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.

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.

Novel, Precise, Accurate Ion-Pairing Method to Determine the Related Substances of the Fondaparinux Sodium Drug Substance: Low-Molecular-Weight Heparin.

Fondaparinux sodium is a synthetic low-molecular-weight heparin (LMWH). This medication is an anticoagulant or a blood thinner, prescribed for the treatment of pulmonary embolism and prevention and treatment of deep vein thrombosis. Its determination in the presence of related impurities was studied and validated by a novel ion-pair HPLC method. The separation of the drug and its degradation products was achieved with the polymer-based PLRPs column (250 mm × 4.6 mm; 5 µm) in gradient elution mode. The mixture of 100 mM n-hexylamine and 100 mM acetic acid in water was used as buffer solution. Mobile phase A and mobile phase B were prepared by mixing the buffer and acetonitrile in the ratio of 90:10 (v/v) and 20:80 (v/v), respectively. Mobile phases were delivered in isocratic mode (2% B for 0-5 min) followed by gradient mode (2-85% B in 5-60 min). An Evaporative Light Scattering Detector (ELSD) was connected to the LC system to detect the responses of chromatographic separation. Further, the drug was subjected to stress studies for acidic, basic, oxidative, photolytic, and thermal degradations as per ICH guidelines and the drug was found to be labile in acid, base hydrolysis, and oxidation, while stable in neutral, thermal, and photolytic degradation conditions. The method provided linear responses over the concentration range of the LOQ to 0.30% for each impurity with respect to the analyte concentration of 12.5 mg/mL, and regression analysis showed a correlation coefficient value (r(2)) of more than 0.99 for all the impurities. The LOD and LOQ were found to be 1.4 µg/mL and 4.1 µg/mL, respectively, for fondaparinux. The developed ion-pair method was validated as per ICH guidelines with respect to accuracy, selectivity, precision, linearity, and robustness.

Leaf Phosphate Status, Photosynthesis, and Carbon Partitioning in Sugar Beet (IV. Changes with Time Following Increased Supply of Phosphate to Low-Phosphate Plants).

Changes in photosynthesis, carbon partitioning, and growth following resupply of orthophosphate (Pi) to moderately P-deficient plants (low-P) were determined for sugar beets (Beta vulgaris L. cv F58-554H1) cultured hydroponically in growth chambers. One set of plants was supplied with 1.0 mM Pi in half-strength Hoagland solution (control plants), and a second set (low-P plants) was supplied with 0.05 mM Pi. At the end of 2 weeks, the low-P plants were resupplied with 1.0 mM Pi. Low-P plants rapidly accumulated large amounts of Pi, and the photosynthesis rate increased to control values within 4 to 6 h. The rate of photosynthesis appeared to be controlled by ribulose-1,5-bisphosphate (RuBP); low P reduced photosynthesis and RuBP levels, and P resupply increased photosynthesis and RuBP in a manner parallel with time. Low-P treatment reduced adenylate levels substantially but not nicotinamide nucleotides; adenylate levels recovered to control values over 3 to 6 h. With low P, more photosynthate is allocated to non-P carbon compounds (e.g. starch, sucrose) than to sugar phosphates. When P is resupplied, sugar phosphates increase as starch and sucrose pools decrease; this increase in leaf (chloroplast) sugar phosphates was most likely responsible for the increases in RuBP and photosynthesis and may have increased adenylate levels (through enhanced levels of ribose-5-phosphate).

LivestockPlus: Forages, sustainable intensification, and food security in the tropics.

The increased use of grain-based feed for livestock during the last two decades has contributed, along with other factors, to a rise in grain prices that has reduced human food security. This circumstance argues for feeding more forages to livestock, particularly in the tropics where many livestock are reared on small farms. Efforts to accomplish this end, referred to as the 'LivestockPlus' approach, intensify in sustainable ways the management of grasses, shrubs, trees, and animals. By decoupling the human food and livestock feed systems, these efforts would increase the resilience of the global food system. Effective LivestockPlus approaches take one of two forms: (1) simple improvements such as new forage varieties and animal management practices that spread from farmer to farmer by word of mouth, or (2) complex sets of new practices that integrate forage production more closely into farms' other agricultural activities and agro-ecologies.

Characterization of progesterone biosynthesis in a transformed granulosa cell line.

The study of regulation of steroidogenesis in primary cultures of rat granulosa cells is difficult because the cells do not undergo more than one cell doubling in culture. Furthermore, there is size and steroidogenic heterogeneity in granulosa cells and it is difficult to obtain pure, functionally defined populations. Hence, it is advantageous to develop a homogeneous population of granulosa cells. In this report we describe the characterization of one such cell line (Rao-gcl-29) developed from diethylstilbestrol treated immature rat granulosa cells by transformation with SV40 T antigen. In this cell line cyclic AMP analogs induce high levels of progesterone biosynthesis, though there was no effect on estradiol biosynthesis. Also, FSH and hCG have no effect on progesterone biosynthesis. In the presence of FBS medium (20% fetal bovine serum in DMEM/F-12) and enriched medium (10% fetal bovine serum, 10% horse serum and 2% UltraSer G in DMEM/F-12 medium), 1 mM cAMP analogs induce high levels of progesterone biosynthesis up to 96 h. Ultrastructural features of the cell line resemble those of primary granulosa cells, in addition to forming gap junctions. Cyclic AMP analogs also induced cytochrome P450scc mRNA in this cell line by 48 h, and this effect is apparent by 24 h. Thus, this cell line could be useful in understanding the molecular mechanisms of regulation of cytochrome P450scc gene regulation.

Valve replacement in children under twenty years of age. Experience with the Björk-Shiley prosthesis.

Prosthetic valve replacement in young patients has been reported to be associated with a high mortality and morbidity because of valve-related problems. Of 549 patients undergoing valve replacement with the Björk-Shiley valve prosthesis, 136 were under the age of 20 years. Sixty-four patients were under 16 years of age, the youngest being 6 years old. Of the 136 patients, 61 underwent mitral valve replacement, 50 received an aortic valve, and 25 received both aortic and mitral valves. Overall operative mortality was 10.3%. Late mortality over a follow-up period of 6 months to 8 years was 4.4%. Actuarial survival curves up to 8 years of follow-up are presented. Results obtained in this group are compared with those obtained in 413 patients over 20 years of age operated during the same period. Valve thrombosis was not seen in any patient under 20 years of age, but it occurred in 4.13% of the patients over 20 years of age. The incidence of thromboembolism and anticoagulant-related hemorrhage was very low. There has been no instance of structural failure of the valve. Long-term results are excellent, with 90% of the survivors returning to New York Heart Association Functional Class I. The Björk-Shiley valve gives excellent and durable long-term palliation in young patients requiring valve replacement.

Fate of thrombectomized Björk-Shiley valves. A long-term cinefluoroscopic, echocardiographic, and hemodynamic evaluation.

Fourteen patients underwent thrombectomy for thrombosis of implanted Björk-Shiley valves (13 in the mitral and one in the aortic position) between January, 1975, and July, 1984. There was no operative mortality or perioperative embolism. Over a follow-up period of 1 to 96 months (average 23.5 months), there was no late mortality. Serial evaluation of valve function by cinefluoroscopy and echocardiography has shown no evidence of rethrombosis or valve dysfunction in any of the patients. Cardiac catheterization and angiocardiography done in 10 patients at various intervals (1 month to 6 years) postoperatively have shown normal valve function in all and normalization of elevated preoperative intracardiac pressures in the majority. Our experience suggests that thrombectomy of thrombosed Björk-Shiley valves provides excellent early and long-term results in terms of patient survival and valve function.

Univentricular repair. Early and midterm results.

A total of 202 patients (62 with tricuspid atresia and 140 without tricuspid atresia) underwent univentricular repair at our unit from January 1990 to September 1994. Of these patients, 182 had nonfenestrated and 20 had fenestrated interatrial baffles. Early mortality was 15.9% (29/182) in the group with nonfenestrated baffles and 5% (1/20) in the group with fenestrated baffles. The follow-up period ranged from 2 to 58 months. Seven late deaths occurred, and five patients were lost to follow-up. Of 160 patients who have been evaluated in the outpatient department in the past 3 months, 142 (88.75%) required no cardiac medicines and were in functional class I. Risk factors analyzed for early mortality and significant effusion were age, preoperative diagnosis, type of Fontan modification, cardiopulmonary bypass time, aortic crossclamp time, pulmonary artery size, associated pulmonary arterioplasty, takedown of systemic-pulmonary artery shunt, and pulmonary artery debanding, along with the Fontan operation. Bypass time exceeding 120 minutes was associated with a higher early mortality (12/47 vs 18/155; p = 0.0187). Bypass time exceeding 120 minutes (p = 0.0456) and aortic crossclamp time exceeding 60 minutes (p = 0.0278) were associated with significant postoperative effusion. Other factors were not associated with any significantly increased risk for early mortality or postoperative effusions. Fenestration of the interatrial baffle appeared to decrease early mortality, although the numbers are too small to be statistically significant. The prevalence of effusions did not differ significantly between the group with fenestrated baffles and the group without fenestrated baffles.

Anterior pulmonary translocation for repair of truncus arteriosus with interrupted arch.

A newborn was found to have truncus arteriosus and an interrupted aortic arch, and underwent primary repair. The patient did well initially, but, by 8 weeks postoperatively, showed evidence of severe compression of the right pulmonary artery. At reoperation, the pulmonary artery was found to be compressed by a large aortic root (truncal root) and the retroaortic area was narrowed. The pulmonary artery bifurcation was therefore translocated anteriorly to alleviate the compression.

Malignant thymoma presenting as intracardiac tumor and superior vena caval obstruction.

A case of malignant thymoma with intracardiac infiltration and intrinsic superior vena caval obstruction due to the tumor is reported. Intracardiac invasion by a thymoma is rare and for this reason is believed worthy of a report.

Strategies for repair of congenital heart defects in infants without the use of blood.

Eleven infants and children with a body weight of less than 10 kg (median weight, 6.8 kg) whose parents were Jehovah's Witnesses underwent repair (n = 10) or palliation (n = 1) of congenital heart defects without the use of blood products and with (n = 9) or without (n = 2) cardiopulmonary bypass (CPB). In 1 neonate (weight, 3.2 kg) with critical aortic stenosis, moderate hypothermia and a 3.5-minute period of inflow occlusion and circulatory arrest allowed an aortic valvotomy; in another patient (weight, 7.0 kg) with tricuspid and pulmonary atresia, transposition of the great arteries, and persistent left superior vena cava, a bilateral bidirectional cavopulmonary shunt procedure was performed without CPB. Use of heparin-bonded tubing allowed reduction of the initial dose of heparin sodium to 1 mg/kg. Tissue perfusion and oxygenation on bypass were adequate, as evidenced by a mean lowest pH of 7.38 +/- 0.09 and a mean lowest venous oxygen tension of 65.0 +/- 36.2 mm Hg. Although the mean postoperative hematocrit (Hct) was lower than the mean preoperative Hct (p < 0.05, analysis of variance and Scheffe's F test), the Hct within 2 hours after CPB was restored to a value (mean Hct, 27.5% +/- 1.0%) between the preoperative Hct (mean value, 42.7% +/- 3.5%) and the lowest Hct on CPB (mean value, 18.4% +/- 1.4%). The Hct at discharge was 31.8% +/- 1.1%. The median postoperative blood loss was 9 mL/kg. There was no perioperative mortality. The median stay in the intensive care unit and the hospital was 2 days and 6 days, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Roots of nutrient-deprived Brachiaria species accumulate 1,3-di-O-trans-feruloylquinic acid.

A novel di-hydroxycinnamoylquinic acid ester, 1,3-di-O-trans-feruloylquinic acid (DFQA), was isolated from roots of nutrient-deprived Brachiaria species--the most widely sown tropical forage grasses in South America. In contrast to other so far characterized quinic-acid esters, DFQA exists in a chair conformation with the carboxylic group in the axial orientation. It accumulates in older parts of the root system, but not in root apices or shoots. Higher levels were found in B. ruziziensis, which is poorly adapted to infertile acid soils, than in well adapted B. decumbens. DFQA was also found in the soil, most likely as a result of root decay, because it was not detected in root exudates of plants cultivated in solution culture. Nitrogen and phosphorus deficiency--but not aluminum toxicity or deprivation of other nutrients--stimulated its synthesis in roots. Its accumulation was correlated with a shift in biomass partitioning toward the root system.

Direct inhibitory effect of gonadotropin releasing hormone in the uterus of rat.

Estradiol induced increase in ornithine decarboxylase (ODC) and glucosamine-6-phosphate synthase activities of rat uterus were inhibited by simultaneous treatment with gonadotropin releasing hormone (GnRH) or its agonists. The direct inhibitory effect of GnRH analogs was found to be dose dependent. It was observed that a higher dose of GnRH analog was needed to cause inhibition of glucosamine-6-phosphate synthase when compared to ODC activity. The inhibitory effect of GnRH was not observed if its injection was delayed following estradiol treatment. These results show that the extra-pituitary inhibitory effects of GnRH involves enzymes associated with cell proliferation.

The combination of a left aortic arch, a right-sided descending thoracic aorta with a left-sided arterial duct.

A nine-year-old male child presented with a history of recurrent chest infections and breathlessness. On investigation, he was found to have a left aortic arch with a right-sided descending thoracic aorta along with a left-sided arterial duct. He also had mild aortic stenosis with regurgitation. The duct was successfully ligated under controlled hypotensive anesthesia through a left posterolateral thoracotomy.

Surgical experience with intracardiac myxomas.

Eighteen patients underwent surgery for intracardiac myxoma (16 left atrial and 2 right atrial) during the last 10 years. Seventeen patients had tumour stalk attached to the oval fossa. The myxoma was excised along with a cuff of the atrial septum, which was reconstructed using a Dacron patch in 15 patients and by direct suture in 2 patients. In the remaining case the myxoma was attached to the left atrial wall and adjacent atrioventricular junction. There was only one early death in a patient who underwent a concomitant lobectomy for lung abscess and one late death due to a noncardiac cause. During the follow-up period of 3-96 months (average 36 months) all the survivors were in New York Heart Association Class I. Scanning electron microscopy of tumour tissue was done in 8 cases. The morphological findings did not help in categorizing the tumours into any pathological subgroups. Postoperative cardiac catheterization done in 3 patients (30-50 months postoperatively) showed return of haemodynamics to normal. Echocardiographic studies done postoperatively have not revealed recurrence of tumour in any patient. Surgical excision of myxomas is possible with very gratifying long-term results.

Thrombotic obstruction of Bjork-Shiley valves--diagnostic and surgical considerations.

We have evaluated 12 patients with thrombotic obstruction of the Bjork-Shiley valve since 1975, 11 in the mitral and 1 in the aortic position. During this period 442 patients with 303 mitral (181 plano-convex and 122 convexo-concave) and 205 aortic (112 plano-convex and 93 convexo-concave) Bjork-Shiley valves were available for follow-up. The incidence of thrombosis for the plano-convex model was 1.06% per patient year for the mitral position and 0.19% per patient year for the aortic position. The new convexo-concave model has brought down the incidence to 0.78% per patient year for the mitral (P less than 0.01) and 0% per patient year for the aortic valve. The onset of symptoms was acute (less than 15 days) in 41.7% and subacute (greater than 15 days) in 58.3% patients. All patients presented with pulmonary edema. Evidence of inadequate anticoagulation was present in only 3 (25%) patients. Reduction of prosthetic sounds and appearance of a new murmur was highly suggestive of valve thrombosis. Echocardiography and cinefluoroscopy was very useful for the instant recognition of this condition and had obviated the need for cardiac catheterisation in the last 6 patients. Emergency surgery was obligatory in all. Thrombectomy alone was successful in 9 patients. Three patients required replacement of the prosthesis. There was one operative death (mortality 8.3%). The long-term follow-up of these patients (3-82 months, mean 34 months) is excellent. We conclude that thrombotic obstruction of the Bjork-Shiley valve is often not related to inadequate anticoagulation, and more than half of the patients do not present with abrupt onset of symptoms. The convexo-concave model has significantly reduced this problem. Emergency surgery with thrombectomy is the procedure of choice for clotted prostheses.

Surgical treatment of major intracardiac lesions associated with discordant atrioventricular connexion.

Thirteen patients with a discordant atrioventricular connexion underwent repair of major associated intracardiac defects. Of the patients, 10 had a discordant ventriculoarterial connexion while 3 had double outlet from the morphologically right ventricle. A ventricular septal defect was the most frequently encountered lesion, present alone or in combination with other lesions in all patients. The other major lesions were pulmonary stenosis in 8, Ebstein's malformation of the left atrioventricular valve in 2, and calcific aortic valve disease in one. The operations performed were closure of the ventricular septal defect in 4 patients, closure of the ventricular septal defect with pulmonary valvotomy in 3 patients (one of whom subsequently underwent replacement of the left atrioventricular valve). Modified Fontan's procedure was performed in 6 patients, one of whom also had replacement of the aortic valve. There was no operative death, although there was one early death on the 40th postoperative day due to septicemia. There has been no late death after an average follow-up of 1.2 years. There was one case of surgically induced complete heart block. All other patients are in normal sinus rhythm in New York Heart Association functional class I or II. Elective repair of major intracardiac anomalies in association with a discordant atrioventricular connexion can now be accomplished safely. The modified Fontan's procedure is a viable alternative in certain cases to the placement of an external valved conduit for relief of pulmonary outflow tract obstruction.

Surgical experience with diseases of the tricuspid valve. Cross-sectional and Doppler echocardiographic evaluation following DeVega's repair.

Seventy-eight patients undergoing mitral valve surgery with or without replacement of the aortic valve also underwent procedures on the tricuspid valve over a period of 10 years. All patients were in functional class III or IV preoperatively. The procedures were performed in all patients with organic disease of the tricuspid valve (N = 44) and in those with moderate or severe functional tricuspid valvar regurgitation (N = 34). Seventy-one patients underwent DeVega's annuloplasty with or without commissurotomy. The overall mortality was 11.5%. 65 long-term survivors were followed up for a period of 6 months to 10 years (mean 5.3 years). Sixty-three patients were in functional class I or II at the last follow-up. Six patients had clinical evidence of mild to moderate tricuspid regurgitation. Regression of cardiomegaly (as judged by the chest radiograph and right ventricular hypertrophy seen in the electrocardiogram) was evident in most cases. Fifty-one of 54 patients evaluated by cross-sectional echocardiography were reported to have a functionally normal tricuspid valve. Doppler echocardiography in 28 patients showed no significant tricuspid regurgitation or stenosis in 26 patients. Eleven consecutive patients undergoing DeVega's annuloplasty were studied prospectively with pre- and postoperative Doppler echocardiography. Good correlation existed between right ventricular systolic pressures predicted by Doppler with those obtained preoperatively at cardiac catheterization. Postoperative Doppler echocardiography in these 11 patients showed complete restoration of competence of the tricuspid valve as well as normalisation of the right ventricular systolic pressure in 10 patients.