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Theodore W. Rall (1928-2015) is an American pharmacologist and biochemist. He is best known for his work on the discovery of the second messenger cAMP. He has also worked with several established scientists, including Nobel prize laureates, Earl Sutherland, Alfred Gilman and Ferid Murad and Shaw Prize laureate, Sir Michael Berridge.

cAMP is a second messenger involved in intracellular signal transduction in many different organisms. cAMP is synthesized from ATP by adenylyl cyclase located at the cell membranes. It is important in regulation of metabolism by transferring the effects of the hormones glucagon and epinephrine into the cell. cAMP is also involved activating protein kinases and regulating the passage of Ca2+ through ion channels.

Biography
Theodore W. Rall was born in Chicago in 1928. His father was a civil engineer for the Illinois Central Railroad and his mother was a homemaker. Rall was the younger of two sons. His family placed a high value on hard work; in fact, his mother re-entered the workforce as an accountant after her sons were grown.

Education
Rall showed an interest in science from a young age. He excelled in chemistry and biology in high school and entered the University of Chicago in 1944. He received a PhB in 1946, a Bachelor of Science in 1948 and a PhD in Biochemistry in 1952. He never formally earned a degree in Pharmacology as the field was underdeveloped when he received his education.

Career
After obtaining his doctorate in Biochemistry, Rall was drafted into the Army. Shortly afterward he learned that the chair of the newly formed Pharmacology department at Case Western University in Cleveland was looking to hire new faculty members. He visited Case Western in Cleveland while on leave and his interest was piqued by the biochemical-sounding projects the department was working on. Rall was hired by Case Western Medical School as a laboratory instructor and the university arranged for him to be excused from serving in the army. He relocated to Cleveland immediately. His first two years were spent teaching medical students procedures in which he knew little more than the students themselves. In 1956 he was given the job of auditing the second year medical school curriculum, which was the year that concentrated mostly on pharmacological material. While taking all the second year courses and exams he became increasingly interested in the field of pharmacology<ref name="interview" / In that same year, Rall began working in the lab of Earl Sutherland who was studying hormone-stimulation action in cells. Sutherland would later win the Nobel Prize for a paper on the discovery of cyclic adenosine monophosphate on which Rall was a contributor. When Sutherland left Case Western University in 1963. Rall established his own lab. Ferid Murad and Alfred Gilman, both of whom would go on to win the Nobel Prize, worked in the lab and both of whom acknowledge Rall as an important mentor. Rall was also a consultant to some of the early experiments conducted by Michael Berridge, a future Shaw Prize winner. Despite never formally obtaining a degree in Pharmacology, Rall had established himself as a prominent figure in the field by the time he left Case Western University in 1975. He took a position as a Professor of Pharmacology at the University Of Virginia School Of Medicine in Charlottesville. He continued to teach and conduct research until his retirement in 1995. His impressive body of work earned him the title of Professor Emeritus. Rall currently resides in Charlottesville, Virginia

Discovery of cAMP
Rall’s work with Sutherland would eventually lead to the discovery of cAMP, the first identified second messenger. The two initially investigated the effects of the hormones epinephrine and glucagon on liver phosphorylase. In the course of their research, they came across a heat-stable, dialyzable factor that was generated when the hormones were present. This factor was subsequently found to be involved in the formation of liver phosphorylase and was thus termed, “active factor. Their experiments were conducted using cell-free systems — a radical idea at the time. The general notion among scientists in the 50s was that intact cells were required when performing hormone studies. It was Rall who convinced Sutherland to use homogenates—prior to this they were using liver slices. Rall initially chose rat liver to work with because of its involvement in much of mammalian biochemical discoveries. After numerous failed attempts, Rall switched to dog liver, which was used in all of Sutherland’s previous experiments on phosphorylation. When he added the hormones to the fortified homogenates, the rate of phosphorylation was observed to be nearly twice as fast as in the liver extracts as he had used an excessive amount of dog liver in performing the first assay. Subsequent experiments involved centrifuging the homogenates as they thought that it would eliminate cellular debris. Rall’s method of centrifuging homogenates did not have a well-defined protocol. He would spin the homogenates using an angle rotor just enough to produce “something reasonably smooth that could be pipetted .” He would then pour out and collect the supernatant. This fraction was initially found to be responsive to hormones. A postdoc in Sutherland’s lab, Jacques Berthet (who also collaborated with Rall and Sutherland on their landmark paper) modified Rall’s procedure to make it more precise. He prescribed the use of a horizontal yoke instead of the angle rotor and set specified times and centrifugation speeds for different amounts of homogenate. The supernatant fractions were collected by aspiration. Rall found that when he used Berthet’s protocol, hormone response was lost in the supernatant fractions. However, they soon discovered that hormone response was restored if particulate (membrane) fractions were added to the supernatant fractions. Follow-up experiments were performed in two stages. In the first stage, they incubated particulate fractions with hormones and heated them. Magnesium and Adenosine triphosphate were added in this stage as a previous study done by Edwin Krebs and Edmond Fischer demonstrated the need for Mg and ATP in phosphorylase activation. In the second stage, they added this mixture to the supernatant fractions. They found that hormone response in homogenate fractions was similar to the response generated in whole homogenates. Two critical points regarding liver phosphorylation can be derived from these experiments. First, hormone response occurs in two stages. Second, a heat-stable factor is produced when the particulate fraction is incubated with the hormones in the first stage. This factor then activates phosphorylase when it is added to the supernatant fraction in the second stage Following the elucidation of the active factor’s components, it was renamed 3'-5'-cyclic adenosine monophosphate. cAMP is now known to be involved in a variety of biological processes, including sugar and lipid metabolism. The discovery of cAMP eventually brought about the concept of a second messenger system, wherein a hormone (the first messenger) binds to a receptor on the cell surface and a second messenger within the cell relays the signal to target molecules in the cytosol/nucleus.

Nucleotide/hormone-induced cAMP production in the brain
In the sixties, Rall collaborated with Shiro Kakiuchi (who would later discover calmodulin ), and Sir Henry McIlwain in investigating the effects of different agents on cAMP accumulation in brain slices. In rabbit cerebellum and cerebral cortex slices, norepinephrine and histamine were found to induce cAMP accumulation. They also tested the effects of a known adenosine receptor antagonist, theophylline. It had little effect on cAMP in rabbit cerebellum slices but when used in conjunction with norepinephrine, cAMP accumulation was found to be greater than with norepinephrine alone. Both hormones were also found to exhibit additive effects. Phenoxybenzamine, diphenhydramine blocked the effect of histamine, though they exerted a lesser influence on norepinephrine; Dichloroisoprenaline had the greatest influence on inhibiting the effects of norepinephrine. In rabbit cerebral cortex slices, theophylline had negligible effects on cAMP accumulation. But when histamine was present with the inhibitor, cAMP increase was threefold. On the other hand, norepinephrine-induced cAMP accumulation was not as high as the numbers observed in cerebellum slices. Electrical pulses also led to an increase in cAMP levels in guinea pig cerebral cortex slices. When norepinephrine or histamine was present in maximal amounts, the effect of the electrical pulses was increased. These results indicate the important regulatory role of cAMP in the central nervous system. Rall also worked with Albert Sattin in studying the effects of adenosine and adenine nucleotides on cAMP levels in guinea pig cerebral cortex slices. Exposure of either adenosine or adenine nucleotides to guinea pig cerebral cortex slices produced an increase in cyclic adenosine 3',5'-phosphate production. Methylxanthines inhibited the effect of adenosine. However this inhibition could be reversed with the further addition of adenosine. When combining adenosine with norepinephrine or histamine, a mutual potentiation effect was observed—higher cAMP accumulation was present compared to hormone alone. For the rest of his career, Rall would devote his research to studying the interaction of adenosine with neural hormones. His work with R.F. Shonk involved examining the effects of norepinephrine, histamine and adenosine (either alone or in combination) on the accumulation of cAMP in guinea pigs’ cerebral cortex at 40 to 68 days of gestation. They observed that histamine induced an increase in cAMP levels at 40 days and reached its maximal value at 55 days, declining afterward. Adenosine caused an observable response at 44 days and reached a peak value at 55 days. On the other hand, Norepinephrine only induced a small increase throughout the whole period. When combinations of pairs of hormones/nucleotide were used, response was much greater compared to hormone/nucleotide alone. Response was apparent at 42 days and reached a peak value by 47 to 48 days. Induced responses in fetal tissue were found to be similar to responses in adult tissue in the following ways: 1) α-adrenergic receptors served as norepinephrine targets (in the presence of either adenosine or histamine) and 2) H1 receptor antagonists inhibited histamine when adenosine was present while H2 receptor antagonists inhibited histamine when adenosine was absent.

Key papers
-	Glutathione reductase of animal tissues -	The relationship of epinephrine and glucagon to liver phosphorylase. III. Reactivation of liver phosphorylase in slices and in extracts -	The relationship of epinephrine and glucagon to liver phosphorylase. IV. Effect of epinephrine and glucagon on the reactivation of phosphorylase in liver homogenates -	 The assay of glucagon and epinephrine with use of liver homogenates -	Fractionation and characterization of a cyclic adenine ribonucleotide formed by tissue particles -	Formation of a Cyclic Adenine Ribonucleotide by Tissue Particles -	Adenyl cylase. I. Distribution, preparation, and properties -	Adenyl cyclase. II. The enzymatically catalyzed formation of adenosine 3',5'-phosphate and inorganic pyrophosphate from adenosine triphosphate -	Adenyl cyclase. III. The effect of catecholamines and choline esters on the formation of adenosine 3',5'-phosphate by preparations from cardiac muscle and liver -	Adenyl cyclase. IV. The effects of neurohormones on the formation of adenosine 3',5'-phosphate by preparations from brain and other tissues -	The potentiation of cardiac inotropic responses to norepinephrine by theophylline -	The influence of chemical agents on the accumulation of adenosine 3',5'-Phosphate in slices of rabbit cerebellum -	Studies on adenosine 3',5'-phosphate in rabbit cerebral cortex -	The effect of electrical stimulation upon the accumulation of adenosine 3',5'-phosphate in isolated cerebral tissue -	Conditions for the formation, partial purification and assay of an inhibitor of adenosine 3',5'-monophosphate -	The effect of adenosine and adenine nucleotides on the cyclic adenosine 3', 5'-phosphate content of guinea pig cerebral cortex slices -	Role of adenosine 3',5'-monophosphate (cyclic AMP) in actions of catecholamines -	Regulation of cyclic adenosine 3',5'-monophosphate levels in guinea-pig cerebral cortex by interaction of alpha adrenergic and adenosine receptor activity -	Ontogeny of adenosine 3',5'-monophosphate metabolism in guinea pig cerebral cortex. I. Development of responses to histamine, norepinephrine and adenosine