Teratology: Difference between revisions
Content deleted Content added
Congenital_disorder#Toxic_substances - definitely human scope |
Extended confirmed users, Pending changes reviewers, Rollbackers 57,701 edits →Teratogenic agents: Moved to talk page |
||
| Line 33: | Line 33: | ||
About 3% of newborns have a "major physical anomaly", meaning a physical anomaly that has cosmetic or functional significance.<ref>Kumar, Abbas and Fausto, eds., ''Robbins and Cotran's Pathologic Basis of Disease, 7th edition'', p.470.</ref> |
About 3% of newborns have a "major physical anomaly", meaning a physical anomaly that has cosmetic or functional significance.<ref>Kumar, Abbas and Fausto, eds., ''Robbins and Cotran's Pathologic Basis of Disease, 7th edition'', p.470.</ref> |
||
=== Teratogenic agents === |
|||
A wide range of different chemicals and environmental factors are suspected or are known to be teratogenic in humans and in animals. A selected few include: |
|||
*Drugs and medications: [[alcohol]] ([[ethanol]]) (see [[fetal alcohol spectrum disorder]]), [[isotretinoin]] (13-cis-retinoic acid, Roaccutane), [[temazepam]] (Restoril; Normisson), [[nitrazepam]] (Mogadon), [[nimetazepam]] (Ermin), [[aminopterin]] or [[methotrexate]], [[androgenic|androgenic hormones]], [[busulfan]], [[captopril]], [[enalapril]], [[coumarin]], [[cyclophosphamide]], [[diethylstilbestrol]], [[phenytoin]] (diphenylhydantoin, Dilantin, Epanutin), Dexamethasone, [[etretinate]], [[lithium]], [[methimazole]], [[penicillamine]], [[tetracyclines]], [[thalidomide]], [[trimethadione]], methoxyethyl [[ethers]], [[Flusilazole]], [[valproic acid]], and many more. |
|||
*Environmental chemicals: [[polycyclic aromatic hydrocarbons]] (polynuclear aromatic hydrocarbons), [[polychlorinated biphenyl]]s (PCBs), [[polychlorinated dibenzodioxins]] a.k.a dioxin, [[polychlorinated dibenzofurans]] (PCDFs), [[hexachlorobenzene]] [[hexachlorophene]], [[mercury (element)|organic mercury]], [[ethidium bromide]], etc. |
|||
*Ionizing radiation:{{Citation needed|date=April 2013}} [[atomic weapons]] fallout ([[iodine-131]], [[uranium]]), [[background radiation]], diagnostic [[x-ray]]s, [[radiation therapy]]{{citation needed|date=April 2013}} |
|||
*Infections: [[cytomegalovirus]], [[herpes virus]], [[parvovirus B19]], [[rubella|rubella virus]] (German measles), [[syphilis]], [[toxoplasmosis]], [[Venezuelan equine encephalitis virus]]. (An easy way to remember maternal infections is TORCH: Toxoplasmosis, Other agents, Rubella, CMV and HSV.) |
|||
*Metabolic imbalance: [[alcoholism]], [[cretinism|endemic cretinism]], [[diabetes]], [[folic acid deficiency]], [[iodine deficiency]], [[hyperthermia]], [[phenylketonuria]], [[rheumatic disease]] and [[heart block|congenital heart block]], [[Virilization|virilizing tumors]] |
|||
The status of some of the above substances (e.g. diphenylhydantoin) is subject to debate, and many other compounds are under varying degrees of suspicion. These include [[Agent Orange]],<ref name="pmid6137083">{{cite journal |author=Linnainmaa K |title=Sister chromatid exchanges among workers occupationally exposed to phenoxy acid herbicides 2,4-D and MCPA |journal=Teratog., Carcinog. Mutagen. |volume=3 |issue=3 |pages=269–79 |year=1983 |pmid=6137083|doi=10.1002/1520-6866(1990)3:3<269::AID-TCM1770030306>3.0.CO;2-F}}</ref> [[nicotine]],<ref name="pmid15033289">{{cite journal |author=Vaglenova J, Birru S, Pandiella NM, Breese CR |title=An assessment of the long-term developmental and behavioral teratogenicity of prenatal nicotine exposure |journal=Behav. Brain Res. |volume=150 |issue=1-2 |pages=159–70 |year=2004 |pmid=15033289|doi=10.1016/j.bbr.2003.07.005}}</ref> [[aspirin]] and other [[NSAID]]s. Other compounds are known as severe teratogens based on veterinary work and animal studies, but aren't listed above because they have not been studied in humans, e.g. [[cyclopamine]]. Teratogenic effects also help to determine the [[pregnancy category]] assigned by regulatory authorities; in the United States, a pregnancy category of X, D, or C may be assigned if teratogenic effects (or other risks in pregnancy) are documented or cannot be excluded. |
|||
==Other animals== |
==Other animals== |
||
Revision as of 00:14, 22 November 2013
 | It has been suggested that this article be merged into Developmental_toxicity. (Discuss) Proposed since April 2013. |
.JPG)
Teratology is the study of abnormalities of physiological development. It is often thought of as the study of human
congenital disorders without any structural malformations.[1]
Etymology
The term stems from the
genitive τέρατος teratos), meaning 'monster' or 'marvel', and λόγος logos, meaning 'the word' or, more loosely, 'the study of'.[2]
As early as the 17th century, teratology referred to a discourse on prodigies and marvels of anything so extraordinary as to seem abnormal. In the 19th century, it acquired a meaning more closely related to biological deformities, mostly in the field of botany. Currently, its most instrumental meaning is that of the medical study of teratogenesis,
congenital malformations
or individuals with significant malformations. There are many pejorative terms that have historically been used to describe individuals with significant physical malformations.
The term was popularized in the 1960s by Dr. Fetal alcohol syndrome.[3] With greater understanding of the origins of birth defects, the field of teratology now overlaps with other fields of basic science, including developmental biology, embryology, and genetics
.
Mammalia
Teratogenesis
Along with this new awareness of the
mammalian embryo came the development and refinement of The Six Principles of Teratology which are still applied today. These principles of teratology were put forth by Jim Wilson in 1959 and in his monograph Environment and Birth Defects.[4]
These principles guide the study and understanding of teratogenic agents and their effects on developing organisms:
- Susceptibility to teratogenesis depends on the genotype of the conceptus and the manner in which this interacts with adverse environmental factors.
- Susceptibility to teratogenesis varies with the developmental stage at the time of exposure to an adverse influence. There are critical periods of susceptibility to agents and organ systems affected by these agents.
- Teratogenic agents act in specific ways on developing cells and tissues to initiate sequences of abnormal developmental events.
- The access of adverse influences to developing tissues depends on the nature of the influence. Several factors affect the ability of a teratogen to contact a developing conceptus, such as the nature of the agent itself, route and degree of maternal exposure, rate of placental transfer and systemic absorption, and composition of the maternal and embryonic/fetal genotypes.
- There are four manifestations of deviant development (Death, Malformation, Growth Retardation and Functional Defect).
- Manifestations of deviant development increase in frequency and degree as dosage increases from the No Observable Adverse Effect Level (NOAEL) to a dose producing 100% Lethality (LD100).
Studies designed to test the teratogenic potential of environmental agents use animal model systems (e.g., rat, mouse, rabbit, dog, and monkey). Early teratologists exposed pregnant animals to environmental agents and observed the fetuses for gross visceral and skeletal abnormalities. While this is still part of the teratological evaluation procedures today, the field of Teratology is moving to a more
Genetically modified
mice are commonly used for this purpose. In addition, pregnancy registries are large, prospective studies that monitor exposures women receive during their pregnancies and record the outcome of their births. These studies provide information about possible risks of medications or other exposures in human pregnancies.
Understanding how a teratogen causes its effect is not only important in preventing congenital abnormalities but also has the potential for developing new therapeutic drugs safe for use with pregnant women.
Humans
In
congenital disorders resulted in about 510,000 deaths globally in 2010.[5]
About 3% of newborns have a "major physical anomaly", meaning a physical anomaly that has cosmetic or functional significance.[6]
Other animals
Fossil record
Evidence for congenital deformities found in the fossil record is studied by
Plantae
In botany, teratology investigates the theoretical implications of abnormal specimens. For example, the discovery of abnormal flowers—for example, flowers with leaves instead of petals, or flowers with staminoid pistils—furnished important evidence for the "foliar theory", the theory that all flower parts are highly specialised leaves.
See also
- Carcinogen
- Congenital abnormalities
- Mutagen
References
- ^ Rogers, J.M., Kavlock, R.J. Developmental toxicology. In C.D. Klaassen (ed.): Casarett & Doull's Toxicology, 5th ed. pp. 301-331. McGraw-Hill, New York, 1996. ISBN0-07-105476-6.
- ^ "Online Etymology Dictionary". http://www.etymonline.com/index.php?term=logos.
{{cite web}}:|access-date=requires|url=(help); Check date values in:|accessdate=(help); External link in|work=|url=(help) - PMID 4126070.)
{{cite journal}}: CS1 maint: multiple names: authors list (link - ISBN 0-12-757750-5.)
{{cite book}}: CS1 maint: extra punctuation (link - )
- ^ Kumar, Abbas and Fausto, eds., Robbins and Cotran's Pathologic Basis of Disease, 7th edition, p.470.
- ^ Molnar, R. E., 2001, Theropod paleopathology: a literature survey: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 337-363.