Alternative Processing of the Amyloid Precursor Protein Family by Rhomboid Protease RHBDL4

The amyloid precursor protein (APP) is an ubiquitously expressed cell surface protein and a key molecule in the etiology of Alzheimer disease. Amyloidogenic processing of APP through secretases leads to the generation of toxic amyloid β (Aβ) peptides, which are regarded as the molecular cause of the disease. We report here an alternative processing pathway of APP through the mammalian intramembrane rhomboid protease RHBDL4. RHBDL4 efficiently cleaves APP inside the cell, thus bypassing APP from amyloidogenic processing, leading to reduced Aβ levels. RHBDL4 cleaves APP multiple times in the ectodomain, resulting in several N- and C-terminal fragments that are not further degraded by classical APP secretases. Knockdown of endogenous RHBDL4 results in decreased levels of C-terminal fragments derived from endogenous APP. Similarly, we found the APP family members APLP1 and APLP2 to be substrates of RHBDL4. We conclude that RHBDL4-mediated APP processing provides insight into APP and rhomboid physiology and qualifies for further investigations to elaborate its impact on Alzheimer disease pathology.

[Infections with respiratory syncytial virus in North Lebanon--prevalence during winter 2008]

Between 1 December 2007 and 31 May 2008, we analysed 120 nasopharyngeal swabs for the presence respiratory syncytial virus (RSV) infection in 120 children aged 15 days to 6 years, hospitalized in 2 hospitals in North Lebanon. Of the 120 samples, 32 were positive (26.7%) for RSV. There was a peak in January which progressively disappeared from February to May. Being positive for RSV was significantly associated with the presence of rhinorrhoea and dyspnoea as clinical symptoms and the absence of pneumonia signs on chest X-ray and the diagnosis of bronchitises or bronchiolitis. Testing for RSV is important in cases of respiratory infections in children as it may limit unnecessary prescription of antibiotics.

[Biological analysis of workers in the food sector in north Lebanon]

We investigated the prevalence of bacterial and parasitic infections among workers in a pastry factory in North Lebanon in 2004. We found 39% of the workers (n = 196) had nasal carriage of Staphylococcus aureus. Resistance of S. aureus isolates was 98.7% to penicillin G, 24.7% to fusidic acid, 14.3% to pefloxacine and tetracycline, 11.7% to erythromycin, 6.5% to oxacillin and amoxicillin-clavulanate. Salmonella typhi was not found in any of the workers. Prevalence of intestinal parasites was 57.8% (n = 308). Amoebae comprised 72.5% (68.3% Entamoeba coli, 15.5% E. histolytica), followed by flagellates (18.0 %) (37.5% Dientamoeba fragilis, 31.3% Giardia lamblia) and nematodes (7.8%) (only Ascaris lumbricoides). The tuberculin test was positive in 16.3% of the workers (n = 301).

Activity concentrations and mean annual effective dose from gamma-emitting radionuclides in the Lebanese diet

Since the primary factor contributing to the internal effective dose in the human organism is contaminated food, the control of radionuclides in food represents the most important means of protection. This study was conducted to determine the levels of the dietary exposure of the Lebanese population to gamma-emitting radioisotopes. The activity concentrations of gamma-emitting radioisotopes have been measured in food samples that represent the market basket of an adult urban population in Lebanon. The artificial radionuclide (137)Cs was measured above detection limits in only fish, meat and milk-based deserts. The most abundant natural radionuclide was 40K (31-121 Bq kg(-1)), with the highest content in fish and meat samples. The annual mean effective dose contributed by 40K in the reference typical diet was estimated equal to 186 microSv y(-1), a value reasonably consistent with findings reported by several other countries.

Dietary exposure to lead, cadmium, mercury and radionuclides of an adult urban population in Lebanon: a total diet study approach

Human exposure to toxic chemicals is suspected of being responsible for a wide range of human health disorders. This study is the first in Lebanon to evaluate the dietary exposure of an adult urban population to three heavy metals (lead, cadmium and mercury) and to radionuclides. Exposure assessment was performed by means of the total diet study approach as recommended by the Word Health Organization. Five 'total diets' were collected during 2003-04. Average and maximal consumer exposure estimates to heavy metals were calculated and compared with appropriate reference values and with intakes reported from other countries. The average dietary intakes of lead, cadmium and mercury represented 7, 17 and 5.6%, respectively, of the appropriate provisional tolerable weekly intakes (PTWI). The mean dietary intake of methylmercury represented 17.5% of the appropriate PTWI. Cs-134 and I-131 were not detected in any of the food samples. Traces of Cs-137 were only found in five food samples. The exposure assessment conducted places Lebanon among countries least exposed to heavy metals through the diet and it highlights the safety of the food supply from radioactive contamination.