Biomedical subjects

J Verhoef

Publications and source records attributed to J Verhoef.

At least 307 records · Page 17Linked to original sources

PubMed1992

Cocaine amplifies HIV-1 replication in cytomegalovirus-stimulated peripheral blood mononuclear cell cocultures.

Cocaine and CMV each have been suggested to promote the progression of HIV-1 infection. In the present study, the interaction of cocaine and CMV was investigated in a PBMC coculture assay in which release of HIV-1 p24 Ag into coculture supernatants was used as an index of HIV-1 replication. CMV was an effective activation signal for HIV-1 replication when PBMC from CMV-seropositive donors were used in the coculture assay, and cocaine markedly increased replication of HIV-1 in these cocultures. The synergistic activity of cocaine was reduced by neutralizing antibodies to TNF-alpha and by pentoxifylline, an inhibitor of TNF-alpha mRNA production. Also, antibodies to transforming growth factor-beta (TGF-beta) eliminated the amplifying effect of cocaine on HIV-1 replication, whereas antibodies to IL-6 were inactive. The potentiating effect of cocaine could be reproduced by addition of rTNF-alpha or rTGF-beta to the cocultures of CMV-activated PBMC, although TGF-beta was substantially more potent than TNF-alpha. The possibility that TNF-alpha may act indirectly through stimulation of TGF-beta was suggested by the finding of reduced TGF-beta levels in culture supernatants of PBMC that were treated with CMV and cocaine in the presence of antibodies to TNF-alpha. Thus, cocaine amplifies HIV-1 replication in cocultures containing CMV-activated PBMC via a mechanism that appears to involve both TNF-alpha and TGF-beta. The results of this study support the possibility that cocaine and CMV could enhance HIV-1 replication and, thus, aggravate HIV-1-related disease.

Cells, Cultured↗

PubMed1992

Intranasal administration of estradiol in combination with progesterone to oophorectomized women: a pilot study.

A pilot study was done to investigate the pharmacokinetics and acceptability of an intranasal 17 beta-estradiol/progesterone formulation. This formulation contained dimethyl-beta-cyclodextrin as a solubilizer and absorption enhancer of the steroid hormones. The study was performed in four oophorectomized and hysterectomized patients. After nasal delivery of 0.34 mg estradiol and 0.85 mg progesterone, concentration-time curves of progesterone, estradiol and its metabolite estrone were established. Rapid absorption of progesterone and estradiol was demonstrated. Progesterone peak-levels (3.9-6.7 nmol/l) exceeded the levels which are found in the follicular phase of the menstrual cycle, but did not reach the levels of the luteal phase. Comparison with an earlier reported study in which only estradiol was administered shows that the addition of progesterone does not alter the absorption and pharmacokinetics of estradiol. The nasal formulation was well accepted by the four patients and no adverse effects were noted.

Administration, Intranasal↗

PubMed1992

Comparison of the autoSCAN-W/A and Vitek Automicrobic systems for identification and susceptibility testing of bacteria.

The identification and susceptibility testing of bacteria by the autoSCAN-W/A rapid panels and Vitek Automicrobic systems were compared. A total of 291 clinical isolates, including 207 members of the Enterobacteriaceae, 41 nonfermentative gram-negative bacilli, 31 Staphylococcus aureus strains and 12 Enterococcus faecalis strains, were tested. autoSCAN-W/A and Vitek correctly identified 93% and 94% respectively of the Enterobacteriaceae, the identification in an additional 2% and 5% of strains respectively being reported as correct with a low probability. autoSCAN-W/A reported all identification results within 2 h after inoculation, whereas Vitek reported the identification results for the majority of gram-negative bacilli between 4 h and 6 h after inoculation. autoSCAN-W/A and Vitek reported 81% and 74% of MIC results respectively after 3-6 h incubation. The rates of very major susceptibility errors were 0.4% and 0.4% for autoSCAN-W/A and Vitek respectively, the rates of major errors 0.4% and 1% respectively, and the rates of minor errors 4% and 3% respectively. Six of 30 Pseudomonas aeruginosa strains failed to grow sufficiently for susceptibility testing in the autoSCAN-W/A system, and four Xanthomonas maltophilia strains had insufficient growth for susceptibility testing in both systems. The majority of results of susceptibility testing of nonfermentative gram-negative bacilli were reported more than 6 h after inoculation. Both systems were reliable and easy to operate, and gave accurate results for common clinical isolates.

Bacteria↗

PubMed1992

Quantitative assay for testing susceptibility of HIV isolates to zidovudine and sCD4 (178)-PE40.

A quantitative coculture assay is described for determining susceptibility of HIV-1 isolates to zidovudine and sCD4 (178)-PE40 (a 60 kDa hybrid protein consisting of the gp120 binding region of CD4 linked to the translocation and ADP-ribosylation regions of Pseudomonas aeruginosa exotoxin). The assay was relatively simple to perform and gave highly reproducible results often within three to five days. IC50 values of zidovudine for HIV-1 strains isolated from two AIDS patients and an asymptomatic seropositive individual were in the range 0.001-0.002 mumol. Isolates obtained after six months of zidovudine treatment had zidovudine IC50 values of 0.01-0.5 mumol. All isolates were equally sensitive to sCD4 (178)-PE40 (IC50 1-5 micrograms/ml). HIV-1 activation in the chronically infected cell line U-1 was inhibited by sCD4 (178)-PE40 but not by zidovudine.

Antiviral Agents↗

PubMed1992

Long-term carriage, and transmission of methicillin-resistant Staphylococcus aureus after discharge from hospital.

The purpose of this study was to determine whether patients who become carriers of methicillin-resistant Staphylococcus aureus (MRSA) during their stay in hospital, remain colonized after discharge. Thirty-six patients colonized with MRSA during one of three outbreaks at Utrecht University Hospital (1986-89) were screened 2 or 3 years after they had become carriers. Patients were also interviewed to determine factors contributing to persistent carriage, such as antibiotics, re-admissions to the hospital, presence of skin lesions and chronic diseases. At the same time transmission of MRSA to family members was determined. The epidemic MRSA strain was still found in three patients (8%). One was a cystic fibrosis patient who had had frequent re-admissions to the hospital and had received several course of antibiotic treatment. Both of the other patients had skin lesions: a fistula and a colostomy respectively. None of the 44 family members of the patients was colonized or infected with MRSA. We conclude that long-term MRSA carriage occurs with low frequency and is comparable to persistent carriage of methicillin-sensitive Staphylococcus aureus (MSSA). Transmission of MRSA to healthy individuals in an antibiotic-free environment is a rare event.

Adolescent↗

PubMed1992

Peritoneal defense in continuous ambulatory versus continuous cyclic peritoneal dialysis.

Several centers have reported a lower rate of peritonitis among adult patients on continuous cyclic peritoneal dialysis (CCPD) as compared to those undergoing continuous ambulatory peritoneal dialysis (CAPD). Preliminary results of our ongoing prospective randomized study comparing CAPD-Y with CCPD also suggest a lower peritonitis incidence among CCPD-treated patients. To investigate whether the two dialysis regimens could result in differences in local host defense, we studied peritoneal macrophage (PMO) function and effluent opsonic activity in eight patients established on CAPD-Y matched with eight chronic CCPD patients. Since short and long dwell times are inherent to both dialysis modalities, and we previously found that dwell time has an impact on PMO function and effluent opsonic activity, patients were studied after both a short (4 hr) and a long (15 hr) dwell time. In both groups PMO phagocytic capacity increased significantly with dwell time (39 +/- 3.3% at 4 hr vs. 58 +/- 4.2% at 15 hr in CAPD patients, and 40 +/- 3.9 vs. 72 +/- 3.3% in CCPD patients; P less than 0.01), as did PMO peak chemiluminescence response (31 +/- 4.9 vs. 77 +/- 7.2 counts.min-1/10(4) cells in CAPD, and 22 +/- 3.9 vs. 109 +/- 21.2 counts.min-1/10(4) cells in CCPD; P less than 0.01) and effluent opsonic activity (41 +/- 7.6 vs. 73 +/- 5.8% in CAPD and 39 +/- 6.2 vs. 70 +/- 5.9% in CCPD; P less than 0.01). However, no significant difference was found in either variable between CAPD and CCPD patients when dwell times were equal.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Antibodies and complement enhance binding and uptake of HIV-1 by human monocytes.

OBJECTIVE: To characterize antibody- and complement-mediated binding and uptake of HIV-1 by human monocytes. DESIGN: The first step in the infection of the monocyte by HIV-1 is binding of the virus to the susceptible cell. Procedures were designed to assess the influence of anti-HIV-1 antibodies and complement on this binding, and to study the process of internalization following binding. METHODS: Human monocytes were incubated with fluorescein-labelled purified HTLV-IIIB virions and human sera with high-titre anti-HIV-1 antibodies and/or complement. Binding and uptake of virus by the monocytes was measured as fluorescence per cell by flow cytometry. RESULTS: Binding of purified HIV-1 to monocytes was increased by complement and, to a lesser extent, by anti-HIV-1 antibodies. Uptake of HIV-1 bound to the monocyte appeared to be mediated by antibodies and was increased further by the presence of complement. Complement alone, however, resulted in the uptake of only a small part of the bound virus. CONCLUSIONS: Complement significantly increases the binding of HIV-1 to human monocytes, and a combination of antibodies and complement efficiently mediates uptake of HIV-1 by monocytes.

Antibodies, Monoclonal↗

PubMed1992

Antibody mediated enhancement of HIV-1 infection of an EBV transformed B cell line is CD4 dependent.

Low levels of anti-viral antibodies may facilitate virus infection of Fc-receptor bearing cells. For human immunodeficiency virus (HIV) it has been reported that antibodies can enhance infection of phagocytic cells. We show that HIV-1 can infect an Epstein-Barr virus transformed B cell line and that low levels of anti-HIV antibodies enhance infection. The enhanced infection was characterized by an increase in viral DNA and increased HIV p24 protein production. Detection of cell surface antigen expression of CD4, the receptor for HIV, Fc-receptor type II for IgG, but not of type I and III could be demonstrated by immunofluorescence cytometry. The enhancement was abrogated when infection was performed in presence of a monoclonal antibody directed against CD4. Based on these results we conclude that antibody mediated enhancement of HIV-1 infection can also occur in non-phagocytic cells in a CD4 dependent manner and that IgG Fc-receptors other than types I or III are involved in this process.

B-Lymphocytes↗

PubMed1992

Steady-state pharmacokinetics and sputum penetration of lomefloxacin in patients with chronic obstructive pulmonary disease and acute respiratory tract infections.

Oral doses of 400 mg of lomefloxacin were administered once daily prior to breakfast to 10 middle-aged to elderly hospitalized patients with chronic obstructive pulmonary disease during treatment for bronchopulmonary infections. Serial plasma and sputum samples and fractional urine samples were obtained over a steady-state dosing interval. Lomefloxacin concentrations were determined in duplicate by a validated agar well diffusion microbiological assay. The maximum plasma lomefloxacin concentration (4.5 +/- 1.8 mg/liter), the time of occurrence of the maximum concentration (1.7 +/- 1.6 h), and the apparent volume of distribution associated with the terminal phase (2.19 +/- 1.05 liter/kg) were comparable to the values reported for healthy, young volunteers. Compared with the data reported for young adults, the elimination half-life (12.7 +/- 4.67 h) was longer and the apparent total body clearance (132 +/- 36.6 ml/min/1.73 m2) was lower in middle-aged to elderly patients. These differences were most likely attributable to age-related decreases in renal function, as evidenced by the lower lomefloxacin renal clearance (70.3 +/- 33.5 ml/min) in patients. The presence of acute respiratory infection per se did not appear to alter lomefloxacin pharmacokinetics. The peak lomefloxacin concentration in purulent, expectorated sputum samples of 4.3 +/- 1.2 mg/liter occurred 3.1 +/- 1.7 h after dose administration and subsequently declined to 1.7 +/- 0.5 mg/liter at the end of the 24-h dosing interval. The percent penetration into sputum, as assessed by comparing the area under the curve for sputum and plasma samples, was 120 +/- 39.8 (range, 70 to 185). The steady-state lomefloxacin concentrations in plasma and sputum samples from ill, older patients were in excess of the MICs for 90% of the strains tested of common, susceptible respiratory pathogens over most of the dosing interval.

Aged↗

PubMed1992

Imipenem versus gentamicin combined with either cefuroxime or cephalothin as initial therapy for febrile neutropenic patients.

A prospective randomized study was conducted to determine the efficacy of imipenem-cilastatin (hereafter referred to as imipenem) (500 mg four times daily) versus combination therapy for febrile neutropenic patients receiving either no prophylaxis or ciprofloxacin for prevention of infections. Combination therapy consisted of gentamicin (80 mg every 8 h) plus either cefuroxime (1,500 mg every 8 h) or cephalothin (1,000 mg every 4 h) for suspected catheter-related infections. Ninety-four neutropenic fever episodes in 87 patients were evaluable for efficacy. The overall clinical rate of response to imipenem was significantly higher than that to combination therapy (91 versus 74%; P = 0.05). The difference in efficacy was most pronounced in patients with microbiologically documented infections (89 versus 53%; P = 0.025), which were predominantly caused by gram-positive bacteria. Differences in susceptibility may have caused the better rate of response to imipenem. Two of 29 gram-positive bacteria were imipenem resistant, whereas 10 were resistant to cephalothin and cefuroxime and 12 were resistant to gentamicin. No causative gram-negative bacterium and 24 gram-positive bacteria were isolated in 61 fever episodes with ciprofloxacin prophylaxis (oral). In contrast, nine causative gram-negative and five gram-positive bacteria were isolated in 33 episodes without prophylaxis. The difference in distribution proved to be statistically significant for gram-negative (P = 0.0001) as well as gram-positive (P = 0.025) bacteria, indicating that ciprofloxacin effectively prevented the occurrence of gram-negative bacteria and may have contributed to the relatively large number of gram-positive bacteria isolated. Empirical initial therapy with imipenem may be a valuable alternative to combination therapy for neutropenic fever episodes.

Adult↗

PubMed1992

Monoclonal antibodies that detect live salmonellae.

Nine immunoglobulin G and nine immunoglobulin M murine monoclonal antibody-producing hybridomas reactive with live Salmonella bacteria were obtained from several fusions of immune spleen cells and Sp2/0 myeloma cells. The antibodies were selected by the magnetic immunoluminescence assay. The monoclonal antibodies were reactive with serogroups A, B, C1, C2, D, E, and K and Salmonella choleraesuis subsp. diarizonae. Each monoclonal antibody proved to be reactive with a distinct serotype. Clinical isolates belonging to these Salmonella serogroups could be detected. Reactivity with non-Salmonella bacteria proved to be minor.

Animals↗

PubMed1992

The magnetic immuno polymerase chain reaction assay for direct detection of salmonellae in fecal samples.

Direct polymerase chain reaction (PCR)-based detection with fecal specimens is hampered by inhibitory compounds, such as bilirubin and bile salts. These fecal compounds showed significant inhibition of PCR at low concentrations (10 to 50 micrograms/ml). For direct PCR analysis, fecal samples must be diluted 500-fold to overcome inhibition. Therefore, the magnetic immuno PCR assay (MIPA), which combines immunomagnetic separation by using specific monoclonal antibodies and PCR, was used to directly detect salmonellae in feces from humans. Immunomagnetically extracted stool samples needed to be diluted only 10-fold when 1 microgram of T4 gene 32 protein was added to the PCR. The MIPA sensitivity obtained was 10(5) CFU/ml of feces. A panel of monoclonal antibodies specific for Salmonella serogroups A to E was used to extract salmonellae from clinical samples. MIPA detection of salmonellae occurred with 11 out of 14 stool samples stored at 4 degrees C for 2 months. MIPA detection of salmonellae in stool samples is a promising, fast method for detection and identification.

Antibodies, Monoclonal↗

PubMed1992

Exposure of surfactant protein A to ozone in vitro and in vivo impairs its interactions with alveolar cells.

This study focused on the question of whether exposure of surfactant protein A (SP-A) to ozone affected properties of this protein that may be involved in regulating alveolar type II cell and alveolar macrophage functions. In vitro exposure of human or canine SP-A to ozone reduced the ability of this protein to inhibit phorbol-ester induced secretion of [3H]phosphatidylcholine by alveolar type II cells in culture. Ozone-exposed human SP-A showed a decreased ability to enhance phagocytosis of herpes simplex virus and to stimulate superoxide anion production by alveolar macrophages. Experiments with elastase showed that ozone-exposed canine SP-A was more susceptible to proteolysis. A conformational change of the protein could underlie this phenomenon. Surfactant isolated from ozone-exposed rats (0.4 ppm ozone for 12 h) was also less able to stimulate superoxide anion production by alveolar macrophages than surfactant from control rats, which suggested that SP-A in vivo was also susceptible to ozone. The results of this study suggest that SP-A-alveolar cell interactions can be inhibited by ozone exposure, which may contribute to the toxicity of ozone in the lungs.

Animals↗

PubMed1992

Human cytomegalovirus-stimulated peripheral blood mononuclear cells induce HIV-1 replication via a tumor necrosis factor-alpha-mediated mechanism.

Human cytomegalovirus (HCMV) is a potential cofactor in HIV-1 infection. To investigate the mechanism whereby HCMV promotes HIV-1 replication, a PBMC coculture assay which measures HIV-1 p24 antigen release was used as an index of viral replication. HCMV-stimulated PBMC were capable of inducing HIV-1 replication in cocultures with acutely infected PBMC; however, this occurred only when the PBMC were from HCMV-seropositive donors (598 +/- 207 versus 27 +/- 10 pg/ml p24 antigen with PBMC from HCMV-seronegative donors on day 6 of coculture). Upon stimulation with HCMV, PBMC obtained exclusively from HCMV-seropositive donors released tumor necrosis factor (TNF)-alpha (270 +/- 79 pg/ml at 18 h of culture). Monoclonal antibodies to TNF-alpha blocked the activity of HCMV-stimulated PBMC in cocultures both with acutely HIV-1-infected PBMC and with the chronically infected promonocytic line U1. Also, treatment of HCMV-stimulated PBMC with pentoxifylline, an inhibitor of TNF-alpha mRNA, markedly reduced HIV-1 replication in cocultures both with acutely and chronically infected cells. These results indicate that TNF-alpha is a key mediator of HIV-1 replication induced by HCMV-stimulated PBMC and support the concept that this cytokine plays an important role in the pathogenesis of HIV-1 infection.

Cells, Cultured↗

PubMed1992

Direct evidence for antibody bipolar bridging on herpes simplex virus-infected cells.

Cells infected with herpes simplex virus type 1 (HSV-1) express a cell-surface receptor able to bind the Fc portion of immunoglobulin G (IgG). In this study we provide direct evidence that bipolar bridging of antibodies, bound to the surface antigens on HSV-infected cells and to the Fc-receptor through the Fc part, offers the virus a survival advantage. Evidence was obtained by comparing the binding of FITC-labelled protein A, which has a similar binding site on IgG as the HSV-FcR, to cell-bound antibodies on HSV-infected cells and non-infected cells. The effectiveness of antibody bipolar bridging was dependent on the concentration of cell-bound IgG. At low concentrations of serum (0.1%) an 80% reduction in protein A-FITC binding to HSV-infected cells compared to non-infected cells was found. Even at higher concentrations of serum, antibody bipolar bridging resulted in a 40% reduction in the number of 'free' available Fc parts on HSV-infected cells compared to non-infected cells. Furthermore, these findings could be confirmed in a functional assay. The Fc-mediated attachment of granulocytes was significantly lower in HSV-infected cells compared to non-infected cells. From this study we conclude that HSV-FcR, by binding immune IgG in a bipolar fashion, provides the virus with an effective defence mechanism.

Animals↗

PubMed1992

Pharmacokinetics of ciprofloxacin after intraperitoneal administration in uninfected patients undergoing CCPD.

Ciprofloxacin is increasingly used to treat peritoneal dialysis related peritonitis. We studied the pharmacokinetics of intraperitoneally administered ciprofloxacin in six uninfected CCPD patients. In a randomized cross-over setting ciprofloxacin was added either to a long dwell exchange (lastbag) or to four short dwell exchanges (dwell time 1.5 h). Addition of ciprofloxacin (25 mg/l) during the four short dwell exchanges resulted in dialysate levels of 21.1-13.3 mg/l during these exchanges. In the subsequent last bag devoid of ciprofloxacin a dialysate Cmax,D of 1.38 mg/l was observed at 30 min. Mean +/- SD serum Cmax,S was 0.59 +/- 0.29 mg/l after 5.4 h. Instillation of 100 mg/l ciprofloxacin in the last-bag yielded Cmax,D of 99.1 mg/l, falling with a t1/2 of 3.3 h towards levels < 2 mg/l at 19.8 h. A mean +/- SD serum Cmax,S of 0.69 +/- 0.19 was reached after 4 h. During four subsequent 1.5h exchanges without ciprofloxacin dialysate levels were < 0.1 mg/l. Instillation of 25 mg/l ciprofloxacin in the last-bag yielded a Cmax,D of 21.7 mg/l, falling towards levels < 2 mg/l at 15 h with a t1/2 of 3.85 h. A mean +/- SD serum Cmax,S of 0.26 +/- 0.03 was reached after 8 h. We conclude that the rapid absorption of ciprofloxacin from the dialysate into the tissues requires ciprofloxacin to be administered to all CCPD bags to ensure bactericidal dialysate levels. When therapeutic serum levels are required higher intraperitoneal doses or an oral or i.v. loading dose is warranted.

Adult↗

PubMed1992

Bacteroides and Staphylococcus glycocalyx: chemical analysis, and the effects on chemiluminescence and chemotaxis of human polymorphonuclear leucocytes.

Glycocalyx (or slime), which is an important virulence factor of many pathogenic bacteria, was isolated from Bacteroides fragilis, Bacteroides thetaiotaomicron and Staphylococcus epidermidis. Organisms were grown for 24 h in a chemically defined, dialysable liquid medium. Bacteria were centrifuged and the supernatant was concentrated and dialysed against distilled water. Total carbohydrate and protein were estimated using standard methods. Thin layer and gas-liquid chromatography of trifluoro acetic acid hydrolysed and non-hydrolysed samples provided evidence for the presence of polysaccharide, the absence of nucleic acids and lipopolysaccharide and for the identification of the individual sugar residues. Glucose, mannose and galactose (B. fragilis), glucose (B. thetaiotaomicron), and glucose and heptose (S. epidermidis) were the sugar residues detected. Uronic acid and hexosamine were detected in all species. Glycocalyx preparations (1 mg/ml) from Bacteroides and Staphylococcus significantly inhibited the chemiluminescence and chemotactic responses of viable human polymorphonuclear leucocytes (PMNL), but were not toxic for PMNL.

Bacteroides↗

PubMed1991

Inactivation of recombinant human tumor necrosis factor-alpha by proteolytic enzymes released from stimulated human neutrophils.

Activated human neutrophils (PMN) degrade rTNF-alpha resulting in a loss of cytotoxic activity against murine L-929 cells (L cells). This inactivation is mediated through proteases released from activated PMN. Exposure of TNF to H2O2, glucose oxidase, xanthine oxidase, or myeloper-oxidase-H2O2-halide did not affect TNF cytotoxicity for L cells. Exposure to trypsin, chymotrypsin, pronase E, or elastase, however, did diminish TNF bioactivity. FMLP-stimulated PMN in the presence, but not in the absence, of cytochalasin B reduced TNF activity, whereas PMA-stimulated PMN did not affect TNF. Stimulation of PMN with opsonized bacteria also induced TNF inactivation as well as the supernatant of FMLP-stimulated cells. Addition of protease inhibitors to the FMLP-stimulated cytochalasin B-treated PMN abrogated the inactivation of TNF cytotoxicity for L cells, whereas scavengers were not protective. In addition, PMN from a chronic granulomatous disease patient also decreased TNF bioactivity. Inactivation of TNF by activated PMN correlated with granule release and not with superoxide production. Exposure of TNF to proteases and FMLP-activated PMN also resulted in a loss of reactivity with anti-TNF antibodies, as measured by ELISA, and in the formation of an approximately 10-kDa split product from the 17-kDa rTNF molecule. Partial degradation of TNF by proteases released from activated PMN may result in a diminished TNF bioactivity and thereby contribute to the regulation of local inflammatory reactions.

Catalase↗