Trypan blue not toxic for retinal pigment epithelium in vitro

PURPOSE: To investigate whether trypan blue has a toxic effect on cultured retinal pigment epithelial (retinal pigment epithelium) cells. DESIGN: Experimental study with a direct live/dead cell staining technique using fluorescent dyes. METHODS: Cultured human retinal pigment epithelium cells were exposed for 5 minutes to various concentrations of trypan blue (0.06%, 0.15%, 0.30%), and cell viability was confocally measured. RESULTS: No increased cell death was found in cultures incubated in any of the trypan blue concentrations used. CONCLUSION: These findings indicate that a short exposure of trypan blue does not have a toxic effect on cultured retinal pigment epithelium cells.     

An atypical presentation of Acanthamoeba keratitis in a noncontact lens wearer

This article presents the case of a 49-year-old man who did not have a history of wearing contact lenses and who developed a rapidly progressive course of Acanthamoeba keratitis. The patient developed stromal keratitis that did not respond to herpes simplex virus therapies. Within 1 week after presentation, the patient progressed from mild anterior stromal haze and edema to a ring infiltrate, epithelial loss, and significant corneal edema. Corneal scrapings demonstrated cysts consistent with Acanthanmoeba keratitis. The patient was admitted to the hospital and placed on intensive medical therapy. He responded to therapy, and at 5 months showed central scarring in a quiet eye. This article presents a case of Acanthamoeba keratitis in a non-contact lens wearer, who was diagnosed clinically and histopathologically within 1 week of onset of symptoms. His case was atypical given his lack of contact lens wear or antecedent trauma and rapid progression to a ring infiltrate, usually seen as late findings.     

N6-cyclopentyl-2-(3-phenylaminocarbonyltriazene-1-yl)adenosine (TCPA), a very selective agonist with high affinity for the human adenosine A1 receptor

Four subtypes of adenosine receptors are currently known, that is, A(1), A(2A), A(2B), and A(3) receptors. Interestingly, quite substantial species differences exist especially between human and rat A(3) receptors. As a result, ligands such as CCPA, which are very selective for the rat A(1) receptor versus the human A(3) receptor, are substantially less selective when the human A(1) and A(3) receptors are compared. New 2-substituted and 2,N(6)-disubstituted adenosines were synthesized, and their affinities for the human adenosine A(1), A(2A), A(2B), and A(3) receptors were determined. Although large substituents on the C2-position are generally thought to yield adenosine A(2A) receptor selective ligands, the reported series of 2-triazeno-substituted adenosines had a very high affinity for the A(1) receptor. For example, 2-(3-phenylaminocarbonyltriazene-1-yl)adenosine had an affinity of 6.1 +/- 1.3 nM for the human adenosine A(1) receptor. Introduction of a diphenethyl substituent at the N(6)-position of this compound resulted in a high-affinity agonist, 3.1 +/- 0.9 nM, for the human adenosine A(1) receptor with 316- and 45-fold selectivity versus the human A(2A) and human A(3) receptors, respectively. The most selective, high-affinity human adenosine A(1) receptor agonist was the disubstituted compound N(6)-cyclopentyl-2-(3-phenylaminocarbonyltriazene-1-yl)adenosine (TCPA). TCPA had an affinity of 2.8 +/- 0.8 nM for the human adenosine A(1) receptor and was 75-fold and 214-fold selective versus the human A(2A) and human A(3) receptors, respectively. In addition, TCPA was a full agonist and inhibited the forskolin-induced cAMP production of CHO cells stably transfected with the human adenosine A(1) receptor with an IC(50) of 1.5 +/- 0.5 nM.     

Development of clinical reasoning from the basic sciences to the clerkships: a longitudinal assessment of medical students' needs and self-perception after a transitional learning unit

BACKGROUND: To facilitate students' transition from basic, science-oriented, problem-based learning (PBL) to clinical reasoning-oriented PBL, the University of Geneva School of Medicine introduced a 12-week unit of Introduction to Clinical Reasoning (ICR) at the beginning of its fourth or clerkship year. PURPOSE: The aims of the present study were to determine, after 12 weeks in the ICR unit, to what extent students had: (1) identified the learning content set by the faculty while adapting to the hypothetico-deductive reasoning approach; (2) familiarised themselves with the clinical reasoning-oriented learning process, and (3) transferred and further developed this process during the clinical years. METHOD: Students' derived objectives from the problems were compared to the objectives preset by the faculty to determine acquisition of intended learning content. To assess their adaptation to the clinical reasoning-oriented PBL approach, students (n = 124) were asked to list and freely comment on aspects of the unit they felt most at ease with or had difficulty with, and to complete a questionnaire on the clinical reasoning process (CRP). The same questionnaire was administered 6 and 12 months later to assess the evolution of the students' self-perception during clerkships. RESULTS: On average, student objectives matched 62% of faculty objectives. Half of the missed (38%) objectives were in basic sciences. Students generated 16% additional objectives, also predominantly in the basic sciences category (41%). Free comments indicated that the difficulties perceived by students were very similar to those previously reported in studies on reasoning and errors, such as difficulty in gathering, interpreting and weighting relevant data, synthesising information, and organising it hierarchically. These results were confirmed with the CRP questionnaire administered at the end of the unit. For most of the competencies assessed on the CRP questionnaire, a gradual improvement was seen to have occurred by 6 and 12 months after the unit. CONCLUSIONS: To ease students' transition from the preclinical to clinical years, a learning unit should give them the opportunity to train their clinical reasoning processes on standardised and prototypical problems, before encountering real patients with more ill-structured problems during clerkships. Such a transitional structure should particularly emphasise a developed repertoire of problem representations, recognition of key findings and a hierarchical classification of working hypotheses. It should foster the creation of links between the acquired basic clinical knowledge and the diagnostic, management and therapy steps of problem solving.     

Mercury exposure evaluation among Pakaanóva Indians,Amazon Region,Brazil

A cross-sectional study was conducted to evaluate mercury (Hg) exposure among 910 Pakaan va Indians from the counties of Guajar Mirim and Nova Marmor , Rond nia State, Brazil. Individual hair samples were taken from the occipital region, and Hg was measured by atomic absorption spectrometry with cold vapor generation. Mean Hg in hair samples was 8.37 micro g/g (range 0.52-83.89), indicating high exposure. Young children (< 2 years old) showed a mean Hg of 10.54 micro g/g, and children from 3 to 5 years old had a mean Hg of 9.34 micro g/g. Mercury levels in women (8,91 micro g/g) were higher than in men (7.55 micro g/g), and this difference was significant (t = 3.26; p < 0.01). These results indicate the need for surveillance programs and complementary studies including the Pakaan va Indians in Rond nia State.     

Polychlorinated biphenyls and reproductive hormones in female polar bears at Svalbard

High concentrations of polychlorinated biphenyls (PCBs) in polar bears from Svalbard have increased concern for that population's reproductive health. We examined whether there were associations between the plasma concentrations of PCBs and reproductive hormones [progesterone (P4)] and 17 beta-estradiol (E2)] in free-living female polar bears from Svalbard. Concentrations of P4 depended on reproductive status, and concentrations were lowest in females with offspring--females with cubs and females with yearlings. In these females, the P4 concentrations were positively correlated with plasma sigma PCBs (sum of all analyzed polychlorinated biphenyl congeners) concentrations. The sigma PCBs concentrations explained 27% of the variation in the P4 concentrations. There were no correlations between sigma PCBs and E2 and cortisol in any of the groups of polar bears, or between sigma PCBs and P4 in single polar bears. Although the sigma PCBs-P4 relationship in female polar bears with offspring is not evidence per se of a direct cause-effect association, the results indicate that PCBs may affect levels of P4 in polar bear females. There is a clear need to further assess the hormone balance and population health of polar bears at Svalbard.     

Inhibition of mitochondrial Na+-Ca2+ exchanger increases mitochondrial metabolism and potentiates glucose-stimulated insulin secretion in rat pancreatic islets

The mitochondrial Na(+)-Ca(2+) exchanger (mNCE) mediates efflux of Ca(2+) from mitochondria in exchange for influx of Na(+). We show that inhibition of the mNCE enhances mitochondrial oxidative metabolism and increases glucose-stimulated insulin secretion in rat islets and INS-1 cells. The benzothiazepine CGP37157 inhibited mNCE activity in INS-1 cells (50% inhibition at IC(50) = 1.5 micro mol/l) and increased the glucose-induced rise in mitochondrial Ca(2+) ([Ca(2+)](m)) 2.1 times. Cellular ATP content was increased by 13% in INS-1 cells and by 49% in rat islets by CGP37157 (1 micro mol/l). Krebs cycle flux was also stimulated by CGP37157 when glucose was present. Insulin secretion was increased in a glucose-dependent manner by CGP37157 in both INS-1 cells and islets. In islets, CGP37157 increased insulin secretion dose dependently (half-maximal efficacy at EC(50) = 0.06 micro mol/l) at 8 mmol/l glucose and shifted the glucose dose response curve to the left. In perifused islets, mNCE inhibition had no effect on insulin secretion at 2.8 mmol/l glucose but increased insulin secretion by 46% at 11 mmol/l glucose. The effects of CGP37157 could not be attributed to interactions with the plasma membrane sodium calcium exchanger, L-type calcium channels, ATP-sensitive K(+) channels, or [Ca(2+)](m) uniporter. In hyperglycemic clamp studies of Wistar rats, CGP37157 increased plasma insulin and C-peptide levels only during the hyperglycemic phase of the study. These results illustrate the potential utility of agents that affect mitochondrial metabolism as novel insulin secretagogues.     

Radiation exposure to cardiologists performing interventional cardiology procedures

Medical doctors, who practice interventional cardiology, receive a noticeable radiation dose. In this study, we measured the radiation dose to 9 cardiologists during 144 procedures (72 coronary angiographies and 70 percutaneus translumined coronary angioplasties) in two Greek hospitals. Absorbed doses were measured with TLD placed underneath and over the lead apron at the thyroid protective collar. Based on these measurements, the effective dose was calculated using the Niklason method. In addition, dose area product (DAP) was registered. The effective doses, E, were normalised to the total DAP measured in each procedure, producing the E/DAP index. The mean effective dose values were found to be in the range of 1.2-2.7 microSv while the mean E/DAP values are in the range of 0.010-0.035 microSv/Gycm2. The dependence of dose to the X-ray equipment, the exposure parameters and the technique of the cardiologist were examined. Taking under consideration the laboratories' annual workload, the maximum annual dose was estimated to be 1.9 and 2.8 mSv in the two hospitals.