Induction of significant intraocular pressure diurnal fluctuation in rats using a modified technique of microbead occlusion

AIM： To investigate the effect of microbead iridocorneal angle occlusion on intraocular pressure（IOP） diurnal fluctuation in rat eyes. METHODS： Male Dark Agouti（DA） rats, 8-10 week old, were each given a single intracameral injection of microbeads, followed by injection of dispersive viscoelastic solution. The right eye served as the experimental eye, while the left eye served as the control. IOP was measured twice daily postoperatively for 3 wk and compared between groups. At the end of 3 wk, the rats were sacrificed and the eyes were harvested for histological analysis and retinal ganglion cell（RGC） counting. RESULTS： After microbead injection, experimental eyes had significantly higher dark time IOP than controls from the second week to the third week [2 nd week： 22.92±1.631 mm Hg（n=5） vs 17.35±0.751 mm Hg（n=5）; 3 rd week： 23.59±1.494 mm Hg vs 17.73±0.592 mm Hg（n=5）], while light time IOP was comparable between groups. The fluctuation levels of IOP in the experimental eyes were 7.21±0.398 mm Hg（n=5）, 9.50±1.017 mm Hg（n=5） and 10.66±0.894 mm Hg（n=5） from the first week to the third week after injection. Comparatively, they were significantly lower in the control eyes, which were 4.69±0.323 mm Hg（n=5）, 2.84±1.122 mm Hg（n=5） and 4.98±0.603 mm Hg（n=5） respectively. However, at the end of 3 wk, the larger fluctuations in IOP in the experimental eyes was not associated with a significant loss of RGCs. CONCLUSION： Microbead occlusion exacerbates diurnal IOP fluctuation in rats. This reported model may serve as a method of investigating the pathological effects of IOP fluctuation. A longer observation period, or repeated injections, may be needed to observe a significant change in RGC density.

Diurnal macular choroidal area fluctuation in normal and primary open angle glaucoma groups

AIM： To assess and compare the diurnal macular choroidal area fluctuation in normal and primary open angle glaucoma （POAG） groups using enhanced depth imaging optical coherence tomography （EDI-OCT）. METHODS： Twenty-eight normal and 27 POAG eyes were enrolled in this study. EDI-OCT was used to measure the macular choroidal area every 3h from 9：00 a.m. to 21：00 p.m. RESULTS： Significant diurnal fluctuations of macular choroidal area were observed in both normal （P=-0.003） and POAG groups （P〈0.001）. But no significant macular choroidal area difference has been found between the two groups at all the five measurement time-points （512778＋166242 vs 455079：1：207278 pm2, P=-0.195 at 9：00 a.m.; 501526168953 vs 447846.：211147 pm2, P=-0.245 at 12：00 a.m.; 501982＋173158 vs 448024#.206653 pm2, P=-0.239 at 15：00 p.m.; 508912＋174589 vs 457783＋-207081 pm2, P=-0.252 at 18：00 p.m.; 503787＋171241 vs 453230＋_205955 pm2, P=-0.274 at 21：00 p.m.; respectively）. Furthermore, neither the fluctuation manners nor the change in macular choroidal area between the two adjacent measurement time points showed significant difference between normal and POAG groups （all P〉0.05）. In the meantime, significant diurnal intraocular pressure fluctuations were also observed in normal and POAG groups （both P〈0.001）. CONCLUSION： In diurnal time, the macular choroidal area in both normal and POAG groups fluctuated significantly; moreover, neither the value of macular choroidal area, nor the fluctuation of macular choroidal area in POAG group is significantly different from that in normal group.

A Preliminary Study of Crassulacean Acid Metabolism (CAM) in the Endangered Aquatic Quillwort Isoetes sinensis Palmer in China

Isoetes sinensis Palmer (Isoetaceae) is an aquatic or amphibious plant that is critically endangered in China. Previous studies have revealed the crassulacean acid metabolism (CAM)-like photosynthetic pathway occurs commonly in submerged leaves in genusIsoetes. Water chemistry parameters and the titratable acidity content of the plant extract were measured from samples obtained in the early morning (7∶00) and late afternoon (15∶00) from twoI. sinensis populations in China. One population occurs in the eulittoral zone of a freshwater tidal river at low elevation (134 m) and another occurs in a densely vegetated, high elevation (1 100 m) alpine shallow pool. Significant differences in pH and titratable acidity of the plant extract were detected between the morning and afternoon samples. These changes are associated with diurnal changes in water chemistry. Our results provide the first evidence for the existence of the CAM pathway in the East Asian endemicIsoetes sinensis Palmer. The magnitude of fluctuations in the titratable acidity of the plant extract may be correlated with the severe carbon limitation imposed on the plants by its aquatic habitat.

Groundwater uptake of different surface cover and its consequences in great Hungarian plain

Introduction:Forest cover in Hungary has increased from 1.1 to 2.0 million hectares during the last century.The EU(European Union)promotes further afforestation;thus,15,000–18,000 ha are being forested each year,mainly in the Hungarian Great Plain.In terms of species used for afforestation,poplar plantations are preferred over native oak woodlands.The groundwater uptake of trees can be a significant water balance element of forested areas in shallow groundwater environments within the Hungarian Great Plain.Forests can cause water table depressions and subsurface salt accumulation in areas with negative water balance.This study examined the hydrological impact of forest cover in the Hungarian Great Plain.Within the framework of this research,climatic water balance,water table depth and salinity,subsoil layering,tree species and stand age were analysed as influencing factors.This paper compares the effect which an oak forest,a poplar plantation and a pasture have on groundwater uptake and salt accumulation.Results:The water table level was roughly 0.4–0.5 m lower beneath the oak forest and the poplar plantation than it was beneath the pasture.Forest groundwater use was 1.5–2 times higher than that of grassland.Groundwater uptake of oak forest was greater than that of poplar plantation during the monitoring period.Salt accumulation,which shows water use in the longer run,was slightly higher for poplar in deeper layers.Conclusions:The greater amount of groundwater used by trees does not lead to a higher salt uptake as only a slight accumulation of salt was measured beneath the forests.Overall,hybrid poplar was slightly less favourable than native oak when considering salinization effects.However,even greater groundwater uptake by trees over longer timescales could cause more significant salt accumulation under pronounced drought conditions due to climate change.