Mouse models of non‐alcoholic steatohepatitis: A reflection on recent literature

Non‐alcoholic steatohepatitis (NASH) is strongly associated with overnutrition, insulin resistance, and predisposition to type 2 diabetes. To critically analyze the translational significance of currently used animal models of NASH, we reviewed articles published during the last 3 years that studied NASH pathogenesis using mouse models. Among 146 articles, 34 (23%) used models in which overnutrition was reported, and 36 (25%) demonstrated insulin resistance, with or without glucose intolerance. Half the articles contained no information on whether mice exhibited overnutrition or insulin resistance. While 75 papers (52%) reported > 2‐fold increase of serum/plasma alanine aminotransferase (ALT) compared with controls, ALT levels were near normal or not reported in 48%. Liver pathology was assessed by a pathologist with an interest in liver pathology in 53% of articles published in gastroenterology/hepatology journals, versus 43–44% in other journals. While there appears to be a trend to use models that are potentially relevant to the pathogenesis of human NASH, journals currently publish data on mouse models in which overnutrition and insulin resistance do not occur, without ALT increase or appropriate analysis of NASH pathology. We recommend that investigators, reviewers, and journal editors carefully consider the validity of NASH models in current use and that moves are made to reach a consensus on what the minimal criteria should be.     

Estrogen receptor of primary breast cancers: evidence for intracellular proteolysis

Iodinated oestradiol-labeled oestrogen receptor (ER) isoforms devoid of amino-terminal ABC domains represent about two-thirds of the whole receptor population detected in cytosol samples from human breast cancers. This high frequency could not be ascribed to the expression of truncated mRNAs, or to the proteolysis of the native ER peptide at the time of homogenization or assay, suggesting an intracellular proteolysis. Free amino-terminal and ligand-binding domains maintained together within oligomeric structure(s); increase of ionic strength separated them. The amino-terminal region was consistently detected in the cell nucleus by specific immunohistochemistry leading to the concept of a potential intranuclear association between ER cleavage products and/or other regulatory proteins.     

Efficient tracing of global isolates of Yersinia pestis by restriction fragment length polymorphism analysis using three insertion sequences as probes

Yersinia pestis is the etiologic agent of plague, a disease that is transmitted from rodent to rodent and from rodent to humans by fleabites. Multiple copies of three insertion sequences (IS100, IS285, and IS1541) are scattered over the Y. pestis genome. The genomic instability generated by these insertion sequences (IS) creates a polymorphism of the hybridizing restriction fragments (restriction fragment length polymorphism [RFLP]) which can be used to subtype this relatively clonal species. The aim of this work was to evaluate and compare the potential of the three IS-RFLP techniques, individually or in combination, to define clusters of strains according to their focus of origin. The analysis of 61 Y. pestis isolates of worldwide origin indicated that no satisfactory strain clustering was observed with each IS-RFLP used individually. In contrast, the combination of the three IS-RFLP data (3IS-RFLP) resulted in both an efficient strain discrimination (D = 0.999) and a robust clustering of the isolates according to their biovar and geographical origin. This geographical clustering was observed even within the Orientalis group, although these strains had only a short period of time (one century) to diverge from the original clone that spread globally. Therefore, 3IS-RFLP is a technique that may be useful for addressing epidemiological problems and forensic issues. When plague reemerges after several decades of silence in a quiescent focus, it may help in determining whether the disease was reimported or reactivated. It may also be of value to identify the origin of a strain when plague cases appear in a previously plague-free region. Finally, this technique could be useful for the tracing of a Y. pestis isolate that has been used as a biological terrorism threat.     

Could heart rate play a role in pericardial inflammation?

Purpose and medical hypothesis: Rest is usually recommended in acute pericarditis, as it could help to lower heart rate (HR) and contribute to limit "mechanical inflammation". Whether HR on admission could be correlated and perhaps participate to inflammation has not been reported. Methods: Between March 2007 and February 2010, we conducted a retrospective study on all patients admitted to our center for acute pericarditis. Diagnosis criteria included two of the following ones: typical chest pain, friction rub, pericardial effusion on cardiac echography, or typical electrocardiogram (ECG) findings. Primary endpoint was biology: CRP on admission, on days 1, 2, 3, and especially peak. Results: We included 73 patients. Median age was 38years (interquartiles 28-51) and median hospitalization duration was 2.0days (1.5-3.0). Median heart rate was 88.0beats per minute (bpm) on admission (interquartiles 76.0-100.0) and 72.0 on discharge (65.0-80.0). Heart rate on admission was significantly correlated with CRP peak (p<0.001), independently of temperature on admission, hospitalization duration and age. Recurrences occurred within 1month in 32% of patients. Heart rate on hospital discharge was correlated with recurrence, independently of age. Conclusion: In acute pericarditis, heart rate on admission is independently correlated with CRP levels and heart rate on discharge seems to be independently correlated to recurrence. This could suggest a link between heart rate and pericardial inflammation.     

Human intrathymic development: a selective approach

Human T lymphocytes can be generated from CD34 progenitor cells from different sources. This can be obtained in an in vivo model wherein human thymic tissue and fetal liver is transplanted in an immunodeficient mouse. However, human T cells are also generated in immunodeficient mice without co-transplantation of human thymus or in in vitro hybrid human-mouse fetal thymus organ culture. This shows that xenogeneic mouse thymus tissue supports human T cell differentiation. Finally, human T cells are generated on co-culture with murine stromal cells that express the Delta-like1 ligand for the Notch receptor. How these different environments influence the human T cell repertoire is reviewed and discussed.     

Naturally occurring substitutions of the human T-cell leukemia virus type 1 3' LTR influence strand-transfer reaction

Having isolated somatically mutated HTLV-1 3' LTR sequences from six infected individuals, the effect of these mutations on the integration process in vitro was investigated. Double-strand pre-processed HTLV-1 3' LTR ends (53-54 bp) were used in an in vitro strand-transfer reaction, together with HTLV-1 purified integrase and using a synthetic double-strand naked DNA oligonucleotide as target. Integration efficiency was measured by a fluorescent PCR assay. No significant difference in the pattern of strand transfer was observed between the distinct patients consensus sequences. For each patient, the effect of acquired somatic mutations was then assessed by comparing the strand-transfer efficiency of the mutated sequences (n=8, each harboring one to two substitutions) with that of the corresponding patient consensus sequence. Five somatic mutations or deletions at positions 7, 10, 21, 30, and 53 from the proviral 3' end did not alter the reaction efficiency. By contrast, a single G-->A transition at position 52 was found to result in 33% gain of function. Furthermore, a C-->T transition at 41 bp from the provirus 3' end decreased the reaction efficiency by 80%. This is the first study investigating the effect of naturally acquired substitutions on the strand-transfer capacity of long LTR sequences in vitro. Disproving the hitherto assumed opinion that integration specificity is restricted to the extreme boundary of the LTR end, i.e. the last 12-20 bp of the unintegrated provirus, the present results demonstrate that naturally occurred substitutions of the HTLV-1 LTR can alter significantly its strand-transfer capacity.     

EUCAST expert rules in antimicrobial susceptibility testing

EUCAST expert rules have been developed to assist clinical microbiologists and describe actions to be taken in response to specific antimicrobial susceptibility test results. They include recommendations on reporting, such as inferring susceptibility to other agents from results with one, suppression of results that may be inappropriate, and editing of results from susceptible to intermediate or resistant or from intermediate to resistant on the basis of an inferred resistance mechanism. They are based on current clinical and/or microbiological evidence. EUCAST expert rules also include intrinsic resistance phenotypes and exceptional resistance phenotypes, which have not yet been reported or are very rare. The applicability of EUCAST expert rules depends on the MIC breakpoints used to define the rules. Setting appropriate clinical breakpoints, based on treating patients and not on the detection of resistance mechanisms, may lead to modification of some expert rules in the future.     

Optimized Multilocus Variable-Number Tandem-Repeat Analysis Assay and Its Complementarity with Pulsed-Field Gel Electrophoresis and Multilocus Sequence Typing for Listeria monocytogenes Clone Identification and Surveillance

Populations of the food-borne pathogen Listeria monocytogenes are genetically structured into a small number of major clonal groups, some of which have been implicated in multiple outbreaks. The goal of this study was to develop and evaluate an optimized multilocus variable number of tandem repeat (VNTR) analysis (MLVA) subtyping scheme for strain discrimination and clonal group identification. We evaluated 18 VNTR loci and combined the 11 best ones into two multiplexed PCR assays (MLVA-11). A collection of 255 isolates representing the diversity of clonal groups within phylogenetic lineages I and II, including representatives of epidemic clones, were analyzed by MLVA-11, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE). MLVA-11 had less discriminatory power than PFGE, except for some clones, and was unable to distinguish some epidemiologically unrelated isolates. Yet it distinguished all major MLST clones and therefore constitutes a rapid method to identify epidemiologically relevant clonal groups. Given its high reproducibility and high throughput, MLVA represents a very attractive first-line screening method to alleviate the PFGE workload in outbreak investigations and listeriosis surveillance.