Parasitoses and immunodepression

The immunodepression, related or not to AIDS, induces the emergence of opportunistic parasitosis and mycosis. Our objective is to analyze these pathogenic agents, their clinical expression and gravity in immunocompromised individuals. Our retrospective 9 years study reported parasitic and fungic infections complicating immunodepression. Among 31 HIV infected patients, we diagnosed the following parasitosis: Cryptosporidium (7 cases), Isospora belli (2 cases) and Enterocytozoon bieneusi (1 case). Pulmonary pneumocystosis was diagnosed in 6 cases, cerebral toxoplasmosis in 6 cases and meningo-cerebral cryptococcosis in 1 case. The systemic candidasis was diagnosed in 13 leukaemic patients. The intestinal anguilluliasis was found in 5 patients treated with cortico?ds for long periods. A case of Kala azar was observed in a 83 years man treated with cortico?ds. A disseminated aspergillosis occurred in a child with a Chediack Higashi syndrome. A gingivo-labial fusariosis was diagnosed in a leukaemic patient. This emergency of the new parasitic and fungal agents requires a better understanding of these affections in order to improve their early diagnosis and treatments.     

Anatamo-pathological aspects of malignant ovarian tumors in children. Apropos of 16 cases

The authors present 16 cases of malignant ovarian tumors in childhood, censed in Pasteur Institute - Tunis. These tumors are scarce, and present in the literature only 3% of the malignant tumors in childhood. In this series, germ cell tumors are the most frequent and present 81.25% of these cases, of which 43.75% of dysgerminoma. Gonadal stromal tumors are more scarce (6.25%). The prognosis of these tumors was transformed by the radiation therapy in dysgerminoma, and the chemotherapy in the other germ cell tumors. These tumors must be diagnosed and treated early.     

Galactolipase activity of Talaromyces thermophilus lipase on galactolipid micelles,monomolecular films and UV-absorbing surface-coated substrate

Talaromyces thermophilus lipase (TTL) was found to hydrolyze monogalactosyl diacylglycerol (MGDG) and digalactosyl diacylglycerol (DGDG) substrates presented in various forms to the enzyme. Different assay techniques were used for each substrate: pHstat with dioctanoyl galactolipid-bile salt mixed micelles, barostat with dilauroyl galactolipid monomolecular films spread at the air-water interface, and UV absorption using a novel MGDG substrate containing α-eleostearic acid as chromophore and coated on microtiter plates. The kinetic properties of TTL were compared to those of the homologous lipase from Thermomyces lanuginosus (TLL), guinea pig pancreatic lipase-related protein 2 and Fusarium solani cutinase. TTL was found to be the most active galactolipase, with a higher activity on micelles than on monomolecular films or surface-coated MGDG. Nevertheless, the UV absorption assay with coated MGDG was highly sensitive and allowed measuring significant activities with about 10?ng of enzymes, against 100?ng to 10?μg with the pHstat. TTL showed longer lag times than TLL for reaching steady state kinetics of hydrolysis with monomolecular films or surface-coated MGDG. These findings and 3D-modelling of TTL based on the known structure of TLL pointed out to two phenylalanine to leucine substitutions in TTL, that could be responsible for its slower adsorption at lipid-water interface. TTL was found to be more active on MGDG than on DGDG using both galactolipid-bile salt mixed micelles and galactolipid monomolecular films. These later experiments suggest that the second galactose on galactolipid polar head impairs the enzyme adsorption on its aggregated substrate.     

Agricultural wastes as substrates for β-glucosidase production by Talaromyces thermophilus: Role of these enzymes in enhancing waste paper saccharification

In the present study, we investigated a potent extracellular β-glucosidases secreted by the thermophilic fungal strain AX4 of Talaromyces thermophilus, isolated from Tunisian soil samples. This strain was selected referring to the highest thermostability of its β-glucosidases compared to the other fungal isolates. The β-glucosidase production was investigated by submerged fermentation. The optimal temperature and initial pH for maximum β-glucosidase production were 50°C and 7.0, respectively. Several carbon sources were assayed for their effects on β-glucosidase production, significant yields were obtained in media containing lactose 1% (3.0?±?0.36?U/ml) and wheat bran 2% (4.0?±?0.4?U/ml). The combination of wheat bran at 2% and lactose at 0.8% as carbon source enhanced β-glucosidase production, which reached 8.5?±?0.28?U/ml. Furthermore, the β-glucosidase-rich enzymatic juice of T. thermophilus exhibited significant synergism with Trichoderma reesei (Rut C30) cellulases for pretreated waste paper (PWP) hydrolysis. Interestingly, the use of this optimal enzymatic cocktail increased 4.23 fold the glucose yield after saccharification of waste paper. A maximum sugar yield (94%) was reached when using low substrate (2%) and enzyme loading (EC1).     

Structure génétique des cécidomyies des céréales en Tunisie

Genetic structure of Hessian flies in Tunisia. The genetic structure of M. destructor and M. hordei was investigated by sampling 21 fields of cereals in 14 localities of central and southern Tunisia. As previously shown, there was no strict association between the cereal species (wheat, barley and oat) and the Mayetiola species. M. destructor males displayed no heterozygosity at the Pgm3 locus, indicating that they were hemizygous as is the PGM locus in North America. In M. hordei, heterozygous males were observed at all loci, but strong heterozygote deficits were found at two loci (Mdh2 et Hk). Since no such deficit was observed in females, the population structure of M. hordei was studied only in females. Although heterozygosity was two fold higher in M. hordei than in M. destructor, the two species were similar for other genetic characteristics, including a low (Fst < 0.05) but significant (P < 0.05) genetic differentiation, no isolation by distance, and similar rates of gene flow (5.7 ≤ Nm ≤ 9.6). These results are discussed in relation to their consequences in the event of controlling Tunisian Hessian flies using wheat cultivars that are resistant to a M. destructor biotype.     

Malignant tumors of the stomach: apropos of 583 anatomo-clinical cases

A retrospective study interesting 582 anatomoclinical cases of gastric malignant tumors was realised in two anatomo-pathological services of Tunis from 1970 to 1985. The average age of patients is 55 years old, with extensive ranges from 17 to 85 years old. The authors point out significative male predominance 64.6% of cases. The ulcered form is the most frequent, about 3.8% of macroscopic aspect cases. Among these last, the authors find 26.7% of ulcerating and polypoid form with invasive characteristics, and 18.83% of linitis plastica. The pyloric area localisation is the most frequent, 68% of cases. Diffuse tumors are observed in 8.47% of cases and numerous stomach localisation in 0.82% of cases. 84% of histological aspect are represented by adenocarcinoma, the most frequent of them (35%) is well differentiated type, then the poorly differentiated (20%) and atypic form (19.75%). Frequency of lymphosarcoma reaches 14.7%, the first is the centroblastic form, then lymphoblastic and lymphoplasmocytic forms. Concerning evolution, gastric cancer is an infiltrative tumor: serosal surface is attempted in 69.5% of cases, and during the first chirurgical act half cases show lymph nodes metastasis.     

A novel hepatopancreatic phospholipase A2 from Hexaplex trunculus with digestive and toxic activities

A marine snail digestive phospholipase A₂ (mSDPL) was purified from delipidated hepatopancreas. Unlike known digestive phospholipases A₂, which are 14 kDa proteins, the purified mSDPL has a molecular mass of about 30 kDa. It has a specific activity of about 180 U/mg measured at 50 °C and pH 8.5 using phosphatidylcholine liposomes as a substrate in the presence of 4 mM NaTDC and 6 mM CaCl₂. The N-terminal amino-acid of the purified mSDPL does not share any homology with known phospholipases.Moreover, the mSDPL exhibits hemolytic activity in intact erythrocytes and can penetrate phospholipid monolayers at high surface pressure, comparable to snake venom PLA₂. These observations suggest that mSDPL could be toxic to mammal cells. However, mSDPL can be classified as a member of a new family of enzymes. It should be situated between the class of toxic phospholipase A₂ from venoms and another class of non toxic pancreatic phospholipase A₂ from mammals.     

A double mutation in AGXT gene in families with primary hyperoxaluria type 1

Primary hyperoxaluria type 1 (PH1) is a severe autosomal recessive inherited disorder of glyoxylate metabolism caused by mutations in the AGXT gene on chromosome 2q37.3 that encodes the hepatic peroxisomal enzyme alanine:glyoxylate aminotransferase. These mutations are found throughout the entire gene and cause a wide spectrum of clinical severity. Rare in Europe, PH1 is responsible for 13% of the end stage renal failure in the Tunisian child. In the present work, we identified the double mutation c.32C>T (Pro11Leu) and c.731T>C (p.Ile244Thr) in AGXT gene in five unrelated Tunisian families with PH1 disease. Our results provide evidence regarding the potential involvement of c.32C>T, originally described as common polymorphism, on the resulting phenotype. We also reported an extreme intrafamilial heterogeneity in clinical presentation of PH1. Despite the same genetic background, the outcome of the affected members differs widely. The significant phenotypic heterogeneity observed within a same family, with a same genotype, suggests the existence of relevant modifier factors.