Scavenging of Hydrogen Peroxide in Prokaryotic and Eukaryotic Algae: Acquisition of Ascorbate Peroxidase during the Evolution of Cyanobacteria

Ascorbate (AsA) peroxidase was found in six species of cyanobacteriaamong ten species tested. Upon the addition of H₂¹⁸O₂ to thecells of AsA peroxidase-containing cyanobacteria, ¹⁶O₂ derivedfrom water and ¹⁸O₂ derived from H₂^I8O₂ were evolved in thelight. The evolution of ¹⁶O₂ was inhibited by DCMU and did notoccur in the dark, but ^I8O₂ was evolved even in the dark orin the presence of DCMU. Similar light-dependent evolution of¹⁶O₂ was observed in the cells of AsA peroxidase-containingEuglena and Chlamydomonas. However, the cells of AsA perox-idase-lackingcyanobacteria evolved only ¹⁸O₂ in either the light or dark.Furthermore, the quenching of chlorophyll fluorescence inducedby hydrogen peroxide was observed only in the cells of the AsAperoxidase-containing Synechocystis 6803, and not in the cellsof Anacystis nidulans which lacks AsA peroxidase. Thus, cyanobacteriacan be divided into two groups, those that has and those thatlacks AsA peroxidase. The first group scavenges hydrogen peroxidewith the peroxidase using a photoreductant as the electron donor,and the second group only scavenges hydrogen peroxide with catalase. (Received July 23, 1990; Accepted October 18, 1990)     

Approach to the Involvement of Influenza B Neuraminidase in the Cleavage of HA by Host Cell Protease Using Low pH-Induced Cell Fusion Reaction

ts7, a temperature-sensitive mutant defective in neuraminidase (NA) of influenza B/Kanagawa/73, lacks NA enzymatic activity at the nonpermissive temperature (37.5 C). When MDCK cells were infected with the mutant at the permissive temperature (32 C) and exposed to pH 5.2 medium, extensive cell fusion occurred. In contrast, at the nonpermissive temperature cells did not show cell fusion at all unless they were pretreated with trypsin, suggesting that at 37.5 C the hemagglutinin (HA) of ts7 is expressed at the cell surface in an uncleaved form. It was also found that the replacement of RNA segment 6 of ts7 with that of wild-type B/Lee resulted in the emergence of low pH-induced fusion activity as well as NA enzymatic activity at the incubation temperature of 37.5 C and that the addition of bacterial NA to the cultures infected with ts7 at 37.5 C early in infection brought about low pH-induced cell fusion. We suggest that the removal of neuraminic acid from the carbohydrate moiety of HA by NA is essential for the cleavage of HA by cellular protease.     

Proadrenomedullin N-Terminal 20 Peptide (PAMP), an Endogenous Anticholinergic Peptide: Its Exocytotic Secretion and Inhibition of Catecholamine Secretion in Adrenal Medulla

Abstract: In cultured bovine adrenal medullary cells, stimulation of nicotinic receptors by carbachol evoked the Ca²⁺-dependent exocytotic cosecretion of proadrenomedullin N-terminal 20 peptide (PAMP) (EC₅₀ = 50.1 µ M ) and catecholamines (EC₅₀ = 63.0 µ M ), with the molar ratio of PAMP/catecholamines secreted being equal to the ratio in the cells. Addition of PAMP[1–20]NH₂ inhibited carbachol-induced ²²Na⁺ influx via nicotinic receptors (IC₅₀ = 2.5 µ M ) in a noncompetitive manner and thereby reduced carbachol-induced ⁴⁵Ca²⁺ influx via voltage-dependent Ca²⁺ channels (IC₅₀ = 1.0 µ M ) and catecholamine secretion (IC₅₀ = 1.6 µ M ). It did not alter high K⁺-induced ⁴⁵Ca²⁺ influx via voltage-dependent Ca²⁺ channels or veratridine-induced ²²Na⁺ influx via voltage-dependent Na⁺ channels. PAMP seems to be a novel antinicotinic peptide cosecreted with catecholamines by a Ca²⁺-dependent exocytosis in response to nicotinic receptor stimulation.     

Model for prediction of immobilizedAcetobacter cell number in calcium alginate gel droplets

The geometry of calcium alginate gel spheres is studied by fractal interpretation for prediction of number of cells to be immobilized. For alginate concentrations from 1 to 5% the simulated results are of 6.65×10⁸, 1.44×10⁸ and 5.27×10⁷ N cell mL⁻¹ for respectively 1.5, 2.5 and 3.5 mm gel sphere diameters. Simulated data are compared with those resulting from literature and particularly with experimental trials where from 10⁷ to 10⁸ N cell mL⁻¹, in 2% alginate beads with a diameter of 1.5 mm, is able to fulfil mechanical and swelling characteristics of alginate gel beads besides to supply good oxygenation.     

Living immobilized Acetobacter in Ca-alginate in vinegar production: Perliminary study on optimum conditions for immobilization

Summary The optimum conditions forAcetobacter immobilization were investigated. The results show that: 1) the maximum oxygen uptake rate (OURm) and cell release are related to alginate and cell concentration in the gel; 2)different alginate concentration does not affect cell viability, but long storage in CaCl₂ reduces the number of living cells; 3)the double alginate gel layers had no influence on cell viability and on the OURm and prevented cell leakage from the gel matrix.     

Functional Analysis of Tcl1 Using Tcl1-Deficient Mouse Embryonic Stem Cells

Tcl1 is highly expressed in embryonic stem (ES) cells, but its expression rapidly decreases following differentiation. To assess Tcl1’s roles in ES cells, we generated Tcl1-deficient and -overexpressing mouse ES cell lines. We found that Tcl1 was neither essential nor sufficient for maintaining the undifferentiated state. Tcl1 is reported to activate Akt and to enhance cell proliferation. We found that Tcl1 expression levels correlated positively with the proliferation rate and negatively with the apoptosis of ES cells, but did not affect Akt phosphorylation. On the other hand, the phosphorylation level of β-catenin decreased in response to Tcl1 overexpression. We measured the β-catenin activity using the TOPflash reporter assay, and found that wild-type ES cells had low activity, which Tcl1 overexpression enhanced 1.8-fold. When the canonical Wnt signaling is activated by β-catenin stabilization, it reportedly helps maintain ES cells in the undifferentiated state. We then performed DNA microarray analyses between the Tcl1-deficient and -expressing ES cells. The results revealed that Tcl1 expression downregulated a distinct group of genes, including Ndp52, whose expression is very high in blastocysts but reduced in the primitive ectoderm. Based on these results, we discuss the possible roles of Tcl1 in ES cells.     

Fundulus as the premier teleost model in environmental biology: opportunities for new insights using genomics

A strong foundation of basic and applied research documents that the estuarine fish Fundulus heteroclitus and related species are unique laboratory and field models for understanding how individuals and populations interact with their environment. In this paper we summarize an extensive body of work examining the adaptive responses of Fundulus species to environmental conditions, and describe how this research has contributed importantly to our understanding of physiology, gene regulation, toxicology, and ecological and evolutionary genetics of teleosts and other vertebrates. These explorations have reached a critical juncture at which advancement is hindered by the lack of genomic resources for these species. We suggest that a more complete genomics toolbox for F. heteroclitus and related species will permit researchers to exploit the power of this model organism to rapidly advance our understanding of fundamental biological and pathological mechanisms among vertebrates, as well as ecological strategies and evolutionary processes common to all living organisms.     

Agenesis of the scapula in Emx2 homozygous mutants

The shoulder and pelvic girdles represent the proximal bones of the appendicular skeleton that connect the anterior and posterior limbs to the body trunk. Although the limb is a well-known model in developmental biology, the genetic mechanisms controlling the development of the more proximal elements of the appendicular skeleton are still unknown. The knock-out of Pax1 has shown that this gene is involved in patterning the acromion, while the expression pattern candidates Hoxc6 as a gene involved in scapula development. Surprisingly, we have found that scapula and ilium do not develop in Emx2 knock-out mice. In the homozygous mutants, developmental abnormalities of the brain cortex, the most anterior structure of the primary axis of the body, are associated with important defects of the girdles, the more proximal elements of the secondary axis. These abnormalities suggest that the molecular mechanisms patterning the more proximal elements of the limb axis are different from those patterning the rest of appendicular skeleton. While Hox genes specify the different segments of the more distal part of the appendicular skeleton forming the limb, Emx2 is concerned with the more proximal elements constituting the girdles.