Biomedical subjects
Publications and source records attributed to R Mendelson.
We present three cases of recurrent pancreatitis that occurred in patients with small islet cell tumours of the pancreas which were obstructing the main pancreatic duct. This is a very uncommon presentation of pancreatic islet cell tumours. The radiological findings in these cases are shown and the implications for imaging of 'idiopathic' relapsing pancreatitis are discussed.
OBJECTIVE: To provide updated, evidence-based recommendations concerning the effects of weight loss and maintenance of healthy weight on the prevention and control of hypertension in otherwise healthy adults (except pregnant women). OPTIONS: The main options are to attain and maintain a healthy body weight (body mass index [BMI] 20-25 kg/m2) or not to do so. For those at risk for hypertension, weight loss and maintenance of healthy weight may prevent the condition. For those who have hypertension, weight loss and maintenance of healthy weight may reduce or obviate the need for antihypertensive medications. OUTCOMES: The health outcome considered was change in blood pressure. Because of insufficient evidence, no economic outcomes were considered. EVIDENCE: A MEDLINE search was conducted for the years 1992-1996 with the terms hypertension and obesity in combination and antihypertensive therapy and obesity in combination. Other relevant evidence was obtained from the reference lists of the articles identified, from the personal files of the authors and through contacts with experts. The articles were reviewed, classified according to study design and graded according to level of evidence. VALUES: A high value was placed on the avoidance of cardiovascular morbidity and premature death caused by untreated hypertension. BENEFITS, HARMS AND COSTS: Weight loss and the maintenance of healthy body weight reduces the blood pressure of both hypertensive and normotensive people. The indirect benefits of a health body weight are well known. The negative effects of weight loss are primarily the frustrations associated with attaining and maintaining a healthy weight. The costs associated with weight loss programs were not measured in the studies reviewed. RECOMMENDATIONS: (1) It is recommended that health care professionals determine weight (in kilograms), height (in metres) and BMI for all adults. (2) To reduce blood pressure in the population at large, it is recommended that Canadians attain and maintain a healthy BMI (20-25). (3) All overweight hypertensive patients (BMI greater than 25) should be advised to reduce their weight. VALIDATION: These recommendations are similar to those of the World Hypertension League, the National High Blood Pressure Education Program Working Group on Primary Prevention of Hypertension, the Canadian Hypertension Society and the Canadian Coalition for High Blood Pressure Prevention and Control. They have not been clinically tested. SPONSORS: The Canadian Hypertension Society, the Canadian Coalition for High Blood Pressure Prevention and Control, the Laboratory Centre for Disease Control at Health Canada, and the Heart and Stroke Foundation of Canada.
The positions and orientations of the myosin heads in relaxed, active, rigor and S1-labelled fish muscle are being determined by analysis both of electron micrographs and of low-angle X-ray diffraction patterns. The X-ray analysis of resting muscle makes use of the head shape defined from the study of S1 crystals, with variable head configurational parameters being used on each of the three different 3-fold symmetric 14.3 nm-spaced 'crowns' of myosin heads within the 42.9 nm axial repeat of the myosin filaments. Diffraction patterns were stripped using CCP13 fibre diffraction software. Searches and optimisation were carried out using simulated annealing and local refinement procedures to give a 'best fit' relaxed structure with a crystallographic R-factor of about 4%. It had heads oriented all the same way up (i.e. with similar rotations around their own long axes) on the myosin filament, but with a small range of axial tilts. Head configuration in rigor fish muscle is being determined by X-ray diffraction and electron microscopy of normal rigor muscle and of skinned muscle soaked with extrinsic myosin S1. Computed 3-D reconstructions of acto-S1 using X-ray amplitudes and phases from electron microscopy are informative and help to analyse the X-ray diffraction data that extend axially to about 1 nm resolution. An ambiguity is the axial direction of the observed resting myosin head array relative to the known polarity of the actin filaments. One polarity would give little axial displacement (2-3 nm) between opposite ends of the resting and rigor heads, and in this case the heads would need to rotate around their own long axes by about 115 degrees to make a rigor attachment. The other (preferred) filament polarity would provide considerable axial swinging (14-15 nm) between the two states. We are attempting to define the absolute polarity of the resting muscle myosin head array using electron microscopy and image processing either of cryo-sections or of replicas from shadowed, freeze-fractured, rapidly frozen fish muscle fibres.
Surmises of how myosin subfragment 1 (S1) interacts with actin filaments in muscle contraction rest upon knowing the relative arrangement of the two proteins. Although there exist crystallographic structures for both S1 and actin, as well as electron microscopy data for the acto-S1 complex (AS1), modeling of this arrangement has so far only been done "by eye." Here we report fitted AS1 structures obtained using a quantitative method that is both more objective and makes more complete use of the data. Using undistorted crystallographic results, the best-fit AS1 structure shows significant differences from that obtained by visual fitting. The best fit is produced using the F-actin model of Holmes et al. [Holmes, K. C., Popp, D., Gebhard, W. & Kabsch, W. (1990) Nature (London) 347, 44-49]. S1 residues at the AS1 interface are now found at a higher radius as well as being translated axially and rotated azimuthally. Fits using S1 plus loops missing from the crystal structure were achieved using a homology search method to predict loop structures. These improved fits favor an arrangement in which the loop at the 50- to 20-kDa domain junction of S1 is located near the N terminus of actin. Rigid-body movements of the lower 50-kDa domain, which further improve the fit, produce closure of the large 50-kDa domain cleft and bring conserved residues in the lower 50-kDa domain into an apparently appropriate orientation for close interaction with actin. This finding supports the idea that binding of ATP to AS1 at the end of the ATPase cycle disrupts the actin binding site by changing the conformation of the 50-kDa cleft of S1.
Fifteen patients with carcinoma of the gastro-oesophageal junction were pre-operatively staged with endoscopic ultrasound (EUS) and computed tomography (CT). The accuracy of tumour and nodal staging using both modalities was compared to the final histological staging of the resected specimens. In staging depth of tumour growth, EUS was significantly more accurate (87% of lesions correctly staged) than CT (40% correctly staged). In staging nodal involvement, EUS was again significantly more accurate (73% correctly staged) than CT (33%). Two-thirds of the lesions were traversable with the endoscopic probe, but most of the nontraversed lesions were correctly staged on EUS. In this study, CT has performed poorly as a staging modality for carcinoma at the gastro-oesophageal junction. Other studies have shown CT to be less accurate at this location than at other oesophageal sites. The orientation of the gastro-oesophageal junction, lack of surrounding fat planes, proximity of adjacent organs and patient motion contribute to the poor staging performance of CT at this location. In contrast, EUS has been an accurate staging modality at the gastro-oesophageal junction in this study and compares well with other studies evaluating EUS in the more proximal oesophagus. Endoscopic ultrasound is therefore a necessary modality if accurate pre-operative staging of gastro-oesophageal junction carcinoma is to be achieved.
The convergence of structures, all determined by independent global searches and subsequent refinement on different electron microscopy data sets, with the X-ray fiber diffraction results strongly suggests that we now have the approximately correct structure for F-actin. This consensus structure will now provide a reliable, well-defined platform upon which to study the structure and function of proteins bound to actin. Among these are capping proteins, such as severin and gelsolin, contractile proteins, such as myosin and its subfragments, and proteins involved in regulation, such as troponin and tropomyosin.
Haemophilus capsular polysaccharide-tetanus toxoid conjugate (PRP-T) and diphtheria-tetanus-pertussis (DTP) vaccines were administered in a single syringe (group 1) or separate syringes (group 2) to 284 infants at 2, 4, and 6 months of age. Group 1 infants had a slightly greater incidence of local reactions. Systemic reactions were similar. The geometric mean titers of polyribosylribitol phosphate (PRP) serum antibody concentrations after the third dose of PRP-T vaccine were 4.8 and 4.3 micrograms/ml for groups 1 and 2, respectively. Antibody responses to DTP antigens were also similar. The immunogenicity and safety of the PRP-T and DTP vaccines are equivalent when the vaccines are administered in separate syringes or the same syringe to infants.
Nineteen women aged 19-64 years (median 38) with intractable constipation were assessed by Indium-111 DTPA colonic transit scan and barium evacuation proctogram. Patients were classified as having an isolated (I) or predominant disorder of colonic transit (II), a mixed disorder of colonic transit and rectal evacuation (III), a predominant disorder of rectal evacuation (IV) or normal colorectal emptying (V). Twelve patients fell into categories I and II and were considered suitable for surgery. Three responded to further vigorous aperient therapy and nine (32-55 years, median 38) underwent subtotal colectomy with ileorectal anastomosis at the level of the sacral promontory. Two patients required re-operation for suspected anastomotic leak. One patient required readmission on two occasions for small bowel obstruction. Follow up has been 2-21 months (median 16). Eight of the nine patients no longer take oral aperients. Eight patients have a satisfactory stool frequency of 2-8 per 24 h; the other patient has an ileostomy and incapacitating postprandial abdominal pain. Abdominal pain is troublesome in two other patients. Two patients require antidiarrhoeal therapy but none experience faecal incontinence. In severely constipated patients with a proven disorder of colonic transit but normal or near normal rectal evacuation subtotal colectomy provides excellent symptomatic relief.
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This multicenter, randomized, parallel treatment, observer-blinded study was designed to evaluate the safety and efficacy of cefpodoxime proxetil (5 mg/kg twice daily for 10 days) compared with penicillin V (13.4 mg/kg three times daily for 10 days) for treatment of Group A streptococcal pharyngitis and tonsillitis in pediatric patients. Clinical and microbiologic results were evaluated before therapy, during therapy (Study Days 3 to 5), at the end of therapy (Study Days 14 to 18) and at long term follow-up (Study Days 30 to 32). Both drugs were well-tolerated in 578 patients evaluable for safety. Mild gastrointestinal complaints were noted in 6.7% of 386 cefpodoxime-treated patients and in 5.2% of 192 penicillin-treated patients. In 413 patients evaluable for efficacy, both treatment regimens resulted in comparably favorable clinical outcome; cure rates were 83.8% for 275 cefpodoxime-treated patients and 77.5% for 138 penicillin-treated patients. However, eradication of S. pyogenes at end of therapy was significantly higher with cefpodoxime (93.1%) than with penicillin (81.2%) (P < 0.01). Cefpodoxime proxetil provides an effective alternative to penicillin V for the treatment of streptococcal pharyngitis and tonsillitis.
Rapid change and marked diversity are expected to characterize the 21st century. If dietitians are to serve as change facilitators in this environment they will have to demonstrate greater flexibility and creativity, practise critical analysis and problem solving and employ creative thinking. Although provision of quality nutrition care will remain the unique contribution of dietitians, practitioners in the future will require a greater understanding of the impact of social, economic and political systems on food availability and food consumption and, in turn, health and well-being. Critical to the future practice of dietetics will be a greater understanding of research methodology, computer technology, quality improvement processes and risk management, principles governing learning and behaviour, personnel management and organizational behaviour, family and group dynamics, interpersonal communication and their application to dietetic practice. The Canadian Dietetic Association recently adopted a framework for the development of baccalaureate programs in dietetics designed to enable the dietetic practitioner to continue to make a unique contribution in the 21st century. The framework allows individual institutions the freedom and flexibility to plan programs that are compatible with their philosophy and organizational structure. In addition, it is predicted on the principle that a career in dietetics entails a lifetime commitment to education, of which the baccalaureate program is only the beginning.
The Healthiest Babies Possible Program (HBP) is a prenatal intervention program for the City of Toronto and is designed to reduce the incidence of low birth weight babies. This study was undertaken to assess the impact of the HBP on dietary change and birth outcome for underweight and overweight expectant mothers. Dietary change was measured by the use of food scores applied to 24-hour dietary recalls throughout the pregnancy. Three recalls collected during the early stage of the program were selected to represent early interventions; three of the results collected during the latter stage of the program represent the late stage of intervention. Birth outcome was determined by weight gain and infant birth weight. For both groups, food scores improved throughout the early intervention period and the improvements were sustained through the remainder of the program. During pregnancy the underweight women gained more weight than the overweight women but delivered infants with lower birth weights.
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Two proprietary sunscreen preparations containing para-aminobenzoic acid and sulisobenzone, respectively, were tested for their ability to block the induction of ornithine decarboxylase by medium wavelength ultraviolet radiation (UV-B) in the epidermis of the hairless mouse. Both preparations were effective, the sunscreen treated animals requiring more radiation for ornithine decarboxylase induction. The UV dose-dependent gradients were reduced by a mean factor of 7.35 (sulisobenzone) and 15 (PABA). These figures correlate well with other in vivo sunscreen assays. This new method provides a simple and reproducible way of evaluating sunscreens in vivo.
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