The use of vesicular stomatitis virus (visna virus) pseudotypes to demonstrate visna virus receptors in cells from different species

Summary Superinfection of visna virus (VV)-infected cells with vesicular stomatitis virus (VSV) resulted in the formation of a pseudotype virus population containing a VSV genome within a VV coat [designated VSV (VV)] as determined by plaque reduction neutralization with antisera to VSV and VV. These VSV (VV) virions were capable of infecting cell cultures from a number of species that were nonpermissive for VV alone. Limited propagation of VV in some mammalian species would thus appear to be due to an intracellular restriction rather than to absence of VV receptors.     

The characterization of Gardnerella vaginalis DNA using non-radioactive DNA probes

DNA restriction profiles of various Gardnerella vaginalis isolates, generated by BamHI, EcoRI, PstI and other restriction enzymes, varied considerably. Only a few DNA fragments were identified as common in ethidium bromide fluorescence profile and Southern-blot hybridization patterns (employing a digoxigenin-labelled G. vaginalis DNA probe and an enzyme-linked immunoassay detection method). While the efficiencies of Southern-blot hybridization appeared inconsistent, in dot-blot assays, DNA from each isolate hybridized readily, enabling the detection of at least 10 ng DNA. A 5.7-kb DNA fragment from G. vaginalis ATCC 14018 genomic library, cloned in the BamHI site of pBR322, could replace the total genomic DNA probe. This specific DNA fragment was present in different sizes in 12 analysed G. vaginalis strains, describing a restriction fragment length polymorphism. In control studies, none of the DNA from bacteria other than G. vaginalis (including some genitourinary tract residents) hybridized with the G. vaginalis total or specific DNA probes. Non-radioactive G. vaginalis DNA probes can thus form the basis of a useful detection method for further studies of this organism.     

Persistent tubular conduction in vacuolated amphibian skeletal muscle following osmotic shock

The transverse (T-)tubules primarily function in conducting the action potentials that initiate excitation– contraction coupling in skeletal muscle but may additionally subserve longer-term roles in volume regulation, membrane fusion and other trafficking processes. Osmotic shock thus both electrically detaches the T-tubules from surface membrane (‘detubulation’) and produces tubular vacuolation. The present experiments separated these effects. An established, reference osmotic shock protocol that exposed muscles to Ca²⁺/Mg²⁺-Ringer and gradual cooling to 10°C after 18 min in glycerol–Ringer accomplished significant detubulation (77.5 ± 13.15%, mean ± SEM; n = 4). In contrast, a test protocol conducted entirely at room temperature using Mg²⁺-rather than Ca²⁺/Mg²⁺-Ringer yielded reduced (P < 0.05, post hoc Duncan's multiple range test) detubulation indices (1.67 ± 1.67%, n = 6) statistically indistinguishable from findings in fibres spared osmotic shock. Yet both osmotic shocks caused a formation of closed vacuoles, demonstrated by Sulphorhodamine B trapping, that occupied statistically similar fractions of total fibre volume (reference procedure: 14.38 ± 2.7%, n = 6; test procedure: 13.36 ± 2.00%, n = 22) in turn higher than determinations in control fibres (P < 0.05). The findings reconcile reports associating detubulation with vacuolation in osmotically shocked muscle [S. Nik-Zainal et al. (1999) J Muscle Res Cell Motil 20: 45–53; K.N. Khan et al. (2000) J Muscle Res Cell Motil 21: 79–90] with the persistence of tubular electrical activity in extensively vacuolated amphibian fibres following fatigue [J. Lannergren and H. Westerblad (1987) Acta Physiol Scand 129: 311–318; J. Lannergren et al. (1999) J Muscle Res Cell Motil 20: 19–32]. Furthermore test protocols produced higher densities of open vacuoles (13.38 ± 2.33%, n = 9) than did reference protocols (6.66 ± 1.63%, n = 20) contrary to their possible involvement in the electrophysiological changes. Abolition of tubular electrophysiological activity thus either follows or is independent of tubular vacuolation whilst sharing some of its underlying osmotic mechanisms. This revised version was published online in July 2006 with corrections to the Cover Date.     

The reproducibility of the mandibular cortical index

OBJECTIVES: To assess the reproducibility and diagnostic validity of Mandibular Cortical Index (MCI) when used by minimally trained observers. METHODS: Four 'experts' and 45 final-year dental students classified the appearance of the lower border of the mandibular cortex in 30 panoramic radiographs using the MCI. Experts viewed the original radiographs. The students received instruction in the MCI and viewed slides of the radiographs in a lecture theatre. RESULTS: For intra-observer agreement, the experts had significantly higher overall values of weighted kappa, indicating substantial agreement in MCI assessment, whereas the students showed moderate agreement. For inter-observer agreement, there was fair agreement between the experts and poor agreement between the students. Using the experts' MCI assessment as the 'gold standard', the mean sensitivity of the students in diagnosis of C3 was 0.71 (maximum 0.95, minimum 0.25) and mean specificity was 0.56 (maximum 0.9, minimum 0.20). CONCLUSIONS: The MCI has important limitations in terms of intra- and inter-observer agreement. Minimal training in its use, such as might be given in a lecture format to dentists, was ineffective and associated with poor inter-observer agreement and limited diagnostic validity in identifying signs of osteoporosis. More lengthy training and experience in using the MCI would be needed for it to be effective as a diagnostic tool in general dental practice.