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Biomedical subjects

D Shen

Publications and source records attributed to D Shen.

At least 19 recordsLinked to original sources
PubMed2006

Past adult lead exposure is linked to neurodegeneration measured by brain MRI.

OBJECTIVE: To determine whether cumulative lead dose in former organolead workers was associated with MRI measures of white matter lesions (WML) and global and structure-specific brain volumes. METHODS: MRIs, tibia lead, and other measures were obtained from 532 former organolead workers with a mean age of 56 years and a mean of 18 years since last occupational exposure to lead. Cumulative lead dose was measured by tibia lead, obtained by X-ray fluorescence, and expressed as microg lead per gram of bone mineral (microg Pb/g). WML were evaluated using the Cardiovascular Health Study grading scale. A total of 21 global and specific brain regions were evaluated. RESULTS: A total of 36% of individuals had WML grade of 1 to 7 (0 to 9 scale). Increasing peak tibia lead was associated with increasing WML grade (p = 0.004). The adjusted OR for a 1 microg Pb/g increase in tibia lead was 1.042 (95% CI = 1.021, 1.063) for a CHS grade of 5+ (> or = 5 vs < 5). In linear regression, the coefficient for tibia lead was negative for associations with all structures. Higher tibia lead was significantly related to smaller total brain volume, frontal and total gray matter volume, and parietal white matter volume. Of nine smaller specific regions of interest, higher tibia lead was associated with smaller volumes for the cingulate gyrus and insula. CONCLUSIONS: These data suggest that cumulative lead dose is associated with persistent brain lesions, and may explain previous findings of a progressive decline in cognitive function.

Adult↗
PubMed2006

Virus-induced chalazion.

PURPOSE: To investigate a viral etiology in certain chalazia. METHODS: A prospective study over 7.5 years of all newly presenting chalazia associated with diffuse follicular conjunctivitis but without any other aetiological factors. Patients were investigated for ocular or systemic infections by history, physical exam, slit-lamp exam, and/or histology of conjunctival biopsy (including transmission electron microscopy). RESULTS: A total of 27 patients developed follicular conjunctivitis without meibomian gland dysfunction, blepharitis, or sexually transmitted diseases. Evidence for a viral aetiology included: recent systemic viral illness (15/27), recent contact with subjects with chalazia or follicular conjunctivitis (5/27), preauricular lymphadenopathy (4/27), viral corneal disease (4/27), or viral particles by ultrastructure (4/4). CONCLUSIONS: Chalazia may be associated with viral conjunctivitis. Intralesional corticosteroids should be considered with great caution for viral-induced chalazia.

Adolescent↗
PubMed2006

Rice endophyte Pantoea agglomerans YS19 promotes host plant growth and affects allocations of host photosynthates.

AIMS: The aims of the study were to identify the effects of rice endophyte Pantoea agglomerans YS19 on host plant growth and allocations of photosynthates. METHODS AND RESULTS: Endophytic diazotrophic YS19 showed nitrogen-fixing activity in N-free medium, and produced four categories of phytohormones which were indole-3-acetic acid, abscisic acid, gibberellic acid and cytokinin in Luria-Bertani medium. Inoculation of YS19 improved the biomass of the 12-day-cultivated host rice seedlings by 63.4% on N-free medium or by 18.7% on N-supplemented medium. Spraying of YS19 cell culture onto the rice plants at the premilk stage enhanced the transportation of the photosynthetic assimilation product from the source (flag leaves) to the sink (stachys) significantly. The formation of the plant sink was obviously inhibited when YS19 cell culture was applied at the late milk stage. CONCLUSIONS: This research suggests that endophyte YS19 promotes host rice plant growth and affects allocations of host photosynthates. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings suggested that YS19 possesses the potential for increasing rice production in field application. Meanwhile, a suitable plant growth stage must be selected for the foliar spraying of YS19 cell culture.

Biomass↗
PubMed2004

Dissemination of CTX-M type beta-lactamases in Enterobacteriaceae isolates in the People's Republic of China.

Previously there have been a number of reports of extended spectrum beta-lactamase (ESBL) producing isolates of the family Enterobacteriaceae in Asia. We first reported the occurrence of bla(CTX-M) in Guangzhou, China, subsequently there have been reports of bla(CTX-M) from a number of other south Asian countries. Initial surveillance study data suggested that bla(CTX-M) might be widely distributed in China. This study examines the type of bla(CTX-M) occurring in other major population centres in China. Initial disk diffusion method susceptibility testing (NCCLS) selected ESBL producing Escherichia coli and Klebsiella pneumoniae isolates from Beijing and near Wuhan, PRC. After screening in both China and the UK, 13 isolates producing CTX-M ESBLs were identified and studied, 11 also produced TEM-1, and 4 also produced SHV-1. Sequence analysis of the bla(CTX-M) containing isolates revealed these isolates contained two different bla(CTX-M), three with bla(CTX-M-3) and 10 with bla(CTX-M-14). After comparison with other previously published studies in the English language, we conclude that the most prevalent bla(CTX-M) so far reported in Asia are bla(CTX-M-14) and bla(CTX-M-3).

Anti-Bacterial Agents↗
PubMed2003

Superinfection of Laodelphax striatellus with Wolbachia from Drosophila simulans.

Wolbachia are maternally inherited, intracellular alpha-proteobacteria that infect a wide range of arthropods. They manipulate the reproduction of hosts to facilitate their spread into host populations, through ways such as cytoplasmic incompatibility (CI), parthenogenesis, feminization and male killing. The influence of Wolbachia infection on host populations has attracted considerable interest in their possible role in speciation and as a potential agent of biological control. In this study, we used both microinjection and nested PCR to show that the Wolbachia naturally infecting Drosophila simulans can be transferred into a naturally Wolbachia-infected strain of the small brown planthopper Laodelphax striatellus, with up to 30% superinfection frequency in the F(12) generation. The superinfected males of L. striatellus showed unidirectional CI when mated with the original single-infected females, while superinfected females of L. striatellus were compatible with superinfected or single-infected males. These results are, to our knowledge, the first to establish a superinfected horizontal transfer route for Wolbachia between phylogenetically distant insects. The segregation of Wolbachia from superinfected L. striatellus was observed during the spreading process, which suggests that Wolbachia could adapt to a phylogenetically distant host with increased infection frequency in the new host population; however, it would take a long time to establish a high-frequency superinfection line. This study implies a novel way to generate insect lines capable of driving desired genes into Wolbachia-infected populations to start population replacement.

Animals↗
PubMed2002

Biocatalytic preparation of enantiopure ( R)-ketoprofen from its racemic ester by a new yeast isolate Citeromyces matriensis CGMCC 0573.

The yeast strain CGMCC 0573 was identified as Citeromyces matriensis and shown to be capable of enantioselectively hydrolyzing ethyl ester of ( R)-Ketoprofen (2-(3-benzoylphenyl)propionic acid). The strain was isolated for the first time from soil samples through a new and efficient screening procedure in which the probability of obtaining active strains was greatly increased by using ethanol and Tween-80 alternatively as additives during the enrichment culture. Studies of the culture conditions and catalytic performance of Citeromyces matriensis CGMCC 0573 showed that the enzyme occurs constitutively in the cells and its production is enhanced by feeding with Tween-80 during the early period of cultivation. Yeast extract was found to be beneficial both for growth and for esterase production. The optimal temperature and pH for the bioconversion were 40 degrees C and pH 8.0, respectively. Biotransformation using resting cells cultured in a flask with baffles and magnetic stirring and in the presence of 50 mM substrate resulted in the production of ( R)-ketoprofen at 93% ee (enantiomeric excess) and at 42.6% conversion.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

[Electric pulse mediated high efficient gene transfer].

OBJECTIVE: To study gene transfer mediated by electric pulse and optimize the parameters of electric pulse in vivo. METHODS: 10 micrograms plasmid pcD2/LacZ was injected into the quadriceps of 220 Kunming mice. One to two minutes after the DNA injection electric pulse with different parameters was given to the injection site. Three days after, activity of beta-galactosidase was measured, and the expression of Laz2 gene in muscle was determined by histochemical staining. RESULTS: The activity of beta-galactosidase in electric pulse group (131.6 U/mg +/- 86.6 U/mg protein) was 30 fold higher than that in direct injection group (4.9 U/mg +/- 1.0 U/mg protein) (P < 0.05). Histochemical analysis of muscles injected with a LacZ expression plasmid also showed that in vivo electric pulse increased both the number of positively stained muscle fibers and the density of staining. When the electric pulse was with the parameters of 200 V/cm, 40 ms, 6 pulses and 1HZ, maximal gene expression was achieved. CONCLUSION: Electric pulse, with optimal parameters, increases gene expression. Electric pulse makes much more gene expression than mere intramuscular DNA injection.

Animals↗
PubMed2001

Cloning, molecular characterization, and application of rice epiphytic Bacillus pumilus promoter fragments.

To establish a constitutive, high-efficiency expression system for Bacillus pumilus (B.P), we cloned random chromosomal DNA into promoter probe shuttle vector ECE7 and selected for strong promoter activity by chloramphenicol resistance of transformed B. pumilus cells. The nucleotide sequences of nine chromosomal fragments were determined. These DNA fragments range from 300 to 2200 bp in size. The transcription strength of these promoters was estimated by determination of CAT enzyme production in both E. coli and B. pumilus. Transcription start (TS) sites of the cat mRNA were located by primer extension by using total RNA. Preliminary analysis showed that three of the promoter sequences contain -35 and -10 regions like E. coli RNA polymerase sigma70 and B. subtilis sigma43 consensus sequences. One is similar to B. subtilis sigma29, the other two have no conserved sequences like any of the typical consensus sequences of the known sigma factors so far. To estimate the feasibility of the utilization of these promoters, one promoter fragment was subcloned and used to drive the expression of green fluorescent protein (GFP) in B. pumilus cells. This is the first report of B. pumilus promoters randomly cloning from total DNA and molecular analysis of their consensus sequences.

Bacillus↗
PubMed2001

Conjunctival T-cell lymphoma caused by human T-cell lymphotrophic virus infection.

PURPOSE: To examine the cause of adult T-cell leukemia/lymphoma. METHODS: We examined a conjunctival biopsy from a 29-year-old Jamaican man who developed bilateral conjunctival masses. Adult T-cell leukemia/lymphoma was diagnosed using routine histology, immunohistochemistry, electron microscopy, microdissection, and the polymerase chain reaction. RESULTS: Histopathologic examination revealed a conjunctival lymphoma. Clonality of the T-cell receptor gamma gene and human T-cell lymphotrophic virus gag gene were detected in the malignant cells. The demonstration of the human T-cell lymphotrophic virus gene and the rearrangement of the T-cell receptor gene in this neoplasm provide proof that human T-cell lymphotrophic virus is the cause of this conjunctival T-cell lymphoma. CONCLUSION: Human T-cell lymphotrophic virus is the cause of adult T-cell leukemia/lymphoma, an aggressive malignancy of CD4+ lymphocytes.

Adult↗
PubMed2001

Characterization of extended spectrum beta-lactamase-producing Klebsiella pneumoniae from Beijing, China.

Fourteen clinical isolates of Klebsiella pneumoniae with extended-spectrum beta-lactamases (ESBLs) were detected by the double disk synergy test and the Etest ESBL strip. Co-resistances included high MICs for aminoglycosides, fluoroquinolones, tetracyclines, and trimethoprim/sulphamethoxazole. Co-resistance was not observed in five of the 14 strains. These isolates were all genetically distinct as determined by the automated ribotyping method. Isoelectric focusing documented the presence of multiple beta-lactamases (one to four per isolate) with pIs ranging from 5.4 to 8.4. The majority of isolates contained beta-lactamases with pI values of 7.6 and 8.4 consistent with SHV-type ESBLs and an Amp C enzyme, respectively. Emerging ESBL strains in K. pneumoniae compromise the use of agents such as cefotaxime, ceftriaxone, ceftazidime in China; leading to the expansion of quality infection control practices and formulary management programmes to minimize clonal expansion.

Anti-Bacterial Agents↗
PubMed2001

A photic visual cycle of rhodopsin regeneration is dependent on Rgr.

During visual excitation, rhodopsin undergoes photoactivation and bleaches to opsin and all-trans-retinal. To regenerate rhodopsin and maintain normal visual sensitivity, the all-trans isomer must be metabolized and reisomerized to produce the chromophore 11-cis-retinal in biochemical steps that constitute the visual cycle and involve the retinal pigment epithelium (RPE; refs. 3-8). A key step in the visual cycle is isomerization of an all-trans retinoid to 11-cis-retinol in the RPE (refs. 9-11). It could be that the retinochrome-like opsins, peropsin, or the retinal G protein-coupled receptor (RGR) opsin12-16 are isomerases in the RPE. In contrast to visual pigments, RGR is bound predominantly to endogenous all-trans-retinal, and irradiation of RGR in vitro results in stereospecific conversion of the bound all-trans isomer to 11-cis-retinal. Here we show that RGR is involved in the formation of 11-cis-retinal in mice and functions in a light-dependent pathway of the rod visual cycle. Mutations in the human gene encoding RGR are associated with retinitis pigmentosa.

Animals↗
PubMed2001

An adaptive-focus statistical shape model for segmentation and shape modeling of 3-D brain structures.

This paper presents a deformable model for automatically segmenting brain structures from volumetric magnetic resonance (MR) images and obtaining point correspondences, using geometric and statistical information in a hierarchical scheme. Geometric information is embedded into the model via a set of affine-invariant attribute vectors, each of which characterizes the geometric structure around a point of the model from a local to a global scale. The attribute vectors, in conjunction with the deformation mechanism of the model, warranty that the model not only deforms to nearby edges, as is customary in most deformable surface models, but also that it determines point correspondences based on geometric similarity at different scales. The proposed model is adaptive in that it initially focuses on the most reliable structures of interest, and gradually shifts focus to other structures as those become closer to their respective targets and, therefore, more reliable. The proposed techniques have been used to segment boundaries of the ventricles, the caudate nucleus, and the lenticular nucleus from volumetric MR images.

Brain↗
PubMed2001

A framework for predictive modeling of anatomical deformations.

A framework for modeling and predicting anatomical deformations is presented, and tested on simulated images. Although a variety of deformations can be modeled in this framework, emphasis is placed on surgical planning, and particularly on modeling and predicting changes of anatomy between preoperative and intraoperative positions, as well as on deformations induced by tumor growth. Two methods are examined. The first is purely shape-based and utilizes the principal modes of co-variation between anatomy and deformation in order to statistically represent deformability. When a patient's anatomy is available, it is used in conjunction with the statistical model to predict the way in which the anatomy will/can deform. The second method is related, and it uses the statistical model in conjunction with a biomechanical model of anatomical deformation. It examines the principal modes of co-variation between shape and forces, with the latter driving the biomechanical model, and thus predicting deformation. Results are shown on simulated images, demonstrating that systematic deformations, such as those resulting from change in position or from tumor growth, can be estimated very well using these models. Estimation accuracy will depend on the application, and particularly on how systematic a deformation of interest is.

Biomechanical Phenomena↗
PubMed2001

Monoclonal antibodies: a new era in the treatment of non-Hodgkin's lymphoma.

Monoclonal antibodies (MAbs) have been used as therapeutic agents for many years. In 1997, Rituxan (IDEC-C2B8, rituximab, MabThera) became the first MAb to be approved by the FDA for a cancer indication. Rituxan served to heighten interest in the therapeutic applications of MAbs. Herceptin (for patients with breast cancer) and Mylotarg (for patients with acute myeloid leukemia) were approved shortly thereafter. Literally dozens of antibodies are currently under investigation for a variety of malignant and non-neoplastic indications. Rituxan is effective in patients with low-grade or follicular, relapsed or refractory non-Hodgkin's lymphoma (NHL). The response rate and time to progression (responders) are in the 50% and 13 months range, respectively. It is also active in intermediate-grade NHL where a large randomized study, in combination with CHOP chemotherapy, has shown a statistically significant increase in complete response (CR) rate (75% vs. 60%), prolongation of 1 year event-free survival (69% vs. 49%) and of overall survival (83% vs. 68%) as compared to CHOP alone. This marks the first time that any agent has shown results superior to CHOP, the curative gold standard for this type of NHL. Other promising antibodies under clinical investigation include: Hu1D10; Anti CD19, 22, 52, and anti-Id antibodies. The safety profile, clinical activity, and mechanism of action of these MAbs make them ideal candidates for combination with chemotherapy or biologicals. Over the next few years, we will see very significant therapeutic advances emerge as this important research yields additional clinical results.

Antibodies, Monoclonal↗
PubMed2001

Isolation of an esterase-producing Trichosporon brassicae and its catalytic performance in kinetic resolution of ketoprofen.

A yeast strain CGMCC 0574, identified as Trichosporon brassicae, was selected from 92 strains for its high (S) selectivity in the hydrolysis of ketoprofen ethyl ester. The effective strains of the microorganisms were isolated from soil samples with the ester as the sole carbon source. The ethyl ester proved to be the best substrate for resolution of ketoprofen among several ketoprofen esters examined. The resting cells of CGMCC 0574 could catalyze the hydrolysis of ketoprofen ethyl ester with an enantiomeric ratio of 44.9, giving (S)-ketoprofen an enantiomeric excess of 91.5% at 42% conversion.

Esterases↗
PubMed2001

[Bioreactor-landfill site for leaching solution treatment].

The study utilizes the system combined bioreactor with landfill site to treat leachate. The results show that the system helped the degradation of the organic pollutants in the leachate to be divided into two-phases, the hydrolytic fermentation and acid-production phases mainly occurred in the landfill site, the acidification rate was 40%-50%, the methane-production chiefly occurred in the bioreactor(UASB). It treated the leachate significantly and benefits the collection and utilization of methane gas. Also, the system accelerates the process of degrading municipal solid waste and stabilizing landfill site.

Bioreactors↗