Catalase and superoxide dismutase in Escherichia coli

We assessed the roles of intrabacterial catalase and superoxide dismutase in the resistance of Escherichia coli to killing by neutrophils. E. coli in which the synthesis of superoxide dismutase and catalase were induced by paraquat 10-fold and 5-fold, respectively, did not resist killing by neutrophils. When bacteria were allowed to recover from the toxicity of paraquat for 1 h on ice and for 30 min at 37 degrees C, they still failed to resist killing by neutrophils. Induction of the synthesis of catalase 9-fold by growth in the presence of phenazine methosulfate did not render E. coli resistant to killing by either neutrophils or by H2O2 itself. The lack of protection by intrabacterial catalase from killing by neutrophils could not be attributed to an impermeable bacterial membrane; the evolution of O2 from H2O2 was no less rapid in suspensions of E. coli than in lysates. The failure of intrabacterial catalase or superoxide dismutase to protect bacteria from killing by neutrophils might indicate either that the flux of O-2 and H2O2 in the phagosome is too great for the intrabacterial enzymes to alter or that the site of injury is at the bacterial surface.     

Cell Surface Sialoglycoproteins of Cultured Rat Cerebellar Interneurons

Abstract: The sialoglycoproteins of cultures of relatively pure rat cerebellar interneurons were labelled by NaIO₄ oxidation/NaB ³H₄ reduction. The labelled molecules were analysed by polyacrylamide gel electrophoresis in sodium dodecyl sulphate followed by fluorography. Faint labelling could be detected in three components if cells were labelled without any oxidation. In young cultures, oxidation by galactose oxidase alone failed to reveal any additional bands. After oxidation by NaIO₄ or galactose oxidase in the presence of neuraminidase, many more components were labelled. After NaIO₄ oxidation, about 80% of the cell-associated radioactivity could be removed by treating the cells with neuraminidase, which left the cells more than 95% viable. The majority of the bands seen after neuraminidase treatment were substantially reduced when compared with untreated controls, supporting a surface localisation of these molecules. Reproducible developmental changes were seen in the profiles of bands labelled by NaIO₄/NaB ³H₄ in time course studies of cultures up to 8 days in vitro . Some bands became more prominent, and others disappeared. The gel profiles of the neuron cultures were quite distinct from those of cerebellar astrocyte cultures, which contain all the cell types likely to be contaminants of the neuron cultures.     

Dictyostelium mutants lacking DIF,a putative morphogen

DIF is an endogenous extracellular signal that may control differentiation of D. discoideum cells. It is a dialyzable, lipid-like factor that induces stalk cell formation among isolated amebae incubated in vitro with cAMP. To examine the consequences of DIF deprivation, we have isolated several mutant strains that are impaired in DIF accumulation, and whose inability to make stalk cells in vitro and during normal development on agar can be corrected by the addition of exogenous DIF. Little DIF is made by the mutants, and morphological development on agar stops after the cells have aggregated, but before a slug forms. In these DIF-deprived conditions, prespore cells can differentiate, but prestalk cells cannot.     

Appearance of functional EGF receptor kinase during rodent embryogenesis.

Mouse and rat embryonic tissues at various stages of development were examined for epidermal growth factor (EGF) receptor kinase activity. The phosphorylated EGF receptor from embryonic tissues appeared as a band of mol. wt. 170 000 daltons on SDS gels. It was clearly demonstrable in the developing mouse fetus from 10 days of gestation onwards. The distribution of the EGF receptor kinase was studied in various tissues of 13 day mouse fetuses. The activity was apparent in the skin, developing skeletal muscles and various internal organs but was notably absent in the liver and brain. The amnion was found to be one of the richest sources of activity while the yolk sac was negative, and the placenta was weakly positive. In 16 day rat fetuses the distribution was quite similar to that of the 13 day mouse fetus. The liver acquired EGF receptor kinase activity by 18 days of gestation and had high activity in neonates. Phosphoamino acid analysis revealed that phosphotyrosine was the major labelled amino acid residue in the embryonic tissues. Thus, the EGF receptor of fetal tissues as studied by immune precipitation and phosphorylation appears to be a similar entity to that found in adult mammalian tissues. This functional EGF receptor kinase activity could first be detected at the time of onset of organogenesis.     

Biophysical and Biochemical Studies on Rhinovirus and Poliovirus II. Chemical and Hydrodynamic Analysis of the Rhinovirion

Chemical analysis of rhinovirus 14 revealed a ribonucleic acid (RNA) content of 29.8% and a high adenylic acid content (35%). A partial specific volume of 0.682 cm³/g was obtained for the rhinovirion. Rhinovirus and poliovirus had identical sedimentation coefficients of 158S. A diffusion coefficient of 1.71 × 10⁻⁷ cm²/sec was consistent with a hydrated diameter of 25 nm for the rhinovirion. The calculated molecular weights of the rhinovirion and its genome were 7.1 × 10⁶ and 2.1 × 10⁶ daltons, respectively. Sedimentation analysis of infectious RNA confirmed the similarity of the molecular size of the poliovirus and rhinovirus genomes.     

The Behaviour of Dasyuroides byrnei (Marsupialia) in Captivity

Das Verhalten des Beuteltiers Dasyuroides byrnei in Gefangenschaft wurde untersucht. Dasyuroides ist nachtaktiv und verbirgt sich tagsüber in einem Bau oder Schlupfwinkel. Körperhaltung, Fortbewegungsarten, Höhlengraben, Beutefang und andere Verhaltensweisen sind beschrieben. Das Duftmarkieren hat Mitteilungswert. Beide Geschlechter setzen Duftstoff ab, indem sie ihre Sternaldrüsen und Kloakengegend an Gegenständen reiben. Freundschaftliche, kämpferische, sexuelle und mütterliche Verhaltensweisen werden beschrieben. Dasyuroides scheint kein geselliges Tier zu sein; Angriffe gegen Artgenossen führen selten zu Verletzungen, weil das Angriffsverhalten stark stilisiert ist. Wachstum und Entwicklung der Jungen wurden verfolgt. Die durchschnittliche Wurfgröße beträgt fünf oder sechs; die Jungen bleiben an den Zitzen des ♀ bis zum 56. Lebenstag. Mit 100 Tagen können sie entwöhnt werden. Das Verhalten dieser Art wird mit anderen Arten der Familie Dasyuridae verglichen, auch mit Plazentaliern.     

Enzymatic studies on the interaction of myosin and heavy meromyosin with 1,N 6 -ethenoadenosine triphosphate ( ATP), a fluorescent analog of ATP

The fluorescent analog of adenosine triphosphate (ATP)¹ 1,N⁶-ethenoadenosine triphosphate, (εATP), has been utilized as a substitute for ATP in the myosin and heavy meromyosin ATPase systems. For myosin, the analog εATP replaced ATP with a somewhat larger K_m (2.6 × 10^?4 mole ?^?1 for εATP as opposed to 8.8 × 10^?5 mole ?^?1 for ATP), indicating that the apparent affinity of the enzyme for εATP is less than for ATP. Perhaps of more interest, further comparison yielded a V_max for εATP about two and one half times the value for ATP (20 μmole PO₄ sec^?1 g protein^?1 as opposed to 8.1 μmole sec^?1 g protein^?1). Results for the HMM-εATPase system were similar, yielding a K_m value of 1.47 × 10^?4 mole ?^?1 and a V_max of 54.2 μmole PO₄ sec^?1 g protein^?1, as opposed to corresponding K_m and V_max values of 1.23 × 10^?4 mole ?^?1 and 20.4 μmole PO₄ sec^?1 g protein^?1, respectively for the HMM-ATP interaction. The pH dependence of εATPase for both systems was comparable to ATP, suggesting a similarity in the mechanism of hydrolysis of the two nucleotides. Activation of εATPase by Ca²⁺ in the presence of 0.5 M KCl was comparable to ATPase for both systems, but inhibition by Mg²⁺ seemed to be more effective for εATPase. These results indicate that εATP is an excellent substitute for ATP in the myosin and heavy meromyosin systems and because of its insertion into the active site of these muscle proteins, it promises to be a very useful probe for conformation studies at this level.