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At least 1,693 records · Page 94Linked to original sources
PubMed2001

[Effect of bioceramics on biological activity of microorganisms].

BACKGROUND AND OBJECTIVE: Biomaterials that come into contact with microorganisms in the middle ear or paranasal sinuses should be tested before clinical application. Thus, it is necessary to test the influence exerted on bacterial growth by biomaterials used as bone substitutes in head and neck surgery before implantation. PATIENTS AND METHODS: In this study, Bioverit, Al2O3 ceramic, and glass carbon were subjected to contamination with typical microorganisms in the middle ear and paranasal sinuses such as Staphylococcus aureus, Streptococcus pneumoniae and salivarius, Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis and Candida albicans. RESULTS: In the suspension test, all gram-negative species were inhibited, but gram-positive microorganisms and Candida albicans were not affected. The Al2O3 ceramic showed the largest inhibition effect while growth inhibition of glass carbon was low. Streptococcus pneumoniae and salivarius can use glass carbon as a nutrient. In contrast, Bioverit and Al2O3 ceramic could not improve the growth of all tested microorganisms. CONCLUSIONS: In conclusion, we think that Bioverit is suitable for implantation in bacterially contaminated regions of the head and neck, whereas glass carbon is unsuitable for this application in reconstructive surgery.

Aluminum Oxide↗
PubMed1992

Media for the detection and enumeration of Bacillus cereus in foods: a review.

Bacillus cereus is an established cause of food poisoning in addition to being a troublesome and persistent contaminant, responsible for a variety of spoilage defects in processed foods and dairy products. A range of diagnostic and selective media has been developed to facilitate the detection and enumeration of B. cereus in routine surveillance situations and food poisoning investigations. These media are reviewed with respect to the selective and diagnostic systems they employ, their ability to recover and differentiate the target organism, and their advantages and limitations in particular applications.

Animals↗
PubMed2001

Marine eutrophication: a proposed data analysis procedure for assessing spatial trends.

A methodology for the discrimination of the different trophic levels at a spatial scale in the marine environment is proposed using spatial analysis methods and non-parametric statistics. Phytoplankton cell number, being a representative parameter to express trophic trends in the marine ecosystem is selected for the methodology development; Saronicos Gulf, Greece is used for the case study. The proposed stepwise methodology includes interpolation for assessing the spatial distribution of phytoplankton cell number, division of the Gulf into a number of quadrates, development of a scale characterising trophic levels and finally characterisation of the trophic state of each quadrate using non-parametric statistics. The advantages of this methodology and the potential applications in coastal management studies are also discussed.

Cell Count↗
PubMed2005

Extraction of dielectric properties of multiple populations from dielectrophoretic collection spectrum data.

In this paper we show how simplifying assumptions can be used to extract useful data from the dielectrophoretic collection spectrum, in particular for the cytoplasm, and hence determine the properties of multiple populations of cells within a sample. Specifically, the observation of the frequencies of onset of dielectric dispersion allows the identification and enumeration of populations of cells according to cytoplasmic conductivity, with particular relevance to the determination of the action of drugs for high-throughput screening applications.

Algorithms↗
PubMedDate not supplied

[Estimation of postnatal life duration of the premature newborns by postnatal involution of hemopoietic tissue of the liver].

140 dead fetuses and neonates of 21-40 week gestation were studied with morphometric study of hemopoietic activity of hepatic parenchyma. The correlation-regression analysis has established that hemopoietic activity of the liver in premature neonates reduces exponentially with duration of their extrauterine life. First, there was hyperplasia of hemopoietic tissue of the liver, its involution was observed 19 hours after birth, on the average, reaching maximum to the end of early neonatal period. Basing on the difference of gestation age estimated by the degree of hemopoietic activity of hepatic parenchyma and neonatal mass, a regression model of determination of neonatal period of life of premature babies was developed. The results of the study can be used for practical application in forensic medical examination of perinatal death cases.

Cell Count↗
PubMedDate not supplied

Statistics of the LS-detector in the case of low counting efficiency.

In the case of high-quenched 3H and 63Ni sources a distinct incompatibility of theoretical and experimental detection efficiency in the triple liquid scintillation (LS) detector was observed (Appl. Radiat. Isot. 52 (2000) 643). The authors concluded, that the Poisson distribution does not properly describe the detection process, when less than one photoelectron is expected in one of the photomultipliers. Application of other distributions of photoelectrons, e.g. binomial, does not solve the observable problem of incompatibility. Measurements of a set of 55Fe sources have been performed with phototubes defocusing and grey filters for decreasing the counting efficiency of the TDCR detector. Differences between counting results of the 55Fe source and the light emitting diode (LED), simulating the scintillation source, excited by a pulse generator have been observed. Various distributions (Poisson, binomial and Polya) were used for the determination of the theoretical counting efficiency in both cases. The Poisson law gave a good result in the case of the LED but the Polya law had to be applied in the case of 55Fe. The results were independent of the scintillator volume. It seems that the validity of the Polya law in the case of LS-sources is related to the scintillator itself. Measurements of the 3H solution confirmed that conclusion.

Algorithms↗
PubMed1997

[Clinicophysiological study of tremor in Parkinson's disease: quantitative tremor-based assessment of motor count using actigraphy].

In Parkinson's disease, resting tremor is often the initial symptom. This report focuses on the mechanism underlying tremor in Parkinson's disease and quantitative assessment of tremor. Central factors including Vim (nucleus ventralis intermedius) in the thalamus, and peripheral factors, such as acceleration of input pathways from muscle spindles via muscle tonus, are important aspects of the tremor mechanism in Parkinson's disease. It has also been suggested that tremor in Parkinson's disease is associated with parasympathetic and sympathetic dysfunctions. Objective assessments of tremor, such as the application of surface electromyography, are useful in the diagnosis and treatment of Parkinson's disease. Actigraph, as introduced herein, is a three dimensional motor sensing apparatus. Therefore, motor counts over 0.01 G can be detected by actigraphy. To date, this device has been used for evaluating akinesia in Parkinson's disease and insomnia. In this study, actigraphy was used in Parkinson patients with tremor, and it reflected motor activity in the wrist and was associated with the severity of hand tremor. Activities of daily living (ADL) are disturbed by hyperkinesia of the hand for Parkinson patients with hand tremor. We demonstrated that actigraphy is a simple and quantitative method of assessing motor activity in Parkinson patients with tremor.

Aged↗
PubMed2004

Accurate estimation of the Fisher information matrix for the PET image reconstruction problem.

The Fisher information matrix (FIM) plays a key role in the analysis and applications of statistical image reconstruction methods based on Poisson data models. The elements of the FIM are a function of the reciprocal of the mean values of sinogram elements. Conventional plug-in FIM estimation methods do not work well at low counts, where the FIM estimate is highly sensitive to the reciprocal mean estimates at individual detector pairs. A generalized error look-up table (GELT) method is developed to estimate the reciprocal of the mean of the sinogram data. This approach is also extended to randoms precorrected data. Based on these techniques, an accurate FIM estimate is obtained for both Poisson and randoms precorrected data. As an application, the new GELT method is used to improve resolution uniformity and achieve near-uniform image resolution in low count situations.

Algorithms↗
PubMedDate not supplied

Genes associated with leukocyte production in mice.

We have investigated the genes influencing leukocyte production in mice by selective breeding for differences in leukocyte count and developed two major lines differing about 8-fold. In these lines we have made counter selective breeding, crossbreeding between them, and developed methods of using marker genes to search for individual genes distributed on different chromosomes. We have revealed an overall dominance of genes for low leukocyte count over those for high counts, and effects of genes at the agouti locus, certain mutant genes, and a gene or genes in the XVI linkage group. We have commented on the application and approach of quantitative genetic experimentation from both a theoretical and practical point of view and, on the basis of present results, discussed the nature of polygenes in relation to genes causing polymorphisms.

Animals↗
PubMed2001

Field efficacy of a 10 per cent pyriproxyfen spot-on for the prevention of flea infestations on cats.

The clinical application of a new method for using the insect growth regulator, pyriproxyfen, for controlling flea populations in cat-owning homes is evaluated for the first time. In a multicentric, controlled and randomised trial, 107 flea-infested cats were treated with a minimum dose of 10 mg/kg bodyweight pyriproxyfen as a 10 per cent spot-on application on two occasions, with a three-month interval between doses. For comparison, 99 cats received lufenuron suspension orally, once a month, for six months. Flea counts decreased significantly over time in each group and were significantly lower in the pyriproxyfen group than in cats treated with the reference product. The percentage of 'zero-flea' cats increased from 49 per cent on day 30 to 88 per cent on day 180 in the pyriproxyfen group and from 30 to 71 per cent in the lufenuron group at the same time points (P<0.05). Appropriately timed topical applications of pyriproxyfen, therefore, offer a method of flea control in the domestic environment.

Administration, Cutaneous↗
PubMed1996

Development and field application of a quantitative method for examining natural assemblages of protists with oligonucleotide probes.

A fluorescent in situ hybridization method that uses rRNA-targeted oligonucleotide probes for counting protists in cultures and environmental water samples is described. Filtration, hybridization, and enumeration of fixed cells with biotinylated eukaryote-specific probes and fluorescein isothiocyanate-conjugated avidin were performed directly on 0.4-microns-pore-size polycarbonate filters of Transwell cell culture inserts (Costar Corp., Cambridge, Mass.). Counts of various species of cultured protists by this probe hybridization method were not significantly different from counts obtained by the 4',6-diamidino-2-phenylindole (DAPI) and acridine orange (AO) staining methods. However, counts of total nanoplankton (TNAN) based on probe hybridizations in several field samples and in samples collected from a mesocosm experiment were frequently higher than TNAN counts obtained by staining with DAPI or AO. On the basis of these results, 25 to 70% of the TNAN determined with probes were not detectable by DAPI or AO staining. The underestimation of TNAN abundances in samples stained with DAPI or AO was attributed to the existence of small nanoplanktonic cells which could be detected with probes but not DAPI or AO and the difficulty associated with distinguishing DAPI- or AO-stained protists attached to or embedded in aggregates. We conclude from samples examined in this study that enumeration of TNAN with oligonucleotide probes provides estimates of natural TNAN abundances that are at least as high as (and in some cases higher than) counts obtained with commonly employed fluorochrome stains. The quantitative in situ hybridization method we have described here enables the direct enumeration of free-living protists in water samples with oligonucleotide probes. When combined with species-specific probes, this method will enable quantitative studies of the abundance and distribution of specific protistan taxa.

Acridine Orange↗
PubMed2006

Microbiological and chemical properties of litter from different chicken types and production systems.

Chicken litter is produced in large quantities from all types of poultry raising activities. It is primarily used for land application, thus it is essential to analyze its properties before it is released to the environment. The objective of this study is to compare the microbiological and chemical properties of litter generated from layer and broiler chickens reared under intensive and free-range production systems. The microbiological analysis consisted of the enumeration of total bacteria, total coliforms, Staphylococcus species, Salmonella species and Clostridium perfringens. Chicken litter from layers reared under intensive and free range systems showed lower mean total bacterial count than the litter collected from chicken broilers reared under either of the two systems (P=0.0291). The litter from intensive layers had the lowest mean total coliform counts (P=0.0222) while the lowest Staphylococcus species count was observed in the litter from free-range layers (P=0.0077). The C. perfringens count was the lowest in chicken litter from intensively raised broilers and layers (P=0.0001). The chemical properties of litter from the different chicken types and production systems were compared based on determination of pH, electrical conductivity, carbon, nitrogen, phosphorus, potassium, cadmium and zinc. Litter from free-range broilers showed the highest pH value (P=0.0005); however, the electrical conductivity was higher in the litter from both intensive and free-range layers compared to the litter from both broiler production systems (P=0.0117). Chicken litter from intensive systems had higher nitrogen content than litter from free-range systems (P=0.0000). The total phosphorus was the lowest in free-range broiler litter (P=0.0001), while the total potassium was the lowest in litter from intensively managed broilers (P=0.0000). Zinc appeared higher in litter from layers compared to that from broilers (P=0.0101). The cadmium content was higher in the litter from free-range broilers and layers compared to that in the litter from intensively managed systems (P=0.0439). Staphylococcus species in the litter as well as cadmium concentrations seem to be the most critical parameters presenting risks on the environment and on human health. Based on the lowest coliform counts (an indication of water pollution), the high nutrient levels and the low cadmium values, litter from intensively managed layers appears as the most suitable for application on agricultural soils.

Animal Husbandry↗
PubMed2006

A new method of body habitus correction for total body potassium measurements.

This paper describes an accurate and time-efficient method for the determination of total body potassium via a combination of measurements in the Birmingham whole body counter and the use of the Monte Carlo n-particle (MCNP) simulation code. In developing this method, MCNP has also been used to derive values for some components of the total measurement uncertainty which are difficult to quantify experimentally. A method is proposed for MCNP-assessed body habitus corrections based on a simple generic anthropomorphic model, scaled for individual height and weight. The use of this model increases patient comfort by reducing the need for comprehensive anthropomorphic measurements. The analysis shows that the total uncertainty in potassium weight determination by this whole body counting methodology for water-filled phantoms with a known amount of potassium is 2.7% (SD). The uncertainty in the method of body habitus correction (applicable also to phantom-based methods) is 1.5% (SD). It is concluded that this new strategy provides a sufficiently accurate model for routine clinical use.

Body Burden↗
PubMed2003

Antimicrobial efficacy and potential application of a newly developed plasma-based ultraviolet irradiation facility.

A low-pressure mercury vapour discharge tube generating high-intensity ultraviolet (UV) resonance radiation at 254 nm was designed to achieve a nearly simultaneous all-round UV irradiation of products. Testing this 'universal homogeneous ultraviolet (UHUV) irradiation facility' with suspended Bacillus subtilis spores, resulted in a 10(6)-fold reduction in viable count within 30 s applying irradiation energy of 0.3 mW/cm(2). Moreover, this irradiation dose reduced the number of immobilized B. subtilis spores on several material surfaces (wood-free paper, aluminium foil, polystyrol, polypropylene, and polyethylene foil) 10(2)-10(4)-fold. To evaluate potential applications of this UHUV irradiation technique under more realistic conditions, dental hand pieces and orthodontic forceps were contaminated by a blood-saliva mix containing Staphylococcus aureus. Under these conditions, a reduction in viable count of 10(5)-10(6)-fold was achieved within 5-15 min, but higher irradiation energy levels up to 13 mW/cm(2) were necessary. Because of its construction, the shape of the newly developed UHUV irradiation device can be adapted to various shapes to achieve a fast and effective antimicrobial treatment.

Bacillus subtilis↗
PubMed2005

Digital image analysis of haematopoietic clusters.

Counting and differentiating cell clusters is a tedious task when performed with a light microscope. Moreover, biased counts and interpretation are difficult to avoid because of the difficulties to evaluate the limits between different types of clusters. Presented here, is a computer-based application able to solve these problems. The image analysis system is entirely automatic, from the stage screening, to the statistical analysis of the results of each experimental plate. Good correlations are found with measurements made by a specialised technician.

Blood Cell Count↗
PubMed2004

Sensitivity analyses for unmeasured confounding assuming a marginal structural model for repeated measures.

Robins introduced marginal structural models (MSMs) and inverse probability of treatment weighted (IPTW) estimators for the causal effect of a time-varying treatment on the mean of repeated measures. We investigate the sensitivity of IPTW estimators to unmeasured confounding. We examine a new framework for sensitivity analyses based on a nonidentifiable model that quantifies unmeasured confounding in terms of a sensitivity parameter and a user-specified function. We present augmented IPTW estimators of MSM parameters and prove their consistency for the causal effect of an MSM, assuming a correct confounding bias function for unmeasured confounding. We apply the methods to assess sensitivity of the analysis of Hernán et al., who used an MSM to estimate the causal effect of zidovudine therapy on repeated CD4 counts among HIV-infected men in the Multicenter AIDS Cohort Study. Under the assumption of no unmeasured confounders, a 95 per cent confidence interval for the treatment effect includes zero. We show that under the assumption of a moderate amount of unmeasured confounding, a 95 per cent confidence interval for the treatment effect no longer includes zero. Thus, the analysis of Hernán et al. is somewhat sensitive to unmeasured confounding. We hope that our research will encourage and facilitate analyses of sensitivity to unmeasured confounding in other applications.

CD4 Lymphocyte Count↗
PubMed2002

The risk of thrombosis in essential thrombocythemia and polycythemia vera.

Thrombotic events are present in 20% to 50% of patients with polycythemia vera (PV) and essential thrombocythemia (ET) at diagnosis and involve major vessels and the microcirculation. Establishing the precise risk of thrombosis in ET and PV is difficult. However, estimates may be obtained from retrospective and prospective studies, and some risk factors have been defined. In ET, increasing age and previous thrombosis emerge as major factors. The level of the platelet count per se does not correlate with thrombotic incidence. However, there is substantial evidence that adequate control of the platelet count reduces the frequency of thrombosis. While aspirin is usually effective at relieving vasomotor and microvascular occlusive symptoms or signs, there is only limited evidence that its use reduces the risk of larger vessel thrombosis. Other suggested risk factors include apparent clonal hematopoiesis in younger patients, hypercholesterolemia, and cigarette smoking. In PV, the overall impression is that the incidence of thrombosis is greater than in ET. As in ET, increasing age and previous thrombosis are significant risk factors. In addition, adequate reduction of the hematocrit reduces the incidence of thrombosis. Identifying the risk associated with thrombocytosis in PV is confounded by the overall myeloproliferation usually found in these patients and the fact that the thrombocytosis is not usually as marked as in ET. However, by analogy with ET, one could argue that the risk associated with the thrombocytosis in ET is equally applicable to PV. In support of this, there is overwhelming evidence that patients treated with adequate myelosuppression with complete normalization of their blood counts have the lowest thrombotic incidence. Essential thrombocythemia and PV patients presenting with thrombosis should be investigated for other congenital or acquired prothrombotic conditions. Establishment of the presence of one or the other of these may alter the long-term management of these patients with the use of either aspirin or anticoagulation in addition to cytoreduction. Thrombotic risk has emerged as a major factor in stratifying patients with myeloproliferative disease. While some clear thrombotic risk factors have been defined, there is a need to identify further additive risk factors in patients considered to be at low risk of thrombosis.

Humans↗