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Biomedical subjects

X Chen

Publications and source records attributed to X Chen.

At least 829 records · Page 46Linked to original sources
PubMed1999

[Study on qualitative analysis method of high performance liquid chromatography by simultaneous multi-wavelength detection].

In this paper, we introduce an HPLC qualitative method, that is, multiwavelength detection qualitative analysis method. According to Beer's law, for a certain compounds the ratio of peak areas at different wavelengths is a constant. Comparing the ratio of peak areas of a component at different wavelengths with that of the standard by means of simultaneous multi-wavelength detection, we established a convenient qualitative method. This method has been applied successfully to qualitative analysis of 18 aromatic amines in the prohibited azo dyes.

Benzidines↗
PubMed1999

[Separation of levonorgestrel, progesterone and testosterone by micellar electrokinetic capillary chromatography].

Separation of levonorgestrel, progesterone and testosterone was achieved by using micellar electrokinetic capillary chromatography (MECC). A column of 53 cm (to the detector) x 50 microns i.d. uncoated fused-silica capillary (totally 68 cm in length) and an ultra-violet detector with fixed wavelength at 254 nm were used throughout all the experiments. MECC analysis was optimized by evaluating three different micelle-forming agents, the concentration of SDS and several of organic additives in a 10 mmol/L borate running buffer (pH 9.2). Complete separations were obtained with either 10%-20% acetonitrile or 20 mmol/L 2,6-dimethyl-beta-cyclodextrin (DM-beta-CD) as the modifier in buffer. When the acetonitrile volume fraction was in the range of 0-15%, the migration times of the three steroids increased with the acetonitrile volume fraction, but in the range of 15%-20% acetonitrile concentrations, the situation was opposite. This behavior of the steroids was attributed to the interaction of two opposite effects, an increased mobility due to decreased partition coefficient and a decreased electroosmotic flow (EOF). Both beta-cyclodextrin (beta-CD) and gamma-cyclodextrin (gamma-CD) were found to be inadequate for a satisfactory separation.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed1999

[Hydrophobic membrane chromatography for fast purification of biological macromolecules].

Cellulose membrane bonded with four commonly used hydrophobic groups, octyl, butyl, phenyl and polyethylene glycol was first investigated for their binding and purification characteristics of protein and enzyme with octyl- and phenyl-Sepharose CL-4 B as controls. Hydrophobic membranes bound BSA effectively by hydrophobic interaction in high salt solution. Their binding capacities were not notably affected by significantly increasing the flow mass rate or decreasing the mass concentration of protein solution, but were much lower than those of octyl- and phenyl-Sepharose CL-4B. 11.8 fold of purification with an approximately 100% recovery of bovine liver catalase was achieved by step gradient elution on the phenyl cellulose membrane cartridge in a single step in only ten mins or a little more. Increase of the flow mass rate had no effect on the purification of catalase, however, the processing time was shortened greatly. Hydrophobic membrane chromatography here reported exibits a potential of fast processing of the protein solution in large volume with low mass concentration of the target protein, such as genetic engineering culture solution.

Animals↗
PubMed1999

[Cloning of DNA fragment related to salt tolerance in Sinorhizobium meliloti 042B].

Total DNA partially digested by EcoR I was prepared for S. meliloti 042B, in which 15-25 kb DNA fragments were collected. Vector pLAFR I was purified and digested by EcoR I, and then the various DNA fragments of 042B were ligated with pLAFR I by T4DNA ligase. Gene library of S. meliloti 042B was constructed with pLAFR I using E. coli S17-1 as recipient. The number of bacterial recombinants obtained was about 8,000 and 95% of them contained foreign DNA fragments. Using NTG, 042B was mutated on FY plates and 12 sensitive strains were screened at 0.5 mol/L NaCl from 2,000 colonies. One of them was named GZ17 and selected as a recipient strain. By biparental mating the foreign DNA fragments were introduced from gene library of strain 042B into recipient strain GZ17 which is sensitive to 0.5 mol/L NaCl. Then the transconjugants were grown on FY plates containing tetracycline (20 micrograms/mL) and 0.5 mol/L NaCl. A 7 kb inserted DNA fragment related to salt tolerance was obtained. In subcloning experiment, a 4 kb DNA fragment related to salt tolerance was obtained.

Cloning, Molecular↗
PubMed1999

[Purification and characterization of a novel antifungal peptide APS-1 produced by Bacillus cereus].

In previous study, we isolated an antagonist Bacillus cereus strain: S-1 from cotton plant. In field experiments, this bacterium was shown strong inhibition to several plant diseases. In this paper, we reported the purification of the antifungal substance produced by the bacterium and its properties. After the steps of acid precipitation, methanol and ethy lether extraction, Sephadex G100 and DEAE52 column chromatography, the antifungal material was purified. The purified material had absorption peak at 275 nm, and was exhibited negative in biuret color reaction. However after hydrolyzed with HCl, this substance shown positive in the same reaction. Amino acid analysis to the hydrolysate of APS-1 showed that APS-1 was composed of Glu, Asp, Tyr, Ser, Thr, Pro, Leu, Ile, Val and an unknown amino acid. Combining with its pratial resistance to proteinases, it was suggested that this antifungal material was a cyclic peptide. This peptide, named APS-1, with strong inhibition on the germination of spores of the phytopathogens tested, was shown high stability against ultraviolet radiation and heat. APS-1 may have potential role in plant diseases biological control.

Amino Acids↗
PubMed1999

[A pilot study on malaria control by using a new strategy of combining strengthening infection source treatment and health education in mountainous areas of Hainan province].

AIM: To explore a new malaria control strategy that fits current epiodemiological condition and coincides with modern medicine model and the principle of cost-benefit. METHODS: The new strategy highlights the risk villages and risk population as the focal point and integrates health education with behavioral intervention. The main anti-malaria measures consists of carrying out health education in risk villages, giving mass drug administrations in risk population staying overnight in the mountain, following up malaria cases for implementing radical cure, but without using traditional residual spraying or impregnating bednets with insecticides. RESULTS: After having adopted the new strategy and taken the control measures, the people's knowledge about malaria increased to a higher level and the indices of malaria reduced to a lower level. The rate of bednet-using in the population was increased from 26.8% to 72.6%. The annual parasite incidence (API) of malaria was declined from 3.5% in 1994 to 1.1% in 1996 and 0.8% in 1997, and the API of falciparum malaria was declined from 1.0% to 0.3% and 0.3% respectively in the townships at the same time. The parasite rate(PR) of malaria was declined from 7.2% in May, 1995 to 2.1% in November, 1996 and 1.2% in October, 1997 and the PR of falciparum malaria was declined from 1.2% in May, 1995 to 0.1% in October, 1997. The proportion of villages without malaria cases was increased from 18.6% in 1994 to 54.2% in 1997, and the number of risk villages with a malaria incidence above 5% was reduced from 14 to 2 at the same time. The ratio of cost/benefit was 1:2.4 in 1995-1996 and 1:4.4 in 1997, showing a better economic benefit. CONCLUSION: The expectant result has been obtained, thereby providing new experience for the malaria control in the mountainous areas of Hainan Province.

China↗
PubMed1999

[Observation on the clinical symptoms and sporocyst excretion in human volunteers experimentally infected with Sarcocystis hominis].

AIM: To investigate the excretion of sporocysts and clinical manifestations in humans experimentally infected of Sarcocystis hominis. METHODS: Three volunteers were infected by eating raw beef containing cysts of S. hominis. One ingested about 1,567 cysts in skeletal muscles of a naturally infected cattle; two volunteers each ingested about 14,740 cysts from an experimentally infected water buffalo meat. Fecal examination by zinc sulfate flotation method was conducted daily since d4 postinfection (pi). RESULTS: Free sporocysts and oocysts were found in their faeces from d11-40, d12-23, d10-30 pi, and peaked at d18, d14, d14. All of them presented clinical symptoms such as abdominal pain, distension, watery diarrhea and eosinophilia 1 wk approximately 4 wk pi and were spontaneously cured within 29 days pi without taking any medicine. CONCLUSION: All the experimentally infected persons had gastrointestinal symptoms and passed sporocysts and oocysts in faeces 10-12 days after infection and persisted for 11-29 days.

Adult↗
PubMed1999

[Morpholgical, histological and histochemical observations on the effect of albendazole on encysted larvae of Trichinella spiralis in mice].

AIM: To study the mechanism of action of albendazole on encysted larvae of Trichinella spiralis in mice. METHODS: Twelve Kunming strain mice each infected with 200 T. spiralis larvae were equally divided into two groups. Six mice of the treatment group were treated with 30 mg of albendazole/kg daily for 5 days. Morphological, histological and histochemical methods were used. RESULTS: The encysted larvae of albendazole-treated group became significantly damaged, most worms were shrunken and surrounded by inflammatory cells. Histochemical study demonstrated that the glycogen and RNA content of the larvae in the treated group was decreased, the activities of SDH, ATPase, ACP were lower than those of the control group. CONCLUSION: Albendazole can affect the physiological function of Trichinella spiralis.

Albendazole↗
PubMed1999

[Safety analysis of dust mite allergen for diagnosis and immunotherapy of asthma and rhinitis].

AIM: To make a retrieval investigation of safety in using Dermatophagoides farinae extract in diagnosis and immunotherapy with patients of asthma and rhinitis. METHODS: A questionnaire evaluation of the safety use of D. farinae extract (SMU-Df) during diagnosis and immunotherapy of patients from 1974 to 1995 was carried out. RESULTS: A total of 8,46,342 injections were statistically analysed, among whom 142 systemic adverse reactions occurred involving urticaria 0.82@10000, severe attack of asthma 0.77@10000, anaphylactic shock 0.07@10000 (CL = 1.4-12.0/million), and angioedma 0.02@10000. The time of onset of systemic reactions of immediate type was < 30 min in 32 cases-times, and 1 h and 2 h in 6 cases-times; the time to onset of late response type was 3 h-48 h in 23 cases-times with highest incidence of severe asthmatic attacks. The systemic reactions occurred in 18 subjects during skin test, in 96 cases-times during increasing dose phase, and in 14 cases-times during. Among them 6 cases were of anaphylactic shock, and none of it after emergency treatment. The major cause of manifestation of systemic reactions for 41 cases after immunotherapy with SMU-Df extract was due to over dosage errors. CONCLUSION: The application of SMU-Df extract in skin test and immunotherapy of asthma and rhinitis sensitive to mite for the past 22 years in this country indicated that the efficacy and safety have been high.

Allergens↗
PubMed1999

[Quantitative analysis of vocal fold vibration].

OBJECTIVE: To measure vocal fold vibration quantitatively and study the effects of gender and phonation mode. METHOD: The authors adopted a new computerized image analysis technique and EGG in 60 normal speakers, and the parameters of vocal fold vibration were measured and analyzed according to the loudness, pitch and gender. RESULT: With frequency increasing, CQ got smaller and OQ larger which expressed longer open phase. As intensity increased, the duration of open phase became shorter and the closing phase got relatively much shorter. Males had a longer closed phase than females. The closing duration appeared relatively shorter than opening duration in phonation. CONCLUSION: The quantitative measures of vocal fold vibration become feasible with modern computers and commercially available image analysis software. Certain features of vocal fold vibration vary with intensity variations, while others vary with gender or frequency variation.

Adolescent↗
PubMed1999

[Observation of curative effect of radical mastoidectomy with rebuilding back wall of external and defect tympanoplasty].

OBJECTIVE: To manage the back wall defect of external acoustic canal and opened mastoid cavity which was remained from radical mastoidectomy. METHOD: 31 ears with cholesteatomatous otitis media and 3 ears with skeletal ulcer were treated by primary operation which consisted of radical mastoidectomy with rebuilding back wall of external canal and tympanoplasty. RESULT: All cases were followed up for 5 years. And all of external anditory canal are normal in appearance. Sixteen ears reached auditory level for social interaction and another 16 for functional audition. CONCLUSION: The Primary operation that we mentioned above may resolve some problems such as mastoid cavity or big external canal which were remained from radical mastoidectomy. It is effective to improve hearing.

Adolescent↗
PubMed1999

[The effect of cAMP on the transcription and regulation of angiotensin II type 1 receptor gene in cardiomyocytes of neonatal rats].

OBJECTIVE: To clarify the effect of cAMP on the transcription of angiotensin II type 1 (AT1) receptor mRNA in cardiomyocytes. METHODS: Cardiomyocytes from SD neonatal rats were cultured in DMEM containing 10% fetal bovine serum (FBS) with 0.1 mmol/L 5-bromodeoxyuridine (Brdu). At day 5-7, primary cultured cells were used. FBS and Brdu were deprived 24 h before the stimulation. The levels of AT1 mRNA in primary cultured cardiomyocytes were examined by RT-PCR. RESULTS: Stimulation of forskolin (30 mumol/L) plus 3-isobutyl-1-methyl-xanthine (IBMX, 30 mumol/L) which induced the accumulation of cellular cAMP decreased the expression of AT1 receptor mRNA to (64.4 +/- 20.3)% of control at 6 h treatment; while it increased the expression of AT1 receptor mRNA to (209.6 +/- 24.0)% of control at 48 h treatment. CONCLUSIONS: cAMP regulated the transcription of AT1 receptor gene.

Animals↗
PubMed1999

[Angiotensin II regulates the expression of collagens in rat heart].

OBJECTIVE: To testify the effect of angiotensin (Agn) II on the regulation and expression of collagen I, III genes in rat heart as well as the influence of DMP811 (a novel nonpeptide selective angiotension type 1 antagonist) on the effect of Ang II. METHODS: Six-week-old male SD rats with osmotic minipump subcutaneously containing either Ang II or saline were used. (1) Saline-infused(control) group (n = 6), (2) Ang II-infused group (n = 6). (3) Ang II-infused and DMP811-treated (3 mg.kg-1.d-1, by gavage) group (n = 6). Ang II (200 ng.kg-1.min-1) or saline was continuously infused for 1 week. After extraction of cardiac total RNA, the levels of collagen I, III mRNA and proteins were measured with RT-PCR and Sirius red staining respectively. RESULTS: Cardiac weight, cardiac weight/body weight radio, the mRNA levels of collagen I, III were increased by (4.7 +/- 0.4)%, (4.9 +/- 0.9)%, (22.0 +/- 4.7)% and (20.6 +/- 4.9)% respectively, in group 2 compared with those in group 1. The analysis of collagen on Sirius red-stained sections showed that Ang II increased the deposits of both collagen I and III. The above changes caused by Ang II could be inhibited fully by DMP811. CONCLUSIONS: Ang II up-regulated the expressions of collagen I, III via angiotension type 1 receptor.

Angiotensin II↗
PubMed1999

[Comparison of effects of Herba Pogostmonis from gaoyao and wuchuan on digestive system].

The effects of the three extracts (decoction, oil-free decoction and volatile oil) of Herba Pogostmonis from Gaoyao and Wuchuan on digestive system were compared. The results demonstrated that the decotion and oil-free decoction from Gaoyao and Wuchuan could depressed gastric evacuation in mice. All the three extracts from Gaoyao and Wuchuan could inhibit the ACh-as well as BaCl2-induced spasmodic and automatic contraction of isolated rabbit intestine. The decoction and oil-free decoction from either Gaoyao or Wuchuan inhibited the normal intestinal propulsion. They also increased gastric secretion of acid and activity of pepsin and amylase. These suggest that both of Herba pogostmonis relief gastrointestinal spasm and improve the digestion. The total effect of Herba pogostmonis from Gaoyao was more potent that from Wuchuan.

Animals↗
PubMed1999

[The use of ultrasound biomicroscope in the diagnosis of anterior segment intraocular foreign bodies].

PURPOSE: To evaluate the use of Ultrasound Biomicroscope(UBM) in the diagnosis of anterior segment intraocular foreign bodies(IOFBs). METHODS: Besides the rountine x-ray photography and B-scan ultrasound examination, 9 cases with difinite IOFBs injury history were examined by UBM. RESULTS: Nine cases of IOFBs were shown in UBM image, among them 4 cases were invisible in x-ray photography and B-scan ultrasound examination. The IOFBs located in anterior chamber(1 case), in posterior chamber (2 cases), in pars plana (5 cases) and in iris root(1 case). The size of IOFBs varied from 0.1 mm x 0.25 mm to 1 mm x 3 mm. The IOFBs were extracted by combined intraocular surgery or direct magnetize extraction. CONCLUSION: Although most IOFBs could be localized by X-ray and B-scan ultrasound, some located in the posterior chamber or ciliary body are hard to detect, especially when they are nonmetal and extremely small. The high resolution image of the anterior segment of the eye created by UBM can help to localize the IOFBs and show the relation between IOFBs and surrounding tissue, which is important in the diagnosis and the choice of surgery method.

Adult↗
PubMed1999

[Pathogenesis and clinical classification of the malignant glaucoma].

PURPOSE: To study the pathogenesis of the malignant glaucoma and the basis for the clinical classification of malignant glaucoma. METHODS: Twelve eyes with malignant glaucoma were examed by ultrasound biomicroscopy (UBM), type A and type B ocular ultrasounographer and other clinical ophthalmic tests and diagnostic therapy. The ocular anatomic structures of all 12 eyes were compared with those of the fellow eyes. RESULTS: Ciliary block were confirmed in four of the twelve eyes (33.3%) with malignant glaucoma while the narrow and small anterior segment were found in the fellow eyes by UBM. Iris lens disphragm anterior displacement were found in the other eight of the twelve eyes (76.6%) and their ciliary bodies were deformed passively. The ciliary bodies and anterior segment of the fellow eyes of these eight eyes were anatomically normal. Diagnostic surgery was performed in seven of the twelve eyes and six cases with fluid existing in the vitreous cavity were identified. CONCLUSION: According to our study, we suggest to classify malignant glaucoma into two tyges. One is ciliary block, which caused by ciliary block and concerned with the narrow and small structure of the anterior segment of eye. The other is lens iris block, which caused by iris lens diaphragm anterior displacement. Both types have the same pathophysiologic characteristics, such as, shallow anterior chamber, posterior chamber disappearance and aqueous humor misdirection to the vitreous cavity. But their pathogengesis may not be completely same.

Adult↗
PubMed1999

[A preliminary report of a new technique: non-penetrating trabecular surgery].

OBJECTIVE: To evaluate the clinical effect of nonpenetrating trabecular surgery with sodium hyaluronate gel implant in Primary Open-Angle Glaucoma(POAG). METHODS: Twenty-four eyes of 22 patients with medically uncontrolled POAG were underwent nonpenetrating trabecular surgery with hyaluronate gel implant. The procedure was performed involing excising a deep-sclera tissue that flush with innerwall of Schlemm' s canal without opening the anterior chamber, then placing a 3 mm x 4.5 mm x 0.5 mm or 3.5 mm x 3.5 mm x 3.5 mm sodium hyaluronate gel implant under the scleral flap respectively. The postoperative Intraocular Pressure (IOP), Inflammation and fitering bleb were analysised. All of patients were undertaken ultrasound biomicroscopy (UBM) to evaluate the surgery site on postoperative 1-3 months. Mean follow-up was 3.9 +/- 2.2 months. RESULTS: The IOP decreased from a mean preoperative value of 24.4 +/- 9.1 mmHg to a mean postoperative value of 15.1 +/- 3.7 mmHg (P < 0.01). The number of anti-glaucomatous medications by topically or systemically was reduced from preoperative sorts of 2.8 +/- 1.4 to postoperative sorts of 0.7 +/- 1.0 (P < 0.01). The visual acuity remained stable, 6 eyes had IOP elevated and 2 eyes had occured hyphema. The complications such as flat chamber, inflammation and detachment of choroid were not observed. The UBM showed that the hyaluronate gel implant wasn't degraded and a transparent liquid space was formed under the scleral flap in all of patients on postoperatively 1-3 month. The filtering blebs were formed in some patients. CONCLUSION: Nonpenetrating trabecular surgery with hyaluronate gel implant can effectively lower IOP and reduce the number of anti-glaucomatous medications. No severe complications occured. With a simple postoperative nursing, it can be performed in clinic. It is proved to be a promising and new special technique to treat glaucoma.

Adolescent↗