摘要:

Summary—The ability to rapidly translocate polystyrene microspheres attached to the surface of a plasma membrane domain reflects a unique form of cellular force transduction occurring in association with the plasma membrane of microtubule based cell extensions. This unusual form of cell motility can be utilized by protistan organisms for whole cell locomotion, the early events in mating, and transport of food organisms along the cell surface, and possibly intracellular transport of certain organelles. Since surface motility is observed in association with cilia and flagella of algae, sea urchin embryos and cultured mammalian cells, it is likely that it serves an additional role beyond those already cited; this is likely to be the transport of precursors for the assembly and turnover of ciliary and flagellar membranes and axonemes. In the case of theChalmyodomonasflagellum, where surface motility has been most extensively studied, it appears that cross‐linking of flagellar surface exposed proteins induces a transmembrane signaling pathway that activates machinery for moving flagellar membrane proteins in the plane of the flagellar membrane. This signaling pathway in vegetativeChlamydomonas reinhardtiiappears to involve an influx of calcium, a rise in intraflagellar free calcium concentration and a change in the level of phosphorylation of specific membrane‐matrix proteins. It is hypothesized that flagellar surface contact with a solid substrate (during gliding), a polystyrene microsphere or another flagellum (during mating) will all activate a signaling pathway similar to the one artificially activated by the use of monoclonal antibodies to flagellar membrane glycoproteins. A somewhat different signaling pathway, involving a transient rise in intracellular cAMP level, may be associated with the mating ofClamydomonasgametes, which is initiated by flagellum‐flagellum contact. The hypothesis that the widespread observation of microsphere movements on various ciliary and flagellar surfaces may reflect a mechanism normally utilized to transport axonemal and membrane subunits along the internal surface of the organelle membrane presents a paradox in that one would expect this to be a constitutive mechanism, not one necessarily activated by a signaling

ISSN:0248-4900    

DOI:10.1016/0248-4900(92)90431-Y

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Summary—By making the hypothetis that the pattern of conserved sequence residues in the vicinity of the hydrolytic ATP‐binding site of dynein would resemble that in myosins from a broad variety of sources, we designed degenerate oligonucleotide primers capable of amplifying this region of multiple dynein isoforms from sea urchin embryo poly(A)+RNA. Quantification of the expression of two of these dynein isoforms has shown that the level of mRNA encoding for the β‐heavy chain, like that of tubulin, increases 2–3‐fold after deciliation of the embryos, whereas the expression of the second dynein isoforms, like that of actin, is essentially unaffected. This second isoform is believed to be the cytoplasmic dynein of sea urch

ISSN:0248-4900    

DOI:10.1016/0248-4900(92)90432-Z

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Summary—An axonemal dynein was purified from the sperm ofCrassostrea gigas, an oyster belonging to Protostomia. The molecular masses of component polypeptides were almost equivalent to those of other dyneins. Biochemical and biophysical properties were also quite similar. For example, UV‐cleavage, inhibition of ATPase by vanadate and induction of microtubule gliding were observed with the axonemal dynein. The oyster dynein had a two‐headed structure as had the outer arm dynein of Deuterostomia such as sea urchin, rainbow trout and bull spermatozoa. On the other hand, dyneins of Protozoa are three‐headed particles. From the evolutional point of view, it is likely that the number of heads of dynein molecule decreased when Metazoa evolved from P

ISSN:0248-4900    

DOI:10.1016/0248-4900(92)90433-2

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Summary—In most models of wave propagation in eucaryotic flagella and cilia, a clear distinction is made between the dynein dependent microtubule sliding which represents the oscillatory motor and the bending mechanism which regulates wave propagation. Little is known about the physical elements regulating the latter: in the present model, the bending propagation is postulated to be supported by an open/close cyclic mechanism protease/ligase dependent, which involves transient covalent links between adjacent microtubular doublets; this open/close cycle propagates in register with the powering action of the dynein motor along the exoneme. The implications of the model are discussed in relation to previous data which involve protease/ligase in the axonemal function as well as other data which can be integrated by the proposed mode

ISSN:0248-4900    

DOI:10.1016/0248-4900(92)90434-3

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Summary—Our previous study suggested that a chymotrypsin‐like protease was involved in the motility of chum salmon sperm (Inaba K, Morisawa M,Biomed Res(1991) 12, 435–437). In this study, we examined the peptidase activity of demembranated sperm of chum salmon using ten synthetic peptides. When spermatozoa were treated with 0.04% Triton X‐100 for extracting the plasma membrane and the suspension was separated into the Triton‐soluble and insoluble fractions by centrifugation, only the hydrolytic activity towards succinyl (Suc)‐Leu‐Leu‐Val‐Tyr‐4‐methylcoumaryl‐7‐amide (MCA), a typical substrate for chymotrypsin‐like protease, was mostly retained in the insoluble fraction. The bulk of the activities toward other substrates was detected in the soluble fraction. Flagellar axonemes isolated from demembranated sperm showed considerable hydrolytic activity toward Suc‐Leu‐Leu‐Val‐Try‐MCA and the activity was still retained in the axoneme even after further washing. The hydrolysis was activated by a low concentration of SDS, suggesting that the protease associated with the axonemes is a multicatalytic ATP‐dependent proteinase (proteasome). Motility of demembranated sperm was inhibited by Suc‐Leu‐Leu‐Val‐Tyr‐MCA in an ATP‐concentration‐dependent manner. These results suggest that proteasomes associat

ISSN:0248-4900    

DOI:10.1016/0248-4900(92)90435-4

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Summary—Even though all human respiratory cilia are similar in structure, they experience a wide range of temperatures between the initial part of the nasal fossae which behave as heat exchangers and the inferior part of the trachea, particularly when we inhale exceedingly cold or hot air. The ciliary beat frequency of ciliated cells from human nasal mucosa and from bronchial mucosa averages 8 Hz when measured at room temperature. In the present study we compared the ciliary beat frequency of human cells from nasal and tracheal mucosa brushings at different temperatures from 5°C to 50°C using two different techniques,ex vivoandin vitro: ex vivoin culture medium less than 24 h after sampling andin vitroafter demembranation and reactivation according to a standard procedure developed in our laboratory. Measuring the ATP‐reactivated ciliary beat frequency allowed us to check the thermal parameters of the dynein ATPase and all the axonemal machinery. No significant difference in frequency was observed between nasal fossae cilia and tracheal cilia when comparing extreme temperatures in both experimental proce

ISSN:0248-4900    

DOI:10.1016/0248-4900(92)90436-5

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Summary—kinetochore spindle fibers in meiosis I and II grasshopper spermatocytes were cut with a heterochromatic ultraviolet (UV) microbeam converging on the specimen to form a slit‐shaped microspot 1.5 × 8 μm or 3 × 8 μm. A total exposure of 3 × 10−8joules per μm2was administered within 0.8–2.4 s, which was sufficient for severing. The cells were observed with a high extinction polarizing microscope or phase contrast optics and a record made by time‐lapse video microscopy, continuously before, during and after the irradiation. When kinetochore fibers were irradiated i anaphase with UV, an area of reduced birefringence (ARB) was produced at the exposed site. The newly created + ends of the microtubules rapidly disassembled poleward, at a constant speed of 17 μm/min. The — ends at the edge of ARB also depolymerized at a slower rate. When a kinetochore fiber was cut with UV in early anaphase at which time its associated chromosome had not disjoined from the partner chromosome, the chromosome of the irradiated kinetochore fiber moved rapidly back to its partner. The speed during this movement was faster than the normal poleward chromosome movement in anaphase by an order to magnitude or more. When a kinetochore and its associated kinetochore fiber were included in the irradiation are, the effects were more pronounced than the effects of irradiation on a kinetochore fiber alone; the direction of the line connecting the irradiated half‐bivalent with the partner half‐bivalent deviated so much from the longitudinal axis of the original spindle with time that the division ass

ISSN:0248-4900    

DOI:10.1016/0248-4900(92)90437-6

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Summary—The dynamics and organization of microtubules associated with axonemes and kinetochoresin vitrowere visualized using video microscopy techniques. Microtubules attached either at the ends of axonemes or to mitotic chromosomes behave accordining to dynamic instability in our conditions. Microtubules attached to kinetochores showed lower rates of elongation and shortening than those nucleated by axonemes in the same conditions. In addition, elementary bundles of microtubules appeared spontaneously in association with kinetochores, with microtubules elongating along previously attached microtubules at even lower rates. Such side interactions, either spontaneous or stabilized by factors such as MAPs, might affect microtubule dynamics directl

ISSN:0248-4900    

DOI:10.1016/0248-4900(92)90438-7

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Summary—Microtubule‐associated proteins (MAPs) are one of the factors which regulate the different properties of microtubules during cell cycle and differentiation. They have been characterized as proteins which promote tubulin assembly in a concentration‐dependent manner and bind to the outer surface of the polymersin vitro. Most of our knowledge comes from studies of neural microtubule‐associated proteins and recent results highlight their implication in neuronal morphogenesis. In contrast, until recently, few data are available about the proteins that associate with plant tubulins. This is due principally to the fact that plant microtubule‐associated proteins cannot be purified by the standard procedures used for neural microtubule‐associated proteins. First, we will describe methods which have been used to isolate these proteins in plant cells. We will then discuss the biochemical and immunological properties of the plant microtubule‐associated proteins which have been isolated. From these results, putative functions can be proposed for these proteins n the particular plant cytoskelet

ISSN:0248-4900    

DOI:10.1016/0248-4900(92)90439-8

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Summary—2–4 nm filaments represent a new class of cytoskeletal components. They are found in ciliary and flagellar roots and centrosomes of all eucaryotes. They are also the major components of paraflagellar rods (PFR) in Euglena, trypanosomes and dinoflagellates.Oxyrrhis marina, a marine dinoflagellate, possesses a transverse and a longitudinal flagellum. Only the longitudinal flagellum carries the PFR along the proximal two‐thirds of its length. This flagellum is not only capable of the classic flagellar beat but is also able to retract and bend, a property mediated by external calcium. To determine if calcium has a direct role in the bending, experimental conditions were established to permeabilization and reactivation. Our conditions to reactivate the axoneme function (wave propagation) appear similar to those observed in the case of the sea urchin sperm. The results show thatin vitro, an increase in calcium concentration induces a conformational change of the longitudinal flagellum in the absence of ATP with a half maximum effect at 0.1 μM. In the presence of ATP, this morphology modification causes a total inhibition of the wave propagation which is replaced by non‐propulsive contractions of low amplitude. As these properties are not shared by reactivated sea urchin sperm flagella or the transverse flagellum ofO marinadevoid of PFR, we propose that PFR are responsible for the bending phenomenon. A calcium shock also induces flagellar excision with a half maximum effect at 0.3 μM, and immunofluorescence results suggest that a centrin‐like protein is present inO marinaand is responsible for th

ISSN:0248-4900    

DOI:10.1016/0248-4900(92)90440-C

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY