Approaches in the understanding of morbillivirus neurovirulence

Certain members of the morbillivirus genus, canine distemper virus, phocine distemper virus, and the cetacean viruses of dolphins and porpoises exhibit high levels of central nervous system (CNS) infection in their natural hosts. CNS complications are rare for measles virus (MV) and are not associated with rinderpest virus (RPV) and peste des petits ruminants virus (PPRV) infection. However, both RPV and PPRV are neurovirulent in permissive murine strains. Human postmortem tissue, neural cell cultures, and animal models have been used to answer major questions concerning morbillivirus neurovirulence. Studies of the MV CNS complication subacute sclerosing panencephalitis (SSPE) indicate that virus could enter the CNS either by direct infection of endothelial cells or in infected leucocytes, followed by infection of predominately neurones and oligodendrocytes. It has been established that MV neurovirulence in mice is partially determined by the virus-receptor specificity. The two known MV receptors, CD46 and SLAM, have been examined in normal and SSPE brain tissue and the findings suggest that further receptors may be necessary to explain infection of the CNS with wild-type strains of MV. In both humans and mice (and in vitro), once infection of neurones has been established, virus spreads transneuronally. It is possible that all morbilliviruses transiently infect the CNS in their natural hosts, but development of disease is dependent on the efficiency of the immune response. Alternatively, for RPV and PPRV, virus entry may be restricted due either to absence of viral receptors or failure of virus to replicate or spread in the CNS.     

ATP suppresses activity in slowly adapting but not rapidly adapting mechanoreceptors in toad skin

To test the possible role of ATP in transducing or modulating touch sensation, an isolated skin-nerve preparation from the toad, Bufo marinus, perfused on the inner side, was used to examine the effects of ATP on slowly adapting (SA) and rapidly adapting (RA) mechanoreceptors, identified by ramp and hold indentation of the skin. ATP (1-50 mM) did not generate impulse activity in either SA or RA mechanoreceptors nor increase their responses to mechanical stimulation. Instead, ATP (> or =5 mM) reversibly and selectively suppressed impulse discharge from SA mechanoreceptors. Our results indicate that while ATP may modulate the responses of specific touch receptors, it is not involved in transducing touch into nerve impulses.     

Preliminary report on the validation of a grammar-based computer system for assessing skeletal maturity with the Tanner-Whitehouse 2 method

A series of hand and wrist radiographs was assessed manually by two individuals and by a fully automated computer system for determining bone age. Assessments were repeated after 1 month to determine variability between and within the methods of bone age assessment. There was slight intra-observer variation, but complete reproducibility when assessments were made by computer. The variation between the human assessors was less than that between human and computer assessments. The difference between overall maturity scores made by the human observer and the computer system was, however, acceptably small, and the majority of assessments were the same. It is concluded this computer system for assessing bone age in normal children is reliable and accurate, but that it needs to be validated against a much larger set of radiographs.