Primary sequence and functional expression of a novel ouabain-resistant Na,K-ATPase. The beta subunit modulates potassium activation of the Na,K-pump.

In order to understand the molecular mechanism of ouabain resistance in the toad Bufo marinus, Na,K-ATPase alpha and beta subunits have been cloned and their functional properties tested in the Xenopus laevis oocyte expression system. According to sequence comparison between species, alpha 1, beta 1, and beta 3 isoforms were identified in a clonal toad urinary bladder cell line (TBM 18-23). The sequence of the alpha 1 isoform is characterized by two positively charged amino acids (Arg, Lys) at the N-terminal border of the H1-H2 extracellular loop and no charged amino acid at the C terminus, a pattern distinct from the ouabain-resistant rat alpha 1 isoform. The coexpression of alpha 1 beta 1 or alpha 1 beta 3 TBM subunits in the Xenopus oocyte resulted in the expression of identical maximum Na,K-pump currents with identical inhibition constant for ouabain (Ki) (alpha 1 beta 1: 53 +/- 3 microM; n = 7 vs. alpha 1 beta 3: 57 +/- 3.0 microM; n = 8) but distinct potassium half activation constant (K1/2) (alpha 1 beta 1: 0.87 +/- 0.08 mM, n = 16; alpha 1 beta 3: 1.29 +/- 0.07 mM, n = 17; p less than 0.005). We conclude that (i) the TBM alpha 1 isoform is necessary and sufficient to confer the ouabain resistant phenotype; (ii) the beta 3 or beta 1 subunit can associate with the alpha 1 equally well without affecting the ouabain-resistant phenotype; (iii) some specific sequence of the beta subunit can modulate the activation of the Na,K-pump by extracellular potassium ions.     

Interactions of interferon with other immunomodulators in the regulation of human natural killer cell activity]

The cytotoxic activity of natural killer (NK) cells isolated from peripheral blood of 20 healthy donors and 34 patients with multiple sclerosis (MS) against labelled with H3-uridine target cells K-562 before and after their 1 hr treatment with reaferon (RF), T-activin (TA), myelopid (MP), opioid preparation dalargin (DL) as well as with combinations of TA, MP and DL with RF was studied in 14 hrs cytotoxic test. It has been shown that combination of RF with TA, MP and DL changed the regulatory action of these peptides on NK cell activity in healthy donors in vitro. The same combination of the preparations in patients with MS caused another changes in regulation of NK activity by them because NK cells in MS patients had had initially changed sensitivity to action of these regulatory polypeptides.     

pH track of expanding bacterial populations

A method of pH distribution measurements in agar nutrient media containing expanding bacterial populations is described. It is based on measuring pH microsamples taken at different points of the media. The sample volume was 10 microliters. A pH sensitive field effect transistor was used as a measuring electrode. Acidification was found to occur in glucose media, while alkalization occurred in the media containing peptone.     

Effects of different doses of perfluorocarbon emulsion on hemodynamics and contractility of ischemic heart]

The effect of different doses of perfluorocarbon emulsion (5, 10, and 15 ml/kg) on the hemodynamics and contractility of heart was studied on anesthetized dogs. The emulsion was introduced intravenously by the 60th minute of acute myocardium ischemia caused by partial coronary occlusion. When pO2 = 120 mm Hg, the emulsion was efficient only at doses of 10 and 15 ml/kg (an increase in cardiac ejection, in the rate of contraction and relaxation of the myocardium, reduction of vascular resistance). However, the efficiency of the emulsion at a dose of 15 ml/kg was lower, possibly, due to hypervolemia and cardiodepressive effect of introduction of excess quantity of the surface-active substance proxanol, a component of the emulsion.     

Characterization of cloned alpha-satellite sequence from the extrachromosomal DNA of HeLa cell culture]

We have obtained the alphoid DNA clones, pK1 and pK2, from the extrachromosomal DNA of Hela cells treated by cycloheximide (30 micrograms/ml). Nucleotide sequences of the clones were aligned. The sides of the pK1 and pK2 are 390 and 184 bp, respectively. The marked RELP for the clones was not observed. The results of in situ hybridization have shown an approximately equal distribution of Ag-grains over major part of human chromosomes, with a slight preference for chromosomes 1, 5 and 19 (the 1-st group of alpha-satellite DNA). Therefore, the obtained alphoid sequences seem to be rather conservative and non-chromosome-specific. We suppose that increase of the alphoid DNA content in the fraction of the extrachromosomal DNA under the cycloheximide treatment is a result of the sporadic statistical processes rather then consequence of the specific excision.     

Characterization of Propionibacterium plasmids

Plasmid DNAs from 15 Propionibacterium strains were characterized by using restriction endonuclease analyses, DNA-DNA hybridizations, and curing experiments. Restriction endonuclease analysis identified seven distinct plasmids (pRGO1 through pRGO7). Detailed restriction maps were constructed for four of these plasmids. DNA-DNA hybridization analysis revealed that plasmids pRGO1 and pRGO2 had extensive sequence homology and that both were homologous to pRGO7 and to similar sequences of pRGO5. Plasmids pRGO4 and pRGO6 did not have any significant sequence homology with any of the other plasmids. Plasmid pRGO3 had partial sequence homology only with pRGO7. Curing of plasmids pRGO1, pRGO2, and pRGO5 was achieved by treatment with acriflavin, but we failed to identify any plasmid-encoded bacteriocin production, carbohydrate fermentation, or antibiotic resistance. However, physical evidence was obtained that tentatively linked the clumping phenotype of Propionibacterium jensenii P38 with plasmid pRGO5.     

Characterisation of Pseudomonas rhamnolipids

The Gram negative organism, Pseudomonas aeruginosa, is often found in the lungs of patients with cystic fibrosis and other forms of severe bronchiectasis, where it secretes a number of extracellular toxins including the mono- and dirhamnolipids. The principal monorhamnolipid from P. aeruginosa has previously been identified as rhamnosyl-3-hydroxydecanoyl-3-hydroxydecanoate (Rh-C10.C10). A number of related mono- and dirhamnolipids have been purified from cultures of a clinical isolate of P. aeruginosa and identified by fast atom bombardment and electron impact mass spectrometry: these contain the 3-hydroxyoctanoyl-3-hydroxydecanoate (C8.C10) and 3-hydroxydecanoyl-3-hydroxydodecanoate (C10.C12) homologues. Structural isomers were also present where the order of the lipid linkage was transposed (Rh-C10.C8 and Rh-C12.C10). Unsaturated mono- and dirhamnolipids containing the 3-hydroxydecanoyl-3-hydroxydodec-5-enoate (C10.C12:1) lipid were also present.     

Recolonisation of four small streams in central Scotland following drought conditions in 1984

Four streams in the Loch Ard Forest in central Scotland dried out almost completely during a drought in the summer of 1984. The recovery of the invertebrate populations in the streams was studied from September 1984 until March 1985 when most of the insect larvae and nymphs were almost full-grown.The appearance of very small larvae belonging to several insect orders within a month of the streams' filling up suggests that they had survived the drought as eggs, or eggs had been laid by adults soon after the drought ended.Statistical analysis showed that with the exception of 3 taxa there was no significant difference between the numbers of animals in November 1984 samples and in samples collected in March 1985.Comparison of samples from March 1984 and March 1985 showed significant difference in population size for a few species; with 2 exceptions the 1984 samples (ie before drought) were larger. In the long term the overall effect of the drought on the invertebrate communities seems to have been limited.