Morphological variability in selected heterocystous cyanobacterial strains as a response to varied temperature, light intensity and medium composition.

The effect of temperature, light and nutrient composition on morphological traits was determined in seven nostocacean cyanobacteria (Anabaena planctonica, A. sphaerica var. conoidea, A. spiroides, Aphanizomenon gracile, Nostoc sp., Scytonema sp., and Tolypothrix sp.). Their morphological variability was high but only some of the features showed changes reflecting varied growth conditions. The frequency of heterocyst occurrence decreased with increasing nitrogen concentration. Within the range studied, the effect of temperature on heterocyst frequency of Tolypothrix sp. and planktonic Anabaena strains could be fitted by a normal curve with a clear optimum while linear correlation was found in Aphanizomenon gracile. T-and S-type branching was observed in both Scytonema sp. and Tolypothrix sp. strains. T-type branching was found to be markedly dependent on nitrogen concentration. The abundance of necridic cells of Tolypothrix sp. increased linearly with temperature and light intensity. Regularity of trichome coiling of A. spiroides depended on culture medium, suggesting that nutrient composition may be the main controlling factor. In contrast, the effect of the experimental conditions on the dimensions of vegetative cells and heterocysts was weak. Their variability was markedly higher within each experimental treatment than between treatments.

[Prolonged culture of human embryos: comparison of coculture on human tubal epithelium and culture in synthetic media]. / Prodlouzená kultivace lidských embryí: srovnání kokultivace na lidských tubárních epiteliích a kultivace v syntetickém médiu.

UNLABELLED: The aim of this work was to evaluate prolongation of cultivation time of human embryos. The prolongation above the standard limit was implemented (1) by coculture of embryos on a monolayer of human epithelial cells and (2) by using a synthetic medium. MATERIAL AND METHODS: Ovarian stimulation, oocyte recovery, insemination and cultivation up to the pronuclear stage were done in our centre in the usual way. Group I: 104 women, prolonged culture by the coculture method. The zygotes were placed on the monolayer and cultivated for an other 24 or 48 hours. Group II: 249 women, prolonged culture in a synthetic medium. The zygotes were cultivated up to the 2- to 4-cell stage in standard IVF medium, and then put into M3 medium for the next 24 or 48 hours. A transfer of a maximum of 4 embryos was done. RESULTS: In group I in 104 women from 341 zygotes 181 embryos (53.1%) reached the eight- and more than eight-cell stage, and 76 transfers were done. 15 pregnancies were achieved (19.4% pregnancy rate). In group II in 249 patients from 672 embryos 49.7% of them reached 8- and more than 8-cell stage. 51 pregnancies were achieved (22.6 pregnancy rate). In the control group of 250 IVF after 48 hours cultivation 165 transfers (66.0%) were done, and 16.4% pregnancies were achieved, i.e. 6.2% less compared to synthetic medium and 3.3% less than in cocultivation. CONCLUSION: There is evidence of better IVF/ET results in case of prolonged culture time. The experience in our centre has shown the need of reevaluation of the coculture method. The exacting character of its preparation and manipulation will have to be replaced by synthetic media in spite of their high price.

Cultured epidermal allografts for the treatment of deep dermal burns.

The paper summarizes the experience with the application of cultured epidermal allografts in the treatment of deep dermal burns. In a series of patients, including 10 adults and 32 children this method allowed to attain an epithelialization in 90% of deep dermal burns. The advantages of this therapeutic method consist particularly in the early epithelialization of the burnt area and the maintenance of all vital layers of the corium. The risk of a transmission of infection by the transplantation of allografts of live human cells can be minimalized by keeping all directions prescribed for the examination of donors. The possibility of cryopreservation and the easy transport of cultured epidermal allografts renders them available for the use as a new therapeutic method in the treatment of deep dermal burns.