GMOS: Technology as nature-killer?

Basics of Genetic Engineering in Plants

How are GM crops generated in the first place? Transgenic plants are the result of application of recombinant DNA technology, which combines DNA from two different species, and often involves manipulation of genes in bacteria (Becker, 2009). The common method in plants involves inserting a gene into the plasmid, or circular DNA piece, of a bacteria called Agrobacterium tumefaciens. The bacteria easily infects plant cells and the desired foreign gene, or transgene, such as one enhancing crop yield or providing insect resistance, gets incorporated into the genome of the plant cells. The cells replicate and generate a plant with a new, special trait.

Becker, 2009.

Environmental Risks

The major risk associated with GM plants is that they will escape and disrupt natural ecosystems as invasive species (Wolfenbarger and Phifer, 2000). The process starts with gene flow, the exchange of alleles, or alternate forms of a gene, between two populations. This can occur either by the transfer of individual plants or by the transfer of gametes in the form of pollen which produces hybrid plants in the wild.

According to a recent review in Nature, gene flow will not necessarily lead to introgression, “the permanent incorporation of genes from one set of differentiated populations (species, subspecies, races and so on) into another” (Stewart et al, 2003).  The scientists recommended looking at risk on a case-by-case basis depending on the transgene, the crop species, and the genetic relationships between the crop and local native species. Some genes such as ones improving fiber quality have neutral effects, while others, such as a gene that produces the herbicide Bt toxin, will give hybrid plants an evolutionary advantage.

Wolfenbarger and Phifer. 2000

Technologies that Limit Gene Flow

Recently, plant scientists have been investigating the possibility of using GURTs, or gene use restriction technologies, which manipulate genetics to reduce the spread of potentially harmful transgenes (Hills et al., 2007). One of the more controversial GURTs is terminator technology, which produces sterile seeds, the idea being that this would stop the spread of transgenes by seed transmission into the environment. Critics argue that this technology will hurt small-scale farmers who traditionally save seeds for the next generation (Monsanto.com). The terminator is a three-step system that makes use of promoter regions, which are regulatory pieces of DNA that control whether a gene is expressed. The last step introduces a sterility gene in a tissue-specific fashion.

Hills et al. 2007

Conclusions and Personal Opinions

Genetic engineering has many potential benefits such as alleviating malnutrition and hunger in the developing world, so I do not think that it should be banned. However, the technology may be harmful to the environment and to farmers under certain circumstances. I think that we need careful regulation driven by science-based risk assessment. The technology alone is not evil, but we have to fully take into account the implications of its use. Scientists should combine their skills with those of politicians and activists towards the ultimate goal of reaping the most benefits with the least harm.

References

Becker, Wayne, Kleinsmith Lewis, Hardin Jeff, and Bertoni Gregory. The World of the Cell. San Francisco: Pearson, 2009. Print.

Hills, M., Halls, L., Arnison, P., and A. Good. "Genetic use restriction technologies (GURTs): strategies to impede transgene movement." Trends in Plant Science. April 2007. 12(4): 177-183.

Shapiro, Robert. "Is Monsanto going to develop or sell terminator seeds." www.monsanto.com

Stewart, C.N., Halfhill, M.D., and S.I. Warwick. "Transgene introgression from genetically modified crops to their wild relatives." Nature reviews: Genetics. October 2003. 4: 806-817.

Wolfenbarger, L.L. and P.R. Phifer. "The Ecological Risks and Benefits of Genetically Engineered Plants." Science. 15 December 2000. 290: 2088.

Is weed actually bad for you?

             Massguns.com.

The legalization and regulation of marijuana use has long been a subject of national debate. Since the legalization in Washington and Colorado, many are closely watching whether other states will follow suit. Supporters of legalization have argued that it could provide tax revenue and reduce drug smuggling. As a medical researcher, I am interested in how science might help inform this debate. I wanted to look at whether or not marijuana actually has detrimental health effects. It is a drug after all, right? Yet marijuana has also been used medicinally to relieve pain, so is it really bad for us? I set out to learn more about our current knowledge of the drug’s effects on the human mind and body.

Marijuana and Mental Health

Is there evidence that smoking marijuana impairs mental health? An article in the British Medical Journal looked at this question in a group of 759 people in New Zealand (Arseneault et al., 2002). These individuals were all born in 1972 or 1973 and provided health data throughout their lives. The study measured drug use at ages 15 and 18 and then followed up on mental prognosis as defined by symptoms and diagnoses of depression and schizophrenia at age 26. They also controlled for psychotic symptoms at age 11 in case drug use was an effect of mental illness rather than a cause. This study did find a positive correlation for adolescent marijuana use and adult schizophrenia but not depression. The youngest cohort was most vulnerable. However, it should be noted that the prevalence of schizophrenia was still only 10% in the 15-year-old drug user group compared to 3% in the control group. The researchers advocated for further study in larger groups. This study suggests that marijuana may have detrimental effects on the brain, but I wanted to understand more about the mechanism of the drug at a neurological level.

Cannabinoids and the Brain

Valesco et al. 2012

The psychoactive ingredient in marijuana is delta-9-tetrahydrocannabinol or THC, which belongs to class of compounds called cannabinoids (Wilson and Nicoll, 2002). THC binds to a receptor in the brain known as CB1. This receptor is present in many locations in the central nervous system including the cortex, hippocampus, and basal ganglia where it is involved in modulating pain, appetite, and memory. Our brains have this receptor because there are compounds known as endocannabinoids with similar structures to THC that are found naturally inside the body and that bind to the same receptor.

Signals propagate in the brain when chemicals known as neurotransmitters are passed from one neuron (presynaptic) to another (postsynaptic) across a divide called the synaptic cleft. Cannabinoids are called retrograde messengers because they travel against the direction of the signal before binding to CB1 on the first neuron. Binding functions to decrease calcium levels in the cell, thereby calming down the signal transmission.

If marijuana can calm down pain signaling, this explains why it has been successful medicinally as a pain killer. A recent study of patients with fibromyalgia, a type of chronic pain, reported relief from pain, joint stiffness, and insomnia after using marijuana for two hours (Fiz et al., 2011). 

Studies in rodents have found that THC can lead to neurotoxicity, but dosage and duration were important. Toxicity did not develop until after the equivalent of 7 to 10 years of usage in humans (Scallet, 1991).

Marijuana and the Immune System

It seemed logical to me that marijuana would have a role in the brain, but I was surprised to find that it also functions to regulate the immune system. This happens because there is a second receptor that responds to cannabinoids called CB2 that is found on the cells of the immune system (Rieder et. al., 2010). Multiple studies have shown that cannabinoids are immunosuppressive. This can be very good for people whose immune systems are too active, and can be used to treat inflammation in multiple sclerosis, diabetes, and rheumatoid arthritis. However, in high doses these compounds can increase susceptibility to infection.

Conclusions and Personal Opinions

So is marijuana actually detrimental to human health based on science? I would say that for people who start smoking during adolescence and continue using the drug heavily for a number of years the answer is yes. However, small doses can be beneficial, particularly for people needing treatment for chronic illnesses of the nervous or immune systems. There is also talk of using cannabinoids as anti-cancer therapy, although I did not go into that here.

References

1. Arseneault L., Cannon M., Poulton R., Murray R., Caspi A., Moffitt T. E. (2002). Cannabis use in adolescence and risk for adult psychosis: longitudinal prospective study. BMJ. 325, 1212–1213.

2. Wilson, R. and R. Nicoll. (2002). Endocannabinoid Signaling in the Brain. Science.296: 678.

3. Fiz J, Durán M, Capellà D, Carbonell J, Farré M. Cannabis use in patients with fibromyalgia: effect on symptoms relief and health-related quality of life. PLoS One. 2011;6(4):e18440

4. Scallet, Andrew. (1991). Neurotoxicology of cannabis and THC: A review of chronic exposure studies in animals. Pharmacology Biochemistry and Behavior. 40(3): 671–676.

5. Rieder, S. A.  Chauhan, A., Singh, U., Nagarkatti, M.,

Nagarkatti. P. (2010). Cannabinoid-induced apoptosis in immune cells as a pathway to

immunosuppression. Immunobiology. 215(8): 598–605.

6. Velasco, G., Sánchez, C., Guzmán, M. (2012). Towards the use of cannabinoids as anti-tumor agents. Nature reviews cancer. 12: 436.

7. Marijuana frond picture. Mass Firearms Attorney. Marijuana and Firearms Licensing. 7 May 2013. www.massguns.com.