No abstract

The effect of methicillin, cloxacillin, 1078/1/1, penicillin G, and cephaloridine upon the penicillin-binding proteins of a permeability mutant of Escherichia coli K-12 and its isogenic wild type have been investigated. Comparison of the 50% inhibition values for the antibiotics against the penicillin-binding proteins of the two strains with the minimal inhibitory concentrations for the same compounds indicates that methicillin, cloxacillin, 1078/1/1, and to a lesser extent penicillin G, owe their poor antibacterial activity to exclusion from the bacterial cell, whereas cephaloridine is not excluded and is equally active against both the mutant and its wild type. The results further suggest that the lesion in the permeability mutant E. coli DC2 allows free access of all the compounds tested to the inner membrane target proteins.

No abstract

Prostaglandin (PG) and thromboxane (TX) synthesizing capacities of the rat ovary were measured at 4-h intervals during the 4-day oestrous cycle of the rat. Production of PGE-2, PGF-2 alpha, 6-oxo-PGF-1 alpha and TXB-2 increased 5-fold, 1.6-fold, 1.7-fold and 1.7-fold, respectively, between 18:00 h on the day of pro-oestrus and 02:00 h at oestrus. This preferential stimulation of ovarian PGE-2 production, after the ovulatory surge of LH before ovulation, provides further evidence for the involvement of ovarian PGE-2 in ovulation in the rat. These increases in ovarian PG production were not due to differences in arachidonic acid availability, PG metabolism, or the interconversion of PGE-2 and PGF-2 alpha. In addition, the greater stimulation of PGE-2 synthesis was not due to an increase in PGH-2 to PGE-2 synthetase activity. It is concluded that the ovulatory LH surge late in the afternoon of pro-oestrus in the rat causes an increase in ovarian cyclo-oxygenase (PGH-2 synthetase) activity with the majority of the PGH-2 synthesized being directed into the PGE-2-forming pathway.

A carbenicillin-resistant mutant of Pseudomonas aeruginosa 18s was found to possess peptidoglycan transpeptidase activity significantly more resistant to inhibition by benzyl penicillin, ampicillin, carbenicillin, and cephaloridine than that of the parent strain. The mutant was more resistant than the parent strain to all of the fl-lactam antibiotics tested, and 50% inhibition values for these compounds against membrane-bound model transpeptidase activity paralleled this increase.