PubMed · 7951719
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B J Smith. 1994. Drying gels.. https://doi.org/10.1385/0-89603-268-x%3A157
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PURPOSE: To present the hypothesis that a visual field defect after pars plana vitrectomy for macular hole may be caused by dehydration injury to the nerve fiber layer during the fluid-air exchange. METHODS: In a consecutive nonrandomized series of 45 operations on 35 eyes of 34 patients with full-thickness macular hole, the surgical method was changed with postoperative visual field testing performed. RESULT: The incidence and location of the post-operative visual field defect was affected only by changing the location of the infusion cannula. CONCLUSION: Dehydration injury of the nerve fiber layer during the fluid-air exchange should be considered as a possible cause of visual field defect after pars plana vitrectomy for macular hole.
Diphytanoylphosphatidylcholine (DPhPC) has often been used in the study of protein-lipid interaction and membrane channel activity, because of the general belief that it has high bilayer stability, low ion leakage, and fatty acyl packing comparable to that of phospholipid bilayers in the liquid-crystalline state. In this solid-state 31P and 2H NMR study, we find that the membrane packing geometry and headgroup orientation of DPhPC are highly sensitive to the temperature studied and its water content. The phosphocholine headgroup of DPhPC starts to change its orientation at a water content as high as approximately 16 water molecules per lipid, as evidenced by hydration-dependent 2H NMR study at room temperature. In addition, a temperature-induced structural transition in the headgroup orientation is detected in the temperature range of approximately 20-60 degrees C for lipids with approximately 8-11 water molecules per DPhPC. Dehydration of the lipid by one more water molecule leads to a nonlamellar, presumably cubic, phase formation. The lipid packing becomes a hexagonal phase at approximately 6 water molecules per lipid. A phase diagram of DPhPC in the temperature range of -40 degrees C to 80 degrees C is thus constructed on the basis of NMR results. The newly observed hydration-dependent DPhPC lipid polymorphism emphasizes the importance of molecular packing in the headgroup region in modulating membrane structure and protein-induced pore formation of the DPhPC bilayer.
Tetanus toxoid and immunoglobulin G (IgG), model proteins for vaccines and targeting ligands respectively, were covalently coupled to preformed dehydration-rehydration vesicles (DRV) to produce vesicles with surface-bound proteins (DRV-protein) or to preformed small unilamellar vesicles (SUV) which were used to generate DRV with bound protein [(SUV-protein)DRV]. Of the amount of protein employed for coupling (1 mg), 13.8-45.1% was recovered with the liposomes, depending on the type of preparations and the proteins used. Microfluidization of similar DRV-protein or (SUV-protein)DRV for up to 10 cycles led to the formation of smaller vesicles (98-136 mm diameter) which, however, had modestly reduced (estimated as 8.8-21.7%) bound proteins, again depending on the type of preparation and protein used. Treatment of DRV-protein and (SUV-protein) DRV with proteinase revealed that 32.9-45.6% of the total bound protein was exposed on the liposomal surface. With microfluidized liposomes, the proportion of surface-exposed protein increased to 63.1-76.2%. Incubation of intact and microfluidized DRV-IgG and (SUV-IgG) DRV with a protein A-Sepharose 4B CL gel confirmed the presence of IgG on the liposomal surface (47.1-68.4 and 80.5-82.1% of total bound protein respectively). These studies were supplemented with freeze-fracture electron microscopy of (SUV-toxoid)DRV which demonstrated the presence of protein particles (up to 3; 12-14 nm diameter) on the surface of both intact and microfluidized individual liposomes.