Sunday, June 17, 2007

ELISA spot in a flash animation

I love using visual aids to educate myself. I wish that I had more of them available when I was growing up. Heck, I wish that I could use them more extensively in my current self-education.

That's why I like this little animated clip. It depicts a biological assay that's used to capture the secretory footprints of blood cells. Certain B cells will secrete certain antibodies, for example. Additionally, different T cells will secrete different types of cytokines. That's the kind of assay that's depicted here. It shows how many T cells responded with a given cytokine to a particular type of stimulus.

Thursday, April 26, 2007


The National Institutes of Health (NIH) is attempting to develop a new, safer vaccine against smallpox. This is part of an ongoing attempt to protect the nation against the threat of bioterrorism and bioweaponry--that is, the use of weaponized pathogens. Similar research is being conducted to protect the populace against other diseases, such as the plague.

Various species of monkeys have been used to test the efficacy of the proposed vaccine (modified vaccinia Ankara, or MVA). Monkeys are inoculated with MVA, then exposed to the monkeypox virus, which closely resembles smallpox. The researchers then determine if the vaccine provides any protection against the virus. Unfortunately, this does result in the monkeys' deaths.

It would clearly be unethical to test the vaccine on humans in the same fashion. (I have a hard enough time thinking about these poor simians.) Fortunately, the ELISPOT technique allows immune response monitoring to be performed ex vivo; that is, without injecting any pathogens into a human host.

Wednesday, April 18, 2007


Nothing earthshaking, folks. I just wanted to plug the SciWeb website. It's pretty neat and a pretty good informational resource for life science research, equipment and so forth.

I especially like the SciJobs section. Oh, I'm not looking for a job, mind you. However, I wish I had known about this resource four years ago, when I was searching for employment. The company directory and press releases sections are also quite nice. So is the product announcements section, although some of the announcements appear to be kinda trivial.

I would kinda like to advertise this job opening that my employer has; however, I don't think we want to spend any money on these job ads.

Tuesday, April 17, 2007

Manipulator grasp classifications

Gripper and fixture grasps can fall under different categories. The two most important grasp classifications are known as form closure and force closure grasps. These terms were first used by Reuleaux in his studies of machine design, and were later applied to robotic grasping by Salisbury. However, recent inconsistent use of these terms has confused their meanings.

A fixed set of contacts on a rigid object is said to exhibit form closure if the object's equilibrium is maintained despite any possible externally applied wrench (i.e. a force, a torque, or a combination thereof). In other words, the geometries and relative poses of the object and the contacting body--a gripper or fixture, for example--suffice to hold the object in place with complete kinematic constraint. Form closure is therefore more preferable to force closure, in which the applied manipulator force is further required as a consideration.

In developing a gripper or fixture, one should therefore strive for form closure. In certain important instances, however, this would be is impossible. For example, any part which is axisymmetric (such as a sphere) cannot be kinematically constrained in form closure. Under such circumstances, a robotic manipulation strategy should strive for frictional form closure (a type of force closure) instead. Under frictional form closure, friction contributes to immobilize a grasped part which is otherwise not fully kinematically constrained by a gripper.

Saturday, April 14, 2007

Multiple sclerosis

Disseminated sclerosis is a chronic, inflammatory disease that affects the central nervous system. It is more commonly known as multiple sclerosis. Its symptoms include changes in sensation, visual problems, muscle weakness, cognitive impairment, dysfunctions in balance, speech and muscular coordination, severe fatigue, depression, overheating, and pain.

Multiple sclerosis is believed to be an autoimmune disease in which some unknown trigger initiates an immune response against brain proteins. This is known as an autoaggressive response, and according to this hypothesis, it causes the breakdown of the myelin sheaths that protect nerve axons. This leads to impaired nerve conduction and subsequent neurodegeneration, both of which are characteristic of MS.

Epitope mapping has applications in understanding multiple sclerosis. This mapping can be performed using ELISPOT assays.

Monday, January 15, 2007

Revisiting ELISA Spot assays

ELISA spot assays are used for the quantitative determination of single cells secreting a specific cytokine. They are known as ELISA spot assays due to their similarities to the ELISA method, but nowadays, they are more commonly referred to as ELISPOT assays.

Kits are available which contain the basic components and protocols required to perform colorimetric assays wherein one spot marks one cell to be identified.