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At least 1,153 records · Page 64Linked to original sources
PubMed2003

Surveillance after positive and negative colonoscopy examinations: issues, yields, and use.

As colorectal cancer screening gains acceptance by the public, the use of colonoscopy will increase. The frequency of surveillance examinations after detection of an adenoma is one of the largest contributors to the cost of colorectal cancer screening. Ten years after the publication of the landmark National Polyp Study, the issue of when to perform surveillance examinations and how often to expect advanced findings remains acute. Current guidelines for surveillance vary across specialty organizations. Individuals with advanced adenomas are at increased risk for recurrent advanced adenomas. The impact of multiple nonadvanced adenomas or a single nonadvanced adenoma on subsequent risk of an advanced adenoma or cancer is less clear. Still less is known about findings on repeat examinations after an initial negative examination, whether after colonoscopy or sigmoidoscopy. The yield after a negative examination is an important consideration in determining the recommended interval for screening colonoscopy. For example, the data supporting a 10-yr interval for screening colonoscopy is only indirect. What little we do know about the yield after negative examinations comes from selected, nonrepresentative populations. Of concern, evidence from several polyp prevention trials demonstrates higher yields for subsequent cancer than would be expected, despite a relatively high use of surveillance procedures in follow-up. Further population-based research on the frequency of use and yield of surveillance examinations is needed. Studies that examine the need and the needed timing of subsequent surveillance are essential to containing costs for screening as well as to informing the public better about what endoscopic screening can and cannot accomplish.

Adenocarcinoma↗
PubMed2005

Yield of repeat wireless video capsule endoscopy in patients with obscure gastrointestinal bleeding.

PURPOSE: Capsule endoscopy (CE) has been shown to have a high diagnostic yield in patients with obscure gastrointestinal bleeding (OGIB). It is not known if repeating CE improves diagnostic yield or changes patient management when the initial CE is negative or nondiagnostic. The aims of this study are (1) to understand the reasons for repeat CE, (2) to determine the diagnostic yield of repeat CE, and (3) to establish if findings on repeat CE resulted in a change in patient management. METHODS: Between August 2001 and October 2003, we performed 391 capsule studies. Of these, 24 were repeat studies in patients with OGIB. We retrospectively reviewed the charts of these 24 patients. RESULTS: The reasons for repeat CE were: recurrent gastrointestinal bleeding (13), limited visualization on first exam due to poor prep or blood (10), complication (1) (capsule impaction at cricopharyngeus). Eighteen of 24 (75%) repeat capsule studies revealed additional findings (7 arteriovenous malformations, 2 gastropathy, 2 erosions, 2 masses, 1 ulcer, 2 red spots, 1 linear streak, 1 erythema). These findings led to changes in patient management in 15 of the 24 (62.5%) cases. CONCLUSIONS: Indications for repeat CE most commonly include recurrent gastrointestinal bleeding and limited visualization on initial study. Repeat CE results in a high yield of new findings that lead to changes in patient management. Repeat CE should be considered in patients with persistent OGIB when the initial study is negative or inconclusive.

Aged↗
PubMed2006

Addition of esophageal impedance monitoring to pH monitoring increases the yield of symptom association analysis in patients off PPI therapy.

BACKGROUND: The additional yield of esophageal impedance monitoring in identification of reflux as the cause of reflux symptoms is unknown. OBJECTIVES: To compare the yield of symptom-reflux association analysis of combined esophageal pH-impedance data with the yield of analysis of pH data alone. METHODS: In 60 patients with symptoms of heartburn and regurgitation combined, 24-h pH-impedance monitoring was performed. Acid-suppressive medication was stopped 1 wk in advance. Patients (48) with at least one symptom during the measurement period were selected for further analysis. Patients were instructed to note the time and nature of their symptoms. Eleven types of reflux episodes were defined, based on combinations of magnitude of the pH drop, nadir pH, and nature of the refluxate (gas and liquid) on impedance tracings. Symptom association analysis-symptom index, the symptom sensitivity index, and the symptom association probability (SAP)-was performed for each definition of reflux. RESULTS: The proportion of patients with a positive SAP (> or =95.0%) varied between 62.5% and 77.1%, depending on the definition of reflux episodes. When both pH and impedance parameters were used to identify reflux, a higher proportion of patients had a positive SAP than with pH alone (77.1%vs 66.7%, p < 0.05). Symptom association analysis for acidic and weakly acidic reflux separately did not result in a higher yield than analysis with all reflux episodes pooled, regardless of pH. CONCLUSION: In patients off proton pump inhibitor, the addition of impedance monitoring to esophageal pH monitoring leads to an increase in the proportion of patients in whom an association between reflux episodes and symptoms can be identified.

Adult↗
PubMed1991

Quantum yields for the cyclization and configurational isomerization of 4E,15Z-bilirubin.

Extraction of a solution of bilirubin configurational isomers in chloroform with an aqueous solution of human serum albumin was found to remove selectively the 4Z,15E-isomer. This phenomenon was used to develop a method for the purification of the 4E,15Z-isomer of bilirubin. The quantum yield for the cyclization and configurational isomerization of the 4E,15Z-isomer bound to a molar excess of human serum albumin was measured at 450 and 510 nm. The quantum yield for cyclization to form lumirubin was 0.12 and 0.19 at 450 and 510 nm, respectively. The quantum yield for configurational isomerization to form 4Z,15Z-bilirubin was 0.03 and 0.05 at 450 and 510 nm. An analysis of previously published data on the quantum yield for the formation of lumirubin from 4Z, 15Z-bilirubin bound to human serum albumin suggests that all of the formation of lumirubin may occur via consecutive photochemical processes with the 4E,15Z-isomer as an intermediate.

Bilirubin↗
PubMed2003

Yield effects of genetically modified crops in developing countries.

Onfarm field trials carried out with Bacillus thuringiensis (Bt) cotton in different states of India show that the technology substantially reduces pest damage and increases yields. The yield gains are much higher than what has been reported for other countries where genetically modified crops were used mostly to replace and enhance chemical pest control. In many developing countries, small-scale farmers especially suffer big pest-related yield losses because of technical and economic constraints. Pest-resistant genetically modified crops can contribute to increased yields and agricultural growth in those situations, as the case of Bt cotton in India demonstrates.

Agriculture↗
PubMed1997

Contribution of stream channel erosion to sediment yield from an urbanizing watershed

Stream channel erosion has long been suspected as the major contributor to long-term sediment yield from urbanizing watersheds. For San Diego Creek in southern California, measurements from 1983 to 1993 showed that stream channel erosion furnished 10(5) megagrams per year of sediment, or about two-thirds of the total sediment yield. Thus, because channel erosion can be a major source of sediment yield from urbanizing areas, channel stabilization should be a priority in managing sediment yield.

Journal Article↗
PubMed1987

Development of a defined medium and two-step culturing method for improved exotoxin A yields from Pseudomonas aeruginosa.

A two-step method is described for the production of exotoxin A by Pseudomonas aeruginosa in which a defined growth medium is modified for the toxin production phase. As a result, specific exotoxin A yields comparable to those obtained with complex media were achieved. In the development of this two-step process, several divalent metallic cations (Ca2+, Cu2+, and Mn2+), in addition to iron, were found to inhibit the yield of exotoxin A while Ca2+ and glycerol were found to increase yields. Northern blot analysis of total RNA isolates suggests that these effects on exotoxin A yields are based on events at the transcription level.

ADP Ribose Transferases↗
PubMed1990

Enhanced yield of shiitake by saccharide amendment of the synthetic substrate.

Three experiments were performed to determine the effect of selected saccharides on mushroom yield and basidiome size of shiitake (Lentinula edodes) when grown on a synthetic substrate. Substrate formulations of sawdust, wheat bran, and millet were nonamended or amended with sucrose, fructose, or glucose. Addition of sucrose (0.6 to 1.2% [dry weight]) to the substrate stimulated mushroom yield by 11 to 20% or more. Addition of fructose at 1.2% and glucose at 0.6% resulted in similar yield increases. Most of the yield increase occurred on the first break. The substrate amended with 1.2% sucrose tended to have a more synchronous maturation for the second break resulting in fewer days when mushrooms were harvested.

Journal Article↗
PubMed2003

Influence of nutritional factors on the nature, yield, and composition of exopolysaccharides produced by Gluconacetobacter xylinus I-2281.

The influence of substrate composition on the yield, nature, and composition of exopolysaccharides (EPS) produced by the food-grade strain Gluconacetobacter xylinus I-2281 was investigated during controlled cultivations on mixed substrates containing acetate and either glucose, sucrose, or fructose. Enzymatic activity analysis and acid hydrolysis revealed that two EPS, gluconacetan and levan, were produced by G. xylinus. In contrast to other acetic acid strains, no exocellulose formation has been measured. Considerable differences in metabolite yields have been observed with regard to the carbohydrate source. It was shown that glucose was inadequate for EPS production since most of this substrate (0.84 C-mol/C-mol) was oxidized into gluconic acid, 2-ketogluconic acid, and 5-ketogluconic acid. In contrast, sucrose and fructose supported a 0.35 C-mol/C-mol gluconacetan yield. In addition, growing G. xylinus on sucrose produced a 0.07 C-mol/C-mol levan yield. The composition of EPS remained unchanged during the course of the fermentations. Levan sucrase activity was found to be mainly membrane associated. In addition to levan production, an analysis of levan sucrase's activity also explained the formation of glucose oxides during fermentation on sucrose through the release of glucose. The biosynthetic pathway of gluconacetan synthesis has also been explored. Although the activity of key enzymes showed large differences to be a function of the carbon source, the ratio of their activities remained similar from one carbon source to another and corresponded to the ratio of precursor needs as deduced from the gluconacetan composition.

Acetic Acid↗
PubMed1979

Interferon production: variation in yields from human cell lines.

A survey of human diploid, aneusomic, transformed and tumor fibroblast or fibroblastoid cell lines for their capacity to produce interferon after polyriboinosinic acid:polycytidylic acid induction showed considerable variation in responsiveness. There was no apparent correlation between karyotype or phenotype and interferon production. Pretreating or "priming" the cells with human interferon generally led to increased yields of interferon after polyriboinosinic acid:polycytidylic acid induction in all cell lines tested. All the cells also showed the "super-induction" phenomenon, although to varying degrees. The combination of priming and superinduction conditions led to the production of very high yields of interferon in some cell lines, but in other lines, yields less than either the primed or superinduced amounts were found. A more limited survey of human cell lines for their capacity to produce interferon after Newcastle disease virus induction also showed that yields varied from line to line. However, there was little evidence to suggest that ability to produce interferon after Newcastle disease virus induction correlated with that after polyriboinosinic acid:polycytidylic acid induction.

Cell Line↗
PubMed1983

Production of cholera toxin-like toxin by Vibrio mimicus and non-O1 Vibrio cholerae: batch culture conditions for optimum yields and isolation of hypertoxigenic lincomycin-resistant mutants.

Vibrio mimicus 61892, isolated in 1977 from a case of watery diarrhea in Bangladesh, produces an enterotoxin which possesses activity in Y-1 mouse adrenal cells and in rabbit ileal loops which is identical to the prototype cholera toxin (CT) produced by Vibrio cholerae 569B. The neutralization of the adrenal cell activity of 61892 toxin and 569B CT by homologous and heterologous antisera generates parallel titration curves which show complete neutralization in all cases. Paired titrations in the ganglioside GM1 enzyme-linked immunosorbent assay (using either CT or Escherichia coli heat-labile toxin antitoxin) of both toxins indicates that 61892 toxin is antigenically indistinguishable from 569B CT. The specific activity of the two toxins in the rabbit ileal loop is virtually identical. Batch culture production of CT-like toxin and CT by isolates of V. mimicus and different biotypes of V. cholerae was found to be highest in shake flask cultures of Casamino Acids-yeast extract broth grown at 27 degrees C with vigorous aeration. Incorporation of lincomycin into the growth medium at a concentration of 50 micrograms/ml increased yields from wild-type strains. Dramatically higher yields were obtained when a spontaneous resistance mutant of strain 61892 was grown in the presence of 200 to 300 micrograms of lincomycin per ml. Under these conditions, yields of CT-like toxin were increased by 300- to 500-fold, and the highest yields reached more than 100 micrograms/ml after 44 h of culture. This is substantially higher than that reported in the literature for CT production by any strain of V. cholerae, including hypertoxigenic strain 569B.

Bacterial Toxins↗
PubMed1974

Reduced cell yields of mouse cell line cultures after exposure to homogenates of multiple sclerosis tissues.

The total cell yields in cultures of a mouse cell line termed "PAM" were reduced markedly after exposure to multiple sclerosis (MS) homogenates. The reductions were noted as early as the second subcultivation. The effect was produced by eight of eight MS brain homogenates and three of three MS spleen homogenates; the samples were from 10 MS cases. The reduction in total cell yields (compared to medium-treated cultures) was not observed after exposure to homogenates, six brain and two spleen, from eight non-MS cases. The effect was produced by the 50-nm filtrate of a pool of MS brain homogenates. Five of the MS-inoculated cultures were maintained for 18 subcultivations, and the reduction in total cell yields persisted throughout the series. The capacity to induce the reduction in cell yields was present in cell-free lysates from five of five MS cultures at passage 18, as was the capacity to cause a decrease in the polymorphonuclear neutrophils in the peripheral blood of mice. Calculation of the dilution effect (at least 10(18)-fold) that had occurred by the end of the passage series proved that the factor(s) causing the cell change in culture and the polymorphonuclear neutrophil change in mice had replicated in PAM cells.

Animals↗
PubMed1975

Energetics of Bacillus stearothermophilus growth: molar growth yield and temperature effects on growth efficiency.

The major growth yield of a prototrophic strain of Bacillus stearothermophilus under aerobic conditions on salts medium containing ammonium nitrate as the nitrogen source and glucose or succinate as the carbon source was maximal at the lowest growth temperature employed and decreased steadily as the temperature was raised. The temperature optima for growth yield and for growth rate were thus different. The molar growth yield values of the thermophile, especially at the lower growth temperatures, were similar to those reported for aerobically grown mesophilic bacteria, both on glucose and on succinate. At the higher growth temperatures, a lower proportion of glucose carbon was incorporated into cells and a correspondingly greater proportion was left incompletely utilized in the medium, mostly as acetate. This suggests a greater inefficiency in the coordination of the nonoxidative and oxidative phases of glucose metabolism at the gigher temperatures. Another factor causing a decreased cell yield at higher temperatures was possibly an uncoupling of energy production from respiration. The rates of respiration by intact cells of the thermophile on glucose and on succinate followed the Arrhenius relationship from 55 C to 20 C, which is some 20 C below the minimal growth temperature of the organism. The Arrhenius constant was 17.1 kcal/mol for glucose oxidation and 13.5 kcal/mol for succinate oxidation. These results are comparable to those reported for some mesophiles, and they suggest that the inability of the thermophile to grow at temperatures below about 41 C is not due to an abnormally high temperature coefficient for the uptake and oxidation of the carbon source.

Acetates↗
PubMed1976

Specialized transduction of D-serine deaminase genes: formation of lysogens that yield high lambda-d dsd/lambda ratios and formation of a dimeric lambda-d dsd.

We have obtained two classes of double lysogens that on induction yield higher titers of lambda-d dsd transducing phage than of helper phage. One class was obtained by lysogenization of strain EM6116 (dsddelta attlambdadelta HfrC) with lambda-dsd type 2 (dsdC+ dsdO+ dsdA+, head-tail substitution). In the absence of either a normal attlambda or the homology of a chromosomal dsd region, the transducing phage integrated at other sites, at least one of which, in strain EM6177, is near the origin of HfrC. On induction, strain EM6177 yields a phage burst of 20 to 50 with a lambdadsd:lambda ratio of 10(4):1. The asnychronously high yield of lambda dsd is attributed to an efficiency of excision greater than that of lambda. The other class was obtained by lysogenization of strain EM1407 (dsdA attlambda+) with lambda-dsd type 2 (dsdO6 dsdA, partial deletion of dsdC). The DNA of mature lambda-dsd type 2 is a complete dimer. It lacks nearly all the phage late genes and b2 and carries about five bacterial genes. It could not be packaged as a monomer but is just within the packaging size limit as a dimer. Models for the derivation of these lambda dsd phages and the high-yielding lysogens are presented.

Chromosome Mapping↗
PubMed2004

Relationship of critical temperature to macromolecular synthesis and growth yield in Psychrobacter cryopegella.

Most microorganisms isolated from low-temperature environments (below 4 degrees C) are eury-, not steno-, psychrophiles. While psychrophiles maximize or maintain growth yield at low temperatures to compensate for low growth rate, the mechanisms involved remain unknown, as does the strategy used by eurypsychrophiles to survive wide ranges of temperatures that include subzero temperatures. Our studies involve the eurypsychrophilic bacterium Psychrobacter cryopegella, which was isolated from a briny water lens within Siberian permafrost, where the temperature is -12 degrees C. P. cryopegella is capable of reproducing from -10 to 28 degrees C, with its maximum growth rate at 22 degrees C. We examined the temperature dependence of growth rate, growth yield, and macromolecular (DNA, RNA, and protein) synthesis rates for P. cryopegella. Below 22 degrees C, the growth of P. cryopegella was separated into two domains at the critical temperature (T(critical) = 4 degrees C). RNA, protein, and DNA synthesis rates decreased exponentially with decreasing temperatures. Only the temperature dependence of the DNA synthesis rate changed at T(critical). When normalized to growth rate, RNA and protein synthesis reached a minimum at T(critical), while DNA synthesis remained constant over the entire temperature range. Growth yield peaked at about T(critical) and declined rapidly as temperature decreased further. Similar to some stenopsychrophiles, P. cryopegella maximized growth yield at low temperatures and did so by streamlining growth processes at T(critical). Identifying the specific processes which result in T(critical) will be vital to understanding both low-temperature growth and growth over a wide range of temperatures.

Bacterial Proteins↗
PubMed1965

INFLUENCE OF AERATION AND OF PANTOTHENATE ON GROWTH YIELDS OF ZYMOMONAS MOBILIS.

Belaïch, Jean-Pierre (Centre National de la Recherche Scientifique, Marseille, France), and Jacques C. Senez. Influence of aeration and of pantothenate on growth yields of Zymomonas mobilis. J. Bacteriol. 89:1195-1200. 1965.-The growth yields and rates of Zymomonas mobilis were measured in aerobic and anaerobic cultures on glucose medium containing yeast extract, amino acids, or ammonium chloride as the nitrogen source. In the absence of yeast extract, pantothenate was required. The growth yield and rate of the cultures in synthetic (amino acids) or minimal (NH(4)Cl) medium supplemented with pantothenate corresponded only to about one-half the "normal" values obtained in the presence of yeast extract, suggesting a situation of energetically uncoupled growth. Attempts to restore normal growth by the addition of various compounds were unsuccessful. Aeration of the cultures resulted in a partial oxidation of ethyl alcohol to acetate, but did not modify the growth yield nor the division time. Both aerobic and anaerobic cells, however, contained cytochrome c and a cytochrome oxidase of the a(2) type, which was completely inhibited by 10(-4)m cyanide. In anaerobically grown cells, an additional cytochrome of the b type was present. The absence of a Pasteur effect suggests that the transfer of electrons by the respiratory chain of Z. mobilis may not be coupled with oxidative phosphorylation. Aeration had no effect on the catalase content of the cells. As shown by C(14)-glucose incorporation, 2 to 3% of the glucose metabolized was assimilated by the cells in both synthetic and rich complex medium. No intracellular glycogen nor poly-beta-hydroxybutyrate was accumulated when growth was limited by nitrogen or by phosphate in the presence of excess glucose.

Amino Acids↗
PubMed1969

Effect of decreasing growth temperature on cell yield of Escherichia coli.

Studies of the relationship between yield coefficient and growth rate, as affected by temperature of growth, in Escherichia coli have shown that, over a wide range of temperature, yield is relatively constant until the specific growth rate falls below about 0.2 hr(-1), at which point the yield begins to fall off precipitously. No intermediates of glucose metabolism in a form utilizable at higher temperatures could be found in the medium, and no toxic product was produced which limited growth. At 10 C, 37% of the carbon from glucose-UL-(14)C was assimilated into cellular material, whereas, at 30 C, 53% was assimilated. Cells grown at 10 C contained more carbohydrate than did cells grown at 37 C, and the glycogen-to-protein ratio of cells grown at 10 C was approximately three times higher than that of cells grown at 37 C. Adenosine triphosphatase activities of cells grown at 10 and 35 C were similar. Growth rates on glucose, glycerol, and succinate were quite similar at 10 C, but at 35 C growth was most rapid on glucose and slowest on succinate. The data suggest that the decrease in yield with decrease in temperature is a result of uncoupling of energy production from energy utilization.

Adenosine Triphosphatases↗
PubMed2006

Correlation of disease severity with fecal toxin levels in patients with Clostridium difficile-associated diarrhea and distribution of PCR ribotypes and toxin yields in vitro of corresponding isolates.

We investigated in vivo and in vitro yields of toxins A and B from and PCR ribotypes of Clostridium difficile isolates from 164 patients with differing severities of C. difficile-associated diarrhea (CDAD) (patients were grouped as follows: <3 loose stools per day, n = 45; 3 to 10 per day, n = 97; >10 per day, n = 22). The median fecal toxin levels in each group were 0.5, 6.8, and 149 U/g feces (P < 0.001), respectively. Patients with severe diarrhea also had more-frequent occurrence of blood in stool and vomiting, but there was no association with fecal toxin levels per se. There was no correlation between fecal toxin level and toxin yield in vitro for the corresponding C. difficile isolate or between its PCR ribotype and disease severity. A broad range of toxin yields among isolates belonging to major PCR ribotypes indicated a presence of many subtypes. We hypothesize that bacterial and host factors that affect C. difficile toxin levels in feces are important determinants of symptoms in CDAD patients. An inverse correlation between toxin yield and spore count (r = 0.66) in stationary-phase cultures supported the notion that toxin production and sporulation represent opposite alternative survival strategies for C. difficile cells facing nutrient shortage.

Adolescent↗