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Biomedical subjects

R S Gupta

Publications and source records attributed to R S Gupta.

At least 163 records · Page 9Linked to original sources
PubMed1988

Cross resistance pattern towards anticancer drugs of a human carcinoma multidrug-resistant cell line.

Puromycin-resistant (PurR) mutants/variants of a human carcinoma cell line (HeLa), which show greatly reduced cellular uptake of 3H-puromycin and 3H-daunomycin have been isolated after one- and two-step selections in presence of the drug. The cross-resistance pattern of these mutant cell lines towards numerous anticancer drugs and other inhibitors has been examined. Both the first- and the second-step mutants exhibited increased resistance to a number of antimitotic drugs (viz. vinblastine, vincristine, colchicine, taxol and maytansine), several protein synthesis inhibitors (viz. chalcomycin, bruceantin, harringtonine, homoharringtonine), a large number of DNA interactive compounds (viz. aclacinomycin A, actinomycin D, adriamycin, m-AMSA, chromomycin A3, coralyne sulphoacetate, daunomycin, ellipticine, mithramycin, mitoxantrone, 5-methoxysterigmatocystin, rubidazone, variamycin, VM26 and VP16-213) and a number of other drugs acting via other mechanisms (viz. Baker's antifol, nitidine chloride and rhodamine 123). Whereas the first-step mutants showed stable resistance to these drugs, the second-step lines partially reverted upon growth in non-selective medium. Further, treatment of these mutant lines with non-cytotoxic doses of the calcium channel blocker verapamil reverted or abolished their resistance to the above drugs in a dose-dependent manner. In contrast to the above compounds, the PurR mutants showed no significant cross-resistance to a large number of other drugs which included asaley, AT-125, 5-azacytidine, azaserine, cyclocytidine, cis-platin, cytosine arabinoside, chlorambucil, chlorpromazine, alpha-difluoromethyl ornithine, 5-fluorouracil, ftorafur, gallium nitrate, hydroxyurea, ICRF-159, ICRF-187, imipramine, methotraxate, 6-methylmercaptopurine riboside, mycophenolic acid, melphalan, mitomycin C, methyl GAG, nafoxidine, reumycin, 6-selenoguanosine, 6-thioguanine, tiazofurin, tamoxifen, thalicarpine, tiapamil and verapamil). These cross-resistance data should prove useful in developing suitable drug combinations to which cellular resistance would not develop readily.

Animals↗
PubMed1988

Robinow syndrome.

Explore the source record for details and available documents.

Abnormalities, Multiple↗
PubMed1987

Human cell mutants affected in the interaction of the 12 beta-OH group of cardiac glycosides with the digitalis receptor.

The cross-resistance patterns of two different types of mutants of HeLa cells selected for resistance to the digoxin analog SC4453 (SCR mutants) in which the Na+/K+-ATPase is affected [A. Chopra and R. S. Gupta, J. biol. Chem. 261, 2034 (1986)], and towards numerous cardiac glycosides (CGs) and genins, were examined. One type of SCR mutant (designated as group C) was highly resistant to all CGs and genins investigated. In contrast, the other type of SCR mutant (group D) showed a high degree of cross-resistance towards selected CG derivatives (viz. digoxin, SC4453, digoxigenin, lanatoside C, alpha- and beta-methyldigoxin, dihydrodigoxin, alpha- and beta-acetyldigoxin, alpha,beta-diacetyldigoxin), all of which contained a free 12 beta-OH group in the steroid structure. Slight cross-resistance of the group D mutants was also observed for other compounds (viz. ouabain, ouabagenin, dihydroouabain) that contain a free 11 alpha-OH group in the molecule. However, these mutants exhibited no cross-resistance to other CG derivatives, which either lacked the above groups (viz. digitoxin, digitoxigenin, dihydrodigitoxin, digitoxigenin mono- and bisdigitoside, nerifolin, gitoxigenin, gitoxin, 16-acetylgitoxin, lanatosides A and B, cymarin, convallatoxin, oleandrin, strophanthidin, actodigin and bufalin) or in which the 12 beta-OH group was acetylated (viz. as in the case of 12-acetyldigoxin). Since the 12 beta-OH group is not required for CG-like activity, to account for these observations it is suggested that the genetic lesion in the group D mutant leads to the creation of a new binding site in the digitalis receptor, which specifically interacts with the 12 beta-OH group (the site presumably also interacts weakly with the 11 alpha-OH group) and either prevents or distorts the binding of the compounds to the drug binding site on the receptor. Further investigations with the different classes of CG-resistant mutants at the molecular level should prove very useful in identifying the drug receptor site and in understanding how these drugs interact with it.

Cardiac Glycosides↗
PubMed1987

Identification of 2-benzimidazolyl urea as a new antimitotic compound based on cross resistance studies with nocodazole resistance mutants of CHO cells.

The cross resistance patterns of a set of nocodazole-resistant (NocR) and podophyllotoxin-resistant (PodR) mutants of Chinese hamster ovary cells, which exhibit highly specific cross resistance towards compounds that show nocodazole-like antimitotic activity, towards a large number of benzimidazole derivatives have been examined. Of the various compounds examined, the NocR and the PodR mutants were found to exhibit increased cross resistance towards only 2-benzimidazolyl urea, indicating that this compound may possess similar biological activity as nocodazole. The nocodazole-like antimitotic activity of 2-benzimidazolyl urea has been confirmed by its ability to block cells in mitosis, and by its competition of 3H-podophyllotoxin binding to microtubule proteins in cell extracts. The nocodazole-like behavior of 2-benzimidazolyl urea and lack of similar activity in other benzimidazole derivatives examined, provides valuable information regarding structural features that are required for this type of biological activity.

Animals↗
PubMed1987

Species-specific differences in the toxicity of rhodamine 123 towards cultured mammalian cells.

The toxicity of cationic fluorescent dye, rhodamine 123, towards a number of independently established cell lines from three different species, namely human, mouse, and Chinese hamster, has been examined. All of the cell lines from any one species that were examined were found to exhibit similar sensitivities towards rhodamine 123 and no appreciable differences were observed between the normal and transformed cell types. However, in comparison to the cells of human origin, mouse and Chinese hamster cell lines exhibited about 10-fold and 70-fold higher resistance, respectively, and these differences appeared to be species related. In contrast to rhodamine 123, no differences in relative toxicities for these cell lines were observed for the structurally related neutral dye, rhodamine B. Fluorescence studies with rhodamine 123 show that in comparison to mouse and Chinese hamster cells, the more sensitive human cells show much higher uptake/binding of the drug, and a good correlation was seen in these studies between the extent of dye uptake/binding and the relative sensitivities of cell lines to rhodamine 123. These results provide evidence that the observed species-related differences in cellular toxicities are due to differences in the cellular uptake/binding of the dye.

Animals↗
PubMed1987

Absence of gene amplification in human cell mutants resistant to cardiac glycosides.

In HeLa cells, four different types of mutants resistant to cardiac glycosides viz. ouabain and SC4453, which differ from each other in cross resistance pattern, have been isolated after single-step selections [J Biol Chem 260 (1985) 6843-6850; J Biol Chem 261 (1986) 2034-2040]. Using cloned cDNA probes specific for the alpha and beta subunits of Na+/K+ ATPase, these mutants have been investigated for amplification and/or increased transcription of Na+/K+ ATPase genes. Results from dot blots, Southern and Northern hybridizations provide evidence that these mutants do not involve any amplification or increased transcription or gross structural alterations in Na+/K+ ATPase genes of their transcripts. Similar results were obtained with the mutant cells grown either in the absence or presence of cardiac glycosides, the latter conditions of which cause 3-4-fold increase in the resistant form of the enzyme within the mutant cells. These results are consistent with the inference that resistance to cardiac glycosides in these mutants may be due to specific point mutations within the structural gene(s) of Na+/K+ ATPase leading to an altered enzyme that is resistant to inhibition by different cardiac glycosides.

Cardiac Glycosides↗
PubMed1987

Effect of chlorpromazine and trifluoperazine on cytoskeletal components and mitochondria in cultured mammalian cells.

Antipsychotic drugs such as chlorpromazine and trifluoperazine have been implicated to mediate their action by inhibiting calmodulin, the general calcium regulatory protein in eukaryotic cells. We observed that both these drugs were cytotoxic to different mammalian cell types at concentrations two- to three-fold lower than those required to inhibit calmodulin-dependent phosphodiesterase activity. These drugs also caused shrinkage and rounding of chicken embryo fibroblast cells without affecting any of the cytoskeletal components, viz. microtubules, microfilaments and intermediate filaments. However, at physiological concentrations of these drugs, a major change was observed in mitochondria which assumed rounded and swollen shapes and concentrated towards the perinuclear region of cells. These studies provide evidence that in contrast to earlier reports, cytoskeletal components are not the primary targets of these drugs. It is suggested that mitochondria may be one of the first structures to be affected by these drugs and the consequent energy depletion may lead to the other observed effects.

Actin Cytoskeleton↗
PubMed1987

Etoposide (VP16) and teniposide (VM26): novel anticancer drugs, strongly mutagenic in mammalian but not prokaryotic test systems.

The mutagenic effect of the antineoplastic drugs VP16 (etoposide; 4'-demethylepipodophyllotoxin-ethylidene-beta-D-glucopyranoside) and VM26 (teniposide; 4'-demethylepipodophyllotoxin-thenylidene-beta-D-glucopyr ano side) in mammalian and prokaryotic test systems have been compared. Both VP16 and VM26 which interact with mammalian DNA topoisomerase II, are strongly mutagenic in Chinese hamster ovary cells as indicated by the induction of mutations at the hypoxanthine-guanine phosphoribosyl transferase and adenosine kinase loci, and production of DNA strand breaks and sister-chromatid exchanges. Mouse L cells treated with these drugs also show a large dose-dependent (0.05-0.2 microgram/ml for VM26 and 0.5-1.5 micrograms/ml for VP16) increase in the frequency of 6-thioguanine-resistant mutants and extensive fragmentation of cellular DNA. In contrast to the results obtained with mammalian cells, VP16, which was extensively investigated, showed no increase in revertant frequencies in the Salmonella typhimurium strains TA98 and TA100 at concentrations up to greater than 500 micrograms/plate, in either the absence or presence of an exogenous rat liver activation system. However, a very weak mutagenic response to VP16 and VM26 (less than 2-fold increase in revertant frequency) at very high drug concentrations was observed in the strain TA102. VP16 also failed to show any mutagenic response (up to greater than 500 micrograms/ml) in an excision repair-proficient Escherichia coli strain 113/143 employing two different forward mutation detection systems [viz. ability to grow in galactose (Gal+) or in presence of 5-methyltryptophan], which are capable of detecting various types of genetic lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Mitochondrial binding of a protein affected in mutants resistant to the microtubule inhibitor podophyllotoxin.

Specific antibodies to a protein P1 Mr approximately equal to 63,000) from Chinese hamster ovary cells, which is affected in mutants resistant to the microtubule inhibitor, podophyllotoxin, and behaves like a microtubule-related protein by certain criteria [14], have been raised. The antibody reacts specifically with the P1 protein in one- and two-dimensional immunoblots, and a cross-reacting protein of similar molecular mass and electrophoretic mobility is also found in cells from various vertebrate and invertebrate species. The observed similarity in the peptide maps of the cross-reacting protein from human, mouse, Chinese hamster and chicken cells indicates that the structure of this protein should be highly conserved. However, no P1-antibody cross-reacting protein was observed in plants (corn, mung), fungus (Neurospora crassa), yeast (Saccharomyces cerevisiae) and bacteria (Escherichia coli and Salmonella typhimurium). Immunofluorescence studies with the P1-antibody show that, in interphase cells of various cross-reacting species, it bound specifically to mitochondria which were associated and distributed on and along the length of microtubules. Similar association and codistribution of mitochondria and microtubules were not observed in mitotic cells. Some implications of the mitochondrial localization of the protein P1 and the observed association between microtubules and mitochondria are discussed.

Actin Cytoskeleton↗
PubMed1987

Mitochondrial matrix localization of a protein altered in mutants resistant to the microtubule inhibitor podophyllotoxin.

Specific antibodies to a protein designated P1 (Mr approximately equal to 63,000), which is specifically altered in mutants resistant to the microtubule inhibitor podophyllotoxin, bind to mitochondria in cells of various vertebrate and invertebrate species (Eur. J. Cell Biol. 44, 278-285 (1987); Can. J. Biochem. Cell Biol. 63, 489-502 (1985)). To investigate the relationship of this protein to mitochondria, rat liver mitochondria have been purified and immunoblot analysis with these provide evidence that the P1 protein is a major component of mitochondria. Two-dimensional gel electrophoretic analysis of mitochondrial proteins from Chinese hamster ovary (CHO) cells also show the P1 protein to be a major mitochondrial component. Subfractionation of rat liver mitochondria into various compartments indicates that the P1 protein is mainly associated with the matrix fraction. Effect of treatment of CHO cells with mitochondrial inhibitors on the synthesis of P1 protein was also investigated. Treatment with the K+ ionophores nonactin and valinomycin, which abolish mitochondrial membrane potential, inhibited synthesis of the mature forms of the P1 protein as well as a number of other mitochondrial proteins, as seen by two-dimensional gel electrophoresis of labeled polypeptides. Treatment of the podophyllotoxin-resistant mutant of CHO cells with the above inhibitors affected both the wild-type and the mutant forms of the P1 protein in a similar manner. Concomitant with the disappearance of the above proteins, new basic proteins of higher molecular masses, related to the P1 and other proteins by peptide analysis, were observed in the drug-treated cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Synthesis and structure-activity relationships among glycosidic derivatives of 4'-demethylepipodophyllotoxin and epipodophyllotoxin, showing VM26- and VP16-213-like activities.

We have synthesized acetal and ketal derivatives of 4'-demethylepipodophyllotoxin-beta-D-glucoside (DMEPG) and epipodophyllotoxin-beta-D-glucoside (EPG) with a number of different aldehydes (viz. acetaldehyde, propionaldehyde, 2-thiophenecarboxaldehyde, 3-thiophenecarboxaldehyde, 2-furancarboxaldehyde, benzaldehyde, phenylacetaldehyde, hydrocinnamaldehyde) and acetone. The cross resistance of these compounds towards a set of Chinese hamster ovary cell mutants resistant to either podophyllotoxin (PodR mutants) or VM26 (VpmR mutants) which exhibit mutually exclusive cross-resistance patterns toward compounds that show either podophyllotoxin- or VM26-like activities have been examined. Results of our studies show that, with the exception of 2-furan derivatives, all the remaining acetals and ketals of DMEPG and EPG showed similar cross-resistance patterns towards the VpmR and the PodR mutants, as seen with VM26 and VP16-213. These results provide strong suggestive evidence that all of these derivatives (except 2-furan) possess biological activities similar to VM26 and VP16-213, and that their cellular toxicities were due to this type of activity. The VM26-like behavior of different EPG derivatives, which lack the free 4'-OH group, provide evidence that a free 4'-OH group is not essential for VM26-like activity. However, in comparison to the EPG derivatives, the corresponding DMEPG compounds showed 10- to 30-fold higher activities, indicating an enhancing effect of the free 4'-OH group on this kind of activity. Some of the newly synthesized DMEPG and EPG derivatives show higher activity in comparison to VM26 and VP16-213, and structure-activity relationship among this group of compounds is discussed.

Antineoplastic Agents↗
PubMed1987

Synthesis and biological activities of the C-4 esters of 4'-demethylepipodophyllotoxin.

To investigate the structure-activity relationship among podophyllotoxin (POD) derivatives, a number of different esters of the C-4 hydroxyl group of 4'-demethylepipodophyllotoxin (DMEP) and 4'-benzyloxycarbonyl-4'-demethylepipodophyllotoxin have been synthesized. Some of these esters contained the same R groups of aldehydes (e.g. methyl, ethyl, 2-thiophene, phenyl) which, when condensed to either 4'-demethylepipodophyllotoxin-beta-D-glucoside or epipodophyllotoxin-beta-D-glucoside, have yielded compounds with VM26-like activities. The cross-resistance patterns of the DMEP esters towards a set of either POD-resistant (PodR) or VM26-resistant (VpmR) mutants of Chinese hamster ovary (CHO) cells which exhibit highly specific cross-resistance patterns toward POD- or VM26-like compounds have been determined. The PodR mutants were found to exhibit proportionately increased cross resistance toward the various DMEP esters, whereas no increased resistance was observed for the VpmR mutants. The observed cross resistance behavior of the DMEP esters strongly suggests that all of these analogues possess similar biological activity as POD and that none of these act in the same manner as VM26 or VP16-213. Treatment of CHO cells with the various DMEP esters caused a large increase in the mitotic index of cells, which supports the above inference. The POD-like behavior of different DMEP esters indicates that specific attachment of the R group to the C-4 glucoside moiety is required for VM26-like activity. The structure-activity studies on various DMEP esters provide information regarding the role of substituents at the C-4 and C-4' positions on POD-like activity of the compounds.

Antineoplastic Agents↗
PubMed1986

Biochemical and cross-resistance studies with HeLa cell mutants resistant to cardiac glycoside SC4453. Regulation of the resistant form of Na+/K+-ATPase in the mutant cells.

In HeLa cells, stable mutants which are between 25-to about 200-fold resistant to the cardiac glycoside derivative SC4453 (a digoxin analog which contains a pyridazine ring in place of a lactone ring in the C-17 position) have been isolated after a single step selection in the presence of the drug. Based on their cross-resistance pattern towards various cardiac glycosides, the mutants resistant to SC4453 (SCR mutants) appear to be of two different kinds and they differ from the two classes of ouabain-resistant mutants described previously (Gupta, R. S., and Chopra, A. (1985) J. Biol. Chem. 260, 6843-6850). One type of SCR mutants (designated as group C) exhibit a high degree of cross-resistance to all cardiac glycosides and their genins (viz. ouabain, digitoxin, digoxin, digoxigenin, convallatoxin, gitoxin, strophanthidin, and bufalin). In contrast, the second type of SCR mutant (group D) exhibit considerable resistance to only SC4453, digoxin, and digoxigenin, but showed very little or no cross-resistance to the other cardiac glycosides examined. The cross-resistance of the mutants towards cardiac glycosides was highly specific as they exhibited no cross-resistance towards a large number of other structurally and functionally related compounds (viz. ethacrynic acid, sanguinarine nitrate, penicillic acid, methyl quinolizinum bromide, 5,5'-diphenylhydantoin, deoxycorticosterone, vanadium pentoxide, and adriamycin). The cellular uptake of 86Rb in the mutant cells was found to be resistant to specific cardiac glycosides. Studies on the sensitivity of plasma membrane Na+/K+-ATPase to cardiac glycosides show that about 10-15% of the enzymic activity in the mutant cells was highly resistant to inhibition by the specific drugs to which the mutants exhibit increased resistance. Very interestingly, when the mutant cells are grown in cardiac glycoside-containing medium, the resistant form of the enzyme accounts for about 50-60% of the total enzyme. These results show that both classes of SCR mutants are affected in Na+/K+-ATPase and that the amount of the resistant enzyme in the mutant cells is regulated in response to cardiac glycosides.

Cardiac Glycosides↗