Reactivation of the Hill reaction of Tris-washed chloroplasts

The Hill reaction of chloroplasts was inhibited by washing themwith 0.8 M Tris buffer. This inhibition was further promotedby adding ferricyanide in the washing medium. When a reducingreagent, such as the 2,6-dichlorophenol indophenol (DCPIP)-ascorbatesystem or the hydroquinone (HQJ-ascorbate system, had been addedto the Tris buffer, Hill reaction activity was unaffected. Hill reaction activity of Tris-washed chloroplasts recoveredup to 70% of the initial level by re-washing the chloroplastswith a preparation medium containing theabove reducing reagents. Photobleaching of carotenoid and chlorophyll is characteristicof Tris-washed chloroplasts. However, reactivated chloroplastsshowed no photobleaching as in the case with intact chloroplasts. (Received April 20, 1970; )     

Photoactivation of Oxygen-evolving System in Dark-grown Spruce Seedlings

Plastids prepared from dark-grown spruce seedlings showed a negligible activity of photosystem II, and no fluorescence variation was observed during actinic illumination. The photosystem II reaction centre, however, was present in primary thylakoids. Exposure of such seedlings to continuous light induced the development of photosystem II activity via three stages (rapid, lagged and gradual), and the variable fluorescence appeared. The rapid development of photosystem II may be attributed to the activation of the oxygen-evolving system, possibly the manganese-catalyzing site, and the lagged and gradual developments may be closely related to the formation of thylakoid membranes and their assembly to grana.     

韩国华津浦湖的鱼类区系

There are sevenlagoons onthe east coast of Korea,including Kyeongpo Lake,Hyang Lake,Mae Lake,Chung-cho Lake,Yeoungrang Lake,Songji Lake and HwajinpoLake.They are all originally natural and brackish waterlakes.Therefore,these lakes are not only historically veryimportant but also have high values for geological,andecological sciences.Natural lakes like lagoons are different from man-made lakes.That is,water level in natural lakes is almostconstant,cline by waterside is not much,and wet la…     

Another Origin of Coloniality in Volvocaleans: The Phylogenetic Position of Pyrobotrys Arnoldi (Spondylomoraceae,Volvocales)

ABSTRACT. Colonial volvocaleans (Chlorophyceae) are used as a standard model of multicellular evolution. However, the phylogenetic position of the colonial volvocalean family Spondylomoraceae has yet to be resolved. To examine this, the molecular phylogenies of Pyrobotrys stellata and Pyrobotrys squarrosa were analyzed using combined 18S rRNA, RUBISCO large subunit, and P700 chl a‐apoprotein A2 gene sequences. In the phylogenetic trees, Pyrobotrys belonged to the clade Caudivolvoxa and was not closely related to other colonial volvocalean flagellates. The results indicate that colony formation of Spondylomoraceae independently evolved from unicellular volvocaleans. The phylogenetic position of problematic “Pascherina tetras” SAG 159‐1 was also analyzed.     

Lacking chloroplasts in guard cells of crumpled leaf attenuates stomatal opening: both guard cell chloroplasts and mesophyll contribute to guard cell ATP levels

Controversies regarding the function of guard cell chloroplasts and the contribution of mesophyll in stomatal movements have persisted for several decades. Here, by comparing the stomatal opening of guard cells with (crl‐ch) or without chloroplasts (crl‐no ch) in one epidermis of crl (crumpled leaf) mutant in Arabidopsis, we showed that stomatal apertures of crl‐no ch were approximately 65–70% those of crl‐ch and approximately 50–60% those of wild type. The weakened stomatal opening in crl‐no ch could be partially restored by imposing lower extracellular pH. Correspondingly, the external pH changes and K⁺ accumulations following fusicoccin (FC) treatment were greatly reduced in the guard cells of crl‐no ch compared with crl‐ch and wild type. Determination of the relative ATP levels in individual cells showed that crl‐no ch guard cells contained considerably lower levels of ATP than did crl‐ch and wild type after 2 h of white light illumination. In addition, guard cell ATP levels were lower in the epidermis than in leaves, which is consistent with the observed weaker stomatal opening response to white light in the epidermis than in leaves. These results provide evidence that both guard cell chloroplasts and mesophyll contribute to the ATP source for H⁺ extrusion by guard cells.     

Melanocyte-Stimulating Properties of Arachidonic Acid Metabolites: Possible Role in Postinflammatory Pigmentation

Normal human epidermal melanocytes became swollen and more dendritic with an increase in the amount of tyrosinase and immunoreactive b-locus protein when they were cultured for 2 days with the following arachidonic acid metabolites: prostaglandin (PG) D₂, leukotriene (LT) B₄, LTC₄, LTD₄, LTE₄, thromboxane (TX) B₂ and 12-hydroxy eicosatetraenoic acid (12-HETE). The effect of LTC₄ was particularly strong compared to that of PGE₂, about which we have previously reported. On the other hand, PGE₁, PGF_2α and 6-ketoPGF_1α did not show any significant stimulatory effect. These data suggest that arachidonate-derived chemical mediators, especially LTC₄, may be responsible for the induction of post-inflammatory hyperpigmentation of the skin.     

The Expression of Tyrosinase,Tyrosinase-Related Proteins 1 and 2 (TRP1 and TRP2), the Silver Protein,and a Melanogenic Inhibitor in Human Melanoma Cells of Differing Melanogenic Activities

The expression of various melanogenic proteins, including tyrosinase, the tyrosinase-related proteins 1 (TRP1) and 2 (TRP2/DOPAchrome tautomerase), and the silver protein in human melanocytes was studied in six different human melanoma cell lines and compared to a mouse derived melanoma cell line. Analysis of the expression of tyrosinase, TRP1, TRP2, and the silver protein using flow cytometry revealed that in general there was a positive correlation between melanin formation and the expression of those melanogenic enzymes. Although several of the melanoma cell lines possessed significant activities of TRP2, the levels of DOPAchrome tautomerase in extracts of human cells were relatively low compared to those in murine melanocytes. Melanins derived from melanotic murine JB/MS cells, from melanotic human Ihara cells and HM-IY cells, from sepia melanin, and from C57BL/6 mouse hair were chemically analyzed. JB/MS cells, as well as Ihara cells and HM-TY cells, possessed significant amounts of 5,6-dihydroxyindole-2-carboxylic acid (DHICA) derived melanins, this being dependent on the activity of TRP2. Kinetic HPLC assays showed that 5,6-dihydroxyindole (DHI) produced during melanogenesis was metabolized quickly to melanin in pigmented KHm-1/4 cells, whereas DHI was stable in amelanotic human SK-MEL-24 cells. A melanogenic inhibitor that has been purified from SK-MEL-24 cells that suppressed oxidation of DHI in the presence or absence of tyrosinase, but had no effect on DHICA oxidation. The sum of these results suggest that the expression of melanogenic enzymes as well as the activity of a melanogenic inhibitor are critical to the production of melanin synthesis in humans.     

The Hill reaction and oxygen uptake in isolated pine chloroplasts

1. The Hill reaction and oxygen uptake in chloroplasts preparedfrom pine leaves were studied. Pine chloroplasts active forthe Hill reaction were isolated from mature leaves in the presenceof 25% PEG in the isolation buffer. Time courses of the Hillreaction in chloroplasts isolated from leaves at different seasonsdiffered. In chloroplasts isolated in the autumn, Hill activitydecreased rapidly with illumination time. This rapid decreaseof Hill activity was inferred to result from concomitant productionof some inhibitory substance(s) during the Hill reaction.
2. Theprotective effect of PEG on inactivation by aging of pinechloroplastswas found. In the presence of PEG, chloroplastswere stabilizedand Hill activity was maintained even afterstorage for 26 hr;whereas, in the absence of PEG inactivationby aging proceededrapidly and oxygen uptake occurred after20 hr.
3. Chloroplastsisolated without PEG had no ability of the Hillreaction; but,inversely showed pronounced oxygen uptake. Oxygenuptake wasalso observed in aged or DCMU-inhibited chloroplasts.The presenceof benzoquinone strongly suppressed oxygen uptake.

¹ Present address: Laboratory of Biology and Chemistry, Universityof Naval Architecture of Nagasaki, Nagasaki, Japan. (Received January 27, 1971; )     

Photoactivation of the latent O2-evolving center in chloroplasts isolated from dark-grown spruce seedlings

The latent O₂-evolving center in chloroplasts isolated from spruce [Picea abies (L.) Karst.] seedlings grown in the dark was readily activated by pre-illuminating the chloroplast suspension with weak white light. The photoactivation depended on pH with the optimum at pH 7–8, and was strongly stimulated by ascorbic acid. The optimal stimulation was also obtained at pH 7–8. The temperature dependence of the photoactivation suggested the involvement of some dark reaction in the activation process.     

FISH FAUNA OF THE HWAJINPO LAKE,KOREA

There are sevenlagoons onthe east coast of Korea,including Kyeongpo Lake,Hyang Lake,Mae Lake,Chung-cho Lake,Yeoungrang Lake,Songji Lake and HwajinpoLake.They are all originally natural and brackish waterlakes.Therefore,these lakes are not only historically veryimportant but also have high values for geological,andecological sciences.Natural lakes like lagoons are different from man-made lakes.That is,water level in natural lakes is almostconstant,cline by waterside is not much,and wet la…