A mathematical foundation to support bidirectional mappings between digital models: an application of multi-scale modelling in manufacturing

With manufacturing going through the Industry 4.0 revolution, a vast amount of data and information exchange leads to an increase in complexity of digitized manufacturing systems. To tackle such complexity, one solution is to design and operate a digital twin model under different levels of abstraction, with different levels of detail, according to the available information and scope of the model. To support efficient, coherent and stable information flows between models with different levels of detail, a mathematical structure, called a delta lens, has been explored and developed to support rigorous bidirectional transitions between the models. To support different types of abstractions in manufacturing, a hybrid delta lens has been proposed and its formal representation is developed to support the generalization of its structure and properties. Benefits of the proposed hybrid delta lenses are demonstrated through an application to an industrial case to support the modelling of an automatic, high-throughput assembly line.

Measurement and Prediction of Progress in Delayed Wound Healing

Thirty chronic leg ulcers have been studied under controlled conditions until complete healing occurred. Measurement was performed weekly using a computer-linked stereocamera which is capable of measuring skin defects noninvasively with errors of less than 2%. There was a significant difference in healing rate for the first two weeks between clean ulcers entering the trial directly and ulcers admitted first for cleansing before joining the trial. The difference suggests that the weekly healing rate of an ulcer may take up to 2 weeks to respond to a new form of treatment. Absolute ulcer size, change in ulcer size and rate of epithelial migration did not correlate well with time to complete healing, but percentage change in area in the third week was found to be the parameter which gave the earliest close correlation with time to complete healing. Using this parameter, on the data available it was found that time to complete healing could be predicted to within one week for 50% of the ulcers, making this a simple and useful early predictor of treatment efficiency.

Evaluation Considerations for Secondary Uses of Clinical Data: Principles for an Evidence-based Approach to Policy and Implementation of Secondary Analysis

Objectives: To set the scientific context and then suggest principles for an evidence-based approach to secondary uses of clinical data, covering both evaluation of the secondary uses of data and evaluation of health systems and services based upon secondary uses of data. Method: Working Group review of selected literature and policy approaches. Results: We present important considerations in the evaluation of secondary uses of clinical data from the angles of governance and trust, theory, semantics, and policy. We make the case for a multi-level and multi-factorial approach to the evaluation of secondary uses of clinical data and describe a methodological framework for best practice. We emphasise the importance of evaluating the governance of secondary uses of health data in maintaining trust, which is essential for such uses. We also offer examples of the re-use of routine health data to demonstrate how it can support evaluation of clinical performance and optimize health IT system design. Conclusions: Great expectations are resting upon "Big Data" and innovative analytics. However, to build and maintain public trust, improve data reliability, and assure the validity of analytic inferences, there must be independent and transparent evaluation. A mature and evidence-based approach needs not merely data science, but must be guided by the broader concerns of applied health informatics.

A framework for promoting scholarship productivity in occupational therapy curricula

This paper describes a curricular model to support the production of quality research and development of occupational therapy professional students, prepared to become leaders in the production and utilization of evidence for practice. This model is designed for programs with faculty challenged by the dual mandate of program excellence and expectations for scholarly productivity needed for tenure and promotion: typically programs at research universities. The essence of the model is the paralleling of research and competencies for clinical practice where faculty and students participate as a community of scholars. It is based on the literature that addresses the tensions between achieving excellence in research and scholarly productivity, and excellence in teaching. The experience of one university with this model over a five-year period of time is shared with the student-faculty productivity outcomes. These outcomes include dissemination of 55 collaborative peer reviewed products and faculty has generated support for 25 paid graduate assistantships. The combination of student outcomes and faculty support for their research has strengthened the ability of the faculty to excel in meeting the University mandate of scholarship while providing a high quality professional educational program.

A collaborative teaching strategy for enhancing learning of evidence-based clinical decision-making

The educational literature cites a lack of student motivation to learn how to use research evidence in clinical decision-making because the students do not observe clinicians using evidence. This lack of motivation presents a challenge to educators as they seek to instill the value of evidence-based clinical decision-making (EBCD) in students. One problem is that students in entry-level programs do not have the experience needed to know what to look for, and secondly, clinical decision-making is contextually based in a patient problem. Our approach offers one solution to bridging the gap between classroom teaching and real-world implementation of EBCD through a three-phase collaborative approach. Occupational and physical therapy students are partnered with clinicians to find and appraise evidence to answer the real-world questions posed by these therapists. This paper describes the implementation of the partnership, teaching/learning outcomes, logistics, and implications for clinicians. We found this approach increased student motivation and greatly enhanced the learning experience. Future directions include implementing a framework which allows for the assessment of the strategy on the facility and creates opportunities to integrate the use of EBCD in all aspects of facility practice.

Freeform surface filtering using the diffusion equation

The measurement of texture for geometric surfaces is well established for surfaces that are of a planar (Euclidean) nature. Gaussian filtering is the fundamental base for scale-limited surfaces used in surface texture, but cannot be applied to non-Euclidean surfaces without distortion of the results. A link exists between Gaussian filtering and solutions of the PDE that models linear isotropic diffusion. In particular, an analytical solution of this diffusion equation over a planar region at a time t is given by the continuous convolution of the initial distribution of the diffused quantity with a Gaussian function of standard deviation . A practical implementation of the standard Gaussian filter on sampled data can be viewed as a discretization of this process. On a non-Euclidean surface, the diffusion equation is formulated by using the Laplace–Beltrami operator. Using this generalization, a method of Gaussian filtering for freeform surface data is proposed by solving the diffusion equation for approximation residuals defined on a freeform least-squares approximation of the measurement surface data. Results of the application of these methods to simulated and experimental data are presented.

ST elevation on the exercise ECG in patients presenting with chest pain and no prior history of myocardial infarction

OBJECTIVE

To assess the aetiology, and prognosis of ST-segment elevation (STE) on the exercise electrocardiogram in patients with chest pain without a prior history of myocardial infarction (MI).

METHODS

Between January 1998 and December 2005, 14 941 exercise stress tests were performed to assess chest pain in patients without a prior history of MI. Those who developed STE were identified.

RESULTS

STE occurred in 0.78% (116/14 941). Coronary angiography was performed in 108 patients. All patients had at least one severe coronary artery stenosis (>70%). The site of STE on exercise ECG was shown to be 95.4% predictive of a severe stenosis in the coronary artery supplying that area. Lateral STE was rare (1/116). Ninety-eight patients underwent revascularisation; 67 patients had percutaneous coronary intervention (PCI) and 31 underwent coronary artery bypass grafting (CABG). Follow-up included recording of death, MI, cerebrovascular event, heart failure and target vessel revascularisation. The projected 7-year event-free survival probability was 62.1% for those undergoing CABG, 77.1% for those who had PCI and 68.6% for those not undergoing revascularisation (no difference between these three groups, log rank p = 0.802).

CONCLUSIONS

STE on the exercise ECG is rare but specific for ischaemic heart disease and is predictive of a severe stenosis in the corresponding coronary artery. Prognosis is favourable following revascularisation.

Outcome after radial forearm, gastro-omental, and jejunal free flaps in oral and oropharyngeal reconstruction

We undertook a retrospective study of the outcome of radial forearm, gastro-omental, and jejunal free tissue transfer for oral and oropharyngeal reconstruction in 30 patients (10 in each group). No significant differences were found between the type of free flap and the clinical outcome. More long-term difficulties were experienced with swallowing than with speech. The selection of free flap did not correlate with speech function (P=0.44), swallowing (P=0.68), or management of saliva (P=0.59). No significant difference was found between the patients' outcome and the site of resection of the tumour. There were more complications after gastro-omental flaps and this may influence the choice of reconstruction.

Clinically integrated studies in pathology: their contribution to atherosclerosis research

This article, prepared in honor of Daria Haust, reviews some features of research into atherosclerosis and coronary heart disease over the past 150 years, and beyond. Attention is drawn to problems arising when people of strong personality dominate a particular field of research to the exclusion of pertinent observations that do not fit neatly into their particular paradigm. As the world becomes more complex and, in theory at least, communications between scientists become easier, these dangers are not necessarily diminished. Clinical medicine in its broadest sense must continue to relate in the traditional way to the specialties grouped within pathology. Undergraduates must receive instruction concerning the importance of the historical record and an understanding of the nature of science, its strengths, limitations, and boundaries.

Does the "Thunderbirds syndrome" still exist

Rationing of resources within both the private and public health care systems is a fact of life. The Thunderbirds TV series encapsulated an idealistic philosophy that life should be saved independent of the pecuniary cost. Doctors, in particular, are trapped between their role as advocates for the patient within the "Thunderbirds" philosophy and as citizens with a responsibility to use resources wisely. This dichotomy is challenged by point of care rationing, which can conflict with clinical responsibilities, undermines the patient-doctor relationship and is often undertaken in a clandestine manner. This form of controlling health costs is difficult to justify from an ethical perspective, particularly when other forms of health care rationing and expenditure are frequently modulated by political expediency and inadequate economic modelling. Indeed, focusing on improving quality and disease prevention, rather than reducing marginal costs can often control the long-term growth in health expenditure. Doctors have a responsibility to ensure that rationing decisions are made but these should be made as part of a transparent, evidence-based and democratic process away from the point of care. While the resources to implement the "Thunderbirds Syndrome" have never been available, the philosophy must remain at the heart of patient-doctor relationship.

Consensus viewpoint on the treatment of postmenopausal osteoporosis. The Ad Hoc Group on Osteoporosis

Treatment for postmenopausal osteoporosis should be offered to those with a history of fractures following minimal trauma or with a bone density significantly below the range seen in young normal adults. Underlying diseases contributing to the reduced bone density should be sought and treated appropriately. Lifestyle issues such as smoking, alcohol intake and exercise should be addressed. A calcium intake of at least 1.5 g/day should be achieved. Hormone replacement therapy is the first line pharmacological intervention. The bisphosphonates provide a satisfactory alternative for those unable or unwilling to take hormone replacement therapy.

Effects of catecholamines on isolated human colonic smooth muscle

1. The effects of catecholamines and some adrenoceptor agonists and antagonists on isolated preparations of human colonic smooth muscle obtained from surgical resections were examined. 2. Strips of circular smooth muscle displayed rhythmic myogenic spontaneous contractions which were inhibited by catecholamines with an order of potency of isoprenaline (1.0) > noradrenaline (0.32) > adrenaline (0.2). Phentolamine (0.7 microM) significantly shifted the noradrenaline concentration-response curve (CRC) to the right but had no significant effect on isoprenaline or adrenaline. Propranolol (1 microM) significantly shifted the isoprenaline to the right but had no significant effect on noradrenaline or adrenaline. 3. Salbutamol (30 microM) had no inhibitory effect on the spontaneous activity and ICI 118,551 (1 microM) had no effect on inhibitory responses to isoprenaline. Betaxolol (1 microM) significantly shifted the CRC to isoprenaline to the right. BRL 37344 had no effect on spontaneous activity. 4. Responsiveness of circular strips to catecholamines was not affected by age of the patient and no consistent differences between males and females were shown. 5. Strips of taenia coli exhibited little or no spontaneous phasic activity. Noradrenaline and isoprenaline relaxed KCl-induced tone. The effects of noradrenaline and isoprenaline were antagonized by propranolol but not by phentolamine. BRL 37344 had no effect on KCl-induced tone. 6. In conclusion, catecholamines relaxed spontaneous activity of human colon circular smooth muscle through an action on both alpha- and beta-adrenoceptors. The alpha-adrenoceptors were of the alpha 1-subtype. The beta-adrenoceptor-mediated relaxation appeared to be primarily beta 1. In taenia coli, catecholamines relaxed KCl-induced tone via beta-adrenoceptors only.

Adhesion receptor phenotypes of murine lung CD4+ T cells during the pulmonary immune response to sheep erythrocytes

Understanding the molecular mechanisms of pulmonary lymphocyte recruitment is a crucial step toward selective control of immune lung diseases and infections in immunocompromised hosts. To dissect these mechanisms, we are studying the response induced in primed C57BL/6 mice by intratracheal challenge with the T cell-dependent antigen, sheep red blood cells (SRBC). This study used four-parameter flow cytometry to examine expression by CD4+ murine T cells in peripheral blood and lungs of receptors known to be differentially expressed on primed human lymphocytes (CD2, CD11a, CD44, CD45RB, CD49d, and L-selectin). Compared with peripheral blood, more lung CD4+ T cells recovered by bronchoalveolar lavage (BAL) showed a primed phenotype. Judged by low expression of CD45RB or L-selectin, 76 to 90% of BAL CD4+ T cells were primed at all times. Adhesion receptor phenotype of CD4+ T cells in BAL and lung interstitium agreed closely, although BAL contained a greater percentage of primed cells. The percentage of CD4+ T cells with high expression of CD44+ and CD49d increased late in the response. However, when considering only upregulated adhesion receptors which might mediate recruitment, 22 to 52% of CD4+ T cells in BAL did not have increased adhesion receptor expression. Longer duration between priming and challenge did not increase adhesion receptor upregulation. High adhesion receptor expression was least evident during the periods of maximal lymphocyte influx, suggesting that factors other than increased surface density of organ-nonspecific adhesion receptors contribute to lymphocyte recruitment during pulmonary immune responses.

No evidence for a general change in contractile responsiveness of the mesenteric artery with aging

Rings of human mesenteric artery (1-3 mm diameter) suspended in Krebs solution were contracted (maximal contraction relative to KCl 80 mM = 100%) by the thromboxane mimetic U46619 (190 +/- 10%), noradrenaline (162 +/- 9%), angiotensin II (107 +/- 11%), and 5-hydroxytryptamine (5-HT) (96 +/- 10%). Reducing extracellular Ca2+ strongly inhibited the maximal contraction to angiotensin II and 5-HT and moderately inhibited the maximal contraction to noradrenaline, but had less effect on the maximal contraction to U46619 (contraction in Ca2+ 1.3 microM was reduced to 24 +/- 5, 20 +/- 3, 38 +/- 4 and 52 +/- 4% respectively of the contraction in 2.5 mM Ca2+). Reducing extracellular Ca2+ lowered sensitivity to 5HT, angiotensin II, and U46619, but did not alter sensitivity to noradrenaline. The EC50 and maximal contraction for each of the 4 agonists did not change with patient age at 2.5 mM Ca2+ or in reduced extracellular Ca2+. It is concluded that aging does not affect the responsiveness of mesenteric arterial smooth muscle to physiological vasoconstrictors.

Helicobacter pylori and chronic antral gastritis in elderly patients

Fifty-five elderly patients with chronic antral gastritis (CAG) were studied to assess the relationship between Helicobacter pylori (H. pylori) status and CAG subtypes as specified in the Sydney System for Gastritis Classification. Twenty-eight patients (51%) were H. pylori positive and 27 (49%) H. pylori negative. H. pylori-positive patients had a significantly greater association with features of severe active CAG (chronic inflammation and polymorph activity) than H. pylori-negative patients. No association was apparent between H. pylori and more advanced stages of CAG (atrophy and intestinal metaplasia) thought to carry pre-malignant potential. The recognized association between dyspeptic symptoms in elderly people and an H. pylori-positive gastritis was confirmed. Use of NSAIDs correlated with a predominantly H. pylori-negative gastritis which was relatively asymptomatic.

Experimental murine pulmonary cryptococcosis. Differences in pulmonary inflammation and lymphocyte recruitment induced by two encapsulated strains of Cryptococcus neoformans

BACKGROUND

Cryptococcus neoformans, the most common cause of lethal mycosis in AIDS, usually causes only subclinical pneumonitis in normal hosts. However, cryptococcosis can induce various pulmonary inflammatory reactions, and pulmonary cellular immunity is postulated to prevent dissemination. We hypothesized that cryptococcal strains possess different capacities to induce recruitment to the lungs of inflammatory cells, especially lymphocytes, which are necessary for cryptococcal clearance.

EXPERIMENTAL DESIGN

We examined the pulmonary response of CBA/J mice to intratracheal inoculation with C. neoformans of either of two strains: 52D (ATCC 24067), which rarely kills immunocompetent mice; and 145A (ATCC 62070), which is uniformly fatal. From 2-42 days after inoculation, lungs were either examined grossly and microscopically or were enzymatically digested and inflammatory cells counted and analyzed by flow cytometry. At 42 days, organism burden in lung and brain was quantified by colony-forming unit assay.

RESULTS

Pulmonary inflammation differed greatly between the two strains. Strain 52D induced dense perivascular and alveolar inflammation; infection progressed to day 21 and then waned. In contrast, strain 145A induced delayed, meager lymphocytic infiltration and slight alveolitis; organisms grew progressively. Recovery of inflammatory cells increased by day 13 with strain 52D, but not until day 31 with strain 145A. Although all lymphocyte subsets were greater in 52D infection, the disparity was greatest for CD4+ T cells. Nevertheless, lymphocytes from paratracheal nodes of infected mice proliferated in vitro to heat-killed cryptococci, indicating immune recognition of both strains. At day 42, strain 52D lightly infected lungs but not brain, whereas strain 145A heavily infected lungs and brain. CONCLUSIONS; Cryptococcal strains differ in their capacity to induce pulmonary cellular inflammation, especially CD4+ T cell recruitment. Our results suggest that strain-specific difference in the organism's ability to induce (or evade) pulmonary inflammation contributes to the outcome of infection.

Imaging of pulmonary vascular disease by intravascular ultrasound

To assess the ability of intravascular ultrasound (IVUS) to image changes in the pulmonary arterial wall associated with pulmonary hypertension (PHT), 10 subjects requiring diagnostic right and left heart catheterization were studied. In addition to measurements of pulmonary artery pressure and pulmonary vascular resistance and pulmonary angiography, when indicated, all underwent simultaneous IVUS imaging in the pulmonary arterial system using a 20 MHz ultrasound transducer mounted on a 2 mm diameter catheter. Four patients had normal pulmonary artery pressures and 6 had varying degrees of PHT. Satisfactory ultrasound images were obtained in 9 out of the 10 patients. In those with normal pulmonary artery pressures ultrasound showed a thin vessel wall with no distinction between separate layers. In patients with systemic PHT, a three-layered vessel wall was apparent and areas compatible with intimal proliferation were seen. In a patient with pulmonary embolic disease areas consistent with mural thrombus were detected at sites of luminal narrowing on the pulmonary angiogram. IVUS is capable of imaging some of the morphological changes in the wall of the pulmonary artery known to occur in longstanding PHT and may therefore become a useful adjunct to haemodynamic measurements and pulmonary angiography for the in vivo assessment of pulmonary vascular disease.

Vasodilator action of cromakalim on human mesenteric artery

Human mesenteric artery rings (1-3 mm diameter obtained from bowel resections), precontracted with KCl 80 mM, were relaxed by cromakalim (IC50 = 0.39 +/- 0.04 microM, maximum inhibition 69 +/- 2%). Cromakalim was more effective at inhibiting KCl 40 mM than KCl 80 mM. Cromakalim also inhibited contraction produced by noradrenaline, and was a more potent inhibitor of the second phase of the noradrenaline contraction than of the first phase.

Apical hypertrophic cardiomyopathy presenting as acute subendocardial myocardial infarction

Two patients with apical hypertrophic cardiomyopathy presented with angina at rest and giant inverted T waves in precordial leads on the electrocardiogram. At cardiac catheterisation one patient had mild coronary artery disease, the other had normal coronary arteries. In both, there was a systolic pressure gradient between the apex and main left ventricular cavity exceeding 100 mmHg. The presence of rest angina with the electrocardiographic findings lead to a mistaken, initial diagnosis of acute subendocardial myocardial infarction.

Bovine internal mammary artery as a conduit for coronary revascularization: long-term results

Graft patency after coronary artery bypass grafting depends largely on the choice of conduit. Because an increasing number of patients have insufficient or poor-quality autologous material, there is a need for a suitable synthetic graft that is readily available and easy to handle and that has good long-term patency. Early results suggest that the bovine internal mammary artery graft may meet these criteria. We have used a total of 26 such grafts in 18 patients. Postoperative angiography has been performed in 19 grafts in 14 patients, 3 to 23 months after operation; of these grafts, 3 are currently patent (15.8%, compared with 85.7% and 75.0% patency for native internal mammary artery and saphenous vein grafts in the same patients). We report the results of clotting studies and an analysis of lipid status. These patients do not, however, appear to represent any atypical group, either in terms of coagulopathy, native coronary artery size, or the type of vessel disease. Nevertheless, our poor results contrast markedly with the early enthusiasm reported from other centers.

Principal alterations to drug kinetics and dynamics in the elderly

People over the age of 64 constitute 15% of the population in the UK, yet they consume approximately 30% of all National Health Service drug prescriptions, and adverse drug reactions account for 10.4% of all admissions to geriatric medical assessment wards. Many published studies concerning the pharmacology of old age are seriously flawed. Problems include failure to measure the drug bio-availability and the selection of subjects with overt or sub-clinical disease. It is difficult to make general rules about the effect of ageing on drug kinetics and dynamics. Each drug has to be tested separately.

Transoesophageal echocardiography in neonates, infants and children: applicability and diagnostic value in everyday practice of a cardiothoracic unit

OBJECTIVE

To determine the applicability of and information obtained by transoesophageal echocardiography in neonates, infants, and children in every day practice of a cardiothoracic unit.

DESIGN

Four month prospective study.

SETTING

Supraregional centre for paediatric cardiothoracic services.

PATIENTS AND METHODS

58 patients aged between four days and 16 years with a wide range of cardiovascular disease underwent transoesophageal echocardiography under sedation or general anaesthetic. One of two paediatric probes (6 or 7 mm diameter), or an adult probe (13 mm in diameter) was used. Whenever possible the investigation was immediately preceded by precordial echocardiography.

MAIN OUTCOME MEASURES

Success, failure, technical difficulties, and complications of probe introduction and, when possible, comparison of the information obtained with that obtained from precordial echocardiography.

RESULTS

Introduction of the probe was successful in 57 of the 58 patients. The only complication encountered was transient bradycardia during manipulation of the probe in a 2.2 kg baby. The adult (13 mm) probe was successfully used in children as small as 7.0 kg. Below this weight a smaller paediatric probe was required. In 56% of cases transoesophageal ultrasound provided information not obtained from the precordial approach. The technique was of particular value perioperatively and in the immediate postoperative period in neonates and infants and in the presence of valve prostheses and the investigation of mediastinal tumours in older children.

CONCLUSIONS

Transoesophageal echocardiography is a valuable additional investigative tool for children of all ages. It is of particular value when acquisition of precordial image is impaired around the time of and after operation and in children with prosthetic valves or mediastinal tumour. Image quality was superior with the adult probe and we recommend the use of this probe unless the patient's weight is below 7 kg, when a paediatric probe allows this technique to be used usefully and safely in babies as small as 2.2 kg.

Age-associated changes in mesenteric arteries

Vascular disease increases in incidence with age and is the commonest cause of morbidity and mortality among elderly people. Hypertension is associated with hypertrophy of the arterial media. This study was designed to investigate changes in arterial structure that may occur with age independent of blood pressure. Collapsed sections of human mesenteric arteries (external diameter 2-3 mm) were measured using a semi-automatic image analysis system. There was a nonlinear increase in both the wall/lumen area ratio and the relative intimal area with age. There were no significant relationships between blood pressure and either the wall/lumen ratio or the relative intimal area.

Repair of asymptomatic aortic valve disease during other cardiac surgery

Repair of asymptomatic aortic valve disease was performed in 12 patients (9 female, 3 male, mean age 57.5 years) undergoing other cardiac surgery. Stenosis was the predominant aortic valve lesion in 7 (group A) with a mean gradient of 33.4 mmHg and regurgitation of mean grade 1.4 was predominant in 5 (group B). Cusp debridement +/- commissurotomy was performed in 9; commissural resuspension in 6 and repair of cusp perforation in 2. Perioperative transoesophageal echocardiography was used to assess the adequacy of repair in 4 patients. Prospective precordial echocardiographic follow-up is complete (mean 4.3 months). In group A there has been a significant reduction is peak aortic pressure gradient (33.4 vs 22.1 mmHg, p less than 0.05) and in cusp thickness (2.25 to 1.64 mm, p less than 0.05). In group B the degree of incompetence has improved in 3 of the 5 patients. Three patients have worsened valve disease following repair; in all these there was mixed valve disease of rheumatic origin. Aortic valve repair of asymptomatic disease during other cardiac surgery is a feasible technique which does not accelerate the disease process in the short term. Long-term follow-up is in progress to assess the prognosis of this preventive intervention.

The use of transoesophageal echocardiography for detecting early recurrence of atrial myxoma

A comparison between praecordial and transoesophageal cross-sectional echocardiography was undertaken in the follow-up of 14 patients who had previously undergone surgical excision of atrial myxoma. The mean interval between surgery and follow-up was 39 months. Evidence of recurrent tumour was seen in two patients by transoesophageal echocardiography but went undetected in one of these using the praecordial approach. Clear visualisation of the atria and interatrial septum was possible in all remaining cases using transoesophageal echocardiography and this allowed confident exclusion of tumour recurrence. Using praecordial echocardiography, technically inadequate studies meant that this was not possible in 4 patients. The significant late recurrence rate of excised atrial myxomas, emphasises the need for serial, postoperative echocardiographic studies. Praecordial echocardiography may be unreliable in the detection of recurrent atrial myxoma in its early stages and for this reason transoesophageal echocardiographic follow-up is justified in high risk patients.

Reconstitution of defective respiratory burst activity with partially purified human neutrophil cytochrome B in two genetic forms of chronic granulomatous disease: possible role of Rap1A

Neutrophil plasma membranes from patients with the X-linked and autosomal recessive forms of chronic granulomatous disease (CGD) that lack cytochrome b are incapable of generating superoxide anion (O2-) in vivo and in vitro. The O2- generating activity of these defective membranes was reconstituted with the addition of partially purified human neutrophil cytochrome b in a detergent-based, cell-free activation system. Depending on the detergent system used, 50% to 100% of the activity of control membranes was recovered, and this activity was directly dependent on the cytochrome b concentration. However, when cytochrome b was purified to 99% homogeneity, the reconstitutive capacity of the cytochrome was lost, possibly because of subtle denaturation of the cytochrome or the removal of an additional required cofactor. Examination of the latter possibility with respect to a protein known to coassociate with the cytochrome, ie, Rap1A, indicated that this ras-like protein was present in the partially purified cytochrome preparation used to reconstitute activity in CGD membranes, but was missing in the highly purified preparation. However, the finding that Rap1A was present in normal amounts in the neutrophil membranes from all four major types of CGD (including those missing cytochrome b) suggested that the conditions required of the reconstitution assay did not favor the reassociation of the membrane-derived Rap1A with exogenously added cytochrome b or that another unidentified membrane component was lost during the final purification step. The normal expression of Rap1A in CGD cell membranes also indicates that this protein is not responsible for the absence of O2- production in the X-linked and autosomal recessive cytochrome b-negative forms of CGD. Finally, these results show that the expression of Rap1A in the plasma membrane is not dependent on the coordinate expression of cytochrome b, despite the close association shown for these two proteins in the normal cell membrane.

Advanced glycosylation end products in the mesenteric artery

We measured advanced glycosylation end products in the mesenteric artery of 37 patients (ages 29-82 years), 34 of whom were nondiabetic. Samples of arterial tissue were obtained during bowel resectioning. Advanced glycosylation end products were measured as collagen-linked fluorescence (excitation wavelength 370 nm, emission wavelength 440 nm) after collagenase digestion of tissue samples. Mean fluorescence of the arterial samples was 15 U/mg (range 5.3-27). Collagen fluorescence correlated with patients' age (r = 0.57; P less than 0.001). No difference in the collagen-linked fluorescence was observed between men and women (P = 0.63), hypertensive and normotensive patients (P = 0.44), smokers and nonsmokers (P = -0.52), and patients with and without symptomatic coronary heart disease (P = 0.7). This study demonstrates, for the first time, the relationship between collagen-linked fluorescence and patients' age in human arterial tissue ex vivo.

Advanced Glycosylation End Products in the Mesenteric Artery

We measured advanced glycosylation end products in the mesenteric artery of 37 patients (ages 29-82 years), 34 of whom were nondiabetic. Samples of arterial tissue were obtained during bowel resectioning. Advanced glycosylation end products were measured as collagen-linked fluorescence (excitation wavelength 370 nm, emission wavelength 440 nm) after collagenase digestion of tissue samples. Mean fluorescence of the arterial samples was 15 U/mg (range 5.3-27). Collagen fluorescence correlated with patients' age (r = 0.57; P less than 0.001). No difference in the collagen-linked fluorescence was observed between men and women (P = 0.63), hypertensive and normotensive patients (P = 0.44), smokers and nonsmokers (P = -0.52), and patients with and without symptomatic coronary heart disease (P = 0.7). This study demonstrates, for the first time, the relationship between collagen-linked fluorescence and patients' age in human arterial tissue ex vivo.

Potent, orally active aldose reductase inhibitors related to zopolrestat: surrogates for benzothiazole side chain

A broad structure-activity program was undertaken in search of effective surrogates for the key benzothiazole side chain of the potent aldose reductase inhibitor, zopolrestat (1). A structure-driven approach was pursued, which spanned exploration of three areas: (1) 5/6 fused heterocycles such as benzoxazole, benzothiophene, benzofuran, and imidazopyridine; (2) 5-membered heterocycles, including oxadiazole, oxazole, thiazole, and thiadiazole, with pendant aryl groups, and (3) thioanilide as a formal equivalent of benzothiazole. Several benzoxazole- and 1,2,4-oxadiazole-derived analogues were found to be potent inhibitors of aldose reductase from human placenta and were orally active in preventing sorbitol accumulation in rat sciatic nerve, in an acute test of diabetic complications. 3,4-Dihydro-4-oxo-3-[(5,7-difluoro-2-benzoxazolyl)methyl]-1- phthalazineacetic acid (124) was the best of the benzoxazole series (IC50 = 3.2 x 10(-9) M); it suppressed accumulation of sorbitol in rat sciatic nerve by 78% at an oral dose of 10 mg/kg. Compound 139, 3,4-dihydro-4-oxo-3-[[(2-fluorophenyl)-1,2,4- oxadiazol-5-yl]methyl]-1-phthalazineacetic acid, with IC50 less than 1.0 x 10(-8) M, caused a 69% reduction in sorbitol accumulation in rat sciatic nerve at an oral dose of 25 mg/kg. The thioanilide side chain featured in 3-[2-[[3-(trifluoromethyl)phenyl]amino]-2-thioxoethyl]-3,4-dihydro - 4-oxo-1-phthalazineacetic acid (195) proved to be an effective surrogate for benzothiazole. Compound 195 was highly potent in vitro (IC50 = 5.2 x 10(-8) M) but did not show oral activity when tested at 100 mg/kg. Additional structure-activity relationships encompassing a variety of heterocyclic side chains are discussed.

Physiological changes due to age. Implications for cardiovascular drug therapy

Cardiovascular disease is the single largest cause of death in the elderly. Many of the published studies concerning the physiology and pharmacology of the aging cardiovascular system are seriously flawed. Problems include failure to measure the drug bioavailability and the selection of subjects with overt or subclinical disease. With exercise, the rise in heart rate is inversely proportional to age and maximum heart rate is reduced. Baroreceptor reflex activity appears to decline with age. Cardiac output is maintained in the elderly, with a slower heart rate and a greater stroke volume than in the young. Plasma noradrenaline (norepinephrine) levels increase in the elderly but there is no change in the sensitivity of the vasoconstrictor alpha 1-adrenoceptor. There is evidence for a decline in the activity of the vasodilator beta 2-adrenoceptor with age. It is difficult to make general rules about the effect of aging on the disposition and elimination of drugs. Each drug must be tested separately.

Left atrial clot in patients with mitral prostheses: increased rate of detection after recent systemic embolism

We studied 70 patients with mitral valvar replacements by both transthoracic and transoesophageal echocardiography. Fifteen subjects had recently suffered a suspected embolic episode. The remainder (55) were studied for other clinical reasons. Transthoracic echocardiography demonstrated thrombus in only 1 of the 70 patients. By contrast, transoesophageal examination revealed thrombus in 8 out of 15 patients with recent suspected embolism and 3 out of 55 without. Thrombus was most commonly seen in patients with biological valvar prostheses whose anticoagulation had been discontinued. When patients with prosthetic mitral valves present with a suspected embolic episode, transoesophageal echocardiography is strongly recommended. This study also suggests that transoesophageal echocardiography may be useful for evaluating patients with biological valves if anticoagulation is withdrawn so as to identify formation of thrombus at the earliest possible stage.

Failure of Doppler ultrasound to detect coarctation of the aorta

Normal velocities of flow in the aortic arch were recorded in a patient presenting with clinical signs of aortic coarctation. Angiography demonstrated complete coarctation with extensive collateral supply to the descending aorta: there was a systolic pressure difference of 40 mm Hg between the ascending and descending segments of the aorta. Despite reports of the value of Doppler ultrasound in the diagnosis of coarctation, the finding of normal velocities of flow within the aortic arch does not necessarily exclude the presence of an obstructive lesion.

The value of transesophageal echocardiography in the investigation of acute prosthetic valve dysfunction

When patients present with suspected prosthetic valve dysfunction, investigation is usually instituted to delineate the site and cause thereof. Precordial cross-sectional echocardiography is often helpful in this respect, but in the patient with acute pulmonary edema, imaging may be impaired because of discomfort and respiratory distress. The information obtained may also be suboptimal as a result of concomitant obesity, chest wall deformity, and pulmonary disease. In addition, further difficulties may relate to the acoustic shadowing produced by the metallic portion of the valve and its sewing ring, especially with valves in the mitral position. In such patients, cardiac catheterization may cause further decompensation and is associated with a recognized increase in morbidity and mortality. Angiography does not accurately site regurgitant jets in relation to the prosthetic valve concerned and will not detect the presence of vegetations. Transesophageal echocardiography circumvents many of these imaging difficulties and we evaluated its use in five patients with prosthetic heart valves who presented acutely ill, in severe pulmonary edema and suspected prosthetic heart valve failure. In each case, the diagnosis of valve dysfunction was established, and precise information regarding the site and cause of the failure was obtained. No complications or deterioration in patient condition resulted from the procedure and the findings were confirmed at surgery performed within 24 hours in all five patients. Transesophageal echocardiography should be included in the assessment of acute prosthetic heart valve failure.

The immuno-suppressed patient--what are the implications?

Dentists, doctors, and other health professionals are increasingly involved in interacting with immunosuppressed and immuno-deficient patients. As the medico-legal and health-economic environments change, an increasing range of progressively more difficult problems is developing. Like other health professionals, dentists must accept their role as advocates for patients, despite the stresses that this will entail. The psychological and social stresses inherent in handling life-long management problems based upon immuno-suppression and immuno-deficiency exceeds the hazards to dentists and others which result from exposure to various viruses and bacteria. There are implications in terms of history taking, organisation of laboratory and organ-imaging investigations, for continuing education, and for intra-professional referral procedures.