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MINISTRY OF PUBLIC HEALTH OF UKRAINE

BUKOVINIAN STATE MEDICAL UNIVERSITY


Approval on methodological meeting

of the department of pathophisiology

Protocol №

Chief of department of the pathophysiology,

professor Yu.Ye.Rohovyy

“___” ___________ 2008 year.


Methodological Instruction

to Practical Lesson



Мodule 1 : GENERAL PATHOLOGY.

Contenting module 2. Typical pathological processes.


Theme9: The role of heredity and constitution in pathology.


Chernivtsi – 2008

1.Actuality of the theme. Hereditary factors play an essential role in human pathology. About 2000 different hereditary diseases are known now. 4 % of new-born suffer from these or other genetically conditioned defects. This testifies importance of ability to participate in exposure methods of hereditary diseases, study ways of their prophylaxis and cure principles. Heredity pathology plays an important role in development of such hereditary conditioned diseases, as atherosclerosis, essential hypertension, rheumatism, diabetes mellitus, gout.

Genetic information is carried from DNA to RNA proteins. Three major processes are involved in the preservation and transmission of genetic information:

1) the first is replication (or copying) of DNA to form identical daughter molecules;

2) the second one is transcription, in which the genetic message encoded within DNA is transcribed into the form of RNA and is carried to the ribosomes, the sites of protein synthesis;

3) the third is translation, in which the genetic messages is decoded and converted into the 20-letter alphabet of protein structure.

Multifactorial disorders result when small variations in genes combine with environmental factors to produce serious defects.

^ 2.Length of the employment – 2 hours.

3.Aim:

To khow hereditary diseases, hereditary predisposition, congenital (innate) diseases.

To be able: to analyse of the pathogenesis of chromosomal diseases, phenylketonuria.

^ To perform practical work: Characterize fragile X-associated mental retardation syndrome produces a-unique combination of phenotypic features that affect the central nervous system, the testes, and the cranial skeleton.

In some respects, fragile X-associated mental retardation syndrome is similar to other genetic conditions caused by X-linked mutations – affected are impaired more severely than affected females, and the condition is never transmitted from father to son.



Penetrance of fragile X-associated mental retardation syndrome. This artificial pedigree of the syndrome shows the each individual will manifest phenotypic features of the condition (penetrance). Penetrance increases with each successive generation owing to the progressive expansion of a triplet repeat element. Expansion is dependent on maternal allele; thus, daughters of normal transmitting males (indicated with a T in ІІ-4) are non-penetrant.


4. Basic level.


The name of the previous disciplines


The receiving of the skills

  1. histology

  2. biochemistry

  3. physiology

Encoding of hereditary information.

Legitimacy and types of hereditary signs transmission in generations.

Cytological genetic base.




^ 5. The advices for students.


1. Identify the criteria used to define multifactorial disease.

Several criteria can be used to define multifactorial inheritance. First, the recurrence risk becomes higher if more than one family is affected. If two siblings have the same defect, the recurrence risk is greater than if only one sibling has the defect. The family has more genetic or environmental risk factors and are more likely to produce an affected child. In single-gene diseases, the recurrence risk is the same regardless of the number of affected siblings.

Second, if the disease is expressed in the proband and is severe, the recurrence risk is higher. A more severe expression indicates that the affected individual is at the extreme end of liability distribution and his or her relatives are at a higher risk to inherit the disease genes.

Third, the recurrence risk is higher if the proband is one of the less commonly affected sex. This is because an affected individual of the less susceptible gender is usually at a more extreme position of the liability distribution.

Fourth, the recurrence risk for the disease usually decreases rapidly in more remotely related relatives. This is because many genes and environmental factors must combine to produce a trait or disease. All risk factors are unlikely to be present in less closely related family members.


2. ^ Complex genetic diseases

Disease

Contributing environmental factors

Gastrointestinal disorders:

Colon cancer

Type I diabetes

Type II diabetes

Obesity


^ Cardiovascular disorders:

Coronary heart disease


Hypertension, stroke


Neuromuscular disorders:


Alzheimer disease

Psychiatric disorders:

Alcoholism

Breast disorders:

Female breast cancer


High fat, low fiber

Viral infections triggering immune

responses

Obesity, dietary sugar

Excessive caloric intake


Fat intake, minimal exercise, smoking,

elevated cholesterol

Fat intake, minimal exercise, smoking,

stress

Enzyme deficiencies, chemicals

(suspected)

Neurochemicals (suspected)

Social, environmental intake


High fat intake, alcohol consumption



3. ^ Characterize chromosome abnormalities.

The chromosome abnormalities: the defect is due to an abnormality in chromosome number or structure.

Normal somatic cells, having two sets of 23 chromosomes are diploid (double) or 2N. Stable types of structural abnormalities include deletion, duplication, inversion, or translocation of a chromosome.

4. ^ Describe inheritance and environmental interactions.

The struggle between nature, or genetic traits, and nature, or environment, is regarded as disease causality today.

However, good epidemiologic data are now making distinctions and establishing relationships. The relative impact of genes and environment varies with the disease. For example, an extra chromosome 21 is observed in man regardless of environment; it has only a genetic basis. However, an individual genetically lacking the enzyme to metabolise the amino-acid phenylalanine could develop brain damage and mental retardation only if exposed to dietary phenylalanine. This, then, is a disease requiring both and inherited defect and an environmental exposure.

5. ^ Cite well-known examples of chromosome disorders.

A common example of a disorder that results form an abnormality of chromosome number is trisomy 21, or Down’s syndrome.

Clinical diagnosis of trisomy 21 is often based on facial appearance. The nose is small, and the facial frontile is flat.

Another chromosomal disorder is the Turner’s syndrome (female phenotype is 45X), the diagnosis is suggested in the newborn by the presence of redundant neck skin and peripheral edema. Later the presence of short stature or primary amenorrhea is suggestive.

Klinefelter syndrome (male is 47XXY). This syndrome is the most common cause of hypogonadism and infertility in men.

6.^ Cite the well-known examples of single-gene disorders.

One of the most well-known autosomal dominant diseases is Huntington’s disease, a neurologic disorder that exhibits progressive dementia and increasingly uncontrollable movements of the limbs. Also called Huntington’s or chronic chorea.

7. Describe the normal and abnormal phenylalanine metabolism (molecular hereditary disease)



If phenylalanine hydroxylase is disturbed, then direct effect of elevated phenylalanine levels on the energy production in protein synthesis, and neurotransmitter homeostasis in the developing brain occur.

Thus, the neurologic manifestations of phenylketonuria are felt to be due to a general effect on the CNS metabolism.

8. What is constitution?

The constitution or make up of the body is an unified complex of morphological, functional, psychological peculiarities being formed on the hereditary basis under the influence of the environmental factors.

^ 9. What is the role of constitution in pathology?

The constitution determines individual reactivity and adaptational possibility to the environment, pathological predisposition to certain diseases.

The constitution plays a key role in the pathogenesis of various diseases (for example, tuberculosis, obesity, hypertension, bronchial asthma and others).

Abnormality of constitution, the so called diathesis, is characterized by pathological reactions to a physiological agent.

^ 5.1. Content of the theme. Identify the criteria used to define multifactorial disease. Complex genetic diseases. Characterize chromosome abnormalities. Describe inheritance and environmental interactions. Cite well-known examples of chromosome disorders. Cite the well-known examples of single-gene disorders. Describe the normal and abnormal phenylalanine metabolism (molecular hereditary disease).What is constitution? What is the role of constitution in pathology?


^ 5.2. Control questions of the theme:

1. Identify the criteria used to define multifactorial disease.

2. Complex genetic diseases.

3. Characterize chromosome abnormalities.

4. Describe inheritance and environmental interactions.

5. Cite well-known examples of chromosome disorders.

6. Cite the well-known examples of single-gene disorders.

7. Describe the normal and abnormal phenylalanine metabolism (molecular hereditary disease)

8. What is constitution?

9. What is the role of constitution in pathology?


^ 5.3. Practice Examination.


Practice examination N 1

I. For each statement write T (true) or F (false) in the blank provided

1. Hypertension is a multifactorial disease.

2. Fat intake is a risk factor for many diseases.

3. A multifactorial trait is expressed when multiple genes and environmental influences blend together.

4. In Down’s syndrome, the pathology is manifested independent of environment.

5. It is easy to distinguish between the effects of shared environmental factors and the effects of a common pool genes.

6. Psychiatric disorders do not manifest familial patterns.

7. Relative risk is a ratio between incidence and individuals.

8. Early type II diabetes may develop when an individual’s diet changes to heavy carbohydrate consumption.

9. Finding and understanding environmental factors that effect penetrance of specific genes is important if chronic familial diseases are to be prevented.

10. A variation in the phenotype for different genotypes caused by the environmental factors is a threshold liability trait.

11. The frequency of genetic disease in the population depends on phenotypes.

12. Risk factors, when removed or eliminated, delay or prevent disease.

13. A proband is the individual beginning the pedigree.

14. The recurrence risk is less when more than one sibling is affected.

15. The existence of a particular risk factor indicates an individual will develop a specific disease.

16. The expression of a disease may require both an inherited defect and environmental exposure.

17. Multifactorial diseases can change substantially from one population to another because gene frequencies and environments differ.

18. Dizygotic twins are identical.

19. Recurrence risk is higher if the disease is more severe in the proband.

20. The prevalence rate is the number of individuals affected with a disease.

21. The incidence rate is the number of persons who have died from the disease.


II. Match the environmental factor(s) with the disease.

A. Wheat gluten

B. High-fat, low-fiber diet

C. Minimal exercise

D. Iron absorption

E. Streptococcal infection

F. Pollen exposure

G. Viral infections

H. Elevated serum cholesterol

22. Type I diabetes

23. Hypertension

24. Colon cancer

25. Coronary artery disease


III. Case study Mrs. C is a 58-year-old recently widowed, black female admitted to the emergency room because of shortness of breath and palpitations. She states that her shortness of breath is worst when lying flat and when climbing stairs. After climbing stairs, Mrs. C indicates that her heart “continues to pound” for several minutes.

Physical examination showed her well oriented and her mucous and nails beds to be pink. Her skin was cool and dry. Mrs. C’s blood pressure was 200/100, and her heart rate was 110 strong, but irregular. Respirations were 30 and labored. The cardiac monitor displayed trial fibrillations with premature ventricular response. Neither of Mrs. C’s electrocardiograms, not her cardiac enzyme levels indicated myocardial infarction. Appropriate in-hospital intervention reduced Mrs. C’s blood pressure.


Literature:

1. Gozhenko A.I., Makulkin R.F., Gurcalova I.P. at al. General and clinical pathophysiology/ Workbook for medical students and practitioners.-Odessa, 2001.- P. 51-60.

2. Gozhenko A.I., Gurcalova I.P. General and clinical pathophysiology/ Study guide for medical students and practitioners.-Odessa, 2003.- P. 47-59.

3. Robbins Pathologic basis of disease.-6th ed./Ramzi S.Cotnar, Vinay Kumar, Tucker Collins.-Philadelphia, London, Toronto, Montreal, Sydney, Tokyo.-1999.

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