American biologists have proved that the cyclic period of
malaria caused by the presence of Plasmodium falciparum own circadian
rhythms that can be observed even in the culture in vitro and during infection “asynchronous”
master. The results of the experiments outlined in two articles in Science (1, 2).
Malaria is a serious infectious disease that is caused by
protozoa of the genus Plasmodium. The pathogen enters the
the victim’s blood with the bite of a certain species of mosquito, and starts to reproduce inside
first liver cells and then in erythrocytes — red blood cells. For
malaria is characterized by periodic fever, which occurs every 24,
48 or 72 hours. The cyclical nature of the disease to the cyclicality of the
parasites, which simultaneously destroys the erythrocytes and come out.
Previously it was believed that the development cycles of the parasite are regulated
the circadian rhythms of the host, however, scientists have found that Plasmodium is mainly guided by
own biological clock, which, however, can adapt
under the watch of their master. Two different teams on two types
Plasmodium followed by the expression of genes of parasites and found her
cycles regardless of the external conditions.
Scientists from southwestern University medical center
Texas worked on a mouse model of malaria, which is caused by simple Plasmodium chabaudi, and studied transcriptom parasite every 3 hours in
for three 24-hour cycles. They found that the expression of 60 percent of the genes
Plasmodium are subject to regular fluctuations in the cycle of 24 hours
preserved in mice with the downed mode. In the first case, infected mice were kept
in the dark, breaking their sleep, and in the second case randomly fed for
one day, violating the diet. It turned out that neither that, nor another does not affect the cycle
development of Plasmodium.
Cycle of Plasmodium was observed even in mutant mice with
off gene Cry,
who from birth lacked any mode of the day. However, 5-7
days of infection synchronicity of cycles of parasites in these mice were missing. In the mutant
mice with extra-long up to 26 hours a day (i.e. their daily functioning fit
at 25.7 hours, while in normal mice at 23.7 hours) life cycle
Plasmodium stretched accordingly master. The researchers concluded
each malaria parasite regulates its life cycle independently
however are capable to perceive signals from the body of the host, which,
apparently help to synchronize the population of parasites.
The research team from Duke University studied
the behavior of four strains of the causative agent of human malaria Plasmodium falciparum in culture in
vitro. Scientists analyzed the composition of the RNA of Plasmodium, with an interval in 3
hour for 60-70 hours. They found that at least 87 percent
transcripts of Plasmodium cycle. It should be noted that
genes homologous to the main circadian regulators are animals, no parasites,
however, even in the culture of their life cycle was 48 hours
variations from strain to strain.
The observations of scientists correspond to existing theories about
what part of the body every cell has its own biological clock
(circadian rhythms), but their cycle is not necessarily exactly 24 hours. For
adjust all cell hours need “master controller”, which in mammals
located in the hypothalamus. For the discovery of the biological clock and mechanism of the
2017 was awarded the Nobel prize in physiology or medicine, read
more info in our article “the clock only monotonous”.