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Biomedical subjects

J M Wilkinson

Publications and source records attributed to J M Wilkinson.

At least 73 records · Page 4Linked to original sources
PubMed1997

Successful non operative management of late infrainguinal polytetrafluoroethylene vascular graft infection with antibiotics alone: a report of two cases.

Polytetrafluoroethylene (PTFE) prosthetic vascular graft infection is a serious complication of arterial reconstructive surgery. Traditional management is primarily surgical and may result in long hospital stay with significant morbidity and mortality. The authors describe two cases of infected femoropoliteal PTFE grafts which were managed non operatively with antibiotic therapy alone, resulting in early return to normal activities and excellent resolution of infection on Indium labelled leucocyte scanning. The authors suggest that in selected cases antibiotic therapy alone is a valuable tool in the management of infrainguinal PTFE prosthetic sepsis.

Aged↗
PubMed1996

A monoclonal antibody, 3/22, to rabbit CD11c which induces homotypic T cell aggregation: evidence that ICAM-1 is a ligand for CD11c/CD18.

The rabbit CD11c molecule has been characterized by use of new monoclonal antibody, mAb 3/22. Expression of the p150,95 integrin (CD11c/CD18) has been shown by flow cytometry and immunohistochemistry to be restricted to monocytes, macrophages, dendritic cells and a small population of lymphocytes in peripheral blood. No expression on neutrophils could be demonstrated. Incubation of the newly derived CD8+ T cell line, BJ/873, with mAb 3/22 causes homotypic aggregation, which has been shown to be cell surface event that is not dependent on intracellular signaling or on receptor cross-linking. Inhibition studies show that the ligands responsible for this aggregation are CD11c/CD18 and ICAM-1, both of which are expressed on BJ/873. One other rabbit T cell line, K34, that also expresses p150,95 and ICAM-1, shows a similar aggregation response when stimulated with 3/22. Cell lines that express p150,95 but not ICAM-1 do not aggregate. These observations suggest that ICAM-1 is a ligand for activated p150,95.

Amino Acid Sequence↗
PubMed1996

The variation in output of symmetric, asymmetric and irregularly shaped wedged radiotherapy fields.

A model for calculating the variation in output of symmetric, asymmetric and irregularly shaped wedged radiotherapy fields is presented. The variation in output from the treatment head when a wedge is used is calculated by dividing the output into a primary component and one due to scattered radiation. The scatter component is then further subdivided into contributions from elements which have a 1 cm x 1 cm cross-sectional area at the isocentre. The scatter from each element is determined as the contribution from the head scatter component modified by the presence of the wedge and a contribution due to additional scattered radiation from the wedge. The relative intensity of the scattered radiation from the wedge is modelled using a simple first scatter approximation. In this approximation the magnitude of the scatter is given by a t exp(-mu t) function where t is the thickness of the wedge for the selected element. The magnitude of the primary component and the relative intensity of scatter from each element are then obtained by an iterative fit to measured data. The technique has been applied to two different internally mounted wedge designs, for a standard treatment head, two asymmetric treatment heads and two similar multileaf collimators, over a range of energies between 4 and 20 MV. Calculations agree with measured values over a range of field sizes and shapes to within 1.5%.

Humans↗
PubMed1994

Preferential antagonism of the interactions of the integrin alpha IIb beta 3 with immobilized glycoprotein ligands by snake-venom RGD (Arg-Gly-Asp) proteins. Evidence supporting a functional role for the amino acid residues flanking the tripeptide RGD in determining the inhibitory properties of snake-venom RGD proteins.

The inhibitory properties of a panel of snake-venom-derived RGD (Arg-Gly-Asp) proteins, including the disintegrins kistrin, elegantin and albolabrin, and the neurotoxin homologue dendroaspin, were investigated in a platelet-adhesion assay using three immobilized ligands of the glycoprotein IIb-IIIa complex (alpha IIb beta 3), namely fibrinogen, fibronectin and von Willebrand factor (vWF). The snake-venom proteins preferentially inhibited the adhesion of ADP-treated platelets to one or more of the immobilized ligands. Kistrin and dendroaspin exhibited similar inhibitory characteristics, abrogating platelet adhesion to fibrinogen and vWF at nanomolar concentrations, but poorly inhibiting adhesion to fibronectin. Kistrin and dendroaspin share little overall amino-acid-sequence identity, but a considerable level of sequence similarity exists around the RGD tripeptide. Synthetic cyclic peptides corresponding to these regions of kistrin and dendroaspin inhibited platelet adhesion to both fibrinogen and fibronectin with approximately equal potency, but were 100-fold weaker antagonists of the interactions of the alpha IIb beta 3 complex with fibrinogen than their parent proteins. The disintegrins elegantin and albolabrin, which share approx. 60% overall amino-acid-sequence similarity with kistrin but have different residues around the RGD tripeptide, exhibited different antagonistic preferences. Elegantin inhibited platelet adhesion to immobilized vWF and fibronectin, but was significantly less effective at disrupting adhesion to fibrinogen. Albolabrin selectively inhibited platelet adhesion to immobilized vWF and was less effective with fibrinogen and fibronectin as adhesive ligands. In contrast with the behaviour of these venom proteins, the adhesion of ADP-treated platelets to immobilized fibrinogen, fibronectin and vWF was inhibited non-selectively by a range of monoclonal antibodies with specificity for the alpha IIb beta 3 complex. These observations, therefore, define antagonistic preferences in this panel of venom proteins towards the interactions of the alpha IIb beta 3 complex with three immobilized glycoprotein ligands.

Amino Acid Sequence↗
PubMed1994

The in vivo and in vitro effects of antibodies against rabbit beta 2-integrins.

Beta 2-integrins play a crucial role in the development of an inflammatory response. In ours study, Abs have been used to investigate the role of individual members of this family of adhesion molecules in both in vivo and in vitro assays. An Ab against rabbit LFA-1 effectively inhibited the adhesion of rabbit polymorphonuclear leukocytes to rabbit endothelial cells in culture and was also effective in blocking cell recruitment to the peritoneum and vascular leakage at dermal sites of inflammation. An Ab that inhibited rabbit complement receptor type 3 function in vitro failed to inhibit cell recruitment to the peritoneum or vascular leakage in response to intradermal FMLP. Histologic studies suggested that the anti-complement receptor type 3 Ab may have modified the cell migration process.

Animals↗
PubMed1994

Long-term results of highly selective vagotomy: a prospective study with implications for future laparoscopic surgery.

Between 1979 and 1984, 141 patients (110 men, 31 women) underwent highly selective vagotomy (HSV) by a standard open technique for duodenal ulcer. All patients had received preoperative treatment with full-dose H2-receptor antagonists. Some 107 of these patients underwent HSV for persistent relapse on withdrawal of H2-receptor antagonists (relapsing responders) and 30 because of non-response to such drugs. After 4 years of follow-up, non-responders were found to be more likely to have symptoms after operation (P < 0.001), but did not have a higher rate of recurrent ulceration. At a median of 11 (range 8-14) years after operation 126 patients were still alive; 115 (91 per cent) of these were followed up. Ten patients (9 per cent) were found to have had endoscopically proven recurrence and eight (7 per cent) still had symptoms without evidence of recurrence. The endoscopic recurrence rate and symptom rate at 11 years were no longer significantly different between relapsing responders and non-responders. The preoperative response to H2-receptor antagonist therapy does not help in predicting the likelihood of ulcer recurrence or long-term symptoms after HSV. Post-operative symptoms do not necessarily predict long-term ulcer recurrence. The long-term endoscopic recurrence rate after HSV is low and, if equally good results can be obtained laparoscopically, this will be an important and cost-effective option in the management of duodenal ulcer.

Adolescent↗
PubMed1994

In utero exposure to caffeine causes delayed neural tube closure in rat embryos.

We have investigated the effect of caffeine on embryo growth and development. Caffeine (25 mg/kg) was administered on gestation day (g.d.) 8-9 and the embryos examined histologically 24 h after the final dose. The crown-rump length of caffeine treated embryos (1.92 +/- 0.08 mm) was significantly smaller (P < 0.001) than the controls (2.91 +/- 0.26 mm) as was the circumferential length (caffeine vs. controls, 3.79 +/- 0.16 mm vs. 6.03 +/- 0.61 mm; P < 0.001). Additional measures, such as development of the heart, eye, and limb buds, were also reduced in the caffeine treated embryos. The most striking difference between the control and caffeine treated embryos was the larger proportion of treated embryos with regions of open neural tube. This was most marked in the caudal region of the embryos where 91% of treated embryos had regions of open neural tube compared with 14% of controls. The amount of open neural tube in any individual caffeine treated embryo did not relate to the crown-rump or circumferential length of that embryo nor was the effect restricted to particular litters. These results indicate that caffeine had a significant effects on embryonic growth and development.

Animals↗
PubMed1994

Advanced gastrointestinal malignancy or benign inflammatory disease? An unusual presentation of sclerosing mesenteritis. Report of a case.

The presentation of change of bowel habit, weight loss, muscle wasting, ascites, and the surgical appearance of "omental cake" are almost pathognomonic of advanced gastrointestinal malignancy. In our case, these symptoms represented a unique presentation of the condition sclerosing mesenteritis. Despite its rarity, the clinician should be aware of this "sheep in wolf's clothing," the clinical importance of which lies in the condition's benign and self-limiting course and imparts to the patient a prognosis and treatment that could not be further removed from that of advanced malignancy. Investigations that may be helpful to the surgeon in distinguishing the condition from carcinomatosis and avoiding unnecessary laparotomy include preoperative colonoscopy, barium enema, cytology of any ascites, and intraoperative frozen section biopsy. Treatment of the condition is conservative unless it has caused extrinsic bowel obstruction.

Ascites↗
PubMed1994

Promoting situational support for nurses in practice.

Situational support entails promoting autonomy, control over practice, group cohesion, manager consideration, and substantive exchange. Support can reinforce nurses' coping mechanisms, preserve their integrity, and thereby promote quality patient care. Using concept clarification and case examples the authors identify support mechanisms and coping styles for nurses at work and discuss how situational support can be used to cope with stress.

Adaptation, Psychological↗
PubMed1994

Calibration of low activity caesium tubes and needles traceable to the therapy level standard.

A technique for deriving the reference air kerma rate for low activity brachytherapy sources that is traceable to the therapy level standard at the National Physical Laboratory is presented. Correction factors have been generated to account for the finite source and detector size. The air kerma rate calibration of the secondary standard for caesium quality has been derived by polynomial curve fitting. The reference air kerma rates for several caesium tubes and needles have been determined and the results compared with the manufacturers' source test reports. For all the source types used the agreement between methods was within 2%.

Brachytherapy↗
PubMed1993

Accumulation of theophylline, theobromine and paraxanthine in the fetal rat brain following a single oral dose of caffeine.

This paper describes the disposition of caffeine and its metabolites, theophylline, theobromine and paraxanthine in the 20-day fetal and adult brains following a single maternal dose of 5 or 25 mg/kg caffeine. Brains and plasma were collected 5 and 30 min, and 1, 3, 8 and 24 h after dosing. It was found that fetal and adult caffeine AUC (area under the concentration-time curve) values did not differ between the brain and plasma at either dose. Caffeine's primary metabolites theophylline, theobromine and paraxanthine did, however, accumulate in the fetal brain at both doses resulting in a 3-fold increase in brain metabolite exposure compared to fetal circulatory levels. In contrast to the fetus, metabolite AUC values after a dose of 25 mg/kg were found to be lower in the brains of adults compared with plasma. This suggests that caffeine's primary metabolites might be selectively excluded from the adult brain. In conclusion we have shown that, unlike the adult, the fetal rat brain accumulates theophylline, theobromine and paraxanthine when exposed to caffeine doses comparable to those attainable by normal human consumption. Since many aspects of caffeine metabolism are similar in the rat and human, we suggested that particular attention should be paid to the consumption of caffeine during pregnancy.

Animals↗
PubMed1993

Immunohistochemical localisation of the 25 kDa heat shock protein in unstressed rats: possible functional implications.

The distribution of the 25 kDa heat shock protein (hsp 25) in a number of tissue types from unstressed rats was investigated. Immunohistochemical analysis showed that hsp 25 was not found in the thymus, brain (cerebral cortex and cerebellum), testis, adrenal, liver, spleen, or kidney. A number of cells in the anterior pituitary showed strong staining. These cells were tentatively identified as being either gonadotropes or thyrotropes. Strong staining was also observed in the blood vessels within these tissues. Hsp 25 was found to be localised predominantly to intestinal smooth muscle of the duodenum and colon and to vascular smooth muscle. Smooth muscle from other sites, such as the trachea, was also intensely stained. Lower and more variable amounts of staining were observed in cardiac and skeletal muscle. These observations suggest that hsp 25 is associated with cytoskeletal elements in muscle, and that the high staining intensity in smooth muscle might be due to the lack of internal architecture present in this muscle type.

Animals↗