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Biomedical subjects

B Hartley-Asp

Publications and source records attributed to B Hartley-Asp.

At least 55 records · Page 3Linked to original sources
PubMed1985

Diethylstilbestrol induces metaphase arrest and inhibits microtubule assembly.

Diethylstilbestrol produced a dose-dependent increase in the mitotic index of the human prostatic tumour cell line DU 145. This is the result of metaphase arrest which may be induced by the action of diethylstilbestrol on spindle microtubules. Evidence is presented to show that diethylstilbestrol affects microtubules. Diethylstilbestrol completely inhibited the assembly of isolated brain microtubules although only partial disassembly could be induced. In contrast to other microtubule poisons, the inhibitory effect of diethylstilbestrol on taxol-induced self-assembly could be reversed by the addition of GTP.

Alkaloids↗
PubMed1985

Effect of estramustine phosphate on the assembly of isolated bovine brain microtubules and fast axonal transport in the frog sciatic nerve.

Estramustine phosphate (0.01 to 0.5 mM), an estradiol mustard derivative used in the therapy of prostatic carcinoma, inhibited the assembly of brain microtubules proteins in vitro and disassembled preformed microtubules. In the presence of estramustine phosphate, the minimum microtubule-protein concentration sufficient for the assembly of microtubules was increased. Low concentrations of taxol (20 microM) completely reversed the inhibition of assembly by estramustine phosphate. The effects were specific to estramustine phosphate since neither estradiol 17 beta-phosphate, the hormonal moiety of the drug, nor nornitrogen mustard, the alkylating moiety, had any effect on assembly. Estramustine phosphate (0.1 to 0.5 mM) was also found to reversibly inhibit fast axonal transport in the frog sciatic nerve. The nerve content of adenosine triphosphate, adenosine diphosphate, and adenosine monophosphate was not significantly affected by estramustine phosphate. Our results suggest that the cytotoxic action of estramustine phosphate could be dependent partially on an interaction with microtubules, probably via the microtubule-associated proteins.

Animals↗
PubMed1984

Estramustine-induced mitotic arrest in two human prostatic carcinoma cell lines DU 145 and PC-3.

In growth proliferation experiments on two human prostatic carcinoma cell lines, DU 145 cells were found to be more sensitive to the cytotoxic effect of estramustine and nor-nitrogen mustard than PC-3 cells. Estramustine was, however, much more cytotoxic in both cell lines than nor-nitrogen mustard. Cytogenetic experiments revealed that estramustine produced a drastic increase of the mitotic index in both these cell lines. This increase could be accounted for by the arrest of cells in their first treatment-metaphase. The arrested metaphases exhibited all the characteristics commonly found for stathmokinetic agents such as colchicine and vinca-analogues. No mitotic arrest was found for nor-nitrogen mustard but chromosomal aberrations were found at toxic concentrations. Estradiol exhibited minimal toxicity and caused no mitotic arrest in these cell lines. The mitotic arrest induced by estramustine was found to be reversible on removal of the drug.

Carcinoma↗
PubMed1984

Cytotoxic properties of estramustine unrelated to alkylating and steroid constituents.

Using cultured HeLa S3 cells an ID50 of 2.5 micrograms/ml was found after a twenty-four-hour incubation with estradiol-17 beta- 3N -bis-(2-chloroethyl) carbamate (estramustine). Similar ID90 values were found in two Walker 256 rat carcinoma cell lines which were either sensitive or resistant to nitrogen mustards. Alkaline elution methodology revealed the complete absence of DNA strand breaks or cross-links in cells receiving up to 10 micrograms/ml estramustine for twenty-four hours. Nuclear uptake was 1.34 per cent of the available drug, one third of which was hydrophobically associated with the protein/phospholipid components of the nuclear matrix. In the human prostatic cell lines DU145 and PC3 , estramustine caused a drastic dose-dependent increase in the mitotic index. This increase resulted from an arrest of cells in metaphase, with highly contracted disoriented chromosomes present. Rapid reverse of the arrest on removal of drug resulted in cell death. Neither nor-nitrogen mustard nor estradiol demonstrated antimitotic properties. The lack of macromolecular alkylation together with the observed antimitotic effects predict a mechanism of action for estramustine which is distinct from either of its constituent components.

Alkylation↗
PubMed1984

Comparative genotoxicity of nitrogen mustard and nor-nitrogen mustard.

Nitrogen mustard and nor-nitrogen mustard were investigated in Salmonella typhimurium and human lymphocytes for genotoxicity. Point mutations were assessed using the plate test, the conventional spot test and a method in which the substances were not in direct contact with the microorganisms. Both compounds were active, but nor-nitrogen mustard was far more potent than nitrogen mustard in all bacterial systems. Cytogenetic experiments with human lymphocytes revealed that both compounds induced a dose dependent increase in chromosomal aberrations and sister chromatid exchanges, but that nitrogen mustard was 10 times more potent than nor-nitrogen mustard. Thus, the spectrum of activity for nor-nitrogen mustard and nitrogen mustard differ. Nor-nitrogen mustard was more effective in inducing point mutation damage than nitrogen mustard and a reversal of potency was found for cytogenetic damage. These results indicate that although these two substances induce the same type of DNA lesions the amounts of the different DNA adducts vary.

Chromosome Aberrations↗
PubMed1983

Acquired drug resistance is accompanied by modification in the karyotype and nuclear matrix of a rat carcinoma cell line.

A Walker 256 breast carcinoma cell line (WR) exhibiting a greater than 20-fold resistance to alkylating agents has been selected from a parent cell line (WS). Karyotypic heterogeneity was apparent, with a number of differences evident between WR and WS cells. The modal chromosome number for WS is 62; for WR, 54; double minutes were found only in WR, whereas spontaneous chromosomal aberrations were present in approx. 40% of the WS cells. No similar aberrations were observed in WR. Using SDS-gel electrophoresis and subsequent silver staining, differences in the profile of nuclear matrix proteins in WR and WS were observed. A diffuse band at approx. 70 kD in the WS was absent in WR cells. This protein was phosphorylated, together with a number of the other major matrix polypeptides. Levels of phosphorylated matrix proteins were approximately equivalent in both WR and WS cell lines, but matrix protein phosphorylation levels were approx. 2-fold higher than corresponding values for bulk nuclear proteins. Selective pressure of drug exposure has resulted in enhanced genetic stability in WR cells and observed karyotype differences are accompanied by modifications in the structural proteins of the nuclear matrix. Whether the observed differences are the cause or result of drug resistance remains to be established.

Animals↗
PubMed1983

Induction of micronuclei in the mouse. Revised timing of the final stage of erythropoiesis.

The early effects of X-rays, vincristine, cyclophosphamide, quinacrine dihydrochloride, cycloheximide, actinomycin D and hydroxyurea on the induction of micronuclei in mouse bone-marrow erythrocytes were studied. A significant increase in the incidence of micronuclei in polychromatic erythrocytes was seen as early as 5 h after a single treatment with vincristine, 6 h after treatment with X-rays and 10 h after treatment with cyclophosphamide. The cell kinetics of the mouse erythropoietic system described by Cole et al. (1981) can be modified to fit these results. According to this revised model, the final mitosis takes place only 5 h before the expulsion of the nucleus.

Animals↗
PubMed1983

Cytotoxicity of estramustine, a steroid-nitrogen mustard derivative, through non-DNA targets.

Estramustine is cytotoxic in HeLa and Walker 256 carcinoma cells (with or without acquired resistance to nitrogen mustards) at concentrations equivalent to other alkylating agents. Even at lethal estramustine levels, no damage to DNA occurs. Instead, a disproportionately high amount of intact estramustine binds hydrophobically to the structural proteins of the nucleus, the nuclear matrix. In HeLa cells, estradiol receptors are absent, and estradiol per se is not toxic. Thus, estramustine has a mechanism of action distinct from that of steroids and alkylating agents and may induce cytotoxicity through interactions with the proteins of the nuclear matrix.

Animals↗
PubMed1982

Growth and cell survival following treatment with estramustine nor-nitrogen mustard, estradiol and testosterone of a human prostatic cancer cell line (DU 145).

Estramustine at concentrations ranging from 3-40 x 10(-6) M inhibited the cell growth and clonogenic survival of a human prostatic carcinoma cell line (DU 145). This cell line was found to be unresponsive to estradiol and testosterone at concentrations ranging from 10(-9) M to 5 x 10(-5) M. Metabolism studies with estramustine showed that only a few per cent of the ester linkage was cleaved during the exposure period. This small amount of metabolism could possibly lead to the release of nor-nitrogen mustard, which was however found not to be as inhibitory as estramustine in this cell line. The results indicate that estramustine per se causes the cell death of hormone unresponsive human prostatic carcinoma cells in cell culture.

Carcinoma↗
PubMed1981

Studies on the mechanism of action of LS 1727, a nitrosocarbamate of 19-nortestosterone.

LS 1727, a nitrosocarbamate of 19-nortestosterone, was active against lymphoid, antimetabolite-sensitive, cell lines in vitro especially L1210 and Ehrlich ascites tumour lines. It was less effective against alkylating agent-sensitive lines such as the Walker 256 carcinosarcoma. These results suggested a possible antimetabolite mode of action but LS 1727 had no effect on deoxy-or ribonucleotide pool sizes in L1210 cells. Studies on macromolecular synthesis showed an early inhibition of DNA synthesis whilst RNA and protein synthesis continued for 24-48 hours. This was reminiscent of a classic alkylating agent-like effect. In vivo studies with specific alkylating agent-sensitive, or antimetabolite-sensitive tumours showed no antitumour activity although significant inhibition of Ehrlich ascites tumour cell growth was observed at high doses. In vitro cytotoxicity studies showed LS 1727 to be inactivated in the presence of mouse, rat and dog liver supernatants. This would explain the poor antitumour effects in vivo compared with the in vitro observations. Because LS 1727 is a nitrosocarbamate its possible mutagenic activity was investigated. LS 1727 was highly mutagenic but this property was also lost in the presence of a rat liver microsomal fraction. Although an effective cytotoxic agent in vitro LS 1727 is only effective in vivo at toxic doses.

Alkylating Agents↗
PubMed1981

Metronidazole: absence of mammalian cytogenicity.

Metronidazole was examined for cytogenicity in vivo and in vitro in mice and humans. In the micronucleus test in mice metronidazole was given either as, 2 oral doses 24 h apart, or, as a daily dose for 7 days. Neither forms of treatment produced any increase in the micronucleus frequency at doses up to 4 000 mg/kg. No increase in the chromosomal aberration frequency was found in human lymphocytes treated in vitro with metronidazole. The lymphocytes of 12 patients receiving metronidazole for vaginal trichomoniasis were examined for chromosomal aberrations. No increase for any type of aberration was found. Thus, metronidazole exhibits no cytogenetic activity in mammalian cells either in vitro or in vivo.

Animals↗
PubMed1978

The influence of caffeine on the mitomycin C-induced chromosome aberration frequency in normal human and xeroderma pigmentosum cells.

The clastogenic effect of mitomycin C (MC) was determined in two normal fibroblast cell lines and two xeroderma pigmentosum (XP) cell lines, a variant and a group A excision-deficient line. The group A xeroderma cell line was substantially more sensitive to MC than either the XP variant or the normal human cells. On caffeine post-treatment potentiation of the MC-induced aberration frequency occurred in all the cell lines. The XP variant cell line exhibited a distinctly higher sensitivity to caffeine than the classical XP or the normal human cell line.

Caffeine↗