February 2010

Ernest Everett Just: Experimental Biologist Par Excellence

In 1938, bereft of funding and rejected by many of his American colleagues because of his opposition to their reductionistic views, Just initiated a self-imposed exile in Europe. He took up research at the Station Biologique at Roscoff, a small French fishing village on the English Channel. But in 1940, the Nazis invaded the region around Paris, including Roscoff, and Just was forced to leave. He returned to the United States and Howard University. In 1941, however, he fell tragically ill with pancreatic cancer, and, by the end of October, he died.

A Variety of Scientific Contributions

Just-Horseshoes
Many researchers and instructors, including Ernest Everett Just, played horseshoes at the Marine Biological Laboratory during the summers.
Photo credit: Alfred Huettner and The Marine Biological Laboratory Archives.

Just’s contributions lay in several areas, including (a) the role of environmental factors in development; (b) the fast and slow blocks to polyspermy during fertilization; (c) experimental parthenogenesis; and (d) embryo morphogenesis.

Role of Environmental Factors in Development

Just investigated the effect of a number of variables – dilute or concentrated sea water, ultraviolet irradiation, temperature, hydration or dehydration— on embryo development. He was intimately familiar with the natural history and breeding habits of the animals whose eggs he studied, and he strove to apply what he learned about development in natural settings to the laboratory. He was very much concerned with what he called the “normality” of the egg, i.e., how well its condition in the laboratory corresponds to the natural, fertilizable state. In these respects, Just’s work shares much in common with what is known today as ecological developmental biology (see 10, 11), which focuses on development in its natural environmental context.

Fast and Slow Blocks to Polyspermy

Using only a light microscope, Just was able to observe the detailed structural changes that occur at the egg surface during fertilization. As early as 1919, he observed the “wave of negativity” that sweeps over the egg cell at the onset of fertilization envelope separation, preventing fertilization by more than one spermatozoon (polyspermy). He correctly reasoned that it was this wave, not the physical separation of the envelope, that is responsible for the initial block to polyspermy. Thus, Just is credited with being the first to infer what is known as the “fast block to polyspermy,” a phenomenon that subsequently has been shown to be due to a shift in egg cell membrane potential. Just also observed the “slow block to polyspermy,” a mechanical block which occurs as a result of the formation of the fertilization envelope itself. Just is best known for his inference and documentation of these two blocks to polyspermy.

Experimental Parthenogenesis

While at Woods Hole, Just investigated the effect of a number of factors on the artificial activation of eggs in the absence of sperm, a phenomenon known as experimental parthenogenesis. His work there led to the public disagreement he had with Jacques Loeb, a prominent biologist at the Rockefeller Institute for Medical Research (now Rockefeller University) in New York. Loeb believed that, by tapping into the power of parthenogenesis, humans could gain mastery over nature and engineer it to their benefit. Just was strongly opposed to Loeb’s reductionism, but he also was critical of what he considered to be Loeb’s sloppy experimental technique, which he felt had led Loeb to conclusions that were not valid. Just proved that the method of experimental parthenogenesis Loeb pioneered, known as the double treatment method, in which the egg is treated with hypertonic sea water and then butyric acid, was not sound. He showed that the order of treatment was entirely inconsequential and that only one of the two agents was needed to induce parthenogenesis. But what Just rebelled against most was Loeb’s notion that the egg’s activation was the result of something being done to the egg. In contrast, Just believed that the critical, operative feature behind the activation was an intrinsic property of the egg itself, namely its “independent irritability.” Moreover, this property of the egg was an epiphenomenon of the ectoplasm (the structured layer below the cell surface), which Just believed played the dominant role in development, heredity and evolution.

Embryo Morphogenesis

There is evidence that two of Just’s discoveries influenced some of the work for which pioneering embryologist Johannes Holtfreter is best known (12). First, Just’s discovery of the developmental stage-dependent adhesiveness of the blastomeres of the starfish cleavage embryo (8) contributed to Holtfreter’s discovery of tissue affinity, which is critically important during amphibian morphogenesis. Second, Just’s discovery of the independent irritability of the egg cell, mentioned above, strongly informed Holtfreter’s elucidation of autoinduction, the process by which amphibian gastrula ectoderm is induced by nonspecific agents to form neural tissue. An acknowledgment of these contributions extends the impact of Just’s work into the area of embryo morphogenesis, and it connects his work to important embryo research that is taking place today.

Challenging Established Views

It is clear from Just’s writings that he believed that life arose out of the complexity and structural integrity of living systems. In “The Biology of the Cell Surface” (7), he wrote that “life is the harmonious communion of events, the resultant of the communion of structures and reactions.” Just rejected purely mechanistic explanations, yet he also was not a vitalist. Rather, he took the middle position (3), embracing what is known as “organicism,” or materialistic holism, which posits that cells and organisms are “more than the sum of their parts” (9). According to this view, the properties of any level of organization (molecule, cell, tissue, whole organism) depend on the properties of the parts of the level below, as well as on the properties of the whole into which they are integrated. Moreover, properties are said to emerge out of the organizational complexity of the living system. This approach to biological investigation has much in common with what is known today as integrative systems biology, in which a top-down view is just as important as a bottom-up view for understanding the system.

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COMMENTS:

Great article, thanks for sharing. Antonio Vidal Pascual Clinical embriologyst

 

kewl

 

1 Comments

  • The Info was great but next time can you give a fuller explanation of the dates and put it in time order....Thanks!!

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