PubMed Health⌕ Search

Biomedical subjects

P Weston

Publications and source records attributed to P Weston.

At least 19 recordsLinked to original sources
PubMed2002

Transfection of HEK cells via DNA-loaded PLGA and P(FASA) nanospheres.

HEK cells were transfected with the GFP gene using various vectors: naked DNA, lipofectamine, and both PLGA and P(FASA) plasmid-loaded nanospheres. All methods were assessed alone and with the use of chloroquine, a lysosomal enzyme inhibitor. Transfection efficiencies were determined and compared at various times post-incubation using a fluorescence standard curve. Neither naked DNA alone nor naked DNA and chloroquine were capable of transfecting cells. No differences were evident between lipofectamine with chloroquine and lipofectamine alone which transfected cells with a constant increase in efficiency up to 2 weeks. While transfection was not feasible with polymeric nanospheres alone, the addition of chloroquine allowed DNA released from nanospheres within cells to escape endosomal degradation and transfect the cells. The increase in transfection efficiency via nanospheres over time was exponential up to 1 week, as compared to the constant rate seen for the bolus-type administration of lipofectamine, indicating that nanospheres delivered DNA to the cells by a controlled release mechanism. Additionally, the effective dose delivered to cells via nanospheres was approximately 25% that of lipofectamine, indicating that transfection via PLGA and P(FASA) nanospheres might actually be more efficient.

Cell Line↗
PubMed2001

Effect of protein molecular weight on release from micron-sized PLGA microspheres.

This study investigates the effect of protein molecular weight on release kinetics from polymeric microspheres (1-3 microm). Proteins were encapsulated at high and low loadings in poly(lactic-co-glycolic acid) (PLGA) by a phase inversion technique. Mechanism of release from this type of microsphere appeared to be dependent on protein molecular weight for microspheres with low loadings (0.5-1.6%), while independent of protein molecular weight for microspheres with high loadings (4.8-6.9%). At low loadings, release of larger proteins was dependent on diffusion through pores for the duration of the study, while smaller proteins seemed to depend on diffusion through pores initially and on degradation at later times. Following an initial diffusion phase from low loaded microspheres, lysozyme and carbonic anhydrase, the two smallest proteins, exhibited lag phases with curtailed protein release followed by a phase of increased protein release between 4 and 8 weeks, a phenomenon not evident for larger proteins. It appears that by 8 weeks, PLGA had degraded enough to allow additional release of smaller proteins which were entrapped efficiently within the microspheres. Higher loaded microspheres, which have more interconnecting channels, did not exhibit the pronounced shift from diffusion-based to polymer degradation-based release seen with the lower loaded microspheres. Interestingly, microspheres encapsulating large proteins maintained sustained release rates for 56 days.

Chromatography, High Pressure Liquid↗
PubMed2001

Methodological considerations when conducting direct observation in an outdoor environment: our experience in local parks.

OBJECTIVE: This paper discusses some of the inherent methodological limitations of gathering data via direct observation using local parks as a case study. METHODS: Direct observation was carried out in five parks on seven non-consecutive days in 1998 and on matched days in 1999. Information recorded for each person included the time of park entry and exit, gender, age group, and activity/ies undertaken while in the park. METHODOLOGICAL CONSIDERATIONS: The location of the observation point, observer reliability, recording and accuracy of data, and specific issues related to outdoor observation areas should all be considered when designing a study incorporating direct observation as a data collection method. CONCLUSIONS: Direct observation can provide valuable information. However, pilot testing is essential for minimising potential problems associated with this method and optimising data quality. IMPLICATIONS: The issues discussed in this paper provide a useful guide for other researchers undertaking direct observation in outdoor environments.

Data Collection↗
PubMed2000

Comparative genome sequence analysis of the Bpa/Str region in mouse and Man.

The progress of human and mouse genome sequencing programs presages the possibility of systematic cross-species comparison of the two genomes as a powerful tool for gene and regulatory element identification. As the opportunities to perform comparative sequence analysis emerge, it is important to develop parameters for such analyses and to examine the outcomes of cross-species comparison. Our analysis used gene prediction and a database search of 430 kb of genomic sequence covering the Bpa/Str region of the mouse X chromosome, and 745 kb of genomic sequence from the homologous human X chromosome region. We identified 11 genes in mouse and 13 genes and two pseudogenes in human. In addition, we compared the mouse and human sequences using pairwise alignment and searches for evolutionary conserved regions (ECRs) exceeding a defined threshold of sequence identity. This approach aided the identification of at least four further putative conserved genes in the region. Comparative sequencing revealed that this region is a mosaic in evolutionary terms, with considerably more rearrangement between the two species than realized previously from comparative mapping studies. Surprisingly, this region showed an extremely high LINE and low SINE content, low G+C content, and yet a relatively high gene density, in contrast to the low gene density usually associated with such regions.

3-Hydroxysteroid Dehydrogenases↗
PubMed1998

A high-resolution microsatellite map of the mouse genome.

The European Collaborative Interspecific Backcross (EUCIB) resource was constructed for the purposes of high-resolution genetic mapping of the mouse genome (). The large Mus spretus/C57BL/6 backcross of 982 progeny has a genetic resolution of 0.3 cM at the 95% confidence level ( approximately 500 kb in the mouse genome). We have used the EUCIB mapping resource to develop a genome-wide high-resolution genetic map incorporating 3368 microsatellites. The microsatellites are distributed among 2302 genetically separated bins with 1.46 markers per bin on average. Average bin separation is 0.61 cM. This high-resolution genetic map will aid the construction of a robust physical map of the mouse genome.

Animals↗
PubMed1997

The reproducibility of cardiac baroreceptor activity assessed non-invasively by spectral sequence techniques.

Baroreceptor sensitivity (BRS) is increasingly used as a prognostic indicator in cardiovascular disease. Traditionally it has been measured using invasive techniques with pharmacological manipulation of blood pressure (BP). With the advent of newer methods to measure pulse interval and beat-to-beat changes in BP it is now possible, using sophisticated mathematical modelling techniques, to calculate cardiac BRS non-invasively. However, there are virtually no data on the reproducibility of these newer techniques and what factors may affect the repeatability of these measurements. We studied 39 subjects, aged 22-82 years, with a supine systolic BP range 97-160 mmHg and a diastolic BP range 57-94 mmHg on two occasions between 1 week and 6 months apart. Cardiac BRS was measured by power spectral analysis using Fast Fourier Transformation (FFT), sequence analysis (using up, down and combined sequences) and from phase IV of the Valsalva manoeuvre. There was no significant difference between visits for any of the methods for measuring cardiac BRS. Mean BRS values were similar for FFT (16.7 +/- 11.2 ms/mmHg) and sequence analysis (15.8 +/- 11.4 ms/mmHg); however, results using phase IV of the Valsalva manoeuvre were significantly lower (8.1 +/- 2.9 ms/mmHg, p < 0.0001). The coefficient of variation for the five measures of cardiac BRS varied from 16.8% for Valsalva-derived values to 26.1% for 'down' sequence analysis. However, in ten subjects BRS could not be calculated from the Valsalva manoeuvre. None of the independent variables tested (including age, BP levels and time between testing) significantly influenced the degree of repeatability. In summary, there appears to be little difference between these non-invasive methods in their degree of reproducibility. These techniques would seem suitable for longitudinal studies of changes in cardiac BRS and overcome many of the problems associated with the invasive pharmacological methods.

Adult↗
PubMed1995

Gliomatosis cerebri or benign intracranial hypertension?

Benign intracranial hypertension is a condition of obscure aetiology which presents with episodic headaches and nausea. It is a diagnosis based on the exclusion of other intracranial pathology and computed tomography is usually normal. We present a case of gliomatosis cerebri which was initially diagnosed and treated as benign intracranial hypertension.

Adult↗
PubMed1994

Value of a second freeze-thaw cycle in cryotherapy of common warts.

A study of open, randomized, parallel-group design was performed to investigate the impact of a second freeze-thaw cycle on the cure rate, at 3 months, from cryotherapy of common warts on the hands and feet. Cryotherapy was performed at 3-week intervals, and subjects were randomized to receive either one or two freeze-thaw cycles. In addition, all subjects used keratolytic wart paints throughout the study, and plantar warts were pared prior to freezing. Three hundred subjects were recruited. At 3 months, 124 were cured, 83 were not cured, and 93 had defaulted. Among those who did not default the cure rate was 57% from the single freeze technique, and 62% from the double freeze technique, a difference of 5% (P = 0.53, 95% CI-8.1-18.6). Separate analyses for subjects with warts on the hands and on the feet demonstrated no effect of double freezing on hand warts. In contrast, for plantar warts, the cure rate was 41% from single freezing and 65% for double freezing, a difference of 24% (P = 0.04, 95% CI 2.9-44.4). The use of a double freeze-thaw cycle confers little or no advantage over a single freeze in the treatment of hand warts, but may be considerably more effective for plantar warts.

Adult↗
PubMed1990

Multiple sclerosis associated with water intoxication.

We present a case of well documented multiple sclerosis which presented with the syndrome of inappropriate antidiuretic hormone secretion, following an exacerbation of the disease. This is a poorly documented association.

Humans↗
PubMed1988

Experience with the Brindley anterior sacral root stimulator.

Brindley anterior sacral root stimulators have been implanted into 22 spinal cord injured patients from the spinal injury units in Cardiff and Sheffield. The group comprised 20 men and 2 women (15 paraplegics and 7 tetraplegics); 16 patients are using the implant, of whom 11 (68%) are continent. Of the remaining 5, 4, who empty completely, are incontinent because of inability to use the implant with sufficient frequency; 6 patients are not using their implant, though 4 are continent. Of 11 patients with detrusor/sphincter dyssynergia, sphincterotomy was necessary in 3 patients before implantation and in a further 3 after implantation. Of 4 patients with abnormal upper tracts prior to implantation, 2 resolved and 2 deteriorated, in the presence of dyssynergia; 1 patient developed hydronephrosis after implantation, having previously had normal upper tracts. Although erectile function with the stimulator was clinically adequate in 6 patients, in no patient has intercourse been achieved because of concurrent lower limb spasm.

Adult↗
PubMed1983

The effects on auditory and linguistic deprivation of lateral preference of deaf children.

In the light of recent evidence for an altered pattern of cerebral specialisation among the deaf, this study compared hand and foot preference of age-matched samples of deaf and hearing children. Significantly fewer deaf children were fully right-handed and there was a small shift to the left on the handedness continuum. This shift was more marked in children with a greater hearing-loss but was not particularly related to the cause of deafness. No significant difference was found in foot preference. The variation in hand preference is thought to be a function of the differences in hemisphere specialisation found in the deaf, but other explanations are also considered.

Child↗