Characterization of Missense Mutations in the SUP45 Gene of Saccharomyces cerevisiaeEncoding Translation Termination Factor eRF1*

Collection of missense mutations in the SUP45 gene of Saccharomyces cerevisiae encoding translation termination factor eRF1 has been obtained by different approaches. It has been shown that most of isolated mutations cause amino acid substitutions in the N-terminal part of eRF1 and do not decrease the eRF1 amount. Most of mutations studied do not abolish eRF1–eRF3 interaction. The role of the N-terminal part of eRF1 in stop codon recognition is discussed.     

Hydrogen peroxide stimulates exocytosis of von Willebrand factor in human umbilical vein endothelial cells

The aim of our research was to study the influence of hydrogen peroxide on the exocytosis of von Willebrand factor (vWF) in human umbilical vein endothelial cells (HUVEC). We have found that H₂O₂ at a non-toxic concentration (100 μM) increases the amount of vWF secreted by HUVEC by 43 ± 14% over control (p < 0.03) and elevates total exposition of vWF on cell surface by 89 ± 5% (p < 0.01). Analysis of immunofluorescent images of HUVEC with CellProfiler program revealed that the average number of antigen positive structures on the single cell surface increases from 11.4 ± 0.16 in control up to 17.5 ± 0.21 after incubation with H₂O₂ (p < 0.01). vWF is exposed on the cell surface as dots with the average sizes around 1–3 μm. H₂O₂ causes an increase in the number of these dots and the appearence of the strings of vWF which are absent in control HUVEC. It is suggested that H₂O₂ may serve as a messenger which stimulates vWF exocytosis.     

Novel non-Mendelian determinant involved in the control of translation accuracy in Saccharomyces cerevisiae.

Two cytoplasmically inherited determinants related by their manifestation to the control of translation accuracy were previously described in yeast. Cells carrying one of them, [PSI(+)], display a nonsense suppressor phenotype and contain a prion form of the Sup35 protein. Another element, [PIN(+)], determines the probability of de novo generation of [PSI(+)] and results from a prion form of several proteins, which can be functionally unrelated to Sup35p. Here we describe a novel nonchromosomal determinant related to the SUP35 gene. This determinant, designated [ISP(+)], was identified as an antisuppressor of certain sup35 mutations. We observed its loss upon growth on guanidine hydrochloride and subsequent spontaneous reappearance with high frequency. The reversible curability of [ISP(+)] resembles the behavior of yeast prions. However, in contrast to known prions, [ISP(+)] does not depend on the chaperone protein Hsp104. Though manifestation of both [ISP(+)] and [PSI(+)] is related to the SUP35 gene, the maintenance of [ISP(+)] does not depend on the prionogenic N-terminal domain of Sup35p and Sup35p is not aggregated in [ISP(+)] cells, thus ruling out the possibility that [ISP(+)] is a specific form of [PSI(+)]. We hypothesize that [ISP(+)] is a novel prion involved in the control of translation accuracy in yeast.     

A permeability transition in liposomes induced by the formation of Ca/palmitic acid complexes

Formation of palmitic acid/Ca²⁺ (PA/Ca²⁺) complexes was suggested to play a key role in the non-classical permeability transition in mitochondria (NCPT), which seems to be involved in the PA-induced apoptosis of cardiomyocytes. Our previous studies of complexation of free fatty acids (FFA) with Ca²⁺ showed that long-chain (C:16-C:22) saturated FFA had an affinity to Ca²⁺, which was much higher than that of other FFA and lipids. The formation of FFA/Ca²⁺ complexes in the black-lipid membrane (BLM) was demonstrated to induce a nonspecific ion permeability of the membrane. In the present work, we have found that binding of Ca²⁺ to PA incorporated into the membrane of sulforhodamine B (SRB)-loaded liposomes results in an instant release of a part of SRB, with the quantity of SRB released depending on the concentration of PA and Ca²⁺. The pH-optimum of this phenomenon, similar to that of PA/Ca²⁺ complexation, is in the alkaline range. The same picture of SRB release has been revealed for stearic, but not for linoleic acid. Along with Ca²⁺, some other bivalent cations (Ba²⁺, Sr²⁺, Mn²⁺, Ni²⁺, Co²⁺) also induce SRB release upon binding to PA-containing liposomes, while Mg²⁺ turns out to be relatively ineffective. As revealed by fluorescence correlation spectroscopy, the apparent size of liposomes does not alter after the addition of PA, Ca²⁺ or their combination. So it has been supposed that the cause of SRB release from liposomes is the formation of lipid pores. The effect of FFA/Ca²⁺-induced permeabilization of liposomal membranes has several analogies with NCPT, suggesting that both these phenomena are of similar nature.     

Effects of growth factors FGF4, TGFα, and TGFβ1 on development of parthenogenetic embryos of C57BL/6 mice

We studied the effects of three growth factors, fibroblast growth factor (FGF4), transforming growth factor (TGF), and transforming growth factor 1 (TGF1), on development of diploid parthenogenetic embryos of C57BL/6 mice, which are not capable of developing to somatic stages. Parthenogenetic embryos were treated with growth factors at optimal doses in vitro at the morula-blastocyst stages and transplanted in the uterus of pseudopregnant females. FGF4 and TGF improved the development of parthenogenetic embryos at the preimplantation stages and the number of blastocysts increased under the influence of TGF. All three growth factors improved the implantation of embryos in the uterus. When FGF4 or TGF1 2.4 were added to the nutrient medium, 2.4 or 1.6%, respectively, of parthenogenetic embryos reached the somatic stages in utero. No somitic embryos were observed in the control. The treatment of parthenogenetic embryos with two growth factors, FGF4 and TGF1 , simultaneously increased the amount of somatic embryos to 7.5%, while combination of three growth factors in creased the amount of such embryos to 16.7%. In the latter case, some parthenogenetic embryos reached the stage of 25–27 pairs of somites and were 2.0–2.5 mm long. The data we obtained suggest that, when combined, the growth factors FGF4, TGF, and TGF1 possessed a synergistic effect leading to a significant improvement of the development of parthenogenetic C57BL/6 embryos.__________Translated from Ontogenez, Vol. 36, No. 2, 2005, pp. 145–150.Original Russian Text Copyright © 2005 by Penkov, Platonov, Dimitrov, Mironova, Konyukhov.     

Analysis of the effect of the loop-tail gene in mouse embryos]

Mitotic index and parameters of the cell cycle were determined in the brain and spinal cord of 10 days old Lp/Lp and +/+ mouse embryos. The mitotic index and duration of the cell cycle periods proved to be the same for embryos of both the genotypes. The generation time of the brain and spinal cord cells both in the mutant and normal embryos is 9 hrs, durations of S- and G2-periods 6 and 1, resp., and the total duration of G1- and M-periods 2. The gene Lp does not interact with the gene Sp in double heterozygotes. The gene Lp does not manifest itself in the cells of differentiating central nervous system and the failure of the neural tube closure is not due to the changes in the proliferative activity of its cells and is a secondary gene effect.     

Na+,K+-ATPase activity and potassium, sodium and calcium levels in the rat myocardium and brain during pain-induced emotional stress

An emotional-algesic stress in the period of its development and after-effect causes a different-directed influence on the state of the ionic transport in the heart and brain of rats. The Na+, K+-ATPase activity in the left ventricle of the heart decreases with a simultaneous increase in the sodium content and decrease in the calcium and potassium content. The Na+, K+-ATPase activation is observed in the cortex of cerebral hemispheres with a simultaneous increase in the content of mentioned ions.     

Efficient use of gentamycin in treating suppurative puerperal mastitis]

A total of 80 patients with postnatal purulent mastitis were treated with gentamicins. The main causative agent was Staph. aureus resistant to the traditionally used antibiotic and sensitive to gentamicin, fusidin, rifampicin and semisynthetic penicillinase-stable penicillins. Gramnegative bacteria contaminated the purulent foci after opening. Gentamicin was highly effective in treatment of postnatal purulent mastitis in cases with mixed Staphylococcus-Proteus infection.     

Characteristics of hospital strains of Staphylococcus]

Some properties of hospital staphylococcal strains isolated from the patients with purulent postnatal mastitis were studied. It was found that all the strains of the phage type 80.81 widely distributed in the obstetric hospitals were polylysogenic and polyresistant to antibiotics. The resistance markers in most of the isolates were located on the plasmids. Elimination of the plasmids carrying the antibiotics resistance markers resulted in a simultaneous change in the strain lysogenic spectrum while the phage type and fermentative properties, such as production of plasmocoagulase, DNAase and lecithinase did not change. The capacity for hemotoxin production was lost simultaneously with antibiotic resistance in 1 out of 17 cultures tested.