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Epithelial-mesodermal tissue interactions have been shown to be required for normal cytodifferentiation of chick embryo skin. Six-day limb skin does not develop in a protein free chemically defined medium, but keratinization has been observed in medium containing chicken serum. In the present study the authors show that the addition of human serum may stimulate the in vitro differentiation of explants of six-day chick embryo skin. Human serum is able to support skin keratinization and this finding has been confirmed by histological and histochemical criteria. Synthesis of proteins in tissue cultures supplemented with human serum has been studied by use of labeled amino acids such as H3-Leucine and C14-Cystine. These incorporation studies show the existence of macromolecular factors in human serum which may be responsible for the observed skin differentiation.

Mucous membrane's phragments from human normal and neoplastic larynx have been maintained in a organ culture system. A set of cultures has been prepared for optical microscope studies and a parallel set for incorporation studies using 3H Thymidine and 3H Leucine. The results show that there is a good incorporation of 3H Thymidine and a greater incorporation of 3H Leucine at the 7th day due to a differentiation in vitro with a new synthesis of cheratin. These data agree with the morphologic evidence of considerable horny structures in the pathological mucous membrane after 11 days at culture.

In the present work the Authors have studied the differentiation and the cellular multiplication of chick embryo skin incubated in vitro with normal human sera or with pathological human sera from patients affected by Kerion Celsi. In the following research the Authors have studied the skin structure by an optical and electron microscope and the thymidine 3H incorporation. The result demonstrates that the pathological human serum does not interfere with the multiplication and the differentiation of the skin in vitro, but displays a cytoaggressive action that induces a noticeable cytoplasmic vacuolation.

In the present study the authors have carried out further researches on the differentiation of six day limb skin from chick embryo cultured "in vitro" in a complete medium supplemented with histones. When histones were added to the medium in the first two days "in vitro", epidermal keratinization was not observed. However the addition of histones after four days "in vitro" did not interfere with epidermal differentiation.

Six-day limb skin from a chick embryo was cultured in vitro for seven days in a complete medium either supplemented or not with histones. At the end of the incubation period, the chick embryo skin cultured in the absence of histones was found to undergo keratinization, the converse being true for the limbs cultured in the presence of histones. In the latter, when H3-leucine and C14-cystine were added to the medium, a sharp decrease in the labeled amino acid incorporation was found.

An eterotopic grafting of their livers has been made between two inbred rats. From 30 to 50 days later the livers has been observed through OM or SEM. In the first case (OM) there was evidence of vacuolar degeneration of liver cells gradually decreasing on the 50th day. In the latter case (SEM) the morphological appearance remained unchanged.

Rat kidneys weighting between 250 and 300 g. were treated in HCl. A single nephron observed through SEM shows that the above treatment doesn't interfere with the ultrastructural morphology of nephron.