A National Science Foundation?     

Powers PN 《Science (New York, N.Y.)》1946,104(2713):614-619

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THE DICTIONARY OF AMERICAN BIOGRAPHY     

Powers WH 《Science (New York, N.Y.)》1929,70(1805):121-122

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A mutation in the catalytic subunit of cAMP-dependent protein kinase that disrupts regulation   总被引：8，自引：0，他引：8  

L R Levin  J Kuret  K E Johnson  S Powers  S Cameron  T Michaeli  M Wigler  M J Zoller 《Science (New York, N.Y.)》1988,240(4848):68-70

A mutant catalytic subunit of adenosine 3',5'-monophosphate (cAMP)-dependent protein kinase has been isolated from Saccharomyces cerevisiae that is no longer subject to regulation yet retains its catalytic activity. Biochemical analysis of the mutant subunit indicates a 100-fold decreased affinity for the regulatory subunit. The mutant catalytic subunit exhibits approximately a threefold increase in Michaelis constant for adenosine triphosphate and peptide cosubstrates, and is essentially unchanged in its catalytic rate. The nucleotide sequence of the mutant gene contains a single nucleotide change resulting in a threonine-to-alanine substitution at amino acid 241. This residue is conserved in other serine-threonine protein kinases. These results identify this threonine as an important contact between catalytic and regulatory subunits but only a minor contact in substrate recognition.  相似文献   

Spatial variation of soil organic carbon concentrations and stable isotopic composition in 1-ha plots of forest and pasture in Costa Rica: implications for the natural abundance technique     

Jennifer S. Powers 《Biology and Fertility of Soils》2006,42(6):580-584

The goal of this study was to examine spatial variation of soil organic C and its stable isotopic composition (δ¹³C) in 1-ha plots of mature rain forest and a cattle pasture dominated by C4 grasses in Costa Rica. Soil samples were taken from 80 mapped locations per plot and analyzed for organic C and δ¹³C. The range of values for soil C concentrations was similar between forest and pasture, although the mean values were higher in the forest. δ¹³C was narrowly constrained in the forest (from −27.96 to −26.09‰) but varied from −15.09 to −28.59‰ in the pasture. Variograms revealed spatial autocorrelation of soil C and δ¹³C in the pasture and organic C concentration in the forest soil. The large range and spatial variability of δ¹³C in the pasture site may be due to varying contributions of C3 and C4 vegetation to the soil C pool, which may limit the usefulness of the natural abundance technique as a precise tracer of soil C dynamics in this pasture.  相似文献   

Effect of pectolytic enzyme preparations on the phenolic composition and antioxidant activity of asparagus juice   总被引：1，自引：0，他引：1  

Sun T  Tang J  Powers JR 《Journal of agricultural and food chemistry》2005,53(1):42-48

Commercial pectolytic enzymes were investigated for their influence on phenolics and antioxidant activities of asparagus juice. The antioxidant activity of asparagus juice was analyzed according to 2,2'-diphenyl-l-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) methods. The enzymes, with the exception of pectinase from Rhizopus sp., contained rutinase, which hydrolyzed rutin to quercetin. Asparagus juice treated with Viscozyme had the highest quercetin content without exhibiting a significant increase in the antioxidant activity. For a pectinase from Aspergillus niger, the antioxidant activity of asparagus juice was markedly reduced. Caution should be paid in the selection of pectolytic enzyme preparations for production of antioxidant activity-rich juice.  相似文献   

Enzyme-electropolymer-based amperometric biosensors: an innovative platform for time-temperature integrators     

Reyes-De-Corcuera JI  Cavalieri RP  Powers JR  Tang J  Kang DH 《Journal of agricultural and food chemistry》2005,53(23):8866-8873

A novel exogenous time-temperature integrator (TTI) based on an amperometric glucose oxidase biosensor is presented. The TTI consists of the enzyme entrapped within an electrochemically generated poly(o-phenylenediamine) (PoPD) thin film deposited on the interior wall of a platinum (Pt) or a platinized stainless steel (Pt-SS) capsule. After thermal treatment, the TTI is mounted in a continuous flow system and connected to a potentiostat for amperometric detection of residual enzyme activity. A measurement is completed within 10 min. Isothermal treatments were carried out between 70 and 79.7 degrees C. Thermal inactivation of the immobilized enzyme followed apparent first-order kinetics with z values of 6.2 +/- 0.6 and 6.6 +/- 0.8 degrees C for Pt and Pt-SS capsules, respectively. These z values suggest that the proposed TTIs have the potential to assess pasteurization processes that target microorganism such as Listeria monocytogenes and Escherichia coli O157:H7.  相似文献   

Surgery and Doxorubicin in Dogs With Hemangiosarcoma   总被引：3，自引：1，他引：2  

Gregory K. Ogilvie DVM    Barbara E. Powers  Craig H. Mallinckrodt  Stephen J. Withrow 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1996,10(6):379-384

Forty-six dogs with histologically confirmed hemangiosarcoma of various locations other than skin were used in a prospective study to determine the efficacy of adjuvant doxorubicin (30 mg/m² IV q 3 weeks for 5 treatments) 10 to 14 days after the tumor was partially or completely excised. Analysis of the data included information on variables that were hypothesized to influence response to therapy, disease-free interval (DFI), or survival time (ST). Other information collected included age, gender, breed, weight, prior therapy, type of surgery, location of the primary tumor, presence of metastases, number of doses of doxorubicin, response to doxorubicin therapy (complete or partial response!, and the following histological criteria: overall differentiation, nuclear pleomorphism, percent necrosis, mitotic score, total histological score, and grade. Surgery outcome (complete versus incomplete surgical excision) markedly influenced survival times (P < .001). Twenty percent of the dogs rendered free of disease were alive at 1 year, whereas none of the dogs that had residual tumor after surgery were alive at 1 year. Most of the histological criteria (nuclear pleomorphism, mitotic score, grade, overall differentiation) had marked (P < .05), or close to marked, independent associations with ST for dogs that had complete tumor removal. Results from analysis of DFI were generally similar to those of ST in dogs with complete excision of the tumor. Twenty-seven of the 46 dogs (58.7%) had all clinical evidence of tumor successfully removed. Logistic regression analysis of surgical outcome (ability to remove all visible tumor) suggested that age of the subject was the only factor markedly influencing surgical outcome (P= .017). As age increased, the probability of success increased. Those dogs that had previous treatment for their hemangiosarcoma tended (P= .08) to have a shorter DFI and ST. Therefore, complete removal of all evidence of tumor followed by 5 doses of doxorubicin may be an effective treatment for dogs with hemangiosarcoma. Dogs that had all tumor successfully removed had a mean and median ST of 267 and 172 days, respectively. Dogs with incomplete tumor removal had a mean and median ST of 172 and 60 days, respectively. Similarly, prognostic variables such as the ability to completely excise all evidence of tumor, histological criteria, and age of the patient are potentially important prognostic variables for predicting outcome.  相似文献   

Monoclonal Antibody C219 Immunohistochemistry Against P-Glycoprotein: Sequential Analysis and Predictive Ability in Dogs With Lymphoma   总被引：1，自引：1，他引：0  

Philip J. Bergman DVM  MPH  MD    Gregory K. Ogilvie  Barbara E. Powers 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1996,10(6):354-359

In the present study, the prevalence of positive staining for P-glycoprotein using C219 monoclonal antibody was assessed in 58 tissue samples of high-grade lymphoma from dogs before initiation of chemotherapy. Samples were also evaluated at relapse in 22 dogs, at necropsy in 34 dogs, and at all 3 times in 15 dogs. The frequency of positive staining was significantly higher than that found prior to the initiation of chemotherapy at the following times: relapse ( P = .0001), necropsy ( P < .0001), and both relapse and necropsy ( P < .001, sequential data). The frequency of positive staining prior to the initiation of chemotherapy was significantly inversely related to remission ( P < .001) and survival times ( P = .0012). Similarly, when populations below and above the median initial C219 score were compared with respect to remission and survival times, the population with scores greater than the median had significantly lower remission ( P < .001) and survival ( P = .008) times, respectively. The frequency of positive staining determined at relapse was significantly inversely related to the time from relapse to death ( P = .0102). Similarly, when populations below and above the median relapse C219 score were compared with respect to the time from relapse to death, the population with C219 scores greater than the median had a significantly lower time from relapse to death ( P = .006). It appears that this immunohistochemical methodology may be used as a predictor of remission time, survival time, and the time from relapse to death. Additional studies are required to confirm the usefulness of C219 as a true marker of P-glycoprotein and to evaluate P-glycoprotein as a useful prognostic factor in dogs with lymphoma.  相似文献   

Prevalence of nephrotoxicosis associated with a short-term saline solution diuresis protocol for the administration of cisplatin to dogs with malignant tumors: 61 cases (1987-1989).     

G K Ogilvie  R C Straw  B E Powers  M F Cooper  S J Withrow 《Journal of the American Veterinary Medical Association》1991,199(5):613-616

The study reported here was undertaken to determine the nephrotoxicosis associated with the administration of cisplatin, an antineoplastic agent, to dogs when administered during 6-hour saline solution diuresis. Cisplatin (70 mg/m2 of body surface, IV, every 21 days) was given to 61 dogs with malignant neoplasia with a total of 185 doses in 1 (n = 9 dogs), 2 (n = 26 dogs), 3 (n = 4 dogs), 4 (n = 9 dogs), 5 (n = 2 dogs), and 6 (n = 11 dogs) treatments. The cisplatin was given over a 20-minute period after 0.9% NaCl solution (saline solution) was administered IV for 4 hours at a rate of 18.3 ml/kg of body weight/h. After the cisplatin infusion, saline solution diuresis was continued at the same rate for 2 hours. Before each treatment with cisplatin, dogs were evaluated with at least a physical examination, CBC, determination of serum urea nitrogen concentration, and in most cases, determination of serum creatinine concentration and urine specific gravity. Four of the 61 dogs (6.6%) developed clinically evident renal disease after 2 (1 dog), 3 (2 dogs), and 4 (1 dog) doses of cisplatin were administered. Three of the 4 dogs had preexisting disease of the urinary tract prior to the start of treatment. The survival time in dogs that developed renal disease (median, 145 days; range, 15 to 150 days) was similar to that of all dogs in this study (median, 154 days; range, 30 to 500 days), with 13 dogs still alive at the conclusion of the study.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

The need for biostatistical education in veterinary medicine     

J. D. Powers  T. E. Powers 《Veterinary research communications》1983,7(1):427-428

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