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At least 487 records · Page 27Linked to original sources
PubMed1983

Evaluation of potential analytical approach for determination of polychlorinated biphenyls in serum: interlaboratory study.

Forty-four laboratories participated in evaluation of a method for determining polychlorinated biphenyls (PCBs) as AR 1254 in serum at the parts per billion level. The method involves deproteinating serum with methanol, extracting with hexane-ethyl ether, and eluting PCBs from deactivated silica gel for gas-liquid chromatographic determination with electron capture detection. Compounds are quantitated by using the Webb-McCall factors. Five serum pools, 4 containing in vivo-fortified PCBs (as AR 1254) or 8 in vitro-fortified chlorinated hydrocarbons (CHs), or both, were used. For PCB fortification levels of 9.89 (EP 2), 24.74 (EP 3), and 74.20 ppb (EP 4), interlaboratory coefficients of variation (CVs) for collaborators that adhered to protocol were 92.7, 67.6, and 25.8%, respectively. CVs on the same pools analyzed by the Centers for Disease Control (CDC) were 7.4, 7.8, and 4.6%, respectively. Average interlaboratory recoveries for pools EP 2, EP 3, and EP 4 were 138.1, 111.2, and 91.1%, respectively, and 99.8, 89.6, and 90.4%, respectively, for CDC on the same pools. There was a general decrease in the mean error for those laboratories that had participated in an earlier study in which they were allowed to use their own methods.

Animals↗
PubMed1978

An analytical approach to the determination of optimal phasing for external counterpulsation.

An inhomogeneous linear one-dimensional mathematical model is constructed as a conceptual approach to the study of the effects of External Counterpulsation (ECP) on the pressure and flow at the root of the aorta. The optimal operation of ECP is defined by two conditions: (1) minimization of the mean systolic pressure; and (b) maximization of the ratio of diastolic area over systolic area under the total pressure curve. The phase shift of the external pressure is determined so as to satisfy these two requirements. It is demonstrated within our approximation that with a given magnitude of external pressure, the phase shifts that satisfy these two requirements are the same. These phase shifts are linear functions of the systolic fraction of the total cardiac period, and depend on the time for the external wave to travel from the site of application up the vascular bed to the root of the aorta, plus the reflection contributions. Even though these results are derived from a simple model far from the complexity of the actual vasculature, the basic concepts would remain valid even if more complex mathematical treatments would have been used.

Aorta↗
PubMed1982

[Factor analytical approach to the functional structure of the properties common to crossmodal senses].

UNLABELLED: In place of actual psychophysical measurements, a checklist with 58 items was compiled, in order to ask the subject's preferences among environmental stimuli in vision, audition, tactile sense and olfaction, and to estimate the extent of their subjective sensitiveness to intense or weak sensory stimuli. The 229 male undergraduate students subjects participated in this research. RESULTS: By VARIMAX rotation, the following six factors were obtained, 1st General sensitivity, 2nd Orientation to the weak stimuli, 3rd Orientation to the intense and prolonged stimuli, 4th Sensory-motor reactivity to the intermittent or rhythmical stimuli, 5th Activation level, and 6th Temporal sensitivity. The 1st, 2nd, 3rd and 6th factors agreed well with the theoretically predicted properties, while the 5th was not necessarily similar to the properties on the hypothesis. The 2nd, and 3rd factors were the factors related to "the culture bounded behavior", on the other hand, the 1st and 6th ones related to "the culture-free behavior." The 5th, Activation level, stand in need of further research.

Factor Analysis, Statistical↗
PubMedDate not supplied

A meta-analytical approach examining the potential relationship between talc exposure and ovarian cancer.

The concern that use of talc or talc-containing substances in the perineal region of women may subject them to an increased risk for ovarian cancer has become an important issue in the study of ovarian cancer. The purpose of this paper is to examine whether this concern, heightened by several epidemiological studies purporting to show an increased risk, is valid. Epidemiological studies examining the possibility of this relationship are reviewed, and meta-analyses of their results are performed. The conclusion reached herein is that the evidence regarding the risk of ovarian cancer associated with talc exposure is equivocal, and further examination of the relationship is required before a sound conclusion can be made.

Adult↗
PubMed1995

Zidovudine for the prevention of vertical HIV transmission: a decision analytic approach.

The purpose of this study was to quantify the benefits of maternal-neonatal zidovudine (ZDV) administration for the prevention of vertical human immunodeficiency virus (HIV) transmission against the potential risks of drug-induced complications in uninfected children. A decision analysis model was created with use of a Markov cohort simulation, for evaluating both survival and quality of life for two hypothetical cohorts of HIV-exposed neonates: one with in utero and neonatal exposure to preventive ZDV therapy and the other not exposed. The model included the probability of congenital HIV infection with and without ZDV treatment (estimates derived from AIDS Clinical Trials Group study 076), the yearly probability of death with and without congenital HIV infection, a range of probabilities of adverse effects from ZDV use, and a range of ages in life when any adverse effect would manifest. In a series of scenarios, the impact of different estimates for the quality-of-life decrement from any adverse ZDV effect in HIV-uninfected children was assessed, and threshold values for this estimate were established, i.e., critical values below which withholding ZDV would be the preferred choice. Across a wide range of estimates for multiple contingencies, ZDV use was associated with a greater number of quality-adjusted life years than was non-use. Only in implausible, pessimistic scenarios (i.e., a high incidence of profound adverse effects beginning early in life) would withholding ZDV be the rational choice for an asymptomatic HIV-infected pregnant woman.(ABSTRACT TRUNCATED AT 250 WORDS)

Decision Support Techniques↗
PubMed1994

[Blood pressure variability during rest and left ventricular hypertrophy in the hypertensive patients. A spectrum analytic approach].

OBJECTIVE: To study the relationship between spectral analysis measurement of blood pressure (BP) and heart rate (HR) at rest, in untreated essential hypertension, and their relationship with the development of left ventricular hypertrophy (LVH). DESIGN AND METHODS: 41 untreated hypertensives (25M/16W, age 50 +/- 12, range 23-73) were measured at rest (WHO criteria DBP > 90 mmHg) by digital continuous photoplethysmography (Finapres 2300 (F), 6 mn of measurement in the dorsal decubitus position and standing up). Measurement of LVH (Devereux criteria, left ventricular mass index LVMI, g/m2) to analyse two groups (LVMI+: LVMI > 107 if women and 120 if men; n = 19; LVMI = 137 +/- 25), and (LVMI-; n = 22; LVMI = 92 +/- 17). The overall variability is standard deviation (SD), spectral analysis variability (SA) is FFT of 256 points over 3 periods low (LF: 0.004-0.07Hz), medium (MF: 0.07-0.13Hz), high (HF: 0.13-0.5Hz). Comparisons by Wilcoxon test and Anova (age, sex) (* p < 0.05, ** p < 0.01). RESULTS: By WHO criteria, the SBP was significantly lower in the LVMI-group (153 +/- 10 vs 165 +/- 18**), the DBP was not significantly different (94 +/- 6 vs 96 +/- 10). By continuous measure (F) at rest there was no significant difference for SBP or DBP. On standing up the SBP was significantly lower in the LVMI-group (148 +/- 20 vs 162 +/- 22**). The SD of the DBP at rest was more elevated in the LVMI-group (3.34 vs 3.06*), but not significantly different standing up. There was no significant difference in SBP at rest (6.7 vs 6.32) or standing (9.13 vs 11.5). The Spectral analysis of the MF was significantly elevated in the LVMI-group at rest for SBP (3.56 vs 3.01*), DBP (1.99 vs 1.19*), and HR (1.79 vs 1.77*). This was not significantly different in the LF and HF for SBP, DBP, HR. CONCLUSION: These results are different from those obtained by invasive ambulatory measures. The spontaneous variability in BP and HR at rest is increased when there is no cardiac effect (LVMI-). SA gives additional information in showing that the increase in variability is due to an increase in the Mayer waves, suggesting the existence of an elevation in adrenergic tone in hypertensive patients not having LVH.

Adult↗
PubMedDate not supplied

[Biological monitoring of exposure to alkylating xenobiotics by determining them using a new analytical approach in complexes with hemoglobin, plasma proteins and mercapturic acids in urine. II. Acrylamide].

A new simple and prompt procedure for measuring acrylamide (propenamide, PA) in PA-derived mercapturic acid, such as N-acetyl-S-(2-propenamide)-L-cysteine (N-Ac-PAC), and in hemoglobin (Hb) and plasma protein adducts in the rats expose to PA was developed, by employing gas chromatography (GC). PA in mercapturic acids or proteins was liberated on high-temperature heating in an injector port during the working procedure of a GC capillary after preoxidation of sulfur atoms in PA-bound cysteine to a sulfoxide form with hydrogen peroxide and analyzed. This method resulted in 87% of PA in authentic N-Ac-PAC. The number of PA released from the protein adducts was proportional to the cumulative dose of PA given at a concentration of 1-75 mg/kg during 1-3 weeks. The alkylating level of Hb was approximately 65 times higher than that of plasma proteins and it was nearly 6.5% of its cumulative dose. The index of binding to Hb and the rate of its alkylation were 163 and 0.75.10(-3) liter/g-1/hour-1, respectively.

Acetylcysteine↗
PubMed1996

A meta-analytical approach to the pooling of blood pressure values in children.

Meta-analysis of blood pressure (BP) studies in children was performed in order to evaluate whether BP readings obtained in various studies may be pooled. In total 30 original reports on BP in children were analyzed and the age and sex-specific BP values reported for 12 and 15-year-old subjects in 11 of these were tested for homogeneity. The differences in sample size-weighted means between the devices used (with 95% confidence intervals) were evaluated. The BP values reported in different studies for systolic Korotkoffs first phase BP (K1) and diastolic Korotkoffs fourth (K4) and fifth (K5) phase BP were shown to be too heterogeneous (p < 0.001) to be pooled. Heterogeneity and measurement biases in the BP results were caused by differences between the devices and the diastolic BP indicator (K4 vs K5) and by observer biases such as uncontrolled terminal digit preference. The device-specific weighted means for K1, K4 and K5 BP in 12 and 15-year-old subjects showed statistically significant differences between random zero (RZS) and ordinary mercury (OMS) sphygmomanometer (p < 0.001) the difference (OMS-RZS) being from 0.7 to 6.6 mmHg for K1 (p < 0.001, except in 12-year-old girls), from 1.1 to 7.1 mmHg for K4 (p < 0.001, except in 12-year-old girls) and from 4.5 to 7.9 mmHg for K5 (p < 0.001). Such a discrepancy was also apparent between ordinary and automated mercury sphygmomanometer (AMS) in the case of diastolic K4 and K5 BP (p < 0.001), but not in K1. BP results obtained in different investigations using different BP devices and Korotkoffs phases as indicator of diastolic BP should not be pooled. More widely accepted recommendations are needed to standardize the measurement of BP in children.

Adolescent↗
PubMed1997

Molecular cytogenetic analysis of a nontumorigenic human breast epithelial cell line that eventually turns tumorigenic: validation of an analytical approach combining karyotyping, comparative genomic hybridization, chromosome painting, and single-locus fluorescence in situ hybridization.

The immortalized, nontumorigenic human breast epithelial cell line HMT-3522 has been used as a model for premalignant and, eventually, malignant development. During cultivation, the karyotype evolution was followed. At an early stage, a very long constant phase showed a near-diploid karyotype, with only five marker chromosomes. DNA from this phase was used for comparative genomic hybridization (CGH) analysis, confirming a previously known MYC amplification, and the integration sites were subsequently determined by single-locus fluorescence in situ hybridization (FISH). Furthermore, gains of 5q22-qter and 20q11-qter and deletion of most of chromosome 6 (6p23-qter) were detected by CGH. Because of uncertainty about some of the indicated changes, including a deletion of Ip35-pter, the CGH findings were investigated more closely by chromosome painting, leading to a revision of the karyotype: 45,XX,del(I)(p35),-6,dup(8)(pter-->qter::qter-->q24),der(12) t(6;12)(p23; p13),der(14)t(5;14)(q22;q32.3),der(17)t(8;17;20)(17pter-->17q25 ::8qter--> 8q23::8q24-->8qter::8q24-->8qter:: 8q23-->8q24.1::20q11-->20qter). Some karyotypic changes were confirmed by CGH; others had to be revised; and, in the Ip35 region, classical cytogenetics seems superior to CGH. However, CGH revealed a karyotypically unsuspected dup(20q) that might be of special relevance to breast tumor initiation or progression. Our study confirms that CGH is supplementary to current technologies, e.g., karyotyping and Southern analysis, but cannot replace them. In addition, our cell line turned out to be an excellent model for comparison among the different methods. The results imply that future cytogenetic analyses of complex karyotypes should be based on a combination of karyotyping, CGH, and FISH.

Breast↗
PubMed1997

[The Parity technique as an example of an analytical approach to designing computerized psychological tests].

The new computer technique "Paritet" for studying the function of attention and visual perception was developed by the author in 1995. This technique has been tested in the combined experiment "ECOPSI-95". The study results reveal the differences in the visual perception of symmetric and nonsymmetric images, combined and separate elements of the image. For solution of the problem of developing the methodology of designing the computer tests it is suggested to develop the system of ranging the visual images to suit the complexity of perception.

Attention↗