Relative content of isoaccepting tRNAs for glycine and proline in avian tendon cells with different rates of procollagen synthesis

The relative amounts of iso-tRNAs^Gly and iso-tRNAs^Pro existing in chick embryo tendon are indicative of a specialization of the tRNA population for collagen synthesis. These amounts are not modified (i) in primary avian tendon (PAT) cells in culture for which the procollagen production varies from about 10% of total protein synthesis to 60% and (ii) in tendons from immature chicks, which show a 3-fold decrease of procollagen production with increasing age. The characteristic tRNA pattern was not maintained in cells which had lost the ability to make high levels of collagen as observed in the cases of: (i) PAT cells reaching confluency; (ii) virus-transformed PAT cells and (iii) tendon from adult chick. Our data are consistent with the idea that tendon tRNA specialization for collagen synthesis is a differentiation feature independent of the expression level of the collagenic function but related to its maintenance.     

Positional cell surface antigens in an insect appendage

Summary Mice were immunized with membrane preparations of epidermal cells taken from different parts (internal and external face of femur and apex and base of tibia) of the metathoracic legs of cockroach larvae. Using indirect immunofluorescence, anti-internal face of femur antibodies were observed to bind preferentially to membranes from the internal face of the femur; similarly, anti-external face of femur antibodies bound preferentially to membranes from the external face of the femur. We also found a preferential binding of anti-apex of tibia antibodies to membranes from the apex of the tibia and anti-base of the tibia antibodies to membranes from the base of the tibia. When anti-tibia sera were tested on membranes from the femur, anti-apex of tibia antibodies bound preferentially to membranes from the apex of the femur, and anti-base of tibia antibodies bound preferentially to membranes from the base of the femur.This demonstrates that epidermal cell membranes from the different parts of the leg differ in their antigenic properties, and that these differences are related to their position around the appendage and along the proximodistal axis of segments.These results are in agreement with those of previous graft experiments and with the concept of ordered sequences in insect appendages.     

Cadmium biosorption properties of the metal‐resistant Ochrobactrum cytisi Azn6.2

The aim of this work was to establish the conditions for using Ochrobactrum cytisi Azn6.2 as a metal biosorbent. Azn6.2 is a novel strain from the legume symbiont O. cytisi that has been isolated from nodules of Medicago polymorpha plants grown on heavy metal‐polluted soils. Compared with the strain ESC1, Azn6.2 showed some biochemical differences, as well as antibiotic susceptibility, Azn6.2 was multi‐resistant to heavy metals, such as Cu, Cd and Zn, and bacterial pellets were able to biosorb high amounts of Cd and Zn. As shown by scanning electron microscopy coupled to energy dispersive X‐ray, most of Cd was attached to the cell surface. Optimal conditions for Cd biosorption were established, being 1 mM Cd ions in solution and 2 h of contact with the biosorbent at room temperature. At these conditions, maximal Cd loading capacity reached 32–34 mg/g. Cd desorption from bacterial pellets was achieved after washing with EDTA or, at higher efficiency, at pH 1.0. These results indicated that biosorption/desorption on O. cytisi Azn6.2 biomass should be a cost‐effective method for Cd recovery from contaminated solutions.     

Cloning and characterization of a dextranase gene (dexS) from Streptococcus suis

A gene (dexS) coding for a Streptococcus suis capsular type 2 dextranase (DexS) was detected in a recombinant gene library constructed in phage λZapII, and its nucleotide sequence was determined. Sequence comparison showed that the dexS gene product had significant similarities with enzymes which hydrolyze glucose polymers. Moreover, conserved amino acids that are suggested to be part of the active site of the glucosidases are also found in DexS. The dexS gene, adjacent to the gene encoding a S. suis IgG-binding protein, encoded a protein of approximately 62 kDa which exhibited DexS activity.