G. Brenci

Sleep and dream characteristics in twins.

A study of sleep and dream characteristics has been carried out by questionnaire on a sample of 77 MZ and 76 DZ same-sex twin pairs of two age groups, 6-8 and 16-18 years. Genetic effects could not be detected in the younger age group and appeared to be rather limited in the older one, possibly as a result of the limited variability of the considered variables and of the levelling influence of the common environment.

HUMAN MONOZYGOTIC AND PLURIZYGOTIC MULTIPLE BIRTHS: HEREDITY AND HORMONE ACTION.

The Authors take once more into consideration the problem of the hereditary nature of twinning on the basis of their own studies and of recent findings on human twinning induced by human menopausal gonadotropin (HMG). Personal studies concern 3,221 cases of twinning drawn from the special files (“Gemelloteca”) of the Mendel Institute. On the basis of this material the Authors state that the occurrence of the cases of twinning in the paternal and maternal ascendancies of the twin index cases is significantly more frequent than would be expected in proportion to the frequency of twinning events in the Italian population. This finding is in agreement with the hypothesis of the hereditary nature of the twinning phenomenon. The same material is used to compare the frequency of twinning in the paternal and maternal families of twins. The observed frequency in the maternal families is significantly higher than in paternal families in which the frequency approximates population values. This finding leads the Authors to formulate the hypothesis that the twinning trait is limited to the female sex and is presently manifested by the occurrence of twins in the next generation. Thus studies on the frequency of twinning as a hereditary phenomenon should be based on the families of the mothers of twins. Original studies also concern the 1,105 triplet sets born in Italy in the years 1952-1961. A study of the experimental and theoretical distribution of sex combinations in this triplet material allowed the Authors to prove that the experimental distribution differs from the theoretical one, based on the hypothesis of independence of the two types of zygosity (MZ and DZ). The absence of independence is considered a proof of the hereditary singleness of twinning. The Authors further take into consideration cases of twinning induced in sterile women by administration of human menopausal gonadotropin (HMG): they observe that cases reported to date seem to be limited to dizygotic or plurizygotic twinning. These findings lead the Authors to believe that in this case hypophyseal FSH, responsible for ovulation, fails to find the usual pathway leading to standard uniparous pregnancy in the human species; the mechanism involved in such pathway is the object of some hypotheses of a hormonal nature. The Authors also believe that FSH stimulates not only the follicle but also follicular gametogenesis and even perhaps the division of the fertilized egg resulting in MZ twinning.

Chronology of the Gene

1. GENETIC DETERMINATION OF BIOLOGICAL T I M E ( T H E ERGON/ CHRONON SYSTEM) 324 1.1. The Times of the Gene 324 1.2. A Scientific and Medical Problem . 325 1.3 Physical Time and Biological Time 325 1.4. The Hereditary Imprint of Biological Time 327 1.5. Variability among Species, Populations, Families, and Individuals . . 327 1.6. The Temporal Dimension of the Gene 330 1.7. Experimental Verification 331 1.8. The ErgonjChronon System . . . . 332

Chronological Development of Bones and Teeth A twin study

The hereditary component of the chronological development of bones and teeth has been studied, in 40 twin pairs aged 5-7 years, through dental age (defined on account of the mineralization of the permanent dentitions dental buds) and bone age (denned on account of the presence and form of the hand ossification nuclei). The statistical analysis shows a correlation coefficient of 0.95 in MZ and 0.84 in DZ twins for dental age; and of 0.94 in MZ and 0.81 in DZ twins for bone age. The following are therefore the estimates of the hereditary component (based on Holzingers formula) for the two parameters studied:

Chronogenetics. Its Foundations, Scope, and Impact

Many chronological correlations in different plant and animal species, in populations, in human families, and between cotwins, prove the existence of characteristic biological times. Some such times also tend to be related to cosmic time, in which they develop and from which they are induced, resulting in peculiar composite times, such as the daily, monthly, or annual rhythms, that are the object of study of chronobiology. Beyond these examples of exogenous chronological induction, the existence of a hereditary biological time is postulated, as the basic phenomenon in the relationship between time and life. The newborn scientific branch of “chronogenetics” is devoted to the study of the fundamental, endogenous genetic time, with its theoretical and practical, normal and pathologic implications. To explain and interpret the mechanisms of the hereditary biological time, the authors have developed a model based on the concepts of “ergon” (i.e., stability of the gene) and “chronon” (i.e., lifespan of the information). This Ergon/Chronon System is related to the gene, bringing into focus the fourth dimension and the dynamic aspects of unit of inheritance. The applications of chronogenetics extend to every expression of life, from the most primitive unicellular to the higher plants and animals. In the area of normal human traits, the study of the hereditary biological time contributes significantly to the interpretation of such phenomena as development, reproduction, homeostasis, and senescence. In the area of medicine, chronogenetics interpretes, unifies, and develops the temporal phenomena of inheritance. In a future perspective, chronogenetics appears to be fundamental for eugenics, preventive medicine, and prognosis.

Proposta del Test Gemellare Azigotico

Considering the development of the twin method the Authors deem it necessary to review the various systems of analysis presently used. They therefore design a method by which the twin material may be used even when zygosity is unknown. The Authors give this method the name of Azygotic Twin Test (T.G.A.), explain it theoretically and also give a practical example of analysis. The Authors plan to make - new studies on the subject, in order to show further possible developments of this method.

Presence of an endothelioid tubelike structure at the interface of the amniotic membranes in twins with single and double placenta. Growth factors involvement.

A histomorphological study of the amniotic membranes in full-term twins with double and single placenta was carried out by means of the silver impregnation staining technique suitably modified. Specimens of interface of amniotic membranes were prepared by means of sections. The constant presence of a tubelike structure was observed. Proceeding from the amniotic cavity, the following histological layers were noted. 1) single layer of amniotic cells; 2) amorphic substance with fibrocytes; 3) single layer of endothelial cells. The same order of single layer is present in the amniotic membrane of the second fetus. This tubelike structure is present only in cases of twins with double placenta. If the placenta is single with two umbilical cords, the tubelike structure is not present and only a central amorphic substance surrounded by two single layers of amniotic cells is observed, to confirm the single embryogenetic derivation (monovular). Therefore, through this histological method, we can recognize the true single placenta of twin pregnancy from the pseudosingle placenta so said for the presence of adherences of adjoining surfaces that make it appear single. On the contrary, by manual dissection it is possible to identify a twin pregnancy with two placentae. From the physiological point of view, the walls of the tubelike structure have probably the function to realize exchanges of amniotic liquids between the two fetuses, so as to obtain a balance of electrolytic ions and of intercavity pressure. Growth factors (vascular endothelial factor) are probably involved in the genesis of the endothelial tubelike structure.

A stochastic model of the genetic predisposition to ageing: an application to twin data.

In previous papers a stochastic model of the ageing process has been proposed. Some genetic parameters (redundance, repair) have been used to explain the observed differential predisposition to the process and family heredity. Because the process is basically due to effective random mutations, any individual of the population would be predisposed differently to ageing according to the structure of his/her genome. In the present paper, the previous model is generalized to take into account an additional genetic parameter, namely, the stability against random mutations, defined as the probability that a random mutation in a codon would produce no mutation in the corresponding protein. Estimation problems connected with the model are approached on the basis of twin data in maximum likelihood estimation as well as in bayesian framework. Some comparisons between the two methods are reported.

The Genetic Conditioning of the Mitotic Index and the Association Index of Acrocentric Chromosomes — A twin study

The authors have studied the variations of the mitotic index and the association index of the acrocentric chromosomes (groups D and G) in eight male twin pairs of assorted age (6 and 60 years) and zygosity. For each individual, two subcultures of peripheral blood lymphocytes have been set up by the standard techniques. After colchicine administration and hypotonic shock, two slides per culture have been prepared and stained with lactoacetic orcein, thus providing the experimental material. The study of variability between individuals, between tests and between age groups indicates the importance of the age factor for the assessment of both indexes. The study of the variability of intrapair differences indicates that the phenomena are both statistically and dynamically genotype-dependent. The weight of heredity, in the sum of all the factors affecting the phenomena, is 0.79 for the mitotic index and 0.51 for the association index.