Isolation and characterization of the rabbit prt gene product

The product of the rabbit prt gene (PRT), a gene linked to the immunoglobulin κ-light chain gene ab, was purified from rabbit serum by precipitation with ammonium sulfate and by chromotography on DEAE-Sephadex and Sephacryl S300. Analysis of PRT indicated that it was associated rabbit hemopexin; the molecular weight of PRT (i.e., 68,000), as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was similar to the reported molecular weight of rabbit hemopexin; the PRT phenotypes correlated with the phenotypes of a hematin binding protein; PRT itself bound hematin; and the amino acid composition of PRT was similar to the amino acid composition of rabbit hemopexin. The prt gene, however, need not be the structural gene for hemopexin; it may encode a glycosyl transferase responsible in part for the carbohydrate associated with the protein.     

Enolase isozymes from Ricinus communis: Partial purification and characterization of the isozymes

The plastid and cytosolic isozymes of enolase from developing endosperm of castor oil seeds, Ricinus communis L. cv. Baker 296, were separated and partially purified. Each purified isozyme had a specific activity of approximately 200 μmol min^?1 mg protein. The isozymes have similar pH optima for the forward reaction, but different optima for the reverse reaction. The divalent metal specificity is the same for both isozymes. In addition to differences in charge, the isozymes can be distinguished by their different kinetic constants, thermostability and sensitivity to fluoride inhibition. Antibodies against yeast enolase isozyme I cross-react with Ricinus plastid enolase but not with the cytosolic isozyme.     

Growth regulation in Hydra: Relationship between epithelial cell cycle length and growth rate

The relationship between epithelial cell production and growth rate was investigated in Hydra attenuata under different feeding regimes. The increase of epithelial cell number was compared to the duration of the epithelial cell cycle using standard methods of cell cycle analysis. The results indicate that cell cycle changes accompanying changes in feeding regime are not sufficient to explain the altered growth rate. Under heavy feeding regimes, epithelial cell production equals tissue growth rate. At low feeding level or under starvation conditions the epithelial cell cycle lengthens and growth rate of epithelial cell population is slowed. However, the cell cycle changes are insufficient to account for the reduction in tissue growth and thus there is an effective overproduction of epithelial cells amounting to 10% per day. Evidence suggests that these excess cells are phagocytized by neighboring cells in the tissue. Thus phagocytosis is directly or indirectly involved in regulating the growth of hydra tissue.     

Mixed-Culture Fermentor for Simulating Methanogenic Digestors

Propionate degradation in an anaerobic digestor degrading animal waste (10-day retention time, 5.75 g liter⁻¹ day⁻¹ volatile solids loading rate, 40°C) was 0.304 mM h⁻¹, measured with [2-¹⁴C]propionate; this value indicated that CH₄ produced from propionate accounted for 14.8% of the CH₄ produced in the digestor (34.5%, including acetate produced from propionate). The mean propionate concentration was 0.67 mM, giving a propionate turnover rate of 0.46 h⁻¹. A continuous-, mixed-culture fermentor was developed to mimic the digestor. When degradation rates of methanogenic precursors (H₂, CO₂, and acetate) equalled those measured in the digestor, propionate degradation was inhibited. When the H₂ turnover rate was lowered by decreasing addition of H₂-generating substrates or by allowing a portion of the H₂ degradation to occur in an isolated compartment, propionate degradation in the fermentor resumed. The possibility is discussed that in digestors, much of the H₂ is produced and degraded within microenvironments associated with particles. Thus, the gross turnover rate of H₂ measured in digestors is an average, and specific microenvironments within the digestor may have different rates of turnover.     

Identification of Frankia Strains by Two-Dimensional Polyacrylamide Gel Electrophoresis

Fifteen Frankia strains from five different plant species were analyzed by two-dimensional polyacryl-amide gel electrophoresis to determine their relatedness by comparing the polypeptide patterns obtained. Three major subgroups (A, C, and D) were found in the Alnus-Comptonia-Myrica cross-inoculation group. An isolate from Purshia tridentata had a unique protein pattern and represents a distinct group of frankiae. Members of group A were isolated from root nodules of Alnus incana subsp. rugosa and Alnus viridis subsp. crispa. Group C organisms were from A. incana subsp. rugosa and Comptonia peregrina nodules, and group D organisms were from A. incana subsp. rugosa, A. viridis subsp. cripsa, and Myrica pensylvanica root nodules. Isolates from each gel group were obtained at several widely separated geographical locations. The results indicate that two-dimensional polyacrylamide gel electrophoresis is useful for identifying Frankia isolates.     

Cell division cycle in mammalian cells : VIII. Mapping of G1 into six segments using temperature-sensitive cell cycle mutants

The G1 blocks in three temperature-sensitive (ts) Syrian hamster cell-cycle mutants have been mapped in relation to other G1 landmarks. Two mutants reported here, ts-559 and ts-694, show defective progression only in G1. When shifted from the permissive temperature of 33 degrees C to the non-permissive temperature of 39 degrees C, G1 cells of these two mutants show no further cell cycle progression, while cells in S, G2 and mitosis progress through the cell cycle but become blocked after entering G1. The two mutants complement each other, and also complement the previously reported mutant ts-550C with blocks in both G1 and G2 of the cell cycle. The locations of the G1 blocks in both ts-559 and ts-694 are before the hydroxyurea arrest point. The G1 ts point in ts-694 is prior to the isoleucine deprivation and serum starvation points, while the G1 block in ts-559 is after the serum starvation point but before the isoleucine block. Other G1 block points which have been reported are in mutants of different species and isolated in different laboratories, causing difficulties for relative positioning of the blocks in G1. The mutants for mapping in this study have been isolated from the same cell line. The G1 ts arrest points of ts-559 and ts-694, and that found in ts-550C, together with nutritional deprivations and metabolic inhibitors, provide seven reference points which divide G1 into six segments, each of which is bracketed by two adjacent points: mitosis, ts-694 block, serum starvation arrest point, ts-559 block, isoleucine deprivation arrest point, ts-550C block, hydroxyurea or excess-thymidine arrest segment.     

Development of tannin vacuoles in chalaza and seed coat of barley in relation to early chalazal necrosis in the seg1 mutant

Structural development of grain tissues of maternal origin in normal and seg1 barley (Hordeum vulgare L. cv. Betzes) was examined using light and electron microscopy. Chalaza and seedcoat cells of normal grains developed prominent tannin vacuoles which persisted throughout the grain-filling period. Tannins were present in the same tissues of seg1, but no large central vacuoles developed. Instead, the chalaza and nucellar projection degenerated and were crushed, presumably terminating sugar flow and causing formation of shrunken grains (35–55% normal dry weight). Tannins were localized using various histochemical stains. Extracts of chalaza and adjacent tissues contained proanthocyanidins which yielded delphinidin and cyanidin upon hydrolysis in boiling HCl. We suggest that the basis of the seg1 phenotype may be abnormal compartmentation of tannins causing precipitation of cytoplasmic proteins and early death of chalazal cells.Abbreviations FAA Formalin-acetic acid-ethanol - PAS periodic acid Schiffs reagent     

A followup study of the academic attainment and classroom behavior of children with elevated dentine lead levels

To investigate the impact of low-level lead exposure on children's behavior within a natural setting, we assessed the school performance of a sample of 141 elementary school children classified according to dentine lead level. Twenty-two children had “elevated” levels (≥20 parts per million), 71 had “midrange” levels (10.0–19.9 parts per million), and 48 had “low” levels (<10 parts per million). Four types of outcome data were collected: (1) scores on a standardized group intelligence test, (2) teachers' ratings, (3) incidence of academic failure (assignment to remedial aid, grade retention), and (4) observations of classroom behavior. In general, higher dentine lead levels were associated with less favorable school performance, with most covariance-adjustedp-values in the range of 0.05–0.15. The incidence of grade retention was the outcome most strongly related to lead level. The pattern of results suggests a consistent, though weak relationship between children's dentine lead levels and elementary school performance.     

Isolated soluble fractions from the murine B16 melanoma induce primary in vitro syngeneic antitumor responses

Summary This paper extends our previous studies, which documented our ability to isolate immunogenic entities from nonimmunogenic or weakly immunogenic tumors.B16 melanoma cells failed, in our in vitro experimental system, to induce anti-B16 cytotoxic responses in spleen cells derived from normal syngeneic C57BL/6 mice. The B16 melanoma cellular homogenate was fractionated on an Ultrogel AcA 34 column, and the various fractions were tested for their ability to induce anti-B16 cytotoxic responses under the same conditions as those used for intact B16, the nonimmungenic tumor cells. Certain fractions, some of them with relatively low protein concentrations, induced anti-B16 cytotoxic responses in spleen cells of normal C57BL/6 mice, whereas others, some of them with relatively high protein concentrations, failed to induce such responses. One fraction (Fr.), designated Fr. 5/6, was examined in detail. It was found that in normal syngeneic spleen cells this fraction induced effector cells that efficiently killed (at various E : T ratios) the relevant B16 target cells and RBL5 syngeneic tumor cells, but not the YAC allogeneic tumor cells or C57BL/6 lymphoblasts. Furthermore, an excess of unlabeled B16 cells most efficiently blocked the ability of these anti-B16 effector cells to kill radiolabeled B16 target cells. RBL5 tumor cells, YAC tumor cells, or C57BL/6 lymphoblasts failed to block these effector cells efficiently. A significant fraction of the effector cells induced with Fr. 5/6 was characterized as thymus-derived cells (Thy-1⁺, Thy-2⁺3⁺ cells). It was suggested that another fraction of the cellular population was natural killer cells, which cytolyzed the RBL5 target cells. Various theoretical and practical aspects of these findings are discussed.