Evaluation of azlocillin-amikacin combination for empirical therapy of infection in febrile neutropenic patients.

We have evaluated the azlocillin-amikacin combination, given at a daily dose of 200 mg/kg and 15 mg/kg respectively, in the treatment of 62 consecutive febrile granulocytopenic patients (less than 500 PMN/microliters) affected by hematological disease. The effectiveness of the treatment was assessed in 60 patients, 44 (73%) of whom responded within 96 hours from the beginning. 36 of the responders showed microbiological and clinical infections, 2 had clinically documented pneumonia and 6 a possible infection. No improvement was obtained in 16 patients; 7 of whom suffered from clinical and microbiological infection, 2 from pulmonary mycosis, 4 from possible infection and 3 from doubtful infection. Seven of these patients subsequently responded to a proven antibiotic treatment, while only one of the remaining responded to a second-line empirical antibiotic schedule. These results suggest that the combination of azlocillin-amikacin was able to overcome about two-thirds of the infections, representing an effective remedy for the empiric treatment of febrile neutropenic patients.

Degradation of thialysine- or selenalysine-containing abnormal proteins in E. coli.

Thialysine and selenalysine can be utilized for protein synthesis by lysine-requiring E. coli cells even in the absence of lysine. Protein synthesis has been determined as labeled leucine incorporation into acid-insoluble material, as increase of cell proteins and as protein-lysine substitution by the analog. Either analog can be incorporated into proteins, in the absence of lysine, for a limited time interval after which cells stop to duplicate. Proteins synthesized during this period contain most of their lysine residues substituted by the analog. Moreover, it has been shown that the analog-containing proteins are unstable and rapidly degraded. Their instability would account for the inability of lysine-requiring E. coli cells to utilize the analog as growth factor.

Studies on recognition of selenahomolysine by aminoacid transport systems and aminocyl-tRNA synthetase.

In E. coli, Se-3 aminopropylselenocysteine or selenahomolysine (SeHL) does not affect intracellular lysine transport, i.e. it cannot bind E. coli lysine transport systems. In CHO cells it inhibits cationic aminoacid transport system, but only in the presence of Na+, this indicating that it behaves like polar neutral aminoacids. On the other hand, it poorly affects leucine transport both in the presence and in the absence of Na+. SeHL is not activated by aminoacyl-tRNA synthetase preparations from bacterial and mammalian sources, thus it cannot be utilized for protein synthesis.

Thialysine- and selenalysine-resistance in a E. coli mutant.

A thialysine-resistant mutant of E. coli strain KL16 also shows a lower sensitivity to selenalysine, the lysine analog containing selenium. No difference between the mutant and the parental strain has been shown regarding the affinities of the transport systems and the lysyl-tRNA synthetase for selenalysine, thialysine and lysine as well as the inhibitory effects of these three aminoacids on the activity of the lysine biosynthetic pathway. A marked difference between the two strains has been evidenced in the AK III repression: in the mutant the repression by selenalysine, thialysine and lysine is much lower than in the parental strain.

Utilization of lysine analogs by a lysine-requiring E. coli mutant.

Thialysine and selenalysine cannot substitute lysine as a growth factor for a lysine-requiring E. coli mutant, but can nevertheless be utilized for protein synthesis in the presence of lysine. In order to have information about the effects of lysine on the utilization of the two analogs, the extent of the incorporation of the three aminoacids into newly synthesized proteins has been determined. The analog starts to be utilized by cells growing in a medium containing either analog and lysine when lysine concentration becomes very low. Of the two analogs, thialysine is more easily utilized. In fact thialysine can be utilized when the lysine/thialysine ratio in the medium is 1/25. Selenalysine starts to be utilized when the lysine/selenalysine ratio is 1/200.

Biochemical characterization of a thialysine-resistant clone of CHO cells.

The intracellular transport and the activation of lysine, thialysine and selenalysine have been investigated in a thialysine-resistant CHO cell mutant strain in comparison with the parental strain. The cationic amino acid transport system responsible for the transport of these 3 amino acids shows no differences between the 2 strains as regards its affinity for each of these amino acids. On the other hand the Vmax of the transport system in the mutant is about double that in the parental strain. The lysyl-tRNA synthetase, assayed both as ATP = PPi exchange reaction and lysyl-tRNA synthesis, shows a lower affinity for thialysine and selenalysine than for lysine in both strains; in the mutant, however, the difference is even greater. Thus the thialysine resistance of the mutant is mainly due to the properties of its lysyl-tRNA synthetase, which shows a greater difference of the affinities for lysine and thialysine with respect to the parental strain.

Degradation of thialysine- or selenalysine-containing abnormal proteins in CHO cells.

CHO cells can incorporate thialysine and selenalysine in their proteins in substitution of lysine. Data are reported in the present paper showing that proteins containing either thialysine or selenalysine are unstable and quite rapidly degraded. The degradation rate is strictly related to the extent of protein lysine substitution. At similar extent of substitution, selenalysine-containing proteins are more unstable that thialysine-containing ones.

Thialysine and selenalysine incorporation into CHO cell proteins and its effects on cell growth.

CHO cells can incorporate into proteins both thialysine and selenalysine when both are present together in the culture medium. Thialysine and selenalysine inhibit cell growth and cell viability. The inhibitory effect of either analog is additive. The inhibition of cell viability is related to the extent of protein lysine substitution by thialysine or selenalysine; it is however irrelevant whether lysine is substituted by one or the other analog or by both.

Intracellular transport of thialysine and selenalysine in CHO cells.

The intracellular transport of thialysine and selenalysine in CHO cells has been studied. Data have been obtained indicating that the two lysine analogs can be transported by both the cationic aminoacid transport system and by the L transport system. The affinity of the cationic aminoacid transport system is similar for the two lysine analogs but lower than that for lysine and the affinity of the L transport system for the two lysine analogs is lower than that for leucine.

Effects of selenalysine on thialysine resistant CHO cells.

A thialisyne resistant variant clone of CHO cells also shows a lower sensitivity to selenasyne, the lysine analog containing selenium. Growth rate, cell viability and protein synthesis rate are less affected by selenasyne in the variant compared to the parental strain. Data are reported showing that during cellular growth of either strain some toxic derivatives of selenasyne are produced and accumulated in the culture medium even in the presence of excess lysine.

[Effectiveness and duration of action of nifedipine in effort angina (author's transl)]. / Efficacia e durata d'azione della nifedipina nell'angor da sforzo. Somministrazione acuta.

The anti-anginal activity of nifedipine was studied after a dosage of 10 and 20 mg in nine patients suffering from a typical, stable effort angina pectoris. The effectiveness and the duration of action of nifedipine was evaluated by serial cycloergometer exercise testing repeated after the administration of the two dosage of nifedipine, for six hours. Nifedipine significantly increased exercise tolerance before angina pectoris, with an action lasting at least two hours after 10 mg and six hours after 20 mg. We also evaluated the changing of hemodynamic parameters (heart rate, blood pressure, double product) before and after the drug in the same day.