Vliv parazita na fenotyp hostitele - úleková reakce

Department of Philosophy and History of ScienceKatedra filosofie a dějin přírodních vědFaculty of SciencePřírodovědecká fakult

Úleková reakce u osob s latentní toxoplasmosou

Possible connection between latent toxoplasmosis and schizophrenia is a very interesting and medically important topic. In this thesis I tried to map current state of knowledge in the interdisciplinary research of schizophrenia and Toxoplasma gondii and their possible connections as well as to show differences in responses between Toxoplasma-positive and Toxoplasma-negative subjects using simple computer-administered tests of prepulse inhibition of startle reaction (PPI). Such differences would suggest another similarity between schizophrenia patients and subjects with latent toxoplasmosis as the sensorimotor gating responsible for PPI was found to be disrupted in schizophrenia patients. Side goal of the study was to test newly developed PC software for testing PPI and to determine its applicability in further research. Subjects for the tests were recruited among adepts of professional military service; 409 subjects completed the test of acoustic PPI and 276 subjects completed the test of visual PPI. All the subjects were tested on presence of specific anti-Toxoplasma IgG in their blood serum. Both tests revealed significant (p<0.001) differences between responses on prepulse-preceded stimuli and plain stimuli without prepulse, no significant results were, however, gained for the effects of latent..

Vliv toxoplasmosy na reakční časy a prepulsní inhibici úlekových reakcí u člověka

Effects of Toxoplasmosis on Reaction Times and Prepulse Inhibition of Startle Reaction in Humans v Abstrakt Toxoplasma gondii, jednobuněčná kokcidie z téměř výhradně parazitického kmene Apicomplexa, zřídka působí u lidí akutní potíže. Ty se týkají převážně imunodeficientních jedinců a těhotných žen, respektive vyvíjejích se plodů. Ve své latentní fázi mohou bradyzoiti z tkáňových cyst umístěných zejména v nervové a svalové soustavě vyvíjet mírný, avšak dlouhodobý tlak na hostitelský organismus, a to v podobě normálních průvodních jevů přítomnosti parazitického organismu v tkáních hostitele, ale pravděpodobně i jako následek adaptivní evoluce parazita směřující ke zvýšení pravděpodobnosti trofického přenosu do definitivního hostitele, kočkovité šelmy. Následkem mohou být v případě člověka mírné změny v osobnostním profilu hostitele, zhoršení psychomotorických i kognitivních funkcí, až rozvoj závažných duševních poruch. Práce se zabývá převážně jedním z aspektů těchto změn - efektem latentní toxoplasmózy na zpracování úlekových signálů samotných a modifikovaných prostřednictvím slabého signálu předcházejícího samotný signál úlekový, neboť právě tento aspekt by mohl souviset s rozvojem schizofrenie u predisponovaných jedinců. Studie provedené v rámci projektu zjistily změny v rychlosti zpracování signálu u...Effects of Toxoplasmosis on Reaction Times and Prepulse Inhibition of Startle Reaction in Humans vi Abstract Toxoplasma gondii, a single-cell coccidia from almost exclusively parasitic phylum Apicomplexa, does not typically cause acute health issues in humans with most exceptions among immunodeficient individuals and pregnant mothers or, more precisely, their offspring. In the latent phase, the bradyzoites in tissue cysts placed most often in neural and muscle tissues can evolve pressure on the host's body both as a collateral effect of the presence of the parasitic organism in host's tissues and as a consequence of adaptive evolution leading to increase in probability of trophic transmission to the final host, a felid. In humans, this can result in slight changes in personality profiles, deterioration of psychomotor and cognitive functions, and development of serious mental disorders. The thesis focuses predominantly on one of the aspects of the changes, namely the effect of latent toxoplasmosis on the processing of startle signals themselves and when modified by a preceding low-intensity signal; this processing may be connected with the development of schizophrenia in predisposed individuals. Studies conducted within the project framework found changes int the speed of signal processing in...Katedra filosofie a dějin přírodních vědDepartment of Philosophy and History of SciencePřírodovědecká fakultaFaculty of Scienc

Effects of Toxoplasmosis on Reaction Times and Prepulse Inhibition of Startle Reaction in Humans

Effects of Toxoplasmosis on Reaction Times and Prepulse Inhibition of Startle Reaction in Humans vi Abstract Toxoplasma gondii, a single-cell coccidia from almost exclusively parasitic phylum Apicomplexa, does not typically cause acute health issues in humans with most exceptions among immunodeficient individuals and pregnant mothers or, more precisely, their offspring. In the latent phase, the bradyzoites in tissue cysts placed most often in neural and muscle tissues can evolve pressure on the host's body both as a collateral effect of the presence of the parasitic organism in host's tissues and as a consequence of adaptive evolution leading to increase in probability of trophic transmission to the final host, a felid. In humans, this can result in slight changes in personality profiles, deterioration of psychomotor and cognitive functions, and development of serious mental disorders. The thesis focuses predominantly on one of the aspects of the changes, namely the effect of latent toxoplasmosis on the processing of startle signals themselves and when modified by a preceding low-intensity signal; this processing may be connected with the development of schizophrenia in predisposed individuals. Studies conducted within the project framework found changes int the speed of signal processing in..

Contrasting effect of prepulse signals on performance of Toxoplasma-infected and Toxoplasma-free subjects in an acoustic reaction times test.

About 30% of people on Earth have latent toxoplasmosis. Infected subjects do not express any clinical symptoms, however, they carry dormant stages of parasite Toxoplasma for the rest of their life. This form of toxoplasmosis is mostly considered harmless, however, recent studies showed its specific effects on physiology, behaviour and its associations with various diseases, including psychiatric disorders such as schizophrenia. Individuals who suffer from schizophrenia have about 2.7 times higher prevalence of Toxoplasma-seropositivity than controls, which suggests that some traits characteristic of schizophrenic patients, including the sex difference in schizophrenia onset, decrease of grey matter density in specific brain areas and modification of prepulse inhibition of startle reaction could in fact be caused by toxoplasmosis for those patients who are Toxoplasma-seropositive.We measured the effect of prepulse inhibition/facilitation of the startle reaction on reaction times. The students, 170 women and 66 men, were asked to react as quickly as possible to a startling acoustic signal by pressing a computer mouse button. Some of the startling signals were without the prepulse, some were 20 msec. preceded by a short (20 msec.) prepulse signal of lower intensity. Toxoplasma-seropositive subjects had longer reaction times than the controls. Acoustic prepulse shorted the reaction times in all subjects. This effect of prepulse on reaction times was stronger in male subjects and increased with the duration of infection, suggesting that it represented a cumulative effect of latent toxoplasmosis, rather than a fading out after effect of past acute toxoplasmosis.Different sensitivity of Toxoplasma-seropositive and Toxoplasma-seronegative subjects on effect of prepulses on reaction times (the toxoplasmosis-prepulse interaction) suggested, but of course did not prove, that the alternations of prepulse inhibition of startle reaction observed in schizophrenia patients probably joined the list of schizophrenia symptoms that are in fact caused by latent toxoplasmosis

Black and White Magic: Efficacy of In-group versus Out-group Rituals

Supernatural beliefs are a cultural universal, but each society has a specific repertoire of such beliefs. Indeed, membership of a group and sharing its beliefs are intertwined. The distinction between helpful white magic typically practiced by in-group members and harmful black magic practiced by out-group members is one aspect of this. These considerations make the cross-cultural study of supernatural belief particularly difficult; hindering assessment of anything like a general level of espousal of supernatural beliefs. We examined how the estimated efficacy of rituals is affected by two factors: 1) whether the ritual performer is an in-group member and 2) whether the ritual is intended to have a helpful or harmful effect. Our subjects were presented with descriptions of three helpful and three harmful rituals and asked to judge their efficacy. The scenarios presented to different subjects were modified only in terms of whether the ritual performer was presented as a member of the same religious group as the subject. The responses were analysed in terms of their relationship to religious identification, self-reported measures of religiosity, and early exposure to religious models. Our hypothesis was that rituals aimed to help and performed by an in-group member would be rated as more effective in comparison with those performed by an out-group member, while we expected opposite results for rituals that aim to harm somebody. The results confirmed our main hypothesis and supported the role of some measures of religiosity and exposure to religious models in the rated efficacy of positive rituals