Season 3, Episode 13: Back to the Future

Although Bob’s eyesight continues to improve, David insists that they stop the experimental treatment. David suspects the virus that was injected into Bob’s optic nerves has traveled up into the brain, causing Bob to become overwhelmed with emotion. The doctors believe that a long dormant part of Bob’s brain is awakening, increasing his compassion – a possibility that leads a man named Olivier Roth to isolate Bob’s brain stem cells, in hopes of using them to improve humanity. Meanwhile, while trying to figure out how the biofilm bacteria were engineered to make RNA in smiley face shapes, David uncovers the secret to killing the biofilm.

IS IT POSSIBLE TO “AWAKEN” JACOBSON’S ORGAN?

Image provided courtesy of AXS Studio Inc and Shaftesbury Films.		During Bob’s treatment, the capsid of the herpes virus vector drifts close to a protein, dyenin (A), on which the capsid hitch-hikes away from the optic nerve and into Bob’s brain (B).

What is a vestigial organ?

The term “vestigial” can be used to describe body parts or behaviors that have lost some or all of their original function through evolution. Vestigial body parts generally are small or rudimentary, like the human tailbone and appendix or pelvis and thigh bones in whales. Although several lizard species reproduce through parthenogenesis, some of the females try to have sex like males. This “fake sex” is thought to be a vestigial behavior because it’s not actually sex, in that it cannot lead to reproduction, which occurs asexually.

What is Jacobson’s organ?

Jacobson’s organ is also known as the vomeronasal organ, which is found in the oral cavity, between the nose and the mouth, of many vertebrate animals, including amphibians, snakes, and some mammals. It is thought to be an auxiliary organ that detects certain chemicals in the air.

Some animals, like snakes, use the organ to sense their prey by picking up scents with their tongue, then touching the tongue to the organ. Other animals, including humans, appear to have a vestigial – or non-functional – vomeronasal organ that doesn’t seem to be connected to the brain with functioning nerve cells.

Can humans sense pheromones?

Pheromones are naturally-produced chemicals that in insects trigger certain behaviors like mating, signaling danger, or protecting territory. Researchers have found evidence of pheromones and proteins that respond to pheromones in rodents, but the possible existence and function of pheromones in humans is very controversial.

The best-studied case of human pheromones involves the synchronization of menstrual cycles among women based on unconscious odor cues. Martha McClintock studied women living in dormitories and noticed that the longer they lived together, the more synchronized their cycles became. McClintock proposed that the synchronization resulted from at least two pheromones.

Studying pheromones in humans is difficult because people can consciously decide to behave certain ways, while animal behavior is driven more by instinct and cues like pheromones.

So…

It is not likely that the Jacobson’s organ could be awakened in humans. Researchers continue to study how pheromones affect behavior in mice and other animals. The parts of the brain that are activated by pheromones generally are found in the olfactory system, the nerves and structures responsible for the sense of smell. Jacobson’s organ isn’t innervated or connected to the brain at all in humans. So even if people do respond to pheromones, they likely are not doing it through Jacobson’s organ.

IS IT POSSIBLE TO HARVEST HUMAN STEM CELLS FROM ADULT BRAINS?

Image provided courtesy of Shaftesbury Films.		Bob gets prepped for surgery to extract stem cells from his brain.

What kinds of adult stem cells are there?

Adult stem cells are cells with the capacity for self-renewal – that is, they make more of themselves – that can also develop into a limited number of cell types. Those cell types generally are restricted to the tissue or organ in which the stem cells reside. The largest populations of adult stem cells are in adipose (fat), hematopoietic (blood), mammary (breast), mesenchymal (tissue that gives rise to muscle, bone, fat, and possibly other types), neural (brain and nerve), and olfactory (nerves and other cells involved in smell) tissues.

How are adult stem cells harvested?

Adult stem cells can be harvested by surgically removing a part of the tissue containing the cells. For example, to obtain blood stem cells, doctors can harvest a patient’s bone marrow, in which new blood cells develop. The cells of the tissue are gently separated and grown in liquid nutrients in a Petri dish in the laboratory. Often the stem cells can be separated from other, non-stem cells using a cell-sorting machine. Another way of separating stem cells from non-stem cells relies on their ability to continue dividing. Cultured together in a dish, the stem cells eventually will be the predominant cell type in the dish because they will outgrow the non-stem cells.

So…

Yes, it is possible to isolate certain types of adult stem cells without seriously harming the cell donor. A bone marrow transplant is an example of a procedure in which adult stem cells are harvested from one person and transferred to another. Adult neural stem cells, however, are difficult to isolate or obtain.

- by Audrey M. Huang, Ph.D.

Want to read and learn more?

To read more about vestigial organs in plants and animals, visit:
http://www.livescience.com/animals/top10_vestigial_organs.html

To read more about mammals and pheromones, visit:
http://www.hhmi.org/senses/d230.html