High Levels Of TP Research Articles

Monitoring planktonic cyanobacteria in Lake Maninjau, West Sumatra, Indonesia

Harmful Cyanobacterial blooms are global environmental issue. Some efforts have been made to prevent and minimize their occurrence in waters. This study aims to monitor the planktonic Cyanobacteria community and environmental factors that influence their dominance in Lake Maninjau. Samples of Phytoplankton and water quality data were collected in 2001, 2005, 2009, 2014, 2015, 2016, 2018, and 2019. Twenty-four species of planktonic Cyanobacteria which belonged to orders Chroococcales, Oscillatoriales, and Nostococales. Percentage of Cyanobacteria abundance ranged from 2.9% to 95.32%. High percentage of Aphanocapsa (76.21%), Anabaena (33.25%), Chroococcus (86.4%), Microcystis aeruginosa (94.37%), Oscillatoria (50.94%), and Aphanizomenon gracile (72.43%) was recorded in different periods. Cylindrosprmopsis raciborskii was often found in the lake with percentage of abundance not more than 20.75%. Cyanobacteria abundance ranged from 734.2 to 4,180,867 individualL-1. The lowest Cyanobacteria abundance was characterized by low total phosphorus and conductivity. High Cyanobacteria abundance was related to the high levels of TP, concentration, conductivity and low TN/TP ratio. Nutrient, conductivity, and temperature were also the factors that influenced the dominance of Cyanobacterial species in Lake.

Silver nanoparticles and silver salt (AgNO3) elicits morphogenic and biochemical variations in callus cultures of sugarcane.

The research work was arranged to check the role of AgNPs and silver ions on callus cells of sugarcane (Saccharum spp. cv CP-77,400). AgNPs were synthesized chemically and characterized by UV-Vis spectra, XRD and SEM. AgNPs and silver ions were applied in various concentrations (0, 20, 40, 60 ppm) to sugarcane calli and the induced stress was characterized by studying various morphological and biochemical parameters. AgNPs and silver ions treatments produced high levels of malondialdehyde, proline, proteins, TP and TF contents. Similarly, CAT, SOD and POX activity was also significant in both treatments. The lower concentration of AgNPs and silver ions (20 ppm) provided maximum intracellular GSH level. This work mainly showed effects of AgNPs and silver ions on sugarcane calli in terms of morphological aberrations and cell membrane damage due to severe oxidative stress and production of enhanced levels of enzymatic and non-enzymatic antioxidants as self-defence to tolerate oxidative stress by scavenging reactive oxygen species. These preliminary findings will provide the way to study ecotoxicity mechanism of the metal ions and NPs in medicine industry and in vitro toxicity research. Furthermore, silver ions alone and their chemically synthesised AgNPs can be used for various biomedical applications in future.

Kinetics mechanism and regulation of native human hepatic thymidine phosphorylase.

Thymidine phosphorylase (TP; EC 2.4.2.4) catalyzes the reversible phosphorolysis of thymidine, deoxyuridine, and their analogues to their respective nucleobases and 2-deoxy-α-d-ribose-1-phosphate (dRib-1-P). TP is a key enzyme in the pyrimidine salvage pathways. Activity of the enzyme is crucial in angiogenesis, cancer chemotherapy, radiotherapy, and tumor imaging, Nevertheless, a complete set of kinetic parameters has never been reported for any human TP. This study describes the kinetic mechanism and regulation of native human hepatic TP. The liver is a main site of pyrimidine metabolism and contains high levels of TP. Initial velocity and product inhibition studies demonstrated that the basic mechanism of this enzyme is a sequential random bi-bi mechanism. Initial velocity studies showed an intersecting pattern, consistent with substrate-enzyme-co-substrate complex formation, and a binding pattern indicating that the binding of the substrate interferes with the binding of the co-substrate and vice versa. Estimated kinetic parameters were KThymidine = 284 ± 55, KPi = 5.8 ± 1.9, KThymine = 244 ± 69, and KdRib-1-P = 90 ± 33 μM. Thymine was a product activator, but becomes a substrate inhibitor at concentrations eight times higher than its Km. dRib-1-P was a non-competitive product inhibitor of the forward reaction. It bounded better to the Enzyme●Pi complex than the free enzyme, but had better affinity to the free enzyme than the Enzyme●Thymidine complex. In the reverse reaction, dRib-1-P enhanced the binding of thymine. The enhancement of the thymine binding along with the fact that dRib-1-P was a non-competitive product inhibitor suggests the presence of another binding site for dRib-1-P on the enzyme.

Distinct substrate specificity and physicochemical characterization of native human hepatic thymidine phosphorylase.

Thymidine phosphorylase (TP; EC 2.4.2.4) is involved regulation of intra- or extracellular thymidine concentration, angiogenesis, cancer chemotherapy, radiotherapy, as well as tumor imaging. Although the liver is main site of pyrimidine metabolism and contains high levels of TP, nonetheless, purification and characterization of human hepatic TP has not been accomplished. We here report the purification and characterization of native human hepatic TP. The enzyme was purified to apparent homogeneity by a procedure shorter and more efficient than previously reported methods. Human hepatic TP has an apparent Kthymidine of 285 ± 55 μM. Like the enzyme from other tissues, it is highly specific to 2'-deoxyribosides. However, in contrast to TP from other normal tissues, the hepatic enzyme is active in the phosphorolysis of 5'-deoxy-5-fluorouridine, and the riboside 5-fluorouridine. Furthermore, native hepatic TP exists in different aggregates of 50 kDa subunits, with unknown aggregation factor(s) while TP from extra tissues exists as a homodimer. Isoelectric point was determined as 4.3. A total of 65 residues in the N-terminal were sequenced. The sequence of these 65 amino acids in hepatic TP has 100% sequence and location homology to the deduced amino acid sequence of the platelet derived-endothelial cell growth factor (PD-ECGF) cDNA. However, and contrary to PD-ECGF, the N-terminal of hepatic TP is blocked. The block was neither N-formyl nor pyrrolidone carboxylic acid moieties. The differences in substrate specificities, existence in multimers, and weak interaction with hydroxyapatite resin strongly suggest that hepatic TP is distinct from the enzyme in normal extrahepatic tissues. These results may have important clinical implications when TP is involved in activation or deactivation of chemotherapeutic agents in different tissues.

한국 서남해역 인공해수욕장의 적합성 판정과 수질관리 방안

This study aimed to determine the swimming suitability of sea and to suggest methods to address the problems on sea water color and green plants growing on sediment in the artificial created swimming in the beach of southwestern Korea. Sea water samples were collected from January to December of 2010 and analysis for SS, COD, , TP, MPN, sediment IL, ORP and plants on sediment. The results showed that the sea water under the swimming suitability level of management based on the relating high levels of SS and TP, but still suitable for swimming on the basis of MPN. Improving exchange seawater flow, dredging, coating and chemical treatment of polluted sediments in addition to removal of point sources and restriction of non point sources in the study area could improve the sea water quality and swimming suitability of the sea.

Heterogeneous ribonucleoprotein K and thymidine phosphorylase are independent prognostic and therapeutic markers for oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the major cancer of head and neck with increasing incidence and mortality in Taiwan. We investigate hnRNP K, TP and FLIP expression and assess the prognostic and therapeutic potential of these markers in oral squamous cell carcinoma (OSCC). We analyzed hnRNP K, TP, and FLIP expression in 110 OSCC patients by immunohistochemistry. Statistical analyses were applied to correlate nuclear and cytoplasmic hnRNP K with elevated TP and FLIP, and to determine the associations of these three markers with clinicopathological manifestations, and assess their prognostic and therapeutic significance. The therapeutic implication of elevated TP was determined by measuring the sensitivity of OSCC cells to the TP-targeting drug, 5-fluoro-5'-deoxyuridine (5'-DFUR). We found that each of these proteins was overexpressed in OSCC tumors. Nuclear hnRNP K and cytoplasmic hnRNP K were strongly associated with TP (r(2)=0.344, P=0.0004) and FLIP (r(2)=0.201, P=0.035), respectively. High hnRNP K and TP levels were associated with clinicopathological parameters predictive of poorer treatment outcome. Multivariate analyses indicated that cytoplasmic hnRNP K and TP are independent predictors of overall survival (P=0.022 and 0.009, respectively) and disease-free survival (P=0.012 and 0.005, respectively). OSCC cells expressing high levels of TP were more sensitive to treatment with 5'-DFUR. Elevated cytoplasmic hnRNP K and TP overexpression are associated with poorer survival in OSCC patients. In vitro experiments suggest that OSCC tumors with high levels of TP are more sensitive to 5'-DFUR treatment. Thus, cytoplasmic hnRNP K and TP may be potential prognostic and therapeutic markers for OSCC.

Nutritive value of Cistus salvifolius shrubs for small ruminants

Natural grasslands play an important role in sheep production in Southern Portugal. The increase of browse species ( e.g., Cistus spp. shrubs) supplies green material to grazing animals and can be the only source of nutrients during some periods of the year, particularly when there is a shortage of conventional feedstuffs. The aim of this study was to characterize leaves, flower buds and fruits from Cistus salvifolius shrubs, harvested at different maturity stages in the Alentejo region of Portugal, by phenological, gas production methods. C. salvifolius shrubs presented leaves during the entire year, with a continuous increase of leaves from November until March. Fruits were found from November to May and flower buds were observed from April to June. Stems constituted the highest dry weight (DW 40°C; weight after drying at 40 °C) proportion of the plant (545 g/kg DW 40°C), followed by the leaves (370 g/kg DW 40°C) and reproductive organs (85 g/kg DW 40°C). The neutral detergent fibre (NDF) and lignin (sa) contents of the leaves ranged from 267 to 350 g/kg DM and 68 to 148 g/kg DM, respectively. Leaf CP and total phenolics levels decreased linearly with time. Linear regressions resulted in R 2 of 0.961 (P=0.00002) and 0.825 (P=0.0128), respectively. Levels in leaves and flower bud fractions reached levels as high as 120 and 85 g/kg DM, respectively. In the fitted models for gas production rates, the maximum rates for the November, December, January and June harvests were approximately one half of those in February, March, April and May. The highest fitted levels of total leaf gas production were in November (31.66 ml/200 mg DM) and the lowest in March (13.35 ml/200 mg DM). The highest fitted gas production levels were for fruits (40.29 ml/200 mg DM) and flower buds (30.74 ml/200 mg DM), which also had the lowest total phenolic contents (44.0 g/kg DM – fruits and 65.0 g/kg DM – flower buds). It is concluded that the use of C. salvifolius shrub (including the leaves) as a feed source for small ruminants in the farming system when there is a shortage of conventional feedstuffs, requires careful monitoring during the flower bud stage, when high TP levels are observed. The potential for metabolic disorders associated with high TP levels implies that diets based only on this shrub should be avoided.

Correlation between metabolic syndrome and clinical progression in patients with benign prostatic hyperplasia

To assess the correlation between metabolic syndrome and clinical progression in patients with benign prostatic hyperplasia (BPH). A total of 382 BPH patients with lower urinary tract symptoms were divided into two groups according to whether or not there was a diagnosis of metabolic syndrome (MS). MS was defined by the International Diabetes Federation (IDF) in 2005. Abdominal B-ultrasound was used to measure the total volume of prostate (TP) and its average annual growth rate was calculated. Body mass index, waist-hip ratio, blood biochemistry, blood pressure, blood glucose and other indicators were compared in these two groups of patients with regards to the clinical progression associated with BPH. A total of 187 MS cases were found in 382 (48.59%) BPH patients. It showed a higher body mass index, high glycemia, high triglycerides, high blood pressure and high IPSS, TP and PSA levels. Also it showed a higher occurrence of surgical rate (P < 0.05); its average annual growth rate of TP was significantly higher than those without MS (1.0 vs 0.64 ml/yr, P < 0.05). TP average annual growth rate and IPSS score are found significantly correlated with blood glucose and triglyceride levels (P < 0.01). Metabolic syndrome affects the clinical progression in patients with BPH. Clinical attention should be paid.

New production and the f ratio around the Crozet Plateau in austral summer 2004–2005 diagnosed from seasonal changes in inorganic nutrient levels

Recent mesoscale iron-fertilisation experiments suggest that iron may be an important micronutrient in HNLC regions but estimates of carbon export from such experiments are inconclusive. An alternative strategy to estimate export from such environments is to observe naturally productive ecosystems associated with topography. One such system is the Crozet islands and associated plateau (Crozet), at 46°S, 52°E. Each year a large bloom of phytoplankton occurs to the north of Crozet with a reduced bloom occurring to the south. We use nitrate data from the Crozet region collected during austral summer 2004–2005 to estimate new production (NP) via the Redfield ratio. Peak integrated values of up to 50 g C m−2 to the north of the plateau and up to 15 g C m−2 to the south are inferred. We estimate total integrated primary production (TP) using satellite techniques and calculate f for each station. Overall NP is linearly related to TP. However, f declines at very high levels of TP because nitrate usage ceases despite continuing PP and because nitrate levels increased from their postbloom low. This results either from a resupply of nitrate from beneath the thermocline due to mixing processes or to the mixed-layer ammonification and nitrification of accumulated organic nitrogen. We discount the first possibility because our estimates of the mixing flux of nitrate appear to be inadequate to cause the entire recovery in nitrate levels, and because any mixing flux of nitrate would likely be accompanied by a resupply of iron, which would induce NP to occur and erode the resupply of nitrate. Instead we consider the recycling of accumulated organic nitrogen to be a more likely explanation based on our observation of high organic nitrogen levels in the mixed layer north of Crozet during the cruise. The implications of this conclusion are that euphotic zone nitrification is a significant process, and that in this system new and export production are not equivalent. This recycling is sufficiently large that it reduces our estimate of NP north of the plateau to a level where it is equivalent to NP in the south. Whether a similar refertilisation of the mixed layer occurred in the south of the study region, which would be consistent with a meridional gradient in carbon export, is unknown due to the limited duration of the shipboard programme.

A possible role of thymidine phosphorylase expression and5‐fluorouracil increased sensitivity in oropharyngeal cancer patients

Thymidine Pi deoxyribosyltransferase (TP) is an enzyme involved in DNA synthesis up-regulated in tumours and it is also a pro-angiogenic factor. TP cannot activate capecitabine, because capecitabine first needs conversion by carboxylesterase and cytidine deaminase into 5-deoxy-fluorouridine. This compound can be activated by TP to 5-fluorouracil (5-FU). Although TP is not necessary for 5-FU toxicity, experimental data suggest that high levels of TP correlate with an enhanced response to 5-FU therapy. In this study, we have analysed by immunohistochemistry CD34, CD68 and TP positive cells in bioptic samples from 53 patients with T1–3 N0–1 M0 oropharyngeal squamous cell carcinoma (OSC) and from 24 patients with non-dysplastic oropharyngeal leukoplakia (NDOLP). Results showed that the mean of TP-positive cells, CD68 positive macrophages and CD34 positive endothelial cells eval-uated as microvessel density (MVD) was significantly higher in OSC than in NDOLP. Moreover, at a median follow-up of 19 months, patients with TP expression and higher MVD showed a better survival rate as compared to those with low MVD, probably as a consequence of 5-FU-based therapy.We hypothesized a role for TP in oropharyngeal tumourigenesis and 5-FU activation in the adjuvant setting of OSC patients.

Molecular Basis for the Inhibition of Anticancer Agents-induced Apoptosis by Thymidine Phosphorylase

An angiogenic factor, platelet-derived endothelial cell growth factor/thymidine phosphorylase (PD-ECGF/TP), stimulates the chemotaxis of endothelial cells and confers resistance to apoptosis induced by hypoxia. 2-Deoxy-D-ribose, a degradation product of thymidine generated by TP enzymatic activity, partially prevented hypoxia-induced apoptosis. TP was expressed at higher levels in tumor tissues compared to the adjacent non-neoplastic tissues in a variety of human carcinomas. High expression of TP is associated with an unfavorable prognosis. To investigate the effect of TP on cisplatin-induced apoptosis, human leukemia Jurkat cells were transfected with wild-type or mutant (L148R) TP cDNA. Jurkat cells transfected with TP cDNA (Jurkat/TP) and mutant TP cDNA (Jurkat/TPMu) expressed high levels of TP, while Jurkat/CV cells which were transfected with a control vector did not express TP. A high TP enzyme activity was detected in Jurkat/TP cells, but not in Jurkat/CV and Jurkat/TPMu cells. Sensitivities to cisplatin of these cells were determined by MTT assay. IC50 values for cisplatin of Jurkat/CV, Jurkat/TP, and Jurkat/TPMu cells were 4.50, 14.08, 13.40 microM, respectively. Jurkat/TP and Jurkat/TPMu cells were about three times more resistant to cisplatin than Jurkat/CV cells. TP inhibited activation of caspase 3, 9 and mitochondrial cytochrome c release induced by cisplatin. These findings suggest a mechanism by which TP confers the resistance to cisplatin-induced apoptosis. Moreover, mutant TP that has no enzymatic activity also suppressed the cisplatin-induced apoptosis. These suggest that TP molecules have cytoprotective functions against cytotoxic agents.

Intratumoral mRNA levels predict clinical outcome in patients with metastatic colorectal cancer treated in a prospective clinical trial with 5-FU and oxaliplatin

10010 Background: 5-flurouracil (5-FU) and Oxaliplatin-based therapy is one of the most frequently used combinations in the treatment of advanced colorectal cancer (CRC). There are no validated and established predictive factors for clinical outcome following 5-FU/Oxaliplatin treatment. We had shown an association between intratumoral mRNA levels of TS and ERCC1 involved in 5-FU metabolism and DNA repair, respectively, and survival to 5-FU/Oxaliplatin chemotherapy in advanced CRC in a retrospective study. Now we investigated whether intratumoral mRNA levels of these two genes and others involved in 5-FU metabolism (DPD, TP, dUTPase), DNA repair (ERCC2, XRCC1), angiogenesis (COX-2, EGFR, IL-8, PLA2), and drug detoxification (GSTP-1) predict the clinical outcome of patients with CRC in a prospectively designed biomarker study. Methods: 85 patients with metastatic CRC treated with second-line 5-FU/Oxaliplatin from the prospective trial were included. mRNA levels of 12 genes were assessed from paraffin- embedded tissue samples using laser capture microdissection and quantitative Real-time PCR. Overall survival (OS) was the primary endpoint. Progression-free survival (PFS), response, and toxicity were the secondary endpoints. Results: There were 40 women and 45 men (median age 60 years; range 29–87), median survival of 9.7 ms, median PFS of 4.2 ms, CR in 1 (1%) patient, PR in 15 (18%), SD in 36 (43%) and PD in 32 (38%) patients. High intratumoral mRNA levels of PLA2, TP, GSPTP-1 and low mRNA levels of COX-2 were each significantly associated with shorter OS (P≤0.05, log-rank test). There was a trend in the association between high mRNA levels of PLA2 and shorter PFS (P=0.08). In addition, high mRNA levels of XRCC1 and IL-8 were each significantly associated with high risk of cumulative grade 3+ toxicity (P≤0.05). No significant association was found between mRNA levels and response to 5-FU/Oxaliplatin. Conclusions: This study suggests that mRNA levels of PLA2, TP, GSTP-1, COX-2, XRCC1, and IL-8 may be useful to predict the outcome of patients with metastatic CRC with second-line 5-FU/Oxaliplatin chemotherapy. These findings should be validated with future basic sciences studies and prospective clinical trials. [Table: see text]

Thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), ERCC1, &amp; thymidine phosphorylase gene expression in primary &amp; metastatic (met) colorectal cancer (CRC) tissue in patients (pts) treated on a phase I trial of oxaliplatin (OX) &amp; capecitabine (Xel)

3549 Background: Overexpression of TS/DPD & ERCC1 in tumor tissue have been associated with insensitivity to 5-FU and OX therapy, respectively, while high TP levels predict for increased sensitivity to Xel. Methods: When feasible, biopsies of met tumor were taken in pts before OX (130 mg/m2 d1)/Xel (1200–3000 mg/m2 d1–5,8–12) q 3wk. Microdissected met & archival primary tumors were analyzed for gene expression (vs b-actin) of these 4 targets by real-time QRT-PCR. Survival (Surv) & time to treatment failure (TTF) were analyzed by log-rank. Gene expression v outcome was assessed using median (med), 25th & 75th percentiles for each target. Results: 90 pts participated. The med # prior chemotherapies was 2; 96% had prior 5-FU; 78% had prior irinotecan. Med mRNA levels were higher in met v primary tumor (table); rank sum analysis of paired samples showed (med): TS, 4.2 vs 2.2, p<0.001; DPD, 1.7 vs 0.4, p=0.005; ERCC1, 2.3 vs 1.1, p=0.002; TP, 6.3 vs 3.9 p=0.018. Pts whose tumor had ERCC1 >75th % had shorter TTF (med 162 d vs 85 d, p=0.026); pts with TP >75th % tended to have longer TTF (med 194 d vs 146 d, p=0.072). Individual mRNA levels in met tumor did not correlate with Surv, but pts whose tumors had both TS & ERCC1 < med had longer Surv (med 502 vs 296 days, p=0.038). Conclusions: In this study, target gene expression in primary tumor did not reflect levels in met tissue. In pre-treated CRC pts, mRNA levels of TP & ERCC1 in met tumor had some predictive value for TTF with OX/Xel therapy. Low levels of TS & ERCC1 predicted for improved Surv. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Response Genetics, Sanofi-Synthelabo Response Genetics

The physico-chemical conditions of Turkwel Gorge Reservoir, a new man made lake in Northern Kenya

Variations in some physical, chemical, and nutrient conditions were investigated at Turkwel Gorge Reservoir and its inflowing river, Suam between 1994 and 1995. Seasonal changes in inflow volume had the greatest impact on the reservoir and river conditions investigated. A wide fluctuation in inflow volume combined with a regulated outflow independent of season resulted in a draw down of over 10 m in each year. Flood inflows during the wet season resulted in the lowest values of Secchi depth (range, 0.09–2.16 m), electrical conductivity (EC, range = 140–200 mS cm −1) and total alkalinity (TA, range = 75–111 mg l −1) while the highest values were measured during the dry season. A functional relation between EC and TA (TA = 0.529 mg l −1, EC: R 2 = 0.876) suggests a predominance of carbonates among the anions. Vertical profiles of temperature and dissolved oxygen (DO) revealed that the reservoir is monomictic with a wide variation in the depth of the daily mixed layer. High values of pH (range = 6.7–8.9) and DO (range = 4.9–9.2 mg l −1) were associated with periods of peak phytoplankton photosynthesis while the lowest values followed reservoir mixing. Peak total nitrogen (TN, range = 119–526 μg l −1) and total phosphorus (TP, range = 8.9–71.6 μg l −1) levels during the wet season resulted from increased river loading. Values of dissolved reactive silica (DRS, range = 0.41–9.77 mg l −1) showed a wet season decline which was related to diatom depletion during the wet season. Annual reservoir areal loading rates of 27.38, 10.90 and 408.5 mg m −2 were computed for TN, TP and DRS respectively based on estimates of inflowing river loads in 1994. At the inflowing river Suam, low levels of EC (range = 107–210 μS cm −1) and TA (range = 62–125 mg l −1) occurred during the wet season while the highest levels occurred shortly before the river dried up. The first flood water at the resumption of river inflow in March was characterized by very low levels of DO (range = 1.8–8.2 mg l −1) and high levels of TN (range = 205–3354 μg l −1) and TP (102–1259 μg l −1). River pII (6.9–7.7) and DRs (range = 9.01–19.93 mg l −1) varied irregularly throughout the year.

Using generalized additive models for prediction of chlorophyll a in Lake Okeechobee, Florida

AbstractLong‐term eutrophication data collected by the South Florida Water Management District at eight stations in the pelagic region of Lake Okeechobee since 1980 were combined with those from littoral region stations collected since 1986. These data were supplemented by those collected by the University of Florida in conjunction with the Lake Okeechobee Ecosystem Study. Generalized additive models (GAM) were fit to the chlorophyll a response for each of five previously documented‘ecological zones’, each using the same predictor variables for comparison between zones. Significant nonlinear increasing relationships between log10 TP and log10 chlorophyll a were found for littoral and near littoral regions of the lake, which change to decreasing at certain (high) levels of log10 TP. This change to a decreasing function suggests light limitation associated with high TP levels due to particle resuspension. The error distribution of the GAM compare favourably to those of linear models. The relationship of the chlorophyll a response to the predictors used in the GAM appear similar for littoral and near littoral regions, as they do for north pelagic and central pelagic ecological zones, with intermediate shapes of these functions found in the transition zone between these two groups.

Soil Phosphorus as a Potential Nonpoint Source for Elevated Stream Phosphorus Levels

AbstractEroded soils, as a potential nonpoint P source, have come under scrutiny, particularly in agricultural watersheds. Surface water and groundwater in the Tualatin River Basin (TRB) of Northwestern Oregon have maximum concentrations of 2.1 and 2.6 mg P/L, respectively. We hypothesized that TRB soils are a major P source in the basin because of their high native soil P concentrations and soil P adsorption characteristics. We sampled eight soil series from both lowland and upland positions in the TRB, with both andic and nonandic mineralogy. All soils sampled had high total P concentrations (660–2304 mg P/kg soil). High average extractable P (Bray P1, 74 mg P/kg soil, and ammonium bicarbonate, 35.7 mg P/kg soil) concentrations were found primarily in lowland, nonandic soils. There was no significant difference between P sorption maxima; however, P affinity was significantly higher in upland soils (0.19 L/mg P) than in lowland soils (0.04 L/mg P). Upland, andic soils, due to their erosion potential and high TP levels (average of 1889 mg P/kg soil), could be a P source for surface waters. Lowland, nonandic soils, due to their high extractable P concentrations and lower P sorption affinity, could be a source for both surface and groundwater. Thus, all soils studied, comprising approximately 50% of TRB soils, are potential nonpoint P sources in this watershed, indicating that native soil P is a potential source of nonpoint P pollution.

Molecular epidemiology of resistance to trimethoprim in enterobacteria isolated in a Parisian hospital

Between January, 1981 and December, 1984, 419 strains of enterobacteria isolated from patients at the Hôpital Saint-Joseph were studied for (1) the level of resistance to trimethoprim (Tp) by determination of minimal inhibitory concentration (MIC), (2) transferability of this resistance by conjugation into Escherichia coli, (3) plasmid content of wild-type strains and transconjugants by agarose gel electrophoresis of crude bacterial lysates and by incompatibility grouping, and (4) type of dihydrofolate reductase (DHFR) by colony hybridization with probes specific for DHFR types I and II. Tp resistance was defined as MIC greater than or equal to 4 micrograms/ml and high-level resistance by MIC greater than or equal to 1000 micrograms/ml. Amongst the strains studied, 90% were resistant to high levels of Tp, while 10% had low-level resistance to Tp was detected in 180 strains corresponding to 185 plasmids. In the vast majority of the plasmids, resistance to Tp was associated with resistance to sulphonamide (94%), streptomycin (75-90%), ampicillin (75-90%) and chloramphenicol (65-80%). Plasmids conferring resistance to Tp were often large, most (84%) ranging in size from 90 to 175 Kb. They belonged to six different incompatibility groups and Inc6-C was the most prevalent (34 to 75%). The study of the distribution of the dfr genes by colony hybridization in 183 transconjugants and 89 strains with non-transferable Tp resistance revealed the presence of dfrI genes in most of these strains (48 and 53%, respectively). DHFR of types I and II were found in only 3% of the transconjugants, but in 15% of the strains with non-transferable resistance. DHFR of other types were found equally (15%) in strains with transferable and non-transferable resistance. The high incidence of the type I enzyme among the Tp-resistant strains probably results from the integration of transposon Tn7 into the chromosome or into a non-transferable plasmid.