Impact of pre-culture on short- and long-term in vitro recovery of the biosynthetic potential and enzymatic and non-enzymatic antioxidant defense of Hypericum rumeliacum Boiss. after cryostorage

Due to its high hypericin and pseudohypericin in vitro biosynthetic capacity, the Balkan endemic Hypericum rumeliacum was selected as a prospective candidate for long-term preservation of valuable medicinal plant germplasm. Initial cryopreservation experiments were previously conducted based on the successful protocol established and reported for the widely studied H. perforatum. This is the first report on the impact of pre-culture duration on the short- and long-term in vitro recovery of the biosynthetic potential and antioxidant defense system of H. rumeliacum cryopreserved by vitrification. Cryopreservation did not impair the phenolics and flavonoids production of the regenerated plants. Moreover, hypericin and pseudohypericin levels even increased substantially in one of the regenerated lines, reaching yields from 0.107 and 0.752?mg?g^?1?DW in the control up to 0.277 and 1.112?mg?g^?1?DW for hypericin and pseudohypericin, respectively. However, the physical injury stress of the pre-culture treatment manipulations affected the physiological status of regenerants in a time dependent manner. Within 6?months after thawing, regenerants with the highest oxidative stress after pre-culture, were characterized with an augmentation of antioxidant metabolites such as phenolics, flavonoids, glutathione and ascorbic acid as well as increased antioxidant enzymatic activities in comparison with both the non-frozen control and the regenerants with the lowest pre-culture oxidative stress. Then, after 18?months of recovery, the same first H. rumeliacum group displayed a marked drop of enzymatic antioxidant activity as compared with the other groups of plants. Further research is needed to target oxidative stress alleviation to optimize H. rumeliacum cryopreservation protocol.     

A unique DNAse associated with mitogen-induced transformation of rat lymphocytes

A unique DNAse was found, following electrophoretic separation, in rat lymphocytes stimulated with either ConA or pokeweed mitogens. This DNAse was absent or minimal in non-stimulated cells. The enzyme was active on native DNA at neutral pH and was activated by EDTA. A possible biological role is discussed as related to DNA replication.     

Mechanism of action of N-acetylglucosaminyl-N-acetylmuramylalanyl-D-isoglutamine on the nonspecific anti-infection resistance of mice

The stimulating influence of glucose-containing muramyldipeptide (GMDP) on the nonspecific resistance of mice was shown to depend on the features of the pathogenesis of the infection. Thus, the intraperitoneal injection of GMDP increased the survival rate of mice infected with Escherichia coli, but had no stimulating effect on the resistance of the animals to Salmonella typhimurium natural infection in whose pathogenesis macrophages played an essential role. Experiments demonstrated that GMDP was capable of enhancing the ingestive function of macrophages, but did not increase their bactericidal activity with respect to this infection.     

Taxonomic identification of gram-negative nonfermenting microorganisms in environmental research

The scheme for the identification of Gram-negative nonfermenting microorganisms is proposed. The scheme comprises the most important key signs, such as the cytochrome oxidase reaction determined by the method of Gaby and Hadley, the oxidation/fermentation test, maltose oxidation and motility, as well as additional key signs, among them gelatinase activity, the oxidation of 10% lactose, nitratase activity with the liberation of free nitrogen, the utilization of the sources of carbon and energy (glucose and sodium acetate) in limited media containing ammonium salts and nitrates as the sources of nitrogen. Additional tests for the identification of nonfermenting microorganisms similar in their main key signs are also recommended.