Alon Margalit

Initiation of RVD response in human platelets: mechanical-biochemical transduction involves pertussis-toxin-sensitive G protein and phospholipase A2.

Platelets revert hypotonic-induced swelling by the process of regulatory volume decrease (RVD). We have recently shown that this process is under the control of endogenous hepoxilin A3. In this work, we investigated the mechanical-biochemical transduction that leads to hepoxilin A3 formation. We demonstrate that this process is mediated by pertussis-toxin-sensitive G protein, which activates Ca2+-insensitive phospholipase A2, and the sequential release of arachidonic acid. This conclusion is supported by the following observations: (i) RVD response is blocked selectively by the phospholipase A2 inhibitors manoalide and bromophenacyl-bromide (0.2 and 5 μm, respectively) but not by phospholipase C inhibitors. The addition of arachidonic acid overcame this inhibition; (ii) extracellular Ca2+ depletion by EGTA (up to 10 mm) does not affect RVD; (iii) intracellular Ca2+ depletion by BAPTAAM (100 μm) inhibits RVD but not hepoxilin A3 formation, as tested by the RVD reconstitution assay; (iv) RVD is inhibited by the G-protein inhibitors, GDPβS (1 μm) and pertussis toxin (1 ng/ml). This inhibition is overcome by addition of arachidonic acid or hypotonic cell-free eluate that contains hepoxilin A3; (v) NaF, 1 mm, induces hepoxilin A3 formation, tested by the RVD reconstitution assay; and (vii) GDPβS inhibits hepoxilin A3 formation associated with flow. Therefore, it seems that G proteins are involved in the initial step of the mechanical-biochemical transduction leading to hepoxilin A3 formation in human platelets.

Promoting a biopsychosocial orientation in family practice: effect of two teaching programs on the knowledge and attitudes of practising primary care physicians

The bio-psychosocial (BPS) approach to patient care has gained acceptance in medical education. However, reported teaching programs rarely describe the efficacy of alternative approaches to continuing medical education aimed at promoting a BPS approach. The objective was to describe and evaluate the effect of two teaching programs on learners’ BPS knowledge, management intentions, patient-centered attitudes, professional self-esteem, burnout, work related strain and mental workload. The learners were Israeli general practitioners. The first (“didactic”) program consisted of problem-based reading assignments, lectures and discussions. The second (“interactive”) program consisted of reading assignments, lectures and discussions, in addition to role-playing exercises, Balint groups and one-to-one counseling by a facilitator. One month before and six months after the teaching interventions, we used structured questionnaires to test for knowledge, management intentions (responses to questions, such as “what would you tell a patient with …”) and attitudes. Both programs led to measurable improvement in knowledge, intentions, patient-centered attitudes and self-esteem. The interactive teaching approach improved significantly more the learners’ professional self-esteem and intentions than the didactic approach. Self-reported burnout significantly increased after the program. It is concluded that teaching intervention enhanced a BPS orientation and led to changes in knowledge, intentions, self-esteem and attitudes. An interactive method of instruction was more effective in achieving some of these objectives than a didactic one. The observed increase in burnout was unexpected and requires further study and confirmation.

Effect of a biopsychosocial approach on patient satisfaction and patterns of care

AbstractBACKGROUND: There is a growing tendency to include in medical curricula teaching programs that promote a biopsychosocial (BPS) approach to patient care. However, we know of no attempts to assess their effect on patterns of care and health care expenditures. OBJECTIVE: To determine whether 1) a teaching intervention aiming to promote a BPS approach to care affects the duration of the doctor-patient encounter, health expenditures, and patient satisfaction with care, and 2) the teaching method employed affects these outcomes. METHODS: We compared two teaching methods. The first one (didactic) consisted of reading assignments, lectures, and group discussions. The second (interactive) consisted of reading assignments, small group discussions, Balint groups, and role-playing exercises. We videotaped patient encounters 1 month before and 6 months after the teaching interventions, and recorded the duration of the videotaped encounters and whether the doctor had prescribed medications, ordered tests, and referred the patient to consultants. Patient satisfaction was measured by a structured questionnaire. RESULTS: Both teaching interventions were followed by a reduction in medications prescribed and by improved patient satisfaction. Compared to the didactic group, the interactive group prescribed even fewer medications, ordered fewer laboratory examinations, and elicited higher scores of patient satisfaction. The average duration of the encounters after the didactic and interactive teaching interventions was longer than that before by 36 and 42 seconds, respectively. CONCLUSIONS: A BPS teaching intervention may reduce health care expenditures and enhance patients’ satisfaction, without changing markedly the duration of the encounter. An interactive method of instruction was more effective in achieving these objectives than a didactic one.

Regulation of prostaglandin biosynthesis in vivo by glutathione.

Intraperitoneal administration of urate crystals to mice reduced subsequent macrophage conversion of arachidonic acid (AA) to prostaglandins (PGs) and 12-hydroxyeicosatetraenoic acid for up to 6 h. In contrast, levels of 12-hydroxyheptadecatrienoic acid (12-HHT) were markedly elevated. This metabolic profile was previously observed in vitro when recombinant cyclooxygenase (COX) enzymes were incubated with reduced glutathione (GSH). Analysis of peritoneal GSH levels revealed a fivefold elevation after urate crystal administration. The GSH synthesis inhibitorl-buthionine-[ S, R]-sulfoximine partially reversed the urate crystal effect on both GSH elevation and PG synthesis. Moreover, addition of exogenous GSH to isolated peritoneal macrophages shifted AA metabolism from PGs to 12-HHT. Urate crystal administration reduced COX-1, but induced COX-2 expression in peritoneal cells. The reduction of COX-1 may contribute to the attenuation of PG synthesis after 1 and 2 h, but PG synthesis remained inhibited up to 6 h, when COX-2 levels were high. Overall, our results indicate that elevated GSH levels inhibit PG production in this model and provide in vivo evidence for the role of GSH in the regulation of PG biosynthesis.Intraperitoneal administration of urate crystals to mice reduced subsequent macrophage conversion of arachidonic acid (AA) to prostaglandins (PGs) and 12-hydroxyeicosatetraenoic acid for up to 6 h. In contrast, levels of 12-hydroxyheptadecatrienoic acid (12-HHT) were markedly elevated. This metabolic profile was previously observed in vitro when recombinant cyclooxygenase (COX) enzymes were incubated with reduced glutathione (GSH). Analysis of peritoneal GSH levels revealed a fivefold elevation after urate crystal administration. The GSH synthesis inhibitor L-buthionine-[S,R]-sulfoximine partially reversed the urate crystal effect on both GSH elevation and PG synthesis. Moreover, addition of exogenous GSH to isolated peritoneal macrophages shifted AA metabolism from PGs to 12-HHT. Urate crystal administration reduced COX-1, but induced COX-2 expression in peritoneal cells. The reduction of COX-1 may contribute to the attenuation of PG synthesis after 1 and 2 h, but PG synthesis remained inhibited up to 6 h, when COX-2 levels were high. Overall, our results indicate that elevated GSH levels inhibit PG production in this model and provide in vivo evidence for the role of GSH in the regulation of PG biosynthesis.

Development of a chemiluminescent optical fiber immunosensor to detect Streptococcus pneumoniae antipolysaccharide antibodies

A chemiluminescent-based optical fiber immunosensor was developed for the detection of antipneumococcal antibodies. This was accomplished by developing a different chemical procedure utilizing 3-aminopropyl trimethoxysilane and cyanuric chloride to conjugate pneumococcal cell wall polysaccharides to the optical fiber tips, and by improving the sensitivity of the photodetection system. The lowest titer of antipneumococcal antibodies detected by the optical fiber was at a 1:819,200 dilution. The lowest corresponding value by standard enzyme-linked immunosorbent assay was at a 1:98,415 dilution. It was concluded that the optical immunosensor system is an accurate and sensitive method to detect antipneumococcal antibodies and may be an adequate tool to monitor antibodies in specimens such as saliva and urine.

Endogenous hepoxilin A3, produced under short duration of high shear-stress, inhibits thrombin-induced aggregation in human platelets.

The effect of short duration of shear-stress (350 dyne/cm2, 20 ms) on platelet-aggregation has been assessed. This treatment inhibits thrombin-induced but not ADP- or collagen-induced aggregation. The inhibitory effect is mediated by endogenous hepoxilin A3. This conclusion is based on the following observations: (a) The shear-stress effect is abolished by lipoxygenase inhibitors. (b) Hepoxilin A3 mimics the shear-stress effect.

A practical assessment of physician biopsychosocial performance

Background: A biopsychosocial approach to care seems to improve patient satisfaction and health outcomes. Nevertheless, this approach is not widely practiced, possibly because its precepts have not been translated into observable skills. Aim: To identify the skill components of a biopsychosocial consultation and develop an tool for their evaluation. Methods: We approached three e-mail discussion groups of family physicians and pooled their responses to the question “what types of observed physician behavior would characterize a biopsychosocial consultation?” We received 35 responses describing 37 types of behavior, all of which seemed to cluster around one of three aspects: patient-centered interview; system-centered and family-centered approach to care; or problem-solving orientation. Using these categories, we developed a nine-item evaluation tool. We used the evaluation tool to score videotaped encounters of patients with two types of doctors: family physicians who were identified by peer ratings to have a highly biopsychosocial orientation (n = 9) or a highly biomedical approach (n = 4); and 44 general practitioners, before and after they had participated in a program that taught a biopsychosocial approach to care. Results: The evaluation tool was found to demonstrate high reliability (α = 0.90) and acceptable interobserver variability. The average scores of the physicians with a highly biopsychosocial orientation were significantly higher than those of physicians with a highly biomedical approach. There were significant differences between the scores of the teaching-program participants before and after the program. Conclusions: A biopsychosocial approach to patient care can be characterized using a valid and easy-to-apply evaluation tool.

Regulation of in Vivo Prostaglandin Biosynthesis by Glutathione

Monosodium urate crystals are a naturally occurring pro-inflammatory agent associated with the manifestations of the rheumatic disorder, gout. This disease is characterized by occasional periods of severe pain and inflammatory swelling that, if untreated, resolves spontaneously within a few days1. Although urate crystals are known to be the etiologic agent for gout, and their accumulation seems to be the major pathophysiological event leading to inflammatory episodes, additional factors influence the inflammatory response. Urate crystal deposition in joints may occur without associated inflammation2 and inflammatory attacks may remit although urate crystals are still present in the joints3. Prostaglandins (PGs) appear to play a prominent role in the onset of gout attacks because non-steroidal anti-inflammatory drugs (NSAIDs), which inhibit PG formation, are considered the drugs of choice for the treatment of acute attacks4. Using a mouse model of urate crystal-induced peritonitis, we have found that while urate crystals triggered an initial burst of eicosanoid products, at later times additional arachidonic acid metabolism was attenuated in a fashion independent of substrate concentration5. The present study further investigate this phenomena and demonstrate that urate crystal administration resulted in five fold elevation of the intracellular and extracellular pools of reduced glutathione (GSH) and that the elevated GSH attenuated PG formation by shifting the cyclooxygenase (COX) products profile from PG to 12-hydroxyheptadecatrienoic acid (12-HHT).