RepD/D*: a protein-DNA adduct arising during plasmid replication.
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Bacterial Proteins↗
Biomedical subjects
C D Thomas
Publications and source records attributed to C D Thomas.
Tumour oxygenation, radiosensitivity, and necrosis before and/or after nicotinamide, carbogen and perflubron emulsion administration.
Hypoxia is one of the factors involved in tumour resistance to radiotherapy. One way to improve tumour oxygenation is to use oxygen carriers such as perflubron emulsion plus carbogen or vasoactive drugs such as nicotinamide. The perflubron emulsion and carbogen act mainly on hypoxia caused by limited diffusion of oxygen; nicotinamide acts mainly on acute hypoxia. The aim was to correlate radiosensitivity and pO2 measurements (computerized pO2 histograph) after nicotinamide, perflubron emulsion and carbogen administration, and to determine the role of necrosis in this correlation. Two human tumour xenografts (HRT18, Na11 +) and one rodent tumour (EMT6) were used. Clonogenic assays and pO2 measurements were performed under similar conditions. The radiosensitization and oxygenation levels increased with all treatments. The maximal effects were found with the combination of nicotinamide (1 g/kg), perflubron emulsion and carbogen. A correlation between the radiosensitization and the pO2 measurements was found for the three cell lines with a cut-off point of 10 mmHg. The presence of necrosis could explain the low pO2 (< 2 mmHg) found even when complete radiosensitization was observed.
Animals↗
Nicotinamide and carbogen: relationship between pO2 and radiosensitivity in three tumour lines.
The effects of carbogen breathing, nicotinamide injection and their combination on tumour radiosensitivity were correlated with changes in tumour O2 tension to determine the relationship between radiosensitivity and measured pO2. The radiosensitivity (in vivo-in vitro colony assay) and O2 tension (computerized pO2 histograph KIMOC 6650) of two human xenografted tumours (HRT18 and Na11+) and one murine tumour (EMT6) were measured under similar experimental conditions. A single dose of radiation was delivered (8 Gy for HRT18 and Na11+, 12 Gy for EMT6). Carbogen breathing, nicotinamide injection, and their combination all significantly increased radiosensitivity in the three cell lines (p < 0.05); the most efficient treatment was carbogen plus nicotinamide. The radiosensitization was optimum for EMT6 and Na11+. Mean and median pO2 increased with all three treatments, except for carbogen breathing in EMT6. Carbogen breathing had little effect on the proportion of low pO2 values, but induced pO2 values > 30 mmHg in all three tumour lines. Nicotinamide decreased the proportion of low pO2 values. This effect is larger with the combination carbogen plus nicotinamide. Almost all pO2 values < 2.5 mmHg were eliminated for HRT18 and EMT6. The relationship between radiosensitization and pO2 was significant when pO2 was expressed as the percentage of values below 7, 8, 9 and 10 mmHg for the three lines.
Animals↗
Correlation between radiosensitivity, percentage hypoxic cells and pO2 measurements in one rodent and two human tumor xenografts.
Computerized pO2 histography has been used to measure the intratumor pO2 in patients for the past few years, and there is now evidence that these tumors contain hypoxic cells. One of the major questions that remains to be answered is the relevance of such data to radiosensitivity. The present study looks for a correlation between intratumor pO2, the percentage of hypoxic cells in the tumor and the radiosensitization induced by carbogen and/or the oxygen carrier, perflubron emulsion. Two human tumor xenografts (HRT18, Na11+) and one rodent tumor (EMT6) were used. The radiosensitivity (clonogenic assay) and the oxygen tension (computerized pO2 histography) were measured. All experiments were performed under similar conditions. Carbogen increased tumor radiosensitivity; sensitization was greatest when 4 ml/kg perflubron emulsion was used in conjunction with carbogen. The pO2 distribution was shifted to higher pO2 values in the tumors whatever the treatment; the shift was greater for perflubron emulsion plus carbogen. The low pO2 values (< 0.4 kPa) were lost for the HRT18 cells. A correlation (EMT6, HRT18) or a link (Na11+) between the radiosensitization and the oxygen tension measurements was found for values below 1.07 or 1.33 kPa. A trend between the percentage of hypoxic cells and pO2 measurements was found taking into account pO2 measurements comprised between 0.27 and 0.67 kPa.
Adenocarcinoma↗
Controlled high-level expression of the lon gene of Escherichia coli allows overproduction of Lon protease.
Lon protease from Escherichia coli is an ATP-dependent protease which plays important roles in regulating the levels of specific proteins and in eliminating abnormal proteins. A major problem of working with Lon protease, the inability to substantially overproduce the enzyme, has been overcome by placing the lon gene under the control of an inducible trp promoter within a copy-number-controllable plasmid. Induction resulted in higher levels of production of the protease (approximately 100 micrograms/ml of cell culture) than were previously possible. The enzyme has been purified to apparent homogeneity and shown to possess the characteristic ATP-dependent proteolytic activity. Sequence verification during DNA manipulations revealed differences from two previously published sequences for the lon gene.
ATP-Dependent Proteases↗
Nutrient balance and energy expenditure during ad libitum feeding of high-fat and high-carbohydrate diets in humans.
To study the influence of diet composition on regulation of body weight, we fed 21 weight-stable subjects (11 lean, 10 obese) high-carbohydrate (HC) and high-fat (HF) diets for 1 wk each. Although diet composition was fixed, total energy intake was unrestricted. Subjects had a higher energy intake on the HF (11,039 +/- 2700 kJ/d) than on the HC (10,672 +/- 2617 kJ/d) diet (P less than 0.05), but energy expenditure was not different between diets. On day 7 of the HC diet, carbohydrate (CHO) oxidation was significantly related to CHO intake with the slope of the regression line 0.99, suggesting that overall CHO balance was near zero. However, the slope of the regression line was greater for obese than for lean subjects. On day 7 of the HF diet, fat oxidation was significantly related to fat intake but the slope of the line was 0.50, suggesting that overall fat balance was positive. However, this relationship was due entirely to lean subjects, with obese subjects showing no relationship between fat intake and oxidation.
Adult↗
Body-image marking. Validity of body-width estimates as operational measures of body image.
The relation of image-marking estimates of body width (IM) to actual widths, to other indices of body-size perception, and to measures of body satisfaction were examined using data obtained in a nonclinical sample of 200 women. The results of regression and correlational analyses were as follows: (a) actual widths accounted for only a small proportion of the variance in IM estimates, (b) the variance in IM estimates remaining after actual width was accounted for was not meaningfully related to other body-image indices, and (c) actual widths were more highly correlated with other body-image indices than were differences between estimated and actual widths (IM estimate-actual width). The current results suggest that most of the variance in IM estimates is error variance. Possible methodological confounds, which may bias women's estimates of body widths in the direction of overestimation, are discussed.
Adult↗
Stable vs unstable weight history, body-image, and weight concern in women of average body weight.
The focus of this study was the effect of unstable weight history on current body-image among women. Participants were 45 college women of average weight (median age = 23 yr.); 15 had stable weight histories, 15 had past lowest weights 15% or more below current weight, and 15 had past highest weights 15% or more above current weight. The women were assessed on perceptual and attitudinal measures of body-image and a self-report measure of preoccupation with weight. In comparison to women with stable weight histories, those with unstable weight histories indicated greater dissatisfaction with the shape and size of their bodies, expressed more negative body attitudes, and reported increased concern about weight. Women with high weight histories overestimated their frontal body-size and expressed greater dissatisfaction with frontal size than women with low weight histories, but the two groups did not differ significantly on any of the other dependent measures. Possible explanations for increased body-image disturbance and weight concern among women with unstable weight histories are presented.
Adult↗
Self-rated competence, current weight, and body-image among college women.
125 female undergraduates (M age = 19.7 yr.) self-rated their academic, social, and psychological competence and were assessed with respect to current weight, weight concern, and body attitudes. Self-rated academic, social, and psychological competence were not related to current weight; however, less positive self-evaluations of social competence were related to weight concern, negative appraisals of appearance, and dissatisfaction with body parts. Subjective ratings of academic and psychological competence were not significantly associated with any of these variables.
Achievement↗
In vitro studies of the initiation of staphylococcal plasmid replication. Specificity of RepD for its origin (oriD) and characterization of the Rep-ori tyrosyl ester intermediate.
Several staphylococcal plasmids from different incompatibility (inc) groups which replicate by a rolling circle mechanism each specify a replication initiator protein (Rep) which is homologous with that of the inc3 tetracycline resistance plasmid pT181. The rep gene sequences of six pT181-like plasmids are known, each encoding proteins of molecular mass 38 kDa with 62% overall amino acid sequence identity. The initiation of replication in vivo by each of the Rep proteins is plasmid specific, acting in trans only at the cognate replication origin (ori) of the encoding plasmid. Previous studies in vitro of the RepC protein of pT181 demonstrated replication initiator, topoisomerase-like, and DNA binding activities, which appeared to be specific for the origin (oriC) of pT181 when compared with unrelated staphylococcal plasmids. Although RepD, specified by the inc4 chloramphenicol resistance plasmid pC221, has a range of activities similar to those noted previously for RepC, manipulation of in vitro conditions has revealed discrete steps in the overall reaction of RepD with oriD. In addition, factors have been identified which are necessary not only for sequence-dependent discrimination in vitro by Rep proteins for all pT181-like plasmids but also for the absolute specificity of RepD for its cognate pC221 replication origin (oriD), the latter occurring in vivo and a function of the topological state of the ori-containing target DNA. Here we also demonstrate the presence of a covalent phosphoryl-tyrosine linkage between the RepD protein of plasmid pC221 and an oligonucleotide substrate corresponding to its replication origin (oriD). The reactive tyrosine (Tyr-188) was identified from amino acid sequences of 32P-labeled peptide-oligonucleotide fragments. Substitution of Tyr-188 with phenylalanine confirms the importance of the tyrosyl hydroxyl group since the Y188F protein retains the sequence-specific DNA-binding capabilities of wild-type RepD but is unable to attach covalently to the replication origin or participate in the nicking-closing reaction in vitro.
Bacterial Proteins↗
The Body Esteem Scale: construct validity of the female subscales.
The female subscales of the Body Esteem Scale (BES) have demonstrated convergent and discriminant validity in two previous studies. However, relationships between BES dimensions, weight, and other body-image measures have not been adequately examined. In this study, 200 women with a mean age of 27.6 years completed the BES, the Eating Disorder Inventory, the Self-Consciousness Scale, the Tennessee Self-Concept Scale, a figure rating task, a phototechnical body-size estimation procedure, and items concerning weight satisfaction and attractiveness. BES Weight Concern was most closely related to weight variables and other body image measures where BES Sexual Attractiveness and Physical Condition were more strongly associated with less specific self-perceptions and attitudes. Results support the construct validity of the BES female subscales and their utility for research in populations at increased risk for body-image or eating-disorder disturbances.
Adult↗
Body attitudes and eating behaviors of female clothing sales personnel.
Recent research suggests that social standards for ideal female beauty are related to negative body-image and dieting among young women. We hypothesized that women who work in settings that emphasize physical appearance (women's fashion clothing sales) would have more disturbed body attitudes and eating behaviors than college women. Sales personnel (n = 21) and students (n = 25) answered questions about their occupational status, weight, and demographic characteristics, and completed the Body-esteem Scale and the Eating Disorder Inventory. Weight and scores on the two scales were similar in both groups except that sales personnel reported more dissatisfaction with their body parts on the Body dissatisfaction scale of the Eating Disorder Inventory. Among sales personnel, those who perceived their appearance to be of greater importance in their work also reported more concern about dieting and weight, as reflected on the Drive for thinness subscale of the Eating Disorder Inventory. Results are discussed with regard to situational influences on women's body attitudes and their implications for eating behaviors.
Adolescent↗
Tooth support in the human mandible.
Prepared surfaces of anterior portions of dentate human mandibles were serially ground in steps of 0.2 mm and the anatomical features traced. The information was stored in a computer and then reassembled and plotted in colour. The percentage porosity of the bone, together with the width of the periodontal space was calculated. The cortical plates of the mandible appear to provide the major boney support for the anterior teeth, trabecular bone only being present in scant amounts in the periapical areas. The apparently random arrangement of trabeculae does not support the commonly accepted picture of trabeculae aligned to resist the functional loads transmitted by the periodontal ligament.
Bone Marrow↗
Insomnia: identification and management.
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Combined Modality Therapy↗
A note on the use of dextran in blood cultures monitored by conductance methods.
The incorporation of dextran into broth for the detection of bacteraemia by conductance monitoring is recommended to eliminate the effect of sedimenting blood cells which may mask early signals from bacteria. Broth containing ten times the recommended concentration of dextran was tested with a wide range of bacteria without demonstrating any reduction in growth or rate of change of conductance.
Bacteria↗
A modified video camera for measuring body image distortion: technical description and reliability.
Previously employed techniques for the measurement of body image are briefly described, with a short consideration of methodological or procedural limitations associated with each technique. A new procedure is described which employs a simple modification to a standard video camera to produce an image which appears from 20% thinner to 40% fatter than the actual person, without other distortion of the image. Reliability and preliminary validity data for the new procedure are presented.
Anorexia Nervosa↗
Membrane filter procedure for enumeration of Vibrio parahaemolyticus.
A membrane filtration procedure has been developed for the enumeration of Vibrio parahaemolyticus in marine waters. Background microbial growth on the primary medium was decreased through the use of sodium cholate and copper sulfate, high pH, 3% NaCl, and an elevated incubation temperature. A series of in situ tests was employed to obviate the picking of colonies for identification; thereby, the enumeration of V. parahaemolyticus was accomplished within 30 h. Confirmation of typical colonies approached 95%. Relative to immediate plating on brain heart infusion agar spread plates, the recovery of V. parahaemolyticus cells suspended in phosphate-buffered saline or in seawater held for 24 h at 4 to 6 degrees C was about 90%. Assay variability did not exceed that expected by chance. Recoveries of V. parahaemolyticus from coastal and estuarine surface waters exceeded those obtainable by other methods examined.
Culture Media↗
Lotka's law and the pattern of scientific productivity in the dental science literature.
Statistical regularities can be observed in many natural and social phenomena. From empirical data on the authorship of scientific papers, Lotka deduced an inverse-square law: the number of authors publishing n papers is 1/n2 of those publishing one paper. The general type for the relation (1/n(c)) has a wide range of applicability to a variety of phenomena. This study examined, by means of bibliometric tools, whether Lotka's law could be applied to the literature of dental science. Data came from 20 leading dental science journals, as reported in Journal Citation Reports. The search was performed with a programme developed using Visual Basic for Applications, which counted the number of authors and analysed their contributions to the literature. Authorship for all contributions, as reported in Medline, was compiled for each of these 20 journals for the last 25 years, 1971 through 1995. The total number of authors was 43,796, responsible for 124,556 authorships. The journals published in countries other than the USA exhibited higher degrees of author concentration. The dental science literature conformed very well to Lotka's model with c = 1.95.
Authorship↗