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Biomedical subjects

G Donelli

Publications and source records attributed to G Donelli.

At least 145 records · Page 8Linked to original sources
PubMed1980

Ultrastructural changes in Escherichia coli grown in divalent cation-deficient medium.

Escherichia coli strains B and K12 could grow in very limiting conditions of divalent cation deficiency. Growth curves showed a long lag period of about 30 h, followed by an exponential phase bringing the bacterial concentration to about 10(7) ml-1, with a 24 min doubling time, while the growth curves of control cultures were characterized by short lag periods, maximum populations of about 10(9) ml-1 and an 18 min doubling time. The DNA/protein ratio in bacteria grown in deficient medium was 0.48 compared with 0.21 for control bacteria. Significant differences were found in the ultrastructure of the two types of bacteria. Freeze-etched control cells showed the typical appearance with the protoplasmic fracture face of the cytoplasmic membrane (PFC) having a random distribution of intramembranous particles. Bacteria growing in deficient medium in exponential phase presented several particle-free areas on the PFC. At the beginning of the stationary phase, the particle-free zones became larger and crystalline structures were formed. These structural modifications, which increased with culture age, were never observed in bacteria grown in control medium. Optical diffraction analysis of the crystalline structures in freeze-etched cells revealed regular periodic arrays with a rhomboid repeating unit approximately 7.6 x 5.4 nm in dimension and an angle between the axes of about 73 degrees. Negative staining of isolated membranes of bacteria grown in deficient medium showed a more complex organization of the crystalline arrays, each unit being clearly composed of subunits.

Calcium↗
PubMed1980

Human eosinophils and parasitic diseases: light and electron microscopy evidence of interaction with sheep erythrocyte.

The aim of this study was to investigate the possible formation of spontaneous rosettes between human eosinophils and sheep erythrocytes. In patients with parasitic diseases a percentage of 15.7 +/- 6 (range 6-23%), eosinophils were able to form rosettes. Each rosette showed as few as four to eight erythrocytes attached per eosinophil. Two types of interaction were observed at the electron microscope: point attachments and large surface contacts. In patients with non-parasite induced eosinophilia the formation of rosettes is decidedly below the above-mentioned percentage (less than 2%) or totally absent. It follows that during parasitic infections with blood eosinophilia, whatever the mechanism responsible, the formation of spontaneous rosettes could be diagnostic significance and might reflect qualitative or quantitative modifications in the eosinophil population.

Cell Survival↗