In vitro studies of piperacilin, a new semisynthetic penicillin

Piperacillin, a new semisynthetic penicillin, was compared with other semisynthetic penicillins, cephalosporins, and aminoglycosides by the agar dilution method against 3,600 isolates of facultative gram-negative bacilli, Bacteroides fragilis, and enterococci. At 64 mug/ml, piperacillin inhibited 90% of the isolates in each group of organisms tested except for Escherichia coli (83% inhibited by 64 mug/ml). Compared with carbenicillin, piperacillin had a 16-fold increase in activity by weight against Pseudomonas aeruginosa and the enterococcus, an 8-fold increase against Serratia marcescens, and a 4-fold increase against B. fragilis and Enterobacter species. Piperacillin was highly active against carbenicillin-resistant Klebsiella pneumoniae and inhibited many aminoglycoside-resistant organisms. Except for P. aeruginosa, the minimum bactericidal concentration of piperacillin was usually within one tube dilution of the minimum inhibitory concentration. Approximately one-third of the gram-negative bacilli were inhibited synergistically by piperacillin plus amikacin, but no synergy could be demonstrated against enterococci. Piperacillin's in vitro activity against gram-negative bacilli was similar to gentamicin's except that it also included B. fragilis, and piperacillin was decidedly superior to presently available penicillins against K. pneumoniae.

Comparison of antitumor activities of pancreatic ribonuclease and its cross-linked dimer

The cross-linked dimer of bovine pancreatic RNase (M.W. 28,000) is significantly more effective than the monomer in inhibiting tumor development in mice when administered i.p. 1 day after inoculation with sarcoma 180J ascites cells. Animals bearing solid tumors were not affected. In AKR/J mice with advanced leukemia, a single i.p. injection of 100 mug of the dimer led to about 50% reduction in the enlarged lymph nodes and the spleen at 24 hr. The half-life of the dimer in the bloodstream has been determined to be 10 min in rats and 6 min in mice, compared to values of 5 and 3.5 min, respectively, for the monomer. Analyses of the tissues of untreated leukemic mice for RNase and RNase inhibitors show that the tumor tissues are not deficient in RNase activity. Considerations of possible mechanisms of action of the dimer indicate that other basic proteins in this size range may merit examination as cytostatic agents toward transformed cells.

Preparation of cross-linked dimers of pancreatic ribonuclease

The cross-linking reaction between diimido esters and ribonuclease has been studied in terms of the yield of cross-linked dimer with optimum activity toward double-stranded RNA. With dimethyl suberimidate the most satisfactory conditions were condensation for 15 min at pH 7.5-8.0 at 21 degrees C with 1.25 mol equiv of the diimido ester and a protein concentration of 6%. The dimer (yield 20%) had 19 unmodified NH2 groups out of a theoretical 20 for a molecule in which two such groups are involved in the cross-linkage; the activity toward poly(A)-poly(U) in 0.14 M salt solution by spectrophotometric assay was 8.5 times that of the monomeric enzyme toward the same substrate.

A crystalline protein-proteinase inhibitor from pinto bean seeds

A crystalline protein-proteinase inhibitor has been isolated from seeds of Pinto bean (Phaseolus vulgaris cultvar. Pinto). It has an average molecular weight of 19 000 as estimated by gel filtration. This crystalline inhibitor is highly active against both bovine pancreatic trypsin and alpha-chymotrypsin. Complexes of both trypsin-inhibitor and alpha-chymotrypsin-inhibitor have been isolated. The inhibitor which was derived from the dissociated trypsin-inhibitor complex was only 62% as effective as the original compound against either enzyme. In contrast, the inhibitor obtained from alpha-chymotrypsin-inhibitor complex retained its full original inhibitory activity for trypsin, but only 25% of its original activity against alpha-chymotrypsin. The dissociated inhibitor from alpha-chymotrypsin-inhibitor compex, despite its full inhibitory activity, had been modified to such an extent that it could no longer form any precipitable complex with trypsin. The crystalline protein-proteinase inhibitor is not homogeneous and has been resolved into two distinct inhibitors in terms of their physical and chemical properties. These two inhibitors are designated as Pinto bean proteinase inhibitor I and II and their respective minimum molecular weights are 9100 and 10 000. They differ most strikingly in their amino acid composition in that inhibitor II is void of both valine and methionine.

Relationship of soil constituents to spore counts and heat resistance of Bacillus stearothermophilus

Spore counts and heat resistance of Bacillus stearothermophilus and thermophilic actinomycetes were influenced by types of crops and were correlated positively with Mn, Ca, P, pHw, and pHs of soil from Sanborn Field, Columbia, Mo. In greenhouse soil, positive correlations were found between thermophilic aerobes and Mg, Ca, K, and cation-exchange capacity. Also, in the greenhouse soil, negative correlations occurred between counts for thermophilic aerobes and pHw and pHs. Spores in soils in Sanborn Field were more heat- resistant than spores in greenhouse soil. The number of germinating spores in dry soil stored at 25Cand 1.1C increased after 1 month and remained at the same relative number for 9 months at which time counts declined at both temperatures.

Biosynthesis of nucleotides in wheat. IV. Metabolism of specifically 14-C-labeled orotic acid

The biosynthesis of pyrimidine nucleotides in wheat leaves was investigated, with specifically14C-labeled orotic acids as precursors. The utilization of orotic acid, unlike uracil, for the synthesis of pyrimidine nucleotides is far more predominant than the degradative process. The labeled orotic acid was rapidly metabolized to uracil nucleotides and the sugar nucleotide, uridine-5′-diphosphate glucose. However, cytosine nucleotides were not significantly labeled within 60 minutes. In spite of the fact that no detectable radioactive OMP was observed, the results presented indicate strongly that the biosynthetic pathway for pyrimidine nucleotides from orotic acid in this plant proceeds according to the following reactions: orotic acid + 5-phosphoribosyl-1-pyrophosphate → orotidine-5′-monophosphate → uridine-5′-monophosphate → uridine-5′-triphosphate → uridine-5′-diphosphate glucose, and uridine-5′-triphosphate → cytidine-5′-triphosphate.