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Biomedical subjects

J Verhoef

Publications and source records attributed to J Verhoef.

At least 577 records · Page 32Linked to original sources
PubMed1977

Effect of protein A on staphylococcal opsonization.

To study the effect of wall protein A on bacterial opsonization, phagocytosis of 10 strains of Staphylococcus aureus with high and low protein A contents was measured. Those strains that contained the highest concentrations of protein A were phagocytized by human neutrophils at a slower rate than strains with little or no protein A when normal human serum and purified immunoglobulin G (IgG) were used as opsonic sources. When IgG-deficient serum was used as an source, however, protein A-rich strains were phagocytized more rapidly than protein A-deficient strains. Extracellular (purified) protein A decrease the opsonic activity of all sera tested including IgG-deficient serum. It is proposed that when IgG is not present in the opsonic medium, cell wall protein A is capable of activating complement at the bacterial surface and thereby opsonization is promoted.

Bacterial Proteins↗
PubMed1977

Opsonic requirements for phagocytosis of Streptococcus pneumoniae types VI, XVIII, XXIII, and XXV.

An assay system employing radiolabeled, heat-killed Streptococcus pneumoniae and human polymorphonuclear leukocytes was utilized to study serum pneumococcal opsonic requirements. Comparing the kinetics of phagocytosis in normal serum, heat-inactivated serum, immunoglobulin G (IgG)-deficient serum, C2-deficient serum, and magnesium dichloride ethyleneglycol-tetraacetic acid (MgEGTA)-chelated serum allowed definition of the opsonic requirements for four pneumococcal serotypes: VI XVIII, XXIII, and XXV. All four serotypes were efficiently opsonized in 10% normal serum. Only type XVIII was opsonized in heat-inactivated serum. All four were also opsonized in IgG-deficient serum but not as efficiently as in normal serum. Opsonization via the alternative pathway was diminished for all four serotypes in 10% MgEGTA-chelated and C2-deficient serum. Furthermore, by varying the concentration of MgEGTA-chelated serum, it was found that type XXV was least efficiently opsonized via the alternative pathway. The quantitative nature of this assay system will permit measurement of bacterial and host factors that may contribute to host susceptibility to pneumococcal infection.

Blood↗
PubMed1977

Opsonic requirements for staphylococcal phagocytosis. Heterogeneity among strains.

Efficient phagocytosis of staphylococci by human neutrophilis is dependent on bacterial opsonization by serum factors. These factors include specific antibodies as well as components of the classical and alternative complement systems. In this study the opsonic requirements of three strains of S. aureus and three strains of S. epidermidis were investigated by incubating [3H]thymidine-labelled bacteria in sera with different opsonic activities and measuring rates of phagocytosis by human neutrophils. Opsonization of S. aureus Cowan I and 502 A depended primarily on activation of the classical complement pathway. Effective opsonization occurred in the absence of immunoglobulin but not in the absence of complement. A protein A deficient mutant of S. aureus Cowan I was poorly opsonized in the absence of IgG, however. S. aureus Wood 46 and two strains of S. epidermidis were opsonized primarily through the alternative complement pathway and depended on the presence of serum IgG. A third S. epidermidis strain was efficiently opsonized in heat-inactivated serum without complement activity. Thus, a heterogeneity of opsonic requirements was found among staphylococcal strains. It is proposed that cell wall protein A may be an important determinant of this heterogeneity.

Complement C2↗
PubMed1976

In vivo fate of a behaviorally active ACTH 4-9 analog in rats after systemic administration.

In vivo fate of a threefold substituted ACTH 4-9 analog with a markedly potentiated behavioral activity, 4-Met(O2), 8-D-Lys, 9-Phe-ACTH 4-9, was investigated. The radioactive labeled [7-3H-Phe] ACTH 4-9 analog was administered IV, SC and orally in a dose of approximately 40 mug. Plasma concentrations of total radioactivity and intact peptide were determined at various periods after administration in urethane anesthetized rats. Oral administration was also performed with conscious animals. Maximal plasma concentrations were found 8 min after SC injection. After oral administration in anesthetized rats maximal plasma levels were reached 8 hr after administration; in conscious animals this took 4 hr. The initial volume of distribution was 5.9% of body weight and the initial half-life (t1/2) for intact peptide 4 min. Shortly after IV and SC administration relatively high and stable plasma levels of intact peptide were obtained, reflecting metabolic stability. This stability was also apparent from the metabolite patterns, which were determined in trichloroacetic acid extracts of plasma and brain by paperchromatography and paperelectrophoresis. The plasma profiles indicated increased stability of the labile 8Lys-9Phe bond by the introduction of an 8D-Lys residue in the peptide analog. Enzymatic attack of the analog took place predominantly at 6His-7Phe and 7Phe-8D-Lys. Formation of tritiated water occcurred in brain and the gastro-intestinal tract and was considerable; proteolysis in these compartments was higher than in plasma. High uptake of radioactivity was found in the kidney, but urinary excretion was low during the first 30 min. Uptake in brain was low and paralleled uptake in cerebrospinal fluid. Intact peptide concentrations/g fresh tissue were in the order of 10(-5)-10(-4) times the administered dose for all three routes.

Adrenocorticotropic Hormone↗
PubMed1976

Extracellular and bacterial factors influencing staphylococcal phagocytosis and killing by human polymorphonuclear leukocytes.

Extracellular and bacterial factors that influence the phagocytosis and killing of staphylococci by human polymorphonuclear leukocytes have been studied. Staphylococcus epidermidis strains were, in general, more rapidly phagocytized than were S. aureus strains. However, two strains of S. epidermidis had a very slow rate of ingestion. Although the rate of phagocytosis of S. aureus Wood 46 was greater than that of S. aureus 502A, the Wood 46 strain was more difficult to kill. Serum was essential for phagocytosis of both S. aureus and S. epidermidis. The opsonic titer of pooled serum was similar for S. aureus and S. epidermidis. In normal pooled serum, heat-labile factors were more important for effective phagocytosis than they were in immune serum. Although a saturation point for ingestion was reached, the percentage of ingested bacteria that remained alive within the leukocyte remained relatively fixed. Heat-killed and live staphylococci were igested in a similar fashion. The rate of phagocytosis was greatly reduced at 41 degrees C.

Blood Bactericidal Activity↗