The effect of sodium on depolarization-induced calcium uptake and acetylcholine release by synaptosomes

The influence of external sodium concentration on potassium (depolarizing agent)-stimulated calcium uptake and Ca⁺-dependent acetylcholine release by rat cerebral cortex synaptosomes has been studied. It was found that increased sodium concentration decreases both the Ca²⁺ uptake and the acetylcholine release, whereas a low external sodium concentration is stimulatory.     

Impact of fishery management on Cladoceran populations

Zooplankton of the fish pond reveals a two-year periodicity, which is induced by the two-year cycle of fishery management. In the first year of each cycle, the biomass of large cladocerans prevailed — mainly adult specimens of the species Daphnia pulicaria Forbes, which were absent in the second year. The species Daphnia galeata Sars was present in both years, however, it is more numerous in the second year. The fraction of small zooplankton (rotifers, nauplii, Bosmina, newborn Daphnia) was abundant in the second years, but scarce in the first years, respectively.     

Expression of constitutive and tissue-specific acyl carrier protein isoforms in Arabidopsis

We have characterized the occurrence and expression of multiple acyl carrier protein (ACP) isoforms in Arabidopsis thaliana (L.) Heynh ecotype Columbia. Immunoblot analysis of ACPs from Arabidopsis tissues separated by native polyacrylamide gel electrophoresis and 1 molar urea polyacrylamide gel electrophoresis revealed a complex pattern of multiple ACP isoforms. All tissues examined (leaves, roots, and seeds) expressed at least three forms of ACP. The immunoblot identifications of ACP bands were confirmed by acylation of ACP extracts with Escherichia coli acyl-ACP synthetase. A full-length cDNA clone has been isolated that has 70% identity with a previously characterized Arabidopsis genomic ACP clone (ACP-1) (MA Post-Beittenmiller, A Hloušek-Radojčić, JB Ohlrogge [1989] Nucleic Acids Res 17: 1777). Based on RNA blot analysis, the cDNA clone represents an ACP that is expressed in leaves, seeds, and roots. In order to identify the protein products of each known ACP gene, their mature coding sequences have been expressed in E. coli. Using polymerase chain reactions, exons II and III of the genomic ACP-1 clone and the mature coding sequences of the ACP-2 cDNA clone were subcloned into E. coli expression vectors. Site-directed mutagenesis was used to convert the amino acid sequence of the ACP-2 cDNA clone to that of the A2 clone of Lamppa and Jacks ([1991] Plant Mol Biol 16: 469-474), ACP-3. The three E. coli-expressed proteins have different mobilities on polyacrylamide gel electrophoresis gels and each comigrates with a different Arabidopsis ACP isoform expressed in leaves, seeds, and roots. Thus, all of the three cloned ACPs appear to be constitutively expressed Arabidopsis ACPs. In addition to these three ACP isoforms, protein blots indicate that seed, leaf, and root each express one or more tissue-specific isoforms.     

Selenium status of patients with Balkan endemic nephropathy

The selenium (Se) contents in common cereals in endemic and nonendemic areas in Serbia are very low. Plasma Se levels of both patients and healthy subjects, were also low, reflecting low Se intakes. Patients with Balkan endemic nephropathy (BEN) had significantly lower (p<0.05) plasma Se levels than healthy individuals, both from regions close to endemic areas, and from Belgrade. Mean plasma Se of BEN patients was slightly but insignificantly higher in samples taken immediately after dialysis than in those taken before, suggesting that very little of the Se present in plasma is dialyzable. Plasma SeGSH-Px activities before and after hemodialysis in both BEN and Nonendemic chronic renal failure (NCRF) patients were not significantly different, but BEN patients had lower enzyme activities than those with NCRF and healthy controls. In BEN patients, a significant correlation between plasma Se and SeGSH-Px activity was found. NCFR patients were with diagnoses: TBC of kidneys, chronic glomerulonephritis, chronic pyelonephritis, and polycystic kidneys.     

Isolation and sequence analysis of the genomic DNA fragment encoding an aspartic proteinase inhibitor homologue from potato (Solanum tuberosum L.)

A genomic DNA clone encoding an aspartic proteinase inhibitor of potato was isolated from a lambda EMBL3 phage library using the aspartic proteinase inhibitor cDNA as a hybridization probe. The gene has all characteristic sequences normally found in eucaryotic genes. Typical CAAT and TATA box sequences were found in the 5-upstream region. In this part are also two putative regulatory AGGA box sequences located. In the genomic sequence there are no intron sequences interrupting the coding region. An open reading frame of the gene encodes a precursor protein of 217 amino acids which shows high percent identity with the aspartic proteinase inhibitor cDNA.     

Functionally-stabilized proteins--a review

The maintenance or stabilization of protein or enzyme function is of vital importance in Biotechnology. Investigations of thermophilic organisms, studies of denaturation and the use of enzymes in organic solvents have each contributed to an understanding of protein stability. Enzymes can reliably and reproducibly be stabilized by variety of means including immobilization, use of additives, chemical modification in solution and protein engineering. Examples of each of these are discussed. With these recent advances it appears that a rational strategy for achieving a particular stabilized enzyme or protein may be within reach.     

Conformation and structure of 2-amino-8-(β-d-ribofuranosyl)imidazo [1,2-a]-s-triazin-4-one (5-aza-7-deaza guanosine), a potent antiviral nucleoside

The crystal and molecular structure of one imidazo[1,2-a]-s-triazine nucleoside and its antiviral activity are described. The crystal structure of 2-amino-8-(β-d-ribofuranosyl)imidazo-[1,2-a]-s-triazin-4-one monohydrate (C₁₀H₁₃N₅O₅·H₂O) was solved by X-ray counter data. The compound crystallizes in the monoclinic space group P2₁ with cell dimensions a = 7.353 (1), b = 6.465 (1), c = 13.701 (1) Å, β = 104.64 (1)°. The structure was solved by direct methods and refined by full matrix least-squares technique to a final value of the conventional R-factor of 0.049 using 1998 observed intensities. The orientation of the base relative to the sugar ring defined in terms of rotation about the C(1′)-N(8) glycosyl bond is anti (47.8°). The ribose moiety exhibits C(2′)-endo, ²E conformation. The conformation around C(4′)-C(5′) is gauche^?. Molecular packing is dominated by hydrogen bonds. Base stacking occurs long the b axis. 5-Aza-7-deazaguanosine has shown a marked antiviral activity in vitro against herpes simplex virus despite the fact that N(3) is effective as the hydrogen acceptor only.     

Sugar and phosphate metabolism and alkaloid production phases in submerged cultures of two Claviceps strains

Summary In submerged cultures of Claviceps sp. CP II, elymoclavine was synthesized only by the growing mycelium (phase P1), whereas cultures of C. purpurea strain 129 produced agroclavine after vegetative growth had also ceased (phase P2). In strain CP II, the peak of activity of malate dehydrogenase, glucose-6-phosphate dehydrogenase and phosphatases was related to the time of maximum growth rate and alkaloid production. Citrate synthase activity paralleled the course of alkaloid synthesis. Strain 129 exhibited a further activity peak of the same magnitude during phase P2. ATP levels in both cultures corresponded to the pattern of change in enzyme activities. Strain CP II contained roughly twice as much orthophosphate and ATP in its cells as strain 129 and exhibited higher average activity of glucose-6-phosphate dehydrogenase. It follows from these results that alkaloid synthesis requires the processes of primary metabolism, even when it occurs after active growth of the culture has ceased. Cultures producing alkaloids oxidized at C-8 exhibit higher glucose-6-phosphate dehydrogenase activity, probably because of a higher NADPH consumption.