Enhanced Reduction of Ferredoxin in PGR5-Deficient Mutant of Arabidopsis thaliana Stimulated Ferredoxin-Dependent Cyclic Electron Flow around Photosystem I.

The molecular entity responsible for catalyzing ferredoxin (Fd)-dependent cyclic electron flow around photosystem I (Fd-CEF) remains unidentified. To reveal the in vivo molecular mechanism of Fd-CEF, evaluating ferredoxin reduction-oxidation kinetics proves to be a reliable indicator of Fd-CEF activity. Recent research has demonstrated that the expression of Fd-CEF activity is contingent upon the oxidation of plastoquinone. Moreover, chloroplast NAD(P)H dehydrogenase does not catalyze Fd-CEF in Arabidopsis thaliana. In this study, we analyzed the impact of reduced Fd on Fd-CEF activity by comparing wild-type and pgr5-deficient mutants (pgr5hope1). PGR5 has been proposed as the mediator of Fd-CEF, and pgr5hope1 exhibited a comparable CO2 assimilation rate and the same reduction-oxidation level of PQ as the wild type. However, P700 oxidation was suppressed with highly reduced Fd in pgr5hope1, unlike in the wild type. As anticipated, the Fd-CEF activity was enhanced in pgr5hope1 compared to the wild type, and its activity further increased with the oxidation of PQ due to the elevated CO2 assimilation rate. This in vivo research clearly demonstrates that the expression of Fd-CEF activity requires not only reduced Fd but also oxidized PQ. Importantly, PGR5 was found to not catalyze Fd-CEF, challenging previous assumptions about its role in this process.

Evaluating the Oxidation Rate of Reduced Ferredoxin in Arabidopsis thaliana Independent of Photosynthetic Linear Electron Flow: Plausible Activity of Ferredoxin-Dependent Cyclic Electron Flow around Photosystem I.

The activity of ferredoxin (Fd)-dependent cyclic electron flow (Fd-CEF) around photosystem I (PSI) was determined in intact leaves of Arabidopsis thaliana. The oxidation rate of Fd reduced by PSI (vFd) and photosynthetic linear electron flow activity are simultaneously measured under actinic light illumination. The vFd showed a curved response to the photosynthetic linear electron flow activity. In the lower range of photosynthetic linear flow activity with plastoquinone (PQ) in a highly reduced state, vFd clearly showed a linear relationship with photosynthetic linear electron flow activity. On the other hand, vFd increased sharply when photosynthetic linear electron flow activity became saturated with oxidized PQ as the net CO2 assimilation rate increased. That is, under higher photosynthesis conditions, we observed excess vFd resulting in electron flow over photosynthetic linear electron flow. The situation in which excess vFd was observed was consistent with the previous Fd-CEF model. Thus, excess vFd could be attributed to the in vivo activity of Fd-CEF. Furthermore, the excess vFd was also observed in NAD(P)H dehydrogenase-deficient mutants localized in the thylakoid membrane. The physiological significance of the excessive vFd was discussed.

Higher Reduced State of Fe/S-Signals, with the Suppressed Oxidation of P700, Causes PSI Inactivation in Arabidopsis thaliana.

Environmental stress increases the risk of electron accumulation in photosystem I (PSI) of chloroplasts, which can cause oxygen (O2) reduction to superoxide radicals and decreased photosynthetic ability. We used three Arabidopsis thaliana lines: wild-type (WT) and the mutants pgr5hope1 and paa1-7/pox1. These lines have different reduced states of iron/sulfur (Fe/S) signals, including Fx, FA/FB, and ferredoxin, the electron carriers at the acceptor side of PSI. In the dark, short-pulse light was repetitively illuminated to the intact leaves of the plants to provide electrons to the acceptor side of PSI. WT and pgr5hope1 plants showed full reductions of Fe/S during short-pulse light and PSI inactivation. In contrast, paa1-7/pox1 showed less reduction of Fe/S and its PSI was not inactivated. Under continuous actinic-light illumination, pgr5hope1 showed no P700 oxidation with higher Fe/S reduction due to the loss of photosynthesis control and PSI inactivation. These results indicate that the accumulation of electrons at the acceptor side of PSI may trigger the production of superoxide radicals. P700 oxidation, responsible for the robustness of photosynthetic organisms, participates in reactive oxygen species suppression by oxidizing the acceptor side of PSI.

Anthracyclines for acute lymphoblastic leukemia in a child with congenital long QT syndrome.

Anthracyclines are key drugs for the treatment of children with acute lymphoblastic leukemia (ALL). However, anthracyclines are known to induce QT prolongation, and life-threatening complications, such as torsades de pointe may also occur. To date, there have been no reports on the use of anthracyclines in patients with congenital long QT syndrome (LQTS). We report a child with ALL complicated by congenital LQTS who was treated with anthracyclines. The administration of anthracyclines caused QT-interval prolongation, but this was uneventful with the concomitant administration of magnesium sulfate.

Excessive alcohol intake enhances the development of synchronous cancerous lesion in colorectal cancer patients.

BACKGROUND AND AIMS: We examined the potential impact of alcohol drinking on the incidence of synchronous colorectal cancer. PATIENTS AND METHODS: This study comprised 191 men with colorectal cancer who had undergone surgical resection. Synchronous colorectal cancer was found in 16 patients (8.4%). The relationship between synchronous colorectal cancer and alcohol intake was analyzed by multivariate methods. Cumulative alcohol intake was assessed by the drinking index (weekly average multiplied by years of drinking). RESULTS: There was higher incidence of associated adenoma in the synchronous cancer group. Heavy cumulative intake (drinking index 9800 or higher) was associated with significantly higher risk synchronous colorectal cancer than in nondrinkers (odds ratio 6.8). The association of alcohol intake with the risk of synchronous colorectal cancer was not affected by the type of alcohol beverages. CONCLUSION: This study demonstrated that excessive alcohol intake might be an independent risk factor for synchronous colorectal cancer. The screening program based on this information may prevent the synchronous lesions being missed.

Serum KL-6 level in newborns with meconium aspiration syndrome.

BACKGROUND: It has been reported that serum KL-6 increases in babies with progressing chronic lung disease (CLD). However, there have been few reports assessing KL-6 in meconium aspiration syndrome (MAS). KL-6 was measured in neonates with respiratory diseases including MAS. METHODS: Thirty-eight neonates with respiratory disease were enrolled in the study. These patients were classified into three groups, 14 patients with respiratory distress syndrome (RDS), 14 with MAS, and 10 with transient tachypnea of the newborn (TTN). The control group consisted of 12 healthy neonates. KL-6 levels were measured 1 day (median) after the birth. In the RDS group, measurement was repeated just prior to 36 weeks' postmenstrual age. RESULTS: The levels of KL-6 were 116 +/- 40 U/mL in the RDS, 281 +/- 138 U/mL in the MAS, and 106 +/- 41 U/mL in the TTN groups. KL-6 levels were significantly higher in the MAS group than in the control group (134 +/- 71 U/mL; P < 0.01). In addition, the levels were significantly higher in those with severe MAS than those with mild MAS (P < 0.05). In patients with RDS, KL-6 increased in patients who developed CLD (P < 0.05), while KL-6 levels did not change in those who did not develop CLD. CONCLUSION: These data confirm the high level of KL-6 in CLD, and suggest that KL-6 is increased in MAS.