Inulin hydrolysis by the Debaryomyces phaffii inulinase immobilized on Deae cellulose

Debaryomyces phaffii inulinase was immobilized by adsorption on DEAE-cellulose. The immobilization caused a drop in optimum pH, a slight increase in optimum temperature and an important increase in the thermal stability of the system. The activity yield of immobilized inulinase was 75%.A continuous reactor operation was carried out. The utilization of this system permited the production of fructose syrup from inulin.     

Oxygen consumption during the fenton-type reaction between hydrogen peroxide and a ferrous-chelate (Fe2+-DTPA)

The Fenton-type reaction between ferrous diethylenetriamine pentaacetic acid (Fe²⁺-DTPA, 50–200 μM) and H₂O₂ (20–1000 μM) in phosphate buffer at pH 7.0 results in consumption of dissolved oxygen. This observation differs from many prior reports that oxygen is liberated when more concentrated solutions of H₂O₂ are decomposed by iron salts. The rate and total quantity of oxygen consumed were dependent upon the concentrations of ferrous chelate, H₂O₂, and excess DTPA. Evidence is provided that both the ferrous-DTPA chelate and free DTPA can participate in the oxygen-consuming reactions. Oxygen was also consumed during the Fenton reaction between ferrous ions and H₂O₂ when DTPA and phosphate buffer were omitted. Under these conditions, oxygen evolution was observed at higher H₂O₂ concentrations (e.g., 400 μM). The consumption of oxygen during the Fenton-type reaction of an iron chelate at neutral pH may be relavant to events that take place in biologic systems.     

Effect of aging on the morphology and function of the thyroid gland of the cream hamster

Summary The effect of aging on the morphology and function of the thyroid gland of the cream hamster was studied by light and electron microscopy coupled with autoradiography or histochemistry.Morphologically, aging induces an accumulation of lysosomal dense bodies and a loss of the phagocytosis of colloid droplets after stimulation with TSH. Iodine uptake and organification occur normally and thyroglobulin synthesis, estimated by autoradiography with ³H-leucine, is not different from that observed in young animals. The basal T₄ and T₃ plasma levels are lower in the old animals. A low iodine diet administered for several months prevents the age related accumulation of lysosomal dense bodies. Hormone secretion seems to proceed by two different mechanisms; phagocytosis of colloid droplets, the classical mechanism that decreases with age, and an additional mechanism, probably micropinocytosis, that is maintained during the whole lifespan.Presented at the First French Congress of Endocrinology, Montpellier, September 1980Work was performed under contracts n 3.4523.79 and n 3.4512.80 of the Fonds de la Recherche Scientifique Médicale, thanks to a grant of the Ministère Belge de la Politique Scientifique (Action concertée) and with the help of the Fondation Interuniversitaire pour la Recherche du Processus du Vieillissement, Belgium     

The Ostrich (Struthio camelus) egg-white lysozyme

Summary The purification of Ostrich (Struthio camelus) egg-white lysozyme is reported. The quantitative amino acid composition, the molecular weight, the N-terminal sequence (34 amino acids) as well as kinetic studies allow to range this enzyme among the goose type lysozymes.106th communication on lysozymes.     

Studies on the mechanism of NADPH oxidation by the granule fraction isolated from human resting polymorphonuclear blood cells

Various factor affecting NADPH-oxidation by resting human leucocyte granules (LG) at acid pH, have been investigated.It was found that:

1) oxidation of NADPH by LG was increasingly inhibited by increased cyanide concentrations in the medium and was abolished by 4 mM cyanide.

2) with or without cyanide in the incubation medium, LG omitted, Mn⁺⁺, in the presence of NADPH induced superoxide anion (O¯₂) production, as evidenced by oxygen consumption and H₂O₂ production, which were abolished (in the absence of cyanide) by cytochrome C (a potent O¯₂ scavenger).

3) Both NADPH oxidation in the presence of 2 mM cyanide (cyanide-resistant) and in its absence (cyanide-sensitive) by LG occured only in the presence of Mn⁺⁺, and both were inhibited by superoxide dismutase.

4) Cyanide-resistant NADPH oxidation by LG generated H₂O₂, was inhibited by H₂O₂ and was not modified by «active catalase. The ratio of cyanide-resistant NADPH oxidation/O₂ uptake was 1 up to 1.25 mM NADPH, and increased above this concentration.

5) Cyanide-sensitive NADPH oxidation was inhibited by catalase and increased upon addition of H₂O₂. The ratio of cyanide-sensitive NADPH oxidation/O₂ uptake was 2.

It was concluded that after initiation by O¯₂, produced independently of LG, two sequential types of LG dependent NADPH oxidations occur. First, an O¯₂-dependent protein mediated NADPH oxidation (cyanide-resistant) which generates H₂O₂ and O¯₂ occurs. Second, NADPH peroxidation (cyanide-sensitive) which utilizes H₂O₂ takes place.     

Electron microscopic study of the mandibular glands of Kalotermes flavicollis Fabr. (Isoptera; Calotermitidae)

Summary The mandibular glands of Kalotermes were examined in different castes. They showed sexual dimorphism in the soldiers and primary reproductives. Moreover, in female soldiers and queens, mandibular gland cells contained numerous crystalline structures of mitochondrial origin. The role of these glands (secretion of saliva or pheromone) is discussed.

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Résumé Les glandes mandibulaires de Calotermes sont étudiées dans les différentes castes. Elles présentent un dimorphisme sexuel chez les soldats et les sexués. Après la mue imaginale, les cellules glandulaires ont toujours une activité sécrétrice. De plus, chez les soldats femelles et les reines, elles contiennent de nombreuses formations cristallines d'origine mitochondriale. Le rôle de ces glandes (sécrétion de salive ou de phéromone) est discuté.

     

Replication of prophage P1 during the cell cycle of Escherichia coli.

Summary We have followed, by DNA-DNA hybridization, the variation in the number of copies of prophage P1 relative to two chromosomal markers when the doubling time of the host cells is modified by a change in carbon source. The ratio of P1/chromosome terminus undergoes a twofold decrease when the cell doubling time increases from 24 to 215 min, whereas the ratio of P1/chromosome origin increases 1.4 fold; both ratios tend towards unity at slow growth rates. This suggests that the replication of prophage P1 is not simultaneous with chromosome initiation or chromosome termination. The chromosome replication time is unaffected by the presence of P1, and remains constant over the range of doubling times studied, with a value of about 40 min. Following amino acid starvation, the P1/chromosome origin ratio increases from 0.7 to 0.9, suggesting that P1 retains the ability to replicate after chromosome initiation has stopped and in the absence of essential amino acids. The results are discussed with reference to similar studies done on F and R1.