A solid-phase radioimmunoassay using digitonin-permeabilized cells to screen surface or intracellular membrane-bound antigens

Membrane-bound receptor or enzyme distribution between cell surface and cell interior can be determined using the non-ionic detergent digitonin. A solid-phase radioimmunoassay using myocardial cells from newborn rats was performed to screen hybridoma culture supernatants and the cells were rendered permeable with increasing concentrations of digitonin (0-0.1%). This was achieved in 5 min at 37 degrees C and did not require the continuous presence of detergent. A characteristic amount of cytoplasmic protein (approximately equal to 45%) was released with subunit molecular weights of up to 200,000. This allowed exogenous molecules such as immunoglobulin G to gain access to the intracellular targets. The binding to rat myocardial cells of 36 monoclonal antibodies was examined by this procedure. The binding assays were carried out for 30 min at 37 degrees C using cells previously treated for 10 min with 0.05% of digitonin. This appears to be a simple and rapid method of screening and selecting the hybridoma culture supernatants.     

Pseudoepidemic of Aspergillus niger infections traced to specimen contamination in the microbiology laboratory

We report a pseudo-outbreak of Aspergillus niger that followed building construction in our clinical microbiology laboratory. Because outbreaks of invasive aspergillosis have been linked to hospital construction, strategies to minimize dust in patient care areas are common practice. We illustrate that the impact of false-positive cultures on patient care should compel laboratories to prevent specimen contamination during construction.     

Hereditary Spastic Paraplegia Type 43 (SPG43) is Caused by Mutation in C19orf12

We report here the genetic basis for a form of progressive hereditary spastic paraplegia (SPG43) previously described in two Malian sisters. Exome sequencing revealed a homozygous missense variant (c.187G>C; p.Ala63Pro) in C19orf12, a gene recently implicated in neurodegeneration with brain iron accumulation (NBIA). The same mutation was subsequently also found in a Brazilian family with features of NBIA, and we identified another NBIA patient with a three‐nucleotide deletion (c.197_199del; p.Gly66del). Haplotype analysis revealed that the p.Ala63Pro mutations have a common origin, but MRI scans showed no brain iron deposition in the Malian SPG43 subjects. Heterologous expression of these SPG43 and NBIA variants resulted in similar alterations in the subcellular distribution of C19orf12. The SPG43 and NBIA variants reported here as well as the most common C19orf12 missense mutation reported in NBIA patients are found within a highly conserved, extended hydrophobic domain in C19orf12, underscoring the functional importance of this domain.