Cloning and expression of the determinant for resistance to a new class of tetracycline in Escherichia coli strains

Tetracycline-resistance determinant of the plasmid pBS221 isolated from a Pseudomonas aeruginosa strain has been cloned on pUC19 vector plasmid. The determinant is expressed under aerobic and anaerobic conditions coding for two proteins: a 36 Kd protein conferring antibiotic resistance and 27 Kd repressor protein. The determinant is not homologous to tet-determinants of the known classes as shown by blot hybridization experiments. The determinant represents a new class--G. Determinants of the new class are widespread among Serratia marcescens strains.     

Modification of blood plasma lipoproteins by a lipid peroxidation product--hexanal

HDL treated with hexanal is shown to lose the ability for the cholesterol absorption. In the case of LDL at low concentration of the modifying agent the rate of their elimination from the blood stream of the rabbit decrease, but their uptake by the rat macrophages do not differ from the uptake of native lipoproteins. At high concentration of hexanal the rate of the elimination of LDL from the blood stream increases considerably and is close to that of acetylated LDL. Thus, the modification of plasma lipoproteins with monoaldehydes occurring in the aorta wall leads to the loss of the functional properties of the lipoprotein particles.     

PAN-1, a P-granule component important for C. elegans fertility, has dual roles in the germline and soma

In Caenorhabditis elegans, P granules are germline-specific, RNA-containing granules that segregate into the germline precursor cell during early embryogenesis. In this short report, PAN-1, which previously has been found by others in screens for genes causing larval molting defects, is identified here as a novel P-granule component and a binding partner of GLH-1 (Germline RNA Helicase-1), a constitutive, germline-specific, P-granule protein. The PAN-1 predicted protein contains multiple leucine-rich repeats (LRRs) and regions with similarities to F-box proteins. Antibodies raised against PAN-1 reveal it is present both in the soma and the germline. In the germline, PAN-1 uniquely localizes to P granules from the first larval stage onward and is unusual for a P-granule component in lacking recognizable RNA binding motifs. Homozygous pan-1(gk142) deletion worms arrest as larvae that are unable to molt and this phenotype is also seen with pan-1(RNAi) into wild type worms. pan-1(RNAi) into the somatic RNAi-defective strain rrf-1(pk1417) bypasses the larval arrest and allows an assessment of PAN-1 function in the germline. We find pan-1(RNAi) is variably effective in knocking down PAN-1 protein and results in adult progeny that display multiple germline defects. These phenocopies range from under-proliferation of the germline, as also seen with loss of GLH-1, to the induction of endomitotic replication in oocytes, both defects that result in sterility, to fertile animals with significantly reduced progeny numbers. Thus, while loss of PAN-1 in the soma inhibits molting, this report demonstrates that PAN-1 is also a P-granule component that is essential for fertility.     

Distribution of strains of spore-forming bacteria of the genus <Emphasis Type="Italic">Bacillus</Emphasis> in the bottom sediments of Lake Khubsugul in Northern Mongolia as an indication of paleoclimate

Data on the distribution and abundance of bacteria of the genus Bacillus in the bottom sediments of Lake Khubsugul have shown the predominance of strains that preferred low temperatures. This indicates fairly cold temperature conditions on the territory of the Khubsugul drainage area. On the whole, the dynamics of interchange of minimums and maximums of abundance of bacteria of the genus Bacillus is similar to the global climate fluctuations. Study of the enzymatic activity of pure cultures revealed that most strains studied possessed proteolytic activity; consequently, the dynamics of bacteria development is correlated with the supply of organic nitrogen-containing compositions.     

T-cadherin suppresses the cell proliferation of mouse melanoma B16F10 and tumor angiogenesis in the model of the chorioallantoic membrane

The influence of T-cadherin on the pigmentation and proliferation of mouse melanoma B16F10 cells in vitro and on the growth and neovascularization of tumor cell masses formed by the B16F10 cells in a model of the chorioallantoic membrane of a chicken embryo is studied. It is found that the proliferative activity of the cells decreases in the cell culture of mouse melanoma upon the overexpression of T-cadherin in comparison with the cells in the control. It is shown in experiments in vitro that the B16F10 cells with the overexpression of T-cadherin are rarely settling are to the chorioallantoic membrane than the control cells. In addition, it is found that the control cells of mouse melanoma form tumors with area more 0.1 mm² more often than the cells with the overexpression of T-cadherin and the amount of the vessels growing to tumor cell masses formed by the cells with the overexpression of T-cadherin is significantly lower than the same index for the cells in the control. Thus, the overexpression of T-cadherin in the B16F10 cells suppresses the proliferation of these cells in vitro and the growth of the tumor masses formed by melanoma cells on the chorioallantoic membrane and their neovascularization in vivo.     

Antiviral activity of lambda-, beta-, and gamma-interferons in the presence of theophylline: involvement of 2',5'-oligo(A) synthetase

Theophylline, an inhibitor of cAMP phosphodiesterase, induces in human ovary carcinoma cells (CaOv) a 2-2.5-fold elevation of intracellular cAMP. This rise in the cAMP level is followed by an increase of the activity of 2',5'-oligo(A) synthetase in CaOv cells -insignificant (1.5-fold) after 16 hr incubation, and substantial (3.7-fold) after 30 hr incubation, as well as the development of antiviral resistance. Once CaOv cells have been incubated with the mixtures containing theophylline (2 mM) and lambda-, beta-, and gamma-interferon preparations (0.5-13 IU/ml), the total antiviral effect of the mixtures exceeds that generated by interferon or theophylline separately; the action of the above agents being additive. These data agree with the previously obtained results and support the suggestion that cAMP phosphodiesterase inhibitors partially mimic the antiviral action of interferon.     

The Methemoglobin Blood Level and Stability of Circulating Erythrocytes of the Rockfish Scorpaena porcus to Osmotic Shock under Conditions of Experimental Hypoxia

Under experimental conditions the oxygen content in water was reduced to 1.3–1.4 mg l^–1 (15% of the saturation) and 2.6–2.7 mg(l^–1 (30% of the saturation). The rockfish (Scorpaena porcus L. ) were kept under these conditions for 90 min. Analysis of samples has shown a decrease of methemoglobin level by 58.2% (p < 0.001) and an increase of erythrocyte stability to the osmotic shock. The cell lysis occurred at lower concentrations of NaCl. It is concluded that the process of natural oxygenation is one of the causes of the rise of the oxidized pigment concentration in the fish blood. This is due to low efficiency of erythrocytic NADH-diaphorases and is compensated by an increase of activity of enzymes of the cell antioxidant protection system. The latter prevents from development of peroxidation processes and lysis of cells during their circulation despite a comparatively high level of methemoglobin in blood.     

Proteolytic cleavage of pertussis toxin S1 subunit is not essential for its activity in mammalian cells

Background  

Pertussis toxin (PT) is an exotoxin virulence factor produced by Bordetella pertussis, the causative agent of whooping cough. PT consists of an active subunit (S1) that ADP-ribosylates the alpha subunit of several mammalian G proteins, and a B oligomer (S2–S5) that binds glycoconjugate receptors on cells. PT appears to enter cells by endocytosis, and retrograde transport through the Golgi apparatus may be important for its cytotoxicity. A previous study demonstrated that proteolytic processing of S1 occurs after PT enters mammalian cells. We sought to determine whether this proteolytic processing of S1 is necessary for PT cytotoxicity.