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Biomedical subjects

L Chen

Publications and source records attributed to L Chen.

At least 739 records · Page 41Linked to original sources
PubMed1998

[Clinical application of TMS-MEP in spinal cord injury].

OBJECTIVE: To evaluate transcranial magnetic stimulation motor evoked potential (TMS-MEP) in the diagnosis of spinal cord injury. METHOD: 56 patients with injury of the spinal cord and cauda equina were examined using TMS-MEP and followed up. RESULT: In 21 patients with complete paralysis, TMS-MEP of bilateral tibialis anterior and gastrocnemius disappeared and paralysis did not recover. Abnormal was noted TMS-MEP and paralysis not recovered in 2 patients with injury of conus medullaris and cauda equina. Incomplete paralysis occurred in 35 patients. TMS-MEPs of more than one muscle in every patient were recorded. Paralysis and TMS-MEPs recovered in different degree in the 33 patients, in which the strength was 0 class and TMS-MEPs were abnormal in 25 target muscles before operation whereas their strength obviously recovered or even normalized after operation except two muscles. CONCLUSION: TMS-MEP is an effective method for diagnosis and prognosis of spinal cord injury.

Adolescent↗
PubMed1998

[Corneal epithelium implantation under corneal flap after excimer laser in situ keratomileusis: a clinical pathological and cytological study and management].

OBJECTIVE: To study the clinical pathological and cytological characteristics of corneal epithelial cells implanted under the cap of laser in situ keratomileusis and the method of management. METHODS: For 4 eyes with epithelial cell implantation, the corneal cap was torn from temporal side to nasal, and the implanted material was removed from the flap and the stromal base. After washing between the interface, the cap was repositioned. RESULT: No epithelial implantation occurred again in these 4 cases after follow-up for 1 similar 12 months. The clinical pathological and cytological studies showed the material removed was degenerated and necrotic epithelial cells mixed with some unknown materials. CONCLUSION: Clinically, the material formed under the cap white and yellow in color should be removed as soon as it happens. The material consists mainly of non-structural material with necrotic and degenerated epithelial cells.

Cornea↗
PubMed1998

[A study on lens epithelial cell ultrastructure in rhesus monkey cataract].

OBJECTIVE: To investigate the ultrastructure of lens epithelial cells of normal eyes and cataractous eyes in rhesus monkeys. METHODS: Anterior capsules were taken from 4 normal lenses and 4 cataractous lenses of rhesus monkey eyes, and the samples were observed under transmission electron microscope. RESULTS: The ultrastructure of the cataractous lens epithelial cells changed obviously. Mitochondria with disappearance of crista were swollen, and vacuolar. Hollow cell with a single large vacuole in the cytoplasm could be seen. The cytoplasm presented dissolution. Cells were swollen and damaged, even cell membrane disruption could be seen. Karyopyknosis, nuclear deformity, disappearance of perinuclear cistern and nuclear pores could be found. The heterochromatin was concentrated and aggregated at the nuclear periphery. CONCLUSIONS: The ultrastructural changes of the lens epithelial cells in monkey cataractous lens are similar to that in human cataractous lens. Rhesus monkey cataract may be a suitable experimental model to investigate the formation of human cataract.

Animals↗
PubMed1998

[Temporary keratoprosthesis for surgery of severe injuries of ocular anterior and posterior segments].

OBJECTIVE: To evaluate the treatment of severe ocular injuries of anterior and posterior segments with temporary keratoprosthesis used in combined operations. METHODS: With temporary keratoprosthesis a combined operation including pars plana vitrectomy, air-fluid exchange, silicone oil fill in, use of perfluorocarbon liquid, foreign body removal and partial penetrating keratoplasty was performed on 18 eyes of 18 patients with severe ocular injuries, and the postoperative changes and recovery were observed. RESULTS: All eyes were rescued, the visual acuity was increased in 12 eyes, above 0.1 being in 5 eyes, retinal detachment recurred in 3 of 10 eyes, vitreous opacity was present in 1 eye, secondary glaucoma in 1 eye, and atrophy in 1 eye as its preoperative status. CONCLUSION: Temporary keratoprosthesis used in the combined surgeries of anterior and posterior ocular segments is an effective method for treatment of severe ocular injuries.

Adolescent↗
PubMed1998

[The analysis of biological characteristics for the tissue-plasminogen activator (t-PA) mutant engineered cell line].

The morphology of t-PA mutant engineered cell line FSGGI48 is similar to that of CHO-dhfr- cell in polygon. When aminopterin (MTX) concentration is 5 x 10(-6) mol/L, a part of cells become slim, but they are still in polygon. Therefore, the morphology of FSGGI48 cell line is normal. The expression level is 4000 IU/10(6) cells/24 h in serum-free medium. The cell line is bequeathed for three months in vitro and revived after freezing three months, the greater part of cells are stable. The expression level is 3000-4000 IU/10(6) cells/24 h. The assay of tumorigenesis shows that the cells, cellular DNA and purified products don't form tumors in nude mice. The cell line hasn't been contaminated by mycoplasma. The results of chromosomal analysis show that the chromosomal number of CHO-dhfr- cell is 20 and the abnormal rate is 6%. FSGGI48 cell line is same as CHO-dhfr- cell in chromosomal number and the abnormal rate is 15%-18%, it is normal in scope. Therefore, the engineered cell line FSGGI48 is excellent.

Animals↗
PubMed1998

[Studies on the crystal structure of ivermectin (H2B1a)].

The crystal structure of ivermectin (H2B1a) was determined by X-ray diffraction. Ivermectin was found to be composed of more than 80% H2B1a and less than 20% H2B1b. The crystal of H2B1a belongs to the space group C2 with a = 40.736(6)A, b = 9.295(3)A, c = 14.966(3)A, beta = 106.93(1) degree. After structure refinement using least-squares method, the final R factor of H2B1a is 0.0658. The space configuration of H2B1a is a long chain along the C-axis. The molecular aggregates are extended into pairs of long chains parallel to each other, some distance apart. The distance between chains is the same, but their direction is opposite. This structure of H2B1a is similar to some biomacromolecules.

Crystallization↗
PubMed1998

[Hemorheologic change after strong blood flow disturbance caused by gunshot and its influence on the prognosis of the wounded animals].

Three types of experimental models were used in this study: 1. Both thighs of dogs were wounded by 5.56 mm bullet. 2. Femoral artery and vein were tied at the time of wounding. 3. Shock caused by simply bleeding the dogs' femoral arteries. We observed the characteristics of change hemorheology and analyzed its effects on the wounded dogs. The results showed that strong blood flow disturbances always brought about hemorheologic changes such as rapidly increased blood viscosity and red cell's aggregation index and the simultaneous phenomenon of blood concentration. These may be related to extensive endothelium injury and destruction of a number of blood cells caused by disturbance wave. The above change may give rise to abnormality of microcirculation and disturbance of matter transmission; in that sense, it may provide the physiopathologic basis for the occurrence and development of the complication.

Animals↗
PubMed1998

[Studies on the chemical constituents of Citrus reticulata].

Four compounds were isolated from the pericarp of Citrus reticulata and three of them were identified as natsudaidai, nobiletin and 3,5,6,7,8,3',4'-heptamethoxyflavone. Natsudaidai and 3,5,6,7,8,3',4'-heptamethoxyflavone were obtained from this plant for the first time.

Citrus↗
PubMed1998

[Effects of artemisia capillaris on blood glucose and lipid in mice].

The effects of Artemisia capillaris Thunb (AC) on blood glucose and lipid in mice were studied and its effective mechanism was explained. The results showed that hyperglycemic effect in aloxan-induced mice was inhibited (P < 0.01); that hyperglycemica in DM mice was decreased (P < 0.05); but the change of fasting blood glucose (FBG) in normal and hyperlipidemia mice was not significant (P < 0.05); that the level of total cholesterol (TC) and/or atherosclerotic index (AI) was decreased (P < 0.01-0.05) and the content of high density lipoprotein cholesterol (HDL-C) was increased in the above different model mice (P < 0.01-0.05). These results indicated that the AC would have the similar hypoglycemic effect as biguanide-drugs, improve endogenous and exogenous metabolic derangement in blood lipid. These suggest that AC could be used to protect and treat DM and its chronic complication.

Alloxan↗
PubMed1998

[An experimental study on limbal stem cells autograft transplantation with cryopreservation].

PURPOSE: The viability of limbal stem cells with cryopreservation and the treatment effect with cryopreserved limbal autograft transplantation for ocular surface disorders (OSDs) of stem cells deficiency in rabbits. METHODS: Limbal grafts included 2 mm of peripheral cornea and 2 mm of conjunctiva and OSDs models of corneal stem cells deficiency were created in right eyes of 12 rabbits. The grafts were cryopreserved in -196 degrees C liquid nitrogen by program-controlled Bio-Freezer. The limbal autograft transplantations for ocular surface reconstruction were performed after cryopreserved 60 days and 30 days. RESULTS: The stem cells deficiency result in corneal epithelium delay healing. Seven of 12 eyes were healed post-operative 22-26 days with a mean time of 24 +/- 1 days and four eyes with recurrent erosion. The swelling and neovascularization appearing with a mean time of 5 +/- 1 days were discovered. The cryopreserved limbal autograft transplantation can increase corneal epithelial healing with a mean time of 10 +/- 2 days. It was observed that corneal stromal swelling and neovascularization were markedly decreased, and neovascularization of two eyes were disappeared. CONCLUSIONS: Cryopreservation in liquid nitrogen can preserve the viability of limbal stem cells, and provide viable limbal grafts to treat OSDs in clinical patients.

Animals↗
PubMed1998

[The penetrating keratoplasty for the pseudophakic bullous keratopathy].

PURPOSE: To investigate the clinical effectiveness of penetrating keratoplasty for pseudophakic bullous keratopathy and the indication for keeping or removing intraocular lens. METHODS: 13 cases(13 eyes) of pseudophakic bullous keratopathy were treated by penetrating keratoplasty. RESULTS: The intraocular lens were kept in 11 eyes and were removed in 2 eyes during operation, The average follow-up time was 16 months. All corneal grafts remain transparent, Visual acuity of most cases were improved, The best-corrected visual acuity of 5 eyes was 0.2 or better. CONCLUSION: The penetrating keratoplasty is an effective treatment for the pseudophakic bullous keratopathy. It should be kept if intraocular lens is in normal position and located in lens capsule, and it is helpful for safety of the surgery and improvement of visual acuity.

Adolescent↗
PubMed1998

A study of clinical characteristics and treatment of Mooren's ulcer.

OBJECTIVE: To investigate the clinical characteristics and to compare the effects of several therapies of Mooren's corneal ulcer. METHODS: 550 consecutive cases of Mooren's corneal ulcer inpatients were analysed, including the age, sex, laterality of the eye, ulcer location, perforative rate, cure rate of surgeries, recurrent rate, and the effects of conjunctiva excision, lamellar keratoplasty (LKP), LKP and plus cyclosporin A eye drop. RESULTS: The average age of onset of the corneal ulcer was 48.4 years old, the ratio of the male to the female patients was 1:0.74, the bilateral disease was 30% of the total cases, 31.5% of the bilateral disease occurred in the younger group, and 68.5% of the bilateral ulcer occurred in the older group, ulcers located at the limbus of the palpebral fissure were 70% of the total cases, perforative rate was 13.3%, 43.2% of the perforation occurred in the younger group, and 56.8% of the perforation occurred in the older group, recurrent rate of the post-operation was 25.6%, the cure rate of the first procedure of LKP and plus cyclosporin A eye drop was 73.7%, the final cure rate was 95.6%, and the preservative rate of the corneal anatomical structure of the surgeries was 99.7%. CONCLUSION: The study primarily provided the clinical characteristics of Mooren's corneal ulcer patients of China. The available data do not support the present concept of the classification of the two clinical types. The bilateral ulcer may be the malignant type of Mooren's ulcer. LKP and plus cyclosporin A eye drop was an effective treatment of Mooren's corneal ulcer.

Adolescent↗
PubMed1998

[Study on the interaction of lauryl sodium sulfate and rhodamine-6G before micellar formation].

The absorption spectra of an aqueous solution of Lauryl sodium sulfate (SDS) and Rhodamine-6G (R6G) over a wide concentration range were studied. The results show that when c(sds) < 1 x 10(-4)mol x L(-1) SDS forms complex with R6G with molar ratio of 1 : 1, but when c(sds) > 1 x 10(-4) mol x L(-1) the premicelle, which affects the aggregate state of R6G obviously, is formed in the solution. With SDS present, the aggregation number and aggregation constant of R6G were determined, and the dissociating of R6G by inorganic salts also investigated.

English Abstract↗
PubMed1998

[Determination of trace lead in copper by enhancing effect FAAS-using derivative technique].

A new method for the determination of trace lead in copper is proposed by enhancing effect-flame atomic absorption spectrometry using derivative technique. Enhancing effect of matrix Cu on lead was investigated. The sensitivity for lead was enhanced 17 times than that of conventional flame atomic absorption spectrometry by combining derivative technique with matrix Cu enhancing effect. Determination result is satisfactory by this method with 0.007 microg/mL detection limit and 0.7% RSD.

English Abstract↗
PubMed1998

Dynorphin block of N-methyl-D-aspartate channels increases with the peptide length.

We examined the non-opioid actions of various forms of dynorphin A (DynA) on N-methyl-D-aspartate (NMDA) receptor channels in isolated rat trigeminal neurons using the whole-cell patch recording technique. All the dynorphins tested blocked NMDA-activated currents. The blocking actions were voltage-independent. The IC50 was 0.26 microM for DynA(1-32), 6.6 microM for DynA(1-17) 7.4 microM for DynA(1-13), 42.0 microM for DynA(1-10). DynA(1-8) had no detectable blocking action on NMDA responses. Thus, the IC50s of dynorphins for NMDA receptors increased 160-fold as the length of the peptides decreased from 32 to 10 amino acids. Amidation of dynorphins dramatically reduced their IC50s and eliminated the large difference in the IC50s of various lengths of dynorphins. The reduction in the IC50s of dynorphin amides could not be explained by the resistance of the peptides to enzymatic degradation. Our observations suggest that peptide processing affects dynorphin blocking actions on NMDA responses. The positively charged residues, lengths of the peptides and amidation may contribute to their affinities for NMDA receptors.

Amino Acid Sequence↗
PubMed1998

Hair cell regeneration and recovery of function in the avian auditory system.

Chickens were exposed to an intense pure tone that destroyed the hair cells and tectorial membrane in a crescent shaped patch along the abneural edge of the basilar papilla. During the following weeks, when the hair cells and tectorial membrane were regenerating, psychophysical and electrophysiological measures were obtained to assess the time course and degree of recovery. Immediately after the exposure, the behavioral thresholds were elevated 30-40 dB and auditory temporal integration was greatly reduced; however, both measures fully recovered by 28 days post-exposure. In addition, tone-on-tone masking patterns recovered to normal. Immediately after the exposure, the thresholds of single cochlear ganglion neurons were elevated more than 30 dB, tuning curves were broader than normal, two-tone rate suppression (TTRS) boundary slopes were shallower than normal and spontaneous activity was reduced. Threshold and spontaneous discharge rate fully recovered after the exposure. Tuning and TTRS also recovered significantly in most neurons; however, some units with characteristic frequencies (CFs) near the exposure frequency showed abnormal tuning and TTRS suppression. The regeneration of the hair cells and lower honeycomb layer of the tectorial membrane is associated with considerable recovery of function; however, the incomplete recovery of tuning and TTRS in some neurons may be linked to the incomplete regeneration of the tectorial membrane.

Acoustic Stimulation↗
PubMed1998

Blood and urine levels of tea catechins after ingestion of different amounts of green tea by human volunteers.

The inhibitory activity of tea against tumorigenesis has been demonstrated in many animal models and has been suggested by some epidemiological studies. Such activity has generally been attributed to tea catechins. To understand the bioavailability of tea catechins in humans, we gave 18 individuals different amounts of green tea and measured the time-dependent plasma concentrations and urinary excretion of tea catechins. After taking 1.5, 3.0, and 4.5 g of decaffeinated green tea solids (dissolved in 500 ml of water), the maximum plasma concentration (Cmax) of (-)-epigallocatechin-3-gallate (EGCG) was 326 ng/ml, the Cmax of (-)-epigallocatechin (EGC) was 550 ng/ml, and the Cmax of (-)-epicatechin (EC) was 190 ng/ml. These Cmax values were observed at 1.4-2.4 h after ingestion of the tea preparation. When the dosage was increased from 1.5 to 3.0 g, the Cmax values increased 2.7-3.4-fold, but increasing the dose to 4.5 g did not increase the Cmax values significantly, which suggested a saturation phenomenon. The half-life of EGCG (5.0-5.5 h) seemed to be higher than the half-life of EGC or EC (2.5-3.4 h). EGC and EC, but not EGCG, were excreted in the urine. Over 90% of the total urinary EGC and EC was excreted within 8 h. When the tea dosage was increased, the amount of EGC and EC excretion seemed to increase, but a clear dose-response relationship was not observed. The present study provides basic pharmacokinetic parameters of green tea catechins in humans; these parameters may be used to estimate the levels of these compounds after drinking tea.

Adult↗