bluuebunny/crossref_metadata_2025 huggingface dataset:
Extensor tendons of the fingers: Arrangement and variations‐ii
Authors: El‐Badawi M. G. Y. , Butt M. M. , Al‐Zuhair A. G. H. , Fadel R. A.
Published: February 2005

One hundred eighty‐one dissected hands were examined to study the pattern of extensor tendons on the dorsum of the hand. Extensor digitorum often had multiple tendons for the middle and ring fingers. Its contribution to the little finger was usually by a bifurcating tendon common with that of the ring finger. The index finger always received a single tendon. Intertendinous connections between the various tendons of the extensor digitorum were variable but were most frequent between ring and middle fingers.

Extensor indicis had one tendon in most of the specimens and it was always on the ulnar side of the extensor digitorum tendon. This remained true even when there were multiple tendons.

Extensor digiti minimi had two tendons in most cases. It was always linked to extensor digitorum either by receiving one or part of its tendon or by an intertendinous connection.

Two accessory muscles were seen, one was extensor indicis brevis replacing the proper muscle. The other, the extensor medii brevis, was distributed to the middle finger. © 1995 WiIey‐Liss, Inc.
Total Synthesis of Mauritines A, B, C, and F: Cyclopeptide Alkaloids with a 14‐Membered Paracyclophane Unit
Authors: Cristau Pierre , Temal‐Laïb Taoues , Bois‐Choussy Michèle , Martin Marie‐Thérèse , Vors Jean‐Pierre , Zhu Jieping
Published: February 2005

A unified strategy for the synthesis of mauritines A (5), B (6), C (7), and F (10) has been developed based on a key intramolecular nucleophilic aromatic substitution reaction (SNAr) for the formation of the strained 14‐membered paracyclophane. It was demonstrated that the outcome of the cycloetherification is independent of the stereochemistry of the peptide backbone and that both (1R)‐16 and (1S)‐16 cyclized smoothly to provide the corresponding macrocycle. On the other hand, dehydration of the secondary benzylic alcohol, via the phenylselenide intermediate, is configuration dependent. (1R)‐25 underwent the two‐step syn‐elimination much more easily than (1S)‐22. A modified reductive deamination procedure via the diazonium intermediate was developed. A complete assignment of proton and carbon NMR spectroscopy signals for these natural products is reported for the first time.
Regioselective Intramolecular Pauson–Khand Reactions of C60: An Electrochemical Study and Theoretical Underpinning
Authors: Martín Nazario , Altable Margarita , Filippone Salvatore , Martín‐Domenech Ángel , Poater Albert , Solà Miquel
Published: February 2005

Suitably functionalized fulleropyrrolidines endowed with one or two propargyl groups at the C‐2 position of the pyrrolidine ring (1,6‐enynes) react efficiently and regioselectively with [Co2(CO)8] to afford the respective Pauson–Khand products with an unprecedented three (5 a–d, 7, and 24) or five (25) pentagonal rings, respectively, fused onto the fullerene sphere. Fulleropyrrolidines with 1,7‐, 1,9‐, 1,10‐, or 1,11‐enyne moieties do not undergo the PK reaction and, instead, the intermediate dicobalt complexes formed with the alkynyl group are isolated in quantitative yields. These differences in reactivity have been studied by DFT calculations with a generalized gradient approximation (GGA) functional and several important energy and structural differences were found for the intermediates formed by the interaction between the coordinatively unsaturated Co atom and the π system of C60 in 1,6‐ and 1,7‐enynes. The different lengths of the alkyne chains are responsible for the observed reactivities. Cyclic voltammetry reveals that the presence of the cyclopentenone's carbonyl group connected directly to the C60 core results in PK compounds with remarkable electron‐accepting ability.
The Silicon Hydride Clusters Si3Hn (n ≤ 8) and Their Anions: Structures, Thermochemistry, and Electron Affinities
Authors: Xu WenGuo , Yang JuCai , Xiao WenSheng
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Structural Phase Transition in Tb5(Si0.6Ge0.4)4 at Low Temperature.
Authors: Kupsch A. , Levin A. A. , Meyer D. C.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Magnetic Properties of TbNi4Al and DyNi4Al Compounds: Investigation via Neutron Diffraction and Magnetometry.
Authors: Tolinski T. , Schaefer W. , Kowalczyk A. , Andrzejewski B. , Hoser A. , Szlaferek A.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Solvothermal Synthesis and Structure of the [Ge2Se7]4‐ Anion in (enH2) [{Mn(en)2(enH)}2(μ‐en)] (Ge2Se7)2 and [Mn(dien)2]2Ge2Se7.
Authors: van Almsick Tobias , Loose Anja , Sheldrick William S.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Vanadium‐Catalyzed Sulfenylation of Indoles and 2‐Naphthols with Thiols under Molecular Oxygen.
Authors: Maeda Yasunari , Koyabu Motonori , Nishimura Takahiro , Uemura Sakae
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Hexafluoroacetone as a Protecting and Activating Reagent. Regioselective Esterification of Aspartic, Malic, and Thiomalic Acid.
Authors: Pumpor Ksenia , Windeisen Elisabeth , Spengler Jan , Albericio Fernando , Burger Klaus
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Efficient and Selective Formation of Mixed Acetals by Nafion‐H SAC‐13 Silica Nanocomposite Solid Acid Catalyst.
Authors: Ledneczki Istvan , Molnar Arpad
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Mizoroki—Heck Arylation of α,β‐Unsaturated Acids with a Hybrid Fluorous Ether, F‐626: Facile Filtrative Separation of Products and Efficient Recycling of a Reaction Medium Containing a Catalyst.
Authors: Fukuyama Takahide , Arai Masashi , Matsubara Hiroshi , Ryu Ilhyong
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Catalytic Sandmeyer Cyanation as a Synthetic Pathway to Aryl Nitriles.
Authors: Beletskaya Irina P. , Sigeev Alexander S. , Peregudov Alexander S. , Petrovskii Pavel V.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Isomerization of Hetaryl Analogues of α‐Benzoins in Basic Media.
Authors: Ivonin Sergey P. , Lapandin Andrey V.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
A Stereoselective Synthesis of Silylated Epoxycyclopentanols Bearing four Contiguous Stereogenic Centers.
Authors: Thorimbert Serge , Taillier Catherine , Bareyt Sebastian , Humiliere Delphine , Malacria Max
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Hypervalent Iodine(III) Mediated Synthesis of 2‐Substituted Benzoxazoles.
Authors: Prakash Om , Batra Anita , Sharma Vijay , Saini Rajesh K. , Verma Rajender S.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Microwave‐Assisted Synthesis of Highly Substituted Aminomethylated 2‐Pyridones.
Authors: Pemberton Nils , Aaberg Veronica , Almstedt Hanna , Westermark Andreas , Almqvist Fredrik
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
The Facile Route to Stereodefined Alkenyl‐Substituted Pyrimidines.
Authors: Tan Jiuqing , Chang Jianhua , Deng Minzhi
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Bismuth Subnitrate Catalyzed Efficient Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones: An Improved Protocol for the Biginelli Reaction.
Authors: Reddy Y. Thirupathi , Rajitha B. , Reddy P. Narsimha , Kumar B. Sunil , Rao V. P.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Synthesis and Reactions of (6‐Methyl‐2‐methylsulfanyl‐4‐oxo‐3,4‐dihydro‐3‐pyrimidinyl)acetyl Azide (II).
Authors: Jakubkene V. , Stura A. , Vainilavicius P.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Easy Access to 3‐ or 5‐Heteroarylamino‐1,2,4‐triazines by SNAr, SNH, and Palladium‐Catalyzed N‐Heteroarylations.
Authors: Garnier Ethel , Audoux Jerome , Pasquinet Eric , Suzenet Franck , Poullain Didier , Lebret Bruno , Guillaumet Gerald
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Periodic Mesoporous Phenylenesilicas with Ether or Sulfide Hinge Groups — A New Class of PMOs with Ligand Channels.
Authors: Hunks William J. , Ozin Geoffrey A.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
New Sesterterpenes from Madagascan Lendenfeldia sponges.
Authors: Chill Liat , Rudi Amira , Aknin Maurice , Loya Shoshana , Hizi Amnon , Kashman Yoel
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Lundurines A—D, Cytotoxic Indole Alkaloids Incorporating a Cyclopropyl Moiety from Kopsia tenuis and Revision of the Structures of Tenuisines A—C.
Authors: Kam Toh‐Seok , Lim Kuan‐Hon , Yoganathan K. , Hayashi Masahiko , Komiyama Kanki
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Increased Cytotoxicity of 2′,2′‐Difluoro‐2′‐deoxycytidine in Human Leukemic Cell‐Lines After a Preincubation with Cyclopentenyl Cytosine
Authors: Verschuur A. C. , Van Gennip A. H. , Leen R. , Van Kuilenburg A. B. P.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Investigation of the Substrate Recognition of Drosophila melanogaster Nucleoside Kinase by Site Directed Mutagenesis
Authors: Solaroli N. , Bjerke M. , Johansson M. , Karlsson A.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Potential Role of Mycophenolate Mofetil in the Management of Neuroblastoma Patients
Authors: Messina E. , Barile L. , Lupi F. , Giacomello A.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Asymmetric Synthesis of Pyrrolidinoindolines. Application for the Practical Total Synthesis of (‐)‐Phenserine.
Authors: Huang Audris , Kodanko Jeremy J. , Overman Larry E.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Chiral Ligands
Authors: Herrmann Wolfgang A. , Eckl Robert W. , Kuehn Fritz E.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Introduction of the Cyano Group by Addition to Alkenes
Authors: Podlech J.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
High‐Pressure Solubility Measurement of Solids in Near‐ and Supercritical Fluids
Authors: Tuma D. , Wagner B. , Schneider G. M.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
Computation of Hyperfine Coupling Tensors to Complement EPR Experiments
Authors: Ban Fuqiang , Gauld James W. , Boyd Russell J.
Published: February 2005

For Abstract see ChemInform Abstract in Full Text.
The formation and elongation of filopodia during transformation of sea urchin coelomocytes
Authors: Edds Kenneth T.
Published: February 2005

Sea urchin coelomocytes were examined during their morphological transformation from petaloid to filopodial forms by scanning electron microscopy and ciné film analysis. Petaloid coelomocytes have a variable morphology but, in general, consist of numerous thin sheets of cytoplasm, the petals, arranged in three dimensions around a central nuclear region. The transition to the filopodial form can occur in either substrate‐attached or suspended cells and begins with the formation of several microspikes at the edge of each petal. These become more apparent as the cytoplasm between each microspike/filopodium is retracted centripetally. Concomitantly, the diameter of the flattened cell is increased by as much as twofold as the filopodia actively lengthen at a uniform, average rate of 0.5 μm/minute. The transformation process requires ca 15 minutes and is complete when the cell diameter no longer increases. These filopodia are functionally distinct from the passively produced retraction fibers observed in cultured mammalian cells. The formation of filopodia is biphasic and includes both a cytoplasmic retraction phase and an active extension phase.
The incorporation of actin and fascin into the cytoskeleton of filopodial sea urchin coelomocytes
Authors: Otto J. J. , Bryan J.
Published: February 2005

Echinoderm coelomocytes transform from petaloid cells with large motile lamellipodia to filopodial forms. During this morphological transformation, actin filaments extensively reorganize from a random meshwork into tight bundles, which become the skeletons or cores of the filopodia. Antibody localization procedures show that fascin, a 58,000 dalton actin cross‐linking protein, becomes incorporated into the filament bundles as they form. Isolated filopodial cores have a pronounced transverse striping pattern, which has been previously identified with fascin crosslinks, and gel electrophoresis identifies a protein in the cores that co‐migrates with purified egg fascin. A few of the core fragments also have a distinctive “cap,” which we presume is the membrane insertion site for actin filaments.

We have developed a radioimmunoassay for fascin and have used it to study the redistribution of this protein during transformation. Data from the assay indicate that fascin constitutes about 5% of the total cell protein and that substantially more fascin, approximately 1.5–2 times more, is found in the Triton‐insoluble cytoskeletons of the filopodial cells than in the petaloid cells. Actin, measured by the DNAase I inhibition assay accounts for approximately 10% of the total cell protein. Approximately 65% of this actin is in a soluble non‐filamentous form in the petaloid cells. Our results show that actin polymerization must occur during the cell shape change, since we find approximately 25% more actin in the filopodial cytoskeleton than in the petaloid cytoskeleton. The results show a preferential incorporation of fascin into the cytoskeleton as the cells form filopodia.
Does the geometric design of centrioles imply their function?
Authors: Albrecht‐Buehler Guenter
Published: February 2005

The paper suggests several principles of construction of a microscopically small device for locating the directions of signal sources in microscopic dimensions. It appears that the simplest and smallest device that is compatible with the scrambling influence of thermal fluctuations as are demonstrated by Brownian motion is a pair of cylinders oriented at right angles to each other. Nine equally spaced blades run in a pitched fashion along the mantle of each cylinder. The blades have a concave cross‐section and bend around the circumference of the cylinder in a certain rotational pattern. Considering the striking similarity of this hypothetical device with centrioles, the paper puts forward the conjecture that centrioles locate the direction of hypothetical signals inside cells.
Calcium‐induced change in form of demembranated sea urchin sperm flagella immobilized by vanadate
Authors: Okuno M. , Brokaw C. J.
Published: February 2005

Increased Ca2+ concentration causes a reversible increase in asymmetry of the flagellar bending waves of “potentially symmetric” demembranated sea urchin spermatozoa. When these flagella are immobilized with 5 μM vanadate, increased Ca2+ concentration causes a reversible increase in the total bend angle between the tip and the base of the immobilized flagella. These effects of Ca2+, and the movement which can be activated by CaATP2−, can be inhibited by vanadate, but in both cases, high concentrations of vanadate, of the order of 100 μM, are required. These observations suggest that ATP, possibly in the form of CaATP2−, is required for the Ca2+‐induced change in shape of the flagella, but other observations suggest that the magnitudes of asymmetry and total bend angle are more closely related to Ca2+ concentration than to CaATP2− concentration.
Intercellular bridges in the embryo of the atlantic squid, loligo pealei. II: Formation of the bridge
Authors: Cartwright Joiner , Arnold John M.
Published: February 2005

Incomplete cytokinesis followed by the disappearance of the midbody and spindle remnant results in intercellular bridges between the cells of the blastoderm of the squid embryo. An electron microscope study of the morphology of the stages of development of the intercellular bridge is presented. Cytokinesis ceased as the furrow base reached a diameter slightly larger than the midbody. As furrowing stopped, a dense material accumulated to form a cylindrical sheath 50 nm thick, lining the inner surface of the furrow base. Proteolytic enzymes showed this material to have a significant protein component. As the midbody broke down, vesicles lined the inner surface of the bridge sheath. In this configuration, there was cyto‐plasmic continuity between the cells, and organelles appeared to pass through the bridge.

The intercellular bridge could become temporarily closed. Vesicles entered the channel and fused with the vesicles lining the inner surface of the sheath. The vesicles enlarged until the channel became occluded with a series of transverse cisternae, the edges of which were embedded in the material of the sheath. When the bridge reopened, the transverse cisterna appeared to dissociate from the sheath, move out of the channel, and break down. Occasionally bridges were seen in which the bridge wall appeared distorted into lobes. It is suggested that such bridges might be in the porcess of breaking down, resulting in the final separation of the cells.
A calcium‐ and pH‐regulated actin binding protein from D. discoideum
Authors: Fechheimer Marcus , Brier Jonathan , Rockwell Mark , Luna Elizabeth J. , Taylor D. Lansing
Published: February 2005

A protein from Dictyostelium discoideum with an apparent subunit molecular weight of 95,000 daltons (95K protein) was previously identified as an actin‐binding protein ‘Hellewell and Taylor, 1979’. In this paper, we present a method for purifying the protein, and characterize some important aspects of its structure and function. Purification of the 95K protein is achieved by fractionation with ammonium sulfate followed by chromatography on DEAE‐cellulose, gel filtration on 6% agarose, and final purification on hydroxyapatite. The 95K protein is a dimer, composed of apparently identical subunits. It is a rod‐shaped molecule, 38 nm in length, with a Stokes radius of 74 Å. In these structural properties, the 95K protein is similar to muscle and nonmuscle α‐actinins. The 95K protein and filamin are equally competent, when compared on a weight basis, to enhance the apparent viscosity of actin as determined by falling ball viscometry. The apparent viscosity of mixtures of the 95K protein and actin is dramatically reduced at pH greater than 7.0 or free ‘Ca2+’ greater than 10−7 M. We also examine the mechanism by which calcium regulates the interaction of the 95K protein and actin. A change in free ‘Ca2+’ induces no detectable change in the quaternary structure of the 95K protein. Our experiments indicate that the 95K protein does not dramatically alter the length distribution of actin filaments in the presence of micromolar free ‘Ca2+’. A large fraction of the 95K protein cosediments with actin in the presence of low free ‘Ca2+’ (ca. 3 × 10−8M), but not in the presence of high free ‘Ca2+’ (ca. 4 × 10−6M). We conclude that increased free ‘Ca2+’ inhibits gelation of actin by the 95K protein by reducing the affinity of the 95K protein for actin. We propose that 95K protein is an important component of the cytoskeletal/contractile system in D. discoideum amoebae.
Novel Forms of epithelial cell motility on collagen and on glass surfaces
Authors: Tchao R.
Published: February 2005

The motility of an epithelial cell line NBT‐II derived from a rat bladder tumor was examined on glass and on collagen. On glass the cells rotate in groups of 2–8 cells. Rotatory migration ceases as cells enter into mitosis; after mitosis, the daughter cells spread out and participate in the rotatory activity of the group. As the number of cells in a group increases the rate of rotatory migration slows, and groups with ten cells or more do not rotate consistently. On collagen NBT‐II cells migrate as single cells in a smooth gliding fashion, with the broad lamellipodia as the leading front. After mitosis, the two daughter cells separate at 180° of each other and migrate away independently. Before totally spreading out on the collagen surface, the pair of daughter cells shows a characteristic twist of about 60° from their original position at telophase. The difference in motility of NBT II cells on glass and on collagen is explained in terms of differences in cell‐to‐cell cohesion and cell‐to‐substrate adhesion.
The structural properties and contractile force of a clot
Authors: Jen Chauying J. , McIntire Larry V.
Published: February 2005

When citrated plasma is recalcified, it forms a viscoelastic gel–a clot. The relationship between platelet contractility and clot rigidity was studied by using a rheological technique which simultaneously measured both the dynamic rigidity modulus and the contractile force during gel formation with platelet rich plasma (PRP). Protein network formation in a clot was accompanied by a contractile force throughout the clotting process. PRP demonstrated a maximum elastic modulus of 6,000 dynes/cm2 and a maximum contractile force/area of 1,500 dynes/cm2. The values of these parameters for a platelet‐free clot (PFP) were 700 dynes/cm2 and less than 100 dynes/cm2 respectively. Sonicated control PRP and PRP from a Glanzmann thrombasthenia patient both clotted in a manner similar to PFP. Metabolic inhibitors, 2‐deoxy‐D‐glucose and KCN (5 mM each), retarded the clotting curves of PRP. Cytochalasin B and E suppressed both structural rigidity and force generation in a concentration‐dependent manner similar to their inhibitory effect on actin polymerization in platelets. Colchicine (2.5 mM) or vinblastine (0.11 mM) did not affect these clotting curves. Thrombi‐activated, fixed platelets did not generate any force, nor did they significantly increase clot rigidity. Streptokinase induced a concurrent decrease of both rigidity and force in PRP clots. The elastic modulus of a PFP clot could be increased to 2,500 dynes/cm2 by externally straining the network with an axial force/area of 1,500 dynes/cm2. Our results indicate that clot structure formation in PRP is strongly coupled to the contractile force generated by the platelet microfilament system and that this force modulates clot rigidity.
Cytoplasmic transport in keratocytes: Direct visualization of particle translocation along microtubules
Authors: Hayden John H. , Allen Robert D. , Goldman Robert D.
Published: February 2005

We report the first direct demonstration that the cytoplasmic transport of organelles and vesicles (collectively called particles) takes place along microtubules. Living keratocytes from the corneal stroma of the frog, Rana pipiens, were observed with Allen video‐enhanced constrast, differential interference constrast (AVEC‐DIC) microscopy [Allen et al, 1981]. In sufficiently thin regions of these cells a network of linear elements was visible. When particles were observed in motion, they always moved along these linear elements. The linear elements remained intact and in focus on the microscope when lysed in a cell lysis solution that stabilized microtubules. Preparations were then fixed in formaldehyde, washed with phosphate‐buffered saline (PBS), incubated with rabbit antitubulin, washed with PBS, stained with rhodamine‐conjugated goat antirabbit, and washed with PBS. The extracted cells continued to remain in place and in focus on the microscope throughout these procedures. The same cells were then observed using epifluorescence optics and a silicon‐intensified target (SIT) video camera. A network of fluorescent linear elements was seen to correspond in number, form, and position to the linear elements seen in the live AVEC‐DIC image. Taken together, the AVEC‐DIC and fluorescence microscopy observations prove that the linear elements along which particles move are microtubules (MTLEs). The observed particle speeds, pause times, and distances moved varied widely, even for the same particle on the same microtubule. Particles were also observed to switch from one microtubule to another as they were transported. The polarity of the microtubules did not seem to affect the particle direction, since particles were observed to move in both directions on the same MTLE. When not in motion these particles behaved as if anchored to the microtubules since they showed negligible Brownian motion. Finally, it was observed that an elongate particle could move onto two intersecting linear elements such that it was deformed into an inverted “Y” shape. This indicates that there may be more than a single site of attachment between the force generator and the particle.
Invited review: Bacterial flagellar sheaths: Structures in search of a function
Authors: Sjoblad Roy D. , Emala Charles W. , Doetsch Raymond N.
Published: February 2005

Although bacterial flagellar sheaths were observed over 30 years ago, they may still be characterized as structures in search of a function. In addition to true sheaths, bacterial flagella may possess other adornments that cause an increase in the organelle's cross‐sectional diameter. These “complex flagella” are sharply differentiated from sheathed flagella. Immunological and chemical distinctions have been found between flagellar sheaths, flagellar cores, and LPS layers inferred to be the sheath sensu stricto. Although complex flagella may serve as specific receptors for flagellotropic phages or in allowing for more efficient swimming in viscous environments, similar functions have not yet been attributed to true sheaths. It is postulated that flagellar sheaths may allow for specific interaction between a bacterium and a surface. In addition, there is a problem as to the relationship between a rapidly rotating flagellum and the sheath.
Bending patterns of chlamydomonas flagella I. Wild‐type bending patterns
Authors: Brokaw C. J. , Luck D. J. L.
Published: February 2005

Using a uniflagellate mutant of Chlamydomonas and flash photomicrography at 300 Hz, we have obtained detailed information on the forward and reverse beating modes of Chlamydomonas flagella and on the relationship between rotation of the uniflagellate cell and the bending cycle of the forward mode. Flagella ranging in length from 5 to 15.5 μm were photographed. There is a decrease in wavelength and an increase in curvature in the principal bends when the length of the flagellum is less than the normal length of 12–13 μm, but these changes are not sufficient to maintain similarity of the bending pattern. In the reverse mode, the flagellum propagates symmetrical, planar, undulatory waves with a shear amplitude which is the same as in the forward mode: there is a 19% increase in beat frequency and a similar decrease in wave length. The reorientation of the flagellar beat direction towards the axis of the cell in the reverse mode is caused both by the decrease in asymmetry of beat and by activation of sliding in the principal bends at an earlier time in the beat cycle, relative to the time of activation of sliding in reverse bends. There are additional rare modes of beating which may be related to intermediate stages in the transition between forward and reverse beating modes.
Cell motility and microtubules in cultured fibroblasts from patients with Kartagener syndrome
Authors: Walter Robert J. , Malech Harry L. , Oliver Janet M.
Published: February 2005

Patients with Kartagener syndrome (KS) show defects in ciliary and flagellar movement that are usually associated with the partial or total absence of dynein side arms from axonemal microtubules. Dynein is essential for such movements, but its involvement in other cellular (particularly microtubule‐related) processes is unknown. It has recently been reported that neutrophils from KS patients show impaired motility including responses to chemotactic stimuli, suggesting that dynein‐like proteins may be generally involved in motile processes. In support of this, we have now found that spontaneous motility of cultured skin fibroblasts from KS patients is also markedly impaired. Three cell lines derived from skin explants of KS patients with deficient dynein side arms in nasal cilia and eight cell lines derived from normal volunteers were studied. Fibroblasts were seeded into dishes containing colloidal gold‐coated cover glasses [Albrecht‐Buehler, 1977], incubated for 24 h at 37°C, and the area of cell “phagokinetic” tracks determined.

Each cell line studied in this manner reproducibly displayed an amount of spontaneous motility characteristic for that cell line. The mean track area (± SE) for all control cells studied was 14.6 ± 0.5 × 103μm2 whereas for KS fibroblasts was 8.7 ± 0.4 × 103μm2 (P < 0.001). Immunofluorescence microscopy using antitubulin and antihuman 210 K MAP antibodies revealed no differences in the staining patterns between control and KS fibroblasts. Pinocytic rates were identical, and the complement of tubulin and major microtubule associated proteins as seen on one‐dimensional SDS polyacrylamide gel autoradio‐graphs appeared similar for control and KS cells. Thus, the observed motility defect is probably not the result of alterations in the occurrence or distribution of microtubules or in the occurrence or binding of the major microtubule‐associated proteins. This defect in cellular motility may be related to the absence of dynein or may reflect another independent cellular defect.
Organization of interdoublet links in tetrahymena cilia
Authors: Warner Fred D.
Published: February 2005

Ciliary axonemes from Tetrahymena extracted by KCl to remove the dynein arms reveal an orderly array of interdoublet links connecting adjacent A‐B or A‐A subfibers. The links repeat every 96 nm at a stable site on the A subfiber positioned near the bases of radial spokes 2 and 3. Both links and radial spokes are in lateral register across the nine successive doublets of unbent axonemes. In contrast, bent axonemes or those reactivated by ATP to undergo partial sliding disintegration exhibit systematic displacement of the interdoublet links. The links show no evidence of having elastic or other extendable properties and, therefore, must have undergone intermittent attachment with nonstructural binding sites on the adjacent subfiber. These observations suggest a more dynamic role for the interdoublet links in ciliary motion than previously has been envisioned.
Changes in cytoskeletal proteins of polymorphonuclear leukocytes induced by chemotactic peptides
Authors: Fechheimer Marcus , Zigmond Sally H.
Published: February 2005

Changes in the state of polymerization of actin and phosphorylation of myosin have been observed in polymorphonuclear leukocytes (PMNs) soon after the addition of the chemotactic peptide N‐formylnorleucylleucylphenylalanine. At a time when the cells are observed to extend many ruffles or lamellipodia from their surface, the fraction of the cellular actin present in a monomeric form is decreased by about 25% as assayed by the ability of the G‐actin to inhibit DNAase. These changes are temporally correlated with an increase in the staining by nitrobenzooxadiazole (NBD)‐phallacidin, a probe that binds F‐actin selectively. The NBD‐phallacidin staining is observed in the surface ruffles. When the peptide concentration is decreased by addition of a tenfold excess of buffer, cells withdraw their surface ruffles and form blebs. These changes correlate with an increase in the G‐actin levels detected with the DNAase inhibition assay. An increase in phosphorylation of the 20,000‐dalton light chain of myosin is also observed in leukocytes stimulated by addition of chemotactic peptide. These observations of changes in cytoskeletal proteins of PMNs provide a beginning for further studies on the regulation of cell motility by chemotactic factors.
Rheological properties of living cytoplasm: A preliminary investigation of squid axoplasm (Loligo pealei)
Authors: Sato Masahiko , Wong Terence Z. , Brown Douglas T. , Allen Robert D.
Published: February 2005

A magnetic sphere viscoelastometer has been developed to peform rheological experiments in living axoplasm of Loligo pealei. The technique includes the use of a calibrated magnetic sphere viscoelastometer on surgically implanted ferro‐magnetic spheres in intact squid giant axons. The axoplasm was discerned to be “living” by the biological criterion of tubulovesicular organelle motility, which was observed before and after experimentation. From these in vivo experiments, new structural characteristics of the axoplasm have been identified. First, analysis of magnetic sphere trajectories has shown the axoplasm to be a complex viscoelastic fluid. Directional experimentation showed that this material is structurally anisotropic, with a greater elastic modulus in the direction parallel to the axon long axis. Second, both magnetic sphere and in vivo capillary experiments suggested that the axoplasm is tenaciously anchored to the axolemma. Third, it was found that axoplasm could be modelled as a linear viscoelastic material in the low shear rate range of 0.0001 to 0.004 s−1. The simplest mechanical model incorporating the discovered properties of the material in this range is Burger's model.
Induction of shape transformation in sea urchin coelomocytes by the calcium ionophore A23187
Authors: Hyatt Hilary A. , Shure Michael S. , Begg David A.
Published: February 2005

We have investigated the ability of the Ca+ + ionophore A23187 to induce the transformation of petaloid sea urchin coleomocytes to the filopodial form. The response of individual cells to different media was observed with time‐lapse phasecontrast video microscopy. In the presence of 1 mM CaCl2, isotonic medium containing 1–5 μM A23187 produces a similar shape transformation to that caused by hypotonic shock. Higher concentrations of ionophore (10–20 μM) induce the formation of filopodia that are thinner and less rigid than those generated by hypotonic shock or low doses of ionophore. A23187 also induces shape transformation in highly flattened cells that do not respond fully to hypotonic shock. The induction of cytoplasmic alkalinization by NH4Cl, methylamine‐HCl, or the Na+ ionophore monensin does not induce shape transformation, suggesting that increased intracellular pH is not the stimulus for this process. Ultrastructural changes in cytoskeletal organization were examined in negatively stained detergent‐extracted cells. Low doses of ionophore produce filopodia that are indistin‐guishable from those of hypotonically shocked cells, with actin filament bundles that are straight and cohesive along their entire length. High concentrations of ionophore produce filopodia with filament bundles that branch repeatedly and splay apart near their tips, forming loops and irregular curves. These results suggest that an increase in intracellular free Ca+ + concentration acts as the trigger that stimulates coelomocyte shape transformation, but that abnormally high concentrations of intracellular Ca+ +, produced by high doses of ionophore, interfere with actin filament bundling.
The effects of serum immunoglobulins on the metachronal coordination of the lateral cilia of Mytilus edulis
Authors: Sanderson Michael J. , Sleigh Michael A.
Published: February 2005

Human IgM and a bovine, IgM‐enriched serum fraction isolated from normal adult serum at concentrations of 0.25–1 mg/ml protein induced a pronounced increase in the metachronal wavelength of the lateral (L) cilia of the sea mussel Mytilus edulis without altering their beat frequency. This change in activity was indistinguishable from that induced by 50% adult human or bovine serum. At protein concentrations ranging from 1–9 mg/ml, human IgG or a bovine, IgG‐enriched serum fraction had no or little effect on the activity of the L cilia. Similarly, neither monomeric (8S) human IgM (0.25 mg/ml) nor monospecific pentameric IgM (1 mg/ml) isolated from Waldenström's macroglobulinemia patients altered the metachrony of the L cilia. Indirect immunofluorescence demonstrated that both bovine and human IgM became attached almost exclusively to the L cilia, while very little bovine or human IgG was found to associate with these cilia.

The results of this study suggest that serum IgM specifically binds to the L cilia of Mytilus in an antigen–antibody manner and agglutinates adjacent cilia into blocks or bundles, thereby increasing the coupling between cilia. As a result, the wavelength of the metachronal coordination is increased. The origin of these ciliary antibodies and their significance to ciliary bioassays used to monitor serum for the detection of cystic fibrosis are discussed.
Taxol stabilization of mitotic spindle microtubules: Analysis using calcium induced depolymerization
Authors: Salmon E. D. , Wolniak Stephen M.
Published: February 2005

Taxol stabilizes or promotes the assembly of microtubules. In this report we characterize the rate, extent, and reversibility of taxol stabilization of calciumlabile microtubules in isolated mitotic spindles, principally from embryos of the sand dollar Echinarachnius parma. The intense depolymerizing action of 100 μM Ca2+ was used to assess the extent of stabilization by taxol. Changes in spindle microtubule assembly were evaluated and recorded by measuring changes in spindle birefringent retardation (BR). Membrane‐free mitotic spindles, isolated with a calcium‐chelating, nonionic detergent buffer, were stored in an EGTA‐gylcerol storage buffer to prevent microtubule depolymerization. When perfused with an EGTA‐buffer without glycerol, microtubules in these isolated spindles depolymerized gradually over 60–120 min; but in isolated spindles perfused with buffer that contained 100 μM Ca2+, BR decreased by 90% within 2–5 sec. In contrast, spindles that were pretreated for 3 min with 1 μM taxol, or for about 30 sec with 10 μM taxol, lost less than 10% of their initial BR when perfused with buffer containing 100 μM Ca2+. The rate and extent of microtubule stabilization by taxol depended on both the concentration and the duration of exposure to taxol. Taxol stabilization was reversible. After a 15 min preincubation with 1 μM or 10 μM taxol then washout, stability of spindle BR to 100 μM Ca2+ decreased exponentially with a time constant of 30–60 min. Thus taxol dissociates from spindle microtubules at significant rates; taxol‐stabilized microtubules are not “fixed.”
Interaction of bimane‐labeled fluorescent tubulin with the isolated mitotic apparatus
Authors: Wadsworth Patricia , Sloboda Roger D.
Published: February 2005

Fluorescent derivatives of cellular proteins that retain their native characteristics have become useful probes to investigate the dynamics of specific cytoskeletal proteins. In the experiments reported here, a previously characterized fluorescent derivative of tubulin, bimane‐tubulin [Wadsworth and Sloboda, 1982a], was used to investigate microtubule assembly in vitro. The results demonstrate that bimanetubulin was competent to assemble onto a variety of organizing centers in vitro, including microtubule organizing centers (MTOCs) present in homogenates of sea urchin eggs, isolated mitotic apparatuses (MAs), and lysed mitotic cells. When homogenates of fertilized sea urchin eggs containing MTOCs were incubated with bimane‐tubulin at 37°C, discrete areas of linear fluorescence were observed. Only diffuse fluorescence was observed when calcium or colchicine was added to the homogenate or if the temperature was maintained at 0°C. Negative‐stain electron microscopy of the fluorescent arrays revealed morphologically normal microtubules radiating from electron dense regions. When mitotic spindles, isolated in glycerol containing buffers and therefore cold stable, were incubated with bimane‐tubulin, linear fluorescence was observed emanating from the spindle poles but not from the region occupied by the kinetochores. MAs incubated with bimane‐labeled bovine serum albumin or bimane‐labeled microtubule‐associated proteins showed only diffuse fluorescence. However, when mitotic cells which were hypotonically lysed in the absence of detergents or microtubule stabilizing solvents, were perfused with bimane‐tubulin intense fluorescence was observed in the asters and throughout the spindle. Two experiments suggested that the fluorescence observed in the results outlined above was due to the assembly of normal microtubules from the fluorescent subunits. First, the observed fluorescence was sensitive to cold temperataure, which is known to disassemble microtubules. Second, when the isolated, fluorescent MAs were examined by thin section electron microscopy, microtubules of normal diameter were seen. No aggregated material appeared associated with the walls of the microtubules, which might have been expected if the fluorescent protein was nonspecifically adsorbed to the microtubules. The results of these experiments demonstrate that isolated, stabilized MAs support the growth of new microtubules from the spindle poles while labile spindles, present in lysed cells, incorporate fluorescent tubulin throughout the spindle and asters. The significance of these results for hypotheses concerning microtubule assembly and disassembly during mitosis is discussed.
A comparison of methods used to characterize gelation of actin in vitro
Authors: Rockwell Mark A. , Fechheimer Marcus , Taylor D. Lansing
Published: February 2005

We have compared the meniscus depletion assay and falling ball viscometry, two means of assessing the extent of gelation in actin‐based systems using mixtures of actin and the actin‐binding protein filamin. We examined the effect of varying the concentrations of actin and filamin in both assays. The interaction of actin and filamin was detected only above a threshold concentration of filamin. This threshold concentration was lower for falling ball viscometry than for the meniscus depletion assay at equal actin concentrations. At constant concentrations of filamin, an increase in actin concentration caused an increase in apparent viscosity measured by the falling ball assay, but a decrease in sedimentability detected by the meniscus depletion assay. The rate of sedimentation of actin was dependent on the molar ratio of actin to filamin. At each molar ratio, the sedimentation of actin was not dependent on the specific concentrations of actin and filamin used. The apparent viscosity was dependent on both the molar ratio and the specific concentrations of actin and filamin. To relate the present results to earlier studies, we examined mixtures of actin and filamin using a macroscopic assay of gelation (tube tipping assay), and polarized light microscopy. The effect of increasing filamin concentration in the four assays was compared at three actin concentrations. Mixtures of actin and filamin whose apparent viscosities were low enough to be estimated by falling ball viscometry were optically isotropic fluids that flowed out of inverted test tubes. Mixtures of actin and filamin in the range of sensitivity of the meniscus depletion assay were either viscous fluids or gels, and were either optically isotropic or anisotropic. Thus, the four assays provide different estimates of gelation. Both the meniscus depletion assay and falling ball viscometry can be used to determine relative gelation activity, but neither can be used as a quantitative assay of gelation.
Direct visualization of particle velocity distribution by pseudostereoscopic viewing of time‐lapsed sequential images: Application to fast axonal transport
Authors: Hodge Alan J. , Adelman William J.
Published: February 2005

We describe a simple method for direct visualization of the velocity distribution of particles moving against an immobile background. The technique involves pseudostereoscopic viewing of image pairs separated by an appropriate time interval in a sequential recording of the subject. Under these conditions, the positive or negative parallax arising from particle motion results in the binocular image of a particle being perceived as raised or lowered relative to an immobile background plane depending on its direction of movement, and with the degree of perceived elevation being proportional to its speed. In effect, the binocular optic axis becomes a velocity (speed) axis under these conditions. The technique is illustrated with examples of image pair sequences showing fast axonal transport in lobster and squid axons using video‐enhanced differential interference contrast microscopy. However, the pseudostereoscopic method is quite generally applicable to both microscopic and macroscopic time‐dependent phenomena. Particle speeds can be quantitated using standard procedures for measuring frame‐to‐frame particle displacements, or alternatively, by determination of parallax using stereogrammatic methods. It should be also readily adaptable for on‐line monitoring of particle velocity distribution, particularly in video systems where frame buffers can be utilized to extract and present serial image pairs having any desired time separation from video‐taped sequences.
Localization of the centriole and keratin intermediate filaments in PtK1 cells by double immunofluorescence
Authors: Eckert Barry S. , Caputi Susan E. , Brinkley B. R.
Published: February 2005

We present observations on the relative location of the centriole and keratin filament cap in motile PtK1 cells. Subconfluent cells were double labeled with anticentriole and antikeratin sera. These preparations revealed that the centriole is separate from, but neighboring, the keratin filament cap. Serial ultrathin sections confirm this observation. These observations are consistent with the idea that the microtubule organizing center and intermediate filament distribution center are not identical or concentric in PtK1 cells.
Actin microfilaments in paramecium: Localization and role in intracellular movements
Authors: Cohen Jean , de Loubresse Nicole Garreau , Beisson Janine
Published: February 2005

Using heavy meromyosin (HMM) or the fragment S1 of myosin as probes for actin microfilaments, we studied their organization in Paramecium both by fluorescence and electron microscopy.

In interphasic cells, HMM decorates (a) most prominently the periphery of nascent and young food vacuoles and their route during the early phase of their intracellular transit; (b) a thin meshwork radiating from the gullet throughout the cytoplasm; (c) a small area beneath the pore of contractile vacuoles and beneath the cytoproct when open to release food residues. Most of these HMM‐decorated structures are in close contact with microtubular arrays. All HMM decoration disappears in dividing cells and in cytochalasin‐treated cells. In vivo, the drug immediately blocks food vacuole formation but does not affect cytokinesis, cyclosis, contractile vacuole pulsation, defecation, or nuclear movements.

The data show that, as in the cells of other organisms, actin microfilaments form defined arrays that undergo physiologically controlled cycles of assembly/disassembly. These arrays contribute (at least in the phagocytotic process) to diverse types of movement: constriction, membrane fusion, and migration of food vacuoles. However, aside from their massive concentration along the phagocytotic tractus, actin microfilaments are neither major structural components of Paramecium cytoplasm nor the only cytoskeletal components ensuring motility or contractility processes.