Biomedical subjects

H Xu

Publications and source records attributed to H Xu.

At least 19 recordsLinked to original sources

PubMed2006

Biomechanics of the porcine basilar artery in hypertension.

Hypertension is a significant risk factor for diverse cerebrovascular diseases ranging from stroke to arteriovenous malformations and saccular aneurysms. Our increasing understanding of vascular mechanobiology reveals that changes in mechanical stimuli, such as increased blood pressure, alter basic cellular functions including the production and degradation of extracellular matrix as well as proliferation, migration, and apoptosis. Understanding changes in the biomechanical properties of the vascular wall is fundamental to correlating mechanobiological responses with the altered loads. In this paper, we present the first biomechanical data on a large cerebral artery in terms of the time of development of hypertension in maturity. Specifically, we report rapid changes in both the structural and the material stiffness of the passive basilar artery in a novel aortic-coarctation model of hypertension in the mini-pig. Histological measurements reveal associated increases in fibrillar collagens in the media and adventitia as well as increased smooth muscle in the media. That such dramatic changes occur within 2 weeks of the initiation of hypertension in maturity necessitates a detailed study of the early changes as well as the potential to reverse these changes at later times.

Animals↗

PubMed2006

Mixed-effects logistic approach for association following linkage scan for complex disorders.

An association study to identify possible causal single nucleotide polymorphisms following linkage scanning is a popular approach for the genetic dissection of complex disorders. However, in association studies cases and controls are assumed to be independent, i.e., genetically unrelated. Choosing a single affected individual per family is statistically inefficient and leads to a loss of power. On the other hand, because of the relatedness of family members, using affected family members and unrelated normal controls directly leads to false-positive results in association studies. In this paper we propose a new approach using mixed-model logistic regression, in which associations are performed using family members and unrelated controls. Thus, the important genetic information can be obtained from family members while retaining high statistical power. To examine the properties of this new approach we developed an efficient algorithm, to simulate environmental risk factors and the genotypes at both the disease locus and a marker locus with and without linkage disequilibrium (LD) in families. Extensive simulation studies showed that our approach can effectively control the type-I error probability. Our approach is better than family-based designs such as TDT, because it allows the use of unrelated cases and controls and uses all of the affected members for whom DNA samples are possibly already available. Our approach also allows the inclusion of covariates such as age and smoking status. Power analysis showed that our method has higher statistical power than recent likelihood ratio-based methods when environmental factors contribute to disease susceptibility, which is true for most complex human disorders. Our method can be further extended to accommodate more complex pedigree structures.

Algorithms↗

PubMed2006

The study of state-selected ion-molecule reactions using the vacuum ultraviolet pulsed field ionization-photoion technique.

This paper presents the methodology to generate beams of ions in single quantum states for bimolecular ion-molecule reaction dynamics studies using pulsed field ionization (PFI) of atoms or molecules in high-n Rydberg states produced by vacuum ultraviolet (VUV) synchrotron or laser photoexcitation. Employing the pseudocontinuum high-resolution VUV synchrotron radiation at the Advanced Light Source as the photoionization source, PFI photoions (PFI-PIs) in selected rovibrational states have been generated for ion-molecule reaction studies using a fast-ion gate to pass the PFI-PIs at a fixed delay with respect to the detection of the PFI photoelectrons (PFI-PEs). The fast ion gate provided by a novel interleaved comb wire gate lens is the key for achieving the optimal signal-to-noise ratio in state-selected ion-molecule collision studies using the VUV synchrotron based PFI-PE secondary ion coincidence (PFI-PESICO) method. The most recent development of the VUV laser PFI-PI scheme for state-selected ion-molecule collision studies is also described. Absolute integral cross sections for state-selected H2+ ions ranging from v+ = 0 to 17 in collisions with Ar, Ne, and He at controlled translational energies have been obtained by employing the VUV synchrotron based PFI-PESICO scheme. The comparison between PFI-PESICO cross sections for the H2+(HD+)+Ne and H2+(HD+)+He proton-transfer reactions and theoretical cross sections based on quasiclassical trajectory (QCT) calculations and three-dimensional quantum scattering calculations performed on the most recently available ab initio potential energy surfaces is highlighted. In both reaction systems, quantum scattering resonances enhance the integral cross sections significantly above QCT predictions at low translational and vibrational energies. At higher energies, the agreement between experiment and quasiclassical theory is very good. The profile and magnitude of the kinetic energy dependence of the absolute integral cross sections for the H2+(v+ = 0-2,N+ = 1)+He proton-transfer reaction unambiguously show that the inclusion of Coriolis coupling is important in quantum dynamics scattering calculations of ion-molecule collisions.

Journal Article↗

PubMed2006

Kinetics and dynamic properties of equilibrium polymers.

The statistical mechanics and scission-recombination mechanism of self-assembling linear micelles are investigated by Brownian dynamics using a newly proposed mesoscopic model representing the micelles as equilibrium polymer chains. A semidilute concentration regime, yet dynamically unentangled, is considered over a wide range of scission/recombination rates. We focus on the analysis of short and long time behaviors of the scission and recombination mechanisms. Our results show that at time scales larger than the life time of the average chain length, the kinetics is in agreement with the mean-field kinetic model proposed by Cates and Candau [J. Phys.: Condens. Matter 2, 6869 (1990)] provided the kinetic constants are estimated as effective ones. These values do take into account through a transmission coefficient that a fraction of scission/recombination events is correlated over a short time (diffusion controlled mechanism) and thus turn out to be ineffective reactive events by annihilation effects. By studying macroscopic relaxation phenomena such as the average micelle length evolution after a T jump, the monomer diffusion, and the zero shear stress relaxation function, we confirm that the effective kinetic constants found are indeed the relevant parameters when macroscopic relaxation is coupled to the kinetics of micelles.

Journal Article↗

PubMed2006

Functional properties of a new low-molecular-weight glutenin subunit gene from a bread wheat cultivar.

Some allelic forms of low-molecular-weight glutenin subunit (LMW-GS) can greatly influence the end-use of wheat flours, understanding the function of each allele of LMW-GS is important to wheat quality breeding. A LMW-GS gene XYGluD3-LMWGS 1(AY263369) has been cloned from bread wheat cultivar Xiaoyan 6. The deduced protein contained nine cystine residues, one more than that in all other LMW-GSs reported previously, indicating that it is either a new gene or a new allele of a known LMW-GS gene. In this study, the gene was expressed in E. coil in large scale for the testing of its functional property. Reactive Red 120-Agarose resin was used efficiently to purify the expressed LMW-GS proteins from bacteria, with the lactic acid-sodium lactate buffer (pH 4.5) which contained low concentration SDS as elution solution. The purified protein (belonging to the LMW-m family, MW about 35 KDa) was supplemented into a base flour, the results of 10 g dough mixing test indicated that incorporation of the LMW-GS increased the strength of the dough, with significant increases in mixing time (MT) and peak width (PW), and decrease in breakdown in resistance (RBD) compared with the control. In addition, the dough with incorporation of the LMW-GS had more glutenin macropolyeric protein than the control, suggesting that the LMW-GS participated in forming larger glutenin polymers, and greatly contributed to dough strength. The changes in mixing parameters and the amount of glutenin macropolyeric protein were related to the quantity of incorporating subunits.

Chromatography↗

PubMed2006

Laparoscopic blockage of uterine artery and myomectomy: a new method of treating symptomatic uterine leiomyomas.

BACKGROUND: The goal of this study was to evaluate the effects of laparoscopic coagulation or blockage of the uterine arteries and myomectomy in treating symptomatic myomas. METHODS: A total of 142 women with symptomatic fibroids warranting surgical treatment and wanting to retain their uteri were treated by laparoscopic coagulation or blocking of the uterine arteries and myomectomy. RESULTS: Most of the 142 patients had multi-myomas of the uterus, as intramural myomas (54), subserous myomas (65), and submucosal myomas (25). The number of myomas in each patient varied from 1 to 4. The size of the myomas in all patients ranged from 2 to 12 cm. In 86 cases (60.4%) the uterine wall was sutured in one layer. Average operating time was 124.2 +/- 33.1 min, and average blood loss was 117.8 +/- 48.6 ml. Mean postoperative hospital stay was 4.8 +/- 1.2 days. All patients underwent technically successful laparoscopic coagulation or blocking of uterine arteries and myomectomy without intraoperative complications. The mean follow-up time was 16.2 months (16-26). Symptomatic improvement was achieved in all patients. Five patients experienced recurrence of myomas. CONCLUSIONS: Laparoscopic coagulation or block of the uterine arteries and myomectomy appears to be a safe, effective, and promising new method for treating symptomatic uterine myomas.

Adult↗

PubMed2006

A coagulation factor VII deficiency protects against acute inflammatory responses in mice.

Upregulation of the activated Factor VII (FVIIa)/Tissue Factor complex, downregulation of natural anticoagulation pathways, and inhibition of fibrinolysis, are major contributors to coagulopathies associated with acute inflammation. Provision of FVIIa, and consequent downstream coagulation-related proteases, also stimulates further inflammatory changes, which can result in disseminated intravascular coagulation. Thus, the potential protective effects in vivo of a genetic-based reduction in FVII levels have been investigated in a murine model of acute inflammation, namely lipopolysaccharide (LPS)-induced lethal endotoxaemia. Mice with a total FVII deficiency do not survive the neonatal period. Therefore mice expressing low levels of FVII (FVII(tTA/tTA)), producing sufficient amounts of FVII for survival (approximately 5% of wild-type (WT) FVII), were employed to investigate in vivo pathways involved in the crosstalk between coagulation, inflammation, and survival, consequent to administration of a lethal dose of LPS. The FVII(tTA/tTA) mice presented with reduced mortality, coagulation, and inflammatory responses in comparison with similarly treated WT mice after administration of LPS. The attenuated inflammatory responses in FVII(tTA/tTA) mice were associated with downregulation of Egr-1 signalling. Administration, in vivo, of specific inhibitors of FXa and thrombin demonstrated that the inflammatory responses were unaltered in WT mice, but further reduced in FVII(tTA/tTA) mice. Therefore, a FVII deficiency enhances survival from lethal endotoxaemia both through attenuation of inflammatory responses that result directly from reduced FVIIa levels, and, indirectly, from downregulation of coagulation proteases downstream of the FVII-dependent cascade.

Ancrod↗

PubMed2006

Prolongation of rat intestinal allograft survival by administration of donor interleukin-12 p35-silenced bone marrow-derived dendritic cells.

Severe graft rejection remains an important obstacle in intestinal transplantation. In this study, we demonstrated that intravenous injection of interleukin (IL)-12 p35 siRNA-transfected dendritic cells (DCs) into recipient rats prolonged the survival of intestinal allografts. Serum IL-2 and interferon-gamma levels in the IL-12 p35 siRNA-transfected DCs treatment group were both significantly lower than in control groups at 7 days after transplantation. Further study is required to investigate the operative pathways and to optimize the strategy targeting dendritic cells to induce tolerance to intestinal allografts.

Animals↗

PubMed2006

Assessment of glomerular filtration rate in renal transplant patients using serum cystatin C.

AIM: Serum cystatin C (SCysC) has been proposed as a better marker of glomerular filtration rate (GFR) than serum creatinine (Scr). However, few data are available in renal transplant patients, especially, during the early postoperative phase. METHODS: Thirty-nine renal transplant patients (22 men/17 women) were recruited for determination of SCysC and Scr before operation, at 1 week and at 4 weeks after operation. SCysC was determined by particle-enhanced turbidimetric immunoassay. Creatinine clearance (Ccr) was calculated using the Cockcroft-Gault formula. RESULTS: SCysC and Scr levels significantly decreased with the recovery of allograft function. SCysC showed a significant correlation with Scr and Ccr. The relationship between SCysC and Scr showed a positive correlation (r = .849 preoperation, and r = .940 postoperation). The relationship between SCysC and Ccr revealed a negative correlation (r = .857 preoperation, and r = .876 postoperation). At the Ccr level of 50 to 80 mL/min/1.73 m(2), the correlation between SCysC and Ccr (r = .778) was significantly better than that between Scr and Ccr (r = .553; P = .032). The concentration of SCysC was not affected by age, gender, height, body weight, hemoglobin, serum protein, glucose, or mycophenolate mofetil or azathioprine dosage. However, corticosteroids slightly increased the level of SCysC and cyclosporine (CsA) decreased it. The area under the curve of the receiver operating characteristic curve for SCysC and Scr are 0.964 and 0.915, respectively (P < .05). CONCLUSION: Although the concentration may be slightly influenced by prednisolone and CsA, SCysC is more sensitive than Scr to detect early and moderate deterioration of GFR in adult renal transplant recipients.

Biomarkers↗

PubMed2006

Cross-species function of the pig C1 esterase inhibitor.

BACKGROUND: The use of a bioartificial liver with pig cells for the treatment of fulminant hepatic failure will require research on the plasma complement regulatory proteins of the pig, because the liver produces most of the complement components and plasma complement regulatory proteins. In our previous study, the pig C1 esterase inhibitor (C1-INH), which functions as an inhibitor of the complement reaction in the first step of the classical pathway in the fluid phase, was cloned and some relevant features of the molecule were characterized, especially its cross-species regulation, in comparison with human C1-INH. In a further analysis, the species specificity of C1-INH was examined, using pig endothelial cells (PEC) and several types of sera. MATERIALS AND METHODS: The cDNA of pig C1-INH was used to produce the membrane type pC1-INH, pC1-INH-PI, and inserted into the cloning site of pCXN2 (chicken beta actin promoter). The pCX/pCl-INH-PI plasmid was then transfected into PEC to establish stable PEC with pCl-INH-PI. The expression of the pCl-INH-PI was evaluated by a FACS analysis, and complement-dependent cell lysis with human, dog, rabbit, and mouse sera was then assessed. RESULTS: The transfectant with pig Cl-INH-PI showed a high level of expression on PEC. The PEC transfectants showed an inhibitory effect on complement-dependent PEC lysis. Pig Cl-INH did not show the same suppressive effect for each serum. However, considering the alternative pathway activation of each serum on the pig cell membrane, it can be concluded that pCl-INH has a relatively small species restriction. CONCLUSION: Pig Cl-INH, having a similar structure to human Cl-INH, shows a strong complement regulatory function on other species sera.

Actins↗

PubMed2006

Relationship of total body fatness and five anthropometric indices in Chinese aged 20-40 years: different effects of age and gender.

OBJECTIVES: We aim to evaluate the ethnic-specific relationship of total fat mass and anthropometric indices in Chinese. DESIGN: Cross-section study. SETTING: This study was performed at the College of Life Sciences, Hunan Normal University, P.R. China. SUBJECTS AND METHOD: To increase our understanding of the relationship of total fat mass and anthropometric indices in Chinese, 793 females and 1091 males aged 20-40 years were randomly recruited from Changsha city of P. R. China. Hip circumference (HC) and waist circumference (WC) were measured using standardized equipments, and other three anthropometric indices of body mass index (BMI), waist-to-hip ratio (WHR), and conicity index (CI) were calculated using weight, height, HC and WC. Total body fatness (TBF) in kg was measured using a Hologic QDR 4500 W dual-energy X-ray absorptiometry (DEXA) scanner. RESULTS: There was an increasing trend of TBF, %TBF (percent total body fatness) and the five anthropometric indices in successively older age groups. Compared with females, males generally had high average BMI, WC, HC, WHR and CI, but had low average TBF and %TBF. Except for some correlations in 25-29 years age groups, TBF and %TBF were significantly correlated with five anthropometric indices with the Pearson's correlation coefficients ranging from 0.07 to 0.87. Principal component analysis (PCA) was performed to form four principal components (PCs) that interpreted over 99% of the total variation of the five related anthropometric indices in all age groups, with over 53% of the total variation accounted for by the PC1. Multiple regression analyses showed that four PCs combined explained a greater variance (R (2)=55.2-80.8%) in TBF than did BMI alone (R (2)=40-74.9%). CONCLUSION: Our results suggest that there is an increasing trend of total fat mass and five anthropometric indices with aging; that age and sex have the important effects on influencing the correlations of TBF and the studied anthropometric indices; and that the accuracy of predicting the TBF using five anthropometric indices is higher than using BMI alone.

Absorptiometry, Photon↗

PubMed2006

Endoscopic ultrasound-guided interstitial brachytherapy of unresectable pancreatic cancer: results of a pilot trial.

BACKGROUND AND STUDY AIMS: Intraoperative interstitial brachytherapy has been found to be effective when used during laparotomy to improve local control in patients with locally advanced pancreatic cancer. In this study, we report the results of using endoscopic ultrasound- (EUS-)guided interstitial brachytherapy in patients with advanced pancreatic cancer, with respect to tumor response, clinical response, safety, and complications. PATIENTS AND METHODS: Fifteen patients (eight men, seven women; median age 61 years) with unresectable pancreatic adenocarcinoma were enrolled into the study, eight patients with stage III disease and seven patients with stage IV disease. A mean number of 22 radioactive seeds per patient were implanted into the tumors by EUS-guided needle puncture. The mean total implanted activity was 20 mCi, the minimum peripheral dose was 14,000 cGy, and the mean volume of implants was 52 cm3. Patients were followed-up by examination and by imaging tests every 2-3 months: clinical end points included the Karnofsky performance status and pain responses, tumor response (assessed by computed tomography and/or EUS), and survival. RESULTS: During a median follow-up period of 10.6 months, the objective tumor response was classified as "partial" in 27% of patients (with a median duration of partial response of 4.5 months), "minimal" in 20% patients, and indicative of "stable disease" in 33% of patients. Clinical benefit was shown in 30% of patients, mostly due to reduction in pain, but this lasted for a limited time. Local complications (pancreatitis and pseudocyst formation) occurred in three patients; grade III hematologic toxicity occurred in three patients without serious clinical sequelae. CONCLUSIONS: EUS-guided intraoperative interstitial brachytherapy had a moderate local tumor effect and showed some clinical benefit in 30% of the patients in this study. Combination of this form of treatment with external radiation and/or chemotherapy should be tested in future trials.

Adenocarcinoma↗

PubMed2006

Metabolism and excretion of imrecoxib in rat.

The metabolism and excretion of imrecoxib, a novel and moderately selective cyclooxygenase-II inhibitor, were investigated in rat. The structures of metabolites were identified by mass spectrometry (MSn) and nuclear magnetic resonance. Metabolic profiles of imrecoxib in urine, bile and faeces were obtained by HPLC and LC/MSn, and cumulative excretion was determined by LC/MSn. Imrecoxib was extensively metabolized in rat after intravenous administration, with less than 2% of the dose excreted as parent drug in either urine or faeces. The major metabolic pathway was that the 4'-methyl group of imrecoxib was first oxidized to the 4'-hydroxymethyl metabolite (M4), followed by additional oxidation to 4'-carboxylic acid metabolite (M2). The dihydroxylated metabolite, 4'-hydroxymethyl-5-hydroxyl imrecoxib (M3), was further oxidized to 4'-hydroxymethyl-5-carbonyl metabolite (M5), and glucuronide conjugates of M2-4 were formed. After intravenous (5 mg kg-1) administration, the majority of the dose was recovered in the faeces. The dose was primarily excreted as the carboxylic acid metabolite in addition to the 4'-hydroxymethyl metabolite. The carboxylic acid metabolite was mainly excreted in faeces, while the 4'-hydroxymethyl metabolite was mainly excreted in urine.

Animals↗

PubMed2006

Severe airflow obstruction and eosinophilic lung disease after Stevens-Johnson syndrome.

Respiratory involvement is a frequent complication of Stevens-Johnson syndrome (SJS). However, there are very few convincing reports of persistent pulmonary sequelae, as demonstrated by spirometry, radiology and pathology. The current study presents a case of a 13-yr-old female with T-cell acute lymphocytic leukaemia who developed persistent, severe, obstructive lung disease following an episode of SJS. A lung biopsy demonstrated bronchiolar submucosal fibrosis consistent with constrictive bronchiolitis, as well as eosinophilic micro-abscesses, which, to the current authors' knowledge, has not been previously described. The present study illustrates specific histopathological features that highlight a possible association between Stevens-Johnson syndrome, constrictive bronchiolitis and eosinophilic micro-abscesses. The eosinophils may be associated with permanent mucosal damage, as seen in the present case, by releasing mediators that have a pro-fibrogenetic role. However, further investigation is warranted.

Adolescent↗

PubMed2006

SLAM expression is not downregulated by measles virus infection.

It has been reported that the signaling lymphocyte-activation molecule (SLAM), the second receptor of Measles virus (MV) on the cell surface appears to be downregulated by MV infection or by expression of MV hemagglutinin (H) (Tanaka et al., 2002; Welsteadt et al., 2004). The aim of this study was to analyze this phenomenon in more detail using a Chinese vaccine strain (S191) of MV. Flow cytometry confirmed apparent downregulation of SLAM in the virus-infected cells and in the cells transfected with a plasmid expressing viral H. Moreover, a similar effect was obtained by incubation of the cells with UV-inactivated virus or soluble viral H. Real-time quantitative PCR showed that the SLAM mRNA level remained stable during the virus infection, and Western blot analysis demonstrated that the SLAM content of total membrane proteins did not change change after the virus infection. Thus we conclude that SLAM expression is stable during the MV infection and that its apparent downregulation reported earlier and confirmed also in this study was just the result of masking of the antibody recognition sites on SLAM with MV H during the flow cytometry assay.

Animals↗

PubMed2006

Apical NA+/H+ exchangers in the mammalian gastrointestinal tract.

The Slc9a family of nine Na(+)/H(+) exchangers (NHE) plays a critical role in neutral sodium absorption in the mammalian intestine as well as other absorptive and secretory epithelia of digestive organs. These transport proteins mediate the electroneutral exchange of Na(+) and H(+) and are crucial in a variety of physiological processes, including the fine tuning of intracellular pH, cell volume control and systemic electrolyte, acid-base and fluid volume homeostasis. Here, we review the role of the Na(+)/H(+) exchange mechanism as it relates to the physiology of organs and cells involved in nutrient absorption, and we describe physiological and molecular aspects of individual isoforms, including their structure, tissue-, and subcellular distribution, as well as their regulation by physiological stimuli at the transcriptional and post-transcriptional levels. A particular emphasis is placed on Na(+)/H(+) exchanger isoforms expressed on the apical (brush border) membrane of the epithelial cells, and the consequences of gene-targeted mutation of individual isoforms are discussed in the context of the physiology of digestive organs. Where available, we also provide a review of pathophysiological states related to aberrant expression and/or activity of Na(+)/H(+) exchangers within the confines of the digestive system.

Animals↗

PubMed2005

Direct acceleration of solid-density plasma bunch by ultraintense laser.

The interaction of a petawatt laser with a small solid-density plasma bunch is studied by particle-in-cell simulation. It is shown that when irradiated by a laser of intensity >10(21) W/cm2, a dense plasma bunch of micrometer size can be efficiently accelerated. The kinetic energy of the ions in the high-density region of the plasma bunch can exceed ten MeV at a density in the 10(23)-cm(-3) level. Having a flux density orders of magnitude higher than that of the traditional charged-particle pulses, the laser-accelerated plasma bunch can have a wide range of applications. In particular, such a dense energetic plasma bunch impinging on the compressed fuel in inertial fusion can significantly enhance the nuclear-reaction cross section and is thus a promising alternative for fast ignition.

Journal Article↗

PubMed2005

Effects of nitrogen deficiency on photosynthetic traits of maize hybrids released in different years.

BACKGROUND AND AIMS: New maize (Zea mays) hybrids outperformed old ones even at reduced N rates. Understanding the mechanisms of the differences in performance between newer and older hybrids under N deficiency could provide avenues for breeding maize cultivars with large yield under N deficiency, and reduce environmental pollution caused by N fertilizers. METHODS: N deficiency effects on grain weight, plant weight, harvest index, leaf area and photosynthetic traits were studied in the field for six maize hybrids released during the past 50 years to compare their tolerance and to explore their physiological mechanisms. KEY RESULTS: N deficiency decreased grain yield and plant weight in all hybrids, especially in the older hybrids. However, there was no significant difference in harvest index, rate of light-saturated photosynthesis (Psat) 20 d before flowering, leaf area or plant weight at flowering between the N-deficient and control plants of all hybrids. Dry matter production after flowering of the N-deficient plants was significantly lower than that of the control plants in all hybrids, especially in the older hybrids, and was mostly due to differences in the rate of decrease in photosynthetic capacity during this stage. The lower Psat of the older hybrids was not due to stomatal limitation, as there was no significant difference in stomatal conductance (gs) and intercellular CO2 concentration (Ci) between the hybrids. N deficiency accelerated senescence, i.e. decreased chlorophyll and soluble protein contents, after anthesis more for the earlier released hybrids than for the later ones. N deficiency decreased phosphoenolpyruvate carboxylase (PEPCase) activity significantly more in older hybrids than newer hybrids, and affected the maximal efficiency of PSII photochemistry (Fv/Fm) only in the old hybrids and at the late stage. CONCLUSIONS: Compared with older (earlier released) hybrids, newer (later released) hybrids maintained greater plant and grain weight under N deficiency because their photosynthetic capacity decreased more slowly after anthesis, associated with smaller non-stomatal limitations due to maintenance of PEPCase activity, and chlorophyll and soluble protein content.

Carbon Dioxide↗