The anti-bacterial iron-restriction defence mechanisms of egg white; the potential role of three lipocalin-like proteins in resistance against Salmonella

Salmonella enterica serovar Enteritidis (SE) is the most frequently-detected Salmonella in foodborne outbreaks in the European Union. Among such outbreaks, egg and egg products were identified as the most common vehicles of infection. Possibly, the major antibacterial property of egg white is iron restriction, which results from the presence of the iron-binding protein, ovotransferrin. To circumvent iron restriction, SE synthesise catecholate siderophores (i.e. enterobactin and salmochelin) that can chelate iron from host iron-binding proteins. Here, we highlight the role of lipocalin-like proteins found in egg white that could enhance egg-white iron restriction through sequestration of certain siderophores, including enterobactin. Indeed, it is now apparent that the egg-white lipocalin, Ex-FABP, can inhibit bacterial growth via its siderophore-binding capacity in vitro. However, it remains unclear whether ex-FABP performs such a function in egg white or during bird infection. Regarding the two other lipocalins of egg white (Cal-γ and α-1-glycoprotein), there is currently no evidence to indicate that they sequester siderophores

Mutations of the ACTH receptor gene in a new family with isolated glucocorticoid deficiency

Isolated glucocorticoid deficiency (IGD) is an autosomal recessive disorder characterized by primary adrenocortical insufficiency, without mineralocorticoid deficiency. Mutations of the ACTH receptor gene have been reported in several families with IGD. We have amplified and directly sequenced the entire intronless ACTH receptor gene in a new family with IGD. The proband was found to be compound heterozygote for two different point mutations, one in each allele: (a) a substitution (360C>G) which changed neutral serine at position 120 in the apolar third transmembrane domain of the receptor to a positively charged arginine (S120R), probably disrupting the ligand-binding site; and (b) a substitution (761A>G) changing tyrosine at position 254 to cysteine (Y254C) in the third extracellular loop of the receptor protein, that also likely disrupts its structure and interferes with ligand binding. Each of the two mutations in the proband has previously been described in a different family, S120R in compound heterozygosity with a stop codon (R201X) and Y254C in homozygote form. Thus, in the absence of in vitro functional studies, our findings confirm the pathogenetic role of the S120R and Y254C mutants in the development of resistance to ACTH. (C) 2000 Academic Press

A single sample GnRHa stimulation test in the diagnosis of precocious puberty

<p>Abstract</p> <p>Context</p> <p>Gonadotropin-releasing hormone (GnRH) has been the standard test for diagnosing central precocious puberty. Because GnRH is no longer available, GnRH analogues (GnRHa) are now used. Random LH concentration, measured by the third-generation immunochemiluminometric assay, is a useful screening tool for central precocious puberty. However, GnRHa stimulation test should be considered, when a basal LH measurement is inconclusive. However optimal sampling times for luteinizing hormone (LH) have yet to be established.</p> <p>Purpose</p> <p>To determine the appropriate sampling time for LH post leuprolide challenge.</p> <p>Methods</p> <p>A retrospective analysis of multi-sample GnRHa stimulation tests performed in 155 children (aged 1–9 years) referred for precocious puberty to Texas Children’s Hospital.</p> <p>After 20 mcg/kg of SQ leuprolide acetate, samples were obtained at 0, 1, 3, and 6 hours.</p> <p>Results</p> <p>Of 71 children with clinical evidence of central precocious puberty, fifty nine children had a peak LH >5 mIU/mL. 52 (88%) of these responders had positive responses at 1 hour (95% CI is 80–96%), whereas all 59 children (100%) had a peak LH response >5 mIU/mL at 3 hours (95% CI is 94-100%), P = 0.005.</p> <p>Conclusions</p> <p>A single serum LH sample collected 3 hours post GnRHa challenge is the optimal sample to establish the diagnosis of central precocious puberty.</p