scholarly journals Adaptive periodicity in the infectivity of malaria gametocytes to mosquitoes

2018 ◽  
Vol 285 (1888) ◽  
pp. 20181876 ◽  
Author(s):  
Petra Schneider ◽  
Samuel S. C. Rund ◽  
Natasha L. Smith ◽  
Kimberley F. Prior ◽  
Aidan J. O'Donnell ◽  
...  
Keyword(s):  
Blood Parasite ◽  
Parasite Development ◽  
Bed Nets ◽  
Immune Defence ◽  
Mosquito Vectors ◽  
Molecular Processes ◽  
Daily Rhythms ◽  
The Earth ◽  
Rotation Of The Earth ◽  
Biting Time

Daily rhythms in behaviour, physiology and molecular processes are expected to enable organisms to appropriately schedule activities according to consequences of the daily rotation of the Earth. For parasites, this includes capitalizing on periodicity in transmission opportunities and for hosts/vectors, this may select for rhythms in immune defence. We examine rhythms in the density and infectivity of transmission forms (gametocytes) of rodent malaria parasites in the host's blood, parasite development inside mosquito vectors and potential for onwards transmission. Furthermore, we simultaneously test whether mosquitoes exhibit rhythms in susceptibility. We reveal that at night, gametocytes are twice as infective, despite being less numerous in the blood. Enhanced infectiousness at night interacts with mosquito rhythms to increase sporozoite burdens fourfold when mosquitoes feed during their rest phase. Thus, changes in mosquito biting time (owing to bed nets) may render gametocytes less infective, but this is compensated for by the greater mosquito susceptibility.

scholarly journals Adaptive periodicity in the infectivity of malaria gametocytes to mosquitoes

2018 ◽  
Author(s):  
Petra Schneider ◽  
Samuel S. C. Rund ◽  
Natasha L. Smith ◽  
Kimberley F. Prior ◽  
Aidan J. O’Donnell ◽  
...  
Keyword(s):  
Blood Feeding ◽  
Blood Parasite ◽  
Parasite Development ◽  
Bed Nets ◽  
Mosquito Vectors ◽  
Plasmodium Chabaudi ◽  
Malaria Parasites ◽  
Rodent Malaria

AbstractThat periodicity in the biting activity of mosquito vectors explains why malaria parasites have evolved rhythms in cycles of asexual replication in the host’s blood was proposed almost 50 years ago. Yet, tests of this hypothesis have proved inconclusive. Using the rodent malaria Plasmodium chabaudi, we examine rhythms in the density and infectivity of transmission forms (gametocytes) in the host’s blood, parasite development inside mosquitoes, and onwards transmission.Moreover, we control for the confounding effects of rhythms in mosquito susceptibility. We reveal that at night, gametocytes are twice as infective to mosquitoes, despite being less numerous in the blood. This enhanced infectiousness at night interacts with mosquito rhythms to increase sporozoite burdens by almost four-fold when mosquitoes feed during their day. Thus, daytime blood-feeding (e.g. driven by the use of bed nets) may render gametocytes less infective, but this is compensated for by the greater susceptibility of mosquitoes.

The Terrestrial Coordinate System and International Earth-rotation Services

1985 ◽  
Vol 38 (02) ◽  
pp. 216-217
Author(s):  
G. A. Wilkins
Keyword(s):  
Coordinate System ◽  
Earth Rotation ◽  
Reference System ◽  
New Techniques ◽  
Crustal Movements ◽  
Earth Observations ◽  
The Earth ◽  
External Reference ◽  
External Objects ◽  
Rotation Of The Earth

New techniques of measurement make it possible in 1984 to determine positions on the surface of the Earth to a much higher precision than was possible in 1884. If we look beyond the requirements of navigation we can see useful applications of global geodetic positioning to centimetric accuracy for such purposes as the control of mapping and the study of crustal movements. These new techniques depend upon observations of external objects, such as satellites or quasars rather than stars, and they require that the positions of these objects and the orientation of the surface of the Earth are both known with respect to an appropriate external reference system that is ‘fixed’ in space. We need networks of observing stations and analysis centres that monitor the motions of the external objects and the rotation of the Earth. Observations of stars by a transit circle are no longer adequate for this purpose.

Sensing the rotation of the Earth

1992 ◽  
Vol 30 (2) ◽  
pp. 111-111
Author(s):  
H. Richard Crane
Keyword(s):  
The Earth ◽  
Rotation Of The Earth

scholarly journals Daily rhythms of both host and parasite affect antimalarial drug efficacy

2021 ◽  
Author(s):  
Alíz T Y Owolabi ◽  
Sarah E Reece ◽  
Petra Schneider
Keyword(s):  
Drug Treatment ◽  
Developmental Stage ◽  
Antimalarial Drug ◽  
Drug Sensitivity ◽  
Drug Efficacy ◽  
Time Of Day ◽  
Parasite Development ◽  
Daily Rhythms ◽  
Parasite Plasmodium

Abstract Background and objectives Circadian rhythms contribute to treatment efficacy in several non-communicable diseases. However, chronotherapy (administering drugs at a particular time-of-day) against infectious diseases has been overlooked. Yet, the daily rhythms of both hosts and disease-causing agents can impact the efficacy of drug treatment. We use the rodent malaria parasite Plasmodium chabaudi, to test if the daily rhythms of hosts, parasites, and their interactions, affect sensitivity to the key antimalarial, artemisinin. Methodology Asexual malaria parasites develop rhythmically in the host’s blood, in a manner timed to coordinate with host daily rhythms. Our experiments coupled or decoupled the timing of parasite and host rhythms, and we administered artemisinin at different times of day to coincide with when parasites were either at an early (ring) or later (trophozoite) developmental stage. We quantified the impacts of parasite developmental stage, and alignment of parasite and host rhythms, on drug sensitivity. Results We find that rings were less sensitive to artemisinin than trophozoites, and this difference was exacerbated when parasite and host rhythms were misaligned, with little direct contribution of host time-of-day on its own. Furthermore, the blood concentration of haem at the point of treatment correlated positively with artemisinin efficacy but only when parasite and host rhythms were aligned. Conclusions and implications Parasite rhythms influence drug sensitivity in vivo. The hitherto unknown modulation by alignment between parasite and host daily rhythms suggests that disrupting the timing of parasite development could be a novel chronotherapeutic approach. Lay Summary We reveal that chronotherapy (providing medicines at a particular time-of-day) could improve treatment for malaria infections. Specifically, parasites’ developmental stage at the time of treatment and the coordination of timing between parasite and host both affect how well antimalarial drug treatment works.

scholarly journals Seasonal variations and north–south asymmetries in polar wind outflow due to solar illumination

2016 ◽  
Vol 34 (11) ◽  
pp. 961-974 ◽  
Author(s):  
Lukas Maes ◽  
Romain Maggiolo ◽  
Johan De Keyser
Keyword(s):  
Seasonal Variations ◽  
Solar Zenith Angle ◽  
The Sun ◽  
Polar Ionosphere ◽  
Polar Cap ◽  
Polar Wind ◽  
Simple Set ◽  
The Earth ◽  
Rotation Of The Earth ◽  
Set Up

Abstract. The cold ions (energy less than several tens of electronvolts) flowing out from the polar ionosphere, called the polar wind, are an important source of plasma for the magnetosphere. The main source of energy driving the polar wind is solar illumination, which therefore has a large influence on the outflow. Observations have shown that solar illumination creates roughly two distinct regimes where the outflow from a sunlit ionosphere is higher than that from a dark one. The transition between both regimes is at a solar zenith angle larger than 90°. The rotation of the Earth and its orbit around the Sun causes the magnetic polar cap to move into and out of the sunlight. In this paper we use a simple set-up to study qualitatively the effects of these variations in solar illumination of the polar cap on the ion flux from the whole polar cap. We find that this flux exhibits diurnal and seasonal variations even when combining the flux from both hemispheres. In addition there are asymmetries between the outflows from the Northern Hemisphere and the Southern Hemisphere.

scholarly journals A Functional Connection between the Circadian Clock and Hormonal Timing in Arabidopsis

Genes ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 567 ◽  
Author(s):  
Manjul Singh ◽  
Paloma Mas
Keyword(s):  
Circadian Clock ◽  
Biological Significance ◽  
Feedback Regulation ◽  
Environmental Cues ◽  
Hormone Signaling ◽  
Functional Connection ◽  
The Earth ◽  
Exogenous Cues ◽  
Rotation Of The Earth ◽  
Molecular Components

The rotation of the Earth entails changes in environmental conditions that pervasively influence an organism’s physiology and metabolism. An internal cellular mechanism known as the circadian clock acts as an internal timekeeper that is able to perceive the changes in environmental cues to generate 24-h rhythms in synchronization with daily and seasonal fluctuations. In plants, the circadian clock function is particularly important and regulates nearly every aspect of plant growth and development as well as proper responses to stresses. The circadian clock does not function in isolation but rather interconnects with an intricate network of different pathways, including those of phytohormones. Here, we describe the interplay of the circadian clock with a subset of hormones in Arabidopsis. The molecular components directly connecting the circadian and hormone pathways are described, highlighting the biological significance of such connections in the control of growth, development, fitness, and survival. We focus on the overlapping as well as contrasting circadian and hormonal functions that together provide a glimpse on how the Arabidopsis circadian system regulates hormone function in response to endogenous and exogenous cues. Examples of feedback regulation from hormone signaling to the clock are also discussed.

scholarly journals Self-Organization of Water Molecules Over 11-Year Solar Cycle

2021 ◽  
Author(s):  
Igor Shevchenko
Keyword(s):  
Solar Activity ◽  
Water Clusters ◽  
The Self ◽  
Self Organization ◽  
Water Molecules ◽  
Annual Variations ◽  
The Earth ◽  
Rate Of Hydrolysis ◽  
Rotation Of The Earth ◽  
Northern And Southern Hemispheres

Abstract The variations of solar activity and distribution of solar energy due to the rotation of the Earth around its axis and around the Sun exert a strong influence on the self-organization of water molecules. As a result, the rate of hydrolytic processes with the participation of water clusters displays diurnal, very large annual variations, and is also modulated by the 11-year cycles of solar activity. It also depends on the geographic latitude and can be different at the same time in the Northern and Southern Hemispheres. This phenomenon is well accounted for by the influence of muons on the self-organization of water molecules. Muons are constantly generated in the upper atmosphere by the solar wind. They reach the surface of the Earth and can penetrate to some depth underground. Buildings also absorb muons. For this reason, the rate of hydrolysis outside and inside buildings, as well as underground, can differ significantly from each other.

scholarly journals Solar Tracker

2020 ◽  
Vol 2 (1) ◽  
pp. 59-65
Author(s):  
Irfan Danial Hashim ◽  
Ammar Asyraf Ismail ◽  
Muhammad Arief Azizi
Keyword(s):  
Fossil Fuels ◽  
Electrical Energy ◽  
Maximum Amount ◽  
Solar Panel ◽  
Angle Of Incidence ◽  
The Sun ◽  
Continuous Change ◽  
The Earth ◽  
Solar Tracker ◽  
Rotation Of The Earth

Solar Tracker The generation of power from the reduction of fossil fuels is the biggest challenge for the next half century. The idea of converting solar energy into electrical energy using photovoltaic panels holds its place in the front row compared to other renewable sources. But the continuous change in the relative angle of the sun with reference to the earth reduces the watts delivered by solar panel. Conventional solar panel, fixed with a certain angle, limits their area of exposure from the sun due to rotation of the earth. Output of the solar cells depends on the intensity of the sun and the angle of incidence. To solve this problem, an automatic solar cell is needed, where the Solar Tracker will track the motion of the sun across the sky to ensure that the maximum amount of sunlight strikes the panels throughout the day. By using Light Dependent Resistors, it will navigate the solar panel to get the best angle of exposure of light from the sun.

scholarly journals Specific Formation of the Bermuda and Dragon Triangles as a Result of a Change in the Axis of the Earth’s Rotation

2020 ◽  
pp. 19-25
Keyword(s):  
South America ◽  
Southeast Asia ◽  
Earth’S Rotation ◽  
Earth's Rotation ◽  
Axis Of Rotation ◽  
The Earth ◽  
Rotation Of The Earth ◽  
North And South America ◽  
North And South

The Bermuda Triangle is located in the area of the archipelago between North and South America and the Dragon Triangle is located in the area of the archipelago in Southeast Asia. There is a great resemblance between these two triangular areas; both were formed following special geological and tectonic conditions. It is herein proposed that their creation stems from the change in location of the axis of rotation of the earth and, accordingly, the change in the location of the equator.

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