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Biomedical subjects

A C Wang

Publications and source records attributed to A C Wang.

At least 19 recordsLinked to original sources
PubMed1996

Burch colposuspension vs. Stamey bladder neck suspension. A comparison of complications with special emphasis on detrusor instability and voiding dysfunction.

OBJECTIVE: To compare long-term results of Burch colposuspension and Stamey bladder neck suspension in women with genuine stress incontinence (GSI). STUDY DESIGN: Five hundred three women with GSI underwent Burch colposuspension or a Stamey operation between 1976 and 1992. They were evaluated preoperatively and at least two years after the operations. The preoperative workup consisted of a history, pelvic examination, urine analysis and culture, cotton-tipped swab test, uroflowmetry, cystometry and urethral profilometry. Three hundred eighty-nine of 503 (77.3%) postoperative urodynamic assessments and a one-hour office pad test were performed. A questionnaire was completed by 114 patients who were not able to return to the hospital. The chi 2 and unpaired Student t test were used for statistical analysis. RESULTS: Two hundred thirty-three complications occurred in 503 procedures, and voiding dysfunction had the highest incidence (12.1%). Detrusor instability following antiincontinence operations was detected in 45 of 389 patients (11.5%) who received follow-up urodynamic assessments at least two years postoperatively. In comparison with postoperatively stable bladders, the cystometric and uroflowmetric findings in these 45 patients revealed that the difference in urodynamic evidence of outflow obstruction was statistically significant. The Stamey operation had a statistically significantly higher incidence of postoperative voiding dysfunction as compared to Burch procedure. CONCLUSION: In this series, detrusor instability following continence procedures might have been the consequence of established postoperative outflow obstruction.

Adult↗
PubMed1995

Sequential backbone assignment of isotopically enriched proteins in D2O by deuterium-decoupled HA(CA)N and HA(CACO)N.

It is demonstrated that sequential resonance assignment of the backbone 1H alpha and 15N resonances of proteins can be obtained without recourse to the backbone amide protons, an approach which should be useful for assignment of regions with rapidly exchanging backbone amide protons and for proteins rich in proline residues. The method relies on the combined use of two 2D experiments, HA(CA)N and HA(CACO)N or their 3D analogs, which correlate 1H alpha with the intraresidue 15N and with the 15N resonance of the next residue. The experiments are preferably conducted in D2O, where very high resolution in the 15N dimension can be achieved by using 2H decoupling. The approach is demonstrated for a sample of human ubiquitin, uniformly enriched in 13C and 15N. Complete backbone and 13C beta/1H beta resonance assignments are presented.

Amino Acid Sequence↗
PubMed1994

1H, 13C, 15N nuclear magnetic resonance backbone assignments and secondary structure of human calcineurin B.

The calmodulin- and calcium-stimulated protein phosphatase calcineurin, PP2B, consists of two subunits: calcineurin B, which binds Ca2+, and calcineurin A, which contains the catalytic site and a calmodulin binding site. Heteronuclear 3D and 4D NMR experiments were carried out on a recombinant human calcineurin B which is a 170-residue protein of molecular mass 19.3 kDa, uniformly labeled with 15N and 13C. The nondenaturing detergent CHAPS was used to obtain a monomeric form of calcineurin B. Three-dimensional triple resonance experiments yielded complete sequential assignment of the backbone nuclei (1H, 13C, and 15N). This assignment was verified by a 4D HN(COCA)NH experiment carried out with 50% randomly deuteriated and uniformly 15N- and 13C-enriched calcineurin B. The secondary structure of calcineurin B has been determined on the basis of the 13C alpha and 13C beta secondary chemical shifts, J(HNH alpha) couplings, and NOE connectivities obtained from 3D 15N-separated and 4D 13C/15N-separated NOESY spectra. Calcineurin B has eight helices distributed in four EF-hand, helix-loop-helix [Kretsinger, R. H. (1980) CRC Crit. Rev. Biochem. 8, 119-174] calcium binding domains. The secondary structure of calcineurin B is highly homologous to that of calmodulin. In comparison to calmodulin, helices B and C are shorter while helix G is considerably longer. As was observed for calmodulin in solution, calcineurin B does not have a single long central helix; rather, helices D and E are separated by a six-residue sequence in a flexible nonhelical conformation.

Amino Acid Sequence↗
PubMed1994

A solid-state 2H NMR investigation of purine motion in a 12 base pair RNA duplex.

Solid-state 2H NMR spectroscopy has been used to investigate the base dynamics of a RNA oligonucleotide with a defined sequence, [r(CGCGAAUUCGCG)]2, which contains the RNA analogue of the EcoRI binding site. The C8 protons of all purines in the self-complementary dodecamer were exchanged for deuterons. The quadrupole-echo lineshapes and spin-lattice relaxation times as a function of hydration for the sample in the form of the Na salt have previously been reported. In that study the 2H NMR lineshapes and T1 values of [r(CG*CG*A*A*UUCG*CG*)]2 were compared with those of the analogously labeled DNA sequence, [(CG*CG*A*A*TTCG*CG*)]2 (Wang et al., J. Am. Chem. Soc. 114, 6583, 1992). It was concluded that the amplitudes of purine motion for DNA and RNA are similar at all hydration levels; however, the rate difference observed at low-hydration levels may or may not persist at high hydration. Here the internal motions of the purine bases in the RNA oligomer have been thoroughly investigated. Three models were used to simulate the motion: (1) two-site jump, (2) diffusion in a cone, and (3) restricted diffusion on the surface of a cone. The purine motion is best simulated by the restricted-diffusion on a cone model with an amplitude of +/- 9.5 degrees and a rate between 8.0 x 10(6) rad/s at 90% RH and 8.4 x 10(8) rad/s at 0% RH. This small amplitude and fast rate of purine motion for RNA are similar to previous results obtained for DNA purines.

Base Sequence↗
PubMed1994

[Surgical treatment for hilar bile duct stricture].

474 patients suffering from hilar bile duct strictures were treated from 1975 to 1992. 74.7% of the patients had a history of biliary surgery for 1-5 times. Causes of strictures were of iatrogenic in 10.9%, of primary in 71.7%, and of suppurative in 7.1%. Site of strictures: LHD in 37.6%, LHD+RHD+CHD in 17.4%, RHD in 9.6%, CHD in 14.7%, and LHD+RHD in 11.5%. The inferior end of the CBD were of spasmodic or flaccid in 23.6% and 48.3%, respectively. Treatment included cholangioplasty in 56.5%, dilatation and stent in 15.2%, lobectomy and segmetectomy of involued liver in 48%, repairing in 11.4%, bilio-enterostomy in 60.7%, and portal vein decompression in 6.3%.

Adolescent↗
PubMed1993

Minimizing the effects of radio-frequency heating in multidimensional NMR experiments.

Application of radio-frequency power in multidimensional NMR experiments can significantly increase the sample temperature compared to that of the surrounding gas flow. Radio-frequency heating effects become more severe at higher magnetic field strengths and ionic strengths. The effects are particularly noticeable for experiments that utilize 1H and/or 13C isotropic mixing and broadband decoupling. If radio-frequency power is applied during the systematically increasing evolution period t1, the sample temperature can change with t1 and thereby cause line-shape distortions. Such distortions are easily avoided by ensuring that the average radio-frequency power remains constant during the entire experiment.

Carbon Isotopes↗
PubMed1993

Measurement of endogenous synthesis of plasma cholesterol in rats and humans using MIDA.

We used the mass isotopomer distribution analysis (MIDA) technique to measure endogenous synthesis of plasma cholesterol in vivo in rats and normal human subjects. Sodium [1-13C]- or [2-13C]acetate was infused, and plasma free cholesterol was analyzed by gas chromatography-mass spectrometry. Frequencies of mass isotopomers M0-M4 (mass-to-charge ratio 368-372) were quantified. The enrichment of the true precursor for cholesterol synthesis (acetyl-coenzyme A in contributing tissues) was determined using the MIDA method. This technique remains mathematically valid even if more than one tissue contributes to circulating free cholesterol. The fractional contribution (f) from endogenous synthesis to free cholesterol in normal women (n = 5) was 2.48 +/- 0.39% after 7 h in the postabsorptive state and 1.27 +/- 0.41% after 8 h of refeeding. In ad libitum-fed rats (n = 12), f was 2.89 +/- 0.44% after 12 h, whereas administration of recombinant tumor necrosis factor increased this value fourfold. Next, the rate constant (k) for removal of labeled free cholesterol from plasma was calculated. Higher masses (M2-M4) were followed to avoid the problem of persistent label incorporation. During the 60 h after cessation of [13C]acetate infusions, k was 0.02490 +/- 0.00298/h in humans. Using these values of k and f, absolute cholesterogenesis was 568 +/- 55 mg/day in normal women (follicular menstrual phase), similar to prior estimates based on whole body sterol balances. Women also exhibited a diurnal variation for endogenous cholesterol synthesis (34.6 +/- 5.4 mg/h nighttime vs. 15.9 +/- 5.2 mg/h daytime) consistent with current knowledge about rhythms in cholesterogenesis. Checks on the model were internally consistent (e.g., comparisons among different isotopomers for calculating precursor enrichment). We conclude that fractional and absolute endogenous cholesterol synthesis can be measured using stable isotopes in vivo by the MIDA technique.

Adult↗
PubMed1993

[Diagnostic value of fiberbronchoscopy on pulmonary tuberculosis].

Result of fiberbronchoscopy in 89 patients with pulmonary tuberculosis were reported. Among them, lesions were located in the right in 49, left 20 and bilateral 1 case. The total positive rate of brushings was 80.28% and of BAL 85.71%, both significantly higher than of biopsy (42.55%). In the area of the congested, swollen and coarse bronchial mucose, brushings and BAL respectively gave positive rates of 86.36% and 90.91%, statistically greater than biopsy (21.88%). But, biopsy of the granulations and nodules was positive for 100%, while brushings for 50% (P < 0.01). When bronchoscopy revealed no obvious abnormality of the visible airways, the positive rate of BAL (80.00%) was remarkably higher than of biopsy (50%).

Adolescent↗
PubMed1992

Errors in RNA NOESY distance measurements in chimeric and hybrid duplexes: differences in RNA and DNA proton relaxation.

Nuclear magnetic resonance experiments reveal that the base H8/H6 protons of oligoribonucleotides (RNA) have T1 relaxation times that are distinctly longer than those of oligodeoxyribonucleotides (DNA). Similarly, the T1 values for the RNA H1' protons are approximately twice those of the corresponding DNA H1' protons. These relaxation differences persist in single duplexes containing covalently linked RNA and DNA segments and cause serious overestimation of distances involving RNA protons in typical NOESY spectra collected with a duty cycle of 2-3 s. NMR and circular dichroism experiments indicate that the segments of RNA maintain their A-form geometry even in the interior of DNA-RNA-DNA chimeric duplexes, suggesting that the relaxation times are correlated with the type of helix topology. The difference in local proton density is the major cause of the longer nonselective T1s of RNA compared to DNA, although small differences in internal motion cannot be completely ruled out. Fortunately, any internal motion differences that might exist are shown to be too small to affect cross-relaxation rates, and therefore reliable distance data can be obtained from time-dependent NOESY data sets provided an adequately long relaxation delay is used. In hybrid or chimeric RNA-DNA duplexes, if the longer RNA relaxation times are not taken into account in the recycle delay of NOESY pulse sequences, serious errors in measuring RNA proton distances are introduced.

Base Sequence↗
PubMed1992

Therapeutic effect of carbon dioxide laser versus single application of trichloroacetic acid for koilocytic squamous papillae.

This paper reports the treatment results of 50 symptomatic females who had clinical features of squamous papillae and histologic evidence of koilocytosis. Either a carbon dioxide laser or a single application of trichloroacetic acid (TCA) was used to treat these patients. All of the patients were alternately and prospectively randomized into one of two groups. Twenty-three of the 25 women treated by laser and 10 of the 25 women treated by TCA had resolution of either the symptoms or the vulvar lesions in a follow-up period ranging from six to 22 months. Hence, we were able to control the symptoms and lesions in 92% of the women following initial laser treatment and 40% of the women following a single application of TCA. In addition, cosmetic results were satisfactory, and complications were minimal in the laser-treated group of patients. However, human papillomavirus DNA was still detected three to four weeks after treatment in 24% of the women treated by laser and 64% of the women treated by TCA. Whether they are at a higher risk of recurrence as compared to those without detectable viral DNA remains to be determined.

Adolescent↗
PubMed1992

Contact Nd:YAG laser and CO2 laser for cylindrical excision of the cervix. A comparative study.

An excess of blood loss and persistence of intraepithelial neoplasia after cervical conization occur with some frequency. Contact Nd:YAG laser conical excision of the uterine cervix is a new technique designed to remedy those problems. In this study, 36 women with histologically confirmed cervical intraepithelial neoplasia were treated with cylindrical excision of the uterine cervix with a contact Nd:YAG laser. The results were compared with those in 30 women who had similar lesions and were treated with the CO2 laser. Use of the Nd:YAG laser resulted in less intraoperative blood loss (mean +/- SD, 3.12 +/- 0.28 vs. 30.3 +/- 2.12 mL for the CO2 laser, P less than .01) and less postoperative blood loss. The volume of early bleeding was 6.23 +/- 1.21 vs. 20.13 +/- 2.24 mL for the CO2 laser (P less than .01), and that of late bleeding was 5.22 +/- 2.21 vs. 31.24 +/- 0.05 mL for the CO2 laser (P less than .01). The operative time was similarly less for the contact Nd:YAG laser (6.2 +/- 2.2 vs. 20.2 +/- 1.2 minutes for the CO2 laser, P less than .01). The dimensions of the excised specimens were similar. These findings suggest that the contact Nd:YAG laser offers distinct advantages over the CO2 laser in performing cylindrical excision of the cervix.

Blood Loss, Surgical↗