Properties of Multidrug-Resistant Mutants Derived from Heterologous Expression Chassis Strain Streptomyces albidoflavus J1074.

Streptomyces albidoflavus J1074 is a popular platform to discover novel natural products via the expression of heterologous biosynthetic gene clusters (BGCs). There is keen interest in improving the ability of this platform to overexpress BGCs and, consequently, enable the purification of specialized metabolites. Mutations within gene rpoB for the ß-subunit of RNA polymerase are known to increase rifampicin resistance and augment the metabolic capabilities of streptomycetes. Yet, the effects of rpoB mutations on J1074 remained unstudied, and we decided to address this issue. A target collection of strains that we studied carried spontaneous rpoB mutations introduced in the background of the other drug resistance mutations. The antibiotic resistance spectra, growth, and specialized metabolism of the resulting mutants were interrogated using a set of microbiological and analytical approaches. We isolated 14 different rpoB mutants showing various degrees of rifampicin resistance; one of them (S433W) was isolated for the first time in actinomycetes. The rpoB mutations had a major effect on antibiotic production by J1074, as evident from bioassays and LC-MS data. Our data support the idea that rpoB mutations are useful tools to enhance the ability of J1074 to produce specialized metabolites.

STRUCTURAL PECULIARITIES OF RATS' TESTES DEVELOPMENT AFTER INTRODUCTION OF FEMALE HORMONES DURING PREGNANCY.

OBJECTIVE: The aim: To de!ne regularities of testicular construction of the rats' offspring at 1-90 days of postnatal life after the introduction of female sex hormones to pregnant rats during the second and third periods of pregnancy. PATIENTS AND METHODS: Materials and methods: The study was conducted on the testes of white laboratory rats' offspring during three months of life. Pregnant rats were exposed to intravaginal injection of Utrozhestan during the second and third periods of pregnancy. histological methods were used. Analysis of the obtained results was conducted by means of statistical methods with the use of computer license program «Statistica for Windows 13¼ (StatSoft Inc., # JPZ804I382130ARCN10-J). RESULTS: Results: Administration of female sex hormones to pregnant female rats leads to a reducing of the relative area, occupied by the convoluted seminiferous tubules with lumen, and increasing in relative area, occupied by extracellular matrix, starting from the 30th and up to the 90th observation day in the offsprings' testes. During the third month after birth, in experimental group a decreasing of the testicles' spermatids differentiation degree is determined. CONCLUSION: Conclusions: During the study, the following results and conclusions were obtained: decreasing of the relative area, occupied by convoluted seminiferous tubules, increasing in relative area, occupied by extracellular matrix, also decreasing Leydig cells relative amount and a delaying of spermatid differentiation process after exposing to female sex hormones during pregnancy, especially during third period, can lead to disruption of spermatogenesis and spermiogenesis in the future.

PECULIARITIES OF ELECTRON MICROSCOPIC HIPPOCAMPAL FORMATION DEVELOPMENT CHARACTERISTICS IN POSTERITY OF RATS AFTER PGE2 INJECTION FOR LABOR INDUCTION.

OBJECTIVE: The aim: To determine the peculiarities of electron microscopic hippocampal formation development characteristics in postetry of rats during two first weeks of postnatal life after intravaginal injection of prostaglandin E2 for labor induction. PATIENTS AND METHODS: Materials and methods: The ultrastructural changes of hippocampal formation in posterity of white syngenic rats at the 1st, 7th and 14th days of postnatal life were examined. In this study we used electron-microscopic method. Brain tissue from experimental animals underwent standart stages necessary for electron microscopy and poured into pure Epon. Epon polymerization was carried out in two stages at 36 ° C (12 h) and 56 ° C (24 h). Ultrathin (50-60 nm) sections were obtained on a PowerTome RMC Boeckeler ultratome and then contrasted according to the E. Reynolds method. Ultrathin sections were studied in a PEM-100 electron microscope with an accelerating voltage 60 kV. RESULTS: Results: Based on the obtained data in the study of the hippocampal formation in postery of rats after induction of labor, analysis of the literature devoted to the electron microscopic study of the brain after ischemic injuries, it can be concluded that on the background of stimulation of labor by PgE2, changes corresponding to ischemic damage take place in the rat brain. CONCLUSION: Conclusions: In posterity of rats after receiving PgE2 for labour induction it was revealed microcirculatory changes; edema of the presynaptic endings, synaptic vesicles aggregation in the center of the presynaptic processes, swelling and destruction of mitochondria; oligodendroglia changes; ultrastructural changes in neurons like edema and vacuolization of mitochondria.

MORPHOLOGICAL FEATURES OF RATS' HEARTS AFTER INTRAFETAL INJECTION OF DEXAMETHASONE.

OBJECTIVE: The aim: Is to study the morphological features of rats' hearts after prenatal administration of glucocorticoids. PATIENTS AND METHODS: Materials and methods: In this study we used histological, immunohistochemical, electron-microscopic and statistical research methods. RESULTS: Results: It is found that at 30th day after birth in rats after intrafetal introduction of dexamethasone in myocardium a relative area occupied by arterial vessels is significantly smaller in comparison with control. Absolute and relative number of Ki-67+-cardiomyocytes in the myocardium of experimental rats is reduced throughout the second week after birth and is significantly less compared to the control group. In the nuclei of cardiomyocytes of experimental rats is rendered the greater amount of heterochromatin in comparison with cardiomyocytes of the control group where euchromatin prevails. CONCLUSION: Conclusions: After intrafetal injection of dexametazone changes in dynamics and significantly smaller index of relative area occupied by arterial vessels in ventricular myocardium at the 30th day after birth are observed; the absolute and relative number of Ki-67+ -cardiomyocytes in myocardium decreases during the second week after birth and is significantly lower compared to the control group; in the nuclei of cardiomyocytes of experimental rats a greater amount of heterochromatin is visualized, and in cardiomyocytes of the control group - euchromatin.