Changes in density of DNA after interaction with dipicolinic acid and its possible role in spore heat resistance

We examined the effect of interacting dipicolinic acid and its calcium chelate on the wet and dry density of DNA. Complexes are produced whose densities are different from those of the individual components. Also, we observed two modes of binding, one strong the other weak, between DPA or CaDPA and DNA. The strength of the binding modes was reflected in the rate of dissolution of the complexes as monitored by changes in wet density with time and temperature. We conclude from these and other data in the literature that the interaction of dipicolinic acid with DNA not only influences the spore wet density and the ratio of core/core⁺ cortex volume, but may also influence the spore heat resistance.     

Components of Selection in X Chromosome Lines of DROSOPHILA MELANOGASTER: Sex Ratio Modification by Meiotic Drive and Viability Selection

Selection coefficients and segregation parameters have been estimated in 18 randomly chosen lines carrying wild X chromosomes on the cn bw genetic background. Each line was studied in replicated crosses of four types, with approximately 100 replications per line per cross. Crosses in which male X chromosomes differed exhibited significant sex ratio heterogeneity. Maximum likelihood estimation of segregation parameters revealed two lines in which the proportion of X-bearing gametes produced by males was significantly different from Mendelian expectations. These observations suggest that segregation distortion is a common feature of naturally occurring genetic variation. Non-Mendelian segregation has important evolutionary implications.     

Growth Kinetics, Cell Shape, and the Cytoskeleton of Primary Astrocyte Cultures

Abstract: We examined correlations among growth kinetics, cell shape, and cytoskeletal protein content in rat astrocytes grown in primary culture. Cell suspensions from brains of newborn rats were seeded at densities from 0.2 to 3 × 10⁵/cm². At initial densities above 1 × 10⁵ the population increased to reach confluency by 10–12 days, after which cell number remained stable for many weeks. At low initial densities, 0.2–0.4 × 10⁵/cm², cells did not increase in number. Final density increased with increasing plating densities. High-density cells had small perikarya and several long cytoplasmic processes; low-density cells appeared flat and polygonal. All cultures were almost entirely astrocytic, as judged by immunofluorescent staining with antiserum against glial fibrillary acidic protein (GFAP). Cytoskeletal proteins were analyzed by gel electrophoresis after extraction from cells with nonionic detergent. Relative amounts of the proteins differed, in that low-density cells contained large amounts of cytoskeletal actin relative to the intermediate filament (IF) proteins vimentin and GFAP, whereas high-density cells contained relatively less actin and more IF proteins. Such differences in cytoskeletal proteins between the high- and low-density cultures were mirrored in the relative rates of synthesis of the cytoskeletal proteins. In the low-density cells amino acid incorporation into cytoskeletal-associated actin was more active than that into the IFs, whereas in the high-density cells higher rates of IF protein synthesis were observed.     

Quantitative measurement of smooth muscle shortening in isolated pig trachea

Matched porcine tracheal rings were exposed to theophylline and increasing doses of carbachol in Krebs solution. Histological sections of each ring were traced and each of the following dimensions measured: the external perimeter (Pe) and external area (Ae) defined by the outer border of smooth muscle and inner surface of cartilage, and the internal perimeter (Pi) and internal area (Ai) defined by the luminal surface of the epithelium and the muscle length (L) along its outer border. Absolute wall area (WA = Ae - Ai) and relative wall area (PW = WA/Ae) were calculated. Carbachol-treated tracheal ring dimensions were compared with those of their matched theophylline-treated rings. In tracheal rings with intact cartilage, maximal smooth muscle shortening of 44% was achieved with 10(-2) M carbachol. In tracheal rings in which anterior and posterior segments of cartilage were excised, the trachealis muscle passively shortened by 20% and maximal shortening (10(-3) M carbachol) was 57%. Although Ai decreased with maximal smooth muscle shortening, there were no changes in the length of Pi or in WA. These data show that the cartilage in the porcine trachea exerts both a preload that passively stretches the trachealis muscle and an afterload that limits maximal smooth muscle shortening.     

Ammonium release by zooplankton in suspensions of heat-killed algae and an evaluation of the flow-cell method

The maximum excretion rate of NH₄ (39 nmol mg dry wt^–1h^–1) was directly measured for Daphnia pulex by measuringNH₄ accumulation in bottles containing D. pulex and dense, satiatingsuspensions of heat-killed algae. Ammonium release rates inthe algal suspensions were compared to those of individual animalsremoved from the suspension and placed in flow cells. Ammoniumrelease rate, R (nmol mg dry wt^–1 h^–1). in the flowcell decreased very rapidly with time, t (min), after removalaccording to the relation R = 26 + 25e^–0.16t. Ammoniumexcretion obtained by the flow cell method after extrapolationto time zero was not significantly different from that obtainedin the bottles. The considerable experiment-to-experiment variationin NH₄ excretion was in large part correlated (r² = 0.73) withthe feeding rate on the algae.     

Fusarenon X and nivalenol production by Gibberella zeae in liquid and rice cultures

Toxigenesis of Gibberella zeae strains NHL-F-1372 and NHL-F-1373 was compared in liquid and rice culture. Growth of both strains in glucose-yeast extract-peptone medium (GYEP) for 25 days resulted in peak levels of fusarenon X (FX) ranging from 40–200 mg/L with lower levels of nivalenol (NIV) (10 mg/L). Growth of these strains in modified Fries medium amended with 4% corn steep liquor (CSL) resulted in a much lower total 8-ketotrichothecene yield than in GYEP, with NIV being the primary compound produced. Although FX appeared initially in this latter medium, the toxin disappeared concurrently as the pH exceeded 8.0. Growth rates and total mycelial accumulation were lower in GYEP cultures than in the modified Fries with CSL cultures. Appearance of FX and NIV in modified Fries medium with CSL paralleled the order of appearance of these compounds in rice, but the total trichothecene yield in rice was much higher. In general, growth and toxigenesis by the nivalenol-producing fusaria in liquid and rice cultures was qualitatively similar to that previously found for deoxynivalenol-producing isolates.Michigan State University Agricultural Experiment Station Article No. 11700.     

Effects of orally administered retinol on natural killer cell activity in wild type BALB/c and congenitally athymic BALB/c mice

Summary Retinoids have been shown to inhibit the growth and development of neoplastic cells in many systems. One mechanism of action may be through activation of the immune system, specifically natural killer (NK) cell activity. The effect of retinol on NK cell cytotoxicity was examined in three groups of mice: BALB/c (wild-type), BALB/c nu/nu (athymic), and BALB/c nu/nu previously injected with human tumor cells. In untreated mice, NK activity was highest in athymic mice without tumors and lowest in wild-type mice, although serum and liver retinol concentrations were identical in all three groups. In mice fed graded, nontoxic doses of retinol daily for 3 weeks, serum retinol levels in all three groups exhibited a sharp peak and decline following daily bolus retinol administration. Retinol stores in the livers showed a dose-dependent increase in all treated animals. However, NK cell activity, differed for each group. Athymic mice without tumors exhibited no change in NK activity as a result of retinol treatment. Athymic mice with tumors had NK levels that tended to increase with increasing retinol doses, but these changes were not statistically significant. Wild-type mice, on the other hand, demonstrated significantly higher NK levels after treatment with retinol doses of 300 and 600 g/day. In subsequent time course experiments, there was a peak in NK activity 1 h following bolus retinol administration similar to the peak seen in serum retinol concentrations, suggesting either an acute activation or recruitment of cytotoxic cells. Retinol thus appears to increase NK activity in wild-type BALB/c mice, and this activity may be an important component of its antineoplastic activity.This investigation was supported by Biomedical Research Support Grant RRO 5424, the Veterans Administration, and PHS Grant number CA 33589-01A2, awarded by the National Cancer Institute, DHHSThis work was done in partial fulfillment of a Ph. D. thesis by L. Fraker in the Department of Pathology, Vanderbilt University School of Medicine     

Dinitrogen fixation by obligate and facultative anaerobic bacteria in association with cellulolytic fungi

The anaerobic bacteriumClostridium butyricum is the major contributor to nitrogen gains by a cellulolytic/nitrogen-fixing population isolated from straw. Growth of the anaerobe is supported by the products of fungal cellulases. The facultative anaerobeEnterobacter cloacae does not make a significant direct contribution to nitrogen fixation but in association withC. butyricum allows the anaerobe to grow under aerobic conditions. The major function ofE. cloacae is though to be provision of oxygen-depleted microsites.     

Cuticular lipids for species recognition of mole crickets (Orthoptera: Gryllotalpidae): II. Scapteriscus abbreviatus,S. acletus,S. vicinus,S. sp., and Neocurtilla hexadactyla

Qualitative analyses were made from whole-body cuticular extracts of Scapteriscus abbreviatus, Scapteriscus acletus, Scapteriscus vicinus, and Neocurtilla hexadactyla by isothermal and temperature-programmed gas chromatography. Adults of both sexes and nymphs of each species were collected in Florida. The chromatographic profiles of peaks were distinct and easily recognizable for each species, regardless of sex or developmental stage. Distinct sexual differences were found in S. acletus and S. abbreviatus. Specimens of S. abbreviatus from Puerto Rico and S. vicinus from Bolivia produced gas chromatography (GC) traces very similar to those of conspecifics collected in Florida. Evidence is presented to illustrate the potential importance of volatile cuticular lipid analysis as a tool for mole cricket identification. Cuticular extracts of an undescribed short-winged species of Scapteriscus from Bolivia were also examined and produced GC traces unlike those of any other species analyzed to date.     

Sensitivity of Tryptophan, Tyrosine and Phenylalanine Mutants of SACCHAROMYCES CEREVISIAE to Phenethyl Alcohol

Phenethyl alcohol inhibits the growth of many microorganisms. It is believed that the growth inhibition is mediated by its effect on the cell membrane. Differences between sensitive and resistant strains are suggested to be due to alterations in membrane structure. We report that, in some strains, an unexpected relationship exists between auxotrophy for tryptophan, tyrosine and phenylalanine and sensitivity to phenethyl alcohol.