Chromosome 13 dementias

The importance of cerebral amyloid deposition in the mechanism of neurodegeneration is still debatable. Classic arguments are usually centered on amyloid beta(Abeta) and its role in the neuronal loss characteristic of Alzheimer's disease, the most common form of human cerebral amyloidosis. Two non-Abeta cerebral amyloidoses, familial British and Danish dementias (FBD and FDD), share many aspects of Alzheimer's disease, including the presence of neurofibrillary tangles, parenchymal preamyloid and amyloid deposits, cerebral amyloid angiopathy and a variety of amyloid-associated proteins and inflammatory components. Both early-onset conditions are linked to specific mutations at or near the stop codon of the chromosome 13 gene BRI2 that cause generation of longer-than-normal protein products. Furin-like processing of these longer precursors releases two de novo-created peptides, ABri and ADan, which deposit as amyloid fibrils in FBD and FDD, respectively. Due to the similar pathology generated by completely unrelated amyloid subunits, FBD and FDD, collectively referred to as chromosome 13 dementias, constitute alternative models for studying the role of amyloid deposition in the mechanism of neuronal cell death.

FlaC, a protein of Campylobacter jejuni TGH9011 (ATCC43431) secreted through the flagellar apparatus, binds epithelial cells and influences cell invasion

Type III secretion systems identified in bacterial pathogens of animals and plants transpose effectors and toxins directly into the cytosol of host cells or into the extracellular milieu. Proteins of the type III secretion apparatus are conserved among diverse and distantly related bacteria. Many type III apparatus proteins have homologues in the flagellar export apparatus, supporting the notion that type III secretion systems evolved from the flagellar export apparatus. No type III secretion apparatus genes have been found in the complete genomic sequence of Campylobacter jejuni NCTC11168. In this study, we report the characterization of a protein designated FlaC of C. jejuni TGH9011. FlaC is homologous to the N- and C-terminus of the C. jejuni flagellin proteins, FlaA and FlaB, but lacks the central portion of these proteins. flaC null mutants form a morphologically normal flagellum and are highly motile. In wild-type C. jejuni cultures, FlaC is found predominantly in the extracellular milieu as a secreted protein. Null mutants of the flagellar basal rod gene (flgF) and hook gene (flgE) do not secrete FlaC, suggesting that a functional flagellar export apparatus is required for FlaC secretion. During C. jejuni infection in vitro, secreted FlaC and purified recombinant FlaC bind to HEp-2 cells. Invasion of HEp-2 cells by flaC null mutants was reduced to a level of 14% compared with wild type, suggesting that FlaC plays an important role in cell invasion.

Anti-leukotriene agents compared to inhaled corticosteroids in the management of recurrent and/or chronic asthma in adults and children

BACKGROUND

Anti-leukotrienes agents are currently being studied as alternative first line agents to inhaled corticosteroids in mild to moderate chronic asthma.

OBJECTIVES

To compare the safety and efficacy of anti-leukotriene agents with inhaled glucocorticoids (ICS) and to determine the dose-equivalence of anti-leukotrienes to daily dose of ICS.

SEARCH STRATEGY

We searched MEDLINE (1966 to Aug 2003), EMBASE (1980 to Aug 2003), CINAHL (1982 to Aug 2003), the Cochrane Airways Group trials register, and the Cochrane Central Register of Controlled Trials (August 2003), abstract books, and reference lists of review articles and trials. We contacted colleagues and international headquarters of anti-leukotrienes producers.

SELECTION CRITERIA

Randomised controlled trials that compared anti-leukotrienes with inhaled corticosteroids during a minimal 30-day intervention period in asthmatic patients aged 2 years and older.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the methodological quality or trials and extracted trial data. The primary outcome was the rate of exacerbations requiring systemic corticosteroids. Secondary outcomes included lung function, indices of chronic asthma control, adverse effects and withdrawal rates.

MAIN RESULTS

27 trials (including 1 trial testing two protocols) met the inclusion criteria; 13 were of high methodological quality; 20 are published in full-text. All trials pertained to patients with mild to moderate persistent asthma. Only 3 trials focused on children and adolescents. Trial duration varied from 4 to 37 weeks. In most trials, daily dose of ICS was 400 mcg of beclomethasone or equivalent. Patients treated with anti-leukotrienes were 65% more likely to suffer an exacerbation requiring systemic steroids [Relative Risk 1.65; 95% Confidence Interval (CI) 1.36 to 2.00]. Twenty six (95% CI: 17 to 47) patients must be treated with anti-leukotrienes instead of inhaled corticosteroids to cause one extra exacerbation. Significant differences favouring ICS were noted in secondary outcomes where()the improvement in FEV(1) reached 130 mL [13 trials; 95% CI: 50, 140 mL ]. Other significant benefits of ICS were seen for symptoms, nocturnal awakenings, rescue medication use, symptom-free days, and quality of life. Anti-leukotriene therapy was associated with 160% increased risk of withdrawals due to poor asthma control. Twenty nine (95% CI 20 to 48) patients must be treated with anti-leukotrienes instead of inhaled corticosteroids to cause one extra withdrawal due to poor control. Risk of side effects was not different between groups.

REVIEWERS' CONCLUSIONS

Inhaled steroids at a dose of 400 mcg/day of beclomethasone or equivalent are more effective than anti-leukotriene agents given in the usual licensed doses. The exact dose-equivalence of anti-leukotriene agents in mcg of ICS remains to be determined. Inhaled glucocorticoids should remain the first line monotherapy for persistent asthma.

Molecularly defined interstitial tandem duplication 6p case with mild manifestations

An interstitial tandem duplication of 6p21.1-p22.2 was found in a girl at 11 months of age when she was evaluated for developmental delay. Previous cases reported with partial 6p duplication usually have involved terminal duplications, with breakpoints ranging from 6p11 to 6p25. Our patient exhibits a milder phenotype compared to the previously reported cases in the literature. Features that she has in common with the other cases include craniofacial anomalies, such as broad nasal bridge and bulbous tip, thin lips, incomplete development of the scapha helix bilaterally, mild spastic paraparesis of the lower extremities, gross motor delay, and mild cognitive delays.

Growth failure in the child with inflammatory bowel disease

Once considered rare in pediatric practice, chronic inflammatory bowel disease (IBD) is now being recognized with increasing frequency in children of all ages. In IBD, growth failure may be the only clinical presentation; it is imperative to perform a detailed history and physical examination to search for other systemic and gastrointestinal manifestations of the disease. IBD can have a significant impact on linear growth, weight gain, and bone mineralization, and can cause delays in the onset of puberty. Delays in growth and sexual development can be early indicators of disease activity, and assessment of growth and development should be performed frequently. Nutritional therapy is important not only to correct undernutrition, but also as therapy for IBD. Delayed puberty can have a significant impact on the self-esteem of the adolescent patient and diminish final adult height. Loss of bone mineral density is especially significant during a period in which the majority of bone accretion is expected to occur. These issues present unique problems to the gastroenterologist caring for a child or adolescent with IBD and require specific types of monitoring and interventions.

The use of capillary electrophoresis in the detection of monomethylamine and benzoate ions in the forensic examination of explosives residues

Capillary electrophoresis (CE) is used in the ATF Forensic Science Laboratories for the analysis of inorganic ions commonly encountered in post-blast residues including monomethylamine (MMA) and benzoate ions. Monomethylamine nitrate is found in Tovex, a water gel explosive. Sodium benzoate is added to Pyrodex, as a fuel and burn rate modifier. In the analysis of explosive residues, these ions are used as an indicator for the presence of Tovex and Pyrodex. Traditionally, these two ions, along with other ions of interest were analyzed by spot tests and ion chromatograph (IC). CE is currently being used in place of spot tests as a confirmation technique for IC.

Acute insulin responses to leucine in children with the hyperinsulinism/hyperammonemia syndrome

Mutations of glutamate dehydrogenase cause the hyperinsulinism/hyperammonemia syndrome by desensitizing glutamate dehydrogenase to allosteric inhibition by GTP. Normal allosteric activation of glutamate dehydrogenase by leucine is thus uninhibited, leading us to propose that children with hyperinsulinism/hyperammonemia syndrome will have exaggerated acute insulin responses to leucine in the postabsorptive state. As hyperglycemia increases beta-cell GTP, we also postulated that high glucose concentrations would extinguish abnormal responsiveness to leucine in hyperinsulinism/hyperammonemia syndrome patients. After an overnight fast, seven hyperinsulinism/hyperammonemia syndrome patients (aged 9 months to 29 yr) had acute insulin responses to leucine performed using an iv bolus of L-leucine (15 mg/kg) administered over 1 min and plasma insulin measurements obtained at -10, -5, 0, 1, 3, and 5 min. The acute insulin response to leucine was defined as the mean increase in insulin from baseline at 1 and 3 min after an iv leucine bolus. The hyperinsulinism/hyperammonemia syndrome group had excessively increased insulin responses to leucine (mean +/- SEM, 73 +/- 21 microIU/ml) compared with the control children and adults (n = 17) who had no response to leucine (1.9 +/- 2.7 microU/ml; P < 0.05). Four hyperinsulinism/hyperammonemia syndrome patients then had acute insulin responses to leucine repeated at hyperglycemia (blood glucose, 150-180 mg/dl). High blood glucose suppressed their abnormal baseline acute insulin responses to leucine of 180, 98, 47, and 28 microU/ml to 73, 0, 6, and 19 microU/ml, respectively. This suppression suggests that protein-induced hypoglycemia in hyperinsulinism/hyperammonemia syndrome patients may be prevented by carbohydrate loading before protein consumption.

Engineering reactions in crystalline solids: photochemical generation of secondary and tertiary enol radical pairs from crystalline ketodiesters

The photochemical decarbonylation of several crystalline 1,3-acetonedicarboxylates has been analyzed in solution and in the solid state. It is shown that the efficiency of the solid-state reaction depends on the stability of the intermediate acyl-alkyl and alkyl-alkyl radical pairs. Reactions proceeding through tertiary enol radicals are more efficient than reactions proceeding through secondary enol radical centers. Solid-state reactions that require the intermediacy of primary enol radicals do not occur. It is also shown that the selectivity of product formation in crystals depends on the structure of the reactant solid phase.

Calcium- and vitamin D-regulated keratinocyte differentiation

Calcium and 1,25 dihydroxyvitamin D (1,25(OH)(2)D) regulate the differentiation of keratinocytes. We have examined the mechanisms by which such regulation takes place, focusing primarily on the events leading to cornified envelope (CE) formation, in particular the mechanisms by which calcium and 1,25(OH)(2)D regulate the induction of involucrin, a component of the CE, and transglutaminase, the enzyme cross-linking involucrin and other substrates to form the CE. Both extracellular calcium (Ca(o)) and 1,25(OH)(2)D raise intracellular free calcium (Ca(i)) as a necessary step toward stimulating differentiation. Cells lacking the calcium sensing receptor (CaR) or phospholipase C-gamma 1 (PLC-gamma 1) fail to respond to Ca(o) or 1,25(OH)(2)D with respect to differentiation. Residing in the promoter of involucrin is a region responsive to calcium and 1,25(OH)(2)D, the calcium response element (CaRE). The CaRE contains an AP-1 site, mutations of which result in loss of responsiveness to Ca(o) and 1,25(OH)(2)D, indicating a role for protein kinases C (PKC). PKC alpha is the major PKC isozyme involved at least for calcium-induced differentiation. Thus, the regulation of keratinocyte differentiation by calcium and 1,25(OH)(2)D involves a number of signaling pathways including PLC and PKC activation, leading to the induction of proteins required for the differentiation process.

Polymorphisms of human paraoxonase 1 gene (PON1) and susceptibility to diabetic nephropathy in type I diabetes mellitus

AIMS/HYPOTHESIS

Oxidative stress is a putative mechanism in the development of diabetic nephropathy. Paraoxonase gene 1 is an HDL-bound enzyme that protects tissues against oxidative damage. Three common polymorphisms of paraoxonase gene 1, T-107C in the promoter, Leu54Met and Gln192Arg, that modify paraoxonase activity have been associated with cardiovascular disease. This study aimed to find whether these polymorphisms also contribute to the development of diabetic nephropathy.

METHODS

The association between diabetic nephropathy and these three polymorphisms was examined in a case-control study. For this purpose, genomic DNA was collected from 188 patients with Type I (insulin-dependent) diabetes mellitus and diabetic nephropathy and from 179 unrelated patients with Type I diabetes but without diabetic nephropathy despite the duration of diabetes of 15 or more years.

RESULTS

The genotype and allele frequencies for each of the three polymorphisms (T-107C, Leu54Met and Gln192Arg) were similar in cases and control subjects.

CONCLUSION/INTERPRETATION

The three polymorphisms in paraoxonase gene 1 that have been associated with serum levels of paraoxonase are not associated with diabetic nephropathy. We show that this genetically determined component of the antioxidant capacity of HDL does not play a critical part in the development of diabetic nephropathy.

In vivo nasal challenge with diesel exhaust particles enhances expression of the CC chemokines rantes, MIP-1alpha, and MCP-3 in humans

Diesel exhaust particles (DEP) enhance allergic inflammation by increasing in vivo IgE and cytokine production in the human upper respiratory mucosa. CC chemokines have been shown to play an important role in inflammation. We examined whether DEP could alter the production of CC chemokines by cells residing in the human nasal mucosa. At both 6 and 24 h following intranasal DEP challenge, the levels of nasal RANTES, MIP-1alpha, and MCP-3 were significantly elevated compared to baseline. In contrast, DEP did not enhance levels of Eotaxin at any time, demonstrating that the action of DEP was not simply a global effect on all CC chemokines. Challenge with saline resulted in no significant change in expression of any chemokine at any time. Challenge with DEP also resulted in an increase in total cell counts in nasal lavage fluids. Increases in lymphocyte, monocyte/macrophage, and neutrophil cells were observed but there was no change in eosinophil cell numbers. In contrast, there was a significant enhancement of ECP protein levels in washes performed 6 to 24 h after DEP challenge. Elevated specific nasal chemokine expression following exposure to DEP likely participates in the inflammation, cellular infiltration, and increase in IgE observed in the absence of allergen.

Identification of Campylobacter jejuni, C. coli, C. lari, C. upsaliensis, arcobacter butzleri, and A. butzleri-like species based on the glyA gene

Currently, the detection and identification of Campylobacter and Arcobacter species remains arduous, largely due to cross-species phenotypic similarities and a relatively narrow spectrum of biochemical reactivity. We have developed a PCR-hybridization strategy, wherein degenerate primers are used to amplify glyA fragments from samples, which are then subjected to species-specific oligodeoxyribonucleotide probe hybridizations, to identify and distinguish between Campylobacter jejuni, C. coli, C. lari, C. upsaliensis, Arcobacter butzleri, and an A. butzleri-like species. Evaluation of this strategy with genomic DNA from different type strains suggests that this approach is both specific and sensitive and thus may be applicable in a diagnostic assay to identify and differentiate these highly related species.

Arginine biosynthesis in Campylobacter jejuni TGH9011: determination of the argCOBD cluster

Arginine biosynthetic genes from Campylobacter jejuni TGH9011 were cloned by functional complementation of the respective Escherichia coli arginine biosynthetic mutants. Complementation of argA, argB, argC, argD, argE, argF, and argH auxotrophs was accomplished using a pBR322-based C. jejuni TGH9011 plasmid library. By cross-complementation analyses, the first four steps of arginine biosynthesis were shown to be closely linked on the genome. Two additional clones complementing the first (ArgA) and fifth (ArgE) steps in arginine biosynthesis were obtained. Neither recombinant showed linkage to the arg cluster, to each other, nor to other arginine biosynthetic functions by cross-complementation. Genes argF and argH were not linked to other arginine biosynthetic genes by cross-complementation analysis. Restriction enzyme patterns of recombinant plasmids fell into five groups. Group I contained the arg(ABCD) complementing locus. Group II and Group III were the two genetic loci corresponding to the argA and argE complementing genes. Group II contains the hipO gene encoding N-benzoylglycine-amino-acid amidohydrolase, also known as hippurate hydrolase. Group III contains the hipO homolog of C. jejuni. Group IV represents the argF gene. Group V is the argH gene. Functional complementation of mutations in the first four steps of the arginine biosynthetic pathway was obtained on recombinant plasmid pARGC2. The predicted order of gene complementation was argCargA(argBargD). The sequence of the insert in plasmid pARGC2 revealed direct homologs for argC, argB, and argD. However, sequence analysis of the gene complementing ArgA function in two separate E. coli argA mutants determined that the C. jejuni gene was not a canonical argA gene. The gene complementing the argA defect, which we call argO, showed limited homology to the streptothricin acetyltransferase gene (sat) of Escherichia coli. The flanking open reading frames in pARGC2 showed no homologies to arginine biosynthetic genes. The structure of the argCOBD gene arrangement is discussed with reference to the presence and location of other arginine biosynthetic genes on the genome of C. jejuni and other bacterial organisms.

An archaebacterial ATPase, homologous to ATPases in the eukaryotic 26 S proteasome, activates protein breakdown by 20 S proteasomes

In eukaryotes, the 20 S proteasome is the proteolytic core of the 26 S proteasome, which degrades ubiquitinated proteins in an ATP-dependent process. Archaebacteria lack ubiquitin and 26 S proteasomes but do contain 20 S proteasomes. Many archaebacteria, such as Methanococcus jannaschii, also contain a gene (S4) that is highly homologous to the six ATPases in the 19 S (PA700) component of the eukaryotic 26 S proteasome. To test if this putative ATPase may regulate proteasome function, we expressed it in Escherichia coli and purified the 50-kDa product as a 650-kDa complex with ATPase activity. When mixed with the well characterized 20 S proteasomes from Thermoplasma acidophilum and ATP, this complex stimulated degradation of several unfolded proteins 8-25-fold. It also stimulated proteolysis by 20 S proteasomes from another archaebacterium and mammals. This effect required ATP hydrolysis since ADP and the nonhydrolyzable analog, 5'-adenylyl beta, gamma-imidophosphate, were ineffective. CTP and to a lesser extent GTP and UTP were also hydrolyzed and also stimulated proteolysis. We therefore named this complex PAN for proteasome-activating nucleotidase. However, PAN did not promote the degradation of small peptides, which, unlike proteins, should readily diffuse into the proteasome. This ATPase complex appears to have been the evolutionary precursor of the eukaryotic 19 S complex, before the coupling of proteasome function to ubiquitination.

Carbon regulation of ribosomal genes in Neurospora crassa occurs by a mechanism which does not require Cre-1, the homologue of the Aspergillus carbon catabolite repressor, CreA

Transcription of the ribosomal protein and 40S rRNA genes is coordinately regulated during steady state growth and carbon shifts in Neurospora crassa. Recognition sequences for the Aspergillus nidulans carbon catabolite repressor, CreA, overlap transcriptional elements of a 40S rRNA gene and the crp-2 ribosomal protein gene. They also occur in similar locations in the promoters of several other ribosomal protein genes. Substitutions encompassing the -74 and -167 CreA consensus sequences in the crp-2 promoter result in a decrease in transcription. A cDNA encoding the N. crassa homologue of CreA was cloned and designated Cre-1. The Cre-1 protein is 45% identical to CreA from A. nidulans. Cre-1 protein produced in Escherichia coli binds to the CreA sites in the promoters of the 40S rRNA and crp-2 genes. An amino acid change from histidine (92) to threonine changed the Cre-1 binding specificity from (5'G/CC/TGGG/AG3') to (5'G/CC/TGGCG3'). Base substitutions in the Cre-1 binding sites of the crp-2 promoter disrupted binding of wildtype Cre-1 in vitro but had no effect on transcription during steady state growth or carbon shifts, indicating that regulation of ribosomal genes by carbon source is not mediated by Cre-1, but via different proteins binding the Cre-1 sites and the Dde boxes.

Enhancement of allergic inflammation by the interaction between diesel exhaust particles and the immune system

There is growing evidence that fossil fuel combustion products act as adjuvants in the immune system and may lead to enhancement of allergic inflammation. Through this mechanism, particulate air pollutants may be an important contributor to the increased prevalence and morbidity of asthma and allergic rhinitis. In this communication we focus on the role of diesel exhaust particles (DEPs) in skewing the immune response towards IgE production and induction of allergic inflammation. We review experimental studies in animals and humans showing that DEPs enhance IgE production by a variety of mechanisms, including effects on cytokine and chemokine production, as well as activation of macrophages and other mucosal cell types. We discuss metabolic and cellular activation pathways linked to chemicals such as polycyclic aromatic hydrocarbons contained in DEPs and demonstrate how these molecular events may impact cytokine, chemokine, and accessory molecule expression in the immune system.

Macrophage activation by polycyclic aromatic hydrocarbons: evidence for the involvement of stress-activated protein kinases, activator protein-1, and antioxidant response elements

Polycyclic aromatic hydrocarbons (PAH) contained in fossil fuel combustion particles enhance the allergic response to common environmental Ags. A key question is: what are molecular pathways in the immune system by which PAH and conversion products drive allergic inflammation? Circumstantial evidence suggests that macrophages are involved in PAH-induced responses. We demonstrate that a representative PAH, beta-napthoflavone (BNF), and a representative quinone metabolite, tert-butylhydroxyquinone (tBHQ), induce Jun kinase and p38 mitogen-activated protein kinase activities in parallel with the generation of activator protein-1 (AP-1) mobility shift complexes in THP-1 and RAW264.7 macrophage cell lines. Activation of mitogen-activated protein kinases was dependent on generation of oxidative stress, and could be inhibited by N-acetylcysteine. Another genetic response pathway linked to PAH is the antioxidant response element (ARE), which regulates expression of detoxifying enzymes. BNF and tBHQ activated a human ARE (hARE) reporter gene in RAW264.7 cells. Interestingly, bacterial lipopolysaccharide also induced hARE/chloramphenicol acetyltransferase activity. While the hARE core, GTGACTCAGC, contains a consensus AP-1 sequence (underlined), AP-1 was not required for hARE activation. This suggests that PAH and their conversion products operate via ARE-specific transcription factors in the immune system. BNF and tBHQ did, however, induce AP-1 binding to the hARE, while constitutively active Jun kinase interfered in hARE/chloramphenicol acetyltransferase activation. This suggests that AP-1 proteins negatively regulate the hARE. These data establish important activation pathways for PAH in the immune system and provide us with targets to modulate the effect of environmental pollutants on allergic inflammation.

Cone-rod dystrophy due to mutations in a novel photoreceptor-specific homeobox gene (CRX) essential for maintenance of the photoreceptor

Genes associated with inherited retinal degeneration have been found to encode proteins required for phototransduction, metabolism, or structural support of photoreceptors. Here we show that mutations in a novel photoreceptor-specific homeodomain transcription factor gene (CRX) cause an autosomal dominant form of cone-rod dystrophy (adCRD) at the CORD2 locus on chromosome 19q13. In affected members of a CORD2-linked family, the highly conserved glutamic acid at the first position of the recognition helix is replaced by alanine (E80A). In another CRD family, a 1 bp deletion (E168 [delta1 bp]) within a novel sequence, the WSP motif, predicts truncation of the C-terminal 132 residues of CRX. Mutations in the CRX gene cause adCRD either by haploinsufficiency or by a dominant negative effect and demonstrate that CRX is essential for the maintenance of mammalian photoreceptors.