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H Tapiero

Publications and source records attributed to H Tapiero.

At least 73 records · Page 4Linked to original sources
PubMed1982

Comparative uptake of adriamycin and daunorubicin in sensitive and resistant friend leukemia cells measured by flow cytometry.

Based on the fluorescence properties of adriamycin (ADM) and daunorubicin (DNR), uptake in sensitive and resistant Friend leukemia cells (FLC) was studied with the aid of the fluorescence activated cell sorter (FACS II). A quantitative cell by cell fluorescence intensity analysis showed a differential affinity of FLC to ADM and DNR. The cellular uptake of these two drugs was temperature dependent and was not hindered by sodium azide treatment; incorporation into isolated nuclei was not temperature dependent, nor hindered by sodium azide. Friend leukemia cell variants resistant to adriamycin (ADM-RFLC) and to daunorubicin (DNR-RFLC) were developed. The rate of uptake of ADM and DNR across the plasma membrane of these two cell variants was lower than in sensitive cells. Although these cells were crossresistant to both ADM and DNR, the drug-induced fluorescence intensity was distributed differently in the corresponding resistant cell variants. We suggest therefore that resistant is the consequence of changes induced in the plasma membrane components. These changes may differ according to which drug is used.

Animals↗
PubMed1982

Uptake, efflux, and hydrolysis of aclacinomycin A in Friend leukemia cells.

The kinetics of uptake by cells and nuclear incorporation of aclacinomycin A was studied in Friend leukemia cells. It was shown that uptake is a very rapid process. The intracellular concentration is maximum in 10 min and mainly (about 75%) localized in the nucleus. Most of the incorporated drug will disappear from the cell by a two-step mechanism: (a) efflux from the nucleus to the cytoplasm; and (b) deglycosidation at C-7 to the alkavinone form in the cytoplasmic fraction. The cellular uptake was temperature dependent but was not prevented by sodium azide treatment. We assumed, therefore, that it is related to the composition and to the dynamic structure of the cell surface membrane. Nuclear outward transport and deglycosidation were inhibited by sodium azide and low temperatures; this suggests that they are regulated by an active transport process and by an enzymatic activity, respectively.

Aclarubicin↗
PubMed1981

The effect of hexamethylene-bis-acetamide on multiparameter analysis of Friend leukemia cells.

Friend leukemia cells were induced to differentiate by hexamethylene-bis-acetamide (HMBA). The relationship between cell growth cell volume distribution, fluorescence intensity and fluorescence anisotropy of the membrane probe 1,6 diphenyl 1,3,5 hexatriene (DPH) was analyzed in differentiated and undifferentiated cells with the aid of the fluorescence activated cell sorter (FACS II). The induction of a differentiated state was associated with a decrease in cell volume and an increase of fluorescence anisotrophy. The inhibition of this induction by dexamethasone prevented the decrease of cell volume without affecting the increase of fluorescence anisotropy. We conclude therefore that the high degree of anisotropy is not correlated to the differentiated state nor with the volume of the cells.

Acetamides↗
PubMed1981

Effect of pH on fluorescence polarization of DMSO induced Friend leukemic cells.

The effect of DMSO on Friend leukemic cell membranes was investigated in an inducible cell line (FLC) and in cell variant resistant to DMSO induction (RFLC). Fluorescence polarization (P) studies carried out at 37 degrees C with diphenyl hexatriene (DPH) have shown that P values change according to the pH, being maximum in alkaline buffer. These changes were altered when cells were grown in the presence of DMSO. Changes in P values according to the pH were abolished by glutaraldehyde and by sodium azide. Fluorescence polarization analysis of FLC cell line carried out at 4 degrees C have shown higher P values which also changed according to the pH. In DMSO induced FLC or in RFLC grown with or without DMSO, these changes were not seen. It is therefore concluded that P value changes related to pH reflect changes in the lipid-protein interactions of cell surface membrane. It is also suggested that these interactions are altered by DMSO.

Animals↗
PubMed1980

Membrane dynamics of Friend leukaemic cells. I. Changes associated with cell growth.

The relationship between membrane dynamics and cellular growth of Friend leukaemic cells (FLC) was studied by fluorescence polarization (P) using diphenyl hexatriene (DPH). The P-value changes as a function of the state of the cells being maximum in the growing state. The P-value is also influenced by serum concentration and this effect appears to be a passive process.

Animals↗
PubMed1980

Membrane dynamics of Friend leukaemic cells. II. Changes associated with cell differentiation.

In a previous study, using fluorescence polarization (P) with diphenyl hexatriene (DPH), it was shown that growing and resting cells have different P-values. This property has now been used to investigate the membrane action of dimethylsulfoxide (DMSO) and hexamethylene bisacetamide (HMBA), two inducers of Friend leukaemic cell (FLC) differentiation. Both an inducible cell line (FLC) and a resistant variant cell line (RFLC), had the same characteristics regarding P-values. During the differentiation process in the FLC cell line, further changes in P-values were observed. In the resistant cell line, these changes in P-value were not seen. This suggests that these inducers of differentiation are acting at the cell membrane.

Acetamides↗
PubMed1979

The effects of mitogens on the expression of Epstein-Barr virus antigens in human lymphoid cell lines.

Treatment of human lymphoblastoid cells with either phytohemagglutinin (PHA), concanavalin A, Staphylococcus protein A, or polyinosinic acid-polycytidylic acid, in combination with 5-iodo-2' deoxyuridine (IUdR) markedly increased the expression of Epstein-Barr virus (EBV) early antigen (EA) relative to IUdR alone. Such treatment did not, however, modify the production of virus capsid antigen in any of the lymphoid cell lines tested. The effect of PHA on EA induction in Raji cells was not accompanied by changes in the incorporation of labeled precursors into cellular DNA, or in the intracellular concentration of either adenosine 3'5' cyclic monophosphate or guanosine 3'5' cyclic monophosphate. However, those mitogens that stimulated EA expression in Raji cells also increased the fluorescence polarization of 1,6 diphenyl 1,3,5-hexatriene-labeled Raji cells. The possible role of cell surface changes in the mitogen activation of latent EBV in human lymphoblastoid cells is discussed.

Antigens, Viral↗
PubMed1977

Isolation of single stranded transcription sites from human nuclear DNA.

Single stranded DNA (ss-DNA) isolated from nuclear DNA of human rhabdomyosarcoma (RD line) cells amounts to 2% of total DNA. As compared with native double-stranded DNA (ds-DNA), ss-DNA has a lower mean sedimentation coefficient, higher buoyant density, contains fewer repeated DNA sequences and a greater proportion of it can be hybridized to human RNAs (up to 35% and less than 8% for ds-DNA). The hybridization kinetics determined by S1 nuclease digestion and verified by other methods (hydroxylapatite chromatography, density gradient centrifugation and thermal melting) indicate that ss-DNA corresponds to a great number and variety of transcripts. These data are discussed as evidence for DNA strand dissociation in the course of gene activity.

Cell Line↗
PubMed1977

Single-stranded DNA from oncornavirus-infected cells enriched in virus-specific DNA sequences.

We previously found that a minor fraction of single-stranded DNA (ss-DNA) isolated from native nuclear DNA of normal chicken embryonic cells and cells of other species hybridized with bulk nuclear DNA or cellular RNA in great excess. At least one-third of ss-DNA belonging to the nonrepetitious part of the cell genome could be hybridized to homologous RNAs. In the present work, similar results were obtained with ss-DNA from cells of chickens infected by avian myeloblastosis virus (AMV). To investigate whether this enrichment of ss-DNA in transcribed DNA sequences involves provirus DNA, radioactive AMV RNA and cDNA copies of AMV RNA were used. Most of the 70S AMV RNA hybridized much faster to ss-DNA from productively infected leukemic cells than to bulk DNA. cDNA, either double-stranded or single-stranded, made in the presence of actinomycin D hybridized to total nuclear DNA with similar kinetics. In contrast, about half of the double-stranded cDNA molecules hybridized 40-50 times faster to ss-DNA than to total DNA, indicating that only one of the provirus DNA strands seems to be present in ss-DNA. This was confirmed by the fact that relatively insignificant amounts of the ss-cDNA molecules made in the presence of actinomycin D could be annealed to ss-DNA as compared with bulk DNA. These results indicate that actively transcribed DNA sequences can be selectively distributed in the ss-DNA fraction, probably because of single strand breaks in the vicinity of transcription sites.

Animals↗
PubMed1976

Isolation of single stranded DNA related to the transcriptional activity of animal cells.

Single stranded DNA (s.s.DNA) comprising 1-2% of the total nuclear DNA was isolated by an improved method of hydroxyapatite chromatography from native nuclear DNA3 of embryonic chick cells, labeled for several cell generations with 3H-thymidine. Small quantities of 3H-DNA were annealed with a large excess of unlabeled DNA or polysomal RNA from chick embryos. Hybridization kinetics (monitored by the use of SI nuclease digestion, hydroxyapatite chromatography and thermalfusion), indicated that s.s.DNA belongs to the non repetitious fraction of the cell genome. One third represents DNA sequences engaged in the transcription of messenger RNA's.

Animals↗
PubMed1974

Distribution of repetitious sequences in chick nuclear DNA.

By an improved method of hydroxylapatite chromatography, the reassociated sequences of chick nuclear DNA were isolated, and their base composition analysed. By increasing the amount of reassociation, the G + C content of the renatured sequences decreased progressively to reach a mean value corresponding to that of the total DNA. In order to study the distribution of the families, or group of families having different amount of reassociation, DNA was fractionated by CsC1 density gradient centrifugation. Fractions having different G + C content were obtained, and their reassociation rates analysed. At high C(o)t value of renaturation (C(o)t=50) the amount of reassociated sequences included in the high or in the low buoyant density DNA fractions was approximately the same, but their G + C content was as expected different. At lower C(o)t values of renaturation (between C(o)t of 0.2 and the C(o)t of 10), the results indicated an heterogeneity of the repeated sequences in the A + T rich DNA fractions, as compared to the G + C rich ones.

Animals↗