Production of monoclonal antibodies recognizing cancer-associated antigens expressed on mucin-type sugar chains

To obtain monoclonal antibodies directed to mucin-type sugar chains, mice were immunized with bovine submaxillary mucin (BSM) that had been conjugated with ovalbumin. Conjugation of BSM with ovalbumin enhanced the antigenicity of BSM to about five to ten times that of intact BSM and resulted in the establishment of ten hybridomas, all of which secreted monoclonal antibodies toward BSM. Most of the antibodies secreted by these hybridomas did not react with glycolipids but did react with glycoproteins. Several antibodies lost their reactivity when sialic acid residues were removed from BSM, indicating that these antibodies recognize carbohydrate moieties of mucins. Immunohistochemical studies revealed that three of the antibodies recognized human ovarian cancer-associated carbohydrate antigens. In addition, one of these three antibodies reacted with a human cultured colonic cancer cell line. The protocol described in this paper was effective in producing monoclonal antibodies that recognize mucin-carbohydrates and some of the generated antibodies can be applied to the detection of cancers.

[Pelvic hyperthermochemotherapy combined with surgery for rectal cancer]

In an attempt to prevent local recurrence, intraoperative pelvic hyperthermochemotherapy (IOPHC) was performed in combination with curative surgery for rectal cancer. One hundred twenty-three patients were divided into four groups: A, 8 patients without nodal involvement (n0) and given IOPHC; B, 22 with nodal involvement (n+) and given IOPHC; C, 47 n0 and no IOPHC; D, 46 n (+) and no IOPHC. Local recurrence developed in one patient in group A (12.5%), 3 in group B (13.6%), 5 in Group C (10.6%), and 16 in Group D (34.8%), respectively. Thus, the rate of local recurrence in group B was low compared to that of Group D, even through there was no statistical difference (p = 0.11). IOPHC may be one option for limiting local recurrence after surgical resection of rectal cancer.

Hypocarbia and cystic periventricular leukomalacia in premature infants

One hundred sixty seven survivors among very low birthweight infants with a gestational age of less than 35 weeks have been studied prospectively. The purpose of this study was to clarify the relationship of severe prenatal and perinatal complications and hypocarbic alkalosis, defined as a carbon dioxide tension (PaCO2) of less than or equal to 2.67 kPa and a pH of 7.50 or greater during the first 24 hours of life, to cystic periventricular leukomalacia (PVL) depicted by serial cranial ultrasonographic examinations. Complications occurred in 16 infants, five of whom presented with PVL, while eight of 151 infants without complications had PVL. Twenty six of the infants had hypocarbic alkalosis, six with evidence of PVL, and seven of the 136 infants without hypocarbic alkalosis had PVL. These results suggest a significant relationship of complications and hypocarbic alkalosis to PVL. Mechanical ventilation should be managed carefully in premature infants to avoid PaCO2 of lower than 2.67 kPa.

Immunohistochemical localization of interferon-gamma in normal human ovary

There is increasing evidence that cytokines are important intraovarian non-steroidal regulators. The aim of the present study was to evaluate the presence in the human ovary of interferon (IFN)-gamma, a cytokine produced by T lymphocytes after mitogenic or antigenic stimulation. Very low levels of IFN-gamma (0.025-0.057 IU/ml) were found in follicular fluid of large spontaneously maturing follicles, in the ovarian vein (< 0.01-0.079 IU/ml) or peripheral blood (< 0.01-0.06 IU/ml). The avidin-biotin immunocytochemical technique, with appropriate monoclonal antibodies, was used to localize IFN-gamma-positive cells, human leukocyte antigen (HLA)-DR molecules, activated T cells, T helper/inducer cells and T cytotoxic/suppressor cells. IFN-gamma-positive cells were only detected in preovulatory follicles, associated with the follicular basal lamina, thecal vessels and interstitial tissue. In the same large follicles very few T helper/inducer cells were detected, but a high proportion of T lymphocytes expressed the CD8 phenotype in the theca, interstitial tissue and follicular cavity. No IFN-gamma-positive cells were observed in preantral and small antral follicles. The results indicate that the human ovary contains immunoreactive IFN-gamma, suggesting that the cytokine plays a paracrine role in human ovarian function.

Toxic effects of bis (tributyltin) oxide on the synthesis and secretion of zymogen granules in the rat exocrine pancreas

Toxic effects of bis (tributyltin) oxide (TBTO) on the rat exocrine pancreas were studied with an electron microscope and X-ray microanalyzer. To measure tin concentrations in the blood, atomic absorption spectrophotometry was carried out. Adult male Wistar rats received an intramuscular injection of TBTO (0.5 ml/kg). At 2 h after injection, a marked swelling of mitochondria and an enlargement of the cisterns of the rough endoplasmic reticulum appeared in the pancreatic acinar cells. Using X-ray microanalysis, tin peaks were preferentially obtained from the swollen mitochondria. Heterogeneous zymogen granules with an electron dense core and a pale central zone increased in number in the acinar cells between 4 and 8 h after TBTO treatment. By 24 h after TBTO injection, the acinar cells had been ultrastructurally restored. Atomic absorption analyses showed that blood tin concentrations peaked at approximately 1 h after TBTO injection and then progressively declined, reaching the zero level at 12 h after injection. The effects of TBTO on the synthesis and secretion of zymogen granules were investigated with and without caerulein as a stimulant of secretion. Data obtained from these experiments indicated that TBTO inhibited both the synthesis and secretion of zymogen granules. The inhibition of the protein synthesis and secretion might be caused partly by mitochondrial dysfunctions due to the toxic effects of TBTO.

Enzyme-linked immunosorbent assay for human pulmonary surfactant protein D

We developed a simple and sensitive enzyme-linked immunosorbent assay (ELISA) for human pulmonary surfactant protein D (SP-D). Human SP-D was purified from bronchoalveolar lavage fluids of patients with pulmonary alveolar proteinosis. Nine monoclonal antibodies (MAbs) were established from BALB/c mice immunized with the purified human SP-D. All MAbs were directed to either 43 kDa SP-D contained in lung lavage fluids of patients with pulmonary alveolar proteinosis or in amniotic fluids from healthy normal pregnancies. The ELISA is based on a sandwich method using two MAbs, 6B2 and 7C6. Cross-reactivity to human SP-A or rat SP-D was evaluated as below 0.6%. The recovery of different concentrations of SP-D ranged from 94.4% to 111.2%, and serial dilutions of amniotic fluids showed good linearity. SP-D concentrations in 21 amniotic fluids from normal pregnancies were measured by the ELISA. The mean concentration in amniotic fluids from pregnancies in the third trimester was significantly higher than that from earlier stages of gestation (p < 0.001), indicating that this ELISA may be applicable for prediction of fetal lung maturity.

Alpha 1-adrenoceptor subtypes mediating contraction of the femoral artery in spontaneously hypertensive rats

alpha 1-Adrenoceptors (ARs) were divided into alpha 1H and alpha 1L subtypes by their different affinities for bunazosin or prazosin. alpha 1H-ARs were further subdivided into alpha 1A, alpha 1B, and alpha 1C subtypes. Therefore, this study was undertaken to determine which alpha 1-AR subtypes were involved in the activation of femoral artery preparations by alpha 1-AR agonists in spontaneously hypertensive rats (SHR). For comparison, aortic strips were also incorporated in the present study. In the presence of propranolol, deoxycorticosterone, and desipramine, norepinephrine (NE) contracted the vascular strips in a dose-dependent manner. Negative log EC50 values and maximum responses of NE-induced contraction of the SHR femoral artery were unchanged and increased, respectively, compared with those of Sprague-Dawley and Wistar-Kyoto rats (WKY). Contractile responses of the SHR aortae to NE were similar to those of the normotensive tissues. Schild plot data for alpha 1-AR antagonists indicated that alpha 1-AR subtypes mediating contraction of the aorta were homogeneous and had high affinities for bunazosin (pA2 9.4, alpha 1H subtype) and WB 4101 (pA2 9.3) and a low affinity for 5-methylurapidil (pA2 7.7). In the femoral artery, because Schild plots for bunazosin had slopes of less than 1.0, there were alpha 1H and alpha 1L subtypes. Bunazosin, at 10(-9) M, which could mask the alpha 1H subtype, yielded a Schild plot for bunazosin with a slope not different from unity and decreased the pA2 value for bunazosin (pA2 9.4 vs. 8.5).(ABSTRACT TRUNCATED AT 250 WORDS)

Efficient retrovirus-mediated gene transduction into murine hematopoietic stem cells and long-lasting expression using a Transwell coculture system

The neomycin phosphotransferase (neo) gene was transduced into murine hematopoietic stem cells by culturing a recombinant retrovirus-producing cell line in a Transwell (Costar, Cambridge, MA) (bottomed with a porous membrane) hung into a Dexter-type long-term bone marrow (BM) culture. Gene transduction into stem cells retaining long-term reconstitution ability was successfully performed by using protocols of total 15 to 18 days of culture including establishment of the Dexter culture, transduction, and G418 selection. In the irradiated recipients of these cells, a large majority of the BM, thymus, and spleen cells as well as peripheral blood (PB) leukocytes were of donor origin and the neo gene was present in these organs up to 21 weeks after cell transfer. One third to two thirds of the in vitro colony-forming cells in the BM of the recipient mice were resistant to cultivation with G418. It was further found that the hematopoietic system of secondary recipients given BM cells from a primary recipient mouse was predominated by original donor-type cells. The transduced neo gene was detected in the PB, BM, thymus, and spleen cells of these secondary recipients. These results indicate that our procedure of retroviral vector-mediated gene transfer is highly effective in safely introducing a gene into pluripotent hematopoietic stem cells.

Left ventricular diastolic function in patients on maintenance hemodialysis: comparison with hypertensive heart disease and hypertrophic cardiomyopathy

To elucidate the differences in the left ventricular diastolic function between patients on maintenance hemodialysis with left ventricular hypertrophy and the those with left ventricular hypertrophy from other causes, 20 patients on maintenance hemodialysis (HD group; mean age 44 +/- 12 years), 12 patients with hypertensive heart disease (HHD group; mean age 43 +/- 10 years), and 10 patients with hypertrophic cardiomyopathy (HCM group; mean age 43 +/- 11 years) were examined non-invasively using diastolic time intervals and digitized echocardiograms. Ten age-matched healthy men (N group; mean age 43 +/- 12 years) were also examined. Compared with the HCM group, the HD and HHD groups had a decreased total left ventricular wall thickness and left atrial dimension, an increased ratio between the left ventricular enddiastolic dimension and total left ventricular wall thickness. The isovolumic relaxation and rapid relaxation periods were prolonged in the order of HCM, HHD, HD and N, but the active suction period was prolonged only in the HCM group. The peak rate of change in the left ventricular dimension during the rapid filling period was decreased in the HCM group, compared with the HD and the HHD groups. These results indicate that hemodialysis patients with left ventricular hypertrophy have some impairment in left ventricular diastolic function, but the degree of the disturbance is similar to that observed in those with hypertensive heart disease, but milder than that observed in those with hypertrophic cardiomyopathy.

Adoptive transfer of a Th2-like cell line prolongs MHC class II antigen disparate skin allograft survival in the mouse

The MHC class II alloantigen-reactive CD4+ Th2-like cell line, HR2, was established. It was derived from the spleen cells of C57BL/6 (B6) mice immune to an MHC class II-disparate mutant mouse, B6.CH-2bm12 (bm12) which carries the I-Abm12 antigen. This cell line, HR2, secretes IL-4 and IL-10 in an antigen-specific manner, and can also proliferate in an autocrine manner through IL-4. To investigate the in vivo role of this Th2-like CD4+ T cell line in transplantation immunity, an adoptive cell transfer study using the skin allograft system was performed. Skins grafted from bm12 to B6 were rejected at 12.1 +/- 0.6 days in control B6 mice which received no treatment. Whereas skin graft survival was prolonged in B6 experimental mice which had received 2 x 10(7) HR2 cells, 75% of the grafts survived for > 40 days. Moreover, since skin grafts from fully allogeneic third party donor BALB/c mice were rejected at 12.0 +/- 0.4 days by B6 mice which had received the same number of HR2 cells, it was demonstrated that HR2 is involved in the regulation of bm12 skin graft rejection. Furthermore, cytotoxic T lymphocyte (CTL) activity by spleen cells from HR2 transferred B6 mice was not induced even by in vitro secondary stimulation, although CTL activity was induced well in spleen cells of control B6 mice which had rejected the graft. The underlying mechanism has not been fully clarified; however, these results demonstrate that Th2-like CD4+ T cells suppress allograft rejection.

Hydroxylation of phenylalanine and salicylate by stimulated polymorphonuclear leukocytes and the accelerating effect of glutathione on their hydroxylation

Incubation of phorbol-myristate acetate-stimulated human polymorphonuclear leukocytes (PMNs) with phenylalanine and salicylate induced significant levels of formation of o- and m-tyrosines, and 2,3- and 2,5-dihydroxybenzoates (DHBAs), respectively, dependent on reaction time. Aromatic hydroxylation reactions were not inhibited by desferrioxamine, nor were they affected by the removal of trace ion contamination from the buffer solution used by treatment with conalbumin. Hydroxylation reactions were largely blocked by superoxide dismutase and hydroxyl radical (OH.) scavengers. The results of the present study suggest that the generation of OH. by human PMNs occurs during the respiratory burst. Hydroxylation of both phenylalanine and salicylate by stimulated human PMNs were significantly accelerated by incubation in the presence of the reduced form of glutathione (GSH). Hydroxylation of phenylalanine by stimulated guinea pig PMNs in the presence of GSH was significantly inhibited by desferrioxamine, although the same hydroxylation in the absence of GSH was not affected. Hydroxylation of phenylalanine by the hypoxanthine (HX)-xanthine oxidase (XO) system by intact PMNs was significantly accelerated by the addition of GSH, although that in the absence of PMNs was largely inhibited. Desferrioxamine showed an inhibitory effect on hydroxylation by the HX-XO system in the presence, but not in the absence, of intact PMNs. The results suggest that the formation of OH. by stimulated PMNs is accelerated by GSH, based on the occurrence of the Harber-Weiss reaction catalyzed by transition metal ions liberated and reduced by GSH from PMNs, and by the effective accumulation of H2O2 by the GSH-induced inhibition of catalase.

On the mechanism of inactivation of active papain by ascorbic acid in the presence of cupric ions

An inactivation mechanism of active papain (EC 3.4.22.2) by the Cu(2+)-ascorbic acid (AsA) system was examined. Incubation of active papain, which contains an active sulfhydryl (SH) group, with the Cu(2+)-AsA system under aerobic conditions resulted in an irreversible loss of enzyme activity. The enzyme was not inactivated at a molar ratio of enzyme to Cu2+ of 1:< 1, whereas at a molar ratio of 1:1-2, the extent of inactivation showed the same dependence on the extent of oxidation of AsA. Saturation kinetics were observed with respect to the concentration of AsA. The degree of inactivation was dependent on the decrease in SH content of the enzyme. Catalase at a low concentration partially protected the enzyme from inactivation, but did not affect the oxidation of AsA. In addition, catalase at a high concentration completely protected both the enzyme from inactivation and AsA from oxidation. The present results suggest that an additional function of H2O2, besides producing hydroxyl radicals (.OH), is to promote the conversion of Cu+ into Cu2+, and that an active SH group of papain is site-specifically modified by the .OH, resulting in inactivation of the enzyme.

A study on the hemostatic effect of sodium alginate on uterocervical hemorrhage

We examined a sodium alginate preparation (Alto) to determine its hemostatic effect, in comparison with other topical drugs, on hemorrhages in the uterocervical area. A total of 149 patients with hemorrhage from cervical erosion or after-treatment bleeding of the cervix uteri were subjects in this trial, and 84 (79%) of 106 patients treated with this preparation experienced a hemostatic effect. A significant positive correlation (p < 0.001) was noted between the degree of tissue adhesiveness and the hemostatic effect in all the drugs tested. As for the tissue adhesiveness, Alto was significantly more favorable (p < 0.001) than both Thrombin and Francetin T powder. Because Alto was softened by tissue moisture, its topical adhesiveness could be increased, which suggested that Alto was superior in hemostasis.

[Studies on clinical usefulness of new tumor markers of ovarian cancer, CA54/61 and CA602--III. Measurement of serum samples from patients with various benign or malignant diseases]

Serum samples from patients with benign or malignant diseases were measured for the newly developed tumor markers CA54/61 and CA602 with the respective EIA kits for assessment of their utility as tumor markers. A total of 5236 patients were entered into the study, consisting of ovarian cancer patients, those with other cancers, pregnant women, and healthy volunteers. The CA54/61-positive rate with a cut-off value of 12 U/ml was 61.2% for ovarian cancers (50.4% with a cut-off value of 20 U/ml). A positive rate of 75.0% (64.4%) was achieved for mucinous cystadenocarcinoma, which was high, compared with that for CA125. On the other hand, the false-positive rate was 12.2%(5.9%) for benign ovarian tumors, and as low as 18.5%(8.7%) for endometriosis. The CA602-positive rate with a cut-off value of 63 U/ml was as high as 76.0% for ovarian cancers (69.8% with a cut-off value of 90 U/ml). On the other hand, the false-positive rate was relatively high at 21.9% (12.6%) for benign ovarian tumors, and 56.7% (40.0%) for endometriosis. These positive rates were therefore similar to those for CA 125. The levels of both CA54/61 and CA602 antigens well reflected the postoperative prognosis. These results suggest the utility of CA54/61 and CA 602 as tumor markers of ovarian cancers.

Lipopolysaccharides from Campylobacter jejuni associated with Guillain-Barré syndrome patients mimic human gangliosides in structure

Lipopolysaccharides extracted from Campylobacter jejuni serostrains (serotype reference strains) for serotypes O:4 and O:19 were found to have core oligosaccharides with terminal structures resembling human gangliosides GM1 and GD1a. High-molecular-weight molecules that reflected the presence of O chains were shown in immunoblots to be immunologically specific for each serostrain. The O:19 antiserum also reacted strongly with core oligosaccharides of two isolates from patients with Guillain-Barré syndrome (GBS), but the banding patterns and molecular structures were different from those of the O:19 serostrain. A neuraminobiose disaccharide unit is attached to the terminal Gal residue in one isolate, and the other isolate lacked terminal N-acetyl glucosamine and galactose with attached sialic acid so that the sialic acid residues were present in a neuraminobiose unit linked to the only remaining galactose. Analysis of the high-M(r) lipopolysaccharides of the O:19 serostrain and the two isolates from GBS patients revealed the presence of a hyaluronic acid-like polymer with disaccharide-repeating units consisting of beta-D-glucuronic acid amidated with 2-amino-2-deoxyglycerol and N-acetyl glucosamine. The results confirm a potential role for the core oligosaccharides in the etiology of GBS but also suggest that the O-chain polysaccharide may be a contributing factor.

Decreased E-cadherin expression in endometrial carcinoma is associated with tumor dedifferentiation and deep myometrial invasion

Decreased E-cadherin expression in tumor cells has been suggested to promote tumor invasiveness. We examined E-cadherin expression in 30 cases of endometrial carcinoma by immunohistochemistry using a monoclonal antibody to E-cadherin and investigated its correlation with other histopathologic features of the tumor. We observed that: (1) E-cadherin expression decreased with loss of differentiation (P < 0.05); (2) E-cadherin expression was inversely correlated with depth of myometrial invasion (P < 0.05); (3) decreased E-cadherin expression was correlated with paraaortic node metastasis (P < 0.01); and (4) multivariate analysis comparing the depth of myometrial invasion to the pattern of E-cadherin expression, histologic grade, nuclear grade, and lymph-vascular space invasion showed that the depth of myometrial invasion was most strongly correlated with decreased E-cadherin expression (P < 0.005). These findings seem to be consistent with the concept that the dissociation of cancer cells due to decreased expression of E-cadherin facilitates invasion of tumor cells.

Clinicopathologic characteristics and survival of elderly patients with gastric cancer

From 1980 to 1991, Japanese patients aged over 49 years with gastric cancer underwent gastric resection in our hospitals. For various studies, two groups, 35 patients over 79 years (advanced age group) and 884 patients aged 50-79 years (mature age group) were prepared. A retrospective study was done with special reference to clinicopathological features and the prognosis. There were no differences in clinicopathological characteristics between the two groups, except for operative procedures and the size, histology and vascular involvement of the primary tumor. The survival rate for the advanced age group was higher than that for the mature age group, with a significant difference at p = 0.00556. However, the postoperative morbidity rate was 48.6% in the advanced age group compared with 5.1% in the mature age group. The most frequent complications were respiratory-related, that is, atelectasis, pneumonia or aspiration pneumonia. Based on these data, advanced age is not a contraindication for resection of a gastric cancer, but patients with serious pulmonary and/or cardiac diseases would not be candidates.

Comparative clinicopathologic features of early gastric cancer in young and older patients

BACKGROUND

The clinicopathologic features of advanced gastric cancer have been analyzed in young or older patients; however, with regard to early gastric cancer, it remains unknown whether the features differ between young and older patients. Reported here is an analysis of clinicopathologic characteristics in young and in older patients.

METHODS

This study is based on a retrospective review of 25 patients less than 40 years of age with early gastric cancer and of 64 patients more than 70 years of age with early gastric cancer. These patients were treated from 1977 through 1991.

RESULTS

Because in the older group there were early double cancers in three patients and quadruple cancers in one, 70 early cancers were present in these 64 patients. Although the young group included a larger percentage of women, the ratio of mucosal cancer to submucosal and the incidence of nodal metastasis did not differ between the groups. Poorly differentiated adenocarcinoma was detected in 13 (52%) of the 25 younger patients, whereas in the older group it was present in 6 cancers (8.6%) alone. The number of metastatic nodes and extent of nodal metastasis were more severe in the young group, but survival rates did not differ between the groups. The depressed type of lesion was present in all patients in the young group, whereas it was only 41 of 70 cancers in the older group.

CONCLUSIONS

These findings suggest that early gastric cancer in young adults has aggressive features as based on the histologic pattern, in particular with cancer invasion into the submucosal layer. For these patients nodal extirpation and postoperative adjuvant chemotherapy should be performed in an attempt to prevent lymphatic or hematogenic metastases.

[Study for modifying activity of solvents on antitumor activity of paclitaxel]

Paclitaxel, a novel diterpenoid compound, has been used by dissolving in Cremophor EL (polyoxyethylene castor oil) due to its poor aqueous solubility. Cremophor EL was shown to reverse multidrug resistant phenotypes of various cell lines as well as to reverse cross-resistance to paclitaxel of a multidrug resistant cell line in vitro. Thus, a study was carried out to determine the modifying activity of Cremophor EL on the antitumor activity of paclitaxel against P388 leukemia, adriamycin-resistant subline (P388/ADM) and vincristine-resistant subline (P388/VCR) in vivo. Dimethyl sulfoxide (DMSO) was used as a counterpart solvent. The results showed that, although no significant antitumor activity was observed by paclitaxel in both solvents against P388/ADM, a significantly higher antitumor activity was induced by paclitaxel dissolved in Cremophor EL-based solvent compared with DMSO-based solvent against P388/VCR. However, more significant difference in the antitumor activity of paclitaxel against P388 parental line was observed between two solvents and both resistant sublines showed an obvious cross-resistance to paclitaxel. Therefore, it appeared that cross-resistance reversing activity of Cremophor EL is not so high as to be detectable at in vivo level.

Cerebral palsy of cystic periventricular leukomalacia in low-birth-weight infants

We studied ultrasound findings and neurodevelopmental outcome of 24 infants weighing 2500 g or less with cystic periventricular leukomalacia. Fourteen infants had symmetrical cysts in the parietal or occipital region (group 1) and 10 had non-symmetrical cysts (group 2). Each infant was followed for more than 4 years of age (mean 5 years and 7 months). Twenty out of 24 (83.3%) children developed cerebral palsy. All of group 1 had cerebral palsy (8 diplegia and 6 ataxic diplegia), while 6 (60%) in group 2 developed cerebral palsy (4 diplegia and 2 hemiplegia). There was a significant difference in the incidence of cerebral palsy and motor ability between the two groups. The size and site of the cyst did not predict cerebral palsy. The presence of symmetrical cysts in the parietal or occipital region is a highly reliable neurosonographic finding for predicting cerebral palsy.

Effect of radical scavengers on the inactivation of papain by ascorbic acid in the presence of cupric ions

Incubation of papain (EC 3.4.22.2) with ascorbic acid (AsA) and Cu2+ in acetate buffer (pH 5.6) results in an irreversible loss of enzyme activity by site-specific generation of free radicals [H. Kanazawa, S. Fujimoto, A. Ohara, Biol. Pharm.Bull., 16, 11 (1993)]. In this study, the effect of some compounds, known free radical scavengers, on the relationship between the inactivation of papain by the Cu(2+)-AsA system and the oxidation of AsA was investigated. Catalase completely protected the enzyme from inactivation by the Cu(2+)-AsA system, although hydrogen peroxide (H2O2) by itself, known to be generated during the autoxidation of AsA, did not inactivate the enzyme. The oxidation of AsA was unaffected by catalase. Both thiourea and sodium thiocyanate completely protected the enzyme from inactivation, while AsA was partially oxidized only in the initial stage. In the presence of potassium iodide, both the inactivation of the enzyme and the oxidation of AsA were characterized by a rapid initial phase followed by a stable phase where no reaction took place and, subsequently, a slower phase. Histidine partially prevented the inactivation of the enzyme and the oxidation of AsA. The present results suggest that H2O2 serves as a source of secondary, highly reactive species, probably hydroxyl radicals, which are responsible for the inactivation, and that the protection from inactivation by some radical scavengers, such as thiourea, sodium thiocyanate, potassium iodide, and histidine, is based on the removal of metal ions (Cu2+ or Cu+) at the specific site of inactivation.