Search PubMed⌕ Search

Biomedical subjects

J Fenton

Publications and source records attributed to J Fenton.

At least 19 recordsLinked to original sources
PubMed2005

Breakdown of weak-field magnetotransport at a metallic quantum critical point.

We show how the collapse of an energy scale in a quantum critical metal can lead to physics beyond the weak-field limit usually used to compute transport quantities. For a density-wave transition we show that the presence of a finite magnetic field at the critical point leads to discontinuities in the transport coefficients as temperature tends to zero. The origin of these discontinuities lies in the breakdown of the weak-field Jones-Zener expansion which has previously been used to argue that magnetotransport coefficients are continuous at simple quantum critical points. The presence of potential scattering and magnetic breakdown rounds the discontinuities over a window determined by tauDelta < 1 where Delta is the order parameter and tau is the quasiparticle elastic lifetime.

Journal Article↗
PubMed2002

Waiting times during the management of head and neck tumours.

The waiting times incurred during the management of 75 consecutive head and neck oncology patients attending for post-treatment follow-up were reviewed. Data were gleaned from general practitioner (GP) referral letters, patient case-notes as well as radiology and histology reports. The mean time for GP referral to ENT was 5.1 weeks. From ENT to endoscopy was 3.1 weeks, to histology 3.5 weeks, to computed tomography (CT) scan 5.6 weeks, to magnetic resonance scan (MR) 4.1 weeks, to primary radiotherapy 10.3 weeks and to surgery 5.5 weeks. The mean symptom duration prior to referral was 4.9 months. Our results compare unfavourably with the standards recommended by the BAO-HNS. Local modifiations may improve matters, but significant increases in funding, manpower and equipment are required to achieve the stipulated standards. Moreover, criteria for referral have to be re-emphasized and patient education has to be addressed as these appear to contribute the longest delay in the diagnosis of head and neck tumours.

Biopsy↗
PubMed2001

Is reflux noted at diagnostic rigid oesophagoscopy clinically significant?

This study assessed the ability of otolaryngologists to diagnose and grade reflux disease at rigid endoscopy. Twenty-one out of 25 senior otolaryngologists who were questioned by means of a telephone survey said that if they find evidence of reflux disease at rigid endoscopy of the oesophagus and larynx, their practice is to place the patient on a proton pump inhibitor for six weeks without requesting pH and manometry studies, and without referral to a gastroenterologist. Over a two year period, 21 patients were diagnosed as having reflux disease at rigid endoscopy. This was based on the finding of fluid and erythema in the aerodigestive tract and upper oesophagus. Subsequent oesophageal pH and manometry was performed. Nine out of 21 patients were confirmed as refluxers. This demonstrated an accuracy of less than 50 per cent when using these findings to diagnose gastro-oesophageal reflux at rigid endoscopy.

Clinical Protocols↗
PubMed2001

Management of a lump in the neck.

This article reviews the management of adults who present with a neck lump, and discusses the potential causes and relevant investigations. The review emphasizes the avoidance of open biopsy and need for early referral to the appropriate specialist.

Adult↗
PubMed2000

A miniature integrated device for automated multistep genetic assays.

A highly integrated monolithic device was developed that automatically carries out a complex series of molecular processes on multiple samples. The device is capable of extracting and concentrating nucleic acids from milliliter aqueous samples and performing microliter chemical amplification, serial enzymatic reactions, metering, mixing and nucleic acid hybridization. The device, which is smaller than a credit card, can manipulate over 10 reagents in more than 60 sequential operations and was tested for the detection of mutations in a 1.6 kb region of the HIV genome from serum samples containing as few as 500 copies of the RNA. The elements in this device are readily linked into complex, flexible and highly parallel analysis networks for high throughput sample preparation or, conversely, for low cost portable DNA analysis instruments in point-of-care medical diagnostics, environmental testing and defensive biological agent detection.

DNA↗
PubMed2000

Comparison between videofluoroscopy and milk-swallow endoscopy in the assessment of swallowing function.

The investigation of swallowing function and the detection of aspiration has evolved over the past 10 years with the introduction of the fibreoptic endoscopic assessment. Practical reasons can limit the use of videofluoroscopy in some patients. A prospective study of 20 sets of videofluoroscopic and endoscopic assessments of swallowing function were compared. Endoscopic assessment was found to be a highly sensitive and specific method of determining swallowing safety. Reduced or absent laryngeal sensation at endoscopy correlates with silent aspiration and thus a high risk of aspiration pneumonia.

Aged↗
PubMed1999

Gastrointestinal sutureless anastomosis in pigs using absorbable intraluminal stents, stent placement devices, and fibrin glue - a summary.

INTRODUCTION AND METHODOLOGY: To develop a practical gastrointestinal sutureless anastomosis technique, 164 end-to-end and end-to-side anastomoses were performed on the small intestine (SI), large intestine (LI), rectum, esophagus and gallbladder in 109 female Landrace pigs weighing 25 kg and 35 kg. There were 116 fibrin glue (FG) and 48 sutured anastomoses. The end-to-end SI and LI anastomoses were divided into five groups: sliding absorbable intraluminal nontoxic stent (SAINT); SAINT placement device (SAINT-PD); nonsliding SAINT (nST); sutureless stapler (SS); and sutured controls. The SAINT had a sucrose base, with some having reinforcing fibers. RESULTS: No deaths from dehiscence occurred in any group except one FG-cylinder attempt in the colon (technique abandoned). Statistical analysis of gross pathology indices showed no significant group differences. However, trends favored the SAINT in many indices, including grade-0 intraluminal tissue ridge formation (70.8% SI, 84.4% LI) and grade-0 adhesion rates (45.8% SI, 73.1% LI). Histologic examination showed fewer giant cells, less inflammation, less scar tissue formation and faster healing in the SAINT and nST anastomoses than controls. Follow-up of 300-540 days demonstrated no signs of necrosis or stenosis in the SAINT anastomoses. The nST had excellent results; however, it seems impractical in SI anastomoses and unsuitable for LI. CONCLUSIONS: The SAINT-PD has potential for all gastrointestinal sites, but needs larger experimental trials. The SS technique is impractical and had high tissue ridge formation and adhesion rates. These preliminary trials suggest the simplicity, versatility and safety of the SAINT technique; however, the small groups limit result interpretation. The results present a starting point for sutureless FG gastrointestinal anastomosis, and future experimental evaluation with more extensive statistical analyses in larger studies are needed.

Absorption↗
PubMed1999

Isolation and characterisation of recombination events involving immunoglobulin heavy chain switch regions in multiple myeloma using long distance vectorette PCR (LDV-PCR).

Immunoglobulin class switching occurs as a result of recombination between pairs of switch region sequences located 5' to each constant heavy chain gene except Cdelta. In the B cell neoplasm multiple myeloma, tumour cells have generally undergone class switching and often contain oncogenic sequences translocated into switch regions, presumably as a result of aberrant switch recombination. We have developed a method (LDV-PCR) which combines long distance PCR with one-sided vectorette PCR that is capable of detecting and isolating both normal and aberrant switch recombination breakpoints from multiple myeloma cell lines and primary multiple myeloma tumour material. Using LDV-PCR we have directly cloned the translocation breakpoints present in two multiple myeloma cell lines and isolated a normal productive switch recombination event from a primary tumour. Furthermore, we have isolated a novel translocation t(14;22)(q32;q12) from a primary tumour sample and have demonstrated that internal deletions within switch regions can occur in multiple myeloma cells. Compared to a Southern blotting approach, LDV-PCR is simpler and more rapid to perform, allows the simultaneous detection and isolation of recombination events, and can also be applied to amounts of DNA which are too low to permit the conventional cloning of recombination breakpoints.

Base Sequence↗
PubMed1999

FICTION-TSA analysis of the B-cell compartment in myeloma shows no significant expansion of myeloma precursor cells.

Studies utilizing flow cytometry and PCR have shown that the B-cell compartment in myeloma contains cells which are clonally related to the myelomatous plasma cells. Current data, however, remains inconclusive regarding the extent of this involvement. By combining fluorescent immunophenotyping, tyramine signal amplification and fluorescence in-situ hybridization (FICTION-TSA), we have used the presence of numerical chromosomal abnormalities within plasma cells as a clonal marker to examine the CD20+ B-cell compartment for the presence of aneuploidy. A series of 54 cases of myeloma were screened for the presence of numerical abnormalities of chromosomes 3 and 11. FICTION-TSA was performed on 13 cases with either trisomy 3 or 11 and on a control group of six cases known to be disomic for the two chromosomes. B-cell numbers were reduced in the myeloma cases compared to the normal controls (median 1.8% v 3.0%, P = 0.05). In the cases with a chromosomal marker, three signals were seen in a median of 1.88% of CD20+ B cells compared to 2.58% within the control group. Comparison of the two groups using a Wilcoxon-Mann-Whitney U test showed no statistical significant difference. Using this data set, it was possible to exclude a 3.03% expansion of clonally related B cells (95% confidence level). We conclude that the B-cell compartment in myeloma does not represent the major site of clonal expansion, and if clonally related cells are present then the numbers are few.

Aneuploidy↗
PubMed1997

Emergence of further serotypes of multiple drug-resistant Streptococcus pneumoniae in Queensland.

We describe 27 cases of multiple drug-resistant pneumococcal infection in Queensland children (7 cases) and adults (20 cases), between February 1995 and October 1996. Seven patients had invasive disease. Serotypes were those commonly associated with paediatric infections and included types 19F (15 strains), 14 (6), 23F (4), 6A (1) and 19A (1). No rifampicin or vancomycin resistance was encountered. However, pneumococci fully resistant to cotrimoxazole, erythromycin and tetracycline were isolated from 25 of 27 cases (93%). Strains with high level resistance to penicillin and chloramphenicol were also recovered from 16 (59%) and 19 (70%) patients respectively. Twelve of 16 penicillin-resistant isolates showed intermediate resistance to ceftriaxone and two strains were fully resistant to this antibiotic. Clones of types 19F and 14 pneumococci, each with two distinctive resistance patterns, appear to be established in south-east Queensland.

Adult↗
PubMed1996

Occult pharyngeal perforation secondary to 'pencil injury'.

Palatopharyngeal injuries due to impaction of rigid objects held in the mouth are common. Most are essentially innocuous injuries requiring no specific treatment. However, there is the potential for perforation of the pharyngeal wall with the subsequent development of serious infection such as retropharyngeal abscess or mediastinitis. This possibility is more likely to be suspected in the presence of a visible laceration or puncture wound at the site of impact in the mouth or pharynx. We report three cases in which occult pharyngeal perforation occurred without any clinical signs of breech of the pharyngeal wall. In all cases a lateral soft tissue neck X-ray was diagnostic of perforation, showing the presence of retropharyngeal air. We, therefore, advocate the routine performance of soft tissue neck X-rays in all patients who present with a history of falling on a rigid object held in the mouth.

Adolescent↗
PubMed1995

The radio-opacity of fishbones: a cadaveric study.

Lateral neck radiographs performed to localize impacted fishbones have a low sensitivity. The differing radio-opacities of the bones of various fish species may be a reason for this. A cadaver head and neck and the rib bones of 10 species of fish were used in this study. A laryngoscope was used to introduce a fishbone into the vallecula and then into the hypopharynx of the cadaver. A lateral radiograph was taken in each case. Ten control films were taken. The radiographs were independently reviewed by a consultant radiologist and otolaryngologist. The presence and position of any bone seen was noted. There was no inter-observer variation. All species of fishbone were visible. One bone was not seen by either observer. Visualization of fishbones is more dependent on position than their degree of radio-opacity. Routine radiography is recommended.

Animals↗
PubMed1995

[Pelvic lymph node invasion in cancer of the uterine cervix].

Pelvic lymph node invasion is an important prognostic factor for cervical cancer. It is generally accepted that iliac lymph nodes must be treated systematically, but the extent of lymph node dissections is open to discussion. One hundred and eighty two cases of cervical cancer with lymph node invasion were treated at the Institut Curie between 1960 and 1988, by colpohysterectomy with lymph node dissection (168 cases) combined with preoperative brachytherapy and, in some cases, pre- and/or postoperative radiotherapy; in 14 cases, only an exploratory operation was performed. External iliac lymph node invasion was found in 95% of cases, situated in the middle and internal chains. Common iliac lymph node invasion was found in 24% of cases, but was only exceptionally isolated (3%). It is therefore possible, by means of well defined, localized external iliac dissection, with frozen section histological examination, to determine the exact lymph node status. Lumboaortic lymph node invasion was found in 8.2% of cases. The overall survival rate was 49% at 5 years and 40.5% at 10 years. Factors which influence survival are: the cervical volume (p = 0.015), the unilateral or bilateral nature of invasion (p = 0.0015), the number of lymph nodes invaded (two or more than two) (p = 0.0001), capsular rupture (p = 0.0008), lymph node adhesions other than venous (p = 0.0002), common iliac invasion (p = 0.0001). On Cox's model, the principal factors were the number of lymph nodes invaded, adhesion other than venous, common iliac invasion; on the other hand, venous adhesion does not modify the prognosis. The five-year survival rates following external iliac dissections and complete pelvic dissections were not significantly different. Finally, postoperative radiotherapy ensured a higher five-year survival rate than preoperative radiotherapy, but the cervical volume was greater and primary invasion was more frequent in these cases. Postoperative radiotherapy of 15 grays after preoperative radiotherapy did not appear to modify the survival and therefore appears to be useless.

Adult↗
PubMed1995

[Prognostic factors in endometrial cancer: apropos of 206 cases treated at the Curie Institute].

From January 1, 1983 to December 31, 1990 two hundred and six patients with an invasive, non metastatic endometrial carcinoma were first treated at Institut Curie. Initial tumoral staging (TNM) was as follows: stage Ia: 48%, stage Ib: 31%, stage II: 15% and stage III-IV: 6%. Total hysterectomy or colpohysterectomy was performed in 186 cases, with a bilateral oophorectomy in 180 cases. Bilateral limited pelvic lymphadenectomy was performed in 116 cases. Brachytherapy was performed in the pre-operative setting in 25 cases, in the post-operative setting in 134 cases. Only five patients had brachytherapy alone, because of poor medical condition. External irradiation was exclusive in 15 cases and added to surgery for 68 patients. Median follow-up is 61 months (8-122 months). Five-year survival rate is 77% (71-83%); 5-year specific survival rate is 81% (75-87%). Independent prognostic factors for survival in multivariate analysis (Cox regression model) are tumoral stage (p < 0.0001), ovarian involvement (p < 0.0001), histologic node involvement (p = 0.005) and grade (p = 0.01). For local relapse, independent risk factors in the same analysis are ovarian involvement (p = 0.0004), tumoral stage (p = 0.01), age (p = 0.02) and histologic involvement of cervix (p = 0.04). For distant failure, independent risk factors are histologic node involvement (p = 0.0001), tumoral stage (p = 0.002) and grade (p = 0.003).

Adenocarcinoma↗
PubMed1994

Tympanostomy tubes and early post-operative otorrhea.

Otorrhea is a recognized complication of tympanostomy tube insertion. This may be caused by external contamination or by the pre-existing conditions in the middle ear cleft. Some surgeons try to reduce the risk of surgical contamination by using a non-touch technique, never allowing the gloved hand to come into contact with the tympanostomy tube. A prospective study was carried out on 66 children to evaluate the efficacy of the non-touch technique. One tympanostomy tube was inserted by the non-touch method with the contralateral ear acting as a touched control in each patient. Postoperative otorrhea occurred within 10 days in 1.67% of the non-touch ears and in 1.67% of the controls. This study demonstrates a low incidence of otorrhea in the early post-operative period with either technique. Time-consuming and costly sterile precautions are unnecessary for this common procedure.

Child↗
PubMed1994

The role of Chlamydia pneumoniae in severe acute tonsillitis.

Chlamydia pneumoniae has been implicated as a cause of tonsillitis and pharyngitis, but the incidence has varied from one to 19 per cent in various studies. We investigated 51 patients admitted to University College Hospital, Galway, with severe tonsillitis. Throat swabs were examined for evidence of Chlamydia pneumoniae using a direct monoclonal antibody test. Blood was taken for serology from 45 patients. A further specimen was taken at six weeks. A control group of 32 blood bank sera was used. Mean hospital stay was three days (one to eight). Five patients (10 per cent) were monospot positive. Chlamydia pneumoniae was identified by direct immunofluorescence on a tonsillar swab from one patient who did not seroconvert. IgG antibody was identified in 13 cases (29 per cent) and in seven of the control group (22 per cent). No serological evidence of recent infection was found. Chlamydia pneumoniae was not found to be a cause of severe acute tonsillitis in our study group.

Acute Disease↗
PubMed1994

alpha-thrombin bound to extracellular endothelial matrix induces pronounced fibrin deposition and platelet thrombus growth in flowing non-anticoagulated human blood.

Previous studies have shown that thrombin binds to the extracellular endothelial matrix and remains biologically active. In the present study, the role of matrix-bound alpha-thrombin in thrombus formation was investigated by utilizing a model system of thrombogenesis. Plastic cover-slips coated with either matrix-bound alpha-thrombin or matrix-bound active site inactivated thrombin (DIP-alpha-thrombin) were positioned in parallel-plate perfusion chambers and subsequently exposed to non-anticoagulated human blood at a venous wall shear rate of 100/s. The blood was drawn directly from an antecubital vein by a roller pump placed distally to the perfusion chamber. The thrombotic deposits on the matrix, fibrin deposition and platelet thrombus volume, were morphologically evaluated. Matrix-bound alpha-thrombin enhanced the fibrin deposition and thrombus volume on matrices of non-stimulated endothelium with 91% (P < 0.001) and 94% (P < 0.05), respectively. In contrast, binding of DIP-alpha-thrombin to matrices of stimulated endothelium reduced the fibrin deposition by 33% (P < 0.05), but had no effect on the platelet thrombus volume. Translocation of thrombin molecules from upstream matrix areas to binding sites farther downstream on the matrix was indicated in experiments with matrices of stimulated endothelium, which showed enhanced fibrin deposition on downstream areas. Our findings are compatible with a prominent role for matrix-bound alpha-thrombin in thrombogenesis, and in particular on endothelial matrices without tissue factor. The role of matrix-bound alpha-thrombin on tissue factor containing matrices appears less prominent, although it is significant.

Blood Coagulation↗