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National Institute of Environmental Health Science.

Annual report : National Institute of Environmental Health Sciences (Volume 1985) online

. (page 112 of 114)
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dependent enzymes in the nephrotoxicity of DCVC was proven by the synthesis
and testing of S-(l ,2-dichlorovinyl )-DL-a-methylcysteine, which cannot be
metabolized by pyridoxal phosphate-dependent enzymes and blocked the nephro-
toxicity of DCVC. To test the hypothesis that 1 ,2-dichlorovinyl mercaptan,
which is a putative metabolite of DCVC is involved in the toxicity of DCVC,
S_-(l ,2-dichlorovinyl )-L-homocysteine (DCVHC) was prepared. 1 ,2-Dichlorovinyl
mercaptan should also be a metabolite of DCVHC. DCVHC was found to be extra-
ordinarily nephrotoxic. Indeed, DCVHC may be the most potent organic nephro -
toxin known . Finally, a role for y-g^utamyl transpeptidase in the
nephrotoxicity of S_-( 1 ,2-dichl orovinyl )-gl utathione (DCVG) was established;
AT-125, a suicide substrate for y-glutamyl transpeptidase, blocked the
toxicity of DCVG.



1153



In several acute toxicity studies, it has been shown that on a molar basis,
selenium (Se) is the most effective cadmium antagonist known. The mechanism
of this interaction in plasma and red blood cells has been shown to involve
the metabolism of ? £e, as sodium selenite or selenide. The selenide then
complexes with Cd and is associated with proteins of specific molecular
weights. The Cd in the Cd-Se-protein complex is believed to be biologically
inactive. The present studies which employ low, chronic exposures to Cd by
using diets differing in selenium and cadmium content are being conducted to
establish the rat as a model for Cd-induced heart disease in humans.

Selenium compounds have been shown to antagonize the effects of mercury com-
pounds in animal toxicity studies as well as in cytotoxicity studies in cell
cultures. Studies are in progress to determine the possible effects of these
compounds on the mercury-induced effects on nucleic acid synthesis in intact
cells, isolated nuclei, and extracted polymerases. In addition, preliminary
studies have shown that while methyl mercury (MeHg) is active in a cell
transformation assay, the activity of MeHg together with N-methyl-N-nitro-N-
nitrosoguanidine (MNNG) is considerably less than additive in this assay.

Long-term studies on the effects of ethanol on initiation and promotion of
esophageal carcinogenesis are underway in rats. For the promotion studies,
animals were initiated with methylbenzyl ni trosamine (MBN) for a period of time
followed by treatment with isocaloric ethanol or control carbohydrate.
Ethanol or control diets will be fed for a period of twelve weeks and the
studies continued for a period of two years. Initiation studies will involve
placing weanlings on an ethanol diet and subsequently exposed to MBN.

One study is concentrating on the enzymology of carbon tetrachloride metabo-
lism and on the effect of hepatotoxic chemicals on liver calcium homeostasis.
The carbon tetrachloride metabolism studies will seek to define the isozymes
of cytochrome P-450 that are involved in the metabolism of carbon tetra-
chloride to phosgene and chloroform and the responsiveness of these isozymes
to alcohol treatment. Carbon tetrachloride, chloroform, and bromobenzene
administration leads to the appearance of glutathiones-transferase activity
in blood and in an alteration of the chromatographic behavior of the trans-
ferases. Moreover, metabolites of bromobenzene and chloroform become co-
valently bound to the transferases. Thus, the transferases are released into
blood from the liver after treatment with hepatotoxic chemicals.

Immunotoxicology

The role of environmental agents in producing adverse effects on the immune
system is becoming more apparent with development and refinement of immuno-
logic techniques applicable to such studies. Moreover, an appreciation for
the role of xenobiotics in the induction of immunotoxicity has significantly
increased. At present, however, only minimal information is available
regarding the molecular events associated with chemical-induced immuno-
toxicity. For most xenobiotics, the ultimate product, molecular target and
subsequent biochemical events responsible for derangements in the immune
system are not well defined.

The NIEHS currently supports a variety of individual research projects in
which immunology plays a key role.



1154



'



Ten adolescent subjects with extrinsic asthma were studied during intermittent
exercise exposure to filtered air, 0.5 ppm sulfur dioxide (SO,,) or 100 yg/m
sulfuric acid (hLSOJ. The purpose of this study was to compare changes in
nasal power (the work of breathing) with pulmonary functional changes depend-
ing on the route of inhalation of the pollutants: oral inhalation through a
mouthpiece or oronasal inhalation via a face mask. Statistically significant
changes in total respiratory resistance, forced expiratory volume in one
second (FEV,) and maximal flow parameters (V co and V -, c ) were seen
following exposures to SO- and H^SO,. The magnitude of change in FEV, and
V c was greater following oral compared to oronasal inhalation of S0~.
Tnfs research demonstrates that S0~ can cause nasal as well as pulmonary func-
tional changes.

Cadmium is an environmental pollutant. The effects of cadmium on phago-
cytosis, a fundamental aspect of immunity, were studied in laboratory mice
exposed to the metallic ion in drinking water for periods up to one year.
There was a decrease in clearance from the circulation of Cr labelled sheep
red blood cells (E) and E coated with immunoglobulin G (IgG). This decrease
was reversed when cadmium was removed from the drinking water. When organ
uptakes of E and E-IgG were analyzed, it was found that as duration of cadmium
exposure increased, the uptake in the liver decreased, whereas uptake in the
spleen increased. Removal of the cadmium again reversed these uptake patterns
towards normal despite a continuing high organ burden of cadmium, particularly
in the liver. These studies are contributing to an understanding of the
mechanism whereby cadmium affects phagocytosis.

Among the toxic effects which have been associated with the aromatic hydro-
carbon (Ah) receptor in mice are hepatic enzyme induction, immunotoxicity ,
cleft-palate formation, and thymic atrophy. By using several PCB congeners
and polycyclic aromatic hydrocarbons, evidence suggests that any ligand for
this receptor should produce these effects. Correlations between Ah-receptor
associated thymic atrophy and the suppression of antibody mediated immunity
were studied. Using a T-independent antigen, it was demonstrated that this
immunosuppression is not a consequence of thymic toxicity.

It has been established that chrysotile asbestos produces a 50 percent inhibi-
tion of migration of normal macrophages at about 100 ug/ml . Tests also have
established that the small standardized fibers are no more active than soni-
cated preparation of chrysotile. Furthermore, preparations of fibers exceed-
ing 50 micrometers in length are more toxic than sonicated preparations of
fibers less than 10 micrometers. The following observations have also been
made: neither chrysotile, amosite or crocidolite can induce a burst in the
hexose monophosphate shunt of BCG immune alveolar macrophages; chrysotile is
the most toxic of the 3 forms tested as measured by migration inhibition and
loss of viability of alveolar macrophages; complement is not involved in the
toxicity of asbestos; and leaching of chrysotile with one normal HC1 for 24
hours (23-25 C) inactivates the toxicity for alveolar macrophages.

The host wide system of macrophages (the mononuclear phagocyte system or MPS)
is a major target of many xenobiotics and environmental pollutants. Altera-
tions in the MPS can be extremely damaging to the body in two distinct ways:
depressed function of the MPS can lead to impaired resistance to the develop-
ment of infections and tumors, while over-exuberance stimulation of the MPS



1155



can lead to profound tissue injury damage and even carcinogenesis. An
hypothesis was formulated that xenobiotics and environmental pollutants alter
the development of the MPS, which is a dynamic system of cells whose state of
development and activation is consistently in flux. A study of 7 environ-
mental pollutants showed that 5 perturbed the development of the MPS. Some
suppressed development, some stimulated development and some actually had both
effects (that is, they induced early development and suppressed late develop-
ment). One of the major changes induced in the MPS by xenobiotics is acquisi-
tion of competence to release reactive oxygen intermediates (ROI) such as
hydrogen peroxide. The data strongly suggests the possibility that xeno-
biotics may perturb the mononuclear phagocyte system to secrete increased or
abberant amounts of ROI, which in turn can induce promutagenic changes in
bystanding normal cells.

Studies were carried out to evaluate both the autoimmune effects of different
dosages of mercuric chloride and the kinetics of autoimmune responses to the
glomerular basement membrane (GBM) observed in BN rats after the administra-
tion of mercury. Preliminary findings confirmed that very low amounts of
mercuric chloride (10 micrograms/lOOg body weight) are still capable of
inducing autoimmune responses to autoantigens of the GBM in 100 percent of
animals. S.C. injection of mercuric chloride in similar low dosages has the
same autoimmune effects in another inbred strain of rats (MAXX) but no effect
in a third strain (M520). In addition, autoantibodies to GBM are present in
the circulation by the ninth day after the first injection with mercuric
chloride. Titers of autoantibodies to GBM reach a peak by day 12-15 and then
decrease rapidly, reaching baseline values in the following 2 weeks. These
results have been obtained by ELISA and PFC assays. These findings suggest
that mercury compounds may be an important cause of autoimmune disease
resulting from environmental pollution.

Asbestos-related diseases are a major public health problem in the U.S. An
estimated 14 million individuals have been exposed to asbestos during their
working lives. Asbestos has been casually linked to interstitial lung
disease, pleural fibrosis, lung cancer, mesothelioma and cancers of the gastro-
intestinal tract, larynx and possibly, kidney. Altered immunoregul ation most
likely plays a role in the pathogenesis of asbestos-related diseases. Pre-
liminary results have suggested increases in T-lymphocyte subsets 0KT3, 0KT8
and 0KT14 in bronchoal veol ar lavage (BAL) and in OKIa in peripheral blood and
BAL from patients with asbestos exposure. In addition, differences in ex-
pression of antigen by peripheral blood monocytes and alveolar macrophages
have been found.

Studies are underway to examine the effects of cadmium, lead, benzene, and
7,12 dimethylbenz(a)anthracene (DMBA) on the immune system of young adult
female B6C3F1. Previous studies have shown that a dose of 12 mg/kg lead
acetate or 0.9 mg/kg cadmium acetate given i.p. depresses the humoral immune
response 3 days later to sheep erythrocytes (SRBC) and TNP-Ficoll, while not
affecting the primary immune response to TNP-LPS. No significant alteration
in cell surface markers (Mac-1 Lyt-1, Lyt-2, Thy 1.2, and pre-B/B cell antigen
14.8) was detected in the spleens of the cadmium or lead-treated animals
examined on days 1, 3, and 5 after exposure. A significant increase in the
number of large cells was noted in the bone marrow following an acute exposure



1156



to cadmium and lead at the doses listed above. A significant decrease in the
number of bone marrow cells expressing Mac-1, Lyt-1, 14.8, and a monocyte/
lymphoid marker known as 55-7.2 was observed.

A number of industrial and environmental chemicals are known to cause allergic
asthmatic reactions in exposed individuals. An animal model is being
developed for this response in order to determine: (a) the potency of various
chemicals for causing sensitization, (b) the mechanism underlying chemical
sensitization, and (c) the permanence of sensitization. In the model, guinea
pigs are exposed via the inhalation route to known concentrations of chemi-
cals. Following a two-week rest period, re-exposure of animals to low concen-
trations of the chemicals has resulted in elicitation of respiratory sensi-
tivity reactions. Using this procedure, sensitization has been achieved to
toluene diisocyanate (TDI), a major component of polyurethane and to bacterial
subtilisin, an enzyme used in laundry detergents. The sensitization was found
to be concentration-dependent since exposure to high concentrations of chemi-
cals resulted in a great percent of animals developing sensitivity and in a
large number of severe sensitization responses. By comparison, exposure to
low concentrations of these materials produced sensitization in very few
animals. Recognition of this relationship and comparison of the concentration
of chemicals required to achieve sensitization in 50 percent of the animals
(SDr n ) will enable comparison of the potencies of chemicals as respiratory
tract sensitizers.

The effects of acute exposure to both lead and cadmium in adult mice have been
evaluated. The data showed that both metals affect antibody formation to
T-dependent and T-independent antigens differently and suggest that there is a
differential susceptibility of T and B lymphocytes to these immunotoxic
agents. Further in vitro studies in adults confirmed this finding and also
showed a transient, enhancing effect at the level of the B cell. Acute
exposure of newborn mice to lead appears to produce an effect on T-dependent
antibody formation of somewhat longer duration than that observed in adults;
but, with time, this depressive effect was no longer evident. An enhancing
effect on T-independent responses, presumably manifested at the level of the B
cell, was of longer duration. The implications of the latter finding on host
immune resistance are not known.

Several studies conducted during the past year have focused on understanding
the cell biology of macrophage (M0) differentiation and alterations induced by
exposure to N-nitrosodimethylamine (DMN). Previous results had demonstrated
that daily exposure to the carcinogen DMN affected cell-mediated immunity
through changes in M0 function. The effects of DMN on the differentiation of
M0 from marrows of treated animals were examined. DMN produced minimal change
in the number of CFU-GM after 7d of culture. The adherent M0 population was
characterized by lower numbers of cells in S-phase and a decrease in the
number of cells expressing la antigens. Bone marrow derived M0 (BMDM) from
vehicle control animals reconstituted the KLH proliferative response to T
cells from both vehicle and DMN exposed animals further demonstrating that T
cells from DMN treated animals are responsive; whereas, M0 from such animals
have altered functional capabilities. These studies suggest that DMN
treatment results in a decrease in the number of M0 expressing la antigen



1157



while these cells have increased effector cell function (tumor cell killing).
DMN exposed animals also exhibited a significant reduction in the number of
pulmonary tumor nodules and a 10-fold increase in cytostasis activity in vitro
when challenged with the B16 melanoma.



1158



INDEX TO INDIVIDUAL PROJECT REPORTS



INTRAMURAL RESEARCH PROGRAM



Project Number



Title



Page



Z01 ES 50005-11 LBNT

Z01 ES 50015-11 LBNT
Z01 ES 50038-07 LBNT

Z01 ES 50076-04 LBNT

Z01 ES 90030-05 LBNT

Z01 ES 90031-04 LBNT

Z01 ES 90033-03 LBNT
Z01 ES 90034-02 LBNT

Z01 ES 90035-02 LBNT

Z01 ES 90036-02 LBNT
Z01 ES 90037-02 LBNT

Z01 ES 90038-02 LBNT
Z01 ES 90039-02 LBNT

Z01 ES 90040-02 LBNT

Z01 ES 90041-01 LBNT



LABORATORY OF BEHAVIORAL AND NEUROLOGICAL TOXICOLOGY

Effects of Noise and Ototoxic Agents on

Energy Balance and Metabolism in Cochlea 63

Effects of Microwaves on Neural Response 66

Effects of 2450 MHz Microwave Radiation on 69
the Cardiovascular System

Effects of Noise and Drugs on Water Control

of the Cochlear Fluids 72

Effects of Toxicants on Membrane-Related
Neurochemistry 76

Assessment of Neurophysiological Effects

of Organometals 80

Milk Bombesin 83

Rabbit Stomach Peptide [Physal aemin-1 ike

Material (PLIM)] in Mammalian Tissue 86

Use of Ornithine Decarboxylase in the

Detection of Tissue Activation 89

Animal Model of Organometal Neurotoxicity 92

Toxicological Perturbations of Behavioral

and Neural Development 97

Animal Model of Organochlorine Neurotoxicity 103

Modulation of Brain Opioid Peptides by

Neuroleptics and Electroconvulsive Shock 107

On the Possible Mechanism of Chlordecone-

Elicited Tremor 112

Sensitivity to Amino Acids in Mouse Spinal

Cord Neuron Culture 117



1159



Project Number Title Page

LABORATORY OF GENETICS

Z01 ES 60099-06 LG Organization-regulation of Mammalian Lactate

Dehydrogenase Genes 134

Z01 ES 60145-03 LG The Mutational Specificity of Purified DNA

Replication and Repair Proteins 138

Z01 ES 60146-03 LG Mutagenic Consequences of Defined Lesions in

DNA ' 142

Z01 ES 60147-02 LG Molecular Mechanisms of SOS-Mutagenesis in

Escherichia Col i 145

Z01 ES 60148-02 LG Error-Prone Repair in Bacteriophage T4 149

Z01 ES 60150-02 LG Gene Induction by Alkylation Treatments in

E. col i 154

Z01 ES 60151-02 LG Role of the recF Gene in DNA Repair 158

ZOl ES 61005-06 LG Biosynthesis and function of RNA Polymerase II

in Drosophi la mel anoqaster 161

ZOl ES 61011-05 LG Organization and Regulation of Gene Function

in p_. mel anoqaster 164

ZOl ES 61018-05 LG DNA Sequence Variation in the Alcohol

Dehydrogenase Gene Region of Drosophi la 165

ZOl ES 61019-05 LG Collaborative Protein Sequencing 171

ZOl ES 61021-04 LG Genetic and Molecular Analysis of the cut

Locus of p_. mel anogaster 174

ZOl ES 61022-04 LG The Population Genetics of Transposable

Elements 177

ZOl ES 61023-03 LG Analysis of Drosophila Germ Cell Determination 180

ZOl ES 61024-03 LG Genetic and Molecular Analysis of Suppressor-

of-Sable Function in Drosophila 184

ZOl ES 61025-02 LG DNA Sequence Variation in the Dopa

Decarboxylase Region of Drosophila 188

ZOl ES 61027-02 LG Transmission of Cryptic Mutations in

Destabilized X Chromosomes of Drosophila 189



1160



Project Number



Title



Page



Z01 ES 61029-03 LG

Z01 ES 61030-02 LG

Z01 ES 61031-02 LG

Z01 ES 61032-02 LG

Z01 ES 61033-02 LG

Z01 ES 61034-01 LG

Z01 ES 61035-01 LG

Z01 ES 61036-01 LG

| Z01 ES 61037-01 LG

Z01 ES 61038-01 LG

Z01 ES 61039-01 LG

Z01 ES 61040-01 LG

Z01 ES 65021-13-LG

Z01 ES 65033-02 LG
Z01 ES 65034-01 LG

Z01 ES 65035-01 LG

Z01 ES 65036-01 LG

I

W Z01 ES 65037-01 LG



Cloning and Characterization of the
Vermilion Locus of Drosophila

Molecular analysis of the Om mutator in
Drosophila ananassae

The Molecular Population Genetics of
Transposable Elements

Structure-function of Mammalian Lactate
Dehydrogenase Isozymes

Molecular Analysis of Genetic Variation in
lens crystal 1 in

Survey of Genetic Variation in Natural
Populations of Drosophila

The Molecular Characterization of
Spontaneous HGPRT Mutations

Naturally occurring DNA Sequence Variation
in Drosophila melanogaster

Mechanism of DNA Replication in Eucaryotes:

I. Yeast as a Model System

Mechanism of DNA Replication in Eucaryotes:

II. SV40 as a Model System

Mechanism of DNA Recombination and Repair in
Yeast Saccharomyces cerevisiae

Genetic and Biochemical Analysis of Yeast DNA
Polymerase I

Investigation of Germinal Mutation Induction
in Mice

In Vivo Mammalian Mutagenesis

The Specificity of Spontaneous and
Induced Mutation

Specificity of Mutagenesis in Mammalian
Genes Using a Natural Gene

Gene Organization and Regulation in
D. melanogaster

Transposon - mediated chromosomes
instabilities in Drosophila



190

194

197

198

201

205

207

210

214

218

221

225

228
232

237

240

244

248



1161



Project Number



Title



Page



LABORATORY OF MOLECULAR BIOPHYSICS



ZOl ES 10003-06 LMB

Z01 ES 10004-06 LMB

ZOl ES 20015-02 LMB

ZOl ES 30003-14 LMB

ZOl ES 30066-09 LMB

ZOl ES 50046-07 LMB

ZOl ES 50077-03 LMB

ZOl ES 50078-03 LMB

ZOl ES 50079-03 LMB

ZOl ES 50080-03 LMB

ZOl ES 50082-02 LMB

ZOl ES 50083-01 LMB

ZOl ES 50084-01 LMB

ZOl ES 50085-01 LMB

ZOl ES 80008-11 LMB

ZOl ES 80035-09 LMB



Synthetic and Analytical Studies in

Bioorganic Chemistry 260

Studies in Nuclear Magnetic Resonance

(NMR) Spectroscopy 263

Estimation of Pollutant Concentrations in
Groundwaters 274

Development of Analytical Methodology 276

Structural Theoretical Basis and Molecular

Mechanisms of Biological Action 280

Mechanisms of Chemically Induced Photosensitivity 281

Free Radical Intermediates of Antiparasitic Drugs 290

Radical Anion Metabolites 296

Free Radical Metabolite Formation by Peroxidases 300

Environmental Health Applications of Mass
Spectrometry 304

Studies on Tumor Promoters and Antipromoters 307

Specific Binding of Halogenated Aromatic Hydro-
carbons to Thyroxine Binding Proteins 310

Modeling Approaches to the Study of Molecular
Mechanisms of Toxic Action 314

Halogenated Aromatic Hydrocarbons as Thyroxine
Agonists (or Antagonists) 318

Biosynthesis of Prostaglandins, Hydroxy-Fatty

Acids and Leukotrienes 322

Cooxidation of Xenobiotics by the Prostaglandin
Synthetase 327



ZOl ES 70132-06 LP
ZOl ES 80001-13 LP



LABORATORY OF PHARMACOLOGY

Regulation of Intestinal Metabolism

Microsmal Mixed-Function Oxidase Systems
Specificity and Function



340



347



1162



Project Number

Z01 ES 80007-14 LP

Z01 ES 80031-09 LP

Z01 ES 80038-02 LP

Z01 ES 80039-02 LP

Z01 ES 80040-02 LP

Z01 ES 80041-02 LP



Title Page



Conjugation and Oxidation Pathways for

Xenobiotic Metabolism 352

Role of Altered Membrane Function in Xenobiotic
Toxicity 362

Suicide Inhibitors of Cytochrome P-450: Isozyme

and Tissue/Cell Selectivity 368

Xenobiotic Transformation in Isolated Cells 372

Developmental Pharmacogenetics of Liver

Microsomal Testosterone Hydroxylases 385

Detection and Quantitation of Cytochrome P-450
Isozymes 393



LABORATORY OF PULMONARY PATHOBIOLOGY



Z01 ES 25001-08 LPP
Z01 ES 25020-03 LPP

Z01 ES 25021-02 LPP

Z01 ES 25022-02 LPP

Z01 ES 25023-02 LPP

Z01 ES 25024-02 LPP

Z01 ES 25025-02 LPP

Z01 ES 25026-02 LPP

Z01 ES 25027-02 LPP

Z01 ES 25028-02 LPP

Z01 ES 25029-01 LPP



Role of Mutagenesis in Carcinogenesis 404

Regulation of the Pulmonary Surfactant System

and its Modification by Toxic Agents 411

Differentiation and Differentiative Functions of
Tracheal Epithelial Cells 414

Study of the Molecular Mechanisms of Action of
Retinoids 420

Studies on the Mechanism of Neoplastic

Development in Airway Epithelial Cells 425

Pathogenesis of Early Pulmonary Lesions Induced

by Inhaled Inorganic Particles 431

Asbestos Activation of Complement-Dependent
Chemotactic Factors for Macrophages 436

Interactions of Inorganic Particles with

Pulmonary Cell Membranes 440

Identification and Characterization of

Materials Secreted by Pulmonary Clara Cells 444

Molecular Basis for Cellular Changes in

Chemical Carcinogenesis 447

Mechanisms of Neoplastic Transformation by

Viral and Cellular Oncogenes 451



1163



Project Number



Title



Page



LABORATORY OF REPRODUCTIVE AND DEVELOPMENTAL TOXICOLOGY



ZOl


ES


70010-09


LRDT


ZOl


ES


70060-12


LRDT


ZOl


ES


70065-09


LRDT


ZOl


ES


70067-02


LRDT


ZOl


ES


70069-03


LRDT


ZO!


ES


70076-01


LRDT


ZOl


ES


70078-02


LRDT


ZOl


ES


70090-02


LRDT


ZOl


S^


70092-02


LRDT


ZOl


ES


70094-01


LRDT


ZOl


ES


70096-01


LRDT



Study of Normal and Abnormal Embryonic

Development 462

Developmental Biology/Toxicology of Estrogenic
Environmental Chemicals 473

Chemical-Receptor Interactions in Reproduction

and Hormonal Toxicity 484

Molecular Mechanism of Steroid Hormone in Sex

Organ Development 495

Role of Peptide Growth Factors in Reproduction

and Development 503

Germ Cell-Specific Molecules of Spermatozoa 509

Characterization of Stage-Specific Surface

Antigens During Mouse Spermatogenesis 518

Neuroendocrine and Neurochemical Regulation of
Gonadal Function 526

Cellular and Molecular Mechanisms Mediating

Peptide Hormone Action 534

Neuroendocrine Regulation of Prolactin and
Pro-Opiomel anocortin-Deri ved Peptides 541

Regulation of Pulsatile Pituitary Hormone

Secretion 550



ZOl ES 22102-04 CMB

ZOl ES 22103-02 CMB

ZOl ES 22104-02 CMB

ZOl ES 22106-01 CMB



COMPARATIVE MEDICINE BRANCH



Online LibraryNational Institute of Environmental Health ScienceAnnual report : National Institute of Environmental Health Sciences (Volume 1985) → online text (page 112 of 114)