Biomedical subjects

J Cummings

Publications and source records attributed to J Cummings.

At least 55 records · Page 3Linked to original sources

PubMed1998

Current issues in the enzymology of mitomycin C metabolic activation.

1. Mitomycin C (MMC) is considered to be the prototype bioreductive drug undergoing activation to toxic species preferentially under hypoxic conditions. Therefore a proper understanding of the enzymology of bioreduction in tumor tissue is of great importance. 2. DT-diaphorase and NADPH:cytochrome P-450 reductase (quinone reductases) are believed to have established roles in this activation pathway, but these roles are now undergoing revision. 3. It is emerging, however, that different reductases prevail under different physiological conditions. Indeed, DT-diaphorase has been found to protect cells from the hypoxic cytotoxicity of MMC in cell lines expressing high levels of the enzyme. 4. A novel mitochondrial reductase(s) has been identified in solid tumor tissue and is active only under hypoxic conditions and is more efficient at metabolizing MMC than are the other reductases identified. 5. Thus, this newly identified mitochondrial reductase(s) is a potential new target for enzyme-directed bioreductive drug therapy if tumor hypoxia can be achieved. However, because most tumors overexpress DT-diaphorase, this enzyme may prove optimal for MMC drug therapy.

Animals↗

PubMed1998

Dose-limiting neurotoxicity in a phase I study of penclomedine (NSC 388720, CRC 88-04), a synthetic alpha-picoline derivative, administered intravenously.

3,5-Dichloro-2,4-dimethoxy-6-(trichloromethyl)pyridine (penclomedine, NSC 338720, CRC 88-04) is an alpha-picoline derivative with anti-tumour activity in preclinical models. Penclomedine administration by 1-h intravenous infusion on 5 consecutive days was repeated 3 weekly in the absence of dose-limiting toxicity (DLT) or disease progression. Five dose levels were investigated (22.5-340 mg m(-2) day[-1]). Eight men and eight women were entered, median age 59 years (range 39-73 years), with good performance status (ECOG 0/1) in 11 patients. A total of 13 out of 16 patients had received previous chemotherapy. Common toxicity criteria grade (CTCg) II vomiting was recorded at all dose levels. Neurotoxicity (cerebellar ataxia and dizziness) was the DLT, CTCg III toxicity occurring in three out of three patients treated at 340 mg m(-2) day(-1). CTCg III dizziness was noted in one out of three patients at 250 mg m(-2) day(-1). Neurotoxicity developed during the 1-h infusion and persisted for a variable period (maximum 5 h) after infusion. Prophylactic antiemetic drugs appeared to reduce associated vomiting but did not prevent ataxia. No antiproliferative toxicities were noted and no anti-tumour responses were documented. Penclomedine pharmacokinetic studies confirmed preclinical evidence of extensive apparent distribution (93 l m[-2]) and rapid clearance (41 l h[-1] m[-2]). Purkinje cell loss has been identified in preclinical models after intraperitoneal administration (O'Reilly et al, 1996a) and further clinical development of penclomedine will focus on oral administration.

Adult↗

PubMed1998

Emergence of artistic talent in frontotemporal dementia.

OBJECTIVE: To describe the clinical, neuropsychological, and imaging features of five patients with frontotemporal dementia (FTD) who acquired new artistic skills in the setting of dementia. BACKGROUND: Creativity in the setting of dementia has recently been reported. We describe five patients who became visual artists in the setting of FTD. METHODS: Sixty-nine FTD patients were interviewed regarding visual abilities. Five became artists in the early stages of FTD. Their history, artistic process, neuropsychology, and anatomy are described. RESULTS: On SPECT or pathology, four of the five patients had the temporal variant of FTD in which anterior temporal lobes are involved but the dorsolateral frontal cortex is spared. Visual skills were spared but language and social skills were devastated. CONCLUSIONS: Loss of function in the anterior temporal lobes may lead to the "facilitation" of artistic skills. Patients with the temporal lobe variant of FTD offer a window into creativity.

Aged↗

PubMed1998

Frontotemporal lobar degeneration: a consensus on clinical diagnostic criteria.

OBJECTIVE: To improve clinical recognition and provide research diagnostic criteria for three clinical syndromes associated with frontotemporal lobar degeneration. METHODS: Consensus criteria for the three prototypic syndromes-frontotemporal dementia, progressive nonfluent aphasia, and semantic dementia-were developed by members of an international workshop on frontotemporal lobar degeneration. These criteria build on earlier published clinical diagnostic guidelines for frontotemporal dementia produced by some of the workshop members. RESULTS: The consensus criteria specify core and supportive features for each of the three prototypic clinical syndromes and provide broad inclusion and exclusion criteria for the generic entity of frontotemporal lobar degeneration. The criteria are presented in lists, and operational definitions for features are provided in the text. CONCLUSIONS: The criteria ought to provide the foundation for research work into the neuropsychology, neuropathology, genetics, molecular biology, and epidemiology of these important clinical disorders that account for a substantial proportion of cases of primary degenerative dementia occurring before the age of 65 years.

Dementia↗

PubMed1997

Mitomycin C-DNA adducts generated by DT-diaphorase. Revised mechanism of the enzymatic reductive activation of mitomycin C.

Mitomycin C (MC) was reductively activated by DT-diaphorase [DTD; NAD(P)H:quinone oxidoreductase] from rat liver carcinoma cells in the presence of Micrococcus lysodeicticus DNA at pH 5.8 and 7.4. The resulting alkylated MC-DNA complexes were digested to the nucleoside level and the covalent MC-nucleoside adducts were separated, identified, and quantitatively analyzed by HPLC. In analogous experiments, two other flavoreductases, NADH-cytochrome c reductase and NADPH-cytochrome c reductase, as well as two chemical reductive activating agents Na2S2O4 and H2/PtO2 were employed as activators for the alkylation of DNA by MC. DTD as well as all the other activators generated the four known major guanine-N2-MC adducts at both pHs. In addition, at the lower pH, the guanine-N7-linked adducts of 2,7-diaminomitosene were detectable in the adduct patterns. At a given pH all the enzymatic and chemical reducing agents generated very similar adduct patterns which, however, differed dramatically at the acidic as compared to the neutral pH. Overall yield of MC adducts was 3-4-fold greater at pH 7.4 than at 5. 8 except in the case of DTD when it was 4-fold lower. Without exception, however, cross-link adduct yields were greater at the acidic pH (2-10-fold within the series). The ratio of adducts of bifunctional activation to those of monofunctional activation was 6-20-fold higher at the acidic as compared to the neutral pH. A comprehensive mechanism of the alkylation of DNA by activated MC was derived from the DNA adduct analysis which complements earlier model studies of the activation of MC. The mechanism consists of three competing activation pathways yielding three different DNA-reactive electrophiles 11, 12, and 17 which generate three unique sets of DNA adducts as endproducts. The relative amounts of these adducts are diagnostic of the relative rates of the competing pathways in vitro, and most likely, in vivo. Factors that influence the relative rates of individual pathways were identified.

Alkylation↗

PubMed1997

Solid-phase extraction and high-performance liquid chromatographic determination of tamoxifen and its major metabolites in breast tumour tissues.

A sensitive (200 ng/g) and selective reversed-phase high-performance liquid chromatography separation has been developed to determine the levels of tamoxifen, 4-hydroxytamoxifen (4-OH) and desmethyltamoxifen (DMT) in tumour tissue taken from patients undergoing tamoxifen therapy. A muBondapak C18 10 microm column (30 cm x 3.8 mm I.D.) was used, with a mobile phase of methanol-1% triethylamine at pH 9 (89:11, v/v). Sample preparation was carried out using a C2 (500 mg sorbent, 3 ml reservoirs) solid-phase extraction method, and extraction efficiencies were followed in individual extracts using a [3H]TAM radiolabelled spike (10000 dpm), with a range of 60-90%. Accuracy and precision (standard deviation) as determined from tumour spiked with radioinert tamoxifen and its metabolites ranged from 83.4-92.3% (+/-23-33%) at 20 microg/g; 85.2-87.7% (+/-18-23%) at 2 microg/g; 88-101% (+/-15-50%) at 0.2 microg/g and 63-94% (+/-13-24%) at 0.02 microg/g. Results from seventy-two patients show mean values (+/-S.D.) of 174+/-203 ng/g for 4-OH; 783+/-1326 ng/g for DMT and 410+/-458 ng/g for TAM, variations reflecting heterogeneity in levels between patients. This methodology can be routinely applied to the determination of tamoxifen and its metabolites in tumour tissues from patients undergoing tamoxifen therapy.

Antineoplastic Agents, Hormonal↗

PubMed1997

Crystal structure of nitrile hydratase reveals a novel iron centre in a novel fold.

BACKGROUND: Nitrile hydratases are unusual metalloenzymes that catalyze the hydration of nitriles to their corresponding amides. They are used as biocatalysts in acrylamide production, one of the few commercial scale bioprocesses, as well as in environmental remediation for the removal of nitriles from waste streams. Nitrile hydratases are composed of two subunits, alpha and beta, and they contain one iron atom per alphabeta unit. We have determined the crystal structure of photoactivated iron-containing nitrile hydratase from Rhodococcus sp. R312 to 2.65 A resolution as a first step in the elucidation of its catalytic mechanism. RESULTS: The alpha subunit consists of a long N-terminal arm and a C-terminal domain that forms a novel fold. This fold can be described as a four layered structure, alpha-beta-beta-alpha, with unusual connectivities between the beta strands. The beta subunit also contains a long N-terminal extension, a helical domain, and a C-terminal domain that folds into a beta roll. The two subunits form a tight heterodimer that is the functional unit of the enzyme. The active site is located in a cavity at the subunit-subunit interface. The iron centre is formed by residues from the alpha subunit only-three cysteine thiolates and two mainchain amide nitrogen atoms are ligands. CONCLUSIONS: Nitrile hydratases contain a novel iron centre with a structure not previously observed in proteins; it resembles a hybrid of the iron centres of heme and Fe-S proteins. The low-spin electronic configuration presumably results in part from two Fe-amide nitrogen bonds. The structure is consistent with the metal ion having a role as a Lewis acid in the catalytic reaction.

Binding Sites↗

PubMed1997

Localization of perlecan (or a perlecan-related macromolecule) to isolated microglia in vitro and to microglia/macrophages following infusion of beta-amyloid protein into rodent hippocampus.

The origin of the heparan sulfate proteoglycan (PG), perlecan, in beta-amyloid protein (A beta)-containing amyloid deposits in Alzheimer's disease (AD) brain is not known. In the present investigation we used indirect immunofluorescence, SDS-PAGE, and Western blotting with a specific perlecan core protein antibody to identify possible cell candidates of perlecan production in both primary cell cultures and in a rat infusion model. Double and triple-labeled indirect immunofluorescence was performed on dissociated primary rat septal cultures using antibodies for specific identification of cell types and for perlecan core protein. In mixed cultures of both embryonic day 18 (containing neurons and glia) and postnatal day 2-3 (devoid of neurons), microglia identified by labeling with OX-42 or anti-ED1 were the only cell type also double labeled with an affinity-purified polyclonal antibody against perlecan core protein. Similar immunolabeling of microglia with the anti-perlecan antibody was also observed in purified cultures of post-natal rat microglia. Analyses of PGs from cultured postnatal rat microglia by Western blotting using a polyclonal antibody against perlecan core protein revealed an approximately 400 kDa band in cell layer, which was intensified following heparitinase/heparinase digestion, suggestive of perlecan core protein. Other lower Mr bands were also found implicating either degradation of the 400 kDa core protein or the presence of separate and distinct gene products immunologically related to perlecan. Reverse transcription followed by polymerase chain reaction using human perlecan domain I specific primers demonstrated perlecan mRNA in cultured human microglia derived from postmortem normal aged and AD brain. Following a 1-week continuous infusion of A beta (1-40) into rodent hippocampus, immunoperoxidase immunocytochemistry and double-labeled immunofluorescent studies revealed perlecan accumulation primarily localized to microglia/macrophages within the A beta infusion site. These studies have identified microglia/macrophages as one potential source of perlecan (or a perlecan-related macromolecule) which may be important for the ongoing accumulation of both perlecan and A beta in the amyloid deposits of AD.

Amyloid beta-Peptides↗

PubMed1997

Processing of [D-Arg1,D-Phe5,D-Trp7,9,Leu11]substance P in xenograft bearing Nu/Nu mice.

[D-Arg1,D-Phe5,D-Trp7,9,Leu11]Substance P is a broad-spectrum neuropeptide growth factor antagonist that has exhibited in vitro activity against a range of human cancer cell lines. The fate of this compound in vivo following i.p. administration at 12 micrograms/g to nu/nu mice bearing the H69 small-cell lung cancer xenograft has been studied. Metabolism was confined to the C-terminus producing [D-Arg1,D-Phe5,D-Trp7,9,Leu11]substance P acid and [D-Arg1,D-Phe5,D-Trp7,9]substance P(1-10). The peptide had a long half-life in plasma (45.9 min) and became widely distributed among the tissues studied with the highest accumulation observed in the liver (AUC 1102 micrograms/g x min) and the lowest in the brain (5 micrograms/g x min). Uptake into the tumor xenograft was poor (AUC 189 micrograms/g x min); however, uptake into the lungs was much greater (AUC 507 micrograms/g x min), offering encouragement that therapeutic concentrations may be targeted to primary lung tumors.

Animals↗

PubMed1997

Preclinical studies on the broad-spectrum neuropeptide growth factor antagonist G.

1. Antagonist G is a broad-spectrum neuropeptide growth factor antagonist that inhibits the growth of small cell lung cancer (SCLC) cells both in vitro and in vivo. 2. Antagonist G is metabolized in peripheral tissues by a chymotrypsin-like serine carboxypeptidase causing C-terminal deamidation and removal of the methionine residue. 3. The metabolites of Antagonist G retain neuropeptide antagonist properties and are thought to contribute to the parent peptide's antitumor activity. 4. Pharmacokinetic studies following systemic (IP) administration to nude mice revealed that the tissue distribution of Antagonist G is likely to be determined by vascular permeability. 5. Preclinical toxicology studies have been completed, and we have now started a phase I clinical trial.

Animals↗

PubMed1997

Cell cycle effects of the novel topoisomerase I inhibitor NU/ICRF 505 in a panel of Chinese hamster ovary cell lines.

The effect of the novel topoisomerase I inhibitor NU/ICRF 505 (20 microM, approximate IC50 concentration) on the cell cycle was studied by flow cytometry in four Chinese hamster ovary (CHO) cell lines. Postdrug treated cells were incubated with optimal concentrations of cytochalasin B to prevent re-entry of daughter cells into the cell cycle. NU/ICRF 505 had no significant effect on cell cycle distribution in the parent cell line (CHO-K1) and two mutants hypersensitive to topo II inhibitors (ADR-1, ADR-3), all of which express similar levels of topo I protein. In the drug-resistant variant ADR-r, which overexpresses topo I 2-fold, a significant accumulation of cells in G1 phase was recorded. These results are broadly consistent with the cell cycle effects expected in CHO cells by a classic topo I poison (camptothecin) and add weight to the view that NU/ICRF 505 induces cell death primarily through topo I inhibition.

Animals↗

PubMed1997

Perceived organizational support, discretionary treatment, and job satisfaction.

A diverse sample of 295 employees drawn from a variety of organizations was surveyed to investigate (a) whether the relationship between the favorableness of job conditions and perceived organizational support (POS) depends on employee perceptions concerning the organization's freedom of action and (b) whether POS and overall job satisfaction are distinct constructs. The favorableness of high-discretion job conditions was found to be much more closely associated with POS than was the favorableness of low-discretion job conditions. No such relationship was found between job conditions and satisfaction. To decide how much the organization values their contributions and well-being, employees distinguish job conditions whose favorableness the organization readily controls versus job conditions whose favorableness is constrained by limits on the organization's discretion.

Adult↗

PubMed1997

Perlecan binds to the beta-amyloid proteins (A beta) of Alzheimer's disease, accelerates A beta fibril formation, and maintains A beta fibril stability.

Perlecan is a specific heparan sulfate proteoglycan that accumulates in the fibrillar beta-amyloid (A beta) deposits of Alzheimer's disease. Perlecan purified from the Engelbreth-Holm-Swarm tumor was used to define perlecan's interactions with A beta and its effects on A beta fibril formation. Using a solid-phase binding immunoassay, freshly solubilized full-length A beta peptides bound immobilized perlecan at two sites, representing both high-affinity [K(D) = approximately 5.8 x 10(-11) M for A beta (1-40); K(D) = approximately 6.5 x 10(-12) M for A beta (1-42)] and lower-affinity [K(D) = 3.5 x 10(-8) M for A beta (1-40); K(D) = 4.3 x 10(-8) M for A beta (1-42)] interactions. An increase in the binding capacity of A beta (1-40) to perlecan correlated with an increase in A beta amyloid fibril formation during a 1-week incubation period. The high-capacity binding of A beta (1-40) to perlecan was similarly observed using perlecan heparan sulfate glycosaminoglycans and was completely abolished by heparin, but not by chondroitin-4-sulfate. Using a thioflavin T fluorometry assay, perlecan accelerated the rate of A beta (1-40) amyloid fibril formation, causing a significant increase in A beta fibril assembly over a 2-week incubation period at 1 h (2.8-fold increase), 1 day (3.6-fold increase), and 3 days (2.8-fold increase) in comparison with A beta (1-40) alone. Perlecan also initially accelerated the formation of A beta (1-42) fibrils within 1 h and maintained significantly higher levels of A beta (1-42) thioflavin T fluorescence throughout a 2-week experimental period in comparison with A beta (1-42) alone, suggesting perlecan's ability to maintain amyloid fibril stability. Perlecan's effects on A beta (1-40) fibril formation and maintenance of A beta (1-42) fibril stability occurred in a dose-dependent manner and was also mediated primarily by perlecan's glycosaminoglycan chains. Perlecan was the most effective enhancer and accelerator of A beta fibril formation when compared directly with other amyloid plaque components, including apolipoprotein E, alpha1-antichymotrypsin, P component, C1q, and C3. This study, therefore, demonstrates that perlecan not only binds to the predominant isoforms of A beta, but also accelerates A beta fibril formation and stabilizes amyloid fibrils once formed, confirming pivotal roles for perlecan in the pathogenesis of A beta amyloidosis in Alzheimer's disease.

Alzheimer Disease↗

PubMed1996

Development of anthracenyl-amino acid conjugates as topoisomerase I and II inhibitors that circumvent drug resistance.

Anthracenyl-amino acid conjugates (AAC) represent a novel class of topoisomerase (topo) inhibitor. The relationship between mechanism of enzyme inhibition and in vitro cytotoxicity has been investigated in a panel of 5 Chinese hamster ovary (CHO) and 2 human ovarian cancer cell lines (A2780) shown to possess different drug resistance phenotypes associated with altered expression of topo I and topo II. From a total of 13 compounds, 4 displayed broad-spectrum activity (IC50 ranging from 3.5-29.7 microM). NU/ICRF 500 (topo II catalytic inhibitor) was 1.4-fold more active against CHO ADR-1, which overexpresses topo II and was essentially noncross-resistant in CHO ADR-r (13.9-fold resistant to doxorubicin (DOX)) and 2780AD (1,460-fold resistant to DOX). NU/ICRF 505, which stabilises topo I cleavable complexes, was noncross-resistant in CHO ADR-3 (3,4-fold resistant to camptothecin) and only 1.8-fold cross-resistant in 2780AD. Hypersensitivity was recorded in ADR-r that overexpresses topo I. The most active compound was NU/ICRF 506, a dual catalytic inhibitor of topo I and II. Hypersensitivity was observed in ADR-r (1.4-fold) but not ADR-1, indicating that topo I is the likely nuclear target, and a low level of resistance was seen in the CHO ADR-6 drug transport mutant and 2780AD. The topo II catalytic inhibitor NU/ICRF 513 only produced hypersensitivity in ADR-r. These data suggest that NU/ICRF 500, 505, and 506 induce cell death, at least partly, through topo inhibition. NU/ICRF 513 appears to be cytotoxic via a nontopo mechanism of action. In addition, NU/ICRF 505 significantly inhibited the growth of two human xenografts (HT-29 colon cancer and NX002 nonsmall-cell lung cancer) in nude mice after i.p. administration at a dose of 25 mg/kg. The important properties of noncross-resistance and in vivo antitumour activity merit further development of AAC as potential new anticancer drugs.

Amino Acids↗

PubMed1996

Determination of the novel topoisomerase I inhibitor NU/ICRF 505 and its major metabolite in plasma, tissue and tumour by high-performance liquid chromatography.

A high-performance liquid chromatographic technique is presented for the determination of the novel topoisomerase I inhibitor NU/ICRF 505 (a tyrosine conjugate of anthraquinone), its major metabolite (NU/ICRF 505/M) and an internal standard (NU/ICRF 513, dihydroxyphenylalanine conjugate). The method uses a reversed-phase (Apex ODS-2) stationary phase and a mobile phase consisting of 0.25 M ammonium acetate adjusted to pH 3 with 25% (v/v) trifluoroacetic acid and methanol with gradient elution. Between-day variation in retention times were less than 1% for NU/ICRF 505 and 513 and 2.4% for the metabolite. Selective detection was achieved at a wavelength of 545 nm giving a limit of detection of 2 ng on column and 50 ng/ml after sample preparation for all three components. Chromatograms were free from interfering peaks even at very high detector sensitivity. Sample preparation was based on incubation of biological specimens (0.5 ml plasma or homogenate) with dimethylsulphoxide and acetonitrile at 4 degrees C for 30 min followed by centrifugation. Liver and tumour were homogenised in phosphate buffered saline. Recoveries were consistently high (81.7-106.7% for NU/ICRF 505; 88.7-103.3% for NU/ICRF 513 and 83.7-98.7% for NU/ICRF 505/M) with between day coefficients of variation of normally less than 10%. The method will contribute significantly to the preclinical evaluation of NU/ICRF 505.

Animals↗

PubMed1996

Enzymology of mitomycin C metabolic activation in tumour tissue. Characterization of a novel mitochondrial reductase.

In this study, the enzymology of mitomycin C (MMC) bioactivation in two murine colon adenocarcinomas, MAC 16 and MAC 26, was examined. Subcellular quinone reductase assessment via cytochrome c reduction confirmed a number of active enzymes. MAC 16 exhibited 22-fold greater levels of cytosolic DT-diaphorase than MAC 26, while microsomal NADPH:cytochrome P-450 reductase levels were similar in both tumour types. Metabolism of MMC by subcellular fractions isolated from both MAC 16 and MAC 26 was quantitated by monitoring the formation of the principle metabolite 2,7-diaminomitosene (2,7-DM) via high-performance liquid chromatography (HPLC). In MAC 16 only, activity displaying the properties of cytosolic DT-diaphorase and microsomal NADPH:cytochrome P-450 reductase was detected and confirmed, using the enzyme inhibitors dicoumarol and cytochrome P-450 reductase antiserum, respectively. The highest level of MMC metabolism was associated with the mitochondrial fraction from both tumours and was the sole enzyme activity detected in MAC 26. The greatest mitochondrial drug metabolism was achieved in the presence of NADPH as cofactor and hypoxia (MAC 16-specific activity, 3.67 +/- 0.58 nmol/30 min/mg; MAC 26 specific-activity, 3.87 +/- 0.71 nmol/30 min/mg) and was unaffected by the addition of the inhibitors dicoumarol and cytochrome P-450 reductase antiserum. NADH-dependent mitochondrial activity was only observed in MAC 16 at approximately 4-fold less than that seen with NADPH. MAC 26 homogenate incubations displayed enhanced metabolism under hypoxia, presumably due to the presence of the identified mitochondrial enzyme. MAC 16 homogenates showed no increase in metabolism under hypoxia, suggesting that other enzyme(s) may be predominant. These data indicate the presence of a novel mitochondrial one-electron reductase capable of metabolising MMC in MAC 16 and MAC 26.

Adenocarcinoma↗

PubMed1996

Solid-phase extraction and high-performance liquid chromatographic determination of tamoxifen and its major metabolites in plasma.

Tamoxifen (TAM) is a triphenylethylene anti-oestrogen, commonly used in the treatment of breast cancer. Patients receiving tamoxifen therapy may experience both de novo and acquired resistance. As one of the mechanisms for this may be extensive peripheral bio-transformation of tamoxifen, there has been considerable interest in the pharmacokinetics and metabolism of tamoxifen. A reversed-phase high-performance liquid chromatography separation has been developed to determine the levels of tamoxifen and its major metabolites in human plasma. The method is highly sensitive (2 ng/ml) and selective for tamoxifen, cis-tamoxifen (CIS), 4-hydroxytamoxifen (4-OH) and desmethyltamoxifen (DMT). A micro Bondapak C18 10 microns column (30 cm x 3.9 mm I.D.) was used, with a mobile phase of methanol-1% triethylamine at pH 8 (89:11, v/v). Sample preparation was carried out using a C2 (500 mg sorbent, 3 ml reservoirs) solid phase extraction method, and extraction efficiencies were approximately 60% for TAM and its metabolites. Accuracy and precision, as determined by spiking plasma samples with a mixture of tamoxifen and its metabolites, ranged from 85-110% (+/- 5-10%) at 1 microgram/ml, 101-118% (+/- 8-20%) at 0.1 microgram/ml and 111-168% (+/- 43-63%) at 0.01 microgram/ml. Results from 59 patients show mean values of 54 ng/ml for 4-OH; 190 ng/ml for DMT; 93 ng/ml for TAM and 30 ng/ml for CIS (detected in three patients only). This methodology can be applied routinely to the determination of TAM and its metabolites in plasma from patients undergoing therapy.

Antineoplastic Agents, Hormonal↗

PubMed1996

Metabolism of the broad-spectrum neuropeptide growth factor antagonist: [D-Arg1, D-Phe5, D-Trp7,9, Leu11]-substance P.

Broad-spectrum neuropeptide growth factor antagonists, such as [D-Arg1, D-Phe5, D-Trp7,9, Leu11]substance P (antagonist D) and [Arg6, D-Trp7,9, NmePhe8]substance P(6-11) (antagonist G), are currently being investigated as possible anti-tumour agents. These compounds are hoped to be effective against neuropeptide-driven cancers such as small-cell lung cancer. Antagonist D possesses a broader antagonistic spectrum than antagonist G and hence may be of greater therapeutic use. The in vitro metabolism of antagonist D has been characterised and the structures of two major metabolites have been elucidated by amino acid analysis and mass spectrometry. Metabolism was confined to the C-terminus where serine carboxypeptidase action produced [deamidated]-antagonist D (metabolite 1) and [des-Leu11]-antagonist D (metabolite 2) as the major metabolites. Biological characterisation of the metabolites demonstrated that these relatively minor changes in structure resulted in a loss of antagonist activity. These results provide some of the first structure-activity information on the factors that determine which neuropeptides these compounds inhibit and on the relative potency of that inhibition.

Amino Acid Sequence↗