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Biomedical subjects

W W Chen

Publications and source records attributed to W W Chen.

At least 19 recordsLinked to original sources
PubMed2005

Three-dimensional etching profiles and surface speciations (via attenuated total reflection-fourier transform infrared spectroscopy) of silicon nanowires in NH4F-buffered HF solutions: a double passivation model.

A systematic study of the etching behavior, in terms of three-dimensional profiles, of one-dimensional (1-D) silicon nanowires (SiNWs) in NH(4)F-buffered hydrofluoric acid (BHF) solutions of varying concentrations and pH values and the surface speciations of the resulting etched SiNW surfaces, as characterized by attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, is reported. It was found that SiNWs are stable only in relatively narrow pH ranges of the BHF solutions. The results are rationalized in terms of a "double passivation" model. When SiNWs are etched in BHF solutions with pH values of 1-3, the surfaces are passivated with hydrogen (inner layer) giving rise to surface moieties such as Si-H(x) species (x = 1-3); at high HF concentrations, the H-terminated Si surfaces are covered with a hydrogen bonding network of HF and related molecules (oligomers, etc.), providing an outer-layer passivation. When SiNWs are etched in BHF solutions with pH values of 11-14 (by adding a strong base such as NaOH), the surfaces are oxygen-terminated with surface moieties such as Si-(O(-))(x)() species (x = 1-3); at high NH(4)F concentrations, the negatively charged Si surfaces are stabilized by NH(4)(+) ions via ionic bonding, again providing outer-layer passivation. In BHF solutions with pH values of 3-11, the surface speciation, consisting of Si-(OH)(x)(O(-))(y) (x + y = 1-3) species, is unstable and etched away rapidly. The surface speciations of SiNWs etched in various BHF solutions were explored via ATR-FTIR spectroscopy. It was found that, while etching SiNWs with HF-rich BHF solutions with pH < 4 gave rise to Si-H(x)() surface species, no surface Si-H(x) species were observed with SiNWs etched in BHF solutions with pH >/= 4 (HF/NH(4)F </= 1:1). In sharp contrast, etching of two-dimensional (2-D) Si wafers with either HF, NH(4)F, or BHF etchants produces Si-H(x) species on the surface. Finally, while HF is a much more efficient etchant than NH(4)F for 2-D Si surfaces, NH(4)F is found to be as efficient an etchant as HF for SiNWs (this work). We believe that these differences can be attributed to the nanometer size (corresponding to the roughness scale in 2-D wafers) of SiNWs on one hand and the lack of "passivation" by the hydrogen bonding network of HF and related molecules at pH >/= 4 on the other. These two factors, among others, contribute to the rapid hydrolysis of the surface Si-H(x)() species (and the etching of the SiNWs), particularly in BHF solutions with low HF/NH(4)F ratios and high pH values (pH >/= 4).

Journal Article↗
PubMed2005

Etching behavior of silicon nanowires with HF and NH4F and surface characterization by attenuated total reflection Fourier transform infrared spectroscopy: similarities and differences between one-dimensional and two-dimensional silicon surfaces.

A systematic study of the etching behavior of one-dimensional (1-D) Si nanowires (SiNWs) in various HF and NH4F etching solutions is reported. The concentration and pH dependences of the etching time (which is inverse to the "stability") of the SiNWs in these solutions were investigated. A V-shaped bimodal etching curve was observed for HF solutions with concentrations of 0.5-40%. Specifically, SiNWs exhibit high stability in both low (0.5%) and high (40%) concentrations of HF solution, with the lowest stability (i.e., fastest etching rate) occurring at 2% (1 M) HF solution. With NH4F, the time needed to totally etch away the SiNWs sample decreases with increasing concentration (from 1-40%). The opposite is true when the pH of the NH4F solution was maintained at 14. These surprising results were rationalized in terms of "passivation" of the SiNW surfaces by HF or related molecules via hydrogen bonding for Si-H-terminated surfaces in HF solutions (with low pH values) and by NH4(+) ions via ionic bonding for Si-O(-)-terminated surfaces in NH4F solutions (with high pH values), respectively. Furthermore, it was found that SiNWs are stable only in relatively narrow pH ranges in these solutions. When SiNWs are etched with HF, the stability range is pH = 1-2 where the surface moieties are Si-H(x) species (x = 1-3). When SiNWs are etched with NH4F, the stability range is pH = 12-14 where the surface moieties are mainly Si-(O-)x species (x = 1-3). These rationales were confirmed by attenuated total reflection Fourier transform infrared spectroscopy measurements, which showed that, while etching SiNWs with HF gave rise to Si-H(x) surface species, no Si-H(x) species were observed when SiNWs were etched with NH4F. The latter finding is at odds with the corresponding results reported for the two-dimensional (2-D) Si wafers where etching with either HF or NH4F produces Si-H(x) species on the surface. This difference suggests either that the etching mechanisms for NH4F versus HF are different for SiNWs or, more likely, that the Si-H(x) surface species produced in NH4F solutions are so unstable that they are hydrolyzed readily at pH > 4. The similarities and differences of the etching behaviors and the resulting surface speciations between the 1-D SiNWs and the 2-D Si wafers suggest that the nanoscale structures as well as the low dimensionality of SiNWs may have contributed to the rapid hydrolysis of the surface Si-H(x) species in NH4F solutions, especially at high pH values.

Journal Article↗
PubMed2001

Evaluation of a tobacco prevention program on knowledge, attitudes, intention and behavior of tobacco use among fourth grade students--a preliminary study.

This was a preliminary study to evaluate the effectiveness of a tobacco prevention program on knowledge, attitude, intention, and behavior of tobacco use among fourth-grade students in four north central Florida counties. The results suggest that the program was effective in improving students' knowledge, attitudes, and intention toward not using tobacco products. Data analysis showed that students in the education group had a greater improvement in knowledge than the comparison group. Students in the education group also improved their attitude and intention scores while the comparison group did not show any improvement. The results also indicated positive responses from the students. In addition, teachers also gave a very positive response to the program.

Child↗
PubMed2001

[Clinical study on regulatory effect of liandai Capsule on p21ras and mutant p53 protein expression in gastrointestinal neoplasm].

OBJECTIVE: To study the regulatory effect of Liandai Capsule on p21ras and mutant p53 protein expression in gastrointestinal (GI) neoplasm. METHODS: Forty-five patients of GI neoplasm in middle or advanced stage were enrolled and divided randomly into the treated group and the control group to observe the changes of their serum p21ras and mutant p53 protein expression as well as their quality of life (QOL) before and after treatment. RESULTS: The content of p21ras and mutant p53 protein expression in the treated group decreased significantly and QOL improved after treatment, P < 0.05 or P < 0.01, while these changes in the control group were not shown. CONCLUSION: Liandai Capsule has regulatory effect on p21ras and mutant p53 protein expression in GI neoplasm.

Adenocarcinoma↗
PubMed1998

Development of rat pancreatic islet cells in vitro.

Islet cell lines were produced by retroviral transduction of SV-40 T antigen to monolayer cultures of neonatal rat islets. One line, RN0-11, showed evolution of phenotypes in vitro. It evolved from a non-hormone secreting cell line to an insulin secreting line. It further developed glucagon producing capability before it lost all hormone producing phenotypes. At passage 8, RN0-11 cells secreted a small amount of insulin 25 ng/10(6) cells/24 hours. They were unresponsive to glucose and secreted 1.7-1.9 ng of insulin/10(6) cells/2 hours under various levels of glucose. At passage 16, they secreted 2,577 ng of insulin/10(6) cells/24 hours and responded to glucose stimulation in static incubation. The insulin secreted by these cells at 0, 2.8, 5.5, 11.1, 16.7, and 27.7 mM of glucose was 6.46 +/- 2.56, 17.74 +/- 2.66, 32.24 +/- 0.58, 30.66 +/- 1.59, 33.55 +/- 4.83, and 20.95 +/- 2.17 ng/10(6) cells/2 hours respectively. The responsiveness to glucose and the ability to secrete insulin diminished as cells were passaged in culture, and by passage 35 no insulin was detectable in medium under any level of glucose tested. Northern blot analyses also showed corresponding changes of insulin expression in these cells at different passages. In addition, glucagon was detectable at passage 14 by immunocytochemistry and at passage 16 by Northern blot analysis. By passage 35, no insulin or glucagon expression was detectable by Northern blot analysis or immunocytochemistry. Immunocytochemical staining of these cells at passage 14 showed insulin-positive and glucagon-positive cells and cells positive for both insulin and glucagon. Presence of insulin and glucagon in the same cells suggests single clonality of the cell line. The evolution of RN0-11 cells in vitro provides an opportunity to study the development of islet cells.

Animals↗
PubMed1996

Cancer patients' knowledge of their diagnoses.

The most frequently discussed ethical issue on the subject of cancer is whether patients should be told their diagnosis. Cancer patients' knowledge of their diagnosis and the relationship between patient characteristics and that knowledge were evaluated in a cross-sectional study. From July 1992 to December 1993 at Tri-Service General Hospital, Taipei, a total of 964 patients with cytologically- or pathologically-proven cancer were studied. Of those studied, 359 patients (37.2%) knew their diagnosis. The proportion of patients who believed that they had a benign tumor was 25.1%; 12.6% believed they had nonneoplastic disease (inflammation or other chronic disease); 7.5% believed they had precancerous changes; and 17.6% knew nothing about their diagnosis. Multivariate analyses showed that patients with the following characteristics were inclined to know their diagnosis: younger age (20-59 yr), higher levels of education (> 9 yr) with relatives of a high socioeconomic status, cancer of a genital organ, cancer requiring disfiguring treatment (osteosarcoma, leukemia), cancer in obvious sites (head and neck), cancer of more than one type (multiple primary lesions), cancer of good prognosis (excluding lung, liver, gall bladder or pancreatic cancers), aggressive anticancer treatment and longer duration of pathologic proof (> 14 d). The results showed that concealing the diagnosis from cancer patients is still very common in Taiwan. Patient's sociodemographic background and disease-related factors were the most important patient characteristics related to their knowledge of the diagnosis.

Adolescent↗
PubMed1995

Difference of lifestyle advice between traditional Chinese medical doctors (TCMDs) and Western-style medical doctors (WSMDs) in People's Republic of China.

The role of physicians in providing lifestyle advice is very important in disease prevention and health promotion. This study was designed to examine (a) the difference of lifestyle advice provided for general practice patients between traditional Chinese medical doctors (TCMDs) and Western-style medical doctors (WSMDs), (b) the difference of lifestyle advice provided for cardiovascular disease (CVD) patients between the TCMDs and WSMDs, (c) the difference of lifestyle advice provided for general practice and CVD patients by the TCMDs, and (d) the difference of lifestyle advice provided for general practice and CVD patients by the WSMDs. One thousand four-hundred and thirty general practice patient records and 640 CVD patient records from a Western-style medical hospital, and 1620 general practice records and 830 CVD patient records from a traditional Chinese medical hospital were selected for comparison. Results indicated that TCMDs were more likely to provide nutrition, exercise, and stress management for their patients than WSMDs. On the other hand, WSMDs were more likely to provide smoking and alcohol consumption for their patients than the TCMDs. In addition, both TCMDs and WSMDs were more likely to provide all categories of lifestyle advice for their CVD patients than their general practice patients.

China↗
PubMed1995

Enhancement of health locus of control through biofeedback training.

The effects of electromyographic (EMG) biofeedback training in enhancing health locus of control were examined. 21 college students were randomly assigned to either biofeedback (BF) group or control group (C). Subjects given biofeedback received 8 sessions of biofeedback training in 4 wk. Analysis indicated these subjects exhibited a greater reduction of muscle tension than control subjects at posttest. They also maintained their low muscle tension at a 1-mo. follow-up. Subjects who received biofeedback training also showed somewhat more internal health locus of control scores, but the change was not significant until the follow-up session. Mean internal locus of control scores also improved significantly for these subjects. No significant correlation between changes in EMG and health locus of control was found.

Adult↗
PubMed1994

A preliminary study of potential dietary risk factors for coronary heart disease among Chinese American adolescents.

This study investigated dietary knowledge, attitudes toward diet, behavioral factors affecting diet, and dietary patterns between American Chinese middle school students and Chinese middle school students living in China. Significant differences occurred in these variables between the two groups of students. Chinese students living in China had less knowledge and a less favorable attitude. However, they exhibited more positive behavioral factors affecting diet which include culture, religion, customs, economic factors, beliefs, and values. As for the dietary pattern, Chinese student living in China consumed less meat, dairy products, fat, sweets and snacks, and fast foods, and consumed more fruits, vegetables, and starch.

Adolescent↗
PubMed1994

[Protective effect of sodium ferulate on damage of the rat liver mitochondria induced by oxygen free radicals].

This paper reports the protective effect of sodium ferulate (SF) on mitochondrial morphology and functions. Sodium ferulate was found to significantly inhibit the mitochondria abnormal swelling and TBA reaction induced by Fe2+/Vit C system. This compound was also shown to modulate the uncoupling effect of malondialdehyde (MDA) on oxidative phosphorylation of mitochondria. Respiratory control rate for blank, MDA and MDA+SF were 4.75, 3.64 and 4.50 respectively. SF was shown to inhibit the cross reaction of MDA with biological macromolecules of rat liver mitochondria assayed by SDS-polyacrylamide gel electrophoresis. The results suggest that the injury action of oxygen free radicals to rat liver mitochondria can be prevented by SF.

Animals↗
PubMed1993

Two years experience with the Palmaz-Schatz coronary stent in a heterogeneous patient population.

Between January 1991 and December 1992, 136 Palmaz-Schatz coronary stents were implanted in 113 native coronary arteries in 106 patients. Forty-seven patients presented with stable angina, 50 with unstable angina, 7 with congestive cardiac failure and unstable angina and 2 were asymptomatic. Stenting was carried out in 15 patients for restenosis after coronary angioplasty (PTCA), 32 for significant dissection during PTCA (with 19 acute and 13 threatened closure), 10 for suboptimal PTCA results and 56 for de novo lesions, 52 (92.9%) of which were either ACC/AHA type B or C. Successful delivery was achieved in 97.2% (103/106) of patients or 97.3% (110/113) of vessels. Percent diameter stenosis was reduced from 78 +/- 13% to 4 +/- 11%. There were two subacute stent thromboses (1.9%), resulting in Q-Wave myocardial infarction. Three deaths (2.9%) occurred, all from the group with congestive cardiac failure and unstable angina. Major bleeding/vascular complications occurred in 4 patients (3.9%). All patients were followed up for a mean of 18 months (6 months to 30 months). Eighty-five patients were asymptomatic. Three patients were angina-free but continued to have, albeit improved, congestive cardiac failure. Ten patients had recurrence of angina, all within 6 months of the stenting procedure. Four were treated medically and 4 had PTCA of whom one eventually had coronary bypass surgery. Two patients had new lesions, successfully treated by PTCA or stenting. In conclusion, a high rate of successful delivery of the Palmaz-Schatz coronary stent can be achieved in a wide spectrum of patients with few complications which are mostly related to anticoagulation. It offers very effective bailout for acute closure during PTCA. Despite the presence of unfavorable pre-procedure patient and lesion characteristics, the acute and long term clinical results are encouraging.

Adult↗
PubMed1991

Low-density particles (W-particles) containing catalase in Zellweger syndrome and normal fibroblasts.

By both histological and biochemical criteria, peroxisomes in patients with Zellweger syndrome appear to be absent or severely deficient. By using 15-30% (wt/vol) Nycodenz/sucrose gradients to study the subcellular localization of extraperoxisomal catalase activity, a commonly used marker for mature peroxisomes, we detected a single peak of activity in Zellweger syndrome fibroblasts at an equilibrium density of 1.13 g/cm3, lower than the expected 1.17 g/cm3 of mature peroxisomes. Upon recentrifugation in either the original gradient or one with a higher salt concentration, essentially all catalase activity was recovered in fractions of the original densities. The activity of the catalase peak was further analyzed by a digitonin titration and filtration assay in combination with Triton X-100 treatment. The catalase activity passed through 0.1-microns and 0.22-microns but was retained on 0.025-microns membrane filters (mean pore size). After treatment with Triton X-100 nearly all catalase activity passed through the filters. The results from fractionations data, digitonin latency measurement, and the detergent effect on the filtration behavior suggest that catalase is not free in the cytosol of Zellweger syndrome fibroblasts as commonly thought but in particles (W-particles). Similar low-density catalase-containing particles, distinct from peroxisomes, are also found in normal fibroblasts. We found that L-alpha-hydroxyacid oxidase, another peroxisomal matrix enzyme, is also present in W-particles derived from normal and Zellweger syndrome fibroblasts. We speculate that the low-density catalase-containing W-particle may represent an immature or incomplete form of peroxisome distinct from previously described "peroxisomal ghosts" in Zellweger syndrome fibroblasts.

Biomarkers↗
PubMed1991

Effect of carboxylic acid xenobiotics and their metabolites on the activity of carnitine acyltransferases.

Salicylyl-CoA and benzoyl-CoA were good inhibitors of carnitine acetyltransferase (CAT), competing with acetyl-CoA with Ki values of 7.5 and 22 microM respectively in the forward direction and with CoA in the reverse reaction with similar Ki values. They were also competitive inhibitors of carnitine octanoyltransferase (Ki = 261 and 295 microM respectively), but were only weakly inhibitory to carnitine palmitoyltransferase. Inhibition of energy production by salicylate may result from the inhibition of CAT by salicylyl-CoA.

Acyl Coenzyme A↗
PubMed1991

Import of human bifunctional enzyme into peroxisomes of human hepatoma cells in vitro.

A polypeptide containing the carboxyl-terminal fragment of human peroxisomal enoyl-CoA hydratase:3-hydroxyacyl-CoA dehydrogenase bifunctional enzyme was synthesized in vitro from its cDNA clone. This expression polypeptide was transported into purified rat liver peroxisomes. When the expression polypeptide was incubated with postnuclear supernatant fractions of human hepatoma cells and analyzed by Nycodenz gradient SDS-PAGE and fluorography, it was imported specifically into peroxisomes as indicated by its resistance to proteinase K degradation. A deletion of the last nine amino acid residues at the carboxyl-terminus of this polypeptide prevents its peroxisomal import. A tripeptide sequence, SKL, located at the carboxyl-terminus of human bifunctional enzyme appears to be the targeting signal for the peroxisomal importation of bifunctional enzyme in human cells.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1991

Affinity chromatography isolation of human cytochrome oxidase and small-scale Western immunoblot probing of the enzyme complex in mitochondrial cytopathy patients.

Isolation of human cytochrome oxidase by a one-step affinity chromatography procedure on a Sepharose 4B-ferrocytochrome c matrix following solubilization with the nonionic detergent laurylmaltoside yields an enzyme isolate of adequate purity for producing polyclonal antisera. Such an antiserum produced a distinctive immunoreactive profile in Western immunoblot studies to that reported using the enzyme isolated with ionic detergents. A sensitive and highly reproducible Western immunoblotting method is described for probing mitochondrial fractions prepared from small frozen skeletal muscle biopsies with an antiserum against the human placenta cytochrome oxidase. Application of this method to mitochondrial cytopathy patients with partial cytochrome oxidase deficiency shows that the detected subunits are synthesized in these patients.

Blotting, Western↗
PubMed1991

A comparison of self-reported health education competencies among selected school health educators in the United States and Taiwan, R.O.C.

Results from a preliminary, cross-national study examining perceived competence of school health educators in Taiwan, R.O.C., and in Florida are reported. The study used the Self-Assessment for the Health Educator instrument, developed by the National Task Force on the Preparation and Practice of Health Educators, Inc., which specifies 79 skills in seven competency areas. School health educators from Taiwan and Florida rated their own perceived competence regarding each skill, and assessed the perceived usefulness of each skill in health education practice. Responses from the two groups were similar on six of seven competency areas regarding usefulness of the items. Yet, teachers from Taiwan expressed greater perceived competence than the Florida teachers in five of seven areas. However, within both groups, teachers rated perceived usefulness higher than their own perceived level of competence. Inservice training, amount of formal training, and years of professional experience affected levels of perceived confidence in both groups. Initial results suggest the self-assessment instrument may prove useful as a tool for examining professional competence in other countries, but more extensive research is needed to determine the instrument's applicability in cross-national comparisons.

Adult↗
PubMed1991

The 22-kD peroxisomal integral membrane protein in Zellweger syndrome--presence, abundance, and association with a peroxisomal thiolase precursor protein.

The primary genetic defect of Zellweger syndrome may be related to defective synthesis or impaired import of peroxisomal proteins. We analyzed the presence and measured the abundance of the 22-kD peroxisomal integral membrane protein (PMP) in patients with Zellweger syndrome. We determined the intracellular localization of the 22-kD PMP and compared it with the localization of a peroxisomal 44-kD thiolase precursor protein. The 22-kD PMP was quantified by immunoblot analyses in liver tissue (n = 7 patients). Immunoblot signals were evaluated using transmission photometry. The intracellular localization of the 22-kD PMP and the peroxisomal 44-kD thiolase precursor protein were determined by immunoblot analyses on fibroblast subcellular fractions prepared by Nycodenz (n = 5 patients) or sucrose density gradient centrifugation (n = 2 patients). The 22-kD PMP was present and associated with membrane fractions in all patients. Its abundance varied in patients as compared with normal human liver controls. The 22-kD PMP was located in subcellular membrane fractions having a lower density than normal peroxisomes or mitochondria. Using two different gradient techniques, the 22-kD PMP and the peroxisomal 44-kD thiolase precursor protein were found in the same low-density gradient fractions. These results suggest that in Zellweger syndrome peroxisome-like elements containing both the 22-kD PMP and a 44-kD thiolase precursor protein are formed. Globally defective synthesis or import of peroxisomal proteins is therefore unlikely to be the primary genetic defect in the patients we studied.

Acetyl-CoA C-Acetyltransferase↗