reduction The part of a redox reaction where the
reactant has a net gain of electrons and in which a dif-
ferent reactant must oxidize (lose electrons).
See alsoOXIDATION.
reductive elimination The reverse of OXIDATIVE
ADDITION.
reductive speciation Complete fusion of two previ-
ously independent evolutionary species—a hybridiza-
tion/intergradation phenomenon.
reflex An active response to a stimulus that is usu-
ally involuntary and reproducible; many types exist
from simple to complex. A common example is the
kick response when a doctor hits a knee with a small
hammer.
refractory period Atthe end of the action potential,
the absolute refractory period (ARP) is the interval
immediately following the discharge of a nerve impulse
(action potential) during which the cell cannot be
induced to fire again. A relative refractory period is the
time following the ARP where a neuron can be induced
to discharge again but only if there is a more intense
stimulus than normal.
regulation Refers to control of activity of an
ENZYME(system) or GENE EXPRESSION.
regulative development(indeterminate development)
A development pattern in which cell fates are not deter-
mined until late in development; depends on interac-
tions with neighboring cells. For example, in mice
gastrulation, if the majority of embryonic cells are
destroyed, a normal mouse can still develop from the
remainder.
Reichstein, Tadeus (1897–1996) SwissChemist
Tadeus Reichstein was born on July 20, 1897, at Wlo-
clawek, Poland, to Isidor Reichstein and Gastava
Brockmann. He was educated at a boarding school at
Jena after his family moved to Zurich in 1906 (where
hewas naturalized). He had a private tutor and then
attended the Oberrealschule (technical school of junior
college grade) and the Eidgenössische Technische
Hochschule (E.T.H.) (state technical college).
In 1916 he began to study chemistry at the E.T.H.
at Zurich and graduated in 1920. In 1922 he began
research on the composition of the flavoring substances
in roasted coffee, a project that lasted for nine years.
In 1931 he turned to other scientific research, and
by 1938 he was professor in pharmaceutical chemistry
and director of the pharmaceutical institute in the Uni-
versity of Basel. From 1946 to 1967 he was professor
of organic chemistry at the University of Basel.
In 1933 he synthesized vitamin C (ascorbic acid)
and worked on plant glycosides. From 1953 to 1954
he worked with several other scientists and was the
first to isolate and explain the constitution of aldo-
sterone, a hormone of the adrenal cortex. He also col-
laborated with E. C. KENDALLand P. S. HENCH in
their work on the hormones of the adrenal cortex. For
this work, Reichstein, Kendall, and Hench were joint-
ly awarded the Nobel Prize in physiology or medicine
in 1950.
After 1967 he worked on the study of ferns and
published many papers on the subject. He died on
August 1, 1996, in Basel.relapsing fever A tropical disease associated with
some 20 species of the bacteria genus Borreliathat is
transmitted to humans by two vectors, soft ticks
(Ornithodorosor Argas)or, in the case of Borrelia
recurrentis,by lice. Louse-borne relapsing fever is more
severe than the tick-borne variety.relative configuration The CONFIGURATIONof any
stereogenic (asymmetric) center with respect to any
other stereogenic center contained within the same
molecular entity. A stereogenic unit is a grouping with-
in a molecular entity that can be considered a focus of
STEREOISOMERism.relative fitness One genotype contributes to the next
generation. If the population is stable, i.e., neitherrelative fitness 289