Mechanism underlying superantigen-induced clonal deletion of mature T lymphocytes

We observed that peripheral T cells activated in vivo or invitro by superantigens are susceptible to cell death when theirantigen receptor is cross-linked with the appropriate anti-ßTCR mAb. TCR ligation by mAbs specifically drove the T cellclonal deletion in both CD4⁺ and CD8⁺ cell subsets. An IL-2/1L-2Rinteraction seems to be a critical step In predisposing superantigenactivated cells to death; In fact, in vivo IL-2R bockade reversedT cell deletion In superantlgen plus anti-ß TCR mAbtreated mice. TCR ligatlon by mAbs also produced cell deathof the relevant targets in in vitro IL-2 activated T cells.Surprisingly, no T cell deletion was demonstrable in IL-2 activatedcells following staphylococcal enterotoxin B - TCR Interaction,ruling out the possibility that superantigen in Itself can inducecell death. Thus, while superantigen activation opens the celldeath program, a subsequent TCR-antigen (self) Interaction appearsnecessary to produce clonal deletion in mature T lymphocytes.     

Comparison of CGS 15943, ZM 241385 and SCH 58261 as antagonists at human adenosine receptors

Three structurally related non-xanthine compounds, CGS 15943, ZM 241385 and SCH 58261, are potent A_2A adenosine receptor antagonists and have been used as tools in many pharmacological studies. We have now characterized their affinity and selectivity profile on human adenosine receptors stably transfected into either CHO cells (A₁ and A_2B receptors) or HEK-293 cells (A_2A and A₃ receptors). In binding studies using [³H]SCH 58261 as a radioligand, the three compounds were equally potent at A_2A receptors, their K _i value being less than 1 nM. Affinity for A₁ and A₃ receptors was measured using [³H]DPCPX and [¹²⁵I]AB-MECA as radioligands. Given the lack of selective ligands, interaction with A_2B receptors was assessed using the cAMP accumulation assay following stimulation by the adenosine receptor agonist N-ethylcarboxamidoadenosine (NECA). CGS 15943 was almost as potent at A₁ receptors (K _i 3.5 nM) as at A_2A receptors, showed moderate affinity for A₃ receptors (K _i 95 nM) and also interacted with A_2B receptors (K _i 44 nM; pA₂ 7.5). ZM 241385 showed little affinity for A₁ receptors (K _i 255 nM), and did not interact with A₃ receptors (K _i>10 μM); however, it displayed moderate affinity for A_2B receptors (K _i 50 nM; pA₂ 7.3). SCH 58261 had weak affinity for A₁ receptors (K _i 287 nM), no interaction with A₃ receptors (K _i>10 μM), and showed negligible interaction with A_2B receptors (K _i 5 μM; pA₂ 6.0). These data indicate that SCH 58261 is the most selective A_2A antagonist currently available. Moreover, the different receptor selectivity of these three chemically related compounds provides useful information to progress with structure-activity relationship studies. Received: 2 July 1998 / Accepted: 6 October 1998     

Physicians and death: Comments and behaviour of 605 doctors in the north-east of Italy

The aim of this study was to determine the influence of socio-demographic and professional factors on physicians' attitudes to the terminally ill. Between May 1992 and May 1993, a survey was conducted in the province of Pordenone (north-east, Italy) in order to analyse a number of specific issues, such as emotional involvement, the need for aggressive treatments and the communication of diagnosis and prognosis. After obtaining a list of board-certified physicians from the Medical Association office in Pordenone, a modification of the cancer questionnaire of Haley and Blanchard (QSPT) was mailed to 916 doctors. Of these, 605 (60%; 487 male, 118 female; mean age 41 ± 11 SD) returned the completed questionnaire. Within the group of responders, we identified three main subgroups, according to their type of activity: general practitioners (175, 29%), hospital doctors (235, 39%) and other doctors (195, 32%). In age, sex and activity, the only significant difference between responders and non-responders was age (mean age 41 and 43 years respeetively). Most of the responders (77%) stated that they were able to deal with the terminally ill patient and his/her needs; 44%, however, admitted that patients' anxiety is sometimes unbearable. For the vast majority of the doctors polled (91%), providing a comfortable environment for an incurable patient was more important than pursuing aggressive treatment, but only 44% were convinced of the uselessness of aggressive care. To the question on whether to disclose information about imminent death to allow patients to prepare spiritually, 37% answered No, 38% Yes, and 25% were uncertain. Almost all responders (95%), however, believed in the beneficial effect of hope on the terminally ill. Ourresults suggest that doctors' professional and, most of all, sociodemographic and cultural factors determine the relationship with the patient on both the emotional and the clinical decision-making levels.     

How pre-marketing data can be used for predicting the weight of drug interactions in clinical practice

Unexpected drug interactions have led to the withdrawal of many drugs, raising concern about the gap between what is known at the time of approval and the risk of serious effects in the longer term, particularly in high-risk populations generally excluded from drug development. This is because the majority of drug interaction studies are done using in vitro methods, or in healthy young volunteers who may not reflect the complexity of patients, and the settings in which the drug will be used in clinical practice. Pre-marketing interaction studies should therefore be designed to make information easily accessible and clinically transferable. They should be adequate in terms of sample size, population, comorbidity, phenotyping and/or genotyping, end-points and outcome measures, and conducted in conditions of dose, route and timing of co-administration that reproduce the proposed therapeutic indications of the new drug. Although young volunteers have the advantage of minimizing some confounding effects introduced by diseases or polypharmacy, patients drawn from populations for whom the drug is intended would be more relevant and accurate, providing the studies are feasible and safe.     

Paracoccidioidomycosis: epidemiological,clinical, diagnostic and treatment up-dating

Paracoccidioidomycosis is an acute - to chronic systemic mycosis caused by fungi of the genus Paracoccidioides. Due to its frequent tegument clinical expression, paracoccidioidomycosis is an important disease for dermatologists, who must be up-to-date about it. This article focuses on recent epidemiological data and discusses the new insights coming from molecular studies, as well as those related to clinical, diagnostic and therapeutic aspects. In the latter section, we give particular attention to the guideline on paracoccidioidomycosis organized by specialists in this subject.     

In vivo and in vitro effects of 42-hydroxy-palytoxin on mouse skeletal muscle: Structural and functional impairment

Palytoxins (PLTXs) are known seafood contaminants and their entrance into the food chain raises concern about possible effects on human health. The increasing number of analogs being identified in edible marine organisms complicates the estimation of the real hazard associated with the presence of PLTX-like compounds. So far, 42-OH-PLTX is one of the few congeners available, and the study of its toxicity represents an important step toward a better comprehension of the mechanism of action of this family of compounds. From this perspective, the aim of this work was to investigate the in vivo and in vitro effect of 42-OH-PLTX on skeletal muscle, one of the most sensitive targets for PLTXs. Our results demonstrate that 42-OH-PLTX causes damage at the skeletal muscle level with a cytotoxic potency similar to that of PLTX. 42-OH-PLTX induces cytotoxicity and cell swelling in a Na⁺-dependent manner similar to the parent compound. However, the limited Ca²⁺-dependence of the toxic insult induced by 42-OH-PLTX suggests a specific mechanism of action for this analog. Our results also suggest an impaired response to the physiological agonist acetylcholine and altered cell elasticity.     

A Case of Compound Mutations in the MYBPC3 Gene Associated with Biventricular Hypertrophy and Neonatal Death

Hypertrophic cardiomyopathy (HCM) is a familial, genetically determined, primary cardiomyopathy caused by mutations in genes coding for proteins of the sarcomere, or, less frequently, genes involved in storage diseases. In pediatric settings, pure HCM has an estimated incidence of 4.7 per million children. The disease is often sub-clinical and goes unrecognized mainly because most patients with HCM have only mild symptoms, if any. However, sudden cardiac death, the most dramatic clinical occurrence and the primary concern for patients and physicians alike, may be the first manifestation of the disease. We describe a case of compound heterozygosity in the MYBPC3 gene (p.Glu258Lys and IVS25-1G>A) associated with biventricular hypertrophy, atrial enlargement and subsequent neonatal death 33 days postpartum. Other studies have reported compound and/or double heterozygosis in the same or different sarcomeric genes during childhood and adulthood, and neonatal presentations have also been described. Our observations show that the combination of a missense (p.Glu258Lys) and a splice-site mutation (IVS25-1G>A) profoundly affects the clinical course. In families in which parental mutations are known, preimplantation (where ethically and legally feasible) or prenatal genetic screening should be adopted because: (1) neonatal HCM in genetic heterozygosity is potentially lethal and (2) heart disease is the most common developmental malformation and the leading cause of neonatal mortality and morbidity.