Cryocoagulation of retinal vessels: an experimental model of intravascular coagulation.

Various amounts of cryothermy were applied to the posterior pole of rabbit eyes to determine changes in retinal tissue and vasculature. Four consecutive freezing and refreezing applications of -60 degrees was the most effective technique for achieving central retinal vessel occlusion. Electron microscopic observations of sequentially sectioned occlusion. Electron microscopic observations of sequentially sectioned occluded vessels showed that the vessels were occluded by a platelet plug distally and packed erythrocytes proximally. Fibrin formation was not found in the occluded retinal vessels but was seen within platelet plugs in choroidal vessels. Because cryocoagulation simulates the normal physiologic means of coagulation more closely than other vessel occluding techniques, cryocoagulation of the primary retinal vessels is suggested as an experimental model for intravascular coagulation.     

Vitrectomy in experimental endophthalmitis: Part I-Fungal infection.

In studying the dose-related ocular toxicity of amphotericin B in vitrectomized eyes, up to 5 micrograms/0.1 ml concentration of amphotericin C was nontoxic to the ocular structure when injected in the anterior part of the vitreous cavity. Intravitreal injection of 2.5 micrograms of amphotericin B halted fungal endophthalmitis, which was experimentally induced in rabbit eyes, even after 16 days of infection. Combined treatment of vitrectomy and intravitreal injection of amphotericin B not only cured the fungal endophthalmitis but it also cleared the ocular media from opacities.     

Biopsy of human scleral-chorioretinal tissue.

The usefulness of a technique for scleral-chorioretinal biopsies was evaluated on a human eye destined for enucleation due to a malignant melanoma of the choroid. The operative procedure was without complication. The biopsy specimen was removed and carefully evaluated both by light and electron microscopy. The underlying choroid and retinal tissues were successfully preserved by this technique.     

The peak oxygen uptake of healthy Turkish children with reference to age and sex: a pilot study

Maximal oxygen uptake (VO2max) has an important place in the assessment of cardiopulmonary fitness. Currently there is insufficient normative data for Turkish children. With this preliminary study, we aimed to set up a normative data for our lab which may also serve as a basis for future large population based studies in Turkey. We assessed the peak oxygen consumption of 80 healthy Turkish children aged 5-13 years and examined the cardiopulmonary responses to exercise test in relation to their age, sex and body size. Dynamic lung functions were positively and significantly correlated with age. A similar correlation was observed for the peak VO2. A significant positive correlation between peak VO2 and body size was demonstrated only in boys for height. There were no differences in all of the test parameters with reference to sex except in the age group of 13 years. Boys who were 13 years old had higher mean values of maximal voluntary ventilation (MVV), oxygen uptake at anaerobic threshold, peak VO2, and exercise test duration than those of girls of the same age (p < 0.05). VO2 plateau was detected only in 25%, and when two groups with and without VO2 plateau were compared, there were no differences regarding the age, sex, weight, height and exercise test results. Assessment of VO2 by graded exercise stress testing by treadmill is accepted as a safe and effective method of evaluating the physical fitness of children. Current study presents normal data for a limited subpopulation of healthy Turkish children.     

A new biomedical sensor for measuring PCO2

Measuring PCO2 (partial pressure of carbon dioxide) in an organ can enable early detection of ischemia. However, there are few clinical applicable solutions for measuring PCO2. Based upon the requirement for clinical applications, a conductivity based PCO2 sensor is proposed. A conductivity based PCO2 sensor measures conductance in an aqueous solution separated from the measured object by a gas-permeable membrane. A bridge design with two cavities is favored for such a sensor. A planar and a cylindrical macro prototype based upon the bridge design were studied. The design criteria were based on the contribution from the electrode polarization, stray capacitances, contact area with the sample and design ability to miniaturize the sensor. The cylindrical sensor is favored because of its large contact area and advantages for miniaturization. Further investigation has to be done to confirm the functionality of such a design in a miniaturized form and its clinical performance.