Biomedical subjects

Bo Chen

Publications and source records attributed to Bo Chen.

126 records · Page 7Linked to original sources

PubMed2003

Correlation of NIRS determined cerebral oxygenation with severity of pilot +Gz acceleration symptoms.

Pilots commonly experience decreased peripheral vision, confusion & disorientation, and/or unconsciousness when exposed to high +Gz acceleration. We correlated NIRS determined delta Hb, delta HbO2, and delta TotalHb with the resultant +Gz stress symptoms that subjects reported after experiencing a 6 to 10 +Gz amplitude pulse. During the hyperemic response phase following the +Gz pulses, an increase of the averaged peak values of delta HbO2 and delta TotalHb as a function of the severity of the subjects' symptoms was observed. Significant increases were found for the averaged peak values of delta HbO2 and delta TotalHb between high vision loss, confusion and disorientation while remaining conscious (A-LOC), and unconsciousness (G-LOC). The results suggest that the confusion and disorientation associated with A-LOC is physiologically based and that A-LOC is an intermediate +Gz stress symptom between high peripheral vision loss and G-LOC. Like G-LOC, pilots who experience A-LOC symptoms momentarily do not have full control of their aircraft.

Acceleration↗

PubMed2003

[A review on mast seeding studies].

Mast seeding means that the plants of a population have a highly variable seed production in different years synchronously, and it is widely existed in perennial plants. The periodic variation of seed yield and synchrony of seed production among individuals are the key characteristics. Several hypotheses, including evolutionary bases and limitations of mast seeding, were reviewed in this paper. Moreover, the synchronous degree among individuals was discussed, and the temporal permanence and spatial heterogeneity were emphasized.

Ecosystem↗

PubMed2003

[Clinical study of pure titanium membranes in oral implant surgery].

OBJECTIVE: To evaluate predictability and treatment outcome of the pure titanium membranes in bone defects around endosseous implants. METHODS: 81 patients and 92 dental implants were included in this study. The defects around implants were filled with bone grafts and Bio-Oss, and then covered by titanium membranes. 6 - 10 months later, all of the membranes were removed. RESULTS: 5 patients showed complications in soft tissue healing with exposure of the membranes. Bone defects around 89 implants were successfully covered with new regenerated bone. CONCLUSIONS: Pure titanium membranes show excellent biocompatibility, exhibit good mechanical properties, avoid grafts displacement, ingrowth of connective tissue and contour collapse.

Adult↗

PubMed2003

[Experimental investigation of laser plasma soft X-ray source with gas target].

This paper describes a debris-free laser plasma soft X-ray source with a gas target, which has high operating frequency and can produce strong soft X-ray radiation. The valve of this light source is drived by a piezoelectrical ceramic whose operating frequency is up to 400 Hz. In comparison with laser plasma soft X-ray sources using metal target, the light source is debris-free. And it has higher operating frequency than gas target soft X-ray sources whose nozzle is controlled by a solenoid valve. A channel electron multiplier (CEM) operating in analog mode is used to detect the soft X-ray generated by the laser plasma source, and the CEM's output is fed to to a charge-sensitive preamplifier for further amplification purpose. Output charges from the CEM are proportional to the amplitude of the preamplifier's output voltage. Spectra of CO2, Xe and Kr at 8-14 nm wavelength which can be used for soft X-ray projection lithography are measured. The spectrum for CO2 consists of separate spectral lines originate mainly from the transitions in Li-like and Be-like ions. The Xe spectrum originating mainly from 4d-5f, 4d-4f, 4d-6p and 4d-5p transitions in multiply charged xenon ions. The spectrum for Kr consists of separate spectral lines and continuous broad spectra originating mainly from the transitions in Cu-, Ni-, Co- and Fe-like ions.

English Abstract↗

PubMed2003

[Studies on flavonoid constituents of Caragana intermediia].

AIM: To study the chemical constituents of Caragana intermedia. METHODS: The compounds were separated by chromatography methods, their structures were identified by spectral analysis. RESULTS: Ten compounds were isolated and identified as 5,7,4'-trihydroxy-3,3'-dimethoxyflavone (1), 3,5,7,8,4'-pentahydroxy-3'-methoxyflavone(2), puercetin(3), limocitrin(4), 5,7,3',4'-tetrahydroxy-3-methoxyflavone(5), 7,3',5'-trihydroxyflavanone(6), 5,7,3',4'-tetrahydroxy-3,8-dimethoxyflavone(7), butein(8), liquiritigenin(9) and 5,7,4'-trihydroxy-3,8-dimethoxyflavone(10). CONCLUSION: Compound 6 is a new compound and the others were obtained from this plant for the first time.

Caragana↗

PubMed2002

SHP-2 mediates target-regulated axonal termination and NGF-dependent neurite growth in sympathetic neurons.

The tyrosine phosphatase SHP-2 has been implicated in a variety of signaling pathways, including those mediated by neurotrophins in neurons. To examine the role of SHP-2 in the development of sympathetic neurons, we inhibited the function of SHP-2 in transgenic mice by overexpressing a catalytically inactive SHP-2 mutant under the control of the human dopamine beta-hydroxylase promoter. Expression of mutant SHP-2 did not influence the survival, axon initiation, or pathfinding abilities of the sympathetic neurons. However, mutant SHP-2 expression resulted in an overproduction of sympathetic fibers in sympathetic target organs. This was due to interference with SHP-2 function, as overexpression of wild type SHP-2 had no such effect. In vitro, NGF-dependent neurite growth was inhibited in neurons expressing mutant SHP-2 but not in those expressing wild type SHP-2. Mutant (but not wt) SHP-2 expression also inhibited NGF-stimulated ERK activation. The NGF-dependent survival pathway was less affected than the neurite growth pathway. Our results suggest that NGF-regulated axon growth signals, and to a lesser degree survival signals, are mediated through a SHP-2-dependent pathway in sympathetic neurons. The increased sympathetic innervation in target tissues of neurons expressing mutant SHP-2 may result from interference with normal "stop" signals dependent on signaling by gradients of NGF.

Animals↗

PubMed2002

Drm/Gremlin transcriptionally activates p21(Cip1) via a novel mechanism and inhibits neoplastic transformation.

Drm/Gremlin, a member of the Dan family of BMP antagonists, is known to function in early embryonic development, but is also expressed in a tissue-specific fashion in adults and is significantly downregulated in transformed cells. In this report, we demonstrate that overexpression of Drm in the tumor-derived cell lines Daoy (primitive neuroectodermal) and Saos-2 (osteoblastic), either under ecdysone-inducible or constitutive promoters, significantly inhibits tumorigenesis. Furthermore, Drm overexpression in these cells increases the level of p21(Cip1) protein and reduces the level of phosphorylated p42/44 MAP kinase. Finally, our data indicate that Drm can induce p21(Cip1) transcriptionally via a novel pathway that is independent of p53 and the p38 and p42/44 MAP kinases. These results provide evidence that Drm can function as a novel transformation suppressor and suggest that this may occur through its affect on the levels of p21(Cip1) and phosphorylated p42/44 MAPK.

Cell Transformation, Neoplastic↗

PubMed2002

[Distraction osteogenesis for treatment of temporomandibular joint ankylosis].

OBJECTIVE: To study the application of distraction osteogenesis in temporomandibular joint (TMJ) ankylosis patients. METHODS: 11 temporomandibular joint ankylosis patients (13 sides of TMJ) were treated by this technique. After removal of bony mass on the ankylosis area, a L-shape osteotomy of the ramus was performed to create the distraction transport disc which connected the mandible by distractor. Distractions were started on the 4 approximately 8th postoperative day. The distraction rhythm and rate were 0.25 mm 4 times a day. Distraction was stopped when contact was made between the transport disc and glenoid fossa. The patients underwent active mouth opening postoperatively. Distractor was kept in place for 3 approximately 4 months after completion of distraction and then removed under local anesthesia. RESULTS: Postoperatively, the range of mouth opening of the 11 patients (13 sides) was increased to normal (33 approximately 45 mm), bone formation in the gaps were perfect and the neocondyle was remodeling and approximated normal shape. No complications were found. CONCLUSION: Distraction osteogenesis for arthroplasty has many advantages compared with traditional methods. It is valuable in clinical practice as a new method for treatment of TMJ ankylosis.

Adolescent↗

PubMed2002

Effect of liquid depth on the synthesis and oxidation of nitric oxide in macrophage cultures.

The effect of liquid depth on the synthesis of NO and O(2)(-) was studied in murine macrophage-like RAW 264.7 cells activated by bacterial lipopolysaccharide and interferon-gamma. Rates of NO(2)(-) and NO(3)(-) accumulation were determined 8-11 h after stimulation. The rate of NO synthesis was computed by using a reaction-diffusion model to correct NO(2)(-) and NO(3)(-) accumulation for physical loss of NO, whereas O(2)(-) synthesis was equated with NO(3)(-) formation. Rates of O(2)(-) synthesis determined by a spectrophotometric (cytochrome c) assay were in good agreement with those from NO(3)(-) accumulation and showed production of O(2)(-) to be detectable immediately, in contrast to the approximately 6 h time lag for NO. The assumption that NO(2)(-) and NO(3)(-) are stable end products of the extracellular oxidation of NO by O(2) and O(2)(-), respectively, was supported by the fact that NO(2)(-) and NO(3)(-) concentrations remained constant in the presence of unstimulated cells or stimulated cells where NO synthesis was inhibited. Data were obtained for media depths ranging from 1 to 4 mm. The physical loss of NO was found to be quite significant, exceeding NO(2)(-) and NO(3)(-) accumulation by an order of magnitude at the smallest depth. The principal finding was that the rates of NO(2)(-) and NO(3)(-) accumulation each remained nearly constant over the 4-fold range of liquid depths. Because greater depths should greatly facilitate the trapping of NO as NO(2)(-), this implies that NO synthesis decreased markedly with increasing depth. In contrast, O(2)(-) synthesis remained approximately constant. Oxygen availability is likely to have affected NO synthesis, in that diffusional limitations will yield the lowest cellular O(2) concentrations when the liquid depth is greatest and NO synthesis is known to decrease when O(2) levels are reduced. Concentrations of NO near the cells were calculated to remain at approximately 1 microM for all conditions examined, suggesting that regulation of NO synthase activity by NO might also have mediated the effect of liquid depth.

Animals↗

PubMed2002

Incorporation of a computerized human patient simulator in critical care training: a preliminary report.

BACKGROUND: The intent of the study was to document initial experience with human patient simulation, using a full-scale computerized mannequin, in evaluating cognitive performance among junior surgery residents. METHODS: This was an observational study of eight postgraduate year-2 surgery residents during initial critical care rotation that assessed their responses to three unknown scenarios using a human patient simulator. RESULTS: No resident successfully completed the first scenario. Of note was a reluctance to call for help until the scenario reached a critical stage. Subsequent performance improved in areas previously neglected. Resident acceptance of simulation scenarios as a teaching tool was excellent. CONCLUSION: The human patient simulator is a valuable tool in critical care education, identifying weaknesses both in individual student performance and in program content.

Adult↗

PubMed2002

[Single instillation of epirubicin for the prophylaxis of recurrent primary superficial bladder carcinoma].

OBJECTIVE: To determine the feasibility of single dose intravesical epirubicin in the prevention of recurrent superficial bladder carcinoma. METHODS: We compared the effect of intravesical epirubicin or mitomycin C on tumor recurrence and disease free interval and their side effects after treatment of superficial bladder tumor. 47 postoperative patients with stages Ta to T1 primary superficial bladder carcinoma of grades 1 or 2 were randomized into groups A: single 80 mg epirubicin; B: 40 mg consecutive epirubicin; C: 40 mg consecutive mitomycin C. Patients were followed up for clinical, analytical, and cystoscopic evaluations every 3 months. RESULTS: The disease free intervals of the three groups were found no significant differences (F = 3.25, P > 0.05). The recurrence rate was 6.25% (1/16), 13.3% (2/15), 12.5% (2/16) (chi(2) = 0.496, P > 0.05) in groups A, B, and C at 1 year, and 33.3% (5/15), 26.7% (4/15), 25% (4/16) (chi(2) = 0.290, P > 0.05) at 3 years after operation, respectively. Side effects of group A (13.3%) were lower than those of group B (46.7%) or C (43.8%) (chi(2) = 14.56, P < 0.01). CONCLUSIONS: Single dose of epirubicin given intravesically immediately after tumor resection is effective in preventing tumor recurrence.

Aged↗

PubMed2002

Factors influencing postoperative satisfaction of orthognathic surgery patients.

The purpose of this study was to investigate the postoperative satisfaction of orthognathic surgery patients and related factors. The authors assessed 108 orthognathic surgery patients using the Minnesota Multiphasic Personality Inventory and the Symptom Checklist 90 preoperatively. The degree of deformity, expectations for surgery, and support of significant others were also evaluated before surgery. The patients were given questionnaires at 4 time points, from 10 days to 1 year after surgery. A multiple regression test was used to analyze the relative importance of psychologic factors and other variables in explaining the degree of patients'satisfaction with surgery. Postoperative satisfaction was high and increased with time. Patients with more education and more severe deformities reported greater satisfaction. During the early stage after surgery, patients with a high degree of interpersonal sensitivity, whose close relatives did not support surgery, or who accepted surgery passively tended to be more dissatisfied. Patients who had realistic expectations were more satisfied in the long term. Complications such as pain and swelling influenced patients' satisfaction soon after surgery, whereas the responses of people around the patients influenced their satisfaction at all stages postoperatively.

Adolescent↗

PubMed2002

Clinical study of alveolar vertical distraction osteogenesis for implant.

OBJECTIVE: To evaluate the clinical result of alveolar vertical distraction osteogenesis for implant. METHODS: 19 cases with severe vertical alveolar defects (more than 10 mm defect) underwent vertical distraction procedure before implant placement. 15 cases were male and 4 cases were female. The alveolar bone defects were caused by tumor resection in 10 cases, by trauma in 8 cases, and due to congenital defect in 1 case. The vertical defects in all cases were over 10 mm. X-ray examination were taken prior to operation and in 1 week, 2 week, 4 week, the end of active distraction and before removing distractor. Implants were placed in 17 cases after removing distractors. The prosthesis were finished 6 month later. RESULTS: 11 cases out of 19 had implant prosthesis. 6 cases had implant in the jaw but waiting for the prosthesis. Altogether 65 dental implants were placed, 2 cases did not receive further implant treatment because of cost problem. The study showed that new bone formed after distraction in all 19 cases. Average gained height of new bone was 13 mm. COMPLICATIONS: Unexpected mandible fracture in 2 cases, infection in 1 case. CONCLUSIONS: Alveolar vertical distraction is a good alterative for severe alveolar defects. The distractor should be further developed and modified.

Alveolar Ridge Augmentation↗

PubMed2000

Composite mandibular allografts in canines.

OBJECTIVE: To evaluate the feasibility of transplanting composite mandibular allografts to repair large mandibular defects. METHODS: Three composite mandibular trans-plantation models were established. The first model consisted of hemimandible with the attached teeth, muscle and skin,and oral mucosa. The second model was transplanted in the same way with the first one excluding oral mucosa and some teeth, and third one excluding the oral mucosa and all dental crowns. Fourteen transplanting operations were performed in canines. Cyclosporine A and methylprednisone were given for immunosuppression. RESULTS: The composite mandibular organs had an effective and closed return circuit. Transplantation of vascularized allograft of mandibular compound organs was feasible. Two longest time survivors of 67 d and 76 d were in the third model group. Cyclosporine A was successful in suppressing rejection of transplanted composite allograft and prolonging survival time of transplantation models. CONCLUSIONS: The composite mandibular allografts were available with large block of living composite tissue, and helpful in restoration of appearance and function for severe mandibular defects.

Journal Article↗

PubMedDate not supplied

Solvent effects on focused microwave assisted extraction of polyphenolic acids from Eucommia ulmodies.

An open microwave-assisted extraction system was used to extract gallic acid, protocatechuic acid, chlorogenic acid and caffeic acid from Eucommia ulmodies. The effect of extraction variables, especially solvent, on the recoveries of these polyphenolic compounds was investigated using factorial design. As extracting solvent for these compounds, methanol produced a higher recovery than pure water. For straight chain alcohol solvents, the lower the carbon number, the higher the recoveries of the polyphenolic acids. The optimal ratio of methanol:water:glacial acetic acid in the solvent mixture used in microwave-assisted extraction was 2:8:0.3 (v/v) and this solvent could be directly used as the mobile phase in HPLC separation without additional intermittent treatment as reported in literature. The extraction under the condition of 50% microwave power and 30 s irradiation at a solvent:sample ratio of 10 (mL/g) was found to be the most advantageous. The repeatability test of extraction and chromatographic analysis was satisfactory for the analysis of these polyphenolic compounds.

Chemistry Techniques, Analytical↗

PubMedDate not supplied

Rapid determination of protopine, allocryptopine, sanguinarine and chelerythrine in fruits of Macleaya cordata by microwave-assisted solvent extraction and HPLC-ESI/MS.

An isocratic high-performance liquid chromatographic method coupled with electrospray mass spectrometry was developed to determine protopine, allocryptopine, sanguinarine and chelerythrine in fruits of Macleaya cordata. The sample was extracted with hydrochloric acid aqueous solution using microwave-assisted extraction method. The extracts were separated on a C8 reversed-phase HPLC column with acetonitrile:acetate buffer as mobile phase, and full elution of all analytes was realized isocratically within 10 min. The abundance of pseudomolecule ions was recorded using selected ion recording at m/z 354.4, 370.1, 332.5, 348.5 and 338.5 for protopine, allocryptopine, sanguinarine, chelerythrine and the internal standard, jatrorrhizine, respectively. Internal standard curves were used for the quantification of protopine, allocryptopine, sanguinarine and chelerythrine, which showed a linear range of 0.745-74.5, 0.610-61.0, 0.525-105 and 0.375-75 microg/mL, respectively, with correlation coefficients of 0.9995, 0.9992, 0.9993 and 0.9989, and limits of detection of 3.73, 3.05, 1.60 and 1.11 ng/mL, respectively.

Alkaloids↗

PubMedDate not supplied

Porcine skin visible lesion thresholds for near-infrared lasers including modeling at two pulse durations and spot sizes.

With the advent of such systems as the airborne laser and advanced tactical laser, high-energy lasers that use 1315-nm wavelengths in the near-infrared band will soon present a new laser safety challenge to armed forces and civilian populations. Experiments in nonhuman primates using this wavelength have demonstrated a range of ocular injuries, including corneal, lenticular, and retinal lesions as a function of pulse duration. American National Standards Institute (ANSI) laser safety standards have traditionally been based on experimental data, and there is scant data for this wavelength. We are reporting minimum visible lesion (MVL) threshold measurements using a porcine skin model for two different pulse durations and spot sizes for this wavelength. We also compare our measurements to results from our model based on the heat transfer equation and rate process equation, together with actual temperature measurements on the skin surface using a high-speed infrared camera. Our MVL-ED50 thresholds for long pulses (350 micros) at 24-h postexposure are measured to be 99 and 83 J cm(-2) for spot sizes of 0.7 and 1.3 mm diam, respectively. Q-switched laser pulses of 50 ns have a lower threshold of 11 J cm(-2) for a 5-mm-diam top-hat laser pulse.

Animals↗

PubMedDate not supplied

Modeling thermal damage in skin from 2000-nm laser irradiation.

An optical-thermal-damage model of the skin under laser irradiation is developed by using finite-element modeling software (FEMLAB 3.1, Comsol, Incorporated, Burlington, Massachusetts). The general model simulates light propagation, heat generation, transient temperature response, and thermal damage produced by a radically symmetric laser beam of normal incidence. Predictions from the model are made of transient surface temperatures and the thermal damage on a pigskin surface generated by 2000-nm laser irradiation, and these predictions are compared to experimental measurements. The comparisons validate the model predictions, boundary conditions, and optical, thermal, and rate process parameters. The model enables the authors to verify the suitability of the American National Standards Institute (ANSI) maximum permissible exposure (MPE) standard for a wavelength of 2000 nm with exposure duration from 0.1 to 1 s and 3.5-mm beam diameter. Compared with the ANSI MPE standard, however, the MPE values predicted by the model are higher for exposure durations less than 0.1 s. The model indicates that it may be necessary to modify the ANSI MPE standard for cases in which the laser-beam diameter is larger than 3.5 mm when a "safety factor" of ten is used. A histopathological analysis of the skin damage is performed to determine the mechanisms of laser-induced damage in the skin.

Burns↗