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PubMedDate not supplied

Removal of magnesium by Mg-dechelatase is a major step in the chlorophyll-degrading pathway in Ginkgo biloba in the process of autumnal tints.

Autumnal tints are one of the most manifest and fascinating natural phenomena, but the mechanism of chlorophyll (Chl)-breakdown in deciduous trees has not been fully elucidated. In this study, we analyzed the composition of Chl-related compounds and determined the activities of initial Chl-degrading enzymes in Ginkgo leaves at various stages in the process of autumnal coloring. Only pheophytin a (Pheo a, Mg-free Chl a) was detected in yellow leaves by HPLC analysis, and the activity of Mg-dechelatase in yellow leaves was found to be higher than in green leaves. These findings showed that the removal of magnesium from Chl a occurred in advance of dephytylation in the Ginkgo.

Carrier Proteins↗

PubMedDate not supplied

Flow cytometric comparison between swim-up and Percoll gradient techniques for the separation of frozen-thawed human spermatozoa.

Viable human spermatozoa were recovered from cryopreservation by either swim-up or Percoll density gradient techniques and their cell-surface oligosaccharide components were compared to those of fresh sperm. Sperm were labeled with FITC-Con A and analyzed by fluorescence microscopy and flow cytometry. By fluorescence microscopy, fresh sperm were uniformly labeled in the neck region alone. Frozen-thawed sperm, obtained by either swim-up or Percoll density gradients, showed two patterns of staining: one sperm population was stained in the neck region only, whilst another showed staining in both the neck and acrosome regions. No difference between sperm recovered by the two techniques was apparent. Flow cytometry profiles of fresh sperm revealed a single peak of fluorescence, whereas cryopreserved sperm gave two peaks of fluorescence. Samples recovered by Percoll density gradient contained significantly more sperm with the same fluorescence pattern as that observed for fresh sperm than did those recovered by swim-up. Cryopreservation alters the cell-surface oligosaccharide components of spermatozoa. Recovery of cryopreserved sperm by Percoll density gradient yields a greater proportion of sperm which resemble fresh sperm than does swim-up.

Cell Separation↗