Changing clinical features of coeliac disease

The classical clinical picture of coeliac disease includes prolonged diarrhoea with failure to thrive. During the past two decades this type of active presentation of coeliac disease has decreased in many European countries, giving the impression that coeliac disease is a disappearing disease. However, this is not true. The disease can be found in older children with a more or less silent presentation. Silent coeliac disease can be detected by active screening with serological tests. Coeliac disease can be suspected in children suffering from mild gastrointestinal symptoms, such as abdominal pain, and in those with signs of nutritional deficiencies, as well as in children of first-degree relatives of already diagnosed coeliacs, patients with IgA-deficiency, patients suffering from dental enamel hypoplasia or dermatitis herpetiformis, and patients with some other disease known to be associated with coeliac disease, such as diabetes mellitus. According to the fundamental criteria of coeliac disease, the intestinal mucosa is flat when the individual is eating gluten-containing foods. However, this is not strictly true. Intolerance to gluten is obviously variable and the intestinal mucosa may be normal. This type of latent coeliac disease can be detected by analysing genetic markers, measuring antibodies in intestinal fluid or counting the density of intra-epithelial gamma/delta T cells which are increased greatly even in the latent phase of coeliac disease. Thus the general concept of the natural history of coeliac disease is changing.     

"Social cognitions as organizers of autonomic and affective responses to social challenge": Correction.

Reports an error in the original article by D. B. Bugental et al (Journal of Personality and Social Psychology, 1993, Vol 64[1], 94–203). On page 97, the sentence "SCL was measured by bipolar silver-silver chloride electrodes placed on the thumb of the nonpreferred hand' should read as follows: "SCL was measured by bipolar silver-silver chloride electrodes placed on the thenar and hypothenar eminences of the nonpreferred hand.' (The following abstract of this article originally appeared in record 1993-21385-001.) Autonomic and affective responses to children were assessed as a function of adult perceptions of interpersonal control. Women (N?=?160) interacted with and provided feedback to computer-simulated children who behaved responsively or unresponsively on a computer game. Women were categorized as low in perceived control (PC) if they attributed high control to children but low control to self over negative events on the Parent Attribution Test. As predicted, low-PC women were maximally reactive to child characteristics, manifesting peak levels of defensive arousal (increased level of heart rate and electrodermal activity) and negative affect with unresponsive children and minimal levels of arousal and negative affect with responsive children … (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The CDK-activating kinase (Cak1p) from budding yeast has an unusual ATP-binding pocket

Cak1p is an essential protein kinase that phosphorylates and thereby activates the major cyclin-dependent kinase in budding yeast, Cdc28p. The sequence of Cak1p differs from other members of the protein kinase superfamily in several conserved regions. Cak1p lacks the highly conserved glycine loop motif (GXGXXG) that is found in the nucleotide binding fold of virtually all protein kinases and also lacks a number of conserved amino acids found at sites throughout the protein kinase core sequence. We have used kinetic and mutagenic analyses to investigate whether these sequence differences affect the nucleotide-binding properties of Cak1p. Although Cak1p differs dramatically from other protein kinases, it binds ATP with a reasonable affinity, with a KM of 4.8 microM. Mutations of the putative invariant lysine in Cak1p (Lys-31), homologous to a residue required for activity in virtually all protein kinases and that interacts with the ATP phosphates, moderately reduced the ability of Cak1p to bind ATP but did not dramatically affect the catalytic rate of the kinase. Similarly, Cak1p is insensitive to the ATP analog 5'-fluorosulfonylbenzoyladenosine, which inhibits most protein kinases through covalent modification of the invariant lysine. We found that Cak1p is tolerant of mutations within its glycine loop region. Remarkably, Cak1p remains functional even following truncation of its first 31 amino acids, including the glycine loop region and the invariant lysine. We conclude that the Cak1p nucleotide-binding pocket differs significantly from those of most other protein kinases and therefore might provide a specific target for an inhibitory drug.     

A role for perforin in downregulating T-cell responses during chronic viral infection

Cytotoxic T cells secrete perforin to kill virus-infected cells. In this study we show that perforin also plays a role in immune regulation. Perforin-deficient (perf -/-) mice chronically infected with lymphocytic choriomeningitis virus (LCMV) contained greater numbers of antiviral T cells compared to persistently infected +/+ mice. The enhanced expansion was seen in both CD4 and CD8 T cells, but the most striking difference was in the numbers of LCMV-specific CD8 T cells present in infected perf -/- mice. Persistent LCMV infection of +/+ mice results in both deletion and anergy of antigen-specific CD8 T cells, and our results show that this peripheral "exhaustion" of activated CD8 T cells occurred less efficiently in perf -/- mice. This excessive accumulation of activated CD8 T cells resulted in immune-mediated damage in persistently infected perf -/- mice; approximately 50% of these mice died within 2 to 4 weeks, and mortality was fully reversed by in vivo depletion of CD8 T cells. This finding highlights an interesting dichotomy between the role of perforin in viral clearance and immunopathology; perforin-deficient CD8 T cells were unable to clear the LCMV infection but were capable of causing immune-mediated damage. Finally, this study shows that perforin also plays a role in regulating T-cell-mediated autoimmunity. Mice that were deficient in both perforin and Fas exhibited a striking acceleration of the spontaneous lymphoproliferative disease seen in Fas-deficient (lpr) mice. Taken together, these results show that the perforin-mediated pathway is involved in downregulating T-cell responses during chronic viral infection and autoimmunity and that perforin and Fas act independently as negative regulators of activated T cells.     

Probing the basis of antibody reactivity with a panel of constrained peptide libraries displayed by filamentous phage

The structural requirements for peptide binding to an antibody may be elucidated by probing it with a variety of peptides having different constraints. To this end, we have constructed and screened a panel of peptide libraries displayed by filamentous bacteriophage. The peptides in most of the libraries have the potential for constraint by fixed Cys residues, which have been placed at different sites within a randomized amino acid sequence of varying length. When taken together, the binding data obtained from screening the panel with a given antibody allow one to determine the types of constraints that promote binding, as well as the residues that are critical for binding. We describe the construction of 11, pVIII-displayed, peptide libraries, whose sizes range from 150 million to 10 billion clones. The libraries were screened with a number of polyclonal and monoclonal antibodies against peptides, proteins and carbohydrates. Cross-reactivity with peptides was always found for antibodies produced against peptides, linear epitopes on folded proteins and, surprisingly, carbohydrates, whereas antibodies against discontinuous epitopes on proteins were found less frequently. The implications of these results are discussed in terms of the structural basis for cross-reactivity with peptides.     

The giant organelles in beige and Chediak-Higashi fibroblasts are derived from late endosomes and mature lysosomes

Chediak-Higashi Syndrome (CHS) is an autosomal recessive disease affecting secretory granules and lysosomes-like organelles. In CHS fibroblasts, acidic organelles are abnormally large and clustered in the perinuclear area. We have analyzed fibroblast cell lines from a CHS patient and from the murine model for CHS, the beige mouse, to determine which lysosome-like compartments are affected. Uptake of neutral red showed that in both beige and CHS cell lines, the acidic organelles were markedly clustered in the perinuclear region of the cells. Giant organelles (> 4 microns) were observed in a fraction of the cells, and these were more dramatic in the beige fibroblasts than in the CHS fibroblasts. The total dye uptake of both mutant cell lines was similar to their respective wild type fibroblasts, suggesting that the overall volume of acidic compartments is unaffected by the disorder. Histochemistry and immunofluorescence showed that the giant organelles in both beige and CHS fibroblasts were positive for cathepsin D, lysosome-associated membrane protein (LAMP) 1, LAMP 2, and a 120-kD lysosomal glycoprotein, all marker proteins for late endosomes and lysosomes. The giant organelles were also negative for transferrin receptor and mannose-6-phosphate receptor, and most of them were also negative for rab 7. This distribution of marker proteins shows that the giant organelles in both beige and CHS are derived from late compartments of the endocytic pathway. This conclusion was confirmed using endocytic tracers. BSA was transported to the giant organelles, but only after long incubation times, and only at 37 degrees C. alpha 2-Macroglobulin was taken up and degraded at similar rates by CHS or beige cells and their respective wild type control cells. Taken together, our results indicate that the mutation in CHS specifically affects late endosomes and lysosomes, with little or no effect on early endosomes. Although the mutation clearly causes mislocalization of these organelles, it appears to have little effect on their endocytic and degradative functions.     

Stimulation or inhibition of A431 cell growth by EGF is directly correlated with receptor tyrosine kinase concentration but not with PLC gamma activity

EGF-induced hydrolysis of phosphatidylinositol 4, 5, biphosphate was compared in A431 cells with respect to their growth response to EGF. A431 cells which express 4- to 5-fold more EGF receptors than A431-4 cells were growth inhibited, while A431-4 cells were growth stimulated by EGF within the same dose range. Treatment of A431 cells with EGF resulted in a 2-fold increase in cellular IP3 levels and the effect in A431-4 cells was not as obvious. In the presence of tyrosine kinase inhibitor coumaric acid (0.2 approximately 2 microM), A431 cell growth was stimulated, rather than inhibited, by EGF in a dose-dependent manner. In contrast, the stimulation of A431-4 cell growth by EGF was reduced under the same conditions. Furthermore, in the presence of coumaric acid (up to 0.5 microM), EGF-induced production of inositol phosphates in A431 cells was not obviously affected. Taken together, the results suggest that EGF-induced growth inhibition of A431 cells may be due to a quantitative changes of EGF-receptor tyrosine kinase activity in areas other than the recruitment and activation of phosphatidylinositol-specific phospholipase C gamma.     

Modulatory role of 5-HT3 receptors in gastric function and ethanol-induced mucosal damage in rat stomachs

The involvement of 5-hydroxytryptamine (5-HT) in gastric function and mucosal damage has been defined. 5-HT also potentiates lesion formation in animals. The current study investigated further whether these actions are mediated through 5-HT3 receptors in rats. Ondansetron, a 5-HT3 receptor antagonist, was given subcutaneously, 2 or 4 mg/kg, 30 min before the gastric parameters were measured. The higher dose of ondansetron, 4 mg/kg, significantly increased gastric mucosal blood flow (GMBF) and also basal acid and Na+ secretion. However, it did not affect pepsin output. 5-HT time dependently reduced GMBF and pepsin secretion, but not that of acid and Na+. These actions were not altered by ondansetron pretreatment. The drug, however, dose dependently reduced ethanol-induced gastric mucosal lesions in the 5-HT-treated animals. These findings indicate that 5-HT3 receptors regulate not only basal GMBF, but also acid and Na+ secretion in stomachs. However, the depressive action of 5-HT on GMBF and pepsin secretion is most likely not mediated through 5-HT3 receptors. Ondansetron also modulates the toxicities of ethanol in the stomach and this action is likely to be mediated through the preservation of GMBF.