Antimetabolic activities of 2-fluoro-L-histidine.

2-Fluoro-L-Histidine inhibits protein synthesis in various cell cultures, as measured by ³H-leucine incorporation. This histidine analog also inhibits the cytopathogenicity of a number of RNA and DNA viruses in primary and continuous cell cultures; it blocks the transformation of normal mouse (MO) cells by murine sarcoma virus, and partially suppresses the release of murine leukemia virus by a continuously infected mouse cell line (JLSV5). In human skin fibroblasts, it reduces the interferon-inducing capacity of poly(I)·poly(C). Inhibition of cell protein synthesis may be the common cause of the various effects. 4-Fluoro-L-histidine is essentially inert in all of the test systems examined.     

Macrophage function in tumor-bearing mice: dissociation of phagocytic and chemotactic responsiveness

Infusion of CBA mice with lymphoid cells from the H-2 compatible but Mls-antigen incompatible C3H × CBA hybrid results in a specifically reduced capacity of the recipients lymphocytes to react in the MLC against C3H-cells. Although this reduction is immunologically specific the results of this investigation have shown that such mice exhibit a strongly reduced capacity to produce humoral antibodies against heterologous erythrocytes and a T-cell independent antigen (PVP).     

Biochemical research on oogenesis. RNA accumulation during oogenesis of the dogfish Scyliorhinus caniculus

Four biochemical mechanisms have been shown to operate in the oocytes of amphibians and teleosts: (1) amplification of the 28 S and 18 S genes, (2) noncoordinate accumulation of 5 S RNA and 28 S + 18 S RNA, (3) storage of 5 S and transfer RNA made in excess by small oocytes within nucleoprotein particles, (4) expression of different 5 S genes in oocytes and somatic cells. We have tried to extend these observations to another group of vertebrates, i.e., selacians (Chondrichthya). Our data suggest that ribosomal gene amplification is low or absent in the oocytes of the dogfish Scyliorhinus caniculus. However, previtellogenic oocytes of this species accumulate more 5 S RNA than needed for ribosome assembly. Transfer and 5 S RNA present in small oocytes are probably not free in the cell sap. A substantial fraction of these RNAs sediments at 10 S when homogenates of immature ovaries are centrifuged in sucrose density gradients. In contrast to what we observed in amphibians and teleosts, 5 S RNA from ovaries of S. caniculus is identical in sequence to 5 S RNA from liver. Among the four mechanisms mentioned above, the second and probably the third one are used by the oocytes of S. caniculus. Mechanism (4) is absent in this species. No definitive conclusion can be drawn concerning mechanism (1), i.e., ribosomal gene amplification.     

Concanavalin A binding to brain particulate preparations and its effect on adenylate cyclase.

[³H] -Concanavalin A binding to brain particulate preparations measured by a filtration technique was found to show a characteristic regional specificity with the caudate-putamen area exhibiting the greatest density of concanavalin A (con A) binding sites. The synaptic membranes were shown to be the most highly enriched of the subcellular fractions examined in terms of lectin-binding glycoproteins. Con A was also shown to inhibit the basal adenylate cyclase activity of cerebral, cerebellar, and caudate-putamen particulate preparations in a concentration-dependent manner. This lectin sensitivity of the adenylate cyclase is apparently an intrinsic property of the enzyme complex since a detergent dispersed preparation of the cerebral cortical enzyme was equally inhibited by con A. It is proposed that one of the membrane con A binding sites in brain tissue is a component of the adenylate cyclase system.