Baeriswyl, C.

Claassen, H.

Howald, H.

Klissouras, V.

Lüthi, Y.

Moesch, H.

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GENETIC BASIS O F I N D I V I D U A L DIFFERENCES I N TISSUE C O M P O S I T I O N TATSUYUKI OHTSUKI, VASSILIS KLISSOURAS University of Tokyo, Japan McGill University, Montreal, Canada A total of 19 pairs of twin adolescent boys, 14 MZ and 5 DZ, were used to determine the relative contribution of the genotype to the individual differences observed in sur-face density of muscle, subcutaneous fat, and bone. The cross-sectional areas of these tissue components were calculated from pho-tographs of the upper arm, taken by means of an ultrasonic apparatus. Results are giv-en in the table below, showing the mean percentage intrapair differences and the F-ratio of (a) the cross-sectional area of the three tissue components (upper part), and Muscle 6-55 7.82 0.231 2.58 5-69 7-783 Fat |H 14.04 19-35 2.072 Bone 6.70 3'-a5 10.834 9-25 24.07 3.267 (b) the relative contribution of the different tissues to the total area (lower part). Interindividual variations in bone only could be ascribed to genetic differences. Prof. Vassilis Klissouras, Mitropoleos 15, Athens, Greece U L T R A S T R U C T U R A L AND ENZYMATIC DIFFERENCES IN SKELETAL MUSCLE O F T W I N S C. BAERISWYL, Y. LUTHI, H. CLAASSEN, H. MOESCH, V. KLISSOURAS, H. HOWALD Research Institute of the Federal School of Physical Edu-cation, Magglingen, Switzerland Biopsies were taken from the vastus lateralis muscle of 16 twin pairs, 10 MZ and 6 DZ, and were analyzed by electron microscopy, stereological and enzymatic methods for (a) the morphometric parameters: volume density of myofibrils, volume density of mitochondria, volume density of cytoplasm, surface density of inner and outer mito-chondrial membranes, and mitochondrial volume to myofibril volume ratio; (b) the activities of mitochondrial enzymes: Succinate Dehydrogenase, Malate Dehydro-genase, and Hydroxyacyl-CoA-Dehydroge-nase; (c) the activities of extramitochondrial en-zymes: Hexokinase and Glyceraldehyde-3 P-Dehydrogenase. A comparison of the intrapair differences between MZ and DZ twins showed no sig-nificant differences for all the above men-tioned variables, but the activity of the Hydroxyacyl-CoA-Dehydrogenase. On the basis of this evidence it was concluded that interindividual variability observed in the cellular metabolic equipment is conditioned primarily by extragenetic influences. More-over, it was noted that cellular intrapair differences could not explain intrapair dif-ferences measured in Vo2 max. Prof. Vassilis Klissouras, Mitropoleos 15, Athens, Greece D I S T R I B U T I O N O F BLOOD GROUPS, SALIVARY B L O O D - G R O U P SUBSTANCES AND NATURAL ANTIBODIES, IN A SAMPLE O F MZ TWINS D. P. PACE, F. SACCUCCI, F. BRITTI, D. CASINI Department of Biology and Genetics, Medical School, Uni-versity of Ancona, Italy The Gregor Mendel Institute of Medical Genetics and Twin Research, Rome, Italy The distribution of AjA^BO, MN, and Rh-Hr blood groups, of salivary ABH sub-stances, and of natural antibodies, was as-sessed in a sample of 60 MZ twin pairs. Titrations were made for ABH substances and for antibodies. The resulting distribu-tion provides indications as to the level of genetic control over the quantitative expres-sion of these traits. Prof. D. P. Pace, Istituto di Biologia e Genetica del-l'Universita di Ancona, Italy 30 https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S1120962300022769Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 11 Jul 2017 at 15:51:03, subject to the Cambridge Core terms of use, available at

Ultrastructural and Enzymatic Differences in Skeletal Muscle of Twins

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