Effect of dilution rate on eicosapentaenoic acid productivity ofPhaeodactylum tricornutum utex 640 in outdoor chemostat culture

Summary Eicosapentaenoic acid (EPA) volumetric productivity from an outdoor chemostat culture ofPhaeodactylum tricornutum UTEX 640 in a 50-l tubular photobioreactor varies with dilution rate, reaching a maximum of 47.8 mg l^–1 d^–1 at D=0.36 d^–1. Continuous culture at high dilution rates' is proposed as the most adequate operating mode to maximize polyunsaturated fatty acid production.     

The role of the medium in long-range electron transfer

 The role of the polypeptide matrix in electron transfer processes in proteins has been studied in two distinct systems: first in a protein where the induced ET is artificial, and second as part of the catalytic cycle of an enzyme. Azurins are structurally well-characterized blue single-copper proteins consisting of a rigid β-sheet polypeptide matrix. We have determined rate constants and activation parameters for intramolecular long-range electron transfer between the disulfide radical anions (generated by pulse radiolysis) and the copper(II) centre as a function of driving force and nature of the intervening medium in a large number of wild-type and single-site-mutated proteins. In ascorbate oxidase, for which the three-dimensional structure is equally well characterized, the internal ET from the type-I Cu(I) to the trinuclear Cu(II) centre has been studied. We find that the results correlate well with distance through well-defined pathways using a through-bond electron tunnelling mechanism. Received: 2 January 1997 / Accepted: 6 February 1997     

Commissural component of the stria terminalis: electrophysiological properties

The commissural component of the stria terminalis (S. T.) was studied in Equi-Thesin (92.7 mg/kg) anesthetized rats after their exposure in the caudothalamic surface of both hemispheres. Two types of connection between right and left S. T. across the anterior commissure are described: A "direct" connection set up by fibres that run through the S. T. and join the contralateral S. T., and another "indirect" component, formed by cell axons that receive excitatory synaptic contacts from fibres running in the S. T.     

Seasonal changes in the activities of glycolytic enzymes from liver and skeletal muscle of Rana perezi

Glycogen phosphorylase (GP), Hexokinase (HK), Phosphofructokinase (PFK), Pyruvate kinase (PK) and Lactate dehydrogenase (LDH) activities from skeletal muscle and liver were measured in Rana perezi for the four seasons of the year. Skeletal muscle showed a decrease in PFK, PK and LDH activity during winter and summer. Liver displayed an increase in GP activity in spring and in PK and LDH in autumn.     

Calcium-Induced Desensitization of Acetylcholine Release from Synaptosomes or Proteoliposomes Equipped with Mediatophore, a Presynaptic Membrane Protein

A "fatigue" of acetylcholine (ACh) release is described in cholinergic synaptosomes stimulated with the calcium ionophore A23187 or gramicidin. A small conditioning calcium entry, which did not trigger a large ACh release, led to a decrease of transmitter release elicited by a second large calcium influx. This fatigue was half-maximal at approximately 30 microM external calcium and developed in a few minutes. In contrast, activation of release by calcium was very rapid and was half-maximal at approximately 0.5 mM external calcium. Activation and desensitization of release could be attributed to the recently identified presynaptic membrane protein, the "mediatophore." Proteoliposomes equipped with purified mediatophore showed a calcium-dependent activation and "fatigue" of ACh release similar to that of synaptosomes. It was found that the ionophore A23187 rapidly equilibrated internal and external calcium concentrations in proteoliposomes. Thus, the external calcium concentration gave the internal concentration required for activation or desensitization of proteoliposomal ACh release. The mediatophore showed remarkable calcium binding properties (20 sites/molecule) with a KD of 25 microM. The physiological implications of desensitization on the organization of release sites are discussed.     

Characterization by cytofluorometry of the different types of adenohypophyseal cells in the rat

The different antehypophysical cell types which synthetize and release somatotroph (GH), corticothroph (ACTH), gonadotroph (LH-FSH) and lactotroph (PRL) hormones were analysed. The experiments were performed on hypophyses from five groups of animals: adult males, 14 days-old female, adult females, gestating adult females and lactating adult females. The cells were analysed by immunofluorescence using flow cytometry. For each of the hormones studied, there was a characteristic spectral distribution of cells. The evolution of cell size and granular content with respect to sex and physiological state of each group was studied by the analysis of diffused light. Small, slightly granular cells represented 50% of the cell population in males and 14 day-old females but only 8% in gestating or lactating females. The study of the cell cycle showed the presence of dividing cells in the population of large, granular cells from gestating and from lactating females. No features of cell division were observed in the population of small, slightly granular cells. This study indicates the potential value of multiparametric analysis in the separation of pure sub-populations of antehypophysial cells.