The effect of smoking on the ocular surface and the precorneal tear film

Background

Smoking, both active and passive, creates a plethora of health-related problems, which primarily affect the cardiovascular and respiratory systems. There is very little evidence on the effects of tobacco smoke on the eye, especially regarding anterior ocular surface related pathology. This study was undertaken to determine the effects of smoking on the ocular surface and the tear film in smokers.

Methods

A total of 51 (102 eyes) smokers and 50 (100 eyes) age-and gender-matched healthy non-smokers were included in this study. The ocular surface was evaluated by measuring tear film break-up time, surface staining with fluorescein, and corneal and conjunctival sensitivities, and by completing the Schirmer''s II test. Data was analysed using Statistical Package for Social Sciences (SPSS) version 11.5. A p value less than 0.05 was considered statistically significant.

Results

The smoker group had significantly lower tear film break-up time, and corneal and conjunctival sensitivity than the nonsmoker group. Punctate staining was significantly higher in the smoker group than the non-smoker group. There was no statistically significant difference in Schirmer''s II test results between the smoker and non-smoker group.

Conclusion

Smoking caused adverse effects on the precorneal tear film and there was strong association between smoking and tear film instability. Although a causative relationship could not be determined, there is a need for further longitudinal studies.     

Influence of phytin phosphorous and dietary fibre on in vitro iron and calcium bioavailability from rice flakes

The study was undertaken with the objective of analysing the bioavailable iron, calcium and related constituents in rice flakes of four different thicknesses. Rice flakes of four different thicknesses were procured from four different commercial sources. They were analysed for moisture, mineral, iron, calcium, phosphorous, dietary fibre and phytin phosphorous using standard methods. Bioavailable iron and calcium were estimated using the equilibrium dialysis method. The thickness of flakes ranged from 0.08 to 1.20 mm for thin to thick flakes. The mineral content of the flakes ranged from 0.5 to 1.2 g, iron content from 3.38 to 6.86 mg and calcium content from 107 to 210 mg/100 g in samples of different thickness. Phosphorous (111–430 mg/100 g), phytin phosphorous (23–164 mg/100 g) and dietary fibre (5.64–11.5 g/100 g) reduced with the degree of flaking. The percentage of available iron ranged from 7% to 26% and that of available calcium from 8% to 25% from thick to thin flakes, but the differences were non-significant. Multiple regression analysis of the data showed a significant association of phytin phosphorous and dietary fibre (dependent variables) for binding of iron and calcium.     

Ability to delay neuropathological events associated with astrocytic MAO-B increase in a Parkinsonian mouse model: implications for early intervention on disease progression

We previously demonstrated that elevation of astrocytic monoamine oxidase B (MAO-B) levels in adoxycycline (dox)-inducible transgenic mouse model following 14 days of dox induction results in several neuropathologic features similar to those observed in the Parkinsonian midbrain (Mallajosyula et al., 2008).These include a specific, selective and progressive loss of dopaminergic neurons of the substantia nigra (SN),selective decreases in mitochondrial complex I (CI) activity and increased oxidative stress. Here, we report that the temporal sequence of events following MAO-B elevation initially involves increased oxidative stress followed by CI inhibition and finally neurodegeneration. Furthermore, dox removal (DR) at days 3 and 5 of MAO-B induction was sufficient to arrest further increases in oxidative stress as well as subsequent neurodegenerative events. In order to assess the contribution of MAO-B-induced oxidative stress to later events, we compared the impact of DR which reverses the MAO-B increase with treatment of animals with the lipophilic antioxidant compound EUK-189. EUK-189 was found to be as effective as DR in halting downstream CI inhibition and also significantly attenuated SN DA cell loss as a result of astrocytic MAO-B induction. This suggests that MAO-B-mediated ROS contributes to neuropathology associated with this model and that antioxidant treatment can arrest further progression of dopaminergic cell death. This has implications for early intervention therapies.     

An evaluation of resampling methods for assessment of survival risk prediction in high-dimensional settings

Resampling techniques are often used to provide an initial assessment of accuracy for prognostic prediction models developed using high-dimensional genomic data with binary outcomes. Risk prediction is most important, however, in medical applications and frequently the outcome measure is a right-censored time-to-event variable such as survival. Although several methods have been developed for survival risk prediction with high-dimensional genomic data, there has been little evaluation of the use of resampling techniques for the assessment of such models. Using real and simulated datasets, we compared several resampling techniques for their ability to estimate the accuracy of risk prediction models. Our study showed that accuracy estimates for popular resampling methods, such as sample splitting and leave-one-out cross validation (Loo CV), have a higher mean square error than for other methods. Moreover, the large variability of the split-sample and Loo CV may make the point estimates of accuracy obtained using these methods unreliable and hence should be interpreted carefully. A k-fold cross-validation with k = 5 or 10 was seen to provide a good balance between bias and variability for a wide range of data settings and should be more widely adopted in practice.