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Biomedical subjects

S Zhou

Publications and source records attributed to S Zhou.

At least 19 recordsLinked to original sources
PubMed2007

Purification and characterization of a 4-hydroxybenzoate decarboxylase from Chlamydophila pneumoniae AR39.

Chlamydophila pneumoniae AR39 is an obligate intracellular pathogen that causes human acute and chronic respiratory tract diseases. One protein from C. pneumoniae AR39 was assigned as 4-hydroxybenzoate decarboxylase (HBDC). Assays done with the purified oxygen-sensitive protein showed that the optimum pH and temperature were 7.5 and 30 degrees C, respectively. The Km and Vmax obtained for 4-hydroxybenzoate were approximately 0.21 mM and 11.9 nM min(-1) mg(-1), respectively. During the period of 4-hydroxybenzoate decarboxylation, overall activity of the thermal-sensitive protein was 5.06 nM min(-1) mg(-1) protein. The 4-hydroxybenzoate decarboxylation was promoted by Mg(2+), Fe(2+), Mn(2+), and Ca(2+) but not by Cu(2+) or Zn(2+). The enzyme also slowly catalyzed the reverse reaction, which was phenol carboxylation.

Amino Acid Sequence↗
PubMed2006

An integrated assessment model of carbon sequestration benefits: a case study of Liping county, China.

This research attempts to model the complexity of planting trees to increase China's CO(2) sequestration potential by using a GIS-based integrated assessment (IA) approach. We use the IA model to assess the impact of China's Grain for Green reforestation and afforestation program on farmer and state incomes as well as CO(2) sequestration in Liping County, Guizhou Province. The IA model consists of five sub-models for carbon sequestration, crop income, timber income, Grain for Green, and carbon credits. It also includes a complementary qualitative module for assessing program impacts by gender and ethnicity. Using four scenarios with various assumptions about types of trees planted, crop incomes by township, CO(2) credit prices, state subsidies, methods for estimating carbon sequestered, and harvesting of trees, we find great variation in the impact of the Grain for Green program on incomes and on carbon sequestered over a 48 year period at both the county and township levels.

Carbon↗
PubMed2006

Social and economic impacts of carbon sequestration and land use change on peasant households in rural China: a case study of Liping, Guizhou Province.

Numerous innovative approaches to mitigate effects of excessive emission of greenhouse gases (GHGs) on global climate change are being proposed and formulated. Sequestering carbon to terrestrial ecosystems represents one of the important clean development mechanisms. Reforestation through converting various non-forest lands to forests is undoubtedly an important dimension of carbon sequestration. Using Liping County in Guizhou Province as a case region, this study examines the perceived change in social and economic livelihoods of peasants and the factors responsible for the variations in the changes. The results of the study reveal that socio-economic changes associated with the government-financed project are multifaceted and profound. Because of the financial subsidies provided by the central government, this environmental action in many aspects can be regarded as a poverty reduction measure in the underdeveloped area where rural poverty is widespread. A majority of peasant households have benefited from project participation. The land conversion project with continued financial support also contributes to the social transformations of traditional rural society in remote areas to a more mobile, less subsistence agriculture-based, and open society.

Agriculture↗
PubMed2006

The costs and benefits of reforestation in Liping County, Guizhou Province, China.

Reducing greenhouse gases in the atmosphere is becoming a pressing issue for the global community. Afforestation and reforestation are promoted worldwide as an effective means of sequestering carbon. For its national interest and global concerns, China has made great efforts to protect its existing forests and develop programs of afforestation and reforestation. Based on two surveys recently conducted in Liping County, Guizhou province, this paper investigates the economic changes associated with the implementation of the "Grain For Green" policy. Based on the analytical framework of benefit cost analysis, this paper concludes that the implementation of the reforestation of sloping agricultural land policy would not be possible if there were no government subsidies for the peasants. The short term economic returns of land and labour from forestation are substantially lower than those generated from grain or cash crop production on the steep slope lands. The government subsidies provide great economic incentives for peasants to take part in the project. The subsidies in fact have elevated peasant income in rural Liping. The estimated potential economic returns of plantations over the long run indicate that the removal of the government financial subsidies would not create an economic crisis for the peasants if the current market conditions continue.

Agriculture↗
PubMed2006

Linking carbon sequestration science with local sustainability: an integrated assessment approach.

This paper introduces an integrated assessment (IA) approach for a Canada-China joint research project that linked forest carbon sequestration, forest resource management, and local sustainability enhancement. The purpose of the IA was to improve the measurement of carbon in different land uses and vegetation covers, as well as to direct decision makers to those land uses or options as an CO(2) emission reduction strategy while supporting rural sustainable development. In this connection, three questions are addressed in this paper: 1) How will forestry carbon sequestration land use policies affect regional sustainability prospects in rural China? 2) How could carbon sequestration land use plans be better integrated into sustainable development strategies? and 3) How can the IA approach assist Chinese government agencies in design effective forestry land use policies? The IA approach was applied in three rural sites of western China. These case studies are described in detail by following articles in this volume. The project improved the capacity of local resource managers in identifying the economic, social and environmental impacts of rural land use decisions that might increase carbon sequestration and enhance local livelihood.

Carbon↗
PubMed2006

Proteomic analysis of hypoxia-induced responses in the syncytialization of human placental cell line BeWo.

Syncytiotrophoblast formation is affected by a number of pathological conditions and suppressed syncytiotrophoblast formation due to hypoxia may play a role in the pathogenesis of preeclampsia. However, the molecular basis of hypoxia-inhibited trophoblast syncytialization is poorly understood. To determine the effect of hypoxia on trophoblast syncytialization, a proteomic analysis was performed in the human cytotrophoblast cell line BeWo using two-dimensional electrophoresis and MALDI-TOF-TOF-MS. Hypoxia induced marked inhibition of BeWo cell fusion and differentiation. The proteomic profiling was established under hypoxia in BeWo cell syncytialization. The results showed that twenty proteins were significantly up-or down-regulated under hypoxia, compared with cells under normoxia. In response to hypoxia, three antioxidants, peroxiredoxin 1, peroxiredoxin 2 and 1-Cys peroxiredoxin, were down-regulated, two proteins involved in glycolysis pathway (malate dehydrogenase and enolase) were up-regulated. The expression of two members of the annexin family (annexin A2 and annexin A5) increased. We also found a decreased expression of 14-3-3 tau protein in hypoxia treated cells. Proteins implied in protein degradation and folding were also identified. The expression of two cytoskeleton components (keratin 1 and beta-actin) was found to be down-regulated. In addition, galectin-3 was up-regulated. These proteins have been implicated in regulating cellular oxidative stress, glycolysis, signal transduction, protein folding and degradation, cell mobility and cytoskeletal structure formation. Western blot analysis revealed that the levels of peroxiredoxin 1 and 14-3-3 tau decreased, whereas the levels of annexin A5 and annexin A2 increased in BeWo cells under hypoxia. These findings provided new insights into the molecular mechanisms in mediating cellular response to hypoxia in trophoblast syncytialization.

Cell Fusion↗
PubMed2006

Methylglyoxal bypass identified as source of chiral contamination in l(+) and d(-)-lactate fermentations by recombinant Escherichia coli.

Two new strains of Escherichia coli B were engineered for the production of lactate with no detectable chiral impurity. All chiral impurities were eliminated by deleting the synthase gene (msgA) that converts dihydroxyacetone-phosphate to methylglyoxal, a precursor for both L: (+)- and D: (-)-lactate. Strain TG113 contains only native genes and produced optically pure D: (-)-lactate. Strain TG108 contains the ldhL gene from Pediococcus acidilactici and produced only L: (+)-lactate. In mineral salts medium containing 1 mM betaine, both strains produced over 115 g (1.3 mol) lactate from 12% (w/v) glucose, >95% theoretical yield.

Biotechnology↗
PubMed2006

A DNA-binding protein, tfp1, involved in juvenile hormone-regulated gene expression in Locusta migratoria.

A partially palindromic 15-nt. sequence upstream from a juvenile hormone-regulated gene (jhp21) was previously identified in the African migratory locust, Locusta migratoria. This sequence was proposed as a juvenile hormone (JH) response element (JHRE), and a protein that bound to it, as a transcription factor (TF). A yeast strain was constructed containing four tandem copies of the JHRE and after transfection with a cDNA library made to fat bodies from vitellogenic females, yeast one-hybrid experiments yielded sequences for four putative binding proteins. One of these sequences, corresponding to a transcript that was present in fat body irrespective of JH stimulation, encodes a 35kDa protein. This was designated tfp1 and appears to have a leucine zipper motif and a lipid-binding motif. Recombinant tfp1 bound to JHRE in electrophoretic mobility shift experiments and addition of tfp1 antibody in the binding reaction resulted in the disappearance or shift of TF. We suggest that JH induces the association of pre-existing proteins, including tfp1, to form an active complex, which binds to the JHRE upstream from jhp21 and regulates its transcription.

Amino Acid Sequence↗
PubMed2006

A comparison study of cerebral protection using Ginkgo biloba extract and Losartan on stroked rats.

It has been well documented that oxidative stress is involved in stroke. Currently, many neuroprotective strategies have been targeted at molecules that are able to act as an oxidant to intervene with free-radical mediated apoptosis in the ischemic penumbra. In particular, natural products which contain antioxidant properties have undoubtedly efficacious for stroke treatment. In the current study, therapeutic effects of Ginkgo biloba extract (EGb) against cerebral protection in Wistar rats underwent middle cerebral artery occlusion (MCAO) was evaluated. A comparison study was conducted by using Losartan, an antihypertensive drug. Gene expression levels of pro-apoptotic genes (AT2 receptor, Fas, Bax and Bcl-xS) have shown to have significant reduction by EGb- and Losartan-treated groups as compared to vehicle group. Significant reduction of immunoreactivity of protein production of these genes, together with least nuclear green fluorescence observed in TUNEL, EGb, as an antioxidant drug, is concluded to have potent and promising therapeutic effect for stroke treatment.

Angiotensin II Type 1 Receptor Blockers↗
PubMed2006

Fermentation of 12% (w/v) glucose to 1.2 M lactate by Escherichia coli strain SZ194 using mineral salts medium.

A non-recombinant mutant of Escherichia coli B, strain SZ194, was developed that produces over 1 M D-lactate from glucose (or sucrose) in 72 h using mineral salts medium supplemented with 1 mM: betaine in simple anaerobic fermentations. Rates and yields were highest at pH 7.5. Yields approached the theoretical maximum with only trace amounts of co-products. Chiral purity of D-lactate was estimated to be 95%. Specific and volumetric productivities for SZ194 in mineral salts medium (pH 7.5) with betaine were equivalent to those in Luria broth.

Base Sequence↗
PubMed2006

Betaine tripled the volumetric productivity of D(-)-lactate by Escherichia coli strain SZ132 in mineral salts medium.

Osmotic stress restricts glycolytic flux, growth (rate and yield), D-lactate productivity, and D-lactate tolerance in Escherichia coli B strain SZ132 during batch fermentation in mineral salts medium with 10% (w/v) sugar. Addition of 1 mM: betaine, a non-metabolized protective osmolyte, doubled cell yield, increased specific productivity of D-lactate and glycolytic flux by 50%, and tripled volumetric productivity (from 8.6 to 25.7 mmol l(-1) h(-1); 0.8 to 2.3 g l(-1) h(-1)). Glycolytic flux and specific productivity in mineral salts medium with betaine exceeded that in Luria broth, substantially eliminating the need for complex nutrients during D-lactate production. In mineral salts medium supplemented with betaine, SZ132 produced approximately 1 mol D-lactate (90 g) per 100 g sugar (glucose or sucrose).

Betaine↗
PubMed2006

The mode of action of insecticidal controlled atmospheres.

Arthropods cope with reduced oxygen and elevated carbon dioxide atmospheres with a reduction in metabolic rate, also called metabolic arrest. The reduction in metabolism lessens the pressure on the organism to initiate anaerobic metabolism, but also leads to a reduction in ATP production. The natural permeability of cellular membranes appears to be important for the survival of the arthropod under low oxygen or high carbon dioxide atmospheres. Despite the similarities in response, arthropod mortality is generally greater in response to high carbon dioxide as apposed to low oxygen atmospheres. There appears to be a greater decrease in ATP and energy charge in arthropods exposed to high carbon dioxide as compared with low oxygen atmospheres, and this may be due to greater membrane permeability under carbon dioxide leading to an inefficient production of ATP. Reduced oxygen and elevated carbon dioxide atmospheres can have an additive effect in some cases, depending on the concentrations used. The effect of these atmospheres on arthropods depends also on temperature, species and life stage. Additional work is needed to fully understand the mode of action of controlled atmospheres on arthropod pests.

Adaptation, Biological↗
PubMed2005

Kainate-induced excitation and sensitization of nociceptors in normal and inflamed rat glabrous skin.

This study investigates contributions of peripheral kainate receptors to acute nociception and persistent inflammatory pain in rat. Immunohistochemical analysis of kainate receptor expression using antibodies recognizing glutamate receptor subunits 5, 6, and 7 demonstrates that 28% of unmyelinated axons in normal digital nerve are positively labeled. Following intraplantar injection of complete Freund's adjuvant, a significant increase in glutamate receptor subunits 5, 6, and 7-labeled axons occurs at 2 days (40%), but not 7 (31%) or 14 days (28%) post-complete Freund's adjuvant. In behavioral studies, we confirm an increased mechanical sensitivity in complete Freund's adjuvant-injected hind paws. Furthermore, activation of kainate receptors following intraplantar injection of 1.0 mM kainate in normal animals results in a mechanical sensitivity similar to that observed in inflamed animals. A 1.0 mM kainate injection into inflamed hind paws further enhances the mechanical sensitivity. Injection of the non-N-methyl-D-aspartate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (0.1 mM) reverses complete Freund's adjuvant-induced mechanical sensitivity through a local effect. In single unit recordings from nociceptors in a glabrous skin-nerve preparation, mechanical sensitization is present in inflamed skin evidenced by a decrease in mechanical threshold and an increase in discharge rate during a suprathreshold, constant force stimulus. Thermal sensitization is also present evidenced by a decrease in heat threshold. There is a dose-dependent increase in kainate-induced nociceptor activity in both normal and inflamed skin but the kainate required to induce activation is reduced in inflamed skin. Although proportions of kainate-activated nociceptors are the same in normal and inflamed skin, the kainate-induced mean discharge rate is significantly enhanced in inflamed skin. Exposure of normal and inflamed nociceptors to 0.3 mM kainate sensitizes fibers to re-application of kainate and heat. This sensitization is blocked in the presence of 6-cyano-7-nitroquinoxaline-2,3-dione or the glutamate receptor subunit 5 selective antagonist 3S,4aR,6S,8aR-6-[4-carboxy-phenyl] methyl-1,2,3,4,4a,5,6,7,8,8a-deca-hydroisoquinoline-3-carboxylic acid. The data indicate that peripheral kainate receptors not only play an important role in normal nociception but also contribute to mechanical sensitivity and heat sensitization accompanying inflammatory pain.

Animals↗
PubMed2005

Detection of aristolochic acid I, tetrandrine and fangchinoline in medicinal plants by high performance liquid chromatography and liquid chromatography/mass spectrometry.

Problems with identification and labeling of medicinal plants, as well as substitution/adulteration of non-toxic plants by toxic ones have previously led to cancer, renal failure and even deaths. The non-toxic Stephania tetrandra (Fangji) has been known to be substituted by Aristolochia fangchi (Guang fangji), which contains the nephrotoxic and carcinogenic aristolochic acid (AA). In this study, 10 samples of "Fangji" were bought from local medicinal shops. HPLC-DAD chromatographic fingerprints of each methanol extract were compared with those of A. fangchi and S. tetrandra, using aristolochic acid I (AAI), tetrandrine and fangchinoline as marker compounds. Nine of the samples were found to be similar to A. fangchi. The presence of AAI in the nine samples was confirmed using LC-MS/MS. Neither tetrandrine nor fangchinoline were detected in these samples. The methods developed in this study allow the simultaneous detection of AAI, fangchinoline and tetrandrine. The results suggest possible substitution of S. tetrandra by A. fangchi at wholesale or retail level. This study highlights the importance of greater control of medicinal plants with toxic components as these may still be readily accessible to the public.

Alkaloids↗
PubMed2005

Fermentation of 10% (w/v) sugar to D: (-)-lactate by engineered Escherichia coli B.

Derivatives of ethanologenic Escherichia coli K011 were constructed for D: (-)-lactate production by deleting genes encoding competing pathways followed by metabolic evolution, a growth-based selection for mutants with improved performance. Resulting strains, SZ132 and SZ186, contain native genes for sucrose utilization. No foreign genes are present in SZ186. Strain SZ132 also contains a chromosomally integrated endoglucanase gene (Erwinia chrysanthemi celY). Strain SZ132 produced over 1 mol lactate per liter of complex medium containing 10% (w/v) sugar (fermentation times of 48 h for glucose, 120 h for sucrose). Both strains produced 667-700 mmol lactate per liter of mineral salts medium. Yields for metabolized sugar ranged from 88% to 95% in both media.

Carboxylic Acids↗
PubMed2005

Alterations of striatal NMDA receptor subunits associated with the development of dyskinesia in the MPTP-lesioned primate model of Parkinson's disease.

The development of dyskinesias and other motor complications greatly limits the use of levodopa therapy in Parkinson's disease (PD). Studies in rodent models of PD suggest that an important mechanism underlying the development of levodopa-related motor complications is alterations in striatal NMDA receptor function. We examined striatal NMDA receptors in the MPTP-lesioned primate model of PD. Quantitative immunoblotting was used to determine the subcellular abundance of NR1, NR2A and NR2B subunits in striata from unlesioned, MPTP-lesioned (parkinsonian) and MPTP-lesioned, levodopa-treated (dyskinetic) macaques. In parkinsonian macaques, NR1 and NR2B subunits in synaptosomal membranes were decreased to 66 +/- 11% and 51.2 +/- 5% of unlesioned levels respectively, while the abundance of NR2A was unaltered. Levodopa treatment eliciting dyskinesia normalized NR1 and NR2B and increased NR2A subunits to 150 +/- 12% of unlesioned levels. No alterations in receptor subunit tyrosine phosphorylation were detected. These results demonstrate that altered synaptic abundance of NMDA receptors with relative enhancement in the abundance of NR2A occurs in primate as well as rodent models of parkinsonism, and that in the macaque model, NR2A subunit abundance is further increased in dyskinesia. These data support the view that alterations in striatal NMDA receptor systems are responsible for adaptive and maladaptive responses to dopamine depletion and replacement in parkinsonism, and highlight the value of subtype selective NMDA antagonists as novel therapeutic approaches for PD.

Animals↗