Human transferrin (Tf) and group-specific component (Gc) subtypes in Tunisia

Summary Simultaneous subtyping of two genetic markers—group-specific component (Gc) and transferrin (Tf)—by electrofocusing enabled us to compute the following gene frequencies for the Tunisian population: Gc ^IS .0.525; Gc ^IF , 0.260; Gc ², 0.215; Tf ^CI , 0.770; Tf ^C2 , 0.215; Tf ^D1 , 0.015.The frequencies of Tf ^D , Tf ^C2 , and Gc ¹ are higher than those found in Caucasoid populations and can be explained by Negroid contribution. A selective advantage related to the metabolic role of this vitamin D-binding protein does not seem very likely for any particular Gc type or subtype. It is postulated that the differences in the frequencies of the Gc alleles might be related to selective advantage for genes belonging to other genetic systems originally closely linked to either Gc ¹ or to Gc ² alleles.This work was supported in part by the Faculté de Pharmacie et de Médecine Dentaire of Monastir and by a grant from the Ambassade de France in Tunisia     

Alzheimer’s disease: analysis of a mathematical model incorporating the role of prions

We introduce a mathematical model of the in vivo progression of Alzheimer’s disease with focus on the role of prions in memory impairment. Our model consists of differential equations that describe the dynamic formation of \(\upbeta \) -amyloid plaques based on the concentrations of A \(\upbeta \)  oligomers, PrP^C proteins, and the A \(\upbeta \) - \(\times \) -PrP^Ccomplex, which are hypothesized to be responsible for synaptic toxicity. We prove the well-posedness of the model and provided stability results for its unique equilibrium, when the polymerization rate of \(\upbeta \) -amyloid is constant and also when it is described by a power law.     

Role of gamma irradiation in regulation of NO3 level in rocket (Eruca vesicaria subsp. sativa) plants

The changes in the growth indices and certain metabolic activities in response to different doses of γ-irradiation (0, 20, 50, 100, and 200 Gy) were studied, using rocket seedlings. The total yield, seed mass, and essential oil content increased significantly by 20 Gy dose of γ-irradiation as compared with the control samples. In addition, total sugars, total free amino acids, total soluble phenols, kinetin, GA₃, nitrate reductase activity, and total protein increased significantly at 20 Gy dose. Meanwhile, NO₃ content decreased significantly at 20 Gy dose. The nitrogen and potassium content increased at the same dose of gamma rays of 20 Gy. While the phosphorus content showed no significant effect at all the γ-irradiation doses used. The results obtained in this work revealed that the most effective dose was 20 Gy of gamma rays. It was suggested that pretreatment of rocket seeds before planting with 20 Gy dose of γ-irradiation, may oppose the harsh effect of NO₃ accumulation and increased the quality and quantity of rocket yield. Published in Russian in Fiziologiya Rastenii, 2006, Vol. 53, No. 2, pp. 215–219. The text was submitted by the author in English.     

Effects of cyanobacterial extracellular products and gibberellic acid on salinity tolerance in Oryza sativa L

The XI International Rotifer Symposium was held during 11–18 March, 2006 at the National Autonomous University of Mexico Campus Iztacala located at the North Mexico City (Mexico). These triennial international meetings, first organized in Austria by Late Ruttner-Kolisko in September 1976, are gradually becoming the focal point of discussion and collaboration from rotifer workers across the world. The present XI symposium was attended by 125 participants from 20 nations. During this meeting, different themes of rotifer research from morphology to molecular biology were considered. In addition, there were four invited lectures and four workshops covering different themes of the symposium. During the last 30 years, rotifer research has witnessed gradual shift from the conventional morphological taxonomy to molecular and evolutionary systematics. While the basic rotifer ecological studies continue today, applied areas such as ecotoxicology and aquaculture have taken key roles in the recent meetings. The international rotifer meetings provide ample opportunities not only for exchange of ideas and recent research, but also for material and in establishing inter-personal relationships. Over the last 30 years, the number of participants attending the rotifer meetings has increased.     

Filamentous brown algae infected by the marine,holocarpic oomycete Eurychasma dicksonii: first results on the organization and the role of cytoskeleton in both host and parasite

The important role of the cytoskeletal scaffold is increasingly recognized in host-pathogen interactions. The cytoskeleton potentially functions as a weapon for both the plants defending themselves against fungal or oomycete parasites, and for the pathogens trying to overcome the resisting barrier of the plants. This concept, however, had not been investigated in marine algae so far. We are opening this scientific chapter with our study on the functional implications of the cytoskeleton in 3 filamentous brown algal species infected by the marine oomycete Eurychasma dicksonii. Our observations suggest that the cytoskeleton is involved in host defense responses and in fundamental developmental stages of E. dicksonii in its algal host.Oomycetes are important plant and animal pathogens and are the cause of significant crop losses every year. Hence, a plethora of studies with different cultivated and model plant species investigate the diversity of parasite infection pathways and host defense responses.¹ However, little information is available on the interactions between algae and marine oomycetes, despite the epidemic outbreaks reported² and the huge impact on intensive algal aquaculture.³Eurychasma dicksonii is a biotrophic, intracellular marine oomycete, capable to infect at least 45 species of brown seaweeds in laboratory cultures.⁴ Molecular data reveal that E. dicksonii has a basal phylogenetic position in the oomycete lineage.^5,6 The basic stages of the infection are known: the attachment of the parasite spore to the host cell wall, the penetration of its cytoplasm into the host cell, the formation of a multinucleated, unwalled thallus, and zoosporogenesis.⁶ Hitherto, though, there was no knowledge about the role of cytoskeleton in the context of infection, which stimulated our research.In land plants, reorganization of the cytoskeleton is part of the reaction to infection by fungal pathogens. The rearrangement of the cytoplasm and the relocation of the nuclei and other organelles are accompanied by rapid rearrangements of the cytoskeletal elements.⁷ The plant cytoskeleton shows an extreme plasticity in order to serve the intracellular realignment.At the same time, this indicates that the plant cytoskeleton could be the parasite’s target by producing anti-cytoskeletal compounds in an effort to overcome plant resistance, a mechanism known in several fungal and oomycete pathogens of higher plants.^8,9Consequently, the changes in microtubule (MT) organization are associated with both the plant defense and/or susceptibility toward oomycetes, respectively.¹⁰ Therefore, our research on the organization and role of cytoskeleton in the host and the parasite sheds some light into the enormous variability in the specificity of the recognition, defense, and infection mechanisms.     

Multilamellar liposomes of triamcinolone acetonide: preparation,stability, and characterization

The aim of this study was to assess and characterize the stability of multilamellar liposomes as a delivery vehicle for triamcinolone acetonide. A standardized preparation method for a liposomal delivery vehicle was developed, after varying composition and storage conditions, and assessing encapsulation efficiency and loss of active principle. The assessment of temperature as a factor in formula stability during storage showed that stability improved under refrigeration (4–6°C) (less early diffusion of active principle through the liposomal wall), in comparison with samples stored at room temperature. To improve stability, cholesterol was added to some formulae, which although resulting in a decrease in average encapsulation efficiency, mitigated subsequent losses of retained active principle (formulae 4, 5, and 6), in comparison with those without cholesterol (formulae 1, 2, and 3). This was evident both under refrigerated and room-temperature conditions. Finally, after testing the effects of adding an antioxidant and/or preservative to the formulae, a liposomal design was achieved with acceptable stability, vesicle dimensions, and encapsulation efficiency.     

Mitochondrial dysfunction contributes to the cytotoxicity of some 3,5-bis(benzylidene)-4-piperidone derivatives in colon HCT-116 cells

The objectives of this study are to investigate the possible ways by which the curcumin analogs 2a and 2b exert their antiproliferative properties. The analogs 2a and 2b have submicromolar IC₅₀ values towards human HCT-116 colon cancer cells but are far less toxic to human non-malignant CRL-1790 colon cells. Both compounds affected a number of mitochondrial functions in HCT-116 cells namely increasing the intracellular concentrations of reactive oxygen species, inhibiting oxygen consumption and decreasing the mitochondrial membrane potential. These molecules also produced swelling of isolated rat liver mitochondria, supporting a mitochondrial mechanism of cytotoxicity. Both compounds reacted with glutathione in the presence of glutathione S-transferase π and hence they may be classified as thiol alkylators.     

Toxicological Study of Sodium Selenite on Fetal Development and DNA Fragmentation in Liver Cells of Pregnant Rats

The present study was carried out to evaluate the effects of sodium selenite on fetal development and DNA in liver of rats. Pregnant rats were divided into three groups: control group, group treated orally with 5 μg Se/kg body wt. and group treated orally with 10 μg Se/kg body wt. Dams were treated orally with sodium selenite from day 7 to 19 of gestation. Sodium selenite treatment revealed decrease in maternal body weight, reduction in fetal weight, length and number of viable fetuses, increased number of resorbed fetuses and post-implantation loss at the two doses tested. Fetal skeleton showed signs of developmental delay in skull and limbs of the treated groups. Sodium selenite treatment revealed significant reduction of placental and liver weights in treated dams. Sodium selenite-induced oxidative stress in liver tissue of rats as evidenced by increase in lipid peroxidation and glutathione peroxidase activity, while catalase was significantly decreased. Also, increase in DNA fragmentation, marked reduction of hepatic DNA content, and many histopathological changes in the liver were recorded. The results demonstrated that treatment of pregnant rats with sodium selenite at the toxic dosages chosen showed maternal and fetal toxicity that may be concerned with hepatic oxidative stress accompanied with DNA fragmentation and depletion of total DNA content.