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Biomedical subjects

S Lin

Publications and source records attributed to S Lin.

At least 235 records · Page 13Linked to original sources
PubMed1999

[Determination of chlorogenic acid in chrysanthemum morifolium Ramat.flower].

OBJECTIVE: To determine the contents of chlorogenic acid in flower of Chrysanthemum morifolium. METHOD: Column: Nova-Pak C18, 4 microns, 4.6 mm x 250 mm, mobile phase: MeOH-0.1 mol.L-1 NaH2PO4(pH 2.65)30:70, detection wavelength: 328 nm. RESULTS: Flowers of 20 batches bought from the market were analysed. Contents of chlorogenic acid were 0.060%-0.467%. CONCLUSION: Chlorogenic acid is a suitable component for the quality control of C. morifolium.

Chlorogenic Acid↗
PubMed1999

[Determination of sarafloxacin by high performance liquid chromatography (HPLC)].

A method for the separation and determination of Sarafloxacin by HPLC was developed. The sample was dissolved in a mixture of V(acetonitrile):V(water) = 1:1. Operating conditions were as follows: mu-Bondapak C18 column (3.9 mm x 300 mm), V(acetonitrile):V(methanol):V(2 mmol/L H3PO4, adjust pH 3.5 with triethylamine) = 30:5:65 as mobile phase with a flow rate of 1 mL/min, UV detection at 278 nm, and column temperature was 15 degrees C. Under the above conditions, Sarafloxacin and other impurities were separated from each other. The method was simple, rapid, sensitive and accurate.

Anti-Infective Agents↗
PubMed1999

[Changes in chloroquine resistance of Plasmodium falciparum in Hainan province].

AIM: To observe the variation in resistance of Plasmodium falciparum after the cessation of chloroquine medication. METHODS: WHO standard in vitro microtest and in vivo test were used. RESULTS: In vitro test showed that the rate of chloroquine-resistant P. falciparum dropped from 97.9% in 1981 to 26.7% in 1997 (P < 0.001). The mean concentration of chloroquine for complete inhibition of schizont formation declined from 10.46 +/- 7.14 pmol/ul blood in 1981 to 1.63 +/- 1.47 pmol/microliter blood in 1997(P < 0.001). In vivo test showed that the rate of chloroquine-resistant P. falciparum decreased from 84.2% in 1981 to 18.4% in 1997(P < 0.001). The proportion of R III cases to the total resistant cases dropped from 53.1% in 1981 to 14.3% in 1997. CONCLUSION: A tendency of progressive decline of resistance of the parasite was revealed after the cessation of chloroquine medication.

Adolescent↗
PubMed1999

[Activated T lymphocytes in epiretinal membranes from eyes of patients with proliferative diabetic retinopathy].

PURPOSE: To investigate the potential contribution of immune-mediated processes to the development of proliferative diabetic retinopathy(PDR), an immunohistochemical study was undertaken to characterize the infiltrating immune cells in epiretinal membrances from the eyes of patients with PDR. METHODS: A total of 15 PDR epiretinal membrane specimens obtained surgically from pars plans vitrectomy were studied by using a panel of monoclonal antibodies against T lymphocytes (CD4), interleukin-2(IL-2) and interleukin-2 recpetors(IL-2R). RESULTS: Twelve of 15 specimens (80%) contained CD4-positive cells. IL-2 was found in 12 of 15 samples (80%), of which 11 also contained CD4-positive cells, and IL-2R was detected in 10 of 15 membranes(67%), of which 9 contained CD4-positive cells and released IL-2. Most of the IL-2R-positive membranes were from type I diabetic patients, 40% of them are younger than 40 years. CONCLUSION: Our study demonstrated the involvement of activated immune cells and release of lymphokine(s) in more than half of the diabetic epiretinal membranes tested and revealed that the processes of immune responses and the biological effects of lymphokines(s) may play an important part in the development of epiretinal membranes of PDR, especially in young-onset and type I diabetes.

CD4 Antigens↗
PubMed1999

[A new anaesthetic method of intraocular surgery: anaesthesia at infrafascia bulbi].

OBJECTIVE: To probe the advantage, indications and its mechanism of anaesthesia at intraocular operation with infrafaseia bulbi anaesthetic (IBA) technique. METHODS: 456 eyes were operated with the anaesthesia in infrafascia bulbi, including 77 eyes for phacoemulsification intraocular lens implantation, 346 eyes for modern surgical extracapsular cataract extraction and intraocular lens implantation, 33 eyes for trabeculectomy. 2 ml of mixture of 2% Lidocaine and 0.75% Bupivacaine were injected at infratemporal near bulbi conjunctiva of limbus through the blunt silicone canal, which entered the fascia bulbi via a small incision and reached the equator of the eyeball. When the injection of the mixture filled up the fascia bulbi the surgery could be performed. RESULTS: IBA applied in 456 eyes had shown the same effect as posterior fascia bulbar and peripheral fascia bulbar anaesthesia. IBA is a safe method. CONCLUSION: It is avoided the mechanical injure to optic nerve, artery, vein, muscle and wall of eyeball with IBA using blunt silicone injecting canal. It is proved in our clinical practice that this is a saft and efficient local anaesthetic method.

Aged↗
PubMed1999

[The design of a reflection sensor of NIRS tissue oximetry].

A design of the reflection light-electric Sensor suited to monitoring the statues of tissue blood oxygen on the surface of body is described. The designed sensors have been used too to detect blood oxygen statues of brain and muscle respectively, and many useful informations have been acquired Therefore The above-mentioned design is reasonalle and Feasikle.

Algorithms↗
PubMed1999

[The application of modularity design in the pulse oximeter].

This paper presents a thought of modularity design and application in our pulse oximeter and its hardware and software composition of the function board, the application can improve the reliability of the instrument greatly and make it easy to expand its function.

Equipment Design↗
PubMed1999

Comparison of bone mass in forearm, lumbar vertebra and hip by single and/or dual energy X-ray absorptiometry.

OBJECTIVE: Bone mineral density (BMD) was measured in normal Chinese women with single X-ray absorptiometry (SXA) and dual energy X-ray absorptiometry (DEXA). These two methods were compared to evaluate the sensitivity in reflecting bone loss. METHODS: Measurements were performed in 300 women aged 20 to approximately 79 (5 for each age). The 8mm distal, 1/4 distal, ultra distal site of the nondominant forearm were measured with SXA; the AP spine (L2-4), right femoral neck (Neck), Ward's triangle (Ward) and trochantor (Troch) were measured with DEXA. Ten women had 5 repeated measurements to evaluate the reproducibility of the equipments. RESULTS: The BMD peak for Neck and Ward was found between age 20 to approximately 29, for ultra distal and L2-4 at age 30 to approximately 39, for 8mm distal, 1/4 distal and Troch at age 40 to approximately 49. After reaching the peak values, BMD at all sites decreased with increasing age. The highest rate of yearly loss of BMD was at 8mm distal. Results of measurement showed significant correlation between SXA and DEXA. Comparing with premenopausal women, the bone loss rate in postmenopausal women was faster and highest up to 11 to approximately 15 years and the highest rate was at the Ward. CONCLUSION: The present study gives the normal values of BMD at seven sites for normal Chinese women. The ages of BMD peak were different at seven sites. The yearly loss of BMD was highest at 8mm distal, it seemed to be the sensitive region for bone loss with age. The postmenopausal women had highly significantly loss bone mass than the premenopausal women. Comparing with premenopause, postmenopause BMD for Ward's triangle with DEXA seemed to be most sensitive to the effect of menopause.

Absorptiometry, Photon↗
PubMed1999

Transgenesis.

Explore the source record for details and available documents.

Animals↗
PubMed1998

Novel analogues of arachidonylethanolamide (anandamide): affinities for the CB1 and CB2 cannabinoid receptors and metabolic stability.

Several analogues of the endogenous cannabinoid receptor ligand arachidonylethanolamide (anandamide) were synthesized and evaluated in order to study (a) the structural requirements for high-affinity binding to the CB1 and CB2 cannabinoid receptors and (b) their hydrolytic stability toward anandamide amidase. The series reported here was aimed at exploring structure-activity relationships (SAR) primarily with regard to stereoelectronic requirements of ethanolamido headgroup for interaction with the cannabinoid receptor active site. Receptor affinities, reported as Ki values, were obtained by a standard receptor binding assay using [3H]CP-55,940 as the radioligand, while stability toward the amidase was evaluated by comparing the Ki of each analogue in the presence and absence of phenylmethanesulfonyl fluoride (PMSF), a serine protease blocker and inhibitor of anandamide amidase. Introduction of a methyl group in the 1'- and 2'-positions or substitution of the ethanolamido headgroup with a butylamido group gave analogues with vastly improved biochemical stability. This is accomplished in some cases with increased receptor affinity. Conversely, oxazolyl and methyloxazolyl headgroups led to low-affinity analogues. Substitution of the hydroxyl group with electronegative substituents such as fluoro, chloro, allyl, and propargyl groups significantly increased receptor affinity but did not influence the biochemical stability. The 2'-chloro analogue of anandamide was found to have the highest affinity for CB1. Additionally, reversing the positions of the carbonyl and NH in the amido group produces retro-anandamides possessing considerably higher metabolic stability. Replacement of the arachidonyl tail with oleyl or linoleyl results in analogues with low affinities for both receptors. All of the analogues in this study showed high selectivity for the CB1 receptor over the peripheral CB2 receptor. The most potent analogues were tested for their ability to stimulate the binding of [35S]GTPgammaS to G-proteins and were shown to be potent cannabimimetic agonists. The results are discussed in terms of pharmacophoric features affecting receptor affinity and enzymatic stability.

Amidohydrolases↗
PubMed1998

Hydrocarbon rulers in UDP-N-acetylglucosamine acyltransferases.

UDP-GlcNAc acyltransferase (LpxA), the first enzyme of lipid A biosynthesis, catalyzes the transfer of an acyl chain activated on acyl carrier protein (ACP) to UDP-GlcNAc. LpxAs are very selective for the lengths of their acyl donor substrates. Escherichia coli LpxA prefers R-3-hydroxymyristoyl-ACP to R-3-hydroxydecanoyl-ACP by a factor of approximately 1000, whereas Pseudomonas aeruginosa LpxA prefers the opposite. E. coli G173M LpxA and the reciprocal P. aeruginosa M169G LpxA show reversed substrate selectivity in vitro and in vivo, demonstrating the existence of precise hydrocarbon rulers in LpxAs.

Acyltransferases↗
PubMed1998

Hepatocyte growth factor/scatter factor and hepatocytes are potent downregulators of tyrosinase expression in B16 melanoma cells.

Reiterated selection in vivo of B16 murine melanoma cells for enhanced liver metastatic ability yielded a cel line (B16-LS9) dramatically overexpressing a constitutively active hepatocyte growth factor/scatter factor (HGF/SF) receptor, the product of the c-met proto-oncogene. Most likely because of their overexpressing c-met, B16-LS9 cells appear to be more responsive than parental B16-F1 cells to HGF stimulation, in terms of motility, invasion, and growth. They are also more pigmented, and express higher levels of tyrosinase as compared to parental B1 6-F1 cells. Therefore, we set out to explore whether HGF/SF and the liver might influence the differentiation state of B1 6 cells. We found that HGF/SF and MSH, two factors which reportedly have a strong influence on the phenotype and the malignant behavior of melanoma cells, may act at different levels, and with opposite results, on the regulation of gene expression. In fact, while MSH induces, at the transcriptional level, an increase in the production of both c-met and tyrosinase, HGF/SF, in contrast, promotes a decrease in the expression of both c-met and tyrosinase, however at a posttranscriptional level. These two opposite effects can counter-balance each other, when the cells are treated with both factors at the same time, apparently through a mechanism involving MAP kinase activation. The effects were, however, additive when morphological changes were considered. Most intriguingly, we also describe a very strong downregulatory activity, limited to tyrosinase expression, by hepatocytes in coculture with B16 cells. This activity, also at the posttranscriptional level, is much stronger than that exerted by HGF/SF, and appears to be due to a labile soluble factor produced by the hepatocytes.

Animals↗
PubMed1998

Disulfide isomerization within the C-terminus of cobrotoxin decelerates by thiol compounds and trinitrophenylation, but accelerates by modification of carboxyl groups.

A disulfide isomerization at the C-terminus of cobrotoxin occurred spontaneously by dissolving in alkali buffer. Irreversible conversion of cobrotoxin into its isomers was completely achieved within 4 days. The isomerization reaction was decelerated by thiol compounds including GSSG, GSH, cystamine, and cysteamine in a pseudo-first-order kinetic, and GSSG was the most effective one among the thiol compounds used. Moreover, the oxidized thiol compounds were always superior to reduced ones in decreasing the rate of disulfide interchange. To further assess the intrinsic elements essential for the occurrence of disulfide isomerization of cobrotoxin, the toxin molecule was subjected to modification on its Arg, Lys, Trp, Tyr, and carboxyl groups. In sharp contrast to other modified derivatives, the isomerization reaction was decelerated by trinitrophenylation on Lys-26, Lys-27, and Lys-47, whereas it was rapidly completed after modification of carboxyl groups. Neither chemical modification nor the toxin's conformation affected the irreversibility of isomerization reaction. Thus, the observed change in the rate of disulfide isomerization reflects the involvement of Lys residues and carboxyl groups in this reaction. Although thiol compounds further decelerated the conversion of trinitrophenylated cobrotoxin into its isomers, they did not exert a notable effect on the isomerization of carboxyl groups-modified derivative. These results clearly indicate that disulfide isomerization of cobrotoxin is, in part, driven by the positively charged Lys residues at positions 26, 27, and 47 of the toxin molecule, and that the thiol compounds are coordinated with the negatively charged groups of cobrotoxin to exert their inhibitory action.

Animals↗
PubMed1998

Identification of contamination sources of Bacillus cereus in pasteurized milk.

In order to determine the sources of Bacillus cereus in pasteurized milk, a total of 232 milk samples from various sampling points along milk processing lines and 122 environmental swabs were collected in two dairy plants between March and September, 1996. The incidence of B. cereus vegetative cells in raw milk from the plants was low (< or = 10%). However, the incidence and the average counts of B. cereus spores in the raw milk were very high and similar to those of B. cereus vegetative cells in pasteurized milk or final products after enrichment (> 80% and 1.1 x 10(5) cfu ml(-1), respectively). The incidence and average count of both vegetative cells and spores of B. cereus in environmental swabs was low. Using the microbial identification system (MIDI), a library of B. cereus fatty acid profiles comprising 229 B. cereus isolates from milk samples and environmental swabs was constructed using a critical Euclidian distance of 6.0 units as the cut-off value. Using this library, the relationship between 546 B. cereus isolates from the different sampling points along the milk processing lines and the environmental swabs was determined. Most B. cereus isolates obtained from the pasteurized milk and final products belonged to the same sub-groups as the B. cereus strains germinated from spores in raw milk. Furthermore, specific sub-groups were found in pasteurized milk, different dairy plants and at different sampling times. The results suggested that B. cereus spores in raw milk were the major source of B. cereus in pasteurized milk and that post-pasteurization contamination along the milk processing lines was possibly a minor source of B. cereus in pasteurized milk.

Animals↗
PubMed1998

Determination of anandamide amidase activity using ultraviolet-active amine derivatives and reverse-phase high-performance liquid chromatography.

Anandamide amidase catalyzes the hydrolysis of anandamide (AEA) to arachidonic acid (AA) and ethanolamine (EA). Recently, we published a method for determining anandamide amidase activity based on the measurement of arachidonic acid with direct UV detection at 204 nm. However, this method cannot be used to determine the hydrolysis of non-UV-active AEA analogs. It also cannot be used to study AEA amidase inhibitors that contain the arachidonic acid tail, and which are also enzyme substrates. Here we report a novel, more general method for measuring amidase activity by o-phthaldialdehyde (OPA) precolumn derivatization and reverse-phase high-performance liquid chromatography (HPLC). The hydrolysis product, ethanolamine, after separation from protein was derivatized with OPA to form a UV-active isoindole derivative which was then detected at 230 nm. The detection limit for derivatized ethanolamine was 1.0 pmol and retention times were typically less than 8 min. Our new method can detect non-UV-active analogs through derivatization of the amine product. It can thus be used after careful selection of the HPLC conditions in competition experiments between AEA and AEA analogs possessing different head groups. The most effective competitive inhibitor tested was (R)-N-(1-methyl-2-hydroxyethyl)arachidonylamide (AM356), which is resistant to enzymatic hydrolysis and yet inhibits AEA hydrolysis in a competition experiment by 43%. Moreover, this method offers several advantages over existing methodologies using radioisotopes or solvent extraction procedures. Our work to date has shown that small structural changes in the AEA molecule can result in significant variation in both affinity and turnover rate for each analog with respect to AEA amidase.

Amidohydrolases↗
PubMed1998

Kinetic analysis of an inhibitor-resistant variant of the OHIO-1 beta-lactamase, an SHV-family class A enzyme.

The Met69-->Ile mutant of the OHIO-1 beta-lactamase, an SHV-family enzyme, is resistant to inactivation by beta-lactamase inhibitors. Analysis of purified Met69-->Ile enzyme reveals that its isoelectric point (pI 7.0) and CD spectrum are identical with those of the OHIO-1 enzyme. Levels of beta-lactamase expression in Escherichia coli as determined by immunoblotting are similar for OHIO-1 and Met69-->Ile beta-lactamase. The kinetic constants of the Met69-->Ile enzyme compared with OHIO-1 are smaller for benzylpenicillin (Km = 6 microM compared with 17 microM; kcat = 234 s-1 compared with 345 s-1 respectively) and carbenicillin (Km = 3 microM compared with 17 microM; kcat = 131 s-1 compared with 320 s-1 respectively). For the cephalosporins cephaloridine and 7-(thienyl- 2-acetamido)-3-[2-(4-N,N- dimethylaminophenylazo)pyridinium-methyl]-3-cephem-4-carboxylic acid (PADAC), a similar pattern is also seen (Km=38 microM compared with 96 microM and 6 microM compared with 75 microM respectively; kcat = 235 s-1 compared with 1023 s-1 and 9 s-1 compared with 50 s-1 respectively). Consistent with minimum inhibitory concentrations that show resistance to beta-lactam beta-lactamase inhibitors, the apparent Ki values, turnover numbers and partition ratios (kcat/kinact) for the mechanism-based inactivators clavulanate, sulbactam and tazobactam are increased. The inactivation rate constants (kinact) are decreased. The difference in activation energy, a measurement of altered affinity for the wild-type and mutant enzymes leading to acylation of the active site, reveals small energy differences of less than 8.4 kJ/mol. In total, these results suggest that the Met-->Ile substitution at position 69 in the OHIO-1 beta-lactamase alters the active site, primarily affecting the interactions with beta-lactamase inhibitors.

Anti-Bacterial Agents↗