Effect of human immunoglobulin preparations on Fc rosette formation between anti-D-coated erythrocytes and lymphocytes

Human immunoglobulin (Ig) preparations were tested for their inhibitory effect on Fc rosette formation between anti-D-coated human erythrocytes and lymphocytes, as compared to their complement activating capacity. Both of the two biological activities ascribed to the sites in the Fc portion of the IgG molecules were found to be reduced in the pepsin-treated, as well as in the S-sulfonated Ig preparations, as compared to the activities of the normal human Ig preparation. In the plasmin-treated Ig preparation, which was found to be composed of three major components: plasmin-Fab, plasmin-Fc and plasmin-resistant IgG, the activity of inhibiting the Fc rosette formation was well retained, in contrast to its low complement activating capacity.

Morphological changes in yeasts as a result of the action of 5-fluorocytosine

The mode of action of 5-fluorocytosine on Candida albicans and Saccharomyces cerevisiae was studied with special reference to morphology and ultrastructure. Shortly after contact of yeast cells with 10 mug of 5-fluorocytosine per ml, marked enlargement of the cells occurred. The initial increase in cell size was almost the same with both yeast strains. As incubation proceeded, further increase in cell volume continued with C. albicans, whereas no further change in cell volume was observed with S. cerevisiae. An electron microscope examination of C. albicans cells after exposure to the drug revealed characteristic changes, consisting of an enlarged nucleus and a thin cell wall. The morphological changes were exactly comparable to those reported with inhibitors of deoxyribonucleic acid synthesis in mammalian cells and some bacteria.

Effect of vagotomy on hyperinsulinemia in obese rats with hypothalamic lesions

With the purpose of investigating the pathogenesis of obesity and hyperinsulinemia in rats with hypothalamic lesions (HTL), HTL were made in vagotomized rats, and the development of obesity was serially followed up to 15 weeks as well as the changes of plasma triglyceride and immunoreactive insulin (IRI) levels. Even in vagotomized rats, obesity developed after HTL and plasma triglyceride and IRI levels increased significantly. However, obesity was slightly less in grade and occurred later as compared with sham-vagotomy-HTL rats. Plasma IRI levels in vagotomized rats significantly correlated with the body weight, Lee's index, the weight of adipose tissue and plasma triglyceride level. Similar results were also obtained in rats with HTL which were pair-fed following vagotomy. These results suggest that the hyperinsulinemia in obese rats with HTL may be involved not only by hypersecretion of insulin mediated by hypothalamo-vagal nerve system but also by some insulin-antagonistic factors such as increases of adipose tissues and plasma lipids.

Dose effect relationship for epilation and late effects on spinal cord in rats exposed to gamma rays

The response of rat spinal cords (T7-T12) exposed to single and multifractionated gamma-ray exposures revealed no significant differences between the threshold doses for 2 fractions given with a 24-hr. interval and 2 fractions given with a 15-day interval. The latent period for spinal cord damage was about 190 days when the incidence of paralysis was high; it was less than this in animals with a lower probability of paralysis. There was a marked sparing effect from dose fractionation: the initial part of a Strandqvist type of isoeffect curve had a slope of 0.44 for doses causing paralysis in 50% of the animals, and 0.36 for "threshold" doses. The level of epilation was not useful for predicting spinal cord damage.

Single dose response curves of normal cells in situ

Analysis of data on the response of normal tissues (skin, lung, spinal cord, intestine, testis) to single and multifractionated irradiation schedules revealed the characteristics of the single dose survival curves of target cells responsible for skin, lung, and spinal cord reactions, and of stem cells of colonic, jejunal, gastric mucosae, and testis exposed in situ to relatively low doses of x- or gamma-rays. The single dose survival curves of these cells seem to be complex (unlike those of cells studied in vitro), that is, simply exponential in the initial portion up to approximately 250 rads, and downward-bending thereafter in a curve which includes one or two linear portions on a semilogarithmic scale.

Killing effect of normal peritoneal exudate cells in guinea pigs on microfilariae of Dirofilaria immitis evoked by passive transfer of immune humoral factor

Parasiticidal activity of normal peritoneal exudate cells on microfilariae of Dirofilaria immitis in diffusion chambers implanted into normal guinea pigs was evoked by intraperitoneal passive transfer of anti-D. immitis serum. The immune serum was fractionated into supernatant and sediment by ammonium sulfate precipitation. The parasiticidal effect was reproduced with the supernatant and, to a less extent, with the sediment. Anti-D. immitis serum from the animals sensitized 5 days before was also effective in this respect. From these results it can be concluded that the factor responsible for the phenomenon is some other factor(s) than the antibody. In addition, the in vitro cytotoxicity test demonstrated an enhanced Mf-killing activity of sensitized peritoneal exudate cells by adding with anti-D. immitis serum.

Effect of viomycin on dihydrostreptomycin binding to bacterial ribosomes

Viomycin, a peptide antibiotic, reduced the amounts of dihydrostreptomycin bound to ribosomes of Myobacterium smegmatis and Escherichia coli, although they have different modes of action. The [3H]dihydrostreptomycin binding to ribosomes could not exchanged with streptomycin or dihydrostreptomycin, but not with unrelated antibiotics, namely, kanamycin, neomycin, spectinomycin, capreomycin, tuberactinomycin-N, chloramphenicol and erythromycin. We suggest that there is a significant interaction between the binding sites of viomycin and streptomycin on ribosomes.

Altered ribosomes in antibiotic-resistant mutants of Mycobacterium smegmatis

Two alleles for viomycin-capreomycin resistance (vic) in Mycobacterium smegmatis affect ribosome structures. One (vicA) affects a component of 50S subunits and the other (vicB) affects a component of 30S subunits. The locus for neomycin-kanamycin resistance (nek), which is linked to vicA and vicB, affects a component of 30S subunits. Although the erythromycin resistance locus (ery) is linked to vic and nek, no ribosomal alterations could be detected. Mutations at the streptomycin locus (str) not linked to vic and nek caused alterations of 30S subunits.

Method of constructing a dose-response curve for normal cells in situ

A method is presented for planning experiments and analysing data with a view to determining in detail the shape of a single-dose survival curve for normal cells exposed in situ to relatively low doses of radiation. Applying this method to data published on the responses of gastric mucosal and colonic stem cells showed that the single-dose survival curves for these cells were linear up to about 250 rads, after which they bent downwards. Some applications of this method are discussed.