Contributions of two cytosolic glutamine synthetase isozymes to ammonium assimilation in Arabidopsis roots

Glutamine synthetase (GS) catalyzes a reaction that incorporates ammonium into glutamate and yields glutamine in the cytosol and chloroplasts. Although the enzymatic characteristics of the GS1 isozymes are well known, their physiological functions in ammonium assimilation and regulation in roots remain unclear. In this study we show evidence that two cytosolic GS1 isozymes (GLN1;2 and GLN1;3) contribute to ammonium assimilation in Arabidopsis roots. Arabidopsis T-DNA insertion lines for GLN1;2 and GLN1;3 (i.e. gln1;2 and gln1;3 single-mutants), the gln1;2:gln1;3 double-mutant, and the wild-type accession (Col-0) were grown in hydroponic culture with variable concentrations of ammonium to compare their growth, and their content of nitrogen, carbon, ammonium, and amino acids. GLN1;2 and GLN1;3 promoter-dependent green fluorescent protein was observed under conditions with or without ammonium supply. Loss of GLN1;2 caused significant suppression of plant growth and glutamine biosynthesis under ammonium-replete conditions. In contrast, loss of GLN1;3 caused slight defects in growth and Gln biosynthesis that were only visible based on a comparison of the gln1;2 single- and gln1;2:gln1;3 double-mutants. GLN1;2, being the most abundantly expressed GS1 isozyme, markedly increased following ammonium supply and its promoter activity was localized at the cortex and epidermis, while GLN1;3 showed only low expression at the pericycle, suggesting their different physiological contributions to ammonium assimilation in roots. The GLN1;2 promoter-deletion analysis identified regulatory sequences required for controlling ammonium-responsive gene expression of GLN1;2 in Arabidopsis roots. These results shed light on GLN1 isozyme-specific regulatory mechanisms in Arabidopsis that allow adaptation to an ammonium-replete environment.

Principal component analysis uncovers cytomegalovirus-associated NK cell activation in Ph+ leukemia patients treated with dasatinib

Dasatinib treatment markedly increases the number of large granular lymphocytes (LGLs) in a proportion of Ph⁺ leukemia patients, which associates with a better prognosis. The lymphocytosis is predominantly observed in cytomegalovirus (CMV)-seropositive patients, yet detectable CMV reactivation exists only in a small fraction of patients. Thus, etiology of the lymphocytosis still remains unclear. Here, we identified NK cells as the dominant LGLs expanding in dasatinib-treated patients, and applied principal component analysis (PCA) to an extensive panel of NK cell markers to explore underlying factors in NK cell activation. PCA displayed phenotypic divergence of NK cells that reflects CMV-associated differentiation and genetic differences, and the divergence was markedly augmented in CMV-seropositive dasatinib-treated patients. Notably, the CMV-associated highly differentiated status of NK cells was already observed at leukemia diagnosis, and was further enhanced after starting dasatinib in virtually all CMV-seropositive patients. Thus, the extensive characterization of NK cells by PCA strongly suggests that CMV is an essential factor in the NK cell activation, which progresses stepwise during leukemia and subsequent dasatinib treatment most likely by subclinical CMV reactivation. This study provides a rationale for the exploitation of CMV-associated NK cell activation for treatment of leukemias.

Pregnancy prediction on the day of embryo transfer (Day 7) and Day 14 by measuring luteal blood flow in dairy cows

This study aimed to assess the suitability of luteal blood flow analyses measured by color Doppler ultrasonography (CDUS), to predict pregnancy at pre- and post-embryo transfer (ET) in dairy cows, and to compare with the established criterion like luteal size and plasma progesterone (P4) concentrations. Lactating Holstein cows (n = 65) with spontaneous (n = 34) or synchronized estrus (n = 31) were examined. Cows with a CL greater than or equal to 20 mm in diameter (n = 58) received embryo transfer on Day 7 (Day 0 = estrus). Brightness mode images were captured for calculation of the CL area, luteal cavity area, and dominant follicle area on Days 3, 5, 7, and 14. Color Doppler ultrasonography examinations were conducted to determine the blood flow area (BFA) within the CL at the maximum diameter and the time-averaged maximum velocity (TAMV) of the base of the spiral artery on the same days. Plasma P4 concentrations were determined from blood samples collected at each ultrasound examination. Pregnancy was diagnosed by an ultrasound on Day 30. There was no significant difference in the proportion of cows received embryo (91.2% vs. 87.1%, P = 0.70) and pregnancy rate (58.1% vs. 59.3%, P = 1.00) between the spontaneous estrus and synchronized groups. The BFA values of the pregnant group (n = 34) were approximately 1.42 and 1.54 times higher than those of the nonpregnant group (n = 24) on Days 7 (0.54 ± 0.04 cm(2) vs. 0.38 ± 0.02 cm(2); P < 0.01) and 14 (0.80 ± 0.23 cm(2) vs. 0.52 ± 0.22 cm(2); P < 0.01), respectively. The TAMV of the pregnant group was approximately 1.45 times higher than that of the nonpregnant group on Day 14 (57.8 ± 3.5 cm/s vs. 40.0 ± 3.3 cm/s; P < 0.01). However, no differences were found in the CL area, CL tissue area, dominant follicle area, and plasma P4 concentrations among these groups. In addition, the best logistic regression model to predict pregnancy included scores for BFA on Day 7, BFA and TAMV on Day 14. Setting the cutoff value of BFA at 0.43 cm(2) yielded the highest sensitivity (79.4%) and specificity (75.0%) on Day 7, indicating the effectiveness of using BFA data for predicting pregnancy on Day 7. Furthermore, setting the cutoff value at one obtained from a sample with BFA 0.63 cm(2) and TAMV 50.60 cm/s yielded the highest sensitivity (85.3%) and specificity (91.7%) on Day 14. In conclusion, the evaluations of BFA on Day 7, and paired BFA and TAMV on Day 14 represent reliable predictors of pregnancy in the cow.

Two patients treated with simeprevir plus pegylated-interferon and ribavirin triple therapy for recurrent hepatitis C after living donor liver transplantation: case report

We previously reported our data on telaprevir (TVR) used in combination with pegylated-interferon and ribavirin (PEG-IFN/RBV) for the treatment of recurrent hepatitis C virus (HCV) genotype 1 infection after liver transplantation (LT). TVR substantially increases the blood levels of immunosuppressive agents such as cyclosporine and tacrolimus for drug-drug interactions. On the other hand, the effect of simeprevir (SMV) on the blood levels of these immunosuppressive agents is unclear. We report 2 patients who achieved viral responses with little effect on the blood levels of cyclosporine and tacrolimus using SMV plus PEG-IFN/RBV treatment. The first was a 71-year-old woman with HCV-related liver cirrhosis and hepatocellular carcinoma who failed to respond to PEG-IFN/RBV after living donor LT. She was treated with 40 mg/d of cyclosporine, and received SMV plus PEG-IFN/RBV treatment. The second was a 65-year-old man with HCV-related liver cirrhosis who failed to respond to PEG-IFN/RBV after living donor LT. He was treated with 3 mg/d of tacrolimus, and received SMV plus PEG-IFN/RBV treatment. Serum HCV RNA became undetectable using TaqMan polymerase chain reaction (PCR) test after 4 weeks of treatment in both patients, and no remarkable fluctuation in blood concentration was observed either in cyclosporine or tacrolimus during the 12 weeks of SMV treatment. Completion of 12-week SMV triple therapy was followed by PEG-IFNα2b plus RBV, and both patients achieved sustained virological response 12 weeks after the end of treatment. SMV plus PEG-IFNRBV treatment showed a remarkable viral response with little effect on blood levels of immunosuppressive agents for recurrent HCV genotype 1 infection after LT.

Fc-Gamma Receptor Polymorphisms Predispose Patients to Infectious Complications After Liver Transplantation

We investigated the impact of polymorphisms in host innate immunoregulatory genes on the development of infectious complications after liver transplantation (LT). The single-nucleotide polymorphisms (SNPs) of C1QA [276A/G], FCGR2A [131H/R], and FCGR3A [158F/V], genes encoding the Fc gamma receptor (FcγR), were analyzed in 89 living donor LT recipients in relation to the occurrences of postoperative infectious complications within 30 days after LT. Consistent with a lower affinity of the isoform encoded by FCGR3A [158F] to both IgG1 and IgG3, a significantly higher incidence of bloodstream infections (BSI) was observed in the FCGR3A [158F/V or F/F] than in the FCGR3A [158V/V] individuals. The combination of FCGR2A and FCGR3A SNPs further stratified the incidence of BSI, regardless of C1QA SNP. The predominant causative pathogen of BSI in the FCGR3A [158F/F or F/V] patients was gram-positive cocci (73.3%), of which one third was methicillin-resistant Staphylococcus aureus. No differences were observed in the incidence of fungal infections or in cytomegalovirus infections with respect to the three gene polymorphisms. Our findings indicate that FcγR SNPs are predisposing factors for BSI and can predict mortality after LT. This study provides a foundation for further prospective studies on a larger scale.

A mathematical model of phloem sucrose transport as a new tool for designing rice panicle structure for high grain yield

Rice (Oryza sativa) is one of the most important food crops in the world. Numerous quantitative trait loci or genes controlling panicle architecture have been identified to increase grain yield. Yet grain yield, defined as the product of the number of well-ripened grains and their weight, is a complex trait that is determined by multiple factors such as source, sink and translocation capacity. Mechanistic modelling capturing capacities of source, sink and transport will help in the theoretical design of crop ideotypes that guarantee high grain yield. Here we present a mathematical model simulating sucrose transport and grain growth within a complex phloem network. The model predicts that the optimal panicle structure for high yield shows a simple grain arrangement with few higher order branches. In addition, numerical analyses revealed that inefficient delivery of carbon to panicles with higher order branches prevails regardless of source capacity, indicating the importance of designing grain arrangement and phloem structure. Our model highlights the previously unexplored effect of grain arrangement on the yield, and provides numerical solutions for optimal panicle structure under various source and sink capacities.

Asparagine synthetase1, but not asparagine synthetase2, is responsible for the biosynthesis of asparagine following the supply of ammonium to rice roots

Asparagine is synthesized from glutamine by the reaction of asparagine synthetase (AS) and is the major nitrogen form in both xylem and phloem sap in rice (Oryza sativa L.). There are two genes encoding AS, OsAS1 and OsAS2, in rice, but the functions of individual AS isoenzymes are largely unknown. Cell type- and NH4(+)-inducible expression of OsAS1 as well as analyses of knockout mutants were carried out in this study to characterize AS1. OsAS1 was mainly expressed in the roots, with in situ hybridization showing that the corresponding mRNA was specifically accumulated in the three cell layers of the root surface (epidermis, exodermis and sclerenchyma) in an NH4(+)-dependent manner. Conversely, OsAS2 mRNA was abundant in leaf blades and sheathes of rice. Although OsAS2 mRNA was detectable in the roots, its content decreased when NH4(+) was supplied. Retrotransposon-mediated knockout mutants lacking AS1 showed slight stimulation of shoot length and slight reduction in root length at the seedling stage. On the other hand, the mutation caused an approximately 80-90% reduction in free asparagine content in both roots and xylem sap. These results suggest that AS1 is responsible for the synthesis of asparagine in rice roots following the supply of NH4(+). Characteristics of the NH4(+)-dependent increase and the root surface cell-specific expression of OsAS1 gene are very similar to our previous results on cytosolic glutamine synthetase1;2 and NADH-glutamate synthase1 in rice roots. Thus, AS1 is apparently coupled with the primary assimilation of NH4(+) in rice roots.

Clinical efficacy of simultaneous splenectomy in liver transplant recipients with hepatitis C virus

BACKGROUND

Interferon (IFN) therapy is a well-established antiviral treatment for hepatitis C virus (HCV) - infected patients. However, susceptibility to thrombocytopenia is a major obstacle in its initiation or continuation, particularly in patients with HCV who underwent liver transplantation (LT). We previously showed that the coexistence of splenomegaly and thrombocytopenia could result in persistent thrombocytopenia after LT. Here we retrospectively evaluated the validity of this criterion for simultaneous splenectomy in recipients with HCV.

PATIENTS AND METHODS

Subjects included 36 recipients with HCV who received LT between January 2006 and February 2012 at Hiroshima University. We analyzed the spleen volume, body surface area, platelet (PLT) count, and rate of completion or continuation with IFN therapy in these recipients.

RESULT

Of these recipients, 30 did not require simultaneous splenectomy according to the criterion, and 24 actually did not receive simultaneous splenectomy. In this group, 21 (87.5%) started IFN therapy. Fifteen (71.4%) of these recipients completed or continued IFN therapy, whereas 13 (61.9%) achieved either a sustained virological response (SVR) or an end-of-treatment response. The PLT count increased to >100,000/mm(3) 1 month after LT in 16 (66.7%) recipients from this group.

CONCLUSION

Our criterion detected the PLT count outcome after LT in recipients with HCV and achieved a better SVR result after IFN therapy.

Lack of cytosolic glutamine synthetase1;2 in vascular tissues of axillary buds causes severe reduction in their outgrowth and disorder of metabolic balance in rice seedlings

The development and elongation of active tillers in rice was severely reduced by a lack of cytosolic glutamine synthetase1;2 (GS1;2), and, to a lesser extent, lack of NADH-glutamate synthase1 in knockout mutants. In situ hybridization using the basal part of wild-type seedlings clearly showed that expression of OsGS1;2 was detected in the phloem companion cells of the nodal vascular anastomoses and large vascular bundles of axillary buds. Accumulation of lignin, visualized using phloroglucin HCl, was also observed in these tissues. The lack of GS1;2 resulted in reduced accumulation of lignin. Re-introduction into the mutants of OsGS1;2 cDNA under the control of its own promoter successfully restored the outgrowth of tillers and lignin deposition to wild-type levels. Transcriptomic analysis using a 5 mm basal region of rice shoots showed that the GS1;2 mutants accumulated reduced amounts of mRNAs for carbon and nitrogen metabolism, including C1 unit transfer in lignin synthesis. Although a high content of strigolactone in rice roots is known to reduce active tiller number, the reduction of outgrowth of axillary buds observed in the GS1;2 mutants was independent of the level of strigolactone. Thus metabolic disorder caused by the lack of GS1;2 resulted in a severe reduction in the outgrowth of axillary buds and lignin deposition.

NADH-dependent glutamate synthase plays a crucial role in assimilating ammonium in the Arabidopsis root

Plant roots under nitrogen deficient conditions with access to both ammonium and nitrate ions, will take up ammonium first. This preference for ammonium rather than nitrate emphasizes the importance of ammonium assimilation machinery in roots. Glutamine synthetase (GS) and glutamate synthase (GOGAT) catalyze the conversion of ammonium and 2-oxoglutarate to glutamine and glutamate. Higher plants have two GOGAT species, ferredoxin-dependent glutamate synthase (Fd-GOGAT) and nicotinamide adenine dinucleotide (NADH)-GOGAT. While Fd-GOGAT participates in the assimilation of ammonium, which is derived from photorespiration in leaves, NADH-GOGAT is highly expressed in roots and its importance needs to be elucidated. While ammonium as a minor nitrogen form in most soils is directly taken up, nitrate as the major nitrogen source needs to be converted to ammonium prior to uptake. The aim of this study was to investigate and quantify the contribution of NADH-GOGAT to the ammonium assimilation in Arabidopsis (Arabidopsis thaliana Columbia) roots. Quantitative real-time polymerase chain reaction (PCR) and protein gel blot analysis showed an accumulation of NADH-GOGAT in response to ammonium supplied to the roots. In addition the localization of NADH-GOGAT and Fd-GOGAT did not fully overlap. Promoter-β-glucuronidase (GUS) fusion analysis and immunohistochemistry showed that NADH-GOGAT was highly accumulated in non-green tissue like vascular bundles, shoot apical meristem, pollen, stigma and roots. Reverse genetic approaches suggested a reduction in glutamate production and biomass accumulation in NADH-GOGAT transfer DNA (T-DNA) insertion lines under normal CO2 condition. The data emphasize the importance of NADH-GOGAT in the ammonium assimilation in Arabidopsis roots.

NADH-dependent glutamate synthase participated in ammonium assimilation in Arabidopsis root

Higher plants have 2 GOGAT species, Fd-GOGAT and NADH-GOGAT. While Fd-GOGAT mainly assimilates ammonium in leaves, which is derived from photorespiration, the function of NADH-GOGAT, which is highly expressed in roots, (1) needs to be elucidated. The aim of this study was to clarify the role of NADH-GOGAT in Arabidopsis roots. The supply of ammonium to the roots caused an accumulation of NADH-GOGAT, while Fd-GOGAT 1 and Fd-GOGAT 2 showed no response. A promoter-GUS fusion analysis and immunohistochemistry showed that NADH-GOGAT was located in non-green tissues like vascular bundles, shoot apical meristem, pollen, stigma, and roots. The localization of NADH-GOGAT and Fd-GOGAT was not overlapped. NADH-GOGAT T-DNA insertion lines showed a reduction of glutamate and biomass under normal CO2 conditions. These data emphasizes the importance of NADH-GOGAT in the ammonium assimilation of Arabidopsis roots.

Renal vein extension using an autologous renal vein in a living donor with double inferior vena cava: a case report

BACKGROUND

When the kidney from a living donor with a double inferior vena cava (IVC) is harvested for renal transplantation, the short length of the renal vein may eventually create a technical problem for graft implantation. Herein, we have reported a rare case of renal vein extension using an autologous renal vein in a living donor with a double IVC.

CASE REPORT

A 70-year-old man with end-stage renal disease owing to autosomal-dominant polycystic kidney disease underwent a living donor kidney graft from his wife who had a double IVC. Because of the enlarged kidneys, the patient underwent a bilateral native nephrectomy with concomitant renal transplantation to create space in the pelvis. At nephrectomy, the recipient's renal vein was used to extend the donor renal vein. On the back table, the vein graft was sutured to the donor renal vein, permitting a 3.0-cm extension.

RESULTS

The transplantation was performed safely without any complications; the recipient's renal function and blood flow were excellent after the operation.

CONCLUSION

This case illustrated that an autologous renal vein graft is a preferable option to extend of short donor renal vein for recipients who require a simultaneous native nephrectomy.

Optimization of immunosuppressive therapy based on a multiparametric mixed lymphocyte reaction assay reduces infectious complications and mortality in living donor liver transplant recipients

AIM

We investigated the clinical relevance of immune monitoring by a multiparametric mixed lymphocyte reaction (MLR) assay, wherein the number and phenotype of alloreactive precursors can be quantified by combining the results of carboxyfluorescein diacetate succinimidyl ester labeling and flow cytometry analysis.

METHODS

In 51 adult patients undergoing living donor liver transplantation (OLT), immunosuppressive drugs were dosed on the basis of immune monitoring by the MLR assay (optimized protocol: group O). In 64 other patients, the agents were prescribed according to empirical regimens (empirical protocol: group E). In group O, MLR assays were performed at 2- to 4-week intervals until 3 months after OLT and thereafter at 3- to 6-month intervals. Therapeutic adjustments for immunosuppressants were determined by tapering the doses in cases of anti-donor hyporesponsiveness for both CD4+ and CD8+ T-cell subsets.

RESULTS

The 1-year patient and graft survivals in groups O versus E were 90.2% versus 76.6%, respectively. The incidence of acute rejection episodes (ARE) among group O (13.7%) were lower than in cohort E (28.1%). None of the patients in group O while four patients (3%) in group E already have shown chronic rejection to date. The incidences of bacteremia and fungal infections in group O (9.8% and 7.5%, respectively) were lower than in cohort E (18.8% and 12.6%, respectively).

CONCLUSION

A multiparametric MLR assay may facilitate the development of adequate immunosuppressive regimens.

Successful treatment of Trichosporon fungemia in a patient with refractory acute myeloid leukemia using voriconazole combined with liposomal amphotericin B

Trichosporon fungemia is a rare and fatal fungal infection that occurs in patients with prolonged neutropenia associated with hematologic malignancies. A 21-year-old male developed Trichosporon fungemia during remission induction therapy for acute myeloid leukemia (AML). Although two courses of induction therapy failed to induce a remission of AML, combination therapy with voriconazole and liposomal amphotericin B (L-AmB) followed by monocyte colony-stimulating factor ameliorated the Trichosporon fungemia and enabled the patient to receive reduced-intensity bone marrow transplantation (BMT) from his human leukocyte antigen-A one-locus mismatched mother. The patient achieved a durable remission after BMT without exacerbation of Trichosporon fungemia. The combination therapy with voriconazole and L-AmB may therefore be useful in controlling Trichosporon fungemia associated with prolonged neutropenia after remission induction therapy for AML.

Allogeneic hematopoietic stem cell transplantation for acute myeloid leukemia with t(6;9)(p23;q34) dramatically improves the patient prognosis: a matched-pair analysis

Acute myeloid leukemia (AML) with t(6;9)(p23;q34) is well known to have a poor prognosis treated with chemotherapy and autotransplantation. The presence of this karyotype is an indicator for allogeneic hematopoietic stem cell transplantation (HSCT); however, the impact of t(6;9)(p23;q34) on the HSCT outcome remains unclear. We conducted a matched-pair analysis of de novo AML patients with and without t(6;9)(p23;q34) using data obtained from the Japanese HSCT data registry. A total of 57 patients with t(6;9)(p23;q34) received transplants between 1996 and 2007, and 171 of 2056 normal karyotype patients matched for age, disease status at HSCT and graft source were selected. The overall survival, disease-free survival, cumulative incidence of relapse and the non-relapse mortality in t(6;9)(p23;q34) patients were comparable to those for normal karyotype patients. A univariate analysis showed that t(6;9)(p23;q34) had no significant impact on the overall survival. These findings suggest that allogeneic HSCT may overcome the unfavorable impact of t(6;9)(p23;q34) as an independent prognostic factor.

mRNA of the pro-apoptotic gene BBC3 serves as a molecular marker for TNF-α-induced islet damage in humans

AIMS/HYPOTHESIS

TNF-α plays important roles in the pathogenesis of type 1 and type 2 diabetes mellitus. In light of this, we examined the involvement of a pro-apoptotic gene, BBC3 (also known as PUMA), in TNF-α-mediated beta cell dysfunction and destruction in human islets.

METHODS

Human islets were exposed in vitro to TNF-α alone or in combination with IFN-γ. Gene expression was assessed by RT-PCR using a set of single islets. Protein abundance and cellular localisation of BBC3 were assessed by immunoblot and immunohistochemistry. A marginal number of islets were transplanted into diabetic NODscid mice to correlate in vivo islet function with BBC3 expression.

RESULTS

BBC3 and IL8 mRNA were upregulated in TNF-α-stimulated islets in a dose-dependent manner and enhanced through addition of IFN-γ, but not upregulated by IFN-γ alone. Immunohistochemistry revealed that TNF-α in combination with IFN-γ upregulated basal BBC3 abundance in the cytoplasm of beta cells along with the perinuclear clustering of mitochondria partially co-localised with BBC3. TNF-α alone did not induce beta cell death, but did abrogate preproinsulin precursor mRNA synthesis in response to high glucose stimulation, which was inversely associated with upregulation of BBC3 mRNA expression by TNF-α. Higher BBC3 mRNA expression in islets correlated with decreased graft function in vivo.

CONCLUSIONS/INTERPRETATION

These results suggest that BBC3 mRNA can serve as a molecular marker to detect early TNF-α-induced beta cell stress and may help identify islet-protective compounds for the treatment of diabetes.