Uultrastructure of Microtubules

Author(s):  
Ariaki Nagayama

Vinblastine(Vb) or vincristine, alkaloid derived from Vinca rosea is known for its antimitotic activity by regrouping of microtubules into paracrystalline form within the cells. A rapid purification method of vinblastine-induced microtubular paracrystals(PC) has provided us with a fresh and pure microtubular material demonstrating the presence of a labile ATPase associated with the PC. The present report is concerned with the fine structure of purified microtubules of mammalian cultured cells.Confluent monolayer cultures of L cells were incubated for 20hrs with 10-5 M Vb (donated from Shionogi Seiyaku & Co., Osaka, Japan).

Author(s):  
Awtar Krishan ◽  
Nestor Bohonos

Cytochalasin B, a mould metabolite from Helminthosporium dermatioideum has been shown to interfere with specific cell activities such as cytoplasmic cleavage and cell movement. Cells undergoing nuclear division in the presence of cytochalasin B are unable to complete the separation of the resulting daughter cells. In time-lapse studies, the daughter cells coalesce after an initial unsuccessful attempt at separation and form large multinucleate polyploid cells. The present report describes the fine structure of the large polyploid cells induced in Earle's L-cell monolayer cultures by exposure to cytochalasin B (lγ/ml) for 92 hours.In the present material we have seen as many as 7 nuclei in these polyploid cells. Treatment with cytochalasin B for longer periods of time (6 to 7 days, with one medium change on the 3rd day) did not increase the number of nuclei beyond the 7 nuclei stage. Figure 1 shows a large polyploid cell with four nuclei. These nuclei are indistinguishable in their fine structure from those of the cells from control cultures but often show unusually large numbers of cytoplasmic invaginations and extensions of the nuclear surface (Figure 2).


1979 ◽  
Author(s):  
W. Nieuwenhuizen ◽  
I. A. M. van Ruijven-Vermeer ◽  
F. Haverkate ◽  
G. Timan

A novel method will be described for the preparation and purification of fibrin(ogen) degradation products in high yields. The high yields are due to two factors. on the one hand an improved preparation method in which the size heterogeneity of the degradation products D is strongly reduced by plasmin digestion at well-controlled calcium concentrations. At calcium concentrations of 2mM exclusively D fragments, M.W.= 93-000 (Dcate) were formed; in the presence of 1OmM EGTA only fragments M.W.= 80.000 (D EGTA) were formed as described. on the other hand a new purification method, which includes Sephadex G-200 filtration to purify the D:E complexes and separation of the D and E fragments by a 16 hrs. preparative isoelectric focussing. The latter step gives a complete separation of D (fragments) (pH = 6.5) and E fragments (at pH = 4.5) without any overlap, thus allowing a nearly 100% recovery in this step. The overall recoveries are around 75% of the theoretical values. These recoveries are superior to those of existing procedures. Moreover the conditions of this purification procedure are very mild and probably do not affect the native configuration of the products. Amino-terminal amino acids of human Dcate, D EGTA and D-dimer are identical i.e. val, asx and ser. in the ratgly, asx and ser were found. E 1% for rat Dcate=17-8 for rat D EGTA=16.2 and for rat D- dimer=l8.3. for the corresponding human fragments, these values were all 20.0 ± 0.2.


FEBS Letters ◽  
1978 ◽  
Vol 93 (2) ◽  
pp. 361-364 ◽  
Author(s):  
Gert Pflugfelder ◽  
Johann Sonnenbichler

1985 ◽  
Vol 33 (8) ◽  
pp. 837-839 ◽  
Author(s):  
A Messing ◽  
A Stieber ◽  
N K Gonatas

The resolution of indirect immunoperoxidase methods for localizing antigens on the surface of plasma membranes of cultured cells was tested using dissociated monolayer cultures of ciliary ganglion neurons prelabeled with cationic ferritin. Clusters of ferritin were produced on the cell surface by warming the cells to 37 degrees C after the ferritin, rabbit anti-ferritin, and goat anti-rabbit immunoglobulin coupled to horseradish peroxidase had all been applied. Intense 3,3'-diaminobenzidine tetrahydrochloride (DAB) staining was limited to the regions immediately surrounding the ferritin clusters. The lateral spread of the DAB reaction product beyond the outer ferritin particles in each cluster averaged 54-81 nm in four experiments. A second type of increased density, coinciding with the thickness of the plasma membrane, was also seen. These stained plasma membranes extended 161-339 nm from the ferritin clusters.


1997 ◽  
Vol 328 (2) ◽  
pp. 415-423 ◽  
Author(s):  
Stéphane NION ◽  
Olivier BRIAND ◽  
Sophie LESTAVEL ◽  
Gérard TORPIER ◽  
Françoise NAZIH ◽  
...  

To elucidate further the binding of high-density-lipoprotein subfraction 3 (HDL3) to cells, the involvement of glycosylphosphatidylinositol-anchored proteins (GPI-proteins) was studied. Treatment of cultured cells, such as fibroblasts or SK-MES-1 cells, with a phosphatidylinositol-specific phospholipase C (PI-PLC) significantly decreases specific HDL3 binding. Moreover, PI-PLC treatment of cultured cells or cellular plasma membrane fractions results in releasing proteins. These proteins have a soluble form and can also bind HDL3, as revealed by ligand blotting experiments with HDL3. In order to obtain enriched GPI-proteins, we used a detergent-free purification method to prepare a caveolar membrane fraction. In the caveolar fraction, we obtained, by ligand blotting experiments, the enrichment of two HDL3-binding proteins with molecular masses of 120 and 80 kDa. These proteins were also revealed in a plasma membrane preparation with two other proteins, with molecular masses of 150 and 104 kDa, and were sensitive to PI-PLC treatment. Electron microscopy also showed the binding of Au-labelled HDL3 inside the caveolar membrane invaginations. In SK-MES-1 cells, HDL3 are internalized into a particular structure, resulting in the accumulation and concentration of such specific membrane domains. To sum up, a demonstration has been made of the implication of GPI-proteins as well as caveolae in the binding of HDL3 to cells.


2018 ◽  
Vol 12 (1) ◽  
pp. 92-102
Author(s):  
Bushra M. Mohammed ◽  
Mahmood Ahmed

The present study was aimed to evaluate the genotoxicity of the aqueous extracts of Nerium oleander leaves and Narcissus tazetta bulbs each alone and together with the antileukemic drug 6-Mercaptopurin (6MP) in order to investigate the extracts ability to elevate the chemotherapeutic drug genotoxicity which may influence its treatment of cancer.  The cytotoxicity test shows that the LD50 of the aqueous extract of Narcissus tazetta was 752.083 mg/kg and for Nerium oleander was 922.023 mg/kg. On the basis of the achieved LD50 values, the doses  92, 46 ,23 mg/kg of Nerium oleander and the doses  75, 37,18 mg/kg of Narcissus tazetta extracts were chosen, depending on chromosome aberrations, Micronuclei and Mitotic index as a powerful cytogenetic assays in bone marrow cells of Swiss albino male mice. The result indicated that Nerium oleander extract alone at the dose 92mg/kg induced significant effect on  centromere break and ring chromosome comparing with the negative control (untreated mice) and significantly increased the mean values of chromatid gap  and ring chromosome when  compared with the positive control ( 6MP ). While only the dose 46 mg/kg and 23 mg/kg of N. oleander aqueous extracts significantly decreased mitotic index and when combined with 6MP it can enhance its antimitotic activity but not significantly. Moreover the extracts alone and when combined with 6MP did not significantly change the total number of red blood micro nucleated cells. For Narcissus tazetta extract, the three experimental doses alone lead to significant increase in chromosomal aberrations like: chromatid break with fragment, chromatid break without fragment, chromatid gap, centromeric break, ring chromosome and dicentric chromosome. While only the dose 75mg/kg had induced significant structural chromosomal abnormalities such as chromatid break with fragment, chromatid break without fragment centromeric break and ring chromosome, when combined with 6MP.  The three doses of N. tazetta extract alone, had led to significant reduction in mitotic index compared with untreated control and also its combination with 6-MP significantly decreased the percentage of mitotic index. Moreover, only the doses 75 mg/kg and 37 mg/kg of N. tazetta extracts, when had given alone caused significant increase of the total micronucleated cells. While only the dose 75mg/kg of N. tazetta had induced significant frequency of the total micronucleated cell when combined with 6MP. In the present report, we attempted to establish that N.tazetta and Nerium oleander aquatic extracts enhance the genotoxicity and bioactivity induced by the  antileukemic drug  6MP , thus preventing the development of cellular drug resistance which is a major  problem that can face cancer patients using this drug .The current study serve the purpose of which is to search for local plants that may contribute to the establishment of novel supportive complementary and alternative medicine (CAM) during the chemotherapy of cancer in Iraq , Further studies are merited to explore this possibility.


1988 ◽  
Vol 89 (3) ◽  
pp. 405-413
Author(s):  
J. Overton

Chick corneal epithelium takes on its mature conformation between 11 and 16 days of incubation. Earlier work has shown that desmosome frequency increases during this period, reaching its highest rate at 15 1/2 days. In the present report aggregation rates of cells from embryos of 11 days and those of 15 1/2 days are compared. Younger cells, which form fewer desmosomes, aggregate at a more moderate rate than older cells. In addition, younger cells bind less concanavalin A (ConA) than older cells. To determine if increase in ConA binding could be related to these cellular responses, aggregating cells were exposed to endoglycosidase H (EndoH) and to deoxymannojirimycin. This treatment should permit comparison of the response of cells that have a normal complement of N-linked oligosaccharides with those that have reduced high-mannose or complex type sugars. The effectiveness of EndoH under the conditions used was confirmed by failure of treated glycoprotein after separation by SDS-PAGE and electroblotting to bind ConA. Aggregation rates of both older and younger cells were unaffected, as measured by disapperance of single cells, though older cells formed somewhat smaller aggregates at the highest dosage used. Desmosome formation was markedly reduced in the presence of the enzyme, even in the absence of other changes in the fine structure. At the highest dose of the enzyme the fine structure of older but not younger cells showed indications of blockage of transport. Deoxymannojirimycin appears to cause a build-up of high-mannose groups, since treated cells showed increased incorporation of [3H]mannose.(ABSTRACT TRUNCATED AT 250 WORDS)


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