Biomedical subjects

P J Taylor

Publications and source records attributed to P J Taylor.

At least 19 recordsLinked to original sources

PubMed2006

Self-fertilization in mosses: a comparison of heterozygote deficiency between species with combined versus separate sexes.

Self-fertilization is a key difference of adaptive significance between species with combined versus separate sexes. In haploid-dominant species such as mosses and ferns, species with either combined or separate sexes (monoicous and dioicous, respectively) have the potential to self-fertilize (intergametophytic selfing), but being monoicous allows an additional mode of selfing (intragametophytic selfing). We used allozyme electrophoresis to estimate deviations from expected levels of heterozygosity under Hardy-Weinberg equilibrium to infer selfing rates in 10 moss species from 36 New Zealand populations. We found that while there were deficiencies of heterozygotes compared to expectation in both monoicous and dioicous mosses, monoicous species had significantly higher levels of heterozygote deficiency than dioicous species (F(IS)=0.89+/-0.12 and 0.41+/-0.11, respectively). Estimated selfing rates suggest that selfing occurs frequently in monoicous populations, and rarely in dioicous populations. However, in two dioicous species (Polytrichadelphus magellanicus and Breutelia pendula), we found significant indications of mixed mating or biparental inbreeding in a handful of populations. These data provide the first analysis of heterozygote deficiency and selfing among haploid-dominant species with breeding system variation, and we discuss our results with respect to the consequences of inbreeding depression and the evolution of breeding systems.

Bryophyta↗

PubMed2006

In vitro production of llama (Lama glama) embryos by intracytoplasmic sperm injection: effect of chemical activation treatments and culture conditions.

Assisted reproductive technologies in the llama (Lama glama) are needed to provide alternative methods for the propagation, selection and genetic improvement; however, recovery of adequate quantity and quality of spermatozoa for conventional IVF is problematic. Therefore, an effort was made to adapt the intracytoplasmic sperm injection (ICSI) procedure for the in vitro production of llama embryos. The specific objectives of this study were: (1) to determine in vitro maturation rates of oocytes recovered by transvaginal ultrasound-guided oocyte aspiration (TUGA) or flank laparotomy; (2) to evaluate the effects of activation treatments following ICSI; (3) to evaluate the development of llama ICSI embryos in CR1aa medium or in an oviduct cell co-culture system. Llamas were superstimulated by double dominant follicle reduction followed by oFSH administered in daily descending doses over a 3-day interval. Oocytes were harvested by flank laparotomy or TUGA and matured in vitro for 30 h. Mature oocytes were subjected to ICSI followed by no chemical activation (Treatment A), ionomycin only (Treatment B) or ionomycin/DMAP activation (Treatment C). More oocytes were recovered by flank laparotomy procedure compared with TUGA (94% versus 61%, P<0.05) and a greater number of oocytes harvested by flank laparotomy reached the metaphase-II stage (77% versus 44%, P<0.05). After ICSI, the proportion of cleaved and 4-8-cell stages embryos was significantly greater when injected oocytes were activated with ionomycin/DMAP combination (63% and 38%, respectively, P<0.05). The co-culture of ICSI embryos with llama oviduct epithelial cells resulted in progression to morula (25%) and blastocyst (12%) stages; whereas, all embryos cultured in CR1aa medium arrested at the 8-16-cell developmental stage.

Animals↗

PubMed2006

Relationships of tacrolimus pharmacokinetic measures and adverse outcomes in stable adult liver transplant recipients.

BACKGROUND AND OBJECTIVES: Alternative measures to trough concentrations [non-trough concentrations and limited area under the concentration-time curve (AUC)] have been shown to better predict tacrolimus AUC. The aim of this study was to determine if these are also better predictors of adverse outcomes in long term liver transplant recipients. METHODS: The associations between tacrolimus trough concentrations (C(0)), non-trough concentrations (C(1), C(2), C(4), C(6/8)), and AUC(0-12) and the occurrence of hypertension, hyperkalaemia, hyperglycaemia and nephrotoxicity were assessed in 34 clinically stable liver transplant patients. RESULTS AND DISCUSSION: The most common adverse outcome was hypertension, prevalence of 36%. Hyperkalaemia and hyperglycaemia had a prevalence of 21% and 13%, respectively. A sequential population pharmacokinetic/pharmacodynamic approach was implemented. No significant association between predicted C(0), C(1), C(2), C(4), C(6/8) or AUC(0-12) and adverse effects could be found. Tacrolimus concentrations and AUC measures were in the same range in patients with and without adverse effects. CONCLUSIONS: Measures reported to provide benefit, preventing graft rejection and minimizing acute adverse effects in the early post-transplant period, were not able to predict adverse effects in stable adult liver recipients whose trough concentrations were maintained in the notional target range.

Adult↗

PubMed2005

Characterization of the human cytochrome P450 forms involved in metabolism of tamoxifen to its alpha-hydroxy and alpha,4-dihydroxy derivatives.

Tamoxifen is a known hepatocarcinogen in rats and is associated with an increased incidence of endometrial cancer in patients. One mechanism for these actions is via bioactivation, where reactive metabolites are generated that are capable of binding to DNA or protein. Several metabolites of tamoxifen have been identified that appear to predispose to adduct formation. These include alpha-hydroxytamoxifen, alpha,4-dihydroxytamoxifen, and alpha-hydroxy-N-desmethyltamoxifen. Previous studies have shown that cytochrome P450 (P450) enzymes play an important role in the biotransformation of tamoxifen. The aim of our work was to determine which P450 enzymes were capable of producing alpha-hydroxylated metabolites from tamoxifen. When tamoxifen (18 or 250 microM) was used as the substrate, P450 3A4, and to a lesser extent, P450 2D6, P450 2B6, P450 3A5, P450 2C9, and P450 2C19 all produced a metabolite with the same HPLC retention time as alpha-hydroxytamoxifen at either substrate concentration tested. This peak was well-separated from 4-hydroxy-N-desmethyltamoxifen, which eluted substantially later under the chromatographic conditions used. No alpha,4-dihydroxytamoxifen was detected in incubations with any of the forms with tamoxifen as substrate. However, when 4-hydroxytamoxifen (100 microM) was used as the substrate, P450 2B6, P450 3A4, P450 3A5, P450 1B1, P450 1A1, and P450 2D6 all produced detectable concentrations of alpha,4-dihydroxytamoxifen. These studies demonstrate that multiple human P450s, including forms found in the endometrium, may generate reactive metabolites in women undergoing tamoxifen therapy, which could subsequently play a role in the development of endometrial cancer.

Antineoplastic Agents, Hormonal↗

PubMed2005

Evaluating the costs of mosquito resistance to malaria parasites.

Costly resistance mechanisms have been cited as an explanation for the widespread occurrence of parasitic infections, yet few studies have examined these costs in detail. A malaria-mosquito model has been used to test this concept by making a comparison of the fitness of highly susceptible lines of mosquitoes with lines that are resistant to infection. Malaria infection is known to cause a decrease in fecundity and fertility of mosquitoes; resistant mosquitoes were thus predicted to be fitter than susceptible ones. Anopheles gambiae were selected for refractoriness/resistance or for increased susceptibility to infection by Plasmodium yoelii nigeriensis. Additional lines that acted as controls for inbreeding depression were raised in parallel but not exposed to selection pressure. Selections were made in triplicate so that founder effects could be detected. Resistance mechanisms that were selected included melanotic encapsulation of parasites within 24 h postinfection and the complete disappearance of parasites from the gut. Costs of immune surveillance were assessed after an uninfected feed, and costs of immune deployment were assessed after exposure to infection and to infection and additional stresses. Mosquito survivorship was unaffected by either resistance to infection or by an increased burden of infection when compared with low levels of infection. In most cases reproductive fitness was equally affected by refractoriness or by infection. Resistant mosquitoes did not gain a fitness advantage by eliminating the parasites. Costs were consistently associated with larval production and egg hatch rate but rarely attributed to changes in blood feeding and never to changes in mosquito size. No advantages appeared to be gained by the offspring of resistant mosquitoes. Furthermore, we were unable to select for refractoriness in groups of mosquitoes in which 100% or 50% of the population were exposed to infection every generation for 22 generations. Under these selection pressures, no population had become completely refractory and only one became more resistant. Variations in fitness relative to control lines in different groups were attributed to founder effects. Our conclusion from these findings is that refractoriness to malaria is as costly as tolerance of infection.

Animals↗

PubMed2003

Young male prisoners in a Young Offenders' Institution: their contact with suicidal behaviour by others.

Prison suicide rates are increasing. The impact of witnessing a suicide or how many people do so is unknown. The aim of this study was to find how many young people detained in a Young Offenders' Institution (YOI) have had contact with another's suicide attempt and to test for association between this and own self-harming behaviour. A questionnaire, developed for the project, was distributed within a YOI. 74% (355/480) responded. One hundred and fifty-one (43%) of the young men reported that they knew someone who had attempted suicide, 48 of them knowing someone who had thereby died. The contact with a non-fatal suicide attempted by others was associated with own self-harm (OR 1.73, CI 1.39-21.4, p<0.01); contact with completed suicide had no such association. The most important factor that increased the chance of knowing a suicide attempter was actual length of time spent in prison up to the time of the study; 95 (63%) of the young men with such contact had it in prison. No other significant vulnerability factors were identified. It seems likely that imprisonment is a specific vulnerability factor for self-harm, one explanation being that it increases the risk of exposure to a contact with suicidal behaviour by others. Further work is called for to test relationships between such exposure and own behaviour over time, and to gather first hand accounts from the young men in such circumstances in order to understand the meaning for them of the contact with suicidal behaviour by others. This would inform appropriate intervention strategies, and could save much morbidity, and even mortality.

Adolescent↗

PubMed2003

Does 'like predict like' when patients discharged from high secure hospitals re-offend? An instrument to describe serious offences.

BACKGROUND: The statement that past behaviour is the best predictor of future behaviour has empirical support in respect of whether an individual will, or will not, commit a criminal offence. People who have offended in the past are more likely to offend in the future. The aims of this study were to develop an instrument and to examine whether the same statement applies in respect of the nature and circumstances of successive offences committed by the same person. METHOD: A rating instrument to describe seven variables relating to the nature and circumstances of a serious offence, the SODI, was developed by the authors. Inter-rater reliability was measured when the instrument was applied to 80 offences committed by 40 patients leaving high secure hospitals. The data were examined for evidence of similarity in the nature and circumstances of successive offences. RESULTS: For five of the seven items of the instrument the kappa coefficients for inter-rater reliability were > 0.65. No significant associations, in terms of SODI ratings, were found between the offence that led to hospital admission and that which was committed after discharge. CONCLUSIONS: The SODI is a reliable instrument for the description of serious offences committed by this group. Risk assessments in psychiatry should be informed by an awareness that in only a proportion of cases will the nature and circumstances of any serious re-offence resemble the nature and circumstances of the offence which contributed to a patient's admission to hospital.

Crime↗

PubMed2003

Population pharmacokinetic analysis of mycophenolic acid in renal transplant recipients following oral administration of mycophenolate mofetil.

AIM: To develop a population pharmacokinetic model for mycophenolic acid in adult kidney transplant recipients, quantifying average population pharmacokinetic parameter values, and between- and within-subject variability and to evaluate the influence of covariates on the pharmacokinetic variability. METHODS: Pharmacokinetic data for mycophenolic acid and covariate information were previously available from 22 patients who underwent kidney transplantation at the Princess Alexandra Hospital. All patients received mycophenolate mofetil 1 g orally twice daily. A total of 557 concentration-time points were available. Data were analysed using the first-order method in NONMEM (version 5 level 1.1) using the G77 FORTRAN compiler. RESULTS: The best base model was a two-compartment model with a lag time (apparent oral clearance was 27 l h(-1), and apparent volume of the central compartment 98 l). There was visual evidence of complex absorption and time-dependent clearance processes, but they could not be successfully modelled in this study. Weight was investigated as a covariate, but no significant relationship was determined. CONCLUSIONS: The complexity in determining the pharmacokinetics of mycophenolic acid is currently underestimated. More complex pharmacokinetic models, though not supported by the limited data collected for this study, may prove useful in the future. The large between-subject and between-occasion variability and the possibility of nonlinear processes associated with the pharmacokinetics of mycophenolic acid raise questions about the value of the use of therapeutic monitoring and limited sampling strategies.

Administration, Oral↗

PubMed2003

Vascular training in the U.K.: femorodistal bypass, an index procedure?

OBJECTIVES: femorodistal bypass operation is one of three index procedures for vascular training in the U.K. Our aim is to determine the suitability of femorodistal bypass to be considered as an index procedure in the era of increasing utilisation of percutaneous transluminal angioplasty (PTA). DESIGN: a retrospective analysis of prospectively collected data. PATIENTS AND METHODS: a total of 526 patients with 608 chronic critically ischaemic limbs admitted to the vascular unit, at the Royal United Hospital, Bath, between January 1994 and December 1999 was included in the study. RESULTS: revascularisation either by PTA, bypass surgery or a combination of both was attempted in 524 limbs (86%). Crural procedures were carried out on 71 limbs (14% of revascularised limbs). Primary crural procedures included 34 PTAs as a sole treatment (48%), and 37 femorodistal bypass operations (52%). CONCLUSIONS: during a 6-year period only 37 primary femorodistal bypass operations were performed in a unit which aggressively treats CLI. PTA is the initial step and increasingly the sole treatment for critical limb ischaemia (CLI), including distal lesions. We question the rationale of including an uncommon operation as a vascular training index procedure.

Angioplasty, Balloon↗

PubMed2003

Isolation of Mycobacterium avium subsp paratuberculosis from environmental samples collected from farms before and after destocking sheep with paratuberculosis.

OBJECTIVE: To determine whether Mycobacterium avium subsp paratuberculosis could be isolated from soil-pasture, faecal, water and sediment samples on farms before and after removal of sheep with paratuberculosis. A feasibility study and subsequent field survey. PROCEDURE: First the analytical sensitivity of radiometric culture of the organism from two types of soil was determined relative to faeces. Then soil-pasture, faecal, water and sediment samples were collected for culture from a range of sites from 6 farms with paratuberculosis affected sheep and goats. Similar samples were collected from 20 farms at least 9 months after removal of infected stock. RESULTS: The analytical sensitivity of culture of M a paratuberculosis from soil samples was 2 orders of magnitude less than that from faeces, and environmental samples required longer incubation periods to yield significant growth in radiometric culture (BACTEC) medium. However, the organism was recovered from approximately 20% of 163 soil-pasture, water and sediment samples from 6 properties with clinically-affected animals with paratuberculosis. The positive samples were from a range of topographic sites, including open exposed and dry areas, however, low lying areas tended to have larger numbers of organisms. When the same sites were sampled again about 5 months later, only 1 was culture positive, and none were culture positive > 12 months later. Of 17 water and dam sediment samples collected from farm 6, which had long-standing high prevalence OJD infection, only one water sample and one sediment from the same dam were culture positive. None of the 5 water samples from the other farms were culture positive. Of 96 water samples, 90 sediment samples and 93 soil samples from farms that had been destocked of infected sheep/goats for 9 to 24 months, one sediment sample from a farm in Victoria (destocked for 12 months) and two sediment samples from a farm in New South Wales (10, 19 months) were culture positive. Recontamination from cattle or water could not be excluded as a cause of the positive cultures from the second farm. CONCLUSION: M a paratuberculosis can be detected by radiometric culture in environmental samples from farms grazed by sheep or goats with paratuberculosis. There is a relatively low likelihood of recovery of the organism from water samples from such farms, and at 5 or more months after removing stock with paratuberculosis the likelihood of positive cultures from environmental samples is very low. Although the analytical sensitivity of culture from environmental samples is less than that from faeces, surveys of environmental sites are nevertheless feasible. However, improved culture methods are needed for critical surveys and to study the movement and fate of the organism in the environment.

Animals↗

PubMed2002

Quantum dot superlattice thermoelectric materials and devices.

PbSeTe-based quantum dot superlattice structures grown by molecular beam epitaxy have been investigated for applications in thermoelectrics. We demonstrate improved cooling values relative to the conventional bulk (Bi,Sb)2(Se,Te)3 thermoelectric materials using a n-type film in a one-leg thermoelectric device test setup, which cooled the cold junction 43.7 K below the room temperature hot junction temperature of 299.7 K. The typical device consists of a substrate-free, bulk-like (typically 0.1 millimeter in thickness, 10 millimeters in width, and 5 millimeters in length) slab of nanostructured PbSeTe/PbTe as the n-type leg and a metal wire as the p-type leg.

Journal Article↗

PubMed2001

Population pharmacokinetics of tacrolimus in children who receive cut-down or full liver transplants.

BACKGROUND: The aim of this study was to investigate the population pharmacokinetics of tacrolimus in pediatric liver transplant recipients and to identify factors that may explain pharmacokinetic variability. METHODS: Data were collected retrospectively from 35 children who received oral immunosuppressant therapy with tacrolimus. Maximum likelihood estimates were sought for the typical values of apparent clearance (CL/F) and apparent volume of distribution (V/F) with the program NONMEM. Factors screened for influence on the pharmacokinetic parameters were weight, age, gender, postoperative day, days since commencing tacrolimus therapy, transplant type (whole child liver or cut-down adult liver), liver function tests (bilirubin, alkaline phosphatase [ALP], aspartate aminotransferase [AST], gamma-glutamyl transferase [GGT], alanine aminotransferase [ALT]), creatinine clearance, hematocrit, corticosteroid dose, and concurrent therapy with metabolic inducers and inhibitors of tacrolimus. RESULTS: No clear correlation existed between tacrolimus dosage and blood concentrations (r2=0.003). Transplant type, age, and liver function test values were the most important factors (P<0.01) that influenced the pharmacokinetics of tacrolimus. CL/F estimates were greater in whole liver recipients, decreased with increasing patient age and AST values, and increased with increasing GGT values. Average parameter estimates were CL/F=5.75 L/h (cut-down liver), CL/F=44 L/h (whole liver), and V/F=617 L. Marked intersubject variability (CV%=110% to 297%) and residual variability (CV%=42%) was observed. CONCLUSIONS: Pharmacokinetic information obtained in this study may assist physicians in making individualized dosage decisions in regard to tacrolimus in pediatric liver transplant recipients. Children who received a whole child's liver appeared to retain "pediatric" clearance, whereas those who received a cut-down adult liver had "adult" clearances (on average 7-fold less).

Adolescent↗

PubMed2001

The frequency of founder mutations in the BRCA1, BRCA2, and APC genes in Australian Ashkenazi Jews: implications for the generality of U.S. population data.

BACKGROUND: Several studies have shown that Ashkenazi Jews in the United States and Israel have a high prevalence of the founder mutations BRCA1 185delAG, BRCA1 5382insC, BRCA2 6174delT, and APC I1307K at frequencies of 1.0--1.1%, 0.2--0.3%, 0.6--1.4%, and 6.1--7.0%, respectively. The objective of this study was to compare the prevalence of these alleles in the Australian Jewish population with that of U.S. Jews. Australian Jews have a different history of migration, with less opportunity for changes in allele frequency due to conversion or intermarriage with non-Jewish Australians. The results obtained therefore can be used to assess whether U.S. data can be generalized to other Jewish populations. SUBJECTS AND METHODS. Subject samples were ascertained through a screening program for Tay-Sachs disease as part of a community-based screening program in New South Wales and Victoria. DNA extracted from 1200 deidentified blood samples was tested using amplification refractory mutation system polymerase chain reaction. RESULTS: The allele frequencies found were as follows: BRCA1 185delAG 1.25% (95% confidence interval [CI], 0.62--1.88%), BRCA1 5382insC 0.25% (95% CI, 0--0.53%), BRCA2 6174delT 1.08% (95% CI, 0.50--1.67%), and APC I1307K 8.67% (95% CI, 7.07--10.26%). The prevalence of breast carcinoma predisposition alleles therefore is greater than 2.5% in Australian Ashkenazim. CONCLUSIONS: There were no significant differences between the allele frequencies in Australian Ashkenazim and those identified in other studies with similar ascertainment strategies, despite the different migration patterns of Australian Jews. This suggests the broad applicability of the U.S. and Israeli data, not only to Australian Ashkenazim, but also to Ashkenazi communities throughout the world.

Adult↗

PubMed2001

A retrospective analysis of mycophenolic acid and cyclosporin concentrations with acute rejection in renal transplant recipients.

OBJECTIVES: Although monitoring of cyclosporin (CsA) is standard clinical practice postrenal transplantation, mycophenolic acid (MPA) concentrations are not routinely measured. There is evidence that a relationship exists between MPA area under the concentration-time curve (AUC) and rejection. In this study, a retrospective analysis was undertaken of 27 adult renal transplant recipients. METHODS: Patients received CsA and MPA therapy and had a four-point MPA AUC investigation. The relationship between MPA AUC performed in the first week after transplantation, as well as median trough cyclosporin concentrations, and clinical outcomes in the first month posttransplant were evaluated. RESULTS: A total of 12 patients experienced biopsy proven rejection (44.4%) and 4 patients had gastrointestinal adverse events (14.8%). A statistically significant relationship was observed between the incidence of biopsy proven rejection and both MPA AUC (p = 0.02) and median trough CsA concentration (p = 0.008). No relationship between trough MPA concentration and rejection was observed (p = 0.21). Only 3 of 11 (27%) patients with an MPA AUC > 30 mg x h/L and a median trough CsA > 175 microg/L experienced acute rejection, compared with a 56% incidence of rejection for the remaining 16 patients. Patients who experienced adverse gastrointestinal events had significantly lower MPA AUC (p = 0.04), but median trough CsA concentrations were not significantly different (p = 0.24). Further, 3 of these 4 patients had rejection episodes. CONCLUSIONS: In addition to standard CsA monitoring, we propose further investigation of the use of a 4-point sampling strategy to predict MPA AUC in the first week posttransplant, which may facilitate optimization of mycophenolate mofetil dose at a time when patients are most vulnerable to acute rejection.

Adult↗

PubMed2001

The influence of host haematocrit on the blood feeding success of Anopheles stephensi: implications for enhanced malaria transmission.

Two studies were carried out to determine the effect of the rodent malaria Plasmodium yoelii nigeriensis on the blood feeding success of Anopheles stephensi. Initially, pairs of mice with similar packed cell volume (PCV) (measured by haematocrit) were selected. Following infection of one of the pair its PCV gradually fell. At various times post-infection, a comparison was made of the bloodmeal size (haemoglobin content) of mosquitoes feeding on these mice. The bloodmeal sizes increased with parasite-induced fall in PCV down to a haematocrit of 43-44%, which occurred approximately 48 h post-infection. Bloodmeals were significantly reduced, however, when mosquitoes fed on mice with higher parasitaemias and a haematocrit of 15-35%. Thus, at early stages of infection, mosquitoes ingested a bloodmeal significantly greater than did the mosquitoes feeding on the control mice. However, mosquitoes were not able to compensate for severe infection-associated anaemia. To compensate for variation due to innate differences in the mice, a second experiment was performed. Mosquitoes were fed on the same mice before (control) and after infection. Again, the bloodmeal size increased with decreasing PCV down to haematocrits of 42-45%, but declined thereafter. In this host-parasite-vector system, haematocrits that maximized erythrocyte intake were produced when gametocytes, capable of exflagellation, were present.

Animals↗

PubMed2001

A tool to measure radiotherapy complexity and workload: derivation from the basic treatment equivalent (BTE) concept.

Radiotherapy workload is poorly represented by simple parameters of patients, fractions or fields treated because these do not contain any measure of treatment complexity. However, complexity is increasing and there is an urgent need to quantify this. We have evaluated the basic treatment equivalent (BTE) model as a measure of radiotherapy workload and complexity. Radiotherapy treatment times, from the patient entering to exiting the treatment room maze, were measured for 1298 treatment sessions on 269 patients. The data were used to assess the original model and derive three new models for predicting treatment duration. The most complicated, the 'Addenbrooke's complex model', contained two additional predictor variables, including 'site/technique', in a linear additive form. Before the study, the department used a standard treatment appointment time of 10 minutes. However, 50% of the measured treatments took longer than 10 minutes, (mean 10.9). Summed over the working day, this discrepancy indicates that a standard 10-minute appointment is a poor basis for scheduling radiotherapy. The original BTE model was effective in predicting treatment times, although this was improved by refinement of the model. The Addenbrooke's complex model correctly predicted 70% of treatment times to within 2 minutes (55% for the original BTE model), 80% to within 2.5 minutes and 95% to within 4.7 minutes. The percentage of the variation in observed times accounted for by the model is 59.4%. The models can represent radiotherapy complexity, can improve scheduling on linear accelerators, and are likely to be applicable to other departments. They are thus tools to assess the impact of changes in complexity from new techniques, trial protocols (e.g. the Medical Research Council prostate radiotherapy trial RTO1), and possible time saving from advanced technology such as multileaf collimators (MLCs) or automated machine set-up. The replacement of manually-lifted shielding blocks by MLCs should save 1.1-1.5 minutes for a three- or four-field pelvic plan (i.e. 12%-13%). The models could also be used to aid planning for future linear accelerator provision and for costing radiotherapy treatment.

Efficiency, Organizational↗

PubMed2001

Functional regulator treatment of Class II division 1 malocclusions.

This controlled retrospective study aimed to identify the contribution of skeletal and dental changes in the correction of Class II division 1 malocclusions using Fränkel's functional regulator II (FRII), with reference to a concurrently recruited control group. One hundred and thirty-eight patients with Class II division 1 malocclusions were identified, those accepting treatment forming the study group and those declining treatment the control group. The study group (n = 70) were treated with a Fränkel appliance. Pre- and post-treatment observation cephalometric radiographs were analysed and compared. Mean values for both skeletal and dental variables in the control group were remarkably consistent throughout the study period; however, this masked individual variations in this group. The skeletal variables in the study group that showed statistically significant differences from the control group were SNB, ANB, BaNA and ANS-Me, but none of these was sufficiently large to be regarded as clinically significant. Dental variables showed clinically and statistically significant differences, including a 10 degree reduction in UI-Max and 3.1 degree increase in LI-Mand. The Fränkel appliance was thus found to be effective in producing desirable occlusal and dental changes in the majority of patients treated.

Adolescent↗

PubMed2001

A detection scheme for paraquat poisoning: validation and a five-year experience in Australia.

We report the validation of a quantitative method for paraquat in plasma and urine using high-performance liquid chromatography (HPLC) with ultraviolet detection (260 nm). Furthermore, we illustrate the use of this method in the clinic (over five years), in conjunction with a qualitative urine paraquat screen. Urine or plasma sample (1 mL) preparation was performed in duplicate using C18 solid-phase extraction. Chromatographic separation was achieved on a Zorbax RX-Silica column (250 x 4.6-mm i.d.). The mobile phase consisted of 96% sodium chloride (5 g/L) and 4% acetonitrile (pH 2.2) pumped at 1.0 mL/min. Using a single-point calibration (1.0 mg/L), the method was found to be linear from 0.1 to 5.0 mg/L. The accuracy and imprecision of the method, over the linear range and for plasma and urine, were 94.7-104.9% and < 12.2%, respectively. The limit of quantitation for both matrices was 0.1 mg/L. The absolute recovery of paraquat from plasma and urine was 79.9 +/- 5.3% and 88.2 +/- 5.3%, respectively. From January 1995 to February 2000, 47 qualitative urine paraquat screens were requested throughout Australia. Nine screens were positive, and eight were confirmed to have paraquat present by our HPLC method. One sample was not analyzed by HPLC because the patient died prior to analysis. Thus, no false-positive results were reported for the qualitative urine screen. An additional 11 samples were referred for patients with positive screens from other sites for HPLC confirmation. The presence of paraquat was confirmed in nine of these samples. In conclusion, a qualitative urine screen combined with our validated HPLC confirmation is an effective protocol for assessing suspected cases of paraquat poisoning.

Calibration↗