The global nitrogen cycle in the twenty-first century

Global nitrogen fixation contributes 413 Tg of reactive nitrogen (Nr) to terrestrial and marine ecosystems annually of which anthropogenic activities are responsible for half, 210 Tg N. The majority of the transformations of anthropogenic Nr are on land (240 Tg N yr(-1)) within soils and vegetation where reduced Nr contributes most of the input through the use of fertilizer nitrogen in agriculture. Leakages from the use of fertilizer Nr contribute to nitrate (NO3(-)) in drainage waters from agricultural land and emissions of trace Nr compounds to the atmosphere. Emissions, mainly of ammonia (NH3) from land together with combustion related emissions of nitrogen oxides (NOx), contribute 100 Tg N yr(-1) to the atmosphere, which are transported between countries and processed within the atmosphere, generating secondary pollutants, including ozone and other photochemical oxidants and aerosols, especially ammonium nitrate (NH4NO3) and ammonium sulfate (NH4)2SO4. Leaching and riverine transport of NO3 contribute 40-70 Tg N yr(-1) to coastal waters and the open ocean, which together with the 30 Tg input to oceans from atmospheric deposition combine with marine biological nitrogen fixation (140 Tg N yr(-1)) to double the ocean processing of Nr. Some of the marine Nr is buried in sediments, the remainder being denitrified back to the atmosphere as N2 or N2O. The marine processing is of a similar magnitude to that in terrestrial soils and vegetation, but has a larger fraction of natural origin. The lifetime of Nr in the atmosphere, with the exception of N2O, is only a few weeks, while in terrestrial ecosystems, with the exception of peatlands (where it can be 10(2)-10(3) years), the lifetime is a few decades. In the ocean, the lifetime of Nr is less well known but seems to be longer than in terrestrial ecosystems and may represent an important long-term source of N2O that will respond very slowly to control measures on the sources of Nr from which it is produced.

Impacts of soil and water pollution on food safety and health risks in China

Environmental pollution and food safety are two of the most important issues of our time. Soil and water pollution, in particular, have historically impacted on food safety which represents an important threat to human health. Nowhere has that situation been more complex and challenging than in China, where a combination of pollution and an increasing food safety risk have affected a large part of the population. Water scarcity, pesticide over-application, and chemical pollutants are considered to be the most important factors impacting on food safety in China. Inadequate quantity and quality of surface water resources in China have led to the long-term use of waste-water irrigation to fulfill the water requirements for agricultural production. In some regions this has caused serious agricultural land and food pollution, especially for heavy metals. It is important, therefore, that issues threatening food safety such as combined pesticide residues and heavy metal pollution are addressed to reduce risks to human health. The increasing negative effects on food safety from water and soil pollution have put more people at risk of carcinogenic diseases, potentially contributing to 'cancer villages' which appear to correlate strongly with the main food producing areas. Currently in China, food safety policies are not integrated with soil and water pollution management policies. Here, a comprehensive map of both soil and water pollution threats to food safety in China is presented and integrated policies addressing soil and water pollution for achieving food safety are suggested to provide a holistic approach.

Use of multiple PCR primer sets for optimal detection of human papillomavirus

Using multiple PCR primer sets, we tried to optimize the detection of human papillomavirus (HPV) in DNA samples isolated from 361 frozen biopsy specimens from patients with invasive cervical carcinomas. The HPVs detected were placed into three distinct groups, including group I/Inex at Telelab (Skien, Norway) and group Ineg and group II at the Norwegian Radium Hospital (Oslo, Norway). The consensus primer sets were Oli-1b-oli-2i, My09-My11, Gp5-Gp6, and Gp(5+)-Gp6+ from the HPV L1 gene and CpI-CpIIG from the E1 gene. Using these consensus primers together with the type-specific primers from E6-E7, we found that 355 patients (98%) were HPV positive. Type-specific primers for HPV types 11, 16, 18, 31, 33, and 35 detected more HPV-infected patients than the most sensitive consensus primer set, while the three consensus primer sets My, Gp/Gp+, and Cp together detected more HPV-positive patients than the type-specific primers. Testing of sensitivity of the PCR with SiHa cells serially diluted in lymphocytes (HPV-negative cells) indicated a detection limit of 6,300 HPV type 16 DNA copies with consensus primers (My, Gp+, and Cp) and 126 original HPV type 16 DNA copies with type-specific primers. Comparison of the amplification results for consensus L1 primers and type-specific E6-E7 primers indicated the presence of L1 deletions in 23 of 56 samples. The conclusion is that in PCR detection systems, multiple consensus primers and type-specific primers should be used in order to detect all patients harboring HPV.

Structural basis for the inhibition of firefly luciferase by a general anesthetic

The firefly luciferase enzyme from Photinus pyralis is probably the best-characterized model system for studying anesthetic-protein interactions. It binds a diverse range of general anesthetics over a large potency range, displays a sensitivity to anesthetics that is very similar to that found in animals, and has an anesthetic sensitivity that can be modulated by one of its substrates (ATP). In this paper we describe the properties of bromoform acting as a general anesthetic (in Rana temporaria tadpoles) and as an inhibitor of the firefly luciferase enzyme at high and low ATP concentrations. In addition, we describe the crystal structure of the low-ATP form of the luciferase enzyme in the presence of bromoform at 2.2-A resolution. These results provide a structural basis for understanding the anesthetic inhibition of the enzyme, as well as an explanation for the ATP modulation of its anesthetic sensitivity.

Brain lesions detected by magnetic resonance imaging in mild and severe head injuries

50 patients were studied by magnetic resonance imaging (MRI) within one week of a head injury. Abnormalities indicating primary brain damage were found in 46 patients, almost twice as many as with computed tomography. Cortical contusions were the most common finding, irrespective of the effect of injury on the level of consciousness. Intracerebral lesions were seen only in patients who had lost consciousness and were present in 29 of 42 patients whose consciousness was still impaired on arrival at hospital. Lesions in the deep white-matter of the cerebral hemispheres were seen in 15 patients; they were significantly more frequent in patients in coma but were also seen in patients who had lost consciousness for no more than 5 min. The findings indicate that lesions in the cerebral hemispheres may be the primary factor in traumatic unconsciousness. MRI studies may also clarify the sequelae of head injuries.

The instep of the foot as a fasciocutaneous island and as a free flap for heel defects

The instep flap needs neither muscle nor a transposition base for survival or innervation. It can be transposed as an island fasciocutaneous flap either on the medial or lateral plantar neurovascular bundles or both, and it can be transferred also as a free flap from the opposite foot. Four cases demonstrating the use of the flap as an island and free flap are presented with follow-up ranging from 1 to 2 years. The absence of muscle in the flap provides greater stability of the heel reconstruction and results in a lesser secondary defect. Sensation in the flaps is diminished but adequate for long-term function, but hyperkeratotic reaction remains an unpredictable problem. The ability to transfer the flap as a free transfer widens the scope of the flap to reconstruct both heel and forefoot defects where local instep tissue or vascularity are inadequate for local reconstruction. The secondary defect, particularly when no muscle is included in the flap, has been minimal.

Effect of processing on digestibility and the blood glucose response: a study of lentils

To test the effect of processing on digestibility and the glycemic response to a leguminous seed, a group of eight healthy volunteers took a series of breakfast test meals containing either lentils which had been processed in four different ways or the same amount of carbohydrate as white bread. Lentils, boiled for 20 min, resulted in a flattened blood glucose response by comparison with bread. This was unaltered by blending the lentils to a paste or boiling them for an additional 40 minutes. However the blood glucose response was significantly enhanced by drying the boiled blended lentils for 12 h at 250 degrees F. In vitro digestion with human saliva showed the rate of sugars released from the food related positively to the blood glucose rise. Breath hydrogen studies indicated that carbohydrate malabsorption was too small to account for differences in the blood glucose response. These results emphasize the importance of processing in determining digestibility and hence the glycemic response to a food.

Cardiac hypertrophy: a matter of translation

1. Left ventricular hypertrophy (LVH) of the heart is an adaptive response to sustained increases in blood pressure and hormone imbalances. Left ventricular hypertrophy is associated with programmed responses at the molecular and biochemical level in different subsets of cardiac cells, including the cardiac muscle cells (cardiomyocytes), fibroblasts, conductive tissue and coronary vasculature. 2. Regardless of the initiating cause, the actual increase in chamber enlargement is, in each case, due to an increase in size of a pre-existing cardiomyocyte population, with little or no change in their number; a process referred to as cellular hypertrophy. 3. An accelerated rate of global protein synthesis is the primary mechanism by which protein accumulation increases during cardiomyocyte hypertrophy. In turn, increased rates of synthesis are a result of increased translational rates of existing ribosomes (translational efficiency) and/or synthesis and recruitment of additional ribosomes (translational capacity). 4. The present review examines the relative importance of translational capacity and translational efficiency in the response of myocytes to acute and chronic demands for increased protein synthesis and the role of these mechanisms in the development of LVH.

Effects of experimental intracerebral hemorrhage on blood flow, capillary permeability, and histochemistry

Experimental intracerebral hemorrhage has been shown to cause extensive cerebral ischemia. This study was performed to ascertain the time course of these changes and also to examine the type of brain damage that may occur under such circumstances. Halothane anesthesia was induced in rats, and 25 microliter autologous blood was injected into the caudate nucleus; the effects were studied with autoradiographic measurement of local cerebral blood flow and capillary permeability, and also by light microscopy and histochemical techniques. Blood flow returned to normal or to slightly increased levels within the first 3 hours, and ischemic levels of flow were found to persist only to a marginal degree beyond 10 minutes after the lesions were made. Capillary permeability was maximum during the first 30 minutes after the hemorrhage and diminished with time. Structural evidence of ischemic damage was localized to the cortex overlying the hemorrhage, but was not seen in the caudate nucleus. Nevertheless, histochemical investigation did reveal an area of disturbed enzyme function in the striatum. This finding of biochemical disturbance without structural evidence of ischemic damage reveals that there is an area around the hematoma that, although demonstrating disturbed function, does not show structural damage, and the milieu of this partially injured brain may be implicated in the delayed development of the ischemic brain damage that follows intracerebral hemorrhage in man.

Screening for atherosclerosis in patients with rheumatoid arthritis: comparison of two in vivo tests of vascular function

OBJECTIVE

Inflammation appears to play a central role in atherosclerosis, and endothelial damage mediated by systemic inflammation may contribute to the increased cardiovascular mortality in rheumatoid arthritis (RA). Brachial artery flow-mediated dilatation (FMD) and pulse wave analysis (PWA) are measures of vascular function. The aim of this study was to determine if FMD and PWA are abnormal in patients with RA.

METHODS

Twenty-five RA patients and 25 matched healthy controls were studied. All were free of traditional cardiovascular risk factors. FMD was measured in all subjects. PWA was performed in 18 RA patients and 18 controls, with results expressed as large and small artery compliance (C1 and C2). Modified Sharp scores were calculated in 13 RA patients.

RESULTS

Results (mean +/- SD) in RA patients and controls, respectively, were as follows: FMD 107.6 +/- 4.6% versus 108.5 +/- 4.1% (P = 0.49), C1 14.8 +/- 2.8 ml/mm Hg x 10 versus 17.9 +/- 3.1 ml/mm Hg x 10 (P = 0.0033), C2 4.5 +/- 2.3 ml/mm Hg x 100 versus 7.7 +/- 3.7 ml/mm Hg x 100 (P = 0.0039). There was an inverse correlation between C2 and modified Sharp scores in the RA patients (Spearman's rho -0.69, P = 0.0085).

CONCLUSION

FMD was normal in these RA patients, whereas arterial compliance was markedly reduced. PWA appears to be a more sensitive measure of vascular dysfunction than FMD in RA and may be the preferred surrogate marker of vascular dysfunction in longitudinal studies of RA patients. The inverse correlation between C2 and the modified Sharp score, a measure that reflects disease activity over time, supports the notion that chronic inflammation plays a role in RA-associated atherosclerosis.

Forty years of reform and opening up: China's progress toward a sustainable path

After 40 years of reform and "opening up," China has made remarkable economic progress. Such economic prosperity, however, has been coupled with environmental degradation. We analyze diverse long-term data to determine whether China is experiencing a decoupling of economic growth and environmental impacts, and where China stands with respect to the Sustainable Development Goals (SDGs) in terms of reducing regional division, urban-rural gap, social inequality, and land-based impacts on oceans. The results highlight that China's desire to achieve "ecological civilization" has resulted in a decoupling trend for major pollutants since 2015, while strong coupling remains with CO₂ emissions. Progress has been made in health care provision, poverty reduction, and gender equity in education, while income disparity continues between regions and with rural-urban populations. There is a considerable way to go toward achieving delivery of the SDGs; however, China's progress toward economic prosperity and concomitant sustainability provides important insights for other countries.

Retinal vein occlusion: an approach to diagnosis, systemic risk factors and management

Retinal vein occlusion (RVO) is the second most common retinal vascular disease after diabetic retinopathy and is a common cause of visual morbidity and blindness in the elderly. A large proportion of patients with RVO have a history of cardiovascular disease, hypertension, diabetes mellitus or open-angle glaucoma. Although RVO is sometimes associated with thrombophilias and coagulation abnormalities, the role of coagulation factors in the development of RVO remains unclear. This review did not find strong evidence to support an extensive work-up for thrombophilic and coagulation diseases for the vast majority of patients. However, when tests for common cardiovascular risk factors for RVO are negative, evaluation for potential coagulation disorders may be indicated, particularly in young patients and in patients with bilateral RVO, a history of previous thromboses or a family history of thrombosis.

Early hemodynamic changes in experimental intracerebral hemorrhage

A model of experimental intracerebral hemorrhage is described in which carefully controlled volumes of autologous blood were injected at arterial pressure into the caudate nucleus of the rat. A comparison of intracranial pressure changes and local cerebral blood flow (CBF) was made between three groups of rats, each receiving different injection volumes, and sham-operated control rats by monitoring intraventricular pressure and by obtaining quantitative autoradiographic measurements of CBF within 1 minute of the experimental hemorrhage. Cerebral blood flow was reduced both around the hematoma and in the surrounding brain. This change was strongly volume-dependent and was not accompanied by significant alterations in cerebral perfusion pressure. This finding suggests that the degree of ischemia at the time of an intracerebral bleed depends on the size of the lesion, and implicates local squeezing of the microcirculation by the hematoma, rather than a generalized alteration in perfusion pressure, as the cause of ischemia.

Stereoselective effects of etomidate optical isomers on gamma-aminobutyric acid type A receptors and animals

BACKGROUND

The intravenous anesthetic etomidate is optically active and exists in two mirror-image enantiomeric forms. However, although the R(+) isomer is used as a clinical anesthetic, quantitative information on the relative potencies of the R(+) and S(-) isomers is lacking. These data could be used to test the relevance of putative molecular targets.

METHODS

The anesthetic concentrations for a half-maximal effect (EC50) needed to induce a loss of righting reflex in tadpoles (Rana temporaria) were determined for both etomidate enantiomers. The effects of the isomers on gamma-aminobutyric acid (GABA)-induced currents in stably transfected mouse fibroblast cells was also investigated using the patch-clamp technique. In addition, the effects of the isomers on a lipid chain-melting phase transition were determined.

RESULTS

The EC50 concentrations for general anesthesia for the R(+) and S(-) isomers were 3.4 +/- 0.1 microM and 57 +/- 1 microM, with slopes of n = 1.9 +/- 0.1 and n = 2.9 +/- 0.2, respectively. The R(+) isomer was also much more effective than the S(-) isomer at potentiating GABA-induced currents, although the degree of stereoselectivity varied with anesthetic concentration. R(+) etomidate potentiated the GABA-induced currents by increasing the apparent affinity of GABA for its receptor. Both isomers were equally effective at disrupting lipid bilayers.

CONCLUSIONS

These data are consistent with the idea that the GABA(A) receptor plays a central role in the actions of etomidate. Etomidate exerts its effects on the receptor by binding directly to a specific site or sites on the protein and allosterically enhancing the apparent affinity of GABA for its receptor.

Changes in calciotrophic hormones and biochemical markers of bone turnover in normal human pregnancy

Plasma concentrations of parathyroid hormone-related protein (PTHrP), parathyroid hormone, alkaline phosphatase, osteocalcin and albumin-adjusted calcium were measured along with nephrogenous cyclic adenosine monophosphate (NcAMP) in 10 normal women longitudinally through pregnancy. In addition, an assessment of bone resorption was made in these same subjects by the measurement in true fasting urine specimens of the calcium/creatinine ratio (Ca/Cr), hydroxyproline/creatinine ratio (HP/Cr), pyridinoline/creatinine ratio (Pyr/Cr) and deoxypyridinoline/creatine ratio (Dpyr/Cr). The PTHrP level rose through pregnancy from (mean +/- SEM) 0.8 +/- 0.2 pmol/l in the first trimester to 2.7 +/- 0.2 pmol/l 6 weeks postpartum (p < 0.0001). Serum alkaline phosphatase rose from 94 +/- 8 U/l (first trimester) to 347 +/- 25 U/l at term (p < 0.0001). A significant positive correlation was evident between PTHrP and alkaline phosphatase up to term (r = 0.44, p < 0.005). Parathyroid hormone concentrations remained unchanged during pregnancy but rose significantly postpartum from 1.8 +/- 0.2 pmol/l (first trimester) to 3.1 +/- 0.5 pmol/l (p < 0.0001). Similarly, osteocalcin, a marker of bone formative activity, remained unchanged through pregnancy but rose significantly at 6 weeks after delivery to 0.38 +/- 0.05 nmol/l from 0.19 +/- 0.03 nmol/l (first trimester) (p = 0.019). No significant change was noted in serum-adjusted calcium or NcAMP, either through pregnancy or at the postpartum assessment. Fasting urinary Ca/Cr fell through pregnancy from 0.70 +/- 0.11 (first trimester) to a nadir of 0.19 +/- 0.04 6 weeks postpartum (p = 0.007).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of fermented and unfermented milks on serum cholesterol

Groups of 10 to 13 healthy volunteers were provided with 11 supplements of 2% butterfat milk (2% milk), whole milk, skim milk, yogurt, buttermilk, and sweet acidophilus milk daily for a 3-wk period. Despite increases in caloric intakes on all supplements, no significant increases were found in total, low-density, and high-density lipoprotein cholesterol. A significant weight gain was seen in subjects taking yogurt and acidophilus groups; these were the only two groups showing significant rises in triglyceride levels. These results in normal volunteers focus attention on the current practice of recommending only skim or 2% milk for hyperlipidemic individuals.

Transforming growth factor beta 1 is an inducer of erythroid differentiation

Normal human bone marrow cells, highly enriched for burst-forming units-erythroid (BFU-E), were cultured in serum-free medium, in the presence and absence of various factors, to investigate the mechanisms involved in regulating erythroid differentiation. In cultures containing interleukin 3 (IL-3), Steel factor (SF), and erythropoietin (Ep), benzidine-positive erythroblasts first became detectable on day 6. Their numbers then rapidly increased until, by day 16, > 99% of the cells, which were 20,000-fold amplified over input numbers, were benzidine-positive. It is interesting to note that omission of either SF or Ep from this assay markedly enhanced the rate of differentiation and reduced total cell numbers, whereas omission of IL-3 had no effect on the rate of differentiation and only slightly reduced cell numbers. Of various agents tested, the most potent erythroid differentiation inducer (and inhibitor of cell proliferation) was found to be transforming growth factor beta 1 (TGF-beta 1). This cytokine stimulated both the rapid appearance of hemoglobin-positive cells and an early cessation of cell proliferation. Using fluorescently tagged antibodies to glycophorin A and fluorescence-activated cell sorter (FACS) analysis, this phenomenon was shown to be due to an early induction of erythroid differentiation rather than an aberrant production of hemoglobin. Methylcellulose assays indicated that the well-documented reduction of BFU-E colony numbers observed with TGF-beta 1 may actually be due to a TGF-beta 1-induced "conversion" of BFU-E into colony-forming units-erythroid (CFU-E). Thus, in vivo, TGF-beta 1 might serve, in part, to decrease the number of mature erythrocytes by stimulating BFU-E to skip a number of cell divisions and differentiate early.

Actions of general anaesthetics on 5-HT3 receptors in N1E-115 neuroblastoma cells

1. NIE-115 mouse neuroblastoma cells were studied under voltage clamp in the whole-cell patch-clamp configuration. Peak currents induced by bath application of 5-hydroxytryptamine (5-HT) were inwardly rectifying, reversed at 0.4 +/- 0.2 mV (mean +/- s.e.mean), and were approximately half-inhibited (at 1 microM 5-HT) by 2 nM of the 5-HT3 selective antagonist MDL-72222 (3-tropanyl-3,5-dichlorobenzoate). 2. Peak inward currents activated by a low concentration of 5-HT at a holding potential of -50 mV were potentiated by volatile general anaesthetics. At their human minimum alveolar concentrations (MACs), the degree of potentiation increased in the order isoflurane < halothane < enflurane < methoxyflurane. Potentiation by methoxyflurane was independent of membrane potential in the range -70 mV to +40 mV. The reversal potential was the same in the presence and absence of methoxyflurane. 3. Methoxyflurane shifted the 5-HT dose-response curve to lower 5-HT concentrations, without significantly changing the Hill coefficient or maximum response. The EC50 concentration for 5-HT decreased from 1.86 +/- 0.02 microM to 1.07 +/- 0.11 microM (means +/- s.e.mean) due to the presence of 1 MAC (270 microM) methoxyflurane. 4. In contrast to the volatile anaesthetics, the barbiturate anaesthetic, thiopentone, inhibited the 5-HT3 receptor. Hill analysis of thiopentone dose-response data gave an average IC50 = 117 +/- 8 microM thiopentone and Hill coefficient = 1.6 +/- 0.2 (means +/- s.e.mean). These parameters were not significantly different for data obtained at 5-HT concentrations above and below the control EC50 concentration for 5-HT, consistent with non-competitive inhibition. 5. The n-alcohols occupied an intermediate position between the volatile and barbiturate anaesthetics. The lower alcohols (butanol and hexanol) potentiated 5-HT responses at low alcohol concentrations but inhibited them at high concentrations. In contrast, the higher alcohols (octanol, decanol, dodecanol, tridecanol, tetradecanol and pentadecanol) produced no potentiation, but only inhibition, at all alcohol concentrations. 6. Inhibition of the 5-HT3 receptor by the n-alcohols exhibited a cutoff in potency similar to those previously found for tadpoles, luciferase enzymes and a neuronal nicotinic acetylcholine receptor channel.

GW190521: A Binary Black Hole Merger with a Total Mass of 150 M_{⊙}

On May 21, 2019 at 03:02:29 UTC Advanced LIGO and Advanced Virgo observed a short duration gravitational-wave signal, GW190521, with a three-detector network signal-to-noise ratio of 14.7, and an estimated false-alarm rate of 1 in 4900 yr using a search sensitive to generic transients. If GW190521 is from a quasicircular binary inspiral, then the detected signal is consistent with the merger of two black holes with masses of 85_{-14}^{+21}  M_{⊙} and 66_{-18}^{+17}  M_{⊙} (90% credible intervals). We infer that the primary black hole mass lies within the gap produced by (pulsational) pair-instability supernova processes, with only a 0.32% probability of being below 65  M_{⊙}. We calculate the mass of the remnant to be 142_{-16}^{+28}  M_{⊙}, which can be considered an intermediate mass black hole (IMBH). The luminosity distance of the source is 5.3_{-2.6}^{+2.4}  Gpc, corresponding to a redshift of 0.82_{-0.34}^{+0.28}. The inferred rate of mergers similar to GW190521 is 0.13_{-0.11}^{+0.30}  Gpc^{-3} yr^{-1}.

Comparison of two high dose corticosteroid aerosol treatments, beclomethasone dipropionate (1500 micrograms/day) and budesonide (1600 micrograms/day), for chronic asthma

Twenty eight patients with chronic asthma took part in a double blind single crossover controlled trial of inhaled budesonide and inhaled beclomethasone dipropionate, using high doses of 1600 micrograms and 1500 micrograms daily respectively. Both drugs were administered by pressurised aerosol inhaler; the inhaler containing budesonide and its matching placebo were fitted with a collapsible spacer device. There was no significant difference in the control of asthma during the two six week treatment periods. There was no significant difference in FEV1 and forced vital capacity after four and six weeks of treatment or in mean morning and evening peak expiratory flow rates for the last 21 days of treatment. There was a small but statistically significant reduction in the daytime wheeze score while they were taking high dose budesonide but there was no difference for daytime activity, cough, and night symptoms. The mean basal cortisol concentrations were significantly lower after six weeks of high dose treatment than before treatment (budesonide p less than 0.01, beclomethasone p less than 0.05). There was no difference between mean basal cortisol values after six weeks of high dose treatment, and there was no effect on the rise of cortisol obtained after a short tetracosactrin test. High dose inhaled corticosteroids produced few side effects and were well tolerated.

Agonist gating and isoflurane potentiation in the human gamma-aminobutyric acid type A receptor determined by the volume of a second transmembrane domain residue

Gamma-aminobutyric acid type A (GABA(A) )receptors are targets for allosteric modulation by general anesthetics. Mutation of Ser270 within the second transmembrane domain of the GABA(A) receptor alpha subunit can ablate the modulation of the receptor by the anesthetic ether isoflurane. To investigate further the function of this critical amino acid residue, we made multiple amino acid substitutions at Ser270 and analyzed the concentration-dependent gating by GABA and regulation by isoflurane in each mutant receptor. There is a strong negative correlation between the EC(50) for GABA and the molecular volume of the amino acid residue at position 270. Replacement of Ser by large residues such as His and Trp produced a shift of the GABA concentration-response curve to the left, whereas replacement of Ser with Gly had the opposite effect. There also was a strong negative association between the molecular volume of the amino acid residue at 270 and the degree of enhancement of submaximal GABA responses by isoflurane. These results indicate the significance of the amino acid at position alpha270 in gating of the GABA(A) receptor. In addition, the data on isoflurane are consistent with the existence of a cavity of finite size in the region of alpha270 that may be filled by the anesthetic molecule or by the side chain of a larger residue at alpha270. The introduction of isoflurane, or of a large residue, into this cavity may stabilize the open state of the GABA(A) receptor relative to the closed state.

Addressing China's grand challenge of achieving food security while ensuring environmental sustainability

China's increasingly urbanized and wealthy population is driving a growing and changing demand for food, which might not be met without significant increase in agricultural productivity and sustainable use of natural resources. Given the past relationship between lack of access to affordable food and political instability, food security has to be given a high priority on national political agendas in the context of globalization. The drive for increased food production has had a significant impact on the environment, and the deterioration in ecosystem quality due to historic and current levels of pollution will potentially compromise the food production system in China. We discuss the grand challenges of not only producing more food but also producing it sustainably and without environmental degradation. In addressing these challenges, food production should be considered as part of an environmental system (soil, air, water, and biodiversity) and not independent from it. It is imperative that new ways of meeting the demand for food are developed while safeguarding the natural resources upon which food production is based. We present a holistic approach to both science and policy to ensure future food security while embracing the ambition of achieving environmental sustainability in China. It is a unique opportunity for China to be a role model as a new global player, especially for other emerging economies.

Volatile anesthetic actions on the GABAA receptors: contrasting effects of alpha 1(S270) and beta 2(N265) point mutations

Previous studies have suggested that two specific amino acid residues in transmembrane segments 2 and 3 of the GABA(A) receptor alpha 2 subunit, Ser270 and Ala291, are critical for the enhancement of GABA(A) receptor function by inhaled anesthetics. The aim of this study was to determine the effects of amino acid substitutions in alpha 1 beta 2 gamma 2s GABA(A) receptors at alpha 1(S270) and at the homologous beta 2(N265) on receptor gating and anesthetic potentiation of GABA-induced responses. The wild-type and mutant receptors were transiently expressed in HEK 293 cells and GABA-induced currents were recorded using whole-cell voltage clamp. Potentiation of responses to a submaximal concentration of GABA by the anesthetics halothane and isoflurane was also examined. Some of the point mutations caused shifts in the GABA dose-response curve, indicating that the mutations changed the apparent affinity of the receptor for GABA. In receptors mutated at alpha 1(S270), the GABA EC(50) is inversely correlated with the volume of the residue of 270. On the contrary, there was no clear relationship between the physical properties of the amino acid residue at 265 in the beta 2 subunit and either the GABA EC(50) or anesthetic modulation, although mutations at N265 altered both parameters in a quantitative manner. These data are consistent with the results of previous work using other subunit combinations, in confirming that alpha 1(S270) may be involved in channel gating, and also may be important in anesthetic binding; the role of beta 2(N265) is less clear.