ABSTRACT
The typical situations found in in situ gamma spectrometry have been simulated by Monte Carlo techniques to obtain the energy spectra of the photon fluence rate existing at 1 m above ground. The main difficulty found with the model is its slow convergence. A method to speed up the calculation has been derived. The results of the model have been thoroughly tested against existing data. In a final stage, the specific activity to H*(10) conversion coefficients have been derived for the typical scenarios encountered in the in situ gamma spectrometry.
Subject(s)
Gamma Rays , Spectrometry, Gamma , Monte Carlo Method , Scattering, RadiationABSTRACT
A phosphatidylcholine-like phospholipid expressed in the outer leaflet of the cell membrane shortly after mitogenic activation of T-cells is described, based on the binding of monoclonal antibody 90. 60.3. Expression of the 90.60.3 phospholipid antigen in T-cells is activation-dependent. Once expressed, the 90.60.3 phospholipid is in direct physical association with the interleukin-2 (IL-2) binding domain of IL-2 receptor alpha subunits, but does not affect IL-2 binding. The association is specific, because the 90.60.3 phospholipid is not found in association with other domains of IL-2 receptor alpha subunits, or near IL-2 receptor beta or gamma subunits. Culturing cytokine-dependent cell lines in the presence of monoclonal antibody 90.60.3 potentiates IL-2-dependent cell survival and proliferation in a dose-dependent manner. In contrast, IL-4-dependent responses are not potentiated. Taken together, the data suggest that specific plasma membrane phospholipids expressed in the outer leaflet after T-cell activation associate with the IL-2 binding domain of IL-2 receptor alpha subunits (and perhaps other cytokine receptors), and may play a role in regulating receptor mobility or signal transduction.
Subject(s)
Cell Membrane/metabolism , Phospholipids/metabolism , Receptors, Interleukin-2/metabolism , T-Lymphocytes/metabolism , Animals , Antibodies, Monoclonal/immunology , Epitopes/immunology , Lymphocyte Activation , Mice , Mitogens , Phospholipids/chemistry , Phospholipids/immunology , Receptors, Interleukin-2/chemistry , Receptors, Interleukin-2/immunology , Signal TransductionABSTRACT
A novel surface receptor complex involved in inhibition of T-cell proliferation is described. Biochemical isolation revealed two non-covalently associated proteins of about M(r) 65,000 (p65) and 95,000 (p95). These polypeptides may be related. The p65 form is expressed after cellular activation and replication and is recognized by monoclonal antibody (mAb) 87.92.6 or reovirus hemagglutinin as unnatural ligands. The p95 species is associated with tyrosine kinase enzymatic activity. Receptor ligation results in rapid alteration of the phosphotyrosine content of cellular substrates, and this activity correlates with antiproliferative effects. The inhibition of proliferation is a time-dependent reversible arrest at the G1-S phase of the cell cycle. Activation through the T-cell receptor, protein kinase C, or addition of cytokines does not reverse the antiproliferative effect. This receptor complex may define novel features of T-cell proliferation.
Subject(s)
Lymphocyte Activation , Receptors, Cell Surface/metabolism , Reoviridae/metabolism , Signal Transduction/physiology , T-Lymphocytes/metabolism , Animals , Antibodies, Monoclonal , G1 Phase , Hemagglutinins, Viral/metabolism , Lymphocyte Activation/drug effects , Mice , Mice, Inbred BALB C , Mice, Inbred CBA , Mitogens/pharmacology , Molecular Weight , Phosphoproteins/metabolism , Protein-Tyrosine Kinases/metabolism , Receptors, Cell Surface/biosynthesis , Receptors, Cell Surface/chemistry , Receptors, Virus/metabolism , T-Lymphocytes/immunologyABSTRACT
Four different strains of Creutzfeldt-Jakob disease virus (2 primary and 2 passaged in primates or mice) were inoculated intra-cerebrally into squirrel monkeys implanted with continuously-recording indwelling electrodes. Simultaneous EEC and videotape recordings were made on unrestrained animals. In addition EEG recordings were made of evoked visual potentials on restrained animals. EEG abnormalities appeared in every animal before the first clinical signs (6 to 20 months after inoculation) and included generalized slowing, epileptiform patterns and occasional episodes of pseudo-periodic activity. Abnormal evoked visual potentials and disturbances of consciousness were also noted. All viral strains produced similar disorders and the death of inoculated animals. The relative frequency of epilepsy seen in the CJD-inoculated squirrel monkey contrasts with its irregular occurrence in most other monkey species, and its total absence in the spider monkey. This could be related to the lesser complexity of neo-cortical evolution in the squirrel monkey and a less pronounced development of inhibitory CNS mechanisms under the general control of GABA-ergic neurons.
