A microbiologist was studying the bacterium, Francisella tularensis, which can i

Question

A microbiologist was studying the bacterium, Francisella tularensis, which can infect human neutrophils (PMNs) and cause the serious disease, tularemia. To study the growth of F tularensis, PMN's are prepared from fresh samples of blood donated by healthy human volunteers. donates blood isolate neutrophil remove samples for experiments healthy volunteer 2 x 107 neutrophils/ml For an assay one day, a volunteer's blood donation yielded a 2.3-mL volume of purified PMN's at 2 x 10? PMNs per mL. Then, an experiment was set up consisting of 4 tubes of PMN's to which F. tularensis was added and 4 tubes with control (uninfected) PMNs. In each tube were 4 x 10° PMNs. After this experiment had been completely set up and all tubes ("control" and "infected") had received PMN's, some volume of isolated neutrophils remained unused. In the box, type the volume (in mL) that was left over from the 2.3-mL neutrophil preparation.

Explanation / Answer

Ans. Total tubes used in experiment = 4 (test) + 4 (control) = 8

PMNs content in each tube = 4.0 x 106

Total PMNs in all tubes = 8 tubes x (4.0 x 106 PMN/ tube) = 3.20 x 107 PMNs.

# Given, [PMN] in fresh blood = 2 x 107 PMN / mL

Now,

            Volume of blood used in experiment = PMN used / [PMB] in blood

                                                            = (3.20 x 107 PMNs) / (2.0 x 107 PMN/ mL)

                                                            = 1.60 mL

# Now,

Remaining (leftover) vol. of blood =

Vol. of fresh blood collected – Vol. used in experiment

                                                = 2.30 mL – 1.60 mL

                                                = 0.70 mL

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