Demonstration of the capacity of nacre to induce bone formation by human osteoblasts maintained in vitro.

Nacre implanted in vivo in bone is osteogenic suggesting that it may possess factor(s) which stimulate bone formation. The present study was undertaken to test the hypothesis that nacre can induce mineralization by human osteoblasts in vitro. Nacre chips were placed on a layer of first passage human osteoblasts. None of the chemical inducers generally required to obtain bone formation in vitro was added to the cultures. Osteoblasts proliferated and were clearly attracted by nacre chips to which they attached. Induction of mineralization appeared preferentially in bundles of osteoblasts surrounding the nacre chips. Three-dimensional nodules were formed by a dense osteoid matrix with cuboidal osteoblasts at the periphery and osteocytic-like cells in the center. These nodules contained foci with features of mineralized structures and bone-like structures, both radiodense to X-ray. Active osteoblasts (e.m.) with abundant rough endoplasmic reticulum, extrusion of collagen fibrils and budding of vesicles were observed. Matrix vesicles induced mineral deposition. Extracellular collagen fibrils appeared cross-banded and electrodense indicating mineralization. These results demonstrate that a complete sequence of bone formation is reproduced when human osteoblasts are cultured in the presence of nacre. This model provides a new approach to study the steps of osteoblastic differentiation and the mechanisms of induction of mineralization.     

Mechanisms towards compensation of long-term haemopoietic injury in mice after 5 Gy irradiation:In vivo andin vitro enhancement of superoxide anion production by granulocytes

This paper analyzes the long-term (6 and 12 months) function of mouse granulocytes after total body irradiation with a single dose (5 Gy) of X-rays. Superoxide anion production has been investigated in granulocytes from peripheral blood, and also in those harvested from long term bone marrow cultures, with the aim of correlating the environmental damage induced by radiation with the functional properties of granulocytes. Anin vivo andin vitro enhancement of superoxide anion production and protein levels in granulocytes from irradiated mice is described. The presence of some colony stimulating factor in the supernatant of cultures from irradiated mice could play an important role in the priming of granulocytes.     

Sequence of the Streptococcus pneumoniae bacteriophage HB-3 amidase reveals high homology with the major host autolysin.

We have sequenced a DNA fragment containing the pneumococcal bacteriophage HB-3 hbl gene, which codes for the phage lytic amidase. A remarkable nucleotide similarity (87.1%) between the lytA gene, coding for the pneumococcal amidase, the major autolysin of Streptococcus pneumoniae, and the hbl gene was found. This similarity completely disappeared outside the open reading frames coding for both amidases. The hbl gene transformed amidase-deficient strains of S. pneumoniae to the wild-type phenotype, and Southern blotting experiments provided evidence for recombination between donor and recipient genes. A comprehensive evaluation of these and previous results on the peptidoglycan hydrolases of S. pneumoniae and its bacteriophages suggested that recombination mechanisms participate in the evolution of the genes coding for these enzymes.     

The photoreaction center of Rhodospirillum rubrum mutant strain F24.1

Rhodospirillum rubrum strain F24.1 is a spontaneous revertant of nonphototrophic mutant F24 derived from wild-type strain S1. Strain F24 shows no detectable photochemical activity and contains, at most, traces of the photoreaction center polypeptides. Strain F24.1 has a phototrophic growth rate close to that of the wild-type strain (Picorel, R., del Valle-Tascón, S. and Ramírez, J.M. (1977) Arch. Biophys. Biochem. 181, 665–670) but shows little photochemical activity. Light-induced absorbance changes in the near-infrared, photoinduced EPR signals and ferricyanide-elicited absorbance changes indicate that strain F24.1 has a photoreaction center content of 7–8% as compared to strain S1. Polyacrylamide gel electrophoresis of isolated F24.1 chromatophores shows the photoreaction center polypeptides to be present in amounts compatible with this value. Photoreaction center was prepared from strain F24.1 and showed no detectable difference with that of strain S1. It is concluded that strain F24.1 photosynthesis is due entirely to its residual 7–8% of typical photoreaction center.     

Biosynthesis of candicidin by phosphate-limited resting cells ofStreptomyces griseus

Summary A phosphate-limited resting cell system ofStreptomyces griseus in a synthetic medium has been developed in which biosynthesis of the polyene macrolide, candicidin, is linear for at least 36 h without cell growth. Glucose and to a lesser degree sucrose, but not lactose, support antibiotic synthesis. Glucose is utilized at a constant rate for antibiotic synthesis without affecting mycelial dry weight. Acetate and propionate, the building units of the macrolide aglycone, stimulate candicidin biosynthesis in cultures supplemented with glucose but do not support its synthesis in the absence of glucose. Maximal stimulation of candicidin biosynthesis was produced by 40 mM propionate or 250 mM acetate. The biosynthetic intermediate, methyl malonate, and the analog, 1-propanol, were more stimulatory than propionate at the same concentration.     

An auto-anti-b in an a1b person. Serological studies.

The serum of a patient (Mr. Lat) with the regular blood group A1 B contains an anti-B reacting with all cells having a B antigen except Bx and cis AB. The anti-B reacts at 4 degrees C and occasionally at room temperature as shown by agglutination, absorption-eluction and by thermo-dynamic assays. The antibody is regarded as an irregular autoantibody belonging to the group of the so called "suppressed" or "latent" antibodies.