Lethality Levels Research Articles

Heat Penetration Characteristics and Quality Evaluation of Pangasius (Pangasius hypophthalmus) Chunks in Masala Using Retort Pouches

A South Indian dish was developed using Pangasius fish (Pangasius hypophthalmus) fillet chunks in masalas as a medium. The aim of the current study was to optimize the various F₀ values for Pangasius fillet chunks packed in masala, using flexible, retortable pouches. After being processed at different lethality levels, the product showed a similar heating and cooling lag factor. For F₀ values of 7.37 and 8.12 minutes, the total process time were 26.94 and 31.37 minutes, respectively. The fh values for products processed at F₀ values of 7.37 and 8.12 minutes were 13 and 16.5 minutes, respectively. The cook value obtained for the thermally processed product was 64.70 minutes for F₀ 7.37 minutes and 65.87 minutes for F₀ 8.12 minutes. Over a storage duration of up to 90 days, all instrumental texture indicators exhibited a declining pattern. The product processed at Fo value of 7.37 and 8.12 minutes were achieved commercial sterility. The product processed at F₀ 7.37 minutes was considered more favourable based on organoleptic assessment.

O-209 Identifying toxicity trends: analysis of over 6700 Mouse Embryo Assays performed on 16 categories of IVF supplies

Abstract Study question What type of disposables and solutions exhibit a higher frequency of Mouse Embryo Assay (MEA) failure and where should manufacturers put special attention during production? Summary answer Flexipet-pipette types, protein supplements, ovum-pick-up needles, catheters, steripettes, culture media, and mineral oils showed higher MEA-failure frequencies and/or lethality levels due to embryotoxicity among IVF-supplies. What is known already The MEA is considered the gold standard assay for quality control of IVF products. It is based on the analysis of in vitro mouse embryonic development under direct or indirect presence of a to-be-tested product, and it requires over 80% expanded blastocyst formation rates (EBFRs) for a product to be considered non-toxic and be released to the market. Recent episodes reported toxicity issues found in embryo culture supplies and IVF industry devices that were recalled by manufacturers. This underscores the necessity for more specific characterization of products, guidelines, and rigorous quality control protocols to prevent potentially adverse clinical outcomes. Study design, size, duration MEAs were conducted over 5 years on 6759 batches encompassing 16 categories of IVF products from various manufacturers. Results were retrospectively analysed based on MEA test outcomes for each category. A total of 217 dishes, 610 catheters, 1182 culture media, 135 steripettes, 1907 mineral oils, 167 glass-pasteur pipettes, 66 protein supplements, 207 flexipet-pipettes, 191 pipette tips, 96 PVPs, 68 syringes, 126 tubes, 1294 vitrification kits, 182 micropipettes, 98 disinfectants, and 213 needles lots were analysed. Participants/materials, setting, methods All procedures adhered to protocols approved by an Ethical Committee. Samples underwent classification as toxic or non-toxic based on MEAs results, and the proportion of samples that tested positive for embryotoxicity was determined for each category. Statistical comparisons were made among categories to identify those most prone to be identified as toxic. Additionally, in failed assays, mean EBFRs were categorized into 0-30%, 30%-70%, and 70%-80% ranges to assess extreme, mild and low sample-toxicity levels, respectively. Main results and the role of chance Out of 16 studied categories, only 5 of them exceeded a 5% of toxic lots. Flexipet-pipette types were reported as the highest toxic-samples rate category, with 72 out of the 207 tested batches (34.8%) failing the MEA. Protein supplements were found to be the second highest toxicity-ranked category, with 14/66 noxious lot samples (21.2%). They were followed by needles and catheters with 36/213 (16.9%) and 68/610 toxic lot samples (11.2%), respectively. Finally, a considerably lower toxicity rate was obtained with steripettes, with 10/135 samples reported as toxic (7.4%). Among these five top toxic-samples rate categories, protein supplements were found to possess a mild lethal effect on embryos, with a 43.6% mean EBFR in failed assays. However, extreme embryotoxic effects were reported for the remaining highest toxic-samples rate categories, based on their mean EBFR in failed assays: 20.8% for flexipet-pipette types, 16.2% for needles, 10.8% for steripettes, and 10.3% for catheters. Interestingly, although culture media and mineral oils were not among the top MEA-failure frequencies, as only 48/1182 (4.1%) and 23/1907 (1.2%) toxic lot samples were registered for each category, respectively, both categories showed a nearly-extreme lethality caused by their toxic-assessed samples, reflected in 31.7 and 35.1% mean EBFRs. Limitations, reasons for caution Increasing the number of sample-providing manufacturers per category might strengthen the wider market representativeness of the results. Moreover, it should be noted that the identification of specific sources of toxicity results highly difficult, hindering the implantation of corrector modifications within the manufacturing process. Wider implications of the findings These findings indicate that protein supplements, flexipet-pipette types, steripettes, catheters and needles exhibit a heightened toxicity tendency. Additionally, toxic mineral oils and culture media-linked high-embryotoxicity levels were observed. Therefore, special attention should be given to the production of these demonstrated potentially embryotoxic products to identify and mitigate clinical toxicity risks. Trial registration number Not applicable

Zebrafish mylipb attenuates antiviral innate immunity through two synergistic mechanisms targeting transcription factor irf3.

IFN regulatory factor 3 (IRF3) is the transcription factor crucial for the production of type I IFN in viral defence and inflammatory responses. The activity of IRF3 is strictly modulated by post-translational modifications (PTMs) to effectively protect the host from infection while avoiding excessive immunopathology. Here, we report that zebrafish myosin-regulated light chain interacting protein b (mylipb) inhibits virus-induced type I IFN production via two synergistic mechanisms: induction of autophagic degradation of irf3 and reduction of irf3 phosphorylation. In vivo, mylipb-null zebrafish exhibit reduced lethality and viral mRNA levels compared to controls. At the cellular level, overexpression of mylipb significantly reduces cellular antiviral capacity, and promotes viral proliferation. Mechanistically, mylipb associates with irf3 and targets Lys 352 to increase K6-linked polyubiquitination, dependent on its E3 ubiquitin ligase activity, leading to autophagic degradation of irf3. Meanwhile, mylipb acts as a decoy substrate for the phosphokinase tbk1 to attenuate irf3 phosphorylation and cellular antiviral responses independent of its enzymatic activity. These findings support a critical role for zebrafish mylipb in the limitation of antiviral innate immunity through two synergistic mechanisms targeting irf3.

Phytochemical profiling of Costus (Saussurea lappa Clarke) root essential oil, and its antimicrobial and toxicological effects

Purpose: To carry out gas chromatography-mass spectrometry (GC-MS) analysis of the phytochemical content of the root essential oil of Saussurea lappa Clarke Asteraceae (Costus, SLEO), and to evaluate its physicochemical, antimicrobial and cytoxic properties.
 Methods: The oil was extracted from the plant’s roots by steam distillation using a Clevenger system. Various physicochemical parameters for the oil including refractive index, color, acid value, saponification number, ester and peroxide values were measured. Flavonoid content was assessed using thin layer chromatography (TLC). Thermoscientific trace ultra gas chromatograph equipped with a Thermoscientific capillary TR-5MS column was utilized to determine the volatile components of SLEO. Antimicrobial activity of SLEO was performed against various Gram (+ve) and Gram (-ve) microorganisms, viz, Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans, while cytotoxic effect was monitored using Artemia salina (brine shrimp) lethality assay.
 Results: Essential oil yield was good (3 %). Concentration-dependent antimicrobial effects were observed on all test microorganisms and no marked difference in lethality levels was observed among the tested SLEO concentrations on brine shrimp (p < 0.05). The main component of SLEO was costunolide or eudesma-5,11(13)-dien-8,12-olide (52.01 %).
 Conclusion: The results indicate the promising therapeutic properties of S. lappa. However, further phytochemical and biological investigations are required to establish the mechanism of action and toxicological the extract.

Quantitative risk analysis of a hazardous jet fire event for hydrogen transport in natural gas transmission pipelines

With the advent of large-scale application of hydrogen, transportation becomes crucial. Reusing the existing natural gas transmission system could serve as catalyst for the future hydrogen economy. However, a risk analysis of hydrogen transmission in existing pipelines is essential for the deployment of the new energy carrier. This paper focuses on the individual risk (IR) associated with a hazardous hydrogen jet fire and compares it with the natural gas case. The risk analysis adopts a detailed flame model and state of the art computational software, to provide an enhanced physical description of flame characteristics.This analysis concludes that hydrogen jet fires yield lower lethality levels, that decrease faster with distance than natural gas jet fires. Consequently, for large pipelines, hydrogen transmission is accompanied by significant lower IR. Howbeit, ignition effects increasingly dominate the IR for decreasing pipeline diameters and cause hydrogen transmission to yield increased IR in the vicinity of the pipeline when compared to natural gas.

Non-Homologous End Joining Factors XLF, PAXX and DNA-PKcs Maintain the Neural Stem and Progenitor Cell Population

Non-homologous end-joining (NHEJ) is a major DNA repair pathway in mammalian cells that recognizes, processes and fixes DNA damage throughout the cell cycle and is specifically important for homeostasis of post-mitotic neurons and developing lymphocytes. Neuronal apoptosis increases in the mice lacking NHEJ factors Ku70 and Ku80. Inactivation of other NHEJ genes, either Xrcc4 or Lig4, leads to massive neuronal apoptosis in the central nervous system (CNS) that correlates with embryonic lethality in mice. Inactivation of either Paxx, Mri or Dna-pkcs NHEJ gene results in normal CNS development due to compensatory effects of Xlf. Combined inactivation of Xlf/Paxx, Xlf/Mri and Xlf/Dna-pkcs, however, results in late embryonic lethality and high levels of apoptosis in CNS. To determine the impact of NHEJ factors on the early stages of neurodevelopment, we isolated neural stem and progenitor cells from mouse embryos and investigated proliferation, self-renewal and differentiation capacity of these cells lacking either Xlf, Paxx, Dna-pkcs, Xlf/Paxx or Xlf/Dna-pkcs. We found that XRCC4-like factor (XLF), DNA-dependent protein kinase catalytic subunit (DNA-PKcs) and paralogue of XRCC4 and XLF (PAXX) maintain the neural stem and progenitor cell populations and neurodevelopment in mammals, which is particularly evident in the double knockout models.

Cardioprotective effect of lipstatin derivative orlistat on normotensive rats submitted to cardiac ischemia and reperfusion

To evaluate in vivo animal model of cardiac ischemia/reperfusion the cardioprotective activity of pancreatic lipase inhibitor of the orlistat. Adult male Wistar rats were anesthetized, placed on mechanical ventilation and underwent surgery to induce cardiac I/R by obstructing left descending coronary artery followed by reperfusion to evaluation of ventricular arrhythmias (VA), atrioventricular block (AVB) and lethality (LET) with pancreatic lipase inhibitor orlistat (ORL). At the end of reperfusion, blood samples were collected for determination of triglycerides (TG), very low-density lipoprotein (VLDL), low-density lipoprotein (LDL), high-density lipoprotein (HDL), lactate dehydrogenase (LDH), creatine kinase (CK), and creatine kinase-MB (CK-MB). Treatment with ORL has been able to decrease the incidence of VA, AVB and LET. Besides that, treatment with ORL reduced serum concentrations of CK and LDL, but did not alter the levels of serum concentration of TG, VLDL and HDL. The reduction of ventricular arrhythmias, atrioventricular block, and lethality and serum levels of creatine kinase produced by treatment with orlistat in animal model of cardiac isquemia/reperfusion injury suggest that ORL could be used as an efficient cardioprotective therapeutic strategy to attenuate myocardial damage related to acute myocardial infarction.

GADD34 suppresses lipopolysaccharide-induced sepsis and tissue injury through the regulation of macrophage activation.

Growth arrest and DNA damage inducible protein 34 (GADD34) is induced by various cellular stresses, such as DNA damage, endoplasmic reticulum stress, and amino-acid deprivation. Although the major roles of GADD34 are regulating ER stress responses and apoptosis, a recent study suggested that GADD34 is linked to innate immune responses. In this report, we investigated the roles of GADD34 in inflammatory responses against bacterial infection. To explore the effects of GADD34 on systemic inflammation in vivo, we employed a lipopolysaccharide (LPS)-induced murine sepsis model and assessed the lethality, serum cytokine levels, and tissue injury in the presence or absence of GADD34. We found that GADD34 deficiency increased the lethality and serum cytokine levels in LPS-induced sepsis. Moreover, GADD34 deficiency enhanced tissue destruction, cell death, and pro-inflammatory cytokine expression in LPS-induced acute liver injury. Pro-inflammatory cytokine production after LPS stimulation is regulated by the Toll-like receptor 4 (TLR4)-mediated NF-κB signaling pathway. In vitro experiments revealed that GADD34 suppressed pro-inflammatory cytokine production by macrophages through dephosphorylation of IKKβ. In conclusion, GADD34 attenuates LPS-induced sepsis and acute tissue injury through suppressing macrophage activation. Targeting this anti-inflammatory role of GADD34 may be a promising area for the development of therapeutic agents to regulate inflammatory disorders.

Abstract 1425: FBXO11 suppresses epithelial plasticity and proliferation by ubiquitinating the Snail family of transcription factors

Abstract Epithelial-to-mesenchymal transition (EMT) is central to embryonic development and carcinoma progression. The cell adhesion molecule E-cadherin critically maintains epithelial property and restricts epithelial cell proliferation and motility. The Snail family of transcription factors are core inducers of EMT in part through direct repression of E-cadherin transcription. The Snail factors are normally under tight control to safeguard epithelial identity and homeostasis. However, their physiological regulation remains largely elusive. In the present study, we show that the F-box protein FBXO11 binds to Snail in a phosphorylation-independent manner and targets it for ubiquitin-mediated proteasomal degradation. FBXO11 promotes the degradation of other Snail family members Slug and SCRT1 as well. Overexpression of FBXO11 in mesenchymal cells reduces Snail protein abundance and activates E-cadherin transcription. Conversely, depletion of endogenous FBXO11 in epithelial cancer cells causes Snail protein accumulation, EMT, and tumor invasion. Human cancer-derived FBXO11 missense mutants are impaired to degrade Snail. In human cancer, FBXO11 expression correlates with E-cadherin, and decreased expression of FBXO11 is robustly associated with adverse clinical outcomes. Inactivation of FBXO11 in mice results in neonatal lethality, increased Snail and Slug protein levels, decreased E-cadherin expression, and epidermal hyperplasia, which phenotypically resemble epidermis-specific transgenic overexpression of Snail or deletion of E-cadherin. These findings establish FBXO11 as a physiological ubiquitin ligase of Snails that is indispensable for suppressing epithelial hyperproliferation and plasticity during embryonic development and carcinoma progression. Note: This abstract was not presented at the meeting. Citation Format: Jianrong Lu, Yue Jin, Anitha K. Shenoy, Hao Chen, Huacheng Luo,Lizi Wu, Kamal A. Mohammed. FBXO11 suppresses epithelial plasticity and proliferation by ubiquitinating the Snail family of transcription factors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1425. doi:10.1158/1538-7445.AM2015-1425

Modelling the impact of the environmental scenario on population recovery from chemical stress exposure: A case study using Daphnia magna

Recovery of organisms is an important attribute for evaluating the acceptability of chemicals’ effects in ecological risk assessment in Europe. Recovery in the field does not depend on the chemical's properties and type of exposure only, but it is strongly linked to important environmental variables and biological interactions as well. Yet, these remain only marginally considered in the European risk assessment of chemicals. Here, we use individual-based modelling to investigate how the environmental scenario affects Daphnia magna population recovery from chemical exposure. Simulation experiments were performed for chemicals with lethality levels ranging from 40% to 90% at different food and temperature conditions. The same toxicity levels were then tested in combination with biological interactions including predation or competition. Results show that for the same chemical effect strength, populations often exhibited different recovery times in a different environmental context. The interactions between the chemical and the environmental variables were the strongest determinants of population recovery. Most important, biotic interactions even induced opposite effects on recovery at low and at high mortality levels. Results of this study infer that no specific role can be attributed to any abiotic or biotic variable in isolation. We conclude that unless the complex interactive mechanisms between the different factors constituting the full environmental scenario are taken into account in risk assessment, we cannot achieve a complete understanding of recovery processes from chemical effects.

Generation of mice encoding a conditional null allele of Gcm2.

Glial cells missing homolog 2 (GCM2) is a transcription factor that is expressed predominately in the pharyngeal pouches and, at later stages, in the developing and mature parathyroid glands. In humans, loss of GCM2 function, either through recessive apomorphic mutations or dominant inhibitor mutations in the human GCM2 gene, leads to isolated hypoparathyroidism. In mice, homozygous disruption of Gcm2 by conventional gene targeting results in parathyroid aplasia and hypoparathyroidism. In this study, we report the generation and functional characterization of mice encoding a conditional null allele of Gcm2. We demonstrate the functional integrity of the conditional Gcm2 allele and report successful in vivo deletion of exon 2 using Cre recombinase. The mice with conditional deletion of Gcm2 displayed phenotypes similar to those previously described for a conventional Gcm2 knockout, including perinatal lethality, hypocalemia, low or undetectable serum levels of parathyroid hormone, and absent parathyroid glands. The production of a conditional mutant allele for Gcm2 represents a valuable resource for the study of the temporal- and spatial-specific roles for Gcm2, and for understanding the postnatal activities of GCM2 protein.

One‐year follow up after admission to an emergency department for drug overdose in Japan

The aim of the study was to investigate the incidence of and risk factors for repetition of suicidal behavior within a year after admission for drug overdose in Japan. Patients admitted to the emergency department of a general public hospital in Tokyo for drug overdose of prescribed medicine and/or over-the-counter drugs between March 2008 and February 2009 were followed up after 1 year. Demographic characteristics, previous suicide attempts, and mental health state were examined by self-report questionnaire and interview at recovery from the initial attempt. Information about suicidal behavior during the follow-up period was obtained from the outpatient psychiatrists by postal questionnaire 1 year after discharge. Of 190 patients admitted to the emergency department, 132 patients answered the questionnaire and had the interview. Information about thefollow-up period for 66 patients was obtained. Of the 66 patients, 28 patients attempted suicide again and two patients committed suicide during the 1-year follow-up period. Psychiatric diagnosis of personality disorder and denial of suicidal intent at the time of recovery were associated with increased risk for another suicide attempt. Lethality levels of suicidal behaviors before and after admission were associated with each other. The rate of fatal and non-fatal suicide attempt within a year after admission for self-poisoning was substantial. Psychiatric diagnosis of personality disorder was a risk factor for repetition of suicide attempt. Clinicians should pay attention to the means of previous suicide attempts even though the patient denies suicidal intent at recovery.

Lyubertsy Study of mortality in patients with acute myocardial infarction (LIS): the analysis of anamnestic predictors of in-hospital mortality

Aim. To identify the main anamnestic predictors of mortality in the acute phase of acute myocardial infarction (AMI). Material and methods. The study included all patients admitted to Lyubertsy District hospitals and diagnosed with AMI (n=1133). Results. Out of 1133 hospitalised patients, 172 died in the hospital; in-hospital lethality was 15,2%. Mean age of diseased patients was significantly higher than that in those survived. The risk of in-hospital death was significantly and independently associated with older age (relative risk 1,07). After adjustment for age and sex, other independent predictors of in-hospital AMI death included diabetes mellitus (DM), low physical activity, and selected psychosocial factors. Conclusion. The in-hospital lethality levels, observed in the LIS Study, were typical for the Russian Federation. The main anamnestic predictors of in-hospital death were low physical activity, DM, and psychosocial risk factors.

Loss of Bright/ARID3a Function Promotes Developmental Plasticity

B-cell regulator of immunoglobulin heavy chain transcription (Bright)/ARID3a, an A+T-rich interaction domain protein, was originally discovered in B lymphocyte lineage cells. However, expression patterns and high lethality levels in knockout mice suggested that it had additional functions. Three independent lines of evidence show that functional inhibition of Bright results in increased developmental plasticity. Bright-deficient cells from two mouse models expressed a number of pluripotency-associated gene products, expanded indefinitely, and spontaneously differentiated into cells of multiple lineages. Furthermore, direct knockdown of human Bright resulted in colonies capable of expressing multiple lineage markers. These data suggest that repression of this single molecule confers adult somatic cells with new developmental options.

Crystal Structure of the BARD1 Ankyrin Repeat Domain and Its Functional Consequences

BARD1 is the constitutive nuclear partner to the breast and ovarian cancer-specific tumor suppressor BRCA1. Together, they form a heterodimeric complex responsible for maintaining genomic stability through nuclear functions involving DNA damage signaling and repair, transcriptional regulation, and cell cycle control. We report the 2.0A structure of the BARD1 ankyrin repeat domain. The structure includes four ankyrin repeats with a non-canonical C-terminal capping ankyrin repeat and a well ordered extended loop preceding the first repeat. Conserved surface features show an acidic patch and an acidic pocket along the surface typically used by ankyrin repeat domains for binding cognate proteins. We also demonstrate that two reported mutations, N470S and V507M, in the ankyrin repeat domain do not result in observable structural defects. These results provide a structural basis for exploring the biological function of the ankyrin repeat domain and for modeling BARD1 isoforms.

Validation Guidelines for a Jerky Pasteurization Process in a Low-Cost Dehydrator~!2008-04-21~!2008-04-30~!2008-06-12~!

Validation of a simple and inexpensive dehydration system used to achieve required lethality levels in jerky products is described. Factors influencing the dehydration process were investigated. Steps in the process can be used as validation guidelines for similar systems. Temperature variations within the drying chamber were reduced by improving air circulation and tuning the ventilation system with regard to fan speed, fan blade clearance and air flow path. The me- chanical complexity of the system was simplified by replacing multiple, high-speed fans with a single, low-speed, high- volume fan. Wet-bulb temperature in the dehydration chamber was compared to the internal temperature of 6 mm thick marinated beef jerky slices during the pasteurization process. There was no significant difference between the dehydrator wet-bulb temperature and the product internal temperature after the wet-bulb temperature reached 60 C. Wet-bulb tem- perature can be used as an effective critical control point (CCP) for product pasteurization for specific cases when verified with field trials.

Comparison of proteins, lethality and immunogenic compounds of Androctonus crassicauda (Olivier, 1807) (Scorpiones: Buthidae) venom obtained by different methods

Scorpions are venomous arthropods of the class Arachnida and are considered relatives of spiders, ticks and mites. There are approximately 1,500 species of scorpions worldwide, which are characterized by an elongated body and a segmented tail that ends in a venomous stinger. No specific treatment is available for scorpion envenomation, except for the use of antivenom. The current study aimed at comparing protein content and lethality of Androctonus crassicauda venom extracted by two different methods (electric stimulation and maceration of telsons). The LD50 calculated by probit analysis was 1.1mg/kg for venom obtained by electric stimulation and 39.19mg/kg for venom obtained by maceration of telsons. In the electrophoretic analysis, protein bands of the venom sample obtained by electric stimulation were between 12 and 53kDa (total: five bands), and those of venom extracted by maceration appeared as multiple protein bands, relative to the other venom sample. Low-molecular-weight proteins, revealed by western blotting, played an important immunogenic role in the production of antivenom. Lethality and protein levels varied according to the extraction method; venom obtained by the maceration technique showed lower toxicity than that obtained by electric stimulation.

Hydrophobicity, Cell Adherence, Cytotoxicity, and Enterotoxigenicity of Starved Vibrio parahaemolyticus

Vibrio parahaemolyticus is a ubiquitous gram-negative enteropathogenic bacterium that may encounter starvation or other environmental stresses during food processing or human infection. Pathogenic V. parahaemolyticus ST550 cultures starved in modified Morita mineral salt solution with 3 or 0.5% NaCl exhibited similar resistance against challenges of environmental stresses. Changes in virulence of the starved V. parahaemolyticus was determined using HEp-2 cell culture and suckling mouse assay. The starved cells exhibited greater cell adherence and hydrophobicity than did the cells in exponential growth phase. Expression of virulence in terms of cytotoxicity and mouse lethality was lower in the starved cells than in the exponential-phase cells at the same postinfection time. An additional 1 h of in vitro or in vivo incubation was required to enable these starved cells to reach the same cytotoxicity and mouse lethality levels as exhibited by the exponential-phase cells.

Keratin mutation in transgenic mice predisposes to Fas but not TNF-induced apoptosis and massive liver injury

Hepatocytes express keratins 8 and 18 (K8/18) as their only cytoskeletal intermediate filament (IF) proteins, and K8/18 mutations predispose their carriers to liver cirrhosis. Transgenic mice that overexpress mutant human K18 (Arg89→Cys [R89C]) develop mild chronic hepatitis, hepatocyte fragility, keratin filament disruption, and increased susceptibility to drug-induced liver injury. K18 is a major caspase substrate during apoptosis, and K8- or K18-null mice are significantly predisposed to Fas- and possibly tumor necrosis factor (TNF)-mediated apoptosis in the liver. Here we tested the potential role of the K18 R89C mutation on Fas- or TNF-mediated apoptotic liver injury by injecting Fas antibody (Ab) or TNF-α plus actinomycin D into mice that overexpress wild-type (WT) human K18 (with intact filament network, termed TG2 mice) or into K18 R89C mice (with disrupted filament network). K18 R89C mice are significantly more susceptible to Fas-mediated liver injury compared with nontransgenic and TG2 mice. This included differences in lethality, histology, apoptosis, and serum transaminase levels. In contrast, K18 WT and R89C mice manifest similar sensitivity to TNF-induced injury. Both Fas- and TNF-induced apoptosis in liver tissues are associated with caspase-mediated K18 degradation and increased keratin phosphorylation on several but not all sites. In conclusion, transgenic mouse K18 mutation and its consequent keratin filament disruption predispose hepatocytes to Fas- but not TNF-mediated apoptotic injury. This supports the association of keratin mutations with cirrhosis in patients with liver disease and suggests that keratins modulate apoptosis induced by Fas but not TNF. (H epatology 2003;37:1006-1014.)

Explaining social learning of food preferences without aversions: an evolutionary simulation model of Norway rats.

Norway rats (Rattus norvegicus) transmit preferences for novel foods socially by smelling each other's breath. However, rats fail to learn aversions, acquiring a preference even if the rat whose breath they smell has been poisoned. Rats can distinguish between sick and healthy conspecifics and social learning of both preferences and aversions is present in other species - hence it is unclear why rats cannot learn aversions socially. We constructed an evolutionary simulation in which a population of rats foraged from a central location, exploiting food sites that could contain edible or toxic foodstuffs. We examined the relationship between toxin lethality and selection for individual versus social learning and discrimination between sick and healthy conspecifics in order to allow learning of both preferences and aversions. At low lethality levels individual learning was selected for and at intermediate levels we found social learning of both preferences and aversions. Finally, given high lethality levels the simulated rats would employ social learning but failed to learn aversions, matching the behaviour of real rats. We argue that Norway rats do not learn aversions socially because their environment may contain only highly lethal toxins which make interaction with a sick conspecific an extremely rare event.