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Biomedical subjects

M LIEBERMAN

Publications and source records attributed to M LIEBERMAN.

At least 19 recordsLinked to original sources
PubMed1959

Leukemogenic activity of filtrates from radiation-induced lymphoid tumors of mice.

Cell-free filtrates of x-ray-induced lymphoid tumors of strain C57BL/ Ka mice have elicited, on injection into newborn isologous hosts, a lymphoma incidence of 15 to 19 percent. In control mice of the same subline, the incidence of spontaneous lymphoma is about 1 percent. No leukemogenic activity could be detected in filtrates from thymi harvested at 2 to 32 days following completion of x-ray treatment. Activity was evident at 64 days and was perhaps somewhat greater at 128 days. Serial cell-free passage of filtrates in newborn F(1) hybrid mice resulted in a marked increase in lymphoma incidence (69 percent), coupled with a shortening of the median latency. Supplementary x-irradiation failed to enhance the activity of filtrates after neonatal injection.

Animals↗
PubMed1957

Lysis from without of S. aureus K1 by the combined action of phage and virolysin.

LYSIS FROM WITHOUT (LFW) OCCURS IN TWO STEPS: (1) sensitization of cells by phage, which renders the cells susceptible to (2) destruction of an essential cell structure by an extracellular lytic enzyme. Virolysin, from phage-infected cells, was used in these studies. Normal cell autolysin is also effective. Evidence is presented that: 1. Neither phage nor lysin alone causes LFW. 2. Sensitization requires phage adsorption. 3. It can be caused by non-infectious particles. This establishes a new biological activity of the particle. 4. Heat, U.V., detergents, penicillin, and other damaging agents also sensitize cells. 5. Sensitization involves a non-lethal, reversible reaction. 6. Sensitization by phage prevents virus synthesis. Following adsorption, a cell can undergo sensitization or infection but not simultaneously. When only a few particles are adsorbed, infection can occur; when sufficient particles are adsorbed, sensitization takes place. 7. Quantitative aspects of LFW are described. Lysis proceeds logarithmically. The lysis end-point depends upon the phage concentration but is independent of the enzyme concentration.

Bacteriophages↗
PubMed1957

Staphylococcal virolysin, a phage-induced lysin; its differentiation from the autolysis of normal cells.

Virolysin is a lysin which appears in Staphylococcus aureus K(1) cells infected with phage P(14); together with phage, virolysin is released from phage-infected cells at the time of lysis. Autolysin is a lysin formed by uninfected cells of the K(1) strain; autolysin is released from uninfected cells by autolysis. They show the following similarities: Both agents act within the genus Micrococcus. They lyse cells only after the cell has been subjected to a damaging or "sensitizing" treatment, such as heat, bacteriophage, acetone, or ultraviolet irradiation. The course of lysis of heated cells by both lysins has been found to proceed in a similar manner. A constant percentage of cells is lysed, independent of the concentration of lysin; the residual cells remain resistant to either lysin. Lysis proceeds logarithmically with time, and the velocity constants K are proportional to the lysin concentration. K increases with increasing temperature. Both lysins are unaffected by antiserum to the phage. They are inhibited alike by a number of chemicals, including known enzyme inhibitors. Both agents are destroyed by proteolytic enzymes and are precipitated by 40 per cent saturation with (NH(4))(2)SO(4). Both lysins are very thermolabile. The two lysins differ with respect to their pH optimum, antigenic relationship and specificity for Micrococcus lysodeikticus. These results suggest that (1) both lysins have many properties associated with enzymes, (2) the lysis of heated cells, which they produce, has some of the characteristics of a chemical reaction, (3) the lysin from the phage-infected cell is clearly different from the lysin of the uninfected cell.

Autolysis↗
PubMed1957

Immunochemical studies on human plasma lipoproteins.

Low density human plasma lipoproteins S(f) 17+, S(f) 13, and S(f) 6, high density lipoproteins 2 and 3, and a lipoprotein-free plasma protein fraction were isolated from human plasma by ultracentrifugal methods. It was found that human plasma lipoproteins are immunochemically distinct from the non-lipoprotein containing plasma protein fraction. Lipoprotein fractions of a given hydrated density, isolated from different individuals, were found to be immunochemically indistinguishable by qualitative absorption tests. Qualitative antigenic differences were shown to exist between low density lipoproteins and high density lipoproteins. Quantitative precipitin reactions showed that low density lipoproteins S(f) 6 and S(f) 13 were immunochemically very similar. However, they differed with respect to the amount of antigen nitrogen required for maximum precipitation. Agar diffusion analyses were performed; the results suggest heterogeneity of lipoproteins by this criterion.

Antigens↗