Analysis of Slow Hyperpolarizing Potentials in Frog Taste Cells Induced by Glossopharyngeal Nerve Stimulation

Chemical Senses, 29,     

Regional distribution of DNA and RNA in rat brain: A sensitive determination using high-performance liquid chromatography with electrochemical detection

DNA and RNA contents in 20 brain regions or nuclei of the rat were determined by a highly sensitive method using high-performance liquid chromatography with electrochemical detection. The high DNA and RNA contents were found in the hypothalamic nuclei, especially the median eminence-arcuate nucleus. These results may be available for the preparation of nucleic acids as the regional control.     

Breeding ofl-threonine hyper-producer ofEscherichia coli W

Summary l-Threonine hyper-producing mutants were obtained fromEscherichia coli W strain KY-8366, by reducingl-threonine degradation activity and enhancingl-threonine biosynthetic activity. Anl-threonine degradation reaction test using resting cells of KY-8366 suggested that the main pathway ofl-threonine degradation by KY-8366 is via glycine. A strain with reducedl-threonine degradation activity was obtained among those mutants that could not utilizel-threonine as sole nitrogen source. Rifampicin-resistant mutants andl-lysine plus methionine-insentitive mutants were isolated. These mutants showed enhanced aspartokinase levels and accumulated morel-threonine than the parental strains. Mutant H-4290 accumulated 58 g/l ofl-threonine.     

Construction of protocellular structures under simulated primitive earth conditions

We have developed experimental approaches for the construction of protocellular structures under simulated primitive earth conditions and studied their formation and characteristics. Three types of envelopes; protein envelopes, lipid envelopes, and lipid-protein envelopes are considered as candidates for protocellular structures. Simple protein envelopes and lipid envelopes are presumed to have originated at an early stage of chemical evolution, interaction mutually and then evolved into more complex envelopes composed of both lipids and proteins.Three kinds of protein envelopes were constructedin situ from amino acids under simulated primitive earth conditions such as a fresh water tide pool, a warm sea, and a submarine hydrothermal vent. One protein envelope was formed from a mixture of amino acid amides at 80 °C using multiple hydration-dehydration cycles. Marigranules, protein envelope structures, were produced from mixtures of glycine and acidic, basic and aromatic amino acids at 105 °C in a modified sea medium enriched with essential transition elements. Thermostable microspheres were also formed from a mixture of glycine, alanine, valine, and aspartic acid at 250 °C and above. The microspheres did not form at lower temperatures and consist of silicates and peptide-like polymers containing imide bonds and amino acid residues enriched in valine. Amphiphilic proteins with molecular weights of 2000 were necessary for the formation of the protein envelopes.Stable lipid envelopes were formed from different dialkyl phospholipids and fatty acids.Large, stable, lipid-protein envelopes were formed from egg lecithin and the solubilized marigranules. Polycations such as polylysine and polyhistidine, or basic proteins such as lysozyme and cytochromec also stabilized lipid-protein envelopes.     

l-threonine production by l-aspartate- and l-homoserine-resistant mutant of Escherichia coli

Summary Growth and l-threonine productivity of l-threonine producer Escherichia coli H-4290 were inhibited by precursor amino acids, l-homoserine and l-aspartate. l-Threonine hyper-producers were isolated among the mutants resistant to l-homoserine and l-aspartate. Mutants H-4351 (Hom^r) and H-4578 (Hom^r, Asp^r) accumulated 22.2 g/l and 24.3 g/l of l-threonine in test tube cultures, while the parental strain H-4290 accumulated 18.2 g/l. The enzyme level of aspartokinase I (first enzyme of the threonine operon) was enhanced 2.3 times (H-4351) and 3 times (H-4578) that of H-4290. Mutant H-4578 accumulated 76 g/l of l-threonine in a 2-l jar fermentor after 75 h cultivation.Abbreviations DAP diaminopimeric acid - Met ^l poor growth in methionine-free medium - AHV -amino--hydroxyvaleric acid - Thr-N^- lack of ability to utilize l-threonine as a nitrogen source - Rif rifampicin - Lys+Met^r resistant to l-lysine and dl-methionine     

Interleukin-4 downregulates interleukin-6 production by human alveolar macrophages at protein and mRNA levels.

Effects of interleukin-4 (IL-4) on IL-6 production by human alveolar macrophages (AM) obtained by bronchoalveolar lavage from healthy donors was examined at the protein and gene levels. IL-6 production was quantitated by enzyme immunoassay (EIA) and bioassay using the IL-6 dependent murine hybridoma cell line MH60.BSF2. Results showed that when activated with LPS, AM released significantly more biologically active IL-6 than blood monocytes. Human rIL-4 significantly suppressed IL-6 production by AM and monocytes stimulated with LPS. Northern blot analysis revealed that IL-4 reduced the expression of IL-6 mRNA in LPS-stimulated AM and monocytes. The inhibitory effect was most pronounced when IL-4 was added with LPS or within the first 4 hr after LPS to AM or monocytes. The suppressive effect of IL-4 was completely neutralized by pretreatment with anti-IL-4 antibody. IL-4 also showed a suppressive effect on IL-6 production by macrophages generated in vitro by maturation of blood monocytes with granulocyte-macrophage colony stimulating factor (GM-CSF). These observations suggest that IL-4 may play a critical role in in situ regulation of immune responses through suppression of IL-6 production.     

Template-directed polymerization of oligoadenylates using cyanogen bromide

Cyanogen bromide (BrCN) condensed oligoadenylates [oligo(A)] on a poly(uridylic acid) [poly(U)] template in an aqueous solution. Imidazole and divalent metal ions such as Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Mg2+, and Fe2+ were required for the condensation. Chain length of oligo(A) and reaction temperature affected the coupling yield. Hexaadenylate [(pA)6] was converted to (pA)12, (pA)18, (pA)24, (pA)30, (pA)36, (pA)42, and (pA)48 in a 68% overall yield for 20 h at 25 degrees C. The coupling yield increased with increase in the poly(U) concentration. Five- to sevenfold molar excess of uridylyl residues of poly(U) to adenylyl residues of oligo(A) gave the best yield (68%). Metal ions affected the formation of linkage isomers of the phosphate bonds: The 2',5'- and 3',5'-phosphodiester bonds were predominant in the presence of Co2+, Zn2+, and Ni2+ and the 5',5'-pyrophosphate bond was predominant in the presence of Mn2+. In particular, Ni2+ gave the highest ratio of the 3',5'-phosphodiester bond (30%). N-Cyanoimidazole (1), N,N'-iminodiimidazole (2), and N-carboxamidoimidazole (3) were formed in a reaction of imidazole with BrCN in an aqueous solution. 1 and 2 had much the same condensing activity for the polymerization of adenylates as BrCN. A reaction pathway was proposed in which 1 and 2 are not only intermediates for the production of 3 but also the true condensing agent in the coupling reaction of oligo(A). Phosphorimidazolide derivative was detected in a reaction of 5'-AMP with either 1 or 2. The condensation would proceed by way of N-cyanoimidazole-phosphate adduct, the phosphorimidazolide derivative, or both.