Fluctuation of algal alkaline phosphatase activity and the possible mechanisms of hydrolysis of dissolved organic phosphorus in Lake Barato

For freshwater cyanobacteria, the autofluorescence of phycocyanin is quite high while the in vivo fluorescence (IVF) yield of chlorophyll-a is relatively low, apparently because of low chlorophyll concentrations associated with photosystem II. In eucaryotic phytoplankton, even those with phycobili-protein accessory pigments (e.g. some cryptophytes), the opposite is true. Thus, an IVF ratio which relates phycocyanin to chlorophyll-a signals could be a good index of relative cyanobacterial abundance in the field. Spectrofluorometric scans of whole cells from laboratory cultures indicated that the ratio Em₆₆₀ @ Ex₆₃₀/Em₆₈₀ @ Ex₄₃₀ could be a very sensitive cyanobacterial indicator. Tandem flowthrough fluorometers were then fitted with the appropriate interference filters and their discriminatory power was evaluated with mixtures of cyanobacterial and eucaryotic phytoplankton. Although subject to many of the constraints of other IVF assays, tandem fluorometry should be particularly appropriate for real-time mapping of the relative spatial and temporal distributions of broad phytoplankton taxa in continuous vertical of horizontal profiles in lakes.     

Autoradiographic demonstration of gastrin binding sites in rat gastric mucosa

The location of 125I-iodotyrosyl gastrin I binding sites in rat gastric mucosa was studied. Peptide specificity was demonstrated by competitive binding studies through the addition of a large dose of cold human gastrin I or cholecystokinin-octapeptide. Autoradiography of the stomach tissue was carried out by freeze-drying, embedding in Epon, wet-sectioning with ethylene glycol, and dry-mounting the emulsion film by means of the wire-loop method to prevent loss of the labeled substance. Specific binding sites for gastrin were found on parietal and chief cells, whereas few binding sites were seen on the surface mucous or mucous neck cells. Binding sites on the parietal cells were dispersed in the cytoplasm, while those on the chief cells were found near the basal plasma membrane.     

Molecular cloning and nucleotide sequencing of oxyR, the positive regulatory gene of a regulon for an adaptive response to oxidative stress in Escherichia coli: homologies between OxyR protein and a family of bacterial activator proteins

Summary Treatment of Escherichia coli and Salmonella typhimurium cells with a low dose of hydrogen peroxide induces expression of a large number of genes, and confers resistance to oxidative stresses. The oxyR gene encodes a positive regulatory protein for a subset of these genes involved in the defense against oxidative damage. We cloned a DNA fragment that contains the E. coli oxyR region on a plasmid vector, and analyzed the nucleotide sequence of the gene. The amino acid sequence of OxyR protein, deduced from the nucleotide sequence, shows a high degree of homology to the sequences of a number of bacterial activator proteins including LysR, cysB, IlvY, MetR and NodD. The product of the oxyR gene identified by the maxicell procedure was a 34 kDa protein, which agrees with the size predicted from the nucleotide sequence of the gene.     

Mutation induction in Escherichia coli incubated in the reaction mixture of NADPH-dependent lipid peroxidation of rat-liver microsomes

Experiments were carried out to examine mutation induction in E. coli cells incubated in the reaction mixture of NADPH-dependent lipid peroxidation of microsomes isolated from rat liver. The results obtained were as follows: (1) Lipid peroxidation of microsomes occurred extensively on incubation with NADPH and Fe2+. In the E. coli WP2uvrA(pKM101) system, the mutation frequency to streptomycin resistance increased markedly when the cells were incubated in the reaction mixture of microsomal lipid peroxidation. The induced mutation frequencies were dependent on the extent of the lipid peroxidation. (2) It was also found that the mutations were induced at the same rate as in the case of (1) when the cells were added to the microsomal suspensions after the reactions due to the short-lived free radicals had terminated. (3) The cytotoxicity of the lipid peroxidation products was larger in the DNA repair-defective mutant, E. coli SR18 (uvrArecA) than the wild-type strain, SR749. From these results it is concluded that some DNA-damaging and mutagenic substances are indeed produced in the degradation process of peroxidized polyunsaturated fatty acids in liver microsomal lipids.     

Muscarinic acetylcholine receptors in rat gastric mucosa

Summary The muscarinic cholinergic innervation of the rat gastric mucosa was investigated by localizing the muscarinic receptors using a tritiated muscarinic antagonist, pirenzepine. Radioautography was performed by freeze drying stomach tissue, which was then embedded in Epon and wet sectioned with ethylene glycol, and dry mounting on emulsion film by the wire-loop method to prevent loss of the labelled substance during fixation and the radioautographic procedure. Light and electron microscopy showed that the specific pirenzepine-binding sites were localized predominantly on parietal cells, chief cells and perivascular plexuses. Analysis of the grain distribution on parietal cells revealed that the silver grains corresponding to the pirenzepine-binding sites were mainly on the basolateral plasma membrane. On the other hand, the surface mucous or mucous neck cells had few pirenzepine-binding sites.     

Differences in Ca2+ mobilization induced by alpha-adrenergic agonist and phosphatidic acid in cultured hepatocytes

In an attempt to elucidate the relationship between phosphatidylinositol breakdown and alpha-adrenergic responses, effects of phosphatidic acid and phosphatidylinositol related metabolites on Ca²⁺ mobilization and glucose output in cultured hepatocytes were examined. Norepinephrine induced the net ⁴⁵Ca²⁺ efflux from preloaded cells and stimulated glucose output via alpha-adrenergic receptor stimulation, whereas phosphatidic acid caused ⁴⁵Ca²⁺ uptake to cells and did not stimulate glucose output. Myo-inositol-monophosphate, diglyceride and arachidonic acid, which are released by phosphatidylinositol breakdown, had no effect on ⁴⁵Ca²⁺ efflux and glucose output in cells. These results suggest that phosphatidic acid and phosphatidylinositol related metabolites can not mimic the alpha-adrenergic actions in cultured hepatocytes.     

The modulating influence of the fluidity of cell membrane on excision repair of DNA in UV-irradiated Escherichia coli

When the extent of liquid holding recovery (LHR) was measured as a function of the temperature at the time of liquid holding and the Arrhenius plot was made, two distinctive phases for the LHR were demonstrated in UV-irradiated RecA- derivative of E. coli ole28E1, which are unable to synthesize and degrade unsaturated fatty acids. The inflection temperatures were 17-18 degrees C, 23-24 degrees C and 28-30 degrees C for linoleate-, oleate- and elaidate-grown cells, respectively. These temperatures well corresponded to the phase transition temperatures of the cell membrane supplemented with the fatty acid. It is therefore concluded that at least a component involved in in vivo excision repair in E. coli is associated with cell membrane.     

Simultaneous determination of cysteine sulfinic acid and cysteic acid in rat brain by high-performance liquid chromatography

A sensitive and specific assay method for cysteine sulfinic acid (CSA) and cysteic acid (CA) using high-performance liquid chromatography has been developed. The method includes post-column derivatization of various amino acids with o-phthalaldehyde in the presence of 2-mercaptoethanol. The column packed with cation-exchange resin ($\text{ISC-07}\text{S1504}$, Shimadzu Sci entific instruments, Inc., Kyoto, Japan) was used for obtaining general separation of amino acids except CSA and CA, while the separation of CSA and CA was achieved using a strong-base anion exchange ($\text{ISA-07}\text{S2504}$, Shimadzu Scientific Instruments) column. The fluorescence peak area for CSA was linear between 20 pmol and 5 nmol, whereas that for CA was 10 pmol to 5 nmol. The regional distribution of CSA, CA, and other amino acids in the rat brain was studied using this new assay method.