[Evaluation of 26G pencil point spinal needle in combined epidural-spinal anesthesia]

Twenty six gauge pencil point spinal needles and an adaptor for the fixation of the spinal needle were developed for combined epidural/spinal anesthesia on an experimental basis and applied on 110 patients. The length of the spinal needles was either 11.7 cm or 13 cm. Fifty out of 110 patients were punctured with the 11.7 cm needle and then were divided into 2 groups. The difference in length of the spinal and epidural needles was 8 mm in group 1 and 15 mm in group 2. In 80% of the patients in group 1 and in 95% of the patients in group 2, the subarachnoidal space was reached on the first puncture. These results indicate that the subarachnoidal space can be more easily punctured when a spinal needle 15 mm longer than the epidural needle is used. On the other hand, when a 13 cm spinal needle was employed, it often did not remain in place during drug injection. This problem could be solved, however, by using an adaptor with which the spinal needle was fixed firmly on the epidural needle at the point of dural puncture. The incidence of the post dural puncture headache was 1.7% (1 out of 60 patients).

Increased risk of mammary carcinoma development following transplacental and trans-breast milk exposure to a food-derived carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), in Sprague-Dawley rats

Effects of transplacental and trans-breast milk exposure to a food-derived mammary and colon carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), were investigated in rats. Female Sprague-Dawley rats were administered PhIP in the diet (100 ppm) for 4 weeks before mating with nontreated males and also during gestation and lactation. As controls, additional females were maintained on the basal diet without PhIP and mated as with the treated animals. The offspring of both groups were subdivided for each sex at weaning into three dietary groups receiving 100, 25, and 0 ppm and were killed at 47 weeks of age. Effects of the transplacental and neonatal exposure to PhIP on mammary carcinogenesis were most evident in females administered 25 ppm PhIP after weaning; the incidence and multiplicity of adenocarcinomas in offspring from the PhIP fed dams (42.9%, 0.62/rat) was significantly higher than the value for offspring from nontreated dams (4.8%, 0.05/rat). Furthermore, in the basal diet groups, the incidence of adenocarcinomas in females was higher, albeit not significantly, in offspring of the PhIP-treated than the nontreated dams (16.7%, 0.22/rat as compared with 3.3%, 0.07/rat). Although the highest incidence of mammary adenocarcinomas was found in the female progeny given 100 ppm PhIP from PhIP-treated dams (70.0%, 1.55/rat), this was only slightly higher than the 61.9% and 0.90/rat of the same dose group from the nontreated dams. In males, no apparent effects of transplacental and neonatal exposures were evident. In a separate experiment, excretion of PhIP into breast milk and transfer of PhIP to fetuses and neonates with resultant hepatic PhIP-DNA adduct formation were demonstrated. Thus, maternal exposure to this food-derived carcinogen may be a critical risk factor for generation of mammary carcinomas.

Aesthetic properties of pictorial perception

The present study assessed the dynamic person-object relationship in pictorial perception as associated with a high-level experience like the aesthetic. A series of experiments was designed to gain insight into the complexities of self-world interactions involving the perceptual experience, which is the basis of artistic communication. Participants were asked to produce line drawings, which were then ranked by a larger group of participants as to whether they conveyed expressive contents. This resulted in considerable agreement among the judges. In addition, the factor structure of the semantic differential responses was determined. The results indicated that considerable semantic space existed between them. A theory of a linkage between affective and cognitive processes in perceptual experience is proposed.

Transduction of LacZ gene into leukemia cells using viral vectors of retrovirus and adenovirus

Recent developments in gene therapy techniques enable us to introduce new genetic information into hematopoietic cells. Among the various techniques, we focused on two viral vector systems, one using a retrovirus and the other an adenovirus. By using an adenoviral vector we could transduce and highly express bacterial beta-galactosidase (LacZ) gene under the control of the CAG (cytomegalovirus enhancer with chicken beta-actin promoter) promoter in various hematopoietic cells, although the expression persisted for only two weeks. The retroviral vector (MFG) could transduce the LacZ gene into hematopoietic cells almost as well as the adenoviral vector using the repetitive infection protocol. The retroviral system could maintain the expression of transduced cells quite longer than the adenoviral system. Differential use of these two vector systems may be helpful for the gene transduction into various kinds of hematopoietic cells (Lin et al., manuscript in preparation).

Interleukin 1 alpha-induced expression of manganous superoxide dismutase reduces myocardial reperfusion injury in the rat

We investigated the effects of pretreatment with interleukin (IL)-1 alpha on the expression of manganous (Mn) superoxide dismutase (SOD) mRNA and reperfusion-induced arrhythmias and the size of myocardial infarct in rats. Male Wistar rats received 10 mg intraperitoneal injections of human recombinant IL-1 alpha. Their hearts were thereafter isolated at 6, 12, 24, 36 h. A Northern analysis showed that Mn-SOD mRNA was mainly expressed in the heart and slightly in kidney, but not in any other organs. The expression of Mn-SOD mRNA peaked at 6 h after the injection of IL-1 alpha. The Mn-SOD protein content was most increased 12 h after injection. In the isolated heart model, the rats were pretreated with IL-1 alpha 24 h earlier and their hearts were perfused by the Langendorff method. After 20 min of ischemia which was induced by a ligation of a coronary artery, reperfusion-induced arrhythmias were observed. There were no significant differences in the incidence of ventricular arrhythmias between the IL-1 alpha pretreated and the untreated hearts. IL-1 alpha pretreatment significantly reduced the mean duration of the ventricular arrhythmias and also delayed the onset of arrhythmias. The effect of IL-1 alpha pretreatment was also investigated in a 30-min model of ischemia followed by a 3-min reperfusion in anesthetized rats. The infarct size expressed as a percentage of the area at risk was significantly reduced in the IL-1 alpha pretreated hearts compared with the untreated hearts. The left ventricular systolic pressure increased significantly in rat hearts pretreated with IL-1 alpha. Our results therefore showed that the pretreatment with IL-1 alpha induced the overexpression of Mn-SOD mRNA in the rat hearts and also suggested that pretreatment with IL-1 alpha 24 h before ischemia reduced the risk of ischemia-reperfusion injury.

[Acquired amylase production induced by radiotherapy in a myeloma patient]

A 55-year-old patient with multiple myeloma (IgG-lambda) diagnosed in November 1988 was admitted because of bone pain throughout the body. After plasmapheresis and several courses of chemotherapy, a massive tumor of the left thoracic wall involving the rib appeared. Radiotherapy was performed to ameliorate the severe chest pain, after which myelomatous pleural effusion appeared on the left side. The serum, urine and pleural effusion revealed increased activity of amylase of the salivary type. Amylase activity was also detected in the supernatant of myeloma cells cultured from pleural effusion. We reviewed 12 cases of ectopic amylase-producing multiple myeloma. All the cases except one have been reported from Japan, and hyperamylasemia in these cases was detected at diagnosis or during course of the illness. Moreover, cytogenetic analysis of myeloma cells of previous reports revealed structural abnormalities including chromosome 1, near the amylase gene locus. This case also showed t (1; 10) (q 21?; q 26) by examination of 8 metaphase derived from bone marrow. These observations suggested that ectopic amylase production was induced by irradiation to the plasmacytoma of thoracic wall.

Lateralized abnormality of high-energy phosphate and bilateral reduction of phosphomonoester measured by phosphorus-31 magnetic resonance spectroscopy of the frontal lobes in schizophrenia

Magnetic resonance spectroscopy (one-dimensional chemical shift imaging) was used to measure membrane phospholipid metabolism and high-energy phosphate metabolism in the left and right frontal lobes of 27 schizophrenic patients. In the schizophrenic patients, the phosphomonoester peak area was decreased in bilateral frontal lobes compared with that in age-matched normal subjects. On the other hand, the peak area of beta-adenosine triphosphate was increased in the left frontal lobe in the schizophrenic group. The phosphocreatine peak area was increased in the left frontal lobe of schizophrenic patients with high scores on the Scale for the Assessment of Negative Symptoms (SANS).

Identification of the overtone of the Fe-CO stretching mode in heme proteins: a probe of the heme active site

Two CO-isotope sensitive lines have been detected in the overtone region of the resonance Raman spectra of CO-bound hemeproteins. One line is assigned as the overtone of the Fe-CO stretching mode and is located in the 1000- to 1070-cm-1 region. The other line is found in the 1180- to 1210-cm-1 region and is assigned as a combination between a porphyrin mode, nu 7, and the Fe-CO stretching mode. The high intensities of these lines, which in the terminal oxidase class of proteins are of the same order as those of the fundamental stretching mode, indicate that the mechanism of enhancement for modes involving the Fe-CO moiety is different from that for the modes of the porphyrin macrocycle and call for reexamination of Raman theory of porphyrins as applied to axial ligands. The anharmonicity of the electronic potential function was evaluated, revealing that in the terminal oxidases the anharmonicity is greater than in the other heme proteins that were examined, suggesting a distinctive interaction of the bound CO with its distal environment in this family. Furthermore, the anharmonicity correlates with the frequency of the C-O stretching mode, demonstrating that both of these parameters are sensitive to the Fe-CO bond energy. The overtone and combination lines involving the bound CO promise to be additional probes of heme protein structural properties.

Involvement of protein kinase in delta 12-prostaglandin J2-induced expression of rat heme oxygenase-1 gene

We recently identified the cis-regulatory element and its specific nuclear binding factors for delta 12-prostaglandin (PG) J2-induced expression of the rat heme oxygenase, HO-1 [Koizumi, T., Odani, N., Okuyama, T., Ichikawa, A. and Negishi, M. (1995) J. Biol. Chem. 270, in press]. Here we further examined the molecular mechanism underlying the delta 12-PGJ2-induced HO-1 gene expression. Protein kinase inhibitors, 2-aminopurine and staurosporine, suppressed the delta 12-PGJ2-induced HO-1 mRNA and the nuclear protein binding to the delta 12-PGJ2-responsive cis-regulatory element in rat basophilic leukemia cells. Furthermore, the nuclear protein binding to the element was suppressed by in vitro phosphatase treatment of the nuclear proteins from delta 12-PGJ2-treated cells. These findings suggest that delta 12-PGJ2 induces the expression of the HO-1 gene through phosphorylation of the nuclear proteins which bind to the delta 12-PGJ2-responsive element.

70-kDa heat shock cognate protein interacts directly with the N-terminal region of the retinoblastoma gene product pRb. Identification of a novel region of pRb-mediating protein interaction

Retinoblastoma protein (pRb) functions as a tumor suppressor, and certain proteins are known to bind to pRb in the C-terminal region. Although the N-terminal region of pRb may also mediate interaction with some proteins, no such protein has been identified yet. We demonstrated previously the in vivo protein association between pRb and 73-kDa heat shock cognate protein (hsc73) in certain human tumor cell lines. In this report we analyzed the interaction between these two proteins in vitro. Our data showed that hsc73 interacts with the novel N-terminal region of pRb; that is, pRb binds directly to hsc73 and dissociates from hsc73 in an ATP-dependent manner. By using deletion mutants of cDNA encoding pRb, the hsc73 binding site of pRb was determined to be located in the region (residues 301-372) outside the so-called A pocket (residues 373-579) of this tumor suppressor protein. This finding was compatible with the fact that the adenovirus E1A oncoprotein, which is known to bind to the E2F binding pocket region of pRb, could not compete with hsc73 for the binding. Furthermore, phosphorylation of pRb by cyclin-dependent kinase inhibited the binding of pRb to hsc73. These data suggest that hsc73 may act exclusively as the molecular chaperone for nonphosphorylated pRb. As a result, hsc73 may function as a molecular stabilizer of nonphosphorylated pRb.

Frequent loss of heterozygosity at 7q31.1 in primary prostate cancer is associated with tumor aggressiveness and progression

Cytogenetic analyses have demonstrated that chromosome region 7q22-32 is commonly altered in prostate adenocarcinomas. In addition, in recent fluorescence in situ hybridization studies, we have observed that aneusomy of chromosome 7 is frequent in prostate cancer and is associated with higher tumor grade, advanced pathological stage, and early prostate cancer death. These findings suggest that genetic alterations of chromosome 7 play a significant role in the development of prostate cancer. To better define the chromosome 7 alterations, PCR analysis of 21 microsatellite loci was performed on 54 paired prostate cancer and control DNAs. Overall, chromosome 7 allelic imbalance was identified in 16 of 54 cases (30%). Allelic imbalances of loci mapped to 7q were observed in 15 of the 16 cases. The allelic imbalances were classified as losses in 15 tumors (28%) and as gains in 1 (2%) by comparative multiplex PCR analysis. The most common site of allelic loss included loci D7S523 and D7S486 at 7q31.1. A comparison with clinicopathological features of the tested tumors revealed that the allelic loss of 7q31.1 correlated with higher tumor grade (P = 0.012) and lymph node metastasis (P = 0.017). These results indicate that 7q31 may be the site of a putative suppressor gene(s) important for the pathogenesis of prostate carcinoma, and that the genetic alterations at 7q31.1 may participate in tumor progression and metastasis.

An anti-tumor necrosis factor antibody suppresses sleep in rats and rabbits

It is hypothesized that tumor necrosis factor (TNF) is an endogenous sleep-promoting substance. In the present experiments we studied the effects of a monoclonal anti-TNF antibody in rats and rabbits. Seven rats and 14 rabbits were implanted with electroencephalographic electrodes, a brain thermistor and an intracerebroventricular guide cannula. The animals were injected with saline, control IgG, and monoclonal hamster anti-murine-TNF antibodies (TNFab) on 3 separate days. Ten micrograms TNFab suppressed non-rapid-eye-movement sleep (NREMS) in rats. In rabbits, 2.5 micrograms TNFab did not affect sleep but decreased brain temperature; in contrast, 25 micrograms TNFab suppressed NREMS without affecting brain temperature. These results are consistent with the hypothesis that endogenous TNF plays an important role in sleep regulation.

[Parasitologic significance of the alteration of the causative Anisakidae worm and of the Pseudoterranova decipiens female immature adult worm, casting off the cuticles, and excreted from human in Kanazawa City]

We have been studying Anisakidae larvae, their intermediate hosts and their final hosts in the northern Japan Sea area. These larvae cause anisakidosis. According to the investigation, the recent burst of pseudoterranovosis in this area can be attributed to the increased presence of sea lions, which proliferate in the Arctic region, then migrate to the northern Japan Sea and eat the intermediate host fish. In a stomach of a male sea lion that was captured in February 1995, we found more than 4,500 Pseudoterranova decipiens. Although there is no known circumstance in which a human would consume an adult worm of Anisakis nematode, an astonishing case of this was found in Kanazawa; a female young adult Pseudoterranova decipiens undergoing the final metamorphosis was emitted from a patient. This indicates that the Anisakis larva can mature into the adult worm in humans. It is postulated that the Pseudoterranova decipiens larva is in the process of adapting to use humans as the final host.

Bone metabolic markers in bone metastases

The efficacy and cost/performance benefit of radionuclide bone scintigraphy in monitoring metastatic bone activity remain controversial. Recently developed bone metabolic markers are expected to play an additional role in the diagnosis of bone metastasis. We measured osteoclastic and osteoblastic markers in 267 patients with breast cancer (100 with bone metastasis), 38 patients with prostatic cancer (25 with bone metastasis), 50 patients with lung cancer (12 with bone metastasis) and 33 patients with miscellaneous cancers (13 with bone metastasis) and compared the values in the presence and absence of bone metastasis. Bone metabolic markers, both osteoclastic and osteoblastic, increased significantly in patients with bone metastasis. In breast cancer (bone metastasis is mostly of the mixed type), osteoclastic markers were good in detecting bone metastasis. In prostatic cancer (bone metastasis is mostly osteoblastic), osteoclastic and osteoblastic markers were equally effective in detecting bone metastasis. In lung cancer (bone metastasis is mostly osteolytic), osteoclastic markers were elevated preferentially in bone metastasis. Over all, osteoclastic markers were more sensitive in the diagnosis of bone metastasis, and among osteoclastic markers, serum pyridionoline-cross-linked carboxyterminal telopeptide was the most efficient in both specificity (91.0%) and sensitivity (48.6%) for detecting bone metastasis.

Biosynthesis of lactacystin

The biosynthesis of lactacystin, a new microbial metabolite which induces differentiation of neuroblastoma cells, was studied by the feeding experiments of various 13C-labeled compounds and NMR spectroscopic analysis. The feeding experiments showed that lactacystin consists of three containing gamma-lactam moiety arises by a condensation between methylmalonic semialdehyde and C alpha position of L-leucine, followed by intramolecular cyclization. Two diastereotopic methyls, C-11 and C-12 of lactacystin were found to originate from the pro-R and pro-S methyls of leucine, respectively, as shown by incorporating a new type of chiral 13C-labeled L-leucine.

Evaluation of large intracranial aneurysm with three-dimensional MRI

OBJECTIVE

The purpose of this study was to evaluate large intracranial aneurysms by contrast-enhanced 3D MRI.

MATERIALS AND METHODS

Eleven patients, nine women and two men, were examined. The aneurysms involved the internal carotid artery in seven patients, the middle cerebral artery in one, the basilar artery in two, and the posterior cerebral artery in one. Contrast-enhanced 3D MR images were obtained using FLASH (fast low angle shot) on a 1.5 T system. We obtained axial images first, then sagittal and coronal images by multiplanar reconstruction. Those images were reviewed for comparison with conventional and MR angiography.

RESULTS

We could easily evaluate the true aneurysmal size, the intraaneurysmal constitution (patent lumen and intraluminal thrombus), and the detailed relationship of the aneurysm to the surrounding vascular and neural structures. Except for the cavernous internal carotid artery, we could identify the aneurysmal neck by carefully observing axial, sagittal, and coronal images. In addition, the progression of intraaneurysmal thrombosis and the patency of the parent arterial lumen after the endovascular treatment were well appreciated.

CONCLUSION

We consider that 3D MRI appears to be useful for evaluation of the large intracranial aneurysm.

Serial neuroimages of acute necrotizing encephalopathy associated with human herpesvirus 6 infection

A previously healthy 8-month-old girl developed exanthem subitum and acute encephalopathy with status epilepticus, quadriplegia and bilateral abducens nerve palsies. Human herpesvirus-6 DNA was found in the cerebrospinal fluid by the polymerase chain reaction at the acute stage. Cranial computed tomography showed low density areas in the thalami and in the cerebellar and abducens nuclei. The distribution of the lesions was consistent with acute necrotizing encephalopathy. As for the thalamic lesions, a T2 weighted magnetic resonance image on the 24th day of the illness demonstrated low signal intensity surrounded by high intensity; 99mTc-ECD SPECT showed hypoperfusion, which suggested irreversible tissue damage. The patient is now 1 year 6 months old and has spastic quadriparesis with mental retardation and abducens nerve palsies.

Low expression of adhesion molecules in a case of cutaneous T-cell lymphoma

A case of cutaneous T-cell lymphoma (CTCL) with low expression of the adhesion molecules lymphocyte function-associated antigen-1 (LFA-1), intercellular adhesion molecule-1 (ICAM-1), and very late antigen-4 (VLA-4) is described. The patient was a 90-year-old man with red round homogeneous tumors on his scalp, trunk, and extremities. He had no history of definite erythema or plaque stage. A biopsy sample taken from a tumor revealed massive infiltration of atypical lymphocytes in the reticular dermis and subcutis with a definite clear zone. The atypical lymphocytes were medium-sized with slightly convoluted nuclei. Immunohistochemically, the infiltrates showed the phenotype of so-called memory T cells. On the basis of these features, the case was diagnosed as CTCL. Expression of LFA-1, ICAM-1 and VLA-4 on the infiltrates was 9%, 13% and 11%, respectively, which is much lower than that in classic mycosis fungoides. This finding suggests that loss of these adhesion molecules may contribute to loss of epidermotropism in the advanced stage of CTCL.

[Pharmacological and biochemical investigation of intracavital fluorinated pyrimidine chemotherapy]

We investigated the biochemical and molecular pharmacological parameters of fluorinated pyrimidines using malignant cells in pleural effusion or ascites from patients with malignant disease both before and after fluorinated pyrimidine chemotherapy, either systemically or intravesically. In four out of fifteen cancer patients, we could analyze the alteration of thymidylate synthase (TS) catalytic activity both before and after the treatment, showing that there was a decrease ranging 28% through 96.9%. We also analyzed a level of TS messenger RNA and TS protein using molecular biotechniques. None of these mutual correlations has so far been demonstrated, indicating that the data were analyzed through samples from patients not responding to the fluorinated pyrimidines. In a responding patient with advanced breast cancer, pre-treatment total TS protein was 130 fmol/mg and the TS activity was 3.27 pmol/mg/min. After intrapleural instillation of a combination of 5-FU 250 mg and leucovorin 3 mg, the total amount and the catalytic activity of TS could be measured. On the 11th day of treatment, the TS protein level decreased to 26 fmol/mg and the TS catalytic activity also decreased to 0.1 pmol/mg/min resulting in a TS inhibition rate of 92.3 percent. On the 17th day, the patient's malignant pleural effusion disappeared almost completely, suggesting that substantial TS inhibition may reflect the clinical evidence. This particular data showed that it would be predictable for clinical outcome to evaluate these parameters before and after fluorinated pyrimidine chemotherapy. Further study is warranted to evaluate the exact role of analyzing these parameters in clinical practice.

Alobar holoprosencephaly with diabetes insipidus and neuronal migration disorder

A 2-year-old girl with alobar holoprosencephaly associated with facial abnormalities, central diabetes insipidus, and a neuronal migration disorder is reported. The diagnosis of diabetes insipidus was based on low urine osmolality and low plasma ADH concentration during a water deprivation test, and clinical and biochemical improvement after desmopressin acetate administration. Because the posterior portion of the pituitary was located in the sella turcica and the hypothalamo-pituitary stalk was intact, the diabetes insipidus was presumed to have been caused by hypothalamic osmoreceptor dysfunction. MRI findings were compatible with alobar holoprosencephaly. In addition, heterotopic gray matter was recognized as a continuous band over a single ventricle. Defective cleavage of the prosencephalon associated with a neuronal migration disorder is characteristic of alobar holoprosencephaly.

Immunohistochemical detection of estrogen receptor in invasive human breast cancer: correlation with heat shock proteins, pS2 and oncogene products

The authors immunohistochemically studied the expression of the estrogen receptor (ER), 27-kD heat shock protein (HSP27) and pS2 in 118 invasive primary human breast cancers. Positive nuclear staining of the ER was detected in 64% of the cases and was closely correlated with the biochemical assay (p < 0.0001). ER-positive tumors were significantly decreased with tumor size and stage (p < 0.001 each), but not with lymph node status. Positivity of the ER was correlated with the cytoplasmic expression of HSP27 (p < 0.005), pS2 (not significant) and HSP70 (not significant). ER negativity was significantly correlated with the expression of p53, epidermal growth factor receptor (EGFR) and c-erbB-2 (p < 0.05 each). Thus, it was concluded that ER-positive breast carcinomas, relatively small in size, preferentially expressed HSP27, HSP70 and pS2 and that ER-negative tumors, relatively large in size, were predisposed to express p53, EGFR and c-erbB-2.

Strong anti-mutagenic activity of the novel lipophilic antioxidant 1-O-hexyl-2,3,5-trimethylhydroquinone against heterocyclic amine-induced mutagenesis in the Ames assay and its effect on metabolic activation of 2-amino-6-methyldipyrido[1,2-a:3',2'-d] imidazole (Glu-p-1)

Antimutagenic effects of a novel lipophilic antioxidant, 1-O-hexyl-2,3,5-trimethylhydroquinone (HTHQ), and other known antioxidants against heterocyclic amine- or other mutagen-induced mutagenesis were examined in the Ames assay using Salmonella strain TA 98 to access the chemo-preventive effects of antioxidants on heterocyclic amine-induced carcinogenesis. Further the mechanisms of inhibition by HTHQ were accessed. HTHQ was shown to potently inhibit mutagenesis induced by all of 8 different heterocyclic amines at rates between 100% and 63% in the presence of S9 mix. When the protection of HTHQ against 2-amino-6- methyldipyrido[1,2-alpha:3',2'-d]imidazole (Glu-P-1)-induced mutagenesis was compared with known antioxidants t-butylhydroquinone, propyl gallate, BHA, BHT and alpha-tocopherol, HTHQ showed the greatest effect. Among hexyl, butyl, ethyl and methyl derivatives of 1-O-alkyl-2,3,5-trimethylhydroquinone, HTHQ was the most effective in inhibiting Glu-P-1-, 3-amino-1-methyl-5-H-pyrido[4,3-b]indole (Trp-P-2)- or 2-amino-3-methylimidazo[4,5-f]quinoline (IQ)-induced mutagenesis. On the other hand, HTHQ did not inhibit mutagenic activity induced by other mutagens such as N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), 2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide (AF-2) and benzo[a]pyrene. HTHQ weakly inhibited that due to direct mutagen 2-nitro derivative of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) only in the presence of S9 mix. No such influence on a 2-nitro derivative of 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) or 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced mutagenesis, was observed with or without the S9 mix. HTHQ slightly inhibited mutagenesis induced by activated Glu-P-1, a direct acting proximate metabolite of Glu-P-1, in the absence of the S9 mix. HPLC analysis revealed activated Glu-P-1 to be formed by incubating Glu-P-1 with the S9 mix, but this was considerably decreased by the addition of HTHQ. These results indicate that HTHQ is a powerful antimutagenic compound and specifically acts against heterocyclic amines. Its antimutagenic activity appeared to exert by both inhibiting metabolic activation of heterocyclic amines and action on activated N-hydroxy species.