Antibody-dependent cellular cytotoxicity-mediated serotherapy against murine neuroblastoma

Summary The in vitro and in vivo activity has been investigated of antisera prepared against a murine (C-1300) neuroblastoma line (MNB) capable of differentiation. An antibody-dependent cellular cytotoxicity (ADCC) reaction was employed using rat spleen cells (RSC). ADCC activity in vitro (using ⁵¹Cr-release) was shown, but a maximum of only 50% of the immunologically releasable ⁵¹Cr was achieved. Nevertheless, in vivo (syngeneic mouse-tumor flank assay) significant delays were obtained in tumor onset and lethality. Under ideal circumstances, i.e., coating of tumor cells prior to inoculation and high RSC effector cell ratios, a significant number of animals could be cured of substantial tumor burdens (10⁶ cells). While close proximity of the site of injection of effector cells was required (ectopic injections of RSC were ineffective), the anti-MNB ADCC was shown to be quite active in vivo without external precoating of the cells with antisera. RCS obtained from BCG-treated rats were more numerous and slightly more effective. RSC obtained from -radiated animals retained normal activity. With appropriate antisera this approach could be useful under selected clinical circumstances.     

The Benzodiazepine/GABA Receptor Complex: Molecular Size in Brain Synaptic Membranes and in Solution

Abstract: The molecular size of the benzodiazepine (BZ) receptor in the synaptic membrane of brain cortex (bovine or rat) was determined by an improved version of the radiation inactivation method to be 220,000. An identical size was found simultaneously for the associated γ-aminobutyric acid (GABA) receptor and for the component binding β-carboline esters. It is proposed that all three activities reside in a single protein or protein complex in the membrane. The size in solution, after extraction into Triton X-100 medium from exhaustively washed membranes, was estimated by sedimentation constant (9.4S) and by gel filtration (∼230,000 apparent MW), again with the BZ and GABA binding activities behaving identically. This size applies to the component that undergoes photoaffinity labelling by [³H]flunitrazepam in the membrane, and contains a 51,000 M_r polypeptide as the BZ-binding subunit. It is concluded that a protein complex or oligomer of 200,000–220,000 MW carries a class of BZ-binding sites and an associated class of GABA_A sites.     

Cell-free synthesis of glial fibrillary acidic protein

Glial fibrillary acidic (GFA) protein has been synthesized in an RNA-dependent cell-free system derived from rabbit reticulocytes. The cell-free synthesized product appears to have the same size as GFA protein isolated from bovine spinal cord, thus showing that GFA protein does not undergo detectable proteolytic processing.     

A Genetically Distinct Form of Cyclic Amp Phosphodiesterase Associated with Chromomere 3d4 in DROSOPHILA MELANOGASTER

Two cyclic AMP phosphodiesterase enzymes (E.C.3.1.4.17) are present in homogenates of adult Drosophila melanogaster. The two enzymes differ from one another in heat stability, affinity for Mg++, Ca++ activation and molecular weight. They do not differ markedly in their affinities for cyclic AMP, and both exhibit anomalous Michaelis-Menten kinetics. The more heat-labile enzyme is controlled in a dosage-dependent manner by chromomere 3D4 of the X chromosome and is absent in flies that are deficient for chromomere 3D4. Chromomere 3D4 is also necessary for the maintenance of normal cAMP levels, for male fertility, and for normal female fertility and oogenesis. The structural gene(s) for the more heat-stable enzyme is located outside of chromomeres 3C12-3D4. Whether 3D4 contains a structural gene, or a regulatory gene necessary for the presence of the labile enzyme, remains to be determined.     

Evidence for antiferromagnetic exchange coupling in the tetranuclear high potential iron-sulfur protein of Rhodopseudomonas gelatinosa.

EPR spectra of oxidized $\text{R. gelatinosa}$ HiPIP demonstrate two kinds of temperature dependent changes which can be analyzed in terms of an excited state at 142 ± 10cm^?1 and a second excited state at 490 ± 100cm^?1. These states represent further verification of antiferromagnetic exchange among the 4 irons in this tetranuclear cluster, with a value for the coupling constant of J = ?44cm^?1. Aside from resonance Raman spectroscopic results, this is the first report of a ladder of excited states predicted for exchange coupled ions.     

Bend propagation in flagella. I. Derivation of equations of motion and their simulation.

A set of nonlinear differential equations describing flagellar motion in an external viscous medium is derived. Because of the local nature of these equations and the use of a Crank-Nicolson-type forward time step, which is stable for large deltat, numerical solution of these equations on a digital computer is relatively fast. Stable bend initiation and propagation, without internal viscous resistance, is demonstrated for a flagellum containing a linear elastic bending resistance and an elastic shear resistance that depends on sliding. The elastic shear resistance is derived from a plausible structural model of the radial link system. The active shear force for the dynein system is specified by a history-dependent functional of curvature characterized by the parameters m0, a proportionality constant between the maximum active shear moment and curvature, and tau, a relaxation time which essentially determines the delay between curvature and active moment.     

Selective pericentromeric heterochromatin dismantling caused by TP53 activation during senescence

Cellular senescence triggers various types of heterochromatin remodeling that contribute to aging. However, the age-related mechanisms that lead to these epigenetic alterations remain elusive. Here, we asked how two key aging hallmarks, telomere shortening and constitutive heterochromatin loss, are mechanistically connected during senescence. We show that, at the onset of senescence, pericentromeric heterochromatin is specifically dismantled consisting of chromatin decondensation, accumulation of DNA breakages, illegitimate recombination and loss of DNA. This process is caused by telomere shortening or genotoxic stress by a sequence of events starting from TP53-dependent downregulation of the telomere protective protein TRF2. The resulting loss of TRF2 at pericentromeres triggers DNA breaks activating ATM, which in turn leads to heterochromatin decondensation by releasing KAP1 and Lamin B1, recombination and satellite DNA excision found in the cytosol associated with cGAS. This TP53–TRF2 axis activates the interferon response and the formation of chromosome rearrangements when the cells escape the senescent growth arrest. Overall, these results reveal the role of TP53 as pericentromeric disassembler and define the basic principles of how a TP53-dependent senescence inducer hierarchically leads to selective pericentromeric dismantling through the downregulation of TRF2.