Whole body of White Leghorn chiks of two different age groups was irradiated with X-raya at a 500r (single) dose.Different blood parameters such as plasma protein, glucose, cholesterol, haemoglobin, total red blod cells, and white blood cell counts, erythrocyte sedimentation rate, pecked cell volume, mean corpuscular haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin concentration, and differential leucosytes count were considered.In most cases X-rays exerted depressive effect causinf inhibition of various synthetic activities but in some cases there was a differential sensitivity towards in the two different age groups of birds.
Ribosomes, which are ?the heart of the protein biosynthesis' have been the focus of structural studies for more than 50 years. The reconstitution of some of the morphological features of the ribosome was performed many years ago. In the past few years, high-resolution structures provided molecular details of different intermediates in ribosome-mediated translation. Together, these studies have revolutionized our understanding of the mechanism of protein biosynthesis. This success depended strictly on the advances in biochemical, biophysical and genetic studies and macromolecular crystallography that have been made during last decades.
The modulatory effect of AET (S-2-aminoethylisothio-uronium bromide hydrobromide) and WR-2721 (S-2-/3-ami- nopropylamino/ethylphosphorothioic acid) on the clastogenic activity of X-rays was assessed by the in vivo mouse micronucleus test. The frequency of micronucleated polychromatic erythrocytes (MNPCEs) in the peripheral blood of adult male Swiss mice exposed to 5 Gy X-rays alone, or treated with AET or WR-2721, at a dose of 200 mg/kg body weight, 15 or 30 minutes prior to X-irradiation, respectively, was determined during a fifteen-day period. The number of micronuclei increased on day 1 post-irradiation in X-irradiated mice and declined thereafter with the frequency of MNPCEs remaining lower in the thiol pre-treated mice. A more effective protection against the clastogenic activity of X-rays in the erythropoietic system was observed after WR-2721 administration than AET application.
The grequency of micronucleated polychromatic erythrocytes (MNPCEs) in the mouse peripheral bloos was assessed after WR-2721 (S-2-/3-aminopropylamino/ethylphosphorothioic acid) application and X-irradiation.The genotoxic was demonstratred for X-rays and WR-2721, as well as a protective effect of the thiol drug against X-ray-induced genotoxicity in the erythropoietic system.After X-irradiation of the mice, the number of MNPCEs was distincly increased.WR-2721 administration prior to X-irradiation resulted in a reduction of the X-ray- induced rise in the frequency of micronuclei.WR-2721 given alone, without subsequent X-irradiation, increased the number of MNPCES.The genotoxic and radioprotective effect of WR-2721 depended on the dose applied and the time interval between the thiol agent treatment and exposure of the mice to X-rays.
The crystal structure of the complex of the large ribosomal subunit of the pathogen model Deinococcus radiodurans with the macrolide antibiotic methymycin, bearing a 12 membered macrolactone ring macrolide that contains a single amino sugar, shows that methymycin binds to the peptidyl transferase center (PTC) rather than to the high affinity macrolide binding pocket at the upper end of the ribosomal exit tunnel. This unexpected binding mode result in fairly efficient blockage of the 3'end of the A-site tRNA location, thus indicating the superiority of spatial-functional considerations over the formation of the typical high affinity macrolide interactions that due to the small size of methymycin could have led to incomplete blockage of the exit tunnel. Its binding involves rearrangements of several PTC nucleotides, some of which shown previously to be flexible. Comparisons between the binding modes of methymycin and other antibiotics are presented and discussed.
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