In this study, a high frequency cyclic secondary somatic embryogenesis system was established for Cyclamen persicum. Moreover, the influence of primary somatic embryos (PSEs) at different stages of development, number of passages, abscisic acid (ABA), and sucrose concentrations on secondary somatic embryogenesis were investigated. Primary somatic embryos, at different stages of development, were incubated on an induction medium consisting of halfstrength Murashige and Skoog (MS) (Physiol Plant 15:473-497, 1962), 2 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D), and 0.2 mg/l 6-benzyladenine (BA). These initial PSE cultures along with calli were transferred to a plant growth regulator (PGR)-free medium to promote secondary somatic embryo (SSE) development. Embryogenic calli were induced at a frequency [90% from all PSE cultures. Both morphology and size of PSEs influenced embryogenic competence. Large-sized globular embryos (GEs) yielded the highest number of SSEs followed by small-and large-sized torpedo-stage embryos (TEs). Passages of induced calli obtained from large-sized GEs had no effects on frequency of secondary embryogenesis; however, they significantly influenced SSE production. Calli from the first passage exhibited the highest competence for secondary embryogenesis, 100% frequency of SSEs, producing 3,306 and 1,296 SSEs per gram fresh weight callus and embryo, respectively.

Successive filtration and comparison show that the stratosphere air temperature in 10 hPa-layer of the Northern Hemisphere (NH) in July continuously increases, which is associated to the increases in greenhouse gases mostly CO 2 , volcanic activities, and solar activity, demonstrating the follows. (a) The increase in CO 2 concentration is largely consistent with that of the stratosphere air temperature in 10 hPa-layer of the NH in July. However, the increase in the air temperature is not in a linear pattern, during which several cooling events interrupt. The cooling events between late 1960s and late 1970s are remarkable ones and so is the one before mid 1990s. Analysis shows that these events are induced by volcanic activities and solar activity. (b) The CO 2 -free variation in the stratosphere air temperature in 10 hPa-layer of the NH is consistent with that of the solar magnetic index. The wave crests and wave troughs of the two curves are consistent in phase, and the curve of solar magnetic index leads the other slightly. In other words, when the solar magnetic pole is southward, a warming in the NH stratosphere corresponds; and on the contrary, the northward solar magnetic pole corresponds to a cooling event. The variation in solar magnetic polarity strongly impacts the variation in the stratosphere temperature.

Proparacaine (PPC) is a widely used topical anaesthetic in the eye clinic; its abuse may damage the cornea and result in impairment of vision. Although PPC has been reported to be cytotoxic to human keratocytes, there is no scientific report about its toxic mechanisms in human corneal stroma. Here, we evaluated the cytotoxicity of PPC to corneal stroma in an model of human corneal stromal (HCS) cells and an model of cat corneas. To postulate the cellular and molecular mechanisms involved in PPC toxicity, changes in the hallmarks of apoptosis as well as in pro-apoptotic signaling pathways were investigated. Our results showed that PPC at concentrations varying from 5.0 to 0.15625 g L induced dose- and time-dependent cell atrophy, vacuolation, cytopathic effects, and viability decline . Moreover, PPC induced G phase arrest, plasma membrane permeability elevation, phosphatidylserine externalization, DNA fragmentation, chromatin condensation, and apoptotic body formation of HCS cells. Furthermore, PPC could induce caspase-2, -3 and -9 activation, and mitochondrial transmembrane potential disruption. Expression of Bcl-xL and Bax were downregulated and upregulated, respectively, and cytoplasmic cytochrome c and apoptosis inducing factor were upregulated remarkably after PPC treatment. The cytotoxicity and pro-apoptotic effects of PPC were also proven by induced corneal edema, apoptotic-like ultrastructural alterations and DNA fragmentation of keratocytes in cat corneas . These results suggest that PPC above 1/32 of its clinical dosage has remarkable cytotoxicity to corneal stromal cells, which is achieved by inducing death receptor-mediated mitochondria-dependent apoptosis of HCS cells.