Possible interactions between environmental factors in determining species optima

Questions: 1. Indicator values, such as those of Ellenberg, for different environmental factors are seen as independent. We tested for the presence of interactions between environmental factors ( soil moisture and reaction) to see if this assumption is simplistic. 2. How close are Ellenberg indicator values (IVs) related to the observed optima of species response curves in an area peripheral to those where they have been previously employed and 3. Can the inclusion of bryophytes add to the utility of IVs?

Location: South Uist, Outer Hebrides, Scotland, UK.

Methods: Two grids (ca. 2000 m x 2000 m) were sampled at 50-m intervals across the transition from machair to upland communities covering an orthogonal gradient of both soil pH ( reaction) and soil moisture content. Percentage cover data for vascular plants, bryophytes and lichens were recorded, along with pH and moisture content of the underlying sand/soil/peat. Reaction optima, derived from species response curves calculated using HOF models, were compared between wet and dry sites, and moisture optima between acidic and basic samples. Optima for the whole data set were compared to Ellenberg IVs to assess their performance in this area, with and without the inclusion of bryophytes.

Results: A number of species showed substantially different pH optima at high and low soil moisture contents (18% of those tested) and different soil moisture optima at high and low pH (49%). For a number of species the IVs were poor predictors of their actual distribution across the sampled area. Bryophytes were poor at explaining local variation in the environmental factors and also their inclusion with vascular plants negatively affected the strength of relationships.

Conclusions: A substantial number of species showed an interaction between soil moisture and reaction in determining their optima on the two respective gradients. It should be borne in mind that IVs such as Ellenberg's may not be independent of one another.

Effect of short-term macrophage depletion in the development of posterior capsule opacification in rodents

Aim: To evaluate the role of macrophages in the development of posterior capsule opacification (PCO). Methods: For this purpose, an extracapsular lens extraction was performed in 18 consecutive Sprague-Dawley rats. Animals were treated with liposomal clodronate (Cl MDP-lip-treated group, n = 10) or phosphate-buffered saline (PBS) (control group, n = 8) 1 day preoperatively and on the first day postoperatively, and sacrificed 3 days postoperatively. Masked clinical, light microscopy and immunohistochemistry studies were conducted. The Fisher exact test and randomisation test were used to assess statistically differences between groups. Results: A statistically significant reduction in the number of macrophages (ED1+, ED7+, ED8+) was found in the Cl MDP-lip-treated group compared with the PBS-lip-treated group (p = 0.048, p = 0.004, p = 0.027, respectively). There were no statistically significant differences with regards to the presence/absence of central opacification (p = 0.29) and capsular wrinkling (p = 0.21) as detected clinically between groups. Similarly, a qualitative evaluation of the degree of PCO with regards to lens epithelial cell (LEC) proliferation, capsular wrinkling and Soemmerring ring formation showed no statistically significance between groups (p = 0.27, p = 0.061, p = 1.0, respectively). However, a statistically significant reduction in the number of lens epithelial cells (LEC) counted in the centre of the posterior capsule was found in the Cl MDP-lip- treated group (p = 0.009). Conclusion: Depletion of macrophages was accompanied by a reduction in LEC in the centre of the posterior capsule in rodents.

Effect of TGF-β2 and anti-TGF-β2 antibody in a new in vivo rodent model of posterior capsule opacification

PURPOSE. This study evaluated the effect of transforming growth factor (TGF)-ß2 and anti-TGF-ß2 antibody in a rodent model of posterior capsule opacification (PCO). METHODS. An extracapsular lens extraction (ECLE) was performed in 72 Sprague-Dawley rats. At the end of the procedure, 10 µL TGF-ß2 (TGF-ß2-treated group), fetal calf serum (FCS)/phosphate- buffered saline (PBS; FCS/PBS-treated control group), a human monoclonal TGF-ß2 antibody (anti-TGF-ß2-treated group), or a null control IgG4 antibody (null antibody-treated control group) was injected into the capsule. Animals were killed 3 and 14 days postoperatively. Eyes were evaluated clinically prior to euthanatization, then enucleated and processed for light microscopy and immunohistochemistry afterward. PCO was evaluated clinically and histopathologically. Student's t-test and ? were used to assess differences between groups. RESULTS. There were no statistically significant clinical or histopathological differences in degree of PCO between the TGF-ß2- and FCS/PBS-treated groups at 3 and 14 days after ECLE. Nor were there differences between the anti-TGF-ß2- and the null antibody-treated groups, with the exception of the histopathology score for capsule wrinkling 3 days after ECLE (P = 0.02). a-Smooth-muscle actin staining was observed in the lens capsular bag only in areas where there was close contact with the iris. CONCLUSIONS. No sustained effect of TGF-ß2 or anti-TGF-ß2 antibody on PCO was found in rodents at the dose and timing administered in this study. Iris cells may play a role in the process of epithelial mesenchymal transition linked to PCO. Copyright © Association for Research in Vision and Ophthalmology.