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PubMed2006

Characteristics of accommodative behavior during sustained reading in emmetropes and myopes.

Accommodation has long been suspected to be involved in the development of myopia because near work, particularly reading, is known to be a risk factor. In this study, we measured several dynamic characteristics of accommodative behavior during extended periods of reading under close-to-natural conditions in 20 young emmetropic and stable myopic subjects. Accommodative responses, errors, and variability (including power spectrum analysis) were analyzed and related to accommodative demand and subject refractive error. All accommodative behaviors showed large inter-subject variability at all of the reading demands. Accommodative lags and variability significantly increased with closer demands for all subjects (ANOVA, p<0.05). Myopes had significantly greater variability in their accommodation responses compared to emmetropes (ANOVA, p<0.05) and had larger accommodative lags at further reading distances (unpaired t test p<0.05). Power spectrum analysis showed a significant increase in the power of accommodative microfluctuations with closer demands (ANOVA, p<0.05) and with increasing myopia at the closest reading demand (ANOVA, p<0.01). The difference in the stability of the accommodative behavior between individuals with different refractive states suggests a possible relationship between variability in accommodation and the development of myopia.

Accommodation, Ocular↗
PubMed1994

[New perspectives in color ultrasound in breast diagnosis].

In recent years, ultrasound has become established as part of the diagnostic evaluation of breast tumours. Not replacing, but complementing mammography, ultrasonic investigations increasingly represent a sensitive means of early diagnosis. Thermography, on the other hand, has proved of relatively little value and doesn't play a significant role today. Lately, Colour Doppler sonography has been used for differentiating tumour-associated blood supply patterns--however, sensitivity and specificity were not as high as initially expected. Colour spectrum analysis of local findings in comparison to the remaining glandular tissue, however, seems to be a promising method in the differentiation of ultrasound findings of uncertain tumour status. A fibroadenoma shows no significantly different colour density as compared to surrounding tissue. In carcinoma, on the other hand, one regularly finds a hyperintensive zone with sharp margins. In 70 patients, who had breast tumours, we attempted the differentiation of benign and malignant findings with the help of colour spectrum analysis. Postoperatively, these results were validated by histology. With the exception of one mesenchymal tumour, the Doppler diagnosis was identical to the histopathological findings.

Breast↗
PubMed1989

Correlation between carotid blood flow and brain atrophy in patients with multi-infarct dementia.

The relation between carotid blood flow measured by Doppler spectrum analysis and brain atrophy on computed tomography (CT) was studied in 22 subjects with multiple lacunar cerebral infarctions. The subjects were divided into two groups, 7 patients with multi-infarct dementia (MID) (mean age 73 years) and 15 nondemented lacunar stroke subjects (NDLS) (mean age 66 years), according to DSM III criteria. All subjects had a score of 7 points or more on Hachinski's ischemic score and showed no carotid artery stenosis. Systolic peak frequency of the common carotid artery (CCA) was measured by Doppler spectrum analysis (Angioscan II). Brain atrophy was measured quantitatively on CT images by two-dimensional measurement using a digitizer. Peak frequencies were lower in MID than in NDLS. Brain atrophy was more severe in MID than in NDLS. There was a significant correlation between peak frequencies and brain atrophy in all subjects. These results indicate that CCA blood flow may reflect brain function in patients with multiple lacunar infarctions.

Aged↗
PubMed1990

Duplex sonography in the diagnosis of renovascular hypertension.

Duplex sonography (DS) has become a well established method for diagnosing peripheral vascular diseases. Technical developments (higher resolution of transducer and deeper penetration) have made also abdominal and retroperitoneal vessels, including renal arteries, accessible for duplex sonography. This method provides the opportunity to recognize renal artery stenoses causing renovascular hypertension without invasive procedures. We therefore examined 86 hypertensive patients with a high likelihood of renovascular hypertension. Due to technical problems (bowel gas, adipositas) we excluded 7 patients. 79 patients (17-79 years) were included in our study. Flow patterns of several renal vascular areas were evaluated while the renal artery was demonstrated on a B-scan. A spectrum analysis included the evaluation of the frequency pattern (widening of the frequency band and loss of a frequency free window below the systolic rise?), the sloping of the diastolic shoulder, and the calculation of different parameters like acceleration index, deceleration index, resistance index, acceleration time, and systolic peak velocity. The accuracy of DS in diagnosing renal artery stenoses was compared with arterial digital subtraction angiography (DSA). Renal artery stenoses was diagnosed in 21 out of 158 renal arteries (13%). Except for the systolic peak velocity no significant correlations could be found of any of the indices from spectrum analysis with hemodynamically significant stenoses (greater than 50%). However, the following 3 criteria proved to be valuable signs of a hemodynamically significant stenoses: 1) Maximal systolic acceleration greater than 3 m/s, 2) Steep sloping diastolic shoulder, and 3) Turbulence of all frequency ranges without a frequency free window below the systolic rise. Compared with DSA the sensitivity of DS was 84.0%, the specificity was 98.5%, and the predictive value 91% in significant stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Circadian rhythm of the autonomic nervous system in long QT syndrome.

The circadian changes in the activity of the autonomic nervous system in a group showing long QT duration in electrocardiogram (ECG) were studied in order to differentiate symptomatic congenital long QT syndrome from asymptomatic. The asymptomatic group presented only long QT duration (QTc > 0.46). Seven girls and two boys, including two subjects experiencing syncope of non-neurological origins, were examined by using heart rate (HR) power spectrum analysis. In three subjects, the peak of the high frequency band, indicating the parasympathetic activity, disappeared during night-time (sleep), which means the possibility of a high risk of sudden cardiac death. In two of three subjects, moreover, the averaged sympathetic activity during daytime was significantly increased compared to that during night-time, in addition to the abrupt increase of sympathetic activity in the morning. These two subjects, in which one boy had a family history of Romano-Ward syndrome, were the same people experiencing the syncope attack. We succeeded in objectively elucidating that congenital long QT syndrome is adrenergic-dependent, and suggest that HR power spectrum analysis may be of value in distinguishing symptomatic congenital long QT syndrome from asymptomatic showing only long QT duration.

Autonomic Nervous System↗
PubMed1999

Autonomic function and baroreflex sensitivity during a normal ovulatory cycle in humans.

OBJECTIVE AND DESIGN: Possible variations occurring in the autonomic function during a normal ovulatory cycle have been poorly investigated and it is not known whether the baroreflex sensitivity may change according to the different phases of the cycle. The aim of this study was to evaluate heart rate variability (power spectrum analysis), and baroreceptor sensitivity (alpha-low frequency coefficient) in 13 young women with regular menses during the two phases of the cycle (phase I: 5 +/- 1 days and phase II: 23 +/- 3 days from bleeding). RESULTS: The low frequency/high frequency ratio was significantly higher in the second phase of the cycle (phase I: 2.8 +/- 2.6; phase II: 5.6 +/- 5.8, p < 0.05), in the presence of increased low frequency and reduced high frequency expressed in normalized units-nu-(phase I: 59.8 +/- 16.7 nu and 32.6 +/- 15.6 nu for low frequency and high frequency, respectively; phase II: 67.7 +/- 18 nu and 25.7 +/- 17.5 nu for low frequency and high frequency, respectively; p < 0.05). The alpha-low frequency coefficient, index of baroreflex sensitivity, did not statistically differ in the two phases (phase I: 10.6 +/- 4.5 msec/mm Hg; phase II: 8.9 +/- 4.9 msec/mm Hg; ns). CONCLUSIONS: The power spectrum analysis suggests that the autonomic function may be affected by the ovulatory cycle, sympathetic activation being relatively increased in the second phase. On the contrary, the baroreceptor function seems to be scarcely influenced by the two phases of the menstrual cycle.

Adult↗
PubMed1994

Assessment of the ocular response to topical beta-adrenoceptor antagonists using accommodative microfluctuations.

Power spectrum analysis of accommodative microfluctuations has identified two dominant frequency components: a low frequency component (LFC < 0.6 Hz) and a high frequency component (1.3 Hz < HFC < 2.5 Hz). Computer-driven models of accommodation and experimental manipulation of accommodative feedback loops indicate that LFCs are likely to have a functional role in monitoring retinal image contrast during sustained accommodation. In contrast HFCs have been shown to be correlated with arterial pulse frequency and consequently their characteristics can be modified by the extra- and intra-ocular vascular (and possibly CNS) effects. For example, topical instillation of the non-selective beta-antagonist timolol maleate has shown previously the ability to modify the HFC. In an attempt to clarify proposed differences between beta-adrenoceptor antagonist agents with regard to their effects on systemic and ocular vasculature, we extend the potential offered by HFCs as a non-invasive method of assessing the ocular response to beta-antagonists to the cardioselective beta-antagonist betaxolol HCl. Accommodative microfluctuations were measured using a continuously recording infrared optometer on 10 emmetropic subjects (mean age 23.9 +/- 2.3 years) who viewed a high contrast target located at a vergence of -4 D. A double-blind protocol was employed between saline and betaxolol (0.5%, 2 x 30 microliters) following corneal anaesthesia. Local and systemic effects were separated by examining the treated and untreated eyes of three subjects. Power spectrum analysis indicated that the root mean square (r.m.s.) value and power of LFCs and HFCs were equivalent for the saline and betaxolol trials.(ABSTRACT TRUNCATED AT 250 WORDS)

Accommodation, Ocular↗
PubMed2000

Referrals from general practice to an outpatient rheumatology clinic: disease spectrum and analysis of referral letters.

Our objective was to study the demographic characteristics of patients referred from general practitioners to a rheumatology outpatient clinic and to analyse the content and quality of the referral letters. During a 12-month period 346 randomly chosen referral letters of new patients from GPs to a rheumatology outpatient clinic were evaluated. The mean age of the 346 referred patients (73.1% females and 26.9% males) was 45.5 years and 17.8% were 60 or older. Mean disease duration at the time of referral was 50.9 months (1-432 months). Only about 10% of the patients referred had a disease duration of 1 month or less. The current clinical problem was appropriately presented in 95% of the referral letters. In only 0.9% of referrals had there been a prior phone consultation. Altogether, 95.1% of the referrals were as a result of diagnosis or treatment, and in nearly half the cases a diagnosis of inflammatory rheumatic disease was suggested. In 23% of the letters the result of clinical examinations were missing. Laboratory tests such as serum rheumatoid factor, antinuclear antibodies and HLA-B27 were used by GPs to screen for rheumatic disease in general. A lack of correlation between clinical manifestations and subsequently requested laboratory examinations was frequently found in the referral letters, exemplified by the use of HLA-B27 in rheumatoid arthritis and serum rheumatoid factors in ankylosing spondylitis. These results show that among GPs the threshold for referring patients to a rheumatology outpatient clinic appears rather high, and that patients are subjected to long observation periods before referral. A more frequent use of phone consultations and an improvement in the diagnostic skills of GPs may positively influence the selection of patients for referral and shorten the long waiting lists in rheumatology. This need for improvement was further strengthened by GPs' inappropriate use of laboratory tests.

Adolescent↗
PubMed1997

Regional correlations between the EEG and oxygen metabolism in dementia of Alzheimer's type.

To determine the relationship between EEG slowing and cerebral hypometabolism in dementia, 10 patients with dementia of Alzheimer's type (DAT) were evaluated with quantitative topographic EEG and positron emission tomography (PET). Power in each 1-Hz frequency band from 2-20 Hz, power ratio index, and normalised PET data from corresponding cortical sites were compared to data obtained from 20 normal volunteers. PET revealed significant parieto-temporal hypometabolism, and topographic EEG mapping and power spectrum analysis revealed a slowing of the background EEG that was most pronounced in the parietal-temporal areas. Correlation analysis between EEG power spectrum data and CMRO2 revealed significant negative correlations for frequencies below 8 Hz and significant positive correlations above 8 Hz in the parieto-temporal regions, which have previously been identified as the areas most severely affected by pathological changes associated with DAT. Correlation coefficients plotted as functions of frequency illustrated the relationships between EEG changes and reduced CMRO2, supporting previous views that EEG slowing in DAT may be related to hypometabolism in cortical regions most affected by the disease.

Aged↗
PubMed2000

Reproducibility of time-domain and three different frequency-domain techniques for the analysis of the signal-averaged electrocardiogram.

Because time-domain (TD) analysis of the signal-averaged ECG (SAECG) has some limitations that limit its use, several frequency-domain analysis techniques were developed in an attempt to improve the diagnostic ability of the SAECG. However, it is not known how reliable these techniques are at detecting late potentials. This prospective study compares the short-term reproducibility of 4 analysis techniques: TD analysis, spectral temporal mapping (STM), spectral turbulence analysis (STA), and acceleration spectrum analysis (ASA), in a large series of normal patients and post-myocardial infarction (MI) patients. Two consecutive SAECGs were recorded in 634 patients that were divided into 3 groups: 117 remote MI patients undergoing programmed electrical stimulation for the inducibility of ventricular tachycardia (Group 1), 407 consecutive acute MI survivors (Group 2), and in 110 healthy volunteers (Group 3). The diagnostic reproducibility of the 4 techniques was evaluated by comparing rates of inconsistent results (1 normal and the other abnormal). The numeric reproducibility for each technique was assessed by comparing the normalized differences of each single SAECG parameter between the 2 recordings. Inconsistent results of diagnostic reproducibility were observed in 4.1%, 6.9%, 9.8%, and 18.0%, with TD, STA, ASA, and STM, respectively. Comparisons of these rates were significantly different (P < .05) except between STA and ASA (P = .07). The numeric reproducibility was highest for TD parameters, lowest for STM factors of normality, and intermediate for STA and ASA indices. TD analysis remains the most reproducible SAECG analysis technique, whereas STM showed the worst reproducibility, which limits its clinical applicability. STA and ASA provide an acceptable intermediate reproducibility, the former being slightly, although not significantly, more reproducible than the latter.

Electrocardiography↗
PubMed2005

Prediction of ethylene content in melt-state random and block polypropylene by near-infrared spectroscopy and chemometrics: influence of a change in sample temperature and its compensation method.

This paper reports on the influence of a change in sample temperature, and a method for its compensation, for the prediction of ethylene (C2) content in melt-state random polypropylene (RPP) and block polypropylene (BPP) by near-infrared (NIR) spectroscopy and chemometrics. Near-infrared (NIR) spectra of RPP in the melt and solid states were measured by a Fourier transform near-infrared (FT-NIR) on-line monitoring system and an FT-NIR laboratory system. There are some significant differences between the solid and melt-state RPP spectra. Moreover, we investigated the predicted values of the C2 content from the RPP or BPP spectra measured at 190 degrees C and 250 degrees C using the calibration model for the C2 content developed using the RPP or BPP spectra measured at 230 degrees C. The errors in the predicted values of the C2 content depend on the pretreatment methods for each calibration model. It was found that multiplicative signal correction (MSC) is very effective in compensating for the influence of the change of temperature for the RPP or BPP samples on the predicted C2 content. From the suggestion of principal component analysis (PCA) and difference spectrum analysis, we propose a new compensation method for the temperature change that uses the difference spectra between two spectra sets measured at different temperatures. We achieved good results using the difference spectra between the RPP/BPP spectra sets measured at 190 degrees C and 250 degrees C after correction and the calibration model developed with the spectra measured at 230 degrees C. The comparison between the method using MSC and the proposed method showed that the predicted error in the latter is slightly better than those in the former.

Algorithms↗
PubMed2006

Central genetic alterations common to all HCV-positive, HBV-positive and non-B, non-C hepatocellular carcinoma: a new approach to identify novel tumor markers.

Hepatocellular carcinoma (HCC) is a common malignancy, but the prognosis remains poor due to the lack of sensitive diagnostic markers. To gain insight into the central molecular features common to all types of HCC, and to identify novel diagnostic markers or therapeutic targets for HCC, we performed a gene expression profiling analysis using a high throughput RT-PCR system. After examining the mRNA expression of 3,072 genes in 204 (119 tumor and 85 non-tumor) liver samples, we identified differential gene expression between the HCV group (n=80), HBV group (n=19) and non-B, non-C group (n=20) with a principal component analysis and a correlation spectrum analysis. After selection of genes differentially expressed between tumor and non-tumor tissues (p<0.01) within each HCC group, a total of 51 differentially expressed genes (23 upregulated and 28 downregulated genes) were found to be common to the three HCC groups. Gene Ontology grouping analysis revealed that genes with functions related to cell proliferation or differentiation and genes encoding extracellular proteins were found to be significantly enriched in these 51 common genes. Using an atelocollagen-based cell transfection array for functional analysis of eight upregulated genes, five (CANX, FAM34A, PVRL2, LAMR1, and GBA) significantly inhibited cellular apoptosis by two independent assays. In conclusion, we identified 51 differentially expressed genes, common to all HCC types. Among these genes, there was a high incidence of anti-apoptotic activity. This combination approach with the advanced statistical methods and the bioinformatical analysis may be useful for finding novel molecular targets for diagnosis and therapy.

Apoptosis↗
PubMed2005

[Application of microwave dielectric spectrum to analysis of low-carbon alcohols in water].

A novel technique for detecting low-carbon alcohols in water at microwave frequency is presented. The technique is based on the measurement of microwave scattering parameters of aqueous solutions containing alcohols. The method employs transmission-line technique at frequency field. The scattering parameters were obtained by measuring the microwave transmission power. The changes in scattering parameters were measured when a sample vessel filled with aqueous solution containing low-carbon alcohols was inserted in the microwave transmission line. It is shown, from the experimental data, that there are good linear relationships between the scattering parameters and the concentrations of alcohols within a certain range.

English Abstract↗