Role of proliferative activity estimated by bromodeoxyuridine labeling index in determining predictive factors of recurrence in superficial intermediately malignant bladder tumors

PURPOSE

Previous studies have shown that factors predictive of tumor recurrence include a history of the disease, multiple tumors at diagnosis, and high tumor grade and stage. Additional biological marker for predicting tumor recurrence could potentially be used in the decision making process and could alter the frequency of clinical cystoscopy. We attempted to clarify whether the tumor proliferative activity estimated by bromodeoxyuridine, which is believed to be a thymidine analogue, and deoxyribonucleic acid (DNA) ploidy status correlates well with tumor recurrence as an objective parameter.

MATERIALS AND METHODS

We evaluated 103 patients with superficial grade 2 transitional cell carcinoma of the bladder treated with transurethral resection. Mean followup plus or minus standard deviation was 49.5 +/- 11.3 months (minimum 36). Tumor specimens were obtained by transurethral cold-cup biopsy, with bromodeoxyuridine in vitro pulse labeling then performed under hyperbaric oxygen. The flow cytometric determination of the bromodeoxyuridine labeled cell index and DNA ploidy were estimated.

RESULTS

When the tumor was classified according to the bromodeoxyuridine labeled cell index the 5-year no recurrence rates were 82.0 and 27.1% for an index of less than 5.3 and more than 5.3%, respectively. Furthermore, the 5-year no recurrence rates were 75.1% for DNA diploid compared to 29.3% for DNA aneuploid tumors, respectively. Multivariate analysis using Cox's proportional hazards model showed that the most important risk factor for tumor recurrence was a bromodeoxyuridine labeled cell index of more than 5.3% (risk ratio 5.31, p < 0.001), followed by DNA ploidy (risk ratio 2.61, p < 0.05). Tumor stage, initial lesion versus recurrence and single versus multiple tumors did not influence the risk factor for tumor recurrence.

CONCLUSIONS

These data indicate that bromodeoxyuridine labeling status can be used as an objective risk factor for bladder cancer recurrence.

Analyses of loss-of-function mutations of the MITF gene suggest that haploinsufficiency is a cause of Waardenburg syndrome type 2A

Waardenburg syndrome type 2 (WS2) is a dominantly inherited disorder characterized by a pigmentation anomaly and hearing impairment due to lack of melanocyte. Previous work has linked a subset of families with WS2 (WS2A) to the MITF gene that encodes a transcription factor with a basic-helix-loop-helix-leucine zipper (bHLH-Zip) motif and that is involved in melanocyte differentiation. Several splice-site and missense mutations have been reported in individuals affected with WS2A. In this report, we have identified two novel point mutations in the MITF gene in affected individuals from two different families with WS2A. The two mutations (C760--> T and C895--> T) create stop codons in exons 7 and 8, respectively. Corresponding mutant alleles predict the truncated proteins lacking HLH-Zip or Zip structure. To understand how these mutations cause WS2 in heterozygotes, we generated mutant MITF cDNAs and used them for DNA-binding and luciferase reporter assays. The mutated MITF proteins lose the DNA-binding activity and fail to transactivate the promoter of tyrosinase, a melanocyte-specific enzyme. However, these mutated proteins do not appear to interfere with the activity of wild-type MITF protein in these assays, indicating that they do not show a dominant-negative effect. These findings suggest that the phenotypes of the two families with WS2A in the present study are caused by loss-of-function mutations in one of the two alleles of the MITF gene, resulting in haploinsufficiency of the MITF protein, the protein necessary for normal development of melanocytes.

Two long-term survivors after microwave coagulation therapy for hepatocellular carcinoma: a case report

We present two long-term survivors who underwent microwave coagulation therapy (MCT) for hepatocellular carcinoma (HCC). One patient was a 55-yr-old man having a solitary HCC of 25 mm in diameter associated with advanced liver cirrhosis. He underwent MCT instead of hepatic resection because he developed bleeding tendency during surgery. The other patient was a 78-yr-old woman having a 7 cm tumor in segment II and a 15 mm satellite lesion in segment IV. Because manipulation of the left hepatic lobe caused prolonged hypotension, only the main tumor was resected. The satellite lesion was treated with MCT. In both cases, tumors and surrounding liver parenchyma were widely coagulated. Postoperative courses were uneventful. The coagulated area shrank subsequently after surgery. Both patients are alive 39 and 55 months after MCT without tumor recurrence. This report proves that MCT is a curative treatment and an alternative to hepatic resection in selected patients with HCCs.

Role of protein phosphatase in malignant osteogenic and soft tissue tumors

The expression of the three catalytic subunits of protein phosphatase (PP) type 1 and 2A, PP1 alpha, PP1 gamma 1, and PP2AC, was examined in osteogenic tumors and soft tissue tumors by immunohistochemical analysis. The percentage of cells stained positively with antiserum against PP1 catalytic subunit isoform PP1 gamma 1, was significantly higher in malignant osteogenic tumors (chondrosarcoma, osteosarcoma, and Ewing's sarcoma) and in malignant soft tissue tumors (liposarcoma and malignant fibrous histiocytoma [M.F.H.]) than in benign tumors (osteochondroma, osteoblastoma, ossifying fibroma, enchondroma and lipoma). Furthermore, the malignant tumor lesions showed a markedly high number of cells in the S-phase fraction of the cell cycle, as compared to benign tumors. These results suggest that PP1 gamma 1 is involved in the accelerated growth of malignant tumor cells.

4-Oxygenated androst-5-en-17-ones and their 7-oxo derivatives as aromatase inhibitors

A series of androst-5-ene-4,7-diones and 4-oxygenated androst-5-enes were synthesized and tested for their ability to inhibit aromatase in human placental microsomes. All of the steroids examined inhibited the enzyme in a competitive manner. The inhibitory activity of 4beta-hydroxy-5-ene steroid 7 (Ki = 25 nM) was much more powerful than that of the parent 5-ene steroid 11 (Ki = 78 nM), whereas 4beta-acetate 8 and 4-oxo analog 5 (Ki = 90 and 120 nM, respectively) were less potent than compound 11. This indicates that a hydrogen bonding between a hydroxy group of the 4beta-ol 7 and a residue of the active site of aromatase plays an important role in its binding. The 5-en-4-one steroid 5 did not cause a time-dependent inactivation of aromatase. In contrast, 5-ene-4,7-dione 13 as well as its 19-hydroxy and 19-oxo analogs 19 and 20 caused the time-dependent inactivation only in the presence of NADPH in air with the k(inact) values ranging from 0.057 to 0.192 min(-1), although their affinities for the enzyme were not high (Ki = 430-6300 nM). The inactivation was prevented by androstenedione, and no significant effect of L-cysteine on the inactivation was observed in each case. These results suggest that oxygenation at C-19 would be at least in part involved in the inactivation caused by the inhibitor 13.

Clinical application of flow cytometry to urological malignancies

Flow cytometric DNA analysis provides rapid, quantitative objective information regarding the biological behavior of urological malignancies. Moreover, clinical applications of the many recent advances made the flow cytometry are expected to materialize soon. For instance, flow cytometric DNA ploidy analysis for human bladder cancers may provide a significant diagnostic and prognostic potential. Also, flow cytometric DNA analysis of irrigation specimens produces a higher sensitivity than conventional cytology for detecting bladder cancer. However, there are obvious pitfalls with this approach since diploid or near-diploid tumors cannot always be recognized by DNA analysis alone. One of the most significant advantages possible with flow cytometry is its capability of analyzing simultaneously multiple parameter on single cells. The integration of the DNA content with proliferative activity should yield important information significant to the biological behavior of individual tumors. Flow cytometric DNA/bromodeoxyuridine bivariate analysis can be used as an effective adjunct to histological examination for prognostication and decision-making in treatment of bladder cancer patients. Therefore, multiparameteric flow cytometric analysis can be used to isolate specific tumor cells from mixed cell populations, and should receive even increased attention as a valuable diagnostic technique and prognostic factor. In the present review, the efficacy of flow cytometric DNA ploidy analysis integrated with cell proliferation markers is discussed.

Synthesis and structure-activity relationships of 6-substituted androst-4-ene analogs as aromatase inhibitors

Series of 6 alpha- and 6 beta-alkyl-substituted androst-4-en-17-ones (18 and 19) and their 17 beta-reduced derivatives (14 and 15)(alkyl: methyl, ethyl, n-propyl, n-pentyl, n-octyl) were synthesized and evaluated as aromatase inhibitors. Androst-4-en-17-ones having an oxygen function (hydroxy, acetoxy, or methoxy group) at C-6 alpha and C-6 beta (4 and 5) were also tested for their abilities to inhibit aromatase. All of the steroids studied inhibited human placental aromatase in a competitive manner. The inhibitory activities of the 6 alpha- and 6 beta-methyl-17-keto steroids 18a and 19a (Ki = 3.1 and 5.3 nM, respectively) as well as the 6 beta- alcohol 5a (Ki = 6.0 nM) were high, and their apparent Ki values were lower than that of the parent 6-unsubstituted 3-deoxy steroid 1 (Ki = 6.8 nM). Elongation of the methyl group decreased affinity for aromatase in relation to carbon number of the alkyl chain in each series, in which the 6 alpha- alkyl steroids 18 essentially had higher affinity for the enzyme than the corresponding 6 beta- isomers 19. The inhibitory activities of the 17 beta-hydroxy analogs 14 and 15 were less potent than those of the corresponding 17-keto steroids. The 6 alpha-ethyl compound 18b, the 6 alpha-oxygenated derivatives 4, and the 6 beta-acetoxy and 6 beta-methoxy analogs 5b and 5c were powerful inhibitors (Ki = 12-24 nM). The methyl steroids (18a and 19a) produced "type I" difference spectra upon interaction with aromatase. These results along with molecular modeling with the PM3 method suggest that compounds 18a and 19a may produce a thermodynamically stable enzyme-inhibitor complex in the hydrophobic binding pocket with a limited accessible volume. A carbonyl group at C-17 of the 6-alkylandrost-4-enes is essential for the tight binding. Moreover, the binding pocket also tolerates a polar hydroxy group at the 6 beta-position rather than at the 6 alpha-position.

Transurethral microwave thermotherapy for management of benign prostatic hyperplasia: durability of response

OBJECTIVES

The durability of clinical efficacy of transurethral microwave thermotherapy (TUMT) by Prostatron using a low-energy protocol (maximum power, 50 W) was evaluated on an outpatient basis in patients with symptomatic benign prostatic hyperplasia (BPH).

METHODS

One hundred eighteen patients were followed up for longer than 3 months (13.4 +/- 9.5 months; mean +/- SD). All evaluations were made at baseline and then 3, 6, 12, 24, and 36 months after therapy.

RESULTS

International Prostate Symptom Score (IPSS) significantly decreased from 18.2 to 10.6 at 6 months (P < 0.01), representing a mean improvement of 41% under the baseline. Peak flow rate increased from the baseline of 8.3 mL/s to 10.3 mL/s at 6 months (P < 0.01). The improvement in terms of mean values of both parameters was sustained up to 24 months. Six of 44 patients (14%) who were followed up for 31 months on average required transurethral resection of the prostate for recurring obstructive symptoms and 10 additional patients (23%) had to be treated with various drug regimens. When the clinical outcome was evaluated in terms of improvement from the baseline according to a response criteria, disease-free rates for IPSS (more than 25% improvement from the baseline) were 76% at 12 months, 77% at 24 months, and 61% at 36 months. Disease-free rate for peak flow rate (more than 2.5 mL/s from the baseline) was sustained in 44% by 12 months and in 48% by 24 months. The overall outcome of the treatment was assessed by adding scores based on both subjective and objective efficacy criteria. At 6 months, 67% of the patients were responders, and 15 of 21 (71%) remained as responders at 24 months. Patients who had estimated prostate volume smaller than 30 cc showed more marked improvement in peak flow rate (P < 0.02), and those with baseline IPSS of 20 or more showed greater reduction of IPSS (P < 0.05) at 24 months compared with each counterpart.

CONCLUSIONS

After TUMT with a low-energy protocol, satisfactory results were obtained and the improvement seems to last at least for 24 months. This low-energy protocol may be most beneficial in patients with relatively small size of the prostate.

Ultrastructural localization of G-protein GS in the lateral wall of the guinea pig cochlear duct

Immunocytochemical localization of a GTP-binding protein, Gs, in the various cells of the lateral wall of guinea pig cochlear duct was investigated using a post-embedding immunogold method with antibody raised against a synthetic decapeptide (RMHLRQYELL) encoding the C-terminus of the alpha-subunit of Gs. In the stria vascularis, labeling was observed on the basolateral membrane infoldings of marginal cells, on the juxtaposed membrane of intermediate cells, and on the cell membrane of basal cell. In contrast, no significant labeling was observed on the luminal membrane of marginal cells. Immunoreactivity also was detected on the cell membranes of various other cells. These include spiral prominence epithelial cells, fibrocytes of spiral ligament, external sulcus cells, and epithelial and mesothelial cells of Reissner's membrane. Adenylylcyclase has been functionally implicated in some of the cell types with membranes labeled in this study. The significance of these findings is briefly discussed.

Simultaneous early gastric cancer in identical twins: report of a case

We report the unusual case of identical male twins developing early gastric cancers that were found almost simultaneously. A 39-year-old man underwent a barium-swallow examination to investigate the cause of right hypochondrial discomfort; the examination revealed evidence of gastric cancer in the upper body of the stomach. A diagnosis of adenocarcinoma was confirmed by endoscopic biopsy, and a total gastrectomy was performed. Subsequent screening of the patient's asymptomatic identical twin revealed gastric cancer in the lower body of the stomach, for which distal gastrectomy with Billroth I reconstruction was performed. The histopathological types of the two cancers were similar and both had infiltrated the submucosa. The relevant etiological factors contributing to the development of gastric adenocarcinoma in these identical twins is discussed, following the case report.

Time-dependent inactivation of aromatase by 6-alkylandrosta-1,4-diene-3,17-diones. Effects of length and configuration of 6-alkyl group

Series of 6alpha- and 6beta-alkylandrosta-1,4-diene-3,17-diones (3 and 4) were synthesized and evaluated as time-dependent inactivators of aromatase in human placental microsomes to gain insights to the structure-activity relationship of varying the 6-n-alkyl substituents (C-1--C-7) to the time-dependent inactivation activity. All of the inhibitors synthesized were powerful to good competitive inhibitors of aromatase, with apparent Ki's ranging from 4.7 to 54 nM. The 6beta-ethyl (4b) and 6beta-n-pentyl (4e) compounds were the most potent among them (Ki = 4.7 and 5.0 nM for 4b and 4e, respectively). In a series of the 6alpha-alkyl steroids, the inhibitors 3a-d having C-1--C-4 at the 6-position as well as the 6 alpha-n-heptyl (3g) compounds did not. In contrast, in the 6beta-alkyl steroid series, only the methyl analog 4a inactivated aromatase in a time-dependent manner, and the other alkyl steroids having more than two carbons at C-6beta did not. The inactivations were prevented by the substrate androstenedione, and no significant effects of L-cysteine on the inactivation were observed in each case. These results along with molecular modeling with the PM3 method indicate that both length and stereochemistry of a straight alkyl substituent at the C-6 position of androsta-1.4-diene-3,17-dione (3h) play an important role in the cause of a time-dependent inactivation of aromatase. No significant correlation between affinity for the enzyme and the inactivation ability in the 6-alkylandrosta-1,4-diene-3,17-diones is observed.

Cytochrome P4502D and -2C enzymes catalyze the oxidative N-demethylation of the parkinsonism-inducing substance 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in rat liver microsomes

We have examined the oxidative N-demethylation of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a parkinsonism-inducing neurotoxin, in liver microsomes from adult Wistar and Dark Agouti (DA) rats. The oxidation of MPTP to 4-phenyl-1,2,3,6-tetrahydropyridine (PTP) in these preparations required NADPH as a cofactor and was significantly inhibited by SKF 525-A (2 mM). MPTP N-demethylation exhibited biphasic kinetics, consistent with two enzymes, a low Km system (Km1, 10.0 +/- 2.2 microM; Vmax1, 0.048 +/- 0.009 nmol/(min.mg of protein)) and a high Km system (Km2, 1180 +/- 91 microM; Vmax2, 4.80 +/- 0.75 nmol/(min.mg of protein)). We thus employed two substrate concentrations, 5 microM and 5 mM, for the low and high Km system, respectively, to assay enzyme activity in subsequent experiments. The oxidation activity was significantly decreased by pretreatment of rats with phenobarbital and beta-naphthoflavone. Furthermore, marked strain (Wistar > DA) and sex (male > female) differences were observed at low (5 microM) and high (5 mM) substrate concentrations, respectively. Reconstitution experiments with cytochrome P450BTL, which belongs to the P4502D subfamily, and P450m1 (P4502C11) demonstrated that MPTP N-demethylase occurs at concentrations of 5 microM and 5 mM. At 5 mM the male-specific P450m1 showed a remarkably high activity, over 400-fold that of P450BTL. Polyclonal antibodies against P450BTL and P450m1 effectively suppressed the activity at the low (5 microM) and the high (5 mM) substrate concentrations, respectively. These results suggest that, in the microsomal preparations used, MPTP N-demethylation is mainly mediated by P4502D enzyme(s) at lower substrate concentrations and by P4502C11 at higher substrate concentrations.

Newly developed equipment and methods in the treatment of BPH: analysis of present status

Benign prostatic hyperplasia (BPH) is the most common disease among the aged male population. A variety of symptoms are mainly caused by obstructive changes at the prostatic urethra. Transurethral resection (TURP) has been the gold standard of treatment, but new equipment and methods such as TUMT, HIFU, TUNA, and laser prostatectomy have been developed and are being tested for clinical application. Our experience with new equipment and methods show that their effectiveness has yet to be conclusively evaluated by objective parameters, while subjective improvements have been seen with less invasive treatments such as TUMT, HIFU and TUNA. Laser prostatectomy confirmed its advantages in hemostasis but comparison of each treatment is difficult because of different pathological changes created by different energy sources shown by MRI. Further studies are required to examine the new equipment and methods and for identification of the treatment of choice for BPH.

Ultrastructural localization of G-protein Gs in the organ of Corti

Immunocytochemical localization of a stimulatory GTP-binding protein Gs in the organ of Corti in the inner ear was examined with a post-embedding immunogold technique, using antibodies raised against a synthetic decapeptide (RMHLRQYELL) of the C-terminus of the alpha subunit of Gs. Immunoreactivity was strong on the membranes of supporting cells in the reticular lamina, including inner and outer pillar cells and the phalangeal process of Deiters' cells. Immunolabeling also was seen on the membranes of cell bodies of those cells which surround nerve fibers, basilar fibers, outer spiral fibers and afferent nerve endings at outer hair cells. Gold particles also labeled the membrane of inner phalangeal cells and border cells. In contrast, outer and inner hair cells were not labeled. Possible roles of Gs in the organ of Corti are discussed.

Establishment of a human cell line secreting neuron-specific enolase from a primitive neuroectodermal tumor of the retroperitoneal cavity

Primitive neuroectodermal tumor (PNET) is one of the small round cell malignancies of presumed neural crest origin for which an effective treatment has not yet been established. In the present study, a human cell line, designated KU-9, was established from a 27-year-old male patient with PNET of the retroperitoneal cavity and has been successfully maintained in nude mice and in culture. On histological examination, the primary tumor was composed of poorly differentiated small round cells arranged in clusters showing a variety of mitotic changes, and contained Homer-Wright rosettes. The histopathological appearance of the KU-9 xenografts was similar to that of the primary tumor. Electron microscopy revealed neurosecretory granules and cytoplasmic processes in the xenograft. No significant amplification of N-myc gene was observed in the KU-9 cells. The KU-9 cells showed chromosome numbers ranging from 56 to 61 with consistent structural abnormalities being add(2)(q31), +add(11)(p11.2), +add(13)(p11.1), and +del(22)(q12). Cultured KU-9 cells grew exponentially with a doubling time of about 50 h and a time-dependent increase in medium levels of neuron-specific enolase (NSE) was noted. Serum levels of NSE in KU-9 tumor-bearing nude mice were significantly elevated and a linear relationship between the serum NSE levels and the tumor NSE content or tumor volume was observed, suggesting that serum levels of NSE may reflect the PNET tumor burden and tumor extent. These results indicate that the KU-9 cell line provides a reproducible model system which could be useful in gaining some insight into the histogenesis and oncogenesis of PNET and in establishing an effective treatment for PNET.

Tumor necrosis factor and coagulopathy in patients with prostate cancer

This study was undertaken to evaluate the relationship between serum tumor necrosis factor (TNF) and coagulopathy in patients with prostate cancer. TNF levels in 104 sera obtained from 101 prostate cancer patients were determined using an enzyme immunoassay. Serum levels of fibrin/fibrinogen degradation product E fragment (FDP) and plasma levels of fibrin degradation product D-dimer in patients with elevated serum TNF levels were 1221.95 +/- 375.94 ng/ml and 27.34 +/- 9.81 micrograms/ml, which were significantly higher than those (FDP, 94.35 +/- 13.17 ng/ml; D-dimer, 1.03 +/- 0.20 micrograms/ml) in patients with undetectable serum TNF levels (P < 0.01). In addition, patients with elevated serum TNF levels showed significant increases in plasma levels of thrombin-antithrombin-III complex and plasmin-alpha 2-antiplasmin inhibitor complex and a significantly higher incidence of positive plasma soluble fibrin monomer complex than did those with undetectable serum TNF levels. The percentage of prothrombin time was significantly decreased in the group with elevated serum levels of TNF. Serum levels of TNF were significantly elevated in patients with serum FDP levels of > or = 200 ng/ml than in those with serum FDP levels of < 200 ng/ml (3.91 +/- 0.45 versus 2.17 +/- 0.08 units/ml) and in patients with plasma D-dimer levels of > or = 2 micrograms/ml than in those with plasma D-dimer levels of < 2 micrograms/ml (3.82 +/- 0.48 versus 2.10 +/- 0.06 units/ml). These results suggest that TNF may be one of the pathogenetic factors that could explain the occurrence of coagulopathy in patients with prostate cancer.

Cloning and nucleotide sequence of the gene encoding dimethyl sulfoxide reductase from Rhodobacter sphaeroides f. sp. denitrificans

The gene encoding dimethyl sulfoxide (DMSO) reductase, which contains a molybdenum cofactor, of the phototrophic bacterium Rhodobacter sphaeroides f. sp. denitrificans was isolated using an oligonucleotide probe, which was synthesized based on a internal amino acid sequence of the purified enzyme. The DMSO reductase gene coded for 822 amino acids (2466 base pairs, M(r) = 89,206) as a precursor form having a signal peptide of 42 amino acids. The deduced amino acid sequence had high homology with those of some enzymes containing a molybdenum cofactor: trimethyl amine N-oxide reductase (48%), biotin sulfoxide reductase (44%), and DMSO reductase (29%) of Escherichia coli.

Agglutination of Staphylococcus saprophyticus: a structural and cytochemical study

Staphylococcus saprophyticus was shown to be agglutinated by wheat germ agglutinin, wheat germ agglutinin-biotin and bovine serum albumin-p-aminophenyl-N-acetyl-beta-D-glucosaminide (GlcNAc-BSA), and sheep red blood cells. In these agglutinations, filamentous or amorphous structures radiating from the surface of S. saprophyticus were demonstrated by electron microscope observation. Cytochemical analyses of the agglutination revealed the binding sites of wheat germ agglutinin in S. saprophyticus and the binding sites of GlcNAc in the sheep red blood cells and S. saprophyticus. Since GlcNAc-BSA contains N-acetylglucosamine to which wheat germ agglutinin can bind, it is most likely that an interaction between a wheat germ agglutinin-bindable substance in S. saprophyticus and an N-acetylglucosamine-bindable substance in sheep red blood cells is involved in the agglutination.

Ca(2+)-dependent Cl- current at the presynaptic terminals of goldfish retinal bipolar cells

In ON-type bipolar cells dissociated from the goldfish retina, a slowly declining inward current (Itail) was observed after the termination of depolarizing voltage step commands, during which a Ca2+ current was elicited. The properties of Itail were investigated under the whole-cell voltage clamp. Introduction of the membrane permeant Ca2+ chelator, BAPTA/AM, into the cell suppressed Itail, indicating that Itail was activated by the increase of intracellular free Ca2+ concentration ([Ca2+]i). The major component of Itail was identified as the Ca(2+)-dependent Cl- current (ICl(Ca)), since the reversal potential of Itail was almost identical to the Cl- equilibrium potential at various extracellular Cl- concentrations ([Cl-]o). The contribution of the Na+/Ca2+ exchanger current to Itail was very small. ICl(Ca) was partially suppressed by 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS) when it was locally applied to the axon terminal but not to the cell body region, suggesting that Ca(2+)-dependent Cl- channels were localized to the axon terminal. The relationship between the peak amplitude of ICl(Ca) and the amount of charge carried by the Ca2+ current was almost linear at levels less than ca. 50 pC, but became saturated at a higher Ca2+ charge.