Biomedical subjects

L S Chang

Publications and source records attributed to L S Chang.

At least 145 records · Page 8Linked to original sources

PubMed1994

Decreased blood flow and defective energy metabolism in the varicocele-bearing testicles of rats.

This study was designed to elucidate the hemodynamic and energetic changes of testicles in experimental varicocele. Partial ligation of the left renal vein was performed in 10 Sprague-Dawley rats to induce dilatation of the internal spermatic vein, and sham operation was performed in the other 10 age-matched Sprague-Dawley rats used as controls. Blood pressure and rectal temperature were maintained at a constant level. Testicular blood flow was detected by laser Doppler flowmeter on the day before surgery and 4 weeks after surgery, respectively. Concentrations of various adenine nucleotides were determined by high-performance liquid chromatography (HPLC). We found a significant decrease from 10.2 +/- 1.5 to 7.4 +/- 1.8 mlLD/min/100 g (p < 0.005) in testicular blood flow after inducing varicocele in the rats. The energy charge of adenine nucleotides of the varicocele-bearing rats was 0.62 +/- 0.07 which was significantly lower than the 0.73 +/- 0.02 of the control group (p < 0.005). These observations have, thus, led us to propose the hypothesis that impaired spermatogenesis may result from defective energy metabolism in the varicocele-bearing testicles of rats.

Adenine Nucleotides↗

PubMed1994

Prediction of lymphatic spreading in prostatic cancer by prostate-specific antigen and Gleason's score.

A total of 58 patients have undergone bilateral pelvic lymphadenectomy as a staging procedure for clinically localized adenocarcinoma of the prostate. Of these, 19 patients (33%) had pelvic lymph node involvement. When a cutoff value of 50 ng/ml was used, the preoperative prostate-specific antigen (PSA) value had a positive predictive value of 57% for pelvic lymph node metastasis. Of the patients with PSA < 20 ng/ml, only 1 (4%) had evidence of lymph node metastasis. None of the patients with well-differentiated tumor (Gleason 2-4) had lymphatic spreading. In contrast, 82% of patients with poorly differentiated tumor (Gleason 8-10) had positive pelvic lymph nodes. Those patients with high PSA (> or = 20 ng/ml) and high Gleason's score (> or = 8) had the highest incidence of nodal extension (90%).

Aged↗

PubMed1994

Chemical modification of Lys-6 in Taiwan cobra phospholipase A2 with 4-chloro-3,5-dinitrobenzoate.

Phospholipase A2 (PLA2) from Naja naja atra snake venom was modified with 4-chloro-3,5-dinitrobenzoate, and one major carboxydinitrophenylated (CDNP) PLA2 was separated by high performance liquid chromato-graphy. CDNP-PLA2 contained only one CDNP group on Lys-6 and showed a 93% drop in enzymatic activity. However, carboxydinitrophenylation did not significantly affect the secondary structure of the enzyme molecule as revealed by the CD spectra, and Ca2+ binding and antigenicity of CDNP-PLA2 were unaffected. Conversion of nitro groups to amino groups resulted in a partial restoration of enzymatic activity of CDNP-PLA2 to 35% of that of native enzyme. These results suggested that the positively charged side chain of Lys-6 played a role in the enzymatic mechanism of PLA2. However, the partial restoration in PLA2 activity reflects that a distortion of the active conformation arising from incorporation of a bulky CDNP group should occur.

Amino Acid Sequence↗

PubMed1994

Improvement in the binding of cobrotoxin to microtiter plates by glutaraldehyde at neutral pH.

The coating of the wells of microtiter plates with cobrotoxin in Tris (pH 9.8) or PBS (pH 7.2) buffer was assessed by enzyme-linked immunoassay (ELISA). It was found that the poor binding in neutral buffer was improved by adding glutaraldehyde (GA), and the bound amount reached the same extent as that measured with alkali buffer. The optimal concentration of GA was approx. 0.02%. A decrease in optical density was observed with GA concentration higher than 0.02%. This may result from the modification of cobrotoxin by GA, which induced a decrease in the antigenicity of the cobrotoxin as revealed by competitive immunoassay. This study implies that the coating of physiological samples with GA for ELISA may be carried out with physiological buffers without the need to change the buffer to one of alkaline pH.

Antibodies↗

PubMed1994

Biochemical regulation of the activity of gamma-glutamylcysteine synthetase from rat liver and kidney by glutathione.

Rat liver and kidney gamma-glutamylcysteine synthetase (gamma GCS) had similar catalytic properties and consisted of heavy and light subunits, but the molecular structure of the two enzymes was not the same as evidenced by the results of SDS-PAGE and disc gel electrophoresis. Unlike kidney enzyme, most of liver gamma GCS was in a reduced enzyme form which did not have disulfide linkage between heavy and light subunits. Although the oxidized form of the two enzymes which subunits were linked with disulfide bond(s) could be dissociated to a similar extent by GSH, liver gamma GCS was inhibited by GSH to a much greater extent. These results suggest that the relative sensitivity of the gamma GCS enzymes to inhibition by GSH might be related to the inherent dissociability of heavy and light subunit of gamma GCS.

Animals↗

PubMed1993

Identification of functional involvement of tryptophan residues in phospholipase A2 from Naja naja atra (Taiwan cobra) snake venom.

Phospholipase A2 (PLA2) from Naja naja atra snake venom was subjected to Trp modification with 2-nitrophenylsulfenyl chloride (NPS-Cl), and six derivatives were separated by HPLC. The results of amino-acid analysis and sequence determination revealed that Trp-18, Trp-19 and Trp-61 were modified by NPS-Cl. The order of accessibilities of the three Trp residues for NPS-Cl was Trp-18 > Trp-19 > Trp-61. Sulfenylation of Trp-18 caused a 92% drop in enzymatic activity. Modification of Trp-19 and Trp-61 resulted in a decrease in enzymatic activity of PLA2 by 45.5% and 51%, respectively. The enzyme modified on both Trp-18 and Trp-19 or on both Trp-18 and Trp-61 retained little PLA2 activity. It is evident that Trp-18 plays a more crucial function in PLA2 than Trp-19 and Trp-61. Sulfenylation did not significantly affect the secondary structure of the enzyme molecule as revealed by the CD spectra, and Ca2+ binding and antigenicity of sulfenylated PLA2 was unaffected. These observations, together with the fact that Trp-18 is involved in the substrate binding of PLA2, suggest that incorporation of a bulky NPS group on Trp-18 might give rise to a direct distortion of the interaction between substrate and the enzyme molecule. Alternatively, modification of Trp-19 and Trp-61 might indirectly affect the interfacial binding of PLA2 with its substrate.

Amino Acid Sequence↗

PubMed1993

Catalytic and regulatory properties of the heavy subunit of rat kidney gamma-glutamylcysteine synthetase.

gamma-Glutamylcysteine synthetase (rat kidney), which catalyzes the first step of GSH synthesis, can be dissociated into subunits (M(r) 73,000 and 27,700) by native gel electrophoresis after treatment with dithiothreitol (DTT); the heavy subunit, which exhibits catalytic activity and feedback inhibition by GSH (Seelig, G. F., Simondsen, R. P., and Meister, A. (1984) J. Biol. Chem. 259, 9345-9347), was cloned and sequenced (Yan, N., and Meister, A. (1990) J. Biol. Chem. 265, 1588-1593). Here, the cDNA for the heavy sub unit was expressed in Escherichia coli, and the recombinant enzyme was separated from E. coli gamma-glutamylcysteine synthetase and purified. The recombinant enzyme and the isolated heavy subunit have much lower affinity for glutamate and higher sensitivity to GSH inhibition than the holoenzyme, suggesting that the heavy subunit alone would not be very active in vivo. A GSH analog, gamma-Glu-alpha-aminobutyryl-Gly (ophthalmic acid), inhibits only slightly, but inhibits much more after treatment of the holoenzyme with DTT. In contrast, ophthalmic acid inhibits the recombinant and isolated heavy subunit enzymes substantially without DTT treatment. We conclude that (a) the light subunit has a regulatory function affecting the affinity of the enzyme for glutamate and GSH and (b) feedback inhibition by GSH involves reduction of the enzyme and also competition between GSH and glutamate for the glutamate site.

Animals↗

PubMed1993

Separation and characterization of the A chain and B chain in beta 1-bungarotoxin from Bungarus multicinctus (Taiwan banded krait) venom.

The interchain disulfide bond between A chain and B chain of beta 1-bungarotoxin (beta 1-Bgt) was selectively cleaved by dithiothreitol, and the A and B chains were separated by HPLC. The separated A and B chains did not show detectable enzymatic activity and lethal toxicity, but exhibited an immunoreactivity with anti-beta 1-Bgt antibody. Analytical isoelectrofocusing revealed that the A chain is a neutral subunit with pI = 7.4, and the B chain is a basic one with pI = 9.6. The A chain exhibited a Ca(2+)-binding ability as revealed by fluorescence measurement. Moreover, fluorescence studies showed that the intact interchain disulfide bond is essential for maintaining the hydrophobic character of substrate binding site in beta 1-Bgt and stabilizing the architectural environment of Trp-19 in the A chain. However, combination of the A chain and B chain failed to restore the biological activities and physiochemical properties which the intact beta 1-Bgt possessed. These, together with our previous result that the Trp-19 of the A chain is involved in substrate binding, suggest that the integrity of the interchain disulfide bond favors the maintenance of the active conformation of beta 1-Bgt.

Anilino Naphthalenesulfonates↗

PubMed1993

Structural determinants of the intrinsic fluorescence emission in notexin and phospholipase A2 enzymes.

Fluorescence measurements of the homologous proteins, notexin and PLA2 enzymes from Naja naja atra, Naja nigricollis, and Hemachatus haemachatus venoms, showed that the wave-length of maximum emission and the quantum yield of their intrinsic fluorescence emission spectra were different. To verify the factors which affected their fluorescence characteristics, the dynamics of tryptophan residues in those homologous proteins were studied by quenching with acrylamide, iodide, and cesium. The degrees of exposure of tryptophanyl groups in notexin and PLA2 enzymes assessed by acrylamide quenching were found to be the major factor that determined their fluorescence characteristics. However, the positively charged groups surrounding tryptophan residues of PLA2 enzymes from N. naja atra and N. nigricollis venoms might affect the quantum yield of their fluorophores. Tryptophan residues of notexin were in an environment with less fluctuation, which did not allow free diffusion of ionic quencher. This might render its tryptophan residues to fluoresce at a shorter wavelength. These results suggested that the structural determinants affecting the intrinsic fluorescence emission of homologous proteins can be easily assessed by quenching studies.

Acrylamide↗

PubMed1993

Efficacy of in vitro stone fragmentation by extracorporeal, electrohydraulic, and pulsed-dye laser lithotripsy.

Fragmentation has become the standard therapy for urinary calculi in the modern era. Stone fragility as well as position and size are important for the determination of a treatment program. To compare the efficacy of stone fragmentation, seven kinds of human urinary calculi with known composition (calcium oxalate monohydrate and dihydrate, dibasic calcium phosphate, uric acid, struvite, calcium phosphate, and cystine) were treated by three fragmentation techniques commonly used, namely extracorporeal shock wave (SWL), electrohydraulic (EHL), and pulsed-dye laser lithotripsy. Uric acid, calcium oxalate dihydrate, and calcium phosphate stones could be destroyed easily by any of these methods. Struvite was soft but sticky and not easy to break into tiny particles. Both dibasic calcium phosphate and calcium oxalate monohydrate stones were resistant to the laser and EHL; SWL is the treatment of choice. For cystine stones, none of the treatments was satisfactory; SWL was the only way to break them into large pieces.

Calcium Oxalate↗

PubMed1993

Histopathological changes in Kock pouch.

To investigate whether tumour recurrence or histological changes occur in the Kock pouch, periodic endoscopy with biopsy of the pouch was performed in 15 patients 6 to 66 months after radical cystectomy and urinary diversion for invasive bladder cancer. Endoscopy was undertaken 1 to 4 times in each patient (a total of 37 times in all patients). During endoscopy, random biopsies were taken from the pouch wall, and from the afferent and the efferent nipples. The histological changes were graded as: (1) villous atrophy (grade 0 to 3, 0: nearly normal; 1: shortening, villi/crypt of Lieberkuhn [length] between 1.5 and 4.0; 2: moderate flattening, villi/crypt < 1.5; and 3: almost complete disappearance of villi); (2) fibrosis; and (3) chronic inflammation (grade 0 to 3, based on the amount of fibrous tissue and inflammatory cell infiltration in the lamina propria, respectively). There was no dysplasia or malignant tumour in the Kock pouch in any of the 15 patients. The histology of the ileum changed in terms of villous atrophy, fibrosis and chronic inflammation in the lamina propria and thickening of the muscularis mucosa. The same grade of villous atrophy of the pouch wall, the afferent and the efferent nipples was only found in 3 patients. More fibrosis and less chronic inflammation in the lamina propria were found at the efferent nipple than at the afferent nipple or pouch wall in 8 patients and 5 patients, respectively. Thickening of the muscularis mucosa was found in 13 of 15 patients (86.7%). In conclusion, there was no dysplasia or recurrent tumour in the Kock pouch in patients who were followed for up to 66 months. Various grades of histological changes of the ileum in terms of villous atrophy, fibrosis and chronic inflammation of the lamina propria, and thickening of the muscularis mucosa were found in the pouch wall, and in the afferent and efferent nipples. More fibrosis and less chronic inflammation were commonly observed at the efferent nipple than at the afferent nipple or pouch wall. The degree of histological changes varied even among patients followed over the same period after operation. The time to progression of villous atrophy also varied. The histological changes in some patients were dissimilar even at the same site of the Kock pouch.

Aged↗

PubMed1993

Deoxyribonucleic acid histogram of testes in primary transsexualism.

The influence of oestrogen on spermatogenesis was evaluated by comparing its effect on the testes of primary male transsexuals and those who had undergone hormone therapy for prostatic carcinoma. Eight primary transsexuals were studied. They had been diagnosed on clinical and psychiatric evidence and had been on oestrogen therapy for several years since puberty. Histological sections of testicular tissue obtained at reassignment surgery from 8 phenotypic male transsexuals (aged 24-32 years) with an XY chromosome complement were studied by light microscopy. The formalin-embedded specimens were analysed by flow cytometry for deoxyribonucleic acid (DNA) histograms. Both the histology and DNA histograms revealed a pattern of maturation arrest in 12 of 16 testes in which the diploid cell compartment occupied most of the spermatogenetic element, followed by tetraploid and monoploid cells. Two testes showed impaired spermatogenesis and 2 were normal. The DNA histograms and pathology were also evaluated in 20 testes after 3 to 8 years of hormone therapy in patients with advanced prostatic carcinoma (aged 60-78 years). No maturation arrest was found in these patients. Sixteen of them had a pattern of fibrosis and atrophy and 4 had impaired spermatogenesis. It was concluded that oestrogen influenced spermatogenesis and affected the maturation of spermatogonia mostly during puberty.

Adult↗

PubMed1993

Long-term stone regrowth and recurrence rates after extracorporeal shock wave lithotripsy.

We reviewed 1055 patients with symptomatic urinary calculi treated by extracorporeal shock wave lithotripsy (ESWL) monotherapy to determine the long-term stone regrowth and recurrence rates as correlated with the pre-treatment stone burden, site and multiplicity. Long-term follow-up (mean 75.8 months) was available in 94 patients, representing 106 renal units. The recurrence of stone was defined as reappearance of stone on follow-up plain abdominal radiographs. The regrowth of stone was defined as stone regrowing larger than one-third of the original residual size. A stone-free rate of 53% was achieved. The overall stone regrowth and recurrence rates were 26 and 15% respectively. It was concluded that the stone recurrence rate after ESWL was not influenced significantly by the stone size or the multiplicity, but that the regrowth rate was. Stone recurrence and regrowth rates after ESWL were both influenced by the stone location.

Adult↗

PubMed1993

Experience using extracorporeal shock-wave lithotripsy to treat urinary calculi in problem kidneys.

Seventeen patients with urolithiasis in problem kidneys which comprised horseshoe kidneys, medullary sponge kidneys (MSKs), polycystic kidneys and duplex kidneys presented to our hospital and were evaluated for treatment with extracorporeal shock-wave lithotripsy (ESWL). A total of 21 renal units were treated with ESWL. Auxiliary procedures included preoperative retrograde ureteral catheterization (1 horseshoe kidney) placement of a retrograde double-J catheter stent (1 MSK), percutaneous nephrolithotomy (PCNL; 2 MSKs) and postoperative PCNL (1 MSK). The outcome showed that 5 renal units (23.8%) were stone free, 15 renal units (71.4%) had a decreased stone load with residual stone and improved symptoms, and 1 renal unit (4.8%) had residual stone with persistent symptoms. We conclude that ESWL can be used as a primary management tool for calculi in problem kidneys.

Female↗

PubMed1993

Local chemolysis of obstructive uric acid stone with 0.1 M THAM and 0.02% chlorhexidine.

We used a modified chemolytic solution by combining 0.1 M THAM (tris[hydroxymethyl] aminomethane) with 0.02% chlorhexidine to treat 10 obstructive uric acid stone patients. A total of 23 local chemolysis sessions were performed. Five patients received 13 sessions (average: 2.6) as an adjuvant chemolysis after extracorporeal shock wave lithotripsy 5 patients received 10 sessions (average: 2) as a primary treatment. The average time of local chemolysis was 2.3 days, ranging from 1 to 4 days. In the 23 local chemolysis sessions, only one patient developed two episodes of fever (8.7%), which were managed successfully by conservative treatment. The mean values of effective renal plasma flow of treated kidney was increased from 108.2 to 155.6 ml/min (p < 0.05). The stone-free rate assessed by IVP and ultrasonography at 3 months follow-up was 80%. Our results indicate that the combined use of 0.1 M THAM and 0.02% chlorhexidine is an effective and safe method to treat obstructive uric acid stones.

Aged↗

PubMed1993

Intradiverticular tumors of the bladder: surgical implications--an eleven-year review.

An 11-year review of all vesical diverticula and bladder tumors was undertaken. Fourteen patients were found to have primary neoplasms arising in the diverticula. The most common type was transitional cell. Hematuria was the most common presentation. Diagnosis is relatively difficult and treatment is not well defined. Lack or thinness of muscular layer of the diverticulum also potentiates early peridiverticular invasion and results in poor prognosis. Early diagnosis and adequate treatment are indicated.

Aged↗

PubMed1993

Acute pancreatitis following transurethral resection of prostate.

Three cases of acute pancreatitis following transurethral resection of the prostate are reported. The incidence is rare. A review of perioperative data failed to disclose any unique factor except in 1 patient who had an underlying biliary tract disease. Hyperamylasemia or hyperlipaemia in association with abdominal pain and vomiting was noted in all patients to establish the diagnosis. Computed tomography also confirmed the existence of acute pancreatitis. One patient died of respiratory and renal failure. However, early diagnosis and prompt treatment are essential to reduce high mortality. In conclusion, acute pancreatitis should be considered as one of the differential diagnoses in the presence of abdominal pain with vomiting, azotemia or oliguria after transurethral resection of the prostate.

Acute Disease↗

PubMed1993

Silica stone--development due to long time oral trisilicate intake.

We report a case of a 30-year-old female who had a long-term history of trisilicate-containing antacid intake for gastric discomfort. She had experienced repeated attacks of renal colic. Neither intravenous pyelography nor ureteroscopy could define the presence of calculi. The metabolic evaluations were normal. However, X-ray diffraction revealed a silicate stone. We suggest that the attack of renal colic in those patients with long-term history of trisilicate intake should arouse the possibility of silica urolithiasis.

Administration, Oral↗