摘要:

AbstractDynamic changes in the spatial organizations of cytoplasmic fibrils (microfilament bundles) related to the contraction‐relaxation cycle in thin‐spread plasmodia ofPhysarum polycephalumwere investigated by fluorescence microscopy, where NBD‐phallacidin was used to stain the fibrils, combined with polarizing light microscopy.The fibrillar organization in the anterior region, which consists of a fanlike spreading plasmodial sheet, strikingly changed according to the phase of the cycle. In the early stage of the contraction, as the endoplasm began to stream backward, the fibrils developed into a number of slender and flabby fibrils emanating from the inside of the cell membrane and the nodes. They became thicker and more straightforward fibrils running parallel to each other at the middle stage, and finally formed a thick framework consisting of a “polygonal network” near the tip of the migrating front and a “parallel array” in the inner part. In the relaxation phase, as the endoplasm streamed forward, the fibrillar framework disintegrated gradually and finally disappeared almost completely, remaining only around the nodes in some cases.The fibrillar patterns in the posterior region, which consists of ramified strands, showed no conspicuous rhythmic change with alternation of the stream

ISSN:0886-1544    

DOI:10.1002/cm.970060502

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe contractility ofPhysarumplasmodium was investigated using cell models that were prepared by treating thin‐spread plasmodia with ice‐cold 0.2% Triton X‐100. Cell models obtained from the anterior regions of the thin‐spread plasmodia in the contraction phase retained many birefringent cytoplasmic fibrils. The fibrils vigorously contracted on addition of ATP, inducing simultaneous contraction of the whole cell models. In contrast, cell models prepared from the anterior regions in the relaxation phase scarcely contained the birefringent fibrils and exhibited only weak contractility on addition of ATP. The posterior regions of the thinspread plasmodia, which were composed of ramified plasmodial strands, always retained many fibrils when treated with the Triton solution and showed intensive contraction on addition of ATP.SDS‐polyacrylamide gel electrophoresis showed that the model was enriched for actin and myosin. About 40% of the actin was extracted from the plasmodium by the Triton treatment, while scarcely any myosin was extracted.Fragmin, a F‐actin‐fragmenting factor, caused the birefringent fibrils to diminish in the presence of Ca2+, but more than 30 minutes was required for their complete disappearance. The birefringent fibrils weakened by 30‐minute fragmin treatment disappeared immediately on addition of

ISSN:0886-1544    

DOI:10.1002/cm.970060503

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractBidirectional organelle movements were observed in fresh and permeabilizedreactivated (0.02% saponin, 5 mM Mg++ATP) walking leg axons of crayfish with video‐enhanced contrast, differential interference contrast (AVEC‐DIC) microscopy; and the cytoskeletal organization of those axons was studied with quickfreeze, deep‐etch electron microscopy (QF,DE) to understand the structure of the microtubule (MT) domain and to determine the basic cytoskeletal structures necessary for organelle transport in vivo. Vesicles and mitochondria moved bidirectionally in the central parts of fresh or permeabilized‐reactivated axons. Although the axoplasm of the fresh axon was composed of longitudinally oriented microtubules and granular materials in which membrane organelles were embedded, a network of fine strands existed in the core of the granular materials. Crossbridges between membrane organelles and microtubules were present. In the central part of reactivated axons, the cytoskeleton consisted of microtubules, highly anastomosing networks of fine strands (6.6 ± 1.4 nm in width) that crosslinked the microtubules with each other, and relatively short, straight crossbridges (25 ± 3.9 nm in length, 5.5 ± 2.1 nm in width) crosslinking membrane organelles with microtubules. It has been shown that a 270KD microtubule associated protein (MAP) could be a main component of crossbridges between MTs [Hirokawa, 1986]. Hence the dynamic conformational change of crossbridges between membrane organelles and microtubules could play an important role when membrane organelles are t

ISSN:0886-1544    

DOI:10.1002/cm.970060504

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractTreatment with 10 μm taxol disrupted mitotic and cytoplasmic arrays of microtubules (MT) in cultured cells of two higher plants,Vicia hajastana(vetch) andZinnia elegans.When treated for 1, 24, and 48 h, cells in both cultures showed similar effects. After 1 h, multipolar arrays of MT were noted in prophase, large aster‐like arrays of MT appeared in metaphase, and extra MT shared poles with otherwise normal‐appearing metaphase and anaphase configurations. After 24 and 48 h, some phragmoplasts were multipartite or misplaced. In interphase cells, micronuclei and multinucleate cells were evidence of irregular mitosis and cytokinesis. Cytoplasmic MT in elongated cells were oriented parallel to, instead of at right angles to the long axis of the cell. Some interphase cells lost asymmetry while maintaining organized arrays of MT. Taxol appears to disrupt mitotic and cytoplasmic arrays of MT, seemingly overriding the mechanism(s) regulating MT polymerization and orienta

ISSN:0886-1544    

DOI:10.1002/cm.970060505

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractLiving vegetative amoebae of NC‐4HDictyostelium discoideumwere studied to determine if a variety of pteridines had any effect on the filopodia. We observed that production, elongation, and branching of these filopodia were stimulated by pteridines that are chemoattractants for cells of this strain. This stimulation occurs at chemotactically effective concentrations and is observed before motility is evident. A relationship between filopodia and chemoattractant signal processing is discusse

ISSN:0886-1544    

DOI:10.1002/cm.970060506

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractPrevious studies of the storage of polymorphonuclear leukocytes (PMNs) have used an empirical approach to define “optimal” conditions. To date, no storage conditions have been described which satisfactorily preserve the chemotactic function of PMNs beyond 24 h. In an effort to define the precise nature of the storage lesion, we studied the chemotactic locomotion of freshly isolated PMNs and PMNs which had been suspended in citrate‐phosphate‐dextrose‐adenine (CPD‐Al) plasma and stored in PVC bags, at 20–22°C for 24 h. We used time‐lapse video recording and computer image analysis to quantitate the motion of PMNs migrating under agarose. The positions of individual motile cells were traced at 1‐min intervals for 5 min. The following parameters were used to quantitate migration: (1) speed (distance/min), (2)) persistence of locomotion index (velocity/speed), (3) orientation angle (the angle of the vector describing the next displacement of a cell relative lo a direct line toward the chemoattractant), and (4) chemotropic index (cosine of the orientation angle). After 24 h of storage, the following changes were observed: (1) fewer cells migrated, (2) (he speed of migrating cells was reduced by 25%, (3) the persistence of locomotion index decreased by 7%, which indicates that migrating cells made slightly more/wider turns, and (4) the chemotropic index was decreased by 30%, which indicates that migrating cells were less accurate in their orientation toward the chemoattractant. Apparently, the storage of PMNs selectively impairs the ability of some cells to orient accurately in a chemotactic gradient and changes the distribution of these locomotor parameters wit

ISSN:0886-1544    

DOI:10.1002/cm.970060507

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractAt metaphase in crane‐fly primary spermatocytes, the two sister kinetochores at the centromere of each homologue in a bivalent normally are adjacent and face the same pole; one homologue has all its kinetochore microtubules (kMTs) extending toward one pole and its partner has all its kMTs extending toward the opposite pole. In contrast, during recovery from exposure to 2°C, one or both homologues in many metaphase bivalents had bipolar malorientations: all kMTs of one kinetochore extended toward one pole and some or all those of its sister extended toward the other. Metaphase sister kinetochores that had most of their kMTs extending toward the same pole were adjacent, and those with most extending toward opposite poles were separated from each other. Distances between homologous centromeres were similar to those in properly oriented bivalents. Maloriented bivalents were tilted relative to the spindle axis, and analysis of living cells showed that tilted configurations were rare during prometaphase in untreated cells but frequently arose in cold‐recovering cells as initial configurations, then persisted through metaphase. This was in contrast to unipolar configurations of bivalents (configurations suggesting orientation of both homologous centromeres toward the same pole), which always reoriented shortly after the configuration arose. We conclude that in cold‐recovering cells, bipolar malorientations are more stable than unipolar malorientations, and the orientation process is affected such that bipolar malorientations arise in bivalents upon initial interaction with the spindle and persist through met

ISSN:0886-1544    

DOI:10.1002/cm.970060508

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractIsolated ciliary axonemes from pig trachea were exposed to increasing concentrations of purifiedPseudomonas aeruginosarhamnolipid. This is a defined ciliary system allowing observation of direct impairment of functional axonemes. Axonemal motility and ATPase activity were decreased in proportion to rhamnolipid concentrations. ATPase‐associated proteins observed in sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) and dynein arms seen in ultrastructural cross sections progressively disappeared from axonemes with exposure to rhamnolipid. These four independent measures establish that the rhamnolipid removes the ATPase‐containing outer dynein arms from the ciliary axoneme, thereby rendering the axoneme i

ISSN:0886-1544    

DOI:10.1002/cm.970060509

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractWhen outer‐row dynein arms are extracted fromChlamydomonasflagellar axonemes, they dissociate into two ATPase complexes with sedimentation coefficients of 12S and 18S. We immunized mice with 18S dynein and generated a library of monoclonal antibodies against the polypeptides in this complex. Antibodies were selected which specifically recognize the 18S α‐ and β‐heavy chains and the 83,000‐dalton and 70,000‐dalton intermediate chains. These antibodies were isolated and characterized for their ability to recognize determinants on both denatured antigens and native 18S dynein; 18S dynein was dissociated in stepwise fashion into smaller aggregates with ionic and nonionic detergents and the resulting subcomplexes were isolated by precipitation with specific monoclonal antibodies. The smallest aggregates isolated were heterodimers between the α‐chain and a 16,000‐dalton light chain and between the two intermediate chains. Additional close associations of the β‐heavy chain with an 18,000‐dalton light chain and 70,000‐dalton intermediate chain, and a weaker interaction between the intermediate chain heterodimer and light chains of 21,000 daltons and 12,500 daltons, were also observed. We present a model of 18S dynein substructure base

ISSN:0886-1544    

DOI:10.1002/cm.970060510

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractReticulomyxais a large, multinucleated freshwater protozoan with striking intracellular transport. Cyloplasmic streaming and saltatory movements of individual organelles (at rates of up to 25 μm/sec) are observed within the naked cell body and the extensive reticulate peripheral network of fine cytoplasmic strands. As demonstrated by video‐enhanced light microscopy, individual organelles move only when associated with cytoskeletal linear elements. The linear elements are composed of mixed colinear bundles of microtubules and actin filaments, which form the backbone of the reticulopodial network. The constant branching, sprouting, and fusion of network stands suggest unique membrane properties and an unusually dynamic cytoskeleton. The electrophoretic mobility ofReticulomyxatubulins and the lack of crossreactivity with several antibodies known to react with many plant and animal tubulins suggest that they may differ from other tubulins more widely than might be expected.Reticulomyxa's large size, the rapidity and pervasiveness of the two forms of transport, and the simple and ordered cytoskeleton make the organism well suited for future studies on the mechanisms of intracellular transpo

ISSN:0886-1544    

DOI:10.1002/cm.970060511

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY