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At least 1,225 records · Page 68Linked to original sources
PubMed1977

In vivo progesterone treatment enhances [3H]estradiol retention by neural tissue of the female rat.

[3H]Estradiol retention was examined for neural tissues of ovariectomized rats as a function of various progesterone pretreatments. Short-term progesterone pretreatment (6 or 24 h) with a 50 mg pellet of progesteron sc resulted in increased in vivo retention of [3H]estradiol when measured at 6 or 24 h following withdrawal of the progesterone source. This increase was greatest in arcuate-median eminence tissue. A less pronounced increase was seen in the preoptic-anterior hypothalamus and cerebral cortex, and no increase was seen in the amygdala or mammilary bodies. Following long term progesterone pretreatment increased [3H]estradiol retention was observed in vivo at 48, 72, 96 or 120 h in the continued presence of the progesterone source for arcuate-median eminence, preoptic-anterior hypothalamus, amygdala and cerebral cortex. Also, when progesterone pretreatment was 24 h, [3H]estradiol retention was still increased at 36, 48, 60 and 72 h following removal of the progesterone source for arcuate-median eminence, preoptic-anterior hypothalamus, amygdala and cerebral cortex. Our demonstration that progesterone pretreatment can significantly increase [3H]estradiol retention by neural tissue suggests a possible mechanism by which progesterone can regulate the timing of ovulation and sex behavior. Furthermore, our observations are in keeping with the finding that progesterone has little or no effect at the organismal or tissue level unless estrogen is present.

Amygdala↗
PubMed2004

Factors influencing turnover and retention of midwives and consultants: a literature review.

This study is a review of literature on the factors affecting the retention and turnover of hospital consultants and midwives. While there is widespread concern and acknowledgement of staff retention problems for professional occupations within the NHS, far less research has analysed the causes of the staff retention problems for the occupations in question. This study shows that there is a dearth of literature in this area and that systematic comparative analysis of retention and turnover factors through both primary and secondary research is urgently required in order that policy-making can take place on the basis of informed choice. Tentative initial findings were that lack of appreciation or perceptions of not being valued are key factors influencing turnover for both occupations. Working hours, workload and work schedules are also common concerns to both groups. In addition, career development, promotion and appreciation of contribution were important retention factors for midwives, while a supportive professional environment, reduction in workload and working hours and more flexible work patterns were important to consultants.

Consultants↗
PubMed1989

Prediction of contaminant retention and transport in soils using kinetic multireaction models.

Mathematical models that describe the retention reactions of contaminants in the soil system are presented. Single and multireaction-type models for simultaneous retention and transport in the soil profile are discussed. Single retention models are classified into two types: equilibrium and kinetic models. Emphasis is given to the nonlinearity and kinetic behavior of solute retention processes in soils. Two-site models that include the equilibrium-kinetic types as well as the fully kinetic type are also examined. A multireaction-type model is also presented, which includes reversible and irreversible retention processes of the equilibrium and kinetic types. Advantages of the multireaction approach over the single or two-site models are discussed. The predictive capability of the two-site model and the multireaction model for their description of experimental results for phosphorus and two heavy metals (Cd and Cr) are examined.

Humans↗
PubMedDate not supplied

Biosolids effects on phosphorus retention and release in some sandy Florida soils.

The soil solid phase components most responsible for P sorption in Florida soils are Fe and Al oxides. Thus, we hypothesized that land application of biosolids would significantly increase a soil's P retention by increasing its content of P-sorbing solids, especially when biosolids with high Fe and Al concentrations are applied to soils that sorb P poorly. Biosolids effects were quantified by a series of single-point isotherms on soils from two field studies sampled for up to 4 yr after initial biosolids application. Biosolids additions had little effect on P retention in a soil with abundant oxalate-extractable Fe and Al and a correspondingly large native P-sorbing capacity. However, biosolids significantly increased P retention in a soil with low oxalate-extractable Fe and Al content and low native P-sorbing capacity. Biosolids effects on P retention lasted 1 to 3 yr after application, depending on biosolids source and rate of application, and generally mimicked persistence of increased extractable Fe and Al concentrations in the poorly P-sorbing soil. Disappearance of added Fe and Al (and, hence, P retention capacity) from the surface horizons over time was relatively rapid, perhaps due to abundant organic acid production associated with biosolids degradation. Phosphorus in biosolids containing (or tailored to contain) abundant Fe and/or Al can be expected to behave as a slowly available P source, and to be less subject to leaching losses than completely soluble P sources.

Absorption↗
PubMed2005

Phosphorus retention in small constructed wetlands treating agricultural drainage water.

The construction of artificial wetlands has become a measure increasingly applied to reduce nonpoint-source (NPS) pollution and to contribute to the restoration of eutrophic lakes and coastal waters. In a 2-yr study monitoring fluxes of particulate and dissolved phosphorus (P) in a small artificial wetland for the treatment of agricultural drainage water in Central Switzerland, water residence time was identified as the main factor controlling P retention in the system. Since most of the annual P load (62% as dissolved reactive phosphorus, DRP) was related to high discharge events, it was not average but minimum water residence time during flood events that determined the wetland's P retention. In agreement with a continuous stirred tank reactor (CSTR) model, our investigations suggest a minimum water residence time of 7 d to retain at least 50% of the bioavailable P. The investigated wetland retained only 2% of the bioavailable P, since the water residence time was shorter than 7 d during 61% of time in both years. Settling of phytoplankton rather than DRP uptake into phytoplankton limited the retention of bioavailable P. The overall retention efficiency of 23% total phosphorus (TP), corresponding to a surface related retention of 1.1 g P m(-2) yr(-1), was due to the efficient trapping of pedogenic particles.

Agriculture↗
PubMed2005

Green roof stormwater retention: effects of roof surface, slope, and media depth.

Urban areas generate considerably more stormwater runoff than natural areas of the same size due to a greater percentage of impervious surfaces that impede water infiltration. Roof surfaces account for a large portion of this impervious cover. Establishing vegetation on rooftops, known as green roofs, is one method of recovering lost green space that can aid in mitigating stormwater runoff. Two studies were performed using several roof platforms to quantify the effects of various treatments on stormwater retention. The first study used three different roof surface treatments to quantify differences in stormwater retention of a standard commercial roof with gravel ballast, an extensive green roof system without vegetation, and a typical extensive green roof with vegetation. Overall, mean percent rainfall retention ranged from 48.7% (gravel) to 82.8% (vegetated). The second study tested the influence of roof slope (2 and 6.5%) and green roof media depth (2.5, 4.0, and 6.0 cm) on stormwater retention. For all combined rain events, platforms at 2% slope with a 4-cm media depth had the greatest mean retention, 87%, although the difference from the other treatments was minimal. The combination of reduced slope and deeper media clearly reduced the total quantity of runoff. For both studies, vegetated green roof systems not only reduced the amount of stormwater runoff, they also extended its duration over a period of time beyond the actual rain event.

Cities↗
PubMedDate not supplied

Nutrient retention efficiency in streams receiving inputs from wastewater treatment plants.

We tested the effect of nutrient inputs from wastewater treatment plants (WWTPs) on stream nutrient retention efficiency by examining the longitudinal patterns of ammonium, nitrate, and phosphate concentrations downstream of WWTP effluents in 15 streams throughout Catalonia (Spain). We hypothesized that large nutrient loadings would saturate stream communities, lowering nutrient retention efficiency (i.e., nutrient retention relative to nutrient flux) relative to less polluted streams. Longitudinal variation in ambient nutrient concentration reflected the net result of physical, chemical, or biological uptake and release processes. Therefore, gradual increases in nutrient concentration indicate that the stream acts as a net source of nutrients to downstream environments, whereas gradual declines indicate that the stream acts as a net sink. In those streams where gradual declines in nutrient concentration were observed, we calculated the nutrient uptake length as an indicator of the stream nutrient retention efficiency. No significant decline was found in dilution-corrected concentrations of dissolved inorganic nitrogen (DIN) and phosphate in 40 and 45% of streams, respectively. In the remaining streams, uptake length (estimated based on the decline of nutrient concentrations at ambient levels) ranged from 0.14 to 29 km (DIN), and from 0.14 to 14 km (phosphate). Overall, these values are longer (lower retention efficiency) than those from nonpolluted streams of similar size, supporting our hypothesis, and suggest that high nutrient loads affect fluvial ecosystem function. This study demonstrates that the efficiency of stream ecosystems to remove nutrients has limitations because it can be significantly altered by the quantity and quality of the receiving water.

Environmental Monitoring↗
PubMed1990

[Micro powder retention for retaining acrylic resin veneers. 1. Application of pressure sensitive adhesive].

Powder retentions are widely used in clinical for retaining acrylic resin facing of veneered crown. These retentions show relatively high bond strength and easy manipulation compared with the traditional retention devices of bar, hole, bead, loop and etc. However, the particle size of powders commercially available are above 250 microns and reduced the thickness of facing resin. Thereupon, smaller diameter of powder were trially applied, however, microparticles were submerged under adhesive and undercut effective for retaining resin was lost. In this research, a new powder retention system adopted pressure sensitive adhesive was studied. The trial adhesive includes volatile solvent like as the traditional adhesives. However, the solvent vapors rapidly and the adhesive applied onto the wax pattern showed pressure sensitivity. Six different sizes of spherical powder were used and the smallest and largest particle size were 90-110 microns and 230-250 microns respectively. New powder retention system applied sensitive adhesive exhibited excellent bond strength to photo polimerized composite facing resin and denture base resin. The powder of 110-130 microns diameter showed shear bond strength values of above 200 kgf/cm2 after 30,000 thermocycles.

Acrylic Resins↗
PubMed2006

Single-session prolonged alcohol-retention sclerotherapy for large hepatic cysts.

OBJECTIVE: Our purpose was to evaluate the safety and therapeutic efficacy of single-session prolonged alcohol sclerotherapy in treating large hepatic cysts. A therapeutic comparison between 4-hour and 2-hour retention techniques was also studied. MATERIALS AND METHODS: Twenty-seven patients with 31 hepatic cysts were enrolled in this study. Seventeen patients (18 cysts) were treated by alcohol retention for 4 hours (group 1) and 10 patients (13 cysts) for 2 hours (group 2). The mean diameter of the hepatic cysts was 12.4 cm (range, 8-23 cm) with a comparable size range in each group. The sclerosing agent used was 95% alcohol, and the maximum amount was limited to 200 mL. Patients changed position and vital signs were monitored every 10-15 minutes. The blood alcohol concentrations were checked hourly for 5 consecutive hours in the initial nine patients. The nonparametric Mann-Whitney U test was used to compare the difference in characteristics and treatment results of the subjects between these two groups. The level of statistical significance was set at a p value of less than 0.05. RESULTS: All but one patient in group 2 tolerated the entire course of sclerotherapy. The mean aspirated volume and mean injected alcohol volume of the hepatic cysts were 730 mL and 138.3 mL, respectively, in group 1 patients, and 931 mL and 139 mL, respectively, in group 2 patients. The mean maximum blood alcohol concentration was 128.2 mg/dL (range, 60-199 mg/dL) at 3-4 hours after alcohol instillation. The mean posttherapy residual cystic diameter was 2.5 cm (range, 0-6 cm), with an average volume reduction rate of 98.3% and 97.7%, respectively, for patients in group 1 and group 2 after a mean follow-up period of 29.6 months (9-59 months). No statistical differences of the mean reduction rate between the two groups were noted. CONCLUSION: Long retention of the alcohol in a single-injection technique is safe and effective. Two-hour alcohol retention has a comparable efficacy to that of 4-hour retention.

Adult↗
PubMed1999

Degradation of two protein sources at three solids retention times in continuous culture.

Effects of solids retention times (SRT) of 10, 20, and 30 h on protein degradation and microbial metabolism were studied in continuous cultures of ruminal contents. Liquid dilution rate was constant across all retention times at .12 h(-1) (8.3 h mean retention time). Two semipurified diets that contained either soybean meal (SBM) or alfalfa hay (ALFH) as the sole nitrogen source were provided in amounts that decreased as SRT was increased. Digestion coefficients for DM, NDF, and ADF increased with increasing SRT. Digestion coefficients for nonstructural carbohydrates were higher in the SBM diet than in the ALFH diet but were not affected by SRT. Protein degradation in the ALFH diet averaged 51% and was unaffected by retention time. In the SBM diet, digestion of protein was 77, 78, and 96% at 10-, 20-, and 30-h retention times, respectively. Microbial efficiency decreased with increasing SRT and was greater for the SBM than for the ALFH diet. Efficiencies ranged from 30.6 to 35.7 and 20.8 to 29.2 g of N/kg of digested DM for the SBM and ALFH diets, respectively, as SRT decreased from 30 to 10 h. The diaminopimelic acid content of the microbes increased as SRT increased, indicating that changes in microbial species occurred owing to passage rates. From these results, we concluded that the digestibility decreases associated with increased ruminal turnover rates may be less for nonstructural carbohydrates and protein than for the fiber fractions.

Animal Feed↗
PubMed1985

Effect of dietary phosphorus on selenium retention in postweaning swine.

Two experiments were conducted to evaluate the effect of dietary Se and P levels on Se retention in postweaning swine. A 20% protein corn-soybean meal diet at two dietary Se levels (.3 and 5.0 ppm) and four total P levels (.50, .70, .90, 1.10%) were fed. Supplemental Se was provided from sodium selenite with inorganic P from dicalcium phosphate. In Exp. I, 151 pigs weaned at 4 wk of age were allotted by sex, litter and weight and fed their treatment diets for 28 d after a 7-d adjustment to a basal diet. Dietary Se level had no effect on performance measurements. As dietary P level increased, there was an increase in daily gain, feed intake and a decrease in feed to gain ratio. Dietary P resulted in similar plasma, longissimus muscle and kidney tissue Se values within each dietary Se level, while liver Se declined as dietary P level increased. Dietary P level had no effect on plasma, heart or liver glutathione peroxidase (GSH-Px) activity. In Exp. II, 32 barrows, after being fed their diets for a 28-d period, were placed in individual metabolism crates where a balance trial was conducted. Dietary P level reduced absolute and percentage Se retention, particularly at dietary P levels of .90 and 1.10%. Phosphorus retention was not affected by dietary Se. Neither dietary P nor Se level had any effect on N retention. These results suggest an effect of dietary P level on Se retention and liver Se, particularly at dietary P levels above the pig's P requirement, while the effect is minimal at or below the pig's P requirement.

Animal Feed↗
PubMed1983

Oral retention and discoloration tendency from a chlorhexidine mouth rinse.

Individual differences in tooth discoloration have been observed after using chlorhexidine mouth rinses. To study the correlation between retention of chlorhexidine and the discoloration tendency, two groups, 'stainers' and 'non-stainers', were selected. The following parameters were tested: initial retention of chlorhexidine in vivo, retention of chlorhexidine to saliva-coated hydroxyapatite in vitro, and prolonged release of chlorhexidine in vivo. The initial oral retention of chlorhexidine was identical for the two groups, whereas in vitro retention of hydroxyapatite and prolonged release of chlorhexidine in vivo were higher among 'stainers'.

Chlorhexidine↗
PubMed1989

Retentive strength of dental composite to metal surfaces.

Retentive strength of the metal-composite interface was studied with tensile tests for 10-mm and 4-mm diameter specimens. In both series nonperforated and perforated metal surfaces with various numbers of holes were used. The specimens were tested after 1 day of storage in air and after thermocycling in water at 7 degrees C and 60 degrees C, respectively. The nonperforated specimens had the highest retentive strength values for both small and large specimens. The retentive strength decreased with increasing number of perforations and for nonperforated specimens with large retentive area. Thermocycling reduced the tensile force required to break the specimens by 4% to 50%. The fracture surface was mostly located close to the metal surface, indicating that this is the zone of stress concentration. With increasing length of the bond edge a reduction of the retentive strength was observed.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1992

Mononuclear cell magnesium and retention of magnesium after intravenous loading in patients with acute myocardial infarction.

A magnesium (Mg++) retention test was performed in 19 patients with acute myocardial infarction (AMI) 4-11 days after admission to the coronary care unit. The retention of Mg++ was 45 +/- 23% of the 30 mmol given intravenously. It has been proposed that a retention of more than 20% represents Mg++ deficiency. The mononuclear cell Mg++ concentration before the retention test was on an average slightly higher in the AMI patients than in 25 healthy volunteers (72.5 +/- 24.2 vs. 62.9 +/- 9.2 mumol g-1 protein) indicating no Mg++ depletion in the first group. The reason why patients during the phase of AMI show an increased retention of Mg++ is unknown, but changes in concentrations of several hormones and a reduction in blood glucose could be of importance. Serum concentrations of Mg++ were lower on admission than after 4-11 days. These initial reductions are probably due to increased concentrations of circulating catecholamines during the early hours of AMI.

Adult↗
PubMed1986

Postoperative urinary retention. I. Incidence and predisposing factors.

198 (3.8% comprising 4.7% of the males and 2.9% of the females) out of 5220 surgical patients developed total urinary retention postoperatively. The frequency of this condition increased with age and was highest after thoracotomies and endoprosthetic surgery of the hip joints. Voiding history was abnormal in 80% of the patients affected. Subclinical obstructive bladder dysfunction, over-distension of the bladder during the operation and in the recovery room after the operation, sympathomimetic and anticholinergic medication during or after anaesthesia, and an inability to stand or sit after surgery were common causes of retention. Premedication, type of anaesthesia, nature of the liquids given and postoperative analgetics seemed not to affect the incidence of retention. Postoperative urinary retention is an underestimated and mostly avoidable complication. Every patient should be asked for a urinary history before an elective operation. Infravesical obstruction should be relieved before any other elective surgical procedures are undertaken. In cases of emergency surgery prophylactic catheterization to prevent postoperative retention is recommended for patients with obstructive symptoms.

Adolescent↗
PubMedDate not supplied

Retention of particles inhaled in boli with and without induced bronchoconstriction.

Large lung retentions (up to 50%) of particles < or = 4 microns inhaled with a bolus technique at a penetration depth less than dead space have been reported to occur after 24 h. This retention may be due to retarded clearance of particles deposited in the airways of the tracheobronchial tract; an alternative explanation could be that particles are deposited in the alveolar region. The purpose of the present study was to confirm the occurrence of retained fractions and to study the influence of a cholinergic drug, which is assumed to give a more central particle deposition, on these retentions in human lungs after shallow aerosol bolus inhalation. Twelve healthy subjects inhaled, with a bolus technique, monodisperse Teflon particles (2.4 microns geometric diameter, 3.5 microns aerodynamic diameter), labeled with 111In. The volumetric lung depth of the inspired bolus was around 60 mL and flow rate was about 300 mL/s. Six subjects inhaled the test particles after a provocation with a cholinergic aerosol, which induced a threefold increase in airway resistance. The other six subjects inhaled a cholinergic aerosol after inhalation of the test particles or inhaled no cholinergic aerosol at all. Radioactivity in the body was measured after 0.5, 24, 48, and 72 h with a whole-body scanner with three 127 x 101-mm Nal detectors. The investigation confirmed results obtained earlier by a group in Frankfurt claiming that great retentions occur after 24 h. The retentions tended to be lower in the group receiving a bronchoconstricting drug before the bolus inhalations. There was a significant lung clearance of particles between 24 and 72 h, in contrast to the findings in earlier studies in healthy subjects and asthmatics who inhaled Teflon particles in large volumes. On the other hand, the clearance agreed well with the clearance in healthy subjects with extensive deposition of Teflon particles in the small ciliated airways, obtained by means of an extremely low inhalation flow rate. The results suggest that a considerable fraction of the particles in the bolus inhalation have been deposited in small ciliated airways in which the mucociliary transport is less efficient or in the alveolar region.

Administration, Inhalation↗
PubMedDate not supplied

In vitro kinetics of drug release and pulmonary retention of microencapsulated antibiotic in liposomal formulations in relation to the lipid composition.

In previous in-vivo studies, we demonstrated that liposomal entrapment of tobramycin resulted in an increased availability of the antibiotic in the lungs without increasing bactericidal efficacy (Omri et al. 1994). With the aim of developing liposomal formulations allowing more efficient liposome-bacteria interactions, we studied the influence of lipid composition on both drug release and pulmonary retention of encapsulated tobramycin. The phase transition temperatures of nine liposome-tobramycin formulations consisting of two synthetic phospholipids (distearoyl phosphatidylcholine (DPSC) or dipalmitoyl phosphatidylcholine (DPPC) with dimyristoyl phosphatidyl-glycerol (DPMG) or dimyristoyl phosphatidylcholine (DMPC) were determined by differential scanning calorimetry. Liposomes, varying in terms of membrane fluidity and charge were submitted to in-vitro and in-vivo kinetic studies while retention and release of tobramycin were measured by high-performance liquid chromatography (HPLC). Five less fluid liposome formulations showed absence or very low tobramycin release in in-vitro tests and long term pulmonary retention of tobramycin. Four fluid liposome formulations showed in vitro tests modulated tobramycin release while pulmonary retention of tobramycin was dependent of the presence of charged phospholipids. Administration of charged fluid liposomes in mice showed a low level of tobramycin in the kidneys; non-charged fluid liposomes exhibited a relatively high level of tobramycin retention in the kidneys.

Animals↗
PubMed1978

Selective platelet immune retention.

Inbred rats were immunized with Freund's Adjuvant containing proteins of Mycogacterium tuberculosis, Mycobacterium butyrium, or dinitrochlorobenzene (DNCB). Native arterial blood was then passed over glass beads coated with those antigens. The platelet retention on the glass beads was measured. Rats immunized with Complete Freund's Adjuvant developed accelerated platelet retention on beads coated with protein derivatives of tuberculosis (PPD) after just 18 seconds of blood flow. Rats immunized twice maintained selective retention longer than those immunized once. The test animals developed no cutaneous hypersensitivity nor precipitin lines on Ouchterlong gels against PPD. Rats sensitized to DNCB had accelerated platelet retention on DNCB-coated beads. Results were temperature and complement dependent, and antigen-specific. Heparin caused a dose-dependent inhibition of the accelerated retention. PPD potentiated the ADP-induced aggregation of plateletrich plasma (PRP) from immunized rats. These experiments suggest that platelets react selectively to antigens in the intravascular spaces in immune reactions.

Animals↗