CgPBA1 may be involved in nuclear degradation during secretory cavity formation by programmed cell death in Citrus grandis 'Tomentosa' fruits.

Caspase-3 is the crucial executor caspase of apoptosis in mammalian cells, which is essential for chromatin condensation and DNA fragmentation. Although plants have no caspase-3 homologs, PBA1 acts as a plant caspase-3-like enzyme in plant programmed cell death (PCD). PCD occurs during the formation of secretory cavities in Citrus fruits; hence, secretory cavities could be utilized as a new cell biology model for investigating the regulatory mechanisms of plant PCD. To further study the association between PBA1 and PCD during secretory cavity development in Citrus fruits, CgPBA1 was identified in the fruit of Citrus grandis 'Tomentosa'. The temporal and spatial expression of CgPBA1 during secretory cavity development were analyzed using quantitative real-time PCR and in situ hybridization, and the morphological changes in the apoptotic cell nuclei were observed using TUNEL assay and ultra-thin section technology. The results revealed that the full-length cDNA of CgPBA1 contains a 711 bp ORF that encodes a putative protein containing 236 amino acid with a proteasome-ß-6 functional domain that belongs to the Ntn hydrolase super family. CgPBA1 was predominantly expressed in the secretory cavities; its expression changes coincided with the morphological changes and DNA fragmentation in apoptotic cell nuclei. The green fluorescent fusion protein of CgPBA1 is also located in the nucleus of tobacco epidermal cells. Based on previous research and the findings of the present study, we speculate that CgPBA1 is a highly functional conserved protein in plants, and it might be involved in nuclear degradation during PCD for secretory cavity formation in C. grandis 'Tomentosa' fruits.

Excimer laser photorefractive keratectomy for myopia: six-month follow-up.

In this study, 108 eyes of 62 patients had photorefractive keratectomy (PRK) with a 193 nm excimer laser to correct myopia. The eyes were assigned to one of three groups: low, moderate, or high myopia. Six months after PRK, 88.9% of eyes in the low myopia group, 90.0% in the moderate myopia group, and 23.8% in the high myopia group achieved an uncorrected visual acuity of 20/40 or better. In the low myopia group, 88.9% were within +/- 1 diopter (D) of attempted correction, as were 70.0% in the moderate group and 18.8% in the high myopia group. There were no significant complications. We conclude that excimer laser PRK appears to be a safe and relatively accurate procedure to correct low to moderate myopia but not high myopia because of regression over time.