Pfiesteria paper

Eric Delich
Dr. Robson
Capstone
1 November 2008
Pfiesteria the Cell from Hell
There are thousands of species of microalgae,Microalgae are comprised of thousands of species which form the base of many marine food chains,. butO only about 60 of these speciesare believed to be toxic or harmful. The toxic organisms (or microalgae, do you want to stay consistent?)*have an unique life cycle in which they have the ability to produce their harmful toxins.*When this small percentage of the toxic organisms develops, through their own unique life cycle, they have the ability to produce harmful toxins, **I was confused here, do the microalgae alter marine habits and human health through or because of their life cycles?alterations of marine habitats, and even human health effects. Included in this group of toxicmicroalgae are dinoflagellates. Dinoflagellates are unicellular eukaryotic organisms which can be found in most aquatic habitats. These creaturesDinoflagellates get their name from the Greek work deinos for whirling or turning, which is This is a rather appropriate name becausegiven dinoflagellates have two dimorphic flagella which give them increased mobility.increasing their mobility. Dinoflagellates can obtain their food by either photosynthesis (autotrophs), phagocytosis (heterotrophs), or through a combination of the previous two methods (mixotrophs). These organismsDinoflagellates are usually found in extremely diverse niches with a wide range depending on the species. Are you still talking about the microalgae or are their different species of dinoflagellates?

Dinoflagellates are able to produce toxins of a hydrophilic or lipid soluble nature. There are mMany previously described human health syndromes areproduced by dinoflagellates. Should you start the paragraph with something about the neurological, digestive and other types of symptoms, then proceed with the different types of poisonings? Paralytic shellfish poisoning (PSP) is a type of dinoflagellate poisoning. This occurs when someone consumesbecause of the consumption of shellfish containing a high concentration of the sodium channel blocker saxitoxin. This poisonSaxitoxin can lead to ataxia, confusion, other neurological problems, and in some cases even death. Neurotoxic shellfish poisoning (NSP) is caused by brevetoxins and like the previous is contracted through consumption of the organismshellfish. Ciguatera fish poisoning is caused by theconsumption offish that prey on coral reef-associated dinoflagellates. Again, with thisThese toxin also cause many neurological effects whichare seen in the first 24 hours. Finally diarrheic shellfish poisoning is also caused by ingesting the dinoflagellate poison okadaic acid. This causes poison causes more digestive problems rather than neurological problems. —One of the most well known toxic dinoflagellates and the one I will be focusing on from here on out is Pfiesteria. Pfiesteria is the most well known of the toxic dinoflagellates. I propose if the correct species, strain, and stage of life are present Pfiesteria can present serious health effects in not only fish but also in humans as well.Not sure about this sentence and the first person.Do you mean, By studing and understanding ……….

. Pfiesteria was first observed as an aqua dinoflagellate by JoAnn Burkholder at North Carolina State University in 1988. This was accomplished by JoAnn Burkholder in a laboratory setting. SheBurkholder became curious when one of her lab assistants became ill while handling aquarium sea water. The lab assistant experienced dermal irritation and neurological problems and lead Burkholder to further investigation (11). Pfiesteria is most commonly linked to massive fish kills across the eastern coast. More specifically the massive fish kill of 1992 in North Carolina estuaries. Between the years 1991-1993 there were 21 similar fish kills reported and in 1998 more than 500,000 fish were killed in the Neuse Estuary. These massive fish kills throughout the 90’s led to what was called Pfiesteria Hysteria.

In 1996 the first species of Pfiesteria was officially described, Pfiesteria piscicida. Compared to other dinoflagellates this organism is relatively small and doesn’t have the distinct armor structure which could have lead to an earlier description. The only other identified species of Pfiesteria is P.shumwayae. It is often said (?) that P. Shumwayae is a non toxic form of Pfiesteria but this is still heavily under debate. is this common knowledge on the streets?In 1998 this species of Pfiesteria was formally described and categorized into the Pfiesteria genus. The interesting this about this species is in 2005 the shumwayae was reclassified into the genus psuedopfiesteria because after further observation they found the outside structure to be significantly different than the P.piscicida. Almost all of these organisms are found in estuaries off the east coast. Pfiesteria live in these estuaries because they rely heavily on environmental factors for survival. They are dependent on water quality such as temperature, pH, water current, mineral content, salinity, and the presence of fish. It is proposed that they are able manipulate their life cycle stage in the presence or absence of fish prey. The enrichment of their waters by agricultural runoff, human sewage, poorly treated wastes from industrialized concentrated animal operations and other nutrient-rich sources encourage the growth of phytoplankton thus indirectly supporting the growth of harmful Pfiesteria blooms (12).
This unique organism has been classified as both heterotrophic and autotrophic. Recently researchers have decided it is more of a mixotrophic organism because during some stages it is able to trap chloroplast, from the algae it eats, inside small vacuoles present in certain life stages. Pfiesteria has been described as having at least 24 polymorphic life stages and as mentioned above they are able to transform between stages depending on the presence of absence of prey (2). It is thought that Pfiesteria can detect a substance in fish excrement, secretions, or tissues causing them to change life stages (13). According to Morris et al. Pfiesteria are at the highest concentrations in costal waters between May and October. It is important to remember during most of the annual cycle, including the aforementioned months, the Pfiesteria exist in their benign or non toxic forms (1). To truly implicate the Pfiesteria in the fish kills or any disease events the water must be tested for the presence of the correct conditions and correct strains of Pfiesteria capable of producing harmful toxins.
Much debate has occurred over the specific chemical signals and mechanisms that produce these harmful toxins. There has even been a great deal of discussion about the number of toxins produced and the actual chemical structure of the produced toxins. Pfiesteria is thought to produce at least two different types of toxins. The toxin or toxins destroys the integrity of the skin in humans and cause fish scales to flake off. The toxins create ulcers in the fish when their scales flake off. Through micropredation the Pfiesteria will increase the size of the ulcers and eventually kill the fish. Many times the fish will die of secondary infections, either fungal or bacterial, due to the big ulcers. The toxin has shown inflammation and dermatitis that were allergic or irritant in nature. Recently in vivo exposure to mice showed localized edema but not lymph node involvement. This suggests the toxic compound is simply a mild irritant not a sensitizer to humans (3). Fish placed in active, toxicity cultures rapidly develop aberrant behavior and epithelial hemorrhage (12). Alot of information, would it be easier to have categories?

There have been many hypotheses as to the exact chemical makeup of the toxins as well as through exactly what mechanism does the chemical effect fish and humans.Hypothesis regarding the chemical makeup of the toxins and their mechanisms have been posed.(Something like that so the sentence is split up.) In order to test these hypothesis….A hydrophilic Pfiesteria toxin was isolated in 1997 has been shown to affect fish and mammal health. In 2004 the hydrophilic Pfiesteria toxin was successfully reproduced and acceptable handling procedures have been created for safety precautions (2). In 2007 there was work with the toxic forms of Pfiesteria piscicida. During these works they were able to isolate metal complexes and free radical toxins, thought to be produced by the Pfiesteria, in the water. (Sound more like bullet points)They (who? )were able to isolate ligated copper compounds from the waters. LIgated copper compounds were isolated from waters.After purifying the toxin and running multiple NMR cycles they ? were able to obtain a chemical structure of the toxin. The metallic toxin is a copper and sulfur based compound (Figure 6) (14). The ligands surrounding the metal ion would vary greatly depending on the environmental conditions and what other materials were available in the water. The true toxicity of this compound comes from the carbon and sulfur interactions that produce free radicals in the water. Free radicals are very unstable and react quickly with other compounds, trying to capture the needed electron to gain stability. Generally, free radicals attack the nearest stable molecule, stealing its electron. When the attacked molecule loses its electron, it becomes a free radical itself, beginning a chain reaction. Once the process is started, it can cascade, finally resulting in the disruption of a living cell. This disruption of living cells is where the harm in this toxin is from. This would explain the trouble detecting this toxin previously because the free radicals are very short lived. The complex estuarial environment with the correct salinity, mineralization, presences and nature of organic material, variations in temperature, light intensity, and nutrients available would all influence the production and concentration of these metal toxins (15). This very unstable toxin has been described as a phantom toxin because of its quick decomposition (14). It is heavily susceptible to white light, pH variations, and prolonged heat. This is why the right environment must be present for toxin production. It is the presence of white light that breaks the initial metal ion down causing the dispersal of the free radicals. For this reason most research of the Pfiesteria toxins must be performed under red light. Another possibility and the one that perhaps scares humans the most is the possibility of a lipophilic toxin. This lipophilic toxin, as of right now, is just a hypothesis of researchers. If this toxin were to exist it would have serious long term effects on humans we are not aware of yet. The lipophilic toxin would be able to safely dissolve into human fat tissue. Researchers are still unaware by what mechanism humans are able to filter the toxins from the body (4). The stored toxins could stay dissolved in the body for years before the effects are seen again.
Recently, researchers have discovered clues as to what mechanisms the toxins travel throughout the body and affect our health. Researchers from the National Oceanic and Atmospheric Administration’s National Ocean Service and from North Carolina State University in Raleigh where able to identify the receptor targeted by the Pfiesteria toxin or toxins. They discovered the Pfiesteria toxins act as an agonist of the P2x7 receptor. This receptor is commonly found in the immune systems of humans and some wildlife such as fish. The toxin can trigger a cascade of inflammatory responses; this overreaction can cause death in some fish and cause some of the documented health problems in humans (16). The P2X7 receptor can be found in macrophages, mast cells, microglia, central nervous system, and pituitary cells. Another idea researchers have proposed is the idea that algae or bacteria are required for the production or activation of the toxin. There are cases of bacteria-free Pfiesteria producing toxins in very small amounts, bacteria and other organisms used as prey by Pfiesteria significantly enhance toxin production through unknown mechanisms (14). This leads researchers to believe the toxicity may not be a fixed component of Pfiesteria metabolism. There is the possibility the extra cellular bacteria gives of excretions or some sort of byproduct necessary for the activation of the Pfiesteria toxin.
The term “Pfiesteria hysteria” was coined during the mid 1990’s simply for the fact the general population was hysterical about the possible human health effects Pfiesteria could cause. Many rat models have been used to research the Pfiesteria toxin effects on mammals. The rat models test the ability of the rats to make choices and to learn while they are infected with the Pfiesteria organism directly. In these studies the majority of the observations are the same. One study tested the rat’s ability to remember choices and learn using the radial arm maze. The rats infected with Pfiesteria had a much high lower entries to repeat (4). It should also be noted that the greater the exposure to Pfiesteria the lower the entries to repeat fell. Other studies have focused on the rat’s ability to obtain learned skills they received before the Pfiesteria infections. Rats who were trained previously on the radial arm maze and then infected with Pfiesteria exhibited a lower number of errors per session than the untrained infected rats (8). It should be noted that in both of these studies the rats had a complete blood work up that turned out to be normal. This leads researchers to believe for mammals Pfiesteria doesn’t effect previously learned abilities but it does significantly hinder the ability to learn new abilities while infected.
The short term human health effects have been determined for some time. Humans exposed to toxic Pfiesteria may experience eye irritation, long term vision problems, respiratory problems, nausea, short term memory lose, disorientation, confusion, loss of find motor skills, skin lesions, rashes, irritation, headaches, irritability, and fatigue (7). The Pfiesteria toxins affect the neural cells in humans more than the endothelial cells. This is why we see the collection of neural problems associated with this toxin. The toxin cause of leakage of lactate dehydrogenase and a lowered ATP count in humans. The lowered ATP count can explain the fatigue seen in most infected patients. A study performed with 123 fishermen in Maryland waters that had previously tested positive for Pfiesteria, showed no difference in health effects between the experimental and control groups (1). This could have been for many reasons other than the lack of Pfiesteria. The environmental conditions may not have been appropriate for the toxin production or they could not have had the toxic strains of Pfiesteria present. A case study following a Pfiesteria researcher, at Duke University, showed serious neural health effects as mentioned above (17). The interesting thing about this study is the participant presented 6 years later with loss of vision and pain in the right eye. All of the patients blood work came back normal just as in the rats. The patient was diagnosed with demyelinating disease. This brings up the serious concerns of the long term effects the toxins may have on human health.
The dinoflagellate Pfiesteria is best associated with the massive fish kills along the eastern shores and estuaries in the mid 1990’s. These fish kills created what was called “Pfiesteria Hysteria” by much of the east coast nation. This fairly new described organism has many questions about the effects it has on humans. Researchers are interested in the long term effects on humans. They want to know by what processes to we metabolize the toxin, how do we store the toxin, and how we excrete the toxin? There are hypotheses about the mechanisms the Pfiesteria uses to produce the toxin but they vary greatly from one to the other. As recently as last year the structure of a toxin has been observed and isolated. This is a big step in learning about the precautions needed to keep humans safe from this organism. I believe that Pfiesteria produce multiple toxins and one or all of them are harmful to human health. In most of the cases the humans that are affected are working in close proximity to a high concentration of Pfiesteria. This leads me to believe that humans need to be exposed to toxins in high quantities for the full effect of the toxins to be seen. In my opinion the future will bring many answers to these questions and will finally come to the conclusion if Pfiesteria is really harmful to humans?

This is a good start with lots of information, but categories to keep the info together would help. Good paper, interesting topic.

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