Separate Intramolecular Targets for Protein Kinase A Control N-Methyl-d-aspartate Receptor Gating and Ca2+ Permeability

Protein kinase A (PKA) enhances synaptic plasticity in the central nervous system by increasing NMDA receptor current amplitude and Ca²⁺ flux in an isoform-dependent yet poorly understood manner. PKA phosphorylates multiple residues on GluN1, GluN2A, and GluN2B subunits in vivo, but the functional significance of this multiplicity is unknown. We examined gating and permeation properties of recombinant NMDA receptor isoforms and of receptors with altered C-terminal domain (CTDs) prior to and after pharmacological inhibition of PKA. We found that PKA inhibition decreased GluN1/GluN2B but not GluN1/GluN2A gating; this effect was due to slower rates for receptor activation and resensitization and was mediated exclusively by the GluN2B CTD. In contrast, PKA inhibition reduced NMDA receptor-relative Ca²⁺ permeability (P_Ca/P_Na) regardless of the GluN2 isoform and required the GluN1 CTD; this effect was due primarily to decreased unitary Ca²⁺ conductance, because neither Na⁺ conductance nor Ca²⁺-dependent block was altered substantially. Finally, we show that both the gating and permeation effects can be reproduced by changing the phosphorylation state of a single residue: GluN2B Ser-1166 and GluN1 Ser-897, respectively. We conclude that PKA effects on NMDA receptor gating and Ca²⁺ permeability rely on distinct phosphorylation sites located on the CTD of GluN2B and GluN1 subunits. This separate control of NMDA receptor properties by PKA may account for the specific effects of PKA on plasticity during synaptic development and may lead to drugs targeted to alter NMDA receptor gating or Ca²⁺ permeability.     

Indian childhood cirrhosis: an inherited disorder of tryptophan metabolism?

Urine samples from members of 29 families of patients with Indian childhood cirrhosis (ICC) and nine families with related disorders gave positive reactions when tested with ferric chloride. Column chromatography showed that this was due to the presence of abnormally large amounts of tryptophan metabolites, notably 3-hydroxyanthranilic acid. Affected pedigrees had a significantly greater prevalence of peptic ulcer, adult cirrhosis, diabetes mellitus, migraine, and Parkinsonism than a control population. ICC may result from an inborn error of tryptophan metabolism in susceptible ethnic groups.     

Neisseria meningitidis: heterogenicity in the outer membrane proteins released into the growth medium

Eight strains of Neisseria meningitidis belonging to different serogroups were analysed for their virulence in mice and their release of outer membrane proteins into the medium during growth. All strains released proteins. No detectable lipopolysaccharide was observed. However, SDS-PAGE showed a heterogenicity in the protein number and profile among the different strains of N. meningitidis tested.     

New and Known Species of Pratylenchus Filipjev, 1936 (Nematoda: Pratylenchidae) from Haryana,India, with Remarks on Intraspecific Variations

Two new monosexual and one bisexual species Pratylenchus Filipjev, 1936 collected from Haryana state of India are described and illustrated. The primary distinguishing features of these species are Pratylenchus microstylus n. sp.: L = 331-458 μm, spear = 11 or 12 μm; Pratylenchus cruciferus n. sp.: L = 648-793 μm, central core of lateral fields with oblique lines, hemizonid 2-8 annules anterior to excretory pore; Pratylenchus ekrami n. sp.: spear = 11-13 μm, spermatheca oblong, post vulval uterine sac with differentiated cells, tail with 26-40 annules, males abundant. Studies on intraspecific variations of P. cruciferus, P. ekrami, and P. coffeae (Zimmermann, 1898) Goodey, 1951 revealed that spear length and value of ''V'' are the least variable characters. Body length and size of post vulval uterine sac varies to varying degrees in different species. Shape of median bulb in P. ekrami, number of incisures in P. coffeae, and tail shape in P. ekrami and P. coffeae exhibit the greatest amount of intraspecific variations. P. zeae Graham, 1936 and P. thornei Sher & Allen, 1953 are the other species collected during the present studies.     

Phenotypic modulation of chronic lymphocytic leukemia cells by phorbol ester: induction of IgM secretion and changes in the expression of B cell-associated surface antigens

Freshly explanted neoplastic populations from 22 cases of phenotypically well-characterized chronic type B lymphocytic leukemia were studied for their capacity to respond to the phorbol ester TPA in vitro. In all but four cases the secretion of IgM was either induced or increased, often to a high level. In contrast, the export of free immunoglobulin (Ig) light chains, an almost consistent feature of the B lymphocytic leukemias, remained relatively constant after TPA treatment. Parallel changes in leukemic cell surface phenotype were probed with both "conventional" and monoclonal antibodies, revealing some modulation of markers in every case investigated. A diminution in the level of surface Ig (preferentially IgD) and the accumulation of cytoplasmic Ig observed after phorbol ester treatment were accompanied by a corresponding reduction or loss of the B1 antigen and usually of B2 when present. The most consistent change induced by TPA was the appearance of BB-1, a marker of activated B lymphocytes, which was rarely expressed on fresh leukemic cells. Another marker of activated lymphocytes, LB-1, was also often induced or increased in its expression after exposure of the cells to TPA. The magnitude of the TPA response appeared to relate to the stage of maturation arrest of the individual leukemic clones rather than to any clinical parameter explored. The significance of the findings to normal B cell differentiation and their potential clinical utility are discussed.     

Purification and properties of the alkaline phosphatase ofSerratia marcescens

1. A hypothesis based on the Hill-Bendall-model of photosynthetic electron transport is proposed to explain positive and negative photo-phobotaxis inPhormidium uncinatum. In the non-cyclic electron chain a pool is located into which photosystem II (e. g. by absorption by C-phycoerythrin, 561 nm) feeds electrons while photosystem I (e.g. 723 nm) drains electrons out of it.
2. Interruption of the electron flow into the pool causes a sudden decrease of the pool size and thus a positive phobic response. This happens e.g. when an organism leaves a trap which is illuminated by a wavelength absorbed by photosystem II pigments (e. g. 561 nm).
3. A negative reaction takes place when electrons are suddenly drained out of the pool; again the pool size decreases. This is the case when an organism enters a light trap illuminated by photosystem I light (723 nm).
4. The net flow of electrons into or out of the pool—and thus the reaction sense—can be manipulated by the relative excitation of the two photosystems or by blocking the electron influx by DCMU.

     

Cryopreservation of non-encapsulated embryogenic tissue of sweet potato (Ipomoea batatas)

Embryogenic tissue of the sweet potato (Ipomoea batatas (L) LAM) genotype TIB 10 was established from in vitro axillary shoot tips on Murashige and Skoog (1962) medium supplemented with 5 M 2,4-dichlorophenoxyacetic acid. Embryogenic aggregates of fresh mass 9.0–12 mg were subjected to a rapid freezing protocol in liquid nitrogen following sucrose preculture and varying degrees of dehydration. Up to 50% of embryogenic explants survived rapid freezing after preculture on 0.4 or 0.7M sucrose only. Dehydration with silica gel to moisture contents in the range 18–41% improved the survival after cryopreservation of embryogenic tissue. Tissue dehydrated for intermediate periods exhibited poor survival. Following freezing, embryogenic tissue appeared to develop normally, retaining its competence to produce mature embryos and plantlets.Abbreviations BA 6-benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - MS Murashige and Skoog (1962) medium     

Methanogenic granular sludge formation in an upflow anaerobic sludge blanket reactir treating synthetic methanolic waste

A laboratory upflow anaerobic sludge blanket reactor, seeded with fine, suspended, bacterial floc with 1.76 g volatile suspended solids/l, was used to treat synthetic methanolic waste. After 180 days of continuous peration, granular sludge with discrete granules of 1 to 2 mm diam. was formed, with 52 g volatile suspended solids/l. Granules were brown, relatively soft and had a settling velocity of 1.61 cm/s. Extracellular polymeric matter extracted from the granular sludge had high carbohydrate content but low nucleic acid content. The ash of the granular sludge contained Na⁺, K⁺ and Mg²⁺ up to 15.0, 11.7 and 3.75 mg/g, respectively. Scanning and transmission electron microscopy revealed that the granular sludge was dominated by methanogens resembling Methanosarcina.The authors are with the Department of Environmental Engineering, Faculty of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565, Japan