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PubMed2004

Sampling in the light of Wigner distribution.

We propose a new method for analysis of the sampling and reconstruction conditions of real and complex signals by use of the Wigner domain. It is shown that the Wigner domain may provide a better understanding of the sampling process than the traditional Fourier domain. For example, it explains how certain non-bandlimited complex functions can be sampled and perfectly reconstructed. On the basis of observations in the Wigner domain, we derive a generalization to the Nyquist sampling criterion. By using this criterion, we demonstrate simple preprocessing operations that can adapt a signal that does not fulfill the Nyquist sampling criterion. The preprocessing operations demonstrated can be easily implemented by optical means.

Journal Article↗
PubMed1989

One-step rapid extractive methylation of plasma nonesterified fatty acids for gas chromatographic analysis.

The present report describes a one-step method for the derivatization and extraction of nonesterified fatty acids in plasma with subsequent analysis by conventional capillary gas-liquid chromatography or gas-liquid chromatography-mass spectrometry. The procedure requires 200 microliters of citrated plasma, dilution with 200 microliters of methanol containing a suitable internal standard, and rapid methylation (10 min) with ethereal diazomethane. An aliquot (60%) of the ether layer is subsequently removed, taken to dryness with nitrogen gas, and the residue is dissolved in a small volume of hexane (usually 50 microliters) for chromatographic analysis (taking 1 microliter for on-column injection). Samples are ready for analysis within 15 min after initial preparation of the plasma. The method has been found to be simple and rapid, providing clean fatty acid profiles. Although the method has been tested with 200 microliters of rat and human plasma, it can easily be adapted to a 40 microliters plasma sample if the esterified plasma extract is suspended in a smaller volume of hexane and/or a larger aliquot of the extract were to be injected into the gas chromatograph through use of a splitless injector.

Animals↗
PubMedDate not supplied

Direct semiquantitative screening of drugs of abuse in serum and whole blood by means of CEDIA DAU urine immunoassays.

The purpose of this study was to test the direct applicability of CEDIA DAU urine immunoassays to serum or whole blood. The performance of the urine assays for sensitive screening of amphetamines (AMP), benzoylecgonine (BZE), benzodiazepines (BENZ), methadone (MET), opiates (OPI), and tetrahydrocannabinol carboxylic acid (THCCOOH) was evaluated on the BM/Hitachi 911 analyzer with unpretreated serum and whole blood. The limit of detection was 0 ng/mL for all tests. Cutoff values were set from 10 to 40 ng/mL for the different assays. The assays were found to be linear between the following concentrations: AMP 0-2500 ng/mL, BZE 0-1200 ng/mL, BENZ 0-1600 ng/mL, MET 0-600 ng/mL, OPI 0-720 ng/mL, and THCCOOH 24-60 ng/mL. Precision results (within run) for different concentrations were as follows: AMP 3.1-5.7%, BZE 2.4-6.6%, BENZ 4.3-8.0%, MET 2.0-5.5%, OPI 2.8-7.6%, and THCCOOH 1.4-2.4%. Between-run results were as follows: AMP 8.7-15.5%, BZE 6.4-7.5%, BENZ 8.2-15.8%, MET 2.7-5.1%, OPI 4.3-11.2%, and THCCOOH 2.6-7.4%. Sensitivity, specificity, and comparison of CEDIA semiquantitation with GC-MS quantitative results were performed on 500 original serum and whole blood samples. The data provided sufficient documentation to use the CEDIA urine-screening technique without any adaptation as a sensitive serum/whole blood screening for BZE, BENZ, MET, OPI, and THCCOOH. Serum screening for amphetamines is not sensitive enough in the unchanged urine mode. It will require some adaptation to a serum mode (probably a higher sample volume [BM/Hitachi 911] combined with protein precipitation of the sample).

Chromatography, High Pressure Liquid↗
PubMed1995

Genotypic analysis of multiple loci in somatic cells by whole genome amplification.

To screen multiple loci in small purified samples of diploid and aneuploid cells a PCR-based technique of whole genome amplification was adapted to the study of somatic lesions. DNA samples from different numbers of flow-sorted diploid and aneuploid cells from biopsies were amplified with a degenerate 15mer primer. Aliquots of these reactions were then used in locus-specific reactions using a single round of PCR cycles with individual sets of primers representing polymorphic markers for different regions. As a result, polymorphic markers for different chromosomal regions, including VNTRs and dinucleotide repeats, can be used to perform up to 30 locus-specific PCR assays with a single sample obtained from fewer than 1000 cells.

Adenocarcinoma↗
PubMed1983

Research on the adaptation of skeletal muscle to hypogravity: past and future directions.

Our current understanding of hypogravity-induced atrophy of skeletal muscles is based primarily on studies comparing pre- and post-flight properties of muscles. Interpretations are necessarily qualified by the assumption that the stress of reentry and readjustment to terrestrial gravity do not alter the parameters being analyzed. The neuromuscular system is highly responsive to changes in functional demands and capable of rapid adaptation, making this assumption questionable. A reexamination of the changes in the connective tissue and synaptic terminals of soleus muscles from rats orbited in biosatellites and sampled postflight indicates that these structural alterations represent adaptative responses of the atrophic muscles to the increased workload of returning to 1 G, rather than hypogravity per se. The atrophy of weightlessness is postulated to result because muscles are both underloaded and used less often. Proper testing of this hypothesis requires quantitation of muscle function by monitoring electromyography, force output and length changes during the flight. Experiments conducted in space laboratories, like those being developed for the Space Shuttle, will avoid the complications of reentry before tissue sampling and allow time course atudies of the rate of development of adaptive changes to zero gravity. Another area of great importance for future studies of muscle atrophy is inflight measurement of plasma levels of hormones and tissue receptor levels. Glucocorticoids, thyroid hormone and insulin exert dramatic regulatory influences on muscle structure. Prevention of neuromuscular atrophy becomes increasingly more important as spaceflights increase in duration. Definition of the atrophic mechanism is essential to developing means of preventing neuromuscular atrophy.

Adaptation, Physiological↗
PubMed2006

The factor structure of the General Health Questionnaire (GHQ): a scaled version for general practice in Spain.

BACKGROUND: The 28-item version of the General Health Questionnaire (GHQ-28) developed by Goldberg and Hillier in 1979 is constructed on the basis of a principal components analysis of the GHQ-60. When used on a Spanish population, a translation of the GHQ-28 developed for an English population may lead to worse predictive values. METHODS: We used our Spanish sample to replicate the entire process of construction of the GHQ-28 administered in a primary-care setting. RESULTS: Two shorter versions were proposed: one with six scales and 30 items, and the other with four scales and 28 items. CONCLUSIONS: The resulting GHQ-28 was a successful adaptation for use on the Spanish sample. When compared with the original version, only 21 items were the same. Moreover, contrary to the English version, which groups sleep problems and anxiety in the same scale, a scale with items related exclusively to 'Sleep disturbances' was found.

Adolescent↗
PubMed1997

Bond strength and interfacial morphology of adhesives to primary teeth dentin.

PURPOSES: To evaluate (1) the shear bond strength to the dentin of primary teeth and failure site of hydrophilic dentin bonding agents, (2) the interfacial micromorphology of these adhesives on primary teeth. MATERIALS AND METHODS: Seventy-six primary noncarious molars stored in distilled water were obtained. The teeth were cleaned with pumice and a rubber cup. The mesio-buccal surface of the teeth was ground flat with hand pressure with a series of SiC paper ending with the 600 grit to provide a uniform surface on superficial dentin to which the adhesives and resin composite could be applied. After preparing the dentin surface, the teeth were stored in distilled water for 48 hours. They were then rinsed and dried with compressed air and divided at random into four groups of 16 specimens each: Group 1: Dentastic; Group 2: One-Step; Group 3: Prime & Bond 2.0; Group 4: Compoglass SCA. Z100 resin was used in all groups. All specimens were thermocycled (500x) and sheared in an Instron machine. After shear testing, the debonding sites of all samples were examined with a stereomicroscope and selected samples were also examined with the scanning electron microscope. Three additional samples per group were used to evaluate the resin adaptation to dentin. RESULTS: The results in MPa were: Dentastic 19.62 (4.67); One-Step 11.24 (3.67), Prime & Bond 22.38 (6.47), Compoglass SCA 18.88 (4.04). ANOVA (P < 0.0001) revealed that there was a significant difference between the groups. The Student-Newman-Keuls test (P < 0.05) showed no statistically significant difference between Dentastic, Prime & Bond and Compoglass SCA. However, these three groups were statistically significantly higher than One Step. In the Dentastic group, 14 of 16 samples revealed resin cohesive failure (resin fracture) while two of 16 displayed dentin cohesive failure (dentin fracture). In the One Step group, 15 samples failed at the resin and one sample showed dentin cohesive failure. In the Prime & Bond group, 12 specimens revealed resin cohesive failure while four displayed dentin cohesive failure. In the Compoglass SCA group, 13 samples had resin cohesive failures while three had dentin cohesive failures. All samples revealed an intimate adaptation to the dentin displaying resin tag formation.

Acid Etching, Dental↗
PubMed2004

Ultrafiltration for proteomic sample preparation.

Proteome analysis represents significant challenges to the existing sample preparation techniques. Traditional methods, such as two-dimensional electrophoresis, typically separate high-molecular-weight proteins while discarding low-molecular-weight species. This approach is well justified considering the complexity of any proteome. However, it is desirable to extract the maximum amount of information from each sample to investigate the entire range of biomolecules. We have demonstrated that ultrafiltration not only improves two-dimensional electrophoresis (2-DE) resolution of the protein fraction but also yields the low-molecular-weight fraction amenable for further analysis by high-resolution mass spectrometry. This approach was successfully adapted to the variety of biological samples including cell and tissue lysates and serum. Therefore, ultrafiltration offers an alternative sample preparation technique that enables more thorough analysis of a proteome.

Animals↗
PubMed2004

Investigating the history of prehistoric glues by gas chromatography-mass spectrometry.

Although organic materials are very sensitive to biochemical alteration processes, they may be preserved for millennia in various archaeological contexts. Remains of adhesives made during prehistory were discovered at different sites, in the form of residues adhering to flint tools and ceramic vessels or as free lumps in sediment. To characterise the natural substances exploited for adhesive production during late prehistory, we undertook GC and GC/MS analysis of 90 samples from 8 sites dating from the Neolithic to Iron Age periods. This paper discusses our approach to the study of organic adhesives preserved in archaeological contexts, with a particular focus on the presentation of the various categories of organic adhesives that we analysed and the choice of chromatographic conditions adapted to the specificity of such samples. The results obtained show that birch bark tar, a triterpenoid adhesive made by destructive distillation of white birch bark, was predominantly used during the neolithic period even though other materials such as various barks or organic fossil substance were also used. During the Bronze and Iron ages, which follow the Neolithic period, adhesive production is evolving through the expansion of the range of the natural substances used (identification of diterpenoid pine resin) and the addition of beeswax as a plasticiser to birch bark tar. By combining chromatographic analysis and archaeological data, it was thus possible to follow the evolution of adhesive making at the end of prehistory, testifying to the inventiveness of the craftsmen whatever the period considered.

Journal Article↗
PubMed2006

The absence of sharks from abyssal regions of the world's oceans.

The oceanic abyss (depths greater than 3000 m), one of the largest environments on the planet, is characterized by absence of solar light, high pressures and remoteness from surface food supply necessitating special molecular, physiological, behavioural and ecological adaptations of organisms that live there. Sampling by trawl, baited hooks and cameras we show that the Chondrichthyes (sharks, rays and chimaeras) are absent from, or very rare in this region. Analysis of a global data set shows a trend of rapid disappearance of chondrichthyan species with depth when compared with bony fishes. Sharks, apparently well adapted to life at high pressures are conspicuous on slopes down to 2000 m including scavenging at food falls such as dead whales. We propose that they are excluded from the abyss by high-energy demand, including an oil-rich liver for buoyancy, which cannot be sustained in extreme oligotrophic conditions. Sharks are apparently confined to ca 30% of the total ocean and distribution of many species is fragmented around sea mounts, ocean ridges and ocean margins. All populations are therefore within reach of human fisheries, and there is no hidden reserve of chondrichthyan biomass or biodiversity in the deep sea. Sharks may be more vulnerable to over-exploitation than previously thought.

Animals↗
PubMed2002

Exact group-sequential designs for clinical trials with randomized play-the-winner allocation.

The use of both sequential designs and adaptive treatment allocation are effective in reducing the number of patients receiving an inferior treatment in a clinical trial. In large samples, when the asymptotic normality of test statistics can be utilized, a standard sequential design can be combined with adaptive allocation. In small samples the planned error rate constraints may not be satisfied if normality is assumed. We address this problem by constructing sequential stopping rules with specified properties by consideration of the exact distribution of test statistics under a particular adaptive allocation scheme, the randomized play-the-winner rule. Using this approach, compared to traditional equal allocation trials, trials with adaptive allocation are shown to require a larger total sample size to achieve a given power. More interestingly, the expected number patients allocated to the inferior treatment may also be larger for the adaptive allocation designs depending on the true success rates.

Binomial Distribution↗
PubMed1998

The bleeding time in pediatrics.

When performed with standardized methods and techniques, the bleeding time (BT) depends on variables that physiologically alter primary hemostasis. These variables include number of platelets and platelet function, white and red blood cell counts, vascular factors, hormones, and temperature. Variations within normal limits reflect the in vivo situation and are of no clinical relevance. If the BT is prolonged far above the upper normal limit, however, defects of primary hemostasis have to be anticipated. These include thrombocytopenia or thrombocytopathy, anemia, leukopenia, and deficiencies of plasmatic factors such as von Willebrand factor (vWF), fibrinogen, the lupus anticoagulant, and factor V. The BT can be used as screening test for patients with bleeding symptoms. As a single test, the BT gives the best information in pediatrics, in which defects of primary hemostasis are more common than coagulopathies. In addition, BT can guide the therapy of these patients, because it reflects clinical improvement. When used as a preoperative screening test, BT should be combined with the activated partial thromboplastin time (aPTT) because BT usually does not recognize patients with coagulopathies. With standardized techniques and the knowledge of its merits and limitations, BT is a useful test for diagnosing hemostatic disorders, guiding their therapy, and warning of unexpected bleeding complications during surgery. The BT is especially suited for use in pediatrics for the following reasons: (1) It does not require a venipuncture and is similar to capillary blood sampling if performed with standardized devices adapted for pediatric use; (2) it is an in vivo test informing mostly on defects of primary hemostasis, which are the most common bleeding diatheses in childhood; (3) the results are immediately available; (4) it requires only minimal amounts of blood; and (5) it does not require unphysiological reagents and preparation of the sample. The test requires a highly motivated and experienced operator who knows of the many variables influencing the BT. The interpretation cannot be done without knowledge of the history and physical status of the patient and of the limitations of the BT.

Bleeding Time↗
PubMed1997

Practical aspects of suppressed ion chromatography for cations in human serum.

In spite of the good accuracy and precision of ion chromatographic methods for the determination of mono- and divalent cations in human serum, the major drawback with these methods were problems with the membrane suppressor's performance. Here, we describe experiments undertaken to solve these problems. We address in particular the use of histidine-sulfuric acid eluents, sample purification with OnGuard-A cartridges and chromatographic "front-cut" for divalent cations. The latter two adaptations, resulting in removal of the anionic species from the sample, were successful in solving the observed suppressor problems. The eluent substitution, moreover, allowed us to switch from the chemical to the electric suppression mode. We believe that these adaptations will allow secure and robust determination of cations in human serum samples with ion chromatography.

Cations↗
PubMedDate not supplied

What African-American middle school youth report about risk-taking behaviors.

INTRODUCTION: African-American youth represent the heaviest burden for HIV in all U.S. ethnic groups. The risk assessment was conducted with a group of suburban and urban African-American middle school children prior to the implementation of a faith-based substance abuse and HIV prevention program. The purpose of the study on risk-taking was to examine the sample's level and predictors of social adaptation and risk-taking processes and to examine their ideas about risk and risk-taking behavior. METHODS: A correlation design was used to determine relationships between risky behaviors and scores for risk taking and social adaptation. A descriptive design guided open-ended questions about risk and risk-taking behaviors. Data were collected in two youth ministries. The nonprobability sample consisted of 45 male and female subjects in the suburban pre-intervention group and 39 male and female subjects in the urban comparison group. RESULTS: Findings include a statistically significant relationship between male gender and alcohol use and risk-taking scores in the suburban pre-intervention group; in addition, sexual activity and drug use were predictive of higher risk-taking scores in the urban comparison group. The urban comparison group also reported significantly higher risk-taking behaviors than did the suburban group. DISCUSSION: Data from this study suggest the need for substance abuse and HIV prevention programs for middle school youth before problem behaviors become established.

Adaptation, Psychological↗
PubMed1990

Sulfur and nitrogen metabolism in the bovine fed different forms of supplemental sulfur.

Twelve growing Angus heifers averaging 282 kg in weight were fed a tall fescue hay-based diet in a completely randomized design experiment to determine sulfur (S) and nitrogen (N) metabolism and bioavailability of different forms of supplemental S:elemental S (E), sodium sulfate (SU) and DL-methionine (M). The study included a 72-h adaptation phase that was followed immediately by a 5-d retention phase. Control (C) heifers were fed a ground fescue hay diet twice daily throughout the study. Supplementation with .15% S from E, SU or M to the basal diet began at h 0. Differences in total blood S, plasma S and ruminal NH3 N were dependent on sampling time in the 72-h adaptation phase. Urinary S excretion during 0 to 72 h was greater for S-supplemented calves than for C. Mean molar proportions of acetate, butyrate, isobutyrate and valerate were affected by form of S supplementation. No treatment differences (P greater than .10) were noted in total VFA concentrations. Sulfur supplementation increased daily urinary sulfate (P less than .01), total urinary S (P less than .01) and fecal S (P less than .01) excretion during the retention phase. Methionine and SU heifers had the greatest urinary S losses, and fecal S was highest for E (P less than .01). No differences (P greater than .10) in DM digestion occurred among treatments. N retention (g/d) and N retention as a percentage of intake averaged 5.9, 8.5; 13.2, 18.7; 13.8, 20.5; and 11.3, 19.2, respectively, for C, E, SU and M. Sulfur retention (g/d) was increased (P less than .10) by S supplementation. Sulfur supplementation of a basal fescue hay diet increased S retention transitorily, although much of the added S was lost through excretory routes. Supplementing S as E, SU or M appeared to be equally beneficial, despite differences in route and extent of S excretion among the three S sources.

Adaptation, Physiological↗
PubMed2000

Development of simultaneous purification methodology for multiple synthetic peptides by reversed-phase sample displacement chromatography.

We have developed a low-pressure protocol, designed as a rapid, simple and cost-effective procedure for the efficient and parallel purification of multiple peptide mixtures. This was achieved through adaptation of our novel reversed-phase sample displacement chromatography (SDC) method, where the major separation process takes place in the absence of organic modifier, to modular solid-phase extraction (SPE) technology. Thus, crude peptide sample is applied at overload conditions to extraction columns consisting of SPE tubes containing silica-based reversed-phase packing. By applying a vacuum to draw the solution through the packing, product separation from hydrophobic and hydrophilic impurities is accomplished in a two-stage purification unit: a short pre-column functions as a trap for hydrophobic impurities, while a second, longer SPE column is used as a product isolation column. Thus, under ideal SDC conditions, washing with a 100% aqueous solvent will achieve retention of hydrophobic impurities on the trap, with displacement of product and hydrophilic impurities from the trap to the product isolation column; hydrophilic impurities are thus displaced off the product isolation to waste, leaving only product retained on the main column. In this initial evaluation, this purification system has demonstrated excellent separation of product, in good yield, from both hydrophilic and hydrophobic impurities over a wide range of peptide hydrophobicity and crude composition for model synthetic peptide systems representing crude peptide mixtures.

Amino Acid Sequence↗
PubMed2006

Beware the airway filter: deadspace effect in children under 2 years.

BACKGROUND: Filters are increasingly used in breathing circuits as they protect the circuit from contamination and facilitate humidification of inspired gas. The use of filters, however, can augment the anatomical deadspace. This can be significant in children because they have much smaller tidal volumes. METHODS: Following institutional ethical approval, 20 healthy children <2 years of age who required tracheal intubation were recruited. Ventilation was adjusted to achieve an endtidal carbon dioxide (P(E)CO(2)) of 4.6 kPa (35 mmHg) when sampled at the tracheal tube (TT) adapter. Following a 10-min period of stabilization, an airway filter (22 ml) was introduced into the circuit. The respiratory rate (RR) was then adjusted to return P(E)CO(2) to 4.6 kPa (35 mmHg). RESULTS: A mean increase in ventilation of 1.42 (0.38) l x min(-1) was required to maintain a normal P(E)CO(2) level. Airway pressure and respiratory rate increased by 7.9 mmHg (4.6) and 19.8 breath x min(-1) (8.7) respectively. The P(E)CO(2) and partial pressure of inspired carbon-di-oxide (PiCO(2)) measured from the TT adapter were higher than measured from the filter port. The mean increase was 3.6 (1.6) mmHg for P(E)CO(2) and 5.9 (3.9) mmHg for PiCO(2). CONCLUSION: Amplified deadspace from airway filters results in a significant increase in ventilation needed to maintain a normal P((E)CO(2) in children <2 years of age with normal lungs. Sampling of P((E)CO(2) and PiCO(2) from the filter significantly underestimates the effect of increased deadspace. The effect of increased deadspace may be predicted using a proposed mathematical model.

Carbon Dioxide↗
PubMed2005

Social environment factors associated with suicide attempt among low-income African Americans: the protective role of family relationships and social support.

BACKGROUND: Suicide and suicide attempts are important public health concerns, and recent decades have witnessed a rising rate of suicide among African Americans. A history of prior attempts is a leading risk factor for completed suicide. Further research is needed into the social environment risk factors for suicide attempt among African Americans. This study focused on two important dimensions of the social environment, family relationships and social support, as well as an important person-level risk factor--depressive symptoms. METHOD: Data were obtained from a case-control study of 200 African American men and women aged 18-64 years, who sought services at a large, urban, public hospital. Odds ratios adjusted for significant sociodemographic differences between groups (aORs) were calculated for environment risk factors for suicide attempt among the cases and controls. The role of depressive symptoms was also studied. RESULTS: Lower levels of family adaptability and family cohesion increased the relative rate of suicide attempt in the sample. The aOR associated with the lowest quartile of family adaptability was 3.90, and the aORs associated with the first and second quartiles of family cohesion were 8.91 and 5.51, respectively. Lower levels of social embeddedness and social support increased the relative rate of suicide attempt in our sample. The aOR associated with the first and second quartiles of social embeddedness were 5.67 and 4.93, respectively, and the aOR associated with the lowest quartile of social support was 6.29. A mediating role of depression was discovered when depressive symptoms were entered into the logistic regression models. CONCLUSIONS: Our findings indicate that social environment factors including deficits in family functioning and social support are associated strongly with suicide attempts among low-income African American men and women seeking treatment in a large, urban hospital. Thus, better family functioning and social supports can be considered protective factors in this population. The presence of depressive symptoms, a well-known risk factor for suicide attempts and suicide, appears to mediate the association between social environment factors and suicide attempt.

Adolescent↗