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Biomedical subjects

M Cushman

Publications and source records attributed to M Cushman.

At least 109 records · Page 6Linked to original sources
PubMed1996

Exploration of the effects of linker chain modifications on anti-HIV activities in a series of cosalane analogues.

The effects of linker chain modifications were investigated in a series of cosalane analogues. The modifications investigated included: (1) shortening the three-carbon linker chain between the dichlorodisalicylmethane and the cholestane moiety by one carbon atom; (2) lengthening the linker chain by one carbon; (3) hydrogenation of the double bond in the linker chain; (4) changing the point of attachment of the linker chain from C-3 to C-6; (5) insertion of a phosphate between the steroid and the linker chain. With the exception of the phosphate modification, which abolished anti-HIV activity and increased cytotoxicity, the linker chain modifications produced relatively minor changes in anti-HIV activity and increased cytotoxicity, the linker chain modifications produced relatively minor changes in anti-HIV potency. The steroid and attached linker chain of cosalane therefore appear only to provide a general lipophilic appendage for the dichlorodisalicylmethane pharmacophore.

Anti-HIV Agents↗
PubMed1996

Correlates of thrombin markers in an elderly cohort free of clinical cardiovascular disease.

Studies suggest that thrombosis is important in the progression of atherosclerotic lesions. The biochemical markers prothrombin fragment 1-2 and fibrinopeptide A reflect in vivo thrombin generation and activity, respectively. As such, they are markers that might be associated with cardiovascular risk. From the Cardiovascular Health Study, a cohort study of 5201 persons over 65 years of age, 399 persons free of clinical cardiovascular disease (CVD) at the baseline examination were selected for study of specialized markers of hemostasis. We report the cross-sectional relationships of the thrombin markers to CVD risk factors and measures of subclinical CVD. The range of fragment 1-2 2 was 0.12 to 0.85 nmol/L. The range of fibrinopeptide A was 0.9 to 44.1 micrograms/L. High levels of fragment 1-2 and fibrinopeptide A were associated with age, with levels higher in women than men. Fragment 1-2 was associated with smoking; high levels of triglyceride, creatinine, and C-reactive protein; and low levels of glucose. Fibrinopeptide A was associated with high C-reactive protein and apolipoprotein(a) and lower ankle-brachial index. There were no significant associations of the thrombin markers with race, fibrinogen, alcohol consumption, diabetes, or most measures of subclinical CVD. Study findings support a hypothesis that there are physiological interrelationships between cardiac risk factors, hemostasis, inflammation, and progression of atherosclerosis.

Aged↗
PubMed1996

Synthesis of a series of cytotoxic 2-acyl-1,2-dihydroellipticines which inhibit topoisomerase II.

An array of novel 2-acyl-1,2-dihydroellipticines was prepared and evaluated for in vitro cytotoxicity in a variety of human cancer cell lines. The ellipticine analogs were also tested for inhibition of topoisomerase II in both decatenation and cleavable complex formation assays. Some of the new ellipticine derivatives were prepared by acylation of ellipticine with acid chlorides in tetrahydrofuran, followed by reduction of the intermediate 2-acylellipticinium ions with sodium cyanoborohydride. Others were synthesized by acylation of ellipticine with p-nitrophenyl chloroformate, reduction of the 2-acylellipticinium ion with sodium cyanoborohydride, and displacement of the p-nitrophenoxide anion with a variety of oxygen and nitrogen nucleophiles. The cytotoxicities of the new 2-acyl-1,2-dihydroellipticines varied widely, and correlated well with their topoisomerase II inhibitory activities.

Antineoplastic Agents, Phytogenic↗
PubMed1995

The mechanism of inactivation of human platelet factor Va from normal and activated protein C-resistant individuals.

The inactivation of human platelet factor Va by activated protein C (APC) was analyzed by functional assessment of cofactor activity and Western blotting analysis to visualize the factor Va fragments accompanying proteolysis. Platelets were treated with thrombin to facilitate both their activation as well as the release and further activation of platelet factor Va, followed by APC addition. The rates of inactivation were donor-dependent such that 15-60% of the initial cofactor activity was lost within 5 min of APC addition with as much as 10-20% of the activity still remaining after 2 h of incubation. Western blot analysis using a monoclonal antibody that recognizes an epitope between amino acid residues 307 and 506 of the factor V molecule suggested that the factor Va activity resistant to APC inactivation was due to residual heavy chain. Furthermore, in contrast to studies with normal plasma-derived factor Va, two possible cleavage mechanisms could explain the platelet factor Va fragments observed. APC can cleave platelet factor Va initially at Arg506, with subsequent cleavages occurring at Arg306 and Arg679. Alternatively, APC can cleave at Arg306 initially, with further cleavage at Arg679 then at Arg506 or at Arg506 followed by cleavage at Arg679. Similar results were obtained if platelets were removed from the inactivation mixtures and phospholipid vesicles were used to supply the membrane surface required for inactivation, suggesting that the order of platelet factor Va peptide bond cleavage or the amount of cofactor activity remaining was not altered by either of these surfaces. Thus, APC is unable to effect the complete inactivation of platelet factor Va, even though it would appear that the same cleavages which render the plasma cofactor inactive are occurring in the platelet cofactor. Analogous protocols were used to study an individual heterozygous for the Arg506-->Gln506 mutation (Factor V Leiden, Factor VR506Q). With respect to the mutant platelet factor Va in the presence of APC, > 70% of the initial cofactor activity remained after 1 min, with 30% activity still remaining after 2 h. As seen in studies of the APC-catalyzed inactivation of plasma factor VaR506Q, proteolysis of the mutant platelet factor Va confirms that even though cleavage at Arg306 will occur in the absence of cleavage at Arg506, the rate of inactivation is slower. Collectively these data suggest that when compared to normal plasma factor Va, differences in normal platelet factor Va which define: 1) whether the heavy chain is susceptible to cleavage at Arg306 or Arg506 and 2) the extent to which it is cleaved initially at Arg306, in contrast to cleavage of Arg506, will define both the extent and rate of inactivation.

Amino Acid Sequence↗
PubMed1995

Synthesis and cytotoxicity of water-soluble ambrosin prodrug candidates.

The potential therapeutic application of the naturally occurring, cytotoxic pseudoguaianolide sesquiterpene lactone ambrosin is limited by its aqueous insolubility. A number of water-soluble ambrosin derivatives have therefore been prepared for potential use as prodrugs. Michael addition of several secondary amines to both the alpha,beta-unsaturated ketone and alpha-methylene lactone moieties of ambrosin afforded tertiary amine diadducts that were converted to water-soluble hydrochloride salts. The salt of the bis-piperidine adduct proved to be the most potent, producing cytotoxic activity only slightly less potent than that of ambrosin itself in a variety of human cancer cell cultures. The sodium salt of the bis-sulfonic acid derivative of ambrosin was inactive, while the sodium salt of the bis-sulfinic acid analog had low activity. Biological evaluation of several ambrosin analogs with reduced and/or isomerized alpha,beta-unsaturated ketone and alpha-methylene lactone moieties demonstrated the importance of both of these functional groups for biological activity.

Antineoplastic Agents↗
PubMed1995

Synthesis, antitubulin and antimitotic activity, and cytotoxicity of analogs of 2-methoxyestradiol, an endogenous mammalian metabolite of estradiol that inhibits tubulin polymerization by binding to the colchicine binding site.

In order to define the structural parameters associated with the antitubulin activity and cytotoxicity of 2-methoxyestradiol, a mammalian metabolite of estradiol, an array of analogs was synthesized and evaluated. The potencies of the new congeners as inhibitors of tubulin polymerization and colchicine binding were determined using tubulin purified from bovine brain, and the cytotoxicities of the new compounds were studied in a variety of cancer cell cultures. Maximum antitubulin activity was observed in estradiols having unbranched chain substituents at the 2-position with three non-hydrogen atoms. 2-Ethoxyestradiol and 2-((E)-1-propenyl)-estradiol were substantially more potent than 2-methoxyestradiol itself. The tubulin polymerization inhibitors in this series displayed significantly higher cytotoxicities in the MDA-MB-435 breast cancer cell line than in the other cell lines studied. The potencies of the analogs as cytotoxic and antimitotic agents in cancer cell cultures correlated with their potencies as inhibitors of tubulin polymerization, supporting the hypothesis that inhibition of tubulin polymerization is the mechanism of the cytotoxic action of 2-methoxyestradiol and its congeners. Several of the more potent analogs were tested in an estrogen receptor binding assay, and their affinities relative to estradiol were found to be very low.

2-Methoxyestradiol↗
PubMed1995

Cosalane analogues with enhanced potencies as inhibitors of HIV-1 protease and integrase.

Several new analogues of the novel anti-HIV agent cosalane have been synthesized and evaluated as inhibitors of HIV-1 integrase and protease, HIV-1 replication, HIV-1 and HIV-2 cytopathicity, HIV-1- and HIV-2-mediated syncytium formation, and cytopathicity of a variety of human pathogenic viruses. The congeners displayed enhanced potencies relative to cosalane itself as inhibitors of HIV-1 integrase and protease. The two most potent analogues against HIV-1 integrase displayed IC50 values of 2.2 microM, while the three most potent compounds against HIV-1 protease had IC50 values in the 0.35-0.39 microM range. In addition to its activity against HIV-1 and HIV-2 cytopathicity, cosalane inhibited the cytopathic effects of herpes simplex virus-1, herpes simplex virus-2, and human cytomegalovirus at concentrations that were well below the cytotoxic concentrations. Potentially useful antiviral activities were also revealed for some of the new cosalane congeners against influenza virus, Junin virus, and Tacaribe virus.

Amino Acid Sequence↗
PubMed1995

Laboratory methods and quality assurance in the Cardiovascular Health Study.

The Cardiovascular Health Study is an observational cohort study of risk factors for cardiovascular disease in 5201 participants, ages > or = 65 years. We report the methods and quality-assurance results for blood procurement, processing, shipping, storage, and sample analysis used during the first examination period (May 1989-June 1990). The most frequent difficulty in phlebotomy and processing was the requirement of more than one venipuncture (in 2.6% of the participants). The CVs for control materials ranged from 0.93% for glucose to 10.7% for insulin; most were < 4%. In addition to standard quality-assurance methods, we applied two other methods: technical error calculation for replicates, and weighted linear regression to assess time trend in results of control materials. After outliers were excluded, technical error values ranged from 1.7 for uric acid to 18.8 for insulin. Factor VII and factor VIII had slight trends over the 12-month analysis period. Results of quality-assurance analyses used to resolve problems were successful, thereby improving the second laboratory examination.

Aged↗
PubMed1994

Synthesis and biochemical evaluation of a series of aminoflavones as potential inhibitors of protein-tyrosine kinases p56lck, EGFr, and p60v-src.

A series of nitroflavones, 8a-p, and their corresponding aminoflavone hydrochloride salts, 10a-p, was synthesized. The preparation of nitroflavones 8b-i,o,p began with commercially available o-hydroxyacetophenones 2b-f which were converted to o-hydroxynitroacetophenones 3a-h via a variety of nitration methods, followed by condensation with nitrobenzoyl chlorides and cyclization under acidic condition. The nitroflavones 8aj-n were prepared by nitration of the corresponding flavones 7a-e. These new compounds were evaluated for their abilities to inhibit the in vitro protein-tyrosine kinase activities of p56lck, EGFr, and p60v-src, and all of the active compounds were amino-substituted flavones. None of the nitroflavones inhibited the enzymes. The most active substance in this series against p56lck was compound 10j, which had an IC50 of 18 microM. When tested versus EGFr, compounds 10a,m displayed IC50's of 8.7 and 7.8 microM, respectively. Against p60v-src, 10a,m showed IC50 values of 28.8 and 38.4 microM, respectively.

Adenosine Triphosphate↗
PubMed1994

Design, synthesis, and biological evaluation of cosalane, a novel anti-HIV agent which inhibits multiple features of virus reproduction.

Cosalane (3), a novel anti-HIV agent having a disalicylmethane unit linked to C-3 of cholestane by a three-carbon linker, was synthesized from commercially available starting materials by a convergent route. Cosalane proved to be a potent inhibitor of HIV with a broad range of activity against a variety of laboratory, drug-resistant, and clinical HIV-1 isolates, HIV-2, and Rauscher murine leukemia virus. The cytotoxicity of cosalane is relatively low as reflected by an in vitro therapeutic index of > 100. Although cosalane inhibits HIV-1 reverse transcriptase and protease, time of addition experiments indicate that it prevents the cytopathic effect of HIV by acting earlier than reverse transcription in the viral replication cycle. The available evidence indicates that the primary mechanism of action of cosalane involves inhibition of gp120-CD4 binding as well as inhibition of a postattachment event prior to reverse transcription.

Antiviral Agents↗
PubMed1994

Design and synthesis of ellipticinium salts and 1,2-dihydroellipticines with high selectivities against human CNS cancers in vitro.

9-Methoxy-2-methylellipticinium acetate (6), along with the 9-methyl and 9-chloro derivatives (7, and 8, respectively) have shown remarkable selectivities in vitro against the NCI human CNS cancer subpanel. In order to target these types of compounds to the CNS in vivo, a series of 1,2-dihydroellipticines was synthesized. 9-Methoxy-2-methyl-1,2-dihydroellipticine (9) retained the potency and selectivity of the parent compound 6 but was unstable toward oxidation to 6. In order to improve the stability of 9, it was converted to the vinylogous amide 33 by introduction of a formyl group in the 4-position. Compound 33 proved to be much more stable than 9, but it was also less potent than 9 by about 1 order of magnitude, and it was less selective for the CNS subpanel than 9. To overcome the limited water solubilities of the ellipticines and dihydroellipticines, several ellipticine analogues incorporating polar groups on the N-2 nitrogen were prepared. The 2-(methoxymethyl)ellipticinium salts 24 and 25, as well as the (methylthio)methyl congener 26, were relatively potent anticancer agents which displayed cytotoxicity selectivity profiles similar to compound 6. The cytotoxic dihydroellipticines 9 and 10 exhibited potencies approaching that of ellipticine itself in facilitating the formation of a "cleavable complex", while the least cytotoxic ellipticine derivatives exhibited no cleavage above background.

Brain Neoplasms↗
PubMed1994

(Trifluoromethyl)lumazine derivatives as 19F NMR probes for lumazine protein.

Lumazine protein acts as an electronic excited state transducer in bioluminescence of Photobacterium species. The protein binds 6,7-dimethyl-8-(D-ribityl)lumazine (1) which serves as the fluorophore. This compound also serves as a biosynthetic precursor of riboflavin and is the substrate of the enzyme riboflavin synthase. This enzyme and lumazine protein show considerable sequence homology. The interaction of lumazine apoprotein with several trifluoromethyl analogs of 6,7-dimethyl-8-ribityllumazine was investigated by 19F NMR spectroscopy. Upon binding to the protein, the 19F NMR resonances of the ligand shift to lower field with broadened line widths to around 30 Hz. By comparison, all ligands studied show more complex NMR spectra when bound to riboflavin synthase. Only one position 7 epimer (designated epimer A) of 6,7-bis(trifluoromethyl)-7-hydroxy-8-(D-ribityl)lumazine binds to lumazine apoprotein and riboflavin synthase. The apoprotein can also bind lumazine derivatives with a quarternary C-7. It is suggested that the binding site of lumazine protein corresponds to the donor binding site of riboflavin synthase.

Fluorine Compounds↗
PubMed1993

Synthesis and protein-tyrosine kinase inhibitory activity of polyhydroxylated stilbene analogues of piceatannol.

A series of hydroxylated trans-stilbenes related to the antileukemic natural product trans-3,3',4,5'-tetrahydroxystilbene (piceatannol) (1) has been prepared and tested for inhibition of the lymphoid cell lineage-specific protein-tyrosine kinase p56lck, which plays an important role in lymphocyte proliferation and immune function. A number of the analogues displayed enhanced enzyme inhibitory activity relative to the natural product. Reduction of the double bond bridging the two aromatic rings and benzylation of the phenolic hydroxyl groups was found to decrease activity significantly. The most potent compounds in the series proved to be trans-3,3',5,5'-tetrahydroxystilbene, trans-3,3',5-trihydroxystilbene, and trans-3,4,4'-trihydroxystilbene.

Hydroxylation↗
PubMed1993

Synthesis and evaluation of a series of benzylaniline hydrochlorides as potential cytotoxic and antimitotic agents acting by inhibition of tubulin polymerization.

Although certain substituted cis-stilbenes have displayed potent tubulin polymerization inhibitory activity and significant cytotoxicities in cancer cell cultures, these compounds have limited aqueous solubility and are therefore difficult to formulate for in vivo evaluation. A series of water-soluble N-(3,4,5-trimethoxybenzyl)aniline salts has therefore been synthesized in which the olefinic bridge of the stilbenes is replaced by an aminomethylene hydrochloride moiety. A relationship was found between the size of the substituent in the 4-position of the aniline ring and both antitubulin activity and cytotoxicity, such that the smaller the substituent, the greater the potency. The most promising of the newly synthesized compounds was 4-methyl-N-(3,4,5-trimethoxybenzyl)aniline hydrochloride, with an IC50 value of 3.5 microM for inhibition of tubulin polymerization and cytotoxicity for a wide variety of cancer cell lines. The cytotoxicities of the benzylaniline hydrochlorides correlated remarkably well with their antitubulin activities.

Aniline Compounds↗
PubMed1992

Synthesis and evaluation of analogues of (Z)-1-(4-methoxyphenyl)-2-(3,4,5-trimethoxyphenyl)ethene as potential cytotoxic and antimitotic agents.

A series of stilbenes has been prepared and tested for cytotoxicity in the five human cancer cell lines A-549 non-small cell lung, MCF-7 breast, HT-29 colon, SKMEL-5 melanoma, and MLM melanoma. The cis stilbenes 6a-f proved to be cytotoxic in all five cell lines, with potencies comparable to that of combretastatin A-4. These cytotoxic compounds were all potent inhibitors of tubulin polymerization. The corresponding trans stilbenes 7b-f were inactive as tubulin polymerization inhibitors and were significantly less cytotoxic in the five cancer cell lines. In the dihydro series, 8b, 8c, and 8f were inactive as tubulin polymerization inhibitors, while 8a, 8d, and 8e were less active than the corresponding cis compounds 6a, 6d, and 6e. The lack of tubulin polymerization inhibitory activity and cytotoxicity displayed by the phenanthrene 23b, which was synthesized as a conformationally rigid analogue of the lead compound 1, indicates that the activity of the stilbenes is not due to a totally planar conformation. Similarly, inactivity of the conformationally restricted analogue 26 suggests that the biologically active conformation of 1a resembles that of the cis alkene 1. Additional inactive compounds prepared include the benzylisoquinoline series 28-32 as well as the protoberberines 38 and 39. Shortening the two-carbon bridge of 1a to a one-carbon bridge in the diphenylmethane 20 resulted in a decrease in cytotoxicity and tubulin polymerization inhibitory activity. Although the corresponding benzophenone 18 was as active as 1a as a tubulin polymerization inhibitor, it was less cytotoxic than 1a, and the benzhydrol 19 was essentially inactive. With the exception of the amide 15c, which displayed low antitubulin activity, all of the phenylcinnamic acid derivatives 14a-c and 15a-f were inactive in the tubulin polymerization inhibition assay. The acid 14b and the ester 15a were cytotoxic in several of the cancer cell cultures in spite of their inactivity as tubulin polymerization inhibitors.

Antineoplastic Agents↗