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Biomedical subjects

L L Wang

Publications and source records attributed to L L Wang.

At least 37 records · Page 2Linked to original sources
PubMed2000

Enzymatic resolution of (S)-(+)-naproxen in a trapped aqueous-organic solvent biphase continuous reactor.

A trapped aqueous-organic biphase system for the continuous production of (S)-(+)-2-(6-methoxy-2-naphthyl) propionic acid (Naproxen) has been developed. The process consists of a stereoselective hydrolysis of the racemic Naproxen methyl ester by Candida rugosa lipase in a trapped aqueous-organic biphase system. The reaction has been carried out in a laboratory-scale continuous-flow stirred tank reactor (CSTR). The staring material has been supplied in and remaining substrate recovered by organic phase. YWG-C(6)H(5), a poorly polar synthetic support, has been employed to immobilize the lipase and to restrict the aqueous phase. Lipase immobilized on YWG-C(6)H(5) containing aqueous phase has been added into the CSTR to catalyze the hydrolysis. A dialysis membrane tube containing a continuous flow closed-loop buffer has been applied in the CSTR for the extraction of product and recruiting of the aqueous part consumed. Various reaction conditions have been studied. The activity of immobilized enzyme was effected by the polarity of support, the substrate concentration, logP value of organic phase and the product inhibition. At steady-state operating conditions, an initial conversion of 35% has been obtained. The CSTR was allowed to operate continuously for 60 days at 30 degrees C with a 30% loss of activity. The hydrolysis reaction yielded (S)-(+)-Naproxen with >90% enantiomeric excess and overall conversion of 30%.

Bioreactors↗
PubMed2000

Subcutaneous or oral administration of rhIL-11 modulated the contact hypersensitivity response.

Recombinant human interleukin 11 (rhIL-11) is a multifunctional cytokine with immunomodulatory activity on both T cells and macrophages. The effects of rhIL-11 in a murine model of contact hypersensitivity (CHS) response have been studied. The CHS response is a T cell-mediated response directed against chemically modified self-proteins following epidermal exposure to haptens. CHS is generated in two phases. The sensitization phase involves dermal dendritic cell recognition of haptenized proteins and antigen presentation. The effector phase involves T cell recognition and activation. In mice sensitized with oxazolone, CHS was induced by secondary challenge to the right ear and measured by ear swelling 24 h later. rhIL-11 significantly suppressed CHS as measured by ear swelling and tissue myeloperoxidase activity when injected subcutaneously for 5 days from the day of sensitization or when administered only on the day before and the day of challenge, but was not effective when administered prior to or on the day of sensitization. These results indicate that subcutaneously administered rhIL-11 may modulate the effector phase of CHS. Administration of rhIL-11 as an oral gavage prior to sensitization also reduced CHS. However oral administration of rhIL-11 after sensitization had no effect. These results suggest that orally and subcutaneously administered rhIL-11 may act through different mechanisms to affect CHS.

Administration, Oral↗
PubMed2000

[Enzymatic resolution of racemic naproxen in a low aqueous-organic biphase system].

A stereoselective hydrolysis of the racemic naproxen methyl ester by immobilized lipase from Candida rugosa in a low aqueous-organic biphase system was studied. Support polar, water content, the logP value of organic phase and product inhibition effected the activity of immobilized enzyme. According to these reaction conditions, a low aqueous-organic biphase system for the continuous production of (S)-(+)-Naproxen was developed. The reaction was carried out in a continuous-flow closed-loop 50 mL stirred bioreactor packed with YWG-C6H5, a poorly polar synthetic support on which the lipase had been immobilized by adsorption. The aqueous phase was permanently remained in the reactor associated with the immobilized enzyme particles; the organic phase containing substrate was pumped through this reactor and emerged with the products. The continous-flow stirred bioreactor containing 75 mg lipase was allowed to operate continuously for 60 days at 30 degrees C with a 25% loss of activity, 900 mg of (S)-(+)-Naproxen (eep 95%) were producted.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2000

[Studies of transgenic tobacco plants expressing beta-1,3-glucanase and chitinase genes and their potential for fungal resistance].

Plant bivalent expression vector pBLGC for basic tobacco beta-1, 3-glucanase and bean chitinase genes were constructed, and the tobacco tissue was transformed. Transgenic tobacco plants were carried out for analysis by PCR, PCR-Southern blot, Dot blot, Western blot, etc., and the results showed that some transgenic plants gave strong positive signal, it suggested that foreign genes have been integrated into tobacco genome, and expressed correctly. Fungal challenge with Alternaria alternata showed that transgenic plants were much more resistant to this pathogenic fungus.

Chitinases↗
PubMed2000

Changes of transforming growth factor beta 1 in rat periodontal tissue during orthodontic tooth movement.

OBJECTIVE: To investigate the distribution and change of transforming growth factor beta 1 (TGF-beta 1) in rat periodontal tissue and understand the role of TGF-beta 1 in orthodontic tooth movement. METHODS: Force was applied on right maxillary first molars in rats, followed by the examination of the decalcified alveolodental connected tissue in different stages of tooth movement. An immunohistochemical staining technique (SP method) was used for this examination. RESULTS: TGF-beta 1 exists in normal periodontal tissue. The expression of it in periodontium increases during orthodontic tooth movement. From 5 to 10 days after applying force, the expression at the tension site was significantly greater than that at the pressure site. CONCLUSIONS: Changes in TGF-beta 1 levels play an important role in the remodeling of periodontal tissue during orthodontic tooth movement, and can powerfully promote bone formation.

Alveolar Process↗
PubMed2000

Effects of MN-9202 on platelet aggregation, 5-HT release, TXB2 synthesis, and calcium mobilization in rabbit platelets in vitro.

AIM: To study the effects of MN-9202, a new effective Ca2+ channel blocker, on platelet aggregation, 5-HT and TXB2 release, and calcium transport induced by platelet activators. METHODS: The mobilization of cytosolic-free calcium induced by thrombin in washed platelets was observed by Ca(2+)-sensitive fluorescent indicator, Fura-2 AM and time scan measurement. Aggregation induced by ADP and thrombin in rabbits citrate platelet-rich plasma (PRP) was measured by aggregometer. 5-HT and TXB2 were assayed by HPLC/ECD and RIA, respectively. RESULTS: MN-9202 inhibited platelet aggregation induced by ADP and thrombin in a concentration-dependent manner. MN-9202 1 mumol.L-1 inhibited release of 5-HT in PRP induced by collagen at 15 mg.L-1 (113 +/- 15 vs 178 +/- 18, P < 0.05), however, MN-9202 did not have effect on 5-HT secreted by high dose of collagen. MN-9202 0.1 and 1 mumol.L-1 blocked extracellular calcium influx and sarcoplasmic calcium release, and the suppression on extracellular calcium influx was more obvious. Furthermore, treatment with MN-9202 0.01, 0.1, and 1 mumol.L-1 markedly decreased ADP-induced TXB2 (pg/10(8) platelet) release from PRP (906 +/- 200, 881 +/- 131, and 793 +/- 169 vs 1264 +/- 202, P < 0.01). CONCLUSION: MN-9202 acts as an effective Ca2+ antagonist and blocks platelet activation by inhibiting platelet Ca2+ influx and arachidonic acid metabolism.

Animals↗
PubMed2000

[Effects of modified SD therapy on Bell's palsy].

OBJECTIVE: To investigate the effects of a modified SD therapy (intravenous high dose hydrocortisone and low molecular dextran) on Bell's palsy(BP), and to avoid the severe side-effects such as hepatic and renal disorders during the treatment. METHOD: Seventy-one BP patients were treated with modified SD method (modified group), thirty-two BP patients took prednisone (control group), and the curative rates of two therapies were compared, in the meanwhile recorded the side effects in detail. RESULT: Curative rate in modified group was 95.8% (House-Brakmsnn I-II) and in control group was 81.2% (P < 0.05). In modified group, the curative rate (I grade) in the patients were treated within 24 hours following onset was 75.0%, and the curative rate in other three subgroups were treated within 24-48 hours, 2-3 day and 3-5 day following onset was 43.8%, 26.7%, 18.8% respectively. Modified group had not shown hepatic and renal disorders or gastric ulcer. CONCLUSION: Modified SD method may increase recoverable rate and can avoid significant side effects for BP, and emphasizes the importance of the administration of SD therapy in the early stage of the disease.

Adult↗
PubMed1999

Leptin immunoreactivity in the central nervous system in normal and diabetic rats.

An anti-leptin polyclonal antiserum was used to detect leptin-immunoreactivity (-ir) in the central nervous system in rats. Leptin-ir was found in perikaryon and processes of neurons in the hypothalamus, including the paraventricular nucleus, and in several regions in the brainstem, including the nucleus of the solitary tract. In streptozotocin-treated diabetic rats, leptin-ir was dramatically attenuated only in the hypothalamus, and was restored by insulin treatment. Our findings that removal or restoration of systemic insulin regulates hypothalamic leptin-ir suggests that the leptin-ir observed in the brain is sensitive to peripheral hormone status. The presence of insulin-regulated leptin in the hypothalamus reveals a new avenue of research on the central actions of leptin in regulating energy balance and metabolism.

Animals↗
PubMed1999

Specificity of the SH2 domains of SHP-1 in the interaction with the immunoreceptor tyrosine-based inhibitory motif-bearing receptor gp49B.

Inhibitory receptors on hemopoietic cells critically regulate cellular function. Despite their expression on a variety of cell types, these inhibitory receptors signal through a common mechanism involving tyrosine phosphorylation of the immunoreceptor tyrosine-based inhibitory motif (ITIM), which engages Src homology 2 (SH2) domain-containing cytoplasmic tyrosine or inositol phosphatases. In this study, we have investigated the proximal signal-transduction pathway of an ITIM-bearing receptor, gp49B, a member of a newly described family of murine NK and mast cell receptors. We demonstrate that the tyrosine residues within the ITIMs are phosphorylated and serve for the association and activation of the cytoplasmic tyrosine phosphatase SHP-1. Furthermore, we demonstrate a physiologic association between gp49B and SHP-1 by coimmunoprecipitation studies from NK cells. To address the mechanism of binding between gp49B and SHP-1, binding studies involving glutathione S-transferase SHP-1 mutants were performed. Utilizing the tandem SH2 domains of SHP-1, we show that either SH2 domain can interact with phosphorylated gp49B. Full-length SHP-1, with an inactivated amino SH2 domain, also retained gp49B binding. However, binding to gp49B was disrupted by inactivation of the carboxyl SH2 domain of full-length SHP-1, suggesting that in the presence of the phosphatase domain, the carboxyl SH2 domain is required for the recruitment of phosphorylated gp49B. Thus, gp49B signaling involves SHP-1, and this association is dependent on tyrosine phosphorylation of the gp49B ITIMs, and an intact SHP-1 carboxyl SH2 domain.

Amino Acid Sequence↗
PubMed1999

[Microdissection of M chromosome in Vicia faba and its library construction].

Microdissection and microcloning technique was employed to construct the library of M chromosome in Vicia faba. The M chromosomes were microdissected with a micromanipulator and were put into a 0.5 ml Eppendorf tube, then digested with Sau3A. Sau3A linker adaptors were ligated to the end of chromosome DNA fragments, and two rounds of PCR were carried out with one chain of linker adaptor as the primer. The PCR products ranged in size from 300 base pair (bp) to 3000 bp with predominant fragments from 500 bp to 1500 bp. Southern hybridization analysis confirmed that PCR products originated from Vicia faba genome. The second round PCR products were cloned and about 102,000 recombinants were obtained. 118 recombinants were selected randomly for analysis. The inserts ranged in size from 150 bp to 3000 bp with an average of 690 bp. Dot blot was carried out for 100 clones with DIG labeled Vicia faba genome DNA as probes. The result revealed that 51% were low and unique copy sequences, 49% were repetitive sequences. M chromosome DNA library has not been reported before.

Chromosome Mapping↗
PubMed1997

Mouse natural killer cells express gp49B1, a structural homologue of human killer inhibitory receptors.

NK cells express MHC class I-specific receptors that inhibit tumor killing. In mice, these receptors belong to the highly polymorphic Ly-49 family, which are type II integral membrane proteins homologous to C-type lectins. In contrast, human killer inhibitory receptors (KIR) are type I transmembrane proteins that display minimal allelism and belong to the Ig superfamily. These structural differences suggested that each species evolved distinct receptors to subserve the same function. In this report, however, we show that mouse NK and LAK cells and NK cell clones express full-length transcripts for gp49B1, an immunoreceptor tyrosine-based inhibitory motif (ITIM)-containing type I transmembrane protein belonging to the Ig superfamily, and displaying minimal allelism by Southern and sequence analysis. By flow cytometry, gp49B1 is expressed on all NK cells. Therefore, we have established that gp49B1, a structural homologue of human KIR, is expressed on mouse NK cells. This strongly suggests that NK cells express two structurally distinct types of inhibitory receptors and that these receptors may act as coreceptors in mediating inhibition.

Animals↗
PubMed1997

Identification, characterization, and developmental regulation of Chlamydia trachomatis 3-deoxy-D-manno-octulosonate (KDO)-8-phosphate synthetase and CMP-KDO synthetase.

The kdsA and kdsB genes from Chlamydia trachomatis encoding 3-deoxy-D-manno-octulosonate (KDO)-8-phosphate synthetase and CMP-KDO synthetase were identified by functional complementation of temperature-sensitive Salmonella typhimurium mutants, homology to known KDO-8-phosphate synthetase and CMP-KDO synthetase proteins, and in vitro enzyme activity. The kdsA gene was transcribed as part of a polycistronic mRNA with two downstream open reading frames (ORFs). One of these ORFs appeared to encode a membrane-anchored protein, while the second encoded a protein showing homology to the ATP-binding component of periplasmic binding protein-dependent ABC transporters. Transcription of kdsA and kdsB in C. trachomatis was evident within 4 h of initiation of the C. trachomatis infection process and continued throughout the chlamydial life cycle.

Aldehyde-Lyases↗
PubMed1996

A single point mutation in CTP synthetase of Chlamydia trachomatis confers resistance to cyclopentenyl cytosine.

A Chlamydia trachomatis strain (L2/CPEC) resistant to the cytotoxic effects of cyclopentenyl cytosine (CPEC) was isolated by a stepwise selection procedure. This strain showed an approximate 350-fold increase in resistance to CPEC. Sequencing of the gene encoding CTP synthetase from this resistant strain revealed a single point mutation, resulting in a change of amino acid 149 from Asp to Glu. This appeared to be the only mutation in L2/CPEC, because no changes in CTP transport, CTP synthetase expression, or incorporation of CPEC into DNA or RNA could be detected. The mutation in the chlamydial CTP synthetase resulted in a loss of CTP feedback inhibition. This was demonstrated both in vivo using Escherichia coli cells carrying the cloned gene, and an in vitro assay using partially purified preparations of CTP synthetase. As a result of the loss of feedback inhibition, E. coli cells carrying the CPECR CTP synthetase showed a 22-fold increase in their CTP pools. However, examination of the CTP pools of L2/CPEC revealed no change in CTP levels when compared with wild type C. trachomatis.

Amino Acid Sequence↗
PubMed1995

P62 association with RNA is regulated by tyrosine phosphorylation.

The ras-GAP associated protein, p62, is a major tyrosine phosphoprotein in transformed and growth factor treated cells. Although its exact function is not known, it can bind directly to src-family tyrosine kinases and has been implicated as a linker protein bridging activated src family tyrosine kinases with downstream effectors. One novel feature of p62, revealed by its predicted amino acid sequence, is the presence of an RNA-binding region, the KH domain. As p62 becomes tyrosine phosphorylated when src-kinases become activated, we compared the RNA binding ability of p62 in both its phosphorylated and unphosphorylated state. The ability of p62 to bind RNA was severely impaired when p62 was tyrosine phosphorylated. This suggests that the ability of p62 to bind RNA is regulated by tyrosine phosphorylation and implicates the regulation of RNA as a component of tyrosine kinase signaling pathways.

Base Sequence↗
PubMed1995

Acid adaptation of Escherichia coli O157:H7 increases survival in acidic foods.

Escherichia coli O157:H7 was adapted to acid by culturing for one to two doublings at pH 5.0. Acid-adapted cells had an increased resistance to lactic acid, survived better than nonadapted cells during a sausage fermentation, and showed enhanced survival in shredded dry salami (pH 5.0) and apple cider (pH 3.4). Acid adaptation is important for the survival of E. coli O157:H7 in acidic foods and should be considered a prerequisite for inocula used in food challenge studies.

Acids↗
PubMed1995

Prevalence of primary Sjögren's syndrome in China.

OBJECTIVE: To determine the prevalence rate of primary Sjögren's syndrome (SS) in a community population of 2066 adults in a Beijing suburban village, and 100 inpatients, who were not necessarily admitted for rheumatic diseases. METHODS: Questionnaire and serological studies of antinuclear antibodies, rheumatoid factor, and anti-SSA, anti-SSB antibodies were done. Possible positive subjects were given eye and oral examinations for objective evidence of xerostomia and keratoconjunctivitis sicca. RESULTS: According to the Copenhagen criteria, the prevalence rate of primary Sjögren's syndrome in China was 0.77%, and it was 0.33% by modified San Diego criteria. In 100 inpatients, we found 4 cases of primary Sjögren's syndrome by Copenhagen criteria, and one case by modified San Diego criteria. CONCLUSION: Primary Sjögren's syndrome is not a rare disease in China, but most cases are overlooked or misdiagnosed.

Adolescent↗
PubMed1994

Characterization of trimethoprim- and sulphisoxazole-resistant Chlamydia trachomatis.

Trimethoprim and sulphisoxazole were used as selective agents in culture to isolate, by a stepwise procedure, a series of Chlamydia trachomatis L2 populations resistant to the cytotoxic effects of the drugs. Two trimethoprim-resistant populations, L2TriR-60 and L2TriR-100, and one sulphonamide-resistant population, L2SulfR-100, were characterized in more detail. In addition to being resistant to trimethoprim, L2TriR-60 was cross-resistant to methotrexate, sensitive to sulphisoxazole and displayed a ribonucleotide auxotrophy similar to that of its parental wild type, C. trachomatis L2. Surprisingly, L2TriR-100 and L2SulfR-100 appeared phenotypically identical. Both mutants were highly resistant to trimethoprim, sulphisoxazole, and methotrexate. In contrast to wild-type C. trachomatis L2, these populations were sensitive to 5-fluorouracil. L2TriR-100 and L2SulfR-100 were incapable of taking pyrimidine ribonucleotides from the host cell and no longer synthesized thymidine nucleotides de novo. The pyrimidine requirement of these mutants was met by salvaging host-cell uracil and thymidine, a property which can account for their drug-resistant characteristics. L2TriR-100 and L2SulfR-100 could also salvage adenine and guanine. Using L2TriR-100 as a starting stock, a mutant population resistant to the cytotoxic effects of trimethoprim and 5-fluorouracil (L2Tri/5-FU) was selected. L2Tri/5-FU was resistant to 5-fluorouracil because it had regained the capacity to take pyrimidine ribonucleotides from the host cell.

Adenosine Triphosphate↗