A role of Hsp60 in autoimmune diabetes: analysis in a transgenic model

A pathogenic role for self-reactive cells against the stress protein Hsp60 has been proposed as one of the events leading to autoimmune destruction of pancreatic beta cells in the diabetes of nonobese diabetic (NOD) mice. To examine this hypothesis, we generated transgenic NOD mice carrying a murine Hsp60 transgene driven by the H-2E alpha class II promoter. This would be expected to direct expression of the transgene to antigen-presenting cells including those in the thymus and so induce immunological tolerance by deletion. Detailed analysis of Hsp60 expression revealed that the endogenous gene is itself expressed strongly in thymic medullary epithelium (and weakly in cortex) yet fails to induce tolerance. Transgenic mice with retargeted Hsp60 showed overexpression of the gene in thymic cortical epithelium and in bone marrow-derived cells. Analysis of spontaneous T-cell responses to a panel of self and heterologous Hsp60 antigens showed that tolerance to the protein had not been induced, although responses to an immunodominant 437-460 epitope implicated in disease were suppressed, probably indicating an epitope shift. This correlated with changes in disease susceptibility: insulitis in transgenic mice was substantially reduced so that pathology rarely progressed beyond periislet infiltration. This was reflected in a substantial reduction in hyperglycemia and disease. These data indicate that T cells specific for some epitopes of murine Hsp60 are likely to be involved in the islet-cell destruction that occurs in NOD mice.     

Causal or casual? The role of causality assessment in pharmacovigilance

As with any other study method, 'spontaneous reporting' in pharmacovigilance is a process of data acquisition, assessment, presentation and interpretation. The provision of information (i.e. of interpreted data) concerning previously unknown, or otherwise important adverse drug reactions is a major goal. The assessment of case reports in spontaneous reporting takes place in 2 steps: first the assessment of each case individually, and secondly the interpretation of the aggregated data. The latter step is only completed for a minority of case reports, such as when actions or measures are deemed necessary. Uncertainty in case reports regarding the involvement of the suspected drugs is an inherent drawback of spontaneous reporting. Standardised case-causality assessment has become a routine at pharmacovigilance centres around the world. It aims at a decrease in ambiguity of the data and plays a role in data exchange and the prevention of erroneous conclusions. A variety of systems for standardised causality assessment have been developed, ranging from short questionnaires to comprehensive algorithms. Since none of the available assessment systems has been validated (i.e. shown to consistently and reproducibly produce a fair approximation of the truth), causality assessment has only limited scientific value. Causality assessment neither eliminates nor quantifies uncertainty but, at best, categorises it in a semiquantitative way. Routine causality assessment is usually part of the first step in case assessment, and is based on a general system that is intended for all reactions and all drugs. During the subsequent phase of aggregated assessment, causality assessment is likely to be repeated and the use of a specific aetiological-diagnostic system may be more appropriate. It may be recommended to restrict case-causality assessment to selected case reports that are likely to play an active role in pharmacovigilance and to use specific systems, adapted to the reaction or problem involved. It is an inherent limitation of spontaneous reporting that, with the exception of rare proof-positive case reports, conclusive evidence cannot usually be produced. Standardised causality assessment has not really changed this situation. As a rule, confirmation of the connection between a drug and an adverse reaction requires further analytical or experimental study.     

Failure to detect intrauterine growth restriction following in utero exposure to MRI

Echo planar imaging is a form of MRI with short image acquisition times, which permits in utero fetal imaging without motion artefacts. Echo planar imaging has been used to measure accurately fetal organ volume and to assess placental function. Two small animal studies have suggested the possibility of intrauterine growth restriction consequent upon MRI. We thus performed a prospective study of pregnancies in which fetuses were exposed to echo planar imaging, compared with a control group in which there was no in utero echo planar imaging exposure. There were no significant differences between the groups when maternal age, parity, proportion of smokers and proportion of Caucasian women were compared. Although the gestational age of delivery was lower in the echo planar imaging group, the proportion of women delivering prematurely was not significantly different. Although infant birthweights were significantly lower in the MRI group, the corrected birthweight for gestational age centiles (individualized birthweight ratio) was not significantly different between the two groups. In utero exposure to echo planar imaging thus did not have a marked effect on intrauterine fetal growth. A 10 year follow-up study of all infants imaged in utero is being performed.     

An investigation of hippocampal theta rhythm of rats as a nonlinear dynamic process

The results of an investigation of the hippocampal theta rhythm of rats in the paradoxical phase of sleep and during orienting behavior by the method of estimation of attractor dimension are presented in this article. It has been demonstrated that the hippocampal theta rhythm consists of a regular constituent and an irregular constituent of high dimension, the interrelationship of which varies within wide limits depending upon the state of the animal. Frequency components of the regular and irregular constituents were identified. The mechanisms of their formation are considered and some hypotheses regarding their biological nature are proposed.     

Genetic counselling and gene mutation analysis in familial adenomatous polyposis in Western Australia

OBJECTIVE: To assess the provision of accurate pre-symptomatic genetic testing with DNA analysis and appropriate counselling for individuals and families known to be at high risk of developing familial adenomatous polyposis coli (FAP). PATIENTS AND METHODS: Thirty-one families with clinically and pathologically documented FAP were ascertained from the Western Australian Polyposis Registry. DNA was collected from over 200 individuals in these families to establish their genetic risk status for FAP, either by direct mutation analysis, or by linkage analysis. Individuals undergoing DNA testing were given intensive psychosocial support and counselling. RESULTS: In 19 families DNA-based counselling could not be offered because either the adenomatous polyposis coli (APC) gene mutation could not be detected or there were insufficient family members for linkage analysis. Gene testing yielded mutations of the APC gene in 87 individuals from 12 families; by gene tracking (or linkage analysis) in three families and by mutation analysis in the remaining nine (four of which had only one affected individual). DNA results conformed with a definite clinicopathological diagnosis in 27 FAP patients and, of the remaining 60 high-risk subjects tested, 14 had inherited the mutated APC gene. CONCLUSIONS: DNA analysis allowed accurate genetic counselling for 12 of 31 families affected by FAP, thus improving the medical and personal management in asymptomatic people who would otherwise be subjected to the uncertainty of long term surveillance and repeated colonic examinations. In future a superior biomolecular approach to gene mutation analysis, such as the protein truncation test, will facilitate management for most FAP individuals and families.     

In vitro-in vivo myotoxicity of intramuscular liposomal formulations

PURPOSE: The first objective was to study the in vitro myotoxicity of empty liposomes and to examine whether liposome size, charge and fluidity affect of liposomal myotoxicity. The second objective was to investigate the effect of liposomal encapsulation on the in vitro and in vivo myotoxicity of loxapine compared to the loxapine commercial preparation (Loxitane). METHODS: The in vitro myotoxicity of empty liposomes and loxapine liposomes was evaluated by the cumulative efflux of the cytosolic enzyme creatine kinase (CK) from the isolated rat extensor digitorum longus (EDL) muscle over a 2 hour period. In the in vivo studies, the area under plasma CK curve over 12 hours was used to evaluate muscle damage. RESULTS: The in vitro myotoxicity for all empty liposomal formulations was not statistically different from negative controls (untreated control muscles and normal saline injected muscles). However, these empty liposomal formulations were significantly less myotoxic than the positive controls (muscles injected with phenytoin and muscle sliced in half). In vitro-in-vivo studies showed that the liposomal encapsulation of loxapine resulted in significant (P < 0.05) reduction in myotoxicity (80% in vitro and 60% in vivo) compared to the commercially available formulation which contains propylene glycol (70% V/V) and polysorbate 80 (5% W/V) prepared at equal concentration. CONCLUSIONS: Results indicate that empty liposomes do not induce myotoxicity. Furthermore, liposomal size, charge and fluidity do not affect myotoxicity. In addition, in vitro and in vivo studies have demonstrated that liposomal encapsulation of loxapine can reduce myotoxicity compared to a formulation containing organic cosolvents.     

Diagnosis of deep vein thrombosis, an overview

This article reviews the role of dendritic cells in cutaneous immunity. Langerhans cells (LC) found in the epidermis are the best-characterized dendritic cell population. They have the ability to process antigen in the periphery, transport it to the draining lymph nodes (DLN) where they are able to cluster with, and activate, antigen-specific naive T cells. During migration LC undergo phenotypic and functional changes which enable them to perform this function. There are other less well-characterized dendritic cells including dendritic epidermal T cells, dermal dendrocytes and dermal "LC-like' cells. Although there is no evidence that dendritic epidermal T cells (DETC) can present antigen or migrate to lymph nodes, they do influence the intensity of cutaneous immune responses to chemical haptens. Antigen-presenting cells (APC) in the dermis may provide alternative routes of antigen presentation which could be important in the regulation of skin immune responses. Therefore, dendritic cells are vital for the induction of immune responses to antigens encountered via the skin. LC are particularly important in primary immune responses due to their ability to activate naive T cells. The faster kinetics of secondary responses, and the ability of nonprofessional APC to induce effector function in previously activated cells, suggest that antigen presentation in the DLN may be less important in responses to previously encountered antigens. In these secondary responses, dendritic and nondendritic APC in the skin may directly induce effector functions from antigen-specific recirculating cells.