tetrahydrofolate Reduced FOLATE derivative that
contains additional hydrogen atoms in positions 5, 6,
7,and 8. Tetrahydrofolates are the carriers of activat-
ed one-carbon units and are important in the biosyn-
thesis of amino acids and precursors needed for DNA
synthesis.
See alsoFOLATE COENZYMES.
tetrapod Any vertebrate organism that has four
limbs, or two sets of limbs, e.g., mammals, reptiles,
birds, amphibians.
thalamus Consists of two egg-shaped masses at the
base of the brain that form the dorsal subdivision of
the diencephalon (forebrain) and that function together
as a unit. The thalamus acts as switching relay, receiv-
ing sensory data from the nervous system and escorting
it to the cerebral cortex and other parts of the brain. In
botany, it is the receptacle or torus of a flower.
thalassemia A chronic inherited disease character-
ized by defective synthesis of HEMOGLOBIN. Defective
synthesis of the αchain of hemoglobin is called α-tha-
lassemia, and defective synthesis of the ß chain of
hemoglobin is called ß-thalassemia. Thalassemias result
in anemia that can be severe and are found more fre-
quently in areas where malaria is endemic.
Theiler, Max (1899–1972) South AfricanMicrobiol-
ogist Max Theiler was born on January 30, 1899, in
Pretoria, South Africa, to Sir Arnold Theiler, a well-
known veterinary scientist, and Emma Theiler (née
Jegge). He attended Rhodes University College, Gra-
hamstown, and the University of Capetown Medical
School (1916–18). He then went to England to study at
St. Thomas’s Hospital and at the London School of
Tropical Medicine, receiving a medical degree in 1922.
In 1922 he joined the department of tropical
medicine at the Harvard Medical School, Boston, Mas-
sachusetts. In 1930 he joined the staff of the Interna-
tional Health Division of the Rockefeller Foundation.
In 1951 he became director of laboratories of the
Rockefeller Foundation’s Division of Medicine and
Public Health, New York.
His early work dealt with amoebic dysentery and
rat-bite fever, but he wanted to produce a vaccine for
yellow fever, at the time a major disease in humans. By
1927 he and his colleagues had showed that the cause
ofyellow fever was not a bacterium but a virus and
was easily transmitted to mice, making research on the
subject cheaper. Theiler and his colleagues produced a
vaccine, 17D, against the disease. He was awarded the
1951 Nobel Prize in physiology or medicine for this
breakthrough.
He contributed to two books, Viral and Rickettsial
Infections of Man(1948) and Yellow Fever(1951), and
wrote many scientific papers. He also received numer-
ous awards, including the Chalmer’s Medal of the
Royal Society of Tropical Medicine and Hygiene (Lon-
don, 1939). He died on August 11, 1972, in New
Haven, Connecticut.Theorell, Axel Hugo Theodor(1903–1982)
SwedishBiochemist Axel Hugo Theodor Theorell
was born in Linköping, Sweden, on July 6, 1903, to
Thure Theorell, surgeon-major to the First Life
Grenadiers practicing medicine in Linköping, and his
wife Armida Bill.
Theorell was educated at a state secondary school
in Linköping and started studying medicine in 1921 at
the Karolinska Institute. In 1924 he graduated with a
bachelor of medicine and spent three months studying
bacteriology at the Pasteur Institute in Paris. He
received an M.D. in 1930 and became lecturer in physi-
ological chemistry at the Karolinska Institute.
In 1924 he became part of the staff of the Medico-
Chemical Institution as an associate assistant and tem-
porary associate professor working on the influence of
the lipids on the sedimentation of the blood corpuscles.
In 1931 at Uppsala University, he studied the molecular
weight of myoglobin. The following year he was
appointed associate professor in medical and physio-
logical chemistry at Uppsala University, and he contin-
ued and extended his work on myoglobin.
From 1933 until 1935 he held a Rockefeller fel-
lowship and became interested in oxidation enzymes.
Heproduced, for the first time, the oxidation enzyme
called “the yellow ferment,” and he succeeded in split-
ting it reversibly into a coenzyme part, which was
found to be flavinmononucleotide, and a colorless
protein part.324 tetrahydrofolate