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M Lees

Publications and source records attributed to M Lees.

At least 19 recordsLinked to original sources
PubMed2005

Chemometric treatment of vanillin fingerprint chromatograms. Effect of different signal alignments on principal component analysis plots.

This study describes the chemometric treatment of vanillin fingerprint chromatograms to distinguish vanillin from different sources. Prior to principal component analysis, which is used to discriminate vanillin from different origins, the fingerprints are aligned. Three alignment algorithms are tested, correlation optimized warping (COW), target peak alignment (TPA) and semi-parametric time warping (STW). The performance of the three algorithms is evaluated and the effect of the different alignments on the PCA score plots is investigated. The alignment obtained with STW differs somewhat from that with COW and TPA. However, equivalent score plots were obtained regarding the different vanillin groups.

Algorithms↗
PubMed2005

The phenotypic spectrum in patients with arginine to cysteine mutations in the COL2A1 gene.

BACKGROUND: The majority of COL2A1 missense mutations are substitutions of obligatory glycine residues in the triple helical domain. Only a few non-glycine missense mutations have been reported and among these, the arginine to cysteine substitutions predominate. OBJECTIVE: To investigate in more detail the phenotype resulting from arginine to cysteine mutations in the COL2A1 gene. METHODS: The clinical and radiographic phenotype of all patients in whom an arginine to cysteine mutation in the COL2A1 gene was identified in our laboratory, was studied and correlated with the abnormal genotype. The COL2A1 genotyping involved DHPLC analysis with subsequent sequencing of the abnormal fragments. RESULTS: Six different mutations (R75C, R365C, R519C, R704C, R789C, R1076C) were found in 11 unrelated probands. Each mutation resulted in a rather constant and site-specific phenotype, but a perinatally lethal disorder was never observed. Spondyloarthropathy with normal stature and no ocular involvement were features of patients with the R75C, R519C, or R1076C mutation. Short third and/or fourth toes was a distinguishing feature of the R75C mutation and brachydactyly with enlarged finger joints a key feature of the R1076C substitution. Stickler dysplasia with brachydactyly was observed in patients with the R704C mutation. The R365C and R789C mutations resulted in classic Stickler dysplasia and spondyloepiphyseal dysplasia congenita (SEDC), respectively. CONCLUSIONS: Arginine to cysteine mutations are rather infrequent COL2A1 mutations which cause a spectrum of phenotypes including classic SEDC and Stickler dysplasia, but also some unusual entities that have not yet been recognised and described as type II collagenopathies.

Adult↗
PubMed2002

Randomized crossover comparison of the proseal with the classic laryngeal mask airway in unparalysed anaesthetized patients.

BACKGROUND: The ProSeal is a wire-reinforced laryngeal mask airway with an additional drain tube that leads to the distal tip of the laryngeal cuff. The design should improve the seal with the larynx. METHODS: The ProSeal and classic laryngeal mask airways were compared in 180 patients in a randomized crossover study. Patients were anaesthetized without neuromuscular blocking drugs. RESULTS: The ProSeal took more time and more attempts to insert successfully than the classic laryngeal mask airway. Insertion was successful on the first attempt in 81% of cases with the ProSeal and 90% with the classic laryngeal mask airway. The ProSeal required more air to achieve an intracuff pressure of 60 cm H2O (6 ml more for size 4 and 12 ml more for size 5). Laryngeal seal pressure was better with the ProSeal than the classic laryngeal mask airway. Median seal pressure was 29 cm H2O with the ProSeal and 18 cm H2O with the classic laryngeal mask airway. Laryngeal seal pressure was greater than 20 cm H2O in 87% of patients with the ProSeal and 41% with the classic laryngeal mask airway. Laryngeal seal pressure was greater than 40 cm H2O in 21% of patients with the ProSeal and in none of the patients with the classic laryngeal mask. Once placed, the ProSeal remained a stable and effective airway. Gastric tube insertion through the drain tube was attempted in 147 cases and was successful in 135 (92%). CONCLUSION: The ProSeal is more difficult to insert than the classic laryngeal mask airway but allows positive pressure ventilation more reliably than the classic laryngeal mask airway.

Adolescent↗
PubMed2002

Economic evaluation of gemcitabine alone and in combination with cisplatin in the treatment of nonsmall cell lung cancer.

OBJECTIVE: To evaluate the cost effectiveness of gemcitabine in the treatment of nonsmall cell lung cancer (NSCLC). METHODS: Gemcitabine was compared with best supportive care and gemcitabine/cisplatin was compared with three standard chemotherapies and four other novel chemotherapy combinations. Costs and effectiveness measures were based on resource and outcome data from previously reported clinical trials. All direct costs associated with NSCLC treatment were included and adjusted to year 2000 values. PERSPECTIVE: UK National Health Service. RESULTS: Gemcitabine plus best supportive care was associated with an incremental cost per progression-free life year gained of pound sterling5228 compared with best supportive care alone. In comparison with standard chemotherapies, gemcitabine/cisplatin was associated with an incremental cost per progression-free life year gained of pound sterling1751 versus etoposide/cisplatin and cost per 1-year survival gain of pound sterling5681 versus mitomycin/vinblastine/platinum. Incremental cost per tumour response was pound sterling2032 relative to etoposide/cisplatin, pound sterling5169 relative to mitomycin/ifosfamide/cisplatin and pound sterling6240 relative to mitomycin/vinblastine/platinum. Compared with four novel (newer) combination chemotherapies gemcitabine/ cisplatin showed cost savings in each case, with the same or better outcome. Thus, gemcitabine/cisplatin showed improved cost effectiveness and dominance. Sensitivity analyses showed the results were robust to variations to the values of key parameters. CONCLUSION: Gemcitabine alone or in combination with cisplatin was assessed to be a cost-effective or cost-saving therapy when compared with best supportive care, standard chemotherapy regimens and novel chemotherapy combinations. Chemotherapy regimens containing gemcitabine therefore represent good value for money and efficient use of healthcare resources in the treatment of advanced NSCLC.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2001

Submicroscopic 8pter deletion, mild mental retardation, and behavioral problems caused by a familial t(8;20)(p23;p13).

Microscopically visible distal 8p deletions have been associated with growth and mental impairment, minor facial anomalies, congenital heart defects, and behavioral problems. We report two cousins with mild retardation and behavioral problems, including inappropriate sexual behavior and pyromania. Familial learning difficulties on the grandfather's side incompatible with Mendelian inheritance prompted telomere screening, which detected a submicroscopic terminal 8p deletion of < 5.1 Mb. The cousins' mothers both carried a t(8;20)(p23;p13) balanced translocation. The frequently observed microcephaly in patients with microscopically visible deletions of 8pter is lacking in both cousins, suggesting that the gene(s) causing the microcephaly is centromeric to the deleted region. The absence of cardiac defects in the cousins confirms the more proximal location of gene(s) causing these abnormalities in other reported cases with microscopically visible 8pter deletions and supports involvement of the GATA4 gene. Moreover, the current cases predict the presence of a putative gene(s) involved in behavior in the most telomeric 5.1 Mb of the p-arm of chromosome 8. This first clinical report of a submicroscopic subtelomeric 8p deletion gives more insight into the so-called 8p- syndrome and demonstrates the difficulty in making a clinical diagnosis for a submicroscopic 8pter deletion in an individual patient with mental retardation.

Behavioral Symptoms↗
PubMed2000

Oculo-ectodermal syndrome: report of two further cases.

We describe the clinical findings in two previously unreported, unrelated cases with aplasia cutis congenita and epibulbar dermoids, similar to the cases reported by Toriello et al. [1993]. In addition, one patient had bladder exstrophy with epispadias. These cases provide further evidence for the identification of the oculo-ectodermal syndrome as a distinct entity.

Bladder Exstrophy↗
PubMed2000

Cost-effectiveness analysis of lamivudine for the treatment of chronic hepatitis B.

OBJECTIVE: To estimate the short term and long term cost effectiveness, from a healthcare perspective, associated with the introduction of lamivudine for chronic hepatitis B. DESIGN: The analysis used a 2-step modelling approach. A decision tree was used to estimate clinical outcomes and costs after 1 year. The 1-year results were then extrapolated to 70 years using a Markov model. PATIENTS: The study population comprised hypothetical cohorts of patients with chronic hepatitis B, representative of those likely to receive treatment in clinical practice in Australia. MAIN OUTCOME MEASURES AND RESULTS: In the short term, more patients sero-converted when lamivudine was available, with an incremental cost-effectiveness ratio of 3341 Australian dollars ($A) per additional seroconversion. In the long term, the introduction of lamivudine increased life expectancy by 3.9 years [3.2 quality-adjusted life-years (QALYs)] compared with when interferon-alpha was the only treatment, or 4.6 years (3.8 QALYs) compared with no treatment. There were reductions in lifetime risk of developing compensated cirrhosis, decompensated cirrhosis and hepatocellular carcinoma of 5, 11 and 11%, respectively, when lamivudine was available. The incremental cost of having lamivudine available, as opposed to interferon-alpha only, was $A633 per year of life saved or $A735 per QALY. CONCLUSION: The introduction of lamivudine is expected to reduce and delay the progression of chronic hepatitis B, increasing the life expectancy and quality of life of patients for a small overall increase in healthcare costs.

Antiviral Agents↗
PubMed1998

Crystal structures of native and recombinant yeast fumarase.

Crystal structures for both native and recombinant forms of yeast fumarase from Saccharomyces cerevisiae have been completed to moderate resolution by two separate laboratories. The recombinant form was obtained by the construction of an expression plasmid for Escherichia coli. Despite a high level of amino acid sequence similarity, purification of the eukaryotic enzyme from the wild-type prokaryotic enzyme was feasible. The crystal structure of the native form, NY-fumarase, encompasses residues R22 through M484, while the recombinant form, RY-fumarase, consists of residues S27 through L485. Both crystal structures lack the N-terminal translocation segment. Each subunit of the homo-tetrameric protein has three domains. The active site is formed by segments from each of three polypeptide chains. The results of these studies on the eukaryotic proteins are unique, since the recombinant form was done in the absence of dicarboxylic acid and has an unoccupied active site. As a comparison, native fumarase was crystallized in the presence of the competitive inhibitor, meso-tartrate. Meso-tartrate occupies a position close to that of the bound citrate molecule found in the active site of the E. coli enzyme. This inhibitor participates in hydrogen bonding to an active-site water molecule. The independent determination of the two structures provides further evidence that an active-site water molecule may play an active role in the fumarase-catalyzed reaction.

Binding Sites↗
PubMed1998

Optic disc anomalies and frontonasal dysplasia.

AIMS: To document the optic disc abnormalities in patients with frontonasal dysplasia in association with basal encephalocele. METHODS: Names and hospital numbers of patients with midline clefts were obtained from the ophthalmology and genetics database. Six patients were identified who had the following common findings: midline facial cleft with midline cleft lip and palate; hypertelorism; absent corpus callosum; basal (sphenoethmoidal) encephalocele; and pituitary deficiency (five out of six cases). Ophthalmic examination was performed with fundal photography where possible. RESULTS: Two patients had unilateral and one a bilateral peripapillary staphyloma. Two patients had bilateral optic disc hypoplasia and one appeared to have a peripapillary staphyloma in one eye and a morning glory disc in the other. CONCLUSION: Optic disc abnormalities were found in all patients with this constellation of clinical findings. This association appears to represent a distinct subgroup within the spectrum of frontonasal dysplasia. The presence of midline facial anomalies and any dysplastic disc should alert the physician as to the presence of an encephalocele.

Abnormalities, Multiple↗
PubMed1997

Mutations of fumarase that distinguish between the active site and a nearby dicarboxylic acid binding site.

Two mutant forms of fumarase C from E. coli have been made using PCR and recombinant DNA. The recombinant form of the protein included a histidine arm on the C-terminal facilitating purification. Based on earlier studies, two different carboxylic acid binding sites, labeled A- and B-, were observed in crystal structures of the wild type and inhibited forms of the enzyme. A histidine at each of the sites was mutated to an asparagine. H188N at the A-site resulted in a large decrease in specific activity, while the H129N mutation at the B-site had essentially no effect. From the results, we conclude that the A-site is indeed the active site, and a dual role for H188 as a potential catalytic base is proposed. Crystal structures of the two mutant proteins produced some unexpected results. Both mutations reduced the affinity for the carboxylic acids at their respective sites. The H129N mutant should be particularly useful in future kinetic studies because it sterically blocks the B-site with the carboxyamide of asparagine assuming the position of the ligand's carboxylate. In the H188N mutation at the active site, the new asparagine side chain still interacts with an active site water that appears to have moved slightly as a result of the mutation.

Binding Sites↗
PubMed1995

Activation of precursors for matrix metalloproteinases 1 (interstitial collagenase) and 3 (stromelysin) by rat mast-cell proteinases I and II.

Histological studies have previously demonstrated an association between mast-cell activation/degranulation and areas of connective-tissue lysis in vivo; in addition, mast-cell extracts have been shown to activate latent forms of collagenase and stromelysin. In the present study we have examined the potential roles of rat mast-cell proteinase (RMCP) I and RMCP II as activators of the precursors of matrix metalloproteinase (MMP)-1 (interstitial collagenase), MMP-2 (gelatinase A) and MMP-3 (stromelysin 1). Both RMCPs I and II activated proMMP-3 by converting the 57 kDa precursor into a 45 kDa polypeptide. The N-terminal amino acid of 45 kDa MMP-3 activated by RMCP II was identified as Phe83. By contrast, only RMCP II activated the 52 kDa proMMP-1 by converting it into a 41 kDa protein and generating the new N-termini, namely Gln80 and Val82. The collagenolytic activity which resulted from this cleavage was only 35% of the full activity, but this could not be augmented by subsequent treatment with MMP-3, the latter being a crucial enzyme for the generation of the fully active MMP-1 with Phe81 at the N-terminus, in conjunction with other serine proteinases. Thus RMCP II activates proMMP-1 via a mechanism different from that reported for the stepwise processing by combinations of other trypsin-like enzymes and MMP-3. ProMMP-2 (pro-gelatinase A) was not activated by either RMCP I or RMCP II, despite processing to smaller products.

Amino Acid Sequence↗
PubMed1995

Comparative studies of collagenase and stromelysin-1 expression by rheumatoid synoviocytes in vitro.

Matrix metalloproteinases such as collagenase and stromelysin are recognised as important cartilage-degrading enzymes in the pathophysiology of rheumatoid arthritis. Synovial fibroblasts and macrophages are the major cellular components of rheumatoid synovium, but the regulation and relative expression of collagenase and stromelysin by these two cell types remains uncertain. Using in vitro cultures of adherent rheumatoid synovial cells we have examined the coordinate or separate expression of collagenase and stromelysin-1 by dual immunolocalisation and Western blotting techniques. Synovial fibroblasts, when activated by macrophage-derived products in primary culture or by interleukin-1/phorbol myristate acetate in subcultures, released significant quantities of collagenase and stromelysin in their inactive, precursor forms. The ratio of released procollagenase: prostromelysin varied between different synovial cell preparations. Dual immunolocalisation studies demonstrated both coordinate and separate expression of the two enzymes by single cells. Approximately 80% of the activated fibroblasts, especially those with stellate morphology, showed co-expression of both enzymes. By contrast synovial macrophages had a modest or negligible capacity to elaborate either enzyme under the same in vitro conditions. In many fibroblastic cells both collagenase and stromelysin were co-localised to the perinuclear Golgi region and the same cytoplasmic compartments. Vesicular structures appear to provide intracellular transport for both enzymes to sites of secretion. Both enzymes showed preferential pericellular binding to a collagenous substratum rather than any association with the plasma membrane/cell surface.

Arthritis, Rheumatoid↗
PubMed1994

Mast cell proteinases activate precursor forms of collagenase and stromelysin, but not of gelatinases A and B.

Mast cell activation in vivo is often associated with areas of oedema and connective-tissue degradation. Tryptase and chymase are the major serine proteinases released by mast cells, but they appear to have little activity on most components of the extracellular matrix. The matrix metalloproteinases (MMP) are purported to degrade almost all connective tissue elements and are secreted by cells in the form of inactive precursors. Since the mechanisms of MMP activation in vivo are poorly understood we have examined the potential of mast cell proteinases to activate the precursor forms of human collagenase (MMP-1), stromelysin (MMP-3), gelatinase A (MMP-2) and gelatinase B (MMP-9). Mast cell proteinases prepared from purified dog mastocytoma cells were shown to process and activate purified precursor forms of both MMP-1 and MMP-3. Using antipain and chymostatin, inhibitors for tryptase and chymase, respectively, it was demonstrated that both pMMP-1 and pMMP-3 were effectively processed and activated by the chymase component. By contrast, tryptase activated only pMMP-3. The mast cell proteinases were unable to process or activate purified precursor forms of MMP-2 and MMP-9. However, MMP-3 previously activated by mast cell proteinases was shown to activate pMMP-9, but not pMMP-2. Since we have no evidence that mast cells express these four metalloenzymes, the release of mast cell serine proteinases following activation/degranulation could contribute to local metalloproteinase activation and subsequent matrix degradation.

Amino Acid Sequence↗