Legislated limits for housestaff training.
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Internship and Residency↗
Biomedical subjects
R K Root
Publications and source records attributed to R K Root.
Respiratory syncytial virus infections on an adult medical ward.
Eleven cases of respiratory syncytial virus (RSV) infection occurred in acutely ill hospitalized adults over a 7-week period. Nosocomial illness was suspected in two patients. Because RSV can cause serious infections in immunocompromised adults with the potential for nosocomial spread, the following recommendations are indicated: (1) during the winter months, early recognition and diagnosis of RSV infections both in hospital staff and in patients should be encouraged; (2) infected hospital personnel should avoid patient contact when possible; (3) during outbreaks, careful attention must be paid to hand washing and gloving; and (4) a high level of vigilance for RSV infection should be maintained on units with immunocompromised patients. Increased awareness of the potential risks of RSV infection is needed on adult medical units.
Adult↗
Leukocyte adhesion proteins: their role in neutrophil function.
In conclusion, the leukocyte proteins of the CD11/18 complex are highly conserved members of the integrin family in mammalian species. They play a key role in phagocytic and adherence mediated activities of neutrophils and appear to be centrally involved in adhesion to endothelial cells as well as transendothelial migration. Their importance in these processes has been documented by the occurrence of the disease now called leukocyte adhesion deficiency and the functional effects of a variety of monoclonal antibodies directed at different epitopes on the heterodimeric glycoprotein chains. These antibodies, as well as those directed at endothelial cell ligands for leukocyte adhesion proteins or peptides which mimic the functional epitopes, offer opportunities to manipulate or modify the inflammatory response in vivo where neutrophil accumulation or action can be harmful. They can also be employed to dissect out the role of PMNs in various repair processes such as wound healing. While bone marrow transplantation can ameliorate the deleterious consequences of severe LAD, continued elucidation of the multiple molecular mechanisms responsible for this disease will pave the way for its future genetic correction.
Antigens, Differentiation↗
Neutrophil function and host resistance.
The part played by the phagocytic cells against invading pathogens has been known since the work of Metchnikoff nearly a century ago. This review deals primarily with the role of the neutrophilic polymorphonuclear leukocyte in host defense against microbial infections. The overall function of these cells in protection from infection is dependent on a number of steps. First, an adequate number of functionally mature neutrophils have to be produced and released into the circulation by the bone marrow. Cells must circulate normally and be capable of adhering to capillary and venule walls overlying inflammatory sites. The next step involves the exit of phagocytes from the blood stream through the capillary wall and emigration into the tissues to establish contact with the invading pathogens. This process is accomplished by the locomotive characteristics of these cells and chemotaxis. Most organisms must then be phagocytized to be killed. Two discrete phases are involved in phagocytosis; the "recognition" and attachment phase followed by the ingestion phase. After phagocytosis a series of coordinated morphologic and biochemical events are set into motion which leads to eventual death and lysis of the ingested microbes. A variety of antimicrobial mechanisms are involved in this final step and indicate that these cells have an appreciable reserve capacity if one mechanism is impaired. Recent evidence which clarifies mechanisms involved in all these stages is discussed.
Animals↗
The role of antibody and complement in phagocytosis by rabbit alveolar macrophages.
The relative importance of antibody and complement in the phagocytosis of Staphylococcus aureus and Pseudomonas aeruginosa, two common bacterial pathogens, by alveolar macrophages from rabbits was studied. Normal rabbit serum was a satisfactory opsonin for the phagocytosis of S. aureus but not for P. aeruginosa. Normal rabbit serum opsonized S. aureus by both the classic and the alternative complement pathways; loss of both pathways destroyed opsonic activity. The presence of complement was not required for maximal phagocytosis when 10% staphylococcal immune serum was used. However, an intact alternative complement pathway enhanced phagocytosis when the concentration of staphlyococcal immune serum was lowered to 0.3%. Similarly, 10% pseudomonas immune serum opsonized P. aeruginosa without complement. When the concentration of pseudomonas immune serum was lowered to 1%, either the classic or the alternative complement pathway could significantly enhance phagocytosis of P. aeruginosa. Similar results were obtained with alveolar macrophages activated with bacille Calmette-Guérin. These studies demonstrate the importance of complement in enhancing phagocytosis by alveolar macrophages of bacterial pathogens when antibody concentration is the limiting factor.
Animals↗
Possible nosocomial transmission of group Y Neisseria meningitidis among oncology patients.
Within 4 days, two oncology patients in the Clinical Research Unit had bacteremia causes by group Y Neisseria meningitidis. Three additional patients, identified by prevalence survey, were found to have nasopharyngeal colonization with that serogroup, compared with only one employee (not associated with patients) and no family contacts. Infected and colonized (case) patients were located in the same or adjacent rooms but did not have close contact. A comparison of host and risk factors showed no significant differences between case patients and the other (control) patients located in the same rooms. In retrospect, the index patient, who had marked sputum production but was not isolated, had unrecognized meningococcal pneumonia and probably was the hospital source of a heavy, airborne dispersal of organisms to other patients. Respiratory isolation is warranted for patients with suspected N. meningitidis infection.
Aged↗
Indium-111-labeled human polymorphonuclear leukocytes: viability, random migration, chemotaxis, bacterial capacity, and ultrastructure.
Human polymorphonuclear leukocytes (PMNs) were labeled with indium-111 oxine in ethanol, and the effects of the labeling procedure, radioactivity, and concentrations of oxine and ethanol on PMN function and structure were studied in vitro. The standard labeling procedure did not alter the viability, random migration, chemotaxis, bactericidal capacity, or the ultrastructure of PMNs. Exposure to higher doses of radioactivity, or to higher concentrations of ethanol, had no appreciable effects on random migration and chemotaxis of PMNs. A dose-dependent reduction in their random migration and chemotaxis was observed when higher concentrations of oxine were used. These results indicate that In-111-labeled PMNs are structurally intact and have normal in vitro locomotion and bactericidal activity. Indium-111-labeled PMNs should be suitable for studying the kinetics and distribution of these cells in health and disease.
Blood Bactericidal Activity↗
Granulocyte function during lithium therapy.
Random migration, chemotaxis, phagocytosis, and bactericidal ability of neutrophils from 5 patients receiving lithium carbonate were compared with those of neutrophils from healthy donors. These cells functioned normally in all respects. Neither sera from patients receiving lithium carbonate nor the addition of lithium chloride to control cells in vitro significantly altered their functional capacity. These findings suggest that neutrophil function in patients receiving lithium therapy is preserved, and they support the potential utility of this drug as a leukopoietic agent in neutropenic states.
Adult↗
Development of Oxidase activity by human bone marrow granulocytes.
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Bone Marrow↗
Preparation and function of 123I-labelled mononuclear phagocytes.
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Blood Bactericidal Activity↗
Impaired response to pneumococcal vaccine in Hodgkin's disease.
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Adult↗
Inhibition of human granulocyte function by methotrexate.
Patients receiving cytotoxic drugs are at an increased risk of bacterial infection. Drug-induced leukopenia may be responsible for depression of host defenses; however, there is little information concerning the qualitative effects, if any, of cytotoxic agents on granulocyte antibacterial activity. Since methotrexate is now being used in massive doses in vivo, we investigated the effects of this drug on antibacterial and metabolic functions of normal polymorphonuclear leukocytes in vitro. Phagocytosis, quantitative protein iodination, and staphylococcal killing of normal polymorphonuclear leukocytes were found to decrease with exposure to increasing concentrations of methotrexate. The effects of methotrexate on these cell functions were rapid in onset and readily reversed by washing the cells, suggesting a locus of action on the cell membrane rather than at the level of nucleic acid synthesis. Exposure of cells to similar concentrations of folic acid or folinic acid produced no impairment of bacterial phagocytosis, suggesting that the observed effects are specific for methotrexate. The concentrations of methotrexate that produced these impairments are readily achieved in vivo and may alter antibacterial defenses in patients receiving this therapy.
Blood Bactericidal Activity↗
Hydrogen peroxide release from mouse peritoneal macrophages: dependence on sequential activation and triggering.
Using a specific and sensitive fluorometric assay, the H2O2 release from as few as 2 X 10(5) mouse peritoneal macrophages could be detected continuously and quantitated. It is emphasized that the assay measured H2O2 release, not production. Induction of H2O2 release required sequential application of two stimuli: the administration of an activating agent to the mice from 4 days to 10 wk before all harvest, and the exposure of the cells in vitro to a triggering agent. BCG was most effective as an activating agent, resulting in peritoneal macrophages which could be triggered to release H2O2 almost as copiously (8 nmol/10(6) macrophages per 5 min) as mouse peritoneal PMN (9 NMOL/10(6) PMN per 5 min). Casein and C. parvum could also serve as activators, but thioglycollate and FCS were ineffective after single injections. PMA was a potent triggering agent, resulting in a maximal rate of H2O2 release after a latency of about 40 s for cells in suspension. Other triggering agents included the ionophore A23187, concanavalin A in the presence of cytochalasin B, and phagocytosis. H2O2 release could be attributed to macrophages and PMN in peritoneal cell suspensions or in preparations of adherent peritoneal cells, but not to lymphocytes. Indirect evidence suggested that the H2O2 detected was formed from superoxide anion. These observations appear to justify renewed interest in the idea that H2O2 may be important in macrohpage antimicrobial and antitumor mechanisms.
Animals↗
Community-acquired Acinetobacter calcoaceticus var anitratus pneumonia.
Two patients had community-acquired Acinetobacter calcoaceticus var anitratus pneumonia. Both patients were alcoholic and one was cirrhotic. One patient died and the other received two weeks of gentamicin therapy and survived. Misinterpretation of the sputum Gram stain delayed diagnosis and institution of proper therapy in both cases. In addition to organisms sensitive to penicillins such as Neisseria or Haemophilus, Acinetobacter must be considered in the differential diagnosis of community-acquired Gram-negative coccobacillary pneumonia.
Acinetobacter↗
A randomized clinical trial of granulocyte transfusions for infection in acute leukemia.
In a prospective, controlled, randomized study to evaluate the efficacy of filtration-leukapheresis granulocytes in granulocytopenic, febrile patients with leukemia, 19 patients received antibiotics alone, and 12 received antibiotics plus daily granulocyte transfusions from ABO-matched donors. In skin-chamber studies the granulocytes appeared at sites of inflammation for at least six hours after transfusion. Infected subjects survived longer if they received granulocytes. Differences between control and transfused patients were greatest in patients with persistent bone-marrow failure, the 21-day survival being 20 per cent in controls, and 75 per cent in transfused patients. Granulocytes appeared to have no effect on the outcome of febrile episodes in which infection was not documented, the 21-day survival being 79 per cent for controls and 88 per cent for transfused patients. The transfusion of granulocytes thus appears to offer a survival advantage to infected, persistently granulocytopenic patients.
Acute Disease↗
Structural analysis of human neutrophil migration. Centriole, microtubule, and microfilament orientation and function during chemotaxis.
Orientation of nucleus, centriole, microtubules, and microfilaments within human neutrophils in a gradient of chemoattractant (5 percent Escherichia coli endotoxin-activated serum) was evaluated by electron microscopy. Purified neutropils (hypaque-Ficoll) were placed in the upper compartment of chemotactic chambers. Use of small pore (0.45 mum) micropore filters permitted pseudopod penetration, but impeded migration. Under conditions of chemotaxis with activated serum beneath the filter, the neutrophil population oriented at the filter surface with nuclei located away from the stimulus, centrioles and associated radial array of microtubules beneath the nuclei, and microfilament-rich pseudopods penetrating the filter pores. Reversal of the direction of the gradient of the stimulus (activated serum above cells) resulted in a reorientation of internal structure which preceded pseudopod formation toward the activated serum and migration off the filter. Coordinated orientation of the entire neutrophil population did not occur in buffer (random migration) or in a uniform concentration of activated serum (activated random migration). Conditions of activated random migration resulted in increased numbers of cells with locomotory morphology, i.e. cellular asymmetry with linear alignment of nucleus, centriole, microtubule array, and pseudopods. Thus, activated serum increased the number of neutrophils exhibiting locomotory morphology, and a gradient of activated serum induced the alignment of neutrophils such that this locomotory morphology was uniform in the observed neutrophil populayion. In related studies, cytochalasin B and colchicines were used to explore the role of microfilaments and microtubules in the neutrophil orientation and migration response to activated serum. Cytochalasin B (3.0 mug/ml) prevented migration and decreased the microfilaments seen, but allowed normal orientation of neutrophil structures. In an activated serum gradient, colchicines, but not lumicolchicine, decreased the orientation of nuclei and centrioles, and caused a decrease in centriole-associated microtubules in concentrations as low as 10(-8) to 10(-7) M. These colchicines effects were associated with the rounding of cells and impairment of pseudopod formation. The impaired pseudopod formation was characterized by an inability to form pseudopods in the absence of a solid substrate, a formation of narrow pseudopods within a substrate, and a defect in pseudopod orientation in an activated serum gradient. Functional studies of migration showed that colchicines, but not lumicolchicine, minimally decreased activated random migration and markedly inhibited directed migration, but had not effect on random migration. These studies show that, although functioning microfilaments are probably necessary for neutrophil migration, intact microtubules are essential for normal pseudopod formation and orientation, and maximal unidirectional migration during chemotaxis.
Blood↗
Granulocyte function in patients with chronic renal failure: surface adherence, phagocytosis, and bactericidal activity in vitro.
The defects in host defense mechanisms that explain the enhanced susceptibility to infection of patients with chronic renal failure are not understood, and previous studies concerning function of polymorphonuclear leukocytes (PMNL), the major antibacterial defense, conflict. Therefore, the antimicrobial functions of PMNL obtained from chronically uremic patients and serum factors essential for PMNL activity were evaluated. The potential modifying effect of high concentrations of serum from uremic patients on PMNL of uremic patients was determined, and granulocyte adherence, an activity related to recruitment of cells to inflammatory sites, was measured. Phagocytosis of 14C-labeled Staphylococcus aureus and bactericidal activity were normal and unaffected by high concentrations of uremic serum. Serum from uremic patients opsonized staphylococci and yeast normally. Oxidative metabolism of PMNL [14C-1]glucose oxidation, O2 consumption, and quantitative protein iodination) was normal, as was PMNL adherence. If the uremic patient has an increased risk of infection, this risk cannot be ascribed to defects of PMNL responses that have been studied in these patients.
Adult↗
H2O2 release from human granulocytes during phagocytosis. Relationship to superoxide anion formation and cellular catabolism of H2O2: studies with normal and cytochalasin B-treated cells.
Normal and cytochalasin B-treated human granulocytes have been studied to determine some of the interrelationships between phagocytosis-induced respiration and superoxide and hydrogen peroxide formation and release into the extracellular medium by intact cells. By using the scopoletin fluorescent assay to continuously monitor extracellular hydrogen peroxide concentrations during contact of cells with opsonized staphylococci, it was demonstrated that the superoxide scavengers ferricytochrome c and nitroblue tetrazolium significantly reduced the amount of H(2)O(2) released with time from normal cells but did not abolish it. This inhibitory effect was reversed by the simultaneous addition of superoxide dismutase (SOD), whereas the addition of SOD alone increased the amount of detectable H(2)O(2) in the medium. The addition of sodium azide markedly inhibited myeloperoxidase-H(2)O(2)-dependent protein iodination and more than doubled H(2)O(2) release, including the residual amount remaining after exposure of the cells to ferricytochrome c, suggesting its origin from an intracellular pool shared by several pathways for H(2)O(2) catabolism. When cells were pretreated with cytochalasin B and opsonized bacteria added, reduced oxygen consumption was observed, but this was in parallel to a reduction in specific binding of organisms to the cells when compared to normal. Under the influence of inhibited phagosome formation by cytochalasin B, the cells released an increased amount of superoxide and peroxide into the extracellular medium relative to oxygen consumption, and all detectable peroxide release could be inhibited by the addition of ferricytochrome c. Decreased H(2)O(2) production in the presence of this compound could not be ascribed to diminished bacterial binding, decreased oxidase activity, or increased H(2)O(2) catabolism and was reversed by the simultaneous addition of SOD. Furthermore, SOD and ferricytochrome c had similar effects on another H(2)O(2)-dependent reaction, protein iodination, in both normal and cytochalasin B cells. When oxygen consumption, O(2.) (-), and H(2)O(2) release were compared in the presence of azide under identical incubation conditions, the molar relationships for normal cells were 1.00:0.34:0.51 and for cytochalasin B-treated cells 1.00:0.99:0.40, respectively. Nonopsonized, or opsonized but disrupted, bacteria did not stimulate any of these metabolic functions. The results indicate that with normal cells approximately 50% of H(2)O(2) released during phagocytosis is derived directly from O(2.) (-) by dismutation, the remainder appearing from an (intra)cellular source shared by azide-inhibitable heme enzymes. With cytochalasin B treatment the evidence is consistent with the derivation of all H(2)O(2) from an O(2.) (-) precursor which is released from the cell surface. Furthermore, when activated by phagocytic particle binding, the neutrophil O(2.) (-) generating system appears to make more of this compound than can be accounted for by dismutation to H(2)O(2). This establishes conditions for the direct participation of both compounds in the microbicidal and cytocidal activity of these cells.
Azides↗