Irreversible binding with biological macromolecules and effects in bacterial mutagenicity tests of the radical cation of promethazine and photoactivated promethazine. Comparison with chlorpromazine

The irreversible binding of the radical cation of promethazine (PMZ+.) to DNA and protein in vitro and bacterial macromolecules in situ has been studied. Binding experiments were performed with synthesized [35S] promethazine. The results are compared to those with the chlorpromazine radical cation (CPZ+.). Secondary reaction products which result from fission of the alkylamino side chain are involved in the macromolecular binding of PMZ+. Compared to CPZ+. the covalent DNA binding of PMZ+. is significantly less. A larger amount of PMZ+. binds to single-stranded DNA than to double-stranded DNA. The extent of binding to proteins and RNA is of the same order as that of CPZ+. Bacterial mutagenicity tests show that the low genotoxicity of PMZ+. is related to the low DNA binding. The bacterial cytotoxicity is possibly related to the covalent protein binding. Similar results have been obtained with photoactivated promethazine (PMZ) and chlorpromazine (CPZ). The role of radical cations in the photosensitization and metabolic activation of phenothiazine drugs is discussed.     

Associations between Lifetime Traumatic Events and Subsequent Chronic Physical Conditions: A Cross-National,Cross-Sectional Study

Background

Associations between lifetime traumatic event (LTE) exposures and subsequent physical ill-health are well established but it has remained unclear whether these are explained by PTSD or other mental disorders. This study examined this question and investigated whether associations varied by type and number of LTEs, across physical condition outcomes, or across countries.

Methods

Cross-sectional, face-to-face household surveys of adults (18+) were conducted in 14 countries (n = 38, 051). The Composite International Diagnostic Interview assessed lifetime LTEs and DSM-IV mental disorders. Chronic physical conditions were ascertained by self-report of physician''s diagnosis and year of diagnosis or onset. Survival analyses estimated associations between the number and type of LTEs with the subsequent onset of 11 physical conditions, with and without adjustment for mental disorders.

Findings

A dose-response association was found between increasing number of LTEs and odds of any physical condition onset (OR 1.5 [95% CI: 1.4–1.5] for 1 LTE; 2.1 [2.0–2.3] for 5+ LTEs), independent of all mental disorders. Associations did not vary greatly by type of LTE (except for combat and other war experience), nor across countries. A history of 1 LTE was associated with 7/11 of the physical conditions (ORs 1.3 [1.2–1.5] to 1.7 [1.4–2.0]) and a history of 5+ LTEs was associated with 9/11 physical conditions (ORs 1.8 [1.3–2.4] to 3.6 [2.0–6.5]), the exceptions being cancer and stroke.

Conclusions

Traumatic events are associated with adverse downstream effects on physical health, independent of PTSD and other mental disorders. Although the associations are modest they have public health implications due to the high prevalence of traumatic events and the range of common physical conditions affected. The effects of traumatic stress are a concern for all medical professionals and researchers, not just mental health specialists.     

Characterisation of P. falciparum antigenic determinants isolated from a genomic expression library by differential antibody screening.

A genomic expression library of P.falciparum has been differentially screened with a number of immune sera. The response of 9 clones to the various sera is presented, together with the DNA sequence encoding the epitopes. All but one clone are extremely A+T rich and unlike the other P.falciparum epitopes described, are not composed of amino acid repeats. One clone, which responds specifically with a protective serum, has been analysed in detail. The epitope is carried on a 160kd antigen which is transcribed from a single gene to give a protein expressed in all of the erythrocytic forms. DNA sequence of this clone reveals it to have more than one open reading frame, only one of which is transcribed in the blood stages. The possible significance of the other open readings frames is discussed.     

The urban environment and mental disorders: Epigenetic links

For the first time in human history, more than half of the world''s population lives in urban areas and this is projected to increase to two-thirds by 2030. This increased urbanity of the world''s population has substantial public health implications. Nearly a century of research has shown higher risk of mental disorder among persons living in urban versus rural areas. Epidemiologic research has documented that associations between particular features of the urban environment, such as concentrated disadvantage, residential segregation and social norms, contribute to the risk of mental illness. We propose that changes in DNA methylation may be one potential mechanism through which features of the urban environment contribute to psychopathology. Recent advances in animal models and human correlation studies suggest DNA methylation as a promising mechanism that can explain how the environment “gets under the skin.” Aberrant DNA methylation signatures characterize mental disorders in community settings. Emerging evidence of associations between exposure to features of the environment and methylation patterns may lead toward the identification of mechanisms that explain the link between urban environments and mental disorders. Importantly, evidence that epigenetic changes are reversible offers new opportunities for ameliorating the impact of adverse urban environments on human health.Key words: urban environment, mental disorders, DNA methylation, epigenetics, posttraumatic stress disorder, depressionThe 20th century has been characterized by the world-wide movement of populations from rural to urban areas. For the first time in human history, more than half of the world''s population lives in urban areas and this is projected to increase to two-thirds by 2030. The movement of populations to urban environments is probably the most important demographic shift in the past century. In particular, the increased urbanity of the world''s population has substantial public health implications. A body of research has long shown that there are different burdens of disease and disability in urban vs. non-urban areas and more recent work has linked specific features of the urban environment to particular health indicators (for reviews of the literature about urban health see refs. ¹ and ²).Some of the more promising work in this area concerns research that has shown relations between urbanity and mental disorders. There is more than a century of work that has shown higher risk of most mental disorders among persons living in urban versus rural areas.^3–8 Early research proposed several factors that may explain this association including selective migration and social disorganization.³ For example, it has been proposed that persons within disadvantaged areas may have a more difficult time building and sustaining supportive social relationships, therefore increasing susceptibility to mental illness. Subsequent work has shown associations between particular features of the urban environment and risk of mental illness. Living in poorer urban neighborhoods is associated with greater risk of new episodes of depression compared to living in richer neighborhoods, even when accounting for individual income or exposure to stressful or adverse circumstances.^6,9,10 Living in neighborhoods characterized by residential racial segregation is associated with a greater risk of depression and anxiety, compared to living in less segregated neighborhoods.¹¹ Other evidence suggests that neighborhood collective efficacy and norms are associated with the risk of substance use disorders12 and suicide attempts,¹³ again when taking into account individual experiences.Coincident with the growing number of studies that have demonstrated links between features of the urban environment and mental health, there has been an increase in work that has sought to understand the mechanisms underlying these epidemiologic observations. In particular, there is an emerging interest in identifying biologic explanations that may clarify the link between features of the urban environment and individual mental health. Existing research has documented a role for changes in immune function,¹⁴ gene-environment interactions¹⁵ and psychological mechanisms,¹⁶ among others, that may explain the links between the urban environment and mental health. This paper adds to this growing field and proposes that changes in DNA methylation may be one potential mechanism through which features of the urban environment contribute to psychopathology.     

Novel mouse model reveals distinct activity-dependent and -independent contributions to synapse development

The balanced action of both pre- and postsynaptic organizers regulates the formation of neuromuscular junctions (NMJ). The precise mechanisms that control the regional specialization of acetylcholine receptor (AChR) aggregation, guide ingrowing axons and contribute to correct synaptic patterning are unknown. Synaptic activity is of central importance and to understand synaptogenesis, it is necessary to distinguish between activity-dependent and activity-independent processes. By engineering a mutated fetal AChR subunit, we used homologous recombination to develop a mouse line that expresses AChR with massively reduced open probability during embryonic development. Through histological and immunochemical methods as well as electrophysiological techniques, we observed that endplate anatomy and distribution are severely aberrant and innervation patterns are completely disrupted. Nonetheless, in the absence of activity AChRs form postsynaptic specializations attracting motor axons and permitting generation of multiple nerve/muscle contacts on individual fibers. This process is not restricted to a specialized central zone of the diaphragm and proceeds throughout embryonic development. Phenotypes can be attributed to separate activity-dependent and -independent pathways. The correct patterning of synaptic connections, prevention of multiple contacts and control of nerve growth require AChR-mediated activity. In contrast, myotube survival and acetylcholine-mediated dispersal of AChRs are maintained even in the absence of AChR-mediated activity. Because mouse models in which acetylcholine is entirely absent do not display similar effects, we conclude that acetylcholine binding to the AChR initiates activity-dependent and activity-independent pathways whereby the AChR modulates formation of the NMJ.     

Acetylcholine receptor channel subtype directs the innervation pattern of skeletal muscle

Acetylcholine receptors (AChRs) mediate synaptic transmission at the neuromuscular junction, and structural and functional analysis has assigned distinct functions to the fetal (alpha2beta(gamma)delta) and adult types of AChR (alpha2beta(epsilon)delta). Mice lacking the epsilon-subunit gene die prematurely, showing that the adult type is essential for maintenance of neuromuscular synapses in adult muscle. It has been suggested that the fetally and neonatally expressed AChRs are crucial for muscle differentiation and for the formation of the neuromuscular synapses. Here, we show that substitution of the fetal-type AChR with an adult-type AChR preserves myoblast fusion, muscle and end-plate differentiation, whereas it substantially alters the innervation pattern of muscle by the motor nerve. Mutant mice form functional neuromuscular synapses outside the central, narrow end-plate band region in the diaphragm, with synapses scattered over a wider muscle territory. We suggest that one function of the fetal type of AChR is to ensure an orderly innervation pattern of skeletal muscle.     

An unusual presentation of a malignant jejunal tumor and a different management strategy

BACKGROUND: Malignant small bowel tumors are very rare and leiomyosarcoma accounts for less than 15% of the cases. Management of these tumors is challenging in view of nonspecific symptoms, unusual presentation and high incidence of metastasis. In this case report, an unusual presentation of jejunal sarcoma and management of liver metastasis with radiofrequency ablation (RFA) is discussed. CASE PRESENTATION: A 45-year-old male presented with anemia and features of small bowel obstruction. Operative findings revealed a mass lesion in jejunum with intussusception of proximal loop. Resection of bowel mass was performed. Histopathological findings were suggestive of leiomyosarcoma. After 3-years of follow-up, the patient developed recurrence in infracolic omentum and a liver metastasis. The omental mass was resected and liver lesion was managed with radiofrequency ablation. CONCLUSION: Jejunal leiomyosarcoma is a rare variety of malignant small bowel tumor and a clinical presentation with intussusception is unusual. We suggest that an aggressive management approach using a combination of surgery and a newer technique like RFA can be attempted in patients with limited metastatic spread to liver to prolong the long-term survival in a subset of patients.     

Identification and characterisation of a novel KCNQ1 mutation in a family with Romano-Ward syndrome

Romano-Ward syndrome (RWS), the autosomal dominant form of the congenital long QT syndrome, is characterised by prolongation of the cardiac repolarisation process associated with ventricular tachyarrhythmias of the torsades de pointes type. Genetic studies have identified mutations in six ion channel genes, KCNQ1, KCNH2, SCN5A, KCNE1 and KCNE2 and the accessory protein Ankyrin-B gene, to be responsible for this disorder. Single-strand conformation polymorphism (SSCP) analysis and subsequent DNA sequence analysis have identified a KCNQ1 mutation in a family that were clinically conspicuous due to several syncopes and prolonged QTc intervals in the ECG. The mutant subunit was expressed and functionally characterised in the Xenopus oocyte expression system. A novel heterozygous missense mutation with a C to T transition at the first position of codon 343 (CCA) of the KCNQ1 gene was identified in three concerned family members (QTc intervals: 500, 510 and 530 ms, respectively). As a result, proline 343 localised within the highly conserved transmembrane segment S6 of the KCNQ1 channel is replaced by a serine. Co-expression of mutant (KCNQ1-P343S) and wild-type (KCNQ1) cRNA in Xenopus oocytes produced potassium currents reduced by approximately 92%, while IKs reconstitution experiments with a combination of KCNQ1 mutant, wild-type and KCNE1 subunits yielded currents reduced by approximately 60%. A novel mutation (P343S) identified in the KCNQ1 subunit gene of three members of a RWS family showed a dominant-negative effect on native IKs currents leading to prolongation of the heart repolarisation and possibly increases the risk of malign arrhythmias with sudden cardiac death.