Novel insight into high solid anaerobic digestion of swine manure after thermal treatment: Kinetics and microbial community properties.

Compared to traditional anaerobic digestion (AD), high solid anaerobic digestion (HSAD) had the advantages of small digester, low heating energy and less digestate. However, the methane production was poor. In our previous study, thermal treatment (70 ±â€¯1 °C, 3 days) without any dilution could satisfactorily enhance the methane production rate of HSAD by up to 39.5%. However, effects of solid content on HSAD after thermal treatment were not yet studied. In this study, HSAD was conducted at 11.7-17.6% solid content, and the control experiment was conducted at low solid content (4.4% solid content). Results showed that HSAD's methane production rate was the highest at 11.7% solid content (158 mL CH4/g VS), and could reach up to 89.2% of that at 4.4% solid content. The utilization of organics was revealed by kinetics analysis that the readily biodegradable organics could be utilized at increasing solid content with decreasing hydrolysis rate. Furthermore, it was notable that methylotrophic methanogens predominated in HSAD with the abundance of 82.6%. This was quite unique from the general belief that AD system was usually dominated by acetoclastic or hydrogenotrophic methanogenic pathways. In this study, the microbial community structure of HSAD after thermal treatment was firstly studied, its unique specific methanogenic pathways was firstly revealed.

Dual effects of sodium aescinate on vascular tension in rat thoracic aorta.

OBJECTIVE: Sodium aescinate (SA) is used as a vasoactive drug in clinical treatment. This study was designed to investigate the effects of SA on rat isolated thoracic aorta and the possible mechanisms. METHODS: Isometric tension was recorded in response to drugs in organ bath. RESULTS: The effects of SA obeyed an all-or-nothing response. SA in relatively low dose (> or = 50 microg/ml) had an endothelium-independent contractile effect in rat aorta (P<0.01), which depended on extracellular Ca(2+) influx via L-type Ca(2+) channel (P<0.05). SA in relatively high dose (> or = 100 microg/ml) also induced vasoconstriction in Ca(2+)-free medium (P<0.01), which was independent of the activity of inositol-1,4,5-trisphosphate receptor (IP(3)R), ryanodine receptor (RYR), and protein kinase C (PKC). SA in relatively high dose (> or = 100 microg/ml) dilated both endothelium-intact and endothelium-denuded aortic rings precontracted by phenylephrine (PE) or KCl (each P<0.01). SA inhibited extracellular Ca(2+) influx induced by PE or KCl (each P<0.01) and had no activation effect on K(+) channels on vascular smooth muscle. The relaxant effect of SA partly depended on the activity of NO synthase but not on the activity of cyclooxygenase. CONCLUSIONS: Taken together, this study indicated that SA had dual effects on vascular tension in rat isolated thoracic aorta.

[Reconstruction of eyelid defect using periosteal stripe from lateral orbital rim as substitute of tarsus].

OBJECTIVE: To evaluate the results of eyelid defect reconstruction using periosteal stripe of the lateral orbital rim. METHODS: This was a retrospective analysis of eyelid defects reconstruction in 13 patients with lateral canthus eyelid defect following the excision of the eyelid tumors including: seven patients with basal cell carcinoma, four patients with sebaceous cell carcinoma and two patients with squamous cell carcinoma. All eyelid defects were reconstructed with zygoma periosteal stripe as the posterior layer of the eyelid. The anterior layer of the eyelid was reconstructed by myocutaneous flap. RESULTS: After follow-up at 8 to 56 months, all reconstructed eyelids showed a normal appearance with good function and without deformities, e.g. eyelid notch, entropion and ectropion. There was no relapse of the eyelid tumor. All patients were satisfied with the results. CONCLUSIONS: This method is good for repairing lateral eyelid defect involving 1/3 to 2/3 eyelids and without the tumor invasion of lateral orbit rim. This procedure obtains satisfactory results, especially for simultaneous reconstruction of upper and lower eyelids defects.

[Optimization of the Parameters for Microalgae Immobilization and Analysis of Its Recovery Potential for Ammonia Nitrogen in Wastewater].

Application of microalgae in wastewater treatment is regarded as a potential green technology. However, its engineering application has been largely hindered because of the difficulty of biomass separation and harvesting. This study aimed to identify the key parameters influencing the process of microalgae immobilization. To do this, the study focused on immobilization technology and Scenedesmus obliquus, and employed the response surface methodology (RSM) and the Box-Behnken design (BBD). In an evaluation of the performance of microalgae beads, the fixing agent concentration, the cross-linking agent concentration, and the cross-linking time were selected as the independent variables, and the mechanical strength, the mass transfer rate, and the growth rate of immobilized microalgae beads were the response values. The optimal conditions and the uptake potential of the microalgae beads with respect to ammonia nitrogen (NH4+-N) were further explored and analyzed. The results showed that the optimal parameters for the preparation of immobilized microalgae beads were 5%, 2%, and 16 h, and the maximum removal capacity was obtained using mixotrophic cultivation with an embedding density of 1×106 cells·mL-1 and an organic matter concentration of 300 mg·L-1. In addition, the removal capacity of immobilized microalgae with respect to high concentrations of NH4+-N was significantly higher than for free-living microalgae. When the initial concentrations of NH4+-N were approximately 50 and 70 mg·L-1, NH4+-N was removed by the immobilized microalgae (after a 5-day mixotrophic cultivation) at a rate of (96.6±0.1)% and (65.2±4.5)%, respectively. With an initial NH4+-N concentration of 30 mg·L-1, the dominance of free-living microalgae was clear, with a removal rate of (97.8±0.6)% after a 3-day cultivation. However, under heterotrophic cultivation, the removal rate of NH4+-N by immobilized microalgae was generally low and gradually decreased with increasing concentrations. When the initial concentration was approximately 30 mg·L-1, the removal rate was only (49.0±3.1)%. This study provides new prospects for sustainable urban wastewater treatment, a new approach for resource recycling, and a strong theoretical foundation for the popularization and application of microalgae in wastewater treatment.

Study of an enhanced dry anaerobic digestion of swine manure: Performance and microbial community property.

Anaerobic digestion could treat organic wastes and recovery energy. Dry anaerobic digestion had advantages of low heating energy, small digester and less digestate, but its methane production was poor. In this study, an enhanced dry anaerobic digestion of swine manure (thermal treatment + dry anaerobic digestion) was proposed, and its feasibility was investigated via semi-continuous experiment. Results showed that methane production rates were 314.6, 416.0, 298.0 and 69.9 mL CH4/g VS at solid retention time (SRT) of 41 d, 35 d, 29 d and 23 d. Volatile solids (VS) removal rate and methane production rate could reached 71.4% and 416.0 mL CH4/g VS respectively at SRT of 35 d. Methane production rate of the enhanced dry anaerobic digestion was 390% higher than that of dry anaerobic digestion. Microbial study indicated that hydrogenotrophic methanogens predominated with the abundance of 90.2%, while acetoclastic methanogens were not detected. This process was feasible, and was of great practical importance.

[Blocking 1800 MHz mobile phone radiation-induced reactive oxygen species production and DNA damage in lens epithelial cells by noise magnetic fields].

OBJECTIVE: To investigate whether the exposure to the electromagnetic noise can block reactive oxygen species (ROS) production and DNA damage of lens epithelial cells induced by 1800 MHz mobile phone radiation. METHODS: The DCFH-DA method and comet assay were used respectively to detect the intracellular ROS and DNA damage of cultured human lens epithelial cells induced by 4 W/kg 1800 MHz mobile phone radiation or/and 2 muT electromagnetic noise for 24 h intermittently. RESULT: 1800 MHz mobile phone radiation at 4 W/kg for 24 h increased intracellular ROS and DNA damage significantly (P<0.05). However, the ROS level and DNA damage of mobile phone radiation plus noise group were not significant enhanced (P>0.05) as compared to sham exposure group. CONCLUSION: Electromagnetic noise can block intracellular ROS production and DNA damage of human lens epithelial cells induced by 1800 MHz mobile phone radiation.

[Effects of different dose microwave radiation on protein components of cultured rabbit lens].

OBJECTIVE: To study the effects of different dose microwave radiation on protein components of cultured rabbit lens, and analyze the mechanisms of lens injury caused by microwave radiation. METHODS: Cultured rabbit lens were exposed to microwave radiation with frequency of 2450 MHz and power density of 0.25, 0.50, 1.00, 2.00, 5.00 mW/cm(2) for 8 hours in vitro. The transparency of lens was observed. Changes of protein concentration were detected after different lens protein components were extracted, including water-soluble protein (WSP), urea soluble protein (USP), alkali soluble protein (ASP) and sonicated protein (SP). The influence of microwave radiation on WSP was analyzed using SDS-PAGE electrophoresis and coomassie-blue staining. RESULTS: Transparency of lens decreased after radiation. There was obvious opacification of lens cortex after 5.00 mW/cm(2) microwave radiation for 8 hours. After 1.00, 2.00 and 5.00 mW/cm(2) radiation, the percentage of WSP decreased while USP increased obviously. There was no change of ASP. The percentage of SP decreased when the power of microwave was 5.00 mW/cm(2). The low molecular weight protein of WSP decreased while high molecular weight protein increased after microwave radiation. CONCLUSION: Microwave radiation higher than 1.00 mW/cm(2) can affect the proportion of WSP and USP in cultured rabbit lens, and cause changes of lens transparency and refractive power, which leads to lens opacity.

[Effects of microwave radiation on lens hydration and expression of PKC-alpha and transcription factors in lens epithelial cells].

OBJECTIVE: To observe the effects of low power microwave radiation on lens hydration and lens epithelial cells in vitro, and detect the expression of PKC-alpha, c-fos and c-jun in lens epithelial cells. METHODS: Rabbit lens were exposed to microwave radiation with frequency of 2450 MHz and power density of 0.5, 2.0 and 5.0 mW/cm(2) in vitro. The hydration of lens was measured after 8 hours. Morphological changes of lens epithelial cells were observed using a phase-contrast microscope and Hoechst 33258 staining. Expression of PKC-alpha, c-fos and c-jun were analyzed using gel electrophoresis and western blot analysis. RESULTS: After 2.0 and 5.0 mW/cm(2) microwave radiation, the hydration of lens was increased compared to control groups (P<0.05), the shape of lens epithelial cells showed shrinking and disorder and cells nuclei appeared chromatin condensation. There was no change of lens and lens epithelial cells after 0.5 mW/cm(2) microwave radiation. The expression of PKC-alpha was significantly increased in cell membrane, however, decreased in cell cytoplasm after 2.0 mW/cm(2) microwave radiation for 2, 4, 6 and 8 hours. There was significantly increased expression of c-fos and c-jun protein compared with control groups (P<0.05, P<0.01). CONCLUSION: Low power microwave radiation higher than 2.0 mW/cm(2) can activate PKC-alpha by increasing its expression in cell membrane, then induce high expression of c-fos and c-jun, which may relate to cellular signaling pathway of microwave radiation injury to lens and lens epithelial cells.

[Mesophilic and Thermophilic Anaerobic Co-Digestion of Food Waste and Straw].

The anaerobic co-digestion of food waste and straw is more efficient in avoiding the accumulation of volatile fatty acids and promoting the degradation of lignocellulose in comparison with their individual digestions. The co-digestion of food waste and straw was investigated under mesophilic(35℃) and thermophilic(55℃) condition, respectively. The results indicated that when feeding volatile solid concentration was 3 kg·m-3, the accumulated methane production yield of the mesophilic reactor reached the peak of 272.0 mL·g-1 at a food waste-to-straw ratio of 9:1, while it reached the peak of 402.3 mL·g-1 at a food waste-to-straw ratio of 5:5 for thermophilic reactor. These amounts were significantly higher than those of food waste digestion alone(218.6 mL·g-1 for mesophilic reactor and 322.0 mL·g-1 for thermophilic reactor). Co-digestion promoted the rate of carbon transfer to methane, and further, the rate of the thermophilic reactor was higher than that of the mesophilic reactor. Degradation rate for lignocellulose of thermophilic reactor was 34.7%-45.8%, higher than that of mesophilic reactor, 12.6%-42.2%. It was confirmed by 16S rRNA gene sequences of bacteria and archaea, ITS sequences of fungi based on high-throughput sequencing techniques, which showed the amounts of lignocellulose degrading bacteria and actinomycetes in the thermophilic reactor were both higher than those in the mesophilic reactor.

Effects of thermal treatment on high solid anaerobic digestion of swine manure: Enhancement assessment and kinetic analysis.

Anaerobic digestion (AD), which is a process for generating biogas, can be applied to the treatment of organic wastes. Owing to its smaller footprint, lower energy consumption, and less digestate, high solid anaerobic digestion (HSAD) has attracted increasing attention. However, its biogas production is poor. In order to improve biogas production and decrease energy consumption, an improved thermal treatment process was proposed. Raw swine manure (>20% solid content) without any dilution was thermally treated at 70±1°C for different retention times, and then its effect on HSAD was investigated via batch AD experiments at 8.9% solid content. Results showed that the main organic components of swine manure hydrolyzed significantly during the thermal treatment, and HSAD's methane production rate was improved by up to 39.5%. Analysis using two kinetic models confirmed that the treatment could increase biodegradable organics (especially the readily biodegradable organics) in swine manure rather than upgrading its hydrolysis rate. It is worth noting that the superimposed first-order kinetics model was firstly applied in AD, and was a good tool to reveal the AD kinetics mechanism of substrates with complex components.

[Microbial Structure of an Enhanced Two-phase High-solid Anaerobic Digestion System Treating Sludge].

High-solid anaerobic digestion (HSAD) of sludge has several advantages like smaller reactor, lower energy consumption and less digestate. However, the understanding about the mechanism especially the microbial mechanism is still limited. In this study, microbial communities of a pilot-scale sludge HSAD system at steady state were investigated with 16S rRNA clone library technology. The system employed an enhanced two-phase anaerobic digestion process, i. e. 'hyperthermophilic acidogenesis (70℃, 3 d)-thermophilic methanogenesis (55℃, 12.5 d)' to treat waste activated sludge with a solid content of about 9%. The volatile solid (VS) removal rate was 35.7% and methane yield (CH4/VSremoved) was 0.648 m3·kg-1. The bacterial compositions of the two phases were significantly different:there were plenty of proteolytic bacteria in hyperthermophilic acidogenesis phase; and the bacteria degrading polysaccharides like cellulose and the bacteria utilizing long-chain fatty acids were found in thermophilic methanogenesis phase; some bacteria degrading simple saccharides existed in both phases. In both phases, the dominant archaea were Methanothermobacter. Especially, 100% of the retrieved archaea in the thermophilic methanogenesis phase belonged to genus Methanothermobacter. This indicated that hydrogenotrophic methanogenesis was the predominant methanogenesis pathway in this system since methane was only detected in the methanogenesis phase.

[DNA damage and repair induced by acute exposure of microwave from mobile phone on cultured human lens epithelial cells].

OBJECTIVE: To investigate the effects of acute exposure of low-power 217 Hz modulated 1. 8 GHz microwave radiation on the DNA damage of human lens epithelial cells (hLECs) and repair. METHODS: Cultured hLECs were exposed to 217 Hz modulated 1. 8 GHz microwave radiation at SAR (specific absorption rate) of 1. 0, 2. 0, 3. O0 and 4. 0 W/kg for 2 hours in an sXc-1800 incubator and irradiate system, the DNA single strand breaks were detected with comet assay ( single-cell gel electrophoresis) in sham-irradiated cells and irradiated cells incubated for varying periods: 0, 30 and 60 minutes after irradiation. Images of comets were digitized and analyzed using an Imagine-pro plus software, and the indexes used in this study were tail length (TL) and tail moment (TM). BrdU was added into the medium with additional one hour incubation after radiation, the cell proliferation rate was determined using a BrdU-kit. RESULTS: The difference of DNA-breaks between the exposure and sham exposure groups induced by 1.0 and 2.0 W/kg irradiation were not significant in each time points (P > 0.05) ; there were significant difference in both groups at the exposure dose of 3. 0 and 4. 0 W/kg immediately and at the time of 30 minutes after irradiation (P <0. 01) ; if the radiation exposure time was beyond one hour no differences were be able to detected in 3.0 W/kg group (P > 0. 05) compared with control, but the evidence of significant DNA damage still existed in 4. 0 W/kg group at the same time point. Cell proliferation rate had no significant difference when the application of SAR was < or = 3. 0 W/kg (P >0. 05) , however the cell proliferation was decreased significantly at the dose of 4. 0 W/kg irradiation ( P < 0. 01). CONCLUSIONS: No effective DNA damage was induced using comet assay after 2 hours irradiation of 1. 8 GHz microwave on hLECs at the dose SAR < or = 3.0 W/kg. 4.0 W/kg irradiation caused significantly DNA damage and inhibition of hLECs proliferation.

[Effect of acute exposure to microwave from mobile phone on DNA damage and repair of cultured human lens epithelial cells in vitro].

OBJECTIVE: To investigate the DNA damage of human lens epithelial cells (LECs) caused by acute exposure to low-power 217 Hz modulated 1.8 GHz microwave radiation and DNA repair. METHODS: Cultured LECs were exposed to 217 Hz modulated 1.8 GHz microwave radiation at SAR (specific absorption rate) of 0, 1, 2, 3 and 4 W/kg for 2 hours in an sXc-1800 incubator and irradiate system. The DNA single strand breaks were detected with comet assay in sham-irradiated cells and irradiated cells incubated for varying periods: 0, 30, 60, 120 and 240 min after irradiation. Images of comets were digitized and analyzed using an Imagine-pro plus software, and the indexes used in this study were tail length (TL) and tail moment (TM). RESULTS: The difference in DNA-breaks between the exposure and sham exposure groups induced by 1 and 2 W/kg irradiation was not significant at every detect time (P > 0.05). As for the dosage of 3 and 4 W/kg there was difference in both group immediately after irradiation (P < 0.01). At the time of 30 min after irradiation the difference went on at both group (P < 0.01). However, the difference disappeared after one hour's incubation in 3 W/kg group (P > 0.05), and existed in 4 W/kg group. CONCLUSION: No or repairable DNA damage was observed after 2 hour irradiation of 1.8 GHz microwave on LECs when SAR < or = 3 W/kg. The DNA damages caused by 4 W/kg irradiation were irreversible.

[Degradation of the Nitrogenous Heterocyclic Compound Quinoline by O3/UV].

The influences of various factors including initial concentration of quionline solution, static duration after reaction, initial pH, HCO3-on the degradation of quinoline by O3/UV were analyzed in this study. In addition, the degradation mechanism and pathways were also analyzed. The results showed that reaction rate constants and removal rate of quinoline decreased with the increase of the initial concentration of quinoline. The best degradation efficiency of quinoline was achieved under the alkaline conditions (pH 7-9). Removal rate of quinoline was obviously influenced by HCO3-, and was reduced by 42.01% within 6 min when the concentration of HCO3- was 100 mg·L-1. There was neglected effect of static duration after reaction on the removal rate and mineralization rate of quinolone. The intermediate products of quinoline were mainly 8-hydroxyquinoline, 5-hydroxyquinoline, 2(1H)-quinoline ketone, 2-pyridinecarboxaldehyde and so on. The main degradation pathways of quinoline in the O3/UV system were addition reaction, substitution reaction and electrophilic substitution mediated by O3 and·OH.

Size effect of anaerobic granular sludge on biogas production: A micro scale study.

This study investigated the influence of anaerobic granular sludge size on its bioactivity at COD concentration of 1000, 3000 and 6000 mg/L. Based on size, granules were categorized as large (3-3.5 mm), medium (1.5-2 mm) and small (0.5-1 mm). A positive relationship was obtained between granule size and biogas production rate. For instance, at COD 6000 mg/L, large granules had highest biogas production rate of 0.031 m(3)/kgVSS/d while medium and small granules had 0.016 and 0.006 m(3)/kgVSS/d respectively. The results were reaffirmed by applying modified Fick's law of diffusion. Diffusion rates of substrate for large, medium and small granules were 1.67×10(-3), 6.1×10(-4)and 1.8×10(-4) mg/s respectively at that COD. Large granules were highly bio-active due to their internal structure, i.e. big pore size, high porosity and short diffusion distance as compared to medium and small granules, thus large granules could improve the performance of reactor.

Computer construction and analysis of protein models of the mutant gammaD-crystallin gene.

BACKGROUND: Gammad-crystallin plays an important role in human cataract formation. Being highly stable, gammaD-crystallin proteins are composed of two domains. In this study we constructed and analyzed protein models of the mutant gammaD-crystallin gene, which caused a special fasciculiform congenital cataract affecting a large Chinese family. METHODS: gammaD-crystallin protein structure was predicted by Swiss-Model software using bovine gammaD-crystallin as a template and Prospect software using human betab2-crystallin as a template. The models were observed with a Swiss-Pdb viewer. RESULTS: The mutant gammaD-crystallin structure predicted by the Swiss-Model software showed that proline23 was an exposed surface residue and P23T change made a decreased hydrogen bond distance between threonine23 and asparagine49. The mutant gammaD-crystallin structure predicted by the Prospect software showed that the P23T change exerted a significant effect on the protein's tertiary structure and yielded hydrogen bonds with aspartic acid21, asparagine24, asparagine49 and serine74. CONCLUSION: The mutant gammaD-crystallin gene has a significant effect on the protein's tertiary structure, supporting that alteration of gamma-crystallin plays an important role in human cataract formation.

[A new discovery of anaerobic sludge granular with big aera minerals core].

A anaerobic sludge granular containing mineral core with a diameter of 1mm was discovered in lab scale expanded granular sludge bed (EGSB) reactor operated only with glucose as substrate. By SEM, the granular was a core packed by compact bacterium, in which minerals distribute equally and there are caves caused by biological self-degradation. By energy spectrum and X-ray, the core is composed of Ca5 (PO4 x CO3)3 (OH). On the basis of its construction characteristics, the developing mechanism was investigated as well as the developing model of the sludge granular was present, the results shown that the contributing factors influencing mineral core formation are external and internal pH value of sludge granular.

[Impact of Thermal Treatment on Biogas Production by Anaerobic Digestion of High-solid-content Swine Manure].

Livestock manure is a kind of waste with high organic content and sanitation risk. In order to investigate the impact of thermal treatment on the anaerobic digestion of high-solid-content swine manure, 70 degrees C thermal treatment was conducted to treat raw manure (solid content 27.6%) without any dilution. The results indicated that thermal treatment could reduce the organic matters and improve the performance of anaerobic digestion. When the thermal treatment time was 1d, 2d, 3d, 4d, the VS removal rates were 15.1%, 15.5%, 17.8% and 20.0%, respectively. The methane production rates (CH4/VSadd) were 284.4, 296.3, 309.2 and 264.4 mL x g(-1), which was enhanced by 49.7%, 55.9%, 62.7% and 39.2%, respectively. The highest methane production rate occurred when the thermal treatment time was 3d. The thermal treatment had an efficient impact on promoting the performance of methane production rate with a suitable energy consumption. On the other hand, thermal treatment could act as pasteurization. This showed that thermal treatment would be of great practical importance.

Low power microwave radiation inhibits the proliferation of rabbit lens epithelial cells by upregulating P27Kip1 expression.

PURPOSE: The goal of this study was to examine the effects of low power microwave radiation (<10 mW/cm2) on the proliferation of cultured rabbit lens epithelial cells (RLEC). METHODS: Cultured RLEC were exposed to continuous microwave radiation at a frequency of 2,450 MHz and power densities of 0.10, 0.25, 0.50, 1.00, and 2.00 mW/cm2 for 8 h. Cell morphologic changes were observed under a phase-contrast microscope. Cell viability was measured using the MTT assay and cell cycle analysis was measured using flow cytometry. After exposure to 2.00 mW/cm2 microwave radiation for 4, 6, and 8 h, the expression of cell cycle-regulatory proteins, P21WAF1 and P27Kip1, was examined using western blot analysis. Finally, the levels of P21WAF1 and P27Kip1 mRNA were analyzed by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: After 8 h of radiation treatment, cells treated with 0.50, 1.00, and 2.00 mW/cm2 microwave radiation exhibited decreased cell viability, increased cell condensation and an inhibition of DNA synthesis. RLEC showed significant G0/G1 arrest. No obvious changes could be detected in the 0.10 and 0.25 mW/cm2 microwave treatment groups. Protein expression of P27Kip1 was markedly increased after microwave radiation. However, the mRNA levels were unchanged. On the other hand, there were no detectable differences in P21WAF1 protein expression and mRNA levels between microwave treatment and control groups. CONCLUSIONS: This study suggests that low power microwave radiation higher than 0.50 mW/cm2 can inhibit lens epithelial cell proliferation, and increase the expression of P27Kip1. These effects may account for the decline of lens epithelial proliferation after exposure to microwave radiation.

Expression and proteolytic activity of calpain in lens epithelial cells of oxidative cataract.

OBJECTIVE: To study the role of calpain in the mechanism of oxidative cataract through detecting the level of intracellular free Ca(2+), the expression and proteolytic activity of calpain in the lens epithelial cells (LECs) of H(2)O(2)-induced cataract. METHODS: Rat lenses were cultured in vitro and cataract was induced by H(2)O(2). The level of intracellular free Ca(2+) was measured by fluorescence determination with fura-2/AM. The expression of m-calpain protein in LECs was detected with immunohistochemical method. The proteolytic activity in LECs was measured using a fluorogenic synthetic substrate. RESULTS: There were significant differences of the level of intracellular free Ca(2+) (P=0.001, 0.000, 0.000), the expression of m-calpain (P=0.001, 0.000, 0.000) and the proteolytic activity of calpain (P=0.001, 0.000, 0.000) between H(2)O(2)-induced and control group at 6, 12 and 24 h, respectively. CONCLUSIONS: H(2)O(2) can increase intracellular free Ca(2+), then enhance the expression and proteolytic activity of calpain which may play a role in the mechanism of oxidative cataract of rat.