Benjamin S. Schwartz

Proteus vulgaris Urease In vitro Inhibition by Urea Analogues.

Summary Thirty-five analogues of urea have been evaluated for their ability to inhibit urease activity and growth of Proteus vulgaris ATCC 881. Enzyme activity was determined by the method of Chaney and Mar-bach. The ureolytic activity in a sonic lysate of Proteus vulgaris was markedly inhibited by thiourea, N-methylthiourea and N-acetyl-thiourea. The inhibition was not reversed by 10-3 and 10-4 M cysteine. None of the aryl substituted urea analogues had activity comparable to that of thiourea. Acetohydroxamic acid (1000 μg/ml) inhibited ureolytic activity of intact cells in Urea Broth (Difco) without concurrent growth inhibition. Chloro-acetylurea inhibited the growth of the test organism (125 μgg/ml), but failed to inhibit urease in Urea Broth or in sonic lysates. The capacity to inhibit urease activity in cell lysate does not appear to be associated with an ability to inhibit growth, or to inhibit ureolytic activity of intact cells.

Antibody formation at various times after previous treatment of mice with endotoxin.

Summary The effects of sheep red blood cells or endotoxins on numbers of hemolysin-forming spleen cells have been studied in mice previously injected with a small dose of endotoxin. One day after pretreatment the response to sheep red cells was greater than normal and the response to endotoxin was smaller than normal. At 10-12 days after pretreatment, the response to sheep red cells was normal but the response to endotoxin, given alone or together with sheep red cells, was greater than normal. Of 5 endotoxin preparations studied, only a protein-free endotoxin failed to alter reactivity to a subsequent injection of the same endotoxin.

Role of Protein Component of Endotoxin in Modification of Host Reactivity.

Summary The influence of endotoxins of varying nitrogen content on water intake and numbers of hemolysin-forming spleen cells in mice and on delayed skin reactivity in rabbits has been investigated. Pretreatment with an aqueous-ether endotoxin of S. enteritidis results in heightened reactivity to a subsequent test dose of the aqueous-ether or protein-free (Ribi) endotoxin, whereas pretreatment with the protein-free endotoxin fails to modify subsequent reactivity to either endotoxin. Similarly, pretreatment with the Boivin endotoxin of S. abortus equi increases reactivity on subsequent test with the Boivin or Westphal endotoxin, whereas pretreatment with the partially deproteinized Westphal endotoxin does not enhance reactivity to subsequent test with either endotoxin. The implications of these findings for the hypothesis that adult host reactivity to endotoxins is contributed to by an acquired delayed hypersensitivity are discussed.