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Biomedical subjects

P Norris

Publications and source records attributed to P Norris.

At least 19 recordsLinked to original sources
PubMed2003

Complete curve fitting of extraction profiles for estimating uncertainties in recovery estimates.

This paper reports the use of improved numerical approaches to modelling extraction profiles, and shows that the approach substantially reduces statistical prediction uncertainties compared to those obtained on the basis of a three-point extrapolation from the later part of the extraction curve. Numerical fitting of manually obtained polycyclic aromatic hydrocarbon extraction data to a spherical particle diffusion model showed uncertainties typically reduced by a factor of three (with extremes at 1.02 and 770). Application to pressurised fluid extraction study of pelletised poly(vinylchloride) containing 30 mass% di(2-ethylhexyl)phthalate also showed good improvements. However, this high precision data showed small but significant lack of fit resulting in residual correlation and visibly biased prediction (more so than simple extrapolation). Re-fitting and uncertainty estimation using a first-order autoregression approximation to the covariance matrix produced more realistic uncertainty estimates and closer parameter estimates and is accordingly recommended for treating residual correlation from other causes, but did not entirely alleviate the problem. Different shape models (spherical, plane sheet and cylindrical) were applied without accounting fully for fitting error, and particle size effects were eliminated by modelling a simple size distribution. However, an approximate model based on linearly concentration-dependent diffusion coefficient showed excellent fit, confirming concentration-dependence as the most likely cause. This semiempirical model led to an uncertainty in total extractable material, at 0.2% of the total extractable value (with allowance for correlation). This is potentially good enough for recovery estimation and correction in certification of reference materials for validation purposes.

Journal Article↗
PubMed2001

Growth and change in the prescribing of anti-depressants in New Zealand: 1993-1997.

AIMS: To examine changes in the prescribing of anti-depressants in New Zealand from 1993-1997, in terms of expenditure, the number of dispensings and days of therapy supplied. METHOD: Data on subsidised dispensings of anti-depressant drugs during 1993 to 1997 were obtained from PHARMAC and analysed using SAS. RESULTS: The overall size of the anti-depressant market increased considerably over the study period. Government expenditure rose 2.25 times, and 1.65 times as many days of anti-depressant medication were supplied in 1997 as in 1993. Most of this was due to the growth in prescribing of newer anti-depressants, but the use of older drugs remained constant. CONCLUSIONS: In common with other countries, the use of newer agents is contributing to increased overall use of anti-depressant medication and government expenditure in New Zealand. Use of older drugs has not diminished substantially.

Antidepressive Agents↗
PubMed2001

Regional variation in anti-depressant dispensings in New Zealand: 1993-1997.

AIMS: To examine regional differences in the prescribing of anti-depressants in New Zealand from 1993 to 1997, and to examine the composition and dynamics of these differences. METHODS: Data on every subsidised dispensing of anti-depressant drugs 1993 to 1997 were obtained from PHARMAC and analysed using SAS. Each dispensing was allocated to a regional council area on the basis of the location of the dispensing pharmacy. RESULTS: Prescribing of anti-depressants increased with time in all regions. However, there was substantial regional variation in prescribing rates per-capita, the highest being 2.28 to 2.49 times the lowest in every year. Regions also varied substantially in the mix of newer and older drugs used, although newer drugs became increasingly important in every region. CONCLUSIONS: Regional differences in anti-depressant prescribing are large. Further research with different data sources is required to explore the reasons for this variation.

Antidepressive Agents↗
PubMed2001

Topical photodynamic therapy at low fluence rates--theory and practice.

Photodynamic Therapy (PDT), with topically applied 5-aminolaevulinic acid as the photosensitiser, is an effective treatment for various malignant and pre-malignant skin conditions. Several studies have shown the importance of fluence rate as well as fluence in the efficacy of PDT. We propose a measure of PDT efficacy, Photodynamic Damage Dose (PDD), which uses the product of instantaneous fluence rates, photosensitiser concentrations and oxygen concentrations in its calculation. We derive a qualitative numerical model of PDT and verify it by demonstrating an inverse fluence rate effect, increased efficacy of fractionated PDT, PDT induced hypoxia, and the dependence of photobleaching on fluence rate under certain circumstances. We recommend that fluence, fluence rate and any fractionation regime used should be detailed when reporting a trial as altering any of these has significant effects on PDT efficacy. The model predicts that low fluence rate irradiations should be as effective as high fluence rate irradiations if carried out over the same length of time. To test this we build a light emitting diode-based lamp (fluence rate of 7 mW cm(-2) at 635 nm) and used it to treat 32 superficial basal cell carcinomas on 22 patients (30 min treatment time, fluence 12.6 J cm(-2)). The complete response rate at one year was 84%, which is comparable to that achieved using higher fluence rate sources for similar treatment times. We conclude that this robust, inexpensive light source is effective for topical PDT.

Administration, Topical↗
PubMed1999

The role of interleukins 1, 6 and 8 as lymphocyte attractants in the photodermatoses polymorphic light eruption and chronic actinic dermatitis.

The two photodermatoses, polymorphic light eruption (PLE) and chronic actinic dermatitis (CAD), are characterized by lymphocyte-rich inflammatory infiltrates, the pathogeneses of which are not fully understood. We have therefore studied suction blister fluid (SBF) samples from patients with these conditions before and at two time points after the induction of experimental lesions by means of a solar simulator; this SBF was then tested for the presence of selected cytokines known to induce peripheral blood lymphocyte (PBL) migration in vitro. A specific EL-4 NOB-1 bioassay was used to detect interleukin (IL)-1 activity, which has already been noted in normal skin and this was found in pre-irradiation control samples as well as 1-3 h and 24 h post-irradiation in both patient groups, but at levels not significantly different from those of controls. Use of a B9 cell proliferation assay showed no detectable IL-6-like activity pre-irradiation, but there was substantial activity in samples at both post-irradiation time points in both patient groups. Further, in other experiments, retained SBF samples were tested in an in vitro PBL migration assay in the presence and absence of neutralizing antibodies against IL-1 alpha, IL-1 beta, IL-6 and IL-8; considerable PBL attractant activity was noted in the pre-irradiation SBF from both patient groups; a finding consistent with previous reports of such activity in samples from normal skin, and at least in CAD patients, a proportion of this activity appeared to be due to IL-1, pre-incubation of SBF with neutralizing antibodies against IL-1 alpha and IL-1 beta reducing the effect significantly. Substantial PBL attractant activity was present also in the SBF from 1-3 h and 24 h post-irradiation samples in both patient groups and again, IL-1 neutralizing antibodies reduced this in the 1-3 h and 24 h CAD samples. In addition, neutralizing antibodies against IL-6 and IL-8 reduced the activity in the 24 h PLE samples significantly and although not fully conclusive in the case of IL-1, these data suggest that IL-6, IL-8 and possibly IL-1 may be involved in the induction of PBL infiltrates, and perhaps other events, in both PLE and CAD.

Adult↗
PubMed1998

The impact of European harmonisation on Norwegian drug policy.

Although not a member of the European Union (EU), Norway is part of the European internal market as a result of the European economic area (EEA) agreement. Before 1994, Norway had a distinctive set of arrangements for the licensing and distribution of medicines. Many of these have undergone considerable change as a result of European harmonisation. This paper describes the previous arrangements and the impact of European harmonisation on them. Significant changes have been made to the Norwegian marketing authorisation system because of the loss of the 'need clause' and changes in price control. These are described and an attempt is made to evaluate their impact. The development of parallel importing and the introduction of private wholesaling companies have led to the development of new players in the Norwegian drug market and an increase in competition both within and between levels of the pharmaceutical distribution chain. New co-operatives have also arisen to increase the negotiating power of purchasers, particularly hospitals. Further significant changes are likely to occur in the Norwegian pharmaceutical sector in the future. The Norwegian case study provides an opportunity to look at the impact of European harmonisation on a particular set of regulatory arrangements and sheds light on the difficulty of implementing European policy in a national setting.

Commerce↗
PubMed1997

Never say die.

Explore the source record for details and available documents.

Ethics, Nursing↗
PubMed1997

5-Deoxy-5-C-(5-ethoxycarbonyl-1,2,3,- triazol-1-yl)-1,2-O-isopropylidene-alpha-D-xylofuranose.

Two unrelated molecules of the title compound, ethyl 1-(5-deoxy-1,2-O-isopropylidene-alpha-D-xylofuranos-5-C- yl)-1,2,3-triazole-5-carboxylate, C13H19N3O6, that are not linked by hydrogen bonding, comprise the asymmetric unit. There are no unusual bond lengths or angles. The two molecules differ in the degree of rotation around the methylene C atom that joins the triazole ring to the sugar part of the molecule. Molecules of the same conformation form infinite chains joined by hydrogen bonding between a H atom on the hydroxyl group of one molecule and an N atom in the triazole ring of another molecule generated by the 2(1) screw axis. Relevant intermolecular N...O distances are 3.013 (3) and 2.806 (3) A.

Crystallization↗
PubMed1997

Humanized anti-CD4 monoclonal antibody therapy of autoimmune and inflammatory disease.

We have investigated the biological and therapeutic properties of a humanized anti-CD4 MoAb, hIgG1-CD4, in patients with refractory psoriasis and rheumatoid arthritis (RA). hIgG1-CD4 is a modulating, non-depleting MoAb, which induced a first-dose reaction in most patients treated. It provided brief symptomatic relief in both conditions, and psoriasis appeared easier to control with conventional agents after MoAb therapy. At the doses used, hIgG1-CD4 did not synergize therapeutically with the panlymphocyte MoAb CAMPATH-1H (C1H) in patients with RA treated sequentially with both agents. There were no serious adverse effects definitely attributable to therapy. Our results are compared with those of other CD4 MoAb studies, and factors influencing the outcome of therapy are discussed.

Adolescent↗
PubMed1996

Characterization and interconversions of 2-S-ethyl-2-thio-D-mannose diethyl dithioacetal and the facile epimerization of 2-thio-D-mannopyranose derivatives.

3,4,5,6-Tetra-O-benzoyl-D-glucose diethyl dithioacetal (2) reacts with ethanethiol under acidic conditions to afford 3,4,5,6-tetra-O-benzoyl-2-S-ethyl-2-thio-D-mannose (3), the stereochemistry at C-2 of which has been assigned by chemical conversions on its debenzoylated derivative, the crystalline 2-S-ethyl-2-thio-D-mannose diethyl dithioacetal (4). In the presence of mercuric chloride (1.1 molar equiv), 4 is converted into crystalline ethyl 2-S-ethyl-1,2-dithio-alpha-D-mannofuranoside (5). Complete demercaptalation of 4 affords syrup 2-S-ethyl-2-thio-D-mannopyranose (6), which was characterized as its phenylhydrazone 7 and the crystalline alpha-pyranose tetraacetate 9. Extended treatment of 4 with mercuric chloride and aqueous sodium hydrogencarbonate resulted in isolation of 6, along with its crystalline 2-epimer, 2-S-ethyl-2-thio-beta-D-glucopyranose (10). Remercaptalation of 6 affords the manno diethyl dithioacetal 4 as the major product, whereas similar treatment of 10 yields ethyl 2-S-ethyl-1,2-dithio-alpha-D-glucopyranoside (13). The mechanism of conversion of 2 into 3, as well as the unusually facile interconversion of 2-S-ethyl-2-thio-D-mannose (6) and its D-gluco epimer 10, has been investigated.

Acetals↗
PubMed1996

Somatic hypermutation of Ig genes in patients with xeroderma pigmentosum (XP-D).

Antibody diversification by somatic hypermutation occurs by the introduction of nucleotide substitutions in and around the rearranged Ig V gene segments. Several characteristics of the process suggest that the introduction of mutations is linked to Ig gene transcription. Since there is a connection between mutation and repair with indications that both processes might show linkage to transcription, we asked whether defects in a component of the transcription factor TFIIH which lead to an inability to carry out nucleotide excision repair also affect somatic hypermutation. A PCR strategy was devised that required small samples of peripheral blood and enabled us to monitor hypermutation of a single, abundantly used VH gene. However, the results showed that in xeroderma pigmentosum patients (complementation group D), somatic hypermutaton appears to take place unaffected as regard both extent and distribution.

Genes, Immunoglobulin↗
PubMed1995

Ranitidine-induced photosensitivity.

We report the case of a 72-year-old male patient who developed a florid photosensitive eruption while on ranitidine therapy. Ultraviolet A sensitivity was detected by irradiation monochromator testing, suggesting drug-induced photosensitivity. Ranitidine was concluded to be the cause of his photosensitivity since the eruption resolved and the phototest abnormalities returned to normal following cessation of therapy. Similar cases have been reported to the Committee on Safety of Medicines but not published.

Aged↗