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J Verhoef

Publications and source records attributed to J Verhoef.

At least 559 records · Page 31Linked to original sources
PubMed1979

Role of Escherichia coli K capsular antigens during complement activation, C3 fixation, and opsonization.

Escherichia coli strains with K capsular polysaccharides are relatively resistant to phagocytosis by polymorphonuclear leukocytes, in contrast to E. coli strains without K antigens. This inhibition of phagocytosis is related to an impaired recognition of the K+ strains by the phagocytes due to ineffective opsonization. All five strains without K antigens were readily phagocytized after opsonization in 5% normal serum, compared with no uptake of the K+ strains. Evidence is presented that the decreased opsonization of the K+ strains in normal serum is caused by a low rate of complement activation of the strains, with subsequent absence of C3b fixation or C3d fixation or both to the cell wall of the bacteria. After removal of the K+ antigens by heating of a K+ E. coli strain, the strain was able to activate complement, to bind C3b or C3d or both, and to become opsonized. Complement was then activated via the classical and alternative pathways, which was comparable to the complement consumption by K- E. coli.

Antigens, Bacterial↗
PubMed1979

Chemotaxigenesis by cell surface components of Staphylococcus aureus.

In an attempt to delineate the staphylococcal cell surface components of importance in chemotaxigenesis, we incubated intact Staphylococcus aureus H, crude cell walls, purified cell walls, peptidoglycan, teichoic acid, and cell membranes with human sera. The results reported indicate that both crude cell walls and purified cell walls, as well as peptidoglycan, were potent chemotaxigens. These particles led to the generation in normal human serum of a factor that was chemotactic for human polymorphonuclear leukocytes. Cell wall peptidoglycan and teichoic acid both appeared to play a role in chemotaxigenesis. Kinetic studies employing C2-deficient serum and immunoglobulin-deficient serum revealed that optimal chemotaxigenesis required the presence of an intact classical complement pathway, as well as antibody. Granulocyte aggregometry studies showed that significant levels of C5a were generated in normal serum and that this activated complement component appears to be a major chemotactic factor produced in serum upon interaction with staphylococcal cell wall components.

Cell Membrane↗
PubMed1979

Quantitation of the third component of human complement attached to the surface of opsonized bacteria: opsonin-deficient sera and phagocytosis-resistant strains.

The role of the third component of human complement (C3) in the opsonization of bacteria in nonimmune human sera was evaluated. The amount of C3 that becomes attached to the surface of bacteria upon incubation in serum was measured in a quantitative fluorescent immunoassay using fluorescein-conjugated monospecific antiserum to human C3. The intensity of the fluorescence from opsonized bacteria was found to be directly proportional to the absolute amount of C3 fixed, and this enabled the detection of as few as 300 molecules of bound C3 per bacterium. In normal serum the rate of C3 fixation was closely correlated with an increase in opsonization of the bacteria for human PMNs. Both C3 fixation and opsonization were maximal after 15 min of incubation. C3 fixation was also observed, albeit at a significantly slower rate, in human serum with a nonfunctional classical pathway but an intact alternative complement pathway and in serum deficient in immunoglobulins. Again, the kinetics of C3 fixation correlated with bacterial opsonization. Using a total of 21 strains of several bacterial species, including Staphylococcus aureus and Escherichia coli, encapsulation of bacteria was found to interfere with the process of C3 fixation in normal human serum, rendering these organisms resistant to subsequent phagocytosis by human polymorphonuclear leukocytes.

Bacteria↗
PubMed1979

Antibiotic sensitivity and synergism of 'penicillin-tolerant' Staphylococcus aureus.

15 Staphylococcus aureus strains were isolated from 15 patients with staphylococcal bacteremia. Eight of these strains were shown to be tolerant for cloxacillin. Cloxacillin-tolerant strains were also tolerant for most of the cephalosporins tested except for cephapirin. Strains were not tolerant for clindamycin and gentamicin. Penicillin-tolerant staphylococci showed a high degree of synergism between gentamicin and cloxacillin or cephalothin and gentamicin.

Anti-Bacterial Agents↗
PubMed1979

Staphylococcus aureus opsonization mediated via the classical and alternative complement pathways. A kinetic study using MgEGTA chelated serum and human sera deficient in IgG and complement factors C1s and C2.

Staphylococcus aureus opsonization was studied kinetically by: (1) determination of the uptake of [3H]-thymidine labelled bacteria by human PMN's; (2) fluorescent anti-C3 and anti-IgG staining of opsonized bacteria; and (3) measuring bacterial complement consumption. Maximum opsonization in normal serum occurred within 5 min of incubation. About 80% of staphylococci were then taken up by PMN's, and IgG and C3b could be detected on the bacterial surface. In the absence of a functional classical complement pathway, as in sera deficient in C1s and C2 and in MgEGTA chelated serum, maximal opsonization was only achieved after 30--60 min incubation. Opsonization in IgG deficient serum occurred at a rate similar to that found in C2 deficient or MgEGTA chelated serum. Opsonization was greatly enhanced when sera were reconstituted. It was concluded that in IgG deficient serum Staphylococcus aureus opsonization is mediated via the alternative complement pathway. Dilution of normal serum primarily affected the classical complement pathway, resulting in a decreased rate of opsonization. In normal serum IgG did not appear to be a rate-limiting factor. S. Aureus opsonization was best studied by the phagocytosis assay and the fluorescent-antibody technique. Measuring haemolytic complement consumption was found to be an insensitive indicator of bacterial complement activation and opsonization.

Complement Activation↗
PubMed1979

The role of Staphylococcus aureus cell-wall peptidoglycan, teichoic acid and protein A in the processes of complement activation and opsonization.

The role of cell-wall peptidoglycan, teichoic acid and protein A in the processes of Staphylococcus aureus complement activation and opsonization was investigated. CH50 consumption studies reveal that, although all cell-surface fractions were capable of activating the classical C pathway, only peptidoglycan consumed C via the alternative pathway. Using a quantitative immunofluorescence assay, peptidoglycan was shown to bind C3 molecules via the classical as well as via the alternative C pathway and in the absence of IgG and IgA class antibodies. C activation via the classical and the alternative pathway could be distinguished by kinetic analysis. By comparing the rates of staphylococcal C consumption, C3 fixation and opsonization it was found that the CH50 consumption assay is a relatively insensitive method and may yield results that do not necessarily reflect the process of bacterial opsonization.

Complement Activation↗
PubMed1978

In vitro activity of cephalosporins against methicillin-resistant, coagulase-negative staphylococci.

The in vitro activity of five cephalosporins, gentamicin, and vancomycin was determined against 41 clinical isolates of methicillin-resistant, coagulase-negative staphylococci. Results obtained with disk diffusion and agar dilution methods failed to show complete cross-resistance between methicillin and four of the five cephalosporins despite the use of a high-salt medium and a large inoculum. Thirty-six (88%) of the 41 isolates were sensitive to cephalothin by a standardized disk diffusion method, whereas 23 isolates (56%) were sensitive to cephalothin with use of an agar dilution method and a large inoculum. Of these 23 isolates, only 11 (47%) were both inhibited and killed by less than or equal to 6.25 microgram of cephalothin/ml. The inhibitory and bactericidal activity of gentamicin was greater than that of vancomycin and cephalothin. These results suggest that the disk diffusion technique has limitations in determining the in vitro activity of cephalosporins against methicillin-resistant, coagulase-negative staphylococci and that cephalothin exhibits poor bactericidal activity against these same isolates.

Cephalosporins↗
PubMed1978

Phagocytosis and killing of staphylococci by human polymorphonuclear and mononuclear leucocytes.

The phagocytosis and killing of 3H-thymidine-labelled Staphylococcus aureus by polymorphonuclear leucocytes (PMNs) and monocytes (MNs) obtained from 50 health donors were evaluated. In addition, extracellular factors that might influence phagocytosis and killing were studied. The method described gave highly reproducible results. No significant difference was observed in the phagocytic and killing functions of a single donor's PMNs and MNs when studied several times in one day and longitudinally over a period of 1-12 weeks for six donors tested. Likewise, no signigicant difference in uptake and killing was observed when bacteria were opsonised with sera from 11 different normal donors. When Staph. aureus opsonised with normal serum was added to the leucocytes in a ratio of 10 bacteria: 1 leucocyte, the uptake by PMNs and MNs from 50 donors after 20 minutes' incubation was 85% +/- 7 standard deviation (SD) (range 75-98%) and 69% +/- 11 SD (range 54-90%), respectively. The rate of uptake by MNs in the first three minutes of the assay period was only 60% of that by PMNs.

Blood Bactericidal Activity↗
PubMed1978

The key role of peptidoglycan in the opsonization of Staphylococcus aureus.

In an effort to determine the staphylococcal cell surface component(s) of importance in opsonization, cell walls (peptidoglycan and teichoic acid) and peptidoglycan were isolated from Staphylococcus aureus strain H grown in [3H]glycine-containing broth. After incubation of the cell walls and peptidoglycan with various opsonic sources, uptake by human polymorphonuclear leukocytes was measured. The opsonic requirements for phagocytosis of cell walls and peptidoglycan were found to be similar to those of intact bacteria. Removal of teichoic acid from the cell wall did not affect opsonization. Likewise, a teichoic acid-deficient mutant strain of S. aureus H was opsonized in a manner similar to that of the parent strain. Immunoglobulin G functioned as the major heat-stable opsonic factor and both the classical and alternative pathways participated in opsonization. Kinetic studies revealed that opsonization of peptidoglycan, as well as C3-C9 consumption by peptidoglycan, proceeded at a slower rate via the alternative pathway (C2-deficient serum) than when the classical pathway was present (normal serum). The ability of peptidoglycan to activate C3-C9 was significantly reduced when normal and C2-deficient sera were preabsorbed with peptidoglycan at 2 degrees C suggesting that antibodies to peptidoglycan may be involved in activation of both the classical and alternative complement pathways. Thus, peptidoglycan appears to be the key cell wall component involved in staphylococcal opsonization, and it is suggested that host response to peptidoglycan, a major cell wall component of most gram-positive bacteria, may be related to the development of "natural immunity" to this group of microorganisms.

Cell Wall↗
PubMed1978

Complement-mediated phagocytosis of Pseudomonas aeruginosa.

The nature of the opsonic factors in nonimmune human serum for six blood culture isolates of Pseudomonas aeruginosa was investigated by measuring uptake of [3H] adenine-labeled bacteria by human PMNs. Normal human serum, C2- and C4-deficient sera, zymosan-treated serum, and immunoglobulin-deficient sera were used as opsonic sources. Heat inactivation of each of these serum sources markedly reduced its opsonic capacity for all Pseudomonas strains, suggesting that the serum C system was essential for opsonization. Five strains were opsonized in the absence of the classical C pathway; however, kinetic studies revealed that opsonization proceeded at a faster rate when the classical pathway was present. In spite of markedly reduced factor B and C3 levels, zymosan-treated serum retained significant opsonic activity for one of the strains tested. Four strains were poorly opsonized by immunoglobulin-deficient serum, and C activation by these strains appeared to depend upon the presence of antibodies. Two strains, however, were effectively opsonized in a relative absence of antibodies. Thus, in the nonimmune state, phagocytosis of P. aeruginosa is mediated primarily via the C system, and antibodies appear to play a role in the opsonization of some but perhaps not all Pseudomonas strains.

Complement Factor B↗
PubMed1978

Atrio-ventricular shuntinfections and endocarditis due to Staphylococcus epidermidis.

Two groups of patients (with endocarditis and with atrioventricular shunt infections due to Staphylococcus epidermidis) are presented together with analysis of the causative agents by bio- and phage-typing. Additionally phagocytic function of polymorphonuclear leukocytes of selected patients was investigated but no decreased phagocytic function was found. A possible way of treatment is discussed.

Cardiac Surgical Procedures↗
PubMed1977

Specific uptake of a behaviorally potent [3H]ACTH4-9 analog in the septal area after intraventricular injection in rats.

Distribution within the brain of a behaviorally potent [3H]ACTH4-9 analog 2 h after intraventricular injection in rats was studied in the presence and absence of behaviorally and structurally similar peptides, to explore the significance of earlier found preferential uptake of the [3H]ACTH4-9 analog in the septal area. Hypophysectomy resulted in significantly enhanced uptake of radioactivity in the septum as compared to normal rats. No increase in this brain area of hypophysectomized rats was observed after intraventricular injection of [3H]Phe. Elevated circulating ACTH levels after adrenalectomy seemed too low to compete with the septal uptake of the ACTH4-9 analong. Subcutaneous substitution of hypophysectomized rats with sustained release zinc phosphate preparations of the behaviorally equipotent peptides ACTH1-24 and ACTH4-10 decreased the accumulation of the [3H]ACTH4-9 analog in the septum, whereas treatment with the behaviorally inactive fragment ACTH11-24 is not effective. Retreatment of hypophysectomized rats with neuropeptides, differing structurally from natural ACTH peptides (7-D-Phe-ACTH4-10, BETA-LPH61-76 and 9-desglycinamide, 8-Lys-vasopressin), did not change the uptake of the ACTH4-9 analog in any of the investigated brain areas. These results give evidence for specific uptake of the ACTH4-9 analog in the septal region, because competitive displacement occurs only with peptides which both behaviorally and structurally are closely related to the ACTH4-9 analog.

Adrenalectomy↗
PubMed1977

Distribution of a behaviorally highly potent ACTH4-9 analog in rat brain after intraventricular administration.

Distribution within the brain of a 3-fold modified ACTH4-9 analog with a remarkably potentiated behavioral activity, 4-MET (O2), 8-d-Lys, 9-Phe-ACTH4-9, was investigated. The radioactive labeled [7-3H-Phe]ACTH4-9 analog was administered intraventricularly in urethane anesthetized rats in a dose of approximately 170 ng. Total radioactivity in CSF, measured in samples drawn from the cisterna magna, decreased over the period of 0.5-4 h after injection from 51 to 2% of the injected dose. Intraventricular injection of the ACTH4-9 analog resulted in high intact peptide levels in the brain. At 2 h after injection the distribution of radioactivity over 2500 micronm and 300 micronm frontal cut brain slices was rather homogenous. Data from distribution studies over topographically defined gross brain structures indicated that the septal area, which is involved in eliciting behavioral activities of ACTH-like neuropeptides, accumulated most of the injected radioactivity per gram wet weight. The distribution profiles within the brain of the [3H]ACTH4-9 analog and [3H]Phe showed considerable differences. Uptake studies in various brain nuclei after intraventricular administration of the [3H]ACTH4-9 analog demonstrated that the greatest part of the investigated nuclei exhibited relative low or medium uptake of radioactivity. This was also true for hippocampal and thalamic nuclei, which have been suggested as effected sites of action for ACTH peptides. Very high accumulation of radioactivity occurred only in the septal nuclei, particularly the dorsal and fimbrial septal nuclei. The results indicate selective uptake of the ACTH4-9 analog in the septal area, suggesting a possible significance of this area as a site of action of ACTH neuro-peptides.

Adrenocorticotropic Hormone↗
PubMed1977

Kinetics of staphylococcal opsonization, attachment, ingestion and killing by human polymorphonuclear leukocytes: a quantitative assay using [3H]thymidine labeled bacteria.

A method has been developed for studying quantitatively the separate processes of bacterial opsonization, phagocytosis, and killing by human polymorphonuclear leukocytes using [3H]thymidine labeled Staphylococcus aureus. Phagocytosis is determined by assaying for leukocytes-associated radioactivity after differential centrifugation and washing the leukocytes. Opsonization is studied by incubating bacteria with an opsonic source for varying durations and then adding leukocytes. By treatment of samples with the muralytic enzyme, lysostaphin, the attachment and ingestion phases of phagocytosis can be separated. Sampling for colony forming units after disruption of the leukocytes permits the measurement of bacterial killing. Using this method, differences in the kinetics of staphylococcal opsonization by normal and C2 deficient sera were defined, opsonic influences on the attachment and ingestion phases of pH agocytosis were delineated, and the influences of different opsonins and leukocyte populations on killing were determined.

Blood Bactericidal Activity↗
PubMed1977

Kinetics of phagocytosis and bacterial killing by human polymorphonuclear leukocytes and monocytes.

The kinetics of phagocytosis and bacterial killing by normal human polymorphonuclear leukocytes (PMNLs) and by monocytes (MNs) were compared by use of [3H]thymidine-labeled Staphylococcus aureus, Escherichia coli, and Listeria monocytogenes. The rate of phagocytosis by PMNLs was approximately twice that by MNs for all three bacterial species. Although a marked difference was found in opsonic requirements for phagocytosis of S. aureus, E. coli, and L. monocytogenes, phagocytosis by PMNLs and MNs was mediated via the same serum factors. All three species were killed rapidly once they were associated with leukocytes; however, the rate of killing by MNs was slower than that of PMNLs. The slower rate of killing appeared to be secondary to slower ingestion of attached bacteria by MNs. Thus, PMNLs and MNs appear to possess receptors with specificity for the same bacterial opsonins; however, PMNLs are capable of more efficienct bacterial phagocytosis (attachment and ingestion) than are MNs.

Escherichia coli↗
PubMed1977

Limiting factors in bacterial phagocytosis by human polymorphonuclear leukocytes.

Limiting factors in neutrophil phagocytosis were studied using a sensitive assay by which attachment, ingestion and intracellular killing of bacteria could be separated. Phagocytosis was found to be limited by the attachment capacity of neutrophils. Ingestion and intracellular killing proceeded at a constant rate proportional to the number of bacteria attached to the neutrophils.

Bacteria↗
PubMed1977

Influence of temperature on opsonization and phagocytosis of staphylococci.

The effect of incubation temperatures of 41, 37, and 4 degrees C on phagocytosis was investigated using human neutrophils and [3H]thymidine-labeled staphylococci. Depressed phagocytosis was observed at 41 and 4 degrees C. At 41 degrees C diminished staphylococcal uptake resulted from decreased attachment of bacteria to leukocytes; the inhibitory effect at 4 degrees C was secondary both to decreased opsonization and to reduced attachment to leukocytes. In contrast to the findings with normal serum, opsonization with heat-inactivated serum appeared to be relatively intact at 4 degrees C. By incubating samples in lysostaphin, it was determined that the process of bacterial ingestion as well as that of attachment was adversely affected by incubation temperatures of 41 and 4 degrees C.

Humans↗