Effects of thioredoxin on the preimplantation development of bovine embryos.

Thioredoxin (TRX) is an ubiquitous protein disulfide reductase, which is known to be involved in the implantation development of mouse embryos. In the present study, recombinant human TRX was used to evaluate its effect on the promotion of preimplantation development of bovine embryos derived from in vitro maturation and fertilization. Supplementation of the medium 24h post insemination with TRX significantly (P<0.05) enhanced the frequency of development to the blastocyst stage in 5% O(2) concentration. The optimal concentration was 0.5 microg/ml (P<0.05, compared with 0, 0.1 and 1.0 microg/ml). This effect of TRX was evident only when added around the time of the first cleavage stage (24 h post insemination); no promotion was found with treatment at 6h (one-cell) or 44 h (six- to eight-cell) after insemination. Moreover, it is of interest that even with the best combination of the dose and timing of TRX treatment (0.5 microg/ml, at 24 h post insemination), no promotion of development was observed when embryos were cultured under 20% O(2). However, a preincubation of TRX in the culture medium under 20% oxygen for 24h did not diminish the promoting effect in the subsequent TRX treatment under optimal conditions, thus suggesting that the possible oxidation of TRX alone may not be the reason for the disappearance of the effect under a high oxygen concentration. These results indicate that TRX does improve the development of bovine embryos in vitro, though unlike the general reducing reagents such as beta-mercaptoethanol or cysteamine, TRX may have to exert its effect at specific times and in more physiologic oxygen environments.

In vitro maturation and glutathione synthesis of porcine oocytes in the presence or absence of cysteamine under different oxygen tensions: role of cumulus cells.

The present study was conducted to evaluate the effect of cumulus cells on the in vitro maturation (IVM) and glutathione (GSH) synthesis of porcine oocytes cultured in the presence or absence of cysteamine under different oxygen tensions, and on their subsequent male pronucleus formation after in vitro fertilization (IVF). Cumulus-oocyte complexes (COCs) and cumulus-denuded oocytes (DOs) were cultured for 45 h in modified TCM-199 supplemented with or without 150 microM cysteamine under a humidified atmosphere of 5% CO2 in air (20% O2) or 5% CO2, 5% O2 and 90% N2. When cultured in medium supplemented with cysteamine under 20% O2 tension, the rates of COC maturation to the metaphase II (MII) stage were significantly higher than those of DOs (P<0.05). Regardless of the addition of cysteamine and oxygen tension, the rates of male pronucleus formation in COCs after IVM and IVF were significantly higher than in DOs (P<0.05). The GSH content of oocytes was significantly increased by the addition of cysteamine to the maturation medium (P<0.05), with significantly higher GSH content in COCs than in DOs (P<0.05). However, the GSH content of COCs and DOs was not significantly different when cultured in medium without cysteamine. These results indicate that cumulus cells play an important role in nuclear maturation to MII, GSH synthesis in porcine oocytes cultured in the presence of cysteamine, and subsequent male pronucleus formation after IVF.

Physical, chemical, and microbiological characteristics of microbial mats (kopara) in the South Pacific atolls of French Polynesia.

Microbial mats that develop in shallow brackish and hyposaline ponds in the rims of two French polynesian atolls (Rangiroa and Tetiaroa) were intensively investigated during the past three years. Comparative assessment of these mats (called kopara in polynesian language) showed remarkable similarities in their composition and structure. Due to the lack of iron, the color of the cyanobacterial pigments produced remained visible through the entire depth of the mats (20-40 cm depth), with alternate green, purple, and pink layers. Profiles of oxygen, sulfide, pH, and redox showed the anoxia of all mats from a depth of 2-3 mm. Analyses of bacterial pigments and bacterial lipids showed that all mats consisted of stratified layers of cyanobacteria (mainly Phormidium, Schizothrix, Scytonema) and purple and green phototrophic bacteria. The purple and green phototrophic bacteria cohabit with sulfate reducers (Desulfovibrio and Desulfobacter) and other heterotrophic bacteria. The microscopic bacterial determination emphasized the influence of salinity on the bacterial diversity, with higher diversity at low salinity, mainly for purple nonsulfur bacteria. Analyses of organic material and of exopolymers were also undertaken. Difference and similarities between mats from geomorphological, microbiological, and chemical points of view are discussed to provide multicriteria of classification of mats.

Microbial communities and exopolysaccharides from Polynesian mats.

Microbial mats present in two shallow atolls of French Polynesia were characterized by high amounts of exopolysaccharides associated with cyanobacteria as the predominating species. Cyanobacteria were found in the first centimeters of the gelatinous mats, whereas deeper layers showing the occurrence of the sulfate reducers Desulfovibrio and Desulfobacter species as determined by the presence of specific biomarkers. Exopolysaccharides were extracted from these mats and partially characterized. All fractions contained both neutral sugars and uronic acids with a predominance of the former. The large diversity in monosaccharides can be interpreted as the result of exopolymer biosynthesis by either different or unidentified cyanobacterial species.

[Role of TNF-alpha and ICAM-1 in pathogenesis of cerebral malaria].

OBJECTIVE: To investigate the role of TNF-alpha and ICAM-1 in the pathogenesis of cerebral malaria. METHODS: Immunohistochemical method and ELISA were employed to examine the expression of ICAM-1 on the brain microvessel endothelium and to detect the production of serum TNF-alpha in P. berghei ANKA strain infected-CBA/J mice. RESULTS: Serum TNF-alpha levels of mice were apparently higher and the ICAM-1 expression was more evident in P. berghei ANKA infected-CBA/J mice than in control groups. rTNF-alpha i.p. injection could enhance the development of CM and the expression of ICAM-1 on brain endothelial cells(EC). CONCLUSION: Excessive production of TNF-alpha may mediate the expression of ICAM-1 on brain EC and hence cause the development of CM.