Ultrastructural and molecular analysis of Bowman's layer corneal dystrophies: an epithelial origin?

PURPOSE: Two mutations (R555Q and R124L) in the BIGH3 gene have been described in anterior or Bowman's layer dystrophies (CDB). The clinical, molecular, and ultrastructural findings of five families with CDB was reviewed to determine whether there is a consistent genotype:phenotype correlation. METHODS: Keratoplasty tissue from each patient was examined by light and electron microscopy (LM and EM). DNA was obtained, and exons 4 and 12 of BIGH3 were analyzed by polymerase chain reaction and single-stranded conformation polymorphism/heteroduplex analysis. Abnormally migrating products were analyzed by direct sequencing. RESULTS: In two families with type I CDB (CDBI), the R124L mutation was defined. There were light and ultrastructural features of superficial granular dystrophy and atypical banding of the "rod-shaped bodies" ultrastructurally. Patients from three families with "honeycomb" dystrophy were found to carry the R555Q mutation and had characteristic features of Bowman's dystrophy type II (CDBII). CONCLUSIONS: There is a strong genotype:phenotype correlation among CBDI (R124L) and CDBII (R555Q). LM and EM findings suggest that epithelial abnormalities may underlie the pathology of both conditions. The findings clarify the confusion over classification of the Bowman's layer dystrophies

Palladium nanoparticle deposition on spherical carbon supports for heterogeneous catalysis in continuous flow

Heterogeneous catalysis is widely exploited by the chemical industry, both in batch reactors and in continuous flow, the latter via the use of packed bed reactors. Unfortunately, the transfer of commercially available heterogeneous catalysts to high pressure flow systems is often difficult, with challenges such as catalyst deactivation through metal leaching, and the crushing of pelleted supports. Thus, the limited availability of suitable catalysts for heterogeneous flow processes, which can satisfy all the requirements for its application, is a major bottle neck in the commercial implementation of these systems. Polymer-based spherical activated carbon beads (diameter = 474 ± 96 μm) offer a promising solution: these small, spherical and monodisperse beads have high mechanical strengths and large surface areas (1583 ± 8 m2 g−1), offering desirable properties for this task, such as reproducible packing and low pressure drops across packed catalyst beds. Two series of Pd/C spherical bead catalysts were synthesised and compared to a commercial catalyst from Johnson Matthey (1 wt% Pd/C pellets), in small scale screenings (20 mg) via a recirculating batch platform, for their activity in a model nitro reduction reaction. It was observed that small, robust, highly active palladium nanoparticles (PdNPs) supported on spherical carbon beads with a narrow size distribution (e.g. 1e – Pd – dNP = 5.0 ± 1.4 nm) can be synthesised via solution phase deposition. In contrast, the NP catalysts made via gas phase deposition were much larger (e.g. 2e – Pd – dNP = 22.8 ± 13.1 nm), less active and unstable due to metal leaching. The applicability of these NP catalysts for use in continuous flow was subsequently demonstrated on a larger scale (0.5–1 g), with a high activity and stability achieved over a two day operating period. This work demonstrates the production of an active, stable heterogeneous catalyst suitable to be employed in a pilot scale continuous flow packed bed reactor, for the production of APIs