Category: Sciences 2502

Available literature demonstrates that malaria is a foremost public concern and a major cause of morbidity and mortality in the worlds most under-developed nations and some regions in developed nations (Ayele, Zewotir, & Mwambi, 2014). The occurrence of malaria, according to these authors, is related to deprived socioeconomic circumstances as the disease inexplicably affects underprivileged individuals who cannot afford treatment or who have constrained access to health care services. The present paper discusses the incubation period and diagnosis of the disease.

The malaria incubation period, according to Brasil et al (2011), is described as the time elapsed between exposure to the infectious agent (through the bite of the Anopheles mosquito) and the manifestation of the first clinical sign or symptom (p. 123). These periods generally differ depending on the species of Plasmodium causing malaria, with available information demonstrating that shorter periods of nine to14 days are observed for infections by P. falciparum, 12 to 17 days for infections by P. vivax, and longer periods of 18 to 40 days for infections by P. malariae (Brasil et al., 2011; Cowan, 2011). It is important to note that antimalarial medicines usually taken for prophylaxis by travelers and visitors to malaria prone regions have the capacity to delay the onset of malaria symptoms by weeks or months, particularly in a scenario where the Plasmodium causing malaria (e.g., P. vivax, P. ovale) generates latent liver stage parasites that may become active and trigger the disease long after the infective bite by the Anopheles mosquito (Centers for Disease Control and Prevention, 2010).

As indicated in the literature, effective malaria diagnosis is important first for the obvious reason that it is necessary to identify cases to treat patients effectively, but also to limit treatment to patients who have malaria and not other febrile illnesses (Wilson, 2013 p. 805). The standard technique for malaria diagnosis in most countries across the world remains the assessment of thick and thin blood films under microscopy for possible demonstration of malaria causing parasites in the blood, as shown in figure 1 (Norgan et al., 2013). In simple terms, this technique entails the employment of light microscopy to scrutinize or assess stained tangential blood smears placed on thick and thin films in normal laboratory settings. This diagnostic technique has found wide usage in most health care settings due to its low cost, availability and relative sensitivity, though critics have persisted in labeling the technique as too laborious and technically challenging.

Available documentation reveals that additional laboratory findings for malaria diagnosis may include mild anemia, mild decrease in blood platelets (thrombocytopenia), elevation of bilirubin, and elevation of aminotransferases (Centers for Disease Control and Prevention, 2010 para. 12). Other conventional methods of diagnosing malaria include histopathologic diagnosis (not a first-line diagnostic technique for malaria due to insensitivity to detect parasites), empirical/syndrome diagnosis (made on the basis of clinical history, signs, and/or symptoms in endemic regions), nucleic acid amplification tests (not available commercially), and malaria rapid diagnostic tests (used in detecting malaria-specific protein antigens or enzymes) (Cowan, 2011; Wilson, 2013).

Overall, this paper has demonstrated that the malaria incubation period ranges from a few days to several weeks or months based on the Plasmodium causing malaria. It has also been demonstrated that there are multiple ways to diagnose malaria, though the gold standard for diagnosis in many parts of the world remains the assessment of thick and thin blood films under light microscopy.

References

Ayele, D.G., Zewotir, T.T., & Mwambi, H.G. (2014). Semiparametric models for malaria rapid diagnosis test result. BMC Public Health, 14(1), 1-20.

Brasil, P., de Pina Costa, A., Pedro, R.S., da Silveira Bressan, C., da Silva, S., Tauil, P.L., & Daniel-Ribeiro, T. (2011). Unexpectedly long incubation period of Plasmodium vivax malaria, in the absence of chemoprophylaxis, in patients diagnosed outside the transmission area in Brazil. Malaria Journal, 10(1), 122-126.

Centers for Disease Control and Prevention. (2010). Malaria. Web.

Cowan, M.K. (2011). Microbiology: A systems approach (3rd ed.). New York, NY: McGraw-Hill Science/Engineering/Math.

Norgan, A.P., Arguello, H.E., Sloan, L.M., Fernholz, E.C., & Pritt, B.S. (2013). A method for reducing the sloughing of thick blood films for malaria diagnosis. Malaria Journal, 12(1), 1-5.

Wilson, M.L. (2013). Laboratory diagnosis of malaria. Archives of Pathology & Laboratory Medicine, 137(6), 805-811.

The scientific investigation of Earth has led to the formation of theories that explain how the planet as it is now changed over time. The archeological evidence, fossils, the placement of volcanoes, and glaciers serve as evidential proofs that provided the basis for the Plate Tectonics Theory. Importantly, the form of the continents and the coastlines indicate that they coincided with each other and were once a unity. The theory is based on the concept of isostasy that allows the tectonic plates to float on a layer placed beneath them and the concept of continental drift. This idea claims that in the late Paleozoic era, a supercontinent named Pangea existed and was later separated into several pieces (modern continents) due to continental drift.

The Precambrian period in the history of Earth was a long period that started with the planets creation and lasted until the first organisms appeared. At the beginning of this era, the planet had a very humid and hot climate, and the atmosphere did not contain any oxygen. With time, the activity of bacteria started producing oxygen; its level grew, thus changing the gas composition of the air. Due to the presence of oxygen in a considerable volume, the planets climate became cooler, the humidity in the atmosphere started condensing, and with time oceans appeared on Earth. Thus, the atmospheric changes during the Precambrian period were pivotal for the development of organisms.

The Paleozoic era was a long period in the geological development of Earth that witnessed the appearance and existence of multiple kinds of animals that have become extinct. For example, during the Paleozoic period that started 542 million years ago, arthropods started evolving into the forms of life that are now known as insects. Diverse forms of sea life evolved, including such arthropods as a trilobite. However, at the later stages of the Paleozoic, more developed land-living animals appeared. Some of them include tetrapods that constituted a large group of animals, some of which lived in the sea, and others inhabited land. The latter became the ancestors of dinosaurs and birds in the later stages of Earths history.

Introduction

The impact of biotechnology is being felt increasingly in modern days across several sectors and disciplines. Biotechnology can be defined as any technological application that makes use of biological systems or living things with an aim of making or altering products or given processes for specified purposes (Thieman & Palladino, 2009). It is an applied field in biology which is involves modification of living organisms by human desires and intentions. Biotechnology borrows heavily from the various pure biological sciences. These include; microbiology, genetics, biochemistry, animal cell culture, cell biology, embryology, and molecular biology (Talbot, 2001). The knowledge and methods used in biotechnology also comes from other fields beside biological sciences. They include information technology, chemical and bioprocess engineering, as well as biorobotics.

Body

Biotechnology has brought about a number of transformations within the sphere of living organisms. Trichoderma reesei has emerged as an industrially useful cellulolytic filamentous and is also a mesophilic fungus (Sparks, 2006). It is characterized by the ability to secret cellulolytic enzymes like the cellulases and hemicellulases in large quantities. Many researchers in this field have emerged and are trying to establish the possibility of developing the Trichoderma reesei as a host which can be used to produce low cost enzymes. The enzymes can be used in turn to convert the cellulose in plant biomass materials into industrially valuable bioproducts. Sugars and bioethanol are some of the bioproducts that are produced in the process. With the developments in biochemistry, Trichoderma reesei is advancing to become a commercially viable alternative in the process of cellulose hydrolysis. Biochemists have already established important strains of Trichoderma reesei which are gaining ground in industrial applications (Thieman & Palladino, 2009). In 2008, biotechnologists released a genome of the Trichoderma reesei which is 33Mb with a total of seven chromosomes. Most of the transformations of Trichoderma reesei are DNA mediated

Transformation in virtually all fungi is now possible with the use of exogenous deoxyribonucleic acid, especially the ones that can be grown in culture (Talbot, 2001). Two major methods have been used in maintaining the transformation process. The use of an autonomously replicating plasmid can be used for transforming DNA. Alternatively, the DNA can be integrated into the chromosomes. Transformation in fungi is useful as far as gene cloning and gene function analysis is concerned (Talbot, 2001). Markers are essentially in ensuring meaningful transformation in fungi. Several markers have been identified for the different fungi. Most useful markers can be selected and counter-selected. The use of marker genes in the transformation of fungi helps in visualizing hyphae on roots, nematodes and in soil as well as in the observation of interactions in situ. One of the most common marker for fungi and other organisms is the gene for jellyfish green fluorescent protein (gfp) (Thieman & Palladino, 2009). Fungi can generally be transformed by the use of either nutritional markers which match an auxotrophic requirement or dominant, selectable antibiotic resistance markers. A gene (bar) coding for phosphinothricin acetyltransferase has been separated from S. hygroscopicus. It is usually used as a selective marker during the transformation of higher plants and a number of filamentous fungi (Talbot, 2001).

There a number of differences between genetically encoded and chemical fluorescent markers. Genetically encoded fluorescent markers, for instance the green fluorescent protein (Aquorea Victoria) can detect localization of cell proteins as well as organelles in living organisms and cells (Sparks, 2006). The changes in the spectral properties of the proteins are useful when tracking all enzyme activities. Chemical fluorescent markers, like calcium are visible, making them useful when it comes to receiving and enhancing sensitivity of specific responses to specified stimulus.

Numerous variants of Discosoma sp. Red Fluorescent Protein, commercially known as DsRed, have been developed over the past decade. The variants include; DsRed2, DsRed-Express, and DsRed1-E5- which is the Fluorescent Timer. Most researchers have made attempts to understand the DsRed fluorophore in terms of its structure, and the light absorbing and emitting characteristics (Bevison & Glick, 2002). The DsRed1-E5 is a variant that contains two amino acid substitutions (V105 and S197T). These acid substitutions serve to increase the fluorescence intensity of DsRed1-E5 giving it a unique spectral property. The variant changes in color as the protein ages (Bevison & Glick, 2002). Once synthesized, the DsRed1-E5 starts emitting fluorescence which is green in color. With time the wavelengths of the fluorescence shifts to the longer regions, causing a change in color. The protein becomes bright red when it is mature. It is the predictable color change that can be used to monitor the on and off phases of gene expression (Talbot, 2001). The DsRed1-E5 enables the detection of the green and red emissions using fluorescence microscopy and flow cytometry. The change in color with time facilitates the tracking of not only up-regulation, but also down-regulation in the process of gene expression (Bevison & Glick, 2002).

Conclusion

The paper has discussed Trichoderma reesei as an industrially useful cellulolytic filamentous fungus. Some of the numerous uses of T. reesei have been highlighted. The types of transformation markers available for fungi have identified. Moreover, the difference between genetically encoded and chemical fluorescent markers has been pointed out. The paper has also explained what DsRed1-E5 is and its uses.

References

Bevison, B. J. & Glick, B. S. (2002). Rapidly maturing variants of the Discosoma red fluorescent protein (DsRed). Journal of National Biotechnology, 20 (3): 839.

Sparks, D. L. (2006). Advances in biotechnology: genetically encoded and chemical fluorescent markers. Academic Press.

Talbot, N. J. (2001). Molecular and cellular biology of filamentous fungi: a practical approach. Oxford University Press.

Thieman, W. J. & Palladino, M. A. (2009). Introduction to Biotechnology (2^nd ed). San Francisco, CA: Pearson.

Background

Prevalence rates of vancomycin-resistant enterococci (VRE) associated with serious clinical infections has been on the rise worldwide for over the past 15 years. Control measures being taken primarily entail the detection of non-infected but gut-colonized patients that might suspected to be harboring the VRE. The use of improved cultural-based methods may lead to a possible alternative for cost-effective VRE surveillance. The performance characteristics of the chromed VRE medium and the CHROMagar TM VRE medium Paris are systematically compared in this study. Special emphasis is put on:

1. Selectivity
2. Permanence of color and growth characteristics within the colony
3. Their ability to recover VRE from clinical stool specimens

With the aim to determine selectivity all characteristics of the genus Enterococcus were investigated. The National Reference Center for Streptococci was the source of VRE reference strains used as positive controls. These media prevented growth of all but one Enterococcus strains monocultures. Only tiny bluish colonies of E. gallinarum were not suppressed and grew on CHR, though neither E. solitarius nor E. were observed on both media. Objective color evaluation of colony appearance was performed by means of analyzing pictures taken during the periods of incubation and use of light and electron microscope

4 Dilutions of VREfm (Enterococcus faecium; n = 7) and VREfs (Enterococcus faecalis; 47 n = 2) reference strains were streaked in pure and mixed culture on both media AC7075 (vancomycin MIC 48 ¼g/ml), and showed a rosy brown color. The CHR medium did not distinguish VREfm from VREfs. However, 24 h of incubation made color hues of the corresponding colonies more divergent than expected to be. For the colonies edges, seven and six color hues were found out for VREfm and VREfs, correspondingly. After 24 h of incubation, VREfs colonies could be recognized by their permanent green color, while there were difficulties in identifying VREfm, which color varied. The more intensive growth of colonies on C-ID compared with CHR succored early detection and distinction of VREfm and VREfs. In general, it can be concluded that C-ID conditions were more favourable for intensive growth of VRE, than CHR agar plates. For routine evaluation stool specimens obtained from suspected patients were used. The results of the preliminary experiment conducted using both direct and indirect plating were not clear due to bacteria and yeast reducing sensitivity. Therefore, before parallel inoculation of these chromogenic media an enrichment culture of the stool specimens was applied for comparative testing. The media were evaluated for growth of suspected VRE colonies after 24 and 48 h of incubation. Suspected VRE colonies were tested implementing using Gram staining and pyrrolidonyl arylamidase paper in order to confirm Entercocci. Further identification of species was done by susceptibility testing for 50 ¼g furazolidone and 10 ¼g mupirocin using Rosco Neo-Sensitabs on Mueller Hinton agar and a rapid D-xylose fermentation. The reaction pattern allowed confirmation of E. faecium or E. faecalis or identification of intrinsically low-level vancomycin resistant enterococci like E. casseliflavus and E. gallinarum. A confirmatory test consisted of two parts: antimicrobial resistance for vancomycin and Teicoplanin applying CLSI breakpoints. The presence of Vancomycin resistance genes were determined by multiplex PCR.

A total of 259 stool samples were screened simultaneously on both chromogenic media revealing 54 VREfm and two E. gallinarum isolates demonstrating 21% of vancomycin colonization rate. The genetic relatedness of the VREfm isolates was determined using multiple-locus variable-number tandem repeat analysis

Since each chromogenic medium failed to detect one VRE strain, which was successfully detected by the other, sensitivity, were 98% for both media. Although the specificity for both media was high, 95% for CHR and 96% for C-ID, there was a risk for false positive VRE identification when solely based on Gram staining and colony pigmentation on chromogenic media. Most strikingly, growth of Pediococcus species on both media was visually indistinguishable from. PYRase testing coupled with furazolidone and mupirocin, the two tests diagnosing agar diffusion susceptibility, aided detecting of Enterococci and thereby precluded Pediococcus. Cultivation of Pediococcus species requires human stool specimens, though patients with chronic underlying diseases or experienced abdominal surgery can have infections, from which the species can be derived too. The prompt xylose fermentation test aided the detecting of species in the case of two E. gallinarum isolates while misleading colony colors were growing on both media. Furthermore, both media created conditions for yeasts growth, resulting in white colour of colonies on CHR and dull green colour of colonies on C-ID; the latter could be confused with VREfs. Yeast cells were differentiated by gram staining. The vanA genotype was found in all but one VREfm isolates. The VanB phenotype was identified in the latter one, while vanB genotype was confirmed with PCR. Cases of isolation of Vancomycin susceptible Efm or Efs from chromogenic media with enriched stool specimens were rare. Overgrowth of other bacteria and following exhaustion of sample substrates might explain it. Our study has demonstrated that the results of C-ID and CHR media experiments contradict hypotheses of rapid VRE identification; direct plating of the stool specimens or plating them after dilution complicates the process of detection. Intensive growth of various bacteria and yeasts on both media prevents media evaluation if stools are plated directly and alters the innate color of stools. Consequently, stool specimens are inapplicable for direct plating onto C-ID and CHR media.

Critical review

General

The paper is introduced by touching on the increased prevalence of the VRE and proceeds on to state how cost effective diagnosis can be achieved by use of improved culture methods. The thesis statement talks about comparison of two media. The introduction did not have anything on the role of sensitivity and specificity in the increased prevalence. The paper is not original; this comparison can be done using the already available laboratory data. The methodology is poor; there is no literature review to show what has been done and where this particular researcher(s) is picking from. The paper however can be important to microbiologist where by the results can be used to guide the choice between the two media investigated. The paper is mixed up with no clear methodology, results and discussion. The use of bacterial names and the elaboration of the procedures is okay but there are slight grammatical mistakes.

Title

The paper is too wide for the title. The title confines the paper to the two media but the researcher escalates out of the boundaries in a bid to confirm the results or identify the isolates. The use of PCR, electron microscopy makes the research to be too expensive; in fact the confirmation tests seem to be expensive than the main comparison of the two media. It is as if the researcher was investigating the appropriateness of these two methods. The researcher could have used gram staining and the basic biochemical tests to confirm the results.

Abstract

The abstract should be a summary of the study and should include all areas. The abstract in this paper is written like a conclusion, it does not give the aims of the study, main methods nor does it reflect the researchers point of view that is seen in the conclusion. In which the authors state that the two media are not sufficient for plating of stool specimens. (Heidrun 2009)

Introduction

The introduction includes the statement of the question to be addressed in the research; Comparison of Two Chromogenic Media for Selective Isolation of Vancomycin-Resistant Enterococci from Stool Specimens. However, the researchers do not provide sufficient literature review for readers to comprehend the question. He does not state the reason that prompted the comparison analysis; he/she only touches on cost effectiveness an issue that is never reflected in the rest of the paper. The authors fail to show how they developed their problem statement, what literature was reviewed and the missing links that prompted the research to be conducted.

Materials and methods

The methodology is not brought up well by the researcher, it is written like a discussion. However, it offers details for replication of the experiment conducted but does not really address the topic or research. For the methodology I think the topic should have something to do with the effectiveness of the two media (CHRC-ID) and not comparison of the two. The researcher repeatedly refers to the manufacturer in the methodology, it could have been better to write a note and state that all the procedures were carried out according to the manufacturers guide. The paper is mixed up and the author s might have done a quality investigation but he/she failed to right the report in the required format. The authors should have dedicated a section in the report for the procedures that were carried out in the study.

Results

The authors have given only the results they have observed in this study, from which they have drawn a very strong conclusion regarding the media C-ID CHR; there is no comparison with results conducted by other scientists. However, there are some instances of reference to the normally expected results as regards to the method and instrument used. The results re not organized, the authors give results after every test and so it is difficult to get a clear picture of the findings without having to go through the whole paper. Some results could have better been presented in tables, for instance the results of the determination of the isolates using the multiplex PCR. The photographs of the media plate to show the color changes should have been more for better differentiation. There is some repetition though the author clarifies that details are found in the table. There is no clear distinction between the result, discussion and conclusion parts in the paper.

Discussion

The authors interpretation of results is okay as per the methodology but he/she is a little off the mark in relation to the title of the research. The title states that the investigation seeks to compare the two chromogenic media for selective isolation of Vancomycin resistant Enterococci from stool. In the discussion the authors state that our study has clearly shown that C-ID and CHR media do not fulfill all expectations regarding rapid VRE detection, especially when plating stool specimens directly or predilution. (Heidrun 2009) The author puts a lot of emphasis on the shortcomings of the two media and this causes the deviation from the main topic of the research which is comparison of the two media. The authors havent distinguished their findings and the findings of others. The discussion is only based on the results of tests conducted in their study. The authors conclusions are minimally competent as regards to the topic of the study. On careful examination the research, one will realize that the research is okay only that the authors failed to articulate the issues appropriately.

Referencing

The referencing page is well done but the in text citations are lacking or poorly done. There are several technical terms in the paper that the author must have lifted from other sources which are not cited in the body of the text. All the references are important for the authors expanded investigation but these could have been better depicted in the literature review which is conspicuously absent.

Tables and figures

The tables are detailed and can be understood without reference to the main text. The table labeled the control table which has been sourced from culture collection of national reference center for streptococci Aachen, Germany shouldnt have been included as part of the report. (Heidrun 2009) The tables are well designed and informative.

Reference

Heidrun, P et al (2009) Comparison of Two Chromogenic Media for Selective Isolation of Vancomycin: Web. 

The very miracle of life on the earth is seen in DNA (Deoxyribose Nucleic Acid) and RNA (Ribonucleic Acid) molecules which contain all the important information needed for the formation of any particular living organism on the planet. DNA alone, though it cannot create life by itself, contains all the important details concerning the building of any particular organism it belongs to. However, all the abundance of information contained in DNA is useless without RNA as this molecule directly participates in the process of protein construction which is exercised in the ribosome. In the following paper, the mechanisms of cooperation between DNA and RNA along with the specific details about them will be examined. Generally, it appears that DNA and RNA are the most important point in the chain of life on the planet without which no living organism on the earth could exist.

First of all, speaking about DNA and RNA, it is important to discuss how they are built. DNA consists of adenine, cytosine, guanine, and thymine nucleotides, whereas RNA has uracil instead of thymine. DNA is also different form RNA as it is a chain consisting of two parallel rows of nucleotides whereas RNA chains consist of only one line of nucleotides. In addition, RNA molecules can be of different types. The first one of them is mRNA which is a messenger RNA, the second one is rRNA which is a ribosomal RNA, and the third one is tRNA which is a transfer RNA. All these three types of RNA are kept: in the different part of the cell, and are responsible for the varied stages of the protein formation.

Further, the differences between DNA and RNA functions are to be addressed. DNA is used as a huge storage of information, but it does not participate in the direct process of constructing new cell-parts. It can be illustrated by the following example. When the builders construct any particular building they do not use the original drawings. Just the same DNA is copied and only its copy is used in the process of formation of new proteins. However, with regards to RNA, it should be mentioned that this molecules function is in participating in the process of cell-part construction in particular. RNA is used just like a blueprint from the original drawing of DNA in order to be a plan for the formation of new proteins.

Concluding on all the information related above, it should be stated that both DNA and RNA are the most important molecules which participate in the process of life formation on the planet. These important molecules are the essential parts of any living organisms. Both of these molecules respond for the process of keeping and using the information concerning the formation of the organism they belong to. However, with regards to RNA, it should be mentioned that this molecules function is in participating in the process of cell-part construction in particular whereas DNA is only used for the storage of the hereditary information. Speaking about the building of these important molecules, it should be stated that DNA consists of adenine, cytosine, guanine, and thymine, whereas RNA has uracil instead of thymine, and DNA is also different form RNA as it is a chain consisting of two parallel rows of nucleotides whereas RNA chains consists of only one line of nucleotides.

It is unimaginable what could be the situation at the present if the smallpox vaccine had not been discovered. One development that has been hailed to save mankind from a dreaded disease is the discovering of the vaccine. From the audio interview, Richard Preston author of Demon in the Freezer and Dr. John Neff a smallpox expert talked about smallpox being the mother of all biological weapons with a death rate of 1 in every 3. They were of the view that mass vaccination cannot be a solution as it will bring some serious complications. At the end of the interview, it was held by Neff that smallpox vaccine confers immunity for a period of between 3 and 5 years meaning that individuals vaccinated in 1970s are no longer immune to the virus. This is the centre for discussion as I tend to hold a contrary view.

Interestingly, people who have survived smallpox infections are known to exhibit a lifelong protection or immunity from the dreadful virus. Similarly, it has been found out that a greater proportion of individuals vaccinated for smallpox do have certain neutralizing antivaccine that is capable of offering protection against smallpox. On the same note when individuals are subjected to multiple vaccinations, there was slight increase in levels of antibodies; however the level of the same doesnt reduce as time elapse. Although it has been suggested that high risk individuals opt to be revaccinated after a period of 5 years, studies have shown that once vaccinated for smallpox, recipients are offered protection from lethal infection of smallpox for longer period. This means that there will be no need for multiple re-vaccinations since a single vaccine elicit functional antibody that will remain stable in human body for lifetime (Taub et al., 2008: 1059). Another study using subjects between the ages of 1 and 52 years were revaccinated; there was no or very little response in the antibody. In conclusion, all people vaccinated either once or several times do maintain antivaccine IgG as well as neutralizing antibody titers. It is worth noting that the titers are stable for about 90 years. Various studies concluded that individuals vaccinated show immunity to vaccinia indefinitely and do not need booster vaccination.

In the article Smallpox Vaccine: Looking beyond the next generation written by Enserink, Martin and published in 2004, the author compares and contrasts DryVax and MVA vaccines. DryVax is older, developed and used to eradicate smallpox back in 1970s and was amazingly very effective in eradicating the infectious disease. However it has been shown to pose some negative effects such as increased rate of encephalitis, severe skin infections and heart inflammation. A more recent vaccine MVA (modified vaccine Ankara) does not result in lesion; it is deemed to be safer than DryVax and other traditional smallpox vaccine developed. However its efficacy cannot be successfully predicted in protecting mankind from smallpox. Using booster doses of the vaccine will help in providing strong immunity.

Because there is need to subject the victims to between 2 and 3 doses of MVA, it will be potentially difficult to use it during high risk situations. It is worth noting that despite the shortcoming mentioned, MVA can be successfully used by individuals who are immune-compromised (suffering from HIV and AIDS, cancer among others). Similarly it can be applied in a pre-event scenario. In my view there is no need to jump into conclusion regarding the vaccine of the future. There is need to carry more research to establish the immunogenicity as well as preventive efficiency of MVA as well as other vaccines with regards to their abilities to curb smallpox epidemic. This is guided by the fact that the experiment was carried using monkey and the results obtained might not be a true reflection of what will happen when used in human beings (Enserink, 2004).

Ring vaccination has been define as the act of giving a vaccine to a group of individuals who are in close contact with those who are infected with a communicable diseases such as polio, smallpox among others (Preson, 2002). This kind of vaccination helps prevent or cure infectious diseases from spreading. It has been hailed to use resources effectively because it is only those primarily affected who are vaccinated. This is followed with closed surveillance of the infected people. It is worth noting that ring vaccination is best suited for dealing with a localized smallpox infection. On the other hand, herd immunity is used to describe a situation in which a given group of people are resistant to a certain pathogen as a result of larger proportion of the population being immune to the pathogen in question. The theory holds that in cases where mankind is faced with contagious diseases, the paths or chains of infection is most likely interfered with when majority of the population are immune or less vulnerable to such kind of diseases. Thus if the number of resistant individuals within a population exists then there is a smaller chance that high risk individuals will come in contact with infected persons (John & Samuel, 2000). Thus the two concepts are distinct but offer the same desired outcome of saving mankind from contracting infectious diseases. Finally people who have been directly exposed to the smallpox virus should indeed get the vaccine, regardless of their health status (Preson, 2002).

References

Enserink, M. (2004). Smallpox Vaccine: Looking beyond the next generation. Science Scope, 304(2): 1.

John, T. & Samuel, R. (2000). Herd immunity and herd effect: new insights and definitions, Eur. J. Epidemiol, 16 (7): 601606.

Preson, R. (2002). The demon in the freezer. New York: Random House.

Taub, D., et al (2008). Immunity from smallpox vaccine persists for decades: A longitudinal study. Am J Med. 2008 December, 121(12): 10581064.

Explaining the Sample

The case study titled Social Work Research: Program Evaluation focused on assisting low-income families. Plummer et al. (2014) mention that analyzing case studies is efficient in developing skills and expertise in social work, and this discussion is used to improve competency in sampling techniques. The program evaluation study sample includes approximately 22,000 families from a large county in the San Francisco Bay Area. The participants were then broken into three groups based on the service that they received. Consequently, 10,000 individuals participated in education and training programs, 9,000 people attended job placement classes, and 3,000 individuals accepted reduced benefits. To ensure generalizability, researchers tried to address the size and representativeness of their sample. Yegidis et al. (2018) explain that representativeness means that the sample is similar to the population. Thus, the study results can be generalizable because the selection consists of a sufficient number of individuals who share features with the population. It is so because the sample includes the representatives of a single county.

Response

In her discussion, Stephanie states that focusing on many participants and using random sampling are researchers steps to generalize the findings. However, it is possible to offer two alternative ways to cope with the task. On the one hand, Yegidis et al. (2018) admit that researchers can calculate the samples statistics to identify the parameters of the population. On the other hand, it could be possible to ensure generalizability by limiting the sampling bias. The program evaluation study mentioned that it predominantly focused on single mothers. It denotes that it could be more useful to avoid this groups overrepresentation in the sample (Yegidis et al., 2018). These steps seem sufficient to ensure the study results generalizability.

References

Plummer, S.-B., Makris, S., & Brocksen, S. M. (Eds.). (2014). Social work case studies: Foundation year. Laureate International Universities Publishing.

Yegidis, B. L., Weinbach, R. W., & Myers, L. L. (2018). Research methods for social workers (8^th ed.). Pearson.

Introduction

Case-control studies and cohort studies are both categories of observational studies and are the most important types of study designs that can serve either similar or different purposes. If designed effectively, observational studies are able to provide results that are similar to the results achieved in randomized controlled trials, putting forward a view that observational studies are not as effective. Both case-control studies and cohort studies are effective in evaluating the connections that exist between a condition and exposure (Song & Chung, 2011).

When it comes to dental practice, cohort studies are commonly used for studying a risk factor of a particular event. For example, researchers can study a risk factor of exposure to sugary drinks and chocolate as well as the subsequent appearance of caries signs. Contrary to the cohort study design, case-control studies explore a particular disease or a condition to find out whether some risk factors can be associated with it. In cohort studies, the end condition is not predetermined while in case-control studies the outcome is already known. Despite that cohort studies can be conducted retrospectively, the majority of them are conducted prospectively so that the slightest changes can be examined within a course of a particular time period. Case-control studies can be conducted in retrospect because the outcome is already known, so there is no need for studying the changes that occurred over a set period of time.

Cohort Studies

Cohort studies relate to a group of people who have been followed by researchers for a long period of time. In the process of conducting a cohort study on any health topic, the study population or outcomes are identified with the use of exposure to a particular event than is then followed for a set period of time for the identified outcome to occur. Because the exposure to an event is already predetermined before the appearance of an outcome, cohort studies are observational studies that are limited to a particular period of time, and therefore, are able to provide strong evidence to support or disprove the initial hypothesis.

For example, a cohort study design was used by Arora, Scott, Bhole, Do, Schwarz, and Blinkhorn (2011) for finding connections between early childhood feeding practices and the development of dental caries in preschool children. Mothers were invited to participate in the study after giving birth to a child (Arora et al., 2011). Data on the feeding practices implemented by mothers, alongside the information on dental practices was gathered through telephone interviews every 4 months since birth. At 2 and 5 years old, children went through a dental assessment to determine the main outcome measures (Arora et al., 2011). Therefore, cohort studies are best implemented when the outcome is identified in accordance with the subjects being exposed to a particular event. Subjects with already identified outcomes are not included in cohort studies because the aim is to conduct examinations and following-up to find connections between the possible outcome and the exposure to an event. In the discussed study, the dental behavior and early childhood feeding practices were associated with dental caries in preschool children; Arora et al. (2011) used the cohort study design so that subjects conditions could be assessed for a long period of time.

Case-Control Studies

Case-control studies are observational studies in which subjects are identified by the status of the outcome as well as the investigations outside. For example, outcomes may include whether study subjects had gone through surgery or were diagnosed with a particular disease. With the identification of the outcome status, the subjects of the study were put into different categories for selecting the subjects with no signs of the identified outcome but those that came from the same population. The process of data collection occurs through interviews, surveys, or records abstractions. In comparison with a cohort study design, case-control studies are effective for investigating unusual and unique outcomes or outcomes that have a long period of latency.

Case-control studies can be effectively used in dentistry because they are quick and inexpensive for implementation, especially when it comes to studies of unique conditions that have not been previously studied. Furthermore, case-control studies are suitable for studying rare dental conditions and diseases that have been selected for assessment and research. For example, a study conducted by Memon, Godward, Williams, Siddique, and Al-Saleh (2010) investigated the usage of dental x-rays and the risk of thyroid cancer. The case-control study design was suitable for investigating the topic of dental x-rays and their effect on the development of thyroid cancer due to the uniqueness of the issue. Additionally, case-control studies were helpful for conducting a conditional logistic regression analysis as well as the population-based case-control interviews among thyroid cancer patients. Therefore, case-control studies can be effectively implemented when subjects of studies have already been identified according to a particular outcome.

References

Arora, A., Scott, J., Bhole, S., Do, L., & Blinkhorn, A. (2011). Early childhood feeding practices and dental caries in preschool children: A multi-center birth cohort study. BMC Public Health, 12, 11-28. 

Memon, A., Godward, S., Williams, D., Siddique, I., & Al-Saleh, K. (2010). Dental x-rays and the risk of thyroid cancer: A case-control study. Acta Oncologica, 49(4), 447-453. 

Song, J., & Chung, K. (2011). Observational studies: Cohort and case-control studies. Plastic and Reconstructive Surgery, 126(6), 2234-2242. 

Introduction

Chlorine is element number 17 and is found in group 17 and period 3 of the periodic table. It is a greenish-yellow pungent, poisonous gas, and is very reactive. it has two isotopes; one with a mass number of 35 and an abundance of 75.75% and the other one with a mass number of 37 and an abundance of 24.23% giving it an atomic weight of 35.4527 g/mol. Chlorine is found in a combined state in common salt(NaCl).

Chlorine is used in the purification of water, bleaching of papers, as a disinfectant, in paints, medicine, solvent, the killing of bacteria and microbes from drinking water and in mustard gas, among others (Chlorine, 2007, p. 6-10). Chlorine exposure in the body causes short-term and long-term chronic health effects. These effects are discussed in this paper. I will support my thesis with compelling arguments by supplying information and examples with proof and evidence on the short-term and long-term chronic health effects that result when a body is exposed to chlorine. Additionally, I will define the difference between exposures from chlorinated drinking water and chlorinated swimming pools. Moreover, I Will also provide counterarguments to show whether chlorine alone is hazardous or a mixture of it and other chemicals.

Short-term and long-term chronic health effects of chlorine exposure in the human body

Exposure of the body to chlorine causes irritation of the nose, eyes, throat and respiratory tract. This leads to tickling of the nose and coughing, eyes becoming red and watery and dryness of the throat. It may also hinder the development of foetus and thus make pregnant women deliver premature children (Nieuwenhuijsen, 2004, p.18). According to WebMD,(2004,para.7), exposure to chlorine causes breathing difficulties , headache, chest pain, dypsnea, vomiting and when it comes into contact with the skin it causes frostbite and may burn and irritate the skin. Additionally, it has also been found to cause airflow obstruction, asthma, hay fever and lung dysfunction of reactive airways (Rushall, 2010, para.6). Cancer of the bladder, heart disease, anaemia and High Blood Pressure may also result from exposure to chlorine (Newsletter, 2008). However, some of these health effects are caused by exposure to a mixture of chlorine and other chemicals as will be discussed later.

Sources of exposure to chlorine

People may be exposed to chlorine either through accidental spill or release, inhalation, eye or skin contact or ingestion of chlorine that is either dissolved in water or food (Thomson, 2002, para.7).

Differences between exposure from chlorinated drinking water and chlorinated swimming pools

Chlorine is added to drinking water so as to kill most of micro organisms such as bacteria and viruses that may be present in water. People become exposed to chlorine when they drink such water that have a high percentage of chlorine and may get some health problems discussed above. On the other hand, chlorine is added to swimming pools so as to kill harmful micro organisms that may be present in the pool. It has been found that exposure to chlorinated swimming pools can cause asthma whose symptoms are bluish colour, nausea, difficulty breathing, high blood pressure and lung collapse among others (New York Times Company,2010).Exposure may also cause hay fever to those people who swim frequently on these pools. However, chlorine alone is not a problem in these exposures.

Counter Argument on whether Chlorine alone is hazardous or a mixture of chemicals and Chlorine

Some of the short- term long- term health effects are caused by exposure to chlorine alone while others are caused by exposure to a mixture of other chemicals and Chlorine. For instance, irritation of the eye, nose and throat may be caused by exposure to chlorine alone while asthma and hay fever which are as a result of exposure to chlorinated swimming pool are caused by exposure to a mixture of other chemicals and chlorine (Goebell, 2004, p.425). For example, Chlorine combines with other substance present in water forming harmful carcinogenic chemicals such as trihalomethanes chlorinated acetic acid.

Conclusion

Chlorine is one of the elements of periodic table and has many uses such as acting as disinfectant and bleaching agents, among others. However exposure to it through inhalation, chlorinated swimming pools, chlorinated drinking water may lead to short term and long term health effects. But some of the health effects are not caused by exposure to chlorine alone but to a mixture of chlorine and other chemicals.

References

Chlorine. (2007).In Saunders comprehensive veterinary Dictionary. Web.

Goebell, PJ. (2004).Environmental Exposure, chlorinated drinking water and Bladder cancer. World journal of urology, 21(6).

Newsletter. (2008). Chlorine is very dangerous for your health. Web.

New York Times Company. (2010).About.com, Chlorinated swimming pools can Cause Asthma in swimmers. Web.

Nieuwenhuijsen, M. (2004).Scientist qualifies swimming pool chlorine risk to Pregnant womens health. Science journal. Web.

Rushall, B. (2010).Chlorine Toxicity: A matter that should be of Concern to all swimmers, coaches, and parents. Swimming Science Journal. Web.

Thomson. (2002).Chlorine in: Sifton DW(Ed), Physicians Desks Reference Guide To Biological and Chemical Warfare Responses, (1st Ed.). Montvale, NJ: Web

MD. (2004).Chlorine in pools may cause Breathing Troubles. Web.

Gas chromatography (GC) is a technique used to separate, identify and quantify analytes in a mixture. A gas chromatograph consists of an injector, column (packed or capillary), oven, and detector. The main manufacturers of gas chromatographs supply the following types of detectors: micro-electron capture detector (micro-ECD), flame ionization detector (FID), flame photometric detector) (FPD), mass selective detector (MSD), nitrogen chemiluminescence detector (NCD), nitrogen-phosphorus detector (NPD), sulfur chemiluminescence detector (SCD). When the gas chromatograph is coupled to a mass selective detector, the system is known as GC-MS. GC-MS is widely used in modern laboratories for research and analytical purposes. Manufactures provide sophisticated MS detectors equipped with triple quadrupole systems that can detect compounds at femtogram levels. However, this type of GC-MS apparatus is very expensive. A femtogram level sensitivity is not essential for all types of analyses, and researchers and analysts can thus use GC-MS systems that are equipped with single quadrupoles or ion traps that are cheaper and give nano to picogram sensitivity.

Sample preparation

A sample is very rarely directly injected into a GC-MS system. An aliquot of the sample is extracted with organic solvents such as methanol, hexane, dichloromethane and ethyl acetate. Solid samples are usually ground to ensure that analytes are quantitatively extracted. Thorough mixing is essential for heterogeneous samples. The extract is dried over anhydrous sodium or magnesium sulfate, and the solvent evaporates on a rotary evaporator. In case there are interfering compounds, the extract is redissolved in a small amount of solvent for subsequent clean-up (silica gel, florisil or other cartridges are normally used). The residue is dissolved in an appropriate solvent and transferred into a vial for GC-MS analysis. For quantitative analysis, loss of extract should be avoided at all stages of the sample preparation and the volume of the reconstituted sample should be properly noted. The reconstituted sample must be properly sealed in vials, and exposure to bright light and temperatures must be avoided. Reconstituted samples are normally stored in a refrigerator when GC-MS analysis cannot be done immediately.

Mode of operation of a GC-MS instrument (Kemp, 1991; University of Colorado, 2011)

The sample is manually or automatically loaded on the injector that is kept at a fairly high temperature. The analytes vaporize at a high temperature and enter a heated capillary or packed column. In the column, there are non-covalent interactions between the analytes and column materials. A carrier gas such as helium carries the analytes through the column. In principle, separation of compounds takes. The volatility and polarity of compounds, column temperature, column packing polarity, a flow rate of gas, length of the column all affect the separation of compounds and their retention times, (RT, the time it takes for an analyte to travel from the injection port to the detector. Volatile components travel faster through columns, that is, they have shorter retention times. Polar column retain polar compounds, while non-polar compounds retain bon-polar ones. Compounds that have similar physical and chemical properties do not separate very well, hence a proper temperature programming is required to separate them. Sometimes longer columns are used to separate compounds in complex mixtures. Compounds that co-elute do not give clean spectra. Once separated, the compounds enter the mass spectrometer in the gaseous phase. When the compounds enter the ionisation chamber, they are bombarded by electrons (electron ionization, it is more frequently used because it gives more structural details) or charged ions (chemical ionisation). At this stage, molecular ions, also known as parent ions, are produced. However, due to the high energy content of the molecular ions, a fragmentation occurs, and smaller ions (daughter ions) are produced. The parent and daughter ions consecutively pass through electrostatic and magnetic analysers. The electrostatic analyser separates the positively and negatively charged ions, whereas the magnetic analyser separate the ions based on their m/z values. The resolution of the ions is greatly dependent on the technical features of these analysers. At the final stage, the ions reach the detector-recorder that measures the intensities of the ions. For every compound that passes through a mass spectrometer, a chart of relative abundance versus m/z is plotted. This chart is known as a mass spectrum and is unique to a particular compound. Ions that have elements such as chlorine give two peaks for every fragment due to the presence of two stable isotopes. Ions that contain a large number of carbon atoms clearly show signals corresponding to carbon-12 and carbon-13 isotopes. For small fragments, the signals corresponding to carbon-13 are not clearly visible. Stereoisomers and diastereomers give similar MS spectra, and caution must exercised in terms of assignment of configuration. An analyst must use other techniques to confirm the configuration of stereoisomers and diastereomers.

Analysis of difenoconazole and lambda-cyhalothrin by GC-MS

Various pesticides are used to control weeds, insects and fungi in plants, fruits and vegetables. However, when pesticides are used excessively and incorrectly, there is a danger of getting an accumulation of these chemicals in plant materials and higher up in the food chain, which in turn constitutes of a health hazard. A proper monitoring is hence required to control the quality of food products. The quality monitoring process has to be systematic and unbiased, and involves quantitative extraction of the pesticides, cleaning and analysis by GC, GC-MS, high performance liquid chromatography (HPLC), HPLC-MS and (ultraviolet) UV spectrophotometry (The Royal Society of Chemistry, 1991; Alder, Greulich, Kemper, G and Viett, 2006).

Many research and analytical laboratories use the GC-MS technique to screen pesticide residues in food products. Difenoconazole (C₁₉H₁₇Cl₂N₃O₃, MW of 406.30) and lambda-cyhalothrin (C₂₃H₁₉ClF₃NO₃, MW of 449.8) are two such pesticides that can be analysed by GC-MS. In two published reports (Siecke, 2011; Whitney and Lyle, 2011), these two compounds were extracted from fruits and vegetables by organic solvents and analysed by GC-MS. They were both detected at concentrations that were below ppm levels. The extraction and analytical procedures maintained the integrity of the products, and the GC-MS technique was found to be appropriate. The GC-MS technique can be also used to analyse natural organic compounds that have been extracted from plants, fruits, vegetables, and marine and other biological samples.

Advantages and disadvantages of a GC-MS technique

Difenoconazole and lambda-cyhalothrin can be also analysed by other techniques such high performance liquid chromatography, HPLC-MS and UV spectroscopy. However, high performance liquid chromatography and UV spectroscopy cannot confirm the identity of a compound. Moreover, solvents are not required to run a GC-MS apparatus, that is, a minimum amount of waste is generated, and the negative impact on the environment and analyst is minimized.

The disadvantage of GC-MS instrument over high performance liquid chromatography and UV systems is that it is more expensive.

References

Alder, L., Greulich, K., Kemper, G and Viett, B., 2006. Residue analysis of 500 high priority pesticides: better by GC-MS or LC-MS/MS? Mass Spectrometry Reviews, 25, pp. 838-865.

Kemp, W., 1991. Organic Spectroscopy. 3^rd ed. Hong Kong: The Macmillan Press Ltd.Siecke,C., 2011. Lambda-cyhalothrin (146).

The Royal Society of Chemistry, 1991. The Agrochemicals Handbook. 3^rd ed. Cambridge. The Royal Society of Chemistry.

University of Colorado, 2011. Gas Chromatography. Web.

Whitney, W. and Lyle C. R., 2011. Rapid Multiresidue Pesticides Analysis Using Fast-GC/MS and Chromatogram Deconvolution Software. Web.