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Biomedical subjects

M Wright

Publications and source records attributed to M Wright.

At least 163 records · Page 9Linked to original sources
PubMed1994

Rhazinilam mimics the cellular effects of taxol by different mechanisms of action.

We have investigated the effects of the microtubule poison rhazinilam on microtubule assembly in vivo and in vitro. In mammalian cells, rhazinilam mimics the effects of taxol and leads to microtubule bundles, multiple asters, and microtubule cold stability. In vitro, rhazinilam protected preassembled microtubules from cold-induced disassembly, but not from calcium ion-induced disassembly. Moreover, both at 0 degrees C and at 37 degrees C, rhazinilam induced the formation of anomalous tubulin assemblies (spirals). This process was prevented by maytansine and vinblastine, but not by colchicine. Preferential saturable and stoichiometric binding of radioactive rhazinilam to tubulin in spirals was observed with a dissociation constant of 5 microM. This binding was abolished in the presence of vinblastine and maytansine. In contrast, specific binding of radioactive rhazinilam to tubulin assembled in microtubules was undetectable. These results demonstrate that rhazinilam alters microtubule stability differently than taxol, and that the overall similar effects of rhazinilam and taxol on the cellular cytoskeleton are the consequence of two distinct mechanisms of action at the molecular level.

Alkaloids↗
PubMed1994

Antibodies that can discriminate between dynein heavy chains and their HUV1 photoproducts.

Dyneins are multi-subunit enzymes that transduce chemical energy into the mechanical energy that makes cilia and flagella beat and moves organelles towards the minus end of microtubules. The ATPase activity is borne by heavy chains, and recent molecular analysis indicates that dynein heavy chain genes form an ancient multigene family: the similarity between the same isoform of two distantly related species is greater than that between different isoforms of the same species. We have exploited sequence identities between a Paramecium axonemal dynein heavy chain gene cloned in our laboratory and sequences of dynein heavy chains from other species to prepare antibodies against active-site peptides capable of recognizing dynein heavy chains regardless of species or isoform. One of the antibodies is perfectly specific for the larger product of V1 photolysis (HUV1) and thus incorporates a unique property of the hydrolytic ATP binding site of all known dynein heavy chains, the capacity for photocleavage in the presence of micromolar vanadate. Our characterization of these reagents suggests that they will be useful for biochemical and in situ studies of known dyneins as well as identification of potential new members of the family.

Amino Acid Sequence↗
PubMed1994

APC mutation analysis by chemical cleavage of mismatch and a protein truncation assay in familial adenomatous polyposis.

Overall, the causative APC mutation has been identified in only 30% of the patients with familial adenomatous polyposis (FAP) who have been included in studies reported in the literature. In order to determine the true frequency of detectable APC mutations, we set out to search exhaustively the entire coding region of APC for causative mutations in ten patients with classical FAP from Scottish kindreds shown to be linked to 5q markers. Chemical cleavage of mismatch analysis was employed as the initial screening technique. Mutations were confirmed by direct DNA sequencing and shown to generate a premature stop codon by an in vitro protein synthesis assay. Mutations resulting in a premature stop codon either by base substitution or by frameshift were identified in nine families. Although the remaining kindred was linked to intragenic APC markers with a lodscore of 1.69 at Zmax = 0.0, further analysis of DNA, RNA and chromosome spreads from the proband failed to detect any abnormality. This was despite employing single-strand conformation polymorphism (SSCP) analysis, heteroduplex analysis, DNA sequencing, reverse transcription-polymerase chain reaction (RT-PCR) analysis for splicing defects, a protein truncation test encompassing the entire APC gene and fluorescent in situ hybridisation chromosome analysis (FISH). These data show that 90% of these FAP kindreds had APC mutations detectable by chemical cleavage of mismatch and that none of the numerous other techniques employed could detect the mutation in the remaining kindred. This study shows the value of screening the APC gene using a combination of chemical cleavage of mismatch analysis and an in vitro protein truncation test.

Adenomatous Polyposis Coli↗
PubMed1994

Centrosome assembly in vitro: role of gamma-tubulin recruitment in Xenopus sperm aster formation.

Centrioles organize microtubules in two ways: either microtubules elongate from the centriole cylinder itself, forming a flagellum or a cilium ("template elongation"), or pericentriolar material assembles and nucleates a microtubule aster ("astral nucleation"). During spermatogenesis in most species, a motile flagellum elongates from one of the sperm centrioles, whereas after fertilization a large aster of microtubules forms around the sperm centrioles in the egg cytoplasm. Using Xenopus egg extracts we have developed an in vitro system to study this change in microtubule-organizing activity. An aster of microtubules forms around the centrioles of permeabilized frog sperm in egg extracts, but not in pure tubulin. However, when the sperm heads are incubated in the egg extract in the presence of nocodazole, they are able to nucleate a microtubule aster after isolation and incubation with pure calf brain tubulin. This provides a two-step assay that distinguishes between centrosome assembly and subsequent microtubule nucleation. We have studied several centrosomal antigens during centrosome assembly. The CTR2611 antigen is present in the sperm head in the peri-centriolar region. gamma-tubulin and certain phosphorylated epitopes appear in the centrosome only after incubation in the egg extract. gamma-tubulin is recruited from the egg extract and associated with electron-dense patches dispersed in a wide area around the centrioles. Immunodepletion of gamma-tubulin and associated molecules from the egg extract before sperm head incubation prevents the change in microtubule-organizing activity of the sperm heads. This suggests that gamma-tubulin and/or associated molecules play a key role in centrosome formation and activity.

Adenosine Triphosphate↗
PubMed1994

Multiple signalling systems controlling expression of luminescence in Vibrio harveyi: sequence and function of genes encoding a second sensory pathway.

Density-dependent expression of luminescence in Vibrio harveyi is regulated by the concentration of extracellular signal molecules (autoinducers) in the culture medium. One signal-response system is encoded by the luxL,M,N locus. The luxL and luxM genes are required for the production of an autoinducer (probably beta-hydroxybutyl homoserine lactone), and the luxN gene is required for the response to that autoinducer. Analysis of the phenotypes of LuxL,M and N mutants indicated that an additional signal-response system also controls density sensing. We report here the identification, cloning and analysis of luxP and luxQ, which encode functions required for a second density-sensing system. Mutants with defects in luxP and luxQ are defective in response to a second autoinducer substance. LuxQ, like LuxN, is similar to members of the family of two-component, signal transduction proteins and contains both a histidine protein kinase and a response regulator domain. Analysis of signalling mutant phenotypes indicates that there are at least two separate signal-response pathways which converge to regulate expression of luminescence in V. harveyi.

4-Butyrolactone↗
PubMed1994

Sequence and function of LuxO, a negative regulator of luminescence in Vibrio harveyi.

Density-dependent expression of luminescence in Vibrio harveyi is regulated by the concentration of extracellular signal molecules (autoinducers) in the culture medium. A recombinant clone that restored function to one class of spontaneous dim mutants was found to encode a function required for the density-dependent response. Transposon Tn5 insertions in the recombinant clone were isolated, and the mutations were transferred to the genome of V. harveyi for examination of mutant phenotypes. Expression of luminescence in V. harveyi strains with transposon insertions in one locus, luxO, was independent of the density of the culture and was similar in intensity to the maximal level observed in wild-type bacteria. Sequence analysis of luxO revealed one open reading frame that encoded a protein, LuxO, similar in amino acid sequence to the response regulator domain of the family of two-component, signal transduction proteins. The constitutive phenotype of LuxO- mutants indicates that LuxO acts negatively to control expression of luminescence, and relief of repression by LuxO in the wild type could result from interactions with other components in the Lux signalling system.

Amino Acid Sequence↗
PubMed1994

Impact of cyanotic heart disease on school performance.

Surgical correction greatly decreases the mortality and cardiac morbidity of cyanotic congenital heart disease, but children remain at risk of long term difficulties in other areas. A historical cohort study was conducted to determine the relation between heart disease and school performance in 29 children aged 7 to 12 years old with simple transposition of the great arteries or tetralogy of Fallot. All children had surgical correction of their lesion before 2.5 years of age. Those at greater risk of school difficulties because of recognised complications of their heart disease or for reasons other than directly attributable to the heart disease were excluded. Comparison was made with 36 children who had presented with cardiac murmurs at a similar age, but who did not require treatment. Children with cyanotic disease showed significantly poorer performance in all academic areas assessed by the Wide Range Achievement Test-Revised; the difference in group mean score (adjusted for differences in maternal education, sex, and parental occupational prestige) for reading was 10.3 points (confidence interval (CI) 1.25 to 19.34), for spelling 7.8 (CI 1.11 to 14.52), and for arithmetic 6.8 (CI 0.19 to 13.39). The differences in adjusted group means for the Wechsler Intelligence Scale for Children-Revised full scale, performance and verbal IQs were significant, particularly the later at 10.1 points (CI 2.59 to 17.61). Teacher reports indicated significant differences in arithmetic when outcome was dichotomised to 'below grade' or 'not below grade'. There were no significant associations between outcome measures and the medical or perioperative parameters, however, including those related to hypoxia. It is concluded that the increased incidence of academic problems and the nature of the cognitive difficulties in children with uncomplicated corrective cardiac surgery for cyanotic heart disease are not fully explained by chronic hypoxia, or by other factors related to the cardiac surgery.

Child↗
PubMed1994

Responding to workload measurement needs.

Workload measurement is a way of capturing and recording the time and/or activities of personnel in the performance of their health care duties. The traditional focus of workload systems in occupational therapy has been on resource allocation, activity tracking and long range planning. The systems are not organized to link with other institutional, financial and management tools to identify and cost client and programme resource use. The position taken in this paper is that occupational therapy workload measurement systems must be expanded to meet these new managerial responsibilities. Occupational therapists must be able to prospectively predict their workload to accommodate the move towards case costing and programme management. The paper also provides information from a national survey which indicates that there is support from the field for this position.

Canada↗
PubMed1994

Staffing and funding of consultation-liaison psychiatry services in Australia and New Zealand.

The aim of the study was to establish the current and desired levels of staffing and funding of the 52 consultation-liaison (C-L) psychiatry training units in Australian and New Zealand general hospitals. Administration of a questionnaire and follow-up verification provided data on referral rates, existing and preferred staffing levels, and staff workloads. The referral rates and staffing levels in most cases fall below those quoted for Europe and the USA, and those considered optimal by the respondents. This, together with the large variation in referral rates and workload, has implications for the type of clinical activity conducted and quality of the training experience in different units.

Australia↗
PubMed1994

Clinical pharmacology and metabolism of Taxol (paclitaxel): update 1993.

Paclitaxel may be one of the most important anticancer agents to be developed over the past 2 decades. With its unique mechanism of action as an inducer of tubulin assembly, paclitaxel has demonstrated impressive antitumor activity in patients with breast, lung (both non-small cell and small cell), head and neck, and advanced and platinum-refractory ovarian carcinomas. Unfortunately, there has been a relative lack of pharmacologic data available for paclitaxel, compared with other agents in similar phases of development. This scarcity of data is due, in part, to the aqueous insolubility of paclitaxel and to difficulties in developing sensitive analytic assays to measure the full range of drug concentrations achieved in small animals, both of which have limited preclinical pharmacologic studies. This report reviews the pharmacology of paclitaxel as ascertained during early clinical trials. Although most early studies used prolonged intravenous administration schedules of the agent as both monotherapy and in chemotherapy combinations, more recent studies have evaluated shorter administration schedules. In addition, available information pertaining to the pharmacodynamic and metabolic profiles of paclitaxel are discussed. Such information may be useful in designing rational treatment regimens of paclitaxel as a single agent and in chemotherapy combinations, potentially resulting in the optimal utilization of this important agent in cancer chemotherapeutics.

Animals↗
PubMed1993

Lignocaine metabolism and liver function testing in primary graft failure following orthotopic liver transplantation.

OBJECTIVE: To report the use of lignocaine and the measurement of its metabolite, monoethylglycinexylidide (MEGX), as a dynamic test of liver function. CLINICAL FEATURES: The conversion of lignocaine to MEGX has been used serially as a test of liver function in a liver transplant recipient for whom retransplantation was necessary because of primary non-function (PNF) of the initial graft. MEGX concentrations were markedly depressed with individual episodes of PNF, cardiac failure and rejection in this patient. CONCLUSION: The test provided useful additional supportive information in assessment of the patient and management of intercurrent problems following liver transplantation.

Female↗
PubMed1993

Experience with 732 acute overdose patients admitted to an intensive care unit over six years.

OBJECTIVE: To determine the outcome in patients with acute overdose requiring admission to the Intensive Care Unit (ICU). DESIGN: Prospective survey of all overdose admissions to an ICU over a six-year period ending January 1991. SETTING: Tertiary referral adult teaching hospital. PATIENTS: 732 consecutive patients with acute overdose. OUTCOME MEASURES: Death rate, use and duration of mechanical ventilation, type of compound taken and compounds associated with a fatal outcome. RESULTS: The 732 patients represented 13.8% of all admissions and 6% of the available ICU bed-days. Comparison with all admissions to the Emergency Department for acute overdose over a 27-month period ending April 1990 indicated that 22% of these patients were admitted to the ICU. Among the patients admitted to the ICU, tricyclic antidepressants, benzodiazepines and alcohol were the most frequently used compounds. More than one compound had been taken by 46.8% of the patients. Mechanical ventilation was required in 79.5% of the patients and 14 (2%) died. CONCLUSIONS: Acute overdose is a common cause of admission to the ICU but has a mortality rate of only 2%. In contrast to the overdoses taken by survivors, patients taking fatal overdoses are more likely to have taken a large dose of a single drug, or a non-medicinal compound.

Adult↗
PubMed1993

The role of alpha-1-protease inhibitor (A1PI) in the inhibition of protease activity in human knee osteoarthritis.

Alpha-1-protease inhibitor (A1PI) is the most abundant serum protease inhibitor, exhibiting inhibition of proteases known to act in osteoarthritis (OA) and rheumatoid arthritis. We have previously purified and sequenced A1PI synthesized by human articular cartilage and demonstrated in vitro protection from IL-1-induced proteoglycan (PG) degradation at a concentration of 1 mg/ml. In this study, the chondroprotective role of A1PI and possible inhibition of protease activity in OA, IL-1 and LPS-induced and aged normal human knee articular cartilage was investigated by immunohistochemical and in vitro methods. A variable low response to PG-degradation induction and to added A1PI protection of aged normal and OA cartilages was noted, while there was decreased constituative A1PI noted in OA cartilages as compared to normal.

Aged↗
PubMed1993

Aspergillosis in children with acquired immune deficiency.

Two children are presented with AIDS and aspergillosis. One child had pulmonary involvement while the other had invasion of the skull and brain. The rarity of aspergillosis in AIDS patients is discussed as well.

AIDS-Related Opportunistic Infections↗