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PubMed2004

The number of unexpected HbA variants may be a greater problem in routine practice than is generally realized.

BACKGROUND: The majority of variant and abnormal haemoglobins are clinically silent but may not be biochemically silent when it comes to HbA1c estimation. CASE REPORT: We describe several cases in which there were problems in the determination of HbA1c for monitoring diabetes in patients that would not normally be classified as being at risk. Four of these cases were sufficiently unusual to warrant individual publication but all came from a very restricted geographical area with a population of only approximately 500,000. The significance of this is not that variant haemoglobins affect HbA1c analysis but that the occurrence of unexpected/unusual variant haemoglobins may be more frequent than most clinicians would expect, considering that only a small proportion of the basal population are diabetic and have their HbA1c monitored. Differences will exist between different areas due to differences in both the prevalence of variants and the analytical methods employed. CONCLUSIONS: Consequently, we propose greater interaction between diabetologists and the laboratory in an attempt to identify these clinically but not biochemically silent variants to achieve a true estimation of the glycaemic control in affected patients.

Adult↗

PubMed2002

Responses of partially immersed elastic structures using a symmetric formulation for coupled boundary element and finite element methods.

Using a coupled BEM/FEM, this work describes a numerical method to compute the response and acoustic radiation for structures partially immersed in fluid. The structures and their responses are assumed to be symmetric about a symmetric plane. A symmetric complex matrix derived from the BEM and a reciprocal principle for surface acoustics is also used to represent the acoustic loading against the structures. In addition, selecting a proper Green's function based on image source method satisfies the boundary conditions of pressure release on the fluid surface and null normal velocity on the symmetric plane. Moreover, a boundary integral equation emerges when the field point approaches the structural surface where the normal derivative of the Green's function over partial, infinitesimal spheres is evaluated. These limiting values depend on locations of the field point on the surface. Owing to the symmetry of the acoustic loading matrix, the matrix for the coupled BEM/FEM is a banded, symmetric one, thereby allowing us to employ a variable banded storage method and invert of the matrix. Doing so markedly increases computational efficiency. Furthermore, an analytical solution of a spherical thin shell with the lower semi-sphere immersed in water is carried out by characteristic function expansions for shell equation and acoustic loading. These analytical solutions compare with the results obtained from the proposed numerical method. A good correlation for low frequencies is obtained and minor discrepancies are observed with an increasing frequency.

Journal Article↗

PubMed1968

Effects of heterogeneous myocardial perfusion on coronary venous H2 desaturation curves and calculations of coronary flow.

The present investigation was intended to evaluate myocardial inert gas desaturation curves for manifestations of heterogeneous coronary perfusion. The test gas was hydrogen (H(2)) and blood H(2) analyses were performed with a gas chromatograph capable of detecting small but prolonged venous-arterial H(2) differences produced by areas of reduced flow. Curves were initially obtained after 4-min left ventricular infusions of H(2)-saturated saline in six patients with arteriographically proven coronary artery disease, three patients with normal coronary arteries, and nine closed-chest dogs. The dogs were studied before and after embolic occlusion of a portion of the left coronary artery. Although the slopes of their semilogarithmically plotted venous desaturation curves varied with time before embolization, they showed more distinct deviations from single exponentials after embolization (after H(2) concentrations had fallen below 15% of their initial values). The human curves divided similarly, those from coronary artery patients deviating appreciably from single exponentials. A similar separation was also evident in studies of coronary venous-arterial H(2) differences after 20 min of breathing 2% H(2): data were obtained in four dogs before and after coronary embolization, and in three normal patients, and five patients with coronary artery disease. Additional data indicated that the findings were not the result of right atrial admixture in sampled coronary venous blood, although admixture occurred frequently when blood was sampled in the first 2 cm of the coronary sinus (as seen in the frontal projection). Finally, average coronary flows calculated from a given set of data varied significantly with different methods of calculation. Areas of below-average flow seemed likely to be overlooked when single rate constants of desaturation, relatively insensitive analytical techniques, or relatively short periods of saturation and (or) desaturation are employed.

Adult↗

PubMed1977

The red and green cone visual pigments of deuternomalous trichromacy.

1. Three "simple" deuteranomalous trichromats match with abnormally low "red" tristimulus values throughout the spectrum and abnormally high "green" tristimulus values in the long wave end of the spectrum which become normal (and then low) in the yellow-green. The spectrum locus of this transition differs from one anomalous to the other. Differences in the matches of two of these cannot be due to differences in eye media transmissivities alone. Therefore these two deuteranomalous have different cone visual pigments. 2. The analytical anomaloscope was used in the confrontation of one deuteranomalous with six deuteranopes in turn. In each confrontation the deuteranope set the anomaloscope in his mode and adjusted the intensity of the monochromatic light for a match. Deuteranomalous matches were rejected by four of these six deuteranopes. 3. They were accepted by two of the six. These two rejected each other's matches in a way not attributable to differences in eye media transmissivity. 4. Three different psychophysical techniques were used to measure the action spectra of the long wave cones of these two deuternopes. All three methods reveal small but systematic differences in lambdamax and shape of the curve for the one deuteranope compared with that of the other. 5. In red-green spectral range, these spectra are accurately described by different linear combinations of the color matching functions of the same deuteranomalous whose matches the two deuteranopes accept. Linear combinations of those of a second deuteranomalous, with at least one different kind of cone, fit less well. 6. The wave length discrimination curve of the former deuteranomalous was measured with a new method. The curves of two normals were also obtained for comparison. Wave-length discrimination predictions from the Stiles (1946) line element theory were compared to the anomalous curve. The deuteranopic action spectra were used in the line element to compute this deuteranomalous' discrimination. There is reasonable first order correspondence between prediction and observation, but the prediction is sensitive to small changes in the derivatives of the logarithms of the action spectra. 7. Line element prediction of the deuteranomalous step-by-step luminous efficiency curve is insensitive to such uncertainties. The agreement with expectation from the above assumptions and the measured step-by-step deuteranomalous luminous efficiency curve in the red-green part of the spectrum is therefore good. 8. It is concluded that the erythrolabe in one deuternope's long wave cones has the action spectrum of this deuteranomalous' long and the erythrolabe in the other deuternope's long wave sensitive cones has that of this deuternomalous' medium wave cones. This leads to a general hypothesis about the nature of all forms of red-green colour vision defects transmitted recessively on the X chromosome.

Color Vision Defects↗

PubMed2006

Biofilms.

Biofilms of bacteria, frequently in association with algae, protozoa and fungi, are found on all submerged structures in the marine environment. Although it is likely that for the majority of organisms a biofilmed surface is not a pre-requisite for settlement, in practice, colonization by spores and larvae of fouling organisms almost always takes place via a biofilmed surface. Therefore, the properties of the latter may be expected to influence colonization, positively or negatively. Biofilms are responsible for a range of surface-associated and diffusible signals, which may moderate the settling behaviour of cells, spores and larvae. However, there is no consensus view regarding either cause and effect or the mechanism(s) by which biofilms moderate settlement. Studies with mixed biofilms, especially field experiments, are difficult to interpret because of the conflicting signals produced by different members of the biofilm community as well as their spatial organisation. Molecular techniques highlight the deficiencies of culture methods in identifying biofilm bacteria; hence, the strains with the most impact on settlement of spores and larvae may not yet have been isolated and cultured. Furthermore, secondary products isolated from cultured organisms may not reflect the situation that pertains in nature. The evidence that bacterial quorum sensing signal molecules stimulate settlement of spores of the green macroalga, Ulva, is discussed in some detail. New molecular and analytical tools should provide the opportunity to improve our fundamental understanding of the interactions between fouling organisms and biofilms, which in turn may inform novel strategies to control biofouling.

4-Butyrolactone↗

PubMed2006

An implanted spherical head model exposed to electromagnetic fields at a mobile communication frequency.

Can cellular phones and personal communication systems base station antennas affect the active or passive implantable medical devices adversely? Concerns over the possible harmful effects of nonionizing irradiaton upon implanted medical devices have been present for many years. Key issues to address are the questions of whether mobile phones have a detrimental effect on implants, and how the interaction of the handset with the body can be minimized in order to both alleviate public fears and improve handset antenna performance and new implant designs. This paper presents a thorough investigation of the scattering of an electromagnetic (EM) wave from a perfectly conducting implant (a cylindrical wire and a very thin cylindrical disk) of electrically small radius (of resonant length), embedded eccentrically into a dielectric spherical head model by a dipole antenna (0.4 wavelength) at 900 MHz. The dyadic Green's function (DGF) for spherical vector wave functions is employed. Analytical expressions for the scattered fields of an implant embedded head model is obtained. Numerical results from analytical expressions are computed for this problem and then compared with the results from the same model using the finite-difference time-domain, EMU-FDTD electromagnetic simulator. Good agreement is observed between the analytical results on the proposed method in comparison with the FDTD method.

Cell Phone↗

PubMed1975

Collaborative study of a spectrophotometric method for determining maleic hydrazide residues in tobacco and vegetables.

A distillation-spectrophotometric method for the determination of maleic hydrazide residues in tobacco and vegetables reported previously was studied collaboratively. Ten laboratories submitted analytical results on 10 samples containing residues resulting either from field treatment or laboratory fortification. The samples were estimated to contain from 0.99 to 16.36 mug maleic hydrazide/0.5 g sample analyzed. The coefficients of variation based on precision standard deviation ranged from 57.7% for the lowest residue content to 32.4% for the highest. The corresponding coefficients of variation based on overall standard deviations were estimated to be at least one-fifth larger. Strong evidence of systematic laboratory differences was found (F-test, significant at 0.1%). Apparent recoveries of 10.0 mug maleic hydrazide added to 0.5 g fluecured tobacco and potato were 97.3 and 89.7%, respectively. Apparent recoveries of 16.0 and 16.5 mug added to 0.5 g green bean were 87.4 and 85.5%, respectively. The precision of the method studied was no better than that of the current official final action method, 29.121--29.127, and its adoption is not recommended.

Pesticide Residues↗

PubMedDate not supplied

Assurance polyclonal enzyme immunoassay for detection of Listeria monocytogenes and related Listeria species in selected foods: collaborative study.

Six foods representing a variety of food products were analyzed by the Assurance Listeria polyclonal enzyme immunoassay (EIA) and by either the Bacteriological Analytical Manual or the U.S. Department of Agriculture culture method for detecting Listeria monocytogenes and related Listeria species. Samples of each food type, at each inoculation level, were analyzed simultaneously by both methods. A total of 19 laboratories representing federal government agencies and private industry in the United States and Canada participated. Food types were inoculated with Listeria species including L. monocytogenes, with the exception of 3 lots of green beans, which were naturally contaminated. During this study, 1764 samples and controls were analyzed and confirmed, of which 492 were positive and 947 were negative by both methods. There were 159 samples that were positive by culture method but negative by the EIA and 188 that were negative by culture method but positive by EIA. Twenty-two samples were negative by EIA and by culture method but confirmed positive when Assurance selective enrichment broths were subcultured to selective agar. The Assurance polyclonal EIA for detecting L. monocytogenes and related Listeria species in foods has been adopted first action by AOAC INTERNATIONAL.

Animals↗

PubMed2007

Continuous nondestructive monitoring of Bordetella pertussis biofilms by Fourier transform infrared spectroscopy and other corroborative techniques.

This work describes the application of several analytical techniques to characterize the development of Bordetella pertussis biofilms and to examine, in particular, the contribution of virulence factors in this development. Growth of surface-attached virulent and avirulent B. pertussis strains was monitored in continuous-flow chambers by techniques such as the crystal violet method, and nondestructive methodologies like fluorescence microscopy and Fourier transform (FT) IR spectroscopy. Additionally, B. pertussis virulent and avirulent strains expressing green fluorescent protein were grown adhered to the base of a glass chamber of 1-microm thickness. Three-dimensional images of mature biofilms, acquired by confocal laser scanning microscopy, were quantitatively analysed by means of the computer program COMSTAT. Our results indicate that only the virulent (Bvg(+)) phase of B. pertussis is able to attach to surfaces and develop a mature biofilm. In the virulent phase these bacteria are capable of producing a biofilm consisting of microcolonies of approximately 200 microm in diameter and 24 microm in depth. FTIR spectroscopy allowed us not only to follow the dynamics of biofilm growth through specific biomass and biofilm marker absorption bands, but also to monitor the maturation of the biofilm by means of the increase of the carbohydrate-to-protein ratio.

Biofilms↗

PubMed1994

Multi-dimensional interaction analysis: a collaborative approach to the study of medical discourse.

This paper reviews the conceptual frameworks of several research approaches to the study of medical interactions. Two methods are discussed: process analysis and microanalysis. Adapted from Robert Bales's study of the behavior of small groups, process analysis sorts and tallies such interviewing processes as questioning and informing, achieving analysis of large numbers of interviews at the expense of attention to the content or context of the interview. When used in medical interaction research, process analysis seeks correlation between processes documented in the interview and outcomes of the interview. The methods of conversation analysts and discourse analysts, microanalyses subject medical conversations to close linguistic study and contextualization. This review focuses on the underlying assumptions, generalizability of findings, and the types of subjective judgment applied by the methods. It then describes the Multi-Dimensional Interaction Analysis (MDIA) system, a linguistic analytic instrument that combines features of process analysis and microanalysis to capture content, process, and context of medical conversations. The MDIA's validity and reliability are reported and implications for future research are outlined.

Communication↗

PubMed2005

Analysis of tea catechins in human plasma by high-performance liquid chromatography with solid-phase extraction.

Accurate monitoring of tea catechins in biological samples might provide a means of better evaluation of their benefits. The aim of the present study was to develop a rapid method for extracting tea catechins from human plasma samples with a solid-phase extraction technique and to subsequently measure their concentrations using an HPLC system. A human plasma sample spiked with known concentrations of the analyte standards was passed through a Waters Oasis HLB cartridge. After repeated washing, tea catechins were eluted with 70% dimethylformamide containing 0.1% phosphoric acid, and the resulting eluate was injected into an HPLC system. Analytes were separated on a reverse-phase C18 column using an isocratic mobile phase and detected electrochemically. The coefficient of variation for inter- and intraday reproducibility was less than 5.0% and 6.4%, respectively. Linearity was established for the concentration range of 0.01-1.0 microM. The method was successfully applied to measure tea catechin concentrations in the plasma of two healthy subjects who received a single ingestion of a green tea beverage. The proposed method enables the rapid and accurate quantitation of plasma tea catechins and might prove useful for the evaluation of beneficial health effects of tea consumption.

Adult↗

PubMed2006

Tristimulus colorimetry using a digital still camera and its application to determination of iron and residual chlorine in water samples.

Tristimulus colorimetry using a digital still camera (DSC) as a colorimeter has been developed. A photograph of a sample and standard solutions was taken simultaneously with the DSC, and it was transferred to a PC. On the PC, the colors of the sample and of the standard solutions were analyzed and L* (brightness), a* (red-green component), and b* (yellow-blue component) values were determined with laboratory-made software. A dedicated light-box containing white-color LEDs as light source was made of white acrylic to make constant exposure at each photograph. Various settings of the DSC, such as exposure mode, white balance, and so on, that affect analytical figures, were studied with determination of iron with 1,10-phenanthroline. This method was successfully applied to the determinations of iron in a river water sample and of residual chlorine in tap water samples with N,N-diethylphenylenediamine (DPD).

Journal Article↗

PubMedDate not supplied

A pattern classification system for automated cervical cytologic screening based on flow microfluorometric analysis.

A data analytic technique is described for use in automated cervical cytology. The method entails the application of a two-dimensional Fourier transform to histogram data obtained by flow microfluorometry and the subsequent use of the Fourier coefficients as parameters for pattern classification. Analyses were performed on 186 samples including material from 62 positive and 124 negative cases. Cell suspensions were stained with propidium iodide and fluorescein isothiocyanate, and red and green cytofluoresence were measured simultaneously. The two-dimensional histogram data were normalized, the Fourier transform was applied, and a multivariate classifier based on 30 coefficients was assembled using a training set of half the original series. Performance was then assessed on the remaining cases. Overall accuracy was 79.6%, with a false-positive rate of 14.8% and a false-negative rate of 31.2%. The potential applicability of this approach as the basis of a practical screening system is discussed.

Adolescent↗

PubMedDate not supplied

Measurement of adrenal corticosteroids by high-performance liquid chromatography.

OBJECTIVE: To develop a high-performance liquid chromatography (HPLC) method for simultaneous measurement of adrenal corticosteroids important for the diagnosis of congenital adrenal hyperplasia. DESIGN: Blind comparison using convenience samples. SETTING: Research laboratory at the Department of Medical Technology, Bowling Green State University. PATIENTS: Referred samples for cortisol, 11-deoxycortisol (S), and 17-hydroxyprogesterone (OHP). Stimulation condition unknown. INTERVENTION: Venous blood collected, processed to serum, and frozen. Adrenal steroids measured by radioimmunoassay (RIA) and by HPLC. MAIN OUTCOME MEASURES: Linearity, analytic sensitivity, accuracy, and precision were evaluated using recovery, coefficient of variation (c.v.), correlation coefficient (r), Student's t test, F test, and linear regression. RESULTS: Calibration curves were linear to at least 50 mumol/L, and the low-end sensitivity was 10 nmol/L. Analytic recovery ranged from 89.8% to 103.9%. The CV was below 7.5% (n = 10) for all three steroids. Comparison to RIA yielded r values of 0.909 (n = 25), 0.932 (n = 10), and 0.983 (n = 10) for cortisol, S, and OHP, respectively. Student's t-test results were 1.13 (p = 0.27), 0.10 (p = 0.93), and 0.48 (p = 0.64) for cortisol, S, and OHP, respectively. F-test results were 1.14 (p = 0.75), 1.37 (p = 0.66), 2.39 (p = 0.21) for cortisol, S, and OHP, respectively. Results for cortisol showed a negative bias of 97.0 nmol/L (3 mug/dL). Linear regression analysis revealed proportional errors of -15.0% -7.0%, and +9.0%, for cortisol, S, and OHP, respectively. CONCLUSION: (ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex Hormones↗

PubMedDate not supplied

Analysis of cyanobacterial toxins by physicochemical and biochemical methods.

Cyanobacteria (blue-green algae) produce a wide range of low molecular weight metabolites that include potent neurotoxins, hepatotoxins, and cytotoxins. The accumulation of such toxins in freshwaters, and in brackish and marine waters presents hazards to human and animal health by a range of exposure routes. A review is presented of developments in the detection and analysis of cyanobacterial toxins, other than bioassays, including application of physicochemical, immunoassays, and enzyme-based methods. Analytical requirements are considered with reference to recently derived guideline levels for the protection of health and to the availability, or otherwise, of purified, quantitative cyanobacterial toxin standards.

Bacterial Toxins↗

PubMed2004

Solid-phase extraction of room-temperature imidazolium ionic liquids from aqueous environmental samples.

Owing to their favorable properties, ionic liquids have recently gained recognition as possibly environmentally benign solvents. Now among the most promising industrial chemicals, they have already been labeled "green", but this appellation seems due entirely to their very low vapor pressure. This growing interest in the various applications of ionic liquids will soon result in their presence in the environment. Therefore, reliable analytical tools for the environmental analysis of ionic liquids need to be developed urgently. This paper presents a newly developed analytical procedure for the enrichment of 1-alkyl- and 1-aryl-3-methylimidazolium ionic liquids from water samples. The method is based on cation exchange solid-phase extraction followed by selective elution. Pre-concentrated samples are subjected to high-performance liquid chromatography (HPLC) with an advanced methodology for qualitative and quantitative analysis. The overall procedure was verified by using standard spiked samples of tap water, seawater, and freshwater.

Journal Article↗

PubMedDate not supplied

Visual immunoprecipitate assay (VIP) for Listeria monocytogenes and related Listeria species detection in selected foods: collaborative study.

Six foods representing a variety of food products were analyzed by the Visual Immunoprecipitate Assay (VIP) and either the Bacteriological Analytical Manual (BAM) or the U.S. Department of Agriculture culture methods for detection of Listeria monocytogenes and related Listeria spp. Samples of each food type at each inoculation level were simultaneously analyzed by both methods. A total of 23 laboratories representing federal agencies and private industry in the United States and Canada participated in this collaborative study. Foods were inoculated with Listeria species including L. monocytogenes, with the exception of 3 lots of green beans that were naturally contaminated. During this study, 1509 samples and controls were analyzed and confirmed, of which 370 were positive and 921 were negative by both methods. One hundred and fifteen samples were positive by culture methods but negative by VIP. One hundred and thirty-two were negative by culture methods but positive by the VIP. Twenty-nine samples were negative by VIP and by culture methods but confirmed positive when VIP selective enrichment broths were subcultured to selective agars. The VIP method for detection of L. monocytogenes and related Listeria spp. in foods has been adopted first action by AOAC INTERNATIONAL.

Animals↗

PubMed2005

On-chip transformation of bacteria.

On-chip transformation of Escherichia coli cells was accomplished for the first time using a microbial array chip. The continuous E. coli transformation procedures were performed on a chip in which the microcompartment was composed of PDMS microfluidic channels and a silicon substrate predeposited with different plasmid DNAs. The PDMS microfluidic device enabled the parallel transformation of E. coli cells with various plasmid DNAs by separating each transformation area. The phenotypic differences reflecting different plasmid DNAs were identified by various approaches such as colorimetry, fluorometry, and electrochemical methods. This microbial array chip could become a versatile tool for many cell biological applications.

DNA, Bacterial↗