Biomedical subjects

C Shen

Publications and source records attributed to C Shen.

At least 37 records · Page 2Linked to original sources

PubMed2001

[A preliminary study on the organic carbon weathering fluxes in Beijiang River drainage].

Riverine water samples were collected from Hekou hydrometric station of Beijiang River in five hydrological seasons. The samples were analyzed of their organic carbon and total suspended substance, which demonstrated that the concentrations of particulate organic carbon (POC) changed synchronically with the concentrations of total suspended substance (TSS) in riverine water. The correlation between the concentrations of TSS and dissolved organic carbon (DOC), however, is sometimes positive and sometimes negative, and the correlation is not so notable as that between TSS and POC. With the concentration of total suspended substances increasing, the quality partition of organic carbon in total suspended substance decreased in a logarithm tendency. The transportation of organic carbon, especially of DOC, mainly takes place in flood peak periods. The weathering flux of organic carbon in Beijiang River drainage basin is about 10.01 x 10(6) g.km-2.a-1, which is constituted by 6.54 x 10(6) g.km-2.a-1 of POC and 3.47 x 10(6) g.km-2.a-1 of DOC. This pattern of organic carbon weathering flux in Beijiang drainage basin is consistent with that of most of the monsoon drainage basins.

Carbon↗

PubMed2001

[Diagnosis and treatment of spontaneous spinal epidural hematoma].

OBJECTIVE: To evaluate the cause of hemorrhage of spontaneous spinal epidural hematoma (SSEH), its clinical manifestations, MR images, treatment, and prognosis. METHODS: Based on literature review, we retrospectively analysed 6 patients with SSEH in terms of pathogenic mechanism, clinical features, neurological function, and the interval between the onset of SSEH and surgery and prognosis. RESULTS: SSEH was liable to occur in young people, and most of cases were acute. MR imaging showed semilunar space occupying mass in the posterior or posteriolateral part inside the spinal canal. The outcome was closely related to the interval between the onset and surgery, whereas it was not related to age, site and size of the hematoma. The better neurological state before surgery and the shorter interval between onset and operation, the better outcome in such patients. CONCLUSIONS: SSEH may be originated from venous bleeding. The process at onset and clinical manifestation depends on the blood supply of the spinal cord. The optimal diagnostic method is MR imaging. Decompression of spinal cord in time is the key procedure for improving the patients' outcome.

Adolescent↗

PubMed2001

[Histological and ultrastructural studies of extraocular muscle proprioceptor in concomitant strabismus].

OBJECTIVE: To investigate the morphological change of extraocular muscle proprioceptor (EMP) in concomitant strabismus and study its pathogenesis. METHODS: The samples were obtained from the extraocular muscles of patients with concomitant strabismus and enucleated eyeballs. After being stained, the samples were examined under light microscopy (LM) and transmission electron microscopy (TEM) to count the number of the mitochondria in each sample in an area of 4,000 mm(2) of the axon under the same amplification. RESULTS: Under light microscopy, at the myotendinous junction of the extraocular muscle, the EMP nerve fibers were ended at the initial site or the bilateral sides of a nearby single extrafusal fiber. Under electron microscopy, the general architecture of the receptors in concomitant strabismus was completely disorganized. The nerve component in them had disappeared. The number of the mitochondria in 4,000 mm(2) of the axon in the experimental group was significantly lower than that in the control group (P < 0.05). CONCLUSION: The results indicate that in concomitant strabismus, the reception and transmission of proprioceptive information are abnormal, and the morphological EMP disturbance plays an important role in the pathogenesis of concomitant strabismus.

Adolescent↗

PubMed2001

[Neuronavigation-assisted resection of gliomas near eloquent regions].

OBJECTIVE: To evaluate the effect of the neuronavigation system in operation of gliomas near eloquent regions. METHOD: The brain LAB VV2 navigation system was used in 11 patients with gliomas near eloquent regions. The value of this system for glioma resection was assessed, and the accuracy and notice for application were discussed. RESULTS: The mean registration error was (1.5 +/- 0.7) mm in the patients. Total lesion removal was achieved in 9 patients (81.8%). The clinical status of all patients improved, and their functions of motor were not significantly affected. No complications were attributed to the use of this system. CONCLUSION: The neuronavigation system is reliable and accurate in surgical treatment of gliomas near eloquent regions. It increases the fraction of radical in glioma resection without injury to the critical functions.

Adolescent↗

PubMed2000

Human immunodeficiency virus type 1-infected women exhibit reduced interferon-gamma secretion after Chlamydia trachomatis stimulation of peripheral blood lymphocytes.

Epidemiologic, animal, and in vitro models suggest an important role for interferon (IFN)-gamma in the clearance of Chlamydia trachomatis infection. IFN-gamma in the supernatants of in vitro-stimulated peripheral blood mononuclear cells (PBMC) from 22 human immunodeficiency virus type 1 (HIV-1)-infected and 73 uninfected women at high risk for C. trachomatis acute pelvic inflammatory disease (PID) was studied. PBMC were stimulated with C. trachomatis purified major outer membrane protein (MOMP) and whole elementary bodies (EBs) from the 4 predominant serovars (E, F, K, and L2) that circulate in Nairobi. PBMC IFN-gamma secretion after stimulation with C. trachomatis EBs was significantly decreased in HIV-1-infected women. Among HIV-1-infected women, CD4 T cell depletion was associated with lower IFN-gamma secretion from PBMC stimulated with either C. trachomatis MOMP or EB antigen. Decreased antigen-specific IFN-gamma production may enhance the susceptibility of HIV-1-infected women to C. trachomatis PID.

Acute Disease↗

PubMed2000

Chlamydia trachomatis infection of epithelial cells induces the activation of caspase-1 and release of mature IL-18.

Th1 cells that secrete IFN-gamma are particularly important in protective immunity against intracellular pathogens, including chlamydiae, and IL-18 together with IL-12 are strong inducers of IFN-gamma secretion by CD4 T cells. Because epithelial cells are known to synthesize IL-18, we investigated the effects of Chlamydia trachomatis infection of human epithelial cell lines on IL-18 secretion. We confirmed that several human epithelial cell lines constitutively express pro-IL-18 and that C. trachomatis infection causes cells to secrete mature IL-18. This was observed for several different serovars and biovars of C. trachomatis. Chlamydia-induced secretion of IL-18 from epithelial cells was regulated at the posttranscriptional level and was dependent on the activation of caspase-1. IL-1alpha or other secreted factor(s) from chlamydia-infected epithelial cells as well as chlamydial structural component(s) were not involved in inducing IL-18 secretion. Activation of caspase-1 and increased secretion of mature IL-18 was correlated with chlamydial, but not with host protein synthesis. In contrast to epithelial cell lines, fibroblast cell lines constitutively expressed much lower levels of pro-IL-18 and did not secrete mature IL-18 after chlamydial infection even though caspase-1 was activated. Taken together, the results suggest that a chlamydia-derived factor(s) is essential for the secretion of mature IL-18 through caspase-1 activation in infected epithelial cells.

Bacterial Proteins↗

PubMed2000

Multimodality imaging for improved detection of epileptogenic foci in tuberous sclerosis complex.

OBJECTIVE: Using interictal alpha-[11C]methyl-l-tryptophan ([11C]AMT) PET scan, the authors have undertaken a quantitative analysis of all tubers visible on MRI or 2-deoxy-2-[18F]fluoro-d-glucose ([18F]FDG) PET, to determine the relationship between [11C]AMT uptake and epileptic activity on EEG. BACKGROUND: Tuberous sclerosis complex (TSC) is an autosomal dominant disorder, often associated with cortical tubers and intractable epilepsy. The authors have shown previously that [11C]AMT PET scans show high tracer uptake in some epileptogenic tubers and low uptake in the remaining tubers. METHODS: Eighteen children, age 7 months to 16 years, were studied. Patients underwent video-EEG monitoring, PET scans of [11C]AMT and [18F]FDG, and T2-weighted or fluid-attenuated inversion recovery (FLAIR) MRI. [11C]AMT uptake values were measured in 258 cortical tubers delineated with coregistered MRI or [18F]FDG scans. Uptake ratios were calculated between the [11C]AMT uptake in tubers and those for normal cortex (tuber/normal cortex). Using the region of epileptiform activity, the authors performed receiver operator characteristics (ROC) analysis and determined the optimal uptake ratio for detecting presumed epileptogenic tubers. RESULTS: Tuber uptake ratios ranged from 0.6 to 2.0. Tuber uptake ratios in the epileptic lobes were higher than those in the nonepileptic lobes (p < 0.0001). All 15 patients with focal seizure activity showed one or more lesions with uptake ratio above 0.98 in the epileptic lobe. ROC analysis showed that a tuber uptake ratio of 0.98 resulted in a specificity of 0.91. CONCLUSIONS: Cortical tubers with [11C]AMT uptake greater than or equal to normal cortex are significantly related to epileptiform activity in that lobe. Together, interictal [11C]AMT PET and FLAIR MRI improve the detection of potentially epileptogenic tubers in patients with TSC being evaluated for epilepsy surgery.

Adolescent↗

PubMed2000

Glial cell type-specific responses to menadione-induced oxidative stress.

Glial cell types in the central nervous system are continuously exposed to reactive oxygen species (ROS) due to their high oxygen metabolism and demonstrate differential susceptibility to certain pathological conditions believed to involve oxidative stress. The purpose of the current studies was to test the hypothesis that mtDNA damage could contribute to the differential susceptibility of glial cell types to apoptosis induced by oxidative stress. Primary cultures of rat astrocytes, oligodendrocytes, and microglia were utilized, and menadione was used to produce the oxidative stress. Apoptosis was detected and quantitated in menadione-treated oligodendrocytes and microglia (but not astrocytes) using either positive annexin-V staining or positive staining for 3'-OH groups in DNA. The apoptotic pathway that was activated involved the release of cytochrome c from the intermitochondrial space and activation of caspase 9. Caspase 8 was not activated after exposure to menadione in any of the cells. Using equimolar concentrations of menadione, more initial damage was observed in mtDNA from oligodendrocytes and microglia. Additionally, using concentrations of menadione that resulted in comparable initial mtDNA damage, more efficient repair was observed in astrocytes compared to either oligodendrocytes or microglia. The differential susceptibility of glial cell types to oxidative damage and apoptosis did not appear related to cellular antioxidant capacity, because under the current culture conditions astrocytes had lower total glutathione content and superoxide dismutase activity than oligodendrocytes and microglia. These results show that the differential susceptibility of glial cell types to menadione-induced oxidative stress and apoptosis appears to correlate with increased oxidative mtDNA damage and support the hypothesis that mtDNA damage could participate in the initiation of apoptosis through the enhanced release of cytochrome c and the activation of caspase 9.

Animals↗

PubMed2000

Genome sequences of Chlamydia trachomatis MoPn and Chlamydia pneumoniae AR39.

The genome sequences of Chlamydia trachomatis mouse pneumonitis (MoPn) strain Nigg (1 069 412 nt) and Chlamydia pneumoniae strain AR39 (1 229 853 nt) were determined using a random shotgun strategy. The MoPn genome exhibited a general conservation of gene order and content with the previously sequenced C.trachomatis serovar D. Differences between C.trachomatis strains were focused on an approximately 50 kb 'plasticity zone' near the termination origins. In this region MoPn contained three copies of a novel gene encoding a >3000 amino acid toxin homologous to a predicted toxin from Escherichia coli O157:H7 but had apparently lost the tryptophan biosyntheis genes found in serovar D in this region. The C. pneumoniae AR39 chromosome was >99.9% identical to the previously sequenced C.pneumoniae CWL029 genome, however, comparative analysis identified an invertible DNA segment upstream of the uridine kinase gene which was in different orientations in the two genomes. AR39 also contained a novel 4524 nt circular single-stranded (ss)DNA bacteriophage, the first time a virus has been reported infecting C. pneumoniae. Although the chlamydial genomes were highly conserved, there were intriguing differences in key nucleotide salvage pathways: C.pneumoniae has a uridine kinase gene for dUTP production, MoPn has a uracil phosphororibosyl transferase, while C.trachomatis serovar D contains neither gene. Chromosomal comparison revealed that there had been multiple large inversion events since the species divergence of C.trachomatis and C.pneumoniae, apparently oriented around the axis of the origin of replication and the termination region. The striking synteny of the Chlamydia genomes and prevalence of tandemly duplicated genes are evidence of minimal chromosome rearrangement and foreign gene uptake, presumably owing to the ecological isolation of the obligate intracellular parasites. In the absence of genetic analysis, comparative genomics will continue to provide insight into the virulence mechanisms of these important human pathogens.

Animals↗

PubMed2000

Statistical parametric mapping: assessment of application in children.

SPM is a powerful technique for the comparison of functional imaging data sets among groups of patients. While this technique has been widely applied in studies of adults, it has rarely been applied to studies of children, due in part to the lack of validation of the spatial normalization procedure in children of different ages. In order to determine if spatial normalization of FDG PET images using SPM96 to an adult template can be successfully applied in children, we applied PET-derived transformation parameters to coregistered MRI images. We then compared contours of spatially normalized MRI images obtained from 13 children with epilepsy (ages 2-14 years, mean 7.6 +/- 3.9 years) with those derived from 17 adult controls (mean age 27.6 +/- 4.5 years). Contours of spatially normalized MRI image volumes derived from the pediatric group were more variable than those obtained from adult controls. The average deviation from the mean adult contour was age-dependent and decreased with age (average deviation (mm) = 2.22 (mm) - 0.021 (mm/year) x years, r = 0.70, P < 0.001). Separate SPM analyses were performed for children less than 6 years (N1 = 6) and for children between 6 and 14 years of age (N2 = 7). SPM analyses performed in both pediatric groups showed significant regions of hypometabolism in locations consistent with their epileptic foci. SPM analyses in the younger group also showed significant artifacts. Therefore, the error associated with spatial normalization of pediatric brains to an adult template in children less than 6 years of age precludes the application of statistical parametric mapping in this age group. Although the error in the spatial normalization procedure for children ages 6 to 14 years is higher than in adults, it appears that this error does not result in artifacts in the SPM analysis. Furthermore, in contrast our previous studies showing large age-related changes in the absolute glucose metabolic rate at puberty, the SPM analysis showed children over 6 years of age appear to display the same pattern of glucose utilization as adults. However, small differences in the pattern of glucose utilization which might occur during late childhood and adolescence may not have been detected due to the sample size.

Adolescent↗

PubMed2000

Intensity fluctuations of ultrasonic scattering in a highly turbulent flow.

Aspects of ultrasound intensity fluctuations backscattered from additive microstructures in a turbulent flow have been investigated theoretically and experimentally for the conditions of a small insonified volume, a high sound frequency and strong turbulence. These conditions are typically found in high resolution Doppler sonar applications. An easily applicable expression for the auto-correlation of scattering intensity fluctuations is obtained by introducing open-channel turbulence theory, a semi-empirical scalar spectrum (including a Batchelor spectrum) and a Gaussian window function. Experiments carried out in a laboratory-clear water, open-channel flow for different turbulence levels verify the underlying assumptions. A good agreement is found with the predictions made with the above-derived expression. The feasibility of extracting flow information from the backscattered intensity fluctuations is discussed.

Acoustics↗

PubMed2000

Differential inhibition of human platelet aggregation by selected Allium thiosulfinates.

Thiosulfinates (TSs) have been implicated as a principle source of the antiplatelet property of raw onion and garlic juice. The in vitro responses of human platelets to dosages of four TSs were measured using whole blood aggregometry and compared by regression analysis. Of the compounds evaluated, methyl methane-TS (MMTS), propyl propane-TS (PPTS), and 2-propenyl 2-propene-TS (allicin) are present in freshly cut Allium vegetables, whereas ethyl ethane-TS (EETS) has not been detected. All TSs were synthesized using a model reaction system. PPTS and allicin had the strongest antiplatelet activity at 0.4 mM, inhibiting aggregation by 90 and 89%, respectively. At the same concentration, EETS and MMTS were significantly weaker, inhibiting 74 and 26%, respectively. Combinations of TSs were not additive in their inhibition of aggregation, indicating that the antiplatelet potential of Allium extracts cannot be easily predicted by quantifying organosulfur components. EETS, PPTS, and allicin were significantly more potent platelet inhibitors than aspirin at nearly equivalent concentrations.

Allium↗

PubMed2000

In vitro biogeneration of pure thiosulfinates and propanethial-S-oxide.

A model reaction system was developed for generating pure thiosulfinates and propanethial-S-oxide (PTSO) using an isolated alliinase (EC 4.4.1.4) and isolated or synthetic alk(en)yl-L-cysteine sulfoxides (ACSO). Reaction yields ranged from 30 to 60% after 3 h at 21-23 degrees C, and organosulfur reaction products were extracted into CHCl3 to yield product preparations of controlled composition. A pure thiosulfinate or PTSO was derived from a single ACSO, and a preparation containing a mixture of four thiosulfinate species was derived from reaction mixtures employing binary ACSO substrate systems. Identities of homologous thiosulfinates and PTSO were confirmed by 1H NMR. This approach has the potential to be used as a preparative tool for yielding pure thiosulfinates and PTSO to facilitate the study of chemical and biological properties of this group of compounds or as a means to study the dynamics of organosulfur chemistry in preparations from Allium spp.

Allium↗

PubMed2000

The relation between Chlamydia pneumoniae infection and abdominal aortic aneurysm: case-control study.

Due to recent interest in the role of Chlamydia pneumoniae as a pathogen of the vascular system, a case-control study was conducted to investigate the association between serological evidence of infection with C. pneumoniae and the occurrence of abdominal aortic aneurysm. Detectable IgG antibody to C. pneumoniae was more common among abdominal aortic aneurysm cases than among control patients (adjusted odds ratio, 5.97; P = .08), as was detectable IgM antibody (10% vs. 0%; P = .02). These findings suggest that infection with C. pneumoniae may play a role in the pathogenesis of abdominal aortic aneurysm; therefore, further research in this area is warranted.

Antibodies, Bacterial↗

PubMed2000

Torsional properties of stainless-steel and nickel-titanium files after multiple autoclave sterilizations.

This study tested the hypothesis that multiple sterilizations of endodontic stainless-steel and nickel-titanium files will lead to a continuous decrease in the resistance of files to separation by torsion. One hundred stainless-steel and 100 nickel-titanium #30 K-type files were divided into 20 groups of 10 and sterilized in increments of 10 cycles, using a full cycle and a fast cycle autoclave. These files were tested by twisting each of them in a clockwise direction until fracture (torque g-cm). Samples of the fractured files were embedded in an epoxy resin and polished for Knoop hardness tests. In addition, the samples were chemically etched to reveal changes in microstructure. The findings of this study indicate that neither the number of sterilization cycles nor the type of autoclave sterilization used affects the torsional properties, hardness, and microstructure of stainless-steel and nickel-titanium files.

Acid Etching, Dental↗

PubMed2000

Priming with Chlamydia trachomatis major outer membrane protein (MOMP) DNA followed by MOMP ISCOM boosting enhances protection and is associated with increased immunoglobulin A and Th1 cellular immune responses.

We previously reported that DNA vaccination was able to elicit cellular immune responses and partial protection against Chlamydia trachomatis infection. However, DNA immunization alone did not generate immune responses or protection as great as that induced by using live organisms. In this study, we evaluated the immunologic effects of a combinational vaccination approach using C. trachomatis mouse pneumonitis (MoPn) major outer membrane protein (MOMP) DNA priming followed by boosting with immune-stimulating complexes (ISCOM) of MOMP protein (MOMP ISCOM) for protection of BALB/c mice against MoPn lung infection. Substantially better protection to challenge infection was observed in mice given combinational vaccination compared with mice given MOMP ISCOM immunization alone, and the protection approximated that induced by live organisms. Enhanced protection was correlated with stronger delayed-type hypersensitivity, higher levels of gamma interferon production, and increased immunoglobulin A antibody responses in lung homogenates. The results indicate that DNA priming followed by ISCOM protein boosting may be useful in designing a fully protective chlamydial vaccine.

Animals↗

PubMed2000

Plasma carbon monoxide levels in term newborn infants with sepsis.

Carbon monoxide (CO) has been implicated as a new endogenously produced mediator similar to nitric oxide (NO). CO was measured in plasma samples from 7 term newborn infants with sepsis and from 30 healthy neonates. Plasma CO levels were significantly higher in the group with sepsis at the time of admission to the neonatal intensive care unit than in the healthy controls (p < 0.05). Moreover, the elevated plasma CO levels were significantly related to increased NO production, as indicated by plasma nitrite/nitrate levels (p < 0.05). The present study suggests that, in addition to NO, CO might be another important mediator taking part in the pathogenesis of neonatal sepsis.

Bacterial Infections↗

PubMed2000

Role of carbon monoxide and nitric oxide in newborn infants with postasphyxial hypoxic-ischemic encephalopathy.

OBJECTIVE: To investigate the role of carbon monoxide (CO) and nitric oxide (NO) in the pathogenesis of neonatal hypoxic-ischemic encephalopathy (HIE). METHODS: Plasma CO and NO levels were studied in 33 asphyxiated term neonates, and 30 healthy neonates served as controls. RESULTS: Among the 33 asphyxiated term neonates, plasma CO and NO levels in 28 neonates with HIE were significantly higher than those in the 5 infants without HIE and in the normal controls. The plasma CO and NO levels in the newborn infants with HIE stage 3 were found to be significantly higher than those in the neonates with HIE stage 1 and 2. Moreover, plasma CO and NO levels were significantly increased in neonates with brain damage and adverse outcome as compared with those in patients with normal neuroimaging and normal outcome. CONCLUSION: Plasma CO and NO levels after perinatal asphyxia are related to the severity of neonatal HIE, brain damage, and neurologic outcome. The present study suggests that CO and NO might play important roles in the pathogenesis of neonatal HIE.

Asphyxia Neonatorum↗