Biomedical subjects

F Xu

Publications and source records attributed to F Xu.

At least 73 records · Page 4Linked to original sources

PubMed2001

Activation of the heat shock response: relationship to energy metabolites. A (31)P NMR study in rat hearts.

Heat shock factor (HSF), the transcription factor for the heat shock proteins, is activated by cardiac ischemia, but the mechanism of activation is unknown. Ischemia is accompanied by changes in the energy state and acid-base conditions. We hypothesized that decreased ATP and/or intracellular pH (pH(i)) might activate HSF. To test this hypothesis, we perfused rat hearts within an NMR spectrometer. NMR data showed that after 6.5, 13, and 20 min of ischemia, ATP dropped to 62.7, 23.1, and 6.9% of the control level, and pH(i) was 6.16, 5.94, and 5.79, respectively. Reperfusion after ischemia partially restored ATP levels, and this was associated with greater activation of HSF1. HSF1 was also activated after 6.5 min of ischemia. Activation of HSF1 was less after 13 min of ischemia and barely detectable after 20 min of ischemia. In conclusion, 1) a moderate decrease in intracellular ATP correlates with activation of HSF1 in the heart; and 2) a severe depletion in ATP correlates with an attenuation in HSF1 activation, and the restoration of ATP leads to greater activation of HSF1, suggesting that a critical ATP level is required for activation of HSF1.

Adenosine Triphosphate↗

PubMed2001

Fastigial nucleus-mediated respiratory responses depend on the medullary gigantocellular nucleus.

Electrical stimulation of the rostral fastigial nucleus (FNr) alters respiration via activation of local neurons. We hypothesized that this FNr-mediated respiratory response was dependent on the integrity of the nucleus gigantocellularis of the medulla (NGC). Electrical stimulation of the FNr in 15 anesthetized and tracheotomized spontaneously breathing rats significantly altered ventilation by 35.2 +/- 11.0% (P < 0.01) with the major effect being excitatory (78%). This respiratory response did not significantly differ from control after lesions of the NGC via bilateral microinjection of kainic or ibotenic acid (4.5 +/- 1.9%; P > 0.05) but persisted in sham controls. Eight other rats, in which horseradish peroxidase (HRP) solution was previously microinjected into the left NGC, served as nonstimulation controls or were exposed to either 15-min repeated electrical stimulation of the right FNr or hypercapnia for 90 min. Histochemical and immunocytochemical data showed that the right FNr contained clustered HRP-labeled neurons, most of which were double labeled with c-Fos immunoreactivity in both electrically and CO(2)-stimulated rats. We conclude that the NGC receives monosynaptic FNr inputs and is required for fully expressing FNr-mediated respiratory responses.

Animals↗

PubMed2001

Microinjection of acetazolamide into the fastigial nucleus augments respiratory output in the rat.

The rostral fastigial nucleus (FNr) of the cerebellum facilitates the respiratory response to hypercapnia. We hypothesized that some FNr sites are chemosensitive to focal tissue acidosis and contribute, at least partially, to respiratory modulation. Minute ventilation (VE) was recorded in 21 anesthetized and spontaneously breathing rats. Acetazolamide (AZ; 50 microM) was microinjected unilaterally into the FNr while an isocapnic condition was maintained throughout the experiment. AZ (1 or 20 nl) injection into the FNr significantly elevated VE (46.0 +/- 6.7%; P < 0.05), primarily via an increase in tidal volume (31.7 +/- 3.8%; P < 0.05), with little effect on arterial blood pressure. This augmented ventilatory response was initiated at 6.3 +/- 0.8 min and reached the peak at 19.7 +/- 4.1 min after AZ administration. The same dose of AZ delivered into the interposed and lateral cerebellar nuclei, or vehicle injection into the FNr, failed to elicit detectable cardiorespiratory responses. To determine whether the ventilatory response to AZ injection into the FNr resulted from an increase in respiratory central drive, the minute phrenic nerve activity (MPN) was recorded in seven paralyzed and ventilated rats. Similar to VE, MPN was increased by 38.9 +/- 8.9% (P < 0.05) after AZ administration. Our results suggest that elevation of CO2/H+ within the FNr facilitates respiratory output, supporting the presence of ventilatory chemoreception in rat FNr.

Acetazolamide↗

PubMed2001

Ultrashort pulse propagation in near-field periodic diffractive structures by use of rigorous coupled-wave analysis.

We present a method for near-field analysis of ultrashort optical pulse propagation in periodic structures-including subwavelength and resonant grating structures-based on the integration of Fourier spectrum decomposition and rigorous coupled-wave analysis (RCWA). We discuss the spectral decomposition, including considerations for computational efficiency, the application of the RCWA method to compute the internal and external fields of the structure, and the synthesis of the resulting fields to obtain the time-domain solution. We apply this tool to the analysis of two photonic structures: (1) a nanostructured polarization-selective mirror that exhibits the desired broadband performance characteristics when operated at the design wavelength but yields strongly diminished polarization selectivity and modulation of the pulse envelope at an offset wave-length and (2) a two-mode coupled waveguide structure that produces from one incident pulse two transmitted pulses whose temporal separation depends on the waveguide geometry. In both examples, we apply our new modeling tool to investigate the near fields and find that near-field effects are critical in determining the performance characteristics of nanostructured devices. Furthermore, detailed observation and understanding of near-field phenomena in nanostructures may be applied to the design of novel photonic devices.

Journal Article↗

PubMed2001

Dioxygen reactivity of laccase: dependence on laccase source, pH, and anion inhibition.

A study was carried out on the dioxygen reactivity of the laccases from Trametes villosa, Rhizoctonia solani, Myceliophthora thermophila, Scytalidium thermophilum, and Coprinus cinereus. At pH 5.5, these laccases showed an apparently constant Km (about 20-50 microM) for O2 with either 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) or methyl syringate as the reducing substrate, in contrast to the kcat, which varied up to 100-fold. O2 reactivity of the Trametes and Myceliophthora laccases was also studied at various pH and NaF concentrations. The apparent Km of Trametes and Myceliophthora laccases varied only slightly when pH changed from 3.0 to 8.0 or when the laccases were inhibited by F- at pH 5.5, although the apparent kcat were more significantly affected by both factors. The dependence of the apparent Km on the source of laccase, pH, and F- inhibition suggested that the fungal laccases might have a conserved O2 pocket and that the F- or OH- inhibition might affect the O2 reduction step (kcat) more than the O2 binding step (Km) under steady-state conditions.

Anions↗

PubMed2001

An outbreak of syphilis in Alabama prisons: correctional health policy and communicable disease control.

OBJECTIVES: After syphilis outbreaks were reported at 3 Alabama State men's prisons in early 1999, we conducted an investigation to evaluate risk factors for syphilis infection and describe patterns of syphilis transmission. METHODS: We reviewed medical, patient interview, and prison transfer records and documented sexual networks. Presumptive source cases were identified. Odds of exposure to unscreened jail populations and transfer from other prisons were calculated for case patients at 1 prison. RESULTS: Thirty-nine case patients with early syphilis were identified from 3 prisons. Recent jail exposure (odds ratio [OR] = 8.0, 95% confidence interval [CI] = 0.3, 158.7, P = .14) and prison transfer (OR = 32.0, 95% CI = 1.6, 1668.1, P < .01) were associated with being a source case patient. CONCLUSIONS: Probable sources of syphilis introduction into and transmission within prisons included mixing of prisoners with unscreened jail populations, transfer of infected inmates between prisons, and multiple concurrent sexual partnerships. Reducing sexual transmission of disease in correctional settings is a public health priority and will require innovative prevention strategies.

AIDS Serodiagnosis↗

PubMed2001

Increased uncoupling protein-2 levels in beta-cells are associated with impaired glucose-stimulated insulin secretion: mechanism of action.

In pancreatic beta-cells, glucose metabolism signals insulin secretion by altering the cellular array of messenger molecules. ATP is particularly important, given its role in regulating cation channel activity, exocytosis, and events dependent upon its hydrolysis. Uncoupling protein (UCP)-2 is proposed to catalyze a mitochondrial inner-membrane H(+) leak that bypasses ATP synthase, thereby reducing cellular ATP content. Previously, we showed that overexpression of UCP-2 suppressed glucose-stimulated insulin secretion (GSIS) in isolated islets (1). The aim of this study was to identify downstream consequences of UCP-2 overexpression and to determine whether insufficient insulin secretion in a diabetic model was correlated with increased endogenous UCP-2 expression. In isolated islets from normal rats, the degree to which GSIS was suppressed was inversely correlated with the amount of UCP-2 expression induced. Depolarizing the islets with KCl or inhibiting ATP-dependent K(+) (K(ATP)) channels with glybenclamide elicited similar insulin secretion in control and UCP-2-overexpressing islets. The glucose-stimulated mitochondrial membrane ((m)) hyperpolarization was reduced in beta-cells overexpressing UCP-2. ATP content of UCP-2-induced islets was reduced by 50%, and there was no change in the efflux of Rb(+) at high versus low glucose concentrations, suggesting that low ATP led to reduced glucose-induced depolarization, thereby causing reduced insulin secretion. Sprague-Dawley rats fed a diet with 40% fat for 3 weeks were glucose intolerant, and in vitro insulin secretion at high glucose was only increased 8.5-fold over basal, compared with 28-fold in control rats. Islet UCP-2 mRNA expression was increased twofold. These studies provide further strong evidence that UCP-2 is an important negative regulator of beta-cell insulin secretion and demonstrate that reduced (m) and increased activity of K(ATP) channels are mechanisms by which UCP-2-mediated effects are mediated. These studies also raise the possibility that a pathological upregulation of UCP-2 expression in the prediabetic state could contribute to the loss of glucose responsiveness observed in obesity-related type 2 diabetes in humans.

Adenosine Triphosphate↗

PubMed2001

Long term inhibition of neointima formation in balloon-injured rat arteries by intraluminal instillation of a matrix-targeted retroviral vector bearing a cytocidal mutant cyclin G1 construct.

Restenosis from neointimal proliferation is a frequent complication of intracoronary stenting and catheter-based revascularization procedures. Currently, there is no known therapeutic strategy that has been sufficiently effective to warrant its widespread use. In the present study, the anti-proliferative properties of a matrix (collagen)-targeted retroviral vector bearing a mutant cyclin G1 (DNT 41-249) construct was evaluated in vitro and in vivo. In controlled one-month efficacy studies, the intraluminal instillation of the mutant cyclin G1 vector significantly inhibited neointima lesion formation in balloon-injured rat arteries without neointimal growth, associated necrosis or intense inflammatory reaction. Taken together, these data extend the potential utility of the matrix-targeted mutant cyclin G1 retroviral vector for management of vascular restenosis.

3T3 Cells↗

PubMed2001

[A study of phenylketonuria heterozygotes screening in married population of Tianjin area].

OBJECTIVE: To find out a method that is simple and reliable for screening phenylketonuria(PKU) heterozygotes. METHODS: Detecting and analyzing plasma phenylalanine(Phe) and tyrosine(Tyr) from 101 known-PKU heterozygotes and 2023 married people by means of a high performance liquid chromatograph. RESULTS: Significant differences were observed between known- PKU heterozygotes and screening population in plasma Phe, Phe/Tyr and Phe(2)/Tyr. The values of plasma Phe, Phe/Tyr and Phe(2)/ Tyr from 94.1% known-PKU heterozygotes were higher than mean+2s of those values from screening population. According to the limits of mean+2s, 81 cases were screened out from the 2023 married people. It was the first time to get the actual heterozygote frequency of 4% from population. CONCLUSION: The biochemical method mentioned above is available for use in screening PKU heterozygotes.

Adult↗

PubMed2001

[Retention of selenium volatility using lime in coal combustion].

For understanding the volatility of selenium, the effect of the contents of exchangeable cations of coal on it, and the retention of selenium using CaO in coal combustion, the sequential chemistry extraction, the fixed bed and circulating fluidized bed (CFB) combustion, X-ray diffraction (XRD) and atomic fluorescence spectrometry (AFS) were undertaken. The results showed that the volatility of selenium was more than 97% in coal combustion at 815 degrees C, and the volatility of selenium was affected by the content of exchangeable cations of coal in low-middle temperature. It was identified that lime can restrain the volatility of selenium. In fixed bed combustion of coal, the retention rates of selenium volatility were between 11.6% and 50.7% using lime. In circulating fluidized bed combustion of coal, partitioning of selenium changed very much in ash of different size fraction between without lime and with lime. Comparing with combustion without lime, the content of selenium in ash from chimney was less than fourth times and that in leaching water from chimney decreased by two orders of magnitude using lime. Retention of selenium volatility using lime is so effective in coal combustion, especially in CFB combustion of coal.

Calcium Compounds↗

PubMed2001

[Estimation of LC50 of chemicals to rainbow trout by fragment constant method].

A fragment constant model for prediction of 96 h LC50 of chemicals to rainbow trout was developed based on measured experimental data of 258 chemicals collected from the literature. The accuracy and the robustness of the model were discussed. The coefficient of determination of the model is 0.9495 and the mean residual is 0.42 log-unit. The model is robust for both individual chemical or chemical class.

Animals↗

PubMed2001

[Mechanism of contour hedgerow's control for non-point pollution in the semiarid region in northwest Hebei Province].

Slope nutrient loss is an important type of non-point pollution. The mechanism of non-point pollution control by using plenty of natural observed data in Hilly Loess region in Northwest Hebei Province, as well as combating with the large-scale artificial simulation rainfall in the field slope was analyzed. The study results show that the critical slope length was 10-15 m on the condition of rainstorm, which led to the generation of rill and made the erosion amount went up obviously. The study show that the nutrient loss in sediment was the main type of non-point pollution, the contour hedgerow the process of non-point pollution by controlling the nutrient loss in sediment, then the study got the erosion control model of the contour hedgerow.

China↗

PubMed2001

[Clinical studies on sternocleidomastoid myoperiosteal flap for cervical tracheal reconstruction].

OBJECTIVE: To introduce the experience of repairing the defect of cervical trachea wall by using the sternocleidomastoid myoperiosteal flap after the anterior or posterior wall of cervical trachea was invaded by cervical neoplasm. METHOD: Between 1989 to 1998 the sternocleidomastoid myoperiosteal flap was applied in 12 patients with different diseases, among which 3 cases were thyroid carcinoma 5 cases were laryngeal carcinoma, 4 cases were cervical esophageal carcinoma. RESULT: The operation was successful. 12 patients were decannuated and had normal exercise tolerance. The time from reconstruction to decannulation was ranging from 20 days to 6 months. CONCLUSION: The sternocleidomastoid myoperiosteal flap is an ideal transplant for cervical tracheal reconstruction.

Adolescent↗

PubMed2001

[Measurement of microvessel density in laryngeal carcinoma and its clinical significance].

OBJECTIVE: To determine the microvessel density (MVD) in laryngeal carcinoma and its clinical significance. METHOD: Thirty-eight tumor specimens were selected from laryngeal cancer patients from January, 1994 to March, 1996. Histological sections of the tumors were stained immunohistochemically for factor VIII. Using light microscopy, we counted microvessels per 400 x field in the most active areas of tumor angiogenesis. RESULT: 1. The tumor blood vessels, composed of only one layer of endothelium were mainly distributed heterogeneously in the interstitial tissue of laryngeal carcinoma with irregular lumen, poorly developed structure. 2. The MVD in the cancer tissues were statistically higher than that in peritumoral tissues (P < 0.01). 3. The MVD in the cancer tissues in group of patients with metastasis to cervical lymphonodes were statistically higher than in group without metastasis (P < 0.01), the MVD in the cancer tissues in group of advanced cases (III, IV stages) were statistically higher than that in group of early cases (I, II stages, P < 0.01). 4. There was no statistically difference in MVD in the cancer tissue between supraglottic and glottic laryngeal carcinoma patients (P > 0.05). 5. There was no statistically difference in MVD in the cancer tissue among the G1, G2 and G3 group (P > 0.05). CONCLUSION: The laryngeal cancer blood vessels have some characteristics that don't appear in normal vessels. It is suggested that tumor angiogenesis can promote tumor growth and metastasis and MVD may be a new prognostic indicator of laryngeal carcinoma.

Adult↗

PubMed2001

[Analysis on the dermal irritation caused by imported cosmetics].

Dermal irritation tests on 902 kinds of cosmetics were conducted. The acute dermal irritation/corrosion tests for 175 samples showed no irritation in 65.1% of them, and 34.9% of them were considered as slight irritation. The chronic dermal irritation/corrosion tests for another 727 samples showed no irritation for 32.2% of them, and 67.8% of them were considered as slight irritation, most of which are lipsticks, eye shadows, fluid powder foundations and powder foundations.

Animals↗

PubMed2001

[Surgical management of subglottic carcinoma].

OBJECTIVE: To explore the surgical management and evaluate the effect on patients with subglottic cancer. METHODS: Fourteen cases with subglottic carcinoma were treated surgically from 1989 to 1998. There were T1-2N0 lesions in 5 cases, T3N0-2 lesions in 3 cases and T4N0-1 lesions in 6 cases. Eleven cases underwent partial laryngectomy and three cases underwent total laryngectomy. The defects of larynx were reconstructed by using uni-pedicled or bi-pedicled stemohyoid myofascial flap, platysma myocutaneous flap, sternocleidomastoid myoperiosteal flap, thyroid perichondral flap and epiglottis flap accordingly. Unilateral neck dissection was performed on 4 cases and bilateral on one. RESULTS: The function of phonation had been restored in all cases except in 3 patients who underwent total laryngectomy. Seven out eleven(63.6%) were decannulated. The swallowing function was restored in all patients. In all cases the 3 and 5 year survival rates were 78.6%(11/14) and 63.6% (7/11), respectively. CONCLUSIONS: The conservative surgery can be used for the majority of the subglottic carcinoma if the lesions were entirely resected. The proficiency in surgical methods is crucial for the preservation of laryngeal function.

Adult↗

PubMed2001

[Preservative surgery of medial wall pyriform sinus cancer].

OBJECTIVE: To study the surgical methods and functional outcome of preservative surgery for medial wall pyriform sinus cancer. METHODS: Seventy-one patients with medial wall pyriform sinus cancer, who were treated surgically between 1985 and 1997, were reviewed. Of the 71 cases, 49 underwent preservative surgery, and 22 total laryngectomy. Preservative surgical procedure was defined as follows: 1. Extent of resection: Supraglottic horizontal partial laryngectomy and resection of medial wall of pyriform sinus were performed in patients without fixation of the true vocal cord, and the section extended to paraglottic space, partial lateral wall of pyriform sinus, preepigottic space, superior-posterior of thyroid cartilage in those with restrained vocal cord motility. Supracricoid hemilaryngopharyngectomy and resection of medical wall and partial lateral wall of pyriform sinus were practiced in those with fixed hemilarynx. Cricoid ring and cervical esophagus were removed partially if the pyriform sinus apex was involved. 2. Reconstruction: Larynx: the remains of epiglottis, perichondrium of thyroid cartilage, the infrahyoid muscular fascia, and the platysmal flap were utilized to restore the defects of larynx. Pyriform sinus: Suturing the remaining pharyngeal mucosa directly to cover the wound if the defect was relatively small. For the large defect produced by extended resections, the pectoralis major myocutaneous flap and deltopectoral flap were used. 3. Surgical treatment of cervical lymphaden: Sixty five out of the 71 cases (91.5%) underwent neck dissection. Of which ipsilateral neck dissection were done in 39 cases, and bilateral neck dissection in 26 cases. 4. All patients received postoperative radiotherapy with doses of 60-75 Gy. RESULTS: In the group of preservative surgery the 3- and 5-year survival rates were 63.4% and 49.6% respectively, whereas those in the total laryngectomy group were 52.4% and 42.4% respectively. Of the 49 cases with preservative surgery, 71.4% (35/49) had all laryngeal functions restored and 28.6% (14/49) partially restored. CONCLUSION: Despite the fact that the medial wall pyriform sinus cancer tends to have laryngeal invasion, preservative surgery can be practiced for the majority of the cases with the lesions entirely removed.

Adult↗

PubMed2001

[Impact of AFP promoter on the expressions of GFP in tumor cells].

OBJECTIVE: To study the impact of AFP 5'flanking promoter (enhancer) on the expression of GFP in hepatocarcinoma cell. METHODS: Green Fluorescent Protein (GFP) reporter gene expression plasmid pcDNA3-GFP-AFP-w under the direction of AFP 5' flanking promoter (enhancer) was constructed by recombinant DNA technology and confirmed by restriction analyses. pcDNA3-GFP-AFP-w, pcDNA3-GFP and pcDNA3 were transfected into Hela and Bel7402 cells by lipofectin and selected by G418 respectively, after amplification of the positive cell clones, expression of GFP was detected by Western blotting and quantitatively analysed by GEL Doc 2000 digital image systems. RESULTS: The expression of GFP was lower in Bel-GFP-AFP-w than in Bel-GFP but was significantly higher than in Hela-GFP-AFP-w. CONCLUSION: GFP reporter gene plasmid pcDNA3-GFP-AFP-w under the direction of the 3.1 kb AFP 5'flanking promoter (enhancer) can be expressed in HCC Bel7402 cell definitely and specifically.

Carcinoma, Hepatocellular↗