Biomedical subjects

Uner Tan

Publications and source records attributed to Uner Tan.

30 records · Page 2Linked to original sources

PubMed2003

Effects of high-frequency electromagnetic fields on human EEG: a brain mapping study.

Cell phones emitting pulsed high-frequency electromagnetic fields (EMF) may affect the human brain, but there are inconsistent results concerning their effects on electroencephalogram (EEG). We used a 16-channel telemetric electroencephalograph (ExpertTM), to record EEG changes during exposure of human skull to EMF emitted by a mobile phone. Spatial distribution of EMF was especially concentrated around the ipsilateral eye adjacent to the basal surface of the brain. Traditional EEG was full of noises during operation of a cellular phone. Using a telemetric electroencephalograph (ExpertTM) in awake subjects, all the noise was eliminated, and EEG showed interesting changes: after a period of 10-15 s there was no visible change, the spectrum median frequency increased in areas close to antenna; after 20-40 s, a slow-wave activity (2.5-6.0 Hz) appeared in the contralateral frontal and temporal areas. These slow waves lasting for about one second repeated every 15-20 s at the same recording electrodes. After turning off the mobile phone, slow-wave activity progressively disappeared; local changes such as increased median frequency decreased and disappeared after 15-20 min. We observed similar changes in children, but the slow-waves with higher amplitude appeared earlier in children (10-20 s) than adults, and their frequency was lower (1.0-2.5 Hz) with longer duration and shorter intervals. The results suggested that cellular phones may reversibly influence the human brain, inducing abnormal slow waves in EEG of awake persons.

Adult↗

PubMed2003

Population-level right-paw preference in rats assessed by a new computerized food-reaching test.

We re-studied the distribution of paw preference in rats using a new computerized food-reaching test, which recorded the times and time intervals between the single right- and left-paw entries. Using the traditional food-reaching test, we found that of 144 rats, 72.7% were right-handed, 19.7% left-handed, and 7.6% mixed-handed. This population-level J-shaped right-hand preference did not fit a binomial chance distribution (25:25:50). Of right -handers, 99.5% first used their right paw and 0.5% left paw; of left-handers, 98.6% first used their left paw and 1.4% right paw. Of mixed-handers, 59% first used the right paw and 41% left paw for food reaching. The time interval between putting the rat into the test cage and the first right-paw entry was significantly shorter than the first left-paw entry in total sample. Males were faster than females (shorter time intervals between right- or left-paw entries). The distribution of the time intervals between right- or left-paw entries was inverse J-shaped, which exhibited a normal distribution after taking the logarithms of the time intervals. There was no significant difference between time intervals for the left-paw entries; time intervals for the right-paw entries were significantly shorter in males than females, accentuating the role of the left brain for sex differences in motor control. The results suggested that humans are not unique in population-level right-hand preference; our new method would be suitable for new developments in handedness research.

Animals↗

PubMed2003

Covariation of sex differences in mental rotation with body size.

Sex difference in mental rotation ability was reconsidered. The Vandenberg-Kuse figures were administered to 120 male and 76 female students from the Medical School of BlackSea Technical University in Trabzon, Turkey to assess the mental rotation ability. Students' height and weight were measured. As expected, men outperformed women on this test and had greater height and weight. Number correct on mental rotation test significantly correlated with height and weight for the total sample and for men, but only with weight for women. Using weight as covariate, the sex difference was no longer significant. The mean mental rotation score was significantly higher for heavy women than for light men. There was a positive correlation between weight and mental rotation test scores for heavy women, but height and weight were negatively correlated with mental rotation test scores for light men. These results suggest that there is no sex difference in mental rotation ability as measured.

Adolescent↗

PubMed2003

Sex differences in verbal and spatial ability reconsidered in relation to body size, lung volume, and sex hormones.

Sex differences in verbal and nonverbal abilities were reconsidered in relation to bodily measures and sex hormones in Turkish university students. Perceptual-verbal ability was evaluated using As Test. To assess the nonverbal abilities, the mental rotation test and Cattell's Culture Fair Intelligence Test were used. As expected, the 53 women performed better than men on the As Test; 79 men had a higher mean than the 53 women on the mental rotation task; there was no sex difference on Cattell's IQ Test. Cattell IQs correlated only with tidal volume of lungs. Scores on the As Test did not show significant correlations with body size and lung capacities. Mental rotation was significantly correlated with height, weight, and lung volume. With covariates of height, weight, and vital capacity, sex differences in mental rotation completely disappeared, but the difference on the As Test increased while Cattell IQ remained sex-neutral. With testosterone as covariate, the sex difference on the As test increased but on the mental rotation task disappeared; Cattell IQ was sex-neutral. With covariates of estradiol and progesterone, sex differences on the As test disappeared; mental rotation scores and Cattell IQ were not influenced. Under a combined covariation of height, weight, and testosterone, sex differences in mental rotation reversed, women scoring better than men; after adding estradiol or progesterone instead of testosterone to this model, sex differences on mental rotation completely disappeared, but verbal ability and Cattell IQ were not changed. These results suggest that Cattell's Culture Fair Intelligence Test is unique in resistance to sex differences; perceptual-verbal ability was the most sex-specific mental trait but with dependence on estradiol; mental rotation, on the contrary, was least sex-specific, depending on body size, lung volume, sex hormones, and their combined actions, which explains women's better performance.

Adolescent↗

PubMed2002

Right- and left-handed dentists using right- and left-sided dental chairs in treatment of calculus.

The aim of the present study was to evaluate the association of hand preference of dentists and the position of dental chairs in treatment of dental calculus. The dentists were last-class students from the School of Dentistry (Erzurum, Turkey). They were directed to dental chairs designed for right- and left-handers (right-sided and left-sided chairs) to remove calculus from the lower anterior teeth in volunteer patients having similar amounts of calculus, which was measured by Calculus index (CI). The right-handed dentists were more successful in right-sided (traditional) chairs than left-sided chairs; the left-handed dentists were more successful on left-sided chairs than right-sided chairs. The highest posttreatment CI (lowest success) was due to the right-handed dentists on the left-sided chairs. The lowest posttreatment CI (highest success) belonged to the left-handers working on the left-sided chairs. The left-handed dentists were better than right-handed dentists in the treatment of the mesial and distal surfaces of teeth, whereas the right-handers were successful only in the treatment of the distal parts of teeth. These results were explained by a better coordination between right and left hands and with higher skill in both hands in left-handers than right-handers.

Adult↗

PubMed2002

Predictability of hand skill and cognitive abilities from craniofacial width in right- and left-handed men and women: relation of skeletal structure to cerebral function.

Recently, a family of homeobox genes involved in brain and craniofacial development was identified. In light of this genetic background, we hypothesized that some functional characteristics of human brain (hand skill, cognition) may be linked to some structural characteristics of human skull (e.g., craniofacial width) in humans. Hand preference was assessed by Oldfield's Handedness Questionnaire. Hand skill was measured by Peg Moving Task. Face width was measured from the anteroposterior cephalograms (x-ray) using right (R) and left (L) zygomatic points. Intelligence "g" was assessed by Cattell's Culture Fair Intelligence Test; the perceptual-verbal ability was assessed by "Finding A's Test"; the spatial ability was assessed by the mental rotation task, in right- and left-handed men and women. The percentages of right-, left-, and mixed-faced subjects were close to those found for paw preference in cats. Women tended to be more right-faced (R--L > 0) and less left-faced (R--L < 0) than men, who tended to be more left-faced and less right-faced than women. R--L face width inversely correlated with L--R PMT (peg moving time) in left-handers; there was a direct relation between these variables in right-handers. Cattell IQ linearly increased with R--L face width in left-handers, negatively correlated in right-handed men and women. Verbal ability inversely related to R--L face width in right- and left-handed men, but directly correlated in right-handed women. The number of correct response on mental-rotation task positively and linearly correlated with R--L face width in left-handers and right-handed women. It was concluded that the structural-functional coupling revealed in the present work may have its origins in parallel development of the craniofacial skeleton and brain under the influence of homeobox genes.

Adult↗

PubMed2002

Validity of spectral analysis of evoked potentials in brain research.

The averaged electronencephologram (EEG) response of the brain to an external stimulus (evoked potential, EP) is usually subjected to spectral analysis using the fast Fourier transform (FFT), especially to discover the relation of cognitive ability to so-called brain dynamics. There is indeed a discrepancy between these two systems, because the brain is a highly complex nonlinear system, analyzed by a linear system (FFT). We present in this work some inaccuracies that occurred when EPs are subjected to spectral analysis, using a model signal. First of all, the EP power spectra depended upon the number of samples used for averaging; the input EP (model signal) and the output EP (from the system) seemed to be similar in forms, but they exhibited completely different spectral power curves. It was concluded that the spectral analysis of evoked responses by using FFT (linear system analysis) in relation to brain (highly complex nonlinear system) may mislead neuroscientists.

Brain↗

PubMed2002

Classical and atypical neuroleptics, and bone mineral density, in patients with schizophrenia.

There are some reports that classical neuroleptics may lead to osteoporosis or reduced bone mineral density (BMD). However, there is no adequate information about the effects of atypical neuroleptics on BMD. The aim of this study was to measure BMD in schizophrenic patients taking classical and atypical neuroleptics, compared to healthy controls. Seventy-five patients with schizophrenia (40 taking classical neuroleptics [CN], 35 taking atypical neuroleptics [AN]) and 20 healthy controls (HC) were included in the study. Spine (L1-L4) BMD was measured by dual-energy X-ray absorptiometry. ANOVA showed that BMD was higher in HC than AN and CN. In addition, there was a negative correlation between the duration of neuroleptic treatment and BMD and the duration of the illness. These findings suggest that atypical neuroleptics may be safer than the classical neuroleptics in terms of reduced BMD.

Adult↗

PubMed2002

Sex difference in susceptibility to picrotoxin-induced seizures in rats following octreotide.

It was previously reported that females with proestrous are more susceptible to picrotoxin-induced epileptic seizures than males, provided that the estrous cycle is taken into consideration (Tan & Tan, 2001). The sex difference in susceptibility to picrotoxin-induced seizures was reconsidered in the present study using rats with a previous octreotide (a stable somatostatin analogue) injection, as somatostatin is known to be involved in epileptic phenomena. Contrary to rats without octreotide, males were more susceptible to picrotoxin-induced seizures than females. Statistical analysis indicated that only males showed decreased latencies to seizures and increased seizure frequencies following octreotide; females were not affected by this experimental procedure. It was suggested that as a GABA antagonist, somatostatin may contribute to the occurrence of epileptic discharges in nervous system, creating a sex difference to epileptic seizures. These results may have implications for understanding the epileptic mechanisms, with possible therapeutic consequences.

Animals↗

PubMed2002

Sex difference in perceptual-verbal ability in relation to body size.

Sex difference in verbal ability was reconsidered in relation to body size. The perceptual-verbal ability (PVA) was assessed using the A's Test. For the raw data, women excelled men, as expected. PVA positively correlated with height and weight of the subjects, but only for women. As a covariate of height, sex difference increased by increasing the women's score; men's score did not change. Tall women had much higher scores than short men. It was concluded that sex difference in PVA is stable despite the smaller body size of females than males, and body height may be predictive for this ability, but only in women.

Adolescent↗

PubMed2002

Blood brain barrier in right- and left-pawed female rats assessed by a new staining method.

The asymmetrical breakdown of the blood-brain barrier (BBB) was studied in female rats. Paw preference was assessed by a food reaching test. Adrenaline-induced hypertension was used to destroy the BBB, which was evaluated using triphenyltetrazolium (TTC) staining of the brain slices just after giving adrenaline for 30 s. In normal rats, the whole brain sections exhibited complete staining with TTC. After adrenaline infusion for 30 s, there were large unstained areas in the left brain in right-pawed animals, and vice versa in left-pawed animals. Similar results were obtained in seizure-induced breakdown of BBB. These results were explained by an asymmetric cerebral blood flow depending upon the paw preference in rats. It was suggested that this new method and the results are consistent with contralateral motor control that may be important in determining the dominant cerebral hemisphere in animals.

Animals↗

PubMed2002

Right- and left-handed dentists in periodontal therapy.

The purpose of this study was to determine whether successful dental therapy (scaling and root planing) depends upon handedness of dentists in right-handed dental chairs (units) Participants were 28 voluntary dentists (14 female and 14 male, ranging in age from 26 to 34 years). Patients (7 female and 7 male with a mean age of 39.6 years) had advanced periodontitis. Handedness was assessed using the Turkish version of the Edinburgh Handedness Inventory. There were two equal groups of dentists: left-handers (7 female, 7 male) and right-handers (7 female, 7 male). Initial examination of patients was performed using a pressure-controlled periodontal probe. During scaling and root planing, the negative interstroke forces were recorded using a piezo-electric receiver, an electronic transducer, and an analogue writer. The results showed that during scaling, mean negative forces reached a mean of 0.74 N in left-handed dentists and 0.52 N in right-handed dentists. During root planing, these forces were 0.86 N in left-handed dentists, and 0.63 N in right-handed dentists. These differences were statistically significant. The right-handed dentists were more successful than the left-handed dentists at scaling and root planing, provided that both of them used the same right-sided dental chairs. The importance of handedness of the dentists was accentuated in dental practice.

Adult↗