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Toxoplasma gondii & Human Phenotype

Compendium of Known Effects and Ongoing Research

evolution

Brain development and plasticity

May 25, 2016
Martinez-Morga, M., Martinez, S.
Revista De Neurologia 2016; 62: 3-8
Click for abstract
Neurodevelopmental disorders are associated to functional anomalies of the brain that become manifest early on in life. Traditionally, they have been related almost exclusively to the appearance of intellectual disability and delayed psychomotor development. The causes of these disorders have been partially described, and include anomalies due to genetic causes (Down syndrome, fragile X syndrome, etc.), exposure to toxic factors during pregnancy (foetal alcohol syndrome), infections (cytomegalovirus, toxoplasmosis, etc.) or other alterations, including a status of great immaturity at birth (very preterm). Epidemiological data based on a better knowledge of the diseases affecting the central nervous system suggest that some mental disorders, which appear in adolescence or early adulthood, also have their origin in anomalies in brain development. This review aims to offer an overview of brain development. Some of the cellular and molecular processes that may account for the similarities and differences in the phenotypes that generate alterations affecting normal development are also analysed. The study is conducted with a view to clearly identifying processes that are susceptible to modification by means of therapeutic intervention consisting in an early care programme

Tagged: brain-development, cerebral cortex, cognition, cortical development, disorders, evolution, fgf8, forebrain, gene-expression, malformations, neural migration, neural regionalisation, neuronal migration, Schizophrenia, structural plasticity, synaptogenesis

Cognitive functionsMental health

Toxoplasma and reaction time: Role of toxoplasmosis in the origin, preservation and geographical distribution of Rh blood group polymorphism

September 26, 2008
Novotná, M., Havlícek, J., Smith, A.P., Kolbeková, P., Skallová, A., Klose, J, Gasová ,Z., Písacka, M., Sechovská, M. , Flegr, J.
Parasitology 2008; 135: 1253-1261
Click for abstract
The RhD protein which is the RHD gene product and a major component of the Rh blood group system carries the strongest blood group immunogen, the D-antigen. This antigen is absent in a significant minority of the human population (RhD-negatives) due to RHD deletion or alternation. The origin and persistence of this RhD polymorphism is an old evolutionary enigma. Before the advent of modern medicine, the carriers of the rarer allele (e.g. RhD-negative women in the population of RhD-positives or RhD-positive men in the population of RhD-negatives) were at a disadvantage as some of their children (RhD-positive children born to pre-immunized RhD-negative mothers) were at a higher risk of foetal or newborn death or health impairment from haemolytic disease. Therefore, the RhD-polymorphism should be unstable, unless the disadvantage of carriers of the locally less abundant allele is counterbalanced by, for example, higher viability of the heterozygotes. Here we demonstrated for the first time that among Toxoplasma -free subjects the RhD-negative men had faster reaction times than Rh-positive subjects and showed that heterozygous men with both the RhD plus and RhD minus alleles were protected against prolongation of reaction times caused by infection with the common protozoan parasite Toxoplasma gondii . Our results suggest that the balancing selection favouring heterozygotes could explain the origin and stability of the RhD polymorphism. Moreover, an unequal prevalence of toxoplasmosis in different countries could explain pronounced differences in frequencies of RhD-negative phenotype in geographically distinct populations

Tagged: balancing selection, blood antigen, blood group system., evolution, heterozygous advantage, Parasite, Rhesus factor

Cognitive functionsMotor functions

Neurophysiological effect of the Rh factor. Protective role of the RhD molecule against Toxoplasma-induced impairment of reaction times in women

January 9, 2008
Flegr, J., Novotná, M., Lindová, J., Havlíček, J.
Neuroendocrinology Letters 2008; 29: 475-481
Click for abstract
BACKGROUND: The biological function of RhD protein, a major component of the Rh blood group system, is largely unknown. No phenotypic effect of RhD protein, except its role in hemolytic disease of newborns and protective role against Toxoplasma-induced impairment of reaction times in men, has been described. METHODS: Here we searched for a protective effect of RhD positivity against Toxoplasma-induced prolongation of reaction times in a set of 110 male and 226 female students of the Faculty of Science tested for latent toxoplasmosis and concentration of testosterone in saliva. RESULTS: RhD-positive subjects have been confirmed to be less sensitive to the influence of latent toxoplasmosis on reaction times than Rh-negative subjects. While a protective role of RhD positivity has been demonstrated previously in four populations of men, the present study has shown a similar effect in 226 female students. Our results have also shown that the concentration of testosterone in saliva strongly influences (reduces) reaction times (especially in men) and therefore, this factor should be controlled in future reaction times studies. CONCLUSIONS: The observed effects of RhD phenotype could provide not only a clue to the long-standing evolutionary enigma of the origin of RhD polymorphism in humans (the effect of balancing selection), differences in the RhD+ allele frequencies in geographically distinct populations (resulting from geographic variation in the prevalence of Toxoplasma gondii), but might also be the missing piece in the puzzle of the physiological function of the RhD molecule.

Tagged: balancing selection, behavioral-changes, blood antigen, blood group system., complement-fixation, evolution, gondii, heterozygous advantage, humans, latent toxoplasmosis, Parasite, psychomotor performance, Rhesus factor, testosterone

Cognitive functionsMotor functions

Decrease of psychomotor performance in subjects with latent “asymptomatic” toxoplasmosis

September 26, 2001
Havlícek, J., Gasová, Z., Smith, A. P. , Zvára, K, J. Flegr, J.
Parasitology 2001; 122: 515-520
Click for abstract
Toxoplasma gondii is known to induce speciÆc behavioural changes in its intermediate hosts. This is usually considered to be an evolutionary adaptation aimed to increase the probability of transmission of the parasite into its deÆnitive host, the cat, by predation. In rodents an increase of reaction time as well as many other speciÆc behavioural patterns have been observed. Here we report the results of our double blind study showing the signiÆcantly longer reaction times of 60 subjects with latent toxoplasmosis in comparison with those of 56 controls. Moreover, the existence of a positive correlation between length of infection and mean reaction time suggested that slow and cumulative effects of latent toxoplasmosis rather than a one-step (and possibly transient) effect of acute toxoplasmosis disease are responsible for the decrease of psychomotor performance of infected subjects. To our knowledge, this is the Ærst study conÆrming the existence of such parasite-induced changes in human behaviour that could be considered in evolutionary history of the human species as adaptive from the point of view of parasite transmission.

Tagged: behaviour, evolution, Human, manipulation hypothesis, Parasite, reaction times, Toxoplasma gondii

Cognitive functionsMotor functions

Topics

  • Behavior 105
  • Cognitive functions 64
  • Mental health 439
  • Morphology 6
  • Motor functions 10
  • Personality 36
  • Physical health 134
  • Reproduction 36
  • Reviews 40
  • Sensory functions 3
  • Uncategorized 2

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Recent articles

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  • The role of latent toxoplasmosis in the aetiopathogenesis of schizophrenia–the risk factor or an indication of a contact with cat? February 6, 2020
  • The Association between Toxoplasma gondii Infection and Risk of Parkinson’s Disease: A Systematic Review and Meta-Analysis February 6, 2020

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