Distribution and density of mixed-input ON bipolar cells of the goldfish (Carassius auratus) during growth.

Neurons are continuously produced at different rates and locations in the teleost retina. Goldfish rods are homogeneously distributed and maintain a stable density throughout growth, whereas little is known about their postsynaptic partners. We examined the distribution and density of mixed-input ON bipolar cells (ON mBCs) in 57 goldfish of various sizes by immunolabeling their retinas with an antibody against PKCα and counting PKCα-positive neurons in wholemounts. Cell densities were correlated with morphometric data for the same animals, and the spatial resolution of the ON mBC mosaic was calculated in each case. The distribution of ON mBCs is homogeneous throughout growth. For a 10-fold change in body size (i.e., from 20 to 200 mm), the total number of ON mBCs increases 2.8 times, while retinal area expands around 10 times. As a consequence, the density of ON mBCs in large fish falls to ∼1/3 of that of small animals, and intercellular spacing doubles. The eye and the lens become around three times larger from small to large fish. This causes the retinal magnification factor (and thereby the image projected onto retina) to augment by the same amount. Because the retinal magnification factor rises more than the intercellular spacing in the same animals, the spatial resolution of the ON mBC mosaic improves from 0.8 to 1.4 cycles/degree as the body size increases from 20 to 200 mm. As ON mBCs are mostly rod-driven, our results suggest that the scotopic acuity of the goldfish may improve as the animal grows.

Ecotoxicological evaluation of waste water from nitrocellulose production.

The present study evaluated the toxic potential and physicochemical characteristics of waste water generated in nitrocellulose production, including effluents from delignification, bleaching, nitration and mixture (composed of these three effluents), from a plant in the Paraiba Valley, São Paulo, Brazil. The test organisms used for toxicity assays were Daphnia similis, Danio rerio, Escherichia coli, Pseudomonas putida and Pseudokircheneriella subcaptata. The results showed that the effluents analyzed present acute and chronic toxicity for the organisms tested. Nitration effluent was the least toxic, while delignification and bleaching effluents were the most toxic. The naturally occurring pollutants in wood fiber and cotton, like lignin, probably contributed to effluents toxicity, in addition to higher concentrations of total dissolved solids, which are in non-compliance with Brazilian legislation, conductivity, chemical oxygen demand and color. The discharge of nitrocellulose effluent into an aquatic environment should only occur after appropriate treatment, due to their toxic characteristics.

Treatment of wastewater from a cotton dyeing process with UV/H2O2 using a photoreactor covered with reflective material.

Wastewater containing several dyes, including sulfur black from the dyeing process in a textile mill, was treated using a UV/H2O2 process. The wastewater was characterized by a low BOD/COD ratio, intense color and high acute toxicity to the algae species Pseudokirchneriella subcaptata. The influence of the pH and H2O2 concentration on the treatment process was evaluated by a full factorial design 22 with three replicates of the central experiment. The removal of aromatic compounds and color was improved by an increase in the H2O2 concentration and a decrease in pH. The best results were obtained at pH 5.0 and 6 g L(-1). With these conditions and 120 min of UV irradiation, the removal of the color, aromatic compounds and COD were 74.1, 55.1 and 44.8%, respectively. Under the same conditions, but using a photoreactor covered with aluminum foil, the removal of the color, aromatic compounds and COD were 92.0, 77.6 and 59.4%, respectively. Moreover, the use of aluminum foil reduced the cost of the treatment by 40.8%. These results suggest the potential application of reflective materials as a photoreactor accessory to reduce electric energy consumption during the UV/H2O2 process.