Effect of latanoprost on intraocular pressure following cataract extraction.

PURPOSE: To compare the effect of latanoprost 0.005% with that of a placebo (balanced salt solution [BSS]) applied after phacoemulsification on intraocular pressure (IOP). SETTING: Pasco Eye Institute, New Port Richey, Florida, USA. METHODS: A group of patients having cataract extraction by phacoemulsification was randomized following surgery to receive one drop of latanoprost 0.005% (1.5 micrograms) or a placebo (BSS). Exclusion criteria included ocular diagnosis in addition to cataract, previous eye surgery, history of glaucoma, previous use of glaucoma medications, or vitreous loss during surgery. Standard phacoemulsification was performed through a scleral tunnel approach and a one-piece, poly(methyl methacrylate) intraocular lens implanted in the capsular bag. Approximately 24 hours after surgery, IOP was measured with a Goldmann applanation tonometer by the surgeon. The anterior chamber reaction was qualitatively graded from 1+ to 4+. RESULTS: The study included 103 eyes (latanoprost = 53; control = 50). Latanoprost treatment resulted in significantly lower postoperative (IOP) (16.4 mm Hg +/- 3.7 [SD]) than preoperative IOP (17.9 +/- 3.0 mm Hg) (P < .025). There was no decrease in postoperative IOP in the control group (18.2 +/- 3.5 mm Hg) compared with preoperative IOP (18.3 +/- 2.6 mm Hg). When two groups were compared, postoperative IOP after treatment with latanoprost was significantly less than control IOP (P < .01). Preoperative IOP was not significantly different in the placebo and latanoprost groups. Anterior chamber reaction was not increased by latanoprost; it averaged 1+ in both groups. CONCLUSIONS: Latanoprost may pharmacologically enhance uveoscleral outflow immediately after cataract extraction. In this study, latanoprost was a safe, effective method of reducing postoperative IOP.

pIV, a filamentous phage protein that mediates phage export across the bacterial cell envelope, forms a multimer.

Filamentous phage pIV is an outer membrane protein required for phage assembly and secretion. Chemical cross-linking and sedimentation experiments have been used to demonstrate that pIV from f1-infected Escherichia coli exists as a homo-multimer, probably composed of 10 to 12 subunits. pIV secreted from spheroplasts remains soluble and does not form multimers. Synthesis of pIV from distantly related filamentous phages or from a bacterial homolog that participates in a specialized form of extra-cellular protein secretion in the same cell with pIVf1 resulted in the formation of mixed multimers. This suggests that the homologous proteins themselves form homo-multimers. These structures could form gated channels that conduct assembling phage or specific substrate proteins across the outer membrane to the extracellular milieu.

A modified TnphoA useful for single-stranded DNA sequencing.

The TnphoA transposon constructed by Manoil and Beckwith [Proc. Natl. Acad. Sci. USA 82 (1985) 8129-8133] has been modified to permit easy isolation of single-stranded (ss) DNA of target plasmids. The intergenic region (IG) of filamentous phage f1, which consists of the phage origin of replication and packaging signal, was inserted into a nonessential region of TnphoA. This modified transposon should be useful for the analysis of genes cloned in plasmids that lack a filamentous phage IG. Transposition of TnphoA-IG into a plasmid carries the IG with it; subsequently, after infection with a filamentous helper phage, ss plasmid DNA suitable for sequence analysis and useful for oligodeoxyribonucleotide-mediated mutagenesis of TnphoA-generated fusions can be isolated. The utility of TnphoA-IG was confirmed by analysis of 'blue hops' into the bla (encoding beta-lactamase) and pspE (encoding phage shock protein) genes whose products are secreted into the Escherichia coli periplasm.

Secondary structural analyses of the nicotinic acetylcholine receptor as a test of molecular models.

Circular dichroism (CD) spectroscopy was used to determine that the secondary structure of purified nicotinic acetylcholine receptor (AChR) of Torpedo californica in both reconstituted vesicles and a cholate-solubilized state is, on average, 23% alpha-helix, 43% beta-sheet, 6% beta-turn, and 28% random coil. These data can serve to test models by placing limits on the particular types of secondary structural motifs which make up the receptor. A number of models proposed for the AChR are discussed in relation to the experimental data presented. Additionally, the protein in both vesicle and solubilized environments was exposed to an agonist, carbamylcholine, or a competitive antagonist, hexamethonium, to monitor net conformational changes upon ligand binding. The protein secondary structure was not changed upon solubilization, nor was any large net conformational change observed upon ligand binding, although small local or compensatory changes cannot be ruled out.

Evaluation of methods for the prediction of membrane protein secondary structures.

With the advent of molecular cloning methods, the amino acid sequences for a number of membrane proteins have been determined. The relative paucity of detailed three-dimensional structural information available for these molecules has led to attempts to predict the secondary structures of membrane proteins based on folding motifs found in soluble proteins of known three-dimensional structure and sequence. In this study, we evaluated the accuracy of several of these methods in predicting the conformation of 15 integral membrane proteins and membrane-spanning polypeptides for which both primary and secondary structural information are available. chi 2 analyses indicated a less than 0.5% correlation between the net predicted secondary structures and the experimental results. A more stringent test of the accuracy of the methods, the index of prediction, was calculated for individual residues in four of the polypeptides for which the crystal structures were known; this criterion also indicated that the predicted assignments for the secondary structures of the residues were inaccurate. Thus, prediction schemes using soluble protein bases appear to be inappropriate for the prediction of membrane protein folding.