A novel MT-CO1 m.6498C>A variation associated with the m.7444G>A mutation in the mitochondrial COI/tRNASer(UCN) genes in a patient with hearing impairment,diabetes and congenital visual loss

Mitochondrial diseases are a clinically heterogeneous group of disorders that arise as a result of dysfunction of the mitochondrial respiratory chain. Sensorineural hearing loss (SNHL) has been described in association to different mitochondrial multisystem syndromes, often involving the central nervous system, neuromuscular, or endocrine organs. In this study, we described a Tunisian young girl with hearing impairment, congenital visual loss and maternally inherited diabetes. No mutation was found in the mitochondrial tRNA^Leu(UUR) and the 12S rRNA genes. However, we detected the m.7444G>A mutation in the mitochondrial COI/tRNA^Ser(UCN) genes. This mutation eliminates the termination codon of the MT-CO1 gene and extends the COI polypeptide by three amino acids (Lys–Gln–Lys) to the C-terminal. The whole mitochondrial genome screening revealed the presence of a novel mutation m.6498C>A (L199I) in the mitochondrial DNA-encoded subunit I of the cytochrome c oxidase (COX). This “probably damaging” transversion affects a highly conserved domain and it was absent in 200 Tunisian controls. The studied patient was classified under the haplogroup H2a.     

Effect of salt stress on the antimicrobial activity of <Emphasis Type="Italic">Ruta chalepensis</Emphasis> essential oils

In the current investigation, the biological activities of essential oils obtained from organs of Ruta chalepensis plants grown under salt stress (0, 50 and 100 mM NaCl) were analyzed. Their chemical composition was often investigated by GC/FID and GC–MS and the antimicrobial activities towards eight bacteria (Salmonella All, Salmonella K, Escherichia coli 45AG, Escherichia coli 45AI, Staphylococcus aureus 9402, Staphylococcus aureus 02B145, Listeria 477 and Pseudomonas aeruginosa ATCC 10145) and five fungi strains (Aspergillus, Saccharomycee crvisiale, Streptomyces griseus, Fusarium solani and Penicillium thomii) were studied. Results revealed that salt increased essential oil production in leaves at 50 and 100 mM NaCl. A total of 20 compounds were identified in leaves, undecan-2-one, nonan-2-one and geijerene being the dominant ones. In stems, 21 compounds were found; they were dominated by decan-2-one, geijerene, nonan-2-one and undecan-2-one. In contrast, roots exhibited a large variation with 25 volatile compounds and octyl acetate, methyl decanoate, phytyl acetate were the major ones. Salt stress induced significant antibacterial activity changes, mainly in leaves and stems. In leaves, the minimum inhibitory and bactericidal concentration decreased at 100 mM NaCl against Listeria 477, the two strains of E. coli (45AG and 45AI) and P. aeruginosa but it increased versus other bacteria. In stems, salt increased oil antibacterial activity against all strains except P. aeruginosa ATCC 10145. Root oil showed the least antibacterial activity under saline conditions versus Listeria 477 and P. aeruginosa ATCC 10145. As regards antifungal activity, NaCl reduced the antifungal activity of essential oils against the majority of fungi strains.     

Biosynthesis of protease by Pseudomonas aeruginosa MN7 grown on fish substrate

Fish powders and fish protein hydrolysates (FPH) from sardinella (Sardinella aurita) were prepared and tested as growth media for alkaline protease production by Pseudomonas aeruginosa MN7. Cultivated in fish substrate as carbon source, the strain exhibited a slightly greater protease production (about 7800 U ml^–1) than that obtained with commercial peptones (about 7222 U ml^–1). Furthermore, P. aeruginosa MN7 produced the same amount of protease when cultivated in medium containing only fish substrate or that containing all ingredients, indicating that the strain can obtain its carbon and nitrogen requirements directly from whole fish proteins. Moreover, it was found that extensive hydrolysis of fish proteins did not increase protease formation. Protease production in media containing only FPH prepared by Alcalase was about 70% of those obtained with MN7 protease digest of fish protein or with meat-fish powder. These results indicate that sardinella substrates are an excellent carbon and nitrogen source for the growth of P. aeruginosa MN7 and the production of protease.     

Protein size distribution and inhibitory effect of wheat hydrolysates on Neutrase

Neutrase^®, used for hydrolysis of wheat proteins, was inhibited by end-product in a competitive uncompetitive way. The inhibition ratio depends on the progress of protein hydrolysis (degree of hydrolysis) and it remains constant beyond a degree of hydrolysis of 7.5%. The inhibitor was separated, on Sephadex G-25 column, in three fractions (>2.4, 2.4–0.5 and <0.5 kDa) generating an inhibition ratio of 29%, 46% and 67% respectively. The peptides size distribution (<1, 1–2, 2–3 and >3 kDa) of fractions was determined using size exclusion-high performance liquid chromatography. The analysis of obtained data, using a simple mathematical regression, showed a correlation factor of 0.98 between the inhibition ratio and the peptides less than 1 kDa and 0.99 when considering the peptides lower than 1 kDa and higher than 3 kDa.     

Interaction of intermittent fasting on the cytotoxic effects of nickel in rats at puberty

This study has been undertaken with the aim of determining if intermittent fasting can be considered as a malnutrition that amplifies, according to numerous authors, the cytotoxic effects of environmental pollutants. We have used 200 male and female rats of 'Wistar' descent (BW approximately 180 g). These rats are distributed into two groups: some nourished daily (N) and others nourished one day over two (J) during a month. By the end of this month, each group is itself split into two subgroups, the first one receiving tap water as drinkable water (group NO and JO); the other one receiving the water enriched by the chloride of nickel at the rate of 100 mg NiCl2 per litre (groups NNi and JNi). Intermittent fasting goes on parallel to treatment during 2, 4, 10, 16, 30 and 60 days. For the exploration of the protein of stress (HSP) and of the metallothioneines (MT), the nickel is administered by injection at the rate of 4 mg NiCl2 per kg during 1 and 5 days. Our results show that the mineral seric and renal balance does not vary in conditions of intermittent fasting compared with conditions of normal nutrition. Our study show than that nickel induced a renal deficiency by decreasing the creatinemia and uraemia rate, which is confirmed by the histological study, and induced a decrease in the induction of the HSP73 and in the synthesis of the (MT). The association of nickel with intermittent fasting would inhibit these effects. In conclusion, intermittent fasting does not manifest itself as a malnutrition that amplifies the nickel's effects. Nevertheless, it seems that the calorific lack provoked by intermittent fasting is beneficial to the body by increasing its performances against the cytotoxic effects induced by nickel.     

Prenatal diagnosis of chromosome disorders in Tunisian population

Cytogenetic prenatal diagnosis (PND) is under national health program in most developed countries, while it concerns a small part of population at risk in developing countries. Finance is common reason of absence of PND development, but socio-cultural believes play an important role in Arab Muslim countries. In this paper we report results of 3110 fetal karyotypes carried out in a Tunisian population, by cultured amniocytes analysis. It is the largest report in a Muslim Arab country in our Knowledge. Abnormal karyotypes rate was 4.18% classified in two groups: bad prognosis (3.05%) and good prognosis (1.13%). Common amniocentesis indication was maternal age. The highest predictive value was observed in balanced karyotype and fetal ultrasound findings indications. Maternal serum markers were not commonly used for trisomy 21 screening. Pregnancy termination that is permitted by legal and religious authorities was accepted by 94,74% parents. Information about PND outcomes was given by genetic counselling prior to fetal sampling, pregnancy interruption was discussed with parents at cytogenetic result announcement. The authors conclude that in order to prevent mental and physical handicap related to cytogenetic disorders we have to promote PND by education for population, genetic counselling and fetal ultrasound screening; all three methods available in Tunisia.     

Secretion of cyclodextrin glucanotransferase in E. coli using Bacillus subtilis lipase signal peptide and optimization of culture medium

The cyclodextrin glycosyltransferase (CGTase) of Paenibacillus pabuli US132 was fused to the secretive lipase signal peptide of B. subtilis. This leads to an efficient secretion of the recombinant enzyme into the culture medium of E. coli as an active and soluble form contrasting with the native construction leading to a periplasmic production. In order to enhance the yield of CGTase production, an experimental design methodology was applied for the optimization of the culture composition. Hence, the media components were submitted to preliminary screening using a Plakett-Burman design. The concentrations of the major operating ones were then optimized to enhance the secretion of CGTase using response surface methodology. The findings revealed that concentrations of 0.5% potato starch, 3% yeast extract, 3% tryptone, 1.5% casein hydrolysate, 0.5% NaCl, 0.2% KH2PO4, and 0.02% MgSO4 were the optimal conditions for CGTase production. The experimental value (9.43 U/mL) obtained for CGTase activity was very close to the predicted value (9.27 U/mL).     

Excretory overexpression of <Emphasis Type="Italic">Paenibacillus pabuli</Emphasis> US132 cyclodextrin glucanotransferase (CGTase) in <Emphasis Type="Italic">Escherichia coli</Emphasis>: gene cloning and optimization of the culture conditions using experimental design

The gene encoding the cyclodextrin glucanotransferase of Paenibacillus pabuli US132 was connected to the amylase signal peptide of Bacillus stearothermophilus. This leads to an efficient secretion of the recombinant enzyme into the culture medium of Escherichia coli as an active form contrasting with the native construction leading to a periplasmic production. The optimum cultivation conditions for the maximum expression were optimized, using a Box-Behnken design under the response surface methodology, and found to be a post-induction temperature of 24°C, an induction-starting A₆₀₀ nm of 0.85, an isopropyl-β-D-thiogalactopyranoside level of 0.045 mM and a post-induction time of 3.9 h. The screening of media components and their concentration were achieved using a Plackett-Burman and a Box-Behnken designs sequentially. Under the optimized conditions selected and in agreement with the predicted model, an activity of 6.03 U/mL was attained. This CGTase production was three-times higher than that using the non-optimized culture conditions (2 U/mL).