摘要:

AbstractThe motility and fine structure of the marine planktonic dinoflagellate Kofoidinium and members of other related genera have been investigated. Several types of shape change were found to occur: slow morphogenetic changes (which also occurred as restitution movements in response to injury), movements associated with the ingestion of food and the evacuation of wastes, and more rapid movements concerned with the capture of prey. All these movements seemed to be brought about by the contraction of refractile tracts within the cytoplasm, which were found to contain 2.3‐nm filaments, some with a complex striated appearance. This and other evidence suggests that these filaments, which have counterparts in many other protists, are not actin filament

ISSN:0271-6585    

DOI:10.1002/cm.970050102

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

年代:1985

数据来源: WILEY

摘要:

AbstractMouse peritoneal macrophages subjected to gradients of activated mouse serum were found by immunofluorescence observations to have their Golgi apparatus and their microtubule‐organizing center largely oriented in the direction of the gradient. By analogy with similar results obtained with motile fibroblasts, it is proposed that these two organelles are rapidly and coordinately reoriented inside the macrophages in order to direct the insertion of new membrane mass, via vesicles derived from the Golgi apparatus, into the leading edge of the cell. Consistent with the importance of such membrane insertion to cell migration, we found that the ionophore monensin, an inhibitor of Golgi functions, inhibited cell motility in the chemostactic gradient. It was further shown that several inhibitors of chemotaxis (monensin, cytochalasin D, cycloheximide) did not inhibit the reorientation of the Golgi apparatus/microtubule‐organizing center in cells exposed to a chemotactic gradient, and that the reorientation required extracellular C

ISSN:0271-6585    

DOI:10.1002/cm.970050103

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

年代:1985

数据来源: WILEY

摘要:

AbstractUnderstanding the molecular basis of mitotic movements in living cells will require correlative experiments on intact cells, cell models, purified tubulin, and perhaps other biopolymers. Birefringence is one assay that is useful in all of these experimental situations. Heretofore, studies of birefringence changes during mitosis have lacked a quantitiative basis for interpretation in terms of microtubule number and packing density. One of the aims of this work was to establish that relationship.Purified calf brain tubulin was polymerized to equilibrium and oriented in the hydrodynamic field of a microcapillary flow birefringence apparatus. The relationship between birefringence and microtubule packing density was determined by a combination of optical, electron microscopic, and biochemical methods. The data correlate surprisingly well with those obtained by others from in vitro measurements on isolated mitotic spindles. Using the flow birefringence data, the sensitivity of polarizing microscopes for detecting microtubules was examined and found to depend on microtubule packing density, object thickness, and instrumental factors that limit both the detection and measurement of weakly birefringent objects. Because of the dependence of measurement sensitivity on object thickness, a method of measuring the thickness of microtubule bundles using the dispersion of birefringence was developed. This method is capable of measuring thickness to within two or three Airy diffraction units and does not require any assumptions regarding object symmetry.

ISSN:0271-6585    

DOI:10.1002/cm.970050104

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

年代:1985

数据来源: WILEY

摘要:

AbstractCa2+has profound effects on the movement of cilia and eukaryotic flagella, including those of Chlamydomonas. Two clear changes seen in Chlamydomonas flagella with changes in Ca2+are beat frequency and symmetry. Photographic and computer assisted analysis of flagellar bending patterns on a uniflagellate mutant of Chlamydomonas have been used to examine details of the effects of Ca2+on the movement of ATP‐reactivated, demembranated flagella. In addition to the forward mode bending pattern seen at low Ca2+concentrations (10−9M), which has a frequency of about 50 Hz and the reverse mode bending pattern seen at high Ca2+concentrations (10−4M) with a frequency around 70 Hz, we carefully examined bending patterns in the intermediate Ca2+concentration range of 1–6.5 × 10−6M. In this intermediate range, the bending patterns have significantly reduced asymmetry and slightly increased frequency, compared to the motility observed at low Ca2+concentrations. These observations indicate that changes in these two parameters of motion do not occur in parallel and suggest that the effects of Ca2+may be a multicomponent process. Physiologically, these changes in the beat pattern at intermediate Ca2+may signal either (1) the beginning stages of transition to the symmetrical, high‐frequency beating seen at high Ca2+, or (2) a more normal forward mode motility for thetransflagellum as suggested by Kamiya and Witman [1984]. No large amplitude bending patterns associated with transitions between forward and reverse mode beating in intact cells were seen at the intermediate Ca2+co

ISSN:0271-6585    

DOI:10.1002/cm.970050105

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

年代:1985

数据来源: WILEY

摘要:

AbstractIn current purification strategies, affinity for microtubules or calmodulin is used to identify and purify cytoplasmic dynein‐like ATPase from cell‐free extracts of unfertilized sea urchin eggs. However, affinity purification procedures, though they define dynein‐like ATPase activity, have not yet proven to be quantitative. An alternative purification strategy capable of producing a high yield of enzyme would require a specific assay in order to monitor cytoplasmic dynein purity at each step.In this study, we make a detailed comparison of the effects of EHNA on 22 different ATP‐metabolizing enzyme activities, including 13 Mg++‐ATPases. We isolate cytoplasmic dynein‐like ATPase activity from three species of sea urchin eggs and sperm and show by means of dose‐response curves that their sensitivities to inhibition by EHNA are very similar to one another. We demonstrate further that the EHNA dose‐response characteristics of fourteen other ATP‐metabolizing enzyme activities, including seven nondynein Mg++‐ATPases, differ quantitatively from those of dynein‐like ATPases.In studies of three other agents (vanadate, Ca++/calmodulin, and Triton X‐100), we find that dynein‐like ATPases vary by two orders of magnitude in their sensitivities to inhibition by vanadate, and little or no stimulation by either Ca++/calmodulin or Triton X‐100 is seen. Our results suggest that inhibition by EHNA is a universal and specific property of dynein‐like ATPases, which ultimately should prove useful in the quantitative purification and characterization of cytop

ISSN:0271-6585    

DOI:10.1002/cm.970050106

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

年代:1985

数据来源: WILEY

ISSN:0271-6585    

DOI:10.1002/cm.970050101

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

年代:1985

数据来源: WILEY