Differential effects of cholesterol and oxidised-cholesterol in egg lecithin bilayers.

Low frequency impedance measurements of pure egg lecithin (phosphatidylcholine) bilayers have revealed the presence of four layers which can be attributed to the acyl chain, carbonyl, glycerol bridge and phosphatidylcholine regions of the lecithin molecule. Measurements on bilayers formed in the presence of unoxidised-cholesterol revealed that cholesterol molecules were located in the hydrocarbon region of the bilayer with its hydroxyl groups aligned with the carbonyl region of the lecithin molecules. Measurements of oxidised-cholesterol lecithin bilayers revealed that these molecules protruded less into the hydrocarbon region and their polar hydroxyl group aligned with the glycerol bridge region of the lecithin molecule.

Iodine-125 irradiation of choroidal melanoma: clinical experience from the Prince of Wales and Sydney Eye Hospitals.

We examined the records of 53 patients treated for choroidal melanoma between 1985 and 1989. The aim of this study was to assess the safety and short-term results of iodine-125 episcleral plaque therapy. There were 28 males and 25 females, aged 20 to 77 years (median 61 years), treated for single tumours with a median diameter of 9 mm (range 5 to 15 mm) and with a median thickness of 4 mm (range 2 to 10 mm). The plaques containing iodine-125 seeds were chosen according to tumour size: 10 mm (16 patients); 15 mm (36 patients); 20 mm (one patient). All patients are alive at last follow-up (median 1.3 years, range 4 months to 3.3 years). Four patients underwent enucleation for melanoma progression. Thirty patients have developed some type of complication (more than one complication occurred in the same eye in 12 patients): retinitis (19), optic neuropathy (7); cataract (4), rubeosis iridis (2). Overall, visual acuity deteriorated in 32 patients, remained stable in 12 patients and improved in 9 patients. Iodine-125 plaque therapy appears to offer patients good prospects of tumour control and preservation of useful vision.

A thin I-125 seed eye plaque to treat intraocular tumors using an acrylic insert to precisely position the sources.

A thin re-usable stainless steel ophthalmic applicator is described. The radioactive Iodine-125 sources are inserted in an acrylic button which fits neatly into a stainless steel shell 1 mm thick. The applicator can be assembled with the radioactive sources precisely positioned without the use of adhesives or mechanical devices such as clamps or screws in a matter of a few minutes, (under sterile conditions if necessary). The applicator can be dismantled in seconds after which it is ready for cleaning and re-sterilization. The overall thickness of the plaque is 2.6 mm, but this has the potential to be reduced to 2.1 mm. Suture holes are provided on a flange subtending 120 degrees around the circumference of the shell and are exactly matched on a stainless steel template.

The development of a thin stainless steel eye plaque to treat tumours of the eye up to 15 mm in diameter.

The development of a thin stainless steel ophthalmic applicator is described. The features of this device are that it can be assembled with the radioactive sources (I-125) precisely positioned without the use of adhesives or mechanical devices such as clamps or screws in a matter of a few minutes under sterile conditions. Dismantling occurs in seconds after which the applicator is ready for cleaning and re-sterilisation. The radioactive sources are contained in an acrylic button which fits neatly into a stainless steel shell 1 mm thick. Different distributions of sources may be accommodated in the same stainless steel shell by inserting a different acrylic button. The overall thickness of the plaque is 2.6 mm but potentially can be reduced to 2.1 mm. Suture holes are provided on a flange subtending 120 degrees around the circumference of the shell and are exactly matched on a stainless steel template. An analysis of the dosimetry suggests that the treatment of the radioactive I-125 seeds as point sources may lead to only small errors in the determination of dose at the scleral surface and tumour apex. The differences in the dosimetry resulting from the treatment of the seeds as line sources appear to be of little consequence. As a result, point source dosimetry with anisotropy factor removed is quite satisfactory.

Effect of dose-rate on total body irradiation: lethality and pathologic findings.

The effect of low dose-rate total body irradation (TBI) on hemopoietic and nonhemopoietic lethality has been studied in BALB/c mice using dose-rates ranging from 25 to 1 cGy/min. Deaths were scored at 10 days, 30 days, and one year after irradiation, and dose-response curves were constructed to determine the dose-rate dependence of deaths from the gastrointestinal syndrome, hemopoietic syndrome, and late lethal syndrome(s), respectively. A plot of the LD50S for each of these lethal syndromes versus dose-rate showed the dose-rate dependence for late lethality to be somewhat greater than that for gut death, but both of these endpoints were markedly more dose-rate dependent than was hemopoietic lethality, particularly at dose rates less than 5 cGy/min. To determine which late responding normal tissues might be critical for low dose-rate TBI, complete necropsies were performed on all mice dying later than 60 days after irradiation and on all mice surviving at one year; all tissues were examined histologically. Morphologic evidence of radiation injury was present in only three tissues, lung (fibrosis and scarring) kidney (tubule depletion), and liver (presence of mitoses). Subjectively, the lung changes were most severe up to 9 months while kidney changes became more prominent after this time, suggesting that late death after low dose-rate TBI may not be entirely attributable to lung injury. However, regardless of which late responding normal tissue is dose-limiting, it is clear that low dose-rate TBI preferentially spares these tissues compared with hemopoietic stem cells.

Silicone plesiotherapy molds.

Plesiotherapy, the treatment of superficial lesions by radioactive molds has largely been replaced by teletherapy techniques involving high energy photon and electron beams. There are, however, situations for which a short distance type treatment, in one form or another, is superior to any other presently available. Traditionally, molds have taken the form of rigid devices incorporating clamps to attach them to the patient. This ensures a reproducible geometry about a localized region since the molds are applied on a daily basis. To make such devices requires considerable skill and patience. This article describes an alternative method that eliminates the use of cumbersome devices in many situations. Silicone molds made from a plaster cast model have been found suitable for the treatment of surface lesions and especially for lesions in the oral and nasal cavities. With the use of radioactive gold seeds the molds may be left in place for a few days without fear of them moving.