Image analysis of fundus photographs. The detection and measurement of exudates associated with diabetic retinopathy.

A computer-based image analysis system was used to detect and measure exudates in fundus photographs. A fundus transparency was imaged, digitized, and stored in image memory. The stored image was then processed by several operators, to reduce shade variations in the image background and enhance the contrast between this background and the exudates. Exudates were separated from the background on the basis of their brightness or "gray level" and were then copied in to a binary image. For comparative purposes, the binary image was superimposed on the original unprocessed image. Exudate areas were measured using the binary image, which was also transferred to a printer to provide a permanent record or "exudate map." The system was able to discriminate between standard photographs used to grade hard exudates in the Early Treatment for Diabetic Retinopathy Study (ETDRS). It was also used to monitor the response of a subject to laser treatment.

Dermatan sulphate proteoglycans from sclera examined by rotary shadowing and electron microscopy.

Two dermatan sulphate-containing proteoglycans from bovine sclera were examined by rotary shadowing and electron microscopy, and the results were compared with previous biochemical findings. Both the large iduronate-poor proteoglycan (PGI) and the small iduronate-rich proteoglycan (PGII) possessed a globular proteinaceous region. Whereas PGI had a branched extension from the globular region, with five to eight side chains attached to it, PGII had only a single tail, which was of glycosaminoglycuronan. PGII aggregated via globular-region interactions, which were much diminished by reduction and alkylation. PGI aggregated via side chains and globular-region interactions. Although a few PGI aggregates were large, and similar to the hyaluronan-cartilage proteoglycan aggregates [Weidemann, Paulsson, Timpl, Engel & Heinegård (1984) Biochem. J. 224, 331-333], hyaluronan did not cause enhanced aggregation. PGII is very similar in shape to the small cartilage chondroitin sulphate proteoglycan, whereas PGI somewhat resembles the large cartilage chondroitin sulphate proteoglycan, although with many fewer glycosaminoglycan side chains, and probably only one globular region as opposed to two in the cartilage proteoglycan.

Collagen self-assembly in vitro: electron microscopy of initial aggregates formed during the lag phase.

Initial aggregates formed in collagen self-assembly were visualized by electron microscopy, using formaldehyde to fix the state of aggregation at various points in the turbidimetric lag phase. Measurements of the length distributions of monomers and small oligomers show that the first-formed aggregates are dimeric, with the most prevalent dimer having a maximal (approximately equal to 4D; D = 67 nm) stagger between constituent molecules.