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At least 631 records · Page 35Linked to original sources
PubMed1984

The effect of prostaglandins I2, E1, E2 and dibutyryl cyclic AMP on the cytoplasmic spreading of rat osteoclasts.

We isolated osteoclasts from neonatal rat bone and assessed the effects of prostaglandins (PGs) I2, E1 and E2 on osteoclastic spreading. We found that although the PGs and dibutyryl cyclic AMP (DB-cAMP) acted as direct inhibitors of osteoclastic spreading, if osteoblasts and osteoclasts were co-cultured, the addition of PGs or DB-cAMP caused a considerable increase in spreading. This suggests that the PGs and DB-cAMP induce osteoblasts to stimulate osteoclasts. Osteoblasts are known to produce PGs, and thus possess the capacity to either inhibit (through PGs) or stimulate osteoclasts. Our results suggest that the balance between stimulation and inhibition of osteoclasts by osteoblasts may be determined by osteoblastic cyclic AMP levels.

Alprostadil↗
PubMedDate not supplied

Interactions between the rough endoplasmic reticulum and the nuclear membrane during increased proliferation of the endoplasmic reticulum.

Flickinger (1978) has shown conclusively that when there is demand for membrane by the nucleus, such as during repair of a damaged nuclear envelope, several membrane continuities develop between the RER and the nuclear envelope. This experiment was set up to determine if reversal of flow of membrane from the nuclear envelope to the RER would occur during phenobarbital-stimulated increased synthesis of RER. During the increased synthesis of RER following the stimulation of liver cells, it was observed that there was increase in the number of membrane continuities between the RER and the nuclear envelope. Increased blebbing and vesicle formation from the nuclear envelope was also seen. These vesicles were liberated as RER into the cytoplasm. It is therefore suggested that the nuclear envelope and the RER are in a state of equilibrium (RER in equilibrium NE) and membrane can be transferred either way depending on demand through the many membrane continuities that develop between the two organelles.

Animals↗
PubMed1978

Microtubules and organelle movements in the rust fungus Uromyces phaseoli var. vignae.

Direct visual observation and time lapse films of in vitro differentiating infection structures of the cowpea rust fungus Uromyces phaseoli var. vignae revealed three categories of movement: a) general movement of cytoplasm, plus organelles, into the developing portions of the fungus during which the nuclei, in particular, maintained their characteristic position with remarkable constancy, b) relatively slow movements of various organelles such that they became displaced relative to one another and to the growing fungal tip, and c) erratic, rapid, saltations of small organelles over short distances. Serial section ultrastructural analysis showed that microtubules were typically orientated parallel to the direction of cytoplasm migration. Simple statistical analyses showed that the microtubules were non-randomly associated with mitochondria but only rarely associated with lipid droplets or microbodies. All microtubules were typically short (less than 2 micrometer) and, in various parts of the cell, were often intimately associated with 3 to 6 nm diameter filaments of unidentified material. Interphase nuclei characteristically lacked microtubules emanating from their variously laterally or posteriorly located NAOs (nucleus associated organelle) but were associated with groups of laterally placed microtubules. The correlations between the observed types of movement and the ultrastructure of the cells discussed in terms of various models for organelle motility.

Basidiomycota↗
PubMed1984

[Effects of pH and ATP on the cytoplasm of Amoeba proteus: relation between cytoplasm motility and actin polymerization].

The effect of pH and ATP was studied on isolated cytoplasm of Amoeba proteus. These two parameters were shown to influence both the motility and the organization of actin filaments in the isolated cytoplasm. Furthermore, our results demonstrate that there is a relationship between the motility and the polymeric state of actin. When the isolated cytoplasm is non-motile, actin is highly polymerized into long filaments arranged parallel in bundles. When this cytoplasm is motile, however, actin can either be weakly polymerized, i.e. observed as few short filaments, or can be polymerized in long branched filaments forming a loose network.

Actins↗
PubMed1984

Cell motility during wound healing in giant algal cells: contraction in detergent-permeabilized cell models of Ernodesmis.

Triton-treated cells of the coenocytic green alga, Ernodesmis verticillata, manifest longitudinal contraction and centripetal closure of the cytoplasm in the presence of exogenous free calcium ions. Complete closure of the cytoplasm around the vacuolar remnants is obtained with 1 mM ATP present in the activation medium. The cytoplasmic contractions in these cell models closely resemble normal wound healing motility phenomena previously reported for this organism, thereby providing a system for studying the contractions associated with cellular wound healing. Dye-exclusion experiments with eosin B reveal that the tritonized models are freely permeable, whereas untreated cells do not take up the stain. Ultrastructurally, activated (contracting) models possess a network of microfilaments beneath the plasma membrane remnants in regions of active contraction. Microtubules are associated with the microfilaments, but they also occur throughout the periphery of the entire cells, even in unactivated models. This suggests that microfilaments may be involved in localized contractions leading to wound healing, whereas microtubules are probably providing a cytoskeletal framework upon which the microfilaments act. Colchicine (5 mM) has no effect on contraction in the models; extensive experiments with cytochalasins B and D (up to 100 micrograms/ml) have failed to show regular, reproducible inhibition of contraction also. Trifluoperazine (10 microM) or La3+ (1 mM) decreases the rate and magnitude of contraction to some extent, perhaps by preventing Ca2+ interaction with the contractile apparatus. The threshold concentration of free Ca2+ necessary to activate contraction in the models appears to be 10(-6) M, an order of magnitude higher than the preliminary value reported for non-permeabilized, wounded cells. Free Mg2+ also must be present for activation of models, with a minimum concentration of ca. 5 mM. The requirement of ATP for contraction can be demonstrated by the fact that either excessive washing of cell models prior to activation or inclusion of uncoupling agents in the solutions largely prevents activation of the models unless ATP is added to the Ca2+ -containing activation medium. These results provide further evidence that cellular wound healing in Ernodesmis is similar to the majority of other non-muscle cell motility phenomena in requiring ATP and micromolar amounts of free Ca2+ and that microfilaments are implicated in the contractile process. Moreover, the Ernodesmis cell models should be excellent systems for the further probing of cytoplasmic contractions associated with wound healing at the cellular level of organization.

Adenosine Triphosphate↗
PubMed1981

An inexpensive "silicone photo device" for transmicroscopic registration of rhythmical movement phenomena.

A highly sensitive electronic unit (called "silicon photo probe") is described, which enables registration of cellular motion phenomena simultaneous with their light microscopic observation. Changes in light intensity caused by movements of the living object are registered by means of a silicon photo diode (silicon blue cell), which can be mounted within the binocular tube of any type of light microscope replacing one of the oculars. Its application during investigations of oscillating contraction activity in Physarum is reported. Advantages and short-comings are discussed with respect to established photometric, tensiometric and infrared registration techniques.

Cell Movement↗
PubMed1981

[Effect of phalloidin on the contractile structures in cytoplasmic preparations of Amoeba proteus].

The effect of phalloidin on ultrastructural components involved in movement have been studied in spread cytoplasmic preparations of Amoeba proteus. In absence of phalloidin, actin filaments are usually rare and only myosin rods are observed. With concentrations of phalloidin between 2 X 10(-6) M and 5 X 10(-6) M, numerous F-actin filaments are present in the preparations. Most of these actin filaments are straight, however some appeared branched and interconnected. Higher concentrations of phalloidin inhibit the movement of naked cytoplasm. Fibrils composed by aggregation of F-actin filaments are present in these preparations. Myosin rods are unaffected by phalloidin.

Actins↗
PubMed1994

Egalitarian and the choice of cell fates in Drosophila melanogaster oogenesis.

Oogenesis in Drosophila females begins with the formation of a cyst of 16 interconnected sister cells, one of which eventually becomes the definitive oocyte. The other 15 become nurse cells, performing nutritive roles for the oocyte. There are four alternative developmental pathways in each cyst: winning pro-oocyte, losing pro-oocyte and cells with three ring canals, all of which enter meiosis, and the twelve obligate pro-nurse cells, which do not. In flies homozygous for the female-sterile mutation egalitarian (egl) all 16 cells follow the same intermediate pathway. All nuclei enter meiosis (shown by their attainment of synaptonemal complex of at least mid-zygotene levels and by their attainment of pachytene numbers and locations of recombination nodules), then all exit it and become morphologically indistinguishable from nurse cells in wild-type flies. The wild-type allele of egl therefore performs two active but opposite roles in cell fate choice. Early on it is necessary for inhibition of meiotic entry in the 'obligate' pro-nurse cells; later it is necessary for meiotic maintenance in the 'winning' pro-oocyte. One can account for both roles from a single function by invoking gradients through the early cyst; the egl+ function appears to be required for the normal function of these gradients.

Animals↗
PubMed1995

[Saltatory movements of the cytoplasmic granules in the cells of an ESK culture].

Saltatory movements of large (0.3-0.8 micron) granules in the cytoplasm of PK cells were described in norm and after nocodazole and sodium azide treatments. In untreated cells the length of single movements was up to 2 micron and even more (sometimes up to 5 micron). Nocodazole at a concentration of 0.2 micron and sodium azide at a concentration of 20 micron inhibited all rapid movements longer than 1.2 micron, but did not affect the frequency of movements shorter than 1 micron. The effect of nocodazole was reversible: the long rapid movements were seen resumed after its removal. A comparison of histograms (length versus frequency) of the rapid movements of granules in norm and after nocodazole and sodium azide treatments made it possible to conclude that real saltations (ATP and microtubule-dependent motions) are rapid translocations which exceed 1 micron.

Animals↗