Sickle Malaria

Sickle-cell hemoglobin confers resistance to malaria... 

In certain reglon.s of Africa, tire. sickle-cell trait Is found In 20% of the people. Wiry does snch a deleterious heritable condition persist in dre popnladon For reasons as yet unknown, individnals widr this trait are less sn.scepdble to dre most virnlent form of malaria. The geographic distribn-don of malaria and dre sickle-cell trait are posidvely correlated. 

It is also important to understand the source and significance of genetic variations. The Pima Indians have the highest rates of diabetes in the world Tay-Sachs disease is primarily found in Ashkenazi Jews. Contemporary literature indicates that these differences stem from reproductive isolation, not race. Genetic traits common to persons with sickle-cell disease are related to malaria frequency and not our social view of race. This is why the disease can be found in high frequency in Yemen, West Africa, Greece, and Saudi Arabia. 

Life and Death for Proteins Chaperonins and Proteasomes Sickle Cell Disease, Malaria, and Blood Substitutes The T-Even Bacteriophages Mitosis, Tetraploid Plants, and Anticancer Drugs... 

BOX 7-B SICKLE CELL DISEASE, MALARIA, AND BLOOD SUBSTITUTES... 

Why is there such a high incidence of the sickle cell gene, estimated to be present in three million Americans The occurrence and spread of the gene in Africa was apparently the result of a balance between its harmful effects and a beneficial effect under circumstances existing there. The malaria parasite, the greatest killer of all time, lives in red blood cells during part of its life cycle (see Fig. 1-9). 

Red cells that contain Hb S as well as Hb A are apparently less suitable than cells containing only Hb A for growth of the malaria organism. Thus, het-erozygotic carriers of the sickle cell gene survived epidemics of malaria but at the price of seeing one-fourth of their offspring die of sickle cell disease. 

Deficiency of the first enzyme of the pentose phosphate pathway, glucose 6-phosphate dehydrogenase, is widespread.11 Its geographical distribution suggests that, like the sickle-cell trait, it confers some resistance to malaria. A partial deficiency of 6-phosphogluconolactonase (Eq. 17-12, step b) has also been detected within a family and may have contributed to the observed hemolytic anemia.1... 

However, the mechanism of the malaria protection is complex (64). It probably involves a sufficient survival time of particularly the malaria-infected heterozygous infant girls to allow them to develop immunological defences against malaria. This could mean that after puberty, their better state of health might render them more fertile than their less protected sisters. Since the occurrence of G-6-PD deficiency, of sickle cell anemia,... 

A disorder related to sickle cell anemia is the HbC disease, which is also found mostly among persons of African ancestry. Its symptoms, however, are less severe than those with the HbS disorder. HbC is a hemoglobin with a /36Glu—>Lys substitution. It is believed that HbS and HbC arose as a means of combating malaria, because red cells containing HbS and HbC are more resistant to the invasion of the malarial parasite than are normal red cells. 

As a result of impaired antioxidant activity in erythrocytes, there may be increased fragility of erythrocyte membranes or reduced membrane fluidity. As in sickle cell trait, which also protects against malaria, this may result in ... 

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