Effects of diet and exercise in preventing NIDDM in people with impaired glucose tolerance. The Da Qing IGT and Diabetes Study

OBJECTIVE

Individuals with impaired glucose tolerance (IGT) have a high risk of developing NIDDM. The purpose of this study was to determine whether diet and exercise interventions in those with IGT may delay the development of NIDDM, i.e., reduce the incidence of NIDDM, and thereby reduce the overall incidence of diabetic complications, such as cardiovascular, renal, and retinal disease, and the excess mortality attributable to these complications.

RESEARCH DESIGN AND METHODS

In 1986, 110,660 men and women from 33 health care clinics in the city of Da Qing, China, were screened for IGT and NIDDM. Of these individuals, 577 were classified (using World Health Organization criteria) as having IGT. Subjects were randomized by clinic into a clinical trial, either to a control group or to one of three active treatment groups: diet only, exercise only, or diet plus exercise. Follow-up evaluation examinations were conducted at 2-year intervals over a 6-year period to identify subjects who developed NIDDM. Cox's proportional hazard analysis was used to determine if the incidence of NIDDM varied by treatment assignment.

RESULTS

The cumulative incidence of diabetes at 6 years was 67.7% (95% CI, 59.8-75.2) in the control group compared with 43.8% (95% CI, 35.5-52.3) in the diet group, 41.1% (95% CI, 33.4-49.4) in the exercise group, and 46.0% (95% CI, 37.3-54.7) in the diet-plus-exercise group (P < 0.05). When analyzed by clinic, each of the active intervention groups differed significantly from the control clinics (P < 0.05). The relative decrease in rate of development of diabetes in the active treatment groups was similar when subjects were stratified as lean or overweight (BMI < or > or = 25 kg/m2). In a proportional hazards analysis adjusted for differences in baseline BMI and fasting glucose, the diet, exercise, and diet-plus-exercise interventions were associated with 31% (P < 0.03), 46% (P < 0.0005), and 42% (P < 0.005) reductions in risk of developing diabetes, respectively.

CONCLUSIONS

Diet and/or exercise interventions led to a significant decrease in the incidence of diabetes over a 6-year period among those with IGT.

OARSI guidelines for the non-surgical management of knee, hip, and polyarticular osteoarthritis

OBJECTIVE

To update and expand upon prior Osteoarthritis Research Society International (OARSI) guidelines by developing patient-focused treatment recommendations for individuals with Knee, Hip, and Polyarticular osteoarthritis (OA) that are derived from expert consensus and based on objective review of high-quality meta-analytic data.

METHODS

We sought evidence for 60 unique interventions. A systematic search of all relevant databases was conducted from inception through July 2018. After abstract and full-text screening by two independent reviewers, eligible studies were matched to PICO questions. Data were extracted and meta-analyses were conducted using RevMan software. Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Evidence Profiles were compiled using the GRADEpro web application. Voting for Core Treatments took place first. Four subsequent voting sessions took place via anonymous online survey, during which Panel members were tasked with voting to produce recommendations for all joint locations and comorbidity classes. We designated non-Core treatments to Level 1A, 1B, 2, 3, 4A, 4B, or 5, based on the percentage of votes in favor, in addition to the strength of the recommendation.

RESULTS

Core Treatments for Knee OA included arthritis education and structured land-based exercise programs with or without dietary weight management. Core Treatments for Hip and Polyarticular OA included arthritis education and structured land-based exercise programs. Topical non-steroidal anti-inflammatory drugs (NSAIDs) were strongly recommended for individuals with Knee OA (Level 1A). For individuals with gastrointestinal comorbidities, COX-2 inhibitors were Level 1B and NSAIDs with proton pump inhibitors Level 2. For individuals with cardiovascular comorbidities or frailty, use of any oral NSAID was not recommended. Intra-articular (IA) corticosteroids, IA hyaluronic acid, and aquatic exercise were Level 1B/Level 2 treatments for Knee OA, dependent upon comorbidity status, but were not recommended for individuals with Hip or Polyarticular OA. The use of Acetaminophen/Paracetamol (APAP) was conditionally not recommended (Level 4A and 4B), and the use of oral and transdermal opioids was strongly not recommended (Level 5). A treatment algorithm was constructed in order to guide clinical decision-making for a variety of patient profiles, using recommended treatments as input for each decision node.

CONCLUSION

These guidelines offer comprehensive and patient-centered treatment profiles for individuals with Knee, Hip, and Polyarticular OA. The treatment algorithm will facilitate individualized treatment decisions regarding the management of OA.

Genome sequence of enterohaemorrhagic Escherichia coli O157:H7

The bacterium Escherichia coli O157:H7 is a worldwide threat to public health and has been implicated in many outbreaks of haemorrhagic colitis, some of which included fatalities caused by haemolytic uraemic syndrome. Close to 75,000 cases of O157:H7 infection are now estimated to occur annually in the United States. The severity of disease, the lack of effective treatment and the potential for large-scale outbreaks from contaminated food supplies have propelled intensive research on the pathogenesis and detection of E. coli O157:H7 (ref. 4). Here we have sequenced the genome of E. coli O157:H7 to identify candidate genes responsible for pathogenesis, to develop better methods of strain detection and to advance our understanding of the evolution of E. coli, through comparison with the genome of the non-pathogenic laboratory strain E. coli K-12 (ref. 5). We find that lateral gene transfer is far more extensive than previously anticipated. In fact, 1,387 new genes encoded in strain-specific clusters of diverse sizes were found in O157:H7. These include candidate virulence factors, alternative metabolic capacities, several prophages and other new functions--all of which could be targets for surveillance.

Obesity-related glomerulopathy: an emerging epidemic

BACKGROUND

We report the first large renal biopsy-based clinicopathologic study on obesity-related glomerulopathy.

METHODS

Obesity was defined as body mass index (BMI)> 30 kg/m2. Obesity-related glomerulopathy (ORG) was defined morphologically as focal segmental glomerulosclerosis and glomerulomegaly (O-FSGS; N = 57) or glomerulomegaly alone (O-GM; N = 14).

RESULTS

Review of 6818 native renal biopsies received from 1986 to 2000 revealed a progressive increase in biopsy incidence of ORG from 0.2% in 1986-1990 to 2.0% in 1996-2000 (P = 0.0001). Mean BMI in ORG was 41.7 (range 30.9 to 62.7). Indications for renal biopsy included proteinuria (N = 40) or proteinuria and renal insufficiency (N = 31). Seventy-one patients with ORG were compared to 50 patients with idiopathic FSGS (I-FSGS). Patients with ORG were older (mean 42.9 vs. 32.6 years, P < 0.001) and more often Caucasian (75% vs. 52%; P = 0.003). ORG patients had a lower incidence of nephrotic range proteinuria (48% vs. 66%; P = 0.007) and nephrotic syndrome (5.6% vs. 54%; P < 0.001), with higher serum albumin (3.9 vs. 2.9 g/dL; P < 0.001), lower serum cholesterol (229 vs. 335 mg/dL; P < 0.001), and less edema (35% vs. 68%; P = 0.003). On renal biopsy, patients with ORG had fewer lesions of segmental sclerosis (10 vs. 39%; P < 0.001), more glomerulomegaly (100% vs. 10%; P < 0.001), and less extensive foot process effacement (40 vs. 75%; P < 0.001). Glomerular diameter in ORG (mean 226 mu) was significantly larger than age- and sex-matched normal controls (mean 168 mu; P < 0.001). Follow-up was available in 56 ORG patients (mean 27 months) and 50 idiopathic FSGS controls (mean 38 months). A total of 75% of ORG patients received angiotensin-converting enzyme (ACE) inhibition or A2 blockade while 78% of the I-FSGS patients received immunosuppressive therapy. ORG patients had less frequent doubling of serum creatinine (14.3% vs. 50%; P < 0.001) and progression to ESRD (3.6% vs. 42%; P < 0.001). On multivariate analysis, presenting serum creatinine and severity of proteinuria were the only predictors of poor outcome in ORG.

CONCLUSION

ORG is distinct from idiopathic FSGS, with a lower incidence of nephrotic syndrome, more indolent course, consistent presence of glomerulomegaly, and milder foot process fusion. The ten-fold increase in incidence over 15 years suggests a newly emerging epidemic. Heightened physician awareness of this entity is needed to ensure accurate diagnosis and appropriate therapy.

Apolipoprotein(a) gene accounts for greater than 90% of the variation in plasma lipoprotein(a) concentrations

Plasma lipoprotein(a) [Lp(a)], a low density lipoprotein particle with an attached apolipoprotein(a) [apo(a)], varies widely in concentration between individuals. These concentration differences are heritable and inversely related to the number of kringle 4 repeats in the apo(a) gene. To define the genetic determinants of plasma Lp(a) levels, plasma Lp(a) concentrations and apo(a) genotypes were examined in 48 nuclear Caucasian families. Apo(a) genotypes were determined using a newly developed pulsed-field gel electrophoresis method which distinguished 19 different genotypes at the apo(a) locus. The apo(a) gene itself was found to account for virtually all the genetic variability in plasma Lp(a) levels. This conclusion was reached by analyzing plasma Lp(a) levels in siblings who shared zero, one, or two apo(a) genes that were identical by descent (ibd). Siblings with both apo(a) alleles ibd (n = 72) have strikingly similar plasma Lp(a) levels (r = 0.95), whereas those who shared no apo(a) alleles (n = 52), had dissimilar concentrations (r = -0.23). The apo(a) gene was estimated to be responsible for 91% of the variance of plasma Lp(a) concentration. The number of kringle 4 repeats in the apo(a) gene accounted for 69% of the variation, and yet to be defined cis-acting sequences at the apo(a) locus accounted for the remaining 22% of the inter-individual variation in plasma Lp(a) levels. During the course of these studies we observed the de novo generation of a new apo(a) allele, an event that occurred once in 376 meioses.

TNF-alpha induction by LPS is regulated posttranscriptionally via a Tpl2/ERK-dependent pathway

Tpl2 knockout mice produce low levels of TNF-alpha when exposed to lipopolysaccharide (LPS) and they are resistant to LPS/D-Galactosamine-induced pathology. LPS stimulation of peritoneal macrophages from these mice did not activate MEK1, ERK1, and ERK2 but did activate JNK, p38 MAPK, and NF-kappaB. The block in ERK1 and ERK2 activation was causally linked to the defect in TNF-alpha induction by experiments showing that normal murine macrophages treated with the MEK inhibitor PD98059 exhibit a similar defect. Deletion of the AU-rich motif in the TNF-alpha mRNA minimized the effect of Tpl2 inactivation on the induction of TNF-alpha. Subcellular fractionation of LPS-stimulated macrophages revealed that LPS signals transduced by Tpl2 specifically promote the transport of TNF-alpha mRNA from the nucleus to the cytoplasm.

Bisphosphonates: a review of their pharmacokinetic properties

Bisphosphonates are a unique class of drugs. As a family, they are characterized pharmacologically by their ability to inhibit bone resorption, whereas, pharmacokinetically, they are classified by their similarity in absorption, distribution, and elimination. Although all bisphosphonates have similar physicochemical properties, their antiresorbing activities differ substantially. Activity is dramatically increased when the amino group is contained in the aliphatic carbon chain. For example, alendronate, an aminobisphosphonate, is approximately 700-fold more potent than etidronate, both in vitro and in vivo. In general, bisphosphonates are poorly absorbed from the gastrointestinal tract as a result of their poor lipophilicity. In vitro and in vivo studies have shown that bisphosphonates are absorbed from the gastrointestinal tract via paracellular transport. Systemically available bisphosphonates disappear very rapidly from plasma, and are partly taken up by the bone and partly excreted by the kidney. The relative contribution of these two processes to overall plasma elimination differs significantly among bisphosphonates. To date, all bisphosphonates studied show no evidence of metabolism. Renal excretion is the only route of elimination. Studies with alendronate in rats indicate that the drug is actively secreted by an uncharacterized renal transport system, and not by the anionic or cationic renal transport systems. Bisphosphonates bind preferentially to bones which have high turnover rates, and their distribution in bone is not homogeneous. After bone uptake, the bisphosphonates are liberated again only when the bone in which they are deposited is resorbed. Thus, the half-life of bisphosphonates in bone is very long, ranging among different species from 1 to 10 years, depending largely on the rate of bone turnover.

Connexins regulate calcium signaling by controlling ATP release

Forced expression of gap junction proteins, connexins, enables gap junction-deficient cell lines to propagate intercellular calcium waves. Here, we show that ATP secretion from the poorly coupled cell lines, C6 glioma, HeLa, and U373 glioblastoma, is potentiated 5- to 15-fold by connexin expression. ATP release required purinergic receptor-activated intracellular Ca2+ mobilization and was inhibited by Cl- channel blockers. Calcium wave propagation also was reduced by purinergic receptor antagonists and by Cl- channel blockers but insensitive to gap junction inhibitors. These observations suggest that cell-to-cell signaling associated with connexin expression results from enhanced ATP release and not, as previously believed, from an increase in intercellular coupling.

Cytokine stimulation of energy expenditure through p38 MAP kinase activation of PPARgamma coactivator-1

Cachexia is a chronic state of negative energy balance and muscle wasting that is a severe complication of cancer and chronic infection. While cytokines such as IL-1alpha, IL-1beta, and TNFalpha can mediate cachectic states, how these molecules affect energy expenditure is unknown. We show here that many cytokines activate the transcriptional PPAR gamma coactivator-1 (PGC-1) through phosphorylation by p38 kinase, resulting in stabilization and activation of PGC-1 protein. Cytokine or lipopolysaccharide (LPS)-induced activation of PGC-1 in cultured muscle cells or muscle in vivo causes increased respiration and expression of genes linked to mitochondrial uncoupling and energy expenditure. These data illustrate a direct thermogenic action of cytokines and p38 MAP kinase through the transcriptional coactivator PGC-1.

ATM phosphorylates p95/nbs1 in an S-phase checkpoint pathway

The rare diseases ataxia-telangiectasia (AT), caused by mutations in the ATM gene, and Nijmegen breakage syndrome (NBS), with mutations in the p95/nbs1 gene, share a variety of phenotypic abnormalities such as chromosomal instability, radiation sensitivity and defects in cell-cycle checkpoints in response to ionizing radiation. The ATM gene encodes a protein kinase that is activated by ionizing radiation or radiomimetic drugs, whereas p95/nbs1 is part of a protein complex that is involved in responses to DNA double-strand breaks. Here, because of the similarities between AT and NBS, we evaluated the functional interactions between ATM and p95/nbs1. Activation of the ATM kinase by ionizing radiation and induction of ATM-dependent responses in NBS cells indicated that p95/nbs1 may not be required for signalling to ATM after ionizing radiation. However, p95/nbs1 was phosphorylated on serine 343 in an ATM-dependent manner in vitro and in vivo after ionizing radiation. A p95/nbs1 construct mutated at the ATM phosphorylation site abrogated an S-phase checkpoint induced by ionizing radiation in normal cells and failed to compensate for this functional deficiency in NBS cells. These observations link ATM and p95/nbs1 in a common signalling pathway and provide an explanation for phenotypic similarities in these two diseases.

Inhibition and induction of cytochrome P450 and the clinical implications

The cytochrome P450s (CYPs) constitute a superfamily of isoforms that play an important role in the oxidative metabolism of drugs. Each CYP isoform possesses a characteristic broad spectrum of catalytic activities of substrates. Whenever 2 or more drugs are administered concurrently, the possibility of drug interactions exists. The ability of a single CYP to metabolise multiple substrates is responsible for a large number of documented drug interactions associated with CYP inhibition. In addition, drug interactions can also occur as a result of the induction of several human CYPs following long term drug treatment. The mechanisms of CYP inhibition can be divided into 3 categories: (a) reversible inhibition; (b) quasi-irreversible inhibition; and (c) irreversible inhibition. In mechanistic terms, reversible interactions arise as a result of competition at the CYP active site and probably involve only the first step of the CYP catalytic cycle. On the other hand, drugs that act during and subsequent to the oxygen transfer step are generally irreversible or quasi-irreversible inhibitors. Irreversible and quasi-irreversible inhibition require at least one cycle of the CYP catalytic process. Because human liver samples and recombinant human CYPs are now readily available, in vitro systems have been used as screening tools to predict the potential for in vivo drug interaction. Although it is easy to determine in vitro metabolic drug interactions, the proper interpretation and extrapolation of in vitro interaction data to in vivo situations require a good understanding of pharmacokinetic principles. From the viewpoint of drug therapy, to avoid potential drug-drug interactions, it is desirable to develop a new drug candidate that is not a potent CYP inhibitor or inducer and the metabolism of which is not readily inhibited by other drugs. In reality, drug interaction by mutual inhibition between drugs is almost inevitable, because CYP-mediated metabolism represents a major route of elimination of many drugs, which can compete for the same CYP enzyme. The clinical significance of a metabolic drug interaction depends on the magnitude of the change in the concentration of active species (parent drug and/or active metabolites) at the site of pharmacological action and the therapeutic index of the drug. The smaller the difference between toxic and effective concentration, the greater the likelihood that a drug interaction will have serious clinical consequences. Thus, careful evaluation of potential drug interactions of a new drug candidate during the early stage of drug development is essential.

Several hydrophobic amino acids in the p53 amino-terminal domain are required for transcriptional activation, binding to mdm-2 and the adenovirus 5 E1B 55-kD protein

The p53 tumor suppressor gene product is a transcriptional activator that may be associated with its ability to suppress tumor cell growth. The acidic amino terminus of the p53 protein has been shown to contain this trans-activation activity as well as the domains for mdm-2 and adenovirus 5 E1B 55-kD protein binding. An extensive genetic analysis of this amino-terminal p53 domain has been undertaken using site-specific mutagenesis. The results demonstrate that the acidic residues in the amino terminus of p53 may contribute to, but are not critical for, this trans-activation activity. Rather, the hydrophobic amino acid residues Leu-22 and Trp-23 of human p53 are both required for trans-activation activity, binding to the adenovirus E1B 55-kD protein and the human mdm-2-p53 protein in vitro. In addition, hydrophobic residues Leu-14 and Phe-19 are crucial for the interactions between p53 and human mdm-2 (hdm-2). Hydrophobic residues Trp-23 and Pro-27 are also important for binding to the adenovirus 5 (Ad5) E1B 55-kD protein in vitro. These mutations have no impact on the ability of the p53 protein to bind to a p53-specific DNA element. These results suggest that 2-4 critical hydrophobic residues in the amino-terminal domain of the p53 protein interact with the transcriptional machinery of the cell resulting in transcriptional activation. These very same hydrophobic residues contact the hdm-2 and Ad5 E1B 55-kD oncogene products.

Randomized, double-blind, placebo-controlled study of brodalumab, a human anti-IL-17 receptor monoclonal antibody, in moderate to severe asthma

RATIONALE

IL-17 signaling has been implicated in development and persistence of asthma. Cytokine-targeted strategies blocking IL-17 receptor signaling may be beneficial in asthma treatment.

OBJECTIVES

To determine efficacy and safety of brodalumab, a human anti-IL-17 receptor A monoclonal antibody, in subjects with inadequately controlled moderate to severe asthma taking regular inhaled corticosteroids.

METHODS

Three hundred two subjects were randomized to brodalumab (140, 210, or 280 mg) or placebo. Primary endpoint was change in Asthma Control Questionnaire (ACQ) score from baseline to Week 12. Secondary endpoints included FEV1, symptom scores, and symptom-free days. Prespecified subgroup analyses were conducted to identify potential responsive subpopulations. Analyses included randomized subjects receiving one or more doses of investigational product using last-observation-carried-forward imputation.

MEASUREMENTS AND MAIN RESULTS

Demographics and baseline characteristics were generally balanced among groups (n = 302; n = 226 brodalumab). For the overall study population, no treatment differences were observed. Nine prespecified subgroups were examined without corrections for multiple testing. In only the high-reversibility subgroup (post-bronchodilator FEV1 improvement ≥ 20%; n = 112) was an ACQ change with nominal significance noted; ACQ responses were nominally significant in the 210-mg group (estimated treatment difference, 0.53) but not significant in the higher 280-mg group (estimated treatment difference, 0.38). Adverse events, generally balanced among groups, were most commonly asthma, upper respiratory tract infection, and injection site reaction.

CONCLUSIONS

Inhibition of IL-17 receptor A did not produce a treatment effect in subjects with asthma. The results of the high-reversibility subgroup analysis are of uncertain significance, requiring further study of brodalumab in this asthma subpopulation. Clinical trial registered with www.clinicaltrials.gov (NCT01199289).

Competitive binding of alpha-actinin and calmodulin to the NMDA receptor

The mechanisms by which neurotransmitter receptors are immobilized at postsynaptic sites in neurons are largely unknown. The activity of NMDA (N-methyl-D-aspartate) receptors is mechanosensitive and dependent on the integrity of actin, suggesting a functionally important interaction between NMDA receptors and the postsynaptic cytoskeleton. alpha-Actinin-2, a member of the spectrin/dystrophin family of actin-binding proteins, is identified here as a brain postsynaptic density protein that colocalizes in dendritic spines with NMDA receptors and the putative NMDA receptor-clustering molecule PSD-95. alpha-Actinin-2 binds by its central rod domain to the cytoplasmic tail of both NR1 and NR2B subunits of the NMDA receptor, and can be immunoprecipitated with NMDA receptors and PSD-95 from rat brain. Intriguingly, NR1-alpha-actinin binding is directly antagonized by Ca2+/calmodulin. Thus alpha-actinin may play a role in both the localization of NMDA receptors and their modulation by Ca2+.

Change in Failure Stress on the Southern San Andreas Fault System Caused by the 1992 Magnitude = 7.4 Landers Earthquake

The 28 June Landers earthquake brought the San Andreas fault significantly closer to failure near San Bernardino, a site that has not sustained a large shock since 1812. Stress also increased on the San Jacinto fault near San Bernardino and on the San Andreas fault southeast of Palm Springs. Unless creep or moderate earthquakes relieve these stress changes, the next great earthquake on the southern San Andreas fault is likely to be advanced by one to two decades. In contrast, stress on the San Andreas north of Los Angeles dropped, potentially delaying the next great earthquake there by 2 to 10 years.

Glutamate release promotes growth of malignant gliomas

Glutamate neurotoxicity has been implicated in stroke, head trauma, multiple sclerosis and neurodegenerative diseases. Although recent data show that cultured glioma cells secrete glutamate, the growth potential of brain tumors has not yet been linked to an excitotoxic mechanism. Using bioluminescence detection of glutamate release from freshly prepared brain slices, we show that implanted glioma cells continue to secrete glutamate. Moreover, gliomas with high glutamate release have a distinct growth advantage in host brain that is not present in vitro. Treatment with the NMDA receptor antagonists MK801 or memantine slowed the growth of glutamate-secreting tumors in situ, suggesting that activation of NMDA receptors facilitates tumor expansion. These findings support a new approach for therapy of brain tumors, based upon antagonizing glutamate secretion or its target receptors.

An induced proximity model for NF-kappa B activation in the Nod1/RICK and RIP signaling pathways

Nod1 is an Apaf-1-like molecule composed of a caspase-recruitment domain (CARD), nucleotide-binding domain, and leucine-rich repeats that associates with the CARD-containing kinase RICK and activates nuclear factor kappaB (NF-kappaB). We show that self-association of Nod1 mediates proximity of RICK and the interaction of RICK with the gamma subunit of the IkappaB kinase (IKKgamma). Similarly, the RICK-related kinase RIP associated via its intermediate region with IKKgamma. A mutant form of IKKgamma deficient in binding to IKKalpha and IKKbeta inhibited NF-kappaB activation induced by RICK or RIP. Enforced oligomerization of RICK or RIP as well as of IKKgamma, IKKalpha, or IKKbeta was sufficient for induction of NF-kappaB activation. Thus, the proximity of RICK, RIP, and IKK complexes may play an important role for NF-kappaB activation during Nod1 oligomerization or trimerization of the tumor necrosis factor alpha receptor.

A role in B cell activation for CD22 and the protein tyrosine phosphatase SHP

CD22 is a membrane immunoglobulin (mIg)-associated protein of B cells. CD22 is tyrosine-phosphorylated when mIg is ligated. Tyrosine-phosphorylated CD22 binds and activates SHP, a protein tyrosine phosphatase known to negatively regulate signaling through mIg. Ligation of CD22 to prevent its coaggregation with mIg lowers the threshold at which mIg activates the B cell by a factor of 100. In secondary lymphoid organs, CD22 may be sequestered away from mIg through interactions with counterreceptors on T cells. Thus, CD22 is a molecular switch for SHP that may bias mIg signaling to anatomic sites rich in T cells.

Comparative analysis of extreme acid survival in Salmonella typhimurium, Shigella flexneri, and Escherichia coli

Several members of the family Enterobacteriaceae were examined for differences in extreme acid survival strategies. A surprising degree of variety was found between three related genera. The minimum growth pH of Salmonella typhimurium was shown to be significantly lower (pH 4.0) than that of either Escherichia coli (pH 4.4) or Shigella flexneri (pH 4.8), yet E. coli and S. flexneri both survive exposure to lower pH levels (2 to 2.5) than S. typhimurium (pH 3.0) in complex medium. S. typhimurium and E. coli but not S. flexneri expressed low-pH-inducible log-phase and stationary-phase acid tolerance response (ATR) systems that function in minimal or complex medium to protect cells to pH 3.0. All of the organisms also expressed a pH-independent general stress resistance system that contributed to acid survival during stationary phase. E. coli and S. flexneri possessed several acid survival systems (termed acid resistance [AR]) that were not demonstrable in S. typhimurium. These additional AR systems protected cells to pH 2.5 and below but required supplementation of minimal medium for either induction or function. One acid-inducible AR system required oxidative growth in complex medium for expression but successfully protected cells to pH 2.5 in unsupplemented minimal medium, while two other AR systems important for fermentatively grown cells required the addition of either glutamate or arginine during pH 2.5 acid challenge. The arginine AR system was only observed in E. coli and required stationary-phase induction in acidified complex medium. The product of the adi locus, arginine decarboxylase, was responsible for arginine-based acid survival.

Mechanisms of acid resistance in enterohemorrhagic Escherichia coli

Enterohemorrhagic strains of Escherichia coli must pass through the acidic gastric barrier to cause gastrointestinal disease. Taking into account the apparent low infectious dose of enterohemorrhagic E. coli, 11 O157:H7 strains and 4 commensal strains of E. coli were tested for their abilities to survive extreme acid exposures (pH 3). Three previously characterized acid resistance systems were tested. These included an acid-induced oxidative system, an acid-induced arginine-dependent system, and a glutamate-dependent system. When challenged at pH 2.0, the arginine-dependent system provided more protection in the EHEC strains than in commensal strains. However, the glutamate-dependent system provided better protection than the arginine system and appeared equally effective in all strains. Because E. coli must also endure acid stress imposed by the presence of weak acids in intestinal contents at a pH less acidic than that of the stomach, the ability of specific acid resistance systems to protect against weak acids was examined. The arginine- and glutamate-dependent systems were both effective in protecting E. coli against the bactericidal effects of a variety of weak acids. The acids tested include benzoic acid (20 mM; pH 4.0) and a volatile fatty acid cocktail composed of acetic, propionic, and butyric acids at levels approximating those present in the intestine. The oxidative system was much less effective. Several genetic aspects of E. coli acid resistance were also characterized. The alternate sigma factor RpoS was shown to be required for oxidative acid resistance but was only partially involved with the arginine- and glutamate-dependent acid resistance systems. The arginine decarboxylase system (including adi and its regulators cysB and adiY) was responsible for arginine-dependent acid resistance. The results suggest that several acid resistance systems potentially contribute to the survival of pathogenic E. coli in the different acid stress environments of the stomach (pH 1 to 3) and the intestine (pH 4.5 to 7 with high concentrations of volatile fatty acids). Of particular importance to the food industry was the finding that once induced, the acid resistance systems will remain active for prolonged periods of cold storage at 4 degrees C.

Signal transduction by the TCR for antigen

The past several years have seen the beginning of a shift in the way that TCR signal transduction is studied. Although many investigators continue to identify new molecules, particularly adaptor proteins, others have attempted to look at signaling events in a larger cellular context. Thus the identification of distinct formations of signaling molecules at junctions between T cells and antigen-presenting cells, the role of the cytoskeleton and the partitioning of molecules into specialized lipid subdomains have been the subjects of many publications. Such concepts are helping to assemble a blueprint of how the myriad adaptors and kinases fit together to effect T cell activation.

ETS gene Er81 controls the formation of functional connections between group Ia sensory afferents and motor neurons

The connections formed between sensory and motor neurons (MNs) play a critical role in the control of motor behavior. During development, the axons of proprioceptive sensory neurons project into the spinal cord and form both direct and indirect connections with MNs. Two ETS transcription factors, ER81 and PEA3, are expressed by developing proprioceptive neurons and MNs, raising the possibility that these genes are involved in the formation of sensory-motor connections. Er81 mutant mice exhibit a severe motor discoordination, yet the specification of MNs and induction of muscle spindles occurs normally. The motor defect in Er81 mutants results from a failure of group Ia proprioceptive afferents to form a discrete termination zone in the ventral spinal cord. As a consequence there is a dramatic reduction in the formation of direct connections between proprioceptive afferents and MNs. ER81 therefore controls a late step in the establishment of functional sensory-motor circuitry in the developing spinal cord.

Gap-junction-mediated propagation and amplification of cell injury

Gap junctions are conductive channels that connect the interiors of coupled cells. We determined whether gap junctions propagate transcellular signals during metabolic stress and whether such signaling exacerbates cell injury. Although overexpression of the human proto-oncogene bcl2 in C6 glioma cells normally increased their resistance to injury, the relative resistance of bcl2+ cells to calcium overload, oxidative stress and metabolic inhibition was compromised when they formed gap junctions with more vulnerable cells. The likelihood of death was in direct proportion to the number and density of gap junctions with their less resistant neighbors. Thus, dying glia killed neighboring cells that would otherwise have escaped injury. This process of glial 'fratricide' may provide a basis for the secondary propagation of brain injury in cerebral ischemia.

High H2 uptake by alkali-doped carbon nanotubes under ambient pressure and moderate temperatures

Lithium- or potassium-doped carbon nanotubes can absorb approximately 20 or approximately 14 weight percent of hydrogen at moderate (200 degrees to 400 degrees C) or room temperatures, respectively, under ambient pressure. These values are greater than those of metal hydride and cryoadsorption systems. The hydrogen stored in the lithium- or potassium-doped carbon nanotubes can be released at higher temperatures, and the sorption-desorption cycle can be repeated with little decrease in the sorption capacity. The high hydrogen-uptake capacity of these systems may be derived from the special open-edged, layered structure of the carbon nanotubes made from methane, as well as the catalytic effect of alkali metals.

Crystal structure of TFIID TATA-box binding protein

The structure of a central component of the eukaryotic transcriptional apparatus, a TATA-box binding protein (TBP or TFIID tau) from Arabidopsis thaliana, has been determined by X-ray crystallography at 2.6 A resolution. This highly symmetric alpha/beta structure contains a new DNA-binding fold, resembling a molecular 'saddle' that sits astride the DNA. The DNA-binding surface is a curved, antiparallel beta-sheet. When bound to DNA, the convex surface of the saddle would be presented for interaction with other transcription initiation factors and regulatory proteins.