Aprotic polar solvents inducing chromosomal malsegregation in yeast interfere with the assembly of porcine brain tubulin in vitro

Maytansine, a novel ansa macrolide (1), has potent anti-tumor and antimitotic activity (2, 3). It blocks cell cycle traverse in mitosis with resultant accumulation of metaphase cells (4). Inhibition of brain tubulin polymerization in vitro by maytansine has also been reported (3). The C-mitotic effect of this drug is similar to that of the well known Vinca- alkaloids, vinblastine and vincristine. This study was carried out to examine the effects of maytansine on the cell cycle traverse and the fine struc- I ture of human lymphoblasts.Log-phase cultures of CCRF-CEM human lymphoblasts were exposed to maytansine concentrations from 10-6 M to 10-10 M for 18 hrs. Aliquots of cells were removed for cell cycle analysis by flow microfluorometry (FMF) (5) and also processed for transmission electron microscopy (TEM). FMF analysis of cells treated with 10-8 M maytansine showed a reduction in the number of G1 cells and a corresponding build-up of cells with G2/M DNA content.

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Isolation of polypeptides with microtubule-translocating activity from phragmoplasts of tobacco BY-2 cells

Journal of Cell Science ◽

10.1242/jcs.107.8.2249 ◽

1994 ◽

Vol 107 (8) ◽

pp. 2249-2257 ◽

Cited By ~ 2

Author(s):

T. Asada ◽

H. Shibaoka

Keyword(s):

Motor Activity ◽

Molecular Basis ◽

Plant Cells ◽

Cell Plate ◽

Gtpase Activity ◽

High Concentration ◽

Higher Plant ◽

Main Components ◽

Brain Tubulin

As part of our efforts to understand the molecular basis of the microtubule-associated motility that is involved in cytokinesis in higher plant cells, an attempt was made to identify proteins with the ability to translocate microtubules in an extract from isolated phragmoplasts. Homogenization of isolated phragmoplasts in a solution that contained MgATP, MgGTP and a high concentration of NaCl resulted in the release from phragmoplasts of factors with ATPase and GTPase activity that were stimulated by microtubules. A protein fraction with microtubule-dependent ATPase and GTPase activity caused minus-end-headed gliding of microtubules in the presence of ATP or GTP. Polypeptides with microtubule-translocating activity cosedimented with microtubules that had been assembled in vitro from brain tubulin and were dissociated from sedimented microtubules by addition of ATP or GTP. After cosedimentation and dissociation procedures, a 125 kDa polypeptide and a 120 kDa polypeptide were recovered in a fraction that supported minus-end-headed gliding of microtubules. The rate of microtubule gliding that was caused by the fraction that contained the 125 kDa and 120 kDa polypeptides as main components was 1.28 microns/minute in the presence of ATP and 0.50 microns/minute in the presence of GTP. This fraction contained some microtubule-associated polypeptides in addition to the 125 kDa and 120 kDa polypeptides, but a fraction that contained only these additional polypeptides did not cause any translocation of microtubules. Thus, it appeared that the 125 kDa and 120 kDa polypeptides were responsible for translocation of microtubules. These polypeptides with plus-end-directed motor activity may play an important role in formation of the cell plate and in the organization of the phragmoplast.

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Synergistic effects of natural products and commercial antibiotics

10.1101/2020.09.01.20186353 ◽

2020 ◽

Author(s):

Lucia Nitsch-Velasquez

Keyword(s):

Natural Products ◽

Synergistic Effects ◽

Gram Negative Bacteria ◽

Polar Solvents ◽

Microbial Strains ◽

Polar Extracts ◽

Review Reports ◽

New Treatments ◽

Discovery Pipeline

Context: The antimicrobial resistant era requires advances in the approaches and technologies to find new treatments. The enhancement of the antimicrobial activity of commercially available drugs (CADs) by natural products (NPs) has successful mixtures (e.g., clavulanic acid and amoxicillin). Objective: To systematically review reports of synergistic effects of CADs and NPs against opportunistic microbial strains from 2010 to April 2016. Methods: The databases and search engines PubMed, Medline, Scifinder, Scopus, ScienceDirect, Scholar Google were systematically searched. Among the keywords utilized were: synergistic effects natural products and antibioitcs, botanicals and antibiotics bioassays, plant extracts interaction with antibioitics and antibiotic adjuvant bioassays. Only synergistic results were tabulated and analyzed according to CADs, NPs and strains. Results: A set of 76 studies that reported in vitro synergistic effects of CADs and NPs against gram−positive or gram−negative bacteria or fungi opportunistic strains was found. From the 60 reports on antibacterial adjuvants, the most frequent designs involved beta−lactamics or aminoglycosides against Methicillin Resistant Staphylococcus aureus. The assayed NPs encompassed extracts or fractions from 22 different species distributed worldwide (45% extracted with non−polar solvents) and 33 purified compounds (flavonoids, other polyphenols and alkaloids). Conclusions: NPs as potential drug hits for antimicrobial adjuvants had been found and should continue in the drug discovery pipeline. The field certainly would benefit of advances in purification technologies, especially for polar extracts and bioassay platforms.

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