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Biomedical subjects

M L Karnovsky

Publications and source records attributed to M L Karnovsky.

At least 127 records · Page 7Linked to original sources
PubMed1973

Biochemical changes during growth and encystment of the cellular slime mold Polysphondylium pallidum.

The growth of the cellular slime mold, Polysphondylium pallidum, was studied on a semidefined medium in shaken suspension. When the medium contained large quantities of particulate material, growth was more rapid and the cellular size and protein content were smaller than when growth occurred on a medium containing less particulate material. The cellular levels of DNA, RNA, and protein; of lysosomal enzymes (acid phosphatase, acid proteinase); and of peroxisomal enzymes (catalase) were assayed during growth and the subsequent stationary phase that led eventually to encystment. Only DNA remained at a constant cellular level. Encystment of exponentially growing cells could also be initiated by washing them and introducing them into a soluble peptone medium. The rate of encystment was proportional to the osmolarity of this medium. The encystment process was followed with respect to the cellular levels of DNA, RNA, protein, carbohydrates, acid phosphatase, acid beta-N-Ac-glucosaminidase, and catalase. The most dramatic change occurred in the cellular cellulose content, which increased by at least an order of magnitude by the time encystment was morphologically complete. It was concluded that the encystment of this slime mold in suspension exhibits a number of biochemical similarities to the development of this and other cellular slime molds on a surface.

Acid Phosphatase↗
PubMed1973

Phagocytosis by the cellular slime mold Polysphondylium pallidum during growth and development.

The phagocytic ability of amoebae of the cellular slime mold Polysphondylium pallidum, grown in shaken suspension, was examined. An established quantitative assay of the uptake of polystyrene (PS) beads was shown to be valid for this organism. The kinetics of phagocytosis were determined, and estimates of the concentration of PS beads necessary to achieve half-maximal phagocytic velocity (K(p)), as well as the maximal velocity itself (V(p) (max)), were made. Comparison with previously published data on Acanthamoeba and guinea pig leukocytes suggested that the P. pallidum amoebae had the lowest K(p), while the leukocytes had the highest V(p) (max). Beads approximately 1 microm in diameter appeared to be the optimal size for ingestion. Simultaneously with phagocytosis, comparable numbers of beads accumulated at the cell surface; this accumulation did not occur when phagocytosis was inhibited. Phagocytosis was depressed by protein in the medium, by increased osmolarity, and by inhibitors of aerobic metabolism. Starvation-initiated development, leading to encystment, was shown to affect the capacity of the cells to phagocytize, mainly by progressively decreasing the time span over which the cells ingested particles at a constant initial rate.

Animals↗
PubMed1973

The depression of phagocytosis by exogenous cyclic nucleotides, prostaglandins, and theophylline.

The effects of agents that elevate intracellular cyclic adenosine 3',5'-monophosphate (cAMP) have been studied with respect to phagocytosis by guinea pig polymorphonuclear leukocytes. The investigation depends upon the use of a precise method for following ingestion. Theophylline, dibutyryl cAMP, and prostaglandins inhibited the phagocytosis of starch particles. The inhibitions caused by prostaglandins E(1), E(2), and F(2alpha) (PGE(1), PGE(2), and PGF(2alpha)) were synergistic with that due to theophylline. Inhibition by PGA(1) and PGA(2) was not. At equal concentrations the order of increasing inhibition of phagocytosis (assayed at 10 min) by the prostaglandins was PGE(1) < PGF(2alpha) < PGE(2) < PGA(1) = PGA(2). Our results are consistent with the hypothesis that increased intracellular levels of cAMP impair the phagocyte's ability to ingest particles. The mechanism of the inhibition has not been defined. The increment in oxidation of [1-(14)C]glucose to (14)CO(2) that normally accompanies phagocytosis was found to be depressed in the presence of PGE(1) or theophylline, together or individually as expected from the inhibition of phagocytosis. Paradoxically, oxygen consumption although depressed by theophylline or PGE(1) plus theophylline, was stimulated by PGE(1) alone.

Animals↗
PubMed1971

Alterations of macrophage functions by mediators from lymphocytes.

Sensitized lymphocytes were incubated in vitro with the specific antigen Supernatants from these cultures were chromatographed on Sephadex G-100 columns. Supernatant fractions containing MIF, chemotactic factor, and lymphotoxin, but free of antigen and antibody, were incubated with normal peritoneal exudate macrophages. Macrophage adherence, phagocytosis, spreading, motility, and direct hexose monophosphate oxidation were enhanced, while protein synthesis was unaffected. Thus, antigen-stimulated lymphocytes secrete a factor or factors which enhance certain macrophage functions. Implications for models of cellular immunity and cellular hypersensitivity are discussed.

Amino Acids↗
PubMed1970

The distributions of some granule-associated enzymes in guinea-pig polymorphonuclear leucocytes.

1. Homogenates of guinea-pig polymorphonuclear leucocytes were separated by differential centrifugation into six particulate fractions and a soluble fraction. 2. The distributions in these fractions of protein, DNA, succinate dehydrogenase, beta-glucuronidase, peroxidase, alkaline phosphatase, acid phosphatase (against p-nitrophenyl phosphate and beta-glycerophosphate), cathepsin, and catalase were compared. 3. Almost all of the DNA sedimented in the first two pellets, indicating that the nuclei were relatively intact. 4. The four hydrolases and peroxidase showed different distribution patterns, although these activities were previously reported to be localized mainly in the single ;granule' fraction isolated from leucocytes. 5. The particles containing peroxidase, acid phosphatase and alkaline phosphatase all exhibited latency. Maximum activity for each enzyme was obtained at roughly similar concentrations of Triton X-100. 6. The acid phosphatase of these cells was distributed between two populations of particles that differed in both sedimentation characteristics and density. The acid phosphatase(s) of the two populations showed slightly different substrate specificities. This bimodal distribution was not an artifact of the procedure used to elicit the cells. 7. Catalase was recovered almost entirely in the soluble fraction and showed no latency in freshly prepared homogenates. No urate oxidase was detected. 8. We conclude that the ;granule' fraction of the polymorphonuclear leucocyte, as isolated by previous workers, contains at least three, probably more, populations of particles with different enzyme contents, and that these cells probably do not contain peroxisomes.

Acid Phosphatase↗
PubMed1970

Respiration and glucose oxidation in human and guinea pig leukocytes: comparative studies.

A comparison has been made of the metabolic shifts in human and guinea pig leukocytes when they phagocytize. Respiration of guinea pig polymorphonuclear leukocytes (PMN) and the increment during phagocytosis were each about 2(1/2)-fold that of human PMN. This was also true of the direct oxidation of glucose-6-P (hexose monophosphate shunt). Enzymes potentially responsible for these phenomena have been compared in each species. Cyanide-insensitive NADH oxidase and NADPH oxidase were measured and only the formed exhibited adequate activity to account for the respiratory stimulus durintg phagocytosis. The hydrogen peroxide formed by this enzyme stimulates the hexose monophosphate shunt by oxidizing glutathione which upon reduction by an NADPH-linked glutathione reductase provides NADP to drive the hexose monophosphate shunt. Other linkages between respiratory stimulation and that of the hexose monophosphate shunt also pertain in the guinea pig.

Animals↗
PubMed1970

Correction of metabolic deficiencies in the leukocytes of patients with chronic granulomatous disease.

Polymorphonuclear leukocytes from patients with chronic granulomatous disease (CGD) exhibit metabolic and bactericidal deficiencies that may be the result of inadequate production of H(2)O(2). A hydrogen peroxide-generating system was, therefore, inserted into CGD leukocytes. This was accomplished by allowing the cells to phagocytize latex spherules coated with glucose oxidase. This produced an amelioration in the known metabolic deficiencies of these cells during phagocytosis: (a) intracellular (catalatic) formate oxidation dependent upon hydrogen peroxide production was enhanced fourfold; and (b) hexose monophosphate shunt activity, which other workers have shown to be at least partially dependent upon the availability of H(2)O(2), was markedly stimulated. These data strengthen the evidence that the fundamental metabolic lesion in CGD cells during phagocytosis is indeed deficient production of hydrogen peroxide, probably, as previously shown, due to diminished oxidase for reduced nicotinamide adenine dinucleotide.

Carbon Isotopes↗