Search PubMed⌕ Search

Biomedical subjects

F Mitchell

Publications and source records attributed to F Mitchell.

At least 19 recordsLinked to original sources
PubMed2005

A phase I pharmacokinetic and pharmacodynamic study of BGC9331 and carboplatin in relapsed gynaecological malignancies.

BGC9331 is a rationally designed, specific nonpolyglutamatable thymidylate synthase (TS) inhibitor that is active in gynaecological malignancies. In the light of the sensitivity of human ovarian tumour cell lines to BGC9331 and non-cross resistance to platinum drugs, we studied the combination BGC9331/carboplatin (BCA) in a phase I (PI) pharmacokinetic (PK) and pharmacodynamic (PD) study in platinum pretreated gynaecological malignancies. Patients were >or=18 years or over, with a histologically confirmed gynaecological malignancy, radiological evidence of relapse, and a platinum treatment free interval of at least 6 months. Up to three prior lines of chemotherapy were permitted. Carboplatin (AUC5) and BGC9331 were administered on day 1, and BGC9331 was also given on day 8 of a 21-day cycle. In total, 14 patients were enrolled, and treated with BGC9331 at four dose levels, 40, 65, 85 and 100 mg m-2. The principal grade 3 and 4 haematological toxicity was neutropaenia. The principal nonhaematological toxicities were lethargy and nausea. Dose-limiting toxicities were seen in two patients at 100 mg m-2 BGC9331 (grade 4 neutropaenia>7 days, and grade 4 fatigue>7 days). Plasma BGC9331 was measured by an ELISA that was adapted for use in humans. Carboplatin was assayed by flameless atomic absorption spectrometry. There was no PK interaction between the two drugs. Plasma deoxyuridine was elevated indicating TS inhibition to at least day 12. Antitumour activity was observed in four out of 14 (28%) of patients. In conclusion, the combination of BGC9331 and carboplatin is well tolerated with no significant PK interaction between the two drugs. There is evidence of TS inhibition with the combination. We have demonstrated antitumour activity in platinum pretreated gynaecological malignancy. Further exploration of this combination in this disease is warranted.

Adult↗
PubMed2004

Safety and efficacy of chimeric yellow Fever-dengue virus tetravalent vaccine formulations in nonhuman primates.

To construct chimeric YF/DEN viruses (ChimeriVax-DEN), the premembrane (prM) and envelope (E) genes of yellow fever (YF) 17D virus were replaced with those of each wild-type (WT) dengue (DEN) virus representing serotypes 1 to 4. ChimeriVax-DEN1-4 vaccine viruses were prepared by electroporation of Vero cells with RNA transcripts prepared from viral cDNA (F. Guirakhoo, J. Arroyo, K. V. Pugachev, C. Miller, Z.-X. Zhang, R. Weltzin, K. Georgakopoulos, J. Catalan, S. Ocran, K. Soike, M. Ratteree, and T. P. Monath, J. Virol. 75:7290-7304, 2001; F. Guirakhoo, K. Pugachev, J. Arroyo, C. Miller, Z.-X. Zhang, R. Weltzin, K. Georgakopoulos, J. Catalan, S. Ocran, K. Draper, and T. P. Monath, Virology 298:146-159, 2002). Progeny viruses were subjected to three rounds of plaque purifications to produce the Pre-Master Seed viruses at passage 7 (P7). Three further passages were carried out using U.S. current Good Manufacturing Practices (cGMP) to produce the Vaccine Lot (P10) viruses. Preclinical studies demonstrated that the vaccine candidates are replication competent and genetically stable and do not become more neurovirulent upon 20 passages in Vero cells. The safety of a tetravalent vaccine was determined and compared to that of YF-VAX in a formal monkey neurovirulence test. Brain lesions produced by the tetravalent ChimeriVax-DEN vaccine were significantly less severe than those observed with YF-VAX. The immunogenicity and protective efficacy of four different tetravalent formulations were evaluated in cynomolgus monkeys following a single-dose subcutaneous vaccination followed by a virulent virus challenge 6 months later. All monkeys developed low levels of viremia postimmunization, and all the monkeys that had received equal concentrations of either a high-dose (5,5,5,5) or a low-dose (3,3,3,3) formulation seroconverted against all four DEN virus serotypes. Twenty-two (92%) of 24 monkeys were protected as determined by lack of viremia post-challenge. This report is the first to demonstrate the safety of a recombinant DEN virus tetravalent vaccine in a formal neurovirulence test, as well as its protective efficacy in a monkey challenge model.

Animals↗
PubMed2004

Overwintering squash bugs harbor and transmit the causal agent of cucurbit yellow vine disease.

Since 1988, cucurbit crops, particularly watermelon, cantaloupe, and squash, grown in Oklahoma and Texas have experienced devastating losses from cucurbit yellow vine disease (CYVD), caused by the phloem-limited bacterium Serratia marcescens Bizio. Squash bug, Anasa tristis (De Geer), is a putative vector of the pathogen. In 2000-2001, overwintering populations of squash bug collected from DeLeon, TX, were tested for their ability to harbor and transmit the bacterium. Individual squash bugs (n = 73) were caged serially for periods of up to 7 d on at least four squash seedlings. Two studies were conducted, one with insects collected in November 2000 placed on first true leaf-stage seedlings and the second with insects from an April 2001 collection, placed on 3-5 true leaf-stage squash. Controls consisted of squash seedlings caged without insects. Squash bug transmission rates of the pathogen in studies I and II were 20 and 7.5%, respectively. Overall, 11.0% of the squash bugs harbored and successfully transmitted the bacterium to squash seedlings. All control plants tested negative for S. marcescens and did not exhibit CYVD. Female squash bugs killed a significantly greater proportion of young first leaf-stage seedlings than males. Feeding on 3-5 leaf-stage squash resulted in no plant mortality regardless of squash bug gender. This study demonstrated that the squash bug harbors S. marcescens in its overwintering state. The squash bug-S. marcescens overwintering relationship reported herein greatly elevates the pest status of squash bug and places more importance on development of integrated strategies for reducing potential overwintering and emerging squash bug populations.

Animals↗
PubMed2004

Custom skiing and trekking adaptations for a trans-tibial and trans-radial quadrilateral amputee.

A keen skier who is a trans-tibial and trans-radial quadrilateral amputee sought an improved adaptation for skiing from the Rehabilitation Engineering Service in Edinburgh. The unpredictable nature of the bending moments and loads that can be imposed on the prostheses during skiing raised concern about the suitability of standard prosthetic components for this purpose. The authors report a ski boot modification that incorporates mechanical protection for the standard prosthetic components and a description of the custom-adapted alpine trekking sticks used also as ski poles. Reference is made to the role of risk assessment, the design and manufacture in providing this type of custom-made rehabilitation device.

Adult↗
PubMed2002

The design and synthesis of water-soluble analogues of CB30865, a quinazolin-4-one-based antitumor agent.

4-[N-[7-Bromo-2-methyl-4-oxo-3,4-dihydroquinazolin-6-ylmethyl]-N-(prop-2-ynyl)amino]-N-(3-pyridylmethyl)benzamide (CB30865) is a quinazolin-4-one antitumor agent whose high growth-inhibitory activity (W1L2 IC(50) = 2.8 +/- 0.50 nM) is believed to have a folate-independent locus of action. In addition, CB30865 represents a class of compounds with unique biochemical characteristics such as a delayed, non-phase specific, cell-cycle arrest. The low aqueous solubility of CB30865 prompted a search for more water-soluble analogues for in vivo evaluation of this class of compounds. It was thought that aqueous solubility could be increased by the introduction of amino functionalities at the 2-position of the quinazolin-4-one ring. A variety of compounds (5a-j, 31a-c, 32, and 33) were synthesized in a linear fashion starting from 3-chloro-4-methylaniline. Most of these compounds (e.g., 5a, 5b, 5g) were significantly more water-soluble than CB30865 (636 microM for 5a at pH 6 and 992 microM for 5g at pH 6). In addition, some of them were up to 6-fold more cytotoxic than CB30865 (e.g., for 5a, W1L2 IC(50) = 0.49 +/- 0.24 nM) and retained its novel biochemical characteristics.

Antineoplastic Agents↗
PubMed2002

Clinical utility of nested multiplex RT-PCR for group F adenovirus, rotavirus and norwalk-like viruses in acute viral gastroenteritis in children and adults.

BACKGROUND: The diagnosis of viral gastroenteritis can be carried out by non-molecular techniques such as electron microscopy (EM), enzyme-immunoassay and latex agglutination tests and various molecular techniques. Normally molecular detection requires the use of three separate protocols to detect the three main causes of viral gastroenteritis, adenoviruses, rotaviruses and norwalk-like viruses (NLV) which have different types of nucleic acid. The development of a sensitive and specific assay which could detect these targets would have major advantages for the clinical virology laboratory. OBJECTIVES: The aims of the present study were to develop a sensitive and specific multiplex molecular assay and to apply it to the detection of viral agents in clinical cases of acute gastroenteritis. STUDY DESIGN: The multiplex assay was designed using Access RT-PCR (Promega). Primers were researched and selected for their specificity and broad range detection of the viral agents across the various genotypes of group A rotaviruses, NLV and group F adenoviruses. RESULTS: From September 2000 to August 2001 we tested 1945 clinical specimens. Rotavirus infections were detected in 190 with an age range from 12 days to 8 years old. Group F adenovirus was detected in 96 patients ranging from 15 days to 10 years old. A further single case of group F adenovirus was detected in an adult of 75 years old. NLVs were detected in 132 patients. There were 55 infections in children less than 7 years old. In 10 different outbreaks involving 130 adult patients there were 57 NLV positives. Sporadic NLV infection was detected in 11 of 600 adult patients. There were 4 patients with dual infections. CONCLUSIONS: The assay detailed here has proved an invaluable tool for the investigation of acute gastroenteritis in specimens from patients of all ages. We found it convenient to use a single mastermix with a single protocol to test all specimens from patients of all ages. NLV in children is often overlooked and/or under reported, particularly where less sensitive assays such as EM are being employed for diagnosis.

Adenoviruses, Human↗
PubMed2001

Gastroenteritis outbreaks associated with Norwalk-like viruses and their investigation by nested RT-PCR.

BACKGROUND: Norwalk-like viruses are the most common cause of gastroenteritis outbreaks and sporadic cases of vomiting and diarrhoea. In healthy individuals infection is often mild and short-lived but in debilitated patients infection can be severe. It is essential that the virus laboratory can offer a sensitive and specific test, delivered in a timely manner. METHODS: We have developed a nested reverse transcriptase PCR based on published primers against the RNA polymerase gene and after comparison with electronmicroscopy used the assay to investigate 31 outbreaks of gastroenteritis. These were in diverse situations including nursing homes, small district hospitals, large general hospitals, a ferry ship, hotels, restaurants and staff canteens. RESULTS: A positive diagnosis was made in 30/31 outbreaks investigated giving an overall outbreak positive detection rate of 97%. At an individual patient level there was a positive diagnostic rate of 11.5% in a large hospital environment to 100% in smaller outbreak situations. The average patient positive rate was 34%. In addition we investigated 532 control faecal specimens from adults. Of these 530 were negative and 2 were repeatedly positive. CONCLUSIONS: It is essential that insensitive electronmicroscopy is replaced with the more sensitive reverse transcription PCR assays. These tests should be made available "on call" at weekends and public holidays. It is also important that outbreaks of NLV infection are monitored using sensitive RT-PCR assays so that the laboratory information can be used in ascertaining the spread and duration of the outbreak.

Adolescent↗
PubMed2001

Modulation of both endogenous folates and thymidine enhance the therapeutic efficacy of thymidylate synthase inhibitors.

Plasma levels of folates and thymidine in mice are about 10-fold higher than in humans and may influence the therapeutic efficacy of thymidylate synthase (TS) inhibitors, such as 5-fluorouracil (5FU) and the antifolates pemetrexed (MTA) and raltitrexed (RTX). Therefore, we tested their therapeutic efficacy in various murine tumor models, grown in mice on a normal and a folate-depleted diet, with high and low thymidine kinase (TK) levels. MTA and RTX were inactive against Colon-26-10 [doubling times gained by treatment; growth delay factor (GDF), 0.5 and 0.3, respectively], whereas 5FU was very active (GDF, >10; complete cures). Colon-26-10/F, grown in mice on a folate-depleted diet, was more sensitive to RTX and MTA (GDF, 2.1 and 1.3, respectively) but not to 5FU (GDF, 1.2); however, leucovorin reversed the effect leading to cures. Folate depletion did not reverse resistance of Colon-26A and Colon-26G (low TK) to MTA and RTX, whereas leucovorin only enhanced the 5FU effect in Colon-26A and Colon-26A/F. Folic acid at 15 mg/kg did not improve the therapeutic efficacy of MTA in folate-deficient mice. The folate-depleted diet decreased the reduced folates in Colon-26A/F and Colon-26-G/F tumors less (4-5-fold; P < 0.01) than in Colon-26-10/F tumors (8-fold; P < 0.001). Folate depletion increased TS levels 2-3-fold in all of the models and TK levels 6-fold (P < 0.01) in Colon-26G/F, explaining the lack of activity of MTA and RTX in Colon-26G/F. In contrast, TK-deficient FM3A/TK tumors were much more sensitive to RTX, MTA, and 5FU than parent FM3A tumors, which have comparable TS levels. The rate of thymidine phosphorylysis varied considerably in all of the tumors without a clear relation to antitumor activity. In conclusion, tumor folates may potentiate (5FU) or protect (antifolates). Murine tumor models should combine low folates and low thymidine rescue to optimize preclinical testing of antifolates.

Animals↗
PubMed2000

Modified high-performance liquid chromatography assay for the measurement of 2'-deoxyuridine in human plasma and its application to pharmacodynamic studies of antimetabolite drugs.

A new method is presented for the HPLC determination of plasma 2'-deoxyuridine (dUrd). Briefly, 1 ml of human plasma is deproteinised with perchloric acid followed by purification by solid-phase extraction using a non-polar high-capacity polymeric sorbent. The dUrd is separated on a C18 reversed-phase column using a mobile-phase of 0.05% v/v trifluoroacetic acid in water, with a retention time of 8.5 min at a flow-rate of 1.25 ml min(-1). Quantitation is by UV detection at 261 nm using a photodiode array detector. The limit of quantitation is 6 nM with a linear response over the measured range 6-400 nM. Both intra- and inter-day RSD and bias are typically less than 13%. Chromatograms and pharmacodynamic data from a Phase 1 Clinical Trial of a new antifolate drug, ZD9331 are included to illustrate the utility of the method. They show the increase in circulating dUrd as a result of drug inhibition of the target enzyme thymidylate synthase. The method has the significant advantages of ease and simplicity over earlier methods and may be applied to the analysis of other nucleoside species.

Antimetabolites, Antineoplastic↗
PubMed2000

Detection of adenoviruses (AdV) in culture-negative environmental samples by PCR during an AdV-associated respiratory disease outbreak.

Since 1954, adenoviruses (AdV) have been recognized as an important cause of acute respiratory disease (ARD) among U.S. military recruits. Until recently, routine oral vaccination for AdV serotypes 4 and 7 eliminated epidemic AdV-associated ARD in this population. Now that the manufacturer has ceased production, vaccination has ended and AdV epidemics have reappeared. As part of a prospective epidemiological study during the high-risk ARD season, serial samples were obtained from ventilation system filters and tested for AdV by culture and PCR. An outbreak occurred during this surveillance. Of 59 air filters, 26 (44%) were AdV positive only by PCR. Sequence analysis confirmed the presence of AdV serotype 4, the implicated outbreak serotype. The number of AdV-related hospitalizations was directly correlated with the proportion of filters containing AdV; correlation coefficients were 0.86 (Pearson) and 0.90 (Spearman's rho). This is the first report describing a PCR method to detect airborne AdV during an ARD outbreak. It suggests that this technique can detect and quantify AdV-associated ARD exposure and may enable further definition of environmental effects on AdV-associated ARD spread.

Adenovirus Infections, Human↗
PubMed2000

Measurement of carbon dioxide production in very low birth weight babies.

BACKGROUND: CO2 production is most commonly measured by using indirect calorimetry to quantify elimination of CO(2) in breath (VCO2). An alternative is to measure the rate at which CO2 appears in the body pool (RaCO2) by infusing a (13)C labelled bicarbonate tracer. VCO2 and RaCO2 generally differ but are related by c, a factor that adjusts for the incomplete recovery of infused tracer in the breath. The literature relating to human studies cites a wide range of values for c but the only neonatal study to determine c empirically estimated a mean value of 0.77. AIM: To estimate fractional recovery rate, c, in very low birthweight babies, and assess the feasibility of using the isotopic technique to measure CO2 production during mechanical ventilation. METHOD: Eleven spontaneously breathing, continuously fed, very low birthweight infants (median birth weight 1060 g, median gestational age 29 weeks) were studied. RESULTS: Mean (SD) VCO2 was 9.0 (2.0) ml/min (standard temperature and pressure dry, STPD) and mean (SD) RaCO2 was 9.6 (2.1) ml/min (STPD). The mean (SD) value of c was estimated as 0.95 (0.13). The 95% confidence intervals of the mean were 0.87-1.03. CONCLUSIONS: The results emphasise the importance of measuring c for a given study population rather than assuming a value based on adult studies. The close approximation of RaCO2 and VCO2 in this group of babies implies that the labelled bicarbonate infusion technique could be used to measure simply CO2 production during mechanical ventilation.

Breath Tests↗
PubMed1998

The renal effects of the water-soluble, non-folylpolyglutamate synthetase-dependent thymidylate synthase inhibitor ZD9331 in mice.

ZD9331 is a novel, potent thymidylate synthase (TS) inhibitor which does not require polyglutamation by folylpolyglutamate synthetase (FPGS) for its activity. In contrast to Tomudex (ZD1694), ZD9331 may therefore be active against tumours with low FPGS activity. ZD9331 shows anti-tumour activity by both 24-h infusion and bolus administration in the murine thymidine kinase-deficient (TK -/-) lymphoma L5178Y. In view of the history of renal toxicity with some earlier TS inhibitors and the possible therapeutic use of bolus ZD9331, we have examined the effects of bolus ZD9331 dose and route of administration on plasma and kidney pharmacokinetics and renal function in mice. Renal function was assessed by measuring [14C]inulin clearance, and drug concentrations were assayed by reverse-phase high-performance liquid chromatography (HPLC). Renal function was unaffected by ZD9331 up to 150 mg kg(-1) either i.v. or i.p. However, at 200 mg kg(-1), glomerular filtration rate was significantly inhibited following i.v. but not i.p. administration. Pharmacokinetic studies showed that these effects were consistent with the markedly higher plasma drug concentrations occurring during early times following i.v. dosing, although the plasma drug profiles were otherwise similar for both routes. Kidney drug concentrations were slightly elevated in i.v.- versus i.p.-treated animals at the low dose (50 mg kg(-1)), with a correspondingly larger area under the curve. However, at the highest dose (200 mg kg(-1)), peak kidney drug concentrations were 20-fold higher following i.v. administration than after i.p., with marked kidney retention, resulting in a 50-fold greater kidney drug exposure for the i.v. versus the i.p. route. These data show that ZD9331 is non-nephrotoxic at active anti-tumour doses (50 mg kg(-1) i.p.) in mice, and only at very high bolus i.v. doses is there impaired renal function as a result of very high peak plasma concentrations. These adverse effects can be readily overcome by i.p. administration, indicating the likely need for short infusions in clinical settings.

Animals↗
PubMed1997

Sequence characterization of the 5' noncoding region of GB virus C/hepatitis G virus.

The nucleotide sequences of the 5' noncoding region of the GB virus C/hepatitis G virus (GBV-C/HGV) were determined in 18 isolates from the United States. Two genotypes have been classified based on the sequence heterogeneity within the 5' noncoding region of GBV-C/HGV. The most distantly related isolates between the two genotypes were 84.6% identical. Sequence identity of the isolates within a genotype was 95-99%. The 5' noncoding region of this virus contains four highly conserved domains. These conserved elements would facilitate the selection of optimal primers for the sensitive detection of GBV-C/HGV RNA by PCR. In addition, they suggest a crucial role for this region in viral replication and/or gene expression. Detection of genotypic variation among GBV-C/HGV infected individuals may provide further insight into the possible pathogenicity and into the transmission of the virus.

Base Sequence↗
PubMed1997

Prevalence of hepatitis G virus in hepatitis C virus (HCV)-infected patients and in HCV-contaminated intravenous immunoglobulin products.

Hepatitis GB virus C/hepatitis G virus (HGV) is an RNA virus, which appears to be transmitted by parenteral exposure to contaminated blood and blood products, and may be associated with clinical hepatitis in humans. The prevalence of HGV was investigated in hepatitis C virus (HCV)-infected patients, and (HCV)-contaminated immune globulin intravenous products (IGIV), manufactured prior to the introduction of viral inactivation processing, and in recipients of these lots. Nested primers, specific for the 5' non-coding region of HGV, were designed and used to test 100 chronic HCV patients, 10 HCV RNA-positive IGIV lots and 36 of the recipients of these products. Hepatitis G virus specificity of the polymerase chain reaction (PCR) products was confirmed by sequencing a number of the amplified products and comparing the results with the published prototype sequence for HGV RNA. HGV RNA was detected in 23 of the 100 (23%) HCV-infected patients. The level of alanine aminotransferase (ALT) was lower in HCV-HGV coinfected patients than those with HCV infection alone. Hence, the severity of HCV infections is not influenced by HGV. Two of the 10 (20%) IGIV lots tested positive for HGV RNA; however, none of the serum samples from recipients of IGIV contained detectable HGV RNA although many were infected with HCV. This suggests that the transmission of HGV RNA from IGIV to the recipients is less efficient than that seen for HCV.

Adult↗
PubMed1997

Effect of hepatitis B virus X protein on the expression of retinoblastoma gene product.

Hepatitis B virus X protein (HBX) was studied for its capacity to form a specific complex with the retinoblastoma tumour suppressor protein (pRB), and for its effect on the expression of pRB. HBX was synthesized by in vitro transcription and translation in the presence of [35S]methionine. The synthesized HBX was assayed for its binding to a glutathione-S-transferase (GST)-pRB fusion protein bound to Sepharose beads. The in vivo binding was investigated by a co-immunoprecipitation and Western blot analysis of the cell extract from a CMV-HBX-transfected hepatoblastoma cell line, Hep G2 cells. These experiments demonstrated that HBX was unable to form a detectable complex with pRB. However, the level of pRB increased considerably in Hep G2 cells transfected with CMV-HBX clone. The alteration of pRB expression by HBX could be a mechanism, contributing to the development of hepatocellular carcinoma (HCC) in human.

Gene Expression Regulation, Neoplastic↗
PubMed1994

Simultaneous amplification and detection of specific hepatitis B virus and hepatitis C virus genomic sequences in serum samples.

A sensitive and specific two-stage polymerase chain reaction (PCR) technique was developed for the simultaneous amplification and detection of specific genomic sequences of hepatitis B virus (HBV) and hepatitis C virus (HCV) in serum samples. Initially, HCV-RNA was reverse transcribed to cDNA. This cDNA and DNA from HBV were then co-amplified using primer pairs derived from conserved regions of HBV and HCV nucleotide sequences. The specificity of PCR products was confirmed by liquid hybridization analysis using 32P end-labeled oligomer probes specific for the target HBV and HCV nucleotide sequences. Independent human serum samples, positive and negative by PCR for both HBV-DNA and HCV-RNA, were used as controls. We tested sera from nine donors, of which seven were reactive for HBsAg, anti-HBc, and anti-HCV (multiantigen test), one of whom was reactive for anti-HCV and anti-HBc, and one of whom was reactive for HBsAg and anti-HBc. The assay detected HBV- and HCV-specific genomic sequences in eight of eight sera reactive for both HBV and HCV serological markers and also in the serum that was reactive for HBV markers only.

Base Sequence↗