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Biomedical subjects

G Barden

Publications and source records attributed to G Barden.

16 recordsLinked to original sources
PubMed1997

Modulation of protein kinase C activity in Plasmodium falciparum-infected erythrocytes.

Infection of human erythrocytes with the malaria parasite Plasmodium falciparum induces many morphological and biochemical changes in the host cell. Host serine/threonine protein kinases could be involved in some of these processes. The aim of this study was to determine the effect of infection on red blood cell protein kinase C (PKC) and establish the importance of this enzyme in parasite growth and sexual stage differentiation. Phorbol myristate acetate (PMA)-induced translocation of erythrocyte PKC activity is impaired in erythrocytes enriched for mature asexual stage infected cells. Western blotting shows that this is due to a relative reduction in membrane PKC protein levels rather than inhibition of enzyme activity and analysis of PKC activity isolated from whole cell lysates by DE52 chromatography suggests that total activatable PKC levels are lower in infected erythrocytes. A reduction in PMA-induced activation is also observed in PKC assays performed in situ. Downregulation of erythrocyte PKC by overnight incubation with PMA before infection causes a significant decrease in the rate of the asexual growth, suggesting that the enzyme, although lost later in infection, may be important in the earlier development of the parasite. By contrast, the lack of PKC had no effect on the production of sexual stage parasites.

Animals↗
PubMed1992

Human monoclonal antibodies specific for blood group antigens demonstrate multispecific properties characteristic of natural autoantibodies.

A panel of 72 human monoclonal antibodies with specificities for blood group antigens, A, Rh D, Rh C, Rh c, Rh E, Rh e, Rh G, Jka and Jkb, has been established from the peripheral blood of deliberately immunized donors. Previous work has established that the antibodies are highly specific for their respective blood group antigens, and a number of them are in routine clinical use as blood grouping reagents. This panel was screened for reactivity against six unrelated foreign and autoantigens by ELISA, for rheumatoid factor activity by ELISA and agglutination techniques, and for reactivity with a number of different tissues by immunofluorescence. Binding of the monoclonal antibodies to unrelated exo- and autoantigens was commonly seen amongst the antibodies of the IgM class, and to a lesser degree amongst the IgG class, with reaction patterns similar to those given by natural autoantibodies. Only five of the IgM antibodies failed to demonstrate any unexpected cross-reactivities and these included 1/13 anti-D, 2/7 anti-E, 1/13 anti-c and 1/2 anti-A. We propose that rather than natural autoantibodies representing a distinct population of immunoglobulins, multispecificity (polyspecificity, or polyreactivity) may be a feature of antibodies produced in response to exogenous antigens. The implications of this for the study of autoantibodies are discussed.

Antibodies, Monoclonal↗
PubMed1991

Ability of unstimulated and phorbol-ester-stimulated human blood-monocyte-derived macrophages to metabolize drugs and its implications.

Solutions containing 5,5-diphenyl[4-14C]hydantoin (15 micrograms/ml) or pheno[2-14C]barbital (20 micrograms/ml) were incubated for 0.5-6 h with monolayers of unstimulated and phorbol-ester-stimulated human blood-monocyte-derived macrophages and suspensions of K562 cells. The incubated solutions were centrifuged and the cell-free supernatants subjected to chromatography on Q-Sepharose Fast Flow anion exchange resin. The interaction with unstimulated macrophages but not with K562 cells resulted in a time-dependent conversion of the original radioactive drug molecules to molecules with a larger negative charge in the case of diphenylhydantoin and a smaller negative charge in the case of phenobarbital. These conversions were prevented by 20 mM tetrahydrofurane and partially inhibited by 300 U/ml superoxide dismutase (SOD) and, therefore, appeared to depend on cytochrome-P-450-mediated reactions and to some extent also on superoxide anion radicals. Macrophages which were stimulated by 20 nM phorbol myristate acetate metabolized both drugs at much faster rates than unstimulated macrophages. Since this increased metabolism was abolished in the presence of SOD, it appeared to be entirely dependent on superoxide anion radicals. These data provide biochemical evidence that unstimulated human monocyte-derived macrophages have a substantial capacity to metabolize certain xenobiotics and that stimulated macrophages have an even greater capacity to do so. This property of macrophages may have considerable biological significance and be important in the pathogenesis both of drug-induced tissue damage and of malignant disease.

Chromatography, Ion Exchange↗
PubMed1991

Human monoclonal antibodies against blood group antigens preferentially express a VH4-21 variable region gene-associated epitope.

An anti-idiotypic antibody has been raised which recognizes human immunoglobulins with cold agglutinin activity of anti-I/i specificity. The pattern of reactivity of the antibody indicates that the structural basis for the epitope is located in the VH4-21 gene segment of the VHIV family, which is preferentially utilized by these cold reactive antibodies. Using this antibody, epitope expression was investigated in a panel of 72 human monoclonal allo-antibodies specific for human blood group antigens, as compared with a control panel of 39 randomly selected human monoclonal IgM antibodies of unknown specificities. The anti-blood group panel included 44 IgM and 28 IgG monoclonal antibodies against a variety of blood group antigens including the A antigen, Rh C, c, D, E, e, G antigens, and the Kidd antigens Jka and Jkb. The epitope was expressed by 64% (28/44) of the IgM anti-blood group antibodies and by 21% (6/28) of the IgG antibodies, but by only 7.7% (3/39) of the control IgM antibodies. These data indicate that the human alloimmune response to blood group antigens is biased in the use of VH gene families, with a preference for the VH4-21 gene segment of the VHIV family, or closely related gene segments. The fact that this mirrors the findings for the autoimmune cold agglutinins suggests a link in immunoglobulin gene usage between antibodies against structurally diverse antigens on the red cell surface.

Antibodies, Monoclonal↗
PubMed1991

Human monoclonal antibodies to human blood group antigens Kidd Jka and Jkb.

Three IgM human monoclonal antibodies to Jkb, and one IgM human monoclonal antibody to Jka were produced from the lymphocytes of two immunized donors. Two of the anti-Jkb monoclonal antibodies (MS-7 and MS-9) are of the IgM (kappa) isotype and one (MS-8) is an IgM(lambda). The anti-Jka monoclonal antibody (MS-15) is of the IgM(kappa) isotype. They are all specific for their respective antigens, and give positive agglutinations in saline by the immediate spin technique, even against Jk(a+b+) cells. The heterohybridomas have been shown to be suitable for bulk culture and produce levels of antibody that reach 18 micrograms/ml in the spent culture supernatant. They offer considerable advantages over currently available reagents in terms of stability, simplicity and speed of use, and will provide a reliable and unlimited supply of what are at the moment rare and unsatisfactory antibodies.

Antibodies, Monoclonal↗
PubMed1990

Human monoclonal antibodies to C, c, E, e and G antigens of the Rh system.

A panel of heterohybridomas secreting human IgG and IgM monoclonal antibodies to the C, c, G, E, and e antigens of the Rh system has been established. Both classes of antibody have been shown to react with red blood cells carrying their respective antigens; those of the IgM class being able to directly agglutinate unmodified red blood cells in saline. The heterohybridomas have been shown to be suitable for bulk culture and produce levels of antibody in the range of 15-73 micrograms/ml in the spent culture supernatant.

Antibodies, Monoclonal↗
PubMed1989

Acetaldehyde-modified serum proteins inhibit mitogen-stimulated human lymphocyte transformation.

Sera obtained from healthy volunteers immediately before and 8 h after the rapid consumption of 1.2 g ethanol/kg body weight were dialysed against RPMI 1640 and added ab initio to microcultures of normal human lymphocytes containing 1-3 micrograms phytohaemagglutinin (PHA)/ml or 2-8 micrograms pokeweed mitogen (PWM)/ml. When compared with the pre-alcohol sera, the post-alcohol sera inhibited lymphocyte transformation after 48 h incubation with either mitogen. In other experiments, acetaldehyde-albumin complexes were generated by reacting solutions of human serum albumin with 45-720 microM acetaldehyde, and the same quantity of either unmodified albumin or acetaldehyde-modified albumin was included in freshly-prepared lymphocyte microcultures containing 3 micrograms PHA/ml or 8 micrograms PWM/ml. When compared with unmodified albumin, acetaldehyde-modified albumin inhibited lymphocyte transformation after 48 h of culture with either mitogen. The inhibition of lymphocyte transformation caused by post-alcohol sera and acetaldehyde-modified albumin was partially corrected after treatment of the proteins with 1.55 mM sodium borohydride at a pH of 9.5. The data indicate that post-alcohol sera contain a non-dialysable activity which inhibits mitogen-stimulated lymphocyte transformation in vitro and that at least part of this activity may reside in acetaldehyde-modified serum albumin.

Acetaldehyde↗
PubMed1989

Differences in the nature and kinetics of the ethanol-related circulating cytotoxic proteins in normal subjects and patients with alcohol-induced cirrhosis.

The kinetics and nature of the nondialyzable cytotoxic activity which appeared in the serum after the consumption of 1.2 g ethyl alcohol per kilogram body weight over 45 min was studied in six healthy volunteers and eight patients with histologically proven alcohol-related cirrhosis of the liver. Whereas the cytotoxic activity in the dialyzed serum showed a single peak with a maximum value 8 hr after the start of ethanol consumption in the healthy volunteers, it showed two peaks with maximum values at 2 and 8 hr in the patients with cirrhosis. Studies of the fractions obtained by Sephacryl-S-300 gel filtration of the 2-hr postalcohol serum samples revealed substantial cytotoxic activity in the fractions containing both the albumin peak and the IgG peak in the patients with cirrhosis and only in the fractions containing the albumin peak in the healthy volunteers. Experiments with pure IgG preparations obtained from prealcohol and 2-hr postalcohol sera by chromatography on Q-Sepharose Fast Flow anion-exchange resin showed considerable cytotoxic activity in the preparations from the patients with cirrhosis and little or no cytotoxic activity in those from the healthy volunteers. Thus, the early peak of the biphasic serum cytotoxicity curve seen after ethanol consumption by patients with cirrhosis appeared to be caused by the development of a substantial cytotoxic activity in the IgG molecules during the first 2 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaldehyde↗
PubMed1987

Circulating cytotoxic protein generated after ethanol consumption: identification and mechanism of reaction with cells.

Serum obtained from healthy volunteers 6-7 h after consumption of 60-95 g of ethanol contained cytotoxic activity against mouse A9 cells and all of six human cell lines tested. Affinity chromatography of such sera demonstrated that at least some of the cytotoxic molecules consisted of altered albumin. Complexes formed by the reaction of 14C-acetaldehyde with 125I-labelled human serum albumin in vitro were also cytotoxic. After treatment with a reducing agent, sodium borohydride, the cytotoxicity of both post-alcohol serum and the acetaldehyde-albumin complexes fell sharply, suggesting that the cytotoxic activity resided in the unstable Schiff bases formed during the first stage of reaction between the acetaldehyde and proteins. A detailed analysis of the reaction between the double-labelled acetaldehyde-albumin complexes and K562 cells revealed that the cytotoxic activity resulted from the release of acetaldehyde from such complexes and the preferential binding of the free acetaldehyde to the target cells.

Acetaldehyde↗
PubMed1987

The capacity of macrophages from different murine tissues to metabolise ethanol and generate an ethanol-dependent non-dialysable cytotoxic activity in vitro.

Tissue macrophages obtained from liver, bone marrow, spleen and thymus of C57 BL/6 mice closely resembled blood-monocyte-derived human macrophages in three characteristics. These were: the rate of metabolism of ethanol to acetate, the biochemical pathways involved in ethanol metabolism and the ability to generate an ethanol-dependent non-dialysable cytotoxic activity in vitro. The metabolism of ethanol by all four types of murine tissue macrophage was only slightly suppressed by pyrazole, 4-iodopyrazole and 3-amino-1,2,4-triazole, which are known to inhibit alcohol dehydrogenase (ADH), pi ADH and catalase respectively. By contrast, ethanol metabolism by these cells was strongly suppressed by three inhibitors of the cytochrome P-450-dependent microsomal ethanol-oxidising system--namely, carbon monoxide, metyrapone and tetrahydrofurane.

Acetates↗
PubMed1986

Cytotoxic protein molecules generated as a consequence of ethanol metabolism in vitro and in vivo.

A non-dialysable cytotoxic activity developed in the supernatants of human blood-monocyte-derived macrophages cultured in the presence of ethanol and in the serum of three healthy volunteers who drank 500-700 ml wine over 20-35 min. On 'Sephacryl S-300' gel filtration of the culture supernatants and the serum samples from the subjects who took alcohol, the cytotoxic activity eluted together with albumin molecules. Studies of human serum and of various commercially purchased human serum protein fractions treated with carbon-14-labelled acetaldehyde and non-radioactive acetaldehyde, respectively, provided strong circumstantial evidence that the cytotoxic proteins were albumin molecules that had become complexed with acetaldehyde generated by the metabolism of ethanol. The cytotoxic activity developing in vivo was greatest 6-10 h after the consumption of ethanol started, when blood alcohol levels were normal or only slightly high. The appearance of a circulating long-acting cytotoxic macromolecule after the ingestion of ethanol may be of considerable importance in clarifying the mechanisms underlying ethanol-induced tissue damage.

Acetaldehyde↗
PubMed1983

Pneumococcal pneumonia in hospitalized patients. Clinical and radiological presentations.

The clinical and radiological features of pneumococcal pneumonia were studied in 94 hospitalized patients. Fifty-seven (61%) had a bronchopneumonic pattern on roentgenogram, and 37 (39%), a lobar pattern. Eighty-two (87%) of the patients in both roentgenographic classifications had one or more underlying disease states. There was no difference in the frequency of heart disease, diabetes, chronic pulmonary disease, or malignancy between the two categories. Sputum Gram's stains were also similar in both patterns. Twenty (54%) of the 37 patients with the lobar pattern were bacteremic compared with only five (9%) of the 57 patients with the bronchopneumonic pattern; all five patients with bronchopneumonia and bacteremia had an associated malignancy. Although a lobar pattern is usually emphasized in the diagnosis of pneumococcal pneumonia, this study showed that the majority of patients hospitalized with pneumococcal pneumonia had a roentgenographic bronchopneumonic pattern rather than the classic lobar pattern. Thus, patients with the bronchopneumonic pneumococcal pneumonia pattern may be underdiagnosed. The implications are important both for treatment and for epidemiologic data used in the selection of pneumococcal types for prophylactic vaccines.

Aged↗
PubMed1976

Polymicrobic bacteriuria: significant association with bacteremia.

Current clinical practice states that a urine culture yielding three or more isolates must be considered a contaminated specimen and discarded. The validity of this practice was tested by reviewing all patients at the West Haven Veterans Administration Hospital with positive blood cultures for 1 year to determine how many were associated with polymicrobic bacteriuria (two or more urine isolates each present at greater than 10(5) colonies/ml). During 1973 there were 18 patients who had bacteremia associated with a urinary tract infection in which the same organism with the identical antibiogram was found in both the blood and the urine of these 18 patients with monomicrobic bacteremia 11(61%) had polymicrobic bacteriuria, with a mean of an additional 1.75 urinary pathogens present in significant quantities. In these patients with polymicrobic bacteriuria, an indwelling bladder catheter was present for a mean period of 4.4 months before the episode of bacteremia. Only 5 of the 11 patients with polymicrobic bacteriuria had temporally associated urinary tract manipulation. Monomicrobic bacteriuria occurred in seven patients (39%). The mean indwelling bladder catheter time was 0.9 days, and urinary tract manipulation near the time of bacteremia occurred in all seven patients. Prospectively, nine other patients with polymicrobic bacteriuria were recultured by one of us to be certain that appropriate collection and transportation methods were used; the presence of polymicrobic bacteriuria was repeatedly demonstrated in 7(78%). This study illustrates the clinical importance of polymicrobic bacteriuria.

Aged↗
PubMed1976

Endemicity of multiple staphylococcal phage types: relation of two common source outbreaks.

An outbreak of Staphylococcus aureus bacteremia occurred among patients treated in the hemodialysis unit in 1971. A second outbreak of S. aureus peritonitis occurred in 1973 in patients with chronic indwelling peritoneal catheters cared for together in the medial intensive care unit. Although the attending personnel, patients, and geographical locations were different in each outbreak, the following similarities were notes: (1) more than one phage type was epidemic: (2) an exogenous mode of spread with cross-contamination between personnel and patient as well as between patient and patient, and (3) breaks in sterile technique when handling the arteriovenous shunt site or the peritoneal catheter were made without the staff conducting the procedure being aware of their occurrence. Culture surveys of the same phage types found during the two epidemics. Thus, an endemic reservoir of several different staphylococcal phage types was present. Careful, consistent application of aseptic technique when handling either arteriovenous shunts or peritoneal catheters and hand washing in between patients was required to prevent the endemic strains from becoming epidemic.

Asepsis↗
PubMed1975

The role of the nurse epidemiologist in infection control and continuing education.

A university affiliated Veterans Administration Hospital had an increase in the number of serratia isolates. An epidemiologic investigation, including personnel and environmental prevalence study, helped correct errors in technique, management and judgment. A nurse epidemiologist prevented a cluster of infections from becoming an epidemic.

Connecticut↗