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Biomedical subjects

Y L Chen

Publications and source records attributed to Y L Chen.

At least 127 records · Page 7Linked to original sources
PubMed1996

Endoscopic sympathectomy treatment for craniofacial hyperhidrosis.

OBJECTIVE: To present endoscopic T-2 sympathectomy as a minimally invasive therapy for craniofacial hyperhidrosis (CH). DESIGN: Follow-up study of 30 patients with CH treated by the new method in a 4-year period. The duration of follow-up was from 8 to 44 months (mean, 15 months). SETTING: University hospital. PATIENTS: Thirty consecutive patients with CH (18 men, 12 women) treated by the new method. All patients were essentially in good health except that they suffered from distressing CH to the extent that their daily activities were often disturbed. Their ages ranged from 7 to 63 years (mean age, 42.8 years). INTERVENTION: Endoscopic sympathectomy on both sides was carried out in a 1-stage operation for all patients. MAIN OUTCOME MEASURES: The patients were interviewed 1 week and then 3 months after surgery and then followed up by telephone interview about the alleviation or recurrence of CH and complications. RESULTS: All of the treated patients obtained a satisfactory alleviation of CH. One case was complicated by a mild and transient ptosis of the left eye. No recurrence of CH was noticed during the follow-up period. CONCLUSIONS: This therapeutic procedure is minimally invasive and effective. It causes minimal discomfort and was associated with no major complications in this series. The patients require only an overnight hospital stay and the operation scars are small. Endoscopic sympathectomy has proven to be an effective method in treating patients with distressing CH.

Adolescent↗
PubMed1996

An isoinertial predictor for maximal acceptable lifting weights of Chinese male subjects.

The practicality of using restrained as well as standard isoinertial strength tests in predicting the maximum acceptable weight of lift (MAWL) of Chinese male subjects was examined using a restrained strength test, which allows the subject to pull on the load in front of the body and to apply force in a functional free posture. Prediction models were constructed and evaluated under task conditions of two lifting ranges, two box sizes, and three lifting frequencies. The following measurements were taken for each subject in each test: (1) the body posture and joint angles, and (2) electromyographic activities of the arm muscles (biceps brachii), back muscles (erector spinae), and leg muscles (rectus femoris). Results indicate that the restrained knuckle height isoinertial strength (RK) was related significantly to the MAWL for all tasks, and the correlation coefficients ranged from 0.42 to 0.69. A step-wise multiple regression analysis based on data from the 22 subjects showed that RK, chest circumference, and thigh length accounted for 90 to 94% of the variance. A validation effort on a different sample (N = 10) showed that the MAWLs can be predicted within an absolute mean (SD) error of 0.84 (3.30) kg. Percentages of muscle activation levels indicated that, other than strength from the erector spinae, the strongest contribution to the RK value was that of biceps brachii strength. Since the strength of the body's upper extremity was also recruited, the weak upper extremity strength of Chinese subjects was better reflected. Evidence for the existence of a close match between MAWL and RK values, and the conditions of the existence, suggest that RK is good predictor for the MAWL.

Adult↗
PubMed1996

Conformity with nature: a theory of Chinese American elders' health promotion and illness prevention processes.

Grounded theory methodology was used to generate a substantive theory that describes and explains the beliefs and behaviors regarding health promotion and illness prevention among Chinese elders in the United States. On the basis of data collected from 21 Chinese elders, the theory, conformity with nature, emerged. Three interrelated subprocesses--harmonizing with the environment, following bliss, and listening to heaven--were identified. This theory facilitates an understanding of ways to promote health and prevent illness and offers a guide for providing quality health care to Chinese elders in the United States.

Aged↗
PubMed1996

Human stratum corneum lipids have a distorted orthorhombic packing at the surface of cohesive failure.

The cohesive strength of the stratum corneum is determined by its unique molecular composition and structural architecture. Whereas the structure responsible for corneocyte cohesion has been visualized at the microscopic level, the structure of the intercellular domain has not been characterized at the molecular level. In this report, new insight into the molecular architecture of the stratum corneum has been provided by atomic force microscopy and x-ray photoelectron spectroscopy. The surface layer of human stratum corneum was stripped, yielding the characteristic polygonal corneocytes shown by scanning electron microscopy as well as low resolution atomic force microscopy. With atomic force microscopy, the resolution was increased to allow imaging of the molecular architecture of the stratum corneum. With the high resolution image, a repetitive pattern characteristic of lipids in an ordered state was visualized. The lattice appeared to be orthorhombic where the lattice distances were about 5.5 and 9 angstroms, and the lattice angle was close to 90 degrees. The atomic composition of the superficial layers was 82% carbon, 16.5% oxygen, and 1.4% nitrogen as determined by x-ray photoelectron spectroscopy. The high nitrogen content compared to the calculated stratum corneum lipid composition and measured model lipid composition suggests that proteins were detected. In summary, although proteins are present, the fracture plane of the stratum corneum is largely composed of lipids that appear to have a distorted orthorhombic packing.

Female↗
PubMed1996

Dilation of isolated skeletal muscle arterioles by insulin is endothelium dependent and nitric oxide mediated.

Studies in humans and animals have shown that insulin administration increases cardiac output and both forearm and hindlimb blood flow. In this study we tested the hypothesis that insulin dilates skeletal muscle arterioles and that the dilation is endothelium dependent. First-order arterioles (77 microns) from rat cremaster muscle were isolated, pressurized (65 mmHg), equilibrated in a Krebs bicarbonate-buffered solution (pH 7.4) gassed with 10% O2 (5% CO2-85% N2), and studied in a no-flow state. Cumulative concentration-response curves to insulin (10 microU/ml-10 mU/ml) were obtained in intact arterioles before and after either endothelium removal or administration of indomethacin (Indo, 10(-5) M) or nitro-L-arginine (L-NNA, 10(-4) M). Insulin evoked concentration-dependent increases in control diameter of 13-61%, which were completely inhibited by endothelium removal or L-NNA. In contrast, Indo had no effect on insulin-evoked arteriolar dilation. These results indicate that dilation to insulin in skeletal muscle arterioles is endothelium dependent and mediated by nitric oxide.

Animals↗
PubMed1996

Participation of galanin in baroreflex inhibition of heart rate by hypothalamic PVN in rat.

We investigated the role of galanin (Gal) in the suppression of baroreceptor reflex (BRR) response by the paraventricular nucleus of the hypothalamus (PVN) in adult male Sprague-Dawley rats that were anesthetized with pentobarbital sodium. Electrical stimulation (10-s train of 1-ms rectangular pulses at 20-40 microA and 10-20 Hz) of, and microinjection of L-glutamate (1 nmol) into, the PVN significantly inhibited BRR response to transient hypertension induced by phenylephrine (5 micrograms/kg iv). Such a PVN-induced BRR suppression was appreciably antagonized by local administration of Gal antiserum (1:20), but not heat-inactivated Gal antiserum (1:20), to the nucleus tractus solitarius (NTS) bilaterally. Microinjection of Gal (100 pmol) into the NTS bilaterally also resulted in a Gal antiserum-reversible inhibition of the BRR response. Immunohistochemical results demonstrated that the distribution of Gal-containing neurons in the parvocellular subnucleus of the PVN overlapped substantially with the hypothalamic loci on which electrical or chemical activation elicited suppression of the BRR response that was significantly blunted by microinjection of Gal antiserum into the NTS. These results suggest that the PVN may participate in central cardiovascular regulation by suppressing the BRR response via galaninergic neurotransmission at the NTS.

Animals↗
PubMed1996

Evidence for cGMP mediation of skeletal muscle arteriolar dilation to lactate.

In this study we tested the hypothesis that lactate, independent of changes in pH, can affect skeletal muscle blood flow through arteriolar dilation that may be mediated by guanosine 3',5'-cyclic monophosphate. Isolated, cannulated, and pressurized first-order rat cremaster skeletal muscle arterioles were studied in a chamber containing Krebs-bicarbonate buffer under no-flow conditions. At pH 7.4 and PO2 of 65 Torr, neutralized lactic acid (lactate) and pyruvic acid (pyruvate) caused arteriolar dilation over the 1-10 mM concentration range. This response to lactate was not altered by 10(-5) M indomethacin, 10(-4) M NG-nitro-L-arginine, or removal of the endothelium. However, responses to 1 and 3 mM pyruvate were significantly inhibited by 100% by endothelium removal, and the response to 10 mM pyruvate was inhibited by 71%. The relaxation of endothelium-denuded arterioles to lactate was inhibited by 10 microM methylene blue, 10 microM LY-83583, hypoxia (PO2 7-10 Torr), and diphenyliodonium, an inhibitor of superoxide-producing flavo-protein enzymes. In contrast, arteriolar dilation to the acidification of the Krebs buffer to pH 7.15, produced by increasing the CO2 concentration of the gas mixture from 5 to 10%, was not inhibited by methylene blue. These results are consistent with lactate-induced skeletal muscle arteriolar dilation being dependent on H2O2-mediated activation of vascular smooth muscle guanylate cyclase and independent of endothelium-derived mediators.

Aminoquinolines↗
PubMed1996

Synthesis and evaluation of coumarin alpha-methylene-gamma-butyrolactones: a new class of platelet aggregation inhibitors.

In a search for new inhibitors of platelet aggregation, certain coumarin-bearing alpha-methylene-gamma-butyrolactones were synthesized and evaluated for inhibitory activity against thrombin (Thr)-, arachidonic acid (AA)-, collagen (Col)-, and platelet-activating factor (PAF)-induced aggregation in washed rabbit platelets. These compounds were efficiently synthesized from commercially available 7-hydroxycoumarin or its derivatives. Among them, 7-[(2,3,4,5-tetrahydro-4-methylene-5-oxo-2-phenyl-2-furanyl) methoxy]-2H-1-benzopyran-2-one (3d) showed the most potent inhibition of AA- and PAF- induced aggregation, with IC50 values of 3.65 and 16.36 microM respectively.

Adenosine Triphosphate↗
PubMed1996

An isometric predictor for maximum acceptable weight of lift for Chinese men.

The aim of this study was to examine the practicality of the modified isometric strength tests to predict the maximum acceptable weight of lift (MAWL) of Chinese men. The modified strength tests allow the participant to pull on the load cell in front of the body and to apply force in a functional free posture. Both the modified and the standard strength data of each participant were used as predictors for the MAWLs. The prediction models were constructed and evaluated under task conditions of two lifting ranges, two box sizes, and three lifting frequencies. To realize the effect of modifications, testing posture was recorded and the joint angles were calculated. A stepwise multiple regression analysis indicated that modified composite strength (MCS), chest circumference, and acromial height accounted for 86% to 91% of the variance. Because the strength of the upper extremity body was also recruited in the test, the weak upper extremity strength of the Chinese participants would therefore be better reflected. Evidence for the existence of a close match between MAWL and MCS values, as well as the task conditions for its existence, suggest that a simple isometric strength measure is a good predictor for the MAWL.

Adult↗
PubMed1996

Role of endothelial cell mitosis in transendothelial transport of low density lipoprotein in hypercholesterolemic and normal rabbits.

BACKGROUND: Atherosclerosis is characterized by focal areas of lipid accumulation and intimal smooth muscle cell proliferation in large arteries. It has been suggested that the permeability of arterial endothelium to lipid is an important factor in the initiation and progression of atherosclerosis. The mechanism by which macromolecules such as low density lipoprotein (LDL) enter the arterial wall, however, is still not completely understood. Our previous studies have demonstrated that there is close association of endothelial cell turnover with transendothelial macromolecular transport in normal rat aorta. Because hypercholesterolemia has been well documented as one of the major risk factors for atherosclerosis, we explore the relationship between endothelial cell mitosis and transendothelial transport of LDL in hypercholesterolemic rabbits. METHODS: The present study is designed to perform on thoracic aortae from 30 male New Zealand white rabbits fed with either 1% cholesterol-enriched diet (HC group; n = 15) or normal diet (NC group; n = 15). The concentrations of serum cholesterol and triglycerides from two groups were measured by enzymatic procedures using commercial kits. The aortae of hypercholesterolemic and normocholesterolemic rabbits underwent perfusion-fixation 10 min following the intravenous injection of low density lipoprotein conjugated with Lucifer yellow (LY-LDL) for fluorescence microscopy. En face preparations of the thoracic aortae stained with hematoxylin allowed the identification of ECs in mitosis. The relationship between LY-LDL leakage and endothelial cell mitosis was determined. RESULTS: Although endothelial cell mitosis is infrequent (NC: 0.0022 +/- 0.0007%; HC: 0.0004 +/- 0.0001%) in the thoracic aorta of New Zealand white rabbits, 68.2 +/- 8.4% (NC) or 74.3 +/- 9.0% (HC) of dividing cells in the M phase were associated with LYLDL leakage. These dividing cells accounted for 65.0 +/- 9.2% (NC) or 64.4 +/- 11.3% (HC) of all LY-LDL leaky spots. CONCLUSIONS: Thus, this study not only confirmed the close association of EC mitosis with macromolecular permeability in normal group, but also demonstrated that the same relationship existed in hypercholesterolemic rabbits. These observations lend support to the theory that transiently open junctions surrounding the endothelial cells undergoing cell turnover provide pathways through which LDL enters the subendothelial space, resulting in lipid accumulation and atherosclerosis.

Animals↗
PubMed1996

Serum trace metals in Blackfoot disease patients.

The purpose of this study was to investigate ultratrace levels of metals in serum of patients with Blackfoot disease (BFD). BFD is an endemic peripheral vascular disorder confined to a limited area along the southwest coast of Taiwan. In this study, graphite furnace atomic absorption spectrophotometry with stabilized temperature platform furnace conditions was used for the determination of selenium, manganese, cobalt, chromium and zinc. This technique includes a dilution of serum with 12 mM ultrapure nitric acid and 1% Triton X-100. The results showed that total manganese, cobalt, chromium and zinc levels in the BFD patients were significantly different from those in normal controls (P < 0.05). The total selenium level in the BFD patients was not different from the normal controls (P > 0.05). The possible connection of these elements with the etiology of the disease is discussed.

Adult↗
PubMed1996

Minimally invasive surgery: video endoscopic thoracic sympathectomy for palmar hyperhidrosis.

Palmar hyperhidrosis (PH) is a common disorder in Taiwan. It often causes social embarrassment and occupational handicaps. So far, there has been no satisfactory treatment for PH. In 1990, we first developed a minimally invasive technique: video endoscopic sympathectomy to treat PH. The procedure has subsequently proven to be a standard treatment for PH. In this study, a survey of 9988 cases of PH patients from 17 hospitals in Taiwan treated by this method during the past 5 years is presented. Although there were some variations in the model of anaesthesia, technique and extent of sympathectomy, the postoperative results were generally satisfactory. Both sides of sympathectomy were mostly accomplished within half an hour in one stage. The operative scars were tiny and concealed in the axillary region. The patients were discharged from the hospital after an overnight stay. Complications such as pneumothorax, haemothorax (0.3%) or Horner's syndrome (0.1%) were rare. There was no surgical mortality in this series. The most common complication was compensatory hyperhidrosis which was usually mild to moderate and tolerable after reassurance. The recurrence rate of PH was approximately 1% in the first year and less than 3% during the 3 years of follow up. Intraoperative monitoring of palmar skin temperature (PST) was advocated to confirm an adequate sympathectomy warranting a definite result. En bloc ablation of T2 segment invariably resulted in a rise of PST to about 2 degrees C and was considered as an adequate extent of sympathectomy for PH. The refined technique was extended to treat young children with PH and patients with craniofacial hyperhidrosis. The therapeutic results were generally excellent with minimal morbidity and rare recurrence. It is concluded that video endoscopic en bloc T2 sympathectomy is a simple, minimally invasive and effective treatment for both adults and children with PH and also for patients with craniofacial hyperhidrosis.

Adolescent↗
PubMed1996

[The terminal monosaccharide of antigenic determinant is involved in the binding of human sperm to specific monoclonal IgA antibody].

In order to know whether terminal monosaccharide of human sperm antigen is involved in stimulating antisperm immune response (especialy IgA production) in mucosal immune system, 33 IgA, 12 IgG and 35 IgM monoclonal antibodies (MAbs) all obtained by intragastrointestinal immunization were used in the present study. The molecular weight (MW) of sperm antigens reactive with MAbs were dectected by Western blotting. The MW range of sperm antigens to the above monclonal IgA, IgM and IgG class, except 12 MAbs not reactive with blotted sperm antigen on nitrocellulose strip, is 10-89 KDa, 11-75 KDa and 12-94 KDa respectively. The sperm antigens were separately blocked and digested with 5 lectins and 4 glycosidases. After that, the capacity of human sperm antigens bind with the above antibodies were determined by ELISA. One or more terminal monosaccharides of sperm antigens are involved with the reaction of most MAbs tested. The loss of terminal alpha-fucose, alpha-N-acetylgalactosamine, alpha-N-acetylglucosamine, mannose and beta-galactose but neuraminic acid in the antigenic determinant of human sperm were found to seriously affect the IgA binding with the corresponding sperm antigen. The binding of IgG with sperm antigen was obviously damaged by the removing of terminal alpha-fucose, alpha-N-acetylgalactosamine and alpha-mannose. The results suggest that the terminal monosaccharides of the sperm antigens play an important role in stimulation of antisperm IgA and other antibodies produced by using intragastrointestinal immunization.

Antibodies, Monoclonal↗
PubMed1995

Structural characterization of the active site of Brucella abortus Cu-Zn superoxide dismutase: a 15N and 1H NMR investigation.

Prokaryotic Cu-Zn superoxide dismutases (SODs) are rare and poorly characterized compared to their eukaryotic counterparts. To better characterize the structure of the prokaryotic enzyme, an NMR investigation of Brucella abortus Cu-Zn SOD in the reduced form was undertaken. The enzyme studied was a recombinant form, expressed in Escherichia coli. The enzyme initially lacked a full complement of Cu and Zn ion. After demetallation and remetallation with a stoichiometric amount of Cu and Zn ion, the specific activity of the recombinant B. abortus Cu-Zn SOD was comparable to the specific activity of the bovine enzyme. The 15N and 1H resonances of seven active site histidine imidazole rings were assigned using two-dimensional NMR methods. A self-consistent set of nuclear Overhauser effects between imidazole ring protons was observed, which was in agreement with the predictions of a model based on the X-ray crystallographic structure of the oxidized bovine enzyme (Tainer, J.A., Getzoff, E. D., Beem, K. M., Richardson, J.S., & Richardson, D.C. (1982) J. Mol. Biol. 160, 181-217). These observations strongly suggest that the structure of the active site of the prokaryotic enzyme is similar to that of the eukaryotic enzyme. Differences in the observed and predicted nuclear Overhauser effects could be ascribed to differences in the oxidation state of the Cu ion (Cu(I) in the reduced B. abortus enzyme and Cu(II) in the oxidized bovine enzyme), as much as they could to the different origins of the enzymes. The NMR data were also compared to a similar 1H NMR study of the human enzyme (Bertini, I., Capozzi, F., Luchinat, C., Piccioli, M., & Viezzoli, M. S. (1991) Eur. J. Biochem. 197, 691-697). The pattern of nuclear Overhauser effects and the chemical shifts of corresponding resonances were very similar in 1H NMR spectra of the human and B. abortus enzymes. Significant differences in the chemical shifts or exchange behavior of a few resonances indicated differences in the environments of several histidines in the active sites of reduced B. abortus and human Cu-Zn SODs. This is consistent with the presence of a number of insertions and deletions in the loop regions that make up the active site as indicated by amino acid sequence alignment studies. The tautomeric and protonation states of the active site histidines were also determined in this study, and the results were in agreement with previous studies. The resonances of nitrogen atoms coordinated to metal ions were found to fall between those of protonated and unprotonated nitrogens on histidine imidazoles.

Bacterial Proteins↗
PubMed1995

5,7-dihydro-3-[2-[1-(phenylmethyl)-4-piperidinyl]ethyl]-6H- pyrrolo[3,2-f]-1,2-benzisoxazol-6-one: a potent and centrally-selective inhibitor of acetylcholinesterase with an improved margin of safety.

A series of N-benzylpiperidines (2a-d, 10) with novel isoxazole-containing tricycles has been prepared. This series has shown potent in vitro inhibition of the enzyme acetylcholinesterase (AChE), with IC50S = 0.33 - 3.6 nM. Compound 2a was the most potent inhibitor with an IC50 = 0.33 +/- 0.09 nM. Derivatives 2a-d and 10 displayed weak in vitro inhibition of butyrylcholinesterase (BuChE) with IC50S = 600 - 23,000 nM. The most selective compound was 2a with a BuChE/AChE ratio in excess of 4 orders of magnitude (> 10,000). Pyrrolobenzisoxazole 2a also displayed a favorable profile in vivo. In microdialysis experiments, 2a produced a 200% increase in extracellular levels of acetylcholine (ACh) at a dose of 0.4 mg/kg in freely moving, conscious rats. Peripheral side effects (salivation ED50 = 26 +/- 1.5 mg/kg) and acute lethality (LD50[1 h] = 42 mg/kg) were observed at > 60-fold higher doses. These data indicate that 2a is an AChE inhibitor with good central selectivity and a favorable margin of safety. Compound 2a, designated as CP-118,954, is currently in clinical development for the treatment of cognitive disorders.

Animals↗
PubMed1995

Crystal structure of abrin-a at 2.14 A.

The crystal structure of abrin-a, a type II ribosome-inactivating protein from the seeds of Abrus precatorius, has been determined from a novel crystalline form by the molecular replacement method using the coordinates of ricin. The structure has been refined at 2.14 A to a R-factor of 18.9%. The root-mean-square deviations of bond lengths and angles from the standard values are 0.013 A and 1.82 degrees, respectively. The overall protein folding is similar to that of ricin, but there are differences in the secondary structure, mostly of the A-chain. Several parts of the molecular surface differ significantly; some of them are quite near the active site cleft, and probably influence ribosome recognition. The positions of invariant active site residues remain the same, except the position of Tyr74. Two water molecules of hydrogen-bonded active site residues have been located in the active site cleft. Both of them may be responsible for hydrolyzing the N-C glycosidic bond. The current abrin-a structure is lactose free; this is probably essential for abrin-a crystallization. The B-chain is a glycoprotein, and the positions of several sugar residues of two sugar chains linked to earlier predicted glycosylation sites were determined. One of the sugar chains is a bridge between two neighboring molecules, since one of its mannose residues is connected to the galactose binding site of the neighboring molecule. Another sugar chain covers the surface of the B-chain.

Abrin↗
PubMed1995

Functional and sequence characterization of agkicetin, a new glycoprotein Ib antagonist isolated from Agkistrodon acutus venom. offf2p4.

A new glycoprotein Ib (GPIb) antagonist, agkicetin, was purified from the venom of Agkistrodon acutus and characterized. It is a disulfide-linked heterodimer consisting subunits of 15 and 14 kDa. The subunits are homologous to each other and to other snake venom proteins of the C-type (Ca(2+)-dependent) lectin superfamily. Agkicetin behaved as a potent antagonist of von Willebrand Factor (vWF)-induced platelet agglutination (IC50 = 12.5 nM) and bound specifically to GPIb of fixed platelets with high affinity (Kd = 38 nM). It did not bind coagulation factor IX and thrombin. Monoclonal antibody against epitope on the N-terminal domain of GPIb competed the binding of agkicetin with platelets. Reduced and alkylated agkicetin lost most of its inhibitory efficacy toward vWF-induced platelet agglutination.

Amino Acid Sequence↗