Clustering in surgical trials : database of intracluster correlations

PMID: 22217216 [PubMed - indexed for MEDLINE] PMCID: PMC3311136 Free PMC ArticlePeer reviewedPublisher PD

Why Can't Rodents Vomit? A Comparative Behavioral, Anatomical, and Physiological Study

The vomiting (emetic) reflex is documented in numerous mammalian species, including primates and carnivores, yet laboratory rats and mice appear to lack this response. It is unclear whether these rodents do not vomit because of anatomical constraints (e.g., a relatively long abdominal esophagus) or lack of key neural circuits. Moreover, it is unknown whether laboratory rodents are representative of Rodentia with regards to this reflex. Here we conducted behavioral testing of members of all three major groups of Rodentia; mouse-related (rat, mouse, vole, beaver), Ctenohystrica (guinea pig, nutria), and squirrel-related (mountain beaver) species. Prototypical emetic agents, apomorphine (sc), veratrine (sc), and copper sulfate (ig), failed to produce either retching or vomiting in these species (although other behavioral effects, e.g., locomotion, were noted). These rodents also had anatomical constraints, which could limit the efficiency of vomiting should it be attempted, including reduced muscularity of the diaphragm and stomach geometry that is not well structured for moving contents towards the esophagus compared to species that can vomit (cat, ferret, and musk shrew). Lastly, an in situ brainstem preparation was used to make sensitive measures of mouth, esophagus, and shoulder muscular movements, and phrenic nerve activity-key features of emetic episodes. Laboratory mice and rats failed to display any of the common coordinated actions of these indices after typical emetic stimulation (resiniferatoxin and vagal afferent stimulation) compared to musk shrews. Overall the results suggest that the inability to vomit is a general property of Rodentia and that an absent brainstem neurological component is the most likely cause. The implications of these findings for the utility of rodents as models in the area of emesis research are discussed. © 2013 Horn et al

A New Isoform of the Histone Demethylase JMJD2A/KDM4A Is Required for Skeletal Muscle Differentiation

In proliferating myoblasts, muscle specific genes are silenced by epigenetic modifications at their promoters, including histone H3K9 methylation. Derepression of the promoter of the gene encoding the myogenic factor myogenin (Myog) is key for initiation of muscle differentiation. The mechanism of H3K9 demethylation at the Myog promoter is unclear, however. Here, we identify an isoform of the histone demethylase JMJD2A/KDM4A that lacks the N-terminal demethylase domain (ΔN-JMJD2A). The amount of ΔN-JMJD2A increases during differentiation of C2C12 myoblasts into myotubes. Genome-wide expression profiling and exon-specific siRNA knockdown indicate that, in contrast to the full-length protein, ΔN-JMJD2A is necessary for myotube formation and muscle-specific gene expression. Moreover, ΔN-JMJD2A promotes MyoD-induced conversion of NIH3T3 cells into muscle cells. ChIP-on-chip analysis indicates that ΔN-JMJD2A binds to genes mainly involved in transcriptional control and that this binding is linked to gene activation. ΔN-JMJD2A is recruited to the Myog promoter at the onset of differentiation. This binding is essential to promote the demethylation of H3K9me2 and H3K9me3. We conclude that induction of the ΔN-JMJD2A isoform is crucial for muscle differentiation: by directing the removal of repressive chromatin marks at the Myog promoter, it promotes transcriptional activation of the Myog gene and thus contributes to initiation of muscle-specific gene expression

Methods and timing of biliary drainage for acute cholangitis: Tokyo Guidelines

Biliary drainage is a radical method to relieve cholestasis, a cause of acute cholangitis, and takes a central part in the treatment of acute cholangitis. Emergent drainage is essential for severe cases, whereas patients with moderate and mild disease should also receive drainage as soon as possible if they do not respond to conservative treatment, and their condition has not improved. Biliary drainage can be achieved via three different routes/procedures: endoscopic, percutaneous transhepatic, and open methods. The clinical value of both endoscopic and percutaneous transhepatic drainage is well known. Endoscopic drainage is associated with a low morbidity rate and shorter duration of hospitalization; therefore, this approach is advocated whenever it is applicable. In endoscopic drainage, either endoscopic nasobiliary drainage (ENBD) or tube stent placement can be used. There is no significant difference in the success rate, effectiveness, and morbidity between the two procedures. The decision to perform endoscopic sphincterotomy (EST) is made based on the patient’s condition and the number and diameter of common bile duct stones. Open drainage, on the other hand, should be applied only in patients for whom endoscopic or percutaneous transhepatic drainage is contraindicated or has not been successfully performed. Cholecystectomy is recommended in patients with gallbladder stones, following the resolution of acute cholangitis with medical treatment, unless the patient has poor operative risk factors or declines surgery

Convergence of Cells from the Progenitor Fraction of Adult Olfactory Bulb Tissue to Remyelinating Glia in Demyelinating Spinal Cord Lesions

Progenitor cells isolated from adult brain tissue are important tools for experimental studies of remyelination. Cells harvested from neurogenic regions in the adult brain such as the subependymal zone have demonstrated remyelination potential. Multipotent cells from the progenitor fraction have been isolated from the adult olfactory bulb (OB) but their potential to remyelinate has not been studied. cell bodies adjacent to and surrounding peripheral-type myelin rings.We report that neural cells from the progenitor fraction of the adult rat OB grown in monolayers can be expanded for several passages in culture and that upon transplantation into a demyelinated spinal cord lesion provide extensive remyelination without ectopic neuronal differentiation

Novel IgG-degrading enzymes of the IgdE protease family link substrate specificity to host tropism of <i>Streptococcus</i> species

Recently we have discovered an IgG degrading enzyme of the endemic pig pathogen S. suis designated IgdE that is highly specific for porcine IgG. This protease is the founding member of a novel cysteine protease family assigned C113 in the MEROPS peptidase database. Bioinformatical analyses revealed putative members of the IgdE protease family in eight other Streptococcus species. The genes of the putative IgdE family proteases of S. agalactiae, S. porcinus, S. pseudoporcinus and S. equi subsp. zooepidemicus were cloned for production of recombinant protein into expression vectors. Recombinant proteins of all four IgdE family proteases were proteolytically active against IgG of the respective Streptococcus species hosts, but not against IgG from other tested species or other classes of immunoglobulins, thereby linking the substrate specificity to the known host tropism. The novel IgdE family proteases of S. agalactiae, S. pseudoporcinus and S. equi showed IgG subtype specificity, i.e. IgdE from S. agalactiae and S. pseudoporcinus cleaved human IgG1, while IgdE from S. equi was subtype specific for equine IgG7. Porcine IgG subtype specificities of the IgdE family proteases of S. porcinus and S. pseudoporcinus remain to be determined. Cleavage of porcine IgG by IgdE of S. pseudoporcinus is suggested to be an evolutionary remaining activity reflecting ancestry of the human pathogen to the porcine pathogen S. porcinus. The IgG subtype specificity of bacterial proteases indicates the special importance of these IgG subtypes in counteracting infection or colonization and opportunistic streptococci neutralize such antibodies through expression of IgdE family proteases as putative immune evasion factors. We suggest that IgdE family proteases might be valid vaccine targets against streptococci of both human and veterinary medical concerns and could also be of therapeutic as well as biotechnological use

Knocking at the brain’s door: intravital two-photon imaging of autoreactive T cell interactions with CNS structures

Since the first applications of two-photon microscopy in immunology 10 years ago, the number of studies using this advanced technology has increased dramatically. The two-photon microscope allows long-term visualization of cell motility in the living tissue with minimal phototoxicity. Using this technique, we examined brain autoantigen-specific T cell behavior in experimental autoimmune encephalitomyelitis, the animal model of human multiple sclerosis. Even before disease symptoms appear, the autoreactive T cells arrive at their target organ. There they crawl along the intraluminal surface of central nervous system (CNS) blood vessels before they extravasate. In the perivascular environment, the T cells meet phagocytes that present autoantigens. This contact activates the T cells to penetrate deep into the CNS parenchyma, where the infiltrated T cells again can find antigen, be further activated, and produce cytokines, resulting in massive immune cell recruitment and clinical disease

Dosage Effects of Cohesin Regulatory Factor PDS5 on Mammalian Development: Implications for Cohesinopathies

Cornelia de Lange syndrome (CdLS), a disorder caused by mutations in cohesion proteins, is characterized by multisystem developmental abnormalities. PDS5, a cohesion protein, is important for proper chromosome segregation in lower organisms and has two homologues in vertebrates (PDS5A and PDS5B). Pds5B mutant mice have developmental abnormalities resembling CdLS; however the role of Pds5A in mammals and the association of PDS5 proteins with CdLS are unknown. To delineate genetic interactions between Pds5A and Pds5B and explore mechanisms underlying phenotypic variability, we generated Pds5A-deficient mice. Curiously, these mice exhibit multiple abnormalities that were previously observed in Pds5B-deficient mice, including cleft palate, skeletal patterning defects, growth retardation, congenital heart defects and delayed migration of enteric neuron precursors. They also frequently display renal agenesis, an abnormality not observed in Pds5B−/− mice. While Pds5A−/− and Pds5B−/− mice die at birth, embryos harboring 3 mutant Pds5 alleles die between E11.5 and E12.5 most likely of heart failure, indicating that total Pds5 gene dosage is critical for normal development. In addition, characterization of these compound homozygous-heterozygous mice revealed a severe abnormality in lens formation that does not occur in either Pds5A−/− or Pds5B−/− mice. We further identified a functional missense mutation (R1292Q) in the PDS5B DNA-binding domain in a familial case of CdLS, in which affected individuals also develop megacolon. This study shows that PDS5A and PDS5B functions other than those involving chromosomal dynamics are important for normal development, highlights the sensitivity of key developmental processes on PDS5 signaling, and provides mechanistic insights into how PDS5 mutations may lead to CdLS

Modelling Human Regulatory Variation in Mouse: Finding the Function in Genome-Wide Association Studies and Whole-Genome Sequencing

An increasing body of literature from genome-wide association studies and human whole-genome sequencing highlights the identification of large numbers of candidate regulatory variants of potential therapeutic interest in numerous diseases. Our relatively poor understanding of the functions of non-coding genomic sequence, and the slow and laborious process of experimental validation of the functional significance of human regulatory variants, limits our ability to fully benefit from this information in our efforts to comprehend human disease. Humanized mouse models (HuMMs), in which human genes are introduced into the mouse, suggest an approach to this problem. In the past, HuMMs have been used successfully to study human disease variants; e.g., the complex genetic condition arising from Down syndrome, common monogenic disorders such as Huntington disease and β-thalassemia, and cancer susceptibility genes such as BRCA1. In this commentary, we highlight a novel method for high-throughput single-copy site-specific generation of HuMMs entitled High-throughput Human Genes on the X Chromosome (HuGX). This method can be applied to most human genes for which a bacterial artificial chromosome (BAC) construct can be derived and a mouse-null allele exists. This strategy comprises (1) the use of recombineering technology to create a human variant–harbouring BAC, (2) knock-in of this BAC into the mouse genome using Hprt docking technology, and (3) allele comparison by interspecies complementation. We demonstrate the throughput of the HuGX method by generating a series of seven different alleles for the human NR2E1 gene at Hprt. In future challenges, we consider the current limitations of experimental approaches and call for a concerted effort by the genetics community, for both human and mouse, to solve the challenge of the functional analysis of human regulatory variation