A scientist who studies the phsyics of sperm "as a hobby" is challenging the current understanding of how sperm swim towards an egg. At the Society for Experimental Biology conference today Dr Christopher Lowe will present the results of his modelling of a sperm`s tail, suggesting we may need to re-think our assumptions of how sperm move through fluid.
Experimental studies of sperm have generated a fairly well established database of parameters on sperm movement. The frequency and wavelength of the tail movement is estimated at around 50 hertz down the tail. The low speed at which sperm swim is well known - perhaps suprisingly low given the urgency of the mission, but understandable because of the sheer force of the fluid it is moving in. "If you were a sperm it would be the equivalent of swimming in a liquid a thousand million times more viscous than air. There is not a substance known to man that is that viscous - even swimming in a pool of thick syrup would be easy going compared to the Olympic feats performed by sperm," says Dr Lowe.
The fluids in which sperm swim are also well-characterised. Using both the sperm and fluid parameters Dr Lowe constructed a computer model which accurately recreated the shape and movement of the sperm`s tail as it swims towards the egg. The simulation also correctly reproduced the swimming speed. But to Dr Lowe`s surprise, he discovered a discrepancy between the computer model and the established theory, related to how stiff the sperm`s tail needs to be to counteract the resistance or drag of the surrounding fluid. "Either the tail is significantly stiffer when the sperm is swimming than previous experiments suggest, or the sperm is doing something very clever indeed to overcome the sticky forces exerted on it by the surrounding fluid. On the grounds that sperm, being on a kamikaze mission, are unlikely to be over-endowed in the brains department, I prefer the former explanation," says Dr Lowe. He suggests the discrepancy arises because many of the previous studies have been performed on sperm parts or on dead sperm. His findings are wholly based on the simulation of a live sperm.
Jenny Gimpel | alphagalileo
Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden
The pyrenoid is a carbon-fixing liquid droplet
22.09.2017 | Max-Planck-Institut für Biochemie
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
22.09.2017 | Medical Engineering
22.09.2017 | Physics and Astronomy
22.09.2017 | Physics and Astronomy