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Biomedical subjects

C A Clark

Publications and source records attributed to C A Clark.

At least 19 recordsLinked to original sources
PubMed1992

Elevated glucose alters A23187-induced release of arachidonic acid from porcine aortic endothelial cells by enhancing reacylation.

Cultured porcine aortic endothelial cells were conditioned in normal (5.2 mM) and elevated (15.6 mM) glucose, prelabeled with [14C]arachidonic acid and stimulated with ionophore A23187. Elevated glucose cultures released less radiolabeled products and less [14C]arachidonic acid. Analysis of cellular lipids revealed that elevated glucose reduced net loss of radiolabel from diacylphosphatidylethanolamine, did not affect early phosphatidylinositol hydrolysis, and increased net loss from diacylphosphatidylcholine and alkenylacylphosphatidylethanolamine. Uptake of radiolabel upon stimulation was examined to measure the role of reacylation on the diminished net release of radiolabel in elevated glucose cultures. Enhanced acylation of [3H]arachidonic acid into cellular lipids, especially PI, was observed in stimulated and resting cultures with elevated glucose. Further, pretreatment of the cultures with an acyltransferase inhibitor, thimerosal, prior to A23187 stimulation in radiolabeled cultures, abolished the effects of glucose on eicosanoid and arachidonic acid release. Differences in the ionophore-induced net loss of radiolabel from diacylphosphatidylethanolamine and phosphatidylinositol of the two glucose treatments were diminished by thimerosal exposure, while net loss of radiolabel from diacylphosphatidylcholine and alkenylacylphosphatidylethanolamine were unaffected. The data indicate that elevated glucose alters deacylation and enhances reacylation of arachidonic acid into endothelial cells and particularly into phosphatidylinositol. Enhanced reacylation may explain some of the altered lipid pathways that have been observed in experiments that elevate glucose concentrations or involve diabetes.

Acylation↗
PubMed1992

Complications associated with the use of an infusion pump during knee arthroscopy.

This is a report of four complications from the use of an automated arthroscopy pump in 283 patients undergoing knee arthroscopy. The first patient had extravasation of fluid into the thigh, requiring discontinuation of the procedure. The second patient developed a compartment syndrome of the leg, necessitating a four-compartment fasciotomy of the leg. The third patient developed severe fluid extravasation into the anterior thigh compartment. A limited fasciotomy of the anterior thigh compartment was performed. The fourth patient developed moderate extravasation into the anterior part of the thigh and groin, necessitating discontinuation of pump irrigation and conversion to gravity irrigation to complete a partial medial meniscectomy. During a 15-month period, a complication rate of 1.4% from fluid extravasation during knee arthroscopy was noted. This review represents our initial experience with the infusion pump. No cases of fluid extravasation have occurred subsequently during a 12-month period.

Adult↗
PubMed1992

Colonization factor antigen CFA/IV (PCF8775) of human enterotoxigenic Escherichia coli: nucleotide sequence of the CS5 determinant.

Human enterotoxigenic Escherichia coli isolates expressing the colonization factor antigen CFA/IV (previously designated PCF8775) produce plasmid-encoded CS5 fimbriae. The nucleotide sequence of the region encoding the major CS5 fimbrial subunit was determined. The subunit is synthesized as a precursor of 203 amino acids (20.85 kDa) with a mature protein of 181 amino acids corresponding to a size of 18.6 kDa. The CS5 subunit shows homology to the corresponding component of porcine enterotoxigenic E. coli F41, particularly within the signal sequence and at the carboxy terminus.

Amino Acid Sequence↗
PubMed1991

Priming of anti-human immunodeficiency virus (HIV) CD8+ cytotoxic T cells in vivo by carrier-free HIV synthetic peptides.

The generation of antiviral cytotoxic T lymphocytes (CTLs) is a critical component of the immune response to viral infections. A safe and nontoxic vaccine for AIDS would optimally use a carrier-free synthetic peptide immunogen containing only components of HIV necessary for induction of protective immune responses. We report that hybrid synthetic peptides containing either a HIV envelope gp120 T-cell determinant (T1) or the envelope gp41 fusion domain (F) N-terminal to HIV CTL determinants are capable of priming murine CD8+, major histocompatibility complex class I-restricted anti-HIV CTLs in vivo. These data demonstrate that carrier-free, nonderivatized synthetic peptides can be used in vivo to induce anti-HIV CTL responses.

Amino Acid Sequence↗
PubMed1991

The oac gene encoding a lipopolysaccharide O-antigen acetylase maps adjacent to the integrase-encoding gene on the genome of Shigella flexneri bacteriophage Sf6.

Lysogens of Shigella flexneri harbouring the temperate bacteriophage, Sf6, have been previously shown to undergo a serotype conversion due to O-acetylation of the O-antigen of the lipopolysaccharide. A partial physical map of the phage genome has been constructed. Analysis of the phage DNA suggests that the phage packages by a headful mechanism and that the mature DNA molecules are terminally redundant. Cloning of the PstI fragments of Sf6 enabled the region encoding the serotype conversion to be localized, showing that this was clearly phage-encoded. The gene was further localized by mutagenesis with Tn5 and the nucleotide sequence of the entire 2693-bp PstI fragment was determined. Two major open reading frames (ORFs) were found capable of encoding proteins of 44.1 and 37.2 kDa. The latter corresponds to the O-antigen acetylase and its gene has been designated oac. The oac gene is capable of converting Sh. flexneri serotypes X, Y, 1a and 4a to 3a, 3b, 1b and 4b, respectively. The Oac protein bears a high degree of homology to the NodX protein of Rhizobium leguminosarum suggesting that it, too, may be a sugar acetylase. The second ORF immediately upstream from oac corresponds to the bacteriophage Sf6 integrase responsible for chromosomal integration and is highly homologous to the integrases of Escherichia coli bacteriophages P4 and phi 80, but less closely related to those of P1, P2, P22, 186 and lambda.

Acetylesterase↗
PubMed1990

Graded exercise testing and postthoracotomy complications.

A controversy exists over whether or not preoperative exercise testing can predict postthoracotomy complications. This study was designed to evaluate the usefulness of a presurgical exercise protocol in patients with lung disease, but no evidence of cardiac disease. Seventy patients underwent baseline pulmonary function testing and split function perfusion studies, when indicated, to calculate predicted postoperative pulmonary function. Noninvasive data were incrementally collected from 17 patients by using a treadmill exercise tolerance test that was designed to elicit maximal performance. Inhaled and exhaled gas flow and volume, the partial pressure of O2 and CO2, maximal O2 consumption (VO2max), and maximal minute ventilation (VE max) were measured. The breathing and heart rate reserves were calculated by standard formulae in an attempt to separate cardiac from pulmonary exercise limitation. Two patients had postoperative cardiopulmonary complications after thoracotomy and lung resection, and six patients had noncardiopulmonary complications. There was no significant prognostic relationship among VO2max, VE max, maximum O2 pulse, and the incidence of postoperative cardiopulmonary complications. The percentages of predicted VE max and predicted maximum heart rate were related to the occurrence of total complications, but not specifically to cardiopulmonary complications. The results emphasize the difficulty in attempting to exercise thoracotomy candidates with chronic lung disease to maximal performance. Excluding patients from further surgical consideration because of exercise limitation is not feasible based on these data.

Aged↗
PubMed1990

The effects of capsular polysaccharide on the capacity of serum to support the killing of type 3 Streptococcus pneumoniae by human neutrophils.

To assess the effects of purified capsular polysaccharide from type 3 S. pneumoniae (PPS-3) on the capacity of serum to support pneumococcal killing by human neutrophils, varying concentrations of PPS-3 (0.01-100 micrograms/ml) were incubated (4 degrees C) with pooled serum for 30 min, and the resulting preparation, termed absorbed serum, was evaluated in bactericidal and phagocytic assays. The ability of serum to promote the killing of type 3 S. pneumoniae was significantly reduced at greater than or equal to 1.0 micrograms/ml PPS-3; similarly, serum absorbed with greater than or equal to 1.0 micrograms/ml PPS-2 failed to support the killing of type 2 S. penumoniae. However, the impact of these penumococcal polysaccharides was serotype specific, since the killing of type 3 S. pneumoniae was not impaired in serum absorbed with PPS-2, and the killing of type 2 S. pneumoniae was not attenuated in serum treated with PPS-3. The failure of serum absorbed with PPS-3 to promote the killing of type 3 S. pneumoniae was primarily a consequence of impaired bacterial ingestion; the reduction in phagocytosis was associated with parallel changes in superoxide anion release. The defects in phagocytosis and killing induced by PPS-3 were not associated with alterations in classical or alternative complement pathway activity; however, they were highly correlated with changes in serum antibody levels to the polysaccharide. The addition of polyclonal human IgG to serum treated with PPS-3 did not restore its capacity to support killing; however, preopsonization of the bacterium with the IgG preparation did partially correct the deficiency. Finally, neutrophils preincubated with serum containing greater than or equal to 10.0 micrograms/ml PPS-3 exhibited an impaired bactericidal activity against type 3 S. pneumoniae. Thus, these studies demonstrate that the presence of PPS-3 decreases the capacity of serum to support the killing of type 3 S. pneumoniae by absorbing immunoglobulins and by generating factors that interfere with neutrophil function.

Adult↗
PubMed1990

In vitro assessment of chemotaxis by peripheral blood neutrophils from adult and senescent C57BL/6 mice: correlation with in vivo responses to pulmonary infection with type 3 Streptococcus pneumoniae.

To assess the effects of advanced age on the ability of circulating neutrophils to respond to biologically relevant chemoattractants, cells were isolated from the peripheral blood of pathogen and disease-free C57BL/6 mice and evaluated in a microchemotaxis chamber. The responses of granulocytes obtained from senescent mice (26-28 months) to the chemotactic peptide, FMLP, and to leukotriene B4 were similar to those found with cells from the younger animals (8-10 months). In contrast, the migration of neutrophils in response to sonicated type 3 Streptococcus pneumoniae was significantly greater with cells from the older animals. Similarly, the chemotactic response of neutrophils to zymosan-activated serum was greater with cells and serum from the senescent animals; however, the enhanced chemotaxis exhibited by granulocytes from the aged mice was a consequence of serum factors. Following the deposition of viable type 3 S. pneumoniae into the lower respiratory tract, the neutrophil influx at 24 h after challenge was significantly greater in the senescent mice; however, age-related differences in survival rates and LD50 were not detected. Thus, in the C57BL/6 mouse, senescence is not associated with deficiencies in the response of neutrophils in vitro to chemoattractants that contribute to lung host defense against the pneumococcus; further, in this murine strain, advanced age does not result in an attenuation of the pulmonary inflammatory reaction to infection with type 3 S. pneumoniae.

Aging↗
PubMed1990

An assessment of the factors contributing to the killing of type 3 Streptococcus pneumoniae by human polymorphonuclear leukocytes in vitro.

To characterize the factors that contribute to the killing of type 3 S. pneumoniae, human neutrophils were obtained from healthy donors and incubated with viable organisms. In contrast to prior observations with other pneumococcal serotypes, killing was not detected when 10(6) colony forming units (cfu) were incubated at 37 degrees C for 2-4 hours with 10(6) neutrophils in the presence of 20-80% fresh autologous serum; further, pneumococcidal activity was not found when preopsonized bacteria and primed neutrophils were employed in the standard assay. However, when the bacterium to cell ratio was reduced to 1:100 and 1:1000, microbicidal action was detected; a 10-fold reduction in the number of viable bacteria was observed when 2 x 10(3) cfu were incubated with 2 x 10(6) neutrophils and 80% autologous serum at 37 degrees C for 4 hours. To assess the effects of serum factors on killing, bactericidal assays were performed in the presence of normal human serum (NHS), heat-inactivated human serum (HIHS) and absorbed human serum (AHS); heating reduced and absorption eliminated the capacity of serum to support killing. Studies performed with mutanolysin, an enzyme that lyses type 3 pneumococci, demonstrated that the effects of HIHS and AHS on bactericidal activity were highly correlated with alterations in the ability of the sera to support phagocytosis. Studies of neutrophil activation revealed changes in the production of superoxide anion that correlated well with phagocytosis and killing; however, the results of assays of leukotriene B4 generation and degranulation (beta-glucuronidase and lactoferrin release) were more variable. In mixing experiments, the capacity of HIHS to support killing was normalized with NHS; however, the ability of AHS to promote killing was not restored with HIHS or NHS. Thus, these studies demonstrate the relatively limited capacity of human serum to support the killing of type 3 pneumococci, and they emphasize the importance of killing assays in assessing interactions between the bacterium and neutrophils.

Blood Bactericidal Activity↗
PubMed1989

The release of neutrophil chemoattractant activity by bronchoalveolar macrophages from adult and senescent mice.

To assess the effects of advanced age on the release of neutrophil chemoattractant activity by resident bronchoalveolar macrophages (BAM), cells from three strains of pathogen- and disease-free mice were secured by lung lavage and stimulated in vitro with unopsonized zymosan or the calcium ionophore, A23187. Chemoattractant release by BAM from adult (5-8 mos) and senescent (19-26 mos) C57BL/6 and DBA/2 mice in response to both stimulants was comparable; however, the generation of chemoattractant activity by BAM from senescent (18-20 mos) BALB/c mice was greater than that observed with cells from younger (4-6 mos) animals with both zymosan and A23187. In the presence of 50 microM piriprost potassium, a 5-lipoxygenase inhibitor, the release of chemoattractant activity and leukotriene B4 (LTB4) in response to zymosan and A23187 by BAM from both groups of C57BL/6 mice was significantly impaired. With BAM from BALB/c mice, 100 microM piriprost potassium was required to produce changes in A23187-stimulated chemoattractant and LTB4 release; of note, the generation of LTB4 in response to A23187 by BAM from aged BALB/c mice was significantly greater than that observed with cells from the younger animals under all conditions studied. Finally, with BAM from DBA/2 mice, 50 microM piriprost potassium significantly reduced chemoattractant activity in both groups of animals, but the lipoxygenase inhibitor had no effect on LTB4 production. Thus, although these studies revealed substantial age and strain-related differences in the release of neutrophil chemoattractant activity by murine BAM, they did not demonstrate deficiencies that might enhance the susceptibility of the senescent host to infection of the lower respiratory tract.

Aging↗
PubMed1989

The cardiac glycoside digoxin disrupts host defense in experimental pneumococcal pneumonia by impairing neutrophil mobilization.

Normal CD-1 mice were administered digoxin (4 micrograms/kg/24 h) and infected with type 3 Streptococcus pneumoniae in order to assess the effects of the cardiac glycoside on the chemotactic responsiveness of peripheral blood neutrophils and the mobilization of granulocytes from storage pools. The chemotactic responses to autologous zymosan-activated serum (C5a) by neutrophils obtained from uninfected digoxin-treated and control animals were similar; comparable observations were made with circulating granulocytes isolated from animals at 24 or 48 h after intratracheal challenge with 5 x 10(5) colony-forming units (cfu) of bacteria. However, at 4 and 6 h after intratracheal pneumococcal challenge, the number of immature neutrophils in the peripheral blood was significantly lower in the glycoside-treated animals versus controls; at 24 and 48 h, these differences were not apparent. Following the intravenous inoculation of pneumococci, the number of circulating immature neutrophils was also found to be significantly lower at 4 and 24 h in animals given the cardiac glycoside versus controls. We conclude that digoxin disrupts host defense in experimental pneumococcal pneumonia and bacteremia by impairing the mobilization of neutrophils.

Animals↗
PubMed1988

An assessment of the respiratory burst and bactericidal activity of alveolar macrophages from adult and senescent mice.

To assess the effects of advanced age on the nonspecific antimicrobial activity of resident alveolar macrophages (AM), superoxide anion (O2-) release and the phagocytic and bactericidal capacity of cells from three genetically distinct murine strains were evaluated. In initial experiments, resident AM, obtained by bronchoalveolar lavage of pathogen-free adult female CD-1 mice and studied in suspension, were found to produce O2- spontaneously and in response to phorbol myristate acetate (PMA) snd unopsonized zymosan. Maximum quantities of O2- were released following stimulation with 1 microgram/ml PMA and by a particle-to-cell ratio of 100:1 with zymosan; responses to the agonists peaked between 60 and 90 min. Resident AM obtained from pathogen and disease-free senescent (18-26-month-old) female C57BL/6, BALB/c, and DBA/2 mice released significantly more O2- in response to both PMA and zymosan than did cells secured from adult (4-8-month-old) animals. In vivo, the capacity of AM from adult and senescent animals to phagocytose Streptococcus pneumoniae (unencapsulated strain) and Staphylococcus aureus was comparable, and although the cells from the senescent mice tended to be more efficient in their ability to kill internalized bacteria, statistically significant differences between the two groups were not observed. The results of these studies indicate that the enhanced susceptibility of the senescent host to infection of the lower respiratory tract cannot be attributed to age-related changes in the nonspecific antimicrobial activity of resident AM.

Aging↗
PubMed1988

Protease inhibitor eglin-c affects superoxide anion release but not bacterial killing by human polymorphonuclear leukocytes.

In order to assess the influence of the protease inhibitor eglin-c on superoxide anion (O-2) release by human polymorphonuclear leukocytes (PMN), cells were secured from normal donors and stimulated with phorbol myristate acetate (PMA), opsonized zymosan, or n-formyl-methionyl-leucyl-phenylalanine (FMLP). In the presence of 100 micrograms/ml eglin-c, the activation time was prolonged and the maximum linear rate of O-2 formation was depressed following stimulation with PMA; a concentration of 1000 micrograms/ml eglin-c was required to produce a similar effect with opsonized zymosan. Eglin-c did not influence the activation time following stimulation with FMLP, but at 2000 micrograms/ml, the protease inhibitor attenuated the rate of O-2 production in response to the chemotactic peptide. In the presence of cytochalasin B, the inhibitory effect of eglin-c on O-2 release following stimulation with FMLP became more pronounced. In spite of these alterations in O-2 formation, the protease inhibitor did not impair the bactericidal activity of PMN against Staphylococcus aureus. Therefore, we conclude that although eglin-c can disrupt the activation and the activity of the superoxide-generating system of human PMN, the effect is stimulus dependent and is not associated with an alteration in the microbicidal capacity of neutrophils against S. aureus.

Anions↗
PubMed1979

Effect of information feedback on temporal discrimination in concurrent and post-feedback measures.

College students estimated time intervals (5, 6, 7, 8, and 9 sec.) where one group (N = 20) received information feedback in terms of actual interval durations and a second group (N = 18) received no information. Theshold measures were then taken for all subjects using the method of constant stimuli (comparison stimuli of 5, 6, 7, 8, and 9 sec. and a 7-sec. standard). In addition to increased accuracy and consistency of judgments, the feedback group showed a decreasing Weber fraction during the estimation phase, while the Weber fraction for the no-feedback group increased. The feedback group retained only a slight advantage in subsequent threshold measures; group differences in difference thresholds and derived nonparametric estimates of d' were nonsignificant.

Differential Threshold↗