Analysis of lymphocyte shape by visual classification, calculated measures of shape or light scattering.

Direct visual assays, calculated measures of shape (Dunn and Brown, 1986) and light scattering were applied to detect shape changes and to identify human peripheral blood lymphocytes displaying different shapes (e.g., spherical cells, polarized cells, non-polar cells with surface projections). Spherical cells could be distinguished from polarized cells and from non-polar cells with surface projections by means of calculated measures of shape obtained from outline drawings, the dispersion parameter being more efficient than extension or elongation parameters. Median values for elongation and extension of polarized cells vs. non-polar cells with surface projections differed significantly provided the cell populations consisted entirely of one particular morphological class. However, if the proportion of cells changing shape is small, this may not be detectable by a significant change in the median values. Therefore, we attempted to apply calculated shape factors to identify individual cells showing a particular type of shape change. Spherical cells could be distinguished relatively easily from non-spherical cells on the basis of the dispersion values. However, it was not possible to distinguish unequivocally between polarized cells and non-polar cells with surface projections because the values overlap to a great extent. For this purpose the visual classification was found to be more reliable. Preliminary experiments with light scattering showed that median values for right angle scatter or forward angle scatter are not sensitive enough to permit the detection of a small proportion of cells changing shape.

Biomechanical model of human cornea based on stromal microstructure.

The optical characteristics of the human cornea depends on the mechanical balance between the intra-ocular pressure and intrinsic tissue stiffness. A wide range of ophthalmic surgical procedures alter corneal biomechanics to induce local or global curvature changes for the correction of visual acuity. Due to the large number of surgical interventions performed every day, a deeper understanding of corneal biomechanics is needed to improve the safety of these procedures and medical devices. The aim of this study is to propose a biomechanical model of the human cornea, based on stromal microstructure. The constitutive mechanical law includes collagen fiber distribution based on X-ray scattering analysis, collagen cross-linking, and fiber uncrimping. Our results showed that the proposed model reproduced inflation and extensiometry experimental data [Elsheikh et al., Curr. Eye Res., 2007; Elsheikh et al., Exp. Eye Res., 2008] successfully. The mechanical properties obtained for different age groups demonstrated an increase in collagen cross-linking for older specimens. In future work such a model could be used to simulate non-symmetric interventions, and provide better surgical planning.

Interaction and pH dependence of effects of nicotine and carbon monoxide in cigarette smoke inhalation experiments with rats.

In view of subacute inhalation studies with cigarette smoke at high concentrations, the toxic properties of combinations of carbon monoxide and nicotine were investigated. Treating rats with fresh diluted cigarette smoke in an inhalation chamber, we established a smoking schedule that resulted in a certain death rate after 13 days. The mortality under the experimental conditions was taken as a measure for the toxicity of different combinations of carbon monoxide and nicotine. Since the absorption and therefore the toxicity of nicotine is pH dependent, the factorial experiments were performed under two pH conditions. The first experiments were conducted between pH 6.5 and 6.9 and then between pH 6.6 and 7.8 where the higher pH is due to the addition of nicotine base to the cigarette filler. After extensive mathematical treatment of the data, the following results were established: (a) Equations for the dose-response surface of CO and nicotine were computed. (b) R2 values (square of the multiple correlation coefficient) for the respective dose-response surfaces were between 87% and 94%. (c) From the respective equations the dose-response surfaces were drawn in the form of several computer plots. From the equations it becomes evident that, under the experimental conditions, there are no synergistic effects between carbon monoxide and nicotine. A simple additivity of the toxic effects was therefore postulated. On the other hand, it has been demonstrated that smoke pH plays an important role, because only from alkaline smoke does the absorption of nicotine seem sufficiently rapid for it to add to the acute toxicity of CO. The total particulate matter apparently does not contribute significantly to the toxicity of the smoke aerosol.

Effects of myocardial revascularization following acute coronary occlusion in pigs.

In a comparative study in pigs the extent of myocardial infarction has been estimated following a temporary three hour coronary occlusion and following a permanent coronary ligation. For evaluation of the cellular injury the infarct size has been determined by a histochemical staining procedure and correlated with serum enzyme studies (creatine phosphokinase, alpha-hydroxybutyric dehydrogenase) in the surviving animal. No significant difference could be detected between the two experimental groups and the extent of cellular damage was similar. A strict linear correlation was found between the serum enzyme activity plotted logarithmically and the morphological infarct size. Likewise the incidence of ventricular fibrillation depended on the extent of cellular injury. Myocardial revascularization does not appear to benefit a pig heart subjected to an acute coronary occlusion lasting three hours or more. Revascularization may even be harmful by creating a haemorrhagic infarct, as found in all the animals submitted to a transient coronary occlusion.

Quantification of retinal lesions in diabetic retinopathy.

A method of quantitative evaluation of the number of microaneurysms is described for clinical research in the therapy of early stages of diabetic retinopathy. In a double-blind study it can be demonstrated that the described method quantifies the progression of retinopathy statistically during only one year of observation in 32 resp. 40 patients. The difficulties of quantification are due to interpretation problems of the photographic documentation and the learning problem of the observer.