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Biomedical subjects

S Hughes

Publications and source records attributed to S Hughes.

At least 19 recordsLinked to original sources
PubMed2007

Single quantum dots for slow and fast light in a planar photonic crystal.

We theoretically investigate slow and fast light propagation and pulse velocity control in a nanocavity containing a single quantum dot side-coupled to a planar-photonic-crystal waveguide. We demonstrate that low coupling strength (i.e., the weak coupling regime) between a cavity and a dot, under on-resonance condition, can lead to delays of about +90 ps for a pulse 1/e-width of 280 ps. The group delay dependence on the various coupling parameters suggests achievable delays of +300 ps and consequently very slow light speeds of around 5000 m/s in a 1.5 microm cavity-waveguide section. We also show that under off-resonant condition one can achieve significant pulse advancement of -60 ps.

Journal Article↗
PubMed2007

Third-harmonic generation in disguise of second-harmonic generation revisited: role of thin-film thickness and carrier-envelope phase.

It has previously been reported that a peak at the spectral position of the second harmonic of an excitation laser can be generated in an inversion-symmetric medium in the regime of extreme nonlinear optics and that this peak may be exploited to measure the carrier-envelope phase of the excitation pulse. Here we revisit this phenomenon with regard to reverse engineering the carrier-envelope phase and demonstrate that the thin-film thickness and the incident field can have a drastic influence on pulse propagation, and so the reverse engineering would likely fail.

Journal Article↗
PubMed2006

Modulation of iron transport proteins in human colorectal carcinogenesis.

BACKGROUND AND AIMS: Total body iron and high dietary iron intake are risk factors for colorectal cancer. To date there is no comprehensive characterisation of iron transport proteins in progression to colorectal carcinoma. In this study, we examined expression of iron import (duodenal cytochrome b (DCYTB), divalent metal transporter 1 (DMT1), and transferrin receptor 1 (TfR1)) and export (hephaestin (HEPH) and ferroportin (FPN)) proteins in colorectal carcinoma. METHODS: Perl's staining was used to examine colonocyte iron content. Real time polymerase chain reaction (PCR) and western blotting were used to examine mRNA and protein levels of the molecules of interest in 11 human colorectal cancers. Semiquantitative immunohistochemistry was used to verify protein levels and information on cellular localisation. The effect of iron loading on E-cadherin expression in SW480 and Caco-2 cell lines was examined by promoter assays, real time PCR and western blotting. RESULTS: Perl's staining showed increased iron in colorectal cancers, and there was a corresponding overexpression of components of the intracellular iron import machinery (DCYTB, DMT1, and TfR1). The iron exporter FPN was also overexpressed, but its intracellular location, combined with reduced HEPH levels, suggests reduced iron efflux in the majority of colorectal cancers examined. Loss of HEPH and FPN expression was associated with more advanced disease. Iron loading Caco-2 and SW480 cells caused cellular proliferation and E-cadherin repression. CONCLUSIONS: Progression to colorectal cancer is associated with increased expression in iron import proteins and a block in iron export due to decreased expression and aberrant localisation of HEPH and FPN, respectively. This results in increased intracellular iron which may induce proliferation and repress cell adhesion.

Antigens, CD↗
PubMed2006

Characterizing the efficacy of calcium channel agonist-release strategies for bone tissue engineering applications.

We have previously reported on the use of Bay K8644-release strategies in combination with perfusion-compression bioreactor systems for up regulating bone formation in three-dimensional PLLA scaffolds. Here we report on the analysis of Bay activity following its release from our PLLA scaffolds over the culture period imposed in our tissue engineering protocol using UV spectroscopy in combination with whole cell patch clamping techniques. Bay was released continually from scaffolds within the physiological range required for agonist activity (1-10 microM). Patch clamping allowed for the effects of Bay released from scaffolds to be monitored directly with respect to osteoblast electrophysiology. A characteristic shift in the current-voltage (I-V) relationship of L-type VOCC currents was observed in rat osteoblast sarcoma (ROS) cells patched in a solution with Bay released from scaffolds following 14 and 28 days incubation, with statistically significant differences observed in peak currents compared to non-Bay controls. An increase in the magnitude of the peak inward currents was also noted. The electrophysiological response of osteoblasts in the presence of Bay released from scaffolds demonstrates that the released Bay is stable and maintains its bioactivity following culture of up to 28 days.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed2006

Preoperative radiotherapy for operable rectal cancer--is a lower dose to a reduced volume acceptable?

AIMS: A retrospective audit was carried out to determine the rate of local recurrence (recurrent tumour within the lesser pelvis or the perineal wound) in 88 rectal cancer patients treated with 20 Gy/four fractions of adjuvant preoperative radiotherapy and curative surgery. MATERIALS AND METHODS: All patients were followed-up by clinical examination with rigid sigmoidoscopy at 6 monthly intervals if the rectum was intact, and computed tomography of the pelvis at 1, 2 and 5 years after surgery. In total, 171 patients with rectal cancer were identified under the care of one surgeon over a period of 11 years from May 1992 to April 2003. We excluded patients with rectal cancer from preoperative adjuvant radiotherapy if they had evidence at presentation of distant metastases, if they had fixed rectal tumours, were treated by local excision and had previous radiotherapy to the pelvis. On this basis, only 88 were considered for preoperative radiotherapy and curative resection with a median follow-up of 5.16 years. RESULTS: The 5-year survival by stage was Dukes A 96%, Dukes B 65% and Dukes C 36%. Overall, four patients (of 88) developed a recurrence within the lesser pelvis or the perineal wound, giving a local recurrence of 4.2% at 3 years (from a Kaplan-Meier graph). CONCLUSIONS: This single-centre audit suggests that a lower dose of radiotherapy to a smaller volume provides an acceptable local recurrence rate that compares very favourably with the well-publicised Swedish and Dutch trials of 25 Gy/five fractions. It was not the intention of this audit to suggest that this dose should be widely adopted. However, given the long-term gastrointestinal morbidity and risk of second malignancies, we advise caution when formulating even more intensive radiotherapy and chemoradiotherapy regimens for rectal cancer.

Adenocarcinoma↗
PubMed2006

Interactions of malnutrition and immune impairment, with specific reference to immunity against parasites.

1. Clinical malnutrition is a heterogenous group of disorders including macronutrient deficiencies leading to body cell mass depletion and micronutrient deficiencies, and these often coexist with infectious and inflammatory processes and environmental problems. 2. There is good evidence that specific micronutrients influence immunity, particularly zinc and vitamin A. Iron may have both beneficial and deleterious effects depending on circumstances. 3. There is surprisingly slender good evidence that immunity to parasites is dependent on macronutrient intake or body composition.

Animals↗
PubMed2005

Microarray comparative genomic hybridisation analysis of intraocular uveal melanomas identifies distinctive imbalances associated with loss of chromosome 3.

Defining regions of genomic imbalance can identify genes involved in tumour development. Conventional cytogenetics has identified several nonrandom copy number alterations (CNA) in uveal melanomas (UVM), which include monosomy 3, chromosome 6 abnormalities and gain of 8q. To gain further insight into the CNAs and define the regions involved more precisely we analysed 18 primary UVMs using 1 Mb BAC microarray comparative genomic hybridisation (CGH). Our analysis showed that the most common genomic imbalances were 8q gain (78%), 6p gain (67%) and monosomy 3 (56%). Two distinct CGH profiles could be delineated on the basis of the chromosome 3 status. The most common genetic changes in monosomy 3 tumours, in our study, were gain of 8q11.21-q24.3, 6p25.1-p21.2, 21q21.2-q21.3 and 21q22.13-q22.3 and loss of 1p36.33-p34.3, 1p31.1-p21.2, 6q16.2-q25.3 and 8p23.3-p11.23. In contrast, disomy 3 tumours showed recurrent gains of only 6p25.3-p22.3 and 8q23.2-q24.3. Our approach allowed definition of the smallest overlapping regions of imbalance, which may be important in the development of UVM.

Adult↗
PubMed2005

Modified spontaneous emission and qubit entanglement from dipole-coupled quantum dots in a photonic crystal nanocavity.

The modified spontaneous emission dynamics of two photon-coupled quantum dots in a planar-photonic crystal are theoretically investigated. Based on a photon Green function technique for quantizing the electromagnetic fields in arbitrary surroundings, pronounced vacuum Rabi oscillations and dipole-dipole interactions are self-consistently incorporated and are shown to result in a high degree of quantum-bit entanglement. Quantum dots with different optical dipole moments are also found to yield a very rich display of quantum dynamics and offer several advantages over coupling identical atoms.

Journal Article↗
PubMed2005

Impact of combined (18)F-FDG PET/CT in head and neck tumours.

To compare the interobserver agreement and degree of confidence in anatomical localisation of lesions using 2-[fluorine-18]fluoro-2-deoxy-D-glucose ((18)F-FDG) positron emission tomography (PET)/computed tomography (CT) and (18)F-FDG PET alone in patients with head and neck tumours. A prospective study of 24 patients (16 male, eight female, median age 59 years) with head and neck tumours was undertaken. (18)F-FDG PET/CT was performed for staging purposes. 2D images were acquired over the head and neck area using a GE Discovery LS PET/CT scanner. (18)F-FDG PET images were interpreted by three independent observers. The observers were asked to localise abnormal (18)F-FDG activity to an anatomical territory and score the degree of confidence in localisation on a scale from 1 to 3 (1=exact region unknown; 2=probable; 3=definite). For all (18)F-FDG-avid lesions, standardised uptake values (SUVs) were also calculated. After 3 weeks, the same exercise was carried out using (18)F-FDG PET/CT images, where CT and fused volume data were made available to observers. The degree of interobserver agreement was measured in both instances. A total of six primary lesions with abnormal (18)F-FDG uptake (SUV range 7.2-22) were identified on (18)F-FDG PET alone and on (18)F-FDG PET/CT. In all, 15 nonprimary tumour sites were identified with (18)F-FDG PET only (SUV range 4.5-11.7), while 17 were identified on (18)F-FDG PET/CT. Using (18)F-FDG PET only, correct localisation was documented in three of six primary lesions, while (18)F-FDG PET/CT correctly identified all primary sites. In nonprimary tumour sites, (18)F-FDG PET/CT improved the degree of confidence in anatomical localisation by 51%. Interobserver agreement in assigning primary and nonprimary lesions to anatomical territories was moderate using (18)F-FDG PET alone (kappa coefficients of 0.45 and 0.54, respectively), but almost perfect with (18)F-FDG PET/CT (kappa coefficients of 0.90 and 0.93, respectively). We conclude that (18)F-FDG PET/CT significantly increases interobserver agreement and confidence in disease localisation of (18)F-FDG-avid lesions in patients with head and neck cancers.

Adult↗
PubMed2005

Energy-efficient recovery of butanol from model solutions and fermentation broth by adsorption.

This article discusses the separation of butanol from aqueous solutions and/or fermentation broth by adsorption. Butanol fermentation is also known as acetone butanol ethanol (ABE) or solvent fermentation. Adsorbents such as silicalite, resins (XAD-2, XAD-4, XAD-7, XAD-8, XAD-16), bone charcoal, activated charcoal, bonopore, and polyvinylpyridine have been studied. Use of silicalite appears to be the more attractive as it can be used to concentrate butanol from dilute solutions (5 to 790-810 g L(-1)) and results in complete desorption of butanol (or ABE). In addition, silicalite can be regenerated by heat treatment. The energy requirement for butanol recovery by adsorption-desorption processes has been calculated to be 1,948 kcal kg(-1) butanol as compared to 5,789 kcal kg(-1) butanol by steam stripping distillation. Other techniques such as gas stripping and pervaporation require 5,220 and 3,295 kcal kg(-1) butanol, respectively.

Adsorption↗
PubMed2005

Extrinsic optical scattering loss in photonic crystal waveguides: role of fabrication disorder and photon group velocity.

Formulas are presented that provide clear physical insight into the phenomenon of extrinsic optical scattering loss in photonic crystal waveguides due to random fabrication imperfections such as surface roughness and disorder. Using a photon Green-function-tensor formalism, we derive explicit expressions for the backscattered and total transmission losses. Detailed calculations for planar photonic crystals yield extrinsic loss values in overall agreement with experimental measurements, including the full dispersion characteristics. We also report that loss in photonic crystal waveguides scales inversely with group velocity, at least, thereby raising serious questions about future low-loss applications based on operating frequencies that approach the photonic band edge.

Journal Article↗
PubMed2005

Virtual reconstruction and morphological analysis of the cranium of an ancient Egyptian mummy.

A mummy of an Egyptian priestess dating from the 22nd dynasty (c. 770 BC), completely enclosed in an anthropoid (human shaped) coffin, was scanned on a CT scanner. An accurate reconstruction of the cranium was generated from 115 x 2 mm CT images using AVS/Express on a SGI computer. Linear measurements were obtained from six orthogonal cranial views and used in a morphometric analysis software package (CRANID). The analyses carried out were both linear and nearest neighbour discriminant analysis. The results show that there is a 52.9% probability that the mummy is an Egyptian female, with a 24.5% probability that the mummy is an African female. Thus the technique confirms that the coffin contains an Egyptian female, which is consistent with the inscription on the coffin and the shape of the pelvic bones as revealed by plain X-rays. These results show that this technique has potential for analysing forensic cases where the bones are obscured by soft tissue and clothing. This technique may have an application in virtual autopsies.

Archaeology↗
PubMed2005

Potentially toxic metals in ombrotrophic peat along a 400 km English-Scottish transect.

Four samples of ombrotrophic peat were collected from each of 10 upland locations in a transect from the southern Pennines to the Highland Boundary Fault, a total distance of ca. 400 km. Bulk compositions and other properties were determined. Total contents of Al and heavy metals (Ni, Cu, Zn, Cd, Pb) were determined following digestion with hydrofluoric acid, and concentrations of metals extractable with dilute nitric acid were also measured. Supernatants obtained from aqueous extractions of the peat samples were analysed for pH, major cations and anions, dissolved organic carbon and dissolved metals, and concentrations of free metal ions (Al(3+), Ni(2+), etc.) were estimated by applying a chemical speciation model. Both total and HNO(3)-extractable metal concentrations varied along the transect, the highest values being found at locations close to industrial and former mining areas. The HNO(3)-extractable soil metal contents of Ni, Cu and Cd were appreciably lower than lowest-observed-effect-concentrations (LOEC) for toxicity towards microorganisms in acid, organic rich soils. However, the contents of Zn at two locations, and of Pb at five locations exceeded LOECs, suggesting that they may be exerting toxic effects in the peats. Soil solution concentrations of free heavy metal ions (Cu(2+), Zn(2+), Cd(2+), Pb(2+)) were substantially lower than LOECs for toxicity towards vascular plants, whereas concentrations of Al(3+) were near to toxic levels at two locations.

Aluminum↗
PubMed2005

Clinician-led surgical site infection surveillance of orthopaedic procedures: a UK multi-centre pilot study.

The UK Department of Health established the Healthcare-associated Infection (HAI) Surveillance Steering Group in 2000 to develop a strategy for implementing a national programme for HAI surveillance in National Health Service trusts. A subgroup of this committee examined the surveillance of surgical site infections following orthopaedic surgery. This group oversaw a pilot scheme that was set up in 12 hospitals around the UK to explore the feasibility of implementing a system of surveillance that engaged clinical staff in its operation, provided a process for continuous data collection and could be maintained as part of routine hospital operation over time. A minimum data set was established by the subgroup, and Centers for Disease Control and Prevention (CDC) definitions of infection were used. By March 2003, the surveillance had been undertaken continuously in 11 sites for one to two years, depending on the date of implementation. Only one hospital had ceased data collection. The information was collected mainly by clinical staff, with support and co-ordination usually provided by infection control teams. Data on more than 5400 procedures were available for analysis for four core procedures: arthroplasty of the hip and knee; hemi-arthroplasty of the hip; and internal fixation of trochanteric fractures of the femur. The data set permitted the calculation of risk-adjusted rates, allowing comparisons between hospitals and within a hospital over time. The methodology enhanced clinical ownership of the surveillance process, re-inforced infection control as the responsibility of all staff, and provided timely feedback and local data analysis. The use of CDC definitions permitted international comparisons of the data.

Adult↗
PubMed2005

Targets and elective colorectal cancer: outcome and symptom delay at surgical resection.

OBJECTIVE: To determine, for elective patients with colorectal cancer, if associations exist between the length of symptom history at surgical resection and Dukes stage, completeness of the surgical procedure and patient survival. PATIENTS AND METHODS: A prospective cohort study was undertaken. Five hundred and eighty-two patients with colorectal cancer, admitted for surgical resection after outpatient consultation, divided into four equal quartiles according to length of symptom history (short: n = 131, 0-103 days; medium: n = 136, 104-177 days; long: n = 136, 178-318 days; very long: n = 137, 319-1997 days). The main outcome measures used were the Extent of tumour (Dukes stage) at resection, completeness of resectional surgery (curative vs palliative), patient survival after resection. RESULTS: For patients undergoing elective surgical resection of colorectal cancer we did not find an association between Dukes stage and duration of patient history (Dukes stage C tumours were seen in 37% (CI: 26.2%-48.0%) of patients with a short symptomatic history as opposed to 34% (CI: 32%-62%) with a very long symptomatic history). Elective curative resection was not associated with a significantly different symptom duration than elective palliative resection (Palliative resections were performed in 24% (CI: 11.7%-36.4%) of patients with a short symptomatic history as opposed to 16% (CI: 2.4%-29.9%) with a very long symptomatic history). The median survival time for the four elective colorectal patient groups defined by length of symptomatic history was not significantly different - (short: n = 131, 4.3 years; medium: n = 136, 5.9 years; long: n = 136, 7.1 years; very long: n = 137, 5.0 years). CONCLUSION: Tumour extent, completeness of resection and patient outcome after elective colorectal cancer resection was not found to have an association with length of patient history at the time of surgery.

Chi-Square Distribution↗
PubMed2005

Does human relaxin-2 affect peripheral blood mononuclear cells to increase inflammatory mediators in pathologic bone loss?

This study was designed to test the hypothesis that relaxin stimulates bone resorption by regulating the production of several mediators that stimulate osteoclast formation. The levels of mediators were measured in response to differing relaxin concentrations in supernatants from peripheral blood mononuclear cells (PBMCs), MCF-7 breast cancer cells, and normal human osteoblasts. Although all cell types expressed mRNA for the relaxin receptor (LGR7), only PBMCs responded to relaxin at physiologic levels by increasing tumor necrosis factor-alpha and interleukin-1beta secretion. The findings indicate that PBMCs should be studied in relation to the effect of relaxin on inflammation and bone destruction caused by osteoclasts.

Bone Resorption↗