Changing patterns of infectious disease

Despite a century of often successful prevention and control efforts, infectious diseases remain an important global problem in public health, causing over 13 million deaths each year. Changes in society, technology and the microorganisms themselves are contributing to the emergence of new diseases, the re-emergence of diseases once controlled, and to the development of antimicrobial resistance. Two areas of special concern in the twenty-first century are food-borne disease and antimicrobial resistance. The effective control of infectious diseases in the new millennium will require effective public health infrastructures that will rapidly recognize and respond to them and will prevent emerging problems.     

Chronic gestational exposure to ethanol causes insulin and IGF resistance and impairs acetylcholine homeostasis in the brain

In fetal alcohol syndrome (FAS), cerebellar hypoplasia is associated with impaired insulin-stimulated survival signaling. This study characterizes ethanol dose-effects on cerebellar development, expression of genes required for insulin and insulin-like growth factor (IGF) signaling, and the upstream mechanisms and downstream consequences of impaired signaling in relation to acetylcholine (ACh) homeostasis. Pregnant Long Evans rats were fed isocaloric liquid diets containing 0%, 2%, 4.5%, 6.5%, or 9.25% ethanol from gestation day 6. Ethanol caused dose-dependent increases in severity of cerebellar hypoplasia, neuronal loss, proliferation of astrocytes and microglia, and DNA damage. Ethanol also reduced insulin, IGF-I, and IGF-II receptor binding, insulin and IGF-I receptor tyrosine kinase activities, ATP, membrane cholesterol, and choline acetyltransferase (ChAT) expression. In vitro studies linked membrane cholesterol depletion to impaired insulin receptor binding and insulin-stimulated ChAT. In conclusion, cerebellar hypoplasia in FAS is mediated by insulin/IGF resistance with attendant impairments in energy production and ACh homeostasis. Received 4 May 2006; received after revision 13 June 2006; accepted 20 June 2006     

Genome-wide meta-analysis increases to 71 the number of confirmed Crohn's disease susceptibility loci

We undertook a meta-analysis of six Crohn's disease genome-wide association studies (GWAS) comprising 6,333 affected individuals (cases) and 15,056 controls and followed up the top association signals in 15,694 cases, 14,026 controls and 414 parent-offspring trios. We identified 30 new susceptibility loci meeting genome-wide significance (P < 5 × 10??). A series of in silico analyses highlighted particular genes within these loci and, together with manual curation, implicated functionally interesting candidate genes including SMAD3, ERAP2, IL10, IL2RA, TYK2, FUT2, DNMT3A, DENND1B, BACH2 and TAGAP. Combined with previously confirmed loci, these results identify 71 distinct loci with genome-wide significant evidence for association with Crohn's disease.     

A cryptic protease couples deubiquitination and degradation by the proteasome

The 26S proteasome is responsible for most intracellular proteolysis in eukaryotes. Efficient substrate recognition relies on conjugation of substrates with multiple ubiquitin molecules and recognition of the polyubiquitin moiety by the 19S regulatory complex--a multisubunit assembly that is bound to either end of the cylindrical 20S proteasome core. Only unfolded proteins can pass through narrow axial channels into the central proteolytic chamber of the 20S core, so the attached polyubiquitin chain must be released to allow full translocation of the substrate polypeptide. Whereas unfolding is rate-limiting for the degradation of some substrates and appears to involve chaperone-like activities associated with the proteasome, the importance and mechanism of degradation-associated deubiquitination has remained unclear. Here we report that the POH1 (also known as Rpn11 in yeast) subunit of the 19S complex is responsible for substrate deubiquitination during proteasomal degradation. The inability to remove ubiquitin can be rate-limiting for degradation in vitro and is lethal to yeast. Unlike all other known deubiquitinating enzymes (DUBs) that are cysteine proteases, POH1 appears to be a Zn(2+)-dependent protease.     

Kant on science and normativity

The aim of this paper is to explore Kant’s account of normativity through the prism of the distinction between the natural and the human sciences. Although the pragmatic orientation of the human sciences is often defined in contrast with the theoretical orientation of the natural sciences, I show that they are in fact regulated by one and the same norm, namely reason’s demand for autonomy.     

Mode of action for inorganic arsenic toxicity and carcinogenesis

Inorganic arsenic(iAs) at high doses is a known human carcinogen, inducing tumors of the skin,urinary bladder, and lung. It is also associated with noncancer toxicities. An understanding of the mode of action(MOA) for arsenic-induced effects is needed to develop a scientifically-based risk assessment. To determine an MOA for iAs induced toxicities, it is necessary to understand the metabolism, kinetics, cell transport, and interaction with specific proteins of iAs. Based on in vitro investigations using animal and human cells, studies from animal models,and clinical and epidemiological studies, we have proposed an MOA involving formation of sufficient levels of reactive trivalent metabolites which interact with critical free sulfhydryl groups, leading to cytotoxicity and regenerative cell proliferation. There is a strong correlation between in vitro cytotoxicity([0.1 lmol/L trivalent arsenicals) and the no effect levels in rodents [approximately 1 ppm(1 ppm = 1 mg/L) of water or diet]. In epithelial target tissues, the cytotoxic effects of iAs result in chronic precursor lesions which have the potential for an increased risk of developing cancer. In non-epithelial tissues, noncancer toxicities such as hypertension and atherosclerosis develop. This MOA implies a non-linear, threshold dose–response relationship for both non-cancer and cancer end points of exposure to iAs.     

Second messenger role for Mg2+ revealed by human T-cell immunodeficiency

The magnesium ion, Mg(2+), is essential for all life as a cofactor for ATP, polyphosphates such as DNA and RNA, and metabolic enzymes, but whether it plays a part in intracellular signalling (as Ca(2+) does) is unknown. Here we identify mutations in the magnesium transporter gene, MAGT1, in a novel X-linked human immunodeficiency characterized by CD4 lymphopenia, severe chronic viral infections, and defective T-lymphocyte activation. We demonstrate that a rapid transient Mg(2+) influx is induced by antigen receptor stimulation in normal T cells and by growth factor stimulation in non-lymphoid cells. MAGT1 deficiency abrogates the Mg(2+) influx, leading to impaired responses to antigen receptor engagement, including defective activation of phospholipase Cγ1 and a markedly impaired Ca(2+) influx in T cells but not B cells. These observations reveal a role for Mg(2+) as an intracellular second messenger coupling cell-surface receptor activation to intracellular effectors and identify MAGT1 as a possible target for novel therapeutics.