Metabolomics

The aim of the experiment was to come up with an easy biomarker that can be used to differentiate between different pollutants and environmental stressors and the effect they cause upon the life cycle of vertebrates and invertebrates. Specifically the experiment addressed the effects of PCB in the embryo of avian and Diporeia.  

The samples were collected manually. The great blue heron eggs were harvested from nests on tree while Diporeia was collected from Lakes Michigan and Superior. The samples were subjected to two main analyzed using Gas chromatography and Mass Spectrometry (GS-MS). Refrigeration and temperature control devises were used in the preparation of the samples as well as in storage. Results indicated that 332 metabolites were observed in the embryo of the heron with different degree of exposure to PCBs while the correlation between the distributions of the metabolites between the two lakes indicates that only eight out of the total possible 332.

It was found out that PCBS and farm herbicides indeed hinder the embryonic development of amino acids and fatty acids as well. The chemicals interfere with the natural metabolic pathway by acting either as inhibitors, parasitic enzymes as well as cancerous cells within the embryo developing within the region of discussion.  

Introduction.
The aim of the paper is to devise an easy sensitive biomarker that can be used to differentiate the effects of different pollutants and environmental stressor on the life development of embryos of great blue heron and account for the decrease of Diporeia especially when exposed to polychlorinated biphenyls (PCBs) and atrazine. The experiment come as a wake up call to discover the environmental effect of PCBs exposed to sediments and waters bodies in the Indiana area. The experiment is to find out how many of the PCBs affected embryo of great blue heron would hatch, try to account for the decrease in population of Diporeia in the Lake Michigan that has in turn led to the decrease of fish population. The method of study included usage of Mass Spectrometry (MS) that according to metabolomics can easily measure the total concentration of metabolites present in an individual.

Two main methods were used in the experiment that involved two more controls experiments. Gas chromatography coupled up with Mass Spectrometry (GC-MS) was used as the separation analytical method since it allows a wide range of metabolites to be measured under high resolution. The Detection method that was applied was Mass Spectrometry (MS) that identified and quantified the metabolites after the GC separation. MS allows identification by use of well established reference in fragmentation patterns. Hence great blue heron metabolomes were exposed to varied concentrations of PCB. Two control experiments were set up whereby freshwater amphipod from Lakes Michigan and Superior were exposed to firstly PCB and a second sample was exposed to atrazine for comparison studies. The results of the experiment confirm that the amount of PCBs exposed to Heron eggs ranged from 164-to-27,703 gkg.  A table summarizes the effects of PCBs in great blue heron embryo indicate that a total of 332 metabolites positively identified and exposed to PCBs at different concentrations.  Figure two (page 18) reveals that 37 metabolites were exposed to low concentration of PCB of 165 to 375 ppb while151 were exposed to moderate concentrations wit some 13 metabolites fell in between the concentrations of the two ranges. In the moderate concentration that was between 1500 and 2000 a total of 151 metabolites were exposed with unique 13 metabolites occupying the space concentration between 376 and 1499 ppb. Other unique metabolites identified include 29 metabolites that strategically occupied the positions between moderate concentration and high concentration of 5500-27,000 ppb that had 43 and 13 metabolites that occupied the concentration between low PCB and high PCB concentrations. Further 35 tactful metabolites were exposed to concern all the three concentrations. The Atrazine study revealed 316 metabolites of which 67 showed a unique sign while 74 got exposed to atrazine. Eventually only eight metabolites were realized to be shared across the two lakes.

The tables and figures used in the research study need to be opened up for better interpretation date since the design are a bit complex and in need of a some time in order to be interpreted. The figures lack more information about the shared populations. At the same time the Figure A should have been separated further to include percentages of the metabolites that were shared and unique for easier interpretation. Also the tables miss to identify key metabolite that acted as inhibitors, parasitic and enzymatic metabolites. A bar graph could have been included to further explain the relationship between high concentration levels of PCB and embryo development at different ages. A possible sigmoid chart is missing to correlate the difference and similarities that can observed during presence of amino acids and fatty acids with the concentration of atrazine.      

The experiment assumed advanced methods with unbiased control elements being applied since metabolites were collected from only two lakes and in specifically identified places in order to keep the results distinctly pronounced. Yolk samples were sampled using GCMS method that gave results that could have been translated to more tables and graphs to reflect peaks and troughs that can be use fragmentation patters to identify apart. Thus the experiment design was laudable in response to the results since the GC-MS combined sampling methods are the best so far doe metabolic experiments that allow easy and well organized coverage of the sample ranges and sizes. Moreover, MS presents a researcher with the ability to simultaneously measure concentrations of many metabolites from a single metabolite with remapping of the profile across the population by using the fragmentation patterns. Therefore possible biased results were controlled at the analytical stage. The only controls employed in the experiment the use of parallel samples from two lakes as to avoid replica of the expected experiment results by application of correlative studies. The range of samples replica that were chosen to be controls were expected to give very accurate information about metabolites according to the guidelines of the experiment.

The experiment concluded that among the avian and other egg-laying vertebrates, the embryonic stage growth is fundamental and prone to egg nutrition set up that can easily be upset by the presence of PCB. Seemingly atrazine reduces the amount of amino acids and fatty acids of the Diporeia species leading to poor growth and reproduction due to direct health impacts. Moreover, rarely does the author delve unto the cause of presence of some fatty acids in Lake Superiors Diporeia that are missing from Lake Michigan species of Diporeia thus preempting the probability that the experiment is non-conclusive.
The authors conclusion is very weak since instead of discussing encompassing information about the meaning and possible conclusions that can be formed about the experiment instead the author informs the audience of the results of the experiment. In the conclusion, a researcher is supposed to mention about the success and failure of the applied methodology and scientific instruments used. Moreover, the conclusion has to state whether the experiment was successful and the same marker methods can be used over and over again by future scholars. Lastly the cost of doing the experiment should be included. Consequently this paper should not be published meanwhile until all scientific research requirements are fully met and applied in the research. The experiment is quite long for the sake of identifying PCB in vertebrates and invertebrates. The methodological description lacks coherency that could be easily replicated by another researcher to ascertain the results obtained. Therefore, since the experiment controls and the actual experiments were done by the same methods that could be biased, the results can be doubted to some degree.    
In conclusion a lot of research parameters need to set in order to ascertain that the lack of amino acids and fatty acids during the experiment is not probably associated with the methodology of the experiment. These two experiments have a long methodology that ends up disrupting the original composition and weights of the samples in use therefore a wide range of differences is expected in the controls. Lastly, there is too much detail involved from the beginning to the conclusion of the experiment whereby in case of repeating the procedure there is a like hood of displaying diverse results that can fail to be used as a biomarker identification guide.      

0 comments:

Post a Comment