Шарль Филипп Леблон: Қанадалық ғалым және жасуша биологиясының іргесін қалаушы

Canadian cell biology researcher, professor

Charles Philippe Leblond (February 5, 1910 – April 10, 2007) was a pioneer of cell biology and stem cell research and a Canadian former professor of anatomy. Leblond is notable for developing autoradiography and his work showing how cells continuously renew themselves, regardless of age.

CP Leblond was born in Lille, France, in 1910, the son of a building contractor who died when Leblond was only 10 years old, leaving his mother to raise four boys on her own. A brilliant student, Leblond debated becoming a film producer, an architect or a scientist. In the end, he decided on science, and enrolled in Medicine at the University of Paris. He was fascinated by his first course in histology and decided to pursue this field as a career. Leblond obtained his M. D. degree from the University of Paris in 1934. His doctoral thesis described the histochemical localizion of ascorbic acid, which he found to predominate in steroid secreting cells. This study led him, with a Rockefeller postdoctoral fellowship in hand, to the endocrinology orientated Department of Anatomy at Yale University in 1935, where he carried out studies on factors influencing maternal behavior. It was here that he met his wife Gertrude Sternschuss, to whom he was married for 64 years. Leblond had 4 children for which he chose names starting with the letter "P": Philippe, Paul, Pierre and (Marie) Pascale. He also had 7 grandchildren. In 1937, Leblond joined the Laboratoire de Synthese Atomique in Paris which was involved in preparing radioactive isotopes for use in investigating the fate of various molecules in biological processes. Under the guidance of Antoine Lacassagne, Leblond injected radioiodine 128, into a rat and found that the label promptly accumulated in the thyroid gland, presumably incorporated into the thyroid hormone precursor thyroglobulin. To localize this label more precisely within the thyroid tissue, Leblond attempted to use the novel technique of autoradiography. Unfortunately, Leblond's first attempt to use autoradiography failed, the reason being that the radioiodine 128 isotope, with its extremely short half life (25 minutes), disintegrated so quickly that too little radioactivity remained to be detected by the photographic emulsion.

In 1941, Leblond moved to McGill University as a lecturer in histology, and quickly rose to assistant (1943), associate (1946), and then full professor of anatomy (1948). He served as the chair of the Department of Anatomy from 1957 to 1974. At McGill, Leblond used the newly available radioiodine 131 with a half life of 8 days, to repeat his autoradiographic experiment on thyroid tissue. With this method, the resolving power was less than 100 μm, but nonetheless he was able to localize the radioactivity to specific thyroid [follicles]. Leblond's early career at McGill was interrupted by World War II, during which he served in the Free French Forces. He was dispatched first to Rio de Janeiro, then to London, where he conducted medical exams of would be soldiers. "In 1946, after returning to Montreal from service with the Free French Forces, it was clear to me that the crude technique previously used for radioautography had to be improved". In collaboration with Leonard Bélanger, Leblond worked on increasing the resolution of the autoradiographic technique. They were advised by physicist Pierre Demers to melt the emulsion from Eastman Kodak lantern slides, paint it directly on the sections, and then develop the emulsion while it was still attached to the histologic sections. This resulted in a tenfold improvement in resolution. Subsequently, Leblond and his colleagues developed a technique in which the histologic slides were dipped directly into liquid emulsion. The use of thinner sections and emulsion coats led to further advances in resolution, and the introduction of tritium was a technical milestone. High Resolution Autoradiography procedure continues to be used today by molecular biologists to detect RNA molecules in situ, and to study the localization of genes and DNA sequences.

Leblond used autoradiography to introduce radioactive precursors of DNA and then examine the renewal and fate of cells of several basic tissue types. He demonstrated for the first time that most cells and tissues in the adult body undergo continued renewal. Using mathematical models and modern methods of quantitation, Leblond and his colleagues estimated with remarkable accuracy the turnover and mitotic rates of numerous cell types. He and his colleagues made fascinating discoveries that resulted in the introduction of "time dimension" to cells and tissues, opening the doors to the understanding of the cell cycle and to the identification of stem cells.

When Leblond and his colleagues used 14C bicarbonate, and then 35S labeled amino acids to investigate protein synthesis, they were astonished to find that virtually all cells in the body incorporated label. This led them to the conclusion, considered heretical at the time, that all cells continually synthesized proteins. This was among the first evidence to replace the Specificity concept with the idea that most cells are multipotential in their functions. It is of interest that autoradiographic studies by Leblond during this period also settled a controversy regarding the cellular site of synthesis of ribonucleic acid. Using radiolabeled cytidine in some forty cell types, he and his colleagues were the first to demonstrate decisively that RNA is continuously synthesized in the nucleus and then migrates to the cytoplasm.

A majority of body proteins is glycosylated, although the proportion of carbohydrates in proteins is quite variable. Leblond had shown in earlier studies that the Golgi region in most cell types was dramatically stained by the periodic acid Schiff staining technique, which is specially directed to carbohydrate rich proteins carrying 1,2 glycols. In the electron microscope, using the periodic acid silver technique, there was a gradient of staining intensity from the cis to the trans side of the Golgi apparatus, suggesting that carbohydrate residues were added to proteins at this site. To test this hypothesis, light and then EM autoradiographic studies were carried out by Leblond and Neutra in 1966 after injecting rats with 3H glucose or 3H galactose. Within ten minutes, the label was dramatically localized to the Golgi apparatus of intestinal goblet cells, indicating that this was the cellular site of addition of sugar residues in the synthesis of the carbohydrate side chains of mucous glycoproteins. This discovery had a tremendous impact on the scientific community, being the first evidence for a functional role of the Golgi apparatus in the synthetic process.

Other classics include: identification of how skeletal bones grow through osteoblast deposition and osteoclast remodeling, early discovery of the biogenesis and metabolism of thyroxine and detection of triiodothyronine, early prediction of DNA semiconservative replication published days after the Watson and Crick Nature article, the discovery of axonal transport, the Warshawsky et al. finding that nascent proteins are processed from the rough endoplasmic reticulum through the Golgi apparatus into pancreatic zymogen granules (made in hot competition with the Palade lab at Rockefeller University), the first realization that the Golgi apparatus is the site of terminal glycosylation, the discovery of the cell coat, the cellular biogenesis of collagen, and new insights into the ultrastructure of basement membrane.

At 65, instead of retiring, Leblond continued his research with an NIH Fogarty Scholarship at the National Institute of Dental Research, where he learned about immunohistochemistry. This launched a twenty year molecular exploration culminating in the concept of the basement membrane as an integrated polymer,

Leblond was preceded in death by his wife of 64 years, Gertrude Sternschuss, who died in 2000. After Gertrude died, Leblond married a childhood friend, Odette Lengrand, in 2001; they were both 91. Odette died in 2004.