Biomedical subjects

L S Chang

Publications and source records attributed to L S Chang.

At least 109 records · Page 6Linked to original sources

PubMed1996

The structural elements of phospholipase A2 affecting the enhancement of 8-anilinonaphthalene-1-sulfonate fluorescence.

The binding of the apolar fluorescent dye 8-anilinonaphthalene-1-sulfonate (ANS) to Naja naja atra and Bungarus multicinctus phospholipase A2 (PLA2) as well as the ANS fluorescence enhancement of PLA2-ANS complexes were pH-dependent. However, the pH-dependent curves and the ionizable groups perturbed by the binding of ANS were essentially different for the two PLA2 enzymes. Methylation of His residue or removal of the N-terminal octapeptide made the ANS fluorescence of PLA2-ANS complexes become less sensitive to pH changes. Moreover, the N-terminus-removed derivatives showed the same fluorescence-pH profiles. These results, together with the findings that the His residue and the N-terminal residues might locate around the ANS-binding site, suggested that the His residue and N-terminus of the two PLA2 enzymes may interact electrostatically with the bound ANS, and that ionization of these residues should appreciably affect the ANS fluorescence.

Anilino Naphthalenesulfonates↗

PubMed1996

Urinary bladder endometriosis: a report of two cases.

Endometriosis of the urinary tract is uncommon, and the most common site of involvement is urinary bladder. Two cases of endometriosis of urinary bladder are presented. The first patient, a 39-year-old woman, complained of dysuria during menstruation and the other 37-year-old woman suffered from intermittent gross hematuria. Pre-operative examinations included ultrasonography, computed tomography and cystoscopic biopsy. Case 1 was in premenopausal status, but the serum estrogen level of case 2 was in postmenopausal status because she was given no exogenous estrogen after previous bilateral salpingo-oophorectomy. Endometriosis of urinary bladder rarely occurs in postmenopausal woman without exogenous estrogen replacement. Case 1 received danazole treatment after transurethral resection of bladder tumor and case 2 received partial cystectomy after transurethral resection of bladder tumor. The patients were followed 36 and 4 months, respectively, and the symptoms kept improving during this period.

Adult↗

PubMed1995

Structure of the gene for the catalytic subunit of human DNA polymerase delta (POLD1).

We have isolated genomic DNA clones covering the gene for human DNA polymerase delta catalytic subunit (POLD1) and its 5' flanking sequence. This gene is divided into 27 exons and is distributed over at least 32 kb of DNA. The exons and most of the introns are relatively small. The sizes of the exons range from 55 to 201 bp. Seven introns are smaller than 100 bp. Intron 1 is the largest intron, with a size of greater than 10 kb. All of the intron-exon junctions match well with the reported consensus sequences. Multiple copies of the Alu repetitive sequence and the variable number of tandem repeats were found in several introns. Transcription of POLD1 appears to initiate at multiple sites. The major start site was 53 nucleotides upstream of the ATG start codon. The sequence of the promoter and upstream DNA is G+C rich and does not contain a TATA sequence. Several potential transcription factor-binding sites, including the AP2-, CTF-, Ets1-, GCF-, MBF-1-, NF-E1-, and Sp1-binding sites, were found in this region. A 1.8-kb pol delta promoter DNA directed the expression of a luciferase reporter gene when transfected into HeLa cells.

Base Sequence↗

PubMed1995

Alterations in local cerebral glucose utilization in rats after chronic amphetamine administration without subsequent challenge.

The 2-deoxyglucose (2-DG) method was used to study regional metabolic changes in rats following chronic d-amphetamine treatment without subsequent challenges. Four groups of rats were pretreated (intraperitoneal administration) with d-amphetamine (0, 1, 5, or 10 mg/kg) once per day for 14 days. After a 7-day abstinence period without further challenge, the 2-DG method was used to measure the rates of local cerebral glucose utilization (LCGU). Significant metabolic changes among the four groups were found in five brain regions, including the nucleus accumbens and the lateral habenular nucleus. Another four groups of rats with the same pretreatment regimens, challenged with 5 mg/kg d-amphetamine, were used for behavioral testing. The results showed intense stereotyped behaviors in the 5 mg/kg and the 10 mg/kg groups. In the steady state, however, there were no significant glucose utilization changes in the nigrostriatal system, which is thought to be related to stereotyped behaviors. During steady state, metabolic changes were found in a limited number of brain regions. No difference in LCGU was found in the sensitization-related regions. Further challenges with stimulants may be necessary to investigate the metabolic responses after sensitization.

Animals↗

PubMed1995

The murine erythrocyte protein-4.2-encoding gene: similarities and differences in structure and expression from its human counterpart.

We have isolated a complete cDNA encoding for the mouse erythrocyte protein 4.2 (P4.2). The entire P4.2 cDNA consists of 3465 nt with an open reading frame (ORF) of 691 amino acids. Northern blot analysis of mouse reticulocyte or spleen RNA using the P4.2 cDNA as a probe, detected a 3.5-kb message. The size of the mouse P4.2 cDNA or message that we obtained, appears to be different from those reported recently. Despite the similarity to the human P4.2 cDNAs, the mouse cDNA has a longer 3' untranslated region. A genomic clone covering the first exon and flanking sequences of the mouse P4.2 gene was isolated. Sequencing results from the first exon-intron junction region and polymerase chain reaction (PCR) experiments revealed that the mouse reticulocyte P4.2 RNA does not exhibit alternative splicing in the region identified in the human P4.2 RNA.

Alternative Splicing↗

PubMed1995

A conserved region in the amino terminus of DNA polymerase delta is involved in proliferating cell nuclear antigen binding.

Synthetic peptides to selected sequences in human DNA polymerase delta (pol delta) were used to identify the region involved in the interaction of pol delta to proliferating cell nuclear antigen. Peptides corresponding to sequences in five regions in the amino terminus of human pol delta and three in the carboxyl terminus, which are conserved with the yeast homologs of pol delta, were tested. These studies showed that the peptide corresponding to the N2 region (residues 129-149) selectively and specifically inhibited the PCNA stimulation of pol delta. This inhibition was relieved by titration with excess PCNA. The identification of the N-2 region as being involved in PCNA binding was supported by studies that demonstrated that the N2 peptide could bind PCNA. Deletion mutants of pol delta expressed in Sf9 cells provided evidence that the binding region for PCNA was located in the first 182 residues of the amino terminus. These studies provide reasonable evidence that residues within the region 129-149 of pol delta are involved in the binding site for PCNA.

Amino Acid Sequence↗

PubMed1995

Blood flow of the urinary bladder: effects of outlet obstruction and correlation with bioenergetic metabolism.

This study investigated the effects of outlet obstruction on blood flow and high energy phosphates content in the rabbit urinary bladder. Mild bladder outlet obstruction was induced by placing a silicon ring (diameter 7 mm) around the bladder neck of each male New Zealand White rabbit (n = 7). Before and immediately after inducing obstruction, and 2 weeks later, the bladders were emptied and regional blood flow measured using laser Doppler flowmetry (LASERFLO BPM2, Vasamedics Inc., St. Paul, Minnesota). Six different areas of each bladder were measured, and the average blood flow calculated for each rabbit. Then, the animals were sacrificed, the bladder excised, and the tissue content of high energy phosphates determined by high performance liquid chromatography (HPLC). Six normal male New Zealand White rabbits served as controls. The results can be summarized as follows: (1) Before surgery, bladder blood flow was similar in all animals (16.3 ml/min/100 g); positioning the silicon ring around the bladder neck did not affect blood perfusion, two weeks after the induction of outlet obstruction, bladder blood flow was significantly decreased (4.9 ml/min/100 g). (2) There was no significant difference between control and obstructed bladders in NAD, AMP, or ADP content. However, the obstructed bladders contained significantly less phosphocreatine (12.0 vs 21.9 nmol/mg protein) and ATP (4.0 vs. 6.1 nmol/mg protein) than control bladders. In summary, this study showed that urinary bladder blood flow was reduced by outlet obstruction, and the reduction in blood flow was associated with decreased tissue high energy phosphates content.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗

PubMed1995

Purification and characterization of a novel phospholipase A2 from king cobra (Ophiophagus hannah) venom.

A novel phospholipase A2, designated as Oh-DE-2, was isolated from the venom of Ophiophagus hannah (king cobra) by successive chromatography on SP-Sephadex C-25, DE-52, and Q-Sepharose columns. Oh-DE-2 with pI 5.1 showed an apparent molecular weight of 14 kD as revealed by SDS-PAGE and gel filtration. The amino acid sequence was homologous with those of PLA2S from Elapidae venoms. Oh-DE-2 was effectively inactivated by p-bromophenacyl bromide, indicating that the conserved His-48 is essential for its enzymatic activity. However, modification of the conserved Trp-19 did not cause a precipitous drop in the enzymatic activity of Oh-DE-2 as observed with PLA2S from Naja naja atra and Bungarus multicinctus venoms. A quenching study showed that the microenvironment of Trp in Oh-DE-2 was inaccessible to acrylamide, iodide, or cesium, a finding which was different from those observed with PLA2S from N. naja atra and B. multicinctus venoms. These results might suggest that, unlike other PLA2 enzymes, Trp-19 in Oh-DE-2 is not directly involved in its enzymatic mechanisms.

Amino Acid Sequence↗

PubMed1995

Chemical modification of tryptophan residues in alpha-neurotoxins from Ophiophagus hannah (king cobra) venom.

Two alpha-neurotoxins, Oh-4 and Oh-7, from the king cobra (Ophiophagus hannah) venom were subjected to Trp modification with 2-nitrophenylsulfenyl chloride (NPS-Cl). One major NPS derivative was isolated from the modified mixtures of Oh-4 and two from Oh-7 by HPLC. Amino acid analysis and sequence determination revealed that Trp-27 in Oh-4, and Trp-30 and Trp-26 and 30 in the two Oh-7 derivatives, were modified, respectively. Sulfenylation of Trp-27 in Oh-4 caused about 70% drop in lethal toxicity and nicotinic acetylcholine receptor-binding activity. Modification of Trp-30 in Oh-7 resulted in the decrease of lethal toxicity by 36% and binding activity by 61%. The activities were further lost when the conserved Trp-26 in Oh-7 was modified. Sulfenylation of the Trp residues did not significantly affect the secondary structure of the toxins as revealed by the CD spectra. These results indicate that the Trp residues in these two long alpha-neurotoxins may be involved in the receptor binding.

Amino Acid Sequence↗

PubMed1995

Effect of orchiectomy on the alpha adrenergic contractile response of dog prostate.

PURPOSE: To investigate the effect of androgen deprivation on the alpha-adrenergic contractile response of the dog prostate using both in vitro and in vivo methods. MATERIALS AND METHODS: In vitro muscle bath study: One month after surgery, responses to KCl (120 mM.) and norepinephrine (10(-8) to 10(-3)M.) of prostatic tissue strips (of the same size) from castrated (n = 6) and sham-operated (n = 6) adult mongrel dogs were determined. In vivo study: Before and 1 month after surgery, the intraprostatic urethral pressure response to intravenous norepinephrine administration of 6 castrated and 5 sham-operated adult dogs was examined. RESULTS: (1) Before castration the serum level of testosterone was 1.24 +/- 0.2 ng./ml.; 1 month after castration, it had dropped to an undetectable level. (2) Histological examination of the prostates from castrated animals revealed profound atrophy of glandular tissue with a relatively increased stromal tissue component in each section. (3) In vitro study: The contractile responses to KCl and norepinephrine of individual prostate strips (same size) from castrated animals were significantly higher than control. However, if the response to norepinephrine was normalized to the response to KCl, there was no significant difference in response to norepinephrine between the 2 groups. In addition, the ED50 of the norepinephrine-stimulated contractile response was not changed by castration. (4) In vivo study: There was no significant change in intraprostatic urethral pressure response to intravenous norepinephrine administration after orchiectomy. CONCLUSIONS: The results of this study show that the sensitivity of the alpha-adrenergic contractile response of the dog prostate is not affected by androgen deprivation, nor is alpha-adrenergic contractile activity of the dog prostate regulated by androgen.

Adrenergic alpha-Agonists↗

PubMed1995

Adrenal cortical carcinoma with tumor thrombus invasion of inferior vena cava.

A case of adrenal cortical carcinoma with inferior vena cava (IVC) involvement is presented. Ultrasonography, computed tomography, and venacavography all presumptively showed a large mass over the upper pole of the left kidney with tumor thrombus in the IVC. However, aortography demonstrated that this mass was receiving its blood supply from the left inferior phrenic artery, aorta, and left renal artery. Radical surgery, including resection of the tumor and its adjacent organs (kidney, distal pancreas, spleen) and the tumor thrombus in the IVC, with the aid of cardiopulmonary bypass, was performed. We emphasize that adrenal cortical carcinoma can have tumor thrombi invading the IVC, and in such cases we suggest radical surgical removal of the tumor and the thrombus.

Adrenal Cortex Neoplasms↗

PubMed1995

Direct needle insufflation for pneumoretroperitoneum: anatomic confirmation and clinical experience.

OBJECTIVES: The feasibility and safety of direct needle insufflation to create pneumoretroperitoneum was assessed by an imaging study and clinical experience. METHODS: A total of 10 patients without previous retroperitoneal surgery or diseases received computed tomography scans of the retroperitoneum 2 cm above the iliac crest. Distances between quadratus lumborum and colon (Q-C distance) were measured in the supine and lateral positions. Changes of Q-C distance were calculated when the patient was changed from the supine to the lateral position. Operative charts on 38 retroperitoneoscopic procedures were collected prospectively to assess complications related to direct needle insufflation, which was performed by inserting a 14 G Veress needle blindly along the posterior axillary line 2 cm above the iliac crest. RESULTS: Q-C distance increased from 8.7 to 27.3 mm (left side) and 4.6 to 18.1 mm (right side) when the patient was changed from the supine to the lateral position, both P values < 0.05. An average distance of 23 mm between colon and quadratus lumborum was found when patients were lying laterally. The misplacement of a Veress needle was encountered in 1 patient, in which a prefascia insufflation resulted in conversion of the endoscopic procedure. Needle puncture caused no visceral or great vessel injury. CONCLUSIONS: Significant anterior movement of the colon was found when patients were changed from the supine to the lateral position. It provided a window for inserting the Veress needle blindly into the retroperitoneum. The high success rate (97%) and low complication rate of direct needle insufflation were found in actual clinical applications. We considered needle insufflation a safe and effective method of establishing a pneumoretroperitoneum for any retroperitoneoscopic procedure.

Adult↗

PubMed1995

Defective mitochondrial oxidative phosphorylation in varicocele-bearing testicles.

OBJECTIVES: Our previous study revealed a decreased blood flow in varicocele-bearing testicles. For further understanding of the possible mechanism of varicocele-induced infertility, we investigated the changes in energy metabolism in varicocele-bearing testicles. METHODS: Partial ligation of the left renal vein was performed in 40 Wistar rats to induce dilation of the internal spermatic vein, and sham operations were performed in 20 other age-matched Wistar rats serving as controls. Orchiectomy was done at 1, 2, 4, and 6 months after induction of varicocele (or sham operation) in both groups. The histologic changes in the testicles were evaluated under the light microscope. The concentration of adenine nucleotides was determined by high-performance liquid chromatography, and various enzyme activities of mitochondria were determined by a spectrophotometer. RESULTS: Histologic studies of varicocele-bearing testicles showed a lower Johnsen score (8.5 +/- 0.7 versus 9.3 +/- 0.5) and a decreased mean testicular tubular diameter (280.0 +/- 3.2 versus 295.0 +/- 1.4 microns) compared with the testicles in the sham-operated group. The energy charge decreased from 0.71 +/- 0.04, 0.70 +/- 0.03, 0.69 +/- 0.06, and 0.64 +/- 0.03 to 0.62 +/- 0.08, 0.59 +/- 0.05, 0.58 +/- 0.05, and 0.56 +/- 0.02 at 1, 2, 4, and 6 months, respectively. The reduced nicotinamide-adenine dinucleotide-cytochrome c reductase activities were decreased from 136.6 +/- 4.9, 127.3 +/- 10.7, 121.6 +/- 7.8, and 118.9 +/- 8.5 to 96.3 +/- 13.9, 95.6 +/- 27.8, 88.3 +/- 13.8, and 80.4 +/- 8.7 nmol/min/mg of protein, respectively; the succinate-cytochrome c reductase activities were decreased from 50.4 +/- 2.7, 49.0 +/- 4.7, 49.6 +/- 7.1, and 42.6 +/- 1.6 to 40.3 +/- 7.3, 41.0 +/- 11.5, 40.2 +/- 5.7, and 32.0 +/- 1.3 nmol/min/mg of protein, respectively; and the cytochrome c oxidase activities were decreased from 361.2 +/- 23.4, 350.3 +/- 25.5, 223.5 +/- 12.9, and 194.1 +/- 18.3 to 253.7 +/- 32.9, 256.4 +/- 38.8, 178.2 +/- 15.7, and 147.1 +/- 17.2 nmol/min/mg of protein at 1, 2, 4, and 6 months, respectively. CONCLUSIONS: We thus suggest that defective energy metabolism plays an important role in the impairment of spermatogenesis of varicocele-bearing testicles.

Animals↗

PubMed1995

Femoral neuropathy after pelvic surgery.

Femoral neuropathy is an uncommon complication following pelvic surgery. We report on 2 cases of femoral nerve injury after pelvic surgery: 1 patient received radical cystectomy due to invasive transitional cell carcinoma of the urinary bladder, and the other patient had a transurethral resection of the bladder and received exploration and biopsy of a tumor mass over the right sacroiliac joint area. Pathogenesis and prevention of the complication of femoral neuropathy are discussed in the following report.

Aged↗

PubMed1995

Laparoscopic nephrolysis for chyluria: case report of long-term success.

Laparoscopic nephrolysis was performed in an 81-year-old man with recurrent chyluria. A total of five trocars were used for approaching the lymphatic ducts over the right ureter and renal hilum. The lymphatic ducts identified were easily ligated under laparoscopic magnification. The recovery of this patient was quick and uneventful. The follow-up urinalysis for chyle was negative, and his serum albumin concentration increased from 3.0 g/dL to 4.2 g/dL at 2 years postoperatively. This case report attests to the long-term efficacy of a laparoscopic approach to ligation of lymphatic fistulas for the treatment of recalcitrant chyluria.

Aged↗

PubMed1995

The structural loop II of cobrotoxin is the main binding region for nAChR and epitope in the region is conformation-dependent.

Modification of positively charged residues, Lys and Arg, in cobrotoxin revealed that Lys-27, Lys-47, Arg-28, Arg-30, Arg-33, and Arg-36 of cobrotoxin were essential for the lethality and binding activity to nicotinic acetylcholine receptor (nAChR). The antigenicity of cobrotoxin was drastically diminished when Lys-47, Arg-28, Arg-30, Arg-33, and Arg-36 were modified, while that of the Lys-27-modified derivative was not significantly changed. The CD spectra of cobrotoxin displayed similar patterns after modification of Lys-27, Lys-47, and Arg-28. These findings suggest that Lys-27, Lys-47, and Arg-28 residues may be related to the direct binding to nAChR, and that there is no involvement of Lys-27 in the antigenic determinants of cobrotoxin. Extending the modification to Arg-30, Arg-33, and Arg-36 caused progressive conformational changes of cobrotoxin and resulted in decreased binding activity to antibody and nAChR. This indicates that Arg-30, Arg-33, and Arg-36 may be of structural importance for maintaining the active conformation of cobrotoxin. These results, together with the facts that Tyr-25, Tyr-35, and Trp-29 of cobrotoxin are important in nAChR binding activity, but Trp-29 and Tyr-35 residues are not essential for the antigenicity, suggest that the structural loop II of cobrotoxin is the main binding region for nAChR and the epitope in that region is conformation-dependent.

Amino Acid Sequence↗

PubMed1995

Analysis of a conformation-independent epitope and a conformational epitope in a protein: a study on cobrotoxin from Taiwan cobra venom.

The antibodies against cobrotoxin were separated into two antibody preparations by successive affinity chromatographies on reduced and S-carboxymethylated (RCM)-cobrotoxin-Sepharose, and cobrotoxin-Sepharose columns. The antibodies (abbreviated as Abcf-i) that bound with the RCM-cobrotoxin-Sepharose were verified to specifically recognize the continuous epitopes of cobrotoxin, which were insensitive to conformational changes. Whilst the antibodies (abbreviated as Abcf-d) that did not bind with the RCM-cobrotoxin-Sepharose column recognized the conformational epitopes in cobrotoxin. The two antibody preparations were employed to screen the antigenic peptides derived from the proteolytic hydrolysate of cobrotoxin and RCM-cobrotoxin. Five antigenic peptides (AP-4, AP-5, AP-10, AP-11, and AP-12) were obtained from the acid protease A-digested hydrolysate of cobrotoxin, and two antigenic peptides (V8-2 and V8-4) were found in the hydrolysate of RCM-cobrotoxin after hydrolysis with Saccharomyces aureus V8 protease. The segments at positions 1-21 and 22-38 encompassed the peptide fractions, AP-4, AP-5, V8-2, and V8-4, that reacted with Abcf-i, indicating that the two segments bore the continuous epitopes of cobrotoxin. Alternatively, AP-10, AP-11, and AP-12 reacted with both Abcf-i and Abcf-d. The structures of the three peptides had a common segment at positions 43-62, suggesting that this region comprised the conformation-independent epitopes as well as conformational epitopes in cobrotoxin. These results reflected that the conformation-independent and conformational epitopes in a protein can be separately identified.

Amino Acid Sequence↗

PubMed1995

Determination of soluble nAChR-binding activity of alpha-neurotoxins by an innovative precipitation with DEAE-Sephacel.

A simple and convenient method for determining the binding activity of alpha-neurotoxins toward soluble nicotinic acetylcholine receptor (snAChR) by precipitation with DEAE-Sephacel was established. The determination was carried out by incubation of 125I-neurotoxin with snAChR, followed by precipitation with DEAE-Sephacel. The DEAE-Sephacel particles bind negatively charged snAChR with high affinity and simultaneously precipitate the 125I-neurotoxin bound to the receptors. After centrifugation, the free 125I-neurotoxin in the supernatant was counted, and the amounts of neurotoxins bound to snAChR could be determined. Two alpha-neurotoxins, cobrotoxin and alpha-bungarotoxin, were employed to verify the feasibility of this determination. The different binding characteristics of cobrotoxin and alpha-bungarotoxin to snAChR could be distinguished. This method required only small quantities of DEAE-Sephacel (7 mg), snAChR (0.54 micrograms), and 125I-neurotoxin (90 fmol) for each reaction, and minimized the handling of isotopic materials as compared with the conventional methods. This method is reliable, reproducible, and superior to current methods for the determination of the snAChR-binding activity for alpha-neurotoxins.

Binding, Competitive↗