Role of H-2 antigens in the host response to methylcholanthrene-induced tumors

H-2 loss variant sublines of a sarcoma (M-AS), induced by methylcholanthrene in an (A × A.SW)F₁ mouse, were used to study the role of the MHC products in the recognition of MC-TSTA. The two reciprocal variant sublines (M-A and M-S) were found to express the TSTA of the original tumor as shown by cross-reactions in graft rejection experiments performed in (A × A.SW)F₁ mice. In the A/Sn and A.SW mice the presence of the reciprocal parental H-2 antigens on the immunizing cells decreased the response against the tumor antigens. An admixture of lymphocytes derived from hyperimmune mice inhibited the outgrowth of the tumor cells. The growth inhibition was mediated by T cells and was H-2 restricted. Cells derived from hyperimmune syngeneic mice inhibited the outgrowth of the variant subline used for immunization but had no effect on the reciprocal variant subline.     

Photoaffinity labeling of mitochondrial adenosine triphosphatase by an azido derivative of the natural adenosine triphosphate inhibitor

The natural mitochondrial ATPase inhibitor (IF1) was modified with a radioactivity labeled heterobifunctional and photosensitive reagent, methyl 4-azido(14C)benzimidate ((14C)MABI). Titration experiments of IF1 by (14C)MABI and tryptic maps of (14C)MABI-IF1 indicated that specific lysine residues in IF1 are preferentially labeled by (14C)MABI. Under appropriate conditions of labeling (1 to 2 lysine residues modified per IF1), MABI-IF1 exhibited the same inhibitory potency as native IF1 on the hydrolytic activity of the coupling factor 1 of mitochondrial ATPase (F1). The same conditions were required for inhibition of F1 by MABI-IF1 and IF1 (slightly acidic pH and presence of ATP and MgCl2). In photolabeling experiments, (14C)MABI-IF1 was used to investigate the localization of IF1 binding sites on F1. Upon photoirradiation, MABI-IF1 bound selectively to the beta subunit of soluble or membrane-bound F1. Adenylyl imidodiphosphate and quercetin, two compounds which partially mimic the inhibitory effect of IF1 on ATPase activity of F1, markedly prevented the binding of (14C)MABI-IF1 to F1; on the other hand, aurovertin, a specific ligand of the beta subunit of F1, did not affect the interaction between (14C)MABI-IF1 and F1. In the absence of light, (14C)MABI-IF1 was used as a reversible radiolabeled ligand with respect to membrane bound F1 to investigate F1-IF1 interactions to inside-out submitochondrial particles as a function of the energy state of the particles. Oxidation of NADH by submitochondrial particles resulted in a decrease of bound (14C)MABI-IF1; the effect was counteracted by antimycin. The data suggested that added (14C)MABI-IF1 is capable of exchanging with IF1 bound to F1 in submitochondrial particles and that the rate and extent of (14C)MABI-IF1 release are triggered by the proton-motive force developed by the particles.     

Interaction of alkyl ammonium derivatives with red cells: Hemolysis and sodium pump inhibition studies

Summary Members of four homologous series of tetra-alkyl ammonium bromides (R ₃N⁺(CH₂) _n–1·CH₃Br^– whereR=H, CH₃ or C₂H₅ andRN⁺H₃Br^– whereR represents the isomeric butyl series) have been synthesized and tested as sodium pump inhibitors, measured as ouabain-sensitive K⁺ influx, and as hemolytic agents on human red cells.Potency for both effects is presented graphically, plotting the logarithm of the concentration for half maximal effect against alkyl chain length. Both hemolysis and pump inhibition studies yielded a biphasic response consisting of two good straight lines, with effectiveness increasing up to C10–12 and then remaining constant up to C20.For hemolysis the alkyl ammonium series was most effective. The calculated free-energy change per methylene group was the same for three series of compounds, but the free-energy contribution from the headgroup was lower for the ammonium series.In contrast, although pump inhibition studies also yielded simple biphasic plots, inhibition occurred at 3- to 50-fold lower concentrations and there were significant differences between the three series, both in the free-energy changes per methylene group and in the headgroup contributions.We have analyzed these results thermodynamically to take account of hydrophobic interactions and the conformation of the alkyl chains.     

Activated T lymphocytes within human solid tumors

Summary The majority of lymphocytes separated from tumor cell suspensions were T cells. Conjugates of T lymphocytes and tumor cells were often seen. Variable numbers of T cells exhibited signs of activation such as the ability to form stable E rosettes and attachment to normal and malignant cells (a phenomenon designated natural attachment: NA). A proportion of T cells activated in vitro by allogeneic stimulation regularly exhibit these properties. The T cell-tumor conjugates in the suspensions may represent the NA phenomenon, but they could also be the product of T cells that adhere on the basis of specific recognition of cell surface antigens.Abbreviations BBS balanced salt solution - E rosettes rosettes formed with sheep erythrocytes - EA rosettes rosettes formed with ox erythrocytes coated with anti-ox IgG - FCS fetal calf serum - MLC mixed lymphocyte cultures - NA natural attachment - PBL peripheral blood lymphocytes - SRBC sheep erythrocytes - T lymphocytes thymusderived lymphocytes     

Population characteristics and the distribution of general medical practitioners.

By applying the logic of the Resource Allocation Working Party to the analysis of the distribution of general medical practitioners, the relevant Family Practitioner Committee (FPC) populations were weighted according to known patterns of use related to specific characteristics--namely, age, sex, marital state, and socioeconomic group. Comparative weightings were also calculated using standardised mortality ratios. Adjusting the populations to take account of differential use has relatively little impact on national variations in list sizes but an appreciable effect on particular FPCs, notably East and West Sussex, Dorset, and the Isle of Wight. Inequalities in the distribution of general practitioners are increased considerably, however, if figures taking account of the inflation of list sizes and cross-boundary flows are used. To formulate and monitor policy about the distribution of general practitioners more sensitive measures of population and its likely demand for services must be developed.     

Large scale preparation of purified exocellular DD-carboxypeptidase–transpeptidase of Streptomyces strain R61

The exocellular DD -carboxypeptidase–transpeptidase that Streptomyces R61 excretes during growth has been produced in large fermentation units of 15 m³ total capacity. The yield from 15,000 liter culture filtrate was 1.080 g purified enzyme (92% purity) with a total recovery of 29% and at least a 2000-fold increased specific activity.     

Cultivation with K562 cells leads to blastogenesis and increased cytotoxicity with changed properties of the active cells when compared to fresh lymphocytes.

Lymphocytes from healthy donors were cultivated with K562, a cell line sensitive to natural cytotoxicity and lacking HLA antigens. Blastogenesis and cytotoxicity were generated in the presence of the serum of the lymphocyte donor. The anti K562 killing effect of the cocultivated populations exceeded considerably that of the fresh lymphocytes. In the majority of cases lymphocytes cultured alone had no cytotoxic activity.We have attempted to characterize the active lymphocyte subset, using the fractionation procedure designed for fresh lymphocytes. Separation of T cells on the basis of SRBC rosetting was not efficient because a high proportion of E rosettes remained in the interface when centrifuged on the Ficoll. Furthermore a high number of E rosetting cells adhered to nylon wool.The cytotoxic potential of various fractions correlated to the presence of blasts and EA positive cells. The least active population was the non-adherent, E rosette sedimented one. The cytotoxicity was not restricted to the sensitizing K562 cell line.     

Electron transport in the cni-1 mutant of Neurospora crassa.

1. Mitochondria from the nuclear mutant cni-1 have no optically detectable cytochrome aa3 in early log phase growth. These mitochondria have a high level of respiration that is not inhibited by cyanide but is inhibited by salicylhydroxamic acid. They also show a substantial amount of cyanide-sensitive respiration. 2. As cultures of mutant cni-1 age, flux through the hydroxamate-sensitive pathway decreases markedly while flux through the cytochrome chain remains constant. 3. Growth studies with mutant cni-1 indicate that the cytochrome chain in this mutant is more important in supporting growth than the hydroxamate-sensitive pathway. 4. Measurements of the steady-state level of reduction of cytochrome c in mutant cni-1 indicate that the rate-limiting step in the cytochrome chain is at the position occupied by cytochrome oxidase. 5. Electron spin resonance studies with cni-1 mitochondria show normal cytochrome oxidase signals in the g approximately 6 region although there is little or no optically detectable cytochrome aa3.