Kinetics of Sulfate Reduction in a Coastal Aquifer Contaminated with Petroleum Hydrocarbons

An integrated field and laboratory study was conducted to quantify the effect of environmental determinants on the activity of sulfate reducers in a freshwater aquifer contaminated with petroleum hydrocarbons (PHC). Within the contaminated zone, PHC-supported in␣situ sulfate reduction rates varied from 11.58±3.12 to 636±53 nmol cm⁻³ d⁻¹ and a linear increase (R ²=0.98) in reduction rate was observed with increasing in situ sulfate concentrations suggesting sulfate limitation. Half-saturation concentration (K _s) for sulfate reduction coupled to PHC mineralization was determined for the first time. At two different sites within the␣aquifer, maximum sulfate reduction rate under␣non-limiting conditions (R _max) was 5,000 nmol cm⁻³ d⁻¹, whereas the retrieved K _s values were 3.5 and 7.5 mM, respectively. The K _s values are the highest ever reported from a natural environment. Furthermore, the K _s values were significantly higher than in situ sulfate concentrations confirming sulfate limited growth. On addition of lactate and formate, sulfate reduction rate increased indicating that reactivity and bioavailability of organic substrate may also have played a role in rate inhibition in certain parts of the aquifer. Experiments with sulfide amendments show statistically minor decrease in sulfate reduction rates on addition of sulfide and analogous increase in sulfide toxicity with increasing sulfide concentrations (0.5–10 mM) was not apparent.     

Adenoviral proteins mimic nutrient/growth signals to activate the mTOR pathway for viral replication

Like tumor cells, DNA viruses have had to evolve mechanisms that uncouple cellular replication from the many intra- and extracellular factors that normally control it. Here we show that adenovirus encodes two proteins that activate the mammalian target of rapamycin (mTOR) for viral replication, even under nutrient/growth factor-limiting conditions. E4-ORF1 mimics growth factor signaling by activating PI3-kinase, resulting in increased Rheb.GTP loading and mTOR activation. E4-ORF4 is redundant with glucose in stimulating mTOR, does not affect Rheb.GTP levels and is the major mechanism whereby adenovirus activates mTOR in quiescent primary cells. We demonstrate that mTOR is activated through a mechanism that is dependent on the E4-ORF4 protein phosphatase 2A-binding domain. We also show that mTOR activation is required for efficient S-phase entry, independently of E2F activation, in adenovirus-infected quiescent primary cells. These data reveal that adenovirus has evolved proteins that activate the mTOR pathway, irrespective of the cellular microenvironment, and which play a requisite role in viral replication.     

Genetic diversity in the invasive <Emphasis Type="Italic">Rubus phoenicolasius</Emphasis> as compared to the native <Emphasis Type="Italic">Rubus argutus</Emphasis> using inter-simple sequence repeat (ISSR) markers

Invasive species are one of most significant factors in human-influenced global change. Management actions that prevent the spread and impacts of invasive species require knowledge of their ecological and genetic characteristics. The genetic characteristics of the invasive wine raspberry, Rubus phoenicolasius Maxim. (Rosaceae) and the native sawtooth blackberry, Rubus argutus Link, were examined in two forest habitats on the Maryland Coastal Plain. Using inter-simple sequence repeat (ISSR) markers we quantified the genetic diversity of both species. We analyzed genetic diversity using analysis of molecular variance (AMOVA) and found less genetic diversity in the invasive species, R. phoenicolasius, with variation between sites was 0.418 between sites and 0.075 within sites as compared to the native, R. argutus, where the variation between sites was 1.538 and 0.370 within sites. The lower genetic diversity in the invasive may be due to a history of limited introductions or frequent self-fertilization and clonal reproduction.     

Ten-Year-Replicated Circadian Profiles for 36 Physiological, Serological and Urinary Variables in Healthy Men

At 3-hr intervals over a 24-hr span, 36 systemic, serologic and urinary variables were examined in 7 men in their mid 20's in the Spring of 1969, and again in the same 7 men in the Spring of 1979 under a similar chronobiologic protocol, using the same chemical and numerical analytical procedures. The variables examined for rhythms by cosinor were: vital signs--blood pressure (systolic, diastolic, pulse pressure and mean arterial pressure), heart rate, intraocular pressure (left and right), oral temperature; serum components--albumin, albumin/globulin ratio, total bilirubin, calcium, carbon dioxide, chlorides, bilirubin, cholesterol, globulin, glucose, potassium, sodium, sodium/potassium ratio, transaminase, triglycerides, total protein, urea nitrogen; and urine components--calcium, calcium/magnesium ratio, creatinine, magnesium, pH, potassium, sodium, sodium/potassium ratio, urea clearance, urea nitrogen, volume and zinc. Although all subjects appeared clinically healthy in 1969 and in 1979, certain inter-study differences were observed in a number of rhythm parameters of different variables. Statistically significant increases in mesor for the group as a whole were observed for serum Ca, cholesterol, Cl, CO2, K, Na, and while statistically significant mesor decreases for a group as a whole were noted in serum glucose and transaminase. Statistically significant increases in amplitude for the group as a whole were observed in serum chloride and urinary Na/K ratio, while statistically significant decreases were observed in amplitude for blood pressure, heart rate, serum albumin, A/G ratio, globulin, glucose, protein, sodium and transaminase.(ABSTRACT TRUNCATED AT 250 WORDS)     

Kinds and spectrum of mutations induced by 1-nitrosopyrene adducts during plasmid replication in human cells.

1-Nitropyrene has been shown in bacterial assays to be the principal mutagenic agent in diesel emission particulates. It has also been shown to be mutagenic in human fibroblasts and carcinogenic in animals. To investigate the kinds of mutations induced by this carcinogen and compare them with those induced by a structurally related carcinogen, (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetra-hydrobenzo [a]pyrene (BPDE) (J.-L. Yang, V. M. Maher, and J. J. McCormick, Proc. Natl. Acad. Sci. USA 84:3787-3791, 1987), we treated a shuttle vector with tritiated 1-nitrosopyrene (1-NOP), a carcinogenic mutagenic intermediate metabolite of 1-nitropyrene which forms the same DNA adduct as the parent compound, and introduced the plasmids into a human embryonic kidney cell line, 293, for DNA replication to take place. The treated plasmid, pZ189, carrying a bacterial suppressor tRNA target gene, supF, was allowed 48 h to replicate in the human cells. Progeny plasmids were then rescued, purified, and introduced into bacteria carrying an amber mutation in the beta-galactosidase gene in order to detect those carrying mutations in the supF gene. The frequency of mutants increased in direct proportion to the number of DNA-1-NOP adducts formed per plasmid. At the highest level of adduct formation tested, the frequency of supF mutants was 26 times higher than the background frequency of 1.4 X 10(-4). DNA sequencing of 60 unequivocally independent mutant derived from 1-NOP-treated plasmids indicated that 80% contained a single base substitution, 5% had two base substitutions, 4% had small insertions or deletions (1 or 2 base pairs), and 11% showed a deletion or insertion of 4 or more base pairs. Sequence data from 25 supF mutants derived from untreated plasmids showed that 64% contained deletions of 4 or more base pairs. The majority (83%) of the base substitution in mutants from 1-NOP-treated plasmids were transversions, with 73% of these being G . C --> T . A. This is very similar to what we found previously in this system, using BPDE, but each carcinogen produced its own spectrum of mutations. Of the five hot spots for base substitution mutations produced in the supF gene with 1-NOP, two were the same as seen with BPDE-treated plasmids. However, the three other hot spots were cold spots for BPDE-treated plasmids. Conversely, four of the other five hot spots seen with BPDE-treated plasmids were cold spots for 1-NOP-treated plasmids. Comparison of the two carcinogens for the frequency of supF mutants induced per DNA adduct showed that 1-NOP-induced adducts were 3.8 times less than BPDE adducts. However, the 293 cell excised 1-NOP-induced adducts faster than BPDE adducts.     

Finding the best antibody dilution by repeated immunostaining of the same tissue section

One can find the optimal antibody dilution for immunostaining by repeated staining on the same tissue section by using a less dilute antibody for each attempt. Using secondary antibody and horseradish peroxidase conjugated to a dextran polymer, a section stained repeatedly with several dilutions of antibody appears as good as a section stained with only the last dilution.