The scanning electron microscope (SEM) has been a basic research tool for 50 years, and for all of those years scientists have been looking for better ways to observe biological samples under its beam. The problem is that biological samples cannot withstand the vacuum inside the SEM. Procedures used today include coating the specimens with an ultra-fine layer of gold, quick-freezing samples in special deep-freezes or treating them with drying solvents.

Now Weizmann Institute researchers have found a way to view samples of biological materials in their natural, “wet” state. The secret lies in producing a very thin but tough polymer capsule to enclose the sample. Dr. Ory Zik, who developed the capsule with Prof. Elisha Moses of the Physics of Complex Systems Department, says: “We came across the capsule material while researching applications for semiconductor industry techniques in the life sciences’ SEMs.”

The capsule’s polymer is unique in that it allows the electrons with which an SEM works to pass through unobstructed, giving scientists a clear view of what lies inside, without the use of tricky, tissue-distorting procedures. Researchers hope the new method will advance the study of such biological materials as lipids, which are easily destroyed by other preparation methods.

The finding was recently published in the Proceedings of the National Academy of Sciences (PNAS), USA. Zik, in cooperation with Yeda, the business arm of the Weizmann Institute, has founded a company, called QuantomiX, based on the technology.

 

Our fingers run over surfaces; our eyes are in constant motion. This is all part of “active sensing,” key principles of which have now been uncovered by the team of Prof. Ehud Ahissar of the Neurobiology Department.

We intuitively understand that fingers moving upon surfaces should provide the brain with information very different from that acquired by merely touching a surface without movement, yet experiments have nearly always kept the organs stationary. Working with doctoral student Marcin Szwed and Dr. Knarik Bagdasarian, Ahissar tracked neuron transmissions of rats’ whiskers, which sweep back and forth to locate objects in their immediate vicinity, and thus are an ideal tool for studying the active aspects of perception. They found that two previously unknown basic types of neurons came into play. The first, which they called whisking neurons, responds solely to the whisking motion itself, even if the whiskers don’t touch an object. The second, which they dubbed touch neurons, informs the brain about the surface being touched. The scientists were able to discern subtypes in the second category, which came into play during different stages of contact. Ahissar’s team published these results in Neuron.