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Biomedical subjects

A Rahman

Publications and source records attributed to A Rahman.

At least 235 records · Page 13Linked to original sources
PubMed1991

Interaction between 5-fluorouracil, [6RS]leucovorin, and recombinant human interferon-alpha 2a in cultured colon adenocarcinoma cells.

Recombinant human interferon-alpha 2a (rIFN-alpha 2a; 500 or 5,000 IU/mL) or [6RS] leucovorin ([6RS]LV; 1 microM) each potentiated the cytotoxic activity of 5-fluorouracil (FUra) by 2.6- to 3.2-fold during 72 hr exposures in two human colon adenocarcinoma cell lines (GC3/c1; VRC5/c1). When all three agents were combined, FUra cytotoxicity was further potentiated by 3.2- to 4.3-fold (total 10- to 14-fold). Potentiation of FUra cytotoxicity occurred at clinically achieveable concentrations of rIFN-alpha 2a and [6RS]LV. Effects were reversed by dThd (20 microM), although the activity of CB3717, a quinazoline-based, specific inhibitor of thymidylate synthase, was not potentiated by rIFN-alpha 2a. Data suggest the requirement of a 5-fluoropyrimidine for biochemical modulation and interaction at the level of thymidylate synthase or DNA.

Adenocarcinoma↗
PubMed1990

Antitumor activity of liposome-encapsulated doxorubicin in advanced breast cancer: phase II study.

Previous studies in animals have demonstrated liposome-encapsulated doxorubicin (LED) has substantially less cardiac toxicity than free doxorubicin but retains antitumor activity. In a phase I clinical study of LED, the maximum tolerated dose was 90 mg/m2 and dose-limiting toxicity was considered to have been reached when granulocytopenia was produced. We used LED to treat 20 patients with advanced, measurable breast cancer. LED was given at doses of 60-75 mg/m2 every 3 weeks as an intravenous infusion. Regression of disease was objectively measured in nine patients; in five of these patients, complete regression of the index lesion occurred. The mean duration of the responses was 7 months. Hematologic toxicity consisted of grade 1-2 leukopenia in some patients. Gastrointestinal toxicity and mucositis were generally mild and tolerable. Alopecia occurred in all patients and usually was complete. Twelve patients received cumulative doses of LED of greater than 400 mg/m2 and were evaluated with radionuclide ventriculograms. In eight patients, the cumulative dose was greater than 500 mg/m2, and five had endomyocardial biopsies. Four of these biopsy results were Billingham grade 0, while one (cumulative LED dose, 750 mg/m2) showed grade 1 changes with mild myofibrillar loss and dilatation of the sarcoplasmic reticulum involving less than 5% of cardiac myocytes. Two patients had decreases in left ventricular ejection fraction. One of these patients had received a total dose of LED of 630 mg/m2 and had a decline of 13% in left ventricular ejection fraction, but had no clinical evidence of congestive heart failure and had a Billingham grade 0 endomyocardial biopsy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Morphological and molecular characterization of spontaneous myogenic differentiation in a human rhabdomyosarcoma cell line.

Skeletal muscle differentiation consists of an ordered withdrawal of committed cells from the cell cycle and their fusion to form multinucleated myotubes. To determine if differentiation of malignant myoblasts parallels that of normal skeletal muscle, a cell line (Rh28) was established from an alveolar rhabdomyosarcoma. Rh28 displays a constant population doubling time of 45-55 h until passage 60, when the doubling time progressively increases until proliferation ceases. Loss of proliferative capacity is associated with morphological evidence of differentiation to multinucleated myotubes, fusion, and the expression of numerous muscle-specific genes. In contrast to normal myogenic differentiation, multinucleated cells continue to synthesize DNA and express abundant c-myc transcripts. These observations suggest synchronous replication and possible arrest in the G2-phase of the cell cycle, since there was no evidence of mitotic activity in differentiated cells. Terminal differentiation of early passage Rh28 cells was induced in the presence of 10% dialyzed fetal calf serum but not by medium containing 2% undialyzed serum, suggesting a role for low molecular weight growth factors in this process. Our data indicate that the Rh28 cell line may be of value in elucidating the relationship between oncogenic transformation and differentiation in rhabdomyosarcoma.

Cell Differentiation↗
PubMed1990

Cellular pharmacology of 5-fluorouracil in a human colon adenocarcinoma cell line selected for thymidine kinase deficiency.

A human colon adenocarcinoma cell line (GC3TK-) was selected for thymidine kinase (TK) deficiency from cloned parental cells (GC3C1) by exposure to 5-bromodeoxyuridine (BrdUrd). The cellular pharmacology of 5-fluorouracil (FUra) and the influence of physiological concentrations of thymidine (dThd; 0.1 to 1 microM) on FUra cytotoxicity during brief exposure in both cell lines were examined. The uptake of FUra during a 1-hr drug exposure, its metabolism to ribo- and deoxyribonucleotides, incorporation into RNA, and inhibition of thymidylate synthase were similar in GC3C1 and GC3TK- cells as were the IC50 values for FUra (26 and 23 microM respectively). TK deficiency did not reduce the intracellular concentrations of FdUMP generated from FUra. In GC3C1, at FUra concentrations up to 100 microM, cytotoxicity was prevented by co-administration of dThd (0.1 to 20 microM). The relationship between cell survival and thymidylate synthase inhibition was close under these conditions. At higher drug concentrations, less dThd protection was observed, and none was detected in GC3TK- cells. Thus, the metabolism of FUra did not appear to be altered substantially in GC3C1 cells selected for TK deficiency. Also in these cells, at concentrations of FUra less than 100 microM, FUra cytotoxicity appeared to be mediated via the inhibition of thymidylate synthase.

Adenocarcinoma↗
PubMed1990

Formation of strand breaks and interstrand cross-links in DNA by methylglyoxal.

Methylglyoxal (MG), a dietary mutagen, is present in various frequently consumed beverages and foods and in cigarette smoke. A combination of S1 nuclease hydrolysis and alkaline unwinding assay was used to demonstrate the formation of single-strand breaks and interstrand cross-links in DNA upon treatment with MG. Calf thymus DNA, when treated with increasing concentrations of MG, showed an increasing degree of S1 nuclease hydrolysis. It also showed the formation of an increasing number of strand breaks per molecule as determined by an alkaline unwinding assay. Incubation of DNA with relatively higher concentrations of methylglyoxal or prolonged treatment gave increased thermal melting temperatures and an enhanced rate of reannealing after thermal denaturation. These results indicated the formation of interstrand cross-links. Upon treatment with MG, A-T base pair depleted DNA showed a reduced number of single-strand break formation. It also showed a significantly lower decrease in Tm as compared with MG-treated normal DNA. These results showed that under the conditions used, MG primarily reacts with A-T base pairs in duplex DNA.

Adenine↗
PubMed1990

Complexes involving quercetin, DNA and Cu(II).

The genotoxic flavonoid, quercetin, was shown to bind to both double-stranded and single-stranded DNA with concomitant changes in absorption spectrum and fluorescence emission spectrum of quercetin. Quercetin and Cu(II) were shown to form a charge transfer complex that decayed in oxygen-dependent reaction(s) and this decay was accelerated by DNA. Analysis of the three component system, DNA--querectin--Cu(II), led to a discussion of the complexes likely to be involved in the initial reactions that lead, ultimately, to strand scission of DNA.

Copper↗
PubMed1990

Strand scission in DNA by quercetin and Cu(II): identification of free radical intermediates and biological consequences of scission.

Quercetin was shown to reduce oxygen to superoxide. In the presence of Cu(II), the hydroxyl radical was formed. The strand scission of DNA was shown to occur under conditions in which Cu(II), quercetin and either hydrogen peroxide or oxygen were present and superoxide was not a necessary intermediate. Strand scission involved the hydroxyl radical and a radical DNA intermediate. The strand scission reaction was shown to account for the biological activity of quercetin as assayed by bacteriophage inactivation.

Copper↗
PubMed1990

Specificity of the in vitro interaction of methylfurfural with DNA.

Methylfurfural (MF) or 5-methyl 2-furaldehyde is a dietary mutagen and is present in various food products and beverages. Alkaline unwinding of calf thymus DNA and the protection of cleavage sites in lambda phage DNA from the action of various restriction enzymes was used to study the interaction of MF with DNA. Alkaline unwinding experiments showed the formation of an increasing number of strand breaks in duplex DNA, both with increasing MF concentration and time of reaction. Treatment of lambda phage DNA with MF protected cleavage with restriction endonucleases EcoRI and EcoRI* but not with SmaI and HaeIII. These results indicate that under the conditions used MF reacts exclusively with AT base pairs. A minimum of three to four consecutive AT base pairs is required for this reaction. This was determined by the use of restriction enzymes whose hexanucleotide recognition sequences contain subsets of AT base pairs. Indirect evidence further indicates that modification (possibly alkylation) of DNA bases and phosphates may also occur.

Alkylating Agents↗
PubMed1990

A phase I clinical trial and pharmacokinetic evaluation of liposome-encapsulated doxorubicin.

We have treated 14 cancer patients with liposome-encapsulated doxorubicin (LED) at doses of 30, 45, 60, and 90 mg/m2. Nausea and vomiting, phlebitis, and stomatitis were minimal or absent at each dose, but dose-limiting granulocytopenia occurred at 90 mg/m2. Thrombocytopenia and/or anemia also occurred in all patients treated at 60 or 90 mg/m2. Complete alopecia was seen in one of three cases at 60 mg/m2 and all cases at 90 mg/m2. No hepatic, renal, or other major organ toxicities were encountered. Clinical cardiac toxicity did not occur in any patient, but the cumulative doxorubicin doses in 13 cases were less than 400 mg/m2. The plasma elimination of LED out to 24 hours was analyzed in terms of a two-compartment model. Depending upon the dose and the infusion time, maximum plasma concentrations ranged from 2.6 mumol/L to 36.89 mumol/L and the area under the plasma concentration x time curve (AUC) values ranged from 1.86 mumol/L x h/L to 49.57 mumol x h/L. These values are significantly higher than those expected for free doxorubicin. Urinary excretion of LED was approximately 10% after 24 hours. Doxorubicinol and doxorubicinone appeared at low levels in plasma 12 to 24 hours after injection. LED pharmacokinetics differ from those of free drug by the higher plasma levels and AUC of doxorubicin achieved, and by the low conversion of LED to metabolites. Overall, LED was well tolerated and produced only moderate nausea and vomiting and little stomatitis at myelosuppressive doses. The study also suggested that LED produces less venous sclerosis than free doxorubicin, but this requires further clinical verification.

Adult↗
PubMed1990

No association between herpes simplex virus type-2 seropositivity or anogenital lesions and HIV seroconversion among homosexual men.

Recent reports have suggested that HSV-2 infection and associated anogenital ulcerations represent an important risk factor for acquisition of HIV infection. Although this is an appealing biological hypothesis, inferences drawn for homosexual men, as well as other at-risk populations, must be made after careful consideration of methods to control for potential confounding data. This report utilized a nested case-control study in which 49 homosexual HIV seroconverters were compared to 49 homosexual seronegative men matched on the prior level of receptive anal intercourse. No differences were observed for prior HSV-2 infection, since 21/49 (43%) of matched HIV seronegative men were HSV-2 antibody positive and 21/49 (43%) of HIV seroconverters were HSV-2 antibody positive at the visit 6 months before HIV seroconversion (odds ratio of 1.0, 95% confidence limits of 0.3-2.9) Similar findings were also observed for prior HSV-1 infection. Both self-reported symptoms and physical exam findings suggestive of HSV infection were rare during the 12 months prior to seroconversion and not associated with HIV seroconversion. These data do not support HSV-2 as a risk factor for seroconversion to HIV among homosexual men studied. These results should not be generalized to heterosexual transmission of HIV, particularly in Africa, where both an increased prevalence of genital ulcerative diseases and different etiologies have been observed.

Adult↗
PubMed1989

Anti-laminin receptor antibody targeting of liposomes with encapsulated doxorubicin to human breast cancer cells in vitro.

The tumor cell laminin receptor is a cell-surface protein that binds laminin with high affinity (Kd = 1.0 nM). The putative ligand-binding domain of the laminin receptor has been molecularly cloned and sequenced. In the present study, we used the predicted amino acid sequence of the laminin receptor to generate synthetic peptide antigens and produced immunoglobulin M (IgM) anti-laminin receptor monoclonal antibodies. The disulfide bond group of the IgM molecule was used to couple the antibodies to the surface of liposomes encapsulating doxorubicin. The anti-laminin receptor monoclonal antibodies coupled to the liposomes bound avidly to the surface of MDA-MB-435S (MDA-435) human breast carcinoma cells, which have high numbers of laminin receptors. These antibody-coupled liposomes exhibited a low degree of binding to Hs 578Bst (Hs 578) normal human breast epithelial cells, which express a low number of laminin receptors. Excess liposomes competed for the binding of unbound laminin to the tumor cell surface, and excess laminin competed for binding with the liposomes. Antibody-coupled liposomes encapsulating doxorubicin were specifically more efficient in inhibiting colony formation by MDA-435 cells in vitro than unbound doxorubicin or liposomes without anti-laminin receptor monoclonal antibodies. Unbound doxorubicin inhibited thymidine uptake by 10%-20% in both Hs 578 and MDA-435 cells, whereas the antibody-coupled liposomes encapsulating doxorubicin inhibited thymidine uptake by 90% in MDA-435 cells but only 15% in Hs 578 cells. Thus, use of anti-laminin receptor monoclonal antibodies coupled with liposomes encapsulating doxorubicin represents a new strategy for selective targeting of doxorubicin to carcinoma cells with exposed laminin receptors.

Antibodies, Monoclonal↗
PubMed1989

Elliptinium: phase II study in advanced measurable breast cancer.

Eighteen patients with advanced measurable breast cancer were treated with elliptinium acetate 100 mg/m2 x 3 days every 3 weeks. Fourteen of these patients had failed prior chemotherapy. Two patients had an objective tumor response of greater than 4 weeks. Myelosuppression, renal insufficiency and thrombophlebitis were rarely encountered and alopecia was not seen at all. This study demonstrates that elliptinium has minimal activity in recurrent breast cancer with a favorable toxicity profile.

Adenocarcinoma↗
PubMed1989

A phase I/II study of intraperitoneally administered doxorubicin entrapped in cardiolipin liposomes in patients with ovarian cancer.

A phase I and II clinical trial of intraperitoneally administered liposome-encapsulated doxorubicin in patients with advanced ovarian cancer is being evaluated. Doxyrubicin liposomes were prepared with cardiolipin, phosphatidyl choline, cholesterol, and sterarylamine and sized by flow cytometry before administration. Fifteen patients have been treated with 42 cycles of intraperitoneal liposome-encapsulated doxrubicin. Liposome-encapsulated doxorubicin in 2 L of normal saline solution was infused over 1 hour through an infusaport into the peritoneal cavity with a dwell time of 4 hours every 21 days. Liposome-encapsulated doxorubicin has been administered at escalating doses up to 100 mg/2 L and has been well tolerated. Increased bowel motility with mild-to-moderate abdominal distress has been encountered during the first 24 hours after administration. There has been one patient with presumed chemically induced peritonitis after a temperature elevation to 39.5 degrees C. There has been no myelosuppression, abnormalities of liver function tests, or alopecia. Nausea and vomiting were minimal. Liposome-encapsulated doxorubicin was extravasated in two patients without sequelae. Drug levels were measured after completion of infusion. At a dose of 70 mg, the peak intraperitoneal concentration was 28.6 micrograms/microliter, which was reduced to 23.6 micrograms/microliter by 2 hours. Concurrent plasma levels were in the range of 0.2 to 0.5 micrograms/microliter. A similar pattern was observed at other doses. The maximum tolerable dose has not yet been obtained. There were three responders in the 10 evaluable patients. The preliminary experience with intraperitoneal liposome-encapsulated doxorubicin is encouraging.

Adult↗
PubMed1989

Determination of ranitidine in plasma by high-performance liquid chromatography.

A high-performance liquid chromatographic method has been developed for the determination of ranitidine in plasma. Ranitidine was extracted with acetonitrile by adding it to the plasma and then salting it out with potassium carbonate. The chromatographic column was 5-microns ODS silica, the mobile phase being acetonitrile-7 mM triethylammonium ion in phosphoric acid (pH 3.00) (30:70, v/v). The ranitidine peak was monitored at a wavelength of 315 nm, the retention time for ranitidine being 4.6 min. A limit of detection of 3 ng ml-1 was obtained for a 100-microliters injection of ranitidine. The method was found to be reproducible with a relative standard deviation (RSD) between 0.8-5.3% (n = 5) over the concentration range 25-80 ng ml-1 in plasma. The ranitidine concentration was determined in 18 different patients' plasmas. Ranitidine and its metabolites ranitidine S-oxide, ranitidine N-oxide and desmethyl-ranitidine, were also studied for chromatographic resolution from each other. It was shown that a group of common drugs did not interfere with ranitidine determination.

Chromatography, High Pressure Liquid↗