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Free Radical Tissue Damage and
Protective Role of Antioxidant Nutrients
Brodv Memorial Lecture XX
Dr. Lawrence J. Machlin
Head, Clinical Nutrition
Roche Vitamins and Fine Chemicals
H Nutley, New Jersey
Special Report'41
November 17, 19£
-^Agricultural Experiment Station
University of Missouri-Columblf'^f^
The Board of Curators established the Samuel Brody Lectureship Fund in April, 1959.
Lectures have been held asoften assufficient income from theendowment fund provided
expenses and a small honorarium for a distinguished lecturer.
The committee will welcome additional contributions from any individual or group.
Such funds will be applied to the principal or endowment fund of the Brody Memorial
Lectureship Fund. Any increases in the endowment fund, of course, will allowlecturesto
be held more frequently.
The present Brody Memorial Lectureship Committee was appointed by Dean Roger
Mitchell. Committee members are:
Dr. Harold D. Johnson, Brody Lecture Chairman
Dr. Ralph Anderson, Gamma Sigma Delta Representative
Dr. Warren Zahler, Sigma Xi Representative.
Previous Brody Lectures
I.
II.
III.
IV.
V.
VI.
Max Kleiber, Dept. Animal Science, Univ. ofCalif.-Berkeley, Dec. 5 1960.
Knut Schmidt-Nielsen, Dept. of Zoology, Duke University, Dec. 7, 1961.
F.W. Went, Director, Missouri Botanical Garden, April 2, 1963.
K.L. Blaxter, Dept. of Nutrition, Hannah Dairy Research Institute, Jan. 27, 1964.
C. Ladd Prosser, Dept. of Physiology, University of Illinois, Feb. 25, 1965.
H.T. Hammel, Physiology Group, John B. Pierce Foundation Laboratory, Feb. 17,
1966.
VII. H.N. Munro, Dept. Physiological Chemistry, Massachusetts Institute ofTechnolo
gy, Feb. 6, 1967.
VIII. James D. Hardy, Dept. of Physiology, Yale University, April 30, 1968.
IX. Loren D. Carlson, Dept. of Physiology, University ofCalif.-Davis, May 10, 1969.
X. R.L. Baldwin, Dept. of Animal Science, University of Calif.-Davis, Feb. 5, 1971.
XI. John R. Brobeck, Dept. of Physiology, The School of Medicine, University of
Pennsylvania, Oct. 5, 1972.
XII. Bruce A. Young, Dept. of Animal Science, University of Alberta, Edmonton,
Canada, April 22, 1974.
XIII. D.E. Johnson, Dept. ofAnimal Science, Colorado State University, Fort Collins, Oct.
23, 1975.
XIV. Albert L. Lehninger, Dept. ofPhysiological Chemistry, The Johns Hopkins School
of Medicine, Baltimore, October 7, 1976.
XV. Henry A. Lardy, Dept. of Biological Science, University of Wisconsin, Madison,
Feb. 8, 1979.
XVI. H. Allen Tucker, Dept. of Dairy Sci. & Dept. of Physiology, Michigan State
University, East Lansing, April 2, 1981.
XVII. H. Russell Conrad, Dept. ofDairy Science, Ohio State University, Oct. 15, 1982.
XVIII. David Robertshaw, Dept. of Physiology and Biophysics, Colorado State University,
Fort Collins, Nov. 15, 1984.
XIX. Allen Munck, Professor of Physiology, Dartmouth Medical School - Oct. 28, 1986.
Free Radical Tissue Damage and the
Protective Role of Antioxidant Nutrients
By: Dr. Lawrence J. Machlin
Director of Clinical Nutrition
Vitamins and Fine Chemicals Division
Hoffmann-La Roche Inc.
Introduction
I'm deeply honored to be invited to present the Brody Lecture. I have
fond memories of the 17 years I spent in Missouri and of the many
rewarding relationships I had with members of the faculty here at
Columbia, particularly, HaroldJohnson, Boyd O'Delland Jimmy Savage.
The subject of free radical tissue damage and the protective role of
antioxidant nutrients has its origins in work of Olcott and Matill almost
50 years ago. They proposed that vitamin E functioned as an in vivo
antioxidant, i.e., it scavenged free radicals in tissues. It took many
decades to provide adequate proof of this hypothesis. When I was at
Monsanto over25yearsago, I contributedto this subject by showing that
a wide variety of synthetic antioxidants can prevent vitamin E deficiency
symptoms in the chicken.
The entire subject of free radical biology has expanded considerably
in the last 10-15 years triggered by studies on antioxidant enzymes such
as superoxide dismutase (SOD) and glutathione peroxidase (GPX), obser
vations on ischemia reperfusion injury and a host of other discoveries.
Several journals are now devoted to the subjectand scientific conferences
abound.
Although there are many scientific issues to be resolved, it is clear
that free radicals are involved in many disease processes and nutrition
plays an important role in protecting the body against the consequences
of free radical tissue damage.
In the following I will discuss what free radicals are, where they come
from, how they damagetissuesand then briefly describe the antioxidant
defense system of the body and the role of nutrition in maintaining this
system and finally give two examples of health conditions influenced by
antioxidant nutrients.
Sources of Free Radicals
If a reactive molecule contains one or more unpaired electrons, the
molecule is termed a free radical. Most of the biological free radicals
contain oxygen (Table 1). Active forms of oxygen such as singlet oxygen
(1O2) and H2O2 although not radicals themselves lead to free radical
formation and can also cause damage.
Endogenous
The formation of highly reactive, oxygen-containing molecular spe
cies is a normal consequence of a variety of essential biochemical
reactions. Endogenous sources of free radicals include those that are
generated and act intracellularly, as well as those that are formed within
the cell and are released into the surrounding area. Intracellular free
radicals are generated from the autoxidation and consequent inactivation
TABLE 1
Potentially Cytotoxic Species of Oxygen
Superoxide anion radical
02H02.
Hydroperoxyl radical
H202
Hydrogen peroxide
•OH
Hydroxyl radical
ROO-
Peroxide radical (R = lipid)
^02
Singlet oxygen
of small molecules such as reduced flavms and thiols, catecholamines,
and from the activity of certain oxidases, cyclooxygenases, lipoxygenases, dehydrogenases, and peroxidases. Oxidases and electron trans
port systems are prime, continuous sources of intracellular, reactive
oxygenated free radicals. Electron transfer from transitionmetals such as
iron to oxygen-containing molecules can initiate free radical reactions.
The sites of free radical generation encompass all cellular constituents
including mitochondria, lysosomes, peroxisomes, and nuclear, endoplasmic reticular, and plasma membranes as well as sites within the
cytosol. (Fig. 1)
FIGURE 1
Cellular Sources of Free Radicals
electron transport system
cytochromes P450 and 65
hemoglobif^
xanthine oxidose
oxidative burst
m^LEUS
ENDOPLASMIC RETICULUM,
myeloperoxidase
enzyme system
DNA
(phagocytes)
LYSOSOMES
oxidases
PEROXISOMES
O
flavoproteins
O
CYTOPLASM
MTOCHONDRON
reduced flavins
transition metals
electron transport system
LIPID BILAYER OF ALL
CELLULAR MEMBRANES
lipid peroxidatlon
lipoxygenoses
prostoglandin synthetase
NADPH oxidase (phagocytes)
Adopted from Freeman, B. A. eta!., 1982
5
Exogenous
Exogenous sources of free radicals include tobacco smoke, certain
pollutants and organic solvents, anesthetics, hyperoxic environments,
and pesticides. Some of these compounds as well as certain medications
are metabolized to free radical intermediate products that have been
shown to cause oxidative damage to the target tissues. Exposure to
radiation results in the formation of free radicals within the exposed
tissues.
Consequences of free radical damage (Fig. 2)
Free radicals can damage DNA, resulting in cell injury and mutagenesis, and protein, resulting in denaturation and, decreased enzyme
activity. The amino acids histidine, tryptophan, methionine and cysteine
are particularly prone to attack. Damage to carbohydrate particularly as
glycoproteins can result in alteration of receptors and depolymerization
of substances such as hyaluronic acid. Free radical - induced lipid
oxidation can cause damage to the membrane directly by causing
alterations in the PUFA and indirectly by formation of secondary
products such as reactive aldehydes {E.g., malondialdehyde, hydroxyalkenals) Figs. 3-4.
FIGURE 2
Transport
Receptor
disturbances
alterations
Increased
turnover ofprotein
Damage to
cartiohydrates
REACTIVE FHEE
RADICAL
-SH dsturfaences
Secondary products
SH-oxidation
Enzyme
changes
DNA-damage, ceoinpry
mutation
upxl perondation
Membrane fi*icti6n
enzyme
•amage to protens
Membrane damage
FIGURE 3
COOH
0H«
/v^Y^w
Initiation
PUFA
A/=V=Vn/
1a/=vw
COOH
r
/VVvV\cQOH
(conjugated diene] (R*)
Propagation VVV^NAcooh
—
'
COOH
0*
WV^A COOH
8*
/V=V^W
Lipid hydroperoxyl radical (RO,* 1
''
V|W\
* A/'V^vV
H
Lipid hydraperoxide
2R*-»Rfl
2 RO,*—0, + ROOR
RO," + R*-»ROOR
RO,* + VitE-^ROOH + VitE*
Termination
FIGURE 4
TRANSMEMBRANE
GLYCOPROTEIN
MEMBRANE SURFACE
PROTEINS
CH,-S
FREE RADICAL DAMAGE
DISULFIDE
CROSSUNKING
^
PROTEIN STRAND
SCJSSION
FIGURE 5
UPIO-PROTBN
CROSSUNKING
PROTBN-PROTEIN
CROSSUNKING
LIPID-LIPID
CROSSUNKING
AMINO ACID
OXIDATION
0
MALONDIALDEHYDE
COOH
RELEASED FROM
OXIDIZED FATTY ACIDS
FATTY ACID
OXIDATION
COOH
Antioxidant function of nutrients
Lipid peroxidation is a chain reaction (Fig. 3) which can be terminated
when two radicals react with each other or when a chain-breaking
antioxidant such as vitamin E reacts with a radical to form a less reactive
radical (tocopheroxy radical). Tocopheroxy radical can be reduced to
tocopherol by ascorbic acid (vitamin C) or reduced glutathione.
Nutrients with antioxidant functions
Vitamin E (alpha tocopherol), the major lipid-soluble antioxidant in all
cellular membranes, not only reacts with the peroxy radical (ROO*) but
with the hydroxyl radical (HO'), superoxide radical (©2"), and also
quench singlet oxygen (^02).
It is clear that vitamin E does function as an in vivo antioxidant as
evidenced by the increased concentration of aldehyde, peroxides, and
lipofuscin in the tissues of vitamin E deficient animals. Furthermore
pentane, a product of peroxidation of n-6 fatty acids, is significantly
increased in the exhaled air of vitamin E deficient animals and humans.
Other vitamins and minerals also have protectiverolesagainst radical
damage either by direct antioxidant activities or as precursors of "antioxi
dant" enzymes. (Table 2)
TABLE 2
Antioxidant micronutrients
Activity
Nutrient
Vitamin C
(ascorbic acid)
Importantwater-soluble cytosolicchain-breaking an
tioxidant; reacts directly with superoxide, singlet
oxygen; regenerates tocopherol from tocopheroxy
radical
Vitamin E
(alpha-tocopherol)
B-Carotene
Major membrane-bound, lipid-soluble chain-break
ing antioxidant; reacts directly with superoxide, sin
glet oxygen
Most potent singlet oxygen quencher, antioxidant
properties particularly at low oxygen pressure, lipid
soluble
Zinc
Constituent of cytosolic superoxide dismutase and
metallothionein, membrane stabilizer
Selenium
Copper
Constituent of glutathione peroxidase
Constituent of cytosolic superoxide dismutase and
ceruloplasmin
Iron
Constituent of catalase
Maganese
Constituent of mitochondrial superoxide dismutase
Ascorbic acid is water soluble and has been shown to react directly
with the 02~, HO- and ^©2 and can also regenerate the reduced
antioxidant form of vitamin E from the vitamin E radical. In the presence
of transition metals ascorbic acid can provoke the formation of free
radicals. However, there is no evidence that this pro-oxidant effectoccurs
in vivo.
Beta carotene, a pigment found in all plants, is the most efficient
quencher of singlet oxygen known in nature and can also function as an
antioxidant. Beta carotene is the major carotenoid precursor of vitamin
A. Vitamin A, however, cannot quench singlet oxygen and has only a
limited capacity to scavenge free radicals.
Following its reaction with 1O2, beta carotene dissipates the energy
taken up in the molecule, and returns to its ground state. One molecule
of beta carotene can deactivate many 1O2 molecules (about 1000).
Several essential minerals are constituents of protective antioxidant
enzymes. Zinc and copper, are required for synthesis of cytosolic
superoxide dismutase (SOD) and manganese for the mitochondrial SOD.
However, dietary deficiencies of copper and manganese have been
shown to lower tissue SOD, whereas a zinc deficiency has had littleeffect
on tissue levels of the enzyme. In fact, high levels of zinc have been
found to lower SOD presumably by inducing a copper deficit. On the
other hand, zinc may be important as a membrane stabilizer and as a
precursor of metallothionein, a protein with antioxidant properties.
Selenium as an essential component of glutathione peroxidase (GPX), an
enzyme important in the decomposition of both hydrogen peroxide and
lipid peroxides. Catalase, a heme protein (iron), catalyzes the decomposi
tion of hydrogen peroxide.
The sulfur amino acids, methionine and cysteine may be important as
precursors of the cysteine-containing peptide, glutathione an important
component of the antioxidant defense system (Figure 5).
It is important to note that the antioxidant enzymes are primarily
intracellular and thus extracellular free radicals, either endogenously
produced or from the environment, must be inactivated by the circulating
antioxidants such as the antioxidant vitamins discussed above as well as
by ceruloplasmin. The level of dietary intake of all the antioxidant
micronutrients directly affects the circulating level of these nutrients and
the activity of the antioxidant metalloenzymes. Thus, low intakes of one
or more of these antioxidant nutrients could reduce the body's defenses
against free radical damage and increase susceptibility to health prob
lems associatedwith free radical damage. Eachtissue or cellhas a unique
composition in regard to antioxidant protection, pro-oxidant compo
nents, and exposure to free radicals. Health or pathology depends upon
the balance of these three factors. Some examples of the special condi
tions that exist in certain tissues and the possible consequences are given
in Table 3.
FIGURE 5
Antioxidant Protection Within The Cell
Vitamin E
/3-carotene
NUCLEUS
Vitamins C and E
ENDOPLASMtC RETICULUM
^-carotene
LYSOSOMES
Catalase
PEROXISOMES
Ki
O
GSH
CYTOPLASM
y' Glutathione
MITOCHONDRION
Peroxidase
Cu/Zn
SOD
/
'Vitamin C
LIPID BILAYER OF ALL
CELLULAR MEMBRANES
Vitamin E
Vitamin E +
(3 carotene
SOD + Glutathione Peroxidase
+ GSH
TABLE 3
Example of special conditions which can predispose
specific tissues to free radical damage
Special
Possible
conditions
consequences
Tissue
Lung
High exposure to O2, O3, Emphysema, cancer
NO2, smoke
Synovial fluid
No SOD, GSH
peroxidase, catalase
Exposure to inflammatory
Arthritis
cells
Retina
High PUFA, High O2
Exposure to light
Retinal degeneration
Lens
Exposure to light
Low protein turnover
Cataract
High PUFA, autoxidation
Parkinson's
Brain
of catecholamines, low
turnover
10
Antioxidant Interactions
In addition to direct quenching of reactive, damaging free radicals,
vitamin C has been clearly shown to interact with the tocopheroxyl
radical and to regenerate the reduced tocopherol. Thus, vitamin C can
have a "sparing effect" on vitamin E.
Vitamin E can protect the conjugated double bonds of beta carotene
from oxidation and thus have a sparingeffect on this vitamin. Vitamin E
can protect against many of the symptoms of selenium deficiency and
vice versa. These sparing as well as synergistic actions are thought to
result from the ability of both tocopherol and selenium-dependent GPX
to decrease the production of lipid autoxidation products. Studies in
animals and man suggest that both vitamin E and selenium are neces
sary for maximum protection against cancer.
As a result of these interactions, there may be other health conditions
where combinations of vitamin E, C, betacarotene and selenium may be
more effective than any single nutrient.
Health implications of free radical damage
The range of antioxidant defenses available within the cell and
extracellularly are generally adequate to protect against oxidative dam
age. However, the balance can be lost because of overproduction of free
radicals, by exposure to sources that overwhelm the antioxidant de
fenses, or by inadequate intakeof nutrients that contribute to the defense
system.
Two examples of health effects of free radical damage where there is
considerable evidence that antioxidant nutrients can protect, are lung
cancer and cataracts. There is considerable evidence that smoking
increases the risk of lung cancerand recently evidence has accumulated
that consumption of foods high in beta carotene reduces the risk oflung
cancer (and some other cancers as well) Fig. 6 & 7.
There is considerable chemical evidence to support the hypothesis
that cataracts are the result of the accumulation of free radical insults over
a course of many years (Table 4). Furthermore, studies in animals have
shown that vitamin E and C both slow the onset of cataracts in animal
models, and that human subjects taking vitamin C or E supplements
have a reduced relative risk of cataracts (Table 5).
There are many other examples of free radical-mediated disease
processes where nutritional intervention could possibly play an impor
tant role. In addition to the diseases mentioned earlier is this report,
cardiovascular disease, arthritis diabetes, macular degeneration photodermatoses, and the aging process itselfare worth continuedexploration.
Of course there are many scientific issues remaining. We need less
equivocal methodologies which would permit us to detect and quantify
free radical injury particularly in vivo. In most cases more information is
11
BETA CAROTENE AND CANCER
19-Year Inodence
of Bronchiogenic
Carcenoma (%j
30-h
0.12.2 '
Duration of
2.3-
3.0Carotene Index
Cigarette Smcriung
(yps)
4.019.2-
mg/day
Bnranate association of carotene ndex and duration of
agarette smoking with 19-year lungcancer ^idence.
SchekeDe et al..(19ai]
FIGURE 7
PROTECTIVE EFFECT OF
CAROTENES ON CANCER
EPIDEMIOLOGIC STUDIES
No Effect
Reduced Risk
Cervix
Esophagus
Or(^arynx/head/neck
Stomach
Bladder
Colon/rectum
I
I
11
p
I
Number of Studies
r
TABLE 4
Evidence for Oxidative Damage to the Lens (Human Studies)
o
Incidence related to exposure to ultraviolet and near ultra
violet light
o
In cataracts find increased:
- H2O2, Malondialdehyde (MDA)
- Disulfides, dityrosine, methionione sulfone
In cataracts find decreased:
o
Superoxide dismutase (SOD), glutathione peroxidase and
cataiase
0
Reduced glutathione early in development
TABLE 5
Effect of Vitamins E & C Supplements on Cataracts*
People Over 55 Years Old
Supplement
Relative risk
None
1.00
Vitamin E
0.40 (P = .003)
Vitamin C
0.25 (P = .04)
Vitamins E & C
0.32 (P = .05)
^Robertson (1987)
GCR N-122113, L J. Machlin
still necessary to establish the casualty between free radical injuries and
eventual pathologies. Finally, there is an enormous opportunity to better
define the role of nutrition in helping prevent or at least delay the onset of
a host of slowly developing chronic health problems.
Summary
In summary, it is clear that the area of free radical biology is emerging
quite rapidly. Free radical injury to tissues is certainly not responsible for
all of the health problems of the world. However, there is already
considerable evidence that a free radical etiology at least partially
13
underlies many pathological processes and that nutrition plays an
important protective role against such processes and their subsequent
health effects.
It will take considerably more effort to completely comprehend and
utilize this emerging science, but in view of the potential rewards in
terms of enhanced public health, the effort is certainly warranted.
References
Armstrong, D., Sohal, S., Cutler, R.G., Slater, XE, (1984) Free radicals in
molecular biology, aging, and disease. Raven Press, New York.
Bendich, A., Machlin, L.J., Scandurra, O., Burton, G.W., Wayner,
D.D.M., (1986) Adv. in Free Radical Biology and Medical 2; 419-444.
Chow, C.K., (1988) Cellular antioxidant defense mechanisms Volumes I,
II, & III. CRC Press, Boca Raton, Florida.
Halliwell, B., Gutteridge, J.M.C., (1985) Free radicals in biology and
medicine. Clarendon Press, Oxford.
Freeman, B.A., (1987) Crapo, J.Q, (1982) Biology of disease: free radicals
and tissue injury. Lab Invest. 47; 412-426.
Machlin, L.J., Bendich, A., (1987) Free radical tissue damage: protective
role of antioxidant nutrients. FASEB J. 1:441-445.
Machlin, L.J., (1987) Protective role of vitamins against free radical
damage. Nutrition pp 51-54.
Slater, T.F., (1987) Free radical mediated tissue damage. Nutrition pp
46-50.
Southom, PA., Powis, A., (1988) Free radicals in medicine. 1.
Chemical nature and biologic reactions. II Involvementin human disease
Mayo Clin. Proc. 63: 381-389, 390-408.
Figure Legends
Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Cellular sources of free radicals (Machlin and Bendich 1987)
Consequences of free radical damage (Adapted from Slater, 1987)
Lipid peroxidation (Southern & Powis 1988)
Free radical damage to membrane (Freeman & Crapo 1982)
Antioxidant protection within the cell (Machlin and Bendich 1987)
Beta-carotene intake and risk of lung cancer. (From Shekelle et. al
1981)
Fig. 7 Beta-carotene and risk of cancer. Summary of epidemiological
studies.
Bibliography of Dr. Lawrence J. Machlin, Ph.D.
LAWRENCE J. MACHLIN, Director Clinical Nutrition, Roche Vitamins and Fine Chemicals
(Hoffman-LaRoche, Inc.). Bom 1927;Married, 3 sons; B.S. Degree, Cornell University, 1948;
M.N.S. Cornell University,1949,Nutrition; Ph.D. Georgetown University,1954,Biochemis14
try, 1984-Present, Director, Clinical Nutrition, Hoffman-LaRoche, Inc.; 1973-1984, Senior
Research Group Chief,Vitaminsand Clinical Nutrition, Hoffman-LaRoche, Inc.; 1963-1974,
Senior Group Leader, Monsanto Company; 1960-1963, Scientist, Monsanto Company;
1956-1960, Biochemist, Monsanto Company; 1950-1956, Biochemist, U.S.D.A.-Atomic Ener
gy Commission; 1949-1950, Nutritionist, U.S.D.A., Beltsville, MD. Professional Activities:
Organized and co-chaired international conference on Vitamin E, 1982 and 1988 and
Vitamin C in 1986; Participant, White House Conference on Food, Nutrition and Health,
1969. Professional Memberships: American Institute of Nutrition; American Society of
Clinical Nutrition; American College of Nutrition (Fellow); Society for Experimental
Biology and Medicine; New York Academy of Science; New York Lipid Club; and
International Association of Vitamin and Nutritional Oncology.
Scientific Achievements:
Established nutritional requirement for sulfate sulfur. Oneoffirst to describe theimportant
interrelationship between linoleic acid and vitamin E. Clarified the etiology of vitamin E
deficiencies in the chicken. Discovered that vitamin E will inhibit prostaglandin synthesis
and platelet aggregation. Established that subjects with sickle-cell anemia are deficientin
vitamin E and that number of irreversibly sickled cells would decrease with vitamin E
treatment. Developed a unique, sensitive and reliable bioassay for vitamin E bioactivity.
Helped demonstrate the specific need for vitamin E for maximal immune response.
Pioneered development of assays for insulin and growth hormone in farm animals. One of
first to unequivocably demonstrate the effects of growth hormone in improving milk
production in dairy cows and lean meat production in the pig.
Publications:
Author and/or Co-author of over 110 scientific papers, including 4 patents and 5 book
chapters.
Editor of 4 books, two on "Vitamin E", a "Handbook of Vitamins" and Conference on
Vitamin C.
Books:
Machlin, L.J. (Ed.)1980. Vitamin E,a Comprehensive Treatise. Marcel Dekker, Inc., New York,
N.Y
Lubin, B. and Machlin, L.J. (Eds.) 1982. Vitamin E: Biochemical, Hemalological, and Clinical
Aspects. Ann. N.Y Acad. Sci., Vol. 393.
Machlin, L.J. (Ed.) 1984. Handbook of Vitamins, Nutritional, Biochemical and Clinical Aspects.
Marcel Dekker, New York, N.Y.
Burns, J.J., J.M. Rivers and L.J. Machlin (Eds.) 1987. Third Conference on Vitamin C. Ann.
N.Y. Acad. Sci., Vol. 498.
Book Chapters:
Machlin, L.J. 1962, Role of antioxidants in the biological fate of lipids. IN: Lipids and Their
Oxidation. H.W. Schults, E.A. Dayand R.W. Sinnhuker (Eds.), The AVI Publishing Co.,
Inc., Westport, CT, pp. 255-268.
Machlin, L.J. 1973. Phosphorus in human nutrition. IN: Environmental Phosphorus
Handbook. E.J. Griffith, A. Beeton, J.M. Spence and D.J. Mitchell (Eds.), John Wiley &
Sons, Inc., New York, pp. 413-423.
Machlin, L.J. 1976. Role of growth hormone in improving farm animal production. IN:
Anabolic Agents in Animal Production. EC. Lu and J. Rendel (Eds.), FAOAVHO
Symposium, Rome, March 1975, Environmental Qualityand Safety, Suppl. Vol. V
Georg Thieme Publishing, Stuttgart, pp. 43-54.
Machlin, L.J. and M. Brin. 1980. Vitamin E. IN: Human Nutrition - A Comprehensive
Treatise, Vol. 3B, Nutrition and the Adult. R. Alfin-Slater and D. Kritchevsky (Eds.),
Plenum Publishing Corp., New York, pp. 245-266.
Machlin, L.J. 1984. Vitamin E. IN: Handbook on Vitamins. L.J. Machlin (Ed.), Marcel
Dekker, Inc., New York, pp. 99-145.
15