A mutation in yeast mitochondrial DNA results in a precise excision of the terminal intron of the cytochrome b gene

The yeast nuclear gene CBP2 was previously proposed to code for a protein necessary for processing of the terminal intron in the cytochrome b pre-mRNA (McGraw, P., and Tzagoloff, A. (1983) J. Biol. Chem. 258, 9459-9468). In the present study we describe a mitochondrial mutation capable of suppressing the respiratory deficiency of cbp2 mutants. The mitochondrial suppressor mutation has been shown to be the result of a precise excision of the last intervening sequence from the cytochrome b gene. Strains with the altered mitochondrial DNA have normal levels of mature cytochrome b mRNA and of cytochrome b and exhibit wild type growth on glycerol. These results confirm that CBP2 codes for a protein specifically required for splicing of the cytochrome b intron and further suggest that absence of the intervening sequence does not noticeably affect the expression of respiratory function in mitochondria.     

Inhibition of chlorophyll synthesis inHordeum vulgare by 3-amino 2,3-dihydrobenzoic acid (gabaculin)

Gabaculin (3-amino 2,3-dihydrobenzoic acid) is shown to be a very potent inhibitor of chlorophyll formation inHordeum vulgate. Exposure of leaf segments to 30/M gabaculin results in an 80% inhibition of chlorophyll synthesis, and this is paralleled by a decrease in carotenoid. Dual-inhibitor studies with dioxoheptanoic acid, which is an inhibitor of inolaevulinic acid dehydratase, show that gabaculin inhibits an earlier step than dioxoheptanoic acid and affects -aminolaevulinic acid synthesis rather than its subsequent metabolism.     

The structure of the cytochrome a3-CuB site of mammalian cytochrome c oxidase as probed by MCD and EPR spectroscopy

The nature of the complexes formed between cytochrome c oxidase and the three inhibitory ligands N3-, CN-, and S2- have been investigated by a combination of MCD and EPR spectroscopy. CN- forms a linear bridge between the Fe III a3 and CuB II, suggesting that the distance between these centers in the oxidized enzyme is between 5 and 5.25 A. This distance is too short to permit N3- to form a linear bridge and the evidence suggests this to be bent. In contrast S2- or SH- is unable to form any bridge and it seems likely that two SH- ions are bound by the bimetallic site, one to Fe III a3 and the other to CuB I. The significance of the a3-CuB distance in terms of oxygen binding and reduction is discussed.     

Activity expressed from cloned Anacystis nidulans large and small subunit ribulose bisphosphate carboxylase genes

Summary The ribulose bisphosphate carboxylase/oxygenase (EC4.1.1.39) (RubisCO) large and small subunit genes from Anacystis nidulans have been cloned as a single fragment into M 13mp10 and pEMBL8 and expressed in Escherichia coli. From M 13mp10 a low yield of enzyme with high specific activity was obtained. The molecular weight of the active enzyme was 260 000 Da and of the inactive enzyme approximately 730 000 Da. The small and large subunits cloned separately did not express activity. The RubisCO gene cloned into pEMBL8 expressed activity up to 22 times that from the M 13 cloned RubisCO DNA. The RubisCO protein produced by the pEMBL cloned gene had a normal MW (550 000). Immunoprecipitation and polyacrylamide gel electrophoresis showed the presence of both large and small subunits.     

Further studies of human whole-body radiofrequency absorption rates

Further studies of human whole-body radiofrequency (RF) absorption rates were carried out using a TEM-cell exposure system. Experiments were done at one frequency near the grounded resonance frequency (approximately 40 MHz), and at several below-resonance frequencies. Absorption rates are small for the K and H orientations of the body, even when grounded. For the body trunk in an E orientation, the absorption rate of a sitting person is about half of the rate for the same person standing with arms at the sides; the latter in turn is about half the rate for the same subject standing with arms over the head. Two-body interactions cause no increase in absorption rates for grounded people. They do, however, increase the absorption rates for subjects in an E orientation in free space; the largest interaction occurs when one subject is lambda/2 behind the other (as seen by the incident wave). When these results are applied to practical occupational exposure situations, the whole-body specific absorption rate does not exceed the ANSI limit of 0.4 W/kg for exposures permitted by the ANSI standard (C95.1-1982) at frequencies from 7 to 40 MHz.     

Complexes prepared from protein A and human serum,IgG, or Fcγ fragments: characterization by immunochemical analysis of ultracentrifugation fractions and studies on their interconversion

Summary Protein A of Staphylococcus aureus is an Fc receptor for IgG that has been used as a therapeutic reagent to treat cancer in humans and experimental animals. We used ultracentrifugation combined with analysis of isolated fractions by radioimmunoprecipitation and competitive radioimmunoassay with chicken antibodies that bind free protein A or protein A in complexes but do bind free immunoglobulin reagents to localize and characterize the types of complexes formed with different molar ratios of ¹²⁵I-protein A and human ¹³¹I-IgG alone or in serum, and ¹³¹1-Fc fragments. This approach offers a distinct advantage over direct counting of radioactivity in the fractions because resolution of complexes and free reagents is much improved. With excess ¹³¹I-IgG or ¹³¹1-Fc, all the ¹²⁵I-protein A is present only in complexes that contained 4 molecules of immunoglobulin reagent and 2 molecules of protein A (4:2 complexes), whereas with excess ¹²⁵I-protein A the stoichiometry of the complexes was 1:1. We have also shown the preformed 4:2 and 1:1 complexes will interconvert in the presence of added excess protein A or IgG, respectively, and that fresh IgG will exchange with IgG or Fc in preformed complexes. Because protein A has been found to elute from an immobilized reagent used in serotherapy of human cancer and is present in a large excess of IgG, the 4:2 complexes may play an active role in the tumoricidal or toxic reactions observed.Abbreviations SpA protein A of Staphyloccus aureus - VBS EDTA gel, 0.0055 M veronal buffered saline containing 0.01 M EDTA and 0.1% gelatin, pH 7.4 - PBS 0.01 M phosphate buffered saline, pH 7.4     

Impact of whooping cough on patients and their families.

The effects of whooping cough were studied in 21 children admitted to hospital with the disease and in their families. The illness caused considerable distress to both child and family. Parents suffered especially from fears for the life and health of their child and from serious loss of sleep. Two months after admission the child''s behaviour was still disturbed, but in most cases the rest of the family had returned to normal. There was much misunderstanding and misinformation about whooping cough among both parents and doctors.     

Effects of the removal of adherent and phagocytic cells on the spleen cell lymphoproliferative response of tumor-bearing mice

Summary Cell-mediated immunity was investigated in two BALB/c mouse tumor systems using the lymphoblastogenesis test with phytohemagglutinin as the mitogen. This lymphoproliferative response was quantitated using the Stimulation Index (SI). There was little evidence for suppressor cell activity in cell mixing experiments in which spleen cells from #51 cell-injected mice were mixed with spleen cells from normal mice. Following macrophage removal by Sephadex G-10 columns and carbonyl iron ingestion, there were no significant changes in the SI values for spleen cells from the #51 cell-injected mice. In contrast, spleen cells from mice injected with H238 cells, a herpes virus-transformed cell line, had a significantly lower SI value than that of normal mice. Suppressor cell activity was demonstrated in cell mixing experiments in which spleen cells from H238 cell-injected mice were mixed with normal spleen cells. Removal of adherent cells from spleen cells from H238 cell-injected mice by Sephadex G-10 columns restored the SI value to that of normal mice. An increased SI value was also seen after removal of phagocytic cells by carbonyl iron. These results suggested that cells with the functional properties of macrophages played an important part in the immunosuppression observed in the H238 tumor system. Comparison of the two macrophage depletion methods suggested that another cell population was also involved in the suppressive effect. Results of immunofluorescent techniques with anti-Lyt-1 and anti-Lyt-2 monoclonal antibodies show these cells to be Ly 1^–, Ly 2,3⁺ phenotypes of T-lymphocytes.