Biomedical subjects

P L Bishop

Publications and source records attributed to P L Bishop.

At least 19 recordsLinked to original sources

PubMed2005

Development of a phosphate ion-selective microelectrode and its use in studies of the enhanced biological phosphorus removal (EBPR) process.

In an enhanced biological phosphorus reactor (EBPR), most poly-phosphate accumulating microorganisms (PAOs) exist as microbial aggregates, or flocs. Information contributing to a better understanding of the internal structure and function of flocs can lead to improvements in the modeling, design and operation of EBPR systems in wastewater treatment. A phosphate ion-selective microelectrode has been developed and was used to measure the phosphate profiles in flocs. The microelectrode uses cobalt as the sensing material and shows very good selectivity towards orthophosphate ions (H2PO4(-), HPO4(2-) and PO4(3-)). The potentiometric response showed a linear relationship with the logarithm of phosphate concentrations, with a slope of 31.5 mV per decade change of concentration. The solution pH did not show a significant effect on the microelectrode performance within the pH range of 7.5 to approximately 8.0. The effect of ionic strength was also investigated. Measurements using this microelectrode were made on activated sludge floc samples taken from a municipal wastewater treatment plant.

Bioreactors↗

PubMed2004

The ACCEND program: a combined BS and MS program in environmental engineering that includes co-operative work experience.

Environmental engineering education has rapidly expanded in recent years and new teaching methods are needed. Many professionals and educators believe that a MS degree in environmental engineering should be the minimum in order to practice the profession, along with practical training. This paper describes an innovative program being offered at the University of Cincinnati that combines an integrated BS in civil engineering and an MS in environmental engineering with extensive practical co-operative education (co-op) experience, all within a five-year period. The program includes distance learning opportunities during the co-op periods. The result is a well-trained graduate who will receive higher pay and more challenging career opportunities, and who will have developed professionalism and maturity beyond that from traditional engineering programs.

Cooperative Behavior↗

PubMed2004

Adsorption and biodegradation of azo dye in biofilm processes.

The removal of a common azo dye, acid orange 7 (AO7), in biofilm systems was investigated in this study. The abiotic and biotic fate of AO7 was examined under a variety of operating conditions: aerobic nitrification, anoxic denitrification and anaerobic digestion. A comparison of the performance between biofilm and activated sludge treatment processes was made. The adsorption of AO7 onto biofilm matrix and activated sludge flocs was found to fit the Langmuir equation. However, there is a significant difference in the adsorption capacities between biofilm and activated sludge. AO7 was recalcitrant in both biofilm and activated sludge systems under aerobic conditions. Under anaerobic conditions, AO7 was readily decolorized. AO7 decolorization was also observed under anoxic conditions. However, the presence of nitrate inhibited AO7 decolorization.

Adsorption↗

PubMed2003

Evaluation of organics leaching from solidified/stabilized hazardous wastes using a powder reactivated carbon additive.

Cement based stabilization/solidification systems have been widely used to minimize leaching of contaminants from hazardous wastes, particularly for stabilization of wastes that contain heavy metals or other inorganic materials. However, few researchers have demonstrated that stabilization/solidification systems can adequately trap and retain organics present in these wastes. Identification of additives that can be used with the inorganic binder to retain organics has attracted much interest. Activated carbon has been found to be the best additive for immobilizing organic contaminants, but it is generally too expensive for routine use. The use of powdered reactivated carbon was studied in this research to prevent organics from leaching from solidified/stabilized waste forms because it is effective and more economically competitive. The Shrinking Unreacted Core leach test method was employed in this study. Stabilization/solidification waste forms were prepared using five organic compounds--phenol, 2-chlorophenol, chlorobenzene, aniline and Methyl Ethyl Ketone (MEK)--that were spiked into the waste forms at two concentration levels each. Reactivated carbon amounts of 0% (as control), 1% and 2% (w/w) were added into each waste form batch to determine how effectively the reactivated carbon can immobilize those organics and the optimum dose of reactivated carbon addition required. Leachate samples were analyzed using gas chromatography. Results show that 1% reactivated carbon addition is generally enough to reduce leaching of all of the organic contaminants by more than 70%, while a 2% addition reduces leaching for most of the organics to less than 1%.

Carbon↗

PubMed2003

Effect of dissolved oxygen concentration on the biofilm and in situ analysis by fluorescence in situ hybridization (FISH) and microelectrodes.

A better understanding of microbiology and ecology of nitrifying bacteria in inner biofilms is an important part of improving process performance and control. Microelectrodes and fluorescent in situ hybridization (FISH) in biofilm research have been used to investigate the spatial distributions of various microbial activities in biofilms and have led to new experimental findings as well as modifications of the homogeneous assumptions in the biofilm kinetic models. The objective of this study is to try the combination of two methods, both FISH and microelectrode measurements, and to provide reliable and in situ information on nitrifying bacterial activity in biofilms. The characteristics of biofilm developed on tygon slides were different according to the change of dissolved oxygen (DO). When the DO increased from 2 to 10 mg DO/L, the rate of the biofilm thickness increased and its dry density changed from 50-70 to 25-90 mg/cm3. Ammonia oxidizing bacteria were not uniformly distributed in biofilm, and were found at the deeper layer where oxygen is depleted, they were detected primarily in the upper and middle layers of the biofilm.

Bacteria↗

PubMed2003

Monitoring the influence of toxic compounds on microbial denitrifying biofilm processes.

Microelectrode measurements were conducted to obtain nitrate, pH and redox potential profiles within anoxic denitrifying biofilms. The influence of a toxic organic compound (acid orange 7) on biofilm microprofiles was also monitored using microelectrodes. The data provide evidence that the denitrifying biofilms were stratified into an anoxic layer and an anaerobic layer. The anaerobic zone might provide a niche for the biodegradation of recalcitrant organic compounds in biofilms. It was found that acid orange 7 and its biodegradation byproducts had only a slight impact on biofilm nitrate, pH and redox potential profiles.

Azo Compounds↗

PubMed2002

In situ identification of azo dye inhibition effects on nitrifying biofilms using microelectrodes.

In this study, the inhibitory effects of acid orange 7 (AO7), a common azo dye, on nitrification in biofilms were investigated in situ using microelectrodes. Biofilms were obtained from laboratory rotating drum biofilm reactor after the nitrification process reached a pseudo-steady state. Dissolved oxygen, pH, NH4+, NO3-, and redox potential microelectrodes, with tip diameters ranging from 3-15 microm, were used to monitor the spatial distribution and change of microbial activities within nitrifying biofilms. It was found that at lower concentration (1 mg/L), AO7 had only a slight impact on the NH4+-N concentration profiles. The ammonium consumption rate decreased as higher AO7 concentrations (15 mg/L and 25 mg/L) were exposed to the biofilms. A similar trend was observed for the NO3(-)-N microprofiles. The nitrate production rate decreased as the AO7 concentration in the bulk solution increased. The dissolved oxygen and pH microprofiles also showed oxygen and alkalinity utilization, but at lower rates throughout the biofilms when the nitrification process was inhibited. No significant redox potential differences were observed in the biofilms after AO7 was applied.

Azo Compounds↗

PubMed2001

Decomposition of hazardous organic materials in the solidification/stabilization process using catalytic-activated carbon.

The application of a catalytic-activated carbon to the solidification/stabilization (S/S) process for immobilization of phenol and 2-chlorophenol and catalytic decomposition was investigated. The effect of the catalytic-activated carbon, in amounts of 0.25-1% (by dry sand wt.), on the leaching of phenol and 2-chlorophenol was studied. H2O2 was added as a source of oxygen in the amounts of 1 or 5%, with respect to liquid solution weight. Toxicity characteristic leaching procedure (TCLP) leaching tests showed that adding the catalytic-activated carbon to the S/S matrix significantly reduced the leachability of both phenol and 2-chlorophenol. Only trace amounts of phenol were found in the leaching solution, while the concentration of 2-chlorophenol was below the detection limit of the gas chromatography (GC). Without addition of the catalytic-activated carbon, 87% of the phenol and 92% of the 2-chlorophenol leached. Additional tests on TCLP leachate solutions using GC-mass spectrometry indicated the existence of simple, less hazardous, hydrocarbons, including alcohol. Catalytic-activated carbons treated with phenol in the presence of H2O2 were also analyzed using time of flight-secondary ion mass spectroscopy (TOF-SIMS). Results indicate that the phenol aromatic ring was broken by the catalytic reaction.

Adsorption↗

PubMed2001

Teaching future professors how to teach.

This paper describes a course designed to provide hands-on teaching experience to future professors and to incorporate techniques for more effective teaching. A team of Ph.D. candidates, under the direction of a senior faculty member, prepared a new course from beginning to end and then offered it to a class of graduate students. The course was developed using the unit map concept so that the presentations by the five student-instructors complemented and built upon one another. Immediately after each class, feedback was given to the student-instructors by the faculty advisor and the other student-instructors. Review of video tapes of the lecture reinforced this feedback. At the completion of the course, both students and student-instructors were surveyed as to the effectiveness of the course and the student-instructors. This teaching experience and the feedback obtained from the surveys will be invaluable to the student-instructors in their future development.

Conservation of Natural Resources↗

PubMed2001

Sludge digestion enhancement and nutrient removal from anaerobic supernatant by Mg(OH)2 application.

Anaerobic sludge digestion is a widely adopted process for sludge stabilization. Phosphate removal from anaerobic supernatant is necessary to limit the phosphate returned to the head of the treatment plant, thereby improving the overall treatment efficiency. In this study, magnesium hydroxide (Mg(OH)2) was used to improve the sludge digestion efficiency and to remove phosphorus from anaerobic supernatant. The anaerobic sludge digestion experiment was conducted at a pilot scale, and the results showed that applying Mg(OH)2 to anaerobic sludge digester resulted in a larger reduction in SS and COD, a higher biogas production rate, a lower level of phosphate and ammonia nitrogen concentrations in the sludge supernatant and an improved sludge dewaterability. Research results at both lab scale and pilot scale on phosphorus removal from anaerobic supernatant using Mg(OH)2 showed that a high removal of phosphorus can be achieved through the addition of Mg(OH)2. The required reaction time depends on the initial phosphorus concentration and the Mg(OH)2 dosage.

Ammonia↗

PubMed1999

Immobilization of phenol in cement-based solidified/stabilized hazardous wastes using regenerated activated carbon: role of carbon.

The use of regenerated activated carbon as an immobilizing additive for phenol in solidification/stabilization (S/S) processes was investigated. The adsorption capacity of regenerated carbon was compared to that of the virgin form and was found to be very close. The effects of pH and Ca(OH)(2) concentration within the S/S monolith on the adsorption process were also examined. Kinetic tests were performed to evaluate the adsorption of phenol on different forms of F400 carbon, including the regenerated form. Kinetic tests were performed in aqueous solutions as well as in liquid-sand mixtures. In both cases, it was found that phenol adsorption on F400 carbon was fairly fast. More than 60% of the equilibrium adsorption amount could be achieved within the first hour for aqueous solutions. For sand-solution kinetics, it was found that 1% carbon (based on dry sand weight) was capable of achieving more than 95% removal of the initial amount of phenol present in solution (1000 and 5000 ppm). Fourier transform infrared (FT-IR) spectroscopy and X-ray mapping tests indicated a homogenous mixing of the carbon into the cement matrix. The carbon was also found to enhance the hydration of cement, which was retarded by the existence of phenol.

Adsorption↗

PubMed1999

Immobilization of phenol in cement-based solidified/stabilized hazardous wastes using regenerated activated carbon: leaching studies.

In this research, we investigated the use of an inexpensive thermally regenerated activated carbon as a pre-adsorbent in the solidification/stabilization of phenol-contaminated sand. Our results show that even the addition of very low amounts of regenerated activated carbon (1%-2% w/w sand) resulted in the rapid adsorption of phenol in the Chemical solidification/stabilization (S/S) matrix, with phenol leaching reduced by as much as 600%. Adsorption studies indicated that the adsorption of phenol on the reactivated carbon was found to be partially irreversible over time in the S/S waste form, indicating possible chemical adsorption. Pore-fluid analyses of the cement paste containing phenol suggested the formation of a calcium-phenol complex, which further reduced the amount of free phenol present in the pores. Studies using several micro-structural techniques, including field emission scanning electron microscopy, X-ray diffraction, fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy, indicated significant morphological changes in the cement matrix upon the addition of phenol and reactivated carbon. The hydration of cement in the presence of phenol was retarded concomitant with formation of amorphous portlandite.

Adsorption↗

PubMed1999

Degradation of azo dyes containing aminonaphthol by Sphingomonas sp strain 1CX.

Sphingomonas sp strain 1CX was isolated from a wastewater treatment plant and is capable of aerobically degrading a suite of azo dyes, using them as a sole source of carbon and nitrogen. All azo dyes known to be decolorized by strain 1CX (Orange II, Acid Orange 8, Acid Orange 10, Acid Red 4, and Acid Red 88) have in their structure either 1-amino-2-naphthol or 2-amino-1-naphthol. In addition, an analysis of the structures of the dyes degraded suggests that there are certain positions and types of substituents on the azo dye which determine if degradation will occur. Growth and dye decolorization occurs only aerobically and does not occur under fermentative or denitrification conditions. The mechanism by which 1CX decolorizes azo dyes appears to be through reductive cleavage of the azo bond. In the case of Orange II, the initial degradation products were sulfanilic acid and 1-amino-2-naphthol. Sulfanilic acid, however, was not used by 1CX as a growth substrate. The addition of glucose or inorganic nitrogen inhibited growth and decoloration of azo dyes by 1CX. Attempts to grow the organism on chemically defined media containing several different amino acids and sugars as sources of nitrogen and carbon were not successful. Phylogenetic analysis of Sphingomonas sp strain 1CX shows it to be related to, but distinct from, other azo dye-decolorizing Sphingomonas spp strains isolated previously from the same wastewater treatment facility.

Journal Article↗

PubMed1995

Epigenetic gene inactivation induced by a cis-acting methylation center.

In this report we test the hypothesis that a cis-acting methylation center can induce epigenetic gene inactivation. The cis-acting element used is an 838-base pair fragment that was shown previously to provide a de novo methylation signal (Mummaneni, P., Bishop, P. L., and Turker, M.S. (1993) J. Biol. Chem. 268, 552-558). Its normal location is approximately 1.3 kilobase pairs upstream of the mouse aprt (adenine phosphoribosyltransferase) gene. To determine if the methylation center could induce inactivation of the aprt gene, a plasmid construct was created in which the methylation center was moved next to the aprt promoter. Transfection experiments demonstrated inactivation of the aprt gene on the hybrid construct. The inactivation event was shown with a Southern blot analysis to correlate with hypermethylation and to be reversible by treatment with 2-deoxy-5'-azacytidine, a demethylating agent. Interestingly, gene inactivation induced by the methylation center required truncation of the aprt promoter. The results demonstrate that epigenetic gene inactivation can be induced by a DNA methylation center.

Adenine Phosphoribosyltransferase↗

PubMed1993

A cis-acting element accounts for a conserved methylation pattern upstream of the mouse adenine phosphoribosyltransferase gene.

A 2.1-kilobase pair region located just upstream of the mouse aprt (adenine phosphoribosyltransferase) gene has a methylation pattern that is conserved in mouse tissues and culture cell lines. This upstream region includes four HpaII/MspI sites. Two of these sites are fully methylated, one is partially methylated, and one is unmethylated. Transfection experiments have demonstrated that the conserved methylation pattern can be reproduced in a mouse embryonal carcinoma stem cell line via de novo methylation (Turker, M.S., Mummaneni, P., and Bishop, P.L. (1991) Somat. Cell Mol. Genet. 17, 151-157). To examine the molecular basis of the conserved methylation pattern, a plasmid-based deletion analysis was conducted by removing and rearranging specific portions of the upstream region. Unmethylated versions of these plasmid constructs were then transfected into the mouse stem cell line and the methylation status of the remaining HpaII/MspI sites determined with a Southern blot analysis. By using this approach, a cis-acting sequence within the upstream region of approximately 0.8 kilobase pairs was identified which appears responsible for the conserved methylation pattern. We use the term "de novo methylation center" to denote this sequence. Based on the results obtained, a model is offered to explain the formation of the conserved methylation pattern in the upstream region.

Adenine Phosphoribosyltransferase↗

PubMed1993

Hemidemethylation is sufficient for chromatin relaxation and transcriptional activation of methylated aprt gene in mouse P19 embryonal carcinoma cell line.

A series of clones displaying a high-frequency "switching" phenotype for expression of the adenine phosphoribosyltransferase (aprt) gene was previously isolated from the P19 mouse embryonal carcinoma stem cell line. In a subset of these clones, loss of aprt expression was correlated with increased DNA methylation, a nuclease-resistant chromatin conformation, and loss of RNA transcription; reactivation was associated with a reversal of these parameters. In this report, the role of DNA methylation in transcriptional inactivation was studied in the H22D3 clone. The cells of this clone contain a single inactive aprt allele that is methylated. Mass cultures of H22D3 were treated with 2-deoxy-5'-azacytidine (5aCdr) and found to reactivate aprt at frequencies ranging from 60 to 90%. Treated cultures were then assayed over time for aprt mRNA, chromatin conformation, and DNA methylation of the aprt gene. These studies demonstrated that 5aCdr treatment resulted in promoter region-specific hemidemethylation and chromatin relaxation starting at 12 h. This was followed by the appearance of RNA transcripts at 18 h and increasing levels of APRT enzymatic activity at 36 h after treatment. Complete demethylation occurred significantly later. Experiments in which cells were treated with 5aCdr for varying periods of time demonstrated that a single round of analog incorporation was sufficient for transcriptional reactivation of aprt in H22D3.

Adenine Phosphoribosyltransferase↗

PubMed1993

Region-specific rates of molecular evolution: a fourfold reduction in the rate of accumulation of "silent" mutations in transcribed versus nontranscribed regions of homologous DNA fragments derived from two closely related mouse species.

We have sequenced homologous DNA fragments of 2.7 and 2.8 kbp derived from the closely related mouse species Mus musculus domesticus (M. domesticus) and Mus musculus musculus (M. musculus), respectively. These two species diverged approximately 1 million years ago. Each DNA fragment contains 1.35 kbp of the 3' end of the constitutively expressed 2.2-kbp aprt (adenine phosphoribosyltransferase) gene and a similarly sized nontranscribed region downstream of the aprt gene. The aprt gene region contains protein coding sequences (0.35 kbp), intronic sequences (0.75 kbp), and a 3' nontranslated sequence (0.25 kbp). Both the M. domesticus and M. musculus downstream regions share three partial copies of the B1 repetitive element with the M. musculus downstream region containing an additional complete copy of this element. A comparison of the 2.7- and 2.8-kbp DNA fragments revealed a total of 63 molecular alterations (i.e., mutations) that were approximately fourfold more abundant in the nontranscribed downstream region than in the transcribed aprt gene. Of the 11 mutations observed in the transcribed region, 7 were found in introns, 3 in the 3' untranslated sequence, and 1 was a synonymous change in an exon. A comparison of the human and M. domesticus aprt genes has previously revealed no homology in either the intronic or 3' nontranslated regions with the exception of a 26-bp sequence in intron 3 and sequences at the exon/intron boundaries necessary for correct mRNA splicing (Broderick et al., Proc. Natl. Acad. Sci. USA, 84:3349, 1987). Therefore, there does not appear to be selective pressure for sequences within these regions. We conclude that there is a lower rate of accumulation of "silent" mutations in the transcribed mouse aprt gene than in a contiguous nontranscribed downstream region. A possible molecular mechanism involving preferential DNA repair for the transcribed region is discussed.

Adenine Phosphoribosyltransferase↗

PubMed1992

At least two distinct epigenetic mechanisms are correlated with high-frequency "switching" for APRT phenotypic expression in mouse embryonal carcinoma stem cells.

A series of clones displaying high frequency "switching" phenotypes for expression of the adenine phosphoribosyltransferase (aprt) gene were previously isolated from the P19 mouse embryonal carcinoma stem cell line. Most clones contained only one aprt allele. We report here the characterization of each of these clones with regards to enzymatic activity, mRNA steady state levels, DNA methylation, and chromatin conformation. When clones were selected for resistance to the purine analog 2,6-diaminopurine, which requires markedly reduced levels of APRT enzymatic activity, two distinct classes were observed. The first class was associated with reduced or undetectable levels of aprt mRNA, hypermethylation of the 5' CpG island, and a closed chromatin conformation within this region. When clones of this class were selected for reacquisition of APRT enzymatic activity they were found to have increased mRNA levels, a hypomethylated CpG island, and an open chromatin conformation. In contrast, the second class of clones displayed wild-type levels of mRNA, CpG island hypomethylation, and an open chromatin conformation regardless of whether they were selected for the presence or absence of APRT enzymatic activity. The implications of these results for general mechanisms of epigenetic change in somatic cells and the possibility that expression of the mouse aprt gene may be developmentally regulated are discussed.

Adenine Phosphoribosyltransferase↗