Teratology

Teratological study in DEVELOPMENTAL BIOLOGY.

1. TOPIC:TERATOLOGY

2. TERATOLOGY: The study of abnormal development in embryos and the cause of congenital malformation or birth defects. It is also the science that study the causes mechanism and patterns of abnormal development.

3. Developmental disorders that present at birth are called congenital anomalies,birth defect or congenital malformation. Congenital anomalies are of four clinically significant types: Malformation ,disruption, deformation,dysplasia .

4. Abnormalities due to exogenous agents (certain chemicals or viruses, radiation, or hyperthermia) are called disruptions . The agents responsible for these disruptions are called teratogens (Greek, "monster-formers"), and the study of how environmental agents disrupt normal development is called teratology. MALFORMATION: Congenital malformation are structural defects that present at birth. They may be gross or microscopic,on the surface of body or within it,hereditary,nonhereditary,single or multipule .

5. TERATOLOGY TERMS: MALFORMATION :is primary structural defect resulting from localized error of morfogensis . DISRUPTIONS: is specific abnormality that results from disruption of normal developmental process ,it depends on time not on agent. DEFORMATION: is an alternation in shape, structure of normally formed part. SYNDROME: recognized pattern of malformation with a given etiology.

6. TERATOGENS; Teratogen: is an agent which can cause a birth defect .it is usually something in the environment that the mother may be exposed to during her pregnancy.it could be a prescribed medication,a street drug,alcoho;l use,or a disease present in the mother,which could increase the chance for the baby to born with birth defect.

7. About 4 to 5 percent birth defect are caused by exposure to a teratogen during pregnancy. Teratogen can impact a baby development as little 10 to 14 days after conception.

8. LIST OF COMMON EXPOSURES: ALCOHOL :dependi ng upon the amount of alcohol you consume , the risk of miscarriage and birth defects vary. A small to moderate amount e.g 2 to 4 drinks can lead to fetal alcohol effect . Which increase the risk of mis carriage , development delay,hyperactivity in child. Heavy use of alcohol can lead to fetal alcohol syndrome , where risk to miscarriage is increased and baby has a small head size,small eyes, and nose, small nails , ear abnormalities , herat defects,learining difficulities etc.

9. CIGARETTE SMOKING: The more a women smoke , the higher the risk of miscarriage,low birth weight,premature birth,sudeen infant death syndrome,increase in developmentak delays. Smoking over two packs per day put your pregnancy at increased defects rate. It is also important to not allow anyone to smoke around newborn infants.

10. Smoking while pregnant significally increase chance of having complication during pregnancy. Cigarettes contain chemicals like nicotine,carbon monoxide,that are harmful to not only adults but definitely to growing babies. These chemicals can prevent the development of healthy babies.

11. ACCUTANE: Accutane is retinoic acid that is given in pill from by prescription only for severe acne. This medication is dangerous for infants exposed to abnormalities like hydrocephalus,brain defects,mental retardation,heart and limb defect etc.

12. ANTI DEPRESSANTS: With anti depressants , there can be less 1 percent increased risk of learning difficulties . There can be premature delivery. Moreover stress can cause host of otherproblems to the baby,and post partum depression can be worse in women who suffer from depression.

13. Many prescription drugs have been proven to be safe for pregnancy. Many antidepressants have pregnancy safe options. The average women takes between three and five medications during her pregnancy. Abusing these medications sometime can cause extremely negative effects to mother and fetus.

14. PRENTAL RADIATION EXPOSURE : Is the exposure of an unborn baby to radiation . This exposure of the fetus can occur when the mother abdomen area is exposed to radiation ( e.g X RAYS) From mother, radioactive debris may pass through the umbilical cord to the baby. Before about 2 weeks health effect of concern from an exposure of 10 rads results death of embryo. Because embryo made up of few cells ,and radiaton can cause death of cells . If embryo will survive,exhibit few congenital abnormalities.

15. RETINOIC ACID: Retinoic acid or vitamin a derivatives are extremely teratogenic in humans . Even a very low doses,oral medications such as isotretinoin , used in treatment of acne are potent teratogen. This cause malformations such as craniofacial dysmorphism , cleft palate,thymic aplasia, and neural tube defect .

16. In 1961 , Lenz and McBride independently accumulated evidence that thalidomide, prescribed as a mild sedative to many pregnant women, caused an enormous increase in a previously rare syndrome of congenital anomalies. The most noticeable of these anomalies was phocomelia , a condition in which the long bones of the limbs are deficient or absent . Over 7000 affected infants were born to women who took this drug, and a woman need only have taken one tablet to produce children with all four limbs deformed.

17. THALIDOMIDE : It is one of the most famous teratogen . This hypnotic agent was used in EUROPE in 1959, after which about 7000 infant was born with thalidomide syndrome . The features of syndrome include limb abnormalities .it also cause malformation of other organs including of external ears, congenital heart diease , and congenital urinary tractmalformation . Infectious agents can also cause a variety of birth defects and mental retardation when they cross the placenta and entre into blood stream.

18. Thalidomide can also cause birth defects. At high risk thalidomide can cause excessive blood clots. Thalidomide can interfare with formation of various kinds of blood cells creating risk of infection via NUTROPENIA,LEUKOPENIA and risk that blood will not clot via THROMBOCYTOPENIA . This drug can also damage the nerves , causing PERIPHRAL NEUROPATHY . It can cause liver damage and also cause TUMOR LYSIS SYNDROME.

19. PRINCIPLE OF TERATOLOGY: JAMES GRAVES WILSON gives six principle of teratology. (1)First principle: Susceptibility to teratogenesis depends on the genotype of the concepts and a manner in which this interacts with adverse environmental factors, has four sections: In section A , Species differences Wilson says some species respond to some teratogens but some are not ,for example ,HUMANS are extremely vulnerable to THALIDOMIDE, a sedative used in 1950 to treat morning sickness. If exposed to thalidomide during embryonic development , fetuses develop limb and facial malformation . Other mammals included Rats and Mice are resistant to Thalidomide.

20. CONTI…… In section B, ‘ ’strain Differences ’’ Wilson notes that animal of the same species with different genetic background can differ in the frequency and intensity of abnormalities caused by Teratogens. In section C ,’ ’ Interractionn of genome and environment’’, Underscores the interplay between environment and genetics that results in different abnormalities between organisms with same genome raised in different environment and between organisms with different genome raised in same environment . e.g ability of pregnant female to metabolites teratogen , partly determine whether or not a fetus will develop abnormalities.

21. Second principle: Susceptibility to teratogenesis varies with developmental stage at the time of exposure to an adverse influence . Having some sections , ‘ ’sub division of developmental span ’’Principle two chronologically illustrates that the stages of development from the early refractory period to birth and afterward. NEXT, Wilson describes embroys susceptibility to teratogens within each stage of development . Highly susceptible period of organogenensis ‘’Wilson studies of teratogen ,and depict the process of organogenesis, the development of organ with an organism along with the increase incidence of malformation caused by teratogens due to differentiation of tissues.

22. ‘ ’What about Germ cells’’ Wilson says that factor such as environment, drugs and dietary deficiency could damage germ cells and the germ layers . However, when Wilson published his principles, reshearches had not determined whether or not teratogens could impact certain stages of gametogenesis , or gamete formation.

23. ( 3) THIRD PRINCIPLE: Teratogenic agents act in specific ways on developing cells and tissues to initiate sequence of abnormal development events. Has two sections, In section A ,’ ’Mechanism of teratogenesis ‘’ In section B , ’’ Pathogenesis of defect’’ In these sections Wilsons asserts that specific teratogenic agents produced malformations. Through this third principle, WILSON indicated that people may be able to take supplements to protect against particular teratogenic agents.

24. 4) FOURTH PRINCIPLE: The access of adverse influence to developing tissues depends on the nature of the influence . Having two agents : physical agents. Chemical agents. The body of pregnant female protect the developing tissues of germ cells , embryos and fetus . According to 4 principle he says that in placental mammals many physical agents such as low energy radiation do not much affect the developing fetus.

25. However Wilson treated ionizing radiations as an exception among physical agents due to its ability to reach developing tissue. Thus , one of the 1 st environmental classified as a teratogens that is X rays. However, Chemical agents almost reach developing tissues, via the maternal blood streams . The concentration of the chemical agents varies by time and the agents reaches the fetus , variations effect the extent of abnormal development.

26. (5 ) Fifth PRINCIPLE: The four manifestation of deviant development are death, malformation, growth retardation, and functional deficit. He argues that encounters with teratogenic agents at any point during development have ability to produce one or more of these manifestations, and some manifestations can occur during stages of development. After an embryo in plants in a uterus wall , but before it cells differentiate ,the most common manifestation of deviant development is the embryo death. Organism sensitive to teratogens are more susceptible to having their embryo die then they are to having those embryo develop with abnormalities.

27. 6)Six principle: Manifestations of deviant development increase in frequency and degree as dosage increase,from no effect to the totally lethal level. He says that while studies indicate that organisms may have threshold to teratogen or that pregnant females may interact with teratogens and have offsprings that show no evidence of defect.

28. CONCLUSION: There are many different types of teratogens ; They can have many negative harmful effects to both mother and the child after its born . Mothers need to be careful about what they surround themselves with r ingest while they are pregnant. Teratogen can affect babies anytime during the pregnancy and can even affect conception .

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