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Biomedical subjects

Peter J Smith

Publications and source records attributed to Peter J Smith.

At least 19 recordsLinked to original sources
PubMed2006

Acridone and furoquinoline alkaloids from Teclea gerrardii (Rutaceae: Toddalioideae) of southern Africa.

The combined hexane/CH(2)Cl(2) extract of the stem bark of Teclea gerrardii (Rutaceae: Toddalioideae) has yielded two acridone alkaloids, 3-hydroxy-1-methoxy-N-methylacridone (tegerrardin A) (1) and 3-hydroxy-N-methyl-1-(gamma,gamma-dimethylallyloxy)acridone (tegerrardin B) (2), three known acridones (3-5), two known furoquinolines (6,7), and the acridone precursor tecleanone (8). Arborinine (3) and evoxine (6) displayed moderate antiplasmodial activity against the CQS D10 strain of Plasmodium falciparum, with IC(50) values of 12.3 and 24.5 microM, respectively.

Acridines↗
PubMed2006

The pharmacokinetics of intravenous artesunate in adults with severe falciparum malaria.

OBJECTIVE: Intravenous artesunate is commonly used in the emergency treatment of patients with severe falciparum malaria in Asia. The choice of doses used has been empirical. To inform dosage recommendations we assessed the pharmacokinetics of intravenous artesunate after the first dose. METHODS: As part of a clinical trial of artesunate in adults with severe falciparum malaria in western Thailand, we assayed plasma concentrations of artesunate and the principal biologically active metabolite dihydroartemisinin (DHA) in 17 patients given an initial dose of 2.4 mg/kg body weight of intravenous artesunate. Drug levels were measured using high performance liquid chromatography with mass spectroscopy-electrospray ionisation detection. RESULTS: Median (range) observed DHA Cmax was 2128 (513-5789) nmol/L, elimination half-life was 0.34 (0.14-0.87) h, and the time to the last detectable DHA was 2 h. CONCLUSION: The large inter-individual variability (10 fold) in DHA Cmax and AUC in patients with potentially lethal, severe malaria, suggests that 2.4 mg/kg should be the minimum daily dose in severe malaria.

Administration, Oral↗
PubMed2006

Multidisciplinary approach to diagnosis and management of osteosarcoma - a review of the St Vincent's Hospital experience.

BACKGROUND: Osteosarcoma is the most common primary malignant bone tumour in children and young adults. Despite advances in the diagnosis and management of osteosarcoma, there have been few recent studies describing the experiences of tertiary referral centres. This paper aims to describe and discuss the clinical features, pre-operative work-up, management and outcomes of these patients at St Vincent's Hospital (Melbourne, Australia). METHODS: Retrospective study of fifty-nine consecutive patients managed for osteosarcoma at St Vincent's Hospital between 1995 and 2005. RESULTS: Median age at diagnosis was 21 (range, 11-84) years. Gender distribution was similar, with thirty-one male and twenty-eight female patients.Twenty-five patients had osteosarcoma in the femur, eleven each were located in the humerus and tibia, six were identified in the pelvis, and one each in the clavicle, maxilla, fibula, sacrum, ulna and radius.Pre-operative tissue diagnosis of osteosarcoma was obtained through computed tomography-guided percutaneous biopsy in over ninety percent of patients. Following initial therapy, over fifty percent of patients remained relapse-free during the follow-up period, with twelve percent and twenty-seven percent of patients documented as having local and distant disease recurrence, respectively. Of patients with recurrent disease, sixty-two percent remained disease-free following subsequent surgical intervention (most commonly, pulmonary metastatectomy). CONCLUSION: Patient outcomes can be optimised through a multidisciplinary approach in a tertiary referral centre. At St Vincent's Hospital, survival and relapse rates of patients managed for osteosarcoma compare favourably with the published literature.

Journal Article↗
PubMed2006

Synthesis, structure, and biological activity of ferrocenyl carbohydrate conjugates.

Seven ferrocenyl carbohydrate conjugates were synthesized. Coupling reactions of monosaccharide derivatives with ferrocene carbonyl chloride produced {6-N-(methyl 2,3,4-tri-O-acetyl-6-amino-6-deoxy-alpha-D-glucopyranoside)}-1-ferrocene carboxamide (3), {1-O-(2,3,4,6-tetra-O-benzyl-D-glucopyranose)}-1-ferrocene carboxylate (4), and {6-O-(1,2,3,4-tetra-O-acetyl-beta-D-glucopyranose)}-1-ferrocene carboxylate (5). Similarly, 1,1'-bis(carbonyl chloride)ferrocene was coupled with the appropriate sugars to produce the disubstituted analogues bis{6-N-(methyl 2,3,4-tri-O-acetyl-6-amino-6-deoxy-alpha-D-glucopyranoside)}-1,1'-ferrocene carboxamide (8), bis{1-O-(2,3,4,6-tetra-O-benzyl-D-glucopyranose)}-1,1'-ferrocene carboxylate (9), and bis{6-O-(1,2,3,4-tetra-O-acetyl-beta-D-glucopyranose)}-1,1'-ferrocene carboxylate (10). {6-N-(Methyl-6-amino-6-deoxy-alpha-D-glucopyranoside)}-1-ferrocene carboxamide monohydrate (12) was synthesized via amide coupling of an activated ferrocenyl ester with the corresponding carbohydrate. All compounds were characterized by elemental analysis, 1H NMR spectroscopy, and mass spectrometry. X-ray crystallography confirmed the solid-state structure of three ferrocenyl carbohydrate conjugates: 2-N-(1,3,4,6-tetra-O-acetyl-2-amino-2-deoxy-D-glucopyranose)-1-ferrocene carboxamide (1), 1-S-(2,3,4,6-tetra-O-acetyl-1-deoxy-1-thio-D-glucopyranose)-1-ferrocene carboxylate (2), and 12. The above compounds, along with bis{2-N-(1,3,4,6-tetra-O-acetyl-2-amino-2-deoxy-D-glucopyranose)}-1,1'-ferrocene carboxamide (6), bis{1-S-(2,3,4,6-tetra-O-acetyl-1-deoxy-1-thio-D-glucopyranose)}-1,1'-ferrocene carboxylate (7), and 2-N-(2-amino-2-deoxy-D-glucopyranose)-1-ferrocene carboxamide (11) were examined for cytotoxicity in cell lines (L1210 and HTB-129) and for antimalarial activity in Plasmodium falciparum strains (D10, 3D7, and K1, a chloroquine-resistant strain). In general, the compounds were nontoxic in the human cell line tested (HTB-129), and compounds 4, 7, and 9 showed moderate antimalarial activity in one or more of the P. falciparum strains.

Animals↗
PubMed2006

Percutaneous radiofrequency ablation for osteoid osteoma: experience with a new treatment.

OBJECTIVE: To review our experience with percutaneous radiofrequency ablation (RFA) for osteoid osteoma. PARTICIPANTS, DESIGN AND SETTING: Retrospective review of 24 patients with osteoid osteoma treated with percutaneous RFA at St Vincent's Hospital, Melbourne, from August 2000 to February 2005. MAIN OUTCOME MEASURES: Initial response to treatment, return of symptoms, time to recurrence, complications and histopathological correlation. RESULTS: In 23 of 24 patients, there was immediate relief of symptoms. One-third of patients had a return of symptoms. The 24 patients underwent a total of 32 RFA procedures. Of the eight patients who had a recurrence, five had an initial lesion > or = 10 mm in maximum diameter. Twenty-three of the 24 patients were pain-free at the end of the study period. Patients were followed up for a median of 26 months. There were no long-term complications. CONCLUSIONS: Percutaneous RFA is a safe and efficacious treatment for osteoid osteoma with a low morbidity rate. Despite recurrence after treatment, re-treatment is simple and effective.

Adolescent↗
PubMed2006

Analysis of P-glycoprotein expression in purified parasite plasma membrane and food vacuole from Plasmodium falciparum.

A P-glycoprotein homologue (Pgh1) is believed to play a role in modulating levels of chloroquine resistance in Plasmodium falciparum. To study the role of Pgh1 in the mechanism of chloroquine (CQ) resistance, antisera were raised against this protein. There was no direct association between the level of Pgh1 expression and chloroquine sensitivity. We also failed to detect phosphorylation of Pgh1 in the food vacuole (FV), suggesting that other mechanisms regulate the chloroquine-resistant (CQR) phenotype. Therefore, high levels of expression of Pgh1 or phosphorylation of this protein in the FV could not account for CQ sensitivity. In addition, the lack of inhibition of CQ accumulation by anti-Pgh1 antibodies suggests that Pgh1 is not involved as a CQ transporter in the plasma membrane of P. falciparum. Furthermore, resistance reversers do not appear to act at the plasma membrane level.

ATP-Binding Cassette Transporters↗
PubMed2006

Variability in the population pharmacokinetics of pyrazinamide in South African tuberculosis patients.

OBJECTIVE: This study was designed to characterize the population pharmacokinetics of pyrazinamide in South African pulmonary tuberculosis patients, with special reference to interindividual and interoccasional variability (IIV and IOV, respectively). METHODS: Concentration-time measurements obtained from 227 patients receiving oral doses of pyrazinamide were pooled to create a dataset containing 3,092 data points spanning multiple dosing occasions. The software program NONMEM was used to analyze the data. RESULTS: A one-compartment model with first-order absorption, including a zero-order component describing release from formulation, and first-order elimination best described the data. The absorption rate constant was estimated to be bimodally distributed between two distinct subgroups, fast and slow, in approximately even proportion. Absorption rate was threefold greater in fast absorbers (3.56 h(-1)) in comparison to slow absorbers (1.25 h(-1)). Typical values of oral clearance and apparent volume of distribution were estimated as 3.42 L h(-1) and 29.2 l, respectively. IOV was supported in oral clearance (0.0238, variance) and absorption rate (0.623, variance). The duration of zero-order absorption was estimated as 0.290 h, and was quite variable between patients (0.957, variance). CONCLUSION: The absorption of pyrazinamide in the studied population was highly variable and two separate subpopulations were identified. IOV accounted for a proportion of the variability in clearance and the absorption rate constant.

Absorption↗
PubMed2006

Dual-acting diamine antiplasmodial and chloroquine resistance modulating agents.

On the basis of structural features known to be critical for the antimalarial activity, accumulation and uptake of chloroquine (CQ), as well as chemosensitization of CQ resistant Plasmodium falciparum, an exploratory novel series of potential dual acting antiplasmodial and chemosensitizing agents was designed and synthesized for biological evaluation. All four compounds contain a common alkyl side chain with two amino groups and differ only in the chemical nature of the hydrophobic aromatic moieties. Among them, N'-[4-(biphenyl-2-ylmethoxy)-benzyl]-N,N-dimethyl-propane-1,3-diamine (P7) displayed the greatest potential as a dual-acting antiplasmodial agent against CQ-resistant strains (IC50K1/RSA11<0.6 microM) and chemosensitizer (RMIK1=0.67; RMIRSA11=0.82) while displaying low in vitro cytotoxicity against a mammalian cell line (CHO). At 1 microM, P7 caused a 8.5 and 4-fold potentiation in CQ accumulation in resistant P. falciparum K1 and RSA11 strains, respectively. In a parallel experiment, 1 microM verapamil showed a 6.5 (K1) and 2 (RSA11)-fold increase in CQ accumulation. The preliminary studies point to structural features that may determine antiplasmodial and/or CQ resistance modulating activity in this new series of compounds. An additive effect was observed against both CQS (D10) and CQR (RSA11) strains when CQ and P7 were used at their corresponding IC50 concentrations in isobologram analysis.

Animals↗
PubMed2006

Sulfadoxine-pyrimethamine pharmacokinetics in malaria: pediatric dosing implications.

OBJECTIVE: Our objective was to characterize the pharmacokinetic properties of sulfadoxine-pyrimethamine in African adults and children with acute falciparum malaria. Despite decades of widespread use, there are few data to inform dose recommendations. METHODS: In a prospective multicenter pharmacokinetic study in 307 patients with acute falciparum malaria, capillary blood concentrations of sulfadoxine and pyrimethamine were determined at 9 visits over a period of 42 days by mass spectrometry. RESULTS: After adjustment for dose, the area under the concentration-time curves (AUCs) of sulfadoxine and pyrimethamine in children aged 2 to 5 years were half of those in adults (median AUC, 410 microg/mL x d [interquartile range (IQR), 126-705 microg/mL x d] versus 816 microg/mL x d [IQR, 536-1150 microg/mL x d] [P = .0001] for sulfadoxine and 620 ng/mL x d [IQR, 229-1399 ng/mL x d] versus 1518 ng/mL x d [IQR, 1117-2013 ng/mL x d] for pyrimethamine). The effect of age on the AUC of sulfadoxine and pyrimethamine reflected higher clearance rates and larger apparent volumes of distribution in children aged 2 to 5 years when compared with adults (median clearance, 64.5 mL x kg(-1) x d(-1) [IQR, 46.2-132.6 mL x kg(-1) x d(-1)] versus 32.7 mL x kg(-1) x d(-1) [IQR, 22.3-52.2 mL x kg(-1) x d(-1)] for sulfadoxine [P = .0001] and 1.77 L x kg(-1) x d(-1) [IQR, 1.0-3.0 L x kg(-1) x d(-1)] versus 0.85 L x kg(-1) x d(-1) [IQR, 0.62-1.21 L x kg(-1) x d(-1)] for pyrimethamine [P = .0001]; median volume of distribution, 413 mL/kg [IQR, 299-711 mL/kg] versus 372 mL/kg [IQR, 267-488 mL/kg] for sulfadoxine [P = .0021] and 6.28 L/kg [IQR, 3.83-11.24 L/kg] versus 3.83 L/kg [IQR, 2.73-5.11 L/kg] for pyrimethamine [P = .0001]). Day 7 concentrations of both sulfadoxine and pyrimethamine provided good surrogate measures (R(2) >or= 0.72) of their respective AUCs. CONCLUSIONS: Pharmacokinetic factors may contribute to the increased risk of sulfadoxine-pyrimethamine antimalarial treatment failure in young children. The current dose recommendations need revision. We predict that children aged 2 to 5 years should be treated with 1 g sulfadoxine/50 mg pyrimethamine to achieve drug concentrations equivalent to those in adults.

Adolescent↗
PubMed2006

Discovering new natural products directly from crude extracts by HPLC-SPE-NMR: chinane diterpenes in Harpagophytum procumbens.

HPLC-SPE-NMR experiments with crude extracts of Harpagophytum procumbens allowed the rapid identification of novel, unstable chinane-type tricyclic diterpenes (1 and 2), along with numerous other constituents. Dramatic sensitivity gains achieved with this novel hyphenated technique establish a new paradigm in natural products research: rapid and rigorous structure determination of multiple extract components, including minor components, without preparative-scale isolation.

Chromatography, High Pressure Liquid↗
PubMed2006

Identification of major and minor constituents of Harpagophytum procumbens (Devil's claw) using HPLC-SPE-NMR and HPLC-ESIMS/APCIMS.

The HPLC-SPE-NMR technique, supported by HPLC-MS measurements, was used to determine structures of major as well as some minor constituents of ethanol and petroleum ether extracts of Harpagophytum procumbens (Devil's claw) roots. This method was also shown to be applicable for rapid and precise on-line identification of secondary metabolites present in commercial herbal products of H. procumbens. A total of 15 compounds (1-14 and 17) were identified from the ethanol and petroleum ether extracts, including a novel Diels-Alder dimer 14. Optimization of the HPLC-SPE-NMR experiments included quantitative (1)H NMR measurements, determination of trapping and elution efficiency, effect of multiple trapping of analytes, use of various deuterated solvents for SPE cartridge elution, and effect of post-column dilution ratio of eluent with water. Linear accumulation of apolar and relatively polar analytes was demonstrated for at least 8-10 repeated trappings, resulting in greatly improved signal-to-noise ratios in NMR spectra and reduced acquisition times. Thus, the HPLC-SPE-NMR technique provides an efficient means of identification of multiple components of crude extracts. By allowing on-line generation of high-quality 2D NMR data without traditional purification of extract components, the HPLC-SPE-NMR methodology represents a paradigm shift in natural products research with respect to structure elucidation.

Chromatography, High Pressure Liquid↗
PubMed2005

Chloroquine accumulation by purified plasma membranes from Plasmodium falciparum.

Resistance of Plasmodium falciparum to chloroquine (CQ) has been associated with a decrease in CQ accumulation by parasitized erythrocytes. This study aimed at investigating the role of parasite plasma membranes (PPM) in the mechanism of CQ accumulation. CQ accumulation capabilities of membranes were determined using tritiated CQ. PPM isolated from chloroquine-sensitive parasites were found to accumulate less CQ than those isolated from chloroquine-resistant parasites. However, CQ accumulation was found to be ATP-independent suggesting that this accumulation results from binding rather than transport.

Animals↗
PubMed2005

Femoral mesenchymal chondrosarcoma with secondary aneurysmal bone cysts mimicking a small-cell osteosarcoma.

Mesenchymal chondrosarcoma is a rare but aggressive, high-grade malignancy of primitive cartilage-forming mesenchyme that arises most commonly from skeletal sites. Although there are radiological findings suggestive of the diagnosis, imaging features often overlap with those of other skeletal sarcomas. The definitive diagnosis relies on the histological finding of a typical bimorphic appearance, consisting of nests of small, round, poorly differentiated cells and more mature cartilaginous tissue. To highlight this, we present the case of a 21-year-old man who was referred to our institution with a history of right knee pain. Initial imaging and histological evaluation of a core biopsy of the lesion suggested osteosarcoma of the distal right femur; after review, however, the correct diagnosis of mesenchymal chondrosarcoma was made. Adequate tissue sampling and thorough histological evaluation of biopsy specimens is vital for the accurate diagnosis of primary bone malignancies, especially those of chondroid origin.

Adult↗
PubMed2005

Osteosarcoma near joints: assessment and implications.

BACKGROUND: The choice of performing surgery when tumors encroach onto joints remains a challenging and controversial issue. Pre-operative assessment by magnetic resonance imaging (MRI) is of critical importance in dictating surgical management and subsequent functional outcome. METHODS: We examined archival samples from 27 patients with osteosarcoma, adjacent to synovial joints for the incidence and mechanism of osteosarcoma extension into the joint space. Histopathologic findings were correlated with pre-operative MRI findings and choice of operation. RESULTS: There was no evidence of penetration across the entire thickness of articular cartilage into the joint cavity in all of the 27 cases. When pre-operative MRI confidently excluded joint involvement by tumor, enabling an intra-articular surgical approach, histopathologic correlation confirmed the absence of joint involvement in all cases. The low incidence of joint involvement was despite the presence of extensive bone and soft tissue involvement in most cases, a tendency for peripheral extension of tumor around the articular margin of the bone, and evidence of joint effusions pre-operatively in more than one-third of cases. CONCLUSIONS: Joint involvement by osteosarcoma is uncommon, with articular cartilage being a relative barrier to tumor invasion. If pre-operative MRI does not show definite evidence of intra-articular tumor involvement, it is likely to be safe to proceed with intra-articular resection.

Adolescent↗
PubMed2005

Tuberculosis masquerading as malignancy: a multimodality approach to the correct diagnosis - a case report.

BACKGROUND: Extrapulmonary tuberculosis is one of the great mimickers of medicine, and often masquerades as malignancy. As a result, patients may be referred to oncologists and surgeons for further evaluation and management, delaying the institution of appropriate anti-tuberculous drug therapy. CASE PRESENTATION: We present the case of a 21 year old man with tuberculous osteomyelitis, who was referred to the Bone and Soft Tissue Sarcoma Service at our institution with a provisional diagnosis of malignancy. Further investigation revealed extensive retroperitoneal abdominal and pelvic lymphadenopathy. The recognition of certain patterns on imaging, and finally the isolation of Mycobacterium tuberculosis from tissue samples obtained under image guidance, enabled the correct diagnosis to be made. CONCLUSION: This case highlights the importance of remaining cognisant of the protean manifestations of extrapulmonary tuberculosis, and illustrates the advantage of a clinically directed multi-modality imaging approach to diagnosis.

Journal Article↗
PubMed2005

Design, synthesis and anti-plasmodial evaluation in vitro of new 4-aminoquinoline isatin derivatives.

A new class of 4-aminoquinoline derivatives based on the natural product isatin scaffold were designed and synthesized for biological evaluation against three strains of the malaria parasite Plasmodium falciparum. These derivatives showed anti-plasmodial IC(50) values in the ranges of 1.3-0.079 and 2.0-0.050muM against a chloroquine-sensitive (D10) and two resistant (K1 and W2) strains of P. falciparum, respectively. In order to determine potential targets for this class of compounds in P. falciparum, selected compounds were also tested against the parasitic cysteine protease falcipain-2. In terms of further development of this class of isatin derivatives, two of the compounds based on a flexible alkyl chain linker and a thiosemicarbazone moiety warrant further investigation as potential anti-plasmodial leads. These two derivatives showed good in vitro activity against K1 and W2 with IC(50) values of 51 and 54nM, respectively, while retaining potency against the D10 strain with IC(50) values of 79 and 95nM, respectively. Generally speaking, the inhibitory potency of all compounds in the series against the parasites did not strongly correlate with inhibitory potency against falcipain-2 for selected compounds tested, which at best was weak to moderate, suggesting other mechanisms of inhibition may also be involved or compounds may be selectively taken up by Plasmodium falciparum.

Aminoquinolines↗
PubMed2005

Reversal of chloroquine resistance in Plasmodium falciparum by 9H-xanthene derivatives.

Four new chemosensitisers against chloroquine-resistant Plasmodium falciparum based on the 9H-xanthene tricyclic scaffold were designed and synthesised in an attempt to identify simplified compounds that are easily accessible from commercially available starting materials. The compounds contain a common hydrophobic tricyclic 9H-xanthene moiety and an alkyl side chain with two amino groups, one of which is a tertiary substituted terminal amine, separated by three carbons and differing only in the chemical nature of the intermediary nitrogen atom. The best chemosensitising compound has a secondary amino group, showed a response modification index of 0.36 and caused a four-fold increase in chloroquine accumulation in a resistant strain of P. falciparum as well as having the highest selective therapeutic index when tested against a mammalian cell line.

Animals↗