ARTICLE FOR THIS ASSIGNMENT CAN BE FOUND AT: http://www.sciencedirect.com/scienc

Question

ARTICLE FOR THIS ASSIGNMENT CAN BE FOUND AT: http://www.sciencedirect.com/science/article/pii/S0092867400810715

1. What is “primary scientific literature”? What is a “scientific journal”?

2. What is a principal investigator? Who is the principal investigator on this article?

3. Define Apicomplexan. How do Apicomplexans move?     

4. What are cytochalasins (CDs) and what do they do? What does the paper mean by “cytochalasin-resistant host cells”? USE YOUR OWN WORDS TO EXPLAIN.

5. How did the authors determine that the Toxoplasma had infected the host cells? USE YOUR OWN WORDS TO EXPLAIN.

6. Why did the authors use Salmonella too? How did the authors determine if Salmonella had entered the cell? USE YOUR OWN WORDS TO EXPLAIN.

7. Describe all of Figure 1A in your own words. (Make sure that you explain what Cyt-1 and KB are and also explain what the x-axis and y-axis are.) What does the result indicate? USE YOUR OWN WORDS TO EXPLAIN.

8. Why did the authors create CD-resistant mutants of Toxoplasma? What happened when these mutants were treated with CD? What did these results indicate? USE YOUR OWN WORDS TO EXPLAIN.

9. Explain Figure 5. What are the authors showing us in these pictures? What does this data indicate? USE YOUR OWN WORDS TO EXPLAIN.

10. How can this paper’s information be used for something useful? (In other words, why did this information get published in a very prestigious journal?)

Explanation / Answer

1) Ans: Science Direct is primary scientific literature and Cell is scientific journal.

2) Ans: Janice M. Dobrowolski is principal investigator on this article and as PI who conduct research in the research centre.

3.)Ans: Apicomplexan and its movement :

         Apicomplexans are a monophyletic group composed entirely of parasitic species .Apicomplexans have no specialized locomotor organelles (except for the flagellated microgamete) yet they are capable of gliding movements.

4)Ans: Cytochalasins are fungal metabolites that disrupt cell motility and cytokinesis in vertebrate cells by destabilizing actin filaments. when Toxoplasma gondii invades into cytochalasins -resistant host cells which was blocked by CD and CD resistance in T.gondii is mediated by a point mutation in the single-copy actin gene ACT1.

5) Because the transfection of mutant act1 allele into wild-type Toxoplasma conferred motility and invasion in the presence of CD.so the author confirmed that Toxoplasma had infected the host cells.

6.) because the examination of host cell internalization of Salmonella typhimurium in the absence or presence of CD and also the confirmed that Salmonella uptake was monitored by protection from gentamicin, which effectively kills only extracellular bacteria.

7.) Invasion of Toxoplasma into both wild-type KB and mutant Cyt-1 cells was significantly inhibited by CD.The inhibition of parasite invasion into Cyt 1 cells, which are resistant to the effects of cytochalasin,the result indicates that the action of CD is primarily on the parsite.

8.) because it can be easily obtained mutant of toxoplasma that were resistant to CD (CydR).Toxoplasma CydR mutants were isolated following chemical mutagenesis using ethyl nitrosourea (ENU) and selecting for growth on HF monolayers in the presand selecting for growth on HF monolayers in the presence
of 0.1 mM CD. This results indicate that the ability of CydR mutants to invade wild-type host cells in the presence of CD demonstrates that an actin-based contractile system in the parasite plays an essential role in host cell invasion.

9)The Mutant act1 Allele Confers a dominant Phenotype for gliding motility in the Presence of CD which affects the  gliding of wild-type (RH strain) and act1 transformants of Toxoplasma on serum-coated glass was detected by immunofluorescent staining of trails containing the surface protein SAG1.

10.) This research paper clears that the process of active penetration that is dependent on the actin-based cytoskeleton of the parasite. The active penetration of the host cell by Toxoplasma represents a novel process of entry distinct from that used by intracellular bacterial pathogens that take advantage of host-mediated endocytic/phagocytic processes for entry.the gliding motility and cell invasion on parasite cytoskeletal system may provide novel target to prevent infection .

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