Kinematic Factors Associated with Hitting Hurdles During the Initial Phase of a 110-m Hurdle Race.

This study aimed to clarify the kinematic factors for the cause and effect of hitting hurdles during the initial phase of a 110-m hurdle run. Nine experienced male hurdlers participated in this study (body height: 1.74 ± 0.04 m, body mass: 67.4 ± 5.9 kg, age: 20.2 ± 1.4 years, personal best: 15.21 ± 0.47 s, seasonal best: 15.33 ± 0.55 s). Hurdlers undertook 12 trials of the initial phase of hurdling from the start to the second hurdle landing. Dual-sided sagittal plane motion was obtained from images from two high-speed cameras operating at 120 Hz. One 'hit' trial which had the largest horizontal displacement of markers fixed on the hurdle and one 'non-hit' trial which had the fastest time of hurdle clearance were extracted for each participant. Kinematic variables were compared between the two trials. Significantly lower height of the whole-body centre of mass at the take-off was found as a possible cause of hitting hurdles, caused by insufficient swing-up of the lead leg thigh. In contrast to conventional understanding, take-off velocity, take-off distance and the take-off angle were comparable between the 'hit' trial and 'non-hit' trial. Regarding the effect of hitting hurdles, it was observed that running velocity during hurdling was not substantially reduced. However, several characteristic movements were identified that might induce inefficient motion to re-accelerate running velocity during the following landing steps.

High serum pentosidine in branch atheromatous disease among small vessels occlusion.

BACKGROUND: Cerebral branch atheromatous disease (BAD) are more likely to experience progressing stroke and neurological deterioration compared with lacunar infarction, although these small vessels occlusions are difficult to discriminate in acute phase of ischemic stroke. Advanced glycation end products including pentosidine have been implicated in atherosclerosis, and were associated with atheroma plaque progression. However, little is known about a relationship between serum pentosidine and small vessels occlusion. METHODS: Serum pentosidine levels were measured in 56 patients (BAD: N.=21; lacunar: N.=35) with small vessels occlusion among consecutive 208 patients with acute ischemic stroke at initial hospitalization as well as other risk factors of stroke. Univariate and multivariate logistic regression analyses were performed to analyze relationship between risk factors including pentosidine and small vessels occlusion. Sensitivity and selectivity of pentosidine to discriminate BAD from lacunar were calculated. RESULTS: Serum pentosidine was significantly higher in BAD group than lacunar group (0.081±0.081 µg/mL and 0.046±0.043 µg/mL, P<0.05). In the univariate logistic regression analyses, BAD was significantly related to high serum pentosidine (P=0.01), absence of dyslipidemia (P=0.04), and worse outcome measured by modified Rankin Scale (P=0.03). Multivariate logistic regression analysis showed that only high level of serum pentosidine was the independent risk factor for BAD (P=0.03). Sensitivity and specificity were 90% and 44%, respectively. CONCLUSIONS: High level of serum pentosidine in acute phase of stroke was associated with BAD, which led to worse outcome among patients with small vessels occlusion.

Serum pentosidine, an advanced glycation end product, indicates poor outcomes after acute ischemic stroke.

BACKGROUND: An advanced glycation end product has been implicated in a wide range of pathologic conditions, including diabetes mellitus, chronic kidney diseases, cardiovascular diseases, and arteriosclerosis. Little is known about its relationship with cerebral ischemia. The authors investigated serum levels of pentosidine and outcomes of patients with acute ischemic stroke METHODS: Serum pentosidine levels were measured in 83 patients with acute ischemic stroke at initial hospitalization and other risk factors of stroke. Outcomes of patients at 30 days from hospitalization were assessed by using modified Rankin Scale (mRS) score. Univariate and multivariate logistic regression analyses were performed to analyze the relationship between pentosidine and patient outcomes. RESULTS: In the univariate logistic regression analyses, poor outcomes, defined as mRS scores of >2, at 30 days were significantly related to high serum pentosidine (P = .001), type of stroke (P = .045), old age (P = .02), male sex (P = .042), and the absence of dyslipidemia (P = .02). Deterioration of mRS was significantly correlated with high serum pentosidine (P = .003) and creatinine (P = .02). Multivariate logistic regression analysis showed that a high level of serum pentosidine was the only independent risk factor for poor outcomes (P = .004) and deterioration of mRS (P = .01) at 30 days. CONCLUSIONS: A high level of serum pentosidine indicates poor and worse outcomes 30 days after acute ischemic stroke. This new biomarker is useful for risk stratification of patients with acute ischemic stroke.

A medium-term, rapid rat bioassay model for the detection of carcinogenic potential of chemicals.

The Ito Liver Model and the Ito Multi-organ Model are used in conjunction and constitute an efficient and rapid bioassay for the identification of both genotoxic and nongenotoxic carcinogenic chemicals. The Ito Liver Model is an 8-week bioassay system that uses the number and size of foci of hepatocytes positive for glutathione S-transferase placental form (GST-P) as the end-point marker. One hundred fifty-nine compounds were tested using the Ito Liver Model: 61 of 66 hepatocarcinogens tested positive, and 10 of 43 nonliver carcinogens were also positive. The false-positive detection of noncarcinogens was low; a single false-positive result was obtained from the 50 noncarcinogens tested. Since more than half of all known carcinogens are hepatocarcinogens in rodents, the initial 8-week bioassay is able to detect most carcinogens. The Ito Multi-organ Model is a 28-week bioassay system for the detection of carcinogens that were not identified by the Ito Liver Model. Results are evaluated by preneoplastic and neoplastic lesions in major organs. Forty-four compounds were tested using the Ito Multi-organ Model: 17 out of 17 liver carcinogens were positive, and 19 out of 22 (86%) nonliver carcinogens were positive. None of the five noncarcinogens tested positive.

Modifying effects of 1'-acetoxychavicol acetate (ACA) and the novel synthetic retinoids Re-80, Am-580 and Am-55P in a two-stage carcinogenesis model in female rats.

Effects of dietary administration of 1'-acetoxychavicol acetate (ACA) and the novel synthetic retinoids 4-[1-hydroxy-3-oxo-3-(5,6,7,8-tetrahydro-3-hydroxy-5,5,8,8-tetramethyl-2-naphthalenyl)-1-propenyl]benzoic acid (Re-80); 4-[(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)carboxamido]benzoic acid (Am-580); and 6-[(3,5-di-tert-butylphenyl) carbamoyl]nicotinic acid (Am-55P) were examined using a two-stage rat carcinogenesis model. A total of 190 female SD rats was treated sequentially with 1,2-dimethylhydrazine (DMH, s.c.); 7,12-dimethylbenz(a)anthracene (DMBA, i.g.); and 2,2'-dihydroxy-di-n-propylnitrosamine (DHPN, in the drinking water) during the first three weeks (DDD-initiation), and an additional 60 rats received the vehicle alone (non-initiation). One week after the completion of the initiation period, they were divided into nine groups and administrated Re-80 (at dose levels of 1.0 or 0.4 ppm), Am-580 (20 or 4 ppm), Am-55P (20 ppm), ACA (100 ppm), all-trans-retinoic acid (10 or 2 ppm) or no supplement in the diet for 33 weeks, until survivors were euthanatized at week 37 weeks. After DDD-initiation, all-trans-retinoic acid at the high dose delayed the development of mammary tumors. The multiplicity of colon tumors in the group fed Am-55P and the incidences of nephroblastomas with ACA or Am-580 were decreased as compared with the control values, but the other chemicals had no modifying effects on tumor development in any organs. Thus, among ACA and the novel synthetic retinoids tested, only Am-55P showed a weak inhibitory effect on a neoplasm of general interest under the present experimental conditions.

Fulminant varicella infection complicated with acute respiratory distress syndrome, and disseminated intravascular coagulation in an immunocompetent young adult.

Primary varicella infection in immunocompetent adults is very rare, but it has a high mortality rate because of serious complications. We describe a case of varicella infection in a previously healthy young adult complicated with acute respiratory distress syndrome (ARDS), rhabdomyolysis, acute hepatitis and disseminated intravascular coagulation (DIC). Acyclovir was administered for varicella infection and the ARDS was successfully treated with steroidpulse therapy, hemofiltration and a mechanical respiratory support with a positive end-expiratory pressure. Early administration of antiviral agents and extensive management were thought to be necessary for such patients with severe complications.

Expression of ephrin-B1 in hepatocellular carcinoma: possible involvement in neovascularization.

BACKGROUND/AIMS: Hepatocellular carcinoma (HCC) is, in general, a hypervascular tumor. Ephrin/Eph molecules have recently been reported as possible regulators of angiogenesis. We aimed to clarify the role of ephrin-Bs (B1-B3) in the progression of HCC. METHODS: Ephrin-Bs transcripts in 26 HCC and their corresponding non-tumor liver tissues were analyzed by the quantitative reverse transcription-polymerase chain reaction. We established ephirn-B1 overexpressing cell in a human HCC cell line, PLC/PRF/5 cell, and their in vivo growth monitored after subcutaneous injection into nude mice. Neovascularization in the inoculated tumors was evaluated by the immunohistochemical staining of CD31. The migration and proliferation of human umbilical vein endothelial cells (HUVECs) in response to soluble ephrin-B1-Fc was examined. RESULTS: The expression of the ephrin-B1 transcript but not -B2 and -B3 transcripts was significantly higher in HCC tissues than in non-tumor tissues (P<0.05). The ephrin-B1 overexpressing cells developed tumors more rapidly than controls in vivo (P<0.05), although in vitro cell growth was not affected. The tumor vessel number significantly increased in the ephrin-B1 overexpressing tumors (P<0.0001). In addition, in vitro studies revealed that ephrin-B1 induced migration and proliferation of HUVECs. CONCLUSIONS: Ephrin-B1 may be involved in in vivo tumor progression by promoting neovascularization in HCC.

A medium-term rat liver bioassay for rapid in vivo detection of carcinogenic potential of chemicals.

A reliable medium-term bioassay system for rapid detection of carcinogenic potential of chemicals in the human environment has been developed. The 8-week-protocol consists of 2 stages; male F344 rats are given a single intraperitoneal injection of diethylnitrosamine (200 mg/kg) for initiation of liver carcinogenesis, followed by a 6-week test chemical treatment starting 2 weeks thereafter. Test chemicals are usually given in the diet or the drinking water and in the 2nd week of test chemical treatment, all rats are subjected to two-thirds partial hepatectomy in order to induce regenerative cell replication. The end-point marker is the glutathione S-transferase placental form (GST-P)-positive hepatic focus, the numbers and sizes of which are analyzed using an image-analyzer and expressed as values per unit liver section (1 cm2). When the yield of GST-P-positive foci is significantly enhanced (P<0.05) over the control value, a chemical is judged to possess carcinogenic or promotion potential for the liver. Among 313 chemicals already tested in this system in our laboratory, 30/31 (97%) mutagenic hepatocarcinogens and 29/33 (88%) non-mutagenic hepatocarcinogens gave positive results. Ten out of 43 (23%) agents known to be carcinogenic in organs other than the liver were also positive. It is particularly important that only one of 48 non-carcinogens gave a very weak positive result, so that the system has a very low false-positivity rate. It is now well documented that the assay system is highly effective for detecting hepatocarcinogens, bridging the gap between traditional long-term carcinogenicity tests and short-term screening assays. At the Fourth International Conference on Harmonization, our medium-term liver bioassay based on an initiation and promotion protocol was recommended in the guidelines as an acceptable alternative to the long-term rodent carcinogenicity test.

Angiotensin II stimulates the nuclear translocation of Smad2 and induces PAI-1 mRNA in rat hepatic stellate cells.

It has recently been reported that angiotensin II (ANGII) stimulates gene expression of transforming growth factor-beta1 (TGF-beta1) and is involved in hepatic fibrosis. This effect is thought to be caused through ANGII type 1 receptor (ATR1). However, a role of ANGII at the postreceptor levels of TGF-beta1 signaling has not been identified. To clarify the role of ANGII on hepatic fibrosis, we investigated the effect of ANGII on rat hepatic stellate cells (HSCs). HSCs were isolated from male Sprague-Dawley rats. TGF-beta1 and matrix protein gene expression in HSCs was assessed by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) using SYBR Green I. The nuclear translocation of Smad2 in HSCs after 20 min ANGII stimulation was analyzed by Western blotting. ANGII was found to induce TGF-beta1 and matrix protein gene expression in HSCs. The nuclear translocation of Smad2 in HSCs was also induced by ANGII stimulation. These effects of ANGII were almost completely blocked by the ATR1 antagonist, CS-866. ANGII induces TGF-beta1 and matrix protein mRNA, and stimulates rapid nuclear translocation of Smad2 in rat HSCs through ATR1, which indicates that the ATR1 blockade represents a novel approach for the possible prevention of hepatic fibrosis.

Liver regeneration in heparin-binding EGF-like growth factor transgenic mice after partial hepatectomy.

BACKGROUND & AIMS: Heparin-binding epidermal growth factor-like growth factor (HB-EGF), a member of the EGF family, is synthesized in the form of a membrane-anchored precursor (proHB-EGF), which subsequently is processed proteolytically to mature HB-EGF. This study describes the effects of HB-EGF on liver regeneration after 70% partial hepatectomy in proHB-EGF transgenic mice with liver-specific expression. METHODS & RESULTS: No significant differences in liver/body weight ratios and in bromodeoxyuridine (BrdU)-labeling index (the ratios of BrdU-positive hepatocyte nuclei) were found between adult transgenic and wild-type mice. However, in regenerating liver after partial hepatectomy, transgenic mice had higher liver/body weight ratios than wild-type mice and at 120 hours reached a level equal to that before partial hepatectomy. The BrdU-labeling index was about 5 times higher in the livers of transgenic mice compared with the wild type (51.5% vs. 10.2%, respectively; P < 0.01) at 48 hours after partial hepatectomy. Activation of microtubule-associated protein kinase after partial hepatectomy was higher and earlier in the transgenic mice as compared with the wild-type mice. Soluble HB-EGF was increased in the liver (at 8 min) after partial hepatectomy, indicating that the shedding of proHB-EGF occurred after partial hepatectomy. CONCLUSIONS: The transgenic expression of HB-EGF accelerates the proliferation of hepatocytes after partial hepatectomy, suggesting that HB-EGF functions as a hepatotrophic factor in vivo.

A critical review of the toxicological effects of carrageenan and processed eucheuma seaweed on the gastrointestinal tract.

Carrageenan is a high-molecular-weight, strongly anionic polymer derived from several species of red seaweed that is used for the textural stabilization of foods. Processed Eucheuma Seaweed (PES) is a form of carrageenan with a higher cellulose content. Food-grade carrageenan has a weight average molecular weight greater than 100,000 Da, with a low percentage of smaller fragments. Carrageenan is not degraded to any extent in the gastrointestinal tract and is not absorbed from it in species examined, such as rodents, dogs, and non-human primates. Systemically administered carrageenan has been reported to have a variety of effects, particularly on the immune system, but these are not pertinent to orally administered carrageenan. The substance poligeenan (formerly referred to as degraded carrageenan) is not a food additive. It exhibits toxicological properties at high doses that do not occur with the food additive carrageenan. In-long term bioassays, carrageenan has not been found to be carcinogenic, and there is no credible evidence supporting a carcinogenic effect or a tumor-promoting effect on the colon in rodents. Also, like many dietary fibers, there is significant cecal enlargement in rodents when it is administered at high doses, but this does not appear to be associated with any toxicological consequences to the rodent. Many toxicological studies on carrageenan have involved administration at doses in excess of today's standards for dietary feeding levels in bioassays, and they are orders of magnitude in excess of those to which humans are exposed. Previous reviews of carrageenan and PES by the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives (JECFA) have recommended a group allowable daily intake (ADI) of "not specified". The lack of carcinogenic, genotoxic, or tumor-promoting activity with carrageenan strongly supports continuing such an ADI, and JECFA, during its most recent review in 2001, continued this recommendation. The various toxicological studies related to orally administered food-grade carrageenan are summarized along with a brief discussion of critical factors in intestinal carcinogenesis.

Genetically modified foods: hazard identification and risk assessment. Session summary.

During a Joint Society of Toxicologic Pathology (STP)/International Federation of Societies of Toxicologic Pathologists (IFSTP) International Symposium, held between June 24 and 28, 2001, in Orlando, FL, USA, there was a session entitled as "Genetically Modified Foods: Hazard Identification and Risk Assessment". The purpose of this session was to present and discuss the current situations in the US, European Union and Japan for the public concerns, safety assessments and regulations on genetically modified (GM) products used as foods or food ingredients. Assuming the wide and fast growing of the usage of GM products, it is the duty for us as toxicologic pathologists, to supply reliable data on their safety and possible risks or hazards as a world-wide basis to not only governments or regulatory agencies but also general public of our countries.

Frequent impairment of the spindle assembly checkpoint in hepatocellular carcinoma.

BACKGROUND: Chromosomal instability (CI) leading to aneuploidy is one form of genetic instability, a characteristic feature of various types of cancers. Recent work has suggested that CI can be induced by a spindle assembly checkpoint defect. The aim of the current study was to determine the frequency of a defect of the checkpoint in hepatocellular carcinoma (HCC) and to establish whether alterations of genes encoding the checkpoint were associated with CI in HCC. METHODS: Aneuploidy and the function of the spindle assembly checkpoint were examined using DNA flow cytometry and morphologic analysis with microtubule disrupting drugs. To explore the molecular basis, the authors examined the expression and alterations of the mitotic checkpoint gene, BUB1, using Northern hybridization and direct sequencing in 8 HCC cell lines and 50 HCC specimens. Furthermore, the authors examined the alterations of other mitotic checkpoint genes, BUBR1, BUB3, MAD2B, and CDC20, using direct sequencing in HCC cell lines with aneuploidy. RESULTS: An impaired spindle assembly checkpoint was found in five (62.5%) of the eight aneuploid cell lines. Transcriptional expressions of the BUB1 gene appeared in all cell lines. While some polymorphic base changes were noted in BUB1, BUBR1, and CDC20, no mutations responsible for impairment of the mitotic checkpoint were found in either the HCC cell lines or HCC specimens, which suggests that these genes did not seem to be involved in tumor development in HCC. CONCLUSIONS: The loss of spindle assembly checkpoint occurred with a high frequency in HCC with CI. However, other mechanisms might also contribute to CI in HCC.

NF-kappaB activation in non-parenchymal liver cells after partial hepatectomy in rats: possible involvement in expression of heparin-binding epidermal growth factor-like growth factor.

BACKGROUND/AIMS: Nuclear factor (NF) B activation plays a critical role in the initiation of liver growth after partial hepatectomy (PH). However, the issue of where specifically NF-B is activated is unclear. We previously reported that heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a hepatotrophic factor. The aims of this study were to identify NF-B-activated cells and to clarify their involvement in HB-EGF expression after PH. METHODS: Using rats, a two-thirds PH was performed, after which NF-B-activated cells and HB-EGF-positive cells were identified by Southwestern histochemistry or immunohistochemistry. NF-B binding activity and HB-EGF gene expression were analyzed in rat hepatocytes and non-parenchymal cells (NPC) in primary culture. RESULTS: NF-B was activated in Kupffer cells and sinusoidal endothelial cells prior to activation in hepatocytes. HB-EGF immunoreactivity was detected after NF-B activation in the sinusoidal cells from those localized in the periportal zones of hepatic lobules. HB-EGF gene expression by tumor necrosis factor was accompanied by an increase in NF-B binding activity in NPC but not in hepatocytes in primary culture, which was abolished by pyrrolidine dithiocarbamate, an inhibitor of NF-B activation. CONCLUSIONS; NF-B was activated in NPC prior to activation in hepatocytes. NF-B activation may be involved in HB-EGF expression in NPC after PH.

Prevention by natural food anthocyanins, purple sweet potato color and red cabbage color, of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-associated colorectal carcinogenesis in rats initiated with 1,2-dimethylhydrazine.

The potential of purple sweet potato color (PSPC) and red cabbage color (RCC), natural anthocyanin food colors, to modify colorectal carcinogenesis was investigated in male F344/DuCrj rats, initially treated with 1,2-dimethylhydrazine (DMH) and receiving 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in the diet. After DMH initiation, PSPC and RCC were given at a dietary level of 5.0% in combination with 0.02% PhIP until week 36. No PSPC or RCC-treatment-related changes in clinical signs and body weight were found. Incidences and multiplicities of colorectal adenomas and carcinomas in rats initiated with DMH were clearly increased by PhIP. In contrast, lesion development was suppressed by RCC, or tended to be inhibited by PSPC administration. Furthermore, in the non-DMH initiation groups, induction of aberrant crypt foci (ACF) by PhIP was significantly decreased by RCC supplementation. The results thus demonstrate that while PhIP clearly exerts promoting effects on DMH-induced colorectal carcinogenesis, these can be reduced by 5.0% PSPC or 5.0% RCC in a diet under the present experimental conditions.

Activation of signal transducer and activator transcription 3 and expression of suppressor of cytokine signal 1 during liver regeneration in rats.

BACKGROUND/AIMS: Recent work has shown that the signal transducer and activator of transcription (STAT) 3 activation is important for the initiation of the proliferative response following partial hepatectomy (PH). However, the issue of where STAT3 is activated and how it is regulated is unclear. The aims of this study were to identify STAT3-activated cells and to clarify the expression of suppressor of cytokine signal (SOCS), a negative feedback molecule of STAT3, after PH. METHODS: STAT3-activated cells and SOCS1-positive cells were identified by immunohistochemistry after a two-thirds PH in rats. SOCS mRNA was examined by Northern analysis. RESULTS: STAT3 was activated in hepatocytes from those localized in the periportal zones of hepatic lobules after PH. STAT3 activation was also detected in Kupffer cells and sinusoidal endothelial cells prior to its detection in hepatocytes. After STAT3 activation, SOCS1 protein in response to PH was detected immunohistochemically in regenerating liver. SOCS1 and SOCS3 mRNA were induced in regenerating liver after PH. CONCLUSIONS: STAT3 signaling can occur in Kupffer cells and sinusoidal endothelial cells prior to in hepatocytes from those localized in the periportal zones. SOCS1 as well as SOCS3 may regulate STAT3 signaling negatively after PH.

Lack of enhancing effect of two Kampo medicines, Sho-saiko-to (TJ-9) and Sairei-to (TJ-114), on rat urinary bladder carcinogenesis initiated with N-butyl-N-(4-hydroxybutyl)nitrosamine.

The modifying potential of two Kampo medicines (Japanese traditional herbal medicines), Sho-saiko-to (TJ-9) and Sairei-to (TJ-114), on urinary bladder carcinogenesis in male F344 rats initiated with N-butyl-N-(4-hydroxybutyl)- nitrosamine (BBN) was evaluated. Groups of 20 animals were given 0.05% BBN in their drinking water for 4 weeks and then 0.7 or 2.8% TJ-9, 0.9 or 3.6% TJ-114, or 3.0% sodium bicarbonate (NaHCO(3)) as a positive control substance in their diet for 32 weeks. All rats were killed after 36 weeks and examined histopathologically. No adverse effects of the test compounds were found in terms of survival, clinical sign, and body weight. Administration of 0.7 and 2.8% TJ-9 and 0.9 and 3.6% TJ-114 in the diet did not affect the incidences or extent of PN hyperplasia in the BBN-treated rats. Incidences and multiplicities of papillomas were also not affected in rats fed 0.7 or 2.8% TJ-9 and 0.9% TJ-114, while they were significantly decreased in animals given 3.6% TJ-114 in the diet. The results thus demonstrated that neither of the test chemicals exerted any promotional activity on urinary bladder carcinogenesis, in clear contrast to NaHCO(3). In addition, bladder carcinogenesis was reduced by 3.6% TJ-114 in the diet, under the present experimental conditions.

Inhibition by Vitamin E of Cholangiocarcinoma Induction due to Combined Nitrite and Aminopyrine.

The present experiment was conducted to assess the influence of vitamin E, given in the diet at 0.5 or 1%, on induction of lesions in the Syrian hamster liver by long term combined administration of sodium nitrite and aminopyrine in the drinking water. Inhibition of both cholangiofibrosis and cholangiocarcinoma development, as well as a reduction in hepatocellular nodules was the result. The underlying mechanisms presumably involve alteration of endogenous dimethylnitrosamine formation by the vitamin, with clear implications for prevention in the human environment.

Marriage of Surrogate Markers with Medium Term Tests for Carcinogenicity and Modification Potential.

Given the immense variety of compounds being developed for introduction into the human environment, reliable medium term alternatives to traditional long term rodent test protocols for carcinogen risk assessment are a high priority. In vivo models are necessary because it has been well established that there is a lack of complete correlation between mutagenicity and carcinogenicity. Optimally, they should be able to detect not only complete carcinogenic or promoting potential, but also any ability to inhibit neoplasia. In order to be effective, they must take into account the detailed available knowledge on mechanisms of action of carcinogens and modulating agents. To allow shortening of the time period, attention must be concentrated on preneoplaqstic lesions and other surrogate For the liver, a uniquely comprehensive set of background data have already been accumulated with the Ito model, for which, has a solid scientific basis, with quantitation of glutathione S transferase positive foci as the preneoplasia-based surrogate endpoint (PSE). A very practical candidate for routine application, its predictive power, flexibility and capacity to incorporate a range of mechanism-based surrogate endpoints (MSEs) can also provide a powerful tool for attainment of the twin goals of detecting carcinogenic agents and identifying promising chemopreventors.

A detecçäo de substâncias cancerígenas em estudos experimentais / The detection of carcinogens substances in experimental study

Atualmente, o método mais importante para a identificaçao de agentes químicos cancerígenos é o teste de longa duraçao in vivo, com roedores. No Brasil nao há condiçoes para a sua execuçao, devido à inexistência de especialistas e de infra-estrutura adequada. Em conseqüência, o país é dependente dos conhecimentos gerados no exterior sobre o risco que determinados compostos químicos impoem às populaçoes e ao meio ambiente. Por outro lado, as desvantagens inerentes ao protocolo deste teste, como a complexidade na execuçao, o tempo prolongado para obtençao das conclusoes e custo elevado, entre outras, levam à procura de alternativas mais convenientes. No presente trabalho sao apresentados dois testes in vivo para detecçao de cancerígenos químicos em ratos, que têm como vantagens o tempo de execuçao e o custo, menores que os do teste convencional. Os sistemas propostos têm só-o-fígado ou vários-órgaos-simultâneos como órgaos-alvo do eventual cancerígeno. Ambos os testes foram avaliados respectivamente com centenas e dezenas de substâncias químicas e reproduziram os resultados já obtidos em testes de longa duraçao, mostrando forte consistência biológica. Os autores destacam as vantagens de sua adoçao em países como o Brasil e propoem sua inclusao na seqüência de testes necessários para caracterizar um agente químico como cancerígeno.