Akihiro Ohsumi

Genotypic variation of stomatal conductance in relation to stomatal density and length in rice (Oryza sativa L.).

Abstract Stomatal conductance (gs) is an important trait responsible for the genotypic difference in gas diffusion for photosynthesis and transpiration in rice (Oryza sativa L.). We measured gs, stomatal density and stomatal length (guard-cell length) at two weeks before heading for 64 accessions from a rice diversity research set of germplasm (RDRS) and for three high-yielding cultivars (HYC) under field conditions. Considerable variations in gs, and stomatal length were observed among varieties in RDRS, and it was considered that RDRS covers the species diversity of the stomatal characteristics in rice. When it was compared among the varieties with similar plant earliness, gs was higher in HYC than in most varieties of RDRS. Stomatal density did not correlate with gs, and there was a negative correlation between stomatal density and stomatal length. However, noticeable variance existed in the latter relation, where HYC exhibited a higher stomatal density and slightly shorter stomatal length than RDRS. High gs in HYC is attributable to their high stomatal density and moderate specific stomatal conductance (gs / stomatal density) while the high-gs varieties in RDRS tended to have a lower stomatal density and higher specific stomatal conductance. Stomatal length is related to specific stomatal conductance, but there are remarkable differences between these traits. Specific stomatal conductance in HYC has not reached the upper limit for their stomatal size, which raises a possibility of further improvement of HYC in gs.

Reconditioning of lungs donated after circulatory death with normothermic ex vivo lung perfusion

BACKGROUND The use of donation-after-circulatory-death (DCD) donors for lung transplantation has come into practice. In this study we investigated whether DCD lungs can be resuscitated after warm ischemia with normothermic ex vivo lung perfusion (EVLP). METHODS Four hours after cardiac arrest, beagle dogs were divided into two groups (n = 6 each): those with static cold storage (SCS group) and those with normothermic EVLP (EVLP group), for 3.5 hours. Physiologic lung functions were evaluated during EVLP. In both groups, the left lungs were then transplanted and reperfused for 4 hours to evaluate post-transplant lung functions. Lung tissue adenosine triphosphate (ATP) levels were measured at given time-points. RESULTS Lung oxygenation was significantly improved with EVLP (p < 0.01), and lung oxygenation at the end of EVLP significantly reflected post-transplant lung oxygenation (r = 0.99, p < 0.01). Post-transplant lung oxygenation was significantly better in the EVLP group than in the SCS group (p < 0.05). Both dynamic pulmonary compliance and wet-to-dry lung weight ratio 4 hours after transplantation were also significantly better in the EVLP group than in the SCS group (p < 0.05). Microthrombi in the donor lungs before transplantation were microscopically detected more often in the SCS group. The lung tissue ATP levels 4 hours after transplantation were significantly higher in the EVLP group compared with the SCS group (p = 0.03). CONCLUSIONS Normothermic ex vivo lung perfusion could resuscitate DCD lungs injured by warm ischemia, and may ameliorate ischemia-reperfusion injury.

Detection of a quantitative trait locus controlling carbon isotope discrimination and its contribution to stomatal conductance in japonica rice.

Increasing leaf photosynthesis offers a possible way to improve yield potential in rice (Oryza sativa L.). Carbon isotope discrimination (Δ13C) has potential as an indirect selection criterion. In this study, we searched for quantitative trait loci (QTLs) controlling Δ13C, and assessed their association with leaf photosynthesis. Substitution mapping by using chromosome segment substitution lines (CSSLs), that carry segments from the indica cultivar Kasalath in the genetic background of the japonica cultivar Koshihikari, identified genomic regions affecting Δ13C on chromosomes (Chr.) 2, 3, 6, 7, and 12. One of the CSSLs, SL208, in which most regions on Chr. 3 were substituted with Kasalath segments, showed higher leaf stomatal conductance for CO2 (gs) and Δ13C than Koshihikari during the vegetative stage although leaf photosynthetic rate did not differ between them. These results suggest an association between Δ13C and gs. To test this association, we performed a QTL analysis for Δ13C at vegetative and heading stages in an F2 population derived from a cross between SL208 and Koshihikari. The results confirmed a QTL controlling Δ13C on the long arm of Chr. 3. By using a near-isogenic line specific to Hd6, we ruled out the possibility that variation in Δ13C was generated through the pleiotropic effect of heading date.

Effects of Soil Temperature on Growth and Root Function in Rice

Abstract The objective of this study was to clarify the effects of soil temperature in the stage from late tillering to panicle initiation (SI) and during the grain-filling stage (SII) on grain setting, dry matter production, photosynthesis, non-structural carbohydrate (NSC), xylem exudation and abscisic acid (ABA) levels in rice (Oryza sativa L. cv. Koshihikari). Rice plants were exposed to four different soil temperatures during SI or SII: 17.5, 25, 31.5 and 36.5°C (ST18, ST25, ST32 and ST37, respectively). The yield, yield components, grain filling and quality in SI were negatively influenced by high soil temperature of 37°C. On the other hand, there was no significant difference in those characters among temperature treatments in SII. The root/shoot ratio was smallest in the ST37 plants in both SI and SII, mainly due to their lighter root weight. At 7 days after initiation of treatment (DAT) in both SI and SII, the photosynthetic and xylem exudation rate tended to increase slightly as soil temperature increased up to 32°C. At 21 DAT, however, the photosynthetic rate was lowest in ST37, with concurrent decrease of diffusion conductance and SPAD value. In addition, decrease of NSC concentration in stem and xylem exudation rate, and increase of ABA level in leaves and xylem exudate were observed in ST37 plants at 21 DAT. These results suggested that high soil temperature before heading especially influenced yield, grain quality and plant growth. Possible mechanisms of the effect of soil temperature are discussed.

Protective effect of plasmin in marginal donor lungs in an ex vivo lung perfusion model

BACKGROUND Donor lung thrombi are considered an important etiology for primary graft dysfunction in lung transplantation. We hypothesized that thrombolysis before lung transplantation could alleviate ischemia-reperfusion injury. This study was designed to evaluate the effect of the fibrinolytic agent plasmin on lungs damaged by thrombi in an ex vivo lung perfusion (EVLP) system. METHODS Rats were divided into control, non-plasmin, and plasmin groups (n = 7 each). In the control and plasmin groups, cardiac arrest was induced by withdrawal of mechanical ventilation without heparinization. Ventilation was restarted 150 minutes after cardiac arrest. The lungs were flushed, and the heart and lungs were excised en bloc. The lungs were perfused in the EVLP system for 60 minutes, and plasmin or placebo was administered upon EVLP initiation. RESULTS Fibrin/fibrinogen degradation products in the perfusate were significantly higher in the plasmin group than in the control and non-control groups (p < 0.001 for both). Plasmin administration significantly decreased pulmonary vascular resistance (plasmin vs non-plasmin, p = 0.011) and inhibited the exacerbation of dynamic compliance (plasmin vs non-plasmin, p = 0.003). Lung weight gain was less in the plasmin group than in the non-plasmin group (p = 0.04). CONCLUSIONS Our results confirmed that plasmin administration in an EVLP model dissolved thrombi in the lungs, resulting in reconditioning of the lungs as assessed by various physiologic parameters.

Response of Leaf Photosynthesis to Vapor Pressure Difference in Rice (Oryza sativa L) Varieties in Relation to Stomatal and Leaf Internal Conductance

Abstract In the afternoon when air humidity decreases, leaf photosynthetic rate (Pn) often declines in rice grown under irrigated conditions. To clarify the genotypic difference of Pn in response to humidity, we measured Pn and stomatal conductance (gs) for nine rice varieties with diverse genetic backgrounds, at various vapor pressure differences (VPD) and developmental stages. Pn and gs of all the varieties decreased with VPD increase from 1.0 to 2.3 kPa of VPD. The variety with high gs at low VPD exhibited a greater decline of gs with VPD increase than the variety with low gs, but cv. Takanari showed the highest gs under altered VPD conditions. Significant logarithmic relations were found between the decreased Pn and gs at the respective developmental stages, suggesting that gs is the dominant factor determining Pn and its response to VPD change. To explicate the effect of decreased gs on Pn, we analyzed the relations by using the model that accurately estimated the genotypic difference in Pn at a low VPD with gs and leaf nitrogen content per unit leaf area in the previous study. The model assuming that leaf internal conductance (gw) remains unchanged well explained the decreased Pn at high VPDs by gs change alone. The analysis also suggested the constancy of gw and carboxylation capacity at high VPD. It is concluded that the genotypic difference in the decrease of Pn at a high VPD is brought mainly by that in decreased gs, and the varieties with a high gs always exhibit a high Pn owing to their relatively high gs at either high or low VPD environments.

Plasmin administration during ex vivo lung perfusion ameliorates lung ischemia–reperfusion injury

BACKGROUND Donor lung thrombus is considered a significant etiology for primary graft dysfunction (PGD). We hypothesized that thrombolysis in ex vivo lung perfusion (EVLP) before lung transplantation could alleviate ischemia-reperfusion injury (IRI), resulting in a decreased incidence of PGD. METHODS Rats were divided into control (n = 5), non-plasmin (n = 7) and plasmin (n = 7) groups. In the non-plasmin and plasmin groups, cardiac arrest was induced by withdrawal of ventilation without heparinization. After 120 minutes of warm ischemia, the lungs were ventilated and flushed. Hearts and both lungs were excised en bloc. The lungs were perfused and ventilated in the EVLP for 30 minutes, and plasmin or placebo was administered on EVLP initiation. The lungs were then stored at 4°C for 90 minutes and finally perfused with rat blood for 80 minutes. We assessed physiologic and histologic findings during reperfusion and the correlation between physiologic data during EVLP and after reperfusion. RESULTS Physiologic results were better in the plasmin group than in the non-plasmin group. The plasmin group lungs had fewer signs of histologic injury. Caspase-3 and -7 activity in the plasmin group was lower in the non-plasmin group. Pulmonary vascular resistance (PVR) during EVLP correlated with that at the end of reperfusion. CONCLUSIONS Plasmin administration during EVLP protected the donor lungs after reperfusion. We also found that several physiologic values in EVLP may be predictive markers of lung function after reperfusion.

Effect of hypogammaglobulinemia after lung transplantation: a single-institution study

OBJECTIVES Recent studies suggest hypogammaglobulinemia (HGG) is frequently associated with infection after solid organ transplantation, although the effects of HGG after lung transplantation are not well recognized. We investigated the incidence and degree of HGG after lung transplantation and its association with infection. METHODS A retrospective cohort study analysing pre- and post-transplant IgA, IgG and IgM levels and infectious events in patients undergoing living-donor lobar and cadaveric lung transplantation at Kyoto University Hospital between June 2008 and March 2013. RESULTS Overall, post-transplant immunoglobulin (Ig) levels were significantly lower than pretransplant levels. In almost all patients who received transplants for bronchiolitis obliterans (BO) after haematopoietic stem cell transplantation (HSCT), interstitial lung diseases and bronchiectasis, post-transplant IgA and IgG levels decreased and were significantly lower than pretransplant levels; pre- and post-transplant IgA and pretransplant IgG levels were significantly lower in patients transplanted for BO after HSCT than in the others. Post-transplant IgG levels in patients transplanted for BO after HSCT also tended to be lower than those in the others, but not significantly. Nineteen of 29 patients had HGG after lung transplantation (65.5%) and had more infections than the normal gammaglobulinemia group, although there was no significant difference. Among them, 2 patients transplanted for BO after HSCT with quite low HGG had severe pneumonia and finally died. CONCLUSIONS Post-transplant Ig levels were significantly lower than pretransplant levels. Although without significant difference, HGG patients had more infections, above all, those with severe HGG transplanted for BO after HSCT could have lethal infections. Ig levels in HGG should be monitored carefully because severe HGG was associated with poor prognosis.

Protective effect of pre-recovery surfactant inhalation on lungs donated after cardiac death in a canine lung transplantation model

BACKGROUND Warm ischemia-reperfusion injury related to donation after cardiac death is a crucial issue in transplantation. Because surfactant function deteriorates in lungs during warm ischemia, we hypothesized pre-recovery surfactant inhalation would mitigate warm ischemia-reperfusion injury. METHODS We rendered donor dogs cardiac dead and left them at room temperature. All animals received ventilation for 60 minutes starting at 240 minutes after cardiac arrest. The animals were divided into 2 groups: NS (normal saline, n = 7) group, which received aerosolized normal saline, and SF (surfactant; n = 5), which received aerosolized surfactant. The lungs were flushed and procured, and the left lung was transplanted into recipient dogs. At 45 minutes of reperfusion, the right pulmonary artery was ligated, and the left transplanted lung function was evaluated. RESULTS In the NS group, 2 of 7 dogs died at 75 minutes after reperfusion, whereas all 5 animals in the SF group survived for 240 minutes after reperfusion. The SF group showed significantly better dynamic compliance, oxygenation, and wet-to-dry weight ratio. Furthermore, the SF group had higher levels of high-energy phosphates in the lung tissues and lower levels of interleukin-8, tumor necrosis factor-α, and protein in the bronchoalveolar lavage fluid. Histologically, the lungs in the SF group showed fewer signs of interstitial edema and hemorrhage and significantly less neutrophilic sequestration than those of the NS group. CONCLUSIONS Our results indicated pre-recovery surfactant inhalation improved graft function, maintained adenine nucleotide levels, and prevented alveolar-capillary barrier leakage, resulting in the attenuation of warm ischemia-reperfusion injury.

Varietal Differences in Biomass Production of Rice Early After Transplanting at Low Temperatures

Abstract Low temperature decreases biomass production and yield in rice through a number of physiological and morphological changes. We evaluated biomass production in 22 high-yielding genotypes and four commercial japonica cultivars early after transplanting under field conditions for 2 years. The seedlings were transplanted on 30 April or 1 May (early transplanting, ET) and 4 weeks later (late transplanting, LT). The mean air temperature during the 18 days after transplanting in ET was about 4ºC lower than that in LT in both years. The seedling length was greater in high-yielding japonica varieties than in indica genotypes, whereas the seedling character index (SCI), which is the product of plant age in leaf number and the ratio of the seedling weight to its length, was the highest in the indica genotypes. Varietal differences in biomass production were greater in ET than in LT in all rice genotypes. The biomass at 18 days after transplanting was largest in the japonica high-yielding varieties Kusayutaka and Beko-aoba in both ET and LT. The biomass production of the indica genotypes was found to decrease severely after transplanting at low temperatures although the indica genotypes with high SCIs showed faster leaf emergence than the high-yielding japonica varieties. There was a strong positive correlation between the varietal differences in biomass production and shoot length at 18 days after transplanting in ET in both years. Our study suggests that superior shoot elongation in the high-yielding japonica varieties with large biomass allocation to the stems may be advantageous in maintaining biomass productivity at low temperatures.