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Biomedical subjects

Yi Chen

Publications and source records attributed to Yi Chen.

216 records · Page 12Linked to original sources
PubMed2002

Duration of acidosis and recovery determine preretinal neovascularization in the rat model of acidosis-induced retinopathy.

PURPOSE: Systemic acidosis is a risk factor for retinopathy of prematurity (ROP). The present study tested the hypotheses that: a) a short period of acidosis is sufficient to produce neovascularization and b) recovery from acidosis is not needed for the development of preretinal neovascularization. METHODS: Newborn Sprague-Dawley rats raised in 38 litters of 25 were randomly assigned within litters to 1, 3, or 6 days of acidosis, induced by twice daily gavage with NH4Cl (10 mM/kg) beginning on the second day of life. Recovery time ranged from 0 to 15 days. All animals were raised in room air. Animals were sacrificed and retinal vasculature was assessed for preretinal neovascularization and retinal vascular areas. RESULTS: Neovascularization occurred in up to 34% of rats exposed to 1 day of acidosis, 38% of rats exposed to 3 days of acidosis, and 55% of rats exposed to 6 days of acidosis. The incidence of neovascularization was maximal after 2 to 5 days of recovery regardless of the duration of NH4Cl exposure. However, recovery was not a requirement for the development of neovascularization. CONCLUSIONS: Periods of systemic acidosis as brief as 24 hours are associated with preretinal neovascularization in our newborn rat model of ROP using expanded litters. Systemic acidosis may damage the developing retinal vasculature and induce neovascularization, even without a period of recovery. A brief episode of systemic acidosis may be a risk factor for ROP in human neonates. Further attention should be directed to systemic acid-base balance in infants at risk for ROP.

Acidosis↗
PubMed2002

Incidence and severity of neovascularization in oxygen- and metabolic acidosis-induced retinopathy depend on rat source.

PURPOSE: We have previously described oxygen-induced retinopathy (OIR) and metabolic acidosis-induced retinopathy (MAIR) in the neonatal rat, both of which are analogous to human retinopathy of prematurity (ROP). Given that rats of identical strain from two commercial suppliers are phenotypically different, we investigated the incidence and severity of preretinal neovascularization (NV) in rats from different suppliers using the OIR and MAIR models. METHODS: Using our established models for OIR and MAIR, 400 newborn Sprague-Dawley rats, obtained from Harlan Laboratories (HSD) and Charles River Laboratories (CRSD), were raised in 16 expanded litters of 25 (6 OIR and 10 MAIR). Beginning at day 1 of life, OIR litters (3 HSD, 3 CRSD) were exposed to 7 daily cycles of hyperoxia (80% O(2), 20.5 hours) and hypoxia (10% O(2), 0.5 hours) with a gradual return to 80% O(2) over 3 hours. OIR rats were sacrificed after 5 days of room air recovery. MAIR litters (5 HSD, 5 CRSD) were raised in room air and gavaged twice daily with NH(4)Cl (10 mM/kg body weight) from day 2 through day 4. MAIR rats were sacrificed after 3 days of recovery. For both OIR and MAIR litters, retinae from left eyes were dissected, ADPase-stained, and flatmounted. Presence and severity of NV was scored and retinal vascular areas measured by a masked observer. RESULTS: In OIR rats, the incidence of NV was higher in CRSD rats than HSD rats (73% vs. 45%, p = 0.002). NV was more severe in CRSD rats than HSD rats (median clock hours 2 vs. 0, p = 0.0001). In MAIR rats, the incidence of NV was comparable between CRSD and HSD rats (29% vs. 34%, p = 0.53) and there was no significant difference in the severity of NV. CONCLUSIONS: Sprague-Dawley rats obtained from two independent commercial sources differed in their incidence and severity of NV associated with OIR, but not with MAIR. Future genetic studies are warranted to investigate the differences between CRSD and HSD rats, which might yield further clues into the pathogenesis of ROP.

Acid-Base Equilibrium↗
PubMed2002

Predictors of hemorrhagic transformation after intravenous recombinant tissue plasminogen activator: prognostic value of the initial apparent diffusion coefficient and diffusion-weighted lesion volume.

BACKGROUND AND PURPOSE: Hemorrhagic transformation (HT) is a potentially dangerous complication of thrombolytic therapy. Recent studies suggest that diffusion-weighted MRI (DWI) can help to predict the risk of intracerebral hemorrhage (ICH) after thrombolysis. We sought to examine which pretreatment DWI parameters and clinical data are predictive of ICH after intravenous thrombolysis. METHODS: We retrospectively reviewed our prospective stroke database for patients with ischemic stroke treated with intravenous recombinant tissue plasminogen activator (rtPA) within 3 hours from symptom onset who had DWI before treatment and MRI with T2* sequence or CT 24 to 48 hours later to assess for ICH over the past 4 years. We measured the volumes and voxel-by-voxel apparent diffusion coefficient (ADC) values of the initial DWI lesions and retrieved demographic data, risk factors, National Institutes of Health Stroke Scale (NIHSS) scores on admission, and blood tests results. We examined several variables using univariate and multivariate regression analyses to determine predictors of ICH. RESULTS: Twenty-nine patients fulfilled our inclusion criteria; 17 patients (58%) had ICH, and of these 4 (13%) had symptomatic ICH and fatal outcome. On univariate analysis, higher systolic blood pressure, NIHSS score, serum glucose level, volume of initial DWI lesion, and absolute number of voxels with ADC value < or =550x10(-6) mm2/s were statistically associated with ICH, and all were subjected to multivariate analysis. However, only the absolute number of voxels, ie, volume of ischemic tissue on DWI, with ADC < or =550x10(-6) mm2/s emerged as an independent predictor of ICH. CONCLUSIONS: Our findings suggest that volumetric ADC analysis can be used to assess ICH risk after thrombolysis. This may be particularly helpful if rtPA is to be given outside the 3-hour window.

Adult↗
PubMed2002

Investigation of the chemico-physical characteristics of the active components in the Chinese herb Gastrodia elata Bl. by capillary zone electrophoresis.

A CE method for investigating the chemico-physical characteristics of the active components of low molecular weight in Gastrodia elata Bl. is described. First, the dissociation constants of five active components were determined based on the relation between the effective mobility of the solutes and the buffer pH value. Second, an equation that describes the relation of the migration time and the molecular weight was developed and used to predict the migration order and to calculate the electroosmotic velocity. The results predicted by theory agreed well with that from experiments.

Chemistry, Physical↗
PubMed2002

[Signal transduction pathways induced by nitric oxide in rat hepatocytes]

OBJECTIVE: To study signal transduction pathways in cultured rat hepatocytes in the high nitric oxide (NO) environment of hepatitis. METHODS: NO levels were assessed by measurement of its stable oxidative products nitrite (NO2(-)) and nitrate (NO3(-)) using the Griess method with or without thiols (GSH or L-Cys). Rat hepatocytes were incubated with Sodium Nitroprusside (SNP) to produce a high NO environment and the intracellular cGMP and s-nitrosoglutathione (GSNO) in the culture media were measured using radioimmunoassay or with the MTT assay absorbed at 334nm respectively. RESULTS: After incubation of 1.543 mmol/L SNP for 30 minutes 0.63+/-0.06 mmol/L and at 25 minutes 0.98+/-0.11 mmol/L of NO was released in containing 25 mmol/L GSH and L-Cys condition. The levels of both cGMP and GSNO were significantly increased (compared with control P<0.05) in a dose related manner. CONCLUSION: Signal transduction of cultured rat hepatocytes in a high NO environment could be a cGMP-dependent as well as a non-cGMP-dependent pathway.

Journal Article↗
PubMed2002

[Analysis of prophylactic antibiotics for cesarean section].

OBJECTIVE: To study the appropriate antibiotic for prophylactic use in cesarean section. METHODS: The effects and side effects of prophylatic antibiotics in 1 266 cesarean section were studied retrospectively. Six regiems were engaged: (1) Penicillin and Ampicillin; (2) Mezlocillin sodium; (3) Sulbactam and Ampicillin; (4) Ciprofloxacin; (5) Clindamycin; (6) Cefacidal. RESULTS: The duration of postoperative body temperature return to normal of 1 - 6 group is (54.0 +/- 28.4) hours, (48.9 +/- 27.8) hours, (49.9 +/- 23.9) hours, (58.6 +/- 33.7) hours, (52.5 +/- 25.2) hours, (63.1 +/- 51.1) hours respectively. It was longer in cefazolin group than the others. There were less puerperal morbidity and side effects of Mezlocillin. CONCLUSIONS: Penicillin and Ampicillin are still the most common choices as prophylatic antibiotic in cesarean section. Mezlocillin is appropriate as well.

Ampicillin↗
PubMed2002

[Curative effect of percutaneous microwave coagulation therapy for hepatocellular carcinoma].

OBJECTIVE: To observe the curative effect of percutaneous microwave coagulation therapy (PMCT) with 2450 MHz microwave antenna for hepatocellular carcinoma. METHODS: Under local or epidural anesthesia, a thin percutaneous microwave antenna was introduced with ultrasound guidance into the tumor in the liver for thermo-coagulation. RESULTS: Among the 97 hepatic cancer lesions in 52 patients, 61(62.9%) with phi < 3 cm were coagulated once. In follow-up of 6-12 months of these lesions, 57(93.4%) showed no recurrence by CT or MRI. Thirty-six (37.1%) with 3 cm < phi < 5 cm coagulated twice showed that 27 (75.0%) gave CR and 9 (25.0%) gave PR by CT or MRI in follow up of 6 months. There were no serious clinical side effects or complications in the PMCT patients. CONCLUSION: Percutaneous microwave coagulation therapy gives good curative effect on liver tumor with phi < 3 cm. It is partly effective on lesions 3 cm < phi < 5 cm.

Adult↗
PubMed2002

Single coronary artery and sick sinus syndrome.

We report 2 patients with recurrent syncope and dizziness, later noted to have single coronary arteries. Both had right heart strain, one having pulmonary hypertension and the other having right ventricular outflow obstruction, which resulted in sinus node dysfunction. Patients were refractory to medical therapy and improved after pacemaker implantation.

Aged↗
PubMed2002

[Chiral separation of enantiomers of synthesized amlodipine and its intermediate by capillary electrophoresis].

A capillary electrophoretic method for the chiral separation of enantiomers of synthesized amlodipine and its intermediate was developed. Several cyclodextrins (CDs) were applied as the chiral selectors and it was found that the ionic modified carboxymethyl-beta-cyclodextrin (CM-beta-CD) could give satisfactory enantioselectivity. In addition, the effects of the pH value of the buffer system, the concentration of the CD and the voltage on the chiral separation were investigated. The optimized buffer for amlodipine and its intermediate enantiomers was a buffer containing 30 mmol/L phosphate and 50 mmol/L CM-beta-CD (pH 6.12). Under these conditions, the resolutions of enantiomers of amlodipine and its intermediate were 1.73 and 1.55, respectively.

Amlodipine↗
PubMed2002

[Application of resilient backpropagation neural network in predicting hydrophobic parameters of alkylbenzenes].

Artificial neural networks have been applied for predicting the hydrophobic parameters of alkylbenzene. Compared with traditional methods it has the advantages of simple operation and wide applications. Based on error back propagation neural networks the relationship among the molecular connectivity index (chi), van der Waals surface area (Aw) and hydrophobic parameter was studied, meanwhile the mathematical model was established and used to predict the hydrophobic parameters. By comparing the hydrophobic parameters of experimental values with those calculated by neural networks, we found they had good agreement. The average relative deviation was less than 1%. Because traditional back propagation network is generally time consuming, resilient backpropagation (RPROP) algorithm was used to solve this problem. By using RPROP algorithm, the hydrophobic parameters were obtained precisely by fast training and simple parameter's selection. It needed less than 1,000 iterations to reach the goal on the computer operated at 1.4 GHz. The present work shows that the artificial neural network is a new powerful tool to predict the physicochemical parameters.

Algorithms↗
PubMed2002

[Capillary electrophoretic enantioseparation of arylglycine amides with highly sulfated beta-cyclodextrin as chiral selector].

Enantiomers of nine arylglycine amides synthesized were successfully separated by capillary electrophoresis (CE) using highly sulfated beta-cyclodextrin (HS-beta-CD) as a chiral selector. Baseline enantioseparation of the analytes was obtained within 6 min at neutral pH but not the commonly used acidic condition. HS-beta-CD content, buffer type and concentration, and non-chiral additive were studied and optimized for high resolution and fast speed. A reproducible running buffer system composed of 15 g/L HS-beta-CD, 0 or 10% (volume fraction) methanol and 20 mmol/L 3-(N-morpholino) propane sulfonic acid at pH 6.5 was obtained. The D-enantiomer always migrated ahead of the L-enantiomer for all the 9 pairs of arylglycine amides. The migration order was found to be dependent on the structure of the solutes.

Amides↗
PubMedDate not supplied

Determination of andrographolide, deoxyandrographolide and neoandrographolide in the Chinese herb Andrographis paniculata by micellar electrokinetic capillary chromatography.

In this paper a micellar electrokinetic capillary chromatographic (MEKC) method has been developed for determining the active components (andrographolide, deoxyandrographolide and neoandrographolide) in water:ethanol extracts of the Chinese crude herb Andrographis paniculata and its preparations (Chuanxinlian and Xiaoyan Lidan tablets). The optimum separation conditions were 15 mM sodium dodecyl sulphate in 30 mM borate buffer (pH 9.5) with UV detection wavelength at 214 nm and a constant voltage of 16 kV. An HPLC method was employed in order to validate the MEKC method with respect to separation efficiency, sensitivity, linearity and repeatability. The two methods are shown to be complementary because of their different selectivity and thus are very suitable for cross-validation studies. The MEKC method is demonstrated to be more appropriate for the analysis of the active compounds in A. paniculata in that it is easier and less expensive to use and does not suffer from contamination of the chromatographic column.

Andrographis↗
PubMedDate not supplied

Determination of diterpenoid triepoxides in Tripterygium wilfordii by micellar electrokinetic capillary chromatography.

A micellar electrokinetic capillary chromatographic (MEKC) method has been established for the identification and determination of diterpenoid triepoxides in the Chinese herb Tripterygium wilfordii Hook F. and its preparations. Studies of the influence of boric acid and borax buffer concentration and pH, and of sodium dodecylsulphate (SDS) concentration have been carried out, and the optimum separation for the triepoxides was achieved using 20 mM boric acid and 10 mM borax with 20 mM SDS as the running buffer. MEKC was found to exhibit good accuracy, precision and repeatability. The sensitivity of the assay was sufficient to monitor the three active components in T. wilfordii and its preparations.

Borates↗
PubMedDate not supplied

A novel method to convert triptolide into tripchlorolide in Tripterygium wilfordii.

A new method has been established to convert triptolide (1) into tripchlorolide (2) directly in the Chinese herbal drug Tripterygium wilfordii Hook F. and the influences of reaction times and pH values have been investigated. It was found that 1 could be most efficiently converted into 2 using a hydrochloric acid-acetic acid system. An HPLC method was devised in order to monitor the conversion and ESI-MS was used to identify the synthetic product 2. The sensitivity of the assay was sufficient to monitor the conversion of the main active components in T. wilfordii.

Diterpenes↗
PubMedDate not supplied

Biological significance of chromosomal imbalance aberrations in gastrointestinal stromal tumors.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Current criteria for the diagnosis of malignant GISTs do not always reliably predict patient outcomes. In order to search for genetic markers with prognostic potential, chromosomal imbalance aberrations (CIAs) were analyzed in 28 subjects with GIST using comparative genomic hybridization and correlated with clinicopathological features. Except for a small rectal tumor, CIAs were identified in all GISTs, including 14 from the stomach, 11 from the small intestine, 1 from the esophagus, and 1 from the rectum. Losses were more common than gains. The median number of CIAs in high-risk GISTs was significantly higher than that in low-risk GISTs (5.60 +/- 2.59 vs. 3.38 +/- 2.55; p < 0.05), especially for losses (4.60 +/- 1.84 vs. 2.63 +/- 2.13; p < 0.01). Loss of 14q was the most common CIA in both low-risk and high-risk GISTs, and can be regarded as an early event of GIST development. Losses of 1p and 15q were also very common, often coexisting, and were slightly more frequent in high-risk GISTs than in low-risk GISTs. Other recurrent CIAs, including losses of 10q, 13q, 15q, 18q, and 22q and gains of 5p, 12q, 17q, and 20q were relatively less common in this series. Among these CIAs, losses of 13q, 10q (with minimal overlapping on q11-q22), and 22q were most likely the chromosomal loci potentially harboring the tumor suppressor gene(s) which may be related to early recurrence and/or metastasis during malignant transformation of GISTs.

Chromosome Aberrations↗
PubMedDate not supplied

Coronary stenting or balloon angioplasty for chronic total coronary occlusions: the Taiwan experience (a single-center report).

The authors conducted this study to compare the restenosis and reocclusion rates of primary balloon angioplasty alone versus angioplasty followed by stenting in Taiwanese patients with chronic total occlusions. They also evaluated whether stenting reduced the incidence of restenosis and improved left ventricular function in these patients. From October 1998 to April 2000, a total of 294 patients with chronic total occlusion (Thrombolysis in Myocardial Infarction grade 0 flow) underwent recanalization using balloon angioplasty alone or followed by stent implantation. Of these, only 129 patients were included after procedural failure and patients lost to follow-up; 62 patients were placed in the stent group, while 67 patients were assigned to the percutaneous transluminal coronary angioplasty (PTCA) group. Coronary angiography was performed at baseline and at 6 months follow-up or earlier if angina or objective evidence of ischemia involving the target vessel or other vessels was present. Procedural success was 60%. Minimal lumen diameter increased significantly after stenting: 2.97 +/-0.41 vs 2.24 +/-0.41 (p < 0.001); 60% of patients in the stent group were free of restenosis, whereas only 33% in the PTCA group were free of restenosis at follow-up. Only 1 patient in the stent group had reocclusion, as opposed to 17 (25%) patients in the PTCA group (p < 0.001). The follow-up minimal lumen diameter (MLD) at 6 months was significantly larger in the stent group: 1.80 +/-0.85 mm vs 1.08 +/-0.82 mm (p < 0.001). Left ventricular function improved in the stent group, but not in the PTCA group (58.44 +/-16.58% to 63.60 +/-14.59% [p < 0.001] vs 54.13 +/-15.66% to 54.31 +/-15.60% [p = 0.885]). More patients had angina in the PTCA group than in the stented group 43 vs 29 (p = 0.053). The postprocedural MLD and reference vessel diameter (RVD) were the strong predictors of restenosis and follow-up MLD (p < 0.001). Stenting of chronically occluded arteries significantly reduced the incidence of reocclusion and restenosis, at the same time improving left ventricular function in these patients. This should be the procedure of choice after successful angioplasty of chronically occluded vessels.

Aged↗
PubMedDate not supplied

Semipermeability imparted by surface-active phospholipid in peritoneal dialysis.

OBJECTIVE: It has previously been demonstrated that a lining of surface-active phospholipid (SAPL) is reversibly bound (adsorbed) to normal peritoneal mesothelium. The lining acts as a boundary lubricant and release (anti-stick) agent preserving mechanical Integrity of the epithelial surface. In a review of clinical trials on the use of SAPL (akin to "surfactant") to restore ultrafiltration (UF) in patients on peritoneal dialysis (PD), speculation is that, by adsorption, the SAPL lining might also be Imparting the semipermeability vital for UF. DESIGN: To evaluate the hypothesis, SAPL harvested from the spent dialysate of 5 patients with normal UF was deposited onto a porous, inert medium, and the resulting 7 "membranes" were clamped in an Ussing chamber used as an osmometer. RESULTS: With every "membrane," a clinical concentration of glucose (2.5%) was able to induce a statistically significant osmotic pressure when dialyzed against saline. We also demonstrated how synthetic SAPL--in the form of dipalmitoyl phosphatidylcholine (DPPC) and an admixture of DPPC with phosphatidylglycerol (PG) called artificial lung-expanding compound (ALEC)--imparts greater osmotic pressure In proportion to an Increasing glucose gradient. Our findings prove that human peritoneal SAPL has the physical capability to Impart semipermeability when adsorbed to a surface. COMMENT: As a lipid lining, adsorbed SAPL could also explain the high permeability of the natural membrane to lipophilic substances in PD. Administered as a very fine powder or as a solution in a lipid solvent, ALEC offers a potential treatment for restoring UF, if applied during the interdialytic Interval. In various physical forms, ALEC and DPPC have both been widely used for two decades with complete safety in the treatment of respiratory distress syndrome in newborns. The question of formulation of exogenous SAPL In restoring UF Is discussed as a complex physicochemical compromise between the higher surface activity of saturated phosphatidylcholine and its lower solubility in water.

Absorption↗