摘要:

AbstractWhen human blood platelets were immersed in an ice‐cold solution containing 1% Triton ×‐1200, 40 mM KCl, 10 mM EGTA, 10 mM imidazole‐HCl, and 2 mM NaN3pH 7.0, a flocculent precipitate appeared immediately in the tube. This precipitate was collected at 3,000g and SDS‐polyacrylamide gel analysis showed it to consist mainly of actin, α‐actinin, actin‐binding protein (ABP), and varying amounts of myosin.Any modifications of this solution used to isolate the platelets' Triton‐insoluble cytoskeleton caused profound changes in the nature of the cytoskeleton isolated. Increasing the KCl concentration resulted in a lower yield of cytoskeletal actin and ABP. Inclusion of EDTA in the solution resulted in an increased amount of myosin associated with the cytoskeleton, whereas including MgATP decreased the myosin yield.Experiments with the purified proteins showed that ABP and myosin can each protect the actin from depolymerizing when dialyzed into the Triton solubilization solution. In addition, it was found that when platelets were stimulated with thrombin for 2 min prior to the addition of the Triton solution, 3–4 times more myosin was associated with the cytoskeletal precipitate.The results suggest, therefore, that any variations in solution conditions used for isolating the cytoskeleton from resting platelets, which results in alterations in the amount of ABP, may have profound effects on the state of actin polymerization. Likewise, in thrombin‐activated platelets, it is suggested that the increased association of myosin with the cytoskeleton results in a greater stabilization of the F‐actin associated with the cytoskeleton. These factors must be considered when interpreting the results regarding the nature of actin transformations in the resting a

ISSN:0271-6585    

DOI:10.1002/cm.970020402

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe 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‐sub

ISSN:0271-6585    

DOI:10.1002/cm.970020403

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe fluorescent derivative of the actin‐binding toxin phallacidin, 7‐nitrobenz‐2‐oxa‐1,3 diazole phallacidin, has been used to cytologically demonstrate the presence of actin in lens epithelium, corneal endothelium, and retinal pigment epithelium. In these noninjured tissues, no stress fibers are observed and fluorescence is confined mainly to an area at or near the cell membrane, although some diffuse cytoplasmic staining can also be seen. However, following injury to either the lens epithelium or corneal endothelium of rats and frogs, stress fibers are detected, but only in those cells that migrate into the wound area. Cells on the periphery of each tissue do not partake in would repair and thus maintain their normal appearance. After the tissue has regenerated, stress fibers disappear, and those cells involved in the injury response return to their normal morphology.When rabbit corneal endothelium is placed in tissue culture, stress fibers are observed as the cells migrate away from the initial explant. Upon reaching confluency, these cells spread out and each is surrounded by thick actin‐containing bands. Furthermore, they exhibit some stress cables within their cytoplasm. This is in contrast to their appearance in vivo where stress fibers are absent and fluorescence is limited to a region near the ce

ISSN:0271-6585    

DOI:10.1002/cm.970020404

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

年代:1982

数据来源: WILEY

摘要:

AbstractElectron microscopic examination of thin sections and freeze fractures of Locusta spermatids revealed that the proacrosome docks to the nuclear membrane and glides around the nucleus during sperm development. Whereas nuclear pore complexes occur in groups distributed at random over the entire nucleus of the early spermatid, they are found only in a narrow ring closely surrounding the centriolar adjunct in later spermatids. The pores appear to be swept caudally in the nuclear envelope, perhaps by a process like capping; they are not merely excluded by structures adhering to the nucleus. The observations suggest that both proacrosome migration and the deployment of pores are facilitated by the inherent fluidity of the nuclear membranes.

ISSN:0271-6585    

DOI:10.1002/cm.970020405

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe male gametes of the parasitic protozoan, Lecudina tuzetae, have a motile flagellum with a “6 + O” ultrastructure ‘Schrével and Besse, 1975’. These gametes were isolated from the cysts in which they develop and were observed and photographed under a variety of conditions. The flagella beat continuously, without stopping and starting, with a beat period of about 2 sec. They can beat in solutions whose viscosities are greater than 0.5 Nsm−2(l Nsm−2= 103cP). The waveform can be approximated by a series of helical arcs and interconnecting straight regions that travel from the base to the tip. The helical regions have a radius of curvature of 3.2 μm and subtend a final angle of 1.7 radians. The straight portions are 2.0 μm in length. There are two sets of opposing bends, but they do not originate in the same plane. The resulting waveform is an approximately helical coil, with a pitch of 9.8 μm, a pitch angle of 0.6 radian and a peak‐to‐peak amplitude of 2.3 μm. The sense of the coil is left handed. The axoneme twists during beating. The main differences between the movement of this flagellum and that of typical 9 + 2 flagella are a low beat frequency and three‐dimensional bends that produce relatively little forward movement of the cell. Twisting is discussed as a means of discriminating between some types of models

ISSN:0271-6585    

DOI:10.1002/cm.970020406

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

年代:1982

数据来源: WILEY

摘要:

AbstractThis is a descriptive study showing the three‐dimensional interrelationship of cytoskeletal elements at the apex of ciliated cells of rat respiratory epithelium. Tissue specimens were serially thin sectioned in various planes and examined by transmission electron microscopy. Thicker sections were also cut at various angles and analyzed stereoscopically. Other specimens were cleared of soluble molecules by glycerination or Triton‐X 100 treatment and sectioned as described above. It was found that C microtubules from the triplets of each basal body diverge from the A and B microtubules, run a short distance, and converge at the basal foot. These microtubules or other microtubules arising anew then dispersed deeper into the cytoplasm. The C fibers also interdigitated with other microtubules running perpendicular to them and parallel to the ciliated surface. Ten‐nanometer intermediate filaments were organized in parallel sheets between adjacent basal bodies. Sixnanometer actin filaments were distributed throughout the apical cytoplasm. Neighboring basal bodies were linked to one another by microtubules and microfilaments. Basal bodies from each cell appear to be structured for stability, flexibility, and arranged to operate as a single

ISSN:0271-6585    

DOI:10.1002/cm.970020407

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

年代:1982

数据来源: WILEY

摘要:

AbstractMotility of the marine filamentous cyanobacterium Spirulina subsalsa is both Ca2+and Na+dependent, and replacement of Na+by mannitol arrests it. The data presented suggest that Ca2+interacts with sites on the surface of the cell membrane. The inhibitory effect of dicyclohexylcarbodiimide (DCCD) hints at the possibility that the role of Ca2+may be associated with a membrane bound Ca‐ATPase. Motility is pH dependent, being nil at pH10.0, with an optimum at 8.5. Norepinephrine abolishes most of the inhibitory effect of low pH on motility. Ca2+has an “all‐or‐none” effect on motility that is triggered at 5 mM. Acetylcholine lowers the threshold of Ca2+necessary for triggering

ISSN:0271-6585    

DOI:10.1002/cm.970020408

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

年代:1982

数据来源: WILEY

ISSN:0271-6585    

DOI:10.1002/cm.970020401

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

年代:1982

数据来源: WILEY