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PubMed1999

Cell membrane orientation visualized by polarized total internal reflection fluorescence.

In living cells, variations in membrane orientation occur both in easily imaged large-scale morphological features, and also in less visualizable submicroscopic regions of activity such as endocytosis, exocytosis, and cell surface ruffling. A fluorescence microscopic method is introduced here to visualize such regions. The method is based on fluorescence of an oriented membrane probe excited by a polarized evanescent field created by total internal reflection (TIR) illumination. The fluorescent carbocyanine dye diI-C(18)-(3) (diI) has previously been shown to embed in the lipid bilayer of cell membranes with its transition dipoles oriented nearly in the plane of the membrane. The membrane-embedded diI near the cell-substrate interface can be fluorescently excited by evanescent field light polarized either perpendicular or parallel to the plane of the substrate coverslip. The excitation efficiency from each polarization depends on the membrane orientation, and thus the ratio of the observed fluorescence excited by these two polarizations vividly shows regions of microscopic and submicroscopic curvature of the membrane, and also gives information regarding the fraction of unoriented diI in the membrane. Both a theoretical background and experimental verification of the technique is presented for samples of 1) oriented diI in model lipid bilayer membranes, erythrocytes, and macrophages; and 2) randomly oriented fluorophores in rhodamine-labeled serum albumin adsorbed to glass, in rhodamine dextran solution, and in rhodamine dextran-loaded macrophages. Sequential digital images of the polarized TIR fluorescence ratios show spatially-resolved time-course maps of membrane orientations on diI-labeled macrophages from which low visibility membrane structures can be identified and quantified. To sharpen and contrast-enhance the TIR images, we deconvoluted them with an experimentally measured point spread function. Image deconvolution is especially effective and fast in our application because fluorescence in TIR emanates from a single focal plane.

Adsorption↗
PubMed2001

Pollutant concentrations of stormwater and captured sediment in flood control sumps draining an urban watershed.

Levee sump systems are used by many riverine communities for temporary storage of urban wet weather flows. The performance and transport of stormwater pollutants in sump systems, however, have not been systematically studied. Although flow of stormwater through a sump system is regulated solely by flood-control requirements, these sumps may function as sedimentation basins that provide purification of stormwater. The objective of this paper is to present a case study of stormwater and sediment analysis for conventional pollutants in flood control sumps in an urban watershed. Two sumps of highly variable physical and hydraulic characteristics were selected for analysis. The results suggest that: (1) first-flush samples may not give an accurate picture of outfall concentrations of stormwater to the sump; (2) time-variable concentrations of pollutants in a sump are related to the hydraulic characteristics of the basin; and, (3) post-event sediment analysis provides verification of pollutant capture in the sumps. This study is an initial step toward development of a more comprehensive management model for flood control sumps that incorporates their hydraulic performance for quantitative assessment of pollutant loads, pollutant discharges, and pollutant removals with respect to the sumps.

Enterobacteriaceae↗
PubMed2003

Blind deconvolution applied to acoustical systems identification with supporting experimental results.

Many acoustical applications require the analysis of a signal that is corrupted by an unknown filtering function. Examples arise in the areas of noise or vibration control, room acoustics, structural vibration analysis, and speech processing. Here, the observed signal can be modeled as the convolution of the desired signal with an unknown system impulse response. Blind deconvolution refers to the process of learning the inverse of this unknown impulse response and applying it to the observed signal to remove the filtering effects. Unlike classical deconvolution, which requires prior knowledge of the impulse response, blind deconvolution requires only reasonable prior estimates of the input signal's statistics. The significant contribution of this work lies in experimental verification of a blind deconvolution algorithm in the context of acoustical system identification. Previous experimental work concerning blind deconvolution in acoustics has been minimal, as previous literature concerning blind deconvolution uses computer simulated data. This paper examines experiments involving three classical acoustic systems: driven pipe, driven pipe with open side branch, and driven pipe with Helmholtz resonator side branch. Experimental results confirm that the deconvolution algorithm learns these systems' inverse impulse responses, and that application of these learned inverses removes the effects of the filters.

Journal Article↗
PubMed1991

Intraoperative recurrent laryngeal nerve monitoring.

Intraoperative nerve monitoring has become common for surgical procedures in which cranial or peripheral nerves may be compromised. Intraoperative monitoring of recurrent laryngeal nerve function can be accomplished by recording electromyographic activity from fine-wire electrodes placed in the vocalis muscle. The technique and instrumentation for this are adapted from those used in intraoperative facial nerve monitoring for acoustic neuroma excision. Specifically, a commercially available instrument, the XOMED-NIM provides the capability for monitoring the vocalis muscle electromyogram by means of visual and auditory display. It also provides the capability for performing evoked electromyographic tests of nerve integrity. Intraoperative monitoring of the recurrent laryngeal nerve during thyroidectomy may assist in the more precise dissection of the nerve as well as in verification of nerve integrity during the operative procedure, thus reducing the risk of injury.

Electrodes↗
PubMedDate not supplied

[The spherical theory of color perception: its verification by the methods of psychophysics and neurophysiology].

In the paper data of experimental verification of "spherical theory of perception" (E. N. Sokolov) are summed on the material of colour perception study. The results of psychophysical experiments with subjects having different forms of colour perception (normal trichromats, colour anomalies) and neurophysiological experiments on animals (carp) are considered within single psychophysiological system--spherical model of colour discrimination. Neuron-like elements of the model reflect the activity of light-sensitive cells of the visual system and at the same time reproduce some rules of subjective colours discrimination at the psychophysical level. Advantages of spherical model are considered allowing to analyze human individual colour functions in norm and pathology and giving the opportunity of strictly quantitative approach to description of neuronal mechanisms of colour vision. From the position of spherical model of colour discrimination neuronal structure of colour analyzer is discussed, which includes layers of photoreceptors, ++predetectors (colour-opponent and achromatic cells) and colour-selective detectors.

Animals↗
PubMed1999

Verification of phylogenetic predictions in vivo and the importance of the tetraloop motif in a catalytic RNA.

M1 RNA, the catalytic subunit of Escherichia coli RNase P, forms a secondary structure that includes five sequence variants of the tetraloop motif. Site-directed mutagenesis of the five tetraloops of M1 RNA, and subsequent steady-state kinetic analysis in vitro, with different substrates in the presence and absence of the protein cofactor, reveal that (i) certain mutants exhibit defects that vary in a substrate-dependent manner, and that (ii) the protein cofactor can correct the mutant phenotypes in vitro, a phenomenon that is also substrate dependent. Thermal denaturation curves of tetraloop mutants that exhibit kinetic defects differ from those of wild-type M1 RNA. Although the data collected in vitro underscore the importance of the tetraloop motif to M1 RNA function and structure, three of the five tetraloops we examined in vivo are essential for the function of E. coli RNase P. The kinetic data in vitro are not in total agreement with previous phylogenetic predictions but the data in vivo are, as only mutants in those tetraloops proposed to be involved in tertiary interactions fail to complement in vivo. Therefore, the tetraloop motif is critical for the stabilization of the structure of M1 RNA and essential to RNase P function in the cell.

Base Sequence↗
PubMed1984

Effects of labelling on income, work and social function among hypertensive employees.

Two hundred and thirty hypertensive Canadian steelworkers were followed for 5 years after screening and referral. Data on income, absenteeism and measures of work and social function were collected on these men and on a matched group of 230 normotensive employees. In the fifth year after screening, hypertensive employees earned an average of Can. $1093 less than normotensive employees despite similar incomes in the year before screening. This adverse effect on income was observed regardless of awareness of hypertension at the time of screening or compliance with treatment. Illness-related absenteeism among hypertensives rose in the year following screening and remained elevated for 4 years after screening. Normotensive and hypertensive employees reported similar levels of physical ability and psychological well-being. These findings need verification in other settings before inclusion in cost-effectiveness analyses of the management of hypertension.

Absenteeism↗
PubMed1992

Remote memory: recalling autobiographical and public events from across the lifespan.

In this study the recall of autobiographical and public events across the lifespan was examined in a sample of middle-aged and older-aged adults. The tasks were modified versions of one first introduced by Galton (1879), and they required subjects to recall events from specific time periods across their entire lifespan. The four tasks differed in the nature of the episodes requested (autobiographical or public) and whether recall was word-cued or non-word-cued. Verification of public events was assessed archivally, and autobiographical events were verified by a sample of relatives for a subgroup of the subjects and reported events. The results indicated that memory for public events decreases with increased age of the subject, but this effect is not generally found for the recall of autobiographical events. The older-aged subjects were able to recall an equal number of autobiographical episodes from all life segments, whereas recall of news events tended to decrease with remoteness of the episode. These data are contrary to those models that posit general memory loss as a function of age or of remoteness of the events.

Aged↗
PubMed2002

Monte Carlo study of a highly efficient gas ionization detector for megavoltage imaging and image-guided radiotherapy.

The imaging characteristics of an arc-shaped xenon gas ionization chamber for the purpose of megavoltage CT imaging were investigated. The detector consists of several hundred 320 microm thick gas cavities separated by thin tungsten plates of the same thickness. Dose response, efficiency and resolution parameters were calculated using Monte Carlo simulations. The calculations were compared to measurements taken in a 4 MV photon beam, assuming that the measured signal in the chambers corresponds to the therein absorbed dose. The measured response profiles for narrow and broad incident photon beams could be well reproduced with the Monte Carlo calculations. They show, that the quantum efficiency is 29.2% and the detective quantum efficiency at zero frequency DQE(0) is 20.4% for the detector arc placed in focus with the photon source. For a detector placed out of focus, these numbers even increase. The efficiency of this kind of radiation detector for megavoltage radiation therefore surpasses the reported efficiency of existing detector technologies. The resolution of the detector is quantified with calculated and measured line spread functions. The corresponding modulation transfer functions were determined for different thicknesses of the tungsten plates. They show that the resolution is only slightly dependent on the plate thickness but is predominantly determined by the cell size of the detector. The optimal plate thickness is determined by a tradeoff between quantum efficiency, total signal generation and resolution. Thicker plates are more efficient but the total signal and the resolution decrease with plate thickness. In conclusion, a gas ionization chamber of the described type is a highly efficient megavoltage radiation detector, allowing to obtain CT images with very little dose for a sufficient image quality for anatomy verification. This kind of detector might serve as a model for a future generation of highly efficient radiation detectors.

Animals↗
PubMed2004

Pathophysiology, diagnosis and treatment of endometriosis.

Endometriosis is generally a benign condition. However, there is a tendency towards progression and in part deep infiltrating processes occur, which can lead to obstruction and even silent loss of organ function such as kidney failure. Hereditary, genetic and immunological peculiarities have been found. Important are symptoms such as pain and infertility, which burden the life of the women involved. In spite of extensive research in the past the pathogenesis and epidemiology of the disease are not definitely clarified as yet. The estimated prevalence of endometriosis ranges between 10% and even more than 50% depending on the underlying problems of the women studied. Besides the main location of the disease within the pelvis also extra pelvic locations have been found (lung, lymph nodes, scars). The diagnosis should be established by histological verification. The main therapeutic modalities consist of surgery and medical treatment or combinations, which need to be individually adjusted, because of the high risk of recurrence and progression of the disease. The aim should be early detection and treatment as complete as possible, since symptom relief, resolution or prevention of infertility and decrease of recurrences are at their best under these circumstances.

Endometriosis↗
PubMed1983

Isotretinoin treatment of acne and related disorders: an update.

In the one year since isotretinoin has been available in the United States for the treatment of severe, recalcitrant, nodulocystic acne, there has been extensive clinical verification of the reports of its dramatic efficacy in the treatment of this troublesome disease. Proper selection of patients, as well as treatment with adequate doses of drug for 3 to 5 months, will most often result in significant clinical improvement or total clearing. Although dosages of less than 1 mg/kg/day may produce a nearly equivalent degree of improvement with somewhat fewer or less severe side effects, the recommended daily dose remains 1 mg/kg/day because lower dosages are associated with more frequent relapses. In severe cases, the daily dosage may be increased to 2 mg/kg/day. Teratogenicity, elevation of serum triglycerides, liver function abnormalities, pancreatitis, and pseudotumor cerebri may all be associated with isotretinoin therapy and require close monitoring of the patient.

Abnormalities, Drug-Induced↗
PubMed1995

On the correction for radioactive decay in pharmacokinetic modeling.

The question of how to include radioactive decay during biological modeling with first-order differential equations was considered. Modeling may involve either experimental data y(t) or decay-corrected data z(t) [identical to exp(lambda t)y(t) where lambda is the decay constant] for each compartment. It is sometimes assumed that the latter are solutions to corresponding purely pharmacokinetic models (no decay). We primarily compared the two analyses in the case where the model did not require simultaneous consideration of both labeled and unlabeled material. A general theorem was found which limits the use of decay-corrected data to pharmacokinetic models containing linear, homogeneous differential equations. By way of verification, an example of this model type was analyzed for a chimeric monoclonal antibody biodistribution in man. Even in this case, statistically significant differences between the two solutions showed that one may find different model parameters depending upon which data set (y or z) was analyzed. For other mathematical forms, the analyst must include the physical decay in all relevant compartments. By analyzing an open, quadratic model, effects of not including decay were seen to be maximized if the biological rate constant was > or = lambda, the physical decay constant. Finally, using monoclonal antibody-antigen reactions, similar discrepancies between the z functions and the pharmacokinetic variables were demonstrated. This result was found to persist even if competitive molecules were included. We conclude that decay-corrected data may be shown, but should not be entered into the modeling equations unless the latter are of the linear, homogeneous form.

Antibodies, Monoclonal↗
PubMed1985

[Acetabular protrusion in Marfan's disease].

The etiologic assessment that had been made on the person of a young girl revealed a protrusio acetabuli which was painful and stiff and the evolution of which was quick, was allowed us to reveal a Marfan's syndrome. On this occasion, we have studied the links between the Marfan's syndrome and the protrusio acetabuli. After having resumed the history of this illness, the author remind us of its main characteristics while insisting upon the orthopedic abnormalities. They define the three steps of a protrusio acetabuli according to the Ruelle and Dubois criteria. For the child, the protrusio acetabuli is said to be primary without any well determined etiology. On the contrary, numerous studies deal with the idiopathic chondrolysis of the hips and describe surprising associations such as scoliosis, kyphosis, deformations of the hands and hereditary characteristics. Twelve observations of the Marfan's syndrome are presented, eleven of which concerning children and one concerning an adult. Among these twenty-four hips, the authors find nineteen protrude hips (80%) which belong to one of the three steps described by Ruelle and Dubois. There is an absence of clinical symptoms in nine cases among the twelve observed and the protrusion is systematically found. In three cases, there existed a functional symptomatology which in two cases, has led us to reveal a Marfan's syndrome. There were great pains of the mechanical type, linked to a limitation of the articular mobility; the radiography revealed an idiopathic chondrolysis of the hips. Moreover, the authors underline the primary importance of the skin-biopsy and of the metacarpal index measure in order to confirm the diagnostic of the Marfan's syndrome. Thus, the protrusio acetabuli appear to be a quasiconstant sign of Marfan's syndrome and has to be included in the long check of the orthopedic abnormalities of such a syndrome. The verification of a deep hip needs to research of the Marfan's syndrome. The primary protrusio acetabuli has to be closely studied, since we have just showed that the Marfan's syndrome was one its rare etiologies known up to now.

Acetabulum↗
PubMed2000

Yield Stress of Concentrated Zirconia Suspensions: Correlation with Particle Interactions.

The presence of a sufficient concentration of solid particles in a solution gives rise to a large increase in its viscosity and, more importantly, to significant deviations with respect to its original Newtonian behavior. Different rheological techniques are available to characterize such deviations, but the simplest one, obtention of steady-state rheograms, is already extremely useful with that purpose. In this work, this technique is applied to suspensions of zirconia particles, both synthesized with spherical geometry and commercial. The sigma(shear stress)-gamma;(shear rate) curves show that the suspensions are nonideal plastic, thus exhibiting a finite yield stress, sigma(0), and a shear-thinning flow. It is through sigma(0) that a connection can be established between steady-state rheological behavior and interaction energy between particles, since sigma(0) can be estimated as the maximum attractive force between particles multiplied by the number of bonds per unit area between a given particle and its neighbors. Having an experimental determination of sigma(0), the verification of its relation with the attractive forces requires estimation of the potential energy of interaction between any pair of particles. Two approaches will be considered: one is the classical DLVO model, in which the potential energy, V, is the sum of the van der Waals (V(LW)) and electrostatic (V(EL)) contributions. The second approach is the so-called extended DLVO theory, in which the acid-base interaction V(AB) (related to the hydrophilic repulsion or hydrophobic attraction between the particles) is considered in addition to V(LW) and V(EL). The three contributions can be calculated as a function of the interparticle distance if the particle-solution interface is characterized from both the electric and the thermodynamic points of view. The former is carried out by means of electrophoretic mobility measurements and the latter by contact angle determinations for three probe liquids on zirconia powder layers. Comparison between measured and calculated sigma(0) values was carried out for suspensions of spherical, monodisperse ZrO(2) particles, with volume fraction of solids, straight phi, ranging between 4.6 and 21.7%, in 10(-3) M NaCl solutions. In the case of commercial particles, the effects of both NaCl concentration (10(-5) to 10(-1) M) and volume fraction (3.5 to 21%) were investigated. It is found that the classical DLVO theory cannot be used to predict the yield stress when [NaCl]=10(-5) M, since the high zeta potentials and thick double layers never yield partial differential V/ partial differential R>0 (the interaction is repulsive for all distances) in such a case. A similar problem was encountered in 10(-1) M solutions, but now because V is always attractive, and no maximum force can be found. On the contrary, the extended DLVO model always yield physically reasonable sigma(0) values (coincident with those deduced from the classical approach when calculation is possible in the latter case). The comparison with experimental data shows that theory clearly underestimates sigma(0) by one order of magnitude or even more. The possible role of particle aggregation in this underestimation is discussed in terms of the scaling behavior of sigma(0) as a function of straight phi. Copyright 2000 Academic Press.

Journal Article↗
PubMed2005

Localization of the ABCG2 mitoxantrone resistance-associated protein in normal tissues.

Reduced drug accumulation due to overexpression of individual members of the ATP binding cassette (ABC) superfamily of membrane transporters has been investigated as a cause of multidrug resistance and treatment failure in oncology. This study was designed to develop an immunohistochemical assay to determine the expression and localization of the 72kDa ABC half-transporter ABCG2 in normal tissues. Formalin-fixed, paraffin embedded archival tissue from 31 distinct normal tissues with an average of eight separate tissue samples of each were immunostained with rabbit-anti-ABCG2 antibody 405 using a modified avidin-biotin procedure. As a negative control, each sample was also stained with antibody pre-adsorbed with peptide to assess background staining. As a means of verification, selected tissues were also stained with the commercially available monoclonal antibody 5D3. ABCG2 positivity was consistently found in alveolar pneumocytes, sebaceous glands, transitional epithelium of bladder, interstitial cells of testes, prostate epithelium, endocervical cells of uterus, squamous epithelium of cervix, small and large intestinal mucosa/epithelial cells, islet and acinar cells of pancreas, zona reticularis layer of adrenal gland, kidney cortical tubules and hepatocytes. Placental syncytiotrophoblasts showed both cytoplasmic and surface staining. Our results support a hypothesis concluding that ABCG2 plays a role in the protection of organs from cytotoxins. However, many of the cell types expressing ABCG2 have a significant secretory function. These data suggest a dual function for ABCG2 in some tissues: the excretion of toxins and xenobiotics including anti-cancer agents and a potential, as-yet undefined role in the secretion of endogenous substrates.

ATP Binding Cassette Transporter, Subfamily G, Mem↗
PubMed2002

The evolution of multicomponent systems at high pressures: VI. The thermodynamic stability of the hydrogen-carbon system: the genesis of hydrocarbons and the origin of petroleum.

The spontaneous genesis of hydrocarbons that comprise natural petroleum have been analyzed by chemical thermodynamic-stability theory. The constraints imposed on chemical evolution by the second law of thermodynamics are briefly reviewed, and the effective prohibition of transformation, in the regime of temperatures and pressures characteristic of the near-surface crust of the Earth, of biological molecules into hydrocarbon molecules heavier than methane is recognized. For the theoretical analysis of this phenomenon, a general, first-principles equation of state has been developed by extending scaled particle theory and by using the technique of the factored partition function of the simplified perturbed hard-chain theory. The chemical potentials and the respective thermodynamic Affinity have been calculated for typical components of the H-C system over a range of pressures between 1 and 100 kbar (1 kbar = 100 MPa) and at temperatures consistent with those of the depths of the Earth at such pressures. The theoretical analyses establish that the normal alkanes, the homologous hydrocarbon group of lowest chemical potential, evolve only at pressures greater than approximately 30 kbar, excepting only the lightest, methane. The pressure of 30 kbar corresponds to depths of approximately 100 km. For experimental verification of the predictions of the theoretical analysis, a special high-pressure apparatus has been designed that permits investigations at pressures to 50 kbar and temperatures to 1,500 degrees C and also allows rapid cooling while maintaining high pressures. The high-pressure genesis of petroleum hydrocarbons has been demonstrated using only the reagents solid iron oxide, FeO, and marble, CaCO3, 99.9% pure and wet with triple-distilled water.

Carbon↗
PubMed2001

Naturally occurring circular permutations in proteins.

A pair of proteins is defined to be related by a circular permutation if the N-terminal region of one protein has significant sequence similarity to the C-terminal of the other and vice versa. To detect pairs of proteins that might be related by circular permutation, we implemented a procedure based on a combination of a fast screening algorithm that we had designed and manual verification of candidate pairs. The screening algorithm is a variation of a dynamic programming string matching algorithm, in which one of the sequences is doubled. This algorithm, although not guaranteed to identify all cases of circular permutation, is a good first indicator of protein pairs related by permutation events. The candidate pairs were further validated first by application of an exhaustive string matching algorithm and then by manual inspection using the dotplot visual tool. Screening the whole Swissprot database, a total of 25 independent protein pairs were identified. These cases are presented here, divided into three categories depending on the level of functional similarity of the related proteins. To validate our approach and to confirm further the small number of circularly permuted protein pairs, a systematic search for cases of circular permutation was carried out in the Pfam database of protein domains. Even with this more inclusive definition of a circular permutation, only seven additional candidates were found. None of these fitted our original definition of circular permutations. The small number of cases of circular permutation suggests that there is no mechanism of local genetic manipulation that can induce circular permutations; most examples observed seem to result from fusion of functional units.

Algorithms↗
PubMed2002

The search for value in health care: a review of the National Committee for Quality Assurance efforts.

Large employers formed the National Committee for Quality Assurance (NCQA) to ensure value to healthcare purchasers. Value in healthcare is a function of quality divided by costs. Through NCQA's role as an accrediting agency for healthcare organizations and the development of performance measures, Health Plan Employer Data and Information Set (HEDIS), gains toward defining the value of health services have materialized. An analysis of the impact of HEDIS data collection on physician practices and the influence of HEDIS data on employer, employee, and governmental health plan selections is examined. This study consisted of a general review, from 1993 to 2001, of HealthStar databases, PubMed databases, and the NCQA website. NCQA accreditation is accepted as an important industry milestone for health plans, credentials verification organizations, and physician organizations. The data for HEDIS is collected from health plan administrative data repositories, whereas health plan members' clinical data may be collected by chart abstraction in physician offices. Data collection in physician offices consumes administrative resources from physician practices and health plans. As commercial and governmental insurers move toward greater adoption of HEDIS measures, complex implications are created for physician practices and vulnerable populations. There are lingering questions regarding the improvements in quality of care for medically underserved populations and physician practice costs attributable to HEDIS.

Accreditation↗