Immunogenetic ontogeny of cellular membrane function: a review

Similarities and dissimilarities of newborn and adolescent rats in the binding capacity of thymic glucocorticoid receptors

The glucocorticoid receptor of the newborn thymus binds dexamethasone with the same specificity, as the adult ones. The best competitors of dexamethasone on the glucocorticoid receptor are dexamethasone itself and mifepristone (RU486). Estradiol can compete with dexamethasone on the glucocorticoid receptor. This is true in the case of newborn or adolescent thymus alike. Allylestrenol can slightly compete with dexamethasone on the glucocorticoid receptor in newborn, however this does not occur in adolescents. The other ligands - causing imprinting or imprinting like phenomenon earlier -- as tocopherol, menadione, retinoic acid, vitamin D(3) -- do not compete in vitro with dexamethasone on the thymic glucocorticoid receptor in newborn and adolescent animals. Possibilities of imprinting mechanism, considering the results are discussed.

Effect of single neonatal vitamin D3 treatment (hormonal imprinting) on the bone mineralization of adult non-treated and dexamethasone treated rats

Hormonal imprinting (the first encounter between the hormone and receptor after birth) is needed for the normal development of receptor. Presence of the appropriate hormone in excess, or its absence, as well as presence of hormone-like molecules able to bind to the maturing receptor in this time, can cause faulty imprinting. In this experiment the effect of neonatal treatment with a single dose of 0.05 mg cholecalciferol (vitamin D3) was studied by bone densitometry. The treatment caused significant decrease of body weight in 3-month old females and also significant reduction of bone mineral density (BMD) and bone mineral content (BMC) in males. Dexamethasone treatment of 3-month old rats for 10 days increased BMD in males and BMC in females without affecting body weight. The double treatment (vitamin D neonatally and dexamethasone when adult) decreased the body weight of both sexes and increased BMD in males, and BMC, BMD/bw and BMC/bw in both sexes, related to the control or the only vitamin D treated groups. Considering the hormonal imprinting effect of neonatal vitamin D treatment at glucocorticoid receptorial level in other experiments, similar effects also can be supposed for vitamin D itself, manifested in the changes of bone mineralization.

Effect of combined neonatal imprinting by vitamin A, vitamin D3, benzpyrene and allylestrenol on adult rat thymus glucocorticoid and uterine estrogen receptors

1. Combined neonatal imprinting with allylestrenol, vitamins A and D3 and benzpyrene significantly increased thymic glucocorticoid receptor capacity in male and female animals and decreased receptors affinity in adult females only. 2. Uterine estrogen receptor affinity or density was not influenced. 3. Considering that perinatal treatment with allylestrenol or vitamin D3 decreased glucocorticoid receptor capacity, the dominance of the positive effect of retinol should be surmised. 4. The experiments call attention to the interrelation of different materials acting simultaneously in the perinatal period.

Transgenerational effect of a single neonatal benzpyrene treatment (imprinting) on the sexual behavior of adult female rats

Male and female rats were neonatally treated with a single dose of benzpyrene. The adult animals were mated inter se, forming control-control, benzpyrene (female)-control, benzpyrene (male)-control, and benzpyrene-benzpyrene treated couples. In the F1 and F2 generations (without any further treatment) the females's sexual behavior was tested to Meyerson index and lordosis quotient after ovariectomy and hormone treatment, using experienced males. In the F1 generation both indices were significantly reduced in the maternally treated, paternally untreated groups, however this reduction was not present in the group where the treatment was maternal and paternal alike. In the F2 generation, beside the more expressed reduction in the grandmaternally treated group, a moderate reduction in the sexual activity of progenies having treated grandfather or two treated grandparents were observed. The experiment call attention to the transgenerational sexual behavioral effect of a dangerous environment pollutant, benzpyrene.

Breastmilk can mediate chemical imprinting. Benzpyrene exposure during lactation reduces the thymic glucocorticoid receptor density of the offspring

1. Prolonged benzpyrene treatment during lactation reduced the number of glucocorticoid receptors of offspring in adulthood significantly without altering the receptor affinity. 2. Dexamethasone treatment identical to benzpyrene exposure had no effect either on receptor number or affinity. 3. The results of the present investigations draw attention to the possible way of receptor alteration via breastmilk.

Impact of neonatal treatment with cardioactive glycosides (digoxin, ouabain) on receptor binding capacity, blood level and cardiac function in the adult rat. Extension of the imprinting theory

A single neonatal treatment with a cardioactive glycoside (ouabain, digoxin) altered the response of the adult rat to digitaloid treatment. As demonstrated by RIA, re-exposure to digoxin at 2 months of age was followed within 30 min by a more than twofold increase in serum digoxin over the not pretreated control and, although a steady concentration decrease followed, the experimental rats still had a higher serum digoxin level than the controls at 4 h. In the not presensitized control group the serum digoxin peak appeared at 60 min at a considerably lower level than the 30-min maximum of the experimental rats. Neonatal pretreatment with ouabain depressed myocardial ouabain binding, but enhanced the Na+ K+ -ATPase activity. The above differences were conspicuous in the functional response, yet a greater atrial response to the positive inotropic action of K-strophanthoside and a greater ventricular response to beta adrenergic excitation were readily seen in the experimental group. It follows that not only hormones, but also other ligands acting at receptor level can be regarded as potential inducers of imprinting.

An attempt to differentiate selection and amplification in hormone receptor development: the unicellular model

Earlier experiments demonstrated that a membrane pattern of Protozoa behaves as a receptor with respect to hormones of higher organisms. This raised the possibility that some selection or strengthening of this unspecific patter is involved in the evolution of the specific membrane patterns of the individual cells of higher organisms. In the present experiments, as a result of continual histamine treatment, the phagocytotic ability of a population of Tetrahymena was increased more intensely than after a single histamine treatment. The phagocytotic rate remained high for some time after the animals were returned from histamine-containing to normal medium. Thus, from the experimental data, it appears likely that as the hormone appears, selection becomes involved in the proliferation of cells possessing receptors. This observation might not only be of phylogenetic interest, but could also be relevant in receptor maturation as manifested in ontogenetic membrane differentiation.

Quantitative variations of three different lectin receptors as a function of establishment and metabolism of normal and leukaemic human cell lines

Lectin binding on the cell surface was measured by the method of Kornfeld [16] using three tritiated lectins: Robinia pseudo acacia, Concanavalin A and Ricinus. It has been shown that the number of binding sites for Robinia and Con A decreases after the establishment of a leukaemic cell line, whereas the affinity constant increases for Robinia. The relationship between lectin binding and cell growth was carried out on 5 cell lines, 3 of leukaemic and 2 of normal origin. In all cases the maximum number of sites was determined at the time of doubling for the cell population; the affinity constant reciprocally decreases at this moment. For Robinia, a difference was found in both cell growth and the number of sites between an Epstein-Barr virus (EBV) negative leukaemic cell line and the other EBV positive cell lines. Lectins offer a quantitative method for measuring membrane structure variations during and after establishment of cell lines.