Properties of human hemoglobin immobilized on Sepharose 4B.

This paper reports the properties of human hemoglobin covalently bound to Sepharose 4B both in 'high-affinity' and 'low-affinity' conformations. The results suggest that the coupling reaction is strongly affected by the conformational changes linked to oxygenation of the protein. The rate and the extent of the reaction are different for the oxy and deoxyderivatives, probably due to the change in reactivity of the amino groups in the liganded and unliganded tetramer. The data on the equilibrium which is established between matrix-bound and soluble subunits, measured by the 'subunit-exchange chromatography', indicate that the system displays a minimal heterogeneity when hemoglobin is coupled to the gel in the deoxy state at intermediate protein concentration and pH 8. Maxtrix-bound hemoglobin is characterized by a higher oxygen affinity and by decreased homotropic and heterotropic interactions with respect to hemoglobin in solution, but the changes depend strongly on the conditions used in the coupling procedure.     

Kinetics of alpha phosphate turnover in the free nucleotides of isolated rabbit hearts during the incorporation of adenosine or uridine]

The isolated rabbit heart was perfused with tritium-labelled adenosine or uridine at constant concentration (respectively 10 and 2 micrometer) and specific activity. The transfer rates of the precursors into free nucleotides were obtained by calculating the uptake of isotope into the products. The rates of phosphorylation of the nucleotides were estimated by following the incorporation of 32PO4 3- into the alpha phosphate groups. The results obtained with the two isotopes show that the rate of labelling of the alpha phosphate groups is a good estimate of the turnover of nucleotides when the mechanism of synthesis involves phosphorylation of a riboside.     

The saccus vasculosus of Anguilla anguilla (L.) from larva to adult

Summary The ultrastructure of coronet cells of the saccus vasculosus has been studied in specimens of Anguilla anguilla (L.) at different stages of its life cycle. At all the stages observed coronet cells are composed of a basal and an apical part, the latter bearing globules with primary vesicles. In the larva (a marine form) and in the fully metamorphosed small eel at the time of entry into freshwater the narrow lumen and the vesicles within the apical globules are filled with electron-dense material. In forms in which adaptation to freshwater has occurred, the saccus lumen appears expanded, the apical globules are better developed, and the electron-dense material has disappeared. It is suggested that the two situations observed represent different functional states of the organ, in relation to different conditions of environmental salinity.The authors gratefully acknowledge the contribution of Dr. G. Andreoli, of the University of Parma, who provided the Atlantic larvae for this study.     

A rapid method for determination of ribonucleotide reductase activity

Ribonucleoside diphosphate reductase activity is determined in centrifuged homogenates by following the conversion of cytosine ribonucleotide to cytosine deoxyribonucleotide. The enzymatic reaction is measured by monitoring the radioactivity of the reaction products separated by thin layer chromatography on PEI-cellulose plates. The method is rapid and permits the simultaneous processing of multiple samples.     

Immunohistological signposts in central nervous system tumours with neuronal differentiation.

25 neuronal tumours with a panel of antibodies were studied and it was found that vimentin was present in 15 tumours. It was also found in a few cells within rosettes. PGP 9.5 showed a somatic pattern of staining with nuclear and perinuclear positivity in 23. Neurofilament reactivity was found in 14. Retinal S-antigen was detected only in one medulloblastoma, 3/4 pineal tumours and 2/2 retinoblastomas. Reactivity, for synaptophysin was present in 2/5 medulloblastomas, 3/10 neuroblastomas and 2/2 retinoblastomas. GFAP was demonstrated in scattered tumour cells in 4/5 medulloblastomas. Two of these were the only tumours featuring bipolar differentiation whilst it was unipolar in the remainder. The significance of these findings in relation to the ontogeny of these tumours is discussed.     

Titanium and iron titanium oxide nanoparticles in antennae of the migratory ant <Emphasis Type="Italic">Pachycondyla marginata</Emphasis>: an alternative magnetic sensor for magnetoreception?

The most accepted hypothesis of magnetoreception for social insects is the ferromagnetic hypothesis which assumes the presence of magnetic material as a sensor coupled to sensitive structures that transmit the geomagnetic field information to the nervous system. As magnetite is the most common magnetic material observed in living beings, it has been suggested as basic constituent of the magnetoreception system. Antennae and head have been pointed as possible magnetosensor organs in social insects as ants, bees and termites. Samples of three antenna joints: head-scape, scape-pedicel and pedicel-third segment joints were embedded in epoxi resin, ultrathin sectioned and analyzed by transmission electron microscopy. Selected area electron diffraction patterns and X-ray energy dispersive spectroscopy were obtained to identify the nanoparticle compound. Besides iron oxides, for the first time, nanoparticles containing titanium have been identified surrounded by tissue in the antennae of ants. Given their dimension and related magnetic characteristics, these nanoparticles are discussed as being part of the magnetosensor system.     

Plasmid transformation of Ruminococcus albus by means of high-voltage electroporation

To apply recombinant DNA techniques to the genetic manipulation of cellulolytic ruminal bacteria, a plasmid vector transformation system must be available. The objective of this work was to develop a system for plasmid transformation of Ruminococcus albus. Using high voltage electrotransformation, pSC22 and pCK17 plasmid vectors, derived from lactic acid bacteria plasmids and replicating via single-stranded DNA intermediate, were successfully introduced into three freshly isolated R. albus strains and into R. albus type strain ATCC 27210. The optimization of the electrotransformation condition raised the electroporation efficiency up to 3 x 10(5) transformants per microgram of pSC22 plasmid.