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Biomedical subjects

W D Taylor

Publications and source records attributed to W D Taylor.

At least 19 recordsLinked to original sources
PubMed2004

A guide to geosmin- and MIB-producing cyanobacteria in the United States.

A guide to confirmed geosmin- and MIB-producing cyanobacteria isolated in the United States is being prepared. This document will include 41 different species or morphologically distinct types from eight states and diverse aquatic sources isolated over a 22-year period. The organisms comprised by this guide demonstrate the importance of attached cyanobacteria as off-flavor agents, the strain specificity of MIB production, the existence of unicellular MIB producers, the occurrence of multiple geosmin and MIB producers in reservoirs, and the relationship of certain planktonic odor producers to species in other countries.

Camphanes↗
PubMed2003

Guidelines for treatment of onychomycosis.

These guidelines for management of onychomycosis have been prepared for dermatologists on behalf of the British Association of Dermatologists. They present evidence-based guidance for treatment, with identification of the strength of evidence available at the time of preparation of the guidelines, and a brief overview of epidemiological aspects, diagnosis and investigation.

Administration, Topical↗
PubMed2001

Evidence of white matter tract disruption in MRI hyperintensities.

BACKGROUND: Diffusion tensor imaging (DTI) of brain tissue measures the apparent diffusion coefficient (ADC), or isotropic diffusion, and anisotropy, or diffusion as influenced by tissue structure. We hypothesized that hyperintensities, when compared with normal tissue by DTI, would show evidence of damage through an increased ADC and decreased anisotropy. We also hypothesized that DTI changes in hyperintensities would be similar between depressed subjects and control subjects. METHODS: Fourteen depressed geriatric patients and nineteen control subjects received DTI. The ADC and aniso-tropy of normal tissue from standard regions were compared with hyperintensities from these regions. The Students' t test compared individual regions and averaged white matter results. RESULTS: Hyperintensities showed higher ADC and lower anisotropy than normal regions. Gray matter exhibited similar trends. There was no significant difference in diffusion characteristics of hyperintensities between subjects and control subjects. CONCLUSIONS: Hyperintensities damage the structure of brain tissue, and do so comparably in depressed subjects and control subjects.

Aged↗
PubMed2001

Preventing experimental vertical transmission of scrapie by embryo transfer.

This study investigated whether the transmission of naturally occurring scrapie in sheep can be prevented using embryo transfer. Embryos were collected from 38 donor ewes in a Suffolk sheep flock with a high incidence of naturally occurring scrapie, treated with a sanitary procedure (embryo washing) recommended by the International Embryo Transfer Society and then transferred to 58 scrapie-free recipient ewes. Ninety-four offspring were produced. None of the offspring or the recipient ewes developed scrapie. Furthermore, offspring derived from embryos collected from donor ewes bred to the immunohistochemically positive ram did not develop scrapie. We conclude that scrapie was not transmitted to offspring via the embryo nor was the infective agent transmitted to recipient ewes during embryo transfer procedures.

Animals↗
PubMed2001

Maintenance of intact sediment box cores as laboratory mesocosms.

Mesocosms consisting of physically and biologically intact segments of natural communities are an ideal compromise between single species tests and ecosystem experiments in the assessment of sediment contamination. Therefore, large intact sediment cores, as mesocosms with naturally co-adapted communities, would allow sediment contamination to be assessed using the replicability and statistical power of laboratory techniques, while retaining much of the ecological realism of field studies. This study investigates the collection and maintenance of such cores, collected from an unimpacted site in Lake Erie. It demonstrates that box cores containing relatively undisturbed freshwater sediments can be brought back to the laboratory and maintained for up to 8 weeks with little change in the resident benthic fauna. Feeding the systems is not required, nor is it deleterious to the indigenous fauna.

Animals↗
PubMed2001

The use of benthic mesocosms for the assessment of sediment contamination.

The diagnostic capability of changes in the benthic macroinvertebrate community composition to determine the cause in contaminated sediments were addressed using box core mesocosms subjected to cadmium, atrazine and nutrient enrichment. Intact cores of lake sediment were collected from Lake Erie at four occasions during 1996 and were returned to laboratory where they were maintained and manipulated. The benthic community composition of the artificially polluted mesocosms was compared with field data, collected at the same time as the intact cores, and to untreated control boxes. Community composition was related to the measured environmental variables using multi-dimensional scaling (MDS) and principle axis correlation (PCC). Community responses to different treatments were both different and consistent, suggesting that the community structure of these mesocosms could be used to identify the primary source of impact.

Animals↗
PubMed2001

Resistance of cattle to scrapie by the oral route.

Early epidemiological information indicated that bovine spongiform encephalopathy (BSE) originated from scrapie in sheep. The question arose if scrapie in North America would induce a BSE-like disease in cattle. Six years ago, we reported that brain tissue from sheep with scrapie caused a neurologic disease when injected directly into the brains of cattle, but the disease induced was different from BSE as it occurs in the United Kingdom and Europe. Here, we report that cattle fed raw brain or meat and bone meal and tallow prepared from sheep with scrapie remained normal for 8 years after exposure. This work indicates that cattle are highly resistant to North American scrapie by the oral route.

Animals↗
PubMed2000

Phosphate concentrations in lakes.

Phosphate is an important nutrient that restricts microbial production in many freshwater and marine environments. The actual concentration of phosphate in phosphorus-limited waters is largely unknown because commonly used chemical and radiochemical techniques overestimate the concentration. Here, using a new steady-state radiobioassay to survey a diverse set of lakes, we report phosphate concentrations in lakes that are orders of magnitude lower than estimates made spectrophotometrically or with the frequently used Rigler radiobioassay. Our results, combined with those from the literature, indicate that microbes can achieve rapid turnover rates at picomolar nutrient concentrations. This occurs even though these concentrations are about two orders of magnitude below the level where phosphate uptake is estimated to be half the saturation level for the pico-plankton community. Also, while phosphate concentration increased with the concentration of total phosphorus and soluble reactive phosphorus in the lakes we sampled, the proportion of phosphate in the total phosphorus pool decreased from oligotrophic to eutrophic lakes. Such information, as revealed by the phosphate assay that we use here, should allow us to address hypotheses concerning the concentration of phosphate available to planktonic microorganisms in aquatic systems.

Animals↗
PubMed1997

Responses of Halobacterium halobium and Sulfolobus solfataricus to hydrogen peroxide and N-methyl-N'-nitro-N-nitrosoguanidine [correction of N-methyl-N-nitrosoguanidine] exposure.

We have examined the capacity of Halobacterium halobium and Sulfolobus solfataricus to withstand the lethal effect of hydrogen peroxide and N-methyl-N'-nitro-N-nitrosoguanidine [corrected]. We tested a variety of pretreatment regimens with both mutagens and all failed to elicit an inducible response to the lethal effects of those compounds in either organism. We have observed AP endonuclease activity in protein extracts from both organisms. In addition, S. solfataricus extracts contain activities that remove 3-methyl-adenine and O(6)-methyl-guanine from methylated DNA. This is the first report of these DNA repair activities in any member of the Archaea.

Carbon-Oxygen Lyases↗
PubMed1993

Immunohistochemical detection of prion protein in sheep with scrapie.

Prion protein (PrP), which is involved in the pathogenesis of scrapie, occurs in 2 forms. The form extracted from scrapie brain is protease resistant (PrP-res), whereas PrP from normal brain is protease sensitive (PrP-sen). This study examined whether PrP-res could be detected in brains of sheep with scrapie by immunohistochemistry (IHC). A suitable IHC procedure was developed using brain tissue from hamsters that had been inoculated with the transmissible mink encephalopathy agent. Tissue samples were fixed in PLP (periodate, lysine, paraformaldehyde) that contained paraformaldehyde at a concentration of 0.125%. Before application of the IHC technique, tissue sections were deparaffinized and treated with formic acid to simultaneously enhance PrP-res immunoreactivity and degrade PrP-sen. Primary antibody was obtained from a rabbit immunized to PrP-res extracted from brains of mice with experimentally induced scrapie. Brain from 21 sheep with histopathologically confirmed scrapie were examined by IHC. In all 21 brains, PrP-res was widely distributed throughout the brain stem. Staining was particularly intense in neuronal cell bodies and around blood vessels. The IHC technique successfully detected PrP-res in brain samples that had been frozen or that were severely autolyzed before fixation in PLP. Brains from 11 scrapie-suspect sheep that were not considered histologically positive were also examined by IHC. PrP-res was found in 4 of these brains. Sections of brains from 14 clinically normal sheep did not have detectable PrP-res. Results of this study indicate that IHC detection of PrP-res is equivalent, and perhaps superior, to histopathology for the diagnosis of scrapie in sheep. Furthermore, IHC is applicable to tissues that have autolytic changes or processing artifacts that prevent satisfactory histopathologic evaluation for lesions of scrapie.

Animals↗
PubMed1992

Cell density dependence of ultraviolet light enhanced reactivation of Herpes simplex type I and the large plaque effect in C3H/10T1/2 mouse fibroblasts.

C3H/10T1/2 mouse fibroblasts were grown to different cell densities either by plating at low density and allowing different growth periods, or by plating at a series of increasing densities and allowing the same growth period. These plates were UV irradiated at 7.5 J/m2 or mock irradiated and 24 h later infected with UV-irradiated Herpes simplex type I virus which had been UV irradiated at 50 or 125 J/m2 or mock irradiated. The numbers and sizes of plaques were measured and these data used to calculate the extent of UV-enhanced host cell reactivation, the capacity enhancement, the large plaque effect (LPE) and the small plaque effect (SME). The influence of cell density on these phenomena was similar for both series of density experiments. Ultraviolet-enhanced host cell reactivation could be demonstrated only for cultures of lower density. The capacity of the cells for Herpes simplex type I virus decreased with cell density, but UV irradiated cells showed an increase in capacity with cell density. Plaque sizes decreased in all cases with cell density but the LPE and SPE were not significantly altered. The greatest variation in the above parameters occurred just as the cells were approaching confluence, where most host cell reactivation experiments are carried out. We conclude that the reproducibility of such experiments depends critically on cell density, a dependence which may be relevant to mechanistic interpretations of the UV-dependent phenomena.

Animals↗
PubMed1991

Ultraviolet light-induced plasmid-chromosome recombination in Escherichia coli: the role of recB and recF.

Bacterial host cells of different rec genotypes were used to investigate genetic requirements of ultraviolet light (UV)-induced homologous plasmid-chromosome recombination. Plasmid DNAs which contained a wt or mutant lacY gene were irradiated with UV prior to transformation into Escherichia coli host strains which contained the complementary lacY allele. Surviving transformants were screened to determine the directions of UV-induced recombinational exchange between the bacterial and plasmid lacY genes, by assaying lactose utilization. Nonreciprocal chromosome-to-plasmid recombination was 100% dependent on the recA gene and greater than 80% dependent on the recF gene, but not dependent upon the recB gene of E. coli. In contrast, reciprocal plasmid-chromosome recombination was strictly dependent on the recA gene, greatly dependent (approx. 80%) on the recF gene, and moderately dependent on the recB gene. Nonreciprocal plasmid-to-chromosome recombination was only induced at very low frequencies, and appeared to be moderately dependent on the recB gene, but not dependent on the recF gene. UV-induced plasmid-chromosome recombination appeared to proceed by a two-step mechanism. In this model, the initial step is recF-dependent, recB-independent, and either resolves to become a nonreciprocal chromosome-to-plasmid recombinant, or proceeds to the second step. The second step is moderately recB-dependent and results in the reciprocal exchange of plasmid-chromosome sequences.

Bacterial Proteins↗
PubMed1990

Recombination between irradiated shuttle vector DNA and chromosomal DNA in African green monkey kidney cells.

An autonomously replicating shuttle vector was used to investigate enhancement of plasmid-chromosome recombination in mammalian host cells by gamma irradiation and UV light. Sequences homologous to the shuttle vector were stably inserted into the genome of African green monkey kidney cells to act as the target substrate for these recombination events. The shuttle vector molecules were irradiated at various doses before transfection into the mammalian host cells that contained the stable insertions. The homologous transfer of the bacterial ampicillin resistance gene from the inserted sequences to replace a mutant ampicillin sensitivity gene on the shuttle vector was identified by the recovery of ampicillin-resistant plasmids after Hirt extraction and transformation into Escherichia coli host cells. Gamma irradiation increased homologous shuttle vector-chromosome recombination, whereas UV light did not increase the frequency of recombinant plasmids detected. Introducing specific double-strand breaks in the plasmid or prolonging the time of plasmid residence in the mammalian host cells also enhanced plasmid-chromosome recombination. In contrast, plasmid mutagenesis was increased by UV irradiation of the plasmid but did not change with time. The ampicillin-resistant recombinant plasmid molecules analyzed appeared to rise mostly from nonconservative exchanges that involved both homologous and possibly nonhomologous interactions with the host chromosome. The observation that similar recombinant structures were obtained from all the plasmid treatments and host cells used suggests a common mechanism for plasmid-chromosome recombination in these mammalian cells.

Animals↗
PubMed1990

Developmental factors and performance in remedial courses.

This study investigated the relations between various developmental factors and performance in remedial courses. The Iowa Developing Autonomy Inventory, Iowa Managing Emotions Inventory, and Iowa Developing Competency Inventory were administered to 231 students enrolled in a developmental studies program at a large state university (enrollment about 25,000). Regression analyses indicated that various developmental measures accounted for a small effect (amount of variance accounted for ranged from 2% to 7%) on performance in remedial courses. The percentage of variance accounted for by the three inventories was similar to what could be accounted for by more traditional measures of SAT scores and high-school grade point averages. The percentage of variance accounted for by traditional measures ranged from 2% to 10%.

Achievement↗