Biomedical subjects

Jaanus Lass

Publications and source records attributed to Jaanus Lass.

6 recordsLinked to original sources

PubMed2005

Study of effects of low level microwave field by method of face masking.

The aim of this study was to examine experimentally effects of low level, modulated microwaves on human central nervous system function utilizing the phenomenon of visual masking. Ten healthy volunteers, four males and six females, were exposed to electromagnetic field (450 MHz, 0.16 mW/cm2) with 7 Hz modulation frequency. Two photo series (visual stimuli) of unfamiliar, young male faces were presented to the subjects, one picture after another. All the photos were frontal views of unfamiliar faces, which could be recognized only by their unique combinations of features. The task was to identify the pictures from a group of six photos and to decide which order they were presented in. The phenomenon of visual masking is revealed as anamorphosis in subject's perception of two instantaneous visual stimuli presented within a short time interval. When both stimuli were to be recognized correctly and put in the right order, there was a statistically significant difference (P < 0.05) between the identification of the stimulus with microwave electromagnetic field and sham exposure. Recognition of both stimuli in a pair was better under the sham exposure conditions but the actual difference was only 5%. It was concluded that early stages of visual information processing are overwhelmingly robust and routine (and adaptively significant) activities, so that the low level 7 Hz modulated electromagnetic field effects exerted upon it are extremely weak.

Adult↗

PubMed2004

Changes in human EEG caused by low level modulated microwave stimulation.

This study focuses on the effect of low level microwave radiation on human EEG alpha and theta rhythms. During the experiment, 20 healthy volunteers were exposed to a 450 MHz microwaves with 7 Hz on-off modulation. The field power density at the scalp was 0.16 mW/cm2. Signals from the following EEG channels were used: FP1, FP2, P3, P4, T3, T4, O1, and O2. The experimental protocol consisted of one cycle of short term photic and ten cycles of the repetitive microwave stimulation. The changes caused by photic as well as microwave stimulation were more regular on the alpha rhythm. In the majority of cases, photic stimulation caused changes in the EEG energy level in the occipital and microwave stimulation in the frontal region. Our experimental results demonstrated that microwave stimulation effects became apparent, starting from the third stimulation cycle. Changes varied strongly from subject to subject. Therefore, photic and microwave exposure did not cause statistically significant changes in the EEG activity level for the whole group. For some subjects, clear tendencies of changes in microwave on-off cycles were noticeable.

Action Potentials↗

PubMed2003

Echocardiographic assessment of the different left ventricular geometric patterns in middle-aged men and women in Tallinn.

The aim of this study was to determine the association of left ventricular (LV) geometry with sex, age, arterial hypertension and obesity in Tallinn. In a framework of a population study for cardiovascular risk factors, echocardiography was carried out in 325 men and 398 women (69.3% of all 1043 participants aged 35-59) in 1999-2001. Left ventricular hypertrophy was defined if left ventricular mass (LVM), LVM/height and LVM/body surface area were 294 g, 163 g/m and 150 g/m2 in men, and 198 g, 121 g/m and 120 g/m2 in women, respectively. LV geometry was analysed according to four types generally recognized (with regard to relative wall thickness > 0.45). The prevalence of concentric hypertrophy was similar in men and women: 7.7% and 9.1%. The prevalence of eccentric hypertrophy was significantly higher in women than in men (33.3% vs 4.9%). Concentric remodelling was also found in women more often than in men (9.5 vs 5.5%; p < 0.05). Regardless of sex and age, concentric hypertrophy was never found in participants with blood pressure < 140/90. In hypertensives, there was a tendency for age-related increase of concentric hypertrophy prevalence: the latter was higher in women than in men: 39.1% vs 25.5%; p < 0.05. In examinees with BMI < 30, this type of LV geometry was seldom found: in 3.1% of men and 5.0% of women; p < 0.05. In obese persons, it increased with age, reaching 26.5% in men and 21.2% in women (p < 0.05). The prevalence of eccentric hypertrophy in men increased with age, and with hypertension and obesity. The prevalence of concentric remodelling in men was not related to BMI; it was significantly more often found in older age groups and in hypertensives. In women, the prevalence of eccentric hypertrophy and concentric remodelling was not related to age, hypertension or obesity.

Age Distribution↗

PubMed2003

QT dispersion in relation to left ventricular geometry and hypertension in a population study.

OBJECTIVE: To study the relationship between QT interval dispersion, arterial hypertension and different left ventricular geometric patterns in the framework of a population study. DESIGN: A random sample of the population of Tallinn, 717 men and women aged 35-59, underwent standard 12-lead ECG at rest and echocardiography. Corrected QT dispersion was considered as prolonged when the duration was > or =70 ms. RESULTS: In hypertensives with concentric and eccentric hypertrophy, the mean values of corrected QT dispersion were significantly higher than in those with normal geometry. In the normotensive group no significant differences of the mean values of corrected QT dispersion were found in relation to left ventricular geometry. Mean values of corrected QT dispersion were higher in hypertensives than in normotensives in each left ventricular geometric pattern. Corrected QT dispersion > or =70 ms was mainly associated with concentric hypertrophy. CONCLUSION: Prolonged corrected QT dispersion is associated with left ventricular geometric abnormalities and arterial hypertension and is mostly related to concentric hypertrophy.

Adult↗

PubMed2003

Self-mixing in a diode laser as a method for cardiovascular diagnostics.

Our aim is the development of a simple optical method for pulse wave profile, pulse wave delay time, and blood flow measurement. The method is based on recording the Doppler frequency shift related to a moving target--blood vessel walls or small particles. The Doppler signal is detected using the self-mixing that occurs in the diode laser cavity when radiation scatters back from the moving target into the laser and interferes with the field inside. Two different ways can be simultaneously used for the self-mixing signal extraction: a photodiode accommodated in the rear facet of the diode laser package and a resistor from the laser pump current. An experimental device with a pigtail laser diode is developed that is able to detect the pulsation of major arteries with potentially useful information, including the pulse wave profile and the pulse wave delay time. The pulse wave delay time in different regions of the human body is measured relative to the electrocardiogram (ECG) signal. Also the flow velocity of a liquid suspension containing particles the size of erythrocytes (equivalent to blood flow) is measured. Registered signals are stored after digitalization and preprocessed using LabView for a Windows environment. The described device has the application of the self-mixing method and highlights significant advantages of simplicity, compactness, and robustness as well as the self-aligning and self-detecting abilities of such method, compared with the use of conventional interferometric method.

Blood Flow Velocity↗

PubMed2003

Arterial hypertension, left ventricular geometry and QT dispersion in a middle-aged Estonian female population.

The aim of the present study was to determine the prevalence of Left ventricular hypertrophy (LVH) and different left ventricular (LV) geometric patterns in the middle-aged women population of Tallinn, to assess the relationship between LV geometry, age, blood pressure and LV repolarization duration and inhomogeneity. A random sample of the population, 482 women aged 35-59, was examined in the framework of a cardiovascular risk factors survey for the WHO/CINDI programme years 1999-2000. Patients with valvular pathology, primary cardiomyopathy, atrial fibrillation, bundle branch blocks and flat T wave on electrocardiography (ECG) were excluded; 398 (82.2%) of the participants underwent echocardiography (Echo) and standard 12-lead ECG at rest and were included in the study. LVH was defined if left ventricular mass (LVM), LVM/height and LVM/BSA were >198 g, >121 g/m and > 120 g/m2, respectively. Arterial hypertension was determined in 23.1% of the women. The prevalence of arterial hypertension was three times higher in those aged 50-59 than in those aged 40-49 (37.4% vs 13.2%; p < 0.05). Different geometric patterns were found as follows: concentric hypertrophy in 9.1%; eccentric hypertrophy 33.9%; concentric remodelling 9.5% and normal geometry 47.5% of the participants. Concentric hypertrophy was found exclusively in hypertensive women and increased with age. No age-related eccentric hypertrophy and concentric remodelling differences were found, either in the normotensive or in the hypertensive group. Prolonged QT dispersion--a marker of increased myocardial electrical instability, was associated with LVH and arterial hypertension and was related mostly to concentric hypertrophy in hypertensives.

Adult↗