Junjun Wang | Brunel University (original) (raw)

Papers by Junjun Wang

Amino Acids, 2009

This study was conducted using the piglet model to test the hypothesis that mucosal cells of the ... more This study was conducted using the piglet model to test the hypothesis that mucosal cells of the neonatal small intestine can degrade nutritionally essential amino acids (EAA). Enterocytes were isolated from the jejunum of 0-, 7-, 14-, and 21-day-old pigs, and incubated for 45 min in Krebs buffer containing plasma concentrations of amino acids and one of the following L-[1-14C]- or L-[U-14C]-amino acids plus unlabeled tracees at 0.5, 2, or 5 mM: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. In these cells, branched-chain amino acids (BCAA) were extensively transaminated and 15–50% of decarboxylated branched-chain α-ketoacids (BCKA) were oxidized to CO2 depending on the age of piglets. BCAA transamination increased but their decarboxylation decreased between 0 and 14 days of age. Addition of 1 and 2 mM α-ketoglutarate to incubation medium dose-dependently stimulated BCAA transamination without affecting their decarboxylation. Western blot analysis revealed that the abundance of mitochondrial BCAA aminotransferase declined but cytosolic BCAA aminotransferase increased between 0 and 14 days of age, with the cytosolic protein being the major isoform in 7- to 21-day-old pigs. BCKA dehydrogenase protein existed primarily as the phosphorylated (inactive) form in enterocytes of newborn pigs and its levels were markedly reduced in older pigs. All measured parameters of BCAA metabolism did not differ between 14- and 21-day-old pigs. In contrast to BCAA, catabolism of methionine and phenylalanine was negligible and that of other EAA was absent in enterocytes from all ages of piglets due to the lack of key enzymes. These results indicate that enterocytes are an important site for substantial degradation of BCAA but not other EAA in the neonatal gut.

Dietary supplementation of glutamine prevents intestinal dysfunction and atrophy in weanling pigl... more Dietary supplementation of glutamine prevents intestinal dysfunction and atrophy in weanling piglets, but the underlying mechanism(s) are largely unknown. This study was conducted to test the hypothesis that weaning or glutamine may modulate expression of genes that are crucial for intestinal metabolism and function. In Expt. 1, we obtained small intestine from 28-d-old pigs weaned at 21 d of age and from age-matched suckling piglets. In Expt. 2, piglets were weaned at 21 d of age and then had free access to diets supplemented with 1% L-glutamine (wt:wt) or isonitrogenous L-alanine (control). At d 28, we collected small intestine for biochemical and morphological measurements and microarray analysis of gene expression using the Operon Porcine Genome Oligo set. Early weaning resulted in increased (52-346%) expression of genes related to oxidative stress and immune activation but decreased (35-77%) expression of genes related to macronutrient metabolism and cell proliferation in the gut. Dietary glutamine supplementation increased intestinal expression (120-124%) of genes that are necessary for cell growth and removal of oxidants, while reducing (34-75%) expression of genes that promote oxidative stress and immune activation. Functionally, the glutamine treatment enhanced intestinal oxidative-defense capacity (indicated by a 29% increase in glutathione concentration), prevented jejunal atrophy, and promoted small intestine growth (112%) and body weight gain (119%) in weaned piglets. These findings reveal coordinate alterations of gene expression in response to weaning and aid in providing molecular mechanisms for the beneficial effect of dietary glutamine supplementation to improve nutrition status in young mammals.

International Journal of Hydrogen Energy, 2008

Quasi-dimensional model Laminar burning velocity Numerical simulation a b s t r a c t Spark ignit... more Quasi-dimensional model Laminar burning velocity Numerical simulation a b s t r a c t Spark ignition engines fuelled by hydrogen enriched compressed natural gas (HCNG) have many advantages compared to traditional gasoline, diesel and natural gas engines, especially in emission control. Experimental researches have been continuously conducted to improve HCNG engine's configuration and control strategy aimed at making full use of this new fuel. With the same target, this work presents a predictive model used to simulate the working cycle of HCNG engines which is applicable for variable hydrogen blending ratios. The fundamentals of the thermodynamic model, the turbulent flame propagation model and related equation were introduced. Considering that the most important factor influencing the applicability of the model for variable hydrogen blending ratio is the laminar flame speed, the methods of how to deal with the laminar burning velocity in the model were then described in some more detail. After the determination of model constants by calibration, simulation results were compared with experimental cylinder pressure data for various hydrogen blending ratios, spark timings and equivalence ratios. The results show that simulation and experimental results match quite well except for extremely fuel lean conditions where problems of incomplete combustion become severe.

Progress in Natural Science, 2008

A total of 407,663 expressed sequence tags (ESTs) of wheat, barley, maize, rice, and sorghum, obt... more A total of 407,663 expressed sequence tags (ESTs) of wheat, barley, maize, rice, and sorghum, obtained from GenBank/dbEST, were used to search for simple sequence repeats (SSRs). A total of 10,253 EST-SSRs, which accounted for 2.52% of all the ESTs, were identified. Using Primer Premier 5.0, 1367 EST-SSR primer pairs were designed, of which 715 with high quality were synthesized. The 715 primer pairs were tested on wheat, rice, maize, cotton, and soybean under the same PCR conditions, and the effective primer pairs in the five crops were 500 (, respectively. This indicated a high transferability of EST-SSR markers between far-ranging species. In addition, 139 EST-SSR primer pairs with 240 loci were localized on all the 21 wheat chromosomes by using Chinese Spring nulli-tetrasomic lines of wheat.

Energy & Fuels, 2008

In order to study the influence of the 0-50 vol % hydrogen addition on idle performance, an exper... more In order to study the influence of the 0-50 vol % hydrogen addition on idle performance, an experimental research was conducted on a six-cylinder throttle body injection natural gas engine. Experiments have been made under various excess air ratios and ignition timings. The results show that hydrogen addition remarkably decreased CH 4 emission whereas it had no significant effect on the reduction of CO. NOx emission was relatively low at idle compared to other emissions. Hydrogen addition combined with ignition timing retardation was an effective way to reduce idle emission. The COV in IMEP and partial-burn ratio could be simultaneously reduced by hydrogen addition, which indicated the improvement of idle stability. In turn, the improvement of idle stability decreased the fuel consumption. Also, the curve for COV in IMEP was smoother versus ignition timing after hydrogen addition, which is desirable at idle because small idle speed error was adjusted by ignition timing in many electric idle control units. It can be concluded hydrogen addition is an effective and applicable approach to improve idle stability and decrease emission.

International Journal of Hydrogen Energy, 2007

In order to analyze the effect of hydrogen addition on natural gas (NG) engine's thermal efficien... more In order to analyze the effect of hydrogen addition on natural gas (NG) engine's thermal efficiency and emission, an experimental research was conducted on a spark ignition NG engine using variable composition hydrogen/CNG mixtures (HCNG). The results showed that hydrogen enrichment could significantly extend the lean operation limit, improve the engine's lean burn ability, and decrease burn duration. However, nitrogen oxides (NO x ) were found to increase with hydrogen addition if spark timing was not optimized according to hydrogen's high burn speed. Also found when spark timing was set at constant was that hydrogen addition actually increases heat transfer out of the cylinder due to smaller quenching distance and higher combustion temperature, thus is not good to improve thermal efficiency if combined with the effect of non-ideal spark timing. But if spark timing was retarded to MBT, taking advantage of hydrogen's high burn speed, NO x emissions exhibited no obvious increase after hydrogen addition and engine thermal efficiency increased with the increase of hydrogen fraction. Unburned hydrocarbon always decreased with the increase of hydrogen fraction. ᭧

International Journal of Hydrogen Energy, 2008

Combustion and emission characteristics of a port-injection SI turbocharged engine fueled with se... more Combustion and emission characteristics of a port-injection SI turbocharged engine fueled with several H 2 =CNG blend ratios (0-50 vol%) under various ignition timings were investigated. The results show that with the increase of hydrogen addition, the maximum brake toque timing decreases and the indicated thermal efficiency increases; the MBT gets close to the top dead center and the indicated thermal efficiency increases with decreased load. The combustion duration is reduced by increasing the hydrogen fraction in HCNG (hydrogen enriched compressed natural gas) mixture. The NO x , CO and HC emissions all descend with the increase of spark advance angle, and ascend with the increase of the load.

Amino Acids, 2009

Amino acids (AA) are not only the building blocks of proteins but are also key regulators of meta... more Amino acids (AA) are not only the building blocks of proteins but are also key regulators of metabolic pathways in cells. However, the mechanisms responsible for the effects of AA are largely unknown. With the completion of human and other mammalian genome projects, revolutionary technologies in life sciences characterized by high throughput, high efficiency, and rapid computation are now available for AA nutrition research. These advanced tools include genetics (the genomic variety), epigenetics (stable and heritable changes in gene expression or cellular phenotype that occurs without changes in DNA sequence), transcriptomics (alternative mRNA splicing, microRNAs, and gene transcription), proteomics (protein expression and interactions), metabolomics (metabolite profiles in cells and tissues), and bioinformatics (analysis of metabolic pathways using systems biology approach). These robust, powerful methods can be employed for the analysis of DNA, RNA, protein, and low-molecular-weight metabolites, whose expression and concentration are affected by the interaction between genes and dietary AA. With the omics and other advanced methodologies, we expect that the molecular actions of AA on target tissues can be defined and that optimal dietary recommendations for these nutrients can be devised for individual humans (personalized nutrition) and animals (targeted feeding) in response to changes in physiological and pathological conditions.

International Journal of Hydrogen Energy, 2008

An experimental study aimed at examining the effects of hydrogen addition on cycle-bycycle variat... more An experimental study aimed at examining the effects of hydrogen addition on cycle-bycycle variation (CCV) in an SI engine was conducted on a 6-cylinder throttle body injection natural gas (NG) engine. Two types of fuels, CNG and 80/20 (in volume) CNG/hydrogen mixtures, were used for comparison purposes. The results showed that coefficient of variation (CoV) in both maximum pressure ðP max Þ and indicated mean effective pressure (IMEP) could be reduced by hydrogen addition and that positive effect would be more obvious as the engine was further leaned out. The duration of flame development and propagation as well as the CCVs in flame propagation duration could be simultaneously reduced by hydrogen addition, all of which are beneficial to improve combustion stability and thought to be reasons for the reduction in CoV imep . Stability of combustion phasing that is crucial to the effectiveness of ignition timing optimization was also improved by hydrogen. Hydrogen addition was also proved to be good to the control of emission of NO x and unburned HC. Hence it is concluded that hydrogen addition is an effective and applicable approach to keep down CCVs in lean burn spark-ignition engines.

BMC Genomics, 2009

Background: MicroRNAs (miRNAs) play critical roles in a wide spectrum of biological processes and... more Background: MicroRNAs (miRNAs) play critical roles in a wide spectrum of biological processes and have been shown to be important effectors in the intricate host-pathogen interaction networks. Avian influenza virus (AIV) not only causes significant economic losses in poultry production, but also is of great concern to human health. The objective of this study was to identify miRNAs associated with AIV infections in chickens.

Energy & Fuels, 2008

A zero-dimensional two-zone model was employed to investigate the influence of the combustion pro... more A zero-dimensional two-zone model was employed to investigate the influence of the combustion process of the spark-ignition (SI) engine on its thermal efficiency. Attention was mainly paid to the effects of combustion phasing, combustion duration, and their cyclic variations. These combustion parameters were varied by changing spark timing and the hydrogen/natural gas blending ratio (hydrogen and natural gas mixtures were used as the fuel). The results show that there always exists an optimized combustion phasing for best engine thermal efficiency. Combustion phasing that deviates from this optimized value would decrease thermal efficiency. The fact that heat transfer loss increases with the advance of combustion phasing was thought to be the reason why best efficiency thermal efficiency does not occur under the condition when the combustion rate peaks at TDC. It is also found unexpectedly that although reduction in combustion duration can increase the degree of constant volume combustion, it does not have obviously positive effects on the final thermal efficiency. Finally, with regard to the cyclic variations, it is concluded that cyclic variations in the combustion process exert a heavy effect on thermal efficiency. The higher the variations, the larger the negative effect.

Amino Acids, 2009

This study was conducted using the piglet model to test the hypothesis that mucosal cells of the ... more This study was conducted using the piglet model to test the hypothesis that mucosal cells of the neonatal small intestine can degrade nutritionally essential amino acids (EAA). Enterocytes were isolated from the jejunum of 0-, 7-, 14-, and 21-day-old pigs, and incubated for 45 min in Krebs buffer containing plasma concentrations of amino acids and one of the following L-[1-14C]- or L-[U-14C]-amino acids plus unlabeled tracees at 0.5, 2, or 5 mM: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. In these cells, branched-chain amino acids (BCAA) were extensively transaminated and 15–50% of decarboxylated branched-chain α-ketoacids (BCKA) were oxidized to CO2 depending on the age of piglets. BCAA transamination increased but their decarboxylation decreased between 0 and 14 days of age. Addition of 1 and 2 mM α-ketoglutarate to incubation medium dose-dependently stimulated BCAA transamination without affecting their decarboxylation. Western blot analysis revealed that the abundance of mitochondrial BCAA aminotransferase declined but cytosolic BCAA aminotransferase increased between 0 and 14 days of age, with the cytosolic protein being the major isoform in 7- to 21-day-old pigs. BCKA dehydrogenase protein existed primarily as the phosphorylated (inactive) form in enterocytes of newborn pigs and its levels were markedly reduced in older pigs. All measured parameters of BCAA metabolism did not differ between 14- and 21-day-old pigs. In contrast to BCAA, catabolism of methionine and phenylalanine was negligible and that of other EAA was absent in enterocytes from all ages of piglets due to the lack of key enzymes. These results indicate that enterocytes are an important site for substantial degradation of BCAA but not other EAA in the neonatal gut.

Dietary supplementation of glutamine prevents intestinal dysfunction and atrophy in weanling pigl... more Dietary supplementation of glutamine prevents intestinal dysfunction and atrophy in weanling piglets, but the underlying mechanism(s) are largely unknown. This study was conducted to test the hypothesis that weaning or glutamine may modulate expression of genes that are crucial for intestinal metabolism and function. In Expt. 1, we obtained small intestine from 28-d-old pigs weaned at 21 d of age and from age-matched suckling piglets. In Expt. 2, piglets were weaned at 21 d of age and then had free access to diets supplemented with 1% L-glutamine (wt:wt) or isonitrogenous L-alanine (control). At d 28, we collected small intestine for biochemical and morphological measurements and microarray analysis of gene expression using the Operon Porcine Genome Oligo set. Early weaning resulted in increased (52-346%) expression of genes related to oxidative stress and immune activation but decreased (35-77%) expression of genes related to macronutrient metabolism and cell proliferation in the gut. Dietary glutamine supplementation increased intestinal expression (120-124%) of genes that are necessary for cell growth and removal of oxidants, while reducing (34-75%) expression of genes that promote oxidative stress and immune activation. Functionally, the glutamine treatment enhanced intestinal oxidative-defense capacity (indicated by a 29% increase in glutathione concentration), prevented jejunal atrophy, and promoted small intestine growth (112%) and body weight gain (119%) in weaned piglets. These findings reveal coordinate alterations of gene expression in response to weaning and aid in providing molecular mechanisms for the beneficial effect of dietary glutamine supplementation to improve nutrition status in young mammals.

International Journal of Hydrogen Energy, 2008

Quasi-dimensional model Laminar burning velocity Numerical simulation a b s t r a c t Spark ignit... more Quasi-dimensional model Laminar burning velocity Numerical simulation a b s t r a c t Spark ignition engines fuelled by hydrogen enriched compressed natural gas (HCNG) have many advantages compared to traditional gasoline, diesel and natural gas engines, especially in emission control. Experimental researches have been continuously conducted to improve HCNG engine's configuration and control strategy aimed at making full use of this new fuel. With the same target, this work presents a predictive model used to simulate the working cycle of HCNG engines which is applicable for variable hydrogen blending ratios. The fundamentals of the thermodynamic model, the turbulent flame propagation model and related equation were introduced. Considering that the most important factor influencing the applicability of the model for variable hydrogen blending ratio is the laminar flame speed, the methods of how to deal with the laminar burning velocity in the model were then described in some more detail. After the determination of model constants by calibration, simulation results were compared with experimental cylinder pressure data for various hydrogen blending ratios, spark timings and equivalence ratios. The results show that simulation and experimental results match quite well except for extremely fuel lean conditions where problems of incomplete combustion become severe.

Progress in Natural Science, 2008

A total of 407,663 expressed sequence tags (ESTs) of wheat, barley, maize, rice, and sorghum, obt... more A total of 407,663 expressed sequence tags (ESTs) of wheat, barley, maize, rice, and sorghum, obtained from GenBank/dbEST, were used to search for simple sequence repeats (SSRs). A total of 10,253 EST-SSRs, which accounted for 2.52% of all the ESTs, were identified. Using Primer Premier 5.0, 1367 EST-SSR primer pairs were designed, of which 715 with high quality were synthesized. The 715 primer pairs were tested on wheat, rice, maize, cotton, and soybean under the same PCR conditions, and the effective primer pairs in the five crops were 500 (, respectively. This indicated a high transferability of EST-SSR markers between far-ranging species. In addition, 139 EST-SSR primer pairs with 240 loci were localized on all the 21 wheat chromosomes by using Chinese Spring nulli-tetrasomic lines of wheat.

Energy & Fuels, 2008

In order to study the influence of the 0-50 vol % hydrogen addition on idle performance, an exper... more In order to study the influence of the 0-50 vol % hydrogen addition on idle performance, an experimental research was conducted on a six-cylinder throttle body injection natural gas engine. Experiments have been made under various excess air ratios and ignition timings. The results show that hydrogen addition remarkably decreased CH 4 emission whereas it had no significant effect on the reduction of CO. NOx emission was relatively low at idle compared to other emissions. Hydrogen addition combined with ignition timing retardation was an effective way to reduce idle emission. The COV in IMEP and partial-burn ratio could be simultaneously reduced by hydrogen addition, which indicated the improvement of idle stability. In turn, the improvement of idle stability decreased the fuel consumption. Also, the curve for COV in IMEP was smoother versus ignition timing after hydrogen addition, which is desirable at idle because small idle speed error was adjusted by ignition timing in many electric idle control units. It can be concluded hydrogen addition is an effective and applicable approach to improve idle stability and decrease emission.

International Journal of Hydrogen Energy, 2007

In order to analyze the effect of hydrogen addition on natural gas (NG) engine's thermal efficien... more In order to analyze the effect of hydrogen addition on natural gas (NG) engine's thermal efficiency and emission, an experimental research was conducted on a spark ignition NG engine using variable composition hydrogen/CNG mixtures (HCNG). The results showed that hydrogen enrichment could significantly extend the lean operation limit, improve the engine's lean burn ability, and decrease burn duration. However, nitrogen oxides (NO x ) were found to increase with hydrogen addition if spark timing was not optimized according to hydrogen's high burn speed. Also found when spark timing was set at constant was that hydrogen addition actually increases heat transfer out of the cylinder due to smaller quenching distance and higher combustion temperature, thus is not good to improve thermal efficiency if combined with the effect of non-ideal spark timing. But if spark timing was retarded to MBT, taking advantage of hydrogen's high burn speed, NO x emissions exhibited no obvious increase after hydrogen addition and engine thermal efficiency increased with the increase of hydrogen fraction. Unburned hydrocarbon always decreased with the increase of hydrogen fraction. ᭧

International Journal of Hydrogen Energy, 2008

Combustion and emission characteristics of a port-injection SI turbocharged engine fueled with se... more Combustion and emission characteristics of a port-injection SI turbocharged engine fueled with several H 2 =CNG blend ratios (0-50 vol%) under various ignition timings were investigated. The results show that with the increase of hydrogen addition, the maximum brake toque timing decreases and the indicated thermal efficiency increases; the MBT gets close to the top dead center and the indicated thermal efficiency increases with decreased load. The combustion duration is reduced by increasing the hydrogen fraction in HCNG (hydrogen enriched compressed natural gas) mixture. The NO x , CO and HC emissions all descend with the increase of spark advance angle, and ascend with the increase of the load.

Amino Acids, 2009

Amino acids (AA) are not only the building blocks of proteins but are also key regulators of meta... more Amino acids (AA) are not only the building blocks of proteins but are also key regulators of metabolic pathways in cells. However, the mechanisms responsible for the effects of AA are largely unknown. With the completion of human and other mammalian genome projects, revolutionary technologies in life sciences characterized by high throughput, high efficiency, and rapid computation are now available for AA nutrition research. These advanced tools include genetics (the genomic variety), epigenetics (stable and heritable changes in gene expression or cellular phenotype that occurs without changes in DNA sequence), transcriptomics (alternative mRNA splicing, microRNAs, and gene transcription), proteomics (protein expression and interactions), metabolomics (metabolite profiles in cells and tissues), and bioinformatics (analysis of metabolic pathways using systems biology approach). These robust, powerful methods can be employed for the analysis of DNA, RNA, protein, and low-molecular-weight metabolites, whose expression and concentration are affected by the interaction between genes and dietary AA. With the omics and other advanced methodologies, we expect that the molecular actions of AA on target tissues can be defined and that optimal dietary recommendations for these nutrients can be devised for individual humans (personalized nutrition) and animals (targeted feeding) in response to changes in physiological and pathological conditions.

International Journal of Hydrogen Energy, 2008

An experimental study aimed at examining the effects of hydrogen addition on cycle-bycycle variat... more An experimental study aimed at examining the effects of hydrogen addition on cycle-bycycle variation (CCV) in an SI engine was conducted on a 6-cylinder throttle body injection natural gas (NG) engine. Two types of fuels, CNG and 80/20 (in volume) CNG/hydrogen mixtures, were used for comparison purposes. The results showed that coefficient of variation (CoV) in both maximum pressure ðP max Þ and indicated mean effective pressure (IMEP) could be reduced by hydrogen addition and that positive effect would be more obvious as the engine was further leaned out. The duration of flame development and propagation as well as the CCVs in flame propagation duration could be simultaneously reduced by hydrogen addition, all of which are beneficial to improve combustion stability and thought to be reasons for the reduction in CoV imep . Stability of combustion phasing that is crucial to the effectiveness of ignition timing optimization was also improved by hydrogen. Hydrogen addition was also proved to be good to the control of emission of NO x and unburned HC. Hence it is concluded that hydrogen addition is an effective and applicable approach to keep down CCVs in lean burn spark-ignition engines.

BMC Genomics, 2009

Background: MicroRNAs (miRNAs) play critical roles in a wide spectrum of biological processes and... more Background: MicroRNAs (miRNAs) play critical roles in a wide spectrum of biological processes and have been shown to be important effectors in the intricate host-pathogen interaction networks. Avian influenza virus (AIV) not only causes significant economic losses in poultry production, but also is of great concern to human health. The objective of this study was to identify miRNAs associated with AIV infections in chickens.

Energy & Fuels, 2008

A zero-dimensional two-zone model was employed to investigate the influence of the combustion pro... more A zero-dimensional two-zone model was employed to investigate the influence of the combustion process of the spark-ignition (SI) engine on its thermal efficiency. Attention was mainly paid to the effects of combustion phasing, combustion duration, and their cyclic variations. These combustion parameters were varied by changing spark timing and the hydrogen/natural gas blending ratio (hydrogen and natural gas mixtures were used as the fuel). The results show that there always exists an optimized combustion phasing for best engine thermal efficiency. Combustion phasing that deviates from this optimized value would decrease thermal efficiency. The fact that heat transfer loss increases with the advance of combustion phasing was thought to be the reason why best efficiency thermal efficiency does not occur under the condition when the combustion rate peaks at TDC. It is also found unexpectedly that although reduction in combustion duration can increase the degree of constant volume combustion, it does not have obviously positive effects on the final thermal efficiency. Finally, with regard to the cyclic variations, it is concluded that cyclic variations in the combustion process exert a heavy effect on thermal efficiency. The higher the variations, the larger the negative effect.