Separation of Lymphocytes, Polymorphonuclear Leukocytes and Monocytes on Glass Columns, Including Tissue Culture Observations

A procedure was described for the separation of lymphocytes, polymorphonuclear (PMN) leukocytes and monocytes on Garvin’s glass bead columns. Dextran-sedimented leukocyte suspensions were added to columnsand incubated at 37 C. Lymphocytes were eluted with fresh serum. Thecolumns were then washed completely free of erythrocytes, platelets andlymphocytes while PMN leukocytes and monocytes continued to adhere. PMNleukocytes and monocytes were released from the glass with EDTA. Monocytes appeared in the effluents somewhat later than the PMN leukocytes,permitting a separation.

A fresh serum, heat labile, Ca^{+ +}- and Mg^{+ +}-requiring PMN leukocyte and monocyte adherence promoting factor was demonstrated andfound to be essential to the procedure.

The viability of column-separated cells was shown by their non-stainingwith trypan blue, motility, phagocytic ability, oxygen consumption, andsurvival or development in tissue culture.

In tissue culture, macrophages developed only from monocytes, whereasNowell’s blast-like, dividing, phytohemagglutinin cells were produced onlyin cultures containing lymphocytes.

Submitted on October 3, 1963 Accepted on December 12, 1963     

The modified essay question: effect of author location on student performance

The Department of Family Medicine at Jefferson Medical College, Philadelphia has utilized the modified essay question (MEQ) as an evaluative instrument in its required third-year clerkship since 1976. Previous analysis had indicated that students who participated in their clerkship at the university family practice centre (FPC) consistently performed at a higher level on their MEQ examinations than students who participated in clerkship activities at affiliated FPCs. In order to test the hypothesis that university-taught students had higher final examination scores because university teachers developed and graded the examinations, MEQs were developed by affiliate teachers and used for one half of five final examinations during the 1982-83 academic year. Students at the university-trained site continued to perform better than affiliated-trained students, even on MEQs developed by their own teachers. These results, as well as the significant administrative time involved in the project, have caused the Department of Family Medicine to revert to its previous policy of university teachers being responsible for the final examination.     

Effect of Phytohemagglutinin on Enzymes of Thymidine Salvage Pathway of Cultured Chronic Lymphatic Leukemic Lymphocytes

N-L and CLL-L prior to cell culture gave evidence of high activities ofTdR phosphorylase, TMP and TDP kinases, while TdR kinase and phosphataseactivities were relatively low. Cells cultured without PHA showed no appreciable alteration in enzyme activities during three to five days of culture.Response to PHA with blast-cell formation in cultures of N-L or CLL-L (low-count cases) was associated with increased TdR kinase activity which becameprominent at the time of increased DNA polymerase activity and DNA synthesis during the second to third day of culture. Cells from cases of CLL-Lwith high WBC counts which failed to respond to PHA showed no increasein TdR kinase activity but did show increased phosphatase activity. IncreasedTdR activity and increased DNA polymerase activity may both be neededfor increased synthesis of DNA to occur in lymphocytes responding to PHA.

Submitted on July 14, 1969 Accepted on September 8, 1969     

DNA Polymerase and Carbohydrate Metabolizing Enzyme Content of Normal and Leukemic Glass Column Separated Leukocytes

1. Enzymes of normal and leukemic glass column separated leukocytes wereassayed with fluorometric (glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, lactic dehydrogenase, glyceraldehyde-3-phosphatedehydrogenase and isocitric dehydrogenase) and radioisotope (DNA polymerase) micromethods.

2. Most results were obtained by direct assay of the specific cell type. Somerequired simple calculation. It was demonstrated that the enzyme activityof mixed cell suspensions was the sum of the enzyme content of the componentcells, at least for the enzymes studied.

3. Assays of mixed cell suspensions may give an erroneous picture. Thuschanges in differential cell counts, as well as alterations in enzyme content ofindividual cells, must be taken into account for correct interpretation.

4. Changes in enzyme content of mixed cell suspensions after therapy weredue chiefly to alterations in the differential cell count rather than to changesin the enzyme content of individual cell types.

5. The patterns of assays of the carbohydrate metabolizing enzymes studied,except isocitric dehydrogenase, paralleled each other. Highest values werefound in mature PMN leukocytes and lowest in blasts. With isocitric dehydrogenase absolute values were much lower, while the highest assays werefound in myelocytes.

6. DNA polymerase content correlated well with the ability of a cell todivide. It was highest in blasts and lowest in mature PMN leukocytes.

Submitted on May 27, 1965 Accepted on August 6, 1965     

A solution to the cueing effects of multiple choice questions: the Un-Q format

Summary. Although the cueing effects inherent in conventional multiple choice questions (MCQs) present serious limitations, this format continues to dominate testing programmes. The present study was undertaken to estimate the effects of cueing when MCQs are used to test medical students, and to evaluate the reliability, validity and feasibility of an alternative testing format. Equivalent items in both MCQ and open-ended, or uncued (Un-Q), formats were administered to 34 third- and fourth-year medical students. The students' mean % correct score on the MCQs was 11 percentage points higher than their mean level of performance on equivalent Un-Qs. When a second set of more difficult items was administered to 16 of these students, their mean performance on the MCQ items was 22 percentage points higher than their performance on equivalent Un-Qs. The results support the feasibility of large group administration of tests constructed in an open-ended format that can be scored by computer. Not only is this format equally reliable and economical when compared with the MCQ, but it also provides important advantages that strengthen its face validity. The Un-Q format can be used to test either simple recall or certain higher level problem-solving skills that cannot be tested by MCQs. Even more important, the results also suggest that the Un-Q format may be a more effective discriminator of academically marginal examinees.