A paradigm shift towards low-nitrifying production systems: the role of biological nitrification inhibition (BNI).

BACKGROUND: Agriculture is the single largest geo-engineering initiative that humans have initiated on planet Earth, largely through the introduction of unprecedented amounts of reactive nitrogen (N) into ecosystems. A major portion of this reactive N applied as fertilizer leaks into the environment in massive amounts, with cascading negative effects on ecosystem health and function. Natural ecosystems utilize many of the multiple pathways in the N cycle to regulate N flow. In contrast, the massive amounts of N currently applied to agricultural systems cycle primarily through the nitrification pathway, a single inefficient route that channels much of this reactive N into the environment. This is largely due to the rapid nitrifying soil environment of present-day agricultural systems. SCOPE: In this Viewpoint paper, the importance of regulating nitrification as a strategy to minimize N leakage and to improve N-use efficiency (NUE) in agricultural systems is highlighted. The ability to suppress soil nitrification by the release of nitrification inhibitors from plant roots is termed 'biological nitrification inhibition' (BNI), an active plant-mediated natural function that can limit the amount of N cycling via the nitrification pathway. The development of a bioassay using luminescent Nitrosomonas to quantify nitrification inhibitory activity from roots has facilitated the characterization of BNI function. Release of BNIs from roots is a tightly regulated physiological process, with extensive genetic variability found in selected crops and pasture grasses. Here, the current status of understanding of the BNI function is reviewed using Brachiaria forage grasses, wheat and sorghum to illustrate how BNI function can be utilized for achieving low-nitrifying agricultural systems. A fundamental shift towards ammonium (NH4(+))-dominated agricultural systems could be achieved by using crops and pastures with high BNI capacities. When viewed from an agricultural and environmental perspective, the BNI function in plants could potentially have a large influence on biogeochemical cycling and closure of the N loop in crop-livestock systems.

Evidence for biological nitrification inhibition in Brachiaria pastures.

Nitrification, a key process in the global nitrogen cycle that generates nitrate through microbial activity, may enhance losses of fertilizer nitrogen by leaching and denitrification. Certain plants can suppress soil-nitrification by releasing inhibitors from roots, a phenomenon termed biological nitrification inhibition (BNI). Here, we report the discovery of an effective nitrification inhibitor in the root-exudates of the tropical forage grass Brachiaria humidicola (Rendle) Schweick. Named "brachialactone," this inhibitor is a recently discovered cyclic diterpene with a unique 5-8-5-membered ring system and a gamma-lactone ring. It contributed 60-90% of the inhibitory activity released from the roots of this tropical grass. Unlike nitrapyrin (a synthetic nitrification inhibitor), which affects only the ammonia monooxygenase (AMO) pathway, brachialactone appears to block both AMO and hydroxylamine oxidoreductase enzymatic pathways in Nitrosomonas. Release of this inhibitor is a regulated plant function, triggered and sustained by the availability of ammonium (NH(4)(+)) in the root environment. Brachialactone release is restricted to those roots that are directly exposed to NH(4)(+). Within 3 years of establishment, Brachiaria pastures have suppressed soil nitrifier populations (determined as amoA genes; ammonia-oxidizing bacteria and ammonia-oxidizing archaea), along with nitrification and nitrous oxide emissions. These findings provide direct evidence for the existence and active regulation of a nitrification inhibitor (or inhibitors) release from tropical pasture root systems. Exploiting the BNI function could become a powerful strategy toward the development of low-nitrifying agronomic systems, benefiting both agriculture and the environment.

What defines a transplant surgeon? A needs assessment for curricular development in transplant surgery fellowship training.

This study compares the perceptions of transplant surgery program directors (PDs) and recent fellowship graduates (RFs) regarding the adequacy of training and relevancy to practice of specific curricular content items in fellowship training. Surveys were sent to all American Society of Transplant Surgery approved fellowship PDs and all RFs in practice <5 years. For operative procedures, the RFs considered the overall training to be less adequate than the PDs (p = 0.0117), while both groups considered the procedures listed to be relevant to practice (p = 0.8281). Regarding nonoperative patient care items, although RFs tended to rank many individual items lower, both groups generally agreed that the training was both adequate and relevant. For nonpatient care related items (i.e. transplant-related ethics, economics, research, etc.), both groups scored them low regarding their adequacy of training although RFs scored them significantly lower than PDs (p = 0.0006). Regarding their relevance to practice, while both groups considered these items relevant, RFs generally considered them more relevant than PDs. Therefore, although there is consensus on many items, significant differences exist between PDs and RFs regarding their perceptions of the adequacy of training and the relevance to practice of specific curriculum items in transplant surgery fellowship training.

Impact of virologic breakthrough and HBIG regimen on hepatitis B recurrence after liver transplantation.

The availability of hepatitis B immune globulin (HBIG) and several oral antiviral therapies has reduced but not eliminated hepatitis B virus (HBV) recurrence. We aimed to determine the rate of HBV recurrence after orthotopic liver transplantation (OLT) in relation to virologic breakthrough pre-OLT and HBIG regimens post-OLT. Data from the NIH HBV-OLT database were analyzed. A total of 183 patients transplanted between 2001 and 2007 followed for a median of 42 months (range 1-81) post-OLT were studied. At transplant, 29% were hepatitis B e antigen (HBeAg) (+), 38.5% had HBV DNA > 5 log(10) copies/mL, 74% were receiving antiviral therapy. Twenty-five patients experienced virologic breakthrough before OLT. Post-OLT, 26%, 22%, 40% and 12% of patients received intravenous (IV) high-dose, IV low-dose, intramuscular low-dose and a finite duration of HBIG, respectively as maintenance prophylaxis. All but two patients also received antiviral therapy. Cumulative rates of HBV recurrence at 1 and 5 years were 3% and 9%, respectively. Multivariate analysis showed that listing HBeAg status and HBV DNA level at OLT were the only factors associated with HBV recurrence. In conclusion, low rates of HBV recurrence can be accomplished with all the HBIG regimens used when combined with antiviral therapy including patients with breakthrough pre-OLT as long as rescue therapy is administered pre- and post-OLT.

Genetic mitigation strategies to tackle agricultural GHG emissions: The case for biological nitrification inhibition technology.

Accelerated soil-nitrifier activity and rapid nitrification are the cause of declining nitrogen-use efficiency (NUE) and enhanced nitrous oxide (N2O) emissions from farming. Biological nitrification inhibition (BNI) is the ability of certain plant roots to suppress soil-nitrifier activity, through production and release of nitrification inhibitors. The power of phytochemicals with BNI-function needs to be harnessed to control soil-nitrifier activity and improve nitrogen-cycling in agricultural systems. Transformative biological technologies designed for genetic mitigation are needed, so that BNI-enabled crop-livestock and cropping systems can rein in soil-nitrifier activity, to help reduce greenhouse gas (GHG) emissions and globally make farming nitrogen efficient and less harmful to environment. This will reinforce the adaptation or mitigation impact of other climate-smart agriculture technologies.

Synechococcus sp. PCC7942 Transformed with Escherichia coli bet Genes Produces Glycine Betaine from Choline and Acquires Resistance to Salt Stress.

Synechococcus sp. PCC7942, a fresh water cyanobacterium, was transformed by a shuttle plasmid that contains a 9-kb fragment encoding the Escherichia coli bet gene cluster, i.e. betA (choline dehydrogenase), betB (betaine aldehyde dehydrogenase), betI (a putative regulatory protein), and betT (the choline transport system). The expression of these genes was demonstrated in the cyanobacterial cells (bet-containing cells) by northern blot analysis, as well as by the detection of glycine betaine by 1H nuclear magnetic resonance in cells supplemented with choline. Endogenous choline was not detected in either control or bet-containing cells. Both control and bet-containing cyanobacterial cells were found to import choline in an energy-dependent process, although this import was restricted only to bet-containing cells in conditions of salt stress. Glycine betaine was found to accumulate to a concentration of 45 mM in bet-containing cyanobacterial cells, and this resulted in a stabilization of the photosynthetic activities of photosystems I and II, higher phycobilisome contents, and general protective effects against salt stress when compared to control cells. The growth of bet-containing cells was much faster in the presence of 0.375 M NaCl than that of control cells, indicating that the transformant acquired resistance to salt stress.

Predictors of graft survival in pediatric living-related kidney transplant recipients.

BACKGROUND: A successful kidney transplant from a living-related donor (LRD) remains the most effective renal replacement therapy for children with end-stage renal failure. The use of LRD kidneys results in decreased time on dialysis, increased graft survival, and better function compared with kidneys transplanted from cadaver donors. We retrospectively analyzed data from the United Network of Organ Sharing (UNOS) Scientific Renal Transplant Registry to determine risk factors for graft loss in children who received an LRD kidney. METHODS: Data was obtained from the UNOS Scientific Renal Transplant Registry on 2418 children ranging in age from 0 to 18 years who underwent an LRD kidney transplantation between January 1988 and December 1994. Multivariate analysis of graft survival was performed using Kaplan-Meier and Cox regression models. RESULTS: The effects of age, pretransplantation dialysis, early rejection, and race were found to significantly affect graft survival. Gender, peak panel-reactive antibody, and ABO blood type were not found to be significant risk factors. Infants <2 years of age initially had the worst graft survival; however, over time their results stabilized, and at 7 years estimated graft survival was good (71%). Adolescents ranging in age from 13-18 years had the best initial graft survival, but as time went on graft survival worsened (55%). Patients who underwent pretransplantation dialysis had a relative risk for graft loss of 1.77 (P<0.001), whereas those who had an early rejection had a relative risk for graft loss of 1.41 (P<0.002). African-Americans had a significantly higher relative risk for graft loss than either Caucasians (1.57, P<0.0005) or Hispanics (2.01, P<0.0003). CONCLUSIONS: Predictors of graft survival for children who receive LRD kidney transplants include age at transplantation, pretransplantation dialysis, early rejection, and race. Over time, adolescents and African-Americans seem to have the lowest graft survival.

Retransplantation of patients with severe posttransplant hepatitis B in the first allograft.

BACKGROUND: The outcome of orthotopic liver transplantation (OLTX) in patients retransplanted for severe hepatitis B virus (HBV) in the first allograft has been poor due to high rates of HBV reinfection and even more aggressive disease in the second graft. Recent data suggest that hepatitis B immunoglobulin (HBIg) given after transplantation can be successful in delaying or preventing HBV reinfection in patients transplanted for chronic hepatitis B cirrhosis. We report the successful retransplantation of patients who developed recurrent or de novo hepatitis B after OLTXY. METHODS: Using similar HBIg regimens, two centers retransplanted seven patients after they developed recurrent or de novo hepatitis B in the first allograft. At retransplantation all seven patients were HBs antigen (Ag) positive; four patients were positive for HBeAg and HBV DNA by immunoblot assay, two patients were negative for HBeAg and HBV DNA, and one patient was positive for HBV DNA and negative for HBeAg. All patients were either HDV Ag or anti-HDV negative. One patient was anti-HCV positive. All patients received HBIg infusions after retransplantation to maintain serum anti-HBs levels >500 IU/L indefinitely. RESULTS: After retransplantation, six of seven patients are alive (86%): all are without evidence of HBV recurrence with serum negative for HBsAg, HBeAg, and HBV DNA by immunoblot assay. Liver biopsies are normal on routine studies with immunohistochemical stains for HBcAg and HBsAg also being negative. Mean follow-up of these six patients is 40.1 months (range 21-63 months). One patient (14%) developed HBV reinfection 7 months after his second transplant, in spite of maintaining target anti-HBs levels. He maintained stable liver function with minimal evidence of clinical hepatitis B, but died 8 months later from an unrelated stroke. CONCLUSIONS: We conclude that patients with recurrent or de novo hepatitis B after OLTX can be successfully retransplanted using aggressive immunoprophylaxis to prevent HBV reinfection. The failure of HBIg therapy in one patient underscores the need for other effective adjunctive anti-HBV modalities.

Improved outcome of orthotopic liver transplantation for chronic hepatitis B cirrhosis with aggressive passive immunization.

Passive immunization with hepatitis B surface antibody (anti-HBs) is important to prevent hepatitis B virus (HBV) recurrence after orthotopic liver transplantation for chronic HBV cirrhosis. Hepatitis B immune globulin (HBIG) dosing regimens have been poorly defined, utilize numerous routes of administration, and result in a high rate of HBV relapse and mortality. Twenty-five of 27 (93%) patients transplanted (four retransplants) for chronic HBV cirrhosis show no evidence of recurrent HBV (range, 2-55 months). Anti-HBs titers necessary to minimize the risk of hepatitis B surface antigen detectability were >500 IU/L for days 0 to 7, >250 IU/L for days 8 to 90, and >100 IU/L thereafter. Pretransplant HBV E antigen (HBeAG)-positive patients required more HBIG to achieve these goals than HBeAG-negative individuals. The elimination of anti-HBs changed continually for the initial 3 posttransplant months. The anti-HBs half-life increased from 0.7 days to 14.1 days. Anti-HBs elimination was significantly different in HBeAG+ and HBeAG- patients for the first week, but was subsequently indistinguishable after week 1. After 3 months, the half-life was statistically less for HBeAG+ patients, but the difference did not influence the clinical treatment regimens. Quantitative hepatitis B DNA levels did not predict the amount of HBIG required. HBV recurrence after orthotopic liver transplantation can be reduced by aggressive passive immunization. Pharmacokinetic analysis of anti-Hbs elimination can improve immunoglobulin therapy and prevent recurrence of clinical hepatitis.

Clinical and histologic patterns of early graft failure due to recurrnet hepatitis C in four patients after liver transplantation.

Hepatitis C viral recurrence after orthotopic liver transplantation is almost universal. Hepatitis C induced graft failure may occur, but the clinical and histologic profiles are not well defined. The aim of this study was to describe the pattern of early graft failure in patients with recurrent hepatitis C after liver transplantation. Thirty patients with hepatitis C underwent liver transplantation from October 1989 through September 1994. Four patients were excluded because of death (2 patients), graft failure unrelated to hepatitis C (1 patient), and lost to follow-up (1 patient). Hepatitis C recurred in 24 of the 26 remaining patients. In 4 patients with hepatitis C virus recurrence and cholestasis, graft failure developed at 5.25, 11.0, 11.0, and 18.5 months. The medical records and liver biopsies were reviewed. In all 4 patients, a histologic pattern characterized by centrilobular ballooning degeneration developed and progressed to involve more than two-thirds of the lobules. Moderate to severe cholestasis and bridging fibrosis were present in all grafts at explant. Two patients had portal inflammation on 3-month biopsies consistent with viral hepatitis. All patients had mild macrovesicular steatosis, but only 1 patient had significant lymphoid aggregates. No patient had evidence of hepatic artery thrombosis. One patient had potential drug-induced cholestasis. One patient had 3 episodes of rejection that were not believed to contribute to graft loss. All 4 patients developed clinical features of hepatic failure and were retransplanted. Two patients had early recurrence of graft failure. We conclude that a pattern of progressive centrilobular ballooning degeneration, bridging fibrosis, and cholestasis occurs in some patients with hepatitis with early graft failure, similar to fibrosing cholestatic hepatitis seen in some transplant patients with recurrent hepatitis B.

Left upper lobe bronchus reimplantation for nonpenetrating thoracic trauma.

Trauma to the tracheobronchial tree has been diagnosed and treated with increasing frequency over the last several decades. However, most reports have dealt with management of injuries to the trachea and main stem bronchi, as approximately 80% of blunt tracheobronchial injuries occur within this area. With few exceptions, injury to the lobar bronchi has resulted in thoracotomy and lobectomy. We describe a patient with an injury to the left upper lobe bronchus who presented with delayed obstruction of the airway by fibrogranulation tissue. A successful segmental resection of the bronchial occlusion with reimplantation was performed, thereby preserving the patient's otherwise normal left upper lobe. This case demonstrates that resection and reimplantation of an injured lobar bronchus are feasible, even in a delayed setting.

Induction of platelet-activating factor in mice by intravenous administration of a neutral fraction of bakers' yeast mannan.

A neutral subfraction of mannan of bakers' yeast (WNM) was found to show a lethal effect in mice when administered intravenously. Symptoms caused by intravenous (i.v.) administration of WNM resembled those resulting from the administration of platelet-activating factor (PAF). CV-3988 and ONO-6240, selective PAF antagonists, prevented hypotension and death caused by the administration of WNM or PAF. A beta-adrenoceptor agonist was shown to prevent death caused by WNM, whereas propranolol increased the lethal activity of WNM. Intravenous administration of WNM into mice produced PAF in gall bladder fluid which was determined by platelet aggregation assay. The findings indicate that WNM is able to induce PAF in mice and that the resultant PAF may participate in the WNM-induced lethal activity observed in mice.

Reversible posterior leukoencephalopathy following organ transplantation. Description of two cases.

Although neurologic changes after organ transplantation are often secondary to opportunistic infections or vascular insults, new pathological entities are emerging. We have recently encountered two patients who, a few days after liver and heart transplant, respectively, developed neurological signs and symptoms. Head computerized tomography (CT) scan showed nonenhancing areas of low attenuation, and magnetic resonance imaging (MRI) demonstrated multiple areas of increased signal intensity in the subcortical white matter on T2-weighted images. Stereotactic biopsy of the intracranial lesions was performed in one case. Light microscopic examination demonstrated only mildly edematous white matter. No infectious organisms were observed on light or electron microscopy. In one patient, follow-up MRI 3 months later showed almost complete resolution of the signal abnormalities. Both patients' clinical condition progressively improved. The neuroradiological abnormalities described are consistent with the 'reversible posterior leukoencephalopathy' syndrome associated with cyclosporine toxicity. The pathophysiology of these lesions is unclear; however, it has been suggested that cyclosporine causes an acute ischemic insult secondary to vascular spasm with resultant axonal swelling. This hypothesis is supported by the hypoattenuation seen on CT, the prolonged T2 relaxation seen on MRI, and the absence of contrast enhancement. Concomitant factors (such as hypocholesterolemia or associated therapy with high dose steroids) are important in the development of these lesions as in both of our patients cyclosporine levels were in the normal range. Fortunately, these lesions and the associated manifestations are most often reversible and regress with adjustments of cyclosporine dosage and/or correction of concomitant facilitating factors.

Kidney transplantation without calcineurin inhibitors using sirolimus.

INTRODUCTION: With the introduction of new immunosuppressive medicines, it has become possible to determine the extent to which nephrotoxic medicines contribute to CAN. The aim of this study is to compare the safety and efficacy of calcineurin inhibitor (CI) free immunosuppression in a prospective, randomized trial comparing sirolimus-mycophenolate mofetil (MMF)-prednisone to tacrolimus- MMF-prednisone. METHODS: Patients are randomized at the time of transplant to receive either tacrolimus (target level 12 to 15 ng/mL in the first month) or sirolimus (target level 12 to 18 ng/mL in the first month). All patients also receive MMF (750 mg bid) and prednisone tapered to 10 mg/d by 3 months and thymoglobulin induction (1.5 mg/kg/d on days 0, 1, 2, 4 and 6). RESULTS: At this point we have 4-month follow-up in 85 patients. The acute rejection rate is 7.5% (3/40) in the tacrolimus group and 6.7% (3/45) in the sirolimus group. We have discontinued sirolimus in eight patients so far, with wound complications being the most common indication. Renal function appears to be better in the sirolimus group at 1 month after transplantation, but the difference is not statistically significant. CONCLUSIONS: While longer follow-up is needed, these results demonstrate that total avoidance of CI can be achieved with extremely low acute cellular rejection rates using sirolimus-based immunosuppression in combination with thymoglobulin, MMF, and prednisone.

Benign testicular tumors in children with congenital adrenal hyperplasia.

The association between testicular tumors/nodules and congenital adrenal hyperplasia (CAH) has been previously reported. From 1960 to 1989, three patients (13 to 18 years old) with long-standing CAH developed testicular masses. Two patients with 21-hydroxylase deficiency were diagnosed in the neonatal period while one other with 11-hydroxylase deficiency was diagnosed at 3 years of age when he presented with sexual precocity. In all three patients, medical compliance was poor. The testicular masses were bilateral in two patients and unilateral in one, measured 1 to 2 cm, and occupied only the upper half of the testicle. Testicular biopsy specimens were obtained after at least 6 months of evidence of compliance with the adrenocorticotrophic hormone (ACTH) suppressive medication and failure of the nodules to regress. On gross examination the masses appeared to be firm yellow brown nodules. Light microscopy showed interlacing strands, cords, and rests of cells resembling interstitial (Leydig) cells but with no Reinke crystalloids. Electronmicroscopy in all patients showed variable amounts of both smooth and rough endoplasmic reticulum, the later with occasional dilated cisternae. Follow-up ranged from 6 months to 6 years. No further surgical treatment has been necessary. There has been no evidence of recurrence, distant metastases, or secondary malignancies during the time of follow-up. These findings suggest that testicular tumors may develop from chronic excessive ACTH stimulation of a putative pluripotential testicular cell, a Leydig cell, or an adrenal cortical rest. Unlike other testicular tumors these do not require orchiectomy as the initial form of therapy.

Laparoscopically applied fibrin glue in experimental liver trauma.

We have investigated the feasibility of applying fibrin glue to liver injuries using laparoscopic guidance and have examined the gross and microscopic changes that occurred in hepatic lacerations treated with fibrin glue. These studies indicate that fibrin glue may be effectively applied to liver injuries using laparoscopic control, hepatic bleeding may be rapidly controlled when fibrin glue is applied into the base of the wound, there is no gross or microscopic evidence of hepatic toxicity related to the use of fibrin glue, and healing of liver lacerations treated by fibrin glue occurs by ingrowth of granulation tissue coupled with fibrinolysis of the fibrin glue.

A single-institution review of portosystemic shunts in children: an ongoing discussion.

PURPOSE: Review the safety and long-term success with portosystemic shunts in children at a single institution. METHODS: An IRB-approved, retrospective chart review of all children ages 19 and undergoing surgical portosystemic shunt from January 1990-September 2008. RESULTS: Ten patients were identified, 8 females and 2 males, with a mean age of 15 years (range 5-19 years). Primary diagnoses were congenital hepatic fibrosis (5), hepatic vein thrombosis (2), portal vein thrombosis (2), and cystic fibrosis (1). Primary indications were repeated variceal bleeding (6), symptomatic hypersplenism (2), and significant liver dysfunction (2). Procedures performed were distal splenorenal bypass (4), side-to-side portocaval shunt (3), proximal splenorenal shunt (2), and an interposition H-graft portocaval shunt (1). There was no perioperative mortality and only minor morbidity. Seventy percent of patients had improvement of their symptoms. Eighty percent of shunts remained patent. Two were occluded at a median follow-up of 50 months (range 0.5-13.16 years). Two patients underwent subsequent liver transplantation. Two patients died at 0.5 and 12.8 years postoperatively, one from multisystem failure with cystic fibrosis and one from post-operative transplant complications. CONCLUSIONS: The need for portosystemic shunts in children is rare. However, in the era of liver transplantation, portosystemic shunts in selected patients with well-preserved liver function remains important. We conclude that portosystemic shunts are safe and efficacious in the control of variceal hemorrhage and symptoms related to hypersplenism.