Biomedical subjects

E Y Chi

Publications and source records attributed to E Y Chi.

At least 19 recordsLinked to original sources

PubMed1992

Human spermatozoa produce C16-platelet-activating factor.

Recent data indicate that human spermatozoa produce platelet-activating factor as determined by the rabbit platelet [3H]serotonin release bioassay. In this report, we examined by fast atom bombardment/mass spectrometry the molecular species of platelet-activating factor generated by these germ cells. Extracted spermatozoal samples that contained platelet-activating factor bioactivity underwent straight-phase high-performance liquid chromatography, and fractions which coeluted with authentic C16- and C18-platelet-activating factor standards were subjected to fast atom bombardment/mass spectrometry. Our mass spectral data indicate that human spermatozoa synthesize C16-platelet-activating factor but not C18-platelet-activating factor.

Fatty Acids↗

PubMed1992

Degranulation of cystic fibrosis nasal polyp mast cells.

The ultrastructure of nasal polyps from cystic fibrosis (CF) patients was compared with non-CF nasal polyps in this study. Morphometric analysis showed that CF nasal polyps contained greater numbers of mast cells, endothelial cells, lymphocytes, and plasma cells compared with the non-CF specimens. Morphologic evidence of degranulation was seen in approximately 30 per cent of the CF mast cells but was not observed in the non-CF mast cells. Increased numbers of small granules, vacuolated granules, and lipid bodies were noted in the CF compared with the non-CF nasal polyp mast cells. Also observed was a decrease in collagen in the extracellular space of the CF nasal polyps compared with the non-CF specimens. Although eosinophils were observed in the non-CF nasal polyp tissue, these leukocytes were absent in the CF nasal polyps. These data indicate that striking morphologic differences exist between CF and non-CF nasal polyps with mast cell degranulation, a salient feature of CF specimens.

Adolescent↗

PubMed1992

Cytotoxic activity of 13-hydroxyoctadecadienoic acid against Toxoplasma gondii.

Recent data indicate that platelets may play an important role in the host defence against Toxoplasma gondii infections. T. gondii-stimulated human platelets release thromboxane A2 (TXA2) and 12-hydroxyeicosatetraenoic acid (12-HETE) from arachidonic acid and 13-hydroxyoctadecadienoic acid (13-HODE) from linoleic acid (Yong et al. 1991; Henderson et al. 1992). We have previously demonstrated that the eicosanoid TXA2 has potent cytotoxic activity against T. gondii trophozoites (Yong et al. 1991). In this study, we examined whether 12-HETE, 13-HODE, and linoleic acid also have toxoplasmacidal activity. 13-HODE at concentrations > or = 10(-8) M rapidly induced cytotoxic changes in T. gondii. Ultrastructural changes induced by 13-HODE in T. gondii included an initial leakage of cytoplasmic contents into a space between the inner and outer parasite bilayer membrane units which was followed by intracellular vacuolation and loss of cytoplasmic contents. In contrast, linoleic acid and 12-HETE lacked toxoplasmacidal activity at 10(-10)-10(-6) M concentrations. These data indicate that 13-HODE, a product of linoleic acid metabolism, has potent cytotoxic activity against T. gondii; this toxoplasmacidal activity may be important in the inflammatory response to this pathogen.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1992

The effect of type-specific polysaccharide capsule on the clearance of group B streptococci from the lungs of infant and adult rats.

To study the importance of the type-specific polysaccharide capsule of group B streptococci (GBS) in the pathogenesis of lung infections, bacterial clearance rates and lung cellular responses to encapsulated and unencapsulated variants of types III and Ia GBS strains were investigated in rats. Bacteria were instilled by direct intratracheal inoculation to simulate aspiration during parturition. Neonates failed to eliminate encapsulated or unencapsulated GBS strains within 6 h of inoculation, whereas adults cleared greater than 90% of each strain within 6 h. Neutrophils accumulated rapidly in the lungs of neonates and adults in response to all GBS strains. Immediately after inoculation, neonatal alveolar macrophages contained fewer encapsulated GBS than did adult alveolar macrophages and fewer encapsulated than unencapsulated GBS, suggesting that the capsule impairs the initial phagocytosis of GBS in the lungs of neonates. Animal age was a more important determinant of bacterial elimination from the lung than the type-specific GBS capsule. However, both age and the bacterial capsule were important determinants of systemic dissemination.

Animals↗

PubMed1992

Respiratory epithelial cell invasion by group B streptococci.

Group B streptococci (GBS) are the most common cause of pneumonia and sepsis during the neonatal period; however, the pathogenesis of this infection is poorly understood. We investigated the ability of GBS to enter epithelial cells in culture. Two strains of GBS were capable of invading immortalized respiratory epithelial cell lines in vitro at different levels, suggesting strain differences in invasiveness. Intracellular replication was not observed. Invasion required actin microfilaments but not microtubular cytoskeletal elements. Active bacterial protein, DNA, and RNA syntheses were required for invasion. These findings are consistent with our previous observation of intracellular GBS in the lungs of infected primates. We hypothesize that this organism may access the bloodstream by direct invasion of the epithelial cell barrier.

Adult↗

PubMed1992

[Study on mast cells in experimental silicosis].

Quantitative and ultrastructural changes of mast cells (MC) were studied in rat lungs after inhalation of quartz particles. The number of degranulating MC was remarkably increased two weeks and 4 weeks after quartz inhalation (P < 0.05). The average number of the MC per unit area (mm2 of tissue section) and distribution in both experimental and control groups were similar and the mast cells were mainly distributed in the subpleural, perivascular and peribronchial connective tissues. The average number of MC per unit area significantly increased with pulmonary fibrosis three months later. Most of them infiltrated in the fibrotic alveolar septa and fibrotic areas, and the number of degranulating MC was also remarkably increased (P < 0.05). In addition, electronic microscopy showed that mast cells came into contact with fibroblast-like cells and the mast cells usually became degranulated in appearance. These results suggest that there is a close relationship between MC and silicotic fibrosis.

Animals↗

PubMed1991

Identification of two neutrophil chemotactic peptides produced by porcine alveolar macrophages.

We have purified to homogeneity two distinct 10-kDa proteins with potent chemotactic activity for neutrophils from porcine alveolar macrophages incubated for 24 h with Escherichia coli endotoxin (lipopolysaccharide (LPS), 10 micrograms/ml). Neutrophil chemotactic activity in alveolar macrophage supernatants was concentrated by adsorption to SP-Sephadex, and purified by cation exchange and reversed phase high performance liquid chromatography. The first peptide, alveolar macrophage chemotactic factor (AMCF)-I, had chemotactic activity for both porcine and human neutrophils. The chemotactic activity for porcine neutrophils was detectable at 3 x 10(-10) M, peaked at 3 x 10(-8) M, and was comparable to that of zymosan-activated porcine serum. Segmental instillation of AMCF-I into porcine lungs caused marked neutrophil accumulation at 4 h in both bronchoalveolar lavage fluid and in lung tissue. The second peptide, AMCF-II, was active at 1.4 x 10(-9) M for porcine neutrophils, but it was less active for human polymorphonuclear neutrophils than was AMCF-I. Oligonucleotide probes to regions of the N-terminal sequences of AMCF-I and AMCF-II hybridized to mRNA recovered from LPS-stimulated alveolar macrophages. The N-terminal sequences and amino acid compositions indicate that AMCF-I and AMCF-II are distinct proteins, but that both have homologies with a family of peptide chemoattractants produced by human blood monocytes and platelets. Thus, alveolar macrophages stimulated with LPS produce two distinct 10-kDa cytokines with potent chemotactic activity for neutrophils. This indicates that there are two different peptide pathways by which alveolar macrophages can recruit neutrophils into the lung.

Amino Acid Sequence↗

PubMed1991

Human platelet-mediated cytotoxicity against Toxoplasma gondii: role of thromboxane.

Human platelets, in the absence of antibody, are cytotoxic to tachyzoites of Toxoplasma gondii as determined by vital staining, transmission electron microscopy, and the failure of Toxoplasma to survive and replicate in mice after in vitro interaction of the organisms with platelets. Platelet to T. gondii ratios as low as 1:3 were toxic to the organisms with direct cell-cell contact essential for platelet-mediated cytotoxicity. Adherence of platelets to T. gondii and disruption of surface membranes and cytoplasmic contents of the organisms were observed ultrastructurally. Reactive oxygen species were not implicated in the platelet-mediated toxicity. The interaction of T. gondii with platelets resulted in a marked increase in thromboxane B2 (TXB2) production compared with that by unstimulated platelets. The cyclooxygenase inhibitors acetylsalicylic acid and indomethacin inhibited platelet-mediated cytolytic activity as did the selective TXA2 synthetase inhibitor dazmegrel, indicating a role for thromboxane in the platelet-induced cytotoxicity. Further, toxoplasmacidal activity was retained in the TXA2 synthetase-containing microsomal fractions of platelets disrupted by freezing and thawing; cytolytic activity was absent in microsome-depleted platelet supernatant fractions. Both the TXA2-generating platelet microsome system and a stable TXA2 analogue induced damage to the cellular membranes of the Toxoplasma as noted by transmission electron microscopy. These findings suggest that platelets may play a role in the host defense against Toxoplasma and that release of thromboxane may be important in this cytolytic process.

Animals↗

PubMed1991

Pathophysiology and histopathology of group B streptococcal sepsis in Macaca nemestrina primates induced after intraamniotic inoculation: evidence for bacterial cellular invasion.

Four pregnant Macaca nemestrina dams at 140-145 days of gestation received an intraamniotic inoculation of group B streptococci (GBS). All four premature infants were born by cesarean delivery, were bacteremic at birth, and showed symptoms of GBS sepsis similar to infected human infants with early-onset disease. Three infants did not receive antibiotics and died of GBS sepsis by 10 h of age despite mechanical ventilation and fluids for blood pressure support. Penicillin treatment of the fourth infant prolonged survival and decreased the requirement for supportive therapy. Quantitative cultures and histopathology were done on all four infants. Transmission electron microscopy of lung tissue demonstrated GBS within membrane-bound vacuoles of type I and II alveolar epithelium and interstitial fibroblasts. This model should be useful for studying the early steps in the pathogenesis of early-onset GBS infections. GBS may enter alveolar epithelial cells to transit this barrier and ultimately disseminate via the blood-stream.

Animals↗

PubMed1991

Complement activation is a secondary rather than a causative factor in rabbit pulmonary artery ischemia/reperfusion injury.

We have previously demonstrated that reperfusion of a rabbit lung in vivo after 24 h of unilateral pulmonary artery occlusion results in edema, transient leukopenia, and intravascular leukocyte aggregation. We hypothesized that complement was activated by reperfusion and that this in turn contributed to lung injury. In the preliminary phase of the study, we found that ischemia followed by reperfusion resulted in a drop in C3 to 15 +/- 10% (mean +/- SEM) of the prereperfusion value as compared with no change in a group of control animals that had undergone an identical thoracotomy but without pulmonary artery occlusion and reperfusion (p less than 0.05). We then studied three groups of animals to determine if complement depletion with cobra venom factor (CVF) prior to ischemia and reperfusion would prevent the injury. Rabbits treated with CVF but without occlusion and reperfusion did not develop significant lung edema, with left and right lung wet/dry ratios of 5.32 +/- 0.11 and 5.26 +/- 0.12, respectively. For rabbits that were not treated with CVF but underwent ischemia and reperfusion, the comparable numbers were 6.15 +/- 0.36 and 5.19 +/- 0.32 (p less than 0.05 for right versus left). For CVF-treated rabbits that underwent ischemia and reperfusion, the right/left difference persisted (6.77 +/- 0.48 versus 5.35 +/- 0.14, p less than 0.01). Immunocytochemistry documented C3 deposition in non-CVF rabbits that underwent ischemia and reperfusion but not in CVF-treated rabbits. We conclude that ischemia/reperfusion of the lung results in complement activation, but it is not a complement-dependent injury.

Animals↗

PubMed1991

Effect of high-frequency ventilation on the development of alveolar edema in premature monkeys at risk for hyaline membrane disease.

High-frequency oscillatory ventilation (HFOV) permits adequate gas exchange but avoids the large phasic pressure-volume excursions of conventional mechanical ventilation (CMV); such avoidance may reduce the lung injury associated with hyaline membrane disease (HMD). We hypothesized that premature monkeys ventilated from birth with HFOV would have reduced lung injury compared to those assigned to CMV. Macaca nemestrina were delivered at 134 days (80% of term gestation) and ventilated from the first breath with either HFOV (n = 10) or CMV (n = 10). The mean airway pressure (Paw) was kept at 15 cm H2O pressure in HFOV animals; in CMV animals Paw was increased from 8 cm H2O at 2 h to 13 cm H2O at 6 h to prevent hypoxemia. At the conclusion of the 6-h experiment the HFOV animals had better oxygenation (p less than 0.05) and less evidence of HMD by chest radiograph (p less than 0.05). At 6 h of age a piece of the right middle lung lobe was removed, divided, and placed in fixatives for light and transmission electron microscopy. The lungs were subsequently inflated to 30 cm H2O pressure, and the right lower lobe was rapidly frozen in situ for morphometric studies. The proportion of peripheral lung tissue occupied by clear alveoli was greater in HFOV animals (66.3 +/- 14.8%) than in those assigned to CMV (44.2 +/- 16.9%, p less than 0.01); less alveolar debris and fluid was present in the HFOV animals (12.7 +/- 9.9%) compared with CMV animals (27.1 +/- 12.5%, p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Pulmonary effects of continuous endotoxin infusion in the rat.

A major hindrance to the elucidation of the pathogenesis of the adult respiratory distress syndrome (ARDS) is the lack of an animal model consistent with the clinical course in humans. A continuous intravenous infusion of endotoxin (LPS) over a several day period was used to more closely parallel the clinical setting. Male Sprague-Dawley rats infused with LPS via indwelling right atrial catheters become tachypneic, lethargic and anorectic with a steady loss in body weight. Serial blood gas analyses demonstrate an early respiratory alkalosis followed by increasing acidosis and hypoxia. Lungs demonstrate 1) pulmonary leukoaggregation, 2) interstitial and intraalveolar edema, 3) Type I pneumocyte injury, 4) proliferation of Type II pneumocytes, and 5) thickening of the microvascular walls. Differential neutrophil count in bronchoalveolar lavage (BAL) fluid increased from 1% to a peak of 59.1% +/- 3.0% and protein content was elevated. A prolonged infusion of LPS in the rat produces a lung injury which mimics many of the pathophysiologic and histologic features associated with sepsis-induced ARDS in humans.

Animals↗

PubMed1990

Inhibition of leukocyte adherence by anti-CD18 monoclonal antibody attenuates reperfusion injury in the rabbit ear.

Tissue injury resulting from ischemia and reperfusion forms the basis of several important disorders including myocardial infarction, stroke, and circulatory shock. To examine the role of neutrophils in this process and to determine the extent to which injury is a consequence of reperfusion, we utilized the monoclonal antibody 60.3, directed to CD18, the human leukocyte adherence glycoprotein, to block intravascular neutrophil aggregation and neutrophil adherence to endothelium in a rabbit model of tissue ischemia and reperfusion. Antibody treatment either before ischemia or after ischemia, but prior to reperfusion, resulted in the same degree of significant protection against endothelial, microvascular, and tissue injury. We conclude that neutrophils and increased neutrophil adhesiveness are important in the development of microvascular and tissue injury after ischemia and reperfusion and that under these circumstances, injury is primarily a consequence of reperfusion.

Animals↗

PubMed1990

Collagen synthesis during lung development and during hyaline membrane disease in the nonhuman primate.

To assess maturational changes in collagen synthesis, lung tissue was obtained from healthy Macaca nemestrina monkeys at different ages, ranging from 68% of term gestation to adulthood. We hypothesized that infants delivered prematurely have a greater rate of collagen synthesis than do older animals because of their greater rate of lung growth during gestation. Secondly, we hypothesized that lung repair in infants with hyaline membrane disease (HMD) is associated with an additional increase in lung collagen synthesis rate. Therefore, lung tissue was obtained during the first week of life from monkeys delivered at 82% of term gestation, a stage at which half of them developed HMD. The rate of total protein synthesis in lung samples was determined by measuring the incorporation of [3H]proline; the rate of collagen synthesis was determined by measuring the conversion of proline into hydroxyproline. Premature monkeys had a higher rate of collagen synthesis (9.9 +/- 2.7 nmol/mg DNA/h) than did term infants (5.3 +/- 1.1) or older animals (2.1 +/- 0.4, p less than 0.05). There was no additional increase in rate of collagen synthesis in animals with HMD from 3 h (14.3 +/- 6.9) to 7 days of age (15.1 +/- 6.1); control premature animals also had no significant change during the first week of life (10.9 +/- 3.0 at 3 h; 11.6 +/- 4.6 at 7 days). The early stage of recovery from HMD in premature monkeys does not appear to be associated with an increase in collagen production beyond the already increased synthesis rate associated with lung growth.

Analysis of Variance↗

PubMed1990

Mechanisms for reduced total lung capacity at birth and during hyaline membrane disease in premature newborn monkeys.

To determine whether the cause of reduced total lung capacity (TLC) in hyaline membrane disease (HMD) is due to alveolar collapse, alveolar edema, or both, TLC was measured by N2-washout in premature Macaca nemestrina monkeys during the first 3 h of life. The TLC of animals with HMD was only one-third that of healthy premature monkeys over the first 3 h of life (p less than 0.01). At 3.5 h, lung tissue was rapidly frozen in situ during lung inflation to TLC. Samples of frozen lung tissue were freeze dried, embedded, sectioned, and examined by point counting. Animals with HMD had alveolar saccules filled with the residue of proteinaceous fluid, but little alveolar collapse was noted. The proportion of points falling on empty alveolar spaces was 74% in the healthy animals but only 18% in animals with HMD (p less than 0.01); there was a 70-fold increase in the residue present in alveoli of animals with HMD (p less than 0.05). In a separate experiment, rapid serial measurements of TLC by N2-washout showed that healthy premature monkeys, but not those with HMD, have a steady increase in TLC during the first few minutes of life, presumably due to clearance of lung liquid. Although the initial cause of reduced TLC in HMD appears to be inadequate clearance of fetal lung liquid, by 3 h of age proteinaceous alveolar edema is primarily responsible.

Animals↗

PubMed1990

Ultrastructural studies on the effect of tumor necrosis factor on the interaction of neutrophils and Naegleria fowleri.

Naegleria fowleri is the common etiologic agent of primary amebic meningoencephalitis (PAM). We investigated the interaction of human neutrophils with Naegleria trophozoites and examined the effect of neutrophil stimulation by the recombinant human tumor necrosis factor (TNF) on this interaction. As indicated by scanning and transmission electron microscopy, TNF stimulated the adherence of neutrophils to N. fowleri with destruction of the ameba. Neutrophil iodination, an indirect measure of stimulation, increased from 0.81 +/- 0.23 nmol/10(7) cells/hr to 2.41 +/- 0.62 nmol/10(7) cells/hr following the addition of TNF to the neutrophil-N. fowleri mixture (P less than 0.05). This was independent of complement or specific immunoglobulin. Ingestion of neutrophils by Naegleria trophozoites was observed following more prolonged incubation, particularly in the absence of TNF. These findings suggest a role for TNF-mediated destruction of Naegleria trophozoites by neutrophils in host defense, and that ingestion of host neutrophils by Naegleria trophozoites may represent a virulence factor.

Animals↗

PubMed1989

The toxicity of constituents of cedar and pine woods to pulmonary epithelium.

Occupational exposure to cedar and pine woods and pine resin (colophony) can cause asthma and chronic lung disease. Prior studies suggest that plicatic and abietic acids are responsible for the asthmatic reactions that occur in cedar-wood and colophony workers; however, the etiologic mechanism(s) of the chronic lung disease is unknown. To determine if plicatic acid from cedar wood and abietic acid from pine resin could directly damage lung cells, we exposed monolayers of rat type II and human A549 alveolar epithelial cells, intact rat lungs, and rat tracheal explants to solutions of plicatic and abietic acids. As indices of injury, we measured lysis of alveolar epithelial cells with a 51Cr technique, quantitative desquamation of epithelial cells from tracheal explants, and histologic alterations in tracheal explants and intact lungs. Plicatic and abietic acids both caused dose- and time-dependent lysis of alveolar epithelial cells. Instillation of plicatic and abietic acids into rat lungs produced bronchial epithelial sloughing. Abietic acid also caused destruction of the alveolar epithelium. The addition of either acid to rat tracheal explants caused epithelial desquamation that was dose- and time-dependent. Our results suggest that plicatic acid, a unique constituent of cedar wood, and abietic acid, the major constituent in pine resin, can produce lytic damage to alveolar, tracheal, and bronchial epithelial cells. We hypothesize that repeated occupational exposure to these substances might promote the chronic lung damage observed in some cedar- and pine-wood workers and in electronic workers exposed to colophony.

Abietanes↗

PubMed1989

Lack of alveolar O2 during lung reperfusion does not decrease edema formation.

We previously reported that pulmonary arterial occlusion for 48 h followed by 4 h of reperfusion in awake dogs results in marked edema and inflammatory infiltrates in both reperfused and contralateral lungs (Am. Rev. Respir. Dis. 134: 752-756, 1986; J. Appl. Physiol. 63: 942-950, 1987). In this experiment we study the effects of alveolar hypoxia on this injury. Anesthetized dogs underwent thoracotomy and occlusion of the left pulmonary artery. Twenty-four hours later the dogs were reanesthetized, and a double-lumen endotracheal tube was placed. The right lung was continuously ventilated with an inspiratory O2 fraction (FIO2) of 0.35. In seven study animals the left lung was ventilated with an FIO2 of 0 for 3 h after the left pulmonary artery occluder was removed. In six control animals the left lung was ventilated with an FIO2 of 0.35 during the same reperfusion period. Postmortem bloodless wet-to-dry weight ratios were 5.87 +/- 0.20 for the left lower lobe and 5.32 +/- 0.12 for the right lower lobe in the dogs with hypoxic ventilation (P less than 0.05 for right vs. left lobes). These values were not significantly different from the control dog lung values of 5.94 +/- 0.22 for the left lower lobe and 5.11 +/- 0.07 for the right lower lobe (P less than 0.05 for right vs. left lobes). All values were significantly higher than our laboratory normal of 4.71 +/- 0.06. We conclude that reperfusion injury is unaffected by alveolar hypoxia during the reperfusion phase.

Animals↗