Optimizing the formation of myosin/high-density lipoprotein composite gels: PH-dependent effects on heat-induced aggregation

This study investigated impact of high-density lipoprotein (HDL) on thermal aggregation and gelling behavior of myosin in relation to varied pHs. Results revealed that HDL modified myosin structure before and after heating, with distinct effects observed at varied pH. Under pH 5.0, both myosin and HDL-MS exhibited larger aggregates and altered microstructure; at pH 7.0 and 9.0, HDL inhibited myosin aggregation, resulting in enhanced solubility, reduced turbidity and particle size. Comparative analysis of surface hydrophobicity, free sulfhydryl groups and secondary structure highlighted distinct thermal aggregation behavior between MS and HDL-MS, with the latter showing inhibitory effects under neutral or alkaline conditions. Gelation behavior was enhanced at pH 7.0 with maximum strength, hardness, water-holding capacity and rheological properties. Under acidic pH, excessive protein aggregation resulted in increased whiteness and rough microstructure with granular aggregates. Under alkaline pH, gel network structure was weaker, possibly due to higher thermal stability of protein molecules. Scanning electron microscopy revealed expanded HDL protein particles at pH 7.0, accounting for decreased gel strength and altered rheological properties compared with myosin gel. Overall, the results indicated a positive role of HDL at varied pH in regulating thermal aggregation of myosin and further impacting heat-induced gel characteristics.

Research advances of molecular docking and molecular dynamic simulation in recognizing interaction between muscle proteins and exogenous additives

During storage and processing, muscle proteins, e.g. myosin and myoglobin, will inevitably undergo degeneration, which is thus accompanied by quality deterioration of muscle foods. Some exogenous additives have been widely used to interact with muscle proteins to stabilize the quality of muscle foods. Molecular docking and molecular dynamics simulation (MDS) are regarded as promising tools for recognizing dynamic molecular information at atomic level. Molecular docking and MDS can explore chemical bonds, specific binding sites, spatial structure changes, and binding energy between additives and muscle proteins. Development and workflow of molecular docking and MDS are systematically summarized in this review. Roles of molecular simulations are, for the first time, comprehensively discussed in recognizing the interaction details between muscle proteins and exogenous additives aimed for stabilizing color, texture, flavor, and other properties of muscle foods. Finally, research directions of molecular docking and MDS for improving the qualities of muscle foods are discussed.

Role of low molecular additives in the myofibrillar protein gelation: underlying mechanisms and recent applications

Understanding mechanisms of myofibrillar protein gelation is important for development of gel-type muscle foods. The protein-protein interactions are largely responsible for the heat-induced gelation. Exogenous additives have been extensively applied to improve gelling properties of myofibrillar proteins. Research has been carried out to investigate effects of different additives on protein gelation, among which low molecular substances as one of the most abundant additives have been recently implicated in the modifications of intermolecular interactions. In this review, the processes of myosin dissociation under salt and the subsequent interaction via intermolecular forces are elaborated. The underlying mechanisms focusing on the role of low molecular additives in myofibrillar protein interactions during gelation particularly in relation to modifications of the intermolecular forces are comprehensively discussed, and six different additives i.e. metal ions, phosphates, amino acids, hydrolysates, phenols and edible oils are involved. The promoting effect of low molecular additives on protein interactions is highly attributed to the strengthened hydrophobic interactions providing explanations for improved gelation. Other intermolecular forces i.e. covalent bonds, ionic and hydrogen bonds could also be influenced depending on varieties of additives. This review can hopefully be used as a reference for the development of gel-type muscle foods in the future.

Exogenous citric acid enhances drought tolerance in tobacco (Nicotiana tabacum)

Organic acids play a pivotal role in improving plant response to long-term drought stress. External application of organic acids has been reported to improve drought resistance in several species. However, whether organic acids have similar effects in tobacco remains unknown. A screening study of the protective function of organic acids in tobacco and understanding the underlying molecular mechanism would be useful in developing a strategy for drought tolerance. Several physiological and molecular adaptations to drought including abscisic acid, stomatal closure, reactive oxygen species homeostasis, amino acid accumulation, and drought-responsive gene expression were observed by exogenous citric acid in tobacco plants. Exogenous application of 50 mm citric acid to tobacco plants resulted in higher chlorophyll content, net photosynthesis, relative water content, abscisic acid content and lower stomatal conductance, transpiration and water loss under drought conditions. Moreover, reactive oxygen species homeostasis was better maintained through increasing activity of antioxidant enzymes and decreasing hydrogen peroxide content after citric acid pretreatment under drought. Amino acids involved in the TCA cycle accumulated after external application of citric acid under drought stress. Furthermore, several drought stress-responsive genes also dramatically changed after application of citric acid. These data support the idea that external application of citric acid enhances drought resistance by affecting physiological and molecular regulation in tobacco. This study provides clear insights into mechanistic details of regulation of amino acid and stress-responsive gene expression by citric acid in tobacco in response to drought, which is promising for minimizing growth inhibition in agricultural fields.

Seeking help by parents for care regarding the socio-emotional development of preschool children

Background

Timely parental help-seeking regarding their child's socio-emotional development is associated with a lower rate and lower severity of psychosocial problems in later life. This study aimed to examine factors associated with parental help-seeking for the socio-emotional development of 3-year-old children.

Methods

Data of parents and children (n = 1507) from a community sample was analyzed. Thirteen potentially related factors were assessed at baseline at child age 2 years, and classified according to Andersen's Behavioral Model: predisposing, enabling, and need factors. Parental help-seeking and 14 formal and informal care (e.g. General practitioner, internet) used in the past 12 months were measured at follow-up at child age 3 years. Logistic regression was applied.

Results

In total, 22.6% of parents reported help-seeking for socio-emotional development of their 3-year-old child; 6.8% addressed formal care and 17.5% addressed informal care. General practitioner (2.7%) and family (12.5%) were the most frequently used formal and informal care, respectively. Among predisposing factors associated with a higher odds of parental help-seeking were child's other western background (OR = 1.66, 95%CI: 1.02-2.68) and parental age = < 29 years old (OR = 1.71, 95%CI: 1.01-2.92). No associated factors were found among enabling factors. The need factors associated with a higher odds of parental help-seeking were having previous help-seeking (OR = 2.52, 95%CI: 1.83-3.48) and discussing child's socio-emotional development in the well-child visit (OR = 2.47, 95%CI: 1.73-3.53).

Conclusions

Predisposing and need factors were associated with parental help-seeking for socio-emotional development of 3-years-old child. The findings can be used to further develop support for parents accessing adequate information, prevention and anticipatory care with regard to the child's socio-emotional development.

Key messages

The study longitudinally investigated parental help-seeking for socio-emotional development of their 3-year old children in a large community sample. The study makes an important contribution to the existing literature on this topic because of its particularly young sample of 3-year-old children.

MiR-195 alleviates ulcerative colitis in rats via MAPK signaling pathway

OBJECTIVE

To study the effect of micro ribonucleic acid (miR)-195 on the inflammatory response of ulcerative colitis (UC) model rats and to explore its regulatory mechanism, thus providing a new scheme for the clinical treatment of UC.

MATERIALS AND METHODS

A rat model of UC was prepared by 2, 4, 6-trinitrobenzenesulfonic acid (TNBS)/ethanol assay, and the rats were randomly divided into Control group, Model group, and miR-195 mimic (miR-195 agomir) group. The disease activity index (DAI) in each group was observed. Hematoxylin and eosin (H&E) staining was utilized to detect the pathological changes in the rat colon tissues in each group. The levels of interleukin-6 (IL-6) and IL-1β in the colon tissues of the rats in each group were detected by enzyme-linked immunosorbent assay (ELISA). In addition, the messenger RNA (mRNA) and protein levels of p38 mitogen-activated protein kinase (p38 MAPK) and tumor necrosis factor-alpha (TNF-α) in the colon tissues of each group of rats were examined via Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and Western blotting, respectively.

RESULTS

Compared with those in Control group, the rats in Model group had an increased DAI score, severely pathologically damaged colon tissues, raised levels of IL-6 and IL-1β in the colon tissues and significantly elevated mRNA and protein levels of p38 MAPK and TNF-α. In comparison with those in Model group, the DAI score was decreased, the pathological damage to the rat colon tissues was improved, the levels of IL-6 and IL-1β in the rat colon tissues were reduced, and the mRNA and protein levels of p38 MAPK and TNF-α were notably lowered in miR-195 agomir group.

CONCLUSIONS

MiR-195 mimics can alleviate the pathological damage to the colon and inflammatory responses in UC model rats, and its mechanism may be related to the inhibition on the p38 MAPK signaling pathway.

The role of protein restriction and interaction with antibiotics in the regulation of compensatory growth in pigs: growth performance, serum hormone concentrations, and messenger RNA levels in component tissues of the endocrine growth axis

The present study investigated the effects of protein restriction and antibiotics on the hypothalamus-pituitary-liver growth axis during the compensatory growth of growing and finishing pigs. Growth performance, serum hormones, and messenger RNA (mRNA) levels of hormones and their receptors in growth axis tissues were recorded for analyses. A total of 64 piglets (large white × Landrace × Duroc cross) with an initial weight of 10.07 ± 0.14 kg were randomly divided into 4 treatment groups of 16 piglets per group. The dietary treatments consisted of 2 protein levels (14% and 20%) and 2 antibiotic levels (no antibiotics and 20 mg/kg colistin sulfate with 50 mg/kg kitasamycin) in a 2 × 2 factorial arrangement. The study was performed over 30 d for the first stage (S1, restriction phase) and 74 d for the second stage (S2, realimentation phase). The 4 treatment diets were maintained throughout the duration in the restriction phase. The 4 groups were fed the same diet in the realimentation phase. The trial period totaled 104 d. Protein restriction decreased BW, average daily food intake, and ADG in weaning pigs (P < 0.01) and induced compensatory growth after feeding a normal diet during the growth of finishing pigs. Average daily gain increased during the last phase of compensatory growth (P < 0.01). Protein restriction increased serum GH and leptin (LEP) and the mRNA levels of liver IGF-1 receptor (IGF-1-R; P < 0.01) but decreased serum IGF-1 (P < 0.01) and the mRNA levels of liver GH receptor (GH-R; P < 0.01) and IGF-1 (P < 0.05) in weaning piglets. Serum GH was increased, but serum IGF-1 was decreased during the realimentation phase (P < 0.05). Antibiotics increased the mRNA levels of GHRH (P < 0.05) and decreased somatostatin (P < 0.01) in the hypothalamus of weaning pigs. Protein restriction and antibiotics had no interactions across the entire trial. In conclusion, the slowing of growth caused by early protein restriction may be compensated for in the later stages of pig raising, and the mechanism of compensation is related to the regulation of GH, IGF-1, GH-R, and IGF-1-R.

A Single Amino Acid Substitution in the Intervening Region of 129K Protein of Cucumber Green Mottle Mosaic Virus Resulted in Attenuated Symptoms

Cucumber green mottle mosaic virus (CGMMV), a member of the genus Tobamovirus, is a major threat to economically important cucurbit crops worldwide. An attenuated strain (SH33b) derived from a severe strain (SH) of CGMMV caused a reduction in the viral RNA accumulation and the attenuation of symptoms, and it has been successfully used to protect muskmelon plants against severe strains in Japan. In this study, we compared GFP-induced silencing suppression by the 129K protein and the methyltransferase domain plus intervening region (MTIR) of the 129K protein between the SH and SH33b strains, respectively. As a result, silencing suppression activity (SSA) in the GFP-silenced plants was inhibited efficiently by the MTIR and 129K protein of SH strain, and it coincided with drastically reduced accumulation of GFP-specific small interfering RNAs (siRNAs) but not by that of SH33b strain. Furthermore, analyses of siRNA binding capability (SBC) by the MTIR of 129K protein and 129K protein using electrophoretic mobility shift assay revealed that SBC was found with the MTIR and 129K protein of SH but not with that of SH33b, suggesting that a single amino acid mutation (E to G) in the MTIR is responsible for impaired SSA and SBC of SH33b. These data suggest that a single amino acid substitution in the intervening region of 129K protein of CGMMV resulted in attenuated symptoms by affecting RNA silencing suppression.

Thatcher wheat line RL6149 carries Lr64 and a second leaf rust resistance gene on chromosome 1DS

The leaf rust resistance gene Lr64 in the Thatcher wheat RL6149 was mapped to chromosome 6AL with SNP and KASP markers and a second leaf rust resistance gene was mapped to chromosome 1DS. RL6149, a near-isogenic line of Thatcher wheat, carries leaf rust resistance gene Lr64 on chromosome arm 6AL. The objective of this study was to develop molecular markers that can be easily used to select wheat lines with Lr64. RL6149 was crossed with Thatcher and F₂ plants derived from a single F₁ plant were advanced to F₆ lines by single seed descent. The 100 F₇ recombinant inbred lines (RIL) were inoculated with two races of P.triticina that differed widely for virulence in order to identify resistant and susceptible RIL. Thirty RIL that differed for resistance and the parental lines were genotyped with the 90 K Infinium iSelect single nucleotide polymorphism (SNP) array to find closely linked markers with Lr64. Seven linked SNPs on chromosome arm 6AL were converted into Kompetitive Allele Specific PCR (KASP) markers that were genotyped on the 100 RIL. A genetic linkage map for the seven KASP markers spanned 19.1 cM on chromosome arm 6AL. KASP marker K-IWB59855 was tightly linked to Lr64. A second unexpected gene for leaf rust resistance also segregated in the F₇ lines. Four KASP markers that spanned 18.6 cM located the gene on chromosome 1DS. The KASP marker K-IWB38437 was tightly linked to the second leaf rust resistance gene.

RNA interference-mediated silencing of aquaporin (AQP)-5 hinders angiogenesis of colorectal tumor by suppressing the production of vascular endothelial growth factor

Aquaporin (AQP)-5 is an essential member of AQP family involved in the tumorigenesis of various malignant tumors. However, its role in the angiogenesis of colorectal cancer is unclear and requires further investigation. In this study, a pRNA-H1.1 vector containing the short hairpin RNA (shRNA) targeting AQP5 mRNA was constructed to inhibit the endogenous expression of AQP5 in human umbilical vein endothelial cells (HUVECs). We found that the AQP5-silenced HUVECs acquired decreased proliferation, migration and tube formation ability. AQP5 shRNA also inhibited the enzyme activity of matrix metalloprotease (MMP)-9 in HUVECs without affecting the MMP-2. Further, two colorectal cancer cell lines (HT29 and HCT116) stably transfected with scrambled or AQP5 shRNA were established. The expression and secretion of vascular endothelial growth factor (VEGF)-A (a pro-angiogenic factor) in colorectal cancer cells were downregulated by AQP5 shRNA. HUVECs cultured in low-VEGF conditioned media (CM) obtained from cancer cells developed less vessel-like tubes and had decreased proliferation and migration. The growth and angiogenesis of xenograft tumors were suppressed when the endogenous AQP5 in HT29 cells was knocked down. Tumor samples were additionally collected from patients with colorectal cancer to analyze the expression of AQP5. The immunofluorescence data indicated that AQP5 was expressed in both inner cancer areas and CD31-positive vessels. Taken together, our study suggests AQP5 as a novel anti-angiogenesis target for colorectal cancer.

A Backcross Line of Thatcher Wheat with Adult Plant Leaf Rust Resistance Derived from Duster Wheat has Lr46 and Lr77

The widely grown hard red winter wheat cultivar Duster released in 2006 has remained highly resistant to leaf rust caused by Puccinia triticina in the southern Great Plains of the United States. In contrast, many of the winter wheat cultivars in this region are susceptible to leaf rust. The goal of this study was to identify the number and chromosome location of leaf rust resistance genes in a line of Thatcher*2/Duster wheat that was selected for adult plant leaf rust resistance. The Thatcher*2/Duster line was crossed with Thatcher (Tc) and a recombinant line inbred line (RIL) population was advanced to the F₆ generation by single-seed descent. The parents and RIL population were phenotyped for leaf rust resistance in three field plot tests and in an adult plant greenhouse test. Single-nucleotide polymorphism (SNP) markers derived from the Illumina Infinium iSelect 90K wheat SNP array, kompetitive allele-specific polymerase chain reaction assays on chromosome 3BL, and a sequence tagged site (STS) marker on chromosome 1BL were used to construct a genetic map of the RIL population. The STS marker csLV46G22 that is linked with resistance gene Lr46 on chromosome 1BL, and SNP marker IWB10344 that is linked with Lr77 on chromosome 3BL, were significantly associated with lower leaf rust severity. Duster has at least three adult plant resistance genes for leaf rust resistance because it was previously determined to also have the adult plant resistance gene Lr34. Duster is a valuable source of durable leaf rust resistance for hard red winter wheat improvement in the Great Plains region.

Adult Plant Leaf Rust Resistance Derived from Toropi Wheat is Conditioned by Lr78 and Three Minor QTL

Leaf rust caused by Puccinia triticina is an important disease of wheat in many regions worldwide. Durable or long-lasting leaf rust resistance has been difficult to achieve because populations of P. triticina are highly variable for virulence to race-specific resistance genes, and respond to selection by resistance genes in released wheat cultivars. The wheat cultivar Toropi, developed and grown in Brazil, was noted to have long-lasting leaf rust resistance that was effective only in adult plants. The objectives of this study were to determine the chromosome location of the leaf rust resistance genes derived from Toropi in two populations of recombinant inbred lines in a partial Thatcher wheat background. In the first population, a single gene with major effects on chromosome 5DS that mapped 2.2 centimorgans distal to IWA6289, strongly reduced leaf rust severity in all 3 years of field plot tests. This gene for adult plant leaf rust resistance was designated as Lr78. In the second population, quantitative trait loci (QTL) with small effects on chromosomes 1BL, 3BS, and 4BS were found. These QTL expressed inconsistently over 4 years of field plot tests. The adult plant leaf rust resistance derived from Toropi involved a complex combination of QTL with large and small effects.

PDK1/Akt/PDE4D axis identified as a target for asthma remedy synergistic with β2 AR agonists by a natural agent arctigenin

BACKGROUND

Asthma is a heterogenetic disorder characterized by chronic inflammation with variable airflow obstruction and airway hyper-responsiveness. As the most potent and popular bronchodilators, β2 adrenergic receptor (β2 AR) agonists bind to the β2 ARs that are coupled via a stimulatory G protein to adenylyl cyclase, thereby improving cAMP accumulation and resulting in airway smooth muscle relaxation. We previously demonstrated arctigenin had a synergistic function with the β2 AR agonist, but the target for this remained elusive.

METHOD

Chemical proteomics capturing was used to enrich and uncover the target of arctigenin in human bronchial smooth muscle cells, and reverse docking and molecular dynamic stimulation were performed to evaluate the binding of arctigenin and its target. In vitro enzyme activities and protein levels were demonstrated with special kits and Western blotting. Finally, guinea pig tracheal muscle segregation and ex vivo function were analysed.

RESULTS

Arctigenin bound to PDK1 with an ideal binding free energy -25.45 kcal/mol and inhibited PDK1 kinase activity without changing its protein level. Additionally, arctigenin reduced PKB/Akt-induced phosphorylation of PDE4D, which was first identified in this study. Attenuation of PDE4D resulted in cAMP accumulation in human bronchial smooth muscle. The inhibition of PDK1 showed a synergistic function with β2 AR agonists and relaxed the constriction of segregated guinea pig tracheal muscle.

CONCLUSIONS

The PDK1/Akt/PDE4D axis serves as a novel asthma target, which may benefit airflow obstruction.

Estradiol modulates visceral hyperalgesia by increasing thoracolumbar spinal GluN2B subunit activity in female rats

BACKGROUND

We previously reported estrogen modulates spinal N-methyl-d-aspartate (NMDA) receptor processing of colorectal pain through changes in spinal GluN1 subunit phosphorylation/expression. The purpose of this study was to investigate whether spinal GluN2B containing NMDA receptors are involved in estrogen modulation of visceral pain processing.

METHODS

Behavioral, molecular, and immunocytochemical techniques were used to determine spinal GluN2B expression/phosphorylation and function 48 h following subcutaneous injection of estradiol (E2) or vehicle (safflower oil, Saff oil) in ovariectomized rats in the absence or presence of colonic inflammation induced by mustard oil.

KEY RESULTS

E2 increased the magnitude of the visceromotor response (VMR) to colorectal distention compared to Saff oil in non-inflamed rats. Intrathecal injection of the GluN2B subunit antagonist, Ro 25-6981, had no effect on the VMR in non-inflamed E2 or Saff oil rats. Colonic inflammation induced visceral hyperalgesia in E2, but not Saff oil rats. Visceral hyperalgesia in E2 rats was blocked by intrathecal GluN2B subunit selective antagonists. In inflamed rats, E2 increased GluN2B protein and gene expression in the thoracolumbar (TL), but not lumbosacral (LS), dorsal spinal cord. Immunocytochemical labeling showed a significant increase in GluN2B subunit in the superficial dorsal horn of E2 rats compared to Saff oil rats.

CONCLUSIONS & INFERENCES

These data support the hypothesis that estrogen increases spinal processing of colonic inflammation-induced visceral hyperalgesia by increasing NMDA receptor activity. Specifically, an increase in the activity of GluN2B containing NMDA receptors in the TL spinal cord by estrogen underlies visceral hypersensitivity in the presence of colonic inflammation.

Expression and significance of molecular biomarkers in esophageal carcinoma in different nationalities patients in Xinjiang

This study aimed to explore some useful biomarkers to focus on the diagnosis and therapy response judgment in esophageal squamous cell carcinoma in Xinjiang. We used enzyme-linked immunosorbent method and immunohistochemistry to detect the expression of VEGF, EGFR, ES, HER-2, and NF-κBp in the serum and tissue with esophageal squamous cell carcinoma, and to analyze the relationship between biomarkers and clinical pathology and curative effects. Our findings were as follows: 1. The serum levels of VEGF and ES in Han patients were obviously higher than those of Uygur and Kazakh patients (P < 0.05). The VEGF positive rate in patients at a later clinical stage was higher than that of the patients at an earlier clinical stage (stages II-IV were 14.29, 50.00, and 50.00%, respectively, P < 0.05), meanwhile it was higher than that of patients without lymph node metastases (78.13 vs 25.00%, P < 0.05). The curative effective rate of patients with negative expression of VEGF was higher than that of patients with positive expression of VEGF (74.67 vs 41.40%, P < 0.05). 2. The expression of EGFR protein in male patients was higher than that of female patients (69.77 vs 35.29%, P < 0.05). Before treatment, the serum EGFR level in patients was higher than the normal group (P < 0.05). 3. The serum ES level in patients before and after treatment was significantly higher than in the normal group (P < 0.05). 4. The HER-2 positive rate in higher differentiated tumor tissue was lower than that in lower differentiated tumor tissue. (The positive rate of I, II, III grade was 70.00, 30.00, and 20.00%, respectively, P < 0.05). 5. The NF-κB positive rate in patients with lymph node metastases was higher than that of patients without lymph node metastases (65.63 vs 39.27%, P < 0.05), meanwhile median survival in the latter group was higher than that of the former group (P < 0.05). Our data suggest that the expression of VEGF and ES were different in Uygur, Han, and Kazakh patients in Xinjiang. The combined detection of tumor markers in serum and tissue is of direct significance for tumor therapy.

[Novel immobilization of arginase I via cellulose-binding domain and its application in producing of L-ornitine]

The recombinant Escherichia coli strain pET35b-ARG, which overexpresses arginase I fused to a cellulose-binding domain (CBD), was developed. After preparing cellulose microspheres, arginase I was immobilized via the CBD of the fusion protein. Under optimal reaction conditions (40 degrees C, pH 9.5, 1 mM of Mn2+, 30 microl/ml of immobilized enzyme, 30 g/l of L-Arg, and for I h), the conversion rate of L-Arg was 98.7%. After 7 reuses of 30 microl of immobilized enzyme in 1 ml of catalytic solution, 153 mg of L-Orn with 97.3% purity was obtained. This indicated that the immobilization method was effective, feasible and could be used for the industrial production of L-Orn in the future.

Draft genome sequence of Streptomyces coelicoflavus ZG0656 reveals the putative biosynthetic gene cluster of acarviostatin family α-amylase inhibitors

AIMS

The aims of this study are to obtain the draft genome sequence of Streptomyces coelicoflavus ZG0656, which produces novel acarviostatin family α-amylase inhibitors, and then to reveal the putative acarviostatin-related gene cluster and the biosynthetic pathway.

METHODS AND RESULTS

The draft genome sequence of S. coelicoflavus ZG0656 was generated using a shotgun approach employing a combination of 454 and Solexa sequencing technologies. Genome analysis revealed a putative gene cluster for acarviostatin biosynthesis, termed sct-cluster. The cluster contains 13 acarviostatin synthetic genes, six transporter genes, four starch degrading or transglycosylation enzyme genes and two regulator genes. On the basis of bioinformatic analysis, we proposed a putative biosynthetic pathway of acarviostatins. The intracellular steps produce a structural core, acarviostatin I00-7-P, and the extracellular assemblies lead to diverse acarviostatin end products.

CONCLUSIONS

The draft genome sequence of S. coelicoflavus ZG0656 revealed the putative biosynthetic gene cluster of acarviostatins and a putative pathway of acarviostatin production.

SIGNIFICANCE AND IMPACT OF THE STUDY

To our knowledge, S. coelicoflavus ZG0656 is the first strain in this species for which a genome sequence has been reported. The analysis of sct-cluster provided important insights into the biosynthesis of acarviostatins. This work will be a platform for producing novel variants and yield improvement.

Enzymatic synthesis oF L-tryptophan from D,L-2-amino-delta2-thiazoline-4-carboxylic acid and indole by Pseudomonas sp. TS1138 L-2-amino-delta2-thiazoline-4-carboxylic acid hydrolase, S-carbamyl-L-cysteine amidohydrolase, and Escherichia coli L-tryptophanase

L-Tryptophan (L-Trp) is an essential amino acid. It is widely used in medical, health and food products, so a low-cost supply is needed. There are 4 methods for L-Trp production: chemical synthesis, extraction, enzymatic synthesis, and fermentation. In this study, we produced a recombinant bacterial strain pET-tnaA of Escherichia coli which has the L-tryptophanase gene. Using the pET-tnaA E. coli and the strain TS1138 of Pseudomonas sp., a one-pot enzymatic synthesis of L-Trp was developed. Pseudomonas sp. TS1138 was added to a solution of D,L-2-amino-delta2-thiazoline-4-carboxylic acid (DL-ATC) to convert it to L-cysteine (L-Cys). After concentration, E. coli BL21 (DE 3) cells including plasmid pET-tnaA, indole, and pyridoxal 5'-phosphate were added. At the optimum conditions, the conversion rates of DL-ATC and L-Cys were 95.4% and 92.1%, respectively. After purifying using macroporous resin S8 and NKA-II, 10.32 g of L-Trp of 98.3% purity was obtained. This study established methods for one-pot enzymatic synthesis and separation of L-Trp. This method of producing L-Trp is more environmentally sound than methods using chemical synthesis, and it lays the foundations for industrial production of L-Trp from DL-ATC and indole.

Taxonomy of the Streptomyces strain ZG0656 that produces acarviostatin alpha-amylase inhibitors and analysis of their effects on blood glucose levels in mammalian systems

AIMS

To clarify the taxonomic status of strain ZG0656 and analyse the effects of its acarviostatin products on blood glucose levels in mammalian systems.

METHODS AND RESULTS

Our program to screen for new alpha-amylase inhibitors led to the isolation of strain ZG0656. The polyphasic taxonomic study revealed that strain ZG0656 represents a novel variation of Streptomyces coelicoflavus, for which we propose the name S. coelicoflavus var. nankaiensis. Four chemically distinct alpha-amylase inhibitors, acarviostatins I03, II03, III03 and IV03, were isolated from strain ZG0656. Acarviostatins III03 and IV03 are both novel oligomers. All four acarviostatins are mixed noncompetitive porcine pancreas alpha-amylase inhibitors. Acarviostatin III03 is the most potent alpha-amylase inhibitor known to date. Moreover, in the in vitro and in vivo experiments, acarviostatins III03 showed significant inhibition of starch hydrolysis and glucose transfer to blood.

CONCLUSIONS

Strain ZG0656 is a novel variation of S. coelicoflavus, whose products are novel effective alpha-amylase inhibitors. Among the products, acarviostatins III03 could significantly depress blood glucose levels in mammalian systems and be developed towards a possible therapeutic agent for diabetes.

SIGNIFICANCE AND IMPACT OF THE STUDY

Acarviostatin III03 is the most potent alpha-amylase inhibitor known to date. The oligomer will benefit the research on the relationship between alpha-amylase and various inhibitors and will offer more choices in diabetes treatments.

Role of peripheral mu-opioid receptors in inflammatory orofacial muscle pain

The aims of this project were to investigate whether inflammation in the orofacial muscle alters mu opioid receptor (MOR) mRNA and protein expressions in trigeminal ganglia (TG), and to assess the contribution of peripheral MORs under acute and inflammatory muscle pain conditions. mRNA and protein levels for MOR were quantified by reverse-transcription-polymerase chain reaction (RT-PCR) and Western blot, respectively, from the TG of naïve rats, and compared with those from the rats treated with complete Freund's adjuvant (CFA) in the masseter. TG was found to express mRNA and protein for MOR, and CFA significantly up-regulated both MOR mRNA and protein by 3 days following the inflammation. The MOR protein up-regulation persisted to day 7 and returned to the baseline level by day 14. We then investigated whether peripheral application of a MOR agonist, D-Ala2, N-Me-Phe4, Gly5-ol-enkephalin acetate salt (DAMGO), attenuates masseter nociception induced by masseteric infusion of hypertonic saline (HS) in lightly anesthetized rats. DAMGO (1, 5, 10 microg) or vehicle was administered directly into the masseter 5-10 min prior to the HS infusion. The DAMGO effects were assessed on mean peak counts (MPC) and overall magnitude as calculated by the area under the curve (AUC) of the HS-evoked behavioral responses. Under this condition, only the highest dose of DAMGO (10 microg) significantly reduced MPC, which was prevented when H-D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2 (CTAP), a selective MOR antagonist, was co-administered. DAMGO pre-treatment in the contralateral masseter did not attenuate MPC. The same doses of DAMGO administered into CFA-inflamed rats, however, produced a greater attenuation of both MPC and AUC of HS-evoked nocifensive responses. These results demonstrated that activation of peripheral MOR provides greater anti-nociception in inflamed muscle, and that the enhanced MOR effect can be partly explained by significant up-regulation of MOR expression in TG.

Muscle inflammation induces a rapid increase in calcitonin gene-related peptide (CGRP) mRNA that temporally relates to CGRP immunoreactivity and nociceptive behavior

Recent data support an important role for calcitonin gene-related peptide (CGRP) in deep tissue nociceptive processing. Using real-time reverse transcriptase polymerase chain reaction (RT-PCR), radioimmunoassay, immunohistochemistry and behavioral testing, we studied the early time course of CGRP mRNA and protein expression as well as nociceptive behavior following muscle inflammation. A rapid and significant increase in CGRP mRNA occurred in the mandibular division (V3) of the ipsilateral trigeminal ganglion at 30 minutes, 4 and 24 h after the injection of complete Freund's adjuvant as an inflammatory agent into rat masseter muscle. No change in mRNA occurred in the ipsilateral ophthalmic and maxillary divisions (V1/V2) or in the contralateral V3. The levels of immunoreactive calcitonin gene-related peptide (iCGRP) in the ipsilateral V3 significantly increased at 1, 4 and 24 h following muscle inflammation. In contrast, no change occurred in iCGRP levels in either the ipsilateral V1/V2 or contralateral V3. When saline was injected into the masseter muscle, the levels of mRNA or iCGRP did not change in the ipsilateral V3 suggesting that the biochemical changes are specific to CFA-induced muscle inflammation. The number of muscle afferent neurons immunoreactive for CGRP was significantly reduced compared with control at 1, 4 and 24 h in the ipsilateral but not in the contralateral trigeminal ganglion following inflammation. This decrease in the ipsilateral ganglion may indicate a loss of intrasomatic CGRP as a result of increased axonal transport away from the neuronal cell body and/or release of CGRP. Behavioral testing showed a reduction in head withdrawal thresholds bilaterally from 30 min through 24 h following muscle inflammation. Thus upregulation of CGRP mRNA and iCGRP levels are temporally related to the development of inflammation and lowered pain thresholds. The present data support the hypothesis that CGRP is upregulated during deep tissue inflammation and suggest that gene transcription is involved in this upregulation.

Effects of continuous water flow on the swelling properties of polyelectrolyte hydrogels

We report the swelling behavior of a polyelectrolyte copolymer gel in water, which consists of poly(N-isopropylacrylamide) and sodium acrylate. The diameter of the cylindrical gels was measured at room temperature under a continuous flow of solvent water (equivalent to an infinite amount of water; open system). After a sufficient water flow, the diameter of the gel in the limited amount of water (closed system) was measured as a function of the temperature. The gel in the open system was found to shrink as a result of the continuous flow of water, and the gel in the closed system began to swell again at the phase transition point by increasing the temperature. The effects of the degree of initial ion exchange by the water flow on the macroscopic swelling behavior were discussed in terms of the exchange of counterions (the ion dissociation of carboxyl groups) and of the creation and destruction of intermolecular forces (hydrogen bonding). It was concluded that the amount of solvent water determines the environmental variables, such as the pH and ion concentration, which affects the swelling properties of polyelectrolyte hydrogels; intermediate re-swollen states can be observed in a closed system.

Ammonia induces the mitochondrial permeability transition in primary cultures of rat astrocytes

Ammonia is a toxin that has been strongly implicated in the pathogenesis of hepatic encephalopathy (HE), and the astrocyte appears to be the principal target of ammonia toxicity. The specific neurochemical mechanisms underlying HE, however, remain elusive. One of the suggested mechanisms for ammonia toxicity is impaired cellular bioenergetics. Because there is evidence that the mitochondrial permeability transition (MPT) is associated with mitochondrial dysfunction, we determined whether the MPT might be involved in the bioenergetic alterations related to ammonia toxicity. Accordingly, we examined the mitochondrial membrane potential (Deltapsi(m)) in cultured astrocytes and neurons using laser-scanning confocal microscopy after loading the cells with the voltage-sensitive dye JC-1. We found that ammonia induced a dissipation of the Deltapsi(m) in a time- and concentration-dependent manner. These findings were supported by flow cytometry using the voltage-sensitive dye tetramethylrhodamine ethyl ester (TMRE). Cyclosporin A, a specific inhibitor of the MPT, completely blocked the ammonia-induced dissipation of the Deltapsi(m). We also found an increase in the mitochondrial permeability to 2-deoxyglucose in astrocytes that had been exposed to 5 mM NH(4)Cl, further supporting the concept that ammonia induces the MPT in these cells. Pretreatment with methionine sulfoximine, an inhibitor of glutamine synthetase, blocked the ammonia-induced collapse of Deltapsi(m), suggesting a role of glutamine in this process. Over a 24-hr period, ammonia had no effect on the Deltapsi(m) in cultured neurons. Collectively, our data indicate that ammonia induces the MPT in cultured astrocytes, which may be a factor in the mitochondrial dysfunction associated with HE and other hyperammonemic states.

Nerve growth factor uses Ras/ERK and phosphatidylinositol 3-kinase cascades to up-regulate the N-methyl-D-aspartate receptor 1 promoter

We reported previously that nerve growth factor (NGF) up-regulates activity of the N-methyl-D-aspartate receptor 1 (NR1) promoter. We have explored the pathways and nuclear targets of NGF signaling in regulating the NR1 promoter. PD98059 and wortmannin, but not rapamycin, significantly attenuated NGF-induced transcriptional activity from an NR1 promoter-luciferase construct. Coexpressing constitutively active forms of Ras, Raf, or MAPK/ERK kinase 1 (MEK1) increased promoter activity dramatically. The MEK1-induced increase was largely prevented by mutations of the tandem GC boxes in the promoter. Promoter activity was also increased significantly by coexpressed GC box-binding proteins (Sp1, 3, or 4) in nonstimulated PC12 cells. Either an extracellular signal-regulated kinase-1 (ERK1)- or Sp1-specific antibody coprecipitated Sp1 with ERKs, and the coprecipitation was enhanced significantly by NGF treatment of PC12 cells. ERK2 also incorporated radioactivity of [gamma(32)P]ATP into recombinant Sp1. However, ERK2-treated Sp1 and PC12 nuclear extracts or nuclear extracts from NGF-treated cells exhibited reduced binding to the promoter or a consensus GC box. Our results suggest that NGF utilizes both the Ras/ERK and phosphatidylinositol 3-kinase pathways to up-regulate NR1 promoter activity and that Sp1 is a novel substrate of NGF-activated ERKs. NGF-increased NR1 promoter activity may involve a complicated mechanism of Sp1 phosphorylation and possible transcription factor exchange.

Ammonia-induced production of free radicals in primary cultures of rat astrocytes

Elevated levels of ammonia in blood and brain result in derangement of cerebral function. Recently, lipid peroxidation and oxidative stress have been implicated in ammonia neurotoxicity. Because ammonia is primarily detoxified in astrocytes, we postulated that pathophysiological concentrations of ammonia might induce free radical formation in these cells. To test this hypothesis, we examined the extent of free radical production in primary cultures of astrocytes that had been preloaded with the fluorescent dye 5- (and 6-)carboxy-2',7'-dichlorodihydrofluorescein diacetate (DCFDA). DCFDA fluorescence was found to be increased in a dose-dependent manner when astrocytes were exposed to 1, 5, and 10 mM NH(4)Cl. This phenomenon was transitory; it peaked at 2.5 min after exposure and declined subsequently. By 2 hr after treatment, DCFDA fluorescence was below control level. Addition of catalase or superoxide dismutase to 5 mM NH(4)Cl-treated astrocytes reduced free radical formation. Pretreatment with 3 mM methionine sulfoximine, an inhibitor of glutamine synthetase, also suppressed free radical formation by 5 mM NH(4)Cl. The results of this study suggest that elevated concentrations of ammonia induce the formation of free radicals in astrocytes and that this process is associated with the synthesis of glutamine. We propose that astrocyte-derived free radicals may be responsible for some of the pathophysiological changes associated with hyperammonemic conditions.

Role of placental tissues in the intrauterine transmission of hepatitis B virus

OBJECTIVE

The purpose of this study was to determine the mechanism of intrauterine transmission of hepatitis B virus.

STUDY DESIGN

Placental tissues from 158 pregnant women who tested positive for hepatitis B surface antigen were examined for hepatitis B virus markers, Fc gamma receptors, and hepatitis B surface antigen-anti-hepatitis B surface antigen in different layers of cells.

RESULTS

It was shown that the hepatitis B virus infection rate among different layers of placental cells gradually decreased from the maternal side to the fetal side. Furthermore, the closer the infected cell layer was to the fetal side, the higher the risk of intrauterine hepatitis B virus infection. Fc gamma receptors were found on cells of both hepatitis B surface antigen positive and negative placentas; Fc gamma receptors III were found on trophoblastic cells and villous mesenchymal cells, and Fc gamma receptors II were found on only villous mesenchymal cells. Hepatitis B surface antigen-antibodies to hepatitis B surface antigen was detected in the cytoplasm and on the membrane of trophoblastic cells and villous mesenchymal cells in 2 hepatitis B surface antigen-positive placentas.

CONCLUSION

The results support the hypothesis that intrauterine hepatitis B virus transmission could be caused through "cellular transfer" in the placenta. One of the means of cellular transfer could be through Fc gamma receptor III-mediated entry of hepatitis B surface antigen-antibodies to hepatitis B surface antigen into cells.

[A retrospective study on cholesteatoma otitis media coexisted with cholesterol granuloma]

OBJECTIVE

To investigate the etiology and pathogenesis of cholesteatoma otitis media accompanied by cholesterol granuloma and the relationship between cholesteatoma and cholesterol granuloma.

METHODS

Sixty three cases of middle ear cholesterol granuloma treated in our hospital during the period from March 1988 to May 2000 were retrospectively reviewed. All cases were verified by surgery and pathology. Fifteen cases of cholesteatoma coexisted with cholesterol granuloma were found among the 63 patients.

RESULTS

All fifteen cases had a long-term history of otitis media, such as otorrhea (sanguine purulent otorrhea and bloody otorrhea in 8 cases) and perforation of the ear drum (perforation of pars flaccida in 8 cases). Temporal bone CT scans showed cholesteatoma in 11 cases. All patients were treated surgically, and cholesteatoma and cholesterol granuloma were found coexisting alternatively, and the latter lied mainly in the tympanic antrum, attic and mastoid air cells. Chocolate-colored mucus was accumulated in well-developed mastoid air cells, and glistening dotty cholesterol crystals were also found. In most cases, enlarged aditus, destruction of lateral attic wall, erosion of ossicular chain, exposition of horizontal segment of facial nerve and tegmen of attic were found. Occlusion of Eustachian tube was found in 6 cases, and occlusion of tympanic isthmus was found in all cases. A post-operative dry ear was obtained, and hearing improved in all 12 cases following tympanoplasty.

CONCLUSIONS

Cholesteatoma and cholesteatoma granuloma in middle ear may share a common pathophysiological etiology, an occlusion of ventilation and a disturbance of drainage. The diagnosis should be considered when patients with chronic otitis media presented with bloody otorrhea. CT and magnetic resonance imaging(MRI) are useful for the diagnosis before operation. The surgical approach depends on the location, extension and severity of the lesion, and the principle of surgery is to clear the lesion and create an adequate drainage.

Basic calcium phosphate crystals up-regulate metalloproteinases but down-regulate tissue inhibitor of metalloproteinase-1 and -2 in human fibroblasts

OBJECTIVE

To examine the effect of basic calcium phosphate (BCP) crystals on expression of tissue inhibitors of metalloproteinases (TIMP)-1 and -2 in human fibroblasts.

METHOD

Using a semi-quantitative reverse transcription-polymerase chain reaction method and phosphocitrate (PC), a specific inhibitor of the biological effects of BCP crystals, we examined the effects of BCP on the steady state transcript levels of metalloproteinase (MMP)-1, -3, -9 and -13 and TIMP-1 and -2 in human fibroblasts. DNA primers against elongation factor were used as internal controls. RNAs isolated from human fibroblasts treated with BCP crystals (50 microg/ml) in the presence or absence of PC (10(-3) M) were used as templates, and RNA from untreated control cultures and cultures treated with Interleukin-1-beta (IL-1beta) were used as negative and positive controls, respectively.

RESULTS

We observed increases in MMP-1, -3, -9 and -13 transcripts by BCP crystals. BCP crystal down-regulated TIMP-1 and -2 over untreated controls. Western blot analysis confirmed that BCP crystals down-regulate the synthesis of TIMP-1 and -2. While IL-1beta up-regulated MMP-1, -3, -9 and -13, it had no significant effect on expression of either TIMP. In all cases, PC specifically reversed the differential regulation of MMPs and TIMPs by BCP crystals but had no effect on IL-1beta induction of MMP expression.

CONCLUSION

The ability of BCP to induce the synthesis of degradative MMPs while down-regulating the synthesis of the naturally occurring counterpart TIMPs may explain the changes consistent with a role of BCP crystal in the pathogenesis of degenerative changes in osteoarthritis. The ability of PC to reverse both degradative effects of BCP crystal suggests that PC can be a potential therapeutic agent for BCP crystal deposition diseases.

Biosurfactant-enhanced solubilization of NAPL mixtures

Remediation of nonaqueous phase liquids (NAPLs) by conventional pump-and-treat methods (i.e., water flushing) is generally considered to be ineffective due to low water solubilities of NAPLs and to mass-transfer constraints. Chemical flushing techniques, such as surfactant flushing, can greatly improve NAPL remediation primarily by increasing the apparent solubility of NAPL contaminants. NAPLs at hazardous waste sites are often complex mixtures. However, the equilibrium and nonequilibrium mass-transfer characteristics between NAPL mixtures and aqueous surfactant solutions are not well understood. This research investigates the equilibrium solubilization behavior of two- and three-component NAPL mixtures (containing akylbenzenes) in biosurfactant solutions. NAPL solubilization is found to be ideal in water (i.e., obeys Raoult's Law), while solubilization in biosurfactant solutions was observed to be nonideal. Specifically, the relatively hydrophobic compounds in the mixture experienced solubility enhancements that were greater than those predicted by ideal enhanced solubilization theory, while the solubility enhancements for the relatively hydrophilic compounds were less than predicted. The degree of nonideality is shown to be a nonlinear function of the NAPL-phase mole fraction. Empirical relationships based on the NAPL-phase mole fraction and/or micelle-aqueous partition coefficients measured in single-component NAPL systems are developed to estimate values for the multicomponent partition coefficients. Empirical relationships that incorporate both the NAPL-phase mole fraction and single-component partition coefficients yield much improved estimates for the multicomponent partition coefficient.

Nitric oxide inhibits a rise of ATP-introduced cytosolic free Ca2+ concentration and release from intracellular stored Ca2+

OBJECTIVE

The effects of ATP-introduced a rise in cytosolic free Ca2+ concentration and inhibition of nitric oxide were investigated.

METHOD

Measurement of free Ca2+ ([Ca2+]i) of cultured rat tail arterial smooth muscle cells using Fura-2/AM dual excitation wavelength spectrofluorometer.

RESULTS

There are two components of [Ca2+]i can be evoked by ATP. One part is Ca2+ entry from Ca2+ channel and formed a plateau. The another part is a peak that released from Ca2+ store. Both of them can be inhibited by NO.

CONCLUSION

The ATP induced [Ca2+]i rise that release Ca2+ from both Insp3 and ryanochine receptors and Ca2+ entry through calcium channels. The inhibition of NO on ATP induced [Ca2+]i rise that was mediated by cGMP.

[Study on hepatitis B virus infection status in placentas of hepatitis B surface antigen positive pregnant women during middle and late period of pregnancy]

OBJECTIVE

To investigate Hepatitis B Virus (HBV) infection status in placentas of Hepatitis B Surface Antigen (HBsAg) positive pregnant women during middle and late period of pregnancy.

METHODS

One hundred and sixty-seven placentas from HBsAg positive pregnant women were collected, including 158 term placentas and 9 aborted second-trimester placentas. HBsAg and hepatitis B core antibody (HBcAg) in placental cytotypes were detected by immunohistochemistry.

RESULTS

Of the 158 term placentas, HBV infection rates in decidual cells (DC), trophoblastic cells (TC), villous mesenchymal cells (VMC) and villous capillary endothelial cells (VCEC) were 66.46% (105/158), 58.23% (92/158), 27.22% (43/158) and 12.66% (20/158), respectively. The HBV infection rates gradually decreased from maternal side to fetal side of placentas. Both HBsAg and HBcAg were mainly located in the cytoplasm of infected cells. The positive cells were mostly in focal distribution. One out of 9 aborted second-trimester placentas was infected.

CONCLUSIONS

HBV infection was found in different cells of term placentas. The positive rates for HBsAg and HBcAg in placentas were gradually decreased from maternal side to fetal side. The positive rate was low in aborted second-trimester placentas.

Elevation of glutathione levels by ammonium ions in primary cultures of rat astrocytes

It is well established that ammonia is detoxified in the brain to form glutamine and that astrocytes play a major role in this process. The synthesis of glutamine requires glutamate and ATP. Since glutamate and ATP are also required for the synthesis of glutathione (GSH), we examined the effect of pathophysiological concentrations of ammonia on levels of GSH in primary cultures of astrocytes. GSH content in the medium increased in a dose- and time-dependent manner in the presence of ammonia. After an initial decrease, cellular GSH content increased in a similar manner. The levels of glutathione disulfide (GSSG) were also increased. A linear relationship was observed between ammonia concentration and the increase in GSH levels. An increase in the efflux of GSH from cells into medium was also observed under these conditions. Buthionine sulfoximine and acivicin, but not methionine sulfoximine, blocked the ammonia induced increase in GSH levels. No, or minor, changes in the activities of enzymes (gamma-glutamyl transpeptidase, GSH reductase and GSH-peroxidase) that might influence GSH levels were identified and thus could not account for the ammonia induced increase in GSH levels in astrocytes. These findings indicate that pathophysiological concentrations of ammonium ions result in increased astroglial levels of GSH which may affect the metabolism and function of astrocytes.

[Relation of pilots symptoms with some physiological parameters under vestibular stimulus]

OBJECTIVE

To investigate the relation of vestibular stimulus induced symptoms to electrogastrogram (EGG), electronystagmogram (ENG), acupoint potential (AP), skin temperature (ST) heart rate variability (HRV) and content of urine hormones.

METHOD

The physiological parameters were recorded before, during and after vestibular stimuli. Graybiel's scoring standard was used, and progressive regression analysis of symptoms and physiological parameters were made.

RESULT

The regression equations were obtained from data before, during and after the stimuli.

CONCLUSION

Three regression equations might be used.

Molecular basis of NMDA receptor-coupled ion channel modulation by S-nitrosylation

Several ion channels are thought to be directly modulated by nitric oxide (NO), but the molecular basis of this regulation is unclear. Here we show that the NMDA receptor (NMDAR)-associated ion channel was modulated not only by exogenous NO but also by endogenous NO. Site-directed mutagenesis identified a critical cysteine residue (Cys 399) on the NR2A subunit whose S-nitrosylation (NO+ transfer) under physiological conditions underlies this modulation. In cell systems expressing NMDARs with mutant NR2A subunits in which this single cysteine was replaced by an alanine, the effect of endogenous NO was lost. Thus endogenous S-nitrosylation can regulate ion channel activity.