Cell proliferation and nuclear abnormalities are increased and apoptosis is decreased in the epidermis of the p53 null mouse after topical application of benzo[a]pyrene

Abstract. Cell proliferation and cell death in mouse epidermis are altered by topical application of benzo[ a ]pyrene (BaP), a procarcinogen, which yields metabolites that can form DNA adducts. The mitotic rate, nuclear abnormalities, labelling index, grain density, necrosis and apoptosis were compared in the epidermis of TSG- p53 null ( p53 ^-/-) and C57BL wild-type (wt) mice after weekly treatments with BaP to determine whether the absence of the p53 gene altered cytokinetic responses to DNA damaging agents in vivo . Acetone alone or 64 μg BaP in 50 μl acetone was applied to the clipped dorsum of mice once, or in four consecutive weekly treatments. Indices of cell proliferation and cell death were the same in both wt and p53 ^-/- mice treated only with acetone. One application of BaP depressed mitosis and slowed the rate of DNA synthesis in both genotypes. After four applications of BaP the number of keratinocytes in S phase increased substantially, while there was no further slowing in the rate of S phase in the wt and p53 ^-/- mice. Cell proliferation rates and numbers of cells with nuclear abnormalities were higher and there were fewer apoptotic cells and apoptotic bodies in the p53 ^-/- mice than in the wt mice. Numbers of 'sunburn'cells were similar in both types.     

Signal Sequence and Promoter Effects on the Efficacy of Toxin-Expressing Baculoviruses as Biopesticides

Baculovirus recombinants expressing a neurotoxin gene,tox34,from the straw itch mitePyemotes triticihave been previously shown to paralyze or kill insects approximately 50% faster than wild-type. We constructed a series of recombinants of the baculovirusAutographa californicanucleopolyhedrovirus which expressedtox34with different signal sequences or were controlled by different promoters to evaluate their influence on toxin expression in cell culture and in insects. Heterologous signal sequences provided no significant increase in the overall levels of the maturetox34gene product, Tox34, secreted into the tissue culture media from infected cells and no improvement in the time required for paralysis of insect hosts. The time required for paralysis was promoter-dependent; the late 6.9K DNA binding protein gene promoter was generally the most effective promoter, although an insect HSP70 promoter was equally or more effective in one of the species.     

Metal distribution across different pools in the organic layer of a forest under acid deposition and its consequences for the metal dynamics

Acid atmospheric deposition can cause losses of metal nutrients from the organic layer of a soil. The size of these losses depend on the sizes of the different pools in which the metals are present, as these pools differ in mobility. The metal pools in an organic soil layer of a Douglas fir forest in the Netherlands subjected to acid deposition were determined by means of extractions and percolations. Na was mainly dissolved and exchangeably adsorbed, K dissolved, exchangeably adsorbed and present in the soil microbial biomass, Ca exchangeably adsorbed and present in organic precipitates, Mg exchangeably adsorbed and present in the soil biomass, and Mn exchangeably adsorbed and present in inorganic precipitates. The main part of the metals was exchangeably adsorbed. The adsorption affinity increased in the order Na < K < Mg < Mn ≈ Ca. The vertical distribution of the metals in the organic layer showed that all metals were continuously lost from the organic layer. The differences between the metals in retention and vertical distribution patterns were in agreement with their differences in deposition rate, pool distribution, and exchange affinity. Since the metals were mainly exchangeably adsorbed, and the acidifying cations dominated the atmospheric deposition, acid deposition and cation exchange must be processes that strongly affect the losses of metals from this organic soil layer. R F Huettl Section editor     

Impact of flooding on the densities of selected aquatic insects

Data from a four-year study of five aquatic insect species,Hydropsyche betteni, H. morosa, H. bronta, Isonychia bicolor, andEphoron leucon, were utilized to evaluate the impact of a 60-year flood and a few lesser floods. The survey began in August, 1984 and was terminated in October, 1987 with the 60-year flood occurring in November, 1985. Four sampling sites were established on the South River and six quantitative samples were taken each month from each site. Gauging stations on the South River provided accurate discharge data for the sampling sites and useful historical data. Densities for the five species were utilized in the evaluation of the floods. The importance of timing is pointed out, that is, floods that occur very close together or near the end of the life cycle of an insect make it difficult to evaluate floods as disturbances. The importance of life history traits, such as behavior and egg diapause, are discussed in respect to floods. Densities were reduced to less than 50% of their average values immediately after the 60-year flood for the threeHydropsyche spp. and at three sites forI. bicolor. Ephoron leucon showed no response to the 60-year flood. Densities of the four impacted species returned to previous levels in the following generation. The 60-year flood was considered a disturbance in the near term but not for more than one generation.     

Relationship between immunoglobulin levels and extremes of solar activity

The possible relationship between epidemics and extremes of solar activity has been discussed previously. The purpose of the present study was to verify whether differences in the levels of immunoglobulins (IgA, IgG, IgM) could be noted at the highest (July 1989) and lowest (September 1986) points of the last (21st) and present (22nd) 11-year solar cycle. The work was divided into a 1-month study (covering the month of minimal or maximal solar activity), a 3-month study (1 month before and after the month of minimal or maximal solar activity) and a 5-month study (2 months before and after the month of minimal or maximal solar activity). A trend of a drop-off for all three immunoglobulins was seen on the far side of the maximal point of the solar cycle. Statistical significance was achieved in the 5-month study for IgM (P=0.04), and a strong trend was shown for IgG (P=0.07). Differences between the sexes were also noted.     

Regulation of DOPA Decarboxylase Activity in Brain of Living Rat

Abstract: To test the hypothesis that l -DOPA decarboxylase (DDC) is a regulated enzyme in the synthesis of dopamine (DA), we developed a model of the cerebral uptake and metabolism of [³H]DOPA. The unidirectional blood-brain clearance of [³H]DOPA ( K ^D₁) was 0.049 ml g⁻¹ min⁻¹. The relative DDC activity ( k ^D₃) was 0.26 min⁻¹ in striatum, 0.04 min⁻¹ in hypothalamus, and 0.02 min⁻¹ in hippocampus. In striatum, 3,4-[³H]dihydroxyphenylacetic acid ([³H]DOPAC) was formed from [³H]DA with a rate constant of 0.013 min⁻¹, [³H]homovanillic acid ([³H]HVA) was formed from [³H]DOPAC at a rate constant of 0.020 min⁻¹, and [³H]HVA was eliminated from brain at a rate constant of 0.037 min⁻¹. Together, these rate constants predicted the ratios of endogenous DOPAC and HVA to DA in rat striatum. Pargyline, an inhibitor of DA catabolism, substantially reduced the contrast between striatum and cortex, in comparison with the contrast seen in autoradiograms of control rats. At 30 min and at 4 h after pargyline, k ^D₃ was reduced by 50% in striatum and olfactory tubercle but was unaffected in hypothalamus, indicating that DDC activity is reduced in specific brain regions after monoamine oxidase inhibition. Thus, DDC activity may be a regulated step in the synthesis of DA.     

Tumor Necrosis Factor-α and Basic Fibroblast Growth Factor Decrease Glial Fibrillary Acidic Protein and Its Encoding mRNA in Astrocyte Cultures and Glioblastoma Cells

Abstract: Tumor necrosis factor-α is a pluripotent cytokine that is reportedly mitogenic to astrocytes. We examined expression of the astrocyte intermediate filament component glial fibrillary acidic protein in astrocyte cultures and the U373 glioblastoma cell line after treatment with tumor necrosis factor-α. Treatment with tumor necrosis factor-α for 72 h resulted in a decrease in content of glial fibrillary acidic protein and its encoding mRNA. At the same time, tumor necrosis factor-α treatment increased the expression of the cytokine interleukin-6 by astrocytes. The decrease in glial fibrillary acidic protein expression was greater when cells were subconfluent than when they were confluent. Thymidine uptake studies demonstrated that U373 cells proliferated in response to tumor necrosis factor-α, but primary neonatal astrocytes did not. However, in both U373 cells and primary astrocytes tumor necrosis factor-α induced an increase in total cellular protein content. Treatment of astrocytes and U373 cells for 72 h with the mitogenic cytokine basic fibroblast growth factor also induced a decrease in glial fibrillary acidic protein content and an increase in total protein level, demonstrating that this effect is not specific for tumor necrosis factor-α. The decrease in content of glial fibrillary acidic protein detected after tumor necrosis factor-α treatment is most likely due to dilution by other proteins that are synthesized rapidly in response to cytokine stimulation.     

A Model for diffusion controlled bioavailability of crude oil components

Crude oil is a complex mixture of several different structural classes of compounds including alkanes, aromatics, heterocyclic polar compounds, and asphaltenes. The rate and extent of microbial degradation of crude oil depends on the interaction between the physical and biochemical properties of the biodegradable compounds and their interactions with the non-biodegradable fraction. In this study we have systematically altered the concentration of non-biodegradable material in the crude oil and analyzed its impact on transport of the biodegradable components of crude oil to the microorganisms. We have also developed a mathematical model that explains and accounts for the dependence of biodegradation of crude oil through a putative bioavailability parameter. Experimental results indicate that as the asphaltene concentration in oil increases, the maximum oxygen uptake in respirometers decreases. The mathematically fitted bioavailability parameter of degradable components of oil also decreases as the asphaltene concentration increases.     

The Yeast Red1 Protein Localizes to the Cores of Meiotic Chromosomes

Mutants in the meiosis-specific RED1 gene of S. cerevisiae fail to make any synaptonemal complex (SC) or any obvious precursors to the SC. Using antibodies that specifically recognize the Red1 protein, Red1 has been localized along meiotic pachytene chromosomes. Red1 also localizes to the unsynapsed axial elements present in a zip1 mutant, suggesting that Red1 is a component of the lateral elements of mature SCs. Anti-Red1 staining is confined to the cores of meiotic chromosomes and is not associated with the loops of chromatin that lie outside the SC. Analysis of the spo11 mutant demonstrates that Red1 localization does not depend upon meiotic recombination. The localization of Red1 has been compared with two other meiosisspecific components of chromosomes, Hop1 and Zip1; Zip1 serves as a marker for synapsed chromosomes. Double labeling of wild-type meiotic chromosomes with anti-Zip1 and anti-Red1 antibodies demonstrates that Red1 localizes to chromosomes both before and during pachytene. Double labeling with anti-Hop1and anti-Red1 antibodies reveals that Hop1 protein localizes only in areas that also contain Red1, and studies of Hop1 localization in a red1 null mutant demonstrate that Hop1 localization depends on Red1 function. These observations are consistent with previous genetic studies suggesting that Red1 and Hop1 directly interact. There is little or no Hop1 protein on pachytene chromosomes or in synapsed chromosomal regions.