Our results indicate that ultrastructural defects in outer and inner segment membranes of bP23H expressing rods differ from those observed in drug-induced apoptosis. We suggest that light-induced retinal degeneration caused by P23H rhodopsin occurs via cell death with autophagy, which may represent an attempt to eliminate the mutant rhodopsin and/or damaged cellular compartments from the secretory pathway.

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In the late 1960s, Melanoides tuberculatus snails were introduced in Brazil from North/East Africa and Southeast Asia. The first records of specimens infected with cercariae were registered in Rio de Janeiro State in 2001. The present study reports the occurrence of M. tuberculatus infected with larval trematodes in Rio de Janeiro City. Bottom sediment was collected with dip nets and sieved through 0.25 inch-mesh screening. Snails were transported to the laboratory in vials with stream water, then measured and individually isolated in glass vials with distilled water. They were exposed to artificial light and temperature to induce cercarial emergence. The most actively emerging cercariae were processed by differential staining and silver nitrate impregnation methods. Negative snails were subsequently dissected. Approximately 700 snails were collected. Snail total lengths ranged from 1.2 to 3.3 cm. The prevalence rate was 15.76% although 53.76% of the snails were found infected in one of the sites. Infected snails were infected with rediae and pleurolophocercous cercariae. Cercarial morphology and chaetotaxy were consistent with those of the family Heterophyidae mostly due to the presence of median dorsal and ventral fins on the tail and the absence of CI dorsal sensory receptors.

The present work aimed to compare the acrophases (peak hours) of emergence of Schistosoma mansoni cercariae among isolated individuals of the snail Biomphalaria glabrata. Laboratory stocks of melanic B. glabrata from the same biotope as the S. mansoni strain (Belo Horizonte, Minas Gerais) were used. Twenty-two snails individually exposed to five miracidia were tested. Chronobiological trials were performed outdoors after an acclimation period of at least a week. Three groups of snails were tested between November 1989 and April 1991. Cercarial emergence from individual isolated snails was quantified every 3 h for 3 consecutive days. In all trials, most cercariae were found to emerge during daytime (94.9%). Time series and chronograms showed recurrent peaks during the daytime. The periodogram suggested that 24 h was the period that best fitted cercarial emergence data in 90.9% of the snails. The single cosinor analysis confirmed 24-h rhythms in 95.5% of the snails. Acrophases of cercarial emergence among individual snails occurred between 14:15 and 17:02. They did not differ significantly. The population cosinor analysis indicated greater homogeneity in the 24-h rhythms of cercarial emergence than in the snail groups of each chronobiological trial. Acrophases of cercarial emergence occurred between 14:53 and 15:27 and did not differ significantly among all trials. Data from the three trials were pooled and analyzed using the population cosinor. This statistical method indicated a homogeneity in the 24-h rhythms of cercarial. emergence from all snails, with acrophase occurring around 15:00. Results showed that the acrophases of cercarial emergence of S. mansoni are similar among isolated B. glabrata specimens. Data support the hypothesis of a "gate" rhythm in the dynamics of cercarial production and emergence. It is suggested that the adaptive importance of the "gate" mechanism is associated with the concentration of cercariae in the water at times when the vertebrate is present, optimizing the contact between the parasite and the host. The emergence of some cercariae at night (5.1% of the total number of emerged cercariae) suggests a flexible "gate" that could be associated with a residual light effect or with experimental procedures in the laboratory.