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Biomedical subjects

A Rahman

Publications and source records attributed to A Rahman.

At least 271 records · Page 15Linked to original sources
PubMed1986

Antitumor and toxicity evaluation of free doxorubicin and doxorubicin entrapped in cardiolipin liposomes.

The antitumor activity of free doxorubicin and doxorubicin entrapped in cardiolipin liposomes was evaluated in P388 ascitic leukemia, disseminated Gross leukemia, and advanced mammary carcinoma. In P388 leukemia, free drug and drug entrapped in liposomes demonstrated equivalent antitumor activity at doses of 2.2 and 4.4 mg/kg, demonstrating 52% and 69% ILS (increase in life-span), respectively. Free doxorubicin at a dose of 10 mg/kg was superior, producing a 185% ILS against 82% with liposomal doxorubicin. With an increase in administered dose the antitumor response with liposomal doxorubicin was much more pronounced; at doses of 20 and 25 mg/kg the ILS was in excess of 376%, with five of ten mice surviving tumor-free. In Gross leukemia, the optimum dose of free doxorubicin, 10 mg/kg, brought about 186% T/C (median survival in treated mice over that in controls, X 100), whereas with liposomal doxorubicin the optimum dose was 16.9 mg/kg, which yielded 214% T/C. In advanced mammary carcinoma, the maximum tumor regression with free doxorubicin was at a dose of 7.5 mg/kg, with two of six mice dying of toxicity. Liposomal doxorubicin caused maximum tumor regression at 10.8 mg/kg dose with no toxic deaths. Doxorubicin entrapped in cardiolipin liposomes was much less toxic than free drug at high doses in normal mice.

AKR murine leukemia virus↗
PubMed1986

Comparative immunotoxicity of free doxorubicin and doxorubicin encapsulated in cardiolipin liposomes.

The immunologic and pharmacologic effects of free doxorubicin and of doxorubicin entrapped in liposomes were compared in mice at a dose of 20 mg/kg. Liposomes for encapsulation of doxorubicin were prepared by using 39.35 mumol drug, 19.65 mumol cardiolipin, 100 mumol phosphatidylcholine, 68.4 mumol cholesterol, and 38.9 mumol stearylamine. Pharmacologic disposition studies after a dose of 20 mg/kg demonstrated 7- to 10-fold higher drug concentrations in the spleen at all time points following administration of doxorubicin entrapped in cardiolipin liposomes than after the free drug. The levels in liver were 4- to 5-fold higher with liposomal drug, whereas the cardiac uptake with liposomal doxorubicin was significantly lower than with free drug. Mice were sacrificed on days 1, 8, 15, and 22 after drug administration and spleen cells were isolated for studies of sensitization to alloantigens for cell-mediated cytolysis and of proliferation in response to mitogens. Mice treated with free doxorubicin demonstrated a decrease of more than 50 fold (compared with saline control) in allospecific cytotoxic activity on day 15; normal levels were recovered by day 22. The animals treated with doxorubicin encapsulated in liposomes showed a similar but not more pronounced fall to low levels. The total lytic activity per spleen after free drug or drug encapsulated in liposomes was markedly reduced at day 8, but this activity was fully recovered by day 15 in animals receiving liposomal doxorubicin; in those receiving free drug it had not recovered fully even at day 22. The proliferative response to concanavalin A was affected by the two forms of doxorubicin in a pattern very similar to the cytotoxic response. The proliferative response to lipopolysaccharide was markedly depressed by doxorubicin delivered in either form, and the kinetics were not altered by the mode of administration. The concentration of doxorubicin in spleen was markedly increased with liposomal delivery, but did not result in greater toxicity than that of free drug according to the immunologic parameters evaluated.

Animals↗
PubMed1986

Ifosfamide by bolus as treatment for advanced non-small cell lung cancer.

Ifosfamide at 5 g/m2 was given as a bolus to 48 patients with advanced progressing non-small cell lung cancer. Mesna (5 g/m2) was also given with the ifosfamide, both over 30 min. Further mesna was then given p.o. (3 g/m2) at 4, 8, and 12 h. If oral mesna was not acceptable then one or, if necessary, two 4-h to 6-h infusions (3 g/m2) were administered. A maximum of six courses at 3-weekly intervals was prescribed. A total of 174 courses was administered, and oral mesna was given during 64 courses: discharge was considered possible within 8-10 h after 55% of courses. Haematological toxicity was mild and no renal dysfunction was noted. Two patients became drowsy shortly after ifosfamide, but recovered 24-36 h later. The objective response rate was 29%, with one complete responder. A further 31% of patients (symptomatic responders) with stable disease symptomatically improved after the chemotherapy, by 20 or more points on the Karnofsky scale. The median survival was 5 months for the whole group, and 8 months each for the objective and symptomatic responder groups. Most patients' Karnofsky and respiratory scores improved with the chemotherapy. Ifosfamide with mesna can be given by short infusions, and the mesna given p.o. prevents any urothelial toxicity. Further exploration of short-infusion ifosfamide and mesna therapy would reduce hospitalization and allow for day-case regimens.

Adult↗
PubMed1986

Effect of alkylation with streptozotocin on the secondary structure of DNA.

S1 nuclease hydrolysis and hydroxyapatite chromatography were used to study the effect of the alkylating antibiotic, streptozotocin, on the secondary structure of DNA. Native calf thymus DNA was alkylated in vitro with increasing concentrations of streptozotocin and subjected to S1 nuclease hydrolysis. An increasing degree of DNA degradation was seen, suggesting a destabilization of the secondary structure. Indirect evidence, deduced from alkaline hydrolysis, effect of NaCl on S1 nuclease hydrolysis, and hydroxyapatite chromatographic analysis of alkylated DNA, suggested a significant alkylation of DNA phosphates in addition to DNA bases. Nicotinamide has been reported to alter the cytotoxic and carcinogenic effects of streptozotocin. Our experiments indicate that in the presence of nicotinamide, streptozotocin causes the formation of a greater proportion of alkylated bases in relation to alkyl phosphotriesters. This may have significance in relation to the differential cytotoxicity of streptozotocin in the absence and presence of nicotinamide.

Alkylation↗
PubMed1986

Immunotoxicity of multiple dosing regimens of free doxorubicin and doxorubicin entrapped in cardiolipin liposomes.

We have shown that doxorubicin entrapped in cardiolipin liposomes retain antitumour efficacy in mice but had diminished cardiac uptake and cardiotoxicity. Such liposomes are preferentially taken up by spleen. In a previous study we showed that a single dose of liposomal doxorubicin is not more toxic than free doxorubicin with regard to immunologic parameters including generation of cytotoxicity for histocompatibility alloantigens and mitogenic responsiveness. In the present study, we have explored clinically relevant multiple dosing at weekly intervals, 2, 3, or 4 times. Again, despite splenic localization of liposomal doxorubicin, the depressive effect on these immunological parameters is not greater than the effect of free drug, and, in addition, the damage is repaired earlier.

Animals↗
PubMed1986

The influence of bile on the bioavailability of polynuclear aromatic hydrocarbons from the rat intestine.

The mechanisms governing absorption of polynuclear aromatic hydrocarbons (PAHs) are important since these carcinogenic compounds occur as solutes in dietary lipids. These highly lipophilic compounds are well absorbed in the intestine. Bile salt micellar solubilization probably facilitates their transport across the unstirred water layer to the enterocytes. To study the role of bile in the intestinal absorption of PAHs, conscious rats with bile duct and duodenal catheters were given isotopically labelled 2,6-dimethylnaphthalene (DMN), phenanthrene, anthracene, 7,12-dimethylbenzanthracene (DMBA), and benzo[alpha]pyrene (BP); the recovery of radioactivity in bile and urine was measured. The PAHs were given intraduodenally in corn oil with or without exogenous bile. Cumulative recovery of radiolabel in bile and urine over 24 h was used to assess the efficiency of absorption of the hydrocarbons with and without bile. The following values for absorption without bile (as percentage of absorption with bile) were obtained: DMN, 91.6%; phenanthrene, 96.7%; anthracene, 70.8%; DMBA, 43.4%; BP, 22.9%. The values for anthracene, DMBA, and BP were significantly less than 100% (P less than 0.05); the values for DMN and phenanthrene were not significantly different from 100%. The dependence of the tricyclic compound anthracene (a structural isomer of phenanthrene) on bile for its absorption correlates with its lower water solubility. These results are consistent with the concept that the unstirred water layer presents a significant barrier to the absorption of this group of compounds and that micellar solubilization facilitates the uptake process.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1986

Comparative pharmacokinetics of free doxorubicin and doxorubicin entrapped in cardiolipin liposomes.

The comparative pharmacokinetics of free doxorubicin and doxorubicin entrapped in cardiolipin liposomes was evaluated in rats at a dose of 6 mg/kg i.v. Doxorubicin was entrapped in cardiolipin liposomes by using 11.2 mumol of drug, 5.6 mumol of cardiolipin, 28.5 mumol of phosphatidylcholine, 19.5 mumol of cholesterol, and 11.1 mumol of stearylamine. The peak plasma concentration with free doxorubicin at 5 min was 1.7 micrograms/ml which was reduced to 0.3 micrograms/ml by 1 h. With cardiolipin liposomes, the peak plasma concentration of doxorubicin achieved at 5 min was 20.9 micrograms/ml. The plasma levels of doxorubicin decreased gradually and by 1 h the drug concentration in plasma was 10 micrograms/ml. The plasma levels of free doxorubicin and doxorubicin entrapped in liposomes were fitted to a 3-compartment computer model. The terminal half-life with free doxorubicin in plasma was 17.3 h whereas it was 69.3 h with drug entrapped in liposomes. The area under the plasma concentration curve with liposomal doxorubicin was 81.4 micrograms X h X ml-1 compared to 1.95 micrograms X h X ml-1 observed with free doxorubicin. The steady state volume of distribution with free doxorubicin was about 23-fold higher than liposomal doxorubicin. The terminal half-life with free doxorubicin in cardiac tissue was 17.9 h compared to 12.6 h with drug encapsulated in liposomes. The terminal half-lives in liver and spleen following administration of liposomal doxorubicin were 15- and 2.3-fold higher, respectively, compared to free drug; furthermore, the concentration X time values of liposomal doxorubicin in liver were 26-fold higher and in spleen 6-fold higher than the free drug. Free doxorubicin and doxorubicin entrapped in liposomes demonstrated 17 and 20% excretion in bile of the injected dose, respectively, in rats. The present studies demonstrate that liposomal encapsulation of doxorubicin significantly alters its pharmacokinetics in plasma and tissues compared to free drug.

Animals↗
PubMed1985

Selective inhibition of cardiac cyclic nucleotide phosphodiesterases by doxorubicin and daunorubicin.

Doxorubicin and daunorubicin, the anthracycline antitumor agents, were evaluated for their in vitro and in vivo effect on phosphodiesterase (PDE) activity in mouse tissues. Doxorubicin at a concentration of 10(-4)M inhibited cardiac c-AMP (adenosine 3',5', monophosphate) PDE activity 50% of the control whereas in lungs and spleen, the activity was inhibited only 20%. On the contrary no effect was seen in kidney and liver. In addition, cardiac c-GMP (guanosine 3',5' monophosphate) PDE appeared less sensitive to doxorubicin than c-AMP PDE though inhibition in heart was more pronounced than in any other tissue. It appears that daunorubicin inhibits c-AMP PDE activity in heart markedly less than doxorubicin. Kinetic studies indicate that both inhibitions of c-AMP and c-GMP PDE by doxorubicin were non-competitive with substrate. Intravenous administration of 20 and 30 mg/kg of free doxorubicin to CDF1 mice resulted in 33 and 39% decreases in cardiac c-AMP PDE activity respectively by 72 hrs. In contrast, similar intravenous injections of same doses of doxorubicin entrapped in cardiolipin liposomes had no effect on c-AMP PDE activity in any tissues. These studies demonstrate the relative selectivity of the cardiac cyclic nucleotide PDE inhibitory effect of doxorubicin suggesting that this inhibition might be one aspect of the mechanism of anthracycline-induced cardiotoxicity.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1985

Phase I study and clinical pharmacology of 6-diazo-5-oxo-L-norleucine (DON).

The toxicity of the glutamine antagonist 6-diazo-5-oxo-L-norleucine (DON) administered as a 24 hour infusion has been evaluated. Studies of the clinical pharmacology of the drug have also been performed in 3 patients. The limiting toxicity of the drug was acute nausea, vomiting and diarrhea that was dose dependent in its severity and duration. The maximum tolerated dose was 600 mg/m2 over 24 hours. The other major toxicity was thrombocytopenia that was maximal 7-10 days after the completion of the infusion. The drug does not exhibit renal, hepatic or central nervous system toxicity. DON achieves steady state levels during these infusions and is eliminated by first order kinetics when the infusion is completed (t1/2 alpha = 1.81 h). The principal route of excretion is renal. A starting dose of 400 mg/m2 would be acceptable for Phase II studies of this drug administered on this schedule.

Adult↗
PubMed1985

Pharmacological, toxicological, and therapeutic evaluation in mice of doxorubicin entrapped in cardiolipin liposomes.

Doxorubicin possesses high affinity for binding to cardiolipin. We have utilized these properties in preparing stable liposomes of doxorubicin and cardiolipin with a net positive charge. Doxorubicin liposomes were formed by using 11.2 mumol of drug, 5.6 mumol of cardiolipin, 28.5 mumol of phosphatidylcholine, 19.5 mumol of cholesterol, and 11.1 mumol of stearylamine. These liposomes were sonicated for 90 min at 37 degrees followed by extensive dialysis against buffer. The pharmacological, toxicological, and therapeutic effects of doxorubicin entrapped in cardiolipin liposomes were compared with those of free doxorubicin in mice. At a dose of 4 mg/kg i.v., the peak cardiac concentration was achieved in 30 min following free doxorubicin administration, the value being 8.1 micrograms/g. The peak cardiac concentration with doxorubicin in cardiolipin liposomes was obtained at 5 min with a value of 2.8 micrograms/g of tissue. The cardiac concentration X time values for free doxorubicin for the 24-hr period of observation were 55.1 micrograms X hr/g, whereas it was only 7.8 micrograms X hr/g with the drug entrapped in cardiolipin liposomes. Compared to free drug, the liposomal entrapped doxorubicin significantly reduced the histopathological lesions in cardiac tissue of mice at a dose of 15 mg/kg as determined by electron microscopy. The nadir of peripheral white blood cell counts in mice with free drug, 6 mg/kg, was observed on Day 3 which was 50% of control, whereas with liposomal encapsulated drug it was reduced only 23% on Day 7. Doxorubicin in cardiolipin liposomes demonstrated enhanced chemotherapeutic potential against murine ascitic P388 leukemia with a 144% increased life span compared to 55% increased life span with free drug at a dose of 7.5 mg/kg on Days 1, 3, and 7. We conclude that doxorubicin liposomes developed in these studies possess improved therapeutic action as demonstrated by their ability to reduce the toxicity of the drug substantially.

Animals↗
PubMed1984

Characterization of deoxyribonuclease activities derived from control and inflammation-associated mouse peritoneal macrophages.

Native DNAase (deoxyribonuclease) activities derived from mouse peritoneal cavity and peripheral blood components were separated, detected, and characterized by electrophoresis into polyacrylamide gels containing DNA, followed by incubation of the gels, and staining of the substrate to reveal only the DNAase activities. Resident peritoneal macrophages contained 12 DNAase-II-like activities that were characteristic of that cell type, whereas lymphocytes and granulocytes each contained five DNAases. Induction of inflammation by peritoneal injection of thioglycollate resulted in changes in macrophage DNAase expression, including: increased total DNAase activity, a decrease in the number of activities from 12 to 11, increased activity of a specific subset of the enzymes, and a change in the apparent size of a specific subset of the enzymes. Electrophoretic and enzymic properties and sensitivity to endo-beta-N-acetylglucosaminidase H indicated that the macrophage activities probably represented charge variants of one or two parent peptide chains.

Animals↗
PubMed1984

Isoelectric focusing--polynucleotide/polyacrylamide-gel electrophoresis. A technique to separate and characterize nuclease activities.

Individual native nuclease activities from human leucocytes are separated by using two-dimensional gel electrophoresis in an apparatus that allows the simultaneous running of 28 gels. Proteins are separated by isoelectric focusing in a disc gel, followed by electrophoresis into a slab gel containing DNA. Protein denaturants are avoided in the second dimension by the use of a running pH well above the optimal pH for DNAase (deoxyribonuclease) activity. Electrophoresed gels are incubated in appropriate buffers to activate nuclease activity. After staining for intact DNA, the positions of active enzymes, unobscured by the presence of other proteins, are revealed as colourless spots in a reddish-purple field. The technique is easy to use and is sensitive to 50pg of DNAase I. Versatility is provided by the use of either acidic or basic electrophoresis running buffers and by the use of specific gel incubation conditions to reveal different sets of enzyme activities. Two DNAases active at pH 7.4 in the presence of Mg2+ and Ca2+, and sixteen DNAases active at acidic pH and not requiring metals, are detected. Treatment of the human enzymes with specific glycosidases reveals that many of the human DNAases are glycoproteins containing negatively charged moieties and may be derived from modification of parent activities.

Deoxyribonucleases↗