogen phosphate (KDP) crystals growing in the tetramethoxysilane gel are described and discussed. It was observed that: (a) in the case of crystal growth in gel both slopes of hillocks and surface kinetic coefficient are smaller than in solution growth, (b) for low supersaturations face growth rate linearly depends on bulk supersaturation and the structure of growth centers depends on the supersaturation and growth rate, and (c) for high supersaturations polyhedral instability appears. Supersaturation threshold for transition to polyhedral instability was estimated and formation of gel inclusions is discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adsorption of 3d‐elements onto zinc oxalate dihydrate in aqueous oxalate solutions
Authors: Pencheva J. , Donkova B. , Djarova M. , Maksimova S.
Published: February 2005

A study of the sorption of 3d‐transition elements onto ZnC2O4.2H2O has been carried out.To reveal the mechanism of the process, the experiments were performed in two media of different oxalate ion concentrations – 1.10‐2 and 4.10‐4 mol/l, by the separate and by the joint presence of the microcomponents in the system. In the latter case, copper was also added, the sorption of which has been previously well studied. Different mechanisms of sorption in the different media were found, the determining role of the neutral oxalate complexes having been manifested. In the case of manganese and cobalt, in the medium with oxalate ions deficit, sorption by neutral complexes in the adsorption layer A is supplemented by ion‐exchange sorption in the first surface layer S. The sorption of nickel under oxalate ion excess is proved to be an irreversible process, and the concept of its sorption by a mixed complex with the participation of the macrocomponent, Zn[Ni(C2O4)2], is advanced. The experimental data show the occurrence of segregation of Mn and Ni by their sorption onto the growth steps, and the absence of segregation of Co by its sorption. An interesting result is the extension of the validity of the Paneth‐Fajans rule in the case of so‐called complex oxalates, growing by neutral oxalate complexes, such as the oxalates of the macro‐ and microcompoments, studied in the present work. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lattice parameter measurements of boron doped Si single crystals
Authors: Kucytowski J. , Wokulska K.
Published: February 2005

The influence of boron dopants and oxygen impurity on lattice parameters of Si single crystals is studied. Concentrations of boron and oxygen were determined by the Bond method. A linear contraction of the crystal lattice was observed due to high boron doping of Si single crystals. Lattice parameters of Si single crystals increased below the lower limit boron concentration NB = 2.1 × 1016 cm‐3. This proves the presence oxygen at low boron concentrations. In highly boron‐doped Si single crystals no oxygen influence on lattice parameter change was observed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Raman scattering study of (SrAl0.5Ta0.5O3)1‐x‐y: (LaAlO3)x : (CaAl0.5Ta0.5O3)y solid solution crystals
Authors: Runka T. , Aleksiyko R. , Berkowski M. , Drozdowski M.
Published: February 2005

The Raman studies of three‐component (SrAl0.5Ta0.5O3)1‐x‐y:(LaAlO3)x:(CaAl0.5Ta0.5O3)y solid solution crystals versus composition are reported. The assignment of vibrational modes in Raman spectra of investigated crystals is proposed. Structural changes of (SrAl0.5Ta0.5O3)1‐x‐y:(LaAlO3)x:(CaAl0.5Ta0.5O3)y crystal from cubic to tetragonal and from tetragonal to orthorhombic phase were observed by Raman spectroscopy, while the change of crystal composition. The most significant changes of Raman spectra manifesting about changes of crystal structure were observed predominantly in the range of lattice modes. Splitting of cubic F2g modes resulting from lowering of the symmetry was observed. Changes of the intensity of Raman bands indicate the increase of disorder of crystal structure with increase of LaAlO3 content. This disorder is connected with the arrangement of B ion sublattice. It was revealed that Raman results supply essential information on complex structure and changes of degree of order of three‐component solid solution crystals. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synchrotron X‐ray investigation of La0.3Sr0.7Al0.65Ta0.35O3 crystals
Authors: Wierzchowski W. , Wieteska K. , Graeff W. , Sakowska H. , Łukasiewicz T. , Pawłowska M.
Published: February 2005

The La0.3Sr0.7Al0.65Ta0.35O3 (LSAT) substrates were studied with a number of X‐ray diffraction methods exploring both synchrotron white and monochromatic beam. The observation of selective etching patterns was performed in neighbouring samples. White beam back‐reflection projection topographs revealed only the segregation fringes around the central core and a delicate grain‐like structure. The most important for verification of dislocation presence were the transmission projection and section topographs. These topographs also did not reveal any images of extended dislocation but only the growth bands and tiny grain‐like structure. The section topographs provided some details of paroboloidal growth surface inside the crystal. It may be concluded that the investigated crystal probably contains small coherent inclusions responsible for the etch pits and the mentioned grain‐like structure. The synchrotron rocking curves revealed a number of maxima, which might be attributed to the regions with different lattice parameter, connected with segregation fringes. The sequence of maxima was different for different regions of the sample. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spatial conditional discrimination learning in developing rats
Authors: Brown Kevin L. , Pagani Jerome H. , Stanton Mark E.
Published: February 2005

The present study established an effective procedure for studying spatial conditional discrimination learning in juvenile rats using a T‐maze. Wire mesh located on the floor of the maze as well as a second, identical T‐maze apparatus served as conditional cues which signaled whether a left or a right response would be rewarded. In Experiment 1, conditional discrimination was evident on Postnatal Day (PND) 30 when mesh + maze or maze‐alone were the conditional cues, but not when mesh‐alone was the cue. Experiment 2 confirmed that mesh‐alone was sufficiently salient to support learning of a simple (nonconditional) discrimination. Its failure to serve as a conditional cue in Experiment 1 does not reflect its general ineffectiveness as a stimulus. Experiment 3 confirmed that the learning shown in Experiment 1 was indeed conditional in nature by comparing performance on conditional versus nonconditional versions of the task. Experiment 4 showed that PND19 and PND23 pups also were capable of performing the task when maze + mesh was the cue; however, the findings indicate that PND19 subjects do not use a conditional strategy to learn this task. The findings suggest postnatal ontogeny of conditional discrimination learning and underscore the importance of conditional cue salience, and of identifying task strategies, in developmental studies of conditional discrimination learning. © 2005 Wiley Periodicals, Inc. Dev Psychobiol 46: 97–110, 2005.
The cost management edge for financial services
Authors: Garg Ashish
Published: February 2005

Holding down costs has long been a corporate objective, yet companies continue to struggle to find ways to generate better‐quality information—either with the help of, or sometimes in spite of, the cost management tools already in place. But as a best‐practices survey shows, cost management—when executed effectively—can be a key contributor to strategic goals. © 2005 Wiley Periodicals, Inc.
Evaluating the “keep‐or‐drop” decision
Authors: Sopariwala Parvez R.
Published: February 2005

Determining the relevant costs for short‐term decision‐making is an important part of every cost/managerial accounting textbook. One of the decisions is the “keep or drop” decision—i.e., should a company keep or drop an existing product line or department in the short term? This article points out that keep‐or‐drop decisions are usually long‐term decisions. As a result, it suggests that only a segmented activity‐based costing (ABC) income statement should be used for determining if a product line or department should be kept or dropped. © 2005 Wiley Periodicals, Inc.
Photographic print defects attributable to point source enlargers
Authors: Mollenhauer Hilton H. , Droleskey Robert E.
Published: February 2005

Point source enlargers may cause unusual types of printing defects. One type is a large spot in the center of the enlarged picture field that sometimes appears when the edges of negatives are not adequately masked during printing. Another type is a blurry image caused by a defect in the polycontrast filter. The defect appears in the filter as a small spot of about 1/8‐inch diameter, formed, presumably, by heat from the focused beam of the point source light. A spot defect of this type is difficult to see by a cursory visual examination of the filter and may develop unnoticed and persist for months before it is finally recognized.
Acetylcholine receptor at neuromuscular junctions by EM autoradiography using mask analysis and linear sources
Authors: Salpeter Miriam M. , Smith Chari D. , Matthews‐Bellinger Julia A.
Published: February 2005

Several methods of analyzing EM autoradiograms are now available. Two such procedures, the grain density distribution (or histogram) method and the mask method use the resolution of the EM autoradiographic technique to generate grain distributions expected from postulated sources, and compare these with the observed grains in the autoradiograms. These two methods are here compared in the analysis of label on linear sources: the distribution of labeled acetylcholine receptor (AChR) down the postjunctional folds of lizard and frog neuromuscular junctions. The receptors were labeled with I‐25‐α‐bungarotoxin and the autoradiograms coated with the high resolution Kodak emulsion 129–01. We found that both methods gave similar results in confirming that the bulk of the AChR is concentrated on the thickened region of the membrane at the top ∼2000 A of the junctional folds, and that there may be a gradient of receptor concentration down the folds. The grain density distribution method is simpler, but does not lend itself easily to quantifying the extent of deviation from simple models. Although computer graphics is not necessary for either method, its use allows the expected grains from linear sources to be generated quickly, making the mask analysis a feasible routine method for assigning the extent of label in different membrane regions.
A quantitative evaluation of the glomerular capillary endothelium in rat and human kidneys: Utilization of vascular perfusion, freeze‐cracking of tissue, and scanning electron microscopy
Authors: Dobyan Dennis C. , Eknoyan Garabed , Magill Linda S. , Sarrafian Myrna , Bulger Ruth Ellen
Published: February 2005

Modern morphological investigation requires the use of a variety of technological approaches and the employment of rigorous morphometric analysis for an adequate evaluation of the structural and ultrastructural features of a tissue or organ. The introduction of the technique of freeze‐cracking of tissue to expose new surfaces has made it possible to quantitate the normal surface characteristics of the glomerular capillaries of the mammalian kidney. This report describes the techniques used for the preparation and quantitative assessment of normal glomerular endothelial morphology. The techniques of in vivo and in vitro vascular perfusion of kidneys as a method of fixation and the freeze‐cracking of tissue are outlined in detail. In addition, a morphometric analysis of the endothelial surface characteristics are described and values are reported for the control rat and human kidneys from transplant donors.