Preparations for a European R&D roadmap for an inertial fusion demo reactor.

A European consortium of 15 laboratories across nine nations have worked together under the EUROFusion Enabling Research grants for the past decade with three principle objectives. These are: (a) investigating obstacles to ignition on megaJoule-class laser facilities; (b) investigating novel alternative approaches to ignition, including basic studies for fast ignition (both electron and ion-driven), auxiliary heating, shock ignition, etc.; and (c) developing technologies that will be required in the future for a fusion reactor. A brief overview of these activities, presented here, along with new calculations relates the concept of auxiliary heating of inertial fusion targets, and provides possible future directions of research and development for the updated European Roadmap that is due at the end of 2020. This article is part of a discussion meeting issue 'Prospects for high gain inertial fusion energy (part 2)'.

Phytoseiid mites (Acari: Mesostigmata: Phytoseiidae) from Mato Grosso State, Central-Western Brazil.

The aim of the present study was to conduct a survey of mites of the family Phytoseiidae associated with plants of the natural vegetation and cultivated forests in sites of three biomes (Amazon Forest, Cerrado and Pantanal) in the Mato Grosso State. Twenty-one species of 11 genera, of the three phytoseiid subfamilies were registered. Amblyseius Berlese was the most diverse genus, with five species. Iphiseiodes zuluagai Denmark & Muma was the most common species, collected from 12 plant species in five collection sites. Eleven phytoseiid species were reported for the first time in the Mato Grosso State.

Clinical activity of programmed cell death 1 (PD-1) blockade in never, light, and heavy smokers with non-small-cell lung cancer and PD-L1 expression ≥50.

BACKGROUND: Immune checkpoint inhibitors (ICIs) are standard therapies for patients with advanced non-small-cell lung cancer (NSCLC) and a programmed death-ligand 1 (PD-L1) tumor proportion score (TPS) ≥50%. Tumor mutation burden (TMB) also predicts response to ICIs but is often not available in real time for decision making in the first-line setting. Smoking exposure can be a proxy for TMB in NSCLC. The impact of smoking status on efficacy of PD-1 blockade in NSCLC patients with PD-L1 TPS ≥50% has not been well defined. PATIENTS AND METHODS: To investigate the relationship between smoking and activity of ICIs in NSCLC, we retrospectively studied 315 patients with NSCLC and PD-L1 TPS ≥50% at five USA academic medical centers. Objective response rates (ORRs), progression-free survival (PFS), and duration of response (DOR) were compared between never (<100 lifetime cigarettes), light (≤10 pack-years), and heavy (>10 pack-years) smokers. A subset of patients underwent next-generation sequencing to estimate TMB. RESULTS: We identified 36 (11%) never, 42 (13%) light, and 237 (75%) heavy smokers with NSCLC and PD-L1 TPS ≥50% treated with ICIs. Objective responses were observed in 27%, 40%, and 40% of never, light, and heavy smokers, respectively (P = 0.180 never versus heavy; P = 1.000 light versus heavy). Median PFS and median DOR were numerically shorter in never and light smokers compared with heavy smokers (PFS 3.0 versus 4.0 versus 5.4 months; median DOR 6.9 versus 10.8 versus 17.8 months), but were not statistically different [PFS: hazard ratio (HR) 1.37, P = 0.135 and HR 1.24, P = 0.272; DOR: HR 1.92, P = 0.217 and HR 1.79, P = 0.141]. CONCLUSIONS: PD-(L)1 inhibitors are associated with antitumor activity in NSCLC with PD-L1 TPS ≥50% regardless of smoking status. Nevertheless, there is a signal of potentially decreased durability among never and light smokers that should be further evaluated. Distinct immunobiologic features may affect initial response versus durability of antitumor immunity to programmed cell death 1 (PD-1) blockade.

A Double-Blind, Comparative Clinical Study of Newly Formulated Retinol Serums vs Tretinoin Cream in Escalating Doses: A Method for Rapid Retinization With Minimized Irritation.

OBJECTIVE: The goal of this 12 week, double-blinded, controlled, clinical study was to compare the efficacy, tolerability, and consumer acceptance of three novel retinol serums to tretinoin. METHOD: Forty-five photoaged females ages 35-65, Fitzpatrick skin types I-IV, with moderate wrinkling were enrolled in the 12-week study. A step-up protocol for increasing the dose of retinol serum (0.25%, 0.5%, 1.0%) or tretinoin cream (0.025%, 0.05%, and 0.1%) in combination with a test moisturizer or currently marketed dermatologist-recommended moisturizing cream was used. Overall severity of investigator graded photodamage, subject assessed photodamage, and tolerability criteria were evaluated using a 5-point ordinal scale at weeks 4, 8, and 12. Facial photography occurred at each visit and TEWL was measured at baseline and week 12. Histologic evaluation of punch biopsies was completed on baseline and week 12 samples. RESULTS: After 12 weeks of use, both retinol serum and tretinoin demonstrated parity across investigator and subject assessment measurements as well as diagnostic measures including TEWL. Retinol serum subjects showed significant week 4 improvement in visual skin smoothness compared to tretinoin subjects (P=0.031). There was highly significant improvement in skin dryness with the retinol serum (P<0.001) not seen in the tretinoin group. Histologic analysis of baseline and 12-week punch biopsies demonstrated newly formed collagen and greater epidermal thickening in retinol serum subjects compared to tretinoin treated subjects. CONCLUSION: Retinol serum (0.25%, 0.5%, 1.0%) was safe and effective with equivalent/or better performance and tolerability than tretinoin creams. J Drugs Dermatol. 2020;19(6): doi:10.36849/JDD.2020.5085.

Outcomes to first-line pembrolizumab in patients with non-small-cell lung cancer and very high PD-L1 expression.

BACKGROUND: In non-small-cell lung cancers with programmed death-ligand 1 (PD-L1) expression on ≥50% of tumor cells, first-line treatment with the PD-1 inhibitor pembrolizumab improves survival compared with platinum-doublet chemotherapy. Whether higher PD-L1 levels within the expression range of 50%-100% predict for even greater benefit to pembrolizumab is currently unknown. PATIENTS AND METHODS: In this multicenter retrospective analysis, we analyzed the impact of PD-L1 expression levels on the overall response rate (ORR), median progression-free survival (mPFS), and median overall survival (mOS) in patients who received commercial pembrolizumab as first-line treatment of non-small-cell lung cancer (NSCLC) with a PD-L1 expression of ≥50% and negative for genomic alterations in the EGFR and ALK genes . RESULTS: Among 187 patients included in this analysis, the ORR was 44.4% [95% confidence interval (CI) 37.1% to 51.8%], the mPFS was 6.5 months (95% CI 4.5-8.5), and the mOS was not reached. The median PD-L1 expression level among patients who experienced a response to pembrolizumab was significantly higher than among patients with stable or progressive disease (90% versus 75%, P < 0.001). Compared with patients with PD-L1 expression of 50%-89% (N = 107), patients with an expression level of 90%-100% (N = 80) had a significantly higher ORR (60.0% versus 32.7%, P < 0.001), a significantly longer mPFS [14.5 versus 4.1 months, hazard ratio (HR) 0.50 (95% CI 0.33-0.74), P < 0.01], and a significantly longer mOS [not reached versus 15.9 months, HR 0.39 (95% CI 0.21-0.70), P = 0.002]. CONCLUSION: Among patients with NSCLC and PD-L1 expression of ≥50% treated with first-line pembrolizumab, clinical outcomes are significantly improved in NSCLCs with a PD-L1 expression of ≥90%. These findings have implications for treatment selection as well as for clinical trial interpretation and design.

Polygenic risk for severe psychopathology among Europeans is associated with major depressive disorder in Han Chinese women.

BACKGROUND: Previous studies have demonstrated that several major psychiatric disorders are influenced by shared genetic factors. This shared liability may influence clinical features of a given disorder (e.g. severity, age at onset). However, findings have largely been limited to European samples; little is known about the consistency of shared genetic liability across ethnicities. METHOD: The relationship between polygenic risk for several major psychiatric diagnoses and major depressive disorder (MDD) was examined in a sample of unrelated Han Chinese women. Polygenic risk scores (PRSs) were generated using European discovery samples and tested in the China, Oxford, and VCU Experimental Research on Genetic Epidemiology [CONVERGE (maximum N = 10 502)], a sample ascertained for recurrent MDD. Genetic correlations between discovery phenotypes and MDD were also assessed. In addition, within-case characteristics were examined. RESULTS: European-based polygenic risk for several major psychiatric disorder phenotypes was significantly associated with the MDD case status in CONVERGE. Risk for clinically significant indicators (neuroticism and subjective well-being) was also associated with case-control status. The variance accounted for by PRS for both psychopathology and for well-being was similar to estimates reported for within-ethnicity comparisons in European samples. However, European-based PRS were largely unassociated with CONVERGE family history, clinical characteristics, or comorbidity. CONCLUSIONS: The shared genetic liability across severe forms of psychopathology is largely consistent across European and Han Chinese ethnicities, with little attenuation of genetic signal relative to within-ethnicity analyses. The overall absence of associations between PRS for other disorders and within-MDD variation suggests that clinical characteristics of MDD may arise due to contributions from ethnicity-specific factors and/or pathoplasticity.

Laser Cooling of a Micromechanical Membrane to the Quantum Backaction Limit.

The radiation pressure of light can act to damp and cool the vibrational motion of a mechanical resonator, but even if the light field has no thermal component, shot noise still sets a limit on the minimum phonon occupation. In optomechanical sideband cooling in a cavity, the finite off-resonant Stokes scattering defined by the cavity linewidth combined with shot noise fluctuations dictates a quantum backaction limit, analogous to the Doppler limit of atomic laser cooling. In our work, we sideband cool a micromechanical membrane resonator to the quantum backaction limit. Monitoring the optical sidebands allows us to directly observe the mechanical object come to thermal equilibrium with the optical bath. This level of optomechanical coupling that overwhelms the intrinsic thermal decoherence was not reached in previous ground-state cooling demonstrations.

First Liquid Layer Inertial Confinement Fusion Implosions at the National Ignition Facility.

The first cryogenic deuterium and deuterium-tritium liquid layer implosions at the National Ignition Facility (NIF) demonstrate D_{2} and DT layer inertial confinement fusion (ICF) implosions that can access a low-to-moderate hot-spot convergence ratio (1230) DT ice layer implosions. Although high CR is desirable in an idealized 1D sense, it amplifies the deleterious effects of asymmetries. To date, these asymmetries prevented the achievement of ignition at the NIF and are the major cause of simulation-experiment disagreement. In the initial liquid layer experiments, high neutron yields were achieved with CRs of 12-17, and the hot-spot formation is well understood, demonstrated by a good agreement between the experimental data and the radiation hydrodynamic simulations. These initial experiments open a new NIF experimental capability that provides an opportunity to explore the relationship between hot-spot convergence ratio and the robustness of hot-spot formation during ICF implosions.

Using citrate-functionalized TiO2 nanoparticles to study the effect of particle size on zebrafish embryo toxicity.

TiO2 nanoparticles (NPs) are photoactive, potentially producing toxicity in vivo in the presence of sunlight. We have previously demonstrated photodependent toxicity in zebrafish embryos exposed to TiO2 NPs. Here we investigate the effect of particle size on developing zebrafish exposed to 6, 12 and 15 nm citrate-functionalized anatase TiO2 NPs under either simulated sunlight illumination or in the dark. All three sizes of TiO2 NPs caused photo-dependent toxicity. Under simulated sunlight illumination, the acute toxicity of the 6 nm citrate-TiO2 NPs (120 h LC50 of 23.4 mg L(-1)) exceeded that of the 12 and 15 nm citrate-TiO2 NPs. Exposure to 6 nm particles under illumination also caused a higher incidence of developmental defects than the larger particles. These abnormalities included pericardial edema, yolk-sac edema, craniofacial malformation, and opaque yolk. To gain insight into the mechanisms of toxicity, we measured hydroxyl radicals (˙OH) generated by NPs in vitro and reactive oxygen species (ROS) produced in vivo. We found that on a mass basis, smaller particles generated higher levels of ROS both in vitro and in vivo, and the 6 nm citrate-TiO2 NPs induced more oxidative stress than larger particles in the zebrafish embryo. We examined oxidative DNA damage by measuring 8-hydroxydeoxyguanosine in zebrafish exposed to different-sized citrate-TiO2 NPs and found that 6 nm particles caused more DNA damage than did larger particles (12 and 15 nm) under illumination. Our results indicate a photo-dependent toxicity of citrate-TiO2 NPs to zebrafish embryos, with an inverse relationship between particle size and toxicity. Production of more ROS, resulting in more oxidative stress and more DNA damage, represents one possible mechanism of the higher toxicity of smaller citrate-TiO2 NPs. These results highlight the relationship between citrate-TiO2 NP size and toxicity/oxidative stress in developing zebrafish embryos.

Dermal irritation of petrolatum in rabbits but not in mice, rats or minipigs.

Petrolatum is widely used in cosmetics, topical pharmaceuticals and also as a vehicle in dermal toxicity studies. New Zealand white rabbits treated with white petrolatum (vehicle control) in a 2-week dermal irritation study exhibited moderate to severe erythema starting on Day 7 that subsided towards the end of the study. Histological examination of abraded and non-abraded petrolatum-treated skin obtained at termination (Day 15) revealed mild acanthosis, hyperkeratosis, dermal edema with mixed inflammatory cells in the dermis. Macroscopic and microscopic features noted in rabbits were consistent with dermal irritation to petrolatum. Wistar-Han rats, CD1 mice, C57/Bl/6J mice and Göttingen minipigs treated topically with white petrolatum did not exhibit clinical or histologic evidence of dermal irritation. Therapeutic agents developed for topical application are generally tested in rabbits during some point in development. Interpretation of skin irritation data from a single species can impact risk assessment for humans and on product labeling.

Phytoseiidae database: a website for taxonomic and distributional information on phytoseiid mites (Acari).

This paper announces a database on the taxonomy and distribution of mites of the family Phytoseiidae Berlese, which is available online at http://www.lea.esalq.usp.br/phytoseiidae/. Synthesis of species diversity per genus, subfamily and country are given. Information about use of the database is provided.

Nutrition as a military capability to deliver human advantage: more people, more ready, more of the time.

Soldiers must achieve high-level mission-preparedness to endure extended periods of physical and cognitive activity, with unpredictable recovery, in all environments. Nutrition provides the foundation for health and performance. Militaries have not maximised the strategic and financial value that considering nutrition as a military capability could deliver. A whole system approach to military nutrition, based on the prepare-perform-recover human capability cycle phases, is presented. Trainee nutrition requirements, through to very-high-readiness forces undertaking arduous roles at reach, must be specifically addressed. Promoting military performance diets in the prepare phase, through practitioner-supported nutrition education and food provision, will ensure mission readiness and mitigate ill health. Delivering nutrition in field settings in the perform phase-through smaller/lighter, nutritionally optimised rations and smart packaging technologies-will improve utility and minimise waste. Strategic dietary supplement use can provide a mission performance-enhancing adjunct to a food-first philosophy. Impact value chain analysis of military nutrition capability investments could support cost-benefit measurement.

Longwave-IR optical parametric oscillator in orientation-patterned GaAs pumped by a 2 µm Tm,Ho:YLF laser.

We demonstrate longwave infrared (LWIR) generation with an optical parametric oscillator (OPO) based on quasi-phasematched orientation-patterned gallium arsenide (OPGaAs). The OPGaAs OPO was directly pumped with a Q-switched λ = 2.054 µm Tm,Ho:YLF laser. OPGaAs samples representing three different grating periods were used to explore the LWIR OPO performance yielding outputs ranging from λ = 2.5-2.7 µm (signal) and λ = 8.8-11.5 µm (idler). Slope efficiencies for the combined signal and idler outputs reach as high as 26% while slope efficiencies for only the idler reached 8%. Spectral measurements of OPO output confirm good agreement with theoretical calculations.

Histology of Convergent Probing Appendages in Mormyridae.

Mormyridae is an early diverging family of Teleostean fishes that produce an electric field for navigation and communication using an electric organ. This clade has a diverse array of soft-tissue rostral appendages, such as the chin-swelling, the Schnauzenorgan, and the tubesnout combined with a Schnauzenorgan, that have evolved multiple times. Here we assess if macroscopically convergent, soft-tissue rostral appendages are also histologically convergent. Further, we investigate how the histology of these appendages can inform their function. We sampled independent gains of the chin-swelling and Schnauzenorgan to understand similarities and differences in their anatomies. We show that macroscopically convergent rostral appendages are also convergent at a histological level, and different types of rostral appendages share a similar anatomy; that said, minor differences likely relate to their specific functions. Based on a comparison of the skeletal muscle distribution and the differing attachment shapes of each appendage to the dentary, we conclude that the Schnauzenorgan is capable of a wider range of movements than the chin swelling. Furthermore, the anatomy suggests that these soft-tissue rostral appendages likely function as electrosensory foveas (i.e., an appendage that focuses a sensory system). Lastly, these histological data support the hypothesis that the chin swelling may be a precursor to the Schnauzenorgan.

ResumenMormyridae es una de las primeras familias divergentes de peces teleósteos que producen un campo eléctrico para la navegación y la comunicación mediante un órgano eléctrico. Este clado tiene una variedad diversa de apéndices rostrales de tejidos blandos, como el mentón hinchado, el Schnauzenorgan y el hocico tubular combinado con un Schnauzenorgan, que han evolucionado varias veces. Aquí evaluamos si los apéndices rostrales de tejido blando macroscópicamente convergentes también son histológicamente convergentes. Además, investigamos cómo la histología de estos apéndices puede informar sus funciones. Tomamos muestras de ganancias independientes del mentón hinchado y del Schnauzenorgan para comprender las similitudes y diferencias en sus anatomías. Mostramos que los apéndices rostrales macroscópicamente convergentes también lo son a nivel histológico, y diferentes tipos de apéndices rostrales comparten una anatomía similar; dicho esto, es probable que las diferencias menores se relacionen con sus funciones específicas. Con base en una comparación de la distribución del músculo esquelético y las diferentes formas de unión de cada apéndice al dentario, concluimos que el Schnauzenorgan es capaz de realizar una gama más amplia de movimientos que el mentón hinchado. Además, la anatomía sugiere que estos apéndices rostrales de tejido blando probablemente funcionen como fóveas electrosensoriales (es decir, un apéndice que enfoca un sistema sensorial). Por último, estos datos histológicos apoyan la hipótesis de que el mentón hinchado puede ser un precursor del Schnauzenorgan.

Distinct developmental trajectories of autonomous behaviors and agency in rodents.

Behavioral interactions within the nuclear family may play a pivotal role in the emergence of autonomy and agency in mammals. While the emergence of a behavior may arise over weeks in line with nervous system maturation, individual events occur on sub-second time scales. This makes it uniquely challenging to track development in the lab where observations are made over minutes to hours or in ecological studies which lack individual specificity and sub-second precision. Here we study families of gerbils, a highly social rodent, raised in enlarged home-cage environments over weeks of development, using continuous video recordings to capture tens of millions of time points per family. Focusing on postnatal day 15 (when pups leave the nest) to day 30 (around the time when pups would disperse) we identify distinct developmental trajectories for both autonomous behaviors (exploration, food and water foraging), and social behaviors (huddling, approach, time spent together). Most of these behaviors emerge in concert with clear diurnal and crepuscular patterns and we find sex differences in both autonomous and social behaviors. Our work supports the emergence of distinct autonomous and social behavior phenotypes as the behavioral correlates of critical developmental periods of maturation of the rodent brain and can form the basis of future research on development from both neuroscience and behavioral biology perspectives.

Low-temperature, high-performance solution-processed metal oxide thin-film transistors formed by a 'sol­gel on chip' process.

At present there is no 'ideal' thin-film transistor technology for demanding display applications, such as organic light-emitting diode displays, that allows combining the low-temperature, solution-processability offered by organic semiconductors with the high level of performance achievable with microcrystalline silicon1. N-type amorphous mixed metal oxide semiconductors, such as ternary oxides Mx1My2Oz, where M1 and M2 are metals such as In, Ga, Sn, or Zn, have recently gained momentum because of their high carrier mobility and stability2, 3 and good optical transparency, but they are mostly deposited by sputtering. So far no route is available for forming high-performance mixed oxide materials from solution at low process temperatures <250 °C. Ionic mixed metal oxides should in principle be ideal candidates for solution-processable materials because the conduction band states derived from metal s-orbitals are relatively insensitive to the presence of structural disorder and high charge carrier mobilities are achievable in amorphous structures2. Here we report the formation of amorphous metal oxide semiconducting thin-films using a 'sol­gel on chip' hydrolysis approach from soluble metal alkoxide precursors, which affords unprecedented high field-effect mobilities of 10 cm2 V−1 s−1, reproducible and stable turn-on voltages Von≈0 V and high operational stability at maximum process temperatures as low as 230 °C.

Ibex-associated malignant catarrhal fever-like disease in a group of bongo antelope (Tragelaphus eurycerus).

A private zoological facility experienced an outbreak of malignant catarrhal fever (MCF) in 3 bongo antelope (Tragelaphus eurycerus). All cases were periparturient bongos that presented acutely anorectic beginning ~6 weeks after being housed with a Nubian ibex. Disease quickly progressed to respiratory distress and death within 24-72 hours of onset of clinical signs. Consistent gross findings in affected bongos were pulmonary edema and small pale tan foci in the livers. Histological lesions included a nonsuppurative vasculitis in multiple tissues, which is well recognized in MCF, but additionally included necrotizing cholangiohepatitis and neutrophilic, necrotizing myocarditis. Ibex-associated viral DNA was detected by polymerase chain reaction and was identical in sequence whether derived from bongos or ibex. The sequence closely matched an MCF viral DNA fragment that had been amplified from an ibex and bongo in a previous case report.

Acceptability and barriers to adopting physical therapy and rehabilitation as standard of care in hernia disease: a prospective national survey of providers and preliminary data.

PURPOSE: Physical therapy (PT) and rehabilitation are widely utilized in a variety of disease processes to improve function, return to activities of daily living (ADLs), and promote overall recovery. However, hernia repair has struggled to adopt this practice despite operations occurring in one of the most dynamic parts of the body - the abdominal core. This study sought to understand perspectives and perceived barriers regarding the incorporation of PT and rehabilitation in hernia care. METHODS: A standardized rehabilitation protocol was developed by the Abdominal Core Health Quality Collaborative (ACHQC), a national quality improvement initiative specific to hernia disease, and launched in 2019. Empiric data from the ACHQC was then obtained to describe preliminary utilization. A prospective electronic survey was then deployed to all surgeons participating in the ACHQC to aid in interpreting the identified trends. The survey included questions regarding the current use of PT in their practice, as well as further opinions on the functionality, benefit, and barriers to its use. RESULTS: We identified 1,544 patients who were listed as receiving some form of postoperative rehabilitation, of which 992 (64.2%) had a primary diagnosis of ventral hernia and 552 (35.8%) had an inguinal hernia. Among patients who had a ventral hernia, 863 (87.0%) received self-directed rehabilitation exercises compared to 488 (88.4%) of inguinal hernia patients. The subsequent survey exploring these trends was completed by 46 ACHQC surgeons (10.2%). More than half (52%) reported using PT for hernia patients, primarily in abdominal wall reconstruction cases (92%). Of those who did not report using PT, 50% cited unknown clinical benefit and another 27% cited unknown PT resources. PT utilization was typically concentrated to the postoperative period (58%), while 42% reported also using it preoperatively. Despite 72% of respondents citing a perceived benefit of PT in hernia patients, overall use of PT was primarily reported as 'occasional' by 42%, with another 27% reporting 'rarely.' Perceived benefits of PT included increased core strength, stability, mobility, patient satisfaction, education, independence, earlier return to work and ADLs, overall improved recovery, and decreased risk of postoperative issues. Reported barriers to implementing PT in practice or adapting the ACHQC Rehabilitation Protocol included lack of education, lack of evidence of clinical benefit, and difficulties operationalizing the protocol. CONCLUSION: A national survey of hernia surgeons demonstrated willingness to adopt PT and rehabilitation protocols in their clinical practices and noted a high perceived benefit to patients. However, lack of education and evidence regarding the protocol may represent important barriers to overcome in widely disseminating these resources to patients. These gaps can be addressed through dedicated educational venues and additional studies establishing PT and rehabilitation as critical future adjuncts for the recovery of hernia repair patients.

Tarsonemid mites (Acari: Tarsonemidae) on myrtaceous plants of the Atlantic Forest, Brazil, with description of a new species of Tarsonemus Canestrini amp; Fanzago.

A survey of tarsonemid mites associated with plants of the family Myrtaceae was conducted in seven areas of the Atlantic Forest biome. Fourteen known species were registered; other 21 morphospecies was identified up to genus level. Additionally, a new species, Tarsonemus conduru Lofego Cavalcante sp. nov. is described based on specimens collected in the Atlantic Forest of Bahia state.

The rate of nitrite reduction in leaves as indicated by O2 and CO2 exchange during photosynthesis.

Light response (at 300 ppm CO(2) and 10-50 ppm O(2) in N(2)) and CO(2) response curves [at absorbed photon fluence rate (PAD) of 550 µmol m(-2) s(-1)] of O(2) evolution and CO(2) uptake were measured in tobacco (Nicotiana tabacum L.) leaves grown on either NO(3)(-) or NH(4)(+) as N source and in potato (Solanum tuberosum L.), sorghum (Sorghum bicolor L. Moench), and amaranth (Amaranthus cruentus L.) leaves grown on NH(4)NO(3). Photosynthetic O(2) evolution in excess of CO(2) uptake was measured with a stabilized zirconia O(2) electrode and an infrared CO(2) analyser, respectively, and the difference assumed to represent the rate of electron flow to acceptors alternative to CO(2), mainly NO(2)(-), SO(4)(2-), and oxaloacetate. In NO(3)(-)-grown tobacco, as well as in sorghum, amaranth, and young potato, the photosynthetic O(2)-CO(2) flux difference rapidly increased to about 1 µmol m(-2) s(-1) at very low PADs and the process was saturated at 50 µmol quanta m(-2) s(-1). At higher PADs the O(2)-CO(2) flux difference continued to increase proportionally with the photosynthetic rate to a maximum of about 2 µmol m(-2) s(-1). In NH(4)(+)-grown tobacco, as well as in potato during tuber filling, the low-PAD component of surplus O(2) evolution was virtually absent. The low-PAD phase was ascribed to photoreduction of NO(2)(-) which successfully competes with CO(2) reduction and saturates at a rate of about 1 µmol O(2) m(-2) s(-1) (9% of the maximum O(2) evolution rate). The high-PAD component of about 1 µmol O(2) m(-2) s(-1), superimposed on NO(2)(-) reduction, may represent oxaloacetate reduction. The roles of NO(2)(-), oxaloacetate, and O(2) reduction in the regulation of ATP/NADPH balance are discussed.