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Biomedical subjects

A Baldi

Publications and source records attributed to A Baldi.

At least 145 records · Page 8Linked to original sources
PubMed1988

Increment of DNA topoisomerases in chemically and virally transformed cells.

The activities of topoisomerases I and II were assayed in subcellular extracts obtained from nontumorigenic BALB/c 3T3 A31 and normal rat kidney (NRK) cell lines and from the same cells transformed by benzo[a]pyrene (BP-A31), Moloney (M-MSV-A31) and Kirsten (K-A31) sarcoma viruses, and simian virus 40 (SV-NRK). The enzymatic activity of topoisomerase I was monitored by the relaxation of negatively supercoiled pBR322 DNA and by the formation of covalent complexes between 32P-labeled DNA and topoisomerase I. Topoisomerase II activity was determined by decatenation of kinetoplast DNA (k-DNA). It was found that nuclear and cytoplasmic type I topoisomerase specific activities were higher in every transformed cell line than in the normal counterparts. These differences cannot be attributed to an inhibitory factor present in A31 cells. When chromatin was treated at increasing ionic strengths, the 0.4 M NaCl extract showed the highest topoisomerase I specific activity. Moreover, in this fraction the transformed cells exhibited the most significant increment in the enzymatic activity as compared with nontransformed cultures. Spontaneously transformed A31 cells showed topoisomerase I activity similar to that of extracts of cells transformed by benzo[a]pyrene. Topoisomerase II specific activity was also increased in SV-NRK cells, as judged by the assay for decatenation of k-DNA to yield minicircle DNA.

Animals↗
PubMed1988

Effects of human transforming growth factors on topoisomerases from normal fibroblasts.

Normal rat kidney fibroblasts (NRK-B F49) treated at transforming doses with a gamma-like TGF, partially purified from human melanoma, showed a 3 to 5 fold increase in DNA type II topoisomerase activity. A similar effect was observed using EGF and a partially purified alfa TGF from rabbit fetuses. DNA type I topoisomerase activity, from the same cells, was not significantly modified by treatment with these growth factors. Topoisomerase II stimulation was dependent on mRNA synthesis. The possible role of topoisomerase II in phenotypical cell transformation induced by TGF is discussed.

Animals↗
PubMed1987

DNA topoisomerase I from Leydig cells is modulated by luteinizing hormone and cyclic adenosine monophosphate.

The action of luteinizing hormone on topoisomerase I activity from rat Leydig cells was studied. Stimulation of the enzyme was observed after long-term (24 and 48 h) gonadotrophin treatment in in vivo experiments. No change could be detected for shorter times than 12 h using two different experimental approaches. Topoisomerase I was stimulated by cAMP in a whole cell extract in a phosphorylation-dependent manner. These results suggest that topoisomerase I could be a target for nuclear events induced by peptide hormone action.

Animals↗
PubMed1986

Rapid purification of topoisomerase I from human breast cancer cells by high-performance liquid chromatography.

The DNA regulatory enzyme topoisomerase I (TpI) from human breast cancer cells has been analyzed by high-performance liquid chromatography (HPLC) for the first time. Cells were homogenized in Tris buffer and TpI activity was extracted with 0.5 M sodium chloride. Negatively supercoiled plasmid pBR322 was used as the substrate to monitor TpI activity, as judged by relaxed products, analyzed on 1% agarose gels. HPLC in the anion-exchange mode (HPIEC) provided an approximately 6-fold purification of the enzyme. Enhanced purification was subsequently obtained by chromatography of a HPIEC eluate on size-exclusion columns (30- to 60-fold). Recovery of TpI from size-exclusion columns, whether used in multistep analysis or as the first step, was dependent on inclusion of organic solvent, 1-propanol (0.5%, v/v), in the mobile phase. Marked resolution of TpI activity was observed with HPIEC on a SynChrom CM-300 column. Enzyme activity was noted in the void volume, at 150-200 mM phosphate and at 250-350 mM phosphate. TpI purification was 10- and 120-fold in the latter two peaks, respectively. Silver-stained polyacrylamide gels of TpI-containing activity, eluted from a CM-300 column, showed considerable purification of all but the void volume fraction. A distinct protein band at approximately 88-90 kD was seen in the peak eluted from the CM-300 column with 250-350 mM phosphate. These results indicate that HPLC is useful for rapid purification of the labile enzyme, TpI, in the analysis of its structure-function relationship.

Breast Neoplasms↗
PubMed1986

Mitoxantrone affects topoisomerase activities in human breast cancer cells.

The effects of mitoxantrone, an antineoplastic DNA intercalator, on topoisomerase I and II were studied in two human breast cancer cell lines. A large increase of topoisomerase I activity was found when cells were exposed to various doses of mitoxantrone. Maximal effect was achieved with 20 and 40 ng/mL in T47D and MCF-7 cells respectively. The enhancement on topoisomerase I activity seemed to be reversible, to be dependent on time of exposure to the drug and to require cellular integrity. Type II topoisomerase was inhibited in T47D cells after treatment for one hour with 10 ng/mL of mitoxantrone and enzyme activity was undetectable at higher doses (40 ng/mL). This inhibitory effect did not take place in vitro unless the concentration of the intercalator was increased to 400-500 ng/mL.

Anthraquinones↗
PubMed1986

Estrogen receptor is associated with protein and phospholipid kinase activities.

The ability of immunopurified estrogen receptor from MCF-7 cells, incubated with [Y-32P]-ATP, to conduct its own phosphorylation and to phosphorylate phosphatidylinositol and 1,2-diacylglycerol was investigated. SDS gel electrophoresis analysis of the phosphorylated products revealed three major labeled phosphopeptides with molecular weights of 57, 47 and 43 kilodaltons. Other polypeptides were detected although in much smaller amounts. When the phosphorylation system was supplemented in vitro with phosphatidylinositol, phosphatidylinositol-4-P, or 1,2-diacylglycerol and the 32P-lipids were analyzed by thin layer chromatography, PI, but not 1,2-diacylglycerol, was converted in part to 32P-phosphatidic acid and phosphatidylinositol-4-32P. Phosphatidylinositol-4-P was also phosphorylated to phosphatidylinositol-4,5-32P. An estrogen receptor-negative cell line (MDA) produced negligible 32P-polypeptides and 32P-lipids under identical conditions used for MCF-7 cells.

Breast Neoplasms↗
PubMed1986

Severe pancytopenia due to copper deficiency. Case report.

A patient with copper deficiency and renal failure was suffering from pancytopenia. Marrow examination showed cytoplasmic and nuclear vacuolizations of the erythroid and myeloid series. These abnormalities disappeared after oral copper therapy. Possible mechanisms causing the pancytopenia are discussed. Copper supplementation is needed for patients receiving dietary changes.

Adult↗
PubMed1985

Transfer of oligosaccharide from oligosaccharide pyrophosphoryl dolichol to endogenous acceptor proteins in human breast malignant and normal tissues.

We have prepared dolichylpyrophosphoryl-[14C]-oligosaccharide (Dol-PP-oligosaccharide) from calf thyroid. Microsomal fractions from human breast tissues catalyzed the transfer of labeled oligosaccharide to endogenous acceptor proteins. Malignant tumors showed higher activity of the oligosaccharide transferring enzyme than normal tissue. With kojibiose (Kj), an inhibitor of (Glc3)-glucosidase, an increase in the radioactivity associated with glycoprotein was observed.

Animals↗
PubMed1985

Dolichol-sugar derivative synthesis in human breast cancer cell line (T47D). Effects of estrogens and antiestrogens.

In the present paper we report evidence about the formation of polyprenyl-phosphate monosaccharides, their elongation products and the assembly of dolichyl-diphosphate-oligosaccharide to endogenous T47D clone 11 proteins upon incubation with [14C]glucose. The influence of estradiol and two nonesteroidal antiestrogens -nafoxidine and tamoxifen- was examined on the dolichol pathway in T47D cell cultures. Estradiol (1 nM) does not change the rate of synthesis of dolichyl-phosphate-sugar derivatives in contrast to nafoxidine and tamoxifen both a micromolar concentration, which induce a remarkable decrease in the formation of dolichol-sugar derivatives. In addition, T47D cells were pretreated with nafoxidine or tamoxifen during one hour, fresh medium supplemented with estradiol was added to the cells simultaneously with [14C]glucose. Results indicated that estradiol after nafoxidine induces a slight increase in the polyprenyl-sugar derivatives formation, however, estradiol after tamoxifen decreases the synthesis of these substances.

Breast Neoplasms↗
PubMed1984

Incidence of estrogen, progesterone and prolactin receptors in human breast cancer.

Analysis of estrogen and progesterone cytosolic receptors (ER, PR) has been studied in human breast carcinoma. ER were assayed by sucrose density gradients and dextran coated-charcoal method. In a series of 109 ER+ breast tumors, 64.2% exhibited the 8S form, 25% the 4S and 11% both the 8S and 4S components. From a total number of 970 specimens, 776 (80%) were primary and 194 (20%) metastatic lesions. In the whole group, ER was positive in 77.6% and PR in 61.4%, while both receptors were found simultaneously in 59%. The concentration of ER was higher in postmenopausal women in comparison to premenopausal women. On the other hand, the levels of PR were rather similar in both groups. In primary lesions, PR was more frequently seen than in secondary tumors and the same holds true for the presence of ER and PR and the frequency of negative tumors. Specific prolactin (PRL) binding assay was performed in a group of 50 breast tumors. Positive and negative distribution was almost equal (48 vs 52%) and there was not correlation between PRL-R and ER. In addition, a limited group of male breast cancer, showed that three out of five patients possess only androgen receptors, whereas the remaining two cases were exclusively ER+. In summary, the present results indicate that the local incidence of steroid receptors in female breast carcinoma, are very likely similar to previous reports either in premenopausal and postmenopausal women and in primary and secondary lesions. The importance of PRL-R assay requires a further evaluation.

Breast Neoplasms↗
PubMed1983

Lipid-bound sugars in malignant human breast tumors. Partial characterization of mannosyl and glucosyl transferase activities.

Microsomal preparations from malignant human breast tumors catalyzed the transfer of mannose and glucose from GDP-[14C]-Man and UDP-[14C]-Glc into lipid-linked sugars and glycoprotein-like substances. As judged by several criteria the obtained lipid-linked monosaccharides behaved as dolichyl phosphate mannose and dolichyl phosphate glucose whereas lipid-linked oligosaccharides behaved as polyprenyl diphosphate derivatives. The optimum conditions for mannosyl- and glucosyl-transfer reactions and the effect of dolichyl phosphate, detergent and EDTA on incubation mixture were described.

Breast Neoplasms↗
PubMed1983

[Initial stages in the mechanism of protein glycosylation in human breast neoplasms].

It is discussed the rol of lipid intermediates in the biosynthesis of eucaryotic glycoproteins. Microsomal fraction isolated from malignant human breast tumors transferred Man and Glc from GDP-(14 C)-Man and UDP-(14 C)-Glc into lipid linked sugars and glycoproteins. The transference of Dol-PP-oligosaccharide to endogenous acceptor proteins was catalyzed for the same microsomal fraction.

Breast Neoplasms↗
PubMed1983

Campylobacter-induced toxic megacolon.

A case of a compromised host with myeloproliferative syndrome who presented with severe, relentless but nonbloody diarrhea, fever, severe colitis, and toxic megacolon is presented. Blood cultures grew out Campylobacter fetus ssp. fetus. Specific treatment with erythromycin reversed the grave clinical picture to normal in a 5-day period.

Campylobacter Infections↗
PubMed1981

Effects of estradiol-receptor complexes on the template activity of human breast tumor chromatin.

The interaction of estradiol-receptor complexes with isolated human breast tumor chromatin was studied under equilibrium conditions. Tumor samples were obtained from mastectomy specimens or biopsies. Chromatin was prepared from these samples and incubated with estradiolreceptor partially purified from cytosol rat uterus or from human hormone-dependent tumors. The two preparations gave similar results in the interactions with human chromatin. The in vitro transcription activity of chromatin from hormone-dependent tumors was dramatically increased by the addition of estradiol-receptor. Maximal enhancement was achieved with 70 fmoles of estradiol-receptor complex in the presence of 50 micrograms of chromatin. These changes in RNA synthesis were not detectable with chromatin isolated from autonomous breast tumors.

Animals↗