A modified method of UDS detection in vitro suitable for screening the DNA-damaging effects of chemicals

The UDS induced in cultured FL cells by exposure to chemicals was measured as hydroxyurea-resistant incorporation of 3H-TdR in the acid-insoluble fraction of the 14C-TdR-prelabelled cells synchronized by the combination of arginine starvation and pretreatment with hydroxyurea. The level of UDS is represented by the ratios of 3H/14C radioactivities which are measures of specific activities of 3H. Two direct-acting alkylating agents, MMS and MNNG, a cross-linking agent, mitomycin C, and 3 procarcinogens, B(a)P, AFB1 and cyclophosphamide elicited UDS in the absence or presence of the liver-metabolizing system. Three chemicals of unknown carcinogenicity were also able to induce UDS in this assay system, i.e., bis-(O,O-diethylphosphinothioyl)-disulphide, 4-chlorophenoxy acetic acid (sodium salt) and caramelized malt sugar. With the exception of 4-chlorophenoxy acetic acid, they were also active in the Ames test.     

Calcium reduces the sodium permeability of luminal membrane vesicles from toad bladder. Studies using a fast-reaction apparatus

Regulation of the sodium permeability of the luminal membrane is the major mechanism by which the net rate of sodium transport across tight epithelia is varied. Previous evidence has suggested that the permeability of the luminal membrane might be regulated by changes in intracellular sodium or calcium activities. To test this directly, we isolated a fraction of the plasma membrane from the toad urinary bladder, which contains a fast, amiloride-sensitive sodium flux with characteristics similar to those of the native luminal membrane. Using a flow-quench apparatus to measure the initial rate of sodium efflux from these vesicles in the millisecond time range, we have demonstrated that the isotope exchange permeability of these vesicles is very sensitive to calcium. Calcium reduces the sodium permeability, and the half-maximal inhibitory concentration is 0.5 microM, well within the range of calcium activity found in cells. Also, the permeability of the luminal membrane vesicles is little affected by the ambient sodium concentration. These results, when taken together with studies on whole tissue, suggest that cell calcium may be an important regulator of transepithelial sodium transport by its effect on luminal sodium permeability. The effect of cell sodium on permeability may be mediated by calcium rather than by sodium itself.     

The use of acetylated cytochrome c in detecting superoxide anion production in rabbit alveolar macrophages

Polymorphonuclear phagocytes have been shown to undergo marked alteration in oxidative metabolism during phagocytosis. These alterations, collectively known as the "respiratory burst", include increased glucose oxidation through the hexose monophosphate shunt (1), increased oxygen consumption (1), and increased superoxide (O-2)3 (2) and H2O2 production (3). Similar metabolic events have also been shown to occur in the rabbit alveolar macrophage (AM). There is consistent evidence that the macrophage undergoes increased oxygen consumption (4-6) and hexose monophosphate shunt activity (4-9) upon phagocytosis. There are conflicting data, however, concerning the ability of the macrophage to produce O-2. Some studies suggest that macrophages are incapable of producing measurable amounts of O-2 upon phagocytosis (7, 10-12). Other studies, however, suggest that macrophages are indeed capable of producing substantial amounts of O-2 during phagocytosis (8, 13-15). This study was designed to resolve the discrepancies in the literature concerning O-2 production in macrophages.     

An analysis of the sensitivity of somatic cell hybrids to natural killer cell- and natural cytotoxic cell-mediated lysis

The analysis of the NK and NC sensitivity of somatic cell hybrids formed between parental cell lines that differ in their NK and NC sensitivity has shown the following. 1) The dominant expression of both NK and NC recognition determinants on target cells; 2) the dominant expression of two post-recognitive NC resistance mechanisms, one requiring protein synthesis and one being protein synthesis independent; and 3) the dominant expression of a post-recognitive NK resistance mechanism, which is protein synthesis independent. The post-recognitive protein synthesis-independent NC resistance mechanism confers no NK resistance and the post-recognitive NK resistance mechanism confers no NC resistance. Whether the post-recognitive protein synthesis-dependent NC resistance mechanism confers NK resistance remains open to question. The analysis of the hybrids indicates that transformed cells become sensitive to either NK- or NC-mediated lysis by losing their resistance to the lytic activity of these effector cells, and it appears that differentiation plays a role in determining whether NK or NC resistance will be lost upon transformation. A model is proposed in which the differentiation into a fibroblast associates the loss of NC resistance with transformation, whereas the differentiation into a lymphocyte associates the loss of NK resistance with transformation. Because the loss of NK resistance is not associated with the transformation of fibroblasts, they remain NK resistant, and because the transformation of lymphocytes is not associated with the loss of NC resistance, they remain NC resistant. This provides the basis for the target specificity exhibited by NK and NC effectors.     

SMAS-platysma face lift

Correction of laxity in the submental area and of hypertrophic neck cords has been enhanced with the SMAS-platysma face life over that which was achieved with a standard skin face lift. Evaluation of a 6-year experience with the SMAS-platysma face lift reveals that the operation can be safely performed with an acceptably low incidence of complications. The incidence of hematoma and associated complications is less than that which occurs when cervical and submental defatting is performed in conjunction with a skin face lift.     

Preparation of [B23-D-alanine]des-(B25-B30)-hexapeptide-insulin by a combination of enzymic and non-enzymic synthesis.

Des-(B25-B30)-hexapeptide-insulin with B23-glycine replaced by D-alanine was prepared by a combination of enzymic and non-enzymic syntheses. The purified product was homogeneous in polyacrylamide-gel electrophoresis and could be crystallized. The biological activity in vivo of crystalline [B23-D-Ala]des-(B25-B30)-hexapeptide-insulin was determined as 58% of that of standard pig insulin (27 i.u./mg).     

Growth and survival of fuel isolates in hydrocarbon-fuel emulsions

Two fuel utilizers, a strain of Pseudomonas aeruginosa and a Hormodendrum sp., and two fuel isolates which did not use fuel, Staphylococcus and Bacillus spp., were tested for ability to survive and grow in systems containing emulsified or nonemulsified forms of JP-4 jet fuel. Neither emulsion (Alamac no. 1 or Alamac no. 2) supported microbial growth without a water phase. Growth of P. aeruginosa in liquid systems containing either emulsion was not significantly different from growth in liquid systems with nonemulsified fuel. The Hormodendrum sp. grew well in a liquid medium containing nonemulsified JP-4, but when either of the emulsions served as carbon source no growth was observed. However, good growth was noted on spread plates with either emulsion. Viable cells of Bacillus sp. did not increase over a 4-day period, and Staphylococcus sp. did not survive in liquid systems containing JP-4 or emulsions.