Biomedical subjects

T Harada

Publications and source records attributed to T Harada.

At least 199 records · Page 11Linked to original sources

PubMed1999

Morphological investigation of the enteric nervous system in Hirschsprung's disease and hypoganglionosis using whole-mount colon preparation.

BACKGROUND/PURPOSE: A suction rectal mucosal biopsy with positive staining for acetylcholinesterase is a useful test for diagnosis of Hirschsprung's disease (HD). However, hypoganglionosis has not been diagnosed by a rectal mucosal biopsy. The authors morphologically examined the enteric nervous systems in HD and hypoganglionosis patients using whole-mount preparations. METHODS: Six HD patients, two hypoganglionosis patients, and 10 with normally innervated colons were examined. Colonic specimens were incubated with the primary antibodies against protein gene product 9.5 (PGP 9.5) mixed with S-100b protein, tyrosine hydroxylase (TH), calcitonin gene-related peptide (CGRP), substance P (SP), and neurofilament protein 200 kDa (NFH). They were observed by histochemical technique using light-microscopy in whole-mount preparations. RESULTS: The aganglionic distal colon had thick nerve strands stained with PGP 9.5 mixed with S100 or NFH located in the layer between the longitudinal muscle and the circular one, and the submucosal layer. The nerve strands in the myenteric layer contained few CGRP- and SP-positive fibers and ran along the long axis of the intestine. Ganglion cells appeared along with those thick nerve strands in the transitional zone of HD. In hypoganglionosis, we found small myenteric ganglia with no thick nerve strands. CONCLUSIONS: The enteric nervous system in oligoganglionic segments of HD morphologically differed from the one in hypoganglionosis. A suction rectal mucosal biopsy would be of no use in the diagnosis of hypoganglionosis.

Child, Preschool↗

PubMed1999

Acute respiratory failure associated with intrathoracic masses in neonates.

BACKGROUND: Intrathoracic masses are uncommon in children. Occasionally, they present with acute respiratory failure in the neonatal period. Although emergency resection usually is the treatment of choice, other modalities are sometimes necessary to stabilize the patient. METHODS: Seven neonates with intrathoracic masses were treated. Five had congenital cystic adenomatoid malformations (CCAM), 1 had a mediastinal teratoma, and 1 had a pneumatocele. These cases were reviewed retrospectively. RESULTS: Four of the 7 infants had respiratory failure in the neonatal period. A patient with a large mediastinal teratoma and 1 with a CCAM that increased rapidly after presentation underwent emergency operation, relieving respiratory distress. The other 2 large CCAMs presented with severe respiratory distress immediately after birth because of pulmonary hypoplasia. One neonate with a Stocker-I CCAM died after emergency resection. One more recent patient with a Stocker-III CCAM survived after successful treatment with delayed resection, performed 3 days after birth. Nitric oxide (NO), and extracorporeal membrane oxygenation (ECMO) were instituted as supportive care because of profound persistent fetal circulation (PFC). CONCLUSIONS: Acute respiratory failure associated with intrathoracic masses in neonates may be managed in 1 of 2 ways. A small mass that increases rapidly should be resected soon after presentation. In neonates with large masses with associated PFC, surgery can be delayed until the patient is stable. ECMO, NO, and high-frequency oscillation (HFO) can be used aggressively for stabilizing such neonates.

Extracorporeal Membrane Oxygenation↗

PubMed1999

Age-related changes in the brainstem auditory evoked potentials of the marmoset.

Changes in brain-stem auditory evoked potentials (BAEPs) with age were recorded in common marmosets (Callithrix jacchus) at the age of 1-2, 6-8 and 10-12 years. The auditory function was assessed by thresholds, latencies and amplitudes of BAEPs evoked by use of tone burst stimulations with audible frequencies ranging from 1 to 99 kHz. Prolongation of the latencies of later waves was observed in the animals at the age of 6-8 and 10-12 years at high frequencies, suggesting that aging in marmosets, as reported previously in humans and other animals, may cause earlier hearing loss at high frequency than at low frequency within the hearing range. At 10-12 years of age, the elevations of BAEP thresholds and the declines of BAEP amplitudes in older animals were also observed. As the differences in the parameters are small, it was suggested that only a moderate hearing loss occurred with onset late in life in common marmoset similar to that in CBA/Ca mice. Based on the results obtained in this study, BAEP latencies appear to be more sensitive indicators than BAEP thresholds and amplitudes for the early detection of hearing impairment.

Aging↗

PubMed1999

Topical treatment of nasal polyps with a beclomethasone dipropionate powder preparation.

The clinical efficacy of a topical preparation consisting of beclomethasone dipropionate (BDP) powder and a mucous membrane adhesive agent (hydroxypropylcellulose, HPC) for nasal polyps was examined. For 1 week, in 31 patients with bilateral nasal polyposis, the clinical efficacy of the topical BDP-HPC powder treatment was examined. The effect of this treatment on the histology of the nasal polyps was also investigated. The controls were six patients with bilateral nasal polyposis, who underwent identical surgery without prior use of the topical steroid therapy. Polyp shrinkage and improvement of some nasal symptoms (rhinorrhea, ease of noseblowing, and nasal blockage) were observed with the topical treatment. Significant clinical improvement (P < 0.05) was seen in the group treated with topical BDP HPC powder compared with the untreated control group. Histological examination of the excised nasal polyps in both groups demonstrated no clear differences attributable to BDP HPC powder. The topical treatment of nasal polyps with BDP HPC powder is a useful conservative therapy.

Administration, Topical↗

PubMed1999

Epidemiological research into nasopharyngeal carcinoma in the Chubu region of Japan.

Although patient death due to nasopharyngeal carcinoma (NPC) is increasing, few epidemiological analyses of NPC in Japan have been conducted since Sawaki's report in 1979. To determine the current incidence of NPC in Japan we examined NPC case in the Chubu area from 1986 to 1995. The leaders and reporting representatives of all otorhinolaryngological groups in the area were asked for their support of this epidemiological research. A total of 607 cases (445 male and 162 female NPC patients) were analyzed epidemiologically, histologically, serologically and clinically in this study. The incidence of NPC gradually increased with age. The mean age of the patients was 54.1 years. The age-standardized annual incidence in the Chubu region was 0.28 per 10(5) persons per year. The incidence in prefectures bordering Japan Sea (0.36) was significantly higher than that of prefectures facing the Pacific Ocean (0.21, P<0.05). On the basis of World Health Organization (WHO) histological criteria, 12%) of the cases were classified as WHO I, 54% as WHO II and 34% as WHO III. As for tumor origin, in 58% of the cases it originated posterosuperiorly, in 32% laterally and in 1% inferiorly. Tumor staging showed 4% to belong to stage I, 9% to stage II, 15% to stage III and 72% to stage IV. The positive rates of serum titers of the antibodies to Epstein Barr virus

Adolescent↗

PubMed1999

A case of bilateral eosinophilic granuloma in the temporal bone.

We present a case of bilateral eosinophilic granuloma in the temporal bone in a 47-year-old woman, who visited our hospital with a headache and a feeling of occlusion in her left ear. Her left tympanic membrane was slightly turbid and pure tone audiometry revealed mild left sensorineural deafness. CT disclosed a shadow of soft tissue in the left mastoid antrum and mastoid cells, which was indicative of marked destruction of the bone. Because MRI findings led us to suspect otitis media cholesteatoma, a mastoidectomy was performed. The mastoid antrum and mastoid cells were filled with easily bleeding granulation, and there was a wide range of bone deficit in the posterior cranial fossa. Histopathologically, the granulation tissue was an eosinophilic granuloma. Her postoperative clinical progress was good and she was discharged. However 2 months after discharge, she had a feeling of occlusion in the right ear and CT revealed a shadow in the right mastoid antrum and cells. Therefore, right tympanoplasty was performed and the same findings as in the left ear were obtained. A histopathological diagnosis of eosinophilic granuloma was made again. To date, there has been no recurrence.

Audiometry, Pure-Tone↗

PubMed1999

Simultaneous determination of ephedrine, pseudoephedrine, norephedrine and methylephedrine in Kampo medicines by high-performance liquid chromatography.

A simultaneous high-performance liquid chromatographic method for the determination of ephedrine, pseudoephedrine, norephedrine and methylephedrine (ephedrine alkaloids) in Kampo medicines which contain Ephedrae Herba was established. The analysis can be accomplished within 25 min with a Wakosil-II 5C18 HG column by isocratic elution using a mixture of water, acetonitrile and sodium dodecyl sulfate (65:35:0.4) as the mobile phase at a flow-rate of 1.0 ml min(-1), and detection at 210 nm. The detection limits of ephedrine alkaloids are 0.37-1.06 microM per injection (5 microl). This method was applied to analyze the quantities in eight Kampo decoctions; Mao-to, Makyo-yokukan-to, Makyo-kanseki-to, Yokuinin-to, Sho-seiryu-to, Keima-kakuhan-to, Kakkon-to and Kakkon-to-ka-senkyu-sin'i. The concentration (per Ephedrae Herba gram) of ephedrine alkaloids was higher in the Makyo-kanseki-to decoction than in the others. Calcium sulfate from Gypsum Fibrosum raised ephedrine alkaloids dissolution in the Makyo-kanseki-to decoction.

Central Nervous System Stimulants↗

PubMed1999

Characteristics of electrograms recorded at reentry circuit sites and bystanders during ventricular tachycardia after myocardial infarction.

OBJECTIVES: The purpose of this study was to determine the relation of isolated potentials (IPs) recorded during ventricular tachycardia (VT) to reentry circuit sites identified by entrainment. BACKGROUND: Reentry circuits causing VT late after myocardial infarction are complex. Both IPs and entrainment have been useful for identifying successful ablation sites, but the relation of IPs to the location in the reentry circuit as determined by entrainment has not been completely defined. METHODS: Data from catheter mapping of 70 monomorphic VTs in 36 patients with prior myocardial infarction were retrospectively analyzed. Entrainment followed by radiofrequency current (RF) ablation was performed at 384 sites. On the basis of entrainment, sites were classified as reentry circuit exit, central-proximal, inner or outer loop sites. Sites outside the circuit were divided into remote and adjacent bystanders. RESULTS: Isolated potentials were recorded at 50% (51 of 101) of reentry circuit exit, central and proximal sites as compared with only 8% (11 of 146, p < 0.001) of inner loop and outer loop sites and only 1.8% (2 of 106) of remote bystander sites (p < 0.001). Isolated potentials were also present at 45% of adjacent bystander sites. At central and proximal sites the presence of an IP increased the incidence of tachycardia termination by RF to 47.5% from 24% (p = 0.05). At exit sites tachycardia termination occurred frequently regardless of the presence or absence of IPs (45% vs. 48%, p = NS). Isolated potentials at exit, central and proximal sites had a shorter duration at sites where ablation terminated VT than at sites without termination (20.9 +/- 9.6 ms vs. 35.7 +/- 15.3 ms, p < 0.001). CONCLUSIONS: Isolated potentials are a useful guide to sites in the central-proximal region of the reentry circuit, but often fail to identify exit sites where ablation is successful. Entrainment and analysis of electrograms provide complementary information during mapping of VT.

Aged↗

PubMed1999

Enhanced expression and differential inducibility of soybean chalcone synthase genes by supplemental UV-B in dark-grown seedlings.

By developing gene-specific RT-PCR and using filters to allow transmission down to 290 nm (UV-B+) or blocking all radiation below 320 nm (UV-B(-)), the effect of UV-B+ and UV-B- light on expression of each of the presently known seven members of soybean chalcone synthase (CHS) gene family in dark-grown seedlings was analyzed. Dark expression was detectable already in 18 h dark-germinating embryos, with progressive increases on successive days, suggesting that chs belongs to a class of genes expressed very early during germination, and that the expression at this stage is either constitutive or induced by non-light-dependent factors present in the seed or made available following imbibition. Exposure of 18 h dark-germinating embryos to UV-B- or to UV-B+ light did not lead to an increase in chs signal. However, the 24 h dark-germinating embryos showed a distinct effect of UV-B+, interestingly coinciding with the stage when the head of seedlings was in the process of being pushed up above ground by stem elongation, suggesting the possibility of a developmental switch modulating the appearance of UV-B response. The response to UV-B- was most prominent in chs1 and almost silent in chs2, while the up-regulation by UV-B+ was most prominent in chs5 and chs6 and much less so in chs2. Interestingly, chs2 was noted to be the only member of the Gmchs gene family devoid of H-box, raising the possibility that the H-box may be a good indicator of the photo-inducibility of a chs gene.

Acyltransferases↗

PubMed1999

Globulins in protein supplements promote the development of preimplantation embryos.

PURPOSE: Our purpose was to investigate the effect of alpha- and beta-globulins contained in protein supplements on the development of preimplantation embryos. METHODS: Mouse one-cell embryos were cultured in medium supplemented with 4 mg/ml human serum albumin (HSA), 4 mg/ml HSA plus human globulins (0.2, 0.4, 0.8, and 1.6 mg/ml) that consisted predominantly of alpha- and beta-globulins, or 10% Plasmanate Cutter (PC). Blastocysts developed in media supplemented with these various protein sources were stained with Hoechst 33342 to determine the number of cells. RESULTS: Supplementation with 0.4 to 1.6 mg/ml globulins or PC significantly increased the rate of blastocyst development compared with that observed with the addition of HSA. Supplementation with globulins significantly increased the hatching rate in a dose-dependent manner. The number of cells in the blastocysts was significantly increased when the embryos were cultured with 0.8 mg/ml of the globulins or PC. CONCLUSIONS: The present observations suggest that alpha- and beta-globulins in protein supplements promote embryo development and hatching.

Alpha-Globulins↗

PubMed1999

Intragenic deletion in the gene encoding ubiquitin carboxy-terminal hydrolase in gad mice.

The gracile axonal dystrophy (gad) mouse is an autosomal recessive mutant that shows sensory ataxia at an early stage, followed by motor ataxia at a later stage. Pathologically, the mutant is characterized by 'dying-back' type axonal degeneration and formation of spheroid bodies in nerve terminals. Recent pathological observations have associated brain ageing and neurodegenerative diseases with progressive accumulation of ubiquitinated protein conjugates. In gad mice, accumulation of amyloid beta-protein and ubiquitin-positive deposits occur retrogradely along the sensory and motor nervous systems. We previously reported that the gad mutation was transmitted by a gene on chromosome 5 (refs 10,11). Here we find that the gad mutation is caused by an in-frame deletion including exons 7 and 8 of Uchl1, encoding the ubiquitin carboxy-terminal hydrolase (UCH) isozyme (Uch-l1) selectively expressed in the nervous system and testis. The gad allele encodes a truncated Uch-l1 lacking a segment of 42 amino acids containing a catalytic residue. As Uch-l1 is thought to stimulate protein degradation by generating free monomeric ubiquitin, the gad mutation appears to affect protein turnover. Our data suggest that altered function of the ubiquitin system directly causes neurodegeneration. The gad mouse provides a useful model for investigating human neurodegenerative disorders.

Amino Acid Sequence↗

PubMed1999

Association of 5' CpG demethylation and altered chromatin structure in the promoter region with transcriptional activation of the multidrug resistance 1 gene in human cancer cells.

Selection of human cells for resistance to vincristine or doxorubicin often induces overexpression of the multidrug resistance 1 gene (MDR1), which encodes the cell surface P-glycoprotein, as a result of gene amplification or transcriptional activation. However, the precise mechanism underlying such transcriptional activation of MDR1 remains unclear. The relation between methylation status of CpG sites in the MDR1 promoter region and transcriptional activation of MDR1 has now been investigated. The P-glycoprotein-overexpressing, multidrug-resistant KB/VJ300 and KB-C1 cells, which were established from human cancer KB3-1 cells, were examined; MDR1 is transcriptionally activated but not amplified in KB/VJ300 cells, whereas it is amplified in KB-C1 cells. Determination of the methylation status revealed that the MDR1 promoter region was hypomethylated in KB/VJ300 and KB-C1 cells, but hypermethylated in KB3-1 cells. Prior treatment of KB3-1 cells with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine resulted in a 90-fold increase in the frequency of vincristine-resistance. Of three lines, KB/CdR-1, KB/CdR-2, and KB/CdR-3, established from KB3-1 cells after exposure to 5-aza-2'-deoxycytidine, MspI/HpaII sites in the MDR1 promoter region were hypomethylated in KB/CdR-1 and KB/CdR-2 cells, but not in KB/CdR-3 cells. MDR1 mRNA expression was detected in KB/CdR-1 and KB/CdR-2 cells, but not in KB/CdR-3 cells. The binding of YB-1 and Sp1, transcription factors implicated in MDR1 expression, in the MDR1 promoter was not affected by the methylation status of a neighboring CpG sites. The MDR1 promoter region in KB/VJ300 cells showed an increased sensitivity to DNase I compared with that in KB3-1 cells, suggesting an altered chromatin structure. The methylation status of the promoter region may plays an important role in MDR1 overexpression and in acquisition of the P-glycoprotein-mediated multidrug resistance phenotype.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

Endoscopic management of gastric varices using a detachable snare and simultaneous endoscopic sclerotherapy and O-ring ligation.

BACKGROUND: Cyanoacrylate injection is highly effective and is regarded as the treatment of choice in bleeding gastric varices in Europe, but intravenous injection of cyanoacrylate is not allowed in the USA and Japan because it may cause embolisms in other organs. Accordingly, we developed a new endoscopic combined treatment of endoscopic management of gastric varices using a detachable snare (EVLs) and simultaneous endoscopic sclerotherapy and O-ring ligation (EISL) (i.e. EVLs + EISL), and we prospectively evaluated its efficacy and safety. METHODS: Gastric varices were ligated with the loop of a detachable snare that opened to a diameter of 4 cm (EVLs). Then the residual varices around the ligated portion were sclerosed by ethanolamine oleate and the injected vessel was ligated using a pneumo-activated EVL device (EISL). The EVLs + EISL was performed in 35 patients: on an emergency basis in eight patients, on an elective basis in six patients and as primary prophylaxis in 21 patients. Liver function was classified as Child-Pugh class A in 12 patients, class B in 12 patients and class C in 11 patients. RESULTS: Endoscopic disappearance of gastric varices was obtained in 97.1% of the patients and they regressed in all patients. Haemostasis was achieved in all eight emergency cases. The 2-year cumulative non-recurrence rate was 85%, the 2-year cumulative non-bleeding rate was 92% and the 2-year cumulative survival was 80%. No patients died of bleeding from gastric varices. There were no serious short-term complications, such as haemorrhage, gastro-oesophageal perforation, ileus, or renal impairment. CONCLUSION: Combined EVLs + EISL appears to be a useful treatment for gastric varices due to its safety and good clinical outcome.

Endoscopy↗

PubMed1999

Evaluation of new monoclonal anti-MyoD1 and anti-myogenin antibodies for the diagnosis of rhabdomyosarcoma.

New monoclonal anti-MyoD1 and anti-myogenin antibodies were evaluated immunohistochemically to determine whether they are useful in discriminating rhabdomyosarcoma (RMS) from other soft tissue tumors in routinely processed sections. Neither MyoD1 nor myogenin was expressed in normal, mature striated muscle. In RMS, nuclear expression of MyoD1 and myogenin was found in 82 and 80% of non-overlapping cases, respectively. MyoD1 was generally expressed in small, primitive tumor cells, and larger cells exhibiting morphological evidence of skeletal muscle differentiation failed to express positive nuclear immunostaining. Positive nuclear staining for myogenin was stronger than that for MyoD1 in cases with abundant differentiated tumor cells, but was less prominent in cases in which small, primitive tumor cells predominated. No leiomyosarcomas, Ewing's sarcomas/peripheral primitive neuroectodermal tumors or other soft tissue tumors exhibited nuclear expression of MyoD1 or myogenin. In conclusion, both anti-MyoD1 and anti-myogenin antibodies are useful for diagnosing RMS and for discriminating RMS from other soft tissue tumors.

Actins↗

PubMed1999

Intestinal adaptation in pediatric patients with short-bowel syndrome.

The purpose of this study is to evaluate 12 pediatric short-bowel syndrome (SBS) patients experienced at Osaka University Hospital and its affiliated hospitals and to study the intestinal length for achieving intestinal adaptation and the metabolic characteristics. The length of the residual small intestine ranged from 0 to 75 cm with an average of 47 cm and an ileocecal valve had been resected in five cases. Total parenteral nutrition (TPN) was started immediately after operation and was gradually substituted by enteral nutrition. No patient died during the follow-up period. Eight of 12 patients could be weaned from TPN with residual intestinal length of 27 to 75 cm (mean 57 cm). Four patients with the residual intestine of 0 to 45 cm (mean 22 cm) were unable to achieve intestinal adaptation. The rate of catheter-related sepsis per 1000 catheter days was 0.63. Fatty liver was detected in two cases, but no patient developed progressive liver failure. Plasma arginine and citrulline were decreased in patients who were unable to achieve intestinal adaptation. Our nutritional support program provided excellent survival for pediatric SBS patients primarily due to the low incidence of catheter-related sepsis and no episode of severe liver disease. Patients with more than 16 cm of residual intestinal length can be expected to be weaned from TPN.

Adaptation, Physiological↗

PubMed1999

Expression of integrins in squamous cell carcinoma of the oral cavity. Correlations with tumor invasion and metastasis.

Integrins are cell adhesion molecules that mediate the cell to extracellular matrix interactions. We sought to determine whether the integrin expression on tumor cells is associated with invasive and metastatic potential. First, in 8 cell lines of oral squamous cell carcinoma, 4 of which were metastatic in nude mice and 4 of which were not, integrin expression was examined. When these cell lines were cultured in vitro or transplanted into the tongues of nude mice, the metastatic cell lines tended to show a stronger expression of alpha 2, alpha 3, alpha 5, and alpha 6 integrins than did the nonmetastatic cell lines. Second, integrin expression was immunohistochemically examined in 65 biopsy specimens of primary oral squamous cell carcinoma. In invasive or metastatic cases, a marked expression of alpha 2, alpha 3, alpha 5, and alpha 6 integrins was frequently observed. The association of integrin expression with the mode of tumor invasion and nodal involvement was found to be statistically significant. These results suggest that integrin expression is closely associated with tumor invasion and nodal involvement in oral squamous cell carcinoma.

Animals↗

PubMed1999

Late-onset familial amyloid polyneuropathy type I (transthyretin Met30-associated familial amyloid polyneuropathy) unrelated to endemic focus in Japan. Clinicopathological and genetic features.

Clinicopathological and genetic features were assessed on 35 Japanese families affected by late-onset familial amyloid polyneuropathy type I (transthyretin Met30-associated familial amyloid polyneuropathy, FAP TTR Met30) whose siblings were unrelated to endemic Japanese foci. In these patients (50 years or older), the most common initial symptom was paraesthesias in the legs. Autonomic symptoms were generally mild and did not seriously affect daily activities. The male-to-female ratio was extremely high (10.7 : 1). A family history was evident in only 11 out of 35 families, and other patients were apparently sporadic. The rate of penetrance was very low. Symptomatic siblings of familial cases showed a late age of onset, male preponderance and clinical features similar to those of the probands. Asymptomatic carriers, predominantly female, were detected relatively late in life. The geographical distribution of these late-onset, FAP TTR Met30 cases was scattered throughout Japan. In three autopsy cases and 20 sural nerve biopsy specimens, neurons in sympathetic and sensory ganglia were relatively preserved. Amyloid deposition was seen in the peripheral nervous system, particularly in the sympathetic ganglia, dorsal root ganglia and proximal nerve trunks such as sciatic nerve. These abnormalities were milder than those seen in typical early-onset FAP TTR Met30, as observed in two Japanese endemic foci of this disease. While axonal degeneration was prominent in myelinated fibres, resulting in severe fibre loss, unmyelinated fibres were relatively preserved. Our cases of late-onset FAP TTR Met30 showed features distinct from those of typical early-onset FAP TTR Met30 that occurred in the two Japanese endemic foci. Factors responsible for clinicopathological differences between these two forms of FAP TTR Met30 need to be identified.

Action Potentials↗

PubMed1999

Enhancement of glutathione S-transferase placental-form positive liver cell foci development by microcystin-LR in aflatoxin B1-initiated rats.

The objective of this study was to elucidate whether microcystin-LR (MC-LR), a hepatotoxic blue-green algal toxin in drinking water, is carcinogenic or possesses the ability to modulate aflatoxin B1 (AFB1)-induced hepatocarcinogenicity. In a medium-term liver bioassay, male Fischer 344 rats were given a single i.p. injection of diethylnitrosamine (DEN, 200 mg/kg) followed by an i.p. injection of MC-LR for 6 weeks after 2 weeks of DEN treatment. To study the synergism between AFB1 and MC-LR, DEN-treated rats were given an i.p. injection of AFB1 (0.5 mg/kg) dissolved in dimethyl sulfoxide (DMSO) followed by MC-LR at 2 weeks after the treatment. In a separate experiment, the rats were first given AFB1 (0.5 mg/kg) and 2 weeks later an i.p. injection of 1 or 10 microg/kg of MC-LR twice a week for 6 weeks. Most rats were subjected to a two-thirds partial hepatectomy (PH) at week 3 and were killed under anesthesia at week 8. Liver sections were analyzed for glutathione S-transferase placental form (GST-P) expression, and subjected to histopathological examination for phenotypic alteration of hepatocellular foci. In rats that did not receive DEN, MC-LR did not cause a significant increase in the numbers of GST-P-positive foci, whereas AFB1 induced a slight increase in GST-P-positive foci development. In rats given DEN, MC-LR enhanced the expression of GST-P-positive foci, as did AFB1 but no synergism was observed. Histopathological analysis revealed that the area of eosinophilic foci, a biomarker for preneoplastic liver lesion, markedly increased because of MC-LR. In rats given AFB1 as an initiator, treatment with MC-LR resulted in a synergistic increase in the development of GST-P-positive foci. These results suggest that the hepatocarcinogenicities of MC-LR and AFB1 can be predicted in experimental animals with a medium-term bioassay. Furthermore, tumor promoting activity of MC-LR was demonstrated in rats treated with AFB1.

Aflatoxin B1↗