Biomedical subjects

Randall K Johnson

Publications and source records attributed to Randall K Johnson.

10 recordsLinked to original sources

PubMed2005

4-Aryl-1,2,3-triazole: a novel template for a reversible methionine aminopeptidase 2 inhibitor, optimized to inhibit angiogenesis in vivo.

Inhibitors of human methionine aminopeptidase type 2 (hMetAP2) are of interest as potential treatments for cancer. A new class of small molecule reversible inhibitors of hMetAP2 was discovered and optimized, the 4-aryl-1,2,3-triazoles. Compound 24, a potent inhibitor of cobalt-activated hMetAP2, also inhibits human and mouse endothelial cell growth. Using a mouse matrigel model, this reversible hMetAP2 inhibitor was also shown to inhibit angiogenesis in vivo.

Aminopeptidases↗

PubMed2005

Polybrominated diphenyl ethers from a sponge of the Dysidea genus that inhibit Tie2 kinase.

Tie2 kinase, an enzyme that supports angiogenesis essential for tumor growth and survival, was selected as a target in a search for naturally occurring inhibitors of potential utility for antitumor therapy. Two polybrominated diphenyl ethers, 3,5-dibromo-2-(2',4'-dibromophenoxy)phenol (1) and 4,6-dibromo-2-(2',4'-dibromophenoxy)phenol (2) were isolated from an extract prepared from Dysidea sp. after bioassay-guided fractionation.

Animals↗

PubMed2004

A DNA-damaging oxoaporphine alkaloid from Piper caninum.

Bioassay-guided fractionation of an active organic extract of Piper caninum, using a sensitive yeast assay to monitor putative double-strand DNA-damaging activity, resulted in the isolation of the 4,5-dioxoaporphine alkaloid cepharadione A (1). Compound 1 exhibited potent inhibitory activity in a yeast cytotoxicity assay with IC(50) values of 50.2 nM toward RS321NpRAD52 grown on glucose versus 293 nM toward the same yeast strain grown on galactose.

Alkaloids↗

PubMed2003

DNA damaging activity of ellagic acid derivatives.

A strain of yeast rendered repair deficient by the conditional expression of the RAD52 locus was used to search for natural products capable of damaging DNA. Four ellagic acid derivatives, namely 3,3'-dimethyl-4'-O-beta-D-glucopyranosyl ellagic acid (1), 3,3',4-trimethyl-4'-O-beta-D-glucopyranosyl ellagic acid (2), 3'-methyl-3,4-O,O-methylidene ellagic acid (3) and 3'-methyl-3,4-O,O-methylidene-4'-O-beta-D-glucopyranosyl ellagic acid (4), were identified by this assay as DNA damaging natural principles from several plants, including Alangium javanicum, Anisophyllea apetala, Crypteronia paniculata, Mouririi sp. and Scholtzia parviflora. Although none of the isolated principles mediated frank strand scission of DNA in vitro, all of them potently inhibited the growth of yeast in the absence of expression of RAD52.

Biological Assay↗

PubMed2003

Successful rotational atherectomy in the setting of extensive coronary dissection: a case of failed balloon angioplasty in a nondilatable calcified lesion complicated by balloon rupture and extensive dissection.

We describe a case of rotational atherectomy (RA) used in the setting of extensive coronary dissection. Unsuccessful predilitation of a heavily calcified proximal LAD stenosis resulted in balloon rupture, which produced occlusive dissection extending into the mid LAD. Limited options for this patient required that we perform RA to permit stent delivery and deployment and avoid anterior myocardial infarction. A brief discussion of reasons for balloon angioplasty failure and the potential role for subsequent RA is given. Predictors for coronary perforation when performing RA are reviewed. Our rationale and strategy to avoid the increased risk of perforation with RA in this contraindicated setting of extensive dissection is given.

Aged↗

PubMed2003

New cytotoxic lupane triterpenoids from the twigs of Coussarea paniculata.

Bioassay-guided fractionation of a CH(2)Cl(2)-MeOH extract of the twigs of Coussarea paniculata using a yeast-based assay for potential DNA-damaging agents resulted in the isolation of three new lupane triterpenoids, 1-3, in addition to eight known triterpenoids, lupeol (4), lupeyl acetate (5), betulin (6), betulinic acid (7), 3-epi-betulinic acid (8), 3-epi-betulinaldehyde (9), oleanolic acid (10), and ursolic acid (11). The structures of the new compounds were established as lup-20(29)-en-3beta,25-diol (1), lup-20(29)-en-11alpha-ol-25,3beta-lactone (2), and 3-deoxybetulonic acid (3), on the basis of extensive 1D and 2D NMR spectroscopic data interpretation and chemical conversion.

Antineoplastic Agents, Phytogenic↗

PubMed2002

Haploscleridamine, a novel tryptamine-derived alkaloid from a sponge of the order haplosclerida: an inhibitor of cathepsin K.

As part of a search for novel inhibitors of cathepsin K, the MeOH extract of a Micronesian sponge of the order Haplosclerida was shown to be active. Bioassay-guided fractionation of the extract yielded halitoxins, tryptamine, and a novel tryptamine-derived alkaloid, haploscleridamine (1). The tetrahydro-beta-carboline structure of haploscleridamine (1) was elucidated through spectral techniques. Haploscleridamine (1) was found to be an inhibitor of cathepsin K with an IC(50) of 26 microM.

Alkaloids↗

PubMed2002

A new dimeric dihydrochalcone and a new prenylated flavone from the bud covers of Artocarpus altilis: potent inhibitors of cathepsin K.

A MeOH/CH(2)Cl(2) extract of the bud covers of Artocarpus altilis collected in Micronesia showed activity in a cathepsin K inhibition assay. In addition to the three known flavonoids isolated from the bud covers of this species, two new compounds have been identified whose structures were determined on the basis of spectral data. These compounds include a dimeric dihydrochalcone, cycloaltilisin 6 (2), and a new prenylated flavone, cycloaltilisin 7 (3). Novel compounds 2 and 3 have IC(50) values of 98 and 840 nM, respectively, in cathepsin inhibition.

Cathepsin K↗

PubMed2002

DNA-damaging agents from Crypteronia paniculata.

A survey of crude plant extracts using a new yeast strain designed to identify DNA-damaging agents resulted in the identification of an extract prepared from Crypteronia paniculata. Bioassay-guided fractionation resulted in the isolation of three active compounds. Two of these were ellagic acid derivatives, namely, 3,3'-di-O-methylellagic acid 4'-O-beta-d-xylopyranoside (1) and 3'-O-methyl-3,4-methylenedioxyellagic acid 4'-O-beta-d-glucopyranoside (2). The third was identified as kaempferol-3-O-alpha-l-rhamnoside (3). The three principles exhibited strong, selective cytotoxity toward the RAD52 repair-deficient yeast strain.

Antifungal Agents↗

PubMedDate not supplied

High-dose recombinant interleukin-18 induces an effective Th1 immune response to murine MOPC-315 plasmacytoma.

Interleukin (IL)-18 has profound antitumor activity when administered at high doses as a single agent for prolonged periods in BALB/c mice bearing late, well-established MOPC-315 tumors. Management with a qD x 27 schedule resulted in regression of tumors in all animals receiving 5 mg/kg/d. A protracted daily management regimen appears to be necessary to induce regression in this advanced tumor model. Biologic markers were assessed and appear to be potentially useful in evaluating the immunologic and antitumor activity of IL-18. The biomarkers of IL-18's immunologic activity include, but are not limited to, IL-1alpha, IL-2, IL-8, IL-10, IL-12, IL-13, interferon-gamma, tumor necrosis factor-alpha, and granulocyte-macrophage colony-stimulating factor. The profile of these circulating cytokines and their expression levels at baseline, and after IL-18 delivery, can be measured in the serum, as well as from splenocytes of mice or human peripheral blood mononuclear cells derived from either normal subjects or patients with cancer. We compared IL-18 and IL-12 alone or in combination for their ability to induce cytokine production and natural killer cytolytic activity. Our data support the notion that IL-18 induces a predominantly Th1 response, and that the mechanism of IL-18 activity differs from that of IL-12. The biologic activity of IL-18 management revealed by increases in serum levels of cytokines and enhancement of natural killer cytolytic activity will be useful as clinical trials initiate in 2002. Expression of interferon-gamma and granulocyte-macrophage colony-stimulating factor serum levels correlates directly over a broad dose escalation with the level of IL-18. Therefore, this provides a convenient pharmacodynamic reference to the biologic response to IL-18 that may serve to guide the conduct of clinical trials.

Animals↗