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The rapid proliferation of planktonic algae induced by eutrophication and climate warming make algae dissolved organic matter (AOM) an important source of dissolved organic matter (DOM) in surface waters, but the understanding of the link between AOM composition and photo-reactivity/photo-transformation of DOM in aquatic systems is limited. Here, intracellular organic matter (IOM) from Microcystis aeruginosa was extracted and subjected to molecular weight (MW) fractionation. Results indicated that IOM had lower aromaticity and higher photosensitive activity compared to Suwannee River fulvic acid (SRFA). The photosensitive activity of IOM relied on both its molecular weight distribution and fluorescence components. The IOM fraction with the highest MW proteins had the lowest quantum yields of reactive intermediates (Φ RIs ), which increased with the decrease of MW, while the fractions with more low-excitation tyrosine-like components had relatively higher Φ RIs . Parallel factor analysis and high-resolution mass spectrometry revealed that light radiation of IOM resulted in the composition transformation from tryptophan-like and tyrosine-like components to humic-like components, forming less aromatic and more saturated recalcitrant dissolved organic carbon. Our findings provide new insights into the photo-reactivity and photo-transformation of algae-derived organic matters and help to predict DOM formation involved in carbon cycling in water environment.

Ovulation is a gonadotropin-controlled process that is essential for the propagation of all mammalian species. In the present study, we used a pregnant mare serum gonodotropin/human chorionic gonadotropin (hCG)-induced, synchronized ovulation model in rhesus monkeys and systematically investigated the roles of the plasminogen activator (PA) system in the ovulatory process of the primate. At different follicular developmental stages throughout the periovulatory period, samples of ovaries, granulosa cells, and theca-interstitial cells as well as follicular fluid were collected, and levels of PA and PA inhibitor type-1 (PAI-1) were evaluated by fibrin overlay, reverse fibrin overlay, Northern blot analysis, and in situ hybridization, respectively. We showed that in response to an injection of ovulation-triggering hCG, which mimics the preovulatory surge of LH in the circulation, granulosa cell-derived tissue-type PA (tPA) was substantially elevated in preovulatory follicles and reached its maximum level just before ovulation. Although theca-interstitial cell-derived PAI-1 was also stimulated by pregnant mare serum gonodotropin and hCG treatments, however, the maximum level of PAI-1 appeared 12 h earlier than that of tPA. When ovulation approached, accompanying the highest tPA level in the preovulatory follicles, the follicular PAI-1 level declined dramatically to its minimum value. Moreover, our data on the expression of follicular PA and PAI-1 over the periovulatory period were reinforced by results obtained at the mRNA level. Our data suggest that the coordinated expression of tPA and PAI-1 may be of importance for the follicular rupture process during ovulation in the primate.

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