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)

Morphological change in the urothelium after electrohydraulic versus pulsed dye laser lithotripsy

OBJECTIVE

To observe morphological changes in the urothelium after exposure to laser beam and electrohydraulic spark.

MATERIALS AND METHODS

The pulse dye laser lithotripter (MDL-2, Candela Corporation, Boston, USA) and the electrohydraulic lithotripter (AEH-2, Circon ACMI Corporation Stamford, USA) were used directly on the bladder mucosa in six pigs. Immediately after treatment, the bladder mucosa was prepared for light microscopic and scanning electron microscopic examination.

RESULTS

Both electrohydraulic spark and laser beam caused mucosal denudation, submucosal swelling and haemorrhage. There was a positive correlation between the degree of urothelial damage and the power and pulse numbers applied.

CONCLUSION

Direct contact of the urothelium in patients treated with laser beam or electrohydraulic spark should be avoided.

Hb E/Hb LeporeHollandia in a family from Bangladesh

We describe a family from Bangladesh in which three children are compound heterozygotes for Hb E (alpha 2 beta 2, beta 26Glu Lys) and Hb Lepore (delta-beta fusion gene). PCR amplification and direct nucleotide sequencing established that the fusion gene is Hb LeporeHollandia, with the cross-over localized to a 40 bp window between codon 22 and IVS-1 nt 16 of the delta- and beta-globin genes. This unusual combination of mutations is associated with a relatively mild clinical phenotype, with all three affected siblings having microcytic anemia of moderate severity without the need for transfusions.

Immunological neutralization of cobrotoxin by its homologous precipitin and non-precipitin antibodies

Anti-cobrotoxin antibodies can be separated into precipitin and non-precipitin antibodies. The precipitin antibody possesses the same binding affinity to cobrotoxin as non-precipitin antibody, but the neutralizing capability of the latter is superior to that of the former in blocking cobrotoxin binding to nicotinic acetylcholine receptor (nAChR). After preincubation with antibodies, cobrotoxin completely lost its binding activity to nAChR. The dissociation of cobrotoxin-nAChR complex by the antibodies was low, and 60% of the complex formation appeared to be irreversible. These results indicate that the neutralization of cobrotoxin by the antibody may predominantly involve unbound, receptor-free cobrotoxin. The relationships of neutralization capacity and binding affinity as well as bond strength between cobrotoxin and its antibodies are incongruous. Different local conformational changes of a unique Trp in cobrotoxin on binding with the precipitin and non-precipitin antibodies seem to lead to different accessibility for fluorescence quenchers. Characterization of the binding domains by immunoprecipitation with the antibodies correlated with the quenching results. Thus, the binding topography of cobrotoxin may play an important role over the binding affinity and bond strength in neutralization by cobrotoxin antibody.

The long-term stone recurrence rate and renal function change in unilateral nephrectomy urolithiasis patients

We evaluated the stone recurrence rate and long-term renal function in 50 patients with a solitary kidney 60 to 84 months (mean 70.6) after unilateral nephrectomy for urinary tract stone disease. Followup evaluation included a detailed history, physical examination, blood and urine biochemistry studies, urinalysis, urine culture, excretory urography, ultrasonography of the kidney and 131iodine-ortho-iodohippurate renography. The overall stone recurrence rate in unilateral nephrectomy urolithiasis patients was 30% (15 of 50). The mean interval until stone recurrence was 31.1 months (range 6 to 74) and the mean episodes of recurrence were 2.1 times per patient (range 1 to 5). Function of the remnant kidney in most patients was unchanged during followup. However, 2 of the 15 patients with recurrent stones had anuria during the acute attack of renal colic and, thus, required percutaneous nephrostomy urinary diversion, while 1 had proteinuria (3 gm. per day) and progressive renal failure 47 months after nephrectomy. The metabolic stone patients seemed to experience recurrence more easily than metabolic stone patients seemed to experience recurrence more easily than infection stone patients (37% versus 13%) but no statistically significant difference was noted (p = 0.198).

Functional involvement of Lys-6 in the enzymatic activity of phospholipase A2 from Bungarus multicinctus (Taiwan banded krait) snake venom

Phospholipase A2 (PLA2) from Bungarus multicinctus snake venom was subjected to Lys modification with 4-chloro-3,5-dinitrobenzoate and trinitrobenzene sulfonic acid, and one major carboxydinitrophenylated (CDNP) PLA2 and two trinitrophenylated (TNP) derivatives (TNP-1 and TNP-2) were separated by high-performance liquid chromatography. The results of amino acid analysis and sequence determination revealed that CDNP-PLA2 and TNP-1 contained one modified Lys residue at position 6, and both Lys-6 and Lys-62 were modified in TNP-2. It seemed that the Lys-6 was more accessible to modified reagents than other Lys residues in PLA2. Modification of Lys-6 caused a 94% drop in enzymatic activity as observed with CDNP-PLA2 and TNP-1. Alternatively, the enzyme modified on both Lys-6 and Lys-62 retained little PLA2 activity. Either carboxydinitrophenylation or trinitrophenylation did not significantly affect the secondary structure of the enzyme molecule as revealed by the CD spectra, and Ca2+ binding and antigenicity of Lys-6-modified PLA2 were unaffected. Conversion of nitro groups to amino groups resulted in a partial restoration of enzymatic activity of CDNP-PLA2 to 32% of that of PLA2. It reflected that the positively charged side chain of Lys-6 might play an exclusive role in PLA2 activity. The TNP derivatives could be regenerated with hydrazine hydrochloride. The biological activity of the regenerated PLA2 is almost the same as that of native PLA2. These results suggest that the intact Lys-6 is essential for the enzymatic activity of PLA2, and that incorporation of a bulky CDNP or TNP group on Lys-6 might give rise to the distortion of the interaction between substrate and the enzyme molecule, and the active conformation of PLA2.

Energy transfer from tryptophan residues of proteins to 8-anilinonaphthalene-1-sulfonate

The binding of the apolar fluorescent dye 8-anilinonaphthalene-1-sulfonate (ANS) to bovine serum albumin (BSA), phospholipase A2 (PLA2), ovalbumin, lysozyme, cobrotoxin and N-acetyltryptophanamide was used to assess the factors affecting the efficiency of energy transfer from Trp residues to the ANS molecule. We found that the efficiency of energy transfer from Trp residues to ANS was associated with the ability of proteins to enhance the ANS fluorescence. At the same molar concentration of protein, BSA enhanced ANS fluorescence most among these proteins; its Trp fluorescence was drastically quenched by the addition of ANS. Fluorescence enhancement of ANS in PLA2-ANS complex increased upon addition of Ca2+ or change of the buffer to acidic pH, resulting in a higher efficiency of energy transfer from Trp residues to ANS. There was limited ANS fluorescence enhancement with ovalbumin, lysozyme, cobrotoxin, and N-acetyltryptophanamide and a less efficient quenching in Trp fluorescence. The capabilities of proteins for binding with ANS correlated with the decrease in their Trp fluorescence being quenching by ANS. However, the microenvironment surrounding Trp residues of proteins did not affect the energy transfer. Based on these results, the factors that affected the energy transfer from Trp residues to ANS are discussed.

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.

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.

The time for serum testosterone to reach castrate level after bilateral orchiectomy or oral estrogen in the management of metastatic prostatic cancer

OBJECTIVE

To understand the time for serum testosterone to reach castrate level after bilateral orchiectomy or oral estrogen in the management of metastatic prostatic cancer.

METHODS

A total of 20 consecutive patients with adenocarcinoma of the prostate with bony metastasis were enrolled in this study. Their mean age was 72.8 years old (range, 57 to 82 years). Pretreatment serum testosterone levels were obtained in all men. Thirteen men were treated with bilateral orchiectomy. Immediately after removal of testes, serial blood samplings for serum testosterone levels were drawn every fifteen minutes for the first two hours, then hourly for another sixteen hours. Seven men were treated with oral estrogen diethylstilbestrol (DES), 3 mg per day. Serum testosterone levels were checked on a weekly basis for two months, and then biweekly for another two months.

RESULTS

Castration time of bilateral orchiectomy ranges from three to twelve hours (mean, 8.6 hours). The biological half-life of serum testosterone was from thirty to sixty minutes (mean, 45 minutes). Castration time of oral estrogen (DES) was from twenty-one to sixty days (mean, 38.3 days).

CONCLUSIONS

Bilateral orchiectomy and oral estrogen were both effective ways of castration for patients with bony metastatic prostatic cancer. Bilateral orchiectomy provides a more rapid castration and is one hundred seven times faster than oral estrogen in reaching castrate level.

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.

The essentiality of B chain in stabilizing the structure of the A chain in beta 1-bungarotoxin from Bungarus multicinctus venom

The dynamic of Trp residue in beta 1-bungarotoxin (beta 1-Bgt), the A chain of beta 1-Bgt and phospholipase A2 (PLA2) was assessed by fluorescence measurement. Acrylamide quenching studies showed that the exposure degree of the Trp in PLA2 is higher than the Trp in beta 1-Bgt. The Trp of beta 1-Bgt had a higher accessibility for iodide, reflecting that the basic nature of the B chain might exert an attractive electrostatic force for iodide and increase the susceptibility of Trp in the A chain to iodide. Removal of the B chain of beta 1-Bgt did not significantly affect the exposure degree of Trp in the A chain. Alternatively, the polarity of the environment around the Trp and the hydrophobic character of ANS and substrate binding sites in the separated A chain changed. Measurement of Trp fluorescence with increasing temperature showed that the stability of structure of beta 1-Bgt was higher than those of the separated A chain and PLA2. These results suggest that the B chain might interact with the A chain and stabilize the conformation of the A chain in beta 1-Bgt.

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%).

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.

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.

Role of the spermatic artery in spermatogenesis and sex hormone synthesis

This study was conducted to determine whether the spermatogenesis of testes and the serum sex hormone synthesis are influenced by the ligation of spermatic arteries. Sixteen adult male dogs were randomly divided into four groups. From our preliminary data the spermatogenic arrest and decrease of testicular volume were noted prominently in dogs after ligation of spermatic arteries. The serum testosterone level decreased and the serum luteinizing hormone level increased significantly in the same groups, while no significant changes were found in the dogs with preserved spermatic arteries. There were no significant differences in the epididymis and serum follicle-stimulating hormone among the four groups. This study attempted to establish the critical role of spermatic arteries in testicular function.

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.

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.

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.

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.

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.

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.

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.

Probing the functional sites in Naja naja atra (Taiwan cobra) cardiotoxin III with monoclonal antibody

One monoclonal antibody (mAb) against Naja naja atra cardiotoxin III was prepared by using the hybridoma technique. The cytotoxic activity of cardiotoxin III which inhibited human lymphocyte proliferation was effectively neutralized by the mAb at a molar ratio of antibody to toxin of 1:2. On the contrary, the mAb did not exert a significant inhibition on the hemolytic activity of cardiotoxin III. These results suggest that the functional site responsible for the cytotoxicity might be different from that for the hemolytic activity of cardiotoxin III.

Status of tryptophan residue in cobrotoxin and alpha-bungarotoxin

Acrylamide quenching studies indicated that the exposure degree of the Trp residue in cobrotoxin was higher than that in alpha-bungarotoxin. The Trp residue of cobrotoxin was in a positively charged environment as revealed by iodide quenching, while the Trp residue of alpha-bungarotoxin was not accessible for iodide. Analysis of hydrophilicity profile and local concentration of positively charged residues of toxin molecule also indicated that Trp in cobrotoxin was in a highly hydrophilic and positively charged environment. Measurement of Trp fluorescence with increasing temperature showed that the stability of environment of Trp in alpha-bungarotoxin was higher than in cobrotoxin. Result of competitive binding for nicotinic acetylcholine receptor (AchR) between cobrotoxin and alpha-bungarotoxin revealed that the molecular interaction of the two toxins with AchR was not the same. These, together with the fact that the cationic groups of the two toxins are involved in the binding with AchR, suggest that the observed different environment surrounded Trp residue and different AchR binding mechanism might fulfill a different requirement of the invariant Trp in the lethality of cobrotoxin and alpha-bungarotoxin.