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Biomedical subjects

W Yan

Publications and source records attributed to W Yan.

At least 145 records · Page 8Linked to original sources
PubMed1996

Comparative study of Nd:YAG laser angioplasty at 1.06 microns, 1.32 microns, and 1.44 microns wavelengths: decreased vascular spasm and early mortality with 1.44 microns laser ablation.

BACKGROUND AND OBJECTIVE: Although laser angioplasty has been demonstrated to be effective for the treatment of long, complex coronary arterial atherosclerotic stenoses, there is an associated risk of acute arterial spasm, dissection, and perforation as well as a significant restenosis rate. It has been postulated that the use of lasers emitting at wavelengths designed for radiation absorption by water would decrease local tissue trauma. STUDY DESIGN/MATERIALS AND METHODS: We have examined the use of a Nd:YAG laser designed to emit at 1.44 microns, an absorption peak for water, and compared the results of laser ablation at 1.06 microns, 1.32 microns, and 1.44 microns wavelengths. Nd:YAG laser angioplasty was performed in the abdominal aorta of White Leghorn roosters. Acute and chronic vascular trauma was assessed by contrast angiography and histological analysis. RESULTS: There was a significant decrease in early mortality with 1.44 microns laser ablation. This decreased mortality after 1.44 microns ablation was associated with a decrease in vascular spasm, perforation, and thermal damage. Atherosclerotic plaque development at follow up was decreased with 1.44 microns ablation but this was not significant. CONCLUSION: 1.44 microns laser ablation decreases early vascular trauma and mortality and may decrease subsequent atherosclerotic plaque development.

Angiography↗
PubMed1996

Tumor necrosis factor decreases thrombin receptor expression in endothelial cells.

We examined the effects of the proinflammatory cytokine, tumor necrosis factor-alpha (TNF alpha) on the expression of proteolytically activated thrombin receptor (PATR) in human umbilical vein endothelial cells (HUVEC). PATR mRNA and protein levels were measured in confluent HUVEC monolayers after challenge with TNF alpha. Northern analysis indicated that TNF alpha treatment resulted in 2- to 3-fold decrease in PATR mRNA in a time- and dose-dependent manner. PATR mRNA level returned to the control level within 6 hr. The nuclear run-on assay indicated that the decreased mRNA signal was due to reduction in the transcription rate. Immunoblotting experiments indicated that the decrease in expression of PATR protein followed in time the decrease in mRNA; the lowest level of protein expression was achieved at 22 hr after TNF alpha treatment. PATR protein returned to basal value within 40 hr after TNA alpha challenge. To assess alterations in endothelial cell function after TNF alpha treatment, we measured thrombin-induced increase in cytosolic Ca2+ ([Ca2+]i) and the cell shape change (measured by decrease in electrical impedance of endothelial cell monolayer). In HUVEC treated with TNF alpha (100 U/ml for 22 hr), the rise in [Ca2+]i after thrombin challenge was approximately 2-fold less than in control thrombin-treated cells. The decrease in electrical impedance of HUVEC monolayers in response to thrombin after TNF alpha treatment was also significantly reduced. However, the rise in [Ca2+]i in response to histamine was not altered by TNF alpha pretreatment. In conclusion, TNF alpha exposure of endothelial cells decreased both mRNA and protein expression of PATR, which explain the decreased activation of thrombin generated signals after the TNF alpha exposure.

Amino Acid Sequence↗
PubMed1996

Steroidal saponins from fruits of Tribulus terrestris.

Further studies on the constituents of the fruits of Tribulus terrestris led to the isolation of five new steroidal saponins (terrestrosin A-E), (25R,S)-5 alpha-spirostan-3 beta-ol-3 -O-beta-D-galactopyranosyl(1-2)-beta-D- glucopyranosyl(1-4)-beta-D-galactopyranoside, (25R,S)-5 alpha-spirostan-3 beta-ol-3-O-beta-D-glucopyranosyl(1-4)-[alpha-L- rhamnopyranosyl(1-2)]-beta-D-galactopyranoside, (25R,S)-5 alpha-spirostan-12-on-3 beta-ol-3-O-beta-D-galactopyranosyl (1-2)-beta-D-glucopyranosyl(1-4)-beta-D-galactopyranoside, hecogenin 3-O-beta-D-galactopyranosyl)1-2)-[beta-D- xylopyranosyl(1-3)]-beta-D-glucopyranosyl(1-4)-beta-D-galactopyranoside and (25R,S)-5 alpha-spirostane-2 alpha, 3 beta-diol-3- O-beta-D-galactopyranosyl(1-2)-beta-D-glucopyranosyl(1-4)-beta-D- galactopyranoside, together with five known steroidal saponins, desgalactotigonin, F-gitonin, desglucolanatigonin, gitonin and tigogenin 3-O-beta-D- xylopyranosyl)1-2)-[beta-D-xylopyranosyl)1-3)]-beta-D-glucopyranosyl)1-4 )- [alpha-L-rhamnopyranosyl(1-2)]-beta-D-galactopyranoside. The structures of the new saponins were elucidated on the basis of spectroscopic analyses, including two-dimensional NMR techniques, and chemical reactions.

Chromatography, High Pressure Liquid↗
PubMed1996

Comparison of the hydrophobic grid-membrane filter DNA probe method and the Health Protection Branch standard method for the detection of Listeria monocytogenes in foods.

The standard Health Protection Branch (HPB) method for the detection of L. monocytogenes in foods involves lengthy enrichment, selection and biochemical testing, requiring up to 8 days to complete. A hydrophobic grid-membrane filter (HGMF) method employing a digoxigenin-labelled listeriolysin O probe required 5 days to complete, and included an image-analysis system for electronic data acquisition. A total of 200 food samples encompassing 8 high-risk food groups (soft and semi-soft cheeses, packaged raw vegetables, frozen cooked shrimp, ground poultry, ground pork, ground beef, jellied meats, and pâté) were screened for the presence of L. monocytogenes by the two methods. Overall, 32 (16%) and 30 (15%) of the naturally-contaminated food samples tested positive for L. monocytogenes by the HPB and DNA methods, respectively. The DNA probe method was highly specific in discriminating L. monocytogenes from other Listeria spp. present in 50 of the samples tested. Results showed 94% sensitivity and 100% specificity between the two methods. The HGMF DNA probe method is an efficient and reliable alternative to the HPB standard method for detecting L. monocytogenes in foods.

DNA Probes↗
PubMed1996

Functional interaction of cytosolic hsp70 and a DnaJ-related protein, Ydj1p, in protein translocation in vivo.

In order to analyze the in vivo role of the SSA class of cytosolic 70-kDa heat shock proteins (hsps) of Saccharomyces cerevisiae, we isolated a temperature-sensitive mutant of SSA1. The effect of a shift of mutant cells (ssa1ts ssa2 ssa3 ssa4) from the permissive temperature of 23 degrees C to the nonpermissive temperature of 37 degrees C on the processing of several precursor proteins translocated into the endoplasmic reticulum or mitochondria was assessed. Of three mitochondrial proteins tested, the processing of only one, the beta subunit of the F1F0 ATPase, was dramatically affected. Of six proteins destined for the endoplasmic reticulum, the translocation of only prepro-alpha-factor and proteinase A was inhibited. The processing of prepro-alpha-factor was inhibited within 2 min of the shift to 37 degrees C, suggesting a direct effect of the hsp70 defect on translocation. More than 50% of radiolabeled alpha-factor accumulated in the precursor form, with the remainder rapidly reaching the mature form. However, the translocation block was complete, as the precursor form could not be chased through the translocation pathway. Since DnaJ-related proteins are known to interact with hsp70s and strains containing conditional mutations in a dnaJ-related gene, YDJ1, are defective in translocation of prepro-alpha-factor, we looked for a genetic interaction between SSA genes and YDJ1 in vivo. We found that a deletion mutation of YDJ1 was synthetically lethal in a ssa1ts ssa2 ssa3 ssa4 background. In addition, a strain containing a single functional SSA gene, SSA1, and a deletion of YDJ1 accumulated the precursor form of alpha-factor. However, no genetic interaction was observed between a YDJ1 mutation and mutations in the SSB genes, which encode a second class of cytosolic hsp70 chaperones. These results are consistent with SSA proteins and Ydj1p acting together in the translocation process.

Adenosine Triphosphatases↗
PubMed1996

Effects of cyclic adenosine 3',5'-monophosphate on chondrocyte terminal differentiation and cartilage-matrix calcification.

We examined the effects of cyclic AMP on terminal differentiation and calcification in rabbit growth plate chondrocyte cultures. Dibutyryl cAMP (dbcAMP), as well as 8-bromo-cAMP abolished the increases in chondrocyte size, alkaline phosphatase activity, type X collagen synthesis, 1 alpha, 25-dihydroxyvitamin D3 receptor synthesis, the incorporation of 45Ca into insoluble material, and the calcium content. All of these occurred in parallel untreated cultures during the hypertrophic (terminal) stage. The inhibition of alkaline phosphatase by dbcAMP was detectable after 24 h, and this effect was reversible. dbcAMP and 8-bromo-cyclic AMP inhibited alkaline phosphatase induction and calcification at low concentrations (3-5 microM), whereas 10-30-fold higher concentrations were required to stimulate proteoglycan synthesis. These findings suggest that cAMP plays a crucial role in suppressing terminal differentiation of chondrocyte and cartilage-matrix calcification.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1996

Searching eye movement, smooth pursuit eye movement and schizophrenia.

OBJECTIVE: To detect whether the smooth pursuit eye movement (SPEM) and searching eye movement (SEM) could be considered as a biological marker of schizophrenia, and used as a tool in helping diagnosis of schizophrenia. METHODS: 88 schizophrenics, 77 patients with mood disorders, 32 with "neurosis", and 74 normal healthy controls were examined for SPEM and SEM individually. The authors verified the results in all the first-visit 150 outpatients in March 1993 by comparing the examination results with the clinical diagnoses after a 6-month follow-up. RESULTS: Significant differences were found in the number of eye fixation (NEF) and total eye scanning length (TESL) of SEM between schizophrenics and normal controls or patients with other disorders. Less NEF and shorter TESL could be helpful in differential diagnosis, and the agreement rate, Kappa coefficient was 0.62. No significant differences were found in SPEM in this investigation between non-medicated schizophrenics and normal controls. CONCLUSION: Searching eye movement (SEM) might be considered as a biological marker of schizophrenia and might be used as a supplementary tool in its diagnosis.

Adult↗
PubMed1996

An investigation of adult outcome of hyperactive children in Shanghai.

OBJECTIVE: To evaluate the outcome of hyperactive children diagnosed 15 years ago at the average age of 25. PATIENTS AND METHODS: Conditions of 197 children who were diagnosed as having minimal brain dysfunction (MBD) in 1979-1980 at our center and 103 normal controls were assessed by the parents in an inquiry form including educational achievement, occupational rank, persistence of attention deficit hyperactive disorder (ADHD) (MBD) symptoms, and pervasive conduct problems after a 15-year follow-up. RESULTS: Compared with normal controls, the probands continued to reveal typical symptoms in 70% of these children, completed less formal schooling, and were less often employed in higher-level professions, but did not exhibit significantly more conduct problems. CONCLUSIONS: Only about 30% of the formerly hyperactive children can get out of the shadow of ADHD (MBD) and succeed in their academic or occupational performance, and the rest continue to reveal some symptoms and some problems in their adult life.

Adult↗
PubMed1996

[Mechanisms of resistance to melphalan in leukemia cell line and reversal by interferon alpha].

OBJECTIVES: To study the mechanisms of resistance to alkylating agent melphalan (Mel) in leukemia cell and to investigate effect of modulation of resistance to Mel by IFN alpha. METHODS: A Mel-resistant variant of the leukemic cell line (K562/Mel) was developed in vitro by continuous exposure to Mel. The level of expression of several resistance-related gene in K562/Mel and the effect of reversal of resistance to Mel by IFN alpha were observed. RESULTS: K562/Mel was 8.0-fold resistant to Mel and also cross-resistant to nitrogen mustand and thiophosphoramide, but not to carmustine and doxorubicin. This enhanced Mel resistance was associated with increased level of GST alpha gene and total GST, but not with increased level of expression of GST pi, GST mu, MDR-1 and Top-II gene. IFN alpha, at 500 IU/ml, a noncytotoxic dosage significantly increased the cytotoxicity of Mel to K562/Mel. The reversal of Mel resistance is related to the decrease of the level of expression of GST alpha gene. CONCLUSION: Resistance to Mel is associated with increased level of GST alpha gene and total GST in leukemic cell. IFN alpha can reverse Mel resistance.

Antineoplastic Agents, Alkylating↗
PubMed1995

Evidence for the elaboration of multiple axons by developing dentate granule cells.

A sample of 185 Neurobiotin-filled dentate granule cells has been collected from rats aged P14 to P120 in a study of the effects of serotonin (5-hydroxytryptamine, 5-HT) depletion on granule cell development. A small number (5.9%) of these neurons exhibit more than one axon. These neurons have morphologies consistent with that described for dentate granule cells. One axon typically arises from the soma while additional axons take origin from either dendrites or the soma. Both axons may be mossy fibers or one axon may be a mossy fiber and the second assume a morphology and distribution similar to that described for interneurons. These latter neurons therefore exhibit a mixed phenotype by having a granule cell morphology and an interneuronal axon type. These data suggest that some granule cells give rise to multiple mossy fibers or express a mixed axonal phenotype during maturation.

Animals↗
PubMed1995

Preferred sites of glycosylphosphatidylinositol modification in folate receptors and constraints in the primary structure of the hydrophobic portion of the signal.

The divergent carboxyl-terminal signal peptides for glycosylphosphatidylinositol (GPI) membrane anchor attachment in folate receptor (FR) types alpha and beta were characterized. All of the candidate amino acid residues for GPI modification were identified and tested by substituting individually and in combination with amino acids that cannot be modified by GPI. Thus the GPI modification in FR-alpha was decreased to 22% by mutation of Ser234 to Thr but unaltered by changing the other candidate, Gly235, to Met. However, the double mutant FR-alpha Ser234-Thr,Gly235-Met showed half of the GPI modification seen in FR-alpha Ser234-Thr. This result suggests that Ser234 is the preferred GPI modification site, while Gly235 is a minor, alternate GPI modification site. Similarly, in FR-beta, mutation of Asn230 to Gln decreased GPI modification to 32%, while mutation of the other candidate site, Gly237, to Met had no effect. However, mutation at both sites further reduced the GPI modification by a half. A five amino acid carboxyl-terminal deletion (FR-beta delta 5) caused no decrease in the extent of GPI modification. However, the same deletion in FR beta Asn230-Gln decreased the residual GPI modification by 66%. These results suggest that Asn230 is the preferred GPI modification site in FR-beta, while Gly235 offers a minor alternate modification site; consistent with this conclusion is the fact that modification at the downstream site is hindered by its proximity to the carboxyl terminus in FR-beta delta 5. Further, the suggestion that the hydrophobic portion of the GPI signal is a random sequence of neutral amino acids with overall moderate hydrophobicity was tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1995

Age estimation on the female sternum by quantification theory I and stepwise regression analysis.

One hundred and nine sternums from Chinese females aged 18-50 years were examined in this study. Six morphological characteristics and their changing degree in the female sternum were observed and scored. The data were statistically processed by quantification theory I and stepwise regression analysis on a computer and the following regression equation for age estimation of the female sternum was calculated: y = 19.28 + 1.83x1 + 1.66x2 + 3.02x3 + 1.57x4 + 3.02x5 + 7.75x6 + 1.25x7 + 3.45x8 + 4.88x9 + 0.82x10 + 2.76x11 + 2.48x12 + 7.84x13 + 1.26x14 + 3.80x15 (the correlation coefficient R = 0.9774, the standard deviation S = 2.20, F > 0.01). For convenience, the changing degree of the morphological characters and the equation were also converted into two tables. This method of age estimation on the female sternum is simple and accurate and is of importance to forensic medicine and anthropology.

Adult↗
PubMed1995

Glutamine metabolism in chick enterocytes: absence of pyrroline-5-carboxylase synthase and citrulline synthesis.

This study was designed to determine whether pyrroline-5-carboxylate (P-5-C) synthase is deficient in chick enterocytes therefore resulting in the lack of synthesis of ornithine and citrulline from glutamine. Post-weaning pig enterocytes, which are known to contain P-5-C synthase and to synthesize both ornithine and citrulline from glutamine, were used as positive controls. Enterocytes were incubated at 37 degrees C for 0-30 min in the presence of 2 mM [U-14C]glutamine or 2 mM ornithine plus 2 mM NH4Cl. In chick enterocytes, glutamine was metabolized to NH3, CO2, glutamate, alanine and aspartate, but not to ornithine, citrulline, arginine or proline. Likewise, there was no formation of citrulline, arginine, alanine or aspartate from ornithine in chick enterocytes. Furthermore, the rate of conversion of ornithine into proline in chick enterocytes was only about 4% of that in cells from pigs. To elucidate the reason for the inability of chick enterocytes to synthesize ornithine and citrulline from glutamine, the activities of the enzymes involved were measured. No activity of P-5-C synthase or ornithine carbamoyltransferase was found in chick enterocytes, in contrast with cells from post-weaning pigs. It was also demonstrated that the activity of ornithine aminotransferase in chick enterocytes was only 3% of that in cells from pigs. Thus the present findings elucidate the biochemical reason for the lack of endogenous synthesis of ornithine and citrulline in chicks. Our results also explain previous observations that ornithine cannot replace arginine or proline in the diet of chicks. We suggest that the absence of P-5-C synthase and ornithine carbamoyltransferase in enterocytes is the metabolic basis for the nutritional requirement of arginine in the chick.

1-Pyrroline-5-Carboxylate Dehydrogenase↗
PubMed1995

Identification of a deoxyribonuclease I-like endonuclease in rat granulosa and luteal cell nuclei.

Apoptosis, a process recently implicated as the cellular mechanism underlying ovarian follicular atresia and luteal regression, is characterized by the internucleosomal degradation of DNA by a Ca2+/Mg(2+)-dependent endonuclease. Although hormones and growth factors have been demonstrated to modulate the DNA degradation associated with ovarian follicular apoptosis, the nature and identity of the endonuclease involved is not known. Ca2+/Mg(2+)-dependent endonuclease activity has a developmental pattern of expression in rat granulosa and luteal cell nuclei. Thus, the present study was conducted to establish the presence of an endonuclease in the nuclei of ovarian granulosa and luteal cells and to examine the biochemical properties of the enzyme relevant to apoptosis. Nuclei from diethyl-stilbestrol (DES)-, eCG-, and hCG-primed rat ovaries were isolated and exposed to Ca2+ and Mg2+ in vitro. Nuclei from rat ovaries primed with eCG and hCG, but not DES, substantially degraded their DNA in an apoptotic fashion, and this DNA degradation was Ca2+/Mg(2+)-dependent and inhibited by Zn2+. Protein extracts from the nuclei of DES-, eCG-, and hCG-treated rat ovaries were tested for endonuclease activity by a plasmid degradation assay. The extracts were found to contain endonuclease activity with the same developmental pattern and cation dependency as found in intact nuclei. These protein extracts were assessed for nuclease activity by zymography, and three nuclease activities were identified depending on the type of DNA used in the gel and the electrophoresis conditions used for protein separation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Extracellular matrix hyaluronan is a determinant of the endothelial barrier.

We measured the hydraulic conductivity (Lp) of the extracellular matrix (ECM) obtained after detaching bovine pulmonary microvascular endothelial (BPMVEC) and bovine pulmonary arterial endothelial cell (BPAEC) monolayers from the ECM at different days postseeding. From day 1 to day 5 in culture, the total Lp (i.e., of cell monolayer + ECM) decreased from basal values of 17.1 +/- 4.0 to 8.5 +/- 1.6 x 10(-6) cm.s-1.cmH2O-1 in BPAEC (P < 0.05) and 7.6 +/- 1.1 to 3.7 +/- 0.8 in BPMVEC (P < 0.05), respectively, and on day 5 the total Lp values were lower in BPMVEC than in BPAEC (P < 0.05). On the 5th day, ECM Lp was 55.0 +/- 8.3 in BPAEC and 10.7 +/- 0.9 cm.s-1.cmH2O-1 in BPMVEC (P < 0.05), indicating that the contribution of ECM to the total Lp was greater in BPMVEC than in BPAEC. Treatment of [3H]acetate-labeled ECM with Streptomyces hyaluronidase (HAse; 6 U/ml for 10 min) released sixfold greater radioactivity in BPMVEC compared with untreated BPMVEC controls; a similar treatment of BPAEC did not release detectable radioactivity indicative of a higher hyaluronan content in the BPMVEC ECM. HAse treatment reduced the differences in total Lp between BPMVEC and BPAEC at different days postseeding. Moreover, on the 5th day after seeding, the ECM Lp of BPMVEC increased to a greater extent after HAse treatment than the ECM of BPAEC. These data indicate that the hyaluronan component of the ECM is an important determinant of the endothelial liquid-exchange barrier.

Animals↗
PubMed1995

Arg-Gly-Asp peptide increases endothelial hydraulic conductivity: comparison with thrombin response.

The contribution of integrin receptors to the regulation of endothelial permeability was studied using cultured bovine pulmonary microvascular endothelial cell (BPMVEC) monolayers by the measurement of hydraulic conductivity (Lp). Treatment of monolayers with a peptide containing the sequence Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) (0.85 mM) to compete for the RGD sequence of extracellular matrix (ECM) proteins increased endothelial Lp threefold, whereas the control peptide Gly-Arg-Gly-Glu-Ser-Pro had no effect on Lp. This action of GRGDSP on Lp was not significantly altered by dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP; 0.5 mM). Endothelial Lp increased twofold when the monolayers were challenged with alpha-thrombin (5 x 10(-8) M for 10 min), and this response was completely reversed by DBcAMP. The strength of adhesion of endothelial cells was estimated by evaluating the ability of endothelial cells to remain attached to ECM after treating the monolayers with 0.05% trypsin plus 0.5 mM EDTA. Exposure of the monolayers to either GRGDSP or alpha-thrombin significantly reduced the strength of adhesion to the ECM. DBcAMP prevented the antiadhesive effect of alpha-thrombin but not that of GRGDSP. Treatment of the monolayers with either alpha-thrombin or GRGDSP caused formation of intercellular gaps, but only the thrombin-induced intercellular gaps were accompanied by reorganization of actin filaments. These results indicate that integrin binding to ECM proteins regulates an important determinant of endothelial permeability and that alpha-thrombin and GRGDSP increase endothelial cell monolayer permeability by different mechanisms.

Amino Acid Sequence↗
PubMed1995

Glutamine and glucose metabolism in enterocytes of the neonatal pig.

Glutamine and glucose metabolism was studied in 0- to 21-day-old pig enterocytes. Cells were incubated at 37 degrees C for 30 min in Krebs-Henseleit bicarbonate buffer (pH 7.4) in the presence of 2 mM [U-14C]glutamine with or without 5 mM glucose, or 5 mM [U-14C]glucose with or without 2 mM glutamine. Glutamine was metabolized to ammonia, glutamate, alanine, aspartate, CO2, citrulline, ornithine, and proline, whereas glucose was converted to lactate, pyruvate, and CO2 in pig enterocytes. CO2 production from glutamine accounted for 32-36% and 3-4% of utilized glutamine carbons in 0- to 7-day-old and 14- to 21-day-old pigs, respectively. The rates of O2 consumption and metabolism of glutamine and glucose decreased in enterocytes from 2- to 14-day-old pigs compared with 0-day-old pigs. By day 14 after birth, the oxidation of glutamine and glucose as well as citrulline production had decreased by 90-95%. Arginine synthesis from glutamine occurred in cells from 0- to 7-day-old pigs but not 14- to 21-day-old ones. Glucose (5 mM) had no effect on glutamine utilization and oxidation or the production of glutamate and arginine but stimulated the formation of alanine, citrulline, and proline at the expense of aspartate. In contrast, glutamine (2 mM) inhibited glycolysis and glucose oxidation in cells from 0- to 7-day-old pigs and had no effects in 14- to 21-day-old pigs. As a result, glutamine contributed approximately 2-fold greater amounts of ATP to 0- to 7-day-old pig enterocytes than glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗