Monday, May 24, 2010

Gulf Oil Spill - An Ecological Disaster

According to Doctor Samantha B. Joye, from the Department of Marine Sciences at the University of Georgia, involved in gathering data from the Gulf oil spill, “There’s a shocking amount of oil in the deep water, relative to what you see in the surface water.” She went on to say that, “There’s a tremendous amount of oil in multiple layers, three or four or five layers deep in the water column.” These plumes were discovered by scientific investigators from a number of universities working from aboard the Pelican, a research vessel.

The controversial chemical dispersants that have been used by British Petroleum (BP) to break the oil down into small droplets may have contributed to the creation of these plumes. The naturally occurring oil-eating bacteria “feeding” on this oil are depleting the oxygen dissolved in the gulf, for as they rapidly grow and divide they are consuming oxygen. Doctor Joye said the oxygen had already dropped 30 percent near some of the plumes in the month that the broken oil well had been flowing and, “If you keep those kinds of rates up, you could draw the oxygen down to very low levels that are dangerous to animals in a couple of months. That is alarming.” In addition, the natural rate of replenishment of oxygen in deep water from the surface is a slow process.

In my estimation this oil spill will prove to be an ecological disaster of immense proportions if the flow of oil is not stopped in a timely fashion. The fowling of the gulf with oil will add an additional insult to the acidification of the oceans that is a direct result of the ever-increasing concentration of carbon dioxide in the atmosphere.

Thursday, May 20, 2010

How Cancerous Tumors Can Avoid the Immune System

The danger that cancer poses to the patient is the ability of cancerous cells to metastasize – spread throughout the body. This is referred to as a malignancy. Cancers can arise in any tissue i.e. from lung, liver, brain, stomach etc. Cancerous cells are characterized by their capacity to divide out of control, their primitive function and their ability to metastasize. The body’s natural defense against malignant tumors is afforded by the immune system through the production of so-called effector T cells or cytotoxic T lymphocytes that circulate throughout the body, and attack cells that have become malignant.

In response, cancerous cells have been shown to be able to suppress the immune system’s effectiveness. One of the mechanisms that they employ is to reduce the expression of certain proteins on their cell surface that can alert the immune system to their presence; substances that trigger immune responses are referred to as antigens. A common example of an antigen is the proteins in ragweed pollen that elicit an allergic response in some individuals. Another method of evasion has been shown to occur, namely that certain tumors can secrete proteins that inhibit effector T cell responses and promote regulatory T cells that can inhibit immune responses.

As a result of the elegant studies of Doctor Jacqueline D. Shields from the Institute of Bioengineering in Switzerland, yet another mechanism of circumventing the immune system has been discovered. It was found that certain melanomas – an aggressive form of skin cancer – can reorganize their cellular environment (stromal microenvironment) into structures that are similar to the lymphoid tissue of the immune system. This reconstruction results in fooling the immune system to the extent that it recruits regulatory T cells that actually promote tolerance and enhance tumor progression.

Studies of this kind shed significant light on the progression of Cancers, and reinforce the important role that immune surveillance plays in the body’s natural defense mechanisms. By elucidating the actual manner in which tumors can thwart these defenses, the possibility of developing effective therapies is appreciably enhanced.

Sunday, May 16, 2010

Atrazine – A Potentially Dangerous Herbicide

Atrazine (1-chloro-3-ethylamino-5-isopropylamino-2,4,6-triazine) is a widely used herbicide in the United States. Atrazine is in a class of compounds that is known to mimic steroid hormones in a variety of animal species. Atrazine is used to stop pre- and post-emergence broadleaf and grassy weeds in major crops. Approximately 36 million kilograms of this substance are applied on U.S. farms yearly. It has been estimated that 225,000 kilograms of the herbicide become airborne and fall with rainfall as far as 1,000 kilometers from its source.

In a study under the direction of Dr. Tyrone Hayes of the Department of Integrative Biology at the University of California Berkeley, 40 male African clawed frogs were exposed to atrazine at a level of 2.5 parts per billion (ppb) in drinking water. This is at a level lower than the 3 ppb allowed in drinking water by the Environmental Protection Agency (EPA). As a result 30 of the frogs were chemically castrated. Interestingly enough, four of the treated frogs turned female and produced viable eggs despite being genetically male. Only six of the frogs resisted atrazine and displayed normal sexual function. This result was confirmed by additional studies. A possible candidate for the apparent sex change effect is the enzyme aromatase that triggers the production of the female hormone, estrogen causing male gonads to become ovaries.

On account of these disturbing data, the European Union has prohibited its use. The rationale for the continued use in the stated by the Environmental Protection Agency (EPA) is, "The total or national economic impact resulting from the loss of atrazine to control grass and broadleaf weeds in corn, sorghum and sugar cane would be in excess of $2 billion per year if atrazine were unavailable to growers." In the same report, it added the "yield loss plus increased herbicide cost may result in an average estimated loss of $28 per acre" if atrazine were unavailable to corn farmers”

In summary, Atrazine is a common agricultural herbicide whose primary effects are reproductive and developmental. The study cited above indicates that for the organism studied, the frog, profound reproductive harm occurred at levels below what is currently allowed in drinking water. This is cause for concern especially in regard to the fact that atrazine is often found far from its original site of application.