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PubMed2005

Statistical modelling of riverine nutrient sources and retention in the Lake Peipsi drainage basin.

Implementation of the Water Framework Directive calls for methodologies and tools to quantify nutrient losses from diffuse sources at a river basin district scale. Here, we examine the possibility of using a statistical model for source apportionment and retention of nutrients in a large transboundary drainage basin (44,000 km2). The model approach uses non-linear regression for simultaneous estimation of e.g. source strength, i.e. export coefficients to surface waters, for the different specified land-use or soil categories and retention coefficients for pollutants in a drainage basin. The model was tested on data from 26 water quality stations with corresponding sub-basin data, i.e., land cover, point sources and atmospheric deposition, from the Estonian part of the Lake Peipsi drainage basin. The model showed that it was statistically possible to derive reliable export coefficients (i.e. unit-area loads) for nitrogen on agricultural land and forests. Moreover, it was shown with simple empirical functions that lake retention was approximately 30-35% for both nitrogen and phosphorus and that the riverine retention was low for both nitrogen and phosphorus (approx. 10%). Results show that the MESAW model is a simple and powerful tool for simultaneous estimation of sources and retention of nutrient loads in a river basin.

Agriculture↗
PubMed2005

[Resection with pyloric retention as a method for prophylaxis of dumping syndrome].

The aim of the study was the evaluation of efficacy of the resection with pyloric retention proposed by the authors as a method for prevention of post gastroresectional damping syndrome in patients with ulcers. Resection with pyloric retention is performed in six modifications of three basic methods of resections. We have the experience of using this approach in 712 clinical cases. Among them 237 were women and 475 were men 19-75 years of age. It was shown that resection with pyloric retention provides rhythmic evacuation and prevents development of damping syndrome and duodenal reflux. It was found that the main reasons of the development of postgastroresectional syndromes include wide-area mobilization of the stomach and resection of the small curvature, which induce insufficiency of cardia, atony, chronic disturbances of the duodenal passing. Due to the retention of pyloric function damping syndrome have been developed only in 3 patients. In all these cases the syndrome was mild. It may be concluded that gastric resection with pyloric retention represents the most "physiological" intervention and has many advantages in comparison with other methods.

Adult↗
PubMed2005

[Effect of vitamin B6 status on selenium retention in the tissues in rats fed selenium from sodium selenate].

OBJECTIVE: To study the effect of vitamin B6 status on selenium retention in tissues. METHODS: Weaning male Wistar, 4-week-old, fed with vitamin B6-selenium-deficient basal diet for 3 weeks was randomly divided into 6 groups. There were six experimental diets, that is basal diet (vitamin B6-selenium-deficient), basal diet supplemented with vitamin B6, and supplemented with Se 0.25 mg/kg as Na2 SeO4 and vitamin B6 0, 1.0 2.5 and 5.0 mg/kg diet as pyridoxine HCl for 4 weeks, three-days metabolic test was carried out before finished the study. RESULTS: Compared with each group supplemented with vitamin B6, the vitamin B6 deficient groups had a significantly low body weight gain and diet availability, and lower selenium retention in heart, liver, and kidneys, however, the status of vitamin B6 had no significant effect on the weight and selenium retention in the testes. Vitamin B6 had no significant influence on the selenium apparent absorption and retention by the three days metabolic test. CONCLUSION: Providing adequate vitamin B6 could be benefit for improving rat growth and development and increasing selenium retention in the tissues.

Animals↗
PubMed2005

[Quantitative structure-retention relationships of monosubstituted alkanes by dividing its molecular structure into substructure].

In order to investigate the quantitative structure-retention relationship in gas chromatography (GC) , the molecular structure of monosubstituted alkane RX (X = halogen, OH, SH, NH2) is divided into two parts, R and X, to obtain molecular structure parameters, and the retention times in GC for 37 monosubstituted alkanes RX were determined. It was proposed that the retention time in GC is affected by three main factors for RX compounds, alkyl group R, substituted group X, and interaction between R and X. Using four parameters, the eigenvalue of bonding orbital-connection matrix EVM, the polarizability effect index of alkyl group PEI, the mass content for substituted group X, and the partial charge deltaN(H) on hydrogen atom of the group X, a quantitative structure-retention correlation model with correlation coefficient (r) of 0.9948 and standard deviation (S) of 0.0991 was obtained for the 37 RX compounds. The model obtained has good predictive and extrapolation ability. The predicted retention indexes are in good agreement with the experimental ones for alcohols.

Alkanes↗
PubMed2006

Retention of restorations placed in noncarious cervical lesions after centric and eccentric occlusal loading in a chewing simulator--A pilot study.

PURPOSE: To evaluate in a pilot study whether (1) loading of restored teeth in a chewing simulator is an adequate method to reproduce clinical data about the retention rate of restorations placed in noncarious cervical lesions by means of the one-step self-etching adhesive system Prompt-L-Pop, and (2) whether eccentric loading contributes to the loss of Class V fillings. MATERIALS AND METHODS: In 12 extracted mandibular premolars with noncarious buccal cervical lesions of similar dimensions, restorations were placed without preparation using Prompt-L-Pop and Tetric Ceram. The adhesive was applied in one layer and cured at 650 mW/cm2 for 10 s, while the composite was placed in two increments and cured at 1200 mW/cm2 for 10 s. After storage in water at 37 degrees C for 7 days, the teeth were mounted in a chewing simulator that uses pneumatic cylinders as force actuators and subjected to a centric load of 50 N and 1,200,000 load cycles at a frequency of 1.6 Hz and simultaneously to 3125 thermocycles (5 degrees C/55 degrees C). The antagonists were standardized and made of Empress ceramic material. Every 100,000 load cycles, the fillings were evaluated with regard to retention. In the second phase, the same teeth were loaded on the lingual cusps with new antagonists for another 1,200,000 cycles. RESULTS: Neither during centric nor eccentric loading was any restoration loss observed. CONCLUSION: The short-term loading of extracted teeth with Class V fillings in a chewing simulator was inadequate to reproduce the data of clinical studies on the retention rate of a self-etching adhesive system. Obviously, long-term degradation mechanisms (eg, hydrolysis) acting on the composite/dentin interface play a more crucial role when it comes to the loss of retention of Class V restorations. Eccentric loading alone did not contribute to the loss of fillings, so that the theory--which maintains that this type of occlusal stress is a major cause for abfractions or the retention loss of restorations placed in abfraction lesions--may be questioned.

Aluminum Silicates↗
PubMed2006

Job dynamics of veterinary professionals in an academic research institution. I. Retention and turnover of veterinary technicians.

The turnover of veterinary technicians within an animal resources program averaged 33% annually over 18 y, peaking at 67% in 1998 to 1999. Insufficient retention of veterinary technicians led to diversion of veterinarian effort to technical tasks and to increased allocation of administrative resources for supervising and managing an expanding team of veterinary technicians. To identify factors and trends related to poor retention, address any causes, and reduce turnover, a retrospective analysis of employment records was done. The retention of veterinary technicians was significantly greater for the 9 technicians hired from veterinary private practice rather than for any of 3 other general sources: promotions from the animal care staff, transfers from other research institutions, and miscellaneous sources. Veterinary technician turnover was reduced from a mean of 60% over 1995 to 1999 to an average of 26% during 2000 to 2004. Higher retention was associated with management practices that included renewed concentration on recruiting and interviewing strategies and emphasis on training and career development including merit raises for technician certification through the American Association for Laboratory Animal Science. Higher retention yielded correspondingly greater experience on the job as the mean tenure increased from 1.1 y in 2000 to 2.8 y in 2004. The most valued attributes related to employment by veterinary technicians as determined by survey were to do meaningful work, earn a good living, and have a committed team of coworkers.

Academic Medical Centers↗
PubMed2006

In-state graduate retention for U.S. dental schools.

Currently, dental school graduates are viewed as a resource by their institutions and those who underwrite their educational costs. The purpose of this study was to determine the percentage of dental school graduates who practiced dentistry in the same state as their dental school. Using the American Dental Association database of approximately 35,000 graduates between 1985 and 1995, the data were analyzed to determine the percentage of graduates who were retained and currently reside in the state of their dental school versus those located outside of that state ("exported"). It was also possible to calculate the number of dentists who moved into each state but were educated elsewhere ("imported"). The ratio of imported to exported graduates was calculated and indicated a positive flow into the state when greater than one and an outflow when less than one. Overall, mean graduate retention was 67.3 percent, 65.4 percent, and 44.3 percent for public, public state-related, and private schools, respectively, while the median graduate retention of 71.1 percent and 71.6 percent for public and public state-related schools made them indistinguishable. The mean import-export ratio for public school graduates was 2.9, indicating that on average nearly three dentists were imported to a state for every public dental school graduate exported. States' total import-export ratio for all types of graduates was 2.2, indicating that on average a little over two dentists were imported to every one exported by a state with a dental school of any kind. The medians for all these ratios were much more modest (0.95 and 0.80 for public dental schools and states with dental schools), indicating that they sent more students out of the state than they imported. Six public dental schools exported greater than 50 percent of their dental graduates, while five public schools retained more than 85 percent of their graduates. Only one private state-related school retained less than 50 percent of its students. In view of these results, it is apparent there is great variability in graduate retention, and the total yield of new dentists for each state is determined by both the retention rate for graduates and its import-export ratio. Most public and public state-related schools do a good job of retaining graduates. When they do send graduates out of state, the median shows they do not gain quite enough to offset those exported. In most instances, this becomes highly problematic only when a low retention rate is paired with a low import-export ratio. Each state must consider its unique situation carefully and consider its yield, the types of problems that face the state in terms of dental workforce, and possible solutions.

Dentists↗
PubMed1991

Analysis of the retention signals of two resident luminal endoplasmic reticulum proteins by in vitro mutagenesis.

Protein disulfide isomerase (PDI, ERp59), ERp72, and ERp61 are luminal proteins of the endoplasmic reticulum (ER) that are characterized by the presence of sequences corresponding to the active site regions of PDI. Each one of these proteins possesses a different COOH-terminal tetrapeptide ER retention signal. In order to investigate what other tetrapeptide sequences could serve as retention signals and to determine to what extent the function of the retention signal is modulated by the protein carrying the signal, we have constructed a set of mutants of two of these resident ER proteins, PDI and ERp72. In each of these proteins, the wild type tetrapeptide sequences were replaced by each member of the set of the 12 possible combinations consisting of (K,R,Q)-(D,E)-(D,E)-L. Analysis of the efficiency of retention of the variant proteins when each was transiently expressed in COS cells showed that the retention efficiencies vary with both the COOH-terminal sequence and with the protein that carries this sequence.

Amino Acid Sequence↗
PubMed1990

[An attempt of experimental study to clarify the rearrangement mechanisms of transseptal fibers during mechanical retention periods].

The present investigation has been attempted to clarify the remodeling mechanisms of transseptal fibers during mechanical retention periods. Orthodontic forces of 25 gm and 150 gm were respectively applied to upper molars of rats for 10 days and retained mechanically. Retention periods were 10, 30 and 60 days. The trend of transseptal fibers after these retention periods was observed by the methods of histology and histochemistry. Histological study was observed rearrangement of fibrous tissue by light and electron microscopy and histochemical one was observed acid phosphatase activity. The following results were obtained: 1. Very little was observed about the rearrangement of transseptal fibers by the orthodontic force applied for 10 days. 2. The mechanical retention was kept longer, stretched transseptal fibers were slowly restored to original shape. This means transseptal fibers were gradually rearranged. 3. The collagen containing fibroblast and fibroblast characterized by abundant rough endoplasmic reticulum and Golgi complex were ultrastructurally observed. 4. The reaction of ACPase activity in some fibroblasts can be observed. These results suggest that transseptal fibers were rearranged during mechanical retention periods and that fibroblasts were engaged in this remodeling by synthesizing and degrading collagen fibers.

Animals↗
PubMed1990

[The relationship between percutaneous rate of drug and its HPLC retention behavior].

A series of 13 p-aminobenzoate esters were selected as model drugs to study correlations between HPLC retention parameters and percutaneous rate. The octanol/water partition coefficient and solubility of these compounds were determined and their permeation through rat skin was measured using a Franz diffusion cell. Capacity factor and retention index were used as HPLC retention parameters and calculated from their retention times. The results indicate that for the p-aminobenzoate esters studied, the capacity factors and retention indices obtained in our experimental conditions are indicators of relative lipophilicity of drugs and can be used to predict their steady-state fluxes and permeation coefficients by using the Hansch equation. They are easy to obtain and reproducible enough to substitute for the more laborious and inaccurate partition coefficient values.

4-Aminobenzoic Acid↗
PubMed1990

Improving the tumor retention of radioiodinated antibody: aryl carbohydrate adducts.

Improved methods for attaching radioiodine to monoclonal antibodies have been developed. Ten aryl carbohydrate adducts were synthesized by the reductive amination of a carbohydrate with an aryl amine, using sodium cyanoborohydride as a reducing agent. After purification by chromatography and characterization by nuclear magnetic resonance they were iodinated using the chloramine-T method. Iodinated adducts were activated with cyanuric chloride and incubated with protein at room temperature. The immunoreactivity and avidity of radioiodinated tyramine cellobiose (TCB) labeled antibody were fully preserved when compared to electrophilically radioiodinated antibody. Radioiodinated TCB-and tyramine glucose-labeled monoclonal antibodies showed much greater intracellular retention of radioiodine when compared to electrophilically radioiodinated monoclonal antibodies. Neither radioiodinated tyramine nor radioiodinated TCB had any specific tissue uptake or retention. In mice the retention of radioiodinated TCB labeled anti-Thy-1.1 antibody (1A14) by Thy-1.1-bearing lymphoma cells was 2 times greater than that of chloramine-T labeled 1A14 antibody, whereas the plasma clearance curve and uptake in normal tissues was not changed. This method of radioiodinating monoclonal antibodies increases the retention time of radioiodine in tumor and thus may obviate the problem of intracellular deiodination, a perceived disadvantage of electrophilically iodinated antibodies, with respect to tumor retention of radioactivity.

Animals↗
PubMed1989

[Changes in retention strength of luting cements by repeated loading].

The retention of crowns cemented on abutment tooth model was examined for three types of luting cements when compressive loads of 2.5 to 10.0 kg were repeatedly applied to the occlusal plane. The chamfer type Ni-Cr alloy crown and abutment tooth model were prepared, and their surfaces to be cemented were sandblasted with glass beads. Loads were applied 7,200 times a day for 1, 3, or 7-day period after cementing. The polycarboxylate and zinc phosphate cements showed higher crown retentions than glass ionomer cements. Although retention strength of glass ionomer cements was significantly increased by storing the cemented specimen in water for 7 days, repeated loading tended to decrease retention. In polycarboxylate cements and one brand of zinc phosphate cement employed, retention strengths were decreased when stored in water over 3 days. However, their highest levels were maintained or even positively impacted by repeated loading for 7 days.

Crowns↗
PubMed1989

[Retention index of essential oil in temperature-programmed capillary column gas chromatography].

Kovats retention indexes of more than 200 kinds of natural and synthetic compounds of alcohol, aldehyde, acetal, ketone, ether, alkene, nitrile, carboxylic acid, ester, etc. were determined on polar liquid phase (DB-WAX) and nonpolar liquid phase (DB-1) by linear temperature-program capillary column gas chromatography. Some rules of part of the homologous series of compounds were summed up from the retention indexes: the rules of RI vs carbon, RI vs boiling point and RI on two columns. In order to keep the retention indexes practical, effects of initial temperature (T0), program rate (r) and average linear carrier gas velocity (u), etc. on the retention indexes were investigated. The conclusion is that the retention indexes are highly reproducible so long as the program parameters change in a certain range. Two kinds of essences, Meigui and Linglan, were identified successfully on IBM-PC/XT microcomputer by the Data Base Management System of essential oil and essence by capillary column gas chromatography and the results are satisfactory.

Chromatography, Gas↗
PubMed1989

[The effect of age and sex on bone retention of radioactive strontium 85Sr in rats].

Retention of radioactive strontium 85Sr (18,5 kBq i.e. 0.5 microCi i.p.)--concerning the whole body and in distal epiphysis, distal metaphysis and in the thigh bone diaphysis--was followed up in two similar experiments for the period of 5-6 weeks in rats of both sexes and different age (younger category 40-45 days, older category 120-140 days). In both experiments bone retention 85Sr in older female rats is lower than in younger female rats. In male rats similar difference has not been constantly proved. Retention seems to be higher in female rats in comparison with males in the category of young rats. On the contrary in the category of older rats the retention is lower in female rats. In epiphysis and diaphysis of the thigh bone the differences are analogous to whole body differences; 85Sr reacts in the opposite way in distal metaphysis--retention is here extensively higher in older rats than in younger ones. The results obtained confirm the conclusion interesting from the point of view of clinical problem: avidity of the skelet to administered radioactive strontium is in younger female rats higher than in young male rats. However it is severely declining especially in female rats--in the second experiment as far as the level significantly lower than in male rats of the same older age category.

Aging↗
PubMed1989

Xenon-133 hepatic retention ratio: a useful index for fatty liver quantification.

Xenon-133 hepatic retention ratio was developed for quantifying fatty liver. Data were acquired in frame mode in the hepatic region and both lung bases for 5 min after rebreathing 20 mCi of gaseous 133Xe and for another 5 min during washout. Static [99mTc]sulfur colloid liver imaging was performed with the patient in the identical position immediately after the ventilation study and data were stored for liver localization. A hepatic time-activity curve corrected for background activity was generated. The 133Xe retention ratio was derived by dividing the activity at 3.5 min after washout by the peak activity. The data of 16 controls and 20 patients with fatty liver were analyzed. The retention ratio (mean +/- s.d.) was greatly increased in patients with fatty infiltration (0.43 +/- 0.20 vs. 0.04 +/- 0.08 in controls, p less than 0.001). There was a strong positive correlation between the 133Xe retention ratios and percentage of fat on biopsy as assessed by the amount of the liver tissue occupied by fat globules on H & E stained sections. The 133Xe hepatic retention ratio is a simple, accurate and clinically useful index of detecting, quantifying and managing fatty infiltration of the liver.

Adult↗
PubMed1988

Retention of lead in growing rats with varying dietary lead supplements.

144 female rats with a beginning weight of 35 +/- 3 g were fed for 23 days a half-synthetic diet with a lead content that varied over 18 concentrations (0.025 to 600 mg/kg). Absolute lead retention was calculated as total body concentration of lead in animals at the end of the experiment minus the average lead concentration in carcasses of reference animals that had been sacrificed at the beginning of the experiment. The relative retention was calculated with regard to lead intake. Absolute lead retention increased in association with a lead supply of 0.225 mg per kg diet, but decreased thereafter. Not until a lead concentration of 5 mg per kg diet was reached did lead retention rise again. Relative lead retention decreased exponentially with an increasing lead supply and finally approached a constant value. Live mass development and feed intake were not affected by an increase in lead supply. Altogether, these results demonstrate that lead metabolism is homeostatically regulated.

Aging↗
PubMed1978

Temporal relationships between urinary salt retention and altered systemic hemodynamics in dogs with experimental cirrhosis.

In the present study, we undertook to examine the relationship between urinary sodium retention and systemic hemodynamics in dogs with experimental portal cirrhosis induced by the sporadic feeding of dimethylnitrosamine. Sodium handling was studied by blanace techniques; plasma volume was measured serially with Evan's blue; and CO, blood pressure, CVP, and PVR were monitored through indwelling catheters. Six dogs were studied while standing quietly in a Pavlov sling, in a serial fashion starting 4 weeks after drug administration and continuing for some 3 months thereafter, until all dogs developed cirrhosis and ascites. Urinary sodium retention commenced generally between the ninth to twelfth week following the initation of treatment, but renal perfusion remained normal. Plasma volume expansion was noted within 1 week following the onset of sodium retention. Ascites was generally detected about 2 weeks following the initiation of sodium retention. No alteration in CO or PVR could be detected until ascites was present in significant amount. At that time, CO rose and PVR fell by about 20%. ABP tended to fall during the period of observation, but this was not significant. The initiation of sodium retention in this canine model does not depend on antecedent changes in CO or PVR.

Alkaline Phosphatase↗
PubMed1980

Antibody isotypes mediating antigen retention in passively immunized mice.

Antibody isotypes vary in their capacity to mediate retention of a readily catabolized protein antigen, human serum albumin (HSA) in spleen, popliteal lymph node (PLN) and hind foot. Hyperimmune anti-HSA mouse sera were separated into fractions highly enriched for IgM, IgG1 and IgG2 via differential elution from protein A-Sepharose. These fractions were used to immunize normal mice passively. Twenty-four hours later the mice were injected with radio-iodinated HSA into the hind footpad. When the amount of HSA retained in the spleen 6 days later was determined, the potency of various antibody fractions to mediate retention could be ranked IgG2=IgG1 > IgM. The amount of HSA retention mediated by various fractions correlated well with autoradiographic evidence demonstrating localization of HSA in splenic follicles. The localization pattern in PLN was similar to the spleen except that the IgM-containing fraction mediated follicular localization of HSA to a considerable degree. In tendons of the hind foot, IgG1 mediated HSA retention five times better than IgG2 or IgM fractions. The amount of radioactivity found in the liver varied inversely with HSA retention in other locations. The results demonstrate differences in antibody isotype requirements for antigen localization in spleen, regional lymph node and collagenous sites of the hind foot.

Animals↗