The splanchnic removal of bacteria from the blood stream of leukopenic rabbits

In rabbits subjected to profound damage of the blood-forming tissues by the use of benzene and mechlorethamine hydrochloride, no impairment of efficiency in the splanchnic removal of M. aureus from the blood stream could be demonstrated by a method involving catheterization of the hepatic vein. All evidence continues to indicate that a bacteriemia cannot be maintained unless the organisms are introduced constantly into the blood stream from some source. The importance of the leukocyte in the establishment and clearing of the bacteriemias appears to lie in its phagocytic activities at the local source of the bacteriemia rather than in any quantitatively significant phagocytosis of organisms circulating in the blood stream. The present studies suggest that in the study of the leukopenic state attention should be directed more especially toward the identification and eradication of the local source of organisms.

Inhibitors of the beta-glucuronidase of rabbit polymorphonuclear leucocytes

As previously reported, rabbit polymorphonuclear leucocytes contain an enzyme capable of hydrolyzing biosynthetic phenolphthalein mono-β-glucuronide. The effect of a number of inhibitors on cell-free preparations of this enzyme was studied. Many of the usual enzyme inhibitors were without effect, but certain dicarboxylic acids were strong inhibitors. These were (in order of activity): D-glucosaccharic acid, D-mucic acid, L-malic acid, mesotartaric acid, DL-malic acid, and L-tartaric acid. The nature of the inhibition was competitive. The Michaelis constant, Ks, was evaluated for phenolphthalein mono-β-glucuronide and values of Ki were estimated for glucosaccharic acid, mucic acid, DL-malic acid, and mesotartaric acid. Heparin in high concentration was slightly inhibitory, but the nature of the inhibition was noncompetitive. For each of the inhibitors studied, the extent of the inhibition was influenced by the hydrogen ion concen tration. At a pH greater than 4.5, the optimum for the enzyme under the conditions used, the degree of inhibition was less, and at a pH less than 4.5 the degree of inhibition was greater.

The survival of staphylococci within human leukocytes

In a study of the phagocytosis of staphylococci by human leukocytes it has been observed that strains of staphylococci producing human infection were phagocytized by human polymorphonuclear leukocytes in vitro under conditions in which virulent pneumococci, streptococci, or Klebsiella were rarely engulfed. In the presence of human leukocytes in plasma there was a rapid fall in the numbers of viable staphylococci of both pathogenic and non-pathogenic strains, the beginning of which was detectable in 10 to 15 minutes. The fall in culturable pathogenic microorganisms was considerably less marked, however, and a rapid resurgence of growth occurred in 4 to 8 hours, whereas the number of culturable non-pathogenic microorganisms remained low for 18 to 24 hours. These differences appear to be explained by the observation that a significant number of microorganisms of pathogenic strains were able to survive within human leukocytes. Such intracellular survival was found to be associated with evidence of destruction of the leukocytes. In contrast, non-pathogenic strains of staphylococci failed to survive within human polymorphonuclear leukocytes following ingestion.

The acceleration and inhibition of migration of human leucocytes in vitro by plasma protein fractions

A new method is described for the quantitative study of leucocyte migration. Blood drawn into a capillary tube is centrifuged, forming a buffy coat. The migration of the leucocytes from the buffy coat into the plasma is measured by means of an ocular micrometer. While there is a great deal of variation from one normal individual to another in the migration rates of leucocytes those of each individual show relatively little variation in migration from day to day (Table I). In all cases of illness studied, the average migration rates fall within the normal range, but there was a wider variation in the day to day migration rate than obtains in normal healthy individuals (Tables II and III). From experiments in which the cells with typically "slow" and "fast" migration rates were tested in both the "slow" and "fast" plasmas, it could be concluded that while the cells invariably have some influence on the migration rate, the major factors influencing leucocyte migration reside in the plasma (Table V). Experiments in which the plasma proteins were fractionated according to the method of Lever et al. indicated the presence of a system of proteins which regulate leucocyte migration. A heat-labile (56°C. for 30 minutes) component of fraction II was able to accelerate leucocyte migration, while fraction III acted as an inhibitor (Tables IX and X).