Thesis (Ph. D.)--University OF MICHIGAN.

Thesis (Ph. D.)--University OF MICHIGAN.

Thesis (Ph. D.)--University OF MICHIGAN.

An "autograph", also known as a "radioautograph", "autoradiography or "historadiograph", is the "signature" left by a radioactive particle in a photographic emulsion, and is, therefore, the visual evidence of the presence of radioactivity in the structure in contact with the photographic emulsion. Radioisotopes present in biological material may be detected in two ways: 1) chemically, using the Geiger counter method and 2) histologically, using the above photographic technique - autography. It is the latter technique, however, that not only reveals the presence of the radioisotope within the specimen but also allows the isotope to be traced to its precise site in the tissue structure.

If one accepts the hypothesis that in general the development of a new structure in the animal kingdom follows closely upon the demand for a new function, then the original function of a given structure can be determined by tracing it backwards in the animal scale to the point at which it first appears and noting the particular functional demand acting on the organism at that time. It will be seen that his original function need not be retained, but rather may be lost or transferred to some other structure, and the original structure adapted to some other use.

Nowadays it is customary to regard all cells as miniature physical-chemical factories with specializations particular to each tissue or organ. The activity of cells may involve only the synthesis of substances for the upkeep of the cells themselves, or, in addition, the synthesis of substances to be released to the outside. In the latter case, raw materials are taken into the cell, incorporated into some new substance, and then released in this new form into the extra-cellular spaces or to the outside. The activity of such a secreting cell can be subdivided into a number of phases. Those may be performed singly or simultaneously.

The use of P32 in biological investigation has contributed greatly to the knowledge of phosphorus metabolism. Soon after this isotope became available in the late 1930’s, many investigators studied the absorption, distribution and excretion of radiophosphorus in plants and animals. A large number of these studies were concerned with the identification and turnover rate of phosphorus compounds as they occur in tissue homogenates or various cellular fractions prepared by centrifugation.

Although during the last decades considerable information has been obtained concerning the nature of biochemical processes during development (Needham, 1942; Brachet, 1947), our knowledge with regard to the synthesis of new protein molecules, the essentialness of such molecules in determining the shape and function of a cell and organ, the reduplication of existing molecules during growth, and the localization of specific molecules in organ primordia, is far from satisfactory.

Ever since the introduction of iodine therapy, in the form of large doses of iodide, for the amelioration of thyrotoxicosis, the mechanism of action of large doses of iodide on the thyroid gland has remained a mystery. The inhibition of thyroid hormone formation has not been limited only to diseases of the gland, such as hyperthyroidism; for iodine has also been shown to have this influence in the thyroids of normal man and animals. Although many investigations of the effect of large doses of iodine on the thyroid gland have been made, the results are as conflicting as the various hypotheses which have been advanced.

The production of spermatozoa by the epithelium lining the seminiferous tubules of the testis is accomplished by a long and elaborate series of cytological transformations referred to as spermatogenesis. This process begins with the proliferation of spermatogonia by mitosis; then follows meiotic division of the spermatocytes with the resultant production of spermatids. These spermatids, without further division, transform slowly into spermatozoa which are subsequently released into the tubular lumen. This latter process of transformation is referred to as spermiogenesis. It is well known that spermatogenesis is under the influence of hormones.