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Biomedical subjects

U Tan

Publications and source records attributed to U Tan.

At least 19 recordsLinked to original sources
PubMed1992

The lateralization of the grasp reflex in human newborns.

The strength of the grasp reflex from the right and left hands was estimated in male and female newborns within the second day after birth. In the total sample (N = 121), the mean strength of the grasp reflex from the right hand was found to be significantly higher than that from the left hand. There was a significant positive linear correlation between reflex strengths from the right and left hands. The mean right minus left (R - L) reflex strength was found to be significantly larger than zero. There was a positive linear relationship between the R-L reflex strength and the reflex strengths from the right and left hands. This was more pronounced for the right hand than the left hand. The reflex strengths from the right and left hands were found to be positively linearly correlated with the weight of the newborn babies. These results indicated a grasp reflex lateralization in newborns. The right-bias in the grasp-reflex asymmetry established in this work would create a basis for the development of the right-hand preference in adulthood.

Body Weight↗
PubMed1992

There is a relatively left-biased grasp-reflex asymmetry in human newborns with familial sinistrality compared to those without familial sinistrality.

Grasp-reflex asymmetry was studied in human newborns with regard to familial sinistrality (FS). In the total sample, the following results were obtained. The mean grasp-reflex strength from the right hand was found to be significantly greater than that from the left hand in FS- subjects. There was no significant difference between these parameters in FS+ subjects. The mean right minus left (R-L) reflex strength was significantly greater than zero in FS- subjects. The mean R-L reflex did not significantly differ from zero in FS+ subjects. The mean reflex strength from the right hand was found to be significantly greater in FS- subjects than FS+ subjects. There was no significant difference between the mean reflex strengths from the left hands of the FS- and FS+ subjects. The mean R-L reflex in subjects FS- was found to be significantly greater than that in FS+ subjects. Similar results were obtained from the male and female subjects. It was concluded that FS is an important factor determining the degree of the grasp-reflex asymmetry in newborns. The relatively left-biased grasp-reflex asymmetry under the influence of FS indicates a genetic origin of the motor asymmetry in newborns. This, in turn, suggests that cerebral lateralization inducing manual asymmetry in humans may have been preprogrammed genetically.

Female↗
PubMed1992

Relation of brain weight to body weight in cats to sex and paw preferences: anomalous results in left-preferent cats.

The well known relationship between brain weight and body weight was restudied in cats considering paw preference assessed by the food reaching test. The brain weight was found to be directly related to the body weight in the total sample, males, females, right-preferents, ambidexters, male right-preferents, male left-preferents, and female right-preferents. There was, however, no significant correlation between these parameters in the left-preferent cats. As a further anomalous result, there was a negative linear correlation between brain and body weights in the left-preferent female cats. It was suggested that the well-known allometric law that brain size increases with body weight should be reanalyzed in studies of neural evolution considering cerebral lateralization and sex-related differences.

Animals↗
PubMed1992

Lateralization of the grasp reflex in male and female human newborns.

The lateralization of the grasp reflex was studied in male and female newborns. The mean grasp-reflex strength of the right hand was found to be higher than that of the left hand in males, but the difference was not significant. The mean grasp-reflex strength of the right hand was found to be significantly higher than that of the left hand in females. There was no significant difference between the mean grasp-reflex strengths of the right hand in the male and female subjects. The mean reflex strength of the left hand was found to be higher in males than females; the difference was only marginally significant. The right minus left (R - L) reflex strength showed a significant positive linear relation to the right-and left-reflex strengths in both sexes. This was, however, much more pronounced for the right-reflex than the left-reflex. There was a significantly positive linear correlation between the reflex strengths of the right and left hands and the body weight in males. The females did not show such a relationship between reflex strength and body weight. These sex-related differences in the grasp reflex in newborns were discussed in light of cerebral lateralization and its hormonal modulation.

Body Weight↗
PubMed1992

The relationships between the degree of grasp-reflex asymmetry, grasp-reflex strength from the right and left hands, and body weight in the male and female newborn with and without familial sinistrality.

The relation of the degree of grasp-reflex asymmetry to the strength of right- and left-hand grasp-reflex strength and body weight was studied in human newborn. In the total sample (N = 103), the right minus left (R-L) reflex strength was found to be positively linearly related to the grasp-reflex strengths from the right and left hands in FS-subjects; the correlation was higher for the right hand than the left hand. In FS+ subjects (N = 17), there was not a significant correlation between R-L and right-reflex strength; left-reflex strength was found to be negatively linearly related to the R-L reflex strength. In FS- subjects, the right- and left-reflex strengths showed a positive linear correlation with body weight. In FS+ subjects, only the left-reflex showed a positive linear correlation with body weight. The R-L reflex tended to be positively correlated with body weight in FS- subjects and negatively correlated in FS+ subjects. In females (N = 58), the relation of R-L to right and left reflex was similar to that for the total sample. There was no significant correlation between grasp reflex and body weight in FS- females. In FS+ females (N = 8), there was a positive linear correlation between the right grasp-reflex and body weight; the left grasp-reflex did not show such a significant correlation. The R-L grasp-reflex strength was not correlated with body weight in females.(ABSTRACT TRUNCATED AT 250 WORDS)

Body Weight↗
PubMed1992

Right-, left-dominance and ambidexterity in grasp reflex in human newborn: importance of left brain in cerebral lateralization.

The grasp reflex was studied in human newborn without familial sinistrality. Of 60 females, 26 (43.3%) were right-handed and 34 (56.7%) ambidextrous. Of 62 males, 20 (32.3%) were right-handed, 39 (62.9%) ambidextrous, and 3 (4.8%) left-handed. There was a nonsignificant preponderance of right-dominance in females and a significant preponderance of nonright-handedness in males. In right-handers, the mean right minus left (R-L) grasp-reflex showed a positive linear correlation with the grasp-reflex from the right and left hands, with a higher correlation for the right hand. In ambidexters, the R-L grasp reflex did not show any significant correlation with the grasp reflex from the right and left hands. The mean grasp-reflex from right and left were found to be significantly smaller in ambidextrous males and females then right-handed males and females, with a much higher significance for the right hand. It was concluded that females tended to have a more pronounced reflex lateralization than males. The results also indicated that the left brain may be more important than the right brain for the development of a spinocerebral motor lateralization in humans.

Brain↗
PubMed1992

Parkinsonian-like tremor induced by a combined application of chlorpromazine and pentobarbitone in cats with left-paw preference.

A Parkinsonian-like tremor can be induced by a combined application of chlorpromazine and pentobarbitone in cats. Interestingly enough, only cats with left-paw preference were found to have a predisposition to this drug-induced tremor. The cats with ambidexterity and right-preference in paw use did not show any visible tremorogenic action of these drugs. Especially the proximal muscles of all four extremities showed oscillations with a frequency of about 12 per second in all animals tested, which completely disappeared after i.v. application of lioresal, atropine and biperiden. It was suggested that this new drug-induced tremor model may reflect an impairment within the cortico-striato-pallido-thalamo-cortical feedback loop. It was also concluded that left-handers may have an increased predisposition to centrally acting drugs than nonleft-handers.

Animals↗
PubMed1992

The relation of body height to handedness in male and female right- and left-handed human subjects.

The association between body size and the degree of hand preference was studied in male and female right- and left-handed human subjects. Hand preference was assessed by the Edinburgh Handedness Inventory. In left-handers (total sample), there was a significant, negative linear correlation between the degree of left-hand preference and body height. There was no significant correlation between these parameters if the males and females were considered separately. In right-handers (total sample), body height was found to be significantly and negatively linearly correlated with the degree of right-hand preference. A similar correlation was observed in males without familial sinistrality (FS-) and in FS+ females. There was no significant correlation between these parameters in FS+ right-handed males and FS- right-handed females. It was suggested that hormones affecting body height and brain size such as human growth hormone and testosterone would also contribute to the development of cerebral lateralization.

Adult↗
PubMed1992

Relationship of serum zinc levels to hand preference, skull length and serum gonadal hormone levels in right-handed young adults.

The association between serum zinc (Zn) level and the degree of hand preference was studied in right-handed young adults. Hand preference was scored by the Waterloo Handedness Questionnaire. Serum Zn level was determined by the flow injection analysis-atomic absorption technique. Zinc was found to be positively linearly and significantly correlated with the degree of right hand preference in the sample of males with familial sinistrality (FS+) and FS- females with right eye and right foot preference. There was a negative linear correlation between these variables in FS+ females. Skull length showed a significant negative linear correlation with zinc in FS+ males and females, but a positive linear correlation in FS- females. In FS- females, there was a significant positive linear correlation between serum gonadal hormone binding globulin (GBG) and serum Zn levels. In FS+ males, there was a significant negative linear correlation between serum GBG and Zn levels, and a significant positive linear correlation between serum free testosterone level and serum Zn level. It was suggested that zinc may influence the degree of the right hand preference by hormonal mechanisms according to genetically established brain organization.

Adolescent↗
PubMed1992

Testosterone and estradiol in right-handed men but only estradiol in right-handed women is inversely correlated with the degree of right-hand preference.

Relations of sex hormones to the degree of right-hand preference was studied in right-handed male and female adult subjects. Hand preference was assessed by the Edinburgh and Waterloo Handedness Questionnaires. Males consisted of weakly, moderately, and strongly right-handed subjects. Females comprised only moderately and strongly right-handed subjects. In females, only serum estradiol was found to be negatively linearly and significantly correlated with the degree of right-hand preference. In males, testosterone, as well as estradiol, showed a significant negative linear correlation with the degree of right-hand preference. Sex hormone binding globulin also showed a similar relation to hand preference in males. Thus, nearly all sex hormones caused a decrease in the degree of right-hand preference in males, whereas only estradiol had the same effect on hand preference in females. This would be the cause of stronger right-hand preference in females than males and vice versa.

Adolescent↗
PubMed1992

Similarities between sylvian fissure asymmetries in cat brain and planum temporale asymmetries in human brain.

Galaburda et al. (1987) have suggested that asymmetry of planum temporale in men would result from an asymmetrical neuronal loss; symmetry would implicate a failure of asymmetrical cell loss. There are several reports indicating a similarity between men and animal in cerebral lateralization. In the present work, a morphological analysis was performed in sylvian fissure (SF) of cats. Asymmetry coefficients (AC) were distributed symmetrically and normally with a mean of zero. However, female cats exhibited a relatively stronger leftward asymmetry (left SF > right SF), and male cats a relatively stronger rightward asymmetry in SF. The results generally supported those of Galaburda and his coworkers. Deviations from their results depended mainly on paw preference. The similarity between human brain and animal brain was accentuated once more concerning cerebral lateralization. The results were not appropriate to conclude about the mechanisms of cerebral lateralization. Testosterone in males and estrogen in females were suggested to be the main hormones contributing to the emergence of cerebral lateralization.

Animals↗
PubMed1992

Associations among right minus left brain weight, right- and left-brain weight and the degree of paw preference in right- and left-preferent male and female cats.

The relation of right and left brain weight to right minus left (R-L) brain weight and the relation of R-L paw use to brain weight were studied in adults cats. The R-L brain weight was significantly larger than zero in right-pawed (RH) male and left-pawed (LH) females. The R-L brain weight was significantly smaller than zero in LH males, not significantly different from zero in RH females. The R-L brain weight was negatively linearly correlated with the left-brain weight in RH and LH males (no significant correlations in females). The R-L paw use showed a significant positive linear correlation with the R-L brain weight in RH male and females. There was a significant negative linear correlation between R-L paw use and R-L brain weight especially in LH males. Total brain weight showed a significant negative linear correlation with R-L paw use in RH males, and a positive linear correlation in LH males (no correlations in female cats). These results indicated that intermanual difference in paw use is associated with interhemispheric weight difference and total brain weight, especially in male cats; the left brain seems to be of importance in cerebral lateralization.

Animals↗
PubMed1991

The relationships between nonverbal intelligence and the strength of left-hand preference in left-handers to sex and familial sinistrality.

The relationship between the strength of left-handedness and spatial reasoning ability was studied in left-handed male and female subjects with and without familial sinistrality (FS). The degree of left-handedness was assessed by the Edinburgh Handedness Inventory. The spatial reasoning ability was measured by Cattell's Culture Fair Intelligence Test. It was found that there was a negative linear correlation between nonverbal IQ and the strength of left-handedness in females with and without FS, a quadratic relationship in male left-handers without FS and a positive linear correlation in male left-handers with FS. These results indicate that the brain may exhibit different patterns of cerebral organization in left-handers to sex and FS. It was concluded that the "crowding" hypothesis may apply only to a subgroup of left-handers, i.e., females with a greater bilaterality of cognitive functions than males.

Adolescent↗
PubMed1991

Serum testosterone levels in male and female subjects with standard and anomalous dominance.

Serum testosterone levels were determined in female and male subjects. Hand preference was assessed by the Edinburgh Handedness Inventory. Subjects with anomalous dominance (left-handers, mixed-handers, and right-handers with familial sinistrality) were compared to subjects with standard dominance (right-handers without familial sinistrality). The mean serum testosterone levels were found to be significantly higher in subjects with anomalous dominance than those with standard dominance. It was concluded that the results are in accord with the testosterone hypothesis of cerebral lateralization.

Adolescent↗
PubMed1978

Electrocorticographic effects of topically applied scopolamine.

The electrocorticographic effects of topically applied scopolamine were investigated in unanesthetized cats with high cervical transection. After subpial injection of 30 cumu scopolamine in concentrations of 10 to 20%, large amplitude intermittent sharp waves appeared in the electrocorticogram, which developed into long-lasting paroxysmal activity. This effect was antagonized by intravenous eserine, 0.1 mg/kg, when it was produced by topical scopolamine in low dosage. The acoustically evoked cortical response and the generalized epileptiform activity produced by topical succinylcholine disappeared after topical scopolamine in low dosage. It is suggested that the seizure-suppressing effect of scopolamine may be due to its cholinolytic action. The convulsive activity of topical scopolamine in high concentrations may be accounted for by its depolarizing, synchronizing, disinhibiting, and acetylcholine-releasing effects.

Administration, Topical↗