Expression of the three influenza virus polymerase proteins in a single cell allows growth complementation of viral mutants

Transformed cell lines derived from murine C127 cells were constructed that express the influenza virus RNA-dependent RNA polymerase proteins (PA, PB1, and PB2). Cell lines that express only one or all three of the proteins were tested for their ability to complement temperature-sensitive viral mutants incubated at the nonpermissive temperature. Two cell lines were isolated that express all three polymerase genes and complement the growth of PB2 temperature-sensitive mutants at the nonpermissive temperature. One of these lines also complemented PA temperature-sensitive mutants. The viral titers obtained in these two cell lines were 12-fold to 1000-fold higher than the viral titers obtained upon growth of the corresponding temperature-sensitive mutant in C127 cells at the nonpermissive temperature.

Comparison of the inhibition of Escherichia coli and Lactobacillus casei dihydrofolate reductase by 2,4-diamino-5-(substituted-benzyl)pyrimidines: quantitative structure-activity relationships, X-ray crystallography, and computer graphics in structure-activity analysis

The inhibition constants (Kiapp) obtained from the action of 44 2,4-diamino-5-(substituted-benzyl)pyrimidines on dihydrofolate reductase (DHFR) from Escherichia coli and Lactobacillus casei bacteria are used to derive quantitative structure-activity relationships (QSAR). These equations bring out a number of differences in the DHFR which can be understood at the atomic level by studying color stereo computer graphics models constructed from the X-ray coordinates of the enzyme-inhibitor complexes. The combination of QSAR and X-ray crystallography interpreted via high-performance computer graphics offers a new level of sophistication to extend our understanding of enzyme-ligand interactions, which, when the crystallography is known, opens up a more scientific approach to drug development.

Inhibition by 5-(substituted-benzyl)-2,4-diaminopyrimidines of murine tumor (L5178Y) cell cultures sensitive to and resistant to methotrexate. Further evidence for the sensitivity of resistant cells to hydrophobic drugs

Forty-three 5-(substituted-benzyl)-2,4-diaminopyrimidines have been studied as inhibitors of murine tumor cell cultures (L5178Y). Two types of cells were used--one resistant to methotrexate and one sensitive to methotrexate. The formulation of quantitative structure--activity relationships showed that the methotrexate-resistant cells are more sensitive to the more hydrophobic congeners. pi 0 for the sensitive cells is about 1.4, while pi 0 for the methotrexate-resistant cells is above 3. These results are similar to those found for 2,4-diaminotriazines (Selassie, C.D.; Guo, Z. R.; Hansch, C.; Khwaja, T. A.; Pentecost, S. J. Med. Chem. 1982, 25, 157).

A comparison of the inhibitory action of 5-(substituted-benzyl)-2,4-diaminopyrimidines on dihydrofolate reductase from chicken liver with that from bovine liver

Forty-four 5-(substituted-benzyl)-2,4-diaminopyrimidines have been tested as inhibitors of chicken and bovine liver dihydrofolate reductase. The chicken enzyme is, on the average, about 10 times less easily inhibited than bovine enzyme. Substituents which show the greatest selectivity are 4-NHCOCH3, 3-OC4H9, 3-I, 3-CF3-4-OCH3, and 3,4,5-(OCH3)3. The inhibition constants have been used to formulate quantitative structure-activity relationships for comparative purposes.

Ureteral injuries during vascular surgery

The rapid increase in the number of vascular surgical procedures done has led to a new class of iatrogenic ureteral injuries. Vena caval ligation, bilateral lumbar sympathectomy, bypass procedures and abdominal aortic aneurysmectomy produce the majority of these injuries. Established principles useful in the repair of iatrogenic injuries following a gynecologic or colonic operation often are inapplicable.

Sensitivity and specificity of early diagnostic tests of lung function in smokers

What are the relative sensitivities and specificities of the "early" tests of lung dysfunction? We describe the findings from a study of virtually the entire population of a rural pollution-free community. Using abnormal spirometry as a marker of obstructive disease, we evaluated the two tests obtained from the single-breath nitrogen curve, closing volume (CV/VC) and the slope of the alveolar plateau (delta N2/L), as well as combinations of the two tests. While CV/VC is highly specific (92.3 percent in male and 94.0 percent in female subjects), it lacks sensitivity (36.8 percent in male and 13.3 percent in female subjects) and is abnormal in only 10.0 and 6.5 percent of male and female smokers, respectively, a percentage not dissimilar from the percentage with abnormal spirometry. However, delta N2/L, abnormal in 24.1 percent of male smokers and 28.8 percent of female smokers, rates reasonably well with regard to both sensitivity (63.2 percent in male and 66.7 percent in female subjects) and specificity (79.3 percent in male and 74.0 percent in female subjects). The group of smokers with abnormal delta N2/L did include fair numbers with abnormal spirometry (20.7 percent in male and 16.1 percent in female subjects). A combination of the two tests (abnormal in either delta N2/L and/or CV/VC) has good sensitivity (68.4 and 80.0 percent for male and female subjects, respectively) and specificity (74.3 and 69.0 percent for male and female subjects, respectively).