A spectral analysis of the normal resting electrocardiogram.
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Adult↗
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Optimal formation of hexyl laurate by Lipozyme IM-77 in solvent-free system.
A medium-chain ester, hexyl laurate, with fruity flavor is primarily used in personal care formulations as an important emollient for cosmetic applications. To conform to the "natural" interests of consumers, the ability of immobilized lipase from Rhizomucor miehei (Lipozyme IM-77) to catalyze the direct esterification of hexanol and lauric acid by using a solvent-free system was investigated in this study. Response surface methodology (RSM) and four-factor-five-level central composite rotatable design (CCRD) were employed to evaluate the effects of synthesis parameters, such as reaction time (10-50 min), temperature (45-85 degrees C), lipase amount (10-30 mg/volume; 0.077-0.231 batch acidolysis units of Novo (BAUN), and pH memory (5-9), on percentage molar conversion of hexyl laurate by lipase-catalyzed direct esterification. Reaction time, temperature, and enzyme amount had significant effects on percent molar conversion. On the basis of ridge maximum analysis, the optimum synthesis conditions for hexyl laurate were a reaction time of 40.6 min, a temperature of 58.2 degrees C, an enzyme amount of 25.4 mg/volume (0.196 BAUN), and a pH memory of 5.9. The predicted percentage molar conversion of hexyl laurate was 69.7 +/- 1.4%.
Enzymes, Immobilized↗
Unilateral exfoliation syndrome: conversion to bilateral exfoliation and to glaucoma: a prospective 10-year follow-up study.
PURPOSE: This prospective 10-year follow-up study was conducted to examine conversion of nonglaucomatous eyes with unilateral exfoliation syndrome (EXS) to bilateral EXS and to glaucoma. Risk factors for conversion to a bilateral condition and to glaucoma were studied. PATIENTS: Sixty-three nonglaucomatous subjects (mean age, 68.6 +/- 6.2 years) with unilateral EXS were enrolled. Of these patients, 56 were followed-up (89%). The effects of age, initial intraocular pressure (IOP), IOP difference between the fellow eyes, angle pigmentation, amount of exfoliation material, pupillary dilatation, optic disc topography, and phenylephrine-induced pigmentary dispersion on occasional conversion to the bilateral form and to glaucoma were studied by multivariate survival analysis. RESULTS: In 10 years, 38% had converted to bilateral EXS. Conversion to exfoliation glaucoma (EG) was 32% in the initially exfoliative eyes and 38% in the initially nonexfoliative (non-EXS) fellow eyes. Primary open-angle glaucoma developed in 3.5% of the non-EXS eyes. In the initially EXS eyes, a significant association was found between the initial IOP and conversion to EG (relative risk = 1.471, = 0.0001). When initial IOP was removed from the model, the pupillary dilatation values (relative risk = 0.488, = 0.035) and the differences in IOP between the fellow eyes (relative risk = 1.224, = 0.0181) were associated with conversion to EG. None of the factors studied was associated with conversion to the bilateral form. CONCLUSION: In unilateral EXS, factors associated with conversion to EG were initial IOP, pupillary dilatation value, and difference in IOP between the fellow eyes. No risk factors for conversion to bilateral EXS were found.
Aged↗
Investigation of derivatization reagents for the analysis of diarrhetic shellfish poisoning toxins by liquid chromatography with fluorescence detection.
Several derivatization reagents for the conversion of okadaic acid and related DSP toxins to fluorescent derivatives for analysis by liquid chromatography have been examined, viz: 9-anthryldiazomethane (ADAM), 1-pyrenyldiazomethane (PDAM), 4-diazomethyl-7-methoxycoumarin (DMMC), 4-bromomethyl-7-methoxycoumarin (BrMMC), 4-bromomethyl-7,8-benzcoumarin (BrMBC), 4-bromomethyl-7-acetoxycoumarin (BrMAC), and 4-bromomethyl-6,7-dimethoxycoumarin (BrDMC). The ADAM reagent provides the greatest selectivity and sensitivity, but its application on a routine basis has been limited by its instability and cost. Improvement of this method was achieved through the production of ADAM in situ from the stable 9-anthraldehyde hydrazone. A detection limit of 30 ng/g hepatopancreas (equivalent to 6 ng/g whole tissue) was achieved. The other aryldiazomethane reagents were found to have insufficient reactivity. Of the bromomethylcoumarin reagents, BrDMC was found to have the greatest promise. The reagent is inexpensive and has excellent stability and purity. Quantitative derivatization may be achieved in a 2 hour reaction at 45 degrees C with N,N-diisopropylethylamine as a catalyst. Unfortunately, the lower reaction selectivity of BrDMC compared to that of ADAM limits its application to isolated toxins, plankton samples, and shellfish tissues with high levels of DSP toxins. The use of BrDMC for the determination of how toxin levels in shellfish tissues will require development of a more extensive clean-up prior to derivatization. Successful application of the ADAM and coumarin derivatization methods to real-world samples has been demonstrated.
Animals↗
Adult-like temporal characteristics of mother-infant vocal interactions.
29 mothers and their 9-month-old-infants participated in a semistructured play episode. The temporal patterning of their vocal behavior was analyzed by means of a computerized analogue-to-digital conversion system (AVTA). Time-series regression analysis was employed to determine interpersonal influence over the course of the exchange for a variety of temporal parameters. The analysis revealed that the dyads engaged in alternating vocalization to a greater degree than simultaneous vocalization, and that there is a pattern of mutual influence (interpersonal accommodation) for switching pauses. The results suggest that some of the formal attributes observed in conversational exchanges between adult speakers are observable prior to the emergence of linguistic competence.
Female↗
Formation of carboxylic acids from small alkanes in zeolite H-ZSM-5
The activation of propane and isobutane in acidic zeolite H-ZSM-5 in the presence of both CO and H2O has been studied by in situ solid-state NMR and GC analysis. Evidence was provided for the conversion of propane to isobutyric acid at 373-473 K by cleavage of the C-C bond; methane and ethane are also produced. Isobutane is transformed into pivalic acid with simultaneous production of hydrogen. The low conversion (1-2%) at this temperature was rationalized by the existence of a small number of sites that are capable of generating carbenium ions which are trapped by CO at this temperature. A formate species was observed when CO and H2O were present on H-ZSM-5. This species disappeared in the presence of the alkane. At 573 K, the generation of large amounts of CO2 indicates a much higher conversion of the alkanes into carboxylic acids which, however, decompose under the reaction conditions.
Journal Article↗
Brief communication: measurement size, precision, and reliability in craniofacial anthropometry: bigger is better.
In this paper we examine the results of an intraobserver measurement error study involving 49 craniofacial variables that ranged in size from less than 1 cm to approximately 20 cm. Repeat measurements were taken on 10 male and 10 female adult subjects (19-59 years old). Our focus is on the relationship between measurement size and measurement error across the 49 variables. We found that the size of the variable showed no relationship with the magnitude of the error as measured by the technical error of measurement. When the error was expressed as a coefficient of relative variation (Malina et al.: Vital and Health Statistics, Series 11, No. 23. Washington, DC: US Department of Health and Human Services, 1973), this quantity was negatively associated with the size of the measurement. Conversely, reliability (Fleiss: The Design and Analysis of Experiments. New York: John Wiley & Sons, 1986) was positively correlated with measurement size. We did not find effects of scale (Marks et al.: Am. J. Epidemiol. 130:578-587, 1989) within the individual measurements. Thus, for the range of size of the craniofacial measurements in this study, measurement size must be added to the list of factors such as ease of locating landmarks, measurement technique, and systematic bias in the application of the technique that can affect precision and reliability in anthropometry.
Adult↗
Human growth hormone 1 (GH1) gene expression: complex haplotype-dependent influence of polymorphic variation in the proximal promoter and locus control region.
The proximal promoter region of the human pituitary expressed growth hormone (GH1) gene is highly polymorphic, containing at least 15 single nucleotide polymorphisms (SNPs). This variation is manifest in 40 different haplotypes, the high diversity being explicable in terms of gene conversion, recurrent mutation, and selection. Functional analysis showed that 12 haplotypes were associated with a significantly reduced level of reporter gene expression whereas 10 haplotypes were associated with a significantly increased level. The former tend to be more prevalent in the general population than the latter (p<0.01), possibly as a consequence of selection. Although individual SNPs contributed to promoter strength in a highly interactive and non-additive fashion, haplotype partitioning was successful in identifying six SNPs as major determinants of GH1 gene expression. The prediction and functional testing of hitherto unobserved super-maximal and sub-minimal promoter haplotypes was then used to test the efficacy of the haplotype partitioning approach. Electrophoretic mobility shift assays demonstrated that five SNP sites exhibit allele-specific protein binding. An association was noted between adult height and the mean in vitro expression value corresponding to an individual's GH1 promoter haplotype combination (p=0.028) although only 3.3% of the variance of adult height was found to be explicable by reference to this parameter. Three additional SNPs, identified within sites I and II of the upstream locus control region (LCR), were ascribed to three distinct LCR haplotypes. A series of LCR-GH1 proximal promoter constructs were used to demonstrate that 1) the LCR enhanced proximal promoter activity by up to 2.8-fold depending upon proximal promoter haplotype, and that 2) the activity of a given proximal promoter haplotype was also differentially enhanced by different LCR haplotypes. The genetic basis of inter-individual differences in GH1 gene expression thus appears to be extremely complex.
Adult↗
Analytical resolution and noise characteristics of linearly reconstructed magnetic resonance data with arbitrary k-space sampling.
The effects of time-varying readout gradients and data sampling with variable dwell times in magnetic resonance imaging are examined. General reconstruction formulas are given for linear reconstruction with even k-space weighting. Closed analytic expressions for estimator variance are given for data sampling during arbitrary gradient waveforms with both uniform kx step size and nonuniform kx step size. It is shown that estimator variance increases (the signal-to-noise ratio decreases) for nonconstant gradient waveforms. It is also shown that estimator variance is greater for constant k-space sampling strategies than for constant time sampling at the Nyquist rate. Data collected during a triangular readout gradient waveform, with either constant time or constant k-space sampling, versus conventional (constant gradient) collection confirms theoretical predictions for estimator variance. The benefits of collecting data while the readout gradient is ramping up from and down to zero are discussed.
Algorithms↗
A real-time reconstruction system for magnetic resonance imaging.
A digital-electronic reconstruction system for MRI has been designed and demonstrated. The system is capable of reconstructing a 128 x 128 pixel image from complex-valued data in approximately 8 ms (122 frames per second) or a 256 x 256 pixel image in 32 ms (30 frames per second) using the standard 2D FFT reconstruction algorithm. Real-time MR imaging can be obtained when this reconstruction system is coupled with fast continuous echo-planar type data acquisition. This provides the unique potential for real-time monitoring of interventional procedures or for rapid patient positioning. The real-time reconstruction system presented here consists of four main subsystems: an analog to digital converter, an interface memory, the Fourier processor, and the display processor. The basic design of this reconstruction system is presented along with results, demonstrating the capability of the system.
Analog-Digital Conversion↗
AAEM minimonograph #16: instrumentation and measurement in electrodiagnostic medicine--Part I.
Technical and instrumentation factors play an important role in obtaining reliable information during electrodiagnostic studies. With contemporary electrodiagnostic equipment, neurophysiologic potentials are detected using a variety of electrodes and undergo differential amplification, filtering, conversion to digital form, and finally, analysis and display. Understanding the signal processing principles, limitations, and sources of errors that can occur during this multistep process can improve the technical quality of studies, minimize preventable errors, and improve clinical interpretation. Part I of this minimonograph reviews the basic principles of action potential generation and overviews electrodiagnostic instrumentation. The concept of waveform frequency content is related to the role of filters in suppressing noise while preserving waveform latency, amplitude, and morphology. The electrical characteristics of various surface and needle electrodes influence instrument design and the nature of the potentials recorded. This is especially important in understanding the differences in motor unit characteristics obtained from monopolar and concentric needle electrodes.
Electrodiagnosis↗
Translational and transcriptional analysis of Sulfolobus solfataricus P2 to provide insights into alcohol and ketone utilisation.
The potential of Sulfolobus solfataricus P2 for alcohol or ketone bioconversion was explored in this study. S. solfataricus was grown in different concentrations (0.1-0.8% w/v) of alcohols or ketones (ethanol, iso-propanol, n-propanol, acetone, phenol and hexanol) in the presence of 0.4% w/v glucose. Consequently, the addition of these alcohols or ketones into the growth media had an inhibitory effect on biomass production, whereby lag times increased and specific growth rates decreased when compared to a glucose control. Complete glucose utilisation was observed in all cultures, although slower rates of glucose consumption were observed in experimental cultures (average of 14.9 mg/L/h compared to 18.9 mg/L/h in the control). On the other hand, incomplete solvent utilisation was observed, with the highest solvent consumption being approximately 51% of the initial concentration in acetone cultures. Translational responses of S. solfataricus towards these alcohols or ketones were then investigated using the isobaric tags for relative and absolute quantitation (iTRAQ) technique. The majority (>80%) of proteins identified and quantified showed no discernable changes in regulation compared to the control. These results, along with those obtained from transcriptional analysis of key genes involved within this catabolic process using quantitative RT-PCR and metabolite analysis, demonstrate successful alcohol or ketone conversion in S. solfataricus.
Alcohols↗
Species-specific tRNA recognition in relation to tRNA synthetase contact residues.
In spite of variations in the sequences of tRNAs, the genetic code (anticodon trinucleotides) is conserved in evolution. However, non-anticodon nucleotides which are species specific are known to prevent a given tRNA from functioning in all organisms. Conversely, species-specific tRNA contact residues in synthetases should also prevent cross-species acylation in a predictable way. To address this question, we investigated the relatively small tyrosine tRNA synthetase where contacts of Escherichia coli tRNA(Tyr) with the alpha2 dimeric protein have been localized by others to four specific sequence clusters on the three-dimensional structure of the Bacillus stearothermophilus enzyme. We used specific functional tests with a previously not-sequenced and not-characterized Mycobacterium tuberculosis enzyme and showed that it demonstrates species-specific aminoacylation in vivo and in vitro. The specificity observed fits exactly with the presence of the clusters characteristic of those established as important for recognition of E. coli tRNA. Conversely, we noted that a recent analysis of the tyrosine enzyme from the eukaryote pathogen Pneumocystis carinii showed just the opposite species specificity of tRNA recognition. According to our alignments, the sequences of the clusters diverge substantially from those seen with the M. tuberculosis, B. stearothermophilus and other enzymes. Thus, the presence or absence of species-specific residues in tRNA synthetases correlates in both directions with cross-species aminoacylation phenotypes, without reference to the associated tRNA sequences. We suggest that this kind of analysis can identify those synthetase-tRNA covariations which are needed to preserve the genetic code. These co-variations might be exploited to develop novel antibiotics against pathogens such as M. tuberculosis and P. carinii.
Acylation↗
A coalescence approach to gene conversion.
In this paper we develop a coalescent model with intralocus gene conversion. Such models are of increasing importance in the analysis of intralocus variability and linkage disequilibrium. We derive the distribution of the waiting time until a gene conversion event occurs in a sample in terms of the distribution of the length of the transferred segment, zeta. We do not assume any specific form of the distribution of zeta. Further, given that a gene conversion event occurs we find the distribution of (sigma, tau), the end points of the transferred segment and derive results on correlations between local trees in positions chi(1) and chi(2). Among other results we show that the correlation between the branch lengths of two local trees in the coalescent with gene conversion (and no recombination) decreases toward a nonzero constant when the distance between chi(1) and chi(2) increases. Finally, we show that a model including both recombination and gene conversion might account for the lack of intralocus associations found in, e.g., Drosophila melanogaster.
Gene Conversion↗
Horseradish peroxidase C.
Horseradish peroxidase C (HRP; ferric) reacts with H2O2 to form Compound I, with an equilibrium constant of about 10(14) M-1. Two-step reduction of Compound I to Compound II and further to the ferric enzyme occurs reversibly at Eo' values of 0.90 and 0.93 V (pH 7.0), respectively. The pH dependence of Eo' values for each one-electron step, ferrous leads to ferric leads to Compound II leads to Compound I indicates that presence of redox-linked ionization at pKa values of 7.3 in the ferrous state, 11.0 in the ferric and 8.6 in Compound II. Zinc-substituted HRP C is oxidized to its free-radical form at an Eo' value of 0.74 (pH 6.0) Comparison of oxidized zinc HRP C with Compound I shows that Compound I contains a porphyrin pi-cation radical. The flash photolysis study on the NO-ferric HRP C complex clearly indicates that the iron is pentacoordinated in HRP C while it is hexacoordinated in metmyoglobin. From the kinetic analysis of the acid-alkaline conversion of HRP C, the second-order rate constants of the reactions with H+ and HO- are estimated to be 1.5 X 10(10) and 6.7 X 10(4) M-1s-1, respectively. The latter rate constant greatly varies with the kind of hemoproteins. In the presence of HRP C and O2, indole-3-acetate is oxidized to its hydroperoxide form, which reacts effectively with HRP C to form Compound I and further converts Compound I to a verdohemoprotein.
Electron Transport↗
Detection of Bordetella pertussis by determination of adenylate cyclase activity.
The adenylate cyclase activity of Bordetella pertussis in clinical isolates was measured in calmodulin-supplemented Stainer-Scholte broth by the rate of conversion of ATP to cyclic AMP. Analysis of 250 stock strains of Bordetella pertussis showed that measurable adenylate cyclase activity was produced by all strains. In clinical tests Bordetella pertussis was isolated from 135 (22%) of 605 swab samples. Increased adenylate cyclase activity was detected in 124 (92%) Stainer-Scholte broth cultures of these samples. A total of 475 swabs contained other bacteria or had no growth; only one of the Stainer-Scholte broth cultures of these swab samples contained measurable adenylate cyclase activity. The results indicate that testing for adenylate cyclase activity provides a specific and sensitive means for detecting Bordetella pertussis in clinical specimens.
Adenosine Monophosphate↗
Respiratory impedance spectral estimation for digitally created random noise.
Measurement of respiratory input mechanical impedance (Zrs) is noninvasive, requires minimal subject cooperation, and contains information related to mechanical lung function. A common approach to measure Zrs is to apply random noise pressure signals at the airway opening, measure the resulting flow variations, and then estimate Zrs using Fast-Fourier Transform (FFT) techniques. The goal of this study was to quantify how several signal processing issues affect the quality of a Zrs spectral estimate when the input pressure sequence is created digitally. Random noise driven pressure and flow time domain data were simulated for three models, which permitted predictions of Zrs characteristics previously reported from 0-4, 4-32, and 4-200 Hz. Then, the quality of the Zrs estimate was evaluated as a function of the number of runs ensemble averaged, windowing, flow signal-to-noise ratio (SNR), and pressure spectral magnitude shape magnitude of P(j omega). For a magnitude of P(j omega) with uniform power distribution and a SNR less than 100, the 0-4 Hz and 4-200 Hz Zrs estimates for 10 runs were poor (minimum coherence gamma 2 less than 0.75) particularly where Zrs is high. When the SNR greater than 200 and 10 runs were averaged, the minimum gamma 2 greater than 0.95. However, when magnitude of P(j omega) was matched to magnitude of Zrs, gamma 2 greater than 0.91 even for 5 runs and a SNR of 20. For data created digitally with equally spaced spectral content, the rectangular window was superior to the Hanning. Finally, coherence alone may not be a reliable measure of Zrs quality because coherence is only an estimate itself. We conclude that an accurate estimate of Zrs is best obtained by matching magnitude of P(j omega) to magnitude of Zin (subject and speaker) and using rectangular windowing.
Airway Resistance↗
Chest wall motion during halothane anaesthesia in infants and young children.
Chest wall motion during anaesthesia may differ from the awake state because of the effect of anaesthetic agents on the muscles of respiration. The purpose of this study was twofold (1) to describe the pattern of chest wall motion in infants and children during halothane anaesthesia (HA) using respiratory inductive plethysmography (RIP) and (2) to calibrate the voltage output of RIP in units of volume. Seven infants (2.3 +/- 1.7 mo, 5.9 +/- 0.7 kg) and five children (2.9 +/- 1.1 yr, 15.5 +/- 1.5 kg) were studied. Since results in both age groups were qualitatively similar they are presented as a single group. Respiratory excursions of the rib cage (RC) and abdomen (ABD) were measured using RIP. Airflow was measured with a pneumotachograph. During spontaneous breathing the analogue signals of airflow, pressure, RC and ABD were recorded. Measurements were taken during (1) halothane anaesthesia and (2) during emergence from anaesthesia. The XY plots of the RC and ABD signals were plotted for each period. In addition the voltage output of the respiratory excursions of the RC and ABD signals was converted to units of volume using the simultaneous solution of equation method. The accuracy of conversion factors was validated by regression analysis of the predicted and measured tidal volume using breaths sampled at random throughout the entire period of study. Regression analysis of this relationship gave a slope between 0.85 and 1.15 (r2 value greater than 0.7) in five of the twelve patients. The pattern of chest wall motion in the XY plots showed synchronous motion between RC and ABD signals during HA in nine of the twelve patients.(ABSTRACT TRUNCATED AT 250 WORDS)
Anesthesia Recovery Period↗