Cardioprotective properties of OMT-28, a synthetic analog of omega-3 epoxyeicosanoids

OMT-28 is a metabolically robust small molecule developed to mimic the structure and function of omega-3 epoxyeicosanoids. However, it remained unknown to what extent OMT-28 also shares the cardio-protective and anti-inflammatory properties of its natural counterparts. To address this question, we analyzed the ability of OMT-28 to ameliorate hypoxia/reoxygenation (HR)-injury and lipopolysaccharide (LPS)-induced endotoxemia in cultured cardiomyocytes. Moreover, we investigated the potential of OMT-28 to limit functional damage and inflammasome activation in isolated perfused mouse hearts subjected to ischemia/reperfusion (IR) injury. In the HR model, OMT-28 (1 μM) treatment largely preserved cell viability (about 75 vs. 40 % with vehicle) and mitochondrial function as indicated by the maintenance of NAD+/NADH-, ADP/ATP- and respiratory control ratios. Moreover, OMT-28 blocked the HR-induced production of mitochondrial reactive oxygen species. Pharmacological inhibition experiments suggested that Gαi, PI3K, PPARα, and Sirt1 are essential components of the OMT-28 mediated pro-survival pathway. Counteracting inflammatory injury of cardiomyocytes, OMT-28 (1 μM) reduced LPS-induced increases in TNFα protein (by about 85 % vs vehicle) and NF-κB DNA binding (by about 70 % vs. vehicle). In the ex vivo model, OMT-28 improved post-IR myocardial function recovery to reach about 40 % of the baseline value compared to less than 20 % with vehicle. Furthermore, OMT-28 (1 μM) limited IR-induced NLRP3 inflammasome activation similarly like a direct NLRP3 inhibitor (MCC950). Overall, this study demonstrates that OMT-28 possesses potent cardio-protective and anti-inflammatory properties supporting the hypothesis that extending the bioavailability of omega-3 epoxyeicosanoids may improve their prospects as therapeutic agents.

Matrix metalloproteinase-2 proteolyzes mitofusin-2 and impairs mitochondrial function during myocardial ischemia-reperfusion injury

During myocardial ischemia and reperfusion (IR) injury matrix metalloproteinase-2 (MMP-2) is rapidly activated in response to oxidative stress. MMP-2 is a multifunctional protease that cleaves both extracellular and intracellular proteins. Oxidative stress also impairs mitochondrial function which is regulated by different proteins, including mitofusin-2 (Mfn-2), which is lost in IR injury. Oxidative stress and mitochondrial dysfunction trigger the NLRP3 inflammasome and the innate immune response which invokes the de novo expression of an N-terminal truncated isoform of MMP-2 (NTT-MMP-2) at or near mitochondria. We hypothesized that MMP-2 proteolyzes Mfn-2 during myocardial IR injury, impairing mitochondrial function and enhancing the inflammasome response. Isolated hearts from mice subjected to IR injury (30 min ischemia/40 min reperfusion) showed a significant reduction in left ventricular developed pressure (LVDP) compared to aerobically perfused hearts. IR injury increased MMP-2 activity as observed by gelatin zymography and increased degradation of troponin I, an intracellular MMP-2 target. MMP-2 preferring inhibitors, ARP-100 or ONO-4817, improved post-ischemic recovery of LVDP compared to vehicle perfused IR hearts. In muscle fibers isolated from IR hearts the rates of mitochondrial oxygen consumption and ATP production were impaired compared to those from aerobic hearts, whereas ARP-100 or ONO-4817 attenuated these reductions. IR hearts showed higher levels of NLRP3, cleaved caspase-1 and interleukin-1β in the cytosolic fraction, while the mitochondria-enriched fraction showed reduced levels of Mfn-2, compared to aerobic hearts. ARP-100 or ONO-4817 attenuated these changes. Co-immunoprecipitation showed that MMP-2 is associated with Mfn-2 in aerobic and IR hearts. ARP-100 or ONO-4817 also reduced infarct size and cell death in hearts subjected to 45 min ischemia/120 min reperfusion. Following myocardial IR injury, impaired contractile function and mitochondrial respiration and elevated inflammasome response could be attributed, at least in part, to MMP-2 activation, which targets and cleaves mitochondrial Mfn-2. Inhibition of MMP-2 activity protects against cardiac contractile dysfunction in IR injury in part by preserving Mfn-2 and suppressing inflammation.

Loss of PI3Kα Mediates Protection From Myocardial Ischemia-Reperfusion Injury Linked to Preserved Mitochondrial Function

Background Identifying new therapeutic targets for preventing the myocardial ischemia-reperfusion injury would have profound implications in cardiovascular medicine. Myocardial ischemia-reperfusion injury remains a major clinical burden in patients with coronary artery disease. Methods and Results We studied several key mechanistic pathways known to mediate cardioprotection in myocardial ischemia-reperfusion in 2 independent genetic models with reduced cardiac phosphoinositide 3-kinase-α (PI3Kα) activity. P3Kα-deficient genetic models (PI3KαDN and PI3Kα-Mer-Cre-Mer) showed profound resistance to myocardial ischemia-reperfusion injury. In an ex vivo reperfusion protocol, PI3Kα-deficient hearts had an 80% recovery of function compared with ≈10% recovery in the wild-type. Using an in vivo reperfusion protocol, PI3Kα-deficient hearts showed a 40% reduction in infarct size compared with wild-type hearts. Lack of PI3Kα increased late Na⁺ current, generating an influx of Na⁺, facilitating the lowering of mitochondrial Ca²⁺, thereby maintaining mitochondrial membrane potential and oxidative phosphorylation. Consistent with these functional differences, mitochondrial structure in PI3Kα-deficient hearts was preserved following ischemia-reperfusion injury. Computer modeling predicted that PIP3, the product of PI3Kα action, can interact with the murine and human Na_V1.5 channels binding to the hydrophobic pocket below the selectivity filter and occluding the channel. Conclusions Loss of PI3Kα protects from global ischemic-reperfusion injury linked to improved mitochondrial structure and function associated with increased late Na⁺ current. Our results strongly support enhancement of mitochondrial function as a therapeutic strategy to minimize ischemia-reperfusion injury.

Cardiomyocyte-specific disruption of soluble epoxide hydrolase limits inflammation to preserve cardiac function

Endotoxemia elicits a multiorgan inflammatory response that results in cardiac dysfunction and often leads to death. Inflammation-induced metabolism of endogenous N-3 and N-6 polyunsaturated fatty acids generates numerous lipid mediators, such as epoxy fatty acids (EpFAs), which protect the heart. However, EpFAs are hydrolyzed by soluble epoxide hydrolase (sEH), which attenuates their cardioprotective actions. Global genetic disruption of sEH preserves EpFA levels and attenuates cardiac dysfunction in mice following acute lipopolysaccharide (LPS)-induced inflammatory injury. In leukocytes, EpFAs modulate the innate immune system through the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome. However, the mechanisms by which both EpFAs and sEH inhibition exert their protective effects in the cardiomyocyte are still elusive. This study investigated whether cardiomyocyte-specific sEH disruption attenuates inflammation and cardiac dysfunction in acute LPS inflammatory injury via modulation of the NLRP3 inflammasome. We use tamoxifen-inducible CreER recombinase technology to target sEH genetic disruption to the cardiomyocyte. Primary cardiomyocyte studies provide mechanistic insight into inflammasome signaling. For the first time, we demonstrate that cardiomyocyte-specific sEH disruption preserves cardiac function and attenuates inflammatory responses by limiting local cardiac inflammation and activation of the systemic immune response. Mechanistically, inhibition of cardiomyocyte-specific sEH activity or exogenous EpFA treatment do not prevent upregulation of NLRP3 inflammasome machinery in neonatal rat cardiomyocytes. Rather, they limit downstream activation of the pathway leading to release of fewer chemoattractant factors and recruitment of immune cells to the heart. These data emphasize that cardiomyocyte sEH is vital for mediating detrimental systemic inflammation.NEW & NOTEWORTHY The cardioprotective effects of genetic disruption and pharmacological inhibition of sEH have been demonstrated in a variety of cardiac disease models, including acute LPS inflammatory injury. For the first time, it has been demonstrated that sEH genetic disruption limited to the cardiomyocyte profoundly preserves cardiac function and limits local and systemic inflammation following acute LPS exposure. Hence, cardiomyocytes serve a critical role in the innate immune response that can be modulated to protect the heart.

P-241 ‘Augmented intelligence’ to possibly shorten euploid identification time: A human-machine interaction study for euploid identification using ERICA, an Artificial Intelligence software to assist embryo ranking

Study question

What is the mean number of transfers needed to achieve a euploid transfer selected by embryologists plus ERICA’s assistance?

Summary answer

Augmented intelligence (ERICA plus human collaboration) outperforms both the embryologists and artificial intelligence's individual performance alone.

What is known already

Euploid embryos are more likely to implant successfully. Artificial intelligence (AI) could improve embryo selection over current techniques, but scepticism exists. Augmented intelligence (AuI) combines both the mathematical reproducibility of machine learning and the knowledge and experience of humans. This approach employs AI tools as an assistant, where the user shall learn to interpret the AI. A recent study suggested that embryologists assisted by AI improved the embryo selection of euploid transfers. ERICA (IVF2.0 Limited, UK) was designed to rank blastocysts according to their probability of euploidy.

Study design, size, duration

We prospectively studied embryo selection for ERICA alone, embryologists only and when interacting (embryologists and ERICA) in 150 synthetically generated (reconstructed on real-data) embryo transfer cycles. Embryos were ranked in order, and performance was assessed by time to identify a euploid embryo within each cycle cohort correctly. Embryologists were allowed to rank a maximum of 10 cycles per day for three weeks starting in January 2022, using a mobile phone application designed for this purpose.

Participants/materials, setting, methods

Using real-life cycle distributions of euploid/aneuploid blastocysts and the number of embryos in a cycle (according to ERICA’s database), we created 150 synthetic cycles, 30 for each age bracket (< 35, 35-37, 38-40, 41-42, and >42). These were randomly populated with blastocyst images preserving their actual ploidy status correspondingly. Each synthetic cycle contained between 2 to 6 authentic embryo images with at least one euploid and one aneuploid.

Main results and the role of chance

The total database had a euploid rate of 37.4% (n = 513), and by age brackets from 1 to 5 were 45.7% (n = 116), 43.8% (n = 105), 35.9% (n = 92), 31.2% (n = 96), and 28.8% (n = 104) respectively.

The mean number of cycles analysed by each participant was 113.5 (CI: 100.8-126.2). The mean time-to-euploid transfer for embryologists alone was 2.07 (CI:2.00-2.13); for the ERICA alone was 1.86 (CI:1.82-1.91); and for embryologists assisted by ERICA was 1.62 (CI:1.55-1.68). All study groups compared to each other were statistically significant using a paired two-tailed student’s t-test (p < 0.001).

The proportion of euploid transfer at the first try for embryologists alone was 0.40 (CI:0.37-0.43), for ERICA alone was 0.54 (CI:0.53-0.54), and for embryologists assisted by ERICA was 0.47 (CI:0.44-0.50). All study groups compared with each other were statistically significant with a paired two-tailed student’s t-test (p < 0.01).

Limitations, reasons for caution

Although our findings suggest that Aul outperforms both AI and humans alone, this study needs to be replicated with a larger cohort of embryologists with different experience levels in different countries to confirm these results.

Wider implications of the findings

Combining machine-human interaction through a well-designed process could improve embryo selection and reduce inter-operator variability amongst staff with different experience levels. It could also set a frame for adequate agency and accountability, and enhance trust and adoption.

Trial registration number

NA

Changes in the Left Ventricular Eicosanoid Profile in Human Dilated Cardiomyopathy

Objective

Metabolites derived from N−3 and N−6 polyunsaturated fatty acids (PUFAs) have both beneficial and detrimental effects on the heart. However, contribution of these lipid mediators to dilated cardiomyopathy (DCM)-associated mitochondrial dysfunction remains unknown. This study aimed to characterize DCM-specific alterations in the PUFA metabolome in conjunction with cardiac mitochondrial quality in human explanted heart tissues.

Methods

Left ventricular tissues obtained from non-failing control (NFC) or DCM explanted hearts, were assessed for N−3 and N−6 PUFA metabolite levels using LC-MS/MS. mRNA and protein expression of CYP2J2, CYP2C8 and epoxide hydrolase enzymes involved in N−3 and N−6 PUFA metabolism were quantified. Cardiac mitochondrial quality was assessed by transmission electron microscopy, measurement of respiratory chain complex activities and oxygen consumption (respiratory control ratio, RCR) during ADP-stimulated ATP production.

Results

Formation of cardioprotective CYP-derived lipid mediators, epoxy fatty acids (EpFAs), and their corresponding diols were enhanced in DCM hearts. These findings were corroborated by increased expression of CYP2J2 and CYP2C8 enzymes, as well as microsomal and soluble epoxide hydrolase enzymes, suggesting enhanced metabolic flux and EpFA substrate turnover. DCM hearts demonstrated marked damage to mitochondrial ultrastructure and attenuated mitochondrial function. Incubation of fresh DCM cardiac fibers with the protective EpFA, 19,20-EDP, significantly improved mitochondrial function.

Conclusions

The current study demonstrates that increased expressions of CYP-epoxygenase enzymes and epoxide hydrolases in the DCM heart correspond with enhanced PUFA-derived EpFA turnover. This is accompanied by severe mitochondrial functional impairment which can be rescued by the administration of exogenous EpFAs.

P–244 ERICA’s (Embryo Ranking Intelligent Classification Assistant) ranking, based on ploidy prediction, is strongly correlated with pregnancy outcomes

Study question

How does ERICA perform when ranking the most suitable embryos for transfer in terms of clinical pregnancy, and the presence of a fetal heartbeat (FHB)?

Summary answer

ERICA’s Artificial Intelligence ranking system was positively correlated with outcomes defined as implantation and presence of FHB. Best-ranking embryos outperformed lower-ranking embryos by statistical significance.

What is known already

ERICA, the Embryo Ranking Intelligent Classification Assistant, is a deep learning AI system trained to rank embryos based on their ploidy status, which is highly correlated with successful treatments.

ERICA ranks the embryos according to their prognosis predictions and labels them into four quality categories: optimal, good, fair, and poor. ERICA’s performance in the clinic remains to be tested.

Study design, size, duration

Retrospective analysis on ERICA’s performance over 4 consecutive months after quality assurance and fine-tuning processes. We compared both the ranking and prognosis of the AI algorithm against clinical outcomes in IVF cycles and subsequent embryo transfers. For this study, all cycles where ERICA was used to assist embryologists during the embryo selection process were included. Double embryo transfers with a single FHB where excluded.

Participants/materials, setting, methods

Total 77 cycles with 81 transfers of 98 embryos (17 cases underwent a double embryo transfer) from two IVF clinics. Evaluated clinical outcomes included biochemical pregnancy test (defined as beta human chorionic gonadotropin >20 mUI/ml), and presence/absence of FHB. We compared the ERICA rankings and predictions against outcome and a sub-analysis was performed on transferred embryos with known ploidy status (14 embryos).

Main results and the role of chance

The distribution of embryos within the ERICA categories are 42% for optimal, 38% for good, 19% for fair, and 6% for poor. The observed biochemical pregnancy rate was 51%, 25%, 47% and 33% respectively, and 39%, 22%, 42%, 17% for FHB. We found statistical significance (Z = 1.78; p = 0.0378) for the proportion of biochemical pregnancy between transfers labelled by ERICA as optimal (51%) and all lower rankings (33%). The proportion of transfers with presence of FHB within the optimal group was 39%, compared with 29% for the rest of the embryos. This did not show statistical significance (Z = 1.141; p = 0.127). Additionally, we observed that the proportion of biochemical pregnancy and presence of FHB in the group of transfers with known ploidy (n = 14) was 50% and 36% respectively, and the transfers with unknown ploidy and labelled as optimal by ERICA (n = 35) was 54% and 43% respectively.

Limitations, reasons for caution

This is the first report on ERICA’s performance on real clinical data, and despite being a relatively small dataset, we observed statistical significance of the embryos labelled by ERICA as having optimal quality. Further studies should be conducted with larger datasets and more clinics included to strengthen the evidence.

Wider implications of the findings: This is the first report on ERICA’s performance on real clinical data, and despite being a relatively small dataset, we observed statistical significance of the embryos labelled by ERICA as having optimal quality. Further studies should be conducted with larger datasets and more clinics included to strengthen the evidence.

Trial registration number

Not applicable

A conserved acetylation switch enables pharmacological control of tubby-like protein stability

Tubby-like proteins (TULPs) are characterized by a conserved C-terminal domain that binds phosphoinositides. Collectively, mammalian TULP1-4 proteins play essential roles in intracellular transport, cell differentiation, signaling, and motility. Yet, little is known about how the function of these proteins is regulated in cells. Here, we present the protein–protein interaction network of TULP3, a protein that is responsible for the trafficking of G-protein-coupled receptors to cilia and whose aberrant expression is associated with severe developmental disorders and polycystic kidney disease. We identify several protein interaction nodes linked to TULP3 that include enzymes involved in acetylation and ubiquitination. We show that acetylation of two key lysine residues on TULP3 by p300 increases TULP3 protein abundance and that deacetylation of these sites by HDAC1 decreases protein levels. Furthermore, we show that one of these sites is ubiquitinated in the absence of acetylation and that acetylation inversely correlates with ubiquitination of TULP3. This mechanism is evidently conserved across species and is active in zebrafish during development. Finally, we identify this same regulatory module in TULP1, TULP2, and TULP4 and demonstrate that the stability of these proteins is similarly modulated by an acetylation switch. This study unveils a signaling pathway that links nuclear enzymes to ciliary membrane receptors via TULP3, describes a dynamic mechanism for the regulation of all tubby-like proteins, and explores how to exploit it pharmacologically using drugs.

Complete genome sequence of the marine Rhodococcus sp. H-CA8f isolated from Comau fjord in Northern Patagonia, Chile

Rhodococcus sp. H-CA8f was isolated from marine sediments obtained from the Comau fjord, located in Northern Chilean Patagonia. Whole-genome sequencing was achieved using PacBio RS II platform, comprising one closed, complete chromosome of 6,19 Mbp with a 62.45% G + C content. The chromosome harbours several metabolic pathways providing a wide catabolic potential, where the upper biphenyl route is described. Also, Rhodococcus sp. H-CA8f bears one linear mega-plasmid of 301 Kbp and 62.34% of G + C content, where genomic analyses demonstrated that it is constituted mostly by putative ORFs with unknown functions, representing a novel genetic feature. These genetic characteristics provide relevant insights regarding Chilean marine actinobacterial strains.

Nosocomial Outbreak of Pseudomonas aeruginosa Endophthalmitis

We describe an outbreak of nosocomial endophthalmitis due to a common source, which was determined to be trypan blue solution prepared in the hospital's pharmacy service. We assume that viable bacteria probably gained access to the trypan blue stock solution during cooling after autoclaving. The temporal cluster of Pseudomonas aeruginosa endophthalmitis was readily perceived on the basis of clinical and microbiological findings, and an exogenous source of contamination was unequivocally identified by means of DNA fingerprinting.

Abstract 410: Link Between Hypertension and Insulin Resistance in South Asians: Implications for Prevention of Cardiovascular Complications

Background: The coexistence of hypertension (HTN) and insulin resistance (IR) substantially increases cardiovascular risk (CVR) and diabetes (DM) perhaps by endothelial dysfunction from low-grade chronic inflammation and oxidative stress. South Asian immigrants in United States (SA-USA) have a high salt consumption, IR, and salt sensitivity. The triglyceride (TG)/ HDL ratio is a known correlate of IR with ratios ≥3.5 associated with high risk. It is unknown whether SA-USA have a coexistence of HTN, IR, and DM resulting in high CVR.

Methods: We reviewed the clinical history and Vertical Auto Profile technology (VAP) + lipid panel utilizing ultracentrifugation to directly measure lipid sub-fractions, for 348 participants (42% women) of the South Asian Cardiovascular Registry. Prevalent DM and Pre-DM were defined as HbA1c ≥ 6.5 and 5.7-6.4, respectively.

Results: Of the 348 participants, mean age 55.3 years, 128 had HTN and were stratified into clinical risk groups based on fasting TG (mg/dL) levels: TG<150 (n=69), TG 150-199 (n=24), TG 200-499 (n=32), TG>500 (n=3). The corresponding TG/HDL ratios were: 1.7, 3.5, 6.2, and 20.4, respectively; the median TG (mg/dL) levels were: 100, 182, 268, and 572, respectively; the median LDL (mg/dL) levels were: 113, 144, 133, 102, respectively; the rates of DM were: 13%, 17%, 38%, and 67%; and the rates of Pre-DM/DM were: 62%, 63%, 78%, and 67%, respectively. Relative Risk for DM with TG/HDL≥ 3.5 was 3.6 (46 % had TG/HDL ≥ 3.5).

Conclusions: South Asian immigrants participating in a community registry have: 1) A high rate of coexistence of HTN and IR portending a very high relative risk of diabetes. 2) A discordance of LDL levels and IR in patients with HTN. As IR gets higher, the relative risk of diabetes goes up but LDL levels decline.

Clinical Implications: South Asian immigrants in the United States have a diet that is very high in salt, simple carbohydrates, and saturated fat. Many are vegetarian with no consumption of fish. Public health efforts to help reduce risk of CVD in South Asian immigrants should focus on low salt diet, with consumption of multigrain complex carbohydrates, poly-unsaturated fatty acids, omega-3 fatty acids, and lifestyle changes to reduce metabolic syndrome, diabetes, and hypertension.

Clinical validation of a real-time polymerase chain reaction assay for rapid detection of Acinetobacter baumannii colonization

Real-time polymerase chain reaction (PCR)-based approaches have not been assessed in terms of their ability to detect patients colonized by Acinetobacter baumannii during active surveillance. This prospective, double-blind study demonstrated that a real-time PCR assay had high sensitivity (100%) and specificity (91.2%) compared with conventional culture for detecting A. baumannii in 397 active surveillance samples, and provided results within 3h. Receiver-operator curve analyses demonstrated that the technique has diagnostic accuracy of 97.7% (95% confidence interval 96.0-99.3%). This method could facilitate the rapid implementation of infection control measures for preventing the transmission of A. baumannii.

Habitat filtering across tree life stages in tropical forest communities

Tropical tree communities are shaped by local-scale habitat heterogeneity in the form of topographic and edaphic variation, but the life-history stage at which habitat associations develop remains poorly understood. This is due, in part, to the fact that previous studies have not accounted for the widely disparate sample sizes (number of stems) that result when trees are divided into size classes. We demonstrate that the observed habitat structuring of a community is directly related to the number of individuals in the community. We then compare the relative importance of habitat heterogeneity to tree community structure for saplings, juveniles and adult trees within seven large (24-50 ha) tropical forest dynamics plots while controlling for sample size. Changes in habitat structuring through tree life stages were small and inconsistent among life stages and study sites. Where found, these differences were an order of magnitude smaller than the findings of previous studies that did not control for sample size. Moreover, community structure and composition were very similar among tree sub-communities of different life stages. We conclude that the structure of these tropical tree communities is established by the time trees are large enough to be included in the census (1 cm diameter at breast height), which indicates that habitat filtering occurs during earlier life stages.

Multispecies coexistence of trees in tropical forests: spatial signals of topographic niche differentiation increase with environmental heterogeneity

Neutral and niche theories give contrasting explanations for the maintenance of tropical tree species diversity. Both have some empirical support, but methods to disentangle their effects have not yet been developed. We applied a statistical measure of spatial structure to data from 14 large tropical forest plots to test a prediction of niche theory that is incompatible with neutral theory: that species in heterogeneous environments should separate out in space according to their niche preferences. We chose plots across a range of topographic heterogeneity, and tested whether pairwise spatial associations among species were more variable in more heterogeneous sites. We found strong support for this prediction, based on a strong positive relationship between variance in the spatial structure of species pairs and topographic heterogeneity across sites. We interpret this pattern as evidence of pervasive niche differentiation, which increases in importance with increasing environmental heterogeneity.

Short communication: Detection of Shiga toxin-producing Escherichia coli (STEC) in healthy cattle and pigs in Lima, Peru

The aim of this study was to determine the prevalence of Shiga toxin-producing Escherichia coli (STEC) in cattle and pigs as a possible STEC reservoir in Lima, Peru. One hundred and fourteen cattle and 112 pigs from 10 and 4 farms, respectively, were studied. Five E. coli colonies per culture were studied by a multiplex real-time PCR to identify Shiga toxin-producing (stx1, stx2, eaeA), enterotoxigenic (lt, st), enteropathogenic (eaeA), enteroinvasive (ipaH), enteroaggregative (aggR), and diffusely adherent E. coli (daaD). Shiga toxin-producing E. coli were isolated from 16 cattle (14%) but none from pigs. stx1 was found in all bovine isolates, 11 of which also carried eaeA genes (69%); only 1 sample had both stx1 and stx2. Thirteen stx-positive strains were classified as Shiga-toxigenic (81%) using an enzymatic immunoassay, 2 STEC strains were from serogroup O157 (13%), and 7 were sorbitol negative (44%). Enteropathogenic E. coli were detected more frequently in cattle (18%, 20/114) than in pigs (5%, 6/112). To our knowledge, this is the first study on the prevalence of STEC in farms animals in Peru using molecular methods. Further studies are needed in a large number of farms to determine the relevance of these findings and its consequences for public health.

The effect of hydraulic conditions on waste stabilisation in bioreactor landfill simulators

Seven bioreactor landfill simulators (mixed gravel, gravel in layers, and controls without gravel with two levels of compaction, i.e. normal and lower density) were used to investigate the effect of different hydraulic conditions on the waste stabilisation process. The simulators with mixed gravel showed a higher degree of waste stabilisation towards the end of the experiment due to higher moisture content, whereas the other simulators were prone to clogging thus reducing the overall treatment effectiveness. Moreover, reaching neutral pH levels seemed to be the "driving force" that enhanced physical, chemical and biological processes contributing to waste stabilisation in the simulators with mixed gravel. After one year of operation, the residues of the different simulators were very close to achieve a final storage quality status comparable to the waste acceptance criteria for inert waste of the European landfill directive.

Alternative treatment for septic tank sludge: co-digestion with municipal solid waste in bioreactor landfill simulators

Co-disposal of septic tank sludge had a positive effect on the municipal solid waste (MSW) stabilisation process in Bioreactor Landfill simulators. Co-disposal experiments were carried out using the Bioreactor Landfill approach aiming to solve the environmental problems caused by indiscriminate and inadequate disposal of MSW and especially of septic tank sludge. The simulator receiving septic tank sludge exhibited a 200 days shorter lag-phase as compared to the 350 days required by the control simulator to start the exponential biogas production. Additionally, the simulator with septic sludge apparently retained more moisture (>60% w/w), which enhanced the overall conversion of organic matter hence increasing the biogas production (0.60 m3 biogas kg(-1)VS(converted)) and removal efficiency of 60% for VS from the simulator. Alkaline pH values (pH>8.5) did not inhibit the biogas production; moreover it contributed to reduce partially the negative effects of NH(4)(+) (>2 g L(-1)) due to NH(3) volatilisation thus reducing the nitrogen content of the residues. Associated risks and hazards with septage disposal were practically eliminated as total coliform and faecal coliform contents were reduced by 99% and 100%, respectively at the end of the experiment. These results indicate that co-disposal has two direct benefits, including the safe and environmentally sound disposal of septic tank sludge and an improvement of the overall performance of the Bioreactor Landfill by increasing moisture retention and supplying a more acclimatised bacterial population.

Achieving "Final Storage Quality" of municipal solid waste in pilot scale bioreactor landfills

Entombed waste in current sanitary landfills will generate biogas and leachate when physical barriers fail in the future, allowing the intrusion of moisture into the waste mass contradicting the precepts of the sustainability concept. Bioreactor landfills are suggested as a sustainable option to achieve Final Storage Quality (FSQ) status of waste residues; however, it is not clear what characteristics the residues should have in order to stop operation and after-care monitoring schemes. An experiment was conducted to determine the feasibility to achieve FSQ status (Waste Acceptance Criteria of the European Landfill Directive) of residues in a pilot scale bioreactor landfill. The results of the leaching test were very encouraging due to their proximity to achieve the proposed stringent FSQ criterion after 2 years of operation. Furthermore, residues have the same characteristics of alternative waste stabilisation parameters (low BMP, BOD/COD ratio, VS content, SO4(2-)/Cl- ratio) established by other researchers. Mass balances showed that the bioreactor landfill simulator was capable of practically achieving biological stabilisation after 2 years of operation, while releasing approximately 45% of the total available (organic and inorganic) carbon and nitrogen into the liquid and gas phases.

The acceptability of a directly-administered antiretroviral therapy (DAART) intervention among patients in public HIV clinics in Los Angeles, California

Directly administered antiretroviral therapy (DAART) is an intensive adherence support strategy for highly active antiretroviral therapy (HAART) that requires patient acceptance to be effective. In one arm of a randomized adherence study, community workers (CW) delivered and observed ingestion of one HAART dose to participants five days a week for six months. We evaluated acceptability by study participation, retention, attendance and a satisfaction survey. Chi-square and nonparametric tests were used to examine differences between participants who did and did not complete DAART. Between November 2001 and March 2004, 416 eligible participants were identified; 250 were enrolled and 166 refused to participate (22 of these (13%) because of DAART specifically). Of the 82 randomized to DAART (70% Latino, 20% African American, 27% female and 69% foreign-born), 65 (79%) completed six months of DAART. Participants attended 6,953/7,390 (94%) appointments. Latinos were more likely to complete DAART compared to African Americans (OR=4.76, 95%CI=1.38, 16.44, p=0.01). In addition, foreign-born participants were more likely to complete DAART than US-born participants (OR=3.38, 95%CI=1.11-10.22, p=0.03). Participants completing DAART reported high rates of satisfaction. Retention, attendance and participant satisfaction suggest that DAART is an acceptable adherence support strategy in this public clinic population, particularly among Latino and foreign-born participants.

Erste Erfahrungen mit einem Flächendetektor-Volumen-CT (fpVCT) in der experimentellen Osteoporosediagnostik am Kleintiermodell

BACKGROUND

Flat-panel volumetric computed tomography (fpVCT) is a new, noninvasive CT imaging modality with increased isotropic resolution. Technical details, potential applications, and our initial experience with a fpVCT prototype scanner in the imaging of osteoporosis in a rat model are presented.

METHODS

To date, 21 rats have been investigated in vivo with fpVCT. Pharmacologic effects on bone mineral density (BMD) and structure were of special interest. Image evaluation focussed on the second lumbar vertebra and the left femoral bone. To validate measurement results, BMD values calculated with fpVCT were correlated with results of BMD measurements from ashing of the second lumbar vertebra and femoral bones.

RESULTS

Our initial results show that fpVCT is capable of detecting differences in BMD between ovariectomized rats treated with estradiol and a control group with high statistical significance (p<0.05), corresponding to ashing as the gold standard.

CONCLUSIONS

In a rat model, fpVCT imaging is especially useful in longitudinal in vivo investigations of BMD measures. Spatial resolution of up to 150 microm allows imaging of the trabecular structure only in human cadaveric bones.

Eigenschaften und Anwendungen der Flächendetektor-basierten Volumen-Computertomographie

PURPOSE

To assess a new flat panel volume computed tomography (FP-VCT) with very high isotropic spatial resolution as well as high Z-axis coverage.

MATERIALS AND METHODS

The prototype of an FP-VCT scanner with a detector cell size of 0.2 mm was used for numerous phantom studies, specimen examinations, and animal research projects.

RESULTS

The high spatial resolution of the new system can be used to accurately determine solid tumor volume, thus allowing for earlier assessment of the therapeutic response. In animal experimentation, whole-body perfusion mapping of mice is feasible. The high spatial resolution also improves the classification of coronary artery atherosclerotic plaques in the isolated post mortem human heart. With the depiction of intramyocardial segments of the coronary arteries, investigations of myocardial collateral circulation are feasible. In skeletal applications, an accurate analysis of the smallest bony structures, e. g., petrous bone and dental preparations, can be successfully performed, as well as investigations of repetitive studies of fracture healing and the treatment of osteoporosis.

CONCLUSION

The introduction of FP-VCT opens up new applications for CT, including the field of molecular imaging, which are highly attractive for future clinical applications. Present limitations include limited temporal resolution and necessitate further improvement of the system.

[Warning systems: a priority in epidemiological surveillance]

One of the functions of public health is to reduce the impact of emergency situations; hence the need to establish an early warning and response system. Community reactions to emerging and reemerging diseases, exposure to environmental risks, and potential terrorist acts are the factors that have that have mainly contributed to the instauration of warning systems based on mathematical models. Information is obtained from diverse sources (for example, laboratory data, sentinel physicians, or visits to particular websites). Once the data are gathered, and the situation provoking the alert is detected, control measures to reduce risks and minimize damage are taken at the earliest.

Temporary shielding of hot spots in the drainage areas of cutaneous melanoma improves accuracy of lymphoscintigraphic sentinel lymph node diagnostics

Detection of the "true" sentinel lymph nodes, permitting correct staging of regional lymph nodes, is essential for management and prognostic assessment in malignant melanoma. In this study, it was prospectively evaluated whether simple temporary shielding of hot spots in lymphatic drainage areas could improve the accuracy of sentinel lymph node diagnostics. In 100 consecutive malignant melanoma patients (45 women, 55 men; age 11-91 years), dynamic and static lymphoscintigraphy in various views was performed after strict intracutaneous application of technetium-99m nanocolloid (40-150 MBq; 0.05 ml/deposit) around the tumour (31 patients) or the biopsy scar (69 patients, safety distance 1 cm). The images were acquired with and without temporary lead shielding of the most prominent hot spots in the drainage area. In 33/100 patients, one or two additional sentinel lymph nodes that showed less tracer accumulation or were smaller (<1.5 cm) were detected after shielding. Four of these patients had metastases in the sentinel lymph nodes; the non-sentinel lymph nodes were tumour negative. In 3/100 patients, hot spots in the drainage area proved to be lymph vessels, lymph vessel intersections or lymph vessel ectasias after temporary shielding; hence, a node interpreted as a non-sentinel lymph node at first glance proved to be the real sentinel lymph node. In two of these patients, lymph node metastasis was histologically confirmed; the non-sentinel lymph nodes were tumour free. In 7/100 patients the exact course of lymph vessels could be mapped after shielding. In one of these patients, two additional sentinel lymph nodes (with metastasis) were detected. Overall, in 43/100 patients the temporary shielding yielded additional information, with sentinel lymph node metastases in 7%. In conclusion, when used in combination with dynamic acquisition in various views, temporary shielding of prominent hot spots in the drainage area of a malignant melanoma of the skin leads to an improvement in the accuracy of identification and localisation of sentinel lymph nodes by lymphoscintigraphy.

Distribution of C-reactive protein and its relation to risk factors and coronary heart disease risk estimation in the National Health and Nutrition Examination Survey (NHANES) III

The authors examined the distribution of, and risk factors associated with, the inflammatory marker C-reactive protein (CRP) among a large sample of non-institutionalized American adults aged 30-74 years of age, and its relation to estimated 10-year coronary heart disease risk. The population studied comprised 4472 men and 5212 women aged 30-74 years, without coronary heart disease, who had CRP measurements in the Third National Health and Nutrition Examination Survey (NHANES III). The 10-year risk of coronary heart disease was estimated from Framingham risk factor algorithms among those with CRP levels of less-than-or-equal0.21 mg/dL, >0.21 to <0.5mg/dL, 0.5 to <1.0 mg/dL, and greater-than-or-equal1.0 mg/dL. Mean (SD) levels of CRP were 0.41 (0.64) mg/dL in men and 0.55 (0.91) mg/dL in women. Levels of at least 1 mg/dL were measured in 6.4% of men and 12.9% of women. CRP levels were highest among non-Hispanic black men and Mexican-American women. According to multiple logistic regression analysis, cigarette smoking and increased age, body mass index, and systolic blood pressure in men, and body mass index and diabetes in women, were strongly associated with a greater likelihood of CRP levels of greater-than-or-equal1.0 mg/dL (p<0.001). Among persons with CRP levels of less-than-or-equal0.21 mg/dL, >0.21 to <0.5 mg/dL, 0.5 to <1.0 mg/dL and greater-than-or-equal1.0 mg/dL, the 10-year estimated risk of coronary heart disease were 13.4%, 17.6%, 19.6%, and 21.1% among men, respectively, and 2.7%, 3.6%, 4.1% and 4.3% among women, respectively (both p<0.001 across CRP categories); higher risks across CRP groups were also found among ethnic/gender subgroups. CRP remained a significant predictor of coronary heart disease risk in unadjusted and age-adjusted analyses. Conclusion. Elevation of CRP is associated with several major coronary heart disease risk factors and with unadjusted and age-adjusted projections of 10-year coronary heart disease risk in both men and women. (c)2001 CHF, Inc. Presented at the Fifth International Conference on Preventive Cardiology, Osaka, Japan, May, 2001.

[Alignment of the sagittal profile after surgical therapy of nonspecific destructive spondylodiscitis: ventral or ventrodorsal method--a comparison of outcomes]

From 1989 to 1998, 129 patients underwent surgery for unspecific spondylodiscitis in the Department of Orthopedics of the Free University of Berlin. Fifty-six of them were followed up, and their clinical and radiological results were evaluated in this study. The surgical results of 40 patients with only ventral removal of a focus and defect coverage with an iliac crest graft were compared to those of 16 with additional dorsal bridging instrumentation by internal fixation. A mean of 2.3 vertebrae were fused in ventral spondylodesis; the mean length of dorsal instrumentation by internal fixation was 3.8 vertebrae. Patients were followed up a mean of 5.1 years after surgery. The mean age of patients was 57.1 years at the time of surgery. Patients were postoperatively mobilized a mean of 5 days after ventrodorsal fusion. A purely ventral procedure required a mean postoperative immobilization period of 3.6 weeks and brace fitting of a mean 8.2 months. There was one case of recurrent spondylodiscitis 25 months postoperatively, which made a revision of the focus necessary. The consolidation rate of the ventral spondylodesis was 84-100% in the different subgroups. A differential view of the spinal areas and ventral fusion segments was used to make a statement about the development of the sagittal spine profile. The segmental position of the spine in the sagittal plane was assessed by comparing the segmental kyphosis angles to normal values in the literature. All subgroups submitted to combined ventrodorsal fusion had a greater preoperative segmental kyphosis angle than those undergoing ventral fusion alone. In marked segmental kyphotic false positioning, the combined ventrodorsal procedure achieved good postoperative repositioning results, and an increase in segmental kyphosis was prevented. Ventral removal of a focus and bone graft spondylodesis seem to be adequate in single-level spondylodiskitis especially in the lumbar spine, but additional dorsal instrumentation should be performed in the case of long ventral fusion.

Phosphate immobilization using an acidic type F fly ash

Batch equilibration experiments using a low calcium ( approximately 1 wt.% as CaO), acidic (pH approximately 4.5) Type F fly ash demonstrated phosphate immobilization on the order of 100% to 75% for 50 and 100 mg P/l solutions, respectively. A loosely compacted column of fly ash similarly removed 10 mg P/l for over 85 pore volumes. While the interactions between phosphate and calcium-rich (Type C) ashes are relatively well understood, insight into the mechanisms of phosphate immobilization in Type F ash necessitated a review of the phosphate chemistry and interactions with acidic geomedia. Phosphate adsorption was subsequently modeled using a constant capacitance model approach (CCM) excluding precipitation reactions. Our CCM predictions of total phosphate immobilization (20%) were substantially less than the results of the batch equilibration experiments and phosphate adsorption predicted by other researchers examining near pure natural and synthetic geomedia due to the compositional heterogeneity of the fly ash. Nevertheless, for the amorphous and crystalline phases studied, the immobilization of phosphate in the Type F fly ash is attributed to the formation of insoluble aluminum and iron phosphates at low to medium values of pH.

Separation and characterization of the main methylated nucleobases from nuclear, cytoplasmic and poly (A)+ RNA by high-performance liquid chromatography and mass spectrometry

We were able to detect nine methylated nucleobases (3-methyluracil, 1-, 2-, 3- and 7-methylguanine, 1-, 2-, 3- and 6-methyladenine) in RNA from rat and calf liver, baker's yeast, Torula and Euglena cells by using reversed-phase high-performance liquid chromatography and thermospray mass spectrometry. Total cellular, nuclear, cytoplasmic and poly (A)+ RNA from rat liver showed marked methylation, mainly of 1- and 3- methylguanine, and 3- and 2-methyladenine. These bases were especially abundant in nuclear RNA and, to a lesser extent, in poly (A)+ RNA. In contrast, 7-methylguanine and 6-methyladenine were poorly represented in poly (A)+ RNA.

Chemical mutagenesis testing in Drosophila. IX. Results of 50 coded compounds tested for the National Toxicology Program

Fifty chemicals were tested for mutagenic activity in post-meiotic and meiotic germ cells of male Drosophila melanogaster using the sex-linked recessive lethal (SLRL) assay. As in the previous studies in this series, feeding was chosen as the first route of administration. If the compound failed to induce mutations by this route, injection exposure was used. One gaseous chemical (1,3-butadiene) was tested only by inhalation. Those chemicals that were mutagenic in the sex-linked recessive lethal assay were further tested for the ability to induce reciprocal translocations. Eleven of the 50 chemicals tested were mutagenic in the SLRL assay. These included bis(2-chloroethyl) ether, 1,4-butanediol diglycidyl ether, 1-chloro-2-propanol, dimethyl methylphosphonate, dimethyl morpholinophosphoramidate, dimethyloldihydroxyethylene urea, 2,2-dimethyl vinyl chloride, hexamethylphosphoramide, isatin-5-sulfonic acid (Na salt), isopropyl glycidyl ether, and urethane. Five of these, including 1,4-butanediol diglycidyl ether, 2,2-dimethyl vinyl chloride, hexamethylphosphoramide, isopropyl glycidyl ether, and urethane, also induced reciprocal translocations.

Chemical mutagenesis testing in Drosophila. X. Results of 70 coded chemicals tested for the National Toxicology Program

Seventy chemicals were tested for the ability to induce sex-linked recessive lethal (SLRL) mutations in postmeiotic and meiotic germ cells of male Drosophila melanogaster. As in the previous studies in this series, adult feeding was chosen as the first route of administration. If the compound failed to induce mutations by this route, injection exposure was used. Two chemicals, n-butane and propylene, were gaseous and therefore tested only by inhalation. One chemical (dimethylcarbamoyl chloride) was tested only by injection. Those chemicals that were mutagenic in the SLRL assay were further tested for the ability to induce reciprocal translocations. Sixteen of the 70 chemicals tested were mutagenic in the SLRL assay: 3-chloro-2-methylpropene, 3-(chloromethyl)pyridine HCl, dimethylcarbamoyl chloride, HC blue 1,3-iodo-1,2-propanediol, malaoxon, N,N'-methylene-bis-acrylamide, 4,4'-methylenedianiline 2HCl, ziram, cis-dichlorodiaminoplatinum II, 1,2-dibromoethane, dibromomannitol, 1,2-epoxypropane, glycidol, myleran, and toluene diisocyanate. The last seven also induced reciprocal translocations. A comparison of the results from the SLRL assay with other assays for mutagens and carcinogens suggests that the SLRL assay is highly specific, but poorly sensitive, both for mutagens and potential carcinogens.

Genetic toxicology of acrylic acid

Acrylic acid was tested for gene mutations in the in vitro CHO/HGPRT assay, for chromosome aberrations in CHO cells in culture, and for potential to induce unscheduled DNA synthesis in rat hepatocytes in culture. In vivo assays performed included the Drosophila sex-linked recessive lethal assay by both the feeding and injection routes, the in vivo cytogenetic assay in rat bone marrow cells after both a 1-day and 5-day oral dosing regimen, and a dominant lethal assay in mice by both an acute and 5-day dosing regimen. All results were negative (non-mutagenic) except for the in vitro chromosome aberration assay. This latter result is consistent with the previously reported possible clastogenic activity suggested by the results of the mouse lymphoma L5178Y TK locus assay in which a predominance of small-colony mutants was observed (Moore et al., Environmental and Molecular Mutagenesis 1988, 11, 49-63). The rapid clearance of acrylic acid in animals and the weight of evidence of genetic toxicity testing, including negative in vivo data in both somatic and germ cells, indicate a lack of genetic toxicity of acrylic acid in vivo.

Modifications of hepatic alpha-1-acid glycoprotein and albumin gene expression in rats treated with phenobarbital

The serum level of alpha 1-acid glycoprotein (alpha 1-AGP) is significantly increased in various animal species by treatment with cytokines, glucocorticoids and phenobarbital. The mechanisms responsible for the cytokine-induced and glucocorticoid-induced increases are now well documented, but not so in the case of phenobarbital. The main purpose of this study was to assess whether phenobarbital acts on alpha 1-AGP synthesis in the liver at the transcriptional or translational level. Male Dark Agouti rats received 70 mg phenobarbital/kg daily for 7 days. The analysis of total hepatic RNA showed that a single injection of phenobarbital induced an 11-fold increase in phenobarbital-dependent cytochrome P450IIB mRNA, whereas seven injections of phenobarbital were required to induce a maximum 5.5-fold increase in alpha 1-AGP mRNA. Concurrently, the transcription rate of the alpha 1-AGP gene rose 3.5-fold. Hepatocytes isolated after the seventh injection of phenobarbital showed a threefold increased capacity to secrete alpha 1-AGP, corresponding to a 3.2-fold increased alpha 1-AGP mRNA content in the liver. In conditions in which its effect on the induction of alpha 1-AGP synthesis was maximum, phenobarbital caused a 30% reduction in liver albumin mRNA and in albumin secretion by isolated hepatocytes, resulting from a 60-70% reduction in the rate of transcription of the albumin gene measured in isolated nuclei. We conclude that the effect of phenobarbital on alpha 1-AGP and albumin gene expression occurs at the transcriptional rather than the translational level.

Amplification of ribosomal DNA in the nucleolus of vitamin B12-deficient Euglena cells

In the nucleoli of vitamin B12-deprived Euglena cells there is a 10-fold amplification of rDNA which correlates with increased numbers of fibrillar centers in the hypertrophic nucleoli. This rDNA amplification was demonstrated by means of molecular hybridization using a specific cytoplasmic rRNA probe. Most of the amplified sequences appear as extrachromosomal copies which were observed without digestion of total cellular or nuclear Euglena DNA. Five different hybridizing sequences, three of high molecular weight and two of 19.0 and 11.5 kb, were identified. The rDNA repeat unit which contains the 11.5-kb transcriptible sequence is 19.0 kb in length and was always more abundant in the undigested total cellular DNA. The possible mechanisms involved in the induction of rDNA amplification in vitamin B12-deficient cells are discussed.

Interleukin 1 beta modulates hepatic synthesis of alpha 1-acid glycoprotein in the fetal rat

The ability of the fetal rat to respond to interleukin 1 beta (IL1 beta) by expressing alpha 1-acid glycoprotein (AGP) was investigated. Eight and 20 h after injection of 7 ng IL1 beta into 19-day fetuses, liver AGP mRNA increased by a factor of 66 and 82 respectively, while serum AGP levels increased by a factor of 3 and 5. Similar treatment of the mothers altered in the fetuses neither AGP serum levels nor the amount of liver AGP mRNA. The induction of AGP gene expression in the fetal liver in response to IL1 beta was similar to that observed in the adult liver. These results demonstrate that at day 19 the fetal rat liver has acquired a mature acute-phase system.

Comparative mutagenicity testing of a drug candidate, U-48753E: mechanism of induction of gene mutations in mammalian cells and quantitation of potential hazard

U-48753E is a potential human drug which was subjected to a battery of short-term assays for genetic activity. The compound was negative in the Salmonella (Ames) test, the in vitro UDS assay, the mouse bone-marrow micronucleus test and the Drosophila sex-linked recessive lethal assay. However, it was weakly positive in the CHO/HPRT assay in the presence of metabolic activation (S9). The weak positive response might easily have been labeled artifactual since there was no dose response and the dose level producing positive findings varied from experiment to experiment. In addition, the weak positive response was not confirmed in V79 cells. However, a reproducible dose-related increase in mutants was observed in the AS52/XPRT assay in the presence of S9. Metabolism of this drug proceeds through conversion of aliphatic N-methyl groups to formaldehyde. Addition of formaldehyde dehydrogenase to the S9 resulted in elimination of the mutagenicity of the compound in AS52 cells. Thus, the mutants were probably induced by formaldehyde. From the endogenous levels of formaldehyde in human blood, and the limiting potential therapeutic dose levels, the genotoxic hazard associated with U-48753E is marginal. This assessment of risk and its quantitation depend upon an understanding metabolism and exposure limits imposed by known side effects of the drug. This study can serve as a model for quantitative genetic risk assessment when mutagenicity is due to N-demethylation and formation of formaldehyde in situ.

Genotoxicity studies of methyl isocyanate in Salmonella, Drosophila, and cultured Chinese hamster ovary cells

The genotoxic effects of methyl isocyanate (MIC) were investigated using four short-term tests: the Salmonella reversion assay (Ames test), the Drosophila sex-linked recessive lethal assay, and the sister chromatid exchange (SCE) and chromosomal aberration assays in cultured Chinese hamster ovary (CHO) cells. No evidence was found for the induction of mutations in either Salmonella or Drosophila. MIC did, however, induce SCEs and chromosomal aberrations in CHO cells both in the presence and absence of Aroclor-induced rat liver S-9.