Distribution of motoneurones innervating extraocular muscles in the brain of the marmoset (Callithrix jacchus)

Extraocular muscle motoneurones were localised in the oculomotor nucleus (ON), trochlear nucleus (TN) and abducens nucleus (AN) in the marmoset brain using the horseradish peroxidase (HRP) retrograde labelling technique. HRP pellets injected into individual extraocular muscles revealed one or more groups of labelled neurones occupying discrete loci within these nuclei. Relatively little overlap of motoneurone pools was observed, except in the case of the inferior oblique and superior rectus muscles. Injections of HRP into the medial rectus muscle revealed three separate populations of labelled cells in the ipsilateral ON. Motoneurones innervating the inferior rectus muscle were mainly localised in the lateral somatic cell column of the ipsilateral ON. A second smaller grouping was observed in the medial longitudinal fasciculus. The inferior oblique muscle motoneurones were localised in the ipsilateral medial somatic cell column intermingled with motoneurones supplying the superior rectus muscle of the opposite eye. The superior oblique muscle motoneurones occupied the entire TN and the lateral rectus muscle motoneurones the AN. It was concluded that the organisation of nuclei and subnuclei responsible for controlling the extraocular muscles in the marmoset is broadly similar to that of other primates.     

Adsorption of 5′-adenosine monophosphate onto precipitated calcium phosphate: Effects of inorganic polyphosphates and carbamyl phosphate

In this paper it is shown that the adsorption of 5-adenosine monophosphate (5-AMP) onto precipitated calcium phosphate exhibits a sigmoidal profile as revealed by isotherms at 45 °C. This result indicates a cooperative behavior in the adsorption of 5-AMP. The relationship between adsorption capacity and surface area of the sedimented matrix may be interpreted as an indication that there is a monolayer of the adsorbed nucleotide on the solid surface. The pH dependence of adsorption suggests that the negatively charged phosphoryl group of 5-AMP interacts with a positively charged site (possibly Ca²⁺) on the matrix surface. The adsorption of the nucleotide is markedly decreased at pH values above 8.0. The Dixon-like plot of the effect of pH suggests an inhibitory role of hydroxyl ions in the adsorption of 5-AMP. At pH 7.5, other anions such as pyrophosphate, tripolyphosphate and carbamyl phosphate also inhibit the adsorption of the nucleotide, probably by interacting with its adsorption site. We suggest that these phosphorylated molecules could have played a role in chemical evolution by modulating the amount of nucleotides adsorbed onto mineral surfaces. The significance of these phenomena in chemical evolution is discussed.     

Divalent cations modify adsorption of 5′-AMP onto precipitated calcium phosphate: A model for cation modulation of adsorptive processes in primitive aqueous environments

The adsorption of 5′-AMP onto precipitated calcium phosphate (CaPi) requires the presence of soluble calcium and this dependence exhibits a Michaelian-like behavior. This result suggests that the formation of a complex between 5′-AMP and free Ca²⁺ (CaAMP) is a prelude to the adsorption of the nucleotide in the solid matrix. At concentrations one order of magnitude higher, Mn²⁺ and Mg²⁺ can substitute for soluble Ca²⁺ in the adsorption of 5′-AMP onto solid CaPi. However, when added simultaneously with 5′-AMP to a heterogeneous mixture that contains CaPi and soluble Ca²⁺, Mn²⁺ and Mg²⁺ inhibit the adsorption of 5′-AMP in a concentration-dependent manner. This suggests the formation of complexes that are much less effective for 5′-AMP adsorption than the CaAMP complex. On the other hand, Mn²⁺ and Mg²⁺ cannot promote desorption of the nucleotide attached to the precipitate in the presence of soluble Ca²⁺ if they are added after adsorption has attained equilibrium. Although desorption of 5′-AMP can be obtained by a sequential dilution of the soluble phase with buffer and no nucleotide in a process that obeys a Langmuir equation, the lack of effect of Mn²⁺ or Mg²⁺ when adsorption has attained its maximal value suggests strong interactions between the CaAMP complex and the solid matrix when adsorption equilibrium is reached. The divalent cations present in the matrix also participate with different selectivity in the attachment of the CaAMP complex, indicating that a cation-exchange mechanism could have acted in the modulation of adsorptive/desorptive processes involving biomonomers and phosphate surfaces in primitive aqueous environments. Received: 11 December 1995 / Accepted: 5 April 1996     

Electrical conductivity dispersion as a probe of membrane modifications in mouse polyomavirus infected cells in culture

In this report we investigate the inhibition of membrane conductivity, due to the murine polyomavirus infection in permissive cells in culture. We define experimental conditions to have reproducible results and demonstrate that the intensity of the effects on the cell membrane, depends upon the virus titer used in the infection. Finally, the virus dependent effects disappear if the infection is performed in the presence of a drug that inhibits polymavirus DNA replication.     

Mouse polyomavirus mediated effects on the infected cell membrane studied by dielectric spectroscopy

The effect of polyomavirus on the infected cell has been investigated by dieclectric spectroscopy. This technique has a great potential in the study of the ion transport properties of the cell membrane. The results presented in this communication suggest a correlation between progression of the viral infection and dielectric features of the infected, cell plasma membrane.     

Separation of inulinase from Kluyveromyces marxianus using reversed micellar extraction

Inulinase from K. marxianus was extracted into a reversed micelle phase of the cationic surfactant BDBAC (n-benzyl-n-dodecyl-n-bis(2-hydroxyethyl)ammonium chloride) in isooctane/hexanol. The extractions carried out with cells (5.9 g/l) presented a recovery yield of 87% and a purification factor 2.8. Similar values were found for inulinase recovered from the clarified medium (91% recovery yield and 2.8 purification factor). For scaled-up (400-fold) extractions, the recovery of the initial activity reached 77% and the enrichment factor was 2.8.     

L-Asparaginase from E. chrysanthemi expressed in glycoswitch®: effect of His-Tag fusion on the extracellular expression

Abstract

L-Asparaginase (L-ASNase) is an important enzyme used to treat acute lymphoblastic leukemia, recombinantly produced in a prokaryotic expression system. Exploration of alternatives production systems like as extracellular expression in microorganisms generally recognized as safe (such as Pichia pastoris Glycoswitch^®) could be advantageous, in particular, if this system is able to produce homogeneous glycosylation. Here, we evaluated extracellular expression into Glycoswitch^® using two different strains constructions containing the asnB gene coding for Erwinia chrysanthemi L-ASNase (with and without His-tag), in order to find the best system for producing the extracellular and biologically active protein. When the His-tag was absent, both cell expression and protein secretion processes were considerably improved. Three-dimensional modeling of the protein suggests that additional structures (His-tag) could adversely affect native conformation and folding from L-ASNase and therefore the expression and cell secretion of this enzyme.