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A number of growth factors have been implicated in the development and perpetuation of preretinal fibrovascular membranes in patients with proliferative diabetic retinopathy (PDR). The aim of this study was to determine the potential role of epidermal growth factor (EGF), transforming growth factor alpha (TGF-a), and their receptor (EGF-R) in PDR development. Immunostaining for EGF, TGF-a, and EGF-R was compared between normal retina, PDR retina, and PDR preretinal membranes. Weak staining for EGF and EGF-R was observed throughout the neural retina from non-diabetic eyes while weak to moderate staining for TGF-a was observed in the ganglion cell layer and the inner and outer nuclear layers. In contrast, intense staining for EGF and TGF-a and moderate staining for EGF-R were observed throughout the PDR retina. Immunoreactivity for EGF, TGF-a, and EGF-R was seen in the majority of the 11 excised membranes studied and, though variable, was generally greater than that observed in normal retinas. These results suggest an autocrine/paracrine role for EGF, TGF-a, and EGF-R in PDR. (BrJ Ophthalmol 1994; 78:

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1. The subcellular localization of dihydroxyacetone-phosphate acyltransferase (DHAPAT) (assayed in the presence of pyrophosphate) and glucose-6-phosphate dehydrogenase (NADP+-dependent) activity in mouse kidney was investigated by density-gradient centrifugation. 2. DHAPAT has a predominantly peroxisomal distribution, and the activity in purified peroxisomes is stimulated by various organic and inorganic phosphate-containing compounds. The pH optimum is acid. 3. Approx. 10% of the cellular NADP+-dependent glucose-6-phosphate dehydrogenase activity is associated with peroxisomal fractions and may provide a source of NADPH for the peroxisomal reduction of acyl-dihydroxyacetone phosphate formed by DHAPAT activity.

Benzamides are potent inhibitors of nuclear ADP-ribosyltransferase and have been extensively used to demonstrate the involvement of ADP-ribosylation in cellular function. When permeabilized L1210 cells are treated with 50 microM 3-acetylamidobenzamide (3-aab) the enzyme is inhibited. However, when 50 nM 3-aab is used a two-fold stimulation of enzyme activity is produced. This anomalous stimulation is obtained with benzamides and nicotinamides and is correlated with their activity as inhibitors. Strikingly the steady-state level of poly(ADP-ribose) in intact cells is increased by these low levels of inhibitors. The mechanisms of this effect and its consequences for the experimental use of benzamides are discussed.